Compositions comprising cellulose nanofibers

Abstract

One embodiment of the present disclosure provides a rubber composition in which cellulose nanofibers are well dispersed in rubber and can form a molded body having excellent elastic modulus, wear resistance, etc. One embodiment of the present disclosure provides a rubber composition comprising cellulose nanofibers, a first rubber component as a liquid rubber, and a surfactant. In one embodiment, the cellulose nanofibers do not have an ionic group. In addition, in one embodiment, the number average molecular weight of the liquid rubber is 1,000 to 80,000.

Description

Technical Field

[0001] One embodiment of the present disclosure relates to a composition including cellulose nanofibers, and the like. Background Art

[0002] In the past, various properties such as mechanical strength, flexibility, wear resistance, and processability were required to be highly balanced in rubber molded products. For example, fillers were generally added to rubber molded products for the purpose of improving elastic modulus, hardness, and wear resistance. In order for such a rubber molded product containing a filler to exhibit the desired properties, it is important to disperse the filler well in the rubber.

[0003] For example, Patent Document 1 describes a rubber composition for a tire, which is characterized in that oxidized cellulose nanofibers are blended into a diene rubber including a modified diene rubber, for the purpose of improving mechanical properties.

[0004] Prior art literature

[0005] Patent Literature

[0006] Patent Document 1: Japanese Patent Application Publication No. 2019-147877 Summary of the invention

[0007] Problems to be solved by the invention

[0008] In recent years, due to the improvement of awareness of environmental issues, various explorations have been made on the utilization of cellulose as a low specific gravity and renewable material as a filler contained in a rubber molded body. Among them, when cellulose nanofibers are combined with various polymers to form a polymer molded body, the reinforcing effect per unit amount given to the polymer molded body is good, so it is very promising as a filler for a polymer molded body. If such cellulose nanofibers can be used for rubber molded bodies, because of their low specific gravity and excellent various physical properties, a rubber molded body that can be used for a variety of purposes and is also advantageous from the perspective of transportation cost and waste cost can be provided. However, in cellulose nanofibers, due to the contribution of hydroxyl groups in cellulose, it is essentially hydrophilic, so it is usually difficult to mix with rubber as a highly hydrophobic material. Patent document 1 describes a rubber composition for tires, which is formed by dispersing oxidized cellulose nanofibers as fillers in a diene rubber including a modified diene rubber. However, this technology is a technology that improves dispersibility by utilizing modified diene rubber to improve the affinity of oxidized cellulose nanofibers relative to diene rubber. There has not yet been provided a rubber molded product in which cellulose nanofibers are well dispersed in rubber even if the cellulose nanofibers do not have an ionic group.

[0009] An object of one embodiment of the present invention is to solve the above-mentioned problems and to provide a rubber composition in which cellulose nanofibers are well dispersed in rubber and a molded body excellent in elastic modulus, wear resistance, etc. can be formed.

[0010] Means for solving problems

[0011] The present disclosure includes the following aspects.

[0012] [1] A rubber composition comprising cellulose nanofibers, a first rubber component as a liquid rubber, and a surfactant.

[0013] [2] The rubber composition according to the above aspect 1, wherein the cellulose nanofibers do not have an ionic group.

[0014] [3] The rubber composition according to aspect 1 or 2 above, wherein the number average molecular weight of the liquid rubber is 1,000 to 80,000.

[0015] [4] The rubber composition according to any one of aspects 1 to 3 above, wherein the ratio (Mw / Mn) of the number average molecular weight (Mn) to the weight average molecular weight (Mw) of the liquid rubber is 1.5 to 5.

[0016] [5] The rubber composition according to any one of aspects 1 to 4 above, wherein the viscosity of the liquid rubber at 80° C. is 1,000,000 mPa·s or less.

[0017] [6] The rubber composition according to any one of aspects 1 to 5 above, wherein the viscosity of the liquid rubber at 25° C. is 1,000,000 mPa·s or less.

[0018] [7] The rubber composition according to any one of aspects 1 to 6 above, wherein the viscosity of the liquid rubber at 0°C is 1,000,000 mPa·s or less.

[0019] [8] The rubber composition according to any one of aspects 1 to 7, wherein the liquid rubber comprises one or more selected from the group consisting of diene rubber, silicone rubber, polyurethane rubber, polysulfide rubber, and hydrogenated products thereof.

[0020] [9] The rubber composition according to any one of aspects 1 to 8 above, wherein the degree of substitution of the cellulose nanofibers is 0.

[0021]

[10] The rubber composition according to any one of aspects 1 to 9 above, comprising 0.5% by mass to 10% by mass of the cellulose nanofibers.

[0022]

[11] The rubber composition according to any one of aspects 1 to 10, wherein the surfactant is contained in an amount of 10 to 200 parts by mass based on 100 parts by mass of the cellulose nanofibers.

[0023]

[12] The rubber composition according to any one of aspects 1 to 11 above, wherein the surfactant is a nonionic surfactant or a cationic surfactant.

[0024]

[13] The rubber composition according to aspect 12 above, wherein the surfactant is a nonionic surfactant.

[0025]

[14] The rubber composition according to the above aspect 13, wherein the nonionic surfactant is a compound having a hydrophilic group selected from the group consisting of a hydroxyl group, a carboxyl group, a sulfonic acid group and an amino group, and a hydrocarbon group.

[0026]

[15] The rubber composition according to the above embodiment 13 or 14, wherein the nonionic surfactant is one or more selected from the group consisting of a compound represented by the following general formula (1) and a compound represented by the following general formula (2),

[0027] R-(OCH 2 CH 2 ) m -OH(1)

[0028] [wherein, R represents a monovalent aliphatic group having 6 to 30 carbon atoms, and m is a natural number smaller than the number of carbon atoms of R],

[0029] R 1 OCH 2 -(CHOH) 4 -CH 2 OR 2 (2)

[0030] [Where R 1 and R 2 each independently represents a hydrogen atom, an aliphatic group having 1 to 30 carbon atoms, -COR 3 {In the formula, R 3 represents an aliphatic group having 1 to 30 carbon atoms}, or -(CH 2 CH 2 O) y -R 4 {In the formula, R 4 represents a hydrogen atom or an aliphatic group having 1 to 30 carbon atoms, and y is an integer of 1 to 30}].

[0031]

[16] The rubber composition according to any one of aspects 1 to 15, wherein at least a portion of the surface of the cellulose nanofibers is covered with the first rubber component.

[0032]

[17] A powder comprising the rubber composition according to any one of aspects 1 to 16 above.

[0033]

[18] The powder according to the above method 17 has a tapped bulk density of 0.01 g / cm 3 ~0.30g / cm 3 .

[0034]

[19] A masterbatch, which is a kneaded product of the powder according to aspect 17 or 18 and a second rubber component.

[0035]

[20] A method for producing a masterbatch, comprising the step of kneading the powder according to aspect 17 or 18 above with a second rubber component to obtain a masterbatch.

[0036]

[21] A rubber composite, which is a kneaded product of the powder according to aspect 17 or 18 or the masterbatch according to aspect 19 and a third rubber component.

[0037]

[22] The rubber composite according to aspect 21, wherein at least a portion of the surface of the cellulose nanofibers is covered with the first rubber component.

[0038]

[23] A method for producing a rubber composite, comprising the step of obtaining the rubber composite by:

[0039] kneading the powder described in the above-mentioned embodiment 17 or 18 with the third rubber component; or

[0040] A masterbatch is formed by the method described in aspect 20, and then the masterbatch and the third rubber component are kneaded.

[0041]

[24] The method according to aspect 23, wherein in the rubber composite, at least a portion of the surface of the cellulose nanofibers is covered with the first rubber component.

[0042]

[25] A rubber cured product, which is a cured product of the rubber composite according to aspect 21 or 22 above.

[0043]

[26] A method for producing a rubber cured product, comprising the following steps:

[0044] A step of obtaining a rubber composite by the method described in the above embodiment 23 or 24; and

[0045] A step of curing the rubber composite to obtain a rubber cured product.

[0046]

[27] A shoe outsole comprising the rubber cured product described in the above method 25.

[0047]

[28] A tire comprising the rubber cured product according to aspect 25 above.

[0048]

[29] An anti-vibration rubber comprising the rubber cured product according to aspect 25 above.

[0049]

[30] A transmission belt comprising the rubber cured product according to aspect 25 above.

[0050] Effects of the Invention

[0051] According to one embodiment of the present invention, there is provided a rubber composition in which cellulose nanofibers are well dispersed in rubber and which can form a molded body having excellent elastic modulus, wear resistance, and the like. BRIEF DESCRIPTION OF THE DRAWINGS

[0052] Figure 1 This is a diagram showing an image of a cross section of the powder obtained in Example 10 observed with a scanning electron microscope. DETAILED DESCRIPTION

[0053] The following is an exemplary embodiment of the present invention (hereinafter referred to as "the present embodiment"), but the present invention is not limited to these embodiments. It should be noted that, unless otherwise specified, the characteristic values ​​of the present invention are values ​​measured by the method described in the [Examples] of the present invention or by a method that is understood by those skilled in the art to be equivalent thereto.

[0054] Rubber composition

[0055] One method of the present disclosure provides a rubber composition, which includes cellulose nanofibers, a surfactant, and a first rubber component as a liquid rubber. Cellulose nanofibers are essentially hydrophilic due to their hydroxyl groups, but on the other hand, rubber is essentially hydrophobic, and cellulose nanofibers are usually difficult to be evenly dispersed in rubber. For example, the dispersibility can be improved to a certain extent by the use of a dispersant, but from the perspective of preventing the physical properties of the molded body from being reduced, it is preferred to minimize the necessity of the additive and evenly disperse the cellulose nanofibers in the rubber. The inventor has conducted various studies from this point of view, and found that the rubber composition is prepared by dispersing cellulose nanofibers in a specific rubber with fluidity at a specified temperature, and then the rubber composition is mixed with rubber in the form of a rubber masterbatch to manufacture a rubber composite, thereby being able to form a rubber cured product that does not damage the physical properties originally expected of the rubber and well exhibits the reinforcing effect based on the cellulose nanofibers. According to the rubber composition of this embodiment, it is possible to form a rubber cured product in which cellulose nanofibers are well dispersed in the rubber and have good properties (especially elastic modulus, hardness, etc.), and such a rubber cured product can form a molded body in which cellulose nanofibers are well dispersed in the rubber and have excellent elastic modulus, wear resistance, etc.

[0056] Preferred examples of the components of the rubber composition according to the present embodiment will be described below.

[0057] <Cellulose Nanofiber>

[0058] As the raw material of cellulose nanofiber, natural cellulose and regenerated cellulose can be used. As natural cellulose, wood pulp obtained from wood species (broadleaf tree or conifer), non-wood pulp obtained from non-wood species (cotton, bamboo, hemp, bagasse, kenaf, cotton lint, sisal, straw, etc.), cellulose aggregates produced by animals (such as sea squirts) or algae, microorganisms (such as acetic acid bacteria) can be used. As regenerated cellulose, regenerated cellulose fibers (viscose, cuprammonia silk, tencel, etc.), cellulose derivative fibers, regenerated cellulose obtained by electrostatic spinning or cellulose derivatives, etc. can be used.

[0059] In one embodiment, cellulose nanofibers are fine cellulose fibers obtained by treating pulp with hot water at 100°C or above, hydrolyzing hemicellulose to make it brittle, and then mechanically opening the fibers using a high-pressure homogenizer, a microfluidizer, a ball mill, a disc mill, a mixer (e.g., a homogeneous mixer) or other pulverization method. In one embodiment, the number average fiber diameter of the cellulose nanofiber is 1 nm or more and 1000 nm or less. As described below, the cellulose nanofiber may be a chemically modified fiber, but from the perspective of the reinforcing effect as a filler, it is preferably not chemically modified. For example, for cellulose nanofibers that are opened by chemical oxidation treatment such as 2,2,6,6-tetramethylpiperidin-1-oxyl (TEMPO) phosphate, there is a tendency for heat resistance to decrease due to the ionic groups (e.g., carboxyl groups) introduced into the cellulose nanofibers, and there is a tendency for the fiber diameter to decrease after opening the fibers. From the perspective of the reinforcing effect as a filler, it is more advantageous for cellulose nanofibers that are only mechanically opened (i.e., chemically opened without oxidation or other treatments). Therefore, in a preferred embodiment, the cellulose nanofibers do not have an ionic group. In the present disclosure, the cellulose nanofibers do not have an ionic group means that the amount of ionic groups measured by conductivity titration is 0.1 mmol / g or less.

[0060] The slurry can be prepared by dispersing the cellulose fibers in a liquid medium. The dispersion can be performed using a high-pressure homogenizer, a microfluidizer, a ball mill, a disc mill, a mixer (e.g., a homogeneous mixer), etc. For example, the above-mentioned fiber-opening product can be obtained as the product of the slurry preparation process of the present disclosure. In addition to water, the liquid medium in the slurry can also optionally further contain other liquid media (e.g., organic solvents) in the form of one or more liquid media alone or in combination. As the organic solvent, a commonly used water-miscible organic solvent can be used, such as alcohols with a boiling point of 50°C to 170°C (e.g., methanol, ethanol, n-propanol, isopropanol, n-butanol, isobutanol, sec-butanol, tert-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.

[0061] The cellulose raw material contains alkali-soluble components and sulfuric acid-insoluble components (lignin, etc.), so the alkali-soluble components and sulfuric acid-insoluble components can be reduced through a refining process such as delignification by steaming treatment and a bleaching process. On the other hand, in the refining process such as delignification by steaming treatment and the bleaching process, the molecular chain of cellulose is cut, and the weight average molecular weight and the number average molecular weight change. Therefore, it is preferable to control the refining process and bleaching process of the cellulose raw material so that the weight average molecular weight of the cellulose nanofiber and the ratio of the weight average molecular weight to the number average molecular weight are within an appropriate range.

[0062] In addition, the delignification and bleaching steps based on steaming treatment reduce the molecular weight of cellulose molecules, so the molecular weight of cellulose nanofibers may be reduced due to these steps, and the cellulose raw material may be deteriorated, thereby increasing the proportion of alkali-soluble components. Since the heat resistance of alkali-soluble components is poor, it is preferred to control the purification and bleaching steps of the cellulose raw material so that the amount of alkali-soluble components contained in the cellulose raw material is within a range below a certain value.

[0063] In one embodiment, from the perspective of obtaining a good effect of improving physical properties by using cellulose nanofibers, the number average fiber diameter of the cellulose nanofibers is preferably 2 to 1000 nm. The number average fiber diameter of the cellulose nanofibers 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.

[0064] From the perspective of improving the mechanical properties of the rubber composite containing cellulose nanofibers by a small amount of cellulose nanofibers, the ratio of average fiber length (L) / fiber diameter (D) of the cellulose nanofibers 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 perspective of handleability.

[0065] In the present disclosure, the fiber length, fiber diameter and L / D ratio of cellulose nanofibers are obtained as follows: an aqueous dispersion of cellulose nanofibers is dispersed using a high shear homogenizer (e.g., manufactured by Nippon Seiki Co., Ltd., trade name "EXCEL AUTOHomogenizer ED-7") at a rotation speed of 15,000 rpm × 5 minutes, the obtained aqueous dispersion is diluted with pure water to 0.1-0.5% by mass, poured on mica, air-dried and used as a measurement sample, and measured using a scanning electron microscope (SEM) or an atomic force microscope (AFM) to obtain the fiber length. Specifically, in an observation field adjusted in magnification so that at least 100 cellulose nanofibers are observed, the length (L) and diameter (D) of 100 randomly selected cellulose nanofibers are measured, and the ratio (L / D) is calculated. For cellulose nanofibers, the number average of the fiber length (L), the number average of the fiber diameter (D) and the number average of the ratio (L / D) are calculated.

[0066] Alternatively, the fiber length, fiber diameter and L / D ratio of cellulose nanofibers contained in a powder, a rubber composition, a rubber masterbatch, a rubber composite or the like can be confirmed by measuring these as measurement samples using the above-mentioned measurement methods.

[0067] Alternatively, the fiber length, fiber diameter, and L / D ratio of cellulose nanofibers contained in powders, rubber compositions, rubber masterbatches, rubber composites, etc. can be determined by dissolving the polymer components contained therein in an organic or inorganic solvent capable of dissolving the polymer components, separating the cellulose nanofibers, and washing them sufficiently with the above-mentioned solvent. Then, an aqueous dispersion in which the solvent is replaced with pure water is prepared, and the dispersion is diluted with pure water until the cellulose nanofiber concentration is 0.1 to 0.5% by mass. The dispersion is poured onto mica, air-dried, and used as a measurement sample, and the measurement is performed using the above-mentioned measurement method to confirm the measurement. At this time, for the cellulose nanofibers to be measured, more than 100 fibers are randomly selected for measurement.

[0068] The crystallinity of the cellulose nanofibers is preferably 55% or more. When the crystallinity is within this range, the mechanical properties (strength, dimensional stability) of cellulose itself are high, so when the cellulose nanofibers are dispersed in rubber, the strength and dimensional stability of the rubber composite tend to increase. The more preferred lower limit of the crystallinity is 60%, further preferably 70%, and most preferably 80%. There is no particular limitation on the upper limit of the crystallinity of the cellulose nanofibers, but the upper limit is preferably high. From the perspective of production, the preferred upper limit is 99%.

[0069] Between the microfibrils of the plant-derived cellulose nanofibers 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, which is hydrogen-bonded with cellulose and plays a role in linking the microfibrils. In addition, lignin is a compound with an aromatic ring, and is known to be covalently bonded with hemicellulose in the cell wall of plants. If the residual amount of impurities such as lignin in the cellulose nanofiber is many, discoloration may be caused due to the heat during processing, so from the aspect of the discoloration of the rubber complex during the extrusion processing and the molding processing, the crystallinity of the cellulose nanofiber is also preferably within the above range.

[0070] The crystallinity referred to herein is determined by the following formula using the Segal method from a diffraction pattern (2θ / deg. 10 to 30) obtained when the cellulose is cellulose I type crystal (derived from natural cellulose) when the sample is measured by wide-angle X-ray diffraction.

[0071] Crystallinity (%) = ([Diffraction intensity due to the (200) plane at 2θ / deg. = 22.5] - [Diffraction intensity due to the amorphous state at 2θ / deg. = 18]) / [Diffraction intensity due to the (200) plane at 2θ / deg. = 22.5] × 100

[0072] In addition, regarding the crystallinity, when the cellulose is a cellulose II type crystal (derived from regenerated cellulose), it can be calculated using the following formula based on the absolute peak intensity h0 at 2θ=12.6° of the (110) plane peak belonging to the cellulose II type crystal in wide-angle X-ray diffraction and the peak intensity h1 from the baseline at the plane spacing.

[0073] Crystallinity (%) = h1 / h0×100

[0074] As the crystal form of cellulose, there are known types I, II, III, and IV, among which types I and II are particularly common, and types III and IV are obtained on a laboratory scale, but are not commonly used on an industrial scale. The cellulose nanofiber disclosed in the present invention has relatively high structural mobility. By dispersing the cellulose nanofiber in rubber, a molded body having a lower linear expansion coefficient and better strength and elongation during stretching and bending deformation can be obtained. Therefore, cellulose nanofibers containing cellulose type I crystals or cellulose type II crystals are preferred, and cellulose nanofibers containing cellulose type I crystals and having a crystallinity of 55% or more are more preferred.

[0075] In addition, the degree of polymerization of the cellulose nanofibers is preferably 100 or more, more preferably 150 or more, more preferably 200 or more, more preferably 300 or more, more preferably 400 or more, more preferably 450 or more, and is preferably 3500 or less, more preferably 3300 or less, more preferably 3200 or less, more preferably 3100 or less, more preferably 3000 or less.

[0076] The degree of polymerization of cellulose nanofibers is preferably within the above range from the viewpoints of processability and mechanical property expression. From the viewpoint of processability, the degree of polymerization is preferably not too high, and from the viewpoint of mechanical property expression, the degree of polymerization is preferably not too low.

[0077] The degree of polymerization of cellulose nanofibers refers to the average degree of polymerization measured by the reduced viscosity method using a copper ethylenediamine solution described in the confirmation test (3) of "Explanation of the Fifteenth Revised Japanese Pharmacopoeia (published by Hirokawa Shoten)".

[0078] In one embodiment, the weight average molecular weight (Mw) of the cellulose nanofiber 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. The larger the weight average molecular weight, the fewer the number of terminal groups of the cellulose molecule. In addition, the ratio (Mw / Mn) of the weight average molecular weight to the number average molecular weight represents the width of the molecular weight distribution, so the smaller the Mw / Mn, the fewer the number of terminals of the cellulose molecule. Since the terminal of the cellulose molecule is the starting point of thermal decomposition, when not only the weight average molecular weight of the cellulose molecule of the cellulose nanofiber is large, but also the width of the molecular weight distribution is narrow when the weight average molecular weight is large, a cellulose nanofiber with high heat resistance and a rubber composition comprising cellulose nanofibers and rubber can be obtained. From the aspect of the ease of obtaining the cellulose raw material, the weight average molecular weight (Mw) of the cellulose nanofiber can be, for example, 600,000 or less, or 500,000 or less. From the perspective of the ease of manufacturing cellulose nanofibers, the ratio of the weight average molecular weight to the number average molecular weight (Mn) (Mw / Mn) can be, for example, 1.5 or more, or 2 or more. Mw can be controlled within the above range by selecting a cellulose raw material having a Mw corresponding to the purpose, and appropriately performing physical and / or chemical treatments on the cellulose raw material within an appropriate range. In addition, Mw / Mn can also be controlled within the above range by selecting a cellulose raw material having a Mw / Mn corresponding to the purpose, and appropriately performing physical and / or chemical treatments on the cellulose raw material within an appropriate range. In one embodiment, the Mw and Mw / Mn of the cellulose raw material can be within the above ranges, respectively. In both the control of Mw and the control of Mw / Mn, as the above-mentioned physical treatment, dry or wet grinding using a microfluidizer, a ball mill, a disc mill, etc., a crusher, a homogeneous mixer, a high-pressure homogenizer, an ultrasonic device, etc., can be exemplified. Shearing, scraping, etc. Examples of the physical treatment using mechanical force such as friction and the chemical treatment include steaming, bleaching, acid treatment, and regenerated cellulose.

[0079] The weight average molecular weight and number average molecular weight of the cellulose nanofibers mentioned here are values ​​obtained by dissolving the cellulose nanofibers in N,N-dimethylacetamide to which lithium chloride is added, and then subjecting the result to gel permeation chromatography using N,N-dimethylacetamide as a solvent.

[0080] As a method for controlling the degree of polymerization (i.e., average degree of polymerization) or molecular weight of cellulose nanofibers, hydrolysis treatment can be cited. The amorphous cellulose inside the cellulose nanofibers is depolymerized by hydrolysis treatment, and the average degree of polymerization is reduced. In addition, by hydrolysis treatment, impurities such as hemicellulose and lignin are removed in addition to the amorphous cellulose, so that the fiber interior becomes porous.

[0081] There is no particular limitation on the method of hydrolysis, and examples include acid hydrolysis, alkaline hydrolysis, hot water decomposition, steam explosion, microwave decomposition, and the like. These methods may be used alone or in combination of two or more. In the method of acid hydrolysis, for example, α-cellulose obtained as pulp from fibrous plants is used as a cellulose raw material and dispersed in an aqueous medium. In this state, a protonic acid, carboxylic acid, Lewis acid, heteropoly acid, etc. are added in appropriate amounts and heated under stirring, thereby making it easy to control the average degree of polymerization. The reaction conditions such as temperature, pressure, and time at this time vary according to the type of cellulose, cellulose concentration, type of acid, acid concentration, etc., and are appropriately adjusted to achieve the target average degree of polymerization. For example, the following conditions may be cited: using an inorganic acid aqueous solution of less than 2% by mass, the cellulose nanofibers are treated at 100°C or above and under pressure for more than 10 minutes. Under this condition, catalyst components such as acid penetrate into the interior of the cellulose nanofibers, hydrolysis is promoted, the amount of catalyst components used is reduced, and subsequent refining becomes easier. In addition, the dispersion liquid of the cellulose raw material during hydrolysis may contain a small amount of an organic solvent in addition to water within a range that does not impair the effects of the present invention.

[0082] The alkali-soluble polysaccharides that cellulose nanofibers may contain include β-cellulose and γ-cellulose in addition to hemicellulose. For those skilled in the art, alkali-soluble polysaccharides may be understood as components obtained in the form of alkali-soluble parts of holocellulose obtained by solvent extraction and chlorine treatment of plants (e.g. wood) (i.e., components from which α-cellulose has been removed from holocellulose). Alkali-soluble polysaccharides are polysaccharides containing hydroxyl groups, which have poor heat resistance and may lead to decomposition when heated, yellowing during heat aging, and reduction in the strength of cellulose nanofibers. Therefore, it is preferred that the alkali-soluble polysaccharide content in the cellulose nanofibers is low.

[0083] In one embodiment, from the perspective of obtaining good dispersibility of the cellulose nanofibers, the average content of the alkali-soluble polysaccharide in the cellulose nanofibers 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 relative to 100% by mass of the cellulose nanofibers. From the perspective of ease of production of the cellulose nanofibers, the above content may be 1% by mass or more, or 2% by mass or more, or 3% by mass or more.

[0084] The average content of alkali-soluble polysaccharides can be obtained by the method described in the non-patent literature (Handbook of Wood Science Experiments, edited by the Japan Wood Society, pages 92-97, 2000), which is obtained by subtracting the α-cellulose content from the total cellulose content (Wise method). It should be noted that this method is understood as a method for determining the amount of hemicellulose in the technical field. The alkali-soluble polysaccharide content is calculated three times for one sample, and the calculated alkali-soluble polysaccharide content is averaged as the average alkali-soluble polysaccharide content.

[0085] In one embodiment, from the perspective of avoiding a decrease in the heat resistance of the cellulose nanofibers and the discoloration associated therewith, the average content of the acid-insoluble components in the cellulose nanofibers is preferably 10% by mass or less, or 5% by mass or less, or 3% by mass or less relative to 100% by mass of the cellulose nanofibers. From the perspective of ease of manufacturing the cellulose nanofibers, the above content may be 0.1% by mass or more, or 0.2% by mass or more, or 0.3% by mass or more.

[0086] About the average content of acid-insoluble components, the Klason method described in the non-patent literature (Handbook of Wood Science Experiments, Japan Wood Society, pp. 92-97, 2000) is used to quantify the acid-insoluble components. It should be noted that this method is understood as a method for determining the amount of lignin in the art. The sample is stirred in a sulfuric acid solution to dissolve cellulose and hemicellulose, and then filtered with a glass fiber filter paper. The resulting residue is equivalent to the acid-insoluble component. The acid-insoluble component content is calculated based on the weight of the acid-insoluble component, and the number average of the acid-insoluble component content calculated for 3 samples is used as the average content of the acid-insoluble component.

[0087] The thermal decomposition starting temperature (T D ), in one embodiment, it is 270°C or higher, preferably 275°C or higher, more preferably 280°C or higher, and further preferably 285°C or higher, from the perspective of being able to exert preferred heat resistance and mechanical strength in vehicle-mounted applications, etc. The higher the thermal decomposition starting temperature, the more preferred it is. From the perspective of ease of manufacturing the cellulose nanofibers, it can be, for example, 320°C or lower, or 300°C or lower.

[0088] In this disclosure, T D The value is obtained from a graph in which the horizontal axis is temperature and the vertical axis is weight residual rate (%) in thermogravimetric (TG) analysis. The weight of cellulose nanofibers at 150°C (a state where water is basically removed) (weight loss 0 wt%) is used as the starting point, and the temperature is further increased to obtain the temperature (T 1％ ) and the temperature at which the weight loss was 2 wt% (T 2％The temperature of the point where the straight line intersects the horizontal line (base line) passing through the starting point of the weight loss of 0 wt% is defined as T D .

[0089] 1% weight loss temperature (T 1％ ) is to use the above T D When the temperature is further increased in the method, 150° C. is taken as the temperature at which the weight decreases by 1% by weight from the starting point.

[0090] Weight loss rate of cellulose nanofibers at 250℃ (T 250℃ ) is the weight loss rate of cellulose nanofibers after keeping them at 250° C. under nitrogen purge for 2 hours in TG analysis.

[0091] (Chemical modification)

[0092] The cellulose nanofibers may be chemically modified cellulose nanofibers. The cellulose nanofibers may be chemically modified in advance at the stage of raw pulp or cotton linters, during the fiberizing process, or after the fiberizing process, or may be chemically modified during or after the pulp preparation process, or during or after the drying (granulation) process.

[0093] As a modifier for cellulose nanofibers, a compound that reacts with the hydroxyl group of cellulose can be used, and esterifying agents, etherifying agents, and silylating agents can be cited. On the other hand, modifiers with polar groups such as carboxylic acids and phosphates have a tendency to reduce heat resistance by introducing ionic groups (such as carboxyl groups) into cellulose nanofibers, and have a tendency to reduce the fiber diameter after fiber opening. Therefore, from the perspective of the reinforcing effect as a filler, it is preferred not to use the modifier. In a preferred embodiment, chemical modification is acylation using an esterifying agent, and acetylation is particularly preferred. As an esterifying agent, acyl halides, acid anhydrides, and carboxylic acid vinyl esters and carboxylic acids are preferred.

[0094] The acid halide may be at least one selected from the group consisting of compounds represented by the following formulae.

[0095] R 1 -C(=O)-X

[0096] (Where 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. )

[0097] As specific examples of acyl halides, 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. can be mentioned, but it is not limited to these. Among them, from the aspect of reactivity and handling, acyl chloride can be preferably used. It should be noted that in the reaction of acyl halides, in order to play a role as a catalyst and neutralize the acidic substance as a by-product, one or more basic compounds can be added. As basic compounds, specifically, tertiary amine compounds such as triethylamine and trimethylamine can be mentioned; and nitrogen-containing aromatic compounds such as pyridine and dimethylaminopyridine can be mentioned, but it is not limited to this.

[0098] As the acid anhydride, any appropriate acid anhydride can be used. For example:

[0099] Anhydrides of saturated aliphatic monocarboxylic acids such as acetic acid, propionic acid, (iso)butyric acid, and valeric acid; anhydrides of unsaturated aliphatic monocarboxylic acids such as (meth)acrylic acid and oleic acid;

[0100] anhydrides of alicyclic monocarboxylic acids such as cyclohexanecarboxylic acid and tetrahydrobenzoic acid;

[0101] Anhydrides of aromatic monocarboxylic acids such as benzoic acid and 4-methylbenzoic acid;

[0102] Examples of the dicarboxylic acid anhydride include anhydrides of saturated aliphatic dicarboxylic acids such as succinic acid and adipic acid; unsaturated aliphatic dicarboxylic acid anhydrides such as maleic anhydride and itaconic anhydride; alicyclic dicarboxylic acid anhydrides such as 1-cyclohexene-1,2-dicarboxylic anhydride, hexahydrophthalic anhydride and methyltetrahydrophthalic anhydride; and aromatic dicarboxylic anhydrides such as phthalic anhydride and naphthalene dicarboxylic anhydride.

[0103] Examples of the trivalent or higher polycarboxylic acid anhydrides include polycarboxylic acids (anhydrides) such as trimellitic anhydride and pyromellitic dianhydride.

[0104] It should be noted that, in the reaction of the acid anhydride, one or more of the following substances may be added as a catalyst: an acidic compound such as sulfuric acid, hydrochloric acid, phosphoric acid, etc.; or a Lewis acid (for example, a Lewis acid compound represented by MYn, where M represents a semimetal element such as B, As, Ge, or a base metal element such as Al, Bi, In, or a transition metal element such as Ti, Zn, Cu, or a lanthanide element, where n is an integer corresponding to the atomic valence of M and represents 2 or 3, and where Y represents a halogen atom, OAc, OCOCF, etc. 3 , ClO 4 , SbF 6 PF 6 or OSO 2 CF 3 (OTf)); or basic compounds such as triethylamine and pyridine.

[0105] As the vinyl carboxylate, the following formula is preferred:

[0106] R-COO-CH=CH 2

[0107] A vinyl carboxylate represented by {wherein R is 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 is more preferably at least one selected from the group consisting of vinyl acetate, vinyl propionate, vinyl butyrate, vinyl caproate, vinyl cyclohexanecarboxylate, vinyl caprylate, vinyl caprate, vinyl laurate, vinyl myristate, vinyl palmitate, vinyl stearate, vinyl pivalate, vinyl caprylate, divinyl adipate, vinyl methacrylate, vinyl crotonate, vinyl caprylate, vinyl benzoate, and vinyl cinnamate. When the esterification reaction based on carboxylic acid vinyl ester is carried out, 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 can be added as a catalyst.

[0108] Examples of the alkali metal hydroxide and alkaline earth metal hydroxide include sodium hydroxide, potassium hydroxide, lithium hydroxide, calcium hydroxide, barium hydroxide, etc. Examples of the alkali metal carbonate, alkaline earth metal carbonate, and alkali metal hydrogen carbonate include lithium carbonate, sodium carbonate, potassium carbonate, cesium carbonate, magnesium carbonate, calcium carbonate, barium carbonate, lithium hydrogen carbonate, sodium hydrogen carbonate, potassium hydrogen carbonate, and cesium hydrogen carbonate, etc.

[0109] Primary to tertiary amines are primary amines, secondary amines and tertiary amines. Specific examples thereof include ethylenediamine, diethylamine, proline, N,N,N',N'-tetramethylethylenediamine, N,N,N',N'-tetramethyl-1,3-propylenediamine, N,N,N',N'-tetramethyl-1,6-hexanediamine, tris(3-dimethylaminopropyl)amine, N,N-dimethylcyclohexylamine, triethylamine and the like.

[0110] Examples of imidazole and derivatives thereof include 1-methylimidazole, 3-aminopropylimidazole, and carbonyldiimidazole.

[0111] Examples of pyridine and derivatives thereof include N,N-dimethyl-4-aminopyridine and picoline.

[0112] Examples of the alkoxide include sodium methoxide, sodium ethoxide, potassium tert-butoxide, and the like.

[0113] Examples of the carboxylic acid include at least one selected from the group consisting of compounds represented by the following formulae.

[0114] R-COOH

[0115] (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.)

[0116] 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, caprylic acid, benzoic acid and cinnamic acid.

[0117] Among these carboxylic acids, at least one selected from the group consisting of acetic acid, propionic acid, and butyric acid is preferred from the viewpoint of reaction efficiency, and acetic acid is particularly preferred.

[0118] It should be noted that, in the reaction of carboxylic acid, one or more of the following substances may be added as a catalyst: an acidic compound such as sulfuric acid, hydrochloric acid, phosphoric acid, etc.; or a Lewis acid (for example, a Lewis acid compound represented by MYn, where M represents a semimetal element such as B, As, Ge, or a base metal element such as Al, Bi, In, or a transition metal element such as Ti, Zn, Cu, or a lanthanide element, where n is an integer corresponding to the atomic valence of M and represents 2 or 3, and where Y represents a halogen atom, OAc, OCOCF, etc. 3 , ClO 4 , SbF 6 PF 6 or OSO 2 CF 3 (OTf)); or basic compounds such as triethylamine and pyridine.

[0119] Among these esterification reaction agents, at least one selected from the group consisting of acetic anhydride, propionic anhydride, butyric anhydride, vinyl acetate, vinyl propionate, vinyl butyrate and acetic acid is particularly preferred from the viewpoint of reaction efficiency, and acetic anhydride and vinyl acetate are particularly preferred.

[0120] When the cellulose nanofibers are chemically modified (for example, by hydrophobization such as acylation), the dispersibility of the cellulose nanofibers in rubber tends to be good, but the cellulose nanofibers of the present disclosure show good dispersibility in rubber even if they are unsubstituted or have a low degree of substitution.

[0121] In one embodiment, the degree of substitution of the cellulose nanofibers is 0 (ie, unsubstituted).

[0122] Alternatively, in one embodiment, from the perspective of obtaining chemically modified cellulose nanofibers with a high thermal decomposition starting temperature, the acyl substitution degree (DS) of the cellulose nanofibers may be greater than 0, or 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 addition, by leaving an unmodified cellulose skeleton in the esterified cellulose nanofibers, it is possible to obtain esterified cellulose nanofibers having both high tensile strength and dimensional stability from cellulose and high thermal decomposition starting temperature from chemical modification. From this perspective, the acyl substitution degree (DS) of the cellulose nanofibers may be 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.

[0123] When the modification group of chemically modified cellulose nanofibers is acyl, the degree of acyl substitution (DS) can be calculated based on the peak intensity ratio of the peak derived from the acyl group to the peak derived from the cellulose skeleton according to the attenuated total reflection (ATR) infrared absorption spectrum of the esterified cellulose nanofibers. The peak of the absorption band based on C=O of the acyl group appears at 1730 cm -1 The peak of the absorption band of CO based on the cellulose backbone chain appears at 1030 cm -1 A correlation curve graph can be prepared between the DS obtained by solid NMR measurement of the esterified cellulose nanofibers described later and the modification rate (IR index 1030) defined by the ratio of the peak intensity of the absorption band based on the C=O of the acyl group to the peak intensity of the absorption band of the cellulose backbone chain CO, and a calibration curve calculated from the correlation curve graph can be used.

[0124] Degree of substitution DS = 4.13 × IR index (1030)

[0125] To determine the DS of esterified cellulose nanofibers.

[0126] From the perspective of obtaining a good reinforcement effect based on the cellulose nanofibers, the content of the cellulose nanofibers in the rubber composition is preferably 0.5 mass% or more, or 1 mass% or more, or 3 mass% or more, and from the perspective of obtaining a rubber molded body having good rubber elasticity, the content is preferably 80 mass% or less, or 60 mass% or less, or 33 mass% or less, or 30 mass% or less, or 20 mass% or less, or 10 mass% or less.

[0127] <First Rubber Component (Liquid Rubber)>

[0128] In the present disclosure, liquid rubber refers to a substance that has fluidity at 23°C and forms a rubber elastic body by crosslinking (more specifically, vulcanization) and / or chain extension. That is, the liquid rubber is a cured product in one embodiment. In addition, having fluidity means that in one embodiment, the liquid rubber dissolved in cyclohexane is placed in a vial with a diameter of 21 mm and a total length of 50 mm at 23°C, and then dried, thereby filling the vial with liquid rubber to a height of 1 mm, sealing it, and leaving the vial in an upside-down state for 24 hours. It can be confirmed that the substance has moved by more than 0.1 mm in the height direction. The liquid rubber can have a monomer composition of a general rubber, and preferably has a lower molecular weight from the perspective of ease of handling and obtaining good dispersibility of cellulose nanofibers. In one embodiment, the liquid rubber is in a liquid form by having a number average molecular weight (Mn) of 80,000 or less. It should be noted that in the present disclosure, the molecular weight and molecular weight distribution of the rubber component are values ​​obtained by measuring the chromatogram using a gel permeation chromatography using three columns connected and using a polystyrene gel as a filler, and calculating using a calibration curve using standard polystyrene. It should be noted that tetrahydrofuran was used as a solvent.

[0129] When the rubber composition is cured to obtain a rubber cured product, the liquid rubber is preferably vulcanized during the curing from the viewpoint of improving the mechanical properties of the rubber cured product.

[0130] From the perspective of obtaining a rubber composition having excellent storage modulus and dispersibility of the matrix component in the rubber composite, the number average molecular weight (Mn) of the liquid rubber is preferably 1,000 or more, or 1,500 or more, or 2,000 or more. From the perspective of having high fluidity suitable for well dispersing the cellulose nanofibers in the liquid rubber and that the liquid rubber does not become too hard after curing and has good rubber elasticity, the number average molecular weight (Mn) of the liquid rubber is preferably 80,000 or less, or 50,000 or less, or 40,000 or less, or 30,000 or less, or 10,000 or less.

[0131] From the perspective of obtaining a rubber composition having excellent storage modulus and dispersibility of the matrix component in the rubber composite, the weight average molecular weight (Mw) of the liquid rubber is preferably 1,000 or more, or 2,000 or more, or 4,000 or more. From the perspective of having high fluidity suitable for well dispersing the cellulose nanofibers in the liquid rubber and that the liquid rubber does not become too hard after curing and has good rubber elasticity, the weight average molecular weight (Mw) of the liquid rubber is preferably 240,000 or less, or 150,000 or less, or 30,000 or less.

[0132] From the perspective of enabling the rubber molded body to highly achieve two or more properties (in one embodiment, highly achieving the storage modulus and rubber elasticity of the rubber molded body) by allowing the molecular weight to have a certain degree of deviation, the ratio (Mw / Mn) of the number average molecular weight (Mn) to the weight average molecular weight (Mw) of the liquid rubber is preferably 1.5 or more, or 1.8 or more, or 2.0 or more. From the perspective of not causing excessive deviation in molecular weight and stably obtaining the desired physical properties of the rubber molded body, the ratio (Mw / Mn) of the number average molecular weight (Mn) to the weight average molecular weight (Mw) of the liquid rubber is preferably 10 or less, or 8 or less, or 5 or less.

[0133] The liquid rubber may be a conjugated diene polymer or a non-conjugated diene polymer or a hydride thereof. The above polymer or its hydride may be an oligomer. In one embodiment, the liquid rubber may have reactive groups (e.g., one or more selected from the group consisting of a hydroxyl group, a carboxyl group, an isocyanate group, a thio group, an amino group, and a halogen group) at both ends, and thus may be bifunctional. These reactive groups contribute to the crosslinking and / or chain extension of the liquid rubber.

[0134] [Conjugated diene polymer]

[0135] The conjugated diene polymer may be a homopolymer, or a copolymer of two or more conjugated diene monomers, or a copolymer of a conjugated diene monomer and other monomers. The copolymer may be either random or block.

[0136] Examples of the conjugated diene monomer include 1,3-butadiene, isoprene, 2,3-dimethyl-1,3-butadiene, 1,3-pentadiene, 3-methyl-1,3-pentadiene, 1,3-heptadiene, and 1,3-hexadiene. These may be used alone or in combination of two or more.

[0137] In one embodiment, the conjugated diene polymer is a copolymer of the above-mentioned conjugated diene monomer and an aromatic vinyl monomer.

[0138] The aromatic vinyl monomer is not particularly limited as long as it is a monomer copolymerizable with the conjugated diene monomer, and examples thereof include styrene, m-methylstyrene or p-methylstyrene, α-methylstyrene, ethylstyrene, p-tert-butylstyrene, vinylethylbenzene, vinylxylene, vinylnaphthalene, diphenylethylene, and divinylbenzene, and these may be used alone or in combination of two or more. Styrene is preferred from the perspective of the molding processability of the rubber composite and the impact resistance of the molded product.

[0139] As random copolymers, there can be mentioned butadiene-isoprene random copolymers, butadiene-styrene random copolymers, isoprene-styrene random copolymers, and butadiene-isoprene-styrene random copolymers. As the composition distribution of each monomer in the copolymer chain, there can be mentioned completely random copolymers that are statistically close to random compositions, and gradient random copolymers with gradient composition distribution. The bonding form of the conjugated diene polymer, i.e., the composition of 1,4-bonding, 1,2-bonding, etc., can be uniform or different between molecules.

[0140] Block copolymers can be copolymers consisting of more than two blocks. For example, it can be a block copolymer of structures such as AB, ABA, ABAB consisting of block A and block B, wherein block A is a block of an aromatic vinyl monomer, and block B is a block of a conjugated diene monomer and / or a copolymer block of an aromatic vinyl monomer and a conjugated diene monomer. It should be noted that the boundaries of each block do not need to be clearly distinguished, for example, in the case where block B is a copolymer of an aromatic vinyl monomer and a conjugated diene monomer, the aromatic vinyl monomer in block B can be uniformly or taperedly distributed. In addition, in block B, there can be more than two uniformly distributed parts of aromatic vinyl monomers and / or tapered distribution parts. In addition, in block B, there can be more than two segments with different aromatic vinyl monomer contents. In the case where there are more than two blocks A and block B in the copolymer, their molecular weight and composition can be the same or different.

[0141] The block copolymer may be a mixture of two or more types that are different from each other in one or more of the bonding form, molecular weight, type of aromatic vinyl compound, type of conjugated diene compound, 1,2-vinyl content or the total amount of 1,2-vinyl content and 3,4-vinyl content, aromatic vinyl compound component content, hydrogenation rate, etc.

[0142] In the conjugated diene polymer, the vinyl bond content (eg, 1,2-bond or 3,4-bond of butadiene) in the conjugated diene bond unit is preferably 10 mol% to 75 mol%, or 13 mol% to 65 mol%.

[0143] The amount of vinyl bonds in the conjugated diene bond units (e.g., the amount of 1,2-bonds in butadiene) can be determined by 13 C-NMR method (quantitative mode). 13 By integrating the peak areas appearing below in C-NMR, a value proportional to the carbon amount of each structural unit can be obtained, and as a result, it can be converted into mass % of each structural unit.

[0144] Styrene 145~147ppm

[0145] Vinyl 110~116ppm

[0146] Diene (cis) 24~28ppm

[0147] Diene (trans) 29~33ppm

[0148] In the copolymer of conjugated diene monomer and aromatic vinyl monomer, the amount of aromatic vinyl monomer bonded to the conjugated diene monomer (also referred to as aromatic vinyl bond amount in the present disclosure) relative to the gross mass of the conjugated diene polymer can be preferably 5.0 mass % to 70 mass % or 10 mass % to 50 mass %. The aromatic vinyl bond amount can be obtained by the ultraviolet absorbance of phenyl, and the conjugated diene bond amount can also be obtained based on this.

[0149] Examples of the hydrogenated product of the conjugated diene polymer include the hydrogenated products of the conjugated diene polymer exemplified above, for example, hydrogenated products of butadiene homopolymer, isoprene homopolymer, styrene-butadiene copolymer and acrylonitrile-butadiene copolymer.

[0150] [Non-conjugated diene polymer]

[0151] The non-conjugated diene polymer may be a homopolymer, or may be a copolymer of two or more non-conjugated diene monomers or a copolymer of a non-conjugated diene monomer and other monomers. The copolymer may be any of random and block. Examples of the non-conjugated diene polymer include:

[0152] Olefin polymers such as ethylene-propylene rubber, ethylene-propylene-diene rubber, ethylene-butene-diene rubber, and ethylene-α-olefin copolymers;

[0153] Butyl rubber, brominated butyl rubber, acrylic rubber, fluororubber, silicone rubber, chlorinated polyethylene rubber, epichlorohydrin rubber, α, β-unsaturated nitrile-acrylate-conjugated diene copolymer rubber, polyurethane rubber, polysulfide rubber, etc.

[0154] Examples of the monomer copolymerizable with the ethylene unit in the ethylene-α-olefin copolymer include: aliphatic substituted vinyl monomers such as propylene, 1-butene, 1-pentene, 4-methyl-1-pentene, 1-hexene, 1-heptene, 1-octene, 1-nonene, 1-decene, 1-undecene, 1-dodecene, 1-tridecene, 1-tetradecene, 1-pentadecene, 1-hexadecene, 1-heptadecene, 1-octadecene, 1-nonadecene, 1-eicosene, and isobutylene; aromatic vinyl monomers such as styrene and substituted styrene; ester vinyl monomers such as vinyl acetate, acrylic acid ester, methacrylic acid ester, glycidyl acrylate, glycidyl methacrylate, and hydroxyethyl methacrylate; nitrogen-containing vinyl monomers such as acrylamide, allylamine, vinyl para-aminobenzene, and acrylonitrile; dienes such as butadiene, cyclopentadiene, 1,4-hexadiene, and isoprene; and the like.

[0155] Preferably, it is a copolymer of ethylene and one or more α-olefins having 3 to 20 carbon atoms, more preferably a copolymer of ethylene and one or more α-olefins having 3 to 16 carbon atoms, and most preferably a copolymer of ethylene and one or more α-olefins having 3 to 12 carbon atoms. In addition, from the perspective of exhibiting impact resistance, the molecular weight of the ethylene-α-olefin copolymer is preferably 10,000 or more, more preferably 10,000 to 100,000, more preferably 10,000 to 80,000, and further preferably 20,000 to 60,000. In addition, from the perspective of achieving both fluidity and impact resistance, the molecular weight distribution (weight average molecular weight / number average molecular weight: Mw / Mn) is preferably 3 or less, and further more preferably 1.8 to 2.7.

[0156] In addition, from the viewpoint of handling properties during processing, the content of ethylene units in the ethylene-α-olefin copolymer is preferably 30 to 95% by mass based on the total amount of the ethylene-α-olefin copolymer.

[0157] These preferred ethylene-α-olefin copolymers can be produced by the production methods described in, for example, JP-A-4-12283, JP-A-60-35006, JP-A-60-35007, JP-A-60-35008, JP-A-5-155930, JP-A-3-163088, U.S. Pat. No. 5,272,236, and the like.

[0158] In one embodiment, the liquid rubber includes one or more selected from the group consisting of diene rubber (in one embodiment, the above-mentioned conjugated diene polymer), silicone rubber, urethane rubber, polysulfide rubber, and hydrogenated products thereof.

[0159] If the viscosity of the liquid rubber at 80°C is below a predetermined value, it is advantageous when the rubber composition is uniformly dispersed in the matrix rubber component in the rubber composite. From the perspective of dispersing the rubber composition well in the matrix rubber component in the rubber composite and dispersing the cellulose nanofibers well in the liquid rubber, the viscosity of the liquid rubber at 80°C is preferably 1,000,000 mPa·s or less, or 500,000 mPa·s or less, or 250,000 mPa·s or less, or 100,000 mPa·s or less, and from the perspective of obtaining a rubber composite having excellent physical properties (particularly storage modulus), the viscosity is preferably 50 mPa·s or more, or 100 mPa·s or more, or 300 mPa·s or more.

[0160] From the perspective of well dispersing the cellulose nanofibers in the liquid rubber, the viscosity of the liquid rubber at 25°C is preferably 1,000,000 mPa·s or less, or 500,000 mPa·s or less, or 200,000 mPa·s or less, and from the perspective of obtaining a rubber composite with excellent physical properties (especially storage modulus), the viscosity is preferably 100 mPa·s or more, or 300 mPa·s or more, or 500 mPa·s or more.

[0161] If the viscosity of the liquid rubber at 0°C is below a predetermined value, it is advantageous when dispersing the cellulose nanofibers in the liquid rubber. From the perspective of dispersing the cellulose nanofibers well in the liquid rubber, the viscosity of the liquid rubber at 0°C is preferably 2,000,000 mPa·s or less, or 1,000,000 mPa·s or less, or 400,000 mPa·s or less, and from the perspective of obtaining a rubber composite having excellent physical properties (particularly storage modulus), the viscosity is preferably 200 mPa·s or more, or 600 mPa·s or more, or 1,000 mPa·s or more.

[0162] It is preferred that the viscosity of the liquid rubber has a low temperature dependency because the cellulose nanofibers can be well dispersed in the liquid rubber over a wide mixing temperature range. In this regard, it is particularly preferred that the viscosity of the liquid rubber at 80°C, 25°C, and 0°C are all within the above range.

[0163] The viscosity of the liquid rubber is a value measured using a B-type viscometer at a rotation speed of 10 rpm.

[0164] In the rubber composition, from the perspective of well obtaining the above-mentioned advantages based on the liquid rubber, the content of the liquid rubber is preferably 0.1 mass % or more, or 0.5 mass % or more, or 1 mass % or more, or 5 mass % or more, or 10 mass % or more, and from the perspective of containing appropriate amounts of other components (cellulose nanofibers, etc.) and well obtaining the advantages based on these components, the content of the liquid rubber is preferably 99 mass % or less, or 95 mass % or less, or 90 mass % or less, or 80 mass % or less, or 70 mass % or less, or 60 mass % or less, or 50 mass % or less.

[0165] In the rubber composition, the mass ratio of the cellulose nanofibers relative to 100 parts by mass of the total of the cellulose nanofibers and the liquid rubber is, in one embodiment, 1 part by mass or more, or 5 parts by mass or more, or 10 parts by mass or more, or 20 parts by mass or more, or 30 parts by mass or more, or 33 parts by mass or more, or 40 parts by mass or more, or 50 parts by mass or more, and in one embodiment, 99 parts by mass or less, or 95 parts by mass or less, or 90 parts by mass or less, or 80 parts by mass or less, or 70 parts by mass or less, or 60 parts by mass or less, or 50 parts by mass or less.

[0166] <Surfactant>

[0167] In one embodiment, the rubber composition includes a surfactant. In one embodiment, the surfactant is a nonionic surfactant, a cationic surfactant, or a combination thereof. As a surfactant, a nonionic surfactant is preferred from the aspect of heat resistance. Nonionic surfactants and cationic surfactants can enter the gaps in the aggregates of cellulose nanofibers, making the aggregates porous. For example, when a nonionic surfactant and / or a cationic surfactant is immersed in the aggregates in a wet state and then dried to form a dry body, compared with a dry body obtained by drying the aggregates without using the nonionic surfactant and the cationic surfactant, shrinkage during drying can be reduced, so when the dry body is mixed with liquid rubber, the cellulose nanofibers are well dispersed.

[0168] The nonionic surfactant is preferably a compound having a hydrophilic group selected from the group consisting of a hydroxyl group, a carboxyl group, a sulfonic acid group, and an amino group, and a hydrocarbon group.

[0169] In one embodiment, the nonionic surfactant has an aliphatic group with 6 to 30 carbon atoms as a hydrophobic part. The cellulose nanofibers of this embodiment typically form loose aggregates, and the nonionic surfactant has good affinity with the rubber component due to the contribution of the carbon chain of the hydrophobic part, and since the carbon chain of the hydrophobic part is not too long, it is easy to penetrate into the gaps of the cellulose nanofiber aggregates, thereby making the aggregates porous. For example, when the nonionic surfactant is immersed in the aggregates in a wet state and then dried to form a dry body, the shrinkage during drying can be reduced compared to the dry body obtained by drying the aggregates without using the nonionic surfactant, so when the dry body is mixed with the rubber component, the cellulose nanofibers can be well dispersed.

[0170] The aliphatic group may be a chain or alicyclic or a combination thereof. The number of carbon atoms in the aliphatic group is 6 or more, 8 or more, or 10 or more in one embodiment, from the aspect of obtaining good dispersibility of the cellulose nanofibers in the rubber component, and is 30 or less, 25 or less, or 20 or less in one embodiment, from the aspect of the infiltration into the voids of the cellulose nanofiber aggregates.

[0171] The nonionic surfactant preferably has one or more structures selected from the group consisting of ethylene oxide, glycerol and sorbitan (specifically, a repeating structure with one or more of them as a repeating unit) as a hydrophilic part. These structures show high hydrophilicity, and various nonionic surfactants can be easily obtained by combining with various hydrophobic parts, which is preferred from this aspect. In the nonionic surfactant having the above-mentioned hydrophilic part, from the aspect of obtaining good dispersibility of cellulose nanofibers in the rubber component, the number of carbon atoms n of the hydrophobic part and the number of repeating units m of the above-mentioned hydrophilic part preferably satisfy the following formula: n>m. Regarding the repetition number m of the above-mentioned hydrophilic part, from the aspect of good penetration of the nonionic surfactant into the gaps of the cellulose nanofiber aggregate, it is preferably 1 or more, or 2 or more, or 3 or more, or 5 or more, and from the aspect of obtaining good dispersibility of cellulose nanofibers in the rubber component, it is preferably 30 or less, or 25 or less, or 20 or less, or 18 or less.

[0172] The nonionic surfactant is preferably one or more selected from the group consisting of compounds represented by the following general formula (1) and compounds represented by the following general formula (2).

[0173] R-(OCH 2 CH 2 ) m -OH(1)

[0174] [In the formula, R represents a monovalent aliphatic group having 6 to 30 carbon atoms, and m is a natural number smaller than the number of carbon atoms of R.]

[0175] R 1 OCH 2 -(CHOH) 4 -CH 2 OR 2 (2)

[0176] [Where R 1 and R 2 each independently represents a hydrogen atom, an aliphatic group having 1 to 30 carbon atoms, -COR 3 {In the formula, R 3 represents an aliphatic group having 1 to 30 carbon atoms}, or -(CH 2 CH 2 O) y -R 4 {In the formula, R 4 represents a hydrogen atom or an aliphatic group having 1 to 30 carbon atoms, and y is an integer of 1 to 30}. ]

[0177] In the general formula (1), R corresponds to the hydrophobic part, (OCH 2 CH 2 ) (i.e., ethylene oxide unit) corresponds to the above-mentioned hydrophilic part. The number of carbon atoms of R and (OCH 2 CH 2 ) is preferably in the same range as the above-mentioned ranges of the number of carbon atoms n of the hydrophobic part and the number of repeating m of the hydrophilic part, respectively.

[0178] In the general formula (2), R 1 , R 2 , R 3 and R 4 In each group of , the aliphatic group having 1 to 30 carbon atoms preferably has 6 or more, 8 or more, or 10 or more carbon atoms, and preferably has 24 or less, 20 or less, or 18 or less carbon atoms.

[0179] In addition, y is 1 or more, preferably 2 or more, or 4 or more, and preferably 30 or less, or 25 or less, or 20 or less.

[0180] Examples of the cationic surfactant include benzalkonium chloride, alkyltrimethylammonium chloride, stearyldimethylammonium chloride, stearyltrimethylammonium chloride, ethylsulfate lanolin fatty acid aminopropylethyldimethylammonium, stearyldimethylbenzyl ammonium chloride, stearylamine acetate, and coconut acetate.

[0181] Regarding the amount of the surfactant in the rubber composition, the amount of the nonionic surfactant, the amount of the cationic surfactant, or the total amount of the nonionic surfactant and the cationic surfactant, it is preferably 10 parts by mass or more, or 15 parts by mass or more, or 20 parts by mass or more, and preferably 200 parts by mass or less, or 150 parts by mass or less, or 100 parts by mass or less, or 90 parts by mass or less, or 80 parts by mass or less, or 70 parts by mass or less, or 60 parts by mass or less, or 50 parts by mass or less, or 45 parts by mass or less, or 40 parts by mass or less, relative to 100 parts by mass of cellulose nanofibers.

[0182] <Additional ingredients>

[0183] In addition to the above-mentioned cellulose nanofibers, liquid rubber and surfactant, the rubber composition may further include additional components. As additional components, additional polymers, dispersants, organic or inorganic fillers, heat stabilizers, antioxidants, antistatic agents, colorants, etc. can be cited. As additional polymers, rubber components and thermoplastic elastomers exemplified below as matrix components of the rubber composite can be exemplified. The proportion of any additional component in the rubber composition can be appropriately selected within the range that does not impair the desired effect of the present invention, for example, it can be 0.01 to 50% by mass or 0.1 to 30% by mass.

[0184] <Manufacturing of Rubber Composition>

[0185] The method for producing the rubber composition is not particularly limited. The components constituting the rubber composition can be mixed using stirring means such as a rotation and revolution mixer, a planetary mixer, a homogenizer, a homogenizer, a screw stirring device, a rotary stirring device, an electromagnetic stirring device, an open mill, a Banbury mixer, a single screw extruder, and a twin screw extruder to obtain a rubber composition. In addition, in order to effectively shear, stirring can be carried out under heating. From the perspective of being able to apply high shear force and pressure to promote dispersion, a mixing method based on a homogenizer is preferred. The order of adding the components during mixing is not limited, and examples thereof include:

[0186] (1) A method of obtaining a rubber composition by simultaneously adding and mixing cellulose nanofibers, a surfactant, a liquid rubber, and optionally other components;

[0187] (2) A method in which components other than the liquid rubber are pre-mixed to obtain a premix, and the premix is ​​then mixed with the liquid rubber to obtain a rubber composition; etc.

[0188] In addition, as the method of the above (2), for example, the following method can be mentioned:

[0189] The surfactant is impregnated into the voids of the cellulose nanofiber aggregates by mixing the cellulose nanofibers with the surfactant;

[0190] Next, liquid rubber is added and mixed, thereby allowing the liquid rubber to penetrate into the gap.

[0191] In the method (2) above, after the premix is ​​obtained, the premix may be dried before being mixed with the liquid rubber. Alternatively, the rubber composition may be dried after it is obtained, or the powder described below may be formed by controlling the drying conditions.

[0192] Powder

[0193] One embodiment of the present disclosure provides a powder composed of the rubber composition of the present disclosure. The powder may have one or more of the following properties. As a result, the powder has excellent processing properties, and the cellulose nanofibers can be excellently dispersed in the rubber component.

[0194] <Surface State of Cellulose Nanofibers>

[0195] In a powder of one embodiment, for the purpose of making the cellulose nanofibers easily dispersed in these rubber components without agglomeration when kneading with the second rubber component or the third rubber component, it is preferred that at least a portion of the surface of the cellulose nanofibers is covered by the first rubber component. In one embodiment, the state in which at least a portion of the surface of the cellulose nanofibers is covered by the first rubber component is a state in which the first rubber component is in direct contact with the cellulose nanofibers and the average length of the contact portion is more than twice the length of the average fiber diameter of the cellulose nanofibers. The state in which the surface of the cellulose nanofibers in the powder is covered by the first rubber component is observed using an electron microscope (a scanning electron microscope in one embodiment) or an atomic force microscope. When it can be confirmed using either an electron microscope or an atomic force microscope, it is confirmed using an electron microscope. The above-mentioned average fiber diameter is a value measured by the method disclosed in the present invention using the powder as a measurement sample. Regarding the average length of the above-mentioned contact portion, the powder is used as a measurement sample and measured using an electron microscope (a scanning electron microscope in one embodiment) or an atomic force microscope. Specifically, in an observation field of view with a magnification adjusted so that at least 30 cellulose nanofibers are observed, the length of the contact portion with the first rubber component is measured for each of 30 randomly selected cellulose nanofibers, and the number average is calculated, which is further averaged using 30 fibers and taken as the average length of the contact portion.

[0196] <Loose bulk density>

[0197] In one embodiment, the loose bulk density of the powder is preferably 0.01 g / cm2 from the viewpoint of good powder fluidity and excellent feeding property into a kneading machine and suppression of migration of the surfactant into the rubber. 3 Above, or 0.05g / cm 3 Above, or 0.10g / cm 3 Above, or 0.15g / cm 3 Above, or 0.20g / cm 3 From the above, the loose bulk density of the powder is preferably 0.50 g / cm2, because the powder is easily broken in the rubber, the cellulose nanofibers can be well dispersed in the rubber, and the powder is not too heavy, which can avoid poor mixing of the powder and the rubber. 3 Below, or 0.40g / cm 3 Below, or 0.30g / cm 3 Below, or 0.25g / cm 3 Below, or 0.20g / cm 3 the following.

[0198] <Tapped Bulk Density>

[0199] The tapped bulk density of the powder is controlled within a range useful for controlling the loose bulk density and the degree of compressibility within an appropriate range, and in one embodiment, is preferably 0.01 g / cm 3 Above, or 0.05g / cm 3 Above, or 0.10g / cm 3 Above, or 0.15g / cm 3 Above, or 0.20g / cm 3 Above, preferably 1.00 g / cm 3 Below, or 0.80g / cm 3 Below, or 0.70g / cm 3 Below, or 0.60g / cm 3 Below, or 0.50g / cm 3 Below, or 0.40g / cm 3 Below, or 0.30g / cm 3 the following.

[0200] The loose bulk density and tapped bulk density are values ​​measured using a powder tester (model: PT-X) manufactured by Hosokawa Micron Co., Ltd. by the procedure described in the section [Examples] of the present disclosure.

[0201] As a method for producing a powder, there can be exemplified a method including a slurry preparation step in which a slurry containing cellulose nanofibers and a liquid medium is prepared and a drying step in which the slurry is dried to form a powder.

[0202] (Slurry preparation process)

[0203] In this step, a slurry is prepared. As a liquid medium, a water-miscible organic solvent can be used, such as an alcohol having a boiling point of 50°C to 170°C (e.g., methanol, ethanol, n-propanol, isopropanol, n-butanol, isobutanol, sec-butanol, tert-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.); and the like. In a representative embodiment, the liquid medium in the slurry is substantially only water. The slurry can be composed of cellulose nanofibers and a liquid medium, and can contain a surfactant and / or a first rubber component, and optional additional components.

[0204] Regarding the concentration of cellulose nanofibers in the slurry, from the aspect of process efficiency in the subsequent drying process, it 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 aspect of avoiding excessive increase in slurry viscosity and solidification due to agglomeration and maintaining good handling properties, it is preferably 60% by mass or less, or 55% by mass or less, or 50% by mass or less, or 45% by mass or less. For example, the manufacture of cellulose nanofibers is mostly carried out in a dilute dispersion, but by concentrating such a dilute dispersion, the concentration of cellulose nanofibers in the slurry can be adjusted to the above-mentioned preferred range. Concentration can use methods such as suction filtration, pressure filtration, centrifugal dehydration, heating, etc.

[0205] (Drying process)

[0206] In this process, the slurry is dried under controlled drying conditions to form a powder. The ingredients other than the cellulose nanofibers may be added before, during and / or after the slurry is dried. Drying may be performed using a spray dryer, an extruder or other drying device. The drying device may be a commercially available product, such as a micro-mist spray dryer (produced by Fujisaki Electric), a spray dryer (produced by Ohkawara Chemical Industry), a twin-screw extruder (produced by Nippon Steel Works), etc. Among the drying conditions, appropriately controlling the drying speed, drying temperature and / or pressure (vacuum degree), especially the drying speed, may be beneficial to achieving the desired shape of the powder.

[0207] The drying rate, i.e., the amount (parts by mass) of the liquid medium released per minute per 100 parts by mass of the slurry, may be, for example, 10% / minute or more, or 50% / minute or more, or 100% / minute or more, from the perspective of rapidly drying the slurry to form a powder of a desired particle size, and may be, for example, 10000% / minute or less, or 1000% / minute or less, or 500% / minute or less, from the perspective of avoiding excessive micronization of the cellulose nanofibers to suppress the aggregation of the cellulose nanofibers and obtain good handling properties. The drying rate is a value obtained according to the following formula (i.e., an average value throughout the drying process).

[0208] Drying speed (% / min) = (slurry moisture content (mass %) at the start of drying - powder moisture content (mass %) at the end of drying) / time required from the start of drying to the end of drying (min)

[0209] Here, the start of drying refers to the moment when the slurry or cake to be dried is supplied to the device and the drying process begins at the target drying temperature, vacuum degree, and shear rate. The time for premixing at a drying temperature, vacuum degree, and shear rate different from those in the drying process is not included in the drying time.

[0210] The drying endpoint refers to the time when the water content first reaches 7% by mass or less when sampling is performed at intervals of up to 10 minutes from the start of drying.

[0211] In the case of a continuous drying device, the time required from the start of drying to the end of drying can be interpreted as the residence time. In the case of a spray dryer, the residence time can be calculated using the heating air volume and the volume of the drying chamber. In addition, when an extruder is used as a drying device, the residence time can be calculated based on the screw speed and the total screw pitch.

[0212] Regarding the drying temperature, from the perspective of drying efficiency and allowing the cellulose nanofibers to moderately agglomerate to form a powder of the desired particle size, it can be, for example, above 20°C, or above 30°C, or above 40°C, or above 50°C. From the perspective of not easily causing thermal degradation of the cellulose nanofibers and additional components and avoiding excessive pulverization of the cellulose nanofibers, the temperature can be, for example, below 200°C, or below 150°C, or below 140°C, or below 130°C, or below 100°C.

[0213] The drying temperature is the temperature of the heat source in contact with the slurry, and is defined by, for example, the surface temperature of the temperature-regulating jacket of the drying apparatus, the surface temperature of the heating cylinder, or the temperature of the hot air.

[0214] Regarding the vacuum degree, from the perspective of drying efficiency and allowing the cellulose nanofibers to moderately agglomerate to form a powder of the desired particle size, it can be below -1 kPa, or below -10 kPa, or below -20 kPa, or below -30 kPa, or below -40 kPa, or below -50 kPa. From the perspective of avoiding excessive pulverization of the cellulose nanofibers, it can be above -100 kPa, or above -95 kPa, or above -90 kPa.

[0215] In the drying process, the residence time of the slurry at a temperature of 20° C. to 200° C. is preferably set to 0.01 to 10 minutes, or 0.05 to 5 minutes, or 0.1 to 2 minutes. By drying under such conditions, the cellulose nanofibers are rapidly dried, and a powder of a desired particle size can be well generated.

[0216] For example, when a spray dryer is used, the slurry is introduced by spraying in a drying chamber where hot gas is circulated, and the slurry is dried. The slurry droplet size during spray introduction can be, for example, 0.01 μm to 500 μm, or 0.1 μm to 100 μm, or 0.5 μm to 10 μm. The hot gas can be an inert gas such as nitrogen, argon, air, etc. The hot gas temperature can be, for example, 50°C to 300°C, or 80°C to 250°C, or 100°C to 200°C. The contact between the droplets of the slurry in the drying chamber and the hot gas can be cocurrent, countercurrent, or co-convection. The granular powder produced by the drying of the droplets is captured by a cyclone separator, a drum, etc.

[0217] In addition, for example, when an extruder is used, the slurry is fed into a kneading section equipped with a screw by a feed hopper, and the slurry is continuously conveyed by the screw in the kneading section under reduced pressure and / or heating, thereby drying the slurry. As the screw mode, a conveying screw, a counterclockwise screw, and a kneading disk can be combined in any order. The drying temperature can be, for example, 50°C to 300°C, or 80°C to 250°C, or 100°C to 200°C.

[0218] Masterbatch

[0219] One embodiment of the present disclosure provides a masterbatch including the rubber composition of the present disclosure. In one embodiment, the masterbatch is a kneaded product of the powder of the present disclosure and a second rubber component.

[0220] <Second Rubber Component>

[0221] The second rubber component can be natural rubber, a conjugated diene polymer or a non-conjugated diene polymer, or a hydride thereof. The above-mentioned polymer or its hydride can be an oligomer. As the monomer composition of the second rubber component, the same composition as the above-mentioned composition of the liquid rubber can be exemplified. The second rubber component can be the above-mentioned liquid rubber, or it can be a rubber that is not a liquid rubber.

[0222] The conjugated diene polymer as the second rubber component constituting the matrix component may be partially or completely hydrogenated. From the perspective of suppressing thermal degradation during processing, the hydrogenation rate of the hydrogenated product is preferably 50% or more, or 80% or more, or 98% or more, and from the perspective of low-temperature toughness, the hydrogenation rate of the hydrogenated product is preferably 50% or less, or 20% or less, or 0% (i.e., non-hydrogenated product).

[0223] From the perspective of suppressing the crystallization of the soft segment, in the conjugated diene polymer as the second rubber component constituting the matrix component, the amount of vinyl bonds in the conjugated diene bond units (e.g., 1,2-bonds or 3,4-bonds of butadiene) is preferably 5 mol% or more, or 10 mol% or more, or 13 mol% or more, or 15 mol% or more, and is preferably 80 mol% or less, or 75 mol% or less, or 65 mol% or less, or 50 mol% or less, or 40 mol% or less.

[0224] In a preferred embodiment, the second rubber component includes one or more selected from the group consisting of styrene-butadiene rubber, butadiene rubber, and isoprene rubber.

[0225] The number average molecular weight (Mn) of the second rubber component is preferably 100,000 or more, or 150,000 or more, or 200,000 or more from the perspective of obtaining a rubber composite having excellent storage modulus, and is preferably 800,000 or less, or 750,000 or less, or 700,000 or less, or 600,000 or less from the perspective of easy dispersion of the cellulose nanofibers in the second rubber component and the aspect that the second rubber component does not become too hard after curing and has good rubber elasticity.

[0226] [Modified rubber]

[0227] The second rubber component may be a modified rubber, for example, a modified group such as an epoxy group, anhydride group, carboxyl group, aldehyde group, hydroxyl group, alkoxy group, amino group, amide group, imide group, nitro group, isocyanate group, mercapto group, etc. may be introduced into the above-mentioned conjugated diene polymer or non-conjugated diene polymer. Examples of the modified rubber include epoxy-modified natural rubber, epoxy-modified butadiene rubber, epoxy-modified styrene-butadiene rubber, carboxyl-modified natural rubber, carboxyl-modified butadiene rubber, carboxyl-modified styrene-butadiene rubber, anhydride-modified natural rubber, anhydride-modified butadiene rubber, anhydride-modified styrene-butadiene rubber, etc.

[0228] From the aspect of the affinity between the cellulose nanofiber and the second rubber component, the amount of the modified group is preferably 0.1 mol% or more, or 0.2 mol% or more, or 0.3 mol% or more relative to 100 mol% of the total monomer units, and preferably 5 mol% or less, or 3 mol% or less. The amount of the modified group can be confirmed by FT-IR (Fourier transform infrared spectroscopy), solid NMR (nuclear magnetic resonance), solution NMR, or a method of calculating the molar ratio of the modified group by combining a predetermined monomer composition with the elements contained in the unmodified rubber based on the quantitative analysis of the element.

[0229] In the masterbatch, the content of the second rubber component is preferably 20 mass % or more, 30 mass % or more, or 40 mass % or more, and is preferably 99 mass % or less, 95 mass % or less, or 90 mass % or less.

[0230] [Thermoplastic elastomer]

[0231] In one embodiment, the second rubber component may contain a thermoplastic elastomer or be a thermoplastic elastomer. In the present disclosure, in one embodiment, an elastomer refers to a substance that is an elastomer at room temperature (23°C) (specifically, a natural or synthetic polymer substance). In addition, in one embodiment, an elastomer means that the storage modulus at 23°C and 10Hz measured by dynamic viscoelasticity measurement is greater than 1 MPa and less than 100 MPa. The thermoplastic elastomer may be a conjugated diene polymer or a non-conjugated diene polymer, and in one embodiment is a cross-linked product. The preferred monomer composition of the thermoplastic elastomer may be the same as the above-mentioned composition in the above-mentioned (conjugated diene polymer) and (non-conjugated diene polymer) items.

[0232] From the viewpoint of achieving both impact strength and fluidity, the number average molecular weight (Mn) of the thermoplastic elastomer is preferably 10,000 to 500,000, or 40,000 to 250,000.

[0233] Thermoplastic elastomer can have a core-shell structure. As an elastomer with a core-shell structure, a core-shell type elastomer having a core (which is a granular rubber) and a shell (which is a glassy graft layer) formed outside the core can be cited. As the core, butadiene rubber, acrylic rubber, silicone-acrylic composite rubber, etc. are suitable. In addition, as the shell, glassy polymers such as styrene resin, acrylonitrile-styrene copolymer, acrylic resin are suitable.

[0234] From the viewpoint of better compatibility with the rubber composition, the thermoplastic elastomer is preferably at least one selected from the group consisting of styrene-butadiene block copolymers, styrene-ethylene-butadiene block copolymers, styrene-ethylene-butylene block copolymers, styrene-butadiene-butylene block copolymers, styrene-isoprene block copolymers, styrene-ethylene-propylene block copolymers, styrene-isobutylene block copolymers, hydrogenated products of styrene-butadiene block copolymers, hydrogenated products of styrene-ethylene-butadiene block copolymers, hydrogenated products of styrene-butadiene-butylene block copolymers, hydrogenated products of styrene-isoprene block copolymers, and styrene homopolymers (polystyrene), and more preferably at least one selected from the group consisting of styrene-butadiene block copolymers, hydrogenated products of styrene-butadiene block copolymers, and polystyrene.

[0235] In one embodiment, at least a portion of the thermoplastic elastomer may have an acidic functional group. In the present disclosure, the thermoplastic elastomer having an acidic functional group means that the acidic functional group is added to the molecular skeleton of the elastomer by chemical bonding. In addition, in the present disclosure, the acidic functional group refers to a functional group that can react with a basic functional group, etc., and specific examples thereof include a hydroxyl group, a carboxyl group, a carboxylate group, a sulfonic group, an acid anhydride group, etc.

[0236] From the aspect of the affinity between the cellulose nanofiber and the elastomer component, the amount of the acidic functional group added to the elastomer is preferably 0.01% by mass or more, more preferably 0.1% by mass or more, and further preferably 0.2% by mass or more, and preferably 5% by mass or less, more preferably 3% by mass or less, and further preferably 2% by mass or less, based on 100% by mass of the elastomer. It should be noted that the number of acidic functional groups is a value obtained by measuring a calibration curve sample pre-mixed with an acidic substance using an infrared absorption spectrometer, and measuring the sample based on a calibration curve prepared using the characteristic absorption band of the acid, thereby obtaining the number of acidic functional groups.

[0237] Examples of elastomers having acidic functional groups include: elastomers having a core-shell structure having a layer as a shell formed using acrylic acid or the like as a copolymer component; elastomers as modified products, wherein an α, β-unsaturated dicarboxylic acid or a derivative thereof is grafted onto an ethylene-α-olefin copolymer, a polyolefin, an aromatic compound-conjugated diene copolymer, or an aromatic compound-conjugated diene copolymer hydrogenated product containing acrylic acid or the like as a monomer, in the presence or absence of a peroxide; and the like.

[0238] In a preferred embodiment, the elastomer is an anhydride-modified elastomer.

[0239] Among these, more preferred are modified products obtained by grafting α,β-unsaturated dicarboxylic acid or its derivatives onto polyolefins, aromatic compound-conjugated diene copolymers or aromatic compound-conjugated diene copolymer hydrogenates in the presence or absence of peroxides, and particularly preferred are modified products obtained by grafting α,β-unsaturated dicarboxylic acid and its derivatives onto ethylene-α-olefin copolymers or aromatic compound-conjugated diene block copolymer hydrogenates in the presence or absence of peroxides.

[0240] Specific examples of the α,β-unsaturated dicarboxylic acid and its derivatives include maleic acid, fumaric acid, maleic anhydride and fumaric anhydride. Among these, maleic anhydride is particularly preferred.

[0241] In one embodiment, the elastomer can be a mixture of an elastomer having an acidic functional group and an elastomer not having an acidic functional group. Regarding the mixing ratio of the elastomer having an acidic functional group and the elastomer not having an acidic functional group, when the total of the two is set to 100% by mass, from the aspect of maintaining the high toughness and physical stability of the rubber composite well, the elastomer having an acidic functional group is preferably 10% by mass or more, more preferably 20% by mass or more, further more preferably 30% by mass or more, and most preferably 40% by mass or more. The upper limit is not particularly limited, and substantially all elastomers can be elastomers having an acidic functional group, but from the aspect that the fluidity does not cause problems, it is preferably 80% by mass or less.

[0242] The content of the thermoplastic elastomer in the masterbatch is preferably 20% by mass or more, or 30% by mass or more, and is preferably 99% by mass or less, or 95% by mass or less, or 90% by mass or less.

[0243] <Vulcanizing agent, vulcanization accelerator>

[0244] In the case where the masterbatch includes uncured rubber, the masterbatch typically includes a vulcanizing agent and may optionally include a vulcanization accelerator. As a vulcanizing agent and a vulcanization accelerator, existing known substances can be suitably selected according to the type of the uncured rubber in the masterbatch. As a vulcanizing agent, organic peroxides, azo compounds, oxime compounds, nitroso compounds, polyamine compounds, sulfur, sulfur-containing compounds, etc. can be used. As sulfur-containing compounds, sulfur monochloride, sulfur dichloride, disulfide compounds, polymer polysulfides, etc. can be cited. The amount of the vulcanizing agent is preferably 0.01 to 20 parts by mass or 0.1 to 15 parts by mass relative to 100 parts by mass of the uncured rubber in the masterbatch.

[0245] As the vulcanization accelerator, sulfenamide, guanidine, thiuram, aldehyde-amine, aldehyde-ammonia, thiazole, thiourea, dithiocarbamate and other vulcanization accelerators can be cited. In addition, as a vulcanization aid, zinc white, stearic acid and the like can be used. The amount of the vulcanization accelerator is preferably 0.01 to 20 parts by mass or 0.1 to 15 parts by mass relative to 100 parts by mass of the uncured rubber in the masterbatch.

[0246] [Additives for rubber]

[0247] The masterbatch may include various known rubber additives (stabilizers, softeners, anti-aging agents, etc.). As a rubber stabilizer, one or more antioxidants such as 2,6-di-tert-butyl-4-hydroxytoluene (BHT), 3-(4'-hydroxy-3',5'-di-tert-butylphenyl) propionate, and 2-methyl-4,6-bis[(octylthio)methyl]phenol may be used. In addition, as a rubber softener, one or more operating oils, extender oils, etc. may be used. However, the masterbatch of the present embodiment can form a soft molded body in one mode, so it may not include a rubber softener in one mode.

[0248] <Additional ingredients>

[0249] In order to improve the performance of the masterbatch, the masterbatch may further include additional components as needed. As additional components, dispersants, organic or inorganic fillers, thermal stabilizers, antioxidants, antistatic agents, colorants, etc. can be cited. The proportion of the optional additional components in the masterbatch can be appropriately selected within the range that does not impair the desired effect of the present invention, for example, 0.01 to 50% by mass or 0.1 to 30% by mass.

[0250] In a preferred embodiment, the masterbatch contains 10 to 50 parts by mass, or 15 to 40 parts by mass, or 20 to 30 parts by mass of cellulose nanofibers, and 1 to 50 parts by mass, or 2 to 40 parts by mass, or 3 to 30 parts by mass of surfactants, relative to 100 parts by mass of the rubber component. In addition, the amount of the rubber component is the total amount of the rubber component present in the masterbatch (in one embodiment, the total amount of the first rubber component and the second rubber component). In one embodiment, the composition of the masterbatch can be the same as the above composition in the rubber composition. The mass ratio (masterbatch / additional component) of the masterbatch and the additional component (in one embodiment, the second rubber component) can be 1 / 99 to 99 / 1, or 5 / 95 to 95 / 5, or 10 / 90 to 90 / 10, or 20 / 80 to 80 / 20, or 30 / 70 to 70 / 30, or 40 / 60 to 60 / 40.

[0251] One embodiment of the present disclosure provides a method for producing a masterbatch, comprising the step of kneading the powder of the present disclosure with a second rubber component to obtain a masterbatch. The kneading conditions are not particularly limited, and for example, a mixer commonly used in rubber kneading, such as a Banbury mixer or an open roll mill, can be used.

[0252] Rubber compound

[0253] One embodiment of the present disclosure also provides a rubber composite, which includes the rubber composition of the present embodiment and a matrix component (i.e., a component other than the rubber composition) (in one embodiment, they are mixed and obtained). In a representative embodiment, the rubber composite is derived from the powder or masterbatch of the present disclosure. The rubber composite includes the above-mentioned cellulose nanofibers, the above-mentioned liquid rubber and the above-mentioned surfactant in one embodiment, and further includes a third rubber component as a matrix component, and an optional additional component. The third rubber component can be one or more selected from the group consisting of uncured rubber and a thermoplastic elastomer.

[0254] In one embodiment, the rubber composite is a mixture of the powder disclosed herein or the masterbatch disclosed herein and a third rubber component. The specific preferred embodiment of the third rubber component may be the same as the above-mentioned embodiment of the second rubber component. In the first, second and third rubber components, one or more of the types of monomer components, the proportion of monomer components and the molecular weight may be different from each other (different types), or in two or more of the first, second and third rubber components, the types of monomer components, the proportion of monomer components and the molecular weight may be the same as each other (same type). In a preferred embodiment of the rubber composite, at least a portion of the surface of the cellulose nanofiber is covered by the first rubber component. The above-mentioned coating state is confirmed by the above-mentioned scanning electron microscope observation or atomic force microscope. However, in the case where the first rubber component and the second and / or third rubber components cannot be distinguished by any one of the scanning electron microscope observation and the atomic force microscope, as long as at least a portion of the surface of the cellulose nanofiber is covered by the undistinguished rubber component, it can be regarded as at least a portion of the surface being covered by the first rubber component. In such a case, the first rubber component and the second and / or third rubber component may be of the same type, or even if they are of different types, their properties are very similar. Therefore, it can be considered that by covering the undifferentiated rubber component with cellulose nanofibers, the advantages obtained when the first rubber component is covered with cellulose nanofibers can be exhibited.

[0255] The mass ratio of the powder to the third rubber component (powder / third rubber component) may be 1 / 99 to 99 / 1, 5 / 95 to 95 / 5, 10 / 90 to 90 / 10, 20 / 80 to 80 / 20, 30 / 70 to 70 / 30, or 40 / 60 to 60 / 40 in one embodiment.

[0256] The mass ratio of the masterbatch to the third rubber component (masterbatch / third rubber component) may be 1 / 99 to 99 / 1, 5 / 95 to 95 / 5, 10 / 90 to 90 / 10, 20 / 80 to 80 / 20, 30 / 70 to 70 / 30, or 40 / 60 to 60 / 40 in one embodiment.

[0257] The rubber composite is manufactured by a method including the steps of kneading the powder of the present disclosure with a third rubber component, or forming a masterbatch by the method for manufacturing a masterbatch of the present disclosure, and then kneading the masterbatch with a third rubber component to obtain the rubber composite. The kneading conditions are not particularly limited, and for example, a mixer commonly used in rubber kneading, such as a Banbury mixer and an open roll mill, can be used.

[0258] The content of cellulose nanofibers in the rubber composite is preferably 0.5 mass % or more, 1 mass % or more, or 2 mass % or more, and preferably 30 mass % or less, 20 mass % or less, 15 mass % or less, or 10 mass % or less.

[0259] The total content of the polymer components in the rubber composite (in one embodiment, the total content of the first, second and third rubber components) is preferably 1 mass % or more, or 2 mass % or more, or 5 mass % or more, and is preferably 99 mass % or less, or 95 mass % or less, or 90 mass % or less.

[0260] The mass ratio of the cellulose nanofibers / polymer components in the rubber composite is preferably 1 / 99 to 50 / 50, or 2 / 98 to 40 / 60, or 3 / 97 to 30 / 70.

[0261] The content of the surfactant in the rubber composite may be 0.1 mass % or more, 0.5 mass % or more, or 1 mass % or more in one embodiment, and may be 10 mass % or less, 5 mass % or less, or 1 mass % or less in one embodiment.

[0262] In the rubber composite of one embodiment, the amount of the vulcanizer and / or vulcanization accelerator relative to the uncured rubber in the rubber composite may be in the same range as exemplified as the amount of the vulcanizer and / or vulcanization accelerator relative to the uncured rubber in the masterbatch.

[0263] In the rubber composite of one embodiment, the amounts of the rubber additive and the additional components in the rubber composite may be in the same range as exemplified as the amount in the masterbatch.

[0264] 《Rubber cured products and molded products》

[0265] One embodiment of the present disclosure provides a rubber cured product, which is a cured product of a curable component of the rubber composition of the present disclosure. In one embodiment, the rubber composition of the present disclosure can be molded into a desired shape together with other desired components, thereby manufacturing a desired molded body. In one embodiment, the rubber composition of the present disclosure can also be mixed with a third rubber component and an optional additional component to form a rubber composite, and the rubber composite can be further molded into a desired shape alone or together with other components to manufacture a desired molded body. The combination method of the mixed components and the molding method are not particularly limited and can be selected according to the desired molded body. As molding methods, the following methods can be cited but are not limited to:

[0266] (1) A method in which a rubber composition or a masterbatch contains an uncured rubber, and the uncured rubber is cured before, during and / or after molding the rubber composition or the masterbatch alone or together with an additional component, thereby obtaining a molded body containing a rubber cured product;

[0267] (2) A method in which the rubber composition contains uncured rubber, a rubber cured product obtained by curing the uncured rubber in the rubber composition is formed into a masterbatch, and the masterbatch is then molded together with an additional component to obtain a molded product;

[0268] (3) A method in which the rubber component in the rubber composition is a thermoplastic elastomer and the rubber composition is melt-molded alone or together with an additional component to obtain a molded product; etc.

[0269] Molding can be performed by injection molding, extrusion molding, extrusion profile molding, blow molding, compression molding, or the like.

[0270] In the method (2) above, the mass ratio of masterbatch / additional components in the rubber cured product may be, for example, 1 / 99 to 99 / 1, or 5 / 95 to 95 / 5, or 10 / 90 to 90 / 10, or 20 / 80 to 80 / 20, or 30 / 70 to 70 / 30, or 40 / 60 to 60 / 40.

[0271] In one embodiment, the rubber cured product is a cured product of the rubber composite of the present disclosure. In one embodiment, the rubber cured product can be produced by a method comprising the following steps: a step of obtaining a rubber composite by the method for producing a rubber composite of the present disclosure; and a step of curing the rubber composite to obtain the rubber cured product. In one embodiment, the rubber cured product can be obtained by a vulcanization press according to JIS K6299.

[0272] The rubber cured product can be formed into a molded body of various shapes. The molded body can be used in a wide range of applications such as industrial machinery parts, general machinery parts, automobiles, railways, vehicles, ships, and aerospace related parts, electronic and electrical parts, construction and civil engineering materials, daily necessities, sports and leisure products, shell parts for wind power generation, and containers and packaging parts. As an example of use, it can be formed into automobile parts (such as tires, bumpers, fenders, door panels, various moldings, logos, engine hoods, wheel covers, roof panels, spoilers, various aerodynamic kits and other exterior parts, and dashboards, console boxes (ConsoleBox), trims and other interior parts), battery parts (on-board secondary battery parts, lithium-ion secondary battery parts, solid methanol battery fuel shells, fuel cell piping, etc.), electronic and electrical equipment parts (such as various computers and their peripherals, junction boxes, various connectors, various OA equipment, TV sets, video recorders, CD players, racks, refrigerators, air conditioners, liquid crystal projectors, etc.), daily necessities (shoe soles, etc.) and other molded products.

[0273] One embodiment of the present disclosure provides a shoe outsole, a tire, an anti-vibration rubber, or a transmission belt, which comprises the rubber cured product of the present disclosure.

[0274] Example

[0275] The present invention will be further described with reference to the following examples, but the present invention is not limited to these examples.

[0276] Evaluation Method

[0277] <Liquid Rubber>

[0278] [Vinyl content, aromatic styrene content]

[0279] The sample was dissolved in deuterated chloroform and 13 C-NMR (ECZ500 from JEOL) was measured under the following conditions.

[0280] Resonance frequency: 125MHz

[0281] Pulse width: 90°

[0282] Repeat time: 8 seconds

[0283] Points: 5120 times

[0284] Temperature: Room temperature

[0285] Chemical shift reference: CDCl 3 77.0ppm

[0286] [Viscosity at 25°C]

[0287] The viscosity of the liquid rubber was measured using a B-type viscometer at a rotation speed of 10 rpm.

[0288] [Number average molecular weight (Mn) and weight average molecular weight (Mw)]

[0289] The chromatogram was measured using a GPC having three columns connected and using polystyrene gel as a filler, and the molecular weight (Mn, Mw) and molecular weight distribution (Mw / Mn) were calculated from a calibration curve using standard polystyrene. Tetrahydrofuran was used as a solvent.

[0290] <Rubber Composition>

[0291] [Appearance (dispersibility of cellulose nanofibers)]

[0292] The rubber compositions obtained in Examples 1 to 5 and Comparative Examples 2 and 3 were observed under an optical microscope under the following conditions. 1 mg of the sample was sandwiched between two cover glasses, flattened and spread to a uniform thickness. The sample was placed on the stage of a polarizing microscope BX51P manufactured by Olympus. A differential interference prism U-DICR manufactured by Olympus was inserted for differential interference observation. The dispersibility of the filler was evaluated according to the following criteria.

[0293] A: Almost uniformly dispersed.

[0294] B: Dispersion occurred, but agglomeration was observed.

[0295] C: A large amount of agglutination was observed.

[0296] [Storage modulus]

[0297] The storage modulus of the rubber compositions of Examples 1 to 5 and Comparative Examples 2 and 3 and the liquid rubber of Comparative Example 1 was measured by frequency dispersion measurement using parallel plates with a gap of 1 mm at 25°C and a strain of 0.002% using a rheometer HAAKE MARS40 manufactured by Thermo Fisher Scientific. A high storage modulus indicates that the cellulose nanofibers are well dispersed in the rubber, which means that when the cellulose nanofibers are kneaded in the rubber as a masterbatch for rubber, the cellulose nanofibers are well dispersed in the rubber, and a rubber composition having excellent mechanical properties such as elastic modulus, storage modulus, and hardness is obtained.

[0298] <Dry powder>

[0299] The dry powder was evaluated as follows using a powder tester (model: PT-X) manufactured by Hosokawa Micron Co., Ltd.

[0300] [Loose bulk density]

[0301] The dried product was added to a 100 mL stainless steel cylindrical container (inner diameter 50.46 mm × depth 50 mm) at a rate of 10 g / min until it overflowed, and the dried product was scraped flat and weighed to an accuracy of 0.01 g. The average of the three weight measurements was divided by the internal volume of the cylindrical container to calculate the loose bulk density.

[0302] [Tapped bulk density]

[0303] A resin die head adapter (inner diameter 50.46mm×length 40mm) with sufficient capacity is connected to the upper part of the bottomed cylindrical container similar to the container used in the loose bulk density in a close manner, and the dried body is added to the overflow amount by the same process as the determination of the loose bulk density. After that, the motor with an eccentric weight installed on the rotating shaft is used to apply vibration of 1.5mm amplitude and 50Hz to the bottomed cylindrical container for 30 seconds. Then the die head adapter is removed, the dried body is scraped flat, and the weight is measured with an accuracy of 0.01g. The number average of the three measurements of the weight is divided by the content volume of the bottomed cylindrical container, and the tapped bulk density is calculated.

[0304] <Rubber Cured Product>

[0305] The following evaluations were performed on the rubber cured products.

[0306] (1) Tensile strength

[0307] Evaluation was performed by the tensile test method of JIS K-6251.

[0308] (2) Storage modulus

[0309] The storage modulus at 50° C., a frequency of 10 Hz, and a strain of 3% was evaluated by a torsional vibration method using a viscoelasticity tester ARES-G2 manufactured by TA INSTRUMENTS.

[0310] (3) Dispersibility of cellulose nanofibers

[0311] The dispersion state of the cellulose nanofibers was evaluated by visual inspection in a 5 cm square area on the vulcanization press surface of the rubber cured product according to the following criteria.

[0312] A: Agglutinates were not visually confirmed.

[0313] B: A small amount (1 to 10) of aggregates were observed.

[0314] C: A large number (11 or more) of aggregates were observed.

[0315] Materials used

[0316] <Liquid Rubber>

[0317] Liquid rubber-1: butadiene-styrene random copolymer (RICON 184, available from Cray Valley Corporation), viscosity at 25°C 40000 cP, number average molecular weight (Mn) 3,200, weight average molecular weight (Mw) 14,000, Mw / Mn 4.3, vinyl content 19 mol%, aromatic styrene content 8 mol%

[0318] Liquid rubber-2: butadiene-styrene random copolymer (RICON 100, available from Cray Valley Corporation), viscosity at 25°C 75000 cP, number average molecular weight (Mn) 2,100, weight average molecular weight (Mw) 4,500, Mw / Mn 2.1, vinyl content 42 mol%, aromatic styrene content 9 mol%

[0319] <Solution Polymerized Rubber>

[0320] Rubber-1: Asaprene Y031 (available from Asahi Kasei Corporation)

[0321] <Cellulose Nanofiber>

[0322] CNF-1: microfibrous cellulose (Celish KY-100G, available from Daicel Miraizu Co., Ltd.)

[0323] CNF-2: Microfibrillar Cellulose

[0324] 3 parts by mass of cotton linter pulp was immersed in 27 parts by mass of water and dispersed by a beater. 170 parts by mass of water was added to 30 parts by mass of the cotton linter pulp slurry (containing 3 parts by mass of cotton linter pulp) treated by the beater, and the slurry was dispersed in water (solid content 1.5% by mass). As a disc refiner device, SDR14 type Lab-Refiner (pressurized DISK type) manufactured by Aikawa Iron Works Co., Ltd. was used, and the gap between the discs was 1 mm. The water dispersion was subjected to a beating treatment for 30 minutes. Then, the beating was carried out thoroughly under the condition that the gap was reduced to almost zero, and a beating water dispersion (solid content concentration: 1.5% by mass) was obtained. The obtained beating water dispersion was directly subjected to a micronization treatment 10 times at an operating pressure of 100 MPa using a high-pressure homogenizer (NSO15H manufactured by NiroSoavi (Italy)) to obtain a microfibrillated cellulose fiber slurry (solid content concentration: 1.5% by mass). Thereafter, the mixture was concentrated using a dehydrator to a solid content of 10% by mass to obtain a concentrated cake of CNF-2.

[0325] <Nonionic surfactant>

[0326] Surfactant-1: Polyoxyethylene (2) monolauryl ether (EMULGEN 102KG, available from Kao Corporation) The number of repetitions of ethylene oxide chains is shown in parentheses

[0327] Surfactant-2: Sorbitan monooleate (Rheodol SP-010V, available from Kao Corporation)

[0328] Surfactant-3: Polyoxyethylene (6) sorbitan monolaurate (Rheodol TW-L106, available from Kao Corporation) The number of repetitions of ethylene oxide chains is shown in parentheses

[0329] Surfactant-4: Ethylene glycol-propylene glycol copolymer (PEG-PPG) (Sanix GL-3000, available from Sanyo Chemical Co., Ltd.)

[0330] <Thermoplastic elastomer>

[0331] SEBS H1052: Product name "Tuftec H1052", manufactured by Asahi Kasei Corporation

[0332] <Silicon Dioxide>

[0333] Silica-1: precipitated silica (ULTRASIL 7000GR, available from Degussa)

[0334] <Silane coupling agent>

[0335] Si75: Bis(3-(triethoxysilyl)propyl) disulfide (available from Evonik Japan Co., Ltd.)

[0336] <Oil>

[0337] PF30: Mineral oil (available from JXTG Energy Corporation)

[0338] <Vulcanization accelerator>

[0339] Zinc oxide: Available from Fujifilm Wako Pure Chemical Industries, Ltd.

[0340] Stearic acid: Available from Fujifilm Wako Pure Chemical Industries, Ltd.

[0341] <Wax>

[0342] Sunnoc: Selected special wax (available from Ouchi Shinko Chemical Co., Ltd.)

[0343] <Anti-aging agent>

[0344] NOCRAC 6C: N-phenyl-N'-(1,3-dimethylbutyl)-p-phenylenediamine (available from Ouchi Shinko Chemical Co., Ltd.)

[0345] <Vulcanization accelerator>

[0346] NOCCELER CZ: N-cyclohexyl-2-benzothiazole sulfenamide (available from Ouchi Shinko Chemical Co., Ltd.)

[0347] NOCCELER D: 1,3-diphenylguanidine (available from Ouchi Shinko Chemical Co., Ltd.)

[0348] 《Preparation of rubber composition》

[0349] <Example 1>

[0350] Purified water was added to Celish KY100G (manufactured by Daicel Finechem) (aqueous dispersion of cellulose fibers) to prepare an aqueous dispersion having a final cellulose nanofiber content of 5% by mass. Liquid rubber-1 (RICON184) and surfactant-1 were added thereto to prepare an aqueous dispersion having a final composition of 90% by mass of water, 5% by mass of cellulose fibers, 2.86% by mass of liquid rubber, and 2.14% by mass of surfactant. The aqueous dispersion was mixed for 5 minutes using an ARE-310 rotary revolution mixer manufactured by Thinky Co., Ltd. to obtain a dispersion of a cellulose nanofiber composition. The obtained dispersion was dried at 80°C using SPH-201 manufactured by Espec Co., Ltd. to obtain a dried body. The obtained dry product was pulverized by a mini high-speed mill MS-05 manufactured by Labonect Co., Ltd., and then 20 parts by mass of the dry product was added to 80 parts by mass of liquid rubber-1 (RICON184), and mixed for 15 minutes using an auto-rotation and revolution mixer ARE-310 manufactured by Thinky Co., Ltd. to obtain a rubber composition.

[0351] <Example 2>

[0352] Purified water was added to Celish KY100G (manufactured by Daicel Finechem) (aqueous dispersion of cellulose fibers) to prepare an aqueous dispersion having a final cellulose nanofiber content of 5% by mass. Surfactant-1 was added thereto to prepare an aqueous dispersion having a final composition of 92.86% by mass of water, 5% by mass of cellulose fibers, and 2.14% by mass of surfactant. The aqueous dispersion was mixed for 5 minutes using an ARE-310 rotary revolution mixer manufactured by Thinky Co., Ltd. to obtain a dispersion of a cellulose nanofiber composition. The obtained dispersion was dried at 80°C using SPH-201 manufactured by Espec Co., Ltd. to obtain a dried product. The obtained dry product was pulverized by a mini high-speed mill MS-05 manufactured by Labonect Co., Ltd., and then 14.29 parts by mass of the dry product was added to 85.71 parts by mass of liquid rubber-1 (RICON 184), and mixed for 15 minutes using an auto-rotation and revolution mixer ARE-310 manufactured by Thinky Co., Ltd. to obtain a rubber composition.

[0353] <Example 3>

[0354] A rubber composition was prepared under the same conditions as in Example 2 except that Surfactant-1 was replaced with Surfactant-2.

[0355] <Example 4>

[0356] A rubber composition was prepared under the same conditions as in Example 2 except that Surfactant-1 was replaced with Surfactant-3.

[0357] <Example 5>

[0358] A rubber composition was prepared under the same conditions as in Example 2 except that Surfactant-1 was replaced with Surfactant-4.

[0359] <Comparative Example 1>

[0360] Liquid rubber-1 (RICON184) was used directly.

[0361] <Comparative Example 2>

[0362] 10 parts by mass of silica-1 were added to 90 parts by mass of liquid rubber-1 (RICON 184), and mixed for 15 minutes using an auto-rotating and orbiting mixer ARE-310 manufactured by Thinky Co., Ltd. to obtain a rubber composition.

[0363] <Comparative Example 3>

[0364] Purified water was added to Celish KY100G (manufactured by Daicel Finechem) (aqueous dispersion of cellulose fibers) to prepare an aqueous dispersion having a final cellulose nanofiber content of 5% by mass. Liquid rubber-1 (RICON184) was added thereto to prepare, as a final composition, an aqueous dispersion having 92.86% by mass of water, 5% by mass of cellulose fibers, and 2.14% by mass of liquid rubber-1. The aqueous dispersion was mixed for 5 minutes using an ARE-310 rotary revolution mixer manufactured by Thinky Co., Ltd. to obtain a dispersion of a cellulose nanofiber composition. The obtained dispersion was dried at 80°C using SPH-201 manufactured by Espec Co., Ltd. to obtain a dried body. The obtained dry product was pulverized by a mini high-speed mill MS-05 manufactured by Labonect Co., Ltd., and then 14.29 parts by mass of the pulverized dry product was added to 85.71 parts by mass of liquid rubber-1 (RICON 184), and mixed for 15 minutes using an auto-rotation and revolution mixer ARE-310 manufactured by Thinky Co., Ltd. to obtain a rubber composition.

[0365] The results are shown in Table 1. In Examples 1 to 5, the cellulose nanofibers were well dispersed in the rubber and the storage elastic modulus at a frequency of 1 Hz was high. In Comparative Example 3, the rubber contained a large number of aggregates, and although the rubber was subjected to storage elastic modulus measurement, no stable measurement value was obtained.

[0366] [Table 1]

[0367] Table 1

[0368]

[0369] <Dispersion of Rubber Composition in Thermoplastic Elastomer>

[0370] <Example 6>

[0371] Purified water was added to Celish KY100G (manufactured by Daicel Finechem) (aqueous dispersion of cellulose fibers) to prepare an aqueous dispersion having a final cellulose nanofiber content of 5% by mass. Liquid rubber-2 (RICON100) and surfactant-1 were added thereto to prepare an aqueous dispersion having a final composition of 90% by mass of water, 5% by mass of cellulose fibers, 7.86% by mass of liquid rubber, and 2.14% by mass of surfactant. The aqueous dispersion was mixed for 15 minutes using an ARE-310 rotary revolution mixer manufactured by Thinky Co., Ltd. to obtain a dispersion of a cellulose nanofiber composition. The obtained dispersion was dried at 80°C using SPH-201 manufactured by Espec Co., Ltd. to obtain a rubber composition.

[0372] Next, using a small mixer (Xplore) manufactured by RheoLabo, 15 g of the rubber composition was added to 85 g of thermoplastic elastomer-1 (SEBSH1052), and melt-kneaded at 200°C for 5 minutes to obtain a rubber strand in which cellulose nanofibers were dispersed. The obtained rubber strand was hot-pressed at 200°C and 10 kN for 10 minutes to obtain a sheet. The sheet was visually observed, and no agglomerates were confirmed.

[0373] <Comparative Example 4>

[0374] Purified water was added to Celish KY100G (manufactured by Daicel Finechem) (aqueous dispersion of cellulose fibers) to prepare an aqueous dispersion having a final cellulose nanofiber content of 5% by mass. Surfactant-1 was added thereto to prepare an aqueous dispersion having a final composition of 92.86% by mass of water, 5% by mass of cellulose fibers, and 2.14% by mass of surfactant. The aqueous dispersion was mixed for 15 minutes using an ARE-310 rotary revolution mixer manufactured by Thinky Co., Ltd. to obtain a dispersion of a cellulose nanofiber composition. The obtained dispersion was dried at 80°C using SPH-201 manufactured by Espec Co., Ltd. to obtain a composition containing cellulose nanofibers.

[0375] Next, using a small mixer (Xplore) manufactured by RheoLabo, 7.1 g of the composition containing cellulose nanofibers was added to 92.9 g of thermoplastic elastomer-1 (SEBSH1052), and melt-kneaded at 200°C for 5 minutes to obtain a rubber strand in which cellulose nanofibers were dispersed. The obtained rubber strand was hot-pressed at 200°C and 10 kN for 10 minutes to obtain a sheet. The sheet was visually observed, and a large amount of agglomerates were confirmed.

[0376] <Manufacturing of Rubber Cured Product>

[0377] <Example 7>

[0378] Purified water was added to CNF-2 (aqueous dispersion of cellulose fibers) to prepare an aqueous dispersion having a final cellulose nanofiber content of 5% by mass. Liquid rubber-1 and surfactant-1 were added thereto to prepare an aqueous dispersion having a final composition of 90% by mass of water, 5% by mass of cellulose fibers, 2.86% by mass of liquid rubber, and 2.14% by mass of surfactant. The aqueous dispersion was mixed for 5 minutes using an auto-revolution mixer ARE-310 manufactured by Thinky Co., Ltd. to obtain a dispersion of a cellulose nanofiber composition. The obtained dispersion was dried at 80°C using an SPH-201 manufactured by Espec Co., Ltd. to obtain a dried body. The obtained dried body was crushed for 30 seconds using a mini high-speed mill MS-05 manufactured by Labonect Co., Ltd. to obtain a powder for the manufacture of rubber cured products. The loose bulk density and tapped bulk density of the obtained dry powder were measured using the above method.

[0379] Next, LABO PLASTOMILL manufactured by Toyo Seiki Co., Ltd. was heated to 70°C, 100 parts by mass of rubber-1 (Asaprene Y031) was added and kneaded for 0.5 minutes, 10 parts by mass of powder for manufacturing rubber solidified material, vulcanization aid (2.5 parts by mass of zinc white and 2 parts by mass of stearic acid), 1.5 parts by mass of wax, 2 parts by mass of antioxidant were added thereto, kneaded for 5.5 minutes, and the first stage kneading was implemented. Then, the first stage kneading composition obtained was added to LABO PLASTOMILL heated to 70°C, kneaded for 0.5 minutes, 1.7 parts by mass of sulfur, vulcanization accelerator (1.7 parts by mass of NOCCELER CZ and 2 parts by mass of NOCCELER D) were added thereto according to the composition shown in Table 2, and kneaded for 2 minutes. The second stage kneading composition obtained was vulcanized at 160°C for 20 minutes using a vulcanization press to obtain a rubber solidified material.

[0380] <Example 8>

[0381] A rubber cured product was obtained in the same manner as in Example 7 except that the dried product was pulverized using a FreDrive hammer mill manufactured by Frevit Corporation instead of the mini high-speed mill MS-05 manufactured by Labonect Corporation.

[0382] <Example 9>

[0383] A rubber cured product was obtained in the same manner as in Example 7 except that the dried product was pulverized using FreDrive cone screening mill manufactured by Frevit instead of Mini High Speed ​​Mill MS-05 manufactured by Labonect Co., Ltd.

[0384] <Example 10>

[0385] A rubber cured product was obtained in the same manner as in Example 7 except that the dried product was pulverized using FreDrive pin mill manufactured by Frevit Corporation instead of Mini High Speed ​​Mill MS-05 manufactured by Labonect Corporation.

[0386] The dried product was pulverized to obtain a powder, and subjected to a 12-hour OsO 4 After dyeing, it was mixed with epoxy resin and placed at room temperature for 48 hours to cure the epoxy resin. The cured sample was cut with an ultrathin slicer to make a smooth cross section, and Os plasma coating was applied for 1 second. The scanning electron microscope (Hitachi High-Technologies Corporation, SU8220) was used for observation under the conditions of accelerating voltage 1.5kV, WD3mm, and upper detector. The results showed that the cellulose nanofibers were covered with rubber components ( Figure 1 ). Figure 1 In the figure, the dark gray part is the cellulose nanofiber, the light gray part around the cellulose nanofiber is the first rubber component, and the black part is the epoxy resin. Figure 1 It was confirmed that the cellulose nanofibers were covered with the first rubber component.

[0387] <Example 11>

[0388] A rubber cured product was obtained in the same manner as in Example 7 except that Surfactant-2 was used instead of Surfactant-1 as the surfactant.

[0389] <Example 12>

[0390] The final composition of the aqueous dispersion prepared was not 90 mass % of water, 5 mass % of cellulose fibers, 2.86 mass % of liquid rubber, and 2.14 mass % of surfactant, but an aqueous dispersion of 92.86 mass % of water, 5 mass % of cellulose fibers, 1.43 mass % of liquid rubber, and 0.71 mass % of surfactant was prepared, and a rubber cured product was obtained in the same manner as in Example 7 except that 7.14 mass parts of powder for producing a rubber cured product were added in place of 10 mass parts during the first stage kneading.

[0391] <Example 13>

[0392] A final composition of the aqueous dispersion in the preparation of the aqueous dispersion was 93.58 mass % of water, 5 mass % of cellulose fibers, 0.71 mass % of liquid rubber and 0.71 mass % of surfactant, instead of 90 mass % of water, 5 mass % of cellulose fibers, 2.86 mass % of liquid rubber and 2.14 mass % of surfactant. A rubber cured product was obtained in the same manner as in Example 7 except that 6.42 mass parts of powder for producing a rubber cured product were added in place of 10 mass parts during the first stage kneading.

[0393] <Example 14>

[0394] A rubber cured product was obtained in the same manner as in Example 7 except that the final composition of the aqueous dispersion during preparation was 85% by mass of water, 5% by mass of cellulose fibers, 7.86% by mass of liquid rubber and 2.14% by mass of surfactant, instead of 90% by mass of water, 5% by mass of cellulose fibers, 2.86% by mass of liquid rubber and 2.14% by mass of surfactant. The dried product was pulverized by freeze pulverization using Freezer Mill 6875 manufactured by SPEX instead of the mini high-speed mill MS-05 manufactured by Labonect Co., Ltd.

[0395] <Example 15>

[0396] LABO PLASTOMILL manufactured by Toyo Seiki Co., Ltd. was heated to 70°C, 100 parts by mass of rubber-1 (Asaprene Y031) was added, and kneading was performed for 0.5 minutes. 30 parts by mass of the powder for producing the rubber cured product prepared in Example 7 was added thereto, and kneading was performed for 5.5 minutes to prepare a masterbatch. Thereafter, LABO PLASTOMILL was heated to 70°C, 67 parts by mass of rubber-1 (Asaprene Y031) and 43 parts by mass of the masterbatch were added, and kneading was performed for 0.5 minutes. A vulcanization aid (2.5 parts by mass of zinc white and 2 parts by mass of stearic acid), 1.5 parts by mass of wax, and 2 parts by mass of antioxidant were added, and kneading was performed for 5.5 minutes to implement the first stage kneading. Then, 1.7 parts by mass of sulfur and a vulcanization accelerator (1.7 parts by mass of NOCCELER CZ and 2 parts by mass of NOCCELER D) were added, and kneading was performed for 2 minutes. The obtained second-stage kneaded composition was vulcanized at 160° C. for 20 minutes using a vulcanization press to obtain a rubber cured product.

[0397] <Reference Example 5>

[0398] A rubber cured product was obtained in the same manner as in Example 7 except that the dried product was dried under reduced pressure at 80°C using a Henschel mixer instead of using SPH-201 manufactured by Espec Corporation, and the dried powder was used without being pulverized.

[0399] <Reference Example 6>

[0400] A rubber cured product was obtained in the same manner as in Example 7 except that the pulverization time of the dried product was changed from 30 seconds to 5 seconds.

[0401] <Reference Example 7>

[0402] Purified water was added to CNF-2 (aqueous dispersion of cellulose fibers) to prepare an aqueous dispersion having a final cellulose nanofiber content of 5% by mass. Liquid rubber-1 and surfactant-1 were added thereto to prepare an aqueous dispersion having a final composition of 82.86% by mass of water, 5% by mass of cellulose fibers, 10% by mass of liquid rubber, and 2.14% by mass of surfactant. The aqueous dispersion was mixed for 5 minutes using an auto-revolution mixer ARE-310 manufactured by Thinky Co., Ltd. to obtain a dispersion of a cellulose nanofiber composition. The obtained dispersion was dried at 80°C using an SPH-201 manufactured by Espec Co., Ltd. to obtain a dried body. The obtained dried body was treated for 30 seconds using a mini high-speed mill MS-05 manufactured by Labonect Co., Ltd. The treated dried body did not become a powder, but was in the form of fragments of several mm in size.

[0403] Next, LABO PLASTOMILL manufactured by Toyo Seiki Co., Ltd. was heated to 70°C, 100 parts by mass of rubber-1 (Asaprene Y031) was added, and kneading was performed for 0.5 minutes. 17.14 parts by mass of powder for manufacturing rubber cured product, vulcanization aid (2.5 parts by mass of zinc white and 2 parts by mass of stearic acid), 1.5 parts by mass of wax, and 2 parts by mass of antioxidant were added thereto, and kneading was performed for 5.5 minutes to implement the first stage kneading. Then, the first stage kneading composition obtained was added to LABO PLASTOMILL heated to 70°C, and kneading was performed for 0.5 minutes. According to the composition shown in Table 2, 1.7 parts by mass of sulfur and vulcanization accelerator (1.7 parts by mass of NOCCELER CZ and 2 parts by mass of NOCCELER D) were added thereto, and kneading was performed for 2 minutes. The second stage kneading composition obtained was vulcanized at 160°C for 20 minutes using a vulcanization press to obtain a rubber cured product.

[0404] <Evaluation Results of Examples 7 to 15 and Reference Examples 5 to 7>

[0405] The evaluation results of Examples 7 to 15 and Reference Examples 5 to 7 are shown in Table 2. In the Examples, the cellulose nanofibers were well dispersed in the rubber, and significant improvement in physical properties was confirmed.

[0406]

[0407] Industrial Applicability

[0408] The rubber composition disclosed herein can be formed into a molded body having excellent physical properties, and thus can be suitably used in a wide range of applications, such as industrial machinery parts, general machinery parts, automobile, railway, vehicle, ship, and aerospace related parts, electronic and electrical parts, construction and civil engineering materials, daily necessities, sports and leisure goods, housing parts for wind power generation, and container and packaging parts.

Claims

1. A rubber composition, in, The composition comprises cellulose nanofibers, a first rubber component as a liquid rubber, and a surfactant. The surfactant is a nonionic surfactant. The degree of substitution of the cellulose nanofibers is 0.

2. The rubber composition according to claim 1, in, The cellulose nanofibers do not have ionic groups.

3. The rubber composition according to claim 1 or 2, in, The number average molecular weight of the liquid rubber is 1,000 to 80,000.

4. The rubber composition according to claim 1 or 2, in, The ratio Mw / Mn of the number average molecular weight Mn to the weight average molecular weight Mw of the liquid rubber is 1.5-5.

5. The rubber composition according to claim 1 or 2, in, The liquid rubber has a viscosity of 1,000,000 mPa·s or less at 80°C.

6. The rubber composition according to claim 1 or 2, in, The liquid rubber has a viscosity of 1,000,000 mPa·s or less at 25°C.

7. The rubber composition according to claim 1 or 2, in, The viscosity of the liquid rubber at 0° C. is 1,000,000 mPa·s or less.

8. The rubber composition according to claim 1 or 2, in, The liquid rubber includes one or more selected from the group consisting of diene rubber, silicone rubber, polyurethane rubber, polysulfide rubber, and hydrogenated products thereof.

9. The rubber composition according to claim 1 or 2, comprising 0.5% to 10% by mass of the cellulose nanofibers, The surfactant is contained in an amount of 10 to 200 parts by mass relative to 100 parts by mass of the cellulose nanofibers. The content of the liquid rubber is 0.1 mass % or more and 99 mass % or less.

10. The rubber composition according to claim 1 or 2, in, The surfactant is contained in an amount of 10 to 200 parts by mass based on 100 parts by mass of the cellulose nanofibers.

11. The rubber composition according to claim 1, in, The nonionic surfactant is a compound having a hydrophilic group, a hydroxyl group, and a hydrocarbon group.

12. The rubber composition according to claim 1 or 11, in, The nonionic surfactant is one or more selected from the group consisting of compounds represented by the following general formula (1) and compounds represented by the following general formula (2), R-(AND 2 CH 2 ) m -OH (1) In the general formula (1), R represents a monovalent aliphatic group having 6 to 30 carbon atoms, and m is a natural number smaller than the number of carbon atoms of R; R 1 AND 2 -(CHOH) 4 -CH 2 OR 2 (2) In the general formula (2), R 1 and R 2 each independently represents a hydrogen atom, an aliphatic group having 1 to 30 carbon atoms, -COR 3 or -(CH 2 CH 2 O) y -R 4 , formula -COR 3 In, R 3 represents an aliphatic group having 1 to 30 carbon atoms, the formula is -(CH 2 CH 2 O) y -R 4 In, R 4 represents a hydrogen atom or an aliphatic group having 1 to 30 carbon atoms, and y is an integer of 1 to 30.

13. The rubber composition according to claim 1 or 2, in, At least a portion of the surface of the cellulose nanofibers is covered with the first rubber component. 14 . A powder consisting of the rubber composition according to claim 1 .

15. The powder according to claim 14, having a tapped bulk density of 0.01 g / cm 3 ~0.30g / cm 3 .

16. A masterbatch, which is a kneaded product of the powder according to claim 14 or 15 and a second rubber component.

17. A method for producing a masterbatch, comprising the step of kneading the powder according to claim 14 or 15 with a second rubber component to obtain a masterbatch.

18. A rubber composite, which is a kneaded product of the powder according to claim 14 or 15 or the masterbatch according to claim 17 and a third rubber component.

19. The rubber composite according to claim 18, in, At least a portion of the surface of the cellulose nanofibers is covered with the first rubber component.

20. A method for producing a rubber composite, comprising the steps of obtaining the rubber composite by: kneading the powder according to claim 14 or 15 with a third rubber component; or A masterbatch is formed by the method according to claim 17, and then the masterbatch is kneaded with the third rubber component.

21. The method of claim 20, in, In the rubber composite, at least a portion of the surface of the cellulose nanofibers is covered with the first rubber component.

22. A rubber cured product, which is a cured product of the rubber composite according to claim 18 or 19.

23. A method for producing a rubber cured product, comprising the following steps: A step of obtaining a rubber composite by the method according to claim 20 or 21; and A step of curing the rubber composite to obtain a rubber cured product.

24. A shoe outsole comprising the rubber cured product according to claim 22.

25. A tire comprising the rubber cured product according to claim 22.

26. A vibration-proof rubber comprising the rubber cured product according to claim 22.

27. A transmission belt comprising the rubber cured product according to claim 22.

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