Tire rubber composition and tire

Abstract

To provide a tire rubber composition that allows a tire to achieve both low fuel consumption and wear resistance.SOLUTION: The tire rubber composition contains: a rubber component containing a copolymer of cyclopentene and a compound represented by the general formula (1); a heterocyclic compound that has a six-membered aromatic heterocyclic ring; and a metal salt.SELECTED DRAWING: None

Description

[Technical field]

[0001] The present invention relates to a rubber composition for a tire and a tire. [Background technology]

[0002] In response to the recent trend toward global carbon dioxide emission regulations in response to growing interest in environmental issues, there is a growing demand for improved fuel efficiency in automobiles. In order to meet these demands, there is also a demand for improved fuel efficiency in tires (i.e., reduced rolling resistance). From the viewpoint of tire economics, in the development of rubber compositions for tires, it is also required to improve abrasion resistance in addition to low fuel consumption.

[0003] However, in general, fuel economy and abrasion resistance are in a trade-off relationship, and it is difficult to achieve both. For example, a method of increasing the amount of filler to improve abrasion resistance is known, but increasing the amount of filler causes the filler to become less dispersed, resulting in a problem of poor fuel economy.

[0004] In response to this, the following Patent Documents 1 and 2 disclose rubber compounds for passenger car tires and rubber compounds for heavy-duty truck and bus tires, each containing a specific long-chain branched cyclopentene ring-opening rubber (LCB-CPR), and these rubber compounds are said to be effective in reducing the rolling resistance of tires, improving wet skid resistance, and improving abrasion resistance. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] International Publication No. 2021 / 178233 [Patent Document 2] International Publication No. 2021 / 178235 Summary of the Invention [Problem to be solved by the invention]

[0006] However, the inventors have conducted research and found that even with the techniques described in Patent Documents 1 and 2, it is difficult to achieve both low fuel consumption and high wear resistance in a tire, and there is still room for improvement.

[0007] Therefore, an object of the present invention is to provide a rubber composition for tires that can solve the above-mentioned problems of the conventional technology and achieve both low fuel consumption and high wear resistance for tires. Another object of the present invention is to provide a tire which achieves both low fuel consumption and high wear resistance. [Means for solving the problem]

[0008] The essential features of the rubber composition for a tire and the tire of the present invention that solve the above problems are as follows.

[0009] [1] A rubber composition comprising a rubber component, a heterocyclic compound having a six-membered aromatic heterocycle, and a metal salt, wherein the rubber component is a rubber composition comprising cyclopentene and a compound represented by the following general formula (1): [ka] [In the formula, R 1 ~R 4 each 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; R 2 and R 3 and m may be bonded to each other to form a ring, and m is an integer of 0 to 2.]. The rubber composition for tires of the present invention described in [1] above can achieve both low fuel consumption and high wear resistance in tires by applying it to tires.

[0010] [2] The rubber composition for tires according to [1], wherein the norbornene-based compound represented by the general formula (1) is 2-norbornene and / or dicyclopentadiene. 2-Norbornene and dicyclopentadiene are readily available, and copolymers of cyclopentene with 2-norbornene and / or dicyclopentadiene are readily available. Therefore, the rubber composition for tires described in [2] above is advantageous in terms of cost.

[0011] [3] The rubber composition for tires according to [1] or [2], wherein the content of the copolymer of cyclopentene and a norbornene-based compound is 20 to 90 parts by mass per 100 parts by mass of the rubber component. The rubber composition for tires described in [3] above has an improved balance between fuel economy and abrasion resistance.

[0012] [4] The rubber composition for a tire according to any one of [1] to [3], wherein the copolymer of cyclopentene and a norbornene-based compound has a weight average molecular weight (Mw) of 200,000 to 1,000,000. The copolymer having a weight average molecular weight (Mw) in the range of 200,000 to 1,000,000 is easy to produce and has good processability. Moreover, the rubber composition for tires described in [4] above has further improved fuel economy and abrasion resistance.

[0013] [5] The rubber composition for a tire according to any one of [1] to [4], wherein the copolymer of cyclopentene and a norbornene-based compound has a content of structural units derived from cyclopentene of 20 to 75 mass %. The rubber composition for tires described in [5] above has further improved fuel economy and abrasion resistance.

[0014] [6] The rubber composition for a tire according to any one of [2] to [5], wherein the copolymer of cyclopentene and a norbornene-based compound has a content of structural units derived from 2-norbornene of 10 to 60 mass %. The rubber composition for tires described in [6] above has further improved fuel economy and abrasion resistance.

[0015] [7] The rubber composition for a tire according to any one of [2] to [6], wherein the copolymer of cyclopentene and a norbornene-based compound has a content of structural units derived from dicyclopentadiene of 10 to 60 mass %. The rubber composition for tires described in [7] above has further improved fuel economy and abrasion resistance.

[0016] [8] The rubber composition for a tire according to any one of [1] to [7], wherein the heterocyclic compound has at least one heterocycle selected from the group consisting of a pyridine ring, a pyrimidine ring, a pyridazine ring, a pyrazine ring, a triazine ring, and a tetrazine ring. The rubber composition for tires described in [8] above has further improved fuel economy.

[0017] [9] The rubber composition for a tire according to any one of [1] to [8], wherein the heterocyclic compound has a triazine ring or a tetrazine ring. The rubber composition for tires described in [9] above has further improved fuel economy.

[0018]

[10] The heterocyclic compound is represented by the following general formula (2): [ka] [where, X 1 and X 2 each independently represents a pyridyl group or a pyrimidinyl group; Y 1 and Y 2 and each independently represents a single bond or a divalent hydrocarbon group.]. The rubber composition for a tire according to any one of [1] to [9], The rubber composition for tires described in

[10] above has further improved fuel economy.

[0019]

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

[10] , wherein the metal salt contains zinc oxide. The rubber composition for tires described in

[11] above has further improved fuel economy.

[0020]

[12] The rubber composition for tires according to

[11] , further comprising a metal salt other than zinc oxide as the metal salt. The rubber composition for tires described in

[12] above has further improved fuel economy.

[0021]

[13] A tire comprising the rubber composition for tires according to any one of [1] to

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

[13] above can achieve both low fuel consumption and high wear resistance. Effect of the Invention

[0022] According to the present invention, it is possible to provide a rubber composition for tires that can achieve both low fuel consumption and high wear resistance for tires. Moreover, according to the present invention, a tire that achieves both low fuel consumption and high wear resistance can be provided. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0023] The rubber composition for a tire and the tire of the present invention will be illustrated in detail below based on embodiments.

[0024] <Definition> The compounds described herein may be derived in whole or in part from fossil sources, from biological sources such as plant sources, from recycled sources such as used tires, or from a mixture of two or more of fossil sources, biological sources, and / or renewable sources.

[0025] <Rubber composition for tires> The rubber composition for tires of the present embodiment includes a rubber component, a heterocyclic compound having a six-membered aromatic heterocycle (also simply referred to as a "heterocyclic compound"), and a metal salt. In the rubber composition for tires of the present embodiment, the rubber component is a compound represented by the formula (1) below, which is a compound represented by the formula (1): [ka] [In the formula, R1 ~R 4 each 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; R 2 and R 3 may be bonded to each other to form a ring, and m is an integer of 0 to 2.] (also simply referred to as "copolymer of cyclopentene and a norbornene compound" or "copolymer").

[0026] In the rubber composition for tires of this embodiment, the copolymer of cyclopentene and norbornene-based compounds is characterized by having crosslinking points and by the entanglement of polymer chains. In general, when a filler is blended into a rubber component, a reinforcing layer made of the filler and the rubber component is formed around the filler, and the reinforcing layer contributes to improving the reinforcing properties of the rubber composition, thereby improving the abrasion resistance, etc. In contrast, in the rubber composition for tires of this embodiment, the rubber component contains the copolymer of cyclopentene and norbornene-based compounds, so that the reinforcing layer formed around the filler is specifically increased by the entanglement of the above-mentioned polymer chains, and the abrasion resistance can be sufficiently improved. In the rubber composition for tires of this embodiment, the heterocyclic compound is added to the main chain of the rubber component. In addition, the rubber composition for tires of this embodiment contains a metal salt, and the metal salt forms a coordinate bond with the heterocyclic compound portion added to the main chain of the rubber component to form a complex. The metal salt forms multiple coordinate bonds, thereby crosslinking multiple rubber components. Here, the crosslinking by the coordinate bond is a reversible crosslinking in which the bond (crosslinking) and dissociation (cleavage) are reversible, and is a weaker bond than the sulfur crosslinking in general crosslinked rubber, but has sufficient strength in a low strain region even if the rubber composition is subjected to strain. In addition, the rubber composition for tires of this embodiment can reduce hysteresis loss and improve fuel efficiency by maintaining a high network density by crosslinking by coordinate bonds in a low strain region. Therefore, by applying the rubber composition for tires of the present embodiment to tires, it is possible to achieve both low fuel consumption and high wear resistance for the tires.

[0027] (Rubber component) The rubber composition for a tire of the present embodiment contains a rubber component, and the rubber component provides rubber elasticity to the composition. The rubber component of the rubber composition for a tire of the present embodiment contains a copolymer of cyclopentene and a norbornene-based compound represented by the above general formula (1), and may further contain other rubbers.

[0028] -Copolymer of cyclopentene and norbornene-based compounds- The copolymer of cyclopentene and a norbornene-based compound contains a structural unit derived from cyclopentene and a structural unit derived from a norbornene-based compound represented by the above general formula (1). In a preferred embodiment, the copolymer of cyclopentene and a norbornene-based compound is a ring-opened copolymer, and in particular, a cyclopentene ring-opened copolymer.

[0029] In the above general formula (1), R 1 ~R 4 each 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; R 2 and R 3 may be bonded to each other to form a ring, and m is an integer of 0 to 2. Here, examples of the hydrocarbon group 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.

[0030] The norbornene-based 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, tetracyclo[9.2.1.02, bicyclo[2.2.1]hept-2-enes, unsubstituted or with hydrocarbon substituents, such as tetracyclo[10.03,8]tetradeca-3,5,7,12-tetraene (also known as "1,4-methano-1,4,4a,9a-tetrahydro-9H-fluorene"), tetracyclo[10.2.1.02,11.04,9]pentadeca-4,6,8,13-tetraene (also known as "1,4-methano-1,4,4a,9,9a,10-hexahydroanthracene"), dicyclopentadiene, methyldicyclopentadiene, and dihydrodicyclopentadiene (also known as "tricyclo[5.2.1.02,6]dec-8-ene"); Tetracyclo[6.2.1.13,6.02,7]dodec-4-ene, 9-methyltetracyclo[6.2.1.13,6.02,7]dodec-4-ene, 9-ethyltetracyclo[6.2.1.13,6.02,7]dodec-4-ene, 9-cyclohexyltetracyclo[6.2.1.13,6.02,7]dodec-4-ene, 9-cyclopentyltetracyclo[6.2.1.13,6.02,7]dodec-4-ene, 9-methylenetetracyclo[6.2.1.13,6.02,7]dodec-4-ene, 9-ethylidenetetracyclo[6.2.1.13,6.02,7] dodec-4-ene, 9-vinyltetracyclo[6.2.1.13,6.02,7]dodec-4-ene, 9-propenyltetracyclo[6.2.1.13,6.02,7]dodec-4-ene, 9-cyclohexenyltetracyclo[6.2.1.13,6.02,7]dodec-4-ene, 9-cyclopentenyltetracyclo[6.2.1.13,6.02,7]dodec-4-ene, 9-phenyltetracyclo[6.2.1.13,6.02,7]dodec-4-ene and other unsubstituted or hydrocarbon-substituted tetracyclo[6.2.1.13,6.02,7]dodec-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[6.2.1.13,6.02,7]dodec-4-enes having an alkoxycarbonyl group, such as methyl tetracyclo[6.2.1.13,6.02,7]dodec-9-ene-4-carboxylate and methyl 4-methyltetracyclo[6.2.1.13,6.02,7]dodec-9-ene-4-carboxylate; Bicyclo[2.2.1]hept-2-enes 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 anhydride; Tetracyclo[6.2.1.13,6.02,7]dodec-4-enes having a hydroxycarbonyl group or an acid anhydride group, such as tetracyclo[6.2.1.13,6.02,7]dodec-9-ene-4-carboxylic acid, tetracyclo[6.2.1.13,6.02,7]dodec-9-ene-4,5-dicarboxylic acid, and tetracyclo[6.2.1.13,6.02,7]dodec-9-ene-4,5-dicarboxylic anhydride; 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[6.2.1.13,6.02,7]dodec-4-enes having a hydroxyl group, such as tetracyclo[6.2.1.13,6.02,7]dodec-9-ene-4-methanol and tetracyclo[6.2.1.13,6.02,7]dodec-9-en-4-ol; Bicyclo[2.2.1]hept-2-enes having a hydrocarbonyl group such as 5-norbornene-2-carbaldehyde; Tetracyclo[6.2.1.13,6.02,7]dodec-4-enes having a hydrocarbonyl group, such as tetracyclo[6.2.1.13,6.02,7]dodec-9-ene-4-carbaldehyde; Bicyclo[2.2.1]hept-2-enes having an alkoxycarbonyl group and a hydroxycarbonyl group, such as 3-methoxycarbonyl-5-norbornene-2-carboxylic acid; bicyclo[2.2.1]hept-2-enes having a carbonyloxy group, such as 5-norbornen-2-yl acetate, 2-methyl-5-norbornen-2-yl acetate, 5-norbornen-2-yl acrylate, and 5-norbornen-2-yl methacrylate; Tetracyclo[6.2.1.13,6.02,7]dodec-4-enes having a carbonyloxy group, such as 9-tetracyclo[6.2.1.13,6.02,7]dodec-4-enyl acetate, 9-tetracyclo[6.2.1.13,6.02,7]dodec-4-enyl acrylate, and 9-tetracyclo[6.2.1.13,6.02,7]dodec-4-enyl methacrylate; 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, and 5-norbornene-2,3-dicarboxylic acid imide; Tetracyclo[6.2.1.13,6.02,7]dodec-4-enes having a functional group containing a nitrogen atom, such as tetracyclo[6.2.1.13,6.02,7]dodec-9-ene-4-carbonitrile, tetracyclo[6.2.1.13,6.02,7]dodec-9-ene-4-carboxamide, and tetracyclo[6.2.1.13,6.02,7]dodec-9-ene-4,5-dicarboxylic acid imide; Bicyclo[2.2.1]hept-2-enes containing halogen atoms, such as 5-chloro-2-norbornene; Tetracyclo[6.2.1.13,6.02,7]dodec-4-enes having halogen atoms such as 9-chlorotetracyclo[6.2.1.13,6.02,7]dodec-4-ene; Bicyclo[2.2.1]hept-2-enes having a functional group containing a silicon atom, such as 5-trimethoxysilyl-2-norbornene and 5-triethoxysilyl-2-norbornene; Examples of the norbornene-based compound include tetracyclo[6.2.1.13,6.02,7]dodec-4-enes having a functional group containing a silicon atom, such as 4-trimethoxysilyltetracyclo[6.2.1.13,6.02,7]dodec-9-ene and 4-triethoxysilyltetracyclo[6.2.1.13,6.02,7]dodec-9-ene. The norbornene-based compound may be used alone or in combination of two or more.

[0031] The norbornene-based compound represented by the above general formula (1) is preferably one in which m is 0 or 1, and more preferably one in which m is 0. In addition, in the above general formula (1), R 1 ~R 4 may be the same or different.

[0032] Among the norbornene-based compounds represented by the above general formula (1), from the viewpoint of fuel economy and wear resistance of the rubber composition, R 1 ~R 4 is preferably a hydrogen atom, a chain 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. 1 ~R 4 are not particularly limited as long as they are groups that are not bonded to each other and do not form a ring, and may be the same or different. R 1 ~R 4 is preferably a hydrogen atom or an alkyl group having 1 to 3 carbon atoms. In this case, m is preferably 0 or 1, and more preferably 0. R in the above general formula (1) is 1 ~R 4 However, as the norbornene-based compound in which the substituent is a hydrogen atom, a chain hydrocarbon group having 1 to 20 carbon atoms, or a halogen atom, a silicon atom, an oxygen atom, or a nitrogen atom, unsubstituted or hydrocarbon-substituted bicyclo[2.2.1]hept-2-enes are preferred, and among these, 2-norbornene is particularly preferred.

[0033] Furthermore, as the norbornene-based compound represented by the above general formula (1), R 2 and R 3 Also preferred are compounds in which R 2 and R 3Specific examples of the ring structure formed by bonding with each other include a cyclopentane ring, a cyclopentene ring, a cyclohexane ring, a cyclohexene ring, a benzene ring, etc., which may form a polycyclic structure and may further have a substituent. Among these, a cyclopentane ring, a cyclopentene ring, and a benzene ring are preferred, and a compound having a single cyclopentene ring or a polycyclic structure of a cyclopentane ring and a benzene ring is particularly preferred. In addition, R forming a ring structure 2 , R 3 Other than R 1 , R 4 may be the same or different, and are preferably a hydrogen atom or an alkyl group having 1 to 3 carbon atoms. In this case, m is preferably 0. R in the above general formula (1) 2 and R 3 As the norbornene-based compound in which the above are bonded to each other to form a ring, bicyclo[2.2.1]hept-2-enes having no substituent or a hydrocarbon substituent are preferred, and among these, dicyclopentadiene is particularly preferred.

[0034] The copolymer of cyclopentene and norbornene-based compound has a content of cyclopentene-derived structural units of preferably 20 to 75 mass%, more preferably 25 to 70 mass%, further preferably 30 to 65 mass%, and particularly preferably 35 to 60 mass%, based on all repeating structural units of the copolymer. By making the content of cyclopentene-derived structural units in the copolymer within the range of 20 to 75 mass%, the fuel economy and wear resistance of the rubber composition containing the copolymer can be further improved.

[0035] The copolymer of cyclopentene and norbornene-based compounds preferably has a content of structural units derived from norbornene-based compounds represented by the above general formula (1) of 10 to 80 mass%, more preferably 20 to 70 mass%, further preferably 25 to 65 mass%, and particularly preferably 40 to 65 mass%, based on the total repeating structural units of the copolymer. By setting the content of structural units derived from norbornene-based compounds represented by general formula (1) in the copolymer to the range of 10 to 80 mass%, the fuel economy and wear resistance of the rubber composition containing the copolymer can be further improved.

[0036] In the copolymer of cyclopentene and a norbornene-based compound, the norbornene-based compound represented by the general formula (1) is preferably 2-norbornene and / or dicyclopentadiene. Since 2-norbornene and dicyclopentadiene are easily available, a copolymer of cyclopentene and 2-norbornene and / or dicyclopentadiene is easily available. Therefore, a rubber composition for tires containing a copolymer of cyclopentene and 2-norbornene and / or dicyclopentadiene is advantageous in terms of cost.

[0037] When 2-norbornene is used as the norbornene compound represented by the general formula (1), the copolymer of cyclopentene and a norbornene compound preferably has a content of 2-norbornene-derived structural units of 10 to 60 mass%, more preferably 20 to 60 mass%, based on the total repeating structural units of the copolymer. By setting the content of 2-norbornene-derived structural units in the copolymer to the range of 10 to 60 mass%, the fuel economy and wear resistance of a rubber composition containing the copolymer can be further improved.

[0038] When dicyclopentadiene is used as the norbornene compound represented by the general formula (1), the copolymer of cyclopentene and a norbornene compound preferably has a dicyclopentadiene-derived structural unit content of 10-60 mass%, more preferably 20-50 mass%, based on the total repeating structural units of the copolymer. By setting the dicyclopentadiene-derived structural unit content in the copolymer to the range of 10-60 mass%, the fuel economy and wear resistance of the rubber composition containing the copolymer can be further improved.

[0039] In one embodiment, a ternary copolymer of cyclopentene (CP), 2-norbornene (NB), and dicyclopentadiene (DCPD) may be used as the copolymer of cyclopentene and a norbornene-based compound. The ternary copolymer of cyclopentene, 2-norbornene, and dicyclopentadiene has a large effect of improving the fuel economy of the rubber composition.

[0040] The copolymer of cyclopentene and a norbornene compound may be a copolymer of cyclopentene and the norbornene compound represented by the general formula (1) with other monomers copolymerizable therewith. 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 a norbornene compound is preferably 40% by mass or less, more preferably 30% by mass or less, based on the total repeating structural units of the copolymer. It is particularly preferable that the copolymer does not substantially contain structural units derived from other monomers.

[0041] The copolymer of cyclopentene and norbornene-based 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. A copolymer having a weight average molecular weight (Mw) in the range of 200,000 to 1,000,000 is easy to manufacture and has good processability (workability). In addition, by setting the weight average molecular weight (Mw) of the copolymer in the range of 200,000 to 1,000,000, the fuel economy and wear resistance of a rubber composition containing the copolymer can be further improved. Furthermore, the copolymer of cyclopentene and a norbornene 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 values ​​calculated as polystyrene, measured by gel permeation chromatography (GPC).

[0042] 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 content ratio (cis / trans ratio) of the cis structure and the trans structure of the double bond present in the repeating unit constituting the copolymer of cyclopentene and norbornene-based compound. By setting the cis / trans ratio of the copolymer in the above range, the fuel economy and wear resistance of the rubber composition containing the copolymer can be further improved.

[0043] The copolymer of cyclopentene and a norbornene-based compound has a glass transition temperature (Tg) of 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 economy and abrasion resistance of a rubber composition containing the copolymer can be further improved. The glass transition temperature of the copolymer can be controlled, for example, by adjusting the type and amount of the norbornene-based compound used.

[0044] The copolymer of cyclopentene and norbornene-based compounds may have a modified group at the polymer chain end. By having such a modified terminal group, the affinity for silica and the like can be further increased, and the dispersibility of silica and the like in the rubber composition can be increased, and as a result, the processability (workability), fuel economy and abrasion resistance of the rubber composition can be further improved. The modified group to be introduced into the polymer chain end of the copolymer is not particularly limited, but is preferably a modified group containing an atom selected from the group consisting of an atom of group 15 of the periodic table, an atom of group 16 of the periodic table, and a silicon atom. As the modified group for forming the modified terminal group, from the viewpoint of increasing the affinity for silica and the like, a modified group containing an atom selected from the group consisting of a nitrogen atom, an oxygen atom, a phosphorus atom, a sulfur atom, and a silicon atom is more preferable, and among these, a modified group containing an atom selected from the group consisting of a nitrogen atom, an oxygen atom, and a silicon atom is even more preferable.

[0045] The modified group containing a nitrogen atom may be an amino group, a pyridyl group, an imino group, an amide group, a nitro group, a urethane bond group, or a hydrocarbon group containing any of these groups. The modified group containing an oxygen atom may be a hydroxyl group, a carboxylic acid group, an ether group, an ester group, a carbonyl group, an aldehyde group, an epoxy group, or a hydrocarbon group containing any of these groups. The modified group containing a silicon atom may be an alkylsilyl group, an oxysilyl group, or a hydrocarbon group containing any of these groups. The modified group containing a phosphorus atom may be a phosphate group, a phosphino group, or a hydrocarbon group containing any of these groups. The modified group containing a sulfur atom may be a sulfonyl group, a thiol group, a thioether group, or a hydrocarbon group containing any of these groups. The modified group may also be a modified group containing a plurality of the above groups. Among these, from the viewpoint of further improving the processability (workability), fuel economy and abrasion resistance of the rubber composition, an amino group, a pyridyl group, an imino group, an amide group, a hydroxyl group, a carboxylic acid group, an aldehyde group, an epoxy group, an oxysilyl group, or a hydrocarbon group containing any of these groups is preferred, and from the viewpoint of affinity for silica, etc., an oxysilyl group is particularly preferred. Here, the oxysilyl group refers to a group having a silicon-oxygen bond.

[0046] The oxysilyl group includes an alkoxysilyl group, an aryloxysilyl group, an acyloxy group, an alkylsiloxysilyl group, and an arylsiloxysilyl group. In addition, an alkoxysilyl group, an aryloxysilyl group, or a hydroxysilyl group obtained by hydrolysis of an acyloxy group can be mentioned. Among these, an alkoxysilyl group is preferred from the viewpoint of affinity to silica. The alkoxysilyl group is a group in which one or more alkoxy groups are bonded to a silicon atom, and specific examples thereof include a trimethoxysilyl group, a dimethoxymethylsilyl group, a methoxydimethylsilyl group, a methoxydichlorosilyl group, a triethoxysilyl group, a diethoxymethylsilyl group, an ethoxydimethylsilyl group, a dimethoxyethoxysilyl group, a methoxydiethoxysilyl group, and a tripropoxysilyl group.

[0047] The introduction ratio of the modified group at the polymer chain end of the copolymer of cyclopentene and norbornene-based compound is not particularly limited, but 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 value of the number of copolymer chain ends into which the modified group has been introduced / the total number of copolymer chain ends. The higher the introduction ratio of the terminal modified group, the higher the affinity for silica and the like, which is preferable. The method for measuring the introduction ratio of the modified group at the polymer chain end is not particularly limited, but an example of the case where an oxysilyl group is introduced as the terminal modified group is as follows: 1 It can be determined from the peak area ratio corresponding to the oxysilyl group determined by H-NMR spectrum measurement and the number average molecular weight (Mn) determined by gel permeation chromatography (GPC).

[0048] The copolymer of cyclopentene and a norbornene-based compound has a Mooney viscosity (ML 1+4 , 100°C) is preferably from 20 to 150, more preferably from 22 to 120, and particularly preferably from 25 to 90.

[0049] The method for producing the copolymer of cyclopentene and a norbornene-based compound is not particularly limited, but may be, for example, a method in which cyclopentene and a norbornene-based compound represented by the above general formula (1) are copolymerized in the presence of a ring-opening polymerization catalyst.

[0050] The ring-opening polymerization catalyst is not particularly limited as long as it can ring-open copolymerize cyclopentene with the norbornene-based compound represented by the above general formula (1), but ruthenium carbene complexes and halogen-containing Group 6 transition metal compounds of the periodic table (hereinafter also referred to as "Group 6 transition metal compounds of the periodic table") are preferred. These ring-opening polymerization catalysts may be used alone or in combination of two or more.

[0051] Examples of the ruthenium carbene complex include bis(tricyclohexylphosphine)benzylidene ruthenium dichloride, bis(triphenylphosphine)-3,3-diphenylpropenylidene ruthenium dichloride, bis(tricyclohexylphosphine)t-butylvinylidene ruthenium dichloride, dichloro-(3-phenyl-1H-inden-1-ylidene)bis(tricyclohexylphosphine)ruthenium, bis(1,3-diisopropylimidazolin-2-ylidene)benzylidene ruthenium dichloride, and bis(1,3-dicyclohexylimidazolin-2-ylidene)benzylidene ruthenium dichloride. Examples of such compounds include (1,3-dimesitylimidazolin-2-ylidene)benzylidene ruthenium dichloride, (1,3-dimesitylimidazolin-2-ylidene)(tricyclohexylphosphine)benzylidene ruthenium dichloride, (1,3-dimesitylimidazolin-2-ylidene)(tricyclohexylphosphine)benzylidene ruthenium dichloride, (1,3-dimesitylimidazolin-2-ylidene)(tricyclohexylphosphine)benzylidene ruthenium dichloride, bis(tricyclohexylphosphine)ethoxymethylidene ruthenium dichloride, and (1,3-dimesitylimidazolin-2-ylidene)(tricyclohexylphosphine)ethoxymethylidene ruthenium dichloride.

[0052] The periodic table group 6 transition metal compound is a compound having a periodic table group 6 transition metal atom (long period periodic table, the same applies below), specifically, a compound having a chromium atom, a molybdenum atom, or a tungsten atom, and a compound having a molybdenum atom or a compound having a tungsten atom is preferable, and a compound having a tungsten atom is more preferable from the viewpoint of high solubility in cyclopentene. Specific examples of the periodic table group 6 transition metal compound include molybdenum compounds such as molybdenum pentachloride, molybdenum oxotetrachloride, and molybdenum (phenylimido) tetrachloride; tungsten compounds such as tungsten hexachloride, tungsten oxotetrachloride, tungsten (phenylimido) tetrachloride, monocatecholate tungsten tetrachloride, bis(3,5-ditertiarybutyl)catecholate tungsten dichloride, and bis(2-chloroetherate) tetrachloride; and the like.

[0053] The usage amount of the ring-opening polymerization catalyst is in the range of usually 1:500 to 1:2,000,000, preferably 1:700 to 1:1,500,000, 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 the Group 6 transition metal compound of the periodic table, the usage amount of the Group 6 transition metal compound of the periodic table is preferably in the range of 1:100 to 1:200,000, more preferably 1:200 to 1:150,000, still 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".

[0054] When using the Group 6 transition metal compound of the periodic table as the ring-opening polymerization catalyst, it is preferably used in combination with an organoaluminum compound represented by the following general formula (3). 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 ··· (3) In the above general formula (3), R 5 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.

[0055] In the above general formula (3), examples of 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.

[0056] Also, in the above general formula (3), x satisfies 0 < x < 3. That is, in the general formula (3), R 5 and OR 6The composition ratios with respect to [substance] 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 in the range of 0.5 < x < 1.5.

[0057] The organoaluminum compound represented by the general formula (3) above can be synthesized, for example, by reacting a trialkylaluminum with an alcohol as shown in the following general formula (4). (R 5 )3Al + xR 6 OH → (R 5 ) 3-x Al(OR 6 ) x + (R 6 ) x H ··· (4)

[0058] Note that x in the general formula (3) above can be arbitrarily controlled by defining the reaction ratio of the corresponding trialkylaluminum to the alcohol as shown in the general formula (4).

[0059] The amount of the organoaluminum compound used varies depending on the type of the organoaluminum compound used. However, it is preferably in a ratio of 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 atom of the Periodic Table that constitutes the Group 6 transition metal compound of the Periodic Table. If the amount of the organoaluminum compound used is too small, the polymerization activity may be insufficient, and if it is too large, side reactions tend to occur easily during ring-opening polymerization.

[0060] The polymerization reaction may be carried out without a solvent 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 can dissolve the cyclopentene used in the copolymerization, the norbornene compound represented by the above general formula (1), the polymerization catalyst, etc., but it is preferable to use a hydrocarbon solvent or a halogen-based solvent. Examples of the hydrocarbon solvent include aromatic hydrocarbons such as benzene, toluene, xylene, and ethylbenzene; aliphatic hydrocarbons such as hexane, n-heptane, and n-octane; alicyclic hydrocarbons such as cyclohexane, cyclopentane, and methylcyclohexane; and the like. Examples of the halogen-based solvent include haloalkanes such as dichloromethane and chloroform; aromatic halogens such as chlorobenzene and dichlorobenzene; and the like. These solvents may be used alone or in combination of two or more.

[0061] When cyclopentene and the norbornene-based compound represented by the above general formula (1) are copolymerized, an olefin compound or a diolefin compound may be added to the polymerization reaction system as a molecular weight regulator, if necessary, in order to adjust the molecular weight of the resulting copolymer. The olefin compound is not particularly limited as long as it is an organic compound having an ethylenically unsaturated bond, and examples thereof 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; disubstituted olefins such as 2-butene and 3-hexene; etc. 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 the olefin compound and diolefin compound used as a molecular weight regulator may be appropriately selected depending on the molecular weight of the copolymer to be produced, but 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 in terms of molar ratio to the monomer used in copolymerization.

[0062] In addition, when the copolymer of cyclopentene and norbornene-based compounds has a modified group at the polymer chain end, it is preferable to use a modified group-containing olefinically unsaturated hydrocarbon compound as a molecular weight regulator instead of the above-mentioned olefin compound or diolefin compound. By using a modified group-containing olefinically unsaturated hydrocarbon compound, the modified group can be suitably introduced at the polymer chain end of the copolymer obtained by copolymerization. The modified group-containing olefinically unsaturated hydrocarbon compound is not particularly limited as long as it has a modified group and has one olefinic carbon-carbon double bond having metathesis reactivity. For example, when it is desired to introduce an oxysilyl group at the polymer chain end of the copolymer, an oxysilyl group-containing olefinically unsaturated hydrocarbon may be present in the polymerization reaction system.

[0063] Examples of the oxysilyl group-containing olefinically unsaturated hydrocarbon include those which introduce a modifying group only at one end (single end) of the polymer chain of the copolymer, such as alkoxysilane compounds such as vinyltrimethoxysilane, vinyltriethoxysilane, allyltrimethoxysilane, allylmethoxydimethylsilane, allyltriethoxysilane, allylethoxydimethylsilane, styryltrimethoxysilane, styryltriethoxysilane, styrylethyltriethoxysilane, allyltriethoxysilylmethyl ether, and allyltriethoxysilylmethylethylamine; vinyltriphenoxysilane, allyltriphenoxysilane, and aryltriethoxysilane; aryloxysilane compounds such as vinyltriacetoxysilane, allyltriacetoxysilane, allyldiacetoxymethylsilane, allylacetoxydimethylsilane, and other acyloxysilane compounds; alkylsiloxysilane compounds such as allyltris(trimethylsiloxy)silane; arylsiloxysilane compounds such as allyltris(triphenylsiloxy)silane; polysiloxane compounds such as 1-allylheptamethyltrisiloxane, 1-allylnonamethyltetrasiloxane, 1-allylnonamethylcyclopentasiloxane, and 1-allylundecamethylcyclohexasiloxane; and the like. In addition, examples of compounds for introducing modifying groups into both ends (both ends) of the polymer chain of a copolymer include alkoxysilane compounds such as 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 such as 2-butene-1,4-di(triphenoxysilane); and 2-butene. acyloxysilane compounds such as 1,4-di(triacetoxysilane); alkylsiloxysilane compounds such as 2-butene-1,4-di[tris(trimethylsiloxy)silane]; arylsiloxysilane compounds such as 2-butene-1,4-di[tris(triphenylsiloxy)silane]; polysiloxane compounds such as 2-butene-1,4-di(heptamethyltrisiloxane) and 2-butene-1,4-di(undecamethylcyclohexasiloxane); and the like.

[0064] The modifying group-containing olefinically unsaturated hydrocarbon compound acts as a molecular weight regulator in addition to the function of introducing a modifying group to the polymer chain terminal of the copolymer. Therefore, the amount of the modifying group-containing olefinically unsaturated hydrocarbon compound used may be appropriately selected depending on the molecular weight of the copolymer to be produced, but 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 in terms of molar ratio to the monomer used in copolymerization.

[0065] 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 particularly 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 particularly preferably less than 80°C. The polymerization reaction time is not particularly limited, but is preferably 1 minute to 72 hours, and more preferably 10 minutes to 20 hours.

[0066] If desired, an antiaging agent such as a phenol-based stabilizer, a phosphorus-based stabilizer, or a sulfur-based stabilizer may be added to the copolymer obtained by the polymerization reaction. The amount of the antiaging agent to be added may be appropriately determined depending on the type of the agent. If desired, an extender oil may be blended into the copolymer. When the copolymer is obtained as a polymerization solution, a known recovery method may be adopted to recover the copolymer from the polymerization solution. For example, a method of separating the solvent by steam stripping or the like, filtering off the solid, and then drying the solid to obtain a solid copolymer may be adopted.

[0067] The content of the copolymer of cyclopentene and norbornene-based compound is preferably 20 to 90 parts by mass, and more preferably 30 to 85 parts by mass, in 100 parts by mass of the rubber component. When the content of the copolymer of cyclopentene and norbornene-based compound is in the range of 20 to 90 parts by mass in 100 parts by mass of the rubber component, the balance between fuel economy and wear resistance of the rubber composition is further improved.

[0068] -Butadiene rubber- The rubber component preferably further contains a butadiene rubber (BR). The butadiene rubber has a low glass transition temperature (Tg), and the rubber component contains the butadiene rubber in addition to the copolymer of cyclopentene and a norbornene compound, so that the fuel economy and abrasion resistance of the rubber composition can be further improved.

[0069] When the rubber component contains a 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, per 100 parts by mass of the rubber component. When the content of the 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 fuel economy and abrasion resistance of the rubber composition is further improved.

[0070] -Other rubber- The rubber component may further contain other rubbers. Examples of such other rubbers include natural rubber (NR), synthetic isoprene rubber (IR), styrene-butadiene rubber (SBR), chloroprene rubber (CR), butyl rubber (IIR), halogenated butyl rubber, ethylene-propylene rubber (EPR, EPDM), fluororubber, silicone rubber, urethane rubber, etc. The content of these other rubbers is preferably 30 parts by mass or less, more preferably 20 parts by mass or less, and even more preferably 10 parts by mass or less, per 100 parts by mass of the rubber component.

[0071] (Heterocyclic compounds having six-membered aromatic heterocycles) The rubber composition for tires of this embodiment includes a heterocyclic compound having a six-membered aromatic heterocycle. The six-membered aromatic heterocycle has a heteroatom in the ring and can be coordinately bonded to a metal salt. The heterocyclic compound having the six-membered aromatic heterocycle can crosslink multiple rubber components together with the metal salt. Here, examples of the heteroatom in the six-membered aromatic heterocycle include a nitrogen atom and a phosphorus atom.

[0072] Examples of the six-membered aromatic heterocycle include nitrogen-containing aromatic heterocycles such as pyridine ring, pyrimidine ring, pyridazine ring, pyrazine ring, triazine ring, and tetrazine ring, and aromatic heterocycles in which the nitrogen in the nitrogen-containing aromatic heterocycle is replaced with phosphorus. Among these, pyridine ring, pyrimidine ring, pyridazine ring, pyrazine ring, triazine ring, and tetrazine ring are preferred. Heterocyclic compounds having a pyridine ring, pyrimidine ring, pyridazine ring, pyrazine ring, triazine ring, or tetrazine ring have high reactivity with rubber components, and are easily combined with metal salts to form crosslinks by coordinate bonds, further improving the fuel economy of the rubber composition.

[0073] Here, the heterocyclic compound preferably has a triazine ring or a tetrazine ring. A heterocyclic compound having a triazine ring or a tetrazine ring has higher reactivity with a rubber component and is more likely to form a crosslink by a coordinate bond in combination with a metal salt, thereby further improving the fuel economy of the rubber composition.

[0074] In addition, the triazine ring or tetrazine ring of the compound having the triazine ring or tetrazine ring is preferably bonded to a pyridyl group or a pyrimidinyl group, and more preferably to two pyridyl groups or pyrimidinyl groups. When a pyridyl group or a pyrimidinyl group is bonded to a triazine ring or a tetrazine ring, the heterocyclic compound and the metal salt are more easily complexed, the bond dissociation energy is more easily increased, and a crosslinked structure with higher strength can be formed. In addition, when two pyridyl groups or pyrimidinyl groups are bonded to a triazine ring or a tetrazine ring, the heterocyclic compound and the metal salt are more easily complexed, the bond dissociation energy is more easily increased, and a crosslinked structure with higher strength can be formed. The pyridyl group may be a 2-pyridyl group, a 3-pyridyl group, or a 4-pyridyl group, with a 2-pyridyl group being preferred.The pyrimidinyl group may be a 2-pyrimidinyl group, a 4-pyrimidinyl group, or a 5-pyrimidinyl group.

[0075] The heterocyclic compound is represented by the following general formula (2): [ka] [where, X 1 and X 2 each independently represents a pyridyl group or a pyrimidinyl group; Y 1 and Y 2 are each independently a single bond or a divalent hydrocarbon group. It is more preferable that the compound represented by the general formula (2) is represented by the following formula. The compound represented by the general formula (2) easily undergoes a Diels-Alder reaction with a rubber component, and is easily combined with a metal salt to form a crosslink by a coordinate bond, thereby further improving the fuel economy of the rubber composition. In addition, the compound represented by the general formula (2) and a metal salt are particularly easily complexed, and the bond dissociation energy is particularly easily increased, so that a crosslinked structure with even higher strength can be formed.

[0076] In the above general formula (2), X 1 and X 2 are each independently a pyridyl group or a pyrimidinyl group. From the viewpoint of ease of synthesis, X 1 and X 2 is preferably a pyridyl group. The pyridyl group may be a 2-pyridyl group, a 3-pyridyl group, or a 4-pyridyl group, with a 2-pyridyl group being preferred. The pyrimidinyl group may be a 2-pyrimidinyl group, a 4-pyrimidinyl group, or a 5-pyrimidinyl group.

[0077] In the above general formula (2), Y 1 and Y 2 are each independently a single bond or a divalent hydrocarbon group. Here, examples of the divalent hydrocarbon group include an alkylene group, an alkenylene group, and an arylene group. More specifically, examples of the alkylene group include a methylene group, an ethylene group, a trimethylene group, and a tetramethylene group. Examples of the alkenylene group include a vinylene group, a propenylene group, and a butenylene group. Examples of the arylene group include a phenylene group, a tolylene group, and a naphthylene group. From the viewpoint of ease of synthesis, Y 1 and Y 2 is preferably a single bond (i.e., X is not attached to the tetrazine ring). 1 and X 2is preferably directly bonded).

[0078] Here, X in the above general formula (2) 1 and X 2 is a pyridyl group, and Y 1 and Y 2 is preferably a single bond. In this case, the compound of formula (2) is easily available, and is particularly easily complexed with a metal salt, and the bond dissociation energy is particularly easily increased, so that a crosslinked structure with even higher strength can be formed.

[0079] The compounds represented by the above general formula (2) include 3,6-di(2-pyridyl)-1,2,4,5-tetrazine, 3,6-di(3-pyridyl)-1,2,4,5-tetrazine, 3,6-di(4-pyridyl)-1,2,4,5-tetrazine, 3,6-di(2-pyridylmethyl)-1,2,4,5-tetrazine, 3,6-di(2-pyridylethyl)-1,2,4,5-tetrazine, 3-(2-pyridyl)-1,2,4,5-tetrazine, lysylmethyl)-6-(2-pyridylethyl)-1,2,4,5-tetrazine, 3,6-di(2-pyrimidinyl)-1,2,4,5-tetrazine, 3,6-di(4-pyrimidinyl)-1,2,4,5-tetrazine, 3,6-di(5-pyrimidinyl)-1,2,4,5-tetrazine and the like. Among these, 3,6-di(2-pyridyl)-1,2,4,5-tetrazine is preferred.

[0080] The content of the heterocyclic compound in the rubber composition is preferably 0.1 parts by mass or more, more preferably 0.2 parts by mass or more, and more preferably 10 parts by mass or less, and more preferably 5.0 parts by mass or less, per 100 parts by mass of the rubber component. When the content of the heterocyclic compound is 0.1 parts by mass or more per 100 parts by mass of the rubber component, crosslinking by coordinate bonds increases, and the network density is further increased by the crosslinking by coordinate bonds, thereby further reducing hysteresis loss and further improving fuel economy. In addition, when the content of the heterocyclic compound is 10 parts by mass or less per 100 parts by mass of the rubber component, a crosslinked rubber having sufficient elastomeric properties is easily obtained.

[0081] The rubber component is preferably modified with the heterocyclic compound. When the rubber component is modified with the heterocyclic compound, the main chains of the rubber components can be crosslinked simply by forming coordinate bonds by complexing a plurality of heterocyclic compound portions with a metal salt. Here, the modification of the rubber component with the heterocyclic compound may be performed at the compounding stage of the rubber composition. In addition, prior to compounding the rubber composition, the rubber component may be modified in advance with the heterocyclic compound (i.e., a master batch of the rubber component and the heterocyclic compound is prepared), and the rubber component modified with the heterocyclic compound (the master batch) may be compounded with a metal salt or the like at the compounding stage of the rubber composition to crosslink the main chains of the rubber components.

[0082] When the rubber component is modified with the heterocyclic compound, the heterocyclic compound is preferably bonded in an amount of 0.01 to 10 mol% relative to the monomer units in the rubber component, more preferably 0.02 to 8 mol%, even more preferably 0.03 to 5 mol%, and particularly preferably 0.03 to 3 mol%. When the heterocyclic compound is bonded in an amount of 0.01 mol% or more relative to the monomer units in the rubber component, crosslinking due to coordinate bonds increases, and the network density is further increased by crosslinking due to coordinate bonds, thereby further reducing hysteresis loss and further improving fuel economy. In addition, when the heterocyclic compound is bonded in an amount of 10 mol% or less relative to the monomer units in the rubber component, a crosslinked rubber having sufficient elastomeric properties is easily obtained.

[0083] (Metal Salts) The rubber composition for tires of this embodiment contains a metal salt. The metal salt forms coordinate bonds with multiple heterocyclic compounds, thereby crosslinking multiple rubber components, and further improving the fuel economy of the rubber composition. Here, the crosslinking by coordinate bonds is a reversible crosslinking in which bonding (crosslinking) and dissociation (cleavage) are reversible, and the bond dissociation energy is relatively low, so that even if it is broken by an external stimulus, it can be reversibly regenerated.

[0084] The metal salt preferably contains at least one metal selected from the group consisting of transition metals and zinc. Metal salts containing a transition metal and / or zinc are easily complexed with the heterocyclic compound. Examples of transition metals include elements in groups 7 to 11 of the periodic table. Specifically, examples of elements in Group 7 of the periodic table include manganese and rhenium. Examples of elements in Group 8 of the periodic table include iron, ruthenium, and osmium. Examples of elements in Group 9 of the periodic table include cobalt, rhodium, and iridium. Examples of elements in Group 10 of the periodic table include nickel, palladium, and platinum. Moreover, examples of elements in Group 11 of the periodic table include copper. The elements of Groups 7 to 11 of the periodic table and zinc tend to form strong bonds with heterocyclic compounds. Regarding the metal ions in the metal salt, the valence of the ions is not particularly limited and may have any valence that each element can have, but is preferably divalent or greater.

[0085] It is particularly preferable that the metal salt contains iron, zinc, copper, or nickel. Iron ions, zinc ions, copper ions, and nickel ions are particularly likely to bond strongly with heterocyclic compounds, and can form a crosslinked structure with higher strength. The valence of the iron ion is divalent (Fe 2+ ) or trivalent (Fe 3+ ) is preferred.

[0086] Examples of the metal salt include zinc oxide (zinc oxide), metal halide salts, metal sulfate salts, metal nitrate salts, metal acrylate salts, metal methacrylate salts, and metal acetate salts, and among these, zinc oxide, metal halide salts, metal acrylate salts, metal methacrylate salts, and metal acetate salts are preferred. Zinc oxide, metal halide salts, metal acrylate salts, metal methacrylate salts, and metal acetate salts are easy to handle and easily form bonds with heterocyclic compounds. The form of the metal salt is not particularly limited, and may be, for example, a hydrate.

[0087] The metal halide salt may be a metal fluoride salt, a metal chloride salt, a metal bromide salt, a metal iodide salt, etc., and among these, a metal chloride salt is preferred. A metal chloride salt is easy to handle and is also easy to form a bond with a heterocyclic compound. The form of the metal halide salt is not particularly limited, and may be, for example, a hydrate.

[0088] Specific examples of the metal salt include ZnO, FeCl2, FeCl2·4H2O, FeCl3, FeCl3·6H2O, ZnCl2, CuCl, CuCl2, CuBr, zinc diacrylate, zinc dimethacrylate, Ni(CH3COO)2·4H2O, etc. The metal salt may be used alone or in combination of two or more kinds.

[0089] The content of the metal salt is preferably 0.1 to 30 parts by mass, more preferably 0.1 to 15 parts by mass, even more preferably 0.1 to 10 parts by mass, and particularly preferably 0.1 to 5 parts by mass, based on 100 parts by mass of the rubber component. When the content of the metal salt is 0.1 parts by mass or more based on 100 parts by mass of the rubber component, crosslinking due to coordinate bonds increases, and the network density is further increased by the crosslinking due to coordinate bonds, thereby further reducing hysteresis loss and further improving fuel economy. When the content of the metal salt is 30 parts by mass or less based on 100 parts by mass of the rubber component, a crosslinked rubber having sufficient elastomeric properties is easily obtained.

[0090] The rubber composition for a tire of this embodiment preferably contains zinc oxide as the metal salt. In addition, in the rubber composition for a tire of this embodiment, it is also preferable that the metal salt further contains a metal salt other than zinc oxide. Even if the rubber composition contains zinc oxide and a metal salt other than zinc oxide, the rubber composition can achieve both low fuel consumption and wear resistance.

[0091] The content of the zinc oxide in the rubber composition is preferably 0.1 parts by mass or more, more preferably 0.5 parts by mass or more, and is preferably 30 parts by mass or less, and more preferably 10 parts by mass or less, based on 100 parts by mass of the rubber component. When the content of the zinc oxide is in the range of 0.1 parts by mass or more and 30 parts by mass or less, based on 100 parts by mass of the rubber component, the fuel economy and wear resistance of the rubber composition are further improved. The mass ratio (A / B) of zinc oxide (A) to metal salt other than zinc oxide (B) is preferably in the range of 0.1-50.

[0092] (Filler) The rubber composition for tires of the present embodiment preferably contains a filler. By containing the filler, the reinforcing property of the rubber composition is improved. Examples of the filler include carbon black, silica, clay, talc, calcium carbonate, aluminum hydroxide, etc., and among these, carbon black is preferred.

[0093] 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. When 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 when the content is 80 parts by mass or less, the fuel economy 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, and even more preferably 20 parts by mass or more, per 100 parts by mass of the rubber component, and from the viewpoint of fuel economy, it is more preferably 70 parts by mass or less, and even more preferably 60 parts by mass or less.

[0094] -Carbon black- The filler preferably contains carbon black, which has a large effect of reinforcing the rubber composition and improving the abrasion resistance of the rubber composition, and therefore a rubber composition for tires containing carbon black as a filler has further improved abrasion resistance.

[0095] 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 abrasion resistance of the rubber composition is further improved, and when the carbon black content is 80 parts by mass or less, the fuel economy of the rubber composition is further improved. From the viewpoint of abrasion resistance, the carbon black content is more preferably 10 parts by mass or more, and even more preferably 20 parts by mass or more, per 100 parts by mass of the rubber component, and from the viewpoint of fuel economy, it is more preferably 70 parts by mass or less, and even more preferably 60 parts by mass or less.

[0096] The proportion of carbon black in the filler is preferably 70% by mass or more, more preferably 80% by mass or more, and even more preferably 90% by mass or more, from the viewpoint of the abrasion resistance of the rubber composition, and may be 100% by mass.

[0097] (others) The rubber composition for tires of this embodiment may contain, in addition to the above-mentioned rubber component, heterocyclic compound having a six-membered aromatic heterocycle, metal salt, and filler, various components usually used in the rubber industry, such as silane coupling agents, antioxidants, hardened fatty acids, tackifiers, vulcanization accelerators, vulcanizing agents, etc., which are appropriately selected as necessary within the range that does not impair the object of the present invention. Commercially available products can be suitably used as these compounding agents.

[0098] Examples of the antiaging agent include N-(1,3-dimethylbutyl)-N'-phenyl-p-phenylenediamine (6C) and 2,2,4-trimethyl-1,2-dihydroquinoline polymer (TMDQ). These antiaging agents may be used alone or in combination of two or more. The content of the antiaging agent is not particularly limited, and is preferably in the range of 0.1 to 5 parts by mass, more preferably 1 to 4 parts by mass, based on 100 parts by mass of the rubber component.

[0099] The hardened fatty acid may be stearic acid, etc. The content of the hardened fatty acid is not particularly limited, and is preferably in the range of 0.1 to 5 parts by mass, more preferably 1 to 4 parts by mass, per 100 parts by mass of the rubber component.

[0100] Examples of the tackifier include rosin resins, terpene resins, petroleum resins, phenolic resins, coal resins, and xylene resins, and among these, petroleum resins are preferred. Examples of the petroleum resins include C5 resins, C5-C9 resins, C9 resins, and dicyclopentadiene resins. The content of the tackifier is not particularly limited, and is preferably in the range of 0.1 to 5 parts by mass, and more preferably 0.5 to 3 parts by mass, based on 100 parts by mass of the rubber component.

[0101] Examples of the vulcanization accelerator include sulfenamide vulcanization accelerators, guanidine vulcanization accelerators, thiazole vulcanization accelerators, thiuram vulcanization accelerators, and dithiocarbamate vulcanization accelerators. These vulcanization accelerators may be used alone or in combination of two or more. The content of the vulcanization accelerator is not particularly limited, and is preferably in the range of 0.1 to 5 parts by mass, more preferably in the range of 0.2 to 4 parts by mass, based on 100 parts by mass of the rubber component.

[0102] The vulcanizing agent may be sulfur, etc. 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, in terms of sulfur content, per 100 parts by mass of the rubber component.

[0103] (Method of manufacturing rubber composition for tires) The method for producing the rubber composition for tires is not particularly limited, but the rubber composition for tires can be produced, for example, by blending the above-mentioned rubber component, the heterocyclic compound having a six-membered aromatic heterocycle, and the metal salt with various components appropriately selected as necessary, and kneading, heating, extruding, etc. The obtained rubber composition can be vulcanized to produce a vulcanized rubber.

[0104] The conditions for the kneading are not particularly limited, and various conditions such as the input volume of the kneading device, the rotation speed of the rotor, the ram pressure, the kneading temperature, the kneading time, the type of the kneading device, etc. can be appropriately selected depending on the purpose. Examples of the kneading device include a Banbury mixer, an intermix, a kneader, a roll, etc. that are usually used for kneading rubber compositions.

[0105] The conditions of the heat-in are not particularly limited, and various conditions such as the heat-in temperature, heat-in time, heat-in equipment, etc. can be appropriately selected depending on the purpose. Examples of the heat-in equipment include a heat-in roller machine usually used for heat-in of a rubber composition.

[0106] The extrusion conditions are not particularly limited, and various conditions such as extrusion time, extrusion speed, extrusion device, and extrusion temperature can be appropriately selected depending on the purpose. Examples of the extrusion device include an extruder that is usually used for extruding a rubber composition. The extrusion temperature can be appropriately determined.

[0107] The vulcanization apparatus, method, conditions, etc. are not particularly limited and can be appropriately selected according to the purpose. As the vulcanization apparatus, a molding vulcanizer using a mold used for vulcanizing a rubber composition can be mentioned. As the vulcanization condition, the temperature is, for example, about 100 to 190°C.

[0108] <Tires> The tire of the present embodiment is characterized by including the above-mentioned rubber composition for tires. Since the tire of the present embodiment includes the above-mentioned rubber composition for tires, it can achieve both low fuel consumption and wear resistance. The rubber composition is applied to the tread rubber of the tire.

[0109] The tire of this embodiment may be obtained by molding an unvulcanized rubber composition and then vulcanizing it, or by molding a semi-vulcanized rubber that has been subjected to a pre-vulcanization process or the like and then further vulcanizing it, depending on the type of tire to be applied. The tire of this embodiment is preferably a pneumatic tire, and the gas to be filled in the pneumatic tire may be normal air or air with an adjusted oxygen partial pressure, or an inert gas such as nitrogen, argon, or helium. EXAMPLES

[0110] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to the following examples in any way.

[0111] <Method of synthesizing copolymer> In 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-inden-1-ylidene)bis(tricyclohexylphosphine)ruthenium(II) dissolved in 1 part by mass of toluene was 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), and the precipitated polymer was collected and washed with methanol, and then vacuum dried at 50°C for 24 hours to obtain 60 parts by mass of copolymer.

[0112] <Analysis of copolymer> The molecular weight of the synthesized copolymer and the ratio of structural units derived from each monomer were measured by the following method. The results are shown in Table 1.

[0113] (1)Molecular weight The measurements were performed using a gel permeation chromatography (GPC) system "HLC-8220" (manufactured by Tosoh Corporation) with two H-type columns "HZ-M" (manufactured by Tosoh Corporation) connected in series, with tetrahydrofuran as the solvent and a column temperature of 40°C. A differential refractometer "RI-8320" (manufactured by Tosoh Corporation) was used. The weight average molecular weight (Mw) of the copolymer was measured as a polystyrene equivalent value.

[0114] (2) Proportion of structural units derived from each monomer The ratio of structural units derived from each monomer constituting the copolymer is 1 It was determined by H-NMR spectrum measurement.

[0115] [Table 1]

[0116] <Preparation of Rubber Composition> According to the compounding recipe shown in Table 2, the components were compounded and kneaded to prepare the rubber compositions of the examples and comparative examples. In Comparative Example 2, Example 1, and Example 2, a modified diene rubber having a heterocyclic compound [3,6-di(2-pyridyl)-1,2,4,5-tetrazine, manufactured by Tokyo Chemical Industry Co., Ltd.] bonded to the main chain of the butadiene rubber or the copolymer of cyclopentene and dicyclopentadiene synthesized as described above was prepared in advance, and in the first stage of kneading, the modified diene rubber prepared in advance was kneaded with any compounding agent, and in the second stage and subsequent stages of kneading, various components appropriately selected as necessary were blended and kneaded.

[0117] In addition, each rubber composition further contained, as compounding ingredients other than the components shown in Table 2, 2 parts by mass of hardened fatty acid, 2.5 parts by mass of antioxidant (total amount of two types), 1 part by mass of resin, 1.4 parts by mass of sulfenamide-based vulcanization accelerator, and 1.05 parts by mass of sulfur per 100 parts by mass of rubber component.

[0118] <Evaluation of Rubber Composition> The rubber compositions thus obtained were evaluated for fuel economy and abrasion resistance by the following methods. The results are shown in Table 2.

[0119] (3) Low fuel consumption The loss tangent (tan δ) of a test piece made from the obtained rubber composition was measured using a viscoelasticity measuring device (TA Instruments) under conditions of a temperature of 30°C, a strain of 10%, and a frequency of 15 Hz. The evaluation results were indexed with the reciprocal of tan δ of Comparative Example 1 set as 100. A larger index value indicates a smaller tan δ and better fuel economy.

[0120] (4) Abrasion resistance In accordance with JIS K 6264-2:2005, sandpaper was attached to the grinding wheel using a Lambourn abrasion tester manufactured by Ueshima Seisakusho, and the amount of wear was measured at room temperature with a slip rate of 12%. The evaluation results were indexed, with the reciprocal of the amount of wear in Comparative Example 1 set as 100. A larger index value indicates a smaller amount of wear and better abrasion resistance.

[0121] [Table 2]

[0122] *1 NR: Natural rubber *2 BR: Butadiene rubber, manufactured by UBE Elastomers, product name "BR150L" *3 BR + heterocyclic compound: Modified diene rubber (masterbatch) in which a heterocyclic compound is bonded to butadiene rubber [manufactured by UBE Elastomers, product name "BR150L"] *4 Copolymer: A copolymer of cyclopentene and dicyclopentadiene synthesized by the above method. *5 Copolymer + heterocyclic compound: Modified diene rubber (masterbatch) in which a heterocyclic compound is bonded to the copolymer of cyclopentene and dicyclopentadiene synthesized by the above method. *6 Carbon black: Cetyltrimethylammonium bromide (CTAB) adsorption specific surface area is 130m 2 / g and dibutyl phthalate (DBP) absorption of 140mL / 100g carbon black *7 ZDMA: Zinc dimethacrylate, manufactured by CRAY VALLEY, product name "DYMALINK 708"

[0123] The results shown in Table 2 show that the rubber composition of the embodiment, which contains a copolymer of cyclopentene and a norbornene compound, a heterocyclic compound having a six-membered aromatic heterocycle, and a metal salt, is able to achieve both low fuel consumption and wear resistance.

[0124] On the other hand, it can be seen that the rubber composition of Comparative Example 2, which contains a heterocyclic compound having a six-membered aromatic heterocycle but does not contain a copolymer of cyclopentene and a norbornene compound, has significantly deteriorated wear resistance. In addition, it can be seen that the rubber composition of Comparative Example 3, which contains a copolymer of cyclopentene and a norbornene-based compound but does not contain a heterocyclic compound having a six-membered aromatic heterocycle, has significantly deteriorated fuel economy.

[0125] [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 the achievement of goals such as "No. 7 - Affordable and clean energy for all," "No. 12 - Responsible consumption and production," and "No. 13 - Take concrete measures against climate change."

Claims

1. The rubber composition includes a rubber component, a heterocyclic compound having a six-membered aromatic heterocycle, and a metal salt, The rubber component is a compound represented by the following general formula (1): 【Chemistry 1】 [In the formula, R １ ~R ４ each 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; R ２ and R ３ may be bonded to each other to form a ring, and m is an integer of 0 to 2.

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

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

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

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

6. 3. The rubber composition for tires according to claim 2, wherein the copolymer of cyclopentene and a norbornene-based compound has a content of structural units derived from 2-norbornene of 10 to 60% by mass.

7. 3. The rubber composition for tires according to claim 2, wherein the copolymer of cyclopentene and a norbornene-based compound has a content of structural units derived from dicyclopentadiene of 10 to 60 mass %.

8. 2. The rubber composition for tires according to claim 1, wherein the heterocyclic compound has at least one heterocycle selected from the group consisting of a pyridine ring, a pyrimidine ring, a pyridazine ring, a pyrazine ring, a triazine ring, and a tetrazine ring.

9. The rubber composition for a tire according to claim 1 , wherein the heterocyclic compound has a triazine ring or a tetrazine ring.

10. The heterocyclic compound is represented by the following general formula (2): 【Chemistry 2】 [In the formula, X １ and X ２ are each independently a pyridyl group or a pyrimidinyl group; Y １ and Y ２ and each independently represents a single bond or a divalent hydrocarbon group.

11. The rubber composition for tires according to claim 1 , wherein the metal salt comprises zinc oxide.

12. The rubber composition for a tire according to claim 11, further comprising a metal salt other than zinc oxide as the metal salt.

13. A tire comprising the rubber composition for tires according to claim 1.

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