Rubber composition for tires, tread rubber, and tire

Abstract

The present invention solves the problem of providing a rubber composition for a tire that can improve the proportion of sustainable materials in a tire and can contribute to reducing environmental burdens throughout the entire process of production, use, and disposal of synthetic rubber. The means for solving the problem is a rubber composition for a tire characterized by: a rubber component (A) containing a rubber (A1) having an isoprene skeleton and a synthetic rubber (A2), wherein the content of the rubber (A1) having an isoprene skeleton is 10 to 90 parts by mass and the content of the synthetic rubber (A2) is 90 to 10 parts by mass in a total of 100 parts by mass of the rubber component (A); and the synthetic rubber (A2) contains a synthetic rubber (A2-1) supplied using a mass balance system.

Description

Technical Field

[0001] This disclosure relates to rubber compositions for use in tires, tread rubbers, and tires. Background Technology

[0002] Typically, tires require various performance characteristics, such as high fuel economy, wear resistance, fracture resistance, handling stability, and grip on various road surfaces. To meet these requirements, various rubber compositions with different formulations are used to constitute the various components of the tire. For example, Patent Documents 1 and 2 below disclose rubber compositions for tire treads, wherein isoprene skeleton rubbers such as natural rubber and polyisoprene, and synthetic rubbers such as polybutadiene and styrene-butadiene rubber are blended, and fillers such as silica and carbon black, as well as resins, are further compounded.

[0003] Existing technical documents

[0004] (Patent Documents)

[0005] Patent Document 1: JP 2022-535367 A

[0006] Patent Document 2: JP 2022-535725 A Summary of the Invention

[0007] (The problem the invention aims to solve)

[0008] At the same time, in recent years, from the perspective of social sustainability, it is necessary to increase the proportion of so-called sustainable materials, such as materials derived from biological resources (biomass resources) and materials derived from renewable resources, in the various components that make up tires.

[0009] However, the use of sustainable materials in synthetic rubber blends for use in tires has not been adequately studied to date, and it is necessary to promote the reduction of environmental impact when considering the entire process of synthetic rubber production, use and disposal.

[0010] Therefore, the object of this disclosure is to provide a rubber composition and tread rubber for tires that can increase the proportion of sustainable materials in tires and promote a reduction in environmental impact when considering the entire process of synthetic rubber production, use and disposal.

[0011] Furthermore, another object of this disclosure is to provide a tire that, when considering the entire process of the production, use, and disposal of synthetic rubber, promotes a reduction in environmental impact and increases the proportion of sustainable materials therein.

[0012] (Solutions for solving the problem)

[0013] The present disclosure provides a rubber composition for tires, tread rubber, and tires that address the aforementioned problems, and the key features of these components are as follows.

[0014] [1] A rubber composition for a tire comprising a rubber component (A), said rubber component (A) comprising an isoprene skeleton rubber (A1) and a synthetic rubber (A2), wherein

[0015] In 100 parts by weight of rubber component (A), the content of isoprene skeleton rubber (A1) is 10 parts by weight to 90 parts by weight, and the content of synthetic rubber (A2) is 90 parts by weight to 10 parts by weight, and

[0016] Synthetic rubber (A2) includes synthetic rubber (A2-1) supplied according to a mass balance method.

[0017] [2] The rubber composition for tires according to [1], wherein the synthetic rubber (A2) comprises at least one of the following: raw materials derived from plants, by-products derived from plants, raw materials obtained by recycling materials derived from plants, or raw materials obtained by recycling materials derived from fossil resources.

[0018] [3] The rubber composition for tires according to [1] or [2], wherein the synthetic rubber (A2) comprises 0.1% by mass to 99% by mass of synthetic rubber derived from biological resources and 99.9% by mass to 1% by mass of synthetic rubber derived from fossil resources.

[0019] [4] A rubber composition for tires according to any one of [1] to [3], further comprising resin (B).

[0020] [5] The rubber composition for tires according to [4], wherein the content of resin (B) is from 1 part by weight to 50 parts by weight relative to 100 parts by weight of rubber component (A).

[0021] [6] A tread rubber comprising a rubber composition for tires according to any one of [1] to [5].

[0022] [7] A tire comprising the tread rubber according to [6].

[0023] (The effect of the invention)

[0024] According to this disclosure, a rubber composition and tread rubber for tires can be provided, which can increase the proportion of sustainable materials in the tire and promote a reduction in environmental impact when the entire process of production, use and disposal of synthetic rubber is taken into account.

[0025] Furthermore, according to this disclosure, a tire can be provided that, when considering the entire process of the production, use, and disposal of synthetic rubber, promotes a reduction in environmental impact and increases the proportion of sustainable materials therein. Attached Figure Description

[0026] [ Figure 1 [ ] is a cross-sectional view of one embodiment of the tire according to this disclosure. Detailed Implementation

[0027] The following will describe in detail, based on examples of embodiments thereof, the rubber composition for tires, tread rubber and tires of this disclosure.

[0028] <Definition>

[0029] The compounds described in this specification may be derived in whole or in part from fossil resources, from biological resources such as plant resources, or from renewable resources such as waste tires. Furthermore, they may be derived from any mixture of two or more of fossil resources, biological resources, and renewable resources.

[0030] In this specification, "the ratio of sustainable materials" refers to the total mass percentage of materials derived from biological resources (biomass resources) to materials derived from renewable resources in the rubber composition, tread rubber, and tire intended for use in tires.

[0031] In this specification, the aforementioned biological resources (biomass resources) refer to carbon-neutral organic resources of biological origin, including, for example, those stored in the form of starch or cellulose, the bodies of animals grown by consuming plants, and products obtained through processing plants or animals, and excluding fossil resources (such as petroleum, coal, natural gas, etc.). Biological resources may be edible or inedible, but from the viewpoint of not competing with food and efficient resource utilization, inedible resources are preferred.

[0032] Specific examples of the aforementioned biological resources include, for example, cellulosic crops (pulp, hibiscus, wheat straw, rice straw, waste paper, papermaking residues, etc.), timber, charcoal, compost, kitchen waste, vegetable oil cake, aquatic product residues, livestock excrement, food waste, sewage sludge, natural rubber, cotton, oils (palm oil, castor oil, cottonseed oil, soybean oil, flaxseed oil, rapeseed oil, coconut oil), peanut oil, tall oil, corn oil, rice bran oil, safflower oil, sesame oil, olive oil, sunflower oil, palm kernel oil, camellia oil, jojoba oil, macadamia nut oil, tung oil, and coconut oil). Carbohydrate-based crops (corn, wheat, rice, rice husks, rice bran, old rice, tubers, buckwheat, cassava, sago palm, sugarcane, etc.), bagasse (i.e., the residue after extracting juice from sugarcane), soybeans, soybean residue (soybean milk), essential oils (pine oil, orange oil, eucalyptus oil, etc.), black liquor from pulp, and algae, etc., can also be used as biological resources in their processed forms (i.e., substances derived from biological resources). Processing methods include, for example, bioprocessing methods utilizing the action of microorganisms, plants, animals, or their tissue cultures; chemical processing methods utilizing acids, alkalis, catalysts, heat energy, light energy, etc.; and physical processing methods such as micronization, compression, microwave treatment, and electromagnetic wave treatment. In addition, substances extracted or purified from the above-mentioned biological resources or processed biological resources (i.e., substances derived from biological resources) can also be used as biological resources. 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 carbohydrates include sucrose, glucose, trehalose, fructose, lactose, galactose, xylose, allose, tarose, gulose, azoose, mannose, idole, arabinose, celery sugar, maltose, cellulose, starch, chitin, etc., derived from biological resources. Examples of proteins include compounds formed by linking amino acids (preferably L-amino acids) derived from biological resources, and also include oligopeptides such as dipeptides. Examples of amino acids include valine, leucine, isoleucine, arginine, lysine, asparagine, glutamine, phenylalanine, etc., derived from biological resources, wherein valine, leucine, isoleucine, arginine, and phenylalanine are preferred. Amino acids can be L-amino acids or D-amino acids, but L-amino acids are preferred from the viewpoint of natural abundance and ease of availability. Examples of fatty acids include butyric acid, palmitic acid, stearic acid, oleic acid, linoleic acid, linolenic acid, etc., derived from biological resources. Examples of fatty acid esters include vegetable oils, animal oils, and modified fats and oils derived from biological resources. Various materials and impurities can be mixed in these biological resources.

[0033] In this specification, the term "recycled resources" refers to resources obtained by regenerating products that have been used, collected but not used, or discarded. For example, resources obtained by regenerating waste rubber products, such as waste tires, may be mentioned as recycled resources.

[0034] Rubber compositions for tires

[0035] The rubber composition for tires according to this embodiment comprises a rubber component (A) comprising isoprene skeleton rubber (A1) and synthetic rubber (A2), wherein in 100 parts by weight of rubber component (A), the content of isoprene skeleton rubber (A1) is 10 to 90 parts by weight, and the content of synthetic rubber (A2) is 90 to 10 parts by weight. Furthermore, in the rubber composition for tires according to this embodiment, the synthetic rubber (A2) is characterized by comprising synthetic rubber (A2-1) supplied according to a mass balance method.

[0036] In the rubber composition for tires of this embodiment, the synthetic rubber (A2-1) supplied according to a mass balance method is a synthetic rubber with properties derived from biological or recycled resources, distributed to it through a mass balance method. Since the rubber composition for tires of this embodiment includes synthetic rubber (A2-1) supplied according to a mass balance method as at least a portion of synthetic rubber (A2), the proportion of sustainable materials is high. Therefore, by applying the rubber composition for tires of this embodiment to tires, the proportion of sustainable materials in tires can be improved. Furthermore, since the rubber composition for tires of this embodiment utilizes synthetic rubber (A2-1) supplied according to a mass balance method, a reduction in environmental impact can be promoted when considering the entire process of synthetic rubber production, use, and disposal.

[0037] Note that even when a rubber composition in which at least a portion of the synthetic rubber (A2) is supplied in a mass-balanced manner as synthetic rubber (A2-1) is applied to a tire, tire performance such as low fuel consumption (low loss) and wet grip (grip performance on wet surfaces) can be made equivalent.

[0038] (Rubber component (A))

[0039] The rubber composition for tires according to this embodiment comprises a rubber component (A), and the rubber component (A) imparts rubber elasticity to the composition. The sustainable ratio of the rubber component is preferably 30% by mass or more, more preferably 40% by mass or more, even more preferably 50% by mass or more, even more preferably 60% by mass or more, still more preferably 70% by mass or more, further preferably 80% by mass or more, even more preferably 90% by mass or more, and particularly preferably 100% by mass.

[0040] Here, the “sustainability ratio” of rubber component (A) refers to the total mass percentage of the rubber component (A) derived from biological resources (biomass resources) to the total mass percentage of the component derived from recycled resources.

[0041] As rubber component (A), rubber derived from biological resources and rubber derived from recycled resources are preferred.

[0042] Here, the proportion of the monomeric component derived from biological resources in the 100 mol% composition of 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, even more preferably 90 mol% or more, particularly preferably 95 mol% or more, and may be 100 mol%.

[0043] Furthermore, the proportion of monomer components derived from recycled resources in the 100 mol% composition of 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, even more preferably 90 mol% or more, particularly preferably 95 mol% or more, and may be 100 mol%.

[0044] The rubber component (A) is a component that facilitates 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, even more preferably 200,000 or more, and also preferably 5,000,000 or less, more preferably 2,000,000 or less, even more preferably 1,500,000 or less, and even more preferably 1,300,000 or less.

[0045] Note that in this specification, the weight-average molecular weight (Mw) of the rubber component (A) can be determined, for example, by converting measurements obtained using gel permeation chromatography (GPC) (GPC-8000 series manufactured by Tosoh Corporation, detector: differential refractometer, column: TSKGEL SUPERMULTIPORE HZ-M manufactured by Tosoh Corporation) to standard polystyrene.

[0046] In the rubber composition for tires of this embodiment, rubber component (A) comprises isoprene skeleton rubber (A1) and synthetic rubber (A2).

[0047] In this specification, synthetic isoprene-based rubber is not included in synthetic rubber (A2), but rather in isoprene-based rubber (A1). In other words, in this specification, "synthetic rubber (A2)" refers to synthetic rubber other than synthetic isoprene-based rubber.

[0048] -Isoprene-backbone rubber (A1)-

[0049] Examples of isoprene-based skeletal rubbers (A1) include natural rubber (NR), synthetic isoprene rubber (IR), modified natural rubber (modified NR), modified natural rubber (modified NR), and modified synthetic isoprene rubber (modified IR). As natural rubber (NR), for example, RSS #3, TSR20 (e.g., SIR20 or STR20), and other types commonly used in the tire industry can be used. There are no particular restrictions on the source of natural rubber (NR), and examples include those derived from the Para rubber tree, galbanum, and Russian dandelion, etc. As for synthetic isoprene rubber (IR), there are no particular restrictions, and for example, IR2200 and other types commonly used in the tire industry can be used. Examples of modified NR include deproteinized natural rubber (DPNR) and high-purity natural rubber (UPNR), etc. Examples of modified NR include epoxidized natural rubber (ENR), hydrogenated natural rubber (HNR), and grafted natural rubber, etc. Examples of modified IR include epoxidized isoprene rubber, hydrogenated isoprene rubber, and grafted isoprene rubber. These isoprene skeleton rubbers can be used alone or in combination of two or more. Among them, NR is preferred as the isoprene skeleton rubber.

[0050] The sustainability ratio of the isoprene skeleton rubber (A1) is preferably 30% by mass or more, more preferably 40% by mass or more, even more preferably 50% by mass or more, even more preferably 60% by mass or more, still 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 100% by mass.

[0051] To ensure the sustainability ratio of the isoprene-based rubber (A1) is within the aforementioned 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 the monomer component. In this case, the synthesized polymer may be a homopolymer of monomers derived from biological resources, a homopolymer of monomers derived from recycled resources, a copolymer of monomers derived from biological resources and monomers derived from recycled resources, or a copolymer of monomers derived from biological resources and / or monomers derived from recycled resources and monomers derived from fossil resources (e.g., petroleum).

[0052] The content of isoprene reinforcing rubber (A1) is 10 to 90 parts by mass, preferably 20 to 80 parts by mass, per 100 parts by mass of rubber component (A). When the content of isoprene reinforcing rubber (A1) is 10 parts by mass or more per 100 parts by mass of rubber component (A), the tensile strength of the rubber composition can be improved, and the durability of the tire using the rubber composition can be improved. Furthermore, when the content of isoprene reinforcing rubber (A1) is 90 parts by mass or less per 100 parts by mass of rubber component (A), the content of synthetic rubber (A2) described below can be set to 10 parts by mass or more, and by blending isoprene reinforcing rubber (A1) with synthetic rubber (A2) as desired for the purpose, it becomes easier to improve the performance of the tire using the rubber composition for the intended purpose.

[0053] -Synthetic Rubber (A2)-

[0054] Synthetic rubber (A2) is characterized by comprising synthetic rubber (A2-1) supplied according to a mass balance method. Synthetic rubber supplied according to a mass balance method (A2-1) is synthetic rubber to which characteristics derived from biological or recycled resources are allocated through a mass balance method. By comprising synthetic rubber to which characteristics derived from biological or recycled resources are allocated through a mass balance method, environmental impact can be reduced when considering the entire process of synthetic rubber production, use, and disposal.

[0055] The content of synthetic rubber (A2) in 100 parts by weight of rubber component (A) is preferably 10 to 90 parts by weight, more preferably 20 to 80 parts by weight. When the content of synthetic rubber (A2) in 100 parts by weight of rubber component (A) is 10 parts by weight or more, it becomes easier to improve the performance of the tire using the rubber composition for the intended purpose by blending it with the aforementioned isoprene reinforcing rubber (A1). Furthermore, when the content of synthetic rubber (A2) in 100 parts by weight of rubber component (A) is 90 parts by weight or less, the content of the aforementioned isoprene reinforcing rubber (A1) can be set to 10 parts by weight or more, which can improve the tensile strength of the rubber composition and improve the durability of the tire using the rubber composition.

[0056] Furthermore, the proportion of synthetic rubber (A2-1) supplied in the synthetic rubber (A2) according to the mass balance method is preferably 10 to 90% by mass, and more preferably 20 to 80% by mass. When the proportion of synthetic rubber (A2-1) supplied in the synthetic rubber (A2) according to the mass balance method is 10% by mass or more, the ratio of sustainable materials in the tire using the rubber composition can be further improved.

[0057] As a certification method for balancing quality, ISCC PLUS certification can be mentioned. ISCC PLUS certification can certify bio-based raw materials, circular raw materials, and renewable raw materials, among which circular raw materials can be classified into bio-circular and non-bio-circular.

[0058] The aforementioned bio-based and renewable raw materials are derived from unused biomass from related industries including agriculture, forestry, and fisheries / aquaculture, and examples include fermented or biodegradable portions of products such as corn, sugarcane, and rapeseed.

[0059] The aforementioned circular raw materials are materials from the beginning of the supply chain, considered waste / treatment residues, but not landfilled or used for energy purposes; rather, they are raw materials that have been reused or recycled. Within circular raw materials, "bio-circulation" refers to the biodegradable portions of waste and residues from biological sources, including those from related industries such as agriculture, forestry, and fisheries / aquaculture, as well as industrial and municipal waste. Examples include waste cooking oil (UCO: used cooking oil), tall oil (a mixture of fatty acids, resinous acids, unsaponifiables, etc., produced as a byproduct when digesting pulp raw materials and separating fibers during pulp production), and food waste. On the other hand, "non-bio-circulation" refers to raw materials derived from non-biological recyclable materials (fossil-based) through mechanical and / or chemical processing, and examples include plastic waste and used tires.

[0060] Furthermore, plant-derived raw materials are preferred as the aforementioned bio-based raw materials, and raw materials obtained from plant-derived byproducts, raw materials obtained through recycling plant-derived materials, and raw materials obtained through recycling fossil resources are preferred as the aforementioned recycled raw materials. In other words, it is preferred that the synthetic rubber (A2) comprises synthetic rubber derived from at least one type of plant-derived raw material, plant-derived byproducts, raw materials obtained through recycling plant-derived materials, or raw materials obtained through recycling fossil resources. Since plant-derived raw materials, plant-derived byproducts, raw materials obtained through recycling plant-derived materials, and raw materials obtained through recycling fossil resources are readily available, it is easy to ensure quantities, and when considering the entire process of synthetic rubber production, use, and disposal, a rubber composition for tires comprising synthetic rubber (A2) derived from at least one of these raw materials can greatly contribute to reducing environmental impact.

[0061] The synthetic rubber (A2) preferably comprises both synthetic rubber derived from biological resources and synthetic rubber derived from fossil resources. Here, it is preferred that the synthetic rubber (A2) comprises 0.1 to 99% by mass of synthetic rubber derived from biological resources and 99.9 to 1% by mass of synthetic rubber derived from fossil resources. By including more than 0.1% by mass of synthetic rubber derived from biological resources in the synthetic rubber (A2), the proportion of sustainable materials in the tires using the rubber composition can be significantly improved, and by including more than 1% by mass of synthetic rubber derived from fossil resources in the synthetic rubber (A2), the flexibility of the source of the synthetic rubber (A2) is improved, making the production of the rubber composition easier. Therefore, the rubber composition for tires in which the synthetic rubber (A2) comprises 0.1 to 99% by mass of synthetic rubber derived from biological resources and 99.9 to 1% by mass of synthetic rubber derived from fossil resources exhibits an excellent balance between reducing environmental impact and productivity.

[0062] Examples of synthetic rubber (A2) include butadiene-based rubbers, such as butadiene rubber (BR) and aromatic vinyl compound-butadiene copolymer rubbers (e.g., styrene-butadiene rubber (SBR)). Here, the term "butadiene-based rubber" refers to rubber containing units derived from butadiene as monomer units. Furthermore, it is preferred that the butadiene used as a raw material for butadiene-based rubber is derived from biological or renewable resources.

[0063] Examples of butadiene rubber (BR) include, for example, high-cis butadiene rubber, low-cis butadiene rubber, and butadiene rubber containing syndiotactic polybutadiene crystals. Commercially available products can be used as butadiene rubber (BR), and examples of such commercially available products include those manufactured by UBE Elastomer Co., Ltd., ENEOS Materials Corporation, Asahi Kasei Corporation, and Zeon Corporation. These butadiene rubbers can be used alone or in combination of two or more.

[0064] Examples of aromatic vinyl compound-butadiene copolymer rubbers (e.g., SBRs) include, for example, emulsion-polymerized aromatic vinyl compound-butadiene copolymer rubbers (e.g., emulsion-polymerized styrene-butadiene rubber (E-SBR)) and solution-polymerized aromatic vinyl compound-butadiene copolymer rubbers (e.g., solution-polymerized styrene-butadiene rubber (S-SBR)). In aromatic vinyl compound-butadiene copolymer rubbers, examples of aromatic vinyl compounds (aromatic vinyl monomers) include styrene, vinylnaphthalene, and divinylnaphthalene. These aromatic vinyl compounds can be used alone or in combination of two or more. Styrene is preferred, and styrene derived from biological resources and styrene derived from recycled resources are particularly preferred. That is, SBR is preferred as an aromatic vinyl compound-butadiene copolymer rubber. Note that styrene may have substituents. Commercially available products can be used as aromatic vinyl compound-butadiene copolymer rubbers, and examples of such commercially available products include those manufactured by companies such as Asahi Kasei Corporation, ENEOSMaterials Corporation, Zeon Corporation, and Sumitomo Chemical Co., Ltd. These aromatic vinyl compound-butadiene copolymer rubbers can be used alone or in combination of two or more.

[0065] The sustainable ratio of butadiene-based rubber is preferably 30% by mass or more, more preferably 40% by mass or more, even more preferably 50% by mass or more, even more preferably 60% by mass or more, still 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 100% by mass.

[0066] To ensure the sustainability ratio of butadiene-based rubbers falls within the aforementioned range, it is sufficient, for example, to use polymers synthesized using butadiene derived from biological resources, butadiene derived from recycled resources, aromatic vinyl compounds derived from biological resources (e.g., styrene derived from biological resources), or aromatic vinyl compounds derived from recycled resources (e.g., styrene derived from recycled resources) as monomer components. In this case, the synthesized polymer can be a homopolymer of monomers derived from biological resources, a homopolymer of monomers derived from recycled resources, a copolymer of monomers derived from biological resources and monomers derived from recycled resources, or a copolymer of monomers derived from biological resources and / or monomers derived from recycled resources and monomers derived from fossil resources (e.g., petroleum). Note that the terms “butadiene rubber (B-BR) derived from biological resources (biomass resources)” and “aromatic vinyl compound-butadiene copolymer rubber (e.g., styrene-butadiene rubber (B-SBR) derived from biological resources (biomass resources)” include not only rubber obtained by polymerizing butadiene and the like according to conventional methods, but also rubber obtained by using reactions or enzymatic reactions of microorganisms, plants, animals and their tissue cultures (hereinafter also referred to as “microorganisms, etc.”).

[0067] In addition, in order to set the sustainability ratio of the entire rubber component (A) within the above-mentioned range, it is preferable to use natural rubber (NR) as rubber component (A), or to use a polymer synthesized using monomer components derived from biological resources or monomer components derived from recycled resources as monomer components.

[0068] Typically, the materials used in tire rubber compositions (rubber and its monomers, fillers, resins, etc.) require large-scale manufacturing equipment and are usually produced in large factories within a specific region, necessitating significant energy expenditure for storing and transporting raw materials and products. In contrast, materials derived from biological resources (biomass resources) originate from agricultural products, forests, etc., within each region and can also be produced on a small scale through microbial fermentation or catalytic reactions. Therefore, by utilizing local products or waste, the energy required for transporting and storing raw materials can be reduced, and furthermore, the energy required for transporting and storing manufactured materials to tire factories is also reduced, making it environmentally friendly. Furthermore, materials derived from recycled resources can be obtained, for example, by dismantling and pyrolyzing waste tires to extract the materials that constitute the tires, such as rubber, fillers, and steel cords. Furthermore, sulfur can be obtained from biological resources or their processed products through a method that includes a desulfurization step to remove sulfur-containing substances from biological resources or their processed products, a recovery step to recover sulfur from the desulfurization residues generated in the desulfurization step, and a processing step to process the recovered sulfur into sulfur for vulcanization (e.g., the method described in Japanese Patent Application No. 2022-140390). Therefore, materials for rubber compositions used in tires can be obtained from various wastes or recycled materials. In this way, by using sustainable materials (materials derived from biological resources or materials derived from recycled resources), the environmental impact of tire manufacturing can be comprehensively reduced, such as reducing carbon dioxide emissions (LCCO2) throughout the entire life cycle, reducing energy consumption (LCE) throughout the entire life cycle, reducing costs (LCC) throughout the entire life cycle, and reducing the use of fossil resources.

[0069] Furthermore, when manufacturing rubber compositions, the ratio of monomer components derived from biological resources, recycled resources, and fossil resources (e.g., monomer components derived from fossil resources) can be appropriately selected based on the availability of biological resources, recycled resources, and fossil resources (e.g., demand for biological resources as food) and / or market demand (e.g., demand for biological resources as food). By polymerizing these monomer components, rubber derived from sustainable materials (either biologically derived or recycledly derived) can be obtained, exhibiting properties comparable to conventional synthetic rubber. Note that when using monomer components derived from recycled resources, it may be difficult to separate them from those derived from fossil resources due to the monomer manufacturing process. In such cases, the environmental impact can be assessed using a mass balance approach.

[0070] The ratio of each monomer unit (e.g., units derived from isoprene, units derived from butadiene, and units derived from aromatic vinyl compounds) in the entire rubber component (A) can be appropriately adjusted according to the component to which it is applied. The ratio of each monomer unit in the entire rubber component can be adjusted, for example, by appropriately combining the aforementioned isoprene-based rubber and butadiene-based rubber. Furthermore, the ratio of cis-bonded units in the butadiene-derived units can also be appropriately adjusted according to the component to which it is applied.

[0071] In this specification, the term "monomer unit" means a structural unit of a polymer, "unit derived from isoprene" means a structural unit in a polymer based on isoprene as a monomer (including isoprene units in natural rubber), "unit derived from butadiene" means a structural unit in a polymer based on butadiene as a monomer, and "unit derived from aromatic vinyl compounds" means a structural unit in a polymer based on aromatic vinyl compounds as monomers.

[0072] In this specification, the ratio of each monomer unit is measured by NMR.

[0073] In addition to the aforementioned isoprene skeleton rubber (A1), butadiene rubber (BR), and aromatic vinyl compound-butadiene copolymer rubber (e.g., SBR), rubber component (A) may further include diene rubbers, such as acrylonitrile-butadiene rubber (NBR), chloroprene rubber (CR), butyl rubber (IIR), and styrene-isoprene-butadiene copolymer rubber (SIBR). These rubber components may be used alone or in combination of two or more.

[0074] The rubber component (A) can be modified to introduce functional groups that interact with fillers such as carbon black and silica. Examples of such functional groups include amino, amide, isocyanate, imino, imidazole, urea, ammonium, imide, hydrazine, azo, diazo, carboxyl, nitrile, pyridinyl, alkoxy, hydroxy, oxygen, epoxy, ether, carbonyl, oxycarbonyl, silyl, alkoxysilyl, mercapto, thioether, disulfide, sulfonyl, sulfinyl, thiocarbonyl, etc., and these functional groups may have substituents. These functional groups can be introduced into the rubber component alone or in combination of two or more. Among them, amino, alkoxy, and alkoxysilyl are preferred, and more preferably, substituted amino groups in which the hydrogen atom of the amino group is replaced by an alkyl group having 1 to 6 carbon atoms, an alkoxy group having 1 to 6 carbon atoms, or an alkoxysilyl group having 1 to 6 carbon atoms.

[0075] Functional groups can be introduced, for example, by reacting the rubber component with a compound (modifier) ​​having such functional groups. Functional groups are modifying functional groups that interact with fillers such as silica and carbon black, and examples include nitrogen-containing, silicon-containing, and oxygen-containing functional groups. Examples of compounds (modifiers) having nitrogen-containing functional groups include amino-containing compounds; examples of compounds (modifiers) having silicon-containing functional groups include silicon halides and alkyloxysilane compounds; and examples of compounds (modifiers) having oxygen-containing functional groups include alkoxy-containing compounds, alkyleneoxy-containing compounds, and trialkylsiloxy-containing compounds. More specifically, reference may be made to the compounds described in WO 2016 / 194316 A1 and WO 2019 / 117256 A1. These modifiers can be used alone or in combination of two or more.

[0076] Rubber derived from sustainable materials (materials derived from biological resources or materials derived from recycled resources) (particularly, synthetic rubber supplied according to a mass balance method (A2-1)) can be produced, for example, by using monomer components derived from biological resources or monomer components derived from recycled resources, and, if necessary, monomer components derived from fossil resources, in the same manner as conventional methods for producing synthetic rubber derived from fossil resources. Furthermore, rubber derived from sustainable materials (particularly, rubber derived from biological resources) can also be obtained through reactions or enzymatic reactions using microorganisms, etc.

[0077] Note that even if a portion of the monomer components in synthetic rubber (A2-1) supplied by allocating characteristics derived from biological resources or recycled resources according to a mass balance method originates from fossil resources, the sustainable material ratio [the total mass ratio of materials derived from biological resources (biomass resources) to materials derived from recycled resources] can be treated as 100% by mass. Because it is a mass balance method, even if a portion of the monomer components in synthetic rubber (A2-1) supplied by allocating characteristics derived from biological resources or recycled resources originates from fossil resources, synthetic rubber with a portion of monomer components derived from biological resources or recycled resources, and synthetic rubber with characteristics derived from fossil resources and treated as having a sustainable material ratio of 0% by mass, are supplied separately from synthetic rubber (A2-1). Therefore, by using synthetic rubber (A2-1), it is possible to greatly help reduce the overall environmental impact of synthetic rubber production, use, and disposal.

[0078] As a method for preparing bio-derived rubber from the aforementioned biological resources, the method described in JP 2022-179158 A can be used, for example. For instance, by using butadiene obtained from biological resources as a monomer component, butadiene rubber (B-BR) derived from biological resources (biomass resources) can be obtained, and by using styrene obtained from biological resources and butadiene obtained from biological resources as monomer components, styrene-butadiene rubber (B-SBR) derived from biological resources (biomass resources) can be obtained. Here, as methods for obtaining B-BR and B-SBR from biological resources, in addition to artificial polymerization, methods such as in vivo polymerization and polymerization using biologically derived enzymes can also be mentioned. The molecular weight, branching, and microstructure of the obtained B-BR and B-SBR can be appropriately adjusted by changing the polymerization conditions according to the desired tire performance using known methods.

[0079] Butadiene derived from biological resources may appropriately be derived from alkyl alcohols (preferably ethanol and butanol, more preferably butanol), olefins (preferably ethylene), and unsaturated carboxylic acids (preferably tiglic acid). These butadienes may be used in combination of two or more.

[0080] As styrene obtained from biological resources, styrene obtained from plants (preferably plants belonging to the Hamamelidaceae, Styraxaceae, or Apocynaceae families, more preferably plants belonging to the Liquidambar, Benzoin, or Vinca minor genera, and even more preferably plants belonging to the Liquidambar formosana, Jasminum nudiflorum, or Vinca minor genera) and styrene obtained from microorganisms (preferably microorganisms belonging to the Penicillium or Escherichia spp. genera, more preferably Penicillium citrinum or transformed Escherichia coli) can be used. These styrene products can also be used in combination of two or more.

[0081] Recently, plans have been made for biomass complexes centered on bioethanol and bioethylene. However, bioethanol and bioethylene are primarily produced using carbohydrates and / or cellulose as biological resources, and cannot effectively utilize other biological resources such as proteins, lipids, and amino acids. Furthermore, carbohydrates compete with food sources, and the overuse of cellulose leads to deforestation. Therefore, in addition to considering the availability of various biological resources, renewable resources, fossil resources, and market demand (e.g., demand for biomass resources as food), it is preferable to use multiple monomeric components derived from biological resources, or to use a combination of monomeric components derived from biological resources, renewable resources, and fossil resources, and further appropriately adjust the ratio of these monomeric components. In this way, a wide range of biological resources (e.g., carbohydrates, proteins, and lipids), as well as renewable resources, can be effectively utilized without relying on a single biological resource to stably supply rubber derived from sustainable materials, and, moreover, the environment is considered according to the circumstances at the time of production.

[0082] When using multiple monomeric components derived from biological resources, it is preferable to use monomeric components derived from different biological resources, i.e., monomeric components obtained from different biological resources. Specifically, as butadiene derived from biological resources, it is preferable to use a mixture of butadiene derived from multiple different biological resources, and / or as styrene derived from biological resources, it is preferable to use a mixture of styrene derived from multiple different biological resources. In this way, multiple biological resources can be utilized effectively.

[0083] --Styrene-butadiene rubber (SBR)--

[0084] Preferably, the synthetic rubber (A2) comprises styrene-butadiene rubber (SBR). By including styrene-butadiene rubber as the synthetic rubber (A2) in the rubber component (A), both the high fuel economy and wear resistance of the tire using the rubber composition can be improved.

[0085] The glass transition temperature of styrene-butadiene rubber is preferably less than -40°C. When the glass transition temperature of styrene-butadiene rubber is below -40°C, both the fuel economy and wear resistance of tires using the rubber composition can be further improved. From the viewpoint of further improving the fuel economy of tires, the glass transition temperature of styrene-butadiene rubber is more preferably below -45°C, and even more preferably below -50°C.

[0086] Furthermore, the glass transition temperature of styrene-butadiene rubber is preferably higher than -90°C. Styrene-butadiene rubber with a glass transition temperature higher than -90°C is easier to synthesize.

[0087] The styrene-butadiene rubber content is preferably 10 parts by mass or more, more preferably 20 parts by mass or more, even more preferably 30 parts by mass or more, even more preferably 40 parts by mass or more, and most preferably 50 parts by mass or more, and preferably 90 parts by mass or less, more preferably 80 parts by mass or less, per 100 parts by mass of rubber component (A). When the styrene-butadiene rubber content is 50 to 80 parts by mass of rubber component (A) per 100 parts by mass, both the high fuel economy and wet road grip performance of the tire using the rubber composition can be further improved.

[0088] The styrene content in the styrene-butadiene rubber is preferably less than 15% by mass. The styrene content in the styrene-butadiene rubber refers to the proportion of styrene units contained in the styrene-butadiene rubber. When the styrene content in the styrene-butadiene rubber is less than 15% by mass, the glass transition temperature tends to be lower. The styrene content in the styrene-butadiene rubber is more preferably 14% by mass or less, even more preferably 13% by mass or less, and most preferably 12% by mass or less. Furthermore, from the viewpoint of the abrasion resistance of tires using the rubber composition, the styrene content in the styrene-butadiene rubber is preferably 5% by mass or more, more preferably 7% by mass or more, and most preferably 8% by mass or more.

[0089] The styrene content in styrene-butadiene rubber can be adjusted by the amount of monomers used in the polymerization of styrene-butadiene rubber and the degree of polymerization.

[0090] Styrene-butadiene rubber is preferably modified with modifiers containing nitrogen-containing functional groups and alkoxy groups. When styrene-butadiene rubber is modified with modifiers containing nitrogen-containing functional groups and alkoxy groups, the balance between wet road grip, high fuel economy and wear resistance of tires using the rubber composition is further improved, and in particular, high fuel economy and wear resistance can be further enhanced.

[0091] Modifiers having nitrogen-containing functional groups and alkoxy groups are a general term for modifiers having at least one nitrogen-containing functional group and at least one alkoxy group.

[0092] Nitrogen-containing functional groups are preferably selected from the following:

[0093] The monovalent hydrocarbon group comprising 1 to 30 carbon atoms of a straight-chain, branched, alicyclic, or aromatic ring, and a monovalent hydrocarbon group also comprising 1 to 30 carbon atoms of a straight-chain, branched, alicyclic, or aromatic ring and optionally having at least one heteroatom selected from oxygen, sulfur, and phosphorus atoms, the monovalent hydrocarbon group comprising a functional group selected from the group consisting of a primary amino group, a primary amino group protected by a hydrolyzable protecting group, an onium salt residue of a primary amine, an isocyanate group, a thioisocyanate group, an imino group, an imine group, an amide group, a secondary amino group protected by 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, a triisocyanate residue, a cyclic tertiary amino group, an acyclic tertiary amino group, a nitrile group, a pyridyl group, an onium salt residue of a cyclic tertiary amine, and an onium salt residue of an acyclic tertiary amine.

[0094] ---First Preferred Embodiment of Modified Styrene-Butadiene Rubber---

[0095] Styrene-butadiene rubber (SBR) is preferably modified with aminoalkoxysilane compounds, and from the viewpoint of high affinity for fillers, it is more preferably modified with aminoalkoxysilane compounds at the ends. When the ends of styrene-butadiene rubber are modified with aminoalkoxysilane compounds, the interaction between the modified styrene-butadiene rubber and the filler (especially silica) becomes particularly strong.

[0096] The modification sites for styrene-butadiene rubber can be the molecular ends as described above, or they can be the main chain.

[0097] Styrene-butadiene rubber with modified molecular ends can be produced, for example, by reacting various modifiers with the ends of a styrene-butadiene copolymer having active ends, according to the methods described in International Publication No. 2003 / 046020 and JP 2007-217562 A.

[0098] In a preferred embodiment, the styrene-butadiene rubber with modified molecular ends can be produced by reacting an aminoalkoxysilane compound with the ends of a styrene-butadiene copolymer having an active end containing more than 75% cis-1,4 bonds, according to the methods described in International Publication No. 2003 / 046020 and JP 2007-217562 A, and then stabilizing it by reacting it with a carboxylic acid ester of a polyol.

[0099] The carboxylic acid ester of a polyol refers to a ester of a polyol and a carboxylic acid, and specifically means a ester having at least one hydroxyl group. Specifically, esters of sugars or modified sugars having 4 or more carbon atoms and fatty acids are preferred. More preferably, the ester is (1) a fatty acid ester of a polyol, particularly a ester (monoester, diester, or triester) of a saturated or unsaturated higher fatty acid having 10 to 20 carbon atoms and a polyol, or (2) an ester compound in which the ester of a polycarboxylic acid and a higher alcohol is bonded to the polyol by 1 to 3 units.

[0100] Polyols used as raw materials for esterification include sugars, glycols, and polyhydroxy compounds having 5 or 6 carbon atoms and at least three hydroxyl groups (which may or may not be hydrogenated). As raw fatty acids, saturated or unsaturated fatty acids with 10 to 20 carbon atoms are preferred, and examples include stearic acid, lauric acid, and palmitic acid.

[0101] Among the fatty acid esters of polyols, sorbitol fatty acid esters are preferred, and specific examples include sorbitol monolaurate, sorbitol monopalmitate, sorbitol monostearate, sorbitol tristearate, sorbitol monooleate, and sorbitol trioleate.

[0102] There are no particular limitations on aminoalkoxysilane compounds, but aminoalkoxysilane compounds represented by the following general formula (i) are preferred.

[0103] R 11 a -Si-(OR 12 )4- a ··· (i)

[0104] In general formula (i), R 11 and R 12 Each can independently represent a monovalent aliphatic hydrocarbon group having 1 to 20 carbon atoms or a monovalent aromatic hydrocarbon group having 6 to 18 carbon atoms, R 11 and R 12 At least one of the nucleotides is substituted with an amino group, where a is an integer from 0 to 2, and when multiple ORs exist... 12 At that time, each OR 12 They can be the same or different, and the molecules do not contain active protons.

[0105] As aminoalkoxysilane compounds, aminoalkoxysilane compounds represented by the following general formula (ii) are also preferred.

[0106] [Chemical Formula 1]

[0107]

[0108] In general formula (ii), n1+n2+n3+n4=4 (where n2 is an integer from 1 to 4, and n1, n3 and n4 are integers from 0 to 3).

[0109] A 1 It is at least one functional group selected from the group consisting of saturated cyclic tertiary amine residues, unsaturated cyclic tertiary amine residues, ketimine residues, nitrile groups, (thio)isocyanate groups, isocyanurate trialkyl ester groups, nitrile groups, pyridyl groups, (thio)ketone groups, amide groups, and primary or secondary amino groups having hydrolyzable groups. When n4 is 2 or more, A 1 They can be the same or different, and A 1 It can be a divalent group that forms a cyclic structure with Si.

[0110] R 21 It is a monovalent aliphatic or alicyclic hydrocarbon group with 1 to 20 carbon atoms, or a monovalent aromatic hydrocarbon group with 6 to 18 carbon atoms, and when n1 is 2 or more, they can be the same or different.

[0111] R 22 It is a monovalent aliphatic or alicyclic hydrocarbon group with 1 to 20 carbon atoms, or a monovalent aromatic hydrocarbon group with 6 to 18 carbon atoms, and may contain nitrogen and / or silicon atoms. When n2 is 2 or more, R 22 They can be the same or different, or they can form a ring together.

[0112] R 23 It is a monovalent aliphatic or alicyclic hydrocarbon group with 1 to 20 carbon atoms, a monovalent aromatic hydrocarbon group with 6 to 18 carbon atoms, or a halogen atom, and when n3 is 2 or more, they can be the same or different.

[0113] R 24 It is a divalent aliphatic or alicyclic hydrocarbon group with 1 to 20 carbon atoms, or a divalent aromatic hydrocarbon group with 6 to 18 carbon atoms, and when n4 is 2 or more, they can be the same or different.

[0114] As the hydrolyzable group in a primary or secondary amino group having a hydrolyzable group, trimethylsilyl or tert-butyldimethylsilyl is preferred, and trimethylsilyl is particularly preferred.

[0115] The aminoalkoxysilane compound represented by the above general formula (ii) is preferably an aminoalkoxysilane compound represented by the following general formula (iii).

[0116] [Chemical Formula 2]

[0117]

[0118] In general formula (iii), p1+p2+p3=2 (where p2 is an integer from 1 to 2, and p1 and p3 are integers from 0 to 1).

[0119] A 2 It is NR a (where R) a It is a monovalent hydrocarbon group, a hydrolyzable group, or a nitrogen-containing organic group.

[0120] R 25 It is a monovalent aliphatic or alicyclic hydrocarbon group with 1 to 20 carbon atoms, or a monovalent aromatic hydrocarbon group with 6 to 18 carbon atoms.

[0121] R 26 It is a monovalent aliphatic or alicyclic hydrocarbon group with 1 to 20 carbon atoms, a monovalent aromatic hydrocarbon group with 6 to 18 carbon atoms, or a nitrogen-containing organic group, and may contain nitrogen atoms and / or silicon atoms. When p2 is 2, R 26 They can be the same or different, or they can form a ring together.

[0122] R 27 It is a monovalent aliphatic or alicyclic hydrocarbon group with 1 to 20 carbon atoms, a monovalent aromatic hydrocarbon group with 6 to 18 carbon atoms, or a halogen atom.

[0123] R 28 It is a divalent aliphatic or alicyclic hydrocarbon group with 1 to 20 carbon atoms, or a divalent aromatic hydrocarbon group with 6 to 18 carbon atoms.

[0124] As a hydrolyzable group, trimethylsilyl or tert-butyldimethylsilyl is preferred, and trimethylsilyl is particularly preferred.

[0125] The aminoalkoxysilane compound represented by the above general formula (ii) is also preferably an aminoalkoxysilane compound represented by the following general formula (iv) or the following general formula (v).

[0126] [Chemical Formula 3]

[0127]

[0128] In general formula (iv), q1 + q2 = 3 (where q1 is an integer from 0 to 2 and q2 is an integer from 1 to 3).

[0129] R 31 It is a divalent aliphatic or alicyclic hydrocarbon group with 1 to 20 carbon atoms, or a divalent aromatic hydrocarbon group with 6 to 18 carbon atoms.

[0130] R 32 and R 33Each can be independently represented as a hydrolyzable group, a monovalent aliphatic or alicyclic hydrocarbon group with 1 to 20 carbon atoms, or a monovalent aromatic hydrocarbon group with 6 to 18 carbon atoms.

[0131] R 34 It is a monovalent aliphatic or alicyclic hydrocarbon group with 1 to 20 carbon atoms, or a monovalent aromatic hydrocarbon group with 6 to 18 carbon atoms, and when q1 is 2, they can be the same or different.

[0132] R 35 It is a monovalent aliphatic or alicyclic hydrocarbon group with 1 to 20 carbon atoms, or a monovalent aromatic hydrocarbon group with 6 to 18 carbon atoms, and when q2 is 2 or more, they can be the same or different.

[0133] [Chemical Formula 4]

[0134]

[0135] In the general formula (v), r1 + r2 = 3 (where r1 is an integer from 1 to 3 and r2 is an integer from 0 to 2).

[0136] R 36 It is a divalent aliphatic or alicyclic hydrocarbon group with 1 to 20 carbon atoms, or a divalent aromatic hydrocarbon group with 6 to 18 carbon atoms.

[0137] R 37 It is dimethylaminomethyl, dimethylaminoethyl, diethylaminomethyl, diethylaminoethyl, methylsilyl(methyl)aminomethyl, methylsilyl(methyl)aminoethyl, methylsilyl(ethyl)aminomethyl, methylsilyl(ethyl)aminoethyl, dimethylsilylaminomethyl, dimethylsilylaminoethyl, or 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.

[0138] R 38 It is an alkyl group with 1 to 20 carbon atoms, a monovalent aliphatic or alicyclic hydrocarbon group with 1 to 20 carbon atoms, or a monovalent aromatic hydrocarbon group with 6 to 18 carbon atoms, and when r2 is 2, they can be the same or different.

[0139] Specific examples of aminoalkoxysilane compounds represented by general formula (v) include N-(1,3-dimethylbutylene)-3-triethoxysilyl-1-propylamine.

[0140] The aminoalkoxysilane compound represented by the above general formula (ii) is also preferably an aminoalkoxysilane compound represented by the following general formula (vi) or the following general formula (vii).

[0141] [Chemical Formula 5]

[0142]

[0143] In the general formula (vi), R 40 It is a trimethylsilyl group, a monovalent aliphatic or alicyclic hydrocarbon group with 1 to 20 carbon atoms, or a monovalent aromatic hydrocarbon group with 6 to 18 carbon atoms.

[0144] R 41 It is an alkyl group with 1 to 20 carbon atoms, a monovalent aliphatic or alicyclic hydrocarbon group with 1 to 20 carbon atoms, or a monovalent aromatic hydrocarbon group with 6 to 18 carbon atoms.

[0145] R 42 It is a divalent aliphatic or alicyclic hydrocarbon group with 1 to 20 carbon atoms, or a divalent aromatic hydrocarbon group with 6 to 18 carbon atoms.

[0146] Here, TMS stands for trimethylsilyl (which also applies below).

[0147] [Chemical Formula 6]

[0148]

[0149] In general formula (vii), R 43 and R 44 Each can be independently represented as a divalent aliphatic or alicyclic hydrocarbon group with 1 to 20 carbon atoms, or a divalent aromatic hydrocarbon group with 6 to 18 carbon atoms.

[0150] R 45 It is a monovalent aliphatic or alicyclic hydrocarbon group with 1 to 20 carbon atoms, or a monovalent aromatic hydrocarbon group with 6 to 18 carbon atoms, and each R 45 They can be the same or different.

[0151] The aminoalkoxysilane compound represented by the above general formula (ii) is also preferably an aminoalkoxysilane compound represented by the following general formula (viii) or the following general formula (ix).

[0152] [Chemical Formula 7]

[0153]

[0154] In general formula (viii), s1 + s2 = 3 (where s1 is an integer from 0 to 2 and s2 is an integer from 1 to 3).

[0155] R 46 It is a divalent aliphatic or alicyclic hydrocarbon group with 1 to 20 carbon atoms, or a divalent aromatic hydrocarbon group with 6 to 18 carbon atoms.

[0156] R 47 and R 48 Each R independently represents a monovalent aliphatic or alicyclic hydrocarbon group with 1 to 20 carbon atoms, or a monovalent aromatic hydrocarbon group with 6 to 18 carbon atoms. 47 or R 48 They can be the same or different.

[0157] [Chemical Formula 8]

[0158]

[0159] In the general formula (ix), X is a halogen atom.

[0160] R 49 It is a divalent aliphatic or alicyclic hydrocarbon group with 1 to 20 carbon atoms, or a divalent aromatic hydrocarbon group with 6 to 18 carbon atoms.

[0161] R 50 and R 51 Each can independently represent a hydrolyzable group, a monovalent aliphatic or alicyclic hydrocarbon group with 1 to 20 carbon atoms, or a monovalent aromatic hydrocarbon group with 6 to 18 carbon atoms, or R 50 and R 51 They bond together to form divalent organic groups.

[0162] R 52 and R 53 Each can independently represent a halogen atom, a hydrocarbon oxygen group, a monovalent aliphatic or alicyclic hydrocarbon group with 1 to 20 carbon atoms, or a monovalent aromatic hydrocarbon group with 6 to 18 carbon atoms.

[0163] Regarding R 50 and R 51 Hydrolyzable groups are preferred, and trimethylsilyl or tert-butyldimethylsilyl is preferred as a hydrolyzable group, with trimethylsilyl being particularly preferred.

[0164] The aminoalkoxysilane compound represented by the above general formula (ii) is also preferably an aminoalkoxysilane compound represented by the following general formula (x), the following general formula (xi), the following general formula (xii) or the following general formula (xiii).

[0165] [Chemical Formula 9]

[0166]

[0167] In general formulas (x) to (xiii), the symbols U and V are each integers from 0 to 2, satisfying U+V=2.

[0168] R in general formulas (x) to (xiii) 54 To R92 They can be the same or different, and are monovalent or divalent aliphatic or alicyclic hydrocarbon groups with 1 to 20 carbon atoms, or monovalent or divalent aromatic hydrocarbon groups with 6 to 18 carbon atoms.

[0169] In the general formula (xiii), α and β are integers from 0 to 5.

[0170] Among the compounds satisfying the general formulas (x), (xi), and (xii), particularly preferred are 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.

[0171] Among the compounds satisfying general formula (xiii), N,N-dimethyl-2-(3-(dimethoxymethylsilyl)propoxy)ethylamine; N,N-bis(trimethylsilyl)-2-(3-(trimethoxysilyl)propoxy)ethylamine; N,N-dimethyl-2-(3-(trimethoxysilyl)propoxy)ethylamine; and N,N-dimethyl-3-(3-(trimethoxysilyl)propoxy)propane-1-amine are particularly preferred.

[0172] ---Second Preferred Embodiment of Modified Styrene-Butadiene Rubber---

[0173] The aforementioned styrene-butadiene rubber (SBR) is also preferably modified with a coupling agent represented by the following general formula (I). In this case, the fuel economy and wear resistance of tires using the rubber composition can be further improved.

[0174] [Chemical Formula 10]

[0175]

[0176] In the above general formula (I), R 1 R 2 and R 3 Each can be used independently to represent a single bond or an alkylene group having 1 to 20 carbon atoms.

[0177] R 4 R 5 R 6 R 7 and R 9Each can be used independently to represent an alkyl group having 1 to 20 carbon atoms.

[0178] R 8 and R 11 Each can be used independently to represent an alkylene group having 1 to 20 carbon atoms.

[0179] R 10 It refers to alkyl or trialkylsilyl groups having 1 to 20 carbon atoms.

[0180] m represents an integer from 1 to 3, and p represents 1 or 2.

[0181] When there are multiple R 1 To R 11 When m and p are used, they are independent of each other.

[0182] i, j, and k each independently represent integers from 0 to 6. However, i+j+k is an integer from 3 to 10.

[0183] "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 not having active hydrogen.

[0184] Here, in general formula (I), the hydrocarbon group represented by A includes saturated, unsaturated, aliphatic, and aromatic hydrocarbon groups. Examples of organic groups that do not have active hydrogen include organic groups that do not have functional groups with active hydrogen, such as hydroxyl (-OH), secondary amino (>NH), primary amino (-NH2), and mercapto (-SH).

[0185] The styrene-butadiene rubber modified with the coupling agent represented by the above general formula (I) preferably has a weight-average molecular weight (Mw) of 20 × 10⁻⁶. 4 Up to 300×10 4 It contains 0.25 to 30% by mass of a substance with a molecular weight of 200 × 10⁻⁶, relative to the total amount of the modified styrene-butadiene rubber. 4 Up to 500×10 4 The modified styrene-butadiene rubber has a shrinkage factor (g') of less than 0.64.

[0186] Typically, when a polymer has branches, its molecular size tends to be smaller compared to a linear polymer with the same absolute molecular weight, and the aforementioned shrinkage factor (g') is an indicator of the ratio of molecular size to linear polymers with the assumed same absolute molecular weight. That is, as the degree of branching of the polymer increases, the shrinkage factor (g') tends to decrease. In this embodiment, intrinsic viscosity is used as an indicator of molecular size, and linear polymers are used as an indicator following the intrinsic viscosity [η] = –3.883M. 0.771The polymers with the relationship. Calculate the shrinkage factor (g') of the modified styrene-butadiene rubber at each absolute molecular weight, and set the absolute molecular weight to 100 × 10⁻⁶. 4 Up to 200×10 4 The average shrinkage factor (g') is defined as the shrinkage factor (g') of the modified styrene-butadiene rubber. Here, "branching" refers to a structure formed by the direct or indirect bonding of one polymer to another. "Degree of branching" refers to the number of polymers directly or indirectly bonded to a branch chain. For example, in the case where the five styrene-butadiene copolymer chains described later are indirectly bonded to each other via coupling residues described later, the degree of branching is 5. Coupling residues are the building blocks of the modified styrene-butadiene rubber bonded to the styrene-butadiene copolymer chains, and are, for example, structural units derived from coupling agents produced by reacting the styrene-butadiene copolymer with a coupling agent, as described later. Styrene-butadiene copolymer chains are the building blocks of the modified styrene-butadiene rubber, and are, for example, structural units derived from styrene-butadiene copolymers produced by reacting the styrene-butadiene copolymer with a coupling agent, as described later.

[0187] The shrinkage factor (g') is preferably less than 0.64, more preferably less than 0.63, even more preferably less than 0.60, further preferably less than 0.59, and even more preferably less than 0.57. There is no particular limitation on the lower limit of the shrinkage factor (g'), and it can be below the detection limit, but it 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 modified styrene-butadiene rubber having a shrinkage factor (g') within this range, the processability of the rubber composition is improved.

[0188] Since the shrinkage factor (g') tends to depend on the degree of branching, for example, the degree of branching can be used as an indicator to control the shrinkage factor (g'). Specifically, when the degree of branching of the modified styrene-butadiene rubber is 6, the shrinkage factor (g') tends to be above 0.59 and below 0.63, and when the degree of branching is 8, the shrinkage factor (g') tends to be above 0.45 and below 0.59.

[0189] The modified styrene-butadiene rubber modified with the coupling agent represented by the above general formula (I) preferably has branches and a branching degree of 5 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, the branching includes 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 such that the branching degree is 5 or more and the branching includes branches in which five or more styrene-butadiene copolymer chains are bonded to one coupling residue, the shrinkage factor (g') can be more reliably set to less than 0.64. The number of styrene-butadiene copolymer chains bonded to one coupling residue can be determined by the value of the shrinkage factor (g').

[0190] Furthermore, the modified styrene-butadiene rubber is more preferably branched with a branching degree of 6 or higher. 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, the branching 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 such that the branching degree is 6 or higher and the branching 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 lower.

[0191] Furthermore, the modified styrene-butadiene rubber is even more preferably branched with a branching degree of 7 or more, and even more preferably with a branching degree of 8 or more. There is no particular upper limit to the branching degree, but it is preferably 18 or less. The modified styrene-butadiene rubber preferably has one or more coupling residues and styrene-butadiene copolymer chains bonded to the coupling residues, and even more preferably, the branching includes branches in which 7 or more styrene-butadiene copolymer chains are bonded to one coupling residue, and particularly preferably, 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 such that the branching degree is 8 or more and the branching includes branches in which 8 or more styrene-butadiene copolymer chains are bonded to one coupling residue, the shrinkage factor (g') can be set to 0.59 or less.

[0192] Preferably, at least one end of the aforementioned styrene-butadiene copolymer chain is bonded to a silicon atom of the coupling residue. In this case, the ends of multiple styrene-butadiene copolymer chains may be bonded to a single silicon atom. Furthermore, the ends of the styrene-butadiene copolymer chains and alkoxy or hydroxyl groups having 1 to 20 carbon atoms may be bonded to a single silicon atom, and as a result, a single silicon atom may constitute an alkoxysilyl or silanol group having 1 to 20 carbon atoms.

[0193] The modified styrene-butadiene rubber described above can be an oil-extended rubber with added additive oil. The modified styrene-butadiene rubber can be non-oil-extended or oil-extended, but from the viewpoint of abrasion resistance, it is preferable to have a Mooney viscosity of 20 or more and 100 or less, and more preferably 30 or more and 80 or less, measured at 100°C.

[0194] The weight-average molecular weight (Mw) of the above-mentioned modified styrene-butadiene rubber is preferably 20 × 10⁻⁶. 4 Above and 300×10 4 Below, 50×10 is preferred. 4 The above, or even better, 64×10 4 The above, and further preferred 80×10 4 The above. The preferred weight-average molecular weight is 250 × 10⁻⁶. 4 The following is a further preferred size: 180×10 4 Below, and even more preferably 150×10 4 The following applies when the weight-average molecular weight is 20 × 10⁻⁶. 4 At the above levels, the low loss and abrasion resistance of the rubber composition can be significantly improved. When the weight-average molecular weight is 300 × 10⁻⁶... 4 The processability of the rubber composition is improved under the following conditions.

[0195] The modified styrene-butadiene rubber, relative to the total amount (100% by mass) of the modified styrene-butadiene rubber, preferably contains 0.25% by mass and 30% by mass of an element with a molecular weight of 200 × 10⁻⁶. 4 Above and 500×10 4 The modified styrene-butadiene rubber (hereinafter also referred to as "specific high molecular weight component") is described below. 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 and abrasion resistance properties of the rubber composition can be sufficiently improved. The modified styrene-butadiene rubber preferably contains 1.0% by mass or more, more preferably 1.4% by mass or more, even more preferably 1.75% by mass or more, even more preferably 2.0% by mass or more, particularly preferably 2.15% by mass or more, and extremely preferably 2.5% by mass or more of the specific high molecular weight component. The modified styrene-butadiene rubber preferably contains 28% by mass or less, more preferably 25% by mass or less, even more preferably 20% by mass or less, and even more preferably 18% by mass or less of the specific high molecular weight component.

[0196] Note that in this specification, the “molecular weight” of the rubber component refers to the equivalent molecular weight of standard polystyrene obtained by GPC (gel permeation chromatography). To obtain modified styrene-butadiene rubber with a specific high molecular weight component content within this range, it is preferable to control the reaction conditions in the polymerization and reaction steps described later. For example, in the polymerization step, the amount of the organic monolithium compound used as the polymerization initiator described later can be adjusted. In continuous or batch polymerization modes in the polymerization step, it is preferable to use a method with a residence time distribution, i.e., broadening the time distribution of the growth reaction.

[0197] In the modified styrene-butadiene rubber described above, the molecular weight distribution (Mw / Mn), expressed as the ratio of weight-average molecular weight (Mw) to number-average molecular weight (Mn), is preferably 1.6 or higher and 3.0 or lower. When the molecular weight distribution of the modified styrene-butadiene rubber is within this range, the processability of the rubber composition becomes good.

[0198] The production method of the above-mentioned modified styrene-butadiene rubber is not particularly limited, but preferably includes a polymerization step and a reaction step. In the polymerization step, an organic monolithium compound is used as a polymerization initiator to copolymerize butadiene and styrene to obtain a styrene-butadiene copolymer. In the reaction step, a reactive compound with five or more functions (hereinafter also referred to as a "coupling agent") reacts with the active ends of the styrene-butadiene copolymer.

[0199] The above polymerization step is preferably a polymerization via a growth reaction through active anionic polymerization, thereby obtaining a styrene-butadiene copolymer with active ends and a modified styrene-butadiene rubber with a high modification rate.

[0200] Styrene-butadiene copolymers are obtained by copolymerizing 1,3-butadiene and styrene.

[0201] The amount of the organic monolithium compound used as the polymerization initiator is preferably determined based on the molecular weight of the target styrene-butadiene copolymer or modified styrene-butadiene rubber. The amount of monomers, such as 1,3-butadiene and styrene, relative to the amount of polymerization initiator is related to the degree of polymerization, i.e., to the number-average molecular weight and / or weight-average molecular weight. Therefore, to increase the molecular weight, the amount of polymerization initiator can be adjusted in the decreasing direction, and to decrease the molecular weight, the amount of polymerization initiator can be adjusted in the increasing direction.

[0202] From the viewpoint of industrial availability and ease of controlling the polymerization reaction, organo-monolithium compounds are preferably alkyl-lithium compounds. In this case, styrene-butadiene copolymers having alkyl groups at the polymerization initiation terminal can be obtained. Examples of alkyl-lithium compounds include n-butyllithium, sec-butyllithium, tert-butyllithium, n-hexyllithium, benzyllithium, phenyllithium, and stilbenelithium. From the viewpoint of industrial availability and ease of controlling the polymerization reaction, n-butyllithium and sec-butyllithium are preferred among alkyl-lithium compounds. These organo-monolithium compounds can be used alone or in combination of two or more.

[0203] Examples of polymerization reaction modes in the above polymerization steps include batch and continuous processes. In a continuous process, one or more reactors connected together can be used. For example, a tank-type or tubular reactor with a stirrer can be used as a continuous reactor. Preferably, monomers, inert solvents, and polymerization initiators are continuously fed into the reactor, a polymer solution containing the polymer is obtained in the reactor, and the polymer solution is continuously discharged. For example, a tank-type reactor with a stirrer can be used as a batch reactor. Preferably, monomers, inert solvents, and polymerization initiators are fed, and monomers can be added continuously or intermittently during polymerization as needed, a polymer solution containing the polymer is obtained in the reactor, and the polymer solution is discharged after polymerization is complete. In this embodiment, a continuous process that allows for continuous discharge of polymer and supply to the next reaction within a short time is preferred in order to obtain a styrene-butadiene copolymer with a high proportion of active ends.

[0204] The polymerization steps described above are preferably carried out in an inert solvent. Examples of solvents include hydrocarbon solvents, such as saturated hydrocarbons and aromatic hydrocarbons. Specific examples of 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 mixtures thereof. By treating the propylene and acetylene compounds, which are impurities, with organometallic compounds prior to the polymerization reaction, it is preferable to obtain styrene-butadiene copolymers with high concentrations of active ends and modified styrene-butadiene rubbers with high modification rates.

[0205] In the polymerization steps described above, polar compounds can be added. By adding polar compounds, styrene can be randomly copolymerized with 1,3-butadiene, and polar compounds also tend to act as vinylizing agents to control the microstructure of the 1,3-butadiene moiety.

[0206] Examples of polar compounds include, but are not limited to, 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-oxacyclopentyl)propane; tertiary amine compounds such as tetramethylethylenediamine, dipiperidinylethane, trimethylamine, triethylamine, pyridine, and quinine rings; alkali metal alkoxides such as potassium tert-pentoxide, potassium tert-butoxide, sodium tert-butoxide, and sodium pentanoxide; and phosphine compounds such as triphenylphosphine. These polar compounds may be used alone or in combination of two or more.

[0207] In the above polymerization steps, from a productive point of view, the polymerization temperature is preferably above 0°C, more preferably below 120°C, and particularly preferably above 50°C and below 100°C. Within this range, after polymerization, it is preferable to ensure a sufficient amount of reaction between the coupling agent and the active terminal.

[0208] The amount of bound butadiene in the above-mentioned 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.

[0209] Furthermore, there is no particular limitation on the amount of bound styrene in the above-mentioned styrene-butadiene copolymer or modified styrene-butadiene rubber, but it is preferably greater than 0% by mass and less than 60% by mass, and more preferably more than 20% by mass and less than 45% by mass.

[0210] When the amounts of butadiene and styrene are within the above ranges, the low-loss and abrasion-resistant properties of the rubber composition can be further improved.

[0211] Note that the amount of styrene bound can be measured by the ultraviolet absorption of phenyl groups, and thus the amount of butadiene bound can also be determined.

[0212] In the aforementioned styrene-butadiene copolymers or modified styrene-butadiene rubbers, the vinyl bond content in the butadiene units is not particularly limited, but is preferably 10 mol% or more and 75 mol% or less, and more preferably 20 mol% or more and 65 mol% or less. When the vinyl bond content is within the above range, the low-loss and abrasion-resistant properties of the rubber composition can be further improved.

[0213] It should be noted that for modified styrene-butadiene rubber, the vinyl bond content (1,2-bond content) in the butadiene unit can be determined by Hampton's method [RR Hampton, Analytical Chemistry, 21, 923 (1949)].

[0214] The alkoxysilyl groups in the coupling agent represented by the above general formula (I) tend to react, for example, with the active ends of the styrene-butadiene copolymer, resulting in the dissociation of alkoxylithium and the formation of bonds between the ends of the styrene-butadiene copolymer chain and the silicon of the coupling residues. The number of alkoxysilyl groups in the coupling residues is obtained by subtracting the number of SiOR groups reduced by the reaction from the total number of SiOR groups in a molecule of the coupling agent. Furthermore, the azirmonocyclic heterocyclic groups in the coupling agent form >N-Li bonds and bonds between the ends of the styrene-butadiene copolymer and the silicon of the coupling residues. It should be noted that the >N-Li bonds tend to readily transform into >NH and LiOH during finishing due to water, etc. Furthermore, unreacted alkoxysilyl groups retained in the coupling agent tend to readily transform into silanols (Si-OH groups) during finishing due to water, etc.

[0215] The reaction temperature in the above reaction steps is preferably the same as the polymerization temperature of the styrene-butadiene copolymer, more preferably above 0°C and below 120°C, and even more preferably above 50°C and below 100°C. The temperature change from the end of the polymerization step until the addition of the coupling agent is preferably below 10°C, and more preferably below 5°C.

[0216] The reaction time in the above reaction steps is preferably 10 seconds or more, and more preferably 30 seconds or more. From the viewpoint of coupling rate, the time from the end of the polymerization step to the start of the reaction step is preferably as short as possible, and more preferably within 5 minutes.

[0217] Mixing in the reaction step can be carried out by mechanical stirring or stirring with a static mixer. When the polymerization step is continuous, it is preferable that the reaction step is also continuous. For example, a tank-type or tubular type reactor with a stirrer can be used as the reactor for the reaction step. The coupling agent can be diluted with an inert solvent and continuously supplied to the reactor. When the polymerization step is batch-type, the coupling agent can be added to the polymerization reactor, or the reaction step can be carried out by transferring it to another reactor.

[0218] In the above general formula (I), A is preferably represented by any of the following general formulas (II) to (V). When A is represented by any of the general formulas (II) to (V), modified styrene-butadiene rubber with even better properties can be obtained.

[0219] [Chemical Formula 11]

[0220]

[0221] In the above general formula (II), B 1 This indicates a single bond or a hydrocarbon group with 1 to 20 carbon atoms, and 'a' represents an integer from 1 to 10. When multiple groups exist, B can be chosen independently for each occurrence.1 .

[0222] [Chemical Formula 12]

[0223]

[0224] In the above general formula (III), B 2 B represents a single bond or a hydrocarbon group with 1 to 20 carbon atoms. 3 This indicates an alkyl group with 1 to 20 carbon atoms, and 'a' represents an integer from 1 to 10. When multiple alkyl groups exist, B can be chosen independently for each occurrence. 2 and B 3 .

[0225] [Chemical Formula 13]

[0226]

[0227] In the above general formula (IV), B 4 This indicates a single bond or a hydrocarbon group with 1 to 20 carbon atoms, and 'a' represents an integer from 1 to 10. When multiple groups exist, B can be chosen independently for each occurrence. 4 .

[0228] [Chemical Formula 14]

[0229]

[0230] In the above general formula (V), B 5 This indicates a single bond or a hydrocarbon group with 1 to 20 carbon atoms, and 'a' represents an integer from 1 to 10. When multiple groups exist, B can be chosen independently for each occurrence. 5 .

[0231] Regarding B in the above general formulas (II) to (V) 1 B 2 B 4 and B 5 Examples of hydrocarbon groups having 1 to 20 carbon atoms include alkylene groups having 1 to 20 carbon atoms.

[0232] Preferably, in the above general formula (I), A is represented by the above general formula (II) or (III), and k represents 0.

[0233] More preferably, in the above general formula (I), A is represented by the above general formula (II) or (III), k represents 0, and in the above general formula (II) or (III), a represents an integer from 2 to 10.

[0234] More preferably, in the above general formula (I), A is represented by the above general formula (II), k represents 0, and in the above general formula (II), a represents an integer from 2 to 10.

[0235] Examples of such coupling agents include bis(3-trimethoxysilylpropyl)-[3-(2,2-dimethoxy-1-aza-2-silazopentanyl)propyl]amine, tris(3-trimethoxysilylpropyl)amine, tris(3-triethoxysilylpropyl)amine, tris(3-trimethoxysilylpropyl)-[3-(2,2-dimethoxy-1-aza-2-silazopentanyl)propyl]-1,3-propanediamine, tetra[3-(2,2-dimethoxy-1-aza-2-silazopentanyl)propyl]-1,3-propanediamine, and tetra[3-(2,2-dimethoxy-1-propanediamine]- ... [3-(2,2-dimethoxy-1-aza-2-silazacyclopentane)propyl]-1,3-propanediamine, tetra(3-trimethoxysilylpropyl)-1,3-propanediamine, tetra(3-trimethoxysilylpropyl)-1,3-diaminomethylcyclohexane, tris(3-trimethoxysilylpropyl)methyl-1,3-propanediamine, and bis[3-(2,2-dimethoxy-1-aza-2-silazacyclopentane)propyl]-(3-trimethoxysilylpropyl)methyl-1,3-propanediamine, etc. Among them, tetra(3-trimethoxysilylpropyl)-1,3-propanediamine and tetra(3-trimethoxysilylpropyl)-1,3-diaminomethylcyclohexane are particularly preferred.

[0236] The amount of the compound represented by the above general formula (I) added as a coupling agent can be adjusted so that the molar ratio of the styrene-butadiene copolymer to the coupling agent reacts at a desired stoichiometric ratio, thereby tending to achieve the desired degree of branching. Specifically, the molar amount of the polymerization initiator relative to the molar amount of the coupling agent is preferably 5.0 times or more, more preferably 6.0 times or more. In this case, in general formula (I), the number of functional groups of the coupling agent ((m-1)×i+p×j+k) is preferably an integer from 5 to 10, and more preferably an integer from 6 to 10.

[0237] To obtain the modified styrene-butadiene rubber having the aforementioned specific polymeric components, the molecular weight distribution (Mw / Mn) of the styrene-butadiene copolymer is preferably 1.5 or more and 2.5 or less, and more preferably 1.8 or more and 2.2 or less. Furthermore, it is preferable that a single peak is detected on the molecular weight curve of the obtained modified styrene-butadiene rubber using GPC.

[0238] When the peak molecular weight of the GPC-modified styrene-butadiene rubber is Mp1 and the peak molecular weight of the styrene-butadiene copolymer is Mp2, it is preferable to satisfy the following formula:

[0239] (Mp1 / Mp2)<1.8×10–12×(Mp2–120×10 4 ) 2 +2

[0240] Mp2 is more preferably 20×10 4 Above and 80×10 4 Below, and Mp1 is more preferably 30×10 4 Above and 150×10 4 Mp1 and Mp2 are determined by the methods described in the following examples.

[0241] The modification rate of the above-mentioned 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 and abrasion-resistant properties of the rubber composition can be further improved.

[0242] Following the above reaction steps, deactivating agents or neutralizing agents may be added to the copolymer solution as needed. Examples of deactivating agents are not limited to the following, but include, for example, water; alcohols, such as methanol, ethanol, and isopropanol. Examples of neutralizing agents are not limited to the following, but include, for example, carboxylic acids, such as stearic acid, oleic acid, tertiary carbonic acid (a highly branched mixture of carboxylic acids with 9 to 11 carbon atoms, centered at carbon 10); aqueous solutions of inorganic acids; and carbon dioxide gas.

[0243] Furthermore, from the viewpoint of preventing gel formation after polymerization and improving stability during processing, it is preferable to add an antioxidant to the modified styrene-butadiene rubber, such as 2,6-di-tert-butyl-4-hydroxytoluene (BHT), n-octadecyl-3-(4'-hydroxy-3',5'-di-tert-butylphenyl)propionate, or 2-methyl-4,6-bis[(octylthio)methyl]phenol.

[0244] As a method for obtaining the above-mentioned modified styrene-butadiene rubber from a polymer solution, known methods can be used. Examples of such methods include: methods that, after separating the solvent by stripping or the like, filter the polymer, further dehydrate and dry it to obtain the polymer; methods that concentrate the solution in a flash tank and further devolatilize it using a degassing extruder or the like; and methods that directly devolatilize the solution using a drum dryer or the like.

[0245] Modified styrene-butadiene rubber obtained by reacting a coupling agent represented by the above general formula (I) with a styrene-butadiene copolymer is, for example, represented by the following general formula (VI).

[0246] [Chemical Formula 15]

[0247]

[0248] In general formula (VI), D represents a styrene-butadiene copolymer chain, and the weight-average molecular weight of the styrene-butadiene copolymer chain is preferably 10 × 10⁻⁶.4 Up to 100×10 4 The styrene-butadiene copolymer chain is a building block of modified styrene-butadiene rubber, and is, for example, derived from the structural units of styrene-butadiene copolymers produced by reacting styrene-butadiene copolymers with a coupling agent.

[0249] R 12 R 13 and R 14 Each can be used independently to represent a single bond or an alkylene group having 1 to 20 carbon atoms.

[0250] R 15 and R 18 Each can be used independently to represent an alkyl group having 1 to 20 carbon atoms.

[0251] R 16 R 19 and R 20 Each can be independently represented as an alkyl group having 1 to 20 hydrogen atoms or carbon atoms.

[0252] R 17 and R 21 Each can be used independently to represent an alkylene group having 1 to 20 carbon atoms.

[0253] R 22 Represents an alkyl group having 1 to 20 hydrogen or carbon atoms.

[0254] m and x each represent an integer from 1 to 3, x≤m, p represents 1 or 2, y represents an integer from 1 to 3, y≤(p+1), and z represents an integer of 1 or 2.

[0255] When there are multiple D, R 12 To R 22 When choosing , m, p, x, y, and z, each can be chosen independently and can be the same or different.

[0256] In addition, 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.

[0257] "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 lacking active hydrogen. The hydrocarbon group represented by A includes saturated, unsaturated, aliphatic, and aromatic hydrocarbon groups. Examples of organic groups lacking active hydrogen include organic groups lacking functional groups with active hydrogen, such as hydroxyl (-OH), secondary amino (>NH), primary amino (-NH2), or mercapto (-SH).

[0258] In the above general formula (VI), it is preferred that A is represented by any of the above general formulas (II) to (V). When A is represented by any of the general formulas (II) to (V), the low-loss and abrasion resistance properties of the rubber composition can be further improved.

[0259] ---Third Preferred Embodiment of Modified Styrene-Butadiene Rubber---

[0260] It is also preferred that the above-mentioned styrene-butadiene rubber (SBR) is modified with a modifier containing at least one of the end-modified compounds (alkoxysilanes) represented by the following general formula (1).

[0261] [Chemical Formula 16]

[0262]

[0263] By using styrene-butadiene rubber modified with a modifier comprising a compound represented by the above general formula (1) containing oligomeric siloxanes and tertiary amines as filler-affinity functional groups as rubber component (A), the dispersibility of fillers such as silica can be enhanced. Therefore, due to the improved dispersibility of fillers in the rubber composition of this disclosure, low-loss properties are greatly improved, the rolling resistance of tires using the rubber composition can be reduced, and fuel economy can be improved.

[0264] In the above general formula (1), R 1 To R 8 Each independently represents an alkyl group having 1 to 20 carbon atoms; L 1 and L 2 Each of the above independently represents an alkylene group having 1 to 20 carbon atoms; and n is an integer from 2 to 4.

[0265] Specifically, in equation (1), R 1 To R 4 Each can be an alkyl group, either substituted or unsubstituted, having a carbon number of 1 to 20, and when R 1 To R 4 When substituted, they may each be independently substituted by one or more substituents selected from the group consisting of: alkyl with 1 to 10 carbon atoms, cycloalkyl with 3 to 10 carbon atoms, alkoxy with 1 to 10 carbon atoms, cycloalkoxy with 4 to 10 carbon atoms, aryl with 6 to 12 carbon atoms, aryloxy with 6 to 12 carbon atoms, alkanoyloxy (Ra-COO-, where Ra is an alkyl with 1 to 9 carbon atoms) with 2 to 12 carbon atoms, arylalkoxy with 7 to 13 carbon atoms, arylalkyl with 7 to 13 carbon atoms, and alkylaryl with 7 to 13 carbon atoms.

[0266] More specifically, R 1To R 4 Each can be an alkyl group, individually or independently, having substituted or unsubstituted carbon atoms, having a carbon number of 1 to 10, and even more specifically, R 1 To R 4 Each can be an alkyl group, either substituted or unsubstituted, having 1 to 6 carbon atoms.

[0267] Furthermore, in equation (1), R 5 To R 8 Each independently represents an alkyl group having 1 to 20 substituted or unsubstituted carbon atoms, specifically, an alkyl group having 1 to 10 substituted or unsubstituted carbon atoms, and even more specifically, an alkyl group having 1 to 6 substituted or unsubstituted carbon atoms, and when substituted, can be referred to as above for R. 1 To R 4 The substituents are substituted.

[0268] It should be noted that if R 5 To R 8 It is not an alkyl group but a hydrolyzable substituent, NR 5 R 6 and NR 7 R 8 The bonds can hydrolyze into NH in the presence of moisture, which may adversely affect the processability of the polymer.

[0269] More specifically, in the compound represented by formula (1), R 1 To R 4 It can be methyl or ethyl, and R 5 To R 8 It can be an alkyl group having 1 to 10 carbon atoms.

[0270] The amino group in the compound represented by formula (1), i.e., NR 5 R 6 and NR 7 R 8 The preferred form is a tertiary amine. When used as a modifier, a tertiary amine allows the compound represented by formula (1) to provide even better processability.

[0271] It should be noted that when R 5 To R 8 When a protecting group containing an amino group is bonded, or when hydrogen is bonded, the effect of the compound represented by formula (1) may be difficult to achieve. When hydrogen is bonded, the anion in the modification process reacts with hydrogen and loses its reactivity, making the modification reaction itself impossible. When a protecting group is bonded, the modification reaction proceeds, but the protecting group is removed by hydrolysis during post-treatment, resulting in a primary or secondary amino group. The deprotected primary or secondary amino group may subsequently cause an increase in the viscosity of the compound during compounding, leading to a decrease in processability.

[0272] Furthermore, L in the compound represented by formula (1) 1 and L 2 Each can be used independently to represent an alkylene group having 1 to 20 carbon atoms, whether substituted or unsubstituted.

[0273] More specifically, L 1 and L 2 Each can be an alkylene group having 1 to 10 carbon atoms, and even more specifically, an alkylene group having 1 to 6 carbon atoms, such as methylene, ethylene, or propylene.

[0274] Regarding L in the compound represented by formula (1) 1 and L 2 The closer the distance between Si and N atoms in the molecule, the better the effect. However, when Si is directly bonded to N, the bond between Si and N may break during subsequent processing steps, and the resulting secondary amine is very likely to be washed away by water during post-processing. This makes it difficult for the amine to promote bonding with fillers such as silica in the produced modified styrene-butadiene rubber, and therefore, the effect of improving filler dispersibility may be reduced. Considering the improved bond length between Si and N, L is more preferable. 1 and L 2 Each can independently represent an alkylene group having 1 to 3 carbon atoms, such as methylene, ethylene, or propylene, and more specifically, it can be propylene. Furthermore, L 1 and L 2 It can be used to target R as described above. 1 To R 4 The substituents are substituted.

[0275] Furthermore, the compound represented by formula (1) is preferably any one of the compounds represented by the following structural formulas (1-1) to (1-5). This is because even lower loss can be achieved.

[0276] [Chemical Formula 17]

[0277]

[0278] The compound represented by formula (1) has an alkoxysilane structure bonded to the active ends of the styrene-butadiene copolymer. The Si-O-Si structure and the three or more amino groups bonded to the ends exhibit affinity for fillers such as silica, thereby promoting bonding between the filler and the modified styrene-butadiene rubber compared to conventional modifiers containing a single amino group intramolecularly. Furthermore, the degree of bonding at the active ends of the styrene-butadiene copolymer is uniform, and when observing changes in molecular weight distribution before and after coupling, the molecular weight distribution remains constant without increase after coupling compared to before coupling. Therefore, the physical properties of the modified styrene-butadiene rubber itself are not degraded, filler aggregation in the rubber composition is prevented, and filler dispersibility is enhanced, thereby improving the processability of the rubber composition. In particular, when the rubber composition is applied to tires, these effects enable an improved balance between high fuel economy and wet road grip.

[0279] The compound represented by formula (1) can be produced by a condensation reaction represented by the following reaction scheme.

[0280] [Chemical Formula 18]

[0281]

[0282] In the above reaction scheme, R 1 To R 8 L 1 and L 2 And n is as defined in equation (1) above, and R' and R'' are any substituents that do not affect the condensation reaction. For example, R' and R'' can each independently react with R 1 To R 4 The same as any one of them.

[0283] The reaction scheme described above is carried out in the presence of an acid, and the acid can be used without restriction, as long as it is typically used for condensation reactions. Those skilled in the art can select the optimal acid based on various process variables, such as the type of reactor in which the reaction takes place, the starting materials, and the reaction temperature.

[0284] Modified styrene-butadiene rubber modified with a modifier containing a compound represented by formula (1) can have a narrow molecular weight distribution (Mw / Mn, also known as the "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, there is a risk that the tensile properties and viscoelasticity may be reduced when applied to rubber compositions. Considering the significant effect of improving 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 above-described modifier, the molecular weight distribution of the modified styrene-butadiene rubber is similar to that of the unmodified styrene-butadiene copolymer.

[0285] The molecular weight distribution of modified styrene-butadiene rubber can be calculated using the ratio of weight-average molecular weight (Mw) to number-average molecular weight (Mn) (Mw / Mn). In this case, the number-average molecular weight (Mn) is the common average of the molecular weights of the individual polymers, calculated by measuring the molecular weights of n polymer molecules, adding these molecular weights together, and dividing by n. The weight-average molecular weight (Mw) represents the molecular weight distribution of the polymer composition. The overall average molecular weight can be expressed in grams per mole (g / mol).

[0286] In addition, the weight-average molecular weight and number-average molecular weight are the converted molecular weights of polystyrene analyzed by gel permeation chromatography (GPC).

[0287] The modified styrene-butadiene rubber, while meeting the above molecular weight distribution conditions, has a number-average molecular weight (Mn) of 50,000 g / mol to 2,000,000 g / mol, and more specifically, 200,000 g / mol to 800,000 g / mol. The modified styrene-butadiene rubber has a weight-average molecular weight (Mw) of 100,000 g / mol to 4,000,000 g / mol, and more specifically, 300,000 g / mol to 1,500,000 g / mol.

[0288] 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, there is a risk of deterioration in tensile properties when it is used in rubber compositions. On the other hand, if the weight-average molecular weight (Mw) exceeds 4,000,000 g / mol or the number-average molecular weight (Mn) exceeds 2,000,000 g / mol, the processability of the modified styrene-butadiene rubber decreases, resulting in poor workability of the rubber composition, making mixing difficult, and potentially making it difficult to adequately improve the physical properties of the rubber composition.

[0289] More specifically, when modified styrene-butadiene rubber simultaneously meets the conditions of weight-average molecular weight (Mw), number-average molecular weight (Mn), and molecular weight distribution, it can improve the viscoelasticity and processability of rubber compositions in a well-balanced manner when applied to rubber compositions.

[0290] The vinyl bond content in the butadiene portion of the modified styrene-butadiene rubber is preferably 5% or more, more preferably 10% or more, and more preferably 60% or less. By setting the vinyl bond content in the butadiene portion within the above range, the glass transition temperature can be adjusted to an appropriate range.

[0291] The Mooney viscosity (MV) of modified styrene-butadiene rubber at 100°C can be from 40 to 140, specifically from 60 to 100. When the Mooney viscosity is within the above range, it exhibits better processability.

[0292] Mooney viscosity can be measured using a Mooney viscometer, such as the Monsanto MV2000E, at 100°C and a rotor speed of 2 ± 0.02 rpm using a large rotor. The sample to be used is left at room temperature (23 ± 3°C) for at least 30 minutes, then 27 ± 3 g is taken, filled into the mold cavity, and the platen is operated for measurement.

[0293] As described above, it is preferred that one end of the modified styrene-butadiene rubber is modified with a modifier comprising a compound represented by general formula (1), and it is further preferred that the other end is further modified with a modifier comprising a compound represented by 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 both high fuel economy and wet road grip performance of the tires using the rubber composition can be achieved at a higher level.

[0294] [Chemical Formula 19]

[0295]

[0296] In the above general formula (2), R 9 To R 11 Each of the following is 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.

[0297] Furthermore, in equation (2), R 12It is a single bond; 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 5 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.

[0298] Furthermore, in equation (2), R 13 It is 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 from 1 to 5, and R 13 At least one of them is a functional group represented by general formula (2a) or general formula (2b), and when m is an integer from 2 to 5, multiple R 13 They can be the same as or different from each other.

[0299] [Chemical Formula 20]

[0300]

[0301] In the above general formula (2a), R 14 It is 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.

[0302] Furthermore, in equation (2a), R 15 and R 16 Each is independently a substituted or unsubstituted alkylene group having 1 to 20 carbon atoms, substituted with 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.

[0303] Furthermore, in equation (2a), R 17 It 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 It does not exist.

[0304] [Chemical Formula 21]

[0305]

[0306] In the above general formula (2b), R 18 It is 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.

[0307] Furthermore, in equation (2b), R 19 and R 20 Each of the following is 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.

[0308] Furthermore, in the compounds represented by the above general formula (2), R 9 To R 11 Each is 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, R 12 It is a single-bonded or unsubstituted alkylene group having 1 to 10 carbon atoms, and R 13 It 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 general formula (2b), wherein in the above general formula (2a), R 14 It is an unsubstituted alkylene group having 1 to 10 carbon atoms, R 15 and R 16 Each is independently an unsubstituted alkylene group having 1 to 10 carbon atoms, R 17 It is 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 It is an unsubstituted alkylene group having 1 to 10 carbon atoms, and R 19 and R 20 Each of them independently is 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.

[0309] 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).

[0310] [Chemical Formula 22]

[0311]

[0312] When a styrene-butadiene copolymer is modified with a modifier containing a compound represented by the above general formula (2), the modifier containing a compound represented by formula (2) is used as a modification initiator.

[0313] Specifically, for example, by polymerizing butadiene monomers and styrene monomers in a hydrocarbon solvent in the presence of a modifier containing a compound represented by formula (2), a modifying group derived from the compound represented by formula (2) can be introduced into a styrene-butadiene copolymer.

[0314] --Butadiene rubber (BR)--

[0315] The synthetic rubber (A2) preferably also includes butadiene rubber (BR). Butadiene rubber has a low glass transition temperature (Tg), and by including butadiene rubber as synthetic rubber (A2) in the rubber component (A), the high fuel economy and wear resistance of tires using the rubber composition can be improved.

[0316] Butadiene rubber can be modified or unmodified.

[0317] From the viewpoint of further improving the high fuel economy and wear resistance of tires using rubber compositions, it is preferred that the butadiene rubber is a modified butadiene rubber having functional groups that have an affinity for fillers.

[0318] Examples of functional groups that have affinity for fillers include functional groups having at least one atom selected from nitrogen, oxygen, sulfur, metalloids and metals.

[0319] As a metalloid atom, at least one atom selected from boron, silicon, germanium, arsenic, antimony and tellurium is preferred, at least one atom selected from boron, silicon and germanium is more preferred, and silicon is particularly preferred.

[0320] As a metallic atom, at least one atom selected from tin, titanium, zirconium, bismuth and aluminum is preferred, at least one atom selected from tin and titanium is more preferred, and tin is particularly preferred.

[0321] The functional groups that have affinity for the filler preferably include at least one selected from the group consisting of nitrogen atoms, oxygen atoms and silicon atoms.

[0322] A functional group having at least one atom selected from nitrogen, oxygen, sulfur, metalloid, and metal is a residue of a compound (hereinafter sometimes referred to as a "heteroatom-containing compound") having at least one atom selected from nitrogen, oxygen, sulfur, metalloid, and metal.

[0323] Modified butadiene rubber can be obtained, for example, by polymerizing 1,3-butadiene to obtain polybutadiene with active ends and reacting the active ends of the polybutadiene with a modifier, or by polymerizing 1,3-butadiene with a functional group to obtain polybutadiene with a functional group at the polymerization initiation end.

[0324] For example, heteroatom-containing compounds can react with the active ends of polybutadiene as a modifier to form modified butadiene rubber, or nitrogen-containing compounds as heteroatom-containing compounds can react with alkali metals to form polymerization initiators for anionic polymerization, and form modified butadiene rubber with nitrogen-containing compound residues at the polymerization initiation ends of polybutadiene.

[0325] Examples of modifiers that react with the active ends of polybutadiene include at least one modifier selected from tin-containing compounds, nitrogen-containing and silicon-containing compounds, oxygen-containing and silicon-containing compounds, sulfur-containing and silicon-containing compounds, and nitrogen-containing compounds that do not contain silicon.

[0326] Examples of tin-containing compounds include at least one tin compound selected from tin tetrachloride and tributyltin chloride.

[0327] Examples of nitrogen- and silicon-containing compounds include silane compounds having a protected primary amino group, such as N,N-bis(trimethylsilyl)aminopropylmethyldimethoxysilane, 1-trimethylsilyl-2,2-dimethoxy-1-aza-2-silazopentanane, N,N-bis(trimethylsilyl)aminopropyltrimethoxysilane, N,N-bis(trimethylsilyl)aminopropyltriethoxysilane, N,N-bis(trimethylsilyl)aminopropylmethyldiethoxysilane, N... N-bis(trimethylsilyl)aminoethyltrimethoxysilane, N,N-bis(trimethylsilyl)aminoethyltriethoxysilane, N,N-bis(trimethylsilyl)aminoethylmethyldimethoxysilane, and N,N-bis(trimethylsilyl)aminoethylmethyldiethoxysilane; and silane compounds having a protected secondary amino group, such as N-methyl-N-trimethylsilylaminopropyl(methyl)dimethoxysilane, N-methyl-N-trimethylsilylaminopropyl(methyl)dimethoxysilane, and N-methyl-N-trimethylsilylaminopropyl(methyl)dimethoxysilane. Propyl(methyl)diethoxysilane, N-trimethylsilyl(hexamethyleneimine-2-yl)propyl(methyl)diethoxysilane, N-trimethylsilyl(hexamethyleneimine-2-yl)propyl(methyl)diethoxysilane, N-trimethylsilyl(pyrrolidine-2-yl)propyl(methyl)diethoxysilane, N-trimethylsilyl(pyrrolidine-2-yl)propyl(methyl)diethoxysilane, N-trimethylsilyl(piperidin-2-yl)propyl(methyl)diethoxysilane Methoxysilane, N-trimethylsilyl(piperidin-2-yl)propyl(methyl)diethoxysilane, N-trimethylsilyl(imidazol-2-yl)propyl(methyl)diethoxysilane, N-trimethylsilyl(imidazol-2-yl)propyl(methyl)diethoxysilane, N-trimethylsilyl(4,5-dihydroimidazol-5-yl)propyl(methyl)diethoxysilane and N-trimethylsilyl(4,5-dihydroimidazol-5-yl)propyl(methyl)diethoxysilane.

[0328] Examples of oxygen- and silicon-containing compounds include at least one hydroxyl group-containing alkyl silane compound selected from 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.

[0329] Examples of sulfur- and silicon-containing compounds include alkyloxysilane compounds containing thioepoxy groups, wherein the epoxy groups of the aforementioned alkyloxysilane compounds containing epoxy groups are replaced by thioepoxy groups.

[0330] As examples of the aforementioned nitrogen-containing compounds that do not contain silicon, suitable examples include one or more compounds selected from bis(diethylamino)benzophenone, dimethylimidazolium ketone, N-methylpyrrolidone and 4-dimethylaminobenzylaniline.

[0331] Anionic polymerization or coordination polymerization can be used as the polymerization method for the above-mentioned polybutadiene.

[0332] When obtaining the above-mentioned polybutadiene by anionic polymerization, an alkali metal compound is used as the polymerization initiator, preferably a lithium compound. There are no particular limitations on the lithium compound used as the polymerization initiator, but hydrocarbon-based lithium and aminated lithium compounds are preferred. When the former (hydrocarbon-based lithium) is used, polybutadiene with a hydrocarbon group at the polymerization initiation end and a polymerization active site at the other end is obtained. When the latter (aminated lithium compound) is used, polybutadiene with a nitrogen-containing functional group at the polymerization initiation end and a polymerization active site at the other end is obtained.

[0333] As the aforementioned hydrocarbon-based lithiums, those having a hydrocarbon group having 2 to 20 carbon atoms are preferred. Examples include ethyl lithium, n-propyl lithium, isopropyl lithium, n-butyl lithium, sec-butyl lithium, tert-octyl lithium, n-decyl lithium, phenyl lithium, 2-naphthyl lithium, 2-butylphenyl lithium, 4-phenylbutyl lithium, cyclohexyl lithium, cyclopentyl lithium, and the reaction products of diisopropenylbenzene and butyl lithium. Among these, n-butyl lithium is particularly preferred.

[0334] Examples of the aforementioned lithium amino compounds include lithium hexamethyleneimine, lithium pyrrolidine, lithium piperidinium, lithium heptamethyleneimine, lithium dodecamethyleneimine, lithium dimethylaminoide, lithium diethylaminoide, lithium dibutylaminoide, lithium dipropylaminoide, lithium diheptylaminoide, lithium dihexylaminoide, lithium dioctylaminoide, lithium di-2-ethylhexylaminoide, lithium didecylaminoide, lithium N-methylpiperazine, lithium ethylpropylaminoide, lithium ethylbutylaminoide, lithium ethylbenzylaminoide, and lithium methylphenylethylaminoide. From the viewpoint of interaction with carbon black and polymerization initiation energy, cyclic lithium amino compounds such as lithium hexamethyleneimine, lithium pyrrolidine, lithium piperidinium, lithium heptamethyleneimine, and lithium dodecamethyleneimine are preferred, with lithium hexamethyleneimine and lithium pyrrolidine being more preferred.

[0335] When lithium hexamethyleneimine is used as a polymerization initiator, modified butadiene rubber with a hexamethyleneimine at the polymerization initiation end of the polybutadiene can be obtained, which is further preferred, wherein the hexamethyleneimine is a nitrogen-containing compound residue containing a functional group containing atoms other than carbon and hydrogen.

[0336] From the viewpoint of further reducing tire rolling resistance, exhibiting excellent fuel economy, and further improving wear resistance and crack resistance, modified butadiene rubber having nitrogen-containing compound residues at the polymerization initiation end of polybutadiene, and having one or more compound residues selected from tin-containing compound residues, nitrogen-containing and silicon-containing compound residues, oxygen-containing and silicon-containing compound residues, sulfur-containing and silicon-containing compound residues, and nitrogen-containing compound residues without silicon at the active end of polybutadiene, is further preferred.

[0337] There are no particular limitations on the method of producing polybutadiene by anionic polymerization using the above-mentioned lithium compounds as polymerization initiators, and conventionally known methods can be used.

[0338] Specifically, the lithium compound described above is used as a polymerization initiator in a hydrocarbon solvent that is inert to the reaction, such as an aliphatic, alicyclic, or aromatic hydrocarbon compound, and optionally in the presence of a randomizing agent, to anionicly polymerize 1,3-butadiene to obtain the desired polybutadiene.

[0339] As hydrocarbon solvents, those with 3 to 8 carbon atoms are preferred, and examples include propane, n-butane, isobutane, n-pentane, isopentane, n-hexane, cyclohexane, propylene, 1-butene, isobutene, trans-2-butene, cis-2-butene, 1-pentene, 2-pentene, 1-hexene, 2-hexene, benzene, toluene, xylene, and ethylbenzene. These can be used alone or in combination of two or more.

[0340] The atacticing agent to be used can be a compound that has the function of controlling the microstructure of polybutadiene (e.g., increasing the 1,2-bonds in polybutadiene). There are no particular limitations on the atacticing agent, and any known compound commonly used as an atacticing agent can be appropriately selected and used. Specific examples include ethers and tertiary amines, such as dimethoxybenzene, tetrahydrofuran, dimethoxyethane, diethylene glycol dibutyl ether, diethylene glycol dimethyl ether, 2,2-bis(2-tetrahydrofuranyl)propane, triethylamine, pyridine, N-methylmorpholine, N,N,N',N'-tetramethylethylenediamine, and 1,2-dipiperidinylethane. Potassium salts such as potassium tert-amyloxide and potassium tert-butoxide, and sodium salts such as sodium tert-amyloxide can also be used. These atacticing agents can be used alone or in combination of two or more. The amount of atacticing agent used is preferably selected in the range of 0.01 to 1000 molar equivalents per mol of lithium compound.

[0341] The temperature in the above polymerization reaction is preferably selected from the range of 0°C to 150°C, more preferably from 20°C to 130°C. The polymerization reaction can be carried out under pressure, but it is generally desirable to operate at a pressure sufficient to keep the monomer 1,3-butadiene essentially in a liquid phase. That is, the pressure depends on the individual substance to be polymerized, the polymerization medium used, the polymerization temperature, etc., but higher pressures can be used if necessary, and such pressures can be obtained by appropriate methods, such as pressurizing the reactor with a gas inert to the polymerization reaction.

[0342] On the other hand, when using rare earth metal compounds as polymerization initiators to produce the above-mentioned polybutadiene via coordination polymerization, it is even more preferable to use a combination of the following components (a), (b) and (c).

[0343] Component (a) used in the above coordination polymerization is selected from rare earth metal compounds and complexes of rare earth metal compounds with Lewis bases. Here, rare earth metal compounds may include carboxylates, alkoxides, β-diketone complexes, phosphates, and phosphonates of rare earth elements. Lewis bases may include acetylacetone, tetrahydrofuran, pyridine, N,N-dimethylformamide, thiophene, diphenyl ether, triethylamine, organophosphorus compounds, and monovalent or divalent alcohols. Lanthanum, neodymium, praseodymium, samarium, and gadolinium are preferred rare earth elements among the above rare earth metal compounds, with neodymium being particularly preferred. Specific examples of component (a) include neodymium tri-2-ethylhexanoate, its complex with acetylacetone, neodymium trinedecanoate, its complex with acetylacetone, and neodymium tri-n-butoxide. These components (a) may be used alone or in combination of two or more.

[0344] Component (b) for coordination polymerization is selected from organoaluminum compounds. Specific examples of organoaluminum compounds include trialkylaluminum compounds represented by the formula: R3Al, alkylaluminum hydrides represented by the formula: R2AlH or RAlH2 (where R is independently a hydrocarbon group having 1 to 30 carbon atoms), and alkylaluminoxane compounds having a hydrocarbon group having 1 to 30 carbon atoms. Specific examples of organoaluminum compounds include trialkylaluminum, dialkylaluminum hydride, alkylaluminum dihydride, and alkylaluminoxanes. These compounds can be used alone or in combination of two or more. Preferably, an aluminumoxane is used in combination with another organoaluminum compound as component (b).

[0345] The (c) component used in coordination polymerization is selected from compounds having hydrolyzable halogens or their complexes with Lewis bases; organohalides having tertiary alkyl halides, benzyl halides, or allyl halides; and ionic compounds consisting of noncoordinate anions and countercations. Specific examples of such (c) components include alkyl aluminum chloride, dialkyl aluminum chloride, silicon tetrachloride, tin tetrachloride, zinc chloride and complexes with alcohols or other Lewis bases, magnesium chloride and complexes with alcohols or other Lewis bases, benzyl chloride, tert-butyl chloride, benzyl bromide, tert-butyl bromide, and triphenylcarbium tetra(pentafluorophenyl)borate. These (c) components can be used alone or in combination of two or more.

[0346] In addition to components (a), (b), and (c) described above, a polymerization initiator may be initially prepared using 1,3-butadiene (which is also a monomer used for polymerization), if desired. Furthermore, part or all of component (a) or component (c) may be loaded onto an inert solid and used. The amount of each component can be suitably set, but typically, component (a) is 0.001 to 0.5 mmol per 100 g of monomer. The molar ratio of component (b) to component (a) is preferably 5 to 1,000, and the molar ratio of component (c) to component (a) is preferably 0.5 to 10.

[0347] 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. As the solvent used in coordination polymerization, a hydrocarbon solvent inert to the reaction exemplified in the anionic polymerization described above can be used, and the concentration of the monomer 1,3-butadiene in the reaction solution is the same as in the case of anionic polymerization. Furthermore, the reaction pressure in coordination polymerization is also the same as in the case of anionic polymerization, and it is desirable that the starting materials used in the reaction are substantially free of reaction inhibitors, such as water, oxygen, carbon dioxide, and protonated compounds.

[0348] As the modified butadiene rubber described above, modified butadiene rubber obtained by anionic polymerization using organoalkali metal compounds, particularly alkyl lithium, is preferred.

[0349] In either anionic polymerization or coordination polymerization, the aforementioned polybutadiene can undergo a modification reaction between the polymeric active ends after polymerization and the aforementioned modifier to obtain modified butadiene rubber. The modification reaction temperature is preferably 20°C or higher, but the polymerization temperature of the polybutadiene can be used as is, and a range of 30°C to 120°C is more preferred. If the reaction temperature is too low, the viscosity of the polybutadiene tends to become too high or the dispersibility of the reactants tends to deteriorate. On the other hand, if the reaction temperature is too high, the polymeric active sites tend to be easily deactivated. The amount of modifier used is preferably in the range of 0.25 to 3.0 mol per mol of polymerization initiator used to produce polybutadiene, and more preferably in the range of 0.5 to 1.5 mol.

[0350] (Resin(B))

[0351] The rubber composition for tires in this embodiment preferably further comprises resin (B). By blending resin (B) into the rubber composition, the elastic modulus of the rubber composition is improved, and both handling stability on dry roads and grip performance on wet roads can be achieved in the tire using the rubber composition.

[0352] The content of the resin (B) is preferably 1 to 50 parts by mass relative to 100 parts by mass of the rubber component (A), more preferably 5 to 30 parts by mass. If the content of resin (B) is 1 part by mass or more relative to 100 parts by mass of the rubber component (A), the wet road grip performance of the tire using the rubber composition is further improved, and if it is 50 parts by mass or less, the decrease in the elastic modulus of the rubber composition can be more easily suppressed. Therefore, when the content of resin (B) is 1 to 50 parts by mass relative to 100 parts by mass of the rubber component (A), the wet road grip performance of the tire using the rubber composition can be further improved.

[0353] As the aforementioned resin (B), C5-based resins, C5 / C9-based resins, C9-based resins, dicyclopentadiene resins, terpene phenol resins, terpene resins, rosin resins, and alkylphenol resins may be mentioned, and it is preferred to select at least one of C5-based resins, C5 / C9-based resins, C9-based resins, dicyclopentadiene resins, rosin resins, and alkylphenol resins. When resin (B) contains at least one of C5-based resins, C5 / C9-based resins, C9-based resins, dicyclopentadiene resins, terpene phenol resins, terpene resins, rosin resins, and alkylphenol resins, the wet road grip performance of the tire using the rubber composition can be further improved. The aforementioned resin (B) may be used alone or in combination of two or more.

[0354] Of the resins (B) described above, C5-based resins, C5 / C9-based resins, and C9-based resins are particularly preferred from the viewpoint of tire wet grip performance. C5 / C9-based resins and C9-based resins exhibit high compatibility with isoprene-based rubber (A1) and further enhance the effect of increasing the elastic modulus of the rubber composition in low-strain regions and decreasing the elastic modulus of the rubber composition in high-strain regions, thereby further improving the wet grip performance of the tire.

[0355] Furthermore, among the resins (B) described above, terpene resins and rosin resins are particularly preferred from the viewpoint of reducing environmental impact. Since terpene resins and rosin resins are naturally sourced and sustainable resins, their environmental impact can be further reduced, and tire performance can be further improved, such as grip performance under various road conditions including dry, wet, snowy, and icy surfaces.

[0356] The resin (B) described above may have functional groups introduced through modification that interact with fillers such as carbon black and silica. Examples of such functional groups include amino, amide, isocyanate, imino, imidazole, urea, ammonium, imide, hydrazine, azo, diazo, carboxyl, nitrile, pyridyl, alkoxy, hydroxy, oxygen, epoxy, ether, carbonyl, oxycarbonyl, silyl, alkoxysilyl, mercapto, thioether, disulfide, sulfonyl, sulfinyl, and thiocarbonyl, etc.

[0357] The aforementioned C5 series resins refer to C5 series synthetic petroleum resins. For example, aliphatic petroleum resins obtained by polymerizing the C5 fraction obtained through the thermal cracking of naphtha in the petrochemical industry using Friedel-Crafts catalysts such as AlCl3 or BF3 can be mentioned. The aforementioned C5 fractions typically contain olefins such as 1-pentene, 2-pentene, 2-methyl-1-butene, 2-methyl-2-butene, and 3-methyl-1-butene, and dienes such as 2-methyl-1,3-butadiene, 1,2-pentadiene, 1,3-pentadiene, and 3-methyl-1,2-butadiene. The aforementioned C5 series resins may be commercially available products, and examples include the “ESCOREZ® (ESCOREZ is a registered trademark of Japan, other countries or both) 1000 series” aliphatic petroleum resins manufactured by ExxonMobil Chemical Company, the “Quintone® (Quintone is a registered trademark of Japan, other countries or both) 100 series” aliphatic petroleum resins (specifically, A100, B170, M100, R100) manufactured by Zeon Corporation, and “T-REZRA100” manufactured by Tonen Chemical Corporation.

[0358] The aforementioned C5 / C9 series resins refer to C5 / C9 series synthetic petroleum resins. For example, solid polymers obtained by polymerizing C5 and C9 fractions derived from petroleum using Friedel-Crafts catalysts such as AlCl3 or BF3 can be mentioned. More specifically, copolymers mainly composed of styrene, vinyltoluene, α-methylstyrene, and indene can be mentioned as the aforementioned C5 / C9 series resins. From the viewpoint of compatibility with rubber components, resins with low content of components with C9 or higher are preferred. Here, "low content of components with C9 or higher" means that the content of components with C9 or higher in the total resin is less than 50% by mass, preferably less than 40% by mass. The aforementioned C5 / C9 series resins can be commercially available products, and examples include "Quintone® G100B" (manufactured by Zeon Corporation), "ECR213" (manufactured by ExxonMobil Chemical Company), and "T-REZ RD104" (manufactured by Tonen Chemical Corporation).

[0359] C9 series resins are, for example, resins polymerized from aromatic compounds having 9 carbon atoms as major monomers, such as vinyltoluene, alkylstyrene, and indene; they are C9 fractions obtained as a byproduct of the thermal cracking of naphtha in the petrochemical industry, along with petrochemical raw materials such as ethylene and propylene. Specific examples of C9 fractions obtained by the thermal cracking of naphtha include vinyltoluene, α-methylstyrene, β-methylstyrene, γ-methylstyrene, o-methylstyrene, p-methylstyrene, and indene. C9 series resins can be produced by, for example, using a Friedel-Crafts catalyst, by combining the C9 fraction with C8 fractions such as styrene, C9... 10 The C9 series resins are obtained by copolymerizing fractions such as methylindene or 1,3-dimethylstyrene, and further by copolymerizing mixtures of naphthalene, vinylnaphthalene, vinylanthracene, and p-tert-butylstyrene as raw materials. C9 series resins can also be modified petroleum resins modified with compounds having hydroxyl groups or unsaturated carboxylic acid compounds. C9 series resins can be commercially available products; for example, as unmodified C9 series petroleum resins, products such as "Nisseki Neopolymer® (Nisseki Neopolymer is a registered trademark of Japan, other countries, or both) L-90", "Nisseki Neopolymer® 120", "Nisseki Neopolymer® 130", and "Nisseki Neopolymer® 140" (manufactured by JX NipponOil & Energy Corporation) can be mentioned.

[0360] Dicyclopentadiene resin is a petroleum resin primarily produced from dicyclopentadiene obtained by dimerizing cyclopentadiene. Dicyclopentadiene resin can be a commercially available product; for example, the “Quintone® 1000 series” (product names “1105”, “1325”, “1340”, etc.) can be mentioned, which is an alicyclic petroleum resin manufactured by Zeon Corporation.

[0361] Terpene phenol resins can be obtained, for example, by reacting terpenes with various phenols using a Friedel-Crafts catalyst, or further by condensation with formalin. There are no particular limitations on the terpenes used as raw materials, but monoterpenes such as α-pinene and limonene are preferred, those containing α-pinene are more preferred, and α-pinene is particularly preferred. Terpene phenol resins can be commercially available products; for example, references may be made to products such as “Tamanol 803L” and “Tamanol 901” (manufactured by Arakawa Chemical Industries, Ltd.), the “YS Polyster® (YS Polyster is a registered trademark of Japan, other countries, or both) U” series, the “YS Polyster® T” series, the “YS Polyster® S” series, the “YSPolyster® G” series, the “YS Polyster® N” series, the “YS Polyster® K” series, and the “YS Polyster® TH” series (manufactured by Yasuhara Chemical Co., Ltd.).

[0362] Terpene resins are solid resins obtained by mixing turpentine oil, obtained simultaneously with rosin from pine trees, or polymeric components separated from it, and polymerizing them using a Friedel-Crafts catalyst. Examples include β-pinene resins and α-pinene resins. Terpene resins can be commercially available products; for example, references may be made to products such as the “YS” series (PX-1250, TR-105, etc.) and the “A” series (A115, S115, etc.) manufactured by Yasuhara Chemical Co., Ltd.

[0363] Rosin resin is a natural resin mainly composed of abietic acids (abscisic acid, longleaf abietic acid, isopyric acid, etc.), and is the residue remaining after distilling turpentine essential oil from resins such as pine resin (pine resin), the sap of pine trees, as well as modified resins and hydrogenated resins obtained by modifying or hydrogenating these. For example, natural resin rosin, its polymerized rosin, or partially hydrogenated rosin; glyceryl ester rosin, its partially hydrogenated rosin, fully hydrogenated rosin, or polymerized rosin; and pentaerythritol ester rosin, its partially hydrogenated rosin, or polymerized rosin, etc. As natural resin rosin, resin rosin, tall oil rosin, and wood rosin contained in raw rosin or tall oil, etc., can be mentioned. Rosin resin can be a commercially available product; for example, products such as “NEOTALL 105” (manufactured by Harima Chemicals Group, Inc.), “SN Tack 754” (manufactured by SanNopco Limited), “Lime Resin No. 1”, “PENSEL A” and “PENSEL AD” (manufactured by Arakawa Chemical Industries, Ltd.), “Poly-Pale” and “Pentalyn C” (manufactured by Eastman Chemical Company), and “Highrosin® (Highrosin is a registered trademark in Japan, other countries or both) S” (manufactured by Taishamatsu essential oil Co., Ltd.) can be mentioned.

[0364] Alkylphenol resins can be obtained, for example, by the condensation reaction of alkylphenol and formaldehyde in the presence of a catalyst. Alkylphenol resins can be commercially available products; for example, references may be made to products such as “Hitanol 1502P” (alkylphenol-formaldehyde resin, manufactured by Hitachi Chemical Co., Ltd.), “TACKIROL 201” (alkylphenol-formaldehyde resin, manufactured by Taoka Chemical Co., Ltd.), “TACKIROL 250-I” (brominated alkylphenol-formaldehyde resin, manufactured by Taoka Chemical Co., Ltd.), “TACKIROL 250-III” (brominated alkylphenol-formaldehyde resin, manufactured by Taoka Chemical Co., Ltd.), and “R7521P”, “SP1068”, “R7510PJ”, “R7572P”, and “R7578P” (manufactured by SI GROUP INC.).

[0365] -Hydrogenated Resin-

[0366] Preferably, the resin (B) is at least partially hydrogenated (i.e., a hydrogenated resin). By at least partially hydrogenating the resin (B), the compatibility with the isoprene skeleton rubber (A1) is further improved, the movement of the rubber component (A) is further controlled, and the hysteresis loss (tanδ) in the low-temperature region can be further improved, thereby further enhancing the wet road grip performance of the tire using the rubber composition.

[0367] The hydrogenated resin preferably has a softening point above 110°C and a polystyrene equivalent weight-average molecular weight of 200 to 1600 g / mol. Applying rubber compositions containing such hydrogenated resins to tires can further improve the tire's wear resistance.

[0368] Here, the softening point of the hydrogenated resin is measured according to JIS-K2207-1996 (ring and ball method).

[0369] In addition, the weight-average molecular weight of the hydrogenated resin was measured by gel permeation chromatography (GPC), and the converted value of polystyrene was calculated.

[0370] When the softening point of the hydrogenated resin is higher than 110°C, the tire using the applied rubber composition can be sufficiently reinforced, and its wear resistance can be further improved. From the viewpoint of tire wear resistance, the softening point of the hydrogenated resin is more 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. 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.

[0371] When the equivalent weight-average molecular weight of the hydrogenated resin in polystyrene is above 200 g / mol, the resin component is unlikely to be released from the tire and the effect of the hydrogenated resin can be fully demonstrated; when it is below 1600 g / mol, the hydrogenated resin is easily compatible with the rubber component (A).

[0372] From the viewpoint of suppressing the precipitation of hydrogenated resin from the tire and suppressing the deterioration of the tire appearance, the equivalent weight-average molecular weight of the polystyrene in the hydrogenated resin is preferably 500 g / mol or more, more preferably 550 g / mol or more, more preferably 600 g / mol or more, more preferably 650 g / mol or more, and even more preferably 700 g / mol or more. From the viewpoint of further improving the compatibility of the hydrogenated resin with the rubber component (A) and further enhancing the effect of the hydrogenated resin, the equivalent weight-average molecular weight of the polystyrene in 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.

[0373] Softening point (Ts) of hydrogenated resin HR (Unit: °C) and converted weight-average molecular weight of polystyrene (Mw) HR The ratio (Ts) of (unit: g / mol) HR / Mw HR The ratio (Ts) is preferably 0.07 or higher, more preferably 0.083 or higher, more preferably 0.095 or higher, more preferably 0.104 or higher, more preferably 0.125 or higher, more preferably 0.135 or higher, more preferably 0.14 or higher, and even more preferably 0.141 or higher. HR / Mw HR The value 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.

[0374] The softening point of hydrogenated resins and the equivalent weight-average molecular weight of polystyrene can be determined by the methods described in the following examples.

[0375] The aforementioned at least partially hydrogenated resin refers to a resin obtained through the reductive hydrogenation of a resin.

[0376] Examples of resins used as raw materials for hydrogenated resins include the aforementioned C5 series resins, C5 / C9 series resins, C9 series resins, dicyclopentadiene resins, terpene phenol resins, terpene resins, rosin resins, and alkylphenol resins, and these resins can be used alone or in combination of two or more.

[0377] The resin used as a raw material for hydrogenated resins may include, for example, a resin obtained by copolymerizing C5 fraction and dicyclopentadiene (DCPD) (C5 / DCPD resin).

[0378] Here, when the content of the component derived from dicyclopentadiene in the total amount of resin is 50% by mass or more, the C5 / DCPD resin is considered a dicyclopentadiene resin. When the content of the component derived from dicyclopentadiene in the total amount of resin is less than 50% by mass, the C5 / DCPD resin is considered a C5 resin. This also applies even when it contains a small amount of a third component, etc.

[0379] From the viewpoint of further improving the compatibility between rubber component (A) and resin (B), further improving the wet road grip performance of tires using the rubber composition, and further reducing rolling resistance, it is preferred that resin (B) is 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, hydrogenated C5 resins. It is also preferred that the resin has at least a hydrogenated DCPD structure or a hydrogenated cyclic structure in the monomer.

[0380] (Silicon dioxide)

[0381] The tire rubber composition of this embodiment preferably comprises silica. Examples of silica include wet silica (hydrated silicates), dry silica (anhydrous silicates), calcium silicate, and aluminum silicate; wet silica is preferred because it has many silanol groups. These silicas can be used alone or in combination of two or more. Silica can be a commercially available product, and products from TosohSilica Corporation, Evonik, Solvay, Solvay Japan, and Tokuyama Corporation can be used as commercially available silica products.

[0382] From the viewpoint of reducing environmental impact, silica derived from plant-based silicates is preferred as silica. Such plant-based silicates are found in plants such as mosses, ferns, horsetails, cucurbitaceae, nettles, and grasses. Among these plants, grasses are preferred. Examples of grasses include rice, bamboo grass, and sugarcane, with rice being the most preferred. Because rice is widely cultivated for consumption, it is readily available locally in a wide range of regions, and rice husks are generated in large quantities as industrial waste, making it easy to secure quantities. Therefore, from the viewpoint of easy availability, silica derived from rice husks (hereinafter also referred to as "rice husk silica") is particularly preferred as silica. By using rice husk silica, rice husks, as industrial waste, can be effectively utilized, and because the raw material can be locally obtained near tire manufacturing plants, the energy and costs of transportation and storage can be reduced, making it environmentally preferable from various perspectives. Rice husk silica can be rice husk charcoal powder obtained by carbonizing rice husks through heating, or it can be precipitated silica produced by preparing an aqueous solution of alkaline silicate from rice husk ash produced when rice husks are burned as fuel in a biomass boiler, and by using this aqueous solution of alkaline silicate via a wet process. There are no particular limitations on the method for producing rice husk charcoal, and various known methods can be used; for example, rice husk charcoal can be obtained by pyrolyzing rice husks using a kiln via steam and roasting. The rice husk charcoal thus obtained can be pulverized using a known pulverizer (e.g., a ball mill), and by selection and classification to a predetermined particle size range, rice husk charcoal powder can be obtained. Precipitated silica derived from rice husks can be produced by methods described in JP 2019-38728 A, etc.

[0383] Furthermore, from the viewpoint of reducing environmental impact, it is also preferable to use silicon dioxide produced by extracting silicate components from silicon wafer waste, which is a raw material for semiconductors, or from glass bottles, and recycling them for manufacturing.

[0384] The nitrogen adsorption specific surface area (N2SA) of silica is preferably 50 m² / s. 2 / g or more, preferably 100m 2 / g or more, and even more preferably 150m 2 / g or more, and preferably 350m 2 / g or less, more preferably 250m 2 / g or less, and more preferably 230m 2 / g or less, and even more preferably 200m 2 / g or less.

[0385] In this specification, the nitrogen adsorption specific surface area (N2SA) of silica is a value measured by the BET method according to ASTM D3037-93.

[0386] The silica content can be appropriately adjusted according to, for example, the tire type, tire component, and target performance. For example, the silica content relative to 100 parts by weight of rubber component (A) is preferably 5 parts by weight or more, more preferably 10 parts by weight or more, more preferably 30 parts by weight or more, more preferably 50 parts by weight or more, more preferably 60 parts by weight or more, and preferably 300 parts by weight or less, more preferably 200 parts by weight or less, even more preferably 180 parts by weight or less, and particularly preferably 150 parts by weight or less.

[0387] (Silane coupling agent)

[0388] When the tire rubber composition of this embodiment contains silica, it is preferred that the rubber composition contains a silane coupling agent to enhance the effect of the silica. Examples of silane coupling agents 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, and 3-triethoxysilylpropyl-N,N-dimethylthiocarbamoyltetrasulfide. - Dimethylthiocarbamoyl tetrasulfide, 2-triethoxysilylethyl-N,N-dimethylthiocarbamoyl tetrasulfide, 3-trimethoxysilylpropylbenzothiazolyl tetrasulfide, 3-triethoxysilylpropylbenzothiazolyl tetrasulfide, 3-triethoxysilylpropyl methacrylate monosulfide, 3-trimethoxysilylpropyl methacrylate monosulfide, bis(3-diethoxymethylsilylpropyl)tetrasulfide, 3-mercaptopropyldimethoxymethylsilane, dimethoxymethylsilylpropyl-N,N-dimethylthiocarbamoyl tetrasulfide, and dimethoxymethylsilylpropylbenzothiazolyl tetrasulfide, etc. Silane coupling agents can be commercially available products; for example, products from Evonik, Momentive, Shin-Etsu Silicone, Dow Corning Toray Co., Ltd., Tokyo Chemical Industry Co., Ltd., and Azumax Co., Ltd. are commercially available products that can be used as silane coupling agents. These silane coupling agents can be used alone or in combination of two or more.

[0389] The content of the silane coupling agent can be appropriately adjusted, for example, according to the target tire type, tire components, and target performance. For example, the content of the silane coupling agent relative to 100 parts by mass of silicon dioxide is preferably 1 part by mass or more, more preferably 6 parts by mass or more, even more preferably 8 parts by mass or more, and 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.

[0390] It should be noted that bioethanol can also be used as a raw material for silane coupling agents. Bioethanol is primarily produced from carbohydrates and / or cellulose as biological resources and cannot effectively utilize other biological resources, such as proteins, lipids, and amino acids. Furthermore, carbohydrates compete with food sources, and the overuse of cellulose leads to deforestation. Therefore, depending on the availability of various biological resources, renewable resources, fossil resources, and market demand (e.g., demand for biomass resources as food), it is preferable to use multiple types of ethanol derived from biological resources (bioethanol) as raw materials for silane coupling agents, or a combination of ethanol derived from biological resources, ethanol derived from renewable resources, and ethanol derived from fossil resources. In this way, a wide range of biological resources, such as carbohydrates, proteins, and lipids, as well as renewable resources, can be effectively utilized without relying on a single biological resource, and environmental factors can be taken into account depending on the manufacturing process.

[0391] (Carbon black)

[0392] The rubber composition for tires according to this embodiment preferably comprises carbon black. Plant-derived carbon black and carbon black obtained through recycling are particularly preferred as carbon black. Examples of plant-derived carbon black include those derived from castor oil and rosin oil. Examples of carbon black obtained through recycling include carbon black obtained through the pyrolysis of waste tires, etc., and carbon black obtained from waste oil. There are no particular limitations on the grade of carbon black, and examples include N134, N110, N220, N234, N219, N339, N330, N326, N351, N550, and N762. Commercially available products can be used as carbon black, and examples of commercially available carbon black products include those from Asahi Carbon Co., Ltd., Cabot Japan KK, Tokai Carbon Co., Ltd., Mitsubishi Chemical Corporation, Lion Corporation, Nippon Steel Carbon Co., Ltd., and Birla Carbon, etc. These carbon blacks can be used alone or in combination of two or more.

[0393] The nitrogen adsorption specific surface area (N2SA) of carbon black is not particularly limited and can be appropriately adjusted, for example, according to the target tire type, tire components, and target performance. For example, the nitrogen adsorption specific surface area (N2SA) of carbon black is preferably 20 m². 2 / g or more, preferably 50m 2 / g or more, and even better 70m 2 / g or higher, or even better 90m 2 / g or more, and preferably 200m 2 / g or less, preferably 150m 2 / g or less, and more preferably 130m 2 / g or less.

[0394] It should be noted that, 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).

[0395] There are no particular limitations on the carbon black content, and it can be appropriately adjusted, for example, according to the target tire type, tire components, and target performance. For example, the carbon black content 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, relative to 100 parts by mass of rubber component (A).

[0396] There is no particular limitation on the proportion of silica in the total content of silica and carbon black, and it can be appropriately adjusted, for example, according to the target tire type, tire components, and target performance. For example, in the case of tread rubber for passenger car tires, 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, and even more preferably 90% by mass or more, and particularly preferably 95% by mass or more. The proportion of silica in the total content of silica and carbon black can be 100% by mass, but it is preferably 98% by mass or less.

[0397] (Rubber powder)

[0398] The rubber composition for tires according to this embodiment may contain rubber powder. Rubber powder can be obtained by shredding waste rubber products, such as waste tires, and, if necessary, removing reinforcing components such as steel and fibers, dust, glass, sand, and stones, or by preparing a new vulcanized rubber composition for the purpose of producing rubber powder and then shredding it. For example, rubber powder can be obtained from vulcanized rubber using the methods described in "Rubber Chemistry and Technology". In the process of obtaining rubber powder by shredding vulcanized rubber, mechanical processing or cryogenic processing can be used. For example, in mechanical processing, various shredding devices such as cracker mills and granulators can be used to mechanically shred vulcanized rubber into fine particles. In cryogenic processing, the shredded fine vulcanized rubber is frozen at extremely low temperatures and then shredded into fine particles. To remove steel, magnetic separators can be used, and to remove fibers, air classifiers can be used. Commercially available products can also be used as rubber powder, and examples of commercially available rubber powder products include those from Global Corporation and Nantong Huili Rubber Corporation. From the perspective of reducing environmental impact, it is preferable to use rubber powder obtained by shredding waste rubber products, such as waste tires. Rubber powder can be used alone or in combination of two or more types.

[0399] The composition of the rubber powder is not particularly limited and depends on the composition of the vulcanized rubber in the waste rubber product (waste tires) used as raw material. In one embodiment, the rubber powder comprises a rubber component, carbon black, and silica, etc. The rubber component, carbon black, and silica contained in the rubber powder may be the same as or different from the rubber component (A), carbon black, and silica contained in the rubber composition of this embodiment described above.

[0400] The volume average particle size 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 size of the rubber powder, the better, and there is no particular limitation on the lower limit.

[0401] It should be noted that in this specification, a laser diffraction particle size distribution measuring device is used to measure the volume average particle size, and for example, a "CAPA500" manufactured by HORIBA, Ltd. can be used for measurement.

[0402] The residue of rubber powder on a 60-mesh sieve is preferably less than 1% by mass, more preferably less than 0.5% by mass, and even more preferably less than 0.1% by mass, with no particular limitation on the lower limit. The residue of rubber powder on an 80-mesh sieve is preferably less than 10% by mass, more preferably less than 1% by mass, and even more preferably less than 0.5% by mass, with no particular limitation on the lower limit.

[0403] It should be noted that in this specification, the sieve residue is measured according to ASTM D5644-01.

[0404] The acetone extract content of the rubber powder is preferably 12% by mass or less, more preferably 11% by mass or less, 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.

[0405] It should be noted that, in this specification, the acetone extract content in the rubber powder refers to the acetone extract content (%) determined by the acetone extraction method according to JIS K6350.

[0406] The content of rubber powder is not particularly limited and can be appropriately adjusted, for example, according to the target tire type, tire components, and target performance. For example, the content of rubber powder relative to 100 parts by weight of rubber component (A) is preferably 1 part by weight or more, more preferably 2 parts by weight or more, even more preferably 3 parts by weight or more, and preferably 200 parts by weight or less, more preferably 150 parts by weight or less, even more preferably 100 parts by weight or less, more preferably 50 parts by weight or less, even more preferably 30 parts by weight or less, even more preferably 15 parts by weight or less, even more preferably 10 parts by weight or less, and particularly preferably 5 parts by weight or less.

[0407] (Liquid softener)

[0408] The rubber composition for tires according to this embodiment may contain a liquid softener. Here, "liquid softener" refers to a compounding agent that is liquid at 25°C (room temperature) and has the function of softening the rubber composition. There are no particular limitations on the liquid softener, and examples include oils and liquid polymers, with oils being preferred. These liquid softeners may be used alone or in combination of two or more.

[0409] The term "oil" is a general term for incremental oils contained in rubber components and liquid oil components added as compounding agents in rubber compositions, and examples include vegetable oils, processing oils, oils obtained by recycling vegetable oils or processing oils, and mixtures thereof. From the viewpoint of reducing environmental impact, vegetable oils and oils obtained through recycling are preferred as oils. Examples of vegetable oils include palm oil, castor oil, cottonseed oil, soybean oil, linseed oil, rapeseed oil, coconut oil, peanut oil, pine oil, pine tar, tall oil, corn oil, rice bran oil, safflower oil, sesame oil, olive oil, sunflower oil, palm kernel oil, camellia oil, jojoba oil, macadamia oil, tung oil, and coconut oil, etc. Examples of processing oils include, for example, paraffin-based processing oils, aromatic processing oils, and naphthenic processing oils, etc. Commercially available products can be used as oils, and examples of commercially available oil products include those from Idemitsu Kosan Co., Ltd., SANKYO YUKA KOGYO KK, ENEOS Corporation, Orisoy, H&R, Toyokuni Oil Co., Ltd., and Nisshin OilliO Group, Ltd. These oils can be used alone or in combination of two or more.

[0410] Liquid diene polymers are preferred as liquid polymers. Examples of liquid diene polymers include liquid styrene-butadiene copolymers (liquid SBR), liquid polybutadiene (liquid BR), liquid polyisoprene (liquid IR), liquid styrene-isoprene copolymers (liquid SIR), liquid styrene-butadiene-styrene block copolymers (liquid SBS block copolymers), liquid styrene-isoprene-styrene block copolymers (liquid SIS block copolymers), liquid farnese, and liquid farnese-butadiene copolymers. These liquid polymers can be hydrogenated, and the ends or main chain can be modified with functional groups (polar groups). These liquid polymers can be used alone or in combination of two or more.

[0411] The content of the liquid softener is not particularly limited and can be appropriately adjusted, for example, according to the target tire type, tire components, and target performance. For example, the content of the liquid softener relative to 100 parts by weight of rubber component (A) is preferably 5 parts by weight or more, more preferably 10 parts by weight or more, and preferably 100 parts by weight or less, more preferably 70 parts by weight or less, even more preferably 50 parts by weight or less, and even more preferably 30 parts by weight or less.

[0412] (Anti-aging agents)

[0413] The rubber composition for tires according to this embodiment may contain an antioxidant. Examples of antioxidants include 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), and 6-anilino-2,2,4-trimethyl-1,2-dihydroquinoline, etc. Commercially available products can be used as antioxidants, and examples of commercially available antioxidant products include those from Ouchi Shinko Chemical Industrial Co., Ltd., Sumitomo Chemical Co., Ltd., Seiko-Chemical Co., Ltd., and Flexsys. These antioxidants can be used alone or in combination of two or more.

[0414] There are no particular limitations on the content of antioxidants, and they can be appropriately adjusted, for example, according to the target tire type, tire components, and target performance. For example, the content of antioxidants relative to 100 parts by weight of rubber component (A) is preferably 1 part by weight or more, more preferably 1.5 parts by weight or more, even more preferably 2 parts by weight or more, and preferably 12 parts by weight or less, more preferably 10 parts by weight or less, and even more preferably 8 parts by weight or less.

[0415] (wax)

[0416] The rubber composition for tires according to this embodiment may contain wax. Examples of waxes include natural waxes, such as plant-based and animal-based waxes; petroleum-based waxes, such as paraffin wax and microcrystalline wax; and synthetic waxes, such as polymers of ethylene and polymers of propylene; etc. Commercially available products may be used as waxes, and examples of commercially available wax products include those from Seiko-Chemical Co., Ltd., Nippon Seiro Co., Ltd., and Ouchi Shinko Chemical Industrial Co., Ltd., etc. These waxes may be used alone or in combination of two or more.

[0417] There are no particular limitations on the wax content, and it can be appropriately adjusted, for example, according to the target tire type, tire components, and target performance. For example, the wax content is preferably 0.5 parts by mass or more, more preferably 1 part by mass or more, and more preferably 10 parts by mass or less, more preferably 6 parts by mass or less, relative to 100 parts by mass of rubber component (A).

[0418] (Stearic acid)

[0419] The rubber composition for tires according to this embodiment may contain stearic acid. Commercially available products can be used as stearic acid, and examples of commercially available stearic acid products include those from NOF Corporation, Kao Corporation, FUJIFILM Wako Pure Chemical Corporation, and Chiba Fatty Acid Co., Ltd. These commercially available stearic acids may be used alone or in combination of two or more.

[0420] The content of stearic acid is not particularly limited and can be appropriately adjusted, for example, according to the target tire type, tire components, and target performance. For example, the content of stearic acid is preferably 1 part by mass or more, more preferably 2 parts by mass or more, and more preferably 10 parts by mass or less, more preferably 6 parts by mass or less, relative to 100 parts by mass of rubber component (A).

[0421] (Zinc oxide)

[0422] The rubber composition for tires according to this embodiment may contain zinc oxide (zinc white). Zinc oxide obtained not only from zinc ingots but also from recycled zinc or zinc slag (i.e., obtained through recycling) is preferred. Commercially available products can be used as zinc oxide, and examples of commercially available zinc oxide products include those from HakusuiTech 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 oxides can be used alone or in combination of two or more.

[0423] The zinc oxide content is not particularly limited and can be appropriately adjusted, for example, according to the target tire type, tire components, and target performance. For example, the zinc oxide content is preferably 1 part by mass or more, more preferably 2 parts by mass or more, and more preferably 10 parts by mass or less, more preferably 6 parts by mass or less, relative to 100 parts by mass of rubber component (A).

[0424] (sulfur)

[0425] The rubber composition for tires according to this embodiment preferably contains sulfur. As sulfur, those derived from fossil resources, those derived from recycled resources, and those obtained by processing materials derived from biological resources can be used, and from the viewpoint of reducing environmental impact, sulfur obtained from waste derived from biological resources is particularly preferred. As a method for obtaining sulfur from waste derived from biological resources, for example, the method described in the aforementioned Japanese Patent Application No. 2022-140390 can be used. As sulfur, powdered sulfur, precipitated sulfur, colloidal sulfur, insoluble sulfur, highly dispersed sulfur, and soluble sulfur, which are commonly used as crosslinking agents in the rubber industry, can also be used. Commercially available products can be used as sulfur, and examples of commercially available sulfur products include those from Tsurumi Chemical Industry Co., Ltd., Hosoi Chemical Industry Co., Ltd., Karuizawa Sulfur Co., Ltd., Shikoku Chemicals Corp., and Flexsys, etc. These sulfurs can be used alone or in combination of two or more.

[0426] The sulfur content is not particularly limited and can be appropriately adjusted, for example, according to the target tire type, tire components, and target performance. For example, the sulfur content relative to 100 parts by weight of rubber component (A) is preferably 0.3 parts by weight or more, more preferably 0.5 parts by weight or more, even more preferably 0.8 parts by weight or more, and preferably 8 parts by weight or less, more preferably 5 parts by weight or less.

[0427] (Vulcanization accelerator)

[0428] Preferably, the rubber composition for tires according to this embodiment includes a vulcanization accelerator. The vulcanization accelerator can be derived from fossil resources, renewable resources, or biological resources, but from the viewpoint of reducing environmental impact, derived from biological resources is preferred. Vulcanization accelerators derived from biological resources can be obtained, for example, by the method disclosed in 2005-139239 A.

[0429] Examples of vulcanization accelerators include sulfenamide-based vulcanization accelerators, such as N-cyclohexyl-2-benzothiazolyl sulfenamide (CBS), N,N-dicyclohexyl-2-benzothiazolyl sulfenamide, N-tert-butyl-2-benzothiazolyl sulfenamide (TBBS), N-oxyethylene-2-benzothiazolyl sulfenamide, and N,N'-diisopropyl-2-benzothiazolyl sulfenamide; and guanidine-based vulcanization accelerators, such as 1,3-diphenylguanidine (DP). G), 1,3-di-o-tolylguanidine and o-tolylbiguanidine; thiazole-based vulcanization accelerators, such as 2-mercaptobenzothiazole (M) and di-2-benzothiazole disulfide (MBTS, DM); and thiuram-based vulcanization accelerators, such as tetramethylthiuram disulfide (TMTD), tetrastearylthiuram disulfide, tetrabenzylthiuram disulfide (TBzTD), and tetra(2-ethylhexyl)thiuram disulfide (TOT-N). Commercially available products can be used as vulcanization accelerators, and products from Ouchi Shinko Chemical Industrial Co., Ltd. and Sumitomo Chemical Co., Ltd., etc., can be used as such commercially available products. These vulcanization accelerators can be used alone or in combination of two or more.

[0430] There is no particular limitation on the content of the vulcanization accelerator, and it can be appropriately adjusted according to, for example, the tire type, tire component, and target performance. For example, the content of the vulcanization accelerator relative to 100 parts by weight of rubber component (A) is preferably 1 part by weight or more, more preferably 2 parts by weight or more, and even more preferably 3 parts by weight or more, and preferably 8 parts by weight or less, more preferably 6 parts by weight or less, and even more preferably 5.5 parts by weight or less.

[0431] (cellulose nanofibers)

[0432] The rubber composition for tires according to this embodiment may contain cellulose nanofibers (CNF). The rubber composition can be reinforced by blending cellulose nanofibers into it. Modified cellulose nanofibers are preferred as cellulose nanofibers, and these modified cellulose nanofibers are fine fibers made from modified cellulose as a raw material. 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 diameter and fiber length obtained by observing each fiber using a scanning electron microscope (SEM), atomic force microscope (AFM), or transmission electron microscope (TEM). Cellulose nanofibers can be obtained by fibrillating cellulose. Furthermore, the average fiber length and average fiber diameter of the fine fibers can be adjusted by oxidation treatment and fibrillation treatment.

[0433] The raw materials for cellulose nanofibers only need to contain cellulose and are not particularly limited, but examples include plants (e.g., wood, bamboo, hemp, jute, hibiscus, agricultural residues, cloth, pulp (unbleached coniferous kraft pulp (NUKP), bleached coniferous kraft pulp (NBKP), unbleached broadleaf kraft pulp (LUKP), bleached broadleaf kraft pulp (LBKP), bleached kraft pulp (BKP), unbleached coniferous sulfite pulp (NUSP), bleached coniferous sulfite pulp (NBSP), thermomechanical pulp (TMP), recycled pulp, waste paper, etc.)), animals (e.g., tunicates), algae, microorganisms (e.g., acetic acid bacteria (Acetobacter)) and microbial products. These cellulose raw materials can be used alone or in combination of two or more.

[0434] The content of cellulose nanofibers is not particularly limited and can be appropriately adjusted according to, for example, the type of tire to which it is applied, the tire component, and the target performance. For example, the content of cellulose nanofibers relative to 100 parts by weight of rubber component (A) is preferably in the range of 1 to 100 parts by weight, more preferably in the range of 5 to 70 parts by weight, and even more preferably in the range of 10 to 40 parts by weight.

[0435] (Porous cellulose particles)

[0436] The rubber composition for tires according to this embodiment may contain porous cellulose particles. The porous cellulose particles preferably have a porous structure with a porosity of 75% to 95%, and by blending them into the rubber composition, ice performance can be improved. When the porosity of the porous cellulose particles is above 75%, the effect of improving ice performance is excellent, and when the porosity is below 95%, the strength of the particles can be increased. A porosity more preferably is 80% to 90%. The porosity of the porous cellulose particles can be determined by measuring the volume of a sample (i.e., porous cellulose particles) of a specific mass using a calibrated measuring cylinder, determining the bulk density, and calculating according to the following formula:

[0437] Porosity (%) = {1 - [bulk density of sample (g / mL)] / [true specific gravity of sample (g / mL)]} × 100

[0438] Here, the true specific gravity of cellulose is 1.5.

[0439] There is no particular limitation on the particle size of porous cellulose particles, but from the viewpoint of abrasion resistance, those with an average particle size of 1000 μm or less are preferred. There is no particular limitation on the lower limit of the average particle size, but it is preferred to be 5 μm or more. The average particle size is more preferably 100 to 800 μm, and even more preferably 200 to 800 μm.

[0440] Spherical particles with an aspect ratio of 1 to 2 are preferred as porous cellulose particles. Using such spherical particles improves dispersibility in the rubber composition, which can help improve ice performance and maintain abrasion resistance, among other things. An aspect ratio of 1.0 to 1.5 is more preferred.

[0441] The average particle size and major-to-minor ratio of porous cellulose particles are determined as follows: images of porous cellulose particles are obtained by observing them under a microscope, and using these images, the major and minor diameters of 100 particles are measured (the length along one axial direction and the length along the axial direction perpendicular to it if the major and minor diameters are the same), and the average value is calculated to obtain the average particle size, and the average ratio of the major diameter to the minor diameter is calculated to obtain the major-to-minor ratio.

[0442] As porous cellulose particles, those that are commercially available from Rengo Co., Ltd. under the trade name "Viscopearl" and those described in JP 2001-323095 A and JP 2004-115284 A may be used appropriately.

[0443] The content of porous cellulose particles is not particularly limited and can be appropriately adjusted according to, for example, the type of tire to which it is applied, the tire component, and the target performance. For example, the content of porous cellulose particles relative to 100 parts by weight of rubber component (A) is preferably in the range of 0.3 to 20 parts by weight, more preferably in the range of 1 to 15 parts by weight, and even more preferably in the range of 3 to 15 parts by weight.

[0444] (Fine solid particles)

[0445] The rubber composition for tires according to this embodiment may contain solid fine particles. By blending the solid fine particles into the rubber composition, ice performance can be improved. The average particle size of the solid fine particles is preferably 1 μm or more, more preferably 1000 μm or less, and even more preferably 300 μm or less. Examples of solid fine particles include plant-derived powders obtained from plants such as rice husks, walnut powder, or walnut shells; animal-derived powders obtained from animals such as eggshells (eggshell powder) and bone meal; powders derived from natural minerals such as white sand (shirasu); inorganic fine particles such as graphite and zinc oxide whiskers; water-soluble metal salt fine particles such as magnesium sulfate and metal salts of lignin sulfonic acid; and non-metallic fibers such as glass fibers. Among these, rice husks, walnut shells, eggshells, and white sand are preferred.

[0446] The content of solid fine particles is not particularly limited and can be appropriately adjusted according to, for example, the type of tire to which it is applied, the tire component, and the target performance. For example, the content of solid fine particles relative to 100 parts by weight of rubber component (A) is preferably in the range of 0.3 to 20 parts by weight, more preferably in the range of 1 to 15 parts by weight, and even more preferably in the range of 3 to 15 parts by weight.

[0447] (other)

[0448] In addition to the components described above, the rubber composition for tires according to this embodiment may further contain various additives commonly used in the tire industry, such as fillers including calcium carbonate, talc, alumina, clay, aluminum hydroxide, and mica; and organic peroxides; etc. The content of these additives is not particularly limited and can be appropriately adjusted according to, for example, the type of tire to which they are applied, the tire component, and the target performance. For example, the content is preferably in the range of 0.1 to 200 parts by weight relative to 100 parts by weight of rubber component (A).

[0449] (Method for producing rubber compositions)

[0450] There are no particular limitations on the method for producing the rubber composition for tires according to this embodiment, but for example, it can be produced by blending various components appropriately selected as needed into rubber component (A), followed by mixing, heating, extrusion, etc. Furthermore, vulcanized rubber can be obtained by vulcanizing the obtained rubber composition.

[0451] There are no particular restrictions on mixing conditions, and various conditions can be appropriately selected according to the purpose, such as the input volume of the mixing equipment, the rotational speed of the rotor, the pressure of the top plug, the mixing temperature, the mixing time, and the type of mixing equipment. Examples of mixing equipment typically include Banbury internal mixers, intermixers, compounding mills, and rollers for mixing rubber compositions.

[0452] There are no particular restrictions on heating conditions, and various conditions can be appropriately selected according to the purpose, such as heating temperature, heating time, and heating equipment. As for heating equipment, heating rollers, which are commonly used to heat rubber compositions, can be mentioned.

[0453] There are no particular restrictions on extrusion conditions, and various conditions, such as extrusion time, extrusion speed, extrusion equipment, and extrusion temperature, can be appropriately selected according to the purpose. As for extrusion equipment, extruders, which are commonly used for extruding rubber compositions, can be mentioned. The extrusion temperature can be appropriately determined.

[0454] There are no particular restrictions on the equipment, methods, and conditions for vulcanization, and they can be appropriately selected according to the purpose. As for vulcanization equipment, a molding vulcanizing machine, such as a mold, is commonly used to vulcanize rubber compositions. For vulcanization conditions, the temperature is, for example, about 100°C to 190°C.

[0455] (use)

[0456] The rubber composition for tires in this embodiment can be applied to various tire components, such as tread (tread crown, tread base, tread layer under buffer layer), buffer rubber, tire shoulder, tire sidewall, clinch stress concentration area, bead filler, coating rubber for tire body, insulator, bead wrapping and liner, etc., and can also be used in the side reinforcement layer of run-flat tires, etc.

[0457] <Tread rubber>

[0458] The tread rubber of this embodiment is characterized by being composed of the above-described rubber composition for tires.

[0459] Since the tread rubber of this embodiment is composed of the aforementioned rubber composition for tires, it has a high proportion of sustainable materials, and when considering the entire process of synthetic rubber production, use, and disposal, it can promote a reduction in environmental impact. Therefore, by applying the tread rubber of this embodiment to tires, it becomes possible to improve the proportion of sustainable materials in tires, and when considering the entire process of synthetic rubber production, use, and disposal, it can promote a reduction in environmental impact.

[0460] The tread rubber in this implementation scheme can be applied to new tires or retreaded tires.

[0461] Furthermore, the tread rubber of this embodiment can be applied to pneumatic tires or non-pneumatic tires.

[0462] <Tires>

[0463] The tire of this embodiment is characterized by including the aforementioned tread rubber.

[0464] Because the tire of this embodiment contains the aforementioned tread rubber, it improves the ratio of sustainable materials and promotes a reduction in environmental impact when considering the entire process of synthetic rubber production, use, and disposal. Furthermore, the tire of this embodiment does not compromise performance.

[0465] The embodiments of the tire disclosed herein will now be described in detail with reference to the accompanying drawings.

[0466] Figure 1 This is a cross-sectional view of an embodiment of the tire disclosed herein. Figure 1The tire 1 of the present embodiment shown includes a pair of bead portions 2, a pair of sidewall portions 3 and a tread portion 4 continuous with the two sidewall portions 3, and includes a tire body 5 extending circumferentially between the pair of bead portions 2 to reinforce each of these portions 2, 3 and 4, and a belt 6 disposed on the radially outer side of the crown portion of the tire body 5.

[0467] Figure 1 The tire 1 shown has a carcass 5 composed of a single carcass ply, which is formed by covering a plurality of parallel cords with coated rubber. The carcass 5 includes a main body extending annularly between bead cores 7 embedded in the bead portion 2, and a folded portion that is radially outwardly wound around each bead core 7 from the inside to the outside along the tire width direction. However, in the tires of this disclosure, the number of plies and the structure of the carcass 5 are not limited thereto.

[0468] also, Figure 1 The belt 6 of the tire 1 shown is composed of two belt layers 6A and 6B; however, in the tires of this disclosure, the number of belt layers constituting the belt 6 is not limited to this, and the number of belt layers can be three or more. Here, belt layers 6A and 6B are typically rubberized layers of cords (preferably steel cords) that extend obliquely relative to the tire equator, and the two belt layers 6A and 6B are stacked such that the cords constituting belt layers 6A and 6B cross each other across the tire equator to form the belt 6.

[0469] The tire 1 of this embodiment has a tread rubber 8 on the outermost surface of the tread portion 4, and the rubber composition for tires described above is used in the tread rubber 8. Therefore, the tire 1 of this embodiment has an improved ratio of sustainable materials.

[0470] Note that the tire disclosed herein only requires a tread rubber composed of the rubber composition for tires described in this embodiment, and various modifications can be made. For example, a belt reinforcement layer can be provided. Figure 1 The belt 6 of the tire 1 shown can be divided into a crown rubber on the outermost surface and a base rubber on the innermost surface of the tire.

[0471] The tire of this embodiment can be produced by using the above-described rubber composition as the tread rubber through conventional methods. For example, the tire of this embodiment can be obtained, depending on the type of tire being applied, by molding an unvulcanized rubber composition and then vulcanizing it, or by molding a semi-vulcanized rubber that has already undergone a pre-vulcanization step and then further vulcanizing it. Note that the tire of this embodiment is preferably a pneumatic tire, and in addition to ordinary air or air with adjusted oxygen partial pressure, inert gases such as nitrogen, argon, and helium can be used as the gas filling the pneumatic tire.

[0472] Example

[0473] The present disclosure will be described in more detail below by way of examples, but the present disclosure is not limited in any way to the following examples.

[0474] <Preparation and Evaluation of Rubber Compositions>

[0475] Each rubber composition was produced using conventional methods according to the formulations shown in Table 1.

[0476] The mass fraction of each compound is described with two significant figures.

[0477] (1) Ratio of sustainable materials

[0478] For each obtained rubber composition, the total mass ratio of materials derived from biological resources (biomass resources) to materials derived from renewable resources is calculated to determine the ratio of sustainable materials.

[0479] The results are shown in Table 1. The larger the value, the better the effect.

[0480] (2) Tire performance

[0481] The following methods were used to evaluate low fuel economy and wet road grip performance.

[0482] (2-1) Low fuel economy

[0483] The loss tangent (tanδ) of a vulcanized rubber test piece prepared from a rubber composition was measured using a viscoelasticity meter (manufactured by GABO) at a temperature of 50°C, a strain of 1%, and a frequency of 15 Hz.

[0484] (2-2) Wet road grip performance

[0485] The loss tangent (tanδ) of a vulcanized rubber test piece prepared from a rubber composition was measured using a viscoelasticity meter (manufactured by GABO) at a temperature of -5°C, a strain of 1%, and a frequency of 15 Hz.

[0486] As a result of the evaluation by the above method, the low fuel economy and wet road grip performance are comparable in Comparative Example 1 and Example 1.

[0487] [Table 1]

[0488]

[0489] 1 NR: Natural Rubber

[0490] 2 SBR-1: Styrene-butadiene rubber modified with hydroxyl silane compounds synthesized by the following method

[0491] 3. SBR-2: A modified styrene-butadiene rubber with nitrogen and alkoxysilyl groups, containing 10.0 parts by weight of oil component per 100 parts by weight of rubber component, with a weight average molecular weight (Mw) of 85.2 × 10⁻⁶. 4

[0492] 4. SBR-3: Modified styrene-butadiene rubber supplied via a mass balance method as in SBR-1, certified by ISCC PLUS as a synthetic rubber derived from bio-based and / or recycled feedstocks via a mass balance method, wherein the percentage of sustainable materials is 100% by mass, corresponding to sustainable materials.

[0493] 5. Carbon Black: Manufactured by Tokai Carbon Co., Ltd., trade name "SEAST 7HM"

[0494] 6. Silica: Manufactured by Tosoh Silica Corporation, trade name "Nipsil AQ"

[0495] 7. Resin: C5 / C9 series resin, manufactured by Tonen Chemical Corporation, trade name "T-REZRD104"

[0496] 8. Other chemicals: Total amount of sulfur, vulcanization accelerator, zinc oxide, stearic acid, workability improver, antioxidant, wax, silane coupling agent, aluminum hydroxide, and retarder. In Comparative Example 1 and Example 1, all were blended in equal parts by mass.

[0497] <SBR-1( 2) Synthesis method >

[0498] In a dried and nitrogen-purged 800 mL pressure-resistant glass container, a cyclohexane solution of 1,3-butadiene and a cyclohexane solution of styrene were added to provide 67.5 g of 1,3-butadiene and 7.5 g of styrene. 0.6 mmol of 2,2-di-tetrahydrofuranylpropane was added, followed by 0.8 mmol of n-butyllithium, and polymerization was carried out at 50 °C for 1.5 h. For the polymerization system where the polymerization conversion was close to 100% at this point, 0.72 mmol of N,N-bis(trimethylsilyl)-3-[diethoxy(methyl)silyl]propylamine was added as a modifier, and the modification reaction was carried out at 50 °C for 30 min. Subsequently, 2 mL of a 5% by mass solution of 2,6-di-tert-butyl-p-cresol (BHT) in isopropanol was added to stop the reaction, and the modified SBR was obtained by drying according to conventional methods.

[0499] As a result of the measurement of the microstructure of the modified SBR, the styrene content was 10% by mass and the glass transition temperature (Tg) was -65℃.

[0500] As can be understood from Table 1, the rubber composition according to the embodiments of this disclosure comprises synthetic rubber supplied in a mass-balanced manner, thereby improving the ratio of sustainable materials, and by applying it to tires, the ratio of sustainable materials in tires can be improved.

[0501] Explanation of reference numerals in the attached figures

[0502] 1: Tires

[0503] 2: Bead area

[0504] 3: Sidewall

[0505] 4: Fetal face

[0506] 5: Fetus

[0507] 6: Belt

[0508] 6A, 6B: Belt layer

[0509] 7: Tire bead core

[0510] 8: Tread rubber

Claims

1. A rubber composition for tires comprising a rubber component (A), said rubber component (A) comprising an isoprene backbone rubber (A1) and a synthetic rubber (A2), wherein In 100 parts by weight of the rubber component (A), the content of the isoprene skeleton rubber (A1) is from 10 parts by weight to 90 parts by weight, and the content of the synthetic rubber (A2) is from 90 parts by weight to 10 parts by weight. The synthetic rubber (A2) comprises synthetic rubber (A2-1) supplied according to a mass balance method.

2. The rubber composition for tires according to claim 1, wherein the synthetic rubber (A2) comprises at least one type of synthetic rubber derived from plant-derived raw materials, plant-derived by-products, raw materials obtained by recycling plant-derived materials, or raw materials obtained by recycling materials derived from fossil resources.

3. The rubber composition for tires according to claim 1, wherein the synthetic rubber (A2) comprises 0.1% to 99% by mass of synthetic rubber derived from biological resources and 99.9% to 1% by mass of synthetic rubber derived from fossil resources.

4. The rubber composition for tires according to claim 1, further comprising resin (B).

5. The rubber composition for tires according to claim 4, wherein the content of the resin (B) is from 1 part by weight to 50 parts by weight relative to 100 parts by weight of the rubber component (A).

6. A tread rubber comprising the rubber composition for tires according to any one of claims 1 to 5.

7. A tire comprising the tread rubber according to claim 6.

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