JP5499689B2 - Rubber composition for tire - Google Patents

Description

  The present invention relates to a tire rubber composition, and more specifically, in a rubber composition containing an unsaturated terpene resin, the anti-aging performance and the grip performance are improved to a level higher than the conventional level without deteriorating the wear resistance. The present invention relates to a tire rubber composition.

  In recent years, high-performance type pneumatic tires for passenger cars have been required to improve grip performance. For this reason, a terpene resin is blended with a rubber composition constituting a tread portion. Terpene resin is a resin component obtained from non-petroleum raw materials such as mandarin oranges and pine ani, so it is also attracting attention as a role to increase the ratio of non-petroleum raw materials in pneumatic tires. .

  However, in general, the terpene resin has a structure having an unsaturated bond in addition to a relatively small molecular weight, and thus has a problem that it is easily oxidized and has a low anti-aging performance. There has also been a demand for further improving the grip performance of the tire.

  In order to improve the anti-aging performance, it is conceivable to increase the amount of antioxidant added. However, if the amount of antioxidant obtained from conventional petroleum-based raw materials is increased, the ratio of non-petroleum-based raw materials will increase. It becomes low and is not preferable.

  As a countermeasure, Patent Document 1 proposes blending a hydrogenated terpene resin obtained by partially or completely hydrogenating an unsaturated bond of a terpene resin. However, the hydrogenated terpene resin has the effect of increasing the anti-aging performance of the rubber composition, but has a problem that the wear resistance of the rubber composition is lowered because of its low affinity with the diene rubber. Moreover, the subject of raising grip performance further could not be achieved.

JP 2008-169296 A

  An object of the present invention is to provide a rubber composition for tires that is improved in anti-aging performance and grip performance to a conventional level without deteriorating wear resistance in a rubber composition containing an unsaturated terpene resin. It is to provide.

  Another object of the present invention is that when silica is compounded for low rolling resistance, not only the wear resistance, anti-aging performance and grip performance are improved, but also the level of low rolling resistance can be improved. An object of the present invention is to provide a tire rubber composition.

The rubber composition for a tire according to the present invention that achieves the above object comprises 5 parts of an unsaturated terpene resin to 100 parts by weight of a rubber component containing 90% by weight or more of a diene rubber having a glass transition temperature of −25 ° C. or less. 50 parts by weight, 0.1 to 5 parts by weight of tea extract containing 5 to 95% by weight of tea polyphenol containing 6 to 85% by weight of catechin, and blending amount of the unsaturated terpene resin (a [parts by weight ]) And the blending amount of tea extract (b [parts by weight]), the weight ratio (a / b) is 1 to 200.

  The unsaturated terpene resin is preferably at least one selected from terpene resins, styrene-modified terpene resins, and phenol-modified terpene resins, and the number-average molecular weight of these unsaturated terpene resins is 500 to 1500. Good.

  Examples of the tea extract include (+)-catechin, (−)-epicatechin, (+)-gallocatechin, (−)-epigallocatechin, (−)-epicatechin gallate, (+)-gallocatechin gallate and What contains at least 1 sort (s) chosen from the group which consists of (-)-epigallocatechin gallate is preferable.

  The tire rubber composition preferably contains 20 to 130 parts by weight of silica with respect to 100 parts by weight of the rubber component. Moreover, this rubber composition for tires can be used suitably as a constituent material of a pneumatic tire.

According to the rubber composition for tires of the present invention, 5 to 50 parts by weight of an unsaturated terpene resin with respect to 100 parts by weight of a rubber component containing 90% by weight or more of a diene rubber having a glass transition temperature of −25 ° C. or less. And 0.1 to 5 parts by weight of tea extract containing 5 to 95% by weight of tea polyphenol containing 6 to 85% by weight of catechin, and the amount of unsaturated terpene resin (a [parts by weight]) Since the weight ratio (a / b) to the blending amount of tea extract (b [parts by weight]) was set to 1 to 200, the catechin in the tea extract functions as an antioxidant and prevents aging of the rubber composition. Enable to improve performance. In addition, by adding a tea extract containing catechin, the grip performance is improved and the affinity between the rubber component and the terpene resin is not deteriorated. it can.

  Further, in the case of a rubber composition containing silica, the catechin in the tea extract unexpectedly functions to improve the dispersibility of the silica, thereby further improving the low rolling resistance of the rubber composition. be able to.

  In the rubber composition for tires of the present invention, the rubber component always includes a diene rubber having a glass transition temperature of −25 ° C. or lower. The glass transition temperature of this diene rubber is −25 ° C. or lower, preferably −27 ° C. to −110 ° C., more preferably −30 ° C. to −105 ° C. By setting the glass transition temperature of the diene rubber to −25 ° C. or less, the wear resistance performance when used in a tire can be increased. The diene rubber may be an oil-extended product containing oil-extended oil, but its glass transition temperature is a glass transition temperature in a state not containing oil-extended oil. In addition, the glass transition temperature is measured by differential scanning calorimetry (DSC) under a temperature increase rate condition of 2 ° C./min, and each of the low temperature side baseline and the transition region slope (inclination straight line) is extended. The temperature at the intersection of the lines.

  Examples of the diene rubber having a glass transition temperature of −25 ° C. or lower include natural rubber, isoprene rubber, styrene-butadiene rubber, butadiene rubber, acrylonitrile-butadiene rubber, and butyl rubber. These diene rubbers can be used alone or as any blend. The content of the diene rubber having a glass transition temperature of −25 ° C. or less in the rubber component is 90% by weight or more, preferably 100% by weight. If the content of the diene rubber having a glass transition temperature of −25 ° C. or lower is less than 90% by weight, the wear resistance cannot be increased.

  Examples of rubber components other than diene rubber having a glass transition temperature of −25 ° C. or lower include ethylene-propylene copolymer rubber (EPR), styrene-ethylenepropylene-styrene copolymer rubber (SEPS), and styrene. Examples thereof include heatable elastomers such as ethylene butylene-styrene copolymer rubber (SEBS), and styrene-butadiene rubber having a glass transition temperature higher than −25 ° C. The content of these other rubber components is 10% by weight or less in the rubber component.

  In the present invention, the grip performance is improved by blending an unsaturated terpene resin. The unsaturated terpene resin means a terpene resin excluding a hydrogenated terpene resin in which at least a part of the unsaturated bond is hydrogenated. Examples of such unsaturated terpene resins include terpene resins, aromatic modified terpene resins, and phenol modified terpene resins. Here, the terpene resin is a polymer of at least one terpene selected from α-pinene, β-pinene, dipentene, limonene and the like. The aromatic modified terpene resin is at least one terpene selected from α-pinene, β-pinene, dipentene, limonene and the like, and at least one fragrance selected from styrene, α-methylstyrene, vinyltoluene, indene and the like. It is a polymer with a group compound. Among these, as the aromatic-modified terpene resin, a styrene-modified terpene resin is preferable. The phenol-modified terpene resin is a polymer of at least one terpene and phenol described above. The unsaturated terpene resin used in the present invention is preferably a terpene resin, a styrene-modified terpene resin, or a phenol-modified terpene resin.

  The molecular weight of the unsaturated terpene resin is not particularly limited, but the number average molecular weight (Mn) is preferably 500 to 1500, more preferably 600 to 1500. If the number average molecular weight of the unsaturated terpene resin is less than 500, the rubber composition is insufficient in hardness and the grip performance cannot be sufficiently increased. Moreover, when a number average molecular weight exceeds 1500, while handling property at the time of mixing of a rubber composition will fall, rolling resistance will deteriorate. The number average molecular weight (Mn) of the unsaturated terpene resin was measured by gel permeation chromatography (GPC) and determined by polystyrene conversion.

  In this invention, the compounding quantity of unsaturated terpene resin is 5-50 weight part with respect to 100 weight part of rubber components, Preferably it is 5-40 weight part. When the blending amount of the unsaturated terpene resin is less than 5 parts by weight, the grip performance cannot be increased. Moreover, when the compounding quantity of unsaturated terpene-type resin exceeds 50 weight part, the handleability of rubber | gum will deteriorate or rolling resistance will become excessive.

  In the tire rubber composition of the present invention, the tea extract containing catechin functions as an antioxidant and acts to increase the anti-aging performance. Moreover, there exists a fact that grip performance improves further by mix | blending the tea extract containing catechin. The reason is presumed that catechin improves the dispersibility of the unsaturated terpene resin. Moreover, since the tea extract does not deteriorate the affinity between the rubber component and the terpene resin, it is possible to ensure wear resistance at or above the conventional level.

  The amount of tea extract containing catechin is 0.1 to 5 parts by weight, preferably 0.2 to 3.0 parts by weight, per 100 parts by weight of the rubber component. The desired effect mentioned above cannot be acquired as the compounding quantity of a tea extract is less than 0.1 weight part. Moreover, when the compounding quantity of a tea extract exceeds 5 weight part, cost will become high too much and it will not become industrial, and even if it adds more, performance improvement will not be seen.

  In the present invention, the weight ratio (a / b) between the amount of unsaturated terpene resin (a [parts by weight]) and the amount of tea extract (b [parts by weight]) is preferably 1 to 200, preferably Is 2 to 200, more preferably 2 to 150. When the weight ratio (a / b) between the unsaturated terpene resin and the tea extract is less than 1, sufficient performance improvement effects cannot be obtained. If the weight ratio (a / b) between the unsaturated terpene resin and the tea extract exceeds 200, the anti-aging performance of the rubber composition cannot be increased. Further, the effect of further improving the grip performance cannot be obtained.

  The tea extract containing catechins used in the present invention is an extract from at least one selected from green tea, oolong tea, and black tea, and water, hot water, or an organic solvent is extracted from these tea leaves or ground tea leaves. As an agent, it can be extracted at an extraction temperature of 5 to 60 ° C. Examples of the organic solvent include methanol, ethanol, isopropanol, ethyl acetate, glycerin and the like. These extractants may be used alone or in combination of two or more.

  As the tea extract containing catechin, a fraction extracted with the above-described extractant can be used. When extracted with water, hot water, or an organic solvent, the extract may be used as it is as a tea extract. However, from the viewpoint of handleability, water is removed from the extract by spray drying or freeze drying. It is recommended to use it in powder form.

The tea extract used in the present invention must contain tea polyphenols containing catechins. In addition to tea polyphenols, it may contain minerals, ash and the like. The content of tea polyphenols tea extract 5 to 95%, good Mashiku is a 7-90 wt%. The balance is mineral, ash, etc. This tea polyphenol has a flavonoid as a main component, and examples of the flavonoid include flavone, flavonol, flavanol, and flavone glycoside. In addition, condensed tannins are generated by combining a plurality of flavonoids. Of the flavonoids, flavanols are catechins having a flavan-3-ol skeleton.

In the present invention, tea polyphenols contained in the tea extract are broadly classified into catechins and other tea polyphenols other than catechins. Examples of the catechin include (+)-catechin, (−)-epicatechin, (+)-gallocatechin, (−)-epigallocatechin, (−)-epicatechin gallate, (+)-gallocatechin gallate, (− ) -Epigallocatechin gallate, free theaflavin, theaflavin monogallate A, theaflavin digallate and the like. Among these, as catechin, (+)-catechin, (−)-epicatechin, (+)-gallocatechin, (−)-epigallocatechin, (−)-epicatechin gallate, (+)-gallocatechin gallate, ( It is good that it is at least one selected from-)-epigallocatechin gallate. The content of catechins in the tea polyphenols, you to 6-85% by weight. When the content of catechin in the tea polyphenol is less than 5% by weight, the anti-aging performance cannot be sufficiently obtained.

  The other tea polyphenols are tea-derived flavonoids other than catechins and tea polyphenols other than flavonoids. By containing these other tea polyphenols, the dispersibility of catechin in the rubber component becomes better than when only catechin is blended. For this reason, while making the effect as an antioxidant of catechin higher, the synergistic effect with the antioxidant effect of other tea polyphenols can be expected.

  As the tea extract used in the rubber composition for tires of the present invention, the tea extract described above may be used as it is, or may be used as a mixture to which other natural compounds and / or surfactants are added. . Examples of natural compounds include plant-derived polyphenols other than tocopherol, ascorbic acid, tea polyphenols, vegetable oils, animal oils, and the like. Examples of the surfactant include monoglycerin fatty acid ester, polyglycerin fatty acid ester, sucrose fatty acid ester, sorbitan fatty acid ester, polyoxyethylene sorbitan fatty acid ester, propylene glycol fatty acid ester, polyglycerin condensed fatty acid ester and the like. .

  Such a tea extract or a mixture thereof is commercially available, for example, Sun Chemical Co., Ltd. Sunphenon DK (tea extract containing 92% by weight of tea polyphenol containing 74% by weight of catechin, 8% by weight of mineral, ash, etc.), Sanflavone HG (tea extract containing 73% by weight of tea polyphenol containing 73% by weight of catechin and 11% by weight of mineral, ash, etc.), Sankatol No1 (a mixture of tea extract containing catechin and treated with surfactant) And the content of tea polyphenol containing 70% by weight of catechin is 10% by weight) and the like.

  The rubber composition for tires of the present invention can contain silica. By compounding silica, an effect of reducing the rolling resistance of the rubber composition can be obtained, and the fuel efficiency of the tire can be improved. Since silica tends to aggregate due to hydrogen bonding of silanol groups present on the particle surface, silica is poorly dispersible in diene rubber, so that a silane coupling agent is blended together as described later. However, by simply adding a silane coupling agent, the dispersibility of silica cannot be improved, and the effect of reducing the low rolling resistance of the rubber composition may not be sufficiently obtained. On the other hand, in this invention, the effect | action which improves the dispersibility of a silica unexpectedly is obtained by mix | blending the tea extract containing catechin. Thereby, the low rolling resistance of the rubber composition can be further reduced. Thus, the effect | action which improves the dispersibility of a silica is not acquired when the antioxidant obtained from the petroleum-type raw material is used.

The silica suitably blended in the present invention preferably has a CTAB adsorption specific surface area of 60 to 250 m ² / g, more preferably 80 to ²⁰⁰ m ² / g, and still more preferably 100 to 190 m ² / g. When the CTAB adsorption specific surface area of silica is less than 60 m ² / g, the rubber strength cannot be sufficiently increased. When the CTAB adsorption specific surface area of silica exceeds 250 m ² / g, the rubber viscosity increases and the processability deteriorates. The CTAB adsorption specific surface area of silica shall be determined according to the standard of ASTM-D3765-80.

  The amount of silica is preferably 20 parts by weight or more, more preferably 30 to 100 parts by weight with respect to 100 parts by weight of the rubber component. If the amount of silica is less than 20 parts by weight, the exothermic properties of the rubber composition cannot be reduced sufficiently. In addition, since silica agglomerates are difficult to form, the effect of improving dispersibility may not be manifested.

  In this invention, it is preferable to mix | blend a silane coupling agent with a silica, and the dispersibility of the silica with respect to a diene rubber can be improved. The amount of the silane coupling agent is preferably 3 to 15% by weight, more preferably 5 to 10% by weight, based on the amount of silica. When the compounding amount of the silane coupling agent is less than 3% by weight, the dispersibility of silica cannot be sufficiently improved. Moreover, when the compounding quantity of a silane coupling agent exceeds 15 weight%, silane coupling agents will aggregate and condense, and it will become impossible to acquire a desired effect.

  Although it does not restrict | limit especially as a kind of silane coupling agent, A sulfur containing silane coupling agent is preferable. Examples of the sulfur-containing silane coupling agent include bis- (3-triethoxysilylpropyl) tetrasulfide, bis (3-triethoxysilylpropyl) disulfide, 3-trimethoxysilylpropylbenzothiazole tetrasulfide, and γ-mercaptopropyl. Examples thereof include triethoxysilane and 3-octanoylthiopropyltriethoxysilane.

  The rubber composition for tires of this invention can mix | blend inorganic fillers other than a silica. The strength of the rubber composition is increased by blending the inorganic filler. Examples of the inorganic filler include carbon black, clay, titanium oxide, talc, calcium carbonate, aluminum hydroxide, mica and the like. The inorganic filler is blended so that the total of silica and the inorganic filler is preferably 20 to 130 parts by weight, more preferably 30 to 100 parts by weight with respect to 100 parts by weight of the rubber component. When the total of silica and inorganic filler is less than 20 parts by weight, the rubber strength cannot be sufficiently increased. Moreover, when the sum total of a silica and an inorganic filler exceeds 130 weight part, the viscosity of the rubber composition for tires will increase, and moldability will deteriorate.

  In the tire rubber composition of the present invention, various additives generally used in tire rubber compositions such as a vulcanizing agent, a vulcanization accelerator, an antioxidant, a plasticizer, and a coupling agent are blended. Such an additive can be kneaded by a general method to obtain a rubber composition for a tire, which can be used for vulcanization or crosslinking. As long as the amount of these additives is not contrary to the object of the present invention, a conventional general amount can be used. Moreover, the rubber composition for tires can be manufactured by mixing said each component using a normal rubber kneading machine, for example, a Banbury mixer, a kneader, a roll, etc.

  In the tire rubber composition of the present invention, since the catechin in the tea extract functions as an antioxidant, it is possible to improve the anti-aging performance of the rubber composition containing the unsaturated terpene resin, and to improve the grip performance. Further improvement. Moreover, since the affinity between the rubber component and the terpene-based resin is not deteriorated, it is possible to ensure wear resistance higher than the conventional level. Furthermore, since the rubber composition containing silica has the characteristics of improving its low rolling resistance to a level higher than the conventional level, the fuel efficiency performance of the pneumatic tire can be further improved. A pneumatic tire using such a rubber composition for tires has high anti-aging performance and wear resistance, is excellent in tire durability, and can improve grip performance and fuel efficiency.

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

  Twelve types of rubber compositions for tires (Examples 1 to 5, Comparative Examples 1 to 7) having the compositions shown in Tables 1 and 2 were weighed for the ingredients except for sulfur and vulcanization accelerator, and 1.8 L. The banbury mixer was kneaded for 5 minutes, and the master batch was discharged at a temperature of 160 ° C. and cooled at room temperature. The master batch was subjected to a 1.8 L Banbury mixer, and sulfur and a vulcanization accelerator were added and mixed to prepare a tire rubber composition.

  Twelve types of rubber compositions for tires (Examples 1 to 5, Comparative Examples 1 to 7) obtained were each vulcanized at 160 ° C. for 20 minutes in molds of predetermined shapes to produce test pieces. Were evaluated for dynamic viscoelasticity (tan δ at 60 ° C.), anti-aging performance and abrasion resistance by a tensile test.

Dynamic viscoelasticity (tan δ at 60 ° C)
Using a viscoelastic spectrometer manufactured by Toyo Seiki Seisakusho, tan δ at a temperature of 60 ° C. was measured under the conditions of static strain 10%, dynamic strain ± 2%, and frequency 20 Hz. The obtained results are shown in Table 1, with the reciprocal of the value of Comparative Example 1 being 100, and in Table 2, the reciprocal of the value of Comparative Example 6 being 100 as an index of “low rolling resistance” in Tables 1 and 2. Shown in the column. The larger the low rolling resistance index, the smaller the tan δ (60 ° C.), which means that the rolling resistance when made into a tire is small and the fuel efficiency is excellent.

Aging prevention performance No. 3 dumbbell-shaped test piece based on JIS K6251 was molded from the obtained test piece. Each dumbbell-shaped test piece was divided into two groups, and one of them was heated at 70 ° C. for 96 hours (aging treatment). Using a dumbbell-shaped test piece before and after the aging treatment, a tensile test was performed under the conditions of a temperature of 20 ° C. and a tensile speed of 500 mm / min, and a stress-strain curve (SS curve) was measured. The stress for each strain of 10% was recorded for each, and the area of the SS curve was determined. Next, the change rate (%) of the area was calculated by (Area after aging treatment / Area before aging treatment × 100), and used as the anti-aging performance of the tensile test. The obtained results are shown in the column of “Anti-aging performance” in Tables 1 and 2 as an index in which Comparative Example 1 is 100 in Table 1 and Comparative Example 6 is 100 in Table 2. A larger index of anti-aging performance means higher anti-aging performance in the tensile test.

Abrasion resistance Abrasion amount of the obtained test piece in accordance with JIS K6264 using a Lambourn abrasion tester (manufactured by Iwamoto Seisakusho) under the conditions of load 49N, slip rate 25%, time 4 minutes, room temperature Was measured. The obtained results are shown in Tables 1 and 2 as an index in which the reciprocal of the wear amount of Comparative Example 1 is 100 in Table 1 and the reciprocal of the wear amount of Comparative Example 6 is 100 in Table 2. It was shown to. The larger the index of wear resistance, the better the wear resistance.

  In addition, pneumatic tires having a tire size of 215 / 60R16, in which a tire tread portion was constituted by the obtained 12 kinds of rubber compositions, were manufactured. Each of the obtained pneumatic tires was assembled to a rim size of 16 × 1 / 2J, adjusted to an air pressure of 230 kPa, and mounted on a domestic passenger car having a displacement of 2000 cc. The test driver measures the lap time for each lap when driving 10 laps on a dry circuit course (approximately 2 km per lap) with each domestic passenger car, and evaluates the grip performance by the following judgment method. The results are shown in Tables 1 and 2.

Grip performance The average time of 3-7 laps when running 10 laps on the circuit course, Table 1 shows the average time of the pneumatic tire of Comparative Example 1, and Table 2 shows the average time of the pneumatic tire of Comparative Example 6 It was set as a reference time and evaluated according to the following criteria. The higher the score, the better the grip performance.
5: The average lap time is 0.5 seconds or more faster than the reference time.
4: The average lap time is 0.2 seconds or more and less than 0.5 seconds faster than the reference time.
3: The difference between the average lap time and the reference time is within a range of less than 0.2 seconds.
2: The average lap time is 0.2 seconds or more and less than 0.5 seconds later than the reference time.
1: The average lap time is 0.5 seconds or more later than the reference time.

The types of raw materials used in Tables 1 and 2 are shown below.
NR: natural rubber, RSS # 1
・ Carbon black: Niteron # 200IN manufactured by Nikka Chemicals
Silica: Nipsil AQ-N (CTAB adsorption specific surface area 157 m ² / g) manufactured by Tosoh Silica
Silane coupling agent: Shin-Etsu Chemical KBE846
Unsaturated terpene resin 1: styrene-modified terpene resin, YS resin TO-125 manufactured by Yasuhara Chemical Co., Ltd. (polymer of dipentene and styrene, number average molecular weight (Mn) = 700, molecular weight distribution (Mw / Mn) = 1.7 )
Unsaturated terpene resin 2: phenol-modified terpene resin, YS Polystar T-130 manufactured by Yasuhara Chemical Co., Ltd. (polymer of dipentene and phenol, number average molecular weight (Mn) = 900, molecular weight distribution (Mw / Mn) = 1.5 )
Unsaturated terpene resin 3: terpene resin, YS resin PX-125 manufactured by Yasuhara Chemical Co., Ltd. (β-pinene polymer, number average molecular weight (Mn) = 1000, molecular weight distribution (Mw / Mn) = 1.9)
Hydrogenated terpene resin: Clearon P-125 manufactured by Yasuhara Chemical Co., Ltd. (resin obtained by hydrogenating a polymer of dipentene, number average molecular weight (Mn) = 650, molecular weight distribution (Mw / Mn) = 1.7)
Epicatechin: (-)-Epicatechin, 99% by weight of catechin manufactured by Nakarai Desk
-Tea extract: Sun Kato No. 1 manufactured by Taiyo Kagaku Co., a mixture obtained by treating a tea extract containing catechin with a surfactant, and a content of tea polyphenol containing 70% by weight of catechin is 10% by weight
Antioxidant 1: SANTOFLEX 6PPD manufactured by Flexis
Antioxidant 2: FLECTOL TMQ manufactured by Flexis
・ Zinc flower: 3 types of zinc oxide manufactured by Shodo Chemical Industry Co., Ltd. ・ Stearic acid: Beads stearic acid manufactured by NOF Corporation ・ Wax: Sunnock manufactured by Ouchi Shinsei Chemical Industry Co., Ltd. Sulfur accelerator: NOCELLER NS-P manufactured by Ouchi Shinsei Chemical Industry Co., Ltd.
・ Sulfur: Hosei Chemical's oil-treated sulfur

  As is clear from Tables 1 and 2, the rubber compositions for tires (Examples 1 to 5) of the present invention have improved anti-aging performance and grip performance to a conventional level or more without deteriorating wear resistance. . Moreover, the low rolling resistance is further improved.

  On the other hand, since the rubber composition of Comparative Examples 1-3, 5, and 6 does not contain a tea extract containing catechin, the grip performance cannot be improved to a level higher than that of the conventional level. Moreover, since the rubber compositions of Comparative Examples 4 and 7 do not contain an unsaturated terpene resin, it is impossible to maintain wear resistance and improve grip performance beyond the conventional level.

Claims (6)

A tea polyphenol containing 5 to 50 parts by weight of an unsaturated terpene resin and 6 to 85% by weight of catechin for 100 parts by weight of a rubber component containing 90% by weight or more of a diene rubber having a glass transition temperature of −25 ° C. or less. While blending 0.1 to 5 parts by weight of tea extract containing 5 to 95% by weight, the blending amount of the unsaturated terpene resin (a [parts by weight]) and the blending amount of tea extract (b [parts by weight] The rubber composition for tires having a weight ratio (a / b) to 1-200.   The tire rubber composition according to claim 1, wherein the unsaturated terpene resin is at least one selected from terpene resins, styrene-modified terpene resins, and phenol-modified terpene resins.   The rubber composition for tires according to claim 1 or 2 whose number average molecular weights of said unsaturated terpene system resin are 500-1500.   The tea extract comprises (+)-catechin, (−)-epicatechin, (+)-gallocatechin, (−)-epigallocatechin, (−)-epicatechin gallate, (+)-gallocatechin gallate and ( The rubber composition for tire according to claim 1, 2 or 3, comprising at least one selected from the group consisting of-)-epigallocatechin gallate.   The rubber composition for tires according to any one of claims 1 to 4, wherein 20 to 130 parts by weight of silica is blended with 100 parts by weight of the rubber component.   The pneumatic tire which used the rubber composition for tires in any one of Claims 1-5 for the tread part.