Rubber composition containing fine cellulose fibers

Abstract

In one embodiment, the objective is to provide a rubber composition, rubber composite, and cured rubber product that exhibit excellent dispersibility and orientation of fine cellulose fibers, and in another embodiment, the objective is to provide a cured rubber product that exhibits good physical properties (particularly tensile properties and modulus) and surface smoothness. [Solution] A rubber composition comprising fine cellulose fibers, a first rubber, a second rubber, and a dispersant, wherein the first rubber is an unmodified liquid rubber and the second rubber is a modified liquid rubber.

Description

[Technical Field]

[0001] One aspect of this disclosure relates to a rubber composition containing fine cellulose fibers, etc. [Background technology]

[0002] Traditionally, rubber molded articles have required a high degree of balance between various properties such as mechanical strength, flexibility, abrasion resistance, and processability. For example, it is common practice to include fillers in rubber molded articles to improve elastic modulus, hardness, abrasion resistance, etc. For such filler-containing rubber molded articles to exhibit desired properties, it is important that the fillers are well dispersed in the rubber. In recent years, with growing awareness of environmental issues, the use of cellulose, a low-density and renewable material, as a filler to be included in rubber molded articles has been explored in various ways. Among these, fine cellulose fibers are particularly promising as a filler for polymer molded articles because they provide a good reinforcing effect per unit of usage when combined with various polymers to construct polymer molded articles. If fine cellulose fibers can be used in rubber molded articles, it will be possible to provide rubber molded articles that are low-density, have excellent physical properties, can be used in a variety of applications, and are advantageous in terms of transportation and disposal costs. However, because fine cellulose fibers are inherently hydrophilic due to the contribution of hydroxyl groups in cellulose, they are difficult to mix with rubber, which is generally a highly hydrophobic material. Therefore, various attempts have been made to improve the miscibility between fine cellulose fibers and rubber.

[0003] For example, Patent Document 1 describes a rubber composition for tires comprising a rubber component, microfibrillated plant fibers which may be cellulose fibers, and a modifier that can covalently bond with the microfibrillated plant fibers.

[0004] Furthermore, Patent Document 2 describes a tire rubber composition characterized by blending 1 to 50 parts by mass of oxidized fine cellulose fibers with 100 parts by mass of diene rubber containing 5% by mass or more of modified diene rubber having 0.1 mol% or more of polar groups. [Prior art documents] [Patent Documents]

[0005] [Patent Document 1] Japanese Patent Publication No. 2020-41076 [Patent Document 2] Japanese Patent Publication No. 2019-147877 [Overview of the Initiative] [Problems that the invention aims to solve]

[0006] The technologies described in Patent Documents 1 and 2 aim to improve the mechanical properties of a rubber composition by dispersing cellulose fibers in the rubber composition. However, even with these technologies, the dispersibility of fine cellulose fibers in the rubber composition is still insufficient, and there is still room for improvement in mechanical properties. In addition, when incorporating fine cellulose fibers into various molded articles, good surface smoothness is sometimes required from the viewpoint of the appearance and sliding properties of the molded article. To obtain good surface smoothness, it is advantageous to properly orient the fine cellulose fibers in the molded article. However, Patent Documents 1 and 2 do not focus on the orientation of fine cellulose fibers.

[0007] The present invention aims to solve the above problems and, in one embodiment, to provide a rubber composition, rubber composite, and rubber cured product that are excellent in the dispersibility and orientation of fine cellulose fibers, and in another embodiment, to provide a rubber cured product that exhibits good physical properties (particularly tensile properties and modulus) and surface smoothness. [Means for solving the problem]

[0008] This disclosure includes the following items: [Item 1] A rubber composition comprising fine cellulose fibers, a first rubber, a second rubber, and a dispersant, A rubber composition in which the first rubber is an unmodified liquid rubber and the second rubber is a modified liquid rubber. [Item 2] The rubber composition according to item 1, wherein the first rubber comprises aromatic vinyl monomer units. [Item 3] The rubber composition according to item 1 or 2, wherein the second rubber is maleic anhydride-modified liquid polyisoprene. [Item 4] The rubber composition according to any one of items 1 to 3, wherein the dispersant is nonionic. [Item 5] A rubber composition according to any one of items 1 to 4, wherein the weight ratio of dispersant to second rubber is 0.01 to 2.0. [Item 6] The rubber composition according to any one of items 1 to 5, wherein the puncture strength of a 2 mm thick sheet obtained by pressurizing the rubber composition with a pressing force of 200 kN for a pressing time of 10 minutes at a temperature of 70°C is 0.3 MPa or more and 3.0 MPa. [Item 7] The rubber composition according to any one of items 1 to 6, wherein the porosity of a 2 mm thick sheet obtained by press-pressing the rubber composition with a pressing force of 200 kN for a pressing time of 10 minutes at a temperature of 70°C is 0.01% or more and 8.0% or less. [Item 8] The rubber composition according to any one of items 1 to 7, wherein the cohesiveness of a 2 mm thick sheet obtained by press-pressing the rubber composition with a pressing force of 200 kN for a pressing time of 10 minutes at a temperature of 70°C is 10% or more and 60% or less. [Item 9] The adhesion of a 2 mm thick sheet obtained by pressurizing the rubber composition with a pressing force of 200 kN for 10 minutes at a temperature of 70°C is 30 kJ / m². 3 More than 300kJ / m 3 The rubber composition described in any of the following items 1 to 8. [Item 10] A rubber composition according to any one of items 1 to 9, further comprising a third rubber. [Item 11] A method for producing a rubber composition as described in any of items 1 to 10, A first step of mixing fine cellulose fibers with the first rubber to obtain a preliminary composition, and A second step of mixing the aforementioned precomposition with the second rubber, Methods that include... [Item 12] A method for producing a rubber composition as described in any of items 1 to 10, A first step involves drying a preliminary composition obtained by mixing fine cellulose fibers with the first rubber to obtain a dried fine cellulose fiber body, and A second step of mixing the dried fine cellulose fiber body with the second rubber, Methods that include... [Item 13] A method for producing a rubber composition as described in any of items 1 to 10, A first step of mixing the first rubber and the second rubber to obtain a preliminary composition, and A second step of mixing the aforementioned pre-composition with the aforementioned fine cellulose fibers, Methods that include... [Item 14] The method according to any one of items 11 to 13, wherein the third rubber is further mixed in the second step described above. [Item 15] The method according to any one of items 11 to 13, wherein a third rubber is further mixed after the second step described above. [Item 16] A rubber composite that is a compound of a rubber composition described in any of items 1 to 10 and a fourth rubber. [Item 17] A cured rubber product, which is a cured product of the rubber composite described in item 16. [Item 18] Tires containing the rubber curing material described in item 17. [Item 19] Vibration-damping rubber, including the rubber curing material described in item 17. [Item 20] Shoe outsoles containing the rubber curing material described in item 17. [Item 21] A conveyor belt containing the rubber curing material described in item 17. [Item 22] A rubber composition sheet comprising any of the rubber compositions described in items 1 to 10. [Item 23] A rubber composition sheet as described in item 22, wherein the breaking stress is 0.1 MPa or more and 20 MPa or less. [Item 24] A rubber composition sheet according to item 22 or 23, having a Shore A hardness of 10 to 90. [Item 25] A method for producing a rubber composition sheet as described in any of items 22 to 24, wherein the rubber composition is formed into a sheet using a powder rolling mill. [Item 26] A method for manufacturing a rubber composition sheet as described in any of items 22 to 24, wherein the rubber composition is formed into a sheet using a press molding machine. [Effects of the Invention]

[0009] According to the present invention, in one embodiment, a rubber composition, a rubber composite, and a cured rubber product can be provided that are excellent in the dispersibility and orientation of fine cellulose fibers, and in one embodiment, a cured rubber product can be provided that exhibits good physical properties (particularly tensile properties and modulus) and surface smoothness. [Modes for carrying out the invention]

[0010] The following describes exemplary embodiments of the present invention (hereinafter abbreviated as "Embodiments"), but the present invention is not limited to these embodiments. Unless otherwise specified, the characteristic values ​​of this disclosure are measured by the methods described in the [Examples] section of this disclosure or by methods that are understood to be equivalent to those of a person skilled in the art.

[0011] Rubber Composition One aspect of the present disclosure provides a rubber composition comprising fine cellulose fibers, a first rubber, and a second rubber. In one aspect, the first and second rubbers are liquid rubbers. Fine cellulose fibers are inherently hydrophilic due to their hydroxyl groups, while rubber is inherently hydrophobic, making it generally difficult to uniformly disperse fine cellulose fibers in rubber. The inventors, after various studies, have found that a specific combination of rubbers is useful for preparing a rubber composition with excellent dispersibility and orientation of fine cellulose fibers. This rubber composition can also be used, for example, in the form of a rubber masterbatch and kneaded with additional rubber to produce a rubber composite. The rubber composition, rubber composite, or rubber cured product of the present disclosure can exhibit good dispersibility and orientation of fine cellulose fibers. Furthermore, in the rubber cured product of the present disclosure, good physical properties (particularly tensile properties and modulus) and good surface smoothness can be achieved simultaneously.

[0012] In one embodiment, the first rubber is an unmodified liquid rubber, and the second rubber is a modified liquid rubber. Typically, of the first and second rubbers, the second rubber may bind to or interact with fine cellulose fibers, while the first rubber may substantially not produce such binding or interaction. The second rubber may have good fluidity due to being a liquid rubber and functionality due to having a modified group. Such a second rubber is expected to have the effect of improving the dispersibility of fine cellulose fibers with respect to the third and / or fourth rubbers of this disclosure. However, the inventors have found that using only the second rubber may not provide the desired level of improvement in the dispersibility of fine cellulose fibers. Although not bound by theory, one possible reason is that the modified groups of the second rubber cause excessive binding or interaction locally between the modified groups of the second rubber, or between the modified groups of the second rubber and the hydroxyl groups of the fine cellulose fibers, resulting in the formation of a dense structure between the second rubbers, or between the second rubber and the fine cellulose fibers. In particular, when the viscosity of the second rubber is relatively high, the second rubber particles may easily form a dense structure. Furthermore, when incorporating fine cellulose fibers into various molded articles, good surface smoothness is sometimes required from the viewpoint of the appearance and sliding properties of the molded article. To obtain good surface smoothness, it is advantageous to orient the fine cellulose fibers well in the molded article. If the mobility of the fine cellulose fibers in the rubber composition or rubber composite during the manufacturing of the molded article is good, it is easier to achieve good orientation of the fine cellulose fibers. However, if a dense structure like the one described above is formed, the orientation of the fine cellulose fibers may decrease. Therefore, the inventors further investigated and found that the above problems can be solved by using a first rubber in addition to the second rubber. The first rubber has the advantage of being a liquid rubber, which gives it excellent fluidity, and also has the advantage of not forming the dense structure described above because it does not have modifying groups. The first rubber can intervene between the second rubbers or between the second rubber and the fine cellulose fibers, thereby suppressing the excessive proximity of functional groups on the second rubber and the fine cellulose fibers to other functional groups.This allows the second advantage of rubber, which is improved dispersibility of fine cellulose fibers, to manifest effectively, making it easier to achieve good dispersibility and orientation of fine cellulose fibers.

[0013] The components of the rubber composition will be described below. Note that the amounts of each component listed as values ​​in the rubber composition of this embodiment may be considered as the amounts of each component in the rubber composition of this embodiment.

[0014] <Fine Cellulose Fibers> Fine cellulose fibers are fibers obtained by finely processing cellulose fiber raw materials through methods such as defibration. Natural cellulose and regenerated cellulose can be used as cellulose fiber raw materials. As natural cellulose, wood pulp obtained from wood species (hardwood or softwood), non-wood pulp obtained from non-wood species (cotton, bamboo, hemp, bagasse, kenaf, cotton linter, sisal, straw, etc.), and cellulose fiber aggregates produced by animals (e.g., sea squirts), algae, and microorganisms (e.g., acetic acid bacteria) can be used. As regenerated cellulose, regenerated cellulose fibers (viscose, cupro, Tencel, etc.), cellulose derivative fibers, and ultrafine threads of regenerated cellulose or cellulose derivatives obtained by electrospinning can be used.

[0015] In one embodiment, defibration is a dry or wet mechanical treatment, preferably a wet treatment in which a slurry obtained by dispersing cellulose fiber raw material in a liquid medium is subjected to mechanical treatment. A single apparatus may be used for defibration once or more times, or multiple apparatuses may be used, each once or more times. The apparatus used for defibration is not particularly limited, but examples include high-speed rotary type, colloid mill type, high-pressure type, roll mill type, ultrasonic type, and high-pressure or ultra-high-pressure homogenizers, refiners, beaters, PFI mills, kneaders, dispersers, high-speed defibration machines, grinders (stone mill type pulverizers), ball mills, vibratory mills, bead mills, conical refiners, disc refiners, single-screw, twin-screw or multi-screw kneaders and extruders. Cellulose fiber raw materials may be subjected to pretreatment before defibration. Pretreatment can be used to adjust the fiber diameter, fiber length, degree of fibrillation, etc., as well as to adjust the content of components other than cellulose (acid-insoluble components such as lignin, alkali-soluble polysaccharides such as hemicellulose, etc.), molecular weight, degree of crystallinity, etc. In one embodiment, the pretreatment may consist of one or more methods selected from chemical treatment, pulverization, grinding, and classification. Chemical treatment is a treatment using chemicals, such as pulverization, bleaching, purification, hydrolysis, enzymatic treatment, regeneration of cellulose, and chemical modification. Pulverization is a dry pulverization of the cellulose fiber raw material. Grinding is a wet pulverization of a slurry obtained by dispersing the cellulose fiber raw material in a liquid medium. Classification is a separation operation to standardize the fiber length of the cellulose fiber raw material, and may be dry classification or wet classification.

[0016] Examples of the liquid medium include water and / or other media (e.g., organic solvents, inorganic acids, bases and / or ionic liquids), and may contain one or more types of media.

[0017] Commonly used organic solvents include, for example: alcohols (e.g., methanol, ethanol, n-propanol, i-propanol, n-butanol, i-butanol, s-butanol, t-butanol, ethylene glycol, diethylene glycol, glycerin, 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 (e.g., dimethylformamide, dimethylacetamide, acetonitrile, etc.); and sulfur-containing solvents (dimethyl sulfoxide). In a typical embodiment, the liquid medium in the slurry is substantially water only.

[0018] [Specific surface area] From the viewpoint of obtaining a good effect of improving physical properties by the microcrystalline cellulose fibers, the specific surface area of the microcrystalline cellulose fibers is preferably 2 m 2 / g or more, preferably 3 m 2 / g or more, preferably 5 m 2 / g or more, preferably 7 m 2 / g or more, preferably 10 m 2 / g or more, preferably 12 m 2 / g or more, preferably 15 m 2 / g or more, preferably 17 m 2 / g or more, preferably 20 m 2 / g or more, preferably 22 m 2 / g or more, preferably 25 m 2 / g or more, preferably 27 m 2 / g or more. Further, from the viewpoint of well dispersing the microcrystalline cellulose fibers in the rubber composition and the rubber cured product, it is preferably 400 m 2 / g or less, preferably 350 m 2 / g or less, preferably 300 m 2 / g or less, preferably 250 m 2 / g or less, preferably 200 m 2 / g or less, preferably 170 m 2 / g or less, preferably 150 m 2 / g or less, preferably 120 m 2 / g or less, preferably 100 m 2 / g or less.

[0019] The specific surface area of the microcrystalline cellulose fibers is measured using nitrogen gas with a specific surface area and pore size distribution measuring device (for example, Nova-4200e, manufactured by Quantachrome Instruments) for the BET specific surface area of the porous sheet of the microcrystalline cellulose fibers. Specifically, after drying about 0.2 g of the porous sheet under vacuum at 105 °C for 5 hours, the adsorption amount of nitrogen gas at the boiling point of liquid nitrogen is measured at 5 points in the range where the relative vapor pressure (P / P0) is 0.05 or more and 0.2 or less (multi-point method), and the BET specific surface area (m 2 / g) is calculated by the program of the same device. The porous sheet is produced by the method described in the section of [Porous Sheet] described later.

[0020] The specific surface area of ​​a fine cellulose fiber can be calculated by assuming the fine cellulose fiber is cylindrical, and the equivalent fiber diameter can be calculated using the following formula. The density of cellulose is 1.5 g / cm³. 3 Therefore, the volume per gram of cellulose is 6.67 × 10⁻⁶. -7 (m 3 It is / g). If the equivalent fiber diameter of a fine cellulose fiber is r (m), then the average outer circumference of the fine cellulose fiber is πr, and the average cross-sectional area of ​​the fine cellulose fiber is 0.25πr. 2 Therefore, per gram of fine cellulose fiber, the total fiber length = 6.67 × 10 -7 (m 3 / g) / average cross-sectional area (=0.25πr 2 ) Total surface area = Specific surface area (m²) 2 / g) = 6.67 × 10 -7 (m 3 / g) / average cross-sectional area (=0.25πr 2 )×average outer circumference length (=πr)=6.67×10 -7 (m 3 / g) / 0.25r = 26.68 × 10 -7 (m 3 / g) / r Therefore, Equivalent fiber diameter r(m) = 26.68 × 10 -7 (m 3 / g) / specific surface area (m 2 / g) For example, the BET specific surface area of ​​a porous sheet is 40 m². 2 The equivalent fiber diameter r of the fine cellulose fibers is calculated to be 66.7 nm.

[0021] In one embodiment, the equivalent fiber diameter of the fine cellulose fibers is preferably 2 to 1000 nm from the viewpoint of obtaining a good effect of improving physical properties by the fine cellulose fibers. More preferably, the equivalent fiber diameter of the fine cellulose fibers is 4 nm or more, or 5 nm or more, or 10 nm or more, or 15 nm or more, or 20 nm or more, and more preferably 900 nm or less, or 800 nm or less, or 700 nm or less, or 600 nm or less, or 500 nm or less, or 400 nm or less, or 300 nm or less, or 200 nm or less.

[0022] [Number average fiber length] In one embodiment, the number-average fiber length L of the fine cellulose fibers is preferably 100 nm or more, or 500 nm or more, 1 μm or more, or 5 μm or more, or 10 μm or more, or 20 μm or more, from the viewpoint of exhibiting a good effect of improving physical properties by the fine cellulose fibers, and preferably 1000 μm or less, or 800 μm or less, or 500 μm or less, or 400 μm or less, or 300 μm or less, or 200 μm or less, from the viewpoint of good dispersion of the fine cellulose fibers in the resin composition.

[0023] In one embodiment, the number-average fiber diameter D of the fine cellulose fibers is preferably 2 to 1000 nm from the viewpoint of obtaining a good effect of improving physical properties by the fine cellulose fibers. The number-average fiber diameter of the fine cellulose fibers is more preferably 4 nm or more, or 5 nm or more, or 10 nm or more, or 15 nm or more, or 20 nm or more, and more preferably 900 nm or less, or 800 nm or less, or 700 nm or less, or 600 nm or less, or 500 nm or less, or 400 nm or less, or 300 nm or less, or 200 nm or less.

[0024] The average fiber length (L) / fiber diameter (D) ratio of fine cellulose fibers is preferably 30 or more, or 50 or more, or 80 or more, or 100 or more, or 120 or more, or 150 or more, from the viewpoint of effectively improving the mechanical properties of the rubber composite containing fine cellulose fibers with a small amount of fine cellulose fibers. There is no particular upper limit, but from the viewpoint of ease of handling, it is preferably 5000 or less, or 3000 or less, or 2000 or less, or 1000 or less.

[0025] In this disclosure, the fiber length, fiber diameter, and L / D ratio of fine cellulose fibers are values ​​measured using a scanning electron microscope (SEM) by the following procedure. An aqueous dispersion of fine cellulose fibers is replaced with tert-butanol, diluted to 0.001-0.1% by mass, dispersed using a high-shear homogenizer (e.g., IKA product, trade name "Ultra-Turrax T18") under processing conditions: rotation speed 15,000 rpm for 3 minutes, cast onto an osmium-deposited silicon substrate, and air-dried. This sample is used as the measurement sample and measured using a high-resolution scanning electron microscope (SEM). Specifically, the length (L) and diameter (D) of 100 randomly selected fine cellulose fibers are measured in an observation field adjusted to the magnification so that at least 100 fine cellulose fibers can be observed, and the ratio (L / D) is calculated. The number average values ​​of these are then taken as the number average fiber diameter L and number average fiber diameter D, and the ratio (L / D) is calculated.

[0026] [Crystal polymorphism] Known crystalline forms of cellulose include Type I, Type II, Type III, and Type IV. Among these, Type I and Type II are particularly widely used, while Type III and Type IV, although obtained on a laboratory scale, are not widely used on an industrial scale. The fine cellulose fibers of this disclosure have relatively high structural mobility, and by dispersing these fine cellulose fibers in rubber, a molded article with a lower coefficient of thermal expansion and superior strength and elongation during tensile and bending deformation can be obtained. Therefore, fine cellulose fibers containing cellulose Type I crystals or cellulose Type II crystals are preferred, and fine cellulose fibers containing cellulose Type I crystals and having a crystallinity of 55% or higher are more preferred.

[0027] [Degree of crystallinity] The degree of crystallinity of the fine cellulose fibers is preferably 55% or higher. The higher the degree of crystallinity, the higher the mechanical properties (strength, dimensional stability) of the cellulose itself, and therefore, when fine cellulose fibers are dispersed in rubber, the rubber composite tends to have higher strength and dimensional stability. A more preferable lower limit for the degree of crystallinity is 60%, even more preferably 70%, and most preferably 80%. There is no particular upper limit for the degree of crystallinity of the fine cellulose fibers, and a higher value is preferable, but from a production standpoint, a preferable upper limit is 99%.

[0028] The degree of crystallinity referred to here, when the fine cellulose fibers are cellulose type I crystals (derived from natural cellulose), can be determined by the Segal method using the following formula based on the diffraction pattern (2θ / deg. of 10 to 30) obtained by measuring the sample by wide-angle X-ray diffraction. Crystallinity (%)=[I (200) -I (amorphous) ] / I (200) ×100 I (200) :Diffraction peak intensity at the 200 plane (2θ=22.5°) in cellulose type I crystals I (amorphous) : The halo peak intensity due to amorphous material in type I cellulose crystals, specifically the peak intensity at an angle 4.5° lower than the diffraction angle of the 200 plane (2θ = 18.0°).

[0029] Furthermore, if the cellulose is a type II cellulose crystal (derived from regenerated cellulose), the degree of crystallinity can be determined by the following formula using wide-angle X-ray diffraction, based on the absolute peak intensity h0 at 2θ=12.6°, which is attributed to the (110) plane peak of the type II cellulose crystal, and the baseline peak intensity h1 at this interplanar spacing (the line connecting 2θ=8° and 15°). Crystallinity (%) = (h0-h1) / h0 ×100

[0030] [Degree of polymerization] The degree of polymerization of the fine cellulose fibers is preferably 100 or more, more preferably 150 or more, more preferably 200 or more, more preferably 300 or more, more preferably 400 or more, more preferably 450 or more, preferably 3500 or less, more preferably 3000 or less, more preferably 2000 or less, more preferably 1500 or less, more preferably 1200 or less, and more preferably 1000 or less.

[0031] From the viewpoint of processability and mechanical property development, it is desirable to keep the degree of polymerization of the fine cellulose fibers within the above-mentioned range. From the viewpoint of processability, it is preferable that the degree of polymerization is not too high, and from the viewpoint of mechanical property development, it is desirable that it is not too low.

[0032] The degree of polymerization of fine cellulose fibers refers to the average degree of polymerization determined by Staudinger's viscosity law using the intrinsic viscosity number measured by JIS P8215:1998 Cellulose dilute solution - Method for determining intrinsic viscosity number - Copper ethylenediamine method.

[0033] In one embodiment, the weight-average molecular weight (Mw) of the fine cellulose fibers is 100,000 or more, more preferably 200,000 or more. The ratio of weight-average molecular weight to number-average molecular weight (Mn) (Mw / Mn) is 6 or less, preferably 5.6 or less, or 5.4 or less. A larger weight-average molecular weight means fewer end groups in the cellulose molecule. Also, since the ratio of weight-average molecular weight to number-average molecular weight (Mw / Mn) represents the width of the molecular weight distribution, a smaller Mw / Mn means fewer end groups in the cellulose molecule. Since the end groups of cellulose molecules are the starting points for thermal decomposition, when the weight-average molecular weight of the cellulose molecules in the fine cellulose fibers is large, and at the same time the width of the molecular weight distribution is narrow, particularly heat-resistant fine cellulose fibers and rubber compositions containing fine cellulose fibers and rubber can be obtained. From the viewpoint of the availability of cellulose raw materials, the weight-average molecular weight (Mw) of the fine cellulose fibers may be, for example, 600,000 or less, or 500,000 or less, or 400,000 or less. The number-average molecular weight (Mn) of fine cellulose fibers may be, for example, 200,000 or less, 150,000 or less, 100,000 or less, 80,000 or less, or 60,000 or less, from the viewpoint of the availability of cellulose fiber raw materials. The ratio of weight-average molecular weight to number-average molecular weight (Mn) (Mw / Mn) may be, for example, 1.5 or more, 1.7 or more, or 2 or more, from the viewpoint of the ease of manufacturing fine cellulose fibers. Mw can be controlled to the above range by selecting a cellulose raw material having an Mw appropriate for the purpose, and by appropriately performing physical and / or chemical treatments on the cellulose raw material within an appropriate range. Mw / Mn can also be controlled to the above range by selecting a cellulose raw material having an Mw / Mn appropriate for the purpose, and by appropriately performing physical and / or chemical treatments on the cellulose raw material within an appropriate range. In one embodiment, each of the Mw and Mw / Mn of the cellulose raw material may be within the above range.

[0034] The weight-average molecular weight and number-average molecular weight of the fine cellulose fibers referred to here are values ​​obtained by dissolving the fine cellulose fibers in N,N-dimethylacetamide to which lithium chloride has been added, and then determining them by gel permeation chromatography using N,N-dimethylacetamide as the solvent.

[0035] [Alkali-soluble polysaccharides] The alkali-soluble polysaccharides that fine cellulose fibers may contain include not only hemicellulose but also β-cellulose and γ-cellulose. Alkali-soluble polysaccharides are understood by those skilled in the art as components obtained as the alkali-soluble portion of holocellulose obtained by solvent extraction and chlorine treatment of plants (e.g., wood) (i.e., components obtained by removing α-cellulose from holocellulose). Since alkali-soluble polysaccharides are polysaccharides containing hydroxyl groups and have poor heat resistance, they can cause problems such as decomposition when heated, yellowing during thermal aging, and a decrease in the strength of fine cellulose fibers. Therefore, it is preferable to have a low alkali-soluble polysaccharide content in fine cellulose fibers.

[0036] In one embodiment, the average content of alkali-soluble polysaccharides in the fine cellulose fibers is preferably 20% by mass or less, 18% by mass or less, 15% by mass or less, or 12% by mass or less, based on 100% by mass of the fine cellulose fibers, from the viewpoint of obtaining good dispersibility of the fine cellulose fibers. The above content may be 1% by mass or more, 2% by mass or more, or 3% by mass or more, from the viewpoint of ease of manufacturing the fine cellulose fibers.

[0037] The average alkali-soluble polysaccharide content can be determined using the method described in non-patent literature (Wood Science Experiment Manual, edited by the Japan Wood Research Society, pp. 92-97, 2000), by subtracting the α-cellulose content from the holocellulose content (Wise method). This method is understood in this industry as a method for measuring hemicellulose content. The alkali-soluble polysaccharide content is calculated three times for each sample, and the number average of the calculated alkali-soluble polysaccharide content is taken as the average alkali-soluble polysaccharide content.

[0038] [Acid-insoluble components] In one embodiment, the average content of acid-insoluble components in the fine cellulose fibers is preferably 10% by mass or less, 5% by mass or less, or 3% by mass or less, based on 100% by mass of the fine cellulose fibers, from the viewpoint of avoiding a decrease in the heat resistance of the fine cellulose fibers and the resulting discoloration. The above content may be 0.1% by mass or more, 0.2% by mass or more, or 0.3% by mass or more, from the viewpoint of ease of manufacturing the fine cellulose fibers.

[0039] The average acid-insoluble component content is determined using the Claesson method described in the non-patent literature (Wood Science Experiment Manual, edited by the Japan Wood Research Society, pp. 92-97, 2000). This method is understood in this industry as a method for measuring lignin content. After stirring the sample in sulfuric acid solution to dissolve cellulose and hemicellulose, etc., the sample is filtered through glass fiber filter paper, and the resulting residue contains the acid-insoluble components. The acid-insoluble component content is calculated from the weight of these acid-insoluble components. The acid-insoluble component content is measured three times for each sample, and the average of these measurements is taken as the average acid-insoluble component content.

[0040] [Chemical modification] The fine cellulose fibers may be chemically modified fine cellulose fibers (also called chemically modified fine cellulose fibers). Examples of chemically modified fine cellulose fibers include inorganic esters such as nitrate esters, sulfate esters, phosphate esters, silicate esters, and borate esters; organic esters such as acetylated and propionylated esters; ethers such as methyl ethers, hydroxyethyl ethers, hydroxypropyl ethers, hydroxybutyl ethers, carboxymethyl ethers, and cyanoethyl ethers; and TEMPO oxides obtained by oxidizing the primary hydroxyl groups of cellulose. Chemically modified fine cellulose fibers may contain one or more types of modifying groups. In a preferred embodiment, the chemical modification is acylation using an esterifying agent, and particularly preferably acetylation. Preferred esterifying agents are acid halides, acid anhydrides, vinyl carboxylates, and carboxylic acids. Among these esterifying reagents, at least one selected from the group consisting of acetic anhydride, propionic anhydride, butyric anhydride, vinyl acetate, vinyl propionate, vinyl butyrate, and acetic acid, with acetic anhydride and vinyl acetate being particularly preferred from the viewpoint of reaction efficiency. The fine cellulose fibers may be chemically modified with a modifying agent, for example, at the stage of cellulose fiber raw material, during or after the defibration process, or they may be chemically modified during or after the preparation of the slurry as a dispersion, or during or after the drying process.

[0041] [Thermal decomposition onset temperature (T D ), temperature at 1% weight loss (T 1% ), 250℃ weight loss rate (T 250℃ )] The temperature at which thermal decomposition of fine cellulose fibers begins (T D In one embodiment, the temperature is preferably 150°C or higher, or 200°C or higher, or 210°C or higher, 220°C or higher, 230°C or higher, 240°C or higher, 250°C or higher, or 260°C or higher, from the viewpoint of avoiding thermal degradation of fine cellulose fibers during rubber compounding and curing and exhibiting excellent reinforcing properties. A higher temperature is preferable for the onset of thermal decomposition, but from the viewpoint of ease of manufacturing fine cellulose fibers, it may be, for example, 320°C or lower, or 310°C or lower, or 300°C or lower, or 290°C or lower, or 280°C or lower.

[0042] Temperature (T) when fine cellulose fibers lose 1 wt% of weight. 1% In one embodiment, the temperature is preferably 230°C or higher, or 240°C or higher, or 250°C or higher, or 260°C or higher, or 270°C or higher, or 275°C or higher, or 280°C or higher, or 285°C or higher, or 290°C or higher, from the viewpoint of avoiding thermal degradation during rubber mixing and curing and being able to exhibit mechanical strength. 1%Higher temperatures are preferable, but from the viewpoint of ease of manufacturing fine cellulose fibers, temperatures of, for example, 330°C or lower, 320°C or lower, or 310°C or lower may also be acceptable.

[0043] Weight loss rate of fine cellulose fibers at 250°C (T 250℃ From the viewpoint of avoiding thermal degradation during rubber mixing and curing and being able to exhibit mechanical strength, in one embodiment, it is preferably 15% or less, or 12% or less, or 10% or less, or 8% or less, or 6% or less, or 5% or less, or 4% or less, or 3% or less. 250℃ While a lower concentration is preferable, from the viewpoint of ease of manufacturing fine cellulose fibers, it may be, for example, 0.1% or more, or 0.5% or more, or 0.7% or more, or 1.0% or more.

[0044] In this disclosure, T D This value is obtained from a graph in thermogravimetric (TG) analysis, where the horizontal axis is temperature and the vertical axis is weight retention percentage. Starting from the weight of fine cellulose fibers in a nitrogen flow at 150°C (a state where moisture has been almost completely removed) (weight loss of 0 wt%), the temperature is further increased until the temperature at which a 1 wt% weight loss occurs (T 1% ) and temperature (T) when weight decreases by 2 wt% 2% Obtain a straight line passing through ( ). The temperature at the point where this line intersects with the horizontal line (baseline) passing through the starting point of the weight loss of 0 wt% is T. D This is how it is defined.

[0045] 1% weight loss temperature (T 1% ) is the above T D This is the temperature at which the weight decreases by 1% by weight, starting from the weight at 150°C, when the heating method is continued. Specifically, 10 mg of a porous sheet of fine cellulose fibers is heated from room temperature to 150°C at a rate of 10°C / min in a nitrogen flow of 100 ml / min, held at 150°C for 1 hour, and then heated from 150°C to 450°C at a rate of 10°C / min.

[0046] Weight loss rate of fine cellulose fibers at 250°C (T 250℃) is the weight loss rate when fine cellulose fibers are held at 250°C under a nitrogen flow for 2 hours in TG analysis. 10 mg of a porous sheet of fine cellulose fibers is heated from room temperature to 150°C at a rate of 10°C / min in a nitrogen flow of 100 ml / min, held at 150°C for 1 hour, then heated from 150°C to 250°C at a rate of 10°C / min, and held at 250°C for 2 hours. The weight W0 at the time of reaching 250°C is taken as the starting point, and the weight after holding at 250°C for 2 hours is taken as W1, which is calculated using the following formula. Weight change rate at 250℃ (%): (W1-W0) / W0×100

[0047] [Porous Sheet] Various physical properties of fine cellulose fibers (specific surface area, degree of crystallinity, polymorphism, degree of polymerization, Mw, Mn, Mw / Mn, average alkali-soluble content, average acid-insoluble content, T D , T 1% , T 250℃ Measurements of (etc.) can vary significantly depending on the form of the sample being measured. To ensure stable and reproducible measurements, a distortion-free porous sheet should be used as the measurement sample. The method for preparing the porous sheet is as follows.

[0048] First, a concentrated cake of fine cellulose fibers with a solid content of 10% by mass or more, where water is the liquid medium, is added to tert-butanol to adjust the fine cellulose fiber solid content to 0.5% by mass and the total weight to 100g. Next, the mixture is dispersed using a mixer or similar device (for example, a high-shear homogenizer (e.g., IKA product, product name "Ultra-Turrax T18", processing conditions: rotation speed 15,000 rpm x 3 minutes)) until no aggregates remain). 100g of the resulting tert-butanol dispersion is filtered onto filter paper. The filtrate is not removed from the filter paper, but sandwiched between two larger sheets of filter paper, and the edges of the larger sheets are pressed down with weights while drying in a 150°C oven for 5 minutes. After that, the filter paper is peeled off to obtain a porous sheet with minimal distortion. The air permeability resistance R of this sheet is 10g / m². 2 Materials with a density of 100 sec / 100 ml or less are treated as porous sheets and used as measurement samples.

[0049] The air permeability resistance R was measured by measuring the basis weight W (g / m²) of a porous sheet sample that had been left standing for one day in an environment of 23°C and 50%RH. 2 After measuring the air permeability resistance (R) (sec / 100ml), the air permeability resistance is measured using a Wangyan-type air permeability resistance tester (for example, Asahi Seiko Co., Ltd., model EG01). At this time, 10 g / m³ is used according to the following formula. 2 Calculate the value per unit area. Weight: 10g / m 2 Air permeability resistance (sec / 100ml) = R / W × 10

[0050] Various physical properties of fine cellulose fibers contained in rubber compositions, rubber composites, etc. (number average fiber length, number average fiber diameter, L / D ratio, degree of crystallinity, crystalline polymorphism, degree of polymerization, Mw, Mn, Mw / Mn, alkali-soluble content, average acid-insoluble content, T D , T 1% , T 250℃ (DS, etc.) are analyzed using the following method. The polymer components contained in the rubber composition, rubber composite, etc., are dissolved in an organic or inorganic solvent capable of dissolving the polymer components, and the fine cellulose fibers are separated. After thoroughly washing with the solvent, the solvent is replaced with tert-butanol. Subsequently, the fine cellulose fiber tert-butanol slurry is analyzed using the same measurement method as described above, and various physical properties of the fine cellulose fibers in the rubber composition, rubber composite, etc., are calculated.

[0051] In one embodiment, the fine cellulose fibers may be provided in the form of a slurry containing a liquid medium, or in the form of a dry material such as particles, a film, or a bulk material. Examples of the liquid medium include water and / or an organic solvent having a boiling point, and may contain one or more types of media. The slurry form has a liquid medium content of 50% by mass or more, while the dry material has a liquid medium content of less than 50% by mass. The liquid medium content is measured when heated at 180°C using an infrared heating type moisture meter (for example, A&D Corporation, product name "MX-50").

[0052] <First rubber and second rubber> In one embodiment, the first rubber is an unmodified liquid rubber, and the second rubber is a modified liquid rubber. Throughout this disclosure, liquid rubber means a substance that is fluid at 23°C and forms a rubber elastic body by crosslinking (more specifically, vulcanization) and / or chain extension. That is, liquid rubber is an uncured product in one embodiment. Furthermore, fluidity means that, in one embodiment, 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 dried, so that when the liquid rubber is filled into the vial to a height of 1 mm, sealed, and left standing upside down for 24 hours, a movement of 0.1 mm or more of the substance in the height direction can be observed. Liquid rubber may have the monomer composition of a general rubber, and is preferably relatively low in molecular weight from the viewpoint of ease of handling and good dispersibility of fine cellulose fibers. In one embodiment, liquid rubber exhibits a liquid form by having a number average molecular weight (Mn) of 150,000 or less. In this disclosure, the molecular weight and molecular weight distribution of the rubber component are obtained by measuring chromatograms using gel permeation chromatography with three columns packed with polystyrene gel and calculating the values ​​using a calibration curve with standard polystyrene. Tetrahydrofuran is used as the solvent.

[0053] When a rubber composition is cured to produce a cured rubber product, it is desirable that the liquid rubber be vulcanized during curing to improve the mechanical properties of the cured rubber product. Alternatively, the liquid rubber may be cured by heat or other means.

[0054] The number-average molecular weight of the first rubber is preferably 1,000 or more, or 1,500 or more, or 2,000 or more, from the viewpoint of obtaining good mechanical properties of the rubber composition, rubber composite, or cured rubber product, and preferably 150,000 or less, or 145,000 or less, or 140,000 or less, from the viewpoint of fluidity and obtaining a cured rubber product that is not too hard and has good rubber elasticity.

[0055] The number-average molecular weight of the second rubber is preferably 4,500 or more, or 5,000 or more, or 5,500 or more, from the viewpoint of obtaining good mechanical properties of the rubber composition, rubber composite, or cured rubber product, and preferably 100,000 or less, or 90,000 or less, or 80,000 or less, from the viewpoint of fluidity and obtaining a cured rubber product that is not too hard and has good rubber elasticity.

[0056] The viscosity η1 of the first rubber at 38°C is preferably 100,000 mPa·s or less, or 95,000 mPa·s or less, or 90,000 mPa·s or less, from the viewpoint of fluidity and obtaining a rubber cured product that is not too hard and has good rubber elasticity, and preferably 5,000 mPa·s or more, or 8,000 mPa·s or more, or 10,000 mPa·s or more, from the viewpoint of obtaining good mechanical properties of the rubber composition, rubber composite, or rubber cured product.

[0057] The viscosity η2 of the second rubber at 38°C is preferably 800,000 mPa·s or less, or 700,000 mPa·s or less, or 600,000 mPa·s or less, from the viewpoint of fluidity and obtaining a rubber cured product that is not too hard and has good rubber elasticity, and preferably 100,000 mPa·s or more, or 120,000 mPa·s or more, or 140,000 mPa·s or more, from the viewpoint of obtaining good mechanical properties of the rubber composition, rubber composite, or rubber cured product.

[0058] In this disclosure, viscosity is a value measured using a Type B viscometer.

[0059] At 38°C, the ratio η2 / η1 of the viscosity of the second rubber to the viscosity η1 of the first rubber is preferably 1.2 or higher, or 1.3 or higher, or 1.4 or higher, in terms of allowing the first rubber to easily penetrate between the second rubbers or between the second rubber and the fine cellulose fibers, and preferably 160 or lower, or 140 or lower, or 120 or lower, in terms of obtaining good affinity between the first rubber and the second rubber.

[0060] The liquid rubber may be a conjugated diene polymer, a non-conjugated diene polymer, or a hydrogenated version thereof. The above polymer or its hydrogenated version may be an oligomer.

[0061] [Conjugated diene polymers] 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 another monomer. The copolymer may be random or block-shaped.

[0062] Examples of conjugated diene monomers 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, which may be used individually or in combination of two or more.

[0063] In one embodiment, the conjugated diene polymer is a copolymer of the above-mentioned conjugated diene monomer and an aromatic vinyl monomer. The aromatic vinyl monomer is not particularly limited as long as it is a monomer copolymerizable with a conjugated diene monomer. Examples include styrene, m or p-methylstyrene, α-methylstyrene, ethylstyrene, p-tert-butylstyrene, vinylethylbenzene, vinylxylene, vinylnaphthalene, diphenylethylene, and divinylbenzene, which may be used individually or in combination of two or more. From the viewpoint of moldability of the rubber composition and impact resistance of the molded article, styrene is preferred.

[0064] Examples of random copolymers include butadiene-isoprene random copolymers, butadiene-styrene random copolymers, isoprene-styrene random copolymers, and butadiene-isoprene-styrene random copolymers. Regarding the compositional distribution of each monomer in the copolymer chain, examples include perfectly random copolymers with a composition close to statistically random, and tapered random copolymers with a gradient in the compositional distribution. The bonding mode of the conjugated diene polymer, i.e., the composition of 1,4-bonds, 1,2-bonds, etc., may be uniform or different between molecules.

[0065] A block copolymer may be a copolymer consisting of two or more blocks. For example, a block copolymer may have a structure such as AB, ABA, or ABAB, where block A is an aromatic vinyl monomer and block B is a block of conjugated diene monomer and / or a copolymer of aromatic vinyl monomer and conjugated diene monomer. The boundaries between each block do not necessarily need to be clearly distinguishable; for example, if block B is a copolymer of aromatic vinyl monomer and conjugated diene monomer, the aromatic vinyl monomer in block B may be distributed uniformly or tapered. Furthermore, block B may have multiple portions where the aromatic vinyl monomer is uniformly distributed and / or tapered. In addition, block B may have multiple segments with different aromatic vinyl monomer content. When multiple blocks A and block B exist in the copolymer, their molecular weights and compositions may be the same or different.

[0066] The block copolymer may be a mixture of two or more types in which one or more of the following are different: bond type, molecular weight, aromatic vinyl compound species, conjugated diene compound species, 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.

[0067] The amount of vinyl bonds in the conjugated diene bond units in a conjugated diene polymer (e.g., 1,2- 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 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. The amount of vinyl bonds in a conjugated diene bond unit (e.g., the amount of 1,2-bonds in butadiene) is, 13 This can be determined by 13C-NMR (quantitative mode). That is, 13 In 1C-NMR, integrating the peak areas shown below yields a value proportional to the carbon content of each structural unit, which can then be converted to the mass percentage of each structural unit. Styrene 145-147 ppm Vinyl 110-116 ppm Diene (cis) 24-28 ppm Diene (trans) 29-33 ppm

[0068] In a copolymer of a conjugated diene monomer and an aromatic vinyl monomer, the amount of aromatic vinyl monomer bonded to the conjugated diene monomer (hereinafter also referred to as the aromatic vinyl bond amount) may preferably be 5.0% by mass or more and 70% by mass or 10% by mass or more and 50% by mass or less, relative to the total mass of the conjugated diene polymer. The aromatic vinyl bond amount can be determined by the ultraviolet absorbance of the phenyl group, and the conjugated diene bond amount can also be determined based on this.

[0069] The conjugated diene polymer may be partially hydrogenated or fully hydrogenated. From the viewpoint of suppressing thermal degradation during processing, the hydrogenation rate of the hydrogenated product is preferably 50% or more, 80% or more, or 98% or more, and from the viewpoint of low-temperature toughness, it is preferably 50% or less, 20% or less, or 0% (i.e., unhydrogenated). Examples of hydrogenated products of conjugated diene polymers include the hydrogenated products of conjugated diene polymers exemplified above, and may be hydrogenated products of butadiene homopolymer, isoprene homopolymer, styrene-butadiene copolymer, or acrylonitrile-butadiene copolymer.

[0070] [Non-conjugated diene polymers] The non-conjugated diene polymer may be a homopolymer, or a copolymer of two or more non-conjugated diene monomers, or a copolymer of a non-conjugated diene monomer and another monomer. The copolymer may be random or block. Examples of non-conjugated diene polymers include: Olefin polymers such as ethylene-propylene rubber, ethylene-propylene-diene rubber, ethylene-butene-diene rubber, and ethylene-α-olefin copolymers. Examples include butyl rubber, brominated butyl rubber, acrylic rubber, fluororubber, silicone rubber, chlorinated polyethylene rubber, epichlorohydrin rubber, α,β-unsaturated nitrile-acrylic acid ester-conjugated diene copolymer rubber, urethane rubber, and polysulfide rubber.

[0071] In ethylene-α-olefin copolymers, monomers that can copolymerize with ethylene units include: propylene, butene-1, pentene-1, 4-methylpentene-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-1, isobutylene, and other aliphatic substituted vinyl monomers; styrene, etc. Examples include aromatic vinyl monomers such as styrene-converted; ester-based vinyl monomers such as vinyl acetate, acrylic acid esters, methacrylic acid esters, glycidyl acrylic acid esters, glycidyl methacrylic acid esters, and hydroxyethyl methacrylic acid esters; nitrogen-containing vinyl monomers such as acrylamide, allylamine, vinyl-p-aminobenzene, and acrylonitrile; and dienes such as butadiene, cyclopentadiene, 1,4-hexadiene, and isoprene.

[0072] Preferably, the copolymer is a copolymer of ethylene and one or more α-olefins having 3 to 20 carbon atoms; more preferably, it is a copolymer of ethylene and one or more α-olefins having 3 to 16 carbon atoms; and most preferably, it is a copolymer of ethylene and one or more α-olefins having 3 to 12 carbon atoms. Furthermore, from the viewpoint of exhibiting impact resistance, the number-average 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 even more preferably 20,000 to 60,000. In addition, from the viewpoint 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 more preferably 1.8 to 2.7.

[0073] Furthermore, the preferred ethylene unit content of the ethylene-α-olefin copolymer is 30 to 95% by mass relative to the total amount of the ethylene-α-olefin copolymer, from the viewpoint of ease of handling during processing.

[0074] These preferred ethylene-α-olefin copolymers can be produced by the manufacturing methods described in, for example, Japanese Patent Publication No. 4-12283, Japanese Unexamined Patent Publication No. 60-35006, Japanese Unexamined Patent Publication No. 60-35007, Japanese Unexamined Patent Publication No. 60-35008, Japanese Unexamined Patent Publication No. 5-155930, Japanese Unexamined Patent Publication No. 3-163088, and U.S. Patent No. 5,272,236.

[0075] The liquid rubber is preferably one or more selected from the group consisting of styrene-butadiene rubber, natural rubber, butadiene rubber, farnesene rubber, and isoprene rubber.

[0076] Preferred examples of the unmodified liquid rubber as the first rubber are the polymers exemplified above. On the other hand, the modified liquid rubber as the second rubber may have a structure in which at least one modifying group is introduced to each of the polymers exemplified above. The modifying group may be one or more of the following: epoxy group, acid anhydride group, carboxyl group, aldehyde group, hydroxyl group, alkoxy group, amino group, amide group, imide group, nitro group, isocyanate group, thio group, mercapto group, etc. Preferably, the modifying group is one or more selected from the group consisting of maleic anhydride group and succinic anhydride group, or maleic anhydride group. Examples of modified liquid rubbers include epoxy-modified natural rubber, epoxy-modified butadiene rubber, epoxy-modified styrene-butadiene rubber, epoxy-modified isoprene rubber, carboxy-modified natural rubber, carboxy-modified butadiene rubber, carboxy-modified styrene-butadiene rubber, carboxy-modified isoprene rubber, acid anhydride-modified natural rubber, acid anhydride-modified butadiene rubber, acid anhydride-modified styrene-butadiene rubber, and acid anhydride-modified isoprene rubber.

[0077] The modified liquid rubber may have reactive groups at both ends (for example, one or more selected from the group consisting of hydroxyl groups, carboxyl groups, isocyanate groups, thio groups, amino groups, and halo groups), and therefore may be bifunctional. These reactive groups contribute to crosslinking and / or chain extension of the modified liquid rubber.

[0078] In modified liquid rubber, the amount of modifying groups per 100 mol% of total monomer units is preferably 0.1 mol% or more, or 0.2 mol% or more, or 0.3 mol% or more, in that good affinity between the fine cellulose fibers and the modified liquid rubber results in good dispersibility and orientation of the fine cellulose fibers. On the other hand, if the amount of modifying groups is excessive, the modified liquid rubbers themselves, or the modified liquid rubber and the fine cellulose fibers, tend to form a dense structure, which tends to reduce the dispersibility and orientation of the fine cellulose fibers. In order to impart the desired mechanical properties and surface smoothness to the cured rubber, it is desirable to suppress the formation of such a dense structure. From the above viewpoint, the amount of modifying groups per 100 mol% of total monomer units is preferably 5 mol% or less, or 3 mol% or less. The above amount of modifying groups can be confirmed by infrared absorption spectroscopy, solid-state NMR (nuclear magnetic resonance), solution NMR, or by calculating the molar ratio of modifying groups by combining a predetermined monomer composition with quantitative analysis of elements not contained in the unmodified rubber.

[0079] The modifying group content of the modified liquid rubber is preferably 0.5% by mass or more, or 0.8% by mass or more, or 1.0% by mass or more, in terms of good affinity between the fine cellulose fibers and the modified liquid rubber, resulting in good dispersibility and orientation of the fine cellulose fibers. From the viewpoint of suppressing the formation of the dense structure described above, it is preferably 20% by mass or less, or 15% by mass or less, or 10% by mass or less. This modifying group content can be confirmed by NMR in one embodiment.

[0080] The means for producing the modified liquid rubber are not particularly limited, but for example, the method described in Japanese Patent Application Publication No. 2016-172859 can be used.

[0081] In one embodiment, the modifying groups of the modified liquid rubber may form covalent bonds with fine cellulose fibers and / or rubber during the production of a rubber composition, rubber composite, or rubber cured product, particularly during heating and mixing. The covalent bonds may be advantageous in that they further enhance the reinforcing effect of the fine cellulose fibers. In one embodiment, covalent bonds may be formed between the modified liquid rubber and fine cellulose fibers during the production of a rubber composition or rubber composite, and covalent bonds may be formed between the modified liquid rubber and a third and / or fourth rubber, either directly or via other components (in one embodiment, a vulcanizing agent), during the production of the rubber cured product (i.e., during curing).

[0082] From the viewpoint of improving the mechanical properties of the cured rubber, the first and / or second rubber may be covalently bonded to the rubber (specifically the third and / or fourth rubber) via a vulcanizing agent during the curing of the rubber composition.

[0083] In one embodiment, the modifying groups of the modified liquid rubber may form chemical bonds (ionic bonds, hydrogen bonds, covalent bonds, etc.), more preferably covalent bonds, with fine cellulose fibers and / or rubber during the production of the rubber composition, rubber composite, or rubber cured product, particularly during heating and mixing. In particular, covalent bonds may be advantageous in that they further enhance the reinforcing effect of the fine cellulose fibers. In one embodiment, chemical bonds may be formed between the modified liquid rubber and the fine cellulose fibers during the production of the rubber composition or rubber composite, and chemical bonds may be formed between the modified liquid rubber and the third and / or fourth rubber directly or via other components (in one embodiment, a vulcanizing agent) during the production of the rubber cured product (i.e., during curing).

[0084] From the viewpoint of improving the mechanical properties of the cured rubber, the first and / or second rubber may be chemically bonded to the rubber (specifically the third and / or fourth rubber) via a vulcanizing agent during the curing of the rubber composition.

[0085] In one embodiment, the presence of chemical bonds can be expressed as the degree of chemical bonding in the following manner. In one embodiment, the degree of chemical bonding is expressed for the residue obtained by removing a rubber composition or rubber composite with a solvent (e.g., hexane, cyclohexane, THF, etc.). 13The residue is analyzed using 1C solid-state NMR, and the ratio of non-cellulose components to cellulose components in the above-mentioned residue is defined as the degree of chemical bonding. Chemical bonding degree = Amount of non-cellulose components in the residue / Amount of cellulose component in the residue

[0086] The degree of chemical bonding is measured specifically as follows: 1 g of rubber composition or rubber composite and 50 ml of THF are placed in a vial and homogenized (IKA product, trade name "Ultra-Turrax T18", processing conditions: rotation speed 15,000 rpm x 3 minutes), then stirred with a magnetic stirrer (200 rpm, 24 hr). After that, the mixture is filtered through a nylon mesh, and the residue on the mesh is washed twice with 20 ml or more of THF, then vacuum dried (80°C, 12 hr) to obtain a dry, fine cellulose fiber residue.

[0087] Next, the dried fine cellulose fiber residue 13 Solid-state NMR measurements are performed, and the degree of chemical bonding is calculated using the following formula, based on the peak area in the 100-110 ppm range (P1), the total peak area in the 58-100 ppm range (P2), and the total peak areas in the 110-220 ppm and 0-58 ppm ranges (P3). Chemical bonding degree ={(P2-P1×5)+P3} / (P1×6) [ 13 C solid-state NMR measurement conditions] (1) Sample tube: 7mm diameter, made of zirconia. (2) Magnetic field strength: 11.75T (3) Observation nucleus: 13 C (4) Observation frequency: 125.8MHz (5) Temperature: room temperature (6) MAS rotation speed: 7kHz (7) Pulse sequence: DD / MAS method (8) Pulse width: 5.6 microseconds (9) Import time: 0.047 seconds (10) Waiting time: 1000 seconds (11) Total number of times: 150 (12) Measuring device: Avance500 (manufactured by Bruker Japan Co., Ltd.) (13) Chemical shift standard: Adamantane (external standard 29.5 ppm)

[0088] The peaks in the 58-110 ppm range are mainly derived from six carbon atoms of cellulose, and the peak in the 100-110 ppm range is attributed to the cellulose C1 carbon. Therefore, the total peak area of ​​the six carbon atoms derived from cellulose is six times the peak area of ​​the 100-110 ppm range (P1) (P1 × 6). On the other hand, in the 58-100 ppm range, peaks from various compounds frequently appear and overlap, so the peak area derived from the five carbon atoms of cellulose in the 58-100 ppm range is taken as five times the peak area of ​​the 100-110 ppm range (P1 × 5), and the difference from the total peak area of ​​the 58-100 ppm range (P2) is taken as the peak area derived from carbon atoms other than cellulose. Furthermore, since the peaks in the 110 ppm-220 ppm and 0 ppm-58 ppm ranges are all derived from carbon atoms other than cellulose, the sum of the total peak area in this range (P3) and the difference peak area mentioned above is taken as the peak area derived from all carbon atoms other than cellulose ((P2 - P1 × 5) + P3). Based on the above, the ratio of the peak area derived from all carbon atoms other than cellulose to the peak area of ​​the six carbon atoms derived from cellulose is considered to be the ratio of the amount of non-cellulose components to the amount of cellulose components in the residue, and is defined as the degree of chemical bonding.

[0089] The degree of chemical bonding is preferably 0.01 or higher, or 0.03 or higher, or 0.05 or higher, or 0.1 or higher, or 0.15 or higher, from the viewpoint of improving the reinforcing properties of cellulose nanofibers through chemical bonding. On the other hand, when a rubber cured product is made using a rubber composition and / or rubber composite, the degree of chemical bonding is preferably 4.0 or lower, or 3.6 or lower, or 3.3 or lower, or 3.0 or lower, or 2.5 or lower, from the viewpoint of excellent dispersibility of cellulose nanofibers in the cured rubber product. If the degree of chemical bonding exceeds 4.0, it is presumed that excessive crosslinking occurs between the modified liquid rubbers that bond to the cellulose nanofibers, and the cellulose nanofibers tend to become difficult to disperse in the rubber matrix during kneading, etc.

[0090] In one embodiment, the cured rubber is analyzed by electron microscopy or atomic force microscopy (AFM). The presence of rubber bonded to cellulose nanofibers is confirmed in one embodiment as a phase present near the cellulose nanofibers (in one embodiment, as a region of material different from the third and / or fourth rubber in the cured rubber), by analysis using NMR, infrared absorption spectroscopy, or Nano-IR.

[0091] In one embodiment, the presence of covalent bonds can be confirmed by the following method: In rubber compositions or rubber composites, the presence of covalent bonds can be confirmed by nano-IR analysis of the residue obtained by removing the rubber with a solvent (e.g., hexane or cyclohexane).

[0092] The first rubber preferably contains aromatic vinyl monomer units, as it has good affinity with fine cellulose fibers, resulting in good dispersibility and orientation of the fine cellulose fibers.

[0093] The second rubber is preferably maleic anhydride-modified liquid polyisoprene, from the viewpoint of miscibility with the third rubber and / or the fourth rubber, and affinity with fine cellulose fibers.

[0094] In the rubber composition, the amount of the first rubber relative to 100 parts by mass of the second rubber is preferably 5 parts by mass or more, or 10 parts by mass or more, or 15 parts by mass or more, from the viewpoint of obtaining the advantages of the first rubber well, and preferably 500 parts by mass or less, or 300 parts by mass or less, or 280 parts by mass or less, or 260 parts by mass or less, from the viewpoint of not hindering the advantages of the second rubber.

[0095] In the rubber composition, the amount of the first rubber per 100 parts by mass of fine cellulose fibers is preferably 1 part by mass or more, or 5 parts by mass or more, or 10 parts by mass or more, or 15 parts by mass or more, from the viewpoint of obtaining the advantages of the first rubber well, and preferably 300 parts by mass or less, or 200 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, from the viewpoint of maintaining the mechanical properties of the molded article well.

[0096] In the rubber composition, the amount of the second rubber per 100 parts by mass of fine cellulose fibers is preferably 1 part by mass or more, or 5 parts by mass or more, or 10 parts by mass or more, or 15 parts by mass or more, or 20 parts by mass or more, from the viewpoint of obtaining the advantages of the second rubber well, and preferably 300 parts by mass or less, or 200 parts by mass or less, or 100 parts by mass or less, from the viewpoint of suppressing excessive bonding or interaction between the second rubbers themselves or between the second rubbers and the fine cellulose fibers.

[0097] In the rubber composition, the content of the second rubber is preferably 1% by mass or more, or 5% by mass or more, or 7% by mass or more, or 10% by mass or more, from the viewpoint of obtaining the advantages of the second rubber well, and preferably 60% by mass or less, or 55% by mass or less, or 50% by mass or less, from the viewpoint of suppressing excessive bonding or interaction between the second rubbers themselves or between the second rubbers and fine cellulose fibers.

[0098] In the rubber composition, the total content of the first and second rubbers is 1% by mass or more, or 10% by mass or more, or 15% by mass or more, or 20% by mass or more, from the viewpoint of improving the dispersibility and orientation of the fine cellulose fibers, and preferably 90% by mass or less, or 85% by mass or less, or 80% by mass or less, or 70% by mass or less, from the viewpoint of obtaining a good reinforcing effect by having a desired amount of fine cellulose fibers present.

[0099] <Dispersant> In one embodiment, the rubber composition includes a dispersant. In one embodiment, it is even more preferable, from the viewpoint of more uniformly dispersing fine cellulose fibers in the rubber composition, that the dispersant has a hydrophilic segment and a hydrophobic segment within the same molecule (i.e., is an amphiphilic molecule).

[0100] [Amphiphilic molecules] In amphiphilic molecules, the hydrophilic segment is the part that exhibits good affinity with fine cellulose fibers by containing a hydrophilic structure. Specifically, hydrophilic structures include hydroxyl groups, thiol groups, carboxyl groups, sulfonic acid groups, sulfate ester groups, phosphate groups, boronic acid groups, silanol groups, groups derived from sugars such as sorbitan and sucrose, groups derived from glycerin, groups represented by -OM, -COOM, -SO3M, -OSO3M, -HMPO4, and -M2PO4 (where M represents an alkali metal or alkaline earth metal), and primary to tertiary amines and quaternary ammonium salts. The counteranions of the above quaternary ammonium salts include one or more hydrophilic groups selected from the group consisting of halogen ions such as hydroxide ions, fluoride ions, chloride ions, bromide ions, and iodide ions, as well as nitrate ions, formate ions, acetate ions, trifluoroacetate ions, p-toluenesulfonate ions, hexafluorophosphate, and tetrafluoroborate.

[0101] Examples of hydrophilic segments include polyethylene glycol segments, segments containing repeating units with quaternary ammonium salt structures, polyvinyl alcohol segments, polyvinylpyrrolidone segments, polyacrylic acid segments, carboxyvinyl polymer segments, cationized guar gum segments, hydroxyethylcellulose segments, methylcellulose segments, carboxymethylcellulose segments, and polyurethane soft segments (specifically diol segments). Nonionic polyoxyethylene derivatives are particularly preferred, and the polyoxyethylene chain length of the polyoxyethylene derivative may be 3 or more, or 5 or more, or 10 or more, or 15 or more. While longer chain lengths increase affinity with fine cellulose fibers, the polyoxyethylene chain length may be 60 or less, or 50 or less, or 40 or less, or 30 or less, or 20 or less, from the viewpoint of balancing with the desired properties (e.g., mechanical properties) of the resin molded article.

[0102] Examples of hydrophobic segments include segments containing hydrocarbons, segments containing fluorinated carbon, segments containing alkylene oxide units with 3 or more carbon atoms (e.g., PPG blocks), and segments containing polymer structures. Preferred hydrocarbon segments include alkyl type, alkenyl type, alkyl ether type, alkenyl ether type, alkylphenyl ether type, alkenylphenyl ether type, rosin ester type, bisphenol A type, β-naphthyl type, styrene-phenyl type, and hydrogenated castor oil type. The number of carbon atoms in the alkyl chain or alkenyl chain of the hydrophobic group (in the case of alkylphenyl or alkenylphenyl, the number of carbon atoms excluding the phenyl group) is preferably 2 or more, or 5 or more, or 10 or more, or 12 or more, or 16 or more. As for the segment having fluorinated carbon, linear or branched alkyl types with 1 to 20 carbon atoms are preferred. Preferred polymer structures include acrylic polymers, styrene resins, vinyl chloride resins, vinylidene chloride resins, polyolefin resins, amino acid lactams including ring-opening polymers of lactams, polymers composed of diamines and dicarboxylic acids, polyacetal resins, polycarbonate resins, polyester resins, polyphenylene sulfide resins, polysulfone resins, polyetherketone resins, polyimide resins, fluorine resins, hydrophobic silicone resins, melamine resins, epoxy resins, phenolic resins, and the like. These hydrophobic segments may have either a linear or branched structure. Furthermore, the hydrophobic segments may have a single-chain structure or a structure of two or more chains, and if they have a structure of two or more chains, they may have multiple types of hydrophobic groups.

[0103] The structure of amphiphilic molecules is not particularly limited, but when the hydrophilic segment is A and the hydrophobic segment is B, examples include linear copolymers such as AB-type block copolymers, ABA-type block copolymers, and BAB-type block copolymers; tribranched copolymers containing A and B; tetrabranched copolymers containing A and B; star-shaped copolymers containing A and B; monocyclic copolymers containing A and B; polycyclic copolymers containing A and B; cage copolymers containing A and B; and graft copolymers containing A and B. When multiple hydrophilic segments are present in a molecule, their molecular structure may be a single type or a combination of two or more types. Similarly, when multiple hydrophobic segments are present in a molecule, their molecular structure may be a single type or a combination of two or more types.

[0104] [Surfactants] Any of the following can be used as the amphiphilic molecule: anionic surfactants, nonionic surfactants, cationic surfactants, and amphoteric surfactants. The dispersant may be a polymeric surfactant, a reactive surfactant, or the like.

[0105] Examples of nonionic surfactants include fatty acid dialkanolamides (e.g., lauric acid diethanolamide), polyoxyalkylene fatty acid amides (e.g., polyoxyethylene stearic acid amide), polyoxyalkylene aryl ethers (e.g., polyoxyethylene phenyl ether), polyoxyalkylene alkylaryl ethers (e.g., polyoxyethylene octylphenyl ether), polyoxyalkylene alkyl or alkenyl ethers (e.g., polyoxyethylene lauryl ether, polyoxyethylene stearyl ether), fatty acid esters of polyhydric alcohols (e.g., polyethylene glycol mono or distearate ester, polyethylene glycol mono or dilaurate ester, polyoxyethylene hydrogenated castor oil), glycerin fatty acid esters (e.g., glyceryl monostearate, glyceryl monooleate), sorbitan fatty acid esters (e.g., sorbitan monolaurate, sorbitan monostearate), and polyoxyethylene-polyoxypropylene block polymers.

[0106] Anionic surfactants (emulsifiers) may be carboxylates, sulfonates, sulfate esters, phosphate esters, etc. Examples of carboxylates include aliphatic monocarboxylic acids and alkyl ether carboxylates; examples of sulfonates include dialkyl sulfosuccinates, alkanesulfonates, alkylbenzenesulfonates, and alkylnaphthalenesulfonates; examples of sulfate esters include alkyl sulfates and oil sulfates; and examples of phosphate esters include alkyl phosphates and polyoxyethylene alkyl ether phosphates.

[0107] Cationic surfactants include amine salts, amidoamine salts, quaternary ammonium salts, and imidazolinium salts. Specific examples, though not particularly limited, include alkylamine salts, polyoxyethylene alkylamine salts, alkylamidoamine salts, amino alcohol fatty acid derivatives, polyamine fatty acid derivatives, amine salt-type surfactants such as imidazoline, alkyltrimethylammonium salts, dialkyldimethylammonium salts, alkyldimethylbenzylammonium salts, alkylpyridinium salts, alkylisoquinolinium salts, and quaternary ammonium salt-type surfactants such as benzethonium chloride.

[0108] Examples of amphoteric surfactants include alkylamine oxides, alanines, imidazolinium betaines, amide betaines, and acetate betaine. Specifically, examples include long-chain amine oxides, lauryl betaine, stearyl betaine, laurylcarboxymethylhydroxyethylimidazolinium betaine, lauryldimethylaminoacetic acid betaine, and fatty acid amidopropyldimethylaminoacetic acid betaine.

[0109] [Hydrophilic polymer] In one embodiment, the dispersant is preferably a hydrophilic polymer. In one embodiment, the hydrophilic polymer is a polymer having a hydrophilic group selected from the group consisting of hydroxyl groups, carboxyl groups, amino groups, ammonium groups, sulfonic acid groups, phosphate groups, etc. As the hydrophilic polymer, one or more can be selected from the group consisting of cellulose derivatives (hydroxyethylcellulose, methylcellulose, carboxymethylcellulose, etc.), polyalkylene glycol, polyvinyl alcohol, polyvinylpyrrolidone, polyacrylic acid, carboxyvinyl polymer, cationized guar gum, water-soluble polyurethane, polymers containing quaternary ammonium salt structures, amides, amines, etc. Among these, cellulose derivatives and polyalkylene glycols are more preferred, and polyalkylene glycols are particularly preferred.

[0110] The amount of dispersant in the rubber composition is preferably 1 part by mass or more, or 3 parts by mass or more, or 5 parts by mass or more, or 10 parts by mass or more, per 100 parts by mass of fine cellulose fibers, and preferably 200 parts by mass or less, or 100 parts by mass or less, or 80 parts by mass or less, or 60 parts by mass or less, or 50 parts by mass or less.

[0111] The content of the dispersant in the rubber composition components may, in one embodiment, be 0.1% by mass or more, or 0.5% by mass or more, or 1% by mass or more, or 3% by mass or more, and in one embodiment, it may be 50% by mass or less, or 40% by mass or less, or 30% by mass or less.

[0112] In one embodiment, the weight ratio of dispersant to the second rubber in the rubber composition components may be preferably 2.0 or less, or 1.0 or less, or 0.8 or less, or 0.75 or less, or 0.7 or less, in order to form a chemical bond between the fine cellulose fibers and the second rubber. On the other hand, from the viewpoint of the dispersibility of the fine cellulose fibers, the presence of a certain amount or more of dispersant is desirable, and the above weight ratio may preferably be 0.01 or more, or 0.03 or more, or 0.05 or more. Furthermore, the dispersant contains hydrophilic functional groups such as hydroxyl groups, or new hydroxyl groups may be formed by molecular cleavage during kneading. Since these hydroxyl groups may react with and be consumed by the maleic anhydride groups of the second rubber, potentially reducing the degree of chemical bonding between the second rubber and the fine cellulose fibers, the above range is preferred.

[0113] <The third type of rubber> In one embodiment, the rubber composition further comprises a third rubber. The third rubber may be one or more selected from the group consisting of natural rubber, conjugated diene polymers or non-conjugated diene polymers, or hydrogenated versions thereof. The above polymers or hydrogenated versions thereof may be modified rubbers or oligomers. Thermoplastic elastomers can also be exemplified as the third rubber. In one embodiment, the third rubber is a rubber other than the first and second rubbers of this embodiment, more specifically a rubber that does not have fluidity at 23°C (in other words, a solid rubber). The first and / or second rubbers and the third rubber may differ from each other (be heterogeneous) in one or more of the constituent monomer component species, constituent monomer component ratios, and molecular weight.

[0114] [Natural rubber] While not particularly limited to natural rubber, examples include: RSS (Ribbed Smoked Sheet) No. 3-5, which are smoke-dried types with a high molecular weight component and excellent fracture strength; TSR (Technically Specified Rubber) types such as SIR (Standard Indonesian Rubber) (from Indonesia), STR (Standard Thai Rubber) (from Thailand), SMR (Standard Malaysian Rubber) (from Malaysia), etc., which are mechanically dried; and epoxidized natural rubber.

[0115] [Conjugated diene polymers] 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 another monomer. The copolymer may be random or block-shaped.

[0116] Examples of conjugated diene monomers 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, which may be used individually or in combination of two or more.

[0117] In one embodiment, the conjugated diene polymer is a copolymer of the above-mentioned conjugated diene monomer and an aromatic vinyl monomer. The aromatic vinyl monomer is not particularly limited as long as it is a monomer copolymerizable with a conjugated diene monomer. Examples include styrene, m or p-methylstyrene, α-methylstyrene, ethylstyrene, p-tert-butylstyrene, vinylethylbenzene, vinylxylene, vinylnaphthalene, diphenylethylene, and divinylbenzene, which may be used individually or in combination of two or more. From the viewpoint of moldability of the rubber composite and impact resistance of the molded article, styrene is preferred.

[0118] Examples of random copolymers include butadiene-isoprene random copolymers, butadiene-styrene random copolymers, isoprene-styrene random copolymers, and butadiene-isoprene-styrene random copolymers. Regarding the compositional distribution of each monomer in the copolymer chain, examples include perfectly random copolymers with a composition close to statistically random, and tapered random copolymers with a gradient in the compositional distribution. The bonding mode of the conjugated diene polymer, i.e., the composition of 1,4-bonds, 1,2-bonds, etc., may be uniform or different between molecules.

[0119] A block copolymer may be a copolymer consisting of two or more blocks. For example, a block copolymer may have a structure such as AB, ABA, or ABAB, where block A is an aromatic vinyl monomer and block B is a block of conjugated diene monomer and / or a copolymer of aromatic vinyl monomer and conjugated diene monomer. The boundaries between each block do not necessarily need to be clearly distinguishable; for example, if block B is a copolymer of aromatic vinyl monomer and conjugated diene monomer, the aromatic vinyl monomer in block B may be distributed uniformly or tapered. Furthermore, block B may have multiple portions where the aromatic vinyl monomer is uniformly distributed and / or tapered. In addition, block B may have multiple segments with different aromatic vinyl monomer content. When multiple blocks A and block B exist in the copolymer, their molecular weights and compositions may be the same or different.

[0120] The block copolymer may be a mixture of two or more types in which one or more of the following are different: bond type, molecular weight, aromatic vinyl compound species, conjugated diene compound species, 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.

[0121] The amount of vinyl bonds in the conjugated diene bond units in a conjugated diene polymer (e.g., 1,2- 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 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. The amount of vinyl bonds in a conjugated diene bond unit (e.g., the amount of 1,2-bonds in butadiene) is, 13 This can be determined by 13C-NMR (quantitative mode). That is, 13 In 1C-NMR, integrating the peak areas shown below yields a value proportional to the carbon content of each structural unit, which can then be converted to the mass percentage of each structural unit. Styrene 145-147 ppm Vinyl 110-116 ppm Diene (cis) 24-28 ppm Diene (trans) 29-33 ppm

[0122] In a copolymer of a conjugated diene monomer and an aromatic vinyl monomer, the amount of aromatic vinyl monomer bonded to the conjugated diene monomer (hereinafter also referred to as the aromatic vinyl bond amount) may preferably be 5.0% by mass or more and 70% by mass or 10% by mass or more and 50% by mass or less, relative to the total mass of the conjugated diene polymer. The aromatic vinyl bond amount can be determined by the ultraviolet absorbance of the phenyl group, and the conjugated diene bond amount can also be determined based on this.

[0123] The conjugated diene polymer may be partially hydrogenated or fully hydrogenated. From the viewpoint of suppressing thermal degradation during processing, the hydrogenation rate of the hydrogenated product is preferably 50% or more, 80% or more, or 98% or more, and from the viewpoint of low-temperature toughness, it is preferably 50% or less, 20% or less, or 0% (i.e., unhydrogenated). Examples of hydrogenated products of conjugated diene polymers include the hydrogenated products of conjugated diene polymers exemplified above, and may be hydrogenated products of butadiene homopolymer, isoprene homopolymer, styrene-butadiene copolymer, or acrylonitrile-butadiene copolymer.

[0124] [Non-conjugated diene polymers] The non-conjugated diene polymer may be a homopolymer, or a copolymer of two or more non-conjugated diene monomers, or a copolymer of a non-conjugated diene monomer and another monomer. The copolymer may be random or block. Examples of non-conjugated diene polymers include: Examples include ethylene-propylene rubber, ethylene-propylene-diene rubber, ethylene-butene-diene rubber, olefin polymers such as ethylene-α-olefin copolymers, butyl rubber, brominated butyl rubber, acrylic rubber, fluororubber, silicone rubber, chlorinated polyethylene rubber, epichlorohydrin rubber, α,β-unsaturated nitrile-acrylic acid ester-conjugated diene copolymer rubber, urethane rubber, and polysulfide rubber.

[0125] In ethylene-α-olefin copolymers, monomers that can copolymerize with ethylene units include: propylene, butene-1, pentene-1, 4-methylpentene-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-1, isobutylene, and other aliphatic substituted vinyl monomers; styrene, etc. Examples include aromatic vinyl monomers such as styrene-converted; ester-based vinyl monomers such as vinyl acetate, acrylic acid esters, methacrylic acid esters, glycidyl acrylic acid esters, glycidyl methacrylic acid esters, and hydroxyethyl methacrylic acid esters; nitrogen-containing vinyl monomers such as acrylamide, allylamine, vinyl-p-aminobenzene, and acrylonitrile; and dienes such as butadiene, cyclopentadiene, 1,4-hexadiene, and isoprene.

[0126] Preferably, the copolymer is a copolymer of ethylene and one or more α-olefins having 3 to 20 carbon atoms; more preferably, it is a copolymer of ethylene and one or more α-olefins having 3 to 16 carbon atoms; and most preferably, it is a copolymer of ethylene and one or more α-olefins having 3 to 12 carbon atoms. Furthermore, from the viewpoint of exhibiting impact resistance, the number-average 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 even more preferably 20,000 to 60,000. In addition, from the viewpoint 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 more preferably 1.8 to 2.7.

[0127] Furthermore, the preferred ethylene unit content of the ethylene-α-olefin copolymer is 30 to 95% by mass relative to the total amount of the ethylene-α-olefin copolymer, from the viewpoint of ease of handling during processing.

[0128] These preferred ethylene-α-olefin copolymers can be produced by the manufacturing methods described in, for example, Japanese Patent Publication No. 4-12283, Japanese Unexamined Patent Publication No. 60-35006, Japanese Unexamined Patent Publication No. 60-35007, Japanese Unexamined Patent Publication No. 60-35008, Japanese Unexamined Patent Publication No. 5-155930, Japanese Unexamined Patent Publication No. 3-163088, and U.S. Patent No. 5,272,236.

[0129] [Modified rubber] The third rubber may be a modified rubber, for example, in the conjugated diene polymer or non-conjugated diene polymer exemplified above, modifying groups such as epoxy groups, acid anhydride groups, carboxyl groups, aldehyde groups, hydroxyl groups, alkoxy groups, amino groups, amide groups, imide groups, nitro groups, isocyanate groups, and mercapto groups may be introduced. Examples of modified rubbers include epoxy-modified natural rubber, epoxy-modified butadiene rubber, epoxy-modified styrene-butadiene rubber, carboxy-modified natural rubber, carboxy-modified butadiene rubber, carboxy-modified styrene-butadiene rubber, acid anhydride-modified natural rubber, acid anhydride-modified butadiene rubber, and acid anhydride-modified styrene-butadiene rubber.

[0130] The amount of modifying groups relative to 100 mol% of total monomer units is preferably 0.1 mol% or more, or 0.2 mol% or more, or 0.3 mol% or more, and more preferably 5 mol% or less, or 3 mol% or less, from the viewpoint of affinity with fine cellulose fibers. The above amount of modifying groups can be confirmed by a method that calculates the molar ratio of modifying groups by combining infrared absorption spectroscopy, solid-state NMR (nuclear magnetic resonance), solution NMR, or quantitative determination by elemental analysis of elements not contained in the unmodified rubber with a predetermined monomer composition.

[0131] [Thermoplastic elastomer] In one embodiment, the third rubber may include or be a thermoplastic elastomer. In this disclosure, elastomer means, in one embodiment, a substance (specifically, a natural or synthetic polymer) that is elastic at room temperature (23°C). In one embodiment, being elastic means that the storage modulus of elasticity measured by dynamic viscoelasticity measurement at 23°C and 10 Hz is between 1 MPa and 100 MPa. The thermoplastic elastomer may be a conjugated diene polymer or a non-conjugated diene polymer, and in one embodiment is a crosslinked product. The preferred monomer composition of the thermoplastic elastomer may be the same as those described above in the sections on [conjugated diene polymers] and [non-conjugated diene polymers].

[0132] The number-average molecular weight (Mn) of the thermoplastic elastomer is preferably 10,000 to 500,000, or 40,000 to 250,000, from the viewpoint of achieving both impact strength and fluidity.

[0133] Thermoplastic elastomers may have a core-shell structure. Examples of elastomers having a core-shell structure include core-shell type elastomers having a core which is particulate rubber and a shell which is a glassy graft layer formed on the outside of the core. Suitable core materials include butadiene rubber, acrylic rubber, and silicone-acrylic composite rubber. Suitable shell materials include glassy polymers such as styrene resin, acrylonitrile-styrene copolymer, and acrylic resin.

[0134] From the viewpoint of excellent compatibility with the first and / or second rubber, the thermoplastic elastomer is preferably at least one selected from the group consisting of styrene-butadiene block copolymer, styrene-ethylene-butadiene block copolymer, styrene-ethylene-butylene block copolymer, styrene-butadiene-butylene block copolymer, styrene-isoprene block copolymer, styrene-ethylene-propylene block copolymer, styrene-isobutylene block copolymer, hydrogenated styrene-butadiene block copolymer, hydrogenated styrene-ethylene-butadiene block copolymer, hydrogenated styrene-butadiene-butylene block copolymer, hydrogenated styrene-isoprene block copolymer, and a homopolymer of styrene (polystyrene), and more preferably one or more selected from the group consisting of styrene-butadiene block copolymer, hydrogenated styrene-butadiene block copolymer, and polystyrene.

[0135] In one embodiment, at least a portion of the thermoplastic elastomer may have an acidic functional group. In this disclosure, "a thermoplastic elastomer having an acidic functional group" means that the acidic functional group is added to the molecular backbone of the elastomer via a chemical bond. In this disclosure, an acidic functional group means a functional group that can react with basic functional groups, etc. Specific examples include hydroxyl groups, carboxyl groups, carboxylate groups, sulfo groups, acid anhydride groups, and the like.

[0136] The amount of acidic functional groups added to the elastomer is preferably 0.01% by mass or more, more preferably 0.1% by mass or more, even more preferably 0.2% by mass or more, preferably 5% by mass or less, more preferably 3% by mass or less, even more preferably 2% by mass or less, and even more preferably less than 1.5% by mass, based on 100% by mass of the elastomer, from the viewpoint of affinity with modified liquid rubber, etc. The number of acidic functional groups is obtained by measuring a calibration curve prepared by measuring a calibration sample mixed with an acidic substance using an infrared absorption spectrum analyzer, and then measuring the sample based on the calibration curve created using the characteristic absorption band of the acid.

[0137] Examples of elastomers having acidic functional groups include elastomers having a core-shell structure with a layer formed using acrylic acid or the like as a copolymer component as a shell, and modified elastomers obtained by grafting α,β-unsaturated dicarboxylic acids or their derivatives onto ethylene-α-olefin copolymers, polyolefins, aromatic compound-conjugated diene copolymers, or hydrogenated aromatic compound-conjugated diene copolymers containing acrylic acid or the like as monomers, in the presence or absence of peroxides.

[0138] In a preferred embodiment, the elastomer is an acid anhydride-modified elastomer.

[0139] Among these, modified products obtained by grafting α,β-unsaturated dicarboxylic acids or their derivatives onto polyolefins, aromatic compound-conjugated diene copolymers, or hydrogenated aromatic compound-conjugated diene copolymers in the presence or absence of peroxides are more preferred, and among these, modified products obtained by grafting α,β-unsaturated dicarboxylic acids and their derivatives onto ethylene-α-olefin copolymers or hydrogenated aromatic compound-conjugated diene block copolymers in the presence or absence of peroxides are particularly preferred.

[0140] Specific examples of α,β-unsaturated dicarboxylic acids and their derivatives include maleic acid, fumaric acid, maleic anhydride, and fumaric anhydride, with maleic anhydride being particularly preferred among these.

[0141] In one embodiment, the elastomer may be a mixture of an elastomer having acidic functional groups and an elastomer not having acidic functional groups. The mixing ratio of the elastomer having acidic functional groups and the elastomer not having acidic functional groups is preferably 10% by mass or more, more preferably 20% by mass or more, even more preferably 30% by mass or more, and most preferably 40% by mass or more, when the total of both is 100% by mass, from the viewpoint of maintaining high toughness and physical stability of the cured rubber product. There is no particular upper limit, and substantially all elastomers may be elastomers having acidic functional groups, but from the viewpoint of not causing problems with fluidity, 80% by mass or less is desirable.

[0142] The third rubber is preferably one or more selected from the group consisting of styrene-butadiene rubber, natural rubber, and isoprene rubber, and more preferably natural rubber, from the viewpoint of providing a rubber cured product with excellent mechanical strength.

[0143] In the rubber composition components, the mass ratio of the total amount of fine cellulose fibers and the first and second rubbers to the third rubber [(total amount of fine cellulose fibers and the first and second rubbers) / third rubber] may, in one embodiment, 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.

[0144] For example, when a preliminary composition containing fine cellulose fibers and first and second rubbers is used in the manufacture of a rubber composition, the mass ratio of the preliminary composition to the third rubber (preliminary composition / third rubber) in the rubber composition components may, in one embodiment, 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.

[0145] The content of the third rubber in the rubber composition components is preferably 10% by mass or more, or 20% by mass or more, and preferably 90% by mass or less, or 85% by mass or less, or 80% by mass or less.

[0146] The total content of the first, second, and third rubbers in the rubber composition is preferably 40% by mass or more, or 45% by mass or more, or 50% by mass or more, and preferably 99% by mass or less, or 95% by mass or less, or 90% by mass or less.

[0147] In the rubber composition components, the total content of the first and second rubbers relative to 100 parts by mass of the total of the first, second, and third rubbers is preferably 5 parts by mass or more, or 10 parts by mass or more, or 15 parts by mass or more, and preferably 70 parts by mass or less, or 65 parts by mass or less, or 60 parts by mass or less.

[0148] The amount of fine cellulose fibers in the rubber composition components is preferably 1 part by mass or more, or 2 parts by mass or more, or 3 parts by mass or more, and preferably 70 parts by mass or less, or 65 parts by mass or less, or 60 parts by mass or less, based on 100 parts by mass of the total of the first, second, and third rubbers.

[0149] The mass ratio of [fine cellulose fibers] / [total of the first, second, and third rubbers] in the rubber composition components is preferably 1 / 99 to 60 / 40, or 2 / 98 to 50 / 50, or 3 / 97 to 40 / 60.

[0150] [Sulfurizing agents, sulfurization accelerators] When the rubber composition components include uncured rubber, the rubber composition components typically include a vulcanizing agent and may optionally include a vulcanization accelerator. Conventionally known vulcanizing agents and vulcanization accelerators may be appropriately selected depending on the type of uncured rubber in the rubber composition components. Examples of vulcanizing agents include organic peroxides, azo compounds, oxime compounds, nitroso compounds, polyamine compounds, sulfur, and sulfur compounds. Examples of sulfur compounds include sulfur monochloride, sulfur dichloride, disulfide compounds, and high-molecular-weight polysulfur compounds.

[0151] The amount of vulcanizing agent in the rubber composition is preferably 0.01 to 20 parts by mass, or 0.1 to 15 parts by mass, per 100 parts by mass of uncured rubber in the rubber composition.

[0152] Examples of vulcanization accelerators include sulfenamide-based, guanidine-based, thiuram-based, aldehyde-amine-based, aldehyde-ammonia-based, thiazole-based, thiourea-based, and dithiocarbamate-based vulcanization accelerators. Zinc oxide, stearic acid, etc., may also be used as vulcanization aids. The amount of vulcanization accelerator is preferably 0.01 to 20 parts by mass, or 0.1 to 15 parts by mass, per 100 parts by mass of uncured rubber in the rubber composition.

[0153] [Rubber additive] The rubber composition components may include various conventionally known rubber additives (stabilizers, softeners, antioxidants, etc.). As rubber stabilizers, one or more antioxidants such as 2,6-di-tert-butyl-4-hydroxytoluene (BHT), n-octadecyl-3-(4'-hydroxy-3',5'-di-tert-butylphenyl)propionate, and 2-methyl-4,6-bis[(octylthio)methyl]phenol may be used. As rubber softeners, one or more process oils, extender oils, etc., may be used. However, in one embodiment, the rubber composition can form a flexible molded article, and therefore, in one embodiment, the rubber composition components may not contain rubber softeners.

[0154] While vulcanizing agents, vulcanization accelerators, and rubber additives are typically added during the manufacture of rubber composites, the manner of addition is not limited thereto.

[0155] <Additional components of the rubber composition> The rubber composition components may further contain additional components. Examples of additional components include additional polymers, organic or inorganic fillers, heat stabilizers, antioxidants, antistatic agents, colorants, etc. The content ratio of any additional component in the rubber composition components is appropriately selected within a range that does not impair the desired effects of the present invention, but may be, for example, 0.01 to 50% by mass, or 0.1 to 30% by mass.

[0156] <Manufacturing of rubber compositions> The rubber composition can be manufactured by mixing rubber composition components, which include fine cellulose fibers, a first rubber, and a second rubber. The method for manufacturing the rubber composition is as follows: (1) A first step of mixing fine cellulose fibers with a first rubber which is an unmodified liquid rubber to obtain a preliminary composition, and A method comprising a second step of mixing the pre-composition with a second rubber which is a modified liquid rubber, (2) A first step of mixing a first rubber, which is an unmodified liquid rubber, with a second rubber, which is a modified liquid rubber, to obtain a preliminary composition, and A method comprising a second step of mixing the pre-composition with fine cellulose fibers, (3) A method comprising the step of mixing fine cellulose fibers, a first rubber which is an unmodified liquid rubber, and a second rubber which is a modified liquid rubber. These are some examples. The mixing conditions are not particularly limited, but for example, the components constituting the rubber composition may be mixed using at least one stirring means selected from mixing means such as a rotational / revolving mixer, a planetary mixer, agitator / mixer, agitator / granulator, propeller-type agitator, rotary agitator, electromagnetic agitator, open roll, Banbury mixer, kneader, single-screw extruder, twin-screw extruder, etc., to obtain the rubber composition. Alternatively, stirring may be performed under heating to efficiently carry out shearing. In the method described in (1) above, by combining the first rubber with fine cellulose fibers in advance, the contact opportunity between the fine cellulose fibers and the second rubber becomes more appropriate and uniform, which can lead to better improvement in the physical properties of the rubber composition, rubber composite, or cured rubber product. The rubber composition may be dried after obtaining it, and a powder may be formed by controlling the drying conditions. In addition, in the method described in (1) above, after obtaining the preliminary composition, the preliminary composition may be dried before mixing it with the modified liquid rubber, and after producing a fine cellulose fiber dry product, the modified liquid rubber may be mixed in.

[0157] In one embodiment, the process may include a step of crushing the rubber composition produced by the above method. If the rubber composition discharged from the mixer is in the form of coarse particles or lumps, it may adversely affect the dispersibility and workability of the fine cellulose fibers when producing rubber composites and hardened rubber products, and may be refined by the crushing step. A coarse crusher, intermediate crusher, fine crusher, etc., can be used in the crushing step. Examples of coarse crushers include jaw crushers, impact crushers, and cone crushers; examples of intermediate crushers include roll crushers and hammer mills; and examples of fine crushers include ball mills, vibratory mills, pin mills, agitator mills, and jet mills. A classifier may also be used as needed.

[0158] If the rubber composition contains a third rubber, in one embodiment, the third rubber may be further mixed in the second step of the methods described in (1) to (2) above. The mixing conditions at this time are not particularly limited, but a general-purpose kneader used for rubber mixing, such as a Banbury mixer, kneader, or open roll, can be used. The rotor of the kneader can be a meshing rotor or a tangential rotor, and a rotor designed for resin mixing can also be used. Examples of meshing rotors include the KIR-II manufactured by Kobe Steel, Ltd. and the EX7 type manufactured by Mitsubishi Heavy Industries, Ltd. Examples of tangential rotors include the 5THR, 4WN, 4WH manufactured by Kobe Steel, Ltd. and the E type manufactured by Mitsubishi Heavy Industries, Ltd. Examples of rotors for resin mixing include the roller type R500B manufactured by Toyo Seiki Mfg. Co., Ltd. Alternatively, after the second step (after preparing the rubber composition) using the methods described in (1) to (3) above, the rubber composition may be mixed with the third rubber to obtain a rubber composition further containing the third rubber. The mixing conditions in this case may be the same as those described above for the case where the rubber composition contains the third rubber. In particular, in the second step of the method described in (1) above, if a third rubber is further mixed in a rubber mixer, the dispersion of fine cellulose fibers can be especially promoted. That is, in such a second step, the viscosity of the mixture can be increased by the presence of the third rubber, and thus the shear force applied to the mixture can be increased. Furthermore, with a rubber mixer, distribution proceeds well even when high-viscosity rubber is used. Therefore, since the second rubber and the fine cellulose fibers come into contact at an appropriate speed and sufficiently, the dispersion of the fine cellulose fibers can be promoted. The rubber compositions containing the third rubber exemplified above can all be suitably used, for example, as masterbatches and can be applied to the manufacture of various rubber composites.

[0159] In one embodiment, as a method for mixing the fine cellulose fibers with the first and / or second rubber described above, the fine cellulose fibers may be added in the form of a dried fine cellulose fiber body. In another embodiment, the fine cellulose fibers may be mixed with the first and / or second rubber in the form of a slurry or cake, and the contained liquid medium may be dried and removed to obtain a dried fine cellulose fiber body or a rubber composition.

[0160] <Drying process> In one embodiment, a dried fine cellulose fiber body can be produced by drying a fine cellulose fiber slurry or cake. The dryers are not particularly limited, but examples include kneaders, planetary mixers, Henschel mixers, high-speed mixers, propeller mixers, ribbon mixers, single-screw or twin-screw extruders, Banbury mixers, freeze dryers, shelf dryers, spray dryers, airflow dryers, fluidized bed dryers, drum dryers, etc. The dryers may be used individually or in combination of at least two types. In one embodiment, when drying after mixing a fine cellulose fiber slurry or cake with the first rubber and / or the second rubber, the mixing and drying operations may be carried out using the dryer alone, or each operation may be carried out using a kneader and the dryer. The mixing machine is not particularly limited, but examples include at least one mixing means selected from among rotating / revolving mixers, planetary mixers, agitators, granulators, propeller-type agitators, rotary agitators, electromagnetic agitators, open roll mixers, Banbury mixers, kneaders, single-screw extruders, twin-screw extruders, and other mixing means. Furthermore, mixing may be performed under heating to ensure efficient mixing.

[0161] The drying temperature may be, for example, 20°C or higher, 30°C or higher, 40°C or higher, or 50°C or higher, from the viewpoint of forming a fine cellulose fiber dry product with excellent powder properties that allow for good drying efficiency and dispersibility of fine cellulose fibers in the rubber composition and cured rubber product. From the viewpoint of minimizing thermal degradation of the fine cellulose fibers and additional components, and from the viewpoint of avoiding excessive pulverization of the fine cellulose fiber dry product due to rapid drying of the slurry, the drying temperature may be, for example, 600°C or lower, 400°C or lower, 300°C or lower, 200°C or lower, 180°C or lower, 160°C or lower, 140°C or lower, 120°C or lower, or 100°C or lower. The drying temperature is the temperature of the heat source in contact with the slurry, and is defined, for example, as the surface temperature of the temperature-controlled jacket of the drying apparatus, the surface temperature of the heating cylinder, or the temperature of the hot air.

[0162] The pressure may be either atmospheric pressure or reduced pressure, but from the viewpoint of forming a fine cellulose fiber dry material with excellent powder properties that are good for drying efficiency and for dispersing the fine cellulose fiber dry material in the rubber composition and cured rubber, it may be -1kPa or less, -10kPa or less, -20kPa or less, -30kPa or less, -40kPa or less, or -50kPa or less, and from the viewpoint of avoiding excessive pulverization of the fine cellulose fiber dry material due to rapid drying of the slurry, it may be -100kPa or more, -95kPa or more, or -90kPa or more. Atmospheric pressure drying may be carried out in an air atmosphere or an inert atmosphere, with an air atmosphere being preferred from an economic standpoint. In one embodiment, an inert atmosphere is preferred, and a nitrogen atmosphere is more preferred, from the viewpoint of preventing oxidative degradation of the dried fine cellulose fibers.

[0163] The concentration of fine cellulose fibers in the fine cellulose fiber slurry subjected to the drying process is preferably 1% by mass or more, or 2% by mass or more, or 3% by mass or more, or 5% by mass or more, or 10% by mass or more, or 15% by mass or more, or 20% by mass or more, or 25% by mass or more, from the viewpoint of process efficiency during drying. From the viewpoint of uniform mixing of additives, avoiding excessive increase in slurry viscosity, and maintaining good handling properties by avoiding solidification due to aggregation, it is preferably 50% by mass or less, or 45% by mass or less, or 40% by mass or less, or 35% by mass or less. For example, fine cellulose fibers are often produced in a dilute dispersion, but the concentration of fine cellulose fibers in the slurry may be adjusted to the above preferred range by concentrating such a dilute dispersion. Methods such as suction filtration, pressure filtration, centrifugal deliquidation, and heating can be used for concentration. When the concentration of fine cellulose fibers in the slurry is 10% by mass or more, it is also called a fine cellulose fiber cake.

[0164] In one embodiment, the fine cellulose fiber dry product may contain the first rubber and / or the second rubber, and any additional components (e.g., the dispersant described above), which may be added before, during, and / or after drying the fine cellulose fiber slurry. In one embodiment, the first rubber and / or the second rubber, and / or any additional components may be added in a dispersed or dissolved state in water and / or an organic solvent. The organic solvent is not particularly limited, but a solvent in which the first rubber and the second rubber dissolve is preferred, and examples of water-insoluble solvents include chloroform, toluene, hexane, and cyclohexane.

[0165] A more specific example of the order of steps is as follows: (i) Prepare a slurry containing fine cellulose fibers and optionally a dispersant → Dry to prepare a dried body of fine cellulose fibers → Prepare a preliminary composition containing the dried body and the first rubber → Prepare a rubber composition containing the preliminary composition and the second rubber. (ii) Prepare a slurry containing fine cellulose fibers and optionally a dispersant → Dry to prepare a dried body of fine cellulose fibers → Prepare a rubber composition containing the dried body, the first rubber, and the second rubber. (iii) Prepare a slurry containing fine cellulose fibers, the first rubber, and optionally a dispersant → Dry to prepare a dried body of fine cellulose fibers → Prepare a rubber composition containing the dried body and the second rubber. (iv) Prepare a slurry containing fine cellulose fibers, the first rubber, the second rubber, and optionally a dispersant → Dry to prepare a rubber composition.

[0166] [Liquid medium content] The liquid medium content of the fine cellulose fiber dry body (including the preliminary composition and the rubber composition) is preferably 90% by mass or less, or 80% by mass or less, or 70% by mass or less, or 60% by mass or less, or 50% by mass or less, or 40% by mass or less, or 30% by mass or less, or 20% by mass or less, or 10% by mass or less, from the viewpoint of workability when kneading with the third rubber and / or the fourth rubber and reduction of time and energy for vaporizing the liquid. The liquid medium content may be 0% by mass, but from the viewpoint of ease of manufacturing the fine cellulose fiber dry body and improvement of dispersibility in the rubber composition and rubber cured product due to the presence of liquid, it may be, for example, 0.1% by mass or more, or 1% by mass or more, or 1.5% by mass or more. The liquid medium content is a value measured using an infrared heating type moisture meter at a heating temperature of 120°C. Examples of the liquid medium include water and / or other media (e.g., organic solvents, inorganic acids, bases and / or ionic liquids), and may contain one or more types of media, but water is preferred.

[0167] [Average particle size] In one aspect, the average particle size of the dried microcrystalline cellulose fibers (including the preliminary composition and the rubber composition) is preferably 1 μm or more, or 10 μm or more, 50 μm or more, or 100 μm or more, or 200 μm or more, or 500 μm or more from the viewpoint of ease of production, and preferably 10,000 μm or less, or 5,000 μm or less, or 4,000 μm or less, or 3,000 μm or less, or 2,000 μm or less in terms of the dried microcrystalline cellulose fibers being easily disintegrated in the rubber composition and the rubber cured product and the microcrystalline cellulose fibers being well dispersed. The above average particle size is a value measured by a dynamic image analysis type particle size distribution measuring device (CAMSIZER X2 manufactured by Microtrac).

[0168] [Loose bulk density] In one aspect, the loose bulk density of the dried microcrystalline cellulose fibers (including the preliminary composition and the rubber composition) is preferably 0.01 g / cm 3 or more, or 0.05 g / cm 3 or more, or 0.10 g / cm 3 or more, or 0.15 g / cm 3 or more, or 0.20 g / cm 3 or more, or 0.25 g / cm 3 or more, or 0.30 g / cm 3 or more, or 0.35 g / cm 3 or more, or 0.40 g / cm 3 or more, or 0.45 g / cm 3 or more, or 0.50 g / cm 3 or more, and preferably 0.85 g / cm 3 or less, or 0.80 g / cm 3 or less, or 0.75 g / cm 3 or less in terms of the dried microcrystalline cellulose fibers being easily disintegrated in the rubber composition and the rubber cured product and the microcrystalline cellulose fibers being well dispersed, and in terms of the dried microcrystalline cellulose fibers not being too heavy and avoiding poor mixing of the dried microcrystalline cellulose fibers with the rubber composition and the rubber cured product.

[0169] [Compact bulk density] In one aspect, the bulk density of the dried microcrystalline cellulose fibers (including the preliminary composition and the rubber composition) is useful for controlling the loose bulk density and the degree of compression within the scope of the present disclosure. The dried microcrystalline cellulose fibers are controlled in terms of easily disintegrating in the rubber composition and the rubber cured product so that the microcrystalline cellulose fibers can be well dispersed. In one aspect, preferably, it is 0.01 g / cm 3 or more, or 0.1 g / cm 3 or more, or 0.15 g / cm 3 or more, or 0.2 g / cm 3 or more, or 0.3 g / cm 3 or more, or 0.4 g / cm 3 or more, or 0.5 g / cm 3 or more, or 0.6 g / cm 3 or more, and preferably, it is 0.9 g / cm 3 or less, or 0.8 g / cm 3 or less, or 0.7 g / cm 3 or less.

[0170] [Degree of Compression] The degree of compression is a value calculated by degree of compression = (bulk density after compression - loose bulk density) / bulk density after compression. The loose bulk density and the bulk density after compression are values measured by the method described in the [Examples] section of the present disclosure. In one aspect, the degree of compression represents the degree of bulk reduction. In one aspect, the degree of compression of the dried microcrystalline cellulose fibers (including the preliminary composition and the rubber composition) is preferably 1% or more, or 5% or more, or 10% or more, or 15% or more, or 20% or more, or 25% or more in that the fluidity of the dried microcrystalline cellulose fibers is not too high. Also, in terms of the fluidity of the dried microcrystalline cellulose fibers being good and the feeding property being excellent, and the handling property being excellent (specifically, it is difficult to cause scattering, floating, or dust formation), and the dried microcrystalline cellulose fibers being well dispersed in the rubber composition and the rubber cured product, the degree of compression is preferably 50% or less, or 45% or less, or 40% or less, or 35% or less, or 30% or less.

[0171] The above-mentioned loose bulk density, firm bulk density, and compression degree are measured using a powder tester (model number: PT-X) manufactured by Hosokawa Micron Corporation. The number of taps for firm bulk density measurement is 180. When filling the cup with powder, sieving is not performed, and the powder is dropped from the funnel with a distance of 10-20 cm between the top of the cup and the end of the funnel's base.

[0172] <Physical properties of rubber compositions> [Median diameter of crushed material] In one embodiment, the rubber composition is composed of crushed material median diameter (50% diameter D 50 The particle size is preferably 8.0 mm or less, or 7.0 mm or less, or 6.0 mm or less. When the rubber composition is kneaded with the third and / or fourth rubber, the small particle size of the rubber composition makes it easy to distribute throughout the mixture, which is advantageous in that it reduces manufacturing inconsistencies. On the other hand, the lower limit of the median diameter of the crushed material is preferably 10 μm or more, or 50 μm or more, or 100 μm or more, for ease of manufacturing and reduction of dust explosiveness. The median diameter of the crushed material of the rubber composition is the particle size of the crushed material after the crushing process using a planetary mixer. In one embodiment, the rubber composition is particulate but contains liquid rubber and is therefore a sticky solid, and may be in the form of loose lumps that can be crushed by hand. In this case, it is preferable that the particle size of the particles obtained by crushing the loose lumps is within the above range.

[0173] Crushing using a planetary mixer is performed by stirring 200g of the rubber composition at 50rpm and 25℃ for 15 minutes using a Hibismix® 2P-1 model (Primix Corporation). Next, the particle size distribution of the crushed material is evaluated by assembling stainless steel sieves (75φ×20mm, plain weave) with mesh sizes (1) 2.00mm, (2) 3.35mm, (3) 4.75mm, (4) 6.7mm, and (5) 9.5mm in order from the bottom up using a mini sieve shaker (AS ONE, MVS-1N). Approximately 15g of the rubber composition is placed on the 9.5mm mesh sieve and vibrated at the fastest vibration speed for 3 minutes. After that, the weight of each sieve is measured and the cumulative distribution below the sieve is calculated from the difference in individual weights. From this cumulative distribution below the sieve, the median diameter (50% diameter D) of the crushed material is calculated. 50 Calculate ). Furthermore, for rubber compositions where the weight of powder passing through a 2.00 mm mesh exceeds 40% by mass of the total powder introduced into the classification, the particle size distribution was measured using a dynamic image analysis particle size distribution analyzer (CAMSIZER X2, Microtrac), and the 50% diameter D of the integrated distribution was determined. 50 This is used as the median diameter of the crushed rubber composition obtained by crushing.

[0174] [Bulk density of loosened crushed material] In one embodiment, the bulk density of the crushed rubber composition is preferably 0.01 g / cm³, from the standpoint of excellent feedability to the equipment when kneading with the third and / or fourth rubber. 3 Above, or 0.05 g / cm³ 3 Above or equal to 0.1 g / cm³ 3 Above, or 0.15 g / cm³ 3 Above, or 0.20 g / cm³ 3 For the reasons described above, the fine cellulose fibers readily disintegrate when kneaded with the third and / or fourth rubber, and their bulkiness allows for good dispersion of the fine cellulose fibers in the rubber composition and / or rubber composite, making a concentration of 0.80 g / cm³ preferable. 3 The following, or 0.7 g / cm³ 3 The following, or 0.6 g / cm³ 3 The following, or 0.55 g / cm³ 3 The following, or 0.5 g / cm³ 3 The following applies. The loose bulk density of the crushed rubber composition is the loose bulk density of the crushed material after the crushing process using a planetary mixer. In one embodiment, the rubber composition is particulate but contains liquid rubber, making it a sticky solid, and may be in the form of loose lumps that can be crushed by hand. It is preferable that the loose bulk density of the particles obtained by crushing the loose lumps is within the range described above. The loose bulk density of the crushed material is measured in accordance with JIS K 7365 (Plastics - Method for determining the apparent density of materials that can be poured from a standard funnel) using the crushed material obtained by the method described above.

[0175] [Format into a sheet] <Rubber composition sheet> In one embodiment, the rubber composition may be in sheet form (hereinafter referred to as a rubber composition sheet). Accordingly, one embodiment of the present invention also provides such a rubber composition sheet. When the smallest of the three sides of the rubber composition sheet is defined as the thickness, the lower limit of the thickness is preferably 0.1 mm or more, or 1 mm or more, or 3 mm or more, or 5 mm or more, from the viewpoint of ease of manufacture and prevention of breakage during transport, and the upper limit is preferably 20 cm or less, or 10 cm or less, or 5 cm or less, or 3 cm or less, or 1 cm or less, from the viewpoint of ease of manufacture, ease of handling in subsequent kneading operations, and ease of dispersion in the rubber composite. Because the rubber composition is in sheet form, when kneaded with the third rubber and / or fourth rubber, there is no concern for health due to dust scattering like with powders, and weighing and loading into the kneader are easy.

[0176] <Manufacturing of rubber composition sheets> The manufacturing method of the rubber composition sheet according to this disclosure is not particularly limited as long as it can be used to form the rubber composition into a sheet, but at least one or more devices selected from roll press molding, rolling molding, die press molding, extrusion molding, etc. may be used. In one preferred embodiment, the rubber composition may be formed into a sheet using a powder rolling mill. In one preferred embodiment, the rubber composition may be formed into a sheet using a press molding machine.

[0177] In the manufacture of rubber composition sheets, the sheets may be formed under heating conditions in order to obtain high-quality sheets. Heating reduces the viscosity of the liquid rubber contained in the rubber composition, allowing for the production of sheets with low porosity. The lower limit of the temperature is preferably 10°C or higher, or 20°C or higher, or 30°C or higher, and the upper limit is preferably 300°C or lower, or 200°C or lower, or 150°C or lower, or 120°C or lower, or 100°C or lower, in order to prevent thermal degradation of the fine cellulose fibers.

[0178] [Sheet samples made from rubber compositions, or properties of rubber composition sheets] Since the rubber composition is a sticky solid regardless of its shape such as particles or lumps, it can be sheeted by pressure pressing. When kneading with the fourth rubber which is a high-viscosity substance, the appropriate stickiness of the rubber composition effectively applies a shearing force, improving the dispersion and orientation of the fine cellulose fibers in the rubber composite. In one aspect, each of a sheet sample which is a 2 mm thick sheet produced by pressure pressing the rubber composition according to one aspect of the present invention, or the rubber composition sheet itself according to one aspect of the present invention, may exhibit the following characteristics in one aspect. The 2 mm thick sheet is produced by pressure pressing at a press force of 200 kN, a press time of 10 minutes, and a temperature of 70°C. More specifically, the production of the sheet of the rubber composition by pressure pressing is carried out by setting 30 g of the rubber composition on a mold with a release sheet laid thereon and performing pressure pressing under the following conditions. Press force: 200 kN Press time: 10 minutes Temperature: 70°C Mold thickness: 2 mm Mold size: 10 cm × 10 cm

[0179] <Porosity> In one aspect, the porosity of the 2 mm thick sheet obtained by pressure pressing the rubber composition, or the rubber composition sheet of the present embodiment, is preferably 0.01% or more, or 0.05% or more, or 0.1% or more, or 0.2% or more, and is preferably 8.0% or less, or 6.0% or less, or 4.0% or less, or 2.0% or less. The larger the porosity, the easier the rubber composition collapses when kneading with the fourth rubber, so the dispersion and orientation of the fine cellulose fibers are excellent. On the other hand, when it is 8.0% or less, the adhesiveness of the rubber composition is appropriate, shearing is easily applied, and the dispersion and orientation of the fine cellulose fibers are excellent.

[0180] The porosity is calculated by the following procedure. A cube sample with a side length of 2 mm is subjected to X-ray CT measurement under the following conditions, and 10 cross-sectional slice images are randomly extracted from the measurement data of each sample (about 800 cross-sectional images). Subsequently, using the image processing software ImageJ, the area ratio of the low-luminance part (i.e., the void part) in the total area of each slice image is calculated from the binary image, and the average value of the area ratios of the 10 images is taken as the porosity of the rubber composition sheet. The measurement conditions for X-ray CT are as follows. Device: Bruker X-CT Skyscan1272 Tube voltage: 40 kV, tube current: 100 μA X-ray filter: None Number of pixels: 2452×1640, pixel resolution: 1.2 μm, number of integrations: 4 times Scan: Every 0.3 degrees, 180-degree scan The binaryization conditions are as follows. ROI setting: 1.6 mm×1.6 mm Binaryization range: 0 - 30 (Full luminance range: 0 - 255 (8-bit))

[0181] <Puncture test> In one aspect, the puncture strength of a 2-mm-thick sheet made by pressing a rubber composition, that is, the maximum strength (also referred to as the highest puncture strength) in the puncture test of a creep meter, is preferably 0.3 MPa or more, or 0.5 MPa or more, or 0.7 MPa or more, and preferably 3.0 MPa or less, or 2.0 MPa or less, or 1.5 MPa or less. When the maximum stress is within the above range, the rubber composition has appropriate adhesiveness, and when kneaded with the third rubber and / or the fourth rubber, a shearing force is easily applied to the rubber composition, and the dispersion and orientation of the microcrystalline cellulose fibers are excellent.

[0182] The puncture test of the sheet is carried out using a creep meter (Yamatake Corporation's "Creep Meter", model number: RE2-330005C (XZ), plunger: cylinder (P-4, diameter 3 mm, made of polyoxymethylene), plunger extender (L-17), puncture pedestal (PG-103, hole diameter 10 mm), measurement mode: puncture strength test) according to the following procedures (1) to (4). (1) Cut a 2mm thick sheet into 2cm x 5cm pieces to use as measurement samples. (2) Disassemble the base and insert the sample to be measured, adjusting it so that the plunger is in contact perpendicularly with the top surface of the sample. (3) Measurement is taken at a compression speed of 1 mm / second and a penetration depth of 10 mm. (4) Calculate the maximum stress (puncture strength), the strain at maximum stress (fracture strain), and the modulus of elasticity. The strain follows the following formula. Distortion (%): Plunger travel distance (mm) / Thickness (2mm) × 100 The modulus of elasticity is calculated for strains between 0% and 5%. If the maximum stress is reached with a strain of 5% or less, the calculation is performed for strains ranging from 0% to the point at which the maximum stress was reached.

[0183] <Texture Evaluation - Hardness> In one embodiment, in the texture evaluation of a 2 mm thick sheet produced by pressurizing a rubber composition, or the rubber composition sheet of this embodiment, the hardness is preferably 1.0 MPa or higher, or 2.0 MPa or higher, or 3.0 MPa or higher, and preferably 20.0 MPa or lower, or 15.0 MPa or lower, or 12.0 MPa or lower, or 10.0 MPa or lower. Hardness, in texture profile analysis, refers to the maximum stress during the first compression. Having hardness within the specified range allows for maintaining the sheet shape while simultaneously achieving excellent breakability during mixing, and results in superior dispersion and orientation of fine cellulose fibers.

[0184] <Texture Evaluation - Cohesion> In one embodiment, in the texture evaluation of a 2 mm thick sheet produced by pressurizing a rubber composition, or the rubber composition sheet of this embodiment, the cohesiveness is preferably 10% or more, 15% or more, or 20% or more, and preferably 60% or less, 55% or less, or 50% or less. In texture profile analysis, cohesion refers to the positive load area ratio (A2 / A1) of the first compression (A1) and the second compression (A2) in the force-deformation curve when the plunger is pulled up and compressed again after the first compression. A larger load area ratio (i.e., a larger cohesion value) indicates greater elasticity and easier return to the original shape, while a smaller load area ratio (i.e., a smaller cohesion value) indicates that deformation due to external force remains and the material is more prone to shattering. The cohesiveness within the above range imparts appropriate adhesiveness to the rubber composition when kneaded with the fourth rubber, resulting in shear force application and ease of crushing, and excellent dispersion and orientation of fine cellulose fibers.

[0185] <Texture Evaluation - Adhesion> In one embodiment, in the texture evaluation of a 2 mm thick sheet made by pressurizing a rubber composition, or the rubber composition sheet of this embodiment, the adhesion is preferably 30 kJ / m 3 Above 40 kJ / m³ 3 Above 50 kJ / m³ 3 The above is the case, preferably 300 kJ / m³ or less, or 200 kJ / m³. 3 The following, or 100 kJ / m³ 3 The following applies:

[0186] Adhesion is the area of ​​the negative load region during lifting in the force-deformation curve of the texture profile analysis method described above. A larger area indicates stronger adhesion and greater tackiness as a sheet. Adhesion of 30 kJ / m 3 As a result, the rubber composition exhibits good tackiness when kneaded with the fourth rubber, is easily sheared, and has excellent dispersion and orientation of fine cellulose fibers. 3 As described below, the fine cellulose fibers can absorb the liquid rubber, making it difficult for the liquid rubber to become detached in the cured rubber product, resulting in superior physical properties of the cured rubber product.

[0187] Texture evaluation is performed using a creep meter (Yamaden Co., Ltd. "Creep Meter", model number: RE2-330005C(XZ), plunger: cylindrical (P-4, 3 mm in diameter, made of polyacetal), plunger extender (L-17), standard base and sample holder with a hole diameter of 16 mm, measurement mode: texture measurement) following the procedure (1) to (4) below. (1) Cut the sheet into 2cm x 5cm pieces to use as measurement samples. If the sheet thickness exceeds the measurement range, cut it to a thickness that can be measured. (2) Place the sample to be measured on the base, clamp it with the sample holder, and adjust so that the plunger contacts the top surface of the sample perpendicularly. (3) After compressing at a compression speed of 1 mm / second and pressing down to 0.6 mm (the strain will be 0.3% if the sheet thickness is 2 mm), pull the plunger up to 1 mm above the sample and repeat the same pressing and pulling process. (4) Measure the maximum stress during the first press, cohesiveness (the ratio of the positive load area during the first press (A1) to the second press (A2) (A2 / A1)), and adhesion (the negative load area during the lifting). The strain follows the following formula. Distortion (%): Plunger travel distance (mm) / Sheet thickness (mm) × 100

[0188] <Breaking stress> In one embodiment, the cutting stress of a 2 mm thick sheet made by pressurizing a rubber composition, or the rubber composition sheet of this embodiment, is preferably 1.0 MPa or more, or 2.0 MPa or more, or 3.0 MPa or more, and preferably 20.0 MPa or less, or 15.0 MPa or less, or 12.0 MPa or less, or 10.0 MPa or less. When the cutting stress is within the above range, crushing of the rubber composition sheet during transportation is suppressed, and when kneading with the fourth rubber, the fine cellulose fibers can be sufficiently dispersed and oriented by a kneader or the like.

[0189] The cutting stress test of the sheet is carried out using a creep meter (manufactured by Yamaden Co., Ltd., model: RE2-330005C(XZ), plunger: knife cutter (P-21, blade length 56 mm), plunger extender (L-17), pedestal (PG102), measurement mode: piercing strength test) according to the following procedures (1) to (4). (1) Cut the sheet into 2 cm × 5 cm to obtain a measurement sample. If the sheet thickness exceeds the measurement range, cut it to a measurable thickness. (2) Disassemble the pedestal, sandwich the measurement sample, and adjust so that the plunger contacts the upper surface of the sample vertically. (3) Measure at a compression speed of 1 mm / second and a moving distance of twice the sheet thickness. (4) Calculate the maximum stress (cutting stress, contact area is 7.6 mm 2 ) and the strain at the maximum stress (fracture strain). The strain follows the following formula. Strain (%): plunger moving distance (mm) / thickness (mm) × 100

[0190] <Shore A hardness> In one aspect, the Shore A hardness of a 2 mm thick sheet produced by pressuring the rubber composition or the rubber composition sheet of the present embodiment is preferably 10 or more, or 15 or more, or 20 or more, and preferably 90 or less, or 80 or less, or 70 or less. When the Shore A hardness is within the above range, crushing during transportation of the rubber composition sheet can be suppressed, and fine cellulose fibers can be sufficiently dispersed and oriented by a kneader or the like when kneading with the fourth rubber. The measurement of the Shore A hardness of the rubber composition sheet follows ISO7619-1. When the thickness of the rubber composition sheet is insufficient, stack multiple sheets to a total thickness of 6 mm or more for measurement.

[0191] ≪Rubber composite, rubber cured product and molded body≫ One aspect of this disclosure provides a rubber composite which is a mixture of the rubber composition of this embodiment and a fourth rubber (base rubber), and a cured rubber which is a cured product of the rubber composite. The mixing conditions for the rubber composition and the fourth rubber are not particularly limited, and a general kneader used for rubber mixing, such as a Banbury mixer, kneader, or open roll, can be used.

[0192] <The Fourth Rubber> The specific embodiment of the fourth rubber may be the same as that of the third rubber. The total content of fine cellulose fibers and the first and second rubbers relative to 100 parts by mass of the third and fourth rubbers is preferably 1 part by mass or more, or 3 parts by mass or more, or 5 parts by mass or more, and preferably 50 parts by mass or less, or 45 parts by mass or less, or 40 parts by mass or less. In one embodiment, the fourth rubber may be one or more selected from the group consisting of natural rubber, styrene-butadiene rubber, isoprene rubber, and butadiene rubber, for example, natural rubber. When the rubber composition contains the third rubber, it is preferable that some or all of the constituent monomers of the third rubber and the fourth rubber are the same.

[0193] In one embodiment, a cured rubber product can be obtained by a vulcanization press in accordance with JIS K6299. A desired molded article may be produced by molding the rubber composite alone or together with other components into a desired shape. The method of combining the compounding components and the molding method are not particularly limited and may be selected according to the desired molded article. The molding method is not limited to these, however (1) A method for obtaining a molded article containing a cured rubber by curing the uncured rubber before, during, and / or after molding when molding a rubber composite, either alone or together with additional components, wherein the third and / or fourth rubber includes uncured rubber. (2) A method in which the third and / or fourth rubber includes uncured rubber, and after curing the uncured rubber in the rubber composite to form a cured rubber product, the product is molded together with additional components to obtain a molded body. (3) A method of obtaining a molded article by melt-molding the third and fourth rubbers, either alone or together with additional components, wherein the rubber composite is a thermoplastic elastomer. Examples include the above. Molding may be carried out by injection molding, extrusion molding, extrusion molding, hollow molding, compression molding, etc.

[0194] <Physical properties of hardened rubber> The tensile stress (modulus) (M100) of the rubber cured material at 100% elongation may, in one embodiment, be 2.0 MPa or more, or 3.0 MPa or more, or 4.0 MPa or more, and in one embodiment, it may be 10.0 MPa or less, or 9.0 MPa or less, or 8.0 MPa or less.

[0195] The tensile stress (M300) of the hardened rubber at 300% elongation may, in one embodiment, be 3.0 MPa or more, or 5.0 MPa or more, or 6.0 MPa or more, and in one embodiment, it may be 20.0 MPa or less, or 15.0 MPa or less, or 13.0 MPa or less.

[0196] The ratio of the tensile stress at 300% elongation (M300) to the tensile stress at 100% elongation (M100) of the hardened rubber (M300 / M100) may, in one embodiment, be 1.3 or more, or 1.4 or more, or 1.5 or more, and in one embodiment, it may be 2.0 or less, or 1.8 or less.

[0197] The storage modulus of the cured rubber may, in one embodiment, be 2.0 MPa or more, or 2.5 MPa or more, and in one embodiment, it may be 4.0 MPa or less, or 3.5 MPa or less, or 3.0 MPa or less.

[0198] Having a loss tangent of a cured rubber product below a predetermined value is advantageous, for example, in terms of fuel efficiency and low heat generation in tire applications. From this viewpoint, the loss tangent may be 0.18 or less, or 0.15 or less, or 0.10 or less, in one embodiment. On the other hand, having a loss tangent of a cured rubber product above a predetermined value is advantageous, for example, in terms of vibration damping performance in vibration-damping rubber applications. From this viewpoint, the loss tangent may be 0.02 or more, or 0.03 or more, or 0.04 or more, in one embodiment. The above storage modulus and loss tangent are values ​​measured using a rheometer in a torsional manner at 50°C and 10Hz.

[0199] The hardened rubber can be used to form molded articles of various shapes. The molded articles can be used in a wide range of applications, including industrial machine parts, general machine parts, automobile, railway, vehicle, ship, and aerospace-related parts, electronic and electrical components, building and civil engineering materials, household goods, sports and leisure goods, wind turbine enclosure components, containers and packaging components, and more. Examples of applications include automotive parts (e.g., exterior parts such as tires, bumpers, fenders, door panels, various moldings, emblems, engine hoods, wheel caps, roofs, spoilers, and various aero parts, as well as interior parts such as instrument panels, console boxes, and trims), battery parts (automotive secondary battery parts, lithium-ion secondary battery parts, fuel cases for solid methanol batteries, fuel cell piping, etc.), electronic and electrical equipment parts (e.g., various computers and their peripherals, junction boxes, various connectors, various office automation equipment, televisions, video players, disc players, chassis, refrigerators, air conditioners, LCD projectors, etc.), and household goods (shoe outsoles, etc.). One aspect of the present disclosure provides a tire, vibration-damping rubber, shoe outsole, or conveyor belt, including a rubber curing product of the present disclosure. [Examples]

[0200] The following describes illustrative embodiments of the present invention with reference to examples, but the present invention is not limited to these examples.

[0201] ≪Evaluation Method≫ <Fine Cellulose Fibers> [Fabrication of porous sheets] To perform the various evaluations described below, a porous sheet of fine cellulose fibers was prepared. First, a concentrated cake was prepared by concentrating a fine cellulose fiber slurry to a solid content of 10% by mass using a Buchner funnel (a press was used as needed). Next, the concentrated cake was added to tert-butanol and adjusted to a fine cellulose fiber solid content concentration of 0.5% by mass and a total weight of 100 g. Then, the mixture was dispersed using a high-shear homogenizer (IKA, product name "Ultra-Turrax T18", processing conditions: rotation speed 15,000 rpm x 3 minutes) until no aggregates remained. 100 g of the obtained tert-butanol dispersion was filtered on filter paper. The filtrate was not removed from the filter paper, but sandwiched between two larger sheets of filter paper, and the edges of the larger sheets were pressed down with weights while drying in a 150°C oven for 5 minutes. After that, the filter paper was removed to obtain a porous sheet with minimal distortion. The air permeability resistance of this sheet was 10 g / m². 2 Porous sheets with a flow rate of 100 sec / 100 ml or less were used as measurement samples. The basis weight (W) of the sample after standing for 1 day in an environment of 23℃ and 50%RH (g / m²) 2 After measuring the air permeability resistance (R) (sec / 100ml), the air permeability resistance was measured using a Wangyan-type air permeability resistance tester (manufactured by Asahi Seiko Co., Ltd., model EG01). At this time, 10 g / m was measured according to the following formula. 2 The value per unit area was calculated. Weight: 10g / m 2 Air permeability resistance (sec / 100ml) = R / W × 10

[0202] [Specific surface area of ​​fine cellulose fibers] The specific surface area of ​​fine cellulose fibers was determined using a specific surface area and pore distribution analyzer (Nova-4200e, Quantachrome Instruments). Approximately 0.2 g of a porous sheet sample was dried under vacuum at 105°C for 5 hours, and the amount of nitrogen gas adsorbed at the boiling point of liquid nitrogen was measured at 5 points within the range of relative vapor pressure (P / P0) between 0.05 and 0.2 (multi-point method). The BET specific surface area (m²) was then calculated using the instrument's program. 2 The value per gram ( / g) was calculated.

[0203] [Degree of polymerization] The degree of polymerization of the fine cellulose fibers was calculated using Staudinger's viscosity law, which utilizes the intrinsic viscosity number measured by the copper-ethylenediamine method, as specified in JIS P8215:1998, Cellulose dilute solution - Method for determining intrinsic viscosity number.

[0204] [Degree of crystallinity] X-ray diffraction measurements were performed on the porous sheet, and the degree of crystallinity was calculated using the following formula. Crystallinity (%)=[I (200) -I (amorphous) ] / I (200) ×100 I (200) :Diffraction peak intensity at the 200 plane (2θ=22.5°) in cellulose type I crystals I (amorphous) : The halo peak intensity due to amorphous material in type I cellulose crystals, specifically the peak intensity at an angle 4.5° lower than the diffraction angle of the 200 plane (2θ = 18.0°). (X-ray diffraction measurement conditions) MiniFlex device (manufactured by Rigaku Corporation) Operation axis 2θ / θ Source CuKα Measurement method: Continuous Voltage 40kV Current 15mA Starting angle 2θ=5° Ending angle 2θ = 30° Sampling width 0.020° Scan speed 2.0° / min Sample: A porous sheet is attached to the sample holder.

[0205] [Average content of alkali-soluble polysaccharides] The alkali-soluble polysaccharide content was determined for fine cellulose fibers by subtracting the α-cellulose content from the holocellulose content (Wise method) using the method described in non-patent literature (Wood Science Experiment Manual, edited by the Japan Wood Research Society, pp. 92-97, 2000). The alkali-soluble polysaccharide content was calculated three times for each sample, and the number average was taken as the average alkali-soluble polysaccharide content of the fine cellulose fibers.

[0206] [Average content of acid-insoluble components] The acid-insoluble components were quantified using the Claesson method described in a non-patent document (Wood Science Experiment Manual, edited by the Japan Wood Research Society, pp. 92-97, 2000) for fine cellulose fibers. The oven-dried fine cellulose fibers were accurately weighed, placed in a designated container, and 72% by mass concentrated sulfuric acid was added. After pressing the contents uniformly with a glass rod, the mixture was autoclaved to dissolve the cellulose and hemicellulose in the acid solution. After cooling, the contents were filtered through glass fiber filter paper to obtain the acid-insoluble components as a residue. The acid-insoluble component content was calculated from the weight of this residue, and the number average of the acid-insoluble component content calculated for three samples was taken as the average acid-insoluble component content.

[0207] [Thermal decomposition start temperature of fine cellulose fibers (T D )] T of fine cellulose fibers D The porous sheet was evaluated using the following measurement method. Device: Rigaku Thermo plus EVO2 Sample: Circular pieces cut from a porous sheet were stacked in aluminum sample pans, with 10 mg of each piece placed on top. Sample amount: 10 mg Measurement conditions: The temperature was increased from room temperature to 150°C at a rate of 10°C / min in a nitrogen flow of 100 ml / min, held at 150°C for 1 hour, and then continued to increase to 450°C at a rate of 10°C / min. T D Calculation Method: The temperature was determined from a graph with temperature on the horizontal axis and weight retention percentage on the vertical axis. Starting from the weight of the porous sheet at 150°C (when moisture is almost completely removed) (weight loss of 0 wt%), the temperature was further increased, and a straight line was obtained that passes through the temperature at which the weight decreased by 1 wt% and the temperature at which the weight decreased by 2 wt%. The temperature at the point where this straight line intersects with the horizontal line (baseline) passing through the starting point of 0 wt% weight loss was defined as the thermal decomposition onset temperature (T D )

[0208] <rubber> [Viscosity at 38°C] The viscosity of the rubber was measured using a Type B viscometer. The results are shown in Table 1.

[0209] [Number average molecular weight (Mn)] The values ​​shown are from the product catalog.

[0210] <Rubber composition> The following evaluations were conducted on the rubber composition. <Rubber composition containing the first and second rubbers> [Fine Cellulose Fiber Content] It was calculated according to the following formula. Fine cellulose fiber content (%) = Weight of fine cellulose fibers / Weight of rubber composition × 100

[0211] [Dispersant / Second rubber weight ratio] Calculated according to the following formula Dispersant / Second Rubber Weight Ratio = Dispersant Mass Parts / Second Rubber Mass Parts

[0212] [Chemical bonding degree] 1 g of rubber composition and 50 ml of THF were placed in a vial and homogenized (IKA, product name "Ultra-Turrax T18", processing conditions: rotation speed 15,000 rpm x 3 minutes), then stirred with a magnetic stirrer (200 rpm, 24 hr). After that, the mixture was filtered through a nylon mesh, and the residue on the mesh was washed twice with more than 20 ml of THF, followed by vacuum drying (80°C, 12 hr) to obtain a dry, fine cellulose fiber residue. Next, the dried fine cellulose fiber residue 13 Solid-state NMR measurements were performed, and the degree of chemical bonding was calculated using the following formula, based on the peak area in the 100-110 ppm range (P1), the total peak area in the 58-100 ppm range (P2), and the total peak areas in the 110-220 ppm and 0-58 ppm ranges (P3). Chemical bonding degree ={(P2-P1×5)+P3} / (P1×6) [ 13 C solid-state NMR measurement conditions] (1) Sample tube: Made of zirconia, 7 mm in diameter (2) Magnetic field strength: 11.75T (3) Observation nucleus: 13 C (4) Observation frequency: 125.8 MHz (5) Temperature: room temperature (6) MAS rotation speed: 7kHz (7) Pulse sequence: DD / MAS method (8) Pulse width: 5.6 microseconds (9) Import time: 0.047 seconds (10) Waiting time: 1000 seconds (11) Total number of times: 150 (12) Measuring device: Avance500 (manufactured by Bruker Japan Co., Ltd.) (13) Chemical shift standard: Adamantane (external standard 29.5 ppm)

[0213] [Production of rubber composition sheets] The rubber composition sheet was prepared by placing 30g of the rubber composition on a mold lined with a release sheet and pressing it under the following conditions. Pressing force: 200kN Pressing time: 10 minutes Temperature: 70℃ Mold thickness: 2mm Mold size: 10cm x 10cm

[0214] [Porosity] A cubic sample with sides of 2 mm was cut from a rubber composition sheet, and X-ray CT measurements were performed under the following conditions. Ten cross-sectional slice images were randomly selected from the measurement data (approximately 800 cross-sectional images) of each sample. Subsequently, using the image processing software ImageJ, the area ratio of low-luminance areas (i.e., voids) in the total area of ​​each slice image was calculated from the binarized image, and the average of the area ratios of the 10 images was taken as the porosity of the rubber composition sheet. The measurement conditions for X-ray CT are as follows: Equipment: Bruker X-CT Skyscan 1272 Tube voltage: 40kV, Tube current: 100μA X-ray filter: None Pixel count: 2452 x 1640, Pixel resolution: 1.2 μm, Number of integrations: 4 Scanning: 0.3-degree intervals, 180-degree scan. The binarization conditions are as follows: ROI setting: 1.6mm×1.6mm Binarization range: 0-30 (Full brightness range: 0-255 (8-bit))

[0215] [Puncture Test - Puncture Strength, Breaking Strain, Elastic Modulus] The puncture test of the rubber composition sheet was performed using a creep meter (Yamaden Co., Ltd. "Creep Meter", model number: RE2-330005C(XZ), plunger: cylindrical (P-4, diameter 3 mm, made of polyacetal), plunger extender (L-17), puncture base (PG-103, hole diameter 10 mm), measurement mode: puncture strength test) according to the following procedure (1) to (4). (1) A rubber composition sheet (2 mm thick) was cut into 2 cm x 5 cm pieces and used as a measurement sample. (2) The base was disassembled, the sample to be measured was placed inside, and the plunger was adjusted so that it was in perpendicular contact with the top surface of the sample. (3) Measurements were taken at a compression speed of 1 mm / second and a penetration depth of 10 mm. (4) The maximum stress (puncture strength), strain at maximum stress (fracture strain), and elastic modulus were calculated. The distortion was calculated according to the following formula. Distortion (%): Plunger travel distance (mm) / Sheet thickness (mm) × 100 Furthermore, the elastic modulus was calculated within the strain range of 0-5%. If the maximum stress was reached with a strain of 5% or less, the calculation was performed within the strain range from 0% to the point where the maximum stress was reached.

[0216] [Texture evaluation - hardness, cohesiveness, adhesion] Texture evaluation was performed using a creep meter (Yamaden Co., Ltd. "Creep Meter", model number: RE2-330005C(XZ), plunger: cylindrical (P-4, 3 mm diameter, made of polyacetal), plunger extender (L-17), standard base and sample holder with a hole diameter of 16 mm, measurement mode: texture measurement) following the procedures (1) to (4) below. (1) A 2mm thick sheet was cut into 2cm x 5cm pieces to be used as a measurement sample. (2) The sample to be measured was placed on the base and held in place by the sample holder, and the plunger was adjusted so that it was in contact perpendicularly with the top surface of the sample. (3) After compressing at a speed of 1 mm / second and pressing down to 0.6 mm, the plunger was raised to 1 mm above the sample, and the same pressing and raising process was repeated. (4) The maximum stress (also called hardness) during the first press, cohesiveness (the ratio of the positive load area between the first press (A1) and the second press (A2) (A2 / A1)), and adhesion (the negative load area during the lifting) were measured.

[0217] <Hardened rubber> The following evaluations were performed on the hardened rubber material. (1)Surface smoothness Small pieces were cut from a hardened rubber sheet with scissors and placed on the stage of a confocal laser microscope (Keyence, VK-X250). Surface topography images were acquired using a 10x objective lens. The arithmetic mean height (Sa) was calculated according to ISO 25178 and indexed with the result of the reference comparison set to 100. A smaller index indicates better surface smoothness.

[0218] (2) Tensile strength, tensile stress (modulus) Tensile strength, tensile stress at 100% elongation (100% modulus, M100), and tensile stress at 300% elongation (300% modulus, M300) were measured according to the tensile test method of JIS K-6251, and the results were indexed with the results of the reference comparison set to 100. A higher index indicates better tensile strength and tensile stress.

[0219] (3) Dispersibility of fine cellulose fibers A cubic sample with sides of 2 mm was cut from a rubber composition sheet and observed by X-ray CT. In 10 randomly selected cross-sectional images of the 2 mm cube, 20,000 μm of material was observed in each cross-section. 2 The number of fine cellulose fiber aggregates of the above size was counted, the average number of aggregates per cross-section was calculated, and the state of fine cellulose fiber dispersion was ranked according to the following criteria. A: 5 or less B: More than 5 but less than 10 C: More than 10 pieces The measurement conditions for X-ray CT are as follows: Equipment: Bruker X-CT Skyscan 1272 Tube voltage: 40kV, Tube current: 100μA Pixel count: 2452 x 1640, Pixel resolution: 1.2 μm, Number of integrations: 8 Scan: 0.2-degree intervals, 180-degree scan.

[0220] (4) Orientation of fine cellulose fibers The degree of orientation of the fine cellulose fibers was calculated by processing the data observed using a transmission electron microscope as follows. When the roll mixing direction of a hardened rubber sheet was defined as MD, the direction perpendicular to the roll mixing direction as TD, and the thickness direction of the sheet as ND, sections with a set thickness of 500 μm were collected from the MD-ND surface of the sample using a cryomicrotome. These sections were observed at 1000x magnification using a transmission electron microscope (JEOL JEM-1400), and images were acquired from five random fields of view. The observed fine cellulose fibers were binarized and subjected to particle analysis using the image processing software ImageJ. In the particle analysis, the fine cellulose fibers were approximated as ellipses, and the angle θ between the major axis of the ellipse and the MD was obtained for each fine cellulose fiber. For the fine cellulose fibers obtained from the five TEM images, (3(cosθ)^2-1) / 2 was calculated, and the average value was taken as the degree of orientation. The orientation of the fine cellulose fibers was evaluated according to the following criteria. A: Orientation degree is 0.7 or higher B: Orientation degree is 0.5 or higher and less than 0.7 C: Orientation degree is less than 0.5

[0221] <Rubber composition sheet> [Sheet thickness] The thickness of five arbitrary points on the rubber composition sheet was measured using a dial gauge, and the average of these measurements was taken as the sheet thickness.

[0222] [Breaking stress] The sheet cutting stress test was performed using a creep meter (Yamaden Co., Ltd. "Creep Meter", model number: RE2-330005C(XZ), plunger: knife cutter (P-21, blade length 56 mm), plunger extender (L-17), base (PG102), measurement mode: puncture strength test) following the procedure (1) to (4) below. (1) The sheet was cut into 2cm x 5cm pieces to be used as measurement samples. (2) The base was disassembled, the sample to be measured was placed inside, and the plunger was adjusted so that it was in perpendicular contact with the top surface of the sample. (3) Compression speed: 1 mm / second, distance traveled: twice the sheet thickness was used for measurement. (4) Maximum stress (breaking stress, contact area is 7.6 mm) 2 ) was calculated.

[0223] [Shore A hardness] The Shore A hardness of the rubber composition sheets was measured according to ISO 7619-1. If the rubber composition sheet thickness was insufficient, multiple sheets were stacked to a total thickness of 6 mm or more for measurement.

[0224] ≪Materials used≫ <Fine Cellulose Fibers> [Fine Cellulose Fiber A] Three parts by mass of cotton linter pulp were immersed in 27 parts by mass of water and dispersed using a pulper. Thirty parts by mass of the pulper-treated cotton linter pulp slurry (of which three parts by mass were cotton linter pulp) were dispersed in water with 170 parts by mass of water (solid content 1.5% by mass). Using an SDR14 type laboratory refiner (pressure-type disk type) manufactured by Aikawa Iron Works Co., Ltd. as a disc refiner, the aqueous dispersion was beaten for 30 minutes with a clearance of 1 mm between the disks. Subsequently, thorough beating was performed under conditions where the clearance was reduced to a level close to zero to obtain a beaten aqueous dispersion (solid content concentration: 1.5% by mass). The obtained beaten aqueous dispersion was then subjected to 10 micronization treatments using a high-pressure homogenizer (NSO15H manufactured by Nilo Soavi (Italy)) at an operating pressure of 100 MPa to obtain a fine cellulose fiber A slurry (solid content concentration: 1.5% by mass). Then, the solid content was concentrated to 10% by mass using a dehydrator to obtain a cake of fine cellulose fibers A. Specific surface area: 53m 2 / g Crystallinity: 82% Degree of polymerization: 1050 Average content of alkali-soluble polysaccharides: 3.6% Average content of acid-insoluble components: 0.9% T d :260℃

[0225] [Fine Cellulose Fiber B] To 200g of dry coniferous pulp, 15L of water, 25g of sodium bromide, and 2.5g of TEMPO were added and thoroughly stirred to disperse the mixture. Then, a 13% by mass aqueous solution of sodium hypochlorite (co-oxidant) was added to a concentration of 6.5 mmol / g of sodium hypochlorite to initiate the reaction. As the reaction progressed, the pH decreased, so a 0.5N aqueous sodium hydroxide solution was added dropwise to maintain the pH at 10-11, and the reaction was continued until no further change in pH was observed. After the reaction was complete, 0.1N hydrochloric acid was added to adjust the pH to 7.0, and the mixture was purified by repeated filtration and washing with water to obtain cellulose fibers with an oxidized fiber surface and a carboxyl group content of 1.83 mmol / g. Next, the cellulose fibers were diluted with pure water to a solid content concentration of 1% by weight, and treated twice using an ultra-high pressure homogenizer at a liquid temperature of 20°C and a pressure of 140 MPa. After visually confirming the transparency of the treated liquid, the defibration process of the cellulose fibers was completed, and TEMPO-oxidized fine cellulose fibers were obtained. Specific surface area: 94m 2 / g Crystallinity: 74% Degree of polymerization: 780 Alkali-soluble polysaccharide content: 12.9% Acid insoluble component content: 1.5% T d :205℃

[0226] [Fine Cellulose Fiber C] Obtained from Sugino Machine Co., Ltd. (BinFis: BMa-10010) Specific surface area: 76m 2 / g Crystallinity: 76% Degree of polymerization: 810 Alkali-soluble polysaccharide content: 12.6% Acid insoluble component content: 3.2% T d :220℃

[0227] <rubber> <First type of rubber / unmodified liquid rubber> Liquid rubber-1: Clay Valley's Ricon 184 (liquid butadiene-styrene random copolymer, Mn=9,400) Liquid rubber-2: Kuraray Co., Ltd.'s LIR-50 (liquid polyisoprene, Mn=54,000)

[0228] <Second type of rubber / modified liquid rubber> Liquid Rubber-3: Kuraray Co., Ltd.'s LIR-403 (maleic anhydride-modified liquid polyisoprene, Mn=34,000, 3 modifying groups per molecular chain) Liquid Rubber-4: Kuraray Co., Ltd.'s LIR-410 (carboxylated liquid polyisoprene, Mn=30,000, 10 modifying groups per molecular chain) Liquid Rubber-5: Clay Valley's Ricon 131MA20 (maleic anhydride-modified liquid polybutadiene, Mn=7,000, 11 modifying groups per molecular chain)

[0229] <Third rubber and fourth rubber> Natural Rubber: RSS No. 3 (Producer: UNIMAC RUBBER CO., LTD. (Thailand), Supplier: Marubeni Techno Rubber) Polyisoprene: JSR IR2200 SBR-1: Manufactured according to the procedure described in the [Manufacturing of SBR-1] section below. SBR-2: Manufactured by Asahi Kasei Corporation, Asaprene (registered trademark) Y031

[0230] [Manufacturing of SBR-1] One autoclave was used, with an internal volume of 10 L, a ratio of internal height (L) to diameter (D) (L / D) of 4.0, an inlet at the bottom, an outlet at the top, and equipped with a stirrer and a jacket for temperature control. In addition, one static mixer was connected to the reactor just before the raw material inlet. 1,3-butadiene, from which impurities such as water had been removed beforehand, was mixed at a rate of 20.2 g / min, styrene at 16.8 g / min, and n-hexane at 137.6 g / min to obtain a mixture. Just before this mixture entered the first reactor, n-butyllithium for impurity deactivation treatment was supplied at 0.020 phm, mixed with the static mixer, and then continuously supplied to the bottom of the first reactor. Furthermore, 2,2-bis(2-oxolanil)propane was continuously supplied at 0.320 phm as a polar substance and NBL (n-butyllithium) was continuously supplied at 0.102 phm as a polymerization initiator to the bottom of the reactor, and the temperature inside the reactor was maintained at 82°C to obtain a rubber solution. The rubber solution produced in the reactor was supplied to a static mixer from the top of the reactor. Before reaching the static mixer, M1 (1,3-bis(N,N-diglycidylaminomethyl)cyclohexane) was continuously supplied as a modifier in a ratio of 1.0 equivalent (where the amount added was calculated assuming that 4 moles of NBL reacted with 1 mole of M1) to the lithium of NBL supplied as a polymerization initiator, and the reaction was carried out to obtain SBR-1.

[0231] <Dispersant> Nonionic dispersant: Sanyo Chemical Industries, Ltd.'s Sannix GL-3000 (polyoxyethylene polyoxypropylene triol)

[0232] <Vulcanization aid> Zinc oxide: Available from Fujifilm Wako Pure Chemical Corporation. Stearic acid: Available from Fujifilm Wako Pure Chemical Corporation.

[0233] <wax> Sunnock: Selected Special Wax (Available from Ouchi Shinko Chemical Co., Ltd.)

[0234] <Anti-aging agent> Nocrack 6C:N-phenyl-N'-(1,3-dimethylbutyl)-p-phenylenediamine (available from Ouchi Shinko Chemical Co., Ltd.)

[0235] <Vulcanization promoter> Noxellar CZ: N-cyclohexyl-2-benzothiazolyl sulfenamide (available from Ouchi Shinko Chemical Co., Ltd.) Noxellar D: 1,3-diphenylguanidine (available from Ouchi Shinko Chemical Co., Ltd.)

[0236] <<Manufacturing of rubber compositions>> <Rubber composition containing the first and second rubbers> [Examples 1-1 to 1-12, Comparative Examples 1-1 to 1-3] To obtain the composition shown in Table 2, 10% by mass of fine cellulose fiber cake, the first rubber, and a dispersant were placed in a 200 ml PP cup, and then mixed using a rotating / revolving mixer (Sinky Co., Ltd., ARE-310) in stirring mode (revolving 2000 rpm, rotating 800 rpm). The resulting mixed cake was vacuum-dried at 50 rpm and 80°C using a planetary mixer (Primix, Hibismix 2P-1) to obtain a dried fine cellulose fiber body. Subsequently, according to the composition shown in Table 2, the dried fine cellulose fiber body and the second rubber were mixed in a sealed kneader (capacity 0.35 L) equipped with a temperature control device, starting with a filling rate of 65% and a device temperature of 120°C. The temperature was raised to 160°C over 10 minutes while adjusting the rotation speed, and then kneaded for a further 5 minutes to obtain a rubber composition. This step was not performed for compositions that did not include the second rubber.

[0237] Comparing Examples 1-1, 1-2, and 1-6, the rubber composition sheets with a high content of fine cellulose fibers tended to have more voids, making them hard and brittle (high elastic modulus and hardness, but quick to break and low puncture strength). Comparing Examples 1-1, 1-3, and 1-5, the rubber composition sheets with a lower fine cellulose fiber content tended to have fewer voids, be softer (lower hardness), and have higher adhesion. Comparing Examples 1-1 and 1-4, the fine cellulose fiber content is almost the same, but the lower weight ratio of dispersant to the second rubber results in a higher degree of chemical bonding and a high-strength sheet. Comparing Examples 1-1 and 1-7, the first rubber had a higher viscosity and a smaller η2 / η1 ratio. This low viscosity ratio made it difficult for the fine cellulose fibers of the second rubber to penetrate between the fibers, resulting in a lower degree of chemical bonding. As a result, the sheet became softer.

[0238] Comparing Examples 1-1 and 1-8, although the η2 / η1 ratio was large, the second rubber was a carboxy-modified liquid polyisoprene, and since the reaction with hydroxyl groups did not occur unless it was dehydrated by heating, the degree of chemical bonding was low. As a result, the sheet became softer. On the other hand, Example 1-9 had a large η2 / η1 ratio similar to Example 1-8, and furthermore, it was a liquid rubber with a high concentration of maleic anhydride groups, resulting in a higher degree of chemical bonding. As a result, the sheet became high strength. Comparing Examples 1-1, 1-10, and 1-11, it is estimated that the reduced fiber diameter of the fine cellulose fibers strengthens the cohesive force of the fine cellulose fibers during drying, making it difficult for the second rubber to penetrate between the fibers, resulting in a lower degree of chemical bonding. Furthermore, fine cellulose fiber B has a high density of carboxyl groups on its surface. It is estimated that the presence of these numerous carboxyl groups reduces the probability of contact between the maleic anhydride groups of the second rubber and the hydroxyl groups of the fine cellulose fibers, and that electrostatic repulsion reduces reactivity, resulting in a lower degree of chemical bonding. It is also estimated that the low degree of chemical bonding is due to the high amount of alkali-soluble polysaccharides contained in fine cellulose fibers B and C, which consume the maleic anhydride and prevent it from directly bonding with the fine cellulose fibers. On the other hand, as mentioned above, the cohesive force of the fine cellulose fibers is strong, and the resulting rubber composition is relatively hard and granular with low tackiness. As a result, the rubber composition sheet has many voids and tends to be brittle, fracturing with low strain. Comparing Example 1-1 with Example 1-12, the viscosity of the first rubber increased, and η2 / η1 became significantly smaller. At this viscosity ratio, the penetration of the second rubber became even more difficult, and the dispersibility of the fine cellulose fibers tended to be low. As a result, the rubber composition sheet tended to have fewer voids, be soft, and have high adhesion. Comparative Example 1-1 did not contain a dispersant, so in the production of the dried fine cellulose fiber, uniform mixing could not be achieved with only the hydrophilic fine cellulose fibers and the hydrophobic first rubber, and the fine cellulose fibers aggregated. As a result, the dispersibility of the fine cellulose fibers was low in the second rubber mixing, and the viscosity of the liquid rubber due to the fine cellulose fibers was insufficient. The sheet of this rubber composition was soft, stretched well, and had high adhesion. Comparative Examples 1-2 did not contain the second rubber, and Comparative Example 1-3 did not contain the first rubber. In both cases, the porosity of the rubber composition sheets was very high.

[0239] [Examples 1-13, Comparative Examples 1-4] According to the composition shown in Table 2, the fine cellulose fiber dry material prepared in the same manner as in Example 1-1 and the second rubber were kneaded in a 0.5 L kneader at a filling rate of 65% and a device temperature of 120°C. The temperature was raised to 160°C over 10 minutes while adjusting the rotation speed, and then kneaded for a further 5 minutes to obtain the rubber composition.

[0240] [Examples 1-14, Comparative Examples 1-5] According to the composition shown in Table 2, the fine cellulose fiber dry material prepared in the same manner as in Example 1-1 and the second rubber were mixed in a 1.6 L Banbury mixer at a filling rate of 65% and a device temperature of 120°C. The mixture was then heated to 160°C over 10 minutes while adjusting the rotation speed, and then mixed for a further 5 minutes to obtain the rubber composition.

[0241] [Examples 1-15] A 10% by mass fine cellulose fiber cake A was placed in a 200 ml PP cup, and then the first rubber and dispersant were added in the proportions shown in Table 2 to prepare an aqueous dispersion with a final composition of 10% by mass fine cellulose fibers. The 200 ml PP cup was placed in a ARE-310 rotary-orbit mixer manufactured by Thinky Co., Ltd., and mixed for 15 minutes in stirring mode (orbit 2000 rpm, rotation 800 rpm). Next, the second rubber was added in the proportions shown in Table 2, and mixed for another 15 minutes in stirring mode (orbit 2000 rpm, rotation 800 rpm). The obtained composition was spread thinly on a release film, dried at 80°C using an ESPEC SPH-201, and then pulverized for 30 seconds using a Labonect MS-05 mini speed mill to obtain a rubber composition. The second rubber compound has maleic anhydride groups, but it is presumed that these groups opened due to water in the fine cellulose fiber cake during mixing in the rotation-orbit mixer, resulting in a low degree of chemical bonding and suppression.

[0242] <Rubber composition (masterbatch) further containing a third rubber> [Examples 1-16 to 1-19] According to the composition shown in Table 2, the rubber composition of Example 1-1 and the third rubber were mixed in a 0.5L kneader at a filling rate of 65% and a device temperature of 120°C. The temperature was raised to 160°C over 10 minutes while adjusting the rotation speed, and then mixed for another 5 minutes to obtain the rubber composition (masterbatch). Furthermore, the degree of chemical bonding was considerably higher compared to Example 1-1. This is presumed to be due to the chemical bonding between the second rubber and the fine cellulose fibers, as well as the third rubber itself undergoing small-scale crosslinking and becoming insoluble during the mixing process.

[0243] <Hardened Rubber - 1> [Examples 2-1 to 2-22, Comparative Examples 2-1 to 2-6] Using a sealed kneader (capacity 0.35L) equipped with a temperature control device, the first stage of kneading involved adding the rubber composition, the fourth type of rubber, zinc oxide, stearic acid, wax, and stabilizer to a filling rate of 65% according to the formulations shown in Tables 4-5, and kneading at 140°C for 3 minutes (resulting in 5 parts by mass of fine cellulose fibers in the cured rubber). Next, in the second stage of kneading, after cooling the resulting mixture to room temperature, it was kneaded again at 140°C for 3 minutes to improve the dispersion of fine cellulose fibers. After cooling, sulfur and vulcanization accelerator were added and kneaded in an open roll set to 70°C, and the mixture was molded into a sheet. Subsequently, the sheet-shaped mixture was vulcanized using a 2.0 mm thick mold at 160°C for 15 minutes in a vulcanization press to obtain a cured rubber sheet. Various evaluations were performed on the obtained cured rubber sheet. The results are shown in Tables 4-5. The reference comparative examples differ for each of the fourth type of rubber, corresponding to Comparative Examples 2-3 to 2-6.

[0244] In Examples 2-1 to 2-14, rubber compositions with a high degree of chemical bonding and low porosity of the sheet tended to exhibit excellent properties of cured rubber. Furthermore, the sheet exhibited excellent properties of cured rubber when its various properties were within an appropriate range. On the other hand, in Comparative Examples 2-1 to 2-3, because neither the dispersant, the first rubber, nor the second rubber was present, the dispersion and orientation of the fine cellulose fibers in the cured rubber was poor, resulting in low performance. Furthermore, in Examples 2-19 to 2-22, although rubber cured products were manufactured from the masterbatch, the third rubber itself underwent small-scale crosslinking and became insoluble, which reduced the dispersibility of the fine cellulose fibers. In addition, the sheets were dense, had low adhesion and high puncture strength, making dispersion and distribution during mixing with the fourth rubber difficult, resulting in a tendency towards low performance.

[0245] <Rubber composition sheet> [Example 3-1, Comparative Example 3-1] A rubber composition sheet was prepared by placing 30g of the rubber composition, as shown in Table 6, on a mold lined with a release sheet, and then press-pressing it under the following conditions. Pressing force: 200kN Pressing time: 10 minutes Press temperature: 70℃ Mold thickness: 2mm Mold size: 10cm x 10cm

[0246] [Examples 3-2 to 3-4] A rubber composition sheet was prepared using the same method as in Example 3-1, except that the weight of the rubber composition was 150g and the mold thickness was 10mm.

[0247] [Comparative Example 3-2] A rubber composition sheet was prepared using the same method as in Example 3-1, except that the press temperature was set to 150°C. While the increased press temperature resulted in a void ratio of 0.5% and a thinner sheet, the liquid rubber partially crosslinked, causing the rubber composition sheet to harden and increasing the cutting stress.

[0248] <Hardened Rubber - 2> [Examples 4-1 to 4-6, Comparative Examples 4-1 to 4-2] Using the method described in Example 2-1, a cured rubber product was obtained using a rubber composition sheet with the composition shown in Table 7 (the fine cellulose fibers in the cured rubber product amounted to 5 parts by mass). Comparative Examples 2-3, 2-5, and 2-6 are the reference comparative examples. In Comparative Example 4-1, the cutting stress and Shore A hardness were low, suggesting that the rubber composition sheet itself was not sufficiently reinforced by fine cellulose fibers, i.e., aggregation of fine cellulose fibers was suspected, resulting in poor properties of the cured rubber product. Furthermore, comparing Example 4-1 and Comparative Example 4-2, the cutting stress increased excessively, leading to a decrease in the properties of the cured rubber product. Although the workability of rubber composite manufacturing was improved by forming the sheet, the sheet manufacturing conditions adversely affected the properties of the cured rubber product.

[0249] [Table 1]

[0250] [Table 2]

[0251] [Table 3]

[0252] [Table 4]

[0253] [Table 5]

[0254] [Table 6]

[0255] [Table 7] [Industrial applicability]

[0256] The rubber composition relating to this disclosure can form molded articles with good physical properties and can therefore be suitably applied to a wide range of applications, such as industrial machine parts, general machine parts, automobile, railway, vehicle, ship, and aerospace-related parts, electronic and electrical components, building and civil engineering materials, household goods, sports and leisure goods, wind turbine housing components, containers and packaging components, etc.

Claims

1. A rubber composition comprising fine cellulose fibers, a first rubber, a second rubber, and a dispersant, A rubber composition in which the first rubber is an unmodified liquid rubber and the second rubber is a modified liquid rubber.

2. The rubber composition according to claim 1, wherein the first rubber comprises aromatic vinyl monomer units.

3. The rubber composition according to claim 1 or 2, wherein the second rubber is maleic anhydride-modified liquid polyisoprene.

4. The rubber composition according to claim 1 or 2, wherein the dispersant is nonionic.

5. The rubber composition according to claim 1 or 2, wherein the weight ratio of the dispersant to the second rubber is 0.01 to 2.

0.

6. The rubber composition according to claim 1 or 2, wherein the puncture strength of a 2 mm thick sheet obtained by press-pressing the rubber composition with a pressing force of 200 kN for a pressing time of 10 minutes at a temperature of 70°C is 0.3 MPa or more and 3.0 MPa.

7. The rubber composition according to claim 1 or 2, wherein the porosity of a 2 mm thick sheet obtained by press-pressing the rubber composition with a pressing force of 200 kN for a pressing time of 10 minutes at a temperature of 70°C is 0.01% or more and 8.0% or less.

8. The rubber composition according to claim 1 or 2, wherein the cohesiveness of a 2 mm thick sheet obtained by press-pressing the rubber composition with a pressing force of 200 kN for a pressing time of 10 minutes at a temperature of 70°C is 10% or more and 60% or less.

9. The adhesion of a 2 mm thick sheet obtained by press-pressing the rubber composition with a pressing force of 200 kN for 10 minutes at a temperature of 70°C is 30 kJ / m². ３ Above, 300kJ / m ３ The rubber composition according to claim 1 or 2, which is as follows:

10. The rubber composition according to claim 1 or 2, further comprising a third rubber.

11. A method for producing the rubber composition according to claim 1 or 2, A first step of mixing fine cellulose fibers and the first rubber to obtain a preliminary composition, and A second step of mixing the aforementioned precomposition with the second rubber, Methods that include...

12. A method for producing the rubber composition according to claim 1 or 2, A first step involves drying a precomposition obtained by mixing fine cellulose fibers with the first rubber to obtain a dried fine cellulose fiber body, and A second step of mixing the dried fine cellulose fiber body with the second rubber, Methods that include...

13. A method for producing the rubber composition according to claim 1 or 2, A first step of mixing the first rubber and the second rubber to obtain a preliminary composition, and A second step of mixing the aforementioned pre-composition with the aforementioned fine cellulose fibers, Methods that include...

14. The method according to claim 11, wherein a third rubber is further mixed in the second step.

15. The method according to claim 11, wherein a third rubber is further mixed after the second step.

16. A rubber composite, which is a compound of the rubber composition according to claim 1 or 2 and a fourth rubber.

17. A cured rubber product, which is a cured product of the rubber composite according to claim 16.

18. A tire comprising the rubber curing product described in claim 17.

19. Vibration-damping rubber comprising the rubber curing product described in claim 17.

20. A shoe outsole comprising the rubber curing product described in claim 17.

21. A conveyor belt comprising the rubber curing material described in claim 17.

22. A rubber composition sheet comprising the rubber composition described in claim 1 or 2.

23. The rubber composition sheet according to claim 22, wherein the breaking stress is 0.1 MPa or more and 20 MPa or less.

24. The rubber composition sheet according to claim 22, wherein the Shore A hardness is 10 to 90.

25. A method for producing a rubber composition sheet according to claim 22, comprising forming a sheet of rubber composition using a powder rolling mill.

26. A method for producing a rubber composition sheet according to claim 22, comprising forming a rubber composition into a sheet using a press molding machine.

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