JP6267419B2 - Rubber composition for tire and pneumatic tire - Google Patents

Description

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

In recent years, the characteristics required for pneumatic tires for automobiles are diverse, such as low fuel consumption (rolling resistance characteristics), grip performance, and wear resistance. Various improvements have been made to improve these performances. Yes. In addition, the studless tire used in winter is required to have performance such as grip performance at low temperatures and steering stability in addition to the above performance.

A technology for blending a triblock copolymer composed of a block segment of a styrene monomer unit and a block segment of a rubber monomer unit into the rubber composition for the purpose of improving fuel economy and wear resistance in the rubber composition is known. However, there is room for further improvement in improving the performance of the tire (see, for example, Patent Document 1).

JP 2004-2622 A

An object of the present invention is to solve the above-mentioned problems and provide a rubber composition for a tire that can improve fuel economy, workability, wear resistance, and performance on ice and snow in a well-balanced manner, and a pneumatic tire using the same. To do.

The present invention relates to a rubber composition for tires containing natural rubber and a modified block copolymer composed of a block segment of a styrene monomer unit and a block segment of a diene monomer unit and having a polar functional group.

The block segment of the diene monomer unit is preferably a butadiene block.

The modified block copolymer is preferably a modified styrene-butadiene-styrene triblock copolymer.

The polar functional group is preferably at least one selected from the group consisting of a hydroxyl group, an epoxy group, an amino group, an amide group, a silanol group, an alkoxysilane group, a cyano group, a carboxyl group, an ester group, and a mercapto group. .

The rubber composition preferably contains carbon black.

The present invention also relates to a pneumatic tire produced using the rubber composition.

According to the present invention, since it is a rubber composition in which natural rubber and a specific modified block copolymer are blended, the fuel efficiency, workability, wear resistance, and performance on ice and snow are improved in a well-balanced manner. Tires can be provided.

The rubber composition of the present invention contains natural rubber and a modified block copolymer composed of a block segment of a styrene monomer unit and a block segment of a diene monomer unit and having a polar functional group.

Examples of the diene monomer constituting the diene monomer unit of the modified block copolymer include 1,3-butadiene (hereinafter abbreviated as butadiene), isoprene, 1,3-pentadiene, 2,3-dimethylbutadiene, 2-phenyl- Examples include 1,3-butadiene and 1,3-hexadiene. These may be used alone or in combination of two or more. Of these, butadiene and isoprene are preferred from the viewpoint of practical advantage such as availability of monomers, and butadiene is more preferred from the viewpoint of high effect of improving tire performance. That is, in the modified block copolymer, the block segment of the diene monomer unit is preferably a butadiene block.

The modified block copolymer is preferably a modified styrene-butadiene-styrene triblock copolymer (modified SBS) from the viewpoint of improving fuel economy, workability, wear resistance, and performance on ice and snow in a well-balanced manner. .

The amount of styrene in the modified block copolymer is preferably 1% by mass or more, more preferably 10% by mass or more, and still more preferably 20% by mass or more. If it is less than 1% by mass, sufficient interaction with the filler cannot be obtained, and the fuel efficiency tends to be poor. The amount of styrene in the modified block copolymer is preferably 60% by mass or less, more preferably 50% by mass or less, and still more preferably 45% by mass or less. If it exceeds 60%, workability may be deteriorated.

The polar functional group possessed by the modified block copolymer is not particularly limited as long as it is a functional group containing a nitrogen atom, an oxygen atom, a sulfur atom, etc., but can be easily introduced, and can be combined with carbon black or silica. It is at least one selected from the group consisting of a hydroxyl group, an epoxy group, an amino group, an amide group, a silanol group, an alkoxysilane group, a cyano group, a carboxyl group, an ester group, and a mercapto group because of its high interaction. Are preferable, and at least one selected from the group consisting of an epoxy group, an amino group, an amide group, and an alkoxysilane group is more preferable.

The modified block copolymer is obtained by reacting a styrene monomer, a diene monomer, and a polar functional group-containing compound. The reaction of the polar functional group-containing compound (introduction of the polar functional group) may be performed either during the polymerization reaction, after the polymerization reaction, or after the block copolymer is produced and isolated, but the effect of improving fuel economy From the viewpoint of high, it is preferable to react a polar group-containing compound with the active terminal of the obtained block copolymer after the polymerization reaction. That is, the modified block copolymer preferably has a polar functional group at the terminal.

The polar group-containing compound is not particularly limited as long as it is a compound capable of reacting with a styrene monomer, diene monomer or block copolymer, but isocyanate compound, isothiocyanate compound, amide compound, imide compound, pyridyl-substituted ketone compound, It is preferably at least one selected from the group consisting of pyridyl-substituted vinyl compounds, silicon compounds, ester compounds, ketone compounds and epoxy compounds, and selected from the group consisting of amide compounds, imide compounds, silicon compounds and epoxy compounds. More preferably, it is at least one. These may be used alone or in combination of two or more.

Specific examples of the isocyanate compound and the isothiocyanate compound include 2,4-tolylene diisocyanate, 2,6-tolylene diisocyanate, diphenylmethane diisocyanate, isophorone diisocyanate, hexamethylene diisocyanate, 1, Preferred examples include 3,5-benzenetriisocyanate and phenyl-1,4-diisothiocyanate.

Specific examples of the amide compound and the imide compound include succinic acid amide, phthalic acid amide, N, N, N ′, N′-tetramethylphthalic acid amide, oxamide, N, N, N ′, N′-tetramethyloxa Amide compounds such as amide, succinimide, N-methylsuccinimide, maleimide, N-methylmaleimide, phthalimide, N-methylphthalimide, and other imide compounds, urea, 1,3-dimethyl-2-imidazolidinone, bis [ Preferable examples include urea derivatives such as 3- (triethoxysilyl) propyl] urea and bis [(trimethoxysilyl) propyl] urea.

Specific examples of the pyridyl-substituted ketone compound and the pyridyl-substituted vinyl compound include dibenzoylpyridine, diacetylpyridine, divinylpyridine and the like.

Specific examples of silicon compounds include triethoxymethylsilane, triphenoxymethylsilane, trimethoxysilane, methyltriethoxysilane, 4,5-epoxyheptylmethyldimethoxysilane, bis (triethoxysilylpropyl) tetrasulfide, N, N -Bis (trimethylsilyl) aminopropylmethyldimethoxysilane, tetraethoxysilane, diethoxydimethylsilane, tetramethoxysilane, dimethoxysilane, 3- (N, N-dimethylamino) propyltriethoxysilane, 2-cyanoethyltriethoxysilane, 2 -(4-pyridylethyl) triethoxysilane, 2- (4-pyridylethyl) trimethoxysilane, 3- (1-hexamethyleneimino) propyl (triethoxy) silane, 3- (1,3-dimethylbutyrate) Den) aminopropyltriethoxysilane, 3- (1,3-dimethylbutylidene) aminopropyltrimethoxysilane, 3- (2-aminoethylaminopropyl) trimethoxysilane, 3- (m-aminophenoxy) propyltrimethoxy Silane, 3- (N, N-diethylamino) propyltriethoxysilane, 3- (N, N-diethylamino) propyltrimethoxysilane, 3- (N-methylamino) propyltriethoxysilane, 3- (N-methylamino) ) Propyltrimethoxysilane, 3- (N-allylamino) propyltrimethoxysilane, 3-aminopropyldimethylethoxysilane, 3-aminopropyltriethoxysilane, 3-aminopropyltrimethoxysilane, 3-aminopropyltris (methoxydi) Ethoxy) silane 3-aminopropyldiisopropylethoxysilane, 3-isocyanatopropyltriethoxysilane, 3-glycidoxypropyltriethoxysilane, 3-glycidoxypropyltrimethoxysilane, 3-glycidoxypropylmethyldimethoxysilane, 3-diethylaminopropyl Trimethoxysilane, 3-diethoxy (methyl) silylpropyl succinic anhydride, 3- (N, N-diethylaminopropyl) triethoxysilane, 3- (N, N-diethylaminopropyl) trimethoxysilane, 3- (N, N -Dimethylaminopropyl) diethoxymethylsilane, 3- (N, N-dimethylaminopropyl) triethoxysilane, 3- (N, N-dimethylaminopropyl) trimethoxysilane, 3-triethoxysilylpropyl succinic anhydride, 3-triethoxysilylpropyl acetic anhydride, 3-triphenoxysilylpropyl succinic anhydride, 3-triphenoxysilylpropyl acetic anhydride, 3-trimethoxysilylpropylbenzothiazole tetrasulfide, 3-hexamethyleneiminopropyltriethoxysilane, 3 -Mercaptopropyltrimethoxysilane etc. can be mentioned as a preferable thing.

Specific examples of the ester compound include diethyl adipate, diethyl malonate, diethyl phthalate, diethyl glutarate, diethyl maleate and the like.

Specific examples of the ketone compound include N, N, N ′, N′-tetramethyl-4,4′-diaminobenzophenone, N, N, N ′, N′-tetraethyl (4,4′-diamino) -benzophenone. N, N-dimethyl-1-aminobenzoquinone, N, N, N ′, N′-tetramethyl-1,3-diaminobenzoquinone, N, N-dimethyl-1-aminoanthraquinone, N, N, N ′, N'-tetramethyl-1,4-diaminoanthraquinone and the like can be mentioned as preferable ones.

Specific examples of the epoxy compound include 3-glycidoxypropyltrimethoxysilane, tetraglycidyl-1,3-bisaminomethylcyclohexane, 1-glycidyl-4-phenylpiperazine, 1-glycidyl-4-methylpiperazine, 1- Preferred examples include glycidyl-4-methylhomopiperazine, 1-benzyl-4-glycidylpiperazine, 1-glycidylhexamethyleneimine, tetraglycidyl-1,3-bisaminomethylcyclohexane and the like.

The weight average molecular weight Mw of the modified block copolymer is preferably 10,000 or more, more preferably 50,000 or more, still more preferably 85,000 or more, and preferably 200,000 or less, more preferably 150. , 000 or less. If it is less than 10,000, the wear resistance and fuel efficiency may be deteriorated. If it exceeds 200,000, the viscosity increases and the processability may be deteriorated.
In the present invention, Mw is a value converted from standard polystyrene using GPC.

The content of the modified block copolymer is preferably 1 part by mass or more, more preferably 5 parts by mass or more, still more preferably 8 parts by mass or more, and preferably 30 parts by mass with respect to 100 parts by mass of the rubber component. Part or less, more preferably 20 parts by weight or less, and still more preferably 15 parts by weight or less. If it is less than 1 part by mass, the effect of improving fuel economy may not be sufficiently exhibited, and if it exceeds 30 parts by mass, rubber elasticity may be inferior.
In the present invention, the modified block copolymer is used as an additive and is not included in the rubber component.

The rubber composition of the present invention contains natural rubber (NR). The natural rubber is not particularly limited, and for example, those generally used in the tire industry such as SIR20, RSS # 3, TSR20, deproteinized natural rubber (DPNR), and high-purity natural rubber (HPNR) can be used. Further, it may be epoxidized (ENR) or other modified ones.

The content of NR in 100% by mass of the rubber component is preferably 20% by mass or more, more preferably 30% by mass or more, and preferably 90% by mass or less, more preferably 80% by mass or less. If it is less than 20% by mass, the wear resistance may be deteriorated. If it exceeds 90% by mass, the performance on ice and snow may be deteriorated.

Examples of rubber components other than NR include diene rubbers such as styrene butadiene rubber (SBR) and butadiene rubber (BR), and butyl rubbers such as butyl rubber and chlorinated butyl rubber. Of these, diene rubber is preferable, and BR is more preferable. These may be condensed or modified.

The cis content of BR is preferably 70% by mass or more, more preferably 90% by mass or more, and still more preferably 97% by mass or more from the viewpoint that good performance on ice and snow can be obtained.

The Mooney viscosity (ML _{1 + 4} (100 ° C.)) of BR is preferably 10 or more, more preferably 30 or more. If it is less than 10, the dispersibility of the filler tends to decrease. The Mooney viscosity of BR is preferably 120 or less, more preferably 80 or less. If it exceeds 120, there is a concern about the occurrence of rubber burn (discoloration) during extrusion processing.

The molecular weight distribution (Mw / Mn) of BR is preferably 1.5 or more, more preferably 2.0 or more. If it is less than 1.5, workability may be deteriorated. The Mw / Mn of BR is preferably 5.0 or less, more preferably 4.0 or less. If it exceeds 5.0, the wear resistance tends to deteriorate.
In the present invention, Mn and Mw are values converted from standard polystyrene using GPC.

The content of BR in 100% by mass of the rubber component is preferably 10% by mass or more, more preferably 15% by mass or more, and further preferably 20% by mass or more. If it is less than 10% by mass, sufficient grip performance (grip performance on ice and snow) may not be obtained. The content of BR is preferably 50% by mass or less, more preferably 40% by mass or less. If it exceeds 50% by mass, sufficient wear resistance may not be obtained.

The rubber composition of the present invention preferably contains carbon black as a filler. By blending carbon black, the reinforcing property is enhanced and good wear resistance is obtained. Examples of carbon black that can be used include GPF, FEF, HAF, ISAF, and SAF, but are not particularly limited.

The nitrogen adsorption specific surface area (N ₂ SA) of carbon black is preferably 20 m ² / g or more, more preferably 35 m ² / g or more, still more preferably 70 m ² / g or more, and particularly preferably 90 m ² / g or more. is there. If it is less than 20 m ² / g, it tends to be difficult to obtain sufficient reinforcement. Further, N ₂ SA of the carbon black is preferably 1400 m ² / g or less, more preferably 200 m ² / g or less, and further preferably 120 m ² / g or less. If it exceeds 1400 m ² / g, it tends to be difficult to disperse well.
The N ₂ SA of carbon black is determined by the A method of JIS K6217.

The content of carbon black is preferably 1 part by mass or more, more preferably 3 parts by mass or more, and still more preferably 10 parts by mass or more with respect to 100 parts by mass of the rubber component. If it is less than 1 part by mass, the improvement effect by carbon black may not be sufficiently obtained. The content of carbon black is preferably 100 parts by mass or less, more preferably 80 parts by mass or less, still more preferably 40 parts by mass or less, and particularly preferably 20 parts by mass or less. If it exceeds 100 parts by mass, the carbon black tends to be difficult to disperse and the workability tends to deteriorate, or the hardness tends to increase too much.

The rubber composition of the present invention preferably contains silica as a filler. By blending silica, low fuel consumption and grip performance on snow and ice can be improved. The silica is not particularly limited, and examples thereof include dry process silica (anhydrous silicic acid), wet process silica (hydrous silicic acid) and the like, and wet process silica is preferred because it has many silanol groups.

The nitrogen adsorption specific surface area (N ₂ SA) of silica is preferably 40 m ² / g or more, more preferably 50 m ² / g or more, still more preferably 100 m ² / g or more, and particularly preferably 150 m ² / g or more. . If it is less than 40 m < ² > / g, there exists a tendency for the fracture strength after vulcanization to fall. The N ₂ SA of silica is preferably 500 m ² / g or less, more preferably 300 m ² / g or less. If it exceeds 500 m ² / g, fuel economy and processability tend to deteriorate.
The _N 2 SA of silica is a value measured by the BET method in accordance with ASTM D3037-81.

The content of silica is preferably 1 part by mass or more, more preferably 5 parts by mass or more, further preferably 10 parts by mass or more, particularly preferably 15 parts by mass or more, and most preferably 40 parts by mass or more. If the amount is less than 1 part by mass, the fuel economy tends not to be sufficiently improved. The content of silica is preferably 200 parts by mass or less, more preferably 150 parts by mass or less, and still more preferably 100 parts by mass or less. If it exceeds 200 parts by mass, the silica is difficult to disperse and the processability tends to deteriorate.

The rubber composition of the present invention preferably contains a silane coupling agent. Although it does not specifically limit as a silane coupling agent, For example, bis (3-triethoxysilylpropyl) tetrasulfide, bis (2-triethoxysilylethyl) tetrasulfide, bis (3-trimethoxysilylpropyl) tetrasulfide, bis (2-trimethoxysilylethyl) tetrasulfide, bis (3-triethoxysilylpropyl) trisulfide, bis (3-trimethoxysilylpropyl) trisulfide, bis (3-triethoxysilylpropyl) disulfide, bis (3- Trimethoxysilylpropyl) disulfide, 3-trimethoxysilylpropyl-N, N-dimethylthiocarbamoyl tetrasulfide, 3-triethoxysilylpropyl-N, N-dimethylthiocarbamoyl tetrasulfide, 2-triethoxy Silylethyl-N, N-dimethylthiocarbamoyl tetrasulfide, 2-trimethoxysilylethyl-N, N-dimethylthiocarbamoyl tetrasulfide, 3-trimethoxysilylpropylbenzothiazolyl tetrasulfide, 3-triethoxysilylpropylbenzothiazole Sulfide systems such as tetrasulfide, 3-triethoxysilylpropyl methacrylate monosulfide, 3-trimethoxysilylpropyl methacrylate monosulfide; 3-mercaptopropyltrimethoxysilane, 3-mercaptopropyltriethoxysilane, 2-mercaptoethyltrimethoxysilane Mercapto type such as 2-mercaptoethyltriethoxysilane; Vinyl type such as vinyltriethoxysilane and vinyltrimethoxysilane; Amino systems such as nopropyltriethoxysilane, 3-aminopropyltrimethoxysilane, 3- (2-aminoethyl) aminopropyltriethoxysilane, 3- (2-aminoethyl) aminopropyltrimethoxysilane; γ-glycid Glycidoxy systems such as xylpropyltriethoxysilane, γ-glycidoxypropyltrimethoxysilane, γ-glycidoxypropylmethyldiethoxysilane, γ-glycidoxypropylmethyldimethoxysilane; 3-nitropropyltrimethoxysilane, 3 -Nitro type such as nitropropyltriethoxysilane; chloro type such as 3-chloropropyltrimethoxysilane, 3-chloropropyltriethoxysilane, 2-chloroethyltrimethoxysilane, 2-chloroethyltriethoxysilane, etc.Moreover, as a mercapto type | system | group, NXT by the Momentive company which has the structure where the mercapto group was protected, NXT-Z, etc. can be used. One of these silane coupling agents may be used alone, or two or more thereof may be used in combination.

The content of the silane coupling agent is preferably 1 part by mass or more, more preferably 2 parts by mass or more with respect to 100 parts by mass of silica. If it is less than 1 part by mass, the viscosity of the unvulcanized rubber composition is high, and the processability tends to deteriorate. The content of the silane coupling agent is preferably 10 parts by mass or less, more preferably 8 parts by mass or less. When the amount exceeds 10 parts by mass, a filler dispersing effect commensurate with the increase in cost cannot be obtained, and further, the reinforcing property and wear resistance may be lowered. In addition, the remaining unreacted silane coupling agent may cause rubber burn during processing and deterioration of the breaking performance of rubber after vulcanization.

The rubber composition of the present invention may contain other fillers in addition to silica and carbon black. Examples of other fillers include, but are not limited to, aluminum hydroxide, clay, calcium carbonate, montmorillonite, cellulose, glass balloon, and various short fibers.

In addition to the above components, the rubber composition of the present invention includes compounding agents generally used in the production of rubber compositions such as zinc oxide, stearic acid, processing aids, various anti-aging agents, oils, and aromatics. A plasticizer such as petroleum resin and wax, a vulcanizing agent such as sulfur, a vulcanization accelerator, and the like can be appropriately blended.

Examples of the plasticizer include mineral oils such as aroma oil, process oil, and paraffin oil, and mineral oil is preferable from the viewpoint of good tire performance at low temperatures. These plasticizers may be used alone or in combination of two or more.

The content of the plasticizer is preferably 5 parts by mass or more, more preferably 15 parts by mass or more with respect to 100 parts by mass of the rubber component. If it is less than 5 parts by mass, sufficient workability and performance on ice and snow may not be obtained. The oil content is preferably 50 parts by mass or less, more preferably 40 parts by mass or less. If it exceeds 50 parts by mass, the fuel efficiency tends to deteriorate.

Examples of the vulcanization accelerator include sulfenamide, thiazole, thiuram, thiourea, guanidine, dithiocarbamic acid, aldehyde-amine, aldehyde-ammonia, imidazoline, and xanthate vulcanization accelerators. Is mentioned. These vulcanization accelerators may be used alone or in combination of two or more. Of these, sulfenamide vulcanization accelerators are preferred.

Examples of the sulfenamide vulcanization accelerator include N-tert-butyl-2-benzothiazolylsulfenamide (TBBS), N-cyclohexyl-2-benzothiazolylsulfenamide (CBS), N, N -Dicyclohexyl-2-benzothiazolylsulfenamide (DCBS) and the like.

The content of the vulcanization accelerator is preferably 0.1 parts by mass or more, more preferably 0.5 parts by mass or more, and preferably 5 parts by mass or less, more preferably 100 parts by mass of the rubber component. Is 3 parts by mass or less. By adjusting within the above range, the effect of the present invention can be obtained more suitably.

The rubber composition of the present invention is produced by a general method. That is, it can be produced by a method of kneading the above components with a kneader such as a Banbury mixer, a kneader, or an open roll, and then vulcanizing.

The rubber composition of this invention can be used for each member of a tire, and can be used conveniently for a tread.

The pneumatic tire of the present invention is produced by a usual method using the rubber composition. That is, by extruding a rubber composition containing the above components in accordance with the shape of a tread or the like at an unvulcanized stage, and molding it with a tire molding machine by a normal method along with other tire members, Form an unvulcanized tire. The pneumatic tire of the present invention can be manufactured by heating and pressurizing the unvulcanized tire in a vulcanizer.

The pneumatic tire of the present invention can be used as passenger car tires, truck / bus tires, motorcycle tires, competition tires, studless tires, and the like. Especially, it can be conveniently used as a studless tire.

The present invention will be specifically described based on examples, but the present invention is not limited to these examples.

First, according to Production Examples 1 to 3, modified block copolymers 1 to 3 according to the present invention were produced according to Reference Production Example 1, and non-modified block copolymers used in Comparative Examples were produced, and the following physical property measurements were performed. It was.

(Measurement of weight average molecular weight Mw)
The weight average molecular weight Mw of the block copolymer was determined by gel permeation chromatograph (GPC) (GPC-8000 series, manufactured by Tosoh Corporation), detector: differential refractometer, column: TSKGEL SUPERMULTIPORE HZ-M manufactured by Tosoh Corporation. ) Based on standard polystyrene conversion.

(Structural identification of block copolymer)
The structure of the block copolymer was identified using an AV400 apparatus manufactured by BRUKER. From the measurement results, the styrene content of the copolymer was calculated.

(Production Example 1)
The autoclave equipped with a stirrer and a jacket was washed, dried and purged with nitrogen, and a cyclohexane solution (concentration 20% by mass) containing 10 parts by mass of styrene purified in advance was added. Then, after adding n-butyllithium and tetramethylethylenediamine and polymerizing at 70 ° C. for 1 hour, a cyclohexane solution containing 80 parts by mass of butadiene purified in advance (concentration 20% by mass) is added and polymerized at 70 ° C. for 1 hour, Furthermore, a cyclohexane solution (concentration 20% by mass) containing 10 parts by mass of styrene was added and polymerized at 70 ° C. for 1 hour. Thereafter, tetraglycidyl-1,3-bisaminomethylcyclohexane as a modifying agent was reacted in an equimolar ratio with n-butyllithium used for polymerization. Thereafter, alcohol was added to stop the reaction, and 1 g of 2,6-tert-butyl-p-cresol was added to the reaction solution, followed by reprecipitation purification to thereby modify modified styrene butadiene styrene triblock copolymer 1 (modified block copolymer). 1) was obtained. The resulting modified block copolymer 1 had a weight average molecular weight Mw of 100,000 and a styrene content of 28% by mass.

(Production Example 2)
The reaction was performed in the same manner as in Production Example 1 except that the modifier was changed to 1,3-dimethyl-2-imidazolidinone. The resulting modified block copolymer 2 had a weight average molecular weight Mw of 100,000 and a styrene content of 30% by mass.

(Production Example 3)
15 parts by weight of styrene charged first, 15 parts by weight of styrene charged last, 70 parts by weight of butadiene, and the modifier was changed to 3- (N, N-dimethylamino) propyltriethoxysilane The reaction was carried out in the same manner as in Production Example 1. The resulting modified block copolymer 3 had a weight average molecular weight Mw of 80,000 and a styrene content of 40% by mass.

(Reference Production Example 1)
The reaction was carried out in the same manner as in Production Example 1 except that no modifier was used. The obtained non-modified block copolymer had a weight average molecular weight Mw of 100,000 and a styrene content of 22% by mass.

Below, various chemical | medical agents used by the Example and the comparative example are demonstrated.
NR: RSS # 3
BR: UBEPOL BR150B manufactured by Ube Industries, Ltd. (cis content: 97% by mass, ML _{1 + 4} (100 ° C.): 40, Mw / Mn: 3.3)
Modified block copolymers 1-3: Synthetic unmodified block copolymers in the above production examples 1-3: Synthetic silica in the above reference production example 1: Ultrasil VN3 (N ₂ SA: 175 m ² / manufactured by EVONIK-DEGUSSA) g)
Carbon black: Diablack I (ISAF carbon, N ₂ SA: 114 m ² / g, average particle size: 23 nm, DBP oil absorption: 114 ml / 100 g) manufactured by Mitsubishi Chemical Corporation
Silane coupling agent: Si69 (bis (3-triethoxysilylpropyl) tetrasulfide) manufactured by EVONIK-DEGUSSA
Stearic acid: Stearic acid “paulownia” manufactured by NOF Corporation
Wax: Ozoace wax manufactured by Nippon Seisaku Co., Ltd. Mineral oil: Diana process oil manufactured by Idemitsu Kosan Co., Ltd. Nocrack 6C (N- (1,3-dimethylbutyl) -N-phenyl-p-phenylenediamine)
Sulfur: Powder sulfur vulcanization accelerator manufactured by Tsurumi Chemical Co., Ltd .: Noxeller NS (N-tert-butyl-2-benzothiazolylsulfenamide) manufactured by Ouchi Shinsei Chemical Co., Ltd.

In accordance with the formulation of Table 1, using a 1.7L Banbury mixer manufactured by Kobe Steel Co., Ltd., chemicals other than sulfur and a vulcanization accelerator were filled to a filling rate of 58%, and 140 ° C. at 80 rpm. Kneaded until reaching a kneaded product.
Next, using an open roll, sulfur and a vulcanization accelerator were added to the obtained kneaded material and kneaded to obtain an unvulcanized rubber composition. Further, the obtained unvulcanized rubber composition was molded into a predetermined size, and a vulcanized rubber composition was obtained by press vulcanization for 20 minutes at 150 ° C., and a vulcanization of about 2 mm × 130 mm × 130 mm was obtained. A rubber sheet was prepared and used as a test sample.
Further, the obtained unvulcanized rubber composition is molded into a tread shape, bonded to another tire member, and vulcanized at 170 ° C. for 15 minutes, whereby a test studless tire (tire size: 195 / 65R15) is obtained. ) Was produced.

The unvulcanized rubber composition, the vulcanized rubber sheet, and the test studless tire were evaluated by the methods shown below.

<Processability>
Based on JIS K6300-1, the Mooney viscosity (ML _{1 + 4} ) of the unvulcanized rubber composition was measured at 130 ° C., and the measurement result was displayed as an index by the following formula. The larger the index, the better the processability when unvulcanized.
(Processability index) = (Mooney viscosity of Comparative Example 1) / (Mooney viscosity of each formulation) × 100

<Low fuel consumption>
Using a viscoelastic spectrometer VES manufactured by Iwamoto Seisakusho, the loss tangent (tan δ) of the vulcanized rubber sheet was measured under conditions of a temperature of 70 ° C., an initial strain of 10%, a dynamic strain of 2%, and a frequency of 10 Hz. The measurement results were displayed as an index according to the following formula. The larger the index, the lower the rolling resistance and the better the fuel efficiency.
(Low fuel consumption index) = (tan δ of Comparative Example 1) / (tan δ of each formulation) × 100

<Performance on ice and snow (braking performance)>
A test studless tire was mounted on an actual vehicle, and the performance on ice and snow was evaluated under the following conditions. The test place was the Hokkaido Nayoro Test Course of Sumitomo Rubber Industries, Ltd. The temperature on ice was -1 to -6 ° C and the temperature on snow was -2 to -10 ° C.
Braking performance (on-ice braking stop distance): The stop distance on ice required to stop by stepping on the lock brake at 30 km / h was measured, and the measurement result was displayed as an index by the following formula. The larger the index, the better the braking performance (grip performance) on ice and snow.
(Performance index on ice and snow) = (stop distance of Comparative Example 1) / (stop distance of each formulation) × 100

<Abrasion resistance>
Wear amount of a sample made of vulcanized rubber sheet with a surface rotation speed of 50 m / min, an additional load of 3.0 kg, a falling sand amount of 15 g / min and a slip rate of 20%, using a Lambone abrasion tester manufactured by Iwamoto Seisakusho Co., Ltd. Was measured, and the measurement result was displayed as an index by the following formula. It shows that it is excellent in abrasion resistance, so that an index | exponent is large.
(Abrasion resistance index) = (Abrasion amount of Comparative Example 1) / (Abrasion amount of each formulation) × 100

As shown in Table 1, in Examples in which the modified block copolymer was blended, fuel economy, workability, wear resistance, and performance on ice and snow were improved in a well-balanced manner as compared with Comparative Example 1. In Example 3, although the performance on ice and snow is slightly reduced, there is no problem. Other performances are greatly improved beyond the decrease in performance on ice and snow, and the wear resistance is the best among the examples. there were.

Claims (8)

Natural rubber, butadiene rubber, and a modified block copolymer composed of a block segment of a styrene monomer unit and a block segment of a diene monomer unit and having a polar functional group,
The polar functional group is a functional group containing at least one selected from the group consisting of a nitrogen atom, an oxygen atom and a sulfur atom;
The modified block copolymer has a weight average molecular weight Mw of 10,000 to 200,000,
The rubber composition for tires whose content of the said modified block copolymer is 1-30 mass parts with respect to 100 mass parts of rubber components. The tire rubber composition according to claim 1, wherein the block segment of the diene monomer unit is a butadiene block. The tire rubber composition according to claim 1 or 2, wherein the modified block copolymer is a modified styrene-butadiene-styrene triblock copolymer. 2. The polar functional group is at least one selected from the group consisting of a hydroxyl group, an epoxy group, an amino group, an amide group, a silanol group, an alkoxysilane group, a cyano group, a carboxyl group, an ester group, and a mercapto group. The rubber composition for tires in any one of -3. The rubber composition for tires according to any one of claims 1 to 4 containing carbon black. The tire rubber composition according to claim 5, wherein the content of silica is 1 to 200 parts by mass and the content of the carbon black is 1 to 100 parts by mass with respect to 100 parts by mass of the rubber component. The rubber composition for tires according to any one of claims 1 to 6, wherein the content of the natural rubber is 20 to 90% by mass and the content of the butadiene rubber is 10 to 50% by mass in 100% by mass of the rubber component. . The pneumatic tire produced using the rubber composition in any one of Claims 1-7.