JP2013091756A - Rubber composition for tire and pneumatic tire - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a rubber composition for a tire, wherein low fuel consumption, wet-grip performance, and breaking performance can be improved well-balancedly; and to provide a pneumatic tire using the same.SOLUTION: A rubber composition for a tire comprises: a rubber component that contains 5 mass% or more of a modified diene rubber having a functional group interacting with a silica; the silica; and a resin obtained by copolymerizing a phenolic compound (a), a terpene compound (b), and an aromatic vinyl compound (c).

Description

The present invention relates to a rubber composition for tires and a pneumatic tire using the same.

In recent years, in response to the demand for lower fuel consumption of automobiles, development of tires that reduce the rolling resistance of the tires and suppress heat generation has been promoted. Among the tire members, excellent low heat generation (low fuel consumption) is required for a tread having a high occupation ratio in the tire. In order to solve such a problem, carbon black that has been conventionally used as a reinforcing agent in tire treads has been partially replaced with silica. Furthermore, as a method of satisfying low fuel consumption, it is known to reduce the amount of silica, which is a reinforcing filler, and to use a filler with a small reinforcing property. There was a problem that the grip performance was greatly reduced.

On the other hand, it is considered that a rubber composition having a good balance between fuel efficiency and grip performance can be obtained if the bond between rubber and silica as a reinforcing filler becomes stronger. Therefore, in order to increase the reinforcing property of the silica by improving the dispersibility of the silica or chemically combining the rubber and the silica in order to make the reinforcing property of the silica the same level as the carbon black, the silane cup Studies have been made on modified polymers for silica having a functional group that interacts with a ring agent or silica (for example, Patent Document 1). However, a polymer having a functional group that interacts with silica has the merit of improving the dispersibility of silica and improving fuel efficiency, but if the reactivity with silica is too strong, the fracture performance may be deteriorated. There are also disadvantages.

In addition, in order to improve wet grip performance, a technique for improving wet grip performance by adding an oligomer such as styrene or α-methylstyrene or a terpene resin as a resin has been known.

When an oligomer such as styrene or α-methylstyrene is blended, the improvement in wet grip performance depends on the addition amount, and increasing the addition amount has a problem that the wet grip performance is improved but the fracture performance is lowered. Moreover, although the terpene resin has an effect of improving the fracture performance at an optimum amount, the effect of improving the wet grip performance is not as effective as that of an oligomer such as styrene or α-methylstyrene.

Therefore, it is conceivable to improve the balance between fuel efficiency, breaking performance, and wet grip performance by blending these resins. However, because each resin has a different compatibility with the polymer, It is difficult to disperse uniformly in the polymer, and the current situation is that the performance cannot be sufficiently improved with a simple blend.

JP 2010-111753 A

An object of the present invention is to solve the above-mentioned problems and to provide a rubber composition for a tire that can improve fuel economy, wet grip performance, and breaking performance in a well-balanced manner, and a pneumatic tire using the same.

The present invention relates to a rubber component containing 5% by mass or more of a modified diene rubber having a functional group that interacts with silica, silica, (a) a phenol compound, (b) a terpene compound, and (c) an aromatic. The present invention relates to a tire rubber composition containing a resin obtained by copolymerizing a vinyl compound.

The phenolic compound (a) is phenol and / or alkylphenol, the terpene compound (b) is a cyclic unsaturated hydrocarbon having no hydroxyl group, and the aromatic vinyl compound (c) is styrene and / or alkyl-substituted styrene. It is preferable that

The terpene compound (b) is preferably at least one selected from the group consisting of α-pinene, β-pinene, 3-carene, limonene and dipentene.

It is preferable that the compounding quantity of resin is 1-25 mass parts with respect to 100 mass parts of rubber components.

（式中、Ｒ^１、Ｒ^２およびＲ^３は、同一若しくは異なって、アルキル基、アルコキシ基、シリルオキシ基、アセタール基、カルボキシル基、メルカプト基またはこれらの誘導体を表す。Ｒ^４およびＲ^５は、同一若しくは異なって、水素原子、アルキル基または環状エーテル基を表す。ｎは整数を表す。） The modified diene rubber is preferably butadiene rubber and / or styrene butadiene rubber modified with a compound represented by the following formula (1).

(Wherein R ¹ , R ² and R ³ are the same or different and each represents an alkyl group, an alkoxy group, a silyloxy group, an acetal group, a carboxyl group, a mercapto group or a derivative thereof. R ⁴ and R ⁵ are (The same or different, and represents a hydrogen atom, an alkyl group or a cyclic ether group. N represents an integer.)

The tire rubber composition is preferably used for a tire tread.

The present invention also relates to a pneumatic tire produced using the rubber composition.

According to the present invention, a resin obtained by copolymerizing a specific amount of the modified diene rubber, silica, (a) a phenol compound, (b) a terpene compound, and (c) an aromatic vinyl compound. Therefore, the use of the rubber composition for tire members (especially cap treads) makes it possible to produce a pneumatic tire with a good balance of fuel efficiency, wet grip performance and breaking performance. Can provide.

The rubber composition for tires of the present invention includes a rubber component containing 5% by mass or more of a modified diene rubber having a functional group that interacts with silica, silica, (a) a phenol compound, and (b) a terpene compound. And (c) a resin obtained by copolymerizing an aromatic vinyl compound.

In the present invention, a specific amount of the modified diene rubber, silica, and a resin obtained by copolymerizing (a) a phenol compound, (b) a terpene compound and (c) an aromatic vinyl compound. Since it contains, it can synergistically improve fuel efficiency, wet grip performance, and breaking performance, and improve fuel economy, wet grip performance, and breaking performance in a well-balanced manner.

In the present invention, a modified diene rubber having a functional group that interacts with silica is used as the rubber component.

As the modified diene rubber, for example, at least one terminal of the diene rubber is modified with a compound (modifier) having a functional group containing at least one atom selected from the group consisting of nitrogen, oxygen and silicon. Terminal modified diene rubber, main chain modified diene rubber having the above functional group in the main chain, main chain terminal modified diene rubber having the above functional group in the main chain and terminal (for example, the above functional group in the main chain) And main chain terminal modified diene rubber having at least one terminal modified with the above modifier.

Examples of the functional groups include amino groups, amide groups, alkoxysilyl groups, isocyanate groups, imino groups, imidazole groups, urea groups, ether groups, carbonyl groups, carboxyl groups, hydroxyl groups, nitrile groups, pyridyl groups, alkoxy groups, and the like. Can be given. These functional groups may have a substituent. Among these, an alkoxy group (preferably an alkoxy group having 1 to 6 carbon atoms), an amino group (preferably a hydrogen atom contained in the amino group has 1 to 6 carbon atoms) because it has a high effect of improving fuel economy and destruction performance An amino group substituted with an alkyl group) or an alkoxysilyl group (preferably an alkoxysilyl group having 1 to 6 carbon atoms).

Examples of the diene rubber (polymer constituting the skeleton of the modified diene rubber) into which the functional group is introduced include natural rubber (NR), isoprene rubber (IR), butadiene rubber (BR), styrene butadiene rubber (SBR), Examples thereof include styrene isoprene butadiene rubber (SIBR), ethylene propylene diene rubber (EPDM), chloroprene rubber (CR), acrylonitrile butadiene rubber (NBR) and the like. Of these, IR, BR, and SBR are preferable, and BR and SBR are more preferable.

（式中、Ｒ^１、Ｒ^２およびＲ^３は、同一若しくは異なって、アルキル基、アルコキシ基（好ましくは炭素数１〜８、より好ましくは炭素数１〜６、更に好ましくは炭素数１〜４のアルコキシ基）、シリルオキシ基、アセタール基、カルボキシル基（−ＣＯＯＨ）、メルカプト基（−ＳＨ）またはこれらの誘導体を表す。Ｒ^４およびＲ^５は、同一若しくは異なって、水素原子、アルキル基（好ましくは炭素数１〜４のアルキル基）または環状エーテル基（好ましくはエーテル結合を１つ有する炭素数３〜５の環状エーテル基（例えば、オキセタン基））を表す。ｎは整数（好ましくは１〜５、より好ましくは２〜４、更に好ましくは３）を表す。） As the modifying agent, a compound represented by the following formula (1) (a compound described in JP 2010-111753 A) is preferable. Thereby, it is easy to control the molecular weight of the polymer, the low molecular weight component that increases tan δ can be reduced, the bond between the silica and the polymer chain is moderately strengthened, and the fuel economy and breaking performance can be further improved.

(In formula, R < ¹ >, R < ² > and R < ³ > are the same or different and are an alkyl group and an alkoxy group (preferably C1-C8, More preferably C1-C6, More preferably C1-C4 An alkoxy group), a silyloxy group, an acetal group, a carboxyl group (—COOH), a mercapto group (—SH) or a derivative thereof, and R ⁴ and R ⁵ are the same or different and represent a hydrogen atom, an alkyl group (preferably Represents an alkyl group having 1 to 4 carbon atoms) or a cyclic ether group (preferably a cyclic ether group having 3 to 5 carbon atoms (for example, oxetane group) having one ether bond), and n is an integer (preferably 1 to 1). 5, more preferably 2-4, still more preferably 3).)

As R ¹ , R ² and R ³ , an alkoxy group is desirable, and as R ⁴ and R ⁵ , an alkyl group is desirable. Thereby, the outstanding low fuel consumption and destruction performance can be obtained.

Specific examples of the compound represented by the above formula (1) include 3-aminopropyldimethylmethoxysilane, 3-aminopropylmethyldimethoxysilane, 2-dimethylaminoethyltrimethoxysilane, 3-diethylaminopropyltrimethoxysilane, 3 -Dimethylaminopropyltrimethoxysilane etc. are mentioned. These may be used alone or in combination of two or more.

Examples of the method for modifying the diene rubber with the compound (modifier) represented by the above formula (1) are described in JP-B-6-53768, JP-B-6-57767, JP-T2003-514078, and the like. A conventionally known method such as a known method can be used. For example, a diene rubber and a modifying agent may be brought into contact with each other. Examples thereof include a method of adding a modifying agent to the prepared diene rubber solution to cause a reaction.

（式中、Ｒ^２１は、炭素数が１〜１０の炭化水素基を表す。） The main chain-modified diene rubber can be polymerized using a conventionally known method. For example, as part of the monomer used for polymerization, a monomer having the above functional group (for example, a compound represented by the following formula (2) such as p-methoxystyrene, 3- or 4- (2-pyrrolidinoethyl) It can be obtained by polymerization using a nitrogen-containing compound such as styrene). The main chain terminal-modified diene rubber is obtained, for example, by bringing a main chain modified diene rubber and a modifier into contact with each other.

(In the formula, R ²¹ represents a hydrocarbon group having 1 to 10 carbon atoms.)

In the above formula ^{(2), R 21} has a carbon number represents 1-10 hydrocarbon group. If the carbon number exceeds 10, the cost tends to be high. In addition, there is a tendency that fuel efficiency and destruction performance cannot be sufficiently improved. The number of carbon atoms is preferably 1 to 8, more preferably 1 to 6, and still more preferably 1 to 3, from the viewpoint that the resulting polymer is highly effective in improving fuel economy and breaking performance.

Examples of the hydrocarbon group represented by R ²¹ include a monovalent aliphatic hydrocarbon group such as an alkyl group, and a monovalent aromatic hydrocarbon group such as an aryl group. R ²¹ is preferably an alkyl group, and more preferably a methyl group, from the viewpoint that the resulting polymer is highly effective in improving fuel economy and breaking performance.

（上記式（２−１）中のＲ^２１は、上記式（２）中のＲ^２１と同様である。） In addition, the compound represented by the following formula (2-1) is preferable among the compounds represented by the formula (2) from the viewpoint that the resulting copolymer has a high fuel economy and an improved effect of breaking performance. .

^{(R 21} in the formula (2-1) is the same as ^{R 21} in the formula (2).)

Examples of the compound represented by the formula (2) include p-methoxystyrene, p-ethoxystyrene, p- (n-propoxy) styrene, p- (tert-butoxy) styrene, m-methoxystyrene, and the like. . These may be used alone or in combination of two or more.

The content of the compound represented by the above formula (2) in 100% by mass of the modified diene rubber (alkoxystyrene component content) is preferably 0.05% by mass or more, more preferably 0.5% by mass or more, More preferably, it is 1 mass% or more. If it is less than 0.05% by mass, it may be difficult to obtain an effect of improving fuel economy and breaking performance. The content is preferably 30% by mass or less, more preferably 15% by mass or less, still more preferably 5% by mass or less, and particularly preferably 2% by mass or less. When it exceeds 30 mass%, there exists a tendency for the effect corresponding to the increase in cost not to be acquired.
The alkoxystyrene component content can be measured using NMR (for example, JNM-ECA series apparatus manufactured by JEOL Ltd.).

Examples of the nitrogen-containing compound include 3- or 4- (2-azetidinoethyl) styrene, 3- or 4- (2-pyrrolidinoethyl) styrene, 3- or 4- (2-piperidinoethyl) styrene, 3- or 4- (2-hexamethyleneiminoethyl) styrene and the like can be mentioned. These may be used alone or in combination of two or more. Among these, 3- or 4- (2-pyrrolidinoethyl) styrene is preferable from the viewpoint that silica can be more favorably dispersed.

The content of the nitrogen-containing compound in 100% by mass of the modified diene rubber is preferably 0.05% by mass or more, more preferably 0.1% by mass or more. If it is less than 0.05% by mass, there is a tendency that it is difficult to obtain an effect of improving fuel economy and breaking performance. The content is preferably 10% by mass or less, more preferably 5% by mass or less. When it exceeds 10 mass%, there exists a tendency for the effect corresponding to the increase in cost not to be acquired.
In addition, content of a nitrogen-containing compound can be measured using NMR (For example, the apparatus of the JNM-ECA series by JEOL Co., Ltd.).

Among the above-mentioned modified diene rubbers, at least one terminal is modified with the compound represented by the above formula (1) because of the high effect of improving fuel economy and breaking performance (particularly fuel economy). A butadiene rubber, preferably a styrene butadiene rubber having at least one terminal modified with a compound represented by the above formula (1), is copolymerized with 1,3-butadiene, styrene and the compound represented by the above formula (2). Obtained by copolymerization of styrene butadiene rubber, 1,3-butadiene and the nitrogen-containing compound modified at least at one end with the compound represented by the above formula (1). A butadiene rubber modified with the compound represented by the above formula (1) is more preferable. Also, a butadiene rubber modified with a compound represented by the above formula (1) at least one end and a styrene butadiene rubber modified with a compound represented by the above formula (1) at least one end are used in combination. It is also preferable to do.

The content of the modified diene rubber in 100% by mass of the rubber component is 5% by mass or more, preferably 15% by mass or more, and more preferably 50% by mass or more. If it is less than 5% by mass, sufficient fuel economy and destructive performance cannot be obtained. The upper limit of the content of the modified diene rubber is not particularly limited, and may be 100% by mass.

Examples of the rubber component that can be used other than the modified diene rubber include the diene rubber. Of these, BR and SBR are preferable.

In the present invention, a resin obtained by copolymerizing (a) a phenol compound, (b) a terpene compound and (c) an aromatic vinyl compound is used.

(A) The phenolic compound is not particularly limited as long as it has a phenolic hydroxyl group. For example, phenol, alkylphenol, alkoxyphenol (the number of carbon atoms of the alkoxy group is the same as that of the alkyl group), chlorine atom. And monovalent phenols such as halogenated phenols containing halogen atoms such as bromine atoms and unsaturated hydrocarbon group-containing phenols. Of these, alkylphenols in which at least one of phenol, o, m, and p-position is substituted with an alkyl group are preferable, and phenol is more preferable, from the viewpoint that fuel economy, wet grip performance, and breaking performance can be improved in a balanced manner.

Carbon number of the alkyl group in the alkylphenol is preferably 1 to 10, more preferably 1 to 5.
Specific examples of the alkylphenol include, for example, methylphenol, ethylphenol, butylphenol, t-butylphenol, octylphenol, nonylphenol, decylphenol, and dinonylphenol, and any of o, m, and p positions may be substituted. Of these, t-butylphenol and methylphenol are preferable.

Examples of the alkoxyphenol include methoxyphenol substituted with an alkoxy group corresponding to the alkyl group of the aforementioned alkylphenol.
Examples of the halogenated phenol include chlorophenol and bromophenol.

Examples of the unsaturated hydrocarbon group-containing phenol include compounds having at least one hydroxyphenyl group in one molecule and at least one of the hydrogen atoms of the phenyl group substituted with an unsaturated hydrocarbon group. . Examples of the unsaturated bond in the unsaturated hydrocarbon group include a double bond and a triple bond. Examples of the unsaturated hydrocarbon group include alkenyl groups having 2 to 10 carbon atoms. Specific examples of the unsaturated substituent-containing phenol include isopropenyl phenol and butenyl phenol. These phenolic compounds may be used alone or in combination of two or more.

(B) The terpene compound is a hydrocarbon represented by a composition of (C ₅ H ₈ ) _n and an oxygen-containing derivative thereof, and includes monoterpene (C ₁₀ H ₁₆ ), sesquiterpene (C ₁₅ H ₂₄ ), diterpene ( And compounds having terpenes classified as C ₂₀ H ₃₂ ) as the basic skeleton. The terpene compound is not particularly limited, but is preferably a cyclic unsaturated hydrocarbon, and is preferably a compound having no hydroxyl group.

Specific examples of the terpene compound include α-pinene, β-pinene, 3-carene (δ-3-carene), dipentene, limonene, myrcene, allocymene, ocimene, α-ferrandrene, α-terpinene, and γ-terpinene. , Terpinolene, 1,8-cineole, 1,4-cineole, α-terpineol, β-terpineol, γ-terpineol and the like. Among these, α-pinene, β-pinene, 3-carene (δ-3-carene), dipentene, and limonene are preferable because of low fuel consumption, wet grip performance, and breakage performance, and α-pinene, β-pinene and 3-carene are more preferable. These terpene compounds may be used alone or in combination of two or more.

(C) The aromatic vinyl compound is not particularly limited as long as it is a compound having an aromatic ring and a vinyl group. For example, styrene; α-methylstyrene, α-ethylstyrene, 4-cyclohexylstyrene, 2,4, Examples include alkyl-substituted styrene such as 6-trimethylstyrene and t-butylstyrene. Other examples include 1-vinylnaphthalene, 3-vinyltoluene, ethylvinylbenzene, divinylbenzene, 4-cyclohexylstyrene, 2,4,6-trimethylstyrene, and the like. These may be used alone or in combination of two or more. Of these, styrene and alkyl-substituted styrene are preferable, and styrene; α-methylstyrene is more preferable because low fuel consumption, wet grip performance, and breaking performance can be improved in a balanced manner. These aromatic vinyl compounds may be used alone or in combination of two or more.

10-70 mass% is preferable and, as for the copolymerization ratio of the phenol type compound (a) in the said resin (100 mass%), 10-50 mass% is more preferable. If it is less than 10% by mass, the fracture performance and wet grip performance tend to be poor, and if it exceeds 70% by mass, the fuel economy and fracture performance tend to be poor.

10-70 mass% is preferable and, as for the copolymerization ratio of a terpene type compound (b), 10-50 mass% is more preferable. If the amount is less than 10% by mass, the breaking performance and fuel efficiency are likely to deteriorate. If the amount exceeds 70% by mass, the wet grip performance and fuel efficiency are likely to deteriorate.

10-70 mass% is preferable and, as for the copolymerization ratio of an aromatic vinyl type compound (c), 10-50 mass% is more preferable. If it is less than 10% by mass, the wet grip performance tends to deteriorate, and if it exceeds 70% by mass, the fracture performance and fuel efficiency tend to deteriorate.

The softening point of the resin is not particularly limited, but is preferably 30 to 180 ° C, more preferably 40 to 150 ° C, and further preferably 50 to 120 ° C. If the softening point is less than 30 ° C, the effect of improving wet grip performance tends to be small, and if it exceeds 180 ° C, fuel efficiency tends to deteriorate.
The softening point of the resin is the temperature at which the sphere descends when the softening point specified in JIS K 6220-1: 2001 is measured with a ring and ball softening point measuring device.

Although the weight average molecular weight Mw of the said resin is not specifically limited, 300-5000 are preferable and 300-2000 are more preferable. If Mw is less than 300, the effect of improving wet grip performance tends to be small, and if it exceeds 5000, fuel efficiency tends to deteriorate.
In this specification, Mw is a value converted from standard polystyrene using a gel permeation chromatograph (GPC).

The resin can be synthesized by copolymerizing (a), (b) and (c) by a known method. For example, prepared by dropping a phenol compound, a terpene compound and an aromatic vinyl compound in an arbitrary order in an organic solvent such as toluene in the presence of a catalyst such as BF ₃ and reacting them at a predetermined temperature and time. it can.

1-25 mass parts is preferable with respect to 100 mass parts of rubber components, as for the compounding quantity of resin, 3-20 mass parts is more preferable, and 5-15 mass parts is more preferable. If it is less than 1 part by mass, sufficient wet grip performance tends not to be obtained, and if it exceeds 25 parts by mass, fuel economy and destruction performance tend to be reduced.

In the present invention, silica is used. By blending silica together with the modified diene rubber and the resin, good fuel efficiency and wet grip performance can be obtained. The silica is not particularly limited, and examples thereof include dry process silica (anhydrous silicic acid), wet process silica (hydrous silicic acid), and the like, but wet process silica is preferable because of its large number of silanol groups.

The nitrogen adsorption specific surface area (N ₂ SA) of silica is preferably 30 m ² / g or more, more preferably 50 m ² / g or more, and still more preferably 80 m ² / g or more. If it is less than 30 m ² / g, the reinforcing effect is small, and the fracture performance may not be sufficiently improved. The _N 2 SA of the silica is preferably not more than 500 meters ² / g, more preferably at most 250m ² / g. When it exceeds 500 m < ² > / g, the dispersibility of a silica will fall and there exists a tendency for low-fuel-consumption property, workability, and destructive performance to fall.
The nitrogen adsorption specific surface area of silica is a value measured by the BET method according to ASTM D3037-81.

The content of silica is preferably 5 parts by mass or more, more preferably 20 parts by mass or more, and still more preferably 50 parts by mass or more with respect to 100 parts by mass of the rubber component. When the amount is less than 5 parts by mass, there is a tendency that a sufficient effect due to silica blending cannot be obtained. The content of the silica is preferably 150 parts by mass or less, more preferably 120 parts by mass or less, and still more preferably 100 parts by mass or less. If it exceeds 150 parts by mass, it will be difficult to disperse silica into rubber, and fuel economy, processability, and breaking performance tend to be reduced.

The rubber composition of the present invention preferably uses a silane coupling agent in combination with silica. As the silane coupling agent, any silane coupling agent conventionally used in combination with silica can be used in the rubber industry. For example, sulfide systems such as bis (3-triethoxysilylpropyl) tetrasulfide, 3 -Mercapto type such as mercaptopropyltrimethoxysilane, vinyl type such as vinyltriethoxysilane, amino type such as 3-aminopropyltriethoxysilane, glycidoxy type of γ-glycidoxypropyltriethoxysilane, 3-nitropropyltri Examples thereof include nitro compounds such as methoxysilane and chloro compounds such as 3-chloropropyltrimethoxysilane. These may be used alone or in combination of two or more. Among these, sulfide type is preferable, and bis (3-triethoxysilylpropyl) tetrasulfide is more preferable.

The content of the silane coupling agent is preferably 3 parts by mass or more, more preferably 6 parts by mass or more with respect to 100 parts by mass of silica. If it is less than 3 parts by mass, the wear resistance and fracture performance tend to deteriorate. Further, the content of the silane coupling agent is preferably 20 parts by mass or less, more preferably 12 parts by mass or less. When it exceeds 20 parts by mass, there is a tendency that an effect commensurate with the increase in cost cannot be obtained.

In the present invention, it is preferable to blend a softener from the viewpoint of grip performance and the like.
Although it does not specifically limit as a softening agent, Oils, such as mineral oil, are mentioned. Examples of the oil include process oils such as paraffinic process oil, aroma based process oil, and naphthenic process oil.

The oil content is preferably 3 parts by mass or more, more preferably 5 parts by mass or more with respect to 100 parts by mass of the rubber component. If it is less than 3 parts by mass, processability and wet grip performance may be deteriorated. The oil content is preferably 40 parts by mass or less, more preferably 30 parts by mass or less. When it exceeds 40 parts by mass, there is a possibility that sufficient low fuel consumption and destruction performance may not be obtained.

The total content of the resin and oil is preferably 3 parts by mass or more with respect to 100 parts by mass of the rubber component. If the amount is less than 3 parts by mass, sufficient grip performance tends not to be obtained. The total content is preferably 65 parts by mass or less, more preferably 40 parts by mass or less, and still more preferably 30 parts by mass or less. When it exceeds 65 parts by mass, the wear resistance and fracture performance tend to deteriorate.

In addition to the above components, the rubber composition of the present invention includes compounding agents generally used in the production of rubber compositions, for example, reinforcing fillers such as carbon black and clay, zinc oxide, stearic acid, various anti-aging agents. A vulcanizing agent such as an agent, wax, sulfur, a vulcanization accelerator, and the like can be appropriately blended.

As a method for producing the rubber composition for tires of the present invention, known methods can be used. For example, the above components are kneaded using a rubber kneader such as an open roll or a Banbury mixer, and then vulcanized. Etc. can be manufactured.

The rubber composition of the present invention can be used for each member of a tire, and among these, it is preferably used for a tread portion, and particularly preferably used for a cap tread. By using it for the cap tread, it is possible to obtain an excellent balance of fuel efficiency, wet grip performance and breaking performance.

The pneumatic tire of the present invention is produced by a usual method using the rubber composition.
That is, the rubber composition containing the above components is extruded in accordance with the shape of each tire member such as a tread at an unvulcanized stage, and is molded together with the other tire members by a normal method on a tire molding machine. By doing so, an unvulcanized tire is formed. The unvulcanized tire is heated and pressurized in a vulcanizer to obtain a tire.

The present invention will be specifically described based on examples, but the present invention is not limited to these examples.

(Production Examples 1-4)
<Chemicals used>
The chemicals used for resin synthesis are shown below. In addition, the chemical | medical agent refine | purified according to the usual method as needed.
Toluene: α-pinene manufactured by Kanto Chemical Co., Ltd. 3-carene manufactured by Tokyo Chemical Industry Co., Ltd .: phenol manufactured by Tokyo Chemical Industry Co., Ltd .: styrene manufactured by Wako Pure Chemical Industries, Ltd. α manufactured by Tokyo Chemical Industry Co., Ltd. -Methylstyrene: Boron trifluoride (BF ₃ ) manufactured by Tokyo Chemical Industry Co., Ltd .: Sodium carbonate manufactured by Tokyo Chemical Industry Co., Ltd .: manufactured by Tokyo Chemical Industry Co., Ltd.

<Synthesis method>
A three-necked flask equipped with a thermometer, a stirrer, a cooler, and a Dean-Stark trap was thoroughly purged with nitrogen, and 200 g of toluene was added thereto. 16g of phenol was added to this, and stirring and refluxing were performed for 2 hours. As a catalyst, 1.2 g of BF ₃ gas was added, 42 g of α-pinene was added dropwise over a period of about 90 minutes, and then 42 g of styrene was added dropwise over a period of about 30 minutes, while stirring at 40 ° C. for 60 minutes under nitrogen. Polymerization was performed. After completion of the reaction, 1.2 g of sodium carbonate dissolved in 100 ml of water was added to stop the reaction, and the catalyst was removed by repeating washing with water. Toluene and unreacted monomers were removed by distillation under reduced pressure to obtain the intended resin A.
Resins B to D were synthesized in the same manner as Resin A, except that 3-carene was used instead of α-pinene, α-methylstyrene was used instead of styrene, and the addition amount was changed to the amount shown in Table 1.
Table 1 shows the composition, softening point, and molecular weight of the synthesized resin. The molecular weight and softening point were measured by the following methods.

(Measurement of weight average molecular weight (Mw), number average molecular weight (Mn))
Mw and Mn are based on values measured by gel permeation chromatograph (GPC) (GPC-8000 series manufactured by Tosoh Corporation, detector: differential refractometer, column: TSKGEL SUPERMALTPORE HZ-M manufactured by Tosoh Corporation). Was obtained by standard polystyrene conversion.

(Softening point)
The softening point was determined by measuring the softening point defined in JIS K 6220-1: 2001 with a ring-and-ball type softening point measuring device and setting the temperature at which the sphere descended as the softening point.

Hereinafter, various chemicals used in Production Examples 5 and 6 will be described together. In addition, the chemical | medical agent refine | purified according to the usual method as needed.
<Chemicals used>
n-hexane: Kanto Chemical Co., Ltd. Styrene: Kanto Chemical Co., Ltd. 1,3-Butadiene: Tokyo Chemical Industry Co., Ltd. p-methoxystyrene: Kanto Chemical Co., Ltd. Tetramethylethylenediamine: Kanto Chemical Co., Ltd. ) N-butyllithium manufactured: 1.6M n-butyllithium hexane solution manufactured by Kanto Chemical Co., Ltd .: 3-dimethylaminopropyltrimethoxysilane manufactured by AMAX Co. (compound represented by the above formula (1))
2,6-tert-butyl-p-cresol: NOCRACK 200 manufactured by Ouchi Shinsei Chemical Co., Ltd.
Cyclohexane: Kanto Chemical Co., Ltd. Pyrrolidine: Kanto Chemical Co., Ltd. divinylbenzene: Sigma Aldrich 1.6M n-butyllithium hexane solution: Kanto Chemical Co., Ltd. Isopropanol: Kanto Chemical Co., Ltd. Tetramethylethylenediamine: manufactured by Kanto Chemical Co., Inc.

(Production Example 5)
(Preparation of main chain terminal modified solution polymerized styrene butadiene rubber)
Add 1500 ml of n-hexane, 100 mmol of styrene, 800 mmol of 1,3-butadiene, 5 mmol of p-methoxystyrene, 0.2 mmol of tetramethylethylenediamine, and 0.12 mmol of n-butyllithium to a heat-resistant container sufficiently purged with nitrogen at 0 ° C. Stir for 48 hours. Thereafter, 0.15 mmol of a modifier was added and stirred at 0 ° C. for 1 hour. Thereafter, alcohol was added to stop the reaction, and 1 g of 2,6-tert-butyl-p-cresol was added to the reaction solution, followed by reprecipitation purification to obtain a main chain terminal modified solution-polymerized styrene butadiene rubber.

(Production Example 6)
(Preparation of main chain terminal modified butadiene rubber)
Add 100 ml of cyclohexane, 4.1 ml (3.6 g) of pyrrolidine, and 6.5 g of divinylbenzene to a 100 ml container sufficiently purged with nitrogen, and then add 0.7 ml of 1.6 M n-butyllithium hexane solution at 0 ° C. and stir. did. After 1 hour, isopropanol was added to stop the reaction, and extraction and purification were performed to obtain a monomer (4- (2-pyrrolidinoethyl) styrene).
Next, 600 ml of cyclohexane, 71.0 ml of 1,3-butadiene (41.0 g), 0.29 g of monomer, and 0.11 ml of tetramethylethylenediamine were added to a 1000 ml pressure-resistant container sufficiently purged with nitrogen. 0.2 ml of 6M n-butyllithium hexane solution was added and stirred. After 3 hours, 0.5 ml (0.49 g) of the modifying agent was added and stirred. After 1 hour, 3 ml of isopropanol was added to terminate the polymerization. After adding 1 g of 2,6-tert-butyl-p-cresol to the reaction solution, it was reprecipitated with methanol and dried by heating to obtain a main chain terminal-modified butadiene rubber.

The obtained modified diene rubber (main chain terminal modified solution polymerized styrene butadiene rubber, main chain terminal modified butadiene rubber) was analyzed by the following method.

(Weight average molecular weight (Mw))
The weight average molecular weight (Mw) is measured by gel permeation chromatograph (GPC) (GPC-8000 series, manufactured by Tosoh Corp., detector: differential refractometer, column: TSKGEL SUPERMALTPORE HZ-M, manufactured by Tosoh Corp.). It calculated | required by standard polystyrene conversion based on the value.

(Measurement of alkoxystyrene component content, styrene component content, and nitrogen-containing compound content in the modified diene rubber)
The alkoxystyrene component content, the styrene component content, and the nitrogen-containing compound content in the modified diene rubber were measured using a JNM-ECA series device manufactured by JEOL Ltd.

Examples and Comparative Examples <Chemicals Used>
Various chemicals used in Examples and Comparative Examples will be described together.
BR: Ubepol BR150B (manufactured by Ube Industries)
Modified BR: main chain terminal-modified butadiene rubber synthesized in Production Example 6 (having a structural unit derived from a nitrogen-containing compound in the main chain, one terminal was modified with a compound represented by the above formula (1) Butadiene rubber) (vinyl content: 18% by mass, Mw: 300,000, content of nitrogen-containing compound: 2% by mass)
SBR: NS116 (manufactured by JSR Corporation, vinyl content: 60% by mass, styrene content: 20% by mass)
Modified SBR: main chain terminal modified solution-polymerized styrene butadiene rubber synthesized in Production Example 5 (having a structural unit derived from the compound represented by the above formula (2) in the main chain, one terminal of the above formula (1 ) (Styrene butadiene rubber modified with a compound represented by the formula) (alkoxy styrene component content: 1.2% by mass, styrene component content: 19% by mass, Mw: 500,000)
Silica: Ultrasil VN3 (Evonik Degussa, N ₂ SA: 175 m ² / g)
Silane coupling agent: Si69 (Evonik Degussa, bis (3-triethoxysilylpropyl) tetrasulfide)
Oil: Process X-140 (Japan Energy Co., Ltd.)
Resins A to D: Synthetic resin E in Production Examples 1 to 4: Kristalex 3085 (α-methylstyrene resin, manufactured by Eastman Chemical Co.)
Resin F: YS Resin PX1250 (terpene resin, manufactured by Yasuhara Chemical Co., Ltd.)
Resin G: YS Polystar T115 (terpene phenol resin, manufactured by Yasuhara Chemical Co., Ltd.)
Zinc oxide: Zinc oxide (Mitsui Metal Mining Co., Ltd.)
Stearic acid: Stearic acid “椿” (manufactured by NOF Corporation)
Anti-aging agent: NOCRACK 6C (Ouchi Shinsei Chemical Co., Ltd.) (N- (1,3-dimethylbutyl) -N'-phenyl-p-phenylenediamine)
Sulfur: Powdered sulfur (manufactured by Tsurumi Chemical Co., Ltd.)
Vulcanization accelerator NS: NOXERA-NS (N-tert-butyl-2-benzothiazolylsulfenamide) manufactured by Ouchi Shinsei Chemical Industry Co., Ltd.
Vulcanization accelerator DPG: Noxeller D (N, N'-diphenylguanidine) manufactured by Ouchi Shinsei Chemical Co., Ltd.

<Method for producing rubber composition>
According to the formulation shown in Table 2, materials other than sulfur and a vulcanization accelerator were kneaded for 5 minutes using a 1.7 L Banbury manufactured by Kobe Steel, and a kneaded product was obtained. Next, sulfur and a vulcanization accelerator were added to the obtained kneaded product, and kneaded for 5 minutes using an open roll to obtain an unvulcanized rubber composition. The obtained unvulcanized rubber composition was press vulcanized at 170 ° C. for 15 minutes to obtain a vulcanized rubber composition.

<Tire manufacturing method>
Using the obtained unvulcanized rubber composition, it was molded into a tread shape, bonded to another tire member, and press vulcanized at 170 ° C. for 10 minutes to produce a test tire of size 195 / 65R15.

<Evaluation method>
(Rolling resistance (low fuel consumption))
Using a viscoelastic spectrometer VES (manufactured by Iwamoto Seisakusho Co., Ltd.), the loss tangent of each compound (vulcanized rubber composition) under the conditions of temperature 50 ° C., initial strain 10%, dynamic strain 2%, frequency 10 Hz ( tan δ) was measured, and the loss tangent tan δ of Comparative Example 1 was set to 100, which was expressed as an index (rolling resistance index) by the following formula. The larger the index, the better the rolling resistance characteristics (low fuel consumption).
(Rolling resistance index) = (tan δ of Comparative Example 1) / (tan δ of each formulation) × 100

(Fracture performance (rubber strength))
Using the resulting vulcanized rubber composition, a No. 3 dumbbell-type rubber test piece was prepared, subjected to a tensile test according to JIS K 6251 “vulcanized rubber and thermoplastic rubber—determining tensile properties”, and fractured. Strength (TB) and elongation at break (EB) were measured, and the product (TB × EB) was calculated. The rubber strength (TB × EB) of each compound (vulcanized product) was indicated by an index according to the following formula. In addition, it shows that it is excellent in fracture performance (rubber strength) and is excellent in durability, so that a rubber strength index is large.
(Rubber Strength Index) = (TB × EB of each formulation) / ((TB × EB of Comparative Example 1) × 100

(Wet grip performance)
A test course with a manufactured test tire mounted on a 2000 cc domestic FR vehicle, watered and wetted, and braked at a speed of 70 km / h. (Brake distance) was measured. The value of the reciprocal of the braking distance was displayed as an index with Comparative Example 1 being 100. It shows that wet grip performance is so high that a numerical value is large.

From the result of Table 2, in Comparative Examples 1-3 which mix | blended the resin of (alpha) -methylstyrene, terpene, and terpene phenol, it was inferior compared with the Example to which low fuel consumption property, wet grip performance, and destruction performance respond | correspond. Also in Comparative Example 4 in which these were blended, the performance balance was quite bad.

On the other hand, a resin obtained by copolymerizing a specific amount of the modified diene rubber, silica, (a) a phenol compound, (b) a terpene compound, and (c) an aromatic vinyl compound (resins A to A). It has been clarified that by containing D), fuel economy, wet grip performance, and breaking performance are improved at the same time, and the performance balance can be remarkably improved.

Comparison between Example 3 and Comparative Examples 2, 5, and 6 shows that a specific amount of the modified diene rubber, silica, (a) a phenol compound, (b) a terpene compound, and (c) an aromatic vinyl compound. It has been found that by using together with a resin obtained by copolymerizing, low fuel consumption, wet grip performance, and breaking performance can be synergistically improved.

Claims (7)

A rubber component containing 5% by mass or more of a modified diene rubber having a functional group that interacts with silica, silica, (a) a phenol compound, (b) a terpene compound, and (c) an aromatic vinyl compound. A rubber composition for tires containing a resin obtained by copolymerization. The phenolic compound (a) is phenol and / or alkylphenol, the terpene compound (b) is a cyclic unsaturated hydrocarbon having no hydroxyl group, and the aromatic vinyl compound (c) is styrene and / or alkyl-substituted styrene. The rubber composition for tires according to claim 1, wherein The tire rubber composition according to claim 2, wherein the terpene compound (b) is at least one selected from the group consisting of α-pinene, β-pinene, 3-carene, limonene and dipentene. The rubber composition for a tire according to any one of claims 1 to 3, wherein the amount of the resin is 1 to 25 parts by mass with respect to 100 parts by mass of the rubber component. The tire rubber composition according to any one of claims 1 to 4, wherein the modified diene rubber is a butadiene rubber and / or a styrene butadiene rubber modified with a compound represented by the following formula (1).

(Wherein R ¹ , R ² and R ³ are the same or different and each represents an alkyl group, an alkoxy group, a silyloxy group, an acetal group, a carboxyl group, a mercapto group or a derivative thereof. R ⁴ and R ⁵ are (The same or different, and represents a hydrogen atom, an alkyl group, or a cyclic ether group. N represents an integer.) The tire rubber composition according to any one of claims 1 to 5, which is used for a tire tread. A pneumatic tire produced using the rubber composition according to claim 1.