JP5420300B2 - Rubber composition and pneumatic tire using the same - Google Patents

Description

  The present invention relates to a rubber composition having excellent wear resistance and low heat build-up, and good processability, and a pneumatic tire obtained using the rubber composition.

  Conventionally, in rubber compositions containing silica as a filler (silica compounded rubber composition), a silane coupling agent is added to chemically bond silica and elastomer in order to obtain high wear resistance. It is necessary to make it. Bis (triethoxypropyl) tetrasulfide is generally used as the silane coupling agent blended for such purposes, but various other silane coupling agents are known.

  Under these circumstances, for example, Patent Document 1 can be obtained by using an organolithium compound as an initiator, (co) polymerizing a diene monomer, and then reacting a polymerization active terminal with a specific alkoxysilane compound. Disclosed is a tire rubber composition containing 10 to 100 parts by weight of a silica filler with respect to 100 parts by weight of a rubber component comprising a modified (co) polymer in a rubber weight fraction of 20% by weight or more. Therefore, the wear resistance of the resulting tire is improved.

Japanese Patent Laid-Open No. 62-50346

However, in silica compounded rubber compositions, although improvement of wear resistance by using the above various silane coupling agents has been studied, such wear resistance can be compared with a rubber composition containing only carbon black. It is still inadequate and further improvements are desired. Further, in the method of improving the abrasion resistance using the modified (co) polymer of Patent Document 1, there is still room for improvement in that the polymer that can be used as the rubber component is limited to the solution polymerization polymer.
Accordingly, the present invention provides a silica-compounded rubber composition that improves wear resistance and has both excellent low heat build-up and vulcanized physical properties, and can also employ an emulsion polymerization polymer as a rubber component. It is aimed.

In order to solve the above problems, the present inventor has found a rubber composition not containing zinc oxide while mixing silica based on a specific copolymer rubber, and has completed the present invention.
That is, the rubber composition of the present invention is
For 100 parts by mass of a rubber component containing at least one styrene / butadiene copolymer rubber in an amount of 50 to 100% by mass,
As a filler, 10 to 150 parts by mass of silica, 0.5 to 5.0 parts by mass of a fatty acid zinc salt, and 0.2 to 5.0 parts by mass of a sulfenamide-based vulcanization accelerator and / or a thiuram-based additive. A sulfur accelerator is blended in an amount of 0.2 to 5.0 parts by mass, a silane coupling agent is blended in an amount of 1 to 20 parts by mass with respect to 100 parts by mass of silica, and zinc oxide is added. It is characterized by not blending.

The styrene / butadiene copolymer rubber is preferably an emulsion polymerization styrene / butadiene copolymer rubber.
The thiuram vulcanization accelerator is preferably tetrakis-2-ethylhexyl thiuram sulfide.

  Further, the sulfenamide vulcanization accelerator is preferably represented by the following formula (I).

（式（Ｉ）中、Ｒ¹は、炭素数３〜１２の分岐アルキル基を示し、Ｒ²は炭素数１〜１０の直鎖アルキル基または炭素数３〜１０の分岐アルキル基を示す。Ｒ³〜Ｒ⁶は、互いに同一であっても異なっていてもよく、Ｈまたは炭素数１〜４のアルキル基或いはアルコキシ基を示す。ｎは０または１を示し、ｘは１または２を示す。）。
本発明の空気入りタイヤは、上記ゴム組成物を用いたことを特徴とし、かかるゴム組成物をトレッドに用いるのが望ましい。

(In Formula (I), R ¹ represents a branched alkyl group having 3 to 12 carbon atoms, and R ² represents a linear alkyl group having 1 to 10 carbon atoms or a branched alkyl group having 3 to 10 carbon atoms. R ^{3 to} R ⁶ may be the same as or different from each other, and represent H, an alkyl group or an alkoxy group having 1 to 4 carbon atoms, n represents 0 or 1, and x represents 1 or 2. ).
The pneumatic tire of the present invention is characterized by using the above rubber composition, and it is desirable to use such a rubber composition for a tread.

  According to the rubber composition of the present invention, it is possible to obtain a tire capable of exhibiting excellent wear resistance and low heat buildup while blending silica as a filler. In addition, the scorch safety is high, the vulcanization speed is high, and the processability is good. Therefore, if such a rubber composition is used, a high-performance pneumatic tire can be obtained, and is particularly suitable as a rubber composition for a tread.

Hereinafter, the present invention will be described in detail.
The rubber composition of the present invention is
For 100 parts by mass of a rubber component containing at least one styrene / butadiene copolymer rubber in an amount of 50 to 100% by mass,
As a filler, 10 to 150 parts by mass of silica, 0.5 to 5.0 parts by mass of a fatty acid zinc salt, and 0.2 to 5.0 parts by mass of a sulfenamide-based vulcanization accelerator and / or a thiuram-based additive. A sulfur accelerator is blended in an amount of 0.2 to 5.0 parts by mass, a silane coupling agent is blended in an amount of 1 to 20 parts by mass with respect to 100 parts by mass of silica, and zinc oxide is added. It is characterized by not blending.

  In the rubber component used in the rubber composition of the present invention, at least one kind of styrene / butadiene copolymer rubber is 50 to 100% by mass, preferably 70 to 100% by mass, and more preferably 80% in 100% by mass of the rubber component. It is contained in an amount of ˜100% by mass. When the content of the styrene / butadiene copolymer rubber is within the above range, the wear resistance and low heat build-up of the resulting rubber composition should be improved while maintaining good dispersibility with silica described later. Is possible.

  The styrene / butadiene copolymer rubber is not particularly limited, and a styrene / butadiene copolymer rubber conventionally used for tires can be employed. Solution polymerized styrene / butadiene copolymer rubber may be used, or these may be used in combination. Of these, emulsion-polymerized styrene / butadiene copolymer rubber is preferable. When the emulsion-polymerized styrene / butadiene copolymer rubber and the solution-polymerized styrene / butadiene copolymer rubber are used in combination, the emulsion polymerized styrene / butadiene copolymer rubber is 50% by mass or more, preferably 70%, in the total amount of 100% by mass. It is desirable that the amount is not less than mass%. These styrene / butadiene copolymer rubbers may be used in at least one kind, or may be used in combination of two or more kinds.

  In addition to the styrene / butadiene copolymer rubber, the rubber component used in the rubber composition of the present invention includes a diene synthetic rubber other than natural rubber (NR) and styrene / butadiene copolymer rubber as necessary. Such a diene synthetic rubber may include polybutadiene rubber (BR), polyisoprene rubber (IR), butyl rubber (IIR) and the like. These rubber components may be used alone or in combination of two or more.

  The rubber composition of the present invention contains silica as a filler in an amount of usually 10 to 150 parts by weight, preferably 30 to 120 parts by weight, more preferably 50 to 100 parts by weight with respect to 100 parts by weight of the rubber component. To do. If the blending amount of silica is less than 10 parts by mass, the effects of the present invention may not be sufficiently exhibited, and if it exceeds 150 parts by mass, the hardness may be unnecessarily high.

Although it does not restrict | limit especially as said silica, It selects suitably from what is conventionally used for rubber reinforcement, for example, wet method silica (hydrous silicic acid), dry method silica (anhydrous silicic acid), various silicates, etc. Among them, synthetic silica by a precipitation method (wet method silica) is preferable. These silicas may be used alone or in a combination of two or more. The nitrogen adsorption specific surface area (N ₂ SA) of the silica is preferably 50 to 300 m ² / g from the viewpoint of improving workability or wear resistance.

  In addition to the above silica, fillers such as carbon black such as SRF, GPF, FEF, HAF, ISAF, SAF, and aluminum hydroxide may be blended in addition to the above silica as a filler. .

  The rubber composition of the present invention further contains a silane coupling agent. The compounding quantity of this silane coupling agent is 1-20 mass parts normally with respect to 100 mass parts of said silica, Preferably it is 3-15 mass parts, More preferably, it is the quantity of 6-12 mass parts. If the blending amount of the silane coupling agent is less than 1 part by mass, the coupling effect may not be sufficiently exhibited, and if it exceeds 20 parts by mass, gelation may occur.

  Specific examples of the silane coupling agent include vinyltrimethoxysilane, vinyltriethoxysilane, vinyltris (2-methoxyethoxy) silane, and N- (2-aminoethyl) -3-aminopropylmethyldimethoxysilane. N- (2-aminoethyl) -3-aminopropylmethyltrimethoxysilane, 3-aminopropyltriethoxysilane, 3-glycidoxypropyltrimethoxysilane, 3-glycidoxypropylmethyldimethoxysilane, 2- ( 3,4-epoxycyclohexyl) ethyltrimethoxysilane, 3-methacryloxypropyltrimethoxysilane, 3-mercaptopropyltrimethoxysilane, 3-aminopropyltrimethoxysilane, bis (3-triethoxysilylpropyl) tetrasulfide, bis (3 -Trimethoxysilylpropyl) tetrasulfide, bis (3-methyldimethoxysilylpropyl) tetrasulfide, bis (3-triethoxysilylethyl) tetrasulfide, bis (3-triethoxysilylpropyl) disulfide, bis (3-trimethoxy Silylpropyl) disulfide, bis (3-triethoxysilylpropyl) trisulfide, 3-octanoylthio-1-propyltriethoxysilane, 3- (2-methyl-1,3-propanedialkoxyethoxysilyl) -1-propylthio Octanoate etc. are mentioned and a commercial item can be used conveniently. These silane coupling agents may be used alone or in a combination of two or more. Among them, bis (3-triethoxysilylpropyl) tetrasulfide, bis (3-triethoxysilylpropyl) disulfide, 3-octanoylthio-1-propyltriethoxysilane, 3- (2-methyl-1,3-propanedioxide Alkoxyethoxysilyl) -1-propylthiooctanoate is preferred, and commercially available products include “Si-69” (bis (3-triethoxysilylpropyl) tetrasulfide) and “Si-75” (bis (3-triethoxysilylpropyl) disulfide), NXT silane (3-octanoylthio-1-propyltriethoxysilane), NXT-LowV (3- (2-methyl-1,3-propane) from Momentive Performance Materials Dialkoxyethoxysilyl) -1-propylthio Kutanoeto) or the like can be used.

  In the rubber composition of the present invention, the fatty acid zinc salt is usually 0.5 to 5.0 parts by mass, preferably 0.8 to 3.0 parts by mass, and more preferably 1.100 parts by mass of the rubber component. It mix | blends in the quantity of 0-2.0 mass parts. Such a fatty acid zinc salt can act as a vulcanization accelerating aid, so that a sufficient vulcanization rate can be secured without blending zinc oxide. If the blending amount of the fatty acid zinc salt is less than 0.5 parts by mass, the effect as a vulcanization accelerating aid may be insufficient and the elastic modulus may decrease. There is a possibility that it becomes easy to do.

  Specific examples of the fatty acid zinc salt include zinc stearate, zinc oleate, zinc palmitate, zinc myristate, zinc laurate, and zinc linoleate. These fatty acid metal salts may be used alone or in a combination of two or more. Of these, zinc stearate is preferred.

  In the rubber composition of the present invention, a sulfenamide vulcanization accelerator or a thiuram vulcanization accelerator, or both a sulfenamide vulcanization accelerator and a thiuram vulcanization accelerator are used as the vulcanization accelerator. Blend. Among these, it is preferable to use a sulfenamide vulcanization accelerator and a thiuram vulcanization accelerator in combination from the viewpoint of utilizing a synergistic effect that can be exhibited mutually.

  When a sulfenamide vulcanization accelerator is used, 0.2 to 5.0 parts by mass, preferably 0.3 to 3.0 parts by mass of the sulfenamide vulcanization accelerator with respect to 100 parts by mass of the rubber component. Parts, more preferably 0.5 to 2.0 parts by mass. A sulfenamide-based vulcanization accelerator has high scorch safety, and can effectively exhibit vulcanization-accelerating performance even in a silica-containing rubber composition. If the blending amount is less than 0.2 parts by mass, vulcanization may not be achieved sufficiently, and if it exceeds 5.0 parts by mass, bloom may be a problem.

  Examples of such sulfenamide-based vulcanization accelerators that are widely used include Nt-butyl-2-benzothiazole sulfenamide (TBBS), N-cyclohexyl-2-benzothiazole sulfenamide (CBS), and the like. A commercially available product can be suitably used. Among these, in the present invention, it is particularly desirable to use a sulfenamide vulcanization accelerator represented by the following formula (I). With such a sulfenamide-based vulcanization accelerator, it is possible to more effectively suppress an increase in Mooney viscosity while ensuring a suitable Mooney scorch time while effectively exhibiting a moderate vulcanization delay effect. it can.

R ¹ in the above formula (I) represents a branched alkyl group having 3 to 12 carbon atoms. When R ¹ is a branched alkyl group having 3 to 12 carbon atoms, good vulcanization acceleration performance can be ensured.

Specific examples of R ¹ include isopropyl, isobutyl, triisobutyl, sec-butyl, tert-butyl, isoamyl (isopentyl), neopentyl, and tert-amyl (tert-pentyl). , Isohexyl group, tert-hexyl group, isoheptyl group, tert-heptyl group, isooctyl group, tert-octyl group, isononyl group, tert-nonyl group, isodecyl group, tert-decyl group, isoundecyl group, tert-undecyl group, isododecyl Group, tert-dodecyl group and the like. Among these, a tert-alkyl group having 1 to 12 carbon atoms is preferable from the viewpoint of obtaining a suitable Mooney scorch time, and in particular, a tert-butyl group, a tert-amyl group (tert-pentyl group), A tert-dodecyl group and a triisobutyl group are preferable, and among them, a tert-butyl group is preferable because it is economically excellent from the viewpoint of synthesis and raw material acquisition.

In the above formula (I), n represents 0 or 1, and is preferably 0 from the viewpoint of effects such as ease of synthesis and raw material costs. X in the formula (I) represents an integer of 1 or 2. When x is 3 or more, the reactivity becomes too high, so that the stability of the sulfenamide vulcanization accelerator is lowered, and the processability may be deteriorated. These are presumed to be because the more Moony scorch time tends to be imparted as the bulky group exists in the vicinity of —N— adjacent to R ¹ .

In the present invention, R ² in the above formula (I) represents a linear alkyl group having 1 to 10 carbon atoms or a branched alkyl group having 3 to 10 carbon atoms. If R ² is a straight chain having 1 to 10 carbon atoms or a branched alkyl group having 3 to 10 carbon atoms, good vulcanization acceleration performance can be maintained.

Specific examples of R ² include methyl group, ethyl group, n-propyl group, isopropyl group, n-butyl group, isobutyl group, sec-butyl group, tert-butyl group, n-amyl group (n-pentyl group). ), Isoamyl group (isopentyl group), neopentyl group, tert-amyl group (tert-pentyl group), n-hexyl group, isohexyl group, n-heptyl group, isoheptyl group, n-octyl group, iso-octyl group, nonyl Group, isononyl group, decyl group, undecyl group, dodecyl group and the like. Among these, from the viewpoint of effects such as ease of synthesis and raw material costs, a straight chain having 1 to 8 carbon atoms or a branched alkyl group having 3 to 8 carbon atoms is preferable, and a straight chain having 1 to 6 carbon atoms is more preferable. It is more preferably a chain or a branched alkyl group having 3 to 6 carbon atoms, and examples include a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group, an isobutyl group, and a sec-butyl group. In particular, the straight-chain alkyl group having the carbon number is more preferable than the branched alkyl group having the carbon number in that a suitable Mooney scorch time can be obtained. If this is a branched alkyl group, the vulcanization is further delayed, so that the productivity may be lowered, or the adhesiveness may be lowered when compared with the same carbon number as that of the linear alkyl group. Among these, a methyl group, an ethyl group, and an n-propyl group are most desirable. If the R ² is a H, may cause vulcanization rate is too fast, the R ² is a bulky group and the range of the long-chain groups such as cyclohexyl groups, contrary to the vulcanization rate is too slow There is a tendency.

R ^{3 to} R ⁶ in the above formula (I) may be the same as or different from each other, and represent H, an alkyl group having 1 to 4 carbon atoms, or an alkoxy group. Examples of the alkyl group having 1 to 4 carbon atoms include a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group, an isobutyl group, a sec-butyl group, and a tert-butyl group. Is preferred. As a C1-C4 alkoxy group, a methoxy group, an ethoxy group, a linear or branched propoxy group, and a butoxy group are mentioned, Especially, a methoxy group is preferable. Among these R ^{3 to} R ⁶ , it is preferable that all of R ^{3 to} R ⁶ are H from the viewpoint of sufficiently functioning the vulcanization acceleration performance. Further, among R ³ to R ^6, when at least a portion is an alkyl group or an alkoxy group having 1 to 4 carbon atoms, from the viewpoint of the synthesis face and economical aspects, R ³ and R ⁵ are 1 to carbon atoms 4 alkyl groups or alkoxy groups, and R ⁴ and R ⁶ are preferably H, R ³ and R ⁵ are methyl groups or methoxy groups, and R ⁴ and R ⁶ are H. More preferred. In the most preferred embodiment, all of R ^{3 to} R ⁶ are H.

  Representative examples of the sulfenamide vulcanization accelerator represented by the above formula (I) include, for example, N-methyl-Nt-butylbenzothiazole-2-sulfenamide (BMBS), N-ethyl- Nt-butylbenzothiazole-2-sulfenamide (BEBS), Nn-propyl-Nt-butylbenzothiazole-2-sulfenamide, N-isopropyl-Nt-butylbenzothiazole-2 -Sulfenamide, Nn-butyl-Nt-butylbenzothiazole-2-sulfenamide (BBBS), N-isobutyl-Nt-butylbenzothiazole-2-sulfenamide, N-sec- Butyl-Nt-butylbenzothiazole-2-sulfenamide, N-methyl-N-isoamylbenzothiazole-2-sulfenamide N-ethyl-N-isoamylbenzothiazole-2-sulfenamide, Nn-propyl-N-isoamylbenzothiazole-2-sulfenamide, N-isopropyl-N-isoamylbenzothiazole-2-sulfenamide, Nn-butyl-N-isoamylbenzothiazole-2-sulfenamide, N-isobutyl-N-isoamylbenzothiazole-2-sulfenamide, N-sec-butyl-N-isoamylbenzothiazole-2-sulfenamide Amides, N-methyl-N-tert-amylbenzothiazole-2-sulfenamide, N-ethyl-N-tert-amylbenzothiazole-2-sulfenamide, Nn-propyl-N-tert-amylbenzo Thiazole-2-sulfenamide, N-isopropyl- -Tert-amylbenzothiazole-2-sulfenamide, Nn-butyl-N-tert-amylbenzothiazole-2-sulfenamide, N-isobutyl-N-tert-amylbenzothiazole-2-sulfenamide N-sec-butyl-N-tert-amylbenzothiazole-2-sulfenamide, N-methyl-N-tert-heptylbenzothiazole-2-sulfenamide, N-ethyl-N-tert-heptylbenzothiazole -2-sulfenamide, Nn-propyl-N-tert-heptylbenzothiazole-2-sulfenamide, N-isopropyl-N-tert-heptylbenzothiazole-2-sulfenamide, Nn-butyl -N-tert-heptylbenzothiazole-2-sulfe Namide, N-isobutyl-N-tert-heptylbenzothiazole-2-sulfenamide, N-sec-butyl-N-tert-heptylbenzothiazole-2-sulfenamide;

  N-methyl-Nt-butyl-4-methylbenzothiazole-2-sulfenamide, N-methyl-Nt-butyl-4,6-dimethoxybenzothiazole-2-sulfenamide, N-ethyl- Nt-butyl-4-methylbenzothiazole-2-sulfenamide, N-ethyl-Nt-butyl-4,6-dimethoxybenzothiazole-2-sulfenamide, Nn-propyl-N- t-butyl-4-methylbenzothiazole-2-sulfenamide, Nn-propyl-Nt-butyl-4,6-dimethoxybenzothiazole-2-sulfenamide, N-isopropyl-Nt- Butyl-4-methylbenzothiazole-2-sulfenamide, N-isopropyl-Nt-butyl-4,6-dimethoxybenzothiazole-2-sulf Nn-butyl-Nt-butyl-4-methylbenzothiazole-2-sulfenamide, Nn-butyl-Nt-butyl-4,6-dimethoxybenzothiazole-2-sulfen Amide, N-isobutyl-Nt-butyl-4-methylbenzothiazole-2-sulfenamide, N-isobutyl-Nt-butyl-4,6-dimethoxybenzothiazole-2-sulfenamide, N- and sec-butyl-Nt-butyl-4-methylbenzothiazole-2-sulfenamide, N-sec-butyl-Nt-butyl-4,6-dimethoxybenzothiazole-2-sulfenamide, and the like. It is done. These may be used individually by 1 type, and 2 or more types may be mixed and used for them.

  Among these, N-methyl-Nt-butylbenzothiazole-2-sulfenamide (BMBS), N-ethyl-Nt-butylbenzothiazole-2-sulfuramide is selected from the viewpoint of improving vulcanization acceleration performance. Fenamide (BEBS), Nn-propyl-Nt-butylbenzothiazole-2-sulfenamide, N-isopropyl-Nt-butylbenzothiazole-2-sulfenamide, N-isobutyl-N- t-Butylbenzothiazole-2-sulfenamide and N-sec-butyl-Nt-butylbenzothiazole-2-sulfenamide are preferable.

When manufacturing the sulfenamide type | system | group vulcanization accelerator represented by the said formula (I), the following method can be mentioned preferably.
That is, N-chloroamine prepared in advance by reaction of a corresponding amine and sodium hypochlorite and bis (benzothiazol-2-yl) disulfide are reacted in an appropriate solvent in the presence of an amine and a base. If an amine is used as the base, neutralize and return to the free amine, then subject to appropriate post-treatment such as filtration, washing with water, concentration and recrystallization according to the properties of the resulting reaction mixture. Sulfenamide is obtained.

  Examples of the base used in this production method include starting amines used in excess, tertiary amines such as triethylamine, alkali hydroxides, alkali carbonates, alkali bicarbonates, sodium alkoxides, and the like. In particular, the reaction is carried out using excess raw material amine as a base or tertiary amine triethylamine, neutralizing the hydrochloride formed with sodium hydroxide, taking out the target product, and then removing the amine from the filtrate. A method of reuse is desirable.

As the solvent used in this production method, alcohol is desirable, and methanol is particularly desirable.
For example, in N-ethyl-Nt-butylbenzothiazole-2-sulfenamide (BEBS), an aqueous sodium hypochlorite solution was added dropwise to Nt-butylethylamine at 0 ° C. or lower and the oil layer was stirred for 2 hours. Was sorted. Bis (benzothiazol-2-yl) disulfide, Nt-butylethylamine and the oil layer described above were suspended in methanol and stirred for 2 hours under reflux. After cooling, the solution is neutralized with sodium hydroxide, filtered, washed with water, concentrated under reduced pressure, and recrystallized to obtain the target BEBS (white solid).

  When a thiuram vulcanization accelerator is used, the thiuram vulcanization accelerator is 0.2 to 5.0 parts by weight, preferably 0.3 to 3 parts by weight, more preferably 0, per 100 parts by weight of the rubber component. It mix | blends in the quantity of 5-2.0 mass parts. The thiuram vulcanization accelerator is excellent in vulcanization acceleration performance and can exhibit an appropriate vulcanization delay effect. Further, when used in combination with the sulfenamide vulcanization accelerator, it can function effectively as a secondary accelerator of the accelerator. If the blending amount is less than 0.2 parts by mass, vulcanization may not be achieved sufficiently, and if it exceeds 5.0 parts by mass, bloom may be a problem.

  Specific examples of the thiuram vulcanization accelerator include tetramethylthiuram monosulfide (TMTM), tetramethylthiuram disulfide (TMTD), tetraethylthiuram disulfide (TETD), tetrabutylthiuram disulfide (TBTD), dith Pentamethylene thiuram hexasulfide (DPTH), dipentamethylene thiuram tetrasulfide (DPTT), tetrakis-2-ethylhexyl thiuram disulfide, tetrakis-2-isopropyl thiuram disulfide, tetrakis-dodecyl thiuram disulfide, tetrakis-benzyl thiuram disulfide, etc. Is mentioned. These may be used individually by 1 type, and 2 or more types may be mixed and used for them. Among them, tetrakis-2-ethylhexyl thiuram disulfide is preferable, and “Noxeller TOT-N” manufactured by Ouchi Shinsei Chemical Co., Ltd. can be used as a commercial product.

  In addition to the above sulfenamide vulcanization accelerator and thiuram vulcanization accelerator, the rubber composition of the present invention may be blended with other vulcanization accelerators within a range not impairing the object of the present invention. . Examples of such vulcanization accelerators include guanidine vulcanization accelerators such as diphenylguanidine (DPG) and di-o-tolylguanidine (DOTG), ethylenethiourea (ETU), 1,3-diethylthiourea (DETU), Examples thereof include thiourea vulcanization accelerators such as 1,3-dibutylthiourea (DBTU) and trimethylthiourea (TMU), dithiocarbamate vulcanization accelerators, xanthogenate vulcanization accelerators, and the like.

  The rubber composition of the present invention comprises the above rubber component, silica, silane coupling agent, fatty acid zinc salt, sulfenamide vulcanization accelerator and / or thiuram vulcanization accelerator, and zinc oxide. It is characterized by not blending. By not blending such zinc oxide, it becomes possible to further improve the wear resistance of the tire using the rubber composition obtained. Further, by blending the fatty acid zinc salt without blending zinc oxide, it is possible to sufficiently ensure the action as a vulcanization acceleration aid, and it is possible to easily realize a suitable vulcanization rate.

  The rubber composition of the present invention includes the rubber component, silica, silane coupling agent, fatty acid zinc salt, sulfenamide vulcanization accelerator and / or thiuram vulcanization accelerator, softener, vulcanization A compounding agent usually used in the rubber industry such as an agent, a vulcanization accelerator, and an anti-aging agent can be appropriately selected and blended within a range not impairing the object of the present invention. As these compounding agents, commercially available products can be suitably used.

  The rubber composition of the present invention can be produced by kneading each of the above components with a Banbury mixer, a kneader or the like. Moreover, when manufacturing pneumatic tires for passenger cars, trucks, buses, motorcycles, etc. using the rubber composition of the present invention, for example, each member such as tread and side tread is produced by an extruder, a calendar, etc. A green tire can be produced by pasting these members on a molding drum, etc., and the green tire can be stored in a tire mold and vulcanized while applying pressure from the inside. In addition to the air, the tire may be filled with nitrogen or an inert gas. Furthermore, the rubber composition of the present invention can be suitably used for thick rubber products such as tire treads, hoses and belt conveyors, and is particularly suitable as a rubber composition used for tire tread base rubber and belt rubber. It is.

  EXAMPLES Hereinafter, although this invention is demonstrated concretely based on an Example, this invention is not limited to these Examples. Each measurement and evaluation of the rubber composition was performed according to the following method.

<< Mooney viscosity (ML _{1 + 4} ), Mooney scorch time >>
The Mooney viscosity (ML _{1 + 4} ) of the obtained unvulcanized rubber composition (before vulcanization at a temperature of 165 ° C., which will be described later) is preheated according to JIS K6300-1-2001 using an L-shaped rotor. The Mooney viscosity was measured for 1 minute, for 4 minutes, and at a temperature of 130 ° C. Further, a time (Mooney scorch time) (unit: minute) until the value after the start of the residual heat rose 5 units from the minimum value Vm was measured. The smaller the Mooney viscosity index, the better the workability, and the larger the Mooney scorch time value, the better the processing stability.

"Vulcanization _{rate: Fmax, T 0.1, T 0.9} , T 0.1 -T 0.9"
In accordance with JIS K6300-2: 2001, the vulcanization curve of the rubber composition was measured at 160 ° C. using a curast meter manufactured by JSR Corporation. The maximum value (Fmax) and minimum value (Fmin) of the torque in the vulcanization curve are measured, and the time (min) until the torque reaches {(Fmax−Fmin) × 0.1 + Fmin} is determined by 10% vulcanization time (T _0.1 ), the time (min) until reaching the torque of {(Fmax−Fmin) × 0.9 + Fmin} is 90% vulcanization time (T _0.9 ), and the difference T _0.1 −T _0.9 (min) is vulcanized. It was used as an index of speed.

<< Tensile test: Elongation at break, strength at break, M300 >>
A dumbbell-shaped No. 3 test piece was punched out from a slab sheet having a thickness of 2 mm vulcanized at 160 ° C. for 20 minutes. The elongation stress (M300) (unit: MPa) was measured.

《Lambourn abrasion test: Lambourn wear resistance》
The test was conducted at room temperature with a slip rate of 50% using a Lambourn abrasion tester. The amount of wear loss was determined and expressed as an index for the amount of wear in Comparative Example 1 according to the following formula. It shows that abrasion resistance is so favorable that a numerical value is large.
Abrasion resistance index = (Abrasion amount of Comparative Example 1 / Abrasion amount of sample) × 100

《Rebound resilience》
Based on JIS K 6255-1996, the value (%) of rebound resilience was measured using a Dunlop trypometer. The larger the value, the better the resilience.

<< Dynamic viscoelasticity test: tan δ >>
Using a spectrometer (dynamic viscoelasticity measuring tester) manufactured by Ueshima Seisakusho, the tan δ value of the rubber composition was tan δ at 60 ° C. at a frequency of 50 Hz, an initial strain rate of 10%, and a dynamic strain rate of 2%. The value of (loss factor) was measured. The smaller the value of tan δ, the lower the heat generation.

[Production Example 1: Synthesis of N-methyl-Nt-butylbenzothiazole-2-sulfenamide (BMBS, vulcanization accelerator A)]
To 14.1 g (0.162 mol) of Nt-butylmethylamine, 148 g of a 12% aqueous sodium hypochlorite solution was added dropwise at 0 ° C. or lower, and after stirring for 2 hours, the oil layer was separated. Bis (benzothiazol-2-yl) disulfide (39.8 g, 0.120 mol), Nt-butylmethylamine (20.9 g, 0.240 mmol) and the aforementioned oil layer were suspended in 120 ml of methanol and refluxed. Stir for 2 hours. After cooling, the solution was neutralized with 6.6 g (0.166 mol) of sodium hydroxide, filtered, washed with water, concentrated under reduced pressure, and then recrystallized to obtain 46.8 g (yield 82%) of the target BMBS as a white solid. (Melting point 56-58 ° C.).

¹ H-NMR (400 MHz, CDCl ₃ ) δ = 1.32 (9H, s, CH ₃ (t-butyl)), 3.02 (3H, s, CH ₃ (methyl)), 7.24 (1H, m), 7.38 (1H, m), 7.77 (1H, m), 7.79 (1H, m).
¹³ C-NMR (100 MHz, CDCl ₃ ) δ = 27.3, 41.9, 59.2, 120.9, 121.4, 123.3, 125.7, 135.0, 155.5, 180. 8).
Mass spectrometry (EI, 70 eV) m / z; 252 (M ⁺ ), 237 (M ⁺ -CH ₃ ), 223 (M ⁺ -C ₂ H ₆ ), 195 (M ⁺ -C ₄ H ₉ ), 167 ( _{^{M + -C 5 H 12 N)}} , 86 (M + -C 7 H 4 NS 2).

[Production Example 2: Synthesis of N-ethyl-Nt-butylbenzothiazole-2-sulfenamide (BEBS, vulcanization accelerator B)]
The same procedure as in Production Example 1 was carried out using 16.4 g (0.162 mol) of Nt-butylethylamine instead of Nt-butylmethylamine, and 41.9 g (66% yield) of BEBS as a white solid ( Obtained as a melting point of 60 to 61 ° C.).
The spectrum data of the obtained BEBS is shown below.

¹ H-NMR (400 MHz, CDCl ₃ ) δ = 1.29 (t, 3H, J = 7.1 Hz, CH ₃ (ethyl)), 1.34 (s, 9H, CH ₃ (t-butyl)), 2.9-3.4 (br-d, CH ₂ ), 7.23 (1H, m), 7.37 (1H, m), 7.75 (1H, m), 7.78 (1H, m ).
¹³ C-NMR (100 MHz, CDCl ₃ ) δ = 15.12, 28.06, 47.08, 60.41, 120.70, 121.26, 123.23, 125.64, 134.75, 154. 93, 182.63.
Mass spectrometry (EI, 70 eV): m / z; 251 (M ⁺ —CH ₄ ), 167 (M ⁺ —C ₆ H ₁₄ N), 100 (M ⁺ —C ₇ H ₅ NS ₂ ): IR (KBr, cm < ^-1 >): 3061, 2975, 2932, 2868, 1461, 1429, 1393, 1366, 1352, 1309, 1273, 1238, 1198, 1103, 1022, 1011, 936, 895, 756, 727.

[Production Example 3: Synthesis of Nn-propyl-Nt-butylbenzothiazole-2-sulfenamide (vulcanization accelerator C)]
The same procedure as in Production Example 1 was carried out using 18.7 g (0.162 mol) of Nn-propyl-t-butylamine instead of Nt-butylmethylamine, and Nn-propyl-Nt-butylbenzo Thiazole-2-sulfenamide was obtained as a white solid (melting point 50-52 ° C.).

¹ H-NMR (400 MHz, CDCl ₃ ) δ = 0.92 (t, J = 7.3 Hz, 3H), 1.34 (s, 9H), 1.75 (br, 2H), 3.03 (brd , 2H), 7.24 (t, J = 7.0 Hz, 1H), 7.38 (t, J = 7.0 Hz, 1H), 7.77 (d, J = 7.5 Hz, 1H), 7 .79 (d, J = 7.5 Hz, 1H).
¹³ C-NMR (100 MHz, CDCl ₃ ) δ = 11.7, 23.0, 28.1, 55.3, 60.4, 120.7, 121.3, 123.3, 125.7, 134. 7, 154.8, 181.3.

[Production Example 4: Synthesis of Ni-propyl-Nt-butylbenzothiazole-2-sulfenamide (vulcanization accelerator D)]
The same procedure as in Production Example 1 was carried out using 18.7 g (0.162 mol) of Ni-propyl-t-butylamine instead of Nt-butylmethylamine, and Ni-propyl-Nt-butylbenzo was used. Thiazole-2-sulfenamide was obtained as a white solid (melting point 68-70 ° C.).

¹ H-NMR (400 MHz, CDCl ₃ ) δ = 1.20-1.25 (dd, (1.22 ppm: J = 6.4 Hz, 1.23 ppm: J = 6.4 Hz) 6H), 1.37 ( s, 9H), 3.78 (m, J = 6.3 Hz, 1H), 7.23 (t, J = 7.0 Hz, 1H), 7.38 (t, J = 7.0 Hz, 1H), 7.77 (d, J = 7.5 Hz, 1H), 7.79 (d, J = 7.5 Hz, 1H).
¹³ C-NMR (100 MHz, CDCl ₃ ) δ = 22.3, 23.9, 29.1, 50.6, 61.4, 120.6, 121.2, 123.2, 125.6, 134. 5, 154.5, 183.3.

[Examples 1-5 , Comparative Examples 1-5 ]
Using a Banbury mixer, each component was kneaded and mixed with the formulation shown in Tables 1 and 2 to prepare an unvulcanized rubber composition, and each item was evaluated according to the above method. The results are shown in Tables 1-2.

* 1: SBR # 1712 (oil-extended SBR containing 37.5 parts of oil for 100 parts of rubber component), manufactured by JSR Corporation * 2: Nip seal AQ, manufactured by Tosoh Silica Corporation * 3: ISAF, Seast 6, Tokai Carbon Co., Ltd. * 4: Kanto Chemical Co., Ltd. * 5: Silan coupling agent Si75, Degussa Co., Ltd. * 6: Nocrack 6C, Ouchi Shinsei Chemical Co., Ltd. * 7: Two types of zinc oxide, * 8: Noxeller D, diphenylguanidine, Ouchi Shinsei Chemical Co., Ltd. * 9: Noxeller DM, dibenzothiazyl disulfide, Ouchi Shinsei Chemical Co., Ltd. * 10: Noxeller NS, N -T-butyl-2-benzothiazylsulfenamide, manufactured by Ouchi Shinsei Chemical Co., Ltd. * 11: Noxeller TOT-N, tetrakis-2-ethylhexylthiuramdisulf I de, Ouchi Shinko Chemical Industrial Co., Ltd.

According to the results of Tables 1 and 2, Examples 1 to 5 are blended with fatty acid zinc salt without blending zinc oxide and Comparative Examples 1 to 3 without blending fatty acid zinc salt. It can be seen that, compared with Comparative Example 4, good vulcanized physical properties, low exothermic properties, and excellent wear resistance are provided in a well-balanced manner.
Especially, Examples 1-5 which used the sulfenamide type | system | group vulcanization accelerator and the thiuram type vulcanization accelerator together are favorable compared with the comparative example 5 of using a sulfenamide type vulcanization accelerator alone. It can be seen that a fast vulcanization rate, superior wear resistance and low heat build-up can be achieved while maintaining processability.

Claims (6)

For 100 parts by mass of a rubber component containing at least one styrene / butadiene copolymer rubber in an amount of 50 to 100% by mass,
10 to 150 parts by mass of silica as filler, 0.5 to 5.0 parts by mass of fatty acid zinc salt, 0.2 to 5.0 parts by mass of sulfenamide vulcanization accelerator, and thiuram vulcanization An accelerator is blended in an amount of 0.2 to 5.0 parts by mass, a silane coupling agent is blended in an amount of 1 to 20 parts by mass with respect to 100 parts by mass of silica, and zinc oxide is blended. A rubber composition characterized by not.   2. The rubber composition according to claim 1, wherein the styrene / butadiene copolymer rubber is an emulsion polymerization styrene / butadiene copolymer rubber.   The rubber composition according to claim 1 or 2, wherein the thiuram vulcanization accelerator is tetrakis-2-ethylhexyl thiuram disulfide. The rubber composition according to any one of claims 1 to 3, wherein the sulfenamide-based vulcanization accelerator is represented by the following formula (I):

(In Formula (I), R ¹ represents a branched alkyl group having 3 to 12 carbon atoms, and R ² represents a linear alkyl group having 1 to 10 carbon atoms or a branched alkyl group having 3 to 10 carbon atoms. R ^{3 to} R ⁶ may be the same as or different from each other, and represent H, an alkyl group or an alkoxy group having 1 to 4 carbon atoms, n represents 0 or 1, and x represents 1 or 2. ).   A pneumatic tire using the rubber composition according to claim 1.   The pneumatic tire according to claim 5, wherein the rubber composition is used for a tread.