Cellulose fiber dry body, 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 cellulose fiber dried body, a method for producing the same, and a method for producing a resin composite containing cellulose fibers and a resin.

Background Art

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

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

Prior Art Documents

Patent Documents

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

[0005] All of the techniques described in Patent Documents 1 to 3 are intended to reduce the aggregation of cellulose nanofibers during drying, so that the dried cellulose nanofibers can be well redispersed in a dispersion medium or a matrix resin. However, even with these techniques, the redispersibility of once-dried cellulose nanofibers is not sufficient. In particular, there has been no established technique that can well disperse the cellulose nanofibers in the resin even when the cellulose nanofibers are mixed with the resin in a dry state. Therefore, with the conventional techniques, the effect of improving the physical properties of the resin by the cellulose nanofibers has not been able to be expressed at a satisfactory level.

[0006] One aspect of the present invention is to solve the above problems, provide a cellulose fiber dried body that can give a highly rigid resin composite by being finely dispersed in a resin and is further excellent in handleability, a method for manufacturing the same, a resin composite including the cellulose fiber dried body and a resin, and a method for manufacturing the same. [Means for Solving the Problems]

[0007] The present invention includes the following aspects. [1] A cellulose fiber dried body containing cellulose fibers and having a degree of compression of 1 to 25%. [2] An angle of repose of less than 45°, a difference angle of more than 10°, a loose bulk density of 0.35 to 0.85 g / cm 3 , and a tapped bulk density of 0.6 to 0.9 g / cm 3The dried cellulose fiber according to the above aspect 1, having one or more selected from the group consisting of [3] Loose bulk density of 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 according to the above aspect 1 or 2, having [4] The dried cellulose fiber according to any one of the above aspects 1 to 3, wherein the number average fiber diameter of the cellulose fiber is 2 nm to 1000 nm. [5] The dried cellulose fiber according to any one of the above aspects 1 to 4, wherein the average fiber length (L) / fiber diameter (D) ratio of the cellulose fiber is 30 to 5000. [6] The dried cellulose fiber according to any one of the above aspects 1 to 5, wherein the cellulose fiber has a weight average molecular weight (Mw) of 100000 or more and a weight average molecular weight (Mw) / number average molecular weight (Mn) ratio of 6 or less. [7] The dried cellulose fiber according to any one of the above aspects 1 to 6, wherein the crystallinity of the cellulose fiber is 60% or more. [8] The dried cellulose fiber according to any one of the above aspects 1 to 7, wherein the alkali-soluble polysaccharide content of the cellulose fiber is 20% by mass or less. [9] The dried cellulose fiber according to any one of the above aspects 1 to 8, wherein the cellulose fiber is chemically modified.

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

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

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

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

[14] Further comprising a dispersant, The cellulose fiber dried body according to any one of the above aspects 1 to 13, wherein the dispersant is a compound having an HLB value of 0.1 or more 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 cellulose fiber dried body according to any one of the above aspects 1 to 14, comprising: a slurry preparation step of preparing a slurry containing cellulose fibers and a liquid medium, and drying the slurry under stirring at a shear rate of 100 to 20,000 s -1 at a drying rate of 0.01 to 10% / min and a drying temperature of 20°C to 160°C to form a cellulose fiber dried body. A method comprising the above steps.

[16] The method according to the above aspect 15, wherein the drying step is performed in a batch process using a mechanical stirring type mixer-granulator.

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

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

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

Advantages of the Invention

[0008] According to one aspect of the present invention, there can be provided a cellulose fiber dried body that can provide a highly rigid resin composite by being finely dispersed in a resin, has excellent handleability, a method for producing the same, a resin composite containing the cellulose fiber dried body and a resin, and a method for producing the same.

Brief Description of the Drawings

[0009]

Figure 1

Figure 2

Mode for Carrying Out the Invention

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

[0011] ≪Dry Cellulose Fibers≫ One aspect of the present invention provides a dried cellulose fiber body containing cellulose fibers, which may be in a particulate form, particularly in a granular form (i.e., relatively coarse particles formed by aggregation of fine powders). In the dried cellulose fiber body according to one aspect, the degree of compression is controlled within a specific range described below. Preferably, at least one selected from the group consisting of the angle of repose, angle of collapse, difference angle, loose bulk density, and tapped bulk density is controlled within a specific range. The dried cellulose fiber body of the present disclosure can have appropriately controlled particle size, cellulose molecular aggregation state, and interparticle interaction in one aspect, and while having excellent handleability, it can show the advantage that aggregation hardly occurs during mixing with a resin. That is, when the dried cellulose fiber body is extremely fine particles, when it is mixed with a resin, the particles tend to aggregate instead, and it is difficult to obtain a good dispersion state. On the other hand, the dried cellulose fiber body can be particles that are not too fine in one aspect. In this case, it is difficult to aggregate in the resin, and the cellulose fibers can be finely dispersed well in the resin. In addition, since the granular dried cellulose fiber body can have a size where its shape is visible, for example, in the case of powder, it is difficult to cause a weighing error such as that caused by the powder dancing in the air, and the handling property during mixing with the resin is good (for example, the feed to the top or side of an extruder can be performed smoothly). In addition, due to the contribution of the size that is not too fine of the granular dried cellulose fiber body, it can efficiently receive the shearing force during mixing (for example, melt kneading) of the dried cellulose fiber body and the resin, and the particles are well crushed by this shearing force, so that the cellulose fibers can be dispersed in the resin in a state where they are defibrated to the nanolevel. On the other hand, the dried cellulose fiber body according to one aspect of the present invention can have an appropriate density, so that it easily collapses in the resin and finely disperses the cellulose fibers well in the resin. By using the dried cellulose fiber body according to one aspect of the present invention, a resin composite with high rigidity can be formed.

[0012] In one aspect, the degree of compression of the dried cellulose fiber is 1 to 25%. The degree of compression represents the degree of bulk reduction. In terms of the fluidity of the dried cellulose fiber not being too high, the degree of compression is 1% or more, preferably 5% or more, or 10% or more, or 12% or more. Also, in terms of the good fluidity of the dried cellulose fiber and excellent handleability (specifically, it is difficult for scattering, floating, and dust formation to occur), the degree of compression is 25% or less, preferably 23% or less.

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

[0014] In one aspect, from the perspective of avoiding the inconvenience that particles scatter due to the dried cellulose fiber being too light or the dried cellulose fiber floats on the resin phase during mixing with the resin in a flowing state, resulting in poor mixing, the loose bulk density of the dried cellulose fiber is preferably 0.35 g / cm 3 or more, or 0.40 g / cm 3 or more, or 0.45 g / cm 3 or more. Also, in terms of the dried cellulose fiber easily disintegrating in the resin and the cellulose fibers being well dispersed in the resin, and the dried cellulose fiber not being too heavy to avoid poor mixing between the dried cellulose fiber and the resin, the loose bulk density is preferably 0.85 g / cm 3 or less, or 0.80 g / cm 3 or less, or 0.75 g / cm 3 or less.

[0015] The compressed bulk density of the dried cellulose fiber is controlled within a range useful for controlling the loose bulk density and the degree of compression within the scope of the present disclosure. In one aspect, it may be 0.6 to 0.9 g / cm 3

[0016] ​In one aspect, the angle of repose of the dried cellulose fiber is preferably less than 45°, or 42° or less, or 40° or less, or 38° or less. The dried cellulose fiber with an angle of repose within the above range contains relatively large particles and has good fluidity, making it easy to mix with the resin. On the other hand, it is difficult to entrap gas between the particles and is less likely to be in a fluidized state (i.e., a state where it behaves like a fluid due to floating suspension), so it is advantageous in that the particles are less likely to scatter. The angle of repose may be, for example, 10° or more, or 20° or more, or 30° or more in terms of the fact that the particle size is not too large and the dispersibility of the cellulose fiber in the resin is good.

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

[0018] In one aspect, the angle of difference (i.e., the difference between the angle of repose and the angle of collapse) of the dried cellulose fiber is preferably more than 10°, or 11° or more, or 12° or more, or 13° or more. The dried cellulose fiber with an angle of difference within the above range has high fluidity due to relatively small interaction (such as frictional force) between particles and excellent handleability. However, in the resin, it can easily collapse and finely disperse the cellulose fiber in the resin. The angle of difference may be, for example, 30° or less, or 25° or less, or 20° or less from the perspective of the ease of manufacturing the dried cellulose fiber.

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

[0020] In a preferred aspect, the degree of compressibility, the loose bulk density, and the tapped bulk density are within the ranges exemplified above. Also, in a preferred aspect, the degree of compressibility, the loose bulk density, and the tapped bulk density, and one or both of the angle of repose and the angle of difference are within the ranges exemplified above.

[0021] In one aspect, the average particle size of the dried cellulose fibers is preferably 50 μm or more, or 100 μm or more, or 200 μm or more, or 500 μm or more, and preferably 5000 μm or less, or 4000 μm or less, or 3000 μm or less, or 2000 μm or less. The above average particle size is a value measured by the laser diffraction / scattering method.

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

[0023] As raw materials for the dried cellulose fibers, natural cellulose fibers and regenerated cellulose fibers can be used. As natural cellulose fibers, wood pulp obtained from wood species (hardwood or softwood), non-wood pulp obtained from non-wood species (cotton, bamboo, hemp, bagasse, kenaf, cotton linter, sisal, straw, etc.), cellulose fiber aggregates produced by animals (e.g., tunicates), algae, and microorganisms (e.g., acetic acid bacteria) can be used. As regenerated cellulose fibers, regenerated cellulose fibers (viscose, cupra, tencel, etc.), cellulose derivative fibers, ultrafine fibers of regenerated cellulose or cellulose derivatives obtained by the electrospinning method, etc. can be used.

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

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

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

[0027] In addition, since the purification process such as delignification and the bleaching process by cooking treatment reduce the molecular weight of cellulose molecules, there is a concern that these processes may result in the reduction of the molecular weight of cellulose fibers and the alteration of the cellulose fiber raw material, leading to an increase in the abundance ratio of alkali-soluble components. Since alkali-soluble components are inferior in heat resistance, it is desirable that the purification process and the bleaching process of the cellulose fiber raw material be controlled so that the amount of alkali-soluble components contained in the cellulose fiber raw material falls within a range not exceeding a certain value.

[0028] In one aspect, from the viewpoint of obtaining a good effect of improving physical properties by cellulose fibers, the number-average fiber diameter of the cellulose fibers is preferably 2 to 1000 nm. The number-average fiber diameter of the cellulose fibers is more preferably 4 nm or more, or 5 nm or more, or 10 nm or more, or 15 nm or more, or 20 nm or more, and more preferably 500 nm or less, or 450 nm or less, or 400 nm or less, or 350 nm or less, or 300 nm or less, or 250 nm or less.

[0029] From the viewpoint of improving the mechanical properties of the resin composite containing cellulose fibers well 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. The upper limit is not particularly limited, but is preferably 5000 or less from the viewpoint of handleability.

[0030] In the present disclosure, the fiber length, fiber diameter, and L / D ratio of the cellulose fibers are determined by measuring a water dispersion of the cellulose fibers that has been dispersed under the treatment conditions of a rotational speed of 15,000 rpm for 5 minutes using a high-shear homogenizer (e.g., manufactured by Nippon Seiki Co., Ltd., product name "Excel Auto Homogenizer ED-7"), diluting the dispersion with pure water to 0.1 to 0.5% by mass, casting it onto mica, and air-drying it to obtain a measurement sample, and measuring with a high-resolution scanning electron microscope (SEM) or an atomic force microscope (AFM). Specifically, in an observation field with a magnification adjusted so that at least 100 cellulose fibers are observed, the lengths (L) and diameters (D) of 100 randomly selected cellulose fibers are measured, and the ratio (L / D) is calculated. For the cellulose fibers, the number average value of the fiber length (L), the number average value of the fiber diameter (D), and the number average value of the ratio (L / D) 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, using the resin composite in solid form as a measurement sample, by the above-described 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 component in the resin composite in an organic or inorganic solvent capable of dissolving the resin component of the resin composite, separating the cellulose fibers, thoroughly washing with the solvent, then preparing a water dispersion in which the solvent is replaced with pure water, diluting the cellulose fiber concentration with pure water to 0.1 to 0.5% by mass, casting it onto mica, and air-drying it to obtain a measurement sample and measuring by the above-described measurement method. At this time, the measurement of the cellulose fibers is performed on 100 or more randomly selected fibers.

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

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

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

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

[0037] As crystal forms of cellulose, type I, type II, type III, type IV, etc. are known. Among them, type I and type II are particularly widely used. Although type III and type IV are obtained on a laboratory scale, they are not widely used on an industrial scale. As the cellulose fiber of the present disclosure, since the structural mobility is relatively high, and by dispersing the cellulose fiber in a resin, a resin composite having a lower linear expansion coefficient and more excellent strength and elongation during tensile and bending deformation can be obtained, cellulose fibers containing cellulose type I crystals or cellulose type II crystals are preferred, and cellulose fibers containing cellulose type I crystals and having a crystallinity of 55% or more are more preferred.

[0038] The degree of polymerization of the cellulose fiber is preferably 100 or more, more preferably 150 or more, more preferably 200 or more, more preferably 300 or more, more preferably 400 or more, more preferably 450 or more, preferably 3500 or less, more preferably 3300 or less, more preferably 3200 or less, more preferably 3100 or less, more preferably 3000 or less.

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

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

[0041] In one aspect, the weight average molecular weight (Mw) of the cellulose fiber is 100,000 or more, more preferably 200,000 or more. The ratio (Mw / Mn) of the weight average molecular weight to the number average molecular weight (Mn) is 6 or less, preferably 5.4 or less. A larger weight average molecular weight means fewer end groups of cellulose molecules. Also, since the ratio (Mw / Mn) of the weight average molecular weight to the number average molecular weight represents the width of the molecular weight distribution, a smaller Mw / Mn means fewer ends of cellulose molecules. Since the ends of cellulose molecules serve as the starting points of thermal decomposition, when the weight average molecular weight of the cellulose molecules in the cellulose fiber is not only large but also the width of the molecular weight distribution is narrow at the same time as the weight average molecular weight is large, cellulose fibers with particularly high heat resistance and resin composites containing cellulose fibers and resins can be obtained. The weight average molecular weight (Mw) of the cellulose fiber may be, for example, 600,000 or less, or 500,000 or less, from the viewpoint of the availability of cellulose fiber raw materials. The ratio (Mw / Mn) of the weight average molecular weight to the number average molecular weight (Mn) may be, for example, 1.5 or more, or 2 or more, from the viewpoint of the ease of manufacturing the cellulose fiber. Mw can be controlled within the above range by selecting a cellulose fiber raw material having an Mw suitable for the purpose, appropriately performing physical and / or chemical treatments on the cellulose fiber raw material within an appropriate range, and the like. Mw / Mn can also be controlled within the above range by selecting a cellulose fiber raw material having an Mw / Mn suitable for the purpose, appropriately performing physical and / or chemical treatments on the cellulose fiber raw material within an appropriate range, and the like. In both the control of Mw and the control of Mw / Mn, examples of the above physical treatments include physical treatments that apply mechanical forces such as impact, shear, shear, and friction by a microfluidizer, ball mill, disk mill, etc. for dry or wet pulverization, a kneader, a homomixer, a high-pressure homogenizer, an ultrasonic device, etc., and examples of the above chemical treatments include steaming, bleaching, acid treatment, regenerated cellulose formation, etc.

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

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

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

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

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

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

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

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

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

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

[0052] The 1% weight reduction temperature (T 1% ) is the temperature at 1 wt% weight reduction starting from the weight at 150 °C when the temperature is continuously increased by the above-described method of T D .

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

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

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

[0056] The acid halide may be at least one selected from the group consisting of compounds represented by the following formula (1). R 1 -C(=O)-X (1) (In the formula, R 1 represents an alkyl group having 1 to 24 carbon atoms, an alkenyl group having 2 to 24 carbon atoms, a cycloalkyl group having 3 to 24 carbon atoms, or an aryl group having 6 to 24 carbon atoms, and X is Cl, Br, or I.) Specific examples of acid halides include, but are not limited to, acetyl chloride, acetyl bromide, acetyl iodide, propionyl chloride, propionyl bromide, propionyl iodide, butyryl chloride, butyryl bromide, butyryl iodide, benzoyl chloride, benzoyl bromide, benzoyl iodide, etc. Among them, acid chlorides can be preferably employed from the viewpoints of reactivity and handleability. In the reaction of acid halides, one or more alkaline compounds may be added for the purpose of neutralizing acidic substances that act as catalysts and are by-products. Specific examples of alkaline compounds include, 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 suitable acid anhydrides can be used. For example, Saturated aliphatic monocarboxylic acid anhydrides such as acetic acid, propionic acid, (iso)butyric acid, valeric acid; unsaturated aliphatic monocarboxylic acid anhydrides such as (meth)acrylic acid, oleic acid; Alicyclic monocarboxylic acid anhydrides such as cyclohexanecarboxylic acid, tetrahydrobenzoic acid; Aromatic monocarboxylic acid anhydrides such as benzoic acid, 4-methylbenzoic acid; As dibasic carboxylic acid anhydrides, for example, saturated aliphatic dicarboxylic acid anhydrides such as succinic anhydride, adipic anhydride, unsaturated aliphatic dicarboxylic acid anhydrides such as maleic anhydride, itaconic anhydride, alicyclic dicarboxylic acid anhydrides such as 1-cyclohexene-1,2-dicarboxylic anhydride, hexahydrophthalic anhydride, methyltetrahydrophthalic anhydride, and aromatic dicarboxylic acid anhydrides such as phthalic anhydride, naphthalic anhydride, etc.; Examples of polybasic carboxylic acid anhydrides having three or more basic groups include (anhydrous) polycarboxylic acids such as trimellitic anhydride and pyromellitic anhydride. In the reaction of acid anhydrides, as catalysts, acidic compounds such as sulfuric acid, hydrochloric acid, phosphoric acid, or Lewis acids (for example, Lewis acid compounds represented by MYn, where M represents a metalloid element such as B, As, Ge, etc., or a base metal element such as Al, Bi, In, etc., or a transition metal element such as Ti, Zn, Cu, etc., or a lanthanoid element, n is an integer corresponding to the valence of M, representing 2 or 3, and Y represents a halogen atom, OAc, OCOCF 3 , ClO 4 , SbF 6 , PF 6 or OSO 2 CF 3 (OTf).), or one or more alkaline compounds such as triethylamine and pyridine may be added.

[0058] As the vinyl carboxylate, the following formula (1): R-COO-CH=CH 2 …Formula (1) {In the formula, R is any one of an alkyl group having 1 to 24 carbon atoms, an alkenyl group having 2 to 24 carbon atoms, a cycloalkyl group having 3 to 16 carbon atoms, or an aryl group having 6 to 24 carbon atoms.} The vinyl carboxylate represented by is preferred. The vinyl carboxylate is more preferably at least one selected from the group consisting of vinyl acetate, vinyl propionate, vinyl butyrate, vinyl caproate, vinyl cyclohexanecarboxylate, vinyl caprylate, vinyl capric acid, vinyl laurate, vinyl myristate, vinyl palmitate, vinyl stearate, vinyl pivalate, vinyl octylate, divinyl adipate, vinyl methacrylate, vinyl crotonate, vinyl pivalate, vinyl octylate, vinyl benzoate, and vinyl cinnamate. In the esterification reaction with vinyl carboxylate, as the catalyst, one or more selected from the group consisting of alkali metal hydroxides, alkaline earth metal hydroxides, alkali metal carbonates, alkaline earth metal carbonates, alkali metal hydrogen carbonates, primary to tertiary amines, quaternary ammonium salts, imidazole and its derivatives, pyridine and its derivatives, and alkoxides may be added.

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

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

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

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

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

[0064] Examples of the carboxylic acids include at least one selected from the group consisting of compounds represented by the following formula (1). R-COOH …(1) (In the formula, R represents an alkyl group having 1 to 16 carbon atoms, an alkenyl group having 2 to 16 carbon atoms, a cycloalkyl group having 3 to 16 carbon atoms, or an aryl group having 6 to 16 carbon atoms.)

[0065] Specific examples of the carboxylic acid include at least one selected from the group consisting of acetic acid, propionic acid, butyric acid, caproic acid, cyclohexanecarboxylic acid, caprylic acid, capric acid, lauric acid, myristic acid, palmitic acid, stearic acid, pivalic acid, methacrylic acid, crotonic acid, pivalic acid, octylic acid, benzoic acid, and cinnamic acid.

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

[0082] Examples of the hydrophobic segment include segments having an alkylene oxide unit with 3 or more carbon atoms (e.g., PPG block), 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-amino cyclohexyl) methane dodecane, etc., polycondensates of organic dicarboxylic acids having 4 to 12 carbon atoms and organic diamines having 2 to 13 carbon atoms, polycondensates of ω-amino acids (e.g., ω-aminoundecanoic acid) (e.g., polyundecanamide (11 nylon), etc.), polycapramide (6 nylon) which is a ring-opening polymer of ε-aminocaprolactam, poly(laurolactam) (12 nylon) which is a ring-opening polymer of ε-aminolaurolactam, etc., amino acid lactams containing ring-opening polymers of lactams, polymers composed of diamines and dicarboxylic acids, polyacetal resins, polycarbonate resins, polyester resins, polyphenylene sulfide resins, polysulfone resins, polyether ketone resins, polyimide resins, fluorine resins, hydrophobic silicone resins, melamine resins, epoxy resins, phenolic resins.

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

[0102] (Slurry preparation step) In this step, a slurry containing cellulose fiber and a liquid medium is prepared. As the liquid medium, the above-mentioned water-miscible organic solvent can be preferably used. From the viewpoint of process efficiency in the subsequent drying step, the concentration of cellulose fiber in the slurry is preferably 5% by mass or more, or 10% by mass or more, or 15% by mass or more, or 20% by mass or more, or 25% by mass or more, and from the viewpoint of avoiding excessive increase in the viscosity of the slurry and solidification due to aggregation and maintaining good handleability, it is preferably 60% by mass or less, or 55% by mass or less, or 50% by mass or less, or 45% by mass or less. For example, the production of cellulose nanofibers is often carried out in a dilute dispersion, but the concentration of cellulose fiber in the slurry may be adjusted to the preferred range by concentrating such a dilute dispersion. For concentration, methods such as suction filtration, pressure filtration, centrifugal dewatering, and heating can be used.

[0103] (Drying step) In this process, the above slurry is dried under controlled drying conditions to form a dried cellulose fiber product. When the dried cellulose fiber product contains cellulose fibers and additional components, the additional components may be added before, during, and / or after drying of the cellulose fiber slurry. Various mixers can be used for drying, but a mechanically stirred mixing granulator is preferred in that it enables drying at a relatively high shear rate. In one aspect, drying is performed in a batch process using a mechanically stirred mixing granulator. The mechanically stirred mixing granulator may be a commercially available product. Examples include devices having stirring blades and chopper blades in a can body, such as a Lodige mixer (e.g., manufactured by Matsubo Corporation) and a high-speed vacuum dryer (e.g., manufactured by Earth Technica Corporation), and fluidized mixers such as a Henschel mixer (FM mixer) (e.g., manufactured by Nippon Coke & Engineering Co., Ltd.) having a plurality of stirring blades (typically upper and lower blades) in a can body. 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 product of the present disclosure.

[0104] For example, when the mechanically stirred mixing granulator is the aforementioned Lodige mixer or high-speed vacuum dryer, the slurry is dried under stirring to form particles, and the particles are chopped and pulverized by a chopper to form a dried product having a desired particle size. The granulator typically includes a vertical or horizontal can body having a material inlet at the upper part, a combination of a low-speed rotating stirring blade disposed at the bottom of the can body and a high-speed rotating chopper blade disposed at the side of the can body, a vacuum mechanism, and optionally a temperature adjustment mechanism. When the measured slurry is introduced into the can body from the material supply port, the slurry is dried under reduced pressure while convecting in the can body by the centrifugal force and upward propelling force of the stirring blade, and particles are generated. The particles move in the can body, hit the chopper blade and are pulverized, and then return to the vicinity of the stirring blade and are stirred again to increase the particle size. In this way, by repeatedly subjecting the particles to stirring and chopper pulverization, a sized (i.e., having a small variation in particle size) dried cellulose fiber product can be produced.

[0105] Also, when the mechanical stirring type mixing granulator is the aforementioned Henschel mixer, a dried body with a desired particle size can be formed by the combination of the upper blades and the lower blades of the mixer. The Henschel mixer typically includes a vertical can body having a material supply port at the upper part and a material discharge port at the side, a lower blade disposed at the bottom of the can body, an upper blade disposed above the lower blade, a pressure reducing mechanism, and optionally a temperature adjusting mechanism. When the measured slurry is introduced into the can body from the material supply port, the slurry is stirred by the lower blade and rises, and further receives a strong shearing force by the upper blade, so that it is dried and granulated while being stirred.

[0106] In the drying process, the shear rate (shearing speed) is 100 seconds -1 or more, or 500 seconds -1 or more, or 750 seconds -1 or more, or 1000 seconds -1 or more, and may be 20000 seconds -1 or less, or 15000 seconds -1 or less, or 12500 seconds -1 or less, or 10000 seconds -1 or less. The shear rate is a value defined by the formula: shear rate (seconds -1 ) = maximum peripheral speed of the rotating blade (unit: m / s) / clearance (unit: m). The maximum peripheral speed is calculated from the blade diameter and the rotational speed, and the clearance is the shortest distance from the blade to the tank wall (stationary surface). In the case of a device having a plurality of rotating blades, the calculation is performed using the rotating blade that generates the maximum shear rate. The shear rate in the drying process by a device that substantially does not have mechanisms such as rotating blades and does not cause shear deformation of the dried body is 0 seconds -1It is calculated as such. The shear rate can be controlled by the rotational speed of the stirring blades or the like according to the configuration of the mixer. Since cellulose fibers are extremely likely to aggregate in a dry state, in a normal dry cellulose fiber body, the cellulose fibers are strongly aggregated with each other, and even if the dry 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 characteristics and bulk density of the dry cellulose fiber body can be controlled within an appropriate range, so that a dry cellulose fiber body having a relatively large particle size and an appropriate bulk density and excellent dispersibility in a resin can be formed.

[0107] As conditions for imparting the shear rate within the above range to the slurry, for example, when using a mixer equipped with stirring blades and chopper blades, the rotation conditions (peripheral speed) of the rotating blades are set 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 above peripheral speed does not necessarily need to be constant throughout the drying process and may be changed within a preferable range.

[0108] Also, the rotational 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 using a mixer equipped with upper blades and lower blades as stirring blades, the rotational 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 above rotational speed does not necessarily need to be constant throughout the drying process and may be changed within a preferable range.

[0110] The drying rate, which is the amount of desorbed liquid medium per minute (parts by mass) 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 aggregating cellulose fibers to form granular cellulose fiber dried bodies with a desirable particle size. From the viewpoint of avoiding excessive pulverization of the cellulose fiber dried bodies due to rapid drying of the slurry, it may be 10% / min or less, or 5% / min or less, or 2% / min or less. The drying rate is the value obtained according to the following formula: Drying rate (% / min) = (Slurry moisture content at the start of drying (mass %) - Moisture content of the dried body at the end of drying (mass %)) / Time required from the start to the end of drying (min) That is, it is the average value throughout the drying process. Here, the start of drying is the point in time when the process of supplying the slurry or cake to be dried to the apparatus and drying it at the target drying temperature, degree of vacuum, and shear rate begins. The time for preliminary mixing in a state where the drying temperature, degree of vacuum, and shear rate are different from those of the drying process is not included in the drying time. Also, the end of drying refers to the point in time when sampling is performed at intervals of at most 10 minutes from the start of drying and the moisture content first becomes 7 mass % or less. In the case of a continuous drying apparatus, the time required from the start to the end of drying can be interpreted as the residence time. In the case of a spray dryer, the residence time can be calculated based on the heating air volume and the volume of the drying chamber. Also, when an extruder is used as the drying apparatus, the residence time can be calculated from the screw rotation speed and the total number of screw pitches.

[0111] The drying temperature may be, for example, 20°C or more, or 30°C or more, or 40°C or more, or 50°C or more from the viewpoints of drying efficiency and appropriately aggregating cellulose fibers to form granular cellulose fiber dried bodies with a desirable particle size. From the viewpoints of making it difficult for thermal degradation of the cellulose fibers and additional components to occur and avoiding excessive pulverization of the cellulose fiber dried bodies due to rapid drying of the slurry, it may be 160°C or less, or 150°C or less, or 140°C or less, or 130°C or less, or 100°C or less. The drying temperature is the temperature of the heat source in contact with the slurry, and is defined, for example, as the surface temperature of the temperature control jacket of the drying apparatus, the surface temperature of the heating cylinder, or the temperature of the hot air.

[0112] The degree of vacuum, from the viewpoints of drying efficiency and appropriately aggregating cellulose fibers to form granular cellulose fiber dried bodies with a desired particle size, 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, and from the viewpoint of avoiding excessive pulverization of the cellulose fiber dried bodies due to rapid drying of the slurry, may be -100 kPa or more, or -95 kPa or more, or -90 kPa or more. The pressure adjustment may be achieved by fully operating a vacuum pump having an appropriate exhaust capacity, or by intentionally introducing air and / or an inert gas using a vacuum regulator, a leak valve, etc. When introducing air and / or an inert gas, it is preferable to provide an intake section in the can body of the drying apparatus or upstream of the can body because the medium vapor can be efficiently exhausted.

[0113] In the drying step, the residence time of the slurry at a temperature of 40°C to 100°C may preferably be set to 30 minutes to 600 minutes, or 45 minutes to 300 minutes, or 60 minutes to 200 minutes. By drying under such conditions, the cellulose fibers aggregate appropriately, and granular cellulose fiber dried bodies with a desired particle size are favorably produced.

[0114] ≪Method for producing resin composite≫ One aspect of the present invention provides a method for producing a resin composite containing cellulose fibers and a resin. The method includes mixing the cellulose fiber dried body of the present disclosure as described above and the resin.

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

[0116] (Thermoplastic resin) When the resin is a thermoplastic resin, the melting point of the thermoplastic resin may be appropriately selected according to the use of the resin composite and the like. As the melting point of the thermoplastic resin, for example, for resins with relatively low melting points (such as polyolefin resins), it can be 150°C to 190°C, or 160°C to 180°C, and for example, for resins with relatively high melting points (such as polyamide resins), it can be 220°C to 350°C, or 230°C to 320°C.

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

[0118] Preferred polyolefin resins as the thermoplastic resin are polymers obtained by polymerizing olefins (such as α-olefins) and / or alkenes as monomer units. Specific examples of polyolefin resins include ethylene-based (co)polymers exemplified by low-density polyethylene (such as linear low-density polyethylene), high-density polyethylene, ultra-low-density polyethylene, ultra-high molecular weight polyethylene, etc., polypropylene-based (co)polymers exemplified by polypropylene, ethylene-propylene copolymer, ethylene-propylene-diene copolymer, etc., and copolymers of ethylene and α-olefins represented by ethylene-acrylic acid copolymer, ethylene-methyl methacrylate copolymer, ethylene-glycidyl methacrylate copolymer, etc.

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

[0120] Also, in order to enhance the affinity with cellulose fibers, an acid-modified polyolefin resin can also be suitably used. As the acid used for acid modification, mono- or polycarboxylic acids can be used, and examples include maleic acid, fumaric acid, succinic acid, phthalic acid and their anhydrides, and citric acid. From the ease of increasing the modification rate, maleic acid or its anhydride is particularly preferred. There are no particular restrictions on the modification method, but a method of heating the polyolefin resin above its melting point and melt-kneading it in the presence or absence of a peroxide is common. As the polyolefin resin to be acid-modified, all of the above-mentioned polyolefin resins can be used, but polypropylene is particularly suitable. The acid-modified polypropylene resin can be used alone, but in order to adjust the modification rate of the entire resin, it is more preferably used by mixing with an unmodified polypropylene resin. The ratio of the acid-modified polypropylene resin to all the polypropylene resins at this time is preferably 0.5% by mass to 50% by mass. A more preferred lower limit is 1% by mass, or 2% by mass, or 3% by mass, or 4% by mass, or 5% by mass. Also, a more preferred upper limit is 45% by mass, or 40% by mass, or 35% by mass, or 30% by mass, or 20% by mass. In order to maintain the interfacial strength between the resin and the cellulose fibers, it is preferably above the lower limit, and in order to maintain the ductility of the resin, it is preferably below the upper limit.

[0121] The melt mass flow rate (MFR) of the acid-modified polypropylene resin measured at 230 °C under a load of 21.2 N in accordance with ISO 1133 is preferably 50 g / 10 min or more, or 100 g / 10 min or more, or 150 g / 10 min or more, or 200 g / 10 min or more, from the viewpoint of enhancing the affinity at the interface between the resin and the cellulose fiber. The upper limit is not particularly limited, but is preferably 500 g / 10 min for maintaining mechanical strength.

[0122] Preferred polyamide resins as the thermoplastic resin include: polyamides obtained by polycondensation reaction 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, 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.) copolymers obtained as polyamides (e.g., polyamide 6,6, polyamide 6,10, polyamide 6,11, polyamide 6,12, polyamide 6,T, polyamide 6,I, polyamide 9,T, polyamide 10,T, polyamide 2M5,T, polyamide MXD,6, polyamide 6,C, polyamide 2M5,C, etc.); and copolymers copolymerized with these respectively (e.g., 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, polyamide 6,12, etc., and alicyclic polyamides such as polyamide 6,C and polyamide 2M5,C are more preferable.

[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. From the viewpoint of the ease of manufacturing the resin composite, the melting point is preferably 350 °C or lower, or 320 °C or lower, or 300 °C or lower.

[0125] There is no particular limitation on the terminal carboxyl group concentration of the polyamide resin, but it is preferably 20 μmol / g or higher, or 30 μmol / g or higher, and preferably 150 μmol / g or lower, or 100 μmol / g or lower, or 80 μmol / g or lower.

[0126] In the polyamide resin, the carboxyl terminal group ratio ([COOH] / [total terminal groups]) to all terminal groups is preferably 0.30 or higher, or 0.35 or higher, or 0.40 or higher, or 0.45 or higher from the viewpoint of the dispersibility in the resin composite of the cellulose fiber, and preferably 0.95 or lower, or 0.90 or lower, or 0.85 or lower, or 0.80 or lower from the viewpoint of the color tone of the resin composite.

[0127] The terminal group concentration of the polyamide resin can be adjusted by a known method. Examples of the adjustment method include adding a terminal modifier (for example, diamine compound, monoamine compound, dicarboxylic acid compound, monocarboxylic acid compound, acid anhydride, monoisocyanate, monoacid halide, monoester, monoalcohol, etc.) that reacts with the terminal group to the polymerization solution so as to obtain a predetermined terminal group concentration during the polymerization of the polyamide.

[0128] Examples of the end-capping agent that reacts with the terminal amino group include aliphatic monocarboxylic acids such as acetic acid, propionic acid, butyric acid, valeric acid, caproic acid, caprylic acid, lauric acid, tridecanoic acid, myristic acid, palmitic acid, stearic acid, pivalic acid, and isobutyric acid; alicyclic monocarboxylic acids such as cyclohexanecarboxylic acid; aromatic monocarboxylic acids such as benzoic acid, toluic acid, α-naphthalenecarboxylic acid, β-naphthalenecarboxylic acid, methylnaphthalenecarboxylic acid, and phenylacetic acid; and a plurality of mixtures arbitrarily selected from these. Among these, from the viewpoints of reactivity, stability of the capped end, price, etc., one or more end-capping agents selected from the group consisting of acetic acid, propionic acid, butyric acid, valeric acid, caproic acid, caprylic acid, lauric acid, tridecanoic acid, myristic acid, palmitic acid, stearic acid, and benzoic acid are preferable, and acetic acid is most preferable.

[0129] Examples of the end-capping agent that reacts with the terminal carboxyl group include aliphatic monoamines such as methylamine, ethylamine, propylamine, butylamine, hexylamine, octylamine, decylamine, stearylamine, dimethylamine, diethylamine, dipropylamine, and dibutylamine; alicyclic monoamines such as cyclohexylamine and dicyclohexylamine; aromatic monoamines such as aniline, toluidine, diphenylamine, and naphthylamine; and any mixtures thereof. Among these, from the viewpoints of reactivity, boiling point, stability of the capped end, price, etc., one or more end-capping agents selected from the group consisting of butylamine, hexylamine, octylamine, decylamine, stearylamine, cyclohexylamine, and aniline are preferable.

[0130] The concentrations of the amino terminal group and the carboxyl terminal group of the polyamide resin 1 can be determined from the integration values of the characteristic signals corresponding to each terminal group by 1H-NMR. This method is preferable in terms of accuracy and simplicity. More specifically, it is recommended to use the method described in JP-A-7-228775, use heavy trifluoroacetic acid as the measurement solvent, and set the number of integrations to 300 scans or more.

[0131] The intrinsic viscosity [η] of the polyamide resin measured under the conditions of 30 °C in concentrated sulfuric acid is preferably 0.6 to 2.0 dL / g, or 0.7 to 1.4 dL / g, or 0.7 to 1.2 dL / g, or 0.7 to 1.0 dL / g from the viewpoint of good fluidity in the mold and good appearance of the molded piece when, for example, injecting and molding the resin composite. In the present disclosure, the "intrinsic viscosity" is synonymous with the viscosity generally called the limiting viscosity. The intrinsic viscosity is obtained by measuring ηsp / c of several measurement solvents with different concentrations in 96% concentrated sulfuric acid under the temperature condition of 30 °C, deriving the relational expression between each ηsp / c and the concentration (c), and extrapolating the concentration to zero. This value extrapolated to zero is the intrinsic viscosity. Details of the above method are described, for example, on pages 291 to 294 of Polymer Process Engineering (Prentice-Hall, Inc 1994). From the viewpoint of accuracy, it is desirable that the concentrations in several measurement solvents with different concentrations be at least 4 points (for example, 0.05 g / dL, 0.1 g / dL, 0.2 g / dL, 0.4 g / dL).

[0132] As the polyester resin preferable as the thermoplastic resin, one or more selected from polyethylene terephthalate (PET), polyethylene naphthalate (PEN), polybutylene terephthalate (PBT), polybutylene succinate (PBS), polybutylene succinate adipate (PBSA), polybutylene adipate terephthalate (PBAT), polyhydroxyalkanoic acid (PHA), polylactic acid (PLA), polyarylate (PAR), etc. can be used. Among them, PET, PBS, PBSA, PBT, and PEN are more preferable, and PBS, PBSA, and PBT are particularly preferable.

[0133] The end groups of the polyester resin can be arbitrarily changed depending on the monomer ratio during polymerization, the presence or absence and amount of the end stabilizer, and the like. The carboxyl end group ratio ([COOH] / [total end groups]) with respect to all the end groups of the polyester resin is preferably 0.30 or more, or 0.35 or more, or 0.40 or more, or 0.45 or more from the viewpoint of the dispersibility of the cellulose fibers in the resin composite, and preferably 0.95 or less, or 0.90 or less, or 0.85 or less, or 0.80 or less from the viewpoint of the color tone of the resin composite.

[0134] Preferred polyacetal resins as the thermoplastic resin include homopolyacetals made from formaldehyde and copolyacetals having trioxane as the main monomer and containing 1,3-dioxolane as the comonomer component. Both can be used, but copolyacetals are preferred from the viewpoint of thermal stability during processing. The amount of the structure derived from the comonomer component (for example, 1,3-dioxolane) is preferably 0.01 mol% or more, or 0.05 mol% or more, or 0.1 mol% or more, or 0.2 mol% or more from the viewpoint of thermal stability during extrusion and molding processes, and preferably 4.0 mol% or less, or 3.5 mol% or less, or 3.0 mol% or less, or 2.5 mol% or less, or 2.3 mol% or less from the viewpoint of mechanical strength.

[0135] (Thermosetting resin) Examples of the thermosetting resin include bisphenol type epoxy resins such as bisphenol A epoxy resin, bisphenol F epoxy resin, bisphenol S epoxy resin, bisphenol E epoxy resin, bisphenol M epoxy resin, bisphenol P epoxy resin, and bisphenol Z epoxy resin; novolac type epoxy resins such as bisphenol A novolac epoxy resin, phenol novolac epoxy resin, and cresol novolac epoxy resin; biphenyl type epoxy resin, biphenyl aralkyl type epoxy resin, aryl alkylene type epoxy resin, tetraphenylol ethane type epoxy resin, naphthalene type epoxy resin, anthracene type epoxy resin, phenoxy type epoxy resin, dicyclopentadiene type epoxy resin, norbornene type epoxy resin, adamantane type epoxy resin, fluorene type epoxy resin, glycidyl methacrylate copolymer type epoxy resin, copolymer epoxy resin of cyclohexyl maleimide and glycidyl methacrylate, epoxy modified polybutadiene rubber derivative, CTBN modified epoxy resin, trimethylolpropane polyglycidyl ether, phenyl-1,3-diglycidyl ether, biphenyl-4,4'-diglycidyl ether, 1,6-hexanediol diglycidyl ether, diglycidyl ether of ethylene glycol or propylene glycol, sorbitol polyglycidyl ether, tris(2,3-epoxypropyl) isocyanurate, triglycidyl tris(2-hydroxyethyl) isocyanurate, novolac type phenol resins such as phenol novolac resin, cresol novolac resin, and bisphenol A novolac resin; resol type phenol resins such as unmodified resol phenol resin and oil-modified resol phenol resin modified with tung oil, linseed oil, walnut oil, etc.; phenol resins such as phenoxy resin, triazine ring-containing resins such as urea (urea) resin and melamine resin, unsaturated polyester resin, bismaleimide resin, diallyl phthalate resin, silicone resin, resin having a benzoxazine ring, norbornene-based resin, cyanate resin, isocyanate resin, urethane resin, benzocyclobutene resin, maleimide resin, bismaleimide triazine resin, polyazomethine resin, thermosetting polyimide, etc.

[0136] (Photocurable resin) Examples of the photocurable resin include (meth)acrylate resins, vinyl resins, epoxy resins, etc. These are generally classified into a radical reaction type in which monomers react with radicals generated by light and a cation reaction type in which monomers undergo cationic polymerization according to the reaction mechanism. Examples of the monomers of the radical reaction type include (meth)acrylate compounds and vinyl compounds (for example, certain vinyl ethers). Examples of the cation reaction type include epoxy compounds and certain vinyl ethers. Note that, for example, an epoxy compound that can be used as the cation reaction type can be a monomer for both thermosetting resins and photocurable resins.

[0137] (Meth)acrylate compounds are compounds having one or more (meth)acrylate groups in the molecule. Examples of (meth)acrylate compounds include monofunctional (meth)acrylates, polyfunctional (meth)acrylates, epoxy acrylates, polyester acrylates, urethane acrylates, etc.

[0138] Examples of vinyl compounds include vinyl ethers, styrene, and styrene derivatives. Examples of vinyl ethers include ethyl vinyl ether, propyl vinyl ether, hydroxyethyl vinyl ether, ethylene glycol divinyl ether, etc. Examples of styrene derivatives include methyl styrene, ethyl styrene, etc. Examples of other vinyl compounds include triallyl isocyanurate, trimethallyl isocyanurate, etc.

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

[0140] (Elastomer) Examples of the elastomer (i.e., rubber) include natural rubber (NR), butadiene rubber (BR), styrene-butadiene copolymer rubber (SBR), isoprene rubber (IR), butyl rubber (IIR), acrylonitrile-butadiene rubber (NBR), acrylonitrile-styrene-butadiene copolymer rubber, chloroprene rubber, styrene-isoprene copolymer rubber, styrene-isoprene-butadiene copolymer rubber, isoprene-butadiene copolymer rubber, chlorosulfonated polyethylene rubber, modified natural rubber (epoxidized natural rubber (ENR), hydrogenated natural rubber, protein-free natural rubber, etc.), ethylene-propylene copolymer rubber, acrylic rubber, epichlorohydrin rubber, polysulfide rubber, silicone rubber, fluororubber, urethane rubber, and the like.

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

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

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

[0144] When the resin is a thermoplastic resin, the minimum processing temperature recommended by the thermoplastic resin supplier is 255 to 270 °C for nylon 66, 225 to 240 °C for nylon 6, 170 to 190 °C for polyacetal resin, and 160 to 180 °C for polypropylene. The heating set temperature is preferably in the range of 20 °C higher than these recommended minimum processing temperatures. By setting the mixing temperature within this temperature range, the cellulose fibers and the resin can be uniformly mixed.

[0145] A resin composite containing a thermoplastic resin as a resin can be provided in various shapes. Specifically, resin pellets, sheets, fibers, plates, rods, etc. can be mentioned, but the resin pellet shape is more preferable from the viewpoints of ease of post-processing and ease of transportation. Preferred pellet shapes at this time include round, elliptical, cylindrical, etc., and these differ depending on the cutting method during extrusion processing. Pellets cut by a cutting method called underwater cut often become round, pellets cut by a cutting method called hot cut often become round or elliptical, and pellets cut by a cutting method called strand cut often become cylindrical. In the case of round pellets, the preferred size is 1 mm or more and 3 mm or less as the pellet diameter. Also, in the case of cylindrical pellets, the preferred diameter is 1 mm or more and 3 mm or less, and the preferred length is 2 mm or more and 10 mm or less. From the viewpoint of operation stability during extrusion, it is desirable that the above diameter and length be equal to or greater than the lower limit, and from the viewpoint of bite-in property into the molding machine in post-processing, it is desirable that they be equal to or less than the upper limit.

[0146] A resin composite containing a thermoplastic resin as a resin can be used as various resin molded articles. There are no particular restrictions on the method for manufacturing the resin molded article, and any manufacturing method may be used, but injection molding, extrusion molding, blow molding, inflation molding, foam molding, etc. can be used. Among these, the injection molding method is the most preferable from the viewpoints of designability and cost.

[0147] When the resin is a thermosetting resin or a photocurable resin, for example, a method of sufficiently dispersing cellulose fibers in a resin solution or a resin powder dispersion and drying, a method of sufficiently dispersing cellulose fibers in a resin monomer solution and polymerizing by heat, UV irradiation, a polymerization initiator, etc., a method of sufficiently impregnating a cellulose fiber dried body with a resin solution or a resin powder dispersion and drying, a method of sufficiently impregnating a cellulose fiber dried body with a resin monomer solution and polymerizing by heat, UV irradiation, a polymerization initiator, etc., etc., a resin composite can be manufactured. 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, after producing a sheet called an uncured or semi-cured prepreg, a method of making the prepreg into a single layer or a laminate and curing and molding the resin by pressure and heating may be used. Examples of the methods of pressure and heating include a press molding method, an autoclave molding method, a bagging molding method, a wrapping tape method, an internal pressure molding method, and the like.

[0149] When the resin is a photocurable resin, a 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 a method of dry-kneading a dried cellulose fiber and a raw rubber, a method of dispersing or dissolving a cellulose fiber and a raw rubber in a dispersion medium and then drying and mixing them, and the like. As the mixing method, a mixing method using a homogenizer is preferable in that high shearing force and pressure can be applied to promote dispersion, but other methods such as a propeller type stirring device, a rotary stirring device, an electromagnetic stirring device, and manual stirring can also be used. A resin composite containing an elastomer is molded using a desired molding method such as die molding, injection molding, extrusion molding, blow molding, foam molding, etc. to obtain an uncured molded body having a desired shape such as a sheet, pellet, powder, etc. The uncured molded body can be vulcanized by heat treatment or the like as necessary to obtain a resin composite.

[0151] A resin composite containing a thermoplastic resin or an elastomer may be heat-treated and melted at a part thereof (for example, at several locations) and then adhered to a substrate such as a resin or metal and used. Further, the resin composite may be a coating film applied to a substrate of a resin or metal, or may form a laminate with the substrate. Further, secondary processing such as annealing treatment, etching treatment, corona treatment, plasma treatment, embossing transfer, cutting, surface polishing, etc. may be performed on the resin composite in the form of a sheet, film or fiber.

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

[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 preferably be 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 the present disclosure.

Examples

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

[0155] ≪Materials Used≫ The materials used for producing the resin composites according to each example and comparative example are as follows.

[0156] <Cellulose Fiber> [CNF-A] Commercially available Celish KY100G (manufactured by Daicel Finechem) was used as a CNF-A cake.

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

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

[0159] After charging slurry S1 into an explosion-proof disperser tank, 3.2 parts by mass of vinyl acetate and 0.49 parts by mass of sodium hydrogen carbonate were added, the temperature inside the tank was set to 50 °C, and stirring was carried out for 120 minutes to obtain a slurry (DMSO solvent) with a solid content rate of 2.9% by mass.

[0160] To stop the reaction, 30 parts by mass of pure water was added and stirred well, then it was put into a dehydrator and concentrated. The obtained wet cake was dispersed, stirred, and concentrated again in 30 parts by mass of pure water, and this washing operation was repeated a total of 5 times to remove unreacted reagents and solvents, etc., and 10 parts by mass of acetylated fine cellulose fiber cake (CNF-B cake) (aqueous solvent) with a solid content rate of 10% by mass was obtained. When a porous sheet was prepared from this cake and the degree of acyl substitution (DS) was determined, DS = 1.0.

[0161] [CNF-C] (CNF treated with a disk refiner) 3 parts by mass of cotton linter pulp was immersed in 27 parts by mass of water and heat-treated in an autoclave at 130 °C for 4 hours. The obtained swollen pulp was washed with water to obtain purified pulp containing water (30 parts by mass). Subsequently, 170 parts by mass of water was added to 30 parts by mass of purified pulp containing water and dispersed in water (solid content rate 1.5% by mass). Using an SDR14 type laboratory refiner (pressure type DISK type) manufactured by Aikawa Iron Works Co., Ltd. as a disk refiner device, with a clearance between disks of 1 mm, the aqueous dispersion was beaten for 20 minutes. Then, it was concentrated by a dehydrator to a solid content rate of 10% by mass to obtain a CNF-C cake (aqueous solvent).

[0162] [CNF-D] (CNF-C further defibrated with a high-pressure homogenizer) The CNF-C cake was thoroughly beaten under conditions where the clearance was reduced to a level almost approaching zero, and a beaten aqueous dispersion (solid content concentration: 1.5% by mass) was obtained. The obtained beaten aqueous dispersion was directly subjected to a micronization treatment 15 times under an operating pressure of 100 MPa using a high-pressure homogenizer (NSO15H manufactured by Niro Soavi, Italy) to obtain a cellulose fiber slurry (solid content concentration: 1.5% by mass). Then, it was concentrated to a solid content ratio of 10% by mass using a dehydrator to obtain a CNF-D cake (water solvent).

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

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

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

[0166] ≪Manufacture of Cellulose Fiber Dry Body≫ To the cellulose fiber cake (10% by mass of solid content), a dispersant was added in an amount of 43 parts by mass with respect to 100 parts by mass of the cellulose fiber solid content, and it was stirred well to obtain a cellulose fiber cake containing the dispersant (for those other than MMSD described later). Alternatively, the cellulose fiber cake (10% by mass of solid content) was diluted with distilled water to a solid content of 1% by mass, and then a dispersant was added in an amount of 43 parts by mass with respect to 100 parts by mass of the cellulose fiber solid content, and it was stirred well to obtain a cellulose fiber slurry (for MMSD described later). These were used as raw materials and charged into a drying apparatus, and drying was carried out at a predetermined shear rate, degree of vacuum, and heating temperature (jacket temperature or hot air temperature). The moisture content was measured using an infrared heating moisture meter (MX - 50 manufactured by A&D), and the time when the moisture content reached 7% by mass or less (solid content mass 93% or more) was taken as the end point of drying. The conditions are as follows.

[0167] [Ladige Mixer (LM)] Equipment: Ladige Mixer (Model No.: VT-20) manufactured by Chuo Kiko Co., Ltd. Conditions: While stirring with a jacket temperature of 100°C, an agitator (peripheral speed 1 m / s), and a chopper (3000 rpm), the pressure was reduced to -90 kPa with a vacuum pump. Vacuum drying was carried out until the product temperature reached 50°C. As the clearance, the minimum distance between the chopper (diameter 100 mm) and the jacket was measured. The drying time under these conditions was 160 minutes. The drying temperature was measured at three points on the surface temperature of the jacket and taken as the average value.

[0168] [High-Speed Vacuum Dryer (HSVD)] Equipment: High-Speed Vacuum Dryer (Model No.: FS10) manufactured by Earth Technica Co., Ltd. Conditions: While stirring with a jacket temperature of 70°C, an agitator (peripheral speed 2 m / s), and a chopper (3500 rpm), the pressure was reduced to -70 kPa with a vacuum pump. Vacuum drying was carried out until the product temperature reached 60°C. As the clearance, the minimum distance between the chopper (diameter 100 mm) and the agitator was measured. The drying time under these conditions was 180 minutes. The drying temperature was measured at three points on the surface temperature of the jacket and taken as the average value.

[0169] [FM Mixer (HM)] Equipment: FM Mixer (Model No.: FM20) manufactured by Nippon Coke & Engineering Co., Ltd. Conditions: While stirring with a jacket temperature of 80°C and stirring blades (500 rpm), the pressure was reduced to -70 kPa with a vacuum pump. Vacuum drying was carried out until the product temperature reached 70°C. As the clearance, the minimum distance between the upper stirring blade (diameter 400 mm) and the jacket was measured. The drying time under these conditions was 180 minutes. The drying temperature was measured at three points on the surface temperature of the jacket, and the average value was used.

[0170] [Paddle dryer (PD)] Device: Paddle dryer (Model No.: NPD-1.6W-12L) manufactured by Nara Machinery Co., Ltd. Conditions: Drying was carried out while heating steam at a temperature of 120 °C and stirring with a stirring blade (30 rpm) until the product temperature reached 100 °C. As the clearance, the minimum distance between the stirring blade (diameter 250 mm) and the jacket was measured. The drying time under these conditions was 50 minutes. The drying temperature was measured at three points on the surface temperature of the stirring blade through which heating steam was passed, and the average value was used.

[0171] [Micro mist spray dryer (MMSD)] Device: Micro mist spray dryer (Model No.: MDL050-M) manufactured by Fujisaki Electric Co., Ltd. Conditions: The cellulose fiber slurry was dried at an inlet temperature of 200 °C, an air supply volume of 1 m 3 / min, a nozzle air flow rate of 80 NL / min, and a slurry of 50 mL / min, and the dried powder was recovered with a cyclone type recovery device. Since the shear rate in this device does not have a stirring mechanism, etc., it was considered that it does not substantially occur. The drying time and residence time under these conditions were 1 minute. The drying temperature was measured three times at the inlet temperature of the hot air during the drying process, and the average value was used.

[0172] [Twin screw extruder (Ex-dry)] Device: Twin screw extruder (Model No.: TEX54αIII: L / D = 63) manufactured by Japan Steel Works, Ltd. Conditions: While rotating the screw at a cylinder temperature of 200 °C and 66 rpm, the raw material was supplied to the uppermost barrel at 20 kg / h using a gravimetric feeder, and dried powder was obtained from the discharge port. As the clearance, the minimum distance between the kneading disk (diameter 54 mm) and the cylinder was measured. The drying time and residence time under these conditions were 1 minute. The drying temperature was measured three times at the temperature of the cylinder where the most downstream kneading disk was placed, and the average value was used.

[0173] [Planetary mixer (PM)] Device: Planetary mixer (model number: ACM-5LVT, hook type) manufactured by Kobayashi Seisakusho Co., Ltd. Conditions: While stirring at a jacket temperature of 60 °C and 307 rpm, the pressure was reduced to -90 kPa with a vacuum pump. Vacuum drying was carried out until the product temperature reached 50 °C. As the clearance, the minimum distance between the hook blade (diameter 100 mm) and the jacket was measured. The drying time under these conditions was 180 minutes. The drying temperature was measured at three points on the surface temperature of the jacket, and the average value was used.

[0174] [Examples 1 to 6, Comparative Examples 1 to 8] Using the CNF shown in Table 1 and using the above device as shown in Table 2, a dried cellulose fiber body was obtained.

[0175] [Examples 7 to 12, Comparative Examples 9 to 12] In LM, a dried cellulose fiber body was obtained in the same manner as in Example 1 except that the CNF, drying temperature, or shear rate was changed as shown in Table 2.

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

[0177] ≪Manufacture of resin composite≫ The dried cellulose fiber body manufactured above and a thermoplastic resin (UBE Nylon 1013B manufactured by Ube Industries, Ltd.) were blended at a ratio such that the cellulose fiber content was 10% by mass in the resin composite, and the resin composite was manufactured by the following procedure.

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

[0179] As for the screw configuration, cylinders 1 to 3 were set as a conveying zone composed only of a conveying screw, and for cylinder 4, two clockwise kneading disks (feeding type kneading disks: hereinafter sometimes simply referred to as RKD) and two neutral kneading disks (non-conveying type kneading disks: hereinafter sometimes simply referred to as NKD) were arranged in order from the upstream side. Cylinder 5 was a conveying zone, cylinder 6 was arranged with 1 RKD and then 2 NKD, cylinders 7 and 8 were conveying zones, and cylinder 9 was arranged with 2 NKD. The subsequent cylinder 10 was a conveying zone, cylinder 11 was arranged with 2 NKD and then 1 counterclockwise screw, and cylinders 12 and 13 were conveying zones. In addition, a vent port was installed at the upper part of cylinder 12 so that decompression suction could be performed, and vacuum suction was carried out.

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

[0181] ≪Evaluation≫ <Evaluation of Cellulose Fibers> [Production of Porous Sheet] First, the wet cake was added to tert-butanol, and further dispersion treatment was carried out with a mixer or the like until there were no aggregates. It was adjusted so that the concentration was 0.5 mass% with respect to 0.5 g of the solid content weight of the cellulose fiber. 100 g of the obtained tert-butanol dispersion was filtered on filter paper, dried at 150°C, and then the filter paper was peeled off to obtain a sheet. The air permeability resistance of this sheet was 10 g / m of the sheet basis weight2 Those with 100 sec / 100 ml or less per 100 ml were used as the porous sheet and as the measurement sample. The basis weight W (g / m 2 ) of the sample left standing for 1 day in an environment of 23°C and 50% RH was measured, and then the air permeability resistance R (sec / 100 ml) was measured using the Oka Laboratory Air Permeability Tester (manufactured by Asahi Seiko Co., Ltd., model EG01). At this time, according to the following formula, the value per basis weight of 10 g / m 2 was calculated. Basis weight 10 g / m 2 Air permeability resistance per basis weight (sec / 100 ml) = R / W × 10

[0182] [Degree of acyl substitution (DS)] The infrared spectra of five locations of the porous sheet by the ATR-IR method were measured with a Fourier transform infrared spectrometer (FT / IR-6200 manufactured by JASCO Corporation). The infrared spectrum measurement was performed under the following conditions. Number of accumulations: 64 times, Wavenumber resolution: 4 cm -1 , Measurement wavenumber range: 4000~600 cm -1 , ATR crystal: Diamond, Incident angle: 45° From the obtained IR spectrum, the IR index was calculated according to the following formula (1): IR index = H1730 / H1030 ··· (1) wherein, H1730 and H1030 are the absorbances at 1730 cm -1 , 1030 cm -1 (absorption band of cellulose backbone chain C-O stretching vibration). However, the absorbances when this baseline is set to absorbance 0 are meant, with the lines connecting 1900 cm -1 and 1500 cm -1 and the lines connecting 800 cm -1 and 1500 cm -1 as the baseline. Then, the average degree of substitution at each measurement location was calculated from the IR index according to the following formula (2), and the average value thereof was taken as DS. DS = 4.13 × IR index ··· (2)

[0183] [Degree of crystallinity] X-ray diffraction measurement of the porous sheet was carried out, and the degree of crystallinity was calculated from the following formula. Degree of crystallinity (%) = [I (200) - I (amorphous) / I (200) × 100 I (200) : Diffraction peak intensity due to the 200 plane (2θ = 22.5°) in cellulose I crystal I (amorphous) : Halo peak intensity due to the amorphous in cellulose I crystal, which is the peak intensity on the low angle side (2θ = 18.0°) 4.5° lower than the diffraction angle of the 200 plane (X-ray diffraction measurement conditions) Apparatus MiniFlex (manufactured by Rigaku Corporation) Operation axis 2θ / θ X-ray source CuKα Measurement method Continuous type Voltage 40 kV Current 15 mA Start angle 2θ = 5° End angle 2θ = 30° Sampling width 0.020° Scan speed 2.0° / min Sample: The porous sheet was attached onto the sample holder

[0184] [Number average fiber diameter] The cellulose fiber cake or cellulose fiber slurry was diluted with tert-butanol to 0.01 mass%, and using a high-shear homogenizer (manufactured by IKA, trade name "Ultra Turrax T18"), it was dispersed under the treatment conditions: rotation speed 25,000 rpm × 5 minutes, cast onto mica, air-dried, and then measured with a high-resolution scanning electron microscope. The measurement was carried out by adjusting the magnification so that at least 100 cellulose fibers were observed. The major axis lengths (L) of 100 randomly selected cellulose fibers were measured, and the additive average of the 100 cellulose fibers was calculated.

[0185] [Weight-average molecular weight (Mw), number-average molecular weight (Mn), and Mw / Mn ratio] Weighed 0.88 g of the porous sheet, cut it into small pieces with scissors, gently stirred it, added 20 mL of pure water, and left it standing for one day. Next, the water and solid content were separated by centrifugation. Subsequently, 20 mL of acetone was added, gently stirred, and left standing for one day. Next, the acetone and solid content were separated by centrifugation. Subsequently, 20 mL of N,N-dimethylacetamide was added, gently stirred, and left standing for one day. Again, after separating the N,N-dimethylacetamide and solid content by centrifugation, 20 mL of N,N-dimethylacetamide was added, gently stirred, and left standing for one day. The N,N-dimethylacetamide and solid content were separated by centrifugation, and 19.2 g of an N,N-dimethylacetamide solution adjusted so that the lithium chloride was 8 mass percent was added to the solid content, stirred with a stirrer, and visually confirmed to dissolve. The solution in which the cellulose fiber was dissolved was filtered through a 0.45 μm filter, and the filtrate was used as a sample for gel permeation chromatography. The apparatus and measurement conditions used are as follows. Apparatus: Tosoh Corporation HLC-8120 Column: TSKgel SuperAWM-H (6.0 mm I.D. × 15 cm) × 2 columns Detector: RI detector Eluent: N,N-dimethylacetamide (lithium chloride 0.2%) Flow rate: 0.6 mL / min Calibration curve: Pullulan conversion

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

[0187] <Evaluation of dry cellulose fiber>[ [Angle of repose, angle of collapse, difference angle, bulk density in loose state, bulk density in compacted state, compressibility] The measurement was carried out using a powder tester (model number: PT-X) manufactured by Hosokawa Micron Corporation.

[0188] (Angle of repose) At the center of a horizontally installed stainless steel measuring table with a diameter of 80 mm, 100 g of dry cellulose fibers were gently dropped at a rate of about 10 g / min from a height where the distance between the lower opening of the funnel (stainless steel, upper opening diameter 70 mm, lower opening diameter 7 mm, inclination angle 60°) and the measuring table was 110 mm via a medicine spoon, and the dry cellulose fibers were deposited in a conical shape on the measuring table. The conical shape was photographed from the side, and the angle between the generatrix of the cone and the horizontal plane was measured. The arithmetic mean value of the three measurements was taken as the angle of repose.

[0189] (Angle of collapse) For the sample whose angle of repose was measured, a 109 g weight on the same pedestal as the measuring table was dropped three times from a height of 160 mm at 2-second intervals. Then, the conical shape of the sample was photographed from the side, and the angle between the generatrix of the cone and the horizontal plane was measured. The arithmetic mean value of the three measurements was taken as the angle of collapse.

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

[0191] (Bulk density in loose state) A stainless steel 100 mL (inner diameter 50.46 mm × depth 50 mm) bottomed cylindrical container was filled with dry cellulose fibers using a medicine spoon at a rate of 10 g / min until it overflowed. After the dry fibers were leveled off, the weight was measured to the nearest 0.01 g. The arithmetic mean value of the three measurements of the weight was divided by the internal volume of the above bottomed cylindrical container to calculate the bulk density in loose state.

[0192] (Bulk density in compacted state) A resin adapter (inner diameter 50.46 mm × length 40 mm) with sufficient capacity was connected to the upper part of the bottomed cylindrical container used at the loose bulk density so as to be in close contact. After putting the dried cellulose fiber into the bottomed cylindrical container until it overflowed in the same procedure as the measurement of the loose bulk density, a vibration with an amplitude of 1.5 mm and a frequency of 50 Hz was applied for 30 seconds using a motor with an eccentric weight attached to the rotating shaft to the bottomed cylindrical container while the adapter was connected. Subsequently, after removing the adapter and rubbing the dried material, the weight was measured to the nearest 0.01 g. The number average value of the three measurements of the weight was divided by the internal volume of the bottomed cylindrical container to calculate the bulk density.

[0193] (Compression degree) From the values of the above-mentioned bulk density and loose bulk density, the following formula: Compression degree = (Bulk density - Loose bulk density) / Bulk density was used to calculate the compression degree.

[0194] [Moisture content] Measurement was carried out using an infrared heating moisture meter (MX-50 (manufactured by A&D)).

[0195] [Degree of dust generation] The dried cellulose fiber was put into the bottomed cylindrical container used in the measurement of the loose bulk density until it overflowed at a rate of 10 g / min using a medicine spoon. After rubbing the dried material, the container held by hand at a height of 1000 mm above the floor was instantly inverted to scatter the powder on the floor. The degree of dust generation 1 second after scattering was evaluated using the following indicators. A No dust generation was observed. B Generation of small dust was observed C Generation of large dust was observed

[0196] <Evaluation of resin composite> [Tensile elongation at break, flexural modulus] From the obtained pellets, using an injection molding machine, molding was carried out under conditions conforming to JIS K6920-2 to mold a multi-purpose test piece conforming to ISO294-3. For the multi-purpose test piece, the tensile elongation at break was measured in accordance with ISO527, and the flexural modulus was measured in accordance with ISO179. Since the polyamide resin undergoes changes due to moisture absorption, it was stored in an aluminum moisture-proof bag immediately after molding to suppress moisture absorption.

[0197]

Table 1

[0198]

Table 2

[0199]

Table 3

[0200]

Table 4

Industrial Applicability

[0201] The high-rigidity resin composite that the present invention can provide can be suitably applied to various resin molded body applications.

Claims

1. A cellulose fiber dry body comprising chemically unmodified cellulose fibers and a dispersing agent, The cellulose fibers have a number average fiber diameter of 2 nm to 1000 nm, The cellulose fiber has a weight average molecular weight (Mw) of 100,000 or more, the cellulose fiber has a ratio (Mw / Mn) of weight average molecular weight (Mw) to number average molecular weight (Mn) of 6 or less; The dried cellulose fiber material has 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 bulk density 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 bulk density 0.6 to 0.9 g / cm 3 The dried cellulose fiber material according to claim 1 or 2, having the following structure:

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

5. The dried cellulose fiber material according to any one of claims 1 to 4, wherein the cellulose fibers have a crystallinity of 60% or more.

6. The dried cellulose fiber material according to any one of claims 1 to 5, wherein the cellulose fiber has an alkali-soluble polysaccharide content of 20 mass% or less.

7. The dried cellulose fiber material according to any one of claims 1 to 6, having a moisture content of 30 mass% or less.

8. The cellulose fiber dried body according to any one of claims 1 to 7, 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.

9. A method for producing a dried cellulose fiber body according to any one of claims 1 to 8, A slurry preparation step of preparing a slurry containing cellulose fibers and a liquid medium; and 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:

10. The method according to claim 9, wherein the drying step is carried out in a batch process using a mechanically agitated mixer granulator.

11. A method for producing a resin composite containing cellulose fibers and a resin, comprising: The method includes mixing the dried cellulose fiber material according to any one of claims 1 to 8 with a resin, The resin composite has a flexural modulus of 3.3 GPa or more.

12. The method of claim 11 , wherein the resin is a thermoplastic resin.

13. The method of claim 12, wherein the thermoplastic resin is a polyamide-based resin.

Images