Rubber composition, vulcanized rubber, and tire

Abstract

A rubber composition which contains a diene-based rubber, a copolymer A, silica, and a silane coupling agent, wherein the copolymer A contains a monomer unit that is derived from an olefin monomer having 2 to 8 carbon atoms, and a monomer unit that has a glycidyl group. A rubber composition which contains a diene-based rubber, a copolymer A, and silica that is surface-treated with a silane coupling agent, wherein the copolymer A contains a monomer unit that is derived from an olefin monomer having 2 to 8 carbon atoms, and a monomer unit that has a glycidyl group.

Description

Rubber compositions, vulcanized rubber, and tires

[0001] This invention relates to rubber compositions, vulcanized rubber, and tires, etc.

[0002] In recent years, land transport using vehicles such as large trucks and express buses has become increasingly active, and there has been progress in improving the performance of vehicles (higher speed, higher horsepower, larger size, etc.) and electrification (increased weight). Under these circumstances, tires used in vehicles are now used under high heat generation conditions, and there is active development of technologies to improve low heat generation (fuel efficiency) while maintaining durability (hardness) in the rubber used in tires. For example, Patent Documents 1 and 2 disclose rubber compositions containing resorcinol or resorcinol derivatives for the purpose of improving low heat generation and fracture strength.

[0003] Japanese Patent Publication No. 2006-232895 Japanese Patent Publication No. 2009-179299

[0004] However, tires (vulcanized rubber) obtained from conventional rubber compositions are not sufficient in terms of tensile strength and low heat generation, and there is still room for improvement.

[0005] One aspect of the present invention aims to provide a rubber composition capable of producing vulcanized rubber having excellent tensile strength and low heat generation. Another aspect of the present invention aims to provide vulcanized rubber and tires obtained using the rubber composition.

[0006] The present invention includes, for example, the following: [1] A rubber composition comprising a diene rubber, copolymer A, silica, and a silane coupling agent, wherein copolymer A comprises monomer units derived from an olefin monomer having 2 to 8 carbon atoms and monomer units having a glycidyl group. [2] A rubber composition comprising a diene rubber, copolymer A, and silica surface-treated with a silane coupling agent, wherein copolymer A comprises monomer units derived from an olefin monomer having 2 to 8 carbon atoms and monomer units having a glycidyl group. [3] The rubber composition according to [1] or [2], wherein the diene rubber comprises at least one selected from the group consisting of natural rubber (NR), butadiene rubber (BR), and styrene-butadiene rubber (SBR). [4] The rubber composition according to any one of [1] to [3], wherein the monomer units derived from an olefin monomer having 2 to 8 carbon atoms are monomer units derived from ethylene. [5] The rubber composition according to any one of [1] to [4], wherein the monomer unit having a glycidyl group is a monomer unit derived from glycidyl (meth)acrylate. [6] The rubber composition according to any one of [1] to [5], wherein the content of copolymer A is 0.1 to 10 parts by mass per 100 parts by mass of the diene rubber. [7] The rubber composition according to any one of [1] to [6], wherein the content of copolymer A is 0.1 to 35 parts by mass per 100 parts by mass of silica. [8] The rubber composition according to [1], wherein the content of copolymer A is 1 to 350 parts by mass per 100 parts by mass of the silane coupling agent. [9] Vulcanized rubber obtained by vulcanizing the rubber composition according to any one of [1] to [8].

[10] A tire comprising a rubber member containing the vulcanized rubber according to [9].

[11] A method for achieving at least one of improving the tensile strength of vulcanized rubber and reducing the heat generation of vulcanized rubber, comprising: obtaining a rubber composition by adding copolymer A, silica, and a silane coupling agent to a diene rubber; and vulcanizing the rubber composition, wherein copolymer A comprises monomer units derived from olefin monomers having 2 to 8 carbon atoms and monomer units having a glycidyl group.

[0007] According to the present invention, it is possible to provide a rubber composition that can produce vulcanized rubber having excellent tensile strength and low heat generation. Furthermore, according to the present invention, it is possible to provide vulcanized rubber and tires obtained using the rubber composition.

[0008] The following describes in detail some examples of the present invention. However, the present invention is not limited to the following examples.

[0009] <Rubber Composition> A rubber composition according to one embodiment of the present invention contains a diene rubber, copolymer A, silica, and a silane coupling agent, wherein copolymer A contains monomer units derived from ethylene and monomer units having a glycidyl group. The vulcanized rubber obtained from such a rubber composition has excellent breaking strength and low heat generation. The inventors speculate on the reason for this as follows: Firstly, by containing silica as a filler in the rubber composition, the heat generation of the vulcanized rubber can be reduced compared to the case where a filler other than silica (e.g., carbon black) is used. However, when silica is used, the breaking strength of the vulcanized rubber tends to decrease compared to the case where a filler other than silica (e.g., carbon black) is used. However, by including copolymer A and a silane coupling agent together with silica in the rubber composition, the surface state of the silica can be controlled, and the balance between the dispersion state of the silica and the bonding state to the diene rubber can be made favorable, thereby improving the breaking strength of the vulcanized rubber. Furthermore, when the rubber composition contains copolymer A along with fillers other than silica (e.g., carbon black), the exothermic properties of the vulcanized rubber tend to increase. However, by including copolymer A and a silane coupling agent along with silica in the rubber composition, the surface state of the silica can be controlled, and a suitable balance can be achieved between the dispersion state of the silica and its bonding state to the diene-based rubber. This allows for lower exothermic properties compared to cases where copolymer A and a silane coupling agent are not included. However, the mechanism of the present invention is not limited to the above.

[0010] Even if the rubber composition contains silica surface-treated with a silane coupling agent instead of silica and a silane coupling agent, the surface state of the silica can be controlled, and a suitable balance can be achieved between the dispersion state of the silica and the bonding state to the diene rubber, thereby improving the tensile strength of the vulcanized rubber and reducing the heat generation. That is, another embodiment of the present invention is a rubber composition containing a diene rubber, copolymer A, and silica surface-treated with a silane coupling agent, wherein copolymer A contains monomer units derived from ethylene and monomer units having a glycidyl group. The silica surface-treated with the silane coupling agent and the silane coupling agent used for surface-treating the silica may be the silica and silane coupling agent described later, respectively.

[0011] [Diene-based rubber] The rubber composition contains diene-based rubber. Diene-based rubber refers to rubber made from diene monomers having conjugated double bonds. Examples of diene-based rubbers include natural rubber (NR), butadiene rubber (BR), styrene-butadiene copolymer rubber (SBR), polyisoprene rubber (IR), nitrile rubber (NBR), chloroprene rubber (CR), isoprene-isobutylene copolymer rubber (IIR), ethylene-propylene-diene copolymer rubber (EPDM), and halogenated butyl rubber (HR). These diene-based rubbers may be liquid rubbers that are liquid at room temperature (23°C). These may be used individually or in combination of two or more types.

[0012] Examples of NR (Natural Ratio) include natural rubber of grades such as RSS#1, RSS#3, TSR20, and SIR20. NR may also be modified natural rubber such as epoxidized natural rubber, deproteinized natural rubber, or hydrogenated natural rubber. Examples of epoxidized natural rubber include those with an epoxidization degree of 10 to 60 mol% (e.g., ENR25 and ENR50 from Kumpulan Guthrie, and EPOXY PRENE25 from MMG). For deproteinized natural rubber, deproteinized natural rubber with a total nitrogen content of 0.3% by mass or less is preferred. Other modified natural rubbers include, for example, modified natural rubber containing polar groups obtained by reacting natural rubber with 4-vinylpyridine, N,N,-dialkylaminoethyl acrylate (e.g., N,N,-diethylaminoethyl acrylate), 2-hydroxyethyl acrylate, hydrazide compounds (e.g., isophthalic acid dihydrazide), etc.; modified natural rubber containing hydroxyl groups obtained by ring-opening the epoxy groups of epoxidized natural rubber; and natural rubber having carbonyl groups at the ends of its molecular chains, obtained by oxidative decomposition of natural rubber.

[0013] As for BR, any BR commonly used in the tire industry can be used. Examples of BR include solution-polymerized BR such as high-cis BR with 90% or more cis-1,4 bonds and low-cis BR with approximately 35% cis bonds, as well as BR having syndiotactic polybutadiene crystals. From the viewpoint of low exothermic properties, BR with a high cis content is preferred, and high-cis BR with a cis content of 95% by mass or more is more preferred. Examples of high-cis BR include "BR01" from ENEOS Material Corporation, "BR1220" from Nippon Zeon Co., Ltd., "BR150B" from Ube Industries, Ltd., and "Buna CB22" from Arlanxeo. Examples of BR having syndiotactic polybutadiene crystals include "UBEPOL VCR" from Ube Industries, Ltd. and "RB830" from ENEOS Material Corporation. These may be used individually or in combination of two or more.

[0014] Examples of SBRs include emulsion polymerized SBR and solution polymerized SBR, as described on pages 210-211 of the "Rubber Industry Handbook (Fourth Edition)" compiled by the Japan Rubber Association. Hydrogenated SBR, in which the diene portion of the SBR is hydrogenated, can also be used. These may be used individually or in combination of two or more types.

[0015] As the solution polymerized SBR, either an unmodified solution polymerized SBR or a modified solution polymerized SBR having at least one element of nitrogen, tin, and silicon, obtained by modifying the molecular ends and main chain with a modifying agent, may be used. Examples of modifying agents include lactam compounds, amide compounds, urea compounds, N,N-dialkylacrylamide compounds, isocyanate compounds, imide compounds, silane compounds having alkoxy groups, silane compounds having vinyl groups, siloxane compounds, aminosilane compounds, and tin compounds. These modifying agents may be used individually or in combination. Examples of modified solution polymerized SBRs include solution polymerized SBRs with molecular ends modified using 4,4'-bis(dialkylamino)benzophenone, such as "Nipol® NS116" manufactured by Nippon Zeon Co., Ltd., and silane-modified solution polymerized SBRs such as "E10" and "E15" manufactured by Asahi Kasei Corporation. Furthermore, oil-polymerized SBRs, which are obtained by adding process oils, aroma oils, or other oils to emulsion-polymerized SBRs or solution-polymerized SBRs, can also be used.

[0016] The diene rubber component preferably contains at least one selected from the group consisting of NR, BR, and SBR. The diene rubber component may be a combination of NR and BR, a combination of NR and SBR, or a combination of SBR and BR. When the diene rubber component contains NR and BR, the total content of NR and BR in the diene rubber component is preferably 50 to 100% by mass, more preferably 70 to 100% by mass, even more preferably 80 to 100% by mass, and particularly preferably 100% by mass, from the viewpoint of easily obtaining vulcanized rubber having excellent breaking strength and low heat generation.

[0017] The mass ratio of the amount of BR to the amount of NR (amount of BR / amount of NR) may be 5 / 95 to 50 / 50, 10 / 90 to 40 / 60, or 15 / 85 to 35 / 65, from the viewpoint of easily obtaining vulcanized rubber having excellent breaking strength and low heat generation. The mass ratio of the amount of BR to the amount of NR (amount of BR / amount of NR) may be 0.05 or more, 0.10 or more, 0.15 or more, or 0.20 or more, from the viewpoint of easily obtaining vulcanized rubber having excellent breaking strength and low heat generation, and from the same viewpoint, it may be 1.00 or less, 0.70 or less, 0.55 or less, 0.40 or less, or 0.30 or less.

[0018] The diene rubber content may be 35% by mass or more, 40% by mass or more, 45% by mass or more, or 50% by mass or more, based on the total amount of the rubber composition, from the viewpoint of easily obtaining vulcanized rubber having excellent breaking strength and low heat generation properties. Similarly, from the viewpoint of ease of obtaining vulcanized rubber having excellent breaking strength and low heat generation properties, it may be 85% by mass or less, 80% by mass or less, 75% by mass or less, or 70% by mass or less. The diene rubber content may be 35 to 85% by mass, 40 to 80% by mass, or 45 to 75% by mass, based on the total amount of the rubber composition.

[0019] [Copolymer A] The rubber composition contains copolymer A. Copolymer A comprises monomer unit a derived from an olefin monomer having 2 to 8 carbon atoms, and monomer unit b having a glycidyl group.

[0020] Monomer unit a may be a monomer unit derived from ethylene, a monomer unit derived from an α-olefin, or a combination thereof, and may also be a monomer unit derived from ethylene. Examples of α-olefins include linear olefins such as propylene, 1-butene, 1-pentene, 1-hexene, 1-heptene, and 1-octene; cyclic olefins such as norbornene, 5-methylnorbornene, and 1-methylnorbornene; and aromatic olefins such as styrene, methylstyrene, and divinylbenzene. From the viewpoint of easily obtaining vulcanized rubber with excellent tensile strength and low heat generation, monomer unit a may be a monomer unit derived from ethylene.

[0021] The proportion of monomer units a in copolymer A (or the total proportion of monomer units derived from ethylene and monomer units derived from α-olefins) may be 50% by mass or more, 55% by mass or more, 60% by mass or more, 65% by mass or more, 70% by mass or more, 75% by mass or more, 80% by mass or more, or 85% by mass or more, based on the total mass of copolymer A, from the viewpoint of easily obtaining vulcanized rubber having excellent breaking strength and low heat generation. The proportion of monomer units a in copolymer A may also be 99.9% by mass or less, 90% by mass or less, 88% by mass or less, 80% by mass or less, or 70% by mass or less, based on the total mass of copolymer A, from a similar viewpoint. The proportion of monomer units a in copolymer A may also be 50 to 99.9% by mass, 60 to 90% by mass, or 60 to 80% by mass, based on the total mass of copolymer A.

[0022] Monomer unit b may be a monomer unit derived from an unsaturated carboxylic acid glycidyl ester, a monomer unit derived from a glycidyl ether having an unsaturated group, or a combination thereof. From the viewpoint of easily obtaining vulcanized rubber with excellent tensile strength and low heat generation, monomer unit b may be a monomer unit derived from an unsaturated carboxylic acid glycidyl ester.

[0023] The unsaturated carboxylic acid glycidyl ester that derives monomer unit b may be a compound represented by the following formula (1), from the viewpoint of easily obtaining vulcanized rubber with excellent tensile strength and low heat generation. In formula (1), R １ The compound represents an alkenyl group having 2 to 18 carbon atoms, and the alkenyl group may have one or more substituents. Examples of compounds represented by formula (1) include glycidyl acrylate, glycidyl methacrylate, and glycidyl itaconic acid ester. The compound represented by formula (1) may be glycidyl methacrylate, from the viewpoint of easily obtaining vulcanized rubber with excellent tensile strength and low heat generation.

[0024]

[0025] A glycidyl ether having an unsaturated group that derives monomer unit b may be a compound represented by the following formula (2), from the viewpoint of easily obtaining vulcanized rubber with excellent tensile strength and low heat generation. In formula (2), R ２ X represents an alkenyl group having 2 to 18 carbon atoms, and the alkenyl group may have one or more substituents. X is CH ２ -O(CH ２ R ２ It represents a (bonded) or oxygen atom. Examples of compounds represented by formula (2) include allyl glycidyl ether, 2-methylallyl glycidyl ether, and styrene-p-glycidyl ether.

[0026]

[0027] The proportion of monomer units b in copolymer A may be 0.1% by mass or more, 0.5% by mass or more, 1% by mass or more, 3% by mass or more, 5% by mass or more, 8% by mass or more, 10% by mass or more, or 12% by mass or more, based on the total mass of copolymer A, from the viewpoint of easily obtaining vulcanized rubber having excellent breaking strength and low heat generation. Similarly, the proportion of monomer units b in copolymer A may be 30% by mass or less, 20% by mass or less, 15% by mass or less, 12% by mass or less, or 10% by mass or less, based on the total mass of copolymer A. The proportion of monomer units b in copolymer A may be 0.1 to 30% by mass, 3 to 20% by mass, or 8 to 20% by mass, based on the total mass of copolymer A.

[0028] The mass ratio of monomer unit b to monomer unit a (ratio of monomer unit b / ratio of monomer unit a) may be 0.01 or more, 0.05 or more, 0.1 or more, 0.13 or more, 0.15 or more, 0.18 or more, or 0.2 or more, from the viewpoint of easily obtaining vulcanized rubber having excellent breaking strength and low heat generation properties. Similarly, it may be 0.6 or less, 0.5 or less, 0.4 or less, 0.3 or less, 0.25 or less, 0.2 or less, 0.18 or less, 0.16 or less, 0.15 or less, or 0.14 or less. From these viewpoints, the mass ratio of monomer unit b to monomer unit a (ratio of monomer unit b / ratio of monomer unit a) may be 0.01 to 0.6, 0.05 to 0.4, or 0.1 to 0.2.

[0029] Copolymer A may have monomer units c other than monomer units a and b, or it may not have any other monomer units. Examples of monomer units c include monomer units derived from (meth)acrylic acid esters and monomer units derived from vinyl ethers. In this specification, "(meth)acrylate" means acrylate or methacrylate, and this is also true for similar compounds.

[0030] Examples of (meth)acrylic acid esters that derive monomer units from (meth)acrylic acid esters include methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, and butyl (meth)acrylate.

[0031] Examples of vinyl ethers that derive monomer units from vinyl ethers include methyl vinyl ether, ethyl vinyl ether, propyl vinyl ether, and phenyl vinyl ether.

[0032] The proportion of monomer units c in copolymer A may be 1% by mass or more, 10% by mass or more, or 20% by mass or more, based on the total mass of copolymer A, from the viewpoint of easily obtaining vulcanized rubber having excellent breaking strength and low heat generation. The proportion of monomer units c in copolymer A may be 50% by mass or less, 40% by mass or less, 30% by mass or less, 20% by mass or less, 10% by mass or less, or 5% by mass or less, based on the total mass of copolymer A. The proportion of monomer units c in copolymer A may be 1 to 50% by mass or 20 to 30% by mass, based on the total mass of copolymer A.

[0033] Examples of copolymer A include ethylene-glycidyl (meth)acrylate copolymer, ethylene-glycidyl (meth)acrylate-methyl (meth)acrylate copolymer, ethylene-glycidyl (meth)acrylate-ethyl (meth)acrylate copolymer, ethylene-glycidyl (meth)acrylate-n-propyl (meth)acrylate copolymer, ethylene-glycidyl (meth)acrylate-isopropyl (meth)acrylate copolymer, ethylene-glycidyl (meth)acrylate-n-butyl (meth)acrylate copolymer, ethylene-glycidyl (meth)acrylate-isobutyl (meth)acrylate copolymer, and ethylene-glycidyl (meth)acrylate-vinyl ether copolymer. Copolymer A may also be an ethylene-glycidyl (meth)acrylate copolymer, from the viewpoint of easily obtaining vulcanized rubber with excellent breaking strength and low heat generation. These may be used individually or in combination of two or more.

[0034] The melt flow rate (MFR) of copolymer A may be 0.2 g / 10 min or more, 0.5 g / 10 min or more, 1 g / 10 min or more, 1.5 g / min or more, 2 g / 10 min or more, 2.5 g / 10 min or more, or 3 g / 10 min or more. The melt flow rate (MFR) of copolymer A may be 400 g / 10 min or less, 300 g / 10 min or less, 200 g / 10 min or less, or 150 g / 10 min or less. The MFR of copolymer A can be measured in accordance with JIS K7210 under conditions of a temperature of 190°C and a load of 2.16 kgf.

[0035] The copolymer A can be synthesized by various methods. The copolymer A can be produced, for example, by bulk polymerization, emulsion polymerization, solution polymerization, etc. using a free radical initiator. An example of a typical polymerization method for synthesizing the copolymer A is a method of copolymerizing ethylene, a monomer having a glycidyl group, and optionally a (meth)acrylate or vinyl ether under the conditions of a polymerization pressure of 500 kg / cm ２ or more, a polymerization temperature of 40 to 300 ° C. The polymerization pressure may be 1000 kg / cm ２ or more, and may be 2000 kg / cm ２ or less. The polymerization temperature may be 100 to 250 ° C, or 150 to 200 ° C. Since ethylene, a monomer having a glycidyl group, and optionally a (meth)acrylate or vinyl ether are randomly copolymerized, the ethylene and the monomer having a glycidyl group are at least present in the main chain.

[0036] From the viewpoint of easily obtaining a vulcanized rubber having excellent breaking strength and low heat generation, the content of the copolymer A is 0.1 part by mass or more, 0.5 part by mass or more, 1 part by mass or more, 1.5 part by mass or more, 2 parts by mass or more, or 2.5 parts by mass or more with respect to 100 parts by mass of the diene rubber. From the same viewpoint, it may be 15 parts by mass or less, 12 parts by mass or less, 10 parts by mass or less, 8 parts by mass or less, 6 parts by mass or less, or 5 parts by mass or less. The content of the copolymer A may be 0.1 to 15 parts by mass, 0.1 to 10 parts by mass, or 1 to 5 parts by mass with respect to 100 parts by mass of the diene rubber.

[0037] From the viewpoint of easily obtaining a vulcanized rubber having excellent breaking strength and low heat generation, the content of the copolymer A is 0.1 part by mass or more, 0.5 part by mass or more, 1 part by mass or more, 2 parts by mass or more, 3 parts by mass or more, 4 parts by mass or more, or 5 parts by mass or more with respect to 100 parts by mass of silica. From the same viewpoint, it may be 50 parts by mass or less, 35 parts by mass or less, 20 parts by mass or less, 15 parts by mass or less, or 10 parts by mass or less. The content of the copolymer A may be 0.1 to 50 parts by mass, 0.1 to 35 parts by mass, or 1 to 15 parts by mass with respect to 100 parts by mass of silica.

[0038] From the perspective of easily obtaining a vulcanized rubber having excellent breaking strength and low heat generation, the content of copolymer A may be 1 part by mass or more, 10 parts by mass or more, 20 parts by mass or more, 30 parts by mass or more, 40 parts by mass or more, 50 parts by mass or more, or 60 parts by mass or more with respect to 100 parts by mass of the silane coupling agent. From the same perspective, it may be 500 parts by mass or less, 350 parts by mass or less, 200 parts by mass or less, 150 parts by mass or less, or 125 parts by mass or less. The content of copolymer A may be 1 to 500 parts by mass, 1 to 350 parts by mass, 20 to 200 parts by mass, or 40 to 150 parts by mass with respect to 100 parts by mass of the silane coupling agent.

[0039] From the perspective of easily obtaining a vulcanized rubber having excellent breaking strength and low heat generation, the content of copolymer A may be 0.1% by mass or more, 0.5% by mass or more, 1.0% by mass or more, or 1.5% by mass or more based on the total amount of the rubber composition. From the same perspective, it may be 10.0% by mass or less, 8.0% by mass or less, 5.0% by mass or less, or 4.0% by mass or less. The content of copolymer A may be 0.1 to 10.0% by mass, 0.5 to 8.0% by mass, or 1.0 to 5.0% by mass based on the total amount of the rubber composition.

[0040] [Silica] The rubber composition contains silica. Examples of the silica include dry silica (anhydrous silicic acid), wet silica (hydrous silicic acid), colloidal silica, and precipitated silica. The BET specific surface area of the silica is preferably 20 to 400 m ２ / g, more preferably 50 to 350 m ２ / g, and still more preferably 100 to 300 m ２ / g. The BET specific surface area is measured by the BET method in accordance with ASTM D1993-03.

[0041] Examples of commercially available silica products include: EVONIC's "ULTRASIL VN3," "ULTRASIL VN3-G," "ULTRASIL 360," "ULTRASIL 5000GR," "ULTRASIL 7000GR," and "ULTRASIL 9100GR"; Tosoh Silica Co., Ltd.'s "Nipsil VN3," "Nipsil AQ," "Nipsil ER," and "Nipsil RS-150"; and Solvay's "Zeosil 175GR," "Zeosil 115GR," "Zeosil 1115MP," "Zeosil 1165MP," "Zeosil 1205MP," "Zeosil 1085GR," and "Zeosil Premium." Examples include "200MP" and "Tokuseal USG-SL," a product name manufactured by Tokuyama Corporation. These may be used individually or in combination of two or more types.

[0042] The silica may be silica whose surface has been treated with a coupling agent to remove silanol groups present on its surface. The method of surface treatment is not particularly limited; for example, the coupling agent may be added and stirred while stirring the silica in a mixer or blender. Alternatively, the coupling agent may be added while the silica is dispersed in a solvent such as water, isopropyl alcohol, or toluene.

[0043] Examples of surface treatment agents include silane compounds (e.g., silane coupling agents), titanium compounds (e.g., titanium coupling agents), and aluminate compounds (e.g., aluminate coupling agents). The surface treatment agent may have alkoxy groups, alkoxysilyl groups, phenyl groups, vinyl groups, epoxy groups, acryloyl groups, methacryloyl groups, amino groups, ureido groups, mercapto groups, isocyanate groups, etc. The surface treatment agent may also contain silane compounds from the viewpoint of easily obtaining excellent dispersibility of silica.

[0044] Examples of silane compounds include bis(3-triethoxysilylpropyl)tetrasulfide, N-phenyl-3-aminopropyltrimethoxysilane, phenyltrimethoxysilane, vinyltrimethoxysilane, epoxytrimethoxysilane, methacrylictrimethoxysilane, aminotrimethoxysilane, ureidotrimethoxysilane, mercaptopropyltrimethoxysilane, isocyanatetopropyltrimethoxysilane, phenylaminotrimethoxysilane, acrylictrimethoxysilane, p-styryltrimethoxysilane, 3-acryloxypropyltrimethoxysilane, 3-methacryloxypropyltrimethoxysilane, 3-isocyanatetopropyltrimethoxysilane, and 3-aminopropyltrimethoxysilane.

[0045] The silica may be hydrophobic silica obtained by surface-treating the silanol groups present on the hydrophilic silica surface with a sulfur-containing silane coupling agent. Examples of commercially available hydrophobic silica include "Coupsil 8113," manufactured by EVONIC Corporation, which is obtained by surface-treating "ULTRASIL VN3" manufactured by EVONIC Corporation with bis(3-triethoxysilylpropyl)tetrasulfide.

[0046] From the viewpoint of easily obtaining vulcanized rubber having excellent breaking strength and low heat generation, the silica content may be 10 parts by mass or more, 20 parts by mass or more, 30 parts by mass or more, 40 parts by mass or more, or 45 parts by mass or more per 100 parts by mass of diene rubber, and from the same viewpoint, it may be 120 parts by mass or less, 100 parts by mass or less, 80 parts by mass or less, 70 parts by mass or less, or 60 parts by mass or less. The silica content may be 10 to 120 parts by mass, 20 to 100 parts by mass, or 40 to 80 parts by mass per 100 parts by mass of diene rubber.

[0047] From the viewpoint of easily obtaining vulcanized rubber having excellent breaking strength and low heat generation, the silica content may be 10% by mass or more, 20% by mass or more, or 30% by mass or more based on the total amount of the rubber composition, and from the same viewpoint, it may be 60% by mass or less, 50% by mass or less, or 40% by mass or less. The silica content may be 10 to 60% by mass, 20 to 50% by mass, or 30 to 40% by mass based on the total amount of the rubber composition.

[0048] [Silane Coupling Agent] The rubber composition contains a silane coupling agent. Examples of silane coupling agents include bis(3-triethoxysilylpropyl)tetrasulfide (e.g., EVONIK's trade name "Si-69"), bis(3-triethoxysilylpropyl) disulfide (e.g., EVONIK's trade name "Si-75"), bis(3-diethoxymethylsilylpropyl)tetrasulfide, bis(3-diethoxymethylsilylpropyl) disulfide, 3-octanoylthiopropyltriethoxysilane (also known as "octanthioate S-[3-(triethoxysilyl)propyl]ester"), e.g., Momentive Performance Materials' trade name "NXT Silane), S-[3-{(2-methyl-1,3-propanedialkoxy)ethoxysilyl}propyl] octanthioate, S-[3-{(2-methyl-1,3-propanedialkoxy)methylsilyl}propyl] octanthioate, methyltrimethoxysilane, methyltriethoxysilane, methyltriacetoxysilane, methyltributoxysilane, ethyltrimethoxysilane, ethyltriethoxysilane, isobutyltrimethoxysilane, isobutyltriethoxysilane, n-octyltrimethoxysilane, n-octyltriethoxysilane, vinyltrimethoxysilane, vinyltris(methoxyethoxy)silane, phenyltrimethoxysilane, phenyltriethoxysilane Examples include phenyltriacetoxysilane, 3-methacryloxypropyltrimethoxysilane, 3-methacryloxypropyltriethoxysilane, 3-aminopropyltrimethoxysilane, 3-aminopropyltriethoxysilane, N-(2-aminoethyl)-3-aminopropyltrimethoxysilane, N-(2-aminoethyl)-3-aminopropyltriethoxysilane, (3-glycidoxypropyl)trimethoxysilane, (3-glycidoxypropyl)triethoxysilane, 2-(3,4-epoxycyclohexyl)ethyltrimethoxysilane, 2-(3,4-epoxycyclohexyl)ethyltriethoxysilane, 3-isocyanatopropyltrimethoxysilane, and 3-isocyanatopropyltriethoxysilane.Silane coupling agents may be used alone or in combination of two or more types. Commercially available products include those manufactured by EVONIC Corporation, such as "Si-69," "Si-75," and "Si-266," and those manufactured by Momentive Performance Materials, such as "NXT Silane," "NXT-Z30," "NXT-Z45," "NXT-Z60," and "NXT-Z100."

[0049] The silane coupling agent content may be 0.1 parts by mass or more, 1 part by mass or more, or 3 parts by mass or more per 100 parts by mass of diene rubber, from the viewpoint of easily obtaining vulcanized rubber having excellent breaking strength and low heat generation, and from the same viewpoint, it may be 20 parts by mass or less, 10 parts by mass or less, or 5 parts by mass or less. The silane coupling agent content may be 0.1 to 20 parts by mass, 1 to 10 parts by mass, or 3 to 5 parts by mass per 100 parts by mass of diene rubber.

[0050] The silane coupling agent content may be 1 part by mass or more, 2 parts by mass or more, or 5 parts by mass or more per 100 parts by mass of silica, from the viewpoint of easily obtaining vulcanized rubber having excellent breaking strength and low heat generation, and from the same viewpoint, it may be 20 parts by mass or less, 15 parts by mass or less, or 10 parts by mass or less. The silane coupling agent content may be 1 to 20 parts by mass, 2 to 15 parts by mass, or 5 to 10 parts by mass per 100 parts by mass of silica.

[0051] Methods for quantifying the silane coupling agent content in a vulcanized rubber composition include hydrogenating the vulcanized rubber composition, then substituting the alkoxy groups in the silane coupling agent with alcohol (e.g., ethanol, 1-propanol, 1-butanol, 2-butanol, 1-pentanol, 2-methyl-1-pentanol, 1-hexanol, 1-heptanol, 1-octanol, 1-decanol, 1-dodecanol), and finally quantifying the amount of components derived from the silane coupling agent by gas chromatography analysis. Another method for quantifying the silane coupling agent content in a vulcanized rubber composition after hydrogenating involves extracting and quantifying components that are not adsorbed onto silica, and then determining the amount of components derived from the silane coupling agent in the solid content using solid-state high-resolution analysis.２９ Quantitative analysis may also be performed using Si-NMR.

[0052] There are no particular limitations on the method of hydrodesulfurization. For example, one method is called the "pan process," in which a regenerating agent (e.g., tall oil, petroleum-based plasticizer) and an oil (e.g., stretching oil) are added to a pulverized vulcanized rubber composition, which is then placed in a pressure vessel and subjected to a heat treatment using 200°C steam for about 5 hours, followed by a refining process using rolls after the treatment, or hydrodesulfurization may be performed by kneading a pulverized vulcanized rubber composition in a twin-screw extruder or batch mixer under high temperature and high shear force.

[0053] When the rubber composition contains silica surface-treated with a silane coupling agent, the content of silica surface-treated with the silane coupling agent may be 10 parts by mass or more, 20 parts by mass or more, 30 parts by mass or more, 40 parts by mass or more, or 45 parts by mass or more per 100 parts by mass of diene rubber, from the viewpoint of easily obtaining vulcanized rubber having excellent breaking strength and low heat generation properties. Similarly, from the same viewpoint, it may be 120 parts by mass or less, 100 parts by mass or less, 80 parts by mass or less, or 60 parts by mass or less. The content of silica surface-treated with the silane coupling agent may be 10 to 120 parts by mass, 20 to 100 parts by mass, or 40 to 80 parts by mass per 100 parts by mass of diene rubber.

[0054] When the rubber composition contains silica surface-treated with a silane coupling agent, the content of silica surface-treated with the silane coupling agent may be 10% by mass or more, 20% by mass or more, or 30% by mass or more, based on the total amount of the rubber composition, from the viewpoint of easily obtaining vulcanized rubber having excellent breaking strength and low heat generation. Similarly, it may be 60% by mass or less, 50% by mass or less, or 40% by mass or less. The content of silica surface-treated with the silane coupling agent may be 10 to 60% by mass, 20 to 50% by mass, or 30 to 40% by mass, based on the total amount of the rubber composition.

[0055] The rubber composition may contain components other than those listed above (hereinafter also referred to as "other components"). Examples of other components include fillers, vulcanizing agents, vulcanization accelerators, vulcanization aids, processing aids, antioxidants, drawstring oils, resins, waxes, and deconjugate agents.

[0056] The rubber composition can also be combined with fillers other than silica, as long as the heat generation is not impaired. Examples of fillers other than silica include carbon black, calcium silicate, aluminum silicate, aluminum hydroxide, bituminous coal pulverized material, talc, clay (especially calcined clay), and titanium oxide. From the viewpoint of easily obtaining vulcanized rubber with excellent tensile strength and excellent mechanical strength, carbon black is preferred as the filler to be combined with silica.

[0057] Examples of carbon black include those listed on page 494 of the "Rubber Industry Handbook (Fourth Edition)" compiled by the Japan Rubber Association. Carbon black may be used alone or in combination of two or more types. Preferred carbon blacks include HAF (High Ablation Furnace), SAF (Super Ablation Furnace), ISAF (Intermediate SAF), ISAF-HM (Intermediate SAF-High Modulus), FEF (Fast Extraction Furnace), MAF (Medium Ablation Furnace), GPF (General Purpose Furnace), and SRF (Semi-Reinforcing Furnace).

[0058] The BET specific surface area of ​​carbon black is preferably 10 to 130 m². ２ / g, more preferably 20 to 130m ２ / g, more preferably 40 to 130m ２The value is / g. The BET specific surface area is measured by the BET method according to ASTM D1993-03. Commercially available carbon black products include "Dia Black N339", "Dia Black N341", "Dia Black A", "Dia Black I", "Dia Black LH", and "SAF Carbon Black UX10" from Mitsubishi Chemical Corporation; "Seast 6", "Seast 7HM", "Seast KH", "Seast SO", "Seast V", "Seast 7H", and "Seast 9" from Tokai Carbon Co., Ltd.; "CK 3" and "Special Black 4A" from Orion Engineered Carbons; and "Ketjenblack EC" from Lion Specialty Chemicals Ltd.

[0059] When silica and carbon black are used in combination, their content is not particularly limited, but the mass ratio of the amount of carbon black to the amount of silica (amount of carbon black / amount of silica) may be 1 / 120 to 3 / 4, 1 / 100 to 1 / 2, or 1 / 100 to 5 / 12, from the viewpoint of easily obtaining vulcanized rubber with excellent breaking strength and low heat generation.

[0060] (Vulcanizing agent) Examples of vulcanizing agents include sulfur and sulfur compounds. Examples of sulfur include powdered sulfur, precipitated sulfur, colloidal sulfur, insoluble sulfur, and surface-treated sulfur.

[0061] The content of the vulcanizing agent may be 0.1 parts by mass or more, 0.3 parts by mass or more, or 0.5 parts by mass or more per 100 parts by mass of diene rubber, and may also be 5 parts by mass or less, 3 parts by mass or less, or 2 parts by mass or less. The content of the vulcanizing agent may be 0.1 to 5 parts by mass per 100 parts by mass of diene rubber.

[0062] As vulcanization accelerators, for example, those listed in the "Rubber Industry Handbook <Fourth Edition>" can be used. Vulcanization accelerators may be used alone or in combination of two or more. Examples of vulcanization accelerators include thiazole-based vulcanization accelerators such as 2-mercaptobenzothiazole (MBT), dibenzothiazyl disulfide (MBTS), 2-mercaptobenzothiazole cyclohexylamine salt (CMBT), and 2-mercaptobenzothiazole zinc salt (ZMBT); and tetramethylthiuram monosulfide, tetramethylthiuram disulfide, tetraethylthiuram disulfide, tetrabutylthiuram disulfide, tetraoctylthiuram disulfide, and tetrabenzylthiuram disulfide. Examples include thiram-based vulcanization accelerators such as N-cyclohexyl-2-benzothiazolyl sulfenamide (CBS), N-tert-butyl-2-benzothiazolyl sulfenamide (BBS), N-oxydiethylene-2-benzothiazolyl sulfenamide (OBS), and N,N-dicyclohexyl-2-benzothiazolyl sulfenamide (DCBS); and guanidine-based vulcanization accelerators such as diphenylguanidine (DPG), diorthototrilguanidine, and orthototrilbiguanidine. These may be used individually or in combination of two or more.

[0063] The content of the vulcanization accelerator may be 0.5 parts by mass or more, 1 part by mass or more, or 2 parts by mass or more, or 8 parts by mass or less, 5 parts by mass or less, or 4 parts by mass or less, per 100 parts by mass of diene rubber. The content of the vulcanization accelerator may be 0.5 to 8 parts by mass, 1 to 5 parts by mass, or 2 to 4 parts by mass, per 100 parts by mass of diene rubber.

[0064] Examples of vulcanization aids include triallyl isocyanurate, N,N'-m-phenylenebismaleimide, methacrylic acid, methyl methacrylate, ethyl methacrylate, propyl methacrylate, isopropyl methacrylate, n-butyl methacrylate, i-butyl methacrylate, sec-butyl methacrylate, t-butyl methacrylate, 2-ethylhexyl methacrylate, cyclohexyl methacrylate, isodecyl methacrylate, lauryl methacrylate, tridecyl methacrylate, stearyl methacrylate, 2-hydroxyethyl methacrylate, hydroxypropyl methacrylate, polyethylene glycol monomethacrylate, polypropylene glycol monomethacrylate, 2-ethoxyethyl methacrylate, tetrahydrofurfuryl methacrylate, allyl methacrylate, glycidyl methacrylate, benzyl methacrylate, dimethylaminoethyl methacrylate, and diethylaminoethyl methacrylate. Examples include methacryloxyethyl phosphate, 1,4-butanediol diacrylate, ethylene glycol dimethacrylate, 1,3-butylene glycol dimethacrylate, neopentyl glycol dimethacrylate, 1,6-hexanediol dimethacrylate, diethylene glycol dimethacrylate, triethylene glycol dimethacrylate, polyethylene glycol dimethacrylate, dipropylene glycol dimethacrylate, polypropylene glycol dimethacrylate, trimethylolethane trimethacrylate, trimethylolpropane trimethacrylate, allyl glycidyl ether, N-methylol methacrylamide, 2,2-bis(4-methacryloxypolyethoxyphenyl)propane, aluminum methacrylate, zinc methacrylate, calcium methacrylate, magnesium methacrylate, 3-chloro-2-hydroxypropyl methacrylate, zinc oxide (zinc oxide), and magnesium oxide. These may be used individually or in combination of two or more.

[0065] The content of the vulcanization aid may be 0.1 parts by mass or more, 15 parts by mass or less, or 8 parts by mass or less, per 100 parts by mass of diene rubber. The content of the vulcanization aid may be 0.1 to 15 parts by mass or 0.1 to 8 parts by mass, per 100 parts by mass of diene rubber.

[0066] Examples of processing aids include fatty acids, fatty acid metal salts, fatty acid amides, and fatty acid esters. The fatty acids in these compounds are not particularly limited and include, for example, octanoic acid, capric acid, lauric acid, myristic acid, pentadecanoic acid, arachidic acid, behenic acid, lignoceric acid, oleic acid, palmitic acid, stearic acid, linoleic acid, linolenic acid, cerotic acid, montanic acid, and melissic acid. Examples of metals in fatty acid metal salts include alkali metal salts such as sodium salts and potassium salts, alkaline earth metal salts such as magnesium salts and calcium salts, and transition metal salts such as zinc salts, cobalt salts, and copper salts. Examples of fatty acid metal salts include calcium laurate, zinc laurate, calcium stearate, calcium 12-hydroxystearate, zinc 12-hydroxystearate, calcium behenate, sodium behenate, and calcium montanate. These may be used individually or in combination of two or more.

[0067] Examples of commercially available processing aids include the following products from Schill & Seilaccher: "STRUKTOL A50P", "STRUKTOL A60", "STRUKTOL A82", "STRUKTOL EF44", "STRUKTOL HT204", "STRUKTOL HT207", "STRUKTOL HT254", "STRUKTOL HT266", and "STRUKTOL WB16"; "ULTRA FLOW500" from Performance Additive; and "Diamid BH" from Mitsubishi Chemical Corporation.

[0068] As a processing aid, a compound containing at least one selected from the group consisting of fatty acid metal salts, fatty acid amides, and fatty acid esters, whose difference between the start and end points of the endothermic peak obtained by measurement using a differential scanning calorimeter is 50°C or more, may be used. Examples of commercially available products include "Aflax 16" (a mixture of 50% fatty acid calcium salt and 50% fatty acid ethanolamide, difference between the start and end points of the endothermic peak: 67°C) from Rhein Chemie, and "ULTRA-FLOW 160" (a mixture of fatty acid calcium salt and fatty acid amide, difference between the start and end points of the endothermic peak: 52°C) from Performance Additive.

[0069] The content of the processing aid may be 0.1 parts by mass or more, 10 parts by mass or less, or 8 parts by mass or less, per 100 parts by mass of diene rubber. The content of the processing aid may be 0.1 to 10 parts by mass or 0.1 to 8 parts by mass, per 100 parts by mass of diene rubber.

[0070] Examples of anti-aging agents include amine-based anti-aging agents and sulfur-based anti-aging agents. Anti-aging agents may be used alone or in combination of two or more types.

[0071] Examples of amine-based antioxidants include naphthylamine-based antioxidants such as phenyl-α-naphthylamine and phenyl-β-naphthylamine; diphenylamine-based antioxidants such as p-(p-toluenesulfonylamide)diphenylamine, 4,4'-bis(α,α-dimethylbenzyl)diphenylamine, alkylated diphenylamine (e.g., octylated diphenylamine), dioctylated diphenylamine (e.g., 4,4'-dioctyldiphenylamine), high-temperature reaction products of diphenylamine and acetone, low-temperature reaction products of diphenylamine and acetone, low-temperature reaction products of diphenylamine, aniline and acetone, and reaction products of diphenylamine and diisobutylene; and N,N'-diphenyl-p-phenylenediamine and N-isopropyl-N'-phenylenediamine. Examples of p-phenylenediamine-based anti-aging agents include nyl-p-phenylenediamine, N,N'-di-2-naphthyl-p-phenylenediamine, N-cyclohexyl-N'-phenyl-p-phenylenediamine, N-phenyl-N'-(3-methacryloyloxy-2-hydroxypropyl)-p-phenylenediamine, N,N'-bis(1-methylheptyl)-p-phenylenediamine, N,N'-bis(1,4-dimethylpentyl)-p-phenylenediamine, N,N'-bis(1-ethyl-3-methylpentyl)-p-phenylenediamine, N-(1,3-dimethylbutyl)-N'-phenyl-p-phenylenediamine (6PPD), N-hexyl-N'-phenyl-p-phenylenediamine, and N-octyl-N'-phenyl-p-phenylenediamine.

[0072] Examples of sulfur-based anti-aging agents include imidazole-based anti-aging agents such as 2-mercaptobenzimidazole, zinc salt of 2-mercaptobenzimidazole, 2-mercaptomethylbenzimidazole, zinc salt of 2-mercaptomethylbenzimidazole, and zinc salt of 2-mercaptomethylimidazole; and aliphatic thioether-based anti-aging agents such as dimyristylthiodipropionate, dilaurylthiodipropionate, distearylthiodipropionate, ditridecylthiodipropionate, and pentaerythritol-tetrakis(β-lauryl-thiopropionate).

[0073] The amount of the antioxidant may be 0.1 parts by mass or more, 0.3 parts by mass or more, or 0.5 parts by mass or more per 100 parts by mass of diene rubber, and may also be 10 parts by mass or less, 5 parts by mass or less, or 3 parts by mass or less. The amount of the antioxidant may be 0.1 to 10 parts by mass, 0.3 to 5 parts by mass, or 0.5 to 3 parts by mass per 100 parts by mass of diene rubber.

[0074] Examples of curing agents include hexamethylenetetramine, hexamethoxymethylolmelamine, pentamethoxymethylolmelamine, hexamethoxymethylmelamine, pentamethoxymethylmelamine, hexaethoxymethylmelamine, hexakis-(methoxymethyl)melamine, N,N',N''-trimethyl-N,N',N''-trimethylolmelamine, N,N',N''-trimethylolmelamine, N-methylolmelamine, N,N'-(methoxymethyl)melamine, N,N',N''-tributyl-N,N',N''-trimethylolmelamine, paraformaldehyde, and the like.

[0075] The curing agent content may be 0.1 parts by mass or more, 0.3 parts by mass or more, or 0.5 parts by mass or more per 100 parts by mass of diene rubber, or it may be 10 parts by mass or less, 5 parts by mass or less, or 3 parts by mass or less. The curing agent content may be 0.1 to 10 parts by mass, 0.3 to 5 parts by mass, or 0.5 to 3 parts by mass per 100 parts by mass of diene rubber.

[0076] Examples of extensible oils include process oils and vegetable oils. Examples of process oils include paraffinic process oils, naphthenic process oils, aromatic process oils, MES (Mild Extract Solvates) oils, and TDAE (Aromatic Extracts of Processed Distillates) oils. Examples of commercially available products include aromatic oils (ENEOS Corporation's product name "NC-140", Showa Shell Sekiyu Corporation's product name "Extract No. 4 S", and ENEOS Corporation's product name "X-140"), process oils (Idemitsu Kosan Corporation's product name "Diana Process PS32", and ENEOS Corporation's product name "P200"), and TDAE oils (H&R Corporation's product name "VivaTec 500").

[0077] The resin is not particularly limited, but examples include C5 petroleum resins, C9 petroleum resins, C5 / C9 petroleum resins, styrene resins, coumarone indene resins, terpene resins, terpene phenol resins, rosin resins, p-t-butylphenol acetylene resins, acrylic resins, dicyclopentadiene resins, and the like. These resins may be modified or hydrogenated. They may be used individually or in combination of two or more.

[0078] Examples of waxes include "Sunnock® Wax" manufactured by Ouchi Shinko Chemical Industry Co., Ltd. and "OZOACE-0355" manufactured by Nippon Seiro Co., Ltd.

[0079] The deconjugating agent is not particularly limited as long as it is commonly used in the rubber field, but examples include aromatic mercaptan-based deconjugating agents, aromatic disulfide-based deconjugating agents, and aromatic mercaptan metal salt-based deconjugating agents, as described on pages 446-449 of the "Rubber Industry Handbook <Fourth Edition>" edited by the Japan Rubber Association. Among these, dixylyl disulfide and o,o'-dibenzamide diphenyl disulfide (Noctizer SS, manufactured by Ouchi Shinko Chemical Industry Co., Ltd.) are preferred. The deconjugating agent may be used alone or in combination of two or more types. When using a deconjugating agent, the amount of deconjugating agent is preferably 0.01 to 1 part by mass, and more preferably 0.05 to 0.5 parts by mass, per 100 parts by mass of the diene-based rubber component.

[0080] The rubber composition may or may not contain a silsesquioxane compound. The silsesquioxane compound may be a cage-like silsesquioxane compound. If the rubber composition contains a silsesquioxane compound, the amount may be less than 0.001 parts by mass per 100 parts by mass of resin in the rubber composition.

[0081] The rubber composition according to this embodiment can be prepared in the following order: (A) and (B). The method for producing the rubber composition according to this embodiment comprises: (A) kneading a mixture containing at least a diene rubber component, silica, and a silane coupling agent, or a mixture containing at least a diene rubber component and silica surface-treated with a silane coupling agent to obtain a kneaded product; and (B) mixing the kneaded product with a vulcanizing agent and a vulcanization accelerator to obtain a rubber composition. In either step (A) or (B), copolymer A is further mixed, and in step (A), the kneaded product is held at 120 to 170°C for 20 to 360 seconds.

[0082] In step (A), for example, a kneaded product containing components other than sulfur and vulcanization accelerators is obtained. In step (A), a kneaded product may be prepared by kneading a mixture containing a diene rubber component, copolymer A, silica, a silane coupling agent, and other components (e.g., fillers), or a mixture containing a diene rubber component, copolymer A, silica surface-treated with a silane coupling agent, and other components.

[0083] Process (A) may be divided into multiple processes. When process (A) is divided into multiple processes, the diene rubber component, copolymer A, silica (silica surface-treated with a silane coupling agent), silane coupling agent, and other components may be added in any of the multiple processes (A). Alternatively, any of the multiple processes may be a milling process in which only kneading is performed without the addition of any additives.

[0084] In step (A), the mixing temperature and mixing time for each component can be set to hold the mixture at 120 to 170°C for 20 to 360 seconds. If step (A) consists of multiple steps, the mixing temperature and mixing time for the mixture can be set to hold it at 120 to 170°C for 20 to 360 seconds in at least one or all of steps (A). In step (A), it is preferable to hold the mixture at 120 to 170°C for 80 to 350 seconds, more preferably 100 to 300 seconds, and even more preferably 120 to 250 seconds. In step (A), the mixture may be held at 145 to 170°C for 10 to 150 seconds, or 15 to 120 seconds. Before step (A), a preliminary mixing step for kneading the diene rubber component may be provided from the viewpoint of making the diene rubber component easier to process. If process (A) consists of multiple processes such as process (A1) and process (A2), the kneaded material obtained in process (A1) may be discharged and cooled before carrying out process (A2), or process (A2) may be carried out immediately after process (A1) without discharging the kneaded material.

[0085] For kneading in step (A), for example, an internal mixer including a Banbury mixer, an open-type kneader, a pressure-type kneader, an extruder, an injection molding machine, etc., can be used. The discharge temperature of the rubber composition after kneading in step (A) is preferably 200°C or lower, and more preferably 120 to 180°C.

[0086] In step (B), the kneaded product obtained in step (A) may be mixed with a vulcanizing agent and a vulcanization accelerator to produce a rubber composition, or it may be mixed with a vulcanizing agent, a vulcanization accelerator and copolymer A to produce a rubber composition, or it may be mixed with a vulcanizing agent, a vulcanization accelerator, copolymer A and other components to produce a rubber composition.

[0087] The mixing temperature in step (B) is usually 120°C or lower, preferably room temperature (20°C) to 100°C. For mixing in step (B), for example, an open roll mixer, a Banbury mixer, a calender, etc., can be used.

[0088] When preparing the rubber composition, the entire amount of copolymer A may be mixed in either step (A) or step (B), or copolymer A may be divided and mixed in both steps (A) and (B). Copolymer A may also be pre-supported on a filler and then kneaded with diene-based rubber components, etc.

[0089] [Vulcanized Rubber] Vulcanized rubber can be produced by vulcanizing the rubber composition according to this embodiment. Vulcanized rubber may also be produced by processing the rubber composition into a specific shape before vulcanization. Vulcanization is usually carried out under normal pressure or under pressure. The vulcanization temperature is usually 120 to 200°C, preferably 140 to 180°C. The vulcanization time can be appropriately set according to the composition of the rubber composition.

[0090] [Tires] The rubber composition and vulcanized rubber according to this embodiment are useful for manufacturing tires and rubber components for tires. A tire according to this embodiment comprises a rubber component containing the above-described rubber composition. The rubber component may be covered with steel cords or carcass fiber cords, or it may be a tread. Examples of rubber components include a tire belt component containing the rubber composition and steel cords, a tire carcass component containing the rubber composition and carcass fiber cords, a tire sidewall component, a tire inner liner component, a tire cap tread component, and a tire undertread component.

[0091] The rubber composition and vulcanized rubber according to this embodiment can be used not only for tire applications but also for vibration-damping rubber applications, rubber belt applications, vibration damping agent applications, seismic isolation rubber applications, and the like. Examples of vibration-damping rubber applications include automotive vibration-damping rubber such as engine mounts, strut mounts, bushings, and exhaust hangers. Examples of rubber belt applications include power transmission belts, conveyor belts, V-belts, and the like.

[0092] [Method for improving the properties of vulcanized rubber] Another embodiment of the present invention relates to a method for achieving at least one of the following: improving the tensile strength of vulcanized rubber and reducing the heat generation of vulcanized rubber. This method comprises at least adding the above-mentioned copolymer A to a rubber composition containing a diene rubber, silica, and a silane coupling agent, and vulcanizing the rubber composition after the addition of copolymer A. The above-mentioned copolymer A can also be described as an additive for improving the tensile strength and reducing the heat generation of vulcanized rubber obtained from a rubber composition containing a diene rubber, silica, and a silane coupling agent.

[0093] The invention will be described in detail below based on the following examples. However, the present invention is not limited to the following examples. 1. Raw materials The following were prepared as raw materials.・Diene rubber NR (natural rubber): "TSR20" BR (butadiene rubber): "BR01" manufactured by ENEOS Material Corporation ・Silica: "Nipsil AQ" manufactured by Tosoh Silica Co., Ltd. ・Silane coupling agent: "Si-75 (bis(triethoxysilylpropyl) disulfide)" manufactured by EVONIK ・Filler: Carbon black ("Seasto 6" manufactured by Tokai Carbon Co., Ltd.) ・Olefin polymer A: Ethylene-glycidyl methacrylate copolymer (Bondfast E manufactured by Sumitomo Chemical Co., Ltd., ethylene unit content: 88% by mass, glycidyl methacrylate unit content: 12% by mass) ・Vulcanization aid: "Zinc oxide type 1" manufactured by Seido Chemical Industry Co., Ltd. ・Processing aid: Stearic acid ("Stearic acid Tsubasa" manufactured by NOF Corporation) ・Anti-aging agent: "Ozonone" manufactured by Seiko Chemical Co., Ltd. 6C (N-phenyl-N'-1,3-dimethylbutyl-p-phenylenediamine) ・Vulcanizing agent: Sulfur ("Kinka-jirushi finely powdered sulfur 200 mesh" manufactured by Tsurumi Chemical Industry Co., Ltd.) ・Vulcanization accelerator (1): "Sunceller CM-G (N-cyclohexyl-2-benzothiazolyl sulfenamide, CBS)" manufactured by Sanshin Chemical Industry Co., Ltd. ・Vulcanization accelerator (2): "Sunceller D (diphenylguanidine, DPG)" manufactured by Sanshin Chemical Industry Co., Ltd.

[0094] 2. Preparation of Rubber Compositions (Examples 1 and 2, and Comparative Examples 1 and 2) Rubber compositions were prepared by mixing each component in the amounts (parts by mass) shown in Table 1 according to the following steps (A) and (B). Step (A) Using a Banbury mixer (manufactured by Toyo Seiki Seisakusho Co., Ltd., 0.6 L), the diene rubber of (A) in Table 1 was pre-mixed for 60 seconds under the conditions of a mixer temperature of 80°C and a rotor rotation speed of 65 rpm. Next, components other than the diene rubber of (A) in Table 1 were added and mixed until the mixer temperature reached 135°C. Then, the rotor rotation speed was changed to 85 rpm, and the mixture was held at 130-140°C for 60 seconds, after which the resulting mixture was released from the mixer and cooled to room temperature (20-25°C). - Process (B) Using an open roll machine with a roll setting temperature of 45°C, the components of (B) in Table 1 were kneaded into the mixture obtained in process (A) to obtain a rubber composition.

[0095] (Comparative Examples 3 and 4) Rubber compositions were prepared by mixing each component in the amounts (parts by mass) shown in Table 1 according to the following steps (A) and (B). Step (A) Using a Banbury mixer (manufactured by Toyo Seiki Seisakusho Co., Ltd., 0.6 L), the diene rubber was pre-mixed for 60 seconds under the conditions of a mixer temperature of 80°C and a rotor rotation speed of 65 rpm. Next, the components other than the diene rubber in Table 1 (A) were added and mixed for a further 180 seconds, after which the resulting mixture was released outside the mixer and cooled to room temperature (20-25°C). Step (B) Using an open roll machine with a roll setting temperature of 45°C, the components in Table 1 (B) were mixed into the mixture obtained in step (A) to obtain a rubber composition.

[0096] 3. Preparation of vulcanized rubber The prepared rubber composition was pressed and heated in a mold at the temperature and time shown in Table 1 to obtain vulcanized rubber.

[0097] 4. Evaluation The physical properties of the manufactured rubber composition and vulcanized rubber were measured using the following test methods. <Degree of Crosslinking> In accordance with JIS K6300-1:2013, the rubber composition was used, and the minimum torque (ML) and maximum torque (MH) were determined from the torque curve at 160°C in accordance with JIS K6296-3:2023 using a curameter (model RLR rotary rheometer manufactured by Toyo Seiki Seisakusho Co., Ltd.), and the degree of crosslinking ME (=MH-ML) was determined from the difference between them.

[0098] <Modus (M100, M300), Breaking Strength (TS), Elongation at Break (Eb)> Dumbbell-shaped test specimens were punched out from vulcanized rubber according to JIS No. 3 standards, and tensile tests were performed at a tensile speed of 500 mm / min in accordance with JIS K-6251:2010. The tensile stress at 100% elongation (M100), the tensile stress at 300% elongation (M300), the breaking strength (TS), and the elongation at break (Eb) were measured under conditions of 23°C.

[0099] <tanδ (80°C), tanδ (100°C)> For vulcanized rubber, the loss tangent tanδ (80°C) was measured using a viscoelasticity measuring device (manufactured by Ueshima Seisakusho Co., Ltd.) under the conditions of a tensile deformation strain of 10 ± 2%, a vibration frequency of 10 Hz, and a temperature of 80°C. Similarly, the loss tangent tanδ (100°C) was measured under the condition of a temperature of 100°C. A smaller value of tanδ indicates superior low heat generation.

[0100]

Claims

1. A rubber composition comprising a diene rubber, copolymer A, silica, and a silane coupling agent, wherein copolymer A comprises monomer units derived from olefin monomers having 2 to 8 carbon atoms and monomer units having a glycidyl group.

2. A rubber composition comprising a diene rubber, copolymer A, and silica surface-treated with a silane coupling agent, wherein copolymer A comprises monomer units derived from olefin monomers having 2 to 8 carbon atoms and monomer units having a glycidyl group.

3. The rubber composition according to claim 1 or 2, wherein the diene rubber comprises at least one selected from the group consisting of natural rubber (NR), butadiene rubber (BR), and styrene-butadiene rubber (SBR).

4. The rubber composition according to claim 1 or 2, wherein the monomer units derived from the olefin monomer having 2 to 8 carbon atoms are monomer units derived from ethylene.

5. The rubber composition according to claim 1 or 2, wherein the monomer unit having a glycidyl group is a monomer unit derived from glycidyl (meth)acrylate.

6. The rubber composition according to claim 1 or 2, wherein the content of copolymer A is 0.1 to 10 parts by mass per 100 parts by mass of the diene rubber.

7. The rubber composition according to claim 1 or 2, wherein the content of copolymer A is 0.1 to 35 parts by mass per 100 parts by mass of silica.

8. The rubber composition according to claim 1, wherein the content of copolymer A is 1 to 350 parts by mass per 100 parts by mass of the silane coupling agent.

9. A vulcanized rubber obtained by vulcanizing the rubber composition according to claim 1 or 2.

10. A tire comprising a rubber member containing the vulcanized rubber described in claim 9.

11. A method for achieving at least one of improving the tensile strength of vulcanized rubber and reducing the heat generation of vulcanized rubber, comprising: adding copolymer A to a rubber composition containing diene rubber, silica, and a silane coupling agent; and vulcanizing the rubber composition after the addition of copolymer A, wherein copolymer A comprises monomer units derived from olefin monomers having 2 to 8 carbon atoms and monomer units having a glycidyl group.

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