Rubber composition for tire

Abstract

The present invention provides a rubber composition for tires, which is excellent in wear resistance and wet performance, and also excellent in moldability, characterized in that, in 100 parts by mass of diene rubbers composed of styrene butadiene rubber (A), styrene butadiene rubber (B), and butadiene rubber, 50 to 150 parts by mass of silica and 10 to 80 parts by mass of a thermoplastic resin are compounded, in 100 mass% of the diene rubbers, the butadiene rubber is 30 mass% or more, the styrene butadiene rubber (A) is 15 to 35 mass%, the styrene butadiene rubber (B) is 1 to 2 times the mass of the styrene butadiene rubber (A), the glass transition temperature of the styrene butadiene rubber (A) is -75 to -50°C, and the weight average molecular weight of the styrene butadiene rubber (B) is 2 times or more the weight average molecular weight of the styrene butadiene rubber (A).

Description

Technical Field

[0001] This invention relates to a tire rubber composition that exhibits excellent wear resistance, wet performance, and molding processability. Background Technology

[0002] Tires targeting the North American market require a high balance between abrasion resistance and wet performance. While using dienes with high glass transition temperatures in the tread rubber composition to improve wet performance can reduce abrasion resistance, making it historically difficult to achieve a tire that combines both. Furthermore, using high molecular weight dienes to improve abrasion resistance increases the viscosity of the rubber composition, worsening its processability. Conversely, using low molecular weight dienes to reduce viscosity presents the challenge of reduced abrasion resistance.

[0003] In Patent Document 1, a pneumatic tire is proposed to achieve good wet skid resistance, low rolling resistance, and wear characteristics. The pneumatic tire has a tread comprising a vulcanizable rubber composition comprising: (A) about 20 to about 100 phr of solution-polymerized styrene-butadiene rubber having a glass transition temperature (Tg) of -85°C to -50°C; (B) 0 to about 40 phr of natural rubber or synthetic polyisoprene; (C) 0 to about 30 phr of cis-1,4-polybutadiene with a Tg of -110°C to -90°C; (D) 0 to 50 phr of process oil; (E) 20 to 80 phr of a hydrocarbon resin having a Tg of at least 30°C; and (F) 90 to 150 phr of silica.

[0004] However, the invention described in Patent Document 1 may not be able to fully achieve the effect of balancing high wear resistance and wet performance with excellent moldability.

[0005] Existing technical documents

[0006] Patent documents

[0007] Patent Document 1: Japanese Patent Application Publication No. 2021-21070 Summary of the Invention

[0008] The problem that the invention aims to solve

[0009] The purpose of this invention is to provide a tire rubber composition that combines high levels of wear resistance and wet performance with low viscosity and good processability.

[0010] Problem-solving methods

[0011] The tire rubber composition of the present invention, which achieves the above-mentioned objective, is characterized in that, in 100 parts by mass of a diene-based rubber composed of styrene-butadiene rubber (A), styrene-butadiene rubber (B), and butadiene rubber, 50 to 150 parts by mass of silica and 10 to 80 parts by mass of thermoplastic resin are incorporated; in the 100% by mass of the diene-based rubber, the butadiene rubber is 30% by mass or more, the styrene-butadiene rubber (A) is 15 to 35% by mass, the styrene-butadiene rubber (B) is 1 to 2 times the weight of the styrene-butadiene rubber (A), the glass transition temperature of the styrene-butadiene rubber (A) is -75°C to -50°C, and the weight-average molecular weight of the styrene-butadiene rubber (B) is more than twice the weight-average molecular weight of the styrene-butadiene rubber (A).

[0012] Invention Effects

[0013] Because the tire rubber composition of the present invention adopts the above-described structure, it can achieve a high level of both wear resistance and wet performance, and has low viscosity and good molding processability.

[0014] The weight-average molecular weight of the styrene-butadiene rubber (A) is preferably between 300,000 and 600,000. Furthermore, the glass transition temperature of the styrene-butadiene rubber (B) is preferably below -30°C.

[0015] The glass transition temperature of the thermoplastic resin can be between 40°C and 120°C. Furthermore, it is preferable that the thermoplastic resin is selected from at least one resin chosen from the following resins and resins formed by hydrogenation of at least a portion of the double bonds of these resins.

[0016] The resin is a terpene, a modified terpene, rosin, rosin ester, or a resin composed of at least one component selected from C5 and C9.

[0017] Rubber compositions for tires may also contain liquid polymers.

[0018] Tires with a tread composed of the above-mentioned tire rubber composition can achieve a high level of both wear resistance and wet performance, and can consistently produce high-quality tires with good processability. Attached Figure Description

[0019] Figure 1 This is a cross-sectional view along the radial direction of a tire, illustrating an embodiment of a tire molded using the tire rubber composition of the present invention. Detailed Implementation

[0020] The rubber composition for tires of the present invention can be applied to the tread or sidewall portion of a tire. Furthermore, the tire can be either a pneumatic tire or a non-pneumatic tire. Figure 1This is a cross-sectional view showing one embodiment of a pneumatic tire. The pneumatic tire consists of a tread portion 1, a sidewall portion 2, and a bead portion 3.

[0021] exist Figure 1 In this tire, two carcass layers are provided between the left and right bead portions 3. Reinforcing cords, arranged at predetermined intervals along the tire circumference and extending radially, are embedded in the rubber layers within the carcass layers. The two ends of the carcass layers are folded back from the inner to the outer side of the tire axial direction by wrapping around the bead core 5 embedded in the bead portion 3 and inserting into the bead filler 6. An inner liner layer 7 is disposed inside the carcass layer 4. On the outer periphery of the carcass layer 4 in the tread portion 1, two belt layers 8 are provided, in which reinforcing cords extending obliquely along the tire circumference are arranged at predetermined intervals along the tire axial direction and embedded in the rubber layers. The reinforcing cords of these two belt layers 8 cross at an oblique direction relative to the tire circumference between the layers, i.e., the cord directions cross in opposite directions. A belt cover layer 9 is disposed on the outer periphery of the belt layers 8. The belt cover layer 9 can be either a full-coverage type covering the entire belt layer or an edge type covering the tire width end of the belt layer, or a combination of both types. A tread portion 1 is disposed on the outer periphery of the belt cover layer 9, and the tread portion 1 is composed of a tread crown 10a and a tread base 10b. The tire rubber composition of the present invention is preferably used in the tread portion 1 or the sidewall portion 2, and more preferably in the tread crown 10a or the tread base 10b.

[0022] In the tire rubber composition of the present invention, the diene-based rubber is composed of styrene-butadiene rubber (A), styrene-butadiene rubber (B), and butadiene rubber. The glass transition temperature of styrene-butadiene rubber (A) is -75°C to -50°C, and its weight-average molecular weight is lower than that of styrene-butadiene rubber (B). By including styrene-butadiene rubber (A), the viscosity of the rubber composition can be reduced, resulting in good molding and processability.

[0023] The glass transition temperature (hereinafter sometimes referred to as "Tg") of styrene-butadiene rubber (A) is preferably -75°C to -50°C, more preferably -70°C to -55°C. In this specification, Tg can be measured as the temperature at the midpoint of the phase transition region, based on a thermogram obtained by differential scanning calorimetry (DSC) at a heating rate of 20°C / min. Furthermore, when the diene rubber is oil-extended, the Tg of the diene rubber in its oil-free state is taken.

[0024] The weight-average molecular weight of styrene-butadiene rubber (A) is preferably 300,000 to 600,000, more preferably 320,000 to 580,000. By keeping the weight-average molecular weight of styrene-butadiene rubber (A) within this range, the viscosity of the rubber composition can be further reduced, resulting in good molding processability. In this document, the weight-average molecular weight can be a polystyrene equivalent value determined by gel permeation chromatography (GPC).

[0025] The styrene content of the styrene-butadiene rubber (A) is preferably 3-35% by mass, more preferably 5-30% by mass. If the styrene content is less than 3% by mass, the wet performance may decrease; if the styrene content exceeds 35% by mass, the abrasion resistance may decrease, and neither is preferred. In this specification, the styrene content is defined as... 1 Values ​​measured by H-NMR.

[0026] The vinyl content of styrene-butadiene rubber (A) is preferably 5-60%, more preferably 10-55%. A vinyl content of less than 5% may reduce wet performance, and a vinyl content exceeding 60% may reduce abrasion resistance; neither is preferred. In this specification, the vinyl content is defined as... 1 Values ​​measured by H-NMR.

[0027] The styrene-butadiene rubber (A) can be either unmodified or modified. In the case of modified styrene-butadiene rubber, at least one end can be modified with a functional group. Examples of functional groups include epoxy, carboxyl, amino, hydroxyl, alkoxy, silyl, alkoxysilyl, amide, oxysilyl, silanol, isocyanate, isothiocyanate, carbonyl, and aldehyde groups, among which functional groups having a polyorganosiloxane or aminosilane structure are preferred. By having functional groups having a polyorganosiloxane or aminosilane structure, silica can be well dispersed, exhibiting excellent wear resistance and wetland performance.

[0028] The styrene-butadiene rubber (A) comprises 15-35% by mass, preferably 17-33% by mass, and more preferably 22-28% by mass, in 100% by mass of the diene rubber. If the styrene-butadiene rubber (A) is less than 15% by mass, the effect of reducing the viscosity of the rubber composition and improving its molding processability cannot be sufficiently obtained. Furthermore, if it exceeds 35% by mass, the effect of reducing the viscosity of the rubber composition and improving its molding processability cannot be sufficiently obtained due to the balance between the styrene-butadiene rubber (B) and the butadiene rubber.

[0029] The tire rubber composition contains styrene-butadiene rubber (B), whose weight-average molecular weight is more than twice that of styrene-butadiene rubber (A). The presence of styrene-butadiene rubber (B) improves the abrasion resistance of the rubber composition. Furthermore, since the Tg of styrene-butadiene rubber (B) is higher than that of styrene-butadiene rubber (A), wet performance is improved.

[0030] The weight-average molecular weight of styrene-butadiene rubber (B) is more than twice that of styrene-butadiene rubber (A), preferably more than 600,000, more preferably 700,000 to 1,600,000, and even more preferably 800,000 to 1,500,000. By keeping the weight-average molecular weight of styrene-butadiene rubber (B) within such a range, the wear resistance of the rubber composition can be further improved.

[0031] The Tg of styrene-butadiene rubber (B) is preferably below -30°C, more preferably -70°C to -31°C, and even more preferably -60°C to -32°C. It is preferable that the Tg of styrene-butadiene rubber (B) is higher than that of styrene-butadiene rubber (A). Maintaining the Tg of styrene-butadiene rubber (B) within this range improves the wetland properties of the rubber composition, and is therefore preferred.

[0032] The styrene content of the styrene-butadiene rubber (B) is preferably 5 to 50% by mass, more preferably 10 to 45% by mass. If the styrene content is less than 5% by mass, the wet performance may be reduced, and if the styrene content is more than 50% by mass, the abrasion resistance may be reduced; neither is preferred.

[0033] The vinyl content of styrene-butadiene rubber (B) is preferably 5-70%, more preferably 10-65%. When the vinyl content is less than 5%, the wet performance may be reduced, and when the vinyl content exceeds 70%, the abrasion resistance may be reduced, neither of which is preferred.

[0034] The content of styrene-butadiene rubber (B) is 1 to 2 times the content of styrene-butadiene rubber (A), preferably 15 to 70% by mass, more preferably 25 to 60% by mass, even more preferably 30 to 55% by mass, or more preferably 34 to 66% by mass, even more preferably 44 to 56% by mass, in 100% of diene rubber. If the content of styrene-butadiene rubber (B) is less than that of styrene-butadiene rubber (A), the effect of improving the wear resistance of the rubber composition cannot be sufficiently obtained. Furthermore, if the content of styrene-butadiene rubber (B) exceeds 2 times the content of styrene-butadiene rubber (A), the effect of reducing the viscosity of the rubber composition and improving its molding processability cannot be sufficiently obtained.

[0035] The tire rubber composition contains 30% or more, preferably 33-50% by mass, and more preferably 35-45% by mass, of butadiene rubber in 100% by mass of a diene-based rubber. If the butadiene rubber content is less than 30% by mass, the abrasion resistance decreases. Furthermore, by keeping the butadiene rubber content below 50% by mass, silica is easily dispersed, ensuring good wet performance. There are no particular limitations on the type of butadiene rubber; rubbers commonly used in tire rubber compositions can be used.

[0036] The rubber composition for tires preferably does not contain natural rubber. The absence of natural rubber tends to improve wet-weather performance, therefore it is preferred. Furthermore, "not containing natural rubber" means that natural rubber is not actively incorporated into the rubber composition for tires. For example, when scraps from other rubber compositions containing natural rubber are incorporated into the preparation of the rubber composition for tires in order to reuse them, i.e., for in-process recycling, a small amount of natural rubber may be present. In the above case, the natural rubber content in 100% by mass of diene rubber is preferably 0-5% by mass, more preferably 0-4% by mass.

[0037] The tire rubber composition incorporates 50 to 150 parts by weight of silica, preferably 60 to 140 parts by weight, and more preferably 70 to 130 parts by weight, of diene-based rubber. Incorporating silica improves wetland performance. When the silica content is less than 50 parts by weight, the improvement in wetland performance is not sufficiently achieved. Furthermore, when the silica content exceeds 150 parts by weight, molding processability decreases.

[0038] As the silica, the silica commonly used in tire rubber compositions can be used, such as wet silica, dry silica, or carbon-silica (dual phase filler) with silica supported on the surface of carbon black, or silica obtained by surface treatment with compounds that are reactive or compatible with both silica and rubber, such as silane coupling agents or polysiloxanes. Among these, wet silica with hydrated silicic acid as the main component is preferred.

[0039] Furthermore, by combining silane coupling agents with silica, the dispersibility of silica can be improved, further enhancing wetland performance, thus making it a preferred choice. There are no particular limitations on the type of silane coupling agent, but sulfur-containing silane coupling agents are preferred. Examples include bis(3-triethoxysilylpropyl)tetrasulfide, bis(3-triethoxysilylpropyl)trisulfide, bis(3-triethoxysilylpropyl)disulfide, bis(2-triethoxysilylethyl)tetrasulfide, bis(3-trimethoxysilylpropyl)tetrasulfide, bis(2-trimethoxysilylethyl)tetrasulfide, 3-mercaptopropyltrimethoxysilane, 3-mercaptopropyldimethoxymethylsilane, 3-mercaptopropyldimethylmethoxysilane, 2-mercaptoethyltriethoxysilane, 3-mercaptopropyltriethoxysilane, and VP manufactured by Ebonick. The mercaptosilane compounds illustrated in Japanese Patent Application Publication No. 2006-249069, such as Si363, and 3-trimethoxysilylpropylbenzothiazolyl tetrasulfide, 3-triethoxysilylpropylbenzothiazolyl tetrasulfide, 3-triethoxysilylpropyl methacrylate monosulfide, 3-trimethoxysilylpropyl methacrylate monosulfide, 3-trimethoxysilylpropyl-N,N-dimethylthiocarbamoyl tetrasulfide, 3-triethoxysilylpropyl-N,N-dimethylthiocarbamoyl tetrasulfide, 2-triethoxysilylethyl-N,N-dimethylthiocarbamoyl tetrasulfide, bis(3-diethoxymethylsilylpropyl)tetrasulfide Dimethoxymethylsilylpropyl-N,N-dimethylthiocarbamoyl tetrasulfide, dimethoxymethylsilylpropylbenzothiazolyl tetrasulfide, 3-octanoylthiopropyltriethoxysilane, 3-propanoylthiopropyltrimethoxysilane, vinyltrimethoxysilane, vinyltriethoxysilane, vinyltri(2-methoxyethoxy)silane, 3-(epoxypropoxy)propyltrimethoxysilane, 3-(epoxypropoxy)propylmethyldimethoxysilane, β-(3,4-epoxycyclohexyl)ethyltrimethoxysilane, 3-aminopropyltrimethoxysilane, N-(β-aminoethyl)-γ-aminopropyltrimethoxysilane, N-(β-aminoethyl)-γ-aminopropylmethyldimethoxysilane, etc.

[0040] The silane coupling agent is preferably formulated at 3 to 20% by mass relative to silica, more preferably at 5 to 15% by mass. When the silane coupling agent is less than 3% by mass of silica, the effect of improving the dispersibility of silica cannot be sufficiently obtained. In addition, if the silane coupling agent exceeds 20% by mass, there is a tendency for the diene-based rubber component to gel easily, thus failing to achieve the desired effect.

[0041] By incorporating fillers other than silica into tire rubber compositions, the strength of the rubber composition can be improved, ensuring tire durability. Examples of such fillers include inorganic fillers such as carbon black, calcium carbonate, magnesium carbonate, talc, clay, alumina, aluminum hydroxide, titanium dioxide, calcium sulfate, mica, and barium sulfate, as well as organic fillers such as cellulose, lecithin, lignin, and dendritic polymers.

[0042] By incorporating carbon black, the rubber composition can achieve excellent strength, thereby improving wear resistance. Other types of carbon black that can be incorporated include furnace black, acetylene black, pyrolytic carbon black, channel black, and graphite. Furnace black is preferred, and specific examples include SAF, ISAF, ISAF-HS, ISAF-LS, IISAF-HS, HAF, HAF-HS, HAF-LS, and FEF. These carbon blacks can be used individually or in combination of two or more. Additionally, surface-treated carbon blacks, prepared by chemically modifying these carbon blacks with various acid compounds, can also be used.

[0043] The tire rubber composition contains 10 to 80 parts by weight, preferably 12 to 78 parts by weight, and more preferably 15 to 75 parts by weight, of thermoplastic resin relative to 100 parts by weight of diene rubber. By incorporating thermoplastic resin, abrasion resistance can be improved, and even when the weight-average molecular weight of styrene-butadiene rubber (A) is low, the reduction in abrasion resistance can be suppressed. Furthermore, the plasticizing effect of the thermoplastic resin improves processability, increases the Tg of the rubber composition, and enhances wet performance. If the thermoplastic resin is less than 10 parts by weight, the effect of improving abrasion resistance cannot be sufficiently obtained. When the thermoplastic resin exceeds 80 parts by weight, the effect of improving abrasion resistance actually decreases.

[0044] Thermoplastic resins are resins commonly compounded in tire rubber compositions, with molecular weights ranging from several hundred to several thousand, and impart adhesive properties to the tire rubber composition. Preferably, the thermoplastic resin is selected from at least one of the following: terpenes, modified terpenes, rosin, rosin esters, and resins composed of at least one of C5 and C9 components, as well as resins in which at least a portion of the double bonds are hydrogenated. Examples include, for instance, natural resins such as terpene-based resins, modified terpene-based resins, rosin-based resins, and rosin ester-based resins, and synthetic resins such as petroleum-based resins, coal-based resins, phenolic resins, and xylene-based resins composed of C5 and / or C9 components.

[0045] Examples of terpene resins include α-pinene resin, β-pinene resin, limonene resin, hydrogenated limonene resin, dipentene resin, terpene phenol resin, terpene styrene resin, aromatic modified terpene resin, and hydrogenated terpene resin. Examples of rosin resins include modified rosins such as gum rosin, tall oil rosin, wood rosin, hydrogenated rosin, disproportionated rosin, polymerized rosin, maleic acid-modified rosin, and fumarate-modified rosin, as well as ester derivatives of these rosins such as glycerol esters, pentaerythritol esters, methyl esters, and triethylene glycol esters, and rosin-modified phenolic resins.

[0046] As petroleum-based resins, examples include aromatic hydrocarbon resins or saturated or unsaturated aliphatic hydrocarbon resins. Examples include C5 series petroleum resins (aliphatic petroleum resins polymerized from fractions such as isoprene, 1,3-pentadiene, cyclopentadiene, methylbutene, and pentene), C9 series petroleum resins (aromatic petroleum resins polymerized from fractions such as α-methylstyrene, o-vinyltoluene, m-vinyltoluene, and p-vinyltoluene), and C5C9 copolymer petroleum resins.

[0047] The glass transition temperature of the thermoplastic resin is preferably 40°C to 120°C, more preferably 45°C to 115°C, and even more preferably 50°C to 110°C. Setting the glass transition temperature of the thermoplastic resin to 40°C or higher improves dry grip performance, and is therefore preferred. Furthermore, setting it to 120°C or lower improves abrasion resistance, and is therefore preferred. The glass transition temperature of the thermoplastic resin can be determined by the method described above.

[0048] Liquid polymers are preferably incorporated into tire rubber compositions. Incorporating liquid polymers improves abrasion resistance. The liquid polymer is preferably incorporated in 0 to 30 parts by weight of diene rubber, more preferably in 3 to 25 parts by weight. When the liquid polymer exceeds 30 parts by weight, wet performance decreases. Examples of liquid polymers include liquid polybutene, liquid polyisobutylene, liquid polyisoprene, liquid polybutadiene, liquid polyalphaolefin, liquid ethylene-propylene copolymer, and liquid ethylene-butene copolymer.

[0049] In addition to the components mentioned above, tire rubber compositions may be formulated with various compounding agents commonly used in tire rubber compositions, such as vulcanizing or crosslinking agents, vulcanization accelerators, anti-aging agents, processing aids, plasticizers, and thermosetting resins, according to conventional methods. These compounding agents can be mixed using conventional methods to prepare a rubber composition for vulcanization or crosslinking. The amounts of these compounding agents can be conventional amounts, provided they do not deviate from the purpose of this invention. Tire rubber compositions can be prepared by mixing the above components using known rubber mixing machinery, such as Banbury mixers, kneaders, rollers, etc.

[0050] Rubber compositions for tires are suitable for forming the tread or sidewall portion of tires, and are particularly suitable for forming the tread portion of high-performance tires. The resulting tires exhibit a high level of both wear resistance and wet performance, and can consistently produce high-quality tires with good processability.

[0051] The present invention will be further illustrated below by way of examples, but the scope of the present invention is not limited to these examples.

[0052] Example

[0053] In preparing 33 tire rubber compositions (standard examples, examples 1-20, and comparative examples 1-12) with the common additive formulations shown in Table 6 and prepared from the formulations shown in Tables 1-5, the components excluding sulfur and vulcanization accelerators were weighed, and the mixtures were mixed in a 1.7-liter closed Banbury mixer for 5 minutes. The masterbatch was then released from the mixer and cooled to room temperature. The masterbatch was then fed into the same Banbury mixer, and sulfur and vulcanization accelerators were added and mixed to obtain the tire rubber compositions. In the table, SBR(B)-1 and SBR(B)-2 are 37.5 parts by mass of oil-extended products; therefore, the amount after removing the oil-extended components is recorded in parentheses below. Furthermore, the additive formulations in Table 6 are recorded in parts by mass relative to 100 parts by mass of diene rubbers recorded in Tables 1-5.

[0054] The Mooney viscosity of the tire rubber composition obtained above was determined by the following method. Additionally, evaluation samples were prepared by vulcanizing the tire rubber composition in molds of a specified shape at 160°C for 20 minutes. Using the obtained evaluation samples, dynamic viscoelasticity (loss tangent tanδ at 0°C) and abrasion resistance were determined by the following method.

[0055] Mooney viscosity (ML) 1+4 )

[0056] The Mooney viscosity of the rubber composition for tires was determined using a Mooney viscometer with an L-shaped rotor (38.1 mm diameter, 5.5 mm thickness) based on JIS K6300, under the following conditions: preheating time of 1 minute, rotor rotation time of 4 minutes, 100°C, and 2 rpm. The results were expressed as an index with the standard example value set to an index of 100, as shown in the "Molding Processability (Viscosity)" column of Tables 1-5. A smaller index indicates lower viscosity and better molding processability.

[0057] Dynamic viscoelasticity (loss angle tangent at 0°C tanδ)

[0058] The dynamic viscoelasticity of evaluation samples of tire rubber compositions was measured using a viscoelastic spectrometer manufactured by Iwamoto Manufacturing Co., Ltd., under conditions of tensile strain rate of 10 ± 2%, frequency of 20 Hz, and temperature of 0 °C. The loss tangent tanδ at 0 °C was calculated. The results were expressed using the index with the standard example value set as the index of 100, as shown in the "Wetland Performance" column of Tables 1-5. The larger the index, the larger the tanδ at 0 °C, and the better the wetland performance.

[0059] abrasion resistance

[0060] Evaluation samples of the obtained tire rubber compositions were tested using a Lambert abrasion tester (manufactured by Iwamoto Manufacturing Co., Ltd.) according to JIS K6264, under conditions of a load of 15.0 kg (147.1 N) and a slip ratio of 25%. The reciprocals of the calculated results were recorded in the "Abrasion Resistance" column of Tables 1-5, with the reciprocal of the wear amount of the standard example set as the index of 100. The larger the index, the less wear and the better the abrasion resistance.

[0061]

[0062]

[0063]

[0064]

[0065]

[0066] The types of raw materials used in Tables 1-5 are shown below.

[0067] SBR(A)-1: End-modified styrene-butadiene rubber with a polyorganosiloxane structure, Nipol NS612 manufactured by Zion Corporation of Japan, with a glass transition temperature of -60°C, a weight-average molecular weight of 450,000, a styrene content of 15% by mass, a vinyl content of 30%, and is non-oil-extended.

[0068] SBR(A)-2: A terminally modified styrene-butadiene rubber with a polyorganosiloxane structure obtained by the following polymerization method, with a glass transition temperature of -70°C, a weight-average molecular weight of 450,000, a styrene content of 18% by mass, a vinyl content of 13%, and is non-oil-extended.

[0069] •SBR(A)-3: Styrene-butadiene rubber, Asahi Kasei Corporation's Tapden 1000, glass transition temperature -73°C, weight average molecular weight 290,000, styrene content 18% by mass, vinyl content 12%, non-oil-extended.

[0070] •SBR(B)-1: Modified styrene-butadiene rubber, Asahi Kasei Corporation's Tapden E581, with a glass transition temperature of -34°C, a weight-average molecular weight of 1.26 million, a styrene content of 36% by mass, a vinyl content of 42%, and 37.5 parts by mass of oil-extended product.

[0071] •SBR(B)-2: Modified styrene-butadiene rubber, Asahi Kasei Corporation's Tapden E680, with a glass transition temperature of -25°C, a weight-average molecular weight of 1.47 million, a styrene content of 36% by mass, a vinyl content of 57%, and 37.5 parts by mass of oil-extended product.

[0072] BR: Butadiene rubber, Nipol BR1220 manufactured by Japan Zeon Corporation, with a glass transition temperature of -105℃ and a weight-average molecular weight of 460,000.

[0073] • Carbon black: DASHBLACK N220 manufactured by OCI Company

[0074] • Silica: ZEOSIL 195MP manufactured by Solbey Co., Ltd.

[0075] • Thermoplastic Resin-1: Aromatic modified terpene resin, YS resin TO-125 manufactured by Yasuharake Mikael Co., Ltd., with a glass transition temperature of 79°C.

[0076] • Thermoplastic Resin-2: Aromatic modified terpene resin, YS resin TO-105 manufactured by Yasuharake Mikael Co., Ltd., with a glass transition temperature of 57°C.

[0077] • Resin-3: C9 resin, Neopolymer S100 manufactured by ENEOSE, with a glass transition temperature of 58°C.

[0078] • Resin-4: C5C9 resin, Neopolymer 170S manufactured by ENEOSE, glass transition temperature 105℃

[0079] ・Oil: Sesacrol No. 4 S produced by Sesacrol Fluid Co., Ltd.

[0080] • Coupling agent: Silane coupling agent, Si69 manufactured by Evonik Degussa.

[0081] SBR(A)-2 polymerization method

[0082] 70.0 g of cyclohexane and 0.77 mmol of tetramethylethylenediamine were added to an 800 ml ampoule purged with nitrogen, followed by 7.69 mmol of n-butyllithium. Then, 27.9 g of isoprene and 2.1 g of styrene were slowly added, and the mixture was reacted in the ampoule at 50 °C for 120 minutes to obtain a polymer block with active ends.

[0083] In a high-pressure reactor equipped with a stirrer, under a nitrogen atmosphere, 4000 g of cyclohexane, 1.50 mmol of tetramethylethylenediamine, 445 g of 1,3-butadiene, and 155 g of styrene were added. Then, the entire amount of the polymer block with active ends obtained above was added, and polymerization was initiated at 50°C. After 10 minutes of polymerization, 355 g of 1,3-butadiene and 40 g of styrene were added continuously over 60 minutes. The maximum temperature during the polymerization reaction was 75°C. After the continuous addition was completed, the polymerization reaction was continued for another 10 minutes to confirm that the polymerization conversion rate was in the range of 95%–100%. Then, 2.44 g of the polyorganosiloxane represented by formula (I) was added in a 40% by mass xylene solution, and the reaction was allowed to proceed for 30 minutes. Finally, methanol, equivalent to twice the molar amount of n-butyllithium used, was added as a polymerization terminator to obtain a solution containing conjugated diene rubber. In this solution, 0.15 parts of Iluganox 1520L (manufactured by BASF) as an anti-aging agent were added relative to 100 parts of conjugated diene rubber. The solvent was removed by steam stripping, and the solution was dried under vacuum at 60°C for 24 hours to obtain solid conjugated diene rubber (SBR(A)-2).

[0084]

[0085] In the above formula (I), m is 80, k is 120, and X 1 X 4 R 1 ~R 3 and R 5 ~R 8 Methyl, X 2 The group is represented by the following formula (II) (here, * indicates the binding position).

[0086]

[0087] surface

[0088]

[0089] The types of raw materials used in Table 6 are shown below.

[0090] • Anti-aging agent: VULANOX 4020 manufactured by LANXESS

[0091] Wax: OZOACE-0015A manufactured by NIPPON SEIRO

[0092] • Zinc oxide: Three types of zinc oxide produced by Zhengdao Chemical Industry Co., Ltd.

[0093] • Stearic acid: Bezel stearic acid produced by Nippon Oil Company

[0094] • Vulcanization accelerator-1: Nocuser CZ-G manufactured by Ouchi Shinsei Chemical Co., Ltd.

[0095] • Vulcanization accelerator-2: Socchinoel DG manufactured by Sumitomo Chemical Co., Ltd.

[0096] • Sulfur: Salfax 5 manufactured by Tsurumi Chemical Industry Co., Ltd.

[0097] As shown in Tables 1-3, the tire rubber compositions of Examples 1-20 have excellent wear resistance, wet performance, and molding processability (Mooney viscosity).

[0098] As shown in Table 4, the tire rubber composition of Comparative Example 1 has low wet performance and cannot improve molding processability (Mooney viscosity) because SBR(A) is less than 15 parts by mass and the mass ratio of SBR(B) / SBR(A) exceeds 2.

[0099] The SBR(A) of the tire rubber composition of Comparative Example 2 exceeded 35 parts by weight, and therefore could not improve molding processability (Mounney viscosity).

[0100] The tire rubber composition of Comparative Example 3 could not improve wet performance because it contained less than 50 parts by weight of silica.

[0101] The tire rubber composition of Comparative Example 4 could not improve molding processability (Mounney viscosity) because the silica content exceeded 150 parts by weight.

[0102] The tire rubber composition of Comparative Example 5 could not improve molding processability (Mounney viscosity) because the thermoplastic resin was less than 10 parts by weight.

[0103] The rubber composition for tires in Comparative Example 6 could not improve molding processability (Mounney viscosity) because the thermoplastic resin exceeded 80 parts by weight.

[0104] As shown in Table 5, the SBR(A) of the tire rubber composition of Comparative Example 7 is less than 15 parts by mass, and therefore cannot improve wet performance.

[0105] In the tire rubber composition of Comparative Example 8, the butadiene rubber was less than 30 parts by weight, and therefore could not improve molding processability (Mooney viscosity) and abrasion resistance.

[0106] The tire rubber composition of Comparative Example 9 does not contain SBR(B), and therefore cannot improve abrasion resistance and wet performance.

[0107] The tire rubber composition of Comparative Example 10 does not contain SBR(A), thus its molding processability (Mounney viscosity) deteriorates.

[0108] The mass ratio of SBR(B) / SBR(A) in the tire rubber composition of Comparative Example 11 is less than 1, and therefore cannot improve wear resistance.

[0109] The mass ratio of SBR(B) / SBR(A) in the tire rubber composition of Comparative Example 12 exceeds 2, and therefore cannot improve molding processability (Mounney viscosity).

[0110] This invention includes the following inventions.

[0111] Invention [1]: A rubber composition for tires, characterized in that, in 100 parts by weight of a diene rubber composed of styrene-butadiene rubber (A), styrene-butadiene rubber (B) and butadiene rubber, 50-150 parts by weight of silica and 10-80 parts by weight of thermoplastic resin are incorporated.

[0112] In the 100% by mass of the diene-based rubber, the butadiene rubber is 30% or more by mass, the styrene-butadiene rubber (A) is 15-35% by mass, the styrene-butadiene rubber (B) is 1-2 times the mass of the styrene-butadiene rubber (A), the glass transition temperature of the styrene-butadiene rubber (A) is -75℃ to -50℃, and the weight-average molecular weight of the styrene-butadiene rubber (B) is more than twice the weight-average molecular weight of the styrene-butadiene rubber (A).

[0113] Invention [2]: The tire rubber composition as described in Invention [1] is characterized in that the weight-average molecular weight of the styrene-butadiene rubber (A) is 300,000 to 600,000.

[0114] Invention [3]: The tire rubber composition as described in invention [1] or [2] is characterized in that the glass transition temperature of the styrene-butadiene rubber (B) is below -30°C.

[0115] Invention [4]: ​​A tire rubber composition according to any one of inventions [1] to [3], characterized in that the thermoplastic resin is at least one resin selected from resins and resins formed by hydrogenation of at least a portion of the double bonds of these resins.

[0116] The resin is a terpene, a modified terpene, rosin, rosin ester, or a resin composed of at least one component selected from C5 and C9.

[0117] The glass transition temperature of the thermoplastic resin is 40–120°C.

[0118] Invention [5]: A tire rubber composition as described in any one of inventions [1] to [4], characterized in that it further contains a liquid polymer.

[0119] Invention [6]: A tire having a tread portion made of a tire rubber composition as described in any one of inventions [1] to [5].

[0120] Explanation of symbols in attached drawings

[0121] First pregnancy face

[0122] 2nd tire side

[0123] 3rd tire bead

[0124] 4-layer body

[0125] 5-Tire Bead

[0126] 6-Tire Bead Filler

[0127] 7 Inner Liner

[0128] 8-band layer

[0129] 9-belt cover layer

[0130] 10a tread and crown

[0131] 10b tread base

Claims

1. A rubber composition for tires, characterized in that, In 100 parts by weight of a diene-based rubber composed of styrene-butadiene rubber A, styrene-butadiene rubber B, and butadiene rubber, 50-150 parts by weight of silica and 10-80 parts by weight of thermoplastic resin are added. In the 100% by mass of the diene-based rubber, the butadiene rubber is 30% or more by mass, the styrene-butadiene rubber A is 15-35% by mass, the styrene-butadiene rubber B is 1-2 times the mass of the styrene-butadiene rubber A, the glass transition temperature of the styrene-butadiene rubber A is -75℃ to -50℃, the glass transition temperature of the styrene-butadiene rubber B is higher than that of the styrene-butadiene rubber A, and the weight-average molecular weight of the styrene-butadiene rubber B is more than twice the weight-average molecular weight of the styrene-butadiene rubber A.

2. The rubber composition for tires as described in claim 1, characterized in that, The weight-average molecular weight of the styrene-butadiene rubber A is 300,000 to 600,000.

3. The tire rubber composition according to claim 1 or 2, characterized in that, The glass transition temperature of the styrene-butadiene rubber B is below -30°C.

4. The tire rubber composition according to claim 1 or 2, characterized in that, The thermoplastic resin is at least one selected from the following resins and resins formed by hydrogenating at least a portion of the double bonds of these resins. The resin is a terpene, a modified terpene, rosin, rosin ester, or a resin composed of at least one component selected from C5 and C9. The glass transition temperature of the thermoplastic resin is 40–120°C.

5. The tire rubber composition as described in claim 1 or 2, characterized in that, It also contains liquid polymers.

6. A tire having a tread portion made of the tire rubber composition of claim 1 or 2.

Images