Cellulose fiber dried body, method for producing the same, and method for producing resin composite

Abstract

To provide a dried cellulose fiber that prevents formation of an aggregate to cause defects such as black points when mixed with resin, reduces the frequency of replacement of screen mesh during molding, offering high productivity, and can give a resin composite having high toughness and a good appearance, and a resin composite containing the dried cellulose fiber and resin.SOLUTION: A dried cellulose fiber contains cellulose fiber and has a repose angle of 40°-60°, a difference angle of 10° or less, an aerated bulk density of 0.01 g / cm3-0.40 g / cm3, a packed bulk density of 0.1 g / cm3-0.55 g / cm3, and a compression level of 20%-40%. The content of particle components with a particle size of 710 μm or less is 50 mass%-90 mass%.SELECTED DRAWING: None

Description

Technical Field

[0001] The present invention relates to a dried cellulose fiber body, a method for producing the same, and a method for producing a resin composite containing a cellulose fiber and a resin.

Background Art

[0002] Since resin materials are light and have excellent processing characteristics, they are widely used in various fields such as automobile members, electric and electronic members, office equipment housings, and precision parts. However, in many cases, the mechanical properties, dimensional stability, etc. of the resin alone are insufficient. Therefore, a composite of a resin and various fillers is generally used. In recent years, the use of nanofibers such as cellulose nanofibers (CNF) as such fillers has been studied. Nanofibers including CNF have a property of being easily aggregated in a dry state, and thus are produced as a dispersion liquid capable of stable dispersion. For example, when applying the above dispersion liquid to various uses, it may be dispersed in a dispersion medium after once drying the dispersion liquid, or redispersed in a matrix resin as a dried body. However, in cellulose nanofibers, aggregation due to hydrogen bonding between cellulose molecules is extremely strong, and thus various methods for suppressing aggregation of cellulose nanofibers in the drying process have been proposed.

[0003] For example, Patent Document 1 describes a powdery nanofiber characterized in that (A) a powdery nanofiber is blended with (B) a dispersant in an amount of 1 to 40% by weight in terms of solid content and has a bulk density of 90 to 200 g / L. Further, Patent Document 2 describes a method for producing dried microfibers having a water content of 0 to 1% by mass by subjecting cellulose nanofibers to a homogenization treatment in the presence of an organic solvent and then removing the organic solvent. Further, Patent Document 3 describes a method for producing a dried solid of cellulose nanofibers, which includes drying a mixture of cellulose nanofibers and a solvent using a vacuum drying device.

Prior Art Documents

Patent Documents

[0004] [Patent Document 1] Japanese Unexamined Patent Application Publication No. 2017-210596 [Patent Document 2] Japanese Unexamined Patent Application Publication No. 2012-224960 [Patent Document 3] International Publication No. 2019 / 189318 [Summary of the Invention] [Problems to be Solved by the Invention]

[0005] All of the techniques described in Patent Documents 1 to 3 are intended to reduce the aggregation of cellulose nanofibers during drying, so that the dried cellulose nanofibers can be redispersed well in a dispersion medium or a matrix resin. However, even with these techniques, the redispersibility of once-dried cellulose nanofibers is not sufficient. In particular, there has been no established technique that can disperse the cellulose nanofibers well in the resin even when the cellulose nanofibers are mixed with the resin in a dry state. Therefore, with the conventional techniques, the effect of improving the physical properties of the resin by the cellulose nanofibers cannot be expressed at a satisfactory level. In addition, since there are agglomerates that do not pass through the screen mesh during mass production, the frequency of screen mesh replacement is very high, and there is a problem that mass production is difficult.

[0006] One aspect of the present invention solves the above problems, is excellent in productivity by reducing the frequency of screen mesh replacement during molding processing, can give a resin composite that is difficult to form aggregates that cause defects such as black spots when mixed with a resin, and is highly tough and excellent in appearance, and provides a dried cellulose fiber body and a resin composite containing the dried cellulose fiber body and a resin. [Means for Solving the Problems]

[0007] The present invention includes the following aspects. [1] Containing cellulose fibers, with an angle of repose of 40° to 60°, a difference angle of 10° or less, and a loose bulk density of 0.01 g / cm 3~0.40 g / cm 3 、 bulk density of 0.1 g / cm 3 ~0.55 g / cm 3 、 and a degree of compression of 20% to 40%, and a cellulose fiber dried body having a content of particle components with a particle size of 710 μm or less of 50% by mass to 90% by mass. [2] The cellulose fiber dried body according to the above aspect 1, wherein the content of particle components with a particle size exceeding 710 μm and 1000 μm or less is 10% by mass to 30% by mass. [3] The cellulose fiber dried body according to the above aspect 1 or 2, wherein the content of particle components with a particle size exceeding 1000 μm is 1% by mass to 10% by mass. [4] The cellulose fiber dried body according to any one of the above aspects 1 to 3, wherein the number average fiber diameter of the cellulose fiber is 2 nm to 1000 nm. [5] The cellulose fiber dried body according to any one of the above aspects 1 to 4, wherein the average fiber length (L) / fiber diameter (D) ratio of the cellulose fiber is 30 to 5000. [6] The cellulose fiber dried body according to any one of the above aspects 1 to 5, wherein the cellulose fiber has a weight average molecular weight (Mw) of 100000 or more and a weight average molecular weight (Mw) / number average molecular weight (Mn) ratio of 6 or less. [7] The cellulose fiber dried body according to any one of the above aspects 1 to 6, wherein the crystallinity of the cellulose fiber is 60% or more. [8] The cellulose fiber dried body according to any one of the above aspects 1 to 7, wherein the content of alkali-soluble polysaccharides in the cellulose fiber is 20% by mass or less. [9] The cellulose fiber dried body according to any one of the above aspects 1 to 8, wherein the cellulose fiber is chemically modified.

[10] The cellulose fiber dried body according to the above aspect 9, wherein the chemical modification is esterification.

[11] The cellulose fiber dried body according to the above aspect 10, wherein the esterification is acetylation.

[12] The cellulose fiber dried body according to any one of the above aspects 9 to 11, wherein the average degree of substitution (DS) of the cellulose fiber is 0.1 to 1.2.

[13] The cellulose fiber dried body according to any one of the above aspects 1 to 12, having a moisture content of 30% by mass or less.

[14] Further comprising a dispersant, The cellulose fiber dried body according to any one of the above aspects 1 to 13, wherein the dispersant is a compound having an HLB value of 0.1 or more, less than 8.0, a melting point of 80°C or less, and a number average molecular weight of 1000 to 50000.

[15] A method for producing the cellulose fiber dried body according to any one of the above aspects 1 to 14, comprising: A slurry preparation step of preparing a slurry containing cellulose fibers and an aqueous medium, and A drying step of drying the slurry under the condition of a drying rate of 10% / min to 10000% / min to form a cellulose fiber dried body. A method comprising the above steps.

[16] The method according to the above aspect 15, wherein the drying step is performed in a continuous process with a residence time at a drying temperature of 20°C to 200°C of 0.01 minutes to 10 minutes.

[17] A method for producing a resin composite containing cellulose fibers and a resin, comprising: Mixing the cellulose fiber dried body according to any one of the above aspects 1 to 16 with a resin, The method, wherein the tensile elongation at break of the resin composite is 8% or more.

[18] The method according to the above aspect 17, wherein the resin is a thermoplastic resin.

[19] The method according to the above aspect 18, wherein the thermoplastic resin is a polyamide-based resin.

Advantages of the Invention

[0008] According to one aspect of the present invention, a cellulose fiber dried body that is less likely to form aggregates that cause defects such as black spots during mixing with a resin, is excellent in productivity by reducing the frequency of screen mesh replacement during molding processing, and can provide a resin composite having high toughness and excellent appearance, and a resin composite containing the cellulose fiber dried body and a resin can be provided.

Brief Description of the Drawings

[0009]

Figure 1

Figure 2

Mode for Carrying Out the Invention

[0010] Exemplary embodiments of the present invention will be specifically described below, but the present invention is not limited to these embodiments.

[0011] ≪Cellulose Fiber Dry Body≫ One aspect of the present invention provides a cellulose fiber dry body which may be particulate. The cellulose fiber dry body according to one aspect has its particle diameter, angle of repose, angle of collapse, difference angle, loose bulk density, tapped bulk density, and compressibility controlled within a specific range. Such a cellulose fiber dry body is less likely to form cellulose aggregates that cause defects such as black spots when dispersed in a resin because the particle size, cellulose molecular aggregation state, and inter-particle interaction are appropriately controlled. Therefore, by using the cellulose fiber dry body according to one aspect of the present invention, a resin composite having high toughness and few defects such as black spots derived from cellulose and presenting a good appearance can be formed.

[0012] In one aspect, the angle of repose of the cellulose fiber dry body is 40° to 60°, preferably 42° or more, or 44° or more, or 46° or more, and preferably 58° or less, or 56° or less, or 54° or less. If the size of the cellulose fiber dry body is too large, it is difficult to disperse it in the resin, but if it is too small, aggregation between particles becomes prominent and the dispersibility in the resin deteriorates instead. The cellulose fiber dry body having an angle of repose within the above range can uniformly disperse the cellulose fibers in the resin because the particle size is within an appropriate range. Although the dispersion size at this time is not necessarily extremely fine, the physical properties (especially toughness) of the resin composite are extremely good due to less generation of aggregates.

[0013] The angle of collapse of the dried cellulose fiber is controlled within a range useful for controlling the angle of repose and the angle of difference within the scope of the present disclosure, and in one aspect, it may be 30° to 50°, or 35° to 48°, or 38° to 46°.

[0014] In one aspect, the angle of difference of the dried cellulose fiber (that is, the difference between the angle of repose and the angle of collapse) is 10° or less, preferably 9° or less, or 8° or less, or 7° or less. The dried cellulose fiber with the angle of difference within the above range is excellent in handleability due to relatively large interaction (such as frictional force) between particles. The angle of difference may be, for example, 1° or more, or 2° or more, or 3° or more from the viewpoint of ease of manufacturing the dried cellulose fiber.

[0015] The angle of repose and the angle of collapse are values measured by the method described in the [Examples] section of the present disclosure. The angle of difference is calculated as the difference between the angle of repose and the angle of collapse.

[0016] In one aspect, the bulk density of the loosened dried cellulose fiber is 0.01 g / cm 3 or more, preferably 0.05 g / cm 3 or more, or 0.08 g / cm 3 or more, or 0.1 g / cm 3 or more. Also, the above-mentioned bulk density of the loosened dried cellulose fiber is 0.40 g / cm 3 or less, preferably 0.38 g / cm 3 or less, or 0.36 g / cm 3 or less, or 0.35 g / cm 3 or less, in terms of the point that the cellulose fiber can be well dispersed in the resin and the point that the dried cellulose fiber is not too heavy to avoid poor mixing of the dried cellulose fiber and the resin.

[0017] The bulk density of the dried cellulose fiber is controlled within a range useful for controlling the bulk density of the loosened dried cellulose fiber and the degree of compression within the scope of the present disclosure, and in one aspect, 0.1 g / cm3 ~0.55 g / cm 3 、 or 0.12 g / cm 3 ~0.52 g / cm 3 、 or 0.13 g / cm 3 ~0.2 g / cm 3 may be.

[0018] In one aspect, the degree of compression of the dried cellulose fiber is 20% - 40%. The degree of compression represents the degree of bulk reduction. In terms of suppressing natural flow without excessive fluidity of the dried cellulose fiber, the degree of compression is 20% or more, preferably 23% or more, or 25% or more, or 27% or more. Also, in terms of good fluidity of the dried cellulose fiber, the degree of compression is 40% or less, preferably 39% or less, or 38% or less, or 37% or less.

[0019] The loose bulk density and the packed bulk density are values measured by the method described in the [Examples] section of the present disclosure. The degree of compression is a value calculated by Degree of compression = (Packed bulk density - Loose bulk density) / Packed bulk density.

[0020] In one aspect, the content rate of the particle component with a particle size of 710 μm or less in the dried cellulose fiber is 50 - 90% by mass, preferably 55 - 85% by mass, or 60 - 80% by mass, or 63 - 77% by mass. Also, the content rate of particles with a particle size exceeding 710 μm and 1000 μm or less is preferably 10 - 30% by mass, or 12 - 25% by mass. Also, the content rate of particles with a particle size exceeding 1000 μm is preferably 1 - 22% by mass, or 5 - 10% by mass. In the dried cellulose fiber, since small particles with a particle size of 710 μm or less are the main component, the dispersion of the dried cellulose fiber in the resin becomes easy, and while improving toughness, clogging of the screen mesh can be suppressed. Also, by appropriately containing particles larger than 710 μm, rigidity can be exhibited, so a resin composite excellent in the balance of physical properties can be obtained. The particle size distribution of the dried cellulose fiber is a value measured by the method described in the [Examples] section of the present disclosure.

[0021] In one aspect, the average particle size of the dried cellulose fibers is preferably 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 the laser diffraction / scattering method.

[0022] In one aspect, the moisture content of the dried cellulose fibers may be 30% by mass or less, or 20% by mass or less, or 10% by mass or less. The moisture content may be 0% by mass, but from the viewpoint of the ease of manufacturing the dried cellulose fibers, for example, it may be 0.1% by mass or more, or 1% by mass or more, or 1.5% by mass or more. The moisture content is a value measured using an infrared heating type moisture meter.

[0023] As raw materials for the dried cellulose fibers, natural cellulose and regenerated cellulose can be used. 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 linter, sisal, straw, etc.), cellulose fiber aggregates produced by animals (e.g., tunicates), algae, and microorganisms (e.g., acetic acid bacteria) can be used. As regenerated cellulose, regenerated cellulose fibers (viscose, cupra, tencel, etc.), cellulose derivative fibers, regenerated cellulose or ultrafine filaments of cellulose derivatives obtained by the electrospinning method can be used.

[0024] In one aspect, the cellulose fibers are cellulose nanofibers. Cellulose nanofibers refer to fine cellulose fibers obtained by treating pulp or the like with hot water at 100 °C or higher to hydrolyze and weaken hemicellulose, and then defibrating by a pulverization method using a high-pressure homogenizer, a microfluidizer, a ball mill, a disk mill, a mixer (e.g., a homomixer), or the like. In one aspect, the cellulose nanofibers have a number average fiber diameter of 1 nm or more and 1000 nm or less. The cellulose fibers may be chemically modified as described later.

[0025] The slurry can be prepared by dispersing cellulose fibers (for example, the cellulose nanofibers obtained through the above fibrillation) in a liquid medium. The dispersion can be carried out using a high-pressure homogenizer, a microfluidizer, a ball mill, a disk mill, a mixer (such as a homomixer), etc. For example, the product of the above fibrillation can be obtained as the product of the slurry preparation step of the present disclosure. The liquid medium in the slurry can, in addition to water, optionally further contain other liquid media (such as organic solvents) singly or in combinations of two or more. As the organic solvent, commonly used water-miscible organic solvents can be used, such as: alcohols with a boiling point of 50°C to 170°C (for example, methanol, ethanol, n-propanol, i-propanol, n-butanol, i-butanol, s-butanol, t-butanol, etc.); ethers (for example, propylene glycol monomethyl ether, 1,2-dimethoxyethane, diisopropyl ether, tetrahydrofuran, 1,4-dioxane, etc.); carboxylic acids (for example, formic acid, acetic acid, lactic acid, etc.); esters (for example, ethyl acetate, vinyl acetate, etc.); ketones (for example, acetone, methyl ethyl ketone, methyl isobutyl ketone, cyclopentanone, cyclohexanone, etc.); nitrogen-containing solvents (dimethylformamide, dimethylacetamide, acetonitrile, etc.), etc. In a typical embodiment, the liquid medium in the slurry is substantially only water. The slurry may contain additional components (dispersants, binders, antioxidants, preservatives, thickeners, etc.) described below in addition to the cellulose fibers and the liquid medium.

[0026] Since the cellulose fiber raw material contains alkali-soluble components and sulfuric acid-insoluble components (such as lignin), purification steps such as delignification through cooking and bleaching steps may be carried out to reduce the alkali-soluble components and sulfuric acid-insoluble components. On the other hand, purification steps such as delignification through cooking and bleaching steps can cleave the molecular chains of cellulose and change the weight-average molecular weight and the number-average molecular weight. Therefore, it is desirable that the purification step and the bleaching step of the cellulose fiber raw material be controlled so that the weight-average molecular weight of cellulose and the ratio of the weight-average molecular weight to the number-average molecular weight do not deviate from an appropriate range.

[0027] In addition, since the purification process such as delignification and the bleaching process by the pulping treatment reduce the molecular weight of cellulose molecules, there is a concern that these processes may reduce the molecular weight of cellulose and cause the cellulose fiber raw material to deteriorate and increase the abundance ratio of alkali-soluble components. Since the alkali-soluble components are inferior in heat resistance, it is desirable that the purification process and the bleaching process of the cellulose fiber raw material be controlled so that the amount of alkali-soluble components contained in the cellulose fiber raw material falls within a range of a certain value or less.

[0028] In one aspect, the number average fiber diameter of the cellulose fiber is preferably 2 to 1000 nm from the viewpoint of obtaining a good physical property improvement effect by the cellulose fiber. The number average fiber diameter of the cellulose fiber is more preferably 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.

[0029] The average L / D of the cellulose fiber is preferably 50 or more, or 80 or more, or 100 or more, or 120 or more, or 150 or more from the viewpoint of improving the mechanical properties of the resin composite containing the cellulose fiber well with a small amount of cellulose fiber. The upper limit is not particularly limited, but is preferably 5000 or less from the viewpoint of handleability.

[0030] In the present disclosure, the length, diameter, and L / D ratio of each cellulose fiber are determined by measuring a water dispersion of cellulose fibers that has been dispersed under the treatment conditions of a high-shear homogenizer (for example, the product name "Excel Auto Homogenizer ED-7" manufactured by Nippon Seiki Co., Ltd.) at a rotation speed of 15,000 rpm for 5 minutes. The water dispersion is diluted with pure water to 0.1 to 0.5% by mass, cast onto mica, and air-dried to obtain a measurement sample, which is then measured using a high-resolution scanning electron microscope (SEM) or an atomic force microscope (AFM). Specifically, in an observation field with a magnification adjusted so that at least 100 cellulose fibers are observed, the lengths (L) and diameters (D) of 100 randomly selected cellulose fibers are measured, and the ratio (L / D) is calculated. For the cellulose fibers, the number average value of the length (L), the number average value of the diameter (D), and the number average value of the ratio (L / D) are calculated.

[0031] Alternatively, the length, diameter, and L / D ratio of the cellulose fibers in the resin composite can be confirmed by measuring the solid resin composite as a measurement sample using the above-described measurement method.

[0032] Alternatively, the length, diameter, and L / D ratio of the cellulose fibers in the resin composite can be confirmed by dissolving the resin component in the resin composite in an organic or inorganic solvent that can dissolve the resin component, separating the cellulose fibers, thoroughly washing them with the solvent, and then preparing a water dispersion in which the solvent is replaced with pure water. The cellulose fiber concentration is diluted with pure water to 0.1 to 0.5% by mass, cast onto mica, and air-dried to obtain a measurement sample, which is then measured using the above-described measurement method. At this time, the measurement of the cellulose fibers is performed on 100 or more randomly selected fibers.

[0033] The crystallinity of the cellulose fiber is preferably 55% or more. When the crystallinity is within this range, since the mechanical properties (strength, dimensional stability) of the cellulose fiber itself are high, when the cellulose fiber is dispersed in a resin, the strength and dimensional stability of the resin composite tend to be high. The lower limit of the more preferable crystallinity is 60%, even more preferably 70%, and most preferably 80%. There is no particular limitation on the upper limit of the crystallinity of the cellulose fiber, and a higher value is preferable, but from the viewpoint of production, the preferable upper limit is 99%.

[0034] Between microfibrils of plant-derived cellulose and between microfibril bundles, there 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 forms a hydrogen bond with cellulose to play a role in connecting between microfibrils. Lignin is a compound having an aromatic ring and is known to be covalently bonded to hemicellulose in the plant cell wall. If the remaining amount of impurities such as lignin in the cellulose fiber is large, discoloration may occur due to heat during processing. Therefore, from the viewpoint of suppressing discoloration of the resin composite during extrusion processing and molding processing, it is desirable that the crystallinity of the cellulose fiber be within the above range.

[0035] When the cellulose is of cellulose I type crystal (derived from natural cellulose), the crystallinity referred to here is determined by the following formula by the Segal method from the diffraction pattern (2θ / deg. is 10 to 30) when the sample is measured by wide-angle X-ray diffraction. Crystallinity (%) = ([Diffraction intensity due to the (200) plane at 2θ / deg. = 22.5] - [Diffraction intensity due to the amorphous at 2θ / deg. = 18]) / [Diffraction intensity due to the (200) plane at 2θ / deg. = 22.5] × 100

[0036] The crystallinity is determined by the following formula from the absolute peak intensity h0 at 2θ = 12.6° attributed to the (110) plane peak of cellulose II crystals and the peak intensity h1 from the baseline at this interplanar spacing in wide-angle X-ray diffraction when the cellulose is cellulose II crystals (derived from regenerated cellulose). Crystallinity (%) = h1 / h0 × 100

[0037] As crystal forms of cellulose, type I, type II, type III, type IV, etc. are known. Among them, type I and type II are particularly widely used. Although type III and type IV are obtained on a laboratory scale, they are not widely used on an industrial scale. As the cellulose fiber of the present disclosure, since the structural mobility is relatively high, and by dispersing the cellulose fiber in a resin, a resin composite having a lower linear expansion coefficient and more excellent strength and elongation during tensile and bending deformation can be obtained, 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 more are more preferred.

[0038] Also, the degree of polymerization of the cellulose fiber 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, more preferably 3000 or less.

[0039] From the viewpoints of processability and manifestation of mechanical properties, it is desirable to set the degree of polymerization of the cellulose fiber within the above range. From the viewpoint of processability, it is preferable that the degree of polymerization is not too high, and from the viewpoint of manifestation of mechanical properties, it is desired that it is not too low.

[0040] The degree of polymerization of the cellulose fiber means the average degree of polymerization measured according to the reduced specific viscosity method using a copper ethylenediamine solution described in the confirmation test (3) of the "Fifteenth Revised Japanese Pharmacopoeia Explanation Book (published by Hirokawa Shoten)".

[0041] In one aspect, the weight average molecular weight (Mw) of the cellulose fiber is 100,000 or more, more preferably 200,000 or more. The ratio (Mw / Mn) of the weight average molecular weight to the number average molecular weight (Mn) is 6 or less, preferably 5.4 or less. A larger weight average molecular weight means fewer end groups of the cellulose molecules. Also, since the ratio (Mw / Mn) of the weight average molecular weight to the number average molecular weight represents the width of the molecular weight distribution, a smaller Mw / Mn means fewer ends of the cellulose molecules. Since the ends of the cellulose molecules serve as the starting points of thermal decomposition, particularly highly heat-resistant cellulose fibers and resin composites containing cellulose fibers and resins can be obtained when the weight average molecular weight of the cellulose molecules in the cellulose fiber is large, and at the same time, the weight average molecular weight is large and the width of the molecular weight distribution is narrow. The weight average molecular weight (Mw) of the cellulose fiber may be, for example, 600,000 or less, or 500,000 or less, from the viewpoint of the availability of the cellulose fiber raw material. The ratio (Mw / Mn) of the weight average molecular weight to the number average molecular weight (Mn) may be, for example, 1.5 or more, or 2 or more, from the viewpoint of the ease of manufacturing the cellulose fiber. Mw can be controlled within the above range by selecting a cellulose fiber raw material having an Mw suitable for the purpose, appropriately performing physical and / or chemical treatments on the cellulose fiber raw material within an appropriate range, and the like. Mw / Mn can also be controlled within the above range by selecting a cellulose fiber raw material having an Mw / Mn suitable for the purpose, appropriately performing physical and / or chemical treatments on the cellulose fiber raw material within an appropriate range, and the like. In both the control of Mw and the control of Mw / Mn, examples of the above physical treatments include physical treatments that apply mechanical forces such as impact, shear, shear, and friction by a microfluidizer, ball mill, disk mill, etc. for dry or wet grinding, a crusher, a homomixer, a high-pressure homogenizer, an ultrasonic device, etc., and examples of the above chemical treatments include steaming, bleaching, acid treatment, regeneration of cellulose, etc.

[0042] The weight-average molecular weight and number-average molecular weight of the cellulose fibers referred to herein are values obtained by dissolving the cellulose fibers in N,N-dimethylacetamide with lithium chloride added thereto and then determining them by gel permeation chromatography using N,N-dimethylacetamide as a solvent.

[0043] Examples of methods for controlling the degree of polymerization (i.e., average degree of polymerization) or molecular weight of cellulose fibers include hydrolysis treatment. By hydrolysis treatment, the depolymerization of amorphous cellulose inside the cellulose fibers proceeds, and the average degree of polymerization decreases. At the same time, by hydrolysis treatment, in addition to the above-mentioned amorphous cellulose, impurities such as hemicellulose and lignin are also removed, so that the inside of the fibrous material becomes porous.

[0044] The method of hydrolysis is not particularly limited, and examples include acid hydrolysis, alkali hydrolysis, hydrothermal hydrolysis, steam explosion, microwave decomposition, and the like. These methods may be used alone or in combination of two or more. In the method of acid hydrolysis, for example, α-cellulose obtained as pulp from fibrous plants is used as a cellulose fiber raw material, and an appropriate amount of a protonic acid, carboxylic acid, Lewis acid, heteropolyacid, etc. is added in a state where this is dispersed in an aqueous medium, and the temperature is raised while stirring, whereby the average degree of polymerization can be easily controlled. The reaction conditions such as temperature, pressure, and time at this time vary depending on the cellulose species, cellulose concentration, acid species, acid concentration, etc., but are appropriately adjusted so as to achieve the target average degree of polymerization. For example, there is a condition of treating the cellulose fibers for 10 minutes or more at 100°C or higher under pressure using an aqueous solution of a mineral acid of 2% by mass or less. Under this condition, the catalytic component such as an acid penetrates into the inside of the cellulose fibers, hydrolysis is promoted, the amount of the catalytic component used is reduced, and subsequent purification becomes easy. In addition, the dispersion of the cellulose fiber raw material during hydrolysis may contain a small amount of an organic solvent within a range that does not impair the effects of the present invention in addition to water.

[0045] Alkaline-soluble polysaccharides that may be contained in cellulose fibers include, in addition to hemicellulose, β-cellulose and γ-cellulose. Alkaline-soluble polysaccharides are understood by those skilled in the art as components obtained as the alkaline-soluble portion of holocellulose obtained by solvent extraction and chlorination treatment of plants (e.g., wood) (i.e., components obtained by removing α-cellulose from holocellulose). Alkaline-soluble polysaccharides are polysaccharides containing hydroxyl groups and have poor heat resistance. When heated, they may decompose, cause yellowing during heat aging, and cause disadvantages such as a decrease in the strength of cellulose fibers. Therefore, it is preferable that the content of alkaline-soluble polysaccharides in cellulose fibers is low.

[0046] In one aspect, from the perspective of obtaining good dispersibility of cellulose fibers, the average content rate of alkaline-soluble polysaccharides in cellulose fibers is preferably 20% by mass or less, or 18% by mass or less, or 15% by mass or less, or 12% by mass or less, based on 100% by mass of cellulose fibers. From the perspective of the ease of manufacturing cellulose fibers, the above content rate may be 1% by mass or more, or 2% by mass or more, or 3% by mass or more.

[0047] The average content rate of alkaline-soluble polysaccharides can be determined by the method described in a non-patent document (Wood Science Experiment Manual, edited by the Japanese Wood Research Society, pages 92-97, 2000), and is determined by subtracting the α-cellulose content rate from the holocellulose content rate (Wise method). This method is understood in the industry as a method for measuring the amount of hemicellulose. The alkaline-soluble polysaccharide content rate is calculated three times for one sample, and the number average of the calculated alkaline-soluble polysaccharide content rates is taken as the average content rate of alkaline-soluble polysaccharides.

[0048] In one aspect, from the perspective of avoiding a decrease in the heat resistance of cellulose fibers and the accompanying discoloration, the average content rate of acid-insoluble components in cellulose fibers is preferably 10% by mass or less, or 5% by mass or less, or 3% by mass or less, based on 100% by mass of cellulose fibers. From the perspective of the ease of manufacturing cellulose fibers, the above content rate may be 0.1% by mass or more, or 0.2% by mass or more, or 0.3% by mass or more.

[0049] The average content rate of acid-insoluble components is determined by quantifying the acid-insoluble components using the Klason method described in the non-patent literature (Wood Science Experiment Manual, edited by the Japanese Wood Research Society, pages 92-97, 2000). This method is understood in the industry as a method for measuring the amount of lignin. After stirring the sample in a sulfuric acid solution to dissolve cellulose, hemicellulose, etc., it is filtered through a glass fiber filter paper, and the resulting residue corresponds to the acid-insoluble components. The acid-insoluble component content rate is calculated from the weight of this acid-insoluble component, and the number average of the acid-insoluble component content rates calculated for 3 samples is defined as the average content rate of acid-insoluble components.

[0050] The thermal decomposition start temperature (T D ) is, from the viewpoint of being able to exhibit heat resistance and mechanical strength desired for in-vehicle applications, etc., in one aspect, 270 °C or higher, preferably 275 °C or higher, more preferably 280 °C or higher, and even more preferably 285 °C or higher. Although a higher thermal decomposition start temperature is more preferable, from the viewpoint of the ease of manufacturing the cellulose fiber, for example, it may be 320 °C or lower, or 300 °C or lower.

[0051] In the present disclosure, T D is, as shown in the explanatory diagram of FIG. 2, a value obtained from a graph in thermogravimetric (TG) analysis where the horizontal axis is temperature and the vertical axis is the weight retention rate %. (Note that FIG. 2(B) is an enlarged view of FIG. 2(A).). Starting from the weight of the cellulose fiber at 150 °C (state where moisture is almost removed) (weight reduction amount 0 wt%), the temperature is further increased, and a straight line passing through the temperature (T 1% ) at 1 wt% weight reduction and the temperature (T 2% ) at 2 wt% weight reduction is obtained. The temperature at the point where this straight line intersects the horizontal line (baseline) passing through the starting point of 0 wt% weight reduction amount is defined as T D .

[0052] The 1% weight reduction temperature (T 1% ) is the temperature at 1 wt% weight reduction starting from the weight at 150 °C when the temperature increase is continued by the method of T D .

[0053] The 250°C weight loss rate (T 250℃ ) of the cellulose fiber is the weight loss rate when the cellulose fiber is held at 250°C for 2 hours under a nitrogen flow in TG analysis.

[0054] (Chemical modification) The cellulose fiber may be a chemically modified cellulose fiber. The cellulose fiber may be pre-chemically modified, for example, at the stage of raw material pulp or linter, during the fibrillation process, or after the fibrillation process, or may be chemically modified during or after the slurry preparation process, or during or after the drying (granulation) process.

[0055] As a modifier for the cellulose fiber, a compound that reacts with the hydroxyl group of cellulose can be used, and examples include an esterifying agent, an etherifying agent, and a silylating agent. In a preferred embodiment, the chemical modification is acylation using an esterifying agent. Preferred esterifying agents include acid halides, acid anhydrides, and vinyl carboxylates and carboxylic acids.

[0056] The acid halide may be at least one selected from the group consisting of compounds represented by the following formula (1). R 1 -C(=O)-X (1) (In the formula, R 1 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, benzoyl iodide, etc. Among them, acid chlorides can be preferably adopted from the viewpoints of reactivity and handleability. In addition, in the reaction of acid halides, one or more alkaline compounds may be added for the purpose of neutralizing acidic substances that act as catalysts and are by-products. Specific examples of alkaline compounds include: tertiary amine compounds such as triethylamine and trimethylamine; and nitrogen-containing aromatic compounds such as pyridine and dimethylaminopyridine; but are not limited thereto.

[0057] As the acid anhydride, any suitable acid anhydrides can be used. For example, Saturated aliphatic monocarboxylic acid anhydrides such as acetic acid, propionic acid, (iso)butyric acid, valeric acid; unsaturated aliphatic monocarboxylic acid anhydrides such as (meth)acrylic acid, oleic acid; Alicyclic monocarboxylic acid anhydrides such as cyclohexanecarboxylic acid, tetrahydrobenzoic acid; Aromatic monocarboxylic acid anhydrides such as benzoic acid, 4-methylbenzoic acid; As dibasic carboxylic acid anhydrides, for example, anhydrous saturated aliphatic dicarboxylic acids such as succinic anhydride, adipic anhydride, anhydrous unsaturated aliphatic dicarboxylic acids such as maleic anhydride, itaconic anhydride, anhydrous alicyclic dicarboxylic acids such as 1-cyclohexene-1,2-dicarboxylic anhydride, hexahydrophthalic anhydride, methyltetrahydrophthalic anhydride, and anhydrous aromatic dicarboxylic acid anhydrides such as phthalic anhydride, naphthalic anhydride, etc.; Examples of polybasic carboxylic acid anhydrides having three or more basic groups include (anhydrous) polycarboxylic acids such as trimellitic anhydride and pyromellitic anhydride. In the reaction of an acid anhydride, as a catalyst, an acidic compound such as sulfuric acid, hydrochloric acid, phosphoric acid, or a Lewis acid (for example, a Lewis acid compound represented by MYn, where M represents a metalloid element such as B, As, Ge, etc., or a base metal element such as Al, Bi, In, etc., or a transition metal element such as Ti, Zn, Cu, etc., or a lanthanoid element, n is an integer corresponding to the valence of M, representing 2 or 3, and Y represents a halogen atom, OAc, OCOCF 3 , ClO 4 , SbF 6 , PF 6 or OSO 2 CF 3 (OTf).), or one or more alkaline compounds such as triethylamine and pyridine may be added.

[0058] As the vinyl carboxylate, the following formula (1): R-COO-CH=CH 2 ... Formula (1) {In the formula, R is any one 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.} The vinyl carboxylate represented by is preferred. The vinyl carboxylate 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 capric acid, vinyl laurate, vinyl myristate, vinyl palmitate, vinyl stearate, vinyl pivalate, vinyl octylate, divinyl adipate, vinyl methacrylate, vinyl crotonate, vinyl pivalate, vinyl octylate, vinyl benzoate, and vinyl cinnamate. In the esterification reaction with the vinyl carboxylate, as a catalyst, one or more selected from the group consisting of alkali metal hydroxides, alkaline earth metal hydroxides, alkali metal carbonates, alkaline earth metal carbonates, alkali metal hydrogen carbonates, primary to tertiary amines, quaternary ammonium salts, imidazole and its derivatives, pyridine and its derivatives, and alkoxides may be added.

[0059] Examples of the alkali metal hydroxides and alkaline earth metal hydroxides include sodium hydroxide, potassium hydroxide, lithium hydroxide, calcium hydroxide, barium hydroxide and the like. Examples of the alkali metal carbonates, alkaline earth metal carbonates and alkali metal hydrogen carbonates include lithium carbonate, sodium carbonate, potassium carbonate, cesium carbonate, magnesium carbonate, calcium carbonate, barium carbonate, lithium hydrogen carbonate, sodium hydrogen carbonate, potassium hydrogen carbonate, cesium hydrogen carbonate and the like.

[0060] The primary to tertiary amines refer to primary amines, secondary amines and tertiary amines. Specific examples thereof 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, triethylamine and the like.

[0061] Examples of imidazole and its derivatives include 1-methylimidazole, 3-aminopropylimidazole, carbonyldiimidazole and the like.

[0062] Examples of pyridine and its derivatives include N,N-dimethyl-4-aminopyridine, picoline and the like.

[0063] Examples of alkoxides include sodium methoxide, sodium ethoxide, potassium-t-butoxide and the like.

[0064] Examples of the carboxylic acid include at least one 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.)

[0065] Specific examples of the carboxylic acid 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, octylic acid, benzoic acid, and cinnamic acid.

[0066] Among these carboxylic acids, at least one selected from the group consisting of acetic acid, propionic acid, and butyric acid, particularly acetic acid, is preferable from the viewpoint of reaction efficiency. In the reaction of the carboxylic acid, as the catalyst, an acidic compound such as sulfuric acid, hydrochloric acid, or phosphoric acid, or a Lewis acid (for example, a Lewis acid compound represented by 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 lanthanoid element, n is an integer corresponding to the valence of M, representing 2 or 3, and Y represents a halogen atom, OAc, OCOCF 3 , ClO 4 , SbF 6 , PF 6 or OSO 2 CF 3 (OTf).), or one or more alkaline compounds such as triethylamine or pyridine may be added.

[0067] Among these esterifying agents, particularly, at least one selected from the group consisting of acetic anhydride, propionic anhydride, butyric anhydride, vinyl acetate, vinyl propionate, vinyl butyrate, and acetic acid, and among them, acetic anhydride and vinyl acetate are preferable from the viewpoint of reaction efficiency.

[0068] When the cellulose fibers in the dried cellulose fiber body are chemically modified (e.g., by hydrophobization such as acylation), the dispersibility of the dried body in the resin tends to be good. However, the dried cellulose fiber body of the present disclosure can exhibit good dispersibility in the resin even when it is unsubstituted or has a low degree of substitution. When the cellulose fibers in the dried cellulose fiber body are esterified cellulose fibers, the acyl substitution degree (DS) is preferably 0.1 or more, or 0.2 or more, or 0.25 or more, or 0.3 or more, or 0.5 or more in terms of obtaining an esterified cellulose fiber and a resin composite containing the same with a high thermal decomposition start temperature. Since an unmodified cellulose skeleton remains in the esterified cellulose fibers, it is possible to obtain an esterified cellulose fiber and a resin composite containing the same that have both high tensile strength and dimensional stability derived from cellulose and a high thermal decomposition start temperature derived from chemical modification. Preferably, it is 1.2 or less, or 1.0 or less, or 0.8 or less, or 0.7 or less, or 0.6 or less, or 0.5 or less.

[0069] When the modifying group of the chemically modified cellulose fiber is an acyl group, the acyl substitution degree (DS) can be calculated from the reflection 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 absorption band of C=O based on the acyl group appears at 1730 cm -1 and the peak of the absorption band of C-O based on the cellulose backbone chain appears at 1030 cm -1 (see Figure 1). The DS of the esterified cellulose fiber is determined by preparing a correlation graph between the DS obtained from the solid NMR measurement of the esterified cellulose fiber described later and the modification rate (IR index 1030) defined by 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 C-O of the cellulose backbone chain, and using the calibration curve Substitution degree DS = 4.13 × IR index (1030) obtained from the correlation graph.

[0070] The method for calculating the DS of esterified cellulose fibers by solid-state NMR is as follows for freeze-ground esterified cellulose fibers. 13 Perform 13C solid-state NMR measurement on the esterified cellulose fibers, and it can be obtained by the following formula from the area intensity (Inf) of the signal attributed to one carbon atom derived from the modifying group with respect to the total area intensity (Inp) of the signals attributed to carbon C1-C6 derived from the pyranose ring of cellulose that appears in the range of 50 ppm to 110 ppm. DS = (Inf) × 6 / (Inp) For example, when the modifying group is an acetyl group, the signal at 23 ppm attributed to -CH 3 can be used. Used 13 The conditions for 13C solid-state NMR measurement are as follows, for example. Apparatus: Bruker Biospin Avance500WB Frequency: 125.77 MHz Measurement method: DD / MAS method Waiting time: 75 sec NMR sample tube: 4 mm φ Number of integrations: 640 times (about 14 Hr) MAS: 14,500 Hz Chemical shift reference: Glycine (external reference: 176.03 ppm)

[0071] The DS non-uniformity ratio (DSs / DSt), which is defined by the ratio of the degree of modification (DSs) of the fiber surface to the degree of modification (DSt) of the entire chemically modified cellulose fiber (which is synonymous with the above-mentioned degree of acyl substitution (DS)), is preferably 1.05 or more. The larger the value of the DS non-uniformity ratio, the more prominent the sheath-core structure-like non-uniform structure (that is, the structure in which the fiber surface layer is highly chemically modified while the fiber core part retains the structure of cellulose that is close to the original unmodified state). While having high tensile strength and dimensional stability derived from cellulose, it is possible to improve the affinity with the resin during the composite formation with the resin and improve the dimensional stability of the resin composite. The DS non-uniformity ratio is more preferably 1.1 or more, or 1.2 or more, or 1.3 or more, or 1.5 or more, or 2.0, and from the viewpoint of the ease of production of the chemically modified cellulose fiber, it is preferably 30 or less, or 20 or less, or 10 or less, or 6 or less, or 4 or less, or 3 or less. The value of DSs varies depending on the degree of modification of the esterified cellulose fiber. As an example, it is preferably 0.1 or more, more preferably 0.2 or more, still more preferably 0.3 or more, still more preferably 0.5 or more, and preferably 3.0 or less, more preferably 2.5 or less, particularly preferably 2.0 or less, still more preferably 1.5 or less, particularly preferably 1.2 or less, and most preferably 1.0 or less. The preferred range of DSt is as described above for the acyl substituent (DS).

[0072] The coefficient of variation (CV) of the DS non-uniformity ratio of the chemically modified cellulose fiber is preferably as small as possible because the variation in various physical properties of the resin composite becomes smaller. The coefficient of variation is preferably 50% or less, or 40% or less, or 30% or less, or 20% or less. The coefficient of variation can be further reduced, for example, in a method of obtaining a chemically modified cellulose fiber by performing chemical modification after defibrating the cellulose fiber raw material (i.e., the sequential method), while it can be increased in a method of simultaneously performing defibrating and chemical modification of the cellulose fiber raw material (i.e., the simultaneous method). Although the mechanism of this action is not clear, in the simultaneous method, chemical modification tends to proceed more easily in the thin fibers generated at the initial stage of defibrating, and as the hydrogen bonds between cellulose microfibrils decrease due to chemical modification and defibrating further proceeds, it is considered that the coefficient of variation of the DS non-uniformity ratio increases.

[0073] The coefficient of variation (CV) of the DS non-uniformity ratio is calculated by the following formula from the standard deviation (σ) and arithmetic mean (μ) of the DS non-uniformity ratio among 10 obtained samples after collecting 100 g of an aqueous dispersion of chemically modified cellulose fiber (solid content of 10 mass% or more), using 10 g portions of the cryo-ground material as measurement samples and calculating the DS non-uniformity ratio from the DSt and DSs of 10 samples. DS non-uniformity ratio = DSs / DSt Coefficient of variation (%) = standard deviation σ / arithmetic mean μ × 100

[0074] The method for calculating DSs is as follows. That is, the esterified cellulose fiber pulverized by cryo-grinding is placed on a dish-shaped sample stage with a diameter of 2.5 mm, the surface is pressed down to make it flat, and measurement is performed by X-ray photoelectron spectroscopy (XPS). The XPS spectrum reflects only the constituent elements and chemical bonding states of the surface layer of the sample (typically about several nm). Peak separation is performed on the obtained C1s spectrum, and it can be obtained by the following formula from the area intensity (Ixf) of the peak attributed to one carbon atom derived from the modifying group with respect to the area intensity (Ixp) of the peak attributed to the carbon C2-C6 derived from the pyranose ring of cellulose (289 eV, C-C bond). DSs = (Ixf) × 5 / (Ixp) For example, when the modifying group is an acetyl group, after peak separation of the C1s spectrum at 285 eV, 286 eV, 288 eV, and 289 eV, the peak at 289 eV can be used for Ixp, and the peak (286 eV) derived from the O-C=O bond of the acetyl group can be used for Ixf. The conditions for the XPS measurement to be used are as follows, for example. Equipment used: ULVAC-PHI VersaProbeII Excitation source: mono.AlKα 15 kV × 3.33 mA Analysis size: approximately 200 μmφ Photoelectron extraction angle: 45° Capture region Narrow scan: C 1s, O 1s Pass Energy: 23.5 eV

[0075] [Additional components] The dried cellulose fiber may further contain additional components such as a dispersant, a binder, an antioxidant, a preservative, a thickener, etc. in addition to the cellulose fiber.

[0076] (Dispersant) The dispersant contributes to improving the dispersibility of the cellulose fiber in the resin. The dispersant may be a single substance or a mixture of two or more substances. In the latter case, the characteristic values (e.g., melting point, molecular weight, HLB value, SP value) of the present disclosure mean the values of the mixture.

[0077] The melting point of the dispersant may be 80°C or lower, or 70°C or lower, and may be -100°C or higher, or -50°C or higher, in that the dispersant can coat the periphery of the cellulose fiber more uniformly and the cellulose fiber can be dispersed more uniformly in the resin. The number average molecular weight of the dispersant may be 1000 or higher, or 2000 or higher, and may be 50000 or lower, or 20000 or lower, in that the dispersant can coat the periphery of the cellulose fiber more uniformly and the cellulose fiber can be dispersed more uniformly in the resin. The number average molecular weight of the dispersant is a value determined by gel permeation chromatography in terms of standard polystyrene conversion.

[0078] The dispersant is preferably a water-soluble polymer from the viewpoint of suppressing the aggregation of cellulose fibers. In the present disclosure, "water-soluble" means dissolving 0.1 g or more in 100 g of water at 23°C. Furthermore, it is more preferable that the dispersant has a hydrophilic segment and a hydrophobic segment (i.e., is an amphiphilic molecule) from the viewpoint of more uniformly dispersing cellulose fibers in the resin. Examples of amphiphilic molecules include those having a carbon atom as a basic skeleton and having a functional group composed of elements selected from carbon, hydrogen, oxygen, nitrogen, chlorine, sulfur, and phosphorus. As long as the above structure is present in the molecule, those in which an inorganic compound and the above functional group are chemically bonded are also preferable. The hydrophilic segment has good affinity with the surface of cellulose fibers, and the hydrophobic segment suppresses the aggregation of cellulose fibers via the hydrophilic segment and is more compatible with the resin. Therefore, it is preferable that the hydrophilic segment and the hydrophobic segment exist in the same molecule in the dispersant.

[0079] The HLB value of the dispersant is preferably 0.1 or more and less than 8.0. The HLB value is a value indicating the balance between the hydrophobicity and hydrophilicity of a surfactant, takes values from 1 to 20, and indicates that the smaller the numerical value, the stronger the hydrophobicity, and the larger the numerical value, the stronger the hydrophilicity. In the present disclosure, the HLB value is a value obtained from the following formula by the Griffin method. In the following formula, "the sum of the formula weights of hydrophilic groups / molecular weight" is the mass percentage of hydrophilic groups. Formula 1) Griffin method: HLB value = 20 × (the sum of the formula weights of hydrophilic groups / molecular weight)

[0080] The lower limit value of the HLB value of the dispersant is preferably 0.1, more preferably 0.2, and most preferably 1 from the viewpoint of easy solubility in water. Also, the upper limit value of the HLB value is preferably less than 8, more preferably 7.5, and most preferably 7 from the viewpoint of the uniform dispersibility of cellulose fibers in the resin.

[0081] In a typical embodiment, the hydrophilic segment is a portion that exhibits good affinity with cellulose fibers by including a hydrophilic structure (e.g., one or more hydrophilic groups selected from hydroxyl groups, carboxy groups, carbonyl groups, amino groups, ammonium groups, amide groups, sulfo groups, etc.). Examples of the hydrophilic segment include segments of polyethylene glycol (i.e., segments of a plurality of oxyethylene units) (PEG blocks), segments containing repeating units with a quaternary ammonium salt structure, segments of polyvinyl alcohol, segments of polyvinyl pyrrolidone, segments of polyacrylic acid, segments of carboxyvinyl polymer, segments of cationized guar gum, segments of hydroxyethyl cellulose, segments of methyl cellulose, segments of carboxymethyl cellulose, soft segments of polyurethane (specifically, diol segments), and the like. In a preferred embodiment, the hydrophilic segment includes oxyethylene units.

[0082] Examples of the hydrophobic segment include segments having an alkylene oxide unit with 3 or more carbon atoms (e.g., PPG blocks), and segments including the following polymer structures: Acrylic polymers, styrene resins, vinyl chloride resins, vinylidene chloride resins, polyolefin resins, polyhexamethylene adipamide (6,6 nylon), polyhexamethylene azelamide (6,9 nylon), polyhexamethylene sebacamide (6,10 nylon), polyhexamethylene dodecanoamide (6,12 nylon), polybis(4 - aminocyclohexyl)methane dodecane, etc., polycondensates of organic dicarboxylic acids having 4 to 12 carbon atoms and organic diamines having 2 to 13 carbon atoms, polycondensates of ω - amino acids (e.g., ω - aminoundecanoic acid) (e.g., polyundecanamide (11 nylon), etc.), polycapramide (6 nylon) which is a ring - opening polymer of ε - aminocaprolactam, poly(lauric lactam) (12 nylon) which is a ring - opening polymer of ε - aminolauryl lactam, etc., amino acid lactams containing ring - opening polymers of lactams, polymers composed of diamines and dicarboxylic acids, polyacetal resins, polycarbonate resins, polyester resins, polyphenylene sulfide resins, polysulfone resins, polyether ketone resins, polyimide resins, fluorine - based resins, hydrophobic silicone resins, melamine resins, epoxy resins, phenolic resins.

[0083] In a preferred embodiment, the dispersant has a PEG block as a hydrophilic group and a PPG block as a hydrophobic group in the molecule.

[0084] The dispersant can have a graft copolymer structure and / or a block copolymer structure. These structures may be used alone or in combination of two or more. In the case of two or more, they may be polymer alloys. Also, partial modified products or terminal modified products (acid - modified) of these copolymers may be used.

[0085] The structure of the dispersant is not particularly limited. When the hydrophilic segment is A and the hydrophobic segment is B, examples include AB-type block copolymers, ABA-type block copolymers, BAB-type block copolymers, ABAB-type block copolymers, ABABA-type block copolymers, BABAB-type copolymers, three-branched copolymers containing A and B, four-branched copolymers containing A and B, star-shaped copolymers containing A and B, monocyclic copolymers containing A and B, polycyclic copolymers containing A and B, cage-shaped copolymers containing A and B, and the like.

[0086] The structure of the dispersant is preferably an AB-type block copolymer, an ABA-type triblock copolymer, a three-branched copolymer containing A and B, or a four-branched copolymer containing A and B, more preferably an ABA-type triblock copolymer, a three-branched structure (i.e., a three-branched copolymer containing A and B), or a four-branched structure (i.e., a four-branched copolymer containing A and B). In order to ensure good affinity with the cellulose fiber, it is desirable that the structure of the dispersant is the above structure.

[0087] Preferred examples of the dispersant include copolymers obtained by using at least one compound that provides a hydrophilic segment (e.g., polyethylene glycol) and at least one compound that provides a hydrophobic segment (e.g., polypropylene glycol, poly(tetramethylene ether) glycol (PTMEG), polybutadiene diol, etc.) (e.g., block copolymers of propylene oxide and ethylene oxide, block copolymers of tetrahydrofuran and ethylene oxide), and the like. The dispersant may be used alone or in combination of two or more. When two or more are used in combination, they may be used as a polymer alloy. In addition, modified products of the above copolymers (e.g., those modified with at least one compound selected from unsaturated carboxylic acids, their acid anhydrides, or their derivatives) can also be used.

[0088] Among these, from the viewpoints of heat resistance (odor property) and mechanical properties, copolymers of polyethylene glycol and polypropylene glycol, copolymers of polyethylene glycol and poly(tetramethylene ether) glycol (PTMEG), and mixtures thereof are preferably mentioned, and copolymers of polyethylene glycol and polypropylene glycol are more preferable from the viewpoints of handleability and cost.

[0089] In a typical embodiment, the dispersant has a cloud point. When the temperature of an aqueous solution of a nonionic surfactant having a polyether chain such as a polyoxyethylene chain as a hydrophilic moiety is raised, the phenomenon that the aqueous solution, which was transparent or translucent, becomes turbid at a certain temperature (this temperature is called the cloud point) is observed. That is, when an aqueous solution that is transparent or translucent at a low temperature is heated, at a certain temperature, the solubility of the nonionic surfactant rapidly decreases, and the surfactants that were dissolved until then aggregate and become turbid and separate from water. This is considered to be because the nonionic surfactant loses its hydration force at high temperatures (the hydrogen bond between the polyether chain and water is broken and the solubility in water rapidly decreases). The cloud point tends to be lower as the polyether chain is longer. Since it dissolves in water at an arbitrary ratio at temperatures below the cloud point, the cloud point serves as a measure of hydrophilicity in the dispersant.

[0090] The cloud point of the dispersant can be measured by the following method. Using a tuning fork type vibrating viscometer (for example, SV-10A manufactured by A&D Company, Limited), adjust the aqueous solution of the dispersant to 0.5 mass%, 1.0 mass%, and 5 mass%, and perform measurements in the temperature range of 0 to 100°C. At this time, the portion showing an inflection point (the point where the viscosity increases or the aqueous solution becomes cloudy) at each concentration is defined as the cloud point.

[0091] The lower limit value of the cloud point of the dispersant is preferably 10°C, more preferably 20°C, and most preferably 30°C from the viewpoint of handleability. The upper limit value of the cloud point is not particularly limited, but is preferably 120°C, more preferably 110°C, further preferably 100°C, and most preferably 60°C. In order to ensure good affinity with cellulose fibers, it is desirable that the cloud point of the dispersant be within the above range.

[0092] As the dispersant, those having a solubility parameter (SP value) of 7.25 or more are more preferable. By the dispersant having an SP value in this range, the dispersibility of cellulose fibers in the resin is improved.

[0093] According to the literature of Foders (R.F. Foders: Polymer Engineering & SCienCe, vol.12(10), p.2359 - 2370(1974)), the SP value depends on both the cohesive energy density and the molar molecular weight of the substance, and these are considered to depend on the type and number of substituents of the substance. According to the literature of Ueda et al. (Research on Paints, No.152, OCt.2010), the SP values (Cal / Cm 3 ) 1 / 2 have been published.

[0094] Experimentally, the SP value of the dispersant can be determined from the boundary between soluble and insoluble when the dispersant is dissolved in various solvents with known SP values. For example, when 1 mL of the dispersant is dissolved in various solvents (10 mL) with different SP values under stirring with a stirrer at room temperature for 1 hour, it can be judged whether the whole amount is dissolved. For example, if the dispersant is soluble in diethyl ether, the SP value of the dispersant is 7.25 or more.

[0095] As the dispersant (especially amphiphilic molecules), those having a boiling point higher than that of water are preferable, and those having a boiling point higher than the melting point of the resin are more preferable from the viewpoint of uniformly dispersing cellulose fibers in the resin during melt-kneading. Note that the boiling point higher than that of water refers to a boiling point higher than the boiling point at each pressure in the vapor pressure curve of water (for example, 100 °C at 1 atm).

[0096] By selecting a dispersant having a boiling point higher than that of water, for example, in the step of drying a slurry containing water as a liquid medium in the presence of a dispersant to obtain a dried cellulose fiber body, water and the dispersant are replaced during the evaporation of water so that the dispersant is present on the surface of the cellulose fiber, and thus the aggregation of the cellulose fiber can be significantly suppressed.

[0097] Note that the method of adding the dispersant is not limited. In the production of a dried cellulose fiber body, a method of mixing a dispersant with the cellulose fiber after the drying step to obtain a dried cellulose fiber body. In the production of a dried cellulose fiber body, a method of adding a dispersant to a slurry in which cellulose fibers are dispersed in a liquid medium and then drying to obtain a dried cellulose fiber body. In the production of a resin composite, a method of pre-mixing and melt-kneading a resin, a dried cellulose fiber body or a redispersion liquid obtained by dispersing the same in a liquid medium, and a dispersant, and then performing a molding process. In the production of a resin composite, a method of adding a dispersant to a resin in advance, optionally pre-kneading, and then adding a dried cellulose fiber body or a redispersion liquid obtained by dispersing the same in a liquid medium, melt-kneading, and performing a molding process. And the like can be mentioned.

[0098] The amount of the dispersant is preferably 5 to 100 parts by mass, more preferably 10 to 70 parts by mass, and most preferably 20 to 50 parts by mass with respect to 100 parts by mass of the cellulose fiber from the viewpoint of uniformly dispersing the cellulose fiber in the resin composite.

[0099] In one aspect, the content of the dispersant in the resin composite is preferably 0.3% by mass or more, or 0.5% by mass or more, or 1.0% by mass or more, and preferably 10.0% by mass or less, or 5.0% by mass or less, or 3.0% by mass or less.

[0100] In the resin composite, the amount of the dispersant can be easily confirmed by a method common to those skilled in the art. The confirmation method is not limited, but the following methods can be exemplified. Using a fragment of the resin composite, when the fragment is dissolved in a solvent that dissolves the resin, the soluble component 1 (resin and dispersant) and the insoluble component 1 (cellulose fiber and dispersant) are separated. The soluble component 1 is reprecipitated with a solvent that does not dissolve the resin but dissolves the dispersant to separate into an insoluble component 2 (resin) and a soluble component 2 (dispersant). Further, the insoluble component 1 is dissolved in a dispersant-soluble solvent to separate into a soluble component 3 (dispersant) and an insoluble component 3 (cellulose fiber). The dispersant can be quantified by concentrating (drying, air-drying, drying under reduced pressure, etc.) the soluble component 2 and the soluble component 3. For the concentrated dispersant, identification and molecular weight measurement can be performed by the method described above.

[0101] ≪Method for producing dried cellulose fiber≫ One aspect of the present invention also provides a method for producing the dried cellulose fiber of the present disclosure. The method includes a slurry preparation step of preparing a slurry containing cellulose fiber and an aqueous medium, and a drying step of drying the slurry to form a dried cellulose fiber.

[0102] (Slurry preparation step) In this step, a slurry containing cellulose fiber and a liquid medium is prepared. As the liquid medium, the above-mentioned water-miscible organic solvent can be preferably used. From the viewpoint of process efficiency in the subsequent drying step, the concentration of cellulose fiber in the slurry 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, and from the viewpoint of avoiding excessive increase in the viscosity of the slurry and solidification due to aggregation and maintaining good handleability, 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. For example, the production of cellulose nanofibers is often carried out in a dilute dispersion, but the concentration of cellulose fiber in the slurry may be adjusted to the preferred range by concentrating such a dilute dispersion. For concentration, methods such as suction filtration, pressure filtration, centrifugal dewatering, and heating can be used.

[0103] (Drying step) In this process, the cellulose fiber dried product is formed by drying the above slurry under controlled drying conditions. When the cellulose fiber dried product contains cellulose fibers and additional components, the additional components may be added before, during, and / or after the drying of the cellulose fiber slurry. For drying, drying apparatuses that enable the above drying rate can be used, such as spray dryers, extruders, etc. The drying apparatus may be a commercially available product, and examples thereof include a micro mist spray dryer (manufactured by Fujisaki Electric Co., Ltd.), a spray dryer (manufactured by Okawara Chemical Machinery Co., Ltd.), a twin-screw extruder (manufactured by Japan Steel Works, Ltd.), etc. Among the drying conditions, controlling the drying rate, drying temperature, and / or pressure (degree of vacuum), particularly the drying rate, is useful for the production of the cellulose fiber dried product of the present disclosure.

[0104] The drying rate, which is the amount of desorbed liquid medium per minute (parts by mass) per 100 parts by mass of the slurry, is, from the viewpoint of forming a cellulose fiber dried product with a desired particle size by rapidly drying the slurry, for example, 10% / min or more, or 50% / min or more, or 100% / min or more, and from the viewpoint of suppressing the aggregation of the cellulose fibers and obtaining good handleability by avoiding excessive pulverization of the cellulose fibers, for example, 10000% / min or less, or 1000% / min or less, or 500% / min or less. The drying rate is a value obtained according to the following formula: Drying rate (% / min) = (slurry moisture content at the start of drying (mass %) - moisture content of the dried product at the end of drying (mass %)) / time required from the start to the end of drying (min) That is, it is an average value throughout the drying process. Here, the start of drying is the time when the process of supplying the slurry or cake to be dried to the apparatus and drying it at the target drying temperature, degree of vacuum, and shear rate is started. The time for preliminary mixing in a state where the drying temperature, degree of vacuum, and shear rate are different from those in the drying process is not included in the drying time. Also, the end of drying refers to the time when sampling is performed at intervals of at most 10 minutes from the start of drying and the moisture content first becomes 7 mass% or less. In the case of a continuous drying device, the time required from the start of drying to the end of drying can be interpreted as the residence time. In the case of a spray dryer, the residence time can be calculated based on the amount of heated air and the volume of the drying chamber. Also, when an extruder is used as the drying device, the residence time can be calculated from the screw rotation speed and the total number of screw pitches.

[0105] The drying temperature may be, for example, 20°C or higher, or 30°C or higher, or 40°C or higher, or 50°C or higher, from the viewpoints of drying efficiency and appropriately aggregating cellulose fibers to form a cellulose fiber dried product with a desirable particle size, and may be, for example, 200°C or lower, or 150°C or lower, or 140°C or lower, or 130°C or lower, or 100°C or lower, from the viewpoints of making it difficult for heat deterioration of cellulose fibers and additional components to occur and avoiding excessive pulverization of cellulose fibers. The drying temperature is the temperature of the heat source in contact with the slurry, and is defined, for example, as the surface temperature of the temperature control jacket of the drying device, the surface temperature of the heating cylinder, or the temperature of the hot air.

[0106] The degree of vacuum may be, for example, -1 kPa or lower, or -10 kPa or lower, or -20 kPa or lower, or -30 kPa or lower, or -40 kPa or lower, or -50 kPa or lower, from the viewpoints of drying efficiency and appropriately aggregating cellulose fibers to form a cellulose fiber dried product with a desirable particle size, and may be, for example, -100 kPa or higher, or -95 kPa or higher, or -90 kPa or higher, from the viewpoint of avoiding excessive pulverization of cellulose fibers.

[0107] In the drying process, the residence time of the slurry at a temperature of 20°C to 200°C may preferably be set to 0.01 minute to 10 minutes, or 0.05 minute to 5 minutes, or 0.1 minute to 2 minutes. By drying under such conditions, the cellulose fibers are rapidly dried, and a cellulose fiber dried product with a desirable particle size is favorably produced.

[0108] For example, when using a spray dryer, a slurry is spray-introduced into a drying chamber through which hot gas flows (using a spraying mechanism such as a rotating disk, a pressure nozzle, etc.) and dried. The size of the slurry droplets at the time of spray introduction may be, for example, 0.01 μm to 500 μm, or 0.1 μm to 100 μm, or 0.5 μm to 10 μm. The hot gas may be an inert gas such as nitrogen or argon, air, etc. The temperature of the hot gas may be, for example, 50°C to 300°C, or 80°C to 250°C, or 100°C to 200°C. The contact between the slurry droplets and the hot gas in the drying chamber may be co-current, counter-current, or cross-current. The particulate cellulose fiber dried product generated by drying the droplets is collected using a cyclone, a drum, etc.

[0109] Also, for example, when using an extruder, the slurry is charged from a hopper into a kneading section equipped with a screw, and the slurry is continuously transported by the screw in the kneading section under reduced pressure and / or heating to dry the slurry. As the mode of the screw, a conveying screw, a counterclockwise screw, and a kneading disk may be combined in any order. The drying temperature may be, for example, 50°C to 300°C, or 80°C to 250°C, or 100°C to 200°C.

[0110] ≪Method for manufacturing resin composite≫ One aspect of the present invention provides a method for manufacturing a resin composite containing cellulose fibers and a resin. The method includes mixing the cellulose fiber dried product of the present disclosure as described above and the resin.

[0111] <Resin> As the resin, a thermoplastic resin, a thermosetting resin, and a photocurable resin can be used. The resin may be an elastomer. From the viewpoints of moldability and productivity, a thermoplastic resin is more preferable.

[0112] (Thermoplastic resin) When the resin is a thermoplastic resin, the melting point of the thermoplastic resin may be appropriately selected according to the use of the resin composite and the like. As the melting point of the thermoplastic resin, for example, for resins with a relatively low melting point (such as polyolefin resins), it can be 150°C to 190°C, or 160°C to 180°C, and for example, for resins with a relatively high melting point (such as polyamide resins), it can be 220°C to 350°C, or 230°C to 320°C.

[0113] The thermoplastic resin is preferably 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.

[0114] Preferred polyolefin resins as the thermoplastic resin are polymers obtained by polymerizing olefins (such as α-olefins) and / or alkenes as monomer units. Specific examples of polyolefin resins include ethylene-based (co)polymers exemplified by low-density polyethylene (such as linear low-density polyethylene), high-density polyethylene, ultra-low-density polyethylene, ultra-high molecular weight polyethylene, etc., polypropylene-based (co)polymers exemplified by polypropylene, ethylene-propylene copolymer, ethylene-propylene-diene copolymer, etc., and copolymers of ethylene and α-olefins represented by ethylene-acrylic acid copolymer, ethylene-methyl methacrylate copolymer, ethylene-glycidyl methacrylate copolymer, etc.

[0115] Here, the most preferred polyolefin resin is polypropylene. In particular, polypropylene with a melt mass flow rate (MFR) measured at 230 °C and a load of 21.2 N in accordance with ISO 1133 of 3 g / 10 min or more and 30 g / 10 min or less is preferred. The lower limit value of the MFR is more preferably 5 g / 10 min, even more preferably 6 g / 10 min, and most preferably 8 g / 10 min. Also, the upper limit value 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 above upper limit value, and from the viewpoint of the fluidity of the resin composite, it is desirable that the MFR does not exceed the above lower limit value.

[0116] Also, in order to enhance the affinity with cellulose fibers, an acid-modified polyolefin resin can also be suitably used. As the acid used for acid modification, mono- or polycarboxylic acids can be used, and examples thereof include maleic acid, fumaric acid, succinic acid, phthalic acid and their anhydrides, and citric acid. From the ease of increasing the modification rate, maleic acid or its anhydride is particularly preferred. There are no particular restrictions on the modification method, but a method of heating the polyolefin resin above its melting point and melt-kneading it in the presence or absence of a peroxide is common. As the polyolefin resin to be acid-modified, all of the above-mentioned polyolefin resins can be used, but polypropylene is particularly suitable. The acid-modified polypropylene resin may be used alone, but in order to adjust the modification rate of the entire resin, it is more preferably used by mixing with an unmodified polypropylene resin. The ratio of the acid-modified polypropylene resin to all the polypropylene resins at this time is preferably 0.5% by mass to 50% by mass. A more preferred lower limit is 1% by mass, or 2% by mass, or 3% by mass, or 4% by mass, or 5% by mass. Also, a more preferred upper limit is 45% by mass, or 40% by mass, or 35% by mass, or 30% by mass, or 20% by mass. In order to maintain the interfacial strength between the resin and the cellulose fibers, it is preferably above the lower limit, and in order to maintain the ductility of the resin, it is preferably below the upper limit.

[0117] The melt mass flow rate (MFR) of the acid-modified polypropylene resin, measured at 230 °C and 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 enhancing the affinity at the interface between the resin and the cellulose fiber. The upper limit is not particularly limited, but is preferably 500 g / 10 min for maintaining mechanical strength.

[0118] Preferred polyamide resins as thermoplastic resins include: polyamides obtained by polycondensation reactions of lactams (e.g., polyamide 6, polyamide 11, polyamide 12, etc.); polyamides obtained as copolymers of 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., butanedioic acid, pentanedioic acid, hexanedioic acid, heptanedioic acid, octanedioic acid, nonanedioic acid, decanedioic 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 respectively (e.g., polyamide 6,T / 6,I, etc.).

[0119] Among these polyamide resins, aliphatic polyamides such as polyamide 6, polyamide 11, polyamide 12, polyamide 6,6, polyamide 6,10, polyamide 6,11, polyamide 6,12, etc., and alicyclic polyamides such as polyamide 6,C and polyamide 2M5,C are more preferable.

[0120] 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, or 250 °C or higher. 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.

[0121] There is no particular limitation on the terminal carboxyl group concentration of the polyamide resin, but it is preferably 20 μmol / g or higher, or 30 μmol / g or higher, and preferably 150 μmol / g or lower, or 100 μmol / g or lower, or 80 μmol / g or lower.

[0122] In the polyamide resin, the carboxyl terminal group ratio ([COOH] / [total terminal groups]) to all 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 the dispersibility of the cellulose fiber 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.

[0123] The terminal group concentration of the polyamide resin can be adjusted by a known method. As an adjustment method, at the time of polymerization of the polyamide, a terminal adjusting agent (for example, diamine compound, monoamine compound, dicarboxylic acid compound, monocarboxylic acid compound, acid anhydride, monoisocyanate, monoacid halide, monoester, monoalcohol, etc.) that reacts with the terminal group so as to have a predetermined terminal group concentration is added to the polymerization solution.

[0124] Examples of the end-capping agent that reacts with the terminal amino group 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 a plurality of mixtures arbitrarily selected from these. Among these, from the viewpoints of reactivity, stability of the capped end, price, etc., one or more end-capping agents 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, and acetic acid is most preferred.

[0125] Examples of the end-capping agent that reacts with the terminal carboxyl group 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 mixtures thereof. Among these, from the viewpoints of reactivity, boiling point, stability of the capped end, price, etc., one or more end-capping agents selected from the group consisting of butylamine, hexylamine, octylamine, decylamine, stearylamine, cyclohexylamine, and aniline are preferred.

[0126] The concentrations of the amino terminal group and the carboxyl terminal group of the polyamide resin 1 can be determined from the integral value of the characteristic signal corresponding to each terminal group by 1H-NMR. This method is preferable in terms of accuracy and simplicity. More specifically, it is recommended to use the method described in JP-A-7-228775, use heavy trifluoroacetic acid as the measurement solvent, and set the number of integrations to 300 scans or more.

[0127] The intrinsic viscosity [η] of the polyamide resin measured under the conditions of 30 °C in concentrated sulfuric acid is preferably 0.6 to 2.0 dL / g, or 0.7 to 1.4 dL / g, or 0.7 to 1.2 dL / g, or 0.7 to 1.0 dL / g from the viewpoints of good fluidity in the mold and good appearance of the molded piece when, for example, molding the resin composite by injection molding. In the present disclosure, the "intrinsic viscosity" is synonymous with the viscosity generally called the limiting viscosity. The intrinsic viscosity is determined by measuring ηsp / c of several measurement solvents with different concentrations in 96% concentrated sulfuric acid under the temperature condition of 30 °C, deriving the relational expression between each ηsp / c and the concentration (c), and extrapolating the concentration to zero. This value extrapolated to zero 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). It is desirable from the viewpoint of accuracy that the concentrations in several measurement solvents with different concentrations be at least 4 points (for example, 0.05 g / dL, 0.1 g / dL, 0.2 g / dL, 0.4 g / dL).

[0128] As the polyester resin preferable as the thermoplastic resin, one or more 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 them, PET, PBS, PBSA, PBT, and PEN are more preferable, and PBS, PBSA, and PBT are particularly preferable.

[0129] The end groups of the polyester resin can be arbitrarily changed depending on the monomer ratio during polymerization, the presence or absence and amount of the end stabilizer, and the like. The carboxyl end group ratio ([COOH] / [total end groups]) with respect to all the end groups of the polyester resin 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 the 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.

[0130] Preferred polyacetal resins as the thermoplastic resin include homopolyacetals made from formaldehyde and copolyacetals having trioxane as the main monomer and containing 1,3-dioxolane as the comonomer component. Both can be used, but copolyacetals are preferred from the viewpoint of thermal stability during processing. The amount of the structure derived from the comonomer component (for example, 1,3-dioxolane) is preferably 0.01 mol% or more, or 0.05 mol% or more, or 0.1 mol% or more, or 0.2 mol% or more from the viewpoint of thermal stability during extrusion processing and molding processing, and preferably 4.0 mol% or less, or 3.5 mol% or less, or 3.0 mol% or less, or 2.5 mol% or less, or 2.3 mol% or less from the viewpoint of mechanical strength.

[0131] (Thermosetting resin) Examples of the thermosetting resin 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, aryl alkylene type epoxy resin, tetraphenylol ethane 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 type epoxy resin, copolymer epoxy resin of cyclohexyl maleimide and glycidyl methacrylate, epoxy modified polybutadiene rubber derivative, CTBN modified epoxy resin, trimethylolpropane polyglycidyl ether, phenyl-1,3-diglycidyl ether, biphenyl-4,4'-diglycidyl ether, 1,6-hexanediol diglycidyl ether, diglycidyl ether of ethylene glycol or propylene glycol, sorbitol polyglycidyl ether, tris(2,3-epoxypropyl) isocyanurate, triglycidyl tris(2-hydroxyethyl) isocyanurate, novolac type phenol resins such as phenol novolac resin, cresol novolac resin, and bisphenol A novolac resin; resol type phenol resins such as unmodified resol phenol resin and oil-modified resol phenol resin modified with tung oil, linseed oil, walnut oil, etc.; phenol resins such as resol type phenol resin; phenoxy resin, triazine ring-containing resins such as urea (urea) resin and melamine resin, unsaturated polyester resin, bismaleimide resin, diallyl phthalate resin, silicone resin, resin having a benzoxazine ring, norbornene resin, cyanate resin, isocyanate resin, urethane resin, benzocyclobutene resin, maleimide resin, bismaleimide triazine resin, polyazomethine resin, thermosetting polyimide, etc.

[0132] (Photo-curable resin) Examples of photo-curable resins include (meth)acrylate resins, vinyl resins, epoxy resins, etc. These can be generally classified, according to the reaction mechanism, into a radical reaction type in which monomers react with radicals generated by light and a cation reaction type in which monomers undergo cationic polymerization. Examples of monomers of the radical reaction type include (meth)acrylate compounds and vinyl compounds (e.g., certain vinyl ethers). Examples of the cation reaction type include epoxy compounds and certain vinyl ethers. Note that, for example, an epoxy compound that can be used as the cation reaction type can be a monomer for both thermosetting resins and photo-curable resins.

[0133] (Meth)acrylate compounds are compounds having one or more (meth)acrylate groups in the molecule. Examples of (meth)acrylate compounds include monofunctional (meth)acrylates, polyfunctional (meth)acrylates, epoxy acrylates, polyester acrylates, urethane acrylates, etc.

[0134] 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, ethylene glycol divinyl ether, etc. Examples of styrene derivatives include methyl styrene, ethyl styrene, etc. Examples of other vinyl compounds include triallyl isocyanurate, trimethallyl isocyanurate, etc.

[0135] As a raw material for the photocurable resin, a so-called reactive oligomer may be used. Examples of the reactive oligomer include an oligomer having any combination selected from (meth)acrylate groups, epoxy groups, urethane bonds, and ester bonds in the same molecule, for example, urethane acrylate having both a (meth)acrylate group and a urethane bond in the same molecule, polyester acrylate having both a (meth)acrylate group and an ester bond in the same molecule, epoxy acrylate derived from an epoxy resin and having both an epoxy group and a (meth)acrylate group in the same molecule, and the like.

[0136] (Elastomer) Examples of the elastomer (i.e., rubber) 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, protein-free natural rubber, etc.), ethylene-propylene copolymer rubber, acrylic rubber, epichlorohydrin rubber, polysulfide rubber, silicone rubber, fluororubber, urethane rubber, and the like.

[0137] 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 the dried product of the present disclosure or a redispersion liquid obtained by dispersing this in a dispersion medium) with the thermoplastic resin. As a more specific production method of the resin composite, - A method in which a resin monomer and cellulose fibers are mixed, a polymerization reaction is carried out, the obtained resin composite is extruded into a strand shape, and cooled and solidified in a water bath to obtain a pellet-shaped molded body. - A method in which a mixture of a resin and cellulose fibers is melt-kneaded using a single-screw or twin-screw extruder, extruded into a strand shape, and cooled and solidified in a water bath to obtain a pellet-shaped molded body. - A method of melt-kneading a mixture of a resin and cellulose fibers using a single-screw or twin-screw extruder, and extruding and cooling it into a rod shape or a cylindrical shape to obtain an extruded molded body. - A method of melt-kneading a mixture of a resin and cellulose fibers using a single-screw or twin-screw extruder, and extruding it from a T-die to obtain a sheet or a film-shaped molded body. Examples include the above. In a preferred embodiment, a mixture of a 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. As a specific example of the method for melt-kneading a resin and cellulose fibers, a method of mixing a resin and cellulose fibers conveyed at a desired ratio and then melt-kneading them can be mentioned.

[0138] For melt-kneading, extruders such as single-screw extruders and twin-screw extruders can be used, but a twin-screw extruder is preferred for controlling the dispersibility of cellulose fibers. The L / D obtained by dividing the cylinder length (L) of the extruder by the screw diameter (D) is preferably 30 or more, particularly preferably 40 or more. Also, the screw rotation speed during kneading is preferably in the range of 50 to 800 rpm, more preferably in the range of 100 to 600 rpm.

[0139] Each screw in the cylinder of the extruder is optimized by combining a conveying screw having an elliptical two-wing screw shape, a kneading element called a kneading disk, etc.

[0140] When the resin is a thermoplastic resin, the minimum processing temperature recommended by the thermoplastic resin supplier is 255 to 270 °C for nylon 66, 225 to 240 °C for nylon 6, 170 to 190 °C for polyacetal resin, and 160 to 180 °C for polypropylene. The heating set temperature is preferably in the range of 20 °C higher than these recommended minimum processing temperatures. By setting the mixing temperature within this temperature range, the cellulose fibers and the resin can be uniformly mixed.

[0141] A resin composite containing a thermoplastic resin as a resin can be provided in various shapes. Specifically, examples include resin pellet form, sheet form, fiber form, plate form, rod form, etc. Among them, the resin pellet shape is more preferable in terms of ease of post-processing and ease of transportation. Preferred pellet shapes at this time include round, oval, cylindrical, etc., and these differ depending on the cutting method during extrusion processing. Pellets cut by a cutting method called underwater cut often become round, pellets cut by a cutting method called hot cut often become round or oval, and pellets cut by a cutting method called strand cut often become cylindrical. In the case of round pellets, the preferred size is 1 mm or more and 3 mm or less as the pellet diameter. Also, in the case of 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 perspective of operation stability during extrusion, it is desirable that the above diameter and length be equal to or greater than the lower limit, and from the perspective of bite-in property into the molding machine in post-processing, it is desirable that they be equal to or less than the upper limit.

[0142] A resin composite containing a thermoplastic resin as a resin can be used as various resin molded articles. There are no particular restrictions on the manufacturing method of the resin molded article, and any manufacturing method may be used, but injection molding methods, extrusion molding methods, blow molding methods, inflation molding methods, foam molding methods, etc. can be used. Among these, the injection molding method is the most preferable from the viewpoints of designability and cost.

[0143] When the resin is a thermosetting resin or a photocurable resin, for example, a method of sufficiently dispersing cellulose fibers in a resin solution or a resin powder dispersion and drying, a method of sufficiently dispersing cellulose fibers in a resin monomer solution and polymerizing by heat, UV irradiation, a polymerization initiator, etc., a method of sufficiently impregnating a cellulose fiber dried body with a resin solution or a resin powder dispersion and drying, a method of sufficiently impregnating a cellulose fiber dried body with a resin monomer solution and polymerizing by heat, UV irradiation, a polymerization initiator, etc., can be used to produce a resin composite. During curing, various polymerization initiators, curing agents, curing accelerators, polymerization inhibitors, etc. can be blended.

[0144] When the resin is a thermosetting resin or a photocurable resin, after producing a sheet called an uncured or semi-cured prepreg, a method of making the prepreg into a single layer or a laminate and curing and molding the resin by pressurization and heating may be used. Examples of the methods of pressurization and heating include a press molding method, an autoclave molding method, a bagging molding method, a wrapping tape method, an internal pressure molding method, and the like.

[0145] When the resin is a photocurable resin, a resin composite can be manufactured using various curing methods using active energy rays.

[0146] When the resin is an elastomer, a resin composite can be manufactured by a method of dry-kneading a dry cellulose fiber and a raw rubber, a method of dispersing or dissolving a cellulose fiber and a raw rubber in a dispersion medium and then drying and mixing them, and the like. As the mixing method, a mixing method using a homogenizer is preferable in terms of applying a high shearing force and pressure to promote dispersion, but other methods such as a propeller type stirring device, a rotary stirring device, an electromagnetic stirring device, and manual stirring can also be used. A resin composite containing an elastomer is molded using a desired molding method such as die molding, injection molding, extrusion molding, blow molding, and foam molding to obtain an uncured molded body having a desired shape such as a sheet, a pellet, or a powder. The uncured molded body can be vulcanized by heat treatment or the like as necessary to obtain a resin composite.

[0147] A resin composite containing a thermoplastic resin or an elastomer may be used by heating and melting a part thereof (for example, several places) and adhering it to a substrate such as a resin or a metal. Further, the resin composite may be a coating film applied to a substrate such as a resin or a metal, or may form a laminate with the substrate. Further, secondary processing such as annealing treatment, etching treatment, corona treatment, plasma treatment, embossing transfer, cutting, and surface polishing may be performed on the sheet-like, film-like, or fiber-like resin composite.

[0148] In the resin composite, the amount of cellulose fiber relative to 100 parts by mass of the resin may preferably be 0.001 part by mass or more, or 0.01 part by mass or more, or 0.1 part by mass or more, or 1 part by mass or more, and may preferably be 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 the balance between processability and mechanical properties.

[0149] In one aspect, the tensile elongation at break of the resin composite can be 5% or more, or 8% or more, or 10% or more. From the viewpoint of the ease of manufacturing the resin composite, in one aspect, the tensile elongation at break may be 200% or less, or 100% or less, or 50% or less.

Examples

[0150] The present invention will be further described based on examples, but the present invention is not limited to these examples.

[0151] ≪Production of Cellulose Fiber Slurry≫ [CNF-A] Commercially available Celish KY100G (manufactured by Daicel Finechem) was used as a CNF-A cake.

[0152] [CNF-B] (Acetylated CNF) 1 part by mass of cotton linter pulp was stirred at 500 rpm for 1 hour at room temperature in 30 parts by mass of dimethyl sulfoxide (DMSO) using a uniaxial stirrer (DKV-1 φ125 mm dissolver manufactured by Imex). Subsequently, it was fed to a bead mill (NVM-1.5 manufactured by Imex) by a hose pump and circulated for 180 minutes only with DMSO to obtain slurry S1 (DMSO solvent) having a solid content fraction of 3.2% by mass as a fine cellulose fiber slurry.

[0153] During the circulation operation, the rotation speed of the bead mill was set at 2500 rpm and the peripheral speed at 12 m / s. The beads used were made of zirconia, with a diameter of φ2.0 mm and a filling rate of 70% (the slit gap of the bead mill was set at 0.6 mm). Also, during the circulation operation, in order to absorb heat generated by friction, the slurry temperature was temperature-controlled at 40 °C by a chiller.

[0154] After charging slurry S1 into an explosion-proof disperser tank, 3.2 parts by mass of vinyl acetate and 0.49 part by mass of sodium hydrogen carbonate were added. The temperature inside the tank was set at 50 °C, and stirring was carried out for 120 minutes to obtain a slurry (DMSO solvent) with a solid content rate of 2.9% by mass.

[0155] To stop the reaction, 30 parts by mass of pure water was added and stirred well, then it was put into a dehydrator and concentrated. The obtained wet cake was dispersed, stirred, and concentrated again in 30 parts by mass of pure water, and this washing operation was repeated a total of 5 times to remove unreacted reagents and solvents, etc., and 10 parts by mass of acetylated fine cellulose fiber cake (CNF-B cake) (aqueous solvent) with a solid content rate of 10% by mass was obtained. When a porous sheet was prepared from this cake to determine the acyl substitution degree (DS), DS = 1.0.

[0156] [CNF-C] (CNF treated with a disk refiner) 3 parts by mass of cotton linter pulp was immersed in 27 parts by mass of water and heat-treated in an autoclave at 130 °C for 4 hours. The obtained swollen pulp was washed with water to obtain purified pulp containing water (30 parts by mass). Subsequently, 170 parts by mass of water was added to 30 parts by mass of purified pulp containing water and dispersed in water (solid content rate 1.5% by mass). Using an SDR14 type laboratory refiner (pressure type DISK type) manufactured by Aikawa Iron Works Co., Ltd. as a disk refiner device, the clearance between the disks was set at 1 mm, and the aqueous dispersion was beaten for 20 minutes. Then, it was concentrated by a dehydrator to a solid content rate of 10% to obtain a CNF-C cake (aqueous solvent).

[0157] [CNF-D] (CNF-C further defibrated with a high-pressure homogenizer) The CNF-C cake was thoroughly disintegrated under conditions where the clearance was reduced to a level close to almost zero, and a disintegrated aqueous dispersion (solid content concentration: 1.5% by mass) was obtained. The obtained disintegrated aqueous dispersion was directly subjected to 15 times of micronization treatment at an operating pressure of 100 MPa using a high-pressure homogenizer (NSO15H manufactured by Niro Soavi, Italy) to obtain a cellulose fiber slurry (solid content concentration: 1.5% by mass). Then, it was concentrated to a solid content ratio of 10% by mass using a dehydrator to obtain a CNF-D cake (aqueous solvent).

[0158] [CNF-E] (Acetylated CNF) It was produced in the same manner as CNF-B except that the reaction time was set to 60 minutes. When a porous sheet was prepared from this cake and the degree of acyl substitution (DS) was determined, DS = 0.5.

[0159] <Resin> Polyamide 6 (manufactured by Ube Industries: 1013B)

[0160] <Dispersant> Polyethylene oxide - polypropylene oxide copolymer (PEG-PPG) (manufactured by Sanyo Chemical Industries: GL-3000)

[0161] ≪Manufacture of Cellulose Fiber Dry Body≫ To the cellulose fiber cake (10% by mass of solid content), a dispersant was added in an amount of 43 parts by mass with respect to 100 parts by mass of the cellulose solid content, and it was stirred well to obtain a cellulose fiber cake containing the dispersant (for those other than MMSD described later). Alternatively, the cellulose fiber cake (10% by mass of solid content) was diluted with distilled water so that the solid content mass became 1%, and then a dispersant was added in an amount of 43 parts by mass with respect to 100 parts by mass of the cellulose solid content, and it was stirred well to obtain a cellulose fiber slurry (for MMSD described later). Using these as raw materials, they were put into a drying device and dried at a predetermined shear rate, degree of vacuum, and heating temperature (jacket temperature or hot air temperature). The moisture content was measured using an infrared heating moisture meter (MX-50 manufactured by A&D), and the time when the moisture content reached 7% by mass or less (solid content mass 93% or more) was taken as the end point of drying. The conditions are as follows.

[0162] [Ladige Mixer (LM)] Device: Ladige Mixer (Model No.: VT-20) manufactured by Chuo Kiko Co., Ltd. Conditions: While stirring with a jacket temperature of 100°C, an agitator (peripheral speed 1 m / s), and a chopper (3000 rpm), the pressure was reduced to -90 kPa with a vacuum pump. Vacuum drying was carried out until the product temperature reached 50°C. As the clearance, the minimum distance between the chopper (diameter 100 mm) and the jacket was measured. The drying time under these conditions was 160 minutes. The drying temperature was measured at three points on the surface temperature of the jacket and taken as the average value.

[0163] [High-Speed Vacuum Dryer (HSVD)] Device: High-Speed Vacuum Dryer (Model No.: FS10) manufactured by Earth Technica Co., Ltd. Conditions: While stirring with a jacket temperature of 70°C, an agitator (peripheral speed 2 m / s), and a chopper (3500 rpm), the pressure was reduced to -70 kPa with a vacuum pump. Vacuum drying was carried out until the product temperature reached 60°C. As the clearance, the minimum distance between the chopper (diameter 100 mm) and the agitator was measured. The drying time under these conditions was 180 minutes. The drying temperature was measured at three points on the surface temperature of the jacket and taken as the average value.

[0164] [FM Mixer (HM)] Device: FM Mixer (Model No.: FM20) manufactured by Nippon Coke & Engineering Co., Ltd. Conditions: While stirring with a jacket temperature of 80°C and stirring blades (500 rpm), the pressure was reduced to -70 kPa with a vacuum pump. Vacuum drying was carried out until the product temperature reached 70°C. As the clearance, the minimum distance between the upper stirring blade (diameter 400 mm) and the jacket was measured. The drying time under these conditions was 180 minutes. The drying temperature was measured at three points on the surface temperature of the jacket and taken as the average value.

[0165] [Paddle dryer (PD)] Device: Paddle dryer manufactured by Nara Machinery Co., Ltd. (Model No.: NPD-1.6W-12L) Condition: Drying was carried out while heating the steam to a temperature of 120°C and stirring with a stirring blade (30 rpm) until the product temperature reached 100°C. As the clearance, the minimum distance between the stirring blade (diameter 250 mm) and the jacket was measured. The drying time under these conditions was 50 minutes. The drying temperature was measured at three points on the surface temperature of the stirring blade through which the heating steam was passed, and the average value was taken.

[0166] [Micro mist spray dryer (MMSD)] Device: Micro mist spray dryer manufactured by Fujisaki Electric Co., Ltd. (Model No.: MDL050-M) Condition: The cellulose fiber slurry was dried at an inlet temperature of 200°C, an air supply volume of 1 m 3 / min, a nozzle air flow rate of 80 NL / min, and a slurry of 50 mL / min, and the dried powder was recovered by a cyclone type recoverer. Since the shear rate in this device does not have a stirring mechanism, etc., it was considered that it did not substantially occur. The drying time and residence time under these conditions were 1 minute. The drying temperature was measured three times at the inlet temperature of the hot air during the drying process, and the average value was taken.

[0167] [Twin-screw extruder (Ex-dry)] Device: Twin-screw extruder manufactured by Japan Steel Works, Ltd. (Model No.: TEX54αIII: L / D = 63) Condition: While rotating the screw at 66 rpm with a cylinder temperature of 200°C, the raw material was supplied to the uppermost barrel at 20 kg / h using a gravimetric feeder, and the dried powder was obtained from the discharge port. As the clearance, the minimum distance between the kneading disk (diameter 54 mm) and the cylinder was measured. The drying time and residence time under these conditions were 1 minute. The drying temperature was measured three times for the temperature of the cylinder where the lowermost kneading disk was placed, and the average value was taken.

[0168] [Planetary mixer (PM)] Device: Planetary mixer manufactured by Kobayashi Seisakusho Co., Ltd. (Model number: ACM-5LVT: Hook type) Conditions: While stirring at a jacket temperature of 60 °C and 307 rpm, the pressure was reduced to -90 kPa with a vacuum pump. Vacuum drying was carried out until the product temperature reached 50 °C. As the clearance, the minimum distance between the hook blade (diameter 100 mm) and the jacket was measured. The drying time under these conditions was 180 minutes. The drying temperature was measured at three points on the surface temperature of the jacket, and the average value was taken.

[0169] [Examples 1 to 12, Comparative Example 8] Using the CNF shown in Table 1 and using the above device as shown in Table 2, with the CNF, drying temperature, and shear rate as shown in Tables 3 and 4, a cellulose fiber dried body was obtained. For Example 12, in the preparation of the raw material, a cellulose fiber slurry was obtained without using a dispersant.

[0170] ≪Manufacture of resin composite≫ The cellulose fiber dried body manufactured above and a thermoplastic resin (UBE Nylon 1013B manufactured by Ube Industries, Ltd.) were blended at a ratio such that the cellulose fiber was 10% by mass in the resin composite, and the resin composite was manufactured by the following procedure.

[0171] [Configuration of extruder] For a twin-screw extruder (OMEGA30H manufactured by STEER, L / D = 60) with 13 cylinder blocks, cylinder 1 was water-cooled, cylinder 2 was set at 80 °C, cylinder 3 was set at 150 °C, and cylinders 4 to the die were set at 250 °C.

[0172] As for the screw configuration, cylinders 1 to 3 are set as a conveying zone composed only of a conveying screw, and in cylinder 4, two clockwise kneading disks (feeding type kneading disks: hereinafter sometimes simply referred to as RKD) and two neutral kneading disks (non-conveying type kneading disks: hereinafter sometimes simply referred to as NKD) are arranged in order from the upstream side. Cylinder 5 is a conveying zone, in cylinder 6, one RKD and subsequently two NKD are arranged, cylinders 7 and 8 are conveying zones, and in cylinder 9, two NKD are arranged. The subsequent cylinder 10 is a conveying zone, in cylinder 11, two NKD and subsequently one counterclockwise screw are arranged, and cylinders 12 and 13 are conveying zones. A vent port was installed at the upper part of cylinder 12 so as to be able to perform decompression suction, and vacuum suction was carried out.

[0173] Cellulose fiber dry matter and a thermoplastic resin were mixed, melt-kneaded at a rotational speed of 250 rpm using a twin-screw extruder, extruded into strands, water-cooled and cut to obtain pellets. The obtained pellets were melted at 260 °C using an attached injection molding machine, and dumbbell-shaped test pieces conforming to JIS K7127 standard were produced and used for evaluation.

[0174] ≪Evaluation≫ <Evaluation of Cellulose Fibers> [Production of Porous Sheet] First, the wet cake was added to tert-butanol, and further dispersed until there were no aggregates using a mixer or the like. It was adjusted so that the concentration became 0.5 mass% with respect to 0.5 g of the cellulose fiber solid content weight. 100 g of the obtained tert-butanol dispersion was filtered on filter paper, dried at 150 °C, and then the filter paper was peeled off to obtain a sheet. The porous sheet was a sheet having an air permeability resistance of 100 sec / 100 ml or less per sheet basis weight of 10 g / m 2 and was used as a measurement sample. The basis weight W (g / m 2After measuring , the air permeability resistance R (sec / 100ml) was measured using Wang's air permeability resistance tester (manufactured by Asahi Seiko Co., Ltd., model EG01). At this time, according to the following formula, the value per unit weight of 10 g / m 2 was calculated. Air permeability resistance per unit weight of 10 g / m 2 = R / W × 10

[0175] [Degree of acyl substitution (DS)] The infrared spectra of five locations of the porous sheet by the ATR-IR method were measured with a Fourier transform infrared spectrophotometer (FT / IR-6200 manufactured by JASCO Corporation). The infrared spectrum measurement was carried out under the following conditions. Number of accumulations: 64 times, Wavenumber resolution: 4 cm -1 , Measurement wavenumber range: 4000~600 cm -1 , ATR crystal: Diamond, Incident angle: 45° From the obtained IR spectrum, the IR index was calculated according to the following formula (1): IR index = H1730 / H1030 ··· (1) In the formula, H1730 and H1030 are the absorbances at 1730 cm -1 , 1030 cm -1 (absorption band of cellulose backbone chain C-O stretching vibration). However, the absorbances when the lines connecting 1900 cm -1 and 1500 cm -1 and the lines connecting 800 cm -1 and 1500 cm -1 are used as the baseline, and it means the absorbance when this baseline is set to absorbance 0. Then, the average degree of substitution at each measurement location was calculated from the IR index according to the following formula (2), and the average value was taken as DS. DS = 4.13 × IR index ··· (2)

[0176] [Crystallinity] X-ray diffraction measurement of the porous sheet was performed, and the crystallinity was calculated from the following formula. Crystallinity (%) = [I (200) - I (amorphous) / I (200) × 100 I (200) : Diffraction peak intensity by the 200 plane (2θ = 22.5°) in cellulose I crystals I (amorphous) : Halo peak intensity due to amorphous in cellulose I crystals, peak intensity on the low angle side (2θ = 18.0°) 4.5° lower than the diffraction angle of the 200 plane (X-ray diffraction measurement conditions) Apparatus MiniFlex (manufactured by Rigaku Corporation) Axis of operation 2θ / θ X-ray source CuKα Measurement method Continuous type Voltage 40 kV Current 15 mA Start angle 2θ = 5° End angle 2θ = 30° Sampling width 0.020° Scan speed 2.0° / min Sample: A porous sheet was attached on the sample holder

[0177] [Average fiber diameter] The cellulose fiber cake or cellulose fiber slurry was diluted with tert-butanol to 0.01% by mass, and using a high-shear homogenizer (manufactured by IKA, product name "Ultra Turrax T18"), treatment conditions: dispersed at a rotation speed of 25,000 rpm for 5 minutes, cast on mica, and air-dried, which was measured with a high-resolution scanning electron microscope. The measurement was carried out by adjusting the magnification so that at least 100 cellulose fibers were observed, measuring the major axis lengths (L) of 100 randomly selected cellulose fibers, and calculating the additive average of 100 cellulose fibers.

[0178] [Weight average molecular weight (Mw), number average molecular weight (Mn) and Mw / Mn ratio] Weighed 0.88 g of the porous sheet, cut it into small pieces with scissors, gently stirred it, added 20 mL of pure water, and left it standing for one day. Next, water and solids were separated by centrifugation. Subsequently, 20 mL of acetone was added, gently stirred, and left standing for one day. Next, acetone and solids were separated by centrifugation. Subsequently, 20 mL of N,N-dimethylacetamide was added, gently stirred, and left standing for one day. Again, after separating N,N-dimethylacetamide and solids by centrifugation, 20 mL of N,N-dimethylacetamide was added, gently stirred, and left standing for one day. N,N-dimethylacetamide and solids were separated by centrifugation, and 19.2 g of an N,N-dimethylacetamide solution adjusted so that lithium chloride was 8 mass percent in the solids was added, stirred with a stirrer, and it was confirmed visually that it dissolved. The solution in which the cellulose fibers were dissolved was filtered through a 0.45 μm filter, and the filtrate was used as a sample for gel permeation chromatography. The apparatus and measurement conditions used are as follows. Apparatus: Tosoh Corporation HLC-8120 Column: TSKgel SuperAWM-H (6.0 mm I.D. × 15 cm) × 2 columns Detector: RI detector Eluent: N,N-dimethylacetamide (lithium chloride 0.2%) Flow rate: 0.6 mL / min Calibration curve: Pullulan conversion

[0179] [Average content rate of alkali-soluble polysaccharides] The alkali-soluble polysaccharide content rate was determined by subtracting the α-cellulose content rate from the holocellulose content rate (Wise method) by the method described in a non-patent document (Wood Science Experiment Manual, edited by the Japan Wood Research Society, pages 92-97, 2000) for cellulose fibers. The alkali-soluble polysaccharide content rate was calculated three times for one sample, and the number average of the calculated alkali-soluble polysaccharide content rates was taken as the average content rate of alkali-soluble polysaccharides of the cellulose fibers.

[0180] <Evaluation of dried cellulose fibers> Measurement was carried out using a Powder Tester (model number: PT-X) manufactured by Hosokawa Micron Corporation.

[0181] [Angle of repose] At the center of a horizontally installed stainless steel measuring table with a diameter of 80 mm, using a medicine spoon, 100 g of the dried cellulose fiber was gently dropped from a height of 110 mm between the lower opening of the funnel (stainless steel, upper opening diameter 70 mm, lower opening diameter 7 mm, inclination angle 60°) and the measuring table at a rate of about 10 g / min via the funnel, and the dried cellulose fiber was deposited in a conical shape on the measuring table. The conical shape was photographed from the side, and the angle between the generatrix of the cone and the horizontal plane was measured. The arithmetic mean value of the three measurements was taken as the angle of repose.

[0182] [Angle of collapse] For the sample for which the angle of repose was measured, a 109 g weight on the same pedestal as the measuring table was dropped three times from a height of 160 mm at 2 - second intervals. After that, the conical shape of the sample was photographed from the side, and the angle between the generatrix of the cone and the horizontal plane was measured. The arithmetic mean value of the three measurements was taken as the angle of collapse.

[0183] [Difference angle] The difference between the angle of repose and the angle of collapse was calculated as the difference angle.

[0184] [Loose bulk density] The dried cellulose fiber was put into a bottomed stainless steel cylinder with a volume of 100 mL (inner diameter 50.46 mm × depth 50 mm) using a medicine spoon at a rate of 10 g / min until it overflowed. After the dried body was leveled off, the weight was measured to the nearest 0.01 g. The arithmetic mean value of the three measurements of the weight was divided by the inner volume of the above - mentioned bottomed cylinder to calculate the loose bulk density.

[0185] [Packed bulk density] A resin adapter (inner diameter 50.46 mm × length 40 mm) with sufficient capacity was connected to the upper part of the bottomed cylindrical container used at the loose bulk density so as to be in close contact. After putting the dried cellulose fiber into the bottomed cylindrical container up to the overflowing amount in the same procedure as the measurement of the loose bulk density, a vibration with an amplitude of 1.5 mm and a frequency of 50 Hz was applied to the bottomed cylindrical container with the adapter connected for 30 seconds using a motor with an eccentric weight attached to the rotating shaft. Subsequently, except for the adapter, after rubbing the dried material, the weight was measured to the nearest 0.01 g. The number average value of the three measurements of the weight was divided by the internal volume of the bottomed cylindrical container to calculate the bulk density.

[0186] [Degree of Compression] From the values of the above-mentioned bulk density and loose bulk density, the following formula: Degree of Compression = (Bulk Density - Loose Bulk Density) / Bulk Density was used to calculate the degree of compression.

[0187] [Moisture Content] Measurement was carried out using an infrared heating moisture meter (MX-50 (manufactured by A&D)).

[0188] [Particle Size Distribution] A precisely weighed sieve with a diameter of φ100 mm was stacked on a precisely weighed receiver with a diameter of φ100 mm in the order of mesh openings of 710 μm, 1000 μm, and 1700 μm. After putting the dried cellulose fiber precisely weighed in the range of 1 to 20 g on the top sieve, a vibration with an amplitude of 1.5 mm and a frequency of 50 Hz was applied for 10 minutes. Subsequently, the fractionated samples were precisely weighed for each sieve, and the weight fraction of each fraction was calculated to obtain the particle size distribution.

[0189] [Screen Mesh Evaluation] With a 50-mesh screen mesh attached between the die adapter and the die head, the extruder was operated at a discharge rate of 20 kg / h for 1 hour, and the amount of particles trapped by the screen mesh was evaluated in the following three stages. A ··· Almost no particles were trapped B ··· Some particles were trapped and the screen mesh needs to be replaced C ··· The die pressure increased before the operation was completed, and it became necessary to replace the screen mesh.

[0190] <Evaluation of resin composite> [Tensile fracture elongation, flexural modulus of elasticity] From the obtained pellets, using an injection molding machine, molding was performed under conditions conforming to JIS K6920-2, and a multipurpose test piece conforming to ISO294-3 was molded. For the multipurpose test piece, the tensile fracture elongation was measured in accordance with ISO527, and the flexural modulus of elasticity was measured in accordance with ISO179. Since the polyamide resin undergoes changes due to moisture absorption, it was stored in an aluminum moisture-proof bag immediately after molding to suppress moisture absorption. The results are shown in Table 1.

[0191]

Table 1

[0192]

Table 2

[0193]

Table 3

[0194]

Table 4

Industrial Applicability

[0195] The high-toughness resin composite that the present invention can provide can be suitably applied to various resin molded article applications.

Claims

1. A cellulose fiber dry material comprising unmodified cellulose fibers and a dispersing agent, The cellulose fibers have a number average fiber diameter of 2 nm to 1000 nm, The cellulose fiber dry body has an angle of repose of 40° to 60° and a difference angle of 10° or less, and a loose bulk density of 0.10 g / cm 3 ~0.40g / cm 3 and a compression ratio of 20% to 40%; In the dried cellulose fiber material, the content of particle components having a particle size of 710 μm or less is 50% by mass to 90% by mass.

2. The dried cellulose fiber body according to claim 1, wherein the content of particulate components having a particle size of more than 710 μm and not more than 1000 μm is 10% by mass to 30% by mass.

3. The dried cellulose fiber body according to claim 1 or 2, wherein the content of particle components having a particle size of more than 1000 μm is 1% by mass to 10% by mass.

4. The dried cellulose fiber material according to any one of claims 1 to 3, wherein the average fiber length (L) / fiber diameter (D) ratio of the cellulose fibers is 30 to 5,000.

5. The cellulose fiber dried body according to any one of claims 1 to 4, wherein the cellulose fiber has a weight average molecular weight (Mw) of 100,000 or more and a weight average molecular weight (Mw) / number average molecular weight (Mn) ratio of 6 or less.

6. The dried cellulose fiber material according to any one of claims 1 to 5, wherein the cellulose fibers have a crystallinity of 60% or more.

7. The dried cellulose fiber material according to any one of claims 1 to 6, wherein the cellulose fiber has an alkali-soluble polysaccharide content of 20 mass% or less.

8. The dried cellulose fiber material according to any one of claims 1 to 7, having a moisture content of 30 mass% or less.

9. The cellulose fiber dried body according to any one of claims 1 to 8, wherein the dispersant is a compound having an HLB value of 0.1 or more and less than 8.0, a melting point of 80°C or less, and a number average molecular weight of 1,000 to 50,000.

10. A method for producing a dried cellulose fiber body according to any one of claims 1 to 9, A slurry preparation step of preparing a slurry containing cellulose fibers and an aqueous medium; and A drying step of drying the slurry under conditions of a drying rate of 10% / min to 10,000% / min to form a dried cellulose fiber body; A method comprising:

11. 11. The method of claim 10, wherein the drying step is carried out in a continuous process with a residence time of 0.01 minutes to 10 minutes at a drying temperature of 20°C to 200°C.

12. A method for producing a resin composite containing cellulose fibers and a resin, comprising: The present invention includes mixing the dried cellulose fiber material according to any one of claims 1 to 9 with a resin, The resin composite has a tensile elongation at break of 8% or more.

13. The method of claim 12 wherein the resin is a thermoplastic resin.

14. The method of claim 13, wherein the thermoplastic resin is a polyamide-based resin.

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