JP7718271B2 - Rubber composition, cross-linked rubber product using the same, and pneumatic tire - Google Patents

Description

The present invention relates to a rubber composition, and more specifically to a rubber composition that has good processability and can produce a cross-linked rubber product that has an excellent balance of rolling resistance and wet grip performance.

In recent years, automobile tires have come to be required to be more fuel efficient due to environmental and resource concerns, while also requiring improved wet grip performance, for example, from a safety perspective. A cross-linked rubber composition containing silica as a filler in the rubber component exhibits lower rolling resistance when used in a tire than a cross-linked rubber composition containing carbon black. Therefore, tires with excellent fuel efficiency can be obtained by using a cross-linked rubber composition containing silica.

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

Furthermore, Patent Document 1 discloses that in order to improve the rolling resistance and wet grip performance of tires, a specific amount of a softener with a specific structure is blended into the rubber component, as well as a specific amount of a hydrocarbon resin with a specific structure.

JP 2010-241965 A

The softeners and hydrocarbon resins with specific structures described in Patent Document 1 can certainly improve both wet grip and rolling resistance when tires are manufactured using the cross-linked elastomer obtained by adding these, but there is still a problem that the results are insufficient.

The present invention was made in consideration of the above problems, and aims to provide a rubber composition that has good processability and can produce a cross-linked rubber product that has an excellent balance of rolling resistance and wet grip performance.

The inventors conducted research to achieve the above-mentioned objective and discovered that a rubber composition obtained by blending a specific hydrocarbon resin with a diene rubber can produce a cross-linked rubber product that has an excellent balance of rolling resistance and wet grip performance while achieving excellent processability, leading to the completion of the present invention.

In other words, the present invention provides 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.

In the rubber composition of the present invention, the hydrocarbon resin contains, in addition to 0.1 to 50% by weight of 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 2 or more The hydrocarbon resin preferably contains 0 to 50% by weight of aromatic monomer units having the above structure in which the cyclic structures are bonded, and the hydrocarbon resin preferably has a number average molecular weight (Mn) in the range of 250 to 2,000, a Z average molecular weight (Mz) in the range of 1,000 to 10,000, a ratio of the weight average molecular weight to the number average molecular weight (Mw/Mn) in the range of 1.0 to 4.0, and a ratio of the Z average molecular weight to the weight average molecular weight (Mz/Mw) in the range of 1.0 to 4.0.
In the rubber composition of the present invention, the hydrocarbon resin preferably contains a tetracyclo[4.4.0.1 ^2,5 . 1 ^7,10 ]dodec-3-ene unit as the monomer unit derived from the tetracyclododecene compound.
In the rubber composition of the present invention, it is preferable that the proportion of tetracyclo[4.4.0.1 ^2,5 . ^{1 7,10} ]dodec-3-ene units in the monomer units derived from the tetracyclododecene compound is 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.

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.

The present invention provides a rubber composition that has good processability and can produce a cross-linked rubber product that has an excellent balance of rolling resistance and wet grip performance.

The rubber composition of the present invention contains a diene rubber and a hydrocarbon resin, with the hydrocarbon resin content being 1 to 200 parts by mass per 100 parts by mass of the diene rubber. The hydrocarbon resin 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. Each component of the rubber composition of the present invention is described below.

<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.

The hydrocarbon resin used in the present invention may contain 0.1 to 50% by weight of monomer units derived from tetracyclododecene compounds. While the content is not particularly limited, it 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 tetracyclododecene compounds 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 of rolling resistance and wet grip performance while also having excellent processability as a rubber composition.

In particular, the inventors conducted extensive research and discovered 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. This results in a rubber composition with excellent processability, and when cross-linked, the resulting cross-linked rubber exhibits an excellent balance of rolling resistance and wet grip performance. If the content of 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.

The tetracyclododecene compound for forming the tetracyclododecene compound-derived monomer unit may be any compound having a 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, etc. The tetracyclododecene compound may be used alone or in combination of two or more, but it is preferred that at least tetracyclo[4.4.0.1 ^2,5 .1 ^7,10 ]dodec-3-ene is contained, and it is more preferred that the proportion of tetracyclo[4.4.0.1 ^2,5 .1 ^7,10 ]dodec-3-ene in the tetracyclododecene compound is 50% by weight or more. That is, the monomer units derived from the tetracyclododecene compound contained in the hydrocarbon resin used in the present invention are tetracyclo[4.4.0.1 ^2,5 . It is preferable that the monomer unit derived from the tetracyclododecene compound contains tetracyclo[4.4.0.1 2,5 .1 ^7,10 ]dodec-3-ene units, and it is more preferable that the proportion of tetracyclo[4.4.0.1 ^2,5 .1 ^7,10 ]dodec-3-ene units is 50% by weight or more.

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 those derived from tetracyclododecene compounds are not particularly limited and any may be contained. However, from the viewpoint of the processability of the rubber composition and the rolling resistance and wet grip performance of the resulting cross-linked rubber, it is preferable for the hydrocarbon resin to contain 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.

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 keeping the content of 1,3-pentadiene monomer units within this range, the rubber composition can be made to have excellent processability, while the resulting cross-linked rubber can have an excellent balance of rolling resistance and wet grip performance. The cis/trans isomer ratio in 1,3-pentadiene may be any ratio and is not particularly limited.

The 4-6 carbon atom alicyclic monoolefin used to form the 4-6 carbon atom alicyclic monoolefin monomer unit is not particularly limited as long as it is a 4-6 carbon atom hydrocarbon compound having one ethylenically unsaturated bond and a non-aromatic ring structure in its molecular structure. Specific examples include cyclobutene, cyclopentene, cyclohexene, methylcyclobutene, and methylcyclopentene. While a single type of 4-6 carbon atom hydrocarbon compound may be used, or two or more types may be used in combination, it is preferable that at least cyclopentene is included, and it is preferable that the proportion of cyclopentene in the 4-6 carbon atom alicyclic monoolefin is 50% by weight or more. In other words, it is preferable that the proportion of cyclopentene units in the 4-6 carbon atom alicyclic monoolefin monomer unit contained in the hydrocarbon resin used in the present invention is 50% by weight or more.

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 ensuring that the content of alicyclic monoolefin monomer units having 4 to 6 carbon atoms falls within the above range, the resulting cross-linked rubber product can have even better rolling resistance and wet grip performance.

The acyclic monoolefin having 4 to 8 carbon atoms used to form 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 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 monoolefin having 4 to 8 carbon atoms 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 monoolefin having 4 to 8 carbon atoms may be used alone or in combination of two or more, but preferably contains 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 monoolefin 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.

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 acyclic monoolefin monomer units having 4 to 8 carbon atoms in the above amount, the resulting cross-linked rubber can have excellent rolling resistance and wet grip performance.

The alicyclic diolefin used to form the alicyclic diolefin monomer units 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 a single alicyclic diolefin may be used, or two or more may be used in combination, it is preferable that at least dicyclopentadiene is included, and it is more preferable that the proportion of dicyclopentadiene in the alicyclic diolefin is 50% by weight or more. In other words, 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.

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 alicyclic diolefin monomer units in the above amount, the resulting cross-linked rubber can have superior rolling resistance and wet grip performance.

The aromatic monoolefin used to form the aromatic monoolefin monomer units 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, and vinyltoluene. A single aromatic monoolefin may be used, or two or more may be used in combination. However, it is preferable that at least styrene is included, 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.

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 including aromatic monoolefin monomer units in the above proportions, the resulting cross-linked rubber can have superior rolling resistance and wet grip performance.

Aromatic monomers having a structure in which two or more cyclic structures are bonded to form aromatic monomer units having a structure in which two or more cyclic structures are bonded may be hydrocarbon compounds having two or more cyclic structures, including aromatic cyclic structures, and are not particularly limited. 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. Aromatic monomers having a structure in which two or more cyclic structures are bonded may be used alone or in combination of two or more.

The hydrocarbon resin used in the present invention preferably contains aromatic monomer units having a structure in which two or more cyclic structures are bonded in an amount of 0 to 50% by weight, more preferably 0 to 40% by weight, and even more preferably 0 to 30% by weight. By including aromatic monomer units having a structure in which two or more cyclic structures are bonded in the above amount, the resulting cross-linked rubber product can have superior rolling resistance and wet grip performance.

The hydrocarbon resin used in the present invention may also contain units of other monomers in addition to the monomer units described above. The other monomers may be any monomer copolymerizable with the monomers, including the tetracyclododecene compound described above, 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 other than those having 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 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.

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 monomers described above. The method of addition polymerization is not particularly limited and can be selected from known addition polymerization methods for producing hydrocarbon resins. After obtaining the hydrocarbon resin by addition polymerization of the 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 produce a hydrogenated product.

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.

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. By having the number average molecular weight (Mn) of the hydrocarbon resin within the above range, the resulting cross-linked rubber product can have superior rolling resistance and wet grip performance.

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. By having the Z-average molecular weight (Mz) of the hydrocarbon resin within the above range, the resulting cross-linked rubber product can have superior rolling resistance and wet grip performance.

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

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

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 measured 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 monomer units derived from tetracyclododecene compounds between 0.1 and 50% by weight, or by adjusting the production conditions in the hydrocarbon resin production method described below.

The softening point of the hydrocarbon resin used in the present invention may be in the range of 80°C to 170°C, but is not particularly limited thereto. It 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 tetracyclododecene compounds at 0.1 to 50% by weight, or by adjusting the production conditions in the hydrocarbon resin production method described below.

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).

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

The Lewis acid catalyst (A) is not limited, but is preferably a metal halide, and from the viewpoint of having 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 ₃ ), aluminum tribromide (AlBr ₃ ), gallium trichloride (GaCl ₃ ), and boron trifluoride diethyl ether complex (BF ₃ ·Et ₂ O). Among these, AlCl ₃ or BF ₃ ·Et ₂ O is preferably used from the viewpoint of versatility. The Lewis acid catalyst (A) may be used alone or in combination of two or more types.

The amount of 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.

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

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 of 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 of activity and ease of handling. It is possible to use only one type of halogenated hydrocarbon (B), or two or more types in combination.

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).

When conducting a polymerization reaction, the order in which the monomer mixture and polymerization catalyst components are added to the polymerization reactor is not particularly limited; they may be added in any order. However, from the perspective of better control of 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.

Furthermore, 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.

To better control the polymerization reaction, it is preferable to add a solvent to the polymerization reaction system before conducting the polymerization reaction. There are no particular restrictions on the type of solvent 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, and more preferably 50 to 500 parts by weight, per 100 parts by weight of the monomer mixture used in the polymerization reaction. It is also possible to add 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, to the polymerization reaction system, and use the addition-polymerizable component as a component of the monomer mixture and the non-addition-polymerizable component as a solvent.

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 selected as appropriate, but is usually selected in the range of 10 minutes to 12 hours, preferably 30 minutes to 6 hours.

Once the desired polymerization conversion rate has been achieved, 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 polymerization terminator is added to deactivate the polymerization catalyst, insoluble catalyst residue is produced, which can be removed by filtration or other methods. After the polymerization reaction has terminated, the unreacted monomer and solvent are removed, and low-molecular-weight oligomer components are further removed by steam distillation or other methods. The resulting mixture is then cooled to yield a solid hydrocarbon resin.

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.

When hydrogenating hydrocarbon resins, the hydrogenation reaction method is not particularly limited, and any known method can be used without limitation, such as contacting the resin with hydrogen in the presence of a nickel catalyst. The nickel catalyst is not particularly limited, but from the perspective of high reactivity, a catalyst containing, as its main component, a compound in which metallic 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.

<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. By using the diene rubber described above, the rubber composition can be made to have excellent processability while providing a cross-linked rubber with an excellent balance of rolling resistance and wet grip performance. The diene rubbers may be used alone or in combination of two or more.

The diene rubber of the present invention is not particularly limited in terms of molecular weight or microstructure, and may be terminally modified with amine, amide, silyl, alkoxysilyl, carboxyl, or hydroxyl groups, or may be epoxidized. The diene rubber of the present invention may be hydrogenated, but is preferably non-hydrogenated.

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

The rubber composition of the present invention may consist solely of a diene rubber and the above-mentioned 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. These other compounding ingredients may be blended in the required amounts.

Fillers that can be compounded into the rubber composition of the present invention include those commonly used in rubber compositions, such as 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.

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 primarily composed of hydrous silicic acid, is preferred. Carbon-silica dual-phase fillers, 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 (measured by the BET method in accordance with ASTM D3037-81) of the silica used is preferably 100 to 400 ^{m 2} /g, more preferably 150 to 350 m ² /g. The pH of the silica is preferably 5 to 10.

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 keeping the amount of silica compounded within this range, the resulting cross-linked rubber product can have even better rolling resistance and wet grip performance.

When using silica 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 is preferably 0.1 to 30 parts by weight, more preferably 1 to 15 parts by weight, per 100 parts by weight of silica.

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 blended is typically 120 parts by mass or less per 100 parts by mass of the rubber component in the rubber composition.

Fillers may be used alone or in combination of two or more. For example, a mixture of silica and carbon black may be used as a filler.

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

The crosslinking agent is not particularly limited, but examples include sulfur, sulfur halides, organic peroxides, quinone dioximes, organic polyamine compounds, and alkylphenol resins having methylol groups. Of these, sulfur is preferably used. The amount of crosslinking agent blended 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.

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. Of these, those containing sulfenamide-based crosslinking accelerators are 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 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.

Examples of crosslinking activators include higher fatty acids such as stearic acid; zinc oxide; and the like. These crosslinking activators may be used alone or in combination of two or more. The amount of crosslinking activator blended 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.

If desired, antioxidants such as amine-based stabilizers, phenol-based stabilizers, phosphorus-based stabilizers, and sulfur-based stabilizers may be added to the rubber composition of the present invention. The amount of antioxidant added may be determined appropriately depending on the type of antioxidant, etc.

Antioxidants may also be added to the rubber composition of the present invention as needed. Examples of antioxidants include, but are not limited to, 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. Antioxidants may be used alone or in combination of two or more. The amount of 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.

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 enhance 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. It can also improve the processability of the rubber composition, similar to the effect of a plasticizer. 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, C9 resins containing indene, 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 incorporated is preferably 25 parts by mass or less per 100 parts by mass of the rubber component in the rubber composition.

The method for producing the rubber composition of the present invention simply involves 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 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. Furthermore, the kneading of the kneaded mixture with the thermally unstable components is carried out after cooling the mixture to preferably 100°C or below, more preferably 80°C or below.

By using the rubber composition of the present invention, a cross-linked rubber product can be obtained that has an excellent balance of 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 components, such as the tread (cap tread, base tread), carcass, sidewall, and bead portions of tires. In particular, the rubber composition can be suitably used for various tire components, such as the tread, carcass, sidewall, and bead portions of various tires, including all-season tires, high-performance tires, and studless tires. It is particularly suitable for use in tire treads, and is particularly preferably used in cap treads.

<Rubber cross-linked product>
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 the rubber composition 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.

Also, depending on the shape, size, etc. of the cross-linked rubber product, even if the surface is cross-linked, the interior may not be sufficiently cross-linked, so secondary cross-linking may be performed by further heating.

The heating method can be selected from commonly used methods for crosslinking rubber compositions, such as press heating, steam heating, oven heating, and hot air heating.

The rubber cross-linked product of the present invention obtained in this manner is obtained using the rubber composition of the present invention described above, and therefore has an excellent balance of rolling resistance and wet grip performance.

The cross-linked rubber product of the present invention, taking advantage of its excellent rolling resistance and wet grip performance, is preferably used, for example, as a material for various tire components such as the tread (cap tread, base tread), carcass, sidewall, and bead portion of tires. In particular, it can be suitably used for various tire components such as the tread, carcass, sidewall, and bead portion of various tires, including all-season tires, high-performance tires, and studless tires. It is particularly suitable for use as a tire tread, and is particularly preferably used for the cap tread.

Next, we will explain the pneumatic tire of the present invention. The pneumatic tire of the present invention is characterized by using the above-mentioned rubber composition in the tread.

The tread is made using the above-mentioned rubber composition, i.e., is formed using the above-mentioned rubber composition, and typically contains the rubber cross-linked product of the present invention obtained by cross-linking the above-mentioned rubber composition of the present invention.

The pneumatic tire may have a tread formed using the rubber composition, and other parts may also be formed using the rubber composition.

The tread formed using the above rubber composition may be a portion of the tread or the entire tread, but it is preferable that it includes at least a cap tread.

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 known methods for manufacturing pneumatic tires can be used.

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.

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

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

[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 value of a reference sample (Comparative Example 1 described below) being set at 100. The smaller the Mooney viscosity value, the better the processability.
Test temperature: 100°C
・Rotor type: L-type ・Testing machine used: Shimadzu Mooney Viscometer SMV-300J manufactured by Shimadzu Corporation

[Tensile strength (MPa) and elongation (%)]
For test pieces of the cross-linked rubber samples, tensile strength (MPa) and elongation (%) 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 numerical value, the better the tensile strength and elongation.
・Test piece preparation method: After preparing a sheet by press crosslinking, punching process ・Test piece shape: Dumbbell-shaped No. 3 ・Test piece collection direction: Parallel to the grain ・Number of test pieces: 3
・Measurement temperature: 23℃
Test speed: 500 mm/min
Testing machine used: ALPHA TECHNOLOGIES TENSOMETER 10k
・Testing machine capacity: Load cell type 1kN

[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 of dynamic strain 0.5% and 10 Hz in accordance with JIS K 7244-4. This property was 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: punched from sheet - Test piece shape: length 50 mm x width 2 mm x thickness 2 mm
Number of test pieces: 1
Distance between clamps: 20 mm

[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, followed by the addition of 1.2 parts of aluminum chloride. Subsequently, a mixture consisting of 24.6 parts of tetracyclododecene (tetracyclo[4.4.0.1 ^2,5 .1 ^7,10 ]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 period of 60 minutes while maintaining the temperature at 75°C, thereby carrying out polymerization. Thereafter, an aqueous sodium hydroxide solution was added to the polymerization reactor to terminate the polymerization reaction. The polymerization conversion rate at this time was 85%, and the composition of the resulting polymer was approximately the same as the proportions of components constituting the monomer mixture. The types and amounts of 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 removing the precipitate formed by polymerization termination by filtration, the resulting polymer solution was charged into a distillation still and heated under a nitrogen atmosphere to remove the polymerization solvent and unreacted monomers. Next, low-molecular-weight oligomer components were distilled off while blowing saturated steam at 240°C or higher. To 100 parts of the molten resin, 1.25 parts of pentaerythritol tetrakis[3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate] (BASF "Irganox 1010") was added as an antioxidant. After mixing, the molten resin was removed from the distillation still and allowed to cool to room temperature, yielding 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 obtained hydrocarbon resin of Production Example 1 were measured. The measurement results are summarized in Table 1.

[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.

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 moieties: 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 6 parts of tetrasulfide (manufactured by Tegussa, trade name "Si69") and 10 parts of the hydrocarbon resin obtained in Production Example 1 were added and kneaded for 90 seconds, after which 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 kneaded for an additional 90 seconds, followed by the addition of 5 parts of process oil (manufactured by Nippon Oil Corporation, trade name "Aromax T-DAE"). Thereafter, the mixture was kneaded (primary kneading) for 60 seconds or more at 145 to 155°C, starting at 90°C, and then the kneaded product was discharged from the mixer.

The resulting kneaded material 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, after which the kneaded material was discharged from the mixer. The temperature of the kneaded material at the end of kneading was 145°C.

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 resulting kneaded mixture using two rolls at 50°C, and after kneading (crosslinking agent kneading), a sheet-shaped rubber composition was removed.

The kneading conditions for the primary kneading, secondary kneading, and crosslinking agent kneading were as shown below.

(Mixing conditions for primary and secondary mixing)
・Testing machine: Toyo Seiki Seisakusho Laboplastomill Banbury type mixer B-600
・Filling rate: 70-75vol%
Rotor rotation speed: 50 rpm
・Test start temperature: 90℃

(Kneading conditions for kneading crosslinking agent)
Testing machine: Electrically heated high-temperature roll machine manufactured by Ikeda Machinery Co., Ltd. Roll size: 6φ x 16
・Front roll rotation speed: 24 rpm
- Front and rear roll rotation ratio: 1:1.22
Roll temperature: 50±5°C
Number of turns: 2 times each on the left and right Rolling width: Roll interval approx. 0.8 mm
・Number of times rolled: 5 times

[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.

〔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 about 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.

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.

As shown in Tables 1 and 2, rubber compositions containing diene rubber and 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 0.1 to 50% by weight of monomer units derived from a tetracyclododecene compound, the weight average molecular weight (Mw) is within the range of 500 to 4,000, and the softening point is within the range of 80 to 170°C, have excellent processability, and the resulting cross-linked rubber has an excellent balance of rolling resistance and wet grip performance, as well as excellent tensile strength and elongation (Examples 1 to 5).

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 obtained cross-linked rubber product was poor in balance between rolling resistance and wet grip performance (Comparative Example 3).

Claims (10)

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. 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 an alicyclic monoolefin monomer unit 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 rubber composition according to claim 1, wherein the hydrocarbon resin contains a tetracyclo[4.4.0.1 ^2,5 . 1 ^7,10 ]dodec-3-ene unit as the monomer unit derived from the tetracyclododecene compound. 4. The rubber composition according to claim 3, wherein the proportion of tetracyclo[4.4.0.1 ^2,5 . ^{1 7,10} ]dodec-3-ene units in the monomer units derived from the tetracyclododecene compound is 50% by weight or more. The rubber composition according to any one of claims 1 to 4, wherein the hydrocarbon resin is a hydride. The rubber composition according to any one of claims 1 to 5, further containing carbon black. The rubber composition according to any one of claims 1 to 6, further comprising a silane coupling agent. The rubber composition according to any one of claims 1 to 7, further containing a crosslinking agent. A cross-linked rubber product obtained by cross-linking the rubber composition described in any one of claims 1 to 8. 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.