JP6686314B2 - Rubber composition for tires - Google Patents

Description

  TECHNICAL FIELD The present invention relates to a rubber composition for a tire, which has wet grip performance and durability and wear resistance at a high level.

  Competition tires for running on wet road surfaces are required to have not only excellent wet grip performance, but also tire durability and wear resistance at high speeds. Generally, in order to obtain excellent wet grip performance, a styrene-butadiene rubber having a high glass transition temperature is blended with a rubber composition for a tread, or a large amount of silica is blended as a reinforcing filler. However, when styrene-butadiene rubber having a high glass transition temperature is blended, the modulus and the rubber strength are likely to be lowered at a high temperature, so that there is a problem that tire durability and wear resistance are reduced.

  In order to improve grip performance, a rubber composition for tire tread has been proposed in which two specific types of carbon black and a low molecular weight styrene-butadiene copolymer are mixed with a styrene-butadiene copolymer rubber (for example, See Patent Document 1). However, the level of wet grip performance, durability performance and wear resistance performance demanded by consumers for competition tires for running on wet road surfaces is higher and further improvement is required.

JP, 2007-246658, A

  An object of the present invention is to provide a rubber composition for a tire, which has both wet grip performance and durability and wear resistance at higher levels than ever before.

（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、Ｒ¹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 a tire of the present invention which achieves the above-mentioned object is an aromatic vinyl based on 100 parts by weight of a diene rubber composed of 100% by weight of an aromatic vinyl-conjugated diene rubber having a glass transition temperature of -35 ° C or higher. A polysiloxane having an average composition formula represented by the following general formula (1), in which a total of 50 to 180 parts by weight of a softening agent component containing 10 to 80 parts by weight of a farnesene copolymer and 120 parts by weight or more of silica are blended. A silane coupling agent consisting of 2 to 20% by weight of the silica is blended, and the aromatic vinyl-farnesene copolymer has a weight fraction of 0.20 to 0.50 in the total amount of the softener components. Is characterized in that.

(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, and R is ¹ 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. The relational expression of 0 <2a + b + c + d + e <4 is satisfied, provided that at least one of a and b is not 0.)

The rubber composition for a tire according to the present invention contains 5 parts by weight of the aromatic vinyl-farnesene copolymer in 100 parts by weight of the diene rubber comprising 100 % by weight of the aromatic vinyl-conjugated diene rubber having a glass transition temperature of -35 ° C or higher. 50 parts by weight or more in total of a softening agent component containing 100 to 100 parts by weight, and a silane coupling agent composed of silica and polysiloxane having a specific average composition formula , and aromatic vinyl-farnesene in the total amount of the softening agent component. Since the weight fraction of the copolymer is set to 0.20 to 0.50 , the wet grip performance, durability and abrasion resistance can be improved to the conventional level or higher.

The softening agent component may include a resin having a softening point of 130 to 200 ° C., and the compounding amount of the resin may be 10 to 60 parts by weight based on 100 parts by weight of the diene rubber . The amount of or the silica to the diene rubber 100 parts by weight, may be at least 150 parts by weight.

  The pneumatic tire using the rubber composition for a tire of the present invention in the tread portion can achieve both wet grip performance, durability and wear resistance at a higher level than before, and is suitable for running on wet road surfaces. Suitable as a pneumatic tire.

  The rubber composition for tires of the present invention comprises a diene rubber as its rubber component, and as the diene rubber, an aromatic vinyl-conjugated diene rubber having a glass transition temperature of -35 ° C or higher is included. Examples of the aromatic vinyl-conjugated diene rubber include styrene butadiene rubber. The glass transition temperature of the aromatic vinyl-conjugated diene rubber is −35 ° C. or higher, preferably −35 ° C. to −10 ° C. By setting the glass transition temperature of the aromatic vinyl-conjugated diene rubber to -35 ° C or higher, the wet grip performance can be enhanced. The glass transition temperature of the aromatic vinyl-conjugated diene rubber is measured by a differential scanning calorimetry (DSC) thermogram under a heating rate condition of 20 ° C./min, and is set to the temperature at the midpoint of the transition region. When the aromatic vinyl-conjugated diene rubber is an oil-extended product containing oil, the glass transition temperature of the aromatic vinyl-conjugated diene rubber excluding oil is used.

  Further, the content of the aromatic vinyl-conjugated diene rubber is preferably 50 to 100% by weight, more preferably 75 to 100% by weight in 100% by weight of the diene rubber.

  The rubber composition for a tire of the present invention can contain other diene rubber in addition to the aromatic vinyl-conjugated diene rubber having a glass transition temperature of -35 ° C or higher. Examples of the diene rubber include natural rubber, isoprene rubber, butadiene rubber, styrene-butadiene rubber having a glass transition temperature of less than -35 ° C, acrylonitrile-butadiene rubber, butyl rubber, chloroprene rubber, and the like. These can be used alone or as an arbitrary blend. The above-mentioned other diene rubber can be contained in 100% by weight of the diene rubber, preferably 0 to 50% by weight, more preferably 0 to 25% by weight, and can enhance tire durability and wear resistance. .

  The rubber composition for a tire of the present invention can be improved in wet grip performance, durability and abrasion resistance by blending an aromatic vinyl-farnesene copolymer, and in particular, has excellent wet grip performance. can do. Further, the aromatic vinyl-farnesene copolymer has a high affinity with the aromatic vinyl-conjugated diene rubber, and has a relatively high molecular weight and a crosslinkable structure, so that the rubber composition for a tire after vulcanization is It is possible to improve mechanical durability to a level higher than conventional levels and improve tire durability and wear resistance.

  The aromatic vinyl-farnesene copolymer is a copolymer composed of at least a monomer composed of an aromatic vinyl compound and a monomer composed of farnesene. Examples of the monomer composed of farnesene include α-farnesene and β-farnesene, which may be used alone or in combination of both. Β-farnesene is preferable. Note that β-farnesene is preferably a copolymer with an aromatic vinyl compound. For example, a homopolymer of β-farnesene has a low glass transition temperature, so that the effect of improving wet grip performance cannot be sufficiently obtained.

  Examples of the monomer composed of an aromatic vinyl compound include styrene, α-methylstyrene, 2-methylstyrene, 3-methylstyrene, 4-methylstyrene, 4-propylstyrene, 4-tert-butylstyrene, 4-cyclohexylstyrene. , 4-dodecylstyrene, 2,4-dimethylstyrene, 2,4-diisopropylstyrene, 2,4,6-trimethylstyrene, 2-ethyl-4-benzylstyrene, 4- (phenylbutyl) styrene, 1-vinylnaphthalene , 2-vinylnaphthalene, vinylanthracene, N, N-diethyl-4-aminoethylstyrene, vinylpyridine, 4-methoxystyrene, monochlorostyrene, dichlorostyrene, divinylbenzene and the like. Of these, styrene, α-methylstyrene and 4-methylstyrene are preferable.

  The weight average molecular weight of the aromatic vinyl-farnesene copolymer is not particularly limited, but it is preferably 2000 to 500000, more preferably 8000 to 450,000, and further preferably 15000 to 300000. When the weight average molecular weight of the aromatic vinyl-farnesene copolymer is less than 2000, the mechanical strength of the rubber composition is lowered, and further bleed out easily from the rubber composition. Further, if the weight average molecular weight of the aromatic vinyl-farnesene copolymer exceeds 500,000, the processability deteriorates.

  The molecular weight distribution (Mw / Mn; Mw is a weight average molecular weight and Mn is a number average molecular weight) of the aromatic vinyl-farnesene copolymer is preferably 1.0 to 4.0, more preferably 1.0 to 3.0. , And more preferably 1.0 to 2.0. When the molecular weight distribution of the aromatic vinyl-farnesene copolymer is within such a range, the variation in viscosity becomes small. In the present specification, the weight average molecular weight Mw and the number average molecular weight Mn of the aromatic vinyl-farnesene copolymer are measured by GPC (gel permeation chromatography) and determined by standard polystyrene conversion.

  The melt viscosity of the aromatic vinyl-farnesene copolymer is preferably 0.1 to 3000 Pa · s, more preferably 0.6 to 2800 Pa · s, and further preferably 1.5 to 2600 Pa · s. When the melt viscosity of the aromatic vinyl-farnesene copolymer is within such a range, the kneading of the rubber composition is facilitated and the dispersibility of silica is improved. In this specification, the melt viscosity of the aromatic vinyl-farnesene copolymer is the melt viscosity at 38 ° C. measured by a Brookfield viscometer.

  The aromatic vinyl-farnesene copolymer may contain a monomer other than the aromatic vinyl compound and farnesene, and examples of the other monomer include butadiene, isoprene, 2,3-dimethyl-1,3-butadiene, and , 3-pentadiene, 2-methyl-1,3-pentadiene, 1,3-hexadiene, 1,3-octadiene, 1,3-cyclohexadiene, 2-methyl-1,3-octadiene, 1,3,7- Examples thereof include octatriene, myrcene, chloroprene and the like. The aromatic vinyl-farnesene copolymer can be obtained by copolymerizing a monomer composed of an aromatic vinyl compound and a monomer composed of farnesene, and optionally other monomers, by an ordinary method, for example, an emulsion polymerization method and a solution polymerization method. It is possible to synthesize it, and it is preferable to synthesize it by a solution polymerization method.

  In the rubber composition for a tire of the present invention, the blending amount of the aromatic vinyl-farnesene copolymer is 5 to 100 parts by weight, preferably 10 to 80 parts by weight, and more preferably 12 parts by weight based on 100 parts by weight of the diene rubber. ˜70 parts by weight. When the blending amount of the aromatic vinyl-farnesene copolymer is less than 5 parts by weight, the effect of improving wet grip performance, tire durability and wear resistance cannot be sufficiently obtained. Further, if the blending amount of the aromatic vinyl-farnesene copolymer exceeds 100 parts by weight, the durability deteriorates.

  In the present invention, the rubber composition for a tire contains the above-mentioned softening agent component containing an aromatic vinyl-farnesene copolymer in an amount of 50 parts by weight or more, preferably 50 to 180 parts by weight, more preferably 100 parts by weight of a diene rubber. Contains 60 to 160 parts by weight. By including the softening agent component in an amount of 50 parts by weight or more, excellent wet grip performance can be obtained.

  The weight fraction of the aromatic vinyl-farnesene copolymer in the softener component is preferably 0.20 to 0.60, more preferably 0.25 to 0.55, still more preferably 0.30 to 0. It is good to be 50. By setting the weight fraction of the aromatic vinyl-farnesene copolymer within the range of 0.20 to 0.60, the balance between the wet grip performance and the tire durability and wear resistance is further improved. be able to.

  In the present specification, the softening agent component includes oil, plasticizer, softening agent, processing aid, resin and the like in addition to the aromatic vinyl-farnesene copolymer. The softener component other than the aromatic vinyl-farnesene copolymer may be one or a combination of a plurality thereof. The oil is an oil-extending component added when producing a diene rubber, and various oils added when preparing a rubber composition. Examples of the resin include petroleum resins and aromatic resins.

  The petroleum-based resin is an aromatic hydrocarbon resin or a saturated or unsaturated aliphatic hydrocarbon resin produced by polymerizing components obtained by subjecting crude oil to treatments such as distillation, cracking and reforming. Examples of petroleum-based resins include C5-based petroleum resins (aliphatic-based petroleum resins obtained by polymerizing distillates such as isoprene, 1,3-pentadiene, cyclopentadiene, methylbutene, and pentene), C9-based petroleum resins (α-methylstyrene, o -Aromatic petroleum resin obtained by polymerizing a fraction such as vinyltoluene, m-vinyltoluene and p-vinyltoluene), and C5C9 copolymerized petroleum resin.

  The aromatic resin is a polymer having at least one segment composed of aromatic hydrocarbon, and includes coumarone resin, phenol resin, alkylphenol resin, terpene resin, rosin resin, novolac resin, resol resin, etc. Can be raised. Of these, aromatic modified terpene resins are preferred. These resins can be used alone or as a blend of two or more. The C9 petroleum resin described above is an aromatic hydrocarbon resin, but is classified as a petroleum resin in this specification.

  The softening point of the resin is not particularly limited, but is preferably 130 to 200 ° C, more preferably 135 to 180 ° C. By setting the softening point of the resin within such a range, the wet grip performance can be made excellent. In the present specification, the softening point of the resin is measured according to JIS K6220-1 (ring and ball method).

  The amount of the resin compounded is not particularly limited as long as it satisfies the amount of the plasticizer component described above, but is preferably 10 to 60 parts by weight, and more preferably 15 to 50 parts by weight with respect to 100 parts by weight of the diene rubber. It is good to be a weight part. By setting the blending amount of the resin within such a range, the wet grip performance can be further improved.

  The rubber composition for tires of the present invention improves wet grip performance by incorporating silica. The content of silica is 120 parts by weight or more, preferably 150 parts by weight or more, and more preferably 150 to 200 parts by weight, based on 100 parts by weight of the diene rubber. If the amount of silica blended is less than 120 parts by weight, wet grip performance cannot be sufficiently enhanced.

The silica used in the present invention preferably has a nitrogen adsorption specific surface area N ₂ SA of 140 to 250 m ² / g, more preferably 150 to 230 m ² / g. By setting the N ₂ SA in such a range, wet grip performance, tire durability, and wear resistance can be balanced. The N ₂ SA of silica is measured according to JIS K6217-2.

（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、Ｒ¹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。） In the tire rubber composition of the present invention, the dispersibility of silica can be improved by incorporating a silane coupling agent composed of polysiloxane having an average composition formula represented by the following general formula (1). The compounding amount of the silane coupling agent is preferably 2 to 20% by weight, more preferably 3 to 15% by weight based on the weight of silica. If the amount of the silane coupling agent is less than 2% by weight, the dispersibility of silica may not be improved. When the compounding amount of the silane coupling agent exceeds 20% by weight, the rubber composition is likely to undergo early vulcanization, which may deteriorate the moldability.

(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, and R is ¹ 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. The relational expression of 0 <2a + b + c + d + e <4 is satisfied, provided that at least one of a and b is not 0.)

  The mercaptosilane compound having the average composition formula represented by the general formula (1) has a siloxane skeleton as its skeleton. The siloxane skeleton may have a linear, branched, or three-dimensional structure, or a combination thereof.

  In the general formula (1), 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 always 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 mercaptosilane compound consisting of the polysiloxane having the average composition formula represented by the above general formula (1) has a monovalent hydrocarbon group B having 5 to 10 carbon atoms, the mercapto group is protected and the Mooney scorch time is increased. At the same time as it becomes longer, it has an excellent affinity with rubber to make it more processable. Therefore, the subscript b of the hydrocarbon group B in the general formula (1) is preferably 0.10 ≦ b ≦ 0.89. Specific examples of the hydrocarbon group B include monovalent hydrocarbon groups having preferably 6 to 10 carbon atoms, more preferably 8 to 10 carbon atoms, such as hexyl group, octyl group and decyl group. This makes it possible to protect the mercapto group, lengthen the Mooney scorch time, improve workability, and further improve wet grip properties and abrasion resistance.

  When the silane compound composed of polysiloxane having the average composition formula represented by the above general formula (1) has a divalent organic group A containing a sulfide group, wet performance, abrasion resistance, workability (especially Mooney) Maintaining and prolonging scorch time). Therefore, the subscript a of the divalent organic group A containing a sulfide group in the general formula (1) is preferably 0 <a ≦ 0.50.

  The divalent organic group A containing a sulfide group can be a hydrocarbon group which 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 (2) from the viewpoint of improving the dispersibility of silica and further improving the processability.

  In the general formula (2), n represents an integer of 1 to 10, and preferably an integer of 2 to 4. Further, x represents an integer of 1 to 6, and preferably an integer of 2 to 4 among them. In addition, * indicates a binding position.

Specific examples of the group represented by the general formula (2), 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 (1) has the hydrolyzable group C, and thereby has excellent affinity and / or reactivity with silica. The subscript c of the hydrolyzable group C in the general formula (1) is 1.2 ≦ c ≦ 2.0 for the reason that the wet characteristic and the processability are more excellent and the dispersibility of silica is more excellent. Good. Specific examples of the hydrolyzable group C include, for example, 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 (3) from the viewpoint of improving the dispersibility of silica and further improving the processability.

In the general formula (3), * indicates a bonding position. R ² 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, and among them, It is preferably an alkyl group having 1 to 5 carbon atoms.

  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 benzyl group and phenylethyl group. Specific examples of the alkenyl group having 2 to 10 carbon atoms include vinyl group, propenyl group, pentenyl group and the like.

The silane compound composed of the polysiloxane having the average composition formula represented by the general formula (1) can interact and / or react with the diene rubber by having the organic group D containing a mercapto group. Excellent in wet performance 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 (4) from the viewpoint of improving the dispersibility of silica and further improving the processability.

  In the general formula (4), m represents an integer of 1 to 10, and preferably an integer of 1 to 5. Further, in the formula, * indicates a bonding position.

Specific examples of the group represented by the general formula _{(4), * - 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 above general formula (1), R ¹ represents a monovalent hydrocarbon group having 1 to 4 carbon atoms. Examples of the hydrocarbon group R ¹ include a methyl group, an ethyl group, a propyl group and a butyl group.

  In the general formula (1), a to e are in the relation of 0 ≦ a <1, 0 ≦ b <1, 0 <c <3, 0 <d <1, 0 ≦ e <2, 0 <2a + b + c + d + e <4. Satisfy the formula. However, either one of a and b is not 0. Here, the fact that either 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.

  In the present invention, other compounding agents other than the above may be added. Other compounding agents include reinforcing fillers other than silica, vulcanizing or crosslinking agents, vulcanization accelerators, antioxidants, liquid polymers, thermosetting resins, thermoplastic resins, etc. Various compounding agents used for tires can be exemplified. The compounding amount of these compounding agents can be a conventional general compounding amount as long as the object of the present invention is not violated. As the kneading machine, a usual kneading machine for rubber, for example, Banbury mixer, kneader, roll or the like can be used.

  Examples of other reinforcing fillers include carbon black, clay, mica, talc, calcium carbonate, aluminum hydroxide, aluminum oxide, titanium oxide and the like. Of these, carbon black is preferred.

  The rubber composition for a tire of the present invention is suitable for use in a pneumatic pneumatic tire for competition running on a wet road surface, and has both wet grip performance and durability and abrasion resistance at a higher level than ever. You can

  Hereinafter, the present invention will be further described with reference to Examples, but the scope of the present invention is not limited to these Examples.

  A component excluding sulfur and a vulcanization accelerator was prepared from 12 types of rubber compositions for tires (Examples 1 to 5 and Comparative Examples 1 to 7) having the compounding agent shown in Table 2 as a common compounding and having the composition shown in Table 1. Was kneaded with a 1.7 L closed Banbury mixer, and after a predetermined time elapsed, it was discharged from the mixer and cooled to room temperature. This was put into a 1.7 L closed Banbury mixer, and sulfur and a vulcanization accelerator were added and mixed to prepare a rubber composition for a tire. In addition, in the column of styrene-butadiene rubber (SBR1, SBR2) in Table 1, in addition to the blending amount of the product, the net blending amount of SBR excluding the oil-extended component is described in parentheses. The "total of softening agent components" shown in Table 1 is the total of the blended amounts of the oil-extended components of SBR1 and SBR2, the aromatic vinyl-farnesene copolymer, the terpene resin, the low molecular weight SBR, and the oil. The blending amounts of the compounding agents shown in Table 2 are shown in parts by weight based on 100 parts by weight of the diene rubber shown in Table 1.

  The obtained 12 kinds of rubber compositions were press-vulcanized in a predetermined mold at 160 ° C. for 30 minutes to prepare test pieces made of the rubber composition for tires. The obtained test pieces were evaluated for tan δ (wet grip performance) at 0 ° C., 300% tensile stress (tire durability), and tensile breaking strength (wear resistance) by the following methods.

Tan δ at 0 ℃ (wet grip performance)
The dynamic viscoelasticity of the obtained test piece was measured by using a viscoelasticity spectrometer manufactured by Toyo Seiki Seisakusho under conditions of initial strain of 10%, amplitude of ± 2%, and frequency of 20 Hz, and tan δ at an atmospheric temperature of 0 ° C. . The obtained results are represented by an index with the value of Comparative Example 1 being 100, and are shown in the column of "wet grip performance" in Table 1. The larger this index, the larger the tan δ at 0 ° C., which means that the wet grip performance when used as a tire is excellent.

300% tensile stress (tire durability) and tensile breaking strength (wear resistance)
From the obtained test piece, a JIS No. 3 dumbbell-shaped test piece was cut out in accordance with JIS K6251. Based on JIS K6251, the tensile stress at 300% elongation and the tensile breaking stress were measured under the conditions of a tensile speed of 500 mm / min and an atmospheric temperature of 23 ° C. The obtained results are shown in the columns of "tire durability" and "wear resistance" in Table 1 as indexes with the value of Comparative Example 1 being 100, respectively. The larger the tire durability index, the greater the tensile stress at 300% elongation, which means that the tire durability is excellent. The larger the index of wear resistance, the larger the tensile rupture stress and the better the wear resistance.

The types of raw materials used in Table 1 are shown below.
SBR1: Styrene-butadiene rubber, Nipol 1739 manufactured by Nippon Zeon Co., Ltd., an oil-extended product in which 100 parts by weight of styrene-butadiene rubber is mixed with 37.5 parts by weight of an oil component, a glass transition temperature is −31 ° C., and a styrene content is 40% by weight. Vinyl unit amount is 14% by weight
SBR2: styrene-butadiene rubber, Nipol 9548 manufactured by Nippon Zeon Co., Ltd., an oil-extended product in which 100 parts by weight of styrene-butadiene rubber is mixed with 37.5 parts by weight of an oil component, a glass transition temperature is -37 ° C., and a styrene content is 36% by weight. Vinyl unit amount is 14% by weight
Carbon black: Tokai Carbon Co. SEAST 9, nitrogen adsorption specific surface area of 142m ² / g, DBP absorption amount of 114cm ³ / 100g
Silica: Zeosil 1165MP manufactured by Rhodia, nitrogen adsorption specific surface area of 165 m ² / g, CTAB specific surface area of 159 m ² / g
Coupling agent 1: Sulfur-containing silane coupling agent, bis (3-triethoxysilylpropyl) tetrasulfide, Evonik Si69
-Coupling agent 2: Silane coupling agent containing mercapto group, Si363 manufactured by Evonik
Coupling agent 3: Polysiloxane / farnesene copolymer synthesized by the following production method: Copolymer of styrene and β-farnesene polymerized by the following Synthesis Example 1, weight average molecular weight of 10,000, molecular weight distribution of 1 0.06, melt viscosity 5.6 Pa · s
Farnesene polymer: a polymer of β-farnesene polymerized by the following synthesis example 2, weight average molecular weight of 140,000, molecular weight distribution of 1.2, melt viscosity of 69 Pa · s.
-Low molecular weight SBR: RICON 100 manufactured by Cray Valley
-Terpene resin: aromatic modified terpene resin, YS Polystar T145 manufactured by Yasuhara Chemical Co., softening point 145 ° C.
・ Oil: Extract No. 4S manufactured by Showa Shell Sekiyu KK

<Method for producing coupling agent 3>
In a 2 L separable flask equipped with a stirrer, a reflux condenser, a dropping funnel, and a thermometer, 107.8 g (0.2 mol) of bis (triethoxysilylpropyl) tetrasulfide (KBE-846 manufactured by Shin-Etsu Chemical Co., Ltd.) and γ-mercapto were placed. 190.8 g (0.8 mol) of propyltriethoxysilane (KBE-803 manufactured by Shin-Etsu Chemical Co., Ltd.), 442.4 g (1.6 mol) of octyltriethoxysilane (KBE-3083 manufactured by Shin-Etsu Chemical Co., Ltd.), and 190.0 g of ethanol were stored. After that, a mixed solution of 0.5N hydrochloric acid 37.8 g (2.1 mol) and ethanol 75.6 g was added dropwise at room temperature. Then, it stirred at 80 degreeC for 2 hours. Then, filtration, 17.0 g of 5% KOH / EtOH solution was added dropwise, and the mixture was stirred at 80 ° C. for 2 hours. Then, it was concentrated under reduced pressure and filtered to obtain 480.1 g of a brown transparent liquid polysiloxane. As a result of measurement by GPC, the average molecular weight was 840 and the average degree of polymerization was 4.0 (set degree of polymerization 4.0). In addition, the mercapto equivalent was measured by the acetic acid / potassium iodide / potassium iodate addition-sodium thiosulfate solution titration method, and as a result, it was confirmed to be 730 g / mol, which was the mercapto group content as set. From the above, it is represented by the following average composition formula.
_{(-C 3 H 6 -S 4 -C} 3 H 6 -) 0.071 (-C 8 H 17) 0.571 (-OC 2 H 5) 1.50 (-C 3 H 6 SH) 0.286 SiO 0.75
The obtained polysiloxane is used as the coupling agent 3.

Synthesis example 1 (polymerization of farnesene copolymer)
In a pressure-resistant container that had been purged with nitrogen and dried, 1500 g of cyclohexane as a solvent and 112.6 g of sec-butyllithium (10.5 mass% cyclohexane solution) as an initiator were charged, and the temperature was raised to 50 ° C., and then 3 g of tetrahydrofuran was added. 1,500 g of a previously prepared mixture of styrene and β-farnesene (345 g of styrene and 1155 g of β-farnesene were mixed in a cylinder) was added at 10 ml / min and polymerization was carried out for 1 hour. The obtained polymerization reaction liquid was treated with methanol, and the polymerization reaction liquid was washed with water. The polymerization reaction liquid after washing and water were separated and dried at 70 ° C. for 12 hours to obtain a random copolymer of styrene and β-farnesene (farnesene copolymer).

Synthesis example 2 (polymerization of farnesene polymer)
To a pressure-resistant container which had been purged with nitrogen and dried, 274 g of hexane and 1.2 g of n-butyllithium (17% by weight hexane solution) were charged, and after heating to 50 ° C., 272 g of β-farnesene was added and polymerization was carried out for 1 hour. . After adding methanol to the obtained polymerization reaction liquid, the polymerization reaction liquid was washed with water. Water was separated, and the polymerization reaction solution was dried at 70 ° C. for 12 hours to obtain a β-farnesene polymer (farnesene polymer).

The types of raw materials used in Table 2 are shown below.
・ Stearic acid: NOF bead stearic acid YR
・ Zinc oxide: 3 types of zinc oxide manufactured by Shodo Chemical Co., Ltd. ・ Anti-aging agent: Santoflex 6PPD manufactured by Flexis
・ Sulfur: Fine powdered sulfur with Tsurumi Chemical Industry Co., Ltd. oil and vulcanization accelerator 1: DPG, Nouchira D from Ouchi Shinko Chemical Co., Ltd.
・ Vulcanization accelerator 2: CBS, Nox Cellar CZ-G manufactured by Ouchi Shinko Chemical Co., Ltd.

  As is clear from Table 1, the rubber compositions for tires manufactured in Examples 1 to 5 were confirmed to have excellent wet grip performance, tire durability and wear resistance.

  The rubber composition of Comparative Example 2 is different from the rubber composition of Comparative Example 1 in SBR2 having a glass transition temperature of lower than −35 ° C., so that tire durability and wear resistance are increased, but wet grip performance is improved. Becomes worse.

  The rubber composition of Comparative Example 3 was different from the rubber composition of Comparative Example 1 in that the coupling agent 1 was changed to the coupling agent 2, so that the wet grip performance was improved, but the tire durability and wear resistance were deteriorated. To do.

  The rubber composition of Comparative Example 4 was different from the rubber composition of Comparative Example 1 in that the coupling agent 1 was changed to the coupling agent 3, so that the wet grip performance and the abrasion resistance were high, but Examples 1 to 1 The improvement effect is smaller than that of the rubber composition of No. 5. Moreover, tire durability cannot be improved.

  The rubber composition of Comparative Example 5 is different from the rubber composition of Example 1 in that the coupling agent 3 is changed to the coupling agent 2, and thus the tire durability and wear resistance are inferior.

  In the rubber composition of Comparative Example 6, since the total amount of the softening agent components is less than 50 parts by weight, the wet grip performance is deteriorated.

  Since the rubber composition of Comparative Example 7 contains the farnesene polymer instead of the aromatic vinyl-farnesene copolymer, the wet grip performance is deteriorated.

Claims (4)

A softener component containing 10 to 80 parts by weight of an aromatic vinyl-farnesene copolymer based on 100 parts by weight of a diene rubber composed of 100% by weight of an aromatic vinyl-conjugated diene rubber having a glass transition temperature of -35 ° C or higher. In a total amount of 50 to 180 parts by weight and 120 parts by weight or more of silica, and a silane coupling agent composed of polysiloxane having an average composition formula represented by the following general formula (1) is contained in an amount of 2 to 20 parts by weight of the silica. %, And the weight fraction of the aromatic vinyl-farnesene copolymer in the total amount of the softening agent components is 0.20 to 0.50.

(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, and R is ¹ 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. The relational expression of 0 <2a + b + c + d + e <4 is satisfied, provided that at least one of a and b is not 0.)   The tire according to claim 1, wherein the softening agent component includes a resin having a softening point of 130 to 200 ° C., and 10 to 60 parts by weight of the resin is mixed with 100 parts by weight of the diene rubber. Rubber composition. Said silica, with respect to the diene rubber 100 parts by weight, tire rubber composition according to claim 1 or 2, characterized in that blended 150 parts by weight or more. Pneumatic tire constituting the tread portion in a tire rubber composition according to any one of claims 1-3.