Rubber composition for tires and tires

Abstract

To provide a tire rubber composition that can achieve both tire fracture resistance and low fuel consumption. [Solution] The solution comprises a rubber component, a filler, and syndiotactic 1,2-polybutadiene, wherein the rubber component is cyclopentene and the following general formula (1): TIFF2026108473000007.tif55151 The product contains a copolymer with a norbornene-based compound represented by [formula], and the syndiotactic 1,2-polybutadiene has a crystalline weight of 7 to 40 J / g and a number-average molecular weight of 3.0 × 10⁻⁶. 4 The above-mentioned characteristics describe a rubber composition for tires.

Description

[Technical Field]

[0001] This invention relates to a rubber composition for tires and a tire. [Background technology]

[0002] In line with the growing global concern for environmental issues and the resulting global movement towards carbon dioxide emission regulations, there is a growing demand for more fuel-efficient automobiles. To meet this demand, tire performance is also required to improve fuel efficiency (i.e., reduce rolling resistance).

[0003] In contrast, Patent Documents 1 and 2 below disclose rubber compounding for passenger car tires and rubber compounding for heavy-duty truck and bus tires that include a specific long-chain branched cyclopentene ring-opening rubber (LCB-CPR). These rubber compoundings are said to be effective in reducing tire rolling resistance, improving wet skid resistance, and improving wear resistance. [Prior art documents] [Patent Documents]

[0004] [Patent Document 1] International Publication No. 2021 / 178233 [Patent Document 2] International Publication No. 2021 / 178235 [Overview of the project] [Problems that the invention aims to solve]

[0005] However, cyclopentene-based polymers, such as the cyclopentene ring-opening rubber disclosed in the above-mentioned Patent Documents 1 and 2, which are characterized by polymer entanglement, have high abrasion resistance but low fracture resistance. In contrast, it is generally possible to improve the fracture resistance of a rubber composition by adding natural rubber to the rubber composition, but the inventors have found that it is difficult to achieve both fracture resistance and low fuel consumption when blending natural rubber and cyclopentene-based polymers.

[0006] Therefore, the object of the present invention is to solve the problems of the above-mentioned prior art and to provide a rubber composition for tires that can achieve both tire fracture resistance and low fuel consumption. Furthermore, a further objective of the present invention is to provide a tire that achieves both resistance to damage and low fuel consumption. [Means for solving the problem]

[0007] The gist of the rubber composition for tires and the tire of the present invention, which solves the above problems, is as follows.

[0008] [1] comprising a rubber component, a filler, and syndiotactic 1,2-polybutadiene, The aforementioned rubber component is cyclopentene and the following general formula (1): [ka] [In the formula, R 1 ~R 4 Each of these independently represents a hydrogen atom, a hydrocarbon group having 1 to 20 carbon atoms, or a substituent containing a halogen atom, a silicon atom, an oxygen atom, or a nitrogen atom, and R 2 and R 3 These may be bonded together to form a ring, and m is an integer from 0 to 2. The copolymer includes a norbornene compound represented by ]. The aforementioned syndiotactic 1,2-polybutadiene has a crystalline weight of 7-40 J / g and a number-average molecular weight of 3.0 × 10⁻⁶ 4 A rubber composition for tires, characterized by the above. The tire rubber composition of the present invention described in [1] above, when applied to a tire, can achieve both tire fracture resistance and low fuel consumption.

[0009] [2] The tire rubber composition according to [1], wherein the content of the copolymer of cyclopentene and norbornene compound is 20 to 90 parts by mass per 100 parts by mass of the rubber component. The tire rubber composition described in [2] above can be applied to tires to improve the balance between fuel efficiency and wear resistance of the tires.

[0010] [3] The rubber composition for tires according to [1] or [2], wherein the copolymer of cyclopentene and norbornene compound has a weight-average molecular weight (Mw) of 200,000 to 1,000,000. The tire rubber composition described in [3] above can improve the fuel efficiency and wear resistance of tires when applied to them.

[0011] [4] The tire rubber composition according to any one of [1] to [3], wherein the norbornene compound represented by the general formula (1) above is 2-norbornene and / or dicyclopentadiene. Since 2-norbornene and dicyclopentadiene are readily available, and copolymers of cyclopentene and 2-norbornene and / or dicyclopentadiene are readily available, the tire rubber compositions described in [4] above are advantageous in terms of cost.

[0012] [5] The tire rubber composition according to any one of [1] to [4], wherein the copolymer of cyclopentene and norbornene-based compound has a content of 20 to 75% by mass of structural units derived from cyclopentene. The tire rubber composition described in [5] above can be applied to tires to improve their fuel efficiency and wear resistance.

[0013] [6] The tire rubber composition according to [4] or [5], wherein the copolymer of cyclopentene and norbornene compound has a content of 10 to 60% by mass of structural units derived from dicyclopentadiene. The tire rubber composition described in [6] above can be applied to tires to improve their fuel efficiency and wear resistance.

[0014] [7] The tire rubber composition according to any one of [1] to [6], wherein the rubber component further comprises isoprene backbone rubber and / or butadiene rubber. The tire rubber compositions described in [7] above can be applied to tires to improve tire fracture resistance, fuel efficiency, and wear resistance.

[0015] [8] The syndiotactic 1,2-polybutadiene has a number average molecular weight of 5.0 × 10 4 ~50.0×10 4 The tire rubber composition described in any one of [1] to [7]. The tire rubber composition described in [8] above can be applied to tires to improve tire fracture resistance and ride comfort.

[0016] [9] The tire rubber composition according to any one of [1] to [8], wherein the syndiotactic 1,2-polybutadiene has a degree of crystallinity of 15 to 60%. The tire rubber composition described in [9] above can improve the tire's resistance to damage when applied to a tire.

[0017]

[10] The tire rubber composition according to any one of [1] to [9], wherein the syndiotactic 1,2-polybutadiene has a melting point of 100 to 160°C. The tire rubber composition described in

[10] above can improve the tire's resistance to damage when applied to a tire.

[0018]

[11] The tire rubber composition according to any one of [1] to

[10] , wherein the syndiotactic 1,2-polybutadiene has a 1,2-bond content of 80% by mass or more. The tire rubber compositions described in

[11] above can improve the tire's resistance to damage when applied to a tire.

[0019]

[12] The tire rubber composition according to any one of [1] to

[11] , wherein the syndiotactic 1,2-polybutadiene has a syndiotacticity of 60% or more in the 1,2-bonds. The tire rubber compositions described in

[12] above can improve the tire's resistance to damage when applied to a tire.

[0020]

[13] The tire rubber composition according to any one of [1] to

[12] , wherein the content of the syndiotactic 1,2-polybutadiene is 1 to 40 parts by mass per 100 parts by mass of the rubber component. The tire rubber compositions described in

[13] above can be applied to tires to improve the fuel efficiency and resistance to damage of the tires.

[0021]

[14] A tire rubber composition according to any one of [1] to

[13] , comprising carbon black as the filler. The tire rubber compositions described in

[14] above can be applied to tires to improve their resistance to breakage and wear.

[0022]

[15] The tire rubber composition according to

[14] , wherein the carbon black content is 5 to 80 parts by mass per 100 parts by mass of the rubber component. The tire rubber compositions described above

[15] can be applied to tires to further improve the tire's resistance to damage, wear resistance, and fuel efficiency.

[0023] A tire characterized by comprising a tire rubber composition described in any one of [1] to

[15] . The tire of the present invention described in

[16] can achieve both high resistance to breakage and low fuel consumption.

Advantages of the Invention

[0024] According to the present invention, it is possible to provide a rubber composition for a tire capable of achieving both high resistance to breakage and low fuel consumption of the tire. Further, according to the present invention, it is possible to provide a tire having both high resistance to breakage and low fuel consumption.

Modes for Carrying Out the Invention

[0025] Hereinafter, the rubber composition for a tire and the tire of the present invention will be specifically illustrated and described based on their embodiments.

[0026] <Definition> The compounds described in this specification may be partially or entirely derived from fossil resources, may be derived from biological resources such as plant resources, or may be derived from recycled resources such as used tires. Further, it may be derived from a mixture of any two or more of fossil resources, biological resources, and recycled resources.

[0027] <Rubber Composition for Tire> The rubber composition for a tire of the present embodiment contains a rubber component, a filler, and syndiotactic 1,2-polybutadiene. And in the rubber composition for a tire of the present embodiment, the rubber component is cyclopentene and the following general formula (1):

Chemical formula

[0028] In the tire rubber composition of this embodiment, the copolymer of cyclopentene and norbornene-based compound is characterized not only by having crosslinking points but also by the entanglement of polymer chains. Generally, when a filler is blended with a rubber component, a reinforcing layer consisting of the filler and the rubber component is formed around the filler, and this reinforcing layer contributes to improving the reinforcing properties of the rubber composition, thereby improving abrasion resistance and other properties. Furthermore, in the tire rubber composition of this embodiment, the reinforcing layer formed around the filler is specifically increased due to the entanglement of the polymer chains as described above, thereby further improving wear resistance and other properties. In addition, in the tire rubber composition of this embodiment, the specific increase in the reinforcing layer due to the entanglement of the polymer chains of the copolymer of cyclopentene and norbornene compound reduces hysteresis loss and improves fuel efficiency. However, as mentioned above, the copolymer of cyclopentene and norbornene-based compounds has low fracture resistance, so when this copolymer is incorporated into a rubber composition, the fracture resistance of the rubber composition decreases. In contrast, the tire rubber composition of this embodiment has a crystal content of 7 to 40 J / g and a number average molecular weight of 3.0 × 10 4 By incorporating the syndiotactic 1,2-polybutadiene described above, the decrease in the fracture resistance of the rubber composition can be suppressed. Therefore, when the tire rubber composition of this embodiment is applied to a tire, it is possible to achieve both tire fracture resistance and low fuel consumption.

[0029] (Rubber component) The tire rubber composition of this embodiment contains a rubber component, which provides the composition with rubber elasticity. The rubber component of the tire rubber composition of this embodiment contains a copolymer of cyclopentene and a norbornene-based compound represented by the above general formula (1), and may further contain other rubbers.

[0030] -Copolymer of cyclopentene and norbornene-based compounds- The copolymer of cyclopentene and norbornene-based compound comprises structural units derived from cyclopentene and structural units derived from the norbornene-based compound represented by the general formula (1) above. In one preferred embodiment, the copolymer of cyclopentene and norbornene-based compound is a ring-opened copolymer, and more particularly, a cyclopentene ring-opened copolymer. In one preferred embodiment, the copolymer of cyclopentene and norbornene-based compound has a branched structure or a linear structure, and more particularly, a linear structure.

[0031] In the above general formula (1), R 1 ~R 4 Each of these independently represents a hydrogen atom, a hydrocarbon group having 1 to 20 carbon atoms, or a substituent containing a halogen atom, a silicon atom, an oxygen atom, or a nitrogen atom, and R 2 and R 3 These groups may bond to each other to form a ring, and m is an integer from 0 to 2. Examples of hydrocarbon groups having 1 to 20 carbon atoms include alkyl groups such as methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, neopentyl, hexyl, and octyl groups; alkenyl groups such as vinyl, allyl, 2-pentenyl, 3-pentenyl, and 4-methyl-3-pentenyl groups; aryl groups such as phenyl, tolyl, 2,6-dimethylphenyl, 2,6-diisopropylphenyl, and naphthyl groups; and aralkyl groups such as benzyl and phenethyl groups.

[0032] Examples of norbornene compounds represented by the above general formula (1) include 2-norbornene, 5-methyl-2-norbornene, 5-ethyl-2-norbornene, 5-butyl-2-norbornene, 5-hexyl-2-norbornene, 5-decyl-2-norbornene, 5-cyclohexyl-2-norbornene, 5-cyclopentyl-2-norbornene, 5-ethylidene-2-norbornene, 5-vinyl-2-norbornene, 5-propenyl-2-norbornene, 5-cyclohexenyl-2-norbornene, 5-cyclopentenyl-2-norbornene, 5-phenyl-2-norbornene, and tetracyclo[9.2.1.0 2,10 .0 3,8 ] Tetradeca-3,5,7,12-tetraene (also called "1,4-methano-1,4,4a,9a-tetrahydro-9H-fluorene"), tetracyclo[10.2.1.0 2,11 .0 4,9 ]Pentadeca-4,6,8,13-tetraene (also called "1,4-methano-1,4,4a,9,9a,10-hexahydroanthracene"), dicyclopentadiene, methyldicyclopentadiene, dihydrodicyclopentadiene ("tricyclo[5.2.1.0 2,6 Also called "deca-8-ene". Bicyclo[2.2.1]hepto-2-enes, which are unsubstituted or have hydrocarbon substituents, such as ) Tetracyclo[6.2.1.1 3,6 .0 2,7 ] Dodeca-4-ene, 9-methyltetracyclo[6.2.1.1 3,6 .0 2,7 ] Dodeca-4-ene, 9-ethyltetracyclo[6.2.1.1 3,6 .0 2,7 ] Dodeca-4-ene, 9-cyclohexyltetracyclo[6.2.1.1 3,6 .0 2,7 ] Dodeca-4-ene, 9-cyclopentyltetracyclo[6.2.1.1 3,6 .0 2,7 ] Dodeca-4-ene, 9-methylenetetracyclo[6.2.1.1 3,6 .0 2,7 ] Dodeca-4-ene, 9-ethylidenetetracyclo[6.2.1.1 3,6 .0 2,7] Dodeca-4-ene, 9-vinyltetracyclo[6.2.1.1 3,6 .0 2,7 ] Dodeca-4-ene, 9-propenyltetracyclo[6.2.1.1 3,6 .0 2,7 ] Dodeca-4-ene, 9-cyclohexenyltetracyclo[6.2.1.1 3,6 .0 2,7 ] Dodeca-4-ene, 9-cyclopentenyltetracyclo[6.2.1.1 3,6 .0 2,7 ] Dodeca-4-ene, 9-phenyltetracyclo[6.2.1.1 3,6 .0 2,7 ] Tetracyclo[6.2.1.1] unsubstituted or hydrocarbon substituents such as dodeca-4-ene 3,6 .0 2,7 Dodeca-4-enes; Bicyclo[2.2.1]hept-2-enes having an alkoxycarbonyl group, such as methyl 5-norbornene-2-carboxylate, ethyl 5-norbornene-2-carboxylate, methyl 2-methyl-5-norbornene-2-carboxylate, and ethyl 2-methyl-5-norbornene-2-carboxylate; Tetracyclo[6.2.1.1 3,6 .0 2,7 ] Dodeca-9-ene-4-carboxylate methyl, 4-methyltetracyclo[6.2.1.1 3,6 .0 2,7 ] Tetracyclo[6.2.1.1 3,6 .0 2,7 Dodeca-4-enes; Bicyclo[2.2.1]hept-2-ene compounds having a hydroxycarbonyl group or an acid anhydride group, such as 5-norbornene-2-carboxylic acid, 5-norbornene-2,3-dicarboxylic acid, and 5-norbornene-2,3-dicarboxylic acid anhydride; Tetracyclo[6.2.1.1 3,6 .0 2,7 ] Dodeca-9-ene-4-carboxylic acid, tetracyclo[6.2.1.1 3,6 .0 2,7 ] Dodeca-9-ene-4,5-dicarboxylic acid, tetracyclo[6.2.1.13,6 .0 2,7 ] Tetracyclo[6.2.1.1 3,6 .0 2,7 Dodeca-4-enes; Bicyclo[2.2.1]hept-2-enes having a hydroxyl group, such as 5-hydroxy-2-norbornene, 5-hydroxymethyl-2-norbornene, 5,6-di(hydroxymethyl)-2-norbornene, 5,5-di(hydroxymethyl)-2-norbornene, 5-(2-hydroxyethoxycarbonyl)-2-norbornene, and 5-methyl-5-(2-hydroxyethoxycarbonyl)-2-norbornene; Tetracyclo[6.2.1.1 3,6 .0 2,7 ] Dodeca-9-ene-4-methanol, tetracyclo[6.2.1.1 3,6 .0 2,7 ] Tetracyclo[6.2.1.1 3,6 .0 2,7 Dodeca-4-enes; Bicyclo[2.2.1]hept-2-ene compounds having a hydrocarbonyl group, such as 5-norbornene-2-carbaldehyde; Tetracyclo[6.2.1.1 3,6 .0 2,7 ] Tetracyclo[6.2.1.1] such as dodeca-9-ene-4-carbaldehyde, which have a hydrocarbonyl group. 3,6 .0 2,7 Dodeca-4-enes; Bicyclo[2.2.1]hept-2-ene compounds having an alkoxycarbonyl group and a hydroxycarbonyl group, such as 3-methoxycarbonyl-5-norbornene-2-carboxylic acid; Bicyclo[2.2.1]hept-2-ene compounds having a carbonyloxy group, such as 5-norbornene-2-yl acetate, 2-methyl-5-norbornene-2-yl acetate, 5-norbornene-2-yl acrylate, and 5-norbornene-2-yl methacrylate; 9-tetracycloacetic acid [6.2.1.1 3,6 .02,7 dodeca-4-enyl, 9-tetracyclo[6.2.1.1 3,6 .0 2,7 dodeca-4-enyl, 9-tetracyclo[6.2.1.1 3,6 .0 2,7 tetracyclo[6.2.1.1 having a carbonyloxy group such as dodeca-4-enyl 3,6 .0 2,7 dodeca-4-enes; Bicyclo[2.2.1]hept-2-enes having a functional group containing a nitrogen atom such as 5-norbornene-2-carbonitrile, 5-norbornene-2-carboxamide, 5-norbornene-2,3-dicarboxylic acid imide; tetracyclo[6.2.1.1 3,6 .0 2,7 dodeca-9-ene-4-carbonitrile, tetracyclo[6.2.1.1 3,6 .0 2,7 dodeca-9-ene-4-carboxamide, tetracyclo[6.2.1.1 3,6 .0 2,7 tetracyclo[6.2.1.1 having a functional group containing a nitrogen atom such as dodeca-9-ene-4,5-dicarboxylic acid imide 3,6 .0 2,7 dodeca-ene-4; Bicyclo[2.2.1]hept-2-enes having a halogen atom such as 5-chloro-2-norbornene; 9-chlorotetracyclo[6.2.1.1 3,6 .0 2,7 tetracyclo[6.2.1.1 having a halogen atom such as dodeca-4-ene 3,6 .0 2,7 [[ID=||45]]]dodeca-4-enes;[[ID=||]] [[ID=||47]]Bicyclo[2.2.1]hept-2-enes having a functional group containing a silicon atom such as 5-trimethoxysilyl-2-norbornene, 5-triethoxysilyl-2-norbornene;[[ID=||48]] [[ID=||49]]4-trimethoxysilyltetracyclo[6.2.1.1[[ID=||50]] 3,6 [[ID=||51]].0[[ID=||52]] 2,7 [[ID=||53]]]dodeca-9-ene, 4-triethoxysilyltetracyclo[6.2.1.1[[ID=||54]] 3,6 [[ID=||55]].0 It should be noted that there seems to be an error in the numbering of the line "" in the original text. It is repeated as "[[ID=||45]]" in the translation for the purpose of showing the corresponding relationship clearly. You may need to check and correct it according to the actual situation.2,7 tetracyclo[6.2.1.1 3,6 .0 2,7 dodeca-4-enes; etc. are exemplified. The norbornene-based compound may be used alone or in combination of two or more.

[0033] As the norbornene-based compound represented by the above general formula (1), in the above general formula (1), those in which m is 0 or 1 are preferable, and those in which m is 0 are more preferable. Further, in the above general formula (1), R 1 ~R 4 may be the same or different.

[0034] Among the norbornene-based compounds represented by the above general formula (1), from the viewpoints of low fuel consumption and abrasion resistance of the rubber composition, R 1 ~R 4 in the above general formula (1) is preferably a hydrogen atom, a linear hydrocarbon group having 1 to 20 carbon atoms, or a substituent containing a halogen atom, a silicon atom, an oxygen atom or a nitrogen atom. In this case, R 1 ~R 4 may be a group that does not bond to each other and does not form a ring, is not particularly limited, may be the same or different, and R 1 ~R 4 is preferably a hydrogen atom or an alkyl group having 1 to 3 carbon atoms. Also in this case, those in which m is 0 or 1 are preferable, and those in which m is 0 are more preferable. As the norbornene-based compound in which R 1 ~R 4 in the above general formula (1) is a hydrogen atom, a linear hydrocarbon group having 1 to 20 carbon atoms, or a substituent containing a halogen atom, a silicon atom, an oxygen atom or a nitrogen atom, bicyclo[2.2.1]hept-2-enes having an unsubstituted or hydrocarbon substituent are preferable, and among them, 2-norbornene is particularly preferable.

[0035] Further, as the norbornene-based compound represented by the above general formula (1), R 2 and R 3Compounds in which R and R are bonded to each other to form a ring are also preferred. Here, R 2 and R 3 Specific examples of ring structures formed by the bonding of these rings include cyclopentane rings, cyclopentene rings, cyclohexane rings, cyclohexene rings, and benzene rings, which may form polycyclic structures and may also have substituents. Among these, cyclopentane rings, cyclopentene rings, and benzene rings are preferred, and compounds having a cyclopentene ring alone, or compounds having a polycyclic structure of a cyclopentane ring and a benzene ring are particularly preferred. 2 , R 3 Other than R 1 , R 4 R may be the same or different, and is preferably a hydrogen atom or an alkyl group having 1 to 3 carbon atoms. In this case, it is also preferable that m is 0. 2 and R 3 As norbornene compounds in which these are bonded to each other to form a ring, bicyclo[2.2.1]hepto-2-enes are preferred, either unsubstituted or having hydrocarbon substituents, and among these, dicyclopentadiene is particularly preferred.

[0036] The copolymer of cyclopentene and norbornene compound preferably contains cyclopentene-derived structural units in a proportion of 20 to 75% by mass, more preferably 25 to 70% by mass, even more preferably 30 to 65% by mass, and particularly preferably 35 to 60% by mass, relative to the total repeating structural units of the copolymer. By setting the proportion of cyclopentene-derived structural units in the copolymer to a range of 20 to 75% by mass, the fuel efficiency and wear resistance of the rubber composition containing the copolymer can be improved, and by applying the rubber composition to a tire, the fuel efficiency and wear resistance of the tire can be improved.

[0037] The copolymer of cyclopentene and norbornene compound has a content of structural units derived from the norbornene compound represented by the general formula (1) that is preferably 10 to 80% by mass, more preferably 20 to 70% by mass, even more preferably 25 to 65% by mass, and particularly preferably 40 to 65% by mass, relative to the total repeating structural units of the copolymer. By setting the content of structural units derived from the norbornene compound represented by the general formula (1) in the copolymer to a range of 10 to 80% by mass, the fuel efficiency and wear resistance of the rubber composition containing the copolymer can be improved, and by applying the rubber composition to a tire, the fuel efficiency and wear resistance of the tire can be improved.

[0038] In the copolymer of cyclopentene and norbornene-based compound, the norbornene-based compound represented by the above general formula (1) is preferably 2-norbornene and / or dicyclopentadiene. Since 2-norbornene and dicyclopentadiene are readily available, copolymers of cyclopentene and 2-norbornene and / or dicyclopentadiene are readily available. Therefore, tire rubber compositions containing copolymers of cyclopentene and 2-norbornene and / or dicyclopentadiene are advantageous in terms of cost.

[0039] When 2-norbornene is used as the norbornene-based compound represented by the above general formula (1), the copolymer of cyclopentene and the norbornene-based compound preferably contains 10 to 60% by mass of structural units derived from 2-norbornene, and more preferably 20 to 60% by mass, relative to the total repeating structural units of the copolymer. By setting the content of structural units derived from 2-norbornene in the copolymer to a range of 10 to 60% by mass, the fuel efficiency and wear resistance of the rubber composition containing the copolymer can be improved, and by applying the rubber composition to a tire, the fuel efficiency and wear resistance of the tire can be improved.

[0040] When dicyclopentadiene is used as the norbornene compound represented by the above general formula (1), the copolymer of cyclopentene and the norbornene compound preferably has a content of dicyclopentadiene-derived structural units of 10 to 60% by mass, and more preferably 20 to 50% by mass, relative to the total repeating structural units of the copolymer. By setting the content of dicyclopentadiene-derived structural units in the copolymer to a range of 10 to 60% by mass, the fuel efficiency and wear resistance of the rubber composition containing the copolymer can be improved, and by applying the rubber composition to a tire, the fuel efficiency and wear resistance of the tire can be improved.

[0041] In one embodiment, a terpolymer of cyclopentene (CP), 2-norbornene (NB), and dicyclopentadiene (DCPD) may be used as the copolymer of cyclopentene and norbornene-based compounds. The terpolymer of cyclopentene, 2-norbornene, and dicyclopentadiene has a significant effect in improving the fuel efficiency of the rubber composition.

[0042] The copolymer of cyclopentene and norbornene compound may be copolymerized with other monomers that can copolymerize with cyclopentene and the norbornene compound represented by the general formula (1) above. Examples of such other monomers include cyclic monoolefins such as cyclopropene, cyclobutene, methylcyclopentene, cyclohexene, methylcyclohexene, cycloheptene, and cyclooctene; cyclic diolefins such as cyclohexadiene, methylcyclohexadiene, cyclooctadiene, and methylcyclooctadiene; and polycyclic cycloolefins having aromatic rings such as phenylcyclooctene, 5-phenyl-1,5-cyclooctadiene, and phenylcyclopentene. The content of structural units derived from other monomers in the copolymer of cyclopentene and norbornene compound is preferably 40% by mass or less, more preferably 30% by mass or less, relative to the total repeating structural units of the copolymer, and it is particularly preferable that structural units derived from other monomers are substantially absent.

[0043] The copolymer of cyclopentene and norbornene compound preferably has a weight-average molecular weight (Mw) of 200,000 to 1,000,000, more preferably 200,000 to 800,000, even more preferably 200,000 to 700,000, and particularly preferably 200,000 to 600,000. Copolymers with a weight-average molecular weight (Mw) in the range of 200,000 to 1,000,000 are easy to manufacture and have good processability (workability). Furthermore, by setting the weight-average molecular weight (Mw) of the copolymer to the range of 200,000 to 1,000,000, the fuel efficiency and wear resistance of the rubber composition containing the copolymer can be improved, and by applying the rubber composition to a tire, the fuel efficiency and wear resistance of the tire can be improved. Furthermore, the copolymer of cyclopentene and norbornene-based compound preferably has a ratio of weight-average molecular weight (Mw) to number-average molecular weight (Mn) (Mw / Mn, also called "molecular weight distribution") of 1.0 to 5.0, more preferably 1.5 to 2.9, even more preferably 1.5 to 2.5, and particularly preferably 1.5 to 2.3. Here, the weight-average molecular weight (Mw) and number-average molecular weight (Mn) of the copolymer are polystyrene-converted values ​​measured by gel permeation chromatography (GPC).

[0044] The copolymer of cyclopentene and norbornene-based compound preferably has a cis / trans ratio of 0 / 100 to 60 / 40, more preferably 5 / 95 to 55 / 45, even more preferably 10 / 90 to 50 / 50, and particularly preferably 15 / 85 to 39 / 61. The cis / trans ratio is the ratio of cis to trans structures of double bonds present in the repeating units constituting the copolymer of cyclopentene and norbornene-based compound. By setting the cis / trans ratio of the copolymer within the above range, the fuel efficiency and wear resistance of the rubber composition containing the copolymer can be improved, and by applying the rubber composition to a tire, the fuel efficiency and wear resistance of the tire can be improved.

[0045] The copolymer of cyclopentene and norbornene compound has a glass transition temperature (Tg) preferably -80°C to 10°C, more preferably -75°C to 0°C, and even more preferably -70°C to -10°C. By setting the glass transition temperature (Tg) of the copolymer within the above range, the fuel efficiency and wear resistance of the rubber composition containing the copolymer can be improved, and by applying the rubber composition to a tire, the fuel efficiency and wear resistance of the tire can be improved. The glass transition temperature of the copolymer can be controlled, for example, by adjusting the type and amount of norbornene compound used. Here, the glass transition temperature (Tg) of the copolymer was measured using a differential scanning calorimeter (DSC) with a heating rate of 10°C / min.

[0046] The copolymer of cyclopentene and norbornene compound may have a modifying group at the end of the polymer chain. Having such a terminal modifying group can further increase the affinity to the filler, improve the dispersibility of the filler in the rubber composition, and as a result, further improve the processability (workability), fuel efficiency, and abrasion resistance of the rubber composition. The modifying group to be introduced at the end of the polymer chain of the copolymer is not particularly limited, but a modifying group containing an atom selected from the group consisting of atoms of Group 15 of the periodic table, atoms of Group 16 of the periodic table, and silicon atoms is preferred. As a modifying group for forming the terminal modifying group, a modifying group containing an atom selected from the group consisting of nitrogen atoms, oxygen atoms, phosphorus atoms, sulfur atoms, and silicon atoms is more preferred from the viewpoint of increasing the affinity to the filler, and among these, a modifying group containing an atom selected from the group consisting of nitrogen atoms, oxygen atoms, and silicon atoms is even more preferred.

[0047] Modified groups containing a nitrogen atom include amino groups, pyridyl groups, imino groups, amide groups, nitro groups, urethane bonding groups, or hydrocarbon groups containing any of these groups. Modified groups containing an oxygen atom include hydroxyl groups, carboxylic acid groups, ether groups, ester groups, carbonyl groups, aldehyde groups, epoxy groups, or hydrocarbon groups containing any of these groups. Modified groups containing a silicon atom include alkylsilyl groups, oxysilyl groups, or hydrocarbon groups containing any of these groups. Modified groups containing a phosphorus atom include phosphoric acid groups, phosphino groups, or hydrocarbon groups containing any of these groups. Modified groups containing a sulfur atom include sulfonyl groups, thiol groups, thioether groups, or hydrocarbon groups containing any of these groups. Furthermore, the modified group may contain multiple of the above-mentioned groups. Among these, from the viewpoint of further improving the processability (workability), fuel efficiency, and abrasion resistance of the rubber composition, amino groups, pyridyl groups, imino groups, amide groups, hydroxyl groups, carboxylic acid groups, aldehyde groups, epoxy groups, oxysilyl groups, or hydrocarbon groups containing any of these groups are preferred, and from the viewpoint of affinity to fillers (especially silica, etc.), oxysilyl groups are particularly preferred. Here, an oxysilyl group refers to a group having a silicon-oxygen bond.

[0048] Examples of the oxysilyl group include alkoxysilyl groups, aryloxysilyl groups, acyloxy groups, alkylsiloxysilyl groups, and arylsiloxysilyl groups. Furthermore, hydroxysilyl groups obtained by hydrolysis of alkoxysilyl groups, aryloxysilyl groups, or acyloxy groups can also be mentioned. Among these, alkoxysilyl groups are preferred from the viewpoint of affinity for silica. The alkoxysilyl group is a group formed by one or more alkoxy groups bonded to a silicon atom. Specific examples include trimethoxysilyl groups, dimethoxymethylsilyl groups, methoxydimethylsilyl groups, methoxydichlorosilyl groups, triethoxysilyl groups, diethoxymethylsilyl groups, ethoxydimethylsilyl groups, dimethoxyethoxysilyl groups, methoxydiethoxysilyl groups, and tripropoxysilyl groups.

[0049] The proportion of modified groups introduced at the polymer chain ends of the copolymer of cyclopentene and norbornene-based compound is not particularly limited, but it is preferably 10% or more, more preferably 20% or more, even more preferably 30% or more, and particularly preferably 40% or more, as a percentage of the number of copolymer chain ends with modified groups / total number of copolymer chain ends. A higher proportion of terminal modified groups is preferable because it increases the affinity to the filler. The method for measuring the proportion of modified groups introduced at the polymer chain ends is not particularly limited, but an example is when an oxysilyl group is introduced as the terminal modified group. 1 It can be determined from the peak area ratio corresponding to the oxysilyl group, which is obtained by 1H-NMR spectroscopy, and the number-average molecular weight (Mn) obtained from gel permeation chromatography (GPC).

[0050] The copolymer of cyclopentene and norbornene-based compound has a Mooney viscosity (ML). 1+4 The temperature (100°C) is preferably 20 to 150°C, more preferably 22 to 120°C, and particularly preferably 25 to 90°C. Here, the Mooney viscosity of the copolymer (ML) 1+4 The values ​​(100°C) were measured according to JIS K6300.

[0051] The method for producing the copolymer of cyclopentene and norbornene-based compound is not particularly limited, but one example is a method of copolymerizing cyclopentene and a norbornene-based compound represented by the above general formula (1) in the presence of a ring-opening polymerization catalyst.

[0052] The ring-opening polymerization catalyst is not particularly limited as long as it can perform ring-opening copolymerization between cyclopentene and a norbornene-based compound represented by the general formula (1) above, but ruthenium carbene complexes and Group 6 transition metal compounds of the periodic table containing halogen atoms (hereinafter also referred to as "Group 6 transition metal compounds of the periodic table") are preferred. These ring-opening polymerization catalysts may be used individually or in combination of two or more.

[0053] The ruthenium carbene complexes include bis(tricyclohexylphosphine)benzylidene ruthenium dichloride, bis(triphenylphosphine)-3,3-diphenylpropenylidene ruthenium dichloride, bis(tricyclohexylphosphine)t-butylvinylidene ruthenium dichloride, dichloro-(3-phenyl-1H-indene-1-ylidene)bis(tricyclohexylphosphine)ruthenium, bis(1,3-diisopropylimidazoline-2-ylidene)benzylidene ruthenium dichloride, and bis(1,3-dicyclohexylimidazoline-2-ylidene). Examples include (dazoline-2-ylidene)benzylidene ruthenium dichloride, (1,3-dimethylimidazoline-2-ylidene)(tricyclohexylphosphine)benzylidene ruthenium dichloride, (1,3-dimethylimidazolidin-2-ylidene)(tricyclohexylphosphine)benzylidene ruthenium dichloride, bis(tricyclohexylphosphine)ethoxymethylidene ruthenium dichloride, and (1,3-dimethylimidazolidin-2-ylidene)(tricyclohexylphosphine)ethoxymethylidene ruthenium dichloride.

[0054] The aforementioned Group 6 transition metal compounds are compounds having a Group 6 transition metal atom of the periodic table (long-period periodic table, the same applies hereinafter), specifically, compounds having a chromium atom, a molybdenum atom, or a tungsten atom. Compounds having a molybdenum atom or a tungsten atom are preferred, and compounds having a tungsten atom are more preferred from the viewpoint of high solubility in cyclopentene. Specific examples of the aforementioned Group 6 transition metal compounds include molybdenum compounds such as molybdenum pentachloride, molybdenum oxotetrachloride, and molybdenum (phenylimide) tetrachloride; and tungsten compounds such as tungsten hexachloride, tungsten oxotetrachloride, tungsten (phenylimide) tetrachloride, monocatecollate tungsten tetrachloride, bis(3,5-diter-butyl)catecollate tungsten dichloride, and bis(2-chloroetherate) tetrachloride.

[0055] The amount of the ring-opening polymerization catalyst used is typically in the range of 1:500 to 1:2,000,000, preferably 1:700 to 1:1,500,000, and more preferably 1:1,000 to 1:1,000,000, in terms of the molar ratio of (ring-opening polymerization catalyst: monomer used for copolymerization). When using a Group 6 transition metal compound, the amount of the Group 6 transition metal compound used is preferably in the range of 1:100 to 1:200,000, more preferably 1:200 to 1:150,000, and even more preferably 1:500 to 1:100,000, in terms of the molar ratio of "Group 6 transition metal atom in the ring-opening polymerization catalyst: monomer used for ring-opening polymerization".

[0056] When using the Group 6 transition metal compound of the periodic table as the ring-opening polymerization catalyst, it is preferable to use it in combination with the organoaluminum compound represented by the following general formula (2). The organoaluminum compound acts as a ring-opening polymerization catalyst together with the Group 6 transition metal compound of the periodic table described above. (R 5 ) 3-x Al(OR 6 ) x ... (2) In the above general formula (2), R5 and R 6 are each independently a hydrocarbon group having 1 to 20 carbon atoms, preferably a hydrocarbon group having 1 to 10 carbon atoms. Also, x satisfies 0 < x < 3.

[0057] In the general formula (2) above, R 5 and R 6 include alkyl groups such as methyl group, ethyl group, isopropyl group, n-propyl group, isobutyl group, n-butyl group, t-butyl group, n-hexyl group, cyclohexyl group, n-octyl group, n-decyl group; aryl groups such as phenyl group, 4-methylphenyl group, 2,6-dimethylphenyl group, 2,6-diisopropylphenyl group, naphthyl group; and the like.

[0058] Also, in the general formula (2) above, x satisfies 0 < x < 3. That is, in the general formula (2), the composition ratios of R 5 and OR 6 can each take any value within the ranges of 0 < 3 - x < 3 and 0 < x < 3, respectively. However, from the perspective of enhancing the polymerization activity, x is preferably 0.5 < x < 1.5.

[0059] The organoaluminum compound represented by the general formula (2) above can be synthesized, for example, by reacting a trialkylaluminum with an alcohol as shown in the following general formula (3). (R 5 )3Al + xR 6 OH → (R 5 ) 3-x Al(OR[[ID=三十二]] 6 ) x + (R 6 ) x H ··· (3)

[0060] Note that x in the general formula (2) above can be arbitrarily controlled by defining the reaction ratio of the corresponding trialkylaluminum and alcohol as shown in the general formula (3).

[0061] The amount of the organoaluminum compound used varies depending on the type of organoaluminum compound used, but is preferably 0.1 to 100 moles, more preferably 0.2 to 50 moles, and even more preferably 0.5 to 20 moles, relative to the Group 6 transition metal atoms constituting the Group 6 transition metal compound. If the amount of organoaluminum compound used is too small, the polymerization activity may be insufficient, and if it is too large, side reactions tend to occur more easily during ring-opening polymerization.

[0062] The polymerization reaction may be carried out in a solvent-free environment or in a solution. When copolymerizing in a solution, the solvent used is not particularly limited as long as it is inert in the polymerization reaction and capable of dissolving cyclopentene, norbornene compounds represented by the general formula (1) above, polymerization catalysts, etc. used in copolymerization, but it is preferable to use a hydrocarbon solvent or a halogen solvent. Examples of hydrocarbon solvents include aromatic hydrocarbons such as benzene, toluene, xylene, and ethylbenzene; aliphatic hydrocarbons such as hexane, n-heptane, and n-octane; and alicyclic hydrocarbons such as cyclohexane, cyclopentane, and methylcyclohexane. Examples of halogen solvents include haloalkanes such as dichloromethane and chloroform; and aromatic halogens such as chlorobenzene and dichlorobenzene. These solvents may be used individually or in mixtures of two or more.

[0063] When copolymerizing cyclopentene with a norbornene-based compound represented by the above general formula (1), an olefin compound or diolefin compound may be added to the polymerization reaction system as a molecular weight adjuster to adjust the molecular weight of the resulting copolymer, if necessary. The olefin compound is not particularly limited as long as it is an organic compound having an ethylenically unsaturated bond, and examples include α-olefins such as 1-butene, 1-pentene, 1-hexene, and 1-octene; styrenes such as styrene and vinyltoluene; halogen-containing vinyl compounds such as allyl chloride; alkenyl alcohols such as allyl alcohol and 5-hexenol; silicon-containing vinyl compounds such as allyltrimethoxysilane, allyltriethoxysilane, allyltrichlorosilane, and styryltrimethoxysilane; and disubstituted olefins such as 2-butene and 3-hexene. In addition, examples of the diolefin compound include non-conjugated diolefins such as 1,4-pentadiene, 1,4-hexadiene, 1,5-hexadiene, 1,6-heptadiene, 2-methyl-1,4-pentadiene, and 2,5-dimethyl-1,5-hexadiene. The amount of olefin and diolefin compounds used as molecular weight adjusters can be appropriately selected according to the molecular weight of the copolymer to be produced, but the molar ratio is usually in the range of 1 / 100 to 1 / 100,000, preferably 1 / 200 to 1 / 50,000, and more preferably 1 / 500 to 1 / 10,000, relative to the monomer used in copolymerization.

[0064] Furthermore, when the copolymer of cyclopentene and norbornene-based compounds has a modifying group at the polymer chain end, it is preferable to use a modifying group-containing olefinic unsaturated hydrocarbon compound as a molecular weight adjuster instead of the olefin or diolefin compounds mentioned above. By using a modifying group-containing olefinic unsaturated hydrocarbon compound, the modifying group can be suitably introduced at the polymer chain end of the copolymer obtained by copolymerization. The modifying group-containing olefinic unsaturated hydrocarbon compound is not particularly limited and can be any compound that has a modifying group and one olefinic carbon-carbon double bond that is metathesis reactive. For example, if it is desired to introduce an oxysilyl group at the polymer chain end of the copolymer, an oxysilyl group-containing olefinic unsaturated hydrocarbon can be present in the polymerization reaction system.

[0065] Examples of the oxysilyl group-containing olefinic unsaturated hydrocarbons include alkoxysilane compounds such as vinyltrimethoxysilane, vinyltriethoxysilane, allyltrimethoxysilane, allylmethoxydimethylsilane, allyltriethoxysilane, allylethoxydimethylsilane, styryltrimethoxysilane, styryltriethoxysilane, styrylethyltriethoxysilane, allyltriethoxysilylmethyl ether, and allyltriethoxysilylmethylethylamine, which introduce a modifying group to only one end (one end) of the polymer chain of the copolymer; vinyltriphenoxysilane, allyltriphenoxysilane, ali Examples include aryloxysilane compounds such as ruphenoxydimethylsilane; asiloxilane compounds such as vinyltriacetoxysilane, allyltriacetoxysilane, allyldiacetoxymethylsilane, and allylacetoxydimethylsilane; alkylsiloxysilane compounds such as allyltris(trimethylsiloxy)silane; arylsiloxysilane compounds such as allyltris(triphenylsiloxy)silane; and polysiloxane compounds such as 1-allylheptamethyltrisiloxane, 1-allylnonamethyltetrasiloxane, 1-allylnonamethylcyclopentasiloxane, and 1-allylundecamethylcyclohexasiloxane. Furthermore, modifying groups are introduced to both ends (both terminals) of the polymer chain of the copolymer, such as alkoxysilane compounds like bis(trimethoxysilyl)ethylene, bis(triethoxysilyl)ethylene, 2-butene-1,4-di(trimethoxysilane), 2-butene-1,4-di(triethoxysilane), and 1,4-di(trimethoxysilylmethoxy)-2-butene; aryloxysilane compounds like 2-butene-1,4-di(triphenoxysilane); and 2-butene Examples include acyloxysilane compounds such as -1,4-di(triacetoxysilane); alkylsiloxysilane compounds such as 2-buten-1,4-di[tris(trimethylsiloxy)silane]; arylsiloxysilane compounds such as 2-buten-1,4-di[tris(triphenylsiloxy)silane]; and polysiloxane compounds such as 2-buten-1,4-di(heptamethyltrisiloxane) and 2-buten-1,4-di(undecamethylcyclohexasiloxane).

[0066] The aforementioned olefinic unsaturated hydrocarbon compound containing the modifying group acts not only to introduce the modifying group to the polymer chain ends of the copolymer, but also as a molecular weight adjuster. Therefore, the amount of the olefinic unsaturated hydrocarbon compound containing the modifying group used can be appropriately selected according to the molecular weight of the copolymer to be produced, but the molar ratio with respect to the monomer used in copolymerization is usually in the range of 1 / 100 to 1 / 100,000, preferably 1 / 200 to 1 / 50,000, and more preferably 1 / 500 to 1 / 10,000.

[0067] The polymerization reaction temperature is not particularly limited, but is preferably -100°C or higher, more preferably -50°C or higher, even more preferably 0°C or higher, and especially preferably 20°C or higher. The upper limit of the polymerization reaction temperature is not particularly limited, but is preferably less than 120°C, more preferably less than 100°C, even more preferably less than 90°C, and especially preferably less than 80°C. The polymerization reaction time is not particularly limited, but is preferably 1 minute to 72 hours, more preferably 10 minutes to 20 hours.

[0068] The copolymer obtained by the polymerization reaction may optionally contain antioxidants such as phenolic stabilizers, phosphorus-based stabilizers, or sulfur-based stabilizers. The amount of antioxidant added should be determined appropriately depending on its type and other factors. Furthermore, the copolymer may optionally contain a spreading oil. When the copolymer is obtained as a polymerization solution, known recovery methods can be used to recover the copolymer from the polymerization solution. For example, a method can be used in which the solvent is separated by steam stripping, the solid is filtered off, and then the solid is dried to obtain a solid copolymer.

[0069] The content of the copolymer of cyclopentene and norbornene compound is preferably 20 to 90 parts by mass, and more preferably 30 to 85 parts by mass, per 100 parts by mass of the rubber component. When the content of the copolymer of cyclopentene and norbornene compound is in the range of 20 to 90 parts by mass per 100 parts by mass of the rubber component, the balance between the low fuel consumption and wear resistance of the rubber composition is further improved, and by applying this rubber composition to a tire, the balance between the low fuel consumption and wear resistance of the tire can be improved.

[0070] -Other rubber- The aforementioned rubber component may further contain other rubbers. Diene rubbers are preferred as such other rubbers. Examples of such diene rubbers include isoprene skeleton rubber, butadiene rubber (BR), styrene-butadiene rubber (SBR), and chloroprene rubber (CR). Other rubbers besides diene rubbers include fluororubber, silicone rubber, and urethane rubber. The content of these other rubbers is preferably 80 parts by mass or less, more preferably 70 parts by mass or less, and even more preferably 60 parts by mass or less, per 100 parts by mass of the rubber component.

[0071] The rubber component preferably includes isoprene skeleton rubber and / or butadiene rubber as the other rubber. Including isoprene skeleton rubber in the rubber component can improve the fracture resistance of the rubber composition. Furthermore, including butadiene rubber in the rubber component can further improve the fuel efficiency and abrasion resistance of the rubber composition. Therefore, by applying a rubber composition containing isoprene skeleton rubber and / or butadiene rubber to a tire, the fracture resistance, or fuel efficiency and abrasion resistance of the tire can be improved. The total content of isoprene skeleton rubber and butadiene rubber is preferably in the range of 10 to 80 parts by mass, more preferably in the range of 15 to 70 parts by mass, and even more preferably in the range of 20 to 60 parts by mass, per 100 parts by mass of the rubber component.

[0072] --Isoprene skeletal rubber-- The isoprene-backed rubber is a rubber whose main backbone is isoprene units, and specifically includes natural rubber (NR), synthetic isoprene rubber (IR), and the like. Including isoprene-backed rubber in the rubber component can improve the fracture resistance of the rubber composition, and can also improve the fracture resistance of tires to which the rubber composition is applied. Furthermore, blending the isoprene-backed rubber with a copolymer of cyclopentene and norbornene-based compounds and using it in the rubber composition can improve the abrasion resistance of the rubber composition. The content of the isoprene skeleton rubber is preferably 10 to 80 parts by mass, more preferably 15 to 70 parts by mass, and even more preferably in the range of 20 to 60 parts by mass per 100 parts by mass of the rubber component. When the content of the isoprene skeleton rubber is in the range of 10 to 80 parts by mass per 100 parts by mass of the rubber component, the balance between the low fuel consumption and abrasion resistance of the rubber composition is further improved.

[0073] --Butadiene rubber-- The aforementioned butadiene rubber has a low glass transition temperature (Tg), and by including butadiene rubber in addition to the copolymer of cyclopentene and norbornene-based compounds mentioned above, the low fuel consumption and abrasion resistance of the rubber composition can be further improved. When the rubber component includes butadiene rubber, the content of the butadiene rubber is preferably in the range of 10 to 80 parts by mass, more preferably in the range of 15 to 70 parts by mass, and even more preferably in the range of 20 to 60 parts by mass, per 100 parts by mass of the rubber component. When the content of butadiene rubber is in the range of 10 to 80 parts by mass per 100 parts by mass of the rubber component, the balance between the low fuel consumption and abrasion resistance of the rubber composition is further improved.

[0074] (Filler) The tire rubber composition of this embodiment includes a filler. The inclusion of a filler improves the reinforcing properties of the rubber composition. Examples of fillers include carbon black, silica, clay, talc, calcium carbonate, and aluminum hydroxide, among which carbon black is preferred.

[0075] The content of the filler is preferably in the range of 5 to 80 parts by mass per 100 parts by mass of the rubber component. If the content of the filler is 5 parts by mass or more per 100 parts by mass of the rubber component, the abrasion resistance of the rubber composition is further improved, and if it is 80 parts by mass or less, the fuel efficiency of the rubber composition is further improved. From the viewpoint of abrasion resistance, the content of the filler is more preferably 10 parts by mass or more per 100 parts by mass of the rubber component, and more preferably 20 parts by mass or more. From the viewpoint of fuel efficiency, it is more preferably 70 parts by mass or less, and more preferably 60 parts by mass or less.

[0076] -Carbon Black- The tire rubber composition of this embodiment preferably contains carbon black as a filler. Since carbon black has a significant effect in reinforcing the rubber composition and improving its fracture resistance and abrasion resistance, applying a tire rubber composition containing carbon black as a filler to a tire can improve the fracture resistance and abrasion resistance of the tire. The carbon black used is not particularly limited and includes, for example, GPF, FEF, HAF, ISAF, and SAF grade carbon blacks. These carbon blacks may be used individually or in combination of two or more types.

[0077] The carbon black content is preferably in the range of 5 to 80 parts by mass per 100 parts by mass of the rubber component. When the carbon black content is 5 parts by mass or more per 100 parts by mass of the rubber component, the fracture resistance and abrasion resistance of the rubber composition are further improved, and when it is 80 parts by mass or less, the fuel efficiency of the rubber composition is further improved. Therefore, a tire rubber composition with a carbon black content of 5 to 80 parts by mass per 100 parts by mass of the rubber component has further improved fracture resistance, abrasion resistance and fuel efficiency, and by applying this rubber composition to a tire, the fracture resistance, abrasion resistance and fuel efficiency of the tire can be further improved. From the viewpoint of fracture resistance and abrasion resistance, the carbon black content is more preferably 10 parts by mass or more per 100 parts by mass of the rubber component, and more preferably 20 parts by mass or more, and from the viewpoint of fuel efficiency, more preferably 70 parts by mass or less, and more preferably 60 parts by mass or less.

[0078] The proportion of carbon black in the filler is preferably 70% by mass or more, more preferably 80% by mass or more, even more preferably 90% by mass or more, and may also be 100% by mass, from the viewpoint of the fracture resistance and abrasion resistance of the rubber composition.

[0079] (Syndiotactic 1,2-polybutadiene) The tire rubber composition of this embodiment contains syndiotactic 1,2-polybutadiene. In the tire rubber composition of this embodiment, the syndiotactic 1,2-polybutadiene has a crystalline content of 7 to 40 J / g and a number average molecular weight of 3.0 × 10⁻¹⁴ 4 That concludes the explanation. Note that the syndiotactic 1,2-polybutadiene is a crystalline polymer (resin) and is not included in the rubber component.

[0080] In the rubber composition of this embodiment, preferably, after vulcanization, a structure (so-called double network structure) is formed in which syndiotactic 1,2-polybutadiene (hereinafter sometimes referred to as "sPB") forms a mesh-like three-dimensional network within the matrix of the rubber component. The sPB is a type of crystalline polymer, and under high strain, its crystals undergo sacrificial fracture, which dissipates input energy. Furthermore, since the sPB also has the property of being compatible with the rubber component, it becomes possible to partially immobilize the sPB within the rubber component, and a three-dimensional network (double network) consisting of the crystalline portion of sPB and the rubber component / sPB compatible portion can be formed in the vulcanized rubber. As a result of this double network structure, a high energy dissipation effect due to the crystalline portion of sPB and flexibility due to the rubber component / sPB compatible portion can be obtained, and the rubber composition of this embodiment can achieve good fracture resistance.

[0081] The syndiotactic 1,2-polybutadiene has a crystalline content of 7 to 40 J / g. By setting the crystalline content of sPB to 7 J / g or more, the double network described above can be more reliably formed in the rubber composition after vulcanization, and the fracture resistance of the rubber composition after vulcanization can be improved. From a similar viewpoint, the crystalline content of sPB is preferably 15 J / g or more, and more preferably 17 J / g or more. On the other hand, if the crystalline content of sPB is too large, the melting point of sPB becomes too high, making it difficult to achieve the vulcanization temperature necessary to form the double network, or if the crystalline content is too large, the crystals may act as fracture nuclei, causing the elongation at break of the rubber to tend to decrease. From this viewpoint, the crystalline content is 40 J / g or less, preferably 36 J / g or less, and more preferably 31 J / g or less. The crystallization amount of sPB refers to the heat of fusion, and is an indicator of the proportion of sPB that has crystallized. The crystallization amount of sPB can be derived from the melting peak measured by a differential scanning calorimeter.

[0082] The aforementioned syndiotactic 1,2-polybutadiene has a number-average molecular weight (Mn) of 3.0 × 10⁻⁶4 That is all. The number average molecular weight of the aforementioned sPB is 3.0 × 10 4 As a result, the double network described above can be more reliably formed in the rubber composition after vulcanization, and the fracture resistance after vulcanization can be improved. Furthermore, from the viewpoint of further improving the fracture resistance after vulcanization, the number average molecular weight of sPB is 5.0 × 10 4 The above is 6.5 × 10 4 The above is 8.0 x 10 4 The above is 10.0 × 10 4 The above is 11.0 × 10 4 The above is 12.0 × 10 4 The above is 13.0 × 10 4 The above is 14.0 × 10 4 The above is 15.0 × 10 4 The above is 16.0 × 10 4 The above is 17.0 x 10 4 The above is 17.9 × 10 4 The above is 18.0 x 10 4 The above is 19.0 x 10 4 The above is 20.0 × 10 4 This can be done. On the other hand, the number-average molecular weight of the aforementioned sPB is set to 50.0 × 10 from the viewpoint of preventing fracture resistance after thermal degradation and a decrease in ride comfort when applied to tires. 4 The following is preferable. Furthermore, from the viewpoint of preventing fracture resistance after thermal degradation and a decrease in ride comfort when applied to tires, the number average molecular weight of the sPB is 40.0 × 10 4 Below, 39.0 × 10 4 Below, 38.0 × 10 4 Below, 37.0 × 10 4 Below, 36.0 × 10 4 Below, 35.0 × 10 4 Below, 34.7 × 10 4 Below, 34.0 × 10 4 Below, 33.0 × 10 4 Below, 32.0 × 10 4 Below, 31.0 × 10 4 Below, 30.0 × 10 4 The following is possible: The aforementioned syndiotactic 1,2-polybutadiene has a number-average molecular weight of 5.0 × 10⁻⁶ 4~50.0×10 4 It is preferable that the number average molecular weight is 5.0 × 10⁻⁶. 4 ~50.0×10 4 The tire rubber composition containing spPB has further improved fracture resistance, and when applied to tires, it can improve the fracture resistance and ride comfort of the tires.

[0083] The syndiotactic 1,2-polybutadiene preferably has a crystallinity of 15-60%. A crystallinity of 15-60% facilitates the formation of a double network, improving the fracture resistance of the rubber composition, and applying this rubber composition to a tire can improve the fracture resistance of the tire. From the viewpoint of fracture resistance, a crystallinity of 25-50% is even more preferable for the syndiotactic 1,2-polybutadiene.

[0084] The syndiotactic 1,2-polybutadiene preferably has a melting point of 100 to 160°C. A tire rubber composition containing sPB with a melting point of 100 to 160°C has improved fracture resistance, and applying this rubber composition to a tire can improve the fracture resistance of the tire. By setting the melting point of sPB to 160°C or lower, the crystallization of sPB is facilitated during the vulcanization of the rubber composition, and the double network described above can be more reliably formed in the rubber composition after vulcanization. On the other hand, by setting the melting point of sPB to 100°C or higher, it is possible to suppress the decrease in heat resistance and strength of the vulcanized rubber. From a similar viewpoint, the melting point of sPB can be 110°C or higher, or 120°C or higher.

[0085] The syndiotactic 1,2-polybutadiene preferably has a 1,2-bond content (amount of 1,2-bonds in the microstructure of sPB) of 80% by mass or more, and more preferably 85% by mass or more. When the 1,2-bond content of the syndiotactic 1,2-polybutadiene is 80% by mass or more, the double network described above can be formed more reliably in the rubber composition after vulcanization, improving the fracture resistance of the rubber composition, and when the rubber composition is applied to a tire, the fracture resistance of the tire can be improved. From the viewpoint of fracture resistance, the 1,2-bond content of sPB can also be 90% by mass or more, 91% by mass or more, 92% by mass or more, 93% by mass or more, 94% by mass or more, or 95% by mass or more. Furthermore, the 1,2-bonded content of the aforementioned spPB is 1 H and 13 It can be determined by 13C nuclear magnetic resonance (NMR) analysis.

[0086] The syndiotactic 1,2-polybutadiene preferably has a syndiotacticity of 60% or more in the 1,2-bonds, and more preferably 65% ​​or more. When the syndiotacticity in the 1,2-bonds of the syndiotactic 1,2-polybutadiene is 60% or more, the above-mentioned double network can be formed more reliably in the rubber composition after vulcanization, improving the fracture resistance of the rubber composition, and when the rubber composition is applied to a tire, the fracture resistance of the tire can be improved. From the viewpoint of fracture resistance, the syndiotacticity in the 1,2-bonds of sPB can be 70% or more, 75% or more, 80% or more, 85% or more, 90% or more, 95% or more, and can also be 100%. Furthermore, the syndiotacticity of the 1,2-bond in the aforementioned spPB is 1 H and 13 It can be determined by 13C nuclear magnetic resonance (NMR) analysis.

[0087] Furthermore, the syndiotactic 1,2-polybutadiene may be a copolymer obtained by copolymerizing 1,3-butadiene with small amounts of conjugated dienes such as 1,3-pentadiene and 1-pentyl-1,3-butadiene, or it may be a homopolymer of 1,3-butadiene. If the sPB contains units derived from conjugated dienes other than 1,3-butadiene, in one embodiment, the proportion of units derived from 1,3-butadiene in the total repeating units of the sPB can be 80% or more, 85% or more, 90% or more, 95% or more, 98% or more, or 99% or more.

[0088] The content of syndiotactic 1,2-polybutadiene is preferably 1 to 40 parts by mass per 100 parts by mass of the rubber component. A content of sPB of 1 part by mass or more per 100 parts by mass of the rubber component enhances the energy dissipation effect and provides superior fracture resistance. From the viewpoint of fracture resistance, the sPB content can be 5 parts by mass or more, or 10 parts by mass or more, per 100 parts by mass of the rubber component. On the other hand, a sPB content of 40 parts by mass or less per 100 parts by mass of the rubber component can suppress the deterioration of fuel efficiency. From the viewpoint of fuel efficiency, the sPB content can also be 35 parts by mass or less, or 30 parts by mass or less, per 100 parts by mass of the rubber component. Furthermore, when the sPB content is 1 to 40 parts by mass per 100 parts by mass of the rubber component, applying the rubber composition to a tire can improve the tire's fuel efficiency and fracture resistance.

[0089] The method for obtaining the aforementioned sPB is not particularly limited; it can be manufactured in-house or commercially available products can be used. For example, 1,3-butadiene monomer can be polymerized in an organic solvent containing an aliphatic solvent using an iron-based catalyst composition, a chromium-based catalyst composition, a cobalt-based catalyst composition, etc. Specifically, it can be prepared by polymerization methods described in Japanese Patent Publication No. 2006-063183, Japanese Patent Publication No. 2000-119324, Japanese Patent Publication No. 2004-528410, Japanese Patent Publication No. 2005-518467, Japanese Patent Publication No. 2005-527641, Japanese Patent Publication No. 2009-108330, Japanese Patent Publication No. Hei 7-25212, Japanese Patent Publication No. Hei 6-306207, Japanese Patent Publication No. Hei 6-199103, Japanese Patent Publication No. Hei 6-92108, Japanese Patent Publication No. Hei 6-87975, etc. Among these catalyst compositions, the amount of sPB crystals is 7 to 40 J / g, and the number average molecular weight is 3.0 × 10 4 From the standpoint of being able to reliably control the situation within the above range, it is preferable to use the iron-based catalyst composition.

[0090] Examples of the iron-based catalyst compositions include a catalyst composition comprising (a) an iron-containing compound, (b) an α-acylphosphonic acid diester, and (c) an organoaluminum compound; a catalyst composition comprising (a) an iron-containing compound, (b) an α-acylphosphonic acid diester, (c) an organoaluminum compound, and another organometallic compound or Lewis base; or a catalyst composition comprising (a) an iron-containing compound, (b) a dihydrocarbyl hydrogen phosphite, and (c) an organoaluminum compound. The iron-containing compounds (a) mentioned above are not particularly limited, but preferred examples include iron carboxylates, iron organophosphates, iron organophosphonates, iron organophosphinates, iron carbamates, iron dithiocarbamates, iron xanthogenicates, iron α-diketonates, iron alkoxides or aryl oxides, and organic iron compounds. Among these compounds, sPB has a crystal content of 7-40 J / g and a number-average molecular weight of 3.0 × 10⁻⁶. 4From the standpoint of being able to reliably control the situation within the above range, it is more preferable that the iron-based catalyst composition contains iron(III) tris(2-ethylhexanoate), bis(2-ethylhexyl) phosphite, triisobutylaluminum, tri-n-butylaluminum, and tri-n-octylaluminum.

[0091] An example of the chromium-based catalyst composition is a three-component catalyst system comprising (a) a chromium-containing compound, (b) an alkylaluminum hydride compound, and (c) a hydrogen phosphite ester. Various chromium-containing compounds can be used as component (a) of the chromium-based catalyst composition. Generally, it is advantageous to use a chromium-containing compound that is soluble in hydrocarbon solvents such as aromatic hydrocarbons, aliphatic hydrocarbons, or alicyclic hydrocarbons, but it is also possible for an insoluble chromium-containing compound simply dispersed in a polymerization medium to generate catalytically active species. Therefore, no limitations should be placed on the chromium-containing compound in order to ensure solubility. Furthermore, (a) examples of chromium in chromium-containing compounds include, but are not limited to, chromium carboxylates, chromium β-diketnates, chromium alkoxides or allyloxides, chromium halides, pseudo-chromium halides, and organochromium compounds.

[0092] Examples of the cobalt-based catalyst composition include catalyst systems comprising soluble cobalt, such as cobalt octoate, cobalt 1-naphthate, and cobalt benzoate; organoaluminum compounds, such as trimethylaluminum, triethylaluminum, tributylaluminum, and triphenylaluminum; and carbon disulfide.

[0093] Furthermore, commercially available sPB products such as the JSR RB® series, including JSR RB® 810, 820, 830, and 840, can also be used.

[0094] (others) In addition to the rubber components, fillers, and syndiotactic 1,2-polybutadiene described above, the tire rubber composition of this embodiment may optionally contain various components commonly used in the rubber industry, such as silane coupling agents, antioxidants, waxes, hardened fatty acids, zinc oxide (zinc oxide), tackifiers, vulcanization accelerators, and vulcanizing agents, selected as appropriate within a range that does not impair the objectives of the present invention. Commercially available products can be suitably used as these compounding agents.

[0095] Examples of the aforementioned antioxidants include N-(1,3-dimethylbutyl)-N'-phenyl-p-phenylenediamine (6C) and 2,2,4-trimethyl-1,2-dihydroquinoline polymer (TMDQ). These antioxidants may be used individually or in combination of two or more. There are no particular restrictions on the content of the antioxidant, but it is preferably in the range of 0.1 to 5 parts by mass, and more preferably 1 to 4 parts by mass, per 100 parts by mass of the rubber component.

[0096] Examples of the wax include paraffin wax and microcrystalline wax. The amount of the wax is not particularly limited, but is preferably in the range of 0.1 to 5 parts by mass, and more preferably 1 to 4 parts by mass, per 100 parts by mass of the rubber component.

[0097] Examples of the hardened fatty acid include stearic acid. The content of the hardened fatty acid is not particularly limited, but is preferably in the range of 0.1 to 5 parts by mass, and more preferably 1 to 4 parts by mass, per 100 parts by mass of the rubber component.

[0098] The content of the zinc oxide (zinc oxide) is not particularly limited, but is preferably in the range of 0.1 to 10 parts by mass, and more preferably 1 to 8 parts by mass, per 100 parts by mass of the rubber component.

[0099] Examples of the tackifier include rosin resins, terpene resins, petroleum resins, phenolic resins, coal resins, and xylene resins, among which petroleum resins are preferred. Examples of petroleum resins include C5 resins, C5-C9 resins, C9 resins, and dicyclopentadiene (DCPD) resins. There are no particular restrictions on the content of the tackifier, but it is preferably in the range of 0.1 to 5 parts by mass, and more preferably 0.5 to 3 parts by mass, per 100 parts by mass of the rubber component.

[0100] Examples of the vulcanization accelerator include sulfenamide-based vulcanization accelerators, guanidine-based vulcanization accelerators, thiazole-based vulcanization accelerators, thiram-based vulcanization accelerators, and dithiocarbamate-based vulcanization accelerators. These vulcanization accelerators may be used individually or in combination of two or more. There are no particular restrictions on the content of the vulcanization accelerator, but it is preferably in the range of 0.1 to 5 parts by mass, and more preferably in the range of 0.2 to 4 parts by mass, per 100 parts by mass of the rubber component.

[0101] Examples of the vulcanizing agent include sulfur. The content of the vulcanizing agent is preferably in the range of 0.1 to 6 parts by mass, and more preferably in the range of 0.5 to 3 parts by mass, as sulfur, per 100 parts by mass of the rubber component.

[0102] (Method for manufacturing rubber composition for tires) The method for producing the aforementioned tire rubber composition is not particularly limited, but for example, it can be produced by blending the aforementioned rubber components, fillers, and syndiotactic 1,2-polybutadiene with various components as needed, and then kneading, heating, extruding, etc. Furthermore, the obtained rubber composition can be vulcanized to produce vulcanized rubber.

[0103] There are no particular restrictions on the mixing conditions, and various conditions such as the input volume of the mixing device, the rotation speed of the rotor, the ram pressure, as well as the mixing temperature, mixing time, and the type of mixing device can be appropriately selected according to the purpose. Examples of mixing devices include Banbury mixers, intermixes, kneaders, and rolls, which are commonly used for mixing rubber compositions.

[0104] There are no particular restrictions on the heat treatment conditions, and various conditions such as heat treatment temperature, heat treatment time, and heat treatment equipment can be appropriately selected according to the purpose. Examples of such heat treatment equipment include heat treatment roll machines commonly used for heat treatment of rubber compositions.

[0105] There are no particular restrictions on the extrusion conditions, and various conditions such as extrusion time, extrusion speed, extrusion equipment, and extrusion temperature can be appropriately selected according to the purpose. Examples of extrusion equipment include extruders typically used for extruding rubber compositions. The extrusion temperature can be determined as appropriate.

[0106] There are no particular restrictions on the apparatus, method, and conditions for performing the vulcanization, and they can be appropriately selected according to the purpose. Typical vulcanization apparatuses include molding vulcanizers using molds, which are commonly used for vulcanizing rubber compositions. The vulcanization temperature is typically around 100-190°C.

[0107] <Tires> The tire of this embodiment is characterized by containing the above-described tire rubber composition. Because the tire of this embodiment contains the above-described tire rubber composition, it can achieve both fracture resistance and low fuel consumption. Examples of parts of the tire to which the rubber composition is applied include the tread rubber and the side rubber.

[0108] The tire of this embodiment may be obtained by molding an unvulcanized rubber composition and then vulcanizing it, depending on the type of tire to be applied, or by molding a semi-vulcanized rubber that has undergone a pre-vulcanization process, and then further vulcanizing it. The tire of this embodiment is preferably a pneumatic tire, and as the gas to fill the pneumatic tire, in addition to ordinary air or air with adjusted oxygen partial pressure, an inert gas such as nitrogen, argon, or helium can be used. [Examples]

[0109] The present invention will be described in more detail below with reference to examples, but the present invention is not limited in any way to the following examples.

[0110] <Method for synthesizing copolymers> Under a nitrogen atmosphere, 77 parts by mass of cyclopentene, 23 parts by mass of dicyclopentadiene, 300 parts by mass of cyclohexane, and 0.069 parts by mass of 1-hexene were added to a glass reaction vessel equipped with a stirrer. Next, 0.024 parts by mass of the ring-opening polymerization catalyst dichloro-(3-phenyl-1H-indene-1-ylidene)bis(tricyclohexylphosphine)ruthenium(II) dissolved in 1 part by mass of toluene were added, and the polymerization reaction was carried out at 40°C for 2 hours. After the polymerization reaction, the polymerization was stopped by adding an excess of vinyl ethyl ether. The polymerization solution was poured into a large excess of methanol containing 2,6-di-t-butyl-p-cresol (BHT), the precipitated polymer was recovered, washed with methanol, and then vacuum-dried at 50°C for 24 hours to obtain 60 parts by mass of copolymer.

[0111] <Analysis of copolymers> The molecular weight of the synthesized copolymer and the proportion of structural units derived from each monomer were measured using the method described below. The results are shown in Table 1.

[0112] (1) Weight average molecular weight (Mw) A gel permeation chromatography (GPC) system "HLC-8220" (manufactured by Tosoh Corporation) was used, with two H-type columns "HZ-M" (manufactured by Tosoh Corporation) connected in series, using tetrahydrofuran as the solvent, and measurements were taken at a column temperature of 40°C. A differential refractometer "RI-8320" (manufactured by Tosoh Corporation) was used as the detector. The weight-average molecular weight (Mw) of the copolymer was measured as a polystyrene equivalent.

[0113] (2) The proportion of structural units derived from each monomer The proportion of structural units derived from each monomer constituting the copolymer is 1 This was determined from 1H-NMR spectroscopy measurements.

[0114] [Table 1]

[0115] <Method for syndiotactic 1,2-polybutadiene synthesis> A 1L (1000cc) glass bottle, dried in an oven, was sealed with a rubber liner and a perforated metal cap. After completely purging the bottle with a stream of dry nitrogen gas, 94g of hexanes and 206g of a 1,3-butadiene / hexane mixture containing 21.8% by mass of 1,3-butadiene were added to the bottle. Next, 0.04 mmol of iron(III) tris(2-ethylhexanoate), 0.16 mmol of bis(2-ethylhexyl) phosphite, 0.24 mmol of triisobutylaluminum, and 0.24 mmol of tri-n-octylaluminum were added to the bottle as catalyst components. The bottle was stirred for 4 hours in a water bath maintained at 50°C. The resulting polymerization reaction mixture was a fluid, slightly cloudy solution. Upon cooling to room temperature, the fluidity of the solution was lost as syndiotactic 1,2-polybutadiene precipitated. The polymerization reaction mixture was flocculated with 3 L of isopropanol containing 2,6-di-tert-butyl-4-methylphenol as an antioxidant. The resulting solid was filtered off and dried under reduced pressure at 60°C to obtain syndiotactic 1,2-polybutadiene.

[0116] <Analysis of syndiotactic 1,2-polybutadiene> The crystalline content, molecular weight, degree of crystallinity, melting point, 1,2-bond content, and syndiotacticity at the 1,2-bonds of syndiotactic 1,2-polybutadiene were measured by the following method. The results are shown in Table 2.

[0117] (3) Crystal content Using a differential scanning calorimeter (TA instrument), the area of ​​the melting peak observed between -100°C and 200°C during melting point measurement was calculated to obtain the crystalline weight (J / g) of syndiotactic 1,2-polybutadiene.

[0118] (4) Number average molecular weight (Mn) The number-average molecular weight (Mn) was measured using gel permeation chromatography [GPC: Tosoh Corporation, HLC-8220 / HT] with a differential refractometer as the detector, and the values ​​were expressed in polystyrene equivalents with monodisperse polystyrene as the standard. The column used was GMHHR-H(S)HT [Tosoh Corporation], the eluent was trichlorobenzene, and the measurement temperature was 140°C.

[0119] (5) Degree of crystallinity The density of 1,2-polybutadiene with 0% crystallinity is 0.889 g / cm³. 3 The density of 1,2-polybutadiene with 100% crystallinity is 0.963 g / cm³. 3 This was calculated by converting the density measured using the water displacement method.

[0120] (6) Melting point The melting point was measured by placing a sample of syndiotactic 1,2-polybutadiene in a differential scanning calorimetry (DSC) system and heating it at a rate of 10°C / min, with the melting peak temperature of the DSC curve being used as the melting point.

[0121] (7) 1,2-bond content and syndiotacticity in 1,2-bonds) The 1,2-bond content and syndiotacticity in the 1,2-bonds of syndiotactic 1,2-polybutadiene are determined. 1 H and 13 This was determined by 13C nuclear magnetic resonance (NMR) analysis.

[0122] [Table 2]

[0123] <Preparation and evaluation of rubber compositions> The rubber compositions for Comparative Examples 1 and 2 were prepared by blending and kneading each component according to the formulations shown in Table 3. The fuel efficiency and fracture resistance of the obtained rubber compositions were evaluated using the following method. The results are shown in Table 3. The rubber compositions for Examples 1 and 2 were prepared by mixing and kneading each component according to the formulations shown in Table 3. The fuel efficiency and fracture resistance of the obtained rubber compositions were evaluated using the following method. The results are shown in Table 3.

[0124] (8) Fuel efficiency Test specimens were prepared from the rubber compositions of Comparative Example 1 and Comparative Example 2. Viscoelasticity tests were performed using TA Instruments' "ARES-G2" under the conditions of a frequency of 15 Hz, shear strain of 3%, and temperature of 30°C to measure the loss tangent (tanδ) of the rubber compositions. The evaluation results were normalized by the reciprocal of the formulation data for each example, with the formulation data of Comparative Example 1 used as the control (index value 100). An index value of 80 or more and less than 100 was classified as "C", 100 or more and less than 120 as "B", and 120 or more and less than 140 as "A". A larger index value indicates a smaller tanδ and superior fuel efficiency.

[0125] (9) Fuel efficiency Test specimens were prepared from the rubber compositions of Example 1 and Example 2, and viscoelasticity tests were performed using TA Instruments' "ARES-G2" under the conditions of a frequency of 15 Hz, shear strain of 3%, and temperature of 30°C to measure the loss tangent (tanδ) of the rubber composition. The evaluation results were normalized by the reciprocal of the formulation data for each example, with the formulation data of Comparative Example 1 used as the control (index value 100). An index value of 80 or more and less than 100 was classified as "C", 100 or more and less than 120 as "B", and 120 or more and less than 140 as "A". A larger index value indicates a smaller tanδ and superior fuel efficiency.

[0126] (10) Destruction resistance Ring test specimens with an inner diameter of 8 mm and an outer diameter of 12 mm were prepared from the rubber compositions of Comparative Example 1 and Comparative Example 2. Using an Instron tensile testing machine, the specimens were stretched at a speed of 100 mm / min to achieve a strain energy of 5 MPa, and then returned to their initial length at the same speed. The area of ​​the loop drawn in the resulting strain-stress curve was defined as the hysteresis loss at a strain energy of 5 MPa. A larger value indicates that energy can be dissipated and crack propagation is less likely, and this was used as an indicator of fracture resistance. The compound data of Comparative Example 1 was used as a control (index value 100), and the compound data of each example was normalized. An index value of 80 or more and less than 100 was classified as "C", 100 or more and less than 120 as "B", and 120 or more and less than 140 as "A". A larger index value indicates a larger loop area drawn in the strain-stress curve and superior fracture resistance.

[0127] (11) Destruction resistance From the rubber compositions of Example 1 and Example 2, ring test specimens with an inner diameter of 8 mm and an outer diameter of 12 mm were prepared. Using an Instron tensile testing machine, the specimens were stretched at a speed of 100 mm / min to achieve a strain energy of 5 MPa, and then returned to their initial length at the same speed. The area of ​​the loop drawn in the resulting strain-stress curve was defined as the hysteresis loss at a strain energy of 5 MPa. A larger value indicates that energy can be dissipated and crack propagation is less likely, thus serving as an indicator of fracture resistance. The data from Comparative Example 1 was used as a control and normalized using the formulation data of each example. An index value of 80 or more and less than 100 was designated as "C", 100 or more and less than 120 as "B", and 120 or more and less than 140 as "A". A larger index value indicates a larger loop area drawn in the strain-stress curve and superior fracture resistance.

[0128] [Table 3]

[0129] *1 NR: Natural rubber *2 BR: Butadiene rubber, manufactured by Ube Industries, Ltd., product name "UBEPOL BR150L" *3 Copolymer: A copolymer of cyclopentene synthesized by the above method and a norbornene-based compound. *4 sPB: Syndiotactic 1,2-polybutadiene having the physical properties shown in Table 2 *5 Carbon Black: ISAF grade, manufactured by Asahi Carbon Co., Ltd., product name "Asahi #78" *6 Resin: DCPD resin, manufactured by Nippon Petrochemical Co., Ltd., product name "Nisseki Neoresin B-100" *7 Vulcanization accelerator: Manufactured by Sanshin Chemical Industry Co., Ltd., product name "Suncellar CM-G" *8 Sulfur: Manufactured by Hosoi Chemical Industry Co., Ltd., product name "HK200-5" *9 Other: The total amount of stearic acid, wax, two types of antioxidants, and retarder is calculated by blending each ingredient in equal proportions.

[0130] From the comparison between Example 1 and Comparative Example 1 in Table 3, it can be seen that the rubber composition of Example 1, which contains a copolymer of cyclopentene and norbornene-based compound and syndiotactic 1,2-polybutadiene, has improved fuel efficiency and fracture resistance compared to the rubber composition of Comparative Example 1, which contains a copolymer of cyclopentene and norbornene-based compound but does not contain syndiotactic 1,2-polybutadiene.

[0131] Furthermore, a comparison of Example 2 and Comparative Example 2 in Table 3 shows that the rubber composition of Example 2, which contains a copolymer of cyclopentene and norbornene-based compounds and syndiotactic 1,2-polybutadiene, exhibits improved fuel efficiency and fracture resistance compared to the rubber composition of Comparative Example 2, which contains a copolymer of cyclopentene and norbornene-based compounds but does not contain syndiotactic 1,2-polybutadiene.

[0132] [Contribution to the United Nations-led Sustainable Development Goals (SDGs)] The SDGs have been proposed to realize a sustainable society. One embodiment of the present invention is considered to be a technology that can contribute to "No. 7 Affordable and Clean Energy," "No. 12 Responsible Consumption and Production," and "No. 13 Climate Action."

Claims

1. It contains rubber components, fillers, and syndiotactic 1,2-polybutadiene. The aforementioned rubber component is cyclopentene and the following general formula (1): 【Chemistry 1】 [In the formula, R １ ~R ４ Each of these independently represents a hydrogen atom, a hydrocarbon group having 1 to 20 carbon atoms, or a substituent containing a halogen atom, a silicon atom, an oxygen atom, or a nitrogen atom, and R ２ and R ３ These may be bonded together to form a ring, and m is an integer from 0 to 2. The copolymer includes a norbornene compound represented by [ ]. The syndiotactic 1,2-polybutadiene has a crystalline weight of 7 to 40 J / g and a number-average molecular weight of 3.0 × 10⁻⁶ ４ A rubber composition for tires, characterized by the above.

2. The tire rubber composition according to claim 1, wherein the content of the copolymer of cyclopentene and norbornene compound is 20 to 90 parts by mass per 100 parts by mass of the rubber component.

3. The rubber composition for tires according to claim 1, wherein the copolymer of cyclopentene and norbornene compound has a weight-average molecular weight (Mw) of 200,000 to 1,000,000.

4. The tire rubber composition according to claim 1, wherein the norbornene compound represented by the above general formula (1) is 2-norbornene and / or dicyclopentadiene.

5. The tire rubber composition according to claim 1, wherein the copolymer of cyclopentene and norbornene-based compound has a content of cyclopentene-derived structural units of 20 to 75% by mass.

6. The tire rubber composition according to claim 4, wherein the copolymer of cyclopentene and norbornene-based compound has a content of dicyclopentadiene-derived structural units of 10 to 60% by mass.

7. The tire rubber composition according to claim 1, wherein the rubber component further comprises isoprene backbone rubber and / or butadiene rubber.

8. The aforementioned syndiotactic 1,2-polybutadiene has a number-average molecular weight of 5.0 × 10⁻⁶ ４ ~50.0 x 10 ４ The tire rubber composition according to claim 1.

9. The tire rubber composition according to claim 1, wherein the syndiotactic 1,2-polybutadiene has a degree of crystallinity of 15 to 60%.

10. The tire rubber composition according to claim 1, wherein the syndiotactic 1,2-polybutadiene has a melting point of 100 to 160°C.

11. The tire rubber composition according to claim 1, wherein the syndiotactic 1,2-polybutadiene has a 1,2-bond content of 80% by mass or more.

12. The tire rubber composition according to claim 1, wherein the syndiotactic 1,2-polybutadiene has a syndiotacticity of 60% or more in the 1,2-bonds.

13. The tire rubber composition according to claim 1, wherein the content of the syndiotactic 1,2-polybutadiene is 1 to 40 parts by mass per 100 parts by mass of the rubber component.

14. The tire rubber composition according to claim 1, comprising carbon black as the filler.

15. The tire rubber composition according to claim 14, wherein the carbon black content is 5 to 80 parts by mass per 100 parts by mass of the rubber component.

16. A tire characterized by comprising the tire rubber composition described in any one of claims 1 to 15.

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