Master batch for rubber modification and highly branched conjugated diene-based polymer composition

Abstract

To provide a master batch for rubber modification comprising rubber and cellulose nanofibers, which gives a rubber composition having excellent processability and mechanical properties after curing in which the cellulose nanofibers are well dispersed in the rubber and to provide a rubber composition using the same.SOLUTION: In one aspect, there is provided a branched conjugated diene-based polymer composition which comprises a highly branched conjugated diene-based polymer having a shrinkage factor (g') of less than 0.72 as determined by GPC-light scattering measurement using gel permeation chromatography (GPC) with a viscosity detector and cellulose nanofibers. In one aspect, there is provided a master batch for rubber modification which comprises 100 pts.mass of a first rubber component containing 50 mass% or more of a highly branched diene-based polymer having a shrinkage factor (g') of less than 0.72 as determined by GPC-light scattering measurement using gel permeation chromatography (GPC) with a viscosity detector and 15 pts.mass or more and 100 pts.mass or less of cellulose nanofibers.SELECTED DRAWING: None

Description

[Technical field]

[0001] The present invention relates to a masterbatch for rubber modification containing cellulose nanofibers and a rubber composition. [Background technology]

[0002] 2. Description of the Related Art Conventionally, it has been common practice to compound a reinforcing filler such as carbon black or silica into a rubber composition for the purpose of improving the properties of the rubber composition, such as elastic modulus, hardness, mechanical strength, and abrasion resistance.

[0003] In recent years, due to the growing awareness of alternatives to petroleum resources and environmental issues, various techniques have been proposed that utilize cellulosic fibers, which have a low specific gravity and are natural materials, as an alternative to the reinforcing fillers that have been used traditionally.

[0004] It is known that compounding a rubber composition with cellulose nanofibers as a filler can reinforce the rubber composition and improve its hardness and tensile modulus (for example, Patent Document 1 and Patent Document 2).

[0005] In this way, cellulose nanofibers function as a reinforcing filler for rubber and can provide high-strength, lightweight, and thin-walled rubber molded articles, and therefore are attracting attention as a reinforcing filler to replace carbon black and silica.

[0006] For example, Patent Document 3 describes a masterbatch composition of a styrene-butadiene copolymer and cellulose nanofibers for the purpose of providing a rubber composition for tires that can improve tensile properties and fuel economy.

[0007] The above-mentioned Patent Document 1 describes a rubber composition of high molecular weight styrene-butadiene rubber and short cellulose fibers for the purpose of providing a rubber composition for tires that can improve the balance between the dry grip performance and abrasion resistance of tires. [Prior art documents] [Patent documents]

[0008] [Patent Document 1] JP 2017-2148 A [Patent Document 2] Patent Publication No. 2021-191841 [Patent Document 3] JP 2020-41076 A Summary of the Invention [Problem to be solved by the invention]

[0009] However, conventionally proposed rubber compositions containing a rubber component and cellulose nanofibers have problems in that the dispersibility of the cellulose nanofibers and the mechanical strength tend to be poor.

[0010] The present invention aims to solve the above problems and provide a rubber modification masterbatch containing rubber and cellulose nanofibers, which allows the cellulose nanofibers to be well dispersed in the rubber and gives a rubber composition having excellent processability and mechanical properties after curing, and a rubber composition using the same. [Means for solving the problem]

[0011] The present invention encompasses the following items. [Item 1] A highly branched conjugated diene-based polymer having a shrinkage factor (g') of less than 0.72 as determined by gel permeation chromatography (GPC)-light scattering measurement using a gel permeation chromatography (GPC) equipped with a viscometer; Cellulose nanofibers, A highly branched conjugated diene-based polymer composition comprising: [Item 2] 100 parts by mass of a first rubber component containing 50% by mass or more of a highly branched conjugated diene polymer having a shrinkage factor (g') of less than 0.72 as determined by gel permeation chromatography (GPC)-light scattering measurement using a viscometer; 15 parts by mass or more and 100 parts by mass or less of cellulose nanofiber; A masterbatch for rubber modification comprising: [Item 3] 3. The rubber modifying masterbatch according to item 2, wherein the highly branched conjugated diene polymer has a weight average molecular weight of 200,000 or more and 2,000,000 or less. [Item 4] 4. The rubber-modifying masterbatch according to item 2 or 3, wherein the highly branched conjugated diene-based polymer contains 3% by mass or more and 60% by mass or less of an aromatic vinyl monomer unit. [Item 5] 5. The rubber modifying masterbatch according to any one of items 2 to 4, wherein the cellulose nanofibers have no ionic groups. [Item 6] 6. The rubber modification masterbatch according to any one of items 2 to 5, further comprising a surfactant. [Item 7] Item 7. The rubber modifying masterbatch according to item 6, wherein the surfactant is a nonionic surfactant. [Item 8] Item 8. The rubber modification masterbatch according to item 7, wherein the nonionic surfactant is a compound having a hydrophilic group selected from the group consisting of a hydroxyl group, a carboxyl group, a sulfonic acid group, and an amino group, and a hydrocarbon group. [Item 9] The nonionic surfactant is represented by the following general formula (1): R-(OCH2CH2)m-OH (1) [wherein R represents a monovalent aliphatic group having 6 to 30 carbon atoms, and m is a natural number smaller than the number of carbon atoms of R], and a compound represented by the following general formula (2): R 1 OCH2-(CHOH)4-CH2OR 2 (2) [In the formula, R 1 and R 2 each independently represents a hydrogen atom, an aliphatic group having 1 to 30 carbon atoms, -COR 3 {where, R 3 represents an aliphatic group having 1 to 30 carbon atoms.}, or -(CH2CH2O)yR 4 {where, R 4represents a hydrogen atom or an aliphatic group having 1 to 30 carbon atoms, and y is an integer of 1 to 30.}. 8. The rubber modifying masterbatch according to item 7, wherein the masterbatch is one or more selected from the group consisting of: [Item 10] 10. The rubber modification masterbatch according to any one of items 6 to 9, further comprising a liquid rubber. [Item 11] Item 11. The rubber modification masterbatch according to item 10, wherein the liquid rubber has a number average molecular weight of 1,000 to 80,000. [Item 12] Item 12. The rubber modification masterbatch according to item 10 or 11, wherein the ratio (Mw / Mn) of the number average molecular weight (Mn) to the weight average molecular weight (Mw) of the liquid rubber is 1.5 to 5. [Item 13] 13. The rubber modification masterbatch according to any one of items 10 to 12, wherein the liquid rubber comprises at least one selected from the group consisting of diene rubber, silicone rubber, urethane rubber, polysulfide rubber, and hydrogenated products thereof. [Item 14] Item 14. The rubber modification masterbatch according to any one of Items 10 to 13, wherein the liquid rubber comprises a modified liquid rubber modified with an unsaturated carboxylic acid and / or a derivative thereof. [Item 15] Item 15. The rubber modification masterbatch according to item 14, comprising 10 parts by mass or more and 200 parts by mass or less of the modified liquid rubber per 100 parts by mass of the first rubber component. [Item 16] 16. A highly branched conjugated diene polymer composition, which is a kneaded product containing the rubber modification masterbatch according to any one of items 2 to 15 and a second rubber component. [Item 17] Item 17. The highly branched conjugated diene-based polymer composition according to item 16, comprising 1 part by mass or more and 15 parts by mass or less of cellulose nanofibers per 100 parts by mass in total of the first rubber component and the second rubber component. [Item 18] Item 18. The highly branched conjugated diene-based polymer composition according to item 16 or 17, comprising 10 parts by mass or more and 80 parts by mass or less of a reinforcing filler relative to 100 parts by mass in total of the first rubber component and the second rubber component. [Item 19] 19. The highly branched conjugated diene-based polymer composition according to any one of items 16 to 18, comprising a modified liquid rubber modified with an unsaturated carboxylic acid and / or a derivative thereof. [Item 20] 20. The highly branched conjugated diene-based polymer composition according to item 19, comprising 1 part by mass or more and 25 parts by mass or less of the modified liquid rubber per 100 parts by mass in total of the first rubber component and the second rubber component. [Item 21] 21. A cured highly branched conjugated diene polymer, which is a cured highly branched conjugated diene polymer composition according to any one of items 16 to 20. [Item 22] 100 parts by mass of a rubber component containing 50% by mass or more of a highly branched conjugated diene polymer having a shrinkage factor (g') of less than 0.72 as determined by gel permeation chromatography (GPC)-light scattering measurement using a viscometer; 1 part by mass or more and 15 parts by mass or less of cellulose nanofiber; A highly branched conjugated diene-based polymer composition comprising: [Item 23] 23. The highly branched conjugated diene polymer composition according to item 22, wherein the highly branched conjugated diene polymer has a weight average molecular weight of 200,000 or more and 2,000,000 or less. [Item 24] 24. The highly branched conjugated diene polymer composition according to item 22 or 23, wherein the highly branched conjugated diene polymer contains 3% by mass or more and 60% by mass or less of an aromatic vinyl monomer unit. [Item 25] 25. The highly branched conjugated diene-based polymer composition according to any one of items 22 to 24, wherein the cellulose nanofibers have no ionic groups. [Item 26] 26. The highly branched conjugated diene polymer composition according to any one of items 22 to 25, further comprising a surfactant. [Item 27] 27. The highly branched conjugated diene-based polymer composition according to Item 26, wherein the surfactant is a nonionic surfactant. [Item 28] 28. The highly branched conjugated diene-based polymer composition according to item 27, wherein the nonionic surfactant is a compound having a hydrophilic group selected from the group consisting of a hydroxyl group, a carboxyl group, a sulfonic acid group, and an amino group, and a hydrocarbon group. [Item 29] The nonionic surfactant is represented by the following general formula (1): R-(OCH2CH2) m -OH (1) [wherein R represents a monovalent aliphatic group having 6 to 30 carbon atoms, and m is a natural number smaller than the number of carbon atoms of R], and a compound represented by the following general formula (2): R 1 OCH2-(CHOH)4-CH2OR 2 (2) [In the formula, R1 and R2 each independently represent a hydrogen atom, an aliphatic group having 1 to 30 carbon atoms, -COR 3 {where, R 3 represents an aliphatic group having 1 to 30 carbon atoms.}, or -(CH2CH2O)yR 4 {where, R 4 represents a hydrogen atom or an aliphatic group having 1 to 30 carbon atoms, and y is an integer of 1 to 30.}. 29. The highly branched conjugated diene-based polymer composition according to item 27 or 28, wherein the highly branched conjugated diene-based polymer composition is one or more selected from the group consisting of: [Item 30] 30. The highly branched conjugated diene polymer composition according to any one of items 26 to 29, wherein the highly branched conjugated diene polymer composition further contains a liquid rubber. [Item 31] 31. The highly branched conjugated diene polymer composition according to item 30, wherein the liquid rubber has a number average molecular weight of 1,000 to 80,000. [Item 32] Item 32. The highly branched conjugated diene-based polymer composition according to item 30 or 31, wherein the ratio (Mw / Mn) of the number average molecular weight (Mn) to the weight average molecular weight (Mw) of the liquid rubber is 1.5 to 5. [Item 33] 33. The highly branched conjugated diene polymer composition according to any one of items 30 to 32, wherein the liquid rubber comprises at least one selected from the group consisting of diene rubber, silicone rubber, urethane rubber, polysulfide rubber, and hydrogenated products thereof. [Item 34] 34. The highly branched conjugated diene-based polymer composition according to any one of items 30 to 33, wherein the liquid rubber comprises a modified liquid rubber modified with an unsaturated carboxylic acid and / or a derivative thereof. [Item 35] Item 35. The highly branched conjugated diene-based polymer composition according to item 34, comprising 1 part by mass or more and 25 parts by mass or less of the modified liquid rubber per 100 parts by mass of the rubber component. [Item 36] 36. The highly branched conjugated diene polymer composition according to any one of items 22 to 35, comprising 10 parts by mass or more and 80 parts by mass or less of a reinforcing filler per 100 parts by mass of the rubber component. [Item 37] 37. A cured highly branched conjugated diene polymer, which is a cured highly branched conjugated diene polymer composition according to any one of items 22 to 36. [Item 38] A method for producing a rubber modification masterbatch according to any one of items 6 to 15, Preparing a cellulose nanofiber composition comprising cellulose nanofibers and a surfactant; and mixing the cellulose nanofiber composition with a first rubber component containing a highly branched conjugated diene-based polymer; A method comprising: [Item 39] A method for producing a rubber modification masterbatch according to any one of items 10 to 15, A step of preparing a cellulose nanofiber composition containing cellulose nanofibers, a liquid rubber, and a surfactant; and mixing the cellulose nanofiber composition with a first rubber component containing a highly branched conjugated diene-based polymer; A method comprising: [Item 40] 40. The method of claim 38 or 39, wherein the cellulose nanofiber composition is a powder. [Item 41] A method for producing the highly branched conjugated diene polymer composition according to any one of items 26 to 36, comprising: A step of preparing a cellulose nanofiber composition containing cellulose nanofibers and a surfactant; A step of mixing the cellulose nanofiber composition with a first rubber component containing a highly branched conjugated diene polymer to prepare a master batch for rubber modification; and A step of mixing the rubber modifying masterbatch with a second rubber component to prepare a highly branched conjugated diene polymer composition; A method comprising: [Item 42] A method for producing the highly branched conjugated diene polymer composition according to any one of items 30 to 36, comprising: A step of preparing a cellulose nanofiber composition containing cellulose nanofibers, a liquid rubber, and a surfactant; A step of mixing the cellulose nanofiber composition with a first rubber component containing a highly branched conjugated diene polymer to prepare a master batch for rubber modification; and A step of mixing the rubber modifying masterbatch with a second rubber component to prepare a highly branched conjugated diene polymer composition; A method comprising: [Item 43] Item 43. The method of item 41 or 42, wherein the cellulose nanofiber composition is a powder. Effect of the Invention

[0012] According to one aspect of the present invention, it is possible to provide a rubber modification masterbatch containing rubber and cellulose nanofibers, which allows the cellulose nanofibers to be well dispersed in the rubber, resulting in a rubber composition having excellent processability and mechanical properties after curing, and a rubber composition using the same. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0013] Hereinafter, an embodiment for carrying out the present invention (hereinafter, referred to as "the present embodiment") will be described in detail. Note that the present embodiment is an example for explaining the present invention, and the present invention is not limited to the following embodiment. The present invention can be carried out by appropriately modifying it within the scope of its gist.

[0014] One aspect of the present invention provides a masterbatch for rubber modification, comprising a highly branched conjugated diene polymer and a cellulose nanofiber. Another aspect of the present invention provides a highly branched conjugated diene polymer composition (also referred to as a rubber composition in the present disclosure) comprising a highly branched conjugated diene polymer and a cellulose nanofiber.

[0015] In one embodiment, the rubber modification masterbatch includes 100 parts by mass of a rubber component (also referred to as the first rubber component in the present disclosure) containing 50% by mass or more of a highly branched conjugated diene polymer, and 15 parts by mass or more and 100 parts by mass or less of cellulose nanofibers.

[0016] In one embodiment, the highly branched conjugated diene polymer composition is a mixture, more specifically a kneaded product, containing the rubber modifying masterbatch of the present embodiment and a second rubber component.

[0017] In one embodiment, the highly branched conjugated diene-based polymer is a polymer having a shrinkage factor (g') of less than 0.72 as determined by gel permeation chromatography (GPC)-light scattering measurement using a viscometer equipped with a gel permeation chromatography (GPC).

[0018] In one embodiment, the highly branched conjugated diene polymer composition includes 100 parts by mass of a rubber component (in one embodiment, the total of a first rubber component and a second rubber component) containing 50% by mass or more of a highly branched conjugated diene polymer, and 1 part by mass or more and 15 parts by mass or less of a cellulose nanofiber.

[0019] In the rubber composition of this embodiment, particularly in the highly branched conjugated diene polymer composition obtained by kneading the rubber modification master batch with the second rubber component, the cellulose nanofibers are well dispersed in the rubber composition, thereby exhibiting a good reinforcing effect. The cured product of the rubber composition of this embodiment has a high tensile modulus and elastic modulus due to the contribution of the highly branched conjugated diene polymer. That is, by curing the rubber composition of this embodiment, a cured product with high strength, high elastic modulus, and high abrasion resistance can be obtained.

[0020] Hereinafter, each component of the rubber modifying masterbatch and the highly branched conjugated diene polymer composition of the present embodiment will be described in detail. The second rubber component to be combined with the rubber modifying masterbatch in the production of the rubber composition may be the same or different from the first rubber component in the rubber modifying masterbatch.

[0021] <Cellulose nanofiber> As the raw material of cellulose nanofiber, natural cellulose and regenerated cellulose can be used. As the natural cellulose, wood pulp obtained from wood species (broadleaf or coniferous), non-wood pulp obtained from non-wood species (cotton, bamboo, hemp, bagasse, kenaf, cotton linters, sisal, straw, etc.), cellulose aggregates produced by animals (e.g., ascidians), algae or microorganisms (e.g., acetic bacteria), etc. can be used. As the regenerated cellulose, regenerated cellulose fibers (viscose, cupra, tencel, etc.), cellulose derivative fibers, regenerated cellulose or cellulose derivative ultrafine threads obtained by electrospinning, etc. can be used.

[0022] The cellulose nanofiber refers to fine cellulose fibers that are mechanically defibrated by a grinding method such as a high-pressure homogenizer, a microfluidizer, a ball mill, a disk mill, or a mixer (e.g., a homomixer) after treating a cellulose raw material such as pulp with hot water at 100°C or higher to hydrolyze and weaken the hemicellulose. In one embodiment, the cellulose nanofiber has a number average fiber diameter of 1 nm or more and 1000 nm or less. The cellulose nanofiber may be chemically modified as described below, but in terms of the reinforcing effect as a filler, it is preferable to use a non-chemically modified cellulose nanofiber. For example, cellulose nanofibers that have been defibrated by chemical oxidation treatment using 2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPO) phosphate ester or the like tend to have low heat resistance due to the ionic groups (e.g., carboxyl groups) introduced into the cellulose nanofibers, and also tend to have a small fiber diameter after defibration. In terms of the reinforcing effect as a filler, cellulose nanofibers that have been defibrated only mechanically (i.e., have not been subjected to chemical defibration treatment such as oxidation) are more advantageous. Therefore, in a preferred embodiment, the cellulose nanofibers have no ionic groups. In this disclosure, the cellulose nanofibers have no ionic groups means that the amount of ionic groups measured by conductometric titration is 0.1 mmol / g or less.

[0023] The slurry can be prepared by dispersing the cellulose fibers in a liquid medium. The dispersion of the cellulose fibers in the slurry can be carried out using a high-pressure homogenizer, a microfluidizer, a ball mill, a disk mill, a mixer (e.g., a homomixer), or the like, and the product of the defibration can be obtained as the product of the slurry preparation process of the present disclosure. The liquid medium in the slurry can further include water, and optionally, a liquid medium other than water (e.g., an organic solvent) in one or more combinations. Examples of the organic solvent include commonly used water-miscible organic solvents, such as alcohols having a boiling point of 50° C. to 170° C. (e.g., methanol, ethanol, n-propanol, i-propanol, n-butanol, i-butanol, s-butanol, t-butanol, etc.); ethers (e.g., propylene glycol monomethyl ether, 1,2-dimethoxyethane, diisopropyl ether, tetrahydrofuran, 1,4-dioxane, etc.); carboxylic acids (e.g., formic acid, acetic acid, lactic acid, etc.); esters (e.g., ethyl acetate, vinyl acetate, etc.); ketones (e.g., acetone, methyl ethyl ketone, methyl isobutyl ketone, cyclopentanone, cyclohexanone, etc.); and nitrogen-containing solvents (e.g., dimethylformamide, dimethylacetamide, acetonitrile, etc.). In a typical embodiment, the liquid medium in the slurry is substantially water alone.

[0024] Since the cellulose raw material contains alkali soluble matter and sulfuric acid insoluble matter (lignin, etc.), the alkali soluble matter and sulfuric acid insoluble matter may be reduced through a refining process such as delignification by cooking, and a bleaching process. On the other hand, the refining process such as delignification by cooking, and the bleaching process cut the molecular chains of cellulose, changing the weight average molecular weight and number average molecular weight, so it is desirable to control the refining process and bleaching process of the cellulose raw material so that the weight average molecular weight of the cellulose nanofiber and the ratio of the weight average molecular weight to the number average molecular weight are within an appropriate range.

[0025] In addition, refining processes such as delignification by cooking and bleaching processes reduce the molecular weight of cellulose molecules, and there is concern that these processes will result in lower molecular weight cellulose nanofibers and alter the cellulose raw material, increasing the proportion of alkali-soluble matter. Because alkali-soluble matter has poor heat resistance, it is desirable to control the refining and bleaching processes of the cellulose raw material so that the amount of alkali-soluble matter contained in the cellulose raw material is within a certain range or less.

[0026] In one aspect, the number average fiber diameter of the cellulose nanofibers is 1 to 1000 nm, and from the viewpoint of obtaining a good effect of improving physical properties by the cellulose nanofibers, is preferably 2 to 1000 nm. The number average fiber diameter of the cellulose nanofibers is more preferably 4 nm or more, or 5 nm or more, or 10 nm or more, or 15 nm or more, or 20 nm or more, and more preferably 500 nm or less, or 450 nm or less, or 400 nm or less, or 350 nm or less, or 300 nm or less, or 250 nm or less.

[0027] From the viewpoint of satisfactorily improving the mechanical properties of a rubber composition containing cellulose nanofibers with a small amount of cellulose nanofibers, the fiber length (L) / fiber diameter (D) ratio of the cellulose nanofibers is preferably 30 or more, or 50 or more, or 80 or more, or 100 or more, or 120 or more, or 150 or more. There is no particular upper limit, but from the viewpoint of handleability, it is preferably 5,000 or less.

[0028] In the present disclosure, the fiber length, fiber diameter, and L / D ratio of the cellulose nanofibers are determined by dispersing an aqueous dispersion of cellulose nanofibers using a high-shear homogenizer (e.g., Nippon Seiki Co., Ltd., product name "Excel Auto Homogenizer ED-7") under processing conditions: rotation speed 15,000 rpm × 5 minutes, diluting the aqueous dispersion with pure water to 0.1 to 0.5 mass%, casting it on mica, and air-drying it to obtain a measurement sample, and measuring it with a scanning electron microscope (SEM) or atomic force microscope (AFM). Specifically, the length (L) and diameter (D) of 100 randomly selected cellulose nanofibers are measured in an observation field where the magnification is adjusted so that at least 100 cellulose nanofibers are observed, and the ratio (L / D) is calculated. The number average value of the fiber length (L), the number average value of the fiber diameter (D), and the number average value of the ratio (L / D) are calculated for the cellulose nanofibers.

[0029] Alternatively, the fiber length, fiber diameter, and L / D ratio of the cellulose nanofibers in the rubber composition can be confirmed by measuring these as a measurement sample using the above-mentioned measurement method.

[0030] Alternatively, the fiber length, fiber diameter, and L / D ratio of the cellulose nanofibers contained in the rubber modification master batch, rubber composition, etc. can be confirmed by dissolving the polymer components contained therein in an organic or inorganic solvent capable of dissolving the polymer components, separating the cellulose nanofibers, thoroughly washing with the solvent, and then replacing the solvent with pure water to prepare an aqueous dispersion, diluting the cellulose nanofiber concentration to 0.1 to 0.5% by mass with pure water, casting on mica, and air-drying the resulting sample to be measured using the above-mentioned measurement method. At this time, the measurement is performed on 100 or more randomly selected cellulose nanofibers.

[0031] The crystallinity of the cellulose nanofibers is preferably 55% or more. When the crystallinity is in this range, the mechanical properties (strength, dimensional stability) of the cellulose itself are high, so that when the cellulose nanofibers are dispersed in rubber, the strength and dimensional stability of the rubber composition tend to be high. A more preferable lower limit of the crystallinity is 60%, even more preferably 70%, and most preferably 80%. There is no particular upper limit for the crystallinity of the cellulose nanofibers, and the higher the better, but from the viewpoint of production, a preferable upper limit is 99%.

[0032] Alkali-soluble polysaccharides such as hemicellulose and acid-insoluble components such as lignin are present between the microfibrils and between the microfibril bundles of plant-derived cellulose nanofibers. Hemicellulose is a polysaccharide composed of sugars such as mannan and xylan, and plays a role in binding the microfibrils together by hydrogen bonding with cellulose. Lignin is also a compound having an aromatic ring, and is known to be covalently bonded to hemicellulose in the cell walls of plants. If there is a large amount of impurities such as lignin remaining in the cellulose nanofibers, discoloration may occur due to heat during processing. Therefore, from the viewpoint of suppressing discoloration of the rubber composition during extrusion processing and molding processing, it is desirable to set the crystallinity of the cellulose nanofibers within the above-mentioned range.

[0033] The degree of crystallinity here, when the cellulose is cellulose type I crystal (derived from natural cellulose), is calculated from the diffraction pattern (2θ / deg. is 10 to 30) obtained by measuring a sample by wide-angle X-ray diffraction using the Segal method, according to the following formula: Crystallinity (%) = ([diffraction intensity due to the (200) plane at 2θ / deg. = 22.5] - [diffraction intensity due to amorphous matter at 2θ / deg. = 18]) / [diffraction intensity due to the (200) plane at 2θ / deg. = 22.5] × 100 When the cellulose is cellulose II type crystal (derived from regenerated cellulose), the degree of crystallinity can be calculated from the absolute peak intensity h0 at 2θ=12.6° assigned to the (110) plane peak of cellulose II type crystal in wide-angle X-ray diffraction and the peak intensity h1 from the baseline at this interplanar spacing, according to the following formula: Crystallinity (%) =h1 / h0 ×100 Known cellulose crystal forms include type I, type II, type III, and type IV, of which types I and II are particularly widely used, and types III and IV have been obtained on a laboratory scale but are not widely used on an industrial scale. The cellulose nanofibers of the present disclosure are preferably cellulose nanofibers containing cellulose type I crystals or cellulose type II crystals, since they have relatively high structural mobility and, by dispersing the cellulose nanofibers in rubber, can provide molded articles with a lower linear expansion coefficient and superior strength and elongation during tensile and bending deformation, and more preferably cellulose nanofibers containing cellulose type I crystals and having a crystallinity of 55% or more.

[0034] In addition, the degree of polymerization of the cellulose nanofiber is preferably 100 or more, more preferably 150 or more, more preferably 200 or more, more preferably 300 or more, more preferably 400 or more, more preferably 450 or more, and preferably 3500 or less, more preferably 3300 or less, more preferably 3200 or less, more preferably 3100 or less, and more preferably 3000 or less.

[0035] From the viewpoint of processability and mechanical property expression, it is desirable that the degree of polymerization of the cellulose nanofiber is within the above-mentioned range. From the viewpoint of processability, it is preferable that the degree of polymerization is not too high, and from the viewpoint of mechanical property expression, it is desirable that the degree of polymerization is not too low.

[0036] The degree of polymerization of cellulose nanofibers refers to the average degree of polymerization measured according to the reduced specific viscosity method using a copper ethylenediamine solution described in the Verification Test (3) of the "15th Revised Japanese Pharmacopoeia Commentary (published by Hirokawa Shoten)."

[0037] In one embodiment, the weight average molecular weight (Mw) of the cellulose nanofiber is 100,000 or more, more preferably 200,000 or more. The ratio (Mw / Mn) of the weight average molecular weight to the number average molecular weight (Mn) is 6 or less, preferably 5.4 or less. The larger the weight average molecular weight, the fewer the number of terminal groups of the cellulose molecule. In addition, since the ratio (Mw / Mn) of the weight average molecular weight to the number average molecular weight represents the width of the molecular weight distribution, the smaller the Mw / Mn, the fewer the number of terminals of the cellulose molecule. Since the terminals of the cellulose molecules are the starting points of thermal decomposition, when the cellulose molecules of the cellulose nanofibers not only have a large weight average molecular weight but also have a narrow molecular weight distribution, a cellulose nanofiber with particularly high heat resistance and a rubber composition containing the cellulose nanofiber and rubber can be obtained. The weight average molecular weight (Mw) of the cellulose nanofiber may be, for example, 600,000 or less, or 500,000 or less, from the viewpoint of the availability of the cellulose raw material. From the viewpoint of ease of production of cellulose nanofibers, the ratio (Mw / Mn) of weight average molecular weight to number average molecular weight (Mn) may be, for example, 1.5 or more, or 2 or more. Mw can be controlled to the above range by selecting a cellulose raw material having an Mw appropriate for the purpose, by appropriately performing physical and / or chemical treatment on the cellulose raw material within an appropriate range, etc. Mw / Mn can also be controlled to the above range by selecting a cellulose raw material having an Mw / Mn appropriate for the purpose, by appropriately performing physical and / or chemical treatment on the cellulose raw material within an appropriate range, etc. Each of the Mw and Mw / Mn of the cellulose raw material may be within the above range in one embodiment. In both the control of Mw and the control of Mw / Mn, examples of the physical treatment include dry or wet grinding using a microfluidizer, ball mill, disk mill, or the like, and physical treatments that apply mechanical forces such as impact, shear, friction, and the like using a crusher, homomixer, high-pressure homogenizer, ultrasonic device, or the like, and examples of the chemical treatment include digestion, bleaching, acid treatment, and conversion to regenerated cellulose.

[0038] The weight average molecular weight and number average molecular weight of the cellulose nanofiber referred to here are values ​​obtained by dissolving the cellulose nanofiber in N,N-dimethylacetamide containing added lithium chloride and then performing gel permeation chromatography using N,N-dimethylacetamide as a solvent.

[0039] Methods for controlling the degree of polymerization (i.e., average degree of polymerization) or molecular weight of cellulose nanofibers include hydrolysis. Hydrolysis promotes depolymerization of amorphous cellulose inside the cellulose nanofibers, decreasing the average degree of polymerization. At the same time, hydrolysis removes impurities such as hemicellulose and lignin in addition to the above-mentioned amorphous cellulose, making the inside of the fiber more porous.

[0040] The hydrolysis method is not particularly limited, and examples thereof include acid hydrolysis, alkali hydrolysis, hydrothermal decomposition, steam explosion, and microwave decomposition. These methods may be used alone or in combination of two or more. In the acid hydrolysis method, for example, α-cellulose obtained as pulp from a fibrous plant is used as a cellulose raw material, and this is dispersed in an aqueous medium, and an appropriate amount of a protonic acid, a carboxylic acid, a Lewis acid, a heteropoly acid, etc. is added, and the mixture is heated while stirring, so that the average degree of polymerization can be easily controlled. The reaction conditions such as temperature, pressure, and time at this time vary depending on the cellulose type, cellulose concentration, acid type, acid concentration, etc., but are appropriately adjusted so that the desired average degree of polymerization is achieved. For example, a condition in which a mineral acid aqueous solution of 2% by mass or less is used and cellulose nanofibers are treated at 100°C or higher under pressure for 10 minutes or more can be mentioned. Under these conditions, the catalyst component such as acid penetrates into the inside of the cellulose nanofibers, promoting hydrolysis, reducing the amount of catalyst component used, and making subsequent purification easier. The dispersion of the cellulose raw material during hydrolysis may contain, in addition to water, a small amount of an organic solvent within a range that does not impair the effects of the present invention.

[0041] Alkali-soluble polysaccharides that may be contained in cellulose nanofibers include hemicellulose, β-cellulose, and γ-cellulose. Alkali-soluble polysaccharides are understood by those skilled in the art as components obtained as the alkali-soluble portion of holocellulose obtained by solvent extraction and chlorine treatment of plants (e.g., wood) (i.e., components obtained by removing α-cellulose from holocellulose). Alkali-soluble polysaccharides are polysaccharides containing hydroxyl groups and have poor heat resistance, and may cause inconveniences such as decomposition when exposed to heat, yellowing during thermal aging, and a decrease in strength of cellulose nanofibers. Therefore, it is preferable that the content of alkali-soluble polysaccharides in cellulose nanofibers is low.

[0042] In one aspect, the average content of alkali-soluble polysaccharides in the cellulose nanofibers is preferably 20% by mass or less, 18% by mass or less, 15% by mass or less, or 12% by mass or less, relative to 100% by mass of the cellulose nanofibers, from the viewpoint of obtaining good dispersibility of the cellulose nanofibers. From the viewpoint of ease of production of the cellulose nanofibers, the above content may be 1% by mass or more, 2% by mass or more, or 3% by mass or more.

[0043] The average alkali-soluble polysaccharide content can be determined by the method described in the non-patent literature (Wood Science Experiment Manual, edited by the Japan Wood Research Society, pages 92-97, 2000), by subtracting the α-cellulose content from the holocellulose content (Wise method). This method is understood in the industry as a method for measuring the amount of hemicellulose. The alkali-soluble polysaccharide content is calculated three times for each sample, and the number average of the calculated alkali-soluble polysaccharide contents is taken as the average alkali-soluble polysaccharide content.

[0044] In one aspect, the average content of acid-insoluble components in the cellulose nanofibers is preferably 10% by mass or less, 5% by mass or less, or 3% by mass or less, relative to 100% by mass of the cellulose nanofibers, from the viewpoint of avoiding a decrease in heat resistance of the cellulose nanofibers and the associated discoloration. From the viewpoint of ease of production of the cellulose nanofibers, the above content may be 0.1% by mass or more, 0.2% by mass or more, or 0.3% by mass or more.

[0045] The average acid-insoluble content is determined as a quantitative determination of the acid-insoluble content using the Clason method described in the non-patent literature (Wood Science Experiment Manual, edited by the Japan Wood Research Society, pages 92-97, 2000). This method is understood in the industry as a method for measuring the amount of lignin. The sample is stirred in a sulfuric acid solution to dissolve cellulose, hemicellulose, etc., and then filtered through a glass fiber filter paper, and the resulting residue corresponds to the acid-insoluble content. The acid-insoluble content is calculated from the weight of the acid-insoluble content, and the number average of the acid-insoluble content calculated for the three samples is taken as the average acid-insoluble content.

[0046] The thermal decomposition temperature of cellulose nanofiber (T D ) is 270° C. or higher in one embodiment, from the viewpoint of being able to exhibit the heat resistance and mechanical strength desired for in-vehicle applications and the like, preferably 275° C. or higher, more preferably 280° C. or higher, and even more preferably 285° C. or higher. The higher the thermal decomposition onset temperature, the more preferable it is, but from the viewpoint of ease of production of cellulose nanofibers, it may be, for example, 320° C. or lower, or 300° C. or lower.

[0047] In this disclosure, T D is a value obtained from a graph in which the horizontal axis is temperature and the vertical axis is the weight residual rate % in thermogravimetry (TG) analysis. Starting from the weight of cellulose nanofiber at 150°C (a state in which most of the moisture has been removed) (weight loss of 0 wt%), the temperature is continued to be increased until the temperature at which the weight loss reaches 1 wt% (T 1% ) and the temperature at which the weight loss reaches 2 wt% (T 2%) is obtained. The temperature at the point where this line intersects with the horizontal line (baseline) that passes through the starting point of 0 wt% weight loss is defined as TD.

[0048] 1% weight loss temperature (T 1% ) is the above T D This is the temperature at which the weight loss reaches 1% by weight, starting from the weight at 150°C, when the temperature is continued to be increased using the method described above.

[0049] Weight loss rate of cellulose nanofiber at 250°C (T 250℃ ) is the weight loss rate when cellulose nanofibers were kept at 250°C under nitrogen flow for 2 hours in TG analysis.

[0050] (chemical modification) The cellulose nanofibers may be chemically modified cellulose nanofibers. The cellulose nanofibers may be chemically modified in advance, for example, at the stage of raw pulp or linters, during or after the defibration treatment, or during or after the slurry preparation process, or during or after the drying (granulation) process.

[0051] As a modifying agent for cellulose nanofibers, a compound that reacts with the hydroxyl groups of cellulose can be used, and examples of such agents include esterifying agents, etherifying agents, and silylation agents. On the other hand, modifying agents having polar groups, such as carboxylic acids and phosphoric esters, tend to reduce the heat resistance of cellulose nanofibers by introducing ionic groups (e.g., carboxyl groups) into the cellulose nanofibers, and also tend to reduce the fiber diameter after defibration, so it is preferable not to use such agents from the viewpoint of the reinforcing effect as a filler. In a preferred embodiment, the chemical modification is acylation using an esterifying agent, and acetylation is particularly preferred. As the esterifying agent, acid halides, acid anhydrides, vinyl carboxylates, and carboxylic acids are preferred.

[0052] The acid halide may be at least one selected from the group consisting of compounds represented by the following formula:

[0053] R 1 -C(=O)-X (In the formula, R 1 represents an alkyl group having 1 to 24 carbon atoms, an alkenyl group having 2 to 24 carbon atoms, a cycloalkyl group having 3 to 24 carbon atoms, or an aryl group having 6 to 24 carbon atoms, and X is Cl, Br, or I. Specific examples of acid halides include, but are not limited to, acetyl chloride, acetyl bromide, acetyl iodide, propionyl chloride, propionyl bromide, propionyl iodide, butyryl chloride, butyryl bromide, butyryl iodide, benzoyl chloride, benzoyl bromide, and benzoyl iodide. Among them, acid chlorides can be preferably used in terms of reactivity and handling. In addition, in the reaction of acid halides, one or more alkaline compounds may be added to act as a catalyst and neutralize the by-product acidic substances. Specific examples of alkaline compounds include, but are not limited to, tertiary amine compounds such as triethylamine and trimethylamine; and nitrogen-containing aromatic compounds such as pyridine and dimethylaminopyridine.

[0054] As the acid anhydride, any suitable acid anhydride can be used, for example, anhydrides of saturated aliphatic monocarboxylic acids such as acetic acid, propionic acid, (iso)butyric acid, valeric acid, etc.; anhydrides of unsaturated aliphatic monocarboxylic acids such as (meth)acrylic acid, oleic acid, etc.; anhydrides of alicyclic monocarboxylic acids such as cyclohexanecarboxylic acid, tetrahydrobenzoic acid, etc.; anhydrides of aromatic monocarboxylic acids such as benzoic acid, 4-methylbenzoic acid, etc.; Examples of dibasic carboxylic acid anhydrides include anhydrides of saturated aliphatic dicarboxylic acids such as succinic acid and adipic acid; unsaturated aliphatic dicarboxylic acid anhydrides such as maleic anhydride and itaconic anhydride; alicyclic dicarboxylic acid anhydrides such as 1-cyclohexene-1,2-dicarboxylic acid anhydride, hexahydrophthalic anhydride, and methyltetrahydrophthalic anhydride; and aromatic dicarboxylic acid anhydrides such as phthalic anhydride and naphthalic anhydride. Examples of polybasic carboxylic anhydrides having three or more bases include polycarboxylic acids (anhydrides) such as trimellitic anhydride and pyromellitic anhydride. In the reaction of an acid anhydride, one or more of acidic compounds such as sulfuric acid, hydrochloric acid, phosphoric acid, etc., or Lewis acids (for example, Lewis acid compounds represented by MYn, where M represents a semimetal element such as B, As, Ge, etc., or a base metal element such as Al, Bi, In, etc., or a transition metal element such as Ti, Zn, Cu, etc., or a lanthanoid element, n is an integer corresponding to the valence of M and represents 2 or 3, and Y represents a halogen atom, OAc, OCOCF3, ClO4, SbF6, PF6, or OSO2CF3(OTf)), or alkaline compounds such as triethylamine and pyridine may be added as a catalyst.

[0055] The vinyl carboxylate may be represented by the following formula: R-COO-CH=CH2 {wherein R is any one of an alkyl group having 1 to 24 carbon atoms, an alkenyl group having 2 to 24 carbon atoms, a cycloalkyl group having 3 to 16 carbon atoms, and an aryl group having 6 to 24 carbon atoms.} is preferred. The vinyl carboxylate is more preferably at least one selected from the group consisting of vinyl acetate, vinyl propionate, vinyl butyrate, vinyl caproate, vinyl cyclohexanecarboxylate, vinyl caprylate, vinyl caprate, vinyl laurate, vinyl myristate, vinyl palmitate, vinyl stearate, vinyl pivalate, vinyl octylate, divinyl adipate, vinyl methacrylate, vinyl crotonate, vinyl octylate, vinyl benzoate, and vinyl cinnamate. In the esterification reaction with a vinyl carboxylate, one or more catalysts selected from the group consisting of alkali metal hydroxides, alkaline earth metal hydroxides, alkali metal carbonates, alkaline earth metal carbonates, alkali metal hydrogencarbonates, primary to tertiary amines, quaternary ammonium salts, imidazole and derivatives thereof, pyridine and derivatives thereof, and alkoxides may be added.

[0056] Examples of the alkali metal hydroxide and alkaline earth metal hydroxide include sodium hydroxide, potassium hydroxide, lithium hydroxide, calcium hydroxide, barium hydroxide, etc. Examples of the alkali metal carbonate, alkaline earth metal carbonate, and alkali metal hydrogen carbonate include lithium carbonate, sodium carbonate, potassium carbonate, cesium carbonate, magnesium carbonate, calcium carbonate, barium carbonate, lithium hydrogen carbonate, sodium hydrogen carbonate, potassium hydrogen carbonate, cesium hydrogen carbonate, etc. The primary to tertiary amines refer to primary amines, secondary amines, and tertiary amines, and specific examples thereof include ethylenediamine, diethylamine, proline, N,N,N',N'-tetramethylethylenediamine, N,N,N',N'-tetramethyl-1,3-propanediamine, N,N,N',N'-tetramethyl-1,6-hexanediamine, tris(3-dimethylaminopropyl)amine, N,N-dimethylcyclohexylamine, and triethylamine.

[0057] Examples of imidazole and its derivatives include 1-methylimidazole, 3-aminopropylimidazole, and carbonyldiimidazole.

[0058] Examples of pyridine and its derivatives include N,N-dimethyl-4-aminopyridine and picoline.

[0059] Examples of the alkoxide include sodium methoxide, sodium ethoxide, and potassium t-butoxide.

[0060] The carboxylic acid may be at least one selected from the group consisting of compounds represented by the following formulas:

[0061] R-COOH (In the formula, R represents an alkyl group having 1 to 16 carbon atoms, an alkenyl group having 2 to 16 carbon atoms, a cycloalkyl group having 3 to 16 carbon atoms, or an aryl group having 6 to 16 carbon atoms.) Specific examples of carboxylic acids include at least one selected from the group consisting of acetic acid, propionic acid, butyric acid, caproic acid, cyclohexane carboxylic acid, caprylic acid, capric acid, lauric acid, myristic acid, palmitic acid, stearic acid, pivalic acid, methacrylic acid, crotonic acid, octylic acid, benzoic acid, and cinnamic acid.

[0062] Among these carboxylic acids, at least one selected from the group consisting of acetic acid, propionic acid, and butyric acid, and particularly acetic acid, is preferred from the viewpoint of reaction efficiency.

[0063] In addition, in the reaction of carboxylic acid, one or more types of acidic compounds such as sulfuric acid, hydrochloric acid, phosphoric acid, etc., or Lewis acids (for example, Lewis acid compounds represented by MYn, where M represents a semimetal element such as B, As, Ge, etc., or a base metal element such as Al, Bi, In, etc., or a transition metal element such as Ti, Zn, Cu, etc., or a lanthanoid element, n is an integer corresponding to the atomic valence of M and represents 2 or 3, and Y represents a halogen atom, OAc, OCOCF3, ClO4, SbF6, PF6, or OSO2CF3(OTf)), or alkaline compounds such as triethylamine, pyridine, etc. may be added as a catalyst.

[0064] Among these esterification reactants, at least one selected from the group consisting of acetic anhydride, propionic anhydride, butyric anhydride, vinyl acetate, vinyl propionate, vinyl butyrate, and acetic acid, and among these, acetic anhydride and vinyl acetate are preferred from the viewpoint of reaction efficiency.

[0065] When cellulose nanofibers are chemically modified (e.g., by hydrophobization such as acylation), the cellulose nanofibers tend to have good dispersibility in rubber, but the cellulose nanofibers of the present disclosure can exhibit good dispersibility in rubber even if they are unsubstituted or have a low degree of substitution.

[0066] In one embodiment, the degree of substitution of the cellulose nanofibers is 0 (i.e., unsubstituted). Alternatively, in one embodiment, from the viewpoint of obtaining chemically modified cellulose nanofibers with a high thermal decomposition onset temperature, the degree of acyl substitution (DS) of the cellulose nanofibers may be greater than 0, or 0.1 or more, or 0.2 or more, or 0.25 or more, or 0.3 or more, or 0.5 or more. In addition, since an unmodified cellulose skeleton remains in the esterified cellulose nanofibers, it is possible to obtain esterified cellulose nanofibers that combine high tensile strength and dimensional stability derived from cellulose with a high thermal decomposition onset temperature derived from chemical modification, the degree of acyl substitution (DS) of the cellulose nanofibers may be 1.2 or less, or 1.0 or less, or 0.8 or less, or 0.7 or less, or 0.6 or less, or 0.5 or less.

[0067] When the modification group of the chemically modified cellulose nanofiber is an acyl group, the degree of acyl substitution (DS) can be calculated based on the peak intensity ratio of the peak derived from the acyl group to the peak derived from the cellulose skeleton from the attenuated total reflectance (ATR) infrared absorption spectrum of the esterified cellulose nanofiber. The peak of the absorption band of C=O based on the acyl group is at 1730 cm -1 The absorption band of CO based on the cellulose backbone appears at 1030 cm -1 The DS of esterified cellulose nanofibers was calculated by plotting a correlation graph between the DS obtained from solid-state NMR measurements of esterified cellulose nanofibers (described below) and the modification ratio (IR index 1030), which is defined as the ratio of the peak intensity of the absorption band of C=O based on acyl groups to the peak intensity of the absorption band of CO in the cellulose backbone chain, and then calculating the calibration curve from the correlation graph. Degree of substitution DS = 4.13 × IR index (1030) It can be found by using

[0068] In one embodiment, the cellulose nanofibers may be added to the system in the form of a cellulose nanofiber composition combined with other components (e.g., a surfactant and / or a liquid rubber) during the production of a rubber-modifying masterbatch or a highly branched conjugated diene-based polymer composition.

[0069] In the rubber modification masterbatch, the content of cellulose nanofibers per 100 parts by mass of the first rubber component is preferably 15 parts by mass or more, or 20 parts by mass or more, from the viewpoint of obtaining a good reinforcing effect of the cellulose nanofibers, and is preferably 100 parts by mass or less, or 70 parts by mass or less, or 50 parts by mass or less, from the viewpoint of obtaining a cured product excellent in mechanical strength and elongation at break by well dispersing the cellulose nanofibers in the rubber in the highly branched conjugated diene polymer composition.

[0070] In the rubber modification masterbatch, the content of cellulose nanofibers per 100 parts by mass of the highly branched conjugated diene polymer is preferably 15 parts by mass or more, or 20 parts by mass or more, or 30 parts by mass or more, and preferably 100 parts by mass or less, or 80 parts by mass or less, or 60 parts by mass or less.

[0071] The content of cellulose nanofibers in the rubber modification masterbatch is, in one embodiment, 10% by mass or more, or 20% by mass or more, or 25% by mass or more, and in one embodiment, 50% by mass or less, or 40% by mass or less, or 30% by mass or less.

[0072] In the highly branched conjugated diene polymer composition, the content of the cellulose nanofibers per 100 parts by mass of the rubber component (in one embodiment, the total of the first and second rubber components) is preferably 1 part by mass or more, more preferably 2 parts by mass or more, and even more preferably 3 parts by mass or more, from the viewpoint of obtaining the effects of blending the cellulose nanofibers well. Also, from the viewpoint of dispersibility of the cellulose nanofibers in the rubber, the content is preferably 15 parts by mass or less, more preferably 10 parts by mass or less.

[0073] The content of cellulose nanofibers in the highly branched conjugated diene polymer composition is preferably 0.5% by mass or more, or 1% by mass or more, or 3% by mass or more from the viewpoint of obtaining a good reinforcing effect of the cellulose nanofibers, and is preferably 30% by mass or less, or 20% by mass or less, or 10% by mass or less from the viewpoint of obtaining a cured product having good rubber elasticity.

[0074] <Surfactant> In one embodiment, the rubber-modifying masterbatch or the highly branched conjugated diene-based polymer composition contains a surfactant. In one embodiment, the surfactant constitutes the cellulose nanofiber composition. In one embodiment, the surfactant is present in the vicinity of the cellulose nanofiber in the rubber-modifying masterbatch or the highly branched conjugated diene-based polymer composition, and thus the surfactant contributes to improving the dispersibility of the cellulose nanofiber in the rubber.

[0075] In one embodiment, the surfactant is a nonionic surfactant. The nonionic surfactant can penetrate into the voids of the cellulose nanofiber aggregate to make the aggregate porous. For example, when the wet aggregate is impregnated with a nonionic surfactant and then dried to form a dried body, shrinkage during drying can be reduced compared to a dried body obtained by drying the aggregate without using the nonionic surfactant, and the cellulose nanofibers are well dispersed when the dried body is mixed with rubber.

[0076] The nonionic surfactant is preferably a compound having a hydrophilic group selected from the group consisting of a hydroxyl group, a carboxyl group, a sulfonic acid group, and an amino group, and a hydrocarbon group.

[0077] In one embodiment, the nonionic surfactant has an aliphatic group having 6 to 30 carbon atoms as the hydrophobic portion. The cellulose nanofibers of this embodiment typically form loose aggregates, and the nonionic surfactant has good affinity with rubber due to the contribution of the carbon chain of the hydrophobic portion, and since the carbon chain of the hydrophobic portion is not too long, it can easily enter the voids of the cellulose nanofiber aggregate to make the aggregate porous. For example, when the nonionic surfactant is impregnated into the wet aggregate and then dried to form a dried body, shrinkage during drying can be reduced compared to a dried body obtained by drying the aggregate without using the nonionic surfactant, and the cellulose nanofibers are well dispersed when the dried body is mixed with rubber.

[0078] The aliphatic group may be linear or alicyclic, or a combination thereof. From the viewpoint of obtaining good dispersibility of the cellulose nanofiber in the rubber, the number of carbon atoms of the aliphatic group is, in one embodiment, 6 or more, or 8 or more, or 10 or more, and from the viewpoint of penetrating into the voids of the cellulose nanofiber aggregate, in one embodiment, 30 or less, or 25 or less, or 20 or less.

[0079] The nonionic surfactant preferably has one or more structures selected from the group consisting of oxyethylene, glycerol, and sorbitan (specifically, a repeating structure having one or more of these as repeating units) as the hydrophilic portion. These structures are preferred in that they exhibit high hydrophilicity and can easily produce various nonionic surfactants in combination with various hydrophobic portions. In the nonionic surfactant having the hydrophilic portion, the carbon number n of the hydrophobic portion and the number of repeating units m of the hydrophilic portion preferably satisfy the following formula: n>m, from the viewpoint of obtaining good dispersibility of the cellulose nanofibers in the rubber. The repeating number m of the hydrophilic portion is preferably 1 or more, or 2 or more, or 3 or more, or 5 or more, from the viewpoint of good penetration of the nonionic surfactant into the voids of the cellulose nanofiber aggregate, and is preferably 30 or less, or 25 or less, or 20 or less, or 18 or less, from the viewpoint of obtaining good dispersibility of the cellulose nanofibers in the rubber.

[0080] The nonionic surfactant is preferably The following general formula (1): R-(OCH2CH2)m-OH (1) [wherein R represents a monovalent aliphatic group having 6 to 30 carbon atoms, and m is a natural number smaller than the number of carbon atoms in R], and The following general formula (2): R 1 OCH2-(CHOH)4-CH2OR 2 (2) [In the formula, R 1 and R 2 each independently represents a hydrogen atom, an aliphatic group having 1 to 30 carbon atoms, -COR 3 {where, R 3 represents an aliphatic group having 1 to 30 carbon atoms.}, or -(CH2CH2O)yR 4 {where, R 4 represents a hydrogen atom or an aliphatic group having 1 to 30 carbon atoms, and y is an integer of 1 to 30.}.

[0081] In general formula (1), R corresponds to the hydrophobic portion described above, and (OCH2CH2) (i.e., oxyethylene unit) corresponds to the hydrophilic portion described above. The carbon number of R and the repeat number m of (OCH2CH2) are preferably in the same range as the carbon number n of the hydrophobic portion and the repeat number m of the hydrophilic portion described above, respectively.

[0082] In the general formula (2), R 1 , R 2 , R 3 and R 4 For each of the above, the aliphatic group having 1 to 30 carbon atoms has preferably 6 or more, or 8 or more, or 10 or more carbon atoms, and preferably 24 or less, or 20 or less, or 18 or less.

[0083] Furthermore, y is 1 or more, preferably 2 or more, or 4 or more, and preferably 30 or less, or 25 or less, or 20 or less.

[0084] The amount of surfactant in the cellulose nanofiber composition, the rubber modification masterbatch, or the highly branched conjugated diene polymer composition is, relative to 100 parts by mass of the cellulose nanofiber, preferably 10 parts by mass or more, or 15 parts by mass or more, or 20 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.

[0085] <Liquid rubber> In one embodiment, the rubber-modifying masterbatch or the highly branched conjugated diene-based polymer composition contains a liquid rubber. In one embodiment, the liquid rubber may constitute the cellulose nanofiber composition. In one embodiment, the liquid rubber is present in the vicinity of the cellulose nanofiber in the rubber-modifying masterbatch or the highly branched conjugated diene-based polymer composition, and thus the liquid rubber contributes to improving the dispersibility of the cellulose nanofiber in the rubber.

[0086] In the present disclosure, liquid rubber means a substance that has fluidity at 23°C and forms a rubber elastomer by crosslinking (more specifically, vulcanization) and / or chain extension. That is, liquid rubber is an uncured material in one embodiment. Also, having fluidity means that, in one embodiment, liquid rubber dissolved in cyclohexane is placed in a vial with a body diameter of 21 mm and a total length of 50 mm at 23°C, dried, the liquid rubber is filled in the vial to a height of 1 mm, sealed, and the vial is left standing for 24 hours in an upside-down state, and a movement of the substance in the height direction of 0.1 mm or more can be confirmed. The rubber constituting the rubber component, the first rubber component, or the second rubber component of the present disclosure is distinguished from liquid rubber in that it does not meet the definition of liquid rubber of the present disclosure.

[0087] The liquid rubber may have a monomer composition of a general rubber, and is preferably a relatively low molecular weight from the viewpoint of ease of handling and good dispersibility of cellulose nanofibers. In one embodiment, the liquid rubber is in a liquid form by having a number average molecular weight (Mn) of 80,000 or less. In this disclosure, the molecular weight and molecular weight distribution of various rubbers are values ​​obtained by measuring a chromatogram using gel permeation chromatography using three columns connected together, each column containing a polystyrene gel as a packing material, and calculating from a calibration curve using standard polystyrene. Tetrahydrofuran is used as the solvent.

[0088] When the rubber composition is cured to form a cured rubber product, it is desirable to vulcanize the liquid rubber during curing in order to improve the mechanical properties of the cured rubber product.

[0089] The number average molecular weight (Mn) of the liquid rubber is preferably 1,000 or more, or 1,500 or more, or 2,000 or more, or 5,000 or more, from the viewpoint of obtaining a cured product having an excellent storage modulus, and, in an embodiment in which the rubber modification masterbatch contains a liquid rubber, from the viewpoint of obtaining a rubber modification masterbatch having excellent dispersibility in the second rubber component; and is preferably 80,000 or less, or 50,000 or less, or 40,000 or less, or 30,000 or less, or 10,000 or less, from the viewpoint of having high fluidity suitable for dispersing cellulose nanofibers well in the liquid rubber, and of the liquid rubber not becoming too hard after curing and having good rubber elasticity.

[0090] The weight average molecular weight (Mw) of the liquid rubber is preferably 1,000 or more, or 2,000 or more, or 4,000 or more, from the viewpoint of obtaining a cured product having an excellent storage modulus, and, in an embodiment in which the rubber modification masterbatch contains a liquid rubber, from the viewpoint of obtaining a rubber modification masterbatch having excellent dispersibility of cellulose nanofibers in the second rubber component; and is preferably 240,000 or less, or 150,000 or less, or 30,000 or less, from the viewpoint of having high fluidity suitable for dispersing cellulose nanofibers well in the liquid rubber, and of the liquid rubber not becoming too hard after curing and having good rubber elasticity.

[0091] The ratio (Mw / Mn) of the number average molecular weight (Mn) to the weight average molecular weight (Mw) of the liquid rubber is preferably 1.5 or more, or 1.8 or more, or 2.0 or more, in that a certain degree of variation in molecular weight allows a high degree of compatibility between multiple properties of the cured product (in one embodiment, a high degree of compatibility between the storage modulus and rubber elasticity of the cured product), and is preferably 10 or less, or 8 or less, or 5 or less, in that the variation in molecular weight is not excessively large and desired physical properties of the cured product can be stably obtained.

[0092] The liquid rubber may be a conjugated diene polymer or a non-conjugated diene polymer, or a hydrogenated product thereof. The above polymer or hydrogenated product thereof may be an oligomer. In one embodiment, the liquid rubber may have reactive groups (e.g., one or more selected from the group consisting of a hydroxyl group, a carboxyl group, an isocyanato group, a thio group, an amino group, and a halo group) at both ends, and may therefore be bifunctional. These reactive groups contribute to crosslinking and / or chain extension of the liquid rubber.

[0093] In a preferred embodiment, the liquid rubber contains at least one selected from the group consisting of diene rubber, silicone rubber, urethane rubber, polysulfide rubber, and hydrogenated products thereof.

[0094] The liquid rubber may be a modified liquid rubber. It is preferable to include the modified liquid rubber in the rubber modification master batch or the highly branched conjugated diene polymer composition in terms of improving the dispersibility of the cellulose nanofibers. In one embodiment, the modified liquid rubber is a compound capable of forming a covalent bond with the cellulose nanofibers. The modified liquid rubber is particularly preferably a modified liquid rubber obtained by modifying an unmodified liquid rubber with an unsaturated carboxylic acid and / or a derivative thereof.

[0095] The unmodified liquid rubber is an unmodified liquid polymer (liquid diene polymer) obtained by polymerizing conjugated diene monomers such as 1,3-butadiene, isoprene, 1,3-pentadiene, 2,3-dimethyl-1,3-butadiene, 2-methyl-1,3-pentadiene, 1,3-hexadiene, 2-methyl-1,3-pentadiene, 4,5-diethyl-1,3-octadiene, and 3-butyl-1,3-octadiene. Examples of unmodified liquid rubber include liquid diene polymers such as liquid polybutadiene, liquid polyisoprene, liquid styrene-butadiene random copolymer, liquid styrene-butadiene block copolymer, liquid butadiene-isoprene random copolymer, liquid styrene-butadiene-isoprene random copolymer, and liquid styrene-butadiene-isoprene block copolymer. These may be used alone or in combination of two or more.

[0096] Examples of the unsaturated carboxylic acid include maleic acid, fumaric acid, itaconic acid, and (meth)acrylic acid. Examples of the unsaturated carboxylic acid derivative include unsaturated carboxylic anhydrides such as maleic anhydride and itaconic anhydride; unsaturated carboxylic esters such as maleic acid esters, fumaric acid esters, itaconic acid esters, glycidyl (meth)acrylate, and hydroxyethyl (meth)acrylate; unsaturated carboxylic amides such as maleic acid amides, fumaric acid amides, and itaconic acid amides; unsaturated carboxylic acid imides such as maleic acid imides and itaconic acid imides; and the like. The modified liquid rubber may be modified with one or more of the unsaturated carboxylic acids and unsaturated carboxylic acid derivatives.

[0097] Among these, from the viewpoint of economy and effects such as tensile properties and elastic modulus, maleic anhydride modified liquid rubber is preferred, and maleic anhydride modified liquid polybutadiene, maleic anhydride modified liquid polyisoprene, and maleic anhydride modified liquid styrene-butadiene random copolymer are more preferred.

[0098] In one embodiment, the modification amount of the modified liquid rubber is 1 or more, or 3 or more, or 5 or more per molecular chain of the modified liquid rubber from the viewpoint of improving tensile properties and elastic modulus, and is preferably 25 or less, 20 or less, or 15 or less from the viewpoint of production cost of the modified liquid rubber and easy handling due to high fluidity. The modification amount is confirmed by H-NMR measurement.

[0099] The weight average molecular weight (Mw) of the modified liquid rubber is preferably 2,000 or more, or 5,000 or more, or 10,000 or more, from the viewpoint of obtaining a cured product having an excellent storage modulus, and, in an embodiment in which the rubber modification masterbatch contains a liquid rubber, from the viewpoint of obtaining a rubber modification masterbatch having excellent dispersibility of cellulose nanofibers in the second rubber component; and is preferably 150,000 or less, or 100,000 or less, or 50,000 or less, from the viewpoint of having high fluidity suitable for favorable dispersion of cellulose nanofibers in the rubber composition, and of the modified liquid rubber not becoming too hard after curing and having good rubber elasticity.

[0100] The content of the liquid rubber or the modified liquid rubber in the rubber modification masterbatch may be, relative to 100 parts by mass of the first rubber component, in one embodiment, 10 parts by mass or more, or 30 parts by mass or more, or 50 parts by mass or more, and in one embodiment, 200 parts by mass or less, or 150 parts by mass or less, or 100 parts by mass or less.

[0101] The content of the liquid rubber or the modified liquid rubber in the highly branched conjugated diene polymer composition may be, in one embodiment, 1 part by mass or more, or 5 parts by mass or more, or 10 parts by mass or more, and in one embodiment, 25 parts by mass or less, or 20 parts by mass or less, or 15 parts by mass or less, per 100 parts by mass of the rubber component (in one embodiment, the total of the first and second rubber components).

[0102] <Cellulose nanofiber composition powder> In one embodiment, the cellulose nanofiber composition may be a powder. The powder may have one or more of the following properties, which may provide excellent processing properties and allow the cellulose nanofibers to exhibit an excellent dispersion state in the rubber.

[0103] (loose bulk density) In one embodiment, the loose bulk density of the powder is preferably 0.01 g / cm from the viewpoints of good powder flowability, excellent feedability to a kneader, and suppression of migration of a surfactant to rubber. 3or more, or 0.05g / cm 3 or more than 0.10g / cm 3 or more than 0.15g / cm 3 or more than 0.20g / cm 3 The powder is preferably 0.50 g / cm or more in that the powder is easily disintegrated in the rubber so that the cellulose nanofibers can be well dispersed in the rubber, and the powder is not too heavy so that poor mixing of the powder and the rubber can be avoided. 3 or less than 0.40g / cm 3 or less than 0.30g / cm 3 or less than 0.25g / cm 3 or less than 0.20g / cm 3 The following is the summary.

[0104] (Packed bulk density) The packed bulk density of the powder is controlled to a range that is useful for controlling the loose bulk density and compressibility to a suitable range, and in one embodiment, preferably is 0.01 g / cm 3 or more than 0.05g / cm 3 or more than 0.10g / cm 3 or more than 0.15g / cm 3 or more, or 0.20 g / cm 3 More preferably, it is 1.00 g / cm 3 or less than 0.80g / cm 3 or less than 0.70g / cm 3 or less than 0.60g / cm 3 or less than 0.50g / cm 3 or less than 0.40g / cm 3 or less than 0.30g / cm 3 The following is the result.

[0105] The loose bulk density and packed bulk density are measured using a powder tester (model: PT-X) manufactured by Hosokawa Micron Corporation according to the procedure described in the section [Examples] of this disclosure.

[0106] An example of a method for producing a powder includes a slurry preparation step of preparing a slurry containing cellulose nanofibers and a liquid medium, and a drying step of drying the slurry to form a powder.

[0107] (Slurry preparation process) In this step, a slurry is prepared. As the liquid medium, a water-miscible organic solvent, for example: alcohols having a boiling point of 50°C to 170°C (e.g., methanol, ethanol, n-propanol, i-propanol, n-butanol, i-butanol, s-butanol, t-butanol, etc.); ethers (e.g., propylene glycol monomethyl ether, 1,2-dimethoxyethane, diisopropyl ether, tetrahydrofuran, 1,4-dioxane, etc.); carboxylic acids (e.g., formic acid, acetic acid, lactic acid, etc.); esters (e.g., ethyl acetate, vinyl acetate, etc.); ketones (e.g., acetone, methyl ethyl ketone, methyl isobutyl ketone, cyclopentanone, cyclohexanone, etc.); nitrogen-containing solvents (dimethylformamide, dimethylacetamide, acetonitrile, etc.), etc. can be used. In a typical embodiment, the liquid medium in the slurry is substantially only water. The slurry may be composed of cellulose nanofibers and a liquid medium, or may contain a surfactant and / or rubber, and may further contain any additional components.

[0108] The concentration of cellulose nanofibers in the slurry is preferably 5% by mass or more, or 10% by mass or more, or 15% by mass or more, or 20% by mass or more, or 25% by mass or more from the viewpoint of process efficiency in the subsequent drying step, and is preferably 60% by mass or less, or 55% by mass or less, or 50% by mass or less, or 45% by mass or less from the viewpoint of maintaining good handleability by avoiding an excessive increase in the viscosity of the slurry and solidification due to aggregation. For example, cellulose nanofibers are often produced in a dilute dispersion, and the cellulose nanofiber concentration in the slurry may be adjusted to the above-mentioned preferred range by concentrating such a dilute dispersion. For concentration, methods such as suction filtration, pressure filtration, centrifugal deliquation, and heating can be used.

[0109] (drying process) In this step, the slurry is dried under controlled drying conditions to form a powder. Components other than cellulose nanofibers may be added before, during, and / or after drying of the slurry. Drying can be performed using drying devices such as a spray dryer or an extruder. The drying device may be a commercially available product, and examples of the drying device include a micromist spray dryer (manufactured by Fujisaki Electric), a spray dryer (manufactured by Okawara Kakoki), and a twin-screw extruder (manufactured by Japan Steel Works). Among the drying conditions, appropriately controlling the drying speed, drying temperature, and / or pressure (degree of reduced pressure), especially the drying speed, can be advantageous in achieving the desired shape of the powder.

[0110] The drying rate, which is the amount of liquid medium desorbed per minute (parts by mass) per 100 parts by mass of slurry, may be, for example, 10% / min or more, or 50% / min or more, or 100% / min or more, from the viewpoint of forming a powder of the desired particle size by rapidly drying the slurry, and may be, for example, 10,000% / min or less, or 1,000% / min or less, or 500% / min or less, from the viewpoint of avoiding excessive pulverization of the cellulose nanofibers, thereby suppressing aggregation of the cellulose nanofibers and obtaining good handleability.

[0111] The drying rate is a value calculated according to the following formula: drying rate (% / min) = (slurry moisture content (mass%) at the start of drying - powder moisture content (mass%) at the end of drying) / time (min) required from the start of drying to the end of drying (i.e., the average value throughout the drying process).

[0112] Here, the start of drying refers to the time when the process of supplying the slurry or cake to be dried to the device and drying at the intended drying temperature, degree of vacuum, and shear rate begins, and the time for premixing under conditions where the drying temperature, degree of vacuum, and shear rate are different from those in the drying process is not included in the drying time.

[0113] The end point of drying refers to the point at which the moisture content first becomes 7% by mass or less when sampling is performed at intervals of at most 10 minutes from the start of drying.

[0114] In the case of a continuous drying device, the time required from the start of drying to the end of drying can be interpreted as the residence time. In the case of a spray dryer, the residence time can be calculated from the heating air volume and the volume of the drying chamber. In addition, when an extruder is used as a drying device, the residence time can be calculated from the screw rotation speed and the total pitch number of the screw.

[0115] The drying temperature may be, for example, 20°C or more, or 30°C or more, or 40°C or more, or 50°C or more from the viewpoints of drying efficiency and of appropriately agglomerating the cellulose nanofibers to form a powder of the desired particle size, and may be, for example, 200°C or less, or 150°C or less, or 140°C or less, or 130°C or less, or 100°C or less from the viewpoints of preventing thermal degradation of the cellulose nanofibers and additional components and avoiding excessive pulverization of the cellulose nanofibers.

[0116] The drying temperature is the temperature of a heat source in contact with the slurry, and is defined, for example, as the surface temperature of a temperature-control jacket of a drying apparatus, the surface temperature of a heating cylinder, or the temperature of hot air.

[0117] The degree of reduced pressure may be -1 kPa or less, or -10 kPa or less, or -20 kPa or less, or -30 kPa or less, or -40 kPa or less, or -50 kPa or less from the viewpoints of drying efficiency and moderately agglomerating the cellulose nanofibers to form a powder of the desired particle size, and may be -100 kPa or more, or -95 kPa or more, or -90 kPa or more from the viewpoint of avoiding excessive pulverization of the cellulose nanofibers.

[0118] In the drying step, the residence time of the slurry at a temperature of 20° C. to 200° C. may be set to preferably 0.01 to 10 minutes, or 0.05 to 5 minutes, or 0.1 to 2 minutes. Drying under such conditions rapidly dries the cellulose nanofibers, and a powder of the desired particle size is successfully produced.

[0119] For example, when a spray dryer is used, the slurry is sprayed and introduced into a drying chamber in which hot gas is circulated using a spray mechanism (rotating disk, pressure nozzle, etc.) and dried. The size of the slurry droplets when sprayed may be, for example, 0.01 μm to 500 μm, or 0.1 μm to 100 μm, or 0.5 μm to 10 μm. The hot gas may be an inert gas such as nitrogen or argon, or air, etc. The hot gas temperature may be, for example, 50° C. to 300° C., or 80° C. to 250° C., or 100° C. to 200° C. The contact between the slurry droplets and the hot gas in the drying chamber may be a parallel flow, a counter flow, or a parallel counter flow. The particulate powder generated by drying the droplets is collected by a cyclone, a drum, or the like. Also, for example, when an extruder is used, the slurry is fed from a hopper into a kneading section equipped with a screw, and the slurry is continuously transported by the screw in the kneading section under reduced pressure and / or heating to dry the slurry. As for the screw mode, a conveying screw, a counterclockwise screw, and a kneading disk may be combined in any order. The drying temperature may be, for example, 50°C to 300°C, or 80°C to 250°C, or 100°C to 200°C.

[0120] <Highly branched conjugated diene polymer> In one embodiment, the rubber-modifying masterbatch or the highly branched conjugated diene polymer composition contains a highly branched conjugated diene polymer. In one embodiment, the "highly branched conjugated diene polymer" of the present disclosure means a conjugated diene polymer having a shrinkage factor (g') of less than 0.72 determined by gel permeation chromatography (GPC)-light scattering measurement using a viscometer. In one embodiment, the highly branched conjugated diene polymer contains 3% by mass or more and 60% by mass or less of a structural unit based on an aromatic vinyl monomer. A branched conjugated diene polymer having the above aromatic vinyl monomer unit ratio and / or the above shrinkage factor (g') can provide a cured product having excellent processability, tensile modulus, and mechanical strength when producing a rubber composition.

[0121] The highly branched conjugated diene polymer of the present embodiment is preferably a random copolymer containing a structural unit based on an aromatic vinyl monomer (also referred to as an "aromatic vinyl monomer unit" in the present disclosure) and a structural unit based on a conjugated diene monomer (also referred to as a "conjugated diene monomer unit" in the present disclosure).

[0122] In the present disclosure, a "random copolymer" refers to a copolymer in which the proportion of chains in which 8 or more consecutive structural units derived from an aromatic vinyl compound are present is 10 mass% or less relative to the total structural units derived from an aromatic vinyl compound.

[0123] The content of chains in which eight or more structural units derived from aromatic vinyl compounds are consecutive was measured by using a copolymer as a solvent in deuterated chloroform. 1 In the H-NMR spectrum, it can be calculated as the ratio of the integral value in the range (A) to the sum of the integral values ​​in each of the following chemical shift ranges (A) to (C). For example, if the aromatic vinyl compound is styrene, the ratio of the integral value in the range (A) to the sum of the integral values ​​in each of the ranges (A) to (C) is calculated, and the ratio of styrene can be calculated by multiplying this value by 2.5. This makes it possible to grasp the state of the chain of structural units derived from the aromatic vinyl compound. (A) Aromatic vinyl compounds with 8 or more chains: 6.00≦S<6.68 (B) Aromatic vinyl compound chains 2-7: 6.68≦S<6.89 (C) Aromatic vinyl compound short chain: 6.89≦S≦8.00

[0124] The highly branched conjugated diene-based polymer according to one embodiment is a random copolymer having a constituent unit based on an aromatic vinyl compound and a constituent unit based on a conjugated diene compound. The aromatic vinyl compound is not particularly limited, but examples thereof include styrene, α-methylstyrene, 1-vinylnaphthalene, 3-vinyltoluene, ethylvinylbenzene, divinylbenzene, 4-cyclohexylstyrene, 2,4,6-trimethylstyrene, etc. These may be used alone or in combination of two or more kinds, but among these, styrene is particularly preferred from the viewpoint of practical aspects such as easy availability of monomers.

[0125] The conjugated diene compound is not particularly limited, but examples thereof include 1,3-butadiene, isoprene, 1,3-pentadiene, 2,3-dimethylbutadiene, 2-phenyl-1,3-butadiene, 1,3-hexadiene, etc. These may be used alone or in combination of two or more kinds, but among these, from the viewpoint of practical aspects such as easy availability of monomers, 1,3-butadiene and isoprene are preferred, and 1,3-butadiene is more preferred.

[0126] The content of aromatic vinyl monomer units in the highly branched conjugated diene polymer is preferably 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 from the viewpoints of improving the dispersibility of cellulose nanofibers in the highly branched conjugated diene polymer, improving the fracture properties of the cured product, and adjusting the glass transition temperature of the rubber composition, and is preferably 60% by mass or less, or 55% by mass or less, or 50% by mass or less from the viewpoints of avoiding a decrease in the abrasion resistance of the cured product and adjusting the glass transition temperature of the rubber composition. The content of aromatic vinyl monomer units is measured by nuclear magnetic resonance (NMR), and more specifically, can be measured by the method of the examples described later.

[0127] In one embodiment, the highly branched conjugated diene polymer has a shrinkage factor (g') of less than 0.72 as determined by gel permeation chromatography (GPC)-light scattering measurement using a viscometer-equipped gel permeation chromatography (GPC), from the viewpoints of processability in producing a rubber composition and improving the tensile modulus and mechanical strength of the cured product. The shrinkage factor (g') of less than 0.72 means that the conjugated diene polymer is highly branched, having substantially 5 or more branches.

[0128] In general, a polymer having branches tends to have a smaller molecular size compared to a linear polymer having the same absolute molecular weight. The shrinkage factor (g') of one embodiment of a highly branched conjugated diene polymer is an index of the ratio of the molecular size to that of a linear polymer having the same absolute molecular weight. In other words, the shrinkage factor (g') tends to be smaller as the degree of branching of the polymer increases.

[0129] In this embodiment, the intrinsic viscosity is used as an index of molecular size. For a linear polymer, the intrinsic viscosity [η] is −3.883M 0.771 (M is the absolute molecular weight).

[0130] The shrinkage factor (g') for each absolute molecular weight of the highly branched conjugated diene polymer was calculated. 4 ~200×10 4 The average value of the contraction factor (g') at this time is defined as the contraction factor (g') of the branched conjugated diene polymer. Here, "branch" refers to a polymer formed by directly or indirectly bonding with another polymer. Also, "degree of branching" refers to the number of polymers directly or indirectly bonded to one branch. For example, when four conjugated diene polymer chains described below are indirectly bonded to each other via a coupling agent residue described below, the degree of branching is 4.

[0131] In one embodiment, the shrinkage factor (g') is less than 0.72, preferably 0.64 or less, more preferably 0.58 or less, and even more preferably 0.53 or less. The lower limit of the shrinkage factor (g') is not particularly limited and may be equal to or less than the detection limit, but is preferably 0.30 or more, more preferably 0.33 or more, even more preferably 0.35 or more, and even more preferably 0.45 or more. A branched conjugated diene-based polymer having a shrinkage factor (g') in this range has excellent processability when producing an unvulcanized rubber composition.

[0132] Since the shrinkage factor (g') tends to depend on the degree of branching, for example, the shrinkage factor (g') can be controlled using the degree of branching as an index. Specifically, in a modified conjugated diene-based polymer having a degree of branching of 8, the shrinkage factor (g') tends to be 0.45 or more and 0.59 or less. The shrinkage factor (g') can be measured by the method described in the examples below.

[0133] In a preferred embodiment, the highly branched conjugated diene polymer is a polymer having branches and a branching degree of at least 5. The branching degree is preferably at least 5, more preferably at least 6. There is no particular upper limit to the branching degree, but from the viewpoint of the balance between processability and mechanical properties, it is preferably at most 24, more preferably at most 20, and particularly preferably at most 18.

[0134] The highly branched conjugated diene polymer has one or more coupling residues and a conjugated diene polymer chain bonded to the coupling residue, and more preferably, the branches include branches in which 5 or more conjugated diene polymer chains are bonded to one coupling residue. By specifying the structure of the highly branched conjugated diene polymer so that the branching degree is 5 or more and the branches include branches in which 5 or more conjugated diene polymer chains are bonded to one coupling residue, the shrinkage factor (g') can be more reliably made less than 0.72.

[0135] The weight average molecular weight of the highly branched conjugated diene polymer is preferably 200,000 or more and 2,000,000 or less from the viewpoints of the shape stability (particularly cold flow resistance) of the rubber component containing the conjugated diene polymer and the tensile strength and abrasion resistance of the cured product of the rubber composition. The weight average molecular weight is more preferably 300,000 or more, or 400,000 or more, or 500,000 or more, and more preferably 1,800,000 or less, or 1,500,000 or less, or 1,000,000 or less.

[0136] The weight average molecular weight of the highly branched conjugated diene polymer is a value measured by GPC (gel permeation chromatography), and more specifically, can be measured by the method described in the Examples below.

[0137] From the viewpoint of processability, the molecular weight distribution (Mw / Mn) of the highly branched conjugated diene polymer is preferably 1.1 or more, more preferably 1.2 or more, and even more preferably 1.3 or more. From the viewpoint of mechanical strength, the molecular weight distribution (Mw / Mn) of the highly branched conjugated diene polymer is preferably 3.0 or less, and more preferably 2.5 or less.

[0138] From the viewpoints of ease of kneading during preparation of a rubber compound and prevention of breakage of the kneaded dough, the Mooney viscosity at 100° C. of the highly branched conjugated diene polymer is preferably 250 or less, more preferably 200 or less, and even more preferably 180 or less. From the viewpoint of obtaining good physical properties of the cured product of the rubber composition, the Mooney viscosity is preferably 35 or more, 40 or more, or 50 or more.

[0139] In the present embodiment, the Mooney viscosity is measured using a Mooney viscometer with an L-shaped rotor in accordance with ISO 289, and more specifically, can be measured by the method described in the Examples below.

[0140] [Production of highly branched conjugated diene polymers] The polymerization method for the highly branched conjugated diene polymer is not particularly limited as long as the above-mentioned desired physical properties can be obtained, and any of solution polymerization, gas phase polymerization, and bulk polymerization can be used, but from the viewpoint of commercial production, solution polymerization is particularly preferred. The polymerization form may be either batch or continuous.

[0141] When a solution polymerization method is used, the monomer concentration in the solution is preferably 5% by mass or more, more preferably 10% by mass or more. When the monomer concentration in the solution is 5% by mass or more, the amount of the obtained conjugated diene polymer is sufficient, and the cost tends to be low. In addition, the monomer concentration in the solution is preferably 50% by mass or less, more preferably 30% by mass or less. When the monomer concentration in the solution is 50% by mass or less, the solution viscosity is low, which makes stirring easy and tends to facilitate polymerization.

[0142] (Polymerization initiator) In one embodiment, the highly branched conjugated diene polymer is obtained by anionic polymerization. The polymerization initiator for anionic polymerization is not particularly limited, but an organic lithium compound is preferably used. The organic lithium compound is preferably one having an alkyl group having 2 to 20 carbon atoms, such as ethyl lithium, n-propyl lithium, isopropyl lithium, n-butyl lithium, sec-butyl lithium, tert-butyl lithium, tert-octyl lithium, n-decyl lithium, phenyl lithium, 2-naphthyl lithium, 2-butyl-phenyl lithium, 4-phenyl-butyl lithium, cyclohexyl lithium, cyclopentyl lithium, and a reaction product of diisopropenylbenzene and butyl lithium. Among these, n-butyl lithium or sec-butyl lithium is preferred from the viewpoints of availability, safety, and the like.

[0143] In one embodiment, the conjugated diene polymer is obtained by coordination polymerization. As a polymerization initiator for coordination polymerization, it is preferable to use the polymerization catalyst composition described in JP-A-2020-45500.

[0144] (Polymerization method) The method for producing the highly branched conjugated diene copolymer by anionic polymerization or coordination polymerization using a polymerization initiator is not particularly limited, and a conventionally known method can be used. Specifically, in an organic solvent inert to the reaction, such as a hydrocarbon solvent such as a chain aliphatic, alicyclic, or aromatic hydrocarbon compound, styrene, 1,3-butadiene, etc. are polymerized using, for example, butyl lithium as a polymerization initiator in the presence of a randomizer as necessary, to obtain the desired conjugated diene copolymer.

[0145] The hydrocarbon solvent is preferably one having 3 to 8 carbon atoms, and examples thereof include propane, n-butane, isobutane, n-pentane, isopentane, n-hexane, cyclohexane, propene, 1-butene, isobutene, trans-2-butene, cis-2-butene, 1-pentene, 2-pentene, 1-hexene, 2-hexene, benzene, toluene, xylene, ethylbenzene, etc. These may be used alone or in combination of two or more.

[0146] (Randomizer in anionic polymerization) The randomizer is a compound that has the effect of controlling the microstructure of the conjugated diene portion in a highly branched conjugated diene copolymer, for example, increasing the number of 1,2-bonds in butadiene and 3,4-bonds in isoprene, or controlling the composition distribution of monomer units in a copolymer, for example, randomizing styrene units or butadiene units in a styrene-butadiene copolymer. There is no particular limitation on this randomizer, and any of the known compounds that have been commonly used as randomizers in the past can be used. For example, ethers such as dimethoxybenzene, tetrahydrofuran, dimethoxyethane, diethylene glycol dibutyl ether, diethylene glycol dimethyl ether, 2,2-di(2-tetrahydrofuryl)propane, triethylamine, pyridine, N-methylmorpholine, N,N,N',N'-tetramethylethylenediamine, and 1,2-dipiperidinoethane, and tertiary amines can be mentioned. In addition, potassium salts such as potassium t-amylate and potassium t-butoxide, and sodium salts such as sodium t-amylate can also be used. These randomizers may be used alone or in combination of two or more. The amount of the randomizer used is preferably 0.01 molar equivalents or more, more preferably 0.05 molar equivalents or more, per mole of the organolithium compound. When the amount of the randomizer used is 0.01 molar equivalents or more, the effect of addition is large and the randomization tends to be easy. The amount of the randomizer used is preferably 1000 molar equivalents or less, more preferably 500 molar equivalents or less, per mole of the organolithium compound. When the amount of the randomizer used is 1000 molar equivalents or less, the reaction rate of the monomer does not change significantly, so that the inconvenience of being difficult to randomize can be avoided.

[0147] (Reaction temperature) The reaction temperature during polymerization is not particularly limited as long as the reaction proceeds favorably, but is usually preferably from -10°C to 100°C, and more preferably from 25°C to 70°C.

[0148] (High branching reaction) The method for producing a highly branched conjugated diene polymer of this embodiment may include, after the polymerization step described above, a reaction step of reacting an active terminal of the conjugated diene polymer obtained in the polymerization step with a predetermined coupling agent, or the reaction step described in JP 2021-152135 A, i.e., a reaction step of reacting an active terminal of a conjugated diene polymer into which a branched structure has been introduced by reacting a styrene derivative as a branching agent in the polymerization step with a predetermined coupling agent.

[0149] The reaction step for achieving high branching is preferably a step of reacting the active terminal of the conjugated diene polymer with a coupling agent having three or more functional groups (i.e., having three or more functional groups that react with the active terminal of the conjugated diene polymer). The number of functional groups of the coupling agent is preferably three or more, four or more, six or more, or eight or more, and preferably 30 or less, 25 or less, or 20 or less.

[0150] The amount of the coupling agent added is preferably such that the number of moles of the functional group of the coupling agent is 0.3 moles or more and less than 0.7 moles per mole of the polymerization catalyst (e.g., an organic monolithium compound) used in the polymerization step. By setting the number of moles of the functional group of the coupling agent within a specific range, the branching degree can be easily controlled within a desired range. In particular, by using a coupling agent having a functional group with three or more functionalities in the above-mentioned amount, the shrinkage factor (g') can be easily controlled to less than 0.72.

[0151] In one embodiment, the number of functional groups of the coupling agent is counted only for those functional groups that actually contribute to the reaction with the active end of the conjugated diene polymer. For example, the number of halogenated silyl groups is counted as the number of functional groups, and the azasilyl group is counted as one functional group, the carbonyl group is counted as one functional group, the epoxy group is counted as one functional group, and the ester group is counted as two functional groups to obtain the total number of functional groups of the compound. In addition, for example, when the coupling agent has an alkoxysilyl group, generally, all alkoxy groups bonded to silicon atoms tend not to react, and one alkoxy group remains per silicon atom. Therefore, the number of functional groups of the alkoxysilyl group is the number obtained by subtracting 1 from the number of alkoxy groups bonded to the same silicon atom. More specifically, the number of functional groups of the coupling agent is calculated by counting trialkoxysilyl groups as two functional groups, dialkoxysilyl groups as one functional group, and monoalkoxysilyl groups as zero functional groups. According to such a calculation method, the amount of coupling agent to be added can be calculated more appropriately.

[0152] In addition, it is preferable that the compound used as the coupling agent does not have active hydrogen. When the coupling agent does not have active hydrogen, side reactions are suppressed, and it tends to be easier to adjust the branching degree and the shrinkage factor (g').

[0153] Examples of the coupling agent include tri- or higher functional coupling agents having a silicon atom, tri- or higher functional coupling agents having a nitrogen atom-containing group, and coupling agents containing a silicon atom and a sulfur atom.

[0154] Examples of the tri- or higher functional coupling agent having a silicon atom include, but are not limited to, halogenated silane compounds, epoxy silane compounds, alkoxy silane compounds, and the like.

[0155] Examples of halogenated silane compounds include, but are not limited to, methyltrichlorosilane, tetrachlorosilane, 1,2-bis(trichlorosilyl)ethane, and the like.

[0156] Examples of the epoxidized silane compound include, but are not limited to, 3-glycidoxypropyltrimethoxysilane, 3-glycidoxypropyltriethoxysilane, 3-glycidoxypropylmethyldiethoxysilane, and the like.

[0157] Examples of alkoxysilane compounds include, but are not limited to, tetramethoxysilane, tetraethoxysilane, triphenoxymethylsilane, 1,2-bis(triethoxysilyl)ethane, and methoxy-substituted polyorganosiloxane.

[0158] Examples of coupling agents having a nitrogen atom-containing group include, but are not limited to, isocyanate compounds, isocyanuric acid derivatives, carbonyl compounds having a nitrogen atom-containing group, vinyl compounds having a nitrogen atom-containing group, epoxy compounds having a nitrogen atom-containing group, and alkoxysilane compounds having a nitrogen atom-containing group.

[0159] Examples of the isocyanate compound include, but are not limited to, 2,4-tolylene diisocyanate, 2,6-tolylene diisocyanate, diphenylmethane diisocyanate, polymeric diphenylmethane diisocyanate (C-MDI), phenyl isocyanate, isophorone diisocyanate, hexamethylene diisocyanate, butyl isocyanate, and 1,3,5-benzene triisocyanate.

[0160] Examples of isocyanuric acid derivatives include, but are not limited to, 1,3,5-tris(3-trimethoxysilylpropyl)isocyanurate, 1,3,5-tris(3-triethoxysilylpropyl)isocyanurate, 1,3,5-tris(oxiran-2-yl)-1,3,5-triazinane-2,4,6-trione, 1,3,5-tris(isocyanatomethyl)-1,3,5-triazinane-2,4,6-trione, and 1,3,5-trivinyl-1,3,5-triazinane-2,4,6-trione.

[0161] Examples of carbonyl compounds having a nitrogen atom-containing group include, but are not limited to, 1,3-dimethyl-2-imidazolidinone, 1-methyl-3-ethyl-2-imidazolidinone, 1-methyl-3-(2-methoxyethyl)-2-imidazolidinone, N-methyl-2-pyrrolidone, N-methyl-2-piperidone, N-methyl-2-quinolone, 4,4'-bis(diethylamino)benzophenone, 4,4'-bis(dimethylamino)benzophenone, methyl-2-pyridyl ketone, methyl-4-pyridyl ketone, propyl-2-pyridyl ketone, di-4-pyridyl ketone, and the like.

[0162] Examples of vinyl compounds having a nitrogen atom-containing group include, but are not limited to, N,N-dimethylacrylamide, N,N-dimethylmethacrylamide, N-methylmaleimide, N-methylphthalimide, N,N-bistrimethylsilylacrylamide, and 3-(2-dimethylaminoethyl)styrene.

[0163] Examples of epoxy compounds having a nitrogen atom-containing group include, but are not limited to, N,N-diglycidyl-4-glycidoxyaniline, 1-N,N-diglycidylaminomethyl-4-glycidoxy-cyclohexane, and 1,3-bis(N,N-diglycidylaminomethyl)cyclohexane.

[0164] Examples of alkoxysilane compounds having a nitrogen atom-containing group include, but are not limited to, 3-dimethylaminopropyltrimethoxysilane, 3-dimethylaminopropylmethyldimethoxysilane, 3-diethylaminopropyltriethoxysilane, 3-morpholinopropyltrimethoxysilane, 3-piperidinopropyltriethoxysilane, and 3-hexamethyleneiminopropylmethyldiethoxysilane.

[0165] The reaction temperature in the reaction step is preferably the same as the polymerization temperature of the conjugated diene polymer, more preferably 0°C or higher and 120°C or lower, and further preferably 50°C or higher and 100°C or lower.

[0166] The reaction time in the reaction step is preferably 10 seconds or more, more preferably 30 seconds or more. In one embodiment, the reaction time may be 15 minutes or less, or 10 minutes or less.

[0167] The mixing in the reaction step may be carried out by any of mechanical stirring, stirring with a static mixer, and the like.

[0168] The coupling agent may be diluted with an inert solvent and continuously fed to the reactor. When the polymerization process is a batch process, the coupling agent may be fed into the polymerization reactor, or the polymerization product may be transferred to another reactor to carry out the reaction process.

[0169] The time from the polymerization step to the reaction step is preferably short from the viewpoint of obtaining a high coupling rate, and is preferably within 10 minutes, more preferably within 5 minutes. Note that the time from the polymerization step to the reaction step means the time from the peak temperature of polymerization to the addition of a coupling agent when the polymerization step is a batch process, and means the time from the exit of a reaction liquid containing a conjugated diene polymer from a polymerization reactor to the addition of a coupling agent when the polymerization step is a continuous process.

[0170] (Reaction stopped) Anionic polymerization can be terminated by adding a reaction terminator commonly used in this field. Such reaction terminators are not particularly limited, but include polar solvents having active protons (e.g., alcohols such as methanol, ethanol, isopropanol, etc., or acetic acid, etc.) and mixtures thereof, or mixtures of one or more of the above polar solvents with non-polar solvents such as hexane and cyclohexane. The amount of reaction terminator added is usually sufficient to be the same molar amount or about twice the molar amount of the anionic polymerization initiator.

[0171] At the end of the polymerization process of the conjugated diene polymer, a deactivator, a neutralizing agent, etc. may be added as necessary. Examples of the deactivator include, but are not limited to, water; alcohols such as methanol, ethanol, isopropanol, etc. The end of the polymerization process here refers to a state in which 95 mol% or more of the added monomers have been consumed in the polymerization. Examples of the neutralizing agent include, but are not limited to, carboxylic acids such as stearic acid, oleic acid, and Versatic acid (a mixture of carboxylic acids with many branches having 9 to 11 carbon atoms, mainly 10 carbon atoms); aqueous solutions of inorganic acids; and carbon dioxide gas.

[0172] (Use of rubber stabilizers) It is preferable to add a rubber stabilizer at the end of the polymerization process of the conjugated diene polymer from the viewpoint of preventing gel formation and improving processing stability. The rubber stabilizer is not limited to the following and any known stabilizer can be used, but for example, antioxidants such as 2,6-di-tert-butyl-4-hydroxytoluene (BHT), n-octadecyl-3-(4'-hydroxy-3',5'-di-tert-butylphenol) propionate, and 2-methyl-4,6-bis[(octylthio)methyl]phenol are preferable.

[0173] (Use of rubber softener) In the final stage of the polymerization process of the conjugated diene polymer, a rubber softener can be added as necessary to improve the productivity of the polymer and the processability when an inorganic filler or the like is blended during the production of the rubber composition. The rubber softener is not particularly limited, but examples thereof include extender oil, liquid rubber, resin, etc. The liquid rubber can be selected from those exemplified above. In terms of processability, productivity, and economic efficiency, extender oil is preferred.

[0174] The method of adding a rubber softener to a conjugated diene polymer is not limited to the following, but a preferred method is to add a rubber softener to a polymer solution, mix, and then remove the solvent from the resulting rubber softener-containing polymer solution.

[0175] Examples of preferred extender oils include aromatic oils, naphthenic oils, and paraffinic oils. Among these, aromatic substitute oils having a polycyclic aromatic (PCA) content of 3% by mass or less according to the IP346 method are preferred from the viewpoints of environmental safety, oil bleeding prevention, and wet grip properties. Examples of aromatic substitute oils include TDAE (Treated Distillate Aromatic Extracts), MES (Mild Extraction Solvate), and RAE (Residual Aromatic Extracts) as shown in Kautschuk Gummi Kunststoffe 52(12)799(1999).

[0176] In terms of suppressing deterioration over time of the cured product, the content of the extender oil is preferably 37.5 parts by mass or less, more preferably 30 parts by mass or less, further preferably 25 parts by mass or less, and most preferably 20 parts by mass or less, per 100 parts by mass of the first rubber component in the rubber modification masterbatch, or per 100 parts by mass of the rubber components (in one embodiment, the total of the first and second rubber components) in the highly branched conjugated diene polymer composition. In one embodiment, the content may be 5 parts by mass or more, 10 parts by mass or more, or 15 parts by mass or more.

[0177] (Solvent removal) A known method can be used as a method for removing a solvent from a polymer solution containing a highly branched conjugated diene polymer to obtain the highly branched conjugated diene polymer, for example, a method for separating the solvent by steam stripping or the like, filtering the polymer, and then dehydrating and drying it to obtain the polymer, a method for concentrating the polymer solution in a flashing tank and further devolatilizing it with a vent extruder or the like, and a method for directly devolatilizing it with a drum dryer or the like.

[0178] In the rubber modification masterbatch, the amount of the highly branched conjugated diene polymer in 100% by mass of the first rubber component is, in one embodiment, 50% by mass or more, 60% by mass or more, or 80% by mass or more, from the viewpoint of improving the processability of the rubber composition and providing a cured product having excellent mechanical strength. The amount may be 100% by mass, but in one embodiment, it may be 90% by mass or less, 80% by mass or less, or 70% by mass or less.

[0179] In the highly branched conjugated diene polymer composition, when the second rubber component contains a highly branched conjugated diene polymer, the amount of the highly branched conjugated diene polymer in 100% by mass of the second rubber component is, in one embodiment, 50% by mass or more, or 60% by mass or more, or 80% by mass or more, from the viewpoint of improving the processability of the rubber composition and providing a cured product excellent in mechanical strength. In one embodiment, the ratio is 95% by mass or less, or 90% by mass or less, or 85% by mass or less.

[0180] In the highly branched conjugated diene polymer composition, the ratio of the highly branched conjugated diene polymer in 100% by mass of the rubber component (in one embodiment, the total of the first rubber and the second rubber) is, in one embodiment, 50% by mass or more, or 60% by mass or more, or 80% by mass or more, from the viewpoint of improving the processability of the rubber composition and providing a cured product excellent in mechanical strength. In one embodiment, the ratio is 95% by mass or less, or 90% by mass or less, or 85% by mass or less.

[0181] <Rubber other than highly branched conjugated diene polymer> The rubber component of the present disclosure may contain rubber other than diene polymer, but is typically composed of diene polymer. The rubber modification master batch or highly branched conjugated diene polymer composition may contain rubber other than highly branched conjugated diene polymer as the rubber component. Such rubbers include, but are not limited to, conjugated diene polymers or hydrogenated products thereof, random copolymers of conjugated diene compounds and vinyl aromatic compounds or hydrogenated products thereof, block copolymers of conjugated diene compounds and vinyl aromatic compounds or hydrogenated products thereof, diene polymers such as natural rubber, and non-diene polymers.

[0182] Specific examples include, but are not limited to, butadiene rubber or hydrogenated products thereof; isoprene rubber or hydrogenated products thereof; styrene-based elastomers such as styrene-butadiene rubber or hydrogenated products thereof, styrene-butadiene block copolymer or hydrogenated products thereof, and styrene-isoprene block copolymer or hydrogenated products thereof; acrylonitrile-butadiene rubber or hydrogenated products thereof, etc.

[0183] In the highly branched conjugated diene polymer composition, the content of the diene polymer other than the highly branched conjugated diene polymer in 100% by mass of the first rubber component, in 100% by mass of the second rubber component, or in the total of 100% by mass of the first and second rubber components is preferably 50% by mass or less, more preferably 40% by mass or less, and even more preferably 20% by mass or less, from the viewpoint of improving the mechanical strength of the rubber molded article. In one embodiment, the content may be 5% by mass or more, 10% by mass or more, or 15% by mass or more.

[0184] <Additives> The rubber modification masterbatch or the highly branched conjugated diene polymer composition may contain additives in addition to the cellulose nanofibers and the rubber component. As the additives, one or more of various materials commonly used in the rubber industry, such as organic or inorganic reinforcing fillers (e.g., carbon black, silica-based inorganic fillers, etc.), silane coupling agents, metal oxides or metal hydroxides, stearic acid, various antioxidants, rubber softeners (oils, waxes, etc.), vulcanizing agents (sulfur, organic peroxides, etc.), and vulcanization accelerators (sulfenamide-based or guanidine-based vulcanization accelerators, etc.), may be used. As the additives, one or more of additional polymers, dispersants, heat stabilizers, antioxidants, antistatic agents, colorants, etc. may also be used.

[0185] (Silica-based inorganic filler) The highly branched conjugated diene polymer composition of the present embodiment may contain a silica-based inorganic filler. In a typical embodiment, the silica-based inorganic filler is combined with a rubber modification masterbatch during the production of the highly branched conjugated diene polymer composition. In the highly branched conjugated diene polymer composition, the content of the silica-based inorganic filler relative to 100 parts by mass of the rubber component (in one embodiment, the total of the first and second rubber components) is preferably 10 parts by mass or more and 80 parts by mass or less from the viewpoint of the mechanical strength and elastic modulus of the rubber molded product, which is the cured product. From the viewpoint of reducing the weight of the rubber molded product, the content of the silica-based inorganic filler is preferably 80 parts by mass or less, or 50 parts by mass or less, or 30 parts by mass or less.

[0186] The silica-based inorganic filler is not particularly limited and any known filler can be used, but solid particles containing SiO2 or Si3Al as a constituent unit are preferred, and it is more preferred that SiO2 or Si3Al is the main constituent unit. Throughout this disclosure, the term "main component" refers to a component that accounts for more than 50 mass%, preferably 70 mass% or more, and more preferably 80 mass% or more of the total.

[0187] Examples of silica-based inorganic fillers include, but are not limited to, inorganic fibrous materials such as silica, clay, talc, mica, diatomaceous earth, wollastonite, montmorillonite, zeolite, and glass fiber. Commercially available silica-based inorganic fillers include, for example, "Ultrasil 7000GR" manufactured by Evonik Degussa. Examples of silica-based inorganic fillers include silica-based inorganic fillers with hydrophobic surfaces and mixtures of silica-based inorganic fillers and inorganic fillers other than silica-based inorganic fillers. Among these, silica and glass fiber are preferred from the viewpoint of strength and abrasion resistance, and silica is more preferred. Examples of silica include dry silica, wet silica, and synthetic silicate silica. Among these, wet silica is more preferred from the viewpoint of excellent balance between the effect of improving fracture properties and wet skid resistance.

[0188] (Carbon Black) The highly branched conjugated diene polymer composition of the present embodiment may contain carbon black. In a typical embodiment, the carbon black is combined with a rubber modification masterbatch during the production of the highly branched conjugated diene polymer composition. In the highly branched conjugated diene polymer composition, the content of carbon black per 100 parts by mass of the rubber component (in one embodiment, the total of the first and second rubber components) is preferably 10 parts by mass or more and 80 parts by mass or less from the viewpoint of the mechanical strength and elastic modulus of the rubber molded product, which is the cured product. From the viewpoint of reducing the weight of the rubber molded product, the content of carbon black is preferably 80 parts by mass or less, or 50 parts by mass or less, or 30 parts by mass or less.

[0189] The carbon black is not particularly limited, and for example, carbon black of each class such as SRF, FEF, HAF, ISAF, SAF, etc. can be used. Among these, from the viewpoint of extrusion moldability and rolling resistance characteristics in tire applications, carbon black having a nitrogen adsorption specific surface area of ​​50 m 2 From the viewpoint of availability of carbon black, the nitrogen adsorption specific surface area is preferably 130 m 2 / g or less, and the dibutyl phthalate (DBP) oil absorption may be 120 mL / 100 g or less in one embodiment.

[0190] In a preferred embodiment, the content of the reinforcing filler per 100 parts by mass of the rubber component (in one embodiment, the total of the first and second rubber components) is preferably 10 parts by mass or more from the viewpoint of the mechanical strength and elastic modulus of the cured rubber molded body, and is preferably 80 parts by mass or less, or 50 parts by mass or less, or 30 parts by mass or less from the viewpoint of reducing the weight of the rubber molded body.

[0191] (Metal oxides, metal hydroxides) The highly branched conjugated diene-based polymer composition of the present embodiment may contain a metal oxide and / or a metal hydroxide. In one embodiment, the metal oxide is represented by the chemical formula M x O y(M represents a metal atom, and x and y each independently represent an integer of 1 to 6) are solid particles having as the main component of the structural unit. Examples of the metal oxide include alumina, titanium oxide, magnesium oxide, and zinc oxide. The metal oxide may be used as a mixture with an inorganic filler. The metal hydroxide is not particularly limited, and examples thereof include aluminum hydroxide, magnesium hydroxide, and zirconium hydroxide.

[0192] (rubber softener) The highly branched conjugated diene polymer composition of the present embodiment may contain a rubber softener for the purpose of improving processability. Suitable rubber softeners include, for example, mineral oil-based rubber softeners and liquid or low molecular weight synthetic softeners. The mineral oil-based rubber softeners are also called process oils or extender oils, and are used to soften rubber, increase its volume, or improve its processability. The mineral oil-based rubber softeners include aromatic rings, naphthene rings, and paraffin chains, and are called paraffin-based when the carbon number of the paraffin chain is 50% or more of the total carbon, naphthene-based when the carbon number of the naphthene ring is 30 to 45%, and aromatic when the aromatic carbon number is more than 30%. As a rubber softener to be used together with a conjugated diene-aromatic vinyl copolymer, one having a moderate aromatic content is preferred because it tends to have good affinity with the copolymer.

[0193] The rubber softener may be blended during the production of the highly branched conjugated diene polymer, during the production of the masterbatch for rubber modification, and / or during the production of the highly branched conjugated diene polymer composition. In the highly branched conjugated diene polymer composition, the content of the rubber softener relative to 100 parts by mass of the rubber component (in one embodiment, the total of the first and second rubber components) is preferably 5 parts by mass or more, more preferably 10 parts by mass or more, and even more preferably 30 parts by mass or more, from the viewpoint of improving processability. In addition, from the viewpoint of suppressing bleed-out and preventing stickiness on the surface of the rubber composition, it is preferably 100 parts by mass or less, more preferably 70 parts by mass or less, and even more preferably 40 parts by mass or less.

[0194] <Masterbatch for rubber modification> The rubber modification masterbatch of the present embodiment contains the first rubber component containing the highly branched conjugated diene polymer of the present embodiment described above and cellulose nanofibers. The content of the first rubber component in the rubber modification masterbatch is, in one aspect, 30% by mass or more, or 40% by mass or more, or 50% by mass or more, and in one aspect, 80% by mass or less, or 70% by mass or less, or 60% by mass or less.

[0195] [Manufacturing masterbatches for rubber modification] The rubber modification masterbatch may be a kneaded product. The method of mixing the constituent materials of the rubber modification masterbatch is not limited to the following, but includes, for example, a melt kneading method using a general mixer such as an open roll, a Banbury mixer, a kneader, a single screw extruder, a twin screw extruder, or a multi-screw extruder, and a method of dissolving and mixing each component and then removing the solvent by heating. Among these, the melt kneading method using a roll, a Banbury mixer, a kneader, or an extruder is preferred from the viewpoint of productivity and kneadability. In addition, both a method of kneading the constituent materials of the rubber modification masterbatch of this embodiment at once and a method of mixing them in multiple batches are applicable. The kneading temperature may be about room temperature (about 15°C to 30°C), but may be high enough not to cause a crosslinking reaction of the rubber component, for example, 140°C or lower, more preferably 120°C or lower. The lower limit is preferably 70°C or higher, or 80°C or higher. In one embodiment, the heating temperature is preferably 80°C to 140°C, or 80°C to 120°C.

[0196] In the case where the rubber modifying masterbatch of the present disclosure contains a surfactant, the production method thereof is as follows: Preparing a cellulose nanofiber composition comprising cellulose nanofibers and a surfactant; and A step of mixing the cellulose nanofiber composition with a first rubber component containing a highly branched conjugated diene-based polymer; An example of a method includes the following.

[0197] In the case where the rubber modification masterbatch of the present disclosure contains a surfactant and a liquid rubber, the production method thereof is as follows: A step of preparing a cellulose nanofiber composition containing cellulose nanofibers, a liquid rubber, and a surfactant; and A step of mixing the cellulose nanofiber composition with a first rubber component containing a highly branched conjugated diene-based polymer; An example of a method includes the following.

[0198] In each of the above methods, the cellulose nanofiber composition may be a powder of the present disclosure.

[0199] When the rubber modification masterbatch contains a modified liquid rubber, it is preferable to set the discharge temperature of the kneading to a high temperature at which the modified liquid rubber reacts with the cellulose nanofibers. This makes it possible to obtain a cured product with a high tensile modulus and a high elastic modulus. From this viewpoint, the preferred kneading temperature is 100°C to 170°C, or 120°C to 160°C, or 150°C to 160°C.

[0200] In order to improve the cohesiveness and handleability, the rubber modification masterbatch is preferably formed into a sheet having a thickness of, for example, 10 mm to 30 mm using a rolling roll. The rubber modification masterbatch may further contain components other than those exemplified in the present disclosure, as long as they do not impair the effects of the present invention.

[0201] <Highly branched conjugated diene polymer composition> The highly branched conjugated diene polymer composition of the present embodiment includes a rubber component and cellulose nanofibers. In one aspect, the highly branched conjugated diene polymer composition is a rubber composition including a rubber modification masterbatch and a second rubber component including a highly branched conjugated diene polymer. By using the rubber modification masterbatch, a rubber composition in which cellulose nanofibers are uniformly dispersed in rubber can be obtained. As a result, the deterioration of rubber properties during the kneading process is prevented, and the dispersibility of fillers and the like is improved, so that excellent tensile modulus and high elasticity can be achieved. In one aspect, the highly branched conjugated diene polymer composition is a kneaded product of the rubber modification masterbatch of the present embodiment, the second rubber component, and one or more optional additives.

[0202] In the highly branched conjugated diene polymer composition, the content of the first rubber component derived from the master batch in 100% by mass of the first and second rubber components is preferably 5% by mass or more, more preferably 10% by mass or more, and even more preferably 15% by mass or more, in order to ensure that the content of the cellulose nanofibers contained in the rubber composition is not too small and the effects of the present invention are well obtained. In one embodiment, the content may be 50% by mass or less, 40% by mass or less, or 30% by mass or less, in terms of dispersibility of the cellulose nanofibers in the rubber composition.

[0203] The content of the rubber component in the highly branched conjugated diene polymer composition (in one embodiment, the total content of the first and second rubber components) is, in one embodiment, 70 mass% or more, or 80 mass% or more, or 90 mass% or more, and in one embodiment, 99 mass% or less, or 95 mass% or less, or 90 mass% or less.

[0204] [Production of highly branched conjugated diene polymer composition] The highly branched conjugated diene polymer composition can be obtained by mixing a rubber component containing a highly branched conjugated diene polymer, cellulose nanofibers (as a cellulose nanofiber composition in one embodiment), and optional additives (for example, silica-based inorganic fillers, carbon black, other fillers, silane coupling agents, rubber softeners, etc.). The method of mixing the constituent materials of the highly branched conjugated diene polymer composition is not limited to the following, but examples thereof include a melt-kneading method using a general mixer such as an open roll, a Banbury mixer, a kneader, a single-screw extruder, a twin-screw extruder, or a multi-screw extruder, and a method of dissolving and mixing each component and then removing the solvent by heating, etc. Among these, the melt-kneading method using a roll, a Banbury mixer, a kneader, or an extruder is preferred from the viewpoints of productivity and kneadability. In addition, both a method of kneading the constituent materials of the rubber composition of the present embodiment at once and a method of mixing them in multiple batches can be applied.

[0205] From the viewpoint of the dispersibility of cellulose nanofibers and properties such as the tensile modulus and elastic modulus of the cured product, it is preferable to prepare in advance a mixture (master batch) of the first rubber component containing a highly branched conjugated diene polymer and the cellulose nanofibers.

[0206] In the case where the highly branched conjugated diene-based polymer composition of the present disclosure contains a surfactant, a production method thereof includes the following steps: A step of preparing a cellulose nanofiber composition containing cellulose nanofibers and a surfactant; A step of mixing a cellulose nanofiber composition and a first rubber component containing a highly branched conjugated diene polymer to prepare a master batch for rubber modification; and A step of mixing the rubber modifying masterbatch and a second rubber component to prepare a highly branched conjugated diene polymer composition; An example of a method includes the following.

[0207] In the case where the highly branched conjugated diene-based polymer composition of the present disclosure contains a surfactant and a liquid rubber, the production method thereof is as follows: A step of preparing a cellulose nanofiber composition containing cellulose nanofibers, a liquid rubber, and a surfactant; A step of mixing a cellulose nanofiber composition and a first rubber component containing a highly branched conjugated diene polymer to prepare a master batch for rubber modification; and A step of mixing the rubber modifying masterbatch and a second rubber component to prepare a highly branched conjugated diene polymer composition; An example of a method includes the following.

[0208] In each of the above methods, the cellulose nanofiber composition may be a powder of the present disclosure.

[0209] <Cured Highly Branched Conjugated Diene Polymer> The highly branched conjugated diene polymer composition of the present embodiment may be a vulcanized composition (highly branched conjugated diene polymer cured product) that has been subjected to a vulcanization treatment with a vulcanizing agent. Examples of the vulcanizing agent include, but are not limited to, radical generators such as organic peroxides and azo compounds, oxime compounds, nitroso compounds, polyamine compounds, sulfur, and sulfur compounds. Examples of sulfur compounds include sulfur monochloride, sulfur dichloride, disulfide compounds, and polymer polysulfur compounds. The content of the vulcanizing agent is preferably 0.01 parts by mass or more and 20 parts by mass or less, and more preferably 0.1 parts by mass or more and 15 parts by mass or less, relative to 100 parts by mass of the rubber component. As the vulcanization method, a conventionally known method can be applied, and the vulcanization temperature is preferably 120°C or more and 200°C or less, and more preferably 140°C or more and 180°C or less.

[0210] In vulcanization, a vulcanization accelerator may be used as necessary. As the vulcanization accelerator, a conventionally known material may be used, and examples thereof include, but are not limited to, sulfenamide-based, guanidine-based, thiuram-based, aldehyde-amine-based, aldehyde-ammonia-based, thiazole-based, thiourea-based, and dithiocarbamate-based vulcanization accelerators. As the vulcanization aid, examples thereof include, but are not limited to, zinc oxide and stearic acid. The content of the vulcanization accelerator is preferably 0.01 parts by mass or more and 20 parts by mass or less, and more preferably 0.1 parts by mass or more and 15 parts by mass or less, relative to 100 parts by mass of the rubber component. EXAMPLES

[0211] The present embodiment will be described in more detail with reference to the following specific examples and comparative examples, but the present embodiment is not limited to the following examples and comparative examples as long as the gist of the present embodiment is not exceeded. Various physical properties in the examples and comparative examples described below were measured by the methods shown below.

[0212] (Weight average molecular weight) The chromatogram was measured using a GPC (gel permeation chromatography) measuring device with three columns packed with polystyrene gel connected together, and the weight average molecular weight (Mw) was calculated based on a calibration curve using standard polystyrene. The specific measurement conditions are shown below. The measurement was performed by injecting 20 μL of the following measurement solution into the GPC measuring device.

[0213] (Measurement conditions) Equipment: Tosoh Corporation product name "HLC-8320GPC" Eluent: 5mmol / L triethylamine in tetrahydrofuran (THF) Guard column: Tosoh Corporation's product name "TSKguardcolumn SuperH-H" Separation column: Tosoh Corporation product names "TSKgel SuperH5000", "TSKgel SuperH6000", and "TSKgel SuperH7000" connected in this order.

[0214] Oven temperature: 40℃ Flow rate: 0.6mL / min Detector: RI detector (Tosoh Corporation product name "HLC8020") Measurement solution: 10 mg of the sample to be measured is dissolved in 20 mL of THF, and 20 μL of the measurement solution is injected into the GPC measurement device.

[0215] (Bound styrene content) 100 mg of the sample was dissolved in 100 mL of chloroform to prepare a measurement sample. The amount of bound styrene (mass%) relative to 100 mass% of the rubber-like polymer sample was measured based on the amount of absorption of ultraviolet light by the phenyl group of styrene (near 254 nm). A Shimadzu UV-2450 spectrophotometer was used as the measurement device.

[0216] (Microstructure of butadiene part: 1,2-vinyl bond content) A conjugated diene polymer was used as a sample, and 50 mg of the sample was dissolved in 10 mL of carbon disulfide to prepare a measurement sample. -1 The absorbance at a predetermined wave number was measured in the range of 1,2-vinyl bond content (mol%) was calculated according to the formula of Hampton's method (method described in R.R. Hampton, Analytical Chemistry 21, 923 (1949)). For the measurement, a Fourier transform infrared spectrophotometer "FT-IR230" manufactured by JASCO Corporation was used.

[0217] (Mooney Viscosity of Conjugated Diene Polymer and Conjugated Diene Polymer Composition) The Mooney viscosity was measured using a Mooney viscometer (manufactured by Ueshima Seisakusho under the trade name "VR1132") with an L-shaped rotor in accordance with JIS K6300. The measurement temperature was 100°C. First, the sample was preheated at the test temperature for 1 minute, and then the rotor was rotated at 2 rpm. The torque was measured after 4 minutes to obtain the Mooney viscosity (ML (1+4) ) was decided.

[0218] (Contraction factor: g') A conjugated diene polymer sample was measured using a gel permeation chromatography (GPC) measuring device (manufactured by Malvern under the trade name "GPCmax VE-2001") having three columns packed with polystyrene gel connected together, and three detectors connected in that order: a light scattering detector, an RI detector, and a viscosity detector (manufactured by Malvern under the trade name "TDA305"). Based on standard polystyrene, the absolute molecular weight was calculated from the measurement results of the light scattering detector and the RI detector, and the intrinsic viscosity was calculated from the measurement results of the RI detector and the viscosity detector.

[0219] The constants (K, α) in the relational equation between intrinsic viscosity and molecular weight ([η]=KMα ([η]: intrinsic viscosity, M: molecular weight)) were set to logK=-3.883 and α=0.771, and the range of molecular weight M was input from 1000 to 2,000,000 to clarify the relationship between the standard intrinsic viscosity [η]0 and the molecular weight M. For this standard intrinsic viscosity [η]0, the intrinsic viscosity [η] at each molecular weight M of the sample obtained by 3D-GPC measurement was calculated as [η] / [η]0 for each molecular weight M as the relationship of the intrinsic viscosity [η] to the standard intrinsic viscosity [η]0, and the average value was taken as the shrinkage factor (g').

[0220] The columns used were a guard column (manufactured by Tosoh Corporation under the trade name "TSKguardcolumn HHR-H") and columns (manufactured by Tosoh Corporation under the trade names "TSKgel G6000HHR", "TSKgel G5000HHR", and "TSKgel G4000HHR"). 10 mg of the measurement sample was dissolved in 20 mL of tetrahydrofuran (THF) to prepare a measurement solution, and 200 μL of the measurement solution was injected into a GPC measurement device and measured under conditions of an oven temperature of 40° C. and a THF flow rate of 1.0 mL / min.

[0221] (Production Example 1) Conjugated diene polymer (SBR-1) The polymerization reactor was a tank-type pressure vessel with an internal volume of 10 L, an internal height (L) to diameter (D) ratio (L / D) of 4.0, an inlet at the bottom, an outlet at the top, and a jacket for temperature control. 1,3-butadiene, which had been previously dehydrated, was mixed at 17.9 g / min, styrene at 9.8 g / min, and n-hexane at 145.3 g / min. In a static mixer installed in the middle of the piping supplying this mixed solution to the inlet of the reactor, n-butyllithium for inactivating remaining impurities was added at 0.104 mmol / min, mixed, and then continuously supplied to the bottom of the reactor. Furthermore, 2,2-bis(2-oxolanyl)propane as a polar substance at a rate of 0.0194 g / min and n-butyllithium as a polymerization initiator at a rate of 0.220 mmol / min were fed to the bottom of the polymerization reactor, which was being vigorously mixed with a stirrer, to continue the polymerization reaction continuously. The temperature of the polymerization solution at the top outlet of the reactor was controlled to be 75°C.

[0222] Next, bis(3-trimethoxysilylpropyl)-[3-(2,2-dimethoxy-1-aza-2-silacyclopentane)propyl]amine diluted to 2.74 mmol / L as a coupling agent was continuously added at a rate of 0.0367 mmol / min (n-hexane solution containing 5.2 ppm water) to the polymer solution flowing out from the outlet of the reactor, and the polymer solution to which the coupling agent was added was mixed by passing through a static mixer to undergo a coupling reaction. At this time, it took 4.8 minutes for the coupling agent to be added to the polymer solution flowing out from the outlet of the reactor, the temperature was 68°C, and the difference between the temperature in the polymerization process and the temperature before the coupling agent was added was 7°C. An antioxidant (BHT) was continuously added to the polymer solution that had undergone the coupling reaction at 0.055 g / min (n-hexane solution) so that the amount was 0.2 g per 100 g of polymer, and the coupling reaction was terminated. The solvent was removed by steam stripping to obtain a conjugated diene polymer (SBR-1). The physical properties of SBR-1 are shown in Table 1.

[0223] (Production Example 2) Conjugated diene polymer (SBR-2) Two tank-type pressure vessels with an internal volume of 10 L, an internal height (L) to diameter (D) ratio (L / D) of 4.0, an inlet at the bottom and an outlet at the top, and a jacket for temperature control were connected as polymerization reactors. 1,3-butadiene, which had been previously dehydrated, was mixed at 18.6 g / min, styrene at 10.0 g / min, and n-hexane at 175.2 g / min. In a static mixer installed in the middle of the piping supplying this mixed solution to the inlet of the reactor, n-butyllithium for inactivating remaining impurities was added at 0.103 mmol / min, mixed, and then continuously supplied to the bottom of the reactor. Furthermore, 2,2-bis(2-oxolanyl)propane as a polar substance at a rate of 0.081 mmol / min and n-butyllithium as a polymerization initiator at a rate of 0.149 mmol / min were fed to the bottom of the first reactor, which was vigorously mixed with a stirrer, and the temperature inside the reactor was maintained at 67°C. The polymer solution was continuously extracted from the top of the first reactor, continuously fed to the bottom of the second reactor, and the reaction was continued at 70°C, and further fed to a static mixer from the top of the second reactor. When the polymerization was sufficiently stable, trimethoxy(4-vinylphenyl)silane as a branching agent was added from the bottom of the second reactor at a rate of 0.0193 mmol / min.

[0224] Next, N,N,N',N'-tetrakis(3-trimethoxysilylpropyl)-1,3-propanediamine was added continuously at a rate of 0.0193mmol / min as a coupling agent to the polymer solution flowing out from the outlet of the reactor, and mixed using a static mixer to carry out a coupling reaction. At this time, it took 4.8 minutes for the coupling agent to be added to the polymer solution flowing out from the outlet of the reactor, the temperature was 68°C, and the difference between the temperature in the polymerization process and the temperature before the coupling agent was added was 2°C. An antioxidant (BHT) was continuously added to the polymer solution that had undergone the coupling reaction at 0.055g / min (n-hexane solution) so that the amount was 0.2g per 100g of polymer, and the coupling reaction was terminated. The solvent was removed by steam stripping to obtain a conjugated diene polymer (SBR-2). The physical properties of SBR-2 are shown in Table 1.

[0225] ((Production Example 3) Conjugated diene polymer (SBR-3) A temperature-controllable autoclave having an internal volume of 10 L, an internal height (L) to diameter (D) ratio (L / D) of 4.0, a stirrer and a jacket was used as a reactor, and 1995 g of cyclohexane and n-butyllithium for neutralizing impurities present in the reactor that may hinder the polymerization reaction were placed in the reactor, stirred at 70°C for 5 minutes, cooled to room temperature, and the solution was removed to empty the reactor.

[0226] Next, 1,680 g of cyclohexane from which impurities had been removed, 112 g of styrene, 208 g of 1,3-butadiene, and 0.092 mmol of 2,2-bis(2-oxolanyl)propane as a polar substance were placed in a reactor, and when the temperature inside the reactor was 58°C, 2.15 mmol of n-butyllithium was added as a polymerization initiator to initiate polymerization.

[0227] Immediately after the polymerization started, the temperature inside the reactor rose and reached a peak temperature of 78°C. When a drop in temperature was confirmed, 0.49 mmol of bis(3-trimethoxysilylpropyl)-N-methylamine was added as a coupling agent and stirred for another 10 minutes. The coupling agent was added 2 minutes after the peak temperature was reached.

[0228] 2.30 mmol of ethanol was added as a polymerization terminator to terminate the reaction, and a polymer solution containing a conjugated diene polymer was obtained. 0.64 g of 2,6-di-tert-butyl-4-hydroxytoluene was added as an antioxidant to the obtained polymerization solution, and the solvent was removed by steam stripping. After vacuum drying, a conjugated diene polymer (SBR-3) was obtained. The analytical results of SBR-3 are shown in Table 1.

[0229] (Production Example 4) Conjugated diene polymer (SBR-4) The polymerization reactor was a tank-type pressure vessel with an internal volume of 10 L, an internal height (L) to diameter (D) ratio (L / D) of 4.0, an inlet at the bottom, an outlet at the top, and a jacket for temperature control. 1,3-butadiene, which had been previously dehydrated, was mixed at 17.9 g / min, styrene at 9.8 g / min, and n-hexane at 145.3 g / min. In a static mixer installed in the middle of the piping supplying this mixed solution to the inlet of the reactor, n-butyllithium for inactivating remaining impurities was added at 0.104 mmol / min, mixed, and then continuously supplied to the bottom of the reactor. Furthermore, 2,2-bis(2-oxolanyl)propane as a polar substance at a rate of 0.0194 g / min and n-butyllithium as a polymerization initiator at a rate of 0.258 mmol / min were fed to the bottom of the polymerization reactor, which was being vigorously mixed with a stirrer, to continue the polymerization reaction continuously. The temperature of the polymerization solution at the top outlet of the reactor was controlled to be 75°C.

[0230] Next, bis(3-trimethoxysilylpropyl)methylamine diluted to 2.74 mmol / L as a coupling agent was continuously added to the polymer solution flowing out from the outlet of the reactor at a rate of 0.0624 mmol / min (n-hexane solution containing 5.2 ppm water), and the polymer solution to which the coupling agent was added was mixed by passing through a static mixer to undergo a coupling reaction. At this time, it took 4.8 minutes for the coupling agent to be added to the polymer solution flowing out from the outlet of the reactor, the temperature was 68°C, and the difference between the temperature in the polymerization process and the temperature before the coupling agent was added was 7°C. An antioxidant (BHT) was continuously added to the polymer solution that had undergone the coupling reaction at 0.055 g / min (n-hexane solution) so that the amount was 0.2 g per 100 g of polymer, and the coupling reaction was terminated. The solvent was removed by steam stripping to obtain a conjugated diene polymer (SBR-3). The physical properties of SBR-3 are shown in Table 1.

[0231] [Table 1]

[0232] <Preparation of cellulose nanofiber composition> The product names used for each component in Table 2 are as follows: <Surfactant-1> Kao Corporation's product name: "Emulgen 102KG" (Polyoxyethylene (2) monolauryl ether (number in parentheses indicates number of repeats of oxyethylene chain) <Surfactant-2> Kao Corporation's product name: "Rheodor SP-O10V" (sorbitan monooleate) <Liquid rubber-1> Cray Valley's product name "Ricon 184" (liquid butadiene-styrene copolymer, Mn=8,600)

[0233] <Cellulose nanofiber> (CNF: Microfibrous cellulose) 3 parts by mass of cotton linter pulp was immersed in 27 parts by mass of water and dispersed with a pulper. 30 parts by mass of the pulper-treated cotton linter pulp slurry (including 3 parts by mass of cotton linter pulp) was added to 170 parts by mass of water to disperse the mixture in water (solid content rate: 1.5% by mass), and the aqueous dispersion was beaten for 30 minutes using a SDR14 lab refiner (pressure type DISK type) manufactured by Aikawa Iron Works Co., Ltd. as a disc refiner device with a clearance between discs of 1 mm. Subsequently, thorough beating was performed under conditions in which 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 directly subjected to a high-pressure homogenizer (NSO15H manufactured by Niro Soavi Co., Ltd. (Italy)) for 10 times of refinement under an operating pressure of 100 MPa to obtain a fine cellulose fiber slurry (solid content concentration: 1.5% by mass). The mixture was then concentrated using a dehydrator to a solid content of 10% by mass to obtain a concentrated cake of CNF.

[0234] <Procedure for preparing the composition> (Production Example 1) CNF composition (CNF-1) Purified water was added to the above CNF (aqueous dispersion of cellulose fibers) to obtain an aqueous dispersion with a final cellulose nanofiber content of 5% by mass. Liquid rubber-1 and surfactant-1 were added to this to prepare an aqueous dispersion with a final composition of 90% by mass of water, 5% by mass of cellulose fibers, 2.86% by mass of liquid rubber, and 2.14% by mass of surfactant. The aqueous dispersion was mixed for 5 minutes using a centrifugal mixer ARE-310 manufactured by Thinky Corporation to obtain a dispersion of a cellulose nanofiber composition. The obtained dispersion was dried at 80°C using SPH-201 manufactured by Espec Corporation to obtain a dried body. The obtained dried body was pulverized for 30 seconds using a mini speed mill MS-05 manufactured by LabNect Co., Ltd. to obtain a CNF composition powder (CNF-1).

[0235] The compacted bulk density of the obtained dried powder was measured using a powder tester PT-X manufactured by Hosokawa Micron Corporation. Specifically, a resin adapter (inner diameter 50.46 mm x length 40 mm) of sufficient capacity was connected to the top of a stainless steel 100 mL (inner diameter 50.46 mm x depth 50 mm) bottomed cylindrical container so as to be in close contact with the container, and the dried material was poured into the bottomed cylindrical container at 10 g / min until it overflowed using a medicine spoon. After that, the bottomed cylindrical container was subjected to vibration with an amplitude of 1.5 mm and 50 Hz for 30 seconds using a motor with an eccentric weight attached to the rotating shaft while the adapter was still connected. Next, the adapter was removed, and the dried material was leveled off, and the weight was measured to the nearest 0.01 g. The number average value of the weight measured three times was divided by the internal volume of the bottomed cylindrical container to calculate the compacted bulk density.

[0236] (Production Example 2) CNF composition (CNF-2) A CNF composition powder (CNF-2) was obtained in the same manner as in Production Example 1, except that liquid rubber-1 and surfactant-1 were added to prepare an aqueous dispersion with a final composition of 91.15 mass% water, 5 mass% cellulose fiber, 2.86 mass% liquid rubber, and 0.99 mass% surfactant.

[0237] (Production Example 3) CNF composition (CNF-3) A CNF composition powder (CNF-3) was obtained in the same manner as in Production Example 1, except that surfactant-1 was added to prepare an aqueous dispersion with a final composition of 92.86 mass% water, 5 mass% cellulose fiber, and 2.14 mass% surfactant.

[0238] (Production Example 4) CNF composition (CNF-4) A CNF composition powder (CNF-4) was obtained in the same manner as in Production Example 1, except that surfactant-2 was added to prepare an aqueous dispersion with a final composition of 92.86 mass% water, 5 mass% cellulose fiber, and 2.14 mass% surfactant.

[0239] [Table 2]

[0240] <Masterbatch manufacturing> The product names used for the liquid rubbers in Table 3 are as follows: <Liquid rubber> LR-1: Cray Valley Ricon131MA20 (maleic anhydride modified liquid polybutadiene, Mn=5,600, 11 maleic anhydride molecules per molecular chain) LR-2: Cray Valley Ricon184MA6 (maleic anhydride modified liquid styrene butadiene copolymer, Mn=9,100, 6 maleic anhydride molecules per molecular chain) LR-3: Kuraray LIR-403 (maleic anhydride modified liquid polyisoprene, Mn=34000, 3 maleic anhydride molecules per molecular chain)

[0241] (Production Example 1) Masterbatch for rubber modification (MB-1) In the first stage of mixing, 100 parts by mass of the conjugated diene polymer (SBR-1) and 50 parts by mass of the CNF composition (CNF-1) were mixed at a filling rate of 65% and a rotor rotation speed of 30 to 50 rpm using an internal mixer (capacity: 0.35 L) equipped with a temperature control device. At this time, the temperature of the internal mixer was controlled, and the discharge temperature was 155 to 160°C to obtain a rubber composition (compound).

[0242] Next, in the second stage of mixing, the mixture obtained above was cooled to room temperature and then mixed again to improve the dispersion of CNF. In this case, the temperature of the internal mixer was also controlled, and the discharge temperature was adjusted to 155-160°C to obtain a master batch for rubber modification (MB-1).

[0243] (Production Examples 2 to 6) Masterbatches for rubber modification (MB-2 to MB-6) Except for changing the raw materials (conjugated diene polymer and CNF composition) and compounding amounts used in the production of the rubber modification masterbatch as shown in Table 3, rubber modification masterbatches (MB-2 to MB-6) were obtained in the same manner as in Production Example 1.

[0244] (Production Example 7) Masterbatch for rubber modification (MB-7) Using an internal mixer (capacity 0.35 L) equipped with a temperature control device, 100 parts by mass of conjugated diene polymer (SBR-1) and 50 parts by mass of CNF composition (CNF-1) were mixed for 1 minute under the conditions of a filling rate of 65% and a rotor rotation speed of 30 to 70 rpm in the first stage of mixing, and then 10 parts by mass of modified liquid polybutadiene (LR-1) were added and mixed. The temperature of the internal mixer was controlled, and the discharge temperature was 155 to 160°C to obtain a rubber composition (compound).

[0245] Next, in the second stage of mixing, the mixture obtained above was cooled to room temperature and then mixed again to improve the dispersion of CNF. In this case, the temperature of the internal mixer was also controlled, and the discharge temperature was adjusted to 155-160°C to obtain a master batch for rubber modification (MB-7).

[0246] (Production Example 8, Production Example 9) Masterbatch for rubber modification (MB-8, MB-9) Except for changing the raw materials (conjugated diene polymer and CNF composition, liquid rubber) and compounding amounts used in the production of the rubber modification masterbatch as shown in Table 3, rubber modification masterbatches (MB8 to MB-9) were obtained in the same manner as in Production Example 6.

[0247] (Production Example 10) Masterbatch for rubber modification (MB-10) A rubber modification masterbatch (MB-10) was obtained in the same manner as in Production Example 1, except that the raw materials (conjugated diene polymer and CNF composition) and compounding amounts used in the production of the rubber modification masterbatch were changed as shown in Table 3.

[0248] (Production Example 11) Masterbatch for rubber modification (MB-11) A rubber modification masterbatch (MB-11) was obtained in the same manner as in Production Example 6, except that the raw materials (conjugated diene polymer and CNF composition, liquid rubber) and compounding amounts used in the production of the rubber modification masterbatch were changed as shown in Table 3.

[0249] [Table 3]

[0250] <Preparation of conjugated diene polymer composition> The product names used for each component in Tables 4 and 5 are as follows: <Liquid rubber> LR-1: Cray Valley Ricon131MA20 (maleic anhydride modified liquid polybutadiene, Mn=5,600, 11 maleic anhydride molecules per molecular chain) LR-2: Cray Valley Ricon184MA6 (maleic anhydride modified liquid styrene butadiene copolymer, Mn=9,100, 6 maleic anhydride molecules per molecular chain) LR-3: Kuraray LIR-403 (maleic anhydride modified liquid polyisoprene, Mn=34000, 3 maleic anhydride molecules per molecular chain) <Silica> Evonik Degussa's product name "Ultrasil 7000GR" (nitrogen adsorption specific surface area 170 m 2 / g) <Carbon black> Product name "Seast KH (N339)" manufactured by Tokai Carbon Co., Ltd. <S-RAEオイル> JX Nippon Oil & Energy Corporation's product name: "Process NC140" <Silane coupling agent> Evonik's product name "Si75" (bis(triethoxysilylpropyl) disulfide) <Zinc oxide> "Zinc oxide" is a product name manufactured by Sakai Chemical Industry Co., Ltd. <Stearic acid> (Product name: "Lunac S-90V" manufactured by Kao Corporation) <Anti-aging agent> Nocrac 6C (N-(1,3-dimethylbutyl)-N'-phenyl-p-phenylenediamine) manufactured by Ouchi Shinko Chemical Co., Ltd. <Wax> "Sunnock" is a product name manufactured by Ouchi Shinko Chemical Co., Ltd. <Sulfur> Tsurumi Chemical Industry Co., Ltd. "Sulfax 200S" (powdered sulfur) <Vulcanization accelerator-1> "Noccela CZ" (N-cyclohexyl-2-benzothiazolyl sulfenamide), a product name manufactured by Ouchi Shinko Chemical Co., Ltd. <Vulcanization accelerator-2> "Noccela D" (1,3-diphenylguanidine), a product name manufactured by Ouchi Shinko Chemical Co., Ltd.

[0251] The properties of the conjugated diene polymer composition before vulcanization (rubber composition) and the conjugated diene polymer composition after vulcanization (cured product) were evaluated by the following methods.

[0252] (Dispersibility of cellulose nanofibers) The cured product of the conjugated diene polymer composition was placed in a mold for vulcanization press, and the dispersion state of the cellulose nanofibers was visually observed in a 5 cm square area on the surface and evaluated according to the following criteria. A: No visible aggregates B: A small number of aggregates (1 to 10) are observed. C: Many aggregates (11 or more) were observed.

[0253] (Sheet processability) The rubber composition after the third stage kneading described below was processed into a sheet-like composition by an open roll set at 70°C.

[0254] The condition of the sheet of the obtained sheet-like composition was visually observed and rated on a 5-point scale according to the following criteria, with a higher score indicating better sheet processability. 5: The sheet holds together well during rolling, the sheet surface is smooth, and the sheet edges are not jagged. 4: The sheet holds together well during rolling, but the sheet surface is slightly rough and the sheet edges are slightly jagged. 3: The sheet is not well-formed during rolling, the sheet surface is slightly rough, and the sheet edges are slightly jagged. 2: The sheet is not well-formed during rolling, the sheet surface is rough, and the sheet edges are jagged. 1: The sheet is not well-formed during rolling, the sheet surface is rough, and the sheet edges are jagged.

[0255] (Mooney Viscosity of Compound) The compound obtained above after the second stage kneading and before the third stage kneading described below was used as a sample, and the viscosity was measured using a Mooney viscometer in accordance with JIS K6300-1 after preheating at 100°C for 1 minute and rotating the rotor at 2 revolutions per minute for 4 minutes. The results of Comparative Example 3 were indexed to 100. The smaller the index, the better the processability.

[0256] (Tensile strength, tensile modulus and tensile elongation) The tensile strength, tensile modulus and tensile elongation were measured according to the tensile testing method of JIS K6251, and indexed based on the result of Comparative Example 3 being 100. A larger index indicates better tensile strength, tensile modulus and tensile elongation.

[0257] (Hardness) The hardness of the vulcanized product was measured using a type A durometer in accordance with JIS K6253 "Testing method for hardness of vulcanized and thermoplastic rubbers." The measurements were performed at 25°C. The results of Comparative Example 3 were indexed as 100. A larger index indicates better hardness. This indicates that.

[0258] (Storage modulus) The storage modulus was evaluated at 25°C, a frequency of 10 Hz, and a strain of 1% by the torsion method using a viscoelasticity tester ARES-G2 manufactured by TA Instruments. The results were indexed with the result of Comparative Example 3 set at 100. A larger index indicates a higher storage modulus.

[0259] (Examples 1 to 11 and Comparative Examples 1 to 2) The master batch and the conjugated diene polymer shown in Table 4 were used as rubber components and kneaded in the following manner according to the formulation shown in Table 4 to obtain conjugated diene polymer compositions. Using an internal mixer (capacity 0.35 L) equipped with a temperature control device, the master batch, conjugated diene polymer, filler (silica, carbon black), silane coupling agent, process oil, zinc oxide, and stearic acid were kneaded in the first stage of mixing under conditions of a filling rate of 65% and a rotor rotation speed of 30 to 70 rpm. At this time, the temperature of the internal mixer was controlled, and each conjugated diene polymer composition (blend) was obtained at a discharge temperature of 155 to 160°C.

[0260] Next, in the second stage of mixing, the mixture obtained above was cooled to room temperature, and then an antioxidant was added and the mixture was mixed again to improve the dispersion of the CNF or filler (silica, carbon black). In this case, the discharge temperature of the mixture was adjusted to 155 to 160°C by controlling the temperature of the mixer.

[0261] After cooling, in the third stage of kneading, sulfur, vulcanization accelerator-1, and vulcanization accelerator-2 were added and kneaded in an open roll set at 70°C. Then, the mixture was molded and vulcanized in a vulcanization press at 160°C for 25 minutes. The properties of the conjugated diene polymer composition before vulcanization and the conjugated diene polymer composition after vulcanization were evaluated. The results are shown in Table 4.

[0262] [Table 4]

[0263] (Examples 12 to 20) The conjugated diene polymers shown in Table 5 were used as raw rubber components and kneaded in the following manner according to the formulation shown in Table 5 to obtain conjugated diene polymer compositions.

[0264] In the first stage of mixing, a conjugated diene polymer, a cellulose nanofiber composition, a modified liquid rubber, a process oil, zinc oxide, and stearic acid were mixed at a filling rate of 65% and a rotor rotation speed of 30 to 70 rpm using an internal mixer (capacity: 0.35 L) equipped with a temperature control device. At this time, the temperature of the internal mixer was controlled, and the discharge temperature was 155 to 160°C to obtain a highly branched conjugated diene polymer composition (blend).

[0265] Next, in the second stage of mixing, the mixture obtained above was cooled to room temperature, and then an antioxidant was added and the mixture was mixed again to improve the dispersion of the cellulose nanofibers. In this case, the discharge temperature of the mixture was adjusted to 155 to 160°C by controlling the temperature of the mixer.

[0266] After cooling, in the third stage of kneading, sulfur, vulcanization accelerator-1, and vulcanization accelerator-2 were added and kneaded in an open roll set at 70°C. Then, the mixture was molded and vulcanized in a vulcanization press at 160°C for 25 minutes. The properties of the conjugated diene polymer composition before vulcanization and the conjugated diene polymer composition after vulcanization were evaluated. The results are shown in Table 5.

[0267] (Examples 21 to 22) The conjugated diene polymers shown in Table 5 were used as raw rubber components and kneaded in the following manner according to the formulation shown in Table 5 to obtain conjugated diene polymer compositions.

[0268] In the first stage of mixing, a conjugated diene polymer, a cellulose nanofiber composition, a reinforcing filler (silica), a modified liquid rubber, a process oil, zinc oxide, and stearic acid were mixed at a filling rate of 65% and a rotor rotation speed of 30 to 70 rpm using an internal mixer (capacity 0.35 L) equipped with a temperature control device. At this time, the temperature of the internal mixer was controlled, and each conjugated diene polymer composition (blend) was obtained at a discharge temperature of 155 to 160°C.

[0269] Next, in the second stage of mixing, the mixture obtained above was cooled to room temperature, and then an antioxidant was added and the mixture was mixed again to improve the dispersion of the cellulose nanofiber and reinforcing filler (silica). In this case, the discharge temperature of the mixture was adjusted to 155 to 160°C by controlling the temperature of the mixer.

[0270] After cooling, in the third stage of kneading, sulfur, vulcanization accelerator-1, and vulcanization accelerator-2 were added and kneaded in an open roll set at 70°C. Then, the mixture was molded and vulcanized in a vulcanization press at 160°C for 25 minutes. The properties of the conjugated diene polymer composition before vulcanization and the conjugated diene polymer composition after vulcanization were evaluated. The results are shown in Table 5.

[0271] (Comparative Examples 3 to 4) The conjugated diene polymers shown in Table 5 were used as raw rubber components and kneaded in the following manner according to the formulation shown in Table 5 to obtain conjugated diene polymer compositions.

[0272] In the first stage of mixing, a conjugated diene polymer, a cellulose nanofiber composition, a modified liquid rubber, a process oil, zinc oxide, and stearic acid were mixed at a filling rate of 65% and a rotor rotation speed of 30 to 70 rpm using an internal mixer (capacity: 0.35 L) equipped with a temperature control device. At this time, the temperature of the internal mixer was controlled, and each conjugated diene polymer composition (blend) was obtained at a discharge temperature of 155 to 160°C.

[0273] Next, in the second stage of mixing, the mixture obtained above was cooled to room temperature, and then an antioxidant was added and the mixture was mixed again to improve the dispersion of the cellulose nanofibers. In this case, the discharge temperature of the mixture was adjusted to 155 to 160°C by controlling the temperature of the mixer.

[0274] After cooling, in the third stage of kneading, sulfur, vulcanization accelerator-1, and vulcanization accelerator-2 were added and kneaded in an open roll set at 70°C. Then, the mixture was molded and vulcanized in a vulcanization press at 160°C for 25 minutes. The properties of the conjugated diene polymer composition before vulcanization and the conjugated diene polymer composition after vulcanization were evaluated. The results are shown in Table 5.

[0275] Comparative Example 5 The conjugated diene polymers shown in Table 5 were used as raw rubber components and kneaded in the following manner according to the formulation shown in Table 5 to obtain conjugated diene polymer compositions.

[0276] In the first stage of kneading, a conjugated diene polymer (SBR-3), silica, a silane coupling agent, process oil, zinc oxide, and stearic acid were kneaded using an internal mixer (capacity: 0.35 L) equipped with a temperature control device under conditions of a filling rate of 65% and a rotor rotation speed of 30 to 70 rpm. At this time, the temperature of the internal mixer was controlled, and each conjugated diene polymer composition (blend) was obtained at a discharge temperature of 155 to 160°C.

[0277] Next, in the second stage of mixing, the mixture obtained above was cooled to room temperature, and then the antioxidant was added and mixed again to improve the dispersion of the silica. In this case, the discharge temperature of the mixture was adjusted to 155 to 160°C by controlling the temperature of the mixer.

[0278] After cooling, in the third stage of kneading, sulfur, vulcanization accelerator-1, and vulcanization accelerator-2 were added and kneaded in an open roll set at 70°C. Then, the mixture was molded and vulcanized in a vulcanization press at 160°C for 25 minutes. The properties of the conjugated diene polymer composition before vulcanization and the conjugated diene polymer composition after vulcanization were evaluated. The results are shown in Table 5.

[0279] [Table 5]

[0280] (Examples 21 to 25, Comparative Example 6) The conjugated diene polymer, natural rubber and polybutadiene shown in Table 6 were used as raw rubber components and kneaded according to the formulation shown in Table 6 by the following method to obtain conjugated diene polymer compositions. In the first stage of mixing, raw rubber (conjugated diene polymer, natural rubber, polybutadiene), cellulose nanofiber composition, modified liquid rubber, process oil, wax, zinc oxide, and stearic acid were mixed at a filling rate of 65% and a rotor rotation speed of 30 to 70 rpm using an internal mixer (capacity 0.35 L) equipped with a temperature control device. At this time, the temperature of the internal mixer was controlled, and each conjugated diene polymer composition (compound) was obtained at a discharge temperature of 155 to 160°C.

[0281] Next, in the second stage of mixing, the mixture obtained above was cooled to room temperature, and then an antioxidant was added and the mixture was mixed again to improve the dispersion of the cellulose nanofibers. In this case, the discharge temperature of the mixture was adjusted to 155 to 160°C by controlling the temperature of the mixer.

[0282] After cooling, in the third stage of kneading, sulfur, vulcanization accelerator-1, and vulcanization accelerator-2 were added and kneaded using an open roll set at 70°C. The mixture was then molded and vulcanized in a vulcanization press at 160°C for 15 minutes. The properties of the conjugated diene polymer composition before vulcanization and the conjugated diene polymer composition after vulcanization were evaluated. The results are shown in Table 6. Each physical property value was indexed, with the result of Comparative Example 6 being set at 100. A larger index indicates a higher physical property value.

[0283] [Table 6]

[0284] As shown in Tables 4 and 5, it was confirmed that the highly branched conjugated diene polymer compositions obtained in Examples 1 to 22 had good sheet processability and low compound Mooney viscosity, and thus excellent rubber composition processability, without sacrificing tensile strength, tensile modulus, and elastic modulus, compared with the conjugated diene polymer compositions obtained in Comparative Examples 1 to 5.

[0285] In addition, it was confirmed that the conjugated diene polymer compositions using the masterbatches obtained in Examples 1 to 11 had excellent tensile strength, high tensile modulus and high elastic modulus compared to the conjugated diene polymer compositions obtained in Examples 12 to 22, and the improvement in physical properties by using the masterbatches was confirmed.

[0286] Furthermore, it was confirmed that the conjugated diene polymer compositions obtained in Examples 7 to 9 and Examples 18 to 20 had excellent tensile strength, high tensile modulus and high elastic modulus compared to the conjugated diene polymer compositions obtained in Examples 1 to 6 and Examples 12 to 17, and the improvement in physical properties by blending the modified liquid rubber was confirmed.

[0287] Furthermore, as shown in Table 6, the conjugated diene polymer compositions obtained in Examples 21 to 25 were confirmed to have higher tensile strength, higher tensile modulus, and higher elastic modulus than the conjugated diene polymer composition obtained in Comparative Example 6, and improved physical properties were also confirmed in the blends containing natural rubber and polybutadiene. [Industrial Applicability]

[0288] The highly branched conjugated diene polymer composition of the present invention is preferably used for applications such as interior and exterior parts of automobiles, anti-vibration rubber, belts, footwear, foams, various industrial products, etc. The highly branched conjugated diene polymer composition can be particularly applied to members using rubber or soft plastics, and is preferably applied to tires. Examples of tire applications include treads and sidewalls of tires for passenger cars, trucks, buses, heavy vehicles, etc.

Claims

1. a highly branched conjugated diene-based polymer having a shrinkage factor (g') of less than 0.72 as determined by gel permeation chromatography (GPC)-light scattering measurement using a viscometer; Cellulose nanofibers, A highly branched conjugated diene-based polymer composition comprising:

2. 100 parts by mass of a first rubber component containing 50% by mass or more of a highly branched conjugated diene-based polymer having a shrinkage factor (g') of less than 0.72 as determined by gel permeation chromatography (GPC)-light scattering measurement using a viscometer-equipped gel permeation chromatography (GPC), 15 parts by mass or more and 100 parts by mass or less of cellulose nanofibers; A masterbatch for rubber modification comprising:

3. 100 parts by mass of a rubber component containing 50% by mass or more of a highly branched conjugated diene polymer having a shrinkage factor (g') of less than 0.72 as determined by gel permeation chromatography (GPC)-light scattering measurement using a gel permeation chromatography (GPC) equipped with a viscosity detector; 1 part by mass or more and 15 parts by mass or less of cellulose nanofibers; A highly branched conjugated diene-based polymer composition comprising:

4. The highly branched conjugated diene polymer composition according to claim 3, wherein the highly branched conjugated diene polymer has a weight average molecular weight of 200,000 or more and 2,000,000 or less.

5. The highly branched conjugated diene polymer composition according to claim 3 , wherein the highly branched conjugated diene polymer contains 3% by mass or more and 60% by mass or less of aromatic vinyl monomer units.

6. The highly branched conjugated diene-based polymer composition according to claim 3 , wherein the cellulose nanofibers do not have an ionic group.

7. The highly branched conjugated diene-based polymer composition according to claim 3 , further comprising a surfactant.

8. The highly branched conjugated diene polymer composition according to claim 7, wherein the surfactant is a nonionic surfactant.

9. The highly branched conjugated diene-based polymer composition according to claim 7, wherein the highly branched conjugated diene-based polymer composition further contains a liquid rubber.

10. 10. The highly branched conjugated diene polymer composition according to claim 9, wherein the liquid rubber has a number average molecular weight of 1,000 to 80,000.

11. The highly branched conjugated diene polymer composition according to claim 9, wherein the ratio (Mw / Mn) of the number average molecular weight (Mn) to the weight average molecular weight (Mw) of the liquid rubber is 1.5 to 5.

12. The highly branched conjugated diene-based polymer composition according to claim 9, wherein the liquid rubber comprises a modified liquid rubber modified with an unsaturated carboxylic acid and / or a derivative thereof.

13. The highly branched conjugated diene polymer composition according to claim 12, comprising 1 part by mass or more and 25 parts by mass or less of the modified liquid rubber per 100 parts by mass of the rubber component.

14. The highly branched conjugated diene polymer composition according to claim 3, comprising 10 parts by mass or more and 80 parts by mass or less of a reinforcing filler per 100 parts by mass of the rubber component.

15. A cured product of a highly branched conjugated diene polymer, which is a cured product of the highly branched conjugated diene polymer composition according to any one of claims 3 to 14.

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