JP2008001747A - Rubber composition and pneumatic tire using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To obtain a rubber composition for providing tires with high-quality driving stability and fracture characteristics by the use in tire tread rubber. <P>SOLUTION: The rubber composition is obtained by mixing 100 parts by mass of a rubber component comprising 40-100 mass% of a polymer (A) which is an aromatic vinyl compound-conjugated diene copolymer or a conjugated diene compound polymer having a weight-average molecular weight of 3.0x10<SP>5</SP>-3.0x10<SP>6</SP>in terms of polystyrene, polymerized by a lithium-based polymerization initiator and in which ≥20% and <60% of the unsaturated bond of a conjugated diene compound part is hydrogenated with 10-200 parts by mass of a polymer (B) which is an aromatic vinyl compound-conjugated diene copolymer or a conjugated diene compound polymer having a weight-average molecular weight of 1.0x10<SP>3</SP>-2.0x10<SP>5</SP>in terms of polystyrene and 5-100 parts by mass of a thermoplastic resin (C) having a softening point of ≥80°C. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  TECHNICAL FIELD The present invention relates to a rubber composition and a pneumatic tire using the rubber composition, and particularly a rubber composition capable of achieving both high steering stability and fracture characteristics when used in a tread rubber of a tire. It is about.

  In response to the evolution of advanced power performance of automobiles in recent years, more excellent handling stability, particularly handling stability on dry road surfaces, has been required as tire characteristics. On the other hand, from the viewpoint of economy and safety, it is also an important issue to sufficiently ensure the fracture characteristics of the tire. On the other hand, various techniques for improving the steering stability of tires have been developed so far. Here, it is known that loss characteristics (tan δ) above room temperature are generally important as a development index of a rubber composition related to tire handling stability. To improve tire handling stability. It is effective to increase the hysteresis loss at room temperature or higher of the rubber composition used for the tread rubber of the tire.

  For example, Japanese Patent Application Laid-Open No. 61-203145 (Patent Document 1) and Japanese Patent Application Laid-Open No. 63-101440 (Patent Document 2) have a weight average molecular weight of tens of thousands as a technique for increasing the hysteresis loss of a rubber composition. A method using a liquid polymer is disclosed.

  Japanese Patent Publication No. 8-30125 (Patent Document 3) discloses, as a technique for increasing the hysteresis loss of a rubber composition, a weight average molecular weight of 5,000 to 200,000 with respect to a partially hydrogenated high molecular weight polymer. A method of blending the hydrogenated liquid polymer is disclosed.

JP-A-61-203145 JP 63-101440 A Japanese Patent Publication No. 8-30125

  However, although the liquid polymers described in JP-A-61-203145 and JP-A-63-101440 have a weight average molecular weight of tens of thousands and a relatively low molecular weight, they have a double bond having crosslinkability. In many cases, a part of the liquid polymer forms a cross-link with the matrix rubber and is taken into the matrix, so that there is a problem that sufficient hysteresis loss does not occur.

  In the method described in JP-B-8-30125, since the hydrogenation rate of the high molecular weight polymer constituting the matrix of the rubber composition is too high, it has an adverse effect on the crosslinked form of the rubber composition, and the fracture strength is low. There was a problem of lowering.

  Accordingly, an object of the present invention is to provide a rubber composition that solves the above-described problems of the prior art and can impart high steering stability and fracture characteristics to the tire by using it in a tire tread rubber. It is in. Another object of the present invention is to provide a pneumatic tire that uses the rubber composition in a tread and is highly compatible in handling stability and fracture characteristics.

  As a result of intensive studies to achieve the above-mentioned object, the present inventor has obtained a high molecular weight aromatic vinyl compound-conjugated diene compound copolymer or conjugated diene compound polymer (component A) having a specific molecular weight and hydrogenation rate. A low molecular weight aromatic vinyl compound-conjugated diene compound copolymer or a conjugated diene compound polymer (component B) having a specific molecular weight and a thermoplastic resin (component C) having a softening point of a certain value or more. Thus, it was found that the breaking strength and hysteresis loss of the obtained rubber composition can be greatly improved, and the present invention has been completed.

That is, the rubber composition of the present invention is an aromatic polymerized with a lithium polymerization initiator having a polystyrene-reduced weight average molecular weight of 3.0 × 10 ^{5 to} 3.0 × 10 ⁶ measured by gel permeation chromatography. 40-100% by mass of a polymer (A), which is a vinyl compound-conjugated diene compound copolymer or a conjugated diene compound polymer, wherein 20% or more and less than 60% of the unsaturated bonds in the conjugated diene compound portion are hydrogenated. For 100 parts by mass of the rubber component contained,
An aromatic vinyl compound-conjugated diene compound copolymer or conjugated diene compound polymer, having a polystyrene-reduced weight average molecular weight of 1.0 × 10 ^{3 to} 2.0 × 10 ⁵ measured by gel permeation chromatography 10 to 200 parts by mass of combined (B),
It is characterized by blending 5 to 100 parts by mass of a thermoplastic resin (C) having a softening point of 80 ° C. or higher.

  In a preferred example of the rubber composition of the present invention, the polymer (A) is a styrene-butadiene copolymer. Here, the amount of bound styrene of the styrene-butadiene copolymer is preferably in the range of 20 to 40% by mass. The vinyl bond content in the butadiene portion of the styrene-butadiene copolymer is preferably in the range of 30 to 60%.

  In another preferred embodiment of the rubber composition of the present invention, 30% to 50% of the unsaturated bonds in the conjugated diene compound portion of the polymer (A) are hydrogenated.

  In another preferred embodiment of the rubber composition of the present invention, the rubber component is a styrene-butadiene copolymer in which the remainder of the polymer (A) is unhydrogenated.

  In another preferred embodiment of the rubber composition of the present invention, the polymer (B) is a styrene-butadiene copolymer. Here, the amount of bound styrene in the polymer (B) is preferably 60% by mass or less.

  In another preferred embodiment of the rubber composition of the present invention, 20% to 100% of the unsaturated bonds in the conjugated diene compound portion of the polymer (B) are hydrogenated. Here, it is preferable that 40% to 90% of the unsaturated bond in the conjugated diene compound portion of the polymer (B) is hydrogenated.

  The rubber composition of the present invention is preferably formed by blending 10 to 120 parts by mass of the polymer (B) with respect to 100 parts by mass of the rubber component.

  In the rubber composition of the present invention, the polymer (B) preferably has a polystyrene equivalent weight average molecular weight of 2,000 or more and less than 12,000 as measured by gel permeation chromatography.

  The pneumatic tire of the present invention is characterized in that the rubber composition is used for a tread rubber.

  According to the present invention, a low molecular weight aromatic vinyl having a specific molecular weight is added to a high molecular weight aromatic vinyl compound-conjugated diene compound copolymer or conjugated diene compound polymer (component A) having a specific molecular weight and hydrogenation rate. Compound-conjugated diene compound copolymer or conjugated diene compound polymer (component B) and a thermoplastic resin (component C) having a softening point equal to or higher than a certain value are used for a tire tread rubber. A rubber composition capable of imparting high steering stability and fracture characteristics to a tire can be provided. Moreover, the pneumatic tire which applied such a rubber composition to tread rubber and was highly compatible in handling stability and fracture characteristics can be provided.

The present invention is described in detail below. The rubber composition of the present invention is an aromatic vinyl compound polymerized with a lithium-based polymerization initiator having a polystyrene-equivalent weight average molecular weight of 3.0 × 10 ^{5 to} 3.0 × 10 ^{6 as} measured by gel permeation chromatography. -Conjugated diene compound copolymer or conjugated diene compound polymer, containing 40 to 100% by mass of polymer (A) in which 20% or more and less than 60% of unsaturated bonds in the conjugated diene compound part are hydrogenated For 100 parts by mass of the rubber component,
An aromatic vinyl compound-conjugated diene compound copolymer or conjugated diene compound polymer, having a polystyrene-reduced weight average molecular weight of 1.0 × 10 ^{3 to} 2.0 × 10 ⁵ measured by gel permeation chromatography 10 to 200 parts by mass of combined (B),
It is characterized by blending 5 to 100 parts by mass of a thermoplastic resin (C) having a softening point of 80 ° C. or higher.

The rubber composition of the present invention is an aromatic vinyl compound-conjugated diene compound copolymer or a conjugated diene compound, and has a weight average molecular weight of 1.0 × 10 ^{3 to} 2.0 × 10 ^5. Since B) is included, the hysteresis loss (tan δ) above room temperature is high. Note that, as in the past, a rubber composition obtained by blending the polymer (B) with a general rubber component has a lower fracture strength as the hysteresis loss (tan δ) increases. Therefore, the rubber composition of the present invention is a high molecular weight aromatic vinyl compound-conjugated diene compound copolymer or a conjugated diene compound polymer, which is formed by hydrogenating an unsaturated bond of a conjugated diene compound portion to a rubber component of a matrix. By using the polymer (A) having a rate of 20% or more and less than 60%, the compatibility between the component (A) and the component (B) can be improved, and the fracture strength can be maintained at a high level. Since the entanglement between the component (A) and the component (B) also increases, the hysteresis loss (tan δ) at room temperature or higher can be further improved. In addition, the rubber composition of the present invention includes a thermoplastic resin (C) having a softening point of 80 ° C. or higher, thereby imparting tackiness, further causing hysteresis loss, and improving the steering stability of the tire. can do. Therefore, by using the rubber composition of the present invention for the tread rubber of a pneumatic tire, both steering stability and fracture characteristics can be greatly improved. Moreover, since the rubber composition of this invention has the above characteristics, it can be suitably applied to belts and various industrial rubber articles.

The polymer (A) used in the rubber composition of the present invention needs to have a polystyrene-equivalent weight average molecular weight of 3.0 × 10 ^{5 to} 3.0 × 10 ⁶ measured by gel permeation chromatography (GPC). 7.0 × 10 ^{5 to} 2.5 × 10 ⁶ is preferable. If the weight average molecular weight in terms of polystyrene of the polymer (A) is less than 3.0 × 10 ⁵ , the fracture characteristics of the rubber composition are lowered. On the other hand, if it exceeds 3.0 × 10 ⁶ , the viscosity of the polymerization solution is high. It becomes too low and productivity becomes low.

  The polymer (A) requires that 20% or more and less than 60% of the unsaturated bonds in the conjugated diene compound portion be hydrogenated, and 30% to 50% be hydrogenated. preferable. When the hydrogenation rate of the unsaturated bond of the conjugated diene compound portion in the polymer (A) is less than 20%, the effect of improving the hysteresis loss of the rubber composition is small, and the steering stability of the tire cannot be sufficiently improved. On the other hand, when the hydrogenation rate is 60% or more, the crosslinked form of the rubber composition is changed, and the breaking strength of the rubber composition is lowered.

  In the rubber composition of the present invention, 40 to 100% by mass of the rubber component of the matrix is the polymer (A). When the proportion of the polymer (A) in the rubber component in which the unsaturated bond of the conjugated diene compound portion is hydrogenated is less than 40% by mass, the effect of improving the hysteresis loss of the rubber composition is small, and the steering stability of the tire is reduced. There is a risk that it will not be possible to secure enough. If the total amount of the rubber component is the polymer (A), the cross-linked form may be adversely affected. Therefore, the rubber composition of the present invention contains a non-hydrogenated general rubber component as necessary. Can be included. Here, as non-hydrogenated general rubber components, specifically, natural rubber (NR), styrene-butadiene copolymer rubber (SBR), polyisoprene rubber (IR), polybutadiene rubber (BR), butyl rubber (IIR), an ethylene-propylene copolymer, and the like can be blended. In addition, a part of these rubber components modified with a polyfunctional modifier such as tin tetrachloride and the like and having a branched structure can be blended. Among these rubber components, styrene-butadiene copolymer rubber (SBR) is preferable from the viewpoint of compatibility.

  The polymer (A) is produced by copolymerizing an aromatic vinyl compound and a conjugated diene compound or polymerizing a conjugated diene compound using a lithium-based polymerization initiator. Here, examples of the aromatic vinyl compound include styrene, α-methylstyrene, 1-vinylnaphthalene, 3-vinyltoluene, ethylvinylbenzene, divinylbenzene, 4-cyclohexylstyrene, and 2,4,6-trimethylstyrene. These aromatic vinyl compounds may be used alone or in combination of two or more. On the other hand, examples of the conjugated diene compound include 1,3-butadiene, isoprene, 1,3-pentadiene, 2,3-dimethylbutadiene, 2-phenyl-1,3-butadiene, 1,3-hexadiene, and the like. These conjugated diene compounds may be used alone or in combination of two or more. Among the aromatic vinyl compounds, styrene is particularly preferable, and among the conjugated diene compounds, 1,3-butadiene is particularly preferable. Therefore, when the polymer (A) is a copolymer of an aromatic vinyl compound and a conjugated diene compound, the polymer (A) is particularly preferably a styrene-butadiene copolymer (SBR).

  When the polymer (A) is an aromatic vinyl compound-conjugated diene compound copolymer and the aromatic vinyl compound as a raw material is styrene, the polymer (A) has a bound styrene content of 20 to 40% by mass. Preferably there is. When the amount of bound styrene in the polymer (A) is less than 20% by mass, the fracture characteristics of the rubber composition are deteriorated. On the other hand, when it exceeds 40% by mass, the wear resistance of the rubber composition is deteriorated.

  Moreover, when the conjugated diene compound as a raw material of the polymer (A) is 1,3-butadiene, the polymer (A) preferably has a vinyl bond content in the butadiene portion of 30 to 60%. If the vinyl bond content of the butadiene portion of the polymer (A) is less than 30%, the wet skid resistance of the rubber composition is insufficient, so that the steering stability of the tire cannot be sufficiently improved, When it exceeds 60%, the abrasion resistance of the rubber composition is lowered.

On the other hand, the polymer (B) used in the rubber composition of the present invention has a polystyrene-reduced weight average molecular weight of 1.0 × 10 ^{3 to} 2.0 × 10 ⁵ measured by gel permeation chromatography (GPC). In short, it is preferably 2,000 or more and less than 12,000. If the weight average molecular weight in terms of polystyrene of the polymer (B) is less than 1.0 × 10 ³ , the fracture characteristics, wear resistance, wet skid resistance and dry grip properties of the rubber composition are insufficient. The fracture characteristics and the steering stability cannot be made highly compatible. On the other hand, if it exceeds 2.0 × 10 ⁵ , the wet skid resistance and the dry grip property of the rubber composition are insufficient. Stability cannot be improved.

  The polymer (B) is produced by copolymerizing an aromatic vinyl compound and a conjugated diene compound or polymerizing a conjugated diene compound. Here, examples of the aromatic vinyl compound include styrene, α-methylstyrene, 1-vinylnaphthalene, 3-vinyltoluene, ethylvinylbenzene, divinylbenzene, 4-cyclohexylstyrene and 2,4,6-trimethylstyrene. These aromatic vinyl compounds may be used alone or in combination of two or more. On the other hand, examples of the conjugated diene compound include 1,3-butadiene, isoprene, 1,3-pentadiene, 2,3-dimethylbutadiene, 2-phenyl-1,3-butadiene, 1,3-hexadiene, and the like. These conjugated diene compounds may be used alone or in combination of two or more. Among the aromatic vinyl compounds, styrene is particularly preferable, and among the conjugated diene compounds, 1,3-butadiene is particularly preferable. Therefore, when the polymer (B) is a copolymer of an aromatic vinyl compound and a conjugated diene compound, the polymer (B) is particularly preferably a styrene-butadiene copolymer (SBR).

  When the polymer (B) is an aromatic vinyl compound-conjugated diene compound copolymer and the aromatic vinyl compound as a raw material is styrene, the polymer (B) has a bound styrene content of 60% by mass. The following is preferable. When the amount of bound styrene of the polymer (B) exceeds 60% by mass, the polymer (B) becomes resinous, so that the rubber composition becomes hard, wet skid resistance and dry grip properties are reduced, and the tire It may not be possible to improve steering stability.

  Furthermore, it is preferable that 20% to 100% of the unsaturated bond in the conjugated diene compound portion is hydrogenated in the polymer (B). When 20% or more of the unsaturated bonds in the conjugated diene compound portion of the polymer (B) are hydrogenated, the effect of improving the hysteresis loss of the rubber composition at room temperature or higher is increased. In the polymer (B), 40% to 90% of the unsaturated bonds in the conjugated diene compound portion are more preferably hydrogenated. When the hydrogenation rate of the unsaturated bond of the conjugated diene compound portion of the polymer (B) is less than 40%, the polymer (B) is involved in the crosslinking of the rubber composition, and the width of improvement in steering stability of the tire is increased. small. On the other hand, the polymer (B) in which the hydrogenation rate of the unsaturated bond in the conjugated diene compound portion exceeds 90% is difficult to produce.

  In the rubber composition of this invention, it is required to mix | blend the said polymer (B) in the ratio of 10-200 mass parts with respect to 100 mass parts of said rubber components, and is mix | blended in the ratio of 10-120 mass parts. It is preferable to do. If the blending amount of the polymer (B) with respect to 100 parts by mass of the rubber component is less than 10 parts by mass, the steering stability of the tire cannot be sufficiently improved, while if it exceeds 200 parts by mass, the rubber composition Mooney viscosity becomes too low, and productivity deteriorates.

  The polymer (A) can be prepared by, for example, anionic polymerization of the aromatic vinyl compound and the conjugated diene compound in a hydrocarbon solvent using a lithium-based polymerization initiator in the presence of an ether or a tertiary amine. ) Obtained by polymerization. The polymer (A) can be hydrogenated according to a conventional method in the presence of a hydrogenation catalyst. On the other hand, the polymer (B) is obtained, for example, by anionic polymerization using the above-mentioned aromatic vinyl compound and conjugated diene compound in a hydrocarbon solvent in the presence of ether or tertiary amine using a lithium-based polymerization initiator. It may be obtained by (co) polymerization and further optionally hydrogenated in the same manner as the polymer (A).

  Here, the hydrocarbon solvent is not particularly limited, but cycloaliphatic hydrocarbons such as cyclohexane, methylcyclopentane, cyclooctane, propane, butane, pentane, hexane, heptane, octane, decane, etc. Aliphatic hydrocarbons, aromatic hydrocarbons such as benzene, toluene, and ethylbenzene can be used. These hydrocarbons may be used alone or in combination of two or more. Of these hydrocarbons, aliphatic hydrocarbons and alicyclic hydrocarbons are preferred.

  The lithium-based polymerization initiator is preferably an organic lithium compound. Examples of the organic lithium compound include alkyl lithium such as ethyl lithium, propyl lithium, n-butyl lithium, sec-butyl lithium, and t-butyl lithium; phenyl Aryl lithium such as lithium and tolyl lithium; Alkenyl lithium such as vinyl lithium and propenyl lithium; Alkylene dilithium such as tetramethylene dilithium, pentamethylene dilithium, hexamethylene dilithium and decamethylene dilithium; 1,3-dilithio In addition to arylene lithium such as benzene and 1,4-dilithiobenzene; 1,3,5-trilithiocyclohexane, 1,2,5-trilithionaphthalene, 1,3,5,8-tetralithiodecane, 1 , 2,3,5-tetralithio-4-hexyl-anthracene, etc. It is below. Among these, n-butyllithium, sec-butyllithium, t-butyllithium and tetramethylenedilithium are preferable, and n-butyllithium is particularly preferable. The amount of the lithium-based polymerization initiator used is determined by the polymerization rate in the reaction operation and the molecular weight of the (co) polymer to be produced, and is usually preferably in the range of 0.02 to 5 mg as a lithium atom per 100 g of the monomer. A range of 0.05 to 2 mg is more preferable.

  The polymerization reaction for obtaining the polymer (A) and the polymer (B) can be performed by either a batch polymerization method or a continuous polymerization method. The polymerization temperature in the polymerization reaction is preferably in the range of 0 to 130 ° C. The polymerization reaction can be carried out by any polymerization method such as isothermal polymerization, temperature rising polymerization and adiabatic polymerization. Furthermore, when performing the polymerization, an allene compound such as 1,2-butadiene may be added in order to prevent the formation of a gel in the reaction vessel.

  In the hydrogenation, for example, the synthesized (co) polymer is supported on a hydrogenation catalyst composed of nickel organic carboxylate, cobalt organic carboxylate, or a group 1-3 organometallic compound; carbon, silica, diatomaceous earth, or the like. Nickel, platinum, palladium, ruthenium, rhodium metal catalyst: One type selected from cobalt, nickel, rhodium, ruthenium complex and the like can be used as a catalyst for hydrogenation under 1-100 atm pressurized hydrogen.

  The thermoplastic resin (C) used in the rubber composition of the present invention requires a softening point of 80 ° C or higher, preferably in the range of 80 to 200 ° C, and in the range of 80 to 170 ° C. Is more preferable. When the softening point of the thermoplastic resin (C) is less than 80 ° C., sufficient steering stability of the tire cannot be ensured, and storage of the thermoplastic resin (C) becomes difficult. On the other hand, when the softening point of the thermoplastic resin (C) exceeds 200 ° C., the dispersibility in the rubber component during kneading is poor, and a uniform rubber composition cannot be obtained.

  The thermoplastic resin (C) is not particularly limited as long as the softening point is 80 ° C. or higher, and can be appropriately selected according to the purpose. For example, phenol resin, C5 petroleum resin, and C9 petroleum resin Etc. are preferable. These thermoplastic resins may be used individually by 1 type, and may be used in combination of 2 or more type. Specific examples of the phenolic resin include a trade name “Cholecin” (manufactured by BASF), which is a pt-butylphenol acetylene resin.

  The C5 petroleum resin is a C5 fraction resin obtained by thermal decomposition of naphtha. Examples of the C5 fraction include olefinic hydrocarbons such as pentene, 2-methylbutene, and 3-methylbutene, and 1, Examples include diolefin hydrocarbons such as 2-pentadiene. Moreover, as said C5 type petroleum resin, a commercial item can be used conveniently, for example, a brand name "Stractol TS30" [made by Stratokol Co., Ltd.], "TX-500" [made by Mitsui Chemicals, Inc.] And “Quinton” [manufactured by Nippon Zeon Co., Ltd.].

  The C9 petroleum resin is a C9 fraction resin obtained by thermal decomposition of naphtha. Examples of the C9 fraction include α-methylstyrene, styrene, indene, vinyltoluene and the like. Moreover, as said C9 type | system | group petroleum resin, a commercial item can be used conveniently, for example, a brand name "neopolymer" [made by Nippon Oil Co., Ltd.] etc. are mentioned.

  In the rubber composition of this invention, it is required to mix | blend the said thermoplastic resin (C) in the ratio of 5-100 mass parts with respect to 100 mass parts of said rubber components, and it is the ratio of 30-80 mass parts. It is preferable to mix. If the blending amount of the thermoplastic resin (C) with respect to 100 parts by mass of the rubber component is less than 5 parts by mass, the steering stability of the tire cannot be sufficiently improved, while if it exceeds 100 parts by mass, the rubber is hard. The steering stability of the tire becomes worse.

  The rubber composition of the present invention preferably contains a reinforcing filler, and is not particularly limited, but preferably contains silica and / or carbon black.

  Examples of the silica include, but are not limited to, wet silica (hydrous silicic acid), dry silica (anhydrous silicic acid), calcium silicate, aluminum silicate, and the like. Wet silica is preferred because it is excellent in the effect of achieving both wet grip properties and low rolling resistance. The rubber composition of the present invention may contain only silica as a filler. In this case, the amount of silica is preferably in the range of 10 to 250 parts by mass with respect to 100 parts by mass of the rubber component. The range of 20 to 150 parts by mass is more preferable from the viewpoint of the reinforcing property and the improvement efficiency of various physical properties thereby. When the compounding amount of silica is less than 10 parts by mass with respect to 100 parts by mass of the rubber component, the fracture characteristics and the like are not sufficient, and when it exceeds 250 parts by mass, the processability of the rubber composition decreases.

  In the rubber composition of the present invention, when silica is used as a filler, it is preferable to add a silane coupling agent at the time of blending from the viewpoint of further improving the reinforcing property. Examples of the silane coupling agent include bis (3-triethoxysilylpropyl) tetrasulfide, bis (3-triethoxysilylpropyl) trisulfide, bis (3-triethoxysilylpropyl) disulfide, and bis (2-triethoxy). Silylethyl) tetrasulfide, bis (3-trimethoxysilylpropyl) tetrasulfide, bis (2-trimethoxysilylethyl) tetrasulfide, 3-mercaptopropyltrimethoxysilane, 3-mercaptopropyltriethoxysilane, 2-mercaptoethyl Trimethoxysilane, 2-mercaptoethyltriethoxysilane, 3-trimethoxysilylpropyl-N, N-dimethylthiocarbamoyl tetrasulfide, 3-triethoxysilylpropyl-N, N-dimethylthiocarbamoyl tetrasulfide, 2-triethoxy Cyril Ethyl-N, N-dimethylthiocarbamoyl tetrasulfide, 3-trimethoxysilylpropylbenzothiazole tetrasulfide, 3-triethoxysilylpropylbenzothiazole tetrasulfide, 3-triethoxysilylpropyl methacrylate monosulfide, 3-trimethoxysilylpropyl Methacrylate monosulfide, bis (3-diethoxymethylsilylpropyl) tetrasulfide, 3-mercaptopropyldimethoxymethylsilane, dimethoxymethylsilylpropyl-N, N-dimethylthiocarbamoyl tetrasulfide, dimethoxymethylsilylpropylbenzothiazole tetrasulfide, etc. Among these, bis (3-triethoxysilylpropyl) tetrasulfide and 3-trimethoxysilyl from the viewpoint of reinforcing effect Propyl benzothiazole tetrasulfide are preferable. These silane coupling agents may be used alone or in combination of two or more.

  On the other hand, the carbon black is not particularly limited, and examples thereof include FEF, SRF, HAF, ISAF, and SAF grades. The carbon black is preferably carbon black having an iodine adsorption amount (IA) of 60 mg / g or more and a dibutyl phthalate (DBP) oil absorption of 80 mL / 100 g or more. By blending carbon black, various physical properties of the rubber composition can be improved, but from the viewpoint of improving the wear resistance, those of HAF, ISAF, and SAF grade are more preferable. The rubber composition of the present invention may contain only carbon black as a filler. In this case, the amount of carbon black is in the range of 10 to 200 parts by mass with respect to 100 parts by mass of the rubber component. The range of 20 to 160 parts by mass is more preferable from the viewpoint of the reinforcing property and the improvement efficiency of various physical properties thereby. When the compounding amount of carbon black is less than 10 parts by mass with respect to 100 parts by mass of the rubber component, the fracture characteristics and the like are not sufficient, and when it exceeds 200 parts by mass, the processability of the rubber composition is lowered.

  In the rubber composition of the present invention, process oil or the like can be used as a softening agent, and examples of the process oil include paraffinic oil, naphthenic oil, and aromatic oil. The amount of these process oils used is preferably in the range of 0 to 200 parts by mass with respect to 100 parts by mass of the rubber component. When the amount of process oil used exceeds 200 parts by mass with respect to 100 parts by mass of the rubber component, the tensile strength and workability of the vulcanized rubber tend to deteriorate.

  Moreover, the rubber composition of this invention can use a general rubber vulcanization system, and it is preferable to use a combination of a vulcanizing agent and a vulcanization accelerator. Here, examples of the vulcanizing agent include sulfur and the use amount of the vulcanizing agent is preferably within a range of 0.1 to 10 parts by mass as a sulfur content with respect to 100 parts by mass of the rubber component. The range of parts by mass is more preferable. When the compounding amount of the vulcanizing agent is less than 0.1 parts by mass as the sulfur content with respect to 100 parts by mass of the rubber component, the fracture strength and wear resistance of the vulcanized rubber are reduced. Lost.

  On the other hand, the vulcanization accelerator is not particularly limited, but 2-mercaptobenzothiazole (M), dibenzothiazyl disulfide (DM), N-cyclohexyl-2-benzothiazylsulfenamide (CZ). ), Thiazole vulcanization accelerators such as Nt-butyl-2-benzothiazolylsulfenamide (NS), and guanidine vulcanization accelerators such as diphenylguanidine (DPG). The amount of the vulcanization accelerator used is preferably in the range of 0.1 to 5 parts by mass, more preferably in the range of 0.2 to 3 parts by mass with respect to 100 parts by mass of the rubber component. These vulcanization accelerators may be used alone or in combination of two or more.

  The rubber composition of the present invention includes the above-described polymer (A), polymer (B), thermoplastic resin (C), general rubber component, filler, silane coupling agent, vulcanizing agent, and vulcanization. In addition to accelerators and softeners, for example, additives commonly used in the rubber industry such as anti-aging agents, zinc oxide, stearic acid, antioxidants, anti-ozone degradation agents, and the like within the range not impairing the object of the present invention. Can be appropriately selected and blended.

  The rubber composition of the present invention is obtained by kneading using a kneader such as a roll or an internal mixer, and after molding, vulcanization is performed, and the tire tread rubber, under tread, carcass, sidewall In addition to tire applications such as beads, it can also be used in anti-vibration rubber, belts, hoses, and other industrial products, but is particularly suitable as a tread rubber for tires.

  The pneumatic tire of the present invention is characterized by using the rubber composition as a tread rubber. Since the tire is formed by applying a rubber composition having a high hysteresis loss (tan δ) to the tread rubber while maintaining a high breaking strength, the tire has good breaking characteristics and excellent handling stability. The tire of the present invention is not particularly limited except that the above rubber composition is used for the tread rubber, and can be produced according to a conventional method. Moreover, as gas with which this tire is filled, inert gas, such as nitrogen, argon, helium other than normal or the air which adjusted oxygen partial pressure, can be used.

  Hereinafter, the present invention will be described in more detail with reference to examples. However, the present invention is not limited to the following examples.

  Copolymers (A-1) to (A-2) and copolymers (B-1) to (B-2) were synthesized by the following method, and the styrene bond amount and vinyl bond of the obtained copolymer. The amount, polystyrene-converted weight average molecular weight and hydrogenation rate were measured by the following methods.

(1) Styrene bond amount The styrene bond amount of the synthesized copolymer was calculated from the integral ratio of ¹ H-NMR spectrum.

(2) Vinyl bond amount The vinyl bond amount of the butadiene part of the synthesized copolymer was analyzed by an infrared method.

(3) Weight average molecular weight in terms of polystyrene (Mw)
The weight average molecular weight in terms of polystyrene of the synthesized copolymer was measured by GPC. Here, 244 type GPC manufactured by Waters is used as GPC, a differential refractometer is used as a detector, columns GMH-3, GMH-6, and G6000H-6 manufactured by Tosoh are used as columns, and tetrahydrofuran is used as a mobile phase. Was used. In addition, using a monodisperse styrene polymer manufactured by Waters as a standard substance, a calibration curve was prepared by previously obtaining the relationship between the molecular weight of the monodisperse styrene polymer peak by GPC and the GPC count number, The molecular weight in terms of polystyrene of the copolymers (A) and (B) was determined.

(4) Hydrogenation rate The hydrogenation rate of the butadiene portion of the synthesized copolymer is the spectrum of the unsaturated bond portion of 100 MHz ¹ H-NMR measured at a concentration of 15% by mass using carbon tetrachloride as a solvent. Calculated from the decrease.

<Synthesis of copolymer (A-1)>
Cyclohexane 3000 g, tetrahydrofuran (THF) 12 g, 1,3-butadiene 200 g, and styrene 125 g were introduced into a 5 liter autoclave with a stirring blade sufficiently purged with nitrogen, and the temperature in the autoclave was adjusted to 21 ° C. Next, 0.1 g of n-butyllithium was added and polymerization was performed for 60 minutes under the temperature-raising condition, and it was confirmed that the monomer conversion rate was 99%. Thereafter, 3.5 g of 2,6-di-t-butyl-p-cresol was added as an anti-aging agent to obtain a copolymer (A-1). The analytical values are shown in Table 1.

<Synthesis of copolymer (A-2)>
Cyclohexane 3000 g, tetrahydrofuran (THF) 12 g, 1,3-butadiene 200 g, and styrene 125 g were introduced into a 5 liter autoclave with a stirring blade sufficiently purged with nitrogen, and the temperature in the autoclave was adjusted to 21 ° C. Next, 0.1 g of n-butyllithium was added and polymerization was performed for 60 minutes under the temperature-raising condition, and it was confirmed that the monomer conversion rate was 99%. Further, a catalyst solution of nickel naphthenate: triethylaluminum: butadiene = 1: 3: 3 (molar ratio) prepared in a separate container in advance was charged to 1 mol of nickel with respect to 1000 mol of the butadiene portion in the copolymer. Thereafter, hydrogen was introduced into the reaction system at a hydrogen pressure of 30 kg / cm ² and reacted at 80 ° C. Thereafter, 3.5 g of 2,6-di-t-butyl-p-cresol was added as an anti-aging agent to obtain a copolymer (A-2). The analytical values are shown in Table 1.

<Synthesis of copolymer (B-1)>
Cyclohexane 3000 g, tetrahydrofuran (THF) 12 g, 1,3-butadiene 200 g and styrene 100 g were introduced into a 5 liter autoclave with a stirring blade sufficiently purged with nitrogen, and the temperature in the autoclave was adjusted to 21 ° C. Next, 1.5 g of n-butyllithium was added and polymerization was carried out for 60 minutes under elevated temperature conditions. After confirming that the monomer conversion was 99%, 4.68 g of tributylsilyl chloride was added to terminate the polymerization. Copolymer (B-1) was obtained. The analytical values are shown in Table 2.

<Synthesis of copolymer (B-2)>
Cyclohexane 3000 g, tetrahydrofuran (THF) 12 g, 1,3-butadiene 200 g and styrene 100 g were introduced into a 5 liter autoclave with a stirring blade sufficiently purged with nitrogen, and the temperature in the autoclave was adjusted to 21 ° C. Next, 1.5 g of n-butyllithium was added and polymerization was carried out for 60 minutes under elevated temperature conditions. After confirming that the monomer conversion was 99%, 4.68 g of tributylsilyl chloride was added to terminate the polymerization. Thereafter, a catalyst solution of nickel naphthenate: triethylaluminum: butadiene = 1: 3: 3 (molar ratio) prepared in a separate container in advance was charged so that the amount of nickel was 1 mol with respect to 1000 mol of the butadiene portion in the copolymer. . Thereafter, hydrogen was introduced into the reaction system at a hydrogen pressure of 30 atm and reacted at 80 ° C. to obtain a copolymer (B-2). The analytical values are shown in Table 2.

  Next, using the copolymers (A-1) to (A-2) and the copolymers (B-1) to (B-2), a rubber composition having a compounding formulation shown in Table 3 is prepared by a conventional method. The rubber composition thus obtained was evaluated for fracture resistance by the following method. Further, a radial tire for a passenger car having a size of 225 / 45R17 was produced according to a conventional method using the rubber composition as a tread rubber, and the steering stability of the obtained tire was evaluated by the following method. The results are shown in Table 3.

(5) Fracture resistance A dumbbell-shaped No. 3 test piece was prepared and subjected to a tensile test at room temperature in accordance with JIS K6251-1993, and the tensile strength (Tb) of the vulcanized rubber composition was measured. Here, the tensile strength of Comparative Example 1 was taken as 100 and displayed as an index. The larger the index value, the better the fracture resistance.

(6) Steering stability Each prototype tire was mounted, a real vehicle running test was performed on a dry road surface, and superiority or inferiority was judged by sensory evaluation of a specialized driver. The other tires were scored based on the handling stability of the tire using the rubber composition of Comparative Example 1.

* 1 BASF, “Cholecin”, softening point of 110 to 130 ° C.
* 2 “TS50” manufactured by Straktor, softening point 48 ° C.
* 3 ISAF, Tokai Carbon Co., Ltd., “Seast 3H”.
* 4 N- (1,3-dimethylbutyl) -N′-phenyl-p-phenylenediamine, manufactured by Ouchi Shinsei Chemical Industry, “NOCRACK 6C”.
* 5 Dibenzothiazyl disulfide.
* 6 Nt-butyl-2-benzothiazolylsulfenamide, manufactured by Ouchi Shinsei Chemical Industry, “Noxeller NS”.

  From the results of Table 3, a low molecular weight aromatic vinyl compound having a specific molecular weight-conjugated to a high molecular weight aromatic vinyl compound-conjugated diene compound copolymer (component A) having the molecular weight and hydrogenation rate specified in the present invention. A rubber composition containing a diene compound copolymer (component B) and a thermoplastic resin (component C) having a softening point equal to or greater than a certain value improves the resistance to breakage and provides a high level of driving stability to the tire. You can see that Further, as apparent from Example 2, even when the copolymer (A-1) in which the unsaturated bond of the butadiene portion is not hydrogenated is contained in the component A, the copolymer is hydrogenated. If (A-2) exists in a fixed ratio, it turns out that the objective of this invention can be achieved.

On the other hand, from the results of Comparative Example 2, the low molecular weight aromatic vinyl compound-conjugated diene compound copolymer that was not hydrogenated was compared with the high molecular weight aromatic vinyl compound-conjugated diene compound copolymer that was not hydrogenated; It can be seen that, when blended with a thermoplastic resin having a softening point equal to or greater than a certain value, steering stability and fracture resistance are improved, but sufficient effects cannot be obtained. Further, from the results of Comparative Example 3, a rubber composition in which aroma oil was blended with a high molecular weight aromatic vinyl compound-conjugated diene compound copolymer (component A) having a molecular weight and a hydrogenation rate specified in the present invention, Compared to Comparative Example 1, it can be seen that the fracture resistance decreases. Furthermore, it can be seen from the results of Comparative Example 3 that even when a thermoplastic resin having a low softening point is blended, a sufficient effect on steering stability cannot be obtained.

Claims (13)

An aromatic vinyl compound-conjugated diene compound copolymer polymerized with a lithium-based polymerization initiator, having a polystyrene-reduced weight average molecular weight of 3.0 × 10 ^{5 to} 3.0 × 10 ⁶ measured by gel permeation chromatography 100 parts by mass of a rubber component containing 40 to 100% by mass of a polymer (A) that is a conjugated diene compound polymer and hydrogenated at 20% to less than 60% of the unsaturated bonds of the conjugated diene compound part. ,
An aromatic vinyl compound-conjugated diene compound copolymer or conjugated diene compound polymer, having a polystyrene-reduced weight average molecular weight of 1.0 × 10 ^{3 to} 2.0 × 10 ⁵ measured by gel permeation chromatography 10 to 200 parts by mass of combined (B),
A rubber composition comprising 5 to 100 parts by mass of a thermoplastic resin (C) having a softening point of 80 ° C. or higher.   The rubber composition according to claim 1, wherein the polymer (A) is a styrene-butadiene copolymer.   The rubber composition according to claim 2, wherein the styrene-butadiene copolymer has a bound styrene content of 20 to 40% by mass.   The rubber composition according to claim 2, wherein the styrene portion of the styrene-butadiene copolymer has a vinyl bond content of 30 to 60%.   2. The rubber composition according to claim 1, wherein 30% to 50% of the unsaturated bond in the conjugated diene compound portion of the polymer (A) is hydrogenated.   The rubber composition according to claim 1, wherein the rubber component is a non-hydrogenated styrene-butadiene copolymer with the remainder of the polymer (A).   The rubber composition according to claim 1, wherein the polymer (B) is a styrene-butadiene copolymer.   The rubber composition according to claim 7, wherein the polymer (B) has a bound styrene content of 60% by mass or less.   2. The rubber composition according to claim 1, wherein 20% to 100% of the unsaturated bond of the conjugated diene compound portion of the polymer (B) is hydrogenated.   10. The rubber composition according to claim 9, wherein 40% to 90% of unsaturated bonds in the conjugated diene compound portion of the polymer (B) are hydrogenated.   The rubber composition according to claim 1, wherein 10 to 120 parts by mass of the polymer (B) is blended with 100 parts by mass of the rubber component.   The rubber composition according to claim 1, wherein the polymer (B) has a polystyrene-reduced weight average molecular weight of 2,000 or more and less than 12,000 as measured by gel permeation chromatography.   A pneumatic tire using the rubber composition according to claim 1 for a tread rubber.