Dried cellulose fiber and method for producing the same, and method for producing resin composite

Abstract

To provide a dried cellulose fiber that is finely dispersed in resin to give a high-rigidity resin composite and also has excellent handleability and a method for producing the same, and a resin composite containing the dried cellulose fiber and a resin and a method for producing the same.SOLUTION: A dried cellulose fiber contains cellulose fiber and has a compression level of 1-25%. There is also provided a method for producing the dried cellulose fiber. In a preferable embodiment, the dried cellulose fiber satisfies one or more conditions selected from the group consisting of a repose angle of less than 45°, a difference angle of more than 10°, an aerated bulk density of 0.35-0.85 g / cm3, and a packed bulk density of 0.6-0.9 g / cm3.SELECTED DRAWING: None

Description

[Technical Field]

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

[0002] Resin materials are lightweight and have excellent processability, making them widely used in a variety of applications, including automotive components, electrical and electronic components, office equipment housings, and precision components. However, resins alone often lack sufficient mechanical properties and dimensional stability, making composites of resins and various fillers commonly used. In recent years, the use of nanofibers, such as cellulose nanofibers (CNFs), as fillers has been explored. Nanofibers, including CNFs, tend to aggregate easily in a dry state, so they are manufactured as stable dispersions. For example, when applying cellulose nanofibers to various applications, the dispersions are sometimes dried and then dispersed in a dispersion medium, or the dried cellulose nanofibers are redispersed in a matrix resin. However, because cellulose nanofibers aggregate strongly due to hydrogen bonding between cellulose molecules, various methods have been proposed to suppress aggregation of cellulose nanofibers during the drying process.

[0003] For example, Patent Document 1 describes powdered nanofibers characterized by a bulk density of 90 to 200 g / L, which are obtained by blending (A) powdered nanofibers with (B) a dispersant in an amount of 1 to 40% by weight (calculated as solid content). Patent Document 2 describes a method for producing dried microfibers with a moisture content of 0 to 1% by mass by homogenizing cellulose nanofibers in the presence of an organic solvent and then removing the organic solvent. Patent Document 3 describes a method for producing a dry cellulose nanofiber solid, which includes drying a mixture of cellulose nanofibers and a solvent using a vacuum dryer. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 2017-210596 [Patent Document 2] Japanese Patent Application Laid-Open No. 2012-224960 [Patent Document 3] International Publication No. 2019 / 189318 Summary of the Invention [Problem to be solved by the invention]

[0005] The techniques described in Patent Documents 1 to 3 all aim to reduce aggregation of cellulose nanofibers during drying, thereby enabling the cellulose nanofibers to be well redispersed in a dispersion medium or matrix resin after drying, but even with these techniques, the redispersibility of cellulose nanofibers once dried is insufficient, and in particular, no technique has been established that enables the cellulose nanofibers to be well dispersed in a resin even when mixed with the resin in a dry state. Therefore, conventional techniques have not been able to achieve a satisfactory level of the effect of cellulose nanofibers in improving the physical properties of the resin.

[0006] One aspect of the present invention aims to solve the above-mentioned problems and to provide a dried cellulose fiber body that can be finely dispersed in a resin to give a highly rigid resin composite that also has excellent handleability, a method for producing the same, and a resin composite containing the dried cellulose fiber body and a resin, and a method for producing the same. [Means for solving the problem]

[0007] The present invention includes the following aspects. [1] A dried cellulose fiber body containing cellulose fibers and having a compression rate of 1 to 25%. [2] Angle of repose less than 45°, angle of difference more than 10°, loose bulk density 0.35 to 0.85 g / cm 3 , and packed bulk density 0.6 to 0.9 g / cm 3The dried cellulose fiber material according to the above-mentioned embodiment 1, having one or more selected from the group consisting of: [3] Loose bulk density 0.35-0.85g / cm 3 , and packed bulk density 0.6 to 0.9 g / cm 3 The dried cellulose fiber material according to the first or second aspect, having the following structure: [4] The dried cellulose fiber material according to any one of the above aspects 1 to 3, wherein the cellulose fibers have a number average fiber diameter of 2 nm to 1000 nm. [5] The dried cellulose fibers according to any one of the above aspects 1 to 4, wherein the cellulose fibers have an average fiber length (L) / fiber diameter (D) ratio of 30 to 5,000. [6] The dried cellulose fiber according to any one of aspects 1 to 5, 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. [7] The dried cellulose fiber material according to any one of the above aspects 1 to 6, wherein the cellulose fiber has a crystallinity of 60% or more. [8] The dried cellulose fiber material according to any one of the above aspects 1 to 7, wherein the cellulose fiber has an alkali-soluble polysaccharide content of 20% by mass or less. [9] The dried cellulose fiber material according to any one of the above aspects 1 to 8, wherein the cellulose fiber is chemically modified.

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

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

[12] The dried cellulose fiber material according to any one of Aspects 9 to 11, wherein the cellulose fiber has an average degree of substitution (DS) of 0.1 to 1.2.

[13] The dried cellulose fiber material 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, 14. The dried cellulose fiber material according to any one of Aspects 1 to 13, 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.

[15] A method for producing a dried cellulose fiber material according to any one of the above aspects 1 to 14, comprising: A slurry preparation step of preparing a slurry containing cellulose fibers and a liquid medium; The slurry is subjected to a shear rate of 100 to 20,000 seconds. -1 a drying step of drying the mixture at a drying rate of 0.01 to 10% / min and a drying temperature of 20°C to 160°C under stirring to form a dried cellulose fiber body; A method comprising:

[16] The method according to aspect 15, wherein the drying step is carried out by a batch process using a mechanically agitating mixer granulator.

[17] A method for producing a resin composite containing cellulose fibers and a resin, comprising: The method includes mixing the dried cellulose fibers according to any one of the above aspects 1 to 14 with a resin, The resin composite has a flexural modulus of 3.3 GPa or more.

[18] The method of claim 17, wherein the resin is a thermoplastic resin.

[19] The method according to claim 18, wherein the thermoplastic resin is a polyamide resin. [Effects of the Invention]

[0008] According to one aspect of the present invention, a dried cellulose fiber body that can be finely dispersed in a resin to give a highly rigid resin composite and that is also easy to handle, a method for producing the same, and a resin composite containing the dried cellulose fiber body and a resin, and a method for producing the same can be provided. [Brief explanation of the drawings]

[0009] [Figure 1] FIG. 10 is an explanatory diagram of a method for calculating the IR index 1730 and the IR index 1030. [Figure 2]FIG. 1 is an explanatory diagram of a method for measuring the thermal decomposition onset temperature (TD) and the 1% weight loss temperature (T1%). DETAILED DESCRIPTION OF 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] <Dried cellulose fiber> One aspect of the present invention provides a dried cellulose fiber material that contains cellulose fibers and may be in the form of particles, particularly granules (i.e., relatively coarse particles formed by the aggregation of fine powder). In the dried cellulose fiber material according to one aspect, the compressibility is controlled within a specific range described below, and preferably, one or more characteristics selected from the group consisting of the angle of repose, angle of collapse, angle of difference, loose bulk density, and packed bulk density are controlled within a specific range. In one aspect, the dried cellulose fiber material of the present disclosure can have appropriately controlled particle size, cellulose molecular aggregation state, and inter-particle interaction, and can exhibit the advantages of excellent handleability and reduced aggregation when mixed with a resin. That is, if the dried cellulose fiber material is an extremely fine particle, mixing it with a resin can result in the particles agglomerating, making it difficult to achieve a good dispersion. On the other hand, in one aspect, the dried cellulose fiber material can be a particle that is not too fine, in which case aggregation is reduced in the resin, allowing the cellulose fibers to be well-finely dispersed in the resin. Furthermore, granular dried cellulose fibers have advantages in that their shape can be visually recognized, thereby reducing the likelihood of measurement errors, which can occur when powders are suspended in the air, and in that they are easy to handle when mixed with resin (e.g., they can be smoothly fed to the top or side of an extruder). Additionally, due to their not-too-fine size, granular dried cellulose fibers can efficiently withstand shear forces when mixing the dried cellulose fibers with resin (e.g., melt-kneading). This shear force effectively breaks down the particles, allowing the cellulose fibers to be dispersed in the resin in a nano-level defibrated state. Meanwhile, the dried cellulose fibers according to one embodiment of the present invention have an appropriate density, allowing them to easily disintegrate in the resin, resulting in excellent fine dispersion of the cellulose fibers in the resin. By using the dried cellulose fibers according to one embodiment of the present invention, a highly rigid resin composite can be formed.

[0012] In one embodiment, the degree of compression of the dried cellulose fiber material is 1 to 25%. The degree of compression represents the degree of bulk loss. In order to ensure that the flowability of the dried cellulose fiber material is not too high, the degree of compression may be 1% or more, preferably 5% or more, 10% or more, or 12% or more. In order to ensure that the flowability of the dried cellulose fiber material is good and that handling is excellent (specifically, scattering, floating, and dust formation are unlikely to occur), the degree of compression may be 25% or less, preferably 23% or less.

[0013] The compressibility is a value calculated by the formula: compressibility = (packed bulk density - loose bulk density) / packed bulk density. The loose bulk density and packed bulk density are values measured by the method described in the [Examples] section of this disclosure.

[0014] In one embodiment, the loose bulk density of the dried cellulose fiber material is preferably 0.35 g / cm from the viewpoint of avoiding problems such as scattering of particles due to the dried cellulose fiber material being too light or floating on the resin phase when mixed with a fluidized resin, resulting in poor mixing. 3 or more, or 0.40 g / cm 3 or more, or 0.45 g / cm 3 The loose bulk density is preferably 0.85 g / cm because the dried cellulose fiber material can be easily disintegrated in the resin, allowing the cellulose fibers to be well dispersed in the resin, and the dried cellulose fiber material is not too heavy, preventing poor mixing of the dried cellulose fiber material with the resin. 3 or less, or 0.80 g / cm 3 or less, or 0.75 g / cm 3 The following is the result.

[0015] The packed bulk density of the dry cellulose fiber body is controlled within a range useful for controlling the loose bulk density and compressibility within the ranges of the present disclosure, and in one embodiment, it is 0.6 to 0.9 g / cm 3 It may be.

[0016] In one embodiment, the angle of repose of the dried cellulose fiber material is preferably less than 45°, or 42° or less, or 40° or less, or 38° or less. Dried cellulose fiber materials having an angle of repose in the above range contain relatively large particles and have good fluidity, making them easy to mix with resin, while being advantageous in that they are less likely to trap gas between particles and become fluidized (i.e., behave like a fluid due to suspension), making them less likely to scatter. The angle of repose may be, for example, 10° or more, 20° or more, or 30° or more, since the particle size is not too large and the cellulose fibers are well dispersible in the resin.

[0017] The collapse angle of the dry cellulose fiber material is controlled within a range that is useful for controlling the angle of repose and the angle of difference within the ranges of the present disclosure, and in one aspect, may be 15° to 35°, or 17° to 33°, or 19° to 31°.

[0018] In one aspect, the difference angle of the dried cellulose fiber material (i.e., the difference between the angle of repose and the angle of collapse) is preferably more than 10°, or 11° or more, or 12° or more, or 13° or more. A dried cellulose fiber material having a difference angle in the above range has high fluidity and excellent handleability due to relatively small interactions between particles (frictional force, etc.), but is easily disintegrated in a resin, allowing the cellulose fibers to be finely dispersed in the resin. From the viewpoint of ease of production of the dried cellulose fiber material, the difference angle may be, for example, 30° or less, 25° or less, or 20° or less.

[0019] The angle of repose and the angle of collapse are values measured by the method described in the "Examples" section of this disclosure. The difference angle is calculated as the difference between the angle of repose and the angle of collapse.

[0020] In a preferred embodiment, the compressibility, loose bulk density and hardened bulk density are within the ranges exemplified above. In a preferred embodiment, the compressibility, loose bulk density, hardened bulk density, and either or both of the angle of repose and angle of difference are set within the ranges exemplified above.

[0021] In one embodiment, 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 is preferably 5000 μm or less, or 4000 μm or less, or 3000 μm or less, or 2000 μm or less. The average particle size is a value measured by a laser diffraction / scattering method.

[0022] In one embodiment, the moisture content of the dried cellulose fiber material 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 ease of production of the dried cellulose fiber material, it may be, for example, 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 moisture meter.

[0023] The raw materials for the dried cellulose fiber body can include natural cellulose fibers and regenerated cellulose fibers. Examples of natural cellulose fibers include wood pulp obtained from wood species (broadleaf or coniferous trees), non-wood pulp obtained from non-wood species (cotton, bamboo, hemp, bagasse, kenaf, cotton linter, sisal, straw, etc.), and cellulose fiber aggregates produced by animals (e.g., sea squirts), algae, and microorganisms (e.g., acetic acid bacteria). Examples of regenerated cellulose fibers include regenerated cellulose fibers (e.g., viscose, cupra, Tencel), cellulose derivative fibers, and ultrafine threads of regenerated cellulose or cellulose derivatives obtained by electrospinning.

[0024] In one embodiment, 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 the hemicellulose, and then defibrating the fibers using a pulverizing method such as a high-pressure homogenizer, microfluidizer, ball mill, disk mill, or mixer (e.g., a homomixer). In one embodiment, the cellulose nanofibers have a number-average fiber diameter of 1 nm or more and 1,000 nm or less. The cellulose fibers may be chemically modified as described below.

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

[0026] Since cellulose fiber raw materials contain alkali-soluble components and sulfuric acid-insoluble components (such as lignin), they may be subjected to a purification process such as delignification by cooking and a bleaching process to reduce the alkali-soluble components and sulfuric acid-insoluble components. On the other hand, purification processes such as delignification by cooking and bleaching processes cut the molecular chains of cellulose, changing the weight-average molecular weight and number-average molecular weight. Therefore, it is desirable that the purification process and bleaching process of the cellulose fiber raw material control the weight-average molecular weight of the cellulose fiber and the ratio of the weight-average molecular weight to the number-average molecular weight so that they do not deviate from appropriate ranges.

[0027] Furthermore, since the refining process, such as delignification by cooking, and the bleaching process reduce the molecular weight of cellulose molecules, there is a concern that these processes will result in a lower molecular weight of cellulose fibers and that the cellulose fiber raw material will be altered to increase the proportion of alkali-soluble components.Since alkali-soluble components have poor heat resistance, it is desirable that the refining process and 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 is within a certain range or less.

[0028] In one aspect, the number average fiber diameter of the cellulose fibers is preferably 2 to 1000 nm from the viewpoint of obtaining a favorable effect of improving physical properties by the cellulose fibers, and 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] From the viewpoint of satisfactorily improving the mechanical properties of a resin composite containing cellulose fibers with a small amount of cellulose fibers, the average fiber length (L) / fiber diameter (D) ratio of the cellulose fibers is preferably 30 or more, or 50 or more, or 80 or more, or 100 or more, or 120 or more, or 150 or more. There is no particular upper limit, but from the viewpoint of handleability, it is preferably 5000 or less.

[0030] In this disclosure, the fiber length, fiber diameter, and L / D ratio of cellulose fibers are determined by dispersing an aqueous dispersion of cellulose fibers using a high-shear homogenizer (e.g., Nippon Seiki Co., Ltd., trade name "Excel Auto Homogenizer ED-7") at 15,000 rpm for 5 minutes, diluting the resulting aqueous dispersion with pure water to 0.1 to 0.5% by mass, casting it on mica, and air-drying it to obtain a measurement sample. The measurement sample is then measured using a high-resolution scanning electron microscope (SEM) or atomic force microscope (AFM). Specifically, the length (L) and diameter (D) of 100 randomly selected cellulose fibers are measured in an observation field adjusted to a magnification such that at least 100 cellulose fibers are visible, and the ratio (L / D) is calculated. The number-average fiber length (L), fiber diameter (D), and ratio (L / D) of the cellulose fibers are calculated.

[0031] Alternatively, the fiber length, fiber 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-mentioned measurement method.

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

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

[0034] Alkali-soluble polysaccharides such as hemicellulose and acid-insoluble components such as lignin are present between the microfibrils and between the microfibril bundles of plant-derived cellulose fibers. Hemicellulose is a polysaccharide composed of sugars such as mannan and xylan, and forms hydrogen bonds with cellulose to bind the microfibrils together. Lignin is a compound with an aromatic ring, and is known to be covalently bonded to hemicellulose in plant cell walls. If a large amount of impurities such as lignin remains in the cellulose fibers, discoloration may occur due to heat during processing. Therefore, from the perspective of suppressing discoloration of resin composites during extrusion and molding, it is desirable to keep the crystallinity of the cellulose fibers within the above-mentioned range.

[0035] When the cellulose is cellulose type I crystals (derived from natural cellulose), the degree of crystallinity can be calculated by the Segal method from the diffraction pattern (2θ / deg. 10 to 30) obtained by measuring the sample by wide-angle X-ray diffraction, using the following formula: Crystallinity (%) = ([diffraction intensity due to the (200) plane at 2θ / deg. = 22.5] - [diffraction intensity due to amorphous phase at 2θ / deg. = 18]) / [diffraction intensity due to the (200) plane at 2θ / deg. = 22.5] × 100

[0036] When the cellulose is cellulose type II crystal (derived from regenerated cellulose), the degree of crystallinity can be calculated from the absolute peak intensity h0 at 2θ=12.6° assigned to the (110) plane peak of cellulose type II crystal in wide-angle X-ray diffraction and the peak intensity h1 from the baseline at this interplanar spacing, using the following formula: Crystallinity (%) =h1 / h0 ×100

[0037] Known crystalline forms of cellulose include type I, type II, type III, and type IV, of which type I and type II are particularly commonly used, while type III and type IV are obtained on a laboratory scale but are not commonly used on an industrial scale. The cellulose fibers of the present disclosure are preferably cellulose fibers containing cellulose type I crystals or cellulose type II crystals, since they have relatively high structural mobility and, by dispersing the cellulose fibers in a resin, a resin composite can be obtained that has a lower linear expansion coefficient and superior strength and elongation during tensile and bending deformation. Cellulose fibers containing cellulose type I crystals and having a crystallinity of 55% or more are more preferred.

[0038] In addition, the degree of polymerization of the cellulose fibers is preferably 100 or more, more preferably 150 or more, more preferably 200 or more, more preferably 300 or more, more preferably 400 or more, more preferably 450 or more, and 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 viewpoint of processability and mechanical property development, it is desirable that the degree of polymerization of the cellulose fiber is within the above-mentioned range. From the viewpoint of processability, it is preferable that the degree of polymerization is not too high, and from the viewpoint of mechanical property development, it is desirable that the degree of polymerization is not too low.

[0040] The degree of polymerization of cellulose fibers means the average degree of polymerization measured according to the reduced specific viscosity method using a copper ethylenediamine solution described in the Verification Test (3) of the "Commentary on the 15th Revised Japanese Pharmacopoeia (published by Hirokawa Shoten)."

[0041] In one embodiment, the weight-average molecular weight (Mw) of the cellulose fibers 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 higher weight-average molecular weight indicates a lower number of terminal groups in the cellulose molecules. Furthermore, 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 lower Mw / Mn indicates a lower number of terminal groups in the cellulose molecules. Since the terminals of cellulose molecules are the starting points for thermal decomposition, particularly high heat-resistant cellulose fibers and resin composites containing cellulose fibers and resins can be obtained when the cellulose molecules of the cellulose fibers not only have a high weight-average molecular weight but also a narrow molecular weight distribution. The weight-average molecular weight (Mw) of the cellulose fibers may be, for example, 600,000 or less, or 500,000 or less, from the viewpoint of the availability of cellulose fiber raw materials. From the viewpoint of ease of production of cellulose fibers, the ratio of weight-average molecular weight to number-average molecular weight (Mn) (Mw / Mn) may be, for example, 1.5 or more, or 2 or more. Mw can be controlled within the above range by selecting a cellulose fiber raw material having an Mw appropriate for the purpose, or by subjecting the cellulose fiber raw material to appropriate physical and / or chemical treatments within an appropriate range, etc. Mw / Mn can also be controlled within the above range by selecting a cellulose fiber raw material having an Mw / Mn appropriate for the purpose, or by subjecting the cellulose fiber raw material to appropriate physical and / or chemical treatments within an appropriate range, etc. In both Mw and Mw / Mn control, examples of the physical treatment include dry or wet grinding using a microfluidizer, ball mill, or disk mill, or physical treatments that apply mechanical forces such as impact, shear, shear, or friction using a crusher, homomixer, high-pressure homogenizer, or ultrasonic device, etc. Examples of the chemical treatment include digestion, bleaching, acid treatment, and conversion to regenerated cellulose.

[0042] The weight average molecular weight and number average molecular weight of the cellulose fiber referred to here are values determined by dissolving the cellulose fiber in N,N-dimethylacetamide containing lithium chloride and then performing gel permeation chromatography using N,N-dimethylacetamide as a solvent.

[0043] Methods for controlling the degree of polymerization (i.e., average degree of polymerization) or molecular weight of cellulose fibers include hydrolysis. Hydrolysis promotes depolymerization of amorphous cellulose inside cellulose fibers, reducing the average degree of polymerization. At the same time, hydrolysis removes impurities such as hemicellulose and lignin in addition to the amorphous cellulose, making the interior of the fibers more porous.

[0044] The hydrolysis method is not particularly limited, and examples include acid hydrolysis, alkaline hydrolysis, hydrothermal decomposition, steam explosion, and microwave decomposition. These methods may be used alone or in combination. In acid hydrolysis, for example, α-cellulose obtained as pulp from fibrous plants is used as the cellulose fiber raw material. This is dispersed in an aqueous medium, and an appropriate amount of a protonic acid, carboxylic acid, Lewis acid, heteropolyacid, or the like is added. The mixture is then heated with stirring, allowing for easy control of the average degree of polymerization. The reaction conditions, such as temperature, pressure, and time, vary depending on the cellulose species, cellulose concentration, acid species, and acid concentration, but are appropriately adjusted to achieve the desired average degree of polymerization. For example, cellulose fibers may be treated with a mineral acid solution containing 2% or less by weight at 100°C or higher under pressure for 10 minutes or longer. Under these conditions, the acid or other catalyst component penetrates deep into the cellulose fibers, promoting hydrolysis. This reduces the amount of catalyst component required, and facilitates subsequent purification. The dispersion of the cellulose fiber raw material during hydrolysis may contain, in addition to water, a small amount of an organic solvent within a range that does not impair the effects of the present invention.

[0045] Alkali-soluble polysaccharides that cellulose fibers may contain include hemicellulose, β-cellulose, and γ-cellulose. Alkali-soluble polysaccharides are understood by those skilled in the art as components obtained as the alkali-soluble portion of holocellulose (i.e., the components obtained by removing α-cellulose from holocellulose), which is obtained by solvent extraction and chlorine treatment of plants (e.g., wood). Alkali-soluble polysaccharides are polysaccharides containing hydroxyl groups and have poor heat resistance, which can lead to problems such as decomposition when heated, yellowing during heat aging, and a decrease in the strength of cellulose fibers. Therefore, it is preferable that the content of alkali-soluble polysaccharides in cellulose fibers is low.

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

[0047] The average alkali-soluble polysaccharide content can be determined by the method described in the non-patent document (Wood Science Experiment Manual, edited by the Japan Wood Research Society, pp. 92-97, 2000), by subtracting the α-cellulose content from the holocellulose content (Wise method). This method is recognized in the industry as a method for measuring hemicellulose content. The alkali-soluble polysaccharide content is calculated three times for each sample, and the number average of the calculated alkali-soluble polysaccharide contents is taken as the average alkali-soluble polysaccharide content.

[0048] In one embodiment, the average content of acid-insoluble components in the cellulose fibers is preferably 10% by mass or less, 5% by mass or less, or 3% by mass or less, relative to 100% by mass of the cellulose fibers, from the viewpoint of preventing a decrease in heat resistance of the cellulose fibers and the resulting discoloration. From the viewpoint of ease of production of the cellulose fibers, the content may be 0.1% by mass or more, 0.2% by mass or more, or 0.3% by mass or more.

[0049] The average acid-insoluble content is determined by quantifying the acid-insoluble content using the Clason method described in the non-patent document (Wood Science Experiment Manual, edited by the Japan Wood Research Society, pp. 92-97, 2000). This method is recognized in the art as a method for measuring lignin content. A sample is stirred in a sulfuric acid solution to dissolve cellulose, hemicellulose, and other components, and then filtered through a glass fiber filter. The resulting residue corresponds to the acid-insoluble component. The acid-insoluble component content is calculated from the weight of the acid-insoluble component, and the number average of the acid-insoluble component contents calculated for three samples is used as the average acid-insoluble component content.

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

[0051] In this disclosure, T D As shown in the explanatory diagram in Figure 2, this is a value obtained from a graph in thermogravimetry (TG) analysis, where the horizontal axis is temperature and the vertical axis is weight retention % (note that Figure 2(B) is an enlarged view of Figure 2(A)). Starting from the weight of cellulose fiber at 150°C (a state where most of the moisture has been removed) (weight loss of 0 wt%), the temperature is further increased, and the temperature at which the weight loss reaches 1 wt% (T 1% ) and the temperature at which 2 wt% weight loss occurs (T 2% The temperature at the point where this line intersects with the horizontal line (baseline) that passes through the starting point of 0 wt% weight loss is called T D It is defined as:

[0052] 1% weight loss temperature (T 1% ) is the above T D This is the temperature at which the weight loss reaches 1% by weight, starting from the weight at 150°C, when the temperature is continued to be increased using the method described above.

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

[0054] (chemical modification) The cellulose fibers may be chemically modified. For example, the cellulose fibers may be chemically modified in advance at the raw pulp or linter stage, during or after the defibration treatment, or during or after the slurry preparation process or the drying (granulation) process.

[0055] As a modifying agent for cellulose fibers, a compound that reacts with the hydroxyl groups of cellulose can be used, and examples thereof include an esterifying agent, an etherifying agent, and a silylating agent. In a preferred embodiment, the chemical modification is acylation using an esterifying agent, and particularly preferably acetylation. As the esterifying agent, acid halides, acid anhydrides, vinyl carboxylic acid esters, and carboxylic acids are preferred.

[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, and benzoyl iodide. Among these, acid chlorides are preferred in terms of reactivity and ease of handling. In the reaction of the acid halides, one or more alkaline compounds may be added to act as a catalyst and neutralize acidic by-products. Specific examples of alkaline compounds include, but are not limited to, tertiary amine compounds such as triethylamine and trimethylamine; and nitrogen-containing aromatic compounds such as pyridine and dimethylaminopyridine.

[0057] As the acid anhydride, any appropriate acid anhydride can be used. For example, Saturated aliphatic monocarboxylic acid anhydrides such as acetic acid, propionic acid, (iso)butyric acid, and valeric acid; unsaturated aliphatic monocarboxylic acid anhydrides such as (meth)acrylic acid and oleic acid; Alicyclic monocarboxylic acid anhydrides such as cyclohexanecarboxylic acid and tetrahydrobenzoic acid; Aromatic monocarboxylic acid anhydrides such as benzoic acid and 4-methylbenzoic acid; Examples of dibasic carboxylic acid anhydrides include saturated aliphatic dicarboxylic acid anhydrides such as succinic anhydride and adipic acid, unsaturated aliphatic dicarboxylic acid anhydrides such as maleic anhydride and itaconic anhydride, alicyclic dicarboxylic acid anhydrides such as 1-cyclohexene-1,2-dicarboxylic acid anhydride, hexahydrophthalic anhydride and methyltetrahydrophthalic anhydride, and aromatic dicarboxylic acid anhydrides such as phthalic anhydride and naphthalic anhydride; Examples of the tri- or higher basic carboxylic acid anhydrides include polycarboxylic acid (anhydrides) such as trimellitic anhydride and pyromellitic anhydride. In the reaction of an acid anhydride, one or more of the following may be added as a catalyst: an acidic compound such as sulfuric acid, hydrochloric acid, or phosphoric acid; a Lewis acid (for example, a Lewis acid compound represented by MYn, where M represents a semimetallic element such as B, As, or Ge; a base metal element such as Al, Bi, or In; a transition metal element such as Ti, Zn, or Cu; or a lanthanoid element; n is an integer corresponding to the valence of M and represents 2 or 3; and Y represents a halogen atom, OAc, OCOCF3, ClO4, SbF6, PF6, or OSO2CF3(OTf)); or an alkaline compound such as triethylamine or pyridine.

[0058] The vinyl carboxylate may be selected from the group consisting of vinyl carboxylates represented by the following formula (1): R-COO-CH=CH2…Formula (1) Preferred are vinyl carboxylate esters represented by the formula: {wherein 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, and an aryl group having 6 to 24 carbon atoms.} More preferably, the vinyl carboxylate ester is at least one selected from the group consisting of vinyl acetate, vinyl propionate, vinyl butyrate, vinyl caproate, vinyl cyclohexanecarboxylate, vinyl caprylate, vinyl caprate, vinyl laurate, vinyl myristate, vinyl palmitate, vinyl stearate, vinyl pivalate, vinyl octylate, divinyl adipate, vinyl methacrylate, vinyl crotonate, vinyl pivalate, vinyl octylate, vinyl benzoate, and vinyl cinnamate. In the esterification reaction with a vinyl carboxylate, one or more catalysts selected from the group consisting of alkali metal hydroxides, alkaline earth metal hydroxides, alkali metal carbonates, alkaline earth metal carbonates, alkali metal hydrogencarbonates, primary to tertiary amines, quaternary ammonium salts, imidazole and derivatives thereof, pyridine and derivatives thereof, and alkoxides may be added.

[0059] Examples of alkali metal hydroxides and alkaline earth metal hydroxides include sodium hydroxide, potassium hydroxide, lithium hydroxide, calcium hydroxide, barium hydroxide, etc. Examples of 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, etc.

[0060] The primary to tertiary amines refer to primary amines, secondary amines, and tertiary amines, and specific examples include ethylenediamine, diethylamine, proline, N,N,N',N'-tetramethylethylenediamine, N,N,N',N'-tetramethyl-1,3-propanediamine, N,N,N',N'-tetramethyl-1,6-hexanediamine, tris(3-dimethylaminopropyl)amine, N,N-dimethylcyclohexylamine, and triethylamine.

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

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

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

[0064] The carboxylic acid may be 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 carboxylic acids include at least one selected from the group consisting of acetic acid, propionic acid, butyric acid, caproic acid, cyclohexanecarboxylic acid, caprylic acid, capric acid, lauric acid, myristic acid, palmitic acid, stearic acid, pivalic acid, methacrylic acid, crotonic acid, pivalic acid, 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, and particularly acetic acid, is preferred from the viewpoint of reaction efficiency. In the reaction of carboxylic acid, one or more of the following may be added as a catalyst: an acidic compound such as sulfuric acid, hydrochloric acid, or phosphoric acid; a Lewis acid (for example, a Lewis acid compound represented by MYn, where M represents a semimetallic element such as B, As, or Ge; a base metal element such as Al, Bi, or In; a transition metal element such as Ti, Zn, or Cu; or a lanthanoid element; n is an integer corresponding to the valence of M and represents 2 or 3; and Y represents a halogen atom, OAc, OCOCF3, ClO4, SbF6, PF6, or OSO2CF3(OTf)); or an alkaline compound such as triethylamine or pyridine.

[0067] Among these esterification reactants, 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 these, acetic anhydride and vinyl acetate are preferred 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 dried cellulose fiber body of the present disclosure tends to have good dispersibility in resins, but even if the cellulose fibers are unsubstituted or have a low degree of substitution, they can exhibit good dispersibility in resins. When the cellulose fibers in the dried cellulose fiber body are esterified cellulose fibers, the degree of acyl substitution (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 order to obtain esterified cellulose fibers and resin composites containing the same with a high thermal decomposition onset temperature. The DS is preferably 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, in order to obtain esterified cellulose fibers and resin composites containing the same with a high thermal decomposition onset temperature due to the remaining unmodified cellulose skeleton in the esterified cellulose fiber.

[0069] When the modifying group of the chemically modified cellulose fiber is an acyl group, the degree of acyl substitution (DS) can be calculated from the peak intensity ratio of the peak derived from the acyl group to the peak derived from the cellulose skeleton in the reflection infrared absorption spectrum of the esterified cellulose fiber. The peak of the absorption band of C=O derived from the acyl group is at 1730 cm. -1 The absorption band of CO based on the cellulose backbone appears at 1030 cm -1 The DS of esterified cellulose fibers was determined by creating a correlation graph between the DS obtained from solid-state NMR measurements of esterified cellulose fibers (described later) and the modification rate (IR index 1030), which is defined as the ratio of the peak intensity of the absorption band of C=O based on acyl groups to the peak intensity of the absorption band of CO in the cellulose backbone chain, and then calculating a calibration curve from the correlation graph. Degree of substitution DS = 4.13 × IR index (1030) It can be found by using

[0070] The method for calculating the DS of esterified cellulose fiber by solid-state NMR is as follows: 13 C solid-state NMR measurements were performed, and the chromaticity can be calculated using the following formula, which is the ratio of the chromatic intensity (Inf) of a signal assigned to one carbon atom derived from the modifying group to the total chromatic intensity (Inp) of signals assigned to carbons C1-C6 derived from the pyranose ring of cellulose, which appear in the range from 50 ppm to 110 ppm. DS=(Inf)×6 / (Inp) For example, when the modifying group is an acetyl group, the signal at 23 ppm assigned to -CH3 can be used. Use 13 The conditions for the C solid-state NMR measurement are, for example, as follows: Equipment:Bruker Biospin Avance500WB Frequency: 125.77MHz Measurement method: DD / MAS method Waiting time: 75 seconds NMR sample tube: 4mmφ Accumulation times: 640 times (approx. 14 hours) MAS: 14,500Hz Chemical shift reference: glycine (external reference: 176.03 ppm)

[0071] The DS heterogeneity ratio (DSs / DSt), defined as the ratio of the degree of modification (DSs) of the fiber surface to the degree of modification (DSt) of the entire fiber (which is synonymous with the above-mentioned degree of acyl substitution (DS)), of chemically modified cellulose fibers is preferably 1.05 or greater. The higher the DS heterogeneity ratio, the more pronounced the sheath-core-like heterogeneous structure (i.e., a structure in which the fiber surface is highly chemically modified while the fiber core retains a structure close to the original unmodified cellulose structure). This allows for the high tensile strength and dimensional stability inherent in cellulose, while improving the affinity with resins during composite formation and the dimensional stability of resin composites. The DS heterogeneity ratio is more preferably 1.1 or greater, or 1.2 or greater, or 1.3 or greater, or 1.5 or greater, or 2.0 or greater. From the viewpoint of ease of production of chemically modified cellulose fibers, 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 DSs value varies depending on the degree of modification of the esterified cellulose fiber, but, for example, is preferably 0.1 or more, more preferably 0.2 or more, even more preferably 0.3 or more, even more preferably 0.5 or more, and is preferably 3.0 or less, more preferably 2.5 or less, particularly preferably 2.0 or less, even more preferably 1.5 or less, especially 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 smaller the coefficient of variation (CV) of the DS heterogeneity of chemically modified cellulose fibers, the smaller the variability in various physical properties of the resin composite. The coefficient of variation is preferably 50% or less, or 40% or less, or 30% or less, or 20% or less. For example, the coefficient of variation can be further reduced in a method in which chemically modified cellulose fibers are obtained by defibrating raw cellulose fiber material and then chemically modifying it (i.e., a sequential method). On the other hand, the coefficient of variation can be increased in a method in which defibration and chemical modification of the raw cellulose fiber material are performed simultaneously (i.e., a simultaneous method). Although the mechanism of this action is unclear, it is thought that in the simultaneous method, chemical modification is more likely to proceed in the thin fibers produced in the early stages of defibration. Furthermore, when the hydrogen bonding between cellulose microfibrils is reduced by chemical modification, defibration proceeds further, resulting in an increase in the coefficient of variation of the DS heterogeneity.

[0073] The coefficient of variation (CV) of the DS heterogeneity ratio can be calculated using the following formula: 100 g of an aqueous dispersion of chemically modified cellulose fiber (solid content of 10 mass% or more) is collected, 10 g of each is freeze-pulverized, and the DS heterogeneity ratio is calculated from the DSt and DSs of 10 samples. The standard deviation (σ) and arithmetic mean (μ) of the DS heterogeneity ratios among the 10 samples are then used to calculate the coefficient of variation (CV) of the DS heterogeneity ratio using the following formula: DS heterogeneity ratio = DSs / DSt Coefficient of variation (%) = standard deviation σ / arithmetic mean μ × 100

[0074] The DSs is calculated as follows. Specifically, esterified cellulose fibers powdered by freeze-pulverization are placed on a 2.5 mm diameter dish-shaped sample stage, pressed down to flatten the surface, and measured by X-ray photoelectron spectroscopy (XPS). The XPS spectrum reflects the constituent elements and chemical bonding state of only the surface layer of the sample (typically about a few nm). Peak separation is performed on the obtained C1s spectrum, and the DSs can be calculated using the following formula: the integrated intensity (Ixf) of the peak assigned to one carbon atom derived from the modifying group relative to the integrated intensity (Ixp) of the peak assigned to carbons C2-C6 derived from the pyranose ring of cellulose (289 eV, C-C bond). DSs = (Ixf) × 5 / (Ixp) For example, if 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 used are, for example, as follows. Equipment used: ULVAC-Phi VersaProbe II Excitation source: mono. AlKα 15kV x 3.33mA Analysis size: approx. 200 μmφ Photoelectron extraction angle: 45° Capture Area Narrow scan: C 1s, O 1s Pass Energy: 23.5 eV

[0075] [Additional Ingredients] The dry cellulose fiber material may further contain additional components such as a dispersant, an antioxidant, a preservative, a thickener, and the like in addition to the cellulose fibers.

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

[0077] The melting point of the dispersant may be 80°C or lower or 70°C or lower, or -100°C or higher or -50°C or higher, so that the dispersant can coat the cellulose fibers more uniformly and disperse the cellulose fibers more uniformly in the resin. The number average molecular weight of the dispersant may be 1,000 or higher or 2,000 or higher, and 50,000 or lower or 20,000 or lower, so that the dispersant can coat the cellulose fibers more uniformly and disperse the cellulose fibers more uniformly in the resin. The number average molecular weight of the dispersant is a value determined using gel permeation chromatography in terms of standard polystyrene.

[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 that it dissolves at least 0.1 g in 100 g of water at 23°C. Furthermore, it is more preferable that the dispersant has both hydrophilic and hydrophobic segments (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 skeleton and functional groups composed of elements selected from carbon, hydrogen, oxygen, nitrogen, chlorine, sulfur, and phosphorus. As long as the molecule has the above structure, those in which an inorganic compound is chemically bonded to the functional group 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 also easily compatible with the resin. Therefore, it is preferable that the hydrophilic and hydrophobic segments exist within the same molecule of the dispersant.

[0079] The HLB value of the dispersant is preferably 0.1 or more and less than 8.0. The HLB value indicates the balance between the hydrophobicity and hydrophilicity of a surfactant, and ranges from 1 to 20, with smaller values indicating stronger hydrophobicity and larger values indicating stronger hydrophilicity. In the present disclosure, the HLB value is a value calculated using the following Griffin method formula. In the formula below, the "sum of formula weights of hydrophilic groups / molecular weight" refers to the mass % of the hydrophilic groups. Equation 1) Griffin method: HLB value = 20 x (sum of formula weights of hydrophilic groups / molecular weight)

[0080] From the viewpoint of easy solubility in water, the lower limit of the HLB value of the dispersant is preferably 0.1, more preferably 0.2, and most preferably 1. From the viewpoint of uniform dispersibility of cellulose fibers in the resin, the upper limit of the HLB value is preferably less than 8.0, more preferably 7.5, and most preferably 7.

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

[0082] Examples of hydrophobic segments include segments having alkylene oxide units with 3 or more carbon atoms (for example, PPG blocks), and segments containing 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)methandodecane, and other polycondensates of organic dicarboxylic acids having 4 to 12 carbon atoms and organic diamines having 2 to 13 carbon atoms, and polycondensates of ω-amino acids (for example, ω-aminoundecanoic acid) (for example, polyundecaneamide (1 Examples of the polymerizable compound include amino acid lactams including ring-opening polymerization products of lactams such as polycapramide (nylon 6), which is a ring-opening polymerization product of ε-aminocaprolactam, and polylauric lactam (nylon 12), which is a ring-opening polymerization product of ε-aminolaurolactam; 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, and 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 may have a graft copolymer structure and / or a block copolymer structure. These structures may be one type alone or two or more types. When two or more types are used, the dispersant may be a polymer alloy. Furthermore, the dispersant may be a partially modified or terminally modified (acid-modified) copolymer.

[0085] The structure of the dispersant is not particularly limited, but examples thereof include AB block copolymers, ABA block copolymers, BAB block copolymers, ABAB block copolymers, ABABA block copolymers, BABAB block copolymers, tri-branched copolymers containing A and B, tetra-branched copolymers containing A and B, star copolymers containing A and B, monocyclic copolymers containing A and B, polycyclic copolymers containing A and B, and cage copolymers containing A and B, where A is the hydrophilic segment and B is the hydrophobic segment.

[0086] The structure of the dispersant is preferably an AB block copolymer, an ABA triblock copolymer, a tri-branched copolymer containing A and B, or a tetra-branched copolymer containing A and B, and more preferably an ABA triblock copolymer, a tri-branched structure (i.e., a tri-branched copolymer containing A and B), or a tetra-branched structure (i.e., a tetra-branched copolymer containing A and B). In order to ensure good affinity with cellulose fibers, the dispersant desirably has the above structure.

[0087] Suitable examples of dispersants include copolymers (e.g., block copolymers of propylene oxide and ethylene oxide, block copolymers of tetrahydrofuran and ethylene oxide) obtained by using one or more compounds that provide hydrophilic segments (e.g., polyethylene glycol) and one or more compounds that provide hydrophobic segments (e.g., polypropylene glycol, poly(tetramethylene ether) glycol (PTMEG), polybutadiene diol, etc.). The dispersants may be used alone or in combination of two or more. When two or more types are used in combination, they may be used as a polymer alloy. Modified versions of the above copolymers (e.g., 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 resistance) and mechanical properties, copolymers of polyethylene glycol and polypropylene glycol, copolymers of polyethylene glycol and poly(tetramethylene ether) glycol (PTMEG), and mixtures thereof are preferred, and copolymers of polyethylene glycol and polypropylene glycol are more preferred 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 increased, a phenomenon occurs in which the transparent or translucent solution becomes cloudy at a certain temperature (this temperature is called the cloud point). That is, when an aqueous solution that is transparent or translucent at low temperatures is heated, the solubility of the nonionic surfactant drops sharply at a certain temperature, and the previously dissolved surfactant aggregates, becomes cloudy, and separates from the water. This is thought to be because the nonionic surfactant loses its hydration ability at high temperatures (the hydrogen bonds between the polyether chain and water are broken, causing a sharp drop in solubility in water). The cloud point tends to be lower as the polyether chain becomes longer. Because dispersants can dissolve in water in any proportion at temperatures below the cloud point, the cloud point serves as a measure of the hydrophilicity of the dispersant.

[0090] The cloud point of a dispersant can be measured using the following method. Using a tuning fork vibration viscometer (e.g., the SV-10A manufactured by A&D Co., Ltd.), aqueous solutions of the dispersant are adjusted to 0.5%, 1.0%, and 5% by mass, and measurements are taken at temperatures ranging from 0 to 100°C. The point at which the solution shows an inflection point (the point at which the viscosity increases or the solution becomes cloudy) at each concentration is taken as the cloud point.

[0091] From the viewpoint of ease of handling, the lower limit of the cloud point of the dispersant is preferably 10° C., more preferably 20° C., and most preferably 30° C. The upper limit of the cloud point is not particularly limited, but is preferably 120° C., more preferably 110° C., even more preferably 100° C., and most preferably 60° C. To ensure good affinity with cellulose fibers, it is desirable that the cloud point of the dispersant be within the above-mentioned range.

[0092] The dispersant preferably has a solubility parameter (SP value) of 7.25 or more. When the dispersant has an SP value in this range, the dispersibility of the cellulose fibers in the resin is improved.

[0093] According to Foders's paper (RF Foders: Polymer Engineering & Science, vol. 12 (10), pp. 2359-2370 (1974)), the SP value depends on both the cohesive energy density and the molar molecular weight of the substance, and these are thought to depend on the type and number of substituents of the substance. According to Ueda et al.'s paper (Paint Research, No. 152, October 2010), the SP values (Cal / Cm) of existing major solvents shown in the examples below are 3 ) 1 / 2 has been released.

[0094] The SP value of a dispersant can be experimentally 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 dispersant is dissolved in various solvents (10 mL) with different SP values at room temperature for 1 hour under stirring with a stirrer, it can be determined whether the entire amount dissolves. For example, if a dispersant is soluble in diethyl ether, the SP value of that dispersant will be 7.25 or higher.

[0095] The dispersant (especially the amphiphilic molecule) preferably has a boiling point higher than that of water, and more preferably a boiling point higher than the melting point of the resin from the viewpoint of uniformly dispersing the cellulose fibers in the resin during melt-kneading. Note that a boiling point higher than that of water refers to a boiling point higher than the boiling point of water at each pressure on its vapor pressure curve (for example, 100°C at 1 atmosphere).

[0096] By selecting a dispersant that has a boiling point higher than that of water, for example, in a process of obtaining dried cellulose fiber by drying a slurry containing water as a liquid medium in the presence of the dispersant, the water and the dispersant are replaced as the water evaporates, and the dispersant becomes present on the surface of the cellulose fiber, thereby achieving the effect of significantly suppressing the aggregation of cellulose fiber.

[0097] The method of adding the dispersant is not limited. A method for producing a dried cellulose fiber body by mixing a dispersant with cellulose fibers after a drying step, A method for producing a dried cellulose fiber body, which comprises adding a dispersant to a slurry in which cellulose fibers are dispersed in a liquid medium, and then drying the slurry to obtain a dried cellulose fiber body; In the production of a resin composite, a resin, a dried cellulose fiber or a redispersion obtained by dispersing the dried cellulose fiber in a liquid medium, and a dispersant are mixed in advance, melt-kneaded, and then molded; In the production of a resin composite, a dispersant is added to the resin in advance, and if necessary, pre-mixing is performed. After that, dried cellulose fiber or a re-dispersion obtained by dispersing the dried cellulose fiber in a liquid medium is added, and the mixture is melt-kneaded and molded; etc.

[0098] The amount of dispersant is preferably 5 to 100 parts by mass per 100 parts by mass of cellulose fibers in order to uniformly disperse the cellulose fibers in the resin composite, more preferably 10 to 70 parts by mass, and most preferably 20 to 50 parts by mass.

[0099] In one embodiment, 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, respectively.

[0100] The amount of dispersant in a resin composite can be easily confirmed by methods commonly known to those skilled in the art. While the confirmation method is not limited, the following method can be exemplified. Using broken fragments of a resin composite, the fragments are dissolved in a solvent that dissolves the resin, and then soluble fraction 1 (resin and dispersant) and insoluble fraction 1 (cellulose fiber and dispersant) are separated. Soluble fraction 1 is reprecipitated in a solvent that dissolves the dispersant but not the resin, and separated into insoluble fraction 2 (resin) and soluble fraction 2 (dispersant). Furthermore, insoluble fraction 1 is dissolved in a solvent that dissolves the dispersant, and then separated into soluble fraction 3 (dispersant) and insoluble fraction 3 (cellulose fiber). The dispersant can be quantified by concentrating soluble fractions 2 and 3 (by drying, air drying, vacuum drying, etc.). The concentrated dispersant can be identified and its molecular weight measured using the method described above.

[0101] <Method for producing dried cellulose fiber body> Another aspect of the present invention provides a method for producing the dried cellulose fiber body of the present disclosure, the method comprising: a slurry preparation step of preparing a slurry containing cellulose fibers and a liquid medium; and a drying step of drying the slurry to form the dried cellulose fiber body.

[0102] (Slurry preparation process) In this step, a slurry containing cellulose fibers and a liquid medium is prepared. The aforementioned water-miscible organic solvents can be suitably used as the liquid medium. The concentration of cellulose fibers 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, from the viewpoint of process efficiency in the subsequent drying step. To avoid excessive increases in the viscosity of the slurry and solidification due to aggregation, and to maintain good handleability, the concentration 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, cellulose nanofibers are often produced in a dilute dispersion. The cellulose fiber concentration in the slurry may be adjusted to the preferred range by concentrating such a dilute dispersion. Concentration can be achieved by suction filtration, pressure filtration, centrifugal deliquoring, heating, or other methods.

[0103] (drying process) In this step, the slurry is dried under controlled drying conditions to form a dried cellulose fiber body. When the dried cellulose fiber body contains cellulose fibers and additional components, the additional components may be added before, during, and / or after the drying of the cellulose fiber slurry. Various mixers can be used for drying, but a mechanically agitated mixer / granulator is preferred because it allows drying at a relatively high shear rate. In one embodiment, drying is performed by a batch process using a mechanically agitated mixer / granulator. Commercially available mechanically agitated mixer / granulators include devices equipped with an agitating blade and a chopper blade inside the casing, such as a Lödige mixer (e.g., manufactured by Matsubo Corporation) and a high-speed vacuum dryer (e.g., manufactured by Earth Technica Corporation), and fluidized bed mixers such as a Henschel mixer (FM mixer) (e.g., manufactured by Nippon Coke & Engineering Co., Ltd.), equipped with multiple agitating blades (typically upper and lower blades) inside the casing. Among the drying conditions, controlling the shear rate, drying rate, drying temperature, and / or pressure (degree of vacuum) is useful for producing the dried cellulose fiber body of the present disclosure.

[0104] For example, when the mechanical agitation mixer granulator is the aforementioned Lödige mixer or high-speed vacuum dryer, the slurry is dried under agitation to form particles, and the particles are then chopped and crushed to form a dried product of the desired particle size. The granulator typically includes a vertical or horizontal can body with a material inlet at the top, a combination of a low-speed agitator blade located at the bottom of the can body and a high-speed chopper blade located on the side of the can body, a pressure reduction mechanism, and, optionally, a temperature control mechanism. When a measured amount of slurry is introduced into the can body through the material inlet, the centrifugal force and upward driving force of the agitator blade cause the slurry to convect within the can body and be dried under reduced pressure to form particles. The particles move within the can body, collide with the chopper blade and are crushed, then return to the vicinity of the agitator blade and are stirred again to increase their particle size. Repeated agitation and chopper crushing of the particles in this way allows the production of a dried cellulose fiber body with a uniform particle size (i.e., with a small particle size variation).

[0105] Furthermore, when the mechanical stirring mixer granulator is the Henschel mixer described above, a dried product of the desired particle size can be formed by combining the upper and lower blades of the mixer. A Henschel mixer typically comprises a vertical can body having a material supply port at the top and a material discharge port at the side, a lower blade disposed at the bottom of the can body and an upper blade disposed above the lower blade, a pressure reducing mechanism, and optionally a temperature control mechanism. When a measured amount of slurry is introduced into the can body through the material supply port, the slurry is stirred and rises by the lower blade, and is further subjected to a strong shear force by the upper blade, whereby it is dried and granulated while being stirred.

[0106] In the drying process, the shear rate is 100 s -1 or more, or 500 seconds -1 or more, or 750 seconds -1 or more, or 1000 seconds -1 may be greater than or equal to 20,000 seconds -1 or less, or 15000 seconds -1 or less, or 12500 seconds -1 or less, or 10,000 seconds -1 The shear rate can be calculated using the formula: shear rate (sec -1 ) = Maximum peripheral speed of rotating blades (unit: m / sec) / Clearance (unit: m). Maximum peripheral speed is calculated from the blade diameter and rotation speed, and clearance is the shortest distance from the blade to the tank wall (stationary surface). In the case of equipment with multiple rotating blades, the calculation is performed using the rotating blade that generates the maximum shear rate. The shear rate in the drying process using equipment that does not substantially have mechanisms such as rotating blades and does not generate shear deformation on the dried material is 0 sec. -1The shear rate is calculated as follows. The shear rate can be controlled by the rotation speed of the stirring blades, etc., depending on the configuration of the mixer. Cellulose fibers are extremely prone to agglomeration in a dry state, and therefore in a typical dried cellulose fiber body, the cellulose fibers are tightly agglomerated together, and even if the dried body is redispersed in a resin, it is not easily redispersed. However, by drying the slurry by stirring at a relatively high shear rate, the flow properties and bulk density of the dried cellulose fiber body can be controlled within an appropriate range, and therefore a dried cellulose fiber body with a relatively large particle size, an appropriate bulk density, and excellent dispersibility in a resin can be formed.

[0107] Conditions under which a shear rate within the above range can be imparted to the slurry include, for example, when using a mixer equipped with a stirring blade and a chopper blade, setting the rotational conditions (circumferential speed) of the rotating blades to 0.5 m / sec or more, or 0.7 m / sec or more, or 1 m / sec or more, or 3 m / sec or more, or 6 m / sec or more, and 100 m / sec or less, or 70 m / sec or less, or 50 m / sec or less, or 40 m / sec or less. The peripheral speed does not need to be constant throughout the drying process and may be varied within a preferred range.

[0108] The rotation speed of the chopper blades may be, for example, 100 rpm or more, or 200 rpm or more, or 500 rpm or more, or 1000 rpm or more, and may be, for example, 10000 rpm or less, or 7000 rpm or less, or 5000 rpm or less, or 4000 rpm or less.

[0109] On the other hand, for example, when a mixer equipped with upper and lower blades as stirring blades is used, the rotation speed of the blades is set to 10 rpm or more, or 100 rpm or more, or 300 rpm or more, and 3000 rpm or less, or 2000 rpm or less, or 1500 rpm or less. The rotation speed does not need to be constant throughout the drying process and may be changed within a preferred range.

[0110] The drying rate, which is the amount (parts by mass) of liquid medium desorbed per minute per 100 parts by mass of the slurry, may be, for example, 0.01% / min or more, or 0.05% / min or more, or 0.1% / min or more, from the viewpoints of drying efficiency and appropriately agglomerating the cellulose fibers to form a granular dried cellulose fiber body of a desired particle size, and may be 10% / min or less, or 5% / min or less, or 2% / min or less, from the viewpoints of avoiding excessive pulverization of the dried cellulose fiber body due to rapid drying of the slurry. The drying rate is calculated by the following formula: Drying rate (% / min) = (slurry moisture content (mass%) at the start of drying - moisture content (mass%) of dried material at the end of drying) / time required from the start of drying to the end of drying (min) (i.e., the average value throughout the drying process). Here, the start of drying refers to the time when the slurry or cake to be dried is supplied to the drying device and the process of drying at the target drying temperature, degree of vacuum, and shear rate begins; the time for premixing under conditions 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. The end point of drying refers to the point at which the moisture content first drops to 7% by mass or less when sampling is performed at intervals of at most 10 minutes from the start of drying. 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 from the heated air volume 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 screw pitch number.

[0111] 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 agglomerating the cellulose fibers to form a granular cellulose fiber dry body of a desired particle size, and may be, for example, 160°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 reducing the likelihood of thermal degradation of the cellulose fibers and additional components and avoiding excessive pulverization of the cellulose fiber dry body due to rapid drying of the slurry. 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-regulating jacket of the drying device, the surface temperature of the heating cylinder, or the temperature of the hot air.

[0112] The degree of vacuum may be -1 kPa or less, or -10 kPa or less, or -20 kPa or less, or -30 kPa or less, or -40 kPa or less, or -50 kPa or less from the viewpoints of drying efficiency and appropriately agglomerating the cellulose fibers to form a granular dried cellulose fiber body of a desired particle size, and may be -100 kPa or more, or -95 kPa or more, or -90 kPa or more from the viewpoint of avoiding excessive pulverization of the dried cellulose fiber body due to rapid drying of the slurry. The pressure may be adjusted by fully operating a vacuum pump with appropriate exhaust capacity, or by intentionally introducing air and / or an inert gas using a vacuum regulator, leak valve, or the like. When introducing air and / or an inert gas, it is preferable to provide an intake section in the dryer body or upstream of the dryer body, because this allows for efficient exhaust of the medium vapor.

[0113] In the drying step, the residence time of the slurry at a temperature of 40° C. to 100° C. may be set to preferably 30 to 600 minutes, 45 to 300 minutes, or 60 to 200 minutes. Drying under such conditions allows the cellulose fibers to be appropriately aggregated, and a granular dried cellulose fiber material having a desired particle size is successfully produced.

[0114] <Method for manufacturing resin composite> One aspect of the present invention provides a method for producing a resin composite containing cellulose fibers and a resin, the method comprising mixing the dried cellulose fiber material of the present disclosure as described above with a resin.

[0115] <Resin> The resin may be a thermoplastic resin, a thermosetting resin, or a photocurable resin. The resin may be an elastomer. From the viewpoints of moldability and productivity, a thermoplastic resin is more preferred.

[0116] (thermoplastic resin) When the resin is a thermoplastic resin, the melting point of the thermoplastic resin may be appropriately selected depending on the application of the resin composite, etc. Examples of the melting point of the thermoplastic resin include 150°C to 190°C or 160°C to 180°C for resins with relatively low melting points (such as polyolefin resins), and 220°C to 350°C or 230°C to 320°C for resins with relatively high melting points (such as polyamide resins).

[0117] The thermoplastic resin may preferably be at least one selected from the group consisting of polyolefin-based resins, polyacetate-based resins, polycarbonate-based resins, polyamide-based resins, polyester-based resins, polyphenylene ether-based resins, and acrylic-based resins.

[0118] The polyolefin resin preferred as the thermoplastic resin is a polymer obtained by polymerizing olefins (e.g., α-olefins) and / or alkenes as monomer units. Specific examples of the polyolefin resin include ethylene (co)polymers such as low-density polyethylene (e.g., linear low-density polyethylene), high-density polyethylene, ultra-low-density polyethylene, and ultra-high-molecular-weight polyethylene, polypropylene (co)polymers such as polypropylene, ethylene-propylene copolymer, and ethylene-propylene-diene copolymer, and copolymers of ethylene and α-olefins such as ethylene-acrylic acid copolymer, ethylene-methyl methacrylate copolymer, and ethylene-glycidyl methacrylate copolymer.

[0119] The most preferred polyolefin resin here is polypropylene. In particular, polypropylene having a melt mass-flow rate (MFR) of 3 g / 10 min or more and 30 g / 10 min or less, measured at 230°C under a load of 21.2 N in accordance with ISO 1133, is preferred. The lower limit of the MFR is more preferably 5 g / 10 min, even more preferably 6 g / 10 min, and most preferably 8 g / 10 min. The upper limit is more preferably 25 g / 10 min, even more preferably 20 g / 10 min, and most preferably 18 g / 10 min. It is desirable that the MFR not exceed the upper limit from the viewpoint of improving the toughness of the resin composite, and from the viewpoint of the fluidity of the resin composite, it is desirable that the MFR not exceed the lower limit.

[0120] In addition, acid-modified polyolefin resins can also be suitably used to enhance affinity with cellulose fibers. Examples of acids used for acid modification include mono- or polycarboxylic acids, such as maleic acid, fumaric acid, succinic acid, phthalic acid, and their anhydrides, as well as citric acid. Maleic acid or its anhydride is particularly preferred because it facilitates increasing the modification rate. While there are no particular limitations on the modification method, a common method involves heating a polyolefin resin above its melting point in the presence or absence of a peroxide and melt-kneading it. While all of the polyolefin resins listed above can be used as the acid-modified polyolefin resin, polypropylene is particularly suitable. While the acid-modified polypropylene resin may be used alone, it is more preferable to use it in combination with an unmodified polypropylene resin to adjust the modification rate of the entire resin. In this case, the ratio of the acid-modified polypropylene resin to all polypropylene resins is preferably 0.5% by mass to 50% by mass. A more preferred lower limit is 1 mass%, 2 mass%, 3 mass%, 4 mass%, or 5 mass%. A more preferred upper limit is 45 mass%, 40 mass%, 35 mass%, 30 mass%, or 20 mass%. To maintain the interfacial strength between the resin and the cellulose fibers, a content equal to or greater than the lower limit is preferred, while to maintain the ductility of the resin, a content equal to or less than the upper limit is preferred.

[0121] The melt mass-flow rate (MFR) of the acid-modified polypropylene resin, measured in accordance with ISO 1133 at 230°C under a load of 21.2 N, is preferably 50 g / 10 min or more, 100 g / 10 min or more, 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. There is no particular upper limit, but it is preferably 500 g / 10 min, from the viewpoint of maintaining mechanical strength.

[0122] Preferred polyamide resins as the thermoplastic resin include polyamides obtained by polycondensation of lactams (e.g., polyamide 6, polyamide 11, polyamide 12, etc.); diamines (e.g., 1,6-hexanediamine, 2-methyl-1,5-pentanediamine, 1,7-heptanediamine, 2-methyl-1-6-hexanediamine, 1,8-octanediamine, 2-methyl-1,7-heptanediamine, 1,9-nonanediamine, 2-methyl-1,8-octanediamine, 1,10-decanediamine, 1,11-undecanediamine, 1,12-dodecanediamine, m-xylylenediamine, etc.) and dicarboxylic acids (e.g., butanedioic acid, pentanedioic acid, hexanedioic acid, etc.) , 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.) (for example, 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 in which these are copolymerized (for example, polyamide 6,T / 6,I, etc.).

[0123] Among these polyamide resins, aliphatic polyamides such as polyamide 6, polyamide 11, polyamide 12, polyamide 6,6, polyamide 6,10, polyamide 6,11, and polyamide 6,12, and alicyclic polyamides such as polyamide 6,C and polyamide 2M5,C are more preferred.

[0124] 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, and from the viewpoint of ease of production of the resin composite, the melting point is preferably 350°C or lower, or 320°C or lower, or 300°C or lower.

[0125] The terminal carboxyl group concentration of the polyamide resin is not particularly limited, but is preferably 20 μmol / g or more, or 30 μmol / g or more, and preferably 150 μmol / g or less, or 100 μmol / g or less, or 80 μmol / g or less.

[0126] In the polyamide resin, the ratio of carboxyl end groups to all end groups ([COOH] / [total end groups]) is preferably 0.30 or more, or 0.35 or more, or 0.40 or more, or 0.45 or more, from the viewpoint of dispersibility of cellulose fibers in the resin composite, and is 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.

[0127] The terminal group concentration of the polyamide resin can be adjusted by a known method, such as adding a terminal modifier (e.g., a diamine compound, a monoamine compound, a dicarboxylic acid compound, a monocarboxylic acid compound, an acid anhydride, a monoisocyanate, a monoacid halide, a monoester, a monoalcohol, etc.) that reacts with the terminal groups to the polymerization solution during polyamide polymerization so as to achieve a predetermined terminal group concentration.

[0128] Examples of terminal modifiers that react with terminal amino groups include aliphatic monocarboxylic acids such as acetic acid, propionic acid, butyric acid, valeric acid, caproic acid, caprylic acid, lauric acid, tridecanoic acid, myristic acid, palmitic acid, stearic acid, pivalic acid, and isobutyric acid; alicyclic monocarboxylic acids such as cyclohexanecarboxylic acid; aromatic monocarboxylic acids such as benzoic acid, toluic acid, α-naphthalenecarboxylic acid, β-naphthalenecarboxylic acid, methylnaphthalenecarboxylic acid, and phenylacetic acid; and mixtures of any of these. Among these, from the standpoints of reactivity, stability of the blocked terminals, cost, and the like, one or more terminal modifiers selected from the group consisting of acetic acid, propionic acid, butyric acid, valeric acid, caproic acid, caprylic acid, lauric acid, tridecanoic acid, myristic acid, palmitic acid, stearic acid, and benzoic acid are preferred, with acetic acid being most preferred.

[0129] Examples of terminal modifiers that react with terminal carboxyl groups include aliphatic monoamines such as methylamine, ethylamine, propylamine, butylamine, hexylamine, octylamine, decylamine, stearylamine, dimethylamine, diethylamine, dipropylamine, and dibutylamine; alicyclic monoamines such as cyclohexylamine and dicyclohexylamine; aromatic monoamines such as aniline, toluidine, diphenylamine, and naphthylamine, and any mixtures thereof. Among these, one or more terminal modifiers selected from the group consisting of butylamine, hexylamine, octylamine, decylamine, stearylamine, cyclohexylamine, and aniline are preferred in terms of reactivity, boiling point, stability of the blocked terminals, cost, and the like.

[0130] The concentrations of amino end groups and carboxyl end groups of the polyamide resin are 1 The NMR spectroscopy can be performed by 1H-NMR, using the integrated values of characteristic signals corresponding to each terminal group. This method is preferred in terms of accuracy and simplicity. More specifically, the method described in JP-A-7-228775 is used, using deuterated trifluoroacetic acid as the measurement solvent, and the number of scans is recommended to be 300 or more.

[0131] The intrinsic viscosity [η] of a polyamide resin measured in concentrated sulfuric acid at 30°C 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 viewpoint of achieving good in-mold fluidity and good appearance of molded pieces when, for example, injection molding a resin composite. In the present disclosure, "intrinsic viscosity" is synonymous with the viscosity generally referred to as intrinsic viscosity. Intrinsic viscosity is determined by measuring the ηsp / c of several measurement solvents of different concentrations in 96% concentrated sulfuric acid at 30°C, deriving a relationship 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). From the viewpoint of accuracy, it is desirable that the concentrations in the measurement solvents having different concentrations be at least four points (for example, 0.05 g / dL, 0.1 g / dL, 0.2 g / dL, and 0.4 g / dL).

[0132] Preferred polyester resins as the thermoplastic resin include 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. Among these, PET, PBS, PBSA, PBT, and PEN are more preferred, and PBS, PBSA, and PBT are particularly preferred.

[0133] The terminal groups of the polyester resin can be varied as desired by adjusting the monomer ratio during polymerization, the presence or absence of addition of a terminal stabilizer, and the amount thereof, etc. The ratio of carboxyl terminal groups to all terminal groups of the polyester resin ([COOH] / [total terminal groups]) is preferably 0.30 or more, or 0.35 or more, or 0.40 or more, or 0.45 or more, from the viewpoint of dispersibility of cellulose fibers in the resin composite, and is 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.

[0134] Preferred polyacetal resins as thermoplastic resins are homopolyacetals derived from formaldehyde and copolyacetals containing trioxane as the main monomer and 1,3-dioxolane as a 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 (e.g., 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 and molding, and is 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.

[0135] (thermosetting resin) Examples of thermosetting resins include bisphenol type epoxy resins such as bisphenol A type epoxy resin, bisphenol F type epoxy resin, bisphenol S type epoxy resin, bisphenol E type epoxy resin, bisphenol M type epoxy resin, bisphenol P type epoxy resin, and bisphenol Z type epoxy resin; novolac type epoxy resins such as bisphenol A novolac type epoxy resin, phenol novolac type epoxy resin, and cresol novolac epoxy resin; biphenyl type epoxy resin, biphenyl aralkyl type epoxy resin, aryl alkylene type epoxy resin, tetraphenylolethane type epoxy resin, naphthalene type epoxy resin, anthracene type epoxy resin, phenoxy type epoxy resin, dicyclopentadiene type epoxy resin, norbornene type epoxy resin, adamantane type epoxy resin, fluorene type epoxy resin, glycidyl methacrylate copolymer epoxy resin, cyclohexylmaleimide and glycidyl methacrylate copolymer epoxy resin, 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 phenolic resins such as phenol novolac resin, cresol novolac resin, and bisphenol A novolac resin, unmodified resol phenolic resin, paulownia Examples of the resin include phenolic resins such as resol-type phenolic resins, such as oil-modified resol phenolic resins modified with oil, linseed oil, walnut oil, etc.; triazine ring-containing resins such as phenoxy resin, 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, and thermosetting polyimide.

[0136] (light curing resin) Examples of photocurable resins include (meth)acrylate resins, vinyl resins, and epoxy resins. These are generally classified according to their reaction mechanism into radical reaction types in which monomers react with radicals generated by light, and cationic reaction types in which monomers undergo cationic polymerization. Radical reaction type monomers include (meth)acrylate compounds and vinyl compounds (e.g., certain vinyl ethers). Cationic reaction types include epoxy compounds and certain vinyl ethers. For example, epoxy compounds that can be used as cationic reaction types can be monomers for both thermosetting resins and photocurable resins.

[0137] The (meth)acrylate compound is a compound having one or more (meth)acrylate groups in the molecule. Examples of the (meth)acrylate compound include monofunctional (meth)acrylates, polyfunctional (meth)acrylates, epoxy acrylates, polyester acrylates, and urethane acrylates.

[0138] Examples of vinyl compounds include vinyl ether, styrene, and styrene derivatives. Examples of vinyl ethers include ethyl vinyl ether, propyl vinyl ether, hydroxyethyl vinyl ether, and ethylene glycol divinyl ether. Examples of styrene derivatives include methylstyrene and ethylstyrene. Other examples of vinyl compounds include triallyl isocyanurate and trimethallyl isocyanurate.

[0139] A so-called reactive oligomer may be used as a raw material for the photocurable resin. Examples of the reactive oligomer include an oligomer having any combination selected from a (meth)acrylate group, an epoxy group, a urethane bond, and an ester bond in the same molecule, such as a urethane acrylate having a (meth)acrylate group and a urethane bond in the same molecule, a polyester acrylate having a (meth)acrylate group and an ester bond in the same molecule, and an epoxy acrylate derived from an epoxy resin and having an epoxy group and a (meth)acrylate group in the same molecule.

[0140] (Elastomer) Examples of elastomers (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, deproteinized natural rubber, etc.), ethylene-propylene copolymer rubber, acrylic rubber, epichlorohydrin rubber, polysulfide rubber, silicone rubber, fluororubber, and urethane rubber.

[0141] When the resin is a thermoplastic resin, a resin composite can be produced by melt-kneading cellulose fibers (which may be in the form of a dried cellulose fiber of the present disclosure or a redispersion obtained by dispersing the cellulose fibers in a dispersion medium) with the thermoplastic resin. - A method in which a resin monomer and cellulose fiber are mixed, a polymerization reaction is carried out, the resulting resin composite is extruded into a strand shape, and the extruded strand is cooled and solidified in a water bath to obtain a pellet-shaped molded product; - A method in which a mixture of resin and cellulose fiber 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 product; - A method in which a mixture of resin and cellulose fiber is melt-kneaded using a single-screw or twin-screw extruder, extruded into a rod-shaped or tubular form, and cooled to obtain an extrusion molded product; - A method in which a mixture of resin and cellulose fiber is melt-kneaded using a single-screw or twin-screw extruder, and extruded through a T-die to obtain a sheet or film-like molded product; In a preferred embodiment, a mixture of resin and cellulose fibers is melt-kneaded using a single-screw or twin-screw extruder, extruded into strands, and cooled and solidified in a water bath to obtain pellet-shaped molded products. A specific example of a method for melt-kneading a resin and cellulose fibers is a method in which a resin and cellulose fibers transported in a desired ratio are mixed together and then melt-kneaded.

[0142] For melt kneading, an extruder such as a single-screw extruder or a twin-screw extruder can be used, but a twin-screw extruder is preferred in terms of controlling the dispersibility of the cellulose fiber. The ratio L / D, obtained by dividing the cylinder length (L) of the extruder by the screw diameter (D), is preferably 30 or more, and particularly preferably 40 or more. The screw rotation speed during kneading is preferably in the range of 50 to 800 rpm, and more preferably in the range of 100 to 600 rpm.

[0143] Each screw in the cylinder of the extruder is optimized by combining a conveying screw with an elliptical two-wing screw shape, a kneading element called a kneading disk, and the like.

[0144] When the resin is a thermoplastic resin, the minimum processing temperatures recommended by thermoplastic resin suppliers are 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 temperature setting is preferably in a range 20°C higher than these recommended minimum processing temperatures. By setting the mixing temperature within this temperature range, the cellulose fiber and resin can be mixed uniformly.

[0145] Resin composites containing a thermoplastic resin as the resin can be provided in various shapes. Specific examples include resin pellets, sheets, fibers, plates, and rods. Resin pellets are preferred for their ease of post-processing and transportation. Preferred pellet shapes include round, oval, and cylindrical shapes, which vary depending on the cutting method used during extrusion. Pellets cut using a cutting method known as underwater cutting are often round, while pellets cut using a cutting method known as hot cutting are often round or oval. Pellets cut using a cutting method known as strand cutting are often cylindrical. For round pellets, the preferred size is a pellet diameter of 1 mm or more and 3 mm or less. For cylindrical pellets, the preferred diameter is 1 mm or more and 3 mm or less, and the preferred length is 2 mm or more and 10 mm or less. The above diameter and length are preferably set to be above the lower limit from the viewpoint of operational stability during extrusion, and below the upper limit from the viewpoint of ease of insertion into a molding machine during post-processing.

[0146] Resin composites containing a thermoplastic resin as the resin can be used as various resin molded articles. There are no particular limitations on the manufacturing method of the resin molded article, and any manufacturing method can be used, including injection molding, extrusion molding, blow molding, inflation molding, and foam molding. Among these, injection molding is most preferred from the standpoints of design and cost.

[0147] When the resin is a thermosetting resin or a photocurable resin, the resin composite can be produced by, for example, a method of thoroughly dispersing cellulose fibers in a resin solution or resin powder dispersion and drying the resulting mixture, a method of thoroughly dispersing cellulose fibers in a resin monomer liquid and polymerizing the resulting mixture by heat, UV irradiation, a polymerization initiator, etc., a method of thoroughly impregnating a dried cellulose fiber body with a resin solution or resin powder dispersion and drying the resulting mixture, or a method of thoroughly impregnating a dried cellulose fiber body with a resin monomer liquid and polymerizing the resulting mixture by heat, UV irradiation, a polymerization initiator, etc. During curing, various polymerization initiators, curing agents, curing accelerators, polymerization inhibitors, etc. can be blended.

[0148] When the resin is a thermosetting resin or a photocurable resin, a method may be used in which an uncured or semi-cured sheet called a prepreg is prepared, the prepreg is formed into a single layer or a laminate, and the resin is cured and molded by applying pressure and heat. Examples of the pressure and heat application method include press molding, autoclave molding, bagging molding, wrapping tape molding, and internal pressure molding.

[0149] When the resin is a photocurable resin, the resin composite can be produced using various curing methods using active energy rays.

[0150] When the resin is an elastomer, a resin composite can be produced by, for example, a method of dry-kneading dried cellulose fibers with raw rubber, or a method of dispersing or dissolving cellulose fibers and raw rubber in a dispersion medium, followed by drying and mixing. Mixing using a homogenizer is preferred because it applies high shear force and pressure to promote dispersion. However, other methods, such as a propeller stirrer, rotary stirrer, electromagnetic stirrer, or manual stirring, can also be used. The resin composite containing the elastomer can be molded using a desired molding method, such as mold molding, injection molding, extrusion molding, blow molding, or foam molding, to obtain an unvulcanized molded product in the desired shape, such as a sheet, pellet, or powder. The unvulcanized molded product can be vulcanized, as needed, by heat treatment or the like, to obtain a resin composite.

[0151] A resin composite containing a thermoplastic resin or elastomer may be partially (e.g., several locations) melted by heat treatment and then bonded to, for example, a resin or metal substrate. The resin composite may be a coating applied to a resin or metal substrate, or may form a laminate with the substrate. Sheet-, film-, or fiber-shaped resin composites may be subjected to secondary processing such as annealing, etching, corona treatment, plasma treatment, embossing, cutting, and surface polishing.

[0152] In the resin composite, the amount of cellulose fiber per 100 parts by mass of resin may be preferably 0.001 parts by mass or more, or 0.01 parts by mass or more, or 0.1 parts by mass or more, or 1 part by mass or more, from the viewpoint of the balance between processability and mechanical properties, and may be preferably 100 parts by mass or less, or 80 parts by mass or less, or 70 parts by mass or less, or 50 parts by mass or less.

[0153] The flexural modulus of the resin composite is preferably 3.3 GPa or more, or 3.4 GPa or more, or 3.5 GPa or more, and may be preferably 20.0 GPa or less, or 10.0 GPa or less, or 8.0 GPa or less. The flexural modulus is a value measured by the method described in the [Examples] section of this disclosure. [Example]

[0154] The present invention will be further explained based on examples, but the present invention is not limited to these examples.

[0155] <Materials used> The materials used in producing the resin composites of the examples and comparative examples are as follows.

[0156] <Cellulose fiber> [CNF-A] Commercially available Celish KY100G (manufactured by Daicel FineChem) was used as the CNF-A cake.

[0157] [CNF-B] (Acetylated CNF) One part by mass of cotton linter pulp was stirred in 30 parts by mass of dimethyl sulfoxide (DMSO) at 500 rpm for 1 hour at room temperature using a uniaxial mixer (Imex DKV-1 φ125 mm dissolver). The mixture was then fed to a bead mill (Imex NVM-1.5) using a hose pump and circulated for 180 minutes using DMSO alone to obtain a fine cellulose fiber slurry, Slurry S1 (DMSO solvent) with a solid content of 3.2% by mass.

[0158] During circulation operation, the rotation speed of the bead mill was 2500 rpm, the peripheral speed was 12 m / s, and the beads used were made of zirconia, φ2.0 mm, and the filling rate was 70% (the slit gap of the bead mill was 0.6 mm). During circulation operation, the slurry temperature was controlled at 40°C using a chiller to absorb heat generated by friction.

[0159] Slurry S1 was placed in an explosion-proof disperser tank, and then 3.2 parts by mass of vinyl acetate and 0.49 parts by mass of sodium bicarbonate were added. The temperature inside the tank was raised to 50°C and the mixture was stirred for 120 minutes to obtain a slurry (DMSO solvent) with a solid content of 2.9% by mass.

[0160] To stop the reaction, 30 parts by mass of pure water was added and thoroughly stirred, and then the mixture was placed in a dehydrator and concentrated. The resulting wet cake was dispersed again in 30 parts by mass of pure water, stirred, and concentrated. This washing procedure was repeated a total of five times to remove unreacted reagents and solvent, yielding 10 parts by mass of acetylated fine cellulose fiber cake (CNF-B cake) (water solvent) with a solids content of 10% by mass. A porous sheet was prepared from this cake, and the degree of acyl substitution (DS) was determined, revealing a value of DS = 1.0.

[0161] [CNF-C] (CNF processed with a disc refiner) Three 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 resulting swollen pulp was washed with water to obtain a purified pulp containing water (30 parts by mass). Next, 30 parts by mass of the purified pulp containing water were dispersed in water by adding 170 parts by mass of water (solid content: 1.5% by mass). The aqueous dispersion was beaten for 20 minutes using an SDR14 lab refiner (pressure type disk type) manufactured by Aikawa Iron Works Co., Ltd. as a disc refiner with a 1 mm inter-disk clearance. The resulting mixture was then concentrated to a solid content of 10% by mass using a dehydrator to obtain a CNF-C cake (water solvent).

[0162] [CNF-D] (CNF-C further defibrated using a high-pressure homogenizer) The CNF-C cake was thoroughly beaten under conditions that reduced the clearance to a level close to zero, yielding a beaten water dispersion (solid content: 1.5% by mass). The resulting beaten water dispersion was then subjected to a high-pressure homogenizer (NSO15H, manufactured by Niro Soavi, Italy) for 15 cycles at an operating pressure of 100 MPa to obtain a cellulose fiber slurry (solid content: 1.5% by mass). The resulting mixture was then concentrated to a solid content of 10% by mass using a dehydrator to obtain a CNF-D cake (water solvent).

[0163] [CNF-E] (Acetylated CNF) It was produced in the same manner as CNF-B, except that the reaction time was 60 minutes. A porous sheet was made from this cake, and the degree of acyl substitution (DS) was determined, which was DS = 0.5.

[0164] <Resin> Polyamide 6 (Ube Industries: 1013B)

[0165] <Dispersant> Polyethylene oxide-polypropylene oxide copolymer (PEG-PPG) (Sanyo Chemical: GL-3000)

[0166] <Production of dried cellulose fiber> A dispersant was added to a cellulose fiber cake (10% solids) in an amount of 43 parts by mass per 100 parts by mass of cellulose fiber solids and stirred thoroughly to obtain a dispersant-infused cellulose fiber cake (for all products except MMSD, described below). Alternatively, a cellulose fiber cake (10% solids) was diluted with distilled water to a solids content of 1%, and then a dispersant was added in an amount of 43 parts by mass per 100 parts by mass of cellulose fiber solids and stirred thoroughly to obtain a cellulose fiber slurry (for MMSD, described below). These were then placed in a drying apparatus as raw materials and dried at a specified shear rate, vacuum level, and heating temperature (jacket temperature or hot air temperature). The moisture content was measured using an infrared moisture meter (MX-50, manufactured by A&D Co., Ltd.). The drying endpoint was determined when the moisture content reached 7% by mass or less (93% by mass or more of solids). The conditions were as follows:

[0167] [Lodige Mixer (LM)] Equipment: Lödige Mixer (model number: VT-20) manufactured by Chuo Kiko Co., Ltd. Conditions: Jacket temperature 100°C, agitation with an agitator (circumferential speed 1 m / s) and a chopper (3000 rpm) was performed, while the pressure was reduced to -90 kPa with a vacuum pump. Drying under reduced pressure was performed until the product temperature reached 50°C. The clearance was measured as the minimum distance between the chopper (diameter 100 mm) and the jacket. The drying time under these conditions was 160 minutes. The drying temperature was calculated by measuring the surface temperature of the jacket at three points and taking the average value.

[0168] [High Speed Vacuum Dryer (HSVD)] Equipment: High-speed vacuum dryer manufactured by Earth Technica Corporation (Model: FS10) Conditions: Jacket temperature 70°C, agitation with an agitator (circumferential speed 2 m / s) and a chopper (3500 rpm) was performed, while the pressure was reduced to -70 kPa with a vacuum pump. Drying under reduced pressure was performed until the product temperature reached 60°C. The clearance was measured as the minimum distance between the chopper (diameter 100 mm) and the agitator. The drying time under these conditions was 180 minutes. The drying temperature was calculated by measuring the surface temperature of the jacket at three points and taking the average value.

[0169] [FM Mixer (HM)] Equipment: FM mixer (model: FM20) manufactured by Nippon Coke & Engineering Co., Ltd. Conditions: Jacket temperature 80°C, stirring with a stirring blade (500 rpm), pressure reduced to -70 kPa with a vacuum pump. Drying under reduced pressure was carried out until the product temperature reached 70°C. The clearance was measured as the minimum distance between the upper stirring blade (diameter 400 mm) and the jacket. The drying time under these conditions was 180 minutes. The drying temperature was calculated by measuring the surface temperature of the jacket at three points and taking the average value.

[0170] [Paddle dryer (PD)] Equipment: Nara Machinery Manufacturing Co., Ltd. paddle dryer (model number: NPD-1.6W-12L) Conditions: Heating steam temperature 120°C, drying was carried out while stirring with a stirring blade (30 rpm) until the product temperature reached 100°C. The clearance was measured as the minimum distance between the stirring blade (diameter 250 mm) and the jacket. The drying time under these conditions was 50 minutes. The surface temperature of the stirring blade through which heated steam was passed was measured at three points, and the average value was used as the drying temperature.

[0171] [Micro Mist Spray Dryer (MMSD)] Equipment: Fujisaki Electric Co., Ltd. Micro Mist Spray Dryer (Model: MDL050-M) Conditions: Cellulose fiber slurry, inlet temperature 200°C, intake air volume 1m 3 The mixture was dried at a nozzle air flow rate of 80NL / min and a slurry flow rate of 50mL / min, and the dried powder was collected in a cyclone collector. Since this device does not have a stirring mechanism or the like, it is assumed that no shear rate is generated. The drying time and residence time under these conditions was 1 minute. The inlet temperature of the hot air was measured three times during the drying process, and the average value was used as the drying temperature.

[0172] [Twin screw extruder (Ex-dry)] Equipment: Twin-screw extruder manufactured by The Japan Steel Works, Ltd. (Model: TEX54αIII: L / D=63) Conditions: cylinder temperature 200°C, screw rotating at 66 rpm, raw material was fed into the uppermost barrel at 20 kg / h using a gravimetric feeder, and dry powder was obtained from the discharge outlet. The clearance was measured as the minimum distance between the kneading disc (diameter 54 mm) and the cylinder. The drying time and residence time under these conditions was 1 minute. The temperature of the cylinder in which the most downstream kneading disc is located was measured three times, and the average value was used as the drying temperature.

[0173] [Planetary Mixer (PM)] Equipment: Planetary mixer manufactured by Kodaira Manufacturing Co., Ltd. (Model: ACM-5LVT: hook type) Conditions: Jacket temperature 60°C, stirring at 307 rpm, pressure reduced to -90 kPa with a vacuum pump. Drying under reduced pressure was carried out until the product temperature reached 50°C. The clearance was measured as the minimum distance between the hook wing (diameter 100 mm) and the jacket. The drying time under these conditions was 180 minutes. The drying temperature was calculated by measuring the surface temperature of the jacket at three points and taking the average value.

[0174] [Examples 1 to 6, Comparative Examples 1 to 8] Using the CNFs shown in Table 1 and the above-mentioned equipment as shown in Table 2, a dried cellulose fiber body was obtained.

[0175] [Examples 7 to 12, Comparative Examples 9 to 12] In the LM, the CNF, drying temperature, or shear rate was changed as shown in Table 2, and the same procedure as in Example 1 was carried out to obtain a dried cellulose fiber material.

[0176] [Example 13] A dried cellulose fiber material was obtained in the same manner as in Example 1, except that a cellulose fiber slurry was obtained without using a dispersant in the preparation of the raw material.

[0177] <Manufacturing of resin composites> The dried cellulose fiber produced above and a thermoplastic resin (UBE Nylon 1013B manufactured by Ube Industries, Ltd.) were blended in such a ratio that the amount of cellulose fiber in the resin composite was 10 mass %, and a resin composite was produced according to the following procedure.

[0178] [Extruder configuration] Cylinder 1 of a twin-screw extruder (OMEGA30H manufactured by STEER, L / D=60) with 13 cylinder blocks was water-cooled, cylinder 2 was set to 80°C, cylinder 3 to 150°C, and cylinder 4 to the die to 250°C.

[0179] Regarding the screw configuration, cylinders 1 to 3 were used as a conveying zone consisting only of a conveying screw, and cylinder 4 was equipped with two clockwise kneading discs (feed-type kneading discs, hereinafter sometimes simply referred to as RKDs) and two neutral kneading discs (non-conveying type kneading discs, hereinafter sometimes simply referred to as NKDs) in that order from the upstream side. Cylinder 5 was used as a conveying zone, cylinder 6 was equipped with one RKD and two subsequent NKDs, cylinders 7 and 8 were used as conveying zones, and cylinder 9 was equipped with two NKDs. The following cylinder 10 was used as a conveying zone, cylinder 11 was equipped with two NKDs and one subsequent counterclockwise screw, and cylinders 12 and 13 were used as conveying zones. A vent port was installed at the top of cylinder 12 to enable reduced pressure suction, and vacuum suction was performed.

[0180] The dried cellulose fiber and thermoplastic resin were mixed in the proportions shown in Table 3 or 4, melt-kneaded using a twin-screw extruder at 250 rpm, extruded into strands, water-cooled, cut, and obtained as pellets. The obtained pellets were melted at 260°C using an attached injection molding machine to prepare dumbbell-shaped test pieces according to JIS K7127 standard, which were used for evaluation.

[0181] <Evaluation> <Evaluation of cellulose fibers> [Preparation of porous sheet] First, the wet cake was added to tert-butanol, and further dispersed using a mixer or the like until no aggregates were present. The concentration was adjusted to 0.5% by mass per 0.5 g of cellulose fiber solids. 100 g of the resulting 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 air resistance of this sheet was 10 g / m2.2 The porous sheet with a permeability of 100 sec / 100 ml or less was used as the measurement sample. The basis weight W (g / m) of the sample left standing for one day in an environment of 23°C and 50% RH 2 After measuring the air permeability, the air permeability resistance R (sec / 100 ml) was measured using an Oken type air permeability resistance tester (manufactured by Asahi Seiko Co., Ltd., model EG01). At this time, the air permeability resistance R was calculated according to the following formula: 2 The value per unit area was calculated. Weight 10g / m 2 Air resistance per unit (sec / 100ml) = R / W x 10

[0182] [Degree of acyl substitution (DS)] The infrared spectrum of the porous sheet was measured by the ATR-IR method at five points using a Fourier transform infrared spectrophotometer (FT / IR-6200 manufactured by JASCO) under the following conditions: Accumulation count: 64 times, Wavenumber resolution: 4cm -1 , Measurement wavenumber range: 4000 to 600 cm -1 , ATR crystal: diamond, Incident angle: 45° From the obtained IR spectrum, the IR index was calculated using the following formula (1): IR index = H1730 / H1030 (1) In the formula, H1730 and H1030 are the values at 1730 cm -1 , 1030cm -1 (absorption band of CO stretching vibration of cellulose backbone chain) -1 and 1500cm -1 The line connecting the -1 and 1500cm -1 The line connecting these points is taken as the baseline, and the absorbance is calculated when this baseline is taken as 0. The average degree of substitution at each measurement point 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)

[0183] [Crystallization] The porous sheet was subjected to X-ray diffraction measurement, and the crystallinity was calculated using the following formula. Crystallinity (%)=[I (200) -I (amorphous) ] / I (200) ×100 I (200) : Diffraction peak intensity due to the 200 plane (2θ=22.5°) in cellulose type I crystals I (amorphous) : The halo peak intensity due to amorphous in cellulose type I crystals, which is the peak intensity at an angle 4.5° lower than the diffraction angle of the 200 plane (2θ=18.0°) (X-ray diffraction measurement conditions) Device: MiniFlex (Rigaku Corporation) Operation axis 2θ / θ Source CuKα Measurement method: Continuous Voltage 40kV Current 15mA Starting angle 2θ=5° End angle 2θ=30° Sampling width 0.020° Scan speed 2.0° / min Sample: A porous sheet is attached to the sample holder.

[0184] [Number average fiber diameter] The cellulose fiber cake or cellulose fiber slurry was diluted with tert-butanol to 0.01% by mass, and dispersed using a high-shear homogenizer (IKA, trade name "Ultra Turrax T18") at 25,000 rpm for 5 minutes. The resulting dispersion was then cast onto mica and air-dried. The resulting dispersion was then analyzed using a high-resolution scanning electron microscope. The magnification was adjusted so that at least 100 cellulose fibers were visible, and the long diameter (L) of 100 randomly selected cellulose fibers was measured, and the arithmetic average of the 100 cellulose fibers was calculated.

[0185] [Weight average molecular weight (Mw), number average molecular weight (Mn) and Mw / Mn ratio] 0.88 g of the porous sheet was weighed, chopped into small pieces with scissors, gently stirred, and then 20 mL of pure water was added and left for one day. The water and solids were then separated by centrifugation. 20 mL of acetone was then added, gently stirred, and left for one day. The acetone and solids were then separated by centrifugation. 20 mL of N,N-dimethylacetamide was then added, gently stirred, and left for one day. The N,N-dimethylacetamide and solids were then separated again by centrifugation. 20 mL of N,N-dimethylacetamide was then added, gently stirred, and left for one day. The N,N-dimethylacetamide and solids were then separated by centrifugation. 19.2 g of N,N-dimethylacetamide solution containing 8% lithium chloride by mass was added to the solids, stirred with a stirrer, and visually confirmed to be dissolved. The cellulose fiber-dissolved solution was filtered through a 0.45 μm filter, and the filtrate was used as a sample for gel permeation chromatography. The equipment and measurement conditions used are as follows. Equipment: Tosoh HLC-8120 Column: TSKgel SuperAWM-H (6.0 mm I.D. x 15 cm) x 2 Detector: RI detector Eluent: N,N-dimethylacetamide (lithium chloride 0.2%) Flow rate: 0.6mL / min Calibration curve: pullulan equivalent

[0186] [Average content of alkali-soluble polysaccharides] The alkali-soluble polysaccharide content was determined by subtracting the α-cellulose content from the holocellulose content (Wise method) using the method described in the non-patent document (Wood Science Experiment Manual, edited by the Japan Wood Research Society, pp. 92-97, 2000) for cellulose fibers. The alkali-soluble polysaccharide content was calculated three times for each sample, and the number average of the calculated alkali-soluble polysaccharide contents was taken as the average alkali-soluble polysaccharide content of the cellulose fibers.

[0187] <Evaluation of dried cellulose fiber> [Angle of repose, angle of collapse, angle of difference, loose bulk density, packed bulk density, compressibility] Measurements were carried out using a powder tester (model number: PT-X) manufactured by Hosokawa Micron Corporation.

[0188] (Angle of repose) Using a medicine spoon, 100 g of dried cellulose fiber was gently dropped at approximately 10 g / min through a stainless steel funnel (made of stainless steel, upper opening diameter 70 mm, lower opening diameter 7 mm, inclination angle 60°) onto the center of a horizontally placed 80 mm diameter stainless steel measuring platform from a height of 110 mm so that the distance between the lower opening of the funnel and the measuring platform was 110 mm, depositing the dried cellulose fiber in a conical shape on the measuring platform. The conical shape was photographed from the side, and the angle between the generatrix of the cone and the horizontal plane was measured. The number average of three measurements was taken as the angle of repose.

[0189] (collapse angle) A 109g weight, placed on the same base as the measuring table, was dropped three times at 2-second intervals onto the sample for which the angle of repose was measured, from a height of 160mm. The conical shape of the sample was then photographed from the side, and the angle between the generatrix of the cone and the horizontal plane was measured. The number average of the three measurements was taken as the angle of repose.

[0190] (difference angle) The difference between the angle of repose and the angle of collapse was calculated as the difference angle.

[0191] (loose bulk density) The dried cellulose fiber was poured into a 100 mL stainless steel cylindrical container (inner diameter 50.46 mm × depth 50 mm) with a spoon at 10 g / min until it overflowed, and after the dried cellulose was leveled off, its weight was measured to the nearest 0.01 g. The number average of three measurements of the weight was divided by the internal volume of the cylindrical container to calculate the loose bulk density.

[0192] (Collected bulk density) A resin adapter (inner diameter 50.46 mm x length 40 mm) of sufficient capacity was tightly attached to the top of a bottomed cylindrical container similar to that used for measuring the loose bulk density, and the dried cellulose fiber mass was poured into the container until it overflowed using the same procedure as for measuring the loose bulk density. Then, with the adapter still attached, the bottomed cylindrical container was subjected to vibrations of 1.5 mm amplitude and 50 Hz for 30 seconds using a motor with an eccentric weight attached to the rotating shaft. The adapter was then removed, and the dried mass was drained to the nearest 0.01 g. The number average of three measurements of the weight was divided by the internal volume of the bottomed cylindrical container to calculate the packed bulk density.

[0193] (Compression degree) From the values of the packed bulk density and loose bulk density, the following formula is used: Compressibility = (packed bulk density - loose bulk density) / packed bulk density The compressibility was calculated according to the following formula.

[0194] [Moisture percentage] Measurements were carried out using an infrared heating moisture meter (MX-50, manufactured by A&D).

[0195] [Degree of dust generation] The dried cellulose fiber was poured into a cylindrical container with a bottom similar to that used for measuring the loose bulk density using a medicine spoon at a rate of 10 g / min until it overflowed. After the dried cellulose fiber was leveled off, the container was held by hand and instantly turned over at a height of 1000 mm above the floor to scatter the powder onto the floor. The degree of dust generation after 1 second of scattering was evaluated using the following index. A No dust generation was observed. B Small dust particles were observed C Large amounts of dust were generated.

[0196] <Evaluation of resin composite> [Tensile elongation at break, flexural modulus] The obtained pellets were molded using an injection molding machine under conditions conforming to JIS K6920-2 to form multipurpose test pieces conforming to ISO294-3. The multipurpose test specimens were measured for tensile elongation at break in accordance with ISO 527 and flexural modulus in accordance with ISO 179. Since polyamide resin changes due to moisture absorption, they were stored in aluminum moisture-proof bags immediately after molding to prevent moisture absorption.

[0197] [Table 1]

[0198] [Table 2]

[0199] [Table 3]

[0200] [Table 4] [Industrial Applicability]

[0201] The highly rigid resin composite that can be provided by the present invention can be suitably used in various resin molding applications.

Claims

1. A dry cellulose fiber body containing cellulose fibers and having a compression degree of 1 to 25%.

2. Angle of repose less than 45°, difference angle more than 10°, loose bulk density 0.35 to 0.85 g / cm 3 , and a packed bulk density of 0.6 to 0.9 g / cm 3 The dried cellulose fiber material according to claim 1, having one or more selected from the group consisting of:

3. Loose bulk density 0.35 to 0.85 g / cm 3 , and a packed bulk density of 0.6 to 0.9 g / cm 3 The dried cellulose fiber material according to claim 1 or 2, having

4. The dried cellulose fiber material according to any one of claims 1 to 3, wherein the number average fiber diameter of the cellulose fibers is 2 nm to 1000 nm.

5. The dried cellulose fiber material according to any one of claims 1 to 4, wherein the cellulose fibers have an average fiber length (L) / fiber diameter (D) ratio of 30 to 5000.

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

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

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

9. The dried cellulose fiber material according to any one of claims 1 to 8, wherein the cellulose fibers are chemically modified.

10. The dried cellulose fiber material according to claim 9, wherein the chemical modification is esterification.

11. The dried cellulose fiber material according to claim 10, wherein the esterification is acetylation.

12. The dried cellulose fiber material according to any one of claims 9 to 11, wherein the average degree of substitution (DS) of the cellulose fiber is 0.1 to 1.

2.

13. The dried cellulose fiber material according to any one of claims 1 to 12, having a moisture content of 30% by mass or less.

14. further comprising a dispersant, The dried cellulose fiber material according to any one of claims 1 to 13, 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 1000 to 50000.

15. The method for producing a dried cellulose fiber body according to any one of claims 1 to 14, A slurry preparation step of preparing a slurry containing cellulose fibers and a liquid medium; The slurry is subjected to a shear rate of 100 to 20,000 seconds. -1 a drying step of drying the mixture at a drying rate of 0.01 to 10% / min and a drying temperature of 20°C to 160°C under stirring to form a dried cellulose fiber body; A method comprising:

16. The method according to claim 15, wherein the drying step is carried out in a batch process using a mechanically agitated mixer granulator.

17. A method for producing a resin composite containing cellulose fibers and a resin, comprising: The method comprises mixing the dried cellulose fiber material according to any one of claims 1 to 14 with a resin, The resin composite has a flexural modulus of 3.3 GPa or more.

18. The method of claim 17, wherein the resin is a thermoplastic resin.

19. 20. The method of claim 18, wherein the thermoplastic resin is a polyamide-based resin.

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