Tire rubber composition, tread rubber, and tire

Abstract

Provided is a rubber composition that is for tires and that is capable of achieving, at a high-level, a balance between low fuel consumption performance and wet-grip performance of a tire.　The rubber composition for tires according to the present invention contains rubber components, a resin component, and a filler, and is characterized in that the rubber components include a diene-based rubber component A containing an isoprene backbone rubber and having a glass transition temperature of -50°C or less and include a diene-based rubber component B containing a butadiene backbone rubber and being uncompatible with the diene-based rubber component A, the total contained amount of styrene in the diene-based rubber component B is 15 mass% or less, the resin component has a weight average molecular weight (Mw) of 200-1600 g / mol, the contained amount of the resin component is 1-45 parts by mass with respect to 100 parts by mass of the rubber components, and 0°C tanδ / 50°C tanδ of the composition is 2.7 or more.

Description

[Technical Field]

[0001] This invention relates to a rubber composition for tires, tread rubber, and tires. [Background technology]

[0002] Conventionally, from the standpoint of improving vehicle safety, various studies have been conducted to improve braking performance on wet road surfaces (hereinafter abbreviated as "wet grip performance"). For example, Patent Document 1 below discloses that applying a rubber composition, which is a blend of a thermoplastic resin and a silica-containing filler to a rubber component containing 70% by mass or more of natural rubber, to the tread rubber of a tire improves the braking performance of the tire on both dry and wet road surfaces. On the other hand, in line with the growing global concern over environmental issues and the resulting global movement towards carbon dioxide emission regulations, there is a growing demand for more fuel-efficient vehicles. To meet this demand, tire performance is also required to improve fuel efficiency (reduce rolling resistance). [Prior art documents] [Patent Documents]

[0003] [Patent Document 1] International Publication No. 2015 / 079703 [Overview of the Initiative] [Problems that the invention aims to solve]

[0004] However, the inventors have found that while the technology described in Patent Document 1 can improve the wet grip performance of tires, there is room for improvement in fuel efficiency.

[0005] Therefore, the object of the present invention is to solve the problems of the above-mentioned prior art and to provide a tire rubber composition that can achieve a high balance between the wet grip performance and fuel efficiency of the tire, and a tread rubber made from such a rubber composition. Furthermore, the present invention aims to provide a tire that achieves a high degree of balance between wet grip performance and fuel efficiency. [Means for solving the problem]

[0006] The gist of the present invention, which solves the above problems, is as follows.

[0007] The present invention relates to a tire rubber composition comprising a rubber component, a resin component, and a filler, The rubber component includes a diene-based rubber component A containing an isoprene skeleton rubber and having a glass transition temperature of -50°C or lower, and a diene-based rubber component B containing a butadiene skeleton rubber and being incompatible with the diene-based rubber component A. The total styrene content in the aforementioned diene rubber component B is 15% by mass or less. The aforementioned resin component has a weight-average molecular weight (Mw) of 200 to 1600 g / mol, and its content is 1 to 45 parts by mass per 100 parts by mass of the rubber component. The content of the filler is 20 to 120 parts by mass per 100 parts by mass of the rubber component. The characteristic feature is that the ratio of tanδ at 0°C (0°C tanδ) to tanδ at 50°C (50°C tanδ) (0°C tanδ / 50°C tanδ) is 2.7 or greater. The rubber composition for tires according to the present invention, when applied to tires, makes it possible to achieve a high level of balance between the wet grip performance and fuel efficiency of the tire. The weight-average molecular weight of the resin component is measured by gel permeation chromatography (GPC), and the value is calculated on a polystyrene basis.

[0008] Furthermore, the tread rubber of the present invention is characterized by comprising the above-described tire rubber composition. When applied to a tire, this tread rubber of the present invention makes it possible to achieve a high degree of balance between the wet grip performance and fuel efficiency of the tire.

[0009] Furthermore, the tire of the present invention is characterized by having the above-mentioned tread rubber. The tire of the present invention achieves a high degree of balance between wet grip performance and fuel efficiency. [Effects of the Invention]

[0010] According to the present invention, it is possible to provide a tire rubber composition that can achieve a high degree of balance between the wet grip performance and fuel efficiency of the tire, and a tread rubber made from such a rubber composition. Furthermore, according to the present invention, it is possible to provide a tire that achieves a high degree of balance between wet grip performance and fuel efficiency. [Modes for carrying out the invention]

[0011] The rubber composition for tires, tread rubber, and tires of the present invention will be described in detail below, based on embodiments thereof.

[0012] <Rubber composition for tires> The present invention relates to a tire rubber composition comprising a rubber component, a resin component, and a filler, The rubber component includes a diene-based rubber component A containing an isoprene skeleton rubber and having a glass transition temperature of -50°C or lower, and a diene-based rubber component B containing a butadiene skeleton rubber and being incompatible with the diene-based rubber component A. Furthermore, the present invention is characterized in that the total styrene content in the diene-based rubber component B is 15% by mass or less. The aforementioned resin component contains 1 to 45 parts by mass of a resin having a weight-average molecular weight (Mw) of 200 to 1600 g / mol per 100 parts by mass of the rubber component. The content of the filler is 20 to 120 parts by mass per 100 parts by mass of the rubber component. The characteristic feature is that the ratio of tanδ at 0°C (0°C tanδ) to tanδ at 50°C (50°C tanδ) (0°C tanδ / 50°C tanδ) is 2.7 or greater.

[0013] In the rubber composition for tires of the present invention, by incorporating a resin having a weight-average molecular weight (Mw) of 200 to 1600 g / mol in an amount of 1 part by mass or more per 100 parts by mass of the rubber component, the wet grip performance of a tire to which the rubber composition is applied can be improved. However, simply incorporating the resin component reduces the fuel efficiency of tires to which the rubber composition is applied, and if the resin component content exceeds 45 parts by mass per 100 parts by mass of rubber component, the fuel efficiency of tires to which the rubber composition is applied deteriorates. In contrast, in the tire rubber composition of the present invention, the resin component content is set to 45 parts by mass or less per 100 parts by mass of rubber component, and the total styrene content in diene-based rubber component B is set to 15% by mass or less, thereby improving the dispersibility of the filler and complementing the fuel efficiency of tires to which the rubber composition is applied. Furthermore, by setting the ratio of tanδ at 0°C (0°C tanδ / 50°C tanδ) to tanδ at 50°C (50°C tanδ) to 2.7 or higher, the rubber composition of the present invention can increase losses at low temperatures while suppressing losses at high temperatures. Therefore, it is possible to achieve a high level of both wet grip performance and fuel efficiency in tires to which the rubber composition is applied.

[0014] Furthermore, in the rubber composition for tires of the present invention, the 0°C tanδ / 50°C tanδ must be 2.7 or higher. However, if the 0°C tanδ / 50°C tanδ is less than 2.7, the effect of increasing losses at low temperatures while suppressing losses at high temperatures is insufficient, and therefore, when the rubber composition is applied to a tire, it is not possible to achieve a high level of both wet grip performance and fuel efficiency. Furthermore, from a similar viewpoint, the 0°C tanδ / 50°C tanδ is preferably 2.7 or greater, and more preferably 2.8 or greater. Also, if the 0°C tanδ / 50°C tanδ is too large, a sufficient reduction in rolling resistance may not be obtained, so the 0°C tanδ / 50°C tanδ is preferably 5.0 or less, and more preferably 4.5 or less.

[0015] In this invention, the 0°C tanδ and 50°C tanδ refer to the 0°C tanδ and 50°C tanδ after vulcanization of the tire rubber composition of the present invention. Furthermore, the measurement of 0°C tanδ and 50°C tanδ is not particularly limited as long as the tanδ values ​​can be obtained accurately using any method, and can be done using commonly used measuring instruments. However, in this invention, 0°C tanδ and 50°C tanδ are measured using a spectrometer manufactured by Ueshima Seisakusho Co., Ltd. Furthermore, when measuring tanδ at 0°C and tanδ at 50°C, possible conditions for initial strain, dynamic strain, and frequency include, for example, an initial strain of 2%, a dynamic strain of 1%, and a frequency of 52 Hz.

[0016] Furthermore, the 50°C tanδ of the tire rubber composition of the present invention is not particularly limited as long as it satisfies the above-mentioned 0°C tanδ / 50°C tanδ relationship. However, from the viewpoint of achieving a higher level of balance between wet grip performance and fuel efficiency when applied to a tire, it is preferably 0.090 to 0.180, and more preferably 0.0950 to 0.170.

[0017] Furthermore, the 0°C tanδ of the tire rubber composition of the present invention is not particularly limited as long as it satisfies the above-mentioned 0°C tanδ / 50°C tanδ relationship. However, from the viewpoint of achieving a higher level of balance between wet grip performance and fuel efficiency when applied to a tire, it is preferably 0.350 to 0.850, and more preferably 0.370 to 0.830.

[0018] The method for adjusting the 0°C tanδ / 50°C tanδ value is not particularly limited, but one example is optimizing the components of the tire rubber composition of the present invention. For example, as will be described later, it is possible to set the 0°C tanδ / 50°C tanδ value within the range of the present invention by limiting the type and content of rubber components, or by adjusting the type and content of fillers and resin components.

[0019] (Rubber component) The tire rubber composition of the present invention contains an isoprene-based rubber component A having a glass transition temperature of -50°C or lower, and a butadiene-based rubber component B that is incompatible with the diene-based rubber component A, and may further contain other rubber components.

[0020] -Diene-based rubber component A- The diene-based rubber component A contains isoprene-backed rubber. Here, the isoprene-backed rubber is rubber whose main backbone is isoprene units, and specifically, at least one of natural rubber (NR) and synthetic isoprene rubber (IR) is included. The rubber component contains isoprene backbone rubber as diene rubber component A, thereby increasing the fracture strength of the rubber composition. As a result, the rolling resistance of tires to which this rubber composition is applied can be reduced, improving fuel efficiency, and also improving the wear resistance of the tires.

[0021] The content of the isoprene skeleton rubber in the rubber component is preferably 1% by mass or more and less than 50% by mass, and more preferably 1 to 40% by mass. When the content of the isoprene skeleton rubber is 1% by mass or more and less than 50% by mass in the rubber component, the fuel efficiency and wet grip performance of the tire to which the rubber composition is applied can be further improved. Furthermore, when the content of the isoprene skeleton rubber is 1 to 40% by mass in the rubber component, the fuel efficiency and wet grip performance of the tire to which the rubber composition is applied can be further improved. Moreover, from the viewpoint of maximizing the compounding effect of the isoprene skeleton rubber, the content of the isoprene skeleton rubber is more preferably 10 parts by mass or more per 100 parts by mass of the rubber component.

[0022] Furthermore, the content ratio of the diene-based rubber component A in the rubber component is preferably 1% by mass or more and less than 50% by mass, and more preferably 1 to 40% by mass. When the content of the diene-based rubber component A is 1% by mass or more and less than 50% by mass, the fuel efficiency and wet grip performance of the tire to which the rubber composition is applied can be further improved. Also, when the content of the isoprene skeleton rubber is 1 to 40% by mass, the fuel efficiency and wet grip performance of the tire to which the rubber composition is applied can be further improved.

[0023] The diene-based rubber component A may consist solely of the isoprene-backed rubber, or it may contain other rubbers as appropriate. In this case, the rubber other than the isoprene-backed rubber is different from the diene-based rubber component B which is incompatible with the diene-based rubber component A. The content of the isoprene-backed rubber in the diene-based rubber component A is preferably 50% by mass or more, more preferably 70% by mass or more, and most preferably 100%.

[0024] -Diene-based rubber component B- The diene-based rubber component B is a rubber component that is incompatible with the diene-based rubber component A, and has a total styrene content of 15% by mass or less. By including the diene-based rubber component B, the fuel efficiency and wear resistance of the tire to which the rubber composition is applied can be sufficiently improved. Here, the total styrene content of the diene-based rubber component B refers to the proportion of styrene units contained in the diene-based rubber component B. When the amount of bound styrene in styrene-butadiene rubber, etc., contained as the diene-based rubber component B is 15% by mass or less, the glass transition temperature tends to be low. The amount of bound styrene in styrene-butadiene rubber is more preferably 14% by mass or less, more preferably 13% by mass or less, and even more preferably 12% by mass or less. Furthermore, from the viewpoint of the wear resistance performance of the tire to which the rubber composition is applied, the amount of bound styrene in styrene-butadiene rubber is preferably 5% by mass or more, more preferably 7% by mass or more, and even more preferably 8% by mass or more. The amount of bound styrene in the styrene-butadiene rubber can be adjusted by the amount of monomers used in the polymerization of the styrene-butadiene rubber, the degree of polymerization, etc. Furthermore, if the total styrene content of the diene-based rubber component B contains multiple types of rubber, the total styrene content is the sum of the styrene units of all the rubbers contained in the diene-based rubber component B. The amount of bound styrene in the diene rubber component B can be adjusted by the amount of monomer used in the polymerization of the rubber constituting the diene rubber component B, the degree of polymerization, etc.

[0025] As described above, the type of rubber constituting the diene-based rubber component B is not particularly limited as long as it is a rubber component that is incompatible with the diene-based rubber component A. For example, at least one of styrene-butadiene rubber (SBR) and butadiene rubber (BR) can be used as the diene-based rubber component B. Furthermore, from the viewpoint of achieving better wet grip performance, it is preferable to include at least styrene-butadiene rubber.

[0026] Furthermore, high-cis polybutadiene is preferred as the butadiene rubber, and it is preferable that the high-cis polybutadiene has a cis-1,4 bond content of 90% by mass or more. Furthermore, if the diene-based rubber component B contains butadiene rubber, the content of the butadiene rubber is preferably in the range of 1 to 35% by mass out of 100% by mass of the rubber component.

[0027] When the diene-based rubber component B contains styrene-butadiene rubber, the content of styrene-butadiene rubber is preferably 30 to 100% by mass, more preferably 40 to 100% by mass, and even more preferably 50 to 100% by mass, based on 100% by mass of the rubber component. This is because when the styrene-butadiene rubber content is 50 to 100% by mass, the fuel efficiency and wet grip performance of the tire to which the tire rubber composition is applied can be further improved.

[0028] Furthermore, the glass transition temperature of the styrene-butadiene rubber is not particularly limited and can be appropriately selected according to the required performance. For example, the glass transition temperature of the styrene-butadiene rubber can be -10°C or lower, -30°C or lower, or less than -40°C. Of these, when the glass transition temperature of the styrene-butadiene rubber is less than -40°C, the fuel efficiency and wear resistance of the tire to which the rubber composition is applied can be sufficiently improved.

[0029] Furthermore, it is preferable that the styrene-butadiene rubber is modified with a modifier having a functional group containing a nitrogen atom and an alkoxy group. When the styrene-butadiene rubber is modified with a modifier having a functional group containing a nitrogen atom and an alkoxy group, the balance between the wet grip performance, fuel efficiency, and wear resistance of the tire to which the rubber composition is applied is further improved, and in particular, the fuel efficiency and wear resistance can be further improved. The modifying agent having a functional group containing a nitrogen atom and an alkoxy group is a general term for modifying agents having a functional group containing at least one nitrogen atom and at least one alkoxy group. The functional group containing a nitrogen atom is preferably selected from the following: A monovalent hydrocarbon group having 1 to 30 carbon atoms, including a linear, branched, alicyclic, or aromatic ring, having 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 imine group, an imine residue, 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, an isocyanuric acid triester residue, a cyclic tertiary amino group, an acyclic tertiary amino group, a nitrile group, a pyridine residue, an onium salt residue of a cyclic tertiary amine, and an onium salt residue of an acyclic tertiary amine, and which may contain a linear, branched, alicyclic, or aromatic ring, or a monovalent hydrocarbon group having 1 to 30 carbon atoms, which may contain at least one heteroatom selected from an oxygen atom, a sulfur atom, and a phosphorus atom.

[0030] --A first preferred embodiment of modified styrene-butadiene rubber-- The styrene-butadiene rubber (SBR) is preferably modified with an aminoalkoxysilane compound, and more preferably, its ends are modified with an aminoalkoxysilane compound, from the viewpoint of having a high affinity for the filler. When the ends of the styrene-butadiene rubber are modified with an aminoalkoxysilane compound, the interaction between the modified styrene-butadiene rubber and the filler (especially silica) becomes particularly large.

[0031] The modified sites of the styrene-butadiene rubber may be at the molecular ends as described above, but they may also be on the main chain. Styrene-butadiene rubber with modified molecular ends can be produced, for example, by reacting the ends of a styrene-butadiene copolymer having active ends with various modifying agents, according to the methods described in International Publication No. 2003 / 046020 and Japanese Patent Application Publication No. 2007-217562. In one 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 active ends with a cis-1,4 bond content of 75% or more, according to the method described in International Publication No. 2003 / 046020 and Japanese Patent Application Publication No. 2007-217562, and then stabilizing it by reacting it with a carboxylic acid partial ester of a polyhydric alcohol.

[0032] The carboxylic acid partial ester of the polyhydric alcohol refers to a partial ester of a polyhydric alcohol and a carboxylic acid, and having one or more hydroxyl groups. Specifically, esters of sugars or modified sugars having 4 or more carbon atoms and fatty acids are preferably used. More preferably, these esters include (1) fatty acid partial esters of polyhydric alcohols, particularly partial esters of saturated or unsaturated higher fatty acids having 10 to 20 carbon atoms and polyhydric alcohols (monoesters, diesters, or triesters), and (2) ester compounds in which one to three partial esters of polyhydric carboxylic acids and higher alcohols are bonded to a polyhydric alcohol. The polyhydric alcohols used as raw materials for partial esters are preferably C5 or C6 sugars having at least three hydroxyl groups (which may or may not be hydrogenated), glycols, and polyhydroxy compounds. The raw material fatty acids are preferably C10 to C20 saturated or unsaturated fatty acids, such as stearic acid, lauric acid, and palmitic acid. Among the fatty acid partial esters of polyhydric alcohols, sorbitan fatty acid esters are preferred, specifically including sorbitan monolaurate, sorbitan monopalmitate, sorbitan monostearate, sorbitan tristearate, sorbitan monooleate, and sorbitan trioleate.

[0033] The above aminoalkoxysilane compound is not particularly limited, but an aminoalkoxysilane compound represented by the following general formula (i) is preferred. R , 21 , , 22 , 1 a -Si-(OR 12 ) 4-a ··· (i)

[0034] In general formula (i), R 11 and R 12 each 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, and at least one of R 11 and R 12 is substituted with an amino group, a is an integer from 0 to 2, and when there are a plurality of OR<00​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​is a monovalent aliphatic or alicyclic hydrocarbon group having 1 to 20 carbon atoms or a monovalent aromatic hydrocarbon group having 6 to 18 carbon atoms, and both may contain a nitrogen atom and / or a silicon atom. When n2 is 2 or more, R 22 These elements may be identical or different from one another, or they may come together to form a ring. R 23 This is a monovalent aliphatic or alicyclic hydrocarbon group having 1 to 20 carbon atoms, a monovalent aromatic hydrocarbon group having 6 to 18 carbon atoms, or a halogen atom, and may be the same or different if n3 is 2 or more. R 24 This is a divalent aliphatic or alicyclic hydrocarbon group having 1 to 20 carbon atoms, or a divalent aromatic hydrocarbon group having 6 to 18 carbon atoms, and may be the same or different if n4 is 2 or more. The hydrolyzable group in the first or second amino group having a hydrolyzable group is preferably a trimethylsilyl group or a tert-butyldimethylsilyl group, with the trimethylsilyl group being particularly preferred.

[0037] The aminoalkoxysilane compound represented by the above general formula (ii) is preferably an aminoalkoxysilane compound represented by the following general formula (iii). [ka]

[0038] In general formula (iii), p1 + p2 + p3 = 2 (where p2 is an integer between 1 and 2, and p1 and p3 are integers between 0 and 1). A 2 This is NRa (where Ra is a monovalent hydrocarbon group, a hydrolyzable group, or a nitrogen-containing organic group). R 25 This is a monovalent aliphatic or alicyclic hydrocarbon group having 1 to 20 carbon atoms, or a monovalent aromatic hydrocarbon group having 6 to 18 carbon atoms. R 26is a monovalent aliphatic or alicyclic hydrocarbon group having 1 to 20 carbon atoms, a monovalent aromatic hydrocarbon group having 6 to 18 carbon atoms, or a nitrogen-containing organic group, all of which may contain a nitrogen atom and / or a silicon atom. When p2 is 2, R 26 These elements may be identical or different from one another, or they may come together to form a ring. R 27 This is a monovalent aliphatic or alicyclic hydrocarbon group having 1 to 20 carbon atoms, a monovalent aromatic hydrocarbon group having 6 to 18 carbon atoms, or a halogen atom. R 28 This is a divalent aliphatic or alicyclic hydrocarbon group having 1 to 20 carbon atoms, or a divalent aromatic hydrocarbon group having 6 to 18 carbon atoms. The hydrolyzable group is preferably a trimethylsilyl group or a tert-butyldimethylsilyl group, with the trimethylsilyl group being particularly preferred.

[0039] 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). [ka]

[0040] In general formula (iv), q1 + q2 = 3 (where q1 is an integer between 0 and 2, and q2 is an integer between 1 and 3). R 31 This is a divalent aliphatic or alicyclic hydrocarbon group having 1 to 20 carbon atoms, or a divalent aromatic hydrocarbon group having 6 to 18 carbon atoms. R 32 and R 33 Each of these is independently a hydrolyzable group, a monovalent aliphatic or alicyclic hydrocarbon group having 1 to 20 carbon atoms, or a monovalent aromatic hydrocarbon group having 6 to 18 carbon atoms. R 34 This is a monovalent aliphatic or alicyclic hydrocarbon group having 1 to 20 carbon atoms, or a monovalent aromatic hydrocarbon group having 6 to 18 carbon atoms, and may be the same or different when q1 is 2. R 35This is a monovalent aliphatic or alicyclic hydrocarbon group having 1 to 20 carbon atoms, or a monovalent aromatic hydrocarbon group having 6 to 18 carbon atoms, and may be the same or different if q2 is 2 or more.

[0041] [ka]

[0042] In general equation (v), r1 + r2 = 3 (where r1 is an integer between 1 and 3, and r2 is an integer between 0 and 2). R 36 This is a divalent aliphatic or alicyclic hydrocarbon group having 1 to 20 carbon atoms, or a divalent aromatic hydrocarbon group having 6 to 18 carbon atoms. R 37 This group is a dimethylaminomethyl group, a dimethylaminoethyl group, a diethylaminomethyl group, a diethylaminoethyl group, a methylsilyl(methyl)aminomethyl group, a methylsilyl(methyl)aminoethyl group, a methylsilyl(ethyl)aminomethyl group, a methylsilyl(ethyl)aminoethyl group, a dimethylsilylaminomethyl group, a dimethylsilylaminoethyl group, a monovalent aliphatic or alicyclic hydrocarbon group having 1 to 20 carbon atoms, or a monovalent aromatic hydrocarbon group having 6 to 18 carbon atoms, and may be the same or different if r1 is 2 or more. R 38 This is a hydrocarbyloxy group having 1 to 20 carbon atoms, a monovalent aliphatic or alicyclic hydrocarbon group having 1 to 20 carbon atoms, or a monovalent aromatic hydrocarbon group having 6 to 18 carbon atoms, and when r2 is 2, it may be the same or different. A specific example of an aminoalkoxysilane compound represented by general formula (v) is N-(1,3-dimethylbutylidene)-3-triethoxysilyl-1-propanamine.

[0043] 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). [ka]

[0044] In general formula (vi), R 40 This is a trimethylsilyl group, a monovalent aliphatic or alicyclic hydrocarbon group having 1 to 20 carbon atoms, or a monovalent aromatic hydrocarbon group having 6 to 18 carbon atoms. R 41 This is a hydrocarbyloxy group having 1 to 20 carbon atoms, a monovalent aliphatic or alicyclic hydrocarbon group having 1 to 20 carbon atoms, or a monovalent aromatic hydrocarbon group having 6 to 18 carbon atoms. R 42 This is a divalent aliphatic or alicyclic hydrocarbon group having 1 to 20 carbon atoms, or a divalent aromatic hydrocarbon group having 6 to 18 carbon atoms. Here, TMS represents a trimethylsilyl group (the same applies hereafter).

[0045] [ka]

[0046] In general formula (vii), R 43 and R 44 Each of these is independently a divalent aliphatic or alicyclic hydrocarbon group having 1 to 20 carbon atoms, or a divalent aromatic hydrocarbon group having 6 to 18 carbon atoms. R 45 R is a monovalent aliphatic or alicyclic hydrocarbon group having 1 to 20 carbon atoms or a monovalent aromatic hydrocarbon group having 6 to 18 carbon atoms, and each R 45 They may be the same or different.

[0047] 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). [ka]

[0048] In the general formula (viii), s1 + s2 is 3 (where s1 is an integer between 0 and 2, and s2 is an integer between 1 and 3). R 46This is a divalent aliphatic or alicyclic hydrocarbon group having 1 to 20 carbon atoms, or a divalent aromatic hydrocarbon group having 6 to 18 carbon atoms. R 47 and R 48 Each of these is independently a monovalent aliphatic or alicyclic hydrocarbon group having 1 to 20 carbon atoms or a monovalent aromatic hydrocarbon group having 6 to 18 carbon atoms. 47 or R 48 They may be the same or different.

[0049] [ka]

[0050] In general formula (ix), X is a halogen atom. R 49 This is a divalent aliphatic or alicyclic hydrocarbon group having 1 to 20 carbon atoms, or a divalent aromatic hydrocarbon group having 6 to 18 carbon atoms. R 50 and R 51 Each of these is independently a hydrolyzable group, a monovalent aliphatic or alicyclic hydrocarbon group having 1 to 20 carbon atoms, or a monovalent aromatic hydrocarbon group having 6 to 18 carbon atoms, or R 50 and R 51 They are bonded together to form a divalent organic group. R 52 and R 53 Each of these is independently a halogen atom, a hydrocarbyl oxy group, a monovalent aliphatic or alicyclic hydrocarbon group having 1 to 20 carbon atoms, or a monovalent aromatic hydrocarbon group having 6 to 18 carbon atoms. R 50 and R 51 As for the hydrolyzable group, a hydrolyzable group is preferred, and among the hydrolyzable groups, a trimethylsilyl group and a tert-butyldimethylsilyl group are preferred, with a trimethylsilyl group being particularly preferred.

[0051] 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). [ka] [ka] [ka] [ka]

[0052] In the general formulas (x) to (xiii), the symbols U and V are integers between 0 and 2, and U + V = 2, respectively. R in general formulas (x) to (xiii) 54 ~ 92 These may be the same or different, and are monovalent or divalent aliphatic or alicyclic hydrocarbon groups having 1 to 20 carbon atoms, or monovalent or divalent aromatic hydrocarbon groups having 6 to 18 carbon atoms. In general formula (xiii), α and β are integers between 0 and 5.

[0053] Among the compounds satisfying general formulas (x), (xi), and (xii), N1,N1,N7,N7-tetramethyl-4-((trimethoxysilyl)methyl)heptane-1,7-diamine, 2-((hexyl-dimethoxysilyl)methyl)-N1,N1,N3,N3-2-pentamethylpropane-1,3-diamine, N1-(3-(dimethylamino)propyl)-N3,N3-dimethyl-N1-(3-(trimethoxysilyl)propyl)propane-1,3-diamine, and 4-(3-(dimethylamino)propyl)-N1,N1,N7,N7-tetramethyl-4-((trimethoxysilyl)methyl)heptane-1,7-diamine are particularly preferred. Furthermore, among the compounds satisfying general formula (xiii), N,N-dimethyl-2-(3-(dimethoxymethylsilyl)propoxy)ethaneamine, N,N-bis(trimethylsilyl)-2-(3-(trimethoxysilyl)propoxy)ethaneamine, N,N-dimethyl-2-(3-(trimethoxysilyl)propoxy)ethaneamine, and N,N-dimethyl-3-(3-(trimethoxysilyl)propoxy)propane-1-amine are particularly preferred.

[0054] --A second preferred embodiment of modified styrene-butadiene rubber-- The styrene-butadiene rubber (SBR) is preferably modified with a coupling agent represented by the following general formula (I). In this case, the fuel efficiency and wear resistance of the tire to which the rubber composition is applied can be further improved. [ka]

[0055] In the above general formula (I), R 1 , R 2 and R 3 Each of these independently represents a single bond or an alkylene group having 1 to 20 carbon atoms. R 4 , R 5 , R 6 , R 7 and R 9 Each of these independently represents an alkyl group having 1 to 20 carbon atoms. R 8 and R 11 Each of these independently represents an alkylene group having 1 to 20 carbon atoms. R 10 This represents an alkyl group or trialkylsilyl group having 1 to 20 carbon atoms. m represents an integer between 1 and 3, and p represents either 1 or 2. R 1 ~R 11 If there are multiple instances of m and p, they are independent of each other. i, j, and k each independently represent integers between 0 and 6, where (i + j + k) is an integer between 3 and 10. A represents an organic group having 1 to 20 carbon atoms, which is a hydrocarbon group or an organic group having at least one atom selected from the group consisting of oxygen, nitrogen, silicon, sulfur, and phosphorus atoms, and which does not have active hydrogen. 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 hydroxyl groups (-OH), secondary amino groups (>NH), primary amino groups (-NH2), sulfhydryl groups (-SH), and other functional groups that do not have active hydrogen.

[0056] The styrene-butadiene rubber modified with the coupling agent represented by the above general formula (I) has a weight-average molecular weight (Mw) of 20 × 10 4 ~300×10 4 g / mol, and the molecular weight is 200 × 10⁶ based on the total amount of the modified styrene-butadiene rubber. 4 ~500×10 4 It is preferable that the material contains 0.25 to 30% by mass of modified styrene-butadiene rubber in a concentration of g / mol, and that the shrinkage factor (g') is less than 0.64.

[0057] Generally, branched polymers tend to have smaller molecular size compared to linear polymers of the same absolute molecular weight, and the shrinkage factor (g') is an indicator of the ratio of the molecular size occupied by the branched polymer to that of a linear polymer of the same assumed absolute molecular weight. That is, the greater the degree of branching of the polymer, the smaller the shrinkage factor (g') tends to be. In this embodiment, intrinsic viscosity is used as an indicator of molecular size, and the linear polymer has an intrinsic viscosity [η] = -3.883M 0.771 The following relationship is assumed to apply. The shrinkage factor (g') is calculated for each absolute molecular weight of modified styrene-butadiene rubber, and the absolute molecular weight is 100 × 10 4 ~200×10 4The average value of the shrinkage factor (g') at that time is taken as the shrinkage factor (g') of the modified styrene-butadiene rubber. Here, "branching" refers to the formation of a polymer by which other polymers directly or indirectly bond to one polymer. The "degree of branching" is the number of polymers that are directly or indirectly bonded to each other for one branch. For example, if 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. A coupling residue is a structural unit of the modified styrene-butadiene rubber that is bonded to a styrene-butadiene copolymer chain, and is a structural unit derived from a coupling agent, for example, produced by reacting the styrene-butadiene copolymer described later with the coupling agent. A styrene-butadiene copolymer chain is a structural unit of the modified styrene-butadiene rubber, and is a structural unit derived from the styrene-butadiene copolymer, for example, produced by reacting the styrene-butadiene copolymer described later with the coupling agent. The shrinkage factor (g') is preferably less than 0.64, more preferably 0.63 or less, even more preferably 0.60 or less, even more preferably 0.59 or less, and even more preferably 0.57 or less. The lower limit of the shrinkage factor (g') is not particularly limited and may be below the detection limit, but is preferably 0.30 or more, more preferably 0.33 or more, even more preferably 0.35 or more, and even more preferably 0.45 or more. By using modified styrene-butadiene rubber with a shrinkage factor (g') within this range, the processability of the rubber composition is improved. Since the shrinkage factor (g') tends to depend on the degree of branching, it is possible to control the shrinkage factor (g') using the degree of branching as an indicator. Specifically, when a modified styrene-butadiene rubber has a branching degree of 6, its shrinkage factor (g') tends to be between 0.59 and 0.63, and when a modified styrene-butadiene rubber has a branching degree of 8, its shrinkage factor (g') tends to be between 0.45 and 0.59.

[0058] The styrene-butadiene rubber modified with the coupling agent represented by the above general formula (I) is preferably branched, with a degree of branching of 5 or more. Furthermore, the modified styrene-butadiene rubber has one or more coupling residues and styrene-butadiene copolymer chains bound to the coupling residues, and it is more preferable that the branches include branches to which five or more styrene-butadiene copolymer chains are bound to one of the coupling residues. By specifying the structure of the modified styrene-butadiene rubber such that the degree of branching is 5 or more and the branches include branches to which five or more styrene-butadiene copolymer chains are bound to one coupling residue, the shrinkage factor (g') can be more reliably reduced to less than 0.64. The number of styrene-butadiene copolymer chains bound to one coupling residue can be confirmed from the value of the shrinkage factor (g'). Furthermore, the modified styrene-butadiene rubber is more preferably branched, with a degree of branching of 6 or more. The modified styrene-butadiene rubber also has one or more coupling residues and styrene-butadiene copolymer chains bound to these coupling residues, and it is even more preferable that the branching includes branches in which 6 or more styrene-butadiene copolymer chains are bound to one of the coupling residues. By specifying the structure of the modified styrene-butadiene rubber such that it has a degree of branching of 6 or more and that the branching includes branches in which 6 or more styrene-butadiene copolymer chains are bound to one coupling residue, the shrinkage factor (g') can be reduced to 0.63 or less. Furthermore, the modified styrene-butadiene rubber has branching, and it is even more preferable that the degree of branching is 7 or more, and even more preferable that the degree of branching is 8 or more. The upper limit of the degree of branching is not particularly limited, but it is preferably 18 or less. In addition, the modified styrene-butadiene rubber has one or more coupling residues and styrene-butadiene copolymer chains bound to the coupling residues, and it is even more preferable that the branching includes branches in which 7 or more styrene-butadiene copolymer chains are bound to one of the coupling residues, and it is particularly preferable that the branching includes branches in which 8 or more styrene-butadiene copolymer chains are bound to one of the coupling residues. By specifying the structure of the modified styrene-butadiene rubber so that the degree of branching is 8 or more, and the branching includes branches in which 8 or more styrene-butadiene copolymer chains are bound to one coupling residue, the shrinkage factor (g') can be reduced to 0.59 or less.

[0059] Preferably, at least one end of the styrene-butadiene copolymer chain is bonded to a silicon atom of a coupling residue. In this case, the ends of multiple styrene-butadiene copolymer chains may be bonded to one silicon atom. Alternatively, the end of a styrene-butadiene copolymer chain may be bonded to an alkoxy or hydroxyl group having 1 to 20 carbon atoms, and as a result, that silicon atom may constitute an alkoxysilyl or silanol group having 1 to 20 carbon atoms.

[0060] The modified styrene-butadiene rubber can be an oil-applied rubber to which an extensible oil has been added. The modified styrene-butadiene rubber may be oil-applied or non-oil-applied, but from the viewpoint of abrasion resistance, it is preferable that the Mooney viscosity measured at 100°C is 20 to 100, and more preferably 30 to 80.

[0061] The weight-average molecular weight (g / mol) of the modified styrene-butadiene rubber is preferably 20 × 10⁻⁶. 4 300 x 10 4The following is more 50 × 10 4 g / mol or more, more preferably 64 × 10 4 g / mol or more, and more preferably 80 × 10 4 That concludes the explanation. Furthermore, the weight-average molecular weight is preferably 250 × 10⁻⁶. 4 It is less than or equal to g / mol, and more preferably 180 × 10⁻⁶ 4 It is less than or equal to g / mol, more preferably 150 × 10 4 It is less than g / mol. The weight-average molecular weight is 20 × 10 4 When the weight-average molecular weight is 300 × 10⁻¹⁰ or higher, the low loss and abrasion resistance of the rubber composition can be sufficiently improved. 4 When the concentration is less than g / mol, the processability of the rubber composition improves.

[0062] The modified styrene-butadiene rubber has a molecular weight of 200 × 10¹⁶ based on the total amount (100% by mass) of the modified styrene-butadiene rubber. 4 g / mol or more 500×10 4 It is preferable to include 0.25% by mass or more and 30% by mass or less of modified styrene-butadiene rubber (hereinafter also referred to as "specific high molecular weight component") having a concentration of g / mol or less. 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 of the rubber composition can be sufficiently improved. The modified styrene-butadiene rubber preferably contains 1.0% by mass or more of the specific high molecular weight component, 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 most preferably 2.5% by mass or more. Furthermore, the modified styrene-butadiene rubber preferably contains 28% by mass or less of the specific high molecular weight component, more preferably 25% by mass or less, even more preferably 20% by mass or less, and even more preferably 18% by mass or less. In this specification, the "molecular weight" of the rubber component refers to the molecular weight equivalent to standard polystyrene, obtained by GPC (gel permeation chromatography). To obtain a modified styrene-butadiene rubber in which the content of a specific high molecular weight component is 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 a polymerization initiator, as described later, can be adjusted. Furthermore, in the polymerization step, whether using a continuous or batch polymerization method, it is preferable to use a method that has a residence time distribution, that is, to broaden the time distribution of the growth reaction.

[0063] In the modified styrene-butadiene rubber, 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 more and 3.0 or less. If the molecular weight distribution of the modified styrene-butadiene rubber is within this range, the processability of the rubber composition will be good.

[0064] The method for producing the modified styrene-butadiene rubber is not particularly limited, but it is preferable to have a polymerization step of copolymerizing butadiene and styrene using an organic monolithium compound as a polymerization initiator to obtain a styrene-butadiene copolymer, and a reaction step of reacting the active end of the styrene-butadiene copolymer with a reactive compound with five or more functionalities (hereinafter also referred to as a "coupling agent").

[0065] The polymerization step is preferably carried out by a growth reaction using a living anionic polymerization reaction, which allows for the acquisition of a styrene-butadiene copolymer having active ends, and thus a modified styrene-butadiene rubber with a high degree of modification. The styrene-butadiene copolymer is obtained by copolymerizing 1,3-butadiene and styrene.

[0066] The amount of the aforementioned organic monolithium compound used as a polymerization initiator is preferably determined by 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 used relative to the amount of polymerization initiator is related to the degree of polymerization, that is, to the number-average molecular weight and / or weight-average molecular weight. Therefore, to increase the molecular weight, it is good to adjust the amount of polymerization initiator to decrease, and to decrease the molecular weight, it is good to adjust the amount of polymerization initiator to increase. The organic monolithium compound is preferably an alkyllithium compound, from the viewpoint of ease of industrial availability and ease of controlling the polymerization reaction. In this case, a styrene-butadiene copolymer having an alkyl group at the polymerization initiation end is obtained. Examples of alkyllithium compounds include n-butyllithium, sec-butyllithium, tert-butyllithium, n-hexyllithium, benzyllithium, phenyllithium, and stilbenilithium. Among the alkyllithium compounds, n-butyllithium and sec-butyllithium are preferred from the viewpoint of ease of industrial availability and ease of controlling the polymerization reaction. These organic monolithium compounds may be used individually or in combination of two or more.

[0067] In the polymerization step, examples of polymerization reaction modes include batch and continuous polymerization reaction modes. In the continuous mode, one or more connected reactors can be used. Continuous reactors include, for example, tank-type or tubular reactors equipped with stirrers. In the continuous mode, monomers, an inert solvent, and a polymerization initiator are preferably fed continuously into the reactor, a polymer solution containing the polymer is obtained in the reactor, and the polymer solution is discharged continuously. Batch reactors include, for example, tank-type reactors equipped with stirrers. In the batch mode, monomers, an inert solvent, and a polymerization initiator are preferably fed, monomers are 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, in order to obtain a styrene-butadiene copolymer with a high proportion of active ends, a continuous mode is preferred, as it allows for the continuous discharge of the polymer and enables it to be used for the next reaction in a short time.

[0068] The polymerization step is preferably carried out in an inert solvent. Examples of solvents include hydrocarbon solvents such as saturated hydrocarbons and aromatic hydrocarbons. Specific hydrocarbon solvents are not limited to the following, but examples include aliphatic hydrocarbons such as butane, pentane, hexane, and heptane; alicyclic hydrocarbons such as cyclopentane, cyclohexane, methylcyclopentane, and methylcyclohexane; and hydrocarbons consisting of aromatic hydrocarbons such as benzene, toluene, and xylene, and mixtures thereof. Treating impurities such as allenes and acetylenes with organometallic compounds before the polymerization reaction tends to yield styrene-butadiene copolymers with high concentrations of active ends, and is therefore preferable because it tends to yield modified styrene-butadiene rubber with a high degree of modification.

[0069] In the polymerization step described above, a polar compound may be added. By adding a polar compound, styrene can be randomly copolymerized with 1,3-butadiene, and polar compounds tend to be used as vinylizing agents to control the microstructure of the 1,3-butadiene moiety. Examples of the polar compounds that can be used include ethers such as tetrahydrofuran, diethyl ether, dioxane, ethylene glycol dimethyl ether, ethylene glycol dibutyl ether, diethylene glycol dimethyl ether, diethylene glycol dibutyl ether, dimethoxybenzene, and 2,2-bis(2-oxolanyl)propane; tertiary amine compounds such as tetramethylethylenediamine, dipiperidinoethane, trimethylamine, triethylamine, pyridine, and quinuclidine; alkali metal alkoxide compounds such as potassium-tert-amylate, potassium-tert-butyrate, sodium-tert-butyrate, and sodium amylate; and phosphine compounds such as triphenylphosphine. These polar compounds may be used individually or in combination of two or more.

[0070] In the polymerization step, the polymerization temperature is preferably 0°C or higher, more preferably 120°C or lower, and particularly preferably 50°C to 100°C, from the viewpoint of productivity. Within this range, it tends to be possible to ensure a sufficient amount of coupling agent reacting with the active ends after polymerization is complete.

[0071] The amount of bound butadiene in the styrene-butadiene copolymer or modified styrene-butadiene rubber is not particularly limited, but is preferably 40% by mass or more and 100% by mass or less, and more preferably 55% by mass or more and 80% by mass or less. Furthermore, the amount of bound styrene in the styrene-butadiene copolymer or modified styrene-butadiene rubber is not particularly limited, but is preferably greater than 0% by mass and 60% by mass or less, and more preferably 20% by mass or more and 45% by mass or less. When the amounts of bound butadiene and bound styrene are within the above range, the low loss and abrasion resistance of the rubber composition can be further improved. Furthermore, the amount of bound styrene can be measured by ultraviolet absorption of the phenyl group, and from this, the amount of bound butadiene can also be determined.

[0072] In the styrene-butadiene copolymer or modified styrene-butadiene rubber, the amount of vinyl bond in the butadiene bond unit is not particularly limited, but is preferably 10 mol% to 75 mol%, and more preferably 20 mol% to 65 mol%. When the amount of vinyl bond is within the above range, the low loss and abrasion resistance of the rubber composition can be further improved. Furthermore, for modified styrene-butadiene rubber, the amount of vinyl bonds (1,2-bonds) in the butadiene bond unit can be determined using Hampton's method [RRHampton, Analytical Chemistry, 21, 923 (1949)].

[0073] The alkoxysilyl groups in the coupling agent represented by the general formula (I) above tend to react with the active end of the styrene-butadiene copolymer, for example, to dissociate alkoxylithium and form a bond between the end of the styrene-butadiene copolymer chain and the silicon of the coupling residue. The number of alkoxysilyl groups in the coupling residue is obtained by subtracting the number of SiOR groups lost due to the reaction from the total number of SiOR groups in one molecule of the coupling agent. In addition, the azasilyl groups in the coupling agent form >N-Li bonds and bonds between the end of the styrene-butadiene copolymer and the silicon of the coupling residue. Note that the >N-Li bonds tend to readily become >NH and LiOH with water during finishing. Furthermore, unreacted alkoxysilyl groups remaining in the coupling agent tend to readily become silanols (Si-OH groups) with water during finishing.

[0074] The reaction temperature in the reaction step is preferably the same as the polymerization temperature of the styrene-butadiene copolymer, more preferably 0°C to 120°C, and even more preferably 50°C to 100°C. Furthermore, the temperature change from the end of the polymerization step until the addition of the coupling agent is preferably 10°C or less, and more preferably 5°C or less. The reaction time in the reaction step is preferably 10 seconds or more, more preferably 30 seconds or more. From the viewpoint of the coupling rate, the time from the end of the polymerization step to the start of the reaction step is preferably shorter, more preferably within 5 minutes. Mixing in the reaction step may be any of mechanical stirring, stirring by a static mixer, etc. When the polymerization step is continuous, the reaction step is preferably continuous. In the reaction step, for example, a tank type or a tube type reactor with a stirrer is used. The coupling agent may be diluted with an inert solvent and continuously supplied to the reactor. When the polymerization step is batchwise, the coupling agent may be added to the polymerization reactor, or the reaction step may be carried out by transferring it to another reactor.

[0075] In the general formula (I), A is preferably represented by any of the following general formulas (II) to (V). By having A represented by any of the general formulas (II) to (V), a modified styrene-butadiene rubber having more excellent performance can be obtained.

[0076]

Chemical formula

[0077]

Chemical formula

[0078]

Chemical formula

[0079]

Chemical formula

[0080] Regarding B in the general formulas (II) to (V) 1 , B 2 , B 4 , B 5 , examples of the hydrocarbon group having 1 to 20 carbon atoms include an alkylene group having 1 to 20 carbon atoms and the like.

[0081] Preferably, in the general formula (I), A is represented by the general formula (II) or (III), and k represents 0. More preferably, in the general formula (I), A is represented by the general formula (II) or (III), k represents 0, and in the general formula (II) or (III), a represents an integer of 2 to 10. Even more preferably, in the general formula (I), A is represented by the general formula (II), k represents 0, and in the general formula (II), a represents an integer of 2 to 10. Examples of such coupling agents include bis(3-trimethoxysilylpropyl)-[3-(2,2-dimethoxy-1-aza-2-silacyclopentane)propyl]amine, tris(3-trimethoxysilylpropyl)amine, tris(3-triethoxysilylpropyl)amine, tris(3-trimethoxysilylpropyl)-[3-(2,2-dimethoxy-1-aza-2-silacyclopentane)propyl]-1,3-propanediamine, tetrakis[3-(2,2-dimethoxy-1-aza-2-silacyclopentane)propyl]-1,3-propanediamine, and tetrakis(3-trimethoxysilylpropyl Examples include tris(3-trimethoxysilylpropyl)-1,3-propanediamine, tetrakis(3-trimethoxysilylpropyl)-1,3-bisaminomethylcyclohexane, tris(3-trimethoxysilylpropyl)-methyl-1,3-propanediamine, bis[3-(2,2-dimethoxy-1-aza-2-silacyclopentane)propyl]-(3-trismethoxysilylpropyl)-methyl-1,3-propanediamine, and among these, tetrakis(3-trimethoxysilylpropyl)-1,3-propanediamine and tetrakis(3-trimethoxysilylpropyl)-1,3-bisaminomethylcyclohexane are particularly preferred.

[0082] The amount of the compound represented by general formula (I) added as the coupling agent can be adjusted so that the number of moles of styrene-butadiene copolymer to the number of moles of the coupling agent reacts in a desired stoichiometric ratio, thereby tending to achieve the desired degree of branching. Specifically, the number of moles of the polymerization initiator is preferably 5.0 times or more, more preferably 6.0 times or more, of the number of moles of the coupling agent. 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 between 5 and 10, and more preferably an integer between 6 and 10.

[0083] To obtain a modified styrene-butadiene rubber having the aforementioned specific polymer component, the molecular weight distribution (Mw / Mn) of the styrene-butadiene copolymer should preferably be 1.5 to 2.5, more preferably 1.8 to 2.2. Furthermore, it is preferable that the resulting modified styrene-butadiene rubber exhibits a single peak in its molecular weight curve determined by GPC. When the peak molecular weight of the modified styrene-butadiene rubber determined by GPC is Mp1 and the peak molecular weight of the styrene-butadiene copolymer is Mp2, it is preferable that the following equation holds true. (Mp1 / Mp2)<1.8×10-12×(Mp2-120×10 4 ) 2 +2 MP2 is 20x10 4 80 x 10 4 Below, MP1 is 30x10 4 The above 150 x 10 4 The following is more preferable. Mp1 and Mp2 are determined by the method described in the examples below.

[0084] The modification rate of the modified styrene-butadiene rubber is preferably 30% by mass or more, more preferably 50% by mass or more, and even more preferably 70% by mass or more. A modification rate of 30% by mass or more further improves the low loss and abrasion resistance of the rubber composition.

[0085] After the reaction step described above, an inactivator, neutralizing agent, etc., may be added to the copolymer solution as needed. Examples of inactivators include, but are not limited to, water; and alcohols such as methanol, ethanol, and isopropanol. Examples of neutralizing agents include, but are not limited to, carboxylic acids such as stearic acid, oleic acid, and versatic acid (a highly branched carboxylic acid mixture with 9 to 11 carbon atoms, mainly centered around 10); aqueous solutions of inorganic acids; and carbon dioxide. Furthermore, from the viewpoint of preventing gel formation after polymerization and improving stability during processing, it is preferable to add antioxidants such as 2,6-di-tert-butyl-4-hydroxytoluene (BHT), n-octadecyl-3-(4'-hydroxy-3',5'-di-tert-butylphenol)propinate, and 2-methyl-4,6-bis[(octylthio)methyl]phenol to the modified styrene-butadiene rubber.

[0086] Known methods can be used to obtain the modified styrene-butadiene rubber from the polymer solution. Examples of such methods include separating the solvent by steam stripping, filtering out the polymer, and then dehydrating and drying it to obtain the polymer; concentrating the solution in a flushing tank and then defoliating it with a vent extruder or the like; and directly defoliating it with a drum dryer or the like.

[0087] A 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). [ka]

[0088] In general formula (VI), D represents a styrene-butadiene copolymer chain, and the weight-average molecular weight of the styrene-butadiene copolymer chain is 10 × 10 4 ~100×10 4 It is preferable that this is the case. The styrene-butadiene copolymer chain is a constituent unit of modified styrene-butadiene rubber, and is a structural unit derived from styrene-butadiene copolymer, for example, produced by reacting styrene-butadiene copolymer with a coupling agent. R 12 , R 13 and R 14 Each of these independently represents either a single bond or an alkylene group having 1 to 20 carbon atoms. R 15 and R 18Each of these independently represents an alkyl group having 1 to 20 carbon atoms. R 16 , R 19 , and R 20 Each of these independently represents either a hydrogen atom or an alkyl group having 1 to 20 carbon atoms. R 17 and R 21 Each of these independently represents an alkylene group having 1 to 20 carbon atoms. R 22 This represents a hydrogen atom or an alkyl group having 1 to 20 carbon atoms. m and x are integers between 1 and 3, where x ≤ m; p is 1 or 2; y is an integer between 1 and 3, where y ≤ (p + 1); and z is an integer between 1 and 2. When there are multiple instances of D and R 12 ~R 22 m, p, x, y, and z are independent of each other and may be the same or different. Furthermore, i represents an integer from 0 to 6, j represents an integer from 0 to 6, k represents an integer from 0 to 6, (i+j+k) is an integer from 3 to 10, and ((x×i)+(y×j)+(z×k)) is an integer from 5 to 30. A represents an organic group having a hydrocarbon group with 1 to 20 carbon atoms, or at least one atom selected from the group consisting of oxygen, nitrogen, silicon, sulfur, and phosphorus atoms, and which does not have active hydrogen. 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 containing active hydrogen, such as hydroxyl groups (-OH), secondary amino groups (>NH), primary amino groups (-NH2), and sulfhydryl groups (-SH).

[0089] In the above general formula (VI), A is preferably represented by any of the above general formulas (II) to (V). By having A represented by any of the above general formulas (II) to (V), the low loss and wear resistance of the rubber composition can be further improved.

[0090] --A third preferred embodiment of modified styrene-butadiene rubber-- It is also preferable that at least one end of the styrene-butadiene rubber (SBR) is modified with a modifying agent containing a compound represented by the following general formula (1) (alkoxysilane). [ka]

[0091] By using styrene-butadiene rubber modified with a modifier containing an oligosiloxane and a tertiary amino group, which are filler affinity groups, as the rubber component, the dispersibility of fillers such as silica can be improved. As a result, the rubber composition of the present invention has improved filler dispersibility, which greatly improves low loss performance, reduces the rolling resistance of tires to which the rubber composition is applied, and improves fuel efficiency.

[0092] In the above general formula (1), R 1 ~R 8 Each of these is an alkyl group having 1 to 20 carbon atoms; L 1 and L 2 Each of these is an alkylene group having 1 to 20 carbon atoms; and n is an integer between 2 and 4.

[0093] Specifically, in equation (1), R 1 ~R 4 Each of these may be independently substituted or unsubstituted alkyl groups having 1 to 20 carbon atoms, and the R 1 ~R 4 When substitution occurs, each can be independently substituted with one or more substituents selected from the group consisting of C1-C10 alkyl groups, C3-C10 cycloalkyl groups, C1-C10 alkoxy groups, C4-C10 cycloalkoxy groups, C6-C12 aryl groups, C6-C12 aryloxy groups, C2-C12 alkanoyloxy groups (Ra-COO-, where Ra is an alkyl group with 1-9 carbon atoms), C7-C13 aralkyloxy groups, C7-C13 arylalkyl groups, and C7-C13 alkylaryl groups. More specifically, the aforementioned R1 ~R 4 R may be a substituted or unsubstituted alkyl group having 1 to 10 carbon atoms, and more specifically, the R 1 ~R 4 Each of these may independently be a substituted or unsubstituted alkyl group having 1 to 6 carbon atoms.

[0094] Also, in equation (1), R 5 ~R 8 Each of these is independently a substituted or unsubstituted alkyl group having 1 to 20 carbon atoms, more specifically a substituted or unsubstituted alkyl group having 1 to 10 carbon atoms, or more specifically a substituted or unsubstituted alkyl group having 1 to 6 carbon atoms, and in the case of substitution, R comes first. 1 ~R 4 It can be substituted with substituents as described above. Note that the above R 5 ~R 8 If the substituent is not an alkyl group but a hydrolyzable substituent, NR 5 R 6 and NR 7 R 8 The bond can be hydrolyzed to NH in the presence of moisture, which can adversely affect the processability of the polymer.

[0095] More specifically, in the compound represented by formula (1) above, R 1 ~R 4 R is a methyl group or an ethyl group, 5 ~R 8 This can be an alkyl group having 1 to 10 carbon atoms.

[0096] The amino group in the compound represented by formula (1), i.e., NR 5 R 6 and NR 7 R 8 It is preferable that the tertiary amino group is a tertiary amino group. The tertiary amino group provides even better processability when the compound represented by formula (1) is used as a modifying agent. Note that the above R 5 ~R 8If a protecting group to protect the amino group is bonded, or if hydrogen is bonded, it may be difficult to realize the effect of the compound represented by formula (1). If hydrogen is bonded, the anion reacts with hydrogen during the modification process and loses its reactivity, making the modification reaction itself impossible. If a protecting group is bonded, the modification reaction takes place, but the bonded group remains at the polymer end and is deprotected by hydrolysis during post-processing, becoming a primary or secondary amino group. This deprotected primary or secondary amino group may cause increased viscosity in the compound during subsequent blending, potentially leading to reduced processability.

[0097] Furthermore, L in the compound represented by formula (1) 1 and L 2 These are, independently, substituted or unsubstituted alkylene groups having 1 to 20 carbon atoms. More specifically, L 1 and L 2 Each of these can be an alkylene group having 1 to 10 carbon atoms, or more specifically, an alkylene group having 1 to 6 carbon atoms, such as a methylene group, an ethylene group, or a propylene group.

[0098] L in the compound represented by formula (1) 1 and L 2 Regarding this, the closer the distance between the Si atom and N atom within the molecule, the better the effect. However, when Si is directly bonded to N, there is a risk that the bond between Si and N may break during subsequent processing steps, and the secondary amino group generated at this time is likely to be washed away by water during post-processing. In the modified styrene-butadiene rubber produced, it becomes difficult for the amino group to bond with fillers such as silica, and as a result, the effect of improving the dispersibility of the filler may decrease. Considering the improvement effect depending on the length of the bond between Si and N, the aforementioned L 1 and L 2 Each of these is more preferably an alkylene group having 1 to 3 carbon atoms, such as a methylene group, an ethylene group, or a propylene group, and more specifically, it can be a propylene group. 1 and L 2 First, R 1 ~R4 It can be substituted with substituents as described above.

[0099] Furthermore, the compound represented by formula (1) is preferably one of the compounds represented by the following structural formulas (1-1) to (1-5), for example, because it is possible to achieve even better low loss performance. [ka]

[0100] The compound represented by formula (1) has an alkoxysilane structure that binds to the active end of the styrene-butadiene copolymer, while the Si-O-Si structure and the three or more amino groups bound to the ends exhibit affinity for fillers such as silica. Compared to conventional modifiers containing one amino group in the molecule, this compound promotes bonding between the filler and the modified styrene-butadiene rubber. Furthermore, the degree of binding to the active end of the styrene-butadiene copolymer is uniform, and when observing the change in molecular weight distribution before and after coupling, the molecular weight distribution remains constant even after coupling, without becoming significantly larger than before. Therefore, there is no deterioration in the physical properties of the modified styrene-butadiene rubber itself, and aggregation of the filler within the rubber composition is prevented, improving the dispersibility of the filler and thus improving the processability of the rubber composition. These effects, in particular, make it possible to improve fuel efficiency and wet grip performance in a balanced manner when the rubber composition is applied to tires.

[0101] The compound represented by formula (1) can be produced through a condensation reaction represented by the following reaction scheme. [ka]

[0102] In the above reaction scheme, R 1 ~R 8 , L 1 and L 2, and n are the same as those defined in formula (1) above, and R' and R'' are arbitrary substituents that do not affect the condensation reaction. For example, R' and R'' are each independently R 1 ~R 4 It can be the same as any one of the following.

[0103] The reaction in the above reaction scheme proceeds in the presence of an acid, and the acid can be any acid that is commonly used in condensation reactions, without limitation. Those skilled in the art can select the optimal acid according to various process variables such as the type of reactor in which the reaction is carried out, the starting materials, and the reaction temperature.

[0104] Furthermore, the styrene-butadiene rubber modified with a modifying agent containing the compound represented by formula (1) above may have a narrow molecular weight distribution of 1.1 to 3.0 (Mw / Mn, also called the "polydispersion index (PDI)"). If the molecular weight distribution of the modified styrene-butadiene rubber exceeds 3.0 or is less than 1.1, the tensile properties and viscoelasticity may decrease when applied to a rubber composition. Considering the remarkable effect of controlling the molecular weight distribution of the modified styrene-butadiene rubber on improving tensile properties and viscoelasticity, the molecular weight distribution of the modified styrene-butadiene rubber is preferably in the range of 1.3 to 2.0. Furthermore, by using the modifying agent, the molecular weight distribution of the modified styrene-butadiene rubber becomes similar to that of the styrene-butadiene copolymer before modification.

[0105] The molecular weight distribution of the modified styrene-butadiene rubber can be calculated from the ratio of the weight-average molecular weight (Mw) to the logarithmic-average molecular weight (Mn) (Mw / Mn). In this case, the number-average molecular weight (Mn) is the common average of the individual polymer molecular weights calculated by measuring the molecular weights of n polymer molecules, summing these molecular weights, and dividing by n, while the weight-average molecular weight (Mw) represents the molecular weight distribution of the polymer composition. The average of the overall molecular weight can be expressed in grams per mole (g / mol). Furthermore, the weight-average molecular weight and number-average molecular weight are polystyrene-equivalent molecular weights, respectively, analyzed by gel permeation chromatography (GPC).

[0106] Furthermore, the modified styrene-butadiene rubber satisfies the above-mentioned molecular weight distribution conditions, and at the same time, its number-average molecular weight (Mn) can be 50,000 g / mol to 2,000,000 g / mol, 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, more specifically, 300,000 g / mol to 1,500,000 g / mol. If the weight-average molecular weight (Mw) of the modified styrene-butadiene rubber is 100,000 g / mol or the number-average molecular weight (Mn) is less than 50,000 g / mol, there is a risk of reduced tensile properties when applied to the rubber composition. Furthermore, 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 will decrease, worsening the workability of the rubber composition, making mixing difficult, and making it difficult to sufficiently improve the physical properties of the rubber composition. More specifically, when the modified styrene-butadiene rubber satisfies the conditions of weight-average molecular weight (Mw) and number-average molecular weight (Mn) simultaneously with the molecular weight distribution, it can improve the viscoelasticity and processability of a rubber composition in a well-balanced manner when applied to it.

[0107] The modified styrene-butadiene rubber preferably has a vinyl bond content of 5% or more in the butadiene portion, more preferably 10% or more, and more preferably 60% or less. By setting the vinyl bond content of the butadiene portion within the above range, the glass transition temperature can be adjusted to an appropriate range.

[0108] The modified styrene-butadiene rubber may have a Mooney viscosity (MV) of 40 to 140, specifically 60 to 100, at 100°C. When the Mooney viscosity is within this range, it can exhibit better processability. The 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 the large rotor. The sample used in this measurement is left at room temperature (23±3°C) for at least 30 minutes, then 27±3g is taken and placed inside the die cavity, and the platen is operated for measurement.

[0109] As described above, it is preferable that one end of the modified styrene-butadiene rubber is modified with a modifying agent containing the compound represented by the general formula (1), but it is preferable that the other end is further modified with a modifying agent containing the compound represented by the general formula (2). By modifying both ends of the modified styrene-butadiene rubber, the dispersibility of the filler in the rubber composition is further improved, and a higher level of both fuel efficiency and wet grip performance can be achieved in the tire to which the rubber composition is applied. [ka]

[0110] In the above general formula (2), R 9 ~R 11 These are, independently of each other, hydrogen; C1-C30 alkyl groups; C2-C30 alkenyl groups; C2-C30 alkynyl groups; C1-C30 heteroalkyl groups, C2-C30 heteroalkenyl groups; C2-C30 heteroalkynyl groups; C5-C30 cycloalkyl groups; C6-C30 aryl groups; or C3-C30 heterocyclic groups. Also, in equation (2), R 12 This is a single bond; a substituent-substituted or unsubstituted C1-C20 alkylene group; a substituent-substituted or unsubstituted C5-C20 cycloalkylene group; or a substituent-substituted or unsubstituted C5-C20 arylene group, where the substituent is a C1-C10 alkyl group, a C5-C10 cycloalkyl group, or a C6-C20 aryl group. Also, in equation (2), R 13is an alkyl group having 1 to 30 carbon atoms; an alkenyl group having 2 to 30 carbon atoms; an alkynyl group having 2 to 30 carbon atoms; a heteroalkyl group having 1 to 30 carbon atoms; a heteroalkenyl group having 2 to 30 carbon atoms; a heteroalkynyl group having 2 to 30 carbon atoms; a cycloalkyl group having 5 to 30 carbon atoms; an aryl group having 6 to 30 carbon atoms; a heterocyclic group having 3 to 30 carbon atoms; or an active group represented by the following general formula (2a) or general formula (2b), where m is an integer from 1 to 5, and R 13 At least one of them is an operator represented by the following general formula (2a) or general formula (2b), and when m is an integer from 2 to 5, multiple R 13 They may be identical or different from one another.

[0111] [ka]

[0112] In the above general formula (2a), R 14 This is a substituent-substituted or unsubstituted C1-C20 alkylene group; a substituent-substituted or unsubstituted C5-C20 cycloalkylene group; or a substituent-substituted or unsubstituted C6-C20 arylene group, where the substituent is a C1-C10 alkyl group, a C5-C10 cycloalkyl group, or a C6-C20 aryl group. Furthermore, in equation (2a), R 15 and R 16 These are, independently of each other, C1-C10 alkyl groups, C5-C10 cycloalkyl groups, or C6-C20 aryl groups, or unsubstituted C1-C20 alkylene groups. Furthermore, in equation (2a), R 17 R is a hydrogen atom; 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, where X is an N, O, or S atom, except when X is O or S, R 17 It does not exist.

[0113] [ka]

[0114] In the above general formula (2b), R 18 This is a substituent-substituted or unsubstituted C1-C20 alkylene group; a substituent-substituted or unsubstituted C5-C20 cycloalkylene group; or a substituent-substituted or unsubstituted C6-C20 arylene group, where the substituent is a C1-C10 alkyl group, a C5-C10 cycloalkyl group, or a C6-C20 aryl group. Also, in equation (2b), R 19 and R 20 These are, independently of each other, C1-C30 alkyl groups; C2-C30 alkenyl groups; C2-C30 alkynyl groups; C1-C30 heteroalkyl groups; C2-C30 heteroalkenyl groups; C2-C30 heteroalkynyl groups; C5-C30 cycloalkyl groups; C6-C30 aryl groups; and C3-C30 heterocyclic groups.

[0115] Furthermore, in the compound represented by the above general formula (2), R 9 ~R 11 R is independently of 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. 12 R is a single bond; or an unsubstituted alkylene group having 1 to 10 carbon atoms. 13 R 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 an active group represented by the above general formula (2a) or general formula (2b), wherein in the above general formula (2a), 14 R is an unsubstituted alkylene group having 1 to 10 carbon atoms. 15 and R 16 These are unsubstituted alkylene groups having 1 to 10 carbon atoms, R 17R 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 R is an unsubstituted alkylene group having 1 to 10 carbon atoms. 19 and R 20 These may be, independently of each other, 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.

[0116] More specifically, the compound represented by the general formula (2) above can be the compound represented by the following structural formulas (2-1) to (2-3). [ka]

[0117] Furthermore, when the styrene-butadiene copolymer is modified with a modifying agent containing the compound represented by the general formula (2), the modifying agent containing the compound represented by formula (2) is used as a modification initiator. Specifically, for example, by polymerizing a butadiene monomer and a styrene monomer in a hydrocarbon solvent in the presence of a modifying agent containing the compound represented by formula (2), a modifying group derived from the compound represented by formula (2) can be imparted to the styrene-butadiene copolymer.

[0118] -Other rubber components- The rubber component may further contain other rubbers (other rubber components) in addition to the above-mentioned diene-based rubber component A and diene-based rubber component B, and the content of other rubber components in the rubber component is preferably 35% by mass or less. Examples of such other rubber components include chloroprene rubber (CR), butyl rubber (IIR), halogenated butyl rubber, ethylene-propylene rubber (EPR, EPDM), fluororubber, silicone rubber, and urethane rubber. Among these, diene-based rubbers such as butadiene rubber (BR) and chloroprene rubber (CR) are preferred, and butadiene rubber (BR) is even more preferred. Furthermore, as the butadiene rubber (BR), high-cis polybutadiene is preferred, and it is preferable that the high-cis polybutadiene has a cis-1,4 bond content of 90% by mass or more. When the rubber component contains butadiene rubber, the butadiene rubber content is preferably in the range of 1 to 35 parts by mass per 100 parts by mass of the rubber component.

[0119] (Resin components) The rubber composition for tires of the present invention further comprises a resin component in addition to the rubber component. The aforementioned resin component has a weight-average molecular weight (Mw) of 200 to 1600 g / mol. Here, the weight-average molecular weight is the weight-average molecular weight (g / mol) on a polystyrene basis. If the molecular weight of the resin component is 200 g / mol or more, the resin component is less likely to precipitate from the tire, and the effects of the resin component can be fully expressed. If it is 1600 g / mol or less, the resin component is easily compatible with the rubber component. Furthermore, from the viewpoint of suppressing the precipitation of the resin component from the tire and suppressing the deterioration of the tire appearance, the weight-average molecular weight of the resin component in terms of polystyrene 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. Furthermore, from the viewpoint of improving the compatibility of the resin component with the rubber component and further enhancing the effect of the resin component, the weight-average molecular weight of the resin component in terms of polystyrene is 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 1250 g / mol or less, more preferably 1200 g / mol or less, more preferably 1150 g / mol or less, more preferably 1100 g / mol or less, preferably 1050 g / mol or less, more preferably 1000 g / mol or less, and even more preferably 950 g / mol or less.

[0120] Furthermore, it is preferable that the resin component is at least partially hydrogenated. By at least partially hydrogenating the resin component, its compatibility with the diene-based rubber component A, such as the isoprene backbone rubber, is increased, the mobility of the rubber component is controlled, and the hysteresis loss (tanδ) in the low-temperature region can be improved, thereby improving the wet grip performance of the tire to which the rubber composition is applied.

[0121] Furthermore, from a similar perspective, the difference in SP value between the resin component and the isoprene skeleton rubber is 1.40 (cal / cm²). 3 ) 1 / 2 The following: The following formula: The mass ratio of the resin component to the isoprene skeleton rubber is ≥ 0.5 It is preferable that the following conditions be met. Furthermore, the difference in SP values ​​between the resin component and the isoprene skeleton rubber is set to 1.40 (cal / cm²) from the viewpoint of further improving compatibility. 3 ) 1 / 2 Preferably, it is 1.35 (cal / cm³). 3 ) 1 / 2 Preferably, it is 0.45 (cal / cm³). 3 ) 1 / 2 Preferably, it is 0.3 (cal / cm³). 3 ) 1 / 2 Preferably, it is 0.25 (cal / cm³). 3 ) 1 / 2 The following is even more preferable:

[0122] Furthermore, by having a mass ratio of the resin component to the isoprene skeleton rubber [mass ratio of resin component / mass ratio of isoprene skeleton rubber] of 0.5 or higher, the strain energy loss of the polymer phase consisting of the isoprene skeleton rubber and the resin component is increased, thereby further improving the wet grip performance of the tire to which the rubber composition is applied. The mass ratio of the resin component to the isoprene skeleton rubber [mass ratio of resin component / mass ratio of isoprene skeleton rubber] is preferably 0.65 or higher, more preferably 0.7 or higher, more preferably 0.8 or higher, preferably 2.0 or lower, more preferably 1.9 or lower, and even more preferably 1.8 or lower.

[0123] Furthermore, it is preferable that the resin component has a softening point higher than 110°C. By applying a rubber composition containing such a resin component to a tire, the wear resistance of the tire can be further improved. If the softening point of the resin component is higher than 110°C, the tire to which the rubber composition is applied can be sufficiently reinforced, and the wear resistance can be further improved. From a similar viewpoint, the softening point of the resin component is preferably 116°C or higher, more preferably 120°C or higher, even more preferably 123°C or higher, and particularly preferably 127°C or higher. Furthermore, from the viewpoint of wet grip performance and processability, the softening point of the resin component is preferably 160°C or lower, more preferably 150°C or lower, even more preferably 145°C or lower, even more preferably 141°C or lower, and particularly preferably 136°C or lower.

[0124] Here, the weight-average molecular weight (Mw) of the resin component in terms of polystyrene. HR The softening point (Ts) of the resin component relative to (unit is g / mol) HR The ratio (Ts) (unit is °C) 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 ) is preferably 0.25 or less, preferably 0.24 or less, preferably 0.23 or less, preferably 0.19 or less, more preferably 0.18 or less, and even more preferably 0.17 or less. The softening point and weight-average molecular weight (in polystyrene equivalent) of the resin component can be determined by the method described in the examples below.

[0125] Furthermore, the content of the resin component is 1 to 45 parts by mass per 100 parts by mass of the rubber component. If the content of the resin component in the rubber composition is 1 part by mass or more per 100 parts by mass of the rubber component, the effect of the resin component is fully expressed, and if it is 45 parts by mass or less, the resin component is less likely to precipitate from the tire, and the effect of the resin component can be fully expressed. On the other hand, if the content of the resin component exceeds 45 parts by mass per 100 parts by mass of the rubber component, the fuel efficiency and wear resistance of the tire to which the rubber composition is applied deteriorates. From the viewpoint of further enhancing the effect of the resin component, the content of the resin component in the rubber composition is preferably 5 parts by mass or more, more preferably 7 parts by mass or more, and even more preferably 9 parts by mass or more, per 100 parts by mass of the rubber component. Furthermore, from the viewpoint of suppressing the precipitation of the resin component from the tire and suppressing the deterioration of the tire appearance, the content of the resin component in the rubber composition is more preferably 40 parts by mass or less, more preferably 35 parts by mass or less, and even more preferably 30 parts by mass or less, per 100 parts by mass of the rubber component.

[0126] Furthermore, the resin component that is at least partially hydrogenated as described above refers to the resin obtained by reducing and hydrogenating the resin. Examples of resins used as raw materials for hydrogenated resin components include C5 resins, C5-C9 resins, C9 resins, terpene resins, dicyclopentadiene resins, and terpene-aromatic compound resins. These resins may be used individually or in combination of two or more types.

[0127] Examples of the aforementioned C5 resins include aliphatic petroleum resins obtained by (co)polymerizing C5 fractions obtained by the thermal decomposition of naphtha in the petrochemical industry. The C5 fraction typically contains olefinic hydrocarbons such as 1-pentene, 2-pentene, 2-methyl-1-butene, 2-methyl-2-butene, and 3-methyl-1-butene, as well as diolefinic hydrocarbons such as 2-methyl-1,3-butadiene, 1,2-pentadiene, 1,3-pentadiene, and 3-methyl-1,2-butadiene. Commercially available C5 resins can be used.

[0128] The aforementioned C5-C9 resin refers to a C5-C9 synthetic petroleum resin, and as a C5-C9 resin, for example, petroleum-derived C5-C 11 Examples include solid polymers obtained by polymerizing fractions using Friedel-Crafts catalysts such as AlCl3 and BF3, and more specifically, copolymers mainly composed of styrene, vinyltoluene, α-methylstyrene, indene, etc. As for C5-C9 resins, resins with a low amount of C9 or higher components are preferred from the viewpoint of compatibility with rubber components. Here, "low amount of C9 or higher components" means that the amount of C9 or higher components in the total resin is less than 50% by mass, preferably 40% by mass or less. Commercially available C5-C9 resins can be used.

[0129] The aforementioned C9 resin refers to a C9 synthetic petroleum resin, specifically a solid polymer obtained by polymerizing a C9 fraction using a Friedel-Crafts type catalyst such as AlCl3 or BF3. Examples of C9 resins include copolymers mainly composed of indene, α-methylstyrene, vinyltoluene, etc.

[0130] The aforementioned terpene resins are solid resins obtained by polymerizing turpentine oil, which is obtained simultaneously when rosin is obtained from pine trees, or polymer components separated therefrom, using a Friedel-Crafts type catalyst. Examples include β-pinene resin and α-pinene resin. As a representative example of terpene-aromatic compound resins, terpene-phenol resins can be cited. These terpene-phenol resins can be obtained by reacting terpenes with various phenols using a Friedel-Crafts type catalyst, or by further condensation with formalin. There are no particular restrictions on the terpenes used as raw materials, but monoterpene hydrocarbons such as α-pinene and limonene are preferred, those containing α-pinene are more preferred, and α-pinene is particularly preferred. The skeleton may also contain styrene or the like.

[0131] The dicyclopentadiene-based resin refers to a resin obtained by polymerizing dicyclopentadiene using a Friedel-Crafts type catalyst such as AlCl3 or BF3.

[0132] In addition, the resin used as a raw material for the hydrogenated resin component may contain, for example, a resin obtained by copolymerizing a C5 fraction and dicyclopentadiene (DCPD) (C5-DCPD resin). Here, when the dicyclopentadiene-derived component in the total amount of the resin is 50% by mass or more, the C5-DCPD resin is considered to be included in the dicyclopentadiene-based resin. When the dicyclopentadiene-derived component in the total amount of the resin is less than 50% by mass, the C5-DCPD resin is considered to be included in the C5 resin. The same applies even when a small amount of a third component or the like is contained.

[0133] From the viewpoint of enhancing the compatibility between the rubber component and the resin component, further improving the wet grip performance of a tire to which the rubber composition is applied, and further reducing the rolling resistance, the resin component is preferably at least one selected from the group consisting of hydrogenated C5 resins, hydrogenated C5-C9 resins, hydrogenated dicyclopentadiene-based resins (hydrogenated DCPD resins), and hydrogenated terpene resins, more preferably at least one selected from the group consisting of hydrogenated C5 resins and hydrogenated C5-C9 resins, and even more preferably a hydrogenated C5 resin. Also, it is preferably a resin having a hydrogenated DCPD structure or a hydrogenated cyclic structure in at least the monomer.

[0134] (Filler) The rubber composition for a tire of the present invention contains a filler. By containing a filler, the reinforcing property of the rubber composition is improved. The amount of filler in the rubber composition is preferably in the range of 40 to 100 parts by mass per 100 parts by mass of the rubber component. If the amount of filler in the rubber composition is 40 parts by mass or more per 100 parts by mass of the rubber component, the reinforcement of the tire to which the rubber composition is applied is sufficient, and the wear resistance can be further improved. If it is 100 parts by mass or less, the elastic modulus of the rubber composition does not become too high, and the wet grip performance of the tire to which the rubber composition is applied is further improved. From the viewpoint of further lowering the rolling resistance of the tire (from the viewpoint of improving fuel efficiency), the amount of filler in the rubber composition is preferably 45 parts by mass or more, more preferably 50 parts by mass or more, and even more preferably 55 parts by mass or more, per 100 parts by mass of the rubber component. Furthermore, from the viewpoint of improving the wet grip performance of the tire, the amount of filler in the rubber composition is preferably 95 parts by mass or less, and even more preferably 90 parts by mass or less, per 100 parts by mass of the rubber component.

[0135] The filler preferably contains silica and has a nitrogen adsorption specific surface area (BET method) of 100 m². 2 / g or more 330m 2 It is even more preferable that the silica content be less than / g. The specific surface area of ​​the silica for nitrogen adsorption (BET method) is 100m². 2 If the amount is 330 m² or more, the tire to which the rubber composition is applied can be sufficiently reinforced, and the rolling resistance of the tire can be further reduced. In addition, if the nitrogen adsorption specific surface area (BET method) of silica is 330 m² 2 If the value is less than / g, the elastic modulus of the rubber composition does not become too high, and the wet grip performance of the tire to which the rubber composition is applied is further improved. From the viewpoint of further lowering rolling resistance and improving the wear resistance of the tire, the nitrogen adsorption specific surface area (BET method) of silica is 110m². 2 It is preferable that it be 130m or more / g. 2 It is more preferable that it be 150m or more per gram. 2 It is more preferable that it be 180m or more per gram. 2 It is even more preferable that the nitrogen adsorption specific surface area of ​​silica be 300 m² or more. Furthermore, from the viewpoint of further improving the wet grip performance of the tire, the nitrogen adsorption specific surface area (BET method) of silica should be 300 m².2 It is preferable that the amount be less than or equal to 280m 2 It is more preferable that it be less than or equal to / g, and 270m 2 It is even more preferable that the amount be less than or equal to / g.

[0136] Examples of the silica include wet silica (hydrated silica), dry silica (anhydrous silica), calcium silicate, and aluminum silicate, with wet silica being preferred among these. These silicas may be used individually or in combination of two or more.

[0137] From the viewpoint of improving the mechanical strength of the tire and further improving its wear resistance, the silica content in the rubber composition is preferably 40 parts by mass or more, more preferably 45 parts by mass or more, more preferably 50 parts by mass or more, and even more preferably 55 parts by mass or more, per 100 parts by mass of the rubber component. Furthermore, from the viewpoint of further improving the wet grip performance of the tire, the silica content in the rubber composition is preferably 125 parts by mass or less, more preferably 105 parts by mass or less, more preferably 100 parts by mass or less, and even more preferably 95 parts by mass or less, per 100 parts by mass of the rubber component.

[0138] The filler may also preferably contain carbon black. The carbon black can reinforce the rubber composition and improve its abrasion resistance. The carbon black used is not particularly limited and includes, for example, GPF, FEF, HAF, ISAF, and SAF grade carbon blacks. These carbon blacks may be used individually or in combination of two or more types.

[0139] From the viewpoint of improving the wear resistance of the rubber composition and the tire to which it is applied, the carbon black content in the rubber composition is preferably 1 part by mass or more, more preferably 3 parts by mass or more, and even more preferably 5 parts by mass or more, per 100 parts by mass of the rubber component. Furthermore, from the viewpoint of the workability of the rubber composition, the carbon black content in the rubber composition is preferably 20 parts by mass or less, and more preferably 15 parts by mass or less, per 100 parts by mass of the rubber component. When the filler contains silica and carbon black, the proportion of silica in the total amount of silica and carbon black is preferably 80% by mass or more and less than 100%, and more preferably 90% by mass or more and less than 100%. A silica proportion of 80% by mass or more improves the mechanical strength of the tire to which the rubber composition is applied and can further reduce rolling resistance.

[0140] -Other fillers- The filler may also contain, in addition to silica and carbon black, inorganic fillers such as clay, talc, calcium carbonate, and aluminum hydroxide. The other fillers mentioned above are preferably included in such a range that the proportion of silica in the filler is 70% by mass or more. A silica proportion of 70% by mass or more in the filler improves the mechanical strength of the tire to which the rubber composition is applied and lowers the rolling resistance. More preferably, the silica proportion in the filler is 80% by mass or more, even more preferably 85% by mass or more, and even more preferably 90% by mass or more and less than 100%.

[0141] (others) The rubber composition for tires of the present invention may contain, as appropriate, the rubber components, resin components, fillers, styrene-based thermoplastic elastomers described above, and, if necessary, various components commonly used in the rubber industry, such as silane coupling agents, antioxidants, waxes, softeners, processing aids, stearic acid, zinc oxide (zinc oxide), vulcanization accelerators, vulcanizing agents, etc., selected within a range that does not impair the purpose of the present invention. Commercially available products can be suitably used as these compounding agents.

[0142] When the tire rubber composition of the present invention contains silica, it is preferable to include a silane coupling agent in order to improve the effect of the silica. The silane coupling agent may be bis(3-triethoxysilylpropyl)tetrasulfide, bis(3-triethoxysilylpropyl)trisulfide, bis(3-triethoxysilylpropyl)disulfide, bis(2-triethoxysilylethyl)tetrasulfide, bis(3-trimethoxysilylpropyl)tetrasulfide, bis(2-trimethoxysilylethyl)tetrasulfide, 3-mercaptopropyltrimethoxysilane, 3-mercaptopropyltriethoxysilane, 2-mercaptoethyltrimethoxysilane, 2-mercaptoethyltriethoxysilane, 3-trimethoxysilylpropyl-N,N-dimethylthiocarbamoyltetrasulfide, 3-triethoxysilylpropyl-N, Examples include N-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. The content of the silane coupling agent is preferably in the range of 2 to 20 parts by mass, and more preferably in the range of 5 to 15 parts by mass, per 100 parts by mass of silica.

[0143] Examples of the aforementioned antioxidants include N-(1,3-dimethylbutyl)-N'-phenyl-p-phenylenediamine (6C), 2,2,4-trimethyl-1,2-dihydroquinoline polymer (TMDQ), 6-ethoxy-2,2,4-trimethyl-1,2-dihydroquinoline (AW), and N,N'-diphenyl-p-phenylenediamine (DPPD). The content of the antioxidant is not particularly limited, but is preferably in the range of 0.1 to 5 parts by mass, and more preferably 1 to 4 parts by mass, per 100 parts by mass of the rubber component.

[0144] Examples of the wax include paraffin wax and microcrystalline wax. The amount of the wax is not particularly limited, but is preferably in the range of 0.1 to 5 parts by mass, and more preferably 1 to 4 parts by mass, per 100 parts by mass of the rubber component.

[0145] The content of the zinc oxide (zinc oxide) is not particularly limited, but is preferably in the range of 0.1 to 10 parts by mass, and more preferably 1 to 8 parts by mass, per 100 parts by mass of the rubber component.

[0146] Examples of the vulcanization accelerator include sulfenamide-based vulcanization accelerators, guanidine-based vulcanization accelerators, thiazole-based vulcanization accelerators, thiram-based vulcanization accelerators, and dithiocarbamate-based vulcanization accelerators. These vulcanization accelerators may be used individually or in combination of two or more. There are no particular restrictions on the content of the vulcanization accelerator, but it is preferably in the range of 0.1 to 5 parts by mass, and more preferably in the range of 0.2 to 4 parts by mass, per 100 parts by mass of the rubber component.

[0147] Examples of the vulcanizing agent include sulfur. The content of the vulcanizing agent is preferably in the range of 0.1 to 10 parts by mass, and more preferably in the range of 1 to 4 parts by mass, as sulfur, per 100 parts by mass of the rubber component.

[0148] (Method for manufacturing rubber composition) The method for manufacturing the rubber composition is not particularly limited. For example, various components appropriately selected as needed are blended with the aforementioned rubber component, resin component, and filler, followed by kneading, heat treatment, extrusion, etc. to manufacture it. Further, by vulcanizing the obtained rubber composition, a vulcanized rubber can be obtained.

[0149] Regarding the kneading conditions, there are no particular restrictions, and various conditions such as the charging volume of the kneading device, the rotation speed of the rotor, the ram pressure, etc., as well as the kneading temperature, kneading time, and type of kneading device, can be appropriately selected according to the purpose. As the kneading device, usually, a Banbury mixer, an internal mixer, a kneader, a roll, etc. used for kneading rubber compositions can be mentioned.

[0150] Regarding the heat treatment conditions, there are no particular restrictions, and various conditions such as the heat treatment temperature, heat treatment time, heat treatment device, etc. can be appropriately selected according to the purpose. As the heat treatment device, usually, a heat treatment roll machine used for heat treatment of rubber compositions can be mentioned.

[0151] Regarding the extrusion conditions, there are no particular restrictions, and various conditions such as the extrusion time, extrusion speed, extrusion device, extrusion temperature, etc. can be appropriately selected according to the purpose. As the extrusion device, usually, an extruder used for extrusion of rubber compositions can be mentioned. The extrusion temperature can be determined appropriately.

[0152] Regarding the device, method, conditions, etc. for performing the vulcanization, there are no particular restrictions, and they can be appropriately selected according to the purpose. As the device for performing the vulcanization, usually, a molding vulcanizer using a mold used for vulcanization of rubber compositions can be mentioned. As the vulcanization conditions, the temperature is, for example, about 100 to 190°C.

[0153] [[ID= (20)]]<Tread rubber> The tread rubber of the present invention is characterized by comprising the above rubber composition for tires. Since such tread rubber of the present invention comprises the above rubber composition for tires, by applying it to a tire, it is possible to highly balance the wet grip performance and the low fuel consumption performance of the tire. The tread rubber of the present invention may be applied to new tires or to retreaded tires.

[0154] <Tires> The tire of the present invention is characterized by having the above-described tread rubber. Because the tire of the present invention has the above-described tread rubber, it achieves a high balance between wet grip performance and fuel efficiency.

[0155] The tire of the present invention may be obtained by molding an unvulcanized rubber composition and then vulcanizing it, depending on the type of tire to be applied, or by molding a semi-vulcanized rubber that has undergone a pre-vulcanization process, and then further vulcanizing it. The tire of the present invention is preferably a pneumatic tire, and as the gas to be filled into the pneumatic tire, in addition to ordinary air or air with adjusted oxygen partial pressure, an inert gas such as nitrogen, argon, or helium can be used. [Examples]

[0156] The present invention will be described in more detail below with reference to examples, but the present invention is not limited in any way to the following examples.

[0157] <Method for analyzing rubber components> The glass transition temperature (Tg), amount of bound styrene, and microstructure of the butadiene portion of styrene-butadiene rubber were measured using the following methods. Furthermore, the SP values ​​(solubility parameters) of natural rubber (isoprene-backed rubber) and styrene-butadiene rubber were calculated according to the Fedors method.

[0158] (1) Glass transition temperature (Tg) Using synthesized styrene-butadiene rubber as a sample, a DSC250 from TA Instruments was used to record the DSC curve while heating from -100°C to 20°C / min under a helium flow of 50 mL / min. The peak top (inflection point) of the DSC differential curve was defined as the glass transition temperature.

[0159] (2) Amount of bound styrene Synthesized styrene-butadiene rubber was used as the sample. 100 mg of the sample was dissolved in chloroform to a volume of 100 mL and prepared as the measurement sample. The amount of bound styrene (mass%) relative to 100% mass% of the sample was measured by the amount of ultraviolet absorption at a wavelength (around 254 nm) by the phenyl group of styrene. A Shimadzu UV-2450 spectrophotometer was used as the measurement device.

[0160] <Method for analyzing resin components> The softening point and weight-average molecular weight of the resin components were measured using the following methods. Furthermore, the SP value (solubility parameter) of the resin components was calculated according to the Fedors method.

[0161] (3) Softening point The softening point of the resin component was measured in accordance with JIS-K2207-1996 (ring-sphere method).

[0162] (4) Weight average molecular weight Under the following conditions, the average molecular weight of the hydrogenated resin was measured by gel permeation chromatography (GPC), and the weight-average molecular weight in terms of polystyrene was calculated. Column temperature: 40°C ·Injection volume: 50μL • Carrier and flow rate: Tetrahydrofuran 0.6 mL / min Sample preparation: Dissolve approximately 2.5 mg of resin component in 10 mL of tetrahydrofuran.

[0163] <Preparation of rubber composition> The rubber compositions of the examples and comparative examples were prepared by mixing and kneading each component according to the formulations shown in Table 1.

[0164] <Vulcanized Rubber Preparation and Evaluation> The rubber compositions of the obtained examples and comparative examples were vulcanized at 145°C for 33 minutes to obtain vulcanized rubber test pieces. The wet grip performance and fuel efficiency performance of the obtained vulcanized rubber test pieces were evaluated using the following method. Furthermore, the tanδ at 0°C (0°C tanδ) and tanδ at 50°C (50°C tanδ) were measured on the obtained vulcanized rubber test specimens using a viscoelasticity measuring device (manufactured by Rheometrics) under the conditions of 0°C, 1% strain, and 52 Hz, and 50°C, 1% strain, and 52 Hz. The measured values ​​of 0°C tanδ and 50°C tanδ, as well as the calculated values ​​of 0°C tanδ / 50°C tanδ, are shown in Table 1.

[0165] (5) Wet grip performance A portable friction tester was used to measure the coefficient of friction of the test specimens on a wet asphalt road surface. The evaluation results were expressed as an index, with the coefficient of friction of Comparative Example 1 set to 100. A higher index value indicates a higher coefficient of friction and superior wet grip performance.

[0166] (6) Fuel efficiency The loss tangent (tanδ) of the test specimen was measured using a viscoelasticity measuring device (manufactured by Rheometrics) under the conditions of a temperature of 50°C, a strain of 1%, and a frequency of 52Hz. The evaluation results were expressed exponentially, with the reciprocal of the tanδ of Comparative Example 1 set to 100. A larger exponential value indicates a smaller tanδ and superior fuel efficiency.

[0167] (7) Overall evaluation The combined evaluation values ​​(indexes) for wet grip performance and fuel efficiency performance were used as the indicator for the overall evaluation. The overall evaluation index indicates that a higher numerical value indicates a higher overall evaluation.

[0168] [Table 1]

[0169] *1 Natural rubber: TSR#20, SP value = 8.20 (cal / cm 3 ) 1 / 2 *2 Low Tg-modified SBR: Hydrocarbyloxysilane compound-modified styrene-butadiene rubber synthesized by the method described below, Tg = -65℃, SP value = 8.65 (cal / cm²)3 ) 1 / 2 *3 Filler: Silica, manufactured by Tosoh Silica Co., Ltd., product name "NipSeal AQ" *4 Resin components: Hydrogenated C5 resin, manufactured by Eastman, trade name "Registered Trademark Impera E1780", softening point = 130℃, weight-average molecular weight (Mw) = 909 g / mol, SP value = 8.35 (cal / cm²) 3 ) 1 / 2 *5 Silane coupling agent: Evonik DeGussa, product name "Si75" *6 Anti-aging agent: Manufactured by Ouchi Shinko Chemical Industry Co., Ltd., product name "Nocrack 6C" *7 Wax: Manufactured by Nippon Seiro Co., Ltd., product name "Ozo Ace 0701" *8 Vulcanization accelerator A: Manufactured by Ouchi Shinko Chemical Industry Co., Ltd., product name "Noxellar DM-P" *9 Vulcanization accelerator B: Manufactured by Sanshin Chemical Industry Co., Ltd., product name "Sunceller NS-G"

[0170] <Synthesis method for low-Tg modified SBR (*2)> In a dried, nitrogen-purged 800 mL pressure-resistant glass container, cyclohexane solutions of 1,3-butadiene and styrene were added to a total volume of 67.5 g of 1,3-butadiene and 7.5 g of styrene. 0.6 mmol of 2,2-ditetrahydrofurylpropane was added, followed by 0.8 mmol of n-butyllithium, and polymerization was carried out at 50°C for 1.5 hours. When the polymerization conversion rate reached nearly 100%, 0.72 mmol of N,N-bis(trimethylsilyl)-3-[diethoxy(methyl)silyl]propylamine was added as a modifying agent, and the modification reaction was carried out at 50°C for 30 minutes. Subsequently, 2 mL of a 5% by mass solution of 2,6-di-t-butyl-p-cresol (BHT) in isopropanol was added to stop the reaction, and the modified SBR was obtained by drying according to a conventional method. Microstructure measurements of the obtained modified SBR revealed that the amount of bound styrene was 10% by mass, the amount of vinyl binding in the butadiene portion was 40%, and the glass transition temperature (Tg) was -65°C.

[0171] The results in Table 1 show that the rubber compositions of the embodiments according to the present invention have a high degree of balance between wet grip performance and fuel efficiency. On the other hand, the rubber compositions of Comparative Examples 3 and 4, which contained too much resin, showed poor fuel efficiency and overall performance. Furthermore, the rubber compositions of Comparative Examples 1 and 2, which had a 0°C tanδ / 50°C tanδ of less than 2.7, showed inferior wet grip performance and fuel efficiency compared to the examples. [Industrial applicability]

[0172] According to the present invention, it is possible to provide a tire rubber composition that can achieve a high degree of balance between the wet grip performance and fuel efficiency of the tire, and a tread rubber made from such a rubber composition. Furthermore, according to the present invention, it is possible to provide a tire that achieves a high degree of balance between wet grip performance and fuel efficiency.

Claims

1. A rubber composition for tires comprising a rubber component, a resin component, and a filler, The rubber component comprises a diene-based rubber component A containing an isoprene skeleton rubber and having a glass transition temperature of -50°C or lower, and a diene-based rubber component B containing a butadiene skeleton rubber and being incompatible with the diene-based rubber component A. The total styrene content in the aforementioned diene-based rubber component B is 15% by mass or less. The resin component has a weight-average molecular weight (Mw) of 200 to 1600 g / mol, and its content is 1 to 45 parts by mass per 100 parts by mass of the rubber component. The content of the filler is 20 to 120 parts by mass per 100 parts by mass of the rubber component. The ratio of the tanδ at 0°C (0°C tanδ) to the tanδ at 50°C (50°C tanδ) (0°C tanδ / 50°C tanδ) is 2.7 or greater. A rubber composition for tires, characterized in that the mass ratio of the resin component to the isoprene skeleton rubber (mass ratio of resin component to isoprene skeleton rubber) is 0.5 or more and 2.0 or less.

2. The tire rubber composition according to claim 1, characterized in that the content ratio of the diene-based rubber component A in the rubber component is 1% by mass or more and less than 50% by mass.

3. The rubber composition for tires according to claim 1 or 2, characterized in that the softening point of the resin component is higher than 110°C.

4. The tire rubber composition according to any one of claims 1 to 3, characterized in that the diene rubber component A includes at least one of natural rubber and isoprene rubber.

5. The tire rubber composition according to any one of claims 1 to 4, characterized in that the diene rubber component B includes at least one of styrene-butadiene rubber and butadiene rubber.

6. The tire rubber composition according to claim 5, wherein the styrene-butadiene rubber is modified with a modifying agent having a functional group containing a nitrogen atom and an alkoxy group.

7. The tire rubber composition according to any one of claims 1 to 6, characterized in that the filler contains carbon black.

8. The rubber composition for tires according to any one of claims 1 to 7, characterized in that the resin component includes 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.

9. A tread rubber characterized by comprising the tire rubber composition described in any one of claims 1 to 8.

10. A tire characterized by comprising the tread rubber described in claim 9.

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