JP2016000792A - Pneumatic tire - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a pneumatic tire having improved dry grip performance, wear resistance performance, and anti-chunking performance in a balanced manner.SOLUTION: A pneumatic tire comprises a tread composed of a rubber composition comprising a rubber component comprising styrene-butadiene rubber of 60-90 mass% and natural rubber of 10-40 mass%, and a resin obtained by copolymerization of a phenolic compound (a), a terpene compound (b) and an aromatic vinyl compound (c).

Description

The present invention relates to a pneumatic tire including a tread composed of a rubber composition.

The rubber composition for treads of pneumatic tires, particularly high performance dry tires, is strongly required to improve the balance between dry grip performance and wear resistance. Various measures have been made to ensure these performances. ing. Among them, a technique for improving dry grip performance by blending styrene butadiene rubber as a rubber component and a technique for improving wear resistance performance by blending natural rubber are known.

However, there is a problem that under the high temperature use conditions such as midsummer, the styrene butadiene rubber and the natural rubber are incompatible with each other. There is also a problem that the dry grip performance is deteriorated on a high-temperature road surface (for example, a road surface of 40 to 50 ° C.) by blending rubber.

There are various methods for improving the dry grip performance of a pneumatic tire obtained from a rubber composition containing natural rubber and styrene butadiene rubber. For grip performance particularly on high temperature road surfaces, resin (resin) ) Is known to be improved (for example, see Patent Document 1). However, for example, a resin made of styrene or α-methylstyrene has a problem in that if the amount added is too large, the fracture performance is deteriorated and sufficient chunking resistance cannot be ensured. Terpenic resins have the effect of improving wear resistance and preventing chunking by acting as a compatibilizer between natural rubber and styrene butadiene rubber. And there is a problem that it is not as effective as a resin made of α-methylstyrene.

Therefore, it is conceivable to improve the balance of dry grip performance, abrasion resistance and chunking resistance by blending these resins. However, since the solubility of each resin in the polymer is different, Since it is difficult for the resin to be uniformly dispersed in the polymer, the performance cannot be sufficiently improved by a simple blend.

On the other hand, a tire rubber composition containing a resin obtained by copolymerizing plural kinds of monomer components constituting these resins has been disclosed (for example, see Patent Documents 2 to 4). However, there is room for improvement in making the above performance balance even better.

JP-A-2005-350535 JP 2013-91755 A JP 2013-91757 A JP 2014-40523 A

An object of the present invention is to solve the above-mentioned problems and to provide a pneumatic tire in which dry grip performance, wear resistance, and chunking resistance are improved in a well-balanced manner.

The present invention relates to a rubber component containing 60 to 90% by mass of styrene butadiene rubber and 10 to 40% by mass of natural rubber, a phenol compound (a), a terpene compound (b), and an aromatic vinyl compound (c). The present invention relates to a pneumatic tire provided with a tread composed of a rubber composition containing a resin obtained by copolymerization of

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 is preferred.

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

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

The ratio of the constituent components of the resin is phenolic compound (a)> terpene compound (b) ≧ aromatic vinyl compound (c), phenol compound (a) is 40 to 70% by mass, terpene compound ( It is preferable that b) and an aromatic vinyl type compound (c) are 15-30 mass%, respectively.

The rubber composition preferably contains 1 to 5 parts by mass of a mixture of an aliphatic carboxylic acid zinc salt and an aromatic carboxylic acid zinc salt with respect to 100 parts by mass of the rubber component.

The rubber composition preferably contains carbon black and / or silica.

The tread is preferably a cap tread.

It is preferable that the tread has a hardness of 25 to 40 in an atmosphere of 100 ° C.

According to the present invention, a pneumatic tire including a tread composed of a rubber composition containing a specific amount of styrene butadiene rubber and a specific amount of natural rubber and a resin obtained by copolymerizing a specific compound. Therefore, dry grip performance, wear resistance, and chunking resistance are improved in a well-balanced manner, and particularly wear resistance and chunking resistance are remarkably improved.

The pneumatic tire of the present invention includes a rubber component containing 60 to 90% by mass of styrene butadiene rubber and 10 to 40% by mass of natural rubber, a phenolic compound (a), a terpene compound (b), and an aromatic vinyl type. A tread composed of a rubber composition containing a resin obtained by copolymerizing the compound (c) is provided. Hereinafter, the rubber composition is also referred to as a rubber composition according to the present invention.

The rubber composition according to the present invention contains styrene butadiene rubber (SBR). Thereby, the effect of this invention is acquired suitably.
The SBR is not particularly limited, and for example, those commonly used in the tire industry such as emulsion polymerization styrene butadiene rubber (E-SBR), solution polymerization styrene butadiene rubber (S-SBR) can be used. Of these, E-SBR is preferable because of its excellent dry grip performance, wear resistance, and chunking resistance.

The styrene content of SBR is preferably 25% by mass or more, and more preferably 35% by mass or more. When the styrene content is less than 25% by mass, there is a tendency that sufficient dry grip performance cannot be obtained. The styrene content is preferably 60% by mass or less, and more preferably 50% by mass or less. When the styrene content exceeds 60% by mass, not only the wear resistance performance decreases, but also the temperature dependency increases, and the performance change with respect to the temperature change tends to increase.
In addition, the styrene content of SBR is calculated by ¹ H-NMR measurement.

The content of SBR in 100% by mass of the rubber component is 60% by mass or more, preferably 62% by mass or more, and more preferably 65% by mass or more. If the SBR content is less than 60% by mass, sufficient dry grip performance cannot be obtained. The SBR content is 90% by mass or less, preferably 80% by mass or less, and more preferably 75% by mass or less. When the SBR content exceeds 90% by mass, the effect of blending SBR with natural rubber (NR) cannot be obtained, and the effect of the present invention cannot be sufficiently obtained. By setting the SBR content within the above range, the effects of the present invention can be suitably obtained. Here, the amount of the rubber component and the amount of SBR mean the amount of each solid content.

The rubber composition according to the present invention contains NR. Thereby, the effect of this invention is acquired suitably.
The NR is not particularly limited, and for example, those commonly used in the tire industry such as SIR20, RSS # 3, TSR20, and the like can be used.

The content of NR in 100% by mass of the rubber component is 10% by mass or more, preferably 20% by mass or more, more preferably 25% by mass or more. When the NR content is less than 10% by mass, the effect of blending rubber cannot be obtained, and the wear resistance performance is deteriorated. The NR content is 40% by mass or less, preferably 38% by mass or less, and more preferably 35% by mass or less. If the NR content exceeds 40% by mass, sufficient dry grip performance cannot be obtained. By making the content of NR within the above range, the effects of the present invention can be suitably obtained.

For the purpose of suitably obtaining the effects of the present invention, the total content of SBR and NR in 100% by mass of the rubber component is preferably 80% by mass or more, more preferably 90% by mass or more, and further preferably 100% by mass.

Examples of other rubber components that can be used other than SBR and NR include, but are not limited to, isoprene rubber (IR), butadiene rubber (BR), styrene isoprene butadiene rubber (SIBR), ethylene propylene diene rubber (EPDM), and chloroprene rubber ( CR), acrylonitrile butadiene rubber (NBR), diene rubber such as butyl rubber (IIR). Another rubber component may be used independently and may use 2 or more types together.

In the present invention, a resin obtained by copolymerizing a phenol compound (a), a terpene compound (b), and an aromatic vinyl compound (c) is used. By using the resin in combination with the specific amount of styrene butadiene rubber and the specific amount of natural rubber described above, the dry grip performance, wear resistance, and chunking resistance can be improved in a well-balanced manner, particularly wear resistance and chunking resistance. Can significantly improve the sex.

The phenolic compound (a) is not particularly limited as long as it has a phenolic hydroxyl group, and examples thereof include phenols, alkylphenols, alkoxyphenols, halogenated phenols containing halogen atoms such as chlorine atoms, bromine atoms, and the like. Examples thereof include monovalent phenols such as saturated hydrocarbon group-containing phenols. Of these, phenol and alkylphenol are preferable from the viewpoint of improving the dry grip performance, wear resistance, and chunking resistance in a well-balanced manner, and alkylphenol substituted at the p-position with an alkyl group is more preferable.

Carbon number of the alkyl group in the alkylphenol is preferably 1-10, more preferably 1-5.
Specific examples of the alkylphenol include, for example, methylphenol, ethylphenol, butylphenol, octylphenol, nonylphenol, decylphenol, and dinonylphenol. Among them, methylphenol and t-butylphenol are preferable.

Examples of the alkoxyphenol include phenol substituted with an alkoxy group corresponding to an alkyl group obtained by adding one oxygen atom to the alkyl group described above (for example, methoxyphenol, t-butoxyphenol), and the like. In addition, the preferable carbon atom number of an alkoxy group is the same as the preferable carbon atom number of the alkyl group mentioned above.
Examples of the halogenated phenol include chlorophenol and bromophenol.

Examples of the unsaturated hydrocarbon group-containing phenol include compounds in which at least one hydroxyphenyl group is contained in one molecule, and at least one of the hydrogen atoms of the phenyl group is substituted with an unsaturated hydrocarbon group. It is done. 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 isopropenylphenol and butenylphenol.
These phenolic compounds (a) may be used alone or in combination of two or more.

The terpene compound (b) is not particularly limited as long as it is a hydrocarbon represented by the composition of (C ₅ H ₈ ) _n and an oxygen-containing derivative thereof. For example, monoterpene (C ₁₀ H ₁₆ ), sesquioxide Examples thereof include compounds having terpenes classified as terpenes (C ₁₅ H ₂₄ ), diterpenes (C ₂₀ H ₃₂ ) and the like as a basic skeleton. The terpene compound (b) is preferably a cyclic unsaturated hydrocarbon, more preferably a cyclic unsaturated hydrocarbon having no hydroxyl group.

Specific examples of the terpene compound (b) include α-pinene, β-pinene, 3-carene (δ-3-carene), limonene, dipentene, myrcene, alloocimene, ocimene, α-ferrandrene, α-terpinene, γ-terpinene, terpinolene, 1,8-cineole, 1,4-cineole, α-terpineol, β-terpineol, γ-terpineol and the like can be mentioned. Among these, α-pinene, β-pinene, 3-carene (δ-3-carene), D-limonene, and dipentene are preferable because dry grip performance, wear resistance, and chunking resistance can be improved in a balanced manner. α-pinene, β-pinene, and 3-carene are more preferable, and α-pinene and β-pinene are more preferable.
These terpene compounds (b) may be used alone or in combination of two or more.

The aromatic vinyl compound (c) 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 , 6-trimethylstyrene, alkyl-substituted styrene such as t-butylstyrene; other aromatic vinyl compounds such as 1-vinylnaphthalene, 3-vinyltoluene, ethylvinylbenzene, divinylbenzene, styrene, alkyl-substituted styrene Are preferable, and styrene and α-methylstyrene are more preferable. Among these, styrene is more preferable from the viewpoint of remarkably improving the chunking resistance. Further, α-methylstyrene is more preferable from the viewpoint of remarkably improving the dry grip performance on a high temperature road surface.
These aromatic vinyl compounds (c) may be used alone or in combination of two or more.

The blending ratio (mass%) of each copolymer component constituting the resin (100 mass%) satisfies the relationship of phenolic compound (a)> terpene compound (b) ≧ aromatic vinyl compound (c). It is preferable. If the amount of the phenolic compound is less than the amount of the terpene compound, the dry grip performance may not be sufficiently exerted. If the amount of the terpene compound is less than the amount of the aromatic vinyl compound, the wear resistance and chunking resistance deteriorate. there is a possibility.

The copolymerization ratio of the phenolic compound (a) in the resin (100% by mass) is preferably 40% by mass or more, more preferably 50% by mass or more, further preferably 56% by mass or more, and 58% by mass or more. It is particularly preferred that In addition, when the copolymerization ratio of the phenol compound (a) is less than 40% by mass, the dry grip performance at a high temperature may not be sufficiently exhibited. 70 mass% or less is preferable, as for the copolymerization ratio of this phenol type compound (a), 65 mass% or less is more preferable, and 62 mass% or less is further more preferable. In addition, when the copolymerization ratio of this phenol type compound (a) exceeds 70 mass%, there exists a tendency for chunking resistance to deteriorate.

The copolymerization ratio of the terpene compound (b) is preferably 15% by mass or more, more preferably 18% by mass or more, and further preferably 20% by mass or more. When the copolymerization ratio of the terpene compound (b) is less than 15% by mass, it tends to be difficult to obtain an effect of improving wear resistance and chunking resistance. The copolymerization ratio of the terpene compound (b) is preferably 30% by mass or less, more preferably 25% by mass or less, and further preferably 24% by mass or less. When the copolymerization ratio of the terpene compound (b) exceeds 30% by mass, the effect of improving dry grip performance and wear resistance tends to be small.

The copolymerization ratio of the aromatic vinyl compound (c) is preferably 15% by mass or more, and more preferably 16% by mass or more. When the copolymerization ratio of the aromatic vinyl compound (c) is less than 15% by mass, the chunking resistance tends to be insufficient. The copolymerization ratio of the aromatic vinyl compound (c) is preferably 30% by mass or less, more preferably 25% by mass or less, and further preferably 18% by mass or less. When the copolymerization ratio of the aromatic vinyl compound (c) exceeds 30% by mass, the effect of improving the wear resistance tends to be small.

The softening point of the resin is not particularly limited, but is preferably 30 ° C or higher, more preferably 50 ° C or higher, further preferably 90 ° C or higher, and particularly preferably 100 ° C or higher. The softening point of the resin is preferably 180 ° C. or lower, more preferably 150 ° C. or lower, and further preferably 120 ° C. or lower. If the softening point is less than 30 ° C., the effects of the present invention tend not to be obtained favorably, and if it exceeds 180 ° C., it tends to be difficult to mix with the polymer and wear resistance 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.

The weight average molecular weight Mw of the resin is not particularly limited, but is preferably 300 or more, more preferably 500 or more, still more preferably 800 or more, still more preferably 950 or more, and particularly preferably 1000 or more. If Mw is less than 300, the effect of improving dry grip performance and wear resistance tends to be small. The Mw is preferably 5000 or less, more preferably 3000 or less, still more preferably 2000 or less, and particularly preferably 1100 or less. When Mw exceeds 5000, the effect of the present invention tends not to be obtained suitably.
In the present specification, Mw is a value converted from standard polystyrene using a gel permeation chromatograph (GPC) method.

The molecular weight distribution of the resin is preferably 1 to 5 and more preferably 1 to 2 in order to improve fuel efficiency. The molecular weight distribution is determined by measuring the number average molecular weight (Mn) and the weight average molecular weight (Mw) by the GPC method and dividing Mw by Mn.

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

The amount of the resin is preferably 1 part by mass or more, more preferably 5 parts by mass or more, still more preferably 15 parts by mass or more, and particularly preferably 22 parts by mass or more with respect to 100 parts by mass of the rubber component. If the blending amount of the resin is less than 1 part by mass, the effect of improving all physical properties tends to be small. The amount of the resin is preferably 100 parts by mass or less, more preferably 40 parts by mass or less, further preferably 30 parts by mass or less, and particularly preferably 28 parts by mass or less. When the amount of the resin exceeds 100 parts by mass, the wear resistance performance tends to deteriorate.

The rubber composition according to the present invention preferably contains a fatty acid and / or a derivative thereof. Thereby, the effect of the present invention can be obtained more suitably.

The fatty acid and / or derivative thereof is not particularly limited, but palm oil, palm kernel oil, camellia oil, olive oil, almond oil, canola oil, peanut oil, rice sugar oil, cocoa butter, palm oil, soybean oil, Aliphatic carboxylic acids derived from vegetable oils such as cottonseed oil, sesame oil, linseed oil, castor oil, rapeseed oil, aliphatic carboxylic acids derived from animal oils such as beef tallow, aliphatic carboxylic acids chemically synthesized from petroleum, stearic acid, palmitic acid, myristic Acid, lauric acid, caprylic acid, oleic acid, linoleic acid and the like can be mentioned. Examples of the fatty acid derivatives include metal salts of the fatty acids. Examples of the metal salt include zinc salt, calcium salt, magnesium salt and the like. Various commercially available processing aids containing these fatty acids can also be suitably used. In these, since the effect of this invention can be acquired more suitably, the metal salt of aliphatic carboxylic acid, especially the zinc salt of aliphatic carboxylic acid are preferable.

The number of carbon atoms of the fatty acid and / or derivative thereof is preferably 4 or more, more preferably 6 or more, and still more preferably 8 or more. If the carbon number is less than 4, the dispersibility tends to deteriorate. The number of carbon atoms is preferably 22 or less, more preferably 18 or less, still more preferably 16 or less, and particularly preferably 14 or less. When the carbon number exceeds 22, the effects of the present invention tend not to be obtained suitably.

The aliphatic group in the fatty acid and / or derivative thereof may be a chain structure such as an alkyl group or a cyclic structure such as a cycloalkyl group.

When the rubber composition according to the present invention contains a fatty acid and / or a derivative thereof, the content of the fatty acid and / or the derivative thereof is preferably 1 part by mass or more, more preferably 1 with respect to 100 parts by mass of the rubber component. .2 parts by mass or more. When the content is less than 1 part by mass, it is difficult to obtain an effect of improving dry grip performance. The content is preferably 5 parts by mass or less, more preferably 4 parts by mass or less, and still more preferably 3 parts by mass or less. When the content exceeds 5 parts by mass, the viscosity is unnecessarily lowered and the processability tends to deteriorate as described later, and the fatty acid and / or the derivative thereof tend to bloom. In addition, content of a fatty acid and / or its derivative means the total content of a fatty acid and a derivative of a fatty acid.

The rubber composition according to the present invention preferably further contains an aromatic carboxylic acid and / or a derivative thereof. By using a fatty acid and / or a derivative thereof in combination with an aromatic carboxylic acid and / or a derivative thereof, the effects of the present invention can be obtained more suitably.

Examples of the aromatic carboxylic acid include benzoic acid, phthalic acid, mellitic acid, hemimellitic acid, trimellitic acid, diphenic acid, toluic acid, and naphthoic acid. Examples of the derivative of the aromatic carboxylic acid include metal salts of the aromatic carboxylic acid. Examples of the metal salt include zinc salt, calcium salt, magnesium metal salt and the like. Especially, since the effect of this invention is acquired more suitably, the metal salt of aromatic carboxylic acid, especially zinc salt are preferable. As the aromatic carboxylic acid, benzoic acid, phthalic acid or naphthoic acid is more preferable.

When the rubber composition according to the present invention contains an aromatic carboxylic acid and / or derivative thereof, the content of the aromatic carboxylic acid and / or derivative thereof is preferably 0.1 with respect to 100 parts by mass of the rubber component. It is at least part by mass, more preferably at least 0.2 part by mass, even more preferably at least 0.3 part by mass. When the content is less than 0.1 part by mass, the effect of the present invention cannot be obtained suitably, and the effect of improving the dry grip performance is difficult to obtain. The content is preferably 2 parts by mass or less, more preferably 1 part by mass or less. When the content exceeds 2 parts by mass, the viscosity is unnecessarily lowered and the processability is deteriorated, and the fatty acid and / or its derivative tends to bloom. In addition, content of aromatic carboxylic acid and / or its derivative means the total content of aromatic carboxylic acid and its derivative.

Among the above, the rubber composition according to the present invention contains a mixture of a zinc salt of an aliphatic carboxylic acid and a zinc salt of an aromatic carboxylic acid, so that particularly wear resistance, chunking resistance, hardness, etc. The effect which improves suitably is acquired and a performance balance can be improved remarkably. When the rubber composition contains the mixture, the content ratio of the aliphatic carboxylic acid zinc salt to the aromatic carboxylic acid zinc salt in the mixture [molar ratio: (aliphatic carboxylic acid zinc salt) / ( (Zinc salt of aromatic carboxylic acid), hereinafter referred to as the content ratio] is preferably 1/20 or more, more preferably 1/15 or more, further preferably 1/10 or more, and more preferably 1/5 or more. / 2 or more is particularly preferable. When the content ratio is less than 1/20, it is not possible to consider the environment or prepare for a future reduction in the amount of petroleum supplied, and the dispersibility and stability of the mixture tend to deteriorate. Further, the content ratio is preferably 20/1 or less, more preferably 15/1 or less, further preferably 10/1 or less, still more preferably 5/1 or less, and particularly preferably 2/1 or less. When the content ratio exceeds 20/1, the effect of the present invention tends not to be obtained suitably.

When using the said mixture, 3 mass% or more is preferable, as for the metal content rate in a mixture, 5 mass% or more is more preferable, and 12 mass% or more is further more preferable. When the metal content is less than 3% by mass, the performance balance tends not to be remarkably improved. The metal content is preferably 30% by mass or less, more preferably 25% by mass or less, and further preferably 22% by mass or less. When the metal content exceeds 30% by mass, the workability tends to decrease and the cost increases unnecessarily.

When the rubber composition according to the present invention contains the above mixture, the content of the mixture is preferably 1 part by mass or more, more preferably 1.1 parts by mass or more, further preferably 100 parts by mass of the rubber component. 1.2 parts by mass or more, particularly preferably 1.3 parts by mass or more. If content of this mixture is less than 1 mass part, there exists a tendency for the effect of this invention to become difficult to be acquired suitably. The content of the mixture is preferably 5 parts by mass or less, more preferably 4 parts by mass or less, still more preferably 3 parts by mass or less, and particularly preferably 2 parts by mass or less. When the content of the mixture exceeds 5 parts by mass, the improvement of the effect on the addition amount becomes small, and the cost tends to increase unnecessarily.

In the present invention, as a reinforcing filler, carbon black, silica, calcium carbonate, alumina, clay, talc, and the like can be arbitrarily selected from those conventionally used in rubber compositions for tires. Carbon black and silica are preferable, and carbon black is more preferable.

For the purpose of suitably obtaining the effects of the present invention, the content of carbon black in 100% by mass of the reinforcing filler is preferably 60% by mass or more, more preferably 80% by mass or more, and still more preferably. 100% by mass.

Examples of the carbon black include furnace black, acetylene black, thermal black, channel black, and graphite. Carbon blacks include channel carbon blacks such as EPC, MPC and CC; furnace carbon blacks such as SAF, ISAF, HAF, MAF, FEF, SRF, GPF, APF, FF, CF, SCF and ECF; FT and MT Thermal carbon black such as acetylene carbon black is exemplified. One or more of these can be used.

The nitrogen adsorption specific surface area _(N 2 SA) of carbon black is preferably not less than 100 m ² / g, more preferably at least 120 m ² / g, still more preferably at least 130m ² / g. If the N ₂ SA of the carbon black is less than 100 m ² / g, the dry grip performance tends to be lowered. Also, _N 2 SA of the carbon black is preferably 500 meters ² / g or less, more preferably 350 meters ² / g, more preferably 150 meters ² / g or less. When the N ₂ SA of the carbon black exceeds 500 m ² / g, good dispersion is difficult to obtain, and the wear resistance tends to decrease. Moreover, the dibutyl phthalate (DBP) oil absorption of carbon black is preferably 50 ml / 100 g or more, and more preferably 100 ml / 100 g or more. If the DBP oil absorption is less than 50 ml / 100 g, sufficient reinforcing properties may not be obtained, and sufficient wear resistance may not be obtained. Further, the DBP oil absorption is preferably 200 ml / 100 g or less, and more preferably 135 ml / 100 g or less. If the DBP oil absorption exceeds 200 ml / 100 g, workability and wear resistance may be reduced. The N ₂ SA of the carbon black is measured according to ASTM D4820-93, and the DBP absorption is measured according to ASTM D2414-93. As a commercial product of carbon black, Tokai Carbon Co., Ltd., trade name 6 SIST, 7 HM, SEAST 9, SEAST KH, Degussa, trade name CK3, Special Black 4A, etc. can be used.

When the rubber composition according to the present invention contains carbon black, the content of carbon black is preferably 50 parts by mass or more, more preferably 65 parts by mass or more, and 80 parts by mass or more with respect to 100 parts by mass of the rubber component. Further preferred. If the content is less than 50 parts by mass, the dry grip performance may be deteriorated or the wear resistance may be deteriorated. The content is preferably 200 parts by mass or less, more preferably 180 parts by mass or less, still more preferably 120 parts by mass or less, and particularly preferably 100 parts by mass or less. When the content exceeds 200 parts by mass, workability tends to deteriorate.

The rubber composition according to the present invention preferably contains a softener from the viewpoint of dry 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 paraffin-based process oil, aroma-based process oil, and naphthenic-process oil, and aroma-based process oil is particularly preferable.

When the rubber composition according to the present invention contains oil, the content of the oil is preferably 1 part by mass or more, more preferably 10 parts by mass or more, and further preferably 30 parts by mass with respect to 100 parts by mass of the rubber component. More than a part. If the content of the oil is less than 1 part by mass, the effect of addition may not be obtained. The oil content is preferably 80 parts by mass or less, more preferably 60 parts by mass or less, and still more preferably 40 parts by mass or less. If the content of the oil exceeds 80 parts by mass, the effects of the present invention may not be suitably obtained. Here, the oil content includes the amount of oil contained in the oil-extended rubber.

The rubber composition according to the present invention preferably contains a liquid diene polymer as part or all of the softening agent. Thereby, the performance balance between durability (chunking resistance) and dry grip performance can be improved. In the present invention, the liquid diene polymer is a diene polymer in a liquid state at normal temperature (25 ° C.).

The liquid diene polymer preferably has a polystyrene-equivalent weight average molecular weight (Mw) measured by gel permeation chromatography (GPC) of 1.0 × 10 ^{3 to} 2.0 × 10 ⁵ . 5 × 10 ^{3 to} 6.0 × 10 ⁴ is more preferable, 2.0 × 10 ^{3 to} 2.0 × 10 ⁴ is further preferable, and 3.0 × 10 ^{3 to} 1.5 × 10 ⁴ is more preferable. ⁴ is particularly preferred. If the Mw is less than 1.0 × 10 ³ , the fracture performance may be reduced, and sufficient chunking resistance may not be ensured. If it exceeds 2.0 × 10 ⁵ , the viscosity of the polymerization solution increases. Productivity may be deteriorated.

Examples of the liquid diene polymer include a liquid styrene butadiene copolymer (liquid SBR), a liquid butadiene polymer (liquid BR), a liquid isoprene polymer (liquid IR), a liquid styrene isoprene copolymer (liquid SIR), and the like. It is done. Especially, it is preferable to use liquid SBR because the chunking resistance and the dry grip performance can be obtained with a good balance.

The vinyl content of the liquid SBR is preferably 10% by mass or more, more preferably 20% by mass or more. If the vinyl content is less than 10% by mass, sufficient dry grip performance may not be obtained. The vinyl content is preferably 90% by mass or less, more preferably 75% by mass or less. When the vinyl content exceeds 90% by mass, the wear resistance tends to deteriorate.
The vinyl content of liquid SBR can be measured by infrared absorption spectrum analysis.

The styrene content of the liquid SBR is preferably 10% by mass or more, more preferably 20% by mass or more, and further preferably 35% by mass or more. If the styrene content is less than 10% by mass, sufficient dry grip performance may not be obtained. The styrene content is preferably 60% by mass or less, more preferably 50% by mass or less. When the styrene content exceeds 60% by mass, the softening point becomes high, the rubber becomes hard, and the dry grip performance may be deteriorated.
The styrene content of the liquid SBR is calculated by ¹ H-NMR measurement.

When the rubber composition according to the present invention contains a liquid diene polymer, the content of the liquid diene polymer is preferably 20 parts by mass or more, more preferably 40 parts by mass with respect to 100 parts by mass of the rubber component. That's it. When the content is less than 20 parts by mass, sufficient dry grip performance tends not to be obtained. Moreover, this content becomes like this. Preferably it is 120 mass parts or less, More preferably, it is 80 mass parts or less. When the content exceeds 120 parts by mass, the wear resistance performance tends to deteriorate.
One or more kinds of these softeners such as oil and liquid diene polymer can be used.

The total content of the resin, oil and liquid diene polymer is preferably 50 parts by mass or more, more preferably 60 parts by mass or more, and still more preferably 70 parts by mass or more, relative to 100 parts by mass of the rubber component. More preferably, it is 80 mass parts or more, Most preferably, it is 90 mass parts or more. If the total content is less than 50 parts by mass, the effects of improving all physical properties tend to be small. The total content is preferably 180 parts by mass or less, more preferably 130 parts by mass or less, and still more preferably 110 parts by mass or less. When the total content exceeds 180 parts by mass, the wear resistance performance tends to deteriorate.

In addition to the above components, the rubber composition according to the present invention includes compounding agents generally used in the production of rubber compositions, for example, vulcanization of zinc oxide, various anti-aging agents, tackifiers, wax, sulfur and the like. An agent, a vulcanization accelerator, and the like can be appropriately blended.

Examples of the sulfur include powdered sulfur, precipitated sulfur, colloidal sulfur, insoluble sulfur, and highly dispersible sulfur. The sulfur content is preferably 0.1 to 15 parts by mass, more preferably 0.3 to 10 parts by mass, and further preferably 0.5 to 5 parts by mass with respect to 100 parts by mass of the rubber component. Particularly preferably, it is 1 to 3 parts by mass.

Examples of the vulcanization accelerator include 2-mercaptobenzothiazole, dibenzothiazyl disulfide, and thiazole vulcanization accelerators such as N-cyclohexyl-2-benzothiazylsulfenamide; tetramethylthiuram monosulfide, tetramethylthiuram. Thiuram vulcanization accelerators such as disulfides; N-cyclohexyl-2-benzothiazole sulfenamide, Nt-butyl-2-benzothiazole sulfenamide, N-oxyethylene-2-benzothiazole sulfenamide, N -Sulfenamide vulcanization accelerators such as oxyethylene-2-benzothiazole sulfenamide and N, N'-diisopropyl-2-benzothiazole sulfenamide; diphenylguanidine, diortolylguanidine, orthotolylbiguanidine What guanidine-based vulcanization accelerator can be exemplified. Of these, sulfenamide-based vulcanization accelerators are preferable and N-cyclohexyl-2-benzothiazole sulfenamide is more preferable because the effects of the present invention can be more suitably obtained. The content of the vulcanization accelerator is preferably 0.1 to 7 parts by mass, more preferably 0.5 to 6 parts by mass, and further preferably 1 to 2 parts by mass with respect to 100 parts by mass of the rubber component. is there.

The rubber composition according to the present invention is produced by a general method. That is, it can be produced by a method of kneading the above components with a Banbury mixer, kneader, open roll or the like and then vulcanizing.

The rubber composition according to the present invention can provide a good balance of dry grip performance, wear resistance, and chunking resistance, and is particularly excellent in wear resistance and chunking resistance.

The rubber composition according to the present invention can be used for each member of a tire, and is particularly preferably used as a tire tread. In the case of a tread having a two-layer structure, it is composed of a surface layer (cap tread) and an inner surface layer (base tread), and the rubber composition according to the present invention can be used for both a cap tread and a base tread. More preferably used as a tread.

A tread having a multilayer structure is manufactured by a method in which a sheet is bonded to a predetermined shape, or a method in which two or more extruders are loaded and two or more layers are formed at the head outlet of the extruder. Can do.

The pneumatic tire of the present invention is produced by a usual method using the rubber composition.
That is, a rubber composition containing SBR, NR, the above resin, and, if necessary, the above various compounding agents is extruded in accordance with the shape of each tire member such as a tread at an unvulcanized stage. Together with the tire member, an unvulcanized tire is formed by molding in a normal manner on a tire molding machine. The pneumatic tire of the present invention is obtained by heating and pressurizing the unvulcanized tire in a vulcanizer.

The tread hardness (Hs) in the pneumatic tire of the present invention is preferably 25 or more, more preferably 27 or more, further preferably 29 or more, and particularly preferably 30 or more in an atmosphere at 100 ° C. The Hs is preferably 40 or less, more preferably 39 or less, still more preferably 38 or less, and particularly preferably 37 or less. If the Hs is less than 25, the effect of improving all physical properties tends to be small, and if it exceeds 40, the rigidity may be excessive.
The hardness of the tread is measured in an atmosphere of 100 ° C. based on JIS K 6253 durometer type A (Shore A).

The pneumatic tire of the present invention is suitably used as a tire for passenger cars, a tire for trucks and buses, a tire for motorcycles, and a high performance tire, and particularly suitable for high performance tires, particularly high performance dry tires used on dry road surfaces. Can be used for In addition, the high-performance tire in this specification is a tire that is particularly excellent in grip performance, and is a concept that includes a competition tire used in a competition vehicle.

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

<Production Examples 1-4>
The chemicals used for resin synthesis are shown below.
Toluene: α-pinene manufactured by Kanto Chemical Co., Ltd .: 3-carene manufactured by Tokyo Chemical Industry Co., Ltd .: Styrene manufactured by Tokyo Chemical Industry Co., Ltd .: α-methylstyrene manufactured by Tokyo Chemical Industry Co., Ltd .: Tokyo Chemical Industry Co., Ltd. Pt-Butylphenol manufactured by: Wako Pure Chemical Industries, Ltd. Boron trifluoride (BF ₃ ): manufactured by Tokyo Chemical Industry Co., Ltd. Sodium carbonate: 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. To this, 40 g of pt-butylphenol was added, followed by stirring and refluxing for 2 hours. As a catalyst, 1.2 g of BF ₃ gas was added, 170 g of α-pinene was added dropwise over a period of about 90 minutes, and then 40 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 as shown in Table 1.
Table 1 shows the composition, softening point, weight average molecular weight (Mw), and number average molecular weight (Mn) of the synthesized resin. The softening point was measured by the method described above, and Mw and Mn were measured by the following methods.

(Measurement of Mw and 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. From the measurement results, the molecular weight distribution Mw / Mn was calculated.

<Examples 1-7 and Comparative Examples 1-9>
Hereinafter, various chemicals used in Examples and Comparative Examples will be described together.
Styrene butadiene rubber (SBR): Nipol 9549 manufactured by Nippon Zeon Co., Ltd. (E-SBR, styrene content: 45% by mass, oil content 37.5 parts by mass with respect to 100 parts by mass of SBR solid content)
Natural rubber (NR): RSS # 3
Carbon black: Seast 9 SAF manufactured by Tokai Carbon Co., Ltd. (N ₂ SA: 142 m ² / g, DBP: 115 ml / 100 g)
Liquid SBR: L-SBR-820 manufactured by Kuraray Co., Ltd. (Liquid SBR, Mw: 1.0 × 10 ⁴ , styrene content: 45% by mass)
Oil: Diana Process AH-24 (aromatic process oil) manufactured by Idemitsu Kosan Co., Ltd.
Resins A to D: Synthetic resin E in Production Examples 1 to 4: Crystallex 3085 (α-methylstyrene resin) manufactured by Eastman Chemical Co., Ltd.
Resin F: TR7125 (terpene resin) manufactured by Arizona Chemical Co., Ltd.
Resin G: Collesin manufactured by BASF (resin obtained by condensing pt-butylphenol and acetylene)
Mixture 1 (mixture of zinc salt of aliphatic carboxylic acid and zinc salt of aromatic carboxylic acid): Activator 73A ((i) zinc salt of aliphatic carboxylic acid (zinc of fatty acid derived from palm oil) Salt [carbon number 8 to 12]) and (ii) a zinc salt of aromatic carboxylic acid (zinc benzoate), molar ratio 1/1, zinc content 17% by mass)
Zinc oxide: Zinc oxide stearic acid manufactured by Mitsui Mining & Smelting Co., Ltd .: Tsubaki anti-aging agent manufactured by NOF Corporation: Antigen 6C manufactured by Sumitomo Chemical Co., Ltd.
Wax: Sunnock N manufactured by Ouchi Shinsei Chemical Industry Co., Ltd.
Sulfur: Powder sulfur vulcanization accelerator manufactured by Karuizawa Sulfur Co., Ltd .: Noxeller CZ (N-cyclohexyl-2-benzothiazole sulfenamide) manufactured by Ouchi Shinsei Chemical Industry Co., Ltd.

<Method for producing rubber composition>
In accordance with the formulation shown in Table 2, materials other than sulfur and a vulcanization accelerator were kneaded using a 1.7 L Banbury mixer manufactured by Kobe Steel Co., Ltd. to obtain a kneaded rubber. Next, sulfur and a vulcanization accelerator were added to the obtained kneaded rubber and kneaded using an open roll to obtain an unvulcanized rubber composition. The obtained unvulcanized rubber composition was vulcanized at 150 ° C. for 30 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 vulcanized to prepare a test tire (high performance dry tire) of size 195 / 65R15.

<Evaluation method>
(Dry grip performance)
The obtained test tire was mounted on a domestic FR vehicle with a displacement of 2000 cc, and the vehicle was run for 10 laps on a dry asphalt road test course with a road surface temperature of 20-30 ° C or 40-50 ° C. At that time, the test driver evaluated the stability of the control at the time of steering. Moreover, the average value of the dry grip performance index in each temperature region was calculated. The larger the value, the higher the grip performance on the dry road surface.

(Abrasion resistance)
Regarding the tensile properties, a physical property test was performed with a tensile No. 6 type dumbbell-shaped test piece (vulcanized rubber composition) in an atmosphere of 100 ° C. based on JIS K 6251, and the modulus (M300) was measured. M300 of each formulation (vulcanized product) was displayed as an index. In addition, it shows that it is excellent in abrasion resistance performance, so that M300 is large.
(Abrasion resistance index) = (M300 of each formulation / M300 of Comparative Example 1) × 100

(Chunking resistance)
The appearance of the tread surface of the tire for which the evaluation of the dry grip performance was finished was observed, and the area (cm ² ) of the chunking (the rubber had been blown away) was measured within a range of 15 cm × 15 cm. The smaller this value, the better the chunking resistance.

(hardness)
According to JIS K 6253 “Method for testing hardness of vulcanized rubber and thermoplastic rubber”, the hardness (Hs) of each vulcanized rubber composition of each example and comparative example was measured with a type A durometer. The measurement was performed in a 100 ° C. atmosphere.

As shown in Table 2, by using a specific resin in combination with a specific amount of styrene butadiene rubber and a specific amount of natural rubber in the present invention, the performance balance of dry grip performance, wear resistance, and chunking resistance is achieved. In particular, the wear resistance and chunking resistance were significantly improved. In addition, by further blending a mixture of a zinc salt of an aliphatic carboxylic acid and a zinc salt of an aromatic carboxylic acid, particularly the wear resistance performance, chunking resistance, hardness, etc. can be suitably improved. The balance has been significantly improved.

Claims (9)

A rubber component containing 60 to 90% by mass of styrene-butadiene rubber and 10 to 40% by mass of natural rubber is copolymerized with a phenolic compound (a), a terpene compound (b), and an aromatic vinyl compound (c). A pneumatic tire provided with a tread composed of a rubber composition containing a resin obtained in this manner. 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 The pneumatic tire according to claim 1, which is alkyl-substituted styrene. The pneumatic tire according to claim 1 or 2, wherein the terpene compound (b) is at least one selected from the group consisting of α-pinene, β-pinene, 3-carene, D-limonene, and dipentene. The pneumatic tire according to any one of claims 1 to 3, wherein an amount of the resin is 1 to 100 parts by mass with respect to 100 parts by mass of the rubber component. The proportion of the constituent components of the resin is phenolic compound (a)> terpene compound (b) ≧ aromatic vinyl compound (c), phenol compound (a) is 40 to 70% by mass, terpene compound ( The pneumatic tire according to any one of claims 1 to 4, wherein b) and the aromatic vinyl compound (c) are each 15 to 30% by mass. The said rubber composition contains 1-5 mass parts of mixtures of zinc salt of aliphatic carboxylic acid and zinc salt of aromatic carboxylic acid with respect to 100 mass parts of rubber components. The described pneumatic tire. The pneumatic tire according to claim 1, wherein the rubber composition contains carbon black and / or silica. The pneumatic tire according to claim 1, wherein the tread is a cap tread. The pneumatic tire according to any one of claims 1 to 8, wherein the tread has a hardness of 25 to 40 in an atmosphere of 100 ° C.