Rubber composition, as well as rubber crosslinked products and pneumatic tires using the same.

Abstract

Provided is a rubber composition that contains a diene-based rubber and a hydrocarbon resin. The contained amount of the hydrocarbon resin is 1-200 parts by mass with respect to 100 parts by mass of the diene-based rubber. The hydrocarbon resin includes: aliphatic monomer units; or aliphatic monomer units and aromatic monomer units. The rubber composition has a number average molecular weight (Mn) in the range of 400-3000, a weight average molecular weight (Mw) in the range of 700-6000, a Z-average molecular weight (Mz) in the range of 1500-20000, a ratio (Mw / Mn) of the weight average molecular weight with respect to the number average molecular weight in the range of 1.0-4.0, a ratio (Mz / Mw) of the Z-average molecular weight with respect to the weight average molecular weight in the range of 1.0-3.5, a ratio (Mp / Mw) of a peak-top molecular weight (Mp) with respect to the weight average molecular weight (Mw) in the range of 0.4-0.8, and a softening temperature in the range of 80-150°C.

Description

Technical Field

[0001] The present invention relates to a rubber composition, and more specifically, to a rubber composition capable of providing a crosslinked rubber product excellent in the balance among rolling resistance, wet grip performance and low-temperature performance.

Background Art

[0002] In recent years, automobile tires are strongly required to have low fuel consumption from the perspective of environmental issues and resource issues, and at the same time, from the perspective of safety, for example, improvement in wet grip performance is required. A crosslinked product of a rubber composition obtained by blending silica as a filler into a rubber component has lower rolling resistance when formed into a tire than a crosslinked product of a rubber composition blended with carbon black. Therefore, by forming a tire using a crosslinked product of a rubber composition blended with silica, a tire excellent in low fuel consumption performance can be obtained.

[0003] However, even if silica is blended into conventional rubber components, the affinity between the rubber components and silica is insufficient, and these components are easily separated. As a result, the crosslinked rubber product obtained by crosslinking these components has problems such as insufficient rolling resistance and insufficient low-temperature performance when formed into a tire.

[0004] For example, Patent Document 1 discloses that for the purpose of improving the rolling resistance and wet grip performance of tires, a specific amount of a softening agent having a specific structure and a specific amount of a hydrocarbon resin having a specific structure are blended into a rubber component.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Summary of the Invention

Problem to be Solved by the Invention

[0006] According to the specific structure of the softener and hydrocarbon resin described in Patent Document 1, when a tire is manufactured using a rubber composition obtained by adding these, it is possible to improve both rolling resistance and wet grip performance to a certain extent. However, from the viewpoint of further improving fuel efficiency and safety, there is a need for further improvement in rolling resistance and wet grip performance, and in addition to these, there is also a need for excellent low-temperature performance.

[0007] This invention has been made in view of the above circumstances, and aims to provide a rubber composition that can provide a rubber crosslinked material with an excellent balance of rolling resistance, wet grip performance, and low-temperature performance. [Means for solving the problem]

[0008] The present inventors conducted studies to achieve the above objectives and discovered that the above objectives can be achieved by a rubber composition obtained by compounding a specific hydrocarbon resin with a diene rubber, specifically by compounding a hydrocarbon resin in which the number average molecular weight (Mn), weight average molecular weight (Mw), Z average molecular weight (Mz), ratio of weight average molecular weight to number average molecular weight (Mw / Mn), ratio of Z average molecular weight to weight average molecular weight (Mz / Mw), and softening point are within a specific range, and the ratio of peak top molecular weight (Mp) to weight average molecular weight (Mw) (Mp / Mw) is controlled to be in the range of 0.4 to 0.8. This led to the completion of the present invention.

[0009] In other words, according to the present invention, a rubber composition containing a diene rubber and a hydrocarbon resin, The hydrocarbon resin content is 1 to 200 parts by mass per 100 parts by mass of the diene rubber. The hydrocarbon resin is Aliphatic monomer units, or units comprising aliphatic monomer units and aromatic monomer units, The number-average molecular weight (Mn) is in the range of 400 to 3000. The weight-average molecular weight (Mw) is in the range of 700 to 6000. The average molecular weight (Mz) is in the range of 1500 to 20000. The ratio of weight-average molecular weight to number-average molecular weight (Mw / Mn) is in the range of 1.0 to 4.0. The ratio of the Z-average molecular weight to the weight-average molecular weight (Mz / Mw) is in the range of 1.0 to 3.5. The ratio of peak-top molecular weight (Mp) to weight-average molecular weight (Mw) (Mp / Mw) is in the range of 0.4 to 0.8. The softening point temperature is in the range of 80 to 150°C. A rubber composition is provided.

[0010] In the rubber composition of the present invention, The hydrocarbon resin is 1,3-pentadiene monomer units: 1-70% by mass, 1 to 30% by mass of alicyclic monoolefin monomer units having 4 to 6 carbon atoms. Isoprene monomer units 0-15% by mass, 0-50% by mass of acyclic monoolefin monomer units having 4-8 carbon atoms. 0-10% by mass of alicyclic diolefin monomer units, and It is preferable that the product contains 0 to 40% by mass of aromatic monoolefin monomer units.

[0011] In the rubber composition of the present invention, it is preferable that the hydrocarbon resin is a hydride. The rubber composition of the present invention preferably further contains a filler. The rubber composition of the present invention preferably further contains a crosslinking agent. The rubber composition of the present invention preferably contains styrene-butadiene copolymer rubber or butadiene rubber as the diene rubber.

[0012] Furthermore, according to the present invention, a crosslinked rubber product is provided, which is obtained by crosslinking the above-mentioned rubber composition. Furthermore, the present invention provides a pneumatic tire characterized by using the above-mentioned rubber composition or the above-mentioned crosslinked rubber product in the tread. [Effects of the Invention]

[0013] According to the present invention, there can be provided a rubber composition capable of providing a crosslinked rubber product excellent in the balance among rolling resistance, wet grip performance and low-temperature performance. MODE FOR CARRYING OUT THE INVENTION

[0014] The rubber composition of the present invention is 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 relative to 100 parts by mass of the diene rubber. Hereinafter, each component of the rubber composition of the present invention will be described.

[0015] <Hydrocarbon Resin> The hydrocarbon resin used in the present invention contains an aliphatic monomer unit, or an aliphatic monomer unit and an aromatic monomer unit, has a number average molecular weight (Mn) in the range of 400 to 3,000, has a weight average molecular weight (Mw) in the range of 700 to 6,000, has a Z-average molecular weight (Mz) in the range of 1,500 to 20,000, has a ratio of weight average molecular weight to number average molecular weight (Mw / Mn) in the range of 1.0 to 4.0, has a ratio of Z-average molecular weight to weight average molecular weight (Mz / Mw) in the range of 1.0 to 3.5, has a ratio of peak top molecular weight (Mp) to weight average molecular weight (Mw) (Mp / Mw) in the range of 0.4 to 0.8, and has a softening point in the range of 80°C to 150°C.

[0016] The hydrocarbon resin used in the present invention only needs to contain at least an aliphatic monomer unit, and may contain an aromatic monomer unit in addition to the aliphatic monomer unit.

[0017] (Aliphatic Monomer Unit) First, we will explain the aliphatic monomer units contained in the hydrocarbon resin used in this invention. The aliphatic monomer used to form aliphatic monomer units can be any aliphatic monomer that does not contain an aromatic ring and contains at least an unsaturated hydrocarbon. Examples of such aliphatic monomers include 1,3-pentadiene, alicyclic monoolefin monomers having 4 to 6 carbon atoms, isoprene, acyclic monoolefin monomers having 4 to 8 carbon atoms, and alicyclic diolefin monomers. In the present invention, a mixture containing these aliphatic monomers may also be added to the polymerization reaction system when producing a hydrocarbon resin. In this case, the aliphatic monomers contained in the mixture are used as components of the monomer units that constitute the hydrocarbon resin. In addition, addition polymerizable components other than aliphatic monomers contained in the mixture may also be used as components of the monomer units of the hydrocarbon resin, and non-addition polymerizable components may be used as solvents during polymerization. As a mixture containing such aliphatic monomers, for example, a C5 fraction containing 1,3-pentadiene, cyclopentene, isobutylene, etc. as aliphatic monomers can be suitably used.

[0018] The hydrocarbon resin preferably contains 1,3-pentadiene monomer units and alicyclic monoolefin monomer units having 4 to 6 carbon atoms as aliphatic monomer units, and may further contain isoprene monomer units, acyclic monoolefin monomer units having 4 to 8 carbon atoms, and alicyclic diolefin monomer units.

[0019] The content of 1,3-pentadiene monomer units in the hydrocarbon resin is not particularly limited, but is preferably 1 to 70% by mass, more preferably 20 to 65% by mass, even more preferably 30 to 60% by mass, and most preferably 35 to 52% by mass. By setting the content of 1,3-pentadiene monomer units within the above range, the resulting crosslinked rubber can be made to have superior rolling resistance, wet grip performance, and low-temperature performance. The cis / trans isomer ratio of 1,3-pentadiene can be any ratio and is not particularly limited.

[0020] Alicyclic monoolefins, which form alicyclic monoolefin monomer units with 4 to 6 carbon atoms, are hydrocarbon compounds with 4 to 6 carbon atoms that have one ethylenically unsaturated bond and a non-aromatic ring structure in their molecular structure. Specific examples of alicyclic monoolefins with 4 to 6 carbon atoms include cyclobutene, cyclopentene, cyclohexene, methylcyclobutene, and methylcyclopentene.

[0021] The content of alicyclic monoolefin monomer units having 4 to 6 carbon atoms in the hydrocarbon resin is not particularly limited, but is preferably 1 to 30% by mass, more preferably 5 to 25% by mass, even more preferably 9 to 22% by mass, even more preferably 11 to 19% by mass, and particularly preferably 13 to 17% by mass. By setting the content of alicyclic monoolefin monomer units having 4 to 6 carbon atoms within the above range, the resulting crosslinked rubber can be made to have superior rolling resistance, wet grip performance, and low-temperature performance.

[0022] Furthermore, the proportion of each compound corresponding to the alicyclic monoolefin having 4 to 6 carbon atoms can be any proportion and is not particularly limited, but it is preferable that at least cyclopentene is included, more preferably that cyclopentene accounts for 50% by mass or more of the alicyclic monoolefin having 4 to 6 carbon atoms, even more preferably 80% by mass or more, and particularly preferably 100% by mass.

[0023] Furthermore, the hydrocarbon resin used in the present invention preferably contains isoprene monomer units, and the inclusion of isoprene monomer units can further enhance the wet grip performance of the resulting crosslinked rubber. The content of isoprene monomer units in the hydrocarbon resin is not particularly limited, but is preferably 0 to 15% by mass, more preferably 0.1 to 12% by mass, even more preferably 0.15 to 10% by mass, and even more preferably 0.2 to 9% by mass. By setting the content of isoprene monomer units within the above range, the wet grip performance of the resulting crosslinked rubber can be more appropriately enhanced. From the viewpoint of further enhancing the wet grip performance of the resulting crosslinked rubber, it is particularly preferable that the content of isoprene monomer units be 6 to 10% by mass, and from the viewpoint of making the resulting crosslinked rubber even better in terms of the balance between rolling resistance, wet grip performance, and low-temperature performance, it is particularly preferable that the content of isoprene monomer units be 0.15 to 0.5% by mass.

[0024] Acyclic monoolefins, which form acyclic monoolefin monomer units with 4 to 8 carbon atoms, are chain-like hydrocarbon compounds with 4 to 8 carbon atoms that have one ethylenically unsaturated bond in their molecular structure and do not have a cyclic structure. Specific examples of acyclic monoolefins having 4 to 8 carbon atoms include butenes such as 1-butene, 2-butene, and isobutylene (2-methylpropene); pentenes such as 1-pentene, 2-pentene, 2-methyl-1-butene, 3-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; octenes such as 1-octene, 2-octene, 2-methyl-1-heptene, and diisobutylene (2,4,4-trimethyl-1-pentene and 2,4,4-trimethyl-1-pentene); and others.

[0025] The content of acyclic monoolefin monomer units having 4 to 8 carbon atoms in the hydrocarbon resin is not particularly limited, but is preferably 0 to 50% by mass, more preferably 8 to 45% by mass, even more preferably 10 to 40% by mass, and particularly preferably 14 to 37% by mass. By setting the content of acyclic monoolefin monomer units having 4 to 8 carbon atoms within the above range, the resulting crosslinked rubber can be made to have superior rolling resistance, wet grip performance, and low-temperature performance.

[0026] Furthermore, the proportion of each compound (including isomers) corresponding to the acyclic monoolefin having 4 to 8 carbon atoms can be any proportion and is not particularly limited, but it is preferable that it contains at least one selected from the group consisting of 2-methyl-2-butene, isobutylene, and diisobutylene, and it is more preferable that the total amount of 2-methyl-2-butene, isobutylene, and diisobutylene in the acyclic monoolefin having 4 to 8 carbon atoms accounts for 50% by mass or more.

[0027] Alicyclic diolefins, which form alicyclic diolefin monomer units, are hydrocarbon compounds that have two or more ethylenically unsaturated bonds and a non-aromatic ring structure in their molecular structure. Specific examples of alicyclic diolefins include cyclopentadiene polymers such as cyclopentadiene and dicyclopentadiene, and methylcyclopentadiene polymers such as methylcyclopentadiene.

[0028] The content of alicyclic diolefin monomer units in the hydrocarbon resin is not particularly limited, but is preferably 0 to 10% by mass, more preferably 0.03 to 5% by mass, even more preferably 0.05 to 4% by mass, and most preferably 0.08 to 3% by mass. By setting the content of alicyclic diolefin monomer units within the above range, the resulting crosslinked rubber can be made to have superior rolling resistance, wet grip performance, and low-temperature performance.

[0029] Furthermore, the hydrocarbon resin of the present invention may also contain other monomer units other than 1,3-pentadiene monomer units, alicyclic monoolefin monomer units having 4 to 6 carbon atoms, isoprene monomer units, acyclic monoolefin monomer units having 4 to 8 carbon atoms, and alicyclic diolefin monomer units.

[0030] Other monomers that form such other monomer units are not particularly limited, as long as they are addition polymerizable compounds that can be addition copolymerized with 1,3-pentadiene, etc. Examples of such other monomers include unsaturated hydrocarbons with 4 to 6 carbon atoms other than 1,3-pentadiene and isoprene, such as 1,3-butadiene, 1,2-butadiene, 1,3-hexadiene, and 1,4-pentadiene; alicyclic monoolefins with 7 or more carbon atoms, such as cycloheptene; and acyclic monoolefins with 4 to 8 carbon atoms, such as ethylene, propylene, and nonene.

[0031] The content of other monomer units in the hydrocarbon resin is usually in the range of 0% to 30% by mass, preferably 0 to 25% by mass, and more preferably 0 to 20% by mass.

[0032] The content of aliphatic monomer units in the hydrocarbon resin is not particularly limited, but is preferably 50% by mass or more, more preferably 60% by mass or more, even more preferably 70% by mass or more, and especially preferably 80% by mass or more. In particular, when the hydrocarbon resin contains both aliphatic monomer units and aromatic monomer units, the content of aliphatic monomer units is not particularly limited, but is preferably 60% by mass or more, more preferably 63-90% by mass, even more preferably 65-85% by mass, and especially preferably 68-81% by mass.

[0033] (Aromatic monomer units) The hydrocarbon resin used in the present invention may contain aromatic monomer units in addition to aliphatic monomer units. By using a hydrocarbon resin that contains aromatic monomer units in addition to aliphatic monomer units, the resulting crosslinked rubber can be made to have superior rolling resistance and wet grip performance. The aromatic monomer for forming the aromatic monomer units can be any monomer that has an aromatic ring and can copolymerize with an aliphatic monomer, for example, an aromatic monoolefin monomer. In addition, in the present invention, a mixture containing aromatic monomers such as aromatic monoolefin monomers may be added to the polymerization reaction system when producing the hydrocarbon resin. In this case, the aromatic monomers contained in the mixture are used as components of the monomer units that constitute the hydrocarbon resin. Furthermore, addition polymerizable components other than aromatic monomers contained in the mixture may also be used as components of the monomer units of the hydrocarbon resin, and non-addition polymerizable components may be used as solvents during polymerization. As such a mixture containing aromatic monomers, for example, a C9 fraction containing styrene compounds, indene compounds, etc., as aromatic monomers can be suitably used.

[0034] Aromatic monoolefin monomers are aromatic compounds that have one ethylenically unsaturated bond in their molecular structure. Specific examples of aromatic monoolefins include styrene compounds such as styrene, α-methylstyrene, β-methylstyrene, and vinyltoluene; indene compounds such as indene and 1-methylindene; and coumarone.

[0035] The content of aromatic monoolefin monomer units in the hydrocarbon resin is not particularly limited, but is preferably 0 to 40% by mass, more preferably 10 to 37% by mass, even more preferably 15 to 35% by mass, and particularly preferably 19 to 32% by mass. By setting the content of aromatic monoolefin monomer units within the above range, the rolling resistance and wet grip performance of the resulting crosslinked rubber can be more appropriately improved.

[0036] The number-average molecular weight (Mn) of the hydrocarbon resin used in the present invention is in the range of 400 to 3000, preferably in the range of 500 to 2000, more preferably in the range of 700 to 1300, and even more preferably in the range of 800 to 1100. The weight-average molecular weight (Mw) of the hydrocarbon resin used in the present invention is in the range of 700 to 6000, preferably in the range of 1000 to 4000, more preferably in the range of 1400 to 3000, and even more preferably in the range of 1600 to 2500. The Z-average molecular weight (Mz) of the hydrocarbon resin used in the present invention is in the range of 1500 to 20000, preferably in the range of 2200 to 10000, more preferably in the range of 2700 to 6500, and even more preferably in the range of 3200 to 5700.

[0037] The ratio of the weight-average molecular weight to the number-average molecular weight (Mw / Mn) of the hydrocarbon resin used in the present invention is in the range of 1.0 to 4.0, preferably in the range of 1.2 to 3.2, more preferably in the range of 1.5 to 2.9, and even more preferably in the range of 1.7 to 2.6. Furthermore, the ratio of the Z-average molecular weight to the weight-average molecular weight (Mz / Mw) of the hydrocarbon resin used in the present invention is in the range of 1.0 to 3.5, preferably in the range of 1.2 to 3.2, more preferably in the range of 1.4 to 2.8, and even more preferably in the range of 1.6 to 2.5.

[0038] By setting the number-average molecular weight (Mn), weight-average molecular weight (Mw), Z-average molecular weight (Mz), the ratio of weight-average molecular weight to number-average molecular weight (Mw / Mn), and the ratio of Z-average molecular weight to weight-average molecular weight (Mz / Mw) of the hydrocarbon resin within the above ranges, the resulting crosslinked rubber can be made to have an excellent balance of rolling resistance, wet grip performance, and low-temperature performance.

[0039] The number-average molecular weight (Mn), weight-average molecular weight (Mw), Z-average molecular weight (Mz), the ratio of weight-average molecular weight to number-average molecular weight (Mw / Mn), and the ratio of Z-average molecular weight to weight-average molecular weight (Mz / Mw) of hydrocarbon resins can be determined as polystyrene-converted values ​​by gel permeation chromatography using tetrahydrofuran as the developing solvent.

[0040] Furthermore, in this invention, in addition to setting the number average molecular weight (Mn), weight average molecular weight (Mw), Z average molecular weight (Mz), the ratio of weight average molecular weight to number average molecular weight (Mw / Mn), and the ratio of Z average molecular weight to weight average molecular weight (Mz / Mw) of the hydrocarbon resin within the above ranges, the ratio of peak top molecular weight (Mp) to weight average molecular weight (Mw) (Mp / Mw) of the hydrocarbon resin is set in the range of 0.4 to 0.8. In this invention, a hydrocarbon resin having a ratio of peak top molecular weight (Mp) to weight average molecular weight (Mw) (Mp / Mw) in the range of 0.4 to 0.8 is used, and by compounding this with a diene-based rubber, the rubber composition obtained in this way can provide a crosslinked rubber with an excellent balance of rolling resistance, wet grip performance, and low-temperature performance. In particular, the inventors have conducted diligent research and found that by using a hydrocarbon resin with a ratio of peak-top molecular weight (Mp) to weight-average molecular weight (Mw) in the range of 0.4 to 0.8, it is possible to include a relatively large amount of low-molecular-weight components compared to cases where the ratio (Mp / Mw) is close to 1. This allows for improved wet grip performance and low-temperature performance while maintaining good rolling resistance, resulting in a well-balanced and excellent product in terms of rolling resistance, wet grip performance, and low-temperature performance.

[0041] If the ratio of peak-top molecular weight (Mp) to weight-average molecular weight (Mw) (Mp / Mw) is too low, rolling resistance will decrease. On the other hand, if the ratio of peak-top molecular weight (Mp) to weight-average molecular weight (Mw) (Mp / Mw) is too high, wet grip performance and low-temperature performance will decrease. The ratio of peak-top molecular weight (Mp) to weight-average molecular weight (Mw) (Mp / Mw) should be in the range of 0.4 to 0.8, preferably in the range of 0.4 to 0.78, more preferably in the range of 0.41 to 0.75, even more preferably in the range of 0.43 to 0.72, particularly preferably in the range of 0.47 to 0.67, and most preferably in the range of 0.5 to 0.64. The peak-top molecular weight (Mp) of the hydrocarbon resin is not particularly limited, but is preferably in the range of 500 to 4000, more preferably in the range of 700 to 2500, and even more preferably in the range of 1000 to 1500.

[0042] The ratio of peak-top molecular weight (Mp) to weight-average molecular weight (Mw) (Mp / Mw) is determined by using tetrahydrofuran as the developing solvent and measuring the weight-average molecular weight (Mw) and peak-top molecular weight (Mp) of the hydrocarbon resin as polystyrene equivalents using gel permeation chromatography (GPC) measurement. The peak-top molecular weight (Mp) is the molecular weight at which the detected value (elution amount) is maximum in the GPC chart obtained by gel permeation chromatography measurement. Mp / Mw represents the relationship between this peak-top molecular weight (Mp), which is the molecular weight at which the detected value (elution amount) is maximum, and the weight-average molecular weight (Mw). A smaller Mp / Mw value tends to indicate a relatively large amount of low molecular weight components, while a larger Mp / Mw value tends to indicate a large amount of high molecular weight components. If there are two or more peaks in the GPC chart, the molecular weight corresponding to the largest peak is taken as the peak-top molecular weight (Mp).

[0043] In the present invention, the number-average molecular weight (Mn), weight-average molecular weight (Mw), Z-average molecular weight (Mz), the ratio of weight-average molecular weight to number-average molecular weight (Mw / Mn), the ratio of Z-average molecular weight to weight-average molecular weight (Mz / Mw), and the ratio of peak-top molecular weight (Mp) to weight-average molecular weight (Mw) of the hydrocarbon resin (Mp / Mw) can be adjusted by the type and amount of monomers used for polymerization, as well as the polymerization conditions. In particular, the ratio of peak-top molecular weight (Mp) to weight-average molecular weight (Mw) of the hydrocarbon resin (Mp / Mw) can be controlled by appropriately combining methods such as adjusting the type and amount of monomers used for polymerization, adjusting the amount of polymerization catalyst used, adjusting the polymerization temperature, and adjusting the mixing temperature and mixing time when the polymerization catalyst is pre-mixed in a volatile solvent. For example, the more polymerization catalyst used and the higher the polymerization temperature, the smaller the ratio of peak-top molecular weight (Mp) to weight-average molecular weight (Mw) of the hydrocarbon resin (Mp / Mw) tends to be. Furthermore, the shorter the mixing time when the polymerization catalyst is pre-mixed into the volatile solvent, the smaller the ratio of the peak-top molecular weight (Mp) to the weight-average molecular weight (Mw) of the hydrocarbon resin (Mp / Mw) tends to be.

[0044] Furthermore, the softening point of the hydrocarbon resin used in this invention is in the range of 80 to 150°C, preferably in the range of 85 to 145°C, more preferably in the range of 90 to 140°C, even more preferably in the range of 90 to 115°C, and particularly preferably in the range of 92 to 105°C. By setting the softening point within the above range, compatibility with diene-based rubber can be improved, thereby appropriately enhancing the rolling resistance, wet grip performance, and low-temperature performance of the resulting crosslinked rubber. The softening point of the hydrocarbon resin can be measured in accordance with JIS K6863.

[0045] <Method for manufacturing hydrocarbon resins> The method for producing the hydrocarbon resin used in the present invention is not particularly limited, but one method is to perform addition polymerization on a monomer mixture to constitute the hydrocarbon resin. For example, a method of addition polymerization using a Friedel-Crafts type cationic polymerization catalyst is preferred.

[0046] While not particularly limited, examples of Friedel-Crafts type cationic polymerization catalysts include halides such as aluminum, iron, tantalum, zirconium, tin, beryllium, boron, antimony, gallium, bismuth, and molybdenum. Among these, aluminum halides such as aluminum chloride (AlCl3) and aluminum bromide (AlBr3) are preferred. The amount of Friedel-Crafts type cationic polymerization catalyst used is preferably 0.05 to 10 parts by mass, more preferably 0.1 to 5 parts by mass, even more preferably 0.5 to 2.0 parts by mass, and particularly preferably 0.7 to 1.7 parts by mass, per 100 parts by mass of the monomer mixture used for polymerization.

[0047] Furthermore, in polymerization, halogenated hydrocarbons may be used in combination with Friedel-Crafts type cationic polymerization catalysts, as this can further enhance catalytic activity.

[0048] Specific examples of halogenated hydrocarbons include halogenated hydrocarbons in which a halogen atom is bonded to a tertiary carbon atom, such as t-butyl chloride, t-butyl bromide, 2-chloro-2-methylbutane, and triphenylmethyl chloride; and halogenated hydrocarbons in which a halogen atom is bonded to a carbon atom adjacent to a carbon-carbon unsaturated bond, such as benzyl chloride, benzyl bromide, (1-chloroethyl)benzene, allyl chloride, 3-chloro-1-propyne, 3-chloro-1-butene, 3-chloro-1-butyne, and cinnamon chloride. Among these, t-butyl chloride and benzyl chloride are preferred from the viewpoint of having an excellent balance between catalytic activity and handling ease. Halogenated hydrocarbons may be used individually or in combination of two or more. The amount of halogenated hydrocarbon used is preferably in the range of 0.05 to 50, more preferably in the range of 0.1 to 10, in molar ratio to the Friedel-Crafts type cationic polymerization catalyst.

[0049] Furthermore, from the viewpoint of better controlling the polymerization reaction, it is preferable to add a volatile solvent to the polymerization reaction system before carrying out the polymerization reaction. There are no particular restrictions on the type of volatile 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 include chain-like 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 include aromatic hydrocarbons having 6 to 10 carbon atoms, such as benzene, toluene, and xylene. The volatile solvent may be used alone or in combination of two or more types. The amount of volatile solvent used is not particularly limited, but is preferably 10 to 1,000 parts by mass, more preferably 50 to 500 parts by mass, per 100 parts by mass of the monomer mixture used for polymerization.

[0050] When carrying out a polymerization reaction, there is no particular order in which the monomer mixture and the components of the polymerization catalyst are added to the polymerization reactor; they can be added in any order. However, from the viewpoint of effectively controlling the polymerization reaction and controlling the ratio of peak-top molecular weight (Mp) to weight-average molecular weight (Mw) (Mp / Mw), it is preferable to pre-add the polymerization catalyst to a volatile solvent and mix it to disperse the polymerization catalyst in the volatile solvent, and then add the monomer mixture to the polymerization reactor to start the polymerization reaction.

[0051] When adding the polymerization catalyst to the volatile solvent in advance and mixing, it is preferable to use conditions that allow some aggregation of the polymerization catalyst to remain in the volatile solvent. The mixing temperature is preferably 45 to 80°C, more preferably 50 to 70°C, and the mixing time is preferably 10 seconds to 4 minutes, more preferably 30 seconds to 3 minutes.

[0052] The polymerization temperature during the polymerization reaction is not particularly limited, but is preferably 50 to 90°C, more preferably 55 to 85°C, and even more preferably 60 to 78°C. The polymerization reaction time can be selected as appropriate, but is usually 10 minutes to 12 hours, preferably 30 minutes to 6 hours.

[0053] The polymerization reaction can be stopped by adding a polymerization inhibitor such as methanol, aqueous sodium hydroxide solution, or aqueous ammonia solution to the polymerization reaction system once the desired polymerization conversion rate is achieved, thereby obtaining a polymer solution containing a hydrocarbon resin.

[0054] After polymerization, a polymerization inhibitor may be added to inactivate the polymerization catalyst. The solvent-insoluble catalyst residue generated during this process may be removed by filtration or other means.

[0055] Furthermore, after polymerization, it is preferable to remove volatile organic compound components such as solvents, unreacted monomers, and low molecular weight oligomer components from the polymer solution containing the hydrocarbon resin by steam distillation or the like.

[0056] Furthermore, the obtained hydrocarbon resin may be subjected to a hydrogenation reaction to hydrogenate the carbon-carbon double bonds in the hydrocarbon resin, if necessary, to obtain a hydride. In other words, it may be obtained as a hydrocarbon resin hydride. Hydrogenation of hydrocarbon resins can be carried out by contacting the hydrocarbon resin with hydrogen in the presence of a hydrogenation catalyst.

[0057] While there are no particular limitations on the hydrogenation catalyst, nickel catalysts are preferred. In particular, from the viewpoint of high reactivity, catalysts mainly comprising a compound in which nickel as a metal is supported on a supported inorganic compound as a support are preferred. Specific examples of supported inorganic compounds as support include silica, alumina, boria, silica-alumina, diatomaceous earth, white clay, clay, magnesia, magnesia-silica (silica-magnesium oxide), titania, and zirconia. Among these, magnesia-silica is preferred from the viewpoint of reactivity.

[0058] <Diene-based 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 compounded together with the hydrocarbon resin. Examples of such diene rubbers include the diene rubber described in Japanese Patent Application Publication No. 2015-189873, specifically natural rubber (NR), isoprene rubber (IR), butadiene rubber (BR), styrene-butadiene copolymer rubber (SBR), ethylene-propylene-diene polymer (EPDM), etc. Among these, styrene-butadiene copolymer rubber and butadiene rubber are preferred, and styrene-butadiene copolymer rubber is more preferred. The Mooney viscosity (ML1 + 4,100℃) of the diene rubber is not particularly limited, but is preferably 20 to 90, and more preferably 30 to 80. If the diene rubber is an oil-expandable rubber, it is preferable that the Mooney viscosity of the oil-expandable rubber is within the above range. Furthermore, the glass transition temperature (Tg) of the diene rubber is not particularly limited, but is preferably -110°C to 20°C, and more preferably -90°C to 0°C. By using such a rubber as the diene rubber, the rubber crosslinked product can be made to have a better balance of rolling resistance, wet grip performance, and low-temperature performance. The diene rubber may be used alone or in combination of two or more types.

[0059] Furthermore, the diene rubber used in the present invention is not particularly limited in terms of its molecular weight or microstructure, and may be end-modified with amine, amide, silyl, alkoxysilyl, carboxyl, or hydroxyl groups, or may be epoxidized. Also, the diene rubber used in the present invention may be hydrogenated, but it is preferable that it is not hydrogenated. When using a diene rubber containing butadiene units, such as styrene-butadiene copolymer rubber or butadiene rubber, the content of butadiene units in the diene rubber is preferably 30% by mass or more, more preferably 50% by mass or more, and the vinyl bond content in the butadiene units is not particularly limited, but is preferably 1 to 90%, more preferably 3 to 85%, and even more preferably 5 to 80%.

[0060] In the rubber composition of the present invention, the blending ratio of the diene rubber to the hydrocarbon resin is such that 1 to 200 parts by mass of hydrocarbon resin are blended per 100 parts by mass of diene rubber, preferably 1 to 70 parts by mass, more preferably 3 to 35 parts by mass, and even more preferably 15 to 25 parts by mass. If the amount of hydrocarbon resin is too small, the resulting crosslinked rubber will have poor wet grip performance and low-temperature performance, while if it is too large, the resulting crosslinked rubber will have poor rolling resistance.

[0061] The rubber composition of the present invention may consist only of diene rubber and the above-mentioned hydrocarbon resin, but may also contain other components. Other components that may be contained in the rubber composition of the present invention include, for example, fillers, silane coupling agents, crosslinking agents, crosslinking accelerators, crosslinking activators, anti-aging agents, antioxidants, activators, process oils, plasticizers, lubricants, tackifiers, and the like, and each of these and other compounding agents can be added in the required amount.

[0062] Fillers that can be incorporated into the rubber composition of the present invention include those commonly used in rubber compositions, such as inorganic hollow fillers like 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.

[0063] Examples of silica include dry-process white carbon, wet-process white carbon, colloidal silica, and precipitated silica. Among these, wet-process white carbon, which mainly consists of hydrated silicic acid, is preferred. Alternatively, a carbon-silica dual-phase filler, in which silica is supported on the surface of carbon black, may be used. These silicas can be used individually or in combination of two or more types. 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 m². 2 / g, more comfortably 150-350m 2 The concentration is / g. Furthermore, the pH of the silica is preferably between 5 and 10.

[0064] The amount of silica 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 rubber components in the rubber composition. By setting the amount of silica within the above range, the resulting crosslinked rubber can be made to have superior rolling resistance, wet grip performance, and low-temperature performance.

[0065] 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-trimethoxysilylpropyldimethylthiocarbamyl tetrasulfide, and γ-trimethoxysilylpropylbenzothiazyl tetrasulfide. These silane coupling agents can be used individually or in combination of two or more. The amount of silane coupling agent is preferably 0.1 to 30 parts by mass, more preferably 1 to 15 parts by mass, per 100 parts by mass of silica.

[0066] Examples of carbon black include furnace black, acetylene black, thermal black, channel black, and graphite. These carbon blacks can be used individually 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 rubber components in the rubber composition.

[0067] Furthermore, the filler may be used alone or in combination of two or more types. For example, silica and carbon black can be used as a filler.

[0068] The content of fillers other than silica and carbon black may be as long as the effects of the present invention are obtained, for example, it may be 120 parts by mass or less per 100 parts by mass of rubber component in the rubber composition.

[0069] The crosslinking agent is not particularly limited, but examples include sulfur, sulfur halides, organic peroxides, quinone dioximes, organic polyvalent amine compounds, and alkylphenol resins having methylol groups. Among these, sulfur is preferably used. The amount of crosslinking agent added 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.

[0070] When sulfur or a sulfur-containing compound is used as a 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; thiram-based crosslinking accelerators; dithiocarbamate-based crosslinking accelerators; xanthogenic acid-based crosslinking accelerators; and others. Among these, those containing sulfenamide-based crosslinking accelerators are preferred. These crosslinking accelerators can be used individually or in combination of two or more. The amount of crosslinking accelerator added 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.

[0071] Examples of crosslinking activators include higher fatty acids such as stearic acid; zinc oxide; and the like. These crosslinking activators can be used individually 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 rubber components in the rubber composition.

[0072] Furthermore, the rubber composition of the present invention may optionally contain antioxidants such as amine-based stabilizers, phenol-based stabilizers, phosphorus-based stabilizers, and sulfur-based stabilizers. The amount of antioxidant added should be determined appropriately depending on its type and other factors.

[0073] Furthermore, antioxidants may be added to the rubber composition of the present invention as needed. While not particularly limited, examples of antioxidants 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 dilaurylthiopropionate; and phosphites such as tris(nonylphenyl)phosphite. The antioxidant may be used alone or in combination of two or more. The antioxidant content 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.

[0074] Furthermore, the rubber composition of the present invention may also contain resins other than diene rubber and the hydrocarbon resins mentioned above. By incorporating resins, tackiness can be imparted to the rubber composition, and the dispersibility of fillers in the rubber composition can be improved. As a result, further improvements in the rolling resistance, wet grip performance, and low-temperature performance of the resulting crosslinked rubber can be expected. In addition, as an effect similar to that of plasticizers, the processability of the rubber composition can also be improved. Examples of resins include C9 petroleum resins, dicyclopentadiene resins, terpene resins, terpene phenol resins, aromatically modified terpene resins, alkylphenol-acetylene resins, rosin resins, rosin ester resins, indene resins, C9 resins containing indene, α-methylstyrene-indene copolymer resins, coumaron-indene resins, farnesene resins, and polylimonene resins. These resins may be modified or hydrogenated. These resins can be used individually 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.

[0075] The rubber composition of the present invention can be produced by kneading each component according to a conventional method. For example, the components excluding heat-unstable components such as crosslinking agents and crosslinking accelerators can be kneaded with a diene rubber and a hydrocarbon resin, and then the heat-unstable components such as crosslinking agents and crosslinking accelerators can be kneaded into the mixture to obtain the desired rubber composition. The kneading temperature when kneading the components excluding heat-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 mixture with the heat-unstable components is preferably carried out after cooling to 100°C or lower, more preferably 80°C or lower.

[0076] By using the rubber composition of the present invention, a crosslinked rubber product with an excellent balance of rolling resistance, wet grip performance, and low-temperature performance can be obtained. Taking advantage of these properties, the rubber composition of the present invention is preferably used as a material for various parts of a tire, such as the tread (cap tread, base tread), carcass, sidewall, and bead. In particular, it can be suitably used for various parts of tires, such as the tread, carcass, sidewall, and bead, in all-season tires, high-performance tires, and studless tires. For example, it can be particularly suitably used for the tread of a tire, and is especially preferable for use in the cap tread.

[0077] <Rubber Crosslinked Products> The rubber crosslinked material of the present invention is obtained by crosslinking the rubber composition of the present invention described above. The crosslinked rubber product of the present invention can be manufactured by using the rubber composition of the present invention, molding it using a molding machine corresponding to the desired shape, such as an extruder, injection molding machine, compressor, or roll, and then heating it to perform a crosslinking reaction and fix the shape as a crosslinked rubber product. In this case, crosslinking may be performed either after molding or simultaneously with molding. The molding temperature is usually 10 to 200°C, preferably 25 to 120°C. The crosslinking temperature is usually 100 to 200°C, preferably 130 to 190°C, and the crosslinking time is usually 1 minute to 24 hours, preferably 2 minutes to 12 hours, and particularly preferably 3 minutes to 6 hours.

[0078] Furthermore, depending on the shape and size of the crosslinked rubber material, even if the surface is crosslinked, the interior may not be sufficiently crosslinked. In such cases, further heating may be performed to carry out secondary crosslinking.

[0079] As for the heating method, a general method used for crosslinking rubber compositions, such as press heating, steam heating, oven heating, or hot air heating, can be appropriately selected.

[0080] The crosslinked rubber 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, wet grip performance, and low-temperature performance.

[0081] The crosslinked rubber material of the present invention, taking advantage of its excellent rolling resistance, wet grip performance, and low-temperature performance, is preferably used as a material for various parts of a tire, such as the tread (cap tread, base tread), carcass, sidewall, and bead portion. In particular, it can be suitably used for various parts of tires, such as the tread, carcass, sidewall, and bead portion, in all-season tires, high-performance tires, and studless tires. For example, it can be particularly suitably used for the tread of a tire, and is especially preferable for use in the cap tread.

[0082] Next, the pneumatic tire of the present invention will be described. The pneumatic tire of the present invention is characterized by using the above-mentioned rubber composition in the tread.

[0083] The above-mentioned tread is made using the above-mentioned rubber composition, that is, it is formed using the above-mentioned rubber composition, and usually includes the crosslinked rubber product of the present invention obtained by crosslinking the above-mentioned rubber composition of the present invention.

[0084] The above-mentioned pneumatic tire may have a tread formed using the above-mentioned rubber composition, and other parts may also be formed using the above-mentioned rubber composition.

[0085] The tread formed using the above rubber composition may be a part of the tread or the entire tread, but it is preferable to include at least a cap tread.

[0086] Furthermore, the method for manufacturing a pneumatic tire according to the present invention can be any method capable of producing a pneumatic tire having a tread formed using the above composition, and known methods for manufacturing pneumatic tires can be used. [Examples]

[0087] The present invention will be described in more detail below with reference to examples and comparative examples, but the present invention is not limited to these examples. Unless otherwise specified, "parts" and "%" are based on mass. The test methods used in this embodiment and comparative example are as follows:

[0088] [Number-average molecular weight (Mn), weight-average molecular weight (Mw), Z-average molecular weight (Mz), peak-top molecular weight (Mp), molecular weight distribution (Mw / Mn, Mz / Mw), ratio of weight-average molecular weight (Mw) to peak-top molecular weight (Mp) (Mp / Mw)] For hydrocarbon resins, gel permeation chromatography analysis was performed to determine the number-average molecular weight (Mn), weight-average molecular weight (Mw), Z-average molecular weight (Mz), and peak-top molecular weight (Mp) in terms of standard polystyrene equivalents. Based on these results, the molecular weight distribution (Mw / Mn, Mz / Mw) and the ratio of weight-average molecular weight (Mw) to peak-top molecular weight (Mp) (Mp / Mw) were determined. For gel permeation chromatography analysis, a Tosoh Corporation "HLC-8320GPC" was used as the measuring instrument, and three Tosoh Corporation "TSKgel SuperMultiporeHZ" columns were linked together. Tetrahydrofuran was used as the solvent, and measurements were taken at 40°C and a flow rate of 1.0 mL / min.

[0089] [Softening point of hydrocarbon resins] The hydrocarbon resin was measured in accordance with JIS K6863.

[0090] [Mooney viscosity of rubber composition (ML1+4)] The Mooney viscosity (ML1+4) of the rubber composition was measured under the following conditions in accordance with JIS K 6300-1:2001. A lower Mooney viscosity value indicates better processability. • Test temperature: 100℃ • Rotor type: L-shaped • Test equipment used: Shimadzu Mooney Viscometer SMV-300J, manufactured by Shimadzu Corporation.

[0091] [Tensile strength (MPa) and elongation (%) of crosslinked rubber materials] The tensile strength (MPa) and elongation (%) of the rubber crosslinked material specimens were measured under the following conditions, in accordance with JIS K 6251:2010. Higher values ​​indicate superior tensile strength and elongation. • Specimen preparation method: Sheets are prepared by press crosslinking, followed by punching. • Test specimen shape: Dumbbell-shaped, type 3 • Specimen sampling direction: Parallel to the grain • Number of test specimens: 3 ·Measurement temperature: 23℃ • Test speed: 500 mm / min • Test equipment used: ALPHA TECHNOLOGIES TENSOMETER 10k • Test machine capacity: Load cell type 1kN

[0092] [Storage modulus E' at -25°C] For the rubber crosslinked material specimens used as samples, the storage modulus E' at -25°C was measured in accordance with JIS K 7244-4 under the following measurement conditions: dynamic strain of 0.5% and 10 Hz. For this characteristic, Examples 1 and Comparative Examples 1 and 2 are shown as an index with Comparative Example 1 (reference sample) set to 100, while Examples 2-4 and Comparative Examples 3-5 are shown as an index with Comparative Example 3 (reference sample) set to 100. A lower storage modulus E' at -25°C indicates superior low-temperature performance. Measurement item: Dynamic storage modulus E' • Sample preparation method: Punching from a sheet. • Test specimen shape: 50mm (length) x 2mm (width) x 2mm (thickness) • Number of test specimens: 1 • Clamping distance: 20mm

[0093] [Loss tangent tanδ] For the rubber crosslinked material specimens used as samples, the loss tangent tanδ at 0°C under the following measurement conditions: dynamic strain of 0.5% and 10Hz, and loss tangent tanδ at 60°C under the conditions of dynamic strain of 2.0% and 10Hz, in accordance with JIS K 7244-4. For these characteristics, Examples 1 and Comparative Examples 1 and 2 are shown as an index with Comparative Example 1 (reference sample) set to 100, while Examples 2-4 and Comparative Examples 3-5 are shown as an index with Comparative Example 3 (reference sample) set to 100. A higher loss tangent tanδ at 0°C indicates superior wet grip performance, and a lower loss tangent tanδ at 60°C indicates superior rolling resistance (lower loss tangent tanδ at 60°C indicates lower rolling resistance). Measurement item: Dynamic storage modulus E' : Dynamic loss modulus E” :loss tangent tanδ • Sample preparation method: Punching from a sheet. • Test specimen shape: 50mm (length) x 2mm (width) x 2mm (thickness) • Number of test specimens: 1 • Clamping distance: 20mm

[0094] [Example 1] (Manufacturing of hydrocarbon resins) 52.7 parts of cyclopentane as a hydrocarbon solvent were charged into the polymerization reactor, and after raising the temperature to 70°C, 1.0 part of aluminum chloride as a polymerization catalyst was added. While maintaining the temperature (70°C), the mixture was mixed for 2 minutes to disperse the aluminum chloride in the cyclopentane, with some aggregation remaining. After the 2 minutes of mixing, a mixture consisting of 48.2 parts of 1,3-pentadiene, 0.3 parts of isoprene, 17.0 parts of cyclopentene, 33.0 parts of isobutylene, 1.0 part of diisobutylene, 0.3 parts of dicyclopentadiene, 0.2 parts of C4-C6 unsaturated hydrocarbon, 15.8 parts of C4-C6 saturated hydrocarbon, and 0.1 parts of toluene was continuously added to the polymerization reactor for 60 minutes while maintaining the temperature (70°C) to carry out polymerization. After that, an aqueous sodium hydroxide solution was added to the polymerization reactor to stop the polymerization reaction. The types and amounts of components in the polymerization reactor during the polymerization reaction are summarized in Table 1. Then, the precipitate formed by the cessation of polymerization was removed by filtration to obtain a polymer solution containing hydrocarbon resin and unreacted monomers. Next, the polymer solution was charged into a distillation vessel and heated under a nitrogen atmosphere to remove the polymerization solvent and unreacted monomers, thereby obtaining the hydrocarbon resin. Since the amount of unreacted monomers was very small, it can be determined that the monomer composition constituting the obtained hydrocarbon resin is almost the same as the monomer composition used in polymerization (the same applies to Examples 2-4 and Comparative Examples 1-5 described later). The obtained hydrocarbon resin was then subjected to the measurement of the number average molecular weight (Mn), weight average molecular weight (Mw), Z average molecular weight (Mz), peak top molecular weight (Mp), molecular weight distribution (Mw / Mn, Mz / Mw), ratio of weight average molecular weight (Mw) to peak top molecular weight (Mp) (Mp / Mw), and softening point according to the method described above. The results are shown in Table 1.

[0095] (Manufacturing of rubber compositions) In a Banbury mixer, 100 parts of solution-polymerized styrene-butadiene rubber (SBR) (product name "Nipol NS612", manufactured by ZS Elastomers, styrene monomer unit content 15% by weight, vinyl bond content of butadiene unit portion 30%, Mooney viscosity (ML1+4, 100℃) 62, glass transition temperature (Tg) -65℃, no spreading oil) were kneaded for 30 seconds, and then silica (manufactured by Tosoh Silica Co., Ltd., product name "Nipsil") was mixed. 46.6 parts of AQ, 5 parts of carbon black (manufactured by Cabot Japan, product name "N339"), 6 parts of silane coupling agent: bis(3-(triethoxysilyl)propyl) tetrasulfide (manufactured by Tegussa, product name "Si69"), and 20 parts of the hydrocarbon resin obtained above were added and kneaded for 90 seconds. Then, 23.4 parts of silica (manufactured by Rhodia, product name "Zeosil1165MP"), 3 parts of zinc oxide, 2 parts of stearic acid, and 2 parts of antioxidant: N-phenyl-N'-(1,3-dimethylbutyl)-p-phenylenediamine (manufactured by Ouchi Shinko Chemical Industry, product name "Nocrac 6C") were added and kneaded for another 90 seconds, and then 10 parts of process oil (manufactured by Nippon Oil Corporation, product name "Aromax T-DAE") were added. Afterward, starting at 90°C, the mixture was kneaded at 145-155°C for at least 60 seconds (primary kneading), and then the kneaded mixture was discharged from the mixer.

[0096] The resulting mixture was cooled to room temperature, then mixed again in a Banbury mixer for 2 minutes starting at 90°C (secondary mixing), and the mixture was discharged from the mixer. The temperature of the mixture at the end of mixing was 145°C.

[0097] Next, using two rolls at 50°C, 1.7 parts of sulfur, 1.8 parts of the crosslinking accelerator N-cyclohexyl-2-benzothiazolyl sulfenamide (CBS, trade name "Noxellar CZ-G", manufactured by Ouchi Shinko Chemical Industry Co., Ltd.), and 1.7 parts of diphenylguanidine (DPG, trade name "Noxellar D", manufactured by Ouchi Shinko Chemical Industry Co., Ltd.) were added to the resulting mixture and kneaded (crosslinking agent kneading). After this, a sheet-like rubber composition was taken out. The Mooney viscosity (ML1+4) of the obtained rubber composition was then measured. The results are shown in Table 2. The mixing conditions for the primary mixing, secondary mixing, and crosslinking agent mixing were as follows.

[0098] (Mixing conditions for primary and secondary mixing) • Testing equipment: Toyo Seiki Seisakusho Co., Ltd. Lab Plast Mill Banbury type mixer B-600 ·Filling rate: 70~75vol% • Rotor speed: 50 rpm • Test start temperature setting: 90°C

[0099] (Kneading conditions for crosslinking agent mixing) • Testing machine: Electrically heated high-temperature roll machine manufactured by Ikeda Machinery Industry Co., Ltd. • Roll size: 6φ x 16 • Front roll rotation speed: 24 rpm • Front-to-rear roll ratio: 1:1.22 • Roll temperature: 50±5℃ • Number of turns: 2 times each side • Rolling width: Roll spacing approximately 0.8mm • Number of times to roll it up: 5 times

[0100] (Manufacturing of crosslinked rubber products) The rubber composition obtained above was then press-crosslinked at a press pressure of approximately 8 MPa and a press temperature of 160°C for 40 minutes. After further aging overnight in a constant temperature room at 23°C, test specimens of crosslinked rubber measuring 150 mm × 150 mm × 2 mm thick were prepared. The tensile strength (MPa), elongation (%), storage modulus E' at -25°C, and loss tangent tanδ (0°C, 60°C) were measured for the obtained crosslinked rubber. The results are shown in Table 2.

[0101] [Comparative Examples 1 and 2] (Manufacturing of hydrocarbon resins) The hydrocarbon resins of Comparative Examples 1 and 2 were obtained in the same manner as in Example 1, except that the type and amount of components added to the polymerization reactor, the mixing temperature and time when mixing aluminum chloride as a polymerization catalyst, and the polymerization temperature were changed as shown in Table 1 below. The obtained hydrocarbon resins were then measured in the same manner as in Example 1. The results are shown in Table 1.

[0102] (Manufacturing of rubber compositions and crosslinked rubber products) Except for using the hydrocarbon resin obtained above, a rubber composition and a rubber crosslinked product were obtained in the same manner as in Example 1, and measurements were performed in the same manner. The results are shown in Table 2.

[0103] [Table 1]

[0104] [Table 2]

[0105] [Examples 2-4] (Manufacturing of hydrocarbon resins) The hydrocarbon resins of Examples 2 to 4 were obtained in the same manner as in Example 1, except that the type and amount of components added to the polymerization reactor, the mixing temperature and time when mixing aluminum chloride as a polymerization catalyst, and the polymerization temperature were changed as shown in Table 3 below. The C9 fraction and styrene, which are not described in Example 1, were mixed with 1,3-pentadiene, etc., and subjected to polymerization. The C9 fraction mainly contains styrene, α-methylstyrene, β-methylstyrene, vinyltoluene, and indene as aromatic monomers, and the amount used in terms of aromatic monomers is shown in Table 3. The obtained hydrocarbon resins were then measured in the same manner as in Example 1. The results are shown in Table 3.

[0106] (Manufacturing of rubber compositions and crosslinked rubber products) Except for using the hydrocarbon resin obtained above, a rubber composition and a rubber crosslinked product were obtained in the same manner as in Example 1, and measurements were performed in the same manner. The results are shown in Table 4.

[0107] [Comparative Examples 3-5] (Manufacturing of hydrocarbon resins) The hydrocarbon resins of Comparative Examples 3 to 5 were obtained in the same manner as in Example 1, except that the type and amount of components added to the polymerization reactor, the mixing temperature and time when mixing aluminum chloride as a polymerization catalyst, and the polymerization temperature were changed as shown in Table 3 below. The C9 fraction and styrene, which are not described in Example 1, were mixed with 1,3-pentadiene, etc., and subjected to polymerization. The C9 fraction mainly contains styrene, α-methylstyrene, β-methylstyrene, vinyltoluene, and indene as aromatic monomers, and the amount used in terms of aromatic monomers is shown in Table 3. The obtained hydrocarbon resins were then measured in the same manner as in Example 1. The results are shown in Table 3.

[0108] (Manufacturing of rubber compositions and crosslinked rubber products) Except for using the hydrocarbon resin obtained above, a rubber composition and a rubber crosslinked product were obtained in the same manner as in Example 1, and measurements were performed in the same manner. The results are shown in Table 4.

[0109] [Table 3]

[0110] [Table 4]

[0111] Based on the results of Example 1 and Comparative Examples 1 and 2 shown in Tables 1 and 2, and the results of Examples 2-4 and Comparative Examples 3-5 shown in Tables 3 and 4, the rubber composition has a hydrocarbon resin whose number average molecular weight (Mn), weight average molecular weight (Mw), Z average molecular weight (Mz), ratio of weight average molecular weight to number average molecular weight (Mw / Mn), ratio of Z average molecular weight to weight average molecular weight (Mz / Mw), and softening point are within the ranges specified by the present invention, and the ratio of peak top molecular weight (Mp) to weight average molecular weight (Mw) is... According to a rubber composition containing a hydrocarbon resin with a (Mp / Mw) in the range of 0.4 to 0.8, the crosslinked rubber obtained using this composition has a low storage modulus E' at -25°C, exhibiting excellent low-temperature performance, a high loss tangent tanδ at 0°C, excellent wet grip performance, and a low loss tangent tanδ at 60°C, resulting in low rolling resistance. Thus, it exhibits an excellent balance of low-temperature performance, wet grip performance, and rolling resistance (Examples 1-4). On the other hand, when a hydrocarbon resin with a ratio of peak-top molecular weight (Mp) to weight-average molecular weight (Mw) (Mp / Mw) exceeding 0.8 was used, the resulting crosslinked rubber had a high storage modulus E' at -25°C, poor low-temperature performance, and a low loss tangent tanδ at 0°C, resulting in poor wet grip performance (Comparative Examples 1-3, 5). Furthermore, when a hydrocarbon resin with an excessively high ratio of the Z-average molecular weight to the weight-average molecular weight (Mz / Mw) was used, the resulting rubber crosslinked material had a low loss tangent tanδ at -0°C, resulting in poor wet grip performance, and a high loss tangent tanδ at 60°C, resulting in high rolling resistance (Comparative Example 4).

Claims

1. A rubber composition containing diene rubber and hydrocarbon resin, The hydrocarbon resin content is 1 to 200 parts by mass per 100 parts by mass of the diene rubber. The hydrocarbon resin is Aliphatic monomer units, or units comprising aliphatic monomer units and aromatic monomer units, The number-average molecular weight (Mn) is in the range of 400 to 3000. The weight-average molecular weight (Mw) is in the range of 700 to 6000. The average molecular weight (Mz) is in the range of 1500 to 20000. The ratio of weight-average molecular weight to number-average molecular weight (Mw / Mn) is in the range of 1.0 to 4.

0. The ratio of the Z-average molecular weight to the weight-average molecular weight (Mz / Mw) is in the range of 1.0 to 3.

5. The ratio of peak-top molecular weight (Mp) to weight-average molecular weight (Mw) (Mp / Mw) is in the range of 0.4 to 0.

8. The softening point temperature is in the range of 80 to 150°C. The content of 1,3-pentadiene monomer units is 20 to 70% by mass. The content of alicyclic monoolefin monomer units having 4 to 6 carbon atoms is 5 to 30% by mass. The content of acyclic monoolefin monomer units having 4 to 8 carbon atoms is 8 to 50% by mass. Rubber composition.

2. The content of isoprene monomer units is 0 to 15% by mass, The content of alicyclic diolefin monomer units is 0 to 10% by mass. The content of aromatic monoolefin monomer units is 0 to 40% by mass. The rubber composition according to claim 1.

3. The rubber composition according to claim 1 or 2, wherein the hydrocarbon resin is a hydride.

4. The rubber composition according to claim 1 or 2, further containing a filler.

5. The rubber composition according to claim 1 or 2, further containing a crosslinking agent.

6. The rubber composition according to claim 1 or 2, wherein the diene rubber contains styrene-butadiene copolymer rubber or butadiene rubber.

7. A crosslinked rubber product obtained by crosslinking the rubber composition according to claim 1 or 2.

8. A pneumatic tire using the rubber crosslinking material described in claim 7 as the tread.

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