JP7045207B2 - 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.

It is known that silica is used as a filler in a rubber composition for a tire in order to improve low rolling resistance that contributes to low fuel consumption. However, silica tends to aggregate due to the silanol groups present on the surface of the particles, and therefore it is difficult to sufficiently bring out the effect of improving the low rolling resistance. Further, in the rubber composition for tires, it is also required to improve the wear resistance and the steering stability. However, there is room for improvement in the conventional rubber composition in that it improves wear resistance and steering stability without deteriorating low rolling resistance.

Patent Documents 1 and 2 propose to add a glycerin monofatty acid ester in order to improve the dispersibility of silica. Patent Document 3 contains a nonionic surfactant composed of a polyethylene glycol monofatty acid ester and / or a polyethylene glycol difatty acid ester in order to improve the appearance of a tire while maintaining or improving fuel efficiency and wear resistance. It is proposed to do. Patent Document 4 proposes using polyoxyethylene hydrogenated castor oil and polyoxyethylene glycerin trifatty acid ester in combination as a dispersant for silica. However, it is not known that the use of an ester of a polyoxyalkylene alkyl ether and a dicarboxylic acid can improve wear resistance and steering stability without deteriorating low rolling resistance.

Japanese Unexamined Patent Publication No. 2016-113602 Japanese Unexamined Patent Publication No. 2016-1131515 JP-A-2015-000972 Japanese Unexamined Patent Publication No. 2014-210829

An object of the present invention is to provide a rubber composition for a tire, which is a rubber composition containing silica and can improve wear resistance and steering stability without deteriorating low rolling resistance. do.

The rubber composition for a tire according to the embodiment of the present invention includes a rubber component containing styrene-butadiene rubber having a glass transition temperature of −70 to −20 ° C., silica, and an ether ester represented by the following general formula (1). Is included.

In the formula, R ¹ and R ² each independently represent a hydrocarbon group having 8 to 30 carbon atoms, R ³ represents a hydrocarbon group having 1 to 30 carbon atoms, and R ⁴ and R ⁵ independently represent carbon atoms. Representing 2 to 4 alkylene groups, a and b each independently represent the average number of moles of oxyalkylene group added, and 60% by mass or more of (R ⁴ O) _a and (R ⁵ O) _b are from oxyethylene groups. Become.

The pneumatic tire according to the embodiment of the present invention is manufactured by using the rubber composition.

According to the embodiment of the present invention, by using a specific styrene-butadiene rubber as a rubber component and blending the above ether ester, the silica-blended rubber composition has wear resistance without deteriorating low rolling resistance. And steering stability can be improved.

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

The rubber component contains styrene butadiene rubber (SBR) having a glass transition temperature (Tg) of −70 to −20 ° C. By using styrene-butadiene rubber having such a glass transition temperature together with an ether ester, wear resistance can be improved while suppressing deterioration of low rolling resistance. The glass transition temperature of the styrene-butadiene rubber is more preferably −50 to −25 ° C. Here, the glass transition temperature is a value measured at a heating rate of 20 ° C./min (measurement temperature range: −150 ° C. to 50 ° C.) by a differential scanning calorimetry (DSC) method in accordance with JIS K7121. Is.

The SBR having a Tg of −70 to −20 ° C. may be solution-polymerized SBR (SSBR), emulsion-polymerized SBR (ESBR), modified SBR, or unmodified SBR.

Examples of the modified SBR include SBRs into which a functional group containing an oxygen atom and / or a nitrogen atom has been introduced, and since the polarity is higher than that of the unmodified SBR, the interaction with silica or ether ester can be improved. ..

Examples of the functional group of the modified SBR 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 SBR 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 at at least one end of the polymer molecular chain, or may be introduced into the molecular chain.

As the rubber component, the above-mentioned Tg may be composed only of SBR having a Tg of −70 to −20 ° C., for example, natural rubber (NR), isoprene rubber (IR), butadiene rubber (BR), styrene-isoprene rubber. , Butadiene-isoprene rubber, and other diene rubbers such as styrene-butadiene-isoprene rubber may be used in combination with one or more.

The rubber component according to a preferred embodiment is SBR having a Tg of −70 to −20 ° C. alone, or a combination of SBR having a Tg of −70 to −20 ° C. and NR and / or IR. For example, 100 parts by mass of the rubber component may be composed of 50 to 100 parts by mass of SBR having a Tg of −70 to −20 ° C. and 0 to 50 parts by mass of NR and / or IR, and Tg may be −50 to 50 parts by mass. The SBR at 70 to −20 ° C. may be composed of 60 to 100 parts by mass, and the NR and / or IR may be composed of 0 to 40 parts by mass. Further, the SBR having a Tg of −70 to −20 ° C. may be composed of 50% by mass or more of the modified SBR.

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 20 to 120 parts by mass, 40 to 120 parts by mass, or 50 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, that is, more than 50% by mass of the filler is preferably 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 1 to 70 parts by mass, 1 to 50 parts by mass, or 5 to 40 parts by mass with respect to 100 parts by mass of the rubber component.

The rubber composition according to the present embodiment contains an ether ester represented by the following general formula (1). The ether ester is a dicarboxylic acid diester having a polyoxyalkylene, and it is considered that the aggregation of silica is suppressed by adsorbing the polyoxyalkylene portion on the silica surface. In addition, it is considered that the hydrocarbon groups at both ends improve the affinity for the rubber component. By the ether ester acting on both the rubber component and silica in this way, in combination with the use of the above-mentioned specific SBR as the rubber component, wear resistance and maneuverability are not deteriorated without deteriorating low rolling resistance. It is thought that stability can be improved.

In formula (1), R ¹ and R ² each independently represent a monovalent hydrocarbon group having 8 to 30 carbon atoms. The hydrocarbon group has more preferably 10 to 24 carbon atoms, still more preferably 12 to 20 carbon atoms. The hydrocarbon group is preferably a linear or branched saturated or unsaturated aliphatic hydrocarbon group, for example, an alkyl group or an alkenyl group is preferable.

In formula (1), R ³ represents a divalent hydrocarbon group having 1 to 30 carbon atoms. The hydrocarbon group has more preferably 1 to 20 carbon atoms, still more preferably 2 to 10 carbon atoms, and may be 2 to 8 carbon atoms. The divalent hydrocarbon group may be a linear or branched saturated or unsaturated aliphatic hydrocarbon group, or may be an aromatic hydrocarbon group. For example, a linear or branched alkanediyl group, a linear or branched alkenyl group, or a phenylene group which may have a substituent (for example, an alkyl group and / or an alkenyl group) can be mentioned. R ³ is a portion of the dicarboxylic acid excluding the carboxyl group, and examples of the dicarboxylic acid include saturated aliphatic dicarboxylic acids such as malonic acid, succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, and sebacic acid. Unsaturated aliphatic dicarboxylic acids such as acids, maleic acid, fumaric acid, citraconic acid, mesaconic acid, itaconic acid, allylmalonic acid and 2,4-hexadienodic acid, aromatic dicarboxylic acids such as phthalic acid, isophthalic acid and terephthalic acid. And so on.

In the formula (1), R ⁴ and R ⁵ each independently represent an alkylene group having 2 to 4 carbon atoms, and a and b each independently represent the average number of moles of oxyalkylene groups added. R ⁴ and R ⁵ more preferably independently represent an alkylene group having 2 or 3 carbon atoms, respectively. The alkylene groups of R ⁴ and R ⁵ may be linear or branched. ^Examples of the oxyalkylene group represented by ^R4O and R5O include an oxyethylene group, an oxypropylene group and an oxybutylene group, respectively. (R ⁴ O) _a and (R ⁵ O) _b in the formula (1) are obtained by addition polymerization of an alkylene oxide having 2 to 4 carbon atoms (for example, ethylene oxide, propylene oxide, butylene oxide, etc.), respectively. It is a polyoxyalkylene chain. 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 ⁴ O) _a and (R ⁵ O) _b in the formula (1) mainly consist of an oxyethylene group, and 60% by mass or more of (R ⁴ O) _a and (R ⁵ O) _b is contained. It preferably consists of an oxyethylene group. That is, the polyoxyalkylene chain represented by (R ⁴ O) _a and the polyoxyalkylene chain represented by (R ⁵ O) _b preferably contain 60% by mass or more of oxyethylene groups as a whole. It is more preferably contained in an amount of 80% by mass or more, and particularly preferably 100% by mass, that is, it is composed of only an oxyethylene group as represented by the following general formula (2). In one embodiment, it is preferable that each of (R ⁴ O) _a and (R ⁵ O) _b consists of 60% by mass or more of oxyethylene groups.

R ¹ , R ² , R ³ , a and b in the formula (2) are the same as R ¹ , R ² , R ³ , a and b in the formula (1).

It is preferable that a and b representing the average number of added moles of the oxyalkylene group are 1 or more, respectively, and the total of a and b, that is, a + b may be 1 to 30, 2 to 25, or 3 to 20. good.

The HLB (hydrophilic lipophilic oil balance) of the ether ester is not particularly limited, and may be, for example, 3 to 15, 4 to 14, or 5 to 12. 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 total)
The molecular weight of the hydrophilic portion in the formula is the molecular weight of the polyoxyalkylene chain represented by (R ⁴ O) _a and (R ⁵ O) _b .

The blending amount of the ether ester is not particularly limited, but is preferably 1 to 10 parts by mass, and more preferably 2 to 8 parts by mass with respect to 100 parts by mass of the rubber component.

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 silica and an ether ester, and then the obtained mixture is mixed. In the final mixing step (professional kneading step), a vulcanizing agent and a vulcanization accelerator can be added and mixed to prepare an unvulcanized rubber composition.

The rubber composition according to this embodiment can be used as a rubber composition for tires. Examples of the tire include tires for passenger cars, tires for heavy loads of trucks and buses, and various sizes of pneumatic tires. Since the rubber composition is excellent in steering stability on a dry road surface, it is suitably used as a rubber composition for summer tires.

The pneumatic tire according to the embodiment is provided with a rubber portion made of the above rubber composition. Examples of the application site of the tire include tread rubber, sidewall rubber and the like, and are preferably used for tread rubber. 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.

The method for manufacturing the pneumatic tire is not particularly limited. For example, the rubber composition is molded into a predetermined shape by extrusion processing according to a conventional method, and combined with other parts to produce an unvulcanized tire (green tire). For example, a tread rubber is produced using the above rubber composition, and an unvulcanized tire is produced by combining with other tire members. Then, for example, by vulcanizing and molding at 140 to 180 ° C., a pneumatic tire can be manufactured.

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

[Synthesis of ether ester]
The ether esters A to H used in Examples and Comparative Examples were synthesized by the following methods.

[Ether ester A]
To 67 g (0.25 mol) of oleyl 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.) 55 g (1. 25 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 92 g (yield 75% by mass) of 5 mol adduct of oleyl alcohol ethylene oxide. Instead of oleyl alcohol, 61 g (0.25 mol) of cetyl alcohol (manufactured by Tokyo Chemical Industry Co., Ltd.) was used, and 87 g (yield 75% by mass) of an adduct of 5 mol of cetyl alcohol ethylene oxide was obtained in the same manner for the others. .. Dichloride dichloride of maleate was dissolved in a dichloromethane solvent at 0 ° C., and 1 molar equivalent of each of the two compounds obtained by the above addition polymerization was added under a triethylamine catalyst. Then, the mixture was stirred at room temperature for 5 hours to obtain ether ester A. The ether ester A has R ¹ , R ² : oleyl group (C ₁₈ H ₃₅ ) and cetyl group (C ₁₆ H ₃₃ ), R ³ : C ₂ H ₂ , a + b = 10 in the formula (2), and is HLB. = 8.5.

[Ether ester B]
Add 0.1 g of potassium hydroxide catalyst to 50 g (0.25 mol) of tridecyl alcohol (manufactured by Tokyo Chemical Industry Co., Ltd.) and stir at 110 to 120 ° C., and 28 g (0) of ethylene oxide (manufactured by Tokyo Chemical Industry Co., Ltd.). .625 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 70 g (yield 90% by mass) of a 2.5 mol adduct of tridecyl alcohol ethylene oxide. Dichloride dichloride of maleate was dissolved in a dichloromethane solvent at 0 ° C., and 2 molar equivalents of the compound obtained by the above addition polymerization was added under a triethylamine catalyst. Then, the mixture was stirred at room temperature for 5 hours to obtain ether ester B. In the formula (2), the ether ester B has R ¹ , R ² : tridecylic group (C ₁₃ H ₂₇ ), R ³ : C ₂ H ₂ , a + b = 5, and HLB = 6.

[Ether ester C]
Add 0.1 g of potassium hydroxide catalyst to 50 g (0.25 mol) of tridecyl alcohol (manufactured by Tokyo Chemical Industry Co., Ltd.) and stir at 110 to 120 ° C. 50 g (1) of ethylene oxide (manufactured by Tokyo Chemical Industry Co., Ltd.). .125 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 86 g (yield 87% by mass) of a 4.5 mol adduct of tridecyl alcohol ethylene oxide. Dichloride dichloride of maleate was dissolved in a dichloromethane solvent at 0 ° C., and 2 molar equivalents of the compound obtained by the above addition polymerization was added under a triethylamine catalyst. Then, the mixture was stirred at room temperature for 5 hours to obtain ether ester C. In the formula (2), the ether ester C has R ¹ , R ² : tridecylic group (C ₁₃ H ₂₇ ), R ³ : C ₂ H ₂ , a + b = 9, and HLB = 9.

[Ether ester D]
To 50 g (0.25 mol) of tridecyl 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.) 72 g (1). .625 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 101 g (yield 83% by mass) of a 6.5 mol adduct of tridecyl alcohol ethylene oxide. Dichloride dichloride of maleate was dissolved in a dichloromethane solvent at 0 ° C., and 2 molar equivalents of the compound obtained by the above addition polymerization was added under a triethylamine catalyst. Then, the mixture was stirred at room temperature for 5 hours to obtain ether ester D. In the formula (2), the ether ester D has R ¹ , R ² : tridecylic group (C ₁₃ H ₂₇ ), R ³ : C ₂ H ₂ , a + b = 13, and HLB = 11.

[Ether Ester E]
Add 0.1 g of potassium hydroxide catalyst to 47 g (0.25 mol) of lauryl alcohol (manufactured by Tokyo Chemical Industry Co., Ltd.) and stir at 110 to 120 ° C. 50 g of ethylene oxide (manufactured by Tokyo Chemical Industry Co., Ltd.) (1. 125 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 108 g (yield 92% by mass) of 4.5 mol adduct of lauryl alcohol ethylene oxide. Dichloride dichloride of maleate was dissolved in a dichloromethane solvent at 0 ° C., and 2 molar equivalents of the compound obtained by the above addition polymerization was added under a triethylamine catalyst. Then, the mixture was stirred at room temperature for 5 hours to obtain ether ester E. In the formula (2), the ether ester E has R ¹ , R ² : lauryl group (C ₁₂ H ₂₅ ), R ³ : C ₂ H ₂ , a + b = 9, and HLB = 9.5.

[Ether Ester F]
Add 0.1 g of potassium hydroxide catalyst to 67 g (0.25 mol) of oleyl alcohol (manufactured by Tokyo Chemical Industry Co., Ltd.) and stir at 110 to 120 ° C. 50 g of ethylene oxide (manufactured by Tokyo Chemical Industry Co., Ltd.) (1. 125 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 93 g (yield 80% by mass) of 4.5 mol adduct of oleyl alcohol ethylene oxide. 61 g (0.25 mol) of cetyl alcohol (manufactured by Tokyo Chemical Industry Co., Ltd.) was used instead of oleyl alcohol, and 88 g (yield 80% by mass) of an adduct of 4.5 mol of cetyl alcohol ethylene oxide was used in the same manner for the others. Obtained. Adipoyl dichloride was dissolved in a dichloromethane solvent at 0 ° C., and 1 molar equivalent of each of the two compounds obtained by the above addition polymerization was added under a triethylamine catalyst. Then, the mixture was stirred at room temperature for 5 hours to obtain ether ester F. The ether ester F has R ¹ , R ² : oleyl group (C ₁₈ H ₃₅ ) and cetyl group (C ₁₆ H ₃₃ ), R ³ : C ₄ H ₈ , a + b = 9 in the formula (2), and is HLB. = 8.

[Ether Ester G]
Add 0.1 g of potassium hydroxide catalyst to 50 g (0.25 mol) of tridecyl alcohol (manufactured by Tokyo Chemical Industry Co., Ltd.) and stir at 110 to 120 ° C. 55 g (1) of ethylene oxide (manufactured by Tokyo Chemical Industry Co., Ltd.). .25 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 85 g (yield 81% by mass) of 5 mol adduct of tridecyl alcohol ethylene oxide. Adipoyl dichloride was dissolved in a dichloromethane solvent at 0 ° C., and 2 mol equivalents of the compound obtained by the above addition polymerization were added under a triethylamine catalyst. Then, the mixture was stirred at room temperature for 5 hours to obtain ether ester G. In the formula (2), the ether ester G has R ¹ , R ² : tridecylic group (C ₁₃ H ₂₇ ), R ³ : C ₄ H ₈ , a + b = 10, and HLB = 9.5.

[Ether Ester H]
To 67 g (0.25 mol) of oleyl alcohol (manufactured by Tokyo Chemical Industry Co., Ltd.), 0.1 g of potassium hydroxide catalyst is added, and while stirring at 110 to 120 ° C., ethylene oxide (manufactured by Tokyo Chemical Industry Co., Ltd.) 55 g (1. 25 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 92 g (yield 75% by mass) of 5 mol adduct of oleyl alcohol ethylene oxide. 61 g (0.25 mol) of cetyl alcohol (manufactured by Tokyo Chemical Industry Co., Ltd.) was used instead of oleyl alcohol, and 87 g (yield 75% by mass) of an adduct of 5 mol of cetyl alcohol ethylene oxide was obtained in the same manner for the others. .. Itaconic acid dichloride was dissolved in a dichloromethane solvent at 0 ° C., and 1 molar equivalent of each of the two compounds obtained by the above addition polymerization was added under a triethylamine catalyst. Then, the mixture was stirred at room temperature for 5 hours to obtain ether ester H. In the formula (2), the ether ester H has R ¹ , R ² : oleyl group (C ₁₈ H ₃₅ ) and cetyl group (C ₁₆ H ₃₃ ), R ³ : C ₃ H ₄ , a + b = 10, and is HLB. = 8.3.

[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 in 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 (Tg = -40 ° C. unmodified ESBR. Oil-extended rubber containing 34 parts by mass of oil with respect to 100 parts by mass of rubber polymer. Rubber polymer content in parentheses in the table. Show.)
SBR2: "HPR350" manufactured by JSR Corporation (Tg = -33 ° C. alkoxyl group and amino group terminal-modified SSBR)
-SBR3: "SE-6592" manufactured by Sumitomo Chemical Co., Ltd. (unmodified SSBR at Tg = -4 ° C)
・ NR: RSS # 3
-Silica: "Nip Seal AQ" manufactured by Tosoh Silica Co., Ltd. (BET: 205m ² / g)
・ Carbon black: "Seast 3" manufactured by Tokai Carbon Co., Ltd.
・ Oil: "JOMO Process NC140" manufactured by JX Nippon Oil Energy Co., Ltd.
・ Zinc Oxide: “Zinc Oxide No. 3” manufactured by Mitsui Mining & Smelting Co., Ltd.
-Stearic acid: "Lunac S-20" manufactured by Kao Corporation
・ Anti-aging agent: "Nocrack 6C" manufactured by Ouchi Shinko Chemical Industry Co., Ltd.
・ Wax: "OZOACE0355" manufactured by Nippon Seiro Co., Ltd.
-Silane coupling agent: "Si69" manufactured by Evonik Degussa
・ Sulfur: "Powdered sulfur" manufactured by Tsurumi Chemical Industry Co., Ltd.
・ Vulcanization accelerator 1: "Noxeller D" manufactured by Ouchi Shinko Chemical Industry Co., Ltd.
・ Vulcanization accelerator 2: "Soxinol CZ" manufactured by Sumitomo Chemical Co., Ltd.

Each of the obtained rubber compositions was used as a tread rubber and vulcanized and molded according to a conventional method to prepare a pneumatic radial tire (tire size: 215 / 45ZR17). The obtained test tires were evaluated for steering stability, wear resistance and low rolling resistance. Each measurement / evaluation method is as follows.

-Maneuvering stability: Four test tires were attached to a passenger car, the sensory (feeling) of the maneuvering stability was evaluated by a test driver on a dry road surface, and the maneuvering stability of Comparative Example 1 was displayed as an index of 100. .. The larger the index, the better the dry steering stability.

-Abrasion resistance: Four test tires were mounted on a passenger car, and the vehicle was run for 10,000 km while rotating left and right every 2500 km on a dry road surface. It is displayed as an index of 100. The larger the index, the larger the residual groove depth and the better the wear resistance.

-Low rolling resistance: Using a rolling resistance measuring drum tester, the rolling resistance of each tire was measured under the conditions of an air pressure of 230 kPa, a load of 4410 N, a temperature of 23 ° C., and 80 km / h, and the reciprocal of the rolling resistance was measured in Comparative Example 1. The value is set to 100 and is shown as an exponent. The larger the index, the smaller the rolling resistance and the better the fuel efficiency.

The results are shown in Table 1. In contrast to Comparative Example 1, in Examples 1 to 13 using the ether ester, both the wear resistance and the low rolling resistance could be improved without deteriorating the low rolling resistance. In Comparative Example 2, although the ether ester was blended, the SBR used as the rubber component had a high glass transition temperature, so that the effect of improving the wear resistance could not be obtained and the low rolling resistance also deteriorated.

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 (3)

A rubber composition for a tire containing a rubber component containing styrene-butadiene rubber having a glass transition temperature of −70 to −20 ° C., silica, and an ether ester represented by the following general formula (1).

In the formula, R ¹ and R ² each independently represent a hydrocarbon group having 12 to 30 carbon atoms, R ³ represents a hydrocarbon group having 1 to 30 carbon atoms, and R ⁴ and R ⁵ independently represent carbon atoms. Representing 2 to 4 alkylene groups, a and b each independently represent the average number of moles of oxyalkylene group added, a + b is 5 to 30, and (R ⁴ O) _a and (R ⁵ O) _b 60. More than mass% consists of oxyethylene groups. The rubber composition for a tire according to claim 1, wherein the silica is contained in an amount of 20 to 120 parts by mass and the ether ester is contained in an amount of 1 to 10 parts by mass with respect to 100 parts by mass of the rubber component. A pneumatic tire produced by using the rubber composition according to claim 1 or 2.