Method for producing dried cellulose fiber powder

Abstract

To provide a manufacturing method of a dry powder of a cellulose fiber showing excellent redispersibility, and a manufacturing method of a resin composite containing using the dry powder prepared by the method.SOLUTION: A method for manufacturing a dry powder of a cellulose fiber, comprising a slurry preparation step for preparing a slurry comprising the cellulose fibers and water, and a granulation step for agitating the slurry under reduced pressure to form a dry powder of the cellulose fibers, in which the granulation step comprises forming the particles of the cellulose fibers by stirring and chopper pulverizing the particles.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a method for producing a dried powder of cellulose fibers, and a method for producing a composite (hereinafter also referred to as a resin composite) containing cellulose fibers and a resin. [Background technology]

[0002] Thermoplastic resins are lightweight and have excellent processability, making them widely used in various applications such as automotive components, electrical and electronic components, office equipment housings, and precision parts. However, since resins alone often have insufficient mechanical properties and dimensional stability, composite resins with various fillers are commonly used. In recent years, the use of nanofibers such as cellulose nanofibers (CNF) as such fillers has been investigated. Because nanofibers, including CNF, tend to aggregate when dry, they are manufactured as dispersions that allow for stable dispersion. When applying cellulose nanofibers to various applications, the above dispersion may be dried and then redispersed in a dispersion medium to prepare a redispersed solution.

[0003] Patent Document 1 describes a method for redispersing a cellulose nanofiber dispersion by drying a manufactured cellulose nanofiber dispersion and then dispersing the resulting cellulose nanofiber powder in an aqueous solvent, characterized in that the cellulose nanofiber powder is stirred and mechanical shear force is applied when redispersing the cellulose nanofiber powder in the aqueous solvent.

[0004] Patent Document 2 describes a method for treating chemically modified fibril cellulose, the method comprising: introducing a chemically modified fibril cellulose material into a thermal drying apparatus (20) including a belt (22), wherein the fibril cellulose material forms at least one rod-shaped body on the belt (22); and dewatering the chemically modified fibril cellulose material on the belt (22) using a heated airflow having a temperature of at least 40°C, and concentrating and / or drying the chemically modified fibril cellulose material such that the dry solid content of the fibril cellulose material is at least 10% after passing through the thermal drying apparatus (20).

[0005] Patent Document 3 describes a powdered nanofiber characterized in that the powdered nanofiber is formed by blending 1 to 40% by weight of (B) a dispersant in terms of solid content with respect to (A) powdered nanofiber, and has a bulk density of 90 to 200 g / L.

[0006] Patent Document 4 describes a method for producing dried microfibers having a water content of 0 to 1% by mass, comprising homogenizing cellulose nanofibers in the presence of an organic solvent, and then removing the organic solvent. [Prior Art Document] [Patent Documents]

[0007] [Patent Document 1] International Publication No. 2017 / 154568 [Patent Document 2] Japanese National Publication of International Patent Application No. 2015-512964 [Patent Document 3] Japanese Unexamined Patent Publication No. 2017-210596 [Patent Document 4] Japanese Unexamined Patent Publication No. 2012-224960 [Summary of the Invention] [Problems to be Solved by the Invention]

[0008] When cellulose fibers, particularly cellulose nanofibers, are stored or transported in the form of a dispersion, problems arise because the cellulose fibers are prone to degradation (such as spoilage) due to being placed in a humid environment, and because the dispersion medium occupies extra volume and weight, increasing storage and transport costs. Storing and transporting cellulose fibers in a dry state reduces volume and weight, and also offers the advantage of easier compounding with other materials depending on the application. However, once cellulose fibers are dried from their dispersion state, it has been difficult to reproduce the good dispersion state of the cellulose fibers before drying (i.e., to obtain good redispersibility) even when they are subsequently redispersed in a dispersion medium.

[0009] The present invention aims to solve the above problems and provide a method for producing a dried cellulose fiber powder that exhibits good redispersibility, and a method for producing a resin composite that includes using the dried powder prepared by this method. [Means for solving the problem]

[0010] As a result of diligent research to solve the above problems, the inventors of the present invention have found that when producing dried cellulose fiber powder under specific drying conditions, it is possible to produce dried cellulose fiber powder with excellent redispersibility, leading to the present invention. That is, the present invention encompasses the following aspects.

[0011] [1] A method for producing a dry powder of cellulose fibers, A slurry preparation step for preparing a slurry containing cellulose fibers and water, and A granulation step in which the slurry is stirred under reduced pressure to form a dry powder of cellulose fibers. Includes, A method wherein the granulation step includes forming particles of cellulose fibers by stirring and crushing the particles with a chopper. [2] The method according to embodiment 1, wherein the slurry contains 5% by mass or more of water at the start of the granulation process. [3] The method according to embodiment 1 or 2, wherein an additional medium, which is a liquid medium different from water, is added to the slurry in the granulation step. [4] The method according to embodiment 3, wherein in the granulation step, an additional medium, which is a liquid medium different from water, is added to the slurry two or more times. [5] The method according to embodiment 3 or 4, wherein the additional medium is selected from the group consisting of alcohols, ethers, carboxylic acids, esters, ketones, and nitrogen-containing solvents having boiling points of 50°C to 170°C. [6] The method according to any one of embodiments 3 to 5, wherein the additional medium is a substance that forms an azeotrope with water. [7] The method according to embodiment 6, wherein the additional medium is added to the slurry in a proportion higher than the azeotropic composition ratio with water. [8] The method according to any one of embodiments 3 to 7, wherein the additional medium is added to the slurry in a mass ratio of water to the additional medium in the slurry ranging from 1:99 to 90:10. [9] A method for producing a dry powder of cellulose fibers, A slurry preparation step for preparing a slurry containing cellulose fibers and a liquid medium, and A granulation step in which the slurry is stirred under reduced pressure to form a dry powder of cellulose fibers. Includes, A method wherein the granulation step includes forming particles of cellulose fibers by stirring and crushing the particles with a chopper.

[10] The method according to embodiment 9, wherein the liquid medium is one or more selected from the group consisting of alcohols, ethers, carboxylic acids, esters, ketones, and nitrogen-containing solvents having a boiling point of 50°C to 170°C.

[11] The method according to any one of embodiments 1 to 10, wherein a binder is added to the slurry in the slurry preparation step and / or the granulation step.

[12] The method according to embodiment 11, wherein the binder is selected from the group consisting of polyalkylene oxides, cellulose ethers, and cellulose esters.

[13] The method according to embodiment 11 or 12, wherein in the slurry preparation step and / or the granulation step, the binder is dissolved in a medium and added to the slurry.

[14] The granulation process is carried out in a granulator equipped with stirring blades, chopper blades and a vacuum mechanism. In the granulation process, stirring is performed by rotating the stirring blades at a peripheral speed of 0.5 m / sec to 40 m / sec, and chopper pulverization is performed by rotating the chopper blades at 100 rpm to 6000 rpm. The method according to any one of embodiments 1 to 13, wherein the granulator is configured such that the chopped particles are further subjected to the stirring.

[15] The granulation process is carried out in a granulator equipped with stirring blades, chopper blades and a vacuum mechanism. In the granulation process, stirring is performed by rotating the stirring blades at a peripheral speed of 0.5 m / sec to 40 m / sec, and chopper pulverization is performed by rotating the chopper blades at a peripheral speed of 0.5 m / sec to 40 m / sec. The method according to any one of embodiments 1 to 14, wherein the granulator is configured such that the chopped particles are further subjected to the stirring.

[16] The method according to embodiment 15, wherein the peripheral speed of the chopper blade is less than or equal to the peripheral speed of the stirring blade.

[17] The method according to any one of embodiments 1 to 16, wherein the granulation step is carried out at a temperature of 20 to 160°C and a reduced pressure of -100 kPa to -1 kPa.

[18] The method according to any one of embodiments 1 to 17, wherein the bulk density of the dry powder is 0.05 g / mL to 1.0 g / mL.

[19] The method according to any one of embodiments 1 to 18 above, using cellulose fibers derived from cotton linters.

[20] The method according to any one of embodiments 1 to 19 above, using chemically modified cellulose fibers.

[21] The method according to any one of embodiments 1 to 20, wherein cellulose fibers are chemically modified with hydrophobic substituents.

[22] The method according to any one of embodiments 1 to 21, wherein the number-average fiber diameter of the cellulose fibers is 10 nm or more and 1000 nm or less.

[23] A method for producing a composite comprising cellulose fibers and a resin, wherein the method comprises preparing a dry powder by the method described in any of the above embodiments 1 to 22, and mixing the dry powder with the resin.

[24] The resin is a thermoplastic resin, The method according to embodiment 23, wherein the dried powder and the resin are mixed by melt kneading. [Effects of the Invention]

[0012] According to one aspect of the present invention, a method for producing a dried cellulose fiber powder exhibiting good redispersibility, and a method for producing a resin composite including using the dried powder prepared by the said method may be provided. [Brief explanation of the drawing]

[0013] [Figure 1] This is an explanatory diagram of the calculation methods for IR Index 1370 and IR Index 1030. [Figure 2] This is an explanatory diagram of the measurement method for the thermal decomposition onset temperature (TD) and the 1% weight loss temperature (T1%). [Modes for carrying out the invention]

[0014] The following describes some exemplary embodiments of the present invention, but the present invention is not limited to these embodiments.

[0015] ≪Method for producing dried cellulose fiber powder≫ One aspect of the present invention provides a method for producing dried cellulose fiber powder, comprising a slurry preparation step of preparing a dispersion (slurry) containing cellulose fibers and a liquid medium (in one aspect, a liquid medium containing water), and a granulation step of stirring the slurry under reduced pressure to form dried cellulose fiber powder, wherein the granulation step includes forming cellulose fiber particles by stirring and pulverizing the particles with a chopper.

[0016] <Slurry preparation process> In this process, a slurry containing cellulose fibers and a liquid medium (in one embodiment, a liquid medium containing water) is prepared. Natural cellulose and regenerated cellulose can be used as raw materials for the cellulose fibers. As natural cellulose, wood pulp obtained from wood species (hardwood or softwood), non-wood pulp obtained from non-wood species (cotton, bamboo, hemp, bagasse, kenaf, cotton linters, sisal, straw, etc.), and cellulose fiber aggregates produced by animals (e.g., sea squirts), algae, or microorganisms (e.g., acetic acid bacteria) can be used. As regenerated cellulose, regenerated cellulose fibers (viscose, cupro, Tencel, etc.), cellulose derivative fibers, and ultrafine threads of regenerated cellulose or cellulose derivatives obtained by electrospinning can be used. Non-wood pulp obtained from cotton linters is preferred because it can yield cellulose fibers of high purity and high crystallinity.

[0017] In one embodiment, the cellulose fiber is a cellulose nanofiber. Cellulose nanofiber refers to fine cellulose obtained by treating pulp or the like with hot water at 100°C or higher to hydrolyze and weaken the hemicellulose, and then defibrating it using a grinding method such as a high-pressure homogenizer, microfluidizer, ball mill, disc mill, or mixer (e.g., homomixer). In one embodiment, the cellulose nanofiber has a number-average fiber diameter of 1 nm to 1000 nm. The cellulose fiber may also be chemically modified as described later.

[0018] The slurry can be prepared by dispersing cellulose fibers (e.g., cellulose nanofibers obtained through the above defibration process) in a liquid medium. Dispersion may be performed using a high-pressure homogenizer, microfluidizer, ball mill, disc mill, mixer (e.g., homomixer), and for example, the product of the above defibration may be obtained as the product of the slurry preparation step of this disclosure. In one embodiment, the liquid medium in the slurry may contain water, and in another embodiment, it may not contain water. In one embodiment, the liquid medium may contain water and optionally other liquid mediums (e.g., organic solvents) one or more in combination. As organic solvents, commonly used water-miscible organic solvents can be used, such as: alcohols with a boiling point of 50°C to 170°C (e.g., methanol, ethanol, n-propanol, i-propanol, n-butanol, i-butanol, s-butanol, t-butanol, etc.); ethers (e.g., propylene glycol monomethyl ether, 1,2-dimethoxyethane, diisopropyl ether, tetrahydrofuran, 1,4-dioxane, etc.); carboxylic acids (e.g., formic acid, acetic acid, lactic acid, etc.); esters (e.g., ethyl acetate, vinyl acetate, etc.); ketones (e.g., acetone, methyl ethyl ketone, methyl isobutyl ketone, cyclopentanone, cyclohexanone, etc.); nitrogen-containing solvents (dimethylformamide, dimethylacetamide, acetonitrile, etc.). It is preferable that these organic solvents form an azeotropic mixture with water. It is especially preferable that the azeotropic mixture has a minimum azeotropic point where the boiling point is lower than the boiling points of water and the organic solvent individually, as this makes it easier to dry the water even at low pressure and / or temperature. In a typical embodiment, the liquid medium in the slurry is substantially water only.

[0019] If the liquid medium does not contain water, the liquid medium is a commonly used water-miscible organic solvent, for example: alcohols with a boiling point of 50°C to 170°C (e.g., methanol, ethanol, n-propanol, i-propanol, n-butanol, i-butanol, s-butanol, t-butanol, etc.); ethers (e.g., propylene glycol monomethyl ether, 1,2-dimethoxyethane, diisopropyl ether, tetrahydrofuran, 1,4-dioxane, etc.); carboxylic acids (e.g., formic acid, acetic acid, lactic acid, etc.); esters (e.g., acetic acid). It may be one or more selected from the group consisting of: chill, vinyl acetate, etc.; ketones (e.g., acetone, methyl ethyl ketone, methyl isobutyl ketone, cyclopentanone, cyclohexanone, etc.); nitrogen-containing solvents (dimethylformamide, dimethylacetamide, acetonitrile, etc.) and hydrophobic organic solvents, such as aromatic hydrocarbons (benzene, toluene, xylene, etc.); aliphatic hydrocarbons (hexane, heptane, octane, decane, etc.); halogenated hydrocarbons (tetrachloromethane, chloroform, dichloromethane, chloroethane, etc.).

[0020] The slurry may contain additives (binders, dispersants, antioxidants, preservatives, thickeners, etc.) in addition to cellulose fibers and a liquid medium.

[0021] Since cellulose raw materials contain alkali-soluble components and sulfuric acid-insoluble components (such as lignin), the alkali-soluble components and sulfuric acid-insoluble components may be reduced through purification processes such as deligninization by pulping and bleaching processes. On the other hand, purification processes such as deligninization by pulping and bleaching processes cleave the molecular chains of cellulose and change the weight-average molecular weight and number-average molecular weight. Therefore, it is desirable that the purification and bleaching processes of the cellulose raw material are controlled to such an extent that the weight-average molecular weight of cellulose and the ratio of weight-average molecular weight to number-average molecular weight do not deviate from an appropriate range.

[0022] Furthermore, purification processes such as lignin removal through pulping and bleaching reduce the molecular weight of cellulose molecules. Therefore, there are concerns that these processes may lead to a decrease in the molecular weight of cellulose and an increase in the proportion of alkali-soluble components due to the alteration of the cellulose raw material. Since alkali-soluble components have poor heat resistance, it is desirable that the purification and bleaching processes of the cellulose raw material be controlled so that the amount of alkali-soluble components contained in the cellulose raw material remains below a certain value.

[0023] In one embodiment, the number-average fiber diameter (D) of the cellulose fibers is preferably 2 to 1000 nm from the viewpoint of obtaining a good effect of improving physical properties by the cellulose fibers. More preferably, the number-average fiber diameter of the cellulose fibers is 4 nm or more, or 5 nm or more, or 10 nm or more, or 15 nm or more, or 20 nm or more, and more preferably 500 nm or less, or 450 nm or less, or 400 nm or less, or 350 nm or less, or 300 nm or less, or 250 nm or less.

[0024] In one embodiment, the number-average fiber length (L) of the cellulose fibers is preferably 100 nm to 1000 μm from the viewpoint of obtaining a good effect of improving physical properties by the cellulose fibers. More preferably, the number-average fiber length of the cellulose fibers is 200 nm or more, or 500 nm or more, or 1 μm or more, or 10 μm or more, or 100 μm or more, and more preferably 500 μm or less, or 300 μm or less, or 200 μm or less.

[0025] The average L / D ratio of cellulose fibers is preferably 50 or higher, or 80 or higher, or 100 or higher, or 120 or higher, or 150 or higher, from the viewpoint of effectively improving the mechanical properties of the resin composite containing cellulose fibers with a small amount of cellulose fibers. There is no particular upper limit, but from the viewpoint of ease of handling, it is preferably 5000 or lower.

[0026] In one embodiment, the number-average fiber diameter (D), number-average fiber length (L), and L / D ratio of the cellulose fibers of this disclosure are values ​​measured using a scanning electron microscope (SEM) by the following procedure. An aqueous dispersion of cellulose fibers is replaced with t-butanol, diluted to 0.001-0.1% by mass, dispersed using a high-shear homogenizer (e.g., IKA product, trade name "Ultra-Turrax T18") under processing conditions: rotation speed 15,000 rpm × 3 minutes, cast onto an osmium-deposited silicon substrate, and air-dried. This is used as a measurement sample and measured using a high-resolution scanning electron microscope (SEM). Specifically, the length (L) and diameter (D) of 100 randomly selected fibrous materials are measured in an observation field adjusted to the magnification so that at least 100 fibrous materials can be observed, and the ratio (L / D) is calculated. For the cellulose fibers, the number-average values ​​of length (L), diameter (D), and ratio (L / D) are calculated.

[0027] In another embodiment, the number-average fiber diameter of the cellulose fibers of this disclosure is the number-average fiber diameter calculated from the specific surface area obtained by the BET method by nitrogen adsorption. For average fiber diameters of 1000 nm or less, the specific surface area is 2.667 m². 2 Supports / g and above.

[0028] The method for calculating the number-average fiber diameter by nitrogen adsorption is as follows: A porous sheet is prepared by replacing the aqueous dispersion of cellulose fibers with t-butanol, then filtering, concentrating, and drying it. The specific surface area of ​​this porous sheet is then measured using the BET method with nitrogen adsorption. The cellulose is in an ideal state where no fusion between fibers has occurred, and the cellulose density is d (g / cm³). 3 When a cylinder has a fiber diameter of D (nm), the relationship between the specific surface area and the fiber diameter is expressed by the following formula. Specific surface area (m 2 / g) = 4000 / (dD) And the cellulose density is 1.50 g / cm³ 3 In this case, the number-average fiber diameter is expressed by the following formula. D(nm)=2667 / specific surface area(m 2 / g) Therefore, the specific surface area when D is 1000 nm is 2.667 m². 2 It is / g.

[0029] Furthermore, the length, diameter, and L / D ratio of the cellulose fibers in the resin composite described later are obtained by dissolving the resin components in the resin composite in an organic or inorganic solvent capable of dissolving the resin components of the resin composite, separating the cellulose fibers, thoroughly washing them with the solvent, substituting with t-butanol to prepare a 0.001-0.1% by mass dispersion, and then redispersing it using a high-shear homogenizer (e.g., IKA product, trade name "Ultra-Turrax T18").

[0030] The degree of crystallinity of the cellulose fibers is preferably 55% or higher. When the degree of crystallinity is within this range, the mechanical properties (strength, dimensional stability) of the cellulose fibers themselves are high, and therefore, when the cellulose fibers are dispersed in the resin, the strength and dimensional stability of the resin composite tend to be high. A more preferable lower limit for the degree of crystallinity is 60%, even more preferably 70%, and most preferably 80%. There is no particular upper limit for the degree of crystallinity of the cellulose fibers, and a higher value is preferable, but from a production standpoint, a preferable upper limit is 99%.

[0031] Between the microfibrils of plant-derived cellulose, and between the bundles of microfibrils, are alkali-soluble polysaccharides such as hemicellulose and acid-insoluble components such as lignin. Hemicellulose is a polysaccharide composed of sugars such as mannan and xylan, and plays a role in linking microfibrils together by hydrogen bonding with cellulose. Lignin is a compound with an aromatic ring and is known to be covalently bonded to hemicellulose in the cell walls of plants. If the amount of impurities such as lignin remaining in the cellulose fibers is high, discoloration may occur due to the heat during processing. Therefore, from the viewpoint of suppressing discoloration of the resin composite during extrusion and molding, it is desirable to keep the crystallinity of the cellulose fibers within the above range.

[0032] The degree of crystallinity referred to here, when the cellulose fiber is a type I cellulose crystal (derived from natural cellulose), can be determined by the Segal method from the diffraction pattern (2θ / deg. of 10 to 30) obtained by measuring the sample by wide-angle X-ray diffraction, using the following formula. Crystallinity (%) = ([Diffraction intensity due to the (200) plane at 2θ / deg.=22.5] - [Diffraction intensity due to amorphous material at 2θ / deg.=18]) / [Diffraction intensity due to the (200) plane at 2θ / deg.=22.5] × 100

[0033] Furthermore, if the cellulose fiber is a type II cellulose crystal (derived from regenerated cellulose), the degree of crystallinity can be determined by the following formula using wide-angle X-ray diffraction, from the absolute peak intensity h0 at 2θ=12.6°, which is attributed to the (110) plane peak of the type II cellulose crystal, and the peak intensity h1 from the baseline at this interplanar spacing. Crystallinity (%) =h1 / h0 ×100 The porous sheet mentioned above will be used as the measurement sample.

[0034] Known crystalline forms of cellulose include type I, type II, type III, and type IV. Among these, types I and II are particularly widely used, while types III and IV, although obtained on a laboratory scale, are not widely used on an industrial scale. The cellulose fibers of this disclosure have relatively high structural mobility, and by dispersing these cellulose fibers in a resin, a resin composite with a lower coefficient of thermal expansion and superior strength and elongation during tensile and bending deformation can be obtained. Therefore, cellulose fibers containing cellulose type I crystals or cellulose type II crystals are preferred, and cellulose fibers containing cellulose type I crystals and having a crystallinity of 55% or higher are more preferred.

[0035] Furthermore, the degree of polymerization of the cellulose fibers is preferably 100 or more, more preferably 150 or more, more preferably 200 or more, more preferably 300 or more, more preferably 400 or more, more preferably 450 or more, preferably 3500 or less, more preferably 3300 or less, more preferably 3200 or less, more preferably 3100 or less, and more preferably 3000 or less.

[0036] From the viewpoint of processability and mechanical property development, it is desirable to keep the degree of polymerization of the cellulose fibers within the above-mentioned range. From the viewpoint of processability, it is preferable that the degree of polymerization is not too high, and from the viewpoint of mechanical property development, it is desirable that it is not too low.

[0037] The degree of polymerization of cellulose fibers refers to the average degree of polymerization measured according to the reduction ratio viscosity method using copper ethylenediamine solution, as described in the confirmation test (3) of the "Fifteenth Revised Japanese Pharmacopoeia Commentary (published by Hirokawa Shoten)".

[0038] In one embodiment, the weight-average molecular weight (Mw) of the cellulose fiber is 100,000 or more, more preferably 200,000 or more. The ratio of weight-average molecular weight to number-average molecular weight (Mn) (Mw / Mn) is 6 or less, preferably 5.4 or less. A larger weight-average molecular weight means fewer end groups in the cellulose molecule. Furthermore, since the ratio of weight-average molecular weight to number-average molecular weight (Mw / Mn) represents the width of the molecular weight distribution, a smaller Mw / Mn means fewer end groups in the cellulose molecule. Since the end groups of cellulose molecules are the starting points for thermal decomposition, when the weight-average molecular weight of the cellulose fiber is large, and at the same time the width of the molecular weight distribution is narrow, particularly heat-resistant cellulose fibers and resin composites containing cellulose fibers and resin can be obtained. From the viewpoint of the availability of cellulose raw materials, the weight-average molecular weight (Mw) of the cellulose fiber may be, for example, 600,000 or less, or 500,000 or less. The ratio of weight-average molecular weight to number-average molecular weight (Mn) (Mw / Mn) may be, for example, 1.5 or higher, or 2 or higher, from the viewpoint of ease of manufacturing cellulose fibers. Mw can be controlled to the above range by selecting a cellulose raw material having an Mw appropriate for the purpose, and by appropriately performing physical and / or chemical treatments on the cellulose raw material within an appropriate range. Mw / Mn can also be controlled to the above range by selecting a cellulose raw material having an Mw / Mn appropriate for the purpose, and by appropriately performing physical and / or chemical treatments on the cellulose raw material within an appropriate range. In both the control of Mw and the control of Mw / Mn, examples of the above physical treatments include dry or wet grinding using microfluidizers, ball mills, disc mills, etc., and physical treatments that apply mechanical forces such as impact, shear, shatter, and friction using grinders, homomixers, high-pressure homogenizers, ultrasonic devices, etc. Examples of the above chemical treatments include pulverization, bleaching, acid treatment, and regenerative cellulose formation.

[0039] The weight-average molecular weight and number-average molecular weight of cellulose referred to here are values ​​obtained by dissolving cellulose in N,N-dimethylacetamide to which lithium chloride has been added, and then determining the values ​​by gel permeation chromatography using N,N-dimethylacetamide as the solvent.

[0040] Methods for controlling the degree of polymerization (i.e., average degree of polymerization) or molecular weight of cellulose fibers include hydrolysis. Hydrolysis promotes the depolymerization of amorphous cellulose inside the cellulose fibers, reducing the average degree of polymerization. At the same time, hydrolysis removes impurities such as hemicellulose and lignin in addition to the amorphous cellulose mentioned above, resulting in a porous structure inside the fibrous material.

[0041] The hydrolysis method is not particularly limited, but examples include acid hydrolysis, alkaline hydrolysis, hydrothermal decomposition, steam explosion, and microwave decomposition. These methods may be used individually or in combination of two or more. In the acid hydrolysis method, for example, α-cellulose obtained as pulp from fibrous plants is used as the cellulose raw material, and while dispersed in an aqueous medium, an appropriate amount of protic acid, carboxylic acid, Lewis acid, heteropoly acid, etc. is added, and the average degree of polymerization can be easily controlled by heating while stirring. The reaction conditions such as temperature, pressure, and time vary depending on the cellulose species, cellulose concentration, acid species, acid concentration, etc., but are adjusted appropriately to achieve the desired average degree of polymerization. For example, one condition is to use an aqueous solution of mineral acid with a concentration of 2% by mass or less, and treat the cellulose at 100°C or higher under pressure for 10 minutes or more. Under these conditions, catalyst components such as acids penetrate into the cellulose fibers, promoting hydrolysis, reducing the amount of catalyst components used, and making subsequent purification easier. Furthermore, the dispersion of cellulose raw materials during hydrolysis may contain a small amount of organic solvent in addition to water, as long as it does not impair the effects of the present invention.

[0042] The alkali-soluble polysaccharides that cellulose fibers may contain include not only hemicellulose but also β-cellulose and γ-cellulose. Alkali-soluble polysaccharides are understood by those skilled in the art to be components obtained as the alkali-soluble part of holocellulose obtained by solvent extraction and chlorine treatment of plants (e.g., wood) (i.e., components obtained by removing α-cellulose from holocellulose). Since alkali-soluble polysaccharides are polysaccharides containing hydroxyl groups and have poor heat resistance, they can cause problems such as decomposition when heated, yellowing during thermal aging, and a decrease in the strength of cellulose fibers. Therefore, it is preferable to have a low alkali-soluble polysaccharide content in cellulose fibers.

[0043] In one embodiment, the average content of alkali-soluble polysaccharides in cellulose fibers is preferably 20% by mass or less, 18% by mass or less, 15% by mass or less, or 12% by mass or less, based on 100% by mass of cellulose fibers, from the viewpoint of obtaining good dispersibility of cellulose fibers. The above content may be 1% by mass or more, 2% by mass or more, or 3% by mass or more, from the viewpoint of ease of manufacturing cellulose fibers.

[0044] The average alkali-soluble polysaccharide content can be determined using the method described in non-patent literature (Wood Science Experiment Manual, edited by the Japan Wood Research Society, pp. 92-97, 2000), by subtracting the α-cellulose content from the holocellulose content (Wise method). This method is understood in this industry as a method for measuring hemicellulose content. The alkali-soluble polysaccharide content is calculated three times for each sample, and the number average of the calculated alkali-soluble polysaccharide content is taken as the average alkali-soluble polysaccharide content.

[0045] In one embodiment, the average content of acid-insoluble components in cellulose fibers is preferably 10% by mass or less, 5% by mass or less, or 3% by mass or less, based on 100% by mass of cellulose fibers, from the viewpoint of avoiding a decrease in the heat resistance of cellulose fibers and the resulting discoloration. From the viewpoint of ease of manufacturing cellulose fibers, the above content may be 0.1% by mass or more, 0.2% by mass or more, or 0.3% by mass or more.

[0046] The average content of acid-insoluble components is determined as the quantification of acid-insoluble components using the Klason method described in a non-patent document (Wood Science Experimental Manual, edited by the Japan Wood Research Society, pages 92 to 97, 2000). This method is recognized in the industry as a method for measuring lignin content. After stirring a sample in a sulfuric acid solution to dissolve components such as cellulose and hemicellulose, the mixture is filtered through a glass fiber filter paper, and the obtained residue corresponds to the acid-insoluble components. The acid-insoluble component content is calculated from the weight of the acid-insoluble components, and the number average of the acid-insoluble component contents calculated for three samples is taken as the average content of acid-insoluble components.

[0047] The thermal decomposition onset temperature of cellulose fibers (T D ) is 270°C or higher in one aspect, preferably 275°C or higher, more preferably 280°C or higher, and still more preferably 285°C or higher, from the viewpoint of enabling the heat resistance and mechanical strength desired for applications such as in-vehicle use. A higher thermal decomposition onset temperature is more preferable, but from the viewpoint of ease of production of cellulose fibers, it may be, for example, 320°C or lower, or 300°C or lower.

[0048] In the present disclosure, T D is a value obtained from a graph in thermogravimetric (TG) analysis where the horizontal axis represents temperature and the vertical axis represents residual weight percentage, as shown in the explanatory diagram of Figure 2 (note that Figure 2(B) is an enlarged view of Figure 2(A)). Starting from the weight of cellulose fibers at 150°C (a state where moisture is substantially removed, weight loss: 0 wt%), the temperature is further increased, and the temperature at 1 wt% weight loss (T 1% ) and the temperature at 2 wt% weight loss (T 2% ) are used to obtain a straight line passing through these two points. The temperature at the intersection point between this straight line and a horizontal line (baseline) passing through the starting point of 0 wt% weight loss is defined as T D .

[0049] The 1% weight loss temperature (T 1% ) is the temperature at which 1% by weight of weight loss occurs starting from the weight at 150°C when the temperature is increased according to the above method for T D .

[0050] Weight loss rate of cellulose fibers at 250°C (T 250℃ ) is the weight loss rate when cellulose fibers are held at 250°C under a nitrogen flow for 2 hours in TG analysis.

[0051] The concentration of cellulose fibers in the slurry used in the process of the present invention is preferably 5% by mass or more, or 10% by mass or more, or 15% by mass or more, or 20% by mass or more, or 25% by mass or more, from the viewpoint of process efficiency in the subsequent granulation process. From the viewpoint of avoiding excessive increase in the viscosity of the slurry and solidification due to aggregation, and maintaining good handling properties, it is preferably 60% by mass or less, or 55% by mass or less, or 50% by mass or less, or 45% by mass or less. Generally, cellulose nanofibers are often produced in dilute dispersions, but the cellulose concentration in the slurry may be adjusted to the above preferred range by concentrating such dilute dispersions. Methods such as suction filtration, pressure filtration, centrifugal deliquidation, and heating can be used for concentration.

[0052] <Granulation process> In this process, the slurry obtained in the slurry preparation process is stirred under reduced pressure to form a dry powder of cellulose fibers. The granulation process can be carried out, for example, using a high-speed stirring granulator equipped with stirring blades, chopper blades, and a vacuum mechanism, and includes forming cellulose fiber particles by stirring and crushing the particles with a chopper.

[0053] The stirring blades and chopper blades may have different or the same axis of rotation.

[0054] A granulator having stirring blades and chopper blades on different rotation axes may, for example, be a vertical or horizontal tank with a material inlet at the top, a combination of low-speed rotating stirring blades located at the bottom of the tank and high-speed rotating chopper blades located at the side of the tank, a pressure reduction mechanism, and optionally a temperature control mechanism.

[0055] A granulator in which the stirring blades and chopper blades have the same axis of rotation may, for example, be equipped with a vertical or horizontal tank with a material inlet at the top, a combination of stirring blades located at the bottom of the tank and chopper blades located above the same axis of rotation, a pressure reduction mechanism, and optionally a temperature control mechanism. When the measured slurry is introduced into the tank through the material supply port, the slurry is circulated within the tank under reduced pressure and dried by the centrifugal force and upward thrust of the stirring blades, generating particles. The particles move within the tank and are crushed by chopper blades with strong shearing force, then return to the vicinity of the stirring blades and are stirred again, increasing their particle size. In this way, the particles are repeatedly subjected to stirring and chopping, making it possible to produce uniformly sized (i.e., with little variation in particle size) dried cellulose fiber powder.

[0056] The stirring blades may be two-bladed, three-bladed, or four-bladed rotors, or multiple blades connected in a ring to form a single integrated rotor. The rotors may also have a multi-stage structure with upper and lower blades. The blade surface of the rotor may be perpendicular or inclined with respect to the axis of rotation, and may be flat, curved, or a combination thereof. From the viewpoint of obtaining good stirring efficiency, it is preferable that the rotors are arranged along the bottom and side walls of the tank, and the clearance between the rotor tip and the bottom and side walls of the tank is minimized to the extent that it does not hinder the rotation of the rotors. The stirring blades generate particles by imparting centrifugal force and upward thrust to the slurry.

[0057] The rotation conditions for the rotor blades are as follows: the lower limit of the peripheral speed is preferably 0.5 m / sec, 0.7 m / sec, 1 m / sec, 3 m / sec, or 6 m / sec, and the upper limit is preferably 40 m / sec, 30 m / sec, 20 m / sec, 15 m / sec, 14 m / sec, 13 m / sec, or 12 m / sec. The peripheral speed does not need to be constant throughout the granulation process and may be varied within a preferred range. By setting the peripheral speed within a preferred range, a dried cellulose fiber powder with excellent redispersibility can be obtained. A peripheral speed below the upper limit is preferable from the viewpoint of preventing deterioration of physical properties due to a decrease in the crystallinity of cellulose. A peripheral speed above the lower limit is preferable from the viewpoint of improving the efficiency of pulverization of the slurry by the chopper blades during drying.

[0058] The shear rate applied to the slurry by the stirring blades is 50 sec. -1 ~7000sec ‐1 , or 150 sec -1 ~5000sec ‐1 , or 250 sec -1 ~3500sec ‐1 This can be used as an example.

[0059] The chopper blades may have one or more chopper blades extending outward from the rotation axis, and the multiple chopper blades may have a multi-stage structure. The rotation axis may protrude inward in a cantilevered manner from the side wall of the can body, or it may penetrate the can body horizontally (i.e., constitute a through-type chopper blade). Multiple chopper blades may be arranged at predetermined intervals in the direction of the rotation axis.

[0060] The conditions for grinding with chopper blades are as follows: the lower limit of the chopper rotation speed is preferably 10 rpm, 50 rpm, 100 rpm, 200 rpm, 500 rpm, or 1000 rpm, and the upper limit is preferably 6000 rpm, 5000 rpm, 4500 rpm, or 4000 rpm. By setting the chopper rotation speed within this preferred range, a dry powder of cellulose fibers with excellent redispersibility can be obtained. A chopper rotation speed below the upper limit is preferable from the viewpoint of preventing deterioration of physical properties due to a decrease in the crystallinity of cellulose. A chopper rotation speed above the lower limit is preferable from the viewpoint of obtaining a good grinding effect from the chopper.

[0061] In one embodiment, the lower limit of the peripheral speed of the chopper blades is preferably 0.5 m / sec, 0.7 m / sec, 1 m / sec, 3 m / sec, or 6 m / sec, and the upper limit is preferably 40 m / sec, 30 m / sec, 20 m / sec, 15 m / sec, 14 m / sec, 13 m / sec, or 12 m / sec. By setting the peripheral speed of the chopper blades within a preferred range, a dry powder of cellulose fibers with excellent redispersibility can be obtained. A peripheral speed of the chopper blades below the upper limit is preferable from the viewpoint of preventing deterioration of physical properties due to a decrease in the crystallinity of cellulose. A peripheral speed of the chopper blades above the lower limit is preferable from the viewpoint of obtaining a good crushing effect of the chopper.

[0062] When the chopper blades and stirring blades are on different rotating shafts, the chopper blade / stirring blade ratios for rotational diameter and peripheral speed can be set arbitrarily as desired, for example, 1.0 / 1.0 to 0.1 / 1.0, or 0.5 / 1.0 to 0.1 / 1.0, or 0.5 / 1.0 to 0.2 / 1.0, or 0.5 / 1.0 to 0.3 / 1.0. In one embodiment, the peripheral speed of the chopper blades is less than or equal to the peripheral speed of the stirring blades, or is smaller than the peripheral speed of the stirring blades. When the diameter and peripheral speed of the chopper blades are less than or equal to the diameter and peripheral speed of the stirring blades, the convection of the slurry by the stirring blades is not disturbed, making it easy to control the shape of the powder, which is preferable. When the diameter and peripheral speed of the chopper blades are 1 / 10 or more of the diameter and peripheral speed of the stirring blades, the grinding effect by the chopper blades is high, which is preferable.

[0063] On the other hand, when the chopper blades and stirring blades are on the same axis of rotation, it is preferable that their rotational speeds are equivalent. It is also preferable that the rotational diameter of the chopper blades is equal to or less than that of the stirring blades, and that the peripheral speed of the chopper blades is equal to or less than that of the stirring blades. If the rotational diameter of the chopper blades is larger than that of the stirring blades, and if the peripheral speed of the chopper blades is greater than that of the stirring blades, the upward thrust force from the stirring blades decreases, and the stirring efficiency tends to decrease. When the chopper blades and stirring blades are on the same axis of rotation, the chopper blade / stirring blade ratios for rotational diameter and peripheral speed are preferably 1.0 / 1.0 to 0.5 / 1.0, or 0.95 / 1.0 to 0.5 / 1.0, or 0.95 / 1.0 to 0.6 / 1.0. In one embodiment, the peripheral speed of the chopper blades is less than or equal to the peripheral speed of the stirring blades, or is smaller than the peripheral speed of the stirring blades.

[0064] Even when the chopper blades and stirring blades are on the same axis of rotation, the centrifugal force and upward thrust from the lower blades, which act as stirring blades, cause the slurry or particles to convect within the tank, and they are dried under reduced pressure to produce particles. In this process, the particles are crushed by the shear force of the upper blades, which act as chopper blades, and the crushed particles return to the vicinity of the stirring blades and are stirred again, increasing their particle size and gradually granulating. Therefore, even if there are two or more blades on the same axis of rotation, the lower blades act as stirring blades and the upper blades act as chopper blades. When the diameter and peripheral speed of the chopper blades are less than or equal to the diameter and peripheral speed of the stirring blades, it is preferable that convection of the slurry by the stirring blades is easily generated and slurry is less likely to remain accumulated in the corners of the tank. When the diameter and peripheral speed of the chopper blades are more than half the diameter and peripheral speed of the stirring blades, the crushing effect by the chopper blades is high, which is preferable.

[0065] For vacuum drying in the granulation process, the lower limit of the jacket temperature is preferably 20°C or higher, 30°C or higher, 40°C or higher, or 50°C or higher, from the viewpoint of increasing the drying speed and improving production efficiency, and the upper limit is 160°C or lower, 150°C or lower, 140°C or lower, or 130°C or lower, from the viewpoint of the thermal stability of cellulose fibers and additives. The lower limit of the degree of vacuum is preferably -1kPa or higher, or -10kPa or higher, -20kPa or higher, -30kPa or higher, -40kPa or higher, or -50kPa or higher, and the upper limit is preferably -100kPa or lower, -95kPa or lower, or -90kPa or lower. Pressure adjustment may be achieved by operating a vacuum pump with appropriate exhaust capacity at full capacity, or by intentionally introducing air and / or inert gas using a vacuum regulator, leak valve, etc. When introducing air and / or inert gas, it is preferable to provide an intake section in or upstream of the tank body so that the medium vapor can be efficiently exhausted.

[0066] Because cellulose fibers are extremely prone to agglomeration in a dry state, in typical dried cellulose fiber powder, the cellulose fibers are strongly aggregated with each other, and even if the dried powder is redispersed in a dispersion medium, it does not easily redisperse. In the granulation step of the method disclosed herein, since granulation is performed by stirring, the shear force applied to the slurry and the generated particles is relatively small, causing the cellulose fibers to agglomerate and generate coarse particles. The generated coarse particles are then finely ground by chopper grinding, but the finely ground particles are further subjected to stirring to increase their particle size. If coarse particles are generated by this stirring, they are finely ground again by chopper grinding. In chopper grinding, coarse particles are ground, but particles that were originally finely ground are not ground any further. Therefore, by repeating particle generation by stirring and chopper grinding, a dried powder with reduced particle size variation can be obtained. Furthermore, by chopping the cellulose fiber particles, the cellulose fibers on the particle surface can be made fluffy (i.e., a sparse structure can be formed on the particle surface), and by repeating this chopping process with stirring, a dry powder with a desired particle size and a sparse structure (i.e., low bulk density) can be produced.

[0067] In terms of stirring efficiency, the slurry at the start of the granulation process preferably contains 5% or more by mass of liquid medium, or 20% or more by mass, or 40% or more by mass, or 60% or more by mass. In terms of process efficiency, the amount of liquid medium in the slurry at the start of the granulation process may be 95% or less by mass, or 90% or less by mass, or 80% or less by mass.

[0068] In terms of stirring efficiency, the slurry at the start of the granulation process preferably contains 5% or more by mass of water, or 20% or more by mass, or 40% or more by mass, or 60% or more by mass. In terms of process efficiency, the amount of water in the slurry at the start of the granulation process may be 95% or less by mass, or 90% or less by mass, or 80% or less by mass.

[0069] In the granulation process when the liquid medium in the slurry contains water, it is preferable to add an additional medium, which is a liquid medium different from water, to the slurry. Examples of additional media include various organic solvents, as exemplified in the <Slurry Preparation Process> section. The additional medium is preferably one or more media selected from the group consisting of: alcohols with a boiling point of 50°C to 170°C (e.g., methanol, ethanol, n-propanol, i-propanol, n-butanol, i-butanol, s-butanol, t-butanol, etc.); ethers (e.g., propylene glycol monomethyl ether, 1,2-dimethoxyethane, diisopropyl ether, tetrahydrofuran, 1,4-dioxane, etc.); carboxylic acids (e.g., formic acid, acetic acid, lactic acid, etc.); esters (e.g., ethyl acetate, vinyl acetate, etc.); ketones (e.g., acetone, methyl ethyl ketone, methyl isobutyl ketone, cyclopentanone, cyclohexanone, etc.); and nitrogen-containing solvents (e.g., dimethylformamide, dimethylacetamide, acetonitrile, etc.), with t-butanol, s-butanol, i-butanol, acetone, etc. being more preferred. It is preferable that these organic solvents are substances that form an azeotrope with water. In particular, it is even more preferable if the azeotropic mixture has a minimum azeotropic point, where the boiling point is lower than the boiling point of water and the organic solvent individually, because this makes it easier to dry the water even at low pressure and / or low temperature. The timing of addition is preferably during the granulation process, for example, after the water content in the slurry has progressed to 80% by mass or less, or 70% by mass or less, or 60% by mass or less, or 50% by mass or less, or 40% by mass or less, or 30% by mass or less, or 20% by mass or less, or 10% by mass or less. With water remaining at these percentages, the additional medium replaces the water, suppressing the aggregation of cellulose fibers and enabling the formation of a dry powder with the desired particle size and good redispersibility.

[0070] In a preferred embodiment, the additional medium is added to the slurry in a mass ratio of water to the additional medium in the slurry ranging from 1:99 to 90:10. More preferably, this mass ratio is 1:99 to 80:20, or 1:99 to 70:30, or 5:95 to 70:30, or 5:95 to 60:40, or 10:90 to 60:40. By adding the additional medium in the above range, strong aggregation between cellulose fibers at a microscopic level of, for example, less than 10 μm can be suppressed, while granulation at a level greater than 10 μm to less than 1000 μm can be promoted, thus enabling both good progress in the granulation process and good redispersibility of the resulting dry powder. If the additional medium is a substance that forms an azeotropic mixture with water, it is preferable to add the additional medium to the slurry in a proportion higher than the azeotropic composition ratio with water (i.e., the minimum proportion of the additional medium that can form an azeotropic mixture with water).

[0071] In another preferred embodiment, additional media are added to the slurry two or more times. By repeatedly adding additional media and drying during the granulation process, the substitution of water with the additional media progresses, and additives such as binders are uniformly mixed with the cellulose fibers, enabling both good redispersibility of the resulting dried powder and the functionality of the binder.

[0072] In another embodiment, the granulation process is preferably further comprising a step of adding an additional medium at a constant flow rate per unit time while continuing vacuum drying, from the viewpoint of reducing the amount of additional medium used and the drying time. In this step, it is particularly preferable to add the additional medium at a constant flow rate per unit time so as to maintain a constant total liquid volume in the slurry (i.e., the total amount of water and additional medium). Depending on the type of additional medium, the total liquid volume in the slurry may be increased or decreased. After such a step, further vacuum drying can be performed to reduce the total liquid volume to obtain the desired dried powder.

[0073] In the granulation process, when forming a slurry with a specific water-to-additional medium ratio, adding the additional medium while allowing the water to evaporate is preferable to adding the entire amount of additional medium at once, as this reduces the total amount of additional medium added. Furthermore, because the additional medium can be added while granulation is in progress, the substitution of water with the additional medium proceeds more easily, and the resulting powder tends to have good redispersibility. The additional liquid may be added, for example, in the form of droplets or mist.

[0074] The moisture content of the slurry in the granulation process can be measured using a heat-drying type moisture meter or a Karl Fischer moisture meter. Furthermore, the mass ratio of water to additional medium in the slurry after the addition of additional medium can be measured, for example, i) A method in which the moisture content of the slurry is measured using a Karl Fischer moisture meter, and the liquid content of the volatile components (water and additional media) in the slurry is measured using a heat-drying type moisture meter, and then calculated. ii) A method in which additional media in the slurry are extracted with a different solvent capable of dissolving the additional media, the content of the additional media is measured by gas chromatography, and the total liquid content of volatile components (water and additional media) in the slurry is measured with a heat-drying type moisture meter and calculated. iii) A method in which water and additional media in the slurry are extracted with a deuterated solvent and calculated by solution NMR is also possible.

[0075] Furthermore, in a manner in which the liquid medium in the slurry prepared in the slurry preparation step does not contain water, an additional medium may be added in the granulation step. As additional media, one or more commonly used water-miscible organic solvents may be used, for example: alcohols with a boiling point of 50°C to 170°C (e.g., methanol, ethanol, n-propanol, i-propanol, n-butanol, i-butanol, s-butanol, t-butanol, etc.); ethers (e.g., propylene glycol monomethyl ether, 1,2-dimethoxyethane, diisopropyl ether, tetrahydrofuran, 1,4-dioxane, etc.); carboxylic acids (e.g., formic acid, acetic acid, lactic acid, etc.); esters (e.g., ethyl acetate, vinyl acetate, etc.); ketones (e.g., acetone, methyl ethyl ketone, methyl isobutyl ketone, cyclopentanone, cyclohexanone, etc.); nitrogen-containing solvents (dimethylformamide, dimethylacetamide, acetonitrile, etc.) or hydrophobic organic solvents, for example, aromatic hydrocarbons (benzene, toluene, xylene, etc.); aliphatic hydrocarbons (hexane, heptane, octane, decane, etc.); halogenated hydrocarbons (tetrachloromethane, chloroform, dichloromethane, chloroethane, etc.). A preferred method of adding the additional medium is to add it all at once or in multiple steps before or after the start of granulation. The additional medium may be added, for example, in the form of droplets or mist while drying under reduced pressure during granulation.

[0076] In one embodiment, the average particle size of the dry cellulose fiber powder is preferably 1 μm or more, or 10 μm or more, or 50 μm or more, or 100 μm or more, or 200 μm or more, or 500 μm or more, and preferably 5000 μm or less, or 4000 μm or less, or 3000 μm or less, or 2000 μm or less. The above average particle size is a value measured by laser diffraction / scattering method or dry sieving method.

[0077] In one embodiment, the bulk density of the dried cellulose fiber powder is 0.05 g / mL or more, or 0.06 g / mL or more, or 0.07 g / mL or more, or 0.08 g / mL or more, or 0.09 g / mL or more, or 0.10 g / mL or more, from the viewpoint of ease of manufacturing and transport efficiency of the dried powder, and 1.0 g / mL or less, or 0.9 g / mL or less, or 0.8 g / mL or less, or 0.7 g / mL or less, or 0.6 g / mL or less, from the viewpoint of good redispersibility of the dried powder. The bulk density in this disclosure is a value measured by a loose bulk density measurement method.

[0078] <Chemical modification> In one embodiment, chemically modified cellulose fibers are used as the cellulose fibers. The cellulose fibers may be chemically modified beforehand, for example, at the raw material pulp or linter stage, during or after the defibration process, or they may be chemically modified during the slurry preparation process, the granulation process, or after the granulation process. In a preferred embodiment, the chemical modification is chemical modification with hydrophobic substituents.

[0079] As cellulose modifiers, compounds that react with the hydroxyl groups of cellulose can be used, including esterifying agents, etherifying agents, and silylating agents. In a preferred embodiment, the chemical modification is acylation using an esterifying agent. Preferred esterifying agents include acid halides, acid anhydrides, vinyl carboxylates, and carboxylic acids.

[0080] The acid halide may be at least one compound selected from the group consisting of compounds represented by the following formula (1). R 1 -C(=O)-X (1) (In the formula, R 1 (where X represents an alkyl group having 1 to 24 carbon atoms, an alkenyl group having 2 to 24 carbon atoms, a cycloalkyl group having 3 to 24 carbon atoms, or an aryl group having 6 to 24 carbon atoms, and X is Cl, Br, or I.) Specific examples of acid halides include, but are not limited to, acetyl chloride, acetyl bromide, acetyl iodide, propionyl chloride, propionyl bromide, propionyl iodide, butyryl chloride, butyryl bromide, butyryl iodide, benzoyl chloride, benzoyl bromide, and benzoyl iodide. Among these, acid chlorides are particularly suitable due to their reactivity and ease of handling. In the reaction of acid halides, one or more alkaline compounds may be added to act as a catalyst and to neutralize the acidic by-products. Specific examples of alkaline compounds include, but are not limited to, tertiary amine compounds such as triethylamine and trimethylamine; and nitrogen-containing aromatic compounds such as pyridine and dimethylaminopyridine.

[0081] Any suitable acid anhydride can be used as the acid anhydride. For example, saturated aliphatic monocarboxylic acid anhydrides such as acetic acid, propionic acid, (iso)butyric acid, and valeric acid; unsaturated aliphatic monocarboxylic acid anhydrides such as (meth)acrylic acid and oleic acid; alicyclic monocarboxylic acid anhydrides such as cyclohexanecarboxylic acid and tetrahydrobenzoic acid; aromatic monocarboxylic acid anhydrides such as benzoic acid and 4-methylbenzoic acid; Examples of dibasic carboxylic acid anhydrides include saturated aliphatic dicarboxylic anhydrides such as succinic anhydride and adipic acid, unsaturated aliphatic dicarboxylic anhydrides such as maleic anhydride and itaconic anhydride, alicyclic dicarboxylic anhydrides such as 1-cyclohexene-1,2-dicarboxylic anhydride, hexahydrophthalic anhydride and methyltetrahydrophthalic anhydride, and aromatic dicarboxylic anhydrides such as phthalic anhydride and naphthalic anhydride; Examples of polybasic carboxylic acid anhydrides with three or more bases include (anhydride) polycarboxylic acids such as trimellitic anhydride and pyromellitic anhydride. Furthermore, in the reaction of acid anhydrides, one or more acidic compounds such as sulfuric acid, hydrochloric acid, or phosphoric acid, or Lewis acids (for example, Lewis acid compounds represented as MYn, where M represents a metalloid element such as B, As, or Ge, or a base metal element such as Al, Bi, or In, or a transition metal element such as Ti, Zn, or Cu, or a lanthanide element; n is an integer corresponding to the valence of M, representing 2 or 3; and Y represents a halogen atom, OAc, OCOCF3, ClO4, SbF6, PF6, or OSO2CF3(OTf)), or alkaline compounds such as triethylamine or pyridine may be added as catalysts.

[0082] As for vinyl carboxylates, see formula (1): R-COO-CH=CH2…Formula (1) A vinyl carboxylate ester represented by the formula {wherein R is any of an alkyl group having 1 to 24 carbon atoms, an alkenyl group having 2 to 24 carbon atoms, a cycloalkyl group having 3 to 16 carbon atoms, or an aryl group having 6 to 24 carbon atoms} is preferred. The vinyl carboxylate ester is more preferably at least one selected from the group consisting of vinyl acetate, vinyl propionate, vinyl butyrate, vinyl caproate, vinyl cyclohexanecarboxylate, vinyl caprylate, vinyl caprate, vinyl laurate, vinyl myristate, vinyl palmitate, vinyl stearate, vinyl pivalate, vinyl octoate, vinyl adipate, vinyl methacrylate, vinyl crotate, vinyl pivalate, vinyl octoate, vinyl benzoate, and vinyl cinnamate. In esterification reactions with vinyl carboxylates, one or more catalysts selected from the group consisting of alkali metal hydroxides, alkaline earth metal hydroxides, alkali metal carbonates, alkaline earth metal carbonates, alkali metal bicarbonates, primary to tertiary amines, quaternary ammonium salts, imidazoles and their derivatives, pyridines and their derivatives, and alkoxides may be added.

[0083] Examples of alkali metal hydroxides and alkaline earth metal hydroxides include sodium hydroxide, potassium hydroxide, lithium hydroxide, calcium hydroxide, and barium hydroxide. Examples of alkali metal carbonates, alkaline earth metal carbonates, and alkali metal bicarbonates include lithium carbonate, sodium carbonate, potassium carbonate, cesium carbonate, magnesium carbonate, calcium carbonate, barium carbonate, lithium bicarbonate, sodium bicarbonate, potassium bicarbonate, and cesium bicarbonate.

[0084] Primary, secondary, and tertiary amines refer to primary, secondary, and tertiary amines, and specific examples include ethylenediamine, diethylamine, proline, N,N,N',N'-tetramethylethylenediamine, N,N,N',N'-tetramethyl-1,3-propanediamine, N,N,N',N'-tetramethyl-1,6-hexanediamine, tris(3-dimethylaminopropyl)amine, N,N-dimethylcyclohexylamine, and triethylamine.

[0085] Examples of imidazoles and their derivatives include 1-methylimidazole, 3-aminopropylimidazole, and carbonyldiimidazole.

[0086] Examples of pyridine and its derivatives include N,N-dimethyl-4-aminopyridine and picoline.

[0087] Examples of alkoxides include sodium methoxide, sodium ethoxide, and potassium t-butoxide.

[0088] The carboxylic acid is selected from the group consisting of compounds represented by the following formula (1). R-COOH …(1) (In the formula, R represents an alkyl group having 1 to 16 carbon atoms, an alkenyl group having 2 to 16 carbon atoms, a cycloalkyl group having 3 to 16 carbon atoms, or an aryl group having 6 to 16 carbon atoms.)

[0089] Specific examples of carboxylic acids include at least one selected from the group consisting of acetic acid, propionic acid, butyric acid, caproic acid, cyclohexanecarboxylic acid, caprylic acid, capric acid, lauric acid, myristic acid, palmitic acid, stearic acid, pivalic acid, methacrylic acid, crotonic acid, pivalic acid, octic acid, benzoic acid, and cinnamic acid.

[0090] Among these carboxylic acids, at least one selected from the group consisting of acetic acid, propionic acid, and butyric acid, particularly acetic acid, is preferred from the viewpoint of reaction efficiency. Furthermore, in the reaction of carboxylic acids, one or more acidic compounds such as sulfuric acid, hydrochloric acid, or phosphoric acid, or Lewis acids (for example, Lewis acid compounds represented as MYn, where M represents a metalloid element such as B, As, or Ge, or a base metal element such as Al, Bi, or In, or a transition metal element such as Ti, Zn, or Cu, or a lanthanide element; n is an integer corresponding to the valence of M, representing 2 or 3; and Y represents a halogen atom, OAc, OCOCF3, ClO4, SbF6, PF6, or OSO2CF3(OTf)), or alkaline compounds such as triethylamine or pyridine may be added as catalysts.

[0091] Among these esterification reagents, at least one selected from the group consisting of acetic anhydride, propionic anhydride, butyric anhydride, vinyl acetate, vinyl propionate, vinyl butyrate, and acetic acid, with acetic anhydride and vinyl acetate being particularly preferred from the viewpoint of reaction efficiency.

[0092] When cellulose fibers are hydrophobized (e.g., by chemical modification such as acylation), the redispersibility of the dried powder tends to be good. However, the dried cellulose fiber powder obtained by the method of this disclosure is advantageous in that it can exhibit good redispersibility even when unsubstituted or with a low degree of substitution. Therefore, in one embodiment, the average degree of substitution (DS) of the dried cellulose fiber powder (the average number of substituted hydroxyl groups per glucose unit, which is the basic constituent unit of cellulose) can be 0.5 or less, 0.3 or less, or 0. On the other hand, the average degree of substitution (DS) may be 0.2 or more, 0.4 or more, or 0.6 or more, depending on the intended use of the cellulose fiber.

[0093] When the modifying group of chemically modified cellulose fibers is an acyl group, the degree of acyl substitution (DS) can be calculated from the reflectivity infrared absorption spectrum of the esterified cellulose fiber based on the peak intensity ratio between the peak derived from the acyl group and the peak derived from the cellulose skeleton. The peak of the C=O absorption band based on the acyl group is at 1730 cm⁻¹. -1 The peak of the CO absorption band based on the cellulose backbone chain appears at 1030 cm⁻¹. -1 It appears in (see Figure 1). The DS of esterified cellulose fibers is obtained by creating a correlation graph between the DS obtained from solid-state NMR measurements of esterified cellulose fibers (described later) and the modification rate (IR index 1030), which is defined as the ratio of the peak intensity of the absorption band of C=O based on the acyl group to the peak intensity of the absorption band of CO in the cellulose backbone chain, and a calibration curve calculated from the correlation graph. Replacement degree DS = 4.13 × IR index (1030) This can be obtained by using [this method].

[0094] The method for calculating the DS of esterified cellulose fibers using solid-state NMR is as follows: For freeze-pulverized esterified cellulose fibers... 13 The following formula can be used to determine the signal intensity (Inf) from a single carbon atom derived from the modifying group, based on the total area intensity (Inp) of the signals attributed to carbon atoms C1-C6 derived from the pyranose ring of cellulose, which appear in the range of 50 ppm to 110 ppm. DS = (Inf) × 6 / (Inp) For example, if the modifying group is an acetyl group, you can use the 23 ppm signal assigned to -CH3. Use 13 The conditions for 13C solid-state NMR measurement are as follows, for example: Equipment:Bruker Biospin Avance500WB Frequency: 125.77MHz Measurement method: DD / MAS method Waiting time: 75 seconds NMR sample tube: 4mmφ Total number of times: 640 (approximately 14 hours) MAS: 14,500Hz Chemical shift reference: Glycine (External reference: 176.03 ppm)

[0095] The DS non-uniformity ratio (DSs / DSt), defined as the ratio of the degree of modification of the fiber surface (DSs) to the degree of modification of the entire fiber (DSt) (which is synonymous with the degree of acyl substitution (DS) above) of chemically modified cellulose fibers, is preferably 1.05 or higher. The larger the value of the DS non-uniformity ratio, the more pronounced the sheath-core-like non-uniform structure (i.e., a structure in which the fiber surface is highly chemically modified while the fiber center retains a structure close to the original unmodified cellulose), which allows for improved affinity with resins during compounding and improved dimensional stability of the resin composition, while maintaining high tensile strength and dimensional stability derived from cellulose. The DS non-uniformity ratio is more preferably 1.1 or higher, or 1.2 or higher, or 1.3 or higher, or 1.5 or higher, or 2.0 or higher, and from the viewpoint of ease of manufacturing chemically modified cellulose fibers, it is preferably 30 or lower, or 20 or lower, or 10 or lower, or 6 or lower, or 4 or lower, or 3 or lower. The value of DSs varies depending on the degree of modification of the esterified cellulose, but as an example, it is preferably 0.1 or higher, more preferably 0.2 or higher, even more preferably 0.3 or higher, even more preferably 0.5 or higher, preferably 3.0 or lower, more preferably 2.5 or lower, particularly preferably 2.0 or lower, even more preferably 1.5 or lower, particularly preferably 1.2 or lower, and most preferably 1.0 or lower. The preferred range for DSt is as described above for acyl substituents (DS).

[0096] A smaller coefficient of variation (CV) of the DS heterogeneity ratio of chemically modified cellulose fibers is preferable because it reduces the variation in various physical properties of the resin composition. Preferably, the coefficient of variation is 50% or less, or 40% or less, or 30% or less, or 20% or less. The coefficient of variation can be further reduced in a method in which chemical modification is performed after defibrillation of the cellulose raw material to obtain chemically modified cellulose fibers (i.e., sequential method), while it can be increased in a method in which defibrillation and chemical modification of the cellulose raw material are performed simultaneously (i.e., simultaneous method). Although the mechanism of action is not clear, it is thought that in the simultaneous method, chemical modification proceeds more easily in the fine fibers generated in the early stages of defibrillation, and as the hydrogen bonds between cellulose microfibrils decrease due to chemical modification, defibrillation proceeds further, resulting in an increase in the coefficient of variation of the DS heterogeneity ratio.

[0097] The coefficient of variation (CV) of the DS heterogeneity ratio can be calculated using the following formula: DS heterogeneity ratio = DSs / DSt. This is achieved by taking 100g of an aqueous dispersion of chemically modified cellulose fibers (solid content of 10% by mass or more), freezing and grinding 10g portions as measurement samples, calculating the DS heterogeneity ratio from the DSt and DSs of 10 samples, and then using the standard deviation (σ) and arithmetic mean (μ) of the DS heterogeneity ratios among the 10 samples. Coefficient of variation (%) = Standard deviation σ / Arithmetic mean μ × 100

[0098] The method for calculating DSs is as follows: Esterified cellulose, powdered by freeze-grinding, is placed on a 2.5 mmφ dish-shaped sample stage, the surface is pressed down to flatten it, and measurement is performed by X-ray photoelectron spectroscopy (XPS). The XPS spectrum reflects the constituent elements and chemical bonding state of only the surface layer of the sample (typically a few nm). Peak separation is performed on the obtained C1s spectrum, and the area intensity (Ixp) of the peak attributed to a single carbon atom derived from the modifying group (Ixf) relative to the area intensity (Ixp) of the peak attributed to the carbon C2-C6 originating from the pyranose ring of cellulose (289 eV, CC bond) can be used to calculate DSs using the following formula. DSs = (Ixf) × 5 / (Ixp) For example, if the modifying group is an acetyl group, after separating the C1s spectrum at 285eV, 286eV, 288eV, and 289eV, the 289eV peak can be used for Ixp and the peak derived from the OC=O bond of the acetyl group (286eV) can be used for Ixf. The conditions used for XPS measurement are as follows, for example: Equipment used: ULVAC-FI VersaProbeII Excitation source: mono.AlKα 15kV × 3.33mA Analysis size: Approximately 200 μmφ Photoelectron extraction angle: 45° Capture area Narrow scan: C 1s, O 1s Pass Energy: 23.5 eV

[0099] <Adding a binder> In one embodiment, a binder can be added to the slurry during the slurry preparation and / or granulation process. The binder contributes to improving the affinity between the cellulose fibers and the resin in the composite. Examples of binders include polymers having hydrophilic groups (e.g., hydroxyl groups, amino groups, etc.) (e.g., polyacrylamide, polyalkylene oxide, polyacrylic acid and its salts, polysaccharides (e.g., cellulose derivatives, starch, alginic acid and its salts (e.g., sodium alginate), guar gum, gellan gum, gelatin, etc.), polyvinyl alcohol, etc.) and monomers having hydrophilic groups (e.g., propylene glycol, N-vinylacetamide, etc.).

[0100] Examples of alkylene oxide units in polyalkylene oxides include alkylene oxides having 2 to 4 carbon atoms, preferably ethylene oxide and propylene oxide. In a preferred embodiment, the polyalkylene oxide is composed of ethylene oxide units and / or propylene oxide units. A particularly preferred polyalkylene oxide is polyethylene oxide.

[0101] Examples of cellulose derivatives include cellulose ethers (e.g., methylcellulose, carboxymethylcellulose, carboxyethylcellulose, hydroxymethylcellulose, hydroxyethylcellulose, hydroxypropylcellulose, hydroxypropylmethylcellulose, etc.).

[0102] The weight-average molecular weight of the binder is preferably 1000 or more, more preferably 5000 or more, and even more preferably 10000 or more, and preferably 5 × 10 8 More preferably 1 × 10 8 More preferably 5 × 10 7 The following applies:

[0103] In one embodiment, the binder is a surfactant. The surfactant has a chemical structure in which a hydrophilic substituent and a hydrophobic substituent are covalently bonded. Any of anionic surfactants, nonionic surfactants, amphoteric surfactants, and cationic surfactants can be used as the surfactant, but nonionic surfactants are preferred in order to obtain good dispersibility of cellulose fibers.

[0104] As hydrophilic groups of surfactants, polyoxyethylene chains, carboxyl groups, and hydroxyl groups are preferred in terms of affinity with cellulose fibers, with polyoxyethylene chains being particularly preferred. Nonionic polyoxyethylene derivatives are particularly preferred. The polyoxyethylene chain length of the polyoxyethylene derivative may be 1 or more, or 4 or more, or 10 or more, or 15 or more. While longer chain lengths increase affinity with hydrophobic cellulose fibers, the polyoxyethylene chain length may be 60 or less, or 50 or less, or 40 or less, or 30 or less, or 20 or less, from the viewpoint of balancing with the properties of the resin composite (e.g., mechanical properties).

[0105] In terms of the structure of the hydrophobic group of the surfactant, alkyl ether type, alkylphenyl ether type, rosin ester type, bisphenol A type, β-naphthyl type, styrene-phenyl type, and hydrogenated castor oil type are preferred due to their high affinity with resins. The number of carbon atoms in the alkyl chain of the hydrophobic group (in the case of alkylphenyl, the number of carbon atoms excluding the phenyl group) is preferably 5 or more, or 10 or more, or 12 or more, or 16 or more. For example, when the resin is a polyolefin resin, the higher the number of carbon atoms in the surfactant, the higher the affinity with the resin. The above number of carbon atoms may be, for example, 30 or less, or 25 or less.

[0106] In a preferred embodiment, the binder is one or more compounds selected from the group consisting of polyalkylene oxides and cellulose derivatives, and particularly preferably one or more compounds selected from the group consisting of polyalkylene oxides, cellulose ethers, and cellulose esters.

[0107] In the slurry preparation and / or granulation process, the binder is preferably dissolved in a medium and added to the slurry to facilitate uniform mixing. The medium used can be selected from water and the additional mediums exemplified in this disclosure. When the binder is added in the slurry preparation process, it is preferable that it has the same composition as the medium used in the slurry preparation process, and when the binder is added in the granulation process, it is preferable that it has the same composition as the medium used in the granulation process.

[0108] The amount of binder may be preferably 5 parts by mass or more, or 10 parts by mass or more, or 20 parts by mass or more, or 30 parts by mass or more, or 40 parts by mass or more, per 100 parts by mass of cellulose fiber, and preferably 100 parts by mass or less, or 70 parts by mass or less, or 50 parts by mass or less.

[0109] The dry powder produced by the method of this disclosure, which has good redispersibility in a dispersion medium, can be well dispersed in the resin, for example, when compounding cellulose fibers with a resin, and therefore has an excellent effect in improving the physical properties of the resin composite containing cellulose fibers and resin. In one embodiment, the dry powder of cellulose fibers of this disclosure has undergone chopper grinding, so that fiber fuzz tends to remain on the powder surface. Such a sparse structure on the powder surface can promote the penetration of the dispersion medium into the powder during redispersion, contributing to improved redispersibility.

[0110] In one embodiment, when a redispersion is prepared by dispersing a dried powder in the same type and amount of liquid medium as the slurry produced in the slurry preparation step, the shear rate of the redispersion is 100s. -1 The viscosity in this case is the shear rate of the slurry obtained in the slurry preparation step, 100s. -1 The viscosity is 30% or more of the aforementioned viscosity. The above ratio is an indicator of how well the dispersibility of the cellulose fibers before drying can be reproduced after redispersion (i.e., redispersibility). The above ratio is preferably 40% or more, or 50% or more, or 60% or more. The higher the above ratio, the better, and most preferably 100%, but from the viewpoint of ease of manufacturing cellulose fibers, it may be, for example, 90% or less, or 80% or less.

[0111] Shear rate of redispersion: 100s -1 The viscosity in the solution is preferably 6 mPa·s or higher, or 7.5 mPa·s or higher, or 9 mPa·s or higher, in that the cellulose fibers are highly dispersed, and preferably 13.5 mPa·s or lower, or 12 mPa·s or lower, in that the redispersed solution can be suitably used, for example, in the production of resin composites.

[0112] ≪Method for manufacturing resin composites≫ One aspect of the present invention provides a method for producing a resin composite comprising cellulose fibers and a resin. The method includes preparing a dried powder of cellulose fibers by the method described above, and mixing the dried powder with a resin.

[0113] <Resin> Thermoplastic resins, thermosetting resins, and photocurable resins can be used as the resin. The resin may also be an elastomer. From the viewpoint of moldability and productivity, thermoplastic resins are more preferred.

[0114] (thermoplastic resin) When the resin is a thermoplastic resin, the melting point of the thermoplastic resin may be appropriately selected depending on the application of the resin composite. Examples of thermoplastic resin melting points include 150°C to 190°C or 160°C to 180°C for resins with relatively low melting points (e.g., polyolefin resins), and 220°C to 350°C or 230°C to 320°C for resins with relatively high melting points (e.g., polyamide resins).

[0115] The thermoplastic resin can preferably be at least one selected from the group consisting of polyolefin resins, polyacetate resins, polycarbonate resins, polyamide resins, polyester resins, polyphenylene ether resins, and acrylic resins.

[0116] Preferred polyolefin resins as thermoplastic resins are polymers obtained by polymerizing olefins (e.g., α-olefins) and / or alkenes as monomer units. Specific examples of polyolefin resins include ethylene-based (co)polymers such as low-density polyethylene (e.g., linear low-density polyethylene), high-density polyethylene, ultra-low-density polyethylene, and ultra-high molecular weight polyethylene; polypropylene-based (co)polymers such as polypropylene, ethylene-propylene copolymer, and ethylene-propylene-diene copolymer; and copolymers of ethylene and α-olefins, such as ethylene-acrylic acid copolymer, ethylene-methyl methacrylate copolymer, and ethylene-glycidyl methacrylate copolymer.

[0117] Polypropylene is the most preferred polyolefin resin. In particular, polypropylene with a melt mass flow rate (MFR) of 3 g / 10 min or more and 30 g / 10 min or less, measured at 230°C and a load of 21.2 N in accordance with ISO 1133, is preferred. The lower limit of the MFR is more preferably 5 g / 10 min, even more preferably 6 g / 10 min, and most preferably 8 g / 10 min. The upper limit is more preferably 25 g / 10 min, even more preferably 20 g / 10 min, and most preferably 18 g / 10 min. From the viewpoint of improving the toughness of the resin composite, it is desirable that the MFR does not exceed the upper limit, and from the viewpoint of the fluidity of the resin composite, it is desirable that it does not exceed the lower limit.

[0118] Furthermore, to enhance affinity with cellulose fibers, acid-modified polyolefin resins can also be suitably used. Mono- or polycarboxylic acids can be used as the acid for acid modification; examples include maleic acid, fumaric acid, succinic acid, phthalic acid and their anhydrides, as well as citric acid. Maleic acid or its anhydride is particularly preferred due to its ease of increasing the modification rate. While there are no particular restrictions on the modification method, a common method involves heating the polyolefin resin above its melting point in the presence or absence of a peroxide and then melt-kneading it. All of the aforementioned polyolefin resins can be used for acid modification, but polypropylene is particularly preferred. Acid-modified polypropylene resin may be used alone, but it is more preferable to mix it with unmodified polypropylene resin to adjust the overall modification rate of the resin. In this case, the ratio of acid-modified polypropylene resin to the total polypropylene resin is preferably 0.5% to 50% by mass. A more preferable lower limit is 1% by mass, or 2% by mass, or 3% by mass, or 4% by mass, or 5% by mass. A more preferable upper limit is 45% by mass, or 40% by mass, or 35% by mass, or 30% by mass, or 20% by mass. To maintain the interfacial strength between the resin and the cellulose fibers, a value above the lower limit is preferable, and to maintain the ductility of the resin, a value below the upper limit is preferable.

[0119] The melt mass flow rate (MFR) of the acid-modified polypropylene resin, measured at 230°C and under a load of 21.2 N in accordance with ISO 1133, is preferably 50 g / 10 min or more, or 100 g / 10 min or more, or 150 g / 10 min or more, or 200 g / 10 min or more, from the viewpoint of increasing the affinity at the interface between the resin and cellulose fibers. There is no particular upper limit, but it is preferably 500 g / 10 min to maintain mechanical strength.

[0120] Preferred polyamide resins as thermoplastic resins include: polyamides obtained by polycondensation reactions of lactams (e.g., polyamide 6, polyamide 11, polyamide 12, etc.); diamines (e.g., 1,6-hexanediamine, 2-methyl-1,5-pentanediamine, 1,7-heptanediamine, 2-methyl-1-6-hexanediamine, 1,8-octanediamine, 2-methyl-1,7-heptanediamine, 1,9-nonanediamine, 2-methyl-1,8-octanediamine, 1,10-decanediamine, 1,11-undecanediamine, 1,12-dodecanediamine, m-xylylenediamine, etc.) and dicarboxylic acids (e.g., butanediamine, pentanediamine, hexanediamine) Examples include polyamides obtained as copolymers with heptaneoic acid, octanedioic acid, nonaneoic acid, decaneoic acid, benzene-1,2-dicarboxylic acid, benzene-1,3-dicarboxylic acid, benzene-1,4-dicarboxylic acid, cyclohexane-1,3-dicarboxylic acid, cyclohexane-1,4-dicarboxylic acid, etc. (e.g., polyamide 6,6, polyamide 6,10, polyamide 6,11, polyamide 6,12, polyamide 6,T, polyamide 6,I, polyamide 9,T, polyamide 10,T, polyamide 2M5,T, polyamide MXD,6, polyamide 6,C, polyamide 2M5,C, etc.) and copolymers obtained by copolymerizing these (e.g., polyamide 6,T / 6,I, etc.).

[0121] Among these polyamide resins, aliphatic polyamides such as polyamide 6, polyamide 11, polyamide 12, polyamide 6,6, polyamide 6,10, polyamide 6,11, and polyamide 6,12, and alicyclic polyamides such as polyamide 6,C and polyamide 2M5,C are more preferred.

[0122] From the viewpoint of improving the heat resistance of the resin composite, the melting point of the polyamide resin is preferably 220°C or higher, or 230°C or higher, or 240°C or higher, or 245°C or higher, and from the viewpoint of ease of manufacturing the resin composite, the above melting point is preferably 350°C or lower, or 320°C or lower, or 300°C or lower.

[0123] There are no particular restrictions on the concentration of terminal carboxyl groups in the polyamide resin, but it is preferably 20 μmol / g or more, or 30 μmol / g or more, and preferably 150 μmol / g or less, or 100 μmol / g or less, or 80 μmol / g or less.

[0124] In polyamide resins, the ratio of carboxyl terminal groups to total terminal groups ([COOH] / [total terminal groups]) is preferably 0.30 or higher, or 0.35 or higher, or 0.40 or higher, or 0.45 or higher, from the viewpoint of dispersibility of cellulose fibers in the resin composite, and preferably 0.95 or lower, or 0.90 or lower, or 0.85 or lower, or 0.80 or lower, from the viewpoint of the color tone of the resin composite.

[0125] The end group concentration of polyamide resins can be adjusted by known methods. One adjustment method involves adding an end group adjusting agent (e.g., diamine compounds, monoamine compounds, dicarboxylic acid compounds, monocarboxylic acid compounds, acid anhydrides, monoisocyanates, monoacid halides, monoesters, monoalcohols, etc.) to the polymerization solution during the polymerization of polyamide so that a predetermined end group concentration is achieved.

[0126] Examples of end modifiers that react with terminal amino groups include aliphatic monocarboxylic acids such as acetic acid, propionic acid, butyric acid, valeric acid, caproic acid, caprylic acid, lauric acid, tridecanoic acid, myristic acid, palmitic acid, stearic acid, pivalic acid, and isobutyric acid; alicyclic monocarboxylic acids such as cyclohexanecarboxylic acid; aromatic monocarboxylic acids such as benzoic acid, toluic acid, α-naphthalenecarboxylic acid, β-naphthalenecarboxylic acid, methylnaphthalenecarboxylic acid, and phenylacetic acid; and mixtures of several of these arbitrarily selected. Among these, from the viewpoint of reactivity, stability of the encapsulated end, and cost, one or more end modifiers selected from the group consisting of acetic acid, propionic acid, butyric acid, valeric acid, caproic acid, caprylic acid, lauric acid, tridecanoic acid, myristic acid, palmitic acid, stearic acid, and benzoic acid are preferred, with acetic acid being the most preferred.

[0127] Examples of end modifiers that react with terminal carboxyl groups include aliphatic monoamines such as methylamine, ethylamine, propylamine, butylamine, hexylamine, octylamine, decylamine, stearylamine, dimethylamine, diethylamine, dipropylamine, and dibutylamine; alicyclic monoamines such as cyclohexylamine and dicyclohexylamine; aromatic monoamines such as aniline, toluidine, diphenylamine, and naphthylamine; and any mixture thereof. Among these, one or more end modifiers selected from the group consisting of butylamine, hexylamine, octylamine, decylamine, stearylamine, cyclohexylamine, and aniline are preferred in terms of reactivity, boiling point, stability of the sealing end, and cost.

[0128] The concentrations of amino-terminated groups and carboxyl-terminated groups in polyamide resins are: 1 The characteristic signal can be determined from the integrated value of the characteristic signal corresponding to each terminal group by 1H-NMR. This method is preferred in terms of accuracy and simplicity. More specifically, it is recommended to use the method described in Japanese Patent Publication No. 7-228775, using deuterated trifluoroacetic acid as the measurement solvent and performing 300 or more scans for integration.

[0129] The intrinsic viscosity [η] of polyamide resins, measured under conditions of 30°C in concentrated sulfuric acid, is preferably 0.6 to 2.0 dL / g, 0.7 to 1.4 dL / g, 0.7 to 1.2 dL / g, or 0.7 to 1.0 dL / g, from the viewpoint of good in-mold fluidity and good appearance of molded pieces when the resin composite is, for example, injection molded. In this disclosure, "intrinsic viscosity" is synonymous with viscosity generally called intrinsic viscosity. The intrinsic viscosity is determined by measuring the ηsp / c of ​​several measurement solvents of different concentrations under conditions of 30°C in 96% concentrated sulfuric acid, deriving a relationship between each ηsp / c and concentration (c), and extrapolating the concentration to zero. This extrapolated value is the intrinsic viscosity. Details of the above method are described, for example, on pages 291 to 294 of Polymer Process Engineering (Prentice-Hall, Inc. 1994). From an accuracy standpoint, it is desirable to use at least four different concentrations of the measurement solvents (e.g., 0.05 g / dL, 0.1 g / dL, 0.2 g / dL, and 0.4 g / dL) for the measurements.

[0130] As a thermoplastic resin, one or more polyester resins selected from polyethylene terephthalate (PET), polyethylene naphthalate (PEN), polybutylene terephthalate (PBT), polybutylene succinate (PBS), polybutylene succinate adipate (PBSA), polybutylene adipate terephthalate (PBAT), polyhydroxyalkanoic acid (PHA), polylactic acid (PLA), polyarylate (PAR), etc., can be used. Among these, PET, PBS, PBSA, PBT, and PEN are more preferred, and PBS, PBSA, and PBT are particularly preferred.

[0131] The end groups of the polyester resin can be arbitrarily changed by the monomer ratio during polymerization, the presence or absence and amount of end stabilizers added, etc. The ratio of carboxyl end groups to the total end groups of the polyester resin ([COOH] / [total end groups]) is preferably 0.30 or more, or 0.35 or more, or 0.40 or more, or 0.45 or more, from the viewpoint of the dispersibility of cellulose fibers in the resin composite, and preferably 0.95 or less, or 0.90 or less, or 0.85 or less, or 0.80 or less, from the viewpoint of the color tone of the resin composite.

[0132] Preferred polyacetal resins as thermoplastic resins include homopolyacetals made from formaldehyde and copolyacetals that use trioxane as the main monomer and contain 1,3-dioxolane as a comonomer component. Both are usable, but copolyacetals are preferred from the viewpoint of thermal stability during processing. The amount of structure derived from the comonomer component (e.g., 1,3-dioxolane) is preferably 0.01 mol% or more, 0.05 mol% or more, 0.1 mol% or more, or 0.2 mol% or more from the viewpoint of thermal stability during extrusion and molding processes, and preferably 4 mol% or less, 3.5 mol% or less, 3.0 mol% or less, 2.5 mol% or less, or 2.3 mol% or less from the viewpoint of mechanical strength.

[0133] (thermosetting resin) Thermosetting resins include bisphenol-type epoxy resins such as bisphenol A type epoxy resin, bisphenol F type epoxy resin, bisphenol S type epoxy resin, bisphenol E type epoxy resin, bisphenol M type epoxy resin, bisphenol P type epoxy resin, and bisphenol Z type epoxy resin; novolac-type epoxy resins such as bisphenol A novolac type epoxy resin, phenol novolac type epoxy resin, and cresol novolac epoxy resin; biphenyl-type epoxy resin, biphenyl aralkyl-type epoxy resin, arylalkylene-type epoxy resin, tetraphenyloleethane-type epoxy resin, naphthalene-type epoxy resin, anthracene-type epoxy resin, phenoxy-type epoxy resin, dicyclopentadiene-type epoxy resin, norbornene-type epoxy resin, adamantane-type epoxy resin, fluorene-type epoxy resin, glycidyl methacrylate copolymer epoxy resin, copolymer epoxy resin of cyclohexylmaleimide and glycidyl methacrylate, epoxy-modified polybutadiene rubber derivatives, CTBN-modified epoxy resin, and trimethylolpropane polyglycidyl ether. Phenyl-1,3-diglycidyl ether, biphenyl-4,4'-diglycidyl ether, 1,6-hexanediol diglycidyl ether, ethylene glycol or propylene glycol diglycidyl ether, sorbitol polyglycidyl ether, tris(2,3-epoxypropyl) isocyanurate, triglycidyl tris(2-hydroxyethyl) isocyanurate, novolac-type phenolic resins such as phenol novolac resin, cresol novolac resin, and bisphenol A novolac resin, unmodified resol phenolic resin, paulownia Examples include phenolic resins such as oil-modified resol phenolic resins modified with oil, linseed oil, walnut oil, etc., phenoxy resins, urea resins, triazine ring-containing resins such as melamine resins, unsaturated polyester resins, bismaleimide resins, diallyl phthalate resins, silicone resins, resins having a benzoxazine ring, norbornene-based resins, cyanate resins, isocyanate resins, urethane resins, benzocyclobutene resins, maleimide resins, bismaleimide triazine resins, polyazomethine resins, and thermosetting polyimides.

[0134] (light curing resin) Examples of photocurable resins include (meth)acrylate resins, vinyl resins, and epoxy resins. These are generally classified into two types based on their reaction mechanism: radical reaction types, where monomers react to radicals generated by light, and cationic reaction types, where monomers undergo cationic polymerization. Monomers used in radical reaction types include (meth)acrylate compounds and vinyl compounds (e.g., certain vinyl ethers). Examples of cationic reaction types include epoxy compounds and certain vinyl ethers. For example, epoxy compounds that can be used as cationic reaction types can be monomers for both thermosetting and photocurable resins.

[0135] (Meth)acrylate compounds are compounds that have one or more (meth)acrylate groups in their molecule. Examples of (meth)acrylate compounds include monofunctional (meth)acrylates, polyfunctional (meth)acrylates, epoxy acrylates, polyester acrylates, and urethane acrylates.

[0136] Examples of vinyl compounds include vinyl ethers, styrene, and styrene derivatives. Examples of vinyl ethers include ethyl vinyl ether, propyl vinyl ether, hydroxyethyl vinyl ether, and ethylene glycol divinyl ether. Examples of styrene derivatives include methylstyrene and ethyl styrene. Examples of other vinyl compounds include triallyl isocyanurate and trimaallyl isocyanurate.

[0137] So-called reactive oligomers may be used as raw materials for photocurable resins. Examples of reactive oligomers include oligomers that have any combination selected from (meth)acrylate groups, epoxy groups, urethane bonds, and ester bonds within the same molecule, such as urethane acrylate having (meth)acrylate groups and urethane bonds within the same molecule, polyester acrylate having (meth)acrylate groups and ester bonds within the same molecule, and epoxy acrylate derived from epoxy resin having epoxy groups and (meth)acrylate groups within the same molecule.

[0138] (Elastomer) Examples of elastomers (i.e., rubbers) include natural rubber (NR), butadiene rubber (BR), styrene-butadiene copolymer rubber (SBR), isoprene rubber (IR), butyl rubber (IIR), acrylonitrile-butadiene rubber (NBR), acrylonitrile-styrene-butadiene copolymer rubber, chloroprene rubber, styrene-isoprene copolymer rubber, styrene-isoprene-butadiene copolymer rubber, isoprene-butadiene copolymer rubber, chlorosulfonated polyethylene rubber, modified natural rubber (epoxidized natural rubber (ENR), hydrogenated natural rubber, deproteinized natural rubber, etc.), ethylene-propylene copolymer rubber, acrylic rubber, epichlorohydrin rubber, polysulfide rubber, silicone rubber, fluororubber, urethane rubber, and the like.

[0139] When the resin is a thermoplastic resin, a resin composite can be produced by melt-kneading cellulose fibers (which may be in the form of a dry powder as disclosed herein, or a redispersed liquid obtained by dispersing them in a dispersion medium) with the thermoplastic resin. A more specific method for producing the resin composite is as follows: - A method for obtaining a pellet-shaped molded body by mixing resin monomers and cellulose fibers, carrying out a polymerization reaction, extruding the resulting resin composite into strands, and cooling and solidifying it in a water bath. - A method of obtaining a pellet-shaped molded body by melting and kneading a mixture of resin and cellulose fibers using a single-screw or twin-screw extruder, extruding it into strands, and cooling and solidifying it in a water bath. - A method of obtaining an extruded molded product by melting and kneading a mixture of resin and cellulose fibers using a single-screw or twin-screw extruder, extruding it into a rod or cylindrical shape, and then cooling it. - A method of obtaining a molded product in the form of a sheet or film by melting and kneading a mixture of resin and cellulose fibers using a single-screw or twin-screw extruder and extruding it from a T-die. Examples include the above. In a preferred embodiment, a mixture of resin and cellulose fibers is melt-kneaded using a single-screw or twin-screw extruder, extruded into strands, and cooled and solidified in a water bath to obtain a pellet-shaped molded body. A specific example of a method for melt-kneading resin and cellulose fibers is a method in which the resin and cellulose fibers, which have been transported in a desired ratio, are mixed, and then melt-kneaded. When the resin is a thermoplastic resin, the minimum processing temperatures recommended by thermoplastic resin suppliers are 255-270°C for nylon 66, 225-240°C for nylon 6, 170-190°C for polyacetal resin, and 160-180°C for polypropylene. The heating setting temperature is preferably within a range of 20°C higher than these recommended minimum processing temperatures. By setting the mixing temperature within this range, the cellulose fibers and resin can be mixed uniformly.

[0140] Resin composites containing thermoplastic resins as the resin can be provided in various shapes. Specifically, these include resin pellets, sheets, fibers, plates, rods, etc., but resin pellets are more preferable due to their ease of post-processing and transportation. Preferred pellet shapes include round, elliptical, and cylindrical shapes, which vary depending on the cutting method used during extrusion. Pellets cut using a method called underwater cutting are often round, pellets cut using a method called hot cutting are often round or elliptical, and pellets cut using a method called strand cutting are often cylindrical. For round pellets, the preferred size is a pellet diameter of 1 mm or more and 3 mm or less. For cylindrical pellets, the preferred diameter is 1 mm or more and 3 mm or less, and the preferred length is 2 mm or more and 10 mm or less. From the viewpoint of operational stability during extrusion, it is desirable that the diameter and length be above the lower limit, and from the viewpoint of ease of engagement with the molding machine during post-processing, it is desirable that they be below the upper limit.

[0141] Resin composites containing thermoplastic resins can be used as various resin molded articles. There are no particular restrictions on the manufacturing method of the resin molded articles; any method is acceptable, but injection molding, extrusion molding, blow molding, inflation molding, and foam molding are among the usable methods. Of these, injection molding is the most preferred method from the standpoint of design and cost.

[0142] When the resin is a thermosetting resin or a photocurable resin, the resin composite can be produced by, for example, a method of thoroughly dispersing cellulose fibers in a resin solution or resin powder dispersion and drying it; a method of thoroughly dispersing cellulose fibers in a resin monomer liquid and polymerizing them by heat, UV irradiation, polymerization initiator, etc.; a method of thoroughly impregnating a dried cellulose fiber powder with a resin solution or resin powder dispersion and drying it; or a method of thoroughly impregnating a dried cellulose fiber powder with a resin monomer liquid and polymerizing it by heat, UV irradiation, polymerization initiator, etc. Various polymerization initiators, curing agents, curing accelerators, polymerization inhibitors, etc., can be added during curing.

[0143] When the resin is a thermosetting resin or a photocuring resin, a method may be used in which an uncured or semi-cured sheet called a prepreg is prepared, and then the prepreg is laid in single layers or in multiple layers, and the resin is cured and molded by pressurization and heating. Examples of pressurization and heating methods include press molding, autoclave molding, bagging molding, wrapping tape method, and internal pressure molding.

[0144] If the resin is a photocurable resin, resin molded articles can be manufactured using various curing methods that utilize active energy rays.

[0145] When the resin is an elastomer, the resin composite can be manufactured by methods such as dry kneading of dried cellulose fiber powder and raw rubber, or by dispersing or dissolving the cellulose fibers and raw rubber in a dispersion medium, then drying and mixing them. Homogenizer mixing is preferred as a mixing method because it can promote dispersion by applying high shear force and pressure. However, other methods such as propeller-type agitators, rotary agitators, electromagnetic agitators, and manual agitation can also be used. The resin composite containing the elastomer can be molded using desired molding methods such as die molding, injection molding, extrusion molding, hollow molding, and foam molding to obtain unvulcanized molded articles in desired shapes such as sheets, pellets, and powders. The unvulcanized molded articles can be vulcanized by heat treatment or other methods as needed to obtain resin molded articles.

[0146] A resin molded article containing a thermoplastic resin or elastomer may be partially (for example, several locations) heat-treated to melt it and then used by bonding it to a substrate, for example, a resin or metal substrate. Alternatively, the resin molded article may be a coating applied to a resin or metal substrate, or it may form a laminate with the substrate. Furthermore, sheet-like, film-like, or fibrous resin molded articles may be subjected to secondary processing such as annealing, etching, corona treatment, plasma treatment, texture transfer, cutting, and surface polishing.

[0147] In a resin composite, the amount of cellulose fibers per 100 parts by mass of resin is preferably 0.001 parts by mass or more, or 0.01 parts by mass or more, or 0.1 parts by mass or more, or 1 part by mass or more, and preferably 100 parts by mass or less, or 80 parts by mass or less, or 70 parts by mass or less, or 50 parts by mass or less, from the viewpoint of balancing processability and mechanical properties. [Examples]

[0148] The present invention will be further described based on examples, but the present invention is not limited to these examples.

[0149] Manufacturing of cellulose fiber wet cakes <Cellulose fiber 1> Daicel Finechem Co., Ltd.'s Celish KY-100G (solid content concentration 10% by mass) was used as is.

[0150] <Cellulose fiber 2> After cutting the cotton linter pulp, the purified pulp was washed with water to remove impurities. This purified pulp was added to pure water to achieve a solid content of 1.5% by mass, and then beaten to highly shorten and fibrillate it, yielding defibrated cellulose. In this beating process, a disc refiner was used, and the pulp was treated for 2.5 hours with a beating blade that had high cutting ability, followed by a further 2 hours of beating with a beating blade that had high defibration ability. The slurry was then filtered and concentrated to obtain the resulting cellulose fibers (solid content concentration 20% by mass).

[0151] <Cellulose fiber 3> In a NETZSCH Vakumix KAPPA VITA (registered trademark) homomixer (tank size 35L), 1 kg of linter pulp and 19 kg of DMSO were loaded and defibrated for 8 hours at a homomixer speed of 6000 rpm (peripheral speed 29 m / s). Subsequently, 0.321 kg of sodium bicarbonate and 2.1 kg of vinyl acetate were added, and acetylation was carried out at 60°C for 4 hours. During acetylation, to prevent stagnation in the circulation line, the homomixer speed was set to 2500 rpm (peripheral speed 12 m / s), just before the shear force began to build up. The reaction mixture was washed with water, then filtered and concentrated to obtain acetylated cellulose fibers with a degree of substitution of 1.0 (solid content concentration 15% by mass).

[0152] Manufacturing of dried cellulose fiber powder [Example 1] Using the cellulose fiber wet cake prepared above, a dried powder was produced according to the following procedure. Equipment: Earth Technica Co., Ltd. high-speed mixer (model number: FS10) Ingredients: Cellulose fiber 1 (5kg) Conditions: The jacket temperature was 70°C, and the mixture was stirred with an agitator (peripheral speed 2 m / s) and a chopper (rotation speed 3500 rpm) while the pressure was reduced to -70 kPa using a vacuum pump. Vacuum drying was performed until the moisture content reached 50% by mass, at which point t-butanol (1 kg) was added, and vacuum drying was continued until the product temperature reached 60°C and the moisture content was less than 5% by mass.

[0153] [Example 2] Using the cellulose fiber wet cake prepared above, a dried powder was produced according to the following procedure. Equipment: Earth Technica Co., Ltd. high-speed mixer (model number: FS10) Ingredients: Cellulose fiber 1 (5kg) + Sanyo Chemical Industries, Ltd.'s Sannix GL-3000 (214g) Conditions: The jacket temperature was 70°C. The mixture was stirred using an agitator (peripheral speed 1 m / s) and a chopper (rotation speed 3500 rpm), while the pressure was reduced to -70 kPa with a vacuum pump. Vacuum drying was performed until the product temperature reached 60°C.

[0154] [Example 3] Using the cellulose fiber wet cake prepared above, a dried powder was produced according to the following procedure. Equipment: Redig mixer manufactured by Chuo Kiko Co., Ltd. (Model number: M20) Ingredients: Cellulose fiber 1 (5kg) + Sanyo Chemical Industries, Ltd.'s Sannix GL-3000 (214g) Conditions: The jacket temperature was 100°C. The mixture was stirred using an agitator (peripheral speed 4 m / s) and a chopper (rotation speed 5000 rpm), while the pressure was reduced to -90 kPa with a vacuum pump. Vacuum drying was performed until the product temperature reached 90°C.

[0155] [Example 4] Vacuum drying was carried out in the same manner as in Example 2, except that cellulose fiber 2 (2.5 kg) was used instead of cellulose fiber 1.

[0156] [Example 5] Vacuum drying was carried out in the same manner as in Example 1, except that cellulose fiber 3 (3.3 kg) was used instead of cellulose fiber 1.

[0157] [Example 6] Vacuum drying was carried out in the same manner as in Example 2, except that cellulose fiber 3 (3.3 kg) was used instead of cellulose fiber 1.

[0158] [Example 7] Using the cellulose fiber wet cake prepared above, a dried powder was produced according to the following procedure. Equipment: Earth Technica Co., Ltd. high-speed mixer (model number: FS10) Raw materials: Cellulose fiber 3 (3.3 kg) + 5% by mass acetone solution of Eastman Chemical Company CAB381-20 (214 g) Conditions: The jacket temperature was 70°C, and the mixture was stirred with an agitator (peripheral speed 1 m / s) and a chopper (3500 rpm) while the pressure was reduced to -70 kPa using a vacuum pump. Vacuum drying was performed until the moisture content reached 50% by mass, at which point acetone (1 kg) was added, and vacuum drying was continued until the product temperature reached 60°C and the residual solvent fraction was less than 3% by mass.

[0159] [Example 8] Except for setting the peripheral speed of the agitator to 15 m / s, the procedure was carried out under reduced pressure in the same manner as in Example 2.

[0160] [Example 9] Except for setting the peripheral speed of the agitator stirring to 0.5 m / s, the mixture was dried under reduced pressure in the same manner as in Example 2.

[0161] [Example 10] Except for setting the peripheral speed of the agitator to 1 m / s and the rotation speed of the chopper to 6000 rpm, vacuum drying was performed in the same manner as in Example 3.

[0162] [Example 11] Except for setting the chopper rotation speed to 200 rpm, the material was dried under reduced pressure in the same manner as in Example 2.

[0163] [Example 12] Using the cellulose fiber wet cake prepared above, a dried powder was produced according to the following procedure. Equipment: Earth Technica Co., Ltd. high-speed mixer (model number: FS10) Ingredients: Cellulose fiber 3 (3.3 kg) Conditions: The jacket temperature was 70°C, and the mixture was stirred with an agitator (peripheral speed 2 m / s) and a chopper (3500 rpm) while the pressure was reduced to -70 kPa using a vacuum pump. When the moisture content reached 50% by mass, t-butanol (1 kg) was added as the first additional medium, and vacuum drying was continued. When the moisture content reached 20% by mass, t-butanol (1 kg) was added as the second additional medium, and vacuum drying was carried out until the product temperature reached 60°C and the residual solvent fraction was less than 3% by mass.

[0164] [Example 13] Using the cellulose fiber wet cake prepared above, a dried powder was produced according to the following procedure. Equipment: Earth Technica Co., Ltd. high-speed mixer (model number: FS10) Ingredients: Cellulose fiber 3 (3.3 kg) Conditions: The jacket temperature was 70°C, and the mixture was stirred with an agitator (peripheral speed 2 m / s) and a chopper (3500 rpm) while the pressure was reduced to -70 kPa using a vacuum pump. Vacuum drying was performed until the moisture content reached 50% by mass, at which point 1-methoxy-2-propanol (1 kg) was added as the first additional medium, and vacuum drying was continued. Vacuum drying was performed until the moisture content reached 10% by mass, at which point t-butanol (1 kg) was added as the second additional medium, and vacuum drying was carried out until the product temperature reached 60°C and the residual solvent fraction was less than 3% by mass.

[0165] [Example 14] Using the cellulose fiber wet cake prepared above, a dried powder was produced according to the following procedure. Equipment: Earth Technica Co., Ltd. high-speed mixer (model number: FS10) Ingredients: Cellulose fiber 3 (3.3 kg) Conditions: The jacket temperature was 100°C, and the mixture was stirred with an agitator (peripheral speed 2 m / s) and a chopper (3500 rpm) while the pressure was reduced to -70 kPa using a vacuum pump. Vacuum drying was performed until the moisture content reached 75% by mass, at which point 2.0 kg of i-butanol was added dropwise as an additional medium over 30 minutes. Vacuum drying continued during this time, and the total liquid content (the sum of water and i-butanol measured with a heat-drying type moisture meter) at the end of the dropwise addition was 72% by mass. Furthermore, the mass ratio of water to i-butanol at the end of the dropwise addition was calculated to be 67:33 using gas chromatography. Vacuum drying was continued after the dropwise addition was completed until the product temperature reached 70°C and the residual solvent fraction was less than 3% by mass.

[0166] [Example 15] Vacuum drying was carried out in the same manner as in Example 14, except that the amount of i-butanol added was 3.0 kg and the adding time was 45 minutes. At the end of the adding process, the total liquid content was 74% by mass, and the mass ratio of water to i-butanol was 31:69.

[0167] [Example 16] Vacuum drying was carried out in the same manner as in Example 14, except that the amount of i-butanol added was 4.0 kg and the adding time was 60 minutes. At the end of the adding process, the total liquid content was 73% by mass, and the mass ratio of water to i-butanol was 4:96.

[0168] [Example 17] Using the cellulose fiber wet cake prepared above, a dried powder was produced according to the following procedure. Equipment: Henschel mixer manufactured by Nippon Coke Industries Co., Ltd. (Model number: FM20) Ingredients: Cellulose fiber 1 (5kg) Conditions: The jacket temperature was 70°C, and the mixture was stirred with an agitator (peripheral speed 8 m / s) and a chopper (peripheral speed 8 m / s) while the pressure was reduced to -70 kPa using a vacuum pump. Vacuum drying was performed until the moisture content reached 50% by mass, at which point t-butanol (1 kg) was added, and vacuum drying was continued until the product temperature reached 60°C and the moisture content was less than 5% by mass.

[0169] [Comparative Example 1] Using the cellulose fiber wet cake prepared above, a dried powder was produced according to the following procedure. Equipment: Primix Co., Ltd. Hibiscus Mix (Model number: 2P-1) Ingredients: Cellulose fiber 1 (0.3 kg) + Sanyo Chemical Industries, Ltd.'s Sannix GL-3000 (13 g) Conditions: The jacket temperature was 70°C, and the material was stirred with two blades (planetary rotation at 50 rpm) while the pressure was reduced to -95 kPa using a vacuum pump. Vacuum drying was performed until the remaining moisture content was less than 5% by mass.

[0170] [Comparative Example 2] Except for stopping the agitator and performing chopper stirring only, the material was dried under reduced pressure in the same manner as in Example 1. Most of the cellulose fibers were dried without coming into contact with the chopper, making redispersion and viscosity measurement difficult using the method described later.

[0171] [Comparative Example 3] Using the cellulose fiber wet cake prepared above, a dried powder was produced according to the following procedure. Equipment: Constant temperature chamber manufactured by ESPEC Corporation (Model number: SPH-201) Ingredients: Cellulose fiber 1 (0.3 kg) Conditions: The mixture was heated at 105°C, without stirring, and under atmospheric pressure, and dried until the remaining moisture content was less than 5% by mass. The cellulose fibers were aggregated and dried, making redispersion and viscosity measurement difficult using the method described later.

[0172] Manufacturing of resin composites The dried cellulose fiber powder produced as described above and a thermoplastic resin (UBE Nylon 1013B, manufactured by Ube Industries, Ltd.) were blended in such a ratio that the cellulose fiber accounted for 10% by mass of the resin composite, and a resin composite was manufactured according to the following procedure. Using a small kneader (manufactured by Xplore Instruments, product name "Xplore"), the torque was checked by circulating kneading at 260°C and 200 rpm (shear rate 1570 (1 / s)) for 5 minutes. The better the dispersibility of cellulose fibers in the thermoplastic resin, the higher the melt viscosity. Subsequently, the molten resin was directly transferred to the attached injection molding machine to prepare dumbbell-shaped test specimens according to ISO 037-3 standard, which were used for evaluation.

[0173] [Comparative Example 4] The torque was observed when only thermoplastic resin (UBE Nylon 1013B, manufactured by Ube Industries, Ltd.) was kneaded, without using dried cellulose fiber powder.

[0174] ≪Rating≫ <Evaluation of cellulose fibers> [Fabrication of porous sheets] First, the wet cake was added to t-butanol and then dispersed using a mixer or similar device until no aggregates remained. The concentration was adjusted to 0.5% by mass for every 0.5 g of cellulose fiber solids. 100 g of the resulting t-butanol dispersion was filtered on filter paper, dried at 150°C, and then the filter paper was peeled off to obtain a sheet. The air permeability resistance of this sheet was 10 g / m². 2 Porous sheets with a flow rate of 100 sec / 100 ml or less were used as measurement samples. The basis weight (W) of the sample after standing for 1 day in an environment of 23℃ and 50%RH (g / m²) 2 After measuring the air permeability resistance (R) (sec / 100ml), the air permeability resistance was measured using a Wangyan-type air permeability resistance tester (manufactured by Asahi Seiko Co., Ltd., model EG01). At this time, 10 g / m was measured according to the following formula. 2 The value per unit area was calculated. Weight: 10g / m 2 Air permeability resistance (sec / 100ml) = R / W × 10

[0175] [Degree of acyl substitution (DS)] Infrared spectral measurements were taken from five locations on a porous sheet using the ATR-IR method with a Fourier transform infrared spectrophotometer (JASCO FT / IR-6200). The infrared spectral measurements were performed under the following conditions. Total number of times: 64 Wavenumber resolution: 4cm -1 , Measurement wavefrequency range: 4000~600cm -1 , ATR crystal: diamond, Incident angle: 45° The IR index from the obtained IR spectrum is calculated using the following formula (1): IR Index = H1730 / H1030···(1) The calculation was performed according to the formula. In the formula, H1730 and H1030 are 1730 cm. -1 , 1030cm -1 This is the absorbance in the absorption band of the CO stretching vibration of the cellulose skeleton chain. However, each value is 1900 cm². -1 and 1500cm -1 The line connecting them is 800cm -1 and 1500cm -1 The line connecting these points is used as the baseline, and this value represents the absorbance when this baseline is set to 0. Then, the average degree of replacement at each measurement location was calculated from the IR index according to the following formula (2), and the average value was defined as DS. DS = 4.13 × IR Index ... (2)

[0176] [DS heterogeneity ratio (CV)] The porous sheets subjected to the above ATR-IR measurement were freeze-dried to prepare powder samples of cellulose fibers. The powder was placed on 10 2.5 mmφ dish-shaped sample holders, flattened by pressing down the surface, and each was subjected to XPS measurement. Peak separation was performed on the obtained C1s spectra, and the DSs of each sample was calculated using the following formula based on the area intensity (Ixf) of the peak derived from the OC=O bond of the acetyl group (286 eV) versus the area intensity (Ixp) of the peak attributed to carbon C2-C6 of the pyranose ring of cellulose (289 eV, CC bond), and the average of these was taken as the DSs of the cellulose fibers. DSs = (Ixf) × 5 / (Ixp)

[0177] The XPS measurement conditions used were as follows: Equipment used: ULVAC-FI VersaProbeII Excitation source: mono.AlKα 15kV × 3.33mA Analysis size: Approximately 200 μmφ Photoelectron extraction angle: 45° Capture area Narrow scan: C 1s, O 1s Pass Energy: 23.5 eV

[0178] Based on the above DS and DSs, the DS heterogeneity ratio (CV) was calculated according to the following formula. DS heterogeneity ratio (CV) = DSs / DS

[0179] [Average fiber diameter equivalent to specific surface area] Using a specific surface area and pore distribution analyzer (Nova-4200e, Quantachrome Instruments), approximately 0.2 g of a porous sheet sample was dried under vacuum at 150°C for 2 hours. The amount of nitrogen gas adsorbed at the boiling point of liquid nitrogen was then measured at five points (multi-point method) within a relative vapor pressure (P / P0) range of 0.05 to 0.2. The BET specific surface area (m²) was then calculated using the same instrument program. 2 The specific surface area ( / g) was calculated. Then, the average fiber diameter equivalent to the specific surface area was calculated from the specific surface area using the following formula, and this was defined as the average fiber diameter D of cellulose. D(nm)=2667 / specific surface area(m 2 / g)

[0180] [Average fiber diameter based on electron microscope images] The wet cake was diluted with t-butanol to 0.01% by mass, dispersed using a high-shear homogenizer (IKA, product name "Ultra-Turrax T18") under the following conditions: rotation speed 15,000 rpm for 3 minutes, cast onto an osmium-deposited silicon substrate, and air-dried. The sample was then measured using a high-resolution scanning electron microscope (Hitachi High-Tech Corporation, Regulus 8220). The measurement was performed by adjusting the magnification so that at least 100 cellulose fibers could be observed. The short diameter (D) of 100 randomly selected cellulose fibers was measured, and the average of the 100 cellulose fibers was calculated.

[0181] [Weight-average molecular weight (Mw), number-average molecular weight (Mn), and Mw / Mn ratio] 0.88 g of porous sheet was weighed, cut into small pieces with scissors, lightly stirred, and then 20 mL of pure water was added and left for 1 day. Next, the water and solids were separated by centrifugation. Then 20 mL of acetone was added, lightly stirred, and left for 1 day. Next, the acetone and solids were separated by centrifugation. Then 20 mL of N,N-dimethylacetamide was added, lightly stirred, and left for 1 day. N,N-dimethylacetamide and solids were separated again by centrifugation, and then 20 mL of N,N-dimethylacetamide was added, lightly stirred, and left for 1 day. N,N-dimethylacetamide and solids were separated by centrifugation, and 19.2 g of N,N-dimethylacetamide solution, prepared so that lithium chloride was 8 mass percent, was added to the solids, stirred with a stirrer, and visually confirmed to be dissolved. The solution in which the cellulose was dissolved was filtered through a 0.45 μm filter, and the filtrate was used as a sample for gel permeation chromatography. The equipment and measurement conditions used are as follows. Equipment: Tosoh Corporation HLC-8120 Column: TSKgel SuperAWM-H (6.0mm I.D. × 15cm) × 2 tubes Detector: RI detector Eluent: N,N-dimethylacetamide (lithium chloride 0.2%) Flow rate: 0.6mL / min Calibration curve: Pullulan equivalent

[0182] [Average content of alkali-soluble polysaccharides] The alkali-soluble polysaccharide content was determined for cellulose fibers by subtracting the α-cellulose content from the holocellulose content (Wise method) using the method described in non-patent literature (Wood Science Experiment Manual, edited by the Japan Wood Research Society, pp. 92-97, 2000). The alkali-soluble polysaccharide content was calculated three times for each sample, and the number average of the calculated alkali-soluble polysaccharide content was taken as the average alkali-soluble polysaccharide content of the cellulose fibers.

[0183] [Average content of acid-insoluble components] The acid-insoluble components were quantified using the Claesson method described in non-patent literature (Wood Science Experiment Manual, edited by the Japan Wood Research Society, pp. 92-97, 2000) for cellulose fibers. Absolutely dried cellulose fibers were accurately weighed, placed in a designated container, and 72% by mass concentrated sulfuric acid was added. After pressing the contents uniformly with a glass rod, the mixture was autoclaved to dissolve the cellulose and hemicellulose in the acid solution. After cooling, the contents were filtered through glass fiber filter paper to obtain the acid-insoluble components as residue. The acid-insoluble component content was calculated from the weight of this residue, and the number average of the acid-insoluble component content calculated for three samples was taken as the average acid-insoluble component content.

[0184] [Thermal decomposition onset temperature (T D )] The thermal analysis of the porous sheet was evaluated using the following measurement method. Device: Rigaku Thermo plus EVO2 Sample: Circular pieces cut from a porous sheet were stacked in aluminum sample pans, with 10 mg of each piece placed on top. Sample amount: 10 mg Measurement conditions: The sample was heated from room temperature to 150°C at a rate of 10°C / min in a nitrogen flow of 100 ml / min, held at 150°C for 1 hour, and then cooled to 30°C. Subsequently, the temperature was increased from 30°C to 450°C at a rate of 10°C / min. T D Calculation Method: The temperature was determined from a graph with temperature on the horizontal axis and weight retention percentage on the vertical axis. Starting from the weight of the porous sheet at 150°C (when moisture is almost completely removed) (weight loss of 0 wt%), the temperature was further increased, and a straight line was obtained that passes through the temperature at which the weight decreased by 1 wt% and the temperature at which the weight decreased by 2 wt%. The temperature at the point where this straight line intersects with the horizontal line (baseline) passing through the starting point of 0 wt% weight loss was defined as the thermal decomposition onset temperature (T D )

[0185] [1wt% weight loss temperature] 1wt% weight loss temperature calculation method: T D The temperature at which a 1 wt% weight loss occurred during the calculation was defined as the 1 wt% weight loss temperature.

[0186] [250℃ weight loss rate] Device: Rigaku Thermo plus EVO2 Sample: Circular pieces cut from a porous sheet were stacked in aluminum sample pans, with 10 mg of each piece placed on top. Sample amount: 10 mg Measurement conditions: The sample was heated from room temperature to 150°C at a rate of 10°C / min in a nitrogen flow of 100 ml / min, held at 150°C for 1 hour, then heated from 150°C to 250°C at a rate of 10°C / min, and held at 250°C for 2 hours. Method for calculating the weight change rate at 250°C: The weight W0 at the time the temperature reaches 250°C is used as the starting point, and the weight W1 after being held at 250°C for 2 hours is used to calculate the rate using the following formula. Weight change rate at 250℃ (%): (W1-W0) / W0×100

[0187] <Bulk density of dry cellulose fiber powder> The dry cellulose fiber powder was placed in a 100 mL stainless steel cylindrical container until it overflowed. After leveling off the excess powder, the weight was measured and calculated.

[0188] <Viscosity of cellulose fiber slurry and redispersion solution> A sample solution prepared by dispersing cellulose fibers before drying or dried powder with a homogenizer so as to obtain a 0.5 mass% aqueous dispersion was subjected to viscosity measurement in a coaxial cylindrical arrangement using a HAAKE MARS rheometer manufactured by Thermo Fisher Scientific. The viscosity at a shear rate of 100 s -1 was read. In order to suppress data variation, after applying a constant shear history, the viscosity at a shear rate of 100 s -1 was read. Specifically, after placing a 0.5 mass% sample solution in a coaxial cylinder cup, the shear rate was increased from 1 s -1 to 100 s -1 over 100 seconds using a rheometer. Thereafter, the shear rate was decreased from 100 s -1 to 1 s -1 over 100 seconds. Thereafter, the shear rate was increased again from 1 s -1 to 100 s -1 over 100 seconds, and the viscosity at the time when the shear rate reached 100 s -1 was read.

[0189] <Moisture Content and Total Liquid Content of CNF Slurry and Dried Powder> A heat-drying moisture meter (model MX-50, manufactured by A&D Company, Limited) was used. 5 g of the slurry or dried powder was placed on an aluminum dish, heated at 150°C, and the moisture content was measured. When the slurry contains a volatile organic solvent, the total liquid content was measured as the total amount of water and the organic solvent.

[0190] <Water:isobutanol Ratio of CNF Slurry> After preparing a DMF solution obtained by diluting CNF slurry to 0.1 mass% with dimethylformamide (DMF), solids were removed using a 0.2 μm syringe filter. The obtained DMF solution was measured by gas chromatography. The mass% of i-butanol in the DMF solution was calculated from the peak area of the obtained chromatogram, and then the mass% of i-butanol in each CNF slurry was calculated from the dilution ratio of the CNF slurry. In calculating the mass% of i-butanol from the peak area, a calibration curve was prepared in advance using DMF standard solutions containing i-butanol at different concentrations (i-butanol concentrations were 50 mass ppm, 100 mass ppm, and 500 mass ppm). Finally, the total liquid content of the CNF slurry (sum of both water and i-butanol) was measured with a heat-drying moisture meter, and the water:i-butanol ratio was calculated by the following formula. Water:i-butanol = (Total liquid content (mass%)) - (i-butanol mass%):i-butanol mass% Gas chromatography measurement was carried out under the following conditions. Apparatus: GC-2010 manufactured by Shimadzu Corporation Column: DB-WAX (30 m × 0.25 mm, film thickness 0.25 μm) Column temperature: 40°C → heated to 100°C at 15°C / min → heated to 200°C at 20°C / min Column flow rate: 1.0 ml / min Inlet temperature: 200°C Injection method: Split method (1:50) Detector temperature: 230°C Injection volume: 1 μl

[0191] <Tensile Strength and Elongation at Break of Resin Composite> Tensile yield strength and elongation at break were measured for the obtained test pieces in accordance with ISO527-1. For molded pieces that broke before yielding, the maximum strength thereof was used as a substitute.

[0192]

Table 1

[0193]

Table 2

[0194] According to the present invention, it is possible to produce a dried powder of cellulose fibers that exhibits good redispersibility, resulting in excellent storage and transportation costs, and which is extremely useful as a physical property improver for resin composites.

Claims

1. A granulation apparatus for producing dried powder of cellulose fibers by drying a slurry containing cellulose fibers having a number average fiber diameter of 10 nm or more and 1000 nm or less and a liquid medium, The granulation apparatus is A container for receiving the slurry, and A granulation mechanism that stirs the slurry inside the container to form the dried powder, Equipped with, The granulation mechanism is configured to form cellulose fiber particles by stirring and to pulverize the particles to form the dry powder. A granulation apparatus wherein the stirring is performed under reduced pressure, and / or the grinding is performed by chopper grinding.

2. The granulation apparatus according to claim 1, wherein the granulation mechanism is configured to be able to agitate a slurry containing 5% to 95% by mass of the liquid medium.

3. The granulation apparatus according to claim 1 or 2, wherein the granulation mechanism is configured to stir the slurry inside the tank to form the particles, apply a shear force to the particles to form pulverized material of the particles, and further supply the pulverized material to the stirring.

4. The granulation apparatus according to claim 1 or 2, wherein the granulation mechanism has a multi-stage structure of rotating blades arranged at predetermined intervals in the direction of rotation axis.

5. The granulation apparatus according to claim 1 or 2, wherein the granulation mechanism comprises a stirring blade and a chopper blade.

6. The stirring blades move the slurry at a shear rate of 50 sec. -1 ~7000sec ‐1 The granulation apparatus according to claim 5, configured to be capable of providing or to be rotatable at a peripheral speed of 0.5 m / sec to 40 m / sec.

7. The granulation apparatus according to claim 5, wherein the chopper blades are configured to be rotatable at a peripheral speed of 0.5 m / sec to 40 m / sec or a rotational speed of 100 rpm to 6000 rpm.

8. The granulation apparatus according to claim 5, wherein the stirring blade and the chopper blade are configured such that the chopper blade can rotate at a peripheral speed less than or equal to the peripheral speed of the stirring blade.

9. The granulation apparatus according to claim 5, wherein the rotation axis of the chopper blades protrudes inward in a cantilevered manner from the side wall of the can body, or penetrates the can body horizontally.

10. The granulation apparatus according to claim 5, wherein the stirring blade and the chopper blade have different axes of rotation.

11. The granulation apparatus according to claim 10, wherein the stirring blade and the chopper blade are configured such that the chopper blade / stirring blade ratios for rotational diameter and peripheral speed, respectively, can be set to 1.0 / 1.0 to 0.1 / 1.

0.

12. The granulation apparatus according to claim 5, wherein the stirring blade and the chopper blade have the same axis of rotation.

13. The granulation apparatus according to claim 12, wherein the rotational diameter of the chopper blade is less than or equal to the rotational diameter of the stirring blade.

14. The granulation apparatus according to claim 12, wherein the stirring blade and the chopper blade are configured such that the chopper blade / stirring blade ratio of the rotational diameter and peripheral speed, respectively, can be set to 1.0 / 1.0 to 0.5 / 1.

0.

15. The granulation apparatus according to claim 12, wherein the chopper blades are positioned above the stirring blades inside the tank.

16. The granulation apparatus according to claim 1 or 2, further comprising a temperature control mechanism for adjusting the temperature inside the container to 20 to 160°C.

17. The granulation apparatus according to claim 1 or 2, further comprising a pressure adjustment mechanism for adjusting the pressure inside the container to -1 kPa to -100 kPa.

18. The granulation apparatus according to claim 1 or 2, further comprising a carrier gas supply mechanism for supplying air and / or an inert gas to the tank body.

19. The granulation apparatus according to claim 1 or 2, further comprising a medium addition mechanism for adding an additional medium to the slurry inside the tank.

20. The granulation apparatus according to claim 19, wherein the medium addition mechanism is configured to add the additional medium to the slurry inside the tank in the form of droplets or mist.

21. The granulation apparatus according to claim 19, wherein the medium addition mechanism is configured to add an amount of the additional medium determined according to the amount of water loss in the slurry inside the tank.

22. The granulation apparatus according to claim 1 or 2, further comprising a binder addition mechanism for adding a binder to the slurry inside the container.

23. The granulation apparatus according to claim 22, wherein the binder addition mechanism is configured to dissolve the binder in a medium and add it to the slurry inside the tank.

24. The granulation apparatus according to claim 1 or 2, wherein the average particle size of the dried powder is 1 μm to 5000 μm.

25. The granulation apparatus according to claim 1 or 2, wherein the bulk density of the dried powder is 0.05 g / mL to 1.0 g / mL.

26. When a redispersion solution is prepared by dispersing the aforementioned dried powder in the same type and amount of liquid medium as the slurry supplied to the container, the shear rate of the redispersion solution is 100s. -1 The viscosity in the can body is the shear rate of the slurry supplied to the can body 100s -1 A granulation apparatus according to claim 1 or 2, which produces the dried powder such that its viscosity is 30% or more.

27. A method for producing dried powder of cellulose fibers by drying a slurry containing cellulose fibers having a number average fiber diameter of 10 nm or more and 1000 nm or less and a liquid medium, The process includes stirring the slurry to form cellulose fiber particles, and crushing the particles to form the dried powder. A method wherein the stirring is performed under reduced pressure, and / or the grinding is performed by chopper grinding.

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