JP7054631B2 - Rubber composition for tires and pneumatic tires - Google Patents

Description

The present invention relates to a rubber composition for a tire and a pneumatic tire using the same.

Conventionally, for example, in UHP (ultra high performance) tires mounted on high performance cars, a tread is formed in order to impart high grip performance (that is, grip performance such as wet performance and dry performance) on wet and dry road surfaces. A large amount of resin may be added to the rubber composition. However, when the resin is blended, the rubber is hardened over time and the tread surface is cracked, which causes a problem of secular variation.

In Patent Document 1, in a rubber composition for a studless tire, in order to improve wet performance and on-ice performance, 10 parts by mass or more of silica is blended with 100 parts by mass of diene-based rubber, and glycerin monofatty acid ester and heat are added. It has been proposed to formulate inflatable microcapsules. However, it is not described that a polyoxyalkylene alkyl ether fatty acid ester is blended.

On the other hand, Patent Document 2 discloses that a polyoxyalkylene alkyl ether fatty acid ester is blended in a rubber composition using a white filler as a filler, that is, silica. However, in this document, the fatty acid ester is blended in order to impart antistatic performance to the rubber composition containing silica, and by blending the fatty acid ester together with the resin, excellent grip performance is exhibited and aged. It is not stated that the variability can be improved. Further, the polyoxyalkylene alkyl ether fatty acid ester specifically used in Patent Document 2 has a high HLB, and it is not described that a polyoxyalkylene alkyl ether fatty acid ester having an HLB of 10 or less is used.

Japanese Unexamined Patent Publication No. 2016-023213 Japanese Unexamined Patent Publication No. 10-330539

An object of the present invention is to provide a rubber composition for a tire, which has excellent grip performance due to the blending of a resin and can improve secular variation.

The rubber composition for a tire according to the embodiment of the present invention contains a rubber component made of a diene rubber, silica, a resin, and an ether ester compound having an HLB of 10 or less represented by the following general formula (1). ..

In the formula, R ¹ and R ² each independently represent a hydrocarbon group having 1 to 30 carbon atoms, R ³ represents an alkylene group having 2 to 4 carbon atoms, and n represents the average number of moles of the oxyalkylene group. , (R ³ O) 60% by mass or more of _n is composed of an oxyethylene group.

The pneumatic tire according to the embodiment of the present invention is provided with a tread made of the rubber composition.

According to the embodiment of the present invention, by blending the above ether ester compound together with the resin, it is possible to improve the secular variation while having grip performance.

The rubber composition according to the present embodiment is formed by blending silica, a resin, and a specific ether ester compound with a rubber component made of a diene-based rubber.

The diene rubber as a rubber component is not particularly limited, and for example, natural rubber (NR), synthetic isoprene rubber (IR), butadiene rubber (BR), styrene butadiene rubber (SBR), nitrile rubber (NBR), and chloroprene. Various diene rubbers usually used in rubber compositions such as rubber (CR), butyl rubber (IIR), styrene-isoprene copolymer rubber, butadiene-isoprene copolymer rubber, styrene-isoprene-butadiene copolymer rubber, etc. Can be mentioned. These diene-based rubbers can be used alone or in combination of two or more.

The rubber component according to a preferred embodiment contains at least one selected from the group consisting of styrene-butadiene rubber, butadiene rubber, and natural rubber, and more preferably contains at least styrene-butadiene rubber. More preferably, it contains styrene-butadiene rubber and butadiene rubber. For example, 100 parts by mass of the rubber component may include 40 to 100 parts by mass of styrene butadiene rubber, 0 to 60 parts by mass of butadiene rubber, and 0 to 30 parts by mass of natural rubber, and 60 to 90 parts by mass of styrene butadiene rubber and butadiene rubber. It may contain 10 to 30 parts by mass and 0 to 20 parts by mass of natural rubber.

The styrene-butadiene rubber, the butadiene rubber, and the natural rubber are not particularly limited, and various NRs, SBRs, and BRs generally used for tire rubber compositions can be used, and may be unmodified rubbers or modified rubbers. Further, as the SBR, solution polymerization SBR (SSBR) may be used, or emulsion polymerization SBR (ESBR) may be used.

Examples of the modified rubber, that is, modified SBR, modified BR and modified NR, include SBR, BR and NR into which a functional group containing an oxygen atom and / or a nitrogen atom has been introduced. Since such a modified rubber has a higher polarity than the non-modified rubber, it is possible to improve the interaction with silica or an ether ester compound.

Examples of the functional group of the modified rubber include at least one selected from the group consisting of an amino group, an alkoxyl group, a hydroxyl group, an epoxy group, a carboxyl group and a carboxylic acid derivative group. The amino group may be not only a primary amino group but also a secondary or tertiary amino group. In the case of a secondary or tertiary amino group, the total number of carbon atoms of the hydrocarbon group as a substituent is preferably 15 or less. Examples of the alkoxyl group include a methoxy group, an ethoxy group, a propoxy group, a butoxy group and the like represented as -OA (where A is an alkyl group having 1 to 4 carbon atoms, for example), and examples thereof include a trialkoxysilyl group and an alkyl. It may be contained as an alkoxysilyl group such as a dialkoxysilyl group or a dialkylalkoxysilyl group (at least one of the three hydrogens of the silyl group is substituted with an alkoxyl group). Examples of the carboxylic acid derivative group include an ester group derived from a carboxylic acid (carboxylic acid ester group) and an acid anhydride group composed of an anhydride of a dicarboxylic acid such as maleic acid or phthalic acid. Examples of the carboxylic acid ester group include an acrylate group (-O-CO-CH = CH ₂ ) and / or a methacrylate group (-O-CO-C (CH ₃ ) = CH ₂ ) (hereinafter, (meth) acrylate group). ) Is mentioned. In one embodiment, the functional group of the modified rubber may be at least one selected from the group consisting of an amino group, an alkoxyl group and a hydroxyl group. These functional groups may be introduced into at least one end of the diene-based rubber, or may be introduced into the molecular chain. As the modified rubber, modified SBR and / or modified BR is preferably used, and more preferably modified SBR is used.

The silica as the filler is not particularly limited, and for example, wet silica such as wet precipitation silica or wet gel silica may be used. The BET specific surface area of silica (measured according to the BET method described in JIS K6430) is not particularly limited, and may be, for example, 100 to 300 m ² / g or 150 to 250 m ² / g.

The blending amount of silica is not particularly limited, and may be 10 to 120 parts by mass or 40 to 100 parts by mass with respect to 100 parts by mass of the rubber component. In the present embodiment, it is preferable to use silica as the main filler, for example, it is preferable that more than 50% by mass of the filler is silica, and more preferably more than 70% by mass of the filler is silica.

As the filler, silica alone may be used, or carbon black may be blended together with silica. The carbon black is not particularly limited, and various known varieties can be used. For example, when used for tire tread rubber, SAF class (N100 series), ISAF class (N200 series), HAF class (N300 series), FEF class (N500 series) (both ASTM grade) are preferably used. Each of these grades of carbon black can be used alone or in combination of two or more. The blending amount of carbon black is not particularly limited, and may be 20 parts by mass or less, or 5 to 15 parts by mass with respect to 100 parts by mass of the rubber component.

A resin is blended in the rubber composition according to the present embodiment. By blending the resin, the grip performance such as wet performance can be improved.

As the resin, a resin having adhesiveness, that is, an adhesive resin is preferably used, and may be solid or liquid. Examples of the resin include rosin-based resin, petroleum resin, kumaron-based resin, terpene-based resin, and the like, and these may be used alone or in combination of two or more.

Examples of the rosin-based resin include natural resin rosin and various rosin-modified resins using the same (for example, rosin-modified maleic acid resin).

Examples of the petroleum resin include an aliphatic petroleum resin, an aromatic petroleum resin, and an aliphatic / aromatic copolymerized petroleum resin. The aliphatic petroleum resin is a resin obtained by cationically polymerizing an unsaturated monomer such as isoprene or cyclopentadiene, which is an petroleum fraction (C5 fraction) equivalent to 4 to 5 carbon atoms (C5 petroleum resin). Also referred to as), it may be water-soaked. Aromatic petroleum resin is a resin obtained by cationically polymerizing monomers such as vinyltoluene, alkylstyrene, and indene, which are petroleum fractions (C9 fractions) equivalent to 8 to 10 carbon atoms (C9 petroleum). It may also be referred to as a resin) or hydrolyzed. The aliphatic / aromatic copolymerized petroleum resin is a resin obtained by copolymerizing the above-mentioned C5 fraction and C9 fraction (also referred to as C5 / C9 based petroleum resin) and hydrogenated. There may be.

The kumaron-based resin is a resin containing kumaron as a main component, and examples thereof include a kumaron resin, a kumaron-inden resin, and a copolymer resin containing kumaron, inden, and styrene as main components.

Examples of the terpene-based resin include polyterpenes and terpene-phenol resins.

The content of the resin is not particularly limited, and may be, for example, 1 to 30 parts by mass, 5 to 20 parts by mass, or 10 to 20 parts by mass with respect to 100 parts by mass of the rubber component. By setting the resin content to 30 parts by weight or less, deterioration of processability (roll adhesion), that is, overadhesion can be suppressed. The content of the resin is preferably blended in a large amount (for example, more than 5 parts by mass) from the viewpoint of improving the grip performance, and the change with time becomes large when blended in a large amount. The improvement effect is more likely to be exhibited.

The rubber composition according to the present embodiment contains an ether ester compound (preferably a polyoxyalkylene alkyl ether fatty acid ester) having an HLB of 10 or less represented by the following general formula (1). Since such an ether ester compound exhibits a plasticizing effect in the rubber composition, it is considered that the viscosity of the rubber composition at the time of kneading can be reduced and the processability can be improved. Further, by optimizing the ratio of the oxyalkylene group so that the HLB of the ether ester compound is 10 or less, the solidification temperature is lowered and the ether ester compound functions as a plasticizer in the polymer. Moreover, since it does not migrate like oil, the flexibility of the rubber is maintained in a good state. Further, it is considered that the aggregation of silica is alleviated by the oxyalkylene group which is a hydrophilic group, and the wet performance of silica can be exhibited to the same level as or higher than the conventional one. As a result, it is considered that the secular variation can be improved while exhibiting excellent wet performance.

In formula (1), R ¹ and R ² each independently represent a hydrocarbon group having 1 to 30 carbon atoms. The number of carbon atoms of the hydrocarbon group is more preferably 5 to 25, still more preferably 8 to 22, and may be 10 to 20. The hydrocarbon group is preferably a linear or branched saturated or unsaturated aliphatic hydrocarbon group, and is preferably an alkyl group or an alkenyl group, for example. In one embodiment, R ¹ is preferably an alkyl group or an alkenyl group having 1 to 25 carbon atoms, more preferably an alkyl group or an alkenyl group having 8 to 20 carbon atoms. Further, R ² is preferably an alkyl group or an alkenyl group having 8 to 25 carbon atoms, and more preferably an alkyl group or an alkenyl group having 12 to 20 carbon atoms.

In the formula (1), R ³ represents an alkylene group having 2 to 4 carbon atoms, and n represents the average number of moles of oxyalkylene group added. The alkylene group of R ³ may be linear or branched. Examples of the oxyalkylene group represented by ^R3O include an oxyethylene group, an oxypropylene group, and an oxybutylene group. ( ^R3O ) _n in the formula (1) is a polyoxyalkylene chain obtained by addition polymerization of an alkylene oxide having 2 to 4 carbon atoms (for example, ethylene oxide, propylene oxide, butylene oxide, etc.). The polymerization form of the alkylene oxide or the like is not particularly limited, and may be a homopolymer, a random copolymer, or a block copolymer.

It is preferable that (R ³ O) _n in the formula (1) is mainly composed of an oxyethylene group, and it is preferable that 60% by mass or more of (R ³ O) _n is composed of an oxyethylene group. That is, the polyoxyalkylene chain represented by ( ^R3O ) _n preferably contains 60% by mass or more of an oxyethylene group, more preferably 80% by mass or more, and particularly preferably 100% by mass, that is, the following. As represented by the general formula (2), it consists only of an oxyethylene group.

R ¹ , R ² and n in the formula (2) are the same as R ¹ , R ² and n in the formula (1).

N representing the average number of moles of the oxyalkylene group added is a number set so that the HLB of the ether ester compound is 10 or less, and varies depending on the types of R ¹ and R ² , but may be, for example, 1 to 20. It may be 2 to 15, or 3 to 10.

The HLB (hydrophilic lipophilic balance) of the ether ester compound is 10 or less, more preferably 3 to 10, and even more preferably 4 to 8 in order to lower the solidification temperature as described above. Here, HLB is a value calculated by the following Griffin's formula, and the larger the value, the larger the proportion of the hydrophilic portion in the whole molecule, and the higher the hydrophilicity.
HLB = 20 × (molecular weight of hydrophilic part) / (molecular weight of the whole)
The molecular weight of the hydrophilic portion in the formula is the molecular weight of the polyoxyalkylene chain represented by ( ^R3O ) _n .

The blending amount of the ether ester compound of the formula (1) is not particularly limited, but is preferably 1 to 20 parts by mass, and more preferably 2 to 15 parts by mass with respect to 100 parts by mass of the rubber component. It may be 3 to 10 parts by mass.

In addition to the above components, the rubber composition according to the present embodiment includes rubber compositions such as a silane coupling agent, oil, zinc oxide, stearic acid, an antioxidant, a wax, a vulcanizing agent, and a vulcanization accelerator. Various commonly used additives can be blended.

Examples of the silane coupling agent include sulfide silane and mercaptosilane. The blending amount of the silane coupling agent is not particularly limited, but is preferably 2 to 20% by mass with respect to the blending amount of silica.

Sulfur is preferably used as the vulcanizing agent. The blending amount of the vulcanizing agent is not particularly limited, but is preferably 0.1 to 10 parts by mass, and more preferably 0.5 to 5 parts by mass with respect to 100 parts by mass of the rubber component. Examples of the vulcanization accelerator include various vulcanization accelerators such as sulfenamide-based, thiuram-based, thiazole-based, and guanidine-based, and any one of them may be used alone or in combination of two or more. Can be done. The blending amount of the vulcanization accelerator is not particularly limited, but is preferably 0.1 to 7 parts by mass, and more preferably 0.5 to 5 parts by mass with respect to 100 parts by mass of the rubber component. ..

The rubber composition according to the present embodiment can be produced by kneading according to a conventional method using a commonly used mixer such as a Banbury mixer, a kneader, or a roll. That is, for example, in the first mixing step (non-professional kneading step), an additive other than the vulcanizing agent and the vulcanization accelerator is added and mixed with the rubber component together with the silica, the resin and the ether ester compound, and then obtained. An unvulcanized rubber composition can be prepared by adding and mixing a vulcanizing agent and a vulcanization accelerator to the mixed mixture in the final mixing step (professional kneading step).

The rubber composition according to the present embodiment can be used for tires for various purposes such as for passenger cars, heavy loads of trucks and buses, and is preferably used for treads of pneumatic tires, that is, rubber compositions for tire treads. be. More preferably, since it has excellent grip performance, it is used as a rubber composition for forming a tread of a UHP (ultra high performance) tire, and it is possible to improve secular variation while maintaining grip performance. That is, it is possible to suppress the occurrence of cracks on the tread surface due to rubber hardening over time.

For the pneumatic tire according to one embodiment, after producing a tread rubber of the tire by a rubber extruder or the like using the above rubber composition and combining it with other tire members to produce an unvulcanized tire (green tire). It can be manufactured, for example, by vulcanizing and molding at 140 to 180 ° C. The tread rubber of a pneumatic tire includes a tread rubber having a two-layer structure of a cap rubber and a base rubber and a single-layer structure in which both are integrated, and is preferably used for the rubber constituting the ground contact surface. That is, in the case of a single-layer structure, the tread rubber is preferably made of the above rubber composition, and in the case of a two-layer structure, the cap rubber is preferably made of the above rubber composition.

Hereinafter, examples will be shown, but the present invention is not limited to these examples.

[Synthesis of ether ester compounds]
Compounds 1 to 5 used in Examples and Comparative Examples were synthesized by the following methods.

[Compound 1]
To 47 g (0.25 mol) of lauryl alcohol (manufactured by Tokyo Chemical Industry Co., Ltd.), 0.1 g of potassium hydroxide catalyst was added, and while stirring at 110 to 120 ° C., ethylene oxide (manufactured by Tokyo Chemical Industry Co., Ltd.) 33 g. (0.75 mol) was press-fitted and an addition reaction was carried out. The reaction was transferred to a flask and the catalyst potassium hydroxide was neutralized with phosphoric acid. Phosphate was filtered off from the neutralized product to obtain 72 g (yield 90% by mass) of 3 mol adduct of lauryl alcohol ethylene oxide. Weigh 60 g (0.19 mol) of the obtained lauryl alcohol ethylene oxide 3 mol adduct, 56 g (0.2 mol) of oleic acid (manufactured by Tokyo Chemical Industry Co., Ltd.), and 0.7 g of dibutyltin oxide as a catalyst. The dehydration esterification reaction was carried out at 225 ° C. with stirring under the blowing of nitrogen to obtain Compound 1. Compound 1 is an ether ester compound having R ¹ = C ₁₂ H ₂₅ , R ² = C ₁₇ H ₃₃ , n = 3 in the formula (2) and HLB = 5.

[Compound 2]
To 47 g (0.25 mol) of lauryl alcohol (manufactured by Tokyo Chemical Industry Co., Ltd.), 0.1 g of potassium hydroxide catalyst was added, and while stirring at 110 to 120 ° C., ethylene oxide (manufactured by Tokyo Chemical Industry Co., Ltd.) 33 g. (1.5 mol) was press-fitted and an addition reaction was carried out. The reaction was transferred to a flask and the catalyst potassium hydroxide was neutralized with phosphoric acid. Phosphate was filtered off from the neutralized product to obtain 150 g (yield 84% by mass) of 6 mol adduct of lauryl alcohol ethylene oxide. Weighed 135 g (0.19 mol) of the obtained 6 mol adduct of lauryl alcohol ethylene oxide, 56 g (0.2 mol) of oleic acid (manufactured by Tokyo Kasei Kogyo Co., Ltd.), and 0.7 g of dibutyltin oxide as a catalyst. The dehydration esterification reaction was carried out at 225 ° C. with stirring under the blowing of nitrogen to obtain compound 2. Compound 2 is an ether ester compound having R ¹ = C ₁₂ H ₂₅ , R ² = C ₁₇ H ₃₃ , n = 6 in the formula (2) and HLB = 7.

[Compound 3]
To 47 g (0.25 mol) of lauryl alcohol (manufactured by Tokyo Chemical Industry Co., Ltd.), 0.1 g of potassium hydroxide catalyst was added, and while stirring at 110 to 120 ° C., ethylene oxide (manufactured by Tokyo Chemical Industry Co., Ltd.) 330 g. (7.5 mol) was press-fitted and an addition reaction was carried out. The reaction was transferred to a flask and the catalyst potassium hydroxide was neutralized with phosphoric acid. Phosphate was filtered off from the neutralized product to obtain 336 g (yield 76% by mass) of 30 mol adduct of lauryl alcohol ethylene oxide. Weigh 200 g (0.11 mol) of the obtained lauryl alcohol ethylene oxide 30 mol adduct, 34 g (0.12 mol) of oleic acid (manufactured by Tokyo Chemical Industry Co., Ltd.), and 0.7 g of dibutyltin oxide as a catalyst. The dehydration esterification reaction was carried out at 225 ° C. with stirring under the blowing of nitrogen to obtain compound 3. Compound 3 is an ether ester compound having R ¹ = C ₁₂ H ₂₅ , R ² = C ₁₇ H ₃₃ , n = 30 in the formula (2) and HLB = 15.

[Compound 4]
To 30 g (0.15 mol) of tridecyl alcohol (manufactured by Tokyo Chemical Industry Co., Ltd.), 0.1 g of potassium hydroxide catalyst is added, and ethylene oxide (manufactured by Tokyo Chemical Industry Co., Ltd.) is stirred while stirring at 110 to 120 ° C. 46 g (1.05 mol) was press-fitted and an addition reaction was carried out. The reaction was transferred to a flask and the catalyst potassium hydroxide was neutralized with phosphoric acid. The phosphate was filtered off from the neutralized product to obtain 64 g (yield 85% by mass) of a 7 mol adduct of tridecyl alcohol ethylene oxide. Weigh 60 g (0.12 mol) of the obtained tridecyl alcohol ethylene oxide 7 mol adduct, 37 g (0.13 mol) of stearic acid (manufactured by Tokyo Chemical Industry Co., Ltd.), and 0.7 g of dibutyltin oxide as a catalyst. Then, a dehydration esterification reaction was carried out at 225 ° C. with stirring under the blowing of nitrogen to obtain compound 4. Compound 4 is an ether ester compound having R ¹ = C ₁₃ H ₂₇ , R ² = C ₁₇ H ₃₅ , n = 7 in the formula (2) and HLB = 8.

[Compound 5]
Add 0.1 g of potassium hydroxide catalyst to 54 g (0.2 mol) of oleyl alcohol (manufactured by Tokyo Chemical Industry Co., Ltd.), and 26 g of ethylene oxide (manufactured by Tokyo Chemical Industry Co., Ltd.) while stirring at 110 to 120 ° C. (0.6 mol) was press-fitted and an addition reaction was carried out. The reaction was transferred to a flask and the catalyst potassium hydroxide was neutralized with phosphoric acid. Phosphate was filtered off from the neutralized product to obtain 69 g (yield 90% by mass) of 3 mol adduct of oleyl alcohol ethylene oxide. Weighed 58 g (0.15 mol) of the obtained oleyl alcohol ethylene oxide 3 mol adduct, 47 g (0.165 mol) of stearic acid (manufactured by Tokyo Chemical Industry Co., Ltd.), and 0.7 g of dibutyltin oxide as a catalyst. The dehydration esterification reaction was carried out at 225 ° C. with stirring under the blowing of nitrogen to obtain compound 5. Compound 5 is an ether ester compound having R ¹ = C ₁₈ H ₃₅ , R ² = C ₁₇ H ₃₅ , n = 3 in the formula (2) and HLB = 4.

[Manufacturing and evaluation of rubber composition and tire]
Using a Banbury mixer, first, in the first mixing step, add a compounding agent excluding sulfur and a vulcanization accelerator to the rubber component and knead according to the compounding (parts by mass) shown in Table 1 below (discharge temperature = 160). (° C.), then sulfur and a vulcanization accelerator were added to the obtained kneaded product at the final mixing step and kneaded (discharge temperature = 90 ° C.) to prepare a rubber composition. The details of each component in Table 1 are as follows.

SBR1: "SBR0122" manufactured by JSR Corporation (emulsion polymerization SBR)
-SBR2: "SBR1502" manufactured by JSR Corporation (emulsion polymerization SBR)
SBR3: "HPR340" manufactured by JSR Corporation (alkoxyl group and amino group end-modified solution polymerization SBR)
・ NR: RSS # 3
・ BR: "BR150B" manufactured by Ube Corporation
-Carbon black: "Seast KH" (N339) manufactured by Tokai Carbon Co., Ltd.
・ Silica: "Nip Seal AQ" manufactured by Tosoh Silica Co., Ltd.
・ Oil: "Process NC140" manufactured by JX Nippon Oil Energy Co., Ltd.
-Silane coupling agent: "Si69" manufactured by Evonik Degussa
-Stearic acid: "Lunac S-20" manufactured by Kao Corporation
・ Zinc Oxide: "Zinc Oxide No. 1" manufactured by Mitsui Mining & Smelting Co., Ltd.
・ Wax: "OZOACE0355" manufactured by Nippon Seiro Co., Ltd.
・ Anti-aging agent: "Nocrack 6C" manufactured by Ouchi Shinko Chemical Industry Co., Ltd.
-Resin 1: Rosin-modified maleic acid resin, Harima Chemicals Co., Ltd. "Harimac R100" (solid)
-Resin 2: C5 / C9 petroleum resin, Tosoh "Petro Tac 90" (solid)
-Resin 3: Aliphatic petroleum resin, "Quinton M100" manufactured by Nippon Zeon Corporation (solid)
・ Vulcanization accelerator: "Noxeller D" manufactured by Ouchi Shinko Chemical Industry Co., Ltd.
・ Sulfur: "Powdered sulfur" manufactured by Tsurumi Chemical Industry Co., Ltd.

The processability of each of the obtained rubber compositions was evaluated, and each rubber composition was used as a tread rubber and vulcanized and molded (160 ° C. x 30 minutes) according to a conventional method to create a pneumatic radial tire (tire size:: 195 / 65R15) was produced. The wet performance and secular variation of the obtained test tires were evaluated. Each measurement / evaluation method is as follows.

-Workability: Using a rotary Mooney measuring machine manufactured by Toyo Seiki Co., Ltd. in accordance with JIS K6300, preheat the unvulcanized rubber at 100 ° C for 1 minute, and then measure the torque value after 4 minutes in Mooney units. The reciprocal of the measured value was displayed as an exponent with the value of Comparative Example 1 as 100. The larger the index, the lower the Mooney viscosity and the better the workability.

-Wet performance: Wet grip performance was evaluated by mounting four test tires on a passenger car, running on a road surface sprinkled with water at a water depth of 2 to 3 mm, and measuring the friction coefficient at 100 km / h. It is displayed as an index with the value of the coefficient of friction of Comparative Example 1 as 100. The larger the index, the higher the coefficient of friction, indicating that the wet grip property is excellent.

-Aging property: The test tire is subjected to air heating aging treatment under the conditions of 80 ° C. and 168 hours, the hardness before and after the aging treatment is measured, and the rate of increase in rubber hardness with heat aging (that is, aging) is measured by the following formula. Hardness increase rate) (%) was calculated. The reciprocal of the obtained aging hardness increase rate was expressed as an index with the value of Comparative Example 1 as 100. The larger the index, the more the hardening of the rubber composition with heat aging was suppressed, that is, the secular variation was improved.
Aging hardness increase rate (%) = (rubber hardness after aging treatment / rubber hardness before aging treatment) x 100

The results are shown in Table 1. In Comparative Example 2 in which the resin was blended, the wet performance was improved, but the secular variation and processability were inferior to those in Comparative Example 1, which was the control. In Comparative Example 3, although the ether ester compound was added to Comparative Example 2, since the compound 3 having a high HLB was used, the effect of improving secular variation and processability was insufficient, and compared to Comparative Example 1 which was a control. Was also inferior. In Comparative Example 4, the ether ester compound was added to Comparative Example 1, and no resin was blended, so that the wet performance was inferior.

On the other hand, in Examples 1 to 10 in which the ether ester compounds (compounds 1, 2, 4, 5) having an HLB of 10 or less were blended together with the resin, the wet performance was superior to that of Comparative Example 1. However, the processability and secular variation were equal to or better than that. That is, there was no deterioration in secular variation and workability as in Comparative Example 2, and these performances were improved.

Although some embodiments of the present invention have been described above, these embodiments are presented as examples and are not intended to limit the scope of the invention. These embodiments can be implemented in various other embodiments, and various omissions, replacements, and changes can be made without departing from the gist of the invention. These embodiments, omissions, replacements, changes, etc. thereof are included in the scope and gist of the invention, as well as in the scope of the invention described in the claims and the equivalent scope thereof.

Claims (5)

A rubber composition for a tire containing a rubber component made of a diene rubber, silica, an adhesive resin, and an ether ester compound having an HLB of 10 or less represented by the following general formula (1).

In the formula, R ¹ and R ² each independently represent a hydrocarbon group having 1 to 30 carbon atoms, R ³ represents an alkylene group having 2 to 4 carbon atoms, and n represents the average number of moles of the oxyalkylene group. , (R ³ O) 60% by mass or more of _n is composed of an oxyethylene group. The rubber composition for a tire according to claim 1, wherein the rubber component comprises styrene-butadiene rubber and butadiene rubber. The rubber composition for a tire according to claim 1 or 2, wherein the adhesive resin is at least one selected from the group consisting of a rosin-based resin, a petroleum resin, a kumaron-based resin, and a terpene-based resin. Claims 1 to 3 which contain 10 to 120 parts by mass of the silica, 1 to 30 parts by mass of the adhesive resin, and 1 to 20 parts by mass of the ether ester compound with respect to 100 parts by mass of the rubber component. The rubber composition for a tire according to any one of the following items. A pneumatic tire provided with a tread made of the rubber composition according to any one of claims 1 to 4.