JP6930071B2 - Rubber composition for tires - Google Patents

Description

The present invention relates to a rubber composition for a tire that improves wet grip performance, its durability and wear resistance.

Pneumatic tires for high-performance automobiles running on circuits and the like are required to have an extremely high level of performance. For example, competitive wet tires are required to have high levels of stability (wet grip performance) and wear resistance on wet road surfaces. In order to improve wet grip performance, a rubber composition for tires containing both carbon black and silica is known. However, if a part of carbon black is replaced with silica, there is a problem that the wear resistance is lowered.

Patent Document 1 proposes to improve wet grip performance by using a rubber composition containing 5 to 150 parts by weight of aluminum hydroxide and carbon black and / or silica with respect to 100 parts by weight of diene rubber. However, this rubber composition also has a problem that the wear resistance cannot be improved as well.

Japanese Unexamined Patent Publication No. 2005-213353

An object of the present invention is to provide a rubber composition for a tire, which has improved wet grip performance, its durability, and wear resistance to a level higher than the conventional level.

The rubber composition for tires of the present invention that achieves the above object has 100 parts by mass of diene rubber containing emulsion-polymerized styrene-butadiene rubber having a weight average molecular weight of 500,000 to 2 million, 120 parts by mass or more of silica, and carbon black. , And 1 to 30 parts by mass of aluminum alkoxide.

In the rubber composition for tires of the present invention, as described above, 100 parts by mass of diene rubber containing emulsion-polymerized styrene-butadiene rubber having a weight average molecular weight of 500,000 to 2 million, 120 parts by mass or more of silica, and carbon black are added. Since less than 20 parts by mass and 1 to 30 parts by mass of aluminum alkoxide are blended, wet grip performance, its durability, and abrasion resistance can be improved more than the conventional level.

The rubber composition for a tire may contain 10 to 60 parts by mass of a hydrocarbon resin having a softening point of 60 to 180 ° C. with respect to 100 parts by mass of the diene rubber, further improving wet grip performance. be able to. The glass transition temperature of the emulsion-polymerized styrene-butadiene rubber is preferably −40 ° C. to 0 ° C.

The above-mentioned rubber composition for tires is suitable for forming a tread of a pneumatic tire. The pneumatic tire made of this rubber composition for a tire can achieve both wet grip performance, its durability and wear resistance at a higher level than before.

In the rubber composition for tires of the present invention, the rubber component is a diene-based rubber containing an aromatic vinyl-conjugated diene rubber. Examples of the aromatic vinyl conjugated diene rubber include styrene-butadiene rubber. The styrene-butadiene rubber may be either a solution-polymerized styrene-butadiene rubber or an emulsion-polymerized styrene-butadiene rubber.

The amount of styrene in the styrene-butadiene rubber is not particularly limited, but is preferably 10 to 50% by mass, preferably 15 to 45% by mass. If the amount of styrene in the styrene-butadiene rubber is less than 10% by mass, the rubber strength may be lowered and the grip performance may be lowered. Further, if the amount of styrene in the styrene-butadiene rubber exceeds 50% by mass, the wear resistance may deteriorate. The amount of styrene in styrene-butadiene rubber shall be measured by ^{1 1 H-NMR.}

The amount of vinyl in the styrene-butadiene rubber is not particularly limited, but is preferably 5 to 80% by mass, and more preferably 8 to 70% by mass. If the amount of vinyl in the styrene-butadiene rubber is less than 5% by mass, the grip performance may deteriorate. If the amount of vinyl in the styrene-butadiene rubber exceeds 80% by mass, it may become too hard and the grip performance may deteriorate. The amount of vinyl in styrene-butadiene rubber shall be measured by ^{1 1 H-NMR.}

The Tg of the styrene-butadiene rubber is not particularly limited, but is preferably −40 ° C. or higher, preferably 35 to 0 ° C. If the Tg of the styrene-butadiene rubber is lower than −40 ° C., the wet grip performance is deteriorated. Further, when the Tg of the styrene-butadiene rubber is higher than 0 ° C., the wear resistance deteriorates. In the present specification, the Tg of styrene-butadiene rubber is measured by a differential scanning calorimetry (DSC) under a heating rate condition of 20 ° C./min, and the temperature is set to the midpoint temperature of the transition region. When the styrene-butadiene rubber is an oil-extended product, it is set to the glass transition temperature of the styrene-butadiene rubber in a state where the oil-extended component (oil) is not contained.

The weight average molecular weight (Mw) of styrene-butadiene rubber is 500,000 to 2 million, preferably 600,000 to 1.8 million. If the Mw of the styrene-butadiene rubber is less than 500,000, the rubber strength is lowered. Further, when Mw exceeds 2 million, the processability of the rubber composition deteriorates. In the present specification, the weight average molecular weight (Mw) of styrene-butadiene rubber shall be measured by gel permeation chromatography (GPC) in terms of standard polystyrene.

The content of the styrene-butadiene rubber in 100% by mass of the diene rubber is preferably 30 to 100% by mass, more preferably 50 to 100% by mass. If the content of the styrene-butadiene rubber is less than 50% by mass, the wet performance deteriorates.

The rubber composition for a tire of the present invention may contain a diene-based rubber other than styrene-butadiene rubber. Other diene rubbers include, for example, natural rubber (NR), polyisoprene rubber (IR), polybutadiene rubber (low cis BR), high cis BR, high trans BR (trans bond content of butadiene part 70 to 95%), styrene. -Isoprene copolymer rubber, butadiene-isoprene copolymer rubber, solution polymerized random styrene-butadiene-isoprene copolymer rubber, emulsified polymerized random styrene-butadiene-isoprene copolymer rubber, emulsified polymerized styrene-acrylonitrile-butadiene copolymer rubber, acrylonitrile- Examples thereof include butadiene copolymer rubber, high vinyl SBR-low vinyl SBR block copolymer rubber, polyisoprene-SBR block copolymer rubber, and polystyrene-polybutadiene-polystyrene block copolymer.

In the rubber composition for tires of the present invention, 1 to 30 parts by mass of aluminum alkoxide is blended with 100 parts by mass of diene-based rubber. By blending aluminum alkoxide, wet grip performance can be improved more than the conventional level while maintaining wear resistance. The blending amount of the aluminum alkoxide is preferably 4 to 26 parts by mass, and more preferably 8 to 22 parts by mass with respect to 100 parts by mass of the diene rubber. If the blending amount of the aluminum alkoxide is less than 1 part by mass, the effect of improving the wet grip performance cannot be sufficiently obtained. Further, if the blending amount of the aluminum alkoxide exceeds 30 parts by mass, the wet grip performance is rather deteriorated.

Aluminum alkoxide is a white powder and is used as a reaction reagent and catalyst in organic synthesis. The alkoxy group of the aluminum alkoxide preferably has 1 to 10 carbon atoms, and more preferably 1 to 6 carbon atoms. Examples of the alkoxy group include methoxy, ethoxy, propyloxy, isopropyloxy, butyloxy, s-butyloxy, t-butyloxy, isobutyloxy, pentyloxy, isoamyloxy, t-amyloxy, hexyloxy, cyclohexyloxy, cyclohexylmethyloxy, and tetrahydrofla. Nyloxy, tetrahydropyranyloxy, 2-methoxyethyloxy, 3-methoxypropyloxy, 4-methoxybutyloxy, 2-butoxyethyloxy, methoxyethoxyethyloxy, methoxyethoxyethoxyethyloxy, 3-methoxybutyloxy, 2 -Methylthioethyloxy, trifluoromethyloxy and the like can be mentioned.

Examples of aluminum alkoxide include aluminum alkyl alkoxide, cyclic aluminum oligomer, aluminum chelate and the like. Examples of aluminum alkyl alkoxides include aluminum methoxydo, aluminum ethoxydo, aluminum isopropoxide, aluminum-n-butoxide, aluminum-s-butoxide, aluminum-t-butoxide, aluminum-n-hexyl, aluminum-n-octyl, and the like. Examples thereof include aluminum-n-decyl, aluminum-n-dodecyl, aluminum-cyclohexyl and the like. Examples of the aluminum chelate include diisopropoxy (ethylacetacetate) aluminum and tris (ethylacetacetate) aluminum. Among them, those having an alkylalkoxy group having 2 to 5 carbon atoms are preferable.

The rubber composition for a tire of the present invention contains carbon black and silica. By blending carbon black and silica, the characteristics of the rubber composition including wet grip performance and wear resistance can be improved.

The blending amount of carbon black is less than 20 parts by mass, preferably 0 to 19 parts by mass, and more preferably 0 to 18 parts by mass with respect to 100 parts by mass of the diene rubber. Wet grip performance can be maintained and improved by reducing the blending amount of carbon black to less than 20 parts by mass.

The blending amount of silica is 120 parts by mass or more, preferably 120 to 250 parts by mass, and more preferably 125 to 220 parts by mass with respect to 100 parts by mass of the diene rubber. Wet grip performance can be maintained and improved by increasing the blending amount of silica to 120 parts by mass or more.

The nitrogen adsorption specific surface area (N ₂ SA) of carbon black is preferably 200 to 400 m ² / g, more preferably 210 to 390 m ² / g. If the carbon black N ₂ SA is ^{less than 200 m 2} / g, the grip performance will deteriorate. If the carbon black N ₂ SA exceeds 400 m ² / g, the wear resistance deteriorates. _{N 2} SA of carbon black shall be obtained in accordance with JIS K6217-2.

The N ₂ SA of silica is preferably 100 to 300 m ² / g, more preferably 110 to 290 m ² / g. If the N ₂ SA of ^{silica is less than 100 m 2} / g, the grip performance will deteriorate. If the N ₂ SA of ^{silica exceeds 300 m 2} / g, processing becomes difficult. N ₂ SA of silica shall be obtained in accordance with JIS K6217-2.

As the silica, silica usually used in rubber compositions for tires, for example, wet silica, dry silica, surface-treated silica and the like can be used.

In the rubber composition for tires of the present invention, by blending a silane coupling agent together with silica, the dispersibility of silica can be improved and the reinforcing property with a diene rubber can be further enhanced. The silane coupling agent is preferably blended in an amount of 2 to 20% by mass, more preferably 5 to 15% by mass, based on the amount of silica blended. When the blending amount of the silane coupling agent is less than 2% by mass of the silica mass, the effect of improving the dispersibility of silica cannot be sufficiently obtained. Further, if the silane coupling agent exceeds 20% by mass, the silane coupling agents will polymerize with each other, and the desired effect cannot be obtained.

The silane coupling agent is not particularly limited, but a sulfur-containing silane coupling agent is preferable, for example, bis- (3-triethoxysilylpropyl) tetrasulfide and bis (3-triethoxysilylpropyl) trisulfide. , Bis (3-triethoxysilylpropyl) disulfide, bis (2-triethoxysilylethyl) tetrasulfide, bis (3-trimethoxysilylpropyl) tetrasulfide, bis (2-trimethoxysilylethyl) tetrasulfide, 3- JP-A-2006 such as mercaptopropyltrimethoxysilane, 3-mercaptopropyldimethoxymethylsilane, 3-mercaptopropyldimethylmethoxysilane, 2-mercaptoethyltriethoxysilane, 3-mercaptopropyltriethoxysilane, and VP Si363 manufactured by Ebonic. 3-Trimethoxysilylpropylbenzothiazole tetrasulfide, 3-triethoxysilylpropylbenzothiazolyltetrasulfide, 3-triethoxysilylpropylmethacrylate monosulfide, 3-triethoxysilylpropylmethacrylate monosulfide, etc. Trimethoxysilylpropyl methacrylate monosulfide, 3-trimethoxysilylpropyl-N, N-dimethylthiocarbamoyltetrasulfide, 3-triethoxysilylpropyl-N, N-dimethylthiocarbamoyltetrasulfide, 2-triethoxysilylethyl-N , N-dimethylthiocarbamoyl tetrasulfide, bis (3-diethoxymethylsilylpropyl) tetrasulfide, dimethoxymethylsilylpropyl-N, N-dimethylthiocarbamoyltetrasulfide, dimethoxymethylsilylpropylbenzothiazolyltetrasulfide, 3- Octanoylthiopropyltriethoxysilane, 3-propionylthiopropyltrimethoxysilane, vinyltrimethoxysilane, vinyltriethoxysilane, vinyltris (2-methoxyethoxy) silane, 3-glycidoxypropyltrimethoxysilane, 3-glycid Xypropylmethyldimethoxysilane, β- (3,4-epylcyclohexyl) ethyltrimethoxysilane, 3-aminopropyltrimethoxysilane, N- (β-aminoethyl) -γ-aminopropyltrimethoxysilane, N- (β) -Aminoethyl) -γ-Aminopropylmethyldimethoxysilane, etc. are exemplified. Can be done. The silane coupling agent is an organic silicon compound, and as the organic silicon compound, polysiloxane, polysiloxane side chain or both ends or one end or both side chains and both ends have an amino group or an epoxy group or a carbinol group or a mercapto. A silicone oil in which one or more organic groups such as a group or a carboxyl group or a hydrogen group or a polyether group or a phenol group or a silanol group or an acrylic group or a methacryl group or a long chain alkyl group is introduced, and one or more kinds of organic silanes are condensed. A silicone oligomer obtained by reaction can also be exemplified. Of these, bis- (3-triethoxysilylpropyl) tetrasulfide and bis (3-triethoxysilylpropyl) disulfide are preferable.

The rubber composition for a tire of the present invention can have better wet grip performance by blending a hydrocarbon resin (resin) having a softening point of preferably 60 to 180 ° C. The softening point of the hydrocarbon resin is more preferably 80 to 170 ° C. If the softening point of the hydrocarbon resin is less than 60 ° C., the action of improving the grip performance cannot be obtained. Further, if the softening point of the hydrocarbon resin exceeds 180 ° C., it becomes difficult to disperse it in the rubber. The softening point of the hydrocarbon resin shall be measured in accordance with JIS K6220-1 (ring ball method).

The blending amount of the hydrocarbon resin is preferably 10 to 60 parts by mass, preferably 10 to 40 parts by mass with respect to 100 parts by mass of the diene rubber. If the blending amount of the hydrocarbon resin is less than 10 parts by mass, the grip performance cannot be sufficiently improved. Further, when the blending amount of the hydrocarbon resin exceeds 60 parts by mass, heat generation becomes excessive and the grip durability is lowered.

The hydrocarbon resin is not particularly limited, but for example, natural resins such as terpene resins and rosin resins, synthetic resins such as petroleum resins, coal resins, phenol resins and xylene resins and synthetic resins and xylene resins and the like. These modified products are exemplified. Of these, terpene-based resins and / or petroleum-based resins are preferable, and modified terpene-based resins are particularly preferable.

As the terpene resin, for example, α-pinene resin, β-pinene resin, limonene resin, hydrogenated limonene resin, dipentene resin, terpene phenol resin, terpene styrene resin, aromatic-modified terpene resin, hydrogenated terpene resin and the like are preferable. Can be mentioned. Of these, aromatic-modified terpene resin is preferable.

The aromatic-modified terpene resin is obtained by polymerizing a terpene and an aromatic compound. Examples of terpenes include α-pinene, β-pinene, dipentene, limonene and the like. Examples of the aromatic compound include styrene, α-methylstyrene, vinyltoluene, indene and the like. Of these, a styrene-modified terpene resin is preferable as the aromatic-modified terpene resin. Since such an aromatic-modified terpene resin has good compatibility with a diene-based rubber, it is possible to modify the dynamic viscoelasticity of the rubber composition and improve wet grip performance and heat generation.

As the petroleum resin, aromatic hydrocarbon resin or a saturated or unsaturated aliphatic hydrocarbon resins. For example C ⁵ petroleum resin (isoprene, 1,3-pentadiene, cyclopentadiene, methylbutene, such as pentene Hydrocarbon petroleum resin obtained by polymerizing a distillate), C ⁹ petroleum resin (aromatic petroleum resin obtained by polymerizing a distillate such as α-methylstyrene, o-vinyltoluene, m-vinyltoluene, p-vinyltoluene) , C ^5- C ⁹ hydrocarbon petroleum resin and the like are exemplified.

The rubber composition for a tire of the present invention may contain a filler other than carbon black and silica. Other fillers include inorganic fillers such as clay, aluminum hydroxide, calcium carbonate, mica, talc, aluminum hydroxide, aluminum oxide, titanium oxide and barium sulfate, and organic fillers such as cellulose, lecithin, lignin and dendrimer. Can be exemplified.

In addition to the above components, the rubber composition for tires of the present invention contains vulcanization or cross-linking agents, vulcanization accelerators, antiaging agents, processing aids, thermoplastics, liquid polymers, thermosetting resins, etc. Various compounding agents generally used in rubber compositions for tires such as thermoplastic resins can be blended. Such a compounding agent can be kneaded by a general method to obtain a rubber composition for a tire, and can be used for vulcanization or cross-linking. The blending amount of these blending agents can be a conventional general blending amount as long as it does not contradict the object of the present invention. The rubber composition for a tire for a tire tread can be prepared by mixing each of the above components using a known rubber kneading machine, for example, a Banbury mixer, a kneader, a roll, or the like.

The rubber composition for a tire of the present invention can be suitably used as a rubber composition for a tread of a pneumatic tire. A pneumatic tire having a tread portion made of this rubber composition can improve the balance between wet grip performance and wear resistance during high-speed running on a circuit or the like more than the conventional level.

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.

11 types of rubber compositions for tires (Examples 1 to 4 and Comparative Examples 1 to 7) containing the compounding agents shown in Table 2 as a common compounding and having the compounding shown in Table 1 are components excluding sulfur and a vulcanization accelerator. Was mixed for 6 minutes using a 1.8 L closed rubbery mixer, discharged from the mixer at 150 ° C., and then cooled to room temperature. Then, the tire was mixed again using a 1.8 liter sealed Banbury mixer for 3 minutes, and after being released, sulfur and a vulcanization accelerator were mixed with an open roll to prepare a rubber composition for a tire.

The tire rubber composition obtained above was used in the tire tread portion to produce a pneumatic tire having a tire size of 195 / 55R15. For these pneumatic tires, the wet grip performance, the durability of the wet grip performance, and the wear resistance were evaluated by the following methods.

Wet grip performance The obtained pneumatic tires are assembled on rims of size 15 x 6J, filled with air pressure of 200 kPa, mounted on the four wheels of the test vehicle, and the test driver is on a circuit course under wet conditions (about 2 km per lap). The lap time for each lap was measured when the tire was continuously run for 10 laps. The obtained results are shown in "Wet grip performance" in Table 1 as an index in which the reciprocal of the average lap time is calculated and the value of Comparative Example 1 is 100. The larger this index, the faster the average lap time and the better the wet grip performance.

Further, when the circuit course was lapped under wet conditions, the time when the average lap time on the 9th to 10th laps became slower than the average lap time on the 3rd to 4th laps was measured, and the reciprocal of the average lap time was calculated. The obtained results are shown in "Grip persistence" in Table 1 as an index with the value of Comparative Example 1 as 100. The larger this index is, the less the average lap time is reduced, and the longer the wet grip performance is maintained.

Abrasion resistance The pneumatic tires obtained above are assembled on rims of size 15 x 6J, filled with air pressure of 200 kPa, mounted on the four wheels of the test vehicle, and the test driver is on a wet circuit course (about one lap). After running 2 km) continuously for 10 laps, the groove depth in the tread of the pneumatic tire was measured. The obtained results are shown in "Abrasion resistance" in Table 1 as an index with the value of Comparative Example 1 as 100. The larger this index is, the better the wear resistance under wet conditions.

In Table 1, the types of raw materials used are as follows.
-SBR: Emulsion-polymerized styrene-butadiene rubber, Nipol 1739 manufactured by Nippon Zeon, styrene content 40% by mass, vinyl content 14%, glass transition temperature -31 ° C, weight average molecular weight 720,000, styrene-butadiene rubber 00 mass Oil-extended product with 37.5 parts by mass of oil component added to the part-Silica: Zeosil 1165MP manufactured by Rhodia, N ₂ SA = 165m ² / g
・ Carbon black, Tokai Carbon Co., Ltd. Seest 9, N ₂ SA = 142m ² / g
-Aluminum hydroxide: Heidi Light H-43 manufactured by Showa Denko Co., Ltd.
-Aluminum alkoxide-1: Aluminum ethoxyde, aluminum ethoxide manufactured by Kawaken Fine Chemical Co., Ltd.-Aluminum alkoxide-2: Aluminum isopropoxide, PADM manufactured by Kawaken Fine Chemical Co., Ltd.
-Silane coupling agent: Bis (3-triethoxysilylpropyl) tetrasulfide, Si69 manufactured by Evonik Industries, Inc.
-Resin: Aromatic modified terpene resin with a softening point of 145 ° C, YS resin T-145 manufactured by Yasuhara Chemical Co., Ltd.
・ Oil: Showa Shell Sekiyu Extract No. 4 S

The types of raw materials used in Table 2 are shown below.
・ Zinc white: Zinc oxide 3 types manufactured by Shodo Chemical Industry Co., Ltd. ・ Stearic acid: Bead stearic acid YR manufactured by NOF Corporation
・ Anti-aging agent: 6PPD manufactured by Flexis
・ Sulfur: Fine powder sulfur containing Jinhua stamp oil manufactured by Tsurumi Chemical Industry Co., Ltd. ・ Vulcanization accelerator-1: Vulcanization accelerator CBS, Noxeller CZ-G manufactured by Ouchi Shinko Chemical Industry Co., Ltd.
-Vulcanization accelerator-2: Vulcanization accelerator DPG, Noxeller D manufactured by Ouchi Shinko Kagaku Kogyo Co., Ltd.

As is clear from Table 1, it was confirmed that the rubber compositions for tires of Examples 1 to 4 were excellent in wet grip performance, durability thereof and wear resistance.

Since the rubber composition for a tire of Comparative Example 2 contains aluminum hydroxide instead of aluminum alkoxide, its wear resistance is inferior. Also, the durability of wet grip performance is low.

Since the amount of silica compounded in the rubber compositions for tires of Comparative Examples 3 and 4 is less than 120 parts by mass, the wet grip performance is inferior.

The rubber compositions for tires of Comparative Examples 5 and 6 are inferior in wet grip performance because the amount of carbon black compounded exceeds 20 parts by mass.

In the rubber composition for tires of Comparative Example 7, since the amount of aluminum alkoxide compounded exceeds 30 parts by mass, the wet grip performance is rather deteriorated.

Claims (5)

100 parts by mass of diene rubber containing emulsified polymerized styrene-butadiene rubber having a weight average molecular weight of 500,000 to 2 million, 120 parts by mass or more of silica, less than 20 parts by mass of carbon black, and 1 to 30 parts by mass of aluminum alkoxide. A rubber composition for tires, which is characterized by being made of. The rubber composition for a tire according to claim 1, wherein a hydrocarbon resin having a softening point of 60 to 180 ° C. is blended in an amount of 10 to 60 parts by mass with respect to 100 parts by mass of the diene rubber. The rubber composition for a tire according to claim 1 or 2, wherein the emulsion-polymerized styrene-butadiene rubber has a glass transition temperature of −40 ° C. to 0 ° C. The rubber composition for a tire according to any one of claims 1 to 3, wherein the tread of a pneumatic tire is formed. A pneumatic tire comprising the rubber composition for a tire according to any one of claims 1 to 4.