JP2023150971A - Preparation method of composite fiber of cellulose fiber and inorganic particle - Google Patents

Abstract

To provide a preparation method of a composite fiber of a cellulose fiber and an inorganic fiber, capable of preserving a composite fiber of a cellulose fiber whose surface is covered with inorganic particles, or transporting the composite fiber to a destination and then disaggregating the same, especially, transporting so as to prevent covering by the inorganic particles from being detached from the surface of fiber, suppressing degeneration of the composite fiber, for example, in a composite fiber of hydrotalcite, suppressing reduction of deodorization performance.SOLUTION: There is provided a preparation method of a composite fiber including: a step for encapsulating a concentrate of a composite fiber of a cellulose fiber whose density is 15-60 mass% and inorganic particles, in a container which can be sealed, then transporting the container to a prescribed preservation place.SELECTED DRAWING: None

Description

The present invention relates to a composite fiber of cellulose fiber and inorganic particles.

Cellulose fibers, including wood fibers, exhibit various properties based on the functional groups on their surfaces. Depending on the application, it may be necessary to modify the surface. Technology has been developed to do so.

For example, fibers can exhibit various properties by attaching inorganic particles to their surfaces. Regarding the technology for precipitating inorganic particles on fibers such as cellulose fibers, Patent Document 1 describes a technology for producing composite fibers of pulp and calcium carbonate by precipitating calcium carbonate in a pulp suspension using a carbon dioxide gas method. is listed.

US Patent No. 5,679,220

An object of the present invention is to store or transport composite fibers of cellulose fibers whose surfaces are coated with inorganic particles to a destination, and then disintegrate them. In particular, it is necessary to transport the inorganic particle coating so that it does not peel off from the fiber surface, and to suppress the deterioration of the composite fiber. For example, in the case of hydrotalcite composite fibers, it is necessary to suppress the deterioration of deodorizing performance. .

Although the present invention is not limited thereto, it includes the following inventions.
(1) A step of concentrating composite fibers of cellulose fibers and inorganic particles to a concentration of 15 to 60% by mass to prepare a concentrate;
a step of enclosing the composite fiber concentrate in a sealable container and storing or transporting it to a predetermined location;
A method for preparing composite fibers, including:
(2) The method for preparing composite fibers according to (1), wherein the concentrate of the composite fibers is sealed in a resin bag and stored in a flexible container-type bag or transported to a predetermined location.
(3) The method according to (1) or (2), comprising the step of disintegrating the stored composite fiber concentrate or the composite fiber concentrate transported to a predetermined location in water.
(4) Any one of (1) to (3), wherein at least a portion of the inorganic particles are metal salts of calcium, silicic acid, magnesium, barium, or aluminum, or metal particles containing titanium, copper, or zinc. The method described in.
(5) The method according to any one of (1) to (4), wherein the inorganic particles contain hydrotalcite.

According to the present invention, composite fibers of cellulose fibers whose surfaces are coated with inorganic particles can be transported and disintegrated. Furthermore, deterioration of the composite fibers can be suppressed, for example, in the case of hydrotalcite composite fibers, deterioration of deodorizing performance can be suppressed.

In one embodiment of the present invention, after the step of synthesizing inorganic particles in a solution containing fibers and producing a composite fiber of the inorganic particles and fibers, a step of concentrating the solution to a concentration of 15 to 60% by mass is provided. The concentration is preferably 20 to 55% by weight, more preferably 25 to 45% by weight. When the concentration of the composite fiber is less than 15% by mass, the residual rate of the inorganic particle composite fiber decreases after disintegration. Furthermore, if the concentration of the composite fiber exceeds 60% by mass, the time required for disintegration after transportation will be longer. Concentration and dehydration of composite fibers are performed using, for example, a centrifugal dehydrator, a sedimentation concentrator, or the like. Examples of this centrifugal dehydrator include a decanter and a screw decanter. When using a filter or dehydrator, there are no particular restrictions on the type, and common types can be used; for example, pressure type dehydrators such as filter presses, drum filters, belt presses, tube presses, etc. A vacuum drum dehydrator such as an Oliver filter can be suitably used.

After concentrating the composite fiber to a concentration of 15 to 60% by mass, it is sealed in a sealable container. After being sealed in a container, it may be stored or transported immediately. As the container, a flexible container type bag is preferred.

In order to make the container airtight, it is preferable to seal the composite fiber in a resin bag and place it in the container. As the resin bag, it is preferable to use one that can suppress oxygen permeation, such as nylon bags; polyethylene bags; nylon film bags with a coating film of aluminum, polyacrylonitrile, polyvinyl alcohol, or polyvinylidene chloride resin; and ethylene-vinyl alcohol bags. A transparent barrier film bag consisting of a vapor-deposited layer of an inorganic oxide such as silicon oxide or aluminum oxide on a base material made of polymer, olefin polymer, olefin-polycarboxylic acid copolymer, or plastic. ; and a barrier film bag provided with a vapor-deposited layer of metal such as aluminum. By storing the composite fibers in an airtight state, oxidation caused by oxygen can be suppressed, and therefore, denaturation of the composite fibers can be suppressed. For example, in the case of hydrotalcite composite fibers, deterioration in deodorizing performance can be suppressed.

At the destination, the composite fibers of inorganic particles and fibers are diluted with water, and then undergo a process of disintegration and processing. Disintegration can normally be carried out at 0.1 to 15%, preferably 0.5 to 5%, and more preferably 1 to 3% in the present invention. If it is less than 0.1%, the residual rate of the inorganic particle composite fibers will decrease after disintegration. If the concentration exceeds 15%, disaggregation becomes difficult. The processing step refers to all the steps of processing a composite fiber of inorganic particles and fibers into a specific form in the process of using or producing a product. For example, the process of processing a composite fiber of inorganic particles and fibers includes a process of forming a composite fiber of fibers and inorganic particles into a sheet, a fluffing process, a granulation process, a molding process, and the like.

Synthesis of Composite Fibers In the present invention, composite fibers can be synthesized by synthesizing inorganic particles in a solution containing fibers such as cellulose fibers. This is because the fiber surface becomes a suitable place for the precipitation of inorganic particles, making it easy to synthesize composite fibers. As a method for synthesizing composite fibers, for example, composite fibers may be synthesized by stirring and mixing a solution containing fibers and inorganic particle precursors in an open reaction tank, or composite fibers may be synthesized by stirring and mixing a solution containing fibers and inorganic particle precursors. It may be synthesized by injecting an aqueous suspension containing into a reaction vessel. As will be described later, cavitation bubbles may be generated when an aqueous suspension of an inorganic precursor is injected into a reaction vessel, and inorganic particles may be synthesized in the presence of cavitation bubbles. Inorganic particles can be synthesized on cellulose fibers by known reactions, respectively.

In general, inorganic particles are generated from a cluster state (where the number of atoms/molecules that gather is small, repeating aggregation and dispersion) to a nucleus (a transition from a cluster to a stable aggregation state, and when the size exceeds a critical size, they are captured). It is known that atoms and molecules no longer become discrete), and growth (new atoms and molecules gather around the nucleus, making the particles larger).The higher the raw material concentration and reaction temperature, the more nucleation occurs. It is said to be easy. The composite fiber of the present invention can be produced on the fiber by mainly adjusting the raw material concentration, pulp beating degree (specific surface area), viscosity of the solution containing the fiber, concentration and addition speed of additive chemicals, reaction temperature, and stirring speed. By efficiently binding nuclei and promoting particle growth, it is possible to obtain composite fibers in which the surface of cellulose fibers is strongly coated with inorganic particles.

In the present invention, the liquid may be injected under conditions that cause cavitation bubbles to be generated in the reaction container, or may be injected under conditions that do not cause cavitation bubbles to occur. Further, the reaction vessel is preferably a pressure vessel in any case. Note that the pressure vessel in the present invention is a vessel capable of applying a pressure of 0.005 MPa or more. In the case of conditions that do not cause cavitation bubbles, the static pressure in the pressure vessel is preferably 0.005 MPa or more and 0.9 MPa or less.

(cavitation bubbles)
When synthesizing the composite fiber according to the present invention, inorganic particles can be precipitated in the presence of cavitation bubbles. In the present invention, cavitation is a physical phenomenon in which bubbles are generated and disappeared in a short period of time due to a pressure difference in a fluid flow, and is also referred to as a cavitation phenomenon. Bubbles caused by cavitation (cavitation bubbles) are generated when the pressure in a fluid becomes lower than the saturated vapor pressure for a very short period of time, with tiny "bubble nuclei" of 100 microns or less existing in the liquid as nuclei.

In the present invention, cavitation bubbles can be generated in the reaction vessel by a known method. For example, cavitation bubbles are generated by injecting a fluid at high pressure, cavitation is generated by high-speed stirring within a fluid, cavitation is generated by causing an explosion within a fluid, and ultrasonic vibrations. Possible causes include cavitation caused by particles (vibration cavitation).

In the present invention, cavitation can be generated by directly using the reaction solution such as a raw material as the injection liquid, or by injecting some kind of fluid into the reaction container to generate cavitation bubbles. The fluid from which the liquid jet forms a jet may be any liquid, gas, solid such as powder or pulp, or a mixture thereof, as long as it is in a fluid state. Furthermore, if necessary, another fluid such as carbon dioxide gas can be added to the above fluid as a new fluid. The above fluid and the new fluid may be sprayed after being uniformly mixed, or may be sprayed separately.

A liquid jet is a jet of liquid or a fluid in which solid particles or gas are dispersed or mixed in the liquid, and refers to a jet of liquid containing raw material slurry of pulp or inorganic particles or bubbles. The gas mentioned here may include bubbles caused by cavitation.

Flow rate and pressure are particularly important because cavitation occurs when a liquid is accelerated and the local pressure is lower than the vapor pressure of the liquid. From this, the cavitation number σ, which is a basic dimensionless number expressing the cavitation state, is preferably 0.001 or more and 0.5 or less, and preferably 0.003 or more and 0.2 or less. It is preferably 0.01 or more and 0.1 or less. If the cavitation number σ is less than 0.001, the effect will be small because the pressure difference with the surroundings when the cavitation bubble collapses is low, and if it is greater than 0.5, the pressure difference in the flow is low and cavitation will not occur. becomes less likely to occur.

In addition, when generating cavitation by injecting the injection liquid through a nozzle or orifice pipe, the pressure of the injection liquid (upstream pressure) is preferably 0.01 MPa or more and 30 MPa or less, and 0.7 MPa or more and 20 MPa or less. It is preferably 2 MPa or more and 15 MPa or less. If the upstream pressure is less than 0.01 MPa, it is difficult to create a pressure difference with the downstream pressure, and the effect is small. Moreover, when the pressure is higher than 30 MPa, a special pump and pressure vessel are required, which increases energy consumption, which is disadvantageous in terms of cost. On the other hand, the pressure in the container (downstream pressure) is preferably 0.005 MPa or more and 0.9 MPa or less in terms of static pressure. Further, the ratio between the pressure inside the container and the pressure of the injection liquid is preferably in the range of 0.001 to 0.5.

In the present invention, inorganic particles can also be synthesized by injecting the injection liquid under conditions that do not generate cavitation bubbles. Specifically, it is more preferable that the pressure of the injection liquid (upstream pressure) be 2 MPa or less, preferably 1 MPa or less, and the pressure of the injection liquid (downstream pressure) be released and be 0.05 MPa or less.

The speed of the jet stream of the injection liquid is desirably in the range of 1 m/sec or more and 200 m/sec or less, and preferably in the range of 20 m/sec or more and 100 m/sec or less. When the jet velocity is less than 1 m/sec, the effect is weak because the pressure drop is low and cavitation is difficult to occur. On the other hand, if the velocity is greater than 200 m/sec, high pressure is required and special equipment is required, which is disadvantageous in terms of cost.

In the present invention, cavitation may be generated within a reaction vessel in which inorganic particles are synthesized. Further, although it is possible to process in one pass, it is also possible to circulate as many times as necessary. Furthermore, multiple generation means can be used to process in parallel or in permutations.

Injection of liquid to generate cavitation may be performed in a container open to the atmosphere, but is preferably performed in a pressure container to control cavitation.

When cavitation is generated by liquid injection, the solid content concentration of the reaction solution is preferably 30% by weight or less, more preferably 20% by weight or less. This is because at such a concentration, cavitation bubbles can be easily caused to act uniformly on the reaction system. Further, from the viewpoint of reaction efficiency, the aqueous suspension of slaked lime that is the reaction solution preferably has a solid content concentration of 0.1% by weight or more.

In the present invention, for example, when composite fibers of calcium carbonate and cellulose fibers are synthesized, the pH of the reaction solution is basic at the start of the reaction, but changes to neutral as the carbonation reaction progresses. Therefore, the reaction can be controlled by monitoring the pH of the reaction solution.

In the present invention, by increasing the injection pressure of the liquid, the flow rate of the injection liquid increases, and the pressure decreases accordingly, making it possible to generate stronger cavitation. In addition, by increasing the pressure inside the reaction vessel, the pressure in the area where the cavitation bubbles collapse increases, and the pressure difference between the bubbles and the surroundings increases, so the bubbles collapse violently and the impact force can be increased. Furthermore, the dissolution and dispersion of the introduced carbon dioxide gas can be promoted. The reaction temperature is preferably 0°C or higher and 90°C or lower, particularly preferably 10°C or higher and 60°C or lower. In general, it is thought that the impact force is maximum at the midpoint between the melting point and the boiling point, so in the case of aqueous solutions, a temperature of around 50°C is suitable, but even if the temperature is lower than that, it will be affected by the vapor pressure. Therefore, high effects can be obtained within the above range.

When producing the composite fiber of the present invention, various known auxiliary agents can be further added. For example, chelating agents can be added, specifically polyhydroxycarboxylic acids such as citric acid, malic acid, and tartaric acid, dicarboxylic acids such as oxalic acid, sugar acids such as gluconic acid, iminodiacetic acid, and ethylenediaminetetraacetic acid. Aminopolycarboxylic acids such as acetic acid and their alkali metal salts, alkali metal salts of polyphosphoric acids such as hexametaphosphoric acid and tripolyphosphoric acid, amino acids such as glutamic acid and aspartic acid and their alkali metal salts, acetylacetone, methyl acetoacetate, acetoacetic acid Examples include ketones such as allyl, sugars such as sucrose, and polyols such as sorbitol. In addition, as surface treatment agents, saturated fatty acids such as palmitic acid and stearic acid, unsaturated fatty acids such as oleic acid and linoleic acid, resin acids such as alicyclic carboxylic acids and abietic acid, their salts, esters and ethers, and alcohol-based Active agents, sorbitan fatty acid esters, amide and amine surfactants, polyoxyalkylene alkyl ethers, polyoxyethylene nonylphenyl ether, sodium alpha olefin sulfonate, long chain alkyl amino acids, amine oxides, alkyl amines, quaternary Ammonium salts, aminocarboxylic acids, phosphonic acids, polyhydric carboxylic acids, condensed phosphoric acids, etc. can be added. Moreover, a dispersant can also be used if necessary. Examples of the dispersant include sodium polyacrylate, sucrose fatty acid ester, glycerin fatty acid ester, acrylic acid-maleic acid copolymer ammonium salt, methacrylic acid-naphthoxypolyethylene glycol acrylate copolymer, methacrylic acid-polyethylene glycol Examples include monomethacrylate copolymer ammonium salt and polyethylene glycol monoacrylate. These can be used alone or in combination. Moreover, the timing of addition may be before or after the synthesis reaction. Such additives can be added in an amount of preferably 0.001 to 20%, more preferably 0.1 to 10%, based on the inorganic particles.

Further, in the present invention, the reaction can be a batch reaction or a continuous reaction. In general, it is preferred to carry out a batch reaction process for the convenience of discharging residues after the reaction. Although the scale of the reaction is not particularly limited, the reaction may be carried out on a scale of 100 L or less, or may be carried out on a scale of more than 100 L. The size of the reaction container may be, for example, about 10L to 100L, or about 100L to 1000L.

Further, the reaction can be controlled by the conductivity of the reaction solution and the reaction time, and specifically, the reaction can be controlled by adjusting the residence time of the reactant in the reaction tank. In addition, in the present invention, the reaction can also be controlled by stirring the reaction solution in the reaction tank or by conducting the reaction in multiple stages.

In the present invention, since the composite fiber, which is a reaction product, is obtained as a suspension, it can be stored in a storage tank, or subjected to treatments such as concentration, dehydration, pulverization, classification, aging, and dispersion, as necessary. can do. These steps can be performed using known processes, and may be appropriately determined in consideration of usage, energy efficiency, and the like. For example, the concentration/dehydration process is performed using a centrifugal dehydrator, a sedimentation concentrator, or the like. Examples of this centrifugal dehydrator include a decanter and a screw decanter. When using a filter or dehydrator, there are no particular restrictions on the type, and common types can be used; for example, pressure type dehydrators such as filter presses, drum filters, belt presses, tube presses, etc. A calcium carbonate cake can be obtained by suitably using a vacuum drum dehydrator such as an Oliver filter. Grinding methods include ball mills, sand grinder mills, impact mills, high pressure homogenizers, low pressure homogenizers, dyno mills, ultrasonic mills, canda grinders, attritors, stone mills, vibration mills, cutter mills, jet mills, disintegrators, and refining machines. , a short-screw extruder, a twin-screw extruder, an ultrasonic stirrer, a household juicer mixer, and the like. Examples of classification methods include mesh sieves, outward or inward slit or round hole screens, vibrating screens, heavy foreign matter cleaners, lightweight foreign matter cleaners, reverse cleaners, sieving testers, and the like. Examples of the dispersion method include a high-speed disperser and a low-speed kneader.

The conjugate fiber in the present invention can be blended into a filler or pigment in the form of a suspension without being completely dehydrated, but it can also be dried into a powder. The dryer in this case is not particularly limited either, but for example, a flash dryer, a band dryer, a spray dryer, etc. 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 can be made hydrophobic to improve miscibility with resins and the like.

In the present invention, water is used for preparing suspensions, etc., but this water can be ordinary tap water, industrial water, ground water, well water, etc., as well as ion exchange water, distilled water, ultraviolet water, etc. Pure water, industrial wastewater, and water obtained when separating and dehydrating the reaction solution can be suitably used.

Further, in the present invention, the reaction solution in the reaction tank can be circulated for use. By circulating the reaction solution in this manner and promoting stirring of the solution, the reaction efficiency is increased and it becomes easy to obtain a desired composite fiber of inorganic particles and fibers.

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

The inorganic particles mentioned here refer to compounds of metal elements or nonmetal elements. Compounds of metal elements include metal cations (e.g., Na ⁺ , Ca ²⁺ , Mg ²⁺ , Al ³⁺ , Ba ^{2+ ,} etc.) and anions (e.g., O ^2- , OH ^- , CO ₃ ^2- , PO ₄ ^3- , SO ₄ ^2- , NO ₃ ^- , Si ₂ O ₃ ^2- , SiO ₃ ^2- , Cl ^- , F ^- , S ^2-, etc.) are combined through ionic bonds, and are generally called inorganic salts. say something The compound of a nonmetallic element is silicic acid (SiO ₂ ) or the like. In the present invention, at least a part of the inorganic particles is a metal salt of calcium, magnesium, or barium, or at least a part of the inorganic particles is a metal salt of silicic acid or aluminum, or a metal salt of titanium, copper, silver, iron, or manganese. , cerium or zinc.

These inorganic particles can be synthesized by a known method, and may be either a gas-liquid method or a liquid-liquid method. An example of a gas-liquid method is a carbon dioxide gas method. For example, magnesium carbonate can be synthesized by reacting magnesium hydroxide with carbon dioxide gas. Examples of liquid-liquid methods include reacting acids (hydrochloric acid, sulfuric acid, etc.) and bases (sodium hydroxide, potassium hydroxide, etc.) by neutralization, reacting inorganic salts with acids or bases, and reacting inorganic salts with each other. Examples include a method of causing a reaction. For example, barium sulfate can be obtained by reacting barium hydroxide with sulfuric acid, aluminum hydroxide can be obtained by reacting aluminum sulfate with sodium hydroxide, and calcium and aluminum can be obtained by reacting calcium carbonate with aluminum sulfate. Composite inorganic particles can be obtained. Furthermore, when synthesizing inorganic particles in this way, it is also possible to coexist any metal or nonmetal compound in the reaction solution, and in this case, those metals or nonmetal compounds are efficiently incorporated into the inorganic particles. , can be combined. 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.

(calcium carbonate)
In the case of synthesizing calcium carbonate, for example, calcium carbonate can be synthesized by the carbon dioxide gas method, soluble salt reaction method, lime/soda method, soda method, etc. In a preferred embodiment, calcium carbonate is synthesized by the carbon dioxide gas method. Synthesize.

Generally, when producing calcium carbonate by the carbon dioxide method, lime is used as a calcium source, and there is a slaking process in which water is added to quicklime CaO to obtain slaked lime Ca(OH) ₂ , and carbon dioxide gas _CO2 is added to the slaked lime. Calcium carbonate is synthesized through a carbonation step in which calcium carbonate is blown into calcium carbonate, CaCO ₃ . At this time, a suspension of slaked lime prepared by adding water to quicklime may be passed through a screen to remove low-solubility lime particles contained in the suspension. Alternatively, slaked lime may be used directly as a calcium source. In the present invention, when calcium carbonate is synthesized by the carbon dioxide method, the carbonation reaction can also be carried out in the presence of cavitation bubbles.

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 even more preferably 1 to 20% by weight. It is about % by weight. If the solid content concentration is low, the reaction efficiency will be low and the manufacturing cost will be high, and if the solid content concentration is too high, the fluidity will be poor and the reaction efficiency will be reduced. In the present invention, since calcium carbonate is synthesized in the presence of cavitation bubbles, the reaction liquid and carbon dioxide gas can be suitably mixed even if a suspension (slurry) with a high solid content concentration is used.

As an aqueous suspension containing slaked lime, those commonly used for calcium carbonate synthesis can be used; for example, slaked lime can be prepared by mixing it with water, or quicklime (calcium oxide) can be slaked (digested) with water. It can be prepared by Conditions for slaked are not particularly limited, but for example, the concentration of CaO can be 0.05% by weight or more, preferably 1% by weight or more, and the temperature can be 20 to 100°C, preferably 30 to 100°C. . Further, the average residence time in the slaking reaction tank (slaker) is not particularly limited, but can be, for example, from 5 minutes to 5 hours, and preferably within 2 hours. Naturally, the slaker may be of a batch type or a continuous type. In addition, in the present invention, the carbonation reaction tank (carbonator) and the slaked reaction tank (slaker) may be separate, or one reaction tank may be used as the carbonation reaction tank and the slaked reaction tank. good.

In the synthesis of calcium carbonate, the higher the concentration of the raw materials (Ca ions, CO ₃ ions) in the reaction solution and the higher the temperature, the easier the nucleation reaction will proceed. Under such conditions, it is difficult for the nuclei to be fixed on the cellulose fibers, and inorganic particles liberated in the suspension are likely to be synthesized. Therefore, in order to produce composite fibers in which calcium carbonate is firmly bound, it is necessary to appropriately control the nucleation reaction. Specifically, this can be achieved by optimizing the Ca ion and pulp concentrations and slowing down the hourly supply of _CO2 . For example, the Ca ion concentration in the reaction vessel is preferably 0.01 mol/L or more and less than 0.20 mol/L. If it is less than 0.01 mol/L, the reaction will be difficult to proceed, and if it is 0.20 mol/L or more, inorganic particles liberated in the suspension will be easily synthesized. The pulp concentration is preferably 0.5% or more and less than 4.0%. If it is less than 0.5%, the frequency of raw materials colliding with the fibers will be reduced, making it difficult for the reaction to proceed, and if it is more than 4.0%, it will be impossible to obtain uniform composite fibers due to poor stirring. The amount of CO ₂ supplied per hour is desirably 0.001 mol/min or more and less than 0.060 mol/min per liter of reaction solution. If it is less than 0.001 mol/min, the reaction will be difficult to proceed, and if it is 0.060 mol/min or more, inorganic particles liberated in the suspension will be easily synthesized.

(magnesium carbonate)
When synthesizing magnesium carbonate, a known method can be used to synthesize magnesium carbonate. For example, magnesium bicarbonate can be synthesized from magnesium hydroxide and carbon dioxide gas, and basic magnesium carbonate can be synthesized from magnesium bicarbonate via magnesium orthocarbonate. Magnesium carbonate can be obtained as magnesium bicarbonate, magnesium orthocarbonate, basic magnesium carbonate, etc. by a synthetic method, but it is particularly preferable that the magnesium carbonate used in the fiber composite fiber of the present invention is basic magnesium carbonate. This is because magnesium bicarbonate has relatively low stability, and magnesium orthocarbonate, which is a columnar (acicular) crystal, may have difficulty fixing to fibers. On the other hand, by chemically reacting basic magnesium carbonate in the presence of fibers, it is possible to obtain a fiber composite fiber of magnesium carbonate and fibers in which the surface of the fibers is coated in a scale-like manner.

Further, in the present invention, the reaction solution in the reaction tank can be circulated for use. By circulating the reaction liquid in this manner and increasing the contact between the reaction liquid and carbon dioxide gas, the reaction efficiency is increased and it becomes easier to obtain desired inorganic particles.

In the present invention, a gas such as carbon dioxide (carbon dioxide) can be blown into the reaction vessel and mixed with the reaction liquid. According to the present invention, carbon dioxide gas can be supplied to the reaction liquid without a gas supply device such as a fan or blower, and the reaction can be carried out efficiently because the carbon dioxide gas is atomized by cavitation bubbles. .

In the present invention, there is no particular restriction on the carbon dioxide concentration of the gas containing carbon dioxide, but it is preferable that the carbon dioxide concentration is high. Further, the amount of carbon dioxide gas introduced into the injector is not limited and can be selected as appropriate.

The carbon dioxide-containing gas of the present invention may be substantially pure carbon dioxide gas or may be a mixture with other gases. For example, in addition to carbon dioxide gas, a gas containing an inert gas such as air or nitrogen can be used as the gas containing carbon dioxide. Further, as the carbon dioxide-containing gas, in addition to carbon dioxide gas (carbon dioxide gas), exhaust gas discharged from incinerators, coal boilers, heavy oil boilers, etc. of paper mills can be suitably used as the carbon dioxide-containing gas. In addition, the carbonation reaction can also be carried out using carbon dioxide generated from the lime calcination process.

In the synthesis of magnesium carbonate, the higher the concentration of the raw materials (Mg ions, CO ₃ ions) in the reaction solution, and the higher the temperature conditions, the easier the nucleation reaction will proceed. Under such conditions, it is difficult for the nuclei to be fixed on the cellulose fibers, and inorganic particles liberated in the suspension are likely to be synthesized. Therefore, in order to produce composite fibers in which magnesium carbonate is firmly bound, it is necessary to appropriately control the nucleation reaction. Specifically, this can be achieved by optimizing the Mg ion and pulp concentrations and slowing down the hourly supply of _CO2 . For example, the Mg ion concentration in the reaction vessel is preferably 0.0001 mol/L or more and less than 0.20 mol/L. If it is less than 0.0001 mol/L, the reaction will be difficult to proceed, and if it is 0.20 mol/L or more, inorganic particles liberated in the suspension will be easily synthesized. The pulp concentration is preferably 0.5% or more and less than 4.0%. If it is less than 0.5%, the frequency of raw materials colliding with the fibers will be reduced, making it difficult for the reaction to proceed, and if it is more than 4.0%, it will be impossible to obtain uniform composite fibers due to poor stirring. The amount of CO ₂ supplied per hour is desirably 0.001 mol/min or more and less than 0.060 mol/min per liter of reaction solution. If it is less than 0.001 mol/min, the reaction will be difficult to proceed, and if it is 0.060 mol/min or more, inorganic particles liberated in the suspension will be easily synthesized.

(barium sulfate)
When synthesizing barium sulfate, barium sulfate (BaSO ₄ ) is an ionic crystalline compound consisting of barium ions and sulfate ions, often in the form of plates or columns, and is poorly soluble in water. be. Pure barium sulfate is a colorless crystal, but when it contains impurities such as iron, manganese, strontium, and calcium, it becomes yellowish brown or blackish gray and translucent. It can be obtained as a natural mineral, but it can also be synthesized through chemical reactions. In particular, products synthesized by chemical reactions are used for medicine (X-ray contrast agents) and are widely used in paints, plastics, storage batteries, etc. due to their chemically stable properties.

In the present invention, composite fibers of barium sulfate and fibers can be produced by synthesizing barium sulfate in a solution in the presence of fibers. For example, methods include reacting an acid (such as sulfuric acid) with a base by neutralization, reacting an inorganic salt with an acid or base, or reacting inorganic salts with each other. For example, barium sulfate can be obtained by reacting barium hydroxide with sulfuric acid or aluminum sulfate, or barium sulfate can be precipitated by adding barium chloride to an aqueous solution containing sulfate.

In the synthesis of barium sulfate, the higher the concentration of raw materials (Ba ions, SO ₄ ions) in the solution, and the higher the temperature, the more likely the nucleation reaction will proceed. Under such conditions, it is difficult for the nuclei to be fixed on the cellulose fibers, and inorganic particles released in the suspension are easily synthesized. Therefore, in order to produce composite fibers in which barium sulfate is firmly bound, it is necessary to appropriately control the nucleation reaction. Specifically, this can be achieved by optimizing the concentration of Ba ions and pulp and slowing down the supply amount of SO ₄ ions per hour. For example, the Ba ion concentration in the reaction vessel is preferably 0.01 mol/L or more and less than 0.20 mol/L. If it is less than 0.01 mol/L, the reaction will be difficult to proceed, and if it is 0.20 mol/L or more, inorganic particles liberated in the suspension will be easily synthesized. The pulp concentration is preferably 0.5% or more and less than 4.0%. If it is less than 0.5%, the frequency of raw materials colliding with the fibers will be reduced, making it difficult for the reaction to proceed, and if it is more than 4.0%, it will be impossible to obtain uniform composite fibers due to poor stirring. The supply amount of SO ₄ ions per hour is desirably 0.005 mol/min or more and less than 0.080 mol/min per liter of reaction solution. If it is less than 0.001 mol/min, the reaction will be difficult to proceed, and if it is 0.080 mol/min or more, inorganic particles liberated in the suspension will be easily synthesized.

(Hydrotalcite)
When synthesizing hydrotalcite, a known method can be used to synthesize hydrotalcite. For example, fibers are immersed in a reaction vessel in an aqueous carbonate solution containing carbonate ions forming the intermediate layer and an alkaline solution (sodium hydroxide, etc.), and then in an acid solution (divalent metal ions and trivalent metal ions forming the base layer). (metal salt aqueous solution containing metal ions) is added, and hydrotalcite is synthesized by a coprecipitation reaction while controlling the temperature, pH, etc. In addition, the fibers are immersed in an acid solution (a metal salt aqueous solution containing divalent metal ions and trivalent metal ions constituting the base layer) in a reaction vessel, and then a carbonate aqueous solution containing carbonate ions constituting the intermediate layer. Hydrotalcite can also be synthesized by adding dropwise an alkaline solution (sodium hydroxide, etc.) and carrying out a coprecipitation reaction while controlling the temperature, pH, etc. Although reaction at normal pressure is common, there is also a method of obtaining it by hydrothermal reaction using an autoclave or the like (Japanese Unexamined Patent Publication No. 60-6619).

In the present invention, various chlorides, sulfides, nitoxides, and sulfides of magnesium, zinc, barium, calcium, iron, copper, cobalt, nickel, and manganese are used as sources of divalent metal ions constituting the basic layer. Can be used. Furthermore, various chlorides, sulfides, nitoxides, and sulfides of aluminum, iron, chromium, and gallium can be used as sources of trivalent metal ions constituting the basic layer.

In the present invention, carbonate ions, nitrate ions, chloride ions, sulfate ions, phosphate ions, etc. can be used as interlayer anions. When carbonate ions are used as interlayer anions, sodium carbonate is used as the source. However, sodium carbonate can be replaced with a gas containing carbon dioxide (carbon dioxide), and may be substantially pure carbon dioxide gas or a mixture with other gases. For example, exhaust gas discharged from incinerators, coal boilers, heavy oil boilers, etc. of paper mills can be suitably used as the carbon dioxide-containing gas. In addition, the carbonation reaction can also be carried out using carbon dioxide generated from the lime calcination process.

In the synthesis of hydrotalcite, the higher the concentration of raw materials in the solution (metal ions forming the basic layer, CO ₃ ions, etc.) and the higher the temperature, the more likely the nucleation reaction will proceed. Under these conditions, when producing composite fibers, it is difficult for the nuclei to be fixed on the cellulose fibers, and inorganic particles liberated in the suspension are likely to be synthesized. Therefore, in order to produce composite fibers in which hydrotalcite is firmly bound, it is necessary to appropriately control the nucleation reaction. Specifically, this can be achieved by optimizing the CO ₃ ion and pulp concentrations and by slowing down the amount of metal ions supplied per hour. For example, the CO ₃ ion concentration in the reaction vessel is preferably 0.01 mol/L or more and less than 0.80 mol/L. If it is less than 0.01 mol/L, the reaction will be difficult to proceed, and if it is 0.80 mol/L or more, inorganic particles liberated in the suspension will be easily synthesized. The pulp concentration is preferably 0.5% or more and less than 4.0%. If it is less than 0.5%, the frequency of raw materials colliding with the fibers will be reduced, making it difficult for the reaction to proceed, and if it is more than 4.0%, it will be impossible to obtain uniform composite fibers due to poor stirring. The amount of metal ions supplied per hour depends on the type of metal, but for example, in the case of Mg ions, it is preferably 0.001 mol/min or more and less than 0.010 mol/min per liter of reaction solution, and 0.001 mol/min or more and less than 0.010 mol/min. More preferably, it is less than .005 mol/min. If it is less than 0.001 mol/min, the reaction will be difficult to proceed, and if it is 0.010 mol/min or more, inorganic particles liberated in the suspension will be easily synthesized.

(Alumina/Silica)
When synthesizing alumina and/or silica, a known method can be used to synthesize alumina and/or silica. When one or more of an inorganic acid or an aluminum salt is used as a starting material for the reaction, the synthesis is performed by adding an alkali silicate salt. Synthesis can also be carried out by using an alkali silicate salt as a starting material and adding one or more of an inorganic acid or an aluminum salt, but it is easier to synthesize when an inorganic acid and/or an aluminum salt is used as a starting material. The adhesion of the material to the fibers is good. The inorganic acid is not particularly limited, and for example, sulfuric acid, hydrochloric acid, nitric acid, etc. can be used. Among these, sulfuric acid is particularly preferred from the viewpoint of cost and handling. Examples of the aluminum salt include aluminum sulfate, aluminum chloride, polyaluminum chloride, alum, potassium alum, and the like, among which aluminum sulfate can be preferably used. Examples of the alkali silicate include sodium silicate and potassium silicate, but sodium silicate is preferred because it is easily available. Although any molar ratio of silicic acid and alkali may be used, the one commonly distributed as No. 3 silicic acid has a molar ratio of SiO2:Na2O=3 to 3.4:1, and this is preferably used. can.

In the present invention, in producing composite fibers with silica and/or alumina attached to the fiber surface, silica and/or alumina are synthesized on the fibers while maintaining the pH of the reaction solution containing the fibers at 4.6 or less. It is preferable. Although the details of the reason why composite fibers with well-covered fiber surfaces can be obtained by this method are not completely clear, the ionization rate to trivalent aluminum ions increases by keeping the pH low. It is thought that composite fibers with high coverage and fixation rate can be obtained.

In the synthesis of silica and/or alumina, the higher the concentration of raw materials (silicate ions, aluminum ions) in the reaction solution and the higher the temperature, the more likely the nucleation reaction will proceed, but when producing composite fibers, Under such conditions, it is difficult for the nuclei to be fixed on the cellulose fibers, and inorganic particles liberated in the suspension are likely to be synthesized. Therefore, in order to produce composite fibers in which silica and/or alumina are firmly bound, it is necessary to appropriately control the nucleation reaction. Specifically, this can be achieved by optimizing the pulp concentration and slowing down the amount of silicate ions and aluminum ions supplied per hour. For example, the pulp concentration is preferably 0.5% or more and less than 4.0%. If it is less than 0.5%, the frequency of raw materials colliding with the fibers will be reduced, making it difficult for the reaction to proceed, and if it is more than 4.0%, it will be impossible to obtain uniform composite fibers due to poor stirring. The amount of silicate ions and aluminum ions added per hour is preferably 0.001 mol/min or more, more preferably 0.01 mol/min or more, and 0.5 mol/min per liter of reaction solution, for example, in the case of aluminum ions. It is preferably less than min, more preferably less than 0.050 mol/min. If it is less than 0.001 mol/min, the reaction will be difficult to proceed, and if it is 0.050 mol/min or more, inorganic particles liberated in the suspension will be easily synthesized.

As one preferred embodiment, the average primary particle size of the inorganic particles in the composite fiber of the present invention can be, for example, 1.5 μm or less, but the average primary particle size can also be 1200 nm or less or 900 nm or less, Furthermore, the average primary particle diameter can also be set to 200 nm or less or 150 nm or less. Moreover, the average primary particle diameter of the inorganic particles can also be 10 nm or more. Note that the average primary particle diameter can be measured using an electron micrograph.

(aluminum hydroxide)
Aluminum hydroxide is an ionic crystalline compound consisting of aluminum ions represented by Al(OH) ₃ and hydroxide ions, is often in the form of particles, and is poorly soluble in water. Synthesized products produced through chemical reactions are used in medicines and adsorbents, and they are also used as flame retardants and noncombustible agents by taking advantage of their property of releasing water when heated.

In the present invention, composite fibers of aluminum hydroxide and fibers can be produced by synthesizing aluminum hydroxide in a solution in the presence of fibers. For example, methods include reacting an acid (such as sulfuric acid) with a base by neutralization, reacting an inorganic salt with an acid or base, or reacting inorganic salts with each other. For example, aluminum hydroxide can be obtained by reacting sodium hydroxide and aluminum sulfate, or aluminum hydroxide can be precipitated by adding aluminum chloride to an aqueous solution containing an alkali salt.

In the synthesis of aluminum hydroxide, the higher the concentration of raw materials (Al ions, OH ions) in the solution, and the higher the temperature conditions, the more likely the nucleation reaction will proceed. Under such conditions, it is difficult for the nuclei to be fixed on the cellulose fibers, and inorganic particles released in the suspension are easily synthesized. Therefore, in order to produce composite fibers in which aluminum hydroxide is firmly bound, it is necessary to appropriately control the nucleation reaction. Specifically, this can be achieved by optimizing the OH ion and pulp concentrations and slowing down the supply amount of Al ions per hour. For example, the OH ion concentration in the reaction vessel is preferably 0.01 mol/L or more and less than 0.50 mol/L. If it is less than 0.01 mol/L, the reaction will be difficult to proceed, and if it is more than 0.50 mol/L, inorganic particles liberated in the suspension will be easily synthesized. The pulp concentration is preferably 0.5% or more and less than 4.0%. If it is less than 0.5%, the frequency of raw materials colliding with the fibers will be reduced, making it difficult for the reaction to proceed, and if it is more than 4.0%, it will be impossible to obtain uniform composite fibers due to poor stirring. The amount of Al ions supplied per hour is desirably 0.001 mol/min or more and less than 0.050 mol/min per liter of reaction solution. If it is less than 0.001 mol/min, the reaction will be difficult to proceed, and if it is 0.050 mol/min or more, inorganic particles liberated in the suspension will be easily synthesized.

Cellulose fiber The composite fiber used in the present invention is a composite of cellulose fiber and inorganic particles. As the cellulose fibers constituting the composite fibers, for example, not only natural cellulose fibers, but also regenerated fibers (semi-synthetic fibers) such as rayon and lyocell, synthetic fibers, and the like can be used without limitation. Examples of raw materials for cellulose fibers include pulp fibers (wood pulp and non-wood pulp), cellulose nanofibers, bacterial cellulose, cellulose derived from animals such as sea squirt, and algae. Wood pulp is produced by pulping wood raw materials. Bye. Wood raw materials include red pine, Japanese black pine, Sakhalin pine, Scots pine, Japanese pine, larch, fir, hemlock, cedar, cypress, larch, white fir, spruce, cypress, Douglas fir, hemlock, white fir, spruce, balsam fir, cedar, pine, Coniferous trees such as Melukushima pine and radiata pine, and mixtures thereof; hardwoods such as beech, birch, alder, oak, tabby, chinquapin, birch, cottonwood, poplar, ash, willow, eucalyptus, mangrove, lauan, acacia, and mixtures thereof. Examples include materials.

The method of pulping natural materials such as wood raw materials (woody raw materials) is not particularly limited, and examples include pulping methods commonly used in the paper manufacturing industry. Wood pulp can be classified by pulping method; for example, chemical pulp that is digested by methods such as the kraft method, sulfite method, soda method, and polysulfide method; mechanical pulp that is obtained by pulping using mechanical force such as a refiner or grinder; and pharmaceutical pulp. Examples include semi-chemical pulp obtained by pretreatment with , followed by pulping by mechanical force; waste paper pulp; deinked pulp, etc. The wood pulp may be in an unbleached state (before bleaching) or in a bleached state (after bleaching).

Examples of pulp derived from non-wood include cotton, hemp, sisal, Manila hemp, flax, straw, bamboo, bagasse, kenaf, sugar cane, corn, rice straw, mulberry, mitsumata, and the like.

The pulp fibers may be either unbeaten or beaten, and may be selected depending on the physical properties of the composite fiber sheet, but beating is preferable. This can be expected to improve sheet strength and promote fixation of inorganic particles.

In addition, these cellulose raw materials can be further processed to produce powdered cellulose, chemically modified cellulose such as oxidized cellulose, cellulose nanofiber: CNF (microfibrillated cellulose: MFC, TEMPO-oxidized CNF, phosphoric acid esterified CNF, carboxymethylated CNF, mechanically ground CNF, etc.). The powdered cellulose used in the present invention is, for example, a rod-shaped particle with a certain diameter that is produced by a method of refining, drying, crushing, and sieving the undecomposed residue obtained after acid hydrolyzing selected pulp. A crystalline cellulose powder having a distribution may be used, or commercially available products such as KC Flock (manufactured by Nippon Paper Industries), Ceolus (manufactured by Asahi Kasei Chemicals), and Avicel (manufactured by FMC) may be used. The degree of polymerization of cellulose in powdered cellulose is preferably about 100 to 1500, the crystallinity of powdered cellulose measured by X-ray diffraction is preferably 70 to 90%, and the volume average particle diameter measured by a laser diffraction particle size distribution analyzer is preferably 70 to 90%. is preferably 500 nm or more and 100 μm or less.

The oxidized cellulose used in the present invention can be obtained, for example, by oxidation in water using an oxidizing agent in the presence of a compound selected from the group consisting of N-oxyl compounds and bromides, iodides, or mixtures thereof. can. For cellulose nanofibers, the method of defibrating the cellulose raw material described above is used. As a defibration method, for example, an aqueous suspension of chemically modified cellulose such as cellulose or oxidized cellulose is mechanically ground or beaten using a refiner, high-pressure homogenizer, grinder, single-screw or multi-screw kneader, bead mill, etc. A method of defibration can be used. Cellulose nanofibers may be manufactured by combining one or more of the above methods. The fiber diameter of the produced cellulose nanofibers can be confirmed by electron microscopic observation, and is preferably in the range of 5 nm to 300 nm, for example. When producing this cellulose nanofiber, an arbitrary compound may be further added and reacted with the cellulose nanofiber before and/or after defibrating and/or making the cellulose into fine particles to make it modified with hydroxyl groups. can. Functional groups to be modified 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, imido group, acryloyl group, methacryloyl group, propionyl group, propioloyl group, butyryl group, 2-butyryl group, pentanoyl group, hexanoyl group, heptanoyl group, octanoyl group, nonanoyl group , acyl groups such as 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, 2-methacryloyloxyethyl isocyanate Isocyanate groups such as noyl group, methyl group, ethyl group, propyl group, 2-propyl group, butyl group, 2-butyl group, tert-butyl group, pentyl group, hexyl group, heptyl group, octyl group, nonyl group, decyl group Examples include alkyl groups such as a group, an undecyl group, a dodecyl group, a myristyl group, a palmityl group, and a stearyl group, an oxirane group, an oxetane group, an oxyl group, a thiirane group, and a thietane group. Hydrogen in these substituents may be substituted with a functional group such as a hydroxyl group or a carboxy group. Moreover, a part of the alkyl group may be an unsaturated bond. The compounds used to introduce these functional groups are not particularly limited, and include, for example, compounds having a phosphoric acid-derived group, compounds having a carboxylic acid-derived group, compounds having a sulfuric acid-derived group, and sulfonic acid-derived groups. Examples include compounds having a group such as , compounds having an alkyl group, and compounds having an amine-derived group. Compounds having a phosphoric acid group are not particularly limited, but include phosphoric acid, lithium salts of phosphoric acid such as lithium dihydrogen phosphate, dilithium hydrogen phosphate, trilithium phosphate, lithium pyrophosphate, and lithium polyphosphate. . Further examples include sodium salts of phosphoric acid, such as sodium dihydrogen phosphate, disodium hydrogen phosphate, trisodium phosphate, sodium pyrophosphate, and sodium polyphosphate. Further examples include potassium salts of phosphoric acid, such as potassium dihydrogen phosphate, dipotassium hydrogen phosphate, tripotassium phosphate, potassium pyrophosphate, and potassium polyphosphate. Further examples include ammonium salts of phosphoric acid such as ammonium dihydrogen phosphate, diammonium hydrogen phosphate, triammonium phosphate, ammonium pyrophosphate, and ammonium polyphosphate. Among these, phosphoric acid, sodium salt of phosphoric acid, potassium salt of phosphoric acid, ammonium salt of phosphoric acid are preferable from the viewpoint of high efficiency of phosphoric acid group introduction and easy industrial application, and sodium dihydrogen phosphate , disodium hydrogen phosphate are more preferred, but are not particularly limited. Compounds having a carboxyl group are not particularly limited, but 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. . Acid anhydrides of compounds having a carboxyl group are not particularly limited, but include acid anhydrides of dicarboxylic acid compounds such as maleic anhydride, succinic anhydride, phthalic anhydride, glutaric anhydride, adipic anhydride, and itaconic anhydride. It will be done. Derivatives of compounds having carboxyl groups are not particularly limited, but include imidized acid anhydrides of compounds having carboxyl groups, and derivatives of acid anhydrides of compounds having carboxyl groups. The imidized product of an acid anhydride of a compound having a carboxyl group is not particularly limited, but includes imidized products of dicarboxylic acid compounds such as maleimide, succinimide, and phthalic acid imide. The acid anhydride derivative of a compound having a carboxyl group is not particularly limited. For example, at least some of the hydrogen atoms of the acid anhydride of a compound having a carboxyl group, such as dimethylmaleic anhydride, diethylmaleic anhydride, diphenylmaleic anhydride, etc., have a substituent group (e.g., alkyl group, phenyl group, etc.). ) is included. Among the compounds having a group derived from a carboxylic acid, maleic anhydride, succinic anhydride, and phthalic anhydride are preferred because they are easy to apply industrially and are easily gasified, but are not particularly limited. Moreover, even if the compound is not chemically bonded, the cellulose nanofibers may be modified in such a manner that the compound to be modified is physically adsorbed onto the cellulose nanofibers. Examples of the physically adsorbable compound include surfactants, and any of anionic, cationic, and nonionic compounds may be used. When the above modification is performed before defibrating and/or pulverizing cellulose, these functional groups can be removed after the defibrating and/or pulverizing to return to the original hydroxyl groups. By performing the above modifications, it is possible to promote the fibrillation of cellulose nanofibers and to make it easier to mix them with various substances when using cellulose nanofibers.

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

In the present invention, in addition to fibers, it is possible to use substances that are incorporated into the product inorganic particles to produce composite particles. In the present invention, fibers such as pulp fibers are used, but these substances can also be incorporated by synthesizing inorganic particles in a solution containing inorganic particles, organic particles, polymers, etc. It is possible to produce composite particles.

The fiber length of the fibers to be composited is not particularly limited, but, for example, the average fiber length can be about 0.1 μm to 15 mm, and may also be 1 μm to 12 mm, 100 μm to 10 mm, 400 μm to 8 mm, etc. Among these, in the present invention, it is preferable that the average fiber length is 400 μm or more (0.4 mm or more).

The average fiber diameter of the fibers to be composited is not particularly limited, but for example, the average fiber diameter can be about 1 nm to 100 μm, and may be 500 nm to 100 μm, 1 μm to 90 μm, 3 μm to 50 μm, 5 μm to 30 μm, etc. Among these, in the present invention, it is preferable that the average fiber diameter is 500 nm or more because production efficiency in subsequent steps can be improved.

The average fiber length and average fiber diameter of the fibers can be measured using a fiber length measuring device. Examples of the fiber length measuring device include Valmet Fractionator (manufactured by Valmet).

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

In a preferred embodiment of the composite fiber according to the present invention, 15% or more of the fiber surface is coated with inorganic particles, and when the cellulose fiber surface is coated with such an area ratio, the characteristics attributable to the inorganic particles become large. However, the features attributable to the fiber surface become smaller.

The composite fiber according to the present invention can be used in various shapes, such as powder, pellet, mold, aqueous suspension, paste, sheet, board, block, and other shapes. Moreover, it is also possible to make a molded article such as a mold, particles, pellets, etc. using composite fibers as a main component together with other materials. There are no particular restrictions on the dryer used for drying to form a powder, but for example, a flash dryer, a band dryer, a spray dryer, etc. can be suitably used.

The composite fiber according to the present invention can be used in various applications, such as paper, fibers, cellulose composite materials, filter materials, paints, plastics and other resins, rubber, elastomers, ceramics, glass, tires, and architecture. Materials (asphalt, asbestos, cement, boards, concrete, bricks, tiles, plywood, fiberboard, ceiling materials, wall materials, flooring materials, roofing materials, etc.), furniture, various carriers (catalyst carriers, pharmaceutical carriers, pesticide carriers, microorganisms) carrier, etc.), adsorbent (impurity removal, deodorization, dehumidification, etc.), antibacterial material, antiviral agent, anti-wrinkle agent, clay, abrasive material, friction material, modifier, repair material, heat insulation material, heat resistant material, heat dissipation material materials, moisture-proofing materials, water-repellent materials, water-resistant materials, light-shielding materials, sealants, shielding materials, insect repellents, adhesives, medical materials, paste materials, anti-tarnishing agents, radio wave absorbing materials, insulation materials, sound-insulating materials, interior materials, waterproof materials. It can be widely used in various applications such as vibration materials, semiconductor sealing materials, radiation shielding materials, and other materials. Moreover, it can be used as various fillers, coating agents, etc. in the above-mentioned applications. Among these, adsorbents, antibacterial materials, antiviral agents, friction materials, radiation shielding materials, flame retardant materials, building materials, and heat insulating materials are preferred.

The composite fiber of the present invention may be applied to paper manufacturing applications, such as printing paper, newsprint, inkjet paper, PPC paper, kraft paper, wood-free paper, coated paper, slightly coated paper, wrapping paper, thin paper, and color-free paper. Paper, cast coated paper, non-carbon paper, label paper, thermal paper, various fancy papers, water-soluble paper, release paper, engineering paper, base paper for wallpaper, flame retardant paper (non-combustible paper), base paper for laminated boards, printed electronics paper, Battery separators, cushion paper, tracing paper, impregnated paper, ODP paper, construction material paper, decorative material paper, envelope paper, tape paper, heat exchange paper, synthetic fiber paper, sterilization paper, water-resistant paper, oil-resistant paper, heat-resistant paper, Photocatalyst paper, cosmetic paper (greasy paper, etc.), various sanitary papers (toilet paper, tissue paper, wipes, diapers, sanitary products, etc.), cigarette paper, paperboard (liner, core paper, white paperboard, etc.), paper plate paper, Examples include cup base paper, baking paper, abrasive paper, and synthetic paper. That is, according to the present invention, it is possible to obtain a composite fiber of inorganic particles and fibers having a small primary particle size and a narrow particle size distribution. It is possible to exhibit the characteristics of Furthermore, unlike the case where inorganic particles are simply blended with fibers, by forming inorganic particles into composite fibers with fibers, it is not only easier to retain the inorganic particles in the sheet, but also to create a sheet in which the inorganic particles are uniformly dispersed without agglomeration. Obtainable. The results of electron microscopy have revealed that, in a preferred embodiment, the inorganic particles of the present invention are not only fixed on the outer surface of fibers and inside the lumen, but also formed inside microfibrils.

Furthermore, when using the composite fiber according to the present invention, particles generally called inorganic fillers and organic fillers and various fibers can be used in combination. For example, as inorganic fillers, calcium carbonate (light calcium carbonate, heavy calcium carbonate), magnesium carbonate, barium carbonate, aluminum hydroxide, calcium hydroxide, magnesium hydroxide, zinc hydroxide, clay (kaolin, calcined kaolin, delamic kaolin) ), talc, zinc oxide, zinc stearate, titanium dioxide, silica produced from sodium silicate and mineral acids (white carbon, silica/calcium carbonate composite fiber, silica/titanium dioxide composite fiber), clay, bentonite, diatomaceous earth, Examples include calcium sulfate, zeolite, inorganic fillers that regenerate and utilize ash obtained from the deinking process, and inorganic fillers that form composite fibers with silica and calcium carbonate during the regeneration process. As the calcium carbonate-silica composite, in addition to calcium carbonate and/or light calcium carbonate-silica composite, amorphous silica such as white carbon may be used in combination. Examples of organic fillers include urea-formalin resin, polystyrene resin, phenolic resin, micro hollow particles, acrylamide composite fibers, wood-derived substances (fine fibers, microfibril fibers, powdered kenaf), modified insolubilized starch, ungelatinized starch, etc. can be mentioned. Fibers include natural fibers such as cellulose, synthetic fibers artificially synthesized from raw materials such as petroleum, recycled fibers (semi-synthetic fibers) such as rayon and lyocell, and even inorganic fibers. can be used. In addition to the above, examples of natural fibers include protein fibers such as wool, silk thread, and collagen fibers, and complex sugar chain fibers such as chitin/chitosan fibers and alginic acid fibers. Examples of cellulose-based raw materials include pulp fibers (wood pulp and non-wood pulp), bacterial cellulose, cellulose derived from animals such as sea squirt, and algae, and wood pulp may be produced by pulping wood raw materials. Wood raw materials include red pine, Japanese black pine, Sakhalin pine, Scots pine, Japanese pine, larch, fir, hemlock, cedar, cypress, larch, white fir, spruce, cypress, Douglas fir, hemlock, white fir, spruce, balsam fir, cedar, pine, Coniferous trees such as Melukushima pine and radiata pine, and mixtures thereof; hardwoods such as beech, birch, alder, oak, tabby, chinquapin, birch, cottonwood, poplar, ash, willow, eucalyptus, mangrove, lauan, acacia, and mixtures thereof. Examples include materials. The method of pulping the wood raw material is not particularly limited, and examples include pulping methods commonly used in the paper manufacturing industry. Wood pulp can be classified by pulping method; for example, chemical pulp that is digested by methods such as the kraft method, sulfite method, soda method, and polysulfide method; mechanical pulp that is obtained by pulping using mechanical force such as a refiner or grinder; and pharmaceutical pulp. Examples include semi-chemical pulp obtained by pretreatment with , followed by pulping by mechanical force; waste paper pulp; deinked pulp, etc. The wood pulp may be in an unbleached state (before bleaching) or in a bleached state (after bleaching). Examples of pulp derived from non-wood include cotton, hemp, sisal, Manila hemp, flax, straw, bamboo, bagasse, kenaf, sugar cane, corn, rice straw, mulberry, mitsumata, and the like. The wood pulp and non-wood pulp may be either unbeaten or beaten. In addition, these cellulose raw materials can be further processed to produce powdered cellulose, chemically modified cellulose such as oxidized cellulose, cellulose nanofiber: CNF (microfibrillated cellulose: MFC, TEMPO-oxidized CNF, phosphoric acid esterified CNF, carboxymethylated It can also be used as CNF (mechanically ground CNF). Examples of synthetic fibers include polyester, polyamide, polyolefin, and acrylic fibers; examples of semi-synthetic fibers include rayon and acetate; examples of inorganic fibers include glass fibers, carbon fibers, and various metal fibers. Regarding the above, these may be used alone or in combination of two or more types.

The average particle diameter, shape, etc. of the inorganic particles constituting the composite fiber of the present invention can be confirmed by observation using an electron microscope. Furthermore, by adjusting the conditions for synthesizing inorganic particles, inorganic particles having various sizes and shapes can be made into fibers and composite fibers.

Form of Composite Fiber In the present invention, the above-described composite fiber can be formed into various molded articles (bodies). For example, when the composite fiber of the present invention is formed into a sheet, a sheet with a high ash content can be easily obtained. Further, the obtained sheets can be bonded together to form a multilayer sheet.

Paper machines (paper making machines) used for sheet production include, for example, Fourdrinier paper machines, cylinder paper machines, gap formers, hybrid formers, roto formers, multilayer paper machines, and known paper machines that combine the paper making methods of these devices. can be mentioned. The press linear pressure in the paper machine and the calender linear pressure when calendering is performed in the subsequent stage can both be determined within a range that does not impede the operability or the performance of the composite fiber sheet. Furthermore, starch, various polymers, pigments, and mixtures thereof may be applied to the formed sheet by impregnation or coating.

During sheet formation, wet and/or dry paper strength agents (paper strength enhancers) can be added. Thereby, the strength of the composite fiber sheet can be improved. Paper strength agents include, for example, urea formaldehyde resin, melamine formaldehyde resin, polyamide, polyamine, epichlorohydrin resin, vegetable gum, latex, polyethyleneimine, glyoxal, gum, mannogalactan polyethyleneimine, polyacrylamide resin, polyvinylamine. , polyvinyl alcohol, and other resins; composite polymers or copolymer polymers consisting of two or more selected from the above resins; starch and processed starch; carboxymethyl cellulose, guar gum, urea resins, and the like. The amount of paper strength agent added is not particularly limited.

Furthermore, a high molecular weight polymer or an inorganic substance may be added in order to promote the fixation of the filler to the fibers or to improve the yield of the filler and the fibers. For example, as coagulants polyethyleneimines and modified polyethyleneimines containing tertiary and/or quaternary ammonium groups, polyalkyleneimines, dicyandiamide polymers, polyamines, polyamine/epichlorohydrin polymers, and dialkyl diallyl quaternary ammonium monomers, dialkyl Cations such as aminoalkyl acrylate, dialkylaminoalkyl methacrylate, dialkylaminoalkylacrylamide and polymers of dialkylaminoalkylmethacrylamide and acrylamide, polymers consisting of monoamines and epihalohydrin, polyvinylamine and polymers having a vinylamine moiety, and mixtures thereof. In addition to cationic polymers, cation-rich amphoteric polymers in which anionic groups such as carboxyl groups and sulfone groups are copolymerized in the polymer molecules, and mixtures of cationic polymers and anionic or amphoteric polymers are used. be able to. Further, as a retention agent, a cationic, anionic, or amphoteric polyacrylamide-based substance can be used. In addition, it is also possible to apply a so-called dual polymer yield system in which at least one kind of cationic or anionic polymer is used, and at least one kind of anionic bentonite, colloidal silica, polysilicate, A multi-component yield system that uses at least one type of inorganic fine particles such as polysilicic acid or polysilicate microgels and aluminum modified products thereof, and organic fine particles with a particle size of 100 μm or less called so-called micropolymers in which acrylamide is crosslinked and polymerized. Good too. In particular, when the polyacrylamide-based material used alone or in combination has a weight average molecular weight of 2 million Daltons or more as determined by the intrinsic viscosity method, a good yield can be obtained, preferably 5 million Daltons or more, and more preferably 5 million Daltons or more. A very high yield can be obtained when the acrylamide material has a weight of 10 million Daltons or more and less than 30 million Daltons. The form of this polyacrylamide-based material may be an emulsion type or a solution type. The specific composition is not particularly limited as long as the substance contains an acrylamide monomer unit as a structural unit, but for example, a copolymer of a quaternary ammonium salt of an acrylic acid ester and acrylamide, or Examples include ammonium salts that are quaternized after copolymerizing and acrylic acid ester. The cationic charge density of the cationic polyacrylamide-based material is not particularly limited.

In addition, depending on the purpose, inorganic particles (so-called fillers), etc. The amount of each additive used is not particularly limited.

The basic weight (basis weight: weight per 1 square meter) of the sheet can be adjusted as appropriate depending on the purpose, but for example, when used as a building material, a value of 60 to 1200 g/m ² provides strong strength, and This is good because the drying load is low. Further, the basis weight of the sheet may be 1200 g/m ² or more, for example, 2000 to 110000 g/m ² .

It is also possible to use molding methods other than forming sheets, for example, a method called pulp molding in which raw materials are poured into a mold and suction dehydrated and dried, or a method in which the material is spread on the surface of molded objects such as resin or metal and dried. Thereafter, molded products having various shapes can be obtained by peeling the molded product from the base material. It can also be mixed with resin and molded into a plastic-like material, or it can be mixed with cement or rubber and used as a reinforcing material. Further, it can also be formed into a board shape or into a block shape by pressure/heat press molding, which is generally used to create inorganic boards such as cement or gypsum. Generally, a sheet can be folded or rolled up, but if more strength is required, it can be made into a board shape. Further, it is also possible to form the material into a thick block, such as a rectangular parallelepiped or a cube.

In the blending, drying, and molding described above, only one type of conjugate fiber can be used, or two or more types of conjugate fibers can be mixed and used. When using two or more types of composite fibers, they can be mixed in advance, or they can be blended, dried, molded, and then mixed together.

Further, various organic substances such as polymers and various inorganic substances such as pigments may be added to the composite fiber molded product afterwards.

Printing can be applied to molded products manufactured using the product of the present invention. This printing method is not particularly limited, but examples include offset printing, silk screen printing, screen printing, gravure printing, microgravure printing, flexo printing, letterpress printing, sticker printing, form printing, on-demand printing, and fan printing. It can be performed by a known method such as shear roll printing or inkjet printing. Among these, inkjet printing is preferable because unlike offset printing, there is no need to prepare a printing plate, it is relatively easy to increase the size of the inkjet printer, and printing on large sheets is also possible. Furthermore, since flexographic printing can suitably print on molded products with relatively large surface irregularities, it can also be suitably used when molded into shapes such as boards, molds, and blocks.

Further, the type of pattern of the printed image formed by printing is not particularly limited, and may include, for example, a wood grain pattern, a stone grain pattern, a cloth grain pattern, an abstract pattern, a geometric pattern, characters, symbols, or a combination thereof. It may be any color as desired, and may be a single solid color.

The present invention will be explained in more detail by giving specific experimental examples, but the present invention is not limited to the following specific examples. Further, unless otherwise specified in this specification, concentrations, parts, etc. are based on weight, and numerical ranges are written including the end points thereof.

[Example 1]
Softwood bleached kraft pulp (NBKP, manufactured by Nippon Paper Industries) and hardwood bleached kraft pulp (LBKP, manufactured by Nippon Paper Industries) were placed in a pulper (manufactured by IHI Voite) at a ratio of 2:8, water was added, and the pulp was disintegrated at a concentration of 5%. , a pulp dispersion was prepared. This was refined using a double disc refiner (DDR, manufactured by Aikawa Tekko Co., Ltd.) until the freeness reached 550 ml.
The obtained pulp dispersion was passed through a screen (manufactured by Aikawa Iron Works Co., Ltd.) to remove foreign substances, and then 10 m ³ of the liquid was poured into a reactor (manufactured by Sumitomo Heavy Industries Process Equipment Co., Ltd.), and sodium hydroxide was added to the liquid while stirring at a temperature of 57°C. and sodium carbonate were added in an amount of 75.3% and 12.5% based on the weight of the pulp, and the pH was adjusted to 13. Thereafter, a mixed solution of 9.7% zinc sulfate and 3.4% aluminum sulfate was added dropwise over 60 minutes to react until the pH reached 7. The suspension of the obtained composite fibers was dehydrated to a concentration of 30% using a dehydrator (manufactured by Fukoku Kogyo Co., Ltd.), and then added to a Proshare mixer (model WB, manufactured by Pacific Kiko Co., Ltd.) and stirred at room temperature. Subsequently, steam was introduced into the Proshare mixer to raise the temperature inside the device to 80° C. or higher, and the mixture was dried while being stirred. After drying until the moisture content was about 10%, it was granulated while adding water (finished particle size after granulation: about 0.5 mm, moisture content after granulation: about 50%). Finally, granules with a particle size of 0.5 mm or less were obtained using a 0.5 mesh sieve.
The composite fiber granules were placed in a flexible con bag with an inner bag (product name: inner bag bottom seal, inner bag: 0.15 mm thick, product number: HS-150420, manufacturer name: Heisei Co., Ltd.) and kept in a sealed state. I kept it there. The solid content contained in this sample was 50%.

[Comparative example 1]
The composite fiber granules prepared in Example 1 were stored in a flexible container bag (without an inner bag) in an unsealed state.

<Evaluation of deodorizing properties>
In Examples and Comparative Examples, composite fiber concentrates were stored for 12 months, and the composite fiber concentrates collected therefrom were prepared into granules and used to evaluate the deodorizing properties of the composite fibers.
The deodorizing test was conducted based on the method of SEK Mark Textile Product Certification Standard (JEC301, Textile Evaluation Technology Council), and the deodorizing property against methyl mercaptan (initial odor concentration 120 ppm) was evaluated. In addition, it was quantified using a detection tube. The results are shown in Table 1.

As shown in Table 1, the conjugate fiber concentrate of Example 1 that was stored in a hermetically sealed condition was more stable during 12 months of storage than the conjugate fiber concentrate of Comparative Example 1 that was not stored in a hermetically sealed condition. It was found that the reduction in methyl mercaptan reduction rate was suppressed, and the deterioration in deodorizing performance was suppressed.

Claims (5)

A step of concentrating composite fibers of cellulose fibers and inorganic particles to a concentration of 15 to 60% by mass to prepare a concentrate;
a step of enclosing the composite fiber concentrate in a sealable container and storing or transporting it to a predetermined location;
A method for preparing composite fibers, including: 2. The method for preparing conjugate fibers according to claim 1, wherein the conjugate fiber concentrate is sealed in a resin bag and stored in a flexible container-type bag or transported to a predetermined location. The method according to claim 1 or 2, comprising the step of disintegrating the stored composite fiber concentrate or the composite fiber concentrate transported to a predetermined location in water. The method according to any one of claims 1 to 3, wherein at least some of the inorganic particles are metal salts of calcium, silicic acid, magnesium, barium, or aluminum, or metal particles containing titanium, copper, or zinc. The method according to any one of claims 1 to 4, wherein the inorganic particles include hydrotalcite.