Resinous modifier for solution polymerized styrene-butadiene rubber and rubber composition for tires

Abstract

The present invention provides a resinous modifier for solution-polymerized styrene-butadiene rubber and a rubber composition for tires that, when used in the tread material of a tire, can improve wet grip performance without degrading rolling resistance performance. [Solution] A resinous modifier for solution polymerized styrene-butadiene rubber, mainly comprising a hydrogenated acyclic terpene resin obtained by cationically polymerizing and then hydrogenating an acyclic terpene monomer and an aromatic vinyl monomer, and a tire rubber composition containing a diene rubber component containing solution polymerized styrene-butadiene rubber and this modifier.

Description

[Technical Field]

[0001] The present invention relates to a resinous modifier for solution-polymerized styrene-butadiene rubber and a rubber composition for tires using the same, and more particularly to a resinous modifier for solution-polymerized styrene-butadiene rubber and a rubber composition for tires that, when used in the tread material of a tire, can improve wet grip performance without degrading rolling resistance performance. [Background technology]

[0002] Styrene-butadiene rubber is used in a wide range of fields, including automobile tires, industrial rubber products, and shoe soles. Styrene-butadiene rubber is broadly classified into emulsion-polymerized styrene-butadiene rubber and solution-polymerized styrene-butadiene rubber depending on the polymerization method. In particular, solution-polymerized styrene-butadiene rubber is easier to control in terms of molecular structure compared to emulsion-polymerized styrene-butadiene rubber, and offers greater flexibility in performance adjustment. Furthermore, it is possible to introduce functional groups that interact with fillers such as silica into the molecular chain, contributing to improved rolling resistance performance by highly dispersing the fillers in the rubber composition. For this reason, solution-polymerized styrene-butadiene rubber is widely used as a rubber component in fuel-efficient tires.

[0003] On the other hand, in addition to improved rolling resistance performance, tires are also required to have braking performance on wet surfaces, i.e., wet grip performance, from a safety perspective. Generally, wet grip performance has a trade-off relationship with rolling resistance performance, and fuel-efficient tires that improve rolling resistance performance tend to have reduced grip performance on wet surfaces. To solve this problem, methods of compounding resin components into rubber compositions have been considered (for example, Patent Documents 1 to 4). [Prior art documents] [Patent Documents]

[0004] [Patent Document 1] Japanese Patent Publication No. 2019-194289 [Patent Document 2] Special Publication No. 2012-512290 [Patent Document 3] Japanese Patent Publication No. 2023-88023 [Patent Document 4] Japanese Patent Publication No. 2019-1860 [Overview of the Initiative] [Problems that the invention aims to solve]

[0005] However, conventionally known resins often make it difficult to achieve a sufficiently high level of both rolling resistance and wet grip performance, and improvements to the resin components are needed to achieve further performance enhancements. Therefore, the present invention aims to provide a resinous modifier for solution-polymerized styrene-butadiene rubber and a rubber composition for tires using the same, which can achieve a high degree of compatibility between wet grip performance and rolling resistance performance. [Means for solving the problem]

[0006] The inventors of the present invention have discovered that a tire rubber composition containing a hydrogenated acyclic terpene resin, obtained by cationic polymerization of acyclic terpene monomers and aromatic vinyl monomers, with a diene rubber component containing solution-polymerized styrene-butadiene rubber achieves both wet grip performance and rolling resistance performance, thereby completing the present invention. In other words, the present invention consists of the following claims 1 to 9. <Claim 1> A resinous modifier for solution polymerized styrene-butadiene rubber, primarily composed of a hydrogenated acyclic terpene resin obtained by cationic polymerization and subsequent hydrogenation of acyclic terpene monomers and aromatic vinyl monomers. <Claim 2> The resinous modifier for solution polymerized styrene-butadiene rubber according to claim 1, wherein the acyclic terpene monomer is one or more selected from dimethyloctatriene, allocimene, ocimene, and myrcene. <Claim 3> The resinous modifier for solution polymerized styrene-butadiene rubber according to claim 1, wherein the aromatic vinyl monomer is one or more selected from styrene and α-methylstyrene. <Claim 4> The resinous modifier for solution polymerized styrene-butadiene rubber according to claim 1, wherein the copolymerization ratio of acyclic terpene monomers is 10% by mass or more of the total monomer components. <Claim 5> Proton nuclear magnetic resonance of hydrogenated acyclic terpene resins ( 1 The resinous modifier for solution polymerized styrene-butadiene rubber according to claim 1, wherein the integral value in the range of 6.0 to 7.8 ppm based on aromatic hydrogen in 1H-NMR is 30% or less of the total integral value. <Claim 6> The resinous modifier for solution polymerized styrene-butadiene rubber according to claim 1, wherein the bromine value of the hydrogenated acyclic terpene resin, as measured according to JIS K2605, is 80 gBr2 / 100 g or less. <Claim 7> The resinous modifier for solution polymerized styrene-butadiene rubber according to claim 1, wherein the softening point of the hydrogenated acyclic terpene resin is 80 to 150°C. <Claim 8> A rubber composition for tires comprising a diene-based rubber component containing solution-polymerized styrene-butadiene rubber and the resinous modifier for solution-polymerized styrene-butadiene rubber according to claim 1. <Claim 9> A tire rubber composition according to claim 8, comprising 5 to 200 parts by mass of the resinous modifier for solution polymerized styrene-butadiene rubber according to claim 1, per 100 parts by mass of the diene-based rubber component. [Effects of the Invention]

[0007] The resinous modifier for solution-polymerized styrene-butadiene rubber of the present invention is a hydrogenated product of an acyclic terpene resin obtained by cationically polymerizing an acyclic terpene monomer and an aromatic vinyl monomer and then subjecting the product to a hydrogenation treatment. When it is blended with a diene rubber component containing solution-polymerized styrene-butadiene rubber, by using the obtained rubber composition for tires as a tread member of a tire, it is possible to improve the wet grip performance without deteriorating the rolling resistance performance.

Embodiments for Carrying Out the Invention

[0008] The resinous modifier for solution-polymerized styrene-butadiene rubber of the present invention is a hydrogenated product of an acyclic terpene resin obtained by cationically polymerizing a monomer component mainly composed of an acyclic terpene monomer and an aromatic vinyl monomer and then subjecting the product to a hydrogenation treatment, and is particularly useful as a modifier for a rubber composition for tires containing solution-polymerized styrene-butadiene rubber as a diene rubber component. In this paragraph, the main component means 50% by mass or more of all monomer components. Hereinafter, the present invention will be described according to its constituent elements.

[0009] <Hydrogenated Product of Acyclic Terpene Resin> The hydrogenated product of an acyclic terpene resin is a resin obtained by cationically polymerizing an acyclic terpene monomer and an aromatic vinyl monomer as main components to obtain an acyclic terpene resin and then further subjecting the product to a hydrogenation treatment (also referred to as hydrogenation).

[0010] The acyclic terpene monomer is a terpene monomer having no alicyclic structure in its molecule. Here, a terpene monomer is generally a hydrocarbon compound having isoprene (C5H8) as a structural unit, and according to the number of isoprene units, monoterpenes (C 10 H 16 ), sesquiterpenes (C 15 H 24 ), diterpenes (C 20 H 32) It is classified into etc. Among these, the acyclic terpene-based monomer is preferably one belonging to monoterpenes, and examples thereof include dimethyloctatriene, alloocimene, myrcene, ocimene, cosmen, etc. In addition, these may be any geometric isomers or positional isomers. Among these, dimethyloctatriene, alloocimene, ocimene, and myrcene are preferable, and they can be used alone or in combination of two or more.

[0011] The aromatic vinyl-based monomer is an aromatic compound having one or more polymerizable vinyl groups, vinylidene groups, and / or vinylene groups. Specific examples include styrene, α-methylstyrene, vinyltoluene, divinylbenzene, divinyltoluene, 2-phenyl-2-butene, vinylnaphthalene, etc. Among these, styrene and α-methylstyrene are preferable, and they can be used alone or in combination of two or more.

[0012] The acyclic terpene-based resin may contain a cyclic terpene-based monomer as a monomer component other than the acyclic terpene-based monomer and the aromatic vinyl-based monomer, as long as the properties of the acyclic terpene-based monomer are not impaired. The cyclic terpene-based monomer is a terpene-based monomer having one or more alicyclic structures in the molecule, and is preferably a monoterpene. Specific examples include α-pinene, β-pinene, d-limonene, l-limonene, dipentene, pironene, Δ-3-carene, etc. These can be used alone or in combination of two or more.

[0013] The copolymerization ratio of the acyclic terpene-based monomer is usually 10% by mass or more and 90% by mass or less, preferably 10% by mass or more and less than 75% by mass of the total monomer components. The copolymerization ratio of the aromatic vinyl-based monomer is usually 10% by mass or more and 90% by mass or less, preferably more than 25% by mass and 90% by mass or less of the total monomer components. The copolymerization ratio of the cyclic terpene-based monomer is usually 0 to 40% by mass or less, preferably 0 to 30% by mass or less of the total monomer components.

[0014] Hydrogenated acyclic terpene resins are obtained by hydrogenating the aforementioned acyclic terpene resins.

[0015] The following describes the manufacturing method for hydrogenated acyclic terpene resins, step by step. <Cational polymerization process> The cationic polymerization process is a step in which an acyclic terpene monomer and an aromatic vinyl monomer are copolymerized in the presence of a cationic polymerization catalyst to synthesize an acyclic terpene resin. The polymerization apparatus is not particularly limited and may be either batch or continuous.

[0016] While not particularly limited, catalysts for cationic polymerization can include halides such as aluminum, iron, tantalum, zirconium, tin, titanium, beryllium, boron, antimony, gallium, bismuth, and molybdenum. Of these, Friedel-Crafts catalysts such as aluminum chloride, boron trifluoride, and their complexes are preferred, and can be used individually or in combination of two or more.

[0017] The preferred amount of catalyst to use varies depending on the type of catalyst, but in the case of a batch reaction, it is 0.1 to 10% by mass, preferably 1 to 5% by mass, relative to the monomer raw material. If the amount of catalyst is less than 0.1% by mass, the reaction yield will be significantly low, while if it exceeds 10% by mass, the catalytic effect will not improve, which is undesirable.

[0018] The solvents used in the polymerization reaction can include saturated hydrocarbons such as paraffinic solvents and naphthenic solvents, aromatic hydrocarbons, and ethers. However, from the viewpoint of reaction rate and product solubility, aromatic hydrocarbons are preferred, and they can be used individually or in combination of two or more. The amount of solvent used in the polymerization process is typically 10 to 300% by mass, preferably 30 to 150% by mass, relative to the monomer raw materials. If the amount of solvent is less than 10% by mass, the viscosity of the reaction solution becomes too high, which may make it difficult to continue the polymerization reaction. On the other hand, if it exceeds 300% by mass, the reaction efficiency decreases significantly, which is undesirable.

[0019] The order in which these raw materials are added to the reaction vessel is not particularly limited; the monomers and, if necessary, the solvent may be added first, followed by the catalyst, or the monomers may be added after the catalyst. Furthermore, the method of adding two or more monomers to the reaction vessel is not particularly limited; they may be mixed beforehand, or each monomer may be added separately.

[0020] The reaction temperature is typically -20 to 100°C, preferably 0 to 70°C, and more preferably 20 to 50°C. Below -20°C, the reaction slows down significantly, while above 100°C, the reaction becomes unstable and undesirable.

[0021] After the reaction, the process may proceed directly to the hydrogenation step, but typically the cationic polymerization catalyst is removed. Alternatively, the acyclic terpene resin may be isolated by desolvation under reduced pressure heating. In this case, it is preferable to adjust the degree of reduced pressure appropriately so that the heating temperature does not exceed 280°C.

[0022] The number-average molecular weight (Mn) of the acyclic terpene resin obtained in this manner is typically 300 to 5,000, preferably 500 to 3,000, in polystyrene terms, as measured by GPC (gel permeation chromatography). The weight-average molecular weight (Mw) is typically 300 to 5,000, preferably 500 to 3,000. The Z-average molecular weight (Mz) is typically 300 to 10,000, preferably 500 to 5,000. The degree of dispersion (Mw / Mn) is typically 1.0 to 2.0, preferably 1.0 to 1.5.

[0023] <Hydrogenation process> Next, the hydrogenation of the acyclic terpene resin obtained in the above process will be described. The hydrogenation method is not particularly limited and can be carried out using precious metals such as palladium, ruthenium, rhodium, and platinum, or precious metal catalysts in which these metals are supported on a carrier such as activated carbon, activated alumina, or diatomaceous earth, or nickel-based catalysts such as stabilized nickel catalysts or sponge nickel catalysts. In this case, it is possible to use a batch method in which the reaction is carried out while suspending and stirring the powdered catalyst, or a continuous method using a reaction column packed with molded catalysts, and there are no particular restrictions on the reaction format.

[0024] The amount of catalyst used in the hydrogenation process is 0.1 to 30% by mass, preferably 1 to 20% by mass, relative to the acyclic terpene resin, when the reaction is carried out in a batch manner. If the amount of catalyst is less than 0.1% by mass, the reaction rate will be slow, while if it exceeds 30% by mass, the catalytic effect will not improve, which is undesirable.

[0025] Solvents used in the hydrogenation process include alcohols, ethers, esters, and saturated hydrocarbons, but alcohols and saturated hydrocarbons, which do not participate in the hydrogenation reaction, are particularly preferred. The amount of reaction solvent used is typically 30 to 500% by mass, preferably 50 to 300% by mass, relative to the raw materials.

[0026] The reaction temperature during hydrogenation is not particularly limited, but is usually 0 to 300°C, preferably 50 to 250°C. If the reaction temperature is below 0°C, the hydrogenation rate will be significantly slower, while if it exceeds 300°C, there is a risk of excessive decomposition of the hydrogenated product.

[0027] After the hydrogenation reaction is complete, the acyclic terpene resin is hydrogenated by desolvation under reduced pressure heating. At this time, it is preferable to adjust the degree of reduced pressure appropriately so that the heating temperature does not exceed 280°C.

[0028] According to the hydrogenation method described above, the double bonds derived from terpene monomer units and / or aromatic rings derived from aromatic vinyl monomers in the acyclic terpene resin are hydrogenated. The amount of double bonds can generally be evaluated by the bromine value measured in accordance with JIS K2605:1996 Petroleum Products - Bromine Value Test Method. The bromine value of hydrogenated acyclic terpene resins is not particularly limited, but is preferably 80 gBr2 / 100g or less, more preferably 70 gBr2 / 100g or less, even more preferably 60 gBr2 / 100g or less, and particularly preferably 40 gBr2 / 100g or less. A bromine value exceeding 80 gBr2 / 100g is undesirable because it can worsen compatibility with rubber components, potentially degrading wet grip performance and rolling resistance performance.

[0029] The amount of aromatic rings is determined by proton nuclear magnetic resonance ( 1 The chemical shift can be evaluated by the ratio of the integrated value within the range of chemical shifts based on aromatic hydrogens to the total integrated value in the 1H-NMR method. The chemical shifts based on aromatic hydrogens are in the range of 6.0 to 7.8 ppm based on tetramethylsilane (TMS). The ratio of the integrated value within the range of chemical shifts based on aromatic hydrogens is not particularly limited, but is preferably 30% or less of the total integrated value, more preferably 20% or less, and even more preferably 10% or less.

[0030] The number-average molecular weight (Mn) of the hydrogenated acyclic terpene resin obtained in this way, on a polystyrene basis, is typically 300 to 5,000, preferably 500 to 3,000. The weight-average molecular weight (Mw) is typically 300 to 5,000, preferably 500 to 3,000. The Z-average molecular weight (Mz) is typically 300 to 7,000, preferably 500 to 5,000. The degree of dispersion (Mw / Mn) is typically 1.0 to 2.0, preferably 1.0 to 1.5.

[0031] The softening point of hydrogenated acyclic terpene resins is not particularly limited, but is preferably 70 to 160°C, more preferably 80 to 150°C, and even more preferably 90 to 140°C. A softening point below 70°C is undesirable because it reduces wet grip performance. On the other hand, a softening point above 160°C is undesirable because it may become difficult to dissolve in rubber or thermoplastic elastomers. This softening point is measured using the JIS K2207 ring-and-ball method.

[0032] The resinous modifier for solution polymerized styrene-butadiene rubber of the present invention mainly comprises a hydrogenated acyclic terpene resin, and other components such as known resin components such as C5 resins, C9 resins, and dicyclopentadiene resins, as well as antioxidants, can be appropriately selected within a range that does not impair the purpose of the present invention and blended in a range of normal blending amounts. In this paragraph, "main component" means 50% by mass or more.

[0033] Next, the rubber composition for tires of the present invention will be described. The tire rubber composition of the present invention contains a diene-based rubber component containing solution-polymerized styrene-butadiene rubber, and a resinous modifier for solution-polymerized styrene-butadiene rubber mainly composed of a hydrogenated acyclic terpene resin.

[0034] <Diene-based rubber components> The diene rubber component used in this invention contains one or more solution-polymerized styrene-butadiene rubbers (hereinafter also referred to as "S-SBR"). The solution-polymerized styrene-butadiene rubber may be unmodified styrene-butadiene rubber or modified styrene-butadiene rubber, or both may be used in combination. Examples of modified styrene-butadiene rubber include styrene-butadiene rubber into which functional groups containing oxygen and / or nitrogen atoms have been introduced. Here, examples of functional groups of modified styrene-butadiene rubber include at least one selected from the group consisting of amino groups, alkoxy groups, hydroxyl groups, epoxy groups, carboxyl groups, and carboxylic acid derivative groups.

[0035] The glass transition temperature of solution-polymerized styrene-butadiene rubber is typically -30°C or lower, preferably -40 to -70°C, and more preferably -55 to -65°C. Here, the glass transition temperature is a value measured by the method for determining the glass transition temperature by differential scanning calorimetry (DSC) according to JIS K6240 Raw Material Rubber. The styrene unit content in solution-polymerized styrene-butadiene rubber is typically 1-40%, preferably 3-30%, and more preferably 5-20%. A styrene unit content of less than 1% is undesirable because it significantly reduces grip performance, while a content exceeding 40% is also undesirable because it may reduce abrasion resistance.

[0036] The diene rubber component may contain diene rubber components other than solution-polymerized styrene-butadiene rubber. Examples of diene rubber components other than solution-polymerized styrene-butadiene rubber include natural rubber (NR), polybutadiene rubber (BR), 1,2-polybutadiene rubber, emulsion-polymerized styrene-butadiene rubber (E-SBR), acrylonitrile-butadiene rubber (NBR), polyisoprene rubber (IR), isobutylene-isoprene rubber (IIR), and all components that fall under the category of diene rubber are included. Of these, polybutadiene rubber is particularly preferred to be used in combination from the viewpoint of improving flexibility in the low-temperature range. The proportion of solution-polymerized styrene-butadiene rubber in the diene-based rubber component is preferably 30% by mass or more, more preferably 50-90% by mass, and even more preferably 60-80% by mass, from the viewpoint of low rolling resistance and improved silica dispersibility.

[0037] The content of hydrogenated acyclic terpene resin per 100 parts by mass of diene rubber component is 5 to 200 parts by mass, preferably 10 to 100 parts by mass, and more preferably 20 to 70 parts by mass. Below 5 parts by mass, the effect of improving wet grip is not easily observed, while above 200 parts by mass, wear resistance and processability decrease, which is undesirable.

[0038] The rubber composition of the present invention mainly consists of hydrogenated diene rubber and acyclic terpene resin, but may also contain reinforcing fillers, crosslinking agents, and the like. Examples of fillers to be incorporated into the present invention include carbon black, silica, alumina, aluminum hydroxide, calcium carbonate, and titanium dioxide, with carbon black and / or silica being preferred among these. These reinforcing fillers may be used individually or in combination of two or more. The amount of filler added is typically 20 to 200 parts by mass per 100 parts by mass of diene-based rubber component.

[0039] For example, sulfur can be used as a crosslinking agent to be incorporated into the rubber composition of the present invention. Specifically, powdered sulfur, precipitated sulfur, insoluble sulfur, colloidal sulfur, surface-treated sulfur, etc., can be used.

[0040] Examples of vulcanization accelerators used in combination with crosslinking agents such as sulfur include tetramethylthiuram disulfide (TMTD), tetramethylthiuram monosulfide (TMTM), N-oxydiethylene-2-benzothiazolyl sulfenamide (OBS), N-cyclohexyl-2-benzothiazolyl sulfenamide (CBS), dibenzothiadyl sulfide (MBTS), 2-mercaptobenzothiazol (MBT), zinc di-n-butyldithiocarbide (ZnBDC), zinc dimethyldithiocarbide (ZnMDC), and diphenylguanidine (DPG). The amount of sulfur-based crosslinking agent added is typically 0.1 to 10 parts by mass per 100 parts by mass of the diene-based rubber component.

[0041] In addition, organic peroxides can also be used as crosslinking agents. Examples of organic peroxides include dicumyl peroxide, 2,5-dimethyl-2,5-di(t-butylperoxy)hexane, 2,5-dimethyl-2,5-di(benzoylperoxy)hexane, 2,5-dimethyl-2,5-di(t-butylperoxy)hexine-3, di-t-butyl peroxide, di-t-butylperoxy-3,3,5-trimethylcyclohexane, and t-dibutylhydroperoxide. Of these, dicumyl peroxide, di-t-butyl peroxide, and di-t-butylperoxy-3,3,5-trimethylcyclohexane are preferred.

[0042] When using organic peroxides as crosslinking agents, the use of vulcanization aids is preferable. Examples of vulcanization aids include sulfur and quinone dioxime-based agents such as p-quinone dioxime; acrylic-based agents such as ethylene glycol dimethacrylate and trimethylolpropane trimethacrylate; allyl-based agents such as diallyl phthalate and triallyl isocyanurate; other maleimide-based agents; and divinylbenzene. The amount of organic peroxide-based crosslinking agent added is typically around 0.1 to 10 parts by mass per 100 parts by mass of diene-based rubber component.

[0043] In addition to the fillers and crosslinking agents mentioned above, the rubber composition of the present invention may contain compounding agents commonly used in the rubber industry, such as known softeners, antioxidants, and coupling agents, selected as appropriate within a range that does not impair the purpose of the present invention, and in amounts within the range of normal compounding. Commercially available products can be suitably used as these compounding agents. The rubber composition of the present invention can be manufactured by mixing, heating, extruding, etc., after incorporating various compounding agents as needed.

[0044] The rubber compositions of the present invention include both uncrosslinked and crosslinked rubbers. Uncrosslinked rubber compositions can be produced by kneading diene rubber components, hydrogenated acyclic terpene resins, and optional components using a Banbury mixer, rolls, kneader, etc. A crosslinked rubber composition (crosslinked rubber composition) can be produced by crosslinking the above-mentioned uncrosslinked rubber composition. The crosslinking temperature is 120°C to 200°C, preferably 140°C to 180°C, and the crosslinking is carried out by heating in hot air. At this time, it is not necessary to apply pressure, and crosslinking can be carried out under atmospheric pressure.

[0045] The rubber composition containing the resinous modifier for solution polymerized styrene-butadiene rubber of the present invention can be used in applications such as tires, belts, rubber tracks, vibration-damping rubber, and shoes, but is particularly useful for tires. When used in the tread material of a tire, it is possible to improve wet grip performance without degrading rolling resistance performance. [Examples]

[0046] The present invention will be described below with reference to examples and comparative examples. However, the present invention is not limited to the examples. The softening point, molecular weight (number average molecular weight (Mn), weight average molecular weight (Mw), Z average molecular weight (Mz)), bromine value, and aromatic hydrogen content of the acyclic terpene resin and its hydrogenated products were measured by the following methods. (softening point) The measurement was performed using the ring-sphere method described in JIS K2207. (molecular weight) The samples were measured using GPC (gel permeation chromatography) under the following equipment and conditions, and their molecular weight in terms of standard polystyrene was determined. • Detector: Differential refractometer WATERS2414 (manufactured by WATERS) • Pump: WATERS515 High-Performance Liquid Chromatography (manufactured by WATERS) • Columns: TSK-gel G2000HXL x 2 and G3000HXL x 1 (manufactured by TOSOH) • Eluent: Tetrahydrofuran ·Flow rate: 1.0mL / min ·Sample concentration: 5 mg / mL ·Injection volume: 250 μL (Bromine number) Measured in accordance with JIS K2605:1996 Petroleum products - Test method for bromine number. (Aromatic hydrogen content) Using a nuclear magnetic resonance apparatus (Bruker AVANCE NEO cryo-500 type), proton nuclear magnetic resonance ( 1 1H-NMR) spectrum was measured. As a deuterated solvent, deuterated tetrachloroethane (TCE-d2) was used, and the ratio of the integral value based on aromatic hydrogen in the range of 6.0 to 7.8 ppm to the total integral value was calculated.

[0047] Synthesis Example 1 Into a flask equipped with a stirrer, reflux condenser, thermometer and nitrogen gas inlet, 600 g of toluene and 12 g of aluminum chloride were charged. Into this, 450 g of alloocimene (purity 95%) manufactured by Yasuhara Chemical and 150 g of styrene were dropped using a metering pump over 1 hour while stirring at a reaction temperature of 30 to 35°C. After completion of the reaction, it was washed with water and distilled under reduced pressure at 255°C and 2 mmHg to obtain 425 g of an acyclic terpene resin. 175 g of the obtained acyclic terpene resin, 175 g of p-menthane, and 5 g of a powdered 5% palladium-supported alumina catalyst were charged into an autoclave. Then, this was sealed, and after replacing the atmosphere with nitrogen gas, hydrogen gas was introduced while applying a pressure of 10 kg / cm 2 . Then, while stirring, it was heated, and when it reached 230°C, the hydrogen pressure was set to 50 kg / cm 2 , and the pressure was maintained at 50 kg / cm 2 by supplementing the absorbed hydrogen and reacted for 1 hour. After the reaction, the catalyst was filtered, and p-menthane was removed by distillation under reduced pressure to obtain 167 g of a hydrogenated product of the acyclic terpene resin (Resin A). The total yield and properties of the hydrogenated product of the obtained acyclic terpene resin from the raw material monomers are shown in Table 1.

[0048] Synthesis Examples 2 to 16 Hydrogenated acyclic terpene resins (resins B to P) were synthesized in the same manner as in Synthesis Example 1, except that the copolymerization ratio of the raw material monomers and the hydrogenation time were as shown in Table 1. The total yield and properties of the obtained hydrogenated acyclic terpene resins from the raw material monomers are shown in Table 1.

[0049] Reference examples 1~4 The copolymerization ratios of the raw material monomers were as shown in Table 1, and acyclic terpene resins (resins Q to T) were synthesized in the same manner as in Synthesis Example 1, except that the hydrogenation step was omitted and only the cationic polymerization step was performed. Reference example 5 Hydrogenated acyclic terpene resins (resin U) were synthesized in the same manner as in Synthesis Example 1, except that the copolymerization ratio of the raw material monomers was as shown in Table 1. The results are shown in Tables 1 and 2.

[0050] [Table 1]

[0051] [Table 2]

[0052] Examples 1-16 and Comparative Examples 1-6 (Evaluation of rubber compositions for tires) According to the following composition, various chemicals, excluding sulfur powder and vulcanization accelerator, were mixed in a Toyo Seiki Laboplast Mill 4C150 Banbury mixer. Subsequently, sulfur powder and vulcanization accelerator were added, and a final mixing was performed to obtain an uncrosslinked rubber composition. The obtained uncrosslinked rubber composition was press-vulcanized for 30 minutes under conditions of 150°C to produce a vulcanized rubber composition, which was then subjected to a viscoelasticity test. The evaluation results are shown in Table 2. (Composition) S-SBR (product name: SL553, manufactured by ENEOS Material) 70 parts by mass BR (Product name: BR T700, manufactured by ENEOS Material) 30 parts by mass Resin 40 parts by mass Carbon black (product name: Seast 3, manufactured by Tokai Carbon) 5 parts by mass Silica (product name: Nipsil AQ, manufactured by Tosoh Silica) 100 parts by mass Sulfur (manufactured by Fujifilm Wako Pure Chemical Industries) 1.5 parts by mass Vulcanization accelerator 1 (product name: Accel CZ, manufactured by Kawaguchi Chemical Industry Co., Ltd.) 1.8 parts by mass Vulcanization accelerator 2 (product name: Accel D, manufactured by Kawaguchi Chemical Industry Co., Ltd.) 1.5 parts by mass Silane coupling agent (product name: Sulfide-based Si75, manufactured by Evonik) 9.6 parts by mass Zinc oxide (manufactured by Fujifilm Wako Pure Chemical Industries) 3 parts by mass Stearic acid (manufactured by Fujifilm Wako Pure Chemical Industries) 2 parts by mass Anti-aging agent (product name: Antige 6C, manufactured by Kawaguchi Chemical Industry Co., Ltd.) 1 part by mass TDAE oil (product name: VivaTec500TH, manufactured by Starry Oil) 10 parts by mass

[0053] The resins used were hydrogenated acyclic terpene resins synthesized in Synthesis Examples 1-16 and Reference Example 5 (resins A-P and U), acyclic terpene resins synthesized in Reference Examples 1-4 (resins Q-T), and commercially available α-methylstyrene resin (trade name: SYLVARES SA85, manufactured by Kraton).

[0054] (Viscoelasticity test) The prepared test specimens were cut to a width of 4.0 mm, a length of 30 mm, and a thickness of 0.5 mm. Using a Hitachi High-Tech Science Corporation DMA7100 viscoelasticity analyzer, the loss tangent tanδ was measured at 0°C and 60°C in a temperature range of -75°C to 180°C, based on JIS K 6394, with a frequency of 10 Hz, average strain of 3.0%, strain amplitude of ±0.5, and a chuck distance of 15 mm. A larger tanδ at 0°C indicates better wet grip characteristics, while a smaller tanδ at 60°C indicates lower rolling resistance and better fuel efficiency. The results are shown in Table 3.

[0055] [Table 3]

[0056] As is clear from Table 3, the tire rubber composition of the present invention exhibits better wet grip performance and rolling resistance performance compared to Comparative Examples 1-4 and 6, and can improve wet grip performance without worsening fuel efficiency. The hydrogenated allo-cimene homopolymer resin of Comparative Example 5 has excellent rolling resistance performance, but its wet grip performance is significantly inferior, resulting in a lack of performance balance. In contrast, using the resinous modifier for solution polymerized styrene-butadiene rubber of the present invention makes it possible to achieve a good balance between both performances. [Industrial applicability]

[0057] The present invention provides a resinous modifier for solution-polymerized styrene-butadiene rubber, primarily composed of a hydrogenated acyclic terpene resin obtained by cationic polymerization and subsequent hydrogenation of acyclic terpene monomers and aromatic vinyl monomers. When compounded with solution-polymerized styrene-butadiene rubber, this modifier can provide tires with excellent rolling resistance and wet grip performance. Furthermore, rubber compositions containing the present invention's resinous modifier for solution-polymerized styrene-butadiene rubber can also be used as a compounding agent for rubber products other than treads, such as tires, belts, rubber tracks, vibration-damping rubber, and shoes.

Claims

1. A resinous modifier for solution polymerized styrene-butadiene rubber, primarily composed of a hydrogenated acyclic terpene resin obtained by cationic polymerization and subsequent hydrogenation of acyclic terpene monomers and aromatic vinyl monomers.

2. The resinous modifier for solution polymerized styrene-butadiene rubber according to claim 1, wherein the acyclic terpene monomer is one or more selected from dimethyloctatriene, allocimene, ocimene, and myrcene.

3. The resinous modifier for solution polymerized styrene-butadiene rubber according to claim 1, wherein the aromatic vinyl monomer is one or more selected from styrene and α-methylstyrene.

4. The resinous modifier for solution polymerized styrene-butadiene rubber according to claim 1, wherein the copolymerization ratio of acyclic terpene monomers is 10% by mass or more of the total monomer components.

5. Proton nuclear magnetic resonance of hydrogenated acyclic terpene resins ( １ The resinous modifier for solution polymerized styrene-butadiene rubber according to claim 1, wherein the integral value in the range of 6.0 to 7.8 ppm based on aromatic hydrogen in 1H-NMR is 30% or less of the total integral value.

6. The bromine value of hydrogenated acyclic terpene resins, as measured according to JIS K2605, is 80 gBr. ２ A resinous modifier for solution polymerized styrene-butadiene rubber according to claim 1, wherein the amount is 100 g or less.

7. The resinous modifier for solution polymerized styrene-butadiene rubber according to claim 1, wherein the softening point of the hydrogenated acyclic terpene resin is 80 to 150°C.

8. A rubber composition for tires containing a diene-based rubber component containing solution-polymerized styrene-butadiene rubber and the resinous modifier for solution-polymerized styrene-butadiene rubber according to claim 1.

9. A tire rubber composition according to claim 8, comprising 5 to 200 parts by mass of the resinous modifier for solution polymerized styrene-butadiene rubber according to claim 1, per 100 parts by mass of the diene-based rubber component.

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