JP2016030815A - Rubber composition for tire - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a rubber composition for tire capable of reducing a heat generation property.SOLUTION: There is provided a rubber composition by blending 30 to 70 pts.wt. of silica with 100 pts.wt. of diene rubber and blending 6 to 20 wt.% of a silane coupling agent based on the silica blended amount, which satisfies that (a) the rubber composition has tanδ at 60°C of less 0.15 and (b) the minimum size of an aggregate forming a hierarchical structure of the silica Ris over 14 nm and 28 nm or less when a scattering profile measured and obtained by an ultra small angle X-ray scattering method fits the Unified-Guinier function.SELECTED DRAWING: None

Description

  The present invention relates to a rubber composition for tires that reduces heat generation.

  In recent years, as seen in the labeling systems in Japan and Europe and the smart way regulations in North America, it is important to reduce the environmental impact of pneumatic tires. For this reason, in the rubber composition used for the pneumatic tire for passenger cars and heavy duty vehicles such as trucks and buses, it is required to reduce the heat generation.

  In general, silica is mixed with a rubber composition for tires in order to reduce heat generation. However, even if silica is blended, there is a problem that the exothermic property cannot be sufficiently reduced unless the dispersibility in the diene rubber is improved.

  In recent years, an ultra-small angle X-ray scattering method (USAXS) has been proposed as a method for examining the hierarchical structure (primary particles, aggregates, agglomerates) of a rubber composition containing silica (see, for example, Non-Patent Document 1). ). However, the relationship between the hierarchical structure of the rubber composition containing silica and its exothermic properties has not yet been clarified.

S. Mihara, in Thesis: Reactive processing of silica filled tire rubber. 2008, Dept. of Elastomer Technol. And Eng., Uviv. Twente (the Netherlands)

  An object of the present invention is to provide a rubber composition for tires that is improved in low heat build-up to a conventional level or more.

In the tire rubber composition of the present invention that achieves the above object, 30 to 70 parts by weight of silica is blended with 100 parts by weight of a diene rubber, and 6 to 20% by weight of a silane coupling agent is blended with respect to the weight of the silica. The rubber composition is characterized by satisfying the following (a) and (b).
(A) The tan δ at 60 ° C. of the rubber composition is less than 0.15 (b) The rubber composition is measured by an ultra small angle X-ray scattering method, and the obtained scattering profile is applied to the Unified-Guiner function. The minimum size R _ss of the aggregates forming the silica hierarchical structure is greater than 14 nm and not greater than 28 nm.

In the tire rubber composition of the present invention, 30 to 70 parts by weight of silica and 6 to 20% by weight of the silane coupling agent are blended with 100 parts by weight of diene rubber, and (a) tan δ at 60 ° C. Less than 0.15, and (b) the minimum size R _{ss of} the silica aggregate measured by the ultra-small angle X-ray scattering method is more than 14 nm and not more than 28 nm. Can be smaller than the level.

  Since this rubber composition is also excellent in bending fatigue resistance, it can be suitably used for the side portion of a pneumatic tire.

  Since the rubber composition for tires of the present invention contains 55% by weight or more of natural rubber in 100% by weight of diene rubber, it can have excellent wear resistance and chipping resistance. It can be suitably used for a tread portion of a pneumatic tire.

The tire rubber composition of the present invention contains a diene rubber, silica and a silane coupling agent, (a) the rubber composition has a tan δ at 60 ° C. of less than 0.15, and (b) ultra-small angle X-ray scattering. The minimum size R _ss of silica aggregates measured by the method is more than 14 nm and not more than 28 nm.

  The rubber component in the tire rubber composition is composed of a diene rubber, and examples of the diene rubber include natural rubber, isoprene rubber, butadiene rubber, styrene butadiene rubber, acrylonitrile butadiene rubber, butyl rubber, and chloroprene rubber. it can. Of these, styrene butadiene rubber, butadiene rubber, and natural rubber are preferable.

  In particular, as a rubber composition for a tire constituting the toled portion of a heavy duty pneumatic tire, natural rubber is preferably 55% by weight or more, more preferably 75% by weight or more, and still more preferably 80% in 100% by weight of a diene rubber. It is good to contain ~ 100% by weight. By containing 55% by weight or more of natural rubber, a tire rubber composition excellent in wear resistance and chipping resistance can be obtained.

  In the tire rubber composition of the present invention, 30 to 70 parts by weight of silica is blended with 100 parts by weight of diene rubber. By adding silica, the exothermic property can be reduced. 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.

The amount of silica is 30 to 70 parts by weight, preferably 32 to 65 parts by weight, based on 100 parts by weight of the diene rubber. If the amount of silica is less than 30 parts by weight, the effect of reducing the heat build-up of the rubber composition cannot be sufficiently obtained. When the compounding amount of silica exceeds 70 parts by weight, it becomes difficult to make the minimum size R _ss of the aggregates forming the hierarchical structure of silica 28 nm or less.

The nitrogen adsorption specific surface area of silica is not particularly limited, but is preferably 150 to 400 m ² / g, more preferably 155 to 330 m ² / g, and further preferably 185 to 270 m ² / g. . When the nitrogen adsorption specific surface area of silica is less than 150 m ² / g, the wear resistance cannot be sufficiently improved. On the other hand, when the nitrogen adsorption specific surface area of silica exceeds 400 m ² / g, it becomes difficult to make the minimum size R _ss of the aggregate forming the hierarchical structure 28 nm or less, and the low heat generation property is deteriorated. In this specification, the nitrogen adsorption specific surface area of silica is a value measured by ISO 9277.

  In the rubber composition for tires of the present invention, the tan δ at 60 ° C. of the rubber composition (a) is less than 0.15. The tan δ at 60 ° C. is less than 0.15, preferably 0.03 to 0.14. When the tan δ at 60 ° C. of the rubber composition is less than 0.15, the heat build-up of the tire rubber composition can be reduced. In the present invention, tan δ at 60 ° C. is a value measured using a viscoelastic spectrometer at an initial strain of 10%, an amplitude of ± 2%, and a frequency of 20 Hz.

In addition, the rubber composition constituting the tread part is (b) when the rubber composition is measured by an ultra-small angle X-ray scattering method, and when the obtained scattering profile is applied to the Unified-Guiner function, it forms a hierarchical structure of silica. The minimum size R _ss of the aggregate is more than 14 nm and not more than 28 nm. That is, by estimating the size of the silica aggregate dispersed in the diene rubber by quantitative analysis based on the Unified-Guiner function of the scattering profile obtained by the ultra-small-angle X-ray scattering (USAXS) measurement, It is necessary to calculate the minimum size R _ss of the aggregate forming the hierarchical structure, and this R _ss needs to be greater than 14 nm and 28 nm or less.

Here, the measurement condition of the ultra-small angle X-ray scattering method (USAXS) is that the wave number q is 0.006 to 0.4 nm ⁻¹ (q = 4π / λsinθ; θ is the scattering angle, λ is 0.62 angstrom (X-ray energy) : 20 keV), exposure time is 488 msec, and camera length is 7.6 m). With respect to the obtained scattered image, an annular average of −90 to 180 ° is made to be one-dimensional, and the scattering profile is fitted using the following general formula (I) to calculate Rss. The rubber composition sample is measured at 100 ° C. using a vulcanized rubber sheet having a thickness of 0.5 mm.

The unified-guiner function is represented by the following general formula (I).

In the above general formula (I), q is the wave number, I (q) is the scattering intensity at the wave number q, A, B, C, D and E are constants, p is a power exponent, and R _ss forms a hierarchical structure. _Rg is the size of the higher-order aggregate, Dm is the mass fractal dimension, Ds is the surface fractal dimension, and d is the Euclidean dimension of the space.

The measurement result of the ultra small angle X-ray scattering method (USAXS) is obtained as a scattering profile with the wave number q as the horizontal axis and the scattering intensity I (q) as the vertical axis. By fitting the scattering profile so as to fit the general formula (I), constants A, B, C, D and E, an index p, a mass fractal dimension Dm, a surface fractal dimension Ds, and a hierarchical structure are formed. The minimum agglomerate size R _ss is estimated. The Euclidean dimension d is 3. Further, the size R _gg of the higher-order aggregate is not observed in the range of the wave number q in the present specification, and is therefore infinite, and the first and second terms of the general formula (I) can be ignored.

In the present invention, the minimum size R _ss of the aggregate forming the hierarchical structure is more than 14 nm and not more than 28 nm, preferably 16 to 24 nm, more preferably 17 to 23 nm. When the minimum size R _ss of the aggregate forming the hierarchical structure exceeds 28 nm, the effect of reducing the heat generation cannot be sufficiently obtained.

The inventors have found that the hierarchical structure of silica is related to the exothermic property of the rubber composition, and have completed the present invention. That is, in the hierarchical structure of the rubber composition containing silica, the exothermic property of the rubber composition can be reduced by reducing the minimum size R _ss of the aggregate forming the silica hierarchical structure. .

  The rubber composition for tires of the present invention contains a silane coupling agent in an amount of 6 to 20% by weight based on the silica weight. By incorporating a silane coupling agent, the dispersibility of silica can be improved. The amount of the silane coupling agent is preferably 3 to 20% by weight, more preferably 4 to 16% by weight, based on the silica weight. If the amount of the silane coupling agent is less than 6% by weight, there is a possibility that the dispersibility of silica cannot be improved sufficiently. When the compounding amount of the silane coupling agent exceeds 20% by weight, the rubber composition is liable to cause early vulcanization and the molding processability may be deteriorated.

  The silane coupling agent is not particularly limited as long as it can be used for a rubber composition for tires. For example, bis- (3-triethoxysilylpropyl) tetrasulfide, bis (3-triethoxy Examples thereof include sulfur-containing silane coupling agents such as (silylpropyl) disulfide, 3-trimethoxysilylpropylbenzothiazole tetrasulfide, γ-mercaptopropyltriethoxysilane, and 3-octanoylthiopropyltriethoxysilane. Of these, a silane coupling agent having a mercapto group (hereinafter sometimes simply referred to as “mercaptosilane”) is preferable, and the affinity with silica can be increased and the dispersibility thereof can be improved. These silane coupling agents may be blended singly or in combination.

（式中、Ｒ³，Ｒ⁴，Ｒ⁵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、Ｒ⁶は炭素数１〜３０のアルキレン基である。）

（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、ｘは１以上の整数である。）

（式中、Ｒ⁹およびＲ¹⁰で環構造を形成してもよく、Ｒ⁹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、Ｒ¹⁰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。）

（式中、Ａはスルフィド基を含有する２価の有機基、Ｂは炭素数５〜１０の１価の炭化水素基、Ｃは加水分解性基、Ｄはメルカプト基を含有する有機基、Ｒ¹¹は炭素数１〜４の１価の炭化水素基であり、ａ〜ｅは、０≦ａ＜１、０≦ｂ＜１、０＜ｃ＜３、０＜ｄ＜１、０≦ｅ＜２、０＜２ａ＋ｂ＋ｃ＋ｄ＋ｅ＜４の関係式を満たす。ただしａ、ｂの少なくとも１つが０でない。） The rubber composition for tires of the present invention is preferably blended with mercaptosilane, so that the minimum size R _ss of the aggregate forming the tan δ at 60 ° C. and the hierarchical structure of silica can be easily adjusted. The mercaptosilane is preferably a mercaptosilane compound represented by the following general formula (2), a copolymer having the structure of the following general formulas (3) and (4), or represented by the following general formula (5). A polysiloxane having an average composition formula is preferable, and the affinity with silica can be increased to improve the dispersibility. Among these, mercaptosilane represented by the formula (5) is preferable. These mercaptosilane compounds may be blended singly or in combination.

(Wherein R ³ , R ⁴ and R ⁵ 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 ⁶ is an alkylene group having 1 to 30 carbon atoms.)

(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 x is an integer of 1 or more.)

(In the formula, R ⁹ and R ¹⁰ may form a ring structure, and R ⁹ 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, R ¹⁰ is an alkylene group having 2 to 30 carbon atoms, R 2 is an alkylene group having 2 to 30 carbon atoms, R 1 is an alkylene group having 2 to 30 carbon atoms, or a group having 2 or more 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 formula, A is a divalent organic group containing a sulfide group, B is a monovalent hydrocarbon group having 5 to 10 carbon atoms, C is a hydrolyzable group, D is an organic group containing a mercapto group, R ¹¹ is a monovalent hydrocarbon group having 1 to 4 carbon atoms, and a to e are 0 ≦ a <1, 0 ≦ b <1, 0 <c <3, 0 <d <1, 0 ≦ e <. 2. 0 <2a + b + c + d + e <4 is satisfied, provided that at least one of a and b is not 0.)

In the mercaptosilane compound represented by the general formula (2), R ³ , R ⁴ , and R ⁵ 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 chain. A linear polyether group having a 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 ¹³ —O) p—R ¹⁴ . In the polyether moiety (R ¹³ —O) p, R ¹³ 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 ¹³ 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 ¹⁴ 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 ³ , R ⁴ , and R ⁵ 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 mercaptosilane compound represented by (2) necessarily has an alkoxy group and a linear polyether group.

R ⁶ 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 general 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.

In the mercaptosilane compound having the segment represented by the general formulas (3) and (4), R ⁷ and R ⁸ may form a ring structure, or R ⁹ and R ¹⁰ may form a ring structure. . R ⁷ and R ⁹ 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 ⁸ and R ¹⁰ 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 general 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 becomes difficult to balance with performance such as workability, bending fatigue resistance, and wear resistance. Moreover, when the content rate of the segment of Formula (3) exceeds 99 mol%, the chemical coupling | bonding of the rubber | gum and silica through a silane compound will not fully arise, but exothermic property will deteriorate.

  The content of the segment represented by the general formula (4) is preferably 1 to 80 mol%, preferably 5 to 70 mol%. If the content rate of the segment represented by Formula (4) is less than 1 mol%, the chemical coupling | bonding of the rubber | gum and silica through a silane compound will not fully arise, but exothermic property will deteriorate. When the content rate of the segment represented by the formula (4) exceeds 80 mol%, it becomes difficult to balance performance such as workability, bending fatigue resistance, and wear resistance.

  The mercaptosilane compound having the average composition formula represented by the general formula (5) has a siloxane skeleton as its skeleton. The siloxane skeleton can be linear, branched, three-dimensional structures, or a combination thereof.

  In the general formula (5), at least one of a and b is not 0. That is, at least one of a and b may be greater than 0, and both a and b may be greater than 0. Therefore, this polysiloxane necessarily contains at least one selected from a divalent organic group A containing a sulfide group and a monovalent hydrocarbon group B having 5 to 10 carbon atoms.

  When the silane compound composed of the polysiloxane having the average composition formula represented by the general formula (5) has a monovalent hydrocarbon group B having 5 to 10 carbon atoms, the mercapto group is protected and the Mooney scorch time is long. At the same time, it has excellent workability by having excellent compatibility with rubber. For this reason, the subscript b of the hydrocarbon group B in the general formula (5) is preferably 0.10 ≦ b ≦ 0.89. Specific examples of the hydrocarbon group B preferably include monovalent hydrocarbon groups having 6 to 10 carbon atoms, more preferably 8 to 10 carbon atoms, such as hexyl group, octyl group, and decyl group. As a result, the mercapto group can be protected, the Mooney scorch time can be extended, the workability can be improved, and the low heat build-up, the bending fatigue resistance, and the wear resistance can be improved.

  When the silane compound composed of the polysiloxane having the average composition formula represented by the general formula (5) has a divalent organic group A containing a sulfide group, low heat build-up, bending fatigue resistance, wear resistance , To improve the workability (especially the maintenance and prolonged Mooney scorch time). For this reason, the subscript a of the divalent organic group A containing a sulfide group in the general formula (5) is preferably 0 <a ≦ 0.50.

  The divalent organic group A containing a sulfide group can be a hydrocarbon group that may have a hetero atom such as an oxygen atom, a nitrogen atom, or a sulfur atom.

The sulfide group-containing organic group A is preferably a group represented by the following general formula (6) from the viewpoint of improving the dispersibility of silica and further improving processability.

  In said general formula (6), n represents the integer of 1-10, and it is preferable that it is an integer of 2-4 especially. Moreover, x represents the integer of 1-6, and it is preferable that it is an integer of 2-4 especially. Note that * indicates a binding position.

Specific examples of the group represented by the general formula (6), for _{example, * - CH 2 -S 2 -CH} 2 - *, * - C 2 H 4 -S 2 -C 2 H 4 - *, * _{-C 3 H 6 -S 2 -C 3} H 6 - *, * - C 4 H 8 -S 2 -C 4 H 8 - *, * - CH 2 -S 4 -CH 2 - *, * - C 2 H ₄ —S ₄ —C ₂ H ₄ — *, * —C ₃ H ₆ —S ₄ —C ₃ H ₆ — *, * —C ₄ H ₈ —S ₄ —C ₄ H ₈ — *, and the like. .

The silane compound composed of the polysiloxane having the average composition formula represented by the general formula (5) has a hydrolyzable group C, so that it has excellent affinity and / or reactivity with silica. The subscript c of the hydrolyzable group C in the general formula (5) is 1.2 ≦ c ≦ 2.0 because of low heat build-up, better processability, and better silica dispersibility. Good. Specific examples of the hydrolyzable group C include an alkoxy group, a phenoxy group, a carboxyl group, an alkenyloxy group, and the like. The hydrolyzable group C is preferably a group represented by the following general formula (7) from the viewpoint of improving the dispersibility of silica and further improving processability.

In the general formula (7), * indicates a bonding position. R ¹² represents an alkyl group having 1 to 20 carbon atoms, an aryl group having 6 to 10 carbon atoms, an aralkyl group having 6 to 10 carbon atoms (arylalkyl group), or an alkenyl group having 2 to 10 carbon atoms, It is preferable that it is a C1-C5 alkyl group.

  Specific examples of the alkyl group having 1 to 20 carbon atoms include a methyl group, an ethyl group, a propyl group, a butyl group, a hexyl group, an octyl group, a decyl group, and an octadecyl group. Specific examples of the aryl group having 6 to 10 carbon atoms include a phenyl group and a tolyl group. Specific examples of the aralkyl group having 6 to 10 carbon atoms include a benzyl group and a phenylethyl group. Specific examples of the alkenyl group having 2 to 10 carbon atoms include a vinyl group, a propenyl group, and a pentenyl group.

The silane compound composed of polysiloxane having the average composition formula represented by the general formula (5) can interact and / or react with the diene rubber by having the organic group D containing a mercapto group. Excellent heat resistance, flex fatigue resistance, and wear resistance. The subscript d of the organic group D containing a mercapto group is preferably 0.1 ≦ d ≦ 0.8. The organic group D containing a mercapto group is preferably a group represented by the following general formula (8) from the viewpoint of improving the dispersibility of silica and further improving processability.

  In said general formula (8), m represents the integer of 1-10, and it is preferable that it is an integer of 1-5 especially. In the formula, * indicates a bonding position.

Specific examples of the group represented by the general formula (8) include * —CH ₂ SH, * —C ₂ H ₄ SH, * —C ₃ H ₆ SH, * —C ₄ H ₈ SH, * —C. _{5 H 10 SH, * - C} 6 H 12 SH, * - C 7 H 14 SH, * - C 8 H 16 SH, * - C 9 H 18 SH, * - C 10 H 20 SH and the like.

In the general formula (5), R ¹¹ represents a monovalent hydrocarbon group having 1 to 4 carbon atoms. Examples of the hydrocarbon group R ¹¹ include a methyl group, an ethyl group, a propyl group, and a butyl group.

  In the general formula (5), a to e are 0 ≦ a <1, 0 ≦ b <1, 0 <c <3, 0 <d <1, 0 ≦ e <2, and 0 <2a + b + c + d + e <4. Satisfy the formula. However, one of a and b is not 0. Here, that one of a and b is not 0 means that 0 <b when a = 0 and 0 <a when b = 0. Note that 0 <a and 0 <b may be satisfied.

Further, the pneumatic tire of the present invention, by incorporating an alkyl silane, it is possible to easily adjust the minimum size R _ss aggregates forming the hierarchical structure below 28nm exceed 14 nm.

  As the alkylsilane, alkyltriethoxysilane having an alkyl group having 7 to 20 carbon atoms is preferable. As an alkyl group having 7 to 20 carbon atoms, heptyl, octyl, nonyl, decyl, undecyl, dodecyl, tridecyl, tetradecyl, pentadecyl, hexadecyl, heptadecyl, octadecyl, nonadecyl, icosyl Groups. Among these, from the viewpoint of compatibility with the diene rubber, an alkyl group having 8 to 10 carbon atoms is more preferable, and an octyl group and a nonyl group are further preferable.

  The compounding amount of the alkylsilane is preferably 1 to 20% by weight, more preferably 2 to 15% by weight, based on the silica weight.

Further, by adjusting the kneading conditions of the rubber composition, the minimum size R _ss of the aggregate forming the hierarchical structure can be made to be more than 14 nm and not more than 28 nm. For example, the kneading conditions of silica to diene rubber are preferably 120 to 170 ° C., more preferably 130 to 160 ° C. when blending mercaptosilane, and preferably 1 to 15 minutes after reaching this temperature. More preferably, it may be kneaded for 2 to 10 minutes. For example, after the kneading temperature reaches 135 ° C., the kneading temperature is preferably adjusted to 135 ° C. for 2 to 10 minutes. By using such a kneading condition, even if the amount of silica is increased, the minimum size R _ss of the aggregate forming the hierarchical structure can be made to exceed 14 nm and not more than 28 nm.

On the other hand, even in a rubber composition containing a sulfur-containing silane coupling agent having no mercapto group instead of mercaptosilane, the minimum size R _ss of the aggregate forming the silica hierarchical structure exceeds 14 nm and is 28 nm or less. can do. The kneading conditions of the rubber composition at this time are preferably 135 to 175 ° C., more preferably 140 to 170 ° C., and preferably 2 to 15 minutes, more preferably 3 to 10 minutes after reaching this temperature. It is good to knead. For example, after the kneading temperature reaches 150 to 170 ° C., kneading is preferably performed for 2 to 10 minutes while adjusting the kneading temperature to the set temperature. As a result, the minimum size R _ss of the aggregates forming the hierarchical structure of silica can be made more than 14 nm and 28 nm or less.

  In the present invention, other compounding agents other than those described above can be added. As other compounding agents, other reinforcing fillers other than silica, vulcanization or crosslinking agents, vulcanization accelerators, anti-aging agents, liquid polymers, thermosetting resins, thermoplastic resins, etc. are generally pneumatic. Various compounding agents used for a tire can be illustrated. The compounding amounts of these compounding agents can be conventional conventional compounding amounts as long as they do not contradict the purpose of the present invention. Moreover, as a kneading machine, a normal rubber kneading machine, for example, a Banbury mixer, a kneader, a roll or the like can be used.

  Examples of other reinforcing fillers include carbon black, clay, mica, talc, calcium carbonate, aluminum hydroxide, aluminum oxide, and titanium oxide. Among these, carbon black is preferable, and the hardness, strength, and wear resistance of the rubber composition can be increased. The compounding amount of carbon black is preferably 3 to 15 parts by weight, more preferably 4 to 10 parts by weight with respect to 100 parts by weight of the diene rubber.

  The rubber composition for tires of the present invention is suitable for constituting a side part and / or a tread part of a pneumatic tire. Since this tire rubber composition is excellent in low heat buildup and fatigue bending resistance, it can be suitably used for a side portion of a pneumatic tire. The pneumatic tire having the side portion made of the rubber composition for tires of the present invention has low rolling resistance and excellent fuel efficiency, and is excellent in bending fatigue resistance and can extend the tire life.

  Further, by blending natural rubber with the tire rubber composition of the present invention, the wear resistance and chipping resistance can be made excellent. This tire rubber composition can be suitably used for a tread portion of a heavy duty pneumatic tire used for trucks and buses. The heavy-duty pneumatic tire of the present invention has a low rolling resistance and excellent fuel efficiency, and also has excellent wear resistance and chipping resistance, so that the tire life can be extended.

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

Examples 1-7, Comparative Examples 1-4
12 types of pneumatic tires (Examples 1 to 7, Standard Example 1 and Comparative Examples 1 to 4) having the formulations shown in Tables 1 and 2 with the compounding agents shown in Table 3 as common formulations, sulfur and vulcanization acceleration. Ingredients excluding the agent were kneaded with a 1.7 L closed Banbury mixer, and after reaching the “mixing temperature” described in Tables 1 and 2, respectively, during the “keep time” described in Tables 1 and 2, Kneading while adjusting the rotation speed of the mixer so as to maintain the temperature, a master batch is prepared. After the “keep time” had elapsed, it was discharged from the mixer and allowed to cool to room temperature. A pneumatic tire was prepared by adding sulfur and a vulcanization accelerator to the cooled master batch and mixing with a 1.7 L closed Banbury mixer. In addition, the compounding quantity of the compounding agent described in Table 3 was shown by the weight part with respect to 100 weight part of diene rubber described in Table 1,2.

The obtained 12 kinds of rubber compositions were press vulcanized at 160 ° C. for 30 minutes in a predetermined mold to prepare test pieces made of pneumatic tires. The minimum size R _ss and tan δ at 60 ° C. of the aggregate forming the hierarchical structure of the obtained test piece were evaluated by the following methods.

Minimum size of aggregate forming a hierarchical structure R _ss
A vulcanized rubber sheet having a thickness of 0.5 mm was prepared as described above, and the ultra small angle X-ray scattering method (USAXS) was measured at 100 ° C. The measurement condition of the ultra small angle X-ray scattering method (USAXS) is that wave number q is 0.006 to 0.4 nm ⁻¹ (q = 4π / λ sin θ; θ is a scattering angle, λ is 0.62 angstrom (X-ray energy: 20 keV). ), The exposure time was 488 msec, and the camera length was 7.6 m). The obtained scattering image was subjected to an annular average of −90 to 180 ° to be one-dimensional, and the scattering profile was fitted using the general formula (I) to calculate Rss. The obtained results are shown in the column of “Minimum Aggregate Size Rss” in Tables 1 and 2.

Tan δ at 60 ° C
The dynamic viscoelasticity of the obtained test piece was measured with a viscoelasticity spectrometer manufactured by Toyo Seiki Seisakusho Co., Ltd. at an initial strain of 10%, an amplitude of ± 2%, and a frequency of 20 Hz, and tan δ at an ambient temperature of 60 ° C. was measured. . The obtained results are shown in the column of “tan δ at 60 ° C.” in Tables 1 and 2.

  A heavy-duty pneumatic tire having a size (11R22.5) using the obtained 12 kinds of rubber compositions as a cap tread was vulcanized. Using each heavy duty tire, the wear resistance and chipping resistance were evaluated by the following methods.

Abrasion resistance Each heavy-duty tire was mounted on a rim (22.5 × 7.5) and the standard air pressure specified by JATMA was used, and mounted on a truck of the same vehicle type. Each truck was repeatedly traveled in a certain section where the general road and the highway were defined as 10:90, and the depth of the remaining groove of each heavy load tire was measured at the same travel distance. The obtained results are represented by an index with the value of standard example 1 being 100, and are shown in the column of “Abrasion resistance” in Tables 1 and 2. The larger this value and the deeper the remaining groove, the better the wear resistance.

Chipping resistance Each heavy-duty tire was mounted on a rim (22.5 × 7.5), the air pressure was set to 2.5 kgf / cm ² , and mounted on the front and rear wheels of a vehicle (Score Trophy Truck). This vehicle is run for 10 laps at an average speed of 50 km, and the number of occurrences of block missing is investigated by running a circumference circuit that includes approximately 70% of irregular road surface (one lap is 1.0 km) at an average speed of 50 km. did. The obtained results are shown in the “chipping resistance” column of Tables 1 and 2 as an index with the reciprocal number of Standard Example 1 being 100. A larger index means less block chipping and better chipping resistance.

The types of raw materials used in Tables 1 and 2 are shown below.
NR: natural rubber, STR20 made in Thailand
BR: Butadiene rubber, Nippon Zeon BR1220
・ Carbon black: Cabot Japan Show Black N110
・ Silica: Solvay Zeosil 165MP, nitrogen adsorption specific surface area of 155 m ² / g
Coupling agent 1: sulfur-containing silane coupling agent, bis (3-triethoxysilylpropyl) tetrasulfide, Si69 manufactured by Evonik
Coupling agent 2: mercaptosilane, VPSi363 manufactured by Evonik
・ Alkylsilane: Shin-Etsu Chemical KBM3083

The types of raw materials used in Table 3 are shown below.
・ Stearic acid: NOF beads stearic acid YR
・ Zinc oxide: Three types of zinc oxide manufactured by Shodo Chemical Co., Ltd. ・ Anti-aging agent: Santoflex 6PPD manufactured by Flexis
-Sulfur: Tsurumi Chemical Industry Co., Ltd. Jinhua Oil-filled fine powder sulfur-Vulcanization accelerator: CBS, Ouchi Shinsei Chemical Noxeller CZ-G

  As is clear from Tables 1 and 2, it was confirmed that the pneumatic tires manufactured according to Examples 1 to 7 were excellent in wet grip performance and wear resistance.

In the rubber composition of Comparative Example 1, a part of natural rubber was replaced with butadiene rubber as compared with Standard Example 1, but the minimum size R _ss of the aggregate forming the silica hierarchical structure exceeded 28 nm. It becomes large, exothermicity becomes large, and chipping resistance deteriorates.

The rubber composition of Comparative Example 2 halved the compounding amount of the silane coupling agent with respect to Standard Example 1 and made it less than 6% by weight of the silica compounding amount, so that the minimum of aggregates forming a hierarchical structure of silica The size R _ss increases beyond 28 nm, the heat buildup increases, and the wear resistance and chipping resistance deteriorate.

In the rubber composition of Comparative Example 3, the amount of the silane coupling agent was increased to 20% by weight of the silica compounding amount relative to the standard example 1, so that tan δ at 60 ° C. was slightly reduced. The minimum size R _ss of the aggregate forming the structure cannot be made 28 nm or less, and the chipping resistance cannot be improved.

In the rubber composition of Comparative Example 4, the compounding amount of silica was increased to 65 parts by weight, but the minimum size R _ss of the aggregate forming the hierarchical structure of silica was larger than 28 nm, and the exothermic property was increased. In addition, wear resistance deteriorates.

Examples 8-14, Comparative Examples 5-8
12 kinds of pneumatic tires (Examples 8 to 14, Standard Example 2 and Comparative Examples 5 to 8) having the composition shown in Table 6 as the common composition and the compositions shown in Tables 4 and 5 were promoted to sulfur and vulcanization. Ingredients other than the agent were kneaded with a 1.7 L closed Banbury mixer, and after reaching the “mixing temperature” described in Tables 4 and 5, respectively, during the “keep time” described in Tables 4 and 5, Kneading while adjusting the rotation speed of the mixer so as to maintain the temperature, a master batch is prepared. After the “keep time” had elapsed, it was discharged from the mixer and allowed to cool to room temperature. A pneumatic tire was prepared by adding sulfur and a vulcanization accelerator to the cooled master batch and mixing with a 1.7 L closed Banbury mixer. In addition, the compounding quantity of the compounding agent described in Table 6 was shown by the weight part with respect to 100 weight part of diene rubbers described in Tables 4 and 5.

The obtained 12 kinds of rubber compositions were press vulcanized at 160 ° C. for 30 minutes in a predetermined mold to prepare test pieces made of pneumatic tires. The minimum size R _ss , tan δ at 60 ° C., and bending fatigue resistance of the aggregate forming the hierarchical structure of the obtained specimen were evaluated by the following methods.

Minimum size of aggregate forming a hierarchical structure R _ss
A vulcanized rubber sheet having a thickness of 0.5 mm was prepared as described above, and the ultra small angle X-ray scattering method (USAXS) was measured at 100 ° C. The measurement condition of the ultra small angle X-ray scattering method (USAXS) is that wave number q is 0.006 to 0.4 nm ⁻¹ (q = 4π / λ sin θ; θ is a scattering angle, λ is 0.62 angstrom (X-ray energy: 20 keV). ), The exposure time was 488 msec, and the camera length was 7.6 m). The obtained scattering image was subjected to an annular average of −90 to 180 ° to be one-dimensional, and the scattering profile was fitted using the general formula (I) to calculate Rss. The obtained results are shown in the column of “Minimum Aggregate Size Rss” in Tables 4 and 5.

Tan δ at 60 ° C
The dynamic viscoelasticity of the obtained test piece was measured with a viscoelasticity spectrometer manufactured by Toyo Seiki Seisakusho Co., Ltd. at an initial strain of 10%, an amplitude of ± 2%, and a frequency of 20 Hz, and tan δ at an ambient temperature of 60 ° C. was measured. . The obtained results are shown in the column of “tan δ at 60 ° C.” in Tables 4 and 5.

Bending fatigue resistance characteristics The obtained test piece was bent 300 times per minute at room temperature according to JIS K6260, and the number of bendings until the crack length reached 20 mm was determined. The obtained results are represented by an index with the value of standard example 2 being 100, and are shown in the column of “Bend fatigue resistance” in Tables 4 and 5. A larger value means better bending fatigue resistance.

The types of raw materials used in Tables 4 and 5 are shown below.
NR: natural rubber, STR20 made in Thailand
BR: Butadiene rubber, Nippon Zeon BR1220
・ Carbon black: Cabot Japan Show Black N110
・ Silica: Solvay Zeosil 165MP, nitrogen adsorption specific surface area of 155 m ² / g
Coupling agent 1: sulfur-containing silane coupling agent, bis (3-triethoxysilylpropyl) tetrasulfide, Si69 manufactured by Evonik
Coupling agent 2: mercaptosilane, VPSi363 manufactured by Evonik
・ Alkylsilane: Shin-Etsu Chemical KBM3083

The types of raw materials used in Table 6 are shown below.
・ Stearic acid: NOF beads stearic acid YR
・ Zinc oxide: Three types of zinc oxide manufactured by Shodo Chemical Co., Ltd. ・ Anti-aging agent: Santoflex 6PPD manufactured by Flexis
-Sulfur: Tsurumi Chemical Industry Co., Ltd. Jinhua Oil-filled fine powder sulfur-Vulcanization accelerator: CBS, Ouchi Shinsei Chemical Noxeller CZ-G

  As is clear from Tables 4 and 5, it was confirmed that the pneumatic tires manufactured according to Examples 8 to 14 were excellent in wet grip performance and wear resistance.

  In the rubber composition of Comparative Example 5, a part of natural rubber was replaced with butadiene rubber as compared with Standard Example 2, but the minimum size Rss of the aggregate forming the silica hierarchical structure was larger than 28 nm. At the same time, since the strength of the rubber is lowered, the bending fatigue resistance is deteriorated.

  In the rubber composition of Comparative Example 6, since the compounding amount of the silane coupling agent is less than 6% by weight of the silica weight, the minimum size Rss of the aggregate forming the hierarchical structure of the silica aggregate is 28 nm. The bending fatigue resistance deteriorates.

  In the rubber composition of Comparative Example 7, since the amount of the silane coupling agent exceeds 20% by weight of the silica weight, the crosslinking density of the rubber increases, and as a result, the heat generation increases and the bending fatigue resistance deteriorates. To do.

  In the rubber composition of Comparative Example 8, the amount of silica was increased to 35 parts by weight, but the minimum size Rss of the agglomerate forming the hierarchical structure of silica was larger than 28 nm, and bending fatigue resistance was increased. Sex worsens.

Claims (4)

A rubber composition comprising 30 to 70 parts by weight of silica in 100 parts by weight of a diene rubber and 6 to 20% by weight of a silane coupling agent based on the weight of the silica, comprising the following (a) and (b) The rubber composition for tires characterized by satisfy | filling.
(A) The tan δ at 60 ° C. of the rubber composition is less than 0.15 (b) The rubber composition is measured by an ultra small angle X-ray scattering method, and the obtained scattering profile is applied to the Unified-Guiner function. The minimum size R _ss of the aggregates forming the silica hierarchical structure is greater than 14 nm and not greater than 28 nm.   The rubber composition for tires according to claim 1, wherein the rubber composition contains 55% by weight or more of natural rubber in 100% by weight of the diene rubber.   The pneumatic tire which comprised the side part with the rubber composition for tires of Claim 1.   A heavy-duty pneumatic tire comprising a tread portion made of the tire rubber composition according to claim 1.