JP2009120845A - Rubber composition for tire tread - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a rubber composition for a high performance tire, which shows a high gripping power from the initial period of running, while having an excellent grip performance at low temperature, and keeps the performance even after the tire has generated much heat by running. <P>SOLUTION: The rubber composition for the tire tread includes 100 pts.wt. of a rubber component composed of 50-95 pts.wt. of a diene base rubber containing 50-100 wt.% of an aromatic vinyl-conjugated diene copolymer rubber and 5-50 pts.wt. of a conjugated diene base rubber gel having 16-70 toluene swelling index Q<SB>i</SB>; and, for 100 pts.wt. of the total amount of the rubber component, 3-40 pts.wt. of a copolymer resin of an aromatic vinyl having a softening point of 100-150°C, with dipentene and/or pinene. The tire with high performance using the composition is also provided. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a rubber composition for a high-performance tire tread that has a high grip force and is suitable for use in a high-performance tire selected from tires for sports cars and racing cars, and a high-performance pneumatic tire using the same. .

  High-performance tires used in sports cars and racing cars are required to have high grip performance at low temperatures and to have small performance degradation when they are laps on a circuit. That is, it is necessary to maintain a high grip force from the beginning of traveling and maintain the performance even after the tires generate a large amount of heat during traveling. From this point of view, the present inventors have previously developed a rubber composition that can improve the grip force of a tire without impairing blowout resistance (see Patent Document 1). However, there is still a need in the industry.

Japanese Patent Laid-Open No. 10-204216

  Accordingly, the object of the present invention is not only low temperature grip performance, but also small performance degradation when the circuit runs repeatedly, i.e., exhibits high grip power from the beginning of travel, and the tire generates significant heat during travel. It is another object of the present invention to provide a rubber composition for a tread for a high performance tire of a sports car or a racing car that can maintain its performance.

According to the present invention, 50 to 95 parts by weight of a diene rubber containing 50 to 100% by weight of an aromatic vinyl-conjugated diene copolymer rubber and a conjugated diene rubber gel 5 to 50 having a toluene swelling index Q _i of 16 to 70. 100 parts by weight of a rubber component comprising 3 parts by weight and 3-40 parts by weight of a copolymer resin of aromatic vinyl having a softening point of 100 to 150 ° C. and dipentene and / or pinene per 100 parts by weight of the total rubber component A rubber composition for a tread of a high performance tire selected from the sports car and racing car tires, and a high performance pneumatic tire using the rubber composition for the tread are provided.

According to the present invention, conjugated diene rubber gel 5 having a toluene swelling index Q _i of 16 to 70 with respect to 50 to 95 parts by weight of diene rubber containing 50 to 100% by weight of aromatic vinyl-conjugated diene copolymer rubber. ~ 50 parts by weight (however, the total amount of rubber components is 100 parts by weight) and a copolymer resin of aromatic vinyl and dipentene and / or pinene having a softening point of 100 to 150 ° C per 100 parts by weight of total rubber components By adding 3 to 40 parts by weight, a rubber composition for a tread of a high-performance tire that exhibits desired grip performance and the like even after the tire generates significant heat due to running in addition to grip performance at low temperatures can be obtained. .

As a result of researches to solve the above-mentioned problems, the present inventors have found that a rubber composition in which a conjugated diene rubber gel having a toluene swelling index Q _i of 16 to 70 is mixed with a diene rubber has a high grip at the beginning of running. In order to confirm that there is a problem in performance degradation during running and to maintain grip performance from the beginning of running, in addition to the diene rubber gel, aromatic vinyl having a softening point of 100 to 150 ° C. The present inventors have found that it is effective to further blend a copolymer resin of dipentene (limonene) and / or pinene.

According to the present invention, 5 to 50 parts by weight of a conjugated diene rubber gel having a toluene swelling index Q _i of 16 to 70 (however, the total amount of rubber components is 100 parts by weight) and 50 to 95 parts by weight of diene rubber A copolymer resin of aromatic vinyl having a softening point of 100 to 150 ° C. and dipentene and / or pinene is blended in an amount of 3 to 40 parts by weight with respect to 100 parts by weight of the total rubber component. Here, “toluene swelling index Q _i ” means that 0.2 g of gelled rubber is immersed in 100 ml of toluene for 24 hours, and the weight (wet weight) of the rubber is weighed and weighed and then dried to weigh the dry weight. And obtained by wet weight / dry weight.

  Examples of the rubber component of the rubber composition of the present invention include aromatic vinyl-conjugated diene copolymer rubber (for example, styrene-butadiene copolymer rubber, styrene-isoprene copolymer rubber, α-methyl-styrene-butadiene copolymer). A diene rubber (for example, aromatic vinyl-conjugated diene copolymer rubber), natural rubber, polybutadiene rubber, polyisoprene rubber, acrylonitrile-butadiene, containing 50 to 100% by weight, preferably 60 to 100% by weight. -Copolymer rubber, butadiene-isoprene-copolymer rubber, etc.). If the blending amount of the aromatic vinyl-conjugated diene copolymer rubber is small, the grip performance becomes insufficient, such being undesirable.

The rubber composition of the present invention includes a conjugated diene rubber gel having a toluene swelling index Q _i of 16 to 70, preferably 20 to 65, relative to 50 to 95 parts by weight, preferably 60 to 93 parts by weight of the diene rubber. 5 to 50 parts by weight, preferably 7 to 40 parts by weight (provided that the total amount of rubber components is 100 parts by weight) and an aromatic vinyl (for example, styrene, α) having a softening point of 100 to 150 ° C., preferably 103 to 140 ° C. 3 to 40 parts by weight of a copolymer resin of -methyl-styrene, p-methyl-styrene, p-chlorostyrene, vinylnaphthalene) and dipentene and / or pinene with respect to 100 parts by weight of the total amount of rubber components; Preferably 5-35 weight part is mix | blended.

Is less than Q _i of the conjugated diene rubber gel is 16, rubber gels is insufficient grip enhancing effect is too hard, can not be expected the effect of the rubber gels exceeds 70 Conversely, the grip is not improved. If the amount of the rubber gel is less than 5 parts by weight, the effect of improving the grip is insufficient, and if it exceeds 50 parts by weight, the processability deteriorates, which is not preferable. When the softening point of the copolymer resin is less than 100 ° C., desired grip durability cannot be improved. When the softening point exceeds 150 ° C., the dispersion of the resin at the time of mixing becomes worse, which is not preferable. The softening point is measured by a method defined in JIS K6220. If the blending amount of the copolymer resin is less than 3 parts by weight, the effect of improving the grip durability is insufficient, and conversely if it exceeds 40 parts by weight, the grip at the initial stage of travel is lowered, which is not preferable.

In a preferred embodiment of the present invention, the diene rubber has an average glass transition temperature T _g (measured at a rate of temperature increase of 20 ° C./min using a differential scanning calorimeter (DSC) and calculated by a midpoint method). −45 ° C. to 0 ° C., preferably −43 ° C. to −5 ° C., and nitrogen adsorption specific surface area (N ₂ SA) (measured by ASTM D3037) is 80 to 400 m ² / g, preferably 85 to 300 m ² / The total amount of carbon and / or silica of g is 50 to 200 parts by weight, preferably 60 to 180 parts by weight, based on 100 parts by weight of the total amount of the rubber components. The T _g of the diene rubber is less than -45 ° C. there is a risk that the grip is lowered, the rubber becomes hard exceeds 0 ° C., the running initial grip may be reduced. If the nitrogen adsorption specific surface area of carbon black and / or silica is less than 80 m ² / g, the grip may be lowered. Conversely, if it exceeds 400 m ² / g, the workability may be deteriorated. If the total blending amount of carbon and / or silica is less than 50 parts by weight, the grip may be lowered. Conversely, if it exceeds 200 parts by weight, the workability may be deteriorated.

The conjugated diene rubber gel having a Q _i of 16 to 70 used in the present invention is a known substance, preferably 49.9 to 99.9% by weight of conjugated diene monomer units, more preferably 51.9 to 89.9 wt%, aromatic vinyl monomer units 50-0 wt%, more preferably 48-10 wt%, polyfunctional monomer units 0.1-1.5 wt%, more preferably 0.8. 1 to 1.2% by weight. If the amount of the polyfunctional monomer unit is small, the effect of improving the grip may be insufficient, whereas if the amount is large, the gel rubber may be too hard and the grip may not be improved. When the amount of aromatic vinyl unit is large, styrene tends to be a block, and the flexibility as rubber may be impaired.

  Examples of the conjugated diene monomer unit include 1,3-butadiene, 2-methyl-1,3-butadiene, 1,3-pentadiene, 2-chloro-1,3-butadiene, and the like. 1,3-butadiene and 2-methyl-1,3-butadiene are preferred, and 1,3-butadiene is most preferred.

  Examples of the aromatic vinyl monomer unit include styrene, o-methylstyrene, m-methylstyrene, p-methylstyrene, 2,4-dimethylstyrene, o-ethylstyrene, m-ethylstyrene, and p-ethylstyrene. , Pt-butylstyrene, α-methylstyrene, α-methyl-p-methylstyrene, o-chlorostyrene, p-chlorostyrene, m-chlorostyrene, p-bromostyrene, 2-methyl-4,6- Examples include dichlorostyrene, 2,4-dibromostyrene, and vinylnaphthalene. Styrene is preferred.

  The polyfunctional monomer unit is a carbon-carbon double bond that can be used to efficiently form a gel structure and can be copolymerized with at least 2, preferably 2 to 4, conjugated diene monomers. A compound having is used. For example, polyvalent vinyl compounds such as diisopropenylbenzene, divinylbenzene, triisopropenylbenzene, and trivinylbenzene; unsaturated α, β-ethylenically unsaturated carboxylic acids such as vinyl acrylate, vinyl methacrylate, and allyl methacrylate Ester compounds; unsaturated ester compounds of polyvalent carboxylic acids such as diallyl phthalate, triallyl cyanurate, triallyl isocyanurate, triallyl trimellitic acid; polyhydric alcohols such as ethylene glycol diacrylate, ethylene glycol dimethacrylate, propylene glycol dimethacrylate And 1,2-polybutadiene, divinyl ether, divinyl sulfone, N, N′-m-phenylmaleimide and the like.

  The conjugated diene rubber gel according to the present invention can be produced, for example, by emulsion polymerization of each of the above components at a temperature of, for example, -5 ° C to 80 ° C.

In the rubber composition of the present invention, 50 to 200 parts by weight of carbon black and / or silica as a total amount can be blended as optional components. There are no particular limitations on the carbon black or silica used. For example, as the carbon black, any carbon black that can be blended in a rubber composition such as furnace black, acetylene black, thermal black, channel black, or graphite is used. Can do. Among these, those having N ₂ SA of 80 to 400 m ² / g are preferable as described above. These carbon blacks can be used alone or in combination of two or more. Silica that can be used in the present invention is not particularly limited, and it can be applied to rubber compositions such as dry method white carbon, wet method white carbon, colloidal silica, and precipitated silica disclosed in JP-A-62-62838. Any silica that can be blended can be used. Among these, wet method white carbon (wet silica) mainly containing hydrous silicic acid is preferable. As described above, these silicas preferably have N ₂ SA of 80 to 400 m ² / g, and can be used alone or in combination of two or more.

  The copolymer resin used in the rubber composition according to the present invention has a dipentene aromatic vinyl copolymer resin, pinene aromatic vinyl copolymer resin, dipentene pinene aromatic vinyl copolymer having a softening point of 100 to 150 ° C. A polymer resin or a mixture thereof, which is known as, for example, a dipentene-styrene copolymer resin or a pinene-styrene copolymer resin. Specifically, various commercially available products can be used. As the dipentene aromatic vinyl copolymer resin, for example, commercially available YS resin TO-105, YS resin TO-125 manufactured by Yasuhara Chemical can be suitably used. As the pinene aromatic vinyl copolymer resin, for example, commercially available YS resin TR-105 manufactured by Yasuhara Chemical can be used.

  In addition to the components described above, the rubber composition according to the present invention includes reinforcing agents (fillers) other than carbon black and silica, vulcanization or crosslinking agents, vulcanization or crosslinking accelerators, various oils, anti-aging agents, plastics Various additives generally blended for tires such as additives and other rubber compositions can be blended, and these additives are kneaded by a general method to form a composition, which is then vulcanized or crosslinked. Can be used to do. The blending amounts of these additives may be conventional conventional blending amounts as long as the object of the present invention is not adversely affected. A method for producing a high-performance tire using the rubber composition of the present invention can also be carried out in accordance with the conventional method.

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

Examples 1-4 and Comparative Examples 1-3
Sample preparation In the formulation shown in Table I, other compounding agents except sulfur and a vulcanization accelerator were mixed for about 5 minutes in a 16 L Banbury mixer. The number of rotations of the rotor was varied, and the temperature at the time of discharge was adjusted to 150 ° C. The obtained master batch was again mixed with a 16 L Banbury mixer for about 3 minutes. Next, the obtained master batch was wound around an 8 × 16 inch roll, and then sulfur and a vulcanization accelerator were added and mixed for about 3 minutes.

Using unvulcanized rubber obtained in the physical property evaluation test , a tire of size 225 / 45R17 was prototyped according to a conventional method, and subjected to a steering stability test. In other words, the prototype tire was mounted on a vehicle with a displacement of 2500 cc, and 10 laps were conducted while meandering a 2.5 km track, and the grip strength at the beginning and end of the run was evaluated.
Based on 3 points, 3.5: Slightly perceptible, 4: Sufficiently perceptible, 4.5: Clearly perceivable, and 2.5: Slightly perceptible did. The results are shown in Table I.

Table I Footnote * 1: Nippon Zeon _{SBR (T g = -31 ℃,} 37.5phr oil Exhibition)
* 2: Natural rubber * 3: Nippon Zeon gel rubber (Q _i = 35, 28phr oil exhibition) (styrene content 41%)
* 4: Rhodia wet silica (N ₂ SA = 160 m ² / g)
* 5: Carbon black made by Tokai Carbon (N ₂ SA = 142 m ² / g)
* 6: manufactured by Shodo Chemical Industry * 7: manufactured by Nippon Oil & Fats * 8: anti-aging agent manufactured by FLEXSYS * 9: dipentene-styrene resin manufactured by Yasuhara Chemical (softening point = 125 ° C)
* 10: Yasuhara Chemical dipentene-styrene resin (softening point = 85 ° C)
* 11: Petroleum softener made by Japan Energy * 12: Made by Tsurumi Chemical Industry * 13: Vulcanization accelerator made by Ouchi Shinsei Chemical Industry

According to the present invention, a diene rubber containing an aromatic vinyl-conjugated diene copolymer is blended with a conjugated diene rubber gel having a toluene swelling index Q _i of 16 to 70, and a softening point of 100 to 150 ° C. By blending an aromatic vinyl-dipentene and / or pinene copolymer resin, a high grip force can be exerted from the beginning of running, and the performance can be maintained even after the tires generate significant heat during running. And / or can be advantageously used as a rubber composition for a tread of a high-performance tire of a racing car.

Claims (5)

(A) From 50 to 95 parts by weight of a diene rubber containing 50 to 100% by weight of an aromatic vinyl-conjugated diene copolymer rubber and 5 to 50 parts by weight of a conjugated diene rubber gel having a toluene swelling index Q _i of 16 to 70 100 parts by weight of the rubber component and (B) 3 to 40 parts by weight of a copolymer resin of aromatic vinyl having a softening point of 100 to 150 ° C. and dipentene and / or pinene per 100 parts by weight of the total rubber component. A rubber composition for a tread of a high-performance tire selected from sports car and racing car tires. The rubber composition for a tread according to claim 1, wherein the copolymer resin is a dipentene-styrene resin having a softening point of 125 to 150 ° C. The average glass transition temperature T _g of the diene rubber is -45 ° C. ~0 ° C., the nitrogen adsorption specific surface area (N ₂ SA) of carbon and / or silica 50 to 200 parts by weight of 80~400m ² / g (total The rubber composition for a tread according to claim 1 or 2 , wherein 100 parts by weight of a rubber component is blended. Conjugated diene-based rubber gel comprises 49.9 to 99.9% by weight of conjugated diene monomer unit, 50 to 0% by weight of aromatic vinyl monomer unit, and 0.1 to 1.5% of polyfunctional monomer unit. The rubber composition for tread according to any one of claims 1 to 3, wherein the rubber composition is composed of%. A high performance pneumatic tire selected from sports car and racing car tires using the rubber composition according to any one of claims 1 to 4 in a tread portion.