JP2014177588A - Rubber composition for tire - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a rubber composition for a tire improving a balance of low rolling resistance, steering stability, and abrasion resistance more than conventional levels.SOLUTION: The rubber composition for a tire comprises, 100 pts.wt. of a diene rubber, 50 to 120 pts.wt. of silica, 2.4 to 12 pts.wt. of a silane coupling agent having a mercapto group and/or a blocked mercapto group, and 0.03 to 2 pts.wt. of S-(aminoalkyl)thiosulfate represented by the formula (1) or a metal salt thereof. In HN-(CH)-SOH (1), n represents an integer of 1 to 10.

Description

  The present invention relates to a rubber composition for tires that improves the balance of low rolling resistance, steering stability and processability.

  In recent years, as a required performance for pneumatic tires, it has been demanded that fuel efficiency performance is excellent with increasing interest in global environmental problems. In order to improve fuel efficiency, it is necessary to reduce rolling resistance. For this reason, by suppressing the heat generation of the rubber composition constituting the pneumatic tire, rolling resistance when the tire is made is reduced. Generally, 60 ° C. tan δ by dynamic viscoelasticity measurement is used as an index of exothermic property of the rubber composition. The smaller the tan δ (60 ° C.) of the rubber composition, the smaller the exothermic property.

  As a method for reducing the tan δ (60 ° C.) of the rubber composition, silica is often added. Since silica easily aggregates in rubber, a silane coupling agent is usually blended with silica. In particular, it is known that the tan δ (60 ° C.) of the rubber composition can be significantly reduced by blending a silane coupling agent having a mercapto group. However, when a silane coupling agent having a mercapto group is blended, the scorch of the rubber composition is shortened and premature vulcanization is likely to occur, and the workability is deteriorated. There was a problem that stability was lowered.

  Patent Document 1 discloses that a tire rubber composition comprising a master batch in which a silane coupling agent having a mercapto group and an imidazole compound are blended with a specific diene rubber reduces the tan δ (60 ° C.) of the rubber composition. It describes that viscosity is suppressed and processability is improved. However, in this rubber composition, the rubber hardness of the rubber composition is ensured, and the effect of maintaining and improving the steering stability is not always sufficient, and further improvement has been demanded.

JP 2012-153865 A

  An object of the present invention is to provide a rubber composition for a tire that improves the balance of low rolling resistance, steering stability and processability to a level higher than that of the conventional level.

（式中、ｎは１〜１０の整数を表す。） The rubber composition for a tire according to the present invention that achieves the above-described object provides a silane coupling agent having 50 to 120 parts by weight of silica, a mercapto group and / or a blocked mercapto group based on 100 parts by weight of a diene rubber. 4 to 12 parts by weight, 0.03 to 2 parts by weight of S- (aminoalkyl) thiosulfuric acid represented by the following formula (1) or a metal salt thereof was blended.

(In the formula, n represents an integer of 1 to 10.)

  In the tire rubber composition of the present invention, silica, a mercapto silane coupling agent, and a specific S- (aminoalkyl) thiosulfuric acid or a metal salt thereof are blended with a diene rubber. While keeping the rubber hardness low, the rubber hardness can be maintained and improved, the deterioration of the scorch can be suppressed, and the workability can be improved to the conventional level or more.

The silica preferably has a CTAB specific surface area of 180 to 280 m ² / g,
The balance between low rolling resistance and steering stability can be further increased.

（式中、Ｒ¹，Ｒ²，Ｒ³は互いに独立して、水素、炭素数１〜８のアルキル基、炭素数１〜８のアルコキシ基、鎖長が４〜３０の直鎖ポリエーテル基、炭素数６〜３０のアリール基から選ばれると共に、少なくとも１つは前記アルコキシ基、少なくとも１つは前記直鎖ポリエーテル基であり、Ｒ⁴は炭素数１〜３０のアルキレン基である。）

（式中、Ｒ⁵およびＲ⁶で環構造を形成してもよく、Ｒ⁵は水素、ハロゲン、炭素数１〜３０のアルキル基或いはアルキレン基、炭素数２〜３０のアルケニル基或いはアルケニレン基、炭素数２〜３０のアルキニル基或いはアルキニレン基、前記アルキル基或いはアルケニル基の末端がヒドロキシル基若しくはカルボキシル基で置換された基から選ばれ、Ｒ⁶は炭素数１〜３０のアルキレン基、炭素数２〜３０のアルケニレン基、炭素数２〜３０のアルキニレン基から選ばれ、ｘは１以上の整数である。）

（式中、Ｒ⁷およびＲ⁸で環構造を形成してもよく、Ｒ⁷は水素、ハロゲン、炭素数１〜３０のアルキル基或いはアルキレン基、炭素数２〜３０のアルケニル基或いはアルケニレン基、炭素数２〜３０のアルキニル基或いはアルキニレン基、前記アルキル基或いはアルケニル基の末端がヒドロキシル基若しくはカルボキシル基で置換された基から選ばれ、Ｒ⁸は炭素数１〜３０のアルキレン基、炭素数２〜３０アルケニレン基、炭素数２〜３０のアルキニレン基から選ばれ、ｙは１以上の整数である。） As the silane coupling agent having a mercapto group, a mercaptosilane compound represented by the following formula (2) or a copolymer having a structure of the following formulas (3) and (4) is preferable.

Wherein R ¹ , R ² and R ³ are independently of each other hydrogen, an alkyl group having 1 to 8 carbon atoms, an alkoxy group having 1 to 8 carbon atoms, and a linear polyether group having a chain length of 4 to 30. And at least one is the alkoxy group, at least one is the linear polyether group, and R ⁴ is an alkylene group having 1 to 30 carbon atoms.)

(In the formula, R ⁵ and R ⁶ may form a ring structure, and R ⁵ is hydrogen, halogen, an alkyl group or alkylene group having 1 to 30 carbon atoms, an alkenyl group or alkenylene group having 2 to 30 carbon atoms, The alkynyl group or alkynylene group having 2 to 30 carbon atoms is selected from groups in which the terminal of the alkyl group or alkenyl group is substituted with a hydroxyl group or a carboxyl group, R ⁶ is an alkylene group having 1 to 30 carbon atoms, 2 carbon atoms Selected from ˜30 alkenylene groups and alkynylene groups having 2 to 30 carbon atoms, and x is an integer of 1 or more.)

(Wherein R ⁷ and R ⁸ may form a ring structure, and R ⁷ is hydrogen, halogen, an alkyl or alkylene group having 1 to 30 carbon atoms, an alkenyl group or alkenylene group having 2 to 30 carbon atoms, The alkynyl group or alkynylene group having 2 to 30 carbon atoms is selected from groups in which the terminal of the alkyl group or alkenyl group is substituted with a hydroxyl group or a carboxyl group, and R ⁸ is an alkylene group having 1 to 30 carbon atoms or 2 carbon atoms. ˜30 alkenylene group and C 2-30 alkynylene group, y is an integer of 1 or more.)

  The pneumatic tire using the rubber composition for tires of the present invention can improve the driving stability to a level higher than the conventional level while reducing rolling resistance and improving fuel efficiency. Moreover, since the processability of the rubber composition for tires is excellent, the quality of the pneumatic tire can be improved and stably manufactured.

  In the tire rubber composition of the present invention, the rubber component is a diene rubber, and examples thereof include natural rubber, isoprene rubber, butadiene rubber, styrene-butadiene rubber, and acrylonitrile-butadiene rubber. Of these, natural rubber, isoprene rubber, butadiene rubber, and styrene-butadiene rubber are preferable. These diene rubbers can be used alone or as any blend.

  The rubber composition for tires of the present invention contains 50 to 120 parts by weight, preferably 55 to 100 parts by weight of silica with respect to 100 parts by weight of the diene rubber. Improve dynamic viscoelastic properties such as loss tangent (tan δ) of rubber composition by blending silica, suppress heat generation, reduce rolling resistance, improve fuel efficiency, and improve wet performance Can do. When the amount of silica is less than 50 parts by weight, the effect of reducing tan δ (60 ° C.) of the rubber composition cannot be sufficiently obtained. If the compounding amount of silica exceeds 120 parts by weight, tan δ (60 ° C.) deteriorates.

  As silica, silica usually used in a rubber composition for tires, for example, wet method silica, dry method silica, or surface-treated silica can be used. Silica can be used by appropriately selecting from commercially available products. Moreover, the silica obtained by the normal manufacturing method can be used.

The CTAB specific surface area of silica is not particularly limited, but is preferably 180 to 280 m ² / g, more preferably 190 to 250 m ² / g. When the CTAB specific surface area of silica is less than 180 m ² / g, the steering stability is deteriorated, which is not preferable. On the other hand, if the CTAB specific surface area of silica exceeds 280 m ² / g, the rolling resistance deteriorates, which is not preferable. In addition, the CTAB specific surface area of a silica shall be calculated | required based on JISK6217-3.

  In the present invention, fillers other than silica can be blended. Examples of other fillers include carbon black, clay, mica, talc, calcium carbonate, aluminum hydroxide, aluminum oxide, and titanium oxide. Of these, carbon black, calcium carbonate, and aluminum hydroxide are preferable. By blending other fillers, the strength and hardness of the rubber composition can be increased, and the handling stability when made into a tire can be improved. Moreover, when the rubber composition for tires contains carbon black, the strength and wear resistance of the rubber composition can be improved.

  In the rubber composition of the present invention, silica is blended with a silane coupling agent having a mercapto group and / or a blocked mercapto group (hereinafter sometimes referred to as “mercapto silane coupling agent”). The dispersibility of the silica can be improved and the performance of silica can be fully expressed. The mercapto-based silane coupling agent is a mercaptosilane compound that always contains at least one of a mercapto group (—SH) and a blocked mercapto group in its chemical structure. This mercaptosilane compound has a Si—O bond in its chemical structure. Examples of the Si—O bond include a structure in which a hydrogen atom, a halogen atom, a carbon atom, a nitrogen atom, a silicon atom, or the like is bonded to an oxygen atom of Si—O—. Among these, a bond having a structure of Si—O—H or Si—O—C is preferable.

  In the present invention, the effect of reducing the tan δ (60 ° C.) of the rubber composition is derived by increasing the affinity with silica by blending a mercapto-based silane coupling agent and improving the dispersibility thereof. be able to. The blending amount of the mercapto silane coupling agent is 2.4 to 12 parts by weight with respect to 100 parts by weight of the diene rubber. When the blending amount of the mercapto-based silane coupling agent is less than 2.4 parts by weight, the effect of improving the dispersibility of silica cannot be obtained sufficiently. On the other hand, if the mercapto silane coupling agent exceeds 12 parts by weight, the silane coupling agents will condense and the desired effect cannot be obtained.

  In relation to silica, the blending amount of the mercapto-based silane coupling agent is preferably 4 to 18% by weight, more preferably 6 to 15% by weight of the silica blending amount.

The silane coupling agent having a mercapto group is not particularly limited as long as it is a silane compound having a mercapto group. The silane coupling agent having a blocked mercapto group is preferably a silane compound in which the hydrogen of the mercapto group of the mercaptosilane compound is substituted with a hydrocarbon group. As the hydrocarbon group, an alkanoyl group having 2 to 10 carbon atoms is preferable, and —CO— (CH ₂ ) ₆ CH ₃ is particularly preferable.

（式中、Ｒ¹，Ｒ²，Ｒ³は互いに独立して、水素、炭素数１〜８のアルキル基、炭素数１〜８のアルコキシ基、鎖長が４〜３０の直鎖ポリエーテル基、炭素数６〜３０のアリール基から選ばれると共に、少なくとも１つは前記アルコキシ基、少なくとも１つは前記直鎖ポリエーテル基であり、Ｒ⁴は炭素数１〜３０のアルキレン基である。）

（式中、Ｒ⁵およびＲ⁶で環構造を形成してもよく、Ｒ⁵は水素、ハロゲン、炭素数１〜３０のアルキル基或いはアルキレン基、炭素数２〜３０のアルケニル基或いはアルケニレン基、炭素数２〜３０のアルキニル基或いはアルキニレン基、前記アルキル基或いはアルケニル基の末端がヒドロキシル基若しくはカルボキシル基で置換された基から選ばれ、Ｒ⁶は炭素数１〜３０のアルキレン基、炭素数２〜３０のアルケニレン基、炭素数２〜３０のアルキニレン基から選ばれ、ｘは１以上の整数である。）

（式中、Ｒ⁷およびＲ⁸で環構造を形成してもよく、Ｒ⁷は水素、ハロゲン、炭素数１〜３０のアルキル基或いはアルキレン基、炭素数２〜３０のアルケニル基或いはアルケニレン基、炭素数２〜３０のアルキニル基或いはアルキニレン基、前記アルキル基或いはアルケニル基の末端がヒドロキシル基若しくはカルボキシル基で置換された基から選ばれ、Ｒ⁸は炭素数１〜３０のアルキレン基、炭素数２〜３０のアルケニレン基、炭素数２〜３０のアルキニレン基から選ばれ、ｙは１以上の整数である。） In the present invention, the mercapto silane coupling agent is preferably a mercaptosilane compound represented by the following formula (2) or a copolymer having the structure of the following formulas (3) and (4).

Wherein R ¹ , R ² and R ³ are independently of each other hydrogen, an alkyl group having 1 to 8 carbon atoms, an alkoxy group having 1 to 8 carbon atoms, and a linear polyether group having a chain length of 4 to 30. And at least one is the alkoxy group, at least one is the linear polyether group, and R ⁴ is an alkylene group having 1 to 30 carbon atoms.)

(In the formula, R ⁵ and R ⁶ may form a ring structure, and R ⁵ is hydrogen, halogen, an alkyl group or alkylene group having 1 to 30 carbon atoms, an alkenyl group or alkenylene group having 2 to 30 carbon atoms, The alkynyl group or alkynylene group having 2 to 30 carbon atoms is selected from groups in which the terminal of the alkyl group or alkenyl group is substituted with a hydroxyl group or a carboxyl group, R ⁶ is an alkylene group having 1 to 30 carbon atoms, 2 carbon atoms Selected from ˜30 alkenylene groups and alkynylene groups having 2 to 30 carbon atoms, and x is an integer of 1 or more.)

(Wherein R ⁷ and R ⁸ may form a ring structure, and R ⁷ is hydrogen, halogen, an alkyl or alkylene group having 1 to 30 carbon atoms, an alkenyl group or alkenylene group having 2 to 30 carbon atoms, The alkynyl group or alkynylene group having 2 to 30 carbon atoms is selected from groups in which the terminal of the alkyl group or alkenyl group is substituted with a hydroxyl group or a carboxyl group, and R ⁸ is an alkylene group having 1 to 30 carbon atoms or 2 carbon atoms. Selected from ˜30 alkenylene groups and alkynylene groups having 2 to 30 carbon atoms, and y is an integer of 1 or more.)

In the mercapto-based silane coupling agent represented by the above general formula (2), R ¹ , R ² , and R ³ are independently of each other hydrogen, an alkyl group having 1 to 8 carbon atoms, and 1 to 8 carbon atoms. An alkoxy group, a linear polyether group having a chain length of 4 to 30, and an aryl group having 6 to 30 carbon atoms. Preferred are hydrogen, an alkyl group having 1 to 8 carbon atoms, an alkoxy group having 1 to 3 carbon atoms, and a linear polyether group having a chain length of 10 to 29. The linear polyether group is preferably represented by the formula —O— (R ¹¹ —O) p—R ¹² . In the polyether moiety (R ¹¹ —O) p, R ¹¹ is an alkylene group having 2 to 4 carbon atoms, preferably an ethylene group, a trimethylene group (—CH ₂ CH ₂ CH ₂ —), or a propylene group. R ¹¹ may be one type or a plurality of types. p is an average value of the repeating number of the ether moiety, and is a number of 2 to 15, preferably 3 to 10, more preferably 3.5 to 8. R ¹² is an alkyl group having 10 to 16 carbon atoms, preferably 11 to 15 carbon atoms. The alkyl polyether group may be a mixture of a plurality of types. For example, —O— (CH ₂ CH ₂ —O) ₅ — (CH ₂ ) ₁₀ CH ₃ , —O— (CH ₂ CH ₂ —O) ₅ — (CH ₂ ) ₁₁ CH ₃ , —O— (CH ₂ CH ₂ —O) ₅ — (CH ₂ ) ₁₂ CH ₃ , —O— (CH ₂ CH ₂ —O) ₅ — (CH ₂ ) ₁₃ CH ₃ , —O— (CH ₂ CH ₂ —O) ₅ — (CH ₂ ) ₁₄ CH ₃ , —O— (CH ₂ CH ₂ —O) ₃ — (CH ₂ ) ₁₂ CH ₃ , —O— (CH ₂ CH ₂ —O) ₄ — (CH ₂ ) ₁₂ CH ₃ , —O— (CH ₂ CH ₂ —O) ₆ — (CH ₂ ) ₁₂ CH ₃ , —O— (CH ₂ CH ₂ —O) ₇ — (CH ₂ ) ₁₂ CH _{3 and the} like are exemplified.

In the formula (2), at least one of R ¹ , R ² and R ³ is an alkoxy group having 1 to 8 carbon atoms, and at least one is a linear polyether group having a chain length of 4 to 30. The mercapto silane coupling agent represented by (2) necessarily has an alkoxy group and a linear polyether group.

R ⁴ is an alkylene group having 1 to 30 carbon atoms, preferably an alkylene group having 1 to 12 carbon atoms.

Examples of the mercaptosilane compound represented by the above formula (2) preferably used in the present invention include [C ₁₁ H ₂₃ O (CH ₂ CH ₂ O) ₅ ] (CH ₂ CH ₂ O) ₂ Si (CH ₂ ) ₃ SH,
_{[C 12 H 25 O (CH} 2 CH 2 O) 3] (CH 2 CH 2 O) 2 Si (CH 2) 3 SH,
_{[C 12 H 25 O (CH} 2 CH 2 O) 4] (CH 2 CH 2 O) 2 Si (CH 2) 3 SH,
_{[C 12 H 25 O (CH} 2 CH 2 O) 5] (CH 2 CH 2 O) 2 Si (CH 2) 3 SH,
_{[C 12 H 25 O (CH} 2 CH 2 O) 6] (CH 2 CH 2 O) 2 Si (CH 2) 3 SH,
_{[C 13 H 27 O (CH} 2 CH 2 O) 3] (CH 2 CH 2 O) 2 Si (CH 2) 3 SH,
_{[C 13 H 27 O (CH} 2 CH 2 O) 4] (CH 2 CH 2 O) 2 Si (CH 2) 3 SH,
_{[C 13 H 27 O (CH} 2 CH 2 O) 5] (CH 2 CH 2 O) 2 Si (CH 2) 3 SH,
_{[C 13 H 27 O (CH} 2 CH 2 O) 6] (CH 2 CH 2 O) 2 Si (CH 2) 3 SH,
_{[C 14 H 29 O (CH} 2 CH 2 O) 3] (CH 2 CH 2 O) 2 Si (CH 2) 3 SH,
_{[C 14 H 29 O (CH} 2 CH 2 O) 4] (CH 2 CH 2 O) 2 Si (CH 2) 3 SH,
_{[C 14 H 29 O (CH} 2 CH 2 O) 5] (CH 2 CH 2 O) 2 Si (CH 2) 3 SH,
_{[C 14 H 29 O (CH} 2 CH 2 O) 6] (CH 2 CH 2 O) 2 Si (CH 2) 3 SH,
_{[C 15 H 31 O (CH} 2 CH 2 O) 5] (CH 2 CH 2 O) 2 Si (CH 2) 3 SH,
_{[C 11 H 23 O (CH} 2 CH 2 O) 5] 2 (CH 2 CH 2 O) Si (CH 2) 3 SH,
_{[C 12 H 25 O (CH} 2 CH 2 O) 3] 2 (CH 2 CH 2 O) Si (CH 2) 3 SH,
_{[C 12 H 25 O (CH} 2 CH 2 O) 4] 2 (CH 2 CH 2 O) Si (CH 2) 3 SH,
_{[C 12 H 25 O (CH} 2 CH 2 O) 5] 2 (CH 2 CH 2 O) Si (CH 2) 3 SH,
_{[C 12 H 25 O (CH} 2 CH 2 O) 6] 2 (CH 2 CH 2 O) Si (CH 2) 3 SH,
_{[C 13 H 27 O (CH} 2 CH 2 O) 3] 2 (CH 2 CH 2 O) Si (CH 2) 3 SH,
_{[C 13 H 27 O (CH} 2 CH 2 O) 4] 2 (CH 2 CH 2 O) Si (CH 2) 3 SH,
_{[C 13 H 27 O (CH} 2 CH 2 O) 5] 2 (CH 2 CH 2 O) Si (CH 2) 3 SH,
_{[C 13 H 27 O (CH} 2 CH 2 O) 6] 2 (CH 2 CH 2 O) Si (CH 2) 3 SH,
_{[C 14 H 29 O (CH} 2 CH 2 O) 3] 2 (CH 2 CH 2 O) Si (CH 2) 3 SH,
_{[C 14 H 29 O (CH} 2 CH 2 O) 4] 2 (CH 2 CH 2 O) Si (CH 2) 3 SH,
_{[C 14 H 29 O (CH} 2 CH 2 O) 5] 2 (CH 2 CH 2 O) Si (CH 2) 3 SH,
_{[C 14 H 29 O (CH} 2 CH 2 O) 6] 2 (CH 2 CH 2 O) Si (CH 2) 3 SH,
_{[C 15 H 31 O (CH} 2 CH 2 O) 5] 2 (CH 2 CH 2 O) Si (CH 2) 3 SH, etc. are exemplified. Among them _{[C 13 H 27 O- (CH} 2 CH 2 O) 5] 2 (CH 2 CH 2 O) Si (CH 2) 3 SH, [C 13 H 27 O- (CH 2 CH 2 O) 5] (CH ₂ CH ₂ O) ₂ Si (CH ₂ ) ₃ SH is preferred.

Examples of the mercaptosilane compound in which the mercapto group of the compound represented by the above formula (2) is blocked include (CH ₃ CH ₂ O) ₃ Si (CH ₂ ) ₃ S—CO— (CH ₂ ) ₆ CH ₃ ( Momentive Performance Materials NXT) is exemplified.

In the mercaptosilane compound having the segment represented by the general formulas (3) and (4), R ⁵ and R ⁶ may form a ring structure, or R ⁷ and R ⁸ may form a ring structure. . R ⁵ and R ⁷ are hydrogen, halogen, an alkyl group or alkylene group having 1 to 30 carbon atoms, an alkenyl group or alkenylene group having 2 to 30 carbon atoms, an alkynyl group or alkynylene group having 2 to 30 carbon atoms, the alkyl group or The terminal is selected from a group in which the terminal of the alkenyl group is substituted with a hydroxyl group or a carboxyl group. The alkyl group, alkynyl group, alkynylene group, alkylene group, alkenylene group and alkynylene group described above may be branched or unbranched, respectively.

R ⁶ and R ⁸ are selected from an alkylene group having 1 to 30 carbon atoms, an alkenylene group having 2 to 30 carbon atoms, and an alkynylene group having 2 to 30 carbon atoms. The alkylene group, alkenylene group and alkynylene group described above may be branched or unbranched, respectively.

  The content of the segment represented by the above formula (3) is preferably 20 to 99 mol%, preferably 30 to 95 mol%. If the content rate of the segment of Formula (3) is less than 20 mol%, it will be difficult to balance low rolling resistance, wet performance, and wear resistance. Moreover, when the content rate of the segment of Formula (3) exceeds 99 mol%, sufficient chemical bonding between the rubber and silica via the silane coupling agent does not occur, and low rolling resistance, wet performance and wear resistance are obtained. Sex worsens.

  The content of the segment represented by the above formula (4) is preferably 1 to 80 mol%, preferably 5 to 70 mol%. When the content of the segment represented by the formula (4) is less than 1 mol%, the chemical bonding between the rubber and the silica via the silane coupling agent does not occur sufficiently, and the low rolling resistance, wet performance and wear resistance are obtained. Gets worse. When the content rate of the segment represented by the formula (4) exceeds 80 mol%, it becomes difficult to balance workability and performance such as low rolling resistance, wet performance, and wear resistance.

In the present invention, as a mercapto-based silane coupling agent having a segment represented by the general formulas (3) and (4) that is preferably used, for example, NXT-Z30 (R ⁵ manufactured by Momentive Performance Materials) , R ⁷ : ethyl group, R ⁶ , R ⁸ : ethylene group, segment represented by formula (3) is 70 mol%, segment represented by formula (4) is 30 mol%, mercapto group content: 4% ), NXT-Z45 (R ⁵ , R ⁷ : ethyl group, R ⁶ , R ⁸ : ethylene group, segment represented by formula (3) is 55 mol%, segment represented by formula (4) is 45 mol%, the content of mercapto group: 6%), NXT-Z60 segments represented by (R ^5, R ^7:: ethyl group, R ^6, R ⁸ ethylene group, the formula (3) 40 mol%, in the formula (4) Expressed Segment 60 mole% that, the content of mercapto group: 9%) and the like.

  As the mercapto-based silane coupling agent used in the present invention, a mercaptosilane compound other than the mercaptosilane compound represented by the above formula (2) and the copolymer having the structures of the formulas (3) and (4) may be used. it can. Examples of such mercapto-based silane coupling agents include 3-mercaptopropyl (trimethoxysilane), 3-mercaptopropyl (triethoxysilane), 3-mercaptopropyl (diethoxymethoxysilane), 3-mercaptopropyl (tripropoxy). Silane), 3-mercaptopropyl (dipropoxymethoxysilane), 3-mercaptopropyl (tributoxysilane), 3-mercaptopropyl (dibutoxymethoxysilane), 3-mercaptopropyl (dimethoxymethylsilane), 3-mercaptopropyl ( Methoxydimethylsilane), 3-mercaptopropyl (diethoxymethylsilane), 3-mercaptopropyl (ethoxydimethylsilane), 3-mercaptopropyl (dipropoxymethylsilane), 3-mercapto Lopyl (propoxydimethylsilane), 3-mercaptopropyl (diisopropoxymethylsilane), 3-mercaptopropyl (isopropoxydimethylsilane), 3-mercaptopropyl (dibutoxymethylsilane), 3-mercaptopropyl (butoxydimethylsilane) 2-mercaptoethyl (trimethoxysilane), 2-mercaptoethyl (triethoxysilane), mercaptomethyl (trimethoxysilane), mercaptomethyl (triethoxysilane), 3-mercaptobutyl (trimethoxysilane), 3-mercapto A butyl (triethoxysilane) etc. can be illustrated. Of these, 3-mercaptopropyl (trimethoxysilane) and 3-mercaptopropyl (triethoxysilane) are preferable.

（式中、ｎは２〜１０の整数を表す。） In the rubber composition of the present invention, 0.03 to 2 parts by weight of S- (aminoalkyl) thiosulfuric acid represented by the following formula (1) or a metal salt thereof is blended with 100 parts by weight of the diene rubber.

(In the formula, n represents an integer of 2 to 10.)

  In said formula (1), n represents the integer of 1-10, Preferably it is 2-6, More preferably, it is an integer of 3-4. As S- (aminoalkyl) thiosulfuric acid, S- (aminomethyl) thiosulfuric acid, S- (2-aminoethyl) thiosulfuric acid, S- (3-aminopropyl) thiosulfuric acid, S- (4-aminobutyl) Thiosulfuric acid, S- (5-aminopentyl), S- (6-aminohexyl) thiosulfuric acid, S- (7-aminopeptyl) thiosulfuric acid, S- (8-aminooctyl) thiosulfuric acid, S- (9-aminononyl) ) Thiosulfuric acid, S- (10-aminodecyl) thiosulfuric acid. Of these, S- (3-aminopropyl) thiosulfuric acid and S- (4-aminobutyl) thiosulfuric acid are preferable.

  Examples of the metal salt of S- (aminoalkyl) thiosulfuric acid represented by the above formula (1) include lithium ions, sodium ions, potassium ions, cesium ions, cobalt ions, copper ions, and zinc ions as metal ions. it can.

  In the rubber composition in which the silane coupling agent having a mercapto group coexists with silica, the strong action of the mercapto group on the silica suppresses the aggregation of the silica and improves the dynamic viscoelastic behavior such as tan δ. On the other hand, it has been a problem in the past to easily react with a vulcanizing compound and easily cause early vulcanization and to reduce rubber hardness. On the other hand, in the present invention, the above-described S- (aminoalkyl) thiosulfuric acid is blended with silica and a mercapto-based silane coupling agent so that the amino group of S- (aminoalkyl) thiosulfuric acid is a mercapto-based silane coupling. By acting on the agent, the scorch resistance of the rubber composition can be improved to suppress early vulcanization, and the rubber component can be modified to improve the rubber hardness. For this reason, the balance of tan δ (60 ° C.), rubber hardness and processability of the rubber composition can be improved to a level higher than the conventional level.

  The amount of S- (aminoalkyl) thiosulfuric acid is 0.03 to 2 parts by weight, preferably 0.05 to 1.5 parts by weight, based on 100 parts by weight of the diene rubber. When the amount of S- (aminoalkyl) thiosulfuric acid is less than 0.03 part by weight, the effect of improving the tan δ (60 ° C.), rubber hardness and processability of the rubber composition cannot be sufficiently obtained. On the other hand, when the amount of S- (aminoalkyl) thiosulfuric acid exceeds 2%, the physical property improving effect is not observed.

  The rubber composition for tires of the present invention includes a rubber tread part, an under tread part, a side wall part, a bead filler part, and a cord covering rubber such as a carcass layer, a belt layer, and a belt cover layer, and a run flat tire. Can be suitably used for a crescent-shaped side reinforcing rubber layer, a rim cushion portion, and the like. Since the pneumatic tire using the rubber composition of the present invention for these members has low heat generation during running, it can reduce rolling resistance and improve fuel efficiency. At the same time, by improving the mechanical properties of the rubber composition, it is possible to maintain and improve the handling stability and processability at or above conventional levels.

  EXAMPLES Hereinafter, although an Example demonstrates this invention further, the scope of the present invention is not limited to these Examples.

  13 types of rubber compositions for tires (Examples 1 to 7 and Comparative Examples 1 to 6) having the composition shown in Tables 1 and 2 were blended with common compounding agents shown in Table 3, sulfur and vulcanization accelerators. The components to be removed were prepared by adding sulfur and a vulcanization accelerator to a master batch which was kneaded and discharged at 160 ° C. for 5 minutes with a 1.8 L closed mixer and kneaded with an open roll.

  In Tables 1 and 2, since SBR contains 37.5 parts by weight of oil-extended oil, the actual amount added in the column for the amount added and the net SBR amount excluding oil-extended oil in parentheses are listed. did. Moreover, the amount of the compounding agent described in Table 3 was expressed in parts by weight with respect to 100 parts by weight (net amount of rubber) of the diene rubber described in Tables 1 and 2.

  The scorch resistance of the obtained 13 kinds of rubber compositions was evaluated by the method shown below.

Scorch resistance The scorch time of the obtained rubber composition was measured in accordance with JIS K6300-1: 2001 using an L-shaped rotor at a test temperature of 125 ° C. The obtained results are shown in the column of “Scorch resistance” as an index with the value of Comparative Example 1 being 100. A larger index means longer scorch time and better scorch resistance.

  Next, 13 types of rubber compositions for tires were respectively vulcanized at 150 ° C. for 15 minutes in molds of predetermined shapes to prepare test pieces. The rubber hardness and dynamic viscoelasticity ( 60 ° C. tan δ) was evaluated.

Rubber hardness Using the obtained test piece, it was measured at a temperature of 25 ° C. with a durometer type A according to JIS K6253. The obtained results are shown in the column of “rubber hardness” with the value of Comparative Example 1 being 100. The larger the rubber hardness index, the better the steering stability.

Dynamic viscoelasticity (tan δ at 60 ° C)
Based on JIS K6394, the obtained test piece was subjected to a loss tangent tan δ at a temperature of 60 ° C. under the conditions of an initial strain of 10%, an amplitude of ± 2%, and a frequency of 20 Hz, using a viscoelastic spectrometer manufactured by Toyo Seiki Seisakusho. It was measured. The obtained results are shown in the column of “tan δ (60 ° C.)” as an index with the value of Comparative Example 1 being 100. The smaller the index of tan δ (60 ° C.), the smaller the heat generation, and the smaller the rolling resistance when the tire is made, the better the fuel efficiency.

The types of raw materials used in Tables 1 and 2 are shown below.
SBR: Styrene-butadiene rubber, Toughden E580 manufactured by Asahi Kasei Chemicals Co., Ltd., an oil exhibition carbon black containing 37.5 parts by weight of oil with respect to 100 parts by weight of the rubber component: Show Black N339 manufactured by Cabot Japan Co., Ltd.
Silica 1: Zeosil 1165MP manufactured by Rhodia, CTAB specific surface area of 160 m ² / g
Silica 2: Rhodia Zeosil 200MP, CTAB specific surface area of 200 m ² / g
Coupling agent 1: Sulfur-containing silane coupling agent, Si69 manufactured by Evonik Degussa, bis (3-triethoxysilylpropyl) tetrasulfide coupling agent 2: mercapto silane coupling agent represented by the above formula (2), Shin-Etsu KBM-803, 3-mercaptopropyltrimethoxysilane (CH ₂ CH ₂ O) Si (CH ₂ ) ₃ SH manufactured by Silicone
Coupling agent 3: Silane coupling agent in which the mercapto group of the compound represented by the formula (2) is blocked, NXT manufactured by Momentive Performance Materials, (CH ₃ CH ₂ O) ₃ Si (CH ₂ ) ₃ S -CO- (CH _{2) 6} CH ₃
Coupling agent 4: Silane coupling agent having a blocked mercapto group, NXT-Z45 manufactured by Momentive Performance Materials, a segment represented by the above formulas (3) and (4), R ⁵ , R ⁷ Is ethyl group, R ⁶ and R ⁸ are ethylene groups, the segment of formula (3) is 55 mol%, the segment of formula (4) is 45 mol%
Coupling agent 5: Mercapto silane coupling agent represented by the formula (2), Si363 manufactured by Evonik Degussa, [C ₁₃ H ₂₇ O (CH ₂ CH ₂ O) ₅ ] ₂ (CH ₂ CH ₂ O) Si (CH ₂ ) ₃ SH
Organic thiosulfuric acid 1: S- (3-aminopropyl) thiosulfuric acid (manufactured by Sumitomo Chemical Co., Ltd.)
Organic thiosulfuric acid 2: S- (4-aminobutyl) thiosulfuric acid (manufactured by Sumitomo Chemical Co., Ltd.)
Vulcanization accelerator 2: Perkacit TBzTD made by Flexis
Vulcanization accelerator 3: Sumokinol DG manufactured by Sumitomo Chemical Co., Ltd.

In addition, the kind of raw material used in Table 3 is shown below.
Aroma oil: Process X-140 manufactured by Japan Energy
Anti-aging agent: Seiko Chemical Co., Ltd. Ozonon 6C
Wax: Extract No. 4 S manufactured by Showa Shell Sekiyu KK
Zinc Hana: Zinc Oxide, manufactured by Shodo Chemical Industry Co., Ltd. Sulfur: Oil treatment sulfur vulcanization accelerator manufactured by Hosoi Chemical Industry Co., Ltd.

  As apparent from Table 2, it was confirmed that the rubber compositions for tires of Examples 1 to 7 improved the balance of scorch resistance, rubber hardness and tan δ (60 ° C.) to the conventional level or more.

  As is clear from Table 1, the rubber compositions of Comparative Examples 2 to 5 reduce tan δ (60 ° C.), but do not contain S- (aminoalkyl) thiosulfuric acid, so that the rubber hardness decreases. Further, the rubber compositions of Comparative Examples 2, 4, and 5 have poor scorch resistance.

  Since the rubber composition of Comparative Example 5 does not use a silane coupling agent having a mercapto group and / or a blocked mercapto group, the scorch resistance is deteriorated and the effect of improving rubber hardness and tan δ (60 The effect of reducing (° C.) is insufficient.

Claims (4)

50 to 120 parts by weight of silica and 2.4 to 12 parts by weight of a silane coupling agent having a mercapto group and / or a blocked mercapto group are represented by the following formula (1) with respect to 100 parts by weight of the diene rubber. A rubber composition for tires, comprising 0.03 to 2 parts by weight of S- (aminoalkyl) thiosulfuric acid or a metal salt thereof.

(In the formula, n represents an integer of 1 to 10.) The tire rubber composition according to claim 1, wherein the silica has a CTAB specific surface area of 180 to 280 m ² / g. The silane coupling agent is a mercaptosilane compound represented by the following formula (2) or a copolymer having a structure of the following formulas (3) and (4). Rubber composition for tires.

Wherein R ¹ , R ² and R ³ are independently of each other hydrogen, an alkyl group having 1 to 8 carbon atoms, an alkoxy group having 1 to 8 carbon atoms, and a linear polyether group having a chain length of 4 to 30. And at least one is the alkoxy group, at least one is the linear polyether group, and R ⁴ is an alkylene group having 1 to 30 carbon atoms.)

(In the formula, R ⁵ and R ⁶ may form a ring structure, and R ⁵ is hydrogen, halogen, an alkyl group or alkylene group having 1 to 30 carbon atoms, an alkenyl group or alkenylene group having 2 to 30 carbon atoms, The alkynyl group or alkynylene group having 2 to 30 carbon atoms is selected from groups in which the terminal of the alkyl group or alkenyl group is substituted with a hydroxyl group or a carboxyl group, R ⁶ is an alkylene group having 1 to 30 carbon atoms, 2 carbon atoms Selected from ˜30 alkenylene groups and alkynylene groups having 2 to 30 carbon atoms, and x is an integer of 1 or more.)

(Wherein R ⁷ and R ⁸ may form a ring structure, and R ⁷ is hydrogen, halogen, an alkyl or alkylene group having 1 to 30 carbon atoms, an alkenyl group or alkenylene group having 2 to 30 carbon atoms, The alkynyl group or alkynylene group having 2 to 30 carbon atoms is selected from groups in which the terminal of the alkyl group or alkenyl group is substituted with a hydroxyl group or a carboxyl group, and R ⁸ is an alkylene group having 1 to 30 carbon atoms or 2 carbon atoms. ˜30 alkenylene group and C 2-30 alkynylene group, y is an integer of 1 or more.)   A pneumatic tire using the rubber composition for tires according to claim 1, 2 or 3.