阅读说明：本技术 阻燃化的复合纤维及其制造方法 (Flame-retardant composite fiber and method for producing same ) 是由 松本宽人 渊濑萌 永原大 于 2019-02-13 设计创作，主要内容包括：本发明的课题在于提供一种阻燃性优异的无机粒子和纤维的复合纤维。根据本发明,提供经阻燃剂处理的无机粒子和纤维的复合纤维。本发明的复合纤维中,纤维表面的15％以上被无机粒子覆盖。(The invention provides a composite fiber of inorganic particles and fibers with excellent flame retardance. According to the present invention, there is provided a composite fiber of inorganic particles and fibers treated with a flame retardant. In the composite fiber of the present invention, at least 15% of the fiber surface is covered with inorganic particles.)

1. A composite fiber obtained by treating a composite fiber of inorganic particles and fibers with a flame retardant, wherein at least 15% of the fiber surface is covered with the inorganic particles.

2. The composite fiber according to claim 1, wherein the flame retardant is a boron-based flame retardant or a silicon-based flame retardant.

3. The composite fiber according to claim 1 or 2, wherein the fiber is a cellulose fiber.

4. The composite fiber according to claim 1 or 2, wherein the inorganic particles are at least 1 kind of inorganic particles selected from barium sulfate, magnesium carbonate, and hydrotalcite.

5. The composite fiber according to any one of claims 1 to 4, wherein the inorganic particles have an average primary particle diameter of 1.5 μm or less.

6. The composite fiber according to any one of claims 1 to 5, wherein the weight ratio of the fiber to the inorganic particles is from 5/95 to 95/5.

7. The composite fiber according to any one of claims 1 to 6, which is in the form of a sheet, a molded article, a sheet or a block.

8. The composite fiber according to any one of claims 1 to 7, wherein the flame retardant is a phosphorus-based agent and/or a nitrogen-based agent.

9. The composite fiber according to any one of claims 1 to 8, wherein the inorganic particles contain calcium carbonate or silica/alumina.

10. A method for producing the composite fiber according to any one of claims 1 to 9, comprising:

and a step of treating the composite fiber of inorganic particles and fibers with a flame retardant.

11. The method according to claim 10, wherein the treatment is performed by impregnating, coating or spraying the flame retardant.

12. The method of claim 10, comprising: and a step of synthesizing inorganic particles in a fiber-containing liquid to obtain the composite fiber.

Technical Field

The present invention relates to a flame-retardant conjugate fiber and a method for producing the same. In particular, the present invention relates to flame-retardant inorganic particles, fiber composite fibers, and methods for producing the same.

Background

Techniques for improving the flame resistance of materials are being studied in various fields. For example, wood materials such as wood and natural fibers are relatively easily combustible, and therefore they are treated with a chemical such as a flame retardant to be hardly combustible (patent documents 1 to 2).

On the other hand, fibers represented by wood fibers exhibit various properties based on functional groups and the like on the surface thereof, and it is sometimes necessary to modify the surface depending on the application, and a technique for modifying the surface of the fibers has been developed. For example, patent document 3 describes a composite in which crystalline calcium carbonate is mechanically bonded to fibers as a technique for depositing inorganic particles on fibers such as cellulose fibers. Patent document 4 describes a technique for producing a composite of pulp and calcium carbonate by precipitating calcium carbonate in a pulp suspension by a carbon dioxide method.

Disclosure of Invention

However, conventionally, when fibers are treated with a flame retardant or the like, the fibers tend to become hard and brittle, and the soft characteristics of the fibers are impaired. Further, the fibers treated with the noncombustible agent are difficult to be printed, and for example, it is difficult to perform processing such as printing on a noncombustible fiber sheet, and therefore the use thereof is sometimes limited.

In view of such circumstances, an object of the present invention is to provide a flame retardant material which maintains the flexibility of fibers and has excellent printing suitability.

As a result of intensive studies on the above problems, it has been found that the above problems can be solved by using a composite (composite fiber) of inorganic particles and fibers as a base material without using paper, and the present invention has been completed. The present invention is not limited to this, but includes the following inventions.

(1) A composite fiber obtained by treating a composite fiber of inorganic particles and fibers with a flame retardant, wherein at least 15% of the fiber surface is covered with inorganic particles.

(2) The composite fiber according to (1), wherein the flame retardant is a boron-based flame retardant or a silicon-based flame retardant.

(3) The composite fiber according to (1) or (2), wherein the fiber is a cellulose fiber.

(4) The composite fiber according to (1) or (2), wherein the inorganic particles are at least 1 kind of inorganic particles selected from barium sulfate, magnesium carbonate, and hydrotalcite.

(5) The composite fiber according to any one of (1) to (4), wherein the inorganic particles have an average primary particle diameter of 1.5 μm or less.

(6) The composite fiber according to any one of (1) to (5), wherein the weight ratio of the fiber to the inorganic particles is 5/95 to 95/5.

(7) The composite fiber according to any one of (1) to (6), which is in the form of a sheet, a molded article, a sheet or a block.

(8) The composite fiber according to any one of (1) to (7), wherein the flame retardant is a phosphorus-based chemical and/or a nitrogen-based chemical.

(9) The composite fiber according to any one of (1) to (8), wherein the inorganic particles contain calcium carbonate or silica/alumina.

(10) A method for producing the composite fiber according to any one of (1) to (9), comprising: and a step of treating the composite fiber of inorganic particles and fibers with a flame retardant.

(11) The method according to (10), wherein the treatment is performed by impregnating, coating or spraying the flame retardant.

(12) The method according to (10), comprising: and a step of synthesizing inorganic particles in a fiber-containing liquid to obtain the composite fiber.

According to the present invention, by using a composite material in which the fiber surface is covered with inorganic particles, the respective fibers are hardly burned by the inorganic particles, and a particularly excellent flame-retardant sheet can be obtained. Further, when the composite fiber of the present invention is formed into a sheet, not only fibers but also inorganic particles are present at a high density, and therefore, the inorganic particles are sandwiched between fibers that become hard and brittle by the flame retardant, and flexibility can be maintained, and by forming the composite fiber sheet into a substrate, deterioration of bleeding and color development due to treatment with a chemical agent is suppressed at the time of inkjet printing, and a composite fiber sheet having excellent printing quality can be obtained.

Drawings

FIG. 1 is a schematic diagram of a synthesis apparatus used in the experiment.

FIG. 2 is a schematic diagram of a synthesis apparatus used in the experiment.

FIG. 3 is an electron micrograph (left: 3000 times, right: 50000 times) of the complex (sample 1) used in the experiment.

FIG. 4 is an electron micrograph (left: 3000 times, right: 10000 times) of the complex (sample 2) used in the experiment.

FIG. 5 is an electron micrograph (left: 3000 times, right: 50000 times) of the complex (sample 3) used in the experiment.

FIG. 6 is an electron micrograph (left: 3000 times, right: 50000 times) of the complex (sample 4) used in the experiment.

FIG. 7 is an electron micrograph (left: 3000 times, right: 50000 times) of the complex (sample 5) used in the experiment.

Fig. 8 is a schematic diagram of an apparatus used in the synthesis of sample 6.

FIG. 9 is a schematic view of an apparatus used in the synthesis of sample 6 (ultrafine bubble generating apparatus).

FIG. 10 is an electron micrograph (left: 3000 times, right: 50000 times) of the complex (sample 6) used in the experiment.

Fig. 11 is a photograph showing the state of the combustibility test of experiment 3.

Fig. 12 is a photograph showing the state of the combustibility test of experiment 3.

Fig. 13 is a photograph showing the results of the combustibility test of experiment 3.

Fig. 14 is a photograph showing the state of the combustibility test of experiment 3.

Fig. 15 is a photograph showing the state of the combustibility test of experiment 3.

Fig. 16 is a photograph showing the state of the combustibility test of experiment 3.

Detailed Description

The present invention relates to a composite fiber (composite) treated with a flame retardant. In the present invention, by using a composite fiber in which inorganic particles are fixed to a fiber as a base material, a fiber product having excellent printability even after treatment with a flame retardant can be obtained.

Flame retardant

In the present invention, "flame-retardant" means that the material is difficult to burn, "flame-retardant composition (also referred to as" flame retardant "or" flame retardant ")" is an additive for making the material difficult to burn. Regulations have been established for detailed reference, evaluation methods for "flame retardancy" have been standardized according to materials and their use. In the present invention, terms such as "non-combustible" indicating that flame combustion cannot be performed, "flame-proof" indicating that flame does not extend, and other terms such as "fire-proof" and "fire-proof" are used, and all of these terms are included and defined as "flame-retardant".

The flame retardant is sometimes called a noncombustible agent, and is an agent for improving the flame resistance of a treated product. The composite fiber is treated by the flame retardant. The flame retardant to be used is not particularly limited, and examples thereof include boron-based flame retardants containing a boron atom such as boric acid or a salt thereof, polyborate, and zinc borate. Silicon-based flame retardants containing silicon atoms such as silicates and silicones can be preferably used. In addition, guanidine or a salt thereof, nitrogen-containing flame retardants such as ammonium sulfate and melamine sulfate, phosphoric acid or a salt thereof, polyphosphates, diethyl ethylphosphonate, dimethyl (methacryloyloxyethyl phosphate), diethyl-2- (acryloyloxy) ethyl phosphate, triethyl phosphate, diethyl-2- (methacryloyloxyethyl) phosphate, triphenyl phosphate, tricresyl phosphate, phosphoric acid esters, phosphorus-containing flame retardants such as red phosphorus, compounds containing phosphorus and nitrogen elements (melamine phosphate, guanidine phosphate, guanylurea phosphate, melamine metaphosphate, melamine polyphosphate, melamine-coated ammonium polyphosphate), halogen-containing amine acid salts such as guanidine hydrochloride and guanidine hydrobromide, decabromodiphenyl ether, tetrabromobisphenol A, hexabromocyclododecane, ethylenebis (tetrabromophthalimide), and the like can be mentioned, Bromine flame retardants such as bis (pentabromophenyl) ethane and hexabromobenzene, flame retardants composed of compounds containing 2 or more of the above-mentioned elements such as ammonium salts of ammonium phosphate, ammonium sulfate, ammonium borate, ammonium sulfamate, ammonium chloride and ammonium polyphosphate, inorganic flame retardants such as hydrated metal compounds such as hydrated aluminum hydroxide, hydrated magnesium hydroxide and hydrotalcite, antimony-containing compounds such as antimony trioxide, antimony tetraoxide and antimony pentoxide, tin compounds such as zinc stannate hydroxide and tin zinc trioxide, and metal compounds used for general pigments such as titanium oxide.

Among the above flame retardants, a chemical agent containing a boron atom (boron-based flame retardant) and a chemical agent containing a silicon atom (silicon-based flame retardant), or a chemical agent containing a phosphorus atom (phosphorus-based flame retardant) and a chemical agent containing a nitrogen atom (nitrogen-based flame retardant) generates little toxic gas during combustion, and is low in environmental load, and is suitable for flame retardant treatment of various materials. Further, boron-based flame retardants and silicon-based flame retardants are known to have good compatibility with saccharide compounds represented by cellulose and the like. The reason for this is that, as described in jp 2006-233006 a, a heat insulating coating is formed by dehydrating hydroxyl groups at high temperatures during combustion, releasing water to exhibit a cooling effect and generating a carbonized layer.

The flame retardants may be used in combination with different flame retardants or in combination with a flame retardant aid, and the amount of the flame retardants may be adjusted depending on the desired performance. The amount of the organic solvent used is, for example, 1 to 50% by weight, preferably 5 to 45% by weight, and more preferably 10 to 40% by weight, based on the weight of the substrate. If the amount is 1% or less, it is difficult to impart sufficient flame retardancy, and if it is 50% or more, the cost becomes high, which is not preferable.

These flame retardants can be treated by impregnation, coating, or spraying, for example, in the case of a liquid, and a general impregnation or coating (painting) method can be used as a method for the treatment. For example, flame retardants are imparted using coaters such as forward roll coaters, air knife coaters, paper currency knife coaters, double-flow coaters, double-edge coaters, rod coaters (rod coaters), gate roll coaters, reverse roll coaters, gravure roll coaters, notch bar coaters (notch bar coaters), die coaters, droplet coaters, curtain coaters, dip coaters, electrostatic coaters, spray coaters, and the like.

The timing of performing the flame-retardant treatment may be any of before, during, and after molding into a sheet, molded article, plate, block, or the like. If the treatment is performed before or during the molding, the process can be shortened, and if the treatment is performed after the molding, the content of the flame retardant can be easily adjusted.

Composite fiber having surface covered with inorganic particles

The present invention uses a fiber whose surface is covered with inorganic particles. In particular, in a preferred embodiment of the present invention, a fiber-inorganic composite in which at least 15% of the fiber surface is covered with inorganic particles is used.

The composite fiber of the present invention is not a fiber and inorganic particles simply mixed together, but a fiber and inorganic particles are bonded by hydrogen bonds or the like, and inorganic particles are less likely to fall off from the fiber even after a dissociation treatment or the like. The strength of the bond between the fibers of the composite and the inorganic particles can be evaluated by, for example, the ash retention (% i.e., ash of sheet ÷ ash of composite before dissociation × 100). Specifically, the composite may be dispersed in water to adjust the solid content concentration to 0.2%, as measured in accordance with JIS P8220-1: 2012 for 5 minutes, according to JIS P8222: 2015 is formed into a sheet by using a 150-mesh wire net, and the ash retention at this time is used for evaluation, and in a preferred embodiment, the ash retention is 20 mass% or more, and in a more preferred embodiment, the ash retention is 50 mass% or more.

(inorganic particles)

In the present invention, the inorganic particles to be combined with the fibers are not particularly limited, and are preferably insoluble or poorly soluble in water. Since inorganic particles are sometimes synthesized in an aqueous system and a fiber composite is sometimes used in an aqueous system, it is preferable that the inorganic particles be insoluble or poorly soluble in water.

The inorganic particles referred to herein mean a metal or a metal compound. In addition, the metal compound is a cation of a metal (e.g., Na)⁺、Ca²⁺、Mg²⁺、Al³⁺、Ba²⁺Etc.) and anions (e.g., O)^2-、OH^-、CO₃ ^2-、PO₄ ^3-、SO₄ ^2-、NO₃－、Si₂O₃ ^2-、SiO₃ ^2-、Cl^-、F^-、S^2-Etc.) are bonded by ionic bonds and are generally referred to as inorganic salts. In the present invention, at least a part of the inorganic particles is preferably a metal salt of calcium, magnesium, or barium, or at least a part of the inorganic particles is preferably a metal salt of silicic acid or aluminum, or a metal particle containing titanium, copper, silver, iron, manganese, or zinc.

The method for synthesizing these inorganic particles can be any of known methods, gas-liquid method and liquid-liquid method. As an example of the gas-liquid method, there is a carbon dioxide method, and for example, magnesium carbonate can be synthesized by reacting magnesium hydroxide with carbon dioxide. Examples of the liquid-liquid method include a method in which an acid (hydrochloric acid, sulfuric acid, etc.) and a base (sodium hydroxide, potassium hydroxide, etc.) are neutralized and reacted to react an inorganic salt with the acid or the base, or inorganic salts are reacted with each other. For example, barium sulfate may be obtained by reacting barium hydroxide with sulfuric acid, aluminum hydroxide may be obtained by reacting aluminum sulfate with sodium hydroxide, or calcium carbonate may be obtained by reacting calcium carbonate with aluminum sulfate to obtain inorganic particles in which calcium and aluminum are combined. In addition, when the inorganic particles are synthesized in this manner, any metal or metal compound may coexist in the reaction solution, and in this case, the metal or metal compound can be efficiently incorporated into the inorganic particles to be composited therewith. For example, when calcium phosphate is synthesized by adding phosphoric acid to calcium carbonate, composite particles of calcium phosphate and titanium can be obtained by allowing titanium dioxide to coexist in the reaction solution.

In the case of synthesizing calcium carbonate, calcium carbonate can be synthesized by, for example, a carbon dioxide method, a soluble salt reaction method, a lime soda method, a soda method, or the like, and in a preferred embodiment, calcium carbonate is synthesized by a carbon dioxide method.

In general, when calcium carbonate is produced by the carbon dioxide method, lime (lime) is used as a calcium source, and water is added to CaO of quicklime to obtain slaked lime Ca (OH)₂And blowing carbon dioxide CO into the slaked lime₂To obtain calcium carbonate CaCO₃The carbonation step of (2) to synthesize calcium carbonate. At this time, a suspension of slaked lime prepared by adding water to quick lime is passed through a screen to remove lime particles having low solubility contained in the suspension. In addition, slaked lime may be used directly as the calcium source. In the present invention, when calcium carbonate is synthesized by the carbon dioxide method, the carbonation reaction may be carried out in the presence of cavitation bubbles.

Generally, as a reaction vessel (carbonator: carbonator) for producing calcium carbonate by the carbon dioxide method, an air-blowing type carbonator and a mechanical stirring type carbonator are known. In the air-blowing carbonator, carbon dioxide is blown into a carbonation reaction tank to which a slaked lime suspension (lime milk) is added to react slaked lime with carbon dioxide, but it is difficult to control the size of bubbles to be uniform and fine by simply blowing carbon dioxide, and there is a limitation in terms of reaction efficiency. On the other hand, in the mechanical agitation type carbonator, a stirrer is provided inside the carbonator, and carbon dioxide is introduced into the vicinity of the stirrer, thereby making the carbon dioxide fine bubbles and improving the reaction efficiency between slaked lime and carbon dioxide ("handbook of cement, gypsum and lime", published by the handbook of cement, gypsum and lime, 1995, page 495).

However, when stirring is performed by a stirrer provided inside a carbonation reaction tank, such as a mechanical stirring type carbonator, since the concentration of the reaction liquid is high or the resistance of the reaction liquid is large during the carbonation reaction and it is difficult to sufficiently stir the reaction liquid, it is difficult to reliably control the carbonation reaction or a considerable load is applied to the stirrer to sufficiently stir the reaction liquid, which is disadvantageous in terms of energy. Further, the gas injection port is located at the lower part of the carbonator, and a blade of a stirrer is provided near the bottom of the carbonator for sufficient stirring. Lime screen residues with low solubility settle quickly and often settle at the bottom, blocking the gas blow-in or disrupting the balance of the blender. Further, the conventional method requires a stirrer and a facility for introducing carbon dioxide into the carbonator in addition to the carbonator, which results in a cost-consuming facility. In addition, in the mechanical stirring type carbonator, the reaction efficiency between slaked lime and carbon dioxide is improved by refining carbon dioxide supplied to the vicinity of the stirrer by the stirrer, but when the concentration of the reaction solution is high, etc., it is not possible to sufficiently refine carbon dioxide, and it is difficult to precisely control the form of calcium carbonate produced in the carbonation reaction. By synthesizing calcium carbonate in the presence of cavitation bubbles, the carbonation reaction can be efficiently performed, and uniform calcium carbonate fine particles can be produced. In particular, by using the cavitation jet, sufficient stirring can be performed without using a mechanical stirrer such as a blade. In the present invention, a conventionally known reaction vessel may be used, but of course, the above-described air-blowing carbonator and mechanical agitation type carbonator may be used without any problem, and a cavitation jet using a nozzle or the like may be combined with these vessels.

When calcium carbonate is synthesized by the carbon dioxide method, the solid content concentration of the aqueous suspension of slaked lime is preferably 0.1 to 40% by weight, more preferably 0.5 to 30% by weight, and still more preferably about 1 to 20% by weight. If the solid content concentration is low, the reaction efficiency is low and the production cost is high, and if the solid content concentration is too high, the fluidity is deteriorated and the reaction efficiency is lowered. When calcium carbonate is synthesized in the presence of cavitation bubbles, the reaction solution and carbon dioxide can be appropriately mixed even if a suspension (slurry) having a high solid content concentration is used.

As the aqueous suspension containing hydrated lime, an aqueous suspension generally used in calcium carbonate synthesis, for example, prepared by mixing hydrated lime in water or prepared by digesting quick lime (calcium oxide) with water (slaking), can be used. The conditions for digestion are not particularly limited, and for example, the CaO concentration may be 0.1 wt% or more, preferably 1 wt% or more, and the temperature may be 20 to 100 ℃, preferably 30 to 100 ℃. The average residence time in the digestion reaction tank (digestion drum) is also not particularly limited, and may be, for example, 5 minutes to 5 hours, preferably within 2 hours. Of course, the digesting drum may be either batch-wise or continuous. In the present invention, the carbonation reaction tank (carbonator) and the digestion reaction tank (digestion drum) may be separated from each other, and one reaction tank may be used as the carbonation reaction tank and the digestion reaction tank.

In the synthesis of magnesium carbonate, a known method can be used for the synthesis of magnesium carbonate. For example, magnesium bicarbonate can be synthesized from magnesium hydroxide and carbon dioxide, and basic magnesium carbonate can be synthesized from magnesium bicarbonate via magnesium ortho carbonate. Magnesium carbonate magnesium bicarbonate, magnesium carbonate, basic magnesium carbonate, and the like can be obtained by a synthetic method, and the magnesium carbonate of the composite fiber of the present invention is preferably basic magnesium carbonate. This is because magnesium bicarbonate has low stability, and a columnar (needle-like) crystal magnesium carbonate is sometimes difficult to fix on a fiber. On the other hand, the chemical reaction to the basic magnesium carbonate in the presence of the fiber can provide a composite fiber of magnesium carbonate and fiber in a form of a scale-like shape or the like covering the fiber surface.

In the present invention, the reaction solution in the reaction tank may be circulated and used. By circulating the reaction solution in this way and increasing the contact between the reaction solution and carbon dioxide, the reaction efficiency is improved and desired inorganic particles are easily obtained.

In the present invention, a gas such as carbon dioxide (carbon dioxide) may be blown into the reaction vessel and mixed with the reaction solution. According to the present invention, carbon dioxide can be supplied to the reaction solution without a gas supply device such as a fan or a blower, and the carbon dioxide can be made fine by cavitation bubbles or ultrafine bubbles, so that the reaction can be efficiently performed.

In the present invention, the carbon dioxide concentration of the carbon dioxide-containing gas is not particularly limited, and a high carbon dioxide concentration is preferred. The amount of carbon dioxide introduced into the injector is not limited, and may be appropriately selected, and for example, it is preferable to use carbon dioxide at a flow rate of 100 to 10000L/hr per 1kg of slaked lime.

The carbon dioxide-containing gas of the present invention may be not substantially pure carbon dioxide gas, but may be a mixture with other gases. For example, as the gas containing carbon dioxide, air or a gas containing an inert gas such as nitrogen can be used in addition to carbon dioxide gas. As the carbon dioxide-containing gas, in addition to carbon dioxide gas (carbon dioxide), exhaust gas discharged from an incinerator of a paper mill, a coal-fired boiler, a heavy oil boiler, or the like can be suitably used as the carbon dioxide-containing gas. In addition, the carbonation reaction may be performed using carbon dioxide generated from the lime calcination step.

Synthesis of barium sulfate (BaSO)₄) In the case of (B), it is prepared from barium sulfate (BaSO)₄) The ionic crystalline compound composed of barium ions and sulfate ions is often in the form of a plate or a column, and is hardly soluble in water. Pure barium sulfate is colorless crystals, but if it contains impurities such as iron, manganese, strontium, and calcium, it is yellowish brown or dark gray, and translucent. Can be obtained as a natural mineral, but can also be synthesized by chemical reactions. In particular, synthetic products obtained by chemical reactions are widely used in paints, plastics, secondary batteries, and the like, taking advantage of their chemically stable properties in addition to medical applications (X-ray contrast agents).

In the present invention, a composite fiber of barium sulfate and fiber can be produced by synthesizing barium sulfate in a solution in the presence of fiber. For example, there is a method of reacting by neutralizing an acid (sulfuric acid or the like) and a base, or reacting an inorganic salt with an acid or a base, or reacting inorganic salts with each other. For example, barium sulfate may be obtained by reacting barium hydroxide with sulfuric acid or aluminum sulfate, or barium chloride may be added to an aqueous solution containing a sulfate to precipitate barium sulfate.

In the synthesis of hydrotalcite, a known method can be used for the synthesis of hydrotalcite. For example, hydrotalcite is synthesized by immersing fibers in an aqueous carbonate solution containing carbonate ions constituting the intermediate layer and an alkaline solution (sodium hydroxide or the like) in a reaction vessel, adding an acid solution (an aqueous metal salt solution containing divalent metal ions and trivalent metal ions constituting the base layer), and controlling the temperature, pH, or the like, and performing a coprecipitation reaction. In addition, the fibers may be impregnated in an acid solution (aqueous metal salt solution containing divalent metal ions and trivalent metal ions constituting the base layer) in a reaction vessel, and then an aqueous carbonate solution containing carbonate ions constituting the intermediate layer and an alkaline solution (sodium hydroxide or the like) may be added dropwise thereto, and hydrotalcite may be synthesized by coprecipitation reaction while controlling the temperature, pH, or the like. In general, the reaction is carried out under normal pressure, but in addition to this, there is a method of obtaining the product by hydrothermal reaction using an autoclave or the like (Japanese patent application laid-open No. 60-6619).

In the present invention, as a supply source of the divalent metal ions constituting the base layer, various chlorides, sulfides, nitrates, and oxysulfides of magnesium, zinc, barium, calcium, iron, copper, cobalt, nickel, and manganese can be used. As a source of the trivalent metal ion constituting the base layer, various chlorides, sulfides, nitrates, and sulfoxides of aluminum, iron, chromium, and gallium can be used.

In the present invention, as the interlayer anion, a carbonate ion, a nitrate ion, a chloride ion, a sulfate ion, a phosphate ion, or the like can be used as an anion. When carbonate ions are used as interlayer anions, sodium carbonate is used as a supply source. However, the sodium carbonate may be replaced by a gas containing carbon dioxide (carbon dioxide), which may be substantially pure carbon dioxide gas or a mixture with other gases. For example, exhaust gas discharged from an incinerator of a paper mill, a coal-fired boiler, a heavy oil boiler, or the like can be suitably used as the gas containing carbon dioxide. In addition to this, the carbonation reaction may be performed using carbon dioxide generated from the lime calcination process.

In the synthesis of alumina and/or silica, at least one of an inorganic acid and an aluminum salt is used as a starting material for the reaction, and an alkali metal silicate is added thereto. It is also possible to use alkali metal silicates as starting materials, with the addition of inorganic substancesThe acid or the aluminum salt is synthesized at least one of, but when the inorganic acid and/or the aluminum salt is used as a starting material, the fixation of the product to the fiber is good. The silica and/or alumina composite fiber obtained in the present invention has Si/Al of 4 or more as a result of measuring ash content of 2 hours of baking in an electric furnace at 525 ℃ by fluorescence X-ray diffraction. Preferably 4 to 30, more preferably 4 to 20, and still more preferably 4 to 10. Further, since the silica and/or alumina obtained in the present invention is amorphous, no clear peak derived from the crystal is detected when the ash is measured by X-ray diffraction. The inorganic acid is not particularly limited, and for example, sulfuric acid, hydrochloric acid, nitric acid, or the like can be used. Among these, sulfuric acid is particularly preferable in view of cost and handling. Examples of the aluminum salt include aluminum sulfate, aluminum chloride, polyaluminum chloride, alum, potassium alum, and the like, and among them, aluminum sulfate is preferably used. The alkali metal silicate includes sodium silicate and potassium silicate, and sodium silicate is preferred because of its ready availability. The molar ratio of the silicic acid to the alkali metal may be arbitrary, and usually the (Japanese) commercial silicic acid No. 3 is SiO₂:Na₂O is 3-3.4: a molar ratio of about 1 can be preferably used. In the present invention, water is used for preparation of a suspension or the like, but as the water, ordinary tap water, industrial water, underground water, well water or the like can be used, and further, ion-exchanged water, distilled water, ultrapure water, industrial wastewater, water obtained in a carbonization process can be suitably used.

In the synthesis of calcium sulfate, a known method can be used for the synthesis of calcium sulfate. For example, a fiber is immersed in a reaction vessel, and calcium sulfate is synthesized in the system as a salt obtained by a neutralization reaction of sulfuric acid and calcium hydroxide.

In the synthesis of calcium silicate, a known method can be used for the synthesis of calcium silicate. For example, it can be obtained by hydrothermal synthesis by charging a calcium source such as calcium oxide or calcium hydroxide and a silica source such as α -quartz into an autoclave.

The composite fiber of the present invention can be obtained by synthesizing inorganic particles in the presence of a fiber such as a cellulose fiber. This is because the fiber surface is a place suitable for precipitation of inorganic particles, and therefore composite fibers are easily synthesized. As a method for synthesizing the composite fiber, for example, a solution containing the fiber and the precursor of the inorganic particle may be stirred and mixed in an open-type reaction tank to synthesize a composite, or an aqueous suspension containing the fiber and the precursor of the inorganic particle may be sprayed into a reaction vessel to synthesize the composite fiber. As described later, when an aqueous suspension of a precursor of an inorganic substance is injected into a reaction vessel, cavitation bubbles or ultrafine bubbles may be generated, and inorganic particles may be synthesized in the presence of the cavitation bubbles or ultrafine bubbles.

In the present invention, the liquid may be ejected under the condition that cavitation bubbles or ultrafine bubbles are generated in the reaction vessel, or may be ejected under the condition that cavitation bubbles or ultrafine bubbles are not generated. In any case, the reaction vessel is preferably a pressure vessel. The pressure vessel in the present invention is a vessel capable of applying a pressure of 0.005MPa or more. Under the condition that cavitation bubbles are not generated, the pressure in the pressure vessel is preferably 0.005MPa to 0.9MPa in terms of static pressure.

(cavitation bubbles)

When the composite fiber of the present invention is synthesized, inorganic particles can be precipitated in the presence of cavitation bubbles. The cavitation in the present invention refers to a physical phenomenon in which bubbles are generated and disappear in a short time due to a pressure difference in the flow of a fluid, and is also referred to as a cavitation phenomenon. Bubbles (cavitation bubbles) generated by cavitation are generated by using as nuclei extremely minute "bubble nuclei" of 100 μm or less existing in a liquid when the pressure in the liquid becomes lower than the saturated vapor pressure in an extremely short time.

In the present invention, cavitation bubbles can be generated in the reaction vessel by a known method. For example, cavitation bubbles may be generated by ejecting a fluid under high pressure, cavitation may be generated by high-speed stirring in the fluid, cavitation may be generated by explosion in the fluid, and cavitation (vibration/cavitation) may be generated by an ultrasonic transducer.

In particular, in the present invention, in order to facilitate generation and control of cavitation bubbles, it is preferable to generate cavitation bubbles by ejecting a fluid under high pressure. In this embodiment, by compressing the ejection liquid using a pump or the like and ejecting the liquid at a high speed through a nozzle or the like, cavitation bubbles are generated along with expansion of the liquid itself due to an extremely high shear force and a rapid pressure reduction in the vicinity of the nozzle. The method of generating cavitation bubbles by using a fluid jet can generate cavitation bubbles having high efficiency of generating cavitation bubbles and having a stronger bursting impact force. In the present invention, controlled cavitation bubbles exist during the synthesis of inorganic particles, which is significantly different from cavitation bubbles that are naturally generated by fluid machinery and bring uncontrollable hazards.

In the present invention, the reaction solution such as the raw material may be used as it is as a jet liquid to generate cavitation, or some fluid may be jetted into the reaction vessel to generate cavitation bubbles. The fluid that forms the jet flow by the liquid jet flow may be any of a liquid, a gas, a solid such as powder or pulp, and may be a mixture thereof, as long as it is in a fluid state. If desired, other fluids such as carbon dioxide may be added as a new fluid to the above fluid. The fluid and the new fluid may be uniformly mixed and ejected, but may be ejected separately.

The liquid jet refers to a jet of solid particles, gas dispersed or mixed in liquid or fluid in liquid, and is a jet of pulp, raw material slurry of inorganic particles, or liquid containing bubbles. The gas referred to herein may contain bubbles generated by cavitation.

Cavitation is the occurrence when a liquid is accelerated and the local pressure becomes lower than the vapor pressure of the liquid, so the flow rate pressure is particularly important. Therefore, the basic dimensionless Number and Cavitation Number (Cavitation Number) σ indicating the Cavitation state are defined by the following mathematical formula 1 (jia tengyang institute "new Cavitation foundation and recent advancement", Maki bookstore, 1999).

[ mathematical formula 1]

Here, a large cavitation number indicates that the flow field is in a state where cavitation is difficult to generate. Particularly, when cavitation is generated by a nozzle or an orifice tube such as a cavitation jet, the cavitation number σ can be rewritten to the following formula (2) depending on the nozzle upstream pressure p1, the nozzle downstream pressure p2, and the saturated vapor pressure pv of the sample water, and the pressure difference between p1, p2, and pv in the cavitation jet is large, and p1 ≧ p2 ≧ pv, so the cavitation number σ can be further approximated to the following formula 2(h.soyama, j.soc.mat.sci.japan,47(4),381,1998).

[ mathematical formula 2]

In the present invention, the cavitation condition is preferably 0.001 to 0.5, preferably 0.003 to 0.2, and particularly preferably 0.01 to 0.1. When the cavitation number σ is less than 0.001, the effect is small because the pressure difference with the surroundings is low when cavitation bubbles are collapsed, and when it exceeds 0.5, the pressure difference of the flow is low and cavitation is hard to occur.

When cavitation is generated by injecting the injection liquid through the nozzle or orifice tube, the pressure of the injection liquid (upstream pressure) is preferably 0.01 to 30MPa, more preferably 0.7 to 20MPa, and still more preferably 2 to 15 MPa. When the upstream pressure is less than 0.01MPa, a pressure difference between the upstream pressure and the downstream pressure is hardly generated, and the effect is small. In addition, if the pressure exceeds 30MPa, a special pump and a pressure vessel are required, and the energy consumption increases, which is disadvantageous in terms of cost. On the other hand, the pressure in the container (downstream side pressure) is preferably 0.005MPa to 0.9MPa in terms of static pressure. Further, the ratio of the pressure in the container to the pressure of the ejection liquid is preferably in the range of 0.001 to 0.5.

In the present invention, inorganic particles may be synthesized by spraying the spray liquid without generating cavitation bubbles. Specifically, the pressure of the injection liquid (upstream pressure) is set to 2MPa or less, preferably 1MPa or less, and the pressure of the injection liquid (downstream pressure) is opened, more preferably 0.05MPa or less.

The velocity of the jet of the ejection liquid is preferably in the range of 1 m/sec to 200 m/sec, and more preferably in the range of 20 m/sec to 100 m/sec. When the jet velocity is less than 1 m/sec, the effect is weak because the pressure drop is small and cavitation is hard to occur. On the other hand, if it exceeds 200 m/sec, high pressure is required and a special apparatus is required, which is disadvantageous in cost.

The cavitation generation site in the present invention may be generated in a reaction vessel for synthesizing inorganic particles. Further, the treatment may be performed once or may be performed in a cycle as many times as necessary. Further, multiple generation mechanisms may be used to perform the process in parallel or in series.

The spraying of the liquid for generating cavitation may be carried out in a vessel open to the atmosphere, but is preferably carried out in a pressure vessel for controlling cavitation.

When cavitation is generated by liquid jetting, the solid content concentration of the reaction solution is preferably 30% by weight or less, more preferably 20% by weight or less. When the concentration is such a range, the cavitation bubbles are likely to act uniformly in the reaction system. In view of the reaction efficiency, the solid content concentration of the aqueous suspension of slaked lime as the reaction solution is preferably 0.1 wt% or more.

In the present invention, for example, when a composite of calcium carbonate and cellulose fiber is synthesized, the pH of the reaction solution is on the alkaline side at the start of the reaction, but becomes neutral as the carbonation reaction proceeds. Therefore, the reaction can be controlled by monitoring the pH of the reaction solution.

In the present invention, the flow velocity of the liquid to be ejected can be increased by increasing the ejection pressure of the liquid, and the pressure is reduced accordingly, thereby generating stronger cavitation. Further, by increasing the pressure in the reaction vessel, the pressure in the region where the cavitation bubbles are broken can be increased, and the pressure difference between the bubbles and the surroundings becomes large, so that the bubbles are broken vigorously to increase the impact force. Further, dissolution and dispersion of the introduced carbon dioxide can be promoted. The reaction temperature is preferably from 0 ℃ to 90 ℃ and particularly preferably from 10 ℃ to 60 ℃. In general, since the impact force is considered to be the largest at the midpoint between the melting point and the boiling point, it is preferable that the impact force is about 50 ℃ in the case of an aqueous solution, and even at a temperature of not higher than this, a high effect can be obtained as long as the impact force is within the above range.

In the present invention, the energy required for generating cavitation can be reduced by adding a surfactant. Examples of the surfactant to be used include known or novel surfactants, for example, nonionic surfactants such as fatty acid salts, higher alkyl sulfate salts, alkylbenzenesulfonates, higher alcohols, alkylphenols, alkylene oxide adducts of fatty acids, etc., anionic surfactants, cationic surfactants, amphoteric surfactants, and the like. The composition may be composed of a single component of these, or may be a mixture of 2 or more components. The amount of addition may be any amount necessary for reducing the surface tension of the ejection liquid and/or the ejection target liquid.

In a preferred embodiment, the average primary particle size of the inorganic particles in the composite fiber of the present invention may be, for example, 1.5 μm or less, but the average primary particle size may be 1200nm or less, 900nm or less, 700nm or less, 500nm or less, or 300nm or less, or further 200nm or less, 150nm or less, or 100 nm. The inorganic particles may have an average primary particle diameter of 10nm or more, 30nm or more, or 50nm or more. The average primary particle size can be measured by electron micrograph.

In addition, the inorganic particles in the composite fiber of the present invention may be in the form of secondary particles obtained by aggregating fine primary particles, and secondary particles corresponding to the application may be produced in the aging step, or aggregates may be made finer by pulverization. Examples of the pulverization method include a ball MILL, a sand MILL, an impact MILL, a high-pressure homogenizer, a low-pressure homogenizer, DYNO-MILL, an ultrasonic MILL, Kanda grind, an attritor, a mortar-type MILL, a vibration MILL, a chopper, a jet MILL, a pulverizer, a beater, a short-shaft extruder, a twin-shaft extruder, an ultrasonic mixer, and a home-use juicer.

(fiber)

The composite fiber used in the present invention is obtained by combining cellulose fibers and inorganic particles. As the cellulose fibers constituting the conjugate fibers, natural cellulose fibers can be used, and regenerated fibers (semi-synthetic fibers) such as rayon and lyocell, synthetic fibers, and the like can be used without limitation. Examples of the raw material of the cellulose fiber include pulp fibers derived from plants, cellulose nanofibers, bacterial cellulose, cellulose derived from animals such as ascidians, and algae, and the wood pulp may be produced by pulping the wood raw material. Examples of the wood material include needle-leaved trees such as red pine, black pine, fir, spruce, red pine, larch, japanese fir, hemlock, japanese cedar, japanese cypress, larch, white fir, scale spruce, cypress, douglas fir, canadian hemlock, white fir, spruce, balsam fir, cedar, pine, southern pine, radiata pine, and mixtures thereof, and broad-leaved trees such as japanese beech, birch, japanese alder, oak, red-leaf nanmu, chestnut, white birch, black poplar, water chestnut, sweet poplar, red tree, eucalyptus, acacia, and mixtures thereof.

The method for pulping natural materials such as wood materials (wood materials) is not particularly limited, and examples thereof include pulping methods generally used in the paper industry. Wood pulp can be classified by a pulping method, and examples thereof include chemical pulp obtained by cooking by a method such as a kraft method, sulfite method, soda method, polysulfide method, or the like; mechanical pulp obtained by pulping with mechanical force of a refiner, a grinder, or the like; a semichemical pulp obtained by mechanical pulping after pretreatment with a chemical; waste paper pulp; deinked pulp, and the like. The wood pulp may be unbleached (before bleaching) or bleached (after bleaching).

Examples of the pulp derived from non-wood include cotton, hemp, sisal, abaca, flax, straw, bamboo, bagasse, kenaf, sugarcane, corn, rice stem, broussonetia papyrifera (grape flat), and daphne.

The pulp fiber may be either unbleached or beaten, and may be selected depending on the physical properties of the composite fiber. By beating, the strength at the time of sheeting, the BET specific surface area, and the inorganic particles can be improved, and fixation of the inorganic particles can be promoted. On the other hand, the composite fiber is used without beating, so that the risk of inorganic substances being detached together with the fibrils when the composite fiber is stirred and/or kneaded in a matrix can be suppressed, and the strength-improving effect is increased because the fiber length is kept long when the composite fiber is used as a reinforcing material such as cement. The degree of beating of the fibers can be determined by JIS P8121-2: 2012 for Canadian Standard Freeness (CSF). As beating proceeds, the water cut-off state of the fibers decreases and the freeness becomes lower. The fiber used for the synthesis of the conjugate fiber may have any degree of drainage, but 600mL or less is preferably used. For example, when a sheet is produced using the conjugate fiber of the present invention, the breaking of the cellulose fiber during continuous papermaking with a drainage of 600mL or less can be suppressed. In other words, in order to improve the strength and specific surface area of the composite fiber sheet, when a treatment for increasing the fiber surface area such as beating is performed, the freeness is lowered, but it is preferable to use cellulose fibers subjected to such a treatment. The lower limit of the freeness of the cellulose fiber is more preferably 50mL or more, and still more preferably 100mL or more. If the freeness of the cellulose fiber is 200mL or more, the workability of continuous papermaking is good.

Further, by further treating these cellulose raw materials, chemically modified cellulose such as powdered cellulose and oxidized cellulose and cellulose nanofibers can be obtained: CNF (microfibrillated cellulose: MFC, TEMPO-oxidized CNF, phosphated CNF, carboxymethylated CNF, mechanically pulverized CNF, etc.) was used. As the powdery cellulose used in the present invention, for example, crystalline cellulose powder having a uniform particle size distribution in a rod shape produced by a method of purifying, drying, pulverizing and sieving an undecomposed residue obtained by subjecting selected pulp to acid hydrolysis may be used, and commercially available products such as KC FLOCK (manufactured by japan paper products), CEOLUS (manufactured by asahi chemicals), Avicel (manufactured by FMC corporation) and the like may be used. The polymerization degree of cellulose in the powdered cellulose is preferably about 100 to 1500, the crystallinity of the powdered cellulose measured by X-ray diffraction method is preferably 70 to 90%, and the volume average particle diameter measured by a laser diffraction particle size distribution measuring apparatus is preferably 1 to 100 μm. The oxidized cellulose used in the present invention can be obtained, for example, by oxidizing in water using an oxidizing agent in the presence of a compound selected from an N-oxyl compound and a bromide, an iodide or a mixture thereof. As the cellulose nanofibers, a method of defibering the above cellulose raw material is used. As the defibration method, for example, the following methods can be used: an aqueous suspension of chemically modified cellulose such as cellulose or oxidized cellulose is mechanically ground or beaten by a refiner, a high-pressure homogenizer, a grinder, a single-or multi-shaft mixer, a bead mill or the like to thereby defibrate the cellulose. The above methods may also be combined with 1 or more to produce cellulose nanofibers. The fiber diameter of the cellulose nanofibers thus produced can be confirmed by electron microscope observation or the like, and is, for example, in the range of 5nm to 1000nm, preferably 5nm to 500nm, and more preferably 5nm to 300 nm. In the production of the cellulose nanofibers, any compound may be further added before and/or after the defibration and/or micronization of the cellulose to react with the cellulose nanofibers to produce hydroxyl group-modified cellulose. Examples of the modified functional group include acetyl group, ester group, ether group, ketone group, formyl group, benzoyl group, acetal, hemiacetal, oxime, isonitrile, allene, thiol group, urea group, cyano group, nitro group, azo group, aryl group, aralkyl group, amino group, amide group, imide group, acryloyl group, methacryloyl group, propionyl group, propioyl group, butyryl group, 2-butyryl group, pentanoyl group, hexanoyl group, heptanoyl group, octanoyl group, nonanoyl group, decanoyl group, undecanoyl group, dodecanoyl group, myristoyl group, palmitoyl group, stearoyl group, pivaloyl group, benzoyl group, naphthoyl group, nicotinoyl group, isonicotinoyl group, furoyl group, cinnamoyl group and other acyl groups, 2-methacryloyloxyethyl isocyanoyl group and other isocyanate groups, methyl group, ethyl group, propyl group, 2-propyl group, butyl group, 2-butyl group, t-butyl-ethyl isocyanoyl, Alkyl groups such as pentyl, hexyl, heptyl, octyl, nonyl, decyl, undecyl, dodecyl, myristyl, palmityl, and stearyl, ethylene oxide, oxetanyl, oxy, thiiranyl, and thietanyl. The hydrogen in these substituents may be substituted with a functional group such as a hydroxyl group or a carboxyl group. In addition, a part of the alkyl group may be an unsaturated bond. The compound for introducing these functional groups is not particularly limited, and examples thereof include a compound having a group derived from phosphoric acid, a compound having a group derived from carboxylic acid, a compound having a group derived from sulfuric acid, a compound having a group derived from sulfonic acid, a compound having an alkyl group, and a compound having a group derived from amine. The compound having a phosphate group is not particularly limited, and examples thereof include phosphoric acid, lithium dihydrogen phosphate, dilithium hydrogen phosphate, trilithium phosphate, lithium pyrophosphate, and lithium polyphosphate, which are lithium salts of phosphoric acid. Further, sodium dihydrogen phosphate, disodium hydrogen phosphate, trisodium phosphate, sodium pyrophosphate, and sodium polyphosphate, which are sodium salts of phosphoric acid, may be mentioned. Further, potassium dihydrogen phosphate, dipotassium hydrogen phosphate, tripotassium phosphate, potassium pyrophosphate, and potassium polyphosphate are potassium salts of phosphoric acid. Examples thereof include monoammonium phosphate, diammonium phosphate, triammonium phosphate, ammonium pyrophosphate, and ammonium polyphosphate which are ammonium salts of phosphoric acid. Among them, phosphoric acid, sodium salts of phosphoric acid, potassium salts of phosphoric acid, and ammonium salts of phosphoric acid are preferable, and sodium dihydrogen phosphate and disodium hydrogen phosphate are more preferable, from the viewpoint of high efficiency of introduction of phosphoric acid group and easy industrial application, but are not particularly limited. The compound having a carboxyl group is not particularly limited, and examples thereof include dicarboxylic acid compounds such as maleic acid, succinic acid, phthalic acid, fumaric acid, glutaric acid, adipic acid, and itaconic acid, and tricarboxylic acid compounds such as citric acid and aconitic acid. The acid anhydride of the compound having a carboxyl group is not particularly limited, and examples thereof include acid anhydrides of dicarboxylic acid compounds such as maleic anhydride, succinic anhydride, phthalic anhydride, glutaric anhydride, adipic anhydride, and itaconic anhydride. The derivative of the compound having a carboxyl group is not particularly limited, and an imide compound of an acid anhydride of the compound having a carboxyl group and a derivative of an acid anhydride of the compound having a carboxyl group are exemplified. The imide compound of the acid anhydride of the compound having a carboxyl group is not particularly limited, and examples thereof include imide compounds of dicarboxylic acid compounds such as maleimide, succinimide, and phthalimide. The acid anhydride derivative of the compound having a carboxyl group is not particularly limited. Examples thereof include compounds obtained by substituting at least a part of hydrogen atoms in an acid anhydride of a compound having a carboxyl group such as dimethylmaleic anhydride, diethylmaleic anhydride, diphenylmaleic anhydride, etc. with a substituent (e.g., an alkyl group, a phenyl group, etc.). Among the compounds having a group derived from a carboxylic acid, maleic anhydride, succinic anhydride, and phthalic anhydride are preferable from the viewpoint of easy industrial application and easy vaporization, but are not particularly limited. In addition, the cellulose nanofibers can be modified in such a manner that the modified compound is physically adsorbed to the cellulose nanofibers, even without chemical bonding. Examples of the physisorbed compound include surfactants, and any of anionic, cationic, and nonionic compounds can be used. When the modification is performed before the cellulose is defibered and/or pulverized, the functional groups may be removed after the defibering and/or pulverization to restore the original hydroxyl groups. By applying such modification, the cellulose nanofibers can be accelerated to be defibered, or when cellulose nanofibers are used, the cellulose nanofibers can be easily mixed with various substances.

The fibers shown above may be used alone or in combination of two or more. For example, fibrous materials recovered from the drainage of a paper mill may also be supplied to the carbonation reaction of the present invention. By supplying such a substance to the reaction tank, various composite particles can be synthesized, and fibrous particles and the like can be synthesized in shape.

In the present invention, in addition to the fibers, a substance mixed with inorganic particles as a product to form composite particles can be used. In the present invention, fibers typified by pulp fibers are used, but in addition to these, composite particles further containing inorganic particles mixed therein may be produced by synthesizing the inorganic particles in a solution containing inorganic particles, organic particles, polymers, and the like.

The fiber length of the composite fiber is not particularly limited, and for example, the average fiber length may be about 0.1 μm to 15mm, or 1 μm to 12mm, 100 μm to 10mm, or 500 μm to 8 mm.

The fiber diameter of the composite fiber is not particularly limited, and for example, the average fiber diameter may be about 1nm to 100 μm, or may be 10nm to 100 μm, 0.15 μm to 100 μm, 1 μm to 90 μm, 3 to 50 μm, 5 to 30 μm, or the like.

The composite fiber is preferably used in such an amount that 15% or more of the fiber surface is covered with inorganic particles, and for example, the weight ratio of the fiber to the inorganic particles may be 5/95 to 95/5, 10/90 to 90/10, 20/80 to 80/20, 30/70 to 70/30, 40/60 to 60/40.

In a preferred embodiment of the composite fiber of the present invention, 15% or more of the fiber surface is covered with the inorganic particles, and if the cellulose fiber surface is covered with such an area ratio, the characteristics due to the inorganic particles are remarkably generated, while the characteristics due to the fiber surface are reduced.

The composite fiber of the present invention can be used in various shapes, for example, in the form of powder, granule, molded article, aqueous suspension, paste, sheet, plate, block, filament, or other shapes. Further, the composite fiber may be used as a main component together with other materials to form molded articles such as molded articles, pellets, and granules. The dryer for drying to obtain powder is not particularly limited, and for example, an air dryer, a belt dryer, a spray dryer, or the like can be suitably used.

The composite fiber obtained by the present invention can be used for various applications, and for example, can be widely used for paper, fiber, cellulose-based composite material, filter material, paint, plastic or other resin, rubber, elastomer, ceramic, glass, tire, building material (asphalt, asbestos, cement, plate material, concrete, brick, tile, plywood, fiberboard, decorative board, ceiling material, wall material, floor material, roof material, etc.), furniture, various carriers (catalyst carrier, medical carrier, pesticide carrier, microorganism carrier, etc.), adsorbent (impurity removal, deodorization, dehumidification, etc.), anti-wrinkle agent, clay, abrasive material, modifier, repair material, heat insulating material, heat-resistant material, heat-dissipating material, moisture-proof material, waterproof material, light-shielding material, sealing agent, shielding material, insect-proofing agent, adhesive, medical material, Paste materials, discoloration inhibitors, electromagnetic wave absorbers, insulators, sound insulators, interior materials, vibration insulators, semiconductor sealing materials, radiation shielding materials, flame retardants, and the like. In addition, the resin composition can be used for various fillers, coating agents, and the like in the above-mentioned applications. Among them, radiation shielding materials, flame retardant materials, building materials, furniture, interior materials, and heat insulating materials are preferable.

The composite fiber of the present invention can be used for paper making applications, and examples thereof include printing paper, newspaper, inkjet paper, PPC paper, kraft paper, fine paper, coated paper, micro-coated paper, wrapping paper, tissue paper, color fine paper, cast paper, carbonless paper, label paper, thermal paper, various pattern paper, water-soluble paper, release paper, craft paper, base paper for wallpaper, flame-retardant paper (non-combustible paper), laminate base paper, printed electronic paper, battery separator, cushion paper, drawing paper, impregnated paper, ODP paper, construction paper (wall paper, etc.), paper for cosmetic materials, envelope paper, tape paper, heat-exchange paper, chemical fiber paper, sterilized paper, water-resistant paper, oil-resistant paper, heat-resistant paper, photocatalytic paper, cosmetic paper (oil-absorbing paper, etc.), various toilet paper (toilet paper, face tissue, wiping paper, diaper, physiological goods, etc.), tobacco paper, cardboard (face paper, paper for cosmetics, etc.), core base paper, white board paper, etc.), paper tray base paper, cup base paper, baking paper, sandpaper, synthetic paper, etc. That is, according to the present invention, since a composite of inorganic particles and fibers having a small primary particle diameter and a narrow particle size distribution can be obtained, it is possible to exhibit characteristics different from those of conventional inorganic fillers having a particle diameter of more than 2 μm. Further, unlike the case where only the inorganic particles are blended with the fibers, the inorganic particles and the fibers are previously combined to obtain a sheet in which the inorganic particles are not easily left on the sheet and are uniformly dispersed without aggregation. As is apparent from the results of electron microscope observation, in a preferred embodiment, the inorganic particles are not only fixed to the outer surface and the inner side of the lumen of the fiber, but also generated on the inner side of the microfiber.

When the composite fiber of the present invention is used, particles and various fibers, which are generally called inorganic filler and organic filler, can be used in combination. Examples of the inorganic filler include calcium carbonate (light calcium carbonate, heavy calcium carbonate), magnesium carbonate, barium carbonate, aluminum hydroxide, calcium hydroxide, magnesium hydroxide, zinc hydroxide, clay (kaolin, calcined kaolin, lamellar kaolin), talc, zinc oxide, zinc stearate, titanium dioxide, silica (white carbon, silica/calcium carbonate composite, silica/titanium dioxide composite) produced from sodium silicate and an inorganic acid, clay, bentonite, diatomaceous earth, calcium sulfate, zeolite, fire clay, an inorganic filler obtained by regenerating and utilizing ash obtained in the deinking step, and an inorganic filler that forms a composite with silica and calcium carbonate in the regeneration step. As the calcium carbonate-silica composite, amorphous silica such as white carbon may be used in combination with calcium carbonate and/or light calcium carbonate-silica composite. Examples of the organic filler include urea resin, polystyrene resin, phenol resin, fine hollow particles, acrylamide composite, wood-derived substances (fine fibers, microfiber fibers, and powdered kenaf), modified insoluble starch, and ungelatinized starch. As the fibers, natural fibers such as cellulose may be used, and synthetic fibers artificially synthesized from raw materials such as petroleum, regenerated fibers (semi-synthetic fibers) such as rayon and lyocell, inorganic fibers, and the like may be used without limitation. Examples of natural fibers include protein fibers such as wool, silk, and collagen fibers, complex carbohydrate fibers such as chitin-chitosan fibers and alginic acid fibers, and the like. Examples of the cellulose-based raw material include pulp fibers derived from plants, cellulose derived from animals such as bacterial cellulose and sea squirt, and algae, and wood pulp can be produced by pulping a wood raw material. Examples of the wood material include needle-leaved trees such as red pine, black pine, fir, spruce, red pine, larch, japanese fir, hemlock, japanese cedar, japanese cypress, larch, white fir, scale spruce, cypress, douglas fir, canadian hemlock, white fir, spruce, balsam fir, cedar, pine, southern pine, radiata pine, and mixtures thereof, and broad-leaved trees such as japanese beech, birch, japanese alder, oak, red-leaf nanmu, chestnut, white birch, black poplar, water chestnut, sweet poplar, red tree, eucalyptus, acacia, and mixtures thereof. The method for pulping the wood material is not particularly limited, and a pulping method generally used in the paper industry can be exemplified. Wood pulp can be classified by a pulping method, and examples thereof include chemical pulp obtained by cooking by a method such as a kraft method, sulfite method, soda method, polysulfide method, or the like; mechanical pulp obtained by pulping with mechanical force of a refiner, a grinder, or the like; semichemical pulp obtained by pulping with mechanical force after pretreatment with a chemical; waste paper pulp; deinked pulp, and the like. The wood pulp may be unbleached (before bleaching) or bleached (after bleaching). Examples of the pulp derived from non-wood include cotton, hemp, sisal, abaca, flax, straw, bamboo, bagasse, kenaf, sugarcane, corn, rice stem, broussonetia papyrifera (grape flat), and daphne. The wood pulp and the non-wood pulp may be any of unbleached and beaten. These cellulose raw materials can also be used as powdered cellulose such as powdered cellulose, chemically modified cellulose such as oxidized cellulose, and cellulose nanofibers by further processing: CNF (microfibrillated cellulose: MFC, TEMPO oxidized CNF, phosphated CNF, carboxymethylated CNF, mechanically comminuted CNF). Examples of the synthetic fibers include polyester, polyamide, polyolefin, and acrylic fibers, examples of the semisynthetic fibers include rayon and acetate fibers, and examples of the inorganic fibers include glass fibers, ceramic fibers, biosoluble ceramic fibers, carbon fibers, and various metal fibers. The above components may be used alone or in combination of 2 or more.

The average particle diameter, shape, and the like of the inorganic particles constituting the composite fiber of the present invention can be confirmed by observation with an electron microscope. Further, inorganic particles having various sizes and shapes can be combined with fibers by adjusting conditions for synthesizing the inorganic particles.

(Synthesis of conjugate fiber)

In one embodiment of the present invention, the composite can be synthesized by synthesizing inorganic particles in a solution containing fibers, but known methods can be used for the synthesis of the inorganic particles.

When barium sulfate is used as the inorganic particles, barium sulfate can be synthesized in a solution containing fibers. For example, when a basic barium sulfate precursor represented by barium hydroxide is used as a raw material, fibers can be dispersed in a solution of the barium sulfate precursor in advance to swell the fibers, and thus a composite of barium sulfate and fibers can be efficiently obtained. The reaction may be started after the fibers are mixed and stirred for 15 minutes or more to promote swelling of the fibers, or may be started immediately after the mixing. The form and stirring conditions of the reaction vessel in which the composite fiber is obtained are not particularly limited, and for example, a solution containing the fiber and the precursor of barium sulfate may be stirred and mixed in an open-type reaction vessel to synthesize a composite, or an aqueous suspension containing the fiber and the precursor of barium sulfate may be sprayed into a reaction vessel to synthesize the composite. In this step, in order to control the particle size of the inorganic substance and optimize the reaction conditions (nucleation reaction and growth reaction), the aging time may be set in the middle of and after the reaction. For example, if the synthesis of inorganic substances is easy at a low pH, the state can be maintained, and if the growth reaction of the inorganic particles takes time, the solution can be continuously stirred. In this case, the aging time and the pH are not particularly limited, and any of a neutral region of pH6 to 8, an acidic region of pH6 or less, and a basic region of pH8 or more may be used.

In the present invention, water is used for preparation of the suspension, but as the water, ordinary tap water, industrial water, underground water, well water, and the like can be used, and ion-exchanged water, distilled water, ultrapure water, industrial wastewater, water obtained when the reaction solution is separated and dehydrated, and the like can be suitably used.

In the present invention, the reaction solution in the reaction tank may be circulated and used. By circulating the reaction solution and promoting the stirring of the solution in this way, the reaction efficiency is improved, and a desired composite of inorganic particles and fibers can be easily obtained.

In the production of the composite fiber of the present invention, various known auxiliaries may be added. For example, a chelating agent may be added, and specific examples thereof include polyhydroxycarboxylic acids such as citric acid, malic acid and tartaric acid, dicarboxylic acids such as oxalic acid, sugar acids such as gluconic acid, aminopolycarboxylic acids such as iminodiacetic acid and ethylenediaminetetraacetic acid and alkali metal salts thereof, alkali metal salts of polyphosphoric acids such as hexametaphosphoric acid and tripolyphosphoric acid, amino acids such as glutamic acid and aspartic acid and alkali metal salts thereof, ketones such as acetylacetone, methyl acetoacetate and allyl acetoacetate, saccharides such as sucrose, and polyhydric alcohols such as sorbitol. Further, as the surface treatment agent, saturated fatty acids such as palmitic acid and stearic acid, unsaturated fatty acids such as oleic acid and linoleic acid, alicyclic carboxylic acids, resin acids such as abietic acid, salts, esters and ethers thereof, alcohol-based active agents, sorbitan fatty acid esters, amide-based or amine-based surfactants, polyoxyalkylene alkyl ethers, polyoxyethylene nonylphenyl ether, sodium α -olefin sulfonate, long-chain alkyl amino acids, amine oxide, alkylamine, quaternary ammonium salts, aminocarboxylic acids, phosphonic acids, polycarboxylic acids, condensed phosphoric acid, and the like may be added. Further, a dispersant may be used as needed. Examples of the dispersant include sodium polyacrylate, sucrose fatty acid ester, glycerin fatty acid ester, acrylic acid-maleic acid copolymer ammonium salt, methacrylic acid-naphthyloxy polyethylene glycol acrylate copolymer, methacrylic acid-polyethylene glycol monomethacrylate copolymer ammonium salt, and polyethylene glycol monoacrylate. They may be used alone or in combination of plural kinds. The timing of addition may be before or after the synthesis reaction. Such an additive may be added in an amount of preferably 0.001 to 20%, more preferably 0.1 to 10%, based on the inorganic particles.

In the synthesis of the composite fiber in the present invention, the reaction conditions are not particularly limited and may be appropriately set according to the application. For example, the temperature of the synthesis reaction may be 0 to 90 ℃, preferably 10 to 70 ℃. The reaction temperature can be controlled by a temperature controller, and if the temperature is low, the reaction efficiency decreases and the cost increases, while if the temperature exceeds 90 ℃, the number of coarse inorganic particles tends to increase.

In the present invention, the reaction may be a batch reaction or a continuous reaction. Generally, it is preferable to perform a batch reaction step from the viewpoint of convenience in discharging a residue after the reaction. The scale of the reaction is not particularly limited, and the reaction may be carried out on a scale of 100L or less, or may be carried out on a scale exceeding 100L. The size of the reaction vessel may be, for example, about 10L to 100L, 100L to 1000L, or 1m³(1000L)～100m³Left and right。

The reaction can be controlled by the conductivity of the reaction solution and the reaction time, specifically, by adjusting the time during which the reactant stays in the reaction vessel. In the present invention, the reaction may be controlled by stirring the reaction solution in the reaction tank or by carrying out the reaction in multiple steps.

In the present invention, the conjugate fiber as a reaction product is obtained as a suspension, and therefore, it may be stored in a storage tank or subjected to treatments such as concentration, dehydration, pulverization, classification, aging, and dispersion, as necessary. These may be determined as appropriate in consideration of the use, energy efficiency, and the like, by using a known process. For example, the concentration and dehydration treatment is performed by using a centrifugal dehydrator, a sedimentation concentrator, or the like. Examples of the centrifugal dehydrator include a decanter and a screw decanter. When a filter or dehydrator is used, the type thereof is not particularly limited, and a general apparatus can be used, and for example, a press type dehydrator such as a filter press, a drum filter, a belt press, a tube press, or a vacuum drum dehydrator such as an orlistat filter can be preferably used to prepare a cake. Examples of the pulverization method include a ball MILL, a sand MILL, an impact MILL, a high-pressure homogenizer, a low-pressure homogenizer, DYNO-MILL, an ultrasonic MILL, Kanda grind, an attritor, a mortar-type MILL, a vibration MILL, a chopper, a jet MILL, a pulverizer, a beater, a short-shaft extruder, a twin-shaft extruder, an ultrasonic mixer, and a home-use juicer. Examples of the classification method include a screen such as a mesh, an external or internal slit or circular hole screen, a vibrating screen, a heavy foreign matter cleaner, a light foreign matter cleaner, a reverse cleaner, and a sieve tester. Examples of the method of dispersion include a high-speed disperser and a low-speed kneader.

The composite fiber in the present invention may be blended in a filler or pigment in a suspension state without being completely dehydrated, or may be dried to be made into a powder. The dryer in this case is also not particularly limited, and for example, an air dryer, a belt dryer, a spray dryer, or the like can be suitably used.

The composite fiber of the present invention can be modified by a known method. For example, in some embodiments, the surface of the resin may be hydrophobized to improve the miscibility with the resin or the like. .

(form of conjugate fiber)

In the present invention, a flame-retardant conjugate fiber having remarkably improved flame resistance can be obtained by treating the conjugate fiber with a flame retardant. The form of the obtained composite fiber is not particularly limited, and various molded articles (bodies) can be produced. For example, when the composite fiber of the present invention is formed into a sheet, a high-ash sheet can be easily obtained. Further, the obtained sheets may be laminated to form a multilayer sheet. Examples of paper machines (papermaking machines) used for sheet production include fourdrinier wire machines, cylinder wire machines, gap wire machines, hybrid forming machines, multi-layer paper machines, and known papermaking machines of a papermaking system combining these machines. The press line pressure in the paper machine and the calendering line pressure in the case of calendering at the subsequent stage can be determined within a range not to impair the workability and the performance of the conjugate fiber sheet. The sheet thus formed may be impregnated or coated with starch, various polymers, pigments, or a mixture thereof.

A wet and/or dry paper strength agent (paper strength enhancer) may be added during sheeting. This can improve the strength of the composite fiber sheet. Examples of the paper strength agent include resins such as urea-formaldehyde resin, melamine-formaldehyde resin, polyamide, polyamine, epichlorohydrin resin, plant rubber, latex, polyethyleneimine, glyoxal, gum, mannogalactan polyethyleneimine, polyacrylamide resin, polyvinylamine, and polyvinyl alcohol; a composite polymer or a copolymer polymer comprising 2 or more selected from the above resins; starch and processed starch; carboxymethyl cellulose, guar gum, urea resins, and the like. The amount of the paper strength agent added is not particularly limited.

In addition, a high molecular polymer or an inorganic substance may be added to facilitate the fixation of the filler to the fiber or to increase the retention of the filler or the fiber. For example, as the coagulant, a cationic polymer such as polyethyleneimine, modified polyethyleneimine containing a tertiary ammonium group and/or a quaternary ammonium group, polyalkyleneimine, dicyandiamide polymer, polyamine/epichlorohydrin polymer, dialkyl diallyl quaternary ammonium monomer, dialkyl aminoalkyl acrylate, dialkyl aminoalkyl methacrylate, dialkyl aminoalkyl acrylamide, a polymer of dialkyl aminoalkyl methacrylamide and acrylamide, a polymer composed of a monoamine and an epihalohydrin, polyvinylamine, a polymer having a vinylamine moiety, or a mixture thereof may be used, in addition to the above, a cation-rich zwitterionic polymer obtained by copolymerizing an anionic group such as a carboxyl group or a sulfone group in the molecule of the polymer, a mixture of a cationic polymer and an anionic or zwitterionic polymer, or the like can be used. As the retention aid, a cationic, anionic or amphoteric polyacrylamide-based material can be used. In addition, other than this, a so-called two-polymer retention system using at least one kind of cationic and anionic polymer in combination, or a multi-component retention system using at least one kind of anionic bentonite, colloidal silica, polysilicic acid or polysilicate microgel, inorganic microparticles such as aluminum modified products thereof, and one or more kinds of acrylamide, and a so-called organic microparticle having a particle size of 100 μm or less, which is obtained by crosslinking polymerization, may be used. In particular, the polyacrylamide-based substance used alone or in combination can provide a good retention rate when it has a weight average molecular weight of 200 kilodaltons or more as measured by an ultimate viscosity method, and can provide a very high retention rate when it is the above acrylamide-based substance of preferably 500 kilodaltons or more, more preferably 1000 kilodaltons or more and less than 3000 kilodaltons. The form of the polyacrylamide-based material may be emulsion type or solution type. The specific composition is not particularly limited as long as the composition contains an acrylamide monomer unit as a structural unit in the material, and examples thereof include a copolymer of acrylamide and a quaternary ammonium salt of an acrylic acid ester, and an ammonium salt obtained by copolymerizing acrylamide and an acrylic acid ester and then performing quaternization. The cationic charge density of the cationic polyacrylamide-based substance is not particularly limited.

In addition, depending on the purpose, there may be mentioned a drainage improver, an internal sizing agent, a pH adjuster, a defoaming agent, a pitch controller, a slime controller, a bulking agent, inorganic particles (so-called fillers) such as calcium carbonate, kaolin, talc, silica and the like. The amount of each additive is not particularly limited.

The weight per unit area of the sheet can be suitably adjusted according to the purpose, but when used as a building material, for example, it is 60 to 1200g/m²The strength is high, and the drying load during production is low, which is preferable. In addition, in order to improve the flame retardancy, the higher the basis weight (weight per unit area: weight per 1 square meter) of the sheet is, the more advantageous, so that the weight per unit area may be 1200g/m²The amount of the surfactant is, for example, 2000 to 110000g/m²。

Molding methods other than sheet molding may be used, and for example, a method of feeding a raw material into a mold to suction-dewater and dry the raw material, such as pulp molding, or a method of coating the surface of a molded product of resin, metal, or the like, drying the coated product, and then peeling the dried product from a base material, can be used to obtain molded products having various shapes. Further, the resin may be mixed and molded into a plastic form, or the mixture may be molded into a plate form by press and heat press molding, which is generally used for manufacturing inorganic boards such as cement and gypsum, and molded into a block form. The sheet is typically bent or curled, but may be formed into a plate shape when greater strength is required. Further, the block-shaped member may be formed into a block having a thickness, for example, a rectangular parallelepiped, a cube, or the like. The pulp molded product, the sheet, or the block may be formed into a concave-convex pattern by patterning a mold during molding, or may be deformed by bending or the like after molding.

In the compounding, drying and molding described above, only 1 type of composite may be used, or 2 or more types of composite may be mixed and used. When 2 or more kinds of the composite are used, a mixture of these may be used in advance, or they may be mixed after each compounding, drying, molding.

After that, various organic materials such as polymers and various inorganic materials such as pigments may be added to the composite molded article.

The molded article produced in the product of the present invention may be subjected to printing. The printing method is not particularly limited, and may be performed by a known method such as offset printing, screen printing (silk screen printing), screen printing, gravure printing, micro-gravure printing, flexo printing, letterpress printing, scotch printing, form printing, on-demand printing, supply roll printing (burn roll printing), and ink jet printing. Among them, ink jet printing is preferable because it is not necessary to produce copies as in offset printing, and it is relatively easy to increase the size of an ink jet printer, and printing on large sheets is possible. In addition, since flexographic printing is suitable for printing on a molded article having a relatively large surface irregularity, it can be suitably used when the molded article is molded into a shape such as a plate, a molded article, or a block.

The type of pattern of the printed image formed by printing is not particularly limited, and may be any desired pattern, such as wood grain, stone grain, cloth grain, abstract pattern, geometric pattern, letters, symbols, or a combination thereof, or may be a pure color.