Use of a rubber composition for producing a tire and pneumatic tires

Abstract

Use of a rubber composition in a tread for producing a tire, the rubber composition comprising: a rubber component, an inorganic filler containing silicon dioxide, a thermoplastic elastomer containing a functional group that reacts or interacts with a surface functional group of the inorganic filler and having a specific gravity of 0.80 to 1.00, wherein the functional group contained in the thermoplastic elastomer is at least one member selected from the group consisting of a hydroxyl group, an amino group, a carboxyl group, a silanol group, an alkoxysilyl group, an epoxy group, a glycidyl group, a polyether group, a polysiloxane group, and a functional group derived from a maleic anhydride, wherein the proportion of the thermoplastic elastomer is 1 to 30 parts by mass per 100 parts by mass of the rubber component, and wherein the thermoplastic elastomer is a block copolymer comprising a polystyrene as a hard segment and at least one member selected from the group comprising a hydrogenated butadiene / isoprene copolymer, a hydrogenated polybutadiene, and a styrene / butadiene copolymer as a soft segment.

Description

Technical field

[0001] The present invention relates to a use of a rubber composition for producing a tire and a pneumatic tire. [State of the art]

[0002] Pneumatic tires must not only deliver excellent fuel efficiency but also have excellent wet road grip. However, these properties are contradictory, making it difficult to simultaneously improve both.

[0003] As a tire capable of reducing the rolling resistance of a tire tread, that is, improving fuel efficiency without impairing other properties, particularly wet grip, PTL 1 discloses a tire characterized in that the tread contains a rubber composition containing at least one kind of a diene elastomer, at least one kind of a reinforcing filler, and more than 10 phr of a hydrogenated thermoplastic styrene (“TPS”) elastomer.

[0004] In addition, in order to improve the adhesion and wear resistance, PTL 2 discloses a rubber composition containing a rubber component blended with a solid resin and a plasticizer such as a phosphate.

[0005] However, PTLs 1 and 2 are silent on fuel efficiency and wet grip performance, and they are also silent on the specific gravity of a thermoplastic elastomer to be blended, and there is still room for further improvement in fuel efficiency and wet grip performance.

[0006] DE 695 09 618 T2 discloses a method for adhering rubber to reinforcing materials by using maleic anhydride-functionalized triblock copolymer with polystyrene end blocks and poly(ethylene / butylene) middle blocks. [List of citations][Patent literature] [PTL 1] JP 2013-510939 T (the term “JP ... T” here means a published Japanese translation of a PCT patent application) [PTL 2] JP 2016-204503 A [PTL 3] JP 2014-189698 A [PTL 3] JP 2015-110703 A [PTL 5] JP 2015-110704 A [Summary of the invention][Problem to be solved by the invention]

[0007] In view of the above points, an object of the invention is to provide a use of a rubber composition in a tread part for manufacturing a tire, which is capable of improving fuel efficiency and wet grip, and also to provide a pneumatic tire using the same.

[0008] Incidentally, PTLs 3 to 5 disclose a rubber composition blended with a hydrogenated thermoplastic elastomer to improve adhesion. However, they are silent regarding fuel efficiency. [Means of solving the problem]

[0009] In order to solve the above-mentioned problems, when a rubber composition is used in a tread part for producing a tire, the rubber composition comprises a rubber component, an inorganic filler containing silica, and a thermoplastic elastomer containing a functional group that reacts or interacts with a surface functional group of the inorganic filler and has a specific gravity of 0.80 to 1.00, the functional group contained in the thermoplastic elastomer comprises at least one member selected from the group consisting of a hydroxyl group, an amino group, a carboxyl group, a silanol group, an alkoxysilyl group, an epoxy group, a glycidyl group, a polyether group, a polysiloxane group, and a functional group derived from a maleic anhydride,and wherein the proportion of the thermoplastic elastomer is 1 to 30 parts by mass per 100 parts by mass of the rubber component, and wherein the thermoplastic elastomer is a block copolymer having a polystyrene as a hard segment and at least one member selected from the group consisting of a hydrogenated butadiene / isoprene copolymer, a hydrogenated polybutadiene, and a styrene / butadiene copolymer as a soft segment.

[0010] It is possible that the thermoplastic elastomer contains 20% or more of styrene by mass.

[0011] The pneumatic tire according to the invention is manufactured with the above-mentioned rubber composition in a tread part. [Advantage of the invention]

[0012] The rubber composition for tires according to the invention makes it possible to obtain a pneumatic tire having improved fuel efficiency and improved wet grip. [Mode for carrying out the invention]

[0013] The aspects relevant to the implementation of the invention are described in detail below.

[0014] A rubber composition for tires according to this embodiment comprises a rubber component, an inorganic filler, and a thermoplastic elastomer containing a functional group that reacts or interacts with a surface functional group of the inorganic filler and having a specific gravity of 1.00 or less.

[0015] The rubber component according to this embodiment is not particularly limited. Examples thereof include natural rubber (NR), isoprene rubber (IR), butadiene rubber (BR), styrene-butadiene rubber (SBR), styrene-isoprene copolymer rubber, butadiene-isoprene copolymer rubber, and styrene-isoprene-butadiene copolymer rubber. These diene rubbers can be used alone, and it is also possible to use a mixture of two or more types.

[0016] The specific examples of the diene rubbers listed above also include modified diene rubbers having and modified with at least one functional group selected from the group consisting of a hydroxyl group, an amino group, a carboxyl group, an alkoxy group, an alkoxysilyl group, and an epoxy group introduced into the molecular terminal or molecular chain. Preferred modified diene rubbers are a modified SBR and / or a modified BR. In this embodiment, the diene rubber may be an unmodified diene rubber alone, a modified diene rubber alone, or a mixture of a modified diene rubber and an unmodified diene rubber.In one embodiment, 100 parts by mass of a diene rubber may contain 10 parts by mass or more of a modified SBR, or 10 to 80 parts by mass of a modified SBR and 90 to 20 parts by mass of an unmodified diene rubber (for example, at least one member selected from an SBR, a BR, and an NR) may be contained.

[0017] The thermoplastic elastomer according to this embodiment is not particularly limited as long as it contains a functional group that reacts or interacts with a surface functional group of the inorganic filler, and it is a thermoplastic elastomer whose functional group is at least one member selected from the group consisting of a hydroxyl group, an amino group, a carboxyl group, a silanol group, an alkoxysilyl group, an epoxy group, a glycidyl group, a polyether group, a polysiloxane group, and a functional group derived from maleic anhydride. As used herein, "interact" means to electrically attract each other. In addition, "polyether group" refers to a group having two or more ether bonds, and "polysiloxane group" refers to a group having two or more siloxane bonds.

[0018] Furthermore, the specific gravity of the thermoplastic elastomer according to this embodiment is not particularly limited as long as it is 1.00 or less and 0.80 or more, but preferably it is 0.80 to 0.95, and more preferably it is 0.85 to 0.95. Incidentally, the specific gravity as used herein is a value calculated in accordance with ISO 1183.

[0019] Commercially available products can also be used as such thermoplastic elastomers. Specific examples include "SEPTON HG-252" manufactured by Kuraray Co., Ltd., and "Tuftec MP10" and "Tuftec M1911" manufactured by Asahi Kasei Corporation. When a thermoplastic elastomer containing a functional group that reacts or interacts with a surface functional group of an inorganic filler is melt-kneaded with a rubber component, a sea-island structure is obtained in which the rubber component serves as the continuous phase and the thermoplastic elastomer serves as the dispersed phase. The uniformly dispersed thermoplastic elastomer functions in the same way as the inorganic fillers, thus likely achieving excellent wet adhesion.In addition, the inorganic filler reacts or interacts with the dispersed thermoplastic elastomer, thereby improving the dispersibility of the inorganic filler and making it likely to obtain excellent fuel efficiency.

[0020] The thermoplastic elastomer is a styrene thermoplastic elastomer having a polystyrene as a hard segment, and a styrene thermoplastic elastomer further having at least one member selected from the group consisting of a hydrogenated butadiene / isoprene copolymer, a hydrogenated polybutadiene, and a styrene / butadiene copolymer as a soft segment.That is, it is particularly preferable that the thermoplastic elastomer is at least one member selected from the group consisting of a triblock copolymer consisting of a polystyrene, a hydrogenated butadiene / isoprene copolymer, and a polystyrene (hereinafter sometimes referred to as SEEPS), a triblock copolymer consisting of a polystyrene, a hydrogenated polybutadiene, and a polystyrene (hereinafter sometimes referred to as SEBS), and a triblock copolymer consisting of a polystyrene, a styrene / butadiene copolymer, and a polystyrene (hereinafter sometimes referred to as S-SB-S).

[0021] The proportion of the thermoplastic elastomer is 1 to 30 parts by mass, preferably 1 to 20 parts by mass, and more preferably 5 to 20 parts by mass per 100 parts by mass of the rubber component.

[0022] In the rubber composition according to this embodiment, reinforcing fillers containing silica are used as the inorganic filler. That is, the inorganic filler may be silica alone or a combination of carbon black and silica. A combination of carbon black and silica is preferred. The proportion of the inorganic filler is not particularly limited, and is preferably, for example, 20 to 120 parts by mass, more preferably 20 to 100 parts by mass, and even more preferably 30 to 80 parts by mass per 100 parts by mass of the rubber component.

[0023] Carbon black is not particularly limited, and various known types can be used. The proportion of carbon black is preferably 1 to 70 parts by mass, and more preferably 1 to 30 parts by mass per 100 parts by mass of the rubber component.

[0024] The silica is also not particularly limited, but it is preferable to use a wet silica such as a wet-precipitated silica or a wet-gelled silica. In the case where silica is included, in consideration of the balance of the tan δ of the rubber, reinforcing properties, and the like, its content is preferably 10 to 100 parts by mass, and more preferably 15 to 70 parts by mass per 100 parts by mass of the rubber component.

[0025] In the case where silicon dioxide is included, a silane coupling agent such as a sulfide silane and a mercaptosilane may be further included. When the silane coupling agent is included, its content is preferably 2 to 20 parts by mass per 100 parts by mass of silicon dioxide.

[0026] In terms of improving wet adhesion, the rubber composition according to this embodiment can be further blended with resins. Examples of such resins include petroleum resins, rosin resins, and styrene resins. They can be used alone, and it is also possible to use a combination of two or more types. As these resins, those with a softening point of 80 to 140°C are preferably used. Here, the softening point is a value measured in accordance with JIS K2207 (ring and ball method).

[0027] Examples of petroleum resins include C5 aliphatic hydrocarbon resins, C9 aromatic hydrocarbon resins, and C5 / C9 aliphatic / aromatic copolymerized hydrocarbon resins. An aliphatic hydrocarbon resin is a resin obtained by the cationic polymerization of an unsaturated monomer, such as isoprene or cyclopentadiene, which has a petroleum fraction containing four to five carbon atoms (C5 fraction) and may be hydrogenated. An aromatic hydrocarbon resin is a resin obtained by the cationic polymerization of a monomer, such as vinyltoluene, alkylstyrene, or indene, which has a petroleum fraction containing eight to ten carbon atoms (C9 fraction) and may be hydrogenated.An aliphatic / aromatic copolymerized hydrocarbon resin is a resin obtained by copolymerizing the above C5 fraction and the C9 fraction by cationic polymerization and may also be hydrogenated.

[0028] Various known rosin resins can be used. Examples thereof include resins such as raw material resins including rosin resin, wood rosin, tall oil rosin, and the like, disproportionate products of the raw material resins, stabilized resins obtained by hydrogenation treatment of the raw material resins, and polymerized resins, as well as esterified products of resins (rosin ester resins), phenol-modified resins, unsaturated acid-modified resins (e.g., maleic acid-modified resins), and formylated resins obtained by reduction treatment of resins. Among these, polymerized resins, phenol-modified resins, unsaturated acid-modified resins, and rosin ester resins are preferred, and unsaturated acid-modified resins such as rosin-modified maleic acid resins are particularly preferred.

[0029] Examples of the styrenic resins include α-methylstyrene homopolymers, styrene / α-methylstyrene copolymers, styrene monomer / aliphatic monomer copolymers, α-methylstyrene / aliphatic monomer copolymers, and styrene monomer / α-methylstyrene / aliphatic monomer copolymers.

[0030] The resins listed above can be used alone, and a combination of two or more types is also possible. The resin content is not particularly limited, but it is preferably 1 to 30 parts by mass, more preferably 3 to 20 parts by mass, and even more preferably 5 to 15 parts by mass per 100 parts by mass of the rubber component. When the content is 1 to 30 parts by mass, excellent fuel efficiency is likely to be achieved.

[0031] In the rubber composition according to this embodiment, in addition to the components described above, formulated chemicals used in the usual rubber industry, such as process oils, a zinc oxide, a stearic acid, a softener, plasticizers, waxes, antioxidants, vulcanizing agents and vulcanization accelerators can be appropriately blended within the usual range.

[0032] Examples of the vulcanizing agent include sulfur components such as sulfur powder, precipitated sulfur, colloidal sulfur, insoluble sulfur, and highly dispersed sulfur. The proportion of the vulcanizing agent is preferably 0.1 to 10 parts by mass, and more preferably 0.5 to 5 parts by mass, per 100 parts by mass of the rubber component. In addition, the proportion of the vulcanization accelerator is preferably 0.1 to 7 parts by mass, and more preferably 0.5 to 5 parts by mass, per 100 parts by mass of the rubber component.

[0033] The rubber composition according to this embodiment can be prepared by kneading in a conventional manner using a commonly used mixer such as a Banbury mixer, a kneader, or a roll. That is, in the first mixing step, a thermoplastic elastomer is added and mixed with other additives except a vulcanizing agent and a vulcanization accelerator to a rubber component. Then, in the final mixing step, a vulcanizing agent and a vulcanization accelerator are added and mixed to the resulting mixture, whereby the rubber composition can be prepared.

[0034] The rubber composition obtained in this way can be used for tires. The rubber composition can be used for various parts of a tire, such as the tread portion and sidewall portion of pneumatic tires of various sizes for various applications, including automobile tires, large tires for trucks and buses, and so on. A pneumatic tire, for example, can be manufactured by extrusion and then combining with other parts, followed by vulcanization molding at 140 to 180°C.

[0035] The type of pneumatic tire according to this embodiment is not particularly limited. Examples include various tires, such as automobile tires and heavy-duty tires for trucks and buses, as described above. [Examples]

[0036] Examples of the invention are shown below, but the invention is not limited to these examples. <Thermoplastisches Elastomer Synthesebeispiel 1>

[0037] In a pressure-resistant container equipped with a stirrer, 800 g of cyclohexane, 38 g of dehydrated styrene, and 7.7 g of a cyclohexane solution of sec-butyllithium (10 mass percent) were added, and the polymerization reaction was carried out at 50 °C for 1 hour. 127 g of a mixture of styrene and butadiene (molar ratio of styrene to butadiene = 3 to 4) was added, and the polymerization reaction was carried out for 1 hour. Further, 38 g of styrene was added, and the polymerization reaction was carried out for 1 hour. Subsequently, 2.5 g of chlorotriethoxysilane was added, and finally, methanol was added to stop the reaction. The reaction solution was distilled under reduced pressure to remove the solvent, thereby obtaining a thermoplastic elastomer 5, which is a styrene-(styrene / butadiene)-styrene block copolymer having an ethoxysilyl group at one end.The number-average molecular weight of the obtained thermoplastic elastomer 5 was 163,000, and the styrene content was 74 mass percent. Incidentally, the number-average molecular weight and styrene content were measured using a GPC (gel permeation chromatography) "HPC-8020" manufactured by Tosoh Corporation. Tetrahydrofuran was used as the solvent, and the measurement was performed with respect to a standard polystyrene. <Thermoplastisches Elastomer Synthesebeispiel 2>

[0038] In a pressure-resistant container equipped with a stirrer, 800 g of cyclohexane, 38 g of dehydrated styrene, and 7.7 g of a cyclohexane solution of sec-butyllithium (10 mass percent) were added, and the polymerization reaction was carried out at 50 °C for 1 hour. 127 g of a mixture of styrene and butadiene (molar ratio of styrene to butadiene = 3 to 4) was added, and the polymerization reaction was carried out for 1 hour. Further, 38 g of styrene was added, and the polymerization reaction was carried out for 1 hour. Subsequently, 1.2 g of epichlorohydrin was added, and finally, methanol was added to stop the reaction. The reaction solution was distilled under reduced pressure to remove the solvent, thereby obtaining a thermoplastic elastomer 6, which is a styrene-(styrene / butadiene)-styrene block copolymer having an epoxy group at one end.The number-average molecular weight of the obtained thermoplastic elastomer 6 was 161,000, and the styrene content was 74 mass percent. Incidentally, the number-average molecular weight and styrene content were measured in the same manner as in the above-mentioned Synthesis Example 1. <Beispiele und Vergleichsbeispiele>

[0039] Using a Banbury mixer, according to the recipe (parts by mass) shown in Table 1 below, first, in the first mixing stage (non-processing kneading step), the components except the vulcanization accelerator and the sulfur were added and mixed (outlet temperature = 160 °C), and in the last mixing stage (processing kneading step), the vulcanization accelerator and the sulfur were added and mixed to the obtained mixture (outlet temperature = 90 °C), thereby preparing the rubber composition.

[0040] The details of the components in Table 1 are as follows. - SBR 1: “VSL5025-0HM”, manufactured by LANXESS - SBR 2: Amino and alkoxy-terminated modified solution-polymerized styrene-butadiene rubber “HPR350” manufactured by JSR Corporation - NO: RSS # 3 - BR: “BR150B”, manufactured by Ube Industries, Ltd. - Thermoplastic elastomer 1: “SEPTON 8006”, manufactured by Kuraray Co. Ltd., a terminally unmodified SEBS copolymer, styrene content: 33% by mass, specific gravity: 0.92 - Thermoplastic elastomer 2: “SEPTON HG-252” manufactured by Kuraray Co. Ltd., a hydroxyl-terminated modified SEEPS copolymer, styrene content: 28% by mass, specific gravity: 0.90 - Thermoplastic elastomer 3: “Tuftec MP10” manufactured by Asahi Kasei Corporation, amino-terminated modified SEBS copolymer, styrene content: 30% by mass, specific gravity: 0.91 - Thermoplastic elastomer 4: “Tuftec M1911” manufactured by Asahi Kasei Corporation, a maleic anhydride-modified SEBS copolymer, styrene content: 30% by mass, specific gravity: 0.91 - Thermoplastic elastomer 5: Thermoplastic elastomer obtained in Synthesis Example 1 above, an alkoxysilyl-terminated modified S-SB-S copolymer, styrene content: 74 mass%, specific gravity: 0.92 - Thermoplastic elastomer 6: Thermoplastic elastomer obtained in Synthesis Example 2 above, an epoxy-terminated modified S-SB-S copolymer, styrene content: 74 mass percent, specific gravity: 0.91 - Thermoplastic elastomer 7: “UH2170”, manufactured by Toagosei Co. Ltd., a hydroxyl-containing styrene-acrylic resin, specific gravity: 1.15 - Thermoplastic elastomer 8: “UC3900”, manufactured by Toagosei Co. Ltd., a carboxyl group-containing styrene-acrylic resin, specific gravity: 1.19 - Silicon dioxide: “Nipsil AQ”, manufactured by Tosoh Silica Corporation - Carbon black: “DIABLACK N341”, manufactured by Mitsubishi Chemical Corporation - Silane coupling agent: “Si69”, manufactured by Evonik - Oil: “Process NC 140”, produced by JX Energy - Resin: “FTR6125” manufactured by Mitsui Chemicals, Inc., styrene / aliphatic monomer copolymer, softening point = 125 °C, weight-average molecular weight: 1950 - Zinc oxide: “Zinc oxide No. 1”, manufactured by Mitsui Mining & Smelting Co. Ltd. - Antioxidant: “Antigen 6C”, manufactured by Sumitomo Chemical Co. Ltd. - Stearic acid: “LUNAC S-20”, manufactured by Kao Corporation - Wax: “OZOACE0355”, manufactured by Nippon Seiro Co. Ltd. - Sulphur: “5% oil-treated sulfur powder” manufactured by Tsurumi Chemical Industry Co. Ltd. - Vulcanization accelerator 1: “SOXINOL CZ”, manufactured by Sumitomo Chemical Co., Ltd. - Vulcanization accelerator 2: “Nocceler D”, manufactured by Ouchi Shinko Chemical Industrial Co. Ltd.

[0041] The specific gravity of each thermoplastic elastomer described above is a value calculated in accordance with ISO 1183.

[0042] The wet grip and fuel efficiency of each obtained rubber composition were evaluated. The evaluation methods are as follows.

[0043] - Wet adhesion: Using a sample of a predetermined shape prepared by vulcanizing the obtained rubber composition at 160°C for 30 minutes, the loss tangent tanδ was measured as the value using a viscoelasticity tester manufactured by Toyo Seiki Co. Ltd. in accordance with JIS K6394. The measurement conditions were as follows: frequency: 10 Hz, static elongation: 10%, dynamic elongation: 1%, temperature: 0°C. The result was expressed as an index, which takes the value 100 for Comparative Example 1. A larger index indicates better wet adhesion.

[0044] - Fuel Efficiency: Using a sample of a predetermined shape prepared by vulcanizing the obtained rubber composition at 160°C for 30 minutes, the loss tangent tanδ was measured as the value using a viscoelasticity tester manufactured by Toyo Seiki Co. Ltd. in accordance with JIS K6394. The measurement conditions were as follows: frequency: 10 Hz, static strain: 10%, dynamic strain: 1%, temperature: 60°C. The result was expressed as an index, which takes the value 100 in Comparative Example 1. A smaller index indicates better fuel efficiency. [Table 1] Comparison example 1 Comparison example 2 Comparison example 3 Comparison example 4 Comparison example 5 Comparison example 6 SBR1 70 - 70 70 70 70 SBR2 - 70 - - - - NR - - - - - - BR 30 30 30 30 30 30 Thermoplastic elastomer 1 - - - 10 - - Thermoplastic elastomer 2 - - - - - - Thermoplastic elastomer 3 - - - - - - Thermoplastic elastomer 4 - - - - - - Thermoplastic elastomer 5 - - - - - - Thermoplastic elastomer 6 - - - - - - Thermoplastic elastomer 7 - - - - 10 - Thermoplastic elastomer 8 - - - - - 10 Silicon dioxide 70 70 70 70 70 70 soot 10 10 10 10 10 10 Silane coupling agent 7 7 7 7 7 7 Öl 20 20 20 20 20 20 resin - - 10 - - - zinc oxide 3,0 3,0 3,0 3,0 3,0 3,0 Antioxidants 2,0 2,0 2,0 2,0 2,0 2,0 Stearic acid 2,0 2,0 2,0 2,0 2,0 2,0 wax 2,0 2,0 2,0 2,0 2,0 2,0 sulfur 1,5 1,5 1,5 1,5 1,5 1,5 Vulcanization accelerator 1 1,8 1,8 1,8 1,8 1,8 1,8 Vulcanization accelerator 2 2,0 2,0 2,0 2,0 2,0 2,0 Adhesion in wet conditions 100 90 114 112 103 102 Fuel efficiency 100 75 110 102 100 101 Example 1 Example 2 Example 3 Example 4 Example 5 Example 6 Example 7 Example 8 Example 9 SBR1 70 70 70 70 70 70 - - - SBR2 - - - - - - 70 70 70 NR - - - - - - - - 30 BR 30 30 30 30 30 30 30 30 - Thermoplastic elastomer 1 - - - - - - - - - Thermoplastic elastomer 2 10 20 - - - - 10 10 10 Thermoplastic elastomer 3 - - 10 - - - - - - Thermoplastic elastomer 4 - - - 10 - - - - - Thermoplastic elastomer 5 - - - - 10 - - - - Thermoplastic elastomer 6 - - - - - 10 - - - Thermoplastic elastomer 7 - - - - - - - - - Thermoplastic elastomer 8 - - - - - - - - - Silicon dioxide 70 70 70 70 70 70 70 70 70 soot 10 10 10 10 10 10 10 10 10 Silane coupling agent 7 7 7 7 7 7 7 7 7 Öl 20 20 20 20 20 20 20 20 20 resin - - - - - - - 10 - zinc oxide 3,0 3,0 3,0 3,0 3,0 3,0 3,0 3,0 3,0 Antioxidants 2,0 2,0 2,0 2,0 2,0 2,0 2,0 2,0 2,0 Stearic acid 2,0 2,0 2,0 2,0 2,0 2,0 2,0 2,0 2,0 wax 2,0 2,0 2,0 2,0 2,0 2,0 2,0 2,0 2,0 sulfur 1,5 1,5 1,5 1,5 1,5 1,5 1,5 1,5 1,5 Vulcanization accelerator 1 1,8 1,8 1,8 1,8 1,8 1,8 1,8 1,8 1,8 Vulcanization accelerator 2 2,0 2,0 2,0 2,0 2,0 2,0 2,0 2,0 2,0 Adhesion in wet conditions 110 116 110 112 118 116 104 116 106 Fuel efficiency 92 88 90 94 90 93 70 80 70

[0045] The results are shown in Table 1. A comparison between Comparative Examples 1 to 6 and Examples 1 to 9 shows that when a predetermined thermoplastic elastomer containing a functional group that reacts or interacts with a surface functional group of the inorganic filler is used, wet adhesion and fuel efficiency are improved. [Industrial applicability]

[0046] The rubber composition for tires of the invention can be used for various tires for automobiles, light trucks, buses and the like.

Claims

[1] Use of a rubber composition in a tread for producing a tire, the rubber composition comprising: a rubber component, an inorganic filler containing silicon dioxide, a thermoplastic elastomer containing a functional group that reacts or interacts with a surface functional group of the inorganic filler and having a specific gravity of 0.80 to 1.00, wherein the functional group contained in the thermoplastic elastomer is at least one member selected from the group consisting of a hydroxyl group, an amino group, a carboxyl group, a silanol group, an alkoxysilyl group, an epoxy group, a glycidyl group, a polyether group, a polysiloxane group, and a functional group derived from a maleic anhydride, wherein the proportion of the thermoplastic elastomer is 1 to 30 parts by mass per 100 parts by mass of the rubber component, and wherein the thermoplastic elastomer is a block copolymer comprising a polystyrene as a hard segment and at least one member selected from the group comprising a hydrogenated butadiene / isoprene copolymer, a hydrogenated polybutadiene, and a styrene / butadiene copolymer as a soft segment. [2] Use of a rubber composition according to claim 1, wherein the thermoplastic elastomer has a styrene content of 20 mass percent or more. [3] A pneumatic tire made with a rubber composition in a tread, the rubber composition comprising: a rubber component, an inorganic filler containing silicon dioxide, a thermoplastic elastomer containing a functional group that reacts or interacts with a surface functional group of the inorganic filler and having a specific gravity of 0.80 to 1.00, wherein the functional group contained in the thermoplastic elastomer is at least one member selected from the group consisting of a hydroxyl group, an amino group, a carboxyl group, a silanol group, an alkoxysilyl group, an epoxy group, a glycidyl group, a polyether group, a polysiloxane group, and a functional group derived from a maleic anhydride, wherein the proportion of the thermoplastic elastomer is 1 to 30 parts by mass per 100 parts by mass of the rubber component, and wherein the thermoplastic elastomer is a block copolymer comprising a polystyrene as a hard segment and at least one member selected from the group comprising a hydrogenated butadiene / isoprene copolymer, a hydrogenated polybutadiene, and a styrene / butadiene copolymer as a soft segment. [4] A tire according to claim 3, wherein the thermoplastic elastomer has a styrene content of 20 mass percent or more.