Rubber composition and crosslinked rubber object

Abstract

Provided is a rubber composition comprising an inorganic material and a copolymer formed by ring-opening copolymerization, the copolymer comprising a structural unit derived from a cyclooctadiene and a structural unit derived from a norbornene compound.

Description

Rubber composition and cross-linked rubber

[0001] The present invention relates to a rubber composition capable of providing a cross-linked rubber product having excellent fracture resistance and chipping resistance, and to the cross-linked rubber product.

[0002] Generally, cyclopentene and norbornene compounds are ６ and MoCl ５ It is known that unsaturated linear ring-opening copolymers can be obtained by metathesis ring-opening polymerization in the presence of a so-called Ziegler-Natta catalyst, which is composed of a Group 6 transition metal compound such as a Group 6 transition metal of the periodic table, and an organometallic activator such as triisobutylaluminum, diethylaluminum chloride, or tetrabutyltin. Also known is a method for improving the affinity of a polymer for inorganic particles by introducing a functional group containing a heteroatom into the polymer chain end.

[0003] For example, Patent Document 1 discloses a composition for a fracture-resistant material, which contains an inorganic material and a ring-opening copolymer containing structural units derived from a monocyclic olefin and structural units derived from a norbornene compound. The technology of Patent Document 1 makes it possible to provide a cross-linked rubber product that is excellent in fracture resistance and chipping resistance and is suitable for use in tires, etc. However, there is a demand for a cross-linked rubber product that has even better fracture resistance and chipping resistance.

[0004] Japanese Patent Application Laid-Open No. 2020-15832

[0005] The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a rubber composition that can give a cross-linked rubber product that is excellent in fracture resistance and chipping resistance, and a cross-linked rubber product obtained by cross-linking such a rubber composition.

[0006] Means for Solving the Problems The present inventors have conducted extensive research to achieve the above object and have found that a rubber composition containing an inorganic material and a ring-opening copolymer containing structural units derived from cyclooctadiene and structural units derived from a norbornene compound allows a cross-linked rubber product obtained using the rubber composition to exhibit excellent fracture resistance and chipping resistance, thereby completing the present invention.

[0007] That is, according to the present invention, there is provided a rubber composition containing an inorganic material and a ring-opening copolymer containing structural units derived from cyclooctadiene and structural units derived from a norbornene compound.

[0008] The inorganic material is preferably a carbon material or silica. The norbornene compound is preferably a norbornene compound represented by the following general formula (1): (In the formula, R １ ~R ４ 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 structure, and m is 0 or 1. １ ~R ４ preferably contains 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. The ring-opening polymer preferably has a weight average molecular weight of 50,000 to 1,000,000. The ring-opening polymer preferably has a glass transition temperature of -80 to 10°C. The rubber composition of the present invention may further contain a rubber other than the ring-opening copolymer.

[0009] According to the present invention, there is also provided a cross-linked rubber product obtained by cross-linking the above rubber composition.

[0010] According to the present invention, it is possible to provide a rubber composition that can give a cross-linked rubber product that is excellent in fracture resistance and chipping resistance, and a cross-linked rubber product obtained by cross-linking such a rubber composition.

[0011] <Rubber Composition> The rubber composition of the present invention contains an inorganic material and a ring-opening copolymer containing structural units derived from cyclooctadiene and structural units derived from a norbornene compound. The rubber composition is a composition that can give a cross-linked rubber product having excellent fracture resistance, and preferably a composition that can give a cross-linked rubber product exhibiting tensile strength and tear strength within the suitable numerical ranges described below.

[0012] The ring-opened copolymer contained in the rubber composition of the present invention contains structural units derived from cyclooctadiene and structural units derived from a norbornene compound.

[0013] The cyclooctadiene of the present invention includes 1,3-cyclooctadiene, 1,4-cyclooctadiene, and 1,5-cyclooctadiene, with 1,5-cyclooctadiene being preferred.

[0014] The norbornene compound in the present invention is a compound having a norbornene ring structure, and is preferably a norbornene compound represented by the following general formula (1).

[0015] In the formula, R １ ~R ４ 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 structure, and m is 0 or 1.

[0016] Specific examples of the norbornene compound represented by the general formula (1) include the following compounds.

[0017] 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[9.2.1.0 ２，１０ .0 ３，８ ]tetradeca-3,5,7,12-tetraene (also known as 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 known as 1,4-methano-1,4,4a,9,9a,10-hexahydroanthracene), dicyclopentadiene, methyldicyclopentadiene, and dihydrodicyclopentadiene (tricyclo[5.2.1.0 ２，６ bicyclo[2.2.1]hept-2-enes, such as unsubstituted or hydrocarbon-substituted bicyclo[2.2.1]hept-2-enes;

[0018] Tetracyclo[6.2.1.1 ３，６ .0 ２，７ ] dodec-4-ene, 9-methyltetracyclo[6.2.1.1 ３，６ .0 ２，７ ] dodec-4-ene, 9-ethyltetracyclo[6.2.1.1 ３，６ .0 ２，７ ] dodec-4-ene, 9-cyclohexyltetracyclo[6.2.1.1 ３，６ .0 ２，７ ] dodec-4-ene, 9-cyclopentyltetracyclo[6.2.1.1 ３，６ .0 ２，７ ] dodec-4-ene, 9-methylenetetracyclo[6.2.1.1 ３，６ .0 ２，７ ] dodec-4-ene, 9-ethylidenetetracyclo[6.2.1.1 ３，６ .0 ２，７ ] dodec-4-ene, 9-vinyltetracyclo[6.2.1.1 ３，６ .0 ２，７ ] dodec-4-ene, 9-propenyltetracyclo[6.2.1.1 ３，６ .0 ２，７ ] dodec-4-ene, 9-cyclohexenyltetracyclo[6.2.1.1 ３，６ .0 ２，７ ] dodec-4-ene, 9-cyclopentenyltetracyclo[6.2.1.1 ３，６ .0 ２，７ ] dodec-4-ene, and 9-phenyltetracyclo[6.2.1.1 ３，６ .0 ２，７ ] tetracyclo[6.2.1.1] unsubstituted or having hydrocarbon substituents, such as dodec-4-ene; ３，６ .0 ２，７ ] dodec-4-enes;

[0019] 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 ] dodec-9-ene-4-carboxylate methyl, and 4-methyltetracyclo[6.2.1.1 ３，６ .0 ２，７ ] tetracyclo[6.2.1.1] having an alkoxycarbonyl group, such as methyl dodec-9-ene-4-carboxylate ３，６ .0 ２，７ ] dodec-4-enes;

[0020] 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 acid anhydride; tetracyclo[6.2.1.1 ３，６ .0 ２，７ ] dodec-9-ene-4-carboxylic acid, tetracyclo[6.2.1.1 ３，６ .0 ２，７ ] dodec-9-ene-4,5-dicarboxylic acid, and tetracyclo[6.2.1.1 ３，６ .0 ２，７ ] dodec-9-ene-4,5-dicarboxylic acid anhydride, or other tetracyclo[6.2.1.1 ３，６ .0 ２，７ ] dodec-4-enes;

[0021] 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]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;３，６ .0 ２，７ ] dodec-9-ene-4-methanol, and tetracyclo[6.2.1.1 ３，６ .0 ２，７ ] dodec-9-en-4-ol and other hydroxyl-containing tetracyclo[6.2.1.1 ３，６ .0 ２，７ ] dodec-4-enes;

[0022] Bicyclo[2.2.1]hept-2-enes having a hydrocarbonyl group such as 5-norbornene-2-carbaldehyde; tetracyclo[6.2.1.1 ３，６ .0 ２，７ ] dodec-9-ene-4-carbaldehyde, and the like. ３，６ .0 ２，７ ] dodec-4-enes;

[0023] bicyclo[2.2.1]hept-2-enes having an alkoxycarbonyl group and a hydroxycarbonyl group, such as 3-methoxycarbonyl-5-norbornene-2-carboxylic acid;

[0024] 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; ３，６ .0 ２，７ ] dodec-4-enyl acrylate, 9-tetracyclo[6.2.1.1 ３，６ .0 ２，７ ] dodec-4-enyl, and 9-tetracyclo[6.2.1.1 methacrylate ３，６ .0 ２，７ ] tetracyclo[6.2.1.1] having a carbonyloxy group such as dodec-4-enyl ３，６ .0 ２，７ ] dodec-4-enes;

[0025] 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[6.2.1.1 ３，６ .0 ２，７ ] dodec-9-ene-4-carbonitrile, tetracyclo[6.2.1.1 ３，６ .0 ２，７ ] dodec-9-ene-4-carboxamide, and tetracyclo[6.2.1.1 ３，６ .0 ２，７ ] dodec-9-ene-4,5-dicarboxylic acid imide and other tetracyclo[6.2.1.1 ３，６ .0 ２，７ ] dodec-4-enes;

[0026] 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] dodec-4-ene having a halogen atom, ３，６ .0 ２，７ ] dodec-4-enes;

[0027] Bicyclo[2.2.1]hept-2-enes having a functional group containing a silicon atom, such as 5-trimethoxy-2-norbornene and 5-triethoxy-2-norbornene; 4-trimethoxysilyltetracyclo[6.2.1.1 ３，６ .0 ２，７ ] dodec-9-ene, 4-triethoxysilyltetracyclo[6.2.1.1 ３，６ .0 ２，７ ] tetracyclo[6.2.1.1] having a functional group containing a silicon atom, such as dodec-9-ene ３，６ .0 ２，７ ] dodec-4-enes;

[0028] The norbornene compound represented by the general formula (1) is preferably a compound represented by the general formula (1) in which m is 0. １ ~R ４may be the same or different.

[0029] Among the norbornene compounds represented by the general formula (1), R in the general formula (1) is particularly preferred because it can provide a cross-linked rubber product that exhibits more excellent fracture resistance and chipping resistance. 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 do not bond 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, the group represented by the general formula in which m is 0 is also preferred.

[0030] R in the above general formula (1) １ ~R ４ Specific examples of norbornene compounds in which R is a substituent containing 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 include the following compounds.

[0031] Bicyclo[2.2.1]hept-2-enes having unsubstituted or chain hydrocarbon substituents, such as 2-norbornene, 5-methyl-2-norbornene, 5-ethyl-2-norbornene, 5-butyl-2-norbornene, 5-hexyl-2-norbornene, 5-decyl-2-norbornene, 5-ethylidene-2-norbornene, 5-vinyl-2-norbornene, and 5-propenyl-2-norbornene;

[0032] 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;

[0033] bicyclo[2.2.1]hept-2-enes having a hydroxycarbonyl group, such as 5-norbornene-2-carboxylic acid and 5-norbornene-2,3-dicarboxylic acid;

[0034] 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;

[0035] Bicyclo[2.2.1]hept-2-enes having a hydroxycarbonyl group such as 5-norbornene-2-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;

[0036] 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;

[0037] bicyclo[2.2.1]hept-2-enes having a functional group containing a nitrogen atom, such as 5-norbornene-2-carbonitrile and 5-norbornene-2-carboxamide;

[0038] bicyclo[2.2.1]hept-2-enes having a halogen atom, such as 5-chloro-2-norbornene;

[0039] bicyclo[2.2.1]hept-2-enes having a functional group containing a silicon atom, such as 5-trimethoxy-2-norbornene and 5-triethoxy-2-norbornene;

[0040] R in the above general formula (1) １ ~R ４However, as the norbornene 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, 5-methyl-2-norbornene, 5-ethyl-2-norbornene, 5-ethylidene-2-norbornene, and 5-vinyl-2-norbornene are more preferred, and from the viewpoint of more easily achieving the effects of the present invention, 2-norbornene, 5-methyl-2-norbornene, and 5-ethyl-2-norbornene are even more preferred.

[0041] Furthermore, as the norbornene compound represented by the general formula (1), R ２ and R ３ When a compound in which R and R are bonded to each other to form a ring is used, specific examples of the ring structure 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. 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, the group represented by the general formula in which m is 0 is also preferred.

[0042] R ２ and R ３and 1,4-dimethyl-1,4-propanol-2,4-one are preferably bonded to each other to form a ring, and more preferably, 1,4-dimethyl-1,4-propanol-2,4-one is preferably bonded to each other to form a ring.

[0043] In the present invention, the norbornene compounds may be used singly or in combination of two or more.

[0044] The content of cyclooctadiene-derived structural units relative to all repeating structural units in the ring-opened copolymer contained in the rubber composition of the present invention is preferably 10 to 75 wt %, more preferably 20 to 65 wt %, even more preferably 30 to 55 wt %, and particularly preferably 35 to 50 wt %. If the content of cyclooctadiene-derived structural units is within the above range, a cross-linked rubber product can be obtained that exhibits better fracture resistance and chipping resistance.

[0045] The content of the structural units derived from norbornene compounds relative to all repeating structural units in the ring-opened copolymer contained in the rubber composition of the present invention is preferably 25 to 90 wt %, more preferably 35 to 80 wt %, even more preferably 45 to 70 wt %, and particularly preferably 50 to 65 wt %. When the content of the structural units derived from norbornene compounds is within the above range, a cross-linked rubber product exhibiting better fracture resistance and chipping resistance can be obtained.

[0046] Furthermore, the ring-opening copolymer of the present invention may be a copolymer of cyclooctadiene and a norbornene compound with other monomers copolymerizable therewith. Examples of such other monomers include monocyclic olefins other than cyclooctadiene and polycyclic cycloolefins having an aromatic ring. The monocyclic olefins other than cyclooctadiene are not particularly limited as long as they are olefins having only one cyclic structure, and examples thereof include cyclic monoolefins such as cyclopropene, cyclobutene, cyclopentene, methylcyclopentene, cyclohexene, methylcyclohexene, cycloheptene, and cyclooctene; and cyclic diolefins such as cyclohexadiene, methylcyclohexadiene, and methylcyclooctadiene. Examples of polycyclic cycloolefins having an aromatic ring include phenylcyclooctene, 5-phenyl-1,5-cyclooctadiene, and phenylcyclopentene. The content of structural units derived from other monomers in the ring-opened copolymer of the present invention relative to all repeating structural units is preferably 40% by weight or less, more preferably 30% by weight or less, and it is particularly preferred that the ring-opened copolymer of the present invention is substantially free of structural units derived from other monomers.

[0047] The weight-average molecular weight (Mw) of the ring-opened copolymer of the present invention, as measured by gel permeation chromatography and converted into polystyrene equivalent, is preferably 50,000 to 1,000,000, more preferably 50,000 to 700,000, even more preferably 100,000 to 500,0000, and particularly preferably 150,000 to 300,000. By setting the weight-average molecular weight (Mw) within the above range, the resulting cross-linked rubber product can be made to exhibit superior fracture resistance and chipping resistance while improving production and handling. If the weight-average molecular weight is too low, particularly 50,000 or less, the resulting cross-linked rubber product will have poor fracture resistance and chipping resistance. If the weight-average molecular weight is too high, particularly 1,000,000 or more, the resulting cross-linked rubber product will have poor processability and will be difficult to produce and handle. The ratio (Mw / Mn) of the weight average molecular weight (Mw) to the number average molecular weight (Mn) of the ring-opened copolymer of the present invention, measured by gel permeation chromatography in terms of polystyrene, is preferably 1.0 to 5.0, more preferably 1.5 to 3.0.

[0048] The cis / trans ratio of the ring-opened copolymer of the present invention is preferably 95 / 5 to 5 / 95, more preferably 90 / 10 to 10 / 90, even more preferably 85 / 15 to 15 / 85, and particularly preferably 60 / 40 to 20 / 80. The cis / trans ratio refers to the ratio of cis to trans double bonds present in the repeating units constituting the ring-opened copolymer of the present invention (cis / trans ratio). By setting the cis / trans ratio within the above range, the cross-linked rubber product of the present invention obtained using the ring-opened copolymer can exhibit superior fracture resistance and chipping resistance. If the cis ratio is too high, a rubber composition containing a carbon material as an inorganic material will produce a cross-linked rubber product that is excellent in abrasion resistance as well as fracture resistance and chipping resistance, as described below, but may have poor handling stability.

[0049] The ring-opened copolymer of the present invention preferably has a glass transition temperature (Tg) of -80 to 10°C, more preferably -65 to -10°C, and even more preferably -50 to -10°C. By adjusting the glass transition temperature (Tg) within the above range, the cross-linked rubber product of the present invention obtained using the ring-opened copolymer can exhibit better fracture resistance and chipping resistance. If the glass transition temperature is too low, properties such as fracture resistance and chipping resistance may be lost, while if the glass transition temperature is too high, processability may be significantly impaired and properties such as elongation may be lost. The glass transition temperature of the ring-opened copolymer can be controlled, for example, by adjusting the type and amount of norbornene compound used.

[0050] Furthermore, the ring-opened copolymer of the present invention may have a modified group at the polymer chain end. By having such a terminal modified group, the ring-opened copolymer of the present invention may be able to further increase its affinity for inorganic materials, which may in turn increase the dispersibility of the inorganic material in the cross-linked rubber when blended with the copolymer. As a result, the cross-linked rubber may have further improved fracture resistance and chipping resistance. The modifying group to be introduced at the polymer chain end is not particularly limited, but is preferably a modifying group containing an atom selected from the group consisting of atoms in Group 15 of the periodic table, atoms in Group 16 of the periodic table, and silicon atoms.

[0051] As the modifying group for forming the terminal modified group, from the viewpoint that the affinity for inorganic materials can be increased, and thus the fracture resistance and chipping resistance can be further improved when a cross-linked rubber is obtained, a modifying 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 preferred, and among these, a modifying group containing an atom selected from the group consisting of a nitrogen atom, an oxygen atom, and a silicon atom is even more preferred.

[0052] Examples of modifying groups containing nitrogen atoms include amino groups, pyridyl groups, imino groups, amide groups, nitro groups, urethane bond groups, and hydrocarbon groups containing any of these groups. Examples of modifying groups containing oxygen atoms include hydroxyl groups, carboxylic acid groups, ether groups, ester groups, carbonyl groups, aldehyde groups, epoxy groups, and hydrocarbon groups containing any of these groups. Examples of modifying groups containing silicon atoms include alkylsilyl groups, oxysilyl groups, and hydrocarbon groups containing any of these groups. Examples of modifying groups containing phosphorus atoms include phosphate groups, phosphino groups, and hydrocarbon groups containing any of these groups. Examples of modifying groups containing sulfur atoms include sulfonyl groups, thiol groups, thioether groups, and hydrocarbon groups containing any of these groups. In addition, the modifying group may be a modifying group containing multiple of the above groups. Among these, specific examples of particularly preferred modifying groups from the viewpoint of further improving the fracture resistance and chipping resistance when a cross-linked rubber is obtained include amino groups, pyridyl groups, imino groups, amide groups, hydroxyl groups, carboxylic acid groups, aldehyde groups, epoxy groups, oxysilyl groups, and hydrocarbon groups containing any of these groups, with oxysilyl groups being particularly preferred from the viewpoint of affinity for silica. Note that the oxysilyl group refers to a group having a silicon-oxygen bond.

[0053] Specific examples of the oxysilyl group include an alkoxysilyl group, an aryloxysilyl group, an acyloxy group, an alkylsiloxysilyl group, and an arylsiloxysilyl group. Also included are hydroxysilyl groups obtained by hydrolyzing an alkoxysilyl group, an aryloxysilyl group, or an acyloxy group. Among these, an alkoxysilyl group is preferred from the viewpoint of affinity with inorganic materials.

[0054] An 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 (dimethoxy)(methyl)silyl group, a (methoxy)(dimethyl)silyl group, a (methoxy)(dichloro)silyl group, a triethoxysilyl group, a (diethoxy)(methyl)silyl group, an (ethoxy)(dimethyl)silyl group, a (dimethoxy)(ethoxy)silyl group, a (methoxy)(diethoxy)silyl group, a tripropoxysilyl group, and a tris(trimethylsiloxy)silyl group.

[0055] The introduction rate of the modified group at the polymer chain end of the ring-opened copolymer 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 of the number of chain ends of the ring-opened copolymer into which the modified group has been introduced / the total number of chain ends of the ring-opened copolymer. The higher the introduction rate of the terminal modified group, the higher the affinity with inorganic materials, which results in better low heat generation, and is therefore preferred. The method for measuring the introduction rate of the modified group at the polymer chain end is not particularly limited, but an example of introducing an oxysilyl group 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 determined by gel permeation chromatography.

[0056] The Mooney viscosity (ML1+4, 100°C) of the ring-opened copolymer in the present invention is preferably 20 to 150, more preferably 22 to 120, and even more preferably 25 to 90. By setting the Mooney viscosity within the above range, kneading at room temperature and at high temperatures can be facilitated, thereby improving processability.

[0057] The method for producing the ring-opened copolymer of the present invention is not particularly limited, but may be, for example, a method in which cyclooctadiene and a norbornene compound are copolymerized in the presence of a ring-opening polymerization catalyst.

[0058] The ring-opening polymerization catalyst may be any catalyst capable of ring-opening copolymerization of cyclooctadiene and a norbornene compound, and among these, ruthenium carbene complexes and so-called Ziegler-Natta catalysts are preferred.

[0059] Specific examples of ruthenium carbene complexes include bis(tricyclohexylphosphine)benzylideneruthenium dichloride, bis(triphenylphosphine)-3,3-diphenylpropenylideneruthenium dichloride, bis(tricyclohexylphosphine)t-butylvinylideneruthenium dichloride, dichloro-(3-phenyl-1H-inden-1-ylidene)bis(tricyclohexylphosphine)ruthenium, bis(1,3-diisopropylimidazolin-2-ylidene)benzylideneruthenium dichloride, and bis(1,3-dicyclohexyl

[0034] Examples of such compounds include (1,3-dimesitylimidazolin-2-ylidene)benzylideneruthenium dichloride, (1,3-dimesitylimidazolin-2-ylidene)(tricyclohexylphosphine)benzylideneruthenium dichloride, (1,3-dimesitylimidazolidin-2-ylidene)(tricyclohexylphosphine)benzylideneruthenium dichloride, (1,3-dimesitylimidazolidin-2-ylidene)(tricyclohexylphosphine)benzylideneruthenium dichloride, bis(tricyclohexylphosphine)ethoxymethylideneruthenium dichloride, and (1,3-dimesitylimidazolidin-2-ylidene)(tricyclohexylphosphine)ethoxymethylideneruthenium dichloride.

[0060] The Ziegler-Natta catalyst is a mixed catalyst of a Group 6 transition metal compound and an organoaluminum compound. Specific examples of the Group 6 transition metal compound include molybdenum compounds such as molybdenum pentachloride, molybdenum oxotetrachloride, molybdenum(phenylimido)tetrachloride, tridodecylammonium molybdate, methyltrioctylammonium molybdate, tridecylammonium molybdate, trioctylammonium molybdate, and tetraphenylammonium molybdate; and tungsten compounds such as tungsten hexachloride, tungsten oxotetrachloride, tungsten(phenylimido)tetrachloride, monocatecholate tungsten tetrachloride, bis(3,5-ditertiarybutyl)catecholate tungsten dichloride, bis(2-chloroetherate)tetrachloride, and tungsten oxotetraphenolate.

[0061] Specific examples of organoaluminum compounds contained in Ziegler-Natta catalysts include diethylaluminum ethoxide, diethylaluminum isopropoxide, diisobutylaluminum butoxide, diisobutylaluminum hexoxide, diethylaluminum (2-trichloroethoxide), diethylaluminum (2-tribromoethoxide), diethylaluminum (1,3-dichloro-2-propoxide), diethylaluminum (1,1,1,3,3,3-hexafluoro-2-propoxide), diethylaluminum (1,1,1-trichloro-2-methyl-2-propoxide), diethylaluminum (2,6-diisopropylphenoxide), ethylaluminum di(2-trichloroethoxide), ethylaluminum di(2-tribromoethoxide), ethylaluminum di(1,3-dichloro-2-propoxide), and ethylaluminum. di(1,1,1,3,3,3-hexafluoro-2-propoxide), ethylaluminum di(1,1,1-trichloro-2-methyl-2-propoxide), ethylaluminum bis(2,6-diisopropylphenoxide), ethyl(chloro)aluminum ethoxide, ethyl(chloro)aluminum isopropoxide, ethyl(chloro)aluminum butoxide, ethyl(chloro)aluminum(2-trichloroethoxide), ethyl(chloro)aluminum(2-tribromoethoxide), ethyl(bromo)aluminum(1,3-dichloro-2-propoxide), ethyl(chloro)aluminum(1,1,1,3,3,3-hexafluoro-2-propoxide), ethyl(chloro)aluminum(1,1,1-trichloro-2-methyl-2-propoxide), ethyl(chloro)aluminum(2,6-diisopropylphenoxide), and the like.

[0062] The ring-opening polymerization catalyst may be used alone or in combination of two or more.

[0063] The amount of the ring-opening polymerization catalyst used is, in terms of the molar ratio of (ring-opening polymerization catalyst:monomer used for copolymerization), usually in the range of 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.

[0064] The polymerization reaction may be carried out in a solventless state or in a solution. When copolymerization is carried out in a solution, the solvent used is not particularly limited as long as it is inert to the polymerization reaction and can dissolve the cyclooctadiene or norbornene compound used in the copolymerization, the polymerization catalyst, and the like. However, it is preferable to use a hydrocarbon solvent or a halogenated 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 halogenated solvents include haloalkanes such as dichloromethane and chloroform; and aromatic halogens such as chlorobenzene and dichlorobenzene. These solvents may be used alone or in combination.

[0065] When ring-opening copolymerizing cyclooctadiene and a norbornene compound, an olefin compound or a diolefin compound may be added to the polymerization reaction system as a molecular weight modifier, if necessary, in order to adjust the molecular weight of the resulting ring-opening copolymer.

[0066] 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; vinyl ethers such as ethyl vinyl ether and i-butyl vinyl ether; amine-containing vinyl compounds such as allylamine, N,N-dimethylallylamine, and N,N-diethylallylamine; and disubstituted olefins such as 2-butene and 3-hexene.

[0067] The diolefin compounds 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.

[0068] The amount of the olefin compound and diolefin compound used as a molecular weight modifier may be appropriately selected depending on the molecular weight of the ring-opening 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 relative to the monomer used in copolymerization.

[0069] Furthermore, when the ring-opening copolymer of the present invention has a modifying group at the polymer chain end, it is preferable to use a modifying group-containing olefinically unsaturated hydrocarbon compound as the molecular weight modifier instead of the above-mentioned olefin compound or diolefin compound. By using such a modifying group-containing olefinically unsaturated hydrocarbon compound, the modifying group can be suitably introduced into the polymer chain end of the ring-opening copolymer obtained by copolymerization.

[0070] The modifying group-containing olefinically unsaturated hydrocarbon compound is not particularly limited as long as it has a modifying group and one metathesis-reactive olefinic carbon-carbon double bond. For example, when it is desired to introduce an oxysilyl group into the polymer chain terminal of a ring-opening copolymer, an oxysilyl group-containing olefinically unsaturated hydrocarbon may be present in the polymerization reaction system.

[0071] Examples of such oxysilyl group-containing olefinically unsaturated hydrocarbons include alkoxysilane compounds such as vinyl(trimethoxy)silane, vinyl(triethoxy)silane, allyl(trimethoxy)silane, allyl(methoxy)(dimethyl)silane, allyl(triethoxy)silane, allyl(ethoxy)(dimethyl)silane, styryl(trimethoxy)silane, styryl(triethoxy)silane, styrylethyl(triethoxy)silane, allyl(triethoxysilylmethyl)ether, and allyl(triethoxysilylmethyl)(ethyl)amine, which introduce a modifying group only at one end (one end) of the polymer chain of the ring-opening copolymer; aryloxysilane compounds such as vinyl(triacetoxy)silane, allyl(triacetoxy)silane, allyl(diacetoxy)methylsilane, and allyl(acetoxy)(dimethyl)silane; acyloxysilane compounds such as vinyl(triacetoxy)silane, allyl(triacetoxy)silane, allyl(diacetoxy)methylsilane, and allyl(acetoxy)(dimethyl)silane; 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.

[0072] Furthermore, examples of compounds for introducing modifying groups into both ends (both ends) of the polymer chain of the ring-opening 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); acyloxysilane compounds such as 2-butene-1,4-di[tris(trimethylsiloxy)silane]; alkylsiloxysilane compounds such as 2-butene-1,4-di[tris(triphenylsiloxy)silane]; arylsiloxysilane compounds such as 2-butene-1,4-di[heptamethyltrisiloxane] and 2-butene-1,4-di(undecamethylcyclohexasiloxane); and the like.

[0073] The modifying group-containing olefinically unsaturated hydrocarbon compound, such as an oxysilyl group-containing olefinically unsaturated hydrocarbon compound, acts as a molecular weight modifier in addition to the function of introducing a modifying group into the polymer chain terminal of the ring-opened 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 ring-opened copolymer to be produced, and 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 relative to the monomers used in copolymerization.

[0074] 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 also not particularly limited, but is preferably 1 minute to 72 hours, and more preferably 10 minutes to 20 hours.

[0075] If desired, an antioxidant such as a phenol-based stabilizer, a phosphorus-based stabilizer, or a sulfur-based stabilizer may be added to the ring-opening copolymer obtained by the polymerization reaction. The amount of the antioxidant to be added may be determined appropriately depending on the type of the antioxidant. Furthermore, if desired, an extender oil may be blended. When the ring-opening copolymer is obtained as a polymerization solution, known recovery methods may be used to recover the ring-opening copolymer from the polymerization solution. For example, a method in which the solvent is separated by steam stripping or the like, the solid is filtered off, and then dried to obtain a solid ring-opening copolymer; a method in which the solvent is directly devolatilized using a twin-screw heating dryer or the like to obtain a solid ring-opening copolymer; or a method in which the ring-opening copolymer is reprecipitated in a poor solvent, the solvent is separated, the solid is filtered, and then dried to obtain a solid ring-opening copolymer.

[0076] The rubber composition of the present invention may contain a rubber other than the ring-opened copolymer as a rubber component. In the present invention, the rubber component refers to the ring-opened copolymer and a rubber other than the ring-opened copolymer. Examples of rubbers other than the ring-opened copolymer include natural rubber (NR), polyisoprene rubber (IR), emulsion-polymerized SBR (styrene-butadiene copolymer rubber), solution-polymerized random SBR (bound styrene 5 to 50% by weight, 1,2-bond content in butadiene portion 10 to 80%), high trans SBR (trans bond content in butadiene portion 70 to 95%), low cis BR (polybutadiene rubber), high cis BR, high trans BR (trans bond content in butadiene portion 70 to 95%), ethylene-propylene-diene rubber, and the like. Examples of suitable rubbers include EPDM, styrene-isoprene copolymer rubber, butadiene-isoprene copolymer rubber, emulsion-polymerized styrene-acrylonitrile-butadiene copolymer rubber, acrylonitrile-butadiene copolymer rubber, high-vinyl SBR-low-vinyl SBR block copolymer rubber, polyisoprene-SBR block copolymer rubber, polystyrene-polybutadiene-polystyrene block copolymer, acrylic rubber, epichlorohydrin rubber, fluororubber, silicone rubber, ethylene-propylene rubber, and urethane rubber. Of these, NR, BR, IR, EPDM, and SBR are preferred, with solution-polymerized random SBR being particularly preferred. These rubbers may be used alone or in combination of two or more.

[0077] In the present invention, the rubber other than the above-mentioned ring-opening copolymer may have a modifying group at the polymer end. The modifying group that can be present at the polymer end of the rubber other than the above-mentioned ring-opening copolymer may be the same as the modifying group that can be present at the polymer end of the above-mentioned ring-opening copolymer, and the same modifying group as the preferred modifying group that can be present at the polymer end of the above-mentioned ring-opening copolymer is preferred.

[0078] The rubber composition of the present invention contains an inorganic material that functions as a filler. The inorganic material contained in the rubber composition of the present invention is preferably a carbon material or silica. The carbon material is preferably carbon black. A rubber composition containing a carbon material as an inorganic material can provide a cross-linked rubber product that is excellent in not only fracture resistance and chipping resistance but also abrasion resistance and handling stability. Furthermore, a rubber composition containing silica as an inorganic material can provide a cross-linked rubber product that is excellent in not only fracture resistance and chipping resistance but also wet grip properties and low heat buildup.

[0079] Examples of carbon black used as the inorganic material contained in the rubber composition of the present invention include furnace black, acetylene black, thermal black, channel black, graphite, etc. Among these, furnace black is preferred, and specific examples thereof include SAF, ISAF, ISAF-HS, ISAF-LS, IISAF-HS, HAF, HAF-HS, HAF-LS, FEF, etc. These carbon blacks can be used alone or in combination of two or more.

[0080] The nitrogen adsorption specific surface area of ​​carbon black (N ２ SA) is preferably 5 to 200 m ２ / g, more preferably 70 to 120m ２ The dibutyl phthalate (DBP) adsorption amount is preferably 5 to 300 ml / 100 g, more preferably 80 to 160 ml / 100 g.

[0081] Examples of silica used as an inorganic material in the rubber composition of the present invention include dry-process white carbon, wet-process white carbon, colloidal silica, and precipitated silica disclosed in Japanese Patent Laid-Open No. 62-62838. Among these, wet-process white carbon containing hydrous silicic acid as the main component is preferred. Alternatively, a carbon-silica dual-phase filler in which silica is supported on the surface of carbon black may be used. These silicas may be used alone or in combination of two or more.

[0082] The nitrogen adsorption specific surface area of ​​the silica (measured by the BET method in accordance with ASTM D3037-81) is preferably 50 to 400 m ２ / g, more preferably 100 to 220m ２ The pH of the silica is preferably less than pH 7, and more preferably from pH 5 to 6.9. Within these ranges, the affinity between the ring-opening copolymer and the silica becomes particularly good.

[0083] When silica is used as the inorganic material, it is preferable to further compound a silane coupling agent in the rubber composition of the present invention for the purpose of further improving the affinity between the ring-opening copolymer and the silica. Examples of silane coupling agents include vinyltriethoxysilane, β-(3,4-epoxycyclohexyl)ethyltrimethoxysilane, N-(β-aminoethyl)-γ-aminopropyltrimethoxysilane, bis(3-(triethoxysilyl)propyl)tetrasulfide, bis(3-(triethoxysilyl)propyl)disulfide, and tetrasulfides such as γ-trimethoxysilylpropyldimethylthiocarbamyltetrasulfide and γ-trimethoxysilylpropylbenzothiazyltetrasulfide, which are described in JP-A-6-248116. Among these, tetrasulfides are preferred. These silane coupling agents can be used alone or in combination of two or more. The amount of the silane coupling agent to be added is preferably 0.1 to 30 parts by weight, more preferably 1 to 15 parts by weight, based on 100 parts by weight of the inorganic material.

[0084] The content of the inorganic material in the present invention is preferably 10 to 150 parts by weight, more preferably 20 to 120 parts by weight, still more preferably 40 to 100 parts by weight, and particularly preferably 40 to 60 parts by weight, per 100 parts by weight of the rubber component.

[0085] In addition to the above components, the rubber composition of the present invention may contain required amounts of compounding agents such as crosslinking agents, crosslinking accelerators, crosslinking activators, fillers other than inorganic materials, antioxidants, activators, process oils, plasticizers, and lubricants according to conventional methods.

[0086] Examples of crosslinking agents include sulfur such as powdered sulfur, precipitated sulfur, colloidal sulfur, insoluble sulfur, and highly dispersible sulfur; sulfur halides such as sulfur monochloride and sulfur dichloride; organic peroxides such as dicumyl peroxide and ditertiary butyl peroxide; quinone dioximes such as p-quinone dioxime and p,p'-dibenzoylquinone dioxime; organic polyamine compounds such as triethylenetetramine, hexamethylenediamine carbamate, and 4,4'-methylenebis-o-chloroaniline; and alkylphenol resins having methylol groups. Among these, sulfur is preferred, and powdered sulfur is more preferred. These crosslinking agents may be used alone or in combination of two or more. The amount of crosslinking agent blended is preferably 0.1 to 15 parts by weight, more preferably 0.5 to 5 parts by weight, per 100 parts by weight of the rubber component in the rubber composition.

[0087] Examples of the crosslinking accelerator include sulfenamide-based crosslinking accelerators such as N-cyclohexyl-2-benzothiazolylsulfenamide, N-(tert-butyl)-2-benzothiazolylsulfenamide, N-oxyethylene-2-benzothiazolylsulfenamide, N-oxyethylene-2-benzothiazolylsulfenamide, and N,N'-diisopropyl-2-benzothiazolylsulfenamide; guanidine-based crosslinking accelerators such as 1,3-diphenylguanidine, 1,3-diorthotolylguanidine, and 1-orthotolylbiguanidine; and diethylthiourea. Examples of suitable crosslinking accelerators include thiourea-based crosslinking accelerators such as 2-mercaptobenzothiazole, dibenzothiazyl disulfide, and 2-mercaptobenzothiazole zinc salt; thiuram-based crosslinking accelerators such as tetramethylthiuram monosulfide and tetramethylthiuram disulfide; dithiocarbamate-based crosslinking accelerators such as sodium dimethyldithiocarbamate and zinc diethyldithiocarbamate; and xanthogenate-based crosslinking accelerators such as sodium isopropylxanthogenate, zinc isopropylxanthogenate, and zinc butylxanthogenate. Among these, those containing sulfenamide-based crosslinking accelerators are preferred, and those containing N-(tert-butyl)-2-benzothiazolylsulfenamide are particularly preferred. These crosslinking accelerators may be used alone or in combination of two or more. The amount of crosslinking accelerator blended is preferably 0.1 to 15 parts by weight, more preferably 0.5 to 5 parts by weight, per 100 parts by weight of the rubber component in the rubber composition.

[0088] As the crosslinking activator, for example, a higher fatty acid such as stearic acid, zinc oxide, etc. The compounding amount of the crosslinking activator is appropriately selected, but the compounding amount of the higher fatty acid is preferably 0.05 to 15 parts by weight, more preferably 0.5 to 5 parts by weight, per 100 parts by weight of the rubber component in the rubber composition, and the compounding amount of the zinc oxide is preferably 0.05 to 10 parts by weight, more preferably 0.5 to 3 parts by weight, per 100 parts by weight of the rubber component in the rubber composition.

[0089] The process oil may be a mineral oil or a synthetic oil. Typical examples of mineral oils include aromatic oils, naphthenic oils, and paraffin oils. Other additives include activators such as diethylene glycol, polyethylene glycol, and silicone oil; non-inorganic fillers such as calcium carbonate, talc, and clay; tackifiers such as petroleum resins and coumarone resins; and waxes.

[0090] The rubber composition of the present invention can be obtained by kneading the components according to a conventional method. For example, the compounding ingredients excluding the crosslinking agent and crosslinking accelerator are kneaded with a rubber component such as a ring-opening copolymer, and then the kneaded mixture is mixed with the crosslinking agent and crosslinking accelerator to obtain the rubber composition. The kneading temperature of the compounding ingredients excluding the crosslinking agent and crosslinking accelerator with the rubber component such as the ring-opening copolymer is preferably 20 to 200°C, more preferably 30 to 180°C, and the kneading time is preferably 30 seconds to 30 minutes. The mixing of the crosslinking agent and crosslinking accelerator is usually carried out at 100°C or lower, preferably 80°C or lower.

[0091] <Rubber Cross-Linked Product> The cross-linked rubber product of the present invention is obtained by cross-linking the rubber composition of the present invention described above. The cross-linked rubber product of the present invention can be produced by using the rubber composition of the present invention to mold into a desired shape using a molding machine such as an extruder, injection molding machine, compressor, or roll, and then heating to cause a cross-linking reaction and fix the shape as a cross-linked rubber product. In this case, cross-linking may be carried out after molding in advance, or simultaneously with molding. The molding temperature is usually 10 to 200°C, preferably 25 to 120°C. The cross-linking temperature is usually 100 to 200°C, preferably 130 to 190°C, and the cross-linking time is usually 1 minute to 24 hours, preferably 2 minutes to 12 hours, and particularly preferably 3 minutes to 6 hours.

[0092] Depending on the shape, size, etc. of the cross-linked rubber product, even if the surface is cross-linked, the inside may not be sufficiently cross-linked, so secondary cross-linking may be carried out by further heating.

[0093] The heating method may be appropriately selected from common methods used for crosslinking rubber, such as press heating, steam heating, oven heating, and hot air heating.

[0094] The cross-linked rubber product of the present invention obtained in this manner has high tensile strength and tear strength. Specifically, the tensile strength of the cross-linked rubber product of the present invention, measured in a tensile test in accordance with JIS K6251:2010, is preferably 20 MPa or more, more preferably 25 MPa or more, even more preferably 30 MPa or more, and particularly preferably 35 MPa or more. Furthermore, the elongation of the cross-linked rubber product of the present invention, measured in a tensile test in accordance with JIS K6251:2010, is preferably 250% or more, more preferably 300% or more, even more preferably 350% or more, and particularly preferably 400% or more. Furthermore, the tear strength of the cross-linked rubber product of the present invention, measured using a tensile tester in accordance with JIS K6252:2007, is preferably 70 N / mm or more, more preferably 75 N / mm or more, and even more preferably 80 N / mm.

[0095] The cross-linked rubber of the present invention can be suitably used in applications such as tires, belts, and vibration-proof rubber, taking advantage of its excellent fracture resistance and chipping resistance.

[0096] Furthermore, a cross-linked rubber product obtained by cross-linking a rubber composition containing a carbon material as an inorganic material is also excellent in abrasion resistance and handling stability, and can be suitably used for tires for large automobiles. Also, a cross-linked rubber product obtained by cross-linking a rubber composition containing silica as an inorganic material is also excellent in wet grip properties and low heat buildup, and can be suitably used for tires for light vehicles.

[0097] The present invention will be described below in more detail with reference to examples, but the present invention is not limited to these examples. In the following, "parts" are by weight unless otherwise specified. Various tests and evaluations were carried out according to the following methods.

[0098] <Molecular Weight of Ring-Opened Copolymer> The number average molecular weight (Mn), weight average molecular weight (Mw), and molecular weight distribution (Mw / Mn) of the ring-opened copolymer were measured as polystyrene equivalent values ​​by gel permeation chromatography (GPC) using tetrahydrofuran as a solvent. The measurement was performed using an "HLC-8320GPC" (manufactured by Tosoh Corporation) column consisting of four "TSKgel Super Multipore HZ-H" columns connected in series under the following conditions: flow rate: 0.35 ml / min, sample injection amount: 10 μml, and column temperature: 40°C.

[0099] <Ratio of structural units derived from norbornene compounds and structural units derived from cyclooctadiene> The ratio of the monomer units in the ring-opened copolymer is １ Specifically, the following was determined by H-NMR spectroscopy: １ H-NMR measurement was carried out, and the ratio of the monomer units in the ring-opened copolymer was determined based on the integral ratio of the signal at 5.0 to 5.5 ppm derived from the double bond and the integral ratio of the signal at 2.3 to 3.0 ppm derived from the norbornene compound.

[0100] <Cis / Trans Ratio of Main Chain Double Bonds> The cis / trans ratio of the main chain double bonds of the ring-opened copolymer is １３ It was determined by C-NMR spectrum measurement.

[0101] <Introduction rate of structural units derived from chain transfer ends> The introduction rate of structural units derived from chain transfer ends in the ring-opening copolymer is １ Specifically, the following was determined by H-NMR spectroscopy: １ H-NMR measurement was carried out, and the ratio of the monomer units in the ring-opened copolymer to the structural units derived from the chain transfer ends was determined based on the integral ratio of the signal at 5.0 to 5.5 ppm derived from the double bond, the integral ratio of the signal at 2.3 to 3.0 ppm derived from the norbornene compound, and, in the case of a chain transfer end having a silyl group, the integral ratio of the signal at −0.5 to 0.5 ppm. The ratio was then compared with the number average molecular weight (Mn) of the ring-opened copolymer calculated from the above-mentioned GPC.

[0102] <Glass Transition Temperature (Tg) of Ring-Opened Copolymer> The glass transition temperature (Tg) of the ring-opened copolymer was measured using a differential scanning calorimeter (DSC "X-DSC7000" (manufactured by Hitachi High-Tech Science Corporation)) from -150 to 40°C at a temperature increase rate of 10°C / min.

[0103] <Tensile Test> A rubber composition was press-crosslinked to produce a sheet-like cross-linked rubber product, and this cross-linked rubber product was punched out parallel to the grain direction into a dumbbell No. 6 shape as defined in JIS K6251:2010 to obtain a dumbbell-shaped test piece. The obtained dumbbell-shaped test piece was then subjected to a tensile test at 23°C and 500 mm / min using a tensile tester (product name "TENSOMETER 10K", manufactured by ALPHA TECHNOLOGIES) in accordance with JIS K6251:2010 to measure the tensile strength and elongation. The higher the tensile strength, the more excellent the fracture resistance properties.

[0104] <Tear Test> A rubber composition was press-crosslinked to prepare a sheet-shaped cross-linked rubber product, and this cross-linked rubber product was punched perpendicular to the grain direction into an angled cutout shape without notches as specified in JIS K6252:2007 to obtain a test piece. The obtained test piece was then subjected to a tear test at 23°C and 500 mm / min using a tensile tester (product name "TENSOMETER 10K", manufactured by ALPHA TECHNOLOGIES) in accordance with JIS K6252:2007 to measure the tear strength. The higher the tear strength, the better the chipping resistance.

[0105] <Rebound Resilience Test> The rubber composition was press-molded under pressure using a mold to obtain a cylindrical cross-linked rubber product for a high resilience material having a diameter of 29 mm and a thickness of 12.5 mm. The rebound resilience of the obtained cylindrical cross-linked rubber product for a high resilience material was measured using a Lübke type rebound resilience tester (manufactured by Kobunshi Keiki Co., Ltd.) as the testing machine in accordance with JIS K6255:1996 under conditions of 23°C and holding force of 29 to 39 N.

[0106] <Wet Grip Property> Test specimens were prepared by press-crosslinking the rubber compositions at 160°C for 20 minutes, and the tan δ of the obtained test specimens was measured at 0°C under conditions of a dynamic strain of 0.5% and 10 Hz using an ARES manufactured by Rheometrics. The obtained measurement results were calculated as an index, with the measured value of the sample of Comparative Example 6 described below being set at 100. The larger this index, the better the wet grip property. The wet grip property was evaluated for Examples 11 to 20 and Comparative Examples 6 to 10.

[0107] <Low Heat Buildup Property> Test specimens were prepared by press-crosslinking the rubber compositions at 160°C for 20 minutes, and the tan δ of the obtained test specimens was measured at 60°C under conditions of a dynamic strain of 2.0% and 10 Hz using an ARES manufactured by Rheometrics Corporation. The obtained measurement results were calculated as an index, with the measured value of the sample of Comparative Example 6 described below being 100. The smaller this index, the better the low heat buildup property. The evaluation of low heat buildup property was performed for Examples 11 to 20 and Comparative Examples 6 to 10.

[0108] <DIN Abrasion Test> The rubber composition was press-molded under pressure using a mold to obtain a cylindrical cross-linked rubber product for a high resilience material having a diameter of 16 mm and a thickness of 6 mm. The specific wear volume of the obtained cylindrical cross-linked rubber product for a high resilience material was measured using a DIN abrasion tester (product name "AB-6110", manufactured by Ueshima Seisakusho Co., Ltd.) in accordance with JIS K6264-2:2005 under the conditions of test method A, applied force of 10 N, friction distance of 40 m, 23°C, and reference test piece D1. A smaller specific wear volume indicates better abrasion resistance. The DIN abrasion test was conducted on Examples 1 to 10 and Comparative Examples 1 to 5.

[0109] <Rubber Hardness> Test specimens were prepared by press-crosslinking the rubber compositions at 160°C for 20 minutes, and the obtained test specimens were measured at a temperature of 20°C using a type A durometer in accordance with JIS K6253. The obtained results were shown with the value of the standard example set at 100. A higher rubber hardness index means better handling stability. The evaluation of rubber hardness was carried out for Examples 1 to 10 and Comparative Examples 1 to 5.

[0110] Polymerization Example 1 (Preparation of Ring-Opened Copolymer (A)) Under a nitrogen atmosphere, 100 parts of 2-norbornene (NB) as a norbornene compound, 60 parts of 1,5-cyclooctadiene (COD), 394 parts of toluene, and 0.10 parts of 1-hexene were added to a glass reaction vessel equipped with a stirrer. Next, 0.005 parts of (1,3-dimesitylimidazolidin-2-ylidene)(tricyclohexylphosphine)benzylideneruthenium(II) dichloride dissolved in 10 parts of toluene was added, and the polymerization reaction was carried out at room temperature for 4 hours. After the polymerization reaction, excess vinyl ethyl ether was added to terminate the polymerization.

[0111] The polymer solution obtained above was poured into a large excess of methanol containing 2,6-di-t-butyl-p-cresol (BHT), and the precipitated polymer was recovered, washed with methanol, and then vacuum-dried at 50°C for 3 days to obtain 159 parts of ring-opened copolymer (A). The resulting ring-opened copolymer (A) had a number-average molecular weight (Mn) of 126,000, a weight-average molecular weight (Mw) of 273,000, a ratio of 2-norbornene structural units / 1,5-cyclooctadiene structural units of 63 / 37 (weight ratio), a cis / trans ratio of 46 / 54, and a glass transition temperature (Tg) of -25°C. The weight ratio of 2-norbornene structural units / 1,5-cyclooctadiene structural units represents the ratio of the content [wt%] of each structural unit. That is, the content of structural units derived from 2-norbornene in the ring-opened copolymer (A) was 63% by weight, and the content of structural units derived from 1,5-cyclooctadiene was 37% by weight. Similarly, the weight ratio of the monomer units in the ring-opened copolymer hereinafter represents the ratio of the content [% by weight] of each monomer unit in the ring-opened copolymer.

[0112] Polymerization Example 2 (Preparation of Ring-Opened Copolymer (B)) Under a nitrogen atmosphere, 110 parts of dicyclopentadiene (DCPD) as a norbornene compound, 90 parts of 1,5-cyclooctadiene (COD), 800 parts of toluene, and 0.11 parts of 1-hexene were added to a glass reaction vessel equipped with a stirrer. Next, 0.010 parts of (1,3-dimesitylimidazolidin-2-ylidene)(tricyclohexylphosphine)benzylideneruthenium(II) dichloride dissolved in 10 parts of toluene was added, and the polymerization reaction was carried out at room temperature for 4 hours. After the polymerization reaction, excess vinyl ethyl ether was added to terminate the polymerization.

[0113] The polymer solution obtained above was poured into a large excess of methanol containing 2,6-di-t-butyl-p-cresol (BHT), and the precipitated polymer was recovered, washed with methanol, and then vacuum dried at 50°C for 3 days to obtain 195 parts of ring-opened copolymer (B). The resulting ring-opened copolymer (B) had a number average molecular weight (Mn) of 124,000, a weight average molecular weight (Mw) of 259,000, a ratio of dicyclopentadiene structural units / 1,5-cyclooctadiene structural units of 55 / 45 (weight ratio), a cis / trans ratio of 42 / 58, and a glass transition temperature (Tg) of -26°C.

[0114] Polymerization Example 3 (Preparation of Ring-Opened Copolymer (C)) Under a nitrogen atmosphere, 41 parts of 2-norbornene (NB) as a norbornene compound, 39 parts of dicyclopentadiene (DCPD) as a norbornene compound, 75 parts of cyclooctadiene, 620 parts of toluene, and 0.14 parts of 1-hexene were added to a glass reaction vessel equipped with a stirrer. Next, 0.005 parts of (1,3-dimesitylimidazolidin-2-ylidene)(tricyclohexylphosphine)benzylideneruthenium(II) dichloride dissolved in 10 parts of toluene was added, and the polymerization reaction was carried out at room temperature for 4 hours. After the polymerization reaction, excess vinyl ethyl ether was added to terminate the polymerization.

[0115] The polymer solution obtained above was poured into a large excess of methanol containing 2,6-di-t-butyl-p-cresol (BHT), and the precipitated polymer was recovered, washed with methanol, and then vacuum dried at 50°C for 3 days to obtain 145 parts of ring-opened copolymer (C). The resulting ring-opened copolymer (C) had a number average molecular weight (Mn) of 133,000, a weight average molecular weight (Mw) of 268,000, a ratio of 2-norbornene structural units / dicyclopentadiene structural units / cyclooctadiene structural units of 27 / 25 / 48 (weight ratio), a cis / trans ratio of 42 / 58, and a glass transition temperature (Tg) of -40°C.

[0116] Polymerization Example 4 (Preparation of Ring-Opened Copolymer (D)) Under a nitrogen atmosphere, 100 parts of dicyclopentadiene (DCPD) as a norbornene compound, 180 parts of 1,5-cyclooctadiene (COD), 1,120 parts of toluene, and 0.15 parts of 1-hexene were added to a glass reaction vessel equipped with a stirrer. Next, 0.011 parts of (1,3-dimesitylimidazolidin-2-ylidene)(tricyclohexylphosphine)benzylideneruthenium(II) dichloride dissolved in 10 parts of toluene was added, and the polymerization reaction was carried out at room temperature for 4 hours. After the polymerization reaction, excess vinyl ethyl ether was added to terminate the polymerization.

[0117] The polymer solution obtained above was poured into a large excess of methanol containing 2,6-di-t-butyl-p-cresol (BHT), and the precipitated polymer was recovered, washed with methanol, and then vacuum dried at 50°C for 3 days to obtain 276 parts of a ring-opened polymer (D). The resulting ring-opened polymer (D) had a number average molecular weight (Mn) of 121,000, a weight average molecular weight (Mw) of 255,000, a ratio of dicyclopentadiene structural units / 1,5-cyclooctadiene structural units of 36 / 64 (weight ratio), a cis / trans ratio of 37 / 63, and a glass transition temperature (Tg) of -43°C.

[0118] Polymerization Example 5 Preparation of Ring-Opened Copolymer (E) In a nitrogen atmosphere, tetracyclo[6.2.1.1] as a norbornene compound was placed in a glass reaction vessel equipped with a stirrer. ３，６ .0 ２，７70 parts of tetracyclododecene (TCD), 180 parts of 1,5-cyclooctadiene (COD), 1,000 parts of toluene, and 0.14 parts of 1-hexene were added. Next, 0.015 parts of (1,3-dimesitylimidazolidin-2-ylidene)(tricyclohexylphosphine)benzylidene ruthenium(II) dichloride dissolved in 10 parts of toluene was added, and polymerization reaction was carried out at room temperature for 4 hours. After the polymerization reaction, excess vinyl ethyl ether was added to terminate the polymerization.

[0119] The polymer solution obtained above was poured into a large excess of methanol containing 2,6-di-t-butyl-p-cresol (BHT), and the precipitated polymer was recovered, washed with methanol, and then vacuum dried at 50°C for 3 days to obtain 242 parts of ring-opened copolymer (E). The resulting ring-opened copolymer (E) had a number average molecular weight (Mn) of 138,000, a weight average molecular weight (Mw) of 262,000, a ratio of tetracyclododecene structural units / 1,5-cyclooctadiene structural units of 28 / 72 (weight ratio), a cis / trans ratio of 34 / 66, and a glass transition temperature (Tg) of -23°C.

[0120] Polymerization Example 6 (Preparation of Ring-Opened Copolymer (F)) Under a nitrogen atmosphere, 100 parts of dicyclopentadiene (DCPD) as a norbornene compound, 245 parts of 1,5-cyclooctadiene (COD), 1,400 parts of toluene, and 0.20 parts of 1-hexene were added to a glass reaction vessel equipped with a stirrer. Next, 0.015 parts of (1,3-dimesitylimidazolidin-2-ylidene)(tricyclohexylphosphine)benzylideneruthenium(II) dichloride dissolved in 10 parts of toluene was added, and the polymerization reaction was carried out at room temperature for 4 hours. After the polymerization reaction, excess vinyl ethyl ether was added to terminate the polymerization.

[0121] The polymer solution obtained above was poured into a large excess of methanol containing 2,6-di-t-butyl-p-cresol (BHT), and the precipitated polymer was recovered, washed with methanol, and then vacuum dried at 50°C for 3 days to obtain 340 parts of ring-opened copolymer (F). The resulting ring-opened copolymer (F) had a number average molecular weight (Mn) of 122,000, a weight average molecular weight (Mw) of 246,000, a ratio of dicyclopentadiene structural units / 1,5-cyclooctadiene structural units of 29 / 71 (weight ratio), a cis / trans ratio of 35 / 65, and a glass transition temperature (Tg) of -50°C.

[0122] Polymerization Example 7 (Preparation of Ring-Opened Copolymer (G)) Under a nitrogen atmosphere, 100 parts of 2-norbornene (NB) as a norbornene compound, 60 parts of 1,5-cyclooctadiene (COD), 394 parts of toluene, and 0.38 parts of 1-hexene were added to a glass reaction vessel equipped with a stirrer. Next, 0.005 parts of (1,3-dimesitylimidazolidin-2-ylidene)(tricyclohexylphosphine)benzylideneruthenium(II) dichloride dissolved in 10 parts of toluene was added, and the polymerization reaction was carried out at room temperature for 4 hours. After the polymerization reaction, excess vinyl ethyl ether was added to terminate the polymerization.

[0123] The polymer solution obtained above was poured into a large excess of methanol containing 2,6-di-t-butyl-p-cresol (BHT), and the precipitated polymer was recovered, washed with methanol, and then vacuum dried at 50°C for 3 days to obtain 158 parts of ring-opened copolymer (G). The resulting ring-opened copolymer (G) had a number average molecular weight (Mn) of 32,000, a weight average molecular weight (Mw) of 67,000, a ratio of 2-norbornene structural units / 1,5-cyclooctadiene structural units of 63 / 37 (weight ratio), a cis / trans ratio of 46 / 54, and a glass transition temperature (Tg) of -27°C.

[0124] Polymerization Example 8 (Preparation of Ring-Opened Copolymer (H)) Under a nitrogen atmosphere, 110 parts of dicyclopentadiene (DCPD) as a norbornene compound, 90 parts of 1,5-cyclooctadiene (COD), 800 parts of toluene, and 0.43 parts of vinyltris(trimethylsiloxy)silane were added to a glass reaction vessel equipped with a stirrer. Next, 1.000 parts of (1,3-dimesitylimidazolidin-2-ylidene)(tricyclohexylphosphine)benzylideneruthenium(II) dichloride dissolved in 10 parts of toluene was added, and the polymerization reaction was carried out at room temperature for 4 hours. After the polymerization reaction, excess vinyl ethyl ether was added to terminate the polymerization.

[0125] The polymer solution obtained above was poured into a large excess of methanol containing 2,6-di-t-butyl-p-cresol (BHT), and the precipitated polymer was recovered, washed with methanol, and then vacuum-dried at 50°C for 3 days to obtain 192 parts of ring-opened copolymer (H). The resulting ring-opened copolymer (H) had a number-average molecular weight (Mn) of 133,000, a weight-average molecular weight (Mw) of 264,000, a dicyclopentadiene structural unit / 1,5-cyclooctadiene structural unit ratio of 55 / 45 (weight ratio), a cis / trans ratio of 42 / 58, and a glass transition temperature (Tg) of -25°C. The introduction rate of oxylyl groups into chain transfer ends, as determined by 1H-NMR, was 94%. That is, the percentage of the number of ring-opened copolymer chain ends into which modifying groups had been introduced / the total number of ring-opened copolymer chain ends was 47%.

[0126] Polymerization Example 9 (Preparation of Ring-Opened Copolymer (I)) Under a nitrogen atmosphere, 110 parts of dicyclopentadiene (DCPD) as a norbornene compound, 90 parts of 1,5-cyclooctadiene (COD), 800 parts of toluene, and 0.11 parts of 1-hexene were added to a glass reaction vessel equipped with a stirrer. Next, 0.030 parts of dichloro-(3-phenyl-1H-inden-1-ylidene)bis(tricyclohexylphosphine)ruthenium(II) dissolved in 10 parts of toluene was added, and the polymerization reaction was carried out at room temperature for 4 hours. After the polymerization reaction, excess vinyl ethyl ether was added to terminate the polymerization.

[0127] The polymer solution obtained above was poured into a large excess of methanol containing 2,6-di-t-butyl-p-cresol (BHT), and the precipitated polymer was recovered, washed with methanol, and then vacuum dried at 50°C for 3 days to obtain 194 parts of ring-opened copolymer (I). The resulting ring-opened copolymer (I) had a number average molecular weight (Mn) of 128,000, a weight average molecular weight (Mw) of 266,000, a ratio of dicyclopentadiene structural units / 1,5-cyclooctadiene structural units of 54 / 46 (weight ratio), a cis / trans ratio of 20 / 80, and a glass transition temperature (Tg) of -26°C.

[0128] Polymerization Example 10 Preparation of Diisobutylaluminum Hexoxide / Toluene Solution Under a nitrogen atmosphere, 88 parts of toluene and 7.8 parts of a 25.4 wt % triisobutylaluminum / n-hexane solution (manufactured by Tosoh Finechem Corporation) were added to a glass vessel containing a stirrer. The mixture was cooled to −45° C., and 1.02 parts of n-hexanol (equimolar amount relative to triisobutylaluminum) was slowly added dropwise with vigorous stirring. The mixture was then allowed to cool to room temperature with stirring to prepare a diisobutylaluminum hexoxide / toluene solution (2.5 wt %).

[0129] (Preparation of Ring-Opened Copolymer (J)) Next, under a nitrogen atmosphere, 17.4 parts of a 1.0 wt % tungsten hexachloride / toluene solution and 8.6 parts of a 2.5 wt % diisobutylaluminum hexoxide / toluene solution were added to a glass reaction vessel equipped with a stirrer, and the mixture was stirred for 10 minutes to obtain a catalyst solution. Next, 110 parts of dicyclopentadiene (DCPD) as a norbornene compound, 90 parts of 1,5-cyclooctadiene (COD), 800 parts of toluene, and 0.35 parts of 1-hexene were added, and a polymerization reaction was carried out at room temperature for 6 hours. After the polymerization reaction, excess methanol was added to terminate the polymerization.

[0130] The polymer solution obtained above was poured into a large excess of methanol containing 2,6-di-t-butyl-p-cresol (BHT), and the precipitated polymer was recovered, washed with methanol, and then vacuum dried at 50°C for 3 days to obtain 193 parts of ring-opened copolymer (J). The resulting ring-opened copolymer (J) had a number average molecular weight (Mn) of 119,000, a weight average molecular weight (Mw) of 245,000, a ratio of dicyclopentadiene structural units / 1,5-cyclooctadiene structural units of 54 / 46 (weight ratio), a cis / trans ratio of 73 / 27, and a glass transition temperature (Tg) of -27°C.

[0131] Polymerization Example 11 (Preparation of Ring-Opened Copolymer (a)) Under a nitrogen atmosphere, 100 parts of 2-norbornene (NB) as a norbornene compound, 100 parts of cyclopentene (CPE), 394 parts of toluene, and 0.12 parts of 1-hexene were added to a glass reaction vessel equipped with a stirrer. Next, 0.006 parts of dichloro-(3-phenyl-1H-inden-1-ylidene)bis(tricyclohexylphosphine)ruthenium dissolved in 10 parts of toluene was added, and a polymerization reaction was carried out at room temperature for 4 hours. After the polymerization reaction, excess vinyl ethyl ether was added to terminate the polymerization.

[0132] The polymer solution obtained above was poured into a large excess of methanol containing 2,6-di-t-butyl-p-cresol (BHT), and the precipitated polymer was recovered, washed with methanol, and then vacuum dried at 50°C for 3 days to obtain 160 parts of ring-opened copolymer (a). The resulting ring-opened copolymer (a) had a number average molecular weight (Mn) of 122,000, a weight average molecular weight (Mw) of 234,000, a ratio of 2-norbornene structural units / cyclopentene structural units of 62 / 38 (weight ratio), a cis / trans ratio of 17 / 83, and a glass transition temperature (Tg) of -24°C.

[0133] Polymerization Example 12 (Preparation of Ring-Opened Copolymer (b)) Under a nitrogen atmosphere, 45 parts of dicyclopentadiene (DCPD) as a norbornene compound, 55 parts of cyclopentene (CPE), 233 parts of toluene, and 0.08 parts of 1-hexene were added to a glass reaction vessel equipped with a stirrer. Next, 0.011 parts of dichloro-(3-phenyl-1H-inden-1-ylidene)bis(tricyclohexylphosphine)ruthenium(II) dissolved in 6 parts of toluene was added, and the polymerization reaction was carried out at room temperature for 3 hours. After the polymerization reaction, excess vinyl ethyl ether was added to terminate the polymerization.

[0134] 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 recovered, washed with methanol, and then vacuum-dried at 50°C for 3 days to obtain 62 parts of ring-opened copolymer (b). The resulting ring-opened copolymer (b) had a number average molecular weight (Mn) of 119,000, a weight average molecular weight (Mw) of 238,000, a ratio of weight average molecular weight (Mw) to number average molecular weight (Mn) (Mw / Mn) of 2.00, a dicyclopentadiene (DCPD) structural unit / cyclopentene structural unit ratio of 55 / 45 (weight ratio), a cis / trans ratio of 17 / 83, and a glass transition temperature (Tg) of -25°C.

[0135] Polymerization Example 13 (Preparation of Ring-Opened Copolymer (c)) Under a nitrogen atmosphere, 41 parts of 2-norbornene (NB) as a norbornene compound, 39 parts of dicyclopentadiene (DCPD) as a norbornene compound, 100 parts of cyclopentene (CPE), 394 parts of toluene, and 0.14 parts of 1-hexene were added to a glass reaction vessel equipped with a stirrer. Next, 0.017 parts of dichloro-(3-phenyl-1H-inden-1-ylidene)bis(tricyclohexylphosphine)ruthenium dissolved in 10 parts of toluene was added, and the polymerization reaction was carried out at room temperature for 4 hours. After the polymerization reaction, excess vinyl ethyl ether was added to terminate the polymerization.

[0136] The polymer solution obtained above was poured into a large excess of methanol containing 2,6-di-t-butyl-p-cresol (BHT), and the precipitated polymer was recovered, washed with methanol, and then vacuum dried at 50°C for 3 days to obtain 145 parts of ring-opened copolymer (c). The resulting ring-opened copolymer (c) had a number average molecular weight (Mn) of 126,000, a weight average molecular weight (Mw) of 254,000, a ratio of 2-norbornene structural units / dicyclopentadiene structural units / cyclopentene structural units of 27 / 25 / 48 (weight ratio), a cis / trans ratio of 18 / 82, and a glass transition temperature (Tg) of -40°C.

[0137] Polymerization Example 14 (Preparation of Ring-Opened Copolymer (d)) Under a nitrogen atmosphere, 72 parts of dicyclopentadiene (DCPD) as a norbornene compound, 188 parts of cyclopentene (CPE), 1,160 parts of toluene, and 0.17 parts of 1-hexene were added to a glass reaction vessel equipped with a stirrer. Next, 0.028 parts of dichloro-(3-phenyl-1H-inden-1-ylidene)bis(tricyclohexylphosphine)ruthenium dissolved in 10 parts of toluene was added, and the polymerization reaction was carried out at room temperature for 4 hours. After the polymerization reaction, excess vinyl ethyl ether was added to terminate the polymerization.

[0138] The polymer solution obtained above was poured into a large excess of methanol containing 2,6-di-t-butyl-p-cresol (BHT), and the precipitated polymer was recovered, washed with methanol, and then vacuum dried at 50°C for 3 days to obtain 217 parts of ring-opened copolymer (d). The resulting ring-opened copolymer (d) had a number average molecular weight (Mn) of 120,000, a weight average molecular weight (Mw) of 248,000, a ratio of dicyclopentadiene structural units / cyclopentene structural units of 36 / 64 (weight ratio), a cis / trans ratio of 17 / 83, and a glass transition temperature (Tg) of -45°C.

[0139] Polymerization Example 15 Preparation of Ring-Opened Copolymer (e) In a nitrogen atmosphere, tetracyclo[6.2.1.1] as a norbornene compound was placed in a glass reaction vessel equipped with a stirrer. ３，６ .0 ２，７] 100 parts of dodec-4-ene (tetracyclododecene; TCD), 300 parts of cyclopentene (CPE), 380 parts of toluene, and 8.6 parts of 1-hexene were added. Next, 0.028 parts of dichloro-(3-phenyl-1H-inden-1-ylidene)bis(tricyclohexylphosphine)ruthenium dissolved in 10 parts of toluene was added, and polymerization reaction was carried out at room temperature for 4 hours. After the polymerization reaction, excess vinyl ethyl ether was added to terminate the polymerization.

[0140] The polymer solution obtained above was poured into a large excess of methanol containing 2,6-di-t-butyl-p-cresol (BHT), and the precipitated polymer was recovered, washed with methanol, and then vacuum dried at 50°C for 3 days to obtain 290 parts of ring-opened copolymer (e). The resulting ring-opened copolymer (e) had a number average molecular weight (Mn) of 131,000, a weight average molecular weight (Mw) of 253,000, a ratio of tetracyclododecene structural units / cyclopentene structural units of 28 / 72 (weight ratio), a cis / trans ratio of 17 / 83, and a glass transition temperature (Tg) of -22°C.

[0141] Example 1 (Preparation of Rubber Composition) 100 parts of the ring-opened copolymer (A) obtained in Polymerization Example 1 was masticated in a 250 ml Banbury mixer, to which 50 parts of carbon black (trade name "Seast 9H", manufactured by Tokai Carbon Co., Ltd.), 3 parts of zinc oxide (zinc oxide No. 1), 2.0 parts of stearic acid (trade name "SA-300", manufactured by ADEKA Corporation), and 2.0 parts of N-phenyl-N'-(1,3-dimethylbutyl)-p-phenylenediamine (trade name "Nocrac 6C", manufactured by Ouchi Shinko Chemical Industry Co., Ltd., antioxidant) were added, and the mixture was kneaded for 4 minutes starting at 80°C, and the rubber composition was discharged from the Banbury mixer. The temperature of the rubber composition at the end of kneading was 160°C. Next, the obtained rubber composition was kneaded with 1.75 parts of sulfur and 1 part of N-cyclohexylbenzothiazole-2-sulfene (trade name "Noccela CZ-G (CZ)", manufactured by Ouchi Shinko Chemical Industry Co., Ltd., crosslinking accelerator) using an open roll at 50°C, and then a sheet-like rubber composition was taken out. The obtained rubber composition was evaluated for tensile strength, elongation, tear strength, rebound resilience, specific wear volume, and rubber hardness. The results are shown in Table 1.

[0142] [Examples 2 to 10] Rubber compositions were obtained in the same manner as in Example 1, except that 100 parts of ring-opening copolymers (B) to (J) shown in Table 1 were used instead of the ring-opening copolymer (A), and evaluations were performed in the same manner.

[0143] Comparative Examples 1 to 5 Rubber compositions were obtained and evaluated in the same manner as in Example 1, except that 100 parts of ring-opening copolymers (a) to (e) shown in Table 1 were used instead of the ring-opening copolymer (A). The results are shown in Table 1.

[0144]

[0145] As shown in Table 1, the cross-linked rubber products obtained by cross-linking the rubber compositions of Examples 1 to 10, which contained an inorganic material and a ring-opening copolymer containing structural units derived from cyclooctadiene and structural units derived from a norbornene compound, exhibited superior tensile strength, elongation, tear strength, and rebound resilience compared to the cases in which cyclopentene was used instead of cyclooctadiene (Comparative Examples 1 to 5). Furthermore, the cross-linked rubber products obtained by cross-linking the rubber compositions of Examples 1 to 10, which used carbon black as the inorganic material, also exhibited excellent abrasion resistance and rubber hardness.

[0146] Example 11 (Preparation of Rubber Composition) 100 parts of the ring-opened copolymer (A) obtained in Polymerization Example 1 was mixed with silica (trade name "Zeosil 1165MP", manufactured by Rhodia, nitrogen adsorption specific surface area (BET method): 163 m ２50 parts of hydroxypropyl methylcellulose (1,2-dichloroisothiazolinone / g), 10 parts of process oil (trade name "Aromax T-DAE") manufactured by Nippon Oil Corporation), and 6.0 parts of a silane coupling agent (bis(3-(triethoxysilyl)propyl)tetrasulfide, trade name "Si69" manufactured by Degussa) were added and kneaded for 1.5 minutes at a starting temperature of 110°C. To the kneaded mixture, 25 parts of silica (trade name "Zeosil 1165MP" manufactured by Rhodia), 3 parts of zinc oxide (zinc oxide No. 1), 2.0 parts of stearic acid (trade name "SA-300" manufactured by Asahi Denka Kogyo Co., Ltd.), and 2.0 parts of an antioxidant (N-phenyl-N'-(1,3-dimethylbutyl)-p-phenylenediamine, trade name "Nocrac 6C" manufactured by Ouchi Shinko Chemical Industry Co., Ltd.) were added and kneaded for 2.5 minutes, and the rubber composition was discharged from the Banbury mixer. The temperature of the rubber composition at the end of kneading was 150°C. After cooling to room temperature, the rubber composition was again kneaded in a Banbury mixer for 3 minutes, and then discharged from the Banbury mixer. The resulting rubber composition was then kneaded with 1.5 parts of sulfur and a crosslinking accelerator (a mixture of 1.8 parts of N-t-butyl-2-benzothiazole sulfenamide (trade name "Noccela NS", manufactured by Ouchi Shinko Chemical Industry Co., Ltd.) and 1.5 parts of diphenyl guanidine (trade name "Noccela D", manufactured by Ouchi Shinko Chemical Industry Co., Ltd.)) using an open roll at 50°C, and the resulting sheet-like rubber composition was removed. The resulting rubber composition was evaluated for tensile strength, elongation, tear strength, rebound resilience, wet grip properties, and low heat buildup. The results are shown in Table 1.

[0147] [Examples 12 to 20] Rubber compositions were obtained and evaluated in the same manner as in Example 11, except that 100 parts of ring-opening copolymers (B) to (J) shown in Table 1 were used instead of the ring-opening copolymer (A). The results are shown in Table 2.

[0148] Comparative Examples 6 to 10 Rubber compositions were obtained and evaluated in the same manner as in Example 11, except that 100 parts of ring-opening copolymers (b) to (e) shown in Table 1 were used instead of the ring-opening copolymer (A). The results are shown in Table 2.

[0149]

[0150] As shown in Table 2, the cross-linked rubber products obtained by cross-linking the rubber compositions of Examples 11 to 20, which contained an inorganic material and a ring-opening copolymer containing structural units derived from cyclooctadiene and structural units derived from a norbornene compound, exhibited superior tensile strength, elongation, tear strength, and rebound resilience compared to the cases in which cyclopentene was used instead of cyclooctadiene (Comparative Examples 6 to 10). Furthermore, the cross-linked rubber products obtained by cross-linking the rubber compositions of Examples 11 to 20, which used silica as the inorganic material, also exhibited excellent wet grip properties and low heat buildup.

Claims

1. A rubber composition comprising an inorganic material and a ring-opening copolymer containing structural units derived from cyclooctadiene and structural units derived from a norbornene compound.

2. The rubber composition according to claim 1, wherein the inorganic material is a carbon material or silica.

3. 3. The rubber composition according to claim 1, wherein the norbornene compound is a norbornene compound represented by the following general formula (1): 【Transformation 3】 (In the formula, R １ ~R ４ 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 structure, and m is 0 or 1.

4. The R １ ~R ４ The rubber composition according to claim 3, wherein is 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.

5. The rubber composition according to claim 1 or 2, wherein the weight average molecular weight of the ring-opening polymer is 50,000 to 1,000,000.

6. The rubber composition according to claim 1 or 2, wherein the glass transition temperature of the ring-opening polymer is -80 to 10°C.

7. The rubber composition according to claim 1 or 2, further comprising a rubber other than the ring-opening copolymer.

8. A cross-linked rubber product obtained by cross-linking the rubber composition according to claim 1 or 2.

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