Rubber composition for tires and use in a pneumatic tire

Abstract

Rubber composition for a tire, which includes the following: a diene rubber; Silica and a modified butadiene polymer, wherein the modified butadiene polymer has a functional group selected from the group consisting of an amino group, a hydroxy group, an epoxy group, an alkylsilyl group, an alkoxysilyl group, and a functional group containing a nitrogen atom and a silicon atom at one terminus, wherein the diene rubber comprises an aromatic vinyl-conjugated diene rubber A and at least one rubber component B selected from the group consisting of an aromatic vinyl-conjugated diene rubber b1, which is not the aromatic vinyl-conjugated diene rubber A, and a butadiene rubber b2 having a molecular weight (average weight) of more than 15000, the aromatic vinyl-conjugated diene rubber A is a terminally modified aromatic vinyl-conjugated diene rubber with an aromatic vinyl content of 35 to 45 wt% and a vinyl unit content of 25 to 45 mol%, and has at least one functional group selected from the group consisting of an amino group, a hydroxy group, an epoxy group, an alkylsilyl group, an alkoxysilyl group, and a carboxyl group at the terminus, in which the diene rubber contains a content of aromatic vinyl-conjugated diene rubber A of 30 to 90 mass-%, and a content of rubber component B of 10 to 70 mass-%, an average glass transition temperature of the diene monomer is from -20 °C to -100 °C, wherein the glass transition temperature (Tg) is measured using a differential scanning calorimeter at a temperature rise rate of 10 °C / min and is determined by multiplying mass fractions of diene monomers with corresponding glass transition temperatures of the diene monomers and subsequently summing the obtained values, wherein the weighted mean of the glass transition temperatures is taken and the sum of the mass fractions of all diene monomers is set to 1. the modified butadiene polymer is a terminally modified butadiene polymer with a molecular weight (average weight) of 1000 to 10000 and a molecular weight distribution of 2.0 or less, a silica content of 80 to 200 parts by mass per 100 parts by mass of diene rubber, and The content of the modified butadiene polymer, based on the silica content, is from 1.0 to 25.0 wt%.

Description

Technical area

[0001] The present invention relates to a rubber composition for a tire and the use thereof in a pneumatic tire. State of the art

[0002] In recent years, there has been a need to reduce tire pyrogenicity (hysteresis loss) from the perspective of fuel efficiency when a vehicle is running. One known method for achieving this goal is a method for reducing tire pyrogenicity by blending silica into a rubber component forming a tire tread.

[0003] However, since silica has low affinity for rubber components and the cohesiveness between silica particles is high, even if silica is simply blended into the rubber component, the silica is not dispersed, resulting in the problem that the effect of reducing pyrogenicity cannot be sufficiently achieved.

[0004] For example, in examples of Patent Document 1, a composition containing a styrene-butadiene rubber (SBR), a butadiene rubber (BR), and silica is described.

[0005] Further, for example, in examples of Patent Document 2, a composition containing two types of styrene-butadiene rubbers (SBR), a butadiene rubber (BR), and silica is described. Patent Document 3 discloses a rubber composition containing a diene rubber containing 5-70 mass% of a modified butadiene rubber obtained by modifying an unmodified butadiene rubber (A) with a nitrone compound (B) having a carboxyl group. The unmodified butadiene rubber (A) contains 2 to 45 parts by mass of an unmodified low molecular weight butadiene rubber (A1) containing 1.5 to 60 mol% of vinyl bonds and having a number average molecular weight (Mn) of 2,000 to 60,000, based on 100 parts by mass of an unmodified butadiene rubber (A2) having a higher number average molecular weight (Mn) than the unmodified low molecular weight butadiene rubber (A1).Patent Document 4 discloses a rubber composition comprising a rubber component (A) containing 10 mass % or more of a modified conjugated diene-based polymer having at least one kind of functional group and having a weight-average molecular weight in terms of polystyrene of 200,000 or more, and, based on 100 parts by mass of (A), (B) 20 parts by mass or more of a reinforcing filler, and (C) 5-60 parts by mass of an unmodified and / or modified low-molecular-weight copolymer of an aromatic vinyl compound and a conjugated diene compound having a weight-average molecular weight of ≥ 5,000 and < 200.000 in its unmodified state or before modification, wherein the modified conjugated diene-based polymer in component (A) has, as functional groups, an amino group protected by a protic amino group or eliminable group and a functional group containing a silicon atom. Literature listPatent literature Patent Document 1: JP 2014-28902 A Patent Document 2: JP 2011-162625 A Patent Document 3: JP 2016-199709 A Patent Document 4: JP 2009-287020 A Brief description of the inventionTechnical problem

[0006] Furthermore, environmental concerns, resource constraints, and the like have led to a demand for even better fuel efficiency in vehicles, which in turn has led to a demand for further improvements in silica dispersibility in a rubber composition in a silica-containing tire. There is also a need for improvements in WET performance (WET steering stability: steering stability on wet road surfaces) in line with the improvement of required safety levels. Furthermore, from the perspective of manufacturing efficiency, there is a need for further improvement in processability (viscosity reduction).

[0007] In this way, when the inventors of the present invention prepared a rubber composition with reference to the examples of Patent Documents 1 and 2, it was clearly found that a rubber composition satisfying all of the above-described features at a high level is not necessarily obtained.

[0008] Therefore, in view of the above circumstances, it is an object of the present invention to provide a rubber composition for a tire which has excellent processability and silica dispersibility and has excellent wet performance (wet steering stability) and fuel efficiency when used in a tire; and a pneumatic tire manufactured using the rubber composition for a tire. Solution to the problem

[0009] As a result of thorough investigation of the above-described problems, the inventors of the present invention have found that the above-described problems can be solved by blending a specific modified butadiene polymer with silica in a specific proportion, and thus completed the present invention.

[0010] In particular, the inventors of the present invention discovered that the problems described above can be solved by the following features. (1) A rubber composition for a tire containing diene rubber; silica; and a modified butadiene polymer, wherein the modified butadiene polymer has a functional group selected from the group consisting of an amino group, a hydroxy group, an epoxy group, an alkylsilyl group, an alkoxysilyl group, and a functional group containing a nitrogen atom and a silicon atom at one terminal, wherein the diene rubber contains an aromatic vinyl-conjugated diene rubber A and at least one rubber component B selected from the group consisting of an aromatic vinyl-conjugated diene rubber b1 other than the aromatic vinyl-conjugated diene rubber A and a butadiene rubber b2 having a weight-average molecular weight of more than 15,000,the aromatic vinyl-conjugated diene rubber A is a terminally modified aromatic vinyl-conjugated diene rubber having an aromatic vinyl content of 35 to 45 mass% and a vinyl unit content of 25 to 45 mol%, and at least one functional group selected from the group consisting of an amino group, a hydroxy group, an epoxy group, an alkylsilyl group, an alkoxysilyl group, and a carboxyl group at the terminus, in which diene rubber there is a content of the aromatic vinyl-conjugated diene rubber A of 30 to 90 mass% and a content of the rubber component B of 10 to 70 mass%, an average glass transition temperature of the diene rubber is from -20°C to -100°C,wherein the glass transition temperature (Tg) is measured using a differential scanning calorimeter at a temperature rise rate of 10 °C / min. measured and determined by multiplying mass fractions of diene rubbers by corresponding glass transition temperatures of the diene rubbers and then summing the obtained values, taking the weighted average of the glass transition temperatures and setting the sum of the mass fractions of all diene rubbers to 1, the modified butadiene polymer is a terminally modified butadiene polymer having a molecular weight (weight average) of 1,000 to 10,000 and a molecular weight distribution of 2.0 or less, a silica content of 80 to 200 parts by mass per 100 parts by mass of the diene rubber, and a content of the modified butadiene polymer, based on the silica content, of 1.0 to 25.0 mass%. (2) The rubber composition for a tire according to (1) above, wherein in the diene rubber, the content of the aromatic vinyl-conjugated diene rubber A may be from 50 to 90 mass%, and the content of the rubber component B may be from 10 to 50 mass%, and the average glass transition temperature of the diene rubber may be -45°C or higher and lower than -20°C. (3) The rubber composition for a tire according to (1) above, wherein the diene rubber, the content of the aromatic vinyl-conjugated diene rubber A may be from 30 to 50 mass% and the proportion of the rubber component B may be from 50 to 70 mass%, and the average glass transition temperature of the diene rubber may be lower than -45 °C. (4) The rubber composition for a tire according to any one of (1) to (3) above, in which the modified butadiene polymer may have a functional group having a nitrogen atom and a silicon atom at a terminal. (5) The rubber composition for a tire according to any one of (1) to (4) above, wherein the silica has a specific surface area for adsorbing cetyltrimethylammonium bromide of 150 to 300 m 2 / g has. (6) The rubber composition for a tire according to any one of the above items (1) to (5), further containing a silane coupling agent, wherein a content of the silane coupling agent may be from 1 to 20 mass% based on the silica content. (7) Use of the rubber composition according to any one of the above items (1) to (6) for a pneumatic tire in which the rubber composition is arranged in a protector tread. Advantageous effects of the invention

[0011] As described below, according to the present invention, it is possible to provide a rubber composition for a tire that has excellent processability and silica dispersibility and has excellent wet performance (wet steering stability) and fuel efficiency when used in a tire; and a pneumatic tire manufactured using the rubber composition for a tire. Brief description of the drawings Fig. 1 is a partial cross-sectional view illustrating an example of a pneumatic tire according to an embodiment of the present invention. Description of embodiments

[0012] Hereinafter, a rubber composition for a tire of one embodiment of the present invention and a pneumatic tire using the rubber composition for a tire will be described.

[0013] In the present specification, numerical ranges indicated using "(from) ... to ..." include the first number as the lower limit and the last number as the upper limit. Furthermore, for each of the components included in the rubber composition for a tire according to an embodiment of the present invention, one type may be used alone, or two or more types may be used in combination. Here, in a case where two or more types of each component are used in combination, the content of the component refers to the entire content unless otherwise specified. Rubber composition for a tire

[0014] A rubber composition for a tire according to an embodiment of the present invention (hereinafter, also referred to as “composition according to an embodiment of the present invention”) contains a diene rubber, silica and a modified butadiene polymer.

[0015] Here, the diene rubber contains an aromatic vinyl-conjugated diene rubber A and at least one rubber component B selected from the group consisting of an aromatic vinyl-conjugated diene rubber b1 other than the aromatic vinyl-conjugated diene rubber A and a butadiene rubber b2 having a weight-average molecular weight of more than 15,000. Further, the aromatic vinyl-conjugated diene rubber A is a terminal-modified aromatic vinyl-conjugated diene rubber having an aromatic vinyl content of 35 to 45 mass% and a vinyl unit content of 25 to 45 mol%.

[0016] In addition, in the diene rubber, a content of the aromatic vinyl-conjugated diene rubber A is from 30 to 90 mass%, and a content of the rubber component B is from 10 to 70 mass%.

[0017] In addition, the average glass transition temperature of the diene rubber is -20 °C or less.

[0018] In addition, the modified butadiene polymer is a terminally modified butadiene polymer having a weight average molecular weight of 1000 to 15000 and a molecular weight distribution of 2.0 or less.

[0019] The silica content is 80 to 200 parts by mass per 100 parts by mass of the diene rubber.

[0020] In addition, the content of the modified butadiene polymer, based on the silica content, is from 1.0 to 25.0 mass%.

[0021] The composition according to one embodiment of the present invention is considered to achieve the desired effects as a result of such a configuration. Although the reason for this is not clear, it is believed that the dispersibility of the silica is improved by the interaction of the modified butadiene polymer with the silica.

[0022] Here, as a result of the present inventors' investigation, it was found that the size (weight-average molecular weight, molecular weight distribution) of the modified butadiene polymer and the dispersibility of silica are critical. The reason for this is believed to be that when the size of the modified butadiene polymer is within a specific range, the modified butadiene polymer easily penetrates into the gap between silica aggregates. Thus, it is believed that extremely high silica dispersibility is achieved by using the modified butadiene polymer with a specific size in one embodiment of the present invention.

[0023] Note that a first preferred aspect of the composition according to one embodiment of the present invention is one in which the diene rubber, the content of aromatic vinyl-conjugated diene rubber A is from 50 to 90 mass%, and the content of rubber component B is from 10 to 50 mass%, and the average glass transition temperature of the diene rubber is -45°C or higher and less than -20°C. The first preferred aspect is useful for a summer tire.

[0024] Note that a first preferred aspect of the composition according to one embodiment of the present invention is one in which the diene rubber, the content of aromatic vinyl-conjugated diene rubber A is from 30 to 50 mass%, and the content of rubber component B is from 50 to 70 mass%, and the average glass transition temperature of the diene rubber is below -45°C. The first preferred aspect is useful for a winter tire.

[0025] Each of the components included in the composition according to one embodiment of the present invention is explained in detail below. Diene rubber

[0026] The diene rubber contained in the composition according to one embodiment of the present invention contains an aromatic vinyl-conjugated diene rubber A and at least one rubber component B selected from the group consisting of an aromatic vinyl-conjugated diene rubber b1 other than the aromatic vinyl-conjugated diene rubber A and a butadiene rubber b2 having a weight-average molecular weight of more than 15,000.

[0027] In addition, the aromatic vinyl-conjugated diene rubber A is a terminal-modified aromatic vinyl-conjugated diene rubber having an aromatic vinyl content of 35 to 45 mass% and a vinyl unit content of 25 to 45 mol%.

[0028] In addition, in the diene rubber, a content of the aromatic vinyl-conjugated diene rubber A is from 30 to 90 mass%, and a content of the rubber component B is from 10 to 70 mass%.

[0029] In addition, the average glass transition temperature of the diene rubber is -20 °C or less. Aromatic vinyl-conjugated diene rubber A

[0030] Aromatic vinyl-conjugated diene rubber A is a terminal-modified aromatic vinyl-conjugated diene rubber with an aromatic vinyl content of 35 to 45 mass% and a vinyl unit content of 25 to 45 mol%. Among them, from the viewpoint of achieving excellent processability and silica dispersibility, excellent wet performance (wet steering stability) and fuel efficiency when used in a tire, and excellent durability (especially high-speed durability), snow braking performance, heat resistance, cold resistance, wear resistance, contamination resistance, lightfastness, and steering stability when used in a tire, a terminal-modified styrene-butadiene rubber (terminus-modified SBR) with an aromatic vinyl content of 35 to 45 mass% and a vinyl unit content of 25 to 45 mol% is preferred.Hereinafter, excellent processability and silica dispersibility, excellent WET performance (WET steering stability) and fuel efficiency when used in a tire, and excellent durability (especially high-speed durability), snow braking performance, heat resistance, cold resistance, wear resistance, contamination resistance, light fastness, and steering stability when used in a tire are also referred to as “superior effect of the present invention”.

[0031] Here, the aromatic vinyl-conjugated diene rubber is a copolymer of aromatic vinyl and conjugated diene, and may be a copolymer of aromatic vinyl, conjugated diene, and other monomers other than aromatic vinyl and conjugated diene. Aromatic vinyl

[0032] Examples of the aromatic vinyl include styrene, 2-methylstyrene, 3-methylstyrene, 4-methylstyrene, alpha-methylstyrene, 2,4-dimethylstyrene, 2,4-diisopropylstyrene, 4-tert-butylstyrene, divinylbenzene, tert-butoxystyrene, vinylbenzyldimethylamine, (4-vinylbenzyl)dimethylaminoethyl ether, N,N-dimethylaminoethylstyrene, and vinylpyridine. Among these, the aromatic vinyl is preferably styrene in view of achieving the superior effect of the present invention. Conjugated diene

[0033] Examples of the conjugated diene include 1,3-butadiene, isoprene (2-methyl-1,3-butadiene), 2,3-dimethyl-1,3-butadiene, 2-chloro-1,3-butadiene, 1,3-pentadiene, and the like. Among them, the conjugated diene is preferably 1,3-butadiene in view of achieving the superior effect of the present invention. Other monomers

[0034] Examples of the other monomers include unsaturated α- and β-nitriles such as acrylonitrile and methacrylonitrile; unsaturated carboxylic acids or acid anhydrides such as acrylic acid, methacrylic acid, and maleic anhydride; unsaturated carboxylic acid esters such as methyl methacrylate, ethacrylate, and butyl acrylate; and non-conjugated dienes such as 1,5-hexadiene, 1,6-heptadiene, 1,7-octadiene, dicyclopentadiene, and 5-ethylidene-2-norbornene.

[0035] The amount of the other monomers used is preferably 10 mass% or less, more preferably 5 mass% or less, and even more preferably from 4 to 0 mass% of the total monomers used in the aromatic vinyl-conjugated diene rubber A, from the viewpoint of achieving the superior effect of the present invention. Aromatic vinyl content

[0036] The aromatic vinyl content of the aromatic vinyl-conjugated diene rubber A (content of repeating units derived from aromatic vinyl in the aromatic vinyl-conjugated diene rubber A) is from 35 to 45 mass%.

[0037] It should be noted that in the present specification, the aromatic vinyl content of the aromatic vinyl-conjugated diene rubber refers to the content (mass %) of repeating units derived from the aromatic vinyl in the aromatic vinyl-conjugated diene rubber. Vinyl unit content

[0038] The vinyl unit content of the aromatic vinyl-conjugated diene rubber A is from 25 to 45 mol%. Among them, in view of achieving the superior effect of the present invention, the vinyl unit content is preferably from 35 to 42 mol%.

[0039] It should be noted that in the present specification, the vinyl unit content of the aromatic vinyl-conjugated diene rubber refers to the proportion (% mol) occupied by a repeating unit having a vinyl structure (for example, 1,2-vinyl structure in a case where the conjugated diene is 1,3-butadiene) among all the repeating units consisting of the conjugated diene in the aromatic vinyl-conjugated diene rubber. Term modification

[0040] As described above, the termini of the aromatic vinyl-conjugated diene rubber A is modified.

[0041] In view of achieving the superior effect of the present invention, the aromatic vinyl-conjugated diene rubber A preferably has at least one functional group selected from the group consisting of an amino group, a hydroxy group, an epoxy group, an alkylsilyl group, an alkoxysilyl group, and a carboxyl group at the terminal, and more preferably a hydroxy group at the terminal. Salary

[0042] The content of the aromatic vinyl-conjugated diene rubber A in the diene rubber is from 30 to 90 mass%.

[0043] In a case where the composition according to an embodiment of the present invention is the above-described first preferred aspect, the content of the aromatic vinyl-conjugated diene rubber A in the diene rubber is preferably 60 mass% or more, and more preferably 70 mass% or more from the viewpoint of achieving the superior effect of the present invention.

[0044] Moreover, in a case where the composition according to an embodiment of the present invention is the second preferred aspect described above, the content of the aromatic vinyl-conjugated diene rubber A in the diene rubber is preferably from 30 to 40 mass% in view of achieving the superior effect of the present invention. Rubber component B

[0045] A rubber component B is at least one rubber component selected from the group consisting of an aromatic vinyl-conjugated diene rubber b1 other than the aromatic vinyl-conjugated diene rubber A and a butadiene rubber b2 having a weight-average molecular weight of more than 15,000. From the viewpoint of achieving the superior effect of the present invention, the rubber component B among these is preferably the diene rubber b2. Aromatic vinyl-conjugated diene rubber b1

[0046] The aromatic vinyl-conjugated diene rubber b1 is a different aromatic vinyl-conjugated diene rubber from the above-described aromatic vinyl-conjugated diene rubber A. Among them, in view of achieving the superior effect of the present invention, the styrene-butadiene rubber (SDB) other than the above-described aromatic vinyl-conjugated diene rubber A is preferable.

[0047] Examples of the aromatic vinyl-conjugated diene rubber b1 include, among the aromatic vinyl-conjugated diene rubbers, an aromatic vinyl-conjugated diene rubber having an aromatic vinyl content of less than 35 mass%, an aromatic vinyl-conjugated diene rubber having an aromatic vinyl content of more than 45 mass%, an aromatic vinyl-conjugated diene rubber having a vinyl unit content of less than 25 mol%, an aromatic vinyl-conjugated diene rubber having a vinyl unit content of more than 45 mol%, and an aromatic vinyl-conjugated diene rubber whose term is not changed.Among them, in view of achieving the superior effect of the present invention, an aromatic vinyl-conjugated diene rubber (particularly, styrene-butadiene rubber (SDB)) having an aromatic vinyl content of less than 35 mass% and a vinyl unit content of more than 45 mol% by which the terminal is modified (particularly having a hydroxy group at the terminal) is preferred.

[0048] It should be noted that the definition of the aromatic vinyl-conjugated diene rubber and specific examples of each monomer are the same as those of the aromatic vinyl-conjugated diene rubber A described above.

[0049] The content of the aromatic vinyl-conjugated diene rubber b1 in the diene rubber is preferably from 20 to 40 mass%, and more preferably from 25 to 35 mass% from the viewpoint of achieving the superior effect of the present invention. Butadiene rubber b2

[0050] The butadiene rubber b2 is a butadiene rubber (BR) with a weight average molecular weight (Mw) of 15000 or more.

[0051] The weight average molecular weight (Mw) and number average molecular weight (Mn) are measured by gel permeation chromatography (GPC) with reference to a polystyrene standard. ▪ Solvent: Tetrahydrofuran ▪ Detector: RI detector

[0052] In view of achieving the superior effect of the present invention, the vinyl unit content of butadiene rubber b2 is preferably 0.1 to 15 mol%.

[0053] It should be noted that the vinyl unit content of the butadiene rubber refers to the proportion (mol%) of a repeating unit having a vinyl structure (e.g., 1,2-vinyl structure in a case where the conjugated diene is 1,3-butadiene) among all the repeating units derived from butadiene in the butadiene rubber.

[0054] The content of the butadiene rubber b2 in the diene rubber is preferably from 20 to 40 mass%, and more preferably from 25 to 35 mass% in view of achieving the superior effect of the present invention. Salary

[0055] the content of the rubber component B in the diene rubber is 10 to 70 mass%.

[0056] In a case where the composition according to an embodiment of the present invention is the first preferred aspect as described above, the content of the rubber component B in the diene rubber is preferably 40 mass% or less, and more preferably 30 mass% or less from the viewpoint of achieving the superior effect of the present invention.

[0057] Moreover, in a case where the composition according to an embodiment of the present invention has the second preferred aspect as described above, the content of the rubber component B in the diene rubber is preferably from 60 to 70 mass% in view of achieving the superior effect of the present invention. Other diene rubbers

[0058] The diene rubber contained in the composition according to one embodiment of the present invention may further contain a diene rubber (other diene rubbers) other than the aromatic vinyl-conjugated diene rubber A or the rubber component B described above. Examples of such a diene rubber include natural rubber (NR), isoprene rubber (IR), acrylonitrile-butadiene copolymer rubber (NBR), butyl rubber (IIR), butyl halide rubber (Br-IIR, CI-IIR), and chloroprene rubber (CR).

[0059] The content of other diene rubbers in the diene rubbers is not particularly limited and is preferably from 0 to 30 mass% from the viewpoint of achieving the superior effect of the present invention. Average glass transition temperature

[0060] An average glass transition temperature (average Tg) of the diene rubber contained in the composition according to one embodiment of the present invention is from -20 °C to -100 °C.

[0061] In a case where the composition according to an embodiment of the present invention is the above-described first preferred aspect, the average Tg of the above-described diene rubber is preferably from -40 to -30 °C in view of achieving the superior effect of the present invention.

[0062] Furthermore, in a case where the composition according to an embodiment of the present invention is the second preferred aspect as described above, the average TG of the above-described diene rubber is preferably less than -50°C in view of achieving the superior effect of the present invention. The lower limit is -100°C or more, and preferably -60 °C or higher.

[0063] Note that the glass transition temperature (Tg) is measured using a differential scanning calorimeter (DSC) at a temperature rise rate of 10 °C / min and calculated by the midpoint method. When the diene rubber is an oil-extended product, the glass transition temperature is the glass transition temperature of the diene rubber that does not contain an oil extender (oil). Furthermore, the average glass transition temperature (Tg) can be determined by multiplying the mass fractions of diene rubbers by the corresponding glass transition temperatures of the diene rubbers and then summing the obtained values ​​(weighted average of the glass transition temperatures), and the sum of the mass fractions of all diene rubbers is set to 1. Molecular weight

[0064] In view of achieving the superior effect of the present invention, the diene rubber as described above preferably has a weight average molecular weight (Mn) of 100,000 to 1,000,000, and more preferably 300,000 to 3,000,000.

[0065] Furthermore, the number average molecular weight (Mw) of the diene rubber contained in the composition according to one embodiment of the present invention is preferably from 50,000 to 5,000,000, and more preferably from 150,000 to 1,500,000 in view of achieving the superior effect of the present invention.

[0066] It should be noted that the Mw and / or Mn of at least one diene rubber contained in the diene rubbers is preferably within the above-described range, and the Mw and / or Mn of all diene rubbers contained in the diene rubbers is particularly preferably within the above-described ranges. Silica

[0067] The silica contained in the composition according to one embodiment of the present invention is not particularly limited, and any conventionally known silica contained in a rubber composition in application fields such as tires can be used.

[0068] Examples of silica include wet silica, dry silica, fumed silica, and diatomaceous earth. One type of silica can be used alone, or two or more types of silica can be used in combination. CTAB Adsorption specific surface area

[0069] A cetyltrimethylammonium bromide (CTAB) adsorption specific surface area of ​​the silica is not particularly limited, and is preferably from 100 to 400 m 2 / g and more preferably from 150 to 300 m 2 / g, and even more preferably from 160 to 250 m 2 / g in view of achieving the superior effect of the present invention.

[0070] Here, the CTAB adsorption specific surface area is a value obtained by measuring the CTAB adsorption amount on the silica surface according to JIS K6217-3:2001 “Part 3: Method for determining specific surface area - CTAB adsorption method”. Salary

[0071] In the composition according to one embodiment of the present invention, the content of the above-described silica is from 80 to 200 parts by mass per 100 parts by mass of the above-described diene rubber. Among these, it is preferably from 85 to 150 parts by mass in view of achieving the superior effect of the present invention. Specifically modified butadiene polymer

[0072] As described above, the composition according to one embodiment of the present invention contains a terminal-modified butadiene polymer having a weight-average molecular weight of 1,000 to 10,000 and a molecular weight distribution of 2.0 or less (hereinafter also referred to as “specifically modified butadiene polymer”). Weight-average molecular weight

[0073] As described above, the weight-average molecular weight (Mw) of the specifically modified butadiene polymer is from 1,000 to 10,000. Among them, it is preferably 5,000 or more and less than 10,000 from the viewpoint of achieving the superior effect of the present invention. Number average molecular weight

[0074] The number average molecular weight (Mw) of the specifically modified butadiene polymer is not particularly limited as long as the weight average molecular weight and the molecular weight distribution of the specifically modified butadiene polymer are within a certain range, but the number average molecular weight (Mn) of the specifically modified butadiene polymer is preferably from 1000 to 15000, and more preferably 5000 or more and less than 10000, from the viewpoint of achieving the superior effect of the present invention. Molecular weight distribution

[0075] As described above, the molecular weight distribution (Mw / Mn) of the specifically modified butadiene polymer is 2.0 or less. Among them, it is preferably 1.7 or less, more preferably 1.5 or less, and even more preferably 1.3 or less, from the viewpoint of achieving the superior effect of the present invention.

[0076] The lower limit is not particularly restricted and is usually 1.0 or more.

[0077] It should be noted that, as described above, the methods for measuring Mw and Mn are determined by gel permeation chromatography (GPS) in the form of a polystyrene standard. ▪ Solvent: Tetrahydrofuran ▪ Detector: RI detector Term modification

[0078] As described above, the specifically modified butadiene polymer is terminally modified.

[0079] In view of achieving the superior effect of the present invention, the specifically modified butadiene polymer has at least one functional group selected from the group consisting of an amino group, a hydroxy group, an epoxy group, an alkylsilyl group, an alkoxysilyl group, a carboxyl group, and a specific functional group described below at a terminal, more preferably has an alkoxysilyl group (particularly a triethoxysilyl group) or a specific functional group described below at a terminal, and even more preferably has a specific functional group described below at a terminal. Specific functional group

[0080] As described above, the specifically modified butadiene polymer has a functional group (specific functional group) containing a nitrogen atom and a silicon atom at one terminal. Note that the specific functional group may be provided at at least one terminal.

[0081] The specific functional group is not particularly limited as long as it is a functional group containing a nitrogen atom and a silicon atom, but in view of achieving the superior effect of the present invention, the specific functional group preferably contains the nitrogen atom as an amino group (-NR2: R is a hydrogen atom or a hydrocarbon group) and preferably contains the nitrogen atom as a hydrocarbyloxysilyl group (=SiOR: R is a hydrocarbon group).

[0082] From the aspect of achieving the superior effect of the present invention, the specific functional group is preferably a group represented by the following formula (M).

[0083] In the above formula (M), R1 and R2 each independently represent a hydrogen atom or a substituent.

[0084] In the above formula (M), L represents a divalent organic group.

[0085] The substituent is not particularly limited as long as the substituent is a monovalent substituent, and examples thereof include hydrocarbon groups which may have a halogen atom, a hydroxyl group, a nitro group, a carboxy group, an alkoxy group, an amino group, a mercapto group, an acyl group, an imide group, a phosphino group, a silyl group, or a heteroatom.

[0086] Examples of the halogen atom include a fluorine atom, a chlorine atom, a bromine atom and an iodine atom.

[0087] Examples of the heteroatom of the hydrocarbon group which may have a heteroatom include an oxygen atom, nitrogen atom, sulfur atom and phosphorus atom.

[0088] Examples of the hydrocarbon group which may have a heteroatom include aliphatic hydrocarbon groups, aromatic hydrocarbon groups and groups having a combination of these.

[0089] The aliphatic hydrocarbon group may be in the form of a straight chain, a branched chain, or a ring. Specific examples of the aliphatic hydrocarbon group include straight-chain or branched alkyl groups (especially those having 1 to 30 carbon atoms), straight-chain or branched alkenyl groups (especially those having 2 to 30 carbon atoms), and straight-chain or branched alkynyl groups (especially those having 2 to 30 carbon atoms).

[0090] Examples of the aromatic hydrocarbon group include aromatic hydrocarbon groups having 6 to 18 carbon atoms, such as a phenyl group, a tolyl group, a xylyl group, and a naphthyl group.

[0091] In the above formula (M), from the viewpoint of achieving the superior effect of the present invention, R1 is preferably a hydrogen atom, an alkyl group (preferably having 1 to 10 carbon atoms), an alkylsilyl group (preferably having 1 to 10 carbon atoms) and an aromatic hydrocarbon group (preferably having 6 to 18 carbon atoms), and more preferably a hydrogen atom.

[0092] It should be noted that the number of R1 units can be the same or different.

[0093] The R2 is preferably a hydrocarbyloxy group (-OR group: R is a hydrocarbon group), and more preferably an alkoxy group (preferably having 1 to 10 carbon atoms), in view of achieving the superior effect of the present invention.

[0094] As described above, L in the above formula (M) represents a single bond or a divalent organic group.

[0095] Examples of the divalent organic group include an aliphatic hydrocarbon group (such as an alkylene group, preferably having 1 to 10 carbon atoms), an aromatic hydrocarbon group (such as an arylene group, preferably having 6 to 18 carbon atoms), -O-, -S-, -SO2-, -N(R)- (R: alkyl group), -CO-, -NH-, -COO-, -CONH- and groups having a combination of these (such as an alkyleneoxy group (-C m H 2m O-: m is a positive integer), an alkyleneoxycarbonyl group, and an alkylenecarbonyloxy group. In view of achieving the superior effect of the present invention, L is preferably an alkylene group (preferably having 1 to 10 carbon atoms).

[0096] In the above formula (M), n represents an integer of 0 to 2. In view of achieving the superior effect of the present invention, n is preferably 2.

[0097] In the above formula (M), m represents an integer of 1 to 3. In view of achieving the superior effect of the present invention, m is preferably 1.

[0098] In the above formula (M), n and m satisfy a relationship of n + m = 3.

[0099] In the above formula (M), * represents a bond position. MicrostructureVinyl structure

[0100] In the specific modified butadiene polymer, the proportion of a vinyl structure (vinyl unit content) is not particularly limited and is preferably from 10 to 50 mol%, and more preferably from 20 to 40 mol%, from the viewpoint of achieving the superior effect of the present invention.

[0101] Here, the proportion of vinyl structure refers to the proportion (mol%) of the repeating unit having a vinyl structure among the repeating units derived from butadiene. 1,4-transstructure

[0102] In the specifically modified butadiene polymer, the proportion of a 1,4-trans structure is not particularly limited and is preferably from 10 to 70 mol%, and more preferably from 30 to 50 mol%, in view of achieving the superior effect of the present invention.

[0103] Here, the proportion of 1,4-trans structure refers to the proportion (mol%) of the repeating unit having a 1,4-trans structure among the repeating units derived from butadiene. 1,4-cis structure

[0104] In the specifically modified butadiene polymer, the proportion of a 1,4-cis structure is not particularly limited and is preferably from 10 to 50 mol%, and more preferably from 20 to 40 mol%, in view of achieving the superior effect of the present invention.

[0105] Here, the proportion of the 1,4-cis structure refers to the proportion (mol%) of the repeating unit having a 1,4-cis structure among the repeating units derived from butadiene.

[0106] It should be noted that hereinafter, “the proportion (mol%) of the vinyl structure, the proportion (mol%) of the 1,4-trans structure and the proportion (mol%) of the 1,4-cis structure” is also represented as “vinyl / trans / cis”. Glass transition temperature

[0107] A glass transition temperature (Tg) of the specifically modified butadiene polymer is not particularly limited, and from the viewpoint of achieving the superior effect of the present invention, it is preferably -100 to -60 °C, more preferably -90 to -70 °C, and even more preferably -85 to -75 °C.

[0108] It should be noted that the glass transition temperature (Tg) is measured using a differential scanning calorimeter (DSC) at a temperature rise rate of 10 °C / min and calculated by the midpoint method. viscosity

[0109] A viscosity of the specifically modified butadiene polymer is not particularly limited, but is preferably 1000 to 10000 pa·s, and more preferably 3000 to 6000 pa·s, in view of achieving the superior effect of the present invention.

[0110] Furthermore, the viscosity of the butadiene polymer before the modification of the specific modified butadiene polymer is not particularly limited and is preferably 500 to 5000 pa·s, and more preferably 1500 to 3000 pa·s from the viewpoint of achieving the superior effect of the present invention.

[0111] Furthermore, in order to achieve the superior effect of the present invention, the viscosity of the specifically modified butadiene polymer is preferably 150% to 240% of the viscosity of the butadiene polymer before modification. Hereinafter, the viscosity of the specifically modified butadiene polymer after modification relative to the viscosity of the specifically modified butadiene polymer before modification is also referred to as "viscosity (after modification / before modification)."

[0112] It should be noted that viscosity is measured using a cone-and-plate viscometer according to JIS K5600-2-3. Process for the preparation of specifically modified butadiene polymer

[0113] A method for producing the specifically modified butadiene polymer is not particularly limited, and known methods can be used. A method for a specific molecular weight and molecular weight distribution range is not particularly limited, and examples thereof include a method for adjusting the quantitative ratio of an initiator, a monomer, and a stopping agent, a reaction temperature, and a rate at which the initiator is added.

[0114] The method for producing the specifically modified butadiene polymer, from the viewpoint of achieving the superior effect of the present invention for a composition to be obtained, is preferably a method of polymerizing butadiene using an organolithium compound and then stopping the polymerization using an electrophile having a nitrogen atom and a silicon atom (hereinafter, also referred to as "a method according to an embodiment of the present invention"). Hereinafter, "achieving the superior effect of the present invention for a composition to be obtained" is also simply referred to as "achieving the superior effect of the present invention." Organolithium compound

[0115] The organolithium compound is not particularly limited, and specific examples thereof include monoorganolithium compounds such as n-butyllithium, sec-butyllithium, tert-butyllithium, n-propyllithium, isopropyllithium, and benzyllithium; and polyfunctional organolithium compounds such as 1,4-dilithiobutane, 1,5-dilithiopentane, 1,6-dilithiohexane, 1,10-dilithiodecane, 1,1-dilithiodiphenylene, dilithiopolybutadiene, dilithiopolyisoprene, 1,4-dilithiobenzene, 1,2-dilithio-1,2-diphenylethane, 1,4-dilithio-2-ethylcyclohexane, 1,3,5-trilithiobenzene, and 1,3,5-trilithio-2,4,6-triethylbenzene. Among them, a monoorganolithium compound such as n-butyllithium, sec-butyllithium and tert-butyllithium is preferred from the viewpoint of achieving the superior effect of the present invention.

[0116] The amount of the organolithium compound used is not particularly limited, and is preferably 0.001 to 10 mol% from the viewpoint of achieving the superior effect of the present invention with respect to butadiene. Copolymerization of butadiene

[0117] The method for polymerizing butadiene using an organolithium compound is not particularly limited, and examples thereof include a method in which the above-described organolithium compound is added to an organic solvent solution containing butadiene and stirred in a temperature range of 0 to 120°C (preferably 30 to 100°C). Specific electrophile

[0118] In the process according to one embodiment of the present invention, the polymerization of butadiene is stopped using an electrophile containing a nitrogen atom and a silicon atom (hereinafter also referred to as a "specific electrophile"). The polymerization is stopped using a specific electrophile to obtain a modified butadiene polymer having the above-described specific functional groups at one terminal.

[0119] The specific electrophile is not particularly limited as long as it is a compound containing a nitrogen atom and a silicon atom, and in view of achieving the superior effect of the present invention, the specific electrophile preferably contains the nitrogen atom as an amino group (-NR2: R is a hydrogen atom or a hydrocarbon group) and preferably contains the nitrogen atom as a hydrocarbyloxysilyl group (=SiOR: R is a hydrocarbon group).

[0120] In order to achieve the superior effect of the present invention, the specific functional group is preferably silazane, and more preferably cyclic silazane. Here, "silazane" refers to a compound (a compound having a Si-N bond) with a structure in which a silicon atom and a nitrogen atom are directly bonded to each other.

[0121] In view of achieving the superior effect of the present invention, the cyclic silazane is preferably a compound represented by the following formula (S).

[0122] In the above formula (S), R1 to R3 each independently represents a hydrogen atom or a substituent. Specific examples and preferred forms of the substituent are identical to those of R1 and R2 in the above formula (M).

[0123] In the above formula (S), L represents a divalent organic group. Specific examples and preferred aspects of the divalent organic group are the same as those of L in formula (M) described above.

[0124] In the above formula (S), from the viewpoint of achieving the superior effect of the present invention, R1 is preferably an alkyl group (preferably having 1 to 10 carbon atoms), an alkylsilyl group (preferably having 1 to 10 carbon atoms) and an aromatic hydrocarbon group (preferably having 6 to 18 carbon atoms), more preferably an alkylsilyl.

[0125] In the above formula (S), from the viewpoint of achieving the superior effect of the present invention, R2 and R3 are preferably each independently a hydrocarbyloxy group (-OR group: R is a hydrocarbon group), and more preferably an alkoxy group (preferably having 1 to 10 carbon atoms), from the viewpoint of achieving the superior effect of the present invention.

[0126] In the above formula (S), in view of achieving the superior effect of the present invention, L is preferably an alkylene group (preferably having 1 to 10 carbon atoms, more preferably having 2 to 8 carbon atoms, and even more preferably having 3 to 5 carbon atoms).

[0127] Examples of the compound represented by the above formula (S) include Nn-butyl-1,1-dimethoxy-2-azasilacyclopentane, N-phenyl-1,1-dimethoxy-2-azasilacyclopentane, N-trimethylsilyl-1,1-dimethoxy-2-azasilacyclopentane and N-trimethylsilyl-1,1-diethoxy-2-azasilacyclopentane.

[0128] It should be noted that the silicon atoms of the cyclic silazane are considered to exhibit electrophilicity.

[0129] The amount of the specific electrophile with respect to the organolithium compound is not particularly limited, and in view of achieving the superior effect of the present invention, it is preferably from 0.1 to 10, and more preferably from 1 to 5 in a molar ratio. Salary

[0130] In the composition according to one embodiment of the present invention, the content of the specifically modified butadiene polymer is from 1.0 to 25.0 mass% relative to the content of the silica described above. Hereinafter, the content of the specifically modified butadiene polymer relative to the silica content is also referred to as "specifically modified butadiene polymer / silica."

[0131] The specifically modified butadiene polymer / silica is preferably from 2.0 to 20.0 mass%, more preferably from 3.0 to 10.0 mass%, and even more preferably from 4.0 to 7.0 mass% in view of achieving the superior effect of the present invention.

[0132] Moreover, the content of the specifically modified butadiene polymer is preferably from 1 to 20 parts by mass, and more preferably from 2 to 10 parts by mass per 100 parts by mass of the diene rubber in view of achieving the superior effect of the present invention. Optional component

[0133] The composition according to one embodiment of the present invention may further contain another ingredient (optional ingredient).

[0134] Examples of such an ingredient include various additives typically used in rubber compounds, such as fillers (such as carbon black) other than silica, silane coupling agents, terpene resins (preferably, aromatically modified terpene resins), heat-expandable microcapsules, zinc oxide (zinc white), stearic acid, antioxidants, wax, processing aids, process oils, liquid polymers, thermosetting resins, vulcanizing agents (such as sulfur), and vulcanization accelerators. Silane coupling agent

[0135] The composition according to one embodiment of the present invention preferably contains a silane coupling agent in order to achieve the superior effect of the present invention. The silane coupling agent is not particularly limited as long as it is a silane compound having a hydrolyzable group and an organic functional group.

[0136] The hydrolyzable group is not particularly limited; however, examples thereof include an alkoxy group, a phenoxy group, a carboxyl group, and an alkenyloxy group. Among them, in view of achieving the superior effect of the present invention, the hydrolyzable group is preferably an alkoxy group. When the hydrolyzable group is an alkoxy group, the number of carbon atoms of the alkoxy group is preferably from 1 to 16, and more preferably from 1 to 4, in view of achieving the superior effect of the present invention. Examples of the alkoxy group having 1 to 4 carbon atoms are a methoxy group, ethoxy group, and propoxy group.

[0137] The organic functional group is not particularly limited and is preferably a group capable of forming a chemical bond with an organic compound. Examples thereof include an epoxy group, a vinyl group, an acryloyl group, a methacryloyl group, an amino group, a sulfide group, a mercapto group, and a block mercapto group (a protected mercapto group) (for example, an octanoylthio group). Among these, a sulfide group (particularly a disulfide group and a tetrasulfide group), a mercapto group, and a block mercapto group are preferred from the viewpoint of achieving the superior effect of the present invention.

[0138] The silane coupling agent can be used alone, or two or more types of them can be used in combination.

[0139] The silane coupling agent is preferably a sulfur-containing silane coupling agent in view of achieving the superior effect of the present invention.

[0140] Specific examples of the silane coupling agent include bis(3-triethoxysilylpropyl)tetrasulfide, bis(3-trimethoxysilylpropyl)tetrasulfide, bis(3-triethoxysilylpropyl)disulfide, mercaptopropyltrimethoxysilane, mercaptopropyltriethoxysilane, 3-trimethoxysilylpropyl-N,N-dimethylthiocarbamoyl tetrasulfide, triethoxysilylpropylmercaptobenzothiazole tetrasulfide, triethoxysilylpropyl methacrylate monosulfide, dimethoxymethylsilylpropyl-N,N-dimethylthiocarbamoyl tetrasulfide, and 3-octanoylthio-1-propyltriethoxysilane. One of these can be used alone, or two or more types of them can be used in combination.

[0141] In view of achieving the superior effect of the present invention, the silane coupling agent is preferably a compound represented by the following formula (S). (C n H 2n + 1 O)3-Si-C m H 2m -S-CO-C k H 2k + 1 Formula (S)

[0142] In formula (S), n represents an integer from 1 to 3, m represents an integer from 1 to 5 (preferably an integer from 2 to 4), and k represents an integer from 1 to 15 (preferably an integer from 5 to 10).

[0143] In the composition according to an embodiment of the present invention, a content of the silane coupling agent is not particularly limited, but is preferably from 1 to 20 mass%, more preferably from 5 to 15 mass% relative to the above-described silica content in view of achieving the superior effect of the present invention.

[0144] Furthermore, in the present invention, the amount of the silane coupling agent is preferably from 1 to 20 parts by mass, and more preferably from 2 to 10 parts by mass, per 100 parts by mass of the diene rubber, from the viewpoint of achieving the superior effect of the present invention. soot

[0145] The composition according to one embodiment of the present invention preferably contains carbon black in order to achieve the superior effect of the present invention. One type of carbon black may be used alone, or two or more types of carbon black may be used in combination.

[0146] There are no special restrictions on carbon black, and different grades of carbon black can be used, such as SAF-HS, SAF, ISAF-HS, ISAF, ISAF-LS, IISAF-HS, HAF-HS, HAF, HAF-LS, FEF, GPF, and SRF.

[0147] The nitrogen adsorption specific surface area (N2SA) of the carbon black is not particularly limited and is preferably from 50 to 200 m in view of achieving the superior effect of the present invention. 2 / g and more preferably from 70 to 150 m 2 / G.

[0148] It should be noted that the specific nitrogen adsorption surface area (N2SA) is a value of the amount of nitrogen adsorbed into the soot surface, measured according to JIS K6217-2:2001 "Part 2: Determination of specific surface area - Nitrogen adsorption methods - Single-point procedures".

[0149] In the composition according to an embodiment of the present invention, a carbon black content is not particularly limited, but is preferably from 1 to 100 parts by mass, more preferably from 2 to 10 parts by mass, with respect to 100 parts by mass of the above-described diene rubber, in view of achieving the superior effect of the present invention. Process for preparing a rubber composition for a tire

[0150] The method for producing the composition according to an embodiment of the present invention is not particularly limited, and specific examples thereof include a method wherein each of the above-mentioned components is kneaded using a publicly known method and apparatus (e.g., Banbury mixer, kneader, and roller). When the rubber composition for a tire according to an embodiment of the present invention contains sulfur or a vulcanization accelerator, the components other than the sulfur and the vulcanization accelerator are preferably first mixed at a high temperature (preferably from 100 to 160°C) and then cooled before blending the sulfur or the vulcanization accelerator.

[0151] Furthermore, the composition according to one embodiment of the present invention can be vulcanized or crosslinked under known vulcanization or crosslinking conditions.

[0152] The rubber composition according to one embodiment of the present invention is useful for a tire (particularly a tire tread).

[0153] Furthermore, as described above, in a case where the composition of an embodiment of the present invention is the first preferred aspect, it is particularly suitable as a summer tire. Furthermore, as described above, in a case where the composition of an embodiment of the present invention is the second preferred aspect, it is particularly suitable as a winter tire. pneumatic tires

[0154] The pneumatic tire according to one embodiment of the present invention is a pneumatic tire using the composition according to one embodiment of the present invention. In particular, a pneumatic tire using the composition according to one embodiment of the present invention in a tread (breaker tread) is preferred.

[0155] Fig. 1 is a partial schematic cross-sectional view of a pneumatic tire, which is a pneumatic tire according to an embodiment of the present invention, however, the present invention is not limited to the pneumatic tire shown in Fig. 1 illustrated embodiment.

[0156] In Fig. 1, reference numeral 1 denotes a bead portion, reference numeral 2 denotes a sidewall portion, and reference numeral 3 denotes a tire tread portion.

[0157] Further, a carcass layer 4 in which a glass fiber thread is embedded is embedded between a left / right pair of bead portions 1, and ends of the carcass layer 4 are wrapped around bead cores 5 and a bead filler 6 by folding them from an inside to an outside of the tire.

[0158] In the tire tread portion 3, a belt layer 7 is provided along the entire circumference of the tire on the outside of the carcass layer 4.

[0159] In addition, wheel rim pads 8 are provided in the sections of the bead sections 1 that rest against a rim.

[0160] It should be noted that the tire tread portion 3 is formed from the composition according to an embodiment of the present invention.

[0161] The pneumatic tire according to an embodiment of the present invention can be manufactured, for example, according to a known method. Furthermore, an inert gas such as nitrogen, argon, or helium, or the like, can be used as the gas with which the pneumatic tire is filled, in addition to ordinary air or air whose oxygen partial pressure is adjusted. [Example]

[0162] The present invention will be described in more detail below using examples. However, the present invention is not limited to these examples.

[0163] Preparation of specifically modified butadiene polymer 1 n-BuLi (n-butyllithium) (available from Kant Chemical Co., Inc.: 1.60 mol / L (hexane solution), 27 mL, 43.2 mmol) was added to a mixed solution of 1,3-butadiene (205 g, 3786 mmol) and 2,2-di(2-tetrahydrofuryl)propane (available from Tokyo Chemical Industry Co., Ltd., 0.1 mL, 0.55 mmol) in cyclohexane (2.96 kg), and the mixture was stirred at room temperature for 6 hours. After the reaction, N-trimethylsilyl-1,1-dimethoxy-2-azasilacyclopentane (structure below) (15 g, 137 mmol) was added to quench the polymerization.

[0164] The resulting solution was taken out and concentrated under reduced pressure. The concentrated solution was poured into methanol (10 L) to separate a methanol-insoluble component. As a result, a modified butadiene polymer (specifically modified butadiene polymer 1) (199 g, Mn = 7600, Mw = 8100, Mw / Mn = 1.1) having a functional group represented by the following formula (m1) (here, * represents a bonding position) at one terminal was obtained in a yield of 97%. Note that cis / trans / vinyl was estimated to be 24 / 40 / 36 by IR analysis. In addition, the Tg value was -80 °C. The viscosity (after modification / before modification) was 204%. Preparation of a rubber composition for a tire (Tables 1 to 3)

[0165] The ingredients shown in Tables 1-3 below were mixed in the proportions (by mass) shown in the same tables. Specifically, mixing was performed using a Banbury mixer at 150°C for 2 minutes. A roller was then used to blend the sulfur and vulcanization accelerator to obtain a rubber composition for a tire.

[0166] It should be noted that, in Tables 1 to 3, for the amount of aromatic vinyl-conjugated diene rubber A, a value of the upper row indicates the amount (unit: parts by mass) of aromatic vinyl-conjugated diene rubber A (oil-extended product), and a value of a lower row indicates the net amount (unit: parts by mass) of SBR in the aromatic vinyl-conjugated diene rubber A. Evaluation

[0167] The obtained rubber composition for a tire was evaluated as follows. Processability

[0168] The Mooney viscosity of the obtained rubber composition for a tire was measured with a preheating time of 1 minute, a rotor rotation time of 4 minutes, and a test temperature of 100 °C using an L-shaped rotor according to JIS K6300-1:2013.

[0169] The results are shown in Tables 1 to 3. The results are expressed as index values, with Standard Example 1-1 being assigned an index value of 100 in Table 1, Standard Example 2-1 being assigned an index value of 100 in Table 2, and Standard Example 3-1 being assigned an index value of 100 in Table 3. A smaller index value indicates lower viscosity and higher processability. Basically, the evaluation result is preferably 99 or less. Silica dispersibility

[0170] The obtained rubber composition for a tire (unvulcanized) was vulcanized at 170 °C for 10 minutes using a shear stress measuring device (RPA2000, available from Alpha and Technology Co., Ltd.), then a shear strain modulus G' of 0.56% strain and a shear strain modulus G' of 100% strain were measured, and the difference of ΔG' = G' (0.56%) - G' (100%) was calculated as a Payne effect.

[0171] The results are shown in Tables 1 to 3. The results are expressed as index values, with Standard Example 1-1 being assigned an index value of 100 in Table 1, Standard Example 2-1 being assigned an index value of 100 in Table 2, and Standard Example 3-1 being assigned an index value of 100 in Table 3. The smaller the index, the better the silica dispersibility. Basically, the evaluation result is preferably 84 or less. WET steering stability

[0172] The resulting tire rubber composition was applied to a tread to produce a pneumatic tire. The resulting pneumatic tire was mounted on a test vehicle, and a sensory evaluation was conducted by a test driver for steering stability on wet road surfaces.

[0173] The results are shown in Tables 1 to 3. The results are expressed as index values, where the standard example 1-1 is assigned an index value of 100 in Table 1, the standard example 2-1 is assigned an index value of 100 in Table 2, and the standard example 3-1 is assigned an index value of 100 in Table 3. The larger the index, the better the wet performance (wet steering stability). Basically, the evaluation result is preferably 95 or higher. Fuel efficiency

[0174] Then, the obtained rubber composition was vulcanized in a predetermined mold at 160 °C for 20 minutes to prepare a vulcanized rubber sample. The tan δ (60 °C) value was measured for each of the prepared vulcanized rubber test pieces with an extension deformation strain of 10% ± 2%, an oscillation frequency of 20 Hz, and a temperature of 60 °C using a viscoelasticity spectrometer (available from Toyo Seiki Seisaku-sho, Ltd.) according to JIS K6394:2007.

[0175] The results are shown in Tables 1 to 3. The results are expressed as index values, where Standard Example 1-1 is assigned an index value of 100 in Table 1, Standard Example 2-1 is assigned an index value of 100 in Table 2, and Standard Example 3-1 is assigned an index value of 100 in Table 3. Smaller index values ​​indicate smaller tan δ (60°C) values, which in turn indicate excellent rolling resistance when used in a pneumatic tire. Basically, the evaluation result is preferably 98 or less, and more preferably 95 or less. Durability during high-speed running (high-speed durability)

[0176] A pneumatic tire was manufactured using the obtained tire rubber composition (Table 3 only) in a tire tread. Then, the durability during high-speed driving (the driving path at which failure occurred) of the obtained pneumatic tire was evaluated according to JIS D4230 High-Speed ​​Performance Test B.

[0177] The results are shown in Table 3. The evaluation results are expressed as index values, with the standard sample 3-1 assigned an index value of 100. The larger the index, the better the durability during high-speed running (high-speed durability). [Table 1-I] Table 1 Standard example 1-1 Example 1-1 Example 1-2 Examples 1-3 Comparison example 1-1 Aromatic vinyl-conjugated diene rubber (A) 110 (80) 110 (80) 110 (80) 68,75 (50) 110 (80) Butadiene rubber b2 20 20 20 50 20 Silica 1 90 90 90 90 90 Silane adhesion promoter 1 7,2 7,2 7,2 7,2 7,2 soot 5 5 5 5 5 Process oil 15 15 15 15 15 Anti-aging agents 1 1 1 1 1 zinc oxide 3 3 3 3 3 Stearic acid 1 1 1 1 1 Specifically modified butadiene polymer 1 4 4 Specifically modified butadiene polymer 2 4 Unmodified butadiene polymer 4 Vulcanization accelerator (DPG) 1,5 1,5 1,5 1,5 1,5 Vulcanization accelerator (CZ) 2 2 2 2 2 sulfur 2 2 2 2 2 Average Tg of diene rubber [°C] -39 -39 -39 -67 -39 Specifically modified butadiene polymer / silica (mass%) 0,0 % 4,4 % 4,4 % 4,4 % 0,0 % Processability 100 97 99 97 94 Silica dispersibility 100 75 82 80 86 Wet steering stability 100 101 102 95 97 Fuel efficiency 100 91 93 97 96 [Table 1-II] Table 1 Comparison example 1-2 Comparison example 1-3 Comparison example 1-4 Comparison example 1-5 Aromatic vinyl-conjugated diene rubber (A) 110 (80) 110 (80) 110 (80) 110 (80) Butadiene rubber b2 20 20 20 20 Silica 1 90 90 50 220 Silane adhesion promoter 1 7,2 7,2 7,2 7,2 soot 5 5 5 5 Process oil 15 15 15 15 Anti-aging agents 1 1 1 1 zinc oxide 3 3 3 3 Stearic acid 1 1 1 1 Specifically modified butadiene polymer 1 0,5 25 4 4 Specifically modified butadiene polymer 2 Unmodified butadiene polymer Vulcanization accelerator (DPG) 1,5 1,5 1,5 1,5 Vulcanization accelerator (CZ) 2 2 2 2 sulfur 2 2 2 2 Average Tg of diene rubber [°C] -39 -39 -39 -39 Specifically modified butadiene polymer / silica (mass%) 0,6 % 27,8 % 8,0 % 1,8 % Processability 100 88 90 104 Silica dispersibility 96 62 79 85 Wet steering stability 100 86 90 112 Fuel efficiency 99 99 95 110 [Table 2-I] Table 2 Standard example 2 -1 Example 2-1 Example 2-2 Example 2-3 Comparison example 2-1 Aromatic vinyl-conjugated diene rubber (A) 110 (80) 110 (80) 110 (80) 68,75 (50) 110 (80) Butadiene rubber b2 20 20 20 50 20 Silica 2 90 90 90 90 90 Silane coupling agent 2 9 9 9 9 9 soot 5 5 5 5 5 Process oil 15 15 15 15 15 Anti-aging agents 1 1 1 1 1 zinc oxide 3 3 3 3 3 Stearic acid 1 1 1 1 1 Specifically modified butadiene polymer 1 4 4 Specifically modified butadiene polymer 2 4 Unmodified butadiene polymer 4 Vulcanization accelerator (DPG) 1,5 1,5 1,5 1,5 1,5 Vulcanization accelerator (CZ) 2 2 2 2 2 sulfur 2 2 2 2 2 Average Tg of diene rubber [°C] -39 -39 -39 -67 -39 Specifically modified butadiene polymer / silica (mass%) 0,0 % 4,4 % 4,4 % 4,4 % 0,0 % Processability 100 95 96 97 94 Silica dispersibility 100 74 81 80 90 Wet steering stability 100 102 103 95 97 Fuel efficiency 100 90 91 98 98 [Table 2-II] Table 2 Comparison example 2-2 Comparison example 2-3 Comparison examples 2-4 Comparison example 2-5 Aromatic vinyl-conjugated diene rubber (A) 110 (80) 110 (80) 110 (80) 110 (80) Butadiene rubber b2 20 20 20 20 Silica 2 90 90 50 220 Silane coupling agent 2 9 9 9 9 soot 5 5 5 5 Process oil 15 15 15 15 Anti-aging agents 1 1 1 1 zinc oxide 3 3 3 3 Stearic acid 1 1 1 1 Specifically modified butadiene polymer 1 0,5 25 4 4 Specifically modified butadiene polymer 2 Unmodified butadiene polymer Vulcanization accelerator (DPG) 1,5 1,5 1,5 1,5 Vulcanization accelerator (CZ) 2 2 2 2 sulfur 2 2 2 2 Average Tg of diene rubber [°C] -39 -39 -39 -39 Specifically modified butadiene polymer / silica (mass%) 0,6 % 27,8 % 8,0 % 1,8 % Processability 100 90 89 105 Silica dispersibility 97 68 80 91 Wet steering stability 100 84 88 113 Fuel efficiency 99 99 95 110 [Table 3-I] Table 3 Standard example 3-1 Example 3-1 Example 3-2 Example 3-3 Comparison example 3-1 Aromatic vinyl-conjugated diene rubber (A) 96,25 (70) 96,25 (70) 96,25 (70) 68,75 (50) 96,25 (70) Butadiene rubber b2 10 10 10 30 10 Natural rubber 20 20 20 20 20 Silica 1 90 90 90 90 90 Silane adhesion promoter 1 7,2 7,2 7,2 7,2 7,2 soot 5 5 5 5 5 Process oil 15 15 15 15 15 Anti-aging agents 1 1 1 1 1 zinc oxide 3 3 3 3 3 Stearic acid 1 1 1 1 1 Specifically modified butadiene polymer 1 4 4 Specifically modified butadiene polymer 2 4 Unmodified butadiene polymer 4 Vulcanization accelerator (DPG) 1,5 1,5 1,5 1,5 1,5 Vulcanization accelerator (CZ) 2 2 2 2 2 sulfur 2 2 2 2 2 Average Tg of diene rubber [°C] -43 -43 -43 -59 -43 Specifically modified butadiene polymer / silica (mass%) 0,0 % 4,4 % 4,4 % 4,4 % 0,0 % Processability 100 97 99 97 94 Silica dispersibility 100 75 82 80 88 Wet steering stability 100 102 101 95 97 Fuel efficiency 100 89 91 98 98 Durability during high-speed running 100 102 101 98 96 [Table 3-II] Table 3 Comparison example 3-2 Comparison example 3-3 Comparison example 3-4 Comparison example 3-5 Aromatic vinyl-conjugated diene rubber (A) 96,25 (70) 96,25 (70) 96,25 (70) 96,25 (70) Butadiene rubber b2 10 10 10 10 Natural rubber 20 20 20 20 Silica 1 90 90 50 220 Silane adhesion promoter 1 7,2 7,2 7,2 7,2 soot 5 5 5 5 Process oil 15 15 15 15 Anti-aging agents 1 1 1 1 zinc oxide 3 3 3 3 Stearic acid 1 1 1 1 Specifically modified butadiene polymer 1 0,5 25 4 4 Specifically modified butadiene polymer 2 Unmodified butadiene polymer Vulcanization accelerator (DPG) 1,5 1,5 1,5 1,5 Vulcanization accelerator (CZ) 2 2 2 2 sulfur 2 2 2 2 Average Tg of diene rubber [°C] -43 -43 -43 -43 Specifically modified butadiene polymer / silica (mass%) 0,6 % 27,8 % 8,0 % 1,8 % Processability 100 88 90 104 Silica dispersibility 96 62 79 85 Wet steering stability 100 88 90 112 Fuel efficiency 99 99 95 110 Durability during high-speed running 100 97 95 110

[0178] The details of the components listed in Tables 1 to 3 are as follows.

[0179] It should be noted that the aromatic vinyl-conjugated diene rubber A is a terminal-modified aromatic vinyl-conjugated diene rubber having an aromatic vinyl content of 35 to 45 mass% and a vinyl unit content of 25 to 45 mol%, and thus the aromatic vinyl-conjugated diene rubber A corresponds to the “aromatic vinyl-conjugated diene rubber A” as described above.

[0180] The butadiene rubber b2 is a butadiene rubber with a molecular weight (weight average) of more than 15,000, and thus corresponds to the “butadiene rubber b2” described above.

[0181] In addition, the specific modified butadiene polymers 1 and 2 are a terminally modified butadiene polymer having a weight-average molecular weight of 1,000 to 15,000 and a molecular weight distribution of 2.0 or less, and thus correspond to the "specifically modified butadiene polymer" described above.

[0110] • Aromatic vinyl-conjugated diene rubber A: E580 (terminal-modified solution-polymerized SBR, aromatic vinyl content (repeating unit content derived from styrene): 35.5 mass%, vinyl unit content: 40 mol%, an oil-extended product having a hydroxy group at one terminal (oil-extended amount: 37.5 mass%, available from Asahi Kasei Corporation) • Butadiene rubber b2: Nipol® BR 1220 (BR, Mw: 490000, available from ZEON CORPORATION) • Natural rubber • Silica 1: ZEOSIL® 1165MR (available from Rhodia, CTAB adsorption specific surface area: 155 m 2 / G) • Silica 2: Ultrasil™ 9000 GR (available from Evonik, CTAB adsorption specific surface area: 197 m 2 / G) • Silane coupling agent 1: Si69 (bis[3-(triethoxysilyl)propyl] tetrasulfide • Silane coupling agent 2: NXT™ silane (available from Momentive Performance Materials, silane coupling agent represented by formula (S) above (here in formula (S) over n = 2, m = 3 and k = 7)) • Carbon black: Show Black N339 (available from Cabot Corporation., Nitrogen adsorption specific surface area (N2SA) = 90 m 2 / G)) • Process oil: Extract No. 4S (available from Showa Shell Sekiyu KK) • Anti-aging agent: Santoflex 6PPD (available from Solutia Europe) • Zinc oxide: Zinc oxide III (available from Seido Chemical Industry Co., Ltd.) • Stearic acid: Stearic acid YR (available from NOF Corporation) • specifically modified butadiene polymer 1: specifically modified butadiene polymer 1, prepared as described above • specifically modified butadiene polymer 2: Polyvest® EPST60 (Mw: 14,100, Mw / Mn: 1.90, modified butadiene polymer with a triethoxysilyl group at one terminus, available from Evonik) • Unmodified butadiene polymer: Polyvest110® (Mw: 8,200, Mw / Mn: 1.90, Terminus unmodified, available from Evonik) • Vulcanization accelerator (DPG): Perkacit® DPG (available from Flexsys Chemicals) • Vulcanization accelerator (CZ): NOCCELER CZ-G (available from Ouchi Shinko Chemical Industrial Co., Ltd.) • Sulfur: Oil treatment sulfur (available from Karuizawa Refinery Ltd.)

[0182] In Tables 1 to 3, “average Tg of diene rubber” refers to the “average glass transition temperature of the diene rubber” as described above.

[0183] Likewise, in Tables 1 to 3, “specifically modified butadiene polymer / silica” refers to the “specifically modified butadiene polymer / silica” as described above.

[0184] As can be seen from Tables 1 to 3, examples in which the specifically modified butadiene polymer was blended with silica in a specific proportion showed excellent processability, silica dispersibility, wet steering stability, and fuel efficiency.From the comparison of Example 1-1 with Example 1-2 (comparison between aspects in which only the type of the specially modified butadiene polymer differs), and the comparison of Example 2-1 with Example 2-2 (comparison between aspects in which only the type of the specially modified butadiene polymer differs), and the comparison and comparison of Example 3-1 with Example 3-2 (comparison between aspects in which only the type of the specially modified butadiene polymer differs), Example 1-1, Example 2-1, and Example 3-1, in which the specially modified butadiene polymer contains a functional group (specific functional group) having a nitrogen atom and a silicon atom at one terminal, showed better processability, silica dispersibility, WET steering stability, and fuel efficiency.Likewise, comparing Example 3-1 with Example 3-2, Example 3-1 in which the specifically modified butadiene polymer contains a functional group (specific functional group) containing a nitrogen atom and a silicon atom at a terminal showed excellent durability at high speed.

[0185] On the other hand, Standard Example 1-1 and Standard Example 2-1, Standard Example 3-1, Comparative Example 1-1, Comparative Example 2-1 and Comparative Example 3-1, Comparative Example 1-2 in which no specifically modified butadiene polymer is contained, Comparative Example 2-2 and Comparative Example 3-2 in which a specifically modified butadiene polymer is contained but the specifically modified butadiene polymer / silica is less than 1.0 mass%, and Comparative Example 1-3, Comparative Example 2-3 and Comparative Example 3-3 in which a specifically modified butadiene polymer is contained but the specifically modified butadiene polymer / silica is more than 25.0 mass%, showed insufficient either processability, silica dispersibility, WET steering stability, or fuel efficiency.

[0186] When Example 1-1 and Example 2-1 were compared, Example 2-1, in which the CTAB adsorption specific surface area of ​​the silica was 160 m 2 / g or more and the silane coupling agent was the compound represented by formula (S) above, better processability, silica dispersibility, WET steering stability and fuel efficiency.

[0187] Similarly, when Example 1-2 and Example 2-2 were compared, Example 2-2, in which the CTAB adsorption specific surface area of ​​the silica was 160 m 2 / g or more and the silane coupling agent was the compound represented by formula (S) above, better processability, silica dispersibility, WET steering stability and fuel efficiency. Preparation of a rubber composition for a tire (Tables 4 and 5)

[0188] The ingredients shown in Tables 4 and 5 below were mixed in the proportions (by mass) shown in Tables 4 and 5 below. Specifically, mixing was performed using a Banbury mixer at 150°C for 2 minutes. Thereafter, a roller was used to blend the sulfur and the vulcanization accelerator to obtain a rubber composition for a tire.

[0189] It should be noted that, in Tables 4 and 5, for the amount of aromatic vinyl-conjugated diene rubber A, a value of the upper row indicates the amount (unit: parts by mass) of aromatic vinyl-conjugated diene rubber A (oil-extended product) and a value of a lower row indicates the net amount (unit: parts by mass) of SBR in the aromatic vinyl-conjugated diene rubber A. Evaluation

[0190] The obtained rubber composition for a tire was evaluated as follows. Processability

[0191] The Mooney viscosity of the obtained rubber composition for a tire tread was measured with a preheating time of 1 minute, a rotor rotation time of 4 minutes, and a test temperature of 100 °C using an L-shaped rotor according to JIS K6300-1:2013.

[0192] The results are presented in Tables 4 and 5. The results are expressed as index values, with Standard Example 1-1 being assigned an index value of 100 in Table 4, and Standard Example 2-1 being assigned an index value of 100 in Table 5. A lower index value indicates lower viscosity and higher processability. Basically, the evaluation result is preferably 99 or less. Silica dispersibility

[0193] The obtained rubber composition for a tire (unvulcanized) was vulcanized at 170 °C for 10 minutes using a shear stress measuring device (RPA2000, available from Alpha and Technology Co., Ltd.), then a shear strain modulus G' of 0.56% strain and a shear strain modulus G' of 100% strain were measured, and the difference of ΔG' = G' (0.56%) - G' (100%) was calculated as a Payne effect.

[0194] The results are shown in Tables 4 and 5. The results are expressed as index values, with Standard Example 1-1 being assigned an index value of 100 in Table 4, and Standard Example 2-1 being assigned an index value of 100 in Table 5. The smaller the index, the better the silica dispersibility. Basically, the evaluation result is preferably 83 or less. WET steering stability

[0195] The resulting tire rubber composition was applied to a tread to produce a pneumatic tire. The resulting pneumatic tire was mounted on a test vehicle, and a sensory evaluation was conducted by a test driver for steering stability on wet road surfaces.

[0196] The results are presented in Tables 4 and 5. The results are expressed as index values, with the standard example 1-1 being assigned an index value of 100 in Table 4, and the standard example 2-1 being assigned an index value of 100 in Table 5. The larger the index, the better the wet performance (wet steering stability). Basically, the evaluation result is preferably 101 or higher. Fuel efficiency

[0197] Then, the obtained rubber composition was vulcanized in a predetermined mold at 160 °C for 20 minutes to prepare a vulcanized rubber sample. The tan δ (60 °C) value was measured for each of the prepared vulcanized rubber test pieces with an extension deformation strain of 10% ± 2%, an oscillation frequency of 20 Hz, and a temperature of 60 °C using a viscoelasticity spectrometer (available from Toyo Seiki Seisaku-sho, Ltd.) according to JIS K6394:2007.

[0198] The results are presented in Tables 4 and 5. The results are expressed as index values, with Standard Example 1-1 being assigned an index value of 100 in Table 4, and Standard Example 2-1 being assigned an index value of 100 in Table 5. Smaller index values ​​indicate smaller tan δ (60°C) values, which in turn indicate excellent rolling resistance when used in a pneumatic tire. Basically, the evaluation result is preferably 103 or less, and more preferably 95 or less. Braking performance on snow:

[0199] The resulting tire rubber composition was applied to a tread to produce a pneumatic tire. The resulting pneumatic tire was mounted on a test vehicle, and a distance of 40 km / h at a first speed to the stopping point was measured on a snow-covered road with a temperature of -11 °C and a snow temperature of -9 °C, and the reciprocal was determined.

[0200] The results are presented in Tables 4 and 5. The results are expressed as index values, with the standard example 1-1 being assigned an index value of 100 in Table 4, and the standard example 2-1 being assigned an index value of 100 in Table 5. The higher the index, the shorter the distance and the better the stability on snow. Basically, the evaluation result is preferably 102 or higher. [Table 4-I] Table 4 Standard example 1-1 Example 1-1 Example 1-2 Examples 1-3 Comparison example 1-1 Aromatic vinyl-conjugated diene rubber (A) 41,25 (30) 41,25 (30) 41,25 (30) 110 (80) 41,25 (30) Aromatic vinyl-conjugated diene rubber b1 35 35 35 35 Butadiene rubber b2 35 35 35 20 35 Silica 1 90 90 90 90 90 Silane adhesion promoter 1 7,2 7,2 7,2 7,2 7,2 soot 5 5 5 5 5 Process oil 15 15 15 15 15 Anti-aging agents 1 1 1 1 1 zinc oxide 3 3 3 3 3 Stearic acid 1 1 1 1 1 Specifically modified butadiene polymer 1 4 4 Specifically modified butadiene polymer 2 4 Unmodified butadiene polymer 4 Vulcanization accelerator (DPG) 1,5 1,5 1,5 1,5 1,5 Vulcanization accelerator (CZ) 2 2 2 2 2 sulfur 2 2 2 2 2 Average Tg of diene rubber [°C] -53 -53 -53 -39 -53 Specifically modified butadiene polymer / silica (mass%) 0,0 % 4,4 % 4,4 % 4,4 % 0,0 % Processability 100 94 96 97 99 Silica dispersibility 100 75 81 80 98 Wet steering stability 100 105 103 117 98 Fuel efficiency 100 91 93 102 99 Braking performance on snow 100 103 102 97 101 [Table 4-II] Table 4 Comparison example 1-2 Comparison example 1-3 Comparison example 1-4 Comparison example 1-5 Aromatic vinyl-conjugated diene rubber (A) 41,25 (30) 41,25 (30) 41,25 (30) 41,25 (30) Aromatic vinyl-conjugated diene rubber b1 35 35 35 35 Butadiene rubber b2 35 35 35 35 Silica 1 90 90 50 220 Silane adhesion promoter 1 7,2 7,2 7,2 7,2 soot 5 5 5 5 Process oil 15 15 15 15 Anti-aging agents 1 1 1 1 zinc oxide 3 3 3 3 Stearic acid 1 1 1 1 Specifically modified butadiene polymer 1 0,5 25 4 4 Specifically modified butadiene polymer 2 Unmodified butadiene polymer Vulcanization accelerator (DPG) 1,5 1,5 1,5 1,5 Vulcanization accelerator (CZ) 2 2 2 2 sulfur 2 2 2 2 Average Tg of diene rubber [°C] -53 -53 -53 -53 Specifically modified butadiene polymer / silica (mass%) 0,6 % 27,8 % 8,0 % 1,8 % Processability 100 88 90 104 Silica dispersibility 101 62 79 84 Wet steering stability 99 92 90 112 Fuel efficiency 99 99 92 110 Braking performance on snow 99 99 92 102 [Table 5-I] Table 5 Standard example 2-1 Example 2-1 Example 2-2 Example 2-3 Comparison example 2-1 Aromatic vinyl-conjugated diene rubber (A) 41,25 (30) 41,25 (30) 41,25 (30) 110 (80) 41,25 (30) Aromatic vinyl-conjugated diene rubber b1 35 35 35 35 Butadiene rubber b2 35 35 35 20 35 Silica 2 90 90 90 90 90 Silane coupling agent 2 9 9 9 9 9 soot 5 5 5 5 5 Process oil 15 15 15 15 15 Anti-aging agents 1 1 1 1 1 zinc oxide 3 3 3 3 3 Stearic acid 1 1 1 1 1 Specifically modified butadiene polymer 1 4 4 Specifically modified butadiene polymer 2 4 Unmodified butadiene polymer 4 Vulcanization accelerator (DPG) 1,5 1,5 1,5 1,5 1,5 Vulcanization accelerator (CZ) 2 2 2 2 2 sulfur 2 2 2 2 2 Average Tg of diene rubber [°C] -53 -53 -53 -39 -53 Specifically modified butadiene polymer / silica (mass%) 0,0 % 4,4 % 4,4 % 4,4 % 0,0 % Processability 100 91 94 96 99 Silica dispersibility 100 74 80 79 98 Wet steering stability 100 106 104 118 99 Fuel efficiency 100 90 92 103 99 Braking performance on snow 100 105 104 96 101 [Table 5-II] Table 5 Comparison example 2-2 Comparison example 2-3 Comparison example 2-4 Comparison example 2-5 Aromatic vinyl-conjugated diene rubber (A) 41,25 (30) 41,25 (30) 41,25 (30) 41,25 (30) Aromatic vinyl-conjugated diene rubber b1 35 35 35 35 Butadiene rubber b2 35 35 35 35 Silica 2 90 90 50 220 Silane coupling agent 2 9 9 9 9 soot 5 5 5 5 Process oil 15 15 15 15 Anti-aging agents 1 1 1 1 zinc oxide 3 3 3 3 Stearic acid 1 1 1 1 Specifically modified butadiene polymer 1 0,5 25 4 4 Specifically modified butadiene polymer 2 Unmodified butadiene polymer Vulcanization accelerator (DPG) 1,5 1,5 1,5 1,5 Vulcanization accelerator (CZ) 2 2 2 2 sulfur 2 2 2 2 Average Tg of diene rubber [°C] -53 -53 -53 -53 Specifically modified butadiene polymer / silica (mass%) 0,6 % 27,8 % 8,0 % 1,8 % Processability 100 87 89 105 Silica dispersibility 101 67 77 86 Wet steering stability 99 92 90 112 Fuel efficiency 99 99 91 112 Braking performance on snow 99 99 93 103

[0201] The details of the components listed in Tables 4 and 5 above are as follows.

[0202] It should be noted that the aromatic vinyl-conjugated diene rubber A is a terminal-modified aromatic vinyl-conjugated diene rubber having an aromatic vinyl content of 35 to 45 mass% and a vinyl unit content of 25 to 45 mol%, and thus the aromatic vinyl-conjugated diene rubber A corresponds to the “aromatic vinyl-conjugated diene rubber A” as described above.

[0203] In addition, the aromatic vinyl-conjugated diene rubber b1 is a different aromatic vinyl-conjugated diene rubber from the aromatic vinyl-conjugated diene rubber A described above because the aromatic vinyl content (repeating unit content derived from styrene) is less than 35 mass% and the vinyl unit content is more than 45 mol%. Thus, the aromatic vinyl-conjugated diene rubber b1 corresponds to the "aromatic vinyl-conjugated diene rubber b1" described above.

[0204] The butadiene rubber b2 is a butadiene rubber with a molecular weight (weight average) of more than 15,000, and thus corresponds to the “butadiene rubber b2” described above.

[0205] In addition, the specific modified butadiene polymers 1 and 2 are a terminally modified butadiene polymer having a weight-average molecular weight of 1,000 to 15,000 and a molecular weight distribution of 2.0 or less, and thus correspond to the "specifically modified butadiene polymer" described above.

[0124] • Aromatic vinyl-conjugated diene rubber A: E580 (terminal-modified solution-polymerized SBR, aromatic vinyl content (repeating unit content derived from styrene): 35.5 mass%, vinyl unit content: 40 mol%, an oil-extended product having a hydroxy group at one terminal (oil-extended amount: 37.5 mass%, available from Asahi Kasei Corporation) • Aromatic vinyl-conjugated diene rubber b1 NS616 (terminally modified solution-polymerized SBR, aromatic vinyl content (repeating unit content derived from styrene): 21 mass%; vinyl unit content: 63 mol%, having a hydroxy group at one terminal, available from Asahi Kasei Corporation) • Butadiene rubber b2: Nipol BR 1220 (BR, Mw: 490000, available from ZEON CORPORATION) • Silica 1: ZEOSIL 1165MR (available from Rhodia, CTAB adsorption specific surface area = 155 m 2 / G) • Silica 2: Ultrasil 9000 GR (available from Evonik, CTAB adsorption specific surface area: 197 2 / G) • Silane coupling agent 1: Si69 (Bis [3-(triethoxysilyl) propyl] tetrasulfide • Silane coupling agent 2: NXT silane (available from Momentive Performance Materials, silane coupling agent represented by formula (S) above (here in formula (S) over n = 2, m = 3 and k = 7)) • Carbon black: Show Black N339 (available from Cabot Corporation., Nitrogen adsorption specific surface area (N2SA) = 90 m 2 / G)) • Process oil: Extract No. 4S (available from Showa Shell Sekiyu KK) • Anti-aging agent: Santoflex 6PPD (available from Solutia Europe) • Zinc oxide: Zinc oxide III (available from Seido Chemical Industry Co., Ltd.) • Stearic acid: Stearic acid YR (available from NOF Corporation) • specifically modified butadiene polymer 1: specifically modified butadiene polymer 1, prepared as described above • specifically modified butadiene polymer 2: Polyvest EPST60 (Mw: 14,100, Mw / Mn: 1.90, modified butadiene polymer with a triethoxysilyl group at one terminus, available from Evonik) • Unmodified butadiene polymer: Polyvest110 (Mw: 8,200, Mw / Mn: 1.90, Terminus unmodified, available from Evonik) • Vulcanization accelerator (DPG): Perkacit DPG (available from Flexsys Chemicals) • Vulcanization accelerator (CZ): NOCCELER CZ-G (available from Ouchi Shinko Chemical Industrial Co., Ltd.) • Sulfur: Oil treatment sulfur (available from Karuizawa Refinery Ltd.)

[0206] In Tables 4 and 5, “average Tg of diene rubber” refers to the “average glass transition temperature of the diene rubber” as described above.

[0207] Likewise, in Tables 4 and 5, “specifically modified butadiene polymer / silica” refers to the “specifically modified butadiene polymer / silica” as described above.

[0208] As can be seen from Tables 4 and 5, examples in which the specifically modified butadiene polymer was blended with silica in a specific proportion showed excellent processability, silica dispersibility, wet steering stability and fuel efficiency, as well as snow braking performance.From the comparison of Example 1-1 with Example 1-2 (comparison between aspects in which only the type of the specially modified butadiene polymer differs), and the comparison of Example 2-1 with Example 2-2 (comparison between aspects in which only the type of the specially modified butadiene polymer differs), Example 1-1 and Example 2-1, in which the specially modified butadiene polymer contains a functional group (specific functional group) having a nitrogen atom and a silicon atom at one terminal, showed better processability, silica dispersibility, WET steering stability, fuel efficiency, and snow braking performance.

[0209] On the other hand, Standard Example 1-1 and Standard Example 2-1, Comparative Example 1-1 and Comparative Example 2-1 in which no specifically modified butadiene polymer is contained, Comparative Example 1-2 and Comparative Example 2-2 in which a specifically modified butadiene polymer is contained but the specifically modified butadiene polymer / silica is less than 1.0 mass%, and Comparative Example 1-3 and Comparative Example 2-3 in which a specifically modified butadiene polymer is contained but the specifically modified butadiene polymer / silica is greater than 25.0 mass% showed insufficient processability, silica dispersibility, WET steering stability, fuel efficiency, or snow braking performance.

[0210] When Example 1-1 and Example 2-1 were compared, Example 2-1, in which the CTAB adsorption specific surface area of ​​the silica was 160 m 2 / g or more and the silane coupling agent was the compound represented by formula (S) above, better processability, silica dispersibility, WET steering stability, fuel efficiency and snow braking performance.

[0211] Similarly, when Example 1-2 and Example 2-2 were compared, Example 2-2, in which the CTAB adsorption specific surface area of ​​the silica was 160 m 2 / g or more and the silane coupling agent was the compound represented by formula (S) above, better processability, silica dispersibility, WET steering stability, fuel efficiency and snow braking performance. List of reference symbols 1 bead section 2 side wall section 3 Tire tread section 4 carcass layers 5 Bead core 6 bead fillers 7 belt layer 8 wheel rim pads

Claims

[1] Rubber composition for a tire, comprising: a diene rubber; Silica and a modified butadiene polymer, wherein the modified butadiene polymer has a functional group selected from the group consisting of an amino group, a hydroxy group, an epoxy group, an alkylsilyl group, an alkoxysilyl group, and a functional group containing a nitrogen atom and a silicon atom at one terminal, wherein the diene rubber contains an aromatic vinyl-conjugated diene rubber A and at least one rubber component B selected from the group consisting of an aromatic vinyl-conjugated diene rubber b1 other than the aromatic vinyl-conjugated diene rubber A and a butadiene rubber b2 having a molecular weight (weight average) of more than 15,000, the aromatic vinyl-conjugated diene rubber A is a terminal-modified aromatic vinyl-conjugated diene rubber having an aromatic vinyl content of 35 to 45 mass% and a vinyl unit content of 25 to 45 mol%, and having at least one functional group selected from the group consisting of an amino group, a hydroxy group, an epoxy group, an alkylsilyl group, an alkoxysilyl group, and a carboxy group at the terminal, in the diene rubber there is a content of the aromatic vinyl-conjugated diene rubber A of 30 to 90 mass%, and a content of the rubber component B of 10 to 70 mass%, an average glass transition temperature of the diene rubber is from -20 °C to -100 °C, wherein the glass transition temperature (Tg) is measured using a differential scanning calorimeter at a temperature rise rate of 10 °C / min and is determined by multiplying mass fractions of diene rubbers by corresponding glass transition temperatures of the diene rubbers and then summing the obtained values, taking the weighted average of the glass transition temperatures and setting the sum of the mass fractions of all diene rubbers to 1, the modified butadiene polymer is a terminally modified butadiene polymer having a weight-average molecular weight of 1,000 to 10,000 and a molecular weight distribution of 2.0 or less, a silica content of 80 to 200 parts by mass per 100 parts by mass of the diene rubber, and a content of the modified butadiene polymer, based on the silica content, of 1.0 to 25.0 mass%. [2] The rubber composition for a tire according to claim 1, wherein in the diene rubber, the content of the aromatic vinyl-conjugated diene rubber A is from 50 to 90 mass%, and the content of the rubber component B is from 10 to 50 mass%, and wherein the average glass transition temperature of the diene rubber is -45°C or more and -20°C or less. [3] A rubber composition for a tire according to claim 1, wherein in the diene rubber, the content of the aromatic vinyl-conjugated diene rubber A is from 30 to 50 mass%, and the content of the rubber component B is from 50 to 70 mass%, and where the average glass transition temperature of the diene rubber is lower than -45°C. [4] The rubber composition for a tire according to any one of claims 1 to 3, wherein the modified butadiene polymer has a functional group containing a nitrogen atom and a silicon atom at a terminal. [5] A rubber composition for a tire according to any one of claims 1 to 4, wherein the silica has an adsorption specific cetyltrimethylammonium bromide (CTAB) surface area of 150 to 300 m 2 / g. [6] A rubber composition for a tire according to any one of claims 1 to 5, further comprising a silane coupling agent, wherein a content of the silane coupling agent, based on the content of the silica, is from 1 to 20 mass%; [7] Use of the rubber composition according to any one of claims 1 to 6 for a pneumatic tire in which the rubber composition is arranged in a protector tread.

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