阅读说明：本技术 吸收性复合体及制造方法、吸收性物品及制造方法、卫生材料、医疗用品 (Absorbent composite and method for producing same, absorbent article and method for producing same, sanitary material, and medical article ) 是由 陈兵 于 2020-05-07 设计创作，主要内容包括：本发明涉及吸收性复合体及制造方法、吸收性物品及制造方法、卫生材料、医疗用品。吸收性复合体,含有吸收性树脂和亲水性纤维,在血细胞比容值90％的血液中浸泡5分钟时的血液吸收量为(2-18)g/g。吸收性复合体的制造方法,至少包括通过吸收性树脂和含水的亲水性纤维混合得到的含水状态复合体的工序、及干燥工序。吸收性物品,包括吸收性复合体、纤维和/或纤维集合体。吸收性物品的制造方法,至少包括分离工序、叠层工序、固定化工序。卫生材料,包含吸收性物品。医疗用品,包含吸收性物品。本发明对于乳、血液等蛋白质,以及含有固体成分的液体皆表现出良好吸收性,具有吸收液的反渗少,不容易漏液,反复吸收时的吸收性好等优良效果。(The present invention relates to an absorbent composite and a method for producing the same, an absorbent article and a method for producing the same, a sanitary material, and a medical article. An absorbent composite comprising an absorbent resin and hydrophilic fibers, wherein the amount of blood absorbed when the composite is immersed in blood having a hematocrit of 90% for 5 minutes is (2-18) g/g. A method for producing an absorbent composite, comprising at least a step of mixing an absorbent resin and hydrophilic fibers containing water to obtain a composite in a water-containing state, and a drying step. An absorbent article includes an absorbent composite, fibers, and/or fiber aggregates. The method for manufacturing an absorbent article includes at least a separation step, a lamination step, and an immobilization step. A hygiene material comprising an absorbent article. Medical articles, including absorbent articles. The present invention has excellent effects of excellent absorbability for proteins such as milk and blood and liquids containing solid components, little reverse osmosis of absorption liquid, little leakage, excellent absorbability during repeated absorption, and the like.)

1. An absorbent composite, characterized by: the absorbent composite comprises an absorbent resin and hydrophilic fibers, and has a blood absorption capacity of (2-18) g/g when soaked in blood having a hematocrit of 90% for 5 minutes.

2. An absorbent composite according to claim 1, wherein: the absorptive composite has a blood concentration dependency characteristic of 0.20 or more; the blood concentration-dependent characteristic is a ratio of a blood absorption capacity (g/g) having a hematocrit value of 70% to a blood absorption capacity (g/g) having a hematocrit value of 20%.

3. An absorbent composite according to claim 1 or 2, wherein: the absorptive complex is obtained by utilizing a total reflection infrared spectroscopy method, wherein the absorption complex is 4000-400cm^-1Has a maximum peak value of 0.18 and a baseline standard of 0 (1650-1500 cm)^-1) The peak intensity of (A) is 0.08 or less.

4. An absorbent composite according to any of claims 1-3, wherein: the absorbent composite is in the form of particles.

5. An absorbent composite according to any of claims 1-4, wherein: the hydrophilic fiber covers the periphery of the absorbent resin.

6. An absorbent composite according to any of claims 1-5, wherein: the hydrophilic fiber comprises cellulose.

7. An absorbent composite according to any one of claims 1-6, wherein: the hydrophilic fiber has an average particle diameter of 10 to 200 μm.

8. An absorbent composite according to any one of claims 1-7, wherein: the absorbent composite has a component ratio of (10-21)%, which is measured by pulse NMR and has a relaxation time of 100 μ s or more, when the water content is adjusted to (5-5.2)%.

9. An absorbent composite according to any one of claims 1-8, wherein: the absorption complex has a zeta potential absolute value of 14.8mV or more, as measured by a streaming potential method.

10. An absorbent composite according to any one of claims 1-9, wherein: the impact resistance index of the absorbent composite is (0.1-12) g/g.

11. An absorbent composite according to any of claims 1-10, wherein: in the absorbent composite, the average particle diameter in a wet state is larger than the average particle diameter in a dry state.

12. An absorbent composite according to any of claims 1-11, wherein: the absorbent composite has a tap density of no greater than 0.50 g/mL.

13. An absorbent composite according to any of claims 1-12, wherein: the absorbent composite has a wetting tension of not less than 45 mN/m.

14. An absorbent composite according to any of claims 1-13, wherein: the hydrophilic fiber in the absorbent composite has a detachment rate of not more than 10%.

15. An absorbent composite according to any of claims 1-14, wherein: the hydrophilic fiber is attached to the surface of the absorbent resin.

16. An absorbent composite according to any one of claims 1-15, wherein: the number of absorbent resins exposed on the surface of the absorbent resin in the absorbent composite is not more than 50 per 500.

17. An absorbent composite according to any of claims 1-16, wherein: in the absorbent composite, the total number of the absorbent composite having a particle diameter of 1mm or more and the absorbent resin having a particle diameter of 1mm or more is not more than 100 per 0.25 g.

18. An absorbent composite according to any one of claims 1-17, wherein: in the absorbent composite, the average particle diameter of the absorbent resin is not more than 300 [ mu ] m.

19. An absorbent composite according to any of claims 1-18, wherein: the absorbent resin has an acid group; the molar ratio of the amount of acid groups on the surface of the absorbent composite to the amount of acid groups of the absorbent resin inside is not more than 10%.

20. A method of making an absorbent composite according to any of claims 1-19, wherein: the method comprises at least a step of mixing an absorbent resin and hydrophilic fibers containing water to obtain a composite in a water-containing state, and a step of drying the composite in a water-containing state to obtain an absorbent composite.

21. The method of manufacturing an absorbent composite according to claim 20, wherein: the production method comprises at least a step of mixing the absorbent resin and the hydrophilic fiber and a step of adding water droplets having an average droplet diameter of 300 [ mu ] m or less.

22. The method of manufacturing an absorbent composite according to claim 20 or 21, wherein: in the step of mixing the absorbent resin and the hydrophilic fiber, a vertical floating mixer is used for mixing.

23. A method of making an absorbent composite according to any of claims 20-22, wherein: before mixing the absorbent resin and the hydrophilic fiber, the relative humidity inside a vertical type floating mixer is adjusted to 55% or less.

24. A method of manufacturing an absorbent composite according to any of claims 20-23, wherein: in the step of mixing the absorbent resin and the hydrophilic fiber, the Froude number of the number of rotations of the blades of the vertical type floating mixer is set to 0.3 to 5.0.

25. An absorbent article comprising the absorbent composite, and further comprising fibers and/or fiber aggregates.

26. An absorbent article according to claim 25, wherein: the absorbent article has a bulk density of (0.004-0.900) g/cm³And the thickness is (0.2-15) mm.

27. An absorbent article according to claim 25 or 26, characterized in that: the absorbent article has a multilayer structure of 2 or more layers, at least one of which is a layer composed of the absorbent composite.

28. An absorbent article according to any of claims 25-27, characterized in that: in the absorbent article, the fibers and/or fiber aggregates are bonded to the absorbent composite by an adhesive.

29. An absorbent article according to any of claims 25-28, characterized in that: the fibers and/or fiber aggregate contain thermoplastic fibers, and are thermally fused to the absorbent composite by the thermoplastic fibers.

30. An absorbent article according to any of claims 25-29, characterized in that: at least a portion of the fibrous layers above and/or below the layer in which the absorbent composite is located in the absorbent article are entangled or fused.

31. An absorbent article according to any of claims 25-30, characterized in that: the absorbent article has a continuous concave linear form with a width of 2mm or less.

32. A method of manufacturing an absorbent article according to any of claims 25-31, characterized in that: the manufacturing method includes at least an absorbent composite separation step, an absorbent composite lamination step, and an absorbent composite immobilization step.

33. The method of manufacturing an absorbent article according to claim 32, wherein: the absorbent composite separation step and the absorbent composite lamination step are both characterized by a screening operation.

34. A sanitary material characterized by: comprising the absorbent article.

35. A medical article, characterized by: comprising the absorbent article.

Technical Field

The present invention relates to an absorbent composite and a method for producing the same, an absorbent article including the absorbent composite and a method for producing the same, a sanitary material including the absorbent article, and a medical article including the absorbent article.

Background

In recent years, gelled absorbent resins that absorb a large amount of water have been developed and mainly used in the field of sanitary materials such as paper diapers and feminine sanitary napkins.

The absorbent resin is usually obtained in a fine powder form, and is inferior in handling properties when used alone, and therefore, in the field of sanitary materials, the absorbent resin is used by mixing with pulp or the like and filling into a bag or processing into a sheet.

For example, patent document 1 (Japanese patent document: No. 3196933) discloses a technique of bonding a water-absorbent resin to a sheet by using a hot-melt adhesive in order to fix the water-absorbent resin to the sheet.

Patent document 2 (japanese patent application laid-open No. 53-4789) discloses a technique in which a mixture of ground pulp and thermoplastic fibers is heated to form a sheet, and a solid water-absorbent resin powder is supported on the sheet-shaped molded article.

Patent document 3 (japanese patent application laid-open No. 56-60556) discloses a technique of fixing water-containing pulp and a water-absorbent resin while drying them by utilizing an adhesive component in the water-absorbent resin.

Patent document 4 (japanese patent publication No. 2003-508647) discloses a technique of uniformly mixing a water-absorbent resin and a fibrous material such as pulp, and forming a sheet-like molding by hydrogen bonding between the pulps with water.

Patent document 5 (japanese patent laid-open No. 2003-11118) discloses a technique of adhering absorbent polymer particles to a fibrous substrate during polymerization and polymerizing a water-absorbent resin on the fibrous substrate.

Patent document 6 (japanese patent document: WO2006/121148) discloses a technique of directly bonding a water-absorbent resin to a hydrophilic substrate.

However, the absorbent resins proposed so far exhibit good absorption of water, but do not exhibit sufficient absorption of proteins such as milk and blood and liquids containing solid components, and in particular, have a problem that they cannot sufficiently absorb water when processed into a sheet form for use.

In addition, the absorbent resins proposed so far have many problems. For example, the blood retention ability after blood absorption is low, the reverse osmosis of the absorbed blood is high, the blood capturing ability is low, leakage is easy, repeated absorption is poor, and the absorption rate is decreased when the absorption amount is increased.

Disclosure of Invention

In order to solve the above-mentioned problems, the present invention provides an absorbent composite having a specific structure and having an absorption amount of blood at a high concentration exceeding a usual level within a specific range, an absorbent article based on the absorbent composite, and a sanitary material and a medical article using the absorbent article.

The technical scheme adopted by the invention for solving the technical problems is as follows:

an absorbent composite comprising an absorbent resin and hydrophilic fibers, wherein the amount of blood absorbed when soaked in blood having a hematocrit of 90% for 5 minutes is (2-18) g/g.

Further, the blood concentration dependency characteristic of the absorbent composite is 0.20 or more; the blood concentration-dependent characteristic is a ratio of a blood absorption capacity (g/g) having a hematocrit value of 70% to a blood absorption capacity (g/g) having a hematocrit value of 20%.

Further, the absorptive complex is obtained by utilizing total reflection infrared spectroscopy to obtain 4000-400cm^-1Has a maximum peak value of 0.18 and a baseline standard of 0 (1650-1500 cm)^-1) The peak intensity of (A) is 0.08 or less.

Further, the absorbent composite is in the form of particles.

Further, the hydrophilic fiber covers the periphery of the absorbent resin.

Further, the hydrophilic fiber comprises cellulose.

Further, the hydrophilic fiber has an average particle diameter of 10 to 200 μm.

Further, the absorbent composite has a component ratio of (10-21)%, which is measured by pulse NMR and has a relaxation time of 100. mu.s or more, when the water content is adjusted to (5-5.2)%.

Further, the absorption composite has a zeta potential absolute value of 14.8mV or more by a streaming potential method.

Further, the impact resistance index of the absorbent composite is (0.1-12) g/g.

Further, in the absorbent composite, the average particle diameter in a wet state is larger than the average particle diameter in a dry state.

Further, the absorbent composite has a tap density of not greater than 0.50 g/mL.

Further, the absorbent composite has a wetting tension of not less than 45 mN/m.

Further, the hydrophilic fiber in the absorbent composite has a detachment rate of not more than 10%.

Further, the hydrophilic fiber is attached to the surface of the absorbent resin.

Further, the number of absorbent resins exposed on the surface of the absorbent resin in the absorbent composite is not more than 50 per 500.

Further, in the absorbent composite, the total number of the absorbent composite having a particle diameter of 1mm or more and the absorbent resin having a particle diameter of 1mm or more is not more than 100 per 0.25 g.

Further, in the absorbent composite, the average particle diameter of the absorbent resin is not more than 300. mu.m.

Further, the absorbent resin has an acid group; the molar ratio of the amount of acid groups on the surface of the absorbent composite to the amount of acid groups of the absorbent resin inside is not more than 10%.

A method for producing an absorbent composite, comprising at least a step of mixing an absorbent resin and hydrophilic fibers containing water to obtain a composite in a water-containing state, and a step of drying the composite in the water-containing state to obtain an absorbent composite.

The production method further comprises at least a step of mixing the absorbent resin and the hydrophilic fiber and a step of adding water droplets having an average droplet diameter of 300 μm or less.

Further, in the step of mixing the absorbent resin and the hydrophilic fiber, the mixing is performed by using a vertical floating mixer.

Further, before the absorbent resin and the hydrophilic fiber are mixed, the relative humidity inside the vertical type floating mixer is adjusted to 55% or less.

Further, in the step of mixing the absorbent resin and the hydrophilic fiber, the Froude number of the number of rotations of the blades of the vertical type floating mixer is set to 0.3 to 5.0.

An absorbent article comprising the absorbent composite, and further comprising fibers and/or fiber aggregates.

Further, the absorbent article has a bulk density of (0.004 to 0.900) g/cm³And the thickness is (0.2-15) mm.

Further, the absorbent article has a multilayer structure of 2 or more layers, at least one of which is a layer composed of the absorbent composite.

Further, in the absorbent article, the fibers and/or the fiber aggregate are bonded to the absorbent composite with an adhesive.

Further, the fibers and/or the fiber aggregate contain thermoplastic fibers, and are thermally fused to the absorbent composite by the thermoplastic fibers.

Further, at least a portion of the fibrous layers above and/or below the layer in the absorbent article in which the absorbent composite is located are intertwined or fused.

Further, the absorbent article has a continuous concave linear form with a width of 2mm or less.

A method for manufacturing an absorbent article includes at least an absorbent composite separation step, an absorbent composite lamination step, and an absorbent composite immobilization step.

Further, the absorbent composite separation step and the absorbent composite lamination step are both characterized by a screening operation.

A sanitary material comprising the absorbent article.

A medical article comprising the absorbent article.

The invention has the advantages that: the present invention is capable of providing an absorbent composite having excellent properties such as less reverse osmosis of an absorbent liquid, less leakage of the liquid, and excellent absorption properties during repeated absorption, and also having practical properties such as an absorption amount and an absorption rate, and an absorbent article based on the absorbent composite, and a sanitary material and a medical article using the absorbent composite, all of which exhibit excellent absorption properties for proteins such as milk and blood, and a liquid containing a solid component, and exhibit excellent effects such as excellent absorption properties when used after being processed into a sheet form.

Detailed Description

Hereinafter, embodiments of the present invention (hereinafter, simply referred to as "the present embodiments") will be described in detail, but the present invention is not limited to the following embodiments. The present invention can be carried out in various modifications without departing from the scope of the invention.

Absorbent composite

The absorbent composite of the present embodiment comprises an absorbent resin and hydrophilic fibers, and has an absorption capacity of 2 to 18g/g when immersed in blood having a hematocrit value of 90% for 5 minutes.

The "hematocrit value" is a value indicating the concentration of solid components (blood cells) in blood.

The hematocrit value of normal blood is about 50%.

The absorbent composite of the present embodiment can absorb blood having a high solid content (blood cell) concentration in a high absorption amount.

Since the absorption capacity when the blood is immersed in the blood having a hematocrit value of 90% for 5 minutes is within the above numerical range, the balance between the absorption capacity and the absorption rate of the blood at a normal concentration is good.

In addition, when the absorbent composite of the present embodiment is used as an absorbent body of a sanitary product, the ability to capture blood is excellent, and therefore, leakage of blood can be suppressed.

The absorption capacity of the absorbent composite of the present embodiment with respect to blood having a hematocrit value of 90% is preferably 2g/g or more, more preferably 3.5g/g or more, particularly preferably 5.5g/g or more, particularly preferably 7g/g or more, and most preferably 9g/g or more, from the viewpoint of the absorption rate.

In addition, from the viewpoint of the balance between the upper limit absorption value of the absorption amount, the amount of blood absorbed and the absorption rate, it is preferably 18g/g or less, more preferably 16g/g or less, particularly preferably 15g/g or less, particularly preferably 14g/g or less, and most preferably 13g/g or less.

By appropriately combining the absorbent resin and the hydrophilic fiber, the amount of blood absorbed at a hematocrit value of 90% in the absorbent composite of the present embodiment can be controlled to 2 to 18 g/g. For example, as described later, water is added when the absorbent resin and the hydrophilic fiber are mixed, water is added after the absorbent resin and the hydrophilic fiber are mixed in advance, and the diameter of water droplets to which water is added is controlled.

As described later, the absorbent composite of a commercially available absorbent article is often processed into a sheet together with other cellulose fibers and the like. In this case, after the absorbent article processed into a film is soaked in isopropyl alcohol, cellulose constituting the sheet-like absorbent article is separated, the cellulose and the absorbent composite are separated, and the floating cellulose is removed, so that the absorbent composite can be taken out; the amount of blood absorbed and various properties of the absorbent composite described below can also be measured using the absorbent composite separated from the absorbent article.

Generally, the amount of blood absorbed by an absorbent composite varies depending on the hematocrit value of blood.

The absorbent composite of the present embodiment preferably has a blood concentration-dependent characteristic of 0.20 or more; wherein the blood concentration dependent characteristic is a ratio of a blood absorption capacity (g/g) having a hematocrit value of 70% to a blood absorption capacity (g/g) having a hematocrit value of 20%; since the blood concentration-dependent characteristic is 0.20 or more, the difference in absorption amount due to blood-interfering substances becomes small, the retention after blood absorption becomes higher, and the repeated absorbability can be better; the blood concentration-dependent property is preferably 0.25 or more, more preferably 0.40 or more, particularly preferably 0.55 or more, particularly preferably 0.6 or more; the higher the blood solid content, the less the amount of blood absorbed by the absorbent composite, so that the blood concentration-dependent characteristic value does not exceed 1.0, but the closer the blood concentration-dependent characteristic is to the upper limit of 1.0, the better the performance; this blood concentration-dependent characteristic can be measured by the method described in the examples described later.

The blood concentration dependency of the absorbent composite of the present embodiment can be controlled to 0.20 or less by compounding the absorbent resin and the hydrophilic fiber into a specific structure. For example, a method of optimizing the mixing conditions and the ratio of the absorbent resin to the hydrophilic fiber when mixing them can be mentioned.

The shape of the absorbent composite of the present embodiment is not particularly limited as long as it has the above-mentioned properties, but from the viewpoint of increasing the surface area and increasing the absorption rate, the particle shape is preferably one containing, for example, an approximately spherical absorbent resin and hydrophilic fibers described later, and it is preferable that the hydrophilic fibers are adhered to at least a part of the surface of the absorbent resin in a covering form, and the periphery of the absorbent resin is covered with the hydrophilic fibers.

The absorbent composite of the present embodiment contains the absorbent resin and the hydrophilic fiber, and therefore, compared with the case where the absorbent resin alone is used, the absorbent composite has a higher water absorption rate and an excellent dry feeling.

In addition, the hydrophilic fiber covers the periphery of the absorbent resin, so that the hydrophilic fiber can replenish liquid and can be rapidly conveyed to the absorbent resin; the hydrophilic fiber prevents contact between the absorbent resins and prevents formation of gel that inhibits expansion of the absorbent resins. The absorbent composite of the present embodiment can prevent the gel from coagulating, and does not require the use of other sanitary materials, so that material saving can be reduced, the manufacturing process of sanitary materials and the like can be simplified, and resource saving can be contributed.

In the absorbent composite of the present embodiment, the exposed portion of the surface of the absorbent resin is small, and the surface is preferably covered with the hydrophilic fiber. Since the hydrophilic fiber suppresses proteins of the charged absorption inhibitor and the blood cells and the like from adhering to the surface of the absorbent resin due to the effect of electric charges, the absorption performance of the absorbent resin can be effectively exhibited.

Absorbent resin

The absorbent composite of the present embodiment includes an absorbent resin.

The absorbent resin refers to a resin having absorption and retention properties for liquid.

The absorbent resin is not particularly limited in kind as long as it has an absorption performance for liquid.

The absorbent resin is not limited to the following, and examples thereof include a crosslinked polymer of a partially neutralized polyacrylic acid (for example, Japanese patent laid-open publication No. 55-84304), a hydrolysate of a starch-acrylonitrile polymer (for example, Japanese patent laid-open publication No. 49-43395), a neutralized starch-acrylic acid polymer (for example, Japanese patent laid-open publication No. 51-125468), a saponified product of a vinyl acetate-acrylic acid ester copolymer (for example, Japanese patent laid-open publication No. 52-14689), a hydrolysate of an acrylonitrile copolymer or an acrylamide copolymer (for example, Japanese patent laid-open publication No. 53-15959), and a polyglutamate salt (for example, Japanese patent laid-open publication No. 2003-192794).

In the absorbent composite of the present embodiment, the absorbent resin used is preferably a polymeric bridge composed mainly of polyacrylic acid, more preferably an acrylic acid salt copolymer and/or an acrylic acid partially neutralized polymeric bridge, and even more preferably a mixture of acrylic acid and acrylic acid salt.

The polyacrylate copolymer includes monomer copolymers shown below. Without being limited thereto, for example, acid or partially neutralized products such as (meta) acrylic acid, itaconic acid, maleic acid, crotonic acid, succinic acid, 2-acrylamido-2-methyl-1-propanesulfonic acid, etc., (meta) methyl acrylate, (meta) ethyl acrylate, (meta) acrylamide, (meta) acrylonitrile, vinyl acetate, hydroxyethyl methacrylate, methoxyethyl methacrylate, methyl hydroxyacrylate, etc.; wherein, (meta) represents a methyl group, and (meta) acrylic acid is exemplified and represented as acrylic acid or methacrylic acid.

As the polymer of the mixture of acrylic acid and acrylic acid salt and the polymer bridge of partially neutralized polyacrylic acid, the constituent units in the polymer molecular chain, specifically, the total of neutralized carboxylic acid and carboxylic acid, are preferably 50 mol% or more, more preferably 80 mol% or more, particularly preferably 90 mol% or more of the total constituent units of the carboxylic acid.

Since the proportion of the constituent unit containing a carboxyl group is 50 mol% or more, sufficient absorption performance can be obtained.

In addition, it is preferable that a part of carboxyl groups in a polymer bridge composed mainly of polyacrylic acid is neutralized (partially neutralized) to form a salt. Examples of the salt include metal salts such as sodium salt, potassium salt, and lithium salt, and salts including nitrogen-based compounds such as ammonia.

30 mol% or more, preferably 50 mol% or more, particularly preferably 70 mol% or more of the carboxyl groups are neutralized.

The absorbent resin has an acid group

The absorbent resin used in the absorbent composite of the present embodiment preferably has an acid group.

Since the absorbent resin has an acid group in a side chain, it is preferable that electrostatic repulsion occurs between acid groups when absorbing liquid, and the absorption rate is increased. Further, if the acid group is neutralized, the osmotic pressure liquid is absorbed into the absorbent resin, and therefore, it is preferable that the salt of the neutralized acid group easily causes the hydrophilic fiber and the absorbent resin to be directly bonded to each other.

The type of the acid group is not particularly limited, but from the viewpoint of increasing the absorption rate, an ionizable acid group such as a carboxyl group or a sulfonic acid group is preferable, and a carboxyl group is more preferable; from the viewpoint of improving the absorption amount, it is preferable that 50 to 90 mol% of the acid groups are partially neutralized; the kind of the neutralized acid-based salt is not particularly limited, and alkali metals such as sodium and potassium, alkaline earth metals such as magnesium and calcium, and ammonia can be exemplified, but it is preferably neutralized with a sodium salt and/or an ammonium salt from the viewpoint of absorption performance; since the action of osmotic pressure is large as a motive force for absorbing water at a high speed, in the present embodiment, an absorbent resin having a structure containing an acid group is preferably used.

However, since the acid group has an electric charge, when a liquid containing a protein and a solid component is absorbed, the acid group adsorbs the solid component such as the protein and is easily bonded to the solid component, and therefore, the whole absorbent composite is likely to be aggregated and the absorption capacity is likely to be reduced; in particular, since the absorbent resin absorbs moisture and the protein and solid components are likely to be concentrated, it is necessary to have a characteristic of absorbing a liquid having a high protein concentration and a high solid content, but the absorption amount, absorption rate, and solid component concentration of the acid-based protein increase, the absorption rate also increases, the protein and solid components are likely to be concentrated, and the absorption function and absorption of the entire absorbent composite are likely to be further reduced; in the absorbent composite of the present embodiment, in order to achieve both the liquid absorbability and the non-absorbability of the acid groups of the absorbent resin with respect to the protein and the solid content, it is preferable to reduce the amount of the acid groups on the surface of the absorbent composite particles while maintaining a high concentration of the acid groups of the absorbent resin in the absorbent composite; in the absorbent composite of the present embodiment, the amount of the surface acid groups of the absorbent composite particles is preferably 10 mol% or less, more preferably less than 5 mol% or less, particularly preferably less than 1 mol% or less, based on the amount of the acid groups (100 mol%) in the absorbent composite particles, that is, in the absorbent resin.

As described above, it is effective to coat the surface of the absorbent resin with hydrophilic fibers so as to reduce the amount of acid groups on the surface of the composite to 10 mol% or less based on the amount of acid groups (100 mol%) of the absorbent resin in the absorbent composite.

The amount of the acid group in the absorbent resin can be quantified, for example, by infrared spectroscopy (IR).

The amount of acid groups on the surface of the absorbent resin particles can be measured by total reflection infrared spectroscopy (ATR), and the number of acid groups in the absorbent resin particles can be measured by ATR after cutting the cross section of the absorbent resin particles.

In the ATR measurement, the pressure at the time of measurement is important, and 4000-400cm is used^-1The pressure at which the maximum peak absorbance of (b) was adjusted to 0.15 to 0.20 was used as the pressure condition.

The quantitative determination of an acid group can be appropriately carried out by utilizing a characteristic absorption peak corresponding to the acid groupFor example, when the acid group is a carboxyl group, 1650-1500cm can be used^-1Characteristic absorption peak of carbonyl stretching vibration (CO stretching vibration) of (1).

When the acid group is sulfonic acid, 1300cm of 1350-^-1Or 1160 and 1120cm^-1SO of (A)₂Absorption peak of telescopic motion.

When the amounts of acid groups on the surface of the absorbent resin particles and in the absorbent resin particles were compared, the normalized region was good and the region having no absorption peak was found (when the absorbent resin was a polyacrylic acid-based absorbent resin and the composition of cellulose fibers was 2500-1800 cm)^-1Field) was normalized with the absorbance of the base line as 0 and the maximum peak size set to 0.18.

When the absorbent composite is regarded as particles, even if there is no carboxylic acid group on the surface of the absorbent composite, peaks of carbonyl groups such as ketone groups and esters are observed on the surface of the absorbent resin particles, that is, on the interface of the hydrophilic fibers, in this case, the absorption peaks can be separated and analyzed, and an analysis method other than IR can be used.

Further, even if there is no carboxylic acid group, the surface of the absorbent composite tends to adsorb proteins and solid substances having carbonyl groups, and therefore, the smaller the peak value of the carbonyl group on the surface of the absorbent composite, the better regardless of the origin.

The comparison of the carbonyl peaks in the absorbent composite, i.e., the surface of the absorbent resin, and the surface of the absorbent composite can be appropriately normalized.

The absorbent resin contained in the absorbent composite of the present embodiment preferably has an average particle size of 300 μm or less, more preferably 270 μm or less, and particularly preferably 240 μm or less, from the viewpoint of increasing the absorption rate.

The lower limit is preferably 80 μm or more from the viewpoint of operability.

The average particle diameter of the absorbent resin can be determined by screening.

The average particle diameter of the absorbent resin can be determined by emulsion polymerization and suspension polymerization, and the gel obtained by aqueous solution polymerization can be controlled by adjusting the particle diameter in which the recovery range is determined by pulverization conditions and screening.

Hydrophilic fiber

The absorbent composite of the present embodiment includes an absorbent resin.

The hydrophilic fiber is a fiber having a function of absorbing a liquid in contact with the fiber into the fiber. The hydrophilic fiber is not particularly limited as long as the liquid that comes into contact with the fiber can be absorbed into the fiber, and can be used as desired. The liquid absorbed into the hydrophilic fibers is transported from the hydrophilic fibers to the absorbent resin, and is held in the absorbent resin.

The material of the hydrophilic fiber is not particularly limited, and examples of the material include hydrophilic cotton, hemp, wool, silk, rayon, kapok, lyocell, cuprammonium, pulp, and the like, and other hydrophilic synthetic fibers such as polyethylene, polypropylene, polyester, nylon, and the like. The hydrophilic fiber is preferably hydrophilic, or nylon, more preferably cellulose-containing, particularly preferably cellulose-based.

Cellulose-based fibers are fibers mainly made of cellulose. The term "main raw material" as used herein means that the cellulose content exceeds 50%. As the cellulose, for example, cellulose induced by esterification, etherification or the like can be used. The hydrophilic fiber may be a mixture of the cellulose fiber and another fiber. Cellulosic fibers, such as cotton, hemp, rayon, tiger kapok, lyocell, cuprammonium, wood pulp, and the like. Among them, pulp is preferable. The pulp may be wood pulp or non-wood pulp. In the wood pulp, coniferous trees and broad-leaved trees can be used. Examples of the non-wood pulp include bagasse, grass, ligusticum, bamboo and the like. Further, pulp may be regenerated from used paper or the like, but when used as a sanitary material, pulp directly produced from wood or the like is preferable.

The shape of the hydrophilic fiber is not particularly limited. Examples of the shape of the hydrophilic fiber include fibrous, particulate, rod-like, scaly, needle-like, and string-like shapes.

Pulp is widely used in sanitary materials for the purpose of supporting an absorbent resin by winding and for the purpose of improving liquid acquisition properties. When pulp is used for such a purpose, the pulp is generally used in a state where a raw material is pulverized into a fibrous form. The entanglement of fibers is utilized as an effective support for resin, and pulp is preferably used when pulp is a long fiber of about 10 to 13mm in general. However, even if the raw material is pulverized for the purpose of obtaining such a long fiber length, there is a possibility that a fine powder unsuitable for use is also produced. The fine particulate sanitary material is diffused to cause material loss in the manufacturing process and is discarded in the past.

In this embodiment, pulp of a small particle size, which has conventionally caused a material loss, can be used as a center; the fine-powder hydrophilic fiber obtained by crushing the pulp raw material can be obtained by a simpler apparatus than that by which a long-fiber hydrophilic fiber can be obtained. In addition, a narrow pulp particle size distribution can be obtained. It is expected that the use of ground pulp having a small particle diameter will result in less material loss and improved production efficiency as compared with the conventional pulp.

The absorbent composite of the present embodiment contains the following hydrophilic fibers: it is preferably from 10 to 200. mu.m, more preferably from 20 to 130. mu.m, particularly preferably from 30 to 120. mu.m, particularly preferably from 50 to 110. mu.m, most preferably from 60 to 100. mu.m. The hydrophilic fibers have an average particle size of 10 to 200 μm, and are capable of preventing the adhesion between the water-absorbent resins, and also capable of suppressing excessive entanglement between the hydrophilic fibers and improving the water absorption rate while having a sufficient thickness as a layer for capturing and transporting a liquid to the water-absorbent resins at one time. When the average particle diameter of the hydrophilic fibers is 10 μm or more, contact between the absorbent resins can be prevented, and direct contact between the surface of the absorbent resin and a liquid can be prevented when the absorbent composite of the present embodiment is in contact with the liquid. On the other hand, when the average particle diameter of the hydrophilic fibers is 200 μm or less, the decrease in liquid permeability due to the cross-linking and aggregation between the hydrophilic fibers can be prevented, and the deterioration of handling performance can be effectively prevented.

The average particle diameter of the hydrophilic fiber can be measured by using a laser diffraction/scattering type particle size distribution measuring apparatus. That is, the average particle diameter of the hydrophilic fiber, which is the diameter of the median value of the volume measurement standard at 25 ℃ in the ultrasonic treatment for 1 minute for the hydrophilic fiber dispersed in water as a dispersion medium, can be obtained. Specifically, examples of the method described later can be measured.

In the absorbent composite of the present embodiment, it is preferable that the hydrophilic fibers are attached to the surface of the absorbent resin from the viewpoint of suppressing solid content and improving the absorption performance by improving hydrophilicity. If the hydrophilic fiber can be peeled off, the average particle diameter of the hydrophilic fiber can be measured in the above-described manner.

The average particle diameter of the hydrophilic fibers may be adjusted in the step of producing the absorbent composite according to the present embodiment, but it is preferable to produce the absorbent composite by using hydrophilic fibers whose average particle diameter is adjusted in advance.

Further, in the absorbent composite, the average particle diameter of the hydrophilic fiber is determined by separating the hydrophilic fiber from the water-absorbent resin by selecting an appropriate method. For example, when the absorbent resin is a polyacrylic resin, the absorbent resin can be water-dissolved by irradiating the resin with ultraviolet rays in a water-absorbing state. If the absorbent resin is dissolved in water, the hydrophilic fibers can be separated by filtration, and the average particle size of the hydrophilic fibers can be determined based on the separation.

As described above, an appropriate separation method may be selected depending on the type of the hydrophilic fiber and the absorbent resin used.

The particle size of the hydrophilic fiber is preferably 50% by mass or more, more preferably 70% by mass or more, particularly preferably 80% by mass or more, and particularly preferably 90% by mass or more, when the particle size is measured on a sieve according to Japanese Standard JISZ 8901. Further, when the sieve having a sieve pore size of 75 μm is used, it is preferable that 50% by weight or more of the particles pass through the sieve, more preferably 70% by weight or more of the particles pass through the sieve, particularly preferably 80% by weight or more of the particles pass through the sieve, and particularly preferably 90% by weight or more of the particles pass through the sieve. The hydrophilic fibers having a particle size within the above numerical range can prevent the hydrophilic fibers from being entangled with each other.

The hydrophilic fiber preferably has a wet tension of 45mN/m or more, more preferably 50mN/m or more, particularly preferably 55mN/m or more. The higher the wet tension of the hydrophilic fiber, the better the absorbency is exhibited. The wet tensile strength of the hydrophilic fiber can be measured by the same method as that of the absorbent composite described later.

The hydrophilic fiber preferably has a blood absorption amount of 2 to 8g/g, more preferably 3 to 6 g/g. The amount of the hydrophilic fiber retained in blood is preferably 2 to 6g/g, more preferably 3 to 5 g/g. Here, the absorption amount is an amount retained after being gently wiped after being immersed in blood, and the retention amount is an amount retained after being completely squeezed after being immersed in blood. The hydrophilic fiber has a blood absorption amount of 2g/g or more, and therefore, the absorbability of the absorbent composite tends to be sufficient in practical use, and the hydrophilic fiber has a blood absorption amount of 8g/g or less, and a liquid absorption rate into the absorbent resin tends to be sufficient in practical use. Further, the hydrophilic fiber has a blood retention amount of 2g/g or more, and can provide an effect of increasing the absorption rate, and a reverse osmosis ratio of 6g/g or less, and can provide a good drying effect.

The bulk density of the hydrophilic fiber is preferably from 0.01 to 0.5g/mL, more preferably from 0.05 to 0.4g/mL, particularly preferably from 0.08 to 0.3g/mL, particularly preferably from 0.1 to 0.25 g/mL. When the bulk density of the hydrophilic fiber is 0.01 to 0.5g/mL, a space of an appropriate size is formed around the absorbent resin, and the aggregation of the colloid can be suppressed, and the water transport property and wetting property of the hydrophilic fiber to the absorbent resin can be improved, thereby increasing the water absorption rate. The bulk density can be measured by the same method as that of the absorbent composite described in examples described later.

The content of the hydrophilic fiber in the absorbent composite of the present embodiment is preferably 25 to 250 mass units, more preferably 30 to 200 mass units, particularly preferably 35 to 160 mass units, and particularly preferably 40 to 120 mass units, based on 100 mass units of the absorbent resin.

Since the content of the hydrophilic fiber is 25 mass units or more, the surface of the absorbent resin can be covered, the performance thereof can be sufficiently exhibited, and the aggregation between the absorbent resins can be prevented. Since the content of the hydrophilic fiber is 250 mass units or less, it can sufficiently adhere to the surface of the absorbent resin. The content of the hydrophilic fiber is preferably adjusted as appropriate in accordance with the surface area of the absorbent resin. Further, since the surface area of the absorbent resin changes depending on the water content, the content of the hydrophilic fiber is preferably adjusted in consideration of the change in the surface area.

Structure of absorbent composite

The absorptive composite of the present embodiment is obtained by measuring 4000-400cm by total reflection infrared spectroscopy (ATR)^-1Has a maximum peak value of 0.18 and a base line of 0 (1650-1500 cm)^-1) The peak intensity of (A) is preferably 0.08 or less; in the ATR measurement, the spectrum of the surface of the absorptive composite is measured.

Since the peak intensity is 0.08 or less, adhesion of components that inhibit absorption by the absorbent composite of the present embodiment can be prevented. The peak intensity is preferably 0.05 or less, more preferably 0.04 or less, particularly preferably 0.02 or less.

The peak strength of the CO stretching vibration of the absorbent composite of the present embodiment can be controlled to 0.08 or less by increasing the coverage of the hydrophilic fibers of the absorbent resin. For example, the mixing ratio of the absorbent resin and the hydrophilic fiber and the conditions during mixing can be controlled.

The amount of acid groups in the particles of the absorbent composite of the present embodiment, and the amount of acid groups on the surface of the particles of the absorbent composite, for example, the amount of carbonyl groups is preferably 49 mol% or less, more preferably 30 mol% or less, particularly preferably 20 mol% or less, and particularly preferably 10 mol% or less, from the viewpoint of preventing the adhesion of the acid groups in the particles to proteins and solid components.

In the absorbent composite of the present embodiment, the "surface layer" on the surface having fewer acid groups than the interior thereof is preferably 0.1 to 100. mu.m, more preferably 1 to 70 μm, particularly preferably 3 to 50 μm, particularly preferably 5 to 30 μm, in view of preventing the adhesion of solid matter and improving the absorption capacity. The thickness of the surface layer of the absorbent composite particles can be confirmed and measured by microscopic IR after cutting off the cross section of the absorbent composite particles. In addition, the thickness of the surface layer of the absorbent composite can be controlled by the composite in a state where the hydrophilic fibers on the surface of the absorbent resin are less overlapped. For example, the mixing strength when the absorbent resin and the hydrophilic fiber are mixed is controlled.

The absorbent composite of the present embodiment is preferably fine particles in shape.

The average particle diameter of the absorbent composite of the present embodiment is preferably 100-800 μm, more preferably 200-800 μm, particularly preferably 250-700 μm, particularly preferably 300-600 μm, most preferably 350-500 μm. The average particle diameter of the absorbent composite is 1000 μm or less, a high absorption rate can be obtained, and a sufficient absorption amount can be obtained by 100 μm or more. The average particle diameter of the absorbent composite is a volume-weighted average particle diameter corresponding to the circle area diameter measured and calculated by a dynamic image-based particle size distribution/shape evaluation device. The volume weighted average particle diameter is a result of calculating the volume of a sphere corresponding to the circle area equivalent diameter measured by image analysis for all particles and weighted averaging based on the volume. Specifically, it is calculated by the following formula.

Volume weighted mean particle size (. mu.m): ∑ EQPC_i×V_i/V_total(ii) a Here, EQPC_iDenotes the circle area equivalent diameter, V, of the i-th particle_iDenotes the volume, V, of the ith particle_totalThe total volume of the total absorbent composite particles is shown.

The following is a specific example of a method for measuring the average particle diameter of the absorbent composite.

For example, the measurement was carried out using a QICPIC system, a dynamic image particle size distribution-shape evaluation device, manufactured by Nippon laser Co. The measurement range used M6 and the dispersion unit used an air flow RODOS/L. The calculation mode is area circle equivalent diameter, sample density is set to 1g/mL, measured concentration is 0.03%, dispersion pressure is 1.00bar, dust absorption is 38.00mbar, rotation is 100%, and FEEDER is conveyed by 70% in the VIBRI mode. A sieve having a 2mm mesh was prepared above the FEEDER, and 7 3/8-inch stainless steel balls manufactured by ASONE corporation were placed on the sieve, and then an absorbent composite of a sample for measurement was placed thereon to perform measurement.

In the present embodiment, when the particle size of the absorbent composite is measured by using a sieve in accordance with japanese standard JISZ8901, the particle size passing through a sieve having an opening of 90 μm is preferably 50% by weight or less, more preferably 30% by weight or less, particularly preferably 10% by weight or less, from the viewpoint of handling. Further, the amount of particles which cannot pass through a 710 μm mesh sieve is preferably 50% by mass or less, more preferably 30% by mass or less.

Various characteristics of the absorbent composite

In the absorbent composite of the present embodiment, the hydrophilic fibers are preferably firmly adhered to the surface of the water-absorbent resin.

The hydrophilic fiber detachment ratio of the absorbent composite of the present embodiment is preferably 10% or less, more preferably 5% or less, particularly preferably 4% or less, and particularly preferably 3% or less, from the viewpoint of increasing the absorption capacity and improving the repeated absorbency. The release rate of the hydrophilic fibers from the absorbent composite can be measured by using a vibrating screen. The detachment rate of the absorbent composite can be measured by the method described in the examples below.

The absorbent composite of the present embodiment preferably has a wet tension of 45mN/m or more, more preferably 48mN/m or more, particularly preferably 50mN/m or more, and particularly preferably 52mN/m or more. When the wet tension of the absorbent composite of the present embodiment is within the above range, the absorbency of a liquid containing a protein can be improved. The wet tensile force can be measured using a wet tensile force standard solution, and can be measured by the method described in the following specific examples.

In the absorbent composite of the present embodiment, the ratio of the absorbent composite in which the surface of the absorbent resin is exposed is 50 or less out of 100, that is, 50% or less, preferably 40% or less, particularly preferably 30% or less, particularly preferably 20% or less, and most preferably 10% or less.

The exposure of the surface of the absorbent resin in the absorbent composite was observed by an optical microscope, and the ratio was measured. The ratio of the absorbent composite exposed on the surface of the absorbent resin is 50% or less, and an absorption amount of blood that sufficiently absorbs 90% of hematocrit can be secured. The ratio of the exposed absorbent composites on the surface of the absorbent resin when observed with an optical microscope can be calculated from the number of exposed absorbent resin surfaces when 100 absorbent composites are observed.

The absorbent composite of the present embodiment preferably does not include a wadding or a clot in the final product from the viewpoint of the texture, because of its absorption performance for a high-viscosity liquid such as blood. The flocculation cake means a cake formed by interlacing and agglomerating the absorbent resin and the hydrophilic fiber. In the case where the absorbent composite is an aggregate, the content of the flocs is preferably 20% by volume or less, more preferably 10% by volume or less, particularly preferably 5% by volume or less, of the total amount of the absorbent composite aggregate, and particularly preferably no flocs are present. The content of flocs can be determined, for example, by analyzing photographs taken by an optical microscope or an electron microscope.

Regarding the content of the flocculated masses in the absorbent composite, the number of masses of the absorbent composite directly counting the minimum Ferris diameter of 1mm or more by placing the specified absorbent composite between two sheets of slidable glass, and the total number of the masses can be defined as the degree of mass and evaluated. The number of blocks of 1mm or more is preferably small.

For example, in 0.25g of the absorbent composite, the total number of the absorbent composite having a particle diameter of 1mm or more and the absorbent resin having a particle diameter of 1mm or more is preferably 100 or less, more preferably 50 or less, particularly preferably 20 or less.

Further, although the absorbent composite having a particle diameter of 1mm or more and the absorbent resin having a particle diameter of 1mm or more are distinguishable from each other as the absorbent composite to which the hydrophilic fibers are attached and the absorbent resin to which the hydrophilic fibers are not attached, since both of them have the same adverse effect on the characteristics, they are not particularly distinguished from each other when the number of flocks is calculated. The number of flocculation lumps having a particle diameter of 1mm or more was counted, and the total number of the number was counted.

In addition, in order to control the total number of the absorbent composites having a particle size of 1mm or more and the absorbent composites having a particle size of 1mm or more to 100 or less in 0.25g of the absorbent composite, it is effective to use an absorbent resin having a predetermined particle size to composite with the hydrophilic fiber in a state in which flocculation is not likely to occur.

The absorbent composite of the present embodiment is preferably capable of substantially retaining a liquid such as an organic solvent that is not absorbed by the absorbent resin. Specifically, in the production of the absorbent composite, it is preferable that the ratio (Wet particle diameter/Dry particle diameter) of the average particle diameter of the absorbent composite in the drying process (drying time) (hereinafter, also simply referred to as "Dry particle diameter") is greater than 1, and the ratio of the peak particle diameter of the absorbent composite (hereinafter, also simply referred to as "Wet particle diameter") in ethanol (wetting time) is measured at 25 ℃ based on the average particle diameter of the absorbent composite in the drying process (drying time) at 80 ℃ for 3 hours. The ratio of Dry particle diameter to Wet particle diameter (Wet particle diameter/Dry particle diameter) of the absorbent composite is preferably more than 1, more preferably more than 1.1, particularly preferably more than 1.2. The Dry particle size and the Wet particle size can be measured using a laser diffraction/scattering particle size analyzer.

In the Wet particle size measurement, the absorbent composite does not absorb ethanol, but merely retains ethanol between fibers due to the expansion of the hydrophilic fibers, and releases ethanol if administered. The fact that the Wet particle diameter is larger than the Dry particle diameter means that there is a space around the absorbent resin, and the hydrophilic fiber is bonded to the absorbent resin in a freely movable state.

With this configuration, the capillary force becomes strong, and even in a high viscosity liquid such as blood, the liquid can be rapidly transported to the surface of the absorbent resin, and therefore, a desired absorption rate and absorption amount are exhibited. Further, since the interaction between cellulose and blood cell components in blood is weak adsorption, and the hydrophilic fiber made of cellulose freely moves around the absorbent resin, the absorbent resin can effectively absorb blood cell components that inhibit absorption, and therefore, it is considered that the absorption amount of the entire absorbent composite is increased. Further, the Wet particle size of the absorbent composite is preferably 100-800. mu.m, more preferably 170-600. mu.m, particularly preferably 250-500. mu.m. The Wet particle diameter/Dry particle diameter can be measured by the method described in the examples described below.

The absorbent composite of the present embodiment has a tap density of preferably 0.50g/mL or less, more preferably 0.42g/mL or less, particularly preferably 0.35g/mL or less, particularly preferably 0.30g/mL or less, particularly preferably 0.25g/mL or less, and most preferably 0.20g/mL or less. Since the absorbent composite has a tap density of 0.5g/mL or less, the hydrophilicity of the liquid can be improved. The tap density of the absorbent composite can be measured using a graduated cylinder. The tap density of the absorbent composite can be measured by the method described in the examples described later.

In the absorbent composite of the present embodiment, the apparent bulk density and the compressed bulk density of the absorbent composite are preferably 1:2 to 1:10, more preferably 4:9 to 1:7, particularly preferably 2:5 to 1:5, and particularly preferably 4:11 to 1: 4.

The ratio of apparent bulk density to compressed bulk density is an index of how much space is secured around the absorbent resin. In the ratio of apparent bulk density to compressed bulk density, if the ratio of apparent bulk density to apparent bulk density is 1 and the compressed bulk density is 2 or more, a sufficient space can be secured around the absorbent resin to prevent gel blocking. On the other hand, in the ratio of apparent bulk density to compressed bulk density, if the ratio of apparent bulk density to compressed bulk density is 1 and the compressed bulk density is 10 or less, the workability in the production process may not be affected.

Apparent bulk density is the weight per unit volume of the particles of the absorbent resin and the voids between the particles in a state where no gravity is applied.

Specifically, an appropriate amount of the absorbent composite was placed in a measuring cylinder, and a cap was placed thereonSwing up and down about 10 times, and stand for about 10 minutes. Then, the apparent bulk density can be calculated by reading the volume, measuring the mass, and dividing the mass by the volume. On the other hand, the bulk density after compression is the weight per unit volume obtained by adding the particles of the absorbent resin and the voids between the particles in a weighted state. The compressed bulk density was measured by placing an appropriate amount of the absorbent composite in a measuring cylinder, covering the cylinder with a lid, swinging the cylinder up and down 10 times or so, standing the cylinder for about 10 minutes, and then setting the volume at 5kg/cm²The weight is increased for 10 minutes and the mass is measured and divided by the corresponding mass can be calculated. These measurements were carried out at 23 ℃ and 30% relative humidity.

In the absorbent composite, the zeta potential obtained by the streaming potential method is an index of the stability of the particles composed of the absorbent composite. The larger the absolute value of the zeta potential is, the more difficult it tends to agglomerate the particles of the absorbent composite.

In the absorbent composite of the present embodiment, the absolute value of the zeta potential is preferably 14.8mV or more, more preferably 15.2mV or more, and particularly preferably 15.5mV or more. The zeta potential of the absorbent composite can be measured by dispersing the absorbent composite in isopropanol. Further, when the cellulose and the absorbent composite are processed into a sheet, the sheet is soaked in isopropyl alcohol to release the cellulose constituting the sheet, the cellulose and the absorbent composite constituting the sheet are separated, the separated floating cellulose is removed to obtain an absorbent composite, and the zeta potential of the obtained absorbent composite can be measured. The zeta potential of the absorbent composite can be measured by the method described in the examples below. The absolute value of the zeta potential of the absorbent resin is small and is in a state of being easily aggregated. The hydrophilic fiber covering the absorbent composite with a zeta potential having a large absolute value can increase the absolute value of the zeta potential of the absorbent composite. The difference between the zeta potential of the absorbent composite and the zeta potential of the covered hydrophilic fiber is preferably 1.5mV or less, more preferably 1.2mV or less, particularly preferably 0.9mV or less, and particularly preferably 0.6mV or less. In the absorbent composite, the less the exposure of the surface of the absorbent resin, the smaller the difference between the zeta potential of the absorbent composite and the zeta potential of the coated hydrophilic fibers. Therefore, when considering the absorption of a liquid such as blood which acts on the surface of the absorbent resin and inhibits the absorption of the substance, it is preferable that the surface of the absorbent resin is not exposed. In the case where the absorbent composite is in a form in which the periphery of the absorbent resin is covered with the hydrophilic fibers, the zeta potential of the absorbent composite is within a range of ± (20% of the absolute value of the difference between the zeta potential of the absorbent resin and the zeta potential of the hydrophilic fibers). That is, the zeta potential of the absorbent composite is ═ zeta potential of the hydrophilic fiber ± | zeta potential of the hydrophilic fiber | × 0.2 zeta potential of the absorbent resin. The zeta potential of the absorbent composite can be measured by the method described in the examples below.

The shape of the absorbent composite is an important factor that affects the absorption performance of the absorbent composite. The circularity, unevenness, elongation, straightness, aspect ratio, and the like, which are indicators of the shape of the absorbent composite, can be measured by image analysis. The shape of the absorbent composite can be measured by the method described in the examples below.

The circularity is a value obtained by dividing the circumferential length of a circle having an area equal to the projected area by the actual circumferential length, and the closer the particle is to a sphere, the closer the value is to 1. The circularity of the absorbent composite of the present embodiment is preferably 0.7 or less, more preferably 0.6 or less, and particularly preferably 0.5 or less. When the circularity is 0.7 or less, it means that the hydrophilic fibers are independently present around the nearly spherical absorbent resin, and the surface of the absorbent resin is covered with the hydrophilic fibers in a state having a unique shape, and good absorbency is exhibited. Further, the difference between the circularity measured with the hydrophilic fiber alone and the circularity of the absorbent composite when compared with the same particle diameter is preferably within 0.3, more preferably within 0.2. The smaller the difference between the circularity of the hydrophilic fiber alone and the circularity of the absorbent composite, the more the shape of the hydrophilic fiber on the surface of the absorbent composite is reflected, and the better the absorbency is exhibited by the coverage with the shape of the hydrophilic fiber itself.

The degree of irregularity of the absorbent composite of the present embodiment is preferably 0.85 or less, more preferably 0.8 or less, particularly preferably 0.75 or less, and particularly preferably 0.7 or less. The roughness is a value obtained by dividing a particle projection region by a convex hull region (ConvexHullArea, i.e., a filling area of a concave portion of a projection image), and the smaller the roughness, the closer the value is to 1. The smaller the degree of unevenness of the absorbent composite, the unique shape of the hydrophilic fiber showing the surface coverage of the absorbent resin was shown, and good absorbency was shown. Further, the difference between the concavity and convexity of the hydrophilic fiber measured alone and the concavity and convexity of the absorbent composite, respectively, compared with the same particle diameter is preferably within 0.4, more preferably within 0.3, particularly preferably within 0.2. The smaller the difference between the concavity and convexity of the hydrophilic fiber alone and the concavity and convexity of the absorbent composite, the shape of the hydrophilic fiber on the surface of the absorbent composite is reflected, and good absorbency is exhibited by the coverage with the shape of the hydrophilic fiber itself.

The elongation of the absorbent composite of the present embodiment is preferably 0.25 or less, more preferably 0.2 or less, and particularly preferably 0.15 or less. The elongation is a value obtained by dividing the fiber diameter by the fiber length when the fiber is approximately fibrous, and the elongation is smaller. When the elongation is 0.25 or less, the hydrophilic fiber itself is covered on the surface of the absorbent resin, and good absorbency is exhibited. In addition, the difference between the elongation measured with the hydrophilic fiber alone and the elongation of the absorbent composite at the same particle diameter is preferably within 0.2, more preferably within 0.15, particularly preferably within 0.1. The smaller the difference between the elongation percentage of the hydrophilic fiber and the elongation percentage of the absorbent composite measured separately, the more the shape of the hydrophilic fiber on the surface of the absorbent composite is reflected, and the better absorbency is exhibited by the shape covering the hydrophilic fiber itself.

In the absorbent composite of the present embodiment, the linearity is preferably 0.9 or less, more preferably 0.87 or less, and particularly preferably 0.85 or less. The straightness is an index of curvature obtained by dividing the length of the hydrophilic fiber by the maximum fisher diameter (maximum value of the constant direction connecting line diameter). When the straightness is small, the surface of the absorbent resin is covered with the hydrophilic fiber alone, and good absorbency is exhibited. In addition, the difference between the linearity of the hydrophilic fiber and the linearity of the absorbent composite, which are measured separately, is preferably within 0.15, more preferably within 0.1, particularly preferably within 0.05, at the same particle diameter. The smaller the difference between the linearity of the hydrophilic fiber measured alone and the linearity of the absorbent composite, the more the shape of the hydrophilic fiber itself is reflected on the surface of the absorbent composite, and the better the absorbency is exhibited by the shape of the hydrophilic fiber itself covered.

The aspect ratio of the absorbent composite of the present embodiment is preferably 0.5 or more, more preferably 0.6 or more. The aspect ratio is the result of dividing the minimum fisher path by the maximum fisher path. Since the aspect ratio is 0.5 or more, the workability tends to be good.

The b value of the absorbent composite is preferably 15 or less, more preferably 13 or less, particularly preferably 10 or less, and particularly preferably 7 or less. The b value of the absorbent composite is preferably 1 or more, more preferably 2 or more, particularly preferably 3 or more. Since the value of b is within the above range, the liquid after absorption hardly shows reverse osmosis even after long-term storage, no blocking, and a high absorption rate is maintained, showing good performance. The b value can be measured by placing 3g of the absorbent composite in a test cell for powder using a spectrophotometer, lightly filling the cell to fill the gap.

In the absorbent composite of the present embodiment, a component having a relaxation time of about ten and several microseconds, a component having a relaxation time of about several tens to one hundred microseconds, and a component having a relaxation time exceeding about several hundred microseconds are observed in a pulse NMR measurement at 25 ℃. In the absorbent composite of the present embodiment, a component having a relaxation time of 100 μ s or more is defined as a high motility component. In the absorbent composite of the present embodiment, the ratio of the high motility component in the pulse NMR measurement in which the water content is adjusted to 5 to 5.2% is preferably 10 to 21%, more preferably 11 to 20%, particularly preferably 12 to 19%, particularly preferably 14 to 18%. Since the ratio of the high motion component is within the specified range, better characteristics are exhibited in both the absorption amount and the absorption speed, and the capturing ability for liquid is higher. The reason for this can be assumed to be described by the following principle but is not limited to the following principle. That is, the high ratio of the high motion component with low water content means that the liquid diffuses fast and the liquid is absorbed faster than the solid in the blood is adsorbed.

In the absorbent composite of the present embodiment, it is effective to control the adhesion state of the interface between the hydrophilic fiber and the absorbent resin so that the ratio of the high-speed motion component is 10 to 21% in the pulse NMR measurement in the state where the water content is 5 to 5.2%. For example, a method of mixing the absorbent resin and the hydrophilic fiber in advance, adding water, controlling the diameter of water droplets of the added water, controlling the rate of water addition, or the like can be employed.

Specific examples of the measurement conditions for pulse NMR in the present embodiment are as follows.

For example, the absorbent composite of the present embodiment is dried in a hot air dryer at 90 ℃ for 3 hours, and then left to stand in an environment of D20 humidity 20% for 3 days. The mass was measured at this time, and the water content was defined as 0%. Then, mass measurement was performed at regular intervals in an environment of 100% humidity of D20, and pulse NMR measurement was performed when the water content reached a predetermined value. The measurement was carried out using a MinispecMQ20 apparatus manufactured by BRUKER corporation, the nuclide was 1H, the measurement was T2, the measurement method was a solid echo method, the number of integrations was 256, the repetition time was 1.0 second, and the temperature was 25 ℃. The method determines the relaxation time T2 of the highly mobile component by combining gaussian-like Sinc functions, lorentz-like functions, lorentz functions.

The absorbent composite of the present embodiment preferably has an impact resistance index of 0.1g/g to 12g/g, more preferably 0.3g/g to 10g/g, particularly preferably 0.5g/g to 8g/g, particularly preferably 0.7g/g to 7g/g, most preferably 1g/g to 6 g/g. The lower the impact resistance index, the higher the retention after blood absorption, and the better the repeated absorbability, so the better. The reason why the blood retention ability and the repeated absorbability are excellent as the impact resistance index is lower is presumed to be that the impact resistance index is a value related to the bonding form, interface, and the like of the hydrophilic fiber and the absorbent resin, and the liquid retention ability in the absorbent resin is improved by the bonding of both in a specific form. In addition, the low impact resistance index means that the absorbent composite is stable in shape even when subjected to an impact in a film or a product during transportation, feeding, distribution, etc., and can exhibit a desired stable absorption performance in any use method. Meanwhile, since fine powder is generated when the sheet is broken by impact, measures such as avoiding breakage by reducing the operating speed and sucking fine powder are required, it is also advantageous to have a low impact resistance index from the viewpoint of production efficiency. The impact resistance index of the absorbent composite can be calculated as follows.

Stainless steel sieves (75X 20. ang. stainless steel, available from ASONE) were sequentially provided with a cover, a 710 μm mesh sieve, a 500 μm mesh sieve, a 300 μm mesh sieve, a 100 μm mesh sieve, and a receiver from the top, and 3 stainless steel balls (SUS 3043/8 inch, available from ASONE) were placed in each section of the sieve outside the receiver. A sample of the absorbent composite (1.5 g) was put on a sieve having a mesh size of 710 μm, and the resultant was put on a vibrating screen (Mini-Screen shaker MVS-1 manufactured by ASONE corporation) and processed for 20 minutes using a storage 9. Samples of the absorbent composite remaining on the 500 μm mesh screen, the 300 μm mesh screen, and the 100 μm mesh screen were recovered. That is, from the initial large particles of 710 μm or more of the sample absorbent composite, small particles of 100 μm or less are excluded. The collected sample of the absorbent composite was placed in a polyethylene bag with a seal (manufactured by Nippon corporation, UnipackC-8), sealed in an air-containing state, and uniformly mixed by hand. In a container (manufactured by SANGDAIYA, Total Aperture screw storage Container, shallow and medium 80cc 55. phi. times.55 h), 1.0g of the above sample and 5 stainless steel balls (SUS 3043/8 inch manufactured by ASONE) were placed, and a lid was screwed. The plate was mounted on a pin-wheel shaving machine R20mini manufactured by ocean chemical industries, and the treatment was carried out at 160rpm for 30 minutes. A sample of the absorbent composite was removed and similarly sieved on a stainless steel screen. The absorbent composite sample remaining in the receiver was collected, the mass was measured, and the amount of absorption of physiological saline was measured. This value represents the resistance to impact of the stainless steel balls on the screen, and is defined as the impact resistance index. The impact resistance index of the absorbent composite can be measured by the method described in examples described later. In order to control the impact resistance index of the absorbent composite to 0.1 to 12g/g, it is effective to completely cover the periphery of the absorbent resin with the hydrophilic fiber and to form a space.

Other components of the absorbent composite

The absorbent composite of the present embodiment may contain other components as the above-mentioned absorbent resin and hydrophilic fiber, depending on the required characteristics.

The other components are not limited to the following, and examples thereof include a crosslinking agent, inorganic particles, a surfactant, a lubricant, and organic fine particles.

The crosslinking agent is not particularly limited, and any known crosslinking agent may be used. In the present embodiment, when the crosslinking agent is reacted with an acid group of the absorbent resin, it is preferable to use a compound having a plurality of functional groups. When the absorbent resin is a resin having a functional group which reacts with an acid group, it is preferable to use a compound having a plurality of acid groups.

The compound having a plurality of functional groups which react with the acid groups of the absorbent resin is not limited to glycidyl ether compounds such as ethylene glycol diglycidyl ether, trimethylolpropane triglycidyl ether, (poly) glycerol diglycidyl ether, diglycerol diglycidyl ether, and propylene glycol diglycidyl ether; polyols such as (poly) glycerol, (poly) ethylene glycol, propanol, 1, 3-propanediol, polyethylene glycol, triethylene glycol, tetraethylene glycol, diethanolamine, and triethanolamine, and polyamines such as ethylenediamine, diethylenediamine, polyethyleneimine, and 1, 6-hexanediamine. From the viewpoint of easiness of reaction rate control, polyhydric alcohols are preferable. Further, polyvalent ions of zinc, calcium, magnesium, aluminum, and the like are also preferably used because they react with acid groups of the absorbent resin and function as a bridging agent.

The amount of the compound having a plurality of functional groups and the polyvalent ion to be reacted with the acid group of the absorbent resin is preferably 0.5 to 10% by mass, more preferably 0.7 to 5% by mass, particularly preferably 1 to 3% by mass, based on the total mass of the absorbent resin. When the acid group of the absorbent resin is neutralized with a sodium salt, an ammonium salt or the like, it is preferable that the acid group other than the neutralized acid group reacts with the compound having a plurality of functional groups which reacts with the acid group of the absorbent resin.

Method for producing absorbent composite

The absorbent composite of the present embodiment can be produced by mixing an absorbent resin and hydrophilic fibers.

The absorbent composite of the present embodiment is preferably in a state in which the hydrophilic fibers are attached to and covered with the absorbent resin, and in order to achieve this state, the hydrophilic fibers can be made to contain water. For example, the hydrophilic fibers can be produced by mixing hydrophilic fibers with water, bringing the hydrophilic fibers containing water into contact with the absorbent resin, transferring water to the absorbent resin (water-containing mixing step), and then drying (drying step). Further, a step including a surface bridging step and a step of classification are preferable.

Hereinafter, a method for producing the absorbent composite will be described.

First, an absorbent resin, hydrophilic fibers and water are mixed. When the hydrophilic fiber is coated on the surface of the absorbent resin, it is preferable to mix the hydrophilic fiber with water to form a hydrous fiber, and then to mix the hydrous fiber with the absorbent resin having surface plasticity quickly. The order of addition is not limited as long as the hydrophilic fiber containing water can be formed.

The specific method for forming the hydrophilic fiber coating on the surface of the absorbent resin is described in the following, in which the surface of the absorbent resin is plasticized with water, and the coating agent comprising solid hydrophilic fibers is brought into contact with the surface of the absorbent resin and then dried.

The method further comprises a water-containing step and a drying step.

Water-containing step

Examples of the water-containing step include: (1) a method of mixing hydrophilic fibers and water with an absorbent resin; (2) a form in which water is preferentially absorbed by the hydrophilic fibers after the absorbent resin and the hydrophilic fibers are mixed.

From the time when the surface of the absorbent resin comes into contact with water (specifically, several seconds after the contact), water is absorbed by the absorbent resin, and the surface thereof starts to be plasticized. In the above method (1), when the hydrophilic fiber in a water-containing state formed by mixing the hydrophilic fiber and water is mixed with the absorbent resin, the surface of the absorbent resin starts to be plasticized.

The method (2) is also substantially the same. When the hydrophilic fiber in a water-containing state comes into contact with the absorbent resin, the surface of the absorbent resin is plasticized while the water in the hydrophilic fiber moves to the absorbent resin.

In the above method (1), water is added to the hydrophilic fiber as a hydrophilic fiber in a hydrous state, and then the hydrophilic fiber in a hydrous state (hereinafter referred to as hydrous fiber) and the absorbent resin are mixed. The hydrophilic fibers in a water-containing state allow water to migrate into the absorbent resin, thereby bonding the absorbent resin and the hydrophilic fibers together in a desired bonding pattern.

When the hydrophilic fiber containing water and the absorbent resin are mixed, it is preferable to mix them by using a mixer which uniformly mixes the absorbent resin in the system faster than the water absorption time of the absorbent resin. This can provide an effect of suppressing aggregation between the absorbent resins. Here, the water absorption time of the absorbent resin means a time 2 times as long as the time measured by the eddy current method. The vortex method is a measurement method in which an absorbent resin is put into physiological saline in a stirred state, and the time when the liquid level becomes horizontal is measured. The measurement time in the vortex method is considered to be a value having a correlation with the absorption time of the liquid from the hydrophilic fiber to the absorbent resin, such as the time taken for the liquid to be absorbed, not the time taken for the liquid to be absorbed, but the time taken for the fluidity to start to decrease, using the physiological saline solution. In the step of mixing the hydrophilic fiber containing water and the absorbent resin, the mixing time is preferably 2 times or less the time measured by the vortex method, more preferably 1.5 times or less the time measured by the vortex method, the mixing time is particularly preferably shorter than the time measured by the vortex method, particularly preferably the mixing time is within 1/2 of the time measured by the vortex method, and most preferably the mixing time is within 1/3 of the time measured by the vortex method. This mixing time is correlated with the time at which water is absorbed by the absorbent resin, and therefore is not limited to the case where a method of suppressing the absorption rate of the absorbent resin is adopted, as long as the mixing is finished before water is absorbed by the absorbent resin. A specific method of the eddy current method will be described in embodiments described later. In view of suppressing the change in the shape, structure and absorption properties of the absorbent composite after mixing, it is preferable to mix rapidly within 30 seconds, more preferably within 20 seconds, particularly preferably within 10 seconds, regardless of the measurement time of the eddy current method.

In the above mixing method, any of a continuous mixer, a batch mixer, and the like can be used. In the case of a continuous mixer, the hydrophilic fiber containing water and the resin absorbent may be supplied in portions in the mixer under stirring. In the case of a batch mixer having a capability of sufficiently mixing a small amount of articles, the hydrophilic fiber and the absorbent resin containing water may be placed at separate positions and may be instantaneously stirred. It is also possible to supply the hydrophilic fiber containing water to the absorbent resin in a stirred state little by little. The batch mixer is a mixer capable of uniformly mixing the powder in the system within the water absorption time of the absorbent resin. Specifically, a laboratory-grade mill (laboratory-grade high-speed rotary mixer), a high-speed rotary mixer of 10L or less (Henschel mixer, etc.), and the like can be exemplified. In the above mixing method, whether or not the powder in the system is uniformly mixed can be checked and judged by the state of the absorbent composite by stopping the stirring. Specifically, the state of the absorbent composite can be confirmed by visual observation and the ratio of the analytical components after drying. When the continuous mixer is used for mixing, the average residence time in the vessel is preferably shorter than the absorption time of the absorbent resin.

In the above method (2), when the absorbent resin and the hydrophilic fiber are mixed and brought into contact with each other, water is added to the mixture if the hydrophilic fiber can preferentially absorb water. In this method, in order to slow the absorption rate of the water by the absorbent resin, it is effective to reduce the particle size of the water droplets, increase the viscosity by adding an additive to the water, and previously add an organic solvent which inhibits the absorption of water to the water. When the method of (2) is used, it is preferable to sufficiently mix the absorbent resin and the hydrophilic fiber in advance. Examples of the mixing device include a vertical floating mixer. The mixed state can be confirmed through a preset sight window of the mixing device. In order to sufficiently improve the mixing property, the mixing of the two is preferably performed when the relative humidity in the vertical type floating mixer is adjusted to 55% or less, more preferably 50% or less, particularly preferably 45% or less. The humidity can be adjusted at any time, but it is preferable to adjust the humidity before the feeding. Any method may be used for adjusting the humidity, but dry air, inert gas such as nitrogen and argon, and the like are preferably introduced into the mixer. From the viewpoint of obtaining a good mixed state, it is preferable that the dry air and the inert gas are continuously supplied during the period after the water is added. It is preferable to add water simultaneously with the mixing of the absorbent resin and the hydrophilic fiber. The rate of addition of water is preferably changed by the mixing method. From the viewpoint of uniformly adding water as a whole, it is preferable that the water is added in a macroscopically longer time than the time for updating the system in the mixing in a dry state. The macro intra-updated time: the coloring material is disposed at one end of the whole material (the whole material including the absorbent resin and the hydrophilic fiber) in an amount of about 10% by mass of the total mass of the whole material including the absorbent resin and the hydrophilic fiber, and the coloring material is disposed at the opposite end in a volume of 10% or less. Microscopically, it is not necessary to mix them uniformly, and the spot shape may be possible. The time of the raw material movement is important on a macroscopic scale. On the other hand, the state in the system changes with the formation of the absorbent composite in a state of containing water, and it becomes difficult to mix them. In the case of mixing in a mixer capable of sufficiently mixing in a hydrous state, water may be slowly added, but when the mixing property of the mixer in a hydrous state is poor, it takes a longer time than the time for which the system is macroscopically updated, and it is preferable that the addition of water is completed within 5 minutes after the start of the change in the state in the system, more preferably within 3 minutes, particularly preferably within 1 minute, and it is particularly preferable that the addition of water is completed before the change in the state in the system. The state of the system can be empirically determined by visual observation.

In the method (2), it is preferable to use a mixer for thoroughly mixing the hydrophilic fiber and the absorbent resin. The batch Mixer is preferably a floating mixing type in which the contents are stirred while being held up, and examples of the high-shear device include henschel mixers and the like, and examples of the low-shear device include proshareMixer, and LODIGE Mixer, Germany. In a continuous apparatus, it is also possible to add hydrophilic fibers, absorbent resin, and water in a manner that makes the hydrophilic fibers contain water and then mix them with the absorbent resin.

In the case of using a continuous mixer or a batch mixer having sufficient mixing ability in the case of small-amount mixing as the water-containing step, the production method of the above (1) is suitable for use, and in the case of using a large-capacity batch mixer or continuous mixer or the like, the production method of the above (2) is suitable for use. When a continuous mixer is used, the method (1) or (2) can be applied depending on its mixing ability.

In the former stage of the drying step described later, the hydrophilic fiber and/or the absorbent resin may contain water, but it is preferable that the absorbent resin contains more water. In the water-containing state before drying, the tap density is preferably smaller than that in a simple blended state of the absorbent resin and the hydrophilic fiber in the dry state. In general, when the tap density of the hydrophilic fiber and the absorbent resin is less than 1g/mL and water having a density of 1g/mL is mixed, the tap density is considered to be increased. However, by the excellent mixing, the absorbent resin and the hydrophilic fiber can be well combined, and the tap density can be reduced. Drying in this state can provide an absorbent composite having a low tap density and a good shape.

In the above methods (1) and (2), since there is a possibility that the absorption performance of the absorbent resin may be deteriorated when the absorbent resin is stored in a state of containing water, it is preferable that the water content of the absorbent resin is controlled to 10% or less when the absorbent resin is stored as a raw material. Since the hydrophilic fiber does not change in absorption performance even when it contains water, the hydrophilic fiber can be stored in a hydrated state. In this case, if the hydrophilic fiber is stored in air with high humidity, water is naturally absorbed. In the case where the absorbent resin is used immediately without storage, the absorbent resin may contain moisture, or the moisture content may be adjusted to an appropriate moisture content range by using an absorbent resin in a state in which the absorbent resin is not completely dried after polymerization. In this case, the shape is preferably controlled in advance so as to achieve an optimum particle diameter range after the drying step described later.

In the above method (2), the droplet size of the water to be added is preferably 300 μm or less, more preferably 200 μm or less, particularly preferably 150 μm or less, particularly preferably 100 μm or less, most preferably 50 μm or less. By reducing the droplet diameter of water, the aggregation between the absorbent resins is easily suppressed. Further, if the droplet diameter of water is small, the absorption rate of the absorbent resin decreases, and therefore the hydrophilic fiber absorbs water before the absorbent resin absorbs water, and liquid is transported from the hydrophilic fiber to the absorbent resin, and therefore a good adhesive surface can be formed. The spray may be appropriately selected so as to reduce the size of the water droplets. It may also be carried out with steam, water vapor or the like. By means of suppressing the absorption rate, the droplet diameter is not particularly problematic when the liquid is added while stirring. Examples of the method for suppressing the absorption rate include adding an additive such as an organic solvent, a thickener, and a pH adjuster to water.

In the above methods (1) and (2), the optimum value of the amount of water differs depending on the amount of the absorbent resin, the surface area of the absorbent resin, the amount of the hydrophilic fiber, and the like, and therefore the amount of water may be appropriately set. For example, when the amount of the absorbent resin is large, a large amount of water is required. In the case where the surface area of the absorbent resin is small, the hydrophilic fiber and the absorbent resin stick together even if the amount of water is small. The amount of water added is preferably such that the tap density in the state of adding water is reduced as compared with the tap density when the absorbent resin and the hydrophilic fiber are simply mixed. When the amount of water is too small, the tackiness may be reduced, and when the amount of water is too large, the absorption performance tends to be reduced. To set the optimum amount of water, the absorbent composite was produced by varying the amount of water and measuring the tap density after drying. If the amount of water added is increased, the tap density initially decreases, but if it exceeds a certain amount, the tap density becomes constant. If the amount of water is further increased, the tap density becomes large. The amount of water to be added is preferably an amount of water in the vicinity of the minimum tap density. The amount of the added water varies depending on the particle diameters of the absorbent resin and the hydrophilic fiber and the ratio of the absorbent resin to the hydrophilic fiber.

When the absorbent resin and the hydrophilic fiber are mixed, the mass ratio of the absorbent resin to the hydrophilic fiber is preferably 20:1 to 1:5, more preferably 15:1 to 1:2, particularly preferably 10:1 to 1:1, and particularly preferably 10:3 to 10:7, compared with the mass ratio of the absorbent resin to the hydrophilic fiber being 2: 1. The water content in this case represents the total water content of the absorbent resin in a hydrated state and the hydrophilic fibers in a hydrated state. When the water content before the drying step described later is low, the portion where the absorbent resin and the hydrophilic fiber are directly bonded tends to be small, and when the water content is too high, the drying time in the subsequent drying step tends to be long. When the mass ratio of the absorbent resin to the hydrophilic fiber is 1:1, the mass ratio of the absorbent resin to water is preferably 1:0.5 to 1:5, more preferably 1:0.6 to 1:3, particularly preferably 1:0.7 to 1:2, particularly preferably 1:0.8 to 1: 1.6.

The water provided may contain impurities. Examples of the impurities include cations such as sodium ion, ammonium ion, and iron ion, anions such as chloride ion, and water-soluble organic compounds such as acetone, alcohols, ethers, and amines.

In order to adjust the pH of the absorbent resin and/or absorbent composite, acidic or basic water may be used.

From the viewpoint of the contact property and absorption capacity of the absorbent resin, the amount of impurities is preferably at the level of tap water, and it is more preferable to use distilled water or ion-exchanged water alone without impurities.

Hereinafter, a method of mixing the absorbent resin and the hydrophilic fiber using a henschel mixer will be described as a preferred mixing step. As the blade of the Henschel mixer, a blade capable of strongly picking up the content is preferably used. The lower blade is preferably a linear curve, and the end of the blade is preferably angled. For example, S0 blade from Nippon coke corporation is preferable. As the upper blade, a blade suitable for high cycle and large-scale treatment is preferably selected. In order to efficiently mix the absorbent resin in a water-containing state and the hydrophilic fiber, it is preferable to use a blade having a portion perpendicular to the horizontal plane, and particularly, a blade having a plate perpendicular to the outer peripheral portion. For example, a CK blade and a Y1 blade from Japan Coke are preferable, and depending on the state of mixing, it is preferable to add a flexible plate in a direction perpendicular to the horizontal plane. Before the raw materials are charged, the humidity inside the mixer is preferably adjusted in advance. The lower shaft seal is preferably used with dry air or an inert gas such as nitrogen, and is more efficient in use.

In the mixing step, a predetermined amount of the absorbent resin and the hydrophilic fibers are put into a predetermined mixing vessel in an arbitrary order. First, fibers having a low density are put in, and a good mixed state can be obtained in a short mixing time. The water content of the absorbent resin as a raw material is preferably 20% or less, more preferably 15% or less, particularly preferably 10% or less, and particularly preferably 5% or less. The water content of the absorbent resin is too high, and the properties thereof change, and the mixing efficiency may decrease. Preferably, the mixer is closed, and the absorbent resin and the hydrophilic fibers are first mixed in a dry state. The number of rotations is optional, but if the rotation is too fast, the absorbent resin may be crushed, and if the rotation is too slow, mixing may not be performed. If a peep window is provided, the number of rotations is preferably set so that the entire interior appears to be substantially white. In general, if the stirring is carried out for about 30 seconds, a sufficiently mixed state can be obtained. Before the addition of water, the number of rotations is preferably adjusted within a predetermined range. The mixing in the dry state may be adjusted to a predetermined rotation number, or the rotation number may be adjusted before adding water after the mixing in the dry state. When mixing is performed in a dry state, the absorbent resin, the fibers, and the like may adhere to the wall surface, and it is preferable that the stirring be once stopped, and the process be switched to the next water addition step after scraping. After the addition of water, the number of revolutions of the blade of the Henschel mixer, which is a mixer used in the step of mixing the absorbent resin and the hydrophilic resin in order to obtain a good mixing state, is preferably in the range of 0.3 to 5.0, more preferably 0.35 to 2.0, particularly preferably 0.4 to 1.6, particularly preferably 0.45 to 1.4, and most preferably 0.5 to 1.25.

Froude number n²× d/9.8 (n: number of rotations of blade(s)^-1) D: diameter (m)) of the blade.

In order to achieve a preferable form, the power requirement of the stirring and mixing device is preferably within a range of a Pv value of 200 or less, more preferably 150 or less, particularly preferably 50 or less, and particularly preferably 35 or less.

Pv value n³×d⁵V,/v; (n: number of rotations of blade(s)^-1) D: diameter (m) of blade, V: effective volume of stirrer (m)³))。

The mixing step, the addition of water, and the liquid particle diameter of the water droplets were controlled within the above-mentioned reasonable range, and the mixing was carried out above the mixing vessel. If water droplets adhere to the wall surface, the blades, and the deflector, large water droplets are formed to cause flocs to be formed, and thus the spray angle needs to be adjusted. Water is preferably added to the spray nozzle of Spraying company, IKEUSHI corporation, for example. In order to prevent the adhesion of the wall surface, the vane, and the deflector, a circular nozzle is preferably used. The water may be sprayed from one site or from a plurality of sites. In a Henschel mixer, macroscopically the whole can be mixed by setting to within a few second units of a predetermined Froude number range. Therefore, the time for adding water may be set arbitrarily. When the aforementioned Pv value is large, the good shape may be broken down if the operation is performed for a long time, and therefore, the value is preferably added quickly.

In order to balance the absorption rate and the mixing time, the mixer temperature is preferably adjusted by the interlayer. When the mixer is controlled to room temperature or lower by a jacket, the absorption rate of the absorbent resin is lowered, and the mixing state is easily controlled. However, if cooled, internal humidity control is necessary to prevent condensation. When mixing, the temperature of the powder is suitably observed, and the interlayer, mixing conditions and the water addition rate are preferably adjusted.

After the addition of water is completed, the mixture is preferably stirred continuously when the mixture is homogeneous. However, the effect of continuing the stirring for a long time is not so great, and usually within 1 minute is sufficient. After the mixing is finished, when the materials are dried in a dryer different from the mixer, the materials need to be taken out. Preferably, the lower discharge port is opened and the rotating vanes remove the material. After the mixing, if drying is carried out in a Henschel mixer, the temperature of the sandwich is preferably increased and the resulting mixture is heated. In this case, it is preferable to reduce the number of henschel blade revolutions in advance until the powder can move to the minimum. The interlayer temperature is preferably 100-200 ℃, more preferably 110-180 ℃, particularly preferably 120-160 ℃. The temperature of the powder, i.e., the mixture of the absorbent resin and the hydrophilic resin, is preferably controlled appropriately while observing it. In order to control the drying rate, it is preferable to perform pressure reduction and blow hot air. After the mixing step, if the crosslinking is carried out in a Henschel mixer, the crosslinking agent dissolved in the solvent may be added after the mixing step.

When the amount of the solvent is sufficiently large, the solvent may be added in a state where stirring is stopped, and when the amount of the solvent is small, the solvent may be slowly added by spraying or the like while stirring, so that the bridging agent is uniformly distributed over the entire surface. Thereafter, the resin composition is heated in the same manner as in the above-mentioned drying step, and the crosslinking reaction can be carried out while drying the resin composition.

Adding a bridging agent

After the water-containing step, a crosslinking agent is added to the mixture of the water-absorbent resin and the hydrophilic fiber in a water-containing state, and the adhesion between the absorbent resin and the hydrophilic fiber can be reinforced by the crosslinking reaction. When the absorbent resin and the hydrophilic fiber are bonded in an ideal form, a strong bonding force can be obtained even without performing a crosslinking reaction. Preferably, the step of adding a bridging agent and bridging is performed before the drying step described later. This can suppress the separation of the hydrophilic fiber from the absorbent resin due to tension during drying, and can make the hydrophilic fiber adhere tightly to the periphery of the absorbent resin.

As the crosslinking agent, a compound having a plurality of functional groups capable of reacting with the functional groups in the absorbent resin and/or the functional groups in the hydrophilic fibers is used. The crosslinking agent is not limited to, for example, a polyepoxy compound such as ethylene glycol diglycidyl ether, trimethylolpropane triglycidyl ether, (poly) glycerol diglycidyl ether, diglycerol diglycidyl ether, and propylene glycol diglycidyl ether; polyhydric alcohols such as (poly) glycerol, (poly) ethylene glycol, propylene glycol, 1, 3-propylene glycol, polyethylene glycol, triethylene glycol, tetraethylene glycol, diethanolamine, triethanolamine and the like; such as polyamines like ethylenediamine, diethylamine, polyethylamine, ethylethylamine, etc. As the bridging agent, a polyvalent epoxy compound is selected for easy control of the reaction rate, and polyvalent alcohols are preferred. Further, polyvalent ions such as zinc, calcium, magnesium, and aluminum are preferably used.

The method of adding the crosslinking agent is not particularly limited, and the crosslinking agent may be added directly or in a solvent. In order to control the permeation rate into the absorbent resin, water is preferably added. It is important to uniformly diffuse the entire composition, and for example, a method of spraying the bridging agent while mixing the absorbent composite is preferable.

By adding the bridging agent after the water-containing step, the bridging agent is preferentially disposed on the surface portion of the absorbent resin which does not come into contact with the hydrophilic fibers. That is, by using a bridging agent having no acid group as the bridging agent, the concentration of the acid group on the surface of the absorbent composite can be effectively reduced.

Drying step

In the method for producing an absorbent composite of the present embodiment, it is preferable to include a drying step of drying the absorbent composite in a water-containing state. The drying treatment method is not particularly limited, and examples thereof include a method of drying by heating, a method of drying under reduced pressure, and a method of drying by air flow. These may be used alone or in combination of a plurality of methods.

The heating and drying method is preferable from the viewpoint of improving the bonding strength between the hydrophilic fiber and the absorbent resin. The heating method is not particularly limited, and may be freely selected depending on the equipment used, and examples thereof include a method of heating with hot air, a method of heating with microwaves, and a method of heating with infrared rays. Although the heating temperature is not particularly limited, it is preferably from 60 to 200 ℃ and more preferably from 80 to 160 ℃. When the temperature is too high, the absorbent composite may be colored, and when the temperature is too low, the drying efficiency may be lowered. Since the water content tends to be less colored at a high temperature, it is preferable that the water content is 10% or more, the water content is at a high temperature of 120 ℃ or more, and the water content is 5% or less, and the water content is at a low temperature of 120 ℃ or less. The drying may be performed by hot air or under reduced pressure.

When a load is applied to the absorbent composite in a water-containing state, a lump aggregate is likely to be formed in some cases. Therefore, it is preferable to perform drying in a thin and spread state or drying while mixing to avoid a load. While more effective drying is possible by vibration and the flow of fluid such as air. The step dryer is used in the intermittent type, and the conveyor belt and the fan are preferably used in the continuous type.

The drying process may be carried out in the same apparatus as that for carrying out the aqueous step as mentioned above, or in a different apparatus. When the treatment is carried out in a different apparatus, it is preferable to adopt a treatment method which is not easily subjected to a load in order to prevent the aggregation of the absorbent composite in a state of containing water. Although the time from the water-containing step to the drying step can be arbitrarily set, it is preferable that the water-containing step and the crosslinking step be carried out before drying as soon as possible, because the soluble component in the hydrophilic fiber migrates into the absorbent resin and the liquid permeability in the hydrophilic fiber is lowered when the absorbent composite is left in a water-containing state for a long time. Specifically, the state in the system changes, specifically, after the density changes, the drying is preferably performed within 60 minutes, and more preferably within 30 minutes. The degree of drying is not particularly limited, and the water content of the absorbent resin after drying is preferably 70% or less, more preferably 50% or less, particularly preferably 30% or less, and particularly preferably 10% or less, compared with the water content of the absorbent resin before drying. The water content after drying is not particularly limited, but is preferably 0.01 to 100 mass%, more preferably 0.1 to 50 mass%, particularly preferably 0.5 to 20 mass%, particularly preferably 2 to 10 wt% based on the mass of the absorbent resin. By setting the above range, an absorbent resin having sufficient absorption capacity can be obtained.

Classification procedure

In the production process of the absorbent composite of the present embodiment, a classification step is preferably included. This is a step of removing the hydrophilic fibers and the like which are extremely aggregated and not bonded. In this classification step, the size of the absorbent composite is preferably 50 to 1000. mu.m, more preferably 70 to 800. mu.m, particularly preferably 100 to 710. mu.m.

Floc causes deterioration of touch or, depending on the case, performance deterioration. Further, fine particles smaller than 50 μm are likely to fly in the air, and this may cause deterioration in the operation performance.

Examples of the classification include a method of classifying by screening, a method of classifying by an air flow, and the like. In the case where the screen is difficult to be screened by being entangled with each other, the screen is appropriately adjusted by incorporating balls or the like having an appropriate weight and size. These stages may be continuous or batch-wise.

Method of using absorbent composite

The absorbent composite of the present embodiment exhibits a sufficient absorption rate for a liquid containing proteins such as milk and blood and solids, and a sufficient liquid retention amount, and can be suitably used for sanitary materials and medical applications.

The absorbent composite of the present embodiment can be used as a pouch-shaped absorbent article or a sheet-shaped absorbent article, and these articles can be used favorably by being incorporated into materials such as sanitary materials and medical supplies.

Absorbent article

The absorbent article of the present embodiment is an article that includes fibers and/or fiber aggregates and the absorbent composite of the present embodiment described above, and is processed using these. Examples of the fiber aggregate include paper and cloth.

Paper, which means paper in the broad sense defined in japanese standard JISP001, and cloth, which means a generic term of a sheet-like fiber product defined in japanese standard JISL 206.

The fabric is classified into woven fabric, knitted fabric, composite, lace, net, nonwoven fabric and the like according to the molding means for forming the sheet, but the fabric, woven fabric, knitted fabric and nonwoven fabric used in the present embodiment are preferable. The nonwoven fabric is defined according to japanese standard JISL 222.

The absorbent articles of the present embodiment are roughly classified into 3 types.

The type 1 is a type a of absorbent article having a bag shape in which the absorbent composite of the present embodiment is contained in a bag made of a fiber aggregate, and the absorbent composite particles can move inside according to the action of external force. That is, the resulting absorbent composite has a relatively high mass per unit area in the bag, can be filled at a high density, and can be used favorably for applications where the movement of the absorbent composite in the bag is recognized.

The 2 nd type is a type B of sheet-like absorbent article. That is, a sheet-like article formed by any method is composed of the absorbent composite and the fiber and/or mixed fiber aggregate.

The type 3 is a type C in which a sheet-like absorbent article (type B) is packed in a bag-like fiber aggregate (bag), or the sheet-like absorbent article (type B) is further covered with an absorbent article processed into a sheet-like fiber aggregate.

The fiber assembly and the covering method are arbitrary, and for example, processing methods such as coating and sandwiching are used.

In order to obtain the absorbent articles of type a and/or type C, the bag made of the fiber aggregate and the fiber aggregate processed into a film should have a function of allowing the target liquid to pass quickly without scattering the absorbent composite outside the bag.

The fiber diameter of the raw material fiber of the fiber aggregate affects the thickness, liquid permeability, flexibility, smoothness, and processability of the fiber aggregate, and the fiber length affects the processability and fuzzing of the fiber. That is, thick and rigid fiber aggregates can be obtained by using coarse fibers, and thin and smooth fiber aggregates can be obtained by using fine fibers. Further, if the fibers are too thin, each fiber is easily broken and fluffed, which results in a decrease in the strength of the fiber assembly. Therefore, the fiber size is preferably 100 μm or less, more preferably 0.1 μm or more and 60 μm or less, particularly preferably 0.5 μm or more and 50 μm or less, particularly preferably 3 μm or more and 25 μm or less, and the fiber length is preferably 0.3mm or more, more preferably 1mm or more, particularly preferably 3mm or more, and particularly preferably 5mm or more. The upper limit of the fiber length may be selected to suit the method for producing the fiber aggregate.

Methods for obtaining fiber aggregates, wet and dry, respectively, with suitable fiber lengths, are described in the literature (recent technical use and development of nonwovens, toronto research center, 11 months 2012), respectively. However, the fiber length is not limited to the fiber length mentioned in the literature. For the same reason, the fiber diameter and the fiber length are also preferable for the fibers of type B and the fibers as the raw material of the fiber aggregate.

The fibers for the absorbent article types a, B, C and the fibers forming the fiber aggregate according to the present embodiment may be natural fibers, regenerated fibers, semisynthetic fibers, synthetic fibers, composite fibers, and these fibers may be used in any mixture. Examples of natural fibers include plant fibers such as wood pulp, non-wood pulp, cotton and hemp, and animal fibers such as silk, wool, cashmere and kefir. The regenerated fiber includes rayon, cuprammonium fiber, tiger kapok, lyocell fiber, etc. Semi-synthetic fibers are fibers composed of a polymer in which a part of the polymer constituting natural fibers is chemically modified. For example, fibers mainly composed of polymers induced by esterification or etherification treatment of cellulose, which is a polymer mainly composed of pulp. The synthetic fibers include polyolefin (polyethylene, polypropylene), Polyester (PET), polyvinyl ether, polyamide (nylon), polyurethane, polyacrylic, polyvinyl alcohol, and spandex. The composite fiber is, for example, a fiber composed of a polymer and/or a double-sided fiber, a core-sheath fiber, a split fiber, an island-in-sea fiber, a hollow fiber, or two or more different polymers mixed or copolymerized in a molten state.

The process for producing the absorbent article according to the present embodiment preferably includes a step of separating the absorbent composites, a step of stacking the absorbent composites, and a step of fixing the absorbent composites. This step is particularly preferable because the absorbent composite is less likely to aggregate in the article. The separation of the absorbent composite uniformly can be performed by the same operation as in the previous classification step. Particularly, when a thin absorbent article is manufactured, it is preferable to sieve the absorbent article together with dispersing balls or the like. The substrate coated with the adhesive composition is continuously fed and spread on the substrate through a screen to produce a uniform laminated sheet.

In particular, in the case of using the sheet-shaped absorbent article in disposable sanitary materials such as diapers, urine pads, and sanitary napkins, and various medical materials, the performance of fitting the body of the wearer and allowing the wearer to fit the absorbent article flexibly with the movement of the wearer is required. When such a use of flexibility is required, if a fiber having latent crimpability (latent crimpable fiber) is used, a flexible absorbent article having a good fit can be obtained. As the latent crimping fiber, a fiber having a property of causing three-dimensional crimping shrinkage in a spiral shape by heating at a predetermined temperature can be used while treating the same as a conventional fiber for nonwoven fabric before heating. The latent crimp fiber is composed of, for example, an eccentric core-sheath type composite fiber or a side type composite fiber composed of two thermoplastic polymer materials having different shrinkage rates. As an example, the contents described in Japanese patent laid-open No. 9-296325 and Japanese patent No. 2759331 are mentioned.

In the present embodiment, the hydrophilic fibers (fibers of the absorbent article of the 1 st type) constituting the absorbent composite and the fibers and/or fiber aggregates (fibers of the absorbent article of the 2 nd type) constituting the absorbent article mixed with the absorbent composite may be the same type of fibers or different types of fibers.

The absorbent article of the present embodiment has a bulk density of 0.004g/cm³Above 0.900g/cm³Preferably, the thickness is 0.2mm to 15 mm.

The liquid diffusibility of the fiber aggregate is strongly influenced by wettability and capillarity of the constituent fibers.

The fiber density is high, that is, the bulk density is not less than a certain value, the liquid diffusibility is good, and the liquid does not accumulate locally such as in the injected portion. On the other hand, if the bulk density is too high, the capillary phenomenon spreads well, but the resulting absorbent article is stiff and gives a poor wearing feeling when used in sanitary materials or medical applications. Therefore, the bulk density of the absorbent article of the present embodiment: 0.004g/cm³Above 0.900g/cm³Preferably, 0.008g/cm or less³Above 0.7g/cm³More preferably, it is 0.01g/cm³Above 0.5g/cm³Particularly preferably, the concentration is 0.03g/cm³Above 0.5g/cm³The following are particularly preferred.

Further, the thickness of the absorbent article tends to be favorable because the space for designing sanitary materials and medical materials is enlarged when the thickness is thin. However, if excessive pressing is performed to make the absorbent composite thin, particles of the absorbent composite may be crushed, resulting in generation of fine powder. Therefore, it is preferable to have a thickness of 0.2mm or more, that is, a thickness of an average particle diameter of the absorbent composite or more. Further, if the thickness of the absorbent article is 15mm or less, the handling property when used for sanitary materials and medical materials is excellent, the mounting feeling is excellent, and the space for product design is expanded. As described above, the thickness of the absorbent article is preferably 0.2mm to 15mm, more preferably 0.3mm to 10mm, particularly preferably 0.4mm to 7mm, particularly preferably 5mm, most preferably 3 mm.

As a method for controlling the bulk density of the absorbent article, for example, a method of rolling with a flat roll, an embossed roll, a roll printed with a convex pattern, or the like can be used. In addition, the fibers on the upper surface and the lower surface of the fiber bag are interlaced by the crochet hook, the upper surface and the lower surface of the absorbent article are made into a point-shaped and discontinuous line shape by using a hot embossing roller, a roller printed with a convex pattern and an ultrasonic terminal, the loose packing density can be controlled by continuous fusion, the shape stability of the absorbent article is improved, and the liquid absorption speed is effectively improved.

The fiber aggregate used in the absorbent article of type A, C described above preferably has a thickness of 1 sheet of 7mm or less, more preferably 3mm or less, particularly preferably 1mm or less. In the case of use for the purpose of preventing the absorbent composite from overflowing, the fiber aggregate is preferably made thinner. In this case, it is preferably 0.5mm or less. When the strength of the fiber aggregate and the absorbent composite are free from problems of scattering and leakage, the thickness of the fiber aggregate is preferably 0.1mm or less, for example, 0.05mm or less. On the other hand, the thickness can be set arbitrarily in consideration of the diffusibility of liquid in the fiber aggregate, strength, texture, and appearance.

The bulk density of the fiber aggregate was 0.004g/cm, which is the same as the bulk density of the absorbent article of the present embodiment³Above 0.500g/cm³Preferably, 0.008g/cm or less³Above 0.4g/cm³More preferably, the concentration is 0.01 to 0.5g/cm³Particularly preferably, the concentration is 0.03g/cm³Above 0.5g/cm³The following are particularly preferred. Control ofThe bulk density and thickness are effectively processed by rolling or the like in the same manner as the method of controlling the absorbent article described above.

As described above, regarding the total weight per unit area of the fibers and/or the fiber aggregate and the absorbent composite, "the bulk density of the absorbent article is 0.004g/cm³Above 0.900g/cm³Below, and a thickness of 0.2mm to 15mm "of 8g/m²Above 500g/m²The following. However, from the viewpoint of strength, flexibility and handling properties of the absorbent article, it is actually 20g/m²Above 1500g/m²The following ranges are preferred.

The fiber aggregate used particularly in the absorbent article of type A, C has a weight per sheet of 8g/m²Above 700g/m²The following are preferred. The weight per unit area is 13g/m for the purpose of making the absorbent composite non-scattering²Above, preferably, 15g/m²The above is more preferably 100g/m²Particularly preferably, the concentration is 60g/m²The following are particularly preferred.

The fiber aggregate used in the absorbent article of type A, C may be used by stacking 2 or more sheets as necessary, and in this case, the total value of the basis weights of the respective fiber aggregates of 2 or more sheets is used for calculation.

The range of the basis weight of the absorbent composite that can be filled in the type a absorbent article can be arbitrarily set according to the use and the amount of the absorbent article, but 1000g/m²The following 5g/m²The above is preferably 20g/m²Above 300g/m²More preferably, it is 50g/m²Above 200g/m²The following are particularly preferred.

In the absorbent article of type B, the ratio of the weight per unit area of the fibers and/or fiber aggregate to the absorbent composite is preferably in the range of 2:1 to 1:2, and the total weight per unit area is preferably 20g/m²Above 1000g/m²Preferably, 50g/m²Above 600g/m²The following is more preferable.

Further, the absorbent composite had a weight per unit area of 10g/m²Above 500g/m²Preferably, 20g/m²Above 200g/m²More preferably, it is 50g/m²The above is particularly preferable.

The absorbent article of the present embodiment may have a multilayer structure of 2 or more layers, or may have a layer not including the absorbent composite of the present embodiment in the multilayer structure of 2 or more layers. In this case, it is preferable that the layer including the absorbent composite and the non-included layer are adhered together all over by the dots/lines.

In this case, the absorbent article, the fibers and/or the fiber aggregate and the absorbent composite are partially bonded by an adhesive, or the fibers contain at least a thermoplastic fiber component, and the thermoplastic fibers and the absorbent composite are thermally fused together.

In addition, an absorbent article can be obtained by passing the absorbent article between a flat roll and an embossing roll or by needle punching, interlacing the upper fibers and the lower fibers of the absorbent composite existing layer, or fusing. When the embossed roll and the flat roll on which the embossed pattern having a width of 2mm or less is engraved are passed through, a continuous linear concave absorbent article having a width of 2mm or less can be obtained. That is, the loose-packing density can be adjusted by the interpenetration and fusion between the fibers constituting the absorbent article and/or the fibers forming the fiber aggregate by the nip between the flat roll and the embossed roll or by the hook-and-loop penetration, and the shape of the absorbent article can be further stabilized.

The absorbent article of the present embodiment has a sufficient absorption rate and a sufficient liquid retention capacity for proteins such as milk and blood and liquids containing solid components, and is useful in the fields of sanitary materials and medical applications.

One of the uses of sanitary materials, sanitary napkins, which have recently been demanded, are narrow in width, thin, and compact. The absorbent article of the present embodiment can be suitably used as an absorbent article for absorbing liquid placed between a water-permeable film in contact with the skin and a water-impermeable film (water-repellent film) not in contact with the skin in a sanitary material. In particular, when the absorbent article of the present embodiment is used as an absorbent body of a sanitary napkin, the surface of the absorbent article is concave, so that the surface area is increased, and therefore, the absorbent article can rapidly absorb liquid and has a dry feeling when worn. Further, since the absorbent article has a shape in which a continuous line having a width of 2mm or less is recessed, it is difficult for liquid in a direction perpendicular to the line to diffuse, and therefore, the diffusion direction in which liquid freely diffuses can be controlled, and therefore, it is possible to prevent liquid leakage even if the width is narrower than the conventional width.

As described above, type B, in which the absorbent composite is processed into a sheet-like form, is an article in which an adhesive solution and a hot melt adhesive (a type in which a non-fibrous material and/or a resin is brought into contact with a high-temperature portion to discharge the resin in a molten state) are dispersed into the absorbent composite, and then the sheet-like article is covered with a fibrous material; a sheet-like article obtained by mixing fibers and/or fiber aggregates with an absorbent composite; a sheet-like article attached to a sheet-like article to which an adhesive solution or a hot-melt adhesive is attached, and having the separated absorbent composite dispersed therein to bond the absorbent composite; the sheet-like article is formed by mixing the absorbent composite from the time when the thermoplastic is extruded from the nozzle (spinning) to the time when the fiber aggregate is formed, and disposing the absorbent composite between the fibers (bonding with part of the fibers is also possible) (that is, the fiber aggregate article is obtained by mixing the absorbent composite in the process in the case of the hot pressing method or the melt blowing method).

The sheet-like absorbent article type B can be obtained by any one of these methods or a combination of any two or more of these methods.

For example, the method for producing an absorbent article with the adhesive solution includes a method of directly spraying an adhesive diluted in a solvent and/or an organic solvent (water) onto an absorbent composite, and heating to evaporate the solvent to fix the absorbent composite; a method of fixing the adhesive by heat curing, and the like. These immobilization methods by dry immobilization are generally referred to as chemical bonding methods.

The thermoplastic resin powder and the hot melt adhesive are used in a method of dispersing the thermoplastic resin powder or the hot melt adhesive in the absorbent composite and heating the resultant mixture to immobilize the absorbent composite. The immobilization method by which immobilization is achieved by heating is generally referred to as a thermal bonding method.

The adhesive material constituting the adhesive solution is generally known, and examples thereof include Nitrile Butadiene Rubber (NBR), Styrene Butadiene Rubber (SBR), natural rubber, polyethylene, polyvinyl acetate, chlorinated polyethylene resin, polyvinyl acetate (EVA), polyacrylate, Chloroprene Rubber (CR), and other adhesive agents.

The method of fixing the fibers and/or the fiber aggregate and the absorbent composite to the sheet-like member by mixing the absorbent composite and the fibers in advance, for example, a method of fixing the absorbent composite and the fibers to the sheet-like member by any of the above-mentioned fixing methods by chemical bonding and/or thermal bonding.

Further, a method of fixing a material in which an absorbent composite and fibers are mixed in advance, such as a method of pressing with a roller or the like, threading with a crochet needle, and mechanically entangling fibers, into a sheet shape; a method of processing and fixing into a sheet shape by a pressing die; a thermal bonding method in which a thermoplastic fiber is used as the fiber mixed with the absorbent composite particles (or a non-thermoplastic fiber may be used in combination with the thermoplastic fiber); a method of covering an absorbent composite with a sheet-like fibrous aggregate; further, the mixture of the absorbent composite and the fibers obtained by these methods is wrapped with a sheet-like fiber aggregate obtained by an arbitrary method, and then fixed in a sheet-like form by an arbitrary method (for example, the above-mentioned chemical bonding method, thermal bonding method, and also extrusion processing such as rolling and punching).

These methods may be used alone or in combination of two or more.

As a method for mixing the particles and the fibers, for example, a method for mixing the particles of the absorbent composite between the steps of defibering the fiber aggregate and forming a uniform sheet-like entangled body (fiber aggregate) by a Carding method (Carding) described in the literature (latest technology and application prospect of nonwoven fabric, tokay, ltd., 11 months, 2012).

Further, Japanese patent laid-open Nos. 7-268752, 9-143850, and 2005-67190 describe an air assist method (Airlaid method) in which an absorbent composite is formed into a sheet-like fiber aggregate while fibers are loosened by air as a medium.

Currently, the Airlaid method, which is commercially successful, is the local model, M & J method, Dan-Web method.

Further, a hybrid method of coating a sheath of a sheet-like fiber aggregate formed by any method such as stacking fibers by using the Carding method or the airlad method may be employed, in which absorbent composite particles are scattered on a sheet-like fiber aggregate not containing the absorbent composite particles formed by the Carding method, the airlad method, or any other method.

When a sheet-like fibrous aggregate is used, the space between fibers on the outermost surface of the fibrous aggregate is preferably 1.5 times or more larger than the 50% average particle diameter of the absorbent composite particles. Thus, the fibers of the fiber aggregate serve as carriers of the absorbent composite particles, and the absorbent composite particles can be arranged three-dimensionally.

In the case of a sheet-like fiber aggregate in which the space between the fiber-absorbent composites is 1.5 times or less the average particle diameter of the particles, it is preferable that 50% of the surface of the fiber aggregate has irregularities 3 times or more the average particle diameter of the particles of the absorbent composites, and that 6 or more protrusions are provided at the 1 × 1cm angle.

The mixture of the absorbent composite particles and the fibers is fixed into a sheet shape by a chemical adhesive method, i.e. a method of dipping or spraying in an adhesive solution and drying; coating a hot melt adhesive on the mixed fibers, and fixing the fibers into a sheet shape while hot pressing and/or hot air blowing by heating and rolling (Airthrough mode); a mode (Airthrough mode) in which thermoplastic fibers are used for part or all of the mixed fibers, and the thermoplastic fibers are fixed into a sheet shape while being hot-pressed and/or blown by hot air by heating and rolling; needle punch, which mechanically winds the fiber together and fixes the fiber into sheet shape; a method of processing and fixing into a sheet shape by a pressing die; one or more of the above methods may be used in any combination.

Further, the thickness and fiber density of the sheet can be adjusted to any desired thickness by pressing with a roller or the like (see, for example, Japanese patent laid-open No. Hei 10-329252).

A method of covering the absorbent composite particles with a sheet-like fiber aggregate, and a method of covering a part of the fiber aggregate, in which the absorbent composite particles are arranged, with another sheet-like fiber aggregate and/or the fiber aggregate in which the absorbent composite particles are dispersed.

By these methods, the binder can be impregnated and/or sprayed onto the fiber aggregate covered with the absorbent composite particles and fixed in a sheet form. A chemical binder method in which a binder is sprayed on the fiber aggregate and/or the absorbent composite particles and fixed in a sheet form; the fiber aggregate covering the absorbent composite particles is prepared by mixing thermoplastic fibers or thermoplastic resins (fibers or powders) and preparing absorbent composite particles, and then is fixed in a sheet form by a method of thermal bonding (airthogh method).

Further, a method of bonding the upper and lower fibers of the absorbent composite particles to the assembly by a NeedlePunch method or a rolling method can also be used.

The fiber diameter of the fibers and/or fiber aggregates in which the absorbent composite and the particles are mixed is preferably at least 100 μm, more preferably 0.1 μm to 60 μm, particularly preferably 0.5 μm to 50 μm, particularly preferably 3 μm to 25 μm. The fiber length of the fiber aggregate to be processed is preferably 1mm or more, more preferably 3mm or more, particularly preferably 5mm or more. The upper limit of the fiber length is the upper limit length suitable for the manufacturing method of the bag.

The fibers and/or fiber aggregates mixed with the absorbent composite particles may be natural fibers, regenerated fibers, semi-synthetic fibers, composite fibers, or the like. These may be used alone or in combination of 2 or more. The natural fiber includes plant fiber, wood pulp, non-wood pulp, cotton, hemp, and animal fiber including silk, wool, cashmere, keslem, etc. The regenerated fiber includes rayon, cuprammonium fiber, tiger kapok, lyocell fiber, etc. Semi-synthetic fibers are fibers composed of a polymer in which a part of the polymer constituting natural fibers is chemically modified. For example, fibers mainly contain polymers induced by esterification or etherification of cellulose, which is a main polymer constituting pulp. The synthetic fibers include polyolefin (polyethylene, polypropylene), Polyester (PET), polyvinyl ether, polyamide (nylon), polyurethane, polyacrylic, polyvinyl alcohol, and spandex. The composite fiber is composed of, for example, a polymer obtained by mixing or copolymerizing two or more different polymers in a molten state, and/or a side-by-side fiber, a core-sheath fiber, a segmented fiber, an island-in-sea fiber, a hollow fiber, or the like. In particular, when disposable sanitary materials such as disposable diapers, diaper pads, and feminine sanitary napkins, which are processed into a sheet form, and various medical materials are used, flexibility is required which constantly changes with the movement of a wearer in close contact with the wearer. In the case of using such applications requiring flexibility, if fibers having latent crimpability (latent crimpable fibers) are used, a flexible absorbent article having a good mounting feeling can be obtained. As the latent crimping fiber, a fiber having a property of developing a helical three-dimensional crimp contraction by heating at a predetermined temperature can be used while treating the same as a conventional fiber for nonwoven fabric before heating. The latent crimp fiber is composed of, for example, a core-sheath type composite fiber or a side-by-side type composite fiber containing two thermoplastic polymer materials having different shrinkage rates as components. For example, Japanese patent laid-open publication No. 9-296325 and Japanese patent No. 2759331 are disclosed in the specification.

The fibers (1 st fibers) constituting the absorbent composite particles and the fibers (2 nd fibers) mixed with the absorbent composite particles may be of the same type or different types.

As the synthetic fiber of the thermoplastic fiber in the thermal bonding method, conventionally known ones can be used. Examples of the polymer include, but are not limited to, olefin polymers such as polyethylene, polypropylene, ethylene-propylene copolymers, ethylene-octene copolymers, and ethylene-vinyl acetate copolymers; thermoplastic polymers such as polyethylene terephthalate copolymers, polybutylene terephthalate copolymers, polyamides, and styrene copolymers. These may be used alone or in combination of two or more.

In addition, as the form of the heat-fusible fiber, in addition to the fiber composed of only the above resin component, there can be mentioned a core-sheath type, a side-by-side type, a sea-island type and other composite fibers having the same as a core component.

The composite fiber is preferably composed of a core component, and the difference between the melting point and the softening point of the sheath component is 20 ℃ or more, and examples thereof include -compatible polymers such as polyethylene terephthalate copolymers, polyesters such as polybutylene terephthalate copolymers, nylon 6, nylon 66, nylon 610, nylon 11, nylon 12, polyhexamethylene isophthalamide, polyamides such as polyhexamethylene terephthalamide, polyacrylonitrile, polyvinyl alcohol, polypropylene, and polyvinyl chloride.

The use of the core-sheath structure fiber is preferable from the viewpoint of easy control of the amount of fusion.

The thickness of the fibers is not particularly limited, but is preferably from 0.01 to 200 denier, more preferably from 0.1 to 100 denier, particularly preferably from 0.5 to 50 denier, and particularly preferably from 1.2 to 15 denier. If the thickness is too small, the space between the hydrophobic fibers becomes small, and the absorption performance may be impaired, and if the thickness is too large, the touch may be deteriorated.

The fiber length is not particularly limited, but is preferably 0.1 to 20mm, more preferably 0.5 to 10mm, particularly preferably 1 to 5 mm. If the length is too short, the joining force may be weak, and if the length is too long, the mixing property may be deteriorated.

The absorbent article composed of the absorbent composite according to the present embodiment is extremely thin and excellent in water absorption rate and dry feeling, and therefore, disposable sanitary materials for diapers, urine pads, feminine sanitary napkins and the like and various medical supplies made by adding auxiliary members such as a water-permeable sheet, a water-impermeable sheet, and pleats as necessary are extremely excellent.

Other absorbent articles of the present embodiment include, but are not limited to, absorbent members of pet animal excrement treatment materials such as animal sheets and pet sheets, absorbent films for preventing water from evaporating when frozen aquatic products are thawed during transportation of frozen aquatic products, films for preventing water from evaporating on bonsais, films for absorbent films such as mats under bonsais, absorbent films around water tanks, absorbent films for preventing dew condensation, mats placed under umbrella stands to absorb water drops falling from umbrellas, covers for vehicles, mats for preventing water from evaporating in helmets or caps, toilet paper seats used after defecation by warm water washing toilets (washlets (registered trademark) toilets produced by toso corporation), absorbent mats on floors for preventing rain from wetting in activity places, automobiles in wet weather, an absorbent mat for preventing wetting on the floor of a transportation means such as a train, an airplane, a hospital in rainy weather, a service area, a department store, a hotel, a shop, an office building, or a leisure facility, a moisture-proof mat in a refrigerator, a moisture-proof mat on the floor in a kitchen, a drip-proof mat for discharging fresh garbage in a cooking room or a cooking room, a water supply facility, a hot water supply facility, an electric power facility, a toilet or the like, a sanitary appliance having a moisture-proof function such as a toilet, a bed sheet for massage therapy, an auxiliary mat for bed, a wrapping material for moisture-retaining of vegetables, fruits or flowers, a food such as live fish, raw meat, subsidiary food, a wrapping material for convenient moisture-retaining or retaining, a wrapping material for seeds, strains, seedlings or rhizomes, the cleaning of machines and windows, the wiping cloth or rag for condensing or wetting the ceiling, wall, window, floor, etc. of buildings, the film for preventing water evaporation in the cultivation of horticultural plants, etc. can be preferably used.