Rubber composition, cross-linked rubber product using the same, and pneumatic tire

Abstract

Provided is a rubber composition with which a rubber crosslinked product having good workability and an excellent balance between rolling resistance and wet grip performance can be obtained. Provided is a rubber composition containing a diene rubber and a hydrocarbon resin, wherein the hydrocarbon resin content is 1-200 parts by mass per 100 parts by mass of the diene rubber, the hydrocarbon resin contains monomer units derived from a tetracyclododecene compound in a proportion of 0.1-50% by weight, the weight-average molecular weight (Mw) is in the range of 500-4,000, and the softening point is in the range of 80-170°C.

Description

[Technical Field]

[0001] The present invention relates to a rubber composition, and more particularly to a rubber composition which has good processability and is capable of giving a cross-linked rubber product having an excellent balance between rolling resistance and wet grip performance. [Background technology]

[0002] In recent years, automobile tires have been strongly required to have low fuel consumption due to environmental and resource issues, while, for example, improved wet grip performance is also required from the viewpoint of safety. A cross-linked product of a rubber composition in which silica is blended as a filler in the rubber component has lower rolling resistance when used in a tire than a cross-linked product of a rubber composition in which carbon black is blended. Therefore, by using a cross-linked product of a rubber composition in which silica is blended to form a tire, a tire with excellent fuel economy can be obtained.

[0003] However, even when silica is compounded into a conventional rubber component, the affinity between the rubber component and silica is insufficient, and they tend to separate, resulting in poor processability of the rubber composition before crosslinking, and furthermore, the crosslinked rubber obtained by crosslinking them has problems such as insufficient rolling resistance when used to form a tire.

[0004] Furthermore, Patent Document 1 discloses that, for the purpose of improving the rolling resistance and wet grip performance of a tire, a specific amount of a softener with a specific structure is blended into the rubber component, and a specific amount of a hydrocarbon resin with a specific structure is blended. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Laid-Open No. 2010-241965 Summary of the Invention [Problem to be solved by the invention]

[0006] When a tire is manufactured using a cross-linked elastomer obtained by adding the softener and hydrocarbon resin having a specific structure described in Patent Document 1, it is certainly possible to improve both wet grip performance and rolling resistance, but there is still a problem that the improvements are insufficient.

[0007] The present invention has been made in view of the above problems, and an object of the present invention is to provide a rubber composition which has good processability and is capable of giving a cross-linked rubber product which has an excellent balance between rolling resistance and wet grip performance. [Means for solving the problem]

[0008] The present inventors have conducted studies to achieve the above object and have found that a rubber composition obtained by blending a specific hydrocarbon resin with a diene rubber can provide a cross-linked rubber product that has an excellent balance between rolling resistance and wet grip performance while realizing excellent processability, and have thus completed the present invention.

[0009] That is, according to the present invention, there is provided a rubber composition containing a diene rubber and a hydrocarbon resin, wherein the content of the hydrocarbon resin is 1 to 200 parts by mass per 100 parts by mass of the diene rubber, the hydrocarbon resin contains monomer units derived from a tetracyclododecene compound in a proportion of 0.1 to 50% by weight, the weight average molecular weight (Mw) is in the range of 500 to 4,000, and the softening point is in the range of 80 to 170°C.

[0010] In the rubber composition of the present invention, the hydrocarbon resin contains, in addition to 0.1 to 50% by weight of the monomer units derived from the tetracyclododecene compound, 1 to 60% by weight of 1,3-pentadiene monomer units, 1 to 30% by weight of alicyclic monoolefin monomer units having 4 to 6 carbon atoms, 0 to 50% by weight of acyclic monoolefin monomer units having 4 to 8 carbon atoms, 0 to 10% by weight of alicyclic diolefin monomer units, 0 to 40% by weight of aromatic monoolefin monomer units, and two or more It is preferable that the hydrocarbon resin contains 0 to 50% by weight of aromatic monomer units having the above structure in which the cyclic structures are bonded, and that the number average molecular weight (Mn) is within the range of 250 to 2,000, the Z average molecular weight (Mz) is within the range of 1,000 to 10,000, the ratio of the weight average molecular weight to the number average molecular weight (Mw / Mn) is within the range of 1.0 to 4.0, and the ratio of the Z average molecular weight to the weight average molecular weight (Mz / Mw) is within the range of 1.0 to 4.0. In the rubber composition of the present invention, the hydrocarbon resin contains, as the monomer unit derived from the tetracyclododecene compound, tetracyclo[4.4.0.1 2,5 .1 7,10 ] Preferably it contains a dodec-3-ene unit. In the rubber composition of the present invention, the monomer units derived from the tetracyclododecene compound are 2,5 .1 7,10 ] The proportion of dodec-3-ene units is preferably 50% by weight or more. In the rubber composition of the present invention, the hydrocarbon resin is preferably a hydride. The rubber composition of the present invention preferably further contains silica. The rubber composition of the present invention preferably further contains a silane coupling agent. The rubber composition of the present invention preferably further contains a crosslinking agent.

[0011] According to the present invention, there is also provided a cross-linked rubber product obtained by cross-linking the above rubber composition. Furthermore, according to the present invention, there is provided a pneumatic tire characterized in that the above rubber composition or the above cross-linked rubber is used in the tread. [Effects of the Invention]

[0012] According to the present invention, it is possible to provide a rubber composition which has good processability and from which a cross-linked rubber product having an excellent balance between rolling resistance and wet grip performance can be obtained. DETAILED DESCRIPTION OF THE INVENTION

[0013] The rubber composition of the present invention contains a diene rubber and a hydrocarbon resin, the content of the hydrocarbon resin being 1 to 200 parts by mass per 100 parts by mass of the diene rubber, the hydrocarbon resin containing 0.1 to 50% by weight of monomer units derived from a tetracyclododecene compound, a weight average molecular weight (Mw) in the range of 500 to 4,000, and a softening point in the range of 80 to 170° C. Each component of the rubber composition of the present invention will now be described.

[0014] <Hydrocarbon resin> The hydrocarbon resin used in the present invention contains 0.1 to 50% by weight of monomer units derived from a tetracyclododecene compound, has a weight average molecular weight (Mw) in the range of 500 to 4,000, and has a softening point in the range of 80 to 170° C. The hydrocarbon resin used in the present invention can be produced, for example, by addition polymerization of a monomer mixture containing a tetracyclododecene compound and a monomer copolymerizable therewith.

[0015] The hydrocarbon resin used in the present invention may contain 0.1 to 50% by weight of monomer units derived from a tetracyclododecene compound, and the content is not particularly limited, but is preferably 5 to 45% by weight, more preferably 10 to 40% by weight, and even more preferably 15 to 35% by weight. In the present invention, by using a hydrocarbon resin that contains the above-mentioned content of monomer units derived from a tetracyclododecene compound and has a weight-average molecular weight (Mw) and softening point within the above-mentioned ranges, it is possible to obtain a cross-linked rubber product that has an excellent balance between rolling resistance and wet grip performance while having excellent processability as a rubber composition.

[0016] In particular, the present inventors have conducted extensive research and found that by incorporating 0.1 to 50% by weight of monomer units derived from a tetracyclododecene compound into a hydrocarbon resin, the weight average molecular weight (Mw) and softening point can be suitably controlled within the above ranges, and that this makes it possible to obtain a rubber composition with excellent processability, and when made into a cross-linked rubber, the resulting cross-linked rubber can have an excellent balance of rolling resistance and wet grip performance.If the content of the monomer units derived from a tetracyclododecene compound is too low or too high, it becomes difficult to obtain a cross-linked rubber with an excellent balance of rolling resistance and wet grip performance.

[0017] The tetracyclododecene compound for forming the monomer unit derived from the tetracyclododecene compound includes tetracyclo[4.4.0.1 2,5 .1 7,10 ] dodec-3-ene structure as a basic skeleton, and specific examples thereof include tetracyclo[4.4.0.1 2,5 .1 7,10 ]dodec-3-ene (tetracyclododecene), 8-methyl-tetracyclo[4.4.0.1 2,5 .1 7,10 ]dodec-3-ene, 8-ethyl-tetracyclo[4.4.0.1 2,5 .1 7,10 ]dodec-3-ene, 8-ethylidene-tetracyclo[4.4.0.1 2,5 .1 7,10 ]dodec-3-ene, 8-vinyl-tetracyclo[4.4.0.1 2,5 .1 7,10 ]dodec-3-ene, 8-propenyl-tetracyclo[4.4.0.1 2,5 .1 7,10 ]dodec-3-ene. The tetracyclododecene compound may be used alone or in combination of two or more, but at least tetracyclo[4.4.0.1 2,5 .1 7,10]dodec-3-ene is preferably contained, and tetracyclo[4.4.0.1 2,5 .1 7,10 It is more preferable that the proportion of tetracyclo[4.4.0.1]dodec-3-ene is 50% by weight or more. 2,5 .1 7,10 ] dodec-3-ene unit, and in the monomer unit derived from the tetracyclododecene compound, tetracyclo[4.4.0.1 2,5 .1 7,10 ] It is more preferable that the proportion of dodec-3-ene units is 50% by weight or more.

[0018] The hydrocarbon resin used in the present invention may contain 0.1 to 50% by weight of monomer units derived from tetracyclododecene compounds. The monomer units other than the monomer units derived from tetracyclododecene compounds are not particularly limited and any monomer units can be contained. However, from the viewpoints of processability of the rubber composition and rolling resistance and wet grip performance of the resulting cross-linked rubber, it is preferable that the hydrocarbon resin contains 1 to 60% by weight of 1,3-pentadiene monomer units, 1 to 30% by weight of alicyclic monoolefin monomer units having 4 to 6 carbon atoms, 0 to 50% by weight of acyclic monoolefin monomer units having 4 to 8 carbon atoms, 0 to 10% by weight of alicyclic diolefin monomer units, 0 to 40% by weight of aromatic monoolefin monomer units, and 0 to 50% by weight of aromatic monomer units having a structure in which two or more cyclic structures are bonded.

[0019] The hydrocarbon resin used in the present invention preferably contains 1,3-pentadiene (piperylene) monomer units in an amount of 1 to 60% by weight, more preferably 10 to 55% by weight, and even more preferably 20 to 50% by weight. By controlling the content of 1,3-pentadiene monomer units within the above range, the rubber composition can be made to have excellent processability, while the resulting cross-linked rubber can have an excellent balance between rolling resistance and wet grip performance. The cis / trans isomer ratio in 1,3-pentadiene may be any ratio and is not particularly limited.

[0020] The 4-6C alicyclic monoolefin for forming the 4-6C alicyclic monoolefin monomer unit is not particularly limited as long as it is a 4-6C hydrocarbon compound having one ethylenically unsaturated bond and a non-aromatic ring structure in its molecular structure, but specific examples include cyclobutene, cyclopentene, cyclohexene, methylcyclobutene, and methylcyclopentene. The 4-6C hydrocarbon compound may be used alone or in combination of two or more, but preferably contains at least cyclopentene, and the proportion of cyclopentene in the 4-6C alicyclic monoolefin is preferably 50% by weight or more. That is, the proportion of cyclopentene units in the 4-6C alicyclic monoolefin monomer unit contained in the hydrocarbon resin used in the present invention is preferably 50% by weight or more.

[0021] The hydrocarbon resin used in the present invention preferably contains alicyclic monoolefin monomer units having 4 to 6 carbon atoms in an amount of 1 to 30% by weight, more preferably 5 to 30% by weight, even more preferably 10 to 30% by weight, and even more preferably 20 to 30% by weight. By keeping the content of alicyclic monoolefin monomer units having 4 to 6 carbon atoms within the above range, the obtained cross-linked rubber can be made to have even better rolling resistance and wet grip performance.

[0022] The acyclic monoolefin having 4 to 8 carbon atoms for forming the acyclic monoolefin monomer unit having 4 to 8 carbon atoms is not particularly limited as long as it has one ethylenically unsaturated bond in its molecular structure and is a chain hydrocarbon compound having 4 to 8 carbon atoms without a ring structure. Specific examples thereof include butenes such as 1-butene, 2-butene, and isobutylene (2-methylpropene); 1-pentene, 2-pentene, 2-methyl-1-butene, 3- Examples of the acyclic monoolefins include pentenes such as methyl-1-butene and 2-methyl-2-butene; hexenes such as 1-hexene, 2-hexene, and 2-methyl-1-pentene; heptenes such as 1-heptene, 2-heptene, and 2-methyl-1-hexene; and octenes such as 1-octene, 2-octene, 2-methyl-1-heptene, and diisobutylene (2,4,4-trimethylpentene-1 and 2,4,4-trimethylpentene-1). The acyclic monoolefins having 4 to 8 carbon atoms may be used alone or in combination of two or more, but preferably contain at least one selected from the group consisting of 2-methyl-2-butene, isobutylene, and diisobutylene, and more preferably the total amount of 2-methyl-2-butene, isobutylene, and diisobutylene accounts for 50% by weight or more of the acyclic monoolefins having 4 to 6 carbon atoms. That is, the total proportion of 2-methyl-2-butene units, isobutylene units and diisobutylene units in the acyclic monoolefin monomer units having 4 to 6 carbon atoms contained in the hydrocarbon resin used in the present invention is preferably 50% by weight or more.

[0023] The hydrocarbon resin used in the present invention preferably contains acyclic monoolefin monomer units having 4 to 8 carbon atoms in an amount of 0 to 50% by weight, more preferably 0 to 40% by weight, even more preferably 1 to 30% by weight, and even more preferably 5 to 30% by weight. By containing the acyclic monoolefin monomer units having 4 to 8 carbon atoms in the above amount, the obtained cross-linked rubber can be made to have even better rolling resistance and wet grip performance.

[0024] The alicyclic diolefin for forming the alicyclic diolefin monomer unit is not particularly limited as long as it is a hydrocarbon compound having two or more ethylenically unsaturated bonds and a non-aromatic ring structure in its molecular structure. Specific examples include cyclopentadiene polymers such as cyclopentadiene and dicyclopentadiene, methylcyclopentadiene, and methylcyclopentadiene polymers. While one type of alicyclic diolefin may be used alone or two or more types may be used in combination, it is preferable that at least dicyclopentadiene is contained, and it is more preferable that the proportion of dicyclopentadiene in the alicyclic diolefin is 50% by weight or more. That is, it is preferable that the proportion of dicyclopentadiene units in the alicyclic diolefin monomer units contained in the hydrocarbon resin used in the present invention is 50% by weight or more.

[0025] The hydrocarbon resin used in the present invention preferably contains alicyclic diolefin monomer units in an amount of 0 to 10% by weight, more preferably 0 to 7.5% by weight, and even more preferably 0 to 5% by weight. By containing the alicyclic diolefin monomer units in the above amount, the resulting cross-linked rubber can be made to have better rolling resistance and wet grip performance.

[0026] The aromatic monoolefin for forming the aromatic monoolefin monomer unit is not particularly limited as long as it is a hydrocarbon compound having one ethylenically unsaturated bond and an aromatic ring structure in its molecular structure, but specific examples include styrene, α-methylstyrene, vinyltoluene, etc. The aromatic monoolefin may be used alone or in combination of two or more types, but it is preferable that at least styrene is contained, and it is more preferable that the proportion of styrene in the aromatic monoolefin is 50% by weight or more. In other words, it is preferable that the proportion of styrene units in the aromatic monoolefin monomer units contained in the hydrocarbon resin used in the present invention is 50% by weight or more.

[0027] The content of aromatic monoolefin monomer units in the hydrocarbon resin used in the present invention is preferably 0 to 40% by weight, more preferably 0 to 35% by weight, and even more preferably 0 to 30% by weight. By containing the aromatic monoolefin monomer units in the above-mentioned proportion, the obtained cross-linked rubber can be made to have even better rolling resistance and wet grip performance.

[0028] The aromatic monomer having a structure in which two or more cyclic structures are bonded to form an aromatic monomer unit having a structure in which two or more cyclic structures are bonded is not particularly limited as long as it is a hydrocarbon compound having two or more cyclic structures, including an aromatic cyclic structure, and specific examples include compounds having a naphthalene skeleton such as naphthalene, compounds having a fluorene skeleton such as fluorene, compounds having a biphenyl skeleton such as biphenyl, compounds having an anthracene skeleton such as anthracene, compounds having a phenanthrene skeleton such as phenanthrene, compounds having an indene skeleton such as indene, and compounds having a benzothiophene skeleton such as benzothiophene. Only one type of aromatic monomer having a structure in which two or more cyclic structures are bonded may be used, or two or more types may be used in combination.

[0029] The content of aromatic monomer units having a structure in which two or more cyclic structures are bonded in the hydrocarbon resin used in the present invention is preferably 0 to 50% by weight, more preferably 0 to 40% by weight, and even more preferably 0 to 30% by weight. By containing aromatic monomer units having a structure in which two or more cyclic structures are bonded in the above-mentioned proportion, the obtained cross-linked rubber can be made to have even better rolling resistance and wet grip performance.

[0030] The hydrocarbon resin used in the present invention may also contain units of other monomers in addition to the above-mentioned monomer units. The other monomers may be any monomer copolymerizable with the above-mentioned monomers, including the tetracyclododecene compound, and are not particularly limited. Examples include acyclic polyenes other than 1,3-pentadiene, such as 1,3-butadiene, 1,2-butadiene, isoprene, 1,3-hexadiene, and 1,4-pentadiene; alicyclic monoolefins having 7 or more carbon atoms, such as cycloheptene; and acyclic monoolefins having other than 4 to 8 carbon atoms, such as ethylene, propylene, and nonene. These may be used alone or in combination of two or more. The content of the other monomer units in the hydrocarbon resin used in the present invention is preferably 0 to 30% by weight, more preferably 0 to 25% by weight, and even more preferably 0 to 20% by weight.

[0031] The hydrocarbon resin used in the present invention can be produced, for example, by addition polymerization of a monomer mixture containing a tetracyclododecene compound and each of the above-mentioned monomers. The method of addition polymerization is not particularly limited and can be selected from known addition polymerization methods for producing hydrocarbon resins. Furthermore, after obtaining a hydrocarbon resin by addition polymerization of a monomer mixture, some or all of the unsaturated bonds remaining in the polymer molecular structure of the hydrocarbon resin may be saturated by a hydrogenation reaction (hydrogenation) to form a hydrogenated product.

[0032] The weight-average molecular weight (Mw) of the hydrocarbon resin used in the present invention is not particularly limited as long as it is in the range of 500 to 4,000, but is preferably in the range of 750 to 3,500, and more preferably in the range of 1,000 to 3,000. If the weight-average molecular weight (Mw) of the hydrocarbon resin is too small, the resulting cross-linked rubber will have a poor balance between rolling resistance and wet grip performance. On the other hand, if the weight-average molecular weight (Mw) of the hydrocarbon resin is too large, the processability as a rubber composition will be poor.

[0033] The number average molecular weight (Mn) of the hydrocarbon resin used in the present invention is preferably in the range of 250 to 2,000, more preferably in the range of 375 to 1,750, and even more preferably in the range of 500 to 1,500. When the number average molecular weight (Mn) of the hydrocarbon resin is within the above range, the obtained cross-linked rubber can have even better rolling resistance and wet grip performance.

[0034] The Z-average molecular weight (Mz) of the hydrocarbon resin used in the present invention is preferably in the range of 1,000 to 10,000, more preferably in the range of 1,500 to 8,500, and even more preferably in the range of 2,000 to 7,000. When the Z-average molecular weight (Mz) of the hydrocarbon resin is within the above range, the obtained cross-linked rubber can have even better rolling resistance and wet grip performance.

[0035] The hydrocarbon resin used in the present invention has a ratio of weight average molecular weight to number average molecular weight (Mw / Mn) in the range of preferably 1.0 to 4.0, more preferably 1.2 to 3.5, and even more preferably 1.4 to 3.0. When this ratio is within the above range, the obtained cross-linked rubber product can have even better rolling resistance and wet grip performance.

[0036] The hydrocarbon resin used in the present invention has a ratio of Z-average molecular weight to weight-average molecular weight (Mz / Mw) in the range of preferably 1.0 to 4.0, more preferably 1.2 to 3.5, and even more preferably 1.4 to 3.0. When this ratio is within the above range, the obtained cross-linked rubber product can have even better rolling resistance and wet grip performance.

[0037] In the present invention, the weight-average molecular weight (Mw), Z-average molecular weight (Mz), and number-average molecular weight (Mn) of the hydrocarbon resin are determined as polystyrene-equivalent values by high-performance liquid chromatography. The weight-average molecular weight (Mw), Z-average molecular weight (Mz), number-average molecular weight (Mn), and their ratios (Mw / Mn, Mz / Mw) of the hydrocarbon resin can be controlled by adjusting the monomer composition while keeping the proportion of the tetracyclododecene compound-derived monomer unit at 0.1 to 50 wt %, or by adjusting the production conditions in the hydrocarbon resin production method described below.

[0038] The softening point of the hydrocarbon resin used in the present invention is not particularly limited as long as it is in the range of 80°C to 170°C, but is preferably 85 to 160°C, and more preferably 90 to 150°C. If the softening point of the hydrocarbon resin is too low or too high, the resulting cross-linked rubber will have a poor balance between rolling resistance and wet grip performance. The softening point of the hydrocarbon resin can be controlled by adjusting the monomer composition while keeping the proportion of monomer units derived from a tetracyclododecene compound at 0.1 to 50% by weight, or by adjusting the production conditions in the production method for the hydrocarbon resin described below.

[0039] The hydrocarbon resin used in the present invention may also be a hydrogenated product in which some or all of the unsaturated bonds remaining in the polymer molecular structure of the hydrocarbon resin have been saturated by a hydrogenation reaction (hydrogenation).

[0040] The method for producing the hydrocarbon resin used in the present invention is not particularly limited, as long as it is possible to obtain a hydrocarbon resin having a weight-average molecular weight (Mw) and softening point within the above-mentioned ranges by addition polymerization of a monomer mixture containing a tetracyclododecene compound and each of the above-mentioned monomers. For example, the hydrocarbon resin can be produced by addition polymerization using a Friedel-Crafts type cationic polymerization catalyst, and in particular, a method using addition polymerization with a Lewis acid catalyst (A) is preferred.

[0041] The Lewis acid catalyst (A) is not limited, but is preferably a metal halide, and from the viewpoint of good reaction activity, a halide of an element belonging to Group III of the periodic table or a complex thereof is preferable. Specific examples of such Lewis acid catalysts include aluminum trichloride (AlCl), aluminum tribromide (AlBr), gallium trichloride (GaCl), and boron trifluoride diethyl ether complex (BF·EtO). Among these, AlCl or BF·EtO is preferred from the viewpoint of versatility. The Lewis acid catalyst (A) may be used alone or in combination of two or more.

[0042] The amount of the Lewis acid catalyst (A) used is not particularly limited, but is preferably 0.05 to 10 parts by weight, more preferably 0.1 to 5 parts by weight, per 100 parts by weight of the monomer mixture used in the polymerization.

[0043] Furthermore, the Lewis acid catalyst (A) may be used in combination with at least one halogenated hydrocarbon (B) selected from the group consisting of a halogenated hydrocarbon (B1) having a halogen atom bonded to a tertiary carbon atom and a halogenated hydrocarbon (B2) having a halogen atom bonded to a carbon atom adjacent to a carbon-carbon unsaturated bond, in order to further enhance the polymerization activity of the Lewis acid catalyst (A).

[0044] Specific examples of halogenated hydrocarbons (B1) in which a halogen atom is bonded to a tertiary carbon atom include t-butyl chloride, t-butyl bromide, 2-chloro-2-methylbutane, and triphenylmethyl chloride. Among these, t-butyl chloride is particularly preferred due to its excellent balance between activity and ease of handling. Specific examples of halogenated hydrocarbons (B2) in which a halogen atom is bonded to a carbon atom adjacent to a carbon-carbon unsaturated bond include benzyl chloride, benzyl bromide, (1-chloroethyl)benzene, allyl chloride, 3-chloro-1-propyne, 3-chloro-1-butene, 3-chloro-1-butyne, and cinnamic chloride. Among these, benzyl chloride is preferred due to its excellent balance between activity and ease of handling. The halogenated hydrocarbons (B) may be used singly or in combination of two or more.

[0045] The amount of halogenated hydrocarbon (B) used is not particularly limited, but is preferably in the range of 0.05 to 50, more preferably 0.1 to 10, in terms of molar ratio to the Lewis acid catalyst (A).

[0046] In carrying out the polymerization reaction, the order in which the monomer mixture and the polymerization catalyst components are added to the polymerization reactor is not particularly limited and may be in any order, but from the viewpoint of well-controlling the polymerization reaction, it is preferable to first add a portion of the monomer components constituting the monomer mixture and the Lewis acid catalyst (A) to the polymerization reactor, contact a portion of the monomer components constituting the monomer mixture with the Lewis acid catalyst (A), and then add the remaining monomer components constituting the monomer mixture to the polymerization reactor to initiate the polymerization reaction. In this case, it is more preferable to use at least an alicyclic monoolefin having 4 to 6 carbon atoms as part of the monomer components constituting the monomer mixture, add the Lewis acid catalyst (A) to the polymerization reactor in advance, contact the alicyclic monoolefin having 4 to 6 carbon atoms with the Lewis acid catalyst (A), and then add the remaining monomer components constituting the monomer mixture to the polymerization reactor to initiate the polymerization reaction.

[0047] When a halogenated hydrocarbon (B) is used in addition to the Lewis acid catalyst (A), it is preferable to add the monomer mixture and the Lewis acid catalyst (A) to a polymerization reactor, initiate the polymerization reaction, and then add the halogenated hydrocarbon (B) to the polymerization reactor. Alternatively, it is also preferable to add the monomer mixture, the Lewis acid catalyst (A), and a portion of the halogenated hydrocarbon (B) to the polymerization reactor, initiate the polymerization reaction, and then add the remainder of the halogenated hydrocarbon (B) to the polymerization reactor.

[0048] From the viewpoint of better controlling the polymerization reaction, it is preferable to add a solvent to the polymerization reaction system and carry out the polymerization reaction. The type of solvent is not particularly limited as long as it does not inhibit the polymerization reaction, but saturated aliphatic hydrocarbons or aromatic hydrocarbons are preferred. Examples of saturated aliphatic hydrocarbons used as solvents include linear saturated aliphatic hydrocarbons having 5 to 10 carbon atoms, such as n-pentane, n-hexane, 2-methylpentane, 3-methylpentane, n-heptane, 2-methylhexane, 3-methylhexane, 3-ethylpentane, 2,2-dimethylpentane, 2,3-dimethylpentane, 2,4-dimethylpentane, 3,3-dimethylpentane, 2,2,3-trimethylbutane, and 2,2,4-trimethylpentane; and cyclic saturated aliphatic hydrocarbons having 5 to 10 carbon atoms, such as cyclopentane, cyclohexane, cycloheptane, and cyclooctane. Examples of aromatic hydrocarbons used as solvents include aromatic hydrocarbons having 6 to 10 carbon atoms, such as benzene, toluene, and xylene. The solvent may be used alone or as a mixed solvent of two or more kinds. The amount of the solvent used is not particularly limited, but is preferably 10 to 1,000 parts by weight, more preferably 50 to 500 parts by weight, per 100 parts by weight of the monomer mixture used in the polymerization reaction. For example, a mixture of an addition-polymerizable component and a non-addition-polymerizable component, such as a mixture of cyclopentane and cyclopentene derived from a C5 fraction, may be added to the polymerization reaction system, and the addition-polymerizable component may be used as a component of the monomer mixture, and the non-addition-polymerizable component may be used as a solvent.

[0049] The polymerization temperature during the polymerization reaction is not particularly limited, but is preferably 85°C or lower, more preferably -20 to 85°C, and even more preferably 0 to 65°C. If the polymerization temperature is too low, the polymerization activity may decrease, resulting in poor productivity, while if the polymerization temperature is too high, the color of the resulting hydrocarbon resin may be poor. The pressure during the polymerization reaction may be atmospheric pressure or increased pressure. The polymerization reaction time can be appropriately selected, but is usually selected within the range of 10 minutes to 12 hours, preferably 30 minutes to 6 hours.

[0050] The polymerization reaction can be terminated by adding a polymerization terminator such as methanol, aqueous sodium hydroxide, or aqueous ammonia to the polymerization reaction system when the desired polymerization conversion rate is achieved. The catalyst residue insoluble in the solvent produced when the polymerization catalyst is inactivated by adding the polymerization terminator may be removed by filtration or the like. After the polymerization reaction is terminated, the unreacted monomer and solvent are removed, and low-molecular-weight oligomer components are further removed by steam distillation or the like. The resulting mixture is then cooled to obtain a solid hydrocarbon resin.

[0051] Furthermore, with regard to the hydrocarbon resin used in the present invention obtained in this manner, if necessary, some or all of the unsaturated bonds remaining in the polymer molecular structure of the hydrocarbon resin may be saturated by a hydrogenation reaction (hydrogenation) to form a hydrogenated product.

[0052] The hydrogenation method used to hydrogenate a hydrocarbon resin is not particularly limited, and any known method can be used without limitation, including, for example, a method of contacting the resin with hydrogen in the presence of a nickel catalyst. The nickel catalyst is not particularly limited, but from the viewpoint of high reactivity, a catalyst containing, as a main component, a compound in which metal nickel is supported on a supported inorganic compound as a support is preferred. Specific examples of supported inorganic compounds as supports include silica, alumina, boria, silica-alumina, diatomaceous earth, white clay, clay, magnesia, magnesia-silica (silica-magnesium oxide), titania, and zirconia.

[0053] <Diene rubber> The rubber composition of the present invention contains a diene rubber in addition to the hydrocarbon resin described above. The diene rubber is not particularly limited as long as it can be blended with the hydrocarbon resin. Examples of such diene rubbers include those described in JP 2015-189873 A. Specific examples include natural rubber (NB), isoprene rubber (IR), butadiene rubber (BR), styrene-butadiene copolymer rubber (SBR), and ethylene-propylene-diene terpolymer (EPDM). Among these, styrene-butadiene copolymer rubber and butadiene rubber are preferred. The use of the diene rubber described above can provide a rubber composition with excellent processability while providing a cross-linked rubber with a better balance of rolling resistance and wet grip performance. The diene rubbers may be used alone or in combination of two or more.

[0054] The diene rubber of the present invention is not particularly limited in terms of molecular weight or microstructure, and may be terminally modified with an amine, amide, silyl, alkoxysilyl, carboxyl, hydroxyl group, etc., or may be epoxidized. The diene rubber of the present invention may be hydrogenated, but is preferably not hydrogenated.

[0055] The blending ratio of the diene rubber and the hydrocarbon resin in the rubber composition of the present invention may be 1 to 200 parts by mass, preferably 1 to 70 parts by mass, and more preferably 3 to 35 parts by mass, of hydrocarbon resin per 100 parts by mass of diene rubber. If the blending amount of hydrocarbon resin is too small, the rubber composition will have poor processability, while if it is too large, the resulting cross-linked rubber will have a poor balance between rolling resistance and wet grip performance.

[0056] The rubber composition of the present invention may consist solely of a diene rubber and the hydrocarbon resin, but may also contain other components. Examples of other components that may be contained in the rubber composition of the present invention include fillers, silane coupling agents, crosslinking agents, crosslinking accelerators, crosslinking activators, antioxidants, antioxidants, activators, process oils, plasticizers, lubricants, and tackifiers, and these other compounding agents may be compounded in the required amounts, respectively.

[0057] Fillers that can be blended into the rubber composition of the present invention include those that are commonly used in rubber compositions, and examples thereof include inorganic hollow fillers such as carbon black, clay, diatomaceous earth, silica, talc, barium sulfate, calcium carbonate, magnesium carbonate, metal oxides, mica, aluminum hydroxide, various metal powders, wood powder, glass powder, ceramic powder, glass balloons, and silica balloons; and organic hollow fillers such as polystyrene, polyvinylidene fluoride, and polyvinylidene fluoride copolymers.

[0058] Examples of silica include dry process white carbon, wet process white carbon, colloidal silica, and precipitated silica. Among these, wet process white carbon, which is mainly composed of hydrous silicic acid, is preferred. Carbon-silica dual phase filler, in which silica is supported on the surface of carbon black, may also be used. These silicas may be used alone or in combination of two or more. The nitrogen adsorption specific surface area of the silica used (measured by the BET method in accordance with ASTM D3037-81) is preferably 100 to 400 m 2 / g, more preferably 150 to 350 m 2 The pH of the silica is preferably 5 to 10.

[0059] The amount of silica compounded in the rubber composition of the present invention is preferably 10 to 200 parts by mass, more preferably 20 to 150 parts by mass, and even more preferably 30 to 75 parts by mass, per 100 parts by mass of the rubber component in the rubber composition. By setting the amount of silica compounded within the above range, the obtained cross-linked rubber product can be made to have even better rolling resistance and wet grip performance.

[0060] When silica is used as a filler, it is preferable to use a silane coupling agent in combination. Examples of silane coupling agents include vinyltriethoxysilane, β-(3,4-epoxycyclohexyl)ethyltrimethoxysilane, N-(β-aminoethyl)-γ-aminopropyltrimethoxysilane, 3-octathio-1-propyl-triethoxysilane, bis(3-(triethoxysilyl)propyl)disulfide, bis(3-(triethoxysilyl)propyl)tetrasulfide, γ-trimethoxysilylpropyldimethylthiocarbamyltetrasulfide, and γ-trimethoxysilylpropylbenzothiazyltetrasulfide. These silane coupling agents can be used alone or in combination of two or more. The amount of silane coupling agent added is preferably 0.1 to 30 parts by mass, more preferably 1 to 15 parts by mass, per 100 parts by mass of silica.

[0061] Examples of carbon black include furnace black, acetylene black, thermal black, channel black, and graphite. These carbon blacks can be used alone or in combination of two or more. The amount of carbon black added is usually 120 parts by mass or less per 100 parts by mass of the rubber component in the rubber composition.

[0062] The filler may be used alone or in combination of two or more kinds, for example, a mixture of silica and carbon black may be used as the filler.

[0063] The content of fillers other than silica and carbon black may be within a range in which the effects of the present invention can be obtained, and for example, can be 120 parts by mass or less per 100 parts by mass of the rubber component.

[0064] The crosslinking agent is not particularly limited, but examples thereof include sulfur, sulfur halides, organic peroxides, quinone dioximes, organic polyamine compounds, and alkylphenol resins having methylol groups. Among these, sulfur is preferably used. The amount of the crosslinking agent to be compounded is preferably 0.1 to 15 parts by mass, more preferably 0.5 to 5 parts by mass, and particularly preferably 1 to 4 parts by mass, per 100 parts by mass of the rubber component in the rubber composition.

[0065] When sulfur or a sulfur-containing compound is used as the crosslinking agent, it is preferable to use a crosslinking accelerator and a crosslinking activator in combination. Examples of crosslinking accelerators include sulfenamide-based crosslinking accelerators, guanidine-based crosslinking accelerators, thiourea-based crosslinking accelerators, thiazole-based crosslinking accelerators, thiuram-based crosslinking accelerators, dithiocarbamic acid-based crosslinking accelerators, and xanthogenic acid-based crosslinking accelerators. Among these, those containing sulfenamide-based crosslinking accelerators are preferred. These crosslinking accelerators are used alone or in combination of two or more. The amount of crosslinking accelerator mixed is preferably 0.1 to 15 parts by mass, more preferably 0.5 to 5 parts by mass, and particularly preferably 1 to 4 parts by mass, per 100 parts by mass of the rubber component in the rubber composition.

[0066] Examples of crosslinking activators include higher fatty acids such as stearic acid, zinc oxide, etc. These crosslinking activators may be used alone or in combination of two or more. The amount of crosslinking activator added is preferably 0.05 to 20 parts by mass, and particularly preferably 0.5 to 15 parts by mass, per 100 parts by mass of the rubber component in the rubber composition.

[0067] If desired, the rubber composition of the present invention may contain an antioxidant such as an amine-based stabilizer, a phenol-based stabilizer, a phosphorus-based stabilizer, or a sulfur-based stabilizer. The amount of antioxidant added may be determined appropriately depending on the type of antioxidant.

[0068] An antioxidant may be added to the rubber composition of the present invention as needed. The antioxidant is not particularly limited, but examples thereof include hindered phenol compounds such as pentaerythritol tetrakis[3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate], octadecyl-3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate, 2,6-di-t-butyl-p-cresol, and di-t-butyl-4-methylphenol; thiodicarboxylate esters such as dilauryl thiopropionate; and phosphites such as tris(nonylphenyl)phosphite. The antioxidant may be used alone or in combination of two or more. The content of the antioxidant is not particularly limited, but is preferably 10 parts by mass or less, and more preferably 0.05 to 5 parts by mass, per 100 parts by mass of the rubber component in the rubber composition.

[0069] In addition, the rubber composition of the present invention may contain a resin other than the diene rubber and the hydrocarbon resin. The incorporation of a resin can impart tack to the rubber composition and improve the dispersibility of fillers in the rubber composition. As a result, further improvements in the rolling resistance and wet grip performance of the resulting cross-linked rubber can be expected. Furthermore, similar to the effect of a plasticizer, the resin can also improve the processability of the rubber composition. Examples of resins include C9 petroleum resins, dicyclopentadiene resins, terpene resins, terpene phenol resins, aromatic-modified terpene resins, alkylphenol-acetylene resins, rosin resins, rosin ester resins, indene resins, indene-containing C9 resins, α-methylstyrene-indene copolymer resins, coumarone-indene resins, farnesene resins, and polylimonene resins. These resins may be modified or hydrogenated. These resins may be used alone or in combination of two or more. The amount of resin added is preferably 25 parts by mass or less per 100 parts by mass of the rubber component in the rubber composition.

[0070] The rubber composition of the present invention can be produced by kneading the components according to conventional methods. For example, the components excluding thermally unstable components such as crosslinking agents and crosslinking accelerators are kneaded with a diene rubber and a hydrocarbon resin, and then the resulting mixture is kneaded with thermally unstable components such as a crosslinking agent and a crosslinking accelerator to obtain the desired rubber composition. The kneading temperature when kneading the components excluding thermally unstable components with the diene rubber and hydrocarbon resin is preferably 80 to 200°C, more preferably 120 to 180°C, and the kneading time is preferably 30 seconds to 30 minutes. The kneading of the kneaded mixture with the thermally unstable components is preferably carried out after cooling to 100°C or below, more preferably 80°C or below.

[0071] By using the rubber composition of the present invention, it is possible to obtain a cross-linked rubber product having an excellent balance between rolling resistance and wet grip performance. Taking advantage of these properties, the rubber composition of the present invention is preferably used as a material for various tire parts such as the tread (cap tread, base tread), carcass, sidewall, and bead part of a tire, and among these, it can be suitably used for various tire parts such as the tread, carcass, sidewall, and bead part of various tires such as all-season tires, high-performance tires, and studless tires, and can be particularly suitably used for, for example, tire tread, and among these, it is particularly preferred to use it for the cap tread.

[0072] <Rubber cross-linked products> The cross-linked rubber product of the present invention is obtained by cross-linking the above-mentioned rubber composition of the present invention. The cross-linked rubber product of the present invention can be produced by using the rubber composition of the present invention, for example, molding it into a desired shape using a molding machine such as an extruder, injection molding machine, compressor, or roll, and then heating it to cause a cross-linking reaction, thereby fixing 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.

[0073] 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.

[0074] The heating method may be appropriately selected from common methods used for crosslinking rubber compositions, such as press heating, steam heating, oven heating, and hot air heating.

[0075] The cross-linked rubber product of the present invention thus obtained is obtained using the rubber composition of the present invention described above, and therefore has an excellent balance between rolling resistance and wet grip performance.

[0076] Taking advantage of its excellent rolling resistance and wet grip performance, the cross-linked rubber product of the present invention is preferably used, for example, in tires as a material for various tire portions such as tread (cap tread, base tread), carcass, sidewall, bead portion, etc., and among these, it can be suitably used in various tire portions such as tread, carcass, sidewall, bead portion, etc. in various tires such as all-season tires, high performance tires, and studless tires, and for example, it can be particularly suitably used for tire tread, and among these, it is particularly preferred to use it for cap tread.

[0077] Next, the pneumatic tire of the present invention will be described. The pneumatic tire of the present invention is characterized in that the above-mentioned rubber composition is used in the tread.

[0078] The tread uses the above-mentioned rubber composition, i.e., is formed using the above-mentioned rubber composition, and usually contains the cross-linked rubber of the present invention obtained by cross-linking the above-mentioned rubber composition of the present invention.

[0079] The pneumatic tire may have a tread formed using the rubber composition, and other portions thereof may also be formed using the rubber composition.

[0080] The tread formed using the rubber composition may be a part of the tread or the entire tread, but preferably includes at least a cap tread.

[0081] Furthermore, the method for manufacturing the pneumatic tire of the present invention may be any method that can manufacture a pneumatic tire having a tread formed using the above composition, and any known method for manufacturing a pneumatic tire may be used. [Example]

[0082] 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" and "%" are by mass unless otherwise specified. The test methods used in the present examples and comparative examples are as follows.

[0083] [Softening point (℃)] The softening point of the sample hydrocarbon resin was measured in accordance with JIS K 2207.

[0084] [Number average molecular weight, weight average molecular weight, Z average molecular weight, and molecular weight distribution] The sample hydrocarbon resin was analyzed by gel permeation chromatography to determine the number-average molecular weight (Mn), weight-average molecular weight (Mw), and Z-average molecular weight (Mz) in terms of standard polystyrene. The molecular weight distribution was expressed as the ratios Mw / Mn and Mz / Mw. The gel permeation chromatography analysis was performed using a Tosoh HLC-8320GPC measuring instrument and three Tosoh TSKgel SuperMultiporeHZ columns connected together. The analysis was performed at 40°C with a flow rate of 1.0 ml / min in tetrahydrofuran.

[0085] [Mooney viscosity (ML1+4)] The sample rubber composition was measured under the following conditions in accordance with JIS K 6300-1:2001. The properties were expressed as an index, with the reference sample (Comparative Example 1 described below) being set at 100. The smaller the Mooney viscosity value, the better the processability. Test temperature: 100℃ Rotor type: L-shaped Testing equipment used: Shimadzu Mooney Viscometer SMV-300J manufactured by Shimadzu Corporation

[0086] [Tensile strength (MPa) and elongation (%)] The tensile strength (MPa) and elongation (%) of test pieces of the cross-linked rubber samples were measured under the following conditions in accordance with JIS K 6251:2010. These properties were expressed as an index, with the reference sample (Comparative Example 1 described below) being set at 100. It can be determined that the larger the value, the better the tensile strength and elongation. Test piece preparation method: After preparing a sheet by press crosslinking, it is punched Test piece shape: Dumbbell-shaped No. 3 - Test piece collection direction: parallel to the grain Number of test specimens: 3 ·Measurement temperature: 23℃ Test speed: 500mm / min Testing equipment used: Alpha Technologies Tensometer 10k Testing machine capacity: Load cell type 1kN

[0087] [Loss tangent tanδ] For test pieces of the cross-linked rubber sample, the loss tangent tanδ was measured at 0°C and 60°C under the following measurement conditions: dynamic strain 0.5% and 10 Hz, in accordance with JIS K 7244-4. This property is expressed as an index with the reference sample (Comparative Example 1 described below) set at 100. It can be determined that the higher the loss tangent tanδ at 0°C, the better the wet grip performance, and that the lower the loss tangent tanδ at 60°C, the better the rolling resistance (the lower the loss tangent tanδ at 60°C, the lower the rolling resistance). Measurement item: Dynamic storage modulus E' : Dynamic loss modulus E” :loss tangent tanδ - Sample preparation method: Punching from sheet Test piece size: 50mm length x 2mm width x 2mm thickness Number of test specimens: 1 Clamp distance: 20mm

[0088] [Production Example 1] A polymerization reactor was charged with 42.7 parts of cyclopentane, 14.8 parts of cyclopentene, and 0.5 parts of toluene, and the temperature was raised to 55°C. Then, 1.2 parts of aluminum chloride was added. Subsequently, tetracyclododecene (tetracyclo[4.4.0.1 2,5 .1 7,10 A mixture consisting of 24.6 parts of 2,4-dichloro-3-ene (dodec-3-ene), 41.1 parts of 1,3-pentadiene, 15.2 parts of cyclopentene, 2.2 parts of isobutylene, 1.2 parts of diisobutylene, 0.4 parts of dicyclopentadiene, 0.5 parts of C4-C6 unsaturated hydrocarbons, and 10.3 parts of C4-C6 saturated hydrocarbons was continuously added to the polymerization reactor over a 60-minute period, maintaining the temperature at 75°C. The polymerization reaction was then terminated by adding aqueous sodium hydroxide to the polymerization reactor. The polymerization conversion rate at this time was 85%, and the composition of the resulting polymer was nearly identical to the proportions of the components constituting the monomer mixture. The types and amounts of the components in the polymerization reactor during the polymerization reaction are summarized in Table 1, divided into the components constituting the monomer mixture (addition-polymerizable components), the components corresponding to the solvent (non-addition-polymerizable components), and the polymerization catalyst. After filtering off the precipitate formed upon polymerization termination, the resulting polymer solution was placed in a distillation still and heated under a nitrogen atmosphere to remove the polymerization solvent and unreacted monomer. Next, saturated steam was blown in at 240°C or higher to distill off low-molecular-weight oligomer components. 1.25 parts of pentaerythritol tetrakis[3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate] (BASF "Irganox 1010") was added as an antioxidant to 100 parts of the molten resin. After mixing, the molten resin was removed from the distillation still and allowed to cool to room temperature to obtain the hydrocarbon resin of Production Example 1. The softening point, number-average molecular weight (Mn), weight-average molecular weight (Mw), Z-average molecular weight (Mz), and molecular weight distribution (Mw / Mn and Mz / Mw) of the resulting hydrocarbon resin of Production Example 1 were measured. The measurement results are summarized in Table 1.

[0089] [Production Examples 2 to 8] The hydrocarbon resins of Production Examples 2 to 8 were obtained in the same manner as Production Example 1, except that the types and amounts of components added to the polymerization reactor and the polymerization temperature were changed as shown in Table 1. The obtained hydrocarbon resins of Production Examples 2 to 8 were subjected to the same measurements as in Production Example 1. The results of these measurements are summarized in Table 1. In Production Examples 2 to 8, the compositions of the obtained polymers were also approximately the same as the proportions of the components constituting the monomer mixture.

[0090] [Table 1]

[0091] Example 1 In a Banbury mixer, 96.3 parts of oil-extended emulsion-polymerized styrene-butadiene rubber (SBR) (trade name "Nipol 1739", manufactured by Nippon Zeon Co., Ltd., bound styrene content: 40%, vinyl bond content in butadiene unit portion: 13.5 mol%, weight average molecular weight: 690,000, molecular weight distribution (Mw / Mn): 3.98, glass transition temperature (Tg): -35°C, containing 37.5 parts of extender oil per 100 parts of rubber component) (rubber component content: 70 parts, extender oil content: 26.3 parts) and 100 parts of solution-polymerized butadiene rubber (BR) (trade name "Nipol BR1220" manufactured by Zeon Corporation, vinyl bond content in butadiene unit portion: 2 mol%, weight average molecular weight: 490,000, molecular weight distribution (Mw / Mn): 2.52, Mooney viscosity (ML1+4, 100°C): 44, glass transition temperature (Tg): -110°C), and 30 parts of the above were masticated for 30 seconds, and then 46.6 parts of silica (manufactured by Rhodia, trade name "Zeosil 1165MP"), 5 parts of carbon black (manufactured by Cabot Japan, trade name "N339"), and a silane coupling agent: bis[3-(triethoxysilyl)propyl]propanol]. Six parts of tetrasulfide (manufactured by Tegussa, trade name "Si69") and 10 parts of the hydrocarbon resin obtained in Production Example 1 were added and mixed for 90 seconds. Then, 23.4 parts of silica (manufactured by Rhodia, trade name "Zeosil 1165MP"), 3 parts of zinc oxide, 2 parts of stearic acid, and 2 parts of an antioxidant, N-phenyl-N'-(1,3-dimethylbutyl)-p-phenylenediamine (manufactured by Ouchi Shinko Chemical Industry Co., Ltd., trade name "Nocrac 6C"), were added and mixed for another 90 seconds. Next, 5 parts of process oil (manufactured by Nippon Oil Corporation, trade name "Aromax T-DAE") were added. The mixture was then mixed for 60 seconds or more (primary mixing) at 145 to 155°C, starting at 90°C, and the mixture was discharged from the mixer.

[0092] The obtained kneaded product was cooled to room temperature, and then kneaded again in the Banbury mixer for 2 minutes (secondary kneading) at a starting temperature of 90°C, and then the kneaded product was discharged from the mixer. The temperature of the kneaded product at the end of kneading was 145°C.

[0093] Next, 1.7 parts of sulfur, 1.8 parts of a crosslinking accelerator: N-cyclohexyl-2-benzothiazolylsulfenamide (CBS, trade name "Noccela CZ-G", manufactured by Ouchi Shinko Chemical Industry Co., Ltd.), and 1.7 parts of diphenylguanidine (DPG, trade name "Noccela D", manufactured by Ouchi Shinko Chemical Industry Co., Ltd.) were added to the obtained kneaded product using two rolls at 50°C, and after kneading (crosslinking agent kneading), a sheet-shaped rubber composition was taken out.

[0094] The kneading conditions for the primary kneading, secondary kneading, and crosslinking agent kneading were as follows:

[0095] (Mixing conditions for primary and secondary mixing) Testing machine: Toyo Seiki Labo Plastomill Banbury type mixer B-600 ·Filling rate: 70~75vol% Rotor speed: 50 rpm Test start temperature: 90℃

[0096] (Kneading conditions for crosslinking agent kneading) Testing machine: Electrically heated high-temperature roll machine manufactured by Ikeda Machinery Co., Ltd. Roll size: 6φ×16 Front roll rotation speed: 24 rpm Front / rear roll ratio: 1:1.22 Roll temperature: 50±5℃ Number of turns: 2 times each Rolling width: Roll spacing approx. 0.8 mm Number of times of rolling: 5 times

[0097] [Examples 2 to 5 and Comparative Examples 1 to 3] As shown in Table 2 below, rubber compositions were obtained in the same manner as in Example 1, except that the hydrocarbon resins obtained in Production Examples 2 to 8 were used instead of the hydrocarbon resin obtained in Production Example 1.

[0098] 〔evaluation〕 The rubber compositions obtained in Examples 1 to 5 and Comparative Examples 1 to 3 were press-crosslinked for 40 minutes at a press pressure of approximately 8 MPa and a press temperature of 160°C, and then further aged overnight in a thermostatic chamber at 23°C, after which test pieces of the cross-linked rubber measuring 150 mm x 150 mm x 2 mm thick were prepared.

[0099] The Mooney viscosity of the rubber composition, and the tensile strength (MPa), elongation (%), and loss tangent tanδ of the cross-linked rubber were measured for the rubber compositions and cross-linked rubber products obtained in Examples 1 to 5 and Comparative Examples 1 to 3. The results are shown in Table 2 below.

[0100] [Table 2]

[0101] As shown in Tables 1 and 2, rubber compositions containing a diene rubber and a hydrocarbon resin, in which the content of the hydrocarbon resin is 1 to 200 parts by mass per 100 parts by mass of the diene rubber, the hydrocarbon resin contains monomer units derived from a tetracyclododecene compound in a proportion of 0.1 to 50% by weight, the weight average molecular weight (Mw) is in the range of 500 to 4,000, and the softening point is in the range of 80 to 170°C, have excellent processability, and the resulting cross-linked rubber products have an excellent balance between rolling resistance and wet grip performance, and further have excellent tensile strength and elongation (Examples 1 to 5).

[0102] On the other hand, when a rubber composition was used that did not contain a monomer unit derived from a tetracyclododecene compound and contained a hydrocarbon resin with an excessively large weight average molecular weight (Mw), the resulting cross-linked rubber was inferior in rolling resistance and wet grip performance (Comparative Examples 1 and 2). Furthermore, when a rubber composition was used that did not contain a monomer unit derived from a tetracyclododecene compound and contained a hydrocarbon resin with an excessively low softening point, the resulting cross-linked rubber was poor in balance between rolling resistance and wet grip performance (Comparative Example 3).

Claims

1. A rubber composition containing a styrene-butadiene copolymer rubber, a hydrocarbon resin, and silica, the content of the hydrocarbon resin is 1 to 200 parts by mass relative to 100 parts by mass of the styrene-butadiene copolymer rubber, The hydrocarbon resin is Contains 10 to 50% by weight of monomer units derived from a tetracyclododecene compound, The weight average molecular weight (Mw) is in the range of 500 to 4,000, A rubber composition having a softening point in the range of 80 to 170°C.

2. The hydrocarbon resin contains, in addition to 10 to 50% by weight of the monomer units derived from the tetracyclododecene compound, 1 to 60% by weight of 1,3-pentadiene monomer units, 1 to 30% by weight of alicyclic monoolefin monomer units having 4 to 6 carbon atoms, 0 to 50% by weight of acyclic monoolefin monomer units having 4 to 8 carbon atoms; 0 to 10% by weight of alicyclic diolefin monomer units, 0 to 40 wt. % aromatic monoolefin monomer units, and Contains 0 to 50% by weight of an aromatic monomer unit having a structure in which two or more cyclic structures are bonded, The hydrocarbon resin is The number average molecular weight (Mn) is in the range of 250 to 2000, Z-average molecular weight (Mz) is in the range of 1,000 to 10,000; the ratio of weight average molecular weight to number average molecular weight (Mw / Mn) is in the range of 1.0 to 4.0; 2. The rubber composition according to claim 1, wherein the ratio of the Z-average molecular weight to the weight-average molecular weight (Mz / Mw) is within the range of 1.0 to 4.

0.

3. The hydrocarbon resin contains, as the monomer unit derived from the tetracyclododecene compound, tetracyclo[4.4.0.1 ２，５ .1 ７，１０ 3. The rubber composition according to claim 1, further comprising a dodec-3-ene unit.

4. In the monomer units derived from the tetracyclododecene compound, tetracyclo[4.4.0.1 ２，５ .1 ７，１０ 4. The rubber composition according to claim 3, wherein the proportion of dodec-3-ene units is 50% by weight or more.

5. 5. The rubber composition according to claim 1, wherein the hydrocarbon resin is a hydride.

6. The rubber composition according to any one of claims 1 to 5, further comprising carbon black.

7. The rubber composition according to any one of claims 1 to 6, further comprising a silane coupling agent.

8. The rubber composition according to any one of claims 1 to 7, further comprising a crosslinking agent.

9. A cross-linked rubber product obtained by cross-linking the rubber composition according to any one of claims 1 to 8.

10. A pneumatic tire characterized by using the rubber composition according to any one of claims 1 to 8 or the cross-linked rubber according to claim 9 in its tread.

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