Rubber composition for tires, tread rubber, and tire

Abstract

To provide a rubber composition for tires which can improve the ratio of sustainable materials of tires and promote a reduction in environmental load from the viewpoint of production, use, and disposal of a modified conjugated diene polymer as a whole.SOLUTION: The rubber composition for tires contains a rubber component (A) and a reinforcing filler (B). The rubber component (A) contains a modified conjugated diene polymer (A1) which has a functional group having an affinity for the reinforcing filler. The modified conjugated diene polymer (A1) contains a modified conjugated diene polymer (A1-1) supplied in a mass balance approach.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a rubber composition for a tire, a tread rubber, and a tire. [Background technology]

[0002] Generally, tires are required to have various performance characteristics, such as low fuel consumption, wear resistance, fracture resistance, steering stability, and grip performance on various road surfaces. To meet these requirements, various rubber compositions are used in the components that make up tires, and modified synthetic rubbers are sometimes used to improve desired performance. For example, Patent Document 1 below discloses a rubber composition containing a filler containing silica with specific physical properties, a rubber component containing a diene polymer that has affinity with the filler, and a fatty acid metal salt, and discloses that the diene polymer that has affinity with the filler is a modified conjugated diene polymer that has a functional group that has affinity with the filler. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] International Publication No. 2019 / 240226 Summary of the Invention [Problem to be solved by the invention]

[0004] Meanwhile, from the perspective of social sustainability, there has been a recent demand for an increase in the proportion of so-called sustainable materials, such as materials derived from biological resources (biomass resources) and materials derived from recycled resources, in the components that make up tires. However, among the materials compounded into rubber compositions for tires, the use of sustainable materials for modified conjugated diene polymers (modified synthetic rubbers) has not been fully considered to date, and it is necessary to promote the reduction of environmental impact in the overall production, use, and disposal of modified conjugated diene polymers.

[0005] Therefore, an object of the present invention is to provide a rubber composition for tires and a tread rubber that can increase the proportion of sustainable materials in tires and promote a reduction in the environmental load when viewed as a whole from the production, use, and disposal of modified conjugated diene-based polymers. Another object of the present invention is to provide a tire that can promote reduction of the environmental load in terms of the overall production, use, and disposal of the modified conjugated diene polymer and that has an increased proportion of sustainable materials. [Means for solving the problem]

[0006] The rubber composition for a tire, tread rubber, and tire of the present invention that solve the above problems are outlined below.

[0007] [1] A rubber composition comprising a rubber component (A) and a reinforcing filler (B), the rubber component (A) contains a modified conjugated diene-based polymer (A1) having a functional group having affinity for the reinforcing filler, A rubber composition for tires, wherein the modified conjugated diene polymer (A1) comprises a modified conjugated diene polymer (A1-1) supplied by a mass balance method. The rubber composition for tires of the present invention described in [1] above can promote a reduction in the environmental load in the overall production, use, and disposal of the modified conjugated diene-based polymer, and can also increase the proportion of sustainable materials in tires to which the rubber composition is applied.

[0008] [2] The rubber composition for tires according to [1], wherein the modified conjugated diene polymer (A1) comprises a modified conjugated diene polymer derived from at least one of plant-derived raw materials, plant-derived by-products, raw materials obtained by recycling plant-derived materials, and raw materials obtained by recycling fossil resource-derived materials. The rubber composition for tires described in [2] above can greatly contribute to reducing the environmental load in terms of the overall production, use and disposal of the modified conjugated diene polymer.

[0009] [3] The rubber composition for tires according to [1] or [2], wherein the modified conjugated diene polymer (A1) comprises 0.1 to 99% by mass of a modified conjugated diene polymer derived from a biological resource and 1 to 99.9% by mass of a modified conjugated diene polymer derived from a fossil resource. The rubber composition for a tire described in the above [3] has an excellent balance between reduced environmental load and productivity.

[0010] [4] The rubber composition for a tire according to any one of [1] to [3], wherein the modified conjugated diene polymer (A1) is modified with a modifier having a nitrogen atom and a silicon atom. The rubber composition for tires described in [4] above can further improve the fuel economy and wear resistance of tires to which the rubber composition is applied.

[0011] [5] The rubber composition for a tire according to any one of [1] to [4], further comprising a resin (C). The rubber composition for tires described in [5] above can achieve both good steering stability on dry road surfaces and good wet grip performance for a tire to which the rubber composition is applied.

[0012] [6] The rubber composition for a tire according to [5], wherein the content of the resin (C) is 1 to 50 parts by mass per 100 parts by mass of the rubber component (A). The rubber composition for a tire according to the above item [6] can further improve the wet grip performance of a tire to which the rubber composition is applied.

[0013] [7] A tread rubber comprising the rubber composition for a tire according to any one of [1] to [6]. The tread rubber of the present invention described in [7] above can promote a reduction in the environmental load in the overall production, use, and disposal of the modified conjugated diene-based polymer, and can also increase the proportion of sustainable materials in tires to which the tread rubber is applied.

[0014] [8] A tire comprising the tread rubber described in [7]. The tire of the present invention described in [8] above can promote reduction of the environmental load in terms of the overall production, use and disposal of the modified conjugated diene polymer, and the proportion of sustainable materials is increased. [Effects of the Invention]

[0015] According to the present invention, it is possible to provide a rubber composition for a tire and a tread rubber that can increase the proportion of sustainable materials in a tire and promote reduction in the environmental load in terms of the overall production, use, and disposal of a modified conjugated diene-based polymer. Furthermore, according to the present invention, it is possible to promote reduction of the environmental load in terms of the overall production, use, and disposal of the modified conjugated diene polymer, and to provide a tire with an increased proportion of sustainable materials. [Brief explanation of the drawings]

[0016] [Figure 1] 1 is a cross-sectional view of one embodiment of a tire of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0017] The rubber composition for a tire, the tread rubber, and the tire of the present invention will be described in detail below by way of example based on embodiments thereof.

[0018] <Definition> The compounds described herein may be derived in part or in whole from fossil sources, biological sources such as plant sources, recycled sources such as used tires, or a mixture of two or more of fossil, biological, and recycled sources.

[0019] In this specification, the "proportion of sustainable materials" refers to the total mass proportion of materials derived from biological resources (biomass resources) and materials derived from renewable resources (recycled resources) in the target rubber composition for tires, tread rubber, and tire.

[0020] In this specification, the term "biological resources (biomass resources)" refers to carbon-neutral organic resources derived from living organisms, and includes, for example, materials stored in the form of starch or cellulose, the bodies of animals that grow by eating plants, and products obtained by processing plants or animals, and is a resource excluding fossil resources (petroleum, coal, natural gas, etc.). Such biological resources may be edible or non-edible, but are preferably non-edible from the viewpoint of not competing with food and of effective resource utilization.

[0021] Specific examples of the biological resources include cellulosic crops (pulp, kenaf, wheat straw, rice straw, waste paper, papermaking residues, etc.), wood, charcoal, compost, food waste, vegetable oil residues, fishery residues, livestock excrement, food waste, wastewater sludge, natural rubber, cotton, oils and fats (palm oil, castor oil, cottonseed oil, soybean oil, linseed oil, rapeseed oil, coconut oil, peanut oil, tall oil, corn oil, rice oil, safflower oil, sesame oil, olive oil, etc.), and the like. Examples of biological resources include: corn oil, sunflower oil, palm kernel oil, camellia oil, jojoba oil, macadamia nut oil, tung oil, coconut oil, etc.), carbohydrate crops (corn, wheat, rice, rice husks, rice bran, used rice, potatoes, buckwheat, cassava, sago palm, sugarcane, etc.), bagasse (i.e., the residue left after sugarcane juicing), soybeans, soybean pulp refuse, essential oils (pine oil, orange oil, eucalyptus oil, etc.), pulp black liquor, and algae. The biological resources may also be processed (i.e., biological resource-derived substances). Examples of processing methods include biological processing methods utilizing the activity of microorganisms, plants, animals, and their tissue cultures; chemical processing methods utilizing acids, alkalis, catalysts, thermal energy, light energy, etc.; and physical processing methods such as pulverization, compression, microwave treatment, and electromagnetic wave treatment. Furthermore, the biological resources may also be extracted and purified from the biological resources or biological resources that have undergone the above-described processing (i.e., biological resource-derived substances). For example, sugars, proteins, amino acids, fatty acids, fatty acid esters, etc., purified from the above-mentioned biological resources can also be used. Examples of the sugars include sucrose, glucose, trehalose, fructose, lactose, galactose, xylose, allose, talose, gulose, altrose, mannose, idose, arabinose, apiose, maltose, cellulose, starch, chitin, etc., derived from biological resources. Examples of the proteins include compounds derived from biological resources and formed by linking amino acids (preferably L-amino acids), including oligopeptides such as dipeptides. Examples of the amino acids include valine, leucine, isoleucine, arginine, lysine, asparagine, glutamine, phenylalanine, etc., derived from biological resources, with valine, leucine, isoleucine, arginine, and phenylalanine being preferred.The amino acids may be either L-amino acids or D-amino acids, but L-amino acids are preferred from the viewpoints of abundance in nature and ease of availability. Examples of the fatty acids include butyric acid, palmitic acid, stearic acid, oleic acid, linoleic acid, linolenic acid, etc., which are derived from biological resources. Examples of the fatty acid esters include modified products of vegetable oils, animal oils, and fats and oils derived from biological resources. These biological resources may contain various materials and impurities.

[0022] In this specification, the term "recycled resources" refers to resources obtained by regenerating (recycling) products that have been used once, or that have been collected without being used, or that have been discarded. For example, recycled resources include resources obtained by regenerating (recycling) used rubber products such as used tires.

[0023] <Rubber composition for tires> The rubber composition for a tire of this embodiment includes a rubber component (A) and a reinforcing filler (B), and the rubber component (A) includes a modified conjugated diene-based polymer (A1) having a functional group having affinity with the reinforcing filler. The modified conjugated diene polymer (A1) is characterized in that it contains a modified conjugated diene polymer (A1-1) supplied by a mass balance method.

[0024] In the rubber composition for tires of this embodiment, the modified conjugated diene polymer (A1-1) supplied by the mass balance method is a modified conjugated diene polymer (modified synthetic rubber) assigned biological resource-derived characteristics or recycled resource-derived characteristics by the mass balance method. The rubber composition for tires of this embodiment contains the modified conjugated diene polymer (A1-1) supplied by the mass balance method as at least a portion of the modified conjugated diene polymer (A1), and therefore has a high proportion of sustainable materials. Therefore, by applying the rubber composition for tires of this embodiment to tires, it is possible to increase the proportion of sustainable materials in the tire. Furthermore, because the rubber composition for tires of this embodiment uses the modified conjugated diene polymer (A1-1) supplied by the mass balance method, it is possible to promote a reduction in the environmental impact of the overall production, use, and disposal of the modified conjugated diene polymer. In addition, even when a rubber composition in which at least a part of the modified conjugated diene polymer (A1) is the modified conjugated diene polymer (A1-1) supplied by the mass balance method is applied to a tire, tire performance such as low fuel consumption performance (low loss) and wet grip performance (grip performance on wet road surfaces) can be maintained at the same level.

[0025] (Rubber component (A)) The rubber composition for a tire of this embodiment contains a rubber component (A), which provides rubber elasticity to the composition. The rubber component (A) preferably has a sustainability rate of 30% by mass or more, more preferably 40% by mass or more, even more preferably 50% by mass or more, still more preferably 60% by mass or more, still more preferably 70% by mass or more, even more preferably 80% by mass or more, still more preferably 90% by mass or more, and particularly preferably 100% by mass. Here, the "sustainability rate" of the rubber component (A) refers to the total mass ratio of components derived from biological resources (biomass resources) and components derived from recycled resources (recycled resources) in the rubber component (A).

[0026] The rubber component (A) is preferably the rubber derived from biological resources or the rubber derived from recycled resources. Here, the proportion of the monomer components derived from biological resources in 100 mol% of the monomer components constituting the rubber derived from biological resources is preferably 50 mol% or more, more preferably 70 mol% or more, even more preferably 80 mol% or more, still more preferably 90 mol% or more, particularly preferably 95 mol% or more, and may be 100 mol%. Furthermore, the proportion of the monomer components derived from recycled resources in 100 mol% of the monomer components constituting the rubber derived from recycled resources is preferably 50 mol% or more, more preferably 70 mol% or more, even more preferably 80 mol% or more, still more preferably 90 mol% or more, particularly preferably 95 mol% or more, and may be 100 mol%.

[0027] The rubber component (A) is a component that contributes to crosslinking, and typically has a weight average molecular weight (Mw) of 10,000 or more, preferably 50,000 or more, more preferably 150,000 or more, and even more preferably 200,000 or more, and is preferably 5,000,000 or less, more preferably 2,000,000 or less, more preferably 1,500,000 or less, and even more preferably 1,300,000 or less. In this specification, the weight average molecular weight (Mw) of the rubber component (A) can be determined, for example, by converting it into standard polystyrene based on a measurement value obtained by gel permeation chromatography (GPC) (GPC-8000 series manufactured by Tosoh Corporation, detector: differential refractometer, column: TSKGEL SUPERMULTIPORE HZ-M manufactured by Tosoh Corporation).

[0028] -Modified conjugated diene polymer (A1)- In the rubber composition for tires of this embodiment, the rubber component (A) comprises a modified conjugated diene polymer (A1) having a functional group that has affinity with the reinforcing filler, and the modified conjugated diene polymer (A1) comprises a modified conjugated diene polymer (A1-1) supplied by the mass balance method. The modified conjugated diene polymer (A1-1) supplied by the mass balance method is a modified conjugated diene polymer (modified synthetic rubber) assigned a biological resource-derived or renewable resource-derived characteristic by the mass balance method, and can be treated as containing 100% sustainable material by mass. The inclusion of the modified conjugated diene polymer assigned a biological resource-derived or renewable resource-derived characteristic by the mass balance method contributes to reducing the environmental impact throughout the entire production, use, and disposal of the modified conjugated diene polymer.

[0029] The content of the modified conjugated diene polymer (A1) is preferably 10 to 90 parts by mass, more preferably 20 to 80 parts by mass, per 100 parts by mass of the rubber component (A). When the content of the modified conjugated diene polymer (A1) per 100 parts by mass of the rubber component (A) is 10 parts by mass or more, the performance of a tire using the rubber composition is easily improved according to its intended purpose. Furthermore, when the content of the modified conjugated diene polymer (A1) per 100 parts by mass of the rubber component (A) is 90 parts by mass or less, the amount of natural rubber, unmodified synthetic rubber, etc. added can be increased, improving the flexibility of the source of the rubber component (A) and facilitating production of the rubber composition.

[0030] The proportion of the modified conjugated diene polymer (A1-1) supplied by the mass balance method in the modified conjugated diene polymer (A1) is preferably 10 to 90 mass%, more preferably 20 to 80 mass%. When the proportion of the modified conjugated diene polymer (A1-1) supplied by the mass balance method in the modified conjugated diene polymer (A1) is 10 mass% or more, the proportion of sustainable materials in a tire using the rubber composition can be further improved.

[0031] An example of the mass balance method is the ISCC PLUS certification, which can certify bio-based raw materials, circular raw materials, and renewable raw materials, and circular raw materials can be classified into bio-circular and non-bio-circular.

[0032] The bio- or renewable feedstocks are derived from unused biomass from agriculture, forestry, fishing, aquaculture and related industries, such as fermented and biodegradable fractions of corn, sugarcane, rapeseed and other products.

[0033] Circular raw materials are materials at the beginning of the supply chain that are considered waste / processing residues but are not landfilled or used for energy production; instead, they are reused or recycled. Among circular raw materials, "biocirque" refers to waste and residues of biological origin from related industries, including agriculture, forestry, and fisheries / aquaculture, as well as biodegradable fractions of industrial and municipal waste. Examples include used cooking oil (UCO), tall oil (a mixture of fatty acids, resin acids, unsaponifiable matter, etc., produced as a by-product during the cooking and fiber separation of pulp raw materials), and food waste. Meanwhile, "non-biocirque" refers to raw materials derived from the mechanical and / or chemical processing of recyclable materials of non-biological origin (fossil-based), such as plastic waste and used tires.

[0034] Furthermore, the bio-based raw materials are preferably plant-derived raw materials, and the circular raw materials are preferably plant-derived by-products, raw materials obtained by recycling plant-derived materials, and raw materials obtained by recycling fossil resource-derived materials. In other words, the modified conjugated diene polymer (A1) preferably contains a modified conjugated diene polymer derived from at least one of plant-derived raw materials, plant-derived by-products, raw materials obtained by recycling plant-derived materials, and raw materials obtained by recycling fossil resource-derived materials. Plant-derived raw materials, plant-derived by-products, raw materials obtained by recycling plant-derived materials, and raw materials obtained by recycling fossil resource-derived materials are available in large quantities, making them easy to secure in sufficient quantities. A rubber composition for tires containing a modified conjugated diene polymer derived from at least one of these raw materials as the modified conjugated diene polymer (A1) can significantly contribute to reducing the environmental impact throughout the entire process of production, use, and disposal of the modified conjugated diene polymer.

[0035] The modified conjugated diene polymer (A1) preferably contains both a modified conjugated diene polymer derived from a biological resource and a modified conjugated diene polymer derived from a fossil resource. The modified conjugated diene polymer (A1) preferably contains 0.1 to 99% by mass of the modified conjugated diene polymer derived from a biological resource and 99.9 to 1% by mass of the modified conjugated diene polymer derived from a fossil resource. When the modified conjugated diene polymer (A1) contains 0.1% by mass or more of the modified conjugated diene polymer derived from a biological resource, the proportion of sustainable materials in tires using the rubber composition can be significantly increased. Furthermore, when the modified conjugated diene polymer (A1) contains 1% by mass or more of the modified conjugated diene polymer derived from a fossil resource, the flexibility of the source of the modified conjugated diene polymer (A1) is improved, facilitating the production of the rubber composition. Therefore, a rubber composition for tires in which the modified conjugated diene polymer (A1) contains 0.1 to 99 mass % of a modified conjugated diene polymer derived from a biological resource and 99.9 to 1 mass % of a modified conjugated diene polymer derived from a fossil resource has an excellent balance between reduced environmental impact and productivity.

[0036] The modified conjugated diene polymer (A1) has a functional group having affinity for a reinforcing filler, and the modified conjugated diene polymer (A1) has a functional group having affinity for a reinforcing filler, thereby improving the dispersibility of the reinforcing filler in the rubber composition.

[0037] Examples of the modified conjugated diene polymer (A1) include modified butadiene polymers such as modified polybutadiene, modified styrene-butadiene copolymer, modified butadiene-isoprene copolymer (BIR), and modified styrene-butadiene-isoprene copolymer.

[0038] Examples of the functional group having affinity with the reinforcing filler include functional groups having one or more atoms selected from a nitrogen atom, an oxygen atom, a sulfur atom, a semi-metal atom, and a metal atom. The metalloid atoms are preferably one or more atoms selected from boron, silicon, germanium, arsenic, antimony, and tellurium, more preferably one or more atoms selected from boron, silicon, and germanium, and particularly preferably silicon. The metal atom is preferably one or more atoms selected from tin, titanium, zirconium, bismuth, and aluminum, more preferably one or more atoms selected from tin and titanium, and particularly preferably tin. The functional group having affinity with the reinforcing filler preferably contains at least one atom selected from the group consisting of a nitrogen atom, an oxygen atom, and a silicon atom.

[0039] The functional group having one or more atoms selected from a nitrogen atom, an oxygen atom, a sulfur atom, a metalloid atom, and a metal atom is a residue of a compound having one or more atoms selected from a nitrogen atom, an oxygen atom, a sulfur atom, a metalloid atom, and a metal atom (hereinafter, sometimes referred to as a "heteroatom-containing compound"). A heteroatom-containing compound may act as a modifier and react with the active terminal of a conjugated diene polymer to form a modified conjugated diene polymer, or a nitrogen-containing compound as a heteroatom-containing compound may react with an alkali metal to form a polymerization initiator for anionic polymerization, thereby forming a modified conjugated diene polymer having a nitrogen-containing compound residue at the initiation terminal of the conjugated diene polymer.

[0040] The modifier that reacts with the active terminal of the conjugated diene polymer may be one or more modifiers selected from the following: a modifier having a tin atom (tin-containing compound), a modifier having a nitrogen atom and a silicon atom (nitrogen- and silicon-containing compound), a modifier having an oxygen atom and a silicon atom (oxygen- and silicon-containing compound), a modifier having a sulfur atom and a silicon atom (sulfur- and silicon-containing compound), and a modifier having a nitrogen atom but not a silicon atom (silicon-free nitrogen-containing compound).

[0041] Suitable examples of the modifying agent having a tin atom (tin-containing compound) include at least one tin compound selected from tin tetrachloride and tributyltin chloride.

[0042] Examples of the modifying agent having a nitrogen atom and a silicon atom (nitrogen- and silicon-containing compound) include N,N-bis(trimethylsilyl)aminopropylmethyldimethoxysilane, 1-trimethylsilyl-2,2-dimethoxy-1-aza-2-silacyclopentane, N,N-bis(trimethylsilyl)aminopropyltrimethoxysilane, N,N-bis(trimethylsilyl)aminopropyltriethoxysilane, N,N-bis(trimethylsilyl)aminopropylmethyldiethoxysilane, N,N-bis(trimethylsilyl)aminopropylmethyldiethoxysilane, N,N-bis(trimethylsilyl)aminopropylmethyldimethoxysilane, N,N-bis(trimethylsilyl)aminopropylmethyldimethoxysilane, N,N-bis(trimethylsilyl)aminopropylmethyldimethoxysilane, N,N-bis(trimethylsilyl)aminopropylmethyldimethoxysilane, N,N-bis(trimethylsilyl)aminopropylmethyldiethoxysilane, N,N-bis(trimethylsilyl)aminopropylmethyldiethoxysilane, N,N-bis(trimethylsilyl)aminopropylmethyldimethoxy ... Suitable examples include silane compounds having a protected primary amino group selected from N-methyl-N-trimethylsilylaminopropyl(methyl)dimethoxysilane, N-methyl-N-trimethylsilylaminopropyl(methyl)diethoxysilane, N-trimethylsilylaminopropyl(methyl)dimethoxysilane, N-trimethylsilylaminopropyl(methyl)diethoxysilane, N-trimethylsilylaminopropyl(methyl)dimethoxysilane, N-trimethylsilylaminopropyl(methyl)dieth ... N-trimethylsilyl(hexamethyleneimin-2-yl)propyl(methyl)dimethoxysilane, N-trimethylsilyl(hexamethyleneimin-2-yl)propyl(methyl)diethoxysilane, N-trimethylsilyl(pyrrolidin-2-yl)propyl(methyl)dimethoxysilane, N-trimethylsilyl(pyrrolidin-2-yl)propyl(methyl)diethoxysilane, N-trimethylsilyl(piperidin-2-yl)propyl(methyl)dimethoxysilane, N-trimethylsilyl(piperidin-2-yl)propyl(methyl)dimethoxysilane Suitable examples of the silane compound having a protected secondary amino group are selected from N-trimethylsilyl(imidazol-2-yl)propyl(methyl)diethoxysilane, N-trimethylsilyl(imidazol-2-yl)propyl(methyl)dimethoxysilane, N-trimethylsilyl(imidazol-2-yl)propyl(methyl)diethoxysilane, N-trimethylsilyl(4,5-dihydroimidazol-5-yl)propyl(methyl)dimethoxysilane and N-trimethylsilyl(4,5-dihydroimidazol-5-yl)propyl(methyl)diethoxysilane.

[0043] Suitable examples of the modifying agent having an oxygen atom and a silicon atom (oxygen- and silicon-containing compound) include epoxy group-containing hydrocarbyloxysilane compounds selected from one or more of 2-glycidoxyethyltrimethoxysilane, 2-glycidoxyethyltriethoxysilane, (2-glycidoxyethyl)methyldimethoxysilane, 3-glycidoxypropyltrimethoxysilane, 3-glycidoxypropyltriethoxysilane, (3-glycidoxypropyl)methyldimethoxysilane, 2-(3,4-epoxycyclohexyl)ethyltrimethoxysilane, 2-(3,4-epoxycyclohexyl)ethyltriethoxysilane, and 2-(3,4-epoxycyclohexyl)ethyl(methyl)dimethoxysilane.

[0044] A suitable example of the modifier having a sulfur atom and a silicon atom (sulfur- and silicon-containing compound) is a thioepoxy group-containing hydrocarbyloxysilane compound in which the epoxy group of the above epoxy group-containing hydrocarbyloxysilane compound is substituted with a thioepoxy group.

[0045] Suitable examples of the modifying agent having a nitrogen atom but not having a silicon atom (a nitrogen-containing compound not containing silicon) include one or more compounds selected from bis(diethylamino)benzophenone, dimethylimidazolidinone, N-methylpyrrolidone, and 4-dimethylaminobenzylideneaniline.

[0046] The modified conjugated diene polymer (A1) is preferably modified with a modifier having a nitrogen atom and a silicon atom. When the modified conjugated diene polymer (A1) is modified with a modifier having a nitrogen atom and a silicon atom, the balance of wet grip performance, fuel economy and wear resistance of a tire using the rubber composition is further improved, and in particular, fuel economy and wear resistance can be further improved.

[0047] The conjugated diene polymer before modification that forms the modified conjugated diene polymer may be a conjugated diene homopolymer obtained by polymerizing one type of conjugated diene monomer, or a conjugated diene copolymer obtained by polymerizing two or more types of monomers. The conjugated diene copolymer may be one obtained by polymerizing two or more types of conjugated diene monomers, or one obtained by copolymerizing one or more types of conjugated diene monomers with one or more types of aromatic vinyl compounds. Examples of the conjugated diene monomer include 1,3-butadiene, isoprene, 1,3-pentadiene, 2,3-dimethyl-1,3-butadiene, 2-phenyl-1,3-butadiene, 1,3-hexadiene, etc. Among these, 1,3-butadiene, isoprene, and 2,3-dimethyl-1,3-butadiene are particularly preferred. Examples of the aromatic vinyl compound include styrene, α-methylstyrene, 1-vinylnaphthalene, 3-vinyltoluene, ethylvinylbenzene, divinylbenzene, 4-cyclohexylstyrene, 2,4,6-trimethylstyrene, etc. Among these, the styrene group is particularly preferred.

[0048] The conjugated diene polymer before modification that forms the modified conjugated diene polymer is preferably polybutadiene, styrene-butadiene copolymer, polyisoprene, isoprene-butadiene copolymer, styrene-isoprene copolymer, or the like.

[0049] The conjugated diene polymer may be polymerized by anionic polymerization or coordination polymerization.

[0050] When the conjugated diene polymer is obtained by anionic polymerization, an alkali metal compound is used as the polymerization initiator, and a lithium compound is preferred. The lithium compound used as the polymerization initiator is not particularly limited, but hydrocarbyllithium and lithium amide compounds are preferably used. When the former hydrocarbyllithium is used, a conjugated diene polymer having a hydrocarbyl group at the polymerization initiation terminal and a polymerization active site at the other terminal is obtained. When the latter lithium amide compound is used, a conjugated diene polymer having a nitrogen-containing group at the polymerization initiation terminal and a polymerization active site at the other terminal is obtained.

[0051] The hydrocarbyllithium is preferably one having a hydrocarbyl group having 2 to 20 carbon atoms, and examples thereof include ethyllithium, n-propyllithium, isopropyllithium, n-butyllithium, sec-butyllithium, tert-octyllithium, n-decyllithium, phenyllithium, 2-naphthyllithium, 2-butyl-phenyllithium, 4-phenyl-butyllithium, cyclohexyllithium, cyclopentyllithium, and a reaction product of diisopropenylbenzene with butyllithium. Of these, n-butyllithium is particularly preferred.

[0052] Examples of the lithium amide compound include lithium hexamethyleneimide, lithium pyrrolidide, lithium piperidide, lithium heptamethyleneimide, lithium dodecamethyleneimide, lithium dimethylamide, lithium diethylamide, lithium dibutylamide, lithium dipropylamide, lithium diheptylamide, lithium dihexylamide, lithium dioctylamide, lithium di-2-ethylhexylamide, lithium didecylamide, lithium-N-methylpiperazide, lithium ethylpropylamide, lithium ethylbutylamide, lithium ethylbenzylamide, lithium methylphenethylamide, etc. Among these, from the viewpoints of the interaction effect with carbon black and polymerization initiation ability, cyclic lithium amides such as lithium hexamethyleneimide, lithium pyrrolidide, lithium piperidide, lithium heptamethyleneimide, and lithium dodecamethyleneimide are preferred, and lithium hexamethyleneimide and lithium pyrrolidide are more suitable.

[0053] The use of lithium hexamethyleneimide as the polymerization initiator is more preferred because it results in a modified conjugated diene polymer having, at the initiation terminal of the conjugated diene polymer, a hexamethyleneimino group, which is a nitrogen-containing compound residue, as a functional group having atoms other than carbon and hydrogen. A modified conjugated diene polymer having, at the initiation terminal of the conjugated diene polymer, a nitrogen-containing compound residue, a hexamethyleneimino group, which is a nitrogen-containing compound residue, as a functional group having atoms other than carbon and hydrogen, and having, at the active terminal of the conjugated diene polymer, one or more compound residues selected from a tin-containing compound residue, a nitrogen- and silicon-containing compound residue, an oxygen- and silicon-containing compound residue, a sulfur- and silicon-containing compound residue, and a silicon-free nitrogen-containing compound residue, is even more preferred from the viewpoints of further reducing rolling resistance, providing excellent fuel economy, and further improving wear resistance and crack resistance.

[0054] The method for producing a conjugated diene polymer by anionic polymerization using the lithium compound as a polymerization initiator is not particularly limited, and any conventionally known method can be used. Specifically, in an organic solvent inert to the reaction, for example, a hydrocarbon solvent such as an aliphatic, alicyclic, or aromatic hydrocarbon compound, a conjugated diene compound or a conjugated diene compound and an aromatic vinyl compound are anionically polymerized using the lithium compound as a polymerization initiator, and optionally in the presence of a randomizer, to obtain the desired conjugated diene polymer. 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.

[0055] The optional randomizer is a compound that controls the microstructure of a conjugated diene polymer, for example, by increasing the number of 1,2 bonds in the butadiene moiety in a butadiene-styrene copolymer or the number of 3,4 bonds in an isoprene polymer, or by controlling the compositional distribution of monomer units in a conjugated diene compound-aromatic vinyl compound copolymer, for example, by randomizing the butadiene units and styrene units in a butadiene-styrene copolymer. The randomizer is not particularly limited, and any of the known compounds commonly used as randomizers can be appropriately selected and used. Specific examples include ethers such as dimethoxybenzene, tetrahydrofuran, dimethoxyethane, diethylene glycol dibutyl ether, diethylene glycol dimethyl ether, 2,2-bis(2-tetrahydrofuryl)propane, triethylamine, pyridine, N-methylmorpholine, N,N,N',N'-tetramethylethylenediamine, and 1,2-dipiperidinoethane, as well as tertiary amines. Potassium salts such as potassium tert-amylate and potassium tert-butoxide, and sodium salts such as sodium tert-amylate can also be used. These randomizers can be used alone or in combination of two or more. The amount of randomizer used is preferably selected from the range of 0.01 to 1000 molar equivalents per mole of lithium compound.

[0056] The temperature in the polymerization reaction is preferably selected in the range of 0 to 150°C, more preferably 20 to 130°C. The polymerization reaction can be carried out under generated pressure, but it is usually desirable to operate at a pressure sufficient to maintain the monomers substantially in a liquid phase. That is, although the pressure depends on the individual substances to be polymerized, the polymerization medium used, the polymerization temperature, etc., a higher pressure can be used if desired, and such a pressure can be obtained by a suitable method such as pressurizing the reactor with a gas inert to the polymerization reaction.

[0057] On the other hand, when the modified conjugated diene polymer is produced by coordination polymerization using a rare earth metal compound as a polymerization initiator, it is more preferable to use the following components (a), (b), and (c) in combination.

[0058] The component (a) used in the coordination polymerization is selected from rare earth metal compounds and complex compounds of rare earth metal compounds with Lewis bases. Examples of rare earth metal compounds include carboxylates, alkoxides, β-diketone complexes, phosphates, and phosphites of rare earth elements. Examples of Lewis bases include acetylacetone, tetrahydrofuran, pyridine, N,N-dimethylformamide, thiophene, diphenyl ether, triethylamine, organic phosphorus compounds, and monohydric or dihydric alcohols. Preferred rare earth elements in the rare earth metal compounds include lanthanum, neodymium, praseodymium, samarium, and gadolinium, with neodymium being particularly preferred. Specific examples of component (a) include neodymium tri-2-ethylhexanoate, its complex compound with acetylacetone, neodymium trineodecanoate, its complex compound with acetylacetone, and neodymium tri-n-butoxide. These components (a) may be used singly or in combination of two or more.

[0059] The component (b) used in the coordination polymerization is selected from organoaluminum compounds. Specific examples of the organoaluminum compound include trihydrocarbylaluminum compounds represented by the formula R3Al, hydrocarbylaluminum hydrides represented by the formula R2AlH or RAlH2 (wherein R is each independently a hydrocarbon group having 1 to 30 carbon atoms), and hydrocarbylaluminoxane compounds having a hydrocarbon group having 1 to 30 carbon atoms. Specific examples of the organoaluminum compound include trialkylaluminum, dialkylaluminum hydrides, alkylaluminum dihydrides, and alkylaluminoxanes. These compounds may be used alone or in combination of two or more. It is preferable to use an aluminoxane in combination with another organoaluminum compound as the component (b).

[0060] The component (c) used in coordination polymerization is selected from compounds containing hydrolyzable halogens or complexes of these with Lewis bases; organic halides containing tertiary alkyl halides, benzyl halides, or allyl halides; and ionic compounds consisting of non-coordinating anions and counter cations. Specific examples of the component (c) include alkylaluminum dichlorides, dialkylaluminum chlorides, silicon tetrachloride, tin tetrachloride, complexes of zinc chloride with Lewis bases such as alcohols, complexes of magnesium chloride with Lewis bases such as alcohols, benzyl chloride, t-butyl chloride, benzyl bromide, t-butyl bromide, and triphenylcarbonium tetrakis(pentafluorophenyl)borate. These components (c) may be used alone or in combination.

[0061] In addition to the above components (a), (b), and (c), the polymerization initiator may be preliminarily prepared using the same conjugated diene compound and / or non-conjugated diene compound as the polymerization monomer, as needed. Also, a portion or all of component (a) or component (c) may be supported on an inert solid before use. The amounts of the above components can be appropriately determined, but typically, component (a) is used in an amount of 0.001 to 0.5 millimoles (mmol) per 100 g of monomer. Furthermore, the molar ratio of component (b) / component (a) is preferably 5 to 1,000, and the molar ratio of component (c) / component (a) is preferably 0.5 to 10.

[0062] The polymerization temperature in coordination polymerization is preferably in the range of -80°C to 150°C, more preferably in the range of -20°C to 120°C. Furthermore, as the solvent used in coordination polymerization, the hydrocarbon solvents inert to the reaction exemplified in the anionic polymerization above can be used, and the concentration of the monomer in the reaction solution is also the same as in the anionic polymerization. Furthermore, the reaction pressure in coordination polymerization is also the same as in the anionic polymerization, and it is desirable that the raw materials used in the reaction are those from which reaction inhibitors such as water, oxygen, carbon dioxide, and protic compounds have been substantially removed.

[0063] The modified conjugated diene polymer is preferably one obtained by anionic polymerization using an organic alkali metal compound, particularly alkyllithium.

[0064] In both anionic polymerization and coordination polymerization, the conjugated diene polymer can be modified by a modification reaction between the active polymerization terminals and the above-mentioned modifier after the polymerization reaction to obtain a modified conjugated diene polymer. The modification reaction is preferably carried out at a temperature of 20°C or higher, but the polymerization temperature of the conjugated diene polymer can be used as is, with a more preferred range being 30 to 120°C. Lower reaction temperatures tend to result in excessively high polymer viscosity and poor dispersibility of the reaction product. On the other hand, higher reaction temperatures tend to result in the easy deactivation of the polymerization active sites. The amount of modifier used is preferably 0.25 to 3.0 mol, more preferably 0.5 to 1.5 mol, per mol of the polymerization initiator used in the production of the conjugated diene polymer.

[0065] In order to set the sustainability rate of the entire rubber component (A) within the above range, it is preferable to use, as the rubber component (A), a modified conjugated diene-based polymer (A1) synthesized using monomer components derived from biological resources or monomer components derived from recycled resources.

[0066] Generally, the raw materials for rubber compositions for tires (rubber and its monomers, fillers, resins, etc.) require large-scale manufacturing equipment and are therefore typically produced in large factories in specific regions, requiring significant amounts of energy for the storage and transportation of raw materials and finished products. In contrast, materials derived from biological resources (biomass resources) are derived from local agricultural products, forests, etc., and can be produced on a small scale through microbial fermentation and catalytic reactions. By utilizing local products and waste, the energy required for transporting and storing raw materials can be reduced, and the energy required for transporting and storing the produced materials to tire factories can also be reduced, making them environmentally friendly. Materials derived from recycled resources can be obtained, for example, by dismantling and pyrolyzing used tires to extract the rubber, fillers, steel cords, and other tire-constituting materials. In addition, sulfur can be obtained from biological resources or processed products of biological resources by a method including a desulfurization step of desulfurizing biological resources or processed products of biological resources to remove sulfur-containing substances from the biological resources or processed products of biological resources, a recovery step of recovering sulfur from the desulfurization residue generated in the desulfurization step, and a processing step of processing the recovered sulfur into sulfur for vulcanization (e.g., the method described in Japanese Patent Application No. 2022-140390), and raw materials for tire rubber compositions can be obtained from various waste products and used items. In this way, the use of sustainable materials (materials derived from biological resources or recycled resources) can reduce the overall environmental impact of tire manufacturing by reducing carbon dioxide emissions over the entire life cycle (LCCO2), reducing energy consumption over the entire life cycle (LCE), reducing life cycle costs (LCC), and reducing the use of fossil resources.

[0067] Furthermore, when producing the rubber composition, the ratios of monomer components derived from biological resources, monomer components derived from recycled resources, and monomer components derived from fossil resources can be appropriately selected depending on the supply situation of biological resources, recycled resources, and fossil resources (e.g., monomer components derived from fossil resources) and / or market demand (e.g., demand for biological resources as food). By polymerizing the monomer components derived from biological resources, monomer components derived from recycled resources, and monomer components derived from fossil resources, rubber derived from sustainable materials (materials derived from biological resources or materials derived from recycled resources) can be obtained that has performance equivalent to that of conventional synthetic rubber. When using monomer components derived from recycled resources, it may be difficult to separate them from monomer components derived from fossil resources due to the manufacturing process of the monomer. In such cases, the environmental impact can be evaluated by adopting the mass balance approach.

[0068] The ratio of each monomer unit (for example, a unit derived from isoprene, a unit derived from butadiene, or a unit derived from an aromatic vinyl compound) in the entire rubber component (A) can be adjusted appropriately depending on the component to which it is applied, etc. In this specification, the term "monomer unit" refers to a structural unit of a polymer, the term "unit derived from isoprene" refers to a structural unit in a polymer constituted based on the monomer isoprene, the term "unit derived from butadiene" refers to a structural unit in a polymer constituted based on the monomer butadiene, and the term "unit derived from an aromatic vinyl compound" refers to a structural unit in a polymer constituted based on the monomer aromatic vinyl compound. In this specification, the ratio of each monomer unit is measured by NMR.

[0069] The rubber (particularly the modified conjugated diene polymer (A1-1) supplied by the mass balance method) derived from the sustainable material (material derived from biological resources or material derived from recycled resources) can be produced, for example, using monomer components derived from biological resources or monomer components derived from recycled resources, and, if necessary, using monomer components derived from fossil resources, in the same manner as in the production method of conventional synthetic rubber derived from fossil resources. Furthermore, the rubber derived from the sustainable material (particularly the rubber derived from biological resources) can also be obtained by a reaction using microorganisms or an enzymatic reaction. The modified conjugated diene polymer (A1-1) supplied with a biological or renewable resource-derived characteristic assigned by the mass balance method can be treated as having a sustainable material ratio (the total mass ratio of materials derived from biological resources (biomass resources) and materials derived from recycled resources (recycled resources)) of 100% by mass, even if it contains a portion of fossil resource-derived monomer components. Because the mass balance method is used, even if the modified conjugated diene polymer (A1-1) supplied with a biological or renewable resource-derived characteristic assigned by the mass balance method contains a portion of fossil resource-derived monomer components, modified conjugated diene polymers containing a portion of biological or renewable resource-derived monomer components or having a sustainable material ratio of 0% by mass are supplied separately from the modified conjugated diene polymer (A1-1). Therefore, the use of the modified conjugated diene polymer (A1-1) can significantly contribute to reducing the environmental impact of the overall production, use, and disposal of the modified conjugated diene polymer.

[0070] Regarding the method for preparing bioresource-derived rubber from the above-mentioned bioresources, for example, the method described in JP 2022-179158 A can be used. For example, by using butadiene obtained from a bioresource as a monomer component, a bioresource (biomass resource)-derived butadiene rubber (B-BR) can be obtained. Furthermore, by using styrene obtained from a bioresource and butadiene obtained from a bioresource as monomer components, a bioresource (biomass resource)-derived styrene-butadiene rubber (B-SBR) can be obtained. Here, methods for obtaining B-BR and B-SBR from bioresources include artificial polymerization methods, in vivo polymerization methods, and polymerization methods using biological enzymes. The molecular weight, branching, microstructure, etc. of the obtained B-BR and B-SBR can be appropriately adjusted by changing the polymerization conditions according to known methods depending on the desired tire performance.

[0071] Suitable butadienes obtained from biological resources include butadienes derived from alkyl alcohols (preferably ethanol and butanol, more preferably butanol), butadienes derived from alkenes (preferably ethylene), and butadienes derived from unsaturated carboxylic acids (preferably tiglic acid). Two or more of these butadienes may also be used in combination. As the styrene obtained from the biological resources, styrene obtained from plants (preferably plants belonging to the Hamamelidaceae, Styraxaceae, and Apocynaceae families, more preferably plants belonging to the genus Liquidambar, Styrax rostrata, and Catharanthus roseus, and even more preferably Sweetgum, Styrax rostrata, and Catharanthus roseus), and styrene obtained from microorganisms (preferably microorganisms belonging to the genus Penicillium or Escherichia, more preferably P. citrinum or transformed E. coli) can be suitably used. Two or more of these styrenes may also be used in combination.

[0072] Recently, biomass industrial complexes centered on bioethanol, bioethylene, and the like have been planned. However, bioethanol and bioethylene are produced primarily from sugars and / or cellulose as biological resources, and do not effectively utilize other biological resources such as proteins, lipids, and amino acids. Furthermore, sugars compete with food, and excessive use of cellulose leads to deforestation. Therefore, depending on the supply status of various biological resources, the supply status of renewable resources, the supply status of fossil resources, and market demands (e.g., demand for biomass resources as food), it is preferable to use multiple types of monomer components derived from biological resources, or to combine monomer components derived from biological resources, monomer components derived from renewable resources, and monomer components derived from fossil resources, and further adjust the ratios of these monomer components appropriately. This allows for the effective use of a wide range of biological resources, such as sugars, proteins, and lipids, as well as renewable resources, without relying on a single type of biological resource. It also allows for a stable supply of rubber derived from sustainable materials and further contributes to environmental considerations depending on the production conditions. When multiple types of monomer components derived from biological resources are used, it is preferable to use monomer components derived from different biological resources, i.e., monomer components obtained from different biological resources. Specifically, it is preferable to use a mixture of butadienes derived from multiple types of biological resources with different origins as the biological resource-derived butadiene, and / or to use a mixture of styrenes derived from multiple types of biological resources with different origins as the biological resource-derived styrene. This allows for effective use of multiple types of biological resources.

[0073] --Modified styrene-butadiene rubber (modified SBR)-- The modified conjugated diene polymer (A1) preferably contains a modified styrene-butadiene rubber (modified SBR). When the rubber component (A) contains a modified styrene-butadiene rubber as the modified conjugated diene polymer (A1), the fuel economy and wear resistance of a tire using the rubber composition can be improved.

[0074] The modified styrene-butadiene rubber preferably has a glass transition temperature of less than -40°C. When the glass transition temperature of the modified styrene-butadiene rubber is less than -40°C, the fuel economy performance and wear resistance of a tire to which the rubber composition is applied can be further improved. From the viewpoint of further improving the fuel economy performance of the tire, the glass transition temperature of the modified styrene-butadiene rubber is more preferably -45°C or lower, and even more preferably -50°C or lower. The modified styrene-butadiene rubber preferably has a glass transition temperature higher than −90° C. Modified styrene-butadiene rubber with a glass transition temperature higher than −90° C. is easy to synthesize.

[0075] The content of the modified styrene-butadiene rubber is preferably 20 to 99 parts by mass, more preferably 30 to 99 parts by mass, more preferably 40 to 99 parts by mass, even more preferably 50 to 99 parts by mass, and still more preferably 60 to 99 parts by mass, based on 100 parts by mass of the rubber component (A). When the content of the modified styrene-butadiene rubber is 60 to 99 parts by mass based on 100 parts by mass of the rubber component (A), the fuel economy and wet grip performance of a tire using the rubber composition can be further improved.

[0076] The modified styrene-butadiene rubber preferably has a bound styrene content of less than 15% by mass. The bound styrene content of the modified styrene-butadiene rubber refers to the proportion of styrene units contained in the styrene-butadiene rubber. If the bound styrene content of the modified styrene-butadiene rubber is less than 15% by mass, the glass transition temperature is likely to be low. The bound styrene content of the modified styrene-butadiene rubber is more preferably 14% by mass or less, more preferably 13% by mass or less, and even more preferably 12% by mass or less. Furthermore, from the viewpoint of the wear resistance of a tire using the rubber composition, the bound styrene content of the modified styrene-butadiene rubber is preferably 5% by mass or more, more preferably 7% by mass or more, and even more preferably 8% by mass or more. The amount of bound styrene in the modified styrene-butadiene rubber can be adjusted by the amount of monomers used in the polymerization of the styrene-butadiene rubber, the degree of polymerization, and the like.

[0077] The modified styrene-butadiene rubber is preferably modified with a modifier having a nitrogen-containing functional group and an alkoxy group. When the modified styrene-butadiene rubber is modified with a modifier having a nitrogen-containing functional group and an alkoxy group, the balance between wet grip performance, fuel economy, and wear resistance of a tire using the rubber composition is further improved, and in particular, fuel economy and wear resistance can be further improved. The modifying agent having a nitrogen atom-containing functional group and an alkoxy group is a general term for modifying agents having at least one nitrogen atom-containing functional group and at least one alkoxy group. The functional group containing a nitrogen atom is preferably selected from the following: The functional group is a monovalent hydrocarbon group having 1 to 30 carbon atoms and containing a straight-chain, branched, alicyclic, or aromatic ring, or a monovalent hydrocarbon group having 1 to 30 carbon atoms and containing a straight-chain, branched, alicyclic, or aromatic ring, which may contain at least one heteroatom selected from oxygen, sulfur, and phosphorus atoms. The functional group is selected from the group consisting of a primary amino group, a primary amino group protected with a hydrolyzable protecting group, an onium salt residue of a primary amine, an isocyanate group, a thioisocyanate group, an imine group, an imine residue, an amide group, a secondary amino group protected with a hydrolyzable protecting group, a cyclic secondary amino group, an onium salt residue of a cyclic secondary amine, an acyclic secondary amino group, an onium salt residue of an acyclic secondary amine, an isocyanuric acid triester residue, a cyclic tertiary amino group, an acyclic tertiary amino group, a nitrile group, a pyridine residue, an onium salt residue of a cyclic tertiary amine, and an onium salt residue of an acyclic tertiary amine, or a monovalent hydrocarbon group having 1 to 30 carbon atoms and containing a straight-chain, branched, alicyclic, or aromatic ring, which may contain at least one heteroatom selected from oxygen, sulfur, and phosphorus atoms.

[0078] ---First Preferred Embodiment of Modified Styrene-Butadiene Rubber--- The modified styrene-butadiene rubber (modified SBR) is preferably modified with an aminoalkoxysilane compound, and from the viewpoint of having a high affinity for fillers, it is more preferable that the terminals are modified with an aminoalkoxysilane compound. When the terminals of the styrene-butadiene rubber are modified with an aminoalkoxysilane compound, the interaction between the modified styrene-butadiene rubber and the filler (especially silica) becomes particularly strong.

[0079] The modified site of the styrene-butadiene rubber may be the molecular terminal as described above, but may also be the main chain. Styrene-butadiene rubber having modified molecular terminals can be produced by reacting various modifiers with the terminals of a styrene-butadiene copolymer having active terminals, for example, according to the methods described in WO 2003 / 046020 and JP 2007-217562 A. In a preferred embodiment, the styrene-butadiene rubber having modified molecular terminals can be produced in accordance with the methods described in WO 2003 / 046020 and JP 2007-217562 A by reacting an aminoalkoxysilane compound with the terminal of a styrene-butadiene copolymer having active terminals with a cis-1,4 bond content of 75% or more, and then reacting the resulting copolymer with a carboxylic acid partial ester of a polyhydric alcohol for stabilization.

[0080] The carboxylic acid partial ester of a polyhydric alcohol refers to an ester of a polyhydric alcohol and a carboxylic acid, which has one or more hydroxyl groups. Specifically, an ester of a sugar or modified sugar having 4 or more carbon atoms and a fatty acid is preferably used. More preferred examples of this ester include (1) a fatty acid partial ester of a polyhydric alcohol, particularly a partial ester (which may be a monoester, diester, or triester) of a saturated higher fatty acid or an unsaturated higher fatty acid having 10 to 20 carbon atoms and a polyhydric alcohol, and (2) an ester compound in which 1 to 3 partial esters of a polycarboxylic acid and a higher alcohol are bonded to a polyhydric alcohol. The polyhydric alcohol used as a raw material for the partial ester is preferably a sugar (which may or may not be hydrogenated) having 5 or 6 carbon atoms and at least three hydroxyl groups, glycol, polyhydroxy compound, etc. The raw material fatty acid is preferably a saturated or unsaturated fatty acid having 10 to 20 carbon atoms, such as stearic acid, lauric acid, or palmitic acid. Among the fatty acid partial esters of polyhydric alcohols, sorbitan fatty acid esters are preferred, and specific examples include sorbitan monolaurate, sorbitan monopalmitate, sorbitan monostearate, sorbitan tristearate, sorbitan monooleate, and sorbitan trioleate.

[0081] The aminoalkoxysilane compound is not particularly limited, but is preferably an aminoalkoxysilane compound represented by the following general formula (i): R 11 a -Si-(OR 12 ) 4-a (i)

[0082] In general formula (i), R 11 and R 12 each independently represents a monovalent aliphatic hydrocarbon group having 1 to 20 carbon atoms or a monovalent aromatic hydrocarbon group having 6 to 18 carbon atoms, and R 11 and R 12 At least one of the groups is substituted with an amino group, a is an integer of 0 to 2, and OR 12 If there are multiple, each OR 12 may be the same or different, and the molecule does not contain any active protons.

[0083] The aminoalkoxysilane compound is also preferably an aminoalkoxysilane compound represented by the following general formula (ii). [ka]

[0084] In the general formula (ii), n1+n2+n3+n4=4 (wherein n2 is an integer of 1 to 4, and n1, n3 and n4 are integers of 0 to 3). A 1 is at least one functional group selected from a saturated cyclic tertiary amine compound residue, an unsaturated cyclic tertiary amine compound residue, a ketimine residue, a nitrile group, a (thio)isocyanate group, an isocyanuric acid trihydrocarbyl ester group, a nitrile group, a pyridine group, a (thio)ketone group, an amide group, and a primary or secondary amino group having a hydrolyzable group. When n4 is 2 or more, A 1 may be the same or different, and A 1 may be a divalent group that bonds with Si to form a cyclic structure. R 21 represents a monovalent aliphatic or alicyclic hydrocarbon group having 1 to 20 carbon atoms or a monovalent aromatic hydrocarbon group having 6 to 18 carbon atoms, and when n1 is 2 or more, may be the same or different. R 22 is a monovalent aliphatic or alicyclic hydrocarbon group having 1 to 20 carbon atoms or a monovalent aromatic hydrocarbon group having 6 to 18 carbon atoms, both of which may contain a nitrogen atom and / or a silicon atom. When n2 is 2 or more, R 22 may be the same or different from each other, or may be joined together to form a ring. R 23 represents a monovalent aliphatic or alicyclic hydrocarbon group having 1 to 20 carbon atoms, a monovalent aromatic hydrocarbon group having 6 to 18 carbon atoms, or a halogen atom, and when n3 is 2 or greater, may be the same or different. R 24 represents a divalent aliphatic or alicyclic hydrocarbon group having 1 to 20 carbon atoms or a divalent aromatic hydrocarbon group having 6 to 18 carbon atoms, and when n4 is 2 or more, may be the same or different. The hydrolyzable group in the hydrolyzable group-containing primary or secondary amino group is preferably a trimethylsilyl group or a tert-butyldimethylsilyl group, and particularly preferably a trimethylsilyl group.

[0085] The aminoalkoxysilane compound represented by the above general formula (ii) is preferably an aminoalkoxysilane compound represented by the following general formula (iii). [ka]

[0086] In the general formula (iii), p1+p2+p3=2 (wherein p2 is an integer of 1 or 2, and p1 and p3 are integers of 0 or 1). A 2 is NRa (Ra is a monovalent hydrocarbon group, a hydrolyzable group, or a nitrogen-containing organic group). R 25 is a monovalent aliphatic or alicyclic hydrocarbon group having 1 to 20 carbon atoms or a monovalent aromatic hydrocarbon group having 6 to 18 carbon atoms. R 26 is a monovalent aliphatic or alicyclic hydrocarbon group having 1 to 20 carbon atoms, a monovalent aromatic hydrocarbon group having 6 to 18 carbon atoms, or a nitrogen-containing organic group, any of which may contain a nitrogen atom and / or a silicon atom. 26 may be the same or different, or may be joined together to form a ring. R 27 is a monovalent aliphatic or alicyclic hydrocarbon group having 1 to 20 carbon atoms, a monovalent aromatic hydrocarbon group having 6 to 18 carbon atoms, or a halogen atom. R 28 is a divalent aliphatic or alicyclic hydrocarbon group having 1 to 20 carbon atoms or a divalent aromatic hydrocarbon group having 6 to 18 carbon atoms. The hydrolyzable group is preferably a trimethylsilyl group or a tert-butyldimethylsilyl group, and particularly preferably a trimethylsilyl group.

[0087] The aminoalkoxysilane compound represented by the above general formula (ii) is also preferably an aminoalkoxysilane compound represented by the following general formula (iv) or (v). [ka]

[0088] In the general formula (iv), q1+q2=3 (wherein q1 is an integer of 0 to 2, and q2 is an integer of 1 to 3). R 31 is a divalent aliphatic or alicyclic hydrocarbon group having 1 to 20 carbon atoms or a divalent aromatic hydrocarbon group having 6 to 18 carbon atoms. R 32 and R 33 are each independently a hydrolyzable group, a monovalent aliphatic or alicyclic hydrocarbon group having 1 to 20 carbon atoms, or a monovalent aromatic hydrocarbon group having 6 to 18 carbon atoms. R 34 represents a monovalent aliphatic or alicyclic hydrocarbon group having 1 to 20 carbon atoms or a monovalent aromatic hydrocarbon group having 6 to 18 carbon atoms, and when q1 is 2, may be the same or different. R 35 represents a monovalent aliphatic or alicyclic hydrocarbon group having 1 to 20 carbon atoms or a monovalent aromatic hydrocarbon group having 6 to 18 carbon atoms, and when q2 is 2 or greater, may be the same or different.

[0089] [ka]

[0090] In the general formula (v), r1+r2=3 (where r1 is an integer of 1 to 3, and r2 is an integer of 0 to 2). R 36 is a divalent aliphatic or alicyclic hydrocarbon group having 1 to 20 carbon atoms or a divalent aromatic hydrocarbon group having 6 to 18 carbon atoms. R 37represents a dimethylaminomethyl group, a dimethylaminoethyl group, a diethylaminomethyl group, a diethylaminoethyl group, a methylsilyl(methyl)aminomethyl group, a methylsilyl(methyl)aminoethyl group, a methylsilyl(ethyl)aminomethyl group, a methylsilyl(ethyl)aminoethyl group, a dimethylsilylaminomethyl group, a monovalent aliphatic or alicyclic hydrocarbon group having 1 to 20 carbon atoms, or a monovalent aromatic hydrocarbon group having 6 to 18 carbon atoms, and when r1 is 2 or more, they may be the same or different. R 38 represents a hydrocarbyloxy group having 1 to 20 carbon atoms, a monovalent aliphatic or alicyclic hydrocarbon group having 1 to 20 carbon atoms, or a monovalent aromatic hydrocarbon group having 6 to 18 carbon atoms, and when r2 is 2, may be the same or different. A specific example of the aminoalkoxysilane compound represented by general formula (v) is N-(1,3-dimethylbutylidene)-3-triethoxysilyl-1-propanamine.

[0091] The aminoalkoxysilane compound represented by the above general formula (ii) is also preferably an aminoalkoxysilane compound represented by the following general formula (vi) or (vii). [ka]

[0092] In general formula (vi), R 40 is a trimethylsilyl group, a monovalent aliphatic or alicyclic hydrocarbon group having 1 to 20 carbon atoms, or a monovalent aromatic hydrocarbon group having 6 to 18 carbon atoms. R 41 is a hydrocarbyloxy group having 1 to 20 carbon atoms, a monovalent aliphatic or alicyclic hydrocarbon group having 1 to 20 carbon atoms, or a monovalent aromatic hydrocarbon group having 6 to 18 carbon atoms. R 42 is a divalent aliphatic or alicyclic hydrocarbon group having 1 to 20 carbon atoms or a divalent aromatic hydrocarbon group having 6 to 18 carbon atoms. Here, TMS represents a trimethylsilyl group (the same applies hereinafter).

[0093] [ka]

[0094] In general formula (vii), R 43 and R 44 are each independently a divalent aliphatic or alicyclic hydrocarbon group having 1 to 20 carbon atoms or a divalent aromatic hydrocarbon group having 6 to 18 carbon atoms. R 45 is a monovalent aliphatic or alicyclic hydrocarbon group having 1 to 20 carbon atoms or a monovalent aromatic hydrocarbon group having 6 to 18 carbon atoms, and each R 45 may be the same or different.

[0095] The aminoalkoxysilane compound represented by the above general formula (ii) is also preferably an aminoalkoxysilane compound represented by the following general formula (viii) or (ix). [ka]

[0096] In the general formula (viii), s1+s2 is 3 (wherein s1 is an integer of 0 to 2, and s2 is an integer of 1 to 3). R 46 is a divalent aliphatic or alicyclic hydrocarbon group having 1 to 20 carbon atoms or a divalent aromatic hydrocarbon group having 6 to 18 carbon atoms. R 47 and R 48 are each independently a monovalent aliphatic or alicyclic hydrocarbon group having 1 to 20 carbon atoms or a monovalent aromatic hydrocarbon group having 6 to 18 carbon atoms. 47 or R 48 may be the same or different.

[0097] [ka]

[0098] In the general formula (ix), X is a halogen atom. R 49 is a divalent aliphatic or alicyclic hydrocarbon group having 1 to 20 carbon atoms or a divalent aromatic hydrocarbon group having 6 to 18 carbon atoms. R 50 and R 51 are each independently a hydrolyzable group, a monovalent aliphatic or alicyclic hydrocarbon group having 1 to 20 carbon atoms, or a monovalent aromatic hydrocarbon group having 6 to 18 carbon atoms, or R 50 and R 51 are bonded to form a divalent organic group. R 52 and R 53 are each independently a halogen atom, a hydrocarbyloxy group, a monovalent aliphatic or alicyclic hydrocarbon group having 1 to 20 carbon atoms, or a monovalent aromatic hydrocarbon group having 6 to 18 carbon atoms. R 50 and R 51 As the hydrolyzable group, a hydrolyzable group is preferred, and as the hydrolyzable group, a trimethylsilyl group or a tert-butyldimethylsilyl group is preferred, and a trimethylsilyl group is particularly preferred.

[0099] The aminoalkoxysilane compound represented by the above general formula (ii) is also preferably an aminoalkoxysilane compound represented by the following general formula (x), (xi), (xii), or (xiii): [ka]

[0100] In the general formulae (x) to (xiii), the symbols U and V are each an integer of 0 to 2 and satisfy U+V=2. R in general formulas (x) to (xiii) 54 ~ 92 may be the same or different and are monovalent or divalent aliphatic or alicyclic hydrocarbon groups having 1 to 20 carbon atoms, or monovalent or divalent aromatic hydrocarbon groups having 6 to 18 carbon atoms. In the general formula (xiii), α and β are integers of 0 to 5.

[0101] Among the compounds satisfying general formula (x), general formula (xi), and general formula (xii), N1,N1,N7,N7-tetramethyl-4-((trimethoxysilyl)methyl)heptane-1,7-diamine, 2-((hexyl-dimethoxysilyl)methyl)-N1,N1,N3,N3-2-pentamethylpropane-1,3-diamine, N1-(3-(dimethylamino)propyl)-N3,N3-dimethyl-N1-(3-(trimethoxysilyl)propyl)propane-1,3-diamine, and 4-(3-(dimethylamino)propyl)-N1,N1,N7,N7-tetramethyl-4-((trimethoxysilyl)methyl)heptane-1,7-diamine are particularly preferred. Furthermore, among the compounds satisfying the general formula (xiii), N,N-dimethyl-2-(3-(dimethoxymethylsilyl)propoxy)ethanamine, N,N-bis(trimethylsilyl)-2-(3-(trimethoxysilyl)propoxy)ethanamine, N,N-dimethyl-2-(3-(trimethoxysilyl)propoxy)ethanamine, and N,N-dimethyl-3-(3-(trimethoxysilyl)propoxy)propan-1-amine are particularly preferred.

[0102] ---Second Preferred Embodiment of Modified Styrene-Butadiene Rubber--- The modified styrene-butadiene rubber (modified SBR) is also preferably modified with a coupling agent represented by the following general formula (I), which can further improve the fuel economy and wear resistance of tires using the rubber composition. [ka]

[0103] In the above general formula (I), R 1 , R 2 and R 3 each independently represents a single bond or an alkylene group having 1 to 20 carbon atoms. R 4 , R 5 , R 6 , R 7 and R 9 are each independently an alkyl group having 1 to 20 carbon atoms. R 8 and R 11 are each independently an alkylene group having 1 to 20 carbon atoms. R 10 represents an alkyl group or a trialkylsilyl group having 1 to 20 carbon atoms. m represents an integer of 1 to 3; p represents 1 or 2; R 1 ~R 11 When there are multiple , m and p, they are independent of each other. i, j, and k each independently represent an integer of 0 to 6, provided that (i+j+k) is an integer of 3 to 10. A represents a hydrocarbon group having 1 to 20 carbon atoms, or an organic group having at least one atom selected from the group consisting of oxygen atoms, nitrogen atoms, silicon atoms, sulfur atoms, and phosphorus atoms, and having no active hydrogen. In general formula (I), the hydrocarbon group represented by A includes saturated, unsaturated, aliphatic, and aromatic hydrocarbon groups. Examples of the organic group without active hydrogen include organic groups without functional groups with active hydrogen, such as a hydroxyl group (-OH), a secondary amino group (>NH), a primary amino group (-NH), and a sulfhydryl group (-SH).

[0104] The styrene-butadiene rubber modified with the coupling agent represented by the general formula (I) has a weight average molecular weight (Mw) of 20×10 4 ~300×10 4 and the molecular weight of the modified styrene-butadiene rubber is 200×10 4 ~500×10 4 It is preferable that the modified styrene-butadiene rubber contains 0.25 to 30 mass % of the modified styrene-butadiene rubber represented by the formula (I) and has a shrinkage factor (g') of less than 0.64.

[0105] Generally, a polymer having branches tends to have a smaller molecular size compared to a linear polymer having the same absolute molecular weight, and the shrinkage factor (g') 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 larger the degree of branching of a polymer, the smaller the shrinkage factor (g') tends to be. In this embodiment, intrinsic viscosity is used as an index of molecular size, and a linear polymer has an intrinsic viscosity [η] = -3.883 M 0.771 The shrinkage factor (g') for each absolute molecular weight of the modified styrene-butadiene rubber is calculated, and the absolute molecular weight is calculated as 100 x 10 4 ~200×10 4 The average value of the shrinkage factor (g') when the above formula is used is the shrinkage factor (g') of the modified styrene-butadiene rubber. Here, "branching" refers to a branch formed by direct or indirect bonding of one polymer to another polymer. Furthermore, the "degree of branching" refers to the number of polymers directly or indirectly bonded to one branch. For example, if five styrene-butadiene copolymer chains (described below) are indirectly bonded to each other via coupling residues (described below), the degree of branching is 5. The coupling residue is a structural unit of the modified styrene-butadiene rubber bonded to the styrene-butadiene copolymer chain, and is, for example, a structural unit derived from a coupling agent, which is generated by reacting the styrene-butadiene copolymer (described below) with a coupling agent. The styrene-butadiene copolymer chain is a structural unit of the modified styrene-butadiene rubber, and is, for example, a structural unit derived from a styrene-butadiene copolymer, which is generated by reacting the styrene-butadiene copolymer (described below) with a coupling agent. The shrinkage factor (g') is preferably less than 0.64, more preferably 0.63 or less, more preferably 0.60 or less, even more preferably 0.59 or less, and even more preferably 0.57 or less. The lower limit of the shrinkage factor (g') is not particularly limited and may be below 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. By using a modified styrene-butadiene rubber having a shrinkage factor (g') in this range, the processability of the rubber composition is improved. Since the shrinkage factor (g') tends to depend on the degree of branching, it is possible to control the shrinkage factor (g') using the degree of branching as an index, for example. Specifically, when a modified styrene-butadiene rubber has a branching degree of 6, its shrinkage factor (g') tends to be 0.59 or more and 0.63 or less, and when a modified styrene-butadiene rubber has a branching degree of 8, its shrinkage factor (g') tends to be 0.45 or more and 0.59 or less.

[0106] The styrene-butadiene rubber modified with the coupling agent represented by the general formula (I) preferably has branches and a degree of branching of 5 or more. Furthermore, the modified styrene-butadiene rubber has one or more coupling residues and styrene-butadiene copolymer chains bonded to the coupling residues, and more preferably, the branches include branches in which five or more styrene-butadiene copolymer chains are bonded to one coupling residue. By specifying the structure of the modified styrene-butadiene rubber so that the degree of branching is 5 or more and the branches include branches in which five or more styrene-butadiene copolymer chains are bonded to one coupling residue, the contraction factor (g') can be more reliably reduced to less than 0.64. The number of styrene-butadiene copolymer chains bonded to one coupling residue can be confirmed from the value of the contraction factor (g'). The modified styrene-butadiene rubber preferably has branches, with a degree of branching of 6 or more. The modified styrene-butadiene rubber preferably has one or more coupling residues and styrene-butadiene copolymer chains bonded to the coupling residues, and more preferably includes branches in which six or more styrene-butadiene copolymer chains are bonded to one coupling residue. By specifying the structure of the modified styrene-butadiene rubber so that the degree of branching is 6 or more and the branch includes branches in which six or more styrene-butadiene copolymer chains are bonded to one coupling residue, the shrinkage factor (g') can be set to 0.63 or less. Furthermore, the modified styrene-butadiene rubber has branches, and the degree of branching is more preferably 7 or more, and even more preferably 8 or more. The upper limit of the degree of branching is not particularly limited, but is preferably 18 or less. The modified styrene-butadiene rubber has one or more coupling residues and styrene-butadiene copolymer chains bonded to the coupling residues, and more preferably the branches include branches in which 7 or more styrene-butadiene copolymer chains are bonded to one coupling residue, and particularly preferably the branches include branches in which 8 or more styrene-butadiene copolymer chains are bonded to one coupling residue. By specifying the structure of the modified styrene-butadiene rubber so that the degree of branching is 8 or more and the branches include branches in which 8 or more styrene-butadiene copolymer chains are bonded to one coupling residue, the shrinkage factor (g') can be made 0.59 or less.

[0107] At least one end of the styrene-butadiene copolymer chain is preferably bonded to a silicon atom of the coupling residue. In this case, the ends of a plurality of styrene-butadiene copolymer chains may be bonded to a single silicon atom. Alternatively, an end of the styrene-butadiene copolymer chain and an alkoxy group or hydroxyl group having 1 to 20 carbon atoms may be bonded to a single silicon atom, and as a result, that single silicon atom may constitute an alkoxysilyl group or silanol group having 1 to 20 carbon atoms.

[0108] The modified styrene-butadiene rubber may be an oil-extended rubber obtained by adding an extender oil. The modified styrene-butadiene rubber may be either non-oil-extended or oil-extended, but from the viewpoint of abrasion resistance, the Mooney viscosity measured at 100°C is preferably 20 or more and 100 or less, more preferably 30 or more and 80 or less.

[0109] The weight average molecular weight (Mw) of the modified styrene-butadiene rubber is preferably 20×10 4 Over 300 x 10 4 or less, more preferably 50×10 4 More preferably, 64×10 4 More preferably, it is 80×10 4 The weight average molecular weight is preferably 250×10 4 or less, and more preferably 180×10 4 or less, and more preferably 150×10 4 The weight average molecular weight is 20 × 10 4 When the weight average molecular weight is 300×10 or more, the low loss property and abrasion resistance of the rubber composition can be sufficiently improved. 4 When it is equal to or less than this, the processability of the rubber composition is improved.

[0110] The modified styrene-butadiene rubber has a molecular weight of 200×10 relative to the total amount (100% by mass) of the modified styrene-butadiene rubber. 4 Over 500 x 10 4It is preferable that the modified styrene-butadiene rubber (hereinafter also referred to as "specific high molecular weight component") contains 0.25% by mass or more and 30% by mass or less of the specific high molecular weight component. When the content of the specific high molecular weight component is 0.25% by mass or more and 30% by mass or less, the low loss property and abrasion resistance of the rubber composition can be sufficiently improved. The modified styrene-butadiene rubber contains the specific high molecular weight component preferably at least 1.0% by mass, more preferably at least 1.4% by mass, even more preferably at least 1.75% by mass, still more preferably at least 2.0% by mass, particularly preferably at least 2.15% by mass, and extremely preferably at least 2.5% by mass. Furthermore, the modified styrene-butadiene rubber contains the specific high molecular weight component preferably at most 28% by mass, more preferably at most 25% by mass, even more preferably at most 20% by mass, and even more preferably at most 18% by mass. In this specification, the "molecular weight" of the rubber component refers to the molecular weight in terms of standard polystyrene obtained by GPC (gel permeation chromatography). In order to obtain a modified styrene-butadiene rubber having a content of a specific high molecular weight component within this range, it is preferable to control the reaction conditions in the polymerization step and reaction step described below. For example, in the polymerization step, the amount of an organic monolithium compound used as a polymerization initiator, described below, can be adjusted. In addition, in the polymerization step, whether the polymerization method is continuous or batchwise, it is preferable to use a method with a residence time distribution, that is, to widen the time distribution of the propagation reaction.

[0111] In the modified styrene-butadiene rubber, the molecular weight distribution (Mw / Mn), which is the ratio of the weight average molecular weight (Mw) to the number average molecular weight (Mn), is preferably 1.6 to 3.0. If the molecular weight distribution of the modified styrene-butadiene rubber is in this range, the rubber composition will have good processability.

[0112] The method for producing the modified styrene-butadiene rubber is not particularly limited, but preferably includes a polymerization step of copolymerizing butadiene and styrene using an organic monolithium compound as a polymerization initiator to obtain a styrene-butadiene copolymer, and a reaction step of reacting an active terminal of the styrene-butadiene copolymer with a pentafunctional or higher reactive compound (hereinafter also referred to as a "coupling agent").

[0113] The polymerization step is preferably a propagation polymerization by living anionic polymerization, which makes it possible to obtain a styrene-butadiene copolymer having active terminals and a modified styrene-butadiene rubber with a high degree of modification. The styrene-butadiene copolymer is obtained by copolymerizing 1,3-butadiene and styrene.

[0114] The amount of the organic monolithium compound used as a polymerization initiator is preferably determined based on the target molecular weight of the styrene-butadiene copolymer or modified styrene-butadiene rubber. The amount of monomers, such as 1,3-butadiene and styrene, used relative to the amount of polymerization initiator is related to the degree of polymerization, i.e., the number average molecular weight and / or weight average molecular weight. Therefore, to increase the molecular weight, it is recommended to adjust the amount of polymerization initiator to decrease, and to decrease the molecular weight, it is recommended to adjust the amount of polymerization initiator to increase. The organic monolithium compound is preferably an alkyllithium compound from the viewpoints of industrial availability and ease of control of the polymerization reaction. In this case, a styrene-butadiene copolymer having an alkyl group at the polymerization initiation terminal is obtained. Examples of the alkyllithium compound include n-butyllithium, sec-butyllithium, tert-butyllithium, n-hexyllithium, benzyllithium, phenyllithium, and stilbenelithium. From the viewpoints of industrial availability and ease of control of the polymerization reaction, n-butyllithium and sec-butyllithium are preferred as the alkyllithium compound. These organic monolithium compounds may be used alone or in combination of two or more.

[0115] In the polymerization step, examples of the polymerization reaction mode include batch and continuous polymerization modes. In a continuous mode, one or more connected reactors can be used. Continuous reactors, for example, tank-type or tubular reactors equipped with a stirrer, are used. In a continuous mode, preferably, monomers, an inert solvent, and a polymerization initiator are continuously fed into the reactor, a polymer solution containing a polymer is obtained in the reactor, and the polymer solution is continuously discharged. Batch reactors, for example, tank-type reactors equipped with a stirrer, are used. In a batch mode, preferably, monomers, an inert solvent, and a polymerization initiator are fed, and if necessary, monomers are added continuously or intermittently during polymerization, a polymer solution containing a polymer is obtained in the reactor, and the polymer solution is discharged after the polymerization is completed. In this embodiment, in order to obtain a styrene-butadiene copolymer having a high proportion of active ends, a continuous mode is preferred, which allows the polymer to be continuously discharged and subjected to the next reaction in a short period of time.

[0116] The polymerization step is preferably carried out in an inert solvent. Examples of the solvent include hydrocarbon solvents such as saturated hydrocarbons and aromatic hydrocarbons. Specific hydrocarbon solvents include, but are not limited to, aliphatic hydrocarbons such as butane, pentane, hexane, and heptane; alicyclic hydrocarbons such as cyclopentane, cyclohexane, methylcyclopentane, and methylcyclohexane; aromatic hydrocarbons such as benzene, toluene, and xylene; and hydrocarbons consisting of mixtures thereof. Treating impurities such as allenes and acetylenes with an organometallic compound before subjecting the mixture to the polymerization reaction tends to produce a styrene-butadiene copolymer having a high concentration of active terminals, and thus tends to produce a modified styrene-butadiene rubber with a high modification rate, which is preferable.

[0117] In the polymerization step, a polar compound may be added. By adding a polar compound, styrene can be randomly copolymerized with 1,3-butadiene, and the polar compound also tends to be usable as a vinylating agent for controlling the microstructure of the 1,3-butadiene moiety. Examples of the polar compound that can be used include ethers such as tetrahydrofuran, diethyl ether, dioxane, ethylene glycol dimethyl ether, ethylene glycol dibutyl ether, diethylene glycol dimethyl ether, diethylene glycol dibutyl ether, dimethoxybenzene, and 2,2-bis(2-oxolanyl)propane; tertiary amine compounds such as tetramethylethylenediamine, dipiperidinoethane, trimethylamine, triethylamine, pyridine, and quinuclidine; alkali metal alkoxide compounds such as potassium tert-amylate, potassium tert-butylate, sodium tert-butylate, and sodium tert-amylate; and phosphine compounds such as triphenylphosphine. These polar compounds may be used alone or in combination of two or more.

[0118] In the polymerization step, from the viewpoint of productivity, the polymerization temperature is preferably 0° C. or higher, more preferably 120° C. or lower, and particularly preferably 50° C. or higher and 100° C. or lower. By keeping the temperature within such a range, it tends to be possible to ensure a sufficient amount of the coupling agent to react with the active terminals after the completion of polymerization.

[0119] The amount of bound butadiene in the styrene-butadiene copolymer or modified styrene-butadiene rubber is not particularly limited, but is preferably 40% by mass or more and 100% by mass or less, and more preferably 55% by mass or more and 80% by mass or less. Furthermore, the amount of bound styrene in the styrene-butadiene copolymer or modified styrene-butadiene rubber is not particularly limited, but is preferably more than 0 mass% and not more than 60 mass%, and more preferably 20 mass% or more and 45 mass% or less. When the bound butadiene amount and the bound styrene amount are within the above ranges, the low loss property and the wear resistance of the rubber composition can be further improved. The amount of bound styrene can be measured by ultraviolet absorption of the phenyl group, and the amount of bound butadiene can also be determined from this.

[0120] In the styrene-butadiene copolymer or modified styrene-butadiene rubber, the amount of vinyl bonds in the butadiene bond units is not particularly limited, but is preferably 10 mol % to 75 mol %, more preferably 20 mol % to 65 mol %. When the amount of vinyl bonds is within the above range, the low loss property and wear resistance of the rubber composition can be further improved. For modified styrene-butadiene rubber, the vinyl bond content (1,2-bond content) in the butadiene bond unit can be determined by Hampton's method [RR Hampton, Analytical Chemistry, 21, 923 (1949)].

[0121] The alkoxysilyl group of the coupling agent represented by the general formula (I) tends to react with, for example, the active terminal of a styrene-butadiene copolymer, dissociating the alkoxylithium and forming a bond between the terminal of the styrene-butadiene copolymer chain and the silicon of the coupling residue. The number of alkoxysilyl groups in the coupling residue is calculated by subtracting the number of SiO R from the total number of SiO R in one molecule of the coupling agent. Furthermore, the azasilacycle group in the coupling agent forms an >N-Li bond and a bond between the terminal of the styrene-butadiene copolymer and the silicon of the coupling residue. The >N-Li bond tends to easily become >NH and LiOH upon exposure to water or other factors during finishing. Furthermore, any remaining unreacted alkoxysilyl groups in the coupling agent tend to easily become silanols (Si-OH groups) upon exposure to water or other factors during finishing.

[0122] The reaction temperature in the reaction step is preferably the same as the polymerization temperature of the styrene-butadiene copolymer, more preferably from 0° C. to 120° C., and even more preferably from 50° C. to 100° C. The temperature change from the end of the polymerization step to the addition of the coupling agent is preferably 10° C. or less, more preferably 5° C. or less. The reaction time in the reaction step is preferably 10 seconds or more, more preferably 30 seconds or more. From the viewpoint of the coupling rate, the time from the end of the polymerization step to the start of the reaction step is preferably shorter, and more preferably within 5 minutes. The mixing in the reaction step may be performed by mechanical stirring, stirring with a static mixer, or the like. When the polymerization step is continuous, it is preferable that the reaction step is also continuous. The reactor used in the reaction step may be, for example, a tank type or a tubular type equipped with a stirrer. The coupling agent may be diluted with an inert solvent and continuously supplied to the reactor. When the polymerization step is batchwise, the coupling agent may be charged into the polymerization reactor, or may be transferred to a separate reactor and the reaction step may be carried out.

[0123] In the general formula (I), A is preferably represented by any one of the following general formulae (II) to (V): When A is represented by any one of the general formulae (II) to (V), a modified styrene-butadiene rubber having better performance can be obtained.

[0124] [ka] In the general formula (II), B 1 represents a single bond or a hydrocarbon group having 1 to 20 carbon atoms, and a represents an integer of 1 to 10. When a plurality of B 1 are each independent of each other.

[0125] [ka] In the general formula (III), B 2 represents a single bond or a hydrocarbon group having 1 to 20 carbon atoms, B3 represents an alkyl group having 1 to 20 carbon atoms, and a represents an integer of 1 to 10. When a plurality of B 2 and B 3 are each independent of each other.

[0126] [ka] In the general formula (IV), B 4 represents a single bond or a hydrocarbon group having 1 to 20 carbon atoms, and a represents an integer of 1 to 10. When a plurality of B 4 are each independent of each other.

[0127] [ka] In the general formula (V), B 5 represents a single bond or a hydrocarbon group having 1 to 20 carbon atoms, and a represents an integer of 1 to 10. When a plurality of B 5 are each independent of each other.

[0128] B in the general formulas (II) to (V) 1 , B 2 , B 4 , B 5 Regarding the above, examples of the hydrocarbon group having 1 to 20 carbon atoms include an alkylene group having 1 to 20 carbon atoms.

[0129] Preferably, in the general formula (I), A is represented by the general formula (II) or (III), and k is 0. More preferably, in the general formula (I), A is represented by the general formula (II) or (III), k represents 0, and in the general formula (II) or (III), a represents an integer of 2 to 10. More preferably, in the general formula (I), A is represented by the general formula (II), k represents 0, and in the general formula (II), a represents an integer of 2 to 10. Examples of such coupling agents include bis(3-trimethoxysilylpropyl)-[3-(2,2-dimethoxy-1-aza-2-silacyclopentane)propyl]amine, tris(3-trimethoxysilylpropyl)amine, tris(3-triethoxysilylpropyl)amine, tris(3-trimethoxysilylpropyl)-[3-(2,2-dimethoxy-1-aza-2-silacyclopentane)propyl]-1,3-propanediamine, tetrakis[3-(2,2-dimethoxy-1-aza-2-silacyclopentane)propyl]-1,3-propanediamine, and tetrakis(3-trimethoxysilylpropyl). bis[3-(2,2-dimethoxy-1-aza-2-silacyclopentane)propyl]-(3-trismethoxysilylpropyl)-methyl-1,3-propanediamine, tetrakis(3-trimethoxysilylpropyl)-1,3-propanediamine, tetrakis(3-trimethoxysilylpropyl)-1,3-bisaminomethylcyclohexane, tris(3-trimethoxysilylpropyl)-methyl-1,3-propanediamine, bis[3-(2,2-dimethoxy-1-aza-2-silacyclopentane)propyl]-(3-trismethoxysilylpropyl)-methyl-1,3-propanediamine, and the like are particularly preferred among these.

[0130] The amount of the compound represented by general formula (I) added as the coupling agent can be adjusted so that the moles of styrene-butadiene copolymer to the moles of coupling agent react in a desired stoichiometric ratio, which tends to achieve a desired degree of branching. Specifically, the moles of the polymerization initiator are preferably 5.0 times or more, more preferably 6.0 times or more, relative to the moles of the coupling agent. In this case, in general formula (I), the number of functional groups of the coupling agent ((m-1) x i + p x j + k) is preferably an integer of 5 to 10, more preferably an integer of 6 to 10.

[0131] In order to obtain a modified styrene-butadiene rubber having the specific polymer component, the molecular weight distribution (Mw / Mn) of the styrene-butadiene copolymer is preferably 1.5 or more and 2.5 or less, more preferably 1.8 or more and 2.2 or less. In addition, it is preferable that the obtained modified styrene-butadiene rubber is one in which a single peak is detected in the molecular weight curve by GPC. When the peak molecular weight of the modified styrene-butadiene rubber measured by GPC is Mp1 and the peak molecular weight of the styrene-butadiene copolymer is Mp2, the following formula preferably holds true. (Mp1 / Mp2)<1.8×10-12×(Mp2-120×10 4 ) 2 +2 Mp2 is 20 x 10 4 Over 80 x 10 4 Below, Mp1 is 30 x 10 4 Over 150 x 10 4 The following is more preferred: Mp1 and Mp2 are determined by the method described in the Examples below.

[0132] The modification rate of the modified styrene-butadiene rubber is preferably 30% by mass or more, more preferably 50% by mass or more, and even more preferably 70% by mass or more. When the modification rate is 30% by mass or more, the low loss property and abrasion resistance of the rubber composition can be further improved.

[0133] After the reaction step, a deactivator, neutralizer, etc. may be added to the copolymer solution as needed. Examples of deactivators include, but are not limited to, water; alcohols such as methanol, ethanol, and isopropanol; and examples of neutralizers include, but are not limited to, carboxylic acids such as stearic acid, oleic acid, and versatic acid (a highly branched carboxylic acid mixture having 9 to 11 carbon atoms, with the majority being 10 carbon atoms); aqueous solutions of inorganic acids; and carbon dioxide gas. Furthermore, from the viewpoint of preventing gel formation after polymerization and improving stability during processing, it is preferable to add an antioxidant such as 2,6-di-tert-butyl-4-hydroxytoluene (BHT), n-octadecyl-3-(4'-hydroxy-3',5'-di-tert-butylphenol)propionate, or 2-methyl-4,6-bis[(octylthio)methyl]phenol to the modified styrene-butadiene rubber.

[0134] The modified styrene-butadiene rubber can be obtained from the polymer solution by any known method, including, for example, a method in which the solvent is separated by steam stripping or the like, the polymer is filtered, and then the polymer is dehydrated and dried to obtain the polymer, a method in which the polymer is concentrated in a flashing tank and then devolatilized using a vent extruder or the like, and a method in which the polymer is directly devolatilized using a drum dryer or the like.

[0135] The modified styrene-butadiene rubber obtained by reacting the coupling agent represented by the above general formula (I) with a styrene-butadiene copolymer is represented, for example, by the following general formula (VI). [ka]

[0136] In the general formula (VI), D represents a styrene-butadiene copolymer chain, and the weight average molecular weight of the styrene-butadiene copolymer chain is 10 × 10 4 ~100×10 4 The styrene-butadiene copolymer chain is a structural unit of a modified styrene-butadiene rubber, and is, for example, a structural unit derived from a styrene-butadiene copolymer, which is generated by reacting a styrene-butadiene copolymer with a coupling agent. R 12 , R 13 and R 14 each independently represents a single bond or an alkylene group having 1 to 20 carbon atoms. R 15 and R 18each independently represents an alkyl group having 1 to 20 carbon atoms. R 16 , R 19 , and R 20 each independently represents a hydrogen atom or an alkyl group having 1 to 20 carbon atoms. R 17 and R 21 each independently represents an alkylene group having 1 to 20 carbon atoms. R 22 represents a hydrogen atom or an alkyl group having 1 to 20 carbon atoms. m and x represent integers of 1 to 3, with x≦m; p represents 1 or 2; y represents an integer of 1 to 3, with y≦(p+1); and z represents an integer of 1 or 2. D and R when there are multiple of each 12 ~R 22 , m, p, x, y, and z are each independent and may be the same or different. Furthermore, i represents an integer from 0 to 6, j represents an integer from 0 to 6, k represents an integer from 0 to 6, (i+j+k) is an integer from 3 to 10, and ((x×i)+(y×j)+(z×k)) is an integer from 5 to 30. A represents a hydrocarbon group having 1 to 20 carbon atoms, or an organic group having at least one atom selected from the group consisting of oxygen, nitrogen, silicon, sulfur, and phosphorus atoms, and having no active hydrogen. The hydrocarbon group represented by A includes saturated, unsaturated, aliphatic, and aromatic hydrocarbon groups. Examples of the organic group having no active hydrogen include organic groups having no functional groups having active hydrogen, such as a hydroxyl group (-OH), a secondary amino group (>NH), a primary amino group (-NH), or a sulfhydryl group (-SH).

[0137] In the general formula (VI), A is preferably represented by any one of the general formulae (II) to (V). When A is represented by any one of the general formulae (II) to (V), the low loss property and abrasion resistance of the rubber composition can be further improved.

[0138] ---Third Preferred Embodiment of Modified Styrene-Butadiene Rubber--- It is also preferable that at least one end of the modified styrene-butadiene rubber (modified SBR) is modified with a modifier containing a compound (alkoxysilane) represented by the following general formula (1). [ka]

[0139] The use of a styrene-butadiene rubber modified with a modifier containing a compound represented by the general formula (1) containing an oligosiloxane and a tertiary amino group, which are filler affinity functional groups, as the rubber component (A) can enhance the dispersibility of fillers such as silica. As a result, the rubber composition of the present invention has improved filler dispersibility, which significantly improves low loss properties, reduces the rolling resistance of tires using the rubber composition, and improves fuel economy.

[0140] In the above general formula (1), R 1 ~R 8 are each independently an alkyl group having 1 to 20 carbon atoms; L 1 and L 2 are each independently an alkylene group having 1 to 20 carbon atoms; and n is an integer of 2 to 4.

[0141] Specifically, in formula (1), R 1 ~R 4 may each independently represent a substituted or unsubstituted alkyl group having 1 to 20 carbon atoms, and 1 ~R 4 When substituted, each independently may be substituted with one or more substituents selected from the group consisting of an alkyl group having 1 to 10 carbon atoms, a cycloalkyl group having 3 to 10 carbon atoms, an alkoxy group having 1 to 10 carbon atoms, a cycloalkoxy group having 4 to 10 carbon atoms, an aryl group having 6 to 12 carbon atoms, an aryloxy group having 6 to 12 carbon atoms, an alkanoyloxy group having 2 to 12 carbon atoms (Ra-COO-, where Ra is an alkyl group having 1 to 9 carbon atoms), an aralkyloxy group having 7 to 13 carbon atoms, an arylalkyl group having 7 to 13 carbon atoms, and an alkylaryl group having 7 to 13 carbon atoms. More specifically, the R 1 ~R 4 may be a substituted or unsubstituted alkyl group having 1 to 10 carbon atoms, and more specifically, 1 ~R 4 may each independently be a substituted or unsubstituted alkyl group having 1 to 6 carbon atoms.

[0142] In addition, in formula (1), R 5 ~R 8 are each independently a substituted or unsubstituted alkyl group having 1 to 20 carbon atoms, specifically a substituted or unsubstituted alkyl group having 1 to 10 carbon atoms, more specifically a substituted or unsubstituted alkyl group having 1 to 6 carbon atoms, and when substituted, they are first 1 ~R 4 It may be substituted with substituents as described above. In addition, the above R 5 ~R 8 If is not an alkyl group but a hydrolyzable substituent, NR 5 R 6 and NR 7 R 8 The bond can be hydrolyzed to NH in the presence of moisture, adversely affecting the processability of the polymer.

[0143] More specifically, in the compound represented by the formula (1), R 1 ~R 4 is a methyl group or an ethyl group, and R 5 ~R 8 can be an alkyl group having 1 to 10 carbon atoms.

[0144] The amino group in the compound represented by the formula (1), i.e., NR 5 R 6 and NR 7 R 8 is preferably a tertiary amino group. The tertiary amino group provides the compound represented by formula (1) with better processability when used as a modifying agent. In addition, the above R 5 ~R 8If a protecting group for protecting the amino group is bonded to the terminal end of the polymer or if hydrogen is bonded to the terminal end of the polymer, it may be difficult to realize the effect of the compound represented by formula (1). If hydrogen is bonded, the anion reacts with hydrogen during the modification process, losing its reactivity and making the modification reaction impossible. If a protecting group is bonded, the modification reaction will occur, but the terminal end of the polymer will be deprotected by hydrolysis during post-processing to become a primary or secondary amino group. The deprotected primary or secondary amino group may cause the compound to become viscous during subsequent blending, potentially resulting in reduced processability.

[0145] In addition, L in the compound represented by the formula (1) 1 and L 2 are each independently a substituted or unsubstituted alkylene group having 1 to 20 carbon atoms. More specifically, L 1 and L 2 may each independently be an alkylene group having 1 to 10 carbon atoms, more specifically, an alkylene group having 1 to 6 carbon atoms such as a methylene group, an ethylene group, or a propylene group.

[0146] L in the compound represented by formula (1) 1 and L 2 Regarding the above, the shorter the distance between the Si atom and the N atom in the molecule, the better the effect. However, if Si is directly bonded to N, there is a risk that the bond between Si and N will break during subsequent processing steps, and the secondary amino group generated in this case is likely to be washed away by water during post-processing. In the modified styrene-butadiene rubber produced, it is difficult for the amino group, which promotes bonding with fillers such as silica, to bond with the filler, and as a result, the effect of improving the dispersibility of the filler may be reduced. In this way, considering the improvement effect depending on the bond length between Si and N, the above L 1 and L 2 More preferably, each of L is independently an alkylene group having 1 to 3 carbon atoms, such as a methylene group, an ethylene group, or a propylene group, and more specifically, can be a propylene group. 1 and L 2 R first 1 ~R4 It may be substituted with substituents as described above.

[0147] The compound represented by the formula (1) is preferably, for example, any one of the compounds represented by the following structural formulas (1-1) to (1-5), because this allows for more excellent low loss properties to be achieved. [ka]

[0148] The compound represented by formula (1) has an alkoxysilane structure that bonds to the active terminal of the styrene-butadiene copolymer, while the Si-O-Si structure and three or more amino groups bonded to the terminals exhibit affinity for fillers such as silica. This promotes bonding between the filler and the modified styrene-butadiene rubber compared to conventional modifiers containing a single amino group per molecule. Furthermore, the degree of bonding at the active terminals of the styrene-butadiene copolymer is uniform, and when observing the change in molecular weight distribution before and after coupling, the molecular weight distribution remains constant without increasing compared to before coupling. This prevents a deterioration in the physical properties of the modified styrene-butadiene rubber itself, prevents filler aggregation within the rubber composition, and enhances filler dispersibility, thereby improving the processability of the rubber composition. These effects, particularly when the rubber composition is applied to tires, enable a balanced improvement in fuel economy and wet grip performance.

[0149] The compound represented by the formula (1) can be produced through a condensation reaction represented by the following reaction scheme. [ka]

[0150] In the above reaction scheme, R 1 ~R 8 , L 1 and L 2and n are the same as those defined in the above formula (1), and R′ and R″ are any substituents that do not affect the condensation reaction. For example, R′ and R″ are each independently R 1 ~R 4 It can be identical to any one of the following:

[0151] The reaction in the above reaction scheme proceeds in the presence of an acid, and any acid generally used in condensation reactions can be used without limitation. Those skilled in the art can select an optimal acid depending on various process variables such as the type of reactor in which the reaction is carried out, starting materials, and reaction temperature.

[0152] The styrene-butadiene rubber modified with a modifier containing the compound represented by formula (1) can have a narrow molecular weight distribution (Mw / Mn, also referred to as "polydispersity index (PDI)") of 1.1 to 3.0. If the molecular weight distribution of the modified styrene-butadiene rubber exceeds 3.0 or is less than 1.1, the tensile properties and viscoelasticity may be reduced when the modified styrene-butadiene rubber is applied to a rubber composition. Considering the remarkable effect of improving the tensile properties and viscoelasticity by controlling the molecular weight distribution of the modified styrene-butadiene rubber, the molecular weight distribution of the modified styrene-butadiene rubber is preferably in the range of 1.3 to 2.0. By using the modifier, the modified styrene-butadiene rubber has a molecular weight distribution similar to that of the styrene-butadiene copolymer before modification.

[0153] The molecular weight distribution of the modified styrene-butadiene rubber can be calculated from the ratio (Mw / Mn) of the weight average molecular weight (Mw) to the number average molecular weight (Mn). The number average molecular weight (Mn) is the common average of the molecular weights of individual polymers calculated by measuring the molecular weights of n polymer molecules, summing the molecular weights, and dividing by n. The weight average molecular weight (Mw) represents the molecular weight distribution of the polymer composition. The average of the total molecular weight can be expressed in grams per mole (g / mol). The weight average molecular weight and number average molecular weight are polystyrene-equivalent molecular weights analyzed by gel permeation chromatography (GPC).

[0154] The modified styrene-butadiene rubber satisfies the above-mentioned molecular weight distribution conditions and may have a number average molecular weight (Mn) of 50,000 g / mol to 2,000,000 g / mol, more specifically, 200,000 g / mol to 800,000 g / mol, and a weight average molecular weight (Mw) of 100,000 g / mol to 4,000,000 g / mol, more specifically, 300,000 g / mol to 1,500,000 g / mol. If the weight-average molecular weight (Mw) of the modified styrene-butadiene rubber is less than 100,000 g / mol or the number-average molecular weight (Mn) is less than 50,000 g / mol, the tensile properties may be reduced when the modified styrene-butadiene rubber is applied to a rubber composition. If the weight-average molecular weight (Mw) is greater than 4,000,000 g / mol or the number-average molecular weight (Mn) is greater than 2,000,000 g / mol, the processability of the modified styrene-butadiene rubber may be reduced, resulting in a deterioration in the workability of the rubber composition, making kneading difficult, and making it difficult to sufficiently improve the physical properties of the rubber composition. More specifically, when the modified styrene-butadiene rubber satisfies the conditions for weight average molecular weight (Mw) and number average molecular weight (Mn) as well as the molecular weight distribution, when the modified styrene-butadiene rubber is applied to a rubber composition, it can improve the viscoelasticity and processability of the rubber composition in a well-balanced manner.

[0155] The modified styrene-butadiene rubber preferably has a vinyl bond content in the butadiene moiety of 5% or more, more preferably 10% or more, and preferably 60% or less. By adjusting the vinyl bond content in the butadiene moiety to fall within the above range, the glass transition temperature can be adjusted to an appropriate range.

[0156] The modified styrene-butadiene rubber may have a Mooney viscosity (MV) at 100° C. of 40 to 140, specifically 60 to 100. When the modified styrene-butadiene rubber has a Mooney viscosity in the above range, it can exhibit better processability. The Mooney viscosity can be measured using a Mooney viscometer, such as Monsanto's MV2000E, at 100°C, a rotor speed of 2±0.02 rpm, and a large rotor. The sample used here is left at room temperature (23±3°C) for 30 minutes or more, and then 27±3 g of the sample is taken and filled into the die cavity, and the platen is operated to measure the viscosity.

[0157] As described above, the modified styrene-butadiene rubber is preferably modified at one end with a modifier containing a compound represented by the above general formula (1), and is preferably further modified at the other end with a modifier containing a compound represented by the following general formula (2). By modifying both ends of the modified styrene-butadiene rubber, the dispersibility of the filler in the rubber composition is further improved, and a tire using the rubber composition can achieve both low fuel consumption performance and wet grip performance at a higher level. [ka]

[0158] In the above general formula (2), R 9 ~R 11 are each independently hydrogen; an alkyl group having 1 to 30 carbon atoms; an alkenyl group having 2 to 30 carbon atoms; an alkynyl group having 2 to 30 carbon atoms; a heteroalkyl group having 1 to 30 carbon atoms, a heteroalkenyl group having 2 to 30 carbon atoms; a heteroalkynyl group having 2 to 30 carbon atoms; a cycloalkyl group having 5 to 30 carbon atoms; an aryl group having 6 to 30 carbon atoms; or a heterocyclic group having 3 to 30 carbon atoms. Also, in formula (2), R 12 represents a single bond; an alkylene group having 1 to 20 carbon atoms which is substituted or unsubstituted; a cycloalkylene group having 5 to 20 carbon atoms which is substituted or unsubstituted; or an arylene group having 5 to 20 carbon atoms which is substituted or unsubstituted, wherein the substituent is an alkyl group having 1 to 10 carbon atoms, a cycloalkyl group having 5 to 10 carbon atoms, or an aryl group having 6 to 20 carbon atoms. Also, in formula (2), R 13is an alkyl group having 1 to 30 carbon atoms; an alkenyl group having 2 to 30 carbon atoms; an alkynyl group having 2 to 30 carbon atoms; a heteroalkyl group having 1 to 30 carbon atoms; a heteroalkenyl group having 2 to 30 carbon atoms; a heteroalkynyl group having 2 to 30 carbon atoms; a cycloalkyl group having 5 to 30 carbon atoms; an aryl group having 6 to 30 carbon atoms; a heterocyclic group having 3 to 30 carbon atoms; or a functional group represented by the following general formula (2a) or general formula (2b), wherein m is an integer of 1 to 5, and R 13 At least one of the functional groups is represented by the following general formula (2a) or (2b), and when m is an integer of 2 to 5, a plurality of R 13 may be the same as or different from each other.

[0159] [ka]

[0160] In the above general formula (2a), R 14 represents a substituted or unsubstituted alkylene group having 1 to 20 carbon atoms; a substituted or unsubstituted cycloalkylene group having 5 to 20 carbon atoms; or a substituted or unsubstituted arylene group having 6 to 20 carbon atoms, wherein the substituent is an alkyl group having 1 to 10 carbon atoms, a cycloalkyl group having 5 to 10 carbon atoms, or an aryl group having 6 to 20 carbon atoms. Also, in formula (2a), R 15 and R 16 are each independently an alkylene group having 1 to 20 carbon atoms which is substituted or unsubstituted with an alkyl group having 1 to 10 carbon atoms, a cycloalkyl group having 5 to 10 carbon atoms, or an aryl group having 6 to 20 carbon atoms. Also, in formula (2a), R 17 is hydrogen; an alkyl group having 1 to 30 carbon atoms; an alkenyl group having 2 to 30 carbon atoms; an alkynyl group having 2 to 30 carbon atoms; a heteroalkyl group having 1 to 30 carbon atoms; a heteroalkenyl group having 2 to 30 carbon atoms; a heteroalkynyl group having 2 to 30 carbon atoms; a cycloalkyl group having 5 to 30 carbon atoms; an aryl group having 6 to 30 carbon atoms; or a heterocyclic group having 3 to 30 carbon atoms; and X is an N, O, or S atom, provided that when X is O or S, R 17 does not exist.

[0161] [ka]

[0162] In the above general formula (2b), R 18 represents a substituted or unsubstituted alkylene group having 1 to 20 carbon atoms; a substituted or unsubstituted cycloalkylene group having 5 to 20 carbon atoms; or a substituted or unsubstituted arylene group having 6 to 20 carbon atoms, wherein the substituent is an alkyl group having 1 to 10 carbon atoms, a cycloalkyl group having 5 to 10 carbon atoms, or an aryl group having 6 to 20 carbon atoms. Also, in formula (2b), R 19 and R 20 are each independently an alkyl group having 1 to 30 carbon atoms; an alkenyl group having 2 to 30 carbon atoms; an alkynyl group having 2 to 30 carbon atoms; a heteroalkyl group having 1 to 30 carbon atoms; a heteroalkenyl group having 2 to 30 carbon atoms; a heteroalkynyl group having 2 to 30 carbon atoms; a cycloalkyl group having 5 to 30 carbon atoms; an aryl group having 6 to 30 carbon atoms; or a heterocyclic group having 3 to 30 carbon atoms.

[0163] In addition, in the compound represented by the general formula (2), R 9 ~R 11 are each independently hydrogen; an alkyl group having 1 to 10 carbon atoms; an alkenyl group having 2 to 10 carbon atoms; or an alkynyl group having 2 to 10 carbon atoms; and R 12 is a single bond; or an unsubstituted alkylene group having 1 to 10 carbon atoms, and R 13 is an alkyl group having 1 to 10 carbon atoms; an alkenyl group having 2 to 10 carbon atoms; an alkynyl group having 2 to 10 carbon atoms; or a functional group represented by the above general formula (2a) or (2b), and in the above general formula (2a), R 14 is an unsubstituted alkylene group having 1 to 10 carbon atoms, and R 15 and R 16 are each independently an unsubstituted alkylene group having 1 to 10 carbon atoms, and R 17is an alkyl group having 1 to 10 carbon atoms; a cycloalkyl group having 5 to 20 carbon atoms; an aryl group having 6 to 20 carbon atoms; or a heterocyclic group having 3 to 20 carbon atoms, and in the above general formula (2b), R 18 is an unsubstituted alkylene group having 1 to 10 carbon atoms, and R 19 and R 20 may each independently be an alkyl group having 1 to 10 carbon atoms; a cycloalkyl group having 5 to 20 carbon atoms; an aryl group having 6 to 20 carbon atoms; or a heterocyclic group having 3 to 20 carbon atoms.

[0164] More specifically, the compound represented by the above general formula (2) can be a compound represented by the following structural formulas (2-1) to (2-3). [ka]

[0165] When the styrene-butadiene copolymer is modified with a modifying agent containing the compound represented by the general formula (2), the modifying agent containing the compound represented by the formula (2) is used as a modification initiator. Specifically, for example, by polymerizing a butadiene monomer and a styrene monomer in a hydrocarbon solvent in the presence of a modifying agent containing a compound represented by formula (2), a modifying group derived from the compound represented by formula (2) can be imparted to the styrene-butadiene copolymer.

[0166] --Modified butadiene rubber (modified BR)-- The modified conjugated diene polymer (A1) preferably contains a modified butadiene rubber (modified BR). Butadiene rubber has a low glass transition temperature (Tg), and when the rubber component (A) contains the modified butadiene rubber as the modified conjugated diene polymer (A1), the fuel economy and wear resistance of a tire using the rubber composition can be improved.

[0167] The modified butadiene rubber may be formed, for example, by polymerizing 1,3-butadiene to obtain polybutadiene having active ends and then reacting the active ends of the polybutadiene with a modifier, or by polymerizing 1,3-butadiene using a polymerization initiator having a functional group to form polybutadiene having a functional group at the polymerization initiation end. For example, the heteroatom-containing compound may act as a modifier and react with the active terminal of polybutadiene to form a modified butadiene rubber, or a nitrogen-containing compound as a heteroatom-containing compound may react with an alkali metal to form a polymerization initiator for anionic polymerization, thereby forming a modified butadiene rubber having a nitrogen-containing compound residue at the polymerization initiation terminal of polybutadiene.

[0168] Examples of the modifier that reacts with the active terminal of the polybutadiene include modifiers having a tin atom (tin-containing compound), modifiers having a nitrogen atom and a silicon atom (nitrogen- and silicon-containing compound), modifiers having an oxygen atom and a silicon atom (oxygen- and silicon-containing compound), modifiers having a sulfur atom and a silicon atom (sulfur- and silicon-containing compound), and modifiers having a nitrogen atom but no silicon atom (silicon-free nitrogen-containing compound), which are exemplified in the section "Modified conjugated diene polymer (A1)".

[0169] The polymerization method for the polybutadiene may be anionic polymerization or coordination polymerization. When the polybutadiene is obtained by anionic polymerization, an alkali metal compound is used as the polymerization initiator, but a lithium compound is preferred. As the lithium compound polymerization initiator, the hydrocarbyl lithium and lithium amide compounds described in the section "Modified Conjugated Diene Polymer (A1)" are preferably used. Here, when a hydrocarbyl lithium is used, a polybutadiene having a hydrocarbyl group at the polymerization initiation terminal and a polymerization active site at the other terminal is obtained. On the other hand, when a lithium amide compound is used, a polybutadiene having a nitrogen-containing functional group at the polymerization initiation terminal and a polymerization active site at the other terminal is obtained.

[0170] It is more preferable to use lithium hexamethyleneimide as the polymerization initiator, because this makes it possible to obtain a modified butadiene rubber having a hexamethyleneimino group, which is a nitrogen-containing compound residue, as a functional group having atoms other than carbon and hydrogen at the polymerization initiation terminal of polybutadiene. A modified butadiene rubber having a nitrogen-containing compound residue at the polymerization initiation terminal of polybutadiene and having one or more compound residues selected from a tin-containing compound residue, a nitrogen- and silicon-containing compound residue, an oxygen- and silicon-containing compound residue, a sulfur- and silicon-containing compound residue, and a silicon-free nitrogen-containing compound residue at the active terminal of polybutadiene is more preferred from the viewpoints of further reducing the rolling resistance of a tire, achieving excellent fuel economy performance, and further improving abrasion resistance and crack resistance.

[0171] On the other hand, when the polybutadiene is produced by coordination polymerization using a rare earth metal compound as a polymerization initiator, it is preferable to use a combination of the components (a), (b), and (c) described in the section "Modified conjugated diene polymer (A1)."

[0172] The modified butadiene rubber is preferably one obtained by anion polymerization using an organic alkali metal compound, particularly alkyl lithium.

[0173] In both anionic polymerization and coordination polymerization, the polybutadiene can be modified by a modification reaction between the polymerization active terminals and the above-mentioned modifier after the polymerization reaction to obtain a modified butadiene rubber. The modification reaction is preferably carried out at a temperature of 20°C or higher, but the polymerization temperature of polybutadiene can be used as is, with a more preferred range being 30°C to 120°C. Lower reaction temperatures tend to result in excessive increases in the viscosity of polybutadiene and poor dispersibility of the reaction product. On the other hand, higher reaction temperatures tend to result in the easy deactivation of polymerization active sites. The amount of modifier used is preferably 0.25 to 3.0 mol, more preferably 0.5 to 1.5 mol, per mol of polymerization initiator used in the production of polybutadiene.

[0174] -Other rubber components- The rubber component (A) may contain, in addition to the modified conjugated diene polymer (A1), other rubbers such as unmodified conjugated diene polymers. The other rubbers are preferably diene rubbers, and the diene rubbers are preferably isoprene rubbers and butadiene rubbers. Here, the term "isoprene rubber" refers to a rubber containing isoprene-derived units as monomer units, and the term "butadiene rubber" refers to a rubber containing butadiene-derived units as monomer units.

[0175] Examples of the isoprene-based rubber include natural rubber (NR) and synthetic isoprene rubber (IR). Examples of natural rubber (NR) that can be used include those commonly used in the tire industry, such as RSS#3 and TSR20 (e.g., SIR20 and STR20). The origin of the natural rubber (NR) is not particularly limited, and examples include those derived from Hevea brasiliensis, guayule, and Russian dandelion. Examples of synthetic isoprene rubber (IR) are not particularly limited, and examples include those commonly used in the tire industry, such as IR2200. These isoprene-based rubbers may be used alone or in combination of two or more. Of these, NR is preferred as the isoprene-based rubber.

[0176] The isoprene-based rubber preferably has a sustainability rate of 30% by mass or more, more preferably 40% by mass or more, even more preferably 50% by mass or more, still more preferably 60% by mass or more, still more preferably 70% by mass or more, even more preferably 80% by mass or more, still more preferably 90% by mass or more, and particularly preferably 100% by mass. To achieve a sustainability ratio of the isoprene-based rubber within the above range, it is preferable to use natural rubber (NR) or a polymer synthesized using isoprene derived from biological resources or isoprene derived from recycled resources as a monomer component. In this case, the synthesized polymer may be a homopolymer of a monomer derived from biological resources, a homopolymer of a monomer derived from recycled resources, a copolymer of a monomer derived from biological resources and a monomer derived from recycled resources, or a copolymer of a monomer derived from biological resources and / or a monomer derived from recycled resources and a monomer derived from fossil resources (petroleum, etc.).

[0177] Examples of the butadiene rubber include butadiene rubber (BR), aromatic vinyl compound-butadiene copolymer rubber (for example, styrene-butadiene rubber (SBR)), etc. Here, butadiene, which is a raw material for butadiene rubber, is preferably derived from biological resources or recycled resources.

[0178] Examples of the butadiene rubber (BR) include high-cis butadiene rubber, low-cis butadiene rubber, and butadiene rubber containing syndiotactic polybutadiene crystals. Commercially available butadiene rubbers can be used as the butadiene rubber (BR), and examples of commercially available butadiene rubbers include products from UBE Elastomers Co., Ltd., ENEOS Materials Corporation, Asahi Kasei Corporation, and Zeon Corporation. These butadiene rubbers may be used alone or in combination of two or more.

[0179] Examples of the aromatic vinyl compound-butadiene copolymer rubber (e.g., SBR) include emulsion-polymerized aromatic vinyl compound-butadiene copolymer rubber (e.g., emulsion-polymerized styrene-butadiene rubber (E-SBR)) and solution-polymerized aromatic vinyl compound-butadiene copolymer rubber (e.g., solution-polymerized styrene-butadiene rubber (S-SBR)). In the aromatic vinyl compound-butadiene copolymer rubber, examples of the aromatic vinyl compound (aromatic vinyl monomer) include styrene, vinylnaphthalene, and divinylnaphthalene. These aromatic vinyl compounds may be used alone or in combination of two or more. Among these, styrene is preferred, and styrene derived from biological resources and styrene derived from recycled resources are particularly preferred. That is, SBR is preferred as the aromatic vinyl compound-butadiene copolymer rubber. The styrene may have a substituent. Commercially available products can be used as the aromatic vinyl compound-butadiene copolymer rubber, and examples of such commercially available products include products from Asahi Kasei Corporation, ENEOS Materials Corporation, Nippon Zeon Corporation, Sumitomo Chemical Co., Ltd., etc. These aromatic vinyl compound-butadiene copolymer rubbers may be used singly or in combination of two or more.

[0180] The butadiene-based rubber preferably has a sustainability rate of 30% by mass or more, more preferably 40% by mass or more, even more preferably 50% by mass or more, still more preferably 60% by mass or more, still more preferably 70% by mass or more, even more preferably 80% by mass or more, still more preferably 90% by mass or more, and particularly preferably 100% by mass. To achieve the sustainability rate of the butadiene-based rubber within the above range, for example, a polymer synthesized using biological resource-derived butadiene, recycled resource-derived butadiene, biological resource-derived aromatic vinyl compounds (e.g., biological resource-derived styrene), or recycled resource-derived aromatic vinyl compounds (e.g., recycled resource-derived styrene) as monomer components may be used. In this case, the synthesized polymer may be a homopolymer of a biological resource-derived monomer, a homopolymer of a recycled resource-derived monomer, a copolymer of a biological resource-derived monomer and a recycled resource-derived monomer, or a copolymer of a biological resource-derived monomer and / or a recycled resource-derived monomer and a fossil resource (e.g., petroleum)-derived monomer. Biological resource (biomass resource)-derived butadiene rubber (B-BR) and biological resource-derived aromatic vinyl compound-butadiene copolymer rubber (e.g., biological resource (biomass resource)-derived styrene-butadiene rubber (B-SBR)) include not only rubber obtained by polymerizing butadiene or the like according to conventional methods, but also rubber obtained by reactions involving microorganisms, plants, animals, and tissue cultures thereof (hereinafter also referred to as "microorganisms, etc.") or enzymatic reactions.

[0181] Examples of the other rubbers include the above-mentioned isoprene-based rubber, butadiene rubber (BR), and aromatic vinyl compound-butadiene copolymer rubber (e.g., SBR), as well as diene-based rubbers such as acrylonitrile-butadiene rubber (NBR), chloroprene rubber (CR), butyl rubber (IIR), and styrene-isoprene-butadiene copolymer rubber (SIBR).

[0182] In order to set the sustainability rate of the entire rubber component (A) within the above range, it is preferable to use natural rubber (NR) as the rubber component (A) or a polymer synthesized using monomer components derived from biological resources or monomer components derived from recycled resources as monomer components.

[0183] (Reinforcing filler (B)) The rubber composition for a tire of this embodiment contains a reinforcing filler (B). The reinforcing filler (B) is a compounding agent that, when blended with a rubber composition, has the effect of improving the reinforcing properties of the rubber composition. As the reinforcing filler (B), silica and carbon black are preferred.

[0184] The content of the reinforcing filler (B) can be adjusted appropriately depending on, for example, the tire category to which the tire is applied, the tire components, the target performance, etc. For example, the content of the reinforcing filler (B) is more preferably 30 parts by mass or more, more preferably 50 parts by mass or more, more preferably 70 parts by mass or more, and even more preferably 80 parts by mass or more, and is preferably 300 parts by mass or less, more preferably 200 parts by mass or less, still more preferably 180 parts by mass or less, and particularly preferably 150 parts by mass or less, relative to 100 parts by mass of the rubber component (A).

[0185] -silica- The rubber composition for a tire according to this embodiment preferably contains silica as the reinforcing filler (B). Examples of the silica include wet silica (hydrated silicic acid), dry silica (anhydrous silicic acid), calcium silicate, and aluminum silicate. Among these, wet silica is preferred due to its high silanol group content. These silicas may be used alone or in combination of two or more. Commercially available silicas are available, including those from Tosoh Silica Corporation, Evonik, Solvay, Solvay Japan, and Tokuyama Corporation.

[0186] From the viewpoint of reducing environmental impact, silica derived from siliceous plants is preferred. Examples of siliceous plants include mosses, ferns, horsetails, Cucurbitaceae, Urticaceae, and Gramineae. Among these plants, grasses are preferred. Examples of grasses include rice, bamboo, and sugarcane, with rice being preferred. Rice is widely cultivated for food and therefore can be procured locally over a wide area. Furthermore, rice husks are generated in large quantities as industrial waste, making them easy to secure. Therefore, from the viewpoint of availability, silica derived from rice husks (hereinafter also referred to as "rice husk silica") is particularly preferred. The use of rice husk silica allows for the effective use of rice husks, which are industrial waste. Furthermore, since the raw material can be procured locally near tire manufacturing plants, the energy and costs for transportation and storage can be reduced, which is environmentally preferable from various viewpoints. The rice husk silica may be a powder of rice husk charcoal obtained by carbonizing rice husks by heating, or may be precipitated silica produced by a wet process using an alkali silicate aqueous solution, which is prepared by extracting rice husk ash generated when rice husks are burned as fuel in a biomass boiler with an alkali. The method for producing the rice husk charcoal is not particularly limited, and various known methods can be used. For example, rice husk charcoal can be obtained by pyrolyzing rice husks by steaming them in a kiln. The rice husk charcoal obtained in this manner can be pulverized using a known pulverizer (e.g., a ball mill), sorted, and classified into a predetermined particle size range to obtain rice husk charcoal powder. The rice husk-derived precipitated silica can be produced by a method such as that described in JP 2019-38728 A. From the viewpoint of reducing the environmental load, it is also preferable to use, as the silica, silica obtained by extracting silicic acid components from scraps of silicon wafers, which are raw materials for semiconductors, glass bottles, etc., and recycling the extracted silica for use in the production.

[0187] The silica has a nitrogen adsorption specific surface area (N2SA) of 50 m 2 / g or more, and 100m 2 / g or more is more preferable, and 150m 2 / g or more is more preferable, and 2 / g or less, and 250m 2 / g or less is more preferable, and 2 / g or less is more preferable, and 2 It is even more preferable that the saturation coefficient is 1 / g or less. In this specification, the nitrogen adsorption specific surface area (N2SA) of silica is a value measured by the BET method in accordance with ASTM D3037-93.

[0188] The content of the silica can be adjusted appropriately depending on, for example, the tire category to which the rubber composition is applied, the tire components, the target performance, etc. For example, the content of silica is preferably 5 parts by mass or more, more preferably 10 parts by mass or more, more preferably 30 parts by mass or more, and even more preferably 50 parts by mass or more, and is preferably 300 parts by mass or less, more preferably 200 parts by mass or less, still more preferably 180 parts by mass or less, and particularly preferably 150 parts by mass or less, relative to 100 parts by mass of the rubber component (A).

[0189] -Carbon black- The rubber composition for tires of this embodiment preferably contains carbon black as the reinforcing filler (B). Plant-derived carbon black and recycled carbon black are particularly preferred. Examples of plant-derived carbon black include those derived from castor oil and pine oil. Examples of recycled carbon black include carbon black obtained by pyrolysis of used tires and carbon black obtained from waste oil. The grade of the carbon black is not particularly limited, and examples include N134, N110, N220, N234, N219, N339, N330, N326, N351, N550, and N762. Commercially available carbon black products can be used, including those from Asahi Carbon Co., Ltd., Cabot Japan Co., Ltd., Tokai Carbon Co., Ltd., Mitsubishi Chemical Corporation, Lion Corporation, Nippon Steel Carbon Co., Ltd., and Birla Carbon. These carbon blacks may be used alone or in combination of two or more.

[0190] The nitrogen adsorption specific surface area (N2SA) of the carbon black is not particularly limited and can be appropriately adjusted depending on, for example, the tire category to which it is applied, the tire components, the target performance, etc. For example, the nitrogen adsorption specific surface area (N2SA) of carbon black is 20 m 2 / g or more is preferable, and 50m 2 / g or more is more preferable, and 70m 2 / g or more is more preferable, and 90m 2 / g or more is more preferable, and 200m 2 / g or less is preferable, and 150m 2 / g or less is more preferable, and 130m 2 / g or less is more preferable. In this specification, the nitrogen adsorption specific surface area (N2SA) of carbon black is determined according to JIS K 6217-2:2017 (ISO 4652:2012).

[0191] The content of the carbon black is not particularly limited and can be adjusted appropriately depending on, for example, the tire category to which the rubber composition is applied, the tire components, the target performance, etc. For example, the content of the carbon black is preferably 1 part by mass or more, more preferably 3 parts by mass or more, and even more preferably 5 parts by mass or more, per 100 parts by mass of the rubber component (A).

[0192] The proportion of silica in the total content of silica and carbon black is not particularly limited and can be adjusted appropriately depending on, for example, the tire category to which it is applied, the tire components, the target performance, etc. For example, in the case of a tread rubber for a passenger car tire, the proportion of silica in the total content of silica and carbon black is preferably 50% by mass or more, more preferably 70% by mass or more, even more preferably 80% by mass or more, even more preferably 90% by mass or more, and particularly preferably 95% by mass or more. Furthermore, the proportion of silica in the total content of silica and carbon black may be 100% by mass, but is preferably 98% by mass or less.

[0193] -Other reinforcing fillers- In the rubber composition for a tire of this embodiment, other than the above-mentioned silica and carbon black, for example, other inorganic compounds represented by the following formula (I) can also be used as the reinforcing filler (B). nM xSiO y zH2O (I) (In the formula, M represents at least one metal selected from the group consisting of Al, Mg, Ti, Ca, and Zr, oxides or hydroxides of these metals, hydrates thereof, and carbonates of these metals; and n, x, y, and z represent an integer of 1 to 5, an integer of 0 to 10, an integer of 2 to 5, and an integer of 0 to 10, respectively.) When the reinforcing filler (B) contains other inorganic compounds, the content thereof is preferably about 5 to 30 parts by mass per 100 parts by mass of the rubber component (A).

[0194] Examples of inorganic compounds of the above formula (I) include alumina (Al2O3) such as γ-alumina and α-alumina; alumina monohydrate (Al2O3·H2O) such as boehmite and diaspore; aluminum hydroxide [Al(OH)3] such as gibbsite and bayerite; aluminum carbonate [Al2(CO3)3], magnesium hydroxide [Mg(OH)2], magnesium oxide (MgO), magnesium carbonate (MgCO3), talc (3MgO·4SiO2·H2O), attapulgite (5MgO·8SiO2·9H2O), titanium dioxide (TiO2), titanium black (TiO 2n-1 ), calcium oxide (CaO), calcium hydroxide [Ca(OH)2], magnesium aluminum oxide (MgO·Al2O3), clay (Al2O3·2SiO2), kaolin (Al2O3·2SiO2·2H2O), pyrophyllite (Al2O3·4SiO2·H2O), bentonite (Al2O3·4SiO2·2H2O), aluminum silicate (Al2SiO5, Al4·3SiO4·5H2O, etc.), magnesium silicate (Mg2SiO4, MgSiO3, etc.), ke Examples include calcium silicate (Ca2SiO4, etc.), calcium aluminum silicate (Al2O3·CaO·2SiO2, etc.), calcium magnesium silicate (CaMgSiO4), calcium carbonate (CaCO3), zirconium oxide (ZrO2), zirconium hydroxide [ZrO(OH)2·nH2O], zirconium carbonate [Zr(CO3)2], and crystalline aluminosilicates containing hydrogen, alkali metals, or alkaline earth metals to compensate for the charge, such as various zeolites.

[0195] (Resin (C)) The rubber composition for a tire of this embodiment preferably further contains a resin (C). By blending the resin (C) into the rubber composition, the elastic modulus of the rubber composition is improved, and a tire using the rubber composition can achieve both steering stability on dry road surfaces and wet grip performance.

[0196] The content of the resin (C) is preferably 1 to 50 parts by mass, and more preferably 5 to 30 parts by mass, per 100 parts by mass of the rubber component (A). When the content of the resin (C) is 1 part by mass or more per 100 parts by mass of the rubber component (A), the wet grip performance of a tire using the rubber composition is further improved, and when the content is 50 parts by mass or less, a decrease in the elastic modulus of the rubber composition is more easily suppressed. Therefore, when the content of the resin (C) is 1 to 50 parts by mass per 100 parts by mass of the rubber component (A), the wet grip performance of a tire using the rubber composition can be further improved.

[0197] Examples of the resin (C) include C5 resins, C5-C9 resins, C9 resins, dicyclopentadiene resins, terpene phenol resins, terpene resins, rosin resins, and alkylphenol resins, and at least one selected from C5 resins, C5-C9 resins, C9 resins, dicyclopentadiene resins, rosin resins, and alkylphenol resins is preferred. When the resin (C) contains at least one of C5 resins, C5-C9 resins, C9 resins, dicyclopentadiene resins, terpene phenol resins, terpene resins, rosin resins, and alkylphenol resins, the wet grip performance of tires using the rubber composition can be further improved. The resin (C) may be used alone or in combination of two or more.

[0198] Among the resins (C), C5 resins, C5-C9 resins, and C9 resins are particularly preferred from the viewpoint of wet grip performance of tires. C5-C9 resins and C9 resins have an even greater effect of increasing the elastic modulus of the rubber composition in a low strain range and decreasing the elastic modulus of the rubber composition in a high strain range, thereby enabling further improvement in wet grip performance of tires. Among the resins (C), terpene resins and rosin resins are particularly preferred from the viewpoint of reducing the environmental impact. Terpene resins and rosin resins are naturally derived, sustainable resins, which can further reduce the environmental impact and can further improve tire performance, such as grip performance on various road surface conditions, including dry roads, wet roads, snow-covered roads, and icy roads.

[0199] Resin (C) may be modified to introduce a functional group that interacts with fillers such as carbon black and silica. Examples of such functional groups include amino groups, amide groups, isocyanate groups, imino groups, imidazole groups, urea groups, ammonium groups, imide groups, hydrazo groups, azo groups, diazo groups, carboxyl groups, nitrile groups, pyridyl groups, alkoxy groups, hydroxyl groups, oxy groups, epoxy groups, ether groups, carbonyl groups, oxycarbonyl groups, silyl groups, alkoxysilyl groups, mercapto groups, sulfide groups, disulfide groups, sulfonyl groups, sulfinyl groups, and thiocarbonyl groups.

[0200] The C5 resin refers to a C5 synthetic petroleum resin, and examples of the C5 resin include aliphatic petroleum resins obtained by polymerizing a C5 fraction obtained by thermal cracking of naphtha in the petrochemical industry using a Friedel-Crafts catalyst such as AlCl3 or BF3. The C5 fraction typically includes olefinic hydrocarbons such as 1-pentene, 2-pentene, 2-methyl-1-butene, 2-methyl-2-butene, and 3-methyl-1-butene, and diolefinic hydrocarbons such as 2-methyl-1,3-butadiene, 1,2-pentadiene, 1,3-pentadiene, and 3-methyl-1,2-butadiene. As the C5 resin, commercially available products can be used, and examples thereof include the "ESCOLETZ (registered trademark) 1000 series" aliphatic petroleum resins manufactured by ExxonMobil Chemical Corporation, "A100, B170, M100, R100" of the "QUINTONE (registered trademark) 100 series" aliphatic petroleum resins manufactured by Zeon Corporation, and "T-REZ RA100" manufactured by Tonen Chemical Industry Co., Ltd.

[0201] The C5-C9 resin refers to a C5-C9 synthetic petroleum resin. Examples of the C5-C9 resin include solid polymers obtained by polymerizing petroleum-derived C5 fractions and C9 fractions using a Friedel-Crafts catalyst such as AlCl3 or BF3. More specifically, examples include copolymers primarily composed of styrene, vinyltoluene, α-methylstyrene, indene, etc. As the C5-C9 resin, a resin with a low content of C9 or higher components is preferred from the viewpoint of compatibility with rubber components. Here, "low content of C9 or higher components" refers to a resin in which the content of C9 or higher components in the total resin is less than 50% by mass, preferably 40% by mass or less. Commercially available C5-C9 resins include those sold under the trade name "Quinton (registered trademark) G100B" (manufactured by Zeon Corporation), "ECR213" (manufactured by ExxonMobil Chemical Corporation), and "T-REZ RD104" (manufactured by Tonen Chemical Industry Co., Ltd.).

[0202] The C9 resin is a resin obtained by polymerizing aromatic compounds having 9 carbon atoms, the main monomers of which are vinyltoluene, alkylstyrene, and indene, which are C9 fractions by-produced together with petrochemical base materials such as ethylene and propylene by thermal decomposition of naphtha in the petrochemical industry. Specific examples of the C9 fraction obtained by thermal decomposition of naphtha include vinyltoluene, α-methylstyrene, β-methylstyrene, γ-methylstyrene, o-methylstyrene, p-methylstyrene, and indene. The C9 resin is obtained by polymerizing aromatic compounds having 9 carbon atoms, the main monomers being vinyltoluene, alkylstyrene, and indene, which are C9 fractions by-produced together with petrochemical base materials such as ethylene and propylene by thermal decomposition of naphtha in the petrochemical industry. Specific examples of the C9 fraction obtained by thermal decomposition of naphtha include vinyltoluene, α-methylstyrene, β-methylstyrene, γ-methylstyrene, o-methylstyrene, p-methylstyrene, and indene. The C9 resin is obtained by polymerizing aromatic compounds having 9 carbon atoms, such as styrene and C8 fractions, together with the C9 fraction. 10 The fractions methylindene, 1,3-dimethylstyrene, etc., as well as naphthalene, vinylnaphthalene, vinylanthracene, p-tert-butylstyrene, etc. are used as raw materials, and these C8 to C 10The C9 resin can be obtained by copolymerizing the fractions as a mixture with, for example, a Friedel-Crafts catalyst. The C9 resin may also be a modified petroleum resin modified with a compound having a hydroxyl group, an unsaturated carboxylic acid compound, or the like. Commercially available C9 resins can be used. Examples of unmodified C9 petroleum resins include those under the trade names "Nippon Oil Neopolymer (registered trademark) L-90," "Nippon Oil Neopolymer (registered trademark) 120," "Nippon Oil Neopolymer (registered trademark) 130," and "Nippon Oil Neopolymer (registered trademark) 140" (manufactured by JX Nippon Oil & Energy Corporation).

[0203] The dicyclopentadiene resin is a petroleum resin produced primarily from dicyclopentadiene obtained by dimerizing cyclopentadiene. Commercially available dicyclopentadiene resins are available, including, for example, alicyclic petroleum resins manufactured by Zeon Corporation under the trade name Quinton (registered trademark) 1000 Series (product names: 1105, 1325, and 1340).

[0204] The terpene phenol resin can be obtained, for example, by reacting terpenes with various phenols using a Friedel-Crafts catalyst or by further condensing them with formalin. The terpenes used as raw materials are not particularly limited, but monoterpene hydrocarbons such as α-pinene and limonene are preferred, with α-pinene being more preferred, and α-pinene being particularly preferred. Commercially available terpene phenol resins include those sold under the trade names "Tamanol 803L" and "Tamanol 901" (manufactured by Arakawa Chemical Industries, Ltd.), and those sold under the trade names "YS Polystar® U" series, "YS Polystar® T" series, "YS Polystar® S" series, "YS Polystar® G" series, "YS Polystar® N" series, "YS Polystar® K" series, and "YS Polystar® TH" series (manufactured by Yasuhara Chemical Co., Ltd.).

[0205] The terpene resin is a solid resin obtained by blending turpentine oil, which is obtained simultaneously when rosin is obtained from pine trees, or a polymerization component separated from the turpentine oil, and polymerizing the blend using a Friedel-Crafts catalyst, and examples of the terpene resin include β-pinene resin and α-pinene resin. Commercially available terpene resins can be used, and examples include the "YS Resin" series (PX-1250, TR-105, etc.) manufactured by Yasuhara Chemical Co., Ltd. and the "Picolite" series (A115, S115, etc.) manufactured by Hercules.

[0206] The rosin resin is the residue remaining after collecting balsams such as pine resin (pine tar), which is the sap of plants in the Pinaceae family, and distilling turpentine essential oil. It is a natural resin whose main component is rosin acid (abietic acid, palustric acid, isopimaric acid, etc.), as well as modified and hydrogenated resins obtained by modifying, hydrogenating, or otherwise processing these. Examples of rosin resin include natural resin rosin, its polymerized rosin, and partially hydrogenated rosin; glycerin ester rosin, its partially hydrogenated rosin, fully hydrogenated rosin, and polymerized rosin; pentaerythritol ester rosin, its partially hydrogenated rosin, and polymerized rosin. Natural resin rosins include gum rosin, tall oil rosin, and wood rosin, which are contained in raw pine resin and tall oil. The rosin resin may be a commercially available product, such as "Neotol 105" (manufactured by Harima Chemical Co., Ltd.), "SN Tack 754" (manufactured by San Nopco Ltd.), "Lime Resin No. 1," "Pensel A," and "Pensel AD" (manufactured by Arakawa Chemical Industries, Ltd.), "Polypale" and "Pentalin C" (manufactured by Eastman Chemical Co., Ltd.), or "Hi-Rosin (registered trademark) S" (manufactured by Taisho Matsu Oil Co., Ltd.).

[0207] The alkylphenol resin can be obtained, for example, by condensation of alkylphenol and formaldehyde in the presence of a catalyst. Commercially available alkylphenol resins include those sold under the trade names "Hitanol 1502P" (an alkylphenol formaldehyde resin, manufactured by Hitachi Chemical Co., Ltd.), "Tackirol 201" (an alkylphenol formaldehyde resin, manufactured by Taoka Chemical Co., Ltd.), "Tackirol 250-I" (a brominated alkylphenol formaldehyde resin, manufactured by Taoka Chemical Co., Ltd.), "Tackirol 250-III" (a brominated alkylphenol formaldehyde resin, manufactured by Taoka Chemical Co., Ltd.), and "R7521P," "SP1068," "R7510PJ," "R7572P," and "R7578P" (manufactured by SI Group Inc.).

[0208] -Hydrogenated resin- It is also preferable that the resin (C) is at least partially hydrogenated (i.e., a hydrogenated resin). By at least partially hydrogenating the resin (C), the mobility of the rubber component (A) is further controlled, and the hysteresis loss (tan δ) in the low temperature range can be further improved, thereby further improving the wet grip performance of a tire using the rubber composition.

[0209] The hydrogenated resin preferably has a softening point higher than 110°C and a weight average molecular weight in terms of polystyrene of 200 to 1600 g / mol. By applying a rubber composition containing such a hydrogenated resin to a tire, the wear resistance of the tire can be further improved. Here, the softening point of the hydrogenated resin is measured in accordance with JIS-K2207-1996 (ring and ball method). The weight average molecular weight of the hydrogenated resin is measured by gel permeation chromatography (GPC) and calculated as a polystyrene equivalent value.

[0210] If the softening point of the hydrogenated resin is higher than 110°C, the tire to which the rubber composition is applied can be sufficiently reinforced, and the wear resistance can be further improved. From the viewpoint of the wear resistance of the tire, the softening point of the hydrogenated resin is preferably 116°C or higher, more preferably 120°C or higher, more preferably 123°C or higher, and even more preferably 127°C or higher. Furthermore, from the viewpoint of processability, the softening point of the hydrogenated resin is preferably 160°C or lower, more preferably 150°C or lower, more preferably 145°C or lower, more preferably 141°C or lower, and even more preferably 136°C or lower.

[0211] When the weight average molecular weight of the hydrogenated resin in terms of polystyrene is 200 g / mol or more, the resin component is less likely to precipitate from the tire, and the effects of the hydrogenated resin can be fully exhibited. When the weight average molecular weight is 1600 g / mol or less, the hydrogenated resin is easily compatible with the rubber component (A). From the viewpoint of suppressing precipitation of the hydrogenated resin from the tire and suppressing deterioration in tire appearance, the weight average molecular weight, in terms of polystyrene, of the hydrogenated resin is preferably 500 g / mol or more, more preferably 550 g / mol or more, still more preferably 600 g / mol or more, still more preferably 650 g / mol or more, and still more preferably 700 g / mol or more. Furthermore, from the viewpoint of improving the compatibility of the hydrogenated resin with the rubber component (A) and further enhancing the effects of the hydrogenated resin, the polystyrene-equivalent weight average molecular weight of the hydrogenated resin is more preferably 1570 g / mol or less, more preferably 1530 g / mol or less, more preferably 1500 g / mol or less, more preferably 1470 g / mol or less, more preferably 1430 g / mol or less, more preferably 1400 g / mol or less, more preferably 1370 g / mol or less, more preferably 1330 g / mol or less, more preferably 1300 g / mol or less, more preferably 1200 g / mol or less, more preferably 1100 g / mol or less, more preferably 1000 g / mol or less, and even more preferably 950 g / mol or less.

[0212] The weight average molecular weight (Mw HR ) (unit: g / mol) versus the softening point (Ts HR ) (unit: °C) ratio (Ts HR / Mw HR ) is preferably 0.07 or more, more preferably 0.083 or more, more preferably 0.095 or more, more preferably 0.104 or more, more preferably 0.125 or more, more preferably 0.135 or more, more preferably 0.14 or more, and even more preferably 0.141 or more. HR / Mw HR ) is preferably 0.25 or less, more preferably 0.24 or less, more preferably 0.23 or less, more preferably 0.19 or less, more preferably 0.18 or less, and even more preferably 0.17 or less. The softening point and polystyrene-equivalent weight average molecular weight of the hydrogenated resin can be determined by the method described in the examples below.

[0213] The above-mentioned at least partially hydrogenated resin means a resin obtained by reducing and hydrogenating a resin. Examples of resins that can be used as raw materials for the hydrogenated resin include the above-mentioned C5 resins, C5-C9 resins, C9 resins, dicyclopentadiene resins, terpene phenol resins, terpene resins, rosin resins, and alkylphenol resins. These resins may be used alone or in combination of two or more.

[0214] Furthermore, the resin that is the raw material for the hydrogenated resin may contain, for example, a resin obtained by copolymerizing a C5 fraction with dicyclopentadiene (DCPD) (C5-DCPD-based resin). Here, if the dicyclopentadiene-derived component is 50% by mass or more of the total resin, the C5-DCPD resin is considered to be included in the dicyclopentadiene resin. If the dicyclopentadiene-derived component is less than 50% by mass of the total resin, the C5-DCPD resin is considered to be included in the C5 resin. The same applies to cases where a small amount of a third component is also contained.

[0215] From the viewpoints of increasing the compatibility between the rubber component (A) and the resin (C), further improving the wet grip performance of a tire using the rubber composition, and further reducing rolling resistance, the resin (C) is preferably at least one selected from the group consisting of hydrogenated C5 resins, hydrogenated C5-C9 resins, hydrogenated dicyclopentadiene resins (hydrogenated DCPD resins), and hydrogenated terpene resins, more preferably at least one selected from the group consisting of hydrogenated C5 resins and hydrogenated C5-C9 resins, and even more preferably a hydrogenated C5 resin. Furthermore, it is preferably a resin having a hydrogenated DCPD structure or a hydrogenated cyclic structure in at least one monomer.

[0216] (Silane coupling agent) When the rubber composition for a tire of this embodiment contains silica as the reinforcing filler (B), the rubber composition preferably contains a silane coupling agent to improve the effect of the silica. Examples of the silane coupling agent include bis(3-triethoxysilylpropyl)tetrasulfide, bis(3-triethoxysilylpropyl)trisulfide, bis(3-triethoxysilylpropyl)disulfide, bis(2-triethoxysilylethyl)tetrasulfide, bis(3-trimethoxysilylpropyl)tetrasulfide, bis(2-trimethoxysilylethyl)tetrasulfide, 3-mercaptopropyltrimethoxysilane, 3-mercaptopropyltriethoxysilane, 2-mercaptoethyltrimethoxysilane, 2-mercaptoethyltriethoxysilane, 3-trimethoxysilylpropyl-N,N-dimethylthiocarbamoyltetrasulfide, 3-triethoxysilylpropyl-N,N-dimethylthiocarbamoyltetrasulfide, and 3-triethoxysilylpropyl-N,N-dimethylthiocarbamoyltetrasulfide. Examples of the silane coupling agent include N-dimethylthiocarbamoyl tetrasulfide, 2-triethoxysilylethyl-N,N-dimethylthiocarbamoyl tetrasulfide, 3-trimethoxysilylpropyl benzothiazolyl tetrasulfide, 3-triethoxysilylpropyl benzothiazolyl tetrasulfide, 3-triethoxysilylpropyl methacrylate monosulfide, 3-trimethoxysilylpropyl methacrylate monosulfide, bis(3-diethoxymethylsilylpropyl)tetrasulfide, 3-mercaptopropyldimethoxymethylsilane, dimethoxymethylsilylpropyl-N,N-dimethylthiocarbamoyl tetrasulfide, and dimethoxymethylsilylpropyl benzothiazolyl tetrasulfide. Commercially available silane coupling agents can be used, and examples of commercially available silane coupling agents that can be used include products from Evonik, Momentive, Shin-Etsu Silicones, Dow Corning Toray Co., Ltd., Tokyo Chemical Industry Co., Ltd., and AZMAX Corporation. These silane coupling agents may be used alone or in combination of two or more.

[0217] The content of the silane coupling agent can be adjusted appropriately depending on, for example, the tire category to which it is applied, the tire component, the target performance, etc. For example, the content of the silane coupling agent is preferably 1 part by mass or more, more preferably 6 parts by mass or more, and even more preferably 8 parts by mass or more, and is preferably 20 parts by mass or less, more preferably 15 parts by mass or less, even more preferably 12 parts by mass or less, and even more preferably 10 parts by mass or less, relative to 100 parts by mass of the silica.

[0218] Bioethanol can also be used as a raw material for the silane coupling agent. Bioethanol is produced primarily from sugars and / or cellulose as biological resources, and does not effectively utilize other biological resources such as proteins, lipids, and amino acids. Furthermore, sugars compete with food, and excessive use of cellulose leads to deforestation. Therefore, depending on the supply status of various biological resources, the supply status of renewable resources, the supply status of fossil resources, and market demands (e.g., demand for biomass resources as food), it is preferable to use multiple types of ethanol derived from biological resources (bioethanol) as a raw material for the silane coupling agent, or to use a combination of ethanol derived from biological resources (bioethanol), ethanol derived from renewable resources, and ethanol derived from fossil resources. This allows for the effective use of a wide range of biological resources and renewable resources, such as sugars, proteins, and lipids, without relying on a single type of biological resource, and also allows for environmental considerations depending on the production conditions.

[0219] (rubber powder) The rubber composition for tires of this embodiment preferably also contains rubber crumb. The rubber crumb may be obtained by pulverizing used rubber products such as used tires and, if desired, removing reinforcing materials such as steel and fibers, dust, glass, sand, stones, etc., or by preparing a new vulcanized rubber composition for the purpose of producing rubber crumb and pulverizing the pulverized rubber. For example, rubber crumb can be obtained from vulcanized rubber by the method described in "Rubber Chemistry and Technology." The process of pulverizing vulcanized rubber to obtain rubber crumb may involve mechanical processing or low-temperature processing. For example, in mechanical processing, various crushing devices such as a cracker mill or granulator can be used to mechanically crush the vulcanized rubber into fine particles. In low-temperature processing, the finely chopped vulcanized rubber is frozen at a cryogenic temperature and then crushed into fine particles. A magnetic separator or the like can be used to remove steel, and an air separator or the like can be used to remove fibers. The rubber crumb may also be commercially available, including products from Global Corporation or Nantong Huili Rubber Corporation. From the viewpoint of reducing the environmental load, it is preferable to use rubber powder obtained by crushing used rubber products such as used tires. The rubber powder may be used alone or in combination of two or more types.

[0220] The composition of the rubber crumb is not particularly limited and depends on the composition of the vulcanized rubber from used rubber products (used tires) or the like that serve as the raw material. In one embodiment, the rubber crumb contains a rubber component, carbon black, silica, etc. The rubber component, carbon black, silica, etc. contained in the rubber crumb may be the same as or different from the rubber component (A), carbon black, silica, etc. contained in the rubber composition of this embodiment described above.

[0221] The volume average particle diameter of the rubber powder is preferably 1000 μm or less, more preferably 500 μm or less, even more preferably 200 μm or less, and even more preferably 100 μm or less. The smaller the volume average particle diameter of the rubber powder, the better, and there is no particular lower limit. In this specification, the volume average particle size is measured by a laser diffraction particle size distribution measuring device, for example, "CAPA500" manufactured by Horiba, Ltd.

[0222] The rubber powder preferably has a 60-mesh sieve residue of less than 1% by mass, more preferably 0.5% by mass or less, and even more preferably 0.1% by mass or less, with no particular lower limit. Also, the rubber powder preferably has an 80-mesh sieve residue of less than 10% by mass, more preferably 1% by mass or less, and even more preferably 0.5% by mass or less, with no particular lower limit. In this specification, the sieve residue is measured in accordance with ASTM D5644-01.

[0223] The rubber powder preferably has an acetone extractable content of 12% by mass or less, more preferably 11% by mass or less, and even more preferably 10% by mass or less, and preferably 1% by mass or more, more preferably 2% by mass or more, and even more preferably 3% by mass or more. In this specification, the acetone extractables in the rubber crumb refers to the acetone extractables (%) determined by the acetone extraction method in accordance with JIS K6350.

[0224] The content of the rubber crumb is not particularly limited and can be adjusted appropriately depending on, for example, the tire category to which the rubber component is applied, the tire components, the target performance, etc. For example, the content of the rubber crumb 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, and is preferably 200 parts by mass or less, more preferably 150 parts by mass or less, more preferably 100 parts by mass or less, more preferably 50 parts by mass or less, more preferably 30 parts by mass or less, even more preferably 15 parts by mass or less, still more preferably 10 parts by mass or less, and particularly preferably 5 parts by mass or less, relative to 100 parts by mass of the rubber component (A).

[0225] (liquid softener) The rubber composition for a tire of this embodiment may contain a liquid softener. Here, the "liquid softener" refers to a compounding agent that is liquid at 25°C (room temperature) and has the effect of softening the rubber composition. The liquid softener is not particularly limited, and examples thereof include oil and liquid polymer, among which oil is preferred. These liquid softeners may be used alone or in combination of two or more.

[0226] The oil is a general term for extender oils contained in rubber components and liquid oils added as compounding agents to rubber compositions. Examples include vegetable oils, process oils, oils obtained by recycling vegetable oils or process oils, and mixtures thereof. From the perspective of reducing environmental impact, vegetable oils and recycled oils are preferred. Examples of vegetable oils include palm oil, castor oil, cottonseed oil, soybean oil, linseed oil, rapeseed oil, coconut oil, pine oil, pine tar, tall oil, corn oil, rice oil, safflower oil, sesame oil, olive oil, sunflower oil, palm kernel oil, camellia oil, jojoba oil, macadamia nut oil, tung oil, and coconut oil. Examples of process oils include paraffin-based process oils, aromatic process oils, and naphthenic process oils. The oil may be a commercially available product, such as products from Idemitsu Kosan Co., Ltd., Sankyo Yuka Kogyo Co., Ltd., ENEOS Corporation, Oriso Co., Ltd., H&R Corporation, Toyokuni Oil Mills Co., Ltd., and Nisshin Oillio Group Co., Ltd. These oils may be used alone or in combination of two or more.

[0227] The liquid polymer is preferably a liquid diene-based polymer. Examples of the liquid diene-based polymer include liquid styrene-butadiene copolymer (liquid SBR), liquid polybutadiene (liquid BR), liquid polyisoprene (liquid IR), liquid styrene-isoprene copolymer (liquid SIR), liquid styrene-butadiene-styrene block copolymer (liquid SBS block polymer), liquid styrene-isoprene-styrene block copolymer (liquid SIS block polymer), liquid polyfarnesene, and liquid farnesene-butadiene copolymer. These liquid polymers may be hydrogenated, or their terminals or main chains may be modified with functional groups (polar groups). These liquid polymers may be used alone or in combination of two or more.

[0228] The content of the liquid softener is not particularly limited and can be adjusted appropriately depending on, for example, the tire category to which it is applied, the tire components, the target performance, etc. For example, the content of the liquid softener is preferably 5 parts by mass or more, and more preferably 10 parts by mass or more, and is preferably 100 parts by mass or less, more preferably 70 parts by mass or less, still more preferably 50 parts by mass or less, and even more preferably 30 parts by mass or less, relative to 100 parts by mass of the rubber component (A).

[0229] (anti-aging agent) The rubber composition for a tire according to the present embodiment may contain an antioxidant, such as N-(1,3-dimethylbutyl)-N'-phenyl-p-phenylenediamine (6PPD), N,N'-bis(1,4-dimethylpentyl)-p-phenylenediamine (77PD), N,N'-diphenyl-p-phenylenediamine (DPPD), N,N'-bis(1-ethyl-3-methylpentyl)-p-phenylenediamine, 2,2,4-trimethyl-1,2-dihydroquinoline polymer (TMDQ), 6-ethoxy-2,2,4-trimethyl-1,2-dihydroquinoline (AW), or 6-anilino-2,2,4-trimethyl-1,2-dihydroquinoline. Commercially available products can be used as the antioxidant, and examples of commercially available antioxidants that can be used include products from Ouchi Shinko Chemical Industry Co., Ltd., Sumitomo Chemical Co., Ltd., Seiko Chemical Co., Ltd., Flexis Co., Ltd., etc. These antioxidants may be used alone or in combination of two or more.

[0230] The content of the antioxidant is not particularly limited and can be adjusted appropriately depending on, for example, the tire category to which it is applied, the tire components, the target performance, etc. For example, the content of the antioxidant is preferably 1 part by mass or more, more preferably 1.5 parts by mass or more, and even more preferably 2 parts by mass or more, and is preferably 12 parts by mass or less, more preferably 10 parts by mass or less, and even more preferably 8 parts by mass or less, per 100 parts by mass of the rubber component (A).

[0231] (wax) The rubber composition for a tire of this embodiment may contain a wax. Examples of the wax include natural waxes such as vegetable wax and animal wax; petroleum waxes such as paraffin wax and microcrystalline wax; and synthetic waxes such as ethylene polymers and propylene polymers. Commercially available waxes can be used, and examples of commercially available waxes include products from Seiko Chemical Co., Ltd., Nippon Seiro Co., Ltd., Ouchi Shinko Chemical Industry Co., Ltd., and the like. These waxes may be used alone or in combination of two or more.

[0232] The content of the wax is not particularly limited and can be adjusted appropriately depending on, for example, the tire category to which the rubber component (A) is applied, the tire components, the target performance, etc. For example, the content of the wax is preferably 0.5 parts by mass or more, more preferably 1 part by mass or more, and is preferably 10 parts by mass or less, more preferably 6 parts by mass or less, per 100 parts by mass of the rubber component (A).

[0233] (stearic acid) The rubber composition for a tire of this embodiment may contain stearic acid. Commercially available stearic acid can be used, and examples of commercially available stearic acid include products from NOF Corporation, Kao Corporation, Fujifilm Wako Pure Chemical Industries, Ltd., Chiba Fatty Acid Co., Ltd., etc. These commercially available stearic acid products may be used alone or in combination of two or more.

[0234] The content of stearic acid is not particularly limited and can be adjusted appropriately depending on, for example, the tire category to which the rubber component (A) is applied, the tire component, the target performance, etc. For example, the content of stearic acid is preferably 1 part by mass or more, more preferably 2 parts by mass or more, and is preferably 10 parts by mass or less, more preferably 6 parts by mass or less, per 100 parts by mass of the rubber component (A).

[0235] (zinc oxide) The rubber composition for tires of this embodiment may contain zinc oxide (zinc white). The zinc oxide is preferably obtained not only from zinc metal but also from recycled zinc or zinc dross (i.e., obtained by recycling). Commercially available zinc oxide can be used, and examples of commercially available zinc oxide include products from Hakusui Tech Co., Ltd., Seido Chemical Industry Co., Ltd., Sakai Chemical Industry Co., Ltd., Mitsui Mining & Smelting Co., Ltd., and Toho Zinc Co., Ltd. These commercially available zinc oxide products may be used alone or in combination of two or more.

[0236] The content of the zinc oxide is not particularly limited and can be adjusted appropriately depending on, for example, the tire category to which the rubber composition is applied, the tire components, the target performance, etc. For example, the content of the zinc oxide is preferably 1 part by mass or more, more preferably 2 parts by mass or more, and is preferably 10 parts by mass or less, more preferably 6 parts by mass or less, per 100 parts by mass of the rubber component (A).

[0237] (sulfur) The rubber composition for tires of this embodiment preferably contains sulfur. The sulfur may be derived from fossil resources, recycled resources, or sulfur obtained by processing biological resource-derived materials. From the perspective of reducing environmental impact, it is particularly preferable to use sulfur obtained from waste derived from biological resources. Examples of methods for obtaining sulfur from waste derived from biological resources include the method described in the aforementioned Japanese Patent Application No. 2022-140390. The sulfur may also be powdered sulfur, precipitated sulfur, colloidal sulfur, insoluble sulfur, highly dispersible sulfur, soluble sulfur, and the like, which are commonly used as crosslinking agents in the rubber industry. Commercially available sulfur products are available, including those from Tsurumi Chemical Industry Co., Ltd., Hosoi Chemical Industry Co., Ltd., Karuizawa Sulfur Co., Ltd., Shikoku Chemical Industry Co., Ltd., and Flexis Corporation. These sulfurs may be used alone or in combination of two or more.

[0238] The sulfur content is not particularly limited and can be adjusted appropriately depending on, for example, the tire category to which the rubber component (A) is applied, the tire components, the target performance, etc. For example, the sulfur content is preferably 0.3 parts by mass or more, more preferably 0.5 parts by mass or more, and even more preferably 0.8 parts by mass or more, and is preferably 8 parts by mass or less, more preferably 5 parts by mass or less, per 100 parts by mass of the rubber component (A).

[0239] (Vulcanization accelerator) The rubber composition for a tire of this embodiment preferably contains a vulcanization accelerator. The vulcanization accelerator may be derived from fossil resources, recycled resources, or biological resources, but is preferably derived from biological resources from the viewpoint of reducing environmental impact. Vulcanization accelerators derived from biological resources can be obtained, for example, by the method disclosed in JP 2005-139239 A. Examples of the vulcanization accelerator include sulfenamide-based vulcanization accelerators such as N-cyclohexyl-2-benzothiazolylsulfenamide (CBS), N,N-dicyclohexyl-2-benzothiazolylsulfenamide, N-tert-butyl-2-benzothiazolylsulfenamide (TBBS), N-oxyethylene-2-benzothiazolesulfenamide, and N,N'-diisopropyl-2-benzothiazolesulfenamide; 1,3-diphenylguanidine (DPG), 1,3-diphenylguanidine (DPG), and 1,3-diphenylguanidine (DPG). Examples of suitable vulcanization accelerators include guanidine-based vulcanization accelerators such as o-tolylguanidine and o-tolylbiguanidine; thiazole-based vulcanization accelerators such as 2-mercaptobenzothiazole (M) and di-2-benzothiazolyl disulfide (MBTS, DM); and thiuram-based vulcanization accelerators such as tetramethylthiuram disulfide (TMTD), tetrastearylthiuram disulfide, tetrabenzylthiuram disulfide (TBzTD), and tetrakis(2-ethylhexyl)thiuram disulfide (TOT-N). Commercially available vulcanization accelerators can be used, including those from Ouchi Shinko Chemical Industry Co., Ltd. and Sumitomo Chemical Co., Ltd. These vulcanization accelerators can be used alone or in combination of two or more.

[0240] The content of the vulcanization accelerator is not particularly limited and can be adjusted appropriately depending on, for example, the tire category to which the vulcanization accelerator is applied, the tire components, the target performance, etc. For example, the content of the vulcanization accelerator 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, and is preferably 8 parts by mass or less, more preferably 6 parts by mass or less, and even more preferably 5.5 parts by mass or less, relative to 100 parts by mass of the rubber component (A).

[0241] (Cellulose nanofiber) The rubber composition for a tire according to this embodiment may contain cellulose nanofibers (CNF). The cellulose nanofibers can reinforce a rubber composition by blending them with the rubber composition. The cellulose nanofibers are preferably modified cellulose nanofibers, which are fine fibers made from modified cellulose. The fiber diameter of the cellulose nanofibers is not particularly limited, but is approximately 3 to 500 nm. The average fiber diameter and average fiber length of the cellulose nanofibers can be obtained by averaging the fiber diameters and fiber lengths obtained from the observation of each fiber using a scanning electron microscope (SEM), an atomic force microscope (AFM), or a transmission electron microscope (TEM). The cellulose nanofibers can be obtained by defibrating cellulose. The average fiber length and average fiber diameter of the fine fibers can be adjusted by oxidation treatment or defibration treatment.

[0242] The raw material for the cellulose nanofibers is not particularly limited as long as it contains cellulose, and examples thereof include plants (e.g., wood, bamboo, hemp, jute, kenaf, agricultural waste, cloth, pulp (e.g., unbleached softwood kraft pulp (NUKP), bleached softwood kraft pulp (NBKP), unbleached hardwood kraft pulp (LUKP), bleached hardwood kraft pulp (LBKP), bleached kraft pulp (BKP), unbleached softwood sulfite pulp (NUSP), bleached softwood sulfite pulp (NBSP), thermomechanical pulp (TMP), recycled pulp, waste paper, etc.), animals (e.g., ascidians), algae, microorganisms (e.g., acetic acid bacteria (Acetobacter)), microbial products, etc. These cellulose raw materials may be used alone or in combination of two or more.

[0243] The content of the cellulose nanofibers is not particularly limited and can be adjusted appropriately depending on, for example, the tire category to which the rubber component (A) is applied, the tire component, the target performance, etc. For example, the content of the cellulose nanofibers is preferably in the range of 1 to 100 parts by mass, more preferably in the range of 5 to 70 parts by mass, and even more preferably in the range of 10 to 40 parts by mass, per 100 parts by mass of the rubber component (A).

[0244] (porous cellulose particles) The rubber composition for a tire of this embodiment may contain porous cellulose particles. The porous cellulose particles are preferably cellulose particles having a porous structure with a porosity of 75 to 95%, and by compounding them with a rubber composition, performance on ice can be improved. When the porosity of the porous cellulose particles is 75% or more, the effect of improving performance on ice is excellent, and when the porosity is 95% or less, the strength of the particles can be increased. The porosity is more preferably 80 to 90%. The porosity of the porous cellulose particles can be calculated by measuring the volume of a certain mass of sample (i.e., porous cellulose particles) with a measuring cylinder, determining the bulk density, and using the following formula: Porosity (%) = {1 - [bulk specific gravity of sample (g / mL)] / [true specific gravity of sample (g / mL)]} x 100 Here, the true specific gravity of cellulose is 1.5.

[0245] The particle size of the porous cellulose particles is not particularly limited, but from the viewpoint of abrasion resistance, an average particle size of 1000 μm or less is preferred. The lower limit of the average particle size is not particularly limited, but it is preferably 5 μm or more. The average particle size is more preferably 100 to 800 μm, and even more preferably 200 to 800 μm. The porous cellulose particles are preferably spherical particles with a major axis / minor axis ratio of 1 to 2. The use of particles with such a spherical structure improves dispersibility in the rubber composition, contributing to improved performance on ice and maintenance of abrasion resistance, etc. The major axis / minor axis ratio is more preferably 1.0 to 1.5. The average particle size and the ratio of major axis to minor axis of the porous cellulose particles are determined as follows: The porous cellulose particles are observed under a microscope to obtain an image, and the images are used to measure the major axis and minor axis of 100 particles (when the major axis and minor axis are the same, the length in a certain axis direction and the length in an axis direction perpendicular to the major axis) and calculate the average value to obtain the average particle size, and the ratio of major axis to minor axis is obtained by averaging the values obtained by dividing the major axis by the minor axis.

[0246] The porous cellulose particles are commercially available from Rengo Co., Ltd. under the name "Viscopearl" and are also described in JP-A Nos. 2001-323095 and 2004-115284, and can be suitably used.

[0247] The content of the porous cellulose particles is not particularly limited and can be appropriately adjusted depending on, for example, the tire category to which the rubber composition is applied, the tire components, the target performance, etc. For example, the content of the porous cellulose particles is preferably in the range of 0.3 to 20 parts by mass, more preferably in the range of 1 to 15 parts by mass, and even more preferably in the range of 3 to 15 parts by mass, per 100 parts by mass of the rubber component (A).

[0248] (solid fine particles) The rubber composition for a tire according to this embodiment may contain solid fine particles. Blending the solid fine particles into the rubber composition can improve performance on ice. The solid fine particles preferably have an average particle diameter of 1 μm or more, preferably 1000 μm or less, and more preferably 300 μm or less. Examples of the solid fine particles include plant-derived powders obtained from plants, such as rice husks, walnut flour, and walnut shells; animal-derived powders obtained from animals, such as eggshells (eggshell powder) and bone meal; powders derived from natural minerals, such as whitebait; inorganic fine particles, such as graphite and zinc oxide whiskers; water-soluble metal salt fine particles, such as magnesium sulfate and metal salts of lignosulfonic acid; and non-metallic fibers, such as glass fiber. Among these, rice husks, walnut shells, eggshells, and whitebait are preferred.

[0249] The content of the solid fine particles is not particularly limited and can be appropriately adjusted depending on, for example, the tire category to which the rubber composition is applied, the tire components, the target performance, etc. For example, the content of the solid fine particles is preferably in the range of 0.3 to 20 parts by mass, more preferably in the range of 1 to 15 parts by mass, and even more preferably in the range of 3 to 15 parts by mass, per 100 parts by mass of the rubber component (A).

[0250] (others) In addition to the above-mentioned components, the rubber composition for tires of this embodiment may further contain various additives commonly used in the tire industry, such as organic peroxides. The content of these additives is not particularly limited and can be appropriately adjusted depending on, for example, the tire category to which they are applied, the tire components, the target performance, etc. For example, the content is preferably in the range of 0.1 to 200 parts by mass per 100 parts by mass of the rubber component (A).

[0251] (Method of manufacturing rubber composition) The method for producing the rubber composition for tires of the present embodiment is not particularly limited, but can be produced, for example, by blending various components appropriately selected as necessary with the rubber component (A), followed by kneading, heating, extruding, etc. The obtained rubber composition can be vulcanized to produce a vulcanized rubber.

[0252] The conditions for the kneading are not particularly limited, and various conditions such as the input volume of the kneading device, the rotation speed of the rotor, the ram pressure, the kneading temperature, the kneading time, the type of kneading device, etc. can be appropriately selected depending on the purpose. Examples of the kneading device include a Banbury mixer, an intermix, a kneader, a roll, etc. that are usually used for kneading rubber compositions.

[0253] The conditions for the heat-in are not particularly limited, and various conditions such as the heat-in temperature, heat-in time, and heat-in device can be appropriately selected depending on the purpose. Examples of the heat-in device include a heat-in roll mill typically used for heat-in of rubber compositions.

[0254] The extrusion conditions are not particularly limited, and various conditions such as extrusion time, extrusion speed, extrusion device, and extrusion temperature can be appropriately selected depending on the purpose. Examples of the extrusion device include an extruder typically used for extruding rubber compositions. The extrusion temperature can be appropriately determined.

[0255] The vulcanization apparatus, method, conditions, etc. are not particularly limited and can be appropriately selected depending on the purpose. Examples of vulcanization apparatus include a molding vulcanizer using a mold used for vulcanizing rubber compositions. The vulcanization temperature is, for example, about 100 to 190°C.

[0256] (Application) The rubber composition for a tire of the present embodiment can be applied to various constituent parts of a tire, such as a tread (cap tread, base tread, undertread), cushion rubber, shoulder, sidewall, clinch, bead filler, carcass coating rubber, insulation, chafer, inner liner, etc., and can also be used as a side reinforcing layer of a run-flat tire, etc.

[0257] <Tread rubber> The tread rubber of this embodiment is characterized by being made of the above-mentioned rubber composition for tires. The tread rubber of this embodiment is made of the above-mentioned rubber composition for tires, and therefore has a high proportion of sustainable materials, and can promote a reduction in the environmental impact from the overall production, use, and disposal of the modified conjugated diene polymer. Therefore, by applying the tread rubber of this embodiment to a tire, it is possible to increase the proportion of sustainable materials in the tire, and can promote a reduction in the environmental impact from the overall production, use, and disposal of the modified conjugated diene polymer.

[0258] The tread rubber of this embodiment may be applied to a new tire or a retread tire. The tread rubber of this embodiment may be applied to a pneumatic tire or a non-pneumatic tire.

[0259] <Tires> The tire of this embodiment is characterized by including the above-mentioned tread rubber. The tire of the present embodiment includes the above-described tread rubber, and therefore the proportion of sustainable materials is increased, and the production, use, and disposal of the modified conjugated diene-based polymer as a whole can promote a reduction in the environmental impact. Furthermore, the tire of the present embodiment does not impair performance.

[0260] Next, one embodiment of the tire of the present invention will be described in detail with reference to the drawings. Fig. 1 is a cross-sectional view of one embodiment of a tire of the present invention. The tire 1 of this embodiment shown in Fig. 1 has a pair of bead portions 2, a pair of sidewall portions 3, and a tread portion 4 continuous with both sidewall portions 3, and is equipped with a carcass 5 extending in a toroidal shape between the pair of bead portions 2 to reinforce these portions 2, 3, and 4, and a belt 6 disposed on the radially outer side of the crown portion of the carcass 5.

[0261] The carcass 5 of the tire 1 shown in FIG. 1 is composed of one carcass ply made of a plurality of parallel-arranged cords covered with a coating rubber, and the carcass 5 is composed of a main body portion extending in a toroidal shape between the bead cores 7 respectively embedded in the bead portions 2, and turned-up portions wound up radially outward around each bead core 7 from the inner side toward the outer side in the tire width direction, but the number of plies and structure of the carcass 5 in the tire of the present invention are not limited to this.

[0262] 1 is composed of two belt layers 6A and 6B, but in the tire of the present invention, the number of belt layers constituting the belt 6 is not limited to this and the number of belt layers may be three or more. Here, the belt layers 6A and 6B are usually composed of rubberized layers of cords (preferably steel cords) extending at an angle with respect to the tire equatorial plane, and the two belt layers 6A and 6B are laminated to constitute the belt 6 such that the cords constituting the belt layers 6A and 6B cross each other with the tire equatorial plane in between.

[0263] The tire 1 of this embodiment has tread rubber 8 on the outermost surface of the tread portion 4, and the above-described rubber composition for a tire of this embodiment is used for the tread rubber 8. Therefore, the tire 1 of this embodiment has an improved proportion of sustainable materials.

[0264] The tire of the present invention may have a tread rubber made of the rubber composition for a tire according to the present embodiment, and various modifications may be made to the tire. For example, a belt reinforcing layer may be disposed on the radially outer side of the belt 6 of the tire 1 shown in Fig. 1, or the tread rubber 8 may be divided into a cap rubber located on the outermost side and a base rubber located on the radially inner side of the cap rubber.

[0265] The tire of this embodiment can be manufactured by a conventional method using the above-mentioned rubber composition as the tread rubber. For example, depending on the type of tire to be applied, the tire of this embodiment may be obtained by molding an unvulcanized rubber composition and then vulcanizing it, or by molding a semi-vulcanized rubber that has been subjected to a pre-vulcanization process or the like and then further vulcanizing it. The tire of this embodiment is preferably a pneumatic tire, and the gas to be filled into the pneumatic tire may be normal air or air with an adjusted oxygen partial pressure, or an inert gas such as nitrogen, argon, or helium. [Example]

[0266] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to the following examples in any way.

[0267] <Preparation and Evaluation of Rubber Compositions> Each rubber composition was produced according to the formulation shown in Table 1 in a conventional manner. The number of parts of each compounding agent is stated to two significant digits.

[0268] (1) Sustainable material ratio For each rubber composition obtained, the total mass ratio of materials derived from biological resources (biomass resources) and materials derived from recycled resources (recycled resources) was calculated to calculate the sustainable material ratio. The results are shown in Table 1. The larger the value, the better the effect.

[0269] (2) Tire performance Fuel economy and wet grip performance were evaluated using the following methods.

[0270] (2-1) Low fuel consumption The loss tangent (tan δ) of a vulcanized rubber test piece prepared from the rubber composition was measured using a viscoelasticity measuring device (manufactured by GABO) under conditions of a temperature of 50°C, a strain of 1%, and a frequency of 15 Hz.

[0271] (2-2) Wet grip performance The loss tangent (tan δ) of a vulcanized rubber test piece prepared from the rubber composition was measured using a viscoelasticity measuring device (manufactured by GABO) under conditions of a temperature of −5° C., a strain of 1%, and a frequency of 15 Hz.

[0272] When evaluated by the above methods, Comparative Example 1 and Example 1 were found to be equivalent in fuel economy and wet grip performance.

[0273] [Table 1]

[0274] *1 NR: Natural rubber *2 SBR-1: Hydrocarbyloxysilane compound modified styrene-butadiene rubber synthesized by the following method *3 SBR-2: Modified styrene-butadiene rubber having nitrogen and alkoxysilyl groups, containing 10.0 parts by mass of oil per 100 parts by mass of rubber component, weight average molecular weight (Mw) = 85.2×10 4 *4 SBR-3: Modified styrene-butadiene rubber supplied by the mass balance method of SBR-1, modified conjugated diene polymer derived from bio-based raw materials and / or circular raw materials by the mass balance method according to ISCC PLUS certification, the ratio of sustainable materials is 100% by mass, corresponding to sustainable materials *5 Carbon black: Manufactured by Tokai Carbon Co., Ltd., trade name "Seast 7HM" *6 Silica: Manufactured by Tosoh Silica Corporation, trade name "Nipsil AQ" *7 Resin: C5-C9 resin, manufactured by Tonen Chemical Corporation, trade name "T-REZ RD104" *8 Other chemicals: Total amount of sulfur, vulcanization accelerator, zinc white, stearic acid, workability improver, anti-aging agent, wax, silane coupling agent, aluminum hydroxide, retarder. In Comparative Example 1 and Example 1, the same number of parts were blended in all cases.

[0275] <Synthesis method of SBR-1 (*2)> Into a dried and nitrogen-substituted 800 mL pressure-resistant glass container, a cyclohexane solution of 1,3-butadiene and a cyclohexane solution of styrene were added so that the amounts were 67.5 g of 1,3-butadiene and 7.5 g of styrene. After adding 0.6 mmol of 2,2-ditetrahydrofurylpropane and 0.8 mmol of n-butyllithium, polymerization was carried out at 50 °C for 1.5 hours. For the polymerization reaction system in which the polymerization conversion rate was almost 100% at this time, 0.72 mmol of N,N-bis(trimethylsilyl)-3-[diethoxy(methyl)silyl]propylamine was added as a modifier, and a modification reaction was carried out at 50 °C for 30 minutes. Then, 2 mL of a 5 mass% solution of 2,6-di-t-butyl-p-cresol (BHT) in isopropanol was added to stop the reaction, and the modified SBR was obtained by drying according to a conventional method. Measurement of the microstructure of the resulting modified SBR revealed that the bound styrene content was 10% by mass and the glass transition temperature (Tg) was -65°C.

[0276] From Table 1, it can be seen that the rubber compositions of the examples according to the present invention contain modified conjugated diene-based polymers supplied by the mass balance method, and therefore have an increased proportion of sustainable materials, and that by applying them to tires, the proportion of sustainable materials in the tires can be increased.

[0277] [Contribution to the United Nations-led Sustainable Development Goals (SDGs)] The SDGs have been proposed to realize a sustainable society. One embodiment of the present invention is expected to be a technology that contributes to the achievement of "No. 13 - Take concrete measures against climate change." [Explanation of symbols]

[0278] 1: Tires 2: Bead part 3: Sidewall 4: Tread section 5: Carcass 6: Belt 6A, 6B: Belt layer 7: Bead core 8: Tread rubber

Claims

1. The rubber composition comprises a rubber component (A) and a reinforcing filler (B), the rubber component (A) contains a modified conjugated diene-based polymer (A1) having a functional group having affinity for the reinforcing filler, A rubber composition for tires, wherein the modified conjugated diene polymer (A1) comprises a modified conjugated diene polymer (A1-1) supplied by a mass balance method.

2. 2. The rubber composition for tires according to claim 1, wherein the modified conjugated diene polymer (A1) comprises a modified conjugated diene polymer derived from at least one of a plant-derived raw material, a plant-derived by-product, a raw material obtained by recycling a plant-derived material, and a raw material obtained by recycling a fossil resource-derived material.

3. 2. The rubber composition for tires according to claim 1, wherein the modified conjugated diene polymer (A1) comprises 0.1 to 99% by mass of a modified conjugated diene polymer derived from a biological resource and 1 to 99.9% by mass of a modified conjugated diene polymer derived from a fossil resource.

4. The rubber composition for a tire according to claim 1, wherein the modified conjugated diene polymer (A1) is modified with a modifier having a nitrogen atom and a silicon atom.

5. The rubber composition for a tire according to claim 1 , further comprising a resin (C).

6. The rubber composition for a tire according to claim 5, wherein the content of the resin (C) is 1 to 50 parts by mass per 100 parts by mass of the rubber component (A).

7. A tread rubber comprising the rubber composition for tires according to any one of claims 1 to 6.

8. A tire comprising a tread rubber according to claim 7.

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