阅读说明：本技术 纤维素纤维干燥体、纤维素纤维树脂复合体、成型体 (Cellulose fiber dried body, cellulose fiber resin composite body, and molded body ) 是由 森本裕辉 峯村淳 永田员也 真田和昭 于 2019-12-31 设计创作，主要内容包括：本发明提供一种纤维素纤维干燥体、包含其的纤维素纤维树脂复合体、以及成型体,其中,所述纤维素纤维干燥体在与树脂复合化时,纤维素纤维能够良好地分散在树脂中,能够使得拉伸弹性率或者拉伸强度这样的物性提升。本发明是一种包含纤维素纤维的纤维素纤维干燥体、包含其的纤维素纤维树脂复合体以及成型体。纤维素纤维的平均纤维直径为0.1μm以上20μm以下,纤维素纤维的构成糖成分中的半纤维素组分的比例为50％以下。纤维素纤维干燥体的含水量为10质量％以下。(The invention provides a dried cellulose fiber body, a cellulose fiber resin composite body containing the same, and a molded body, wherein the cellulose fiber body can be well dispersed in a resin when being compounded with the resin, and the physical properties such as tensile elasticity and tensile strength can be improved. The present invention relates to a dried cellulose fiber product containing cellulose fibers, a cellulose fiber resin composite containing the same, and a molded article. The cellulose fiber has an average fiber diameter of 0.1 to 20 μm, and the proportion of hemicellulose component in the constituent sugar components of the cellulose fiber is 50% or less. The water content of the dried cellulose fiber is 10 mass% or less.)

1. A dried cellulose fiber characterized by comprising the following components:

cellulose fibers having an average fiber diameter of 0.1 to 20 μm and a proportion of hemicellulose component in the constituent sugar component of 50% or less; and 10% by mass or less of water.

2. The dried cellulose fiber body according to claim 1,

the cellulose fibers have cellulose type I crystals.

3. The cellulose fiber dried body according to claim 1 or 2,

the viscosity average molecular weight of the cellulose fiber is more than 10 ten thousand.

4. The cellulose fiber dry body according to any one of claims 1 to 3,

further, a surfactant is included.

5. The dried cellulose fiber body according to claim 4,

the surfactant is at least one selected from stearic acid derivatives, oleic acid derivatives, glycerin derivatives, and polyglycerin derivatives.

6. The cellulose fiber dry body according to any one of claims 1 to 5,

the surfactant is contained in an amount of 1 to 30 parts by mass per 100 parts by mass of the cellulose fiber.

7. A cellulose fiber-resin composite characterized in that,

comprising the dried cellulose fiber product of claim 6 and a thermoplastic resin.

8. The cellulose fiber-resin composite according to claim 7,

the aggregate of the dried cellulose fiber bodies having a maximum diameter of 200 μm or more is 5/cm²The following.

9. The cellulose fiber-resin composite according to claim 7 or 8,

the thermoplastic resin is at least one selected from the group consisting of polyolefin resins and polyamide resins, and the content of the dried cellulose fiber is 1 mass% or more.

10. The cellulose fiber-resin composite according to any one of claims 7 to 9,

the tensile modulus of elasticity defined in JIS K7161 is 1550MPa or more, and the tensile strength is 36MPa or more.

11. A molded article characterized by comprising, in a molded article,

formed from the cellulosic fiber resin composite of any one of claims 7-10.

Technical Field

The present invention relates to a dried cellulose fiber, a cellulose fiber resin composite, and a molded body.

Background

Cellulose is a main component of plant cell walls, and functions to support plant bodies in the coexistence of lignin and hemicellulose. Cellulose is a resource that produces the largest amount of production and accumulates on the earth, and it is desired that the cellulose can be effectively utilized. Cellulose is used in various industrial fields, and one of them is used as a filler. The filler is a particulate or fibrous substance added to a resin, rubber, paint, or the like for the purpose of improving strength, functionality, or reducing cost.

In the development of polymer materials, the compounding of a functional filler with a polymer is an important development factor. The influence on the physical properties of the composite material varies greatly depending on the shape of the filler. In particular, the acicular or fibrous filler has characteristics such as high mechanical and thermal reinforcing effects, high electrical conductivity, and imparting vibration damping properties.

Further, a filler having no fixed shape or a spherical shape has characteristics such as easy processability, isotropy of physical properties, less adverse effect on toughness, and less deformation after molding.

Among the above, cellulose, which is a natural polymer having glucose linked by β -1, 4-glycosidic bonds, is expected to be a fibrous filler having a high aspect ratio.

As a filler for fiber-reinforced resins, glass fibers are relatively inexpensive, easy to mold, hole-forming, and the like, and have a good reinforcing effect, and are currently widely used in many fields. However, for glass fibers, the density was 2.55g/cm³It is relatively heavy as compared with a resin, and is disadvantageous in applications requiring weight reduction.

In recent years, CFRPs obtained by compositing carbon fibers with a resin have been used as aircraft parts. The density of the carbon fiber (PAN system) was 1.82g/cm³And is a lighter and higher strength material than glass fiber. CFRP is mainly carried out in the process of transmissionThe application development of the transportation machinery as the central application.

However, a reinforced resin obtained by compounding glass fibers or carbon fibers with a resin still has a problem that it is poor in recyclability and cannot be subjected to a combustion treatment. Therefore, there has been a long-standing alternative to natural fibers such as cellulose and chitin/chitosan, which are readily available and environmentally friendly. For cellulose, the density is 1.5g/cm³Lighter than glass fiber or carbon fiber and higher in rigidity, and therefore, the possibility thereof as a fiber-reinforced filler has been attracting attention, and some cellulose-compounded resins have been marketed. In addition, unlike glass fibers or carbon fibers, cellulose is combustible and has thermal cyclability. Further, in recent years, studies have been continuously conducted to achieve a reinforcing effect by adding nanofibers, called nanocellulose and cellulose nanofibers, having a fiber diameter of 100nm or less to a resin.

Cellulose is a natural product, the fiber diameter thereof is determined by the plant species, and the fiber diameter of a typical plant fiber is 20 to 50 μm, and it is very difficult to further reduce the original average fiber diameter and adjust the fiber diameter.

For example, in japanese patent No. 3867117 (hereinafter, referred to as "patent document 1"), cellulose having a fiber diameter of 20 μm or less is prepared as an additive for rubber or resin.

Japanese patent No. 5592696 (hereinafter, referred to as "patent document 2") discloses a method of increasing crystallinity by adding cellulose fibers to an aliphatic polyester resin to shorten the crystallization peak time.

Japanese patent No. 4260045 (hereinafter referred to as "patent document 3") discloses the use of cellulose fibers as a dewatering aid, the cellulose fibers having a fiber diameter of 10 to 30 μm.

Japanese patent No. 6005470 (hereinafter, referred to as "patent document 4") discloses, as a method for producing a resin containing cellulose fibers, a method in which cellulose fibers are uniformly dispersed in a resin after defibration without using an aqueous medium.

Japanese patent No. 5675066 (hereinafter referred to as "patent document 5") discloses a resin composition containing a fine cellulose fiber and a method for producing the same.

Disclosure of Invention

However, the cellulose described in the example of patent document 1 is not fibrous but flat cellulose particles, and a cellulose fiber having a fibrous shape cannot be obtained.

The cellulose found to be effective in patent document 2 is a cellulose fiber in a flat shape and has an average diameter exceeding 20 μm.

The cellulose fiber obtained in patent document 3 is a hydrate, and it is assumed that it is used in water. That is, there is no mention of producing cellulose fibers having an average fiber diameter of 0.1 to 20 μm in a dry state.

In patent document 4, in the production method, cellulose fibers having an average fiber diameter of 0.1 to 20 μm after drying cannot be obtained as a monomer, and it is necessary to disperse the cellulose fibers in a solvent and perform a polymerization reaction, and it is not possible to add and mix the cellulose fibers as a general filler to a thermoplastic resin, rubber, or the like.

Patent document 5 discloses that the average fiber diameter of cellulose fibers produced specifically in examples is less than 0.1 μm, and does not actually mention the production of cellulose fibers having an average fiber diameter of 0.1 to 20 μm in a dry state.

As described above, there is no specific mention in the prior art about obtaining cellulose fibers having an average fiber diameter of 0.1 to 20 μm in a dry state. Therefore, when a dried body of cellulose fibers having such a fiber shape is combined with a resin, it is not known that the dried body exhibits excellent properties.

On the other hand, it is known that a fine cellulose fiber having an average fiber diameter of 20nm can be obtained by decomposing a cellulose fiber by a water jet, a grinder, a high-pressure homogenizer, a bead mill, or the like. In addition, a technique is known in which the fiber diameter of cellulose is decomposed to about 3nm by chemical treatment. In these methods, nanofibers having a fiber diameter of 0.1 μm or less can be obtained as an aqueous dispersion. However, if the resulting aqueous dispersion is dried purely, a hornification phenomenon occurs, and the cellulose forms a strong macrostructure through hydrogen bonds in the process of removing moisture. In particular, cellulose fibers having an average fiber diameter of 0.1 μm or less have a strong aggregating action during drying, and it is very difficult to obtain dried cellulose fibers in a state of decomposed fibers.

In view of the above, the present invention has been made in view of the above circumstances, and an object thereof is to provide a dried cellulose fiber product in which cellulose fibers are well dispersed in a resin when the dried cellulose fiber product is combined with the resin, and physical properties such as tensile modulus and tensile strength are improved, a cellulose fiber-resin composite including the same, and a molded body.

The present inventors have intensively studied to solve the above problems, and found that the problems can be solved by a dried cellulose fiber product having an average fiber diameter of 0.1 to 20 μm and a hemicellulose component content of the constituent sugar components of the cellulose fiber of 50% or less, and completed the present invention.

Namely, the present invention is as follows:

a dried body of cellulose fibers comprising:

the following ingredients:

an average fiber diameter of 0.1 to 20 μm,

cellulose fibers having a proportion of hemicellulose component in the constituent sugar component of 50% or less; and 10% by mass or less of water.

A cellulose fiber resin composite containing a dried cellulose fiber and a thermoplastic resin.

A molded article formed of a cellulose fiber-resin composite.

According to the present invention, it is possible to provide a dried cellulose fiber product which, when combined with a resin, can improve physical properties such as tensile modulus and tensile strength by dispersing cellulose fibers in the resin satisfactorily. Further, a cellulose fiber resin composite containing such a dried cellulose fiber and a molded article can be provided.

Drawings

Fig. 1 is an electron microscope image of the cellulose fiber dried product of production example 1.

Fig. 2 is an electron microscope image of the cellulose fiber dried product of production example 2.

Fig. 3 is an electron microscope image of the dried cellulose fiber of production example 3.

Fig. 4 is an electron microscope image of the dried cellulose fiber of production example 4.

Fig. 5 is an electron microscope image of the dried cellulose fiber of production example 5.

Fig. 6 is an electron microscope image of the dried cellulose fiber of production example 6.

Detailed Description

[ 1 ] cellulose fiber dried body ]

An embodiment (the present embodiment) of the dried cellulose fiber of the present invention will be described in detail below.

The present embodiment is a dried cellulose fiber product including cellulose fibers and water. Here, the average fiber diameter of the cellulose fibers is 0.1 to 20 μm, and the proportion of the hemicellulose component in the constituent sugar components of the cellulose fibers is 50% or less. Then, the moisture content of the dried cellulose fiber is 10 mass% or less. In the present specification, a cellulose fiber containing water in an amount of at most 10 mass% is referred to as a "dried cellulose fiber".

In the present embodiment, the average fiber diameter of the cellulose fibers is preferably 0.1 μm or more and 20 μm or less. By forming the fibers with a diameter larger than the fiber diameter of nanofibers (so-called cellulose nanofibers), the retention of the fiber shape can be ensured well. That is, if the cellulose fibers are dried, there may be a case where the retention of the fiber shape is reduced due to hornification, but the present invention can suppress the occurrence thereof. In addition, when the cellulose fiber is combined with a resin, a dried cellulose fiber body in which the tensile strength or tensile modulus of the fiber-resin composite can be greatly improved can be obtained. Further, the proportion of the hemicellulose component in the constituent sugar components of the cellulose fibers is preferably 50% or less. By making the proportion of the hemicellulose component within this range, the decomposed dry state can be maintained even if the average fiber diameter is 0.1 μm or more and 20 μm or less.

When the average fiber diameter of the cellulose fibers is less than 0.1 μm, the above problem of hornification occurs, and when it exceeds 20 μm, it becomes difficult to greatly improve the tensile strength or tensile modulus of the fiber-resin composite obtained by combining the cellulose fibers with a resin. The average fiber diameter of the cellulose fibers is preferably 0.5 μm or more, and more preferably 1 μm or more. Further, the average fiber diameter of the cellulose fibers is preferably 17 μm or less, more preferably 10 μm or less.

The average fiber diameter of the cellulose fibers can be measured by the method described in examples.

In the conventional method for obtaining nanofibers, for example, when the average fiber diameter of cellulose fibers is controlled to be 0.1 μm or more and 20 μm or less, it is considered to adjust the number of pulverization, the pressure, or the number of rotation. However, if a cellulose raw material containing a large amount of hemicellulose component is used, a portion which is likely to become nanofibers and a portion which is difficult to become nanofibers coexist, and therefore, the fiber diameter distribution of the obtained fiber becomes broad. Therefore, it is preferable to use cellulose having a proportion of glucose of 50% or more, that is, cellulose having a hemicellulose component of 50% or less, when the total amount of the constituent sugars of the cellulose fiber is 100%, by the analysis of the constituent sugars, for the obtained fiber having an average fiber diameter of 0.1 to 20 μm.

If the proportion of hemicellulose in the cellulose fibers exceeds 50%, the decomposed cellulose fibers in a dry state cannot be obtained. The proportion of hemicellulose is preferably 35% or less, more preferably 30% or less, and further preferably 5% or less. In addition, the proportion of hemicellulose is preferably low.

The proportion of hemicellulose can be measured by the method described in examples.

When the proportion of hemicellulose in the cellulose fiber is 50% or less, for example, kraft pulp or cotton having a low proportion of hemicellulose may be used as the raw material cellulose. Further, the cellulose fibers can be mercerized by alkali treatment depending on the raw material, and the proportion of hemicellulose can be set to 50% or less.

Here, hemicellulose is a generic term for polysaccharides other than cellulose contained in wood pulp and non-wood pulp. The main component of pulp is cellulose, which is a polysaccharide of crystalline substances obtained by linear polymerization of only glucose. On the other hand, hemicellulose is a polysaccharide having a branch chain containing monosaccharides such as xylose, mannose, arabinose, galactose, glucuronic acid, and galacturonic acid. Hemicellulose is a polysaccharide of lower molecular weight and non-crystalline material than cellulose. As representative hemicelluloses, for example, there are known: polysaccharides such as xylan, arabinoxylan, mannan, glucomannan, and glucuronoxylan.

The cellulose fiber of the present embodiment preferably has cellulose I-type crystals. Since cellulose type I crystals have a high crystal elastic modulus compared to other crystal structures (cellulose type ii, iii, and iv structures), it is effective for obtaining cellulose fibers having a high elastic modulus, high strength, and a low linear expansion coefficient.

In a curve profile (wide-angle X-ray diffraction image) obtained by wide-angle X-ray diffraction image measurement of cellulose fibers, cellulose fibers can be identified to have an I-type crystal structure by having typical peaks at two positions in the vicinity of a scanning angle 2 θ of 14 to 17 ° and in the vicinity of a scanning angle 2 θ of 22 to 23 °.

The viscosity average molecular weight of the cellulose fiber is preferably 10 ten thousand or more, more preferably 12 ten thousand or more, and further preferably 20 ten thousand or more. The viscosity average molecular weight is 10 ten thousand or more, whereby more excellent physical properties of the fiber-resin composite due to the cellulose fibers can be obtained. The viscosity average molecular weight is preferably 30 ten thousand or less.

The viscosity average molecular weight of the cellulose fiber can be measured by the method described in examples.

The dried cellulose fiber product according to the present embodiment preferably further contains a surfactant. By including the surfactant, the dried cellulose fiber can be more favorably dispersed in the resin.

The surfactant used in the present embodiment may be an anionic surfactant or a nonionic surfactant which is soluble and dispersible in water or a water-soluble alcohol such as ethanol or methanol, or a mixture thereof, and specifically includes: stearic acid derivatives, oleic acid derivatives, glycerin derivatives, and polyglycerin derivatives, but are not limited thereto.

Stearic acid is a saturated fatty acid having the highest content in animal and plant fats, and is widely distributed in nature as an oil component. Specific examples of the stearic acid derivative include: stearic acid, stearamide, aluminum stearate, magnesium stearate, sodium stearate, calcium stearate, barium stearate, stearate PEG, PEG-glyceryl stearate, stearate PG, ascorbyl stearate, isooctyl stearate, ethylene glycol monostearate, glyceryl stearate, cholesterol stearate, diethanolamide stearate, diethylaminoethylamide stearate, ethyl stearate, vinyl stearate, sucrose stearate, sorbitan fatty acid ester, sodium stearate, batyl stearate, butyl stearate, cetyl stearate, methyl stearate, cetyl stearate, stearyl stearate, glyceryl distearate, isocetyl stearate, glyceryl monostearate, 12-hydroxystearic acid, 2-ethylhexyl stearate, glyceryl monoisostearate, calcium stearate, barium stearate, PEG-glyceryl stearate, PG stearate, glyceryl monostearate, sodium stearate, stearyl stearate, glyceryl monostearate, 12, N, N' -ethylene bis stearamide, stearate, etc.

Specific examples of the oleic acid derivative include: oleic acid, oleic anhydride, ethyl oleate, butyl oleate, methyl oleate, oleyl oleate, sodium oleate, glycidyl oleate, copper (ii) oleate, cholesterol oleate, glyceryl dioleate, glyceryl monooleate, oleate, butyl oleate, propyl oleate, dibutyl oleate, potassium oleate, ethyl oleate, N-diethanol oleamide, N-diethanol oleamide, 4-methylumbelliferone oleate, trimethylolpropane trioleate, sulfosuccinimidyl oleate sodium salt, N' -ethylene bis oleamide, 5-bromo-4-chloro-3-indolyl oleate, and the like.

Specific examples of the glycerin derivative and the polyglycerin derivative include: glycerol, diglycerol, PPG-9 diglycerol, PPG-14 polyglycerin-2 ether, glyceryl dicaprylate, POP (9) polyglycerin ether, POP (14) polyglycerin ether, POP (24) polyglycerin ether, POE (13) polyglycerin ether, POE (20) polyglycerin ether, POE (30) polyglycerin ether, POE (40) polyglycerin ether, polyglycerin, glycerin fatty acid ester, polyglycerin monoisostearate, polyglycerin diisostearate, polyglycerin monolaurate, myristyl myristate, polyglycerin monooleate, polyglycerin monostearate, polyglycerin distearate, condensed polyglycerin ricinoleate, tetraisostearic acid diglyceride, polyglycerin pentahydroxystearate, adipic acid, diethylene glycol, ethylhexyl glycerin, octyloxy glycerin, ozone oil, cyclohexyl glycerin, thioglycerol, disodium diglyceride dioleoyl glycerophosphate, polyglycerin dicaprylate, polyglycerin octanoate, polyglycerin, and glycerin, Hexyl glycerin, polyglycerin-4, polyglycerin-6, polyglycerin-10, polyglycerin-20, polyglycerin fatty acid ester, diglycerin fatty acid ester, polyoxyethylene polyglycerin ether, glycerin fatty acid ester, monoglyceride, acetylated monoglyceride, organic acid monoglyceride, medium-chain fatty acid monoglyceride, polyglycerin fatty acid ester, sorbitan fatty acid ester, propylene glycol fatty acid ester, and the like.

In addition, as other glycerin derivatives, there can be mentioned: and glycerides such as laurate, myristate, caprylate, behenate, erucate and condensed ricinoleate.

The surfactant is preferably at least one selected from stearic acid derivatives, oleic acid derivatives, glycerin derivatives, and polyglycerin derivatives, from the viewpoint of further improving the dispersibility of the dried cellulose fiber in the resin. Among these, polyglycerol derivatives are preferred, and polyglycerol condensed ricinoleate comprising polyglycerol and condensed ricinoleic acid is more preferred.

The surfactant is preferably contained in an amount of 1 to 30 parts by mass based on 100 parts by mass of the cellulose fiber (solid content). When the surfactant is contained in an amount of 1 part by mass or more, the aggregation inhibition effect of the cellulose fibers can be easily obtained. On the other hand, if the surfactant is contained in an amount of 30 parts by mass or less, the amount of the surfactant is not excessive for the cellulose fibers, and as a result, discoloration and poor drying of the cellulose fibers are suppressed.

The content of the surfactant is more preferably 3 parts by mass or more, and still more preferably 5 parts by mass or more, per 100 parts by mass of the cellulose fiber (solid content). Further, it is more preferably 20 parts by mass or less, and still more preferably 15 parts by mass or less.

The dried cellulose fiber product according to the present embodiment as described above can be obtained, for example, by preparing a cellulose fiber aqueous dispersion from a cellulose raw material as described below through a mechanical treatment step or the like, and subjecting the cellulose fiber aqueous dispersion to a drying treatment or the like.

The term "aqueous" in the cellulose fiber aqueous dispersion means that the solvent or the dispersant contains 50 mass% or more of water. The solvent or the dispersant may be an aqueous dispersion composed of water alone, but may contain various organic substances soluble in water due to additives and the like.

(cellulose Material)

The raw material cellulose used for the production of the cellulose fiber aqueous dispersion preferably has cellulose I-type crystals. Examples of the raw material cellulose include: woody (coniferous and broad-leaved), herbaceous, kraft, cotton, hemp, algae, sea squirt or bacterial cellulose. Among them, sulfate pulp or cotton (cotton cellulose) is preferable. The constituent sugar of cellulose is preferably low in hemicellulose content and high in cellulose purity. Specifically, when the total amount of sugar detected by analysis such as composition is 100%, the ratio of glucose constituting sugar is preferably 50% or more. In other words, the proportion of the hemicellulose component in the constituent sugar components of the cellulose fibers is preferably 50% or less. These cellulose fibers may be used alone or in combination of two or more. The cellulose-based raw material is preferably in the form of a fiber, a powder, a flake, or a sheet, and may be a mixture of these materials, from the viewpoint of ease of handling.

(mechanical treatment Process)

The mechanical treatment step is a step of fibrillating cellulose fibers having a fiber diameter of 20 to 50 μm to an average fiber diameter of 0.1 to 20 μm. Fibrillation refers to the process of breaking down the fibers and further fluffing them. Preferably, the cellulose raw material is diluted and dispersed in water to adjust the cellulose concentration to a dispersion liquid of 0.1 to 30 mass% before the mechanical treatment. In the fibrillation, it is more preferable to use 1 to 20 mass% of a dispersion liquid. Particularly, when the concentration of the cellulose is 1 to 20 mass%, the increase in the viscosity of the dispersion liquid can be suppressed, and the fibrillation efficiency of the cellulose fibers can be improved.

In the mechanical treatment step, a pulverizer capable of wet pulverization can be used. Examples of the pulverizing apparatus include: a wet type micronizing apparatus, a high-pressure homogenizer, an ultrahigh-pressure homogenizer, a grinder (mortar mill), a high-speed defibrator, a ball mill, a bead mill, a disc refiner, a conical refiner, a twin-screw kneader, a vibration mill, a homomixer (homomixer), an ultrasonic disperser, a beater, and the like.

A wet type micronizing device is effective as a device capable of fibrillating while maintaining the fiber length, and is therefore preferable. Specifically, the fibrillation of the fibers using the wet-type micronizing device is performed by a high-pressure jet process at 100 to 245MPa through a jet nozzle having a diameter of 0.1 to 0.8mm to collide with the collision hard material or collide with each other to thereby disintegrate the fibers. The fibrillation method may be not only a shearing force generated by passing a dispersion fluid along a narrow flow path at a high pressure and a low speed as in a commercially available high-pressure homogenizer, but also a collision force generated by colliding with a hard material for collision or by colliding with each other, or continuous defibration under a high pressure by cavitation. In the uniform cellulose fiber obtained by this method, the collision treatment is performed once as 1 step (パス), preferably 1 to 30 steps, and more preferably 1 to 20 repeated collisions are performed.

In this step, the raw material cellulose fibers are preferably defibrated to have a fiber diameter of 0.1 to 20 μm. This can suppress aggregation of the defibrated cellulose fibers due to strong hydrogen bonds during drying. Although aggregation is slightly progressed in the drying process, the fiber can be decomposed into a fibrous form having an average fiber diameter of 0.1 μm to 20 μm by the dry pulverization process. That is, even in a dry state, the average fiber diameter of the cellulose fibers in the cellulose fiber aqueous dispersion of the present embodiment can be maintained.

(addition and mixing of surfactant)

The cellulose fiber aqueous dispersion of the present embodiment is prepared by adding an anionic or nonionic surfactant that is soluble and dispersible in water, a water-soluble alcohol such as ethanol or methanol to the cellulose fiber aqueous dispersion prepared by the mechanical treatment step, and uniformly stirring and mixing the resultant dispersion by a commercially available screw stirrer, ribbon mixer, rotary and revolving stirring and defoaming machine, planetary mixer, or the like. Alternatively, the surfactant may be added to the cellulose fibers before the mechanical treatment step, and wet grinding may be performed thereafter.

The cellulose fiber median particle diameter of the cellulose fiber aqueous dispersion according to the present embodiment produced in the above manner is preferably 10 μm or more, more preferably 15 μm or more, and still more preferably 20 μm or more, from the viewpoint of improving the physical properties of the fiber-resin composite obtained by combining a resin and cellulose fibers. From the viewpoint of maintaining the dispersibility of the cellulose fibers in the resin, the median particle diameter is preferably 80 μm or less, more preferably 70 μm or less, and still more preferably 60 μm or less. In addition, with respect to the median particle diameter, if the dispersion of the cellulose fibers in the aqueous dispersion is within the above range, it can be said that good dispersion of the cellulose fibers into the resin is maintained.

The median particle diameter of the cellulose fibers in the cellulose fiber aqueous dispersion can be measured by the method described in examples.

From the viewpoint of more efficiently producing a dried cellulose fiber product, the proportion (solid content concentration) of cellulose fibers in the cellulose fiber aqueous dispersion is preferably 0.1 mass% or more, more preferably 1 mass% or more, still more preferably 10 mass% or more, and particularly preferably 15 mass% or more. From the viewpoint of practicality, the upper limit is about 30 mass%.

In general, the solid content concentration in the cellulose fiber aqueous dispersion is at most about 10 mass% in practical use, but the cellulose fiber aqueous dispersion of the present embodiment has good dispersibility of the cellulose fibers, and therefore the solid content concentration can be made relatively high.

The cellulose fiber aqueous dispersion as described above can be dried by a known drying treatment (drying step), thereby forming a dried cellulose fiber. In order to improve the dispersibility of the dried cellulose fiber in the resin, the drying step may be followed by a pulverization step.

(drying Process)

The drying method is not particularly limited, and may be performed using a commercially available drying apparatus. Examples thereof include: a spray drying apparatus using a spray drying method, a drying apparatus using a vacuum drying method, an air flow drying apparatus using an air flow drying method, a hot air drying apparatus using hot air, a steam drying apparatus using steam, a rotary drying apparatus using centrifugal force, a vibration drying apparatus using vibration force, a fluidized bed drying apparatus using a fluidized bed drying method, a drum drying apparatus for performing adhesion drying on the surface of a rotating heating drum, and a freeze drying apparatus for drying a frozen slurry dispersion in vacuum. Then, the amount of water (water content) contained in the dried cellulose fiber is 10 mass% or less by the drying treatment. The water content of the dried cellulose fiber can be adjusted to 10 mass% or less by the method described in examples.

The water content can be measured by, for example, a heat drying type moisture meter.

(grinding step)

The pulverization step is not particularly limited, and may be carried out by using a commercially available pulverization apparatus. Examples thereof include: a roller mill that presses a rotating table-like or bowl-like grinding container by the gravity and centrifugal force of a roller and performs compression grinding; a jet mill that ejects a few of high-pressure air or high-pressure gas, which is extruded at a pressure of at least atmospheric pressure, accelerates raw material particles by a jet stream, and pulverizes the particles by collision and impact action of the particles; a hammer mill for crushing the feed particles by impacting the feed particles with a high-speed rotating hammer; a pin mill for fixing tens of pins to the surfaces of two circular plates facing each other and pulverizing an object by rotating the object at a high speed; a rotary mill in which a grinding medium is filled in an amount of one third of the volume of the rotary cylinder around a horizontal axis, and the object is ground by rotation; a vibration mill in which a cylindrical or groove-shaped mill is filled with a grinding medium and the grinding medium is moved and ground by applying vibration to the mill; a planetary mill for milling by a collision force of a mechanism for rotating and revolving a container filled with a milling medium and an object; an attrition mill for milling the object by a rod-shaped stirring arm using a ball of about 3 to 10 mm; a bead mill that fills beads as a medium in a container, and causes the beads to collide and be crushed by rotation of a stirrer; the air flow type pulverizer pulverizes raw materials by causing the raw materials to collide with each other by an air flow generated by rotating an impeller.

The dried cellulose fiber obtained by the above method is in a decomposed and dried state having an average fiber diameter of 0.1 μm to 20 μm, and therefore, the cellulose fiber can be present in a resin while maintaining good dispersibility while improving the handleability when it is combined with a resin or the like, and thus, the properties of the fiber-resin composite such as tensile modulus and tensile strength can be improved.

[ 2 ] cellulose fiber-resin composite and molded article ]

The cellulose fiber resin composite of the present embodiment includes a dried cellulose fiber and a thermoplastic resin. In this case, the aggregates of the dried cellulose fibers having a maximum diameter of 200 μm or more are preferably 5/cm²The following. The aggregate of the dried cellulose fiber was 5 pieces/cm²As described below, the dispersibility of the dried cellulose fiber in the thermoplastic resin can be ensured well, and desired physical properties can be easily obtained.

The number of aggregates can be measured by the method described in examples using a resin compressed tablet obtained by combining cellulose fibers.

(thermoplastic resin)

Examples of the resin to be mixed include thermoplastic resins having a melting temperature of 300 ℃ or lower, and specifically, include: polyolefin such AS polyethylene and polypropylene, polystyrene, AS resin (acrylonitrile styrene), ABS resin, polyvinyl chloride, vinyl chloride resin, acrylic resin, methacrylic resin, PET resin, polyethylene terephthalate, PVA resin, polyvinyl alcohol, polyvinylidene chloride, polyvinylidene fluoride, nylon 6, nylon 66, nylon 11, nylon 12, acetal resin, polyacetal, polycarbonate, PBT resin, polybutylene terephthalate, polyphenylene sulfide, polyetherimide, polysulfone, polychlorotrifluoroethylene, fluororesin, polyamideimide, acetyl cellulose, cellulose acetate, nitrocellulose, cellulose propionate, ethyl cellulose, and the like. These thermoplastic resins may be used alone or in combination of two or more. In the above, at least one selected from the group consisting of polyolefin resins and polyamide resins is preferable.

The content of the dried cellulose fibers (cellulose fibers) in the cellulose fiber-resin composite according to the present embodiment is preferably 0.3 mass% or more, more preferably 0.5 mass% or more, and even more preferably 1 mass%, from the viewpoint of obtaining preferable physical properties of the fiber-resin composite, although the content depends on the type of the resin. Further, it is preferably 50% by mass or less, and more preferably 40% by mass or less.

In the cellulose fiber resin composite of the present embodiment, known additives (a compatibilizing agent, a heat stabilizer, an antioxidant, and the like) may be mixed in a range not to impair the effects thereof.

In order to produce the cellulose fiber-resin composite, first, a dried cellulose fiber is mixed with a resin by a known method. Thereafter, it is preferable to dry-mix using a Henschel (Henschel) mixer, a stirrer such as a stirrer or a three-arm stirrer (trimix), and a mixing device as the pre-dispersion. Thereafter, the mixture is kneaded using various kneading machines at a predetermined number of revolutions and at a predetermined temperature for a predetermined time, thereby producing a cellulose fiber-resin composite.

In the cellulose fiber resin composite according to the present embodiment, the tensile modulus of elasticity defined by jis k7161 is preferably 1550MPa or more and the tensile strength is preferably 36MPa or more. When the amount is within the above range, the practicability of the cellulose fiber-resin composite can be further improved. The cellulose fiber resin composite has a tensile modulus of elasticity of more preferably 2000MPa or more and a tensile strength of more preferably 38MPa or more.

Further, by using the cellulose fiber resin composite as described above, the molded body according to the present embodiment can be obtained. That is, the molded body according to the present embodiment is formed of the cellulose fiber resin composite of the present invention. As the molding method, a known molding method such as extrusion molding, injection molding, press molding, casting molding, or solvent casting can be suitably used.

[ 3 ] other configurations of dried cellulose fiber, cellulose fiber-resin composite, and molded article

The resin used when the cellulose fiber in the dried cellulose fiber is used as the filler is not limited to a vinyl resin such as polyolefin, a polycondensation resin such as polyamide, and the like, and any thermoplastic resin having a melting point of 300 ℃ or lower may be used. Further, by compounding with a transparent base material (resin) such as an epoxy resin having a refractive index equal to that of cellulose, a novel functional transparent film or transparent resin can be synthesized. In particular, the dried cellulose fiber according to the present embodiment can be combined with a polymer such as a phenol resin, polyethylene glycol, polyethylene terephthalate, or polyvinyl alcohol capable of forming a hydrogen bond, whereby the strength and surface properties of the polymer can be changed.

Further, by compounding the dried cellulose fiber according to the present embodiment with a biodegradable resin such as polylactic acid, polybutylene succinate, or polycaprolactone, the strength, heat resistance, and other properties of these resins can be improved.

According to the present embodiment, the cellulose fibers can be combined with a hydrophobic resin having a resin other than the above-described one, for example, a hydrophobic resin such as an acrylic resin, by modifying (chemically modifying) the surfaces of the cellulose fibers, for example, acetylating the cellulose fibers to impart the hydrophobic property.

In addition, a cosmetic (sunscreen cream) or a liquid crystal substrate using optical characteristics obtained by using fine cellulose fibers, or a filter using a nano-scale gap generated between cellulose fibers can be manufactured. By substituting hydroxyl groups of cellulose with various functional groups, separation/filtration materials having different properties and functions can be produced. In addition, the size of the voids can be varied by controlling the diameter of the cellulose fibers. Since the specific surface area is increased by microfibrillating cellulose fibers, it is suitable for use as an adsorbent. Since the membrane that can be dried is a porous membrane having voids controlled in the micro-scale, it can be applied to an immobilized carrier for a biocatalyst such as an enzyme, a carrier for chromatography such as separation and purification, or a cell culture substrate. The dried cellulose fiber product according to the present embodiment can be coated on the surface of an acoustic diaphragm such as a speaker to uniformly form a hard coating film, and can obtain the same effect. In order to obtain excellent acoustic characteristics, a rigid body is required to be a hard material having high strength and high elasticity and vibrating uniformly as a whole. The dried cellulose fiber product according to the present embodiment can be miniaturized while ensuring high crystallinity, and therefore, can be used as a material for an acoustic diaphragm having high elastic modulus.

Further, by combining chitosan fibers, which are cationic polymers derived from natural products, with cellulose fibers, which are anionic polymers, an effect of enhancing electrostatic attraction by charges of anions and cations is expected, and thus stronger composite fibers can be created. The most important factor regarding the strength of paper is the bonding strength between fibers, which is determined by hydrogen bonds between hydroxyl groups of cellulose. Therefore, in order to increase the strength of paper, hydrogen bonds may be added and the paper strength enhancer may be used.

The dried cellulose fiber body according to the present embodiment can be carbonized by performing a high-temperature treatment under oxygen-free conditions (under an inert gas atmosphere such as nitrogen or argon). That is, carbon fibers derived from biomass can be produced. Porous carbon containing a large number of micro-sized pores is used as a deodorizing agent, a decolorizing agent, or a filter for water purification, and in the present embodiment, bio-filamentous nanocarbon capable of carbonizing natural fibers can also be used in such fields. In addition, the porous carbon can capture not only smelly or dirty molecules in its pores (micropores) but also ions (charged atoms or molecules) by electric force. The trapped electric charges can be removed, and therefore, a large-capacity capacitor (capacitance) can be developed using the same. Such a capacitor is also used as an auxiliary power source for a fuel cell vehicle or a storage for storing surplus power at night, and therefore has attracted attention in recent years. The capacitance of the electric double layer capacitor is determined by the amount of charge accumulated in the electric double layer, and therefore, the larger the surface area of the electrode, the larger the capacitance, and therefore, activated carbon having high conductivity and specific surface area is used as the electrode material. In the present embodiment, a mesoporous activated carbon having a high specific surface area and pores controlled to a nanometer order can be used as an electrode material for dramatically improving the capacitance of an electric double layer capacitor or the like.

The cellulose fiber dried body according to the present embodiment can also be applied as a laundry detergent. From ancient times, cellulose or cellulose derivatives have been used as recontamination inhibitors in cleaning agents. The anti-redeposition agent has a function of preventing stain components detached from the object to be washed from adhering to the clothes again by the action of the surfactant of the detergent, and is an important technology accompanying the popularization of water-saving washing machines. In the present embodiment, the specific surface area is increased by microfibrillating cellulose, and thus a more effective reattachment prevention effect than that of conventional cellulose materials can be expected. In addition, cellulose has a wide range of applications, and applications to cosmetic raw materials, drug delivery vehicles, applications to food additives, coating agents for pharmaceutical preparations, heat insulating materials, catalysts, and the like are also expected.

Although the above description assumes the cellulose fiber dried product according to the present embodiment, similar effects can be obtained with chitin, chitosan, silk, carboxymethyl cellulose, and the like, which are biomass-derived materials having a similar fiber structure to cellulose.