Rubber composition for tires

Abstract

Provided is a rubber composition for tires, which has excellent wear resistance and wet performance, and also has excellent moldability. The present invention relates to a rubber composition comprising 50-150 parts by mass of silica and 10-80 parts by mass of a thermoplastic resin per 100 parts by mass of a diene rubber comprising a styrene butadiene rubber (A), a styrene butadiene rubber (B), and a butadiene rubber, characterized in that the butadiene rubber is 30% by mass or more, the styrene butadiene rubber (A) is 15-35% by mass, and the thermoplastic resin is 10-80 parts by mass per 100 parts by mass of the diene rubber. The amount of 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 DEG C to-50 DEG C, and the weight-average molecular weight of the styrene butadiene rubber (B) is at least two times the weight-average molecular weight of the styrene butadiene rubber (A).

Description

Technical Field

[0001] The present invention relates to a rubber composition for a tire having excellent wear resistance, wet performance and molding processability. Background Art

[0002] Tires for the North American market require both high levels of wear resistance and wet performance. If wet performance is improved by using a diene rubber with a high glass transition temperature in the rubber composition forming the tread, wear resistance is reduced, so it has been difficult to obtain a tire that has both. In addition, if a high molecular weight diene rubber is used to improve wear resistance, the viscosity of the rubber composition becomes high and molding processability deteriorates. On the contrary, if a low molecular weight diene rubber is used to reduce viscosity, there is a problem of reduced wear resistance.

[0003] In Patent Document 1, in order to achieve good wet skid resistance, low rolling resistance and wear characteristics, a pneumatic tire is proposed, which has a tread, wherein the tread comprises a vulcanizable rubber composition, wherein the rubber composition comprises: (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 having 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 does not necessarily achieve the effect of achieving both high levels of wear resistance and wet performance and excellent molding processability.

[0005] Prior art literature

[0006] Patent Literature

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

[0008] Problems to be solved by the invention

[0009] An object of the present invention is to provide a rubber composition for a tire which has both high levels of wear resistance and wet performance and has low viscosity and good molding processability.

[0010] Solution

[0011] The tire rubber composition of the present invention for achieving the above-mentioned object is characterized in that 50 to 150 parts by mass of silica and 10 to 80 parts by mass of a thermoplastic resin are blended into 100 parts by mass of a diene rubber composed of styrene butadiene rubber (A), styrene butadiene rubber (B) and butadiene rubber, wherein in 100 parts by mass of the diene rubber, the butadiene rubber accounts for 30% by mass or more, the styrene butadiene rubber (A) accounts for 15 to 35% by mass, the styrene butadiene rubber (B) is 1 to 2 times by mass 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 at least twice the weight average molecular weight of the styrene butadiene rubber (A).

[0012] Effects of the Invention

[0013] Since the rubber composition for a tire of the present invention has the above-mentioned structure, it can achieve both high levels of 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 300,000 to 600,000. The glass transition temperature of the styrene butadiene rubber (B) is preferably lower than -30°C.

[0015] The glass transition temperature of the thermoplastic resin may be 40° C. to 120° C., and the thermoplastic resin may be at least one resin selected from the following resins and resins in which at least a part of the double bonds of these resins are hydrogenated:

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

[0017] The rubber composition for a tire may further contain a liquid polymer.

[0018] A tire having a tread portion formed of the above-mentioned tire rubber composition can achieve both high levels of wear resistance and wet performance, and can stably produce a high-quality tire having excellent molding processability. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 It is a cross-sectional view in the tire meridian direction illustrating an embodiment of a tire molded using the rubber composition for a tire of the present invention. DETAILED DESCRIPTION

[0020] The rubber composition for a tire of the present invention can be applied to a tread portion or a sidewall portion of a tire. In addition, the tire may be either a pneumatic tire or a non-pneumatic tire. Figure 11 is a cross-sectional view showing an example of an embodiment of a pneumatic tire. The pneumatic tire includes a tread portion 1 , a sidewall portion 2 , and a bead portion 3 .

[0021] exist Figure 1 In the embodiment, two carcass layers are arranged between the left and right bead portions 3, and the reinforcing cords arranged at a predetermined interval along the circumferential direction of the tire and extending in the radial direction of the tire are buried in the rubber layer in the carcass layer, and the two ends of the carcass layer are folded back from the inner side of the tire axial direction to the outer side in a manner of sandwiching the bead filler 6 around the bead core 5 buried in the bead portion 3. An inner liner 7 is arranged on the inner side of the carcass layer 4. On the outer peripheral side of the carcass layer 4 of the tread portion 1, two belt layers 8 are arranged in which the reinforcing cords extending obliquely along the circumferential direction of the tire are arranged at a predetermined interval along the axial direction of the tire and buried in the rubber layer. The reinforcing cords of the two belt layers 8 cross each other in an oblique direction relative to the circumferential direction of the tire between the layers, that is, the cord directions cross each other in opposite directions. A belt covering layer 9 is arranged on the outer peripheral side of the belt layer 8. The belt covering layer 9 can be either a full covering type covering the entire belt layer or an edge type covering the ends of the belt layer in the tire width direction, or a combination of the two types. The tread portion 1 is disposed on the outer peripheral side of the belt cover layer 9. The tread portion 1 is composed of a tread cap 10a and a tread base 10b. The tire rubber composition of the present invention is preferably used for the tread portion 1 or the sidewall portion 2, and more preferably for the tread cap 10a or the tread base 10b.

[0022] In the tire rubber composition of the present invention, the diene 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 containing styrene butadiene rubber (A), the viscosity of the rubber composition can be reduced, and the molding processability can be improved.

[0023] The glass transition temperature (hereinafter sometimes referred to as "Tg") of the styrene-butadiene rubber (A) is preferably -75°C to -50°C, more preferably -70°C to -55°C. In the present specification, Tg can be measured as the temperature of the midpoint of the phase transition region based on a thermal diagram obtained by differential scanning calorimetry (DSC) under a temperature increase rate of 20°C / min. In addition, when the diene rubber is an oil-extended product, the Tg of the diene rubber in a state without the oil-extending component (oil) is taken.

[0024] The weight average molecular weight of the styrene butadiene rubber (A) is preferably 300,000 to 600,000, more preferably 320,000 to 580,000. By making the weight average molecular weight of the styrene butadiene rubber (A) within such a range, the viscosity of the rubber composition can be further reduced, so that the molding processability is good. In this article, the weight average molecular weight can be a polystyrene conversion value measured by gel permeation chromatography (GPC).

[0025] The styrene content of the styrene butadiene rubber (A) is preferably 3 to 35% by mass, more preferably 5 to 30% by mass. If the styrene content is less than 3% by mass, the wet performance may be reduced, and if the styrene content exceeds 35% by mass, the wear resistance may be reduced, both of which are not preferred. In this specification, the styrene content is expressed by 1 Value measured by H-NMR.

[0026] The vinyl content of the styrene butadiene rubber (A) is preferably 5 to 60%, more preferably 10 to 55%. When the vinyl content is less than 5%, the wet performance may be reduced, and when the vinyl content exceeds 60%, the wear resistance may be reduced, both of which are not preferred. In this specification, the vinyl content is expressed by 1 Value measured by H-NMR.

[0027] Styrene butadiene rubber (A) may be unmodified styrene butadiene rubber or modified styrene butadiene rubber. In the case of modified styrene butadiene rubber, at least one end may be modified with a functional group. As the functional group, for example, epoxy, carboxyl, amino, hydroxyl, alkoxy, silyl, alkoxysilyl, amide, oxygen silyl, silanol, isocyanate, isothiocyanate, carbonyl, aldehyde, etc. may be listed, wherein preferably a functional group having a polyorganosiloxane structure or an aminosilane structure. By having a functional group having a polyorganosiloxane structure or an aminosilane structure, the dispersibility of silicon dioxide can be made good, and the wear resistance and wet performance are excellent.

[0028] The content of the styrene-butadiene rubber (A) is 15 to 35% by mass, preferably 17 to 33% by mass, and more preferably 22 to 28% by mass in 100% by mass of the diene rubber. If the content of the styrene-butadiene rubber (A) is less than 15% by mass, the effect of reducing the viscosity of the rubber composition and improving the molding processability cannot be fully obtained. In addition, if the content exceeds 35% by mass, the effect of reducing the viscosity of the rubber composition and improving the molding processability cannot be fully 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) having a weight average molecular weight of at least twice that of the styrene butadiene rubber (A). By containing the styrene butadiene rubber (B), the wear resistance of the rubber composition can be improved. In addition, since the Tg of the styrene butadiene rubber (B) is higher than the Tg of the styrene butadiene rubber (A), the wet performance can be improved.

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

[0031] The Tg of the styrene butadiene rubber (B) is preferably lower than -30°C, more preferably -70°C to -31°C, and further preferably -60°C to -32°C. Among them, the Tg of the styrene butadiene rubber (B) is preferably higher than the Tg of the styrene butadiene rubber (A). By setting the Tg of the styrene butadiene rubber (B) within such a range, the wet performance of the rubber composition can be improved, which is 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, wet performance may be reduced, and if the styrene content exceeds 50% by mass, wear resistance may be reduced, both of which are not preferred.

[0033] The vinyl content of the styrene butadiene rubber (B) is preferably 5 to 70%, more preferably 10 to 65%. A vinyl content of less than 5% may reduce wet performance, and a vinyl content of more than 70% may reduce wear resistance, both of which are not 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, further preferably 30 to 55% by mass, or more preferably 34 to 66% by mass, further preferably 44 to 56% by mass in 100% by mass of the 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 fully obtained. In addition, 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 the molding processability cannot be fully obtained.

[0035] The tire rubber composition contains 30% by mass or more, preferably 33 to 50% by mass, and more preferably 35 to 45% by mass of butadiene rubber in 100% by mass of diene rubber. If the butadiene rubber is less than 30% by mass, the wear resistance is reduced. In addition, by making the butadiene rubber less than 50% by mass, it is easy to disperse silica well, and good wet performance can be ensured. The type of butadiene rubber is not particularly limited, and rubber commonly used in tire rubber compositions can be used.

[0036] The rubber composition for tires preferably does not contain natural rubber. By not containing natural rubber, there is a tendency to improve wet performance, so it is preferred. In addition, not containing natural rubber means that natural rubber is not actively mixed in the rubber composition for tires. For example, in order to reuse scraps of other rubber compositions containing natural rubber, that is, to recycle them within the process, when they are mixed in the preparation of the rubber composition for tires, as a result, a small amount of natural rubber may be contained. In the above case, the natural rubber is preferably 0 to 5% by mass, and more preferably 0 to 4% by mass in 100% by mass of the diene rubber.

[0037] The tire rubber composition contains 50 to 150 parts by mass of silica, preferably 60 to 140 parts by mass, and more preferably 70 to 130 parts by mass of silica in 100 parts by mass of diene rubber. By adding silica, wet performance can be improved. When silica is less than 50 parts by mass, the effect of improving wet performance cannot be fully obtained. In addition, when silica exceeds 150 parts by mass, molding processability is reduced.

[0038] As silica, silica commonly used in tire rubber compositions can be used, for example, wet silica, dry silica, carbon-silica (dual phase filler) in which silica is supported on the surface of carbon black, silica surface-treated with a compound reactive or compatible with both silica and rubber, such as a silane coupling agent or polysiloxane, etc. Among them, wet silica having hydrous silicic acid as a main component is preferred.

[0039] In addition, by adding a silane coupling agent together with silica, the dispersibility of silica can be improved, and the wetland performance can be further improved, so it is preferred. The type of silane coupling agent is not particularly limited, and sulfur-containing silane coupling agents are preferred, and examples thereof 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 Co., Ltd. Si363 and other mercaptosilane compounds exemplified in Japanese Patent Application Laid-Open No. 2006-249069, as well as 3-trimethoxysilylpropylbenzothiazolyl tetrasulfide, 3-triethoxysilylpropylbenzothiazolyl tetrasulfide, 3-triethoxysilylpropylmethacrylate monosulfide, 3-trimethoxysilylpropylmethacrylate 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, dimethoxymethylsilylpropyl benzothiazolyl tetrasulfide, 3-octanoylthiopropyl triethoxysilane, 3-propionylthiopropyl trimethoxysilane, vinyl trimethoxysilane, vinyl triethoxysilane, vinyl tri(2-methoxyethoxy)silane, 3-(glycidoxy)propyl trimethoxysilane, 3-(glycidoxy)propyl methyldimethoxysilane, β-(3,4-epoxycyclohexyl)ethyl trimethoxysilane, 3-aminopropyl trimethoxysilane, N-(β-aminoethyl)-γ-aminopropyl trimethoxysilane, N-(β-aminoethyl)-γ-aminopropyl methyldimethoxysilane, etc.

[0040] The silane coupling agent is preferably mixed with 3 to 20% by mass, more preferably 5 to 15% by mass relative to the mass of silica. When the silane coupling agent is less than 3% by mass of the mass of silica, the effect of improving the dispersibility of silica cannot be fully obtained. In addition, if the silane coupling agent exceeds 20% by mass, there is a tendency for the diene rubber component to gel easily, so the desired effect cannot be obtained.

[0041] By adding fillers other than silica to the rubber composition for tires, the strength of the rubber composition can be improved and the durability of the tire can be ensured. Examples of other fillers include inorganic fillers such as carbon black, calcium carbonate, magnesium carbonate, talc, clay, aluminum oxide, aluminum hydroxide, titanium oxide, calcium sulfate, mica, and barium sulfate, and organic fillers such as cellulose, lecithin, lignin, and dendrimers.

[0042] Among them, by combining carbon black, the strength of the rubber composition can be made excellent, thereby improving wear resistance. As carbon black, furnace black, acetylene black, thermal black, channel black, graphite and other carbon blacks can also be combined. Among them, furnace black is preferred, and as its specific example, SAF, ISAF, ISAF-HS, ISAF-LS, IISAF-HS, HAF, HAF-HS, HAF-LS, FEF and the like can be listed. These carbon blacks can be used alone, or two or more can be used in combination. In addition, surface treated carbon blacks formed 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 mass, preferably 12 to 78 parts by mass, and more preferably 15 to 75 parts by mass of a thermoplastic resin relative to 100 parts by mass of the diene rubber. By adding a thermoplastic resin, wear resistance can be improved, and even if the weight average molecular weight of the styrene-butadiene rubber (A) is small, the reduction in wear resistance can be suppressed. In addition, due to the plasticizer effect of the thermoplastic resin, molding processability is good, and the Tg of the rubber composition becomes higher, and wet performance is improved. If the thermoplastic resin is less than 10 parts by mass, the effect of improving wear resistance cannot be fully obtained. When the thermoplastic resin exceeds 80 parts by mass, the effect of improving wear resistance is reduced.

[0044] Thermoplastic resin is a resin that is usually added to a tire rubber composition, has a molecular weight of several hundred to several thousand, and has the function of imparting adhesiveness to the tire rubber composition. As the thermoplastic resin, it is preferably selected from at least one of the following resins: terpene, modified terpene, rosin, rosin ester, and a resin composed of at least one selected from a C5 component and a C9 component, and a resin in which at least a part of the double bonds of these resins is hydrogenated. For example, natural resins such as terpene resins, modified terpene resins, rosin resins, and rosin ester resins, and synthetic resins such as petroleum resins, coal resins, phenolic resins, and xylene resins composed of C5 components and / or C9 components can be cited.

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

[0046] Examples of petroleum-based resins include aromatic hydrocarbon resins or saturated or unsaturated aliphatic hydrocarbon resins, such as C5 petroleum resins (aliphatic petroleum resins obtained by polymerizing fractions of isoprene, 1,3-pentadiene, cyclopentadiene, methylbutene, pentene, etc.), C9 petroleum resins (aromatic petroleum resins obtained by polymerizing fractions of α-methylstyrene, o-vinyltoluene, m-vinyltoluene, p-vinyltoluene, etc.), 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. By setting the glass transition temperature of the thermoplastic resin to 40°C or higher, dry grip performance can be improved, so it is preferred. Furthermore, by setting it to 120°C or lower, wear resistance is improved, so it is preferred. The glass transition temperature of the thermoplastic resin can be measured by the above method.

[0048] It is preferred to add a liquid polymer to the rubber composition for tires. By adding a liquid polymer, the wear resistance is improved. The liquid polymer is preferably added in an amount of 0 to 30 parts by mass, more preferably 3 to 25 parts by mass, relative to 100 parts by mass of the diene rubber. When the liquid polymer exceeds 30 parts by mass, the wet performance is reduced. Examples of the liquid polymer include liquid polybutene, liquid polyisobutylene, liquid polyisoprene, liquid polybutadiene, liquid poly-α-olefin, liquid ethylene-propylene copolymer, and liquid ethylene-butene copolymer.

[0049] In the rubber composition for tires, in addition to the above-mentioned components, various compounding agents commonly used in rubber compositions for tires such as vulcanization or crosslinking agents, vulcanization accelerators, anti-aging agents, processing aids, plasticizers, thermosetting resins, etc. can be mixed according to conventional methods. Such compounding agents can be mixed by a general method to make a rubber composition for vulcanization or crosslinking. The amount of these compounding agents can be the general amount in the past as long as it does not violate the purpose of the present invention. The rubber composition for tires can be prepared by mixing the above-mentioned components using a known rubber mixing machine, such as a Banbury mixer, a kneading machine, a roller, etc.

[0050] The tire rubber composition is suitable for forming a tread portion or a sidewall portion of a tire, and is particularly suitable for forming a tread portion of a high-performance tire. The tire obtained thereby can have both high levels of wear resistance and wet performance, and can stably obtain a high-quality tire with good molding processability.

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

[0052] Example

[0053] When preparing 33 kinds of rubber compositions for tires (standard examples, examples 1 to 20, comparative examples 1 to 12) having the common additive formulation shown in Table 6 and made from the formulations shown in Tables 1 to 5, the components other than sulfur and vulcanization accelerator were weighed separately, and after kneading for 5 minutes in a 1.7-liter closed Banbury mixer, the masterbatch was released outside the mixer and cooled to room temperature. The masterbatch was supplied to the same Banbury mixer, sulfur and vulcanization accelerator were added and mixed to obtain a rubber composition for tires. In the table, SBR (B) -1 and SBR (B) -2 are 37.5 parts by mass of oil-filled products, so the amount of compounding after removing the oil-filling component is recorded in the brackets on the lower line. In addition, the additive formulations in Table 6 are recorded in parts by mass relative to 100 parts by mass of the diene rubber recorded in Tables 1 to 5.

[0054] The Mooney viscosity of the tire rubber composition obtained above was measured by the following method. In addition, the tire rubber composition was vulcanized at 160°C for 20 minutes in a mold of a predetermined shape to prepare an evaluation sample. Using the obtained evaluation sample, the dynamic viscoelasticity (loss tangent tanδ at 0°C) and wear resistance were measured by the following method.

[0055] Mooney viscosity (ML 1+4 )

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

[0057] Dynamic viscoelasticity (0℃ loss tangent tanδ)

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

[0059] Wear resistance

[0060] The evaluation samples of the obtained tire rubber composition were measured for wear amount using a Lamborn abrasion tester (manufactured by Iwamoto Seisakusho Co., Ltd.) based on JIS K6264 under the conditions of a load of 15.0 kg (147.1 N) and a slip rate of 25%. The reciprocal of each result obtained was calculated, and the index when the reciprocal of the wear amount of the standard example was set as 100 was recorded in the "wear resistance" column of Tables 1 to 5. The larger the index, the less wear amount and the better the wear resistance.

[0061]

[0062]

[0063]

[0064]

[0065]

[0066] The types of raw materials used in Tables 1 to 5 are as follows.

[0067] SBR (A)-1: terminal-modified styrene butadiene rubber having a polyorganosiloxane structure, Nipol NS612 produced by Zeon Co., Ltd. of Japan, glass transition temperature of -60°C, weight average molecular weight of 450,000, styrene content of 15% by mass, vinyl content of 30%, non-oil-extended product.

[0068] SBR (A)-2: a terminal-modified styrene butadiene rubber having a polyorganosiloxane structure obtained by the following polymerization method, having 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 being a non-oil-extended product.

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

[0070] SBR (B)-1: modified styrene butadiene rubber, Tafden E581 manufactured by Asahi Kasei Corporation, glass transition temperature -34°C, weight average molecular weight 1.26 million, styrene content 36% by mass, vinyl content 42%, 37.5 parts by mass of oil-extended product.

[0071] SBR (B)-2: modified styrene butadiene rubber, Tafden E680 manufactured by Asahi Kasei Corporation, glass transition temperature -25°C, weight average molecular weight 1,470,000, styrene content 36% by mass, vinyl content 57%, 37.5 parts by mass of oil-extended product.

[0072] BR: Butadiene rubber, Nipol BR1220 produced by Zeon Co., Ltd. of Japan, glass transition temperature of -105°C, weight average molecular weight of 460,000.

[0073] Carbon black: DASHBLACK N220 produced by OCI Carbon

[0074] Silica: ZEOSIL 195MP produced by Solbi

[0075] Thermoplastic resin-1: Aromatic modified terpene resin, YS resin TO-125 produced by Yashara Chemical Co., Ltd., glass transition temperature is 79°C

[0076] Thermoplastic resin-2: Aromatic modified terpene resin, YS resin TO-105 produced by Yashara Chemical Co., Ltd., glass transition temperature is 57°C

[0077] Resin-3: C9 resin, Neopolymer S100 produced by ENEOSE, glass transition temperature 58°C

[0078] Resin-4: C5C9 resin, Neopolymer 170S produced by ENEOSE, glass transition temperature 105°C

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

[0080] Coupling agent: silane coupling agent, Si69 produced by Evonik Degussa

[0081] Polymerization method of SBR(A)-2

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

[0083] In an autoclave with a stirrer, 4000 g of cyclohexane, 1.50 mmol of tetramethylethylenediamine, 445 g of 1,3-butadiene and 155 g of styrene were added under a nitrogen atmosphere, and then all the polymer blocks with active ends obtained above were added, and polymerization was started at 50°C. 10 minutes after the start of polymerization, 355 g of 1,3-butadiene and 40 g of styrene were added continuously for 60 minutes. The highest temperature during the polymerization reaction was 75°C. After the continuous addition was completed, the polymerization reaction was continued for another 10 minutes, and it was confirmed that the polymerization conversion rate became in the range of 95% to 100%, and then 2.44 g of the polyorganosiloxane represented by the following formula (I) was added in the state of a 40% by mass concentration xylene solution, and it was reacted for 30 minutes. Then, methanol equivalent to 2 times the molar amount of n-butyl lithium used was added as a polymerization terminator to obtain a solution containing a conjugated diene rubber. To this solution, 0.15 parts of Ilganox 1520L (manufactured by BASF) as an antioxidant was added per 100 parts of the conjugated diene rubber, and the solvent was removed by steam stripping, followed by vacuum drying at 60°C for 24 hours to obtain a 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 is methyl, X 2 It is a group represented by the following formula (II) (here, * indicates a bonding position).

[0086]

[0087] surface

[0088]

[0089] The types of raw materials used in Table 6 are as follows.

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

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

[0092] Zinc oxide: 3 types of zinc oxide manufactured by Seito Chemical Industry Co., Ltd.

[0093] · Stearic acid: β-stearic acid produced by NOF Corporation

[0094] · Vulcanization accelerator-1: Noxera CZ-G produced by Ouchi Shinko Chemical Industry Co., Ltd.

[0095] · Vulcanization accelerator-2: Soxhinolu DG produced by Sumitomo Chemical Co., Ltd.

[0096] Sulfur: Tsurumi Chemical Industry Co., Ltd., Sulfux 5

[0097] As can be seen from Tables 1 to 3, the tire rubber compositions of Examples 1 to 20 are excellent in abrasion resistance and wet performance, and are also excellent in molding processability (Mooney viscosity).

[0098] As can be seen from Table 4, the tire rubber composition of Comparative Example 1 has low wet performance and poor 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] Since the SBR (A) of the tire rubber composition of Comparative Example 2 exceeded 35 parts by mass, the molding processability (Mooney viscosity) could not be improved.

[0100] The rubber composition for a tire of Comparative Example 3 cannot improve wet performance because the silica content is less than 50 parts by mass.

[0101] Since the rubber composition for a tire of Comparative Example 4 contained more than 150 parts by mass of silica, the molding processability (Mooney viscosity) could not be improved.

[0102] Since the rubber composition for a tire of Comparative Example 5 contained less than 10 parts by mass of the thermoplastic resin, the molding processability (Mooney viscosity) could not be improved.

[0103] Since the rubber composition for a tire of Comparative Example 6 contained more than 80 parts by mass of the thermoplastic resin, the molding processability (Mooney viscosity) could not be improved.

[0104] As can be seen from Table 5, the tire rubber composition of Comparative Example 7 has an SBR (A) content of 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 content was less than 30 parts by mass, so the molding processability (Mooney viscosity) and the wear resistance could not be improved.

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

[0107] Since the rubber composition for a tire of Comparative Example 10 does not contain SBR (A), the molding processability (Mooney viscosity) is deteriorated.

[0108] The tire rubber composition of Comparative Example 11 had a mass ratio of SBR(B) / SBR(A) of less than 1, and thus could not improve wear resistance.

[0109] Since the mass ratio of SBR(B) / SBR(A) of the tire rubber composition of Comparative Example 12 exceeded 2, the molding processability (Mooney viscosity) could not be improved.

[0110] The present invention includes the following inventions.

[0111] Invention [1]: A rubber composition for a tire, characterized in that 50 to 150 parts by mass of silica and 10 to 80 parts by mass of a thermoplastic resin are blended into 100 parts by mass of a diene rubber consisting of styrene butadiene rubber (A), styrene butadiene rubber (B) and butadiene rubber,

[0112] In 100% by mass of the diene rubber, the butadiene rubber accounts for 30% by mass or more, the styrene butadiene rubber (A) accounts for 15 to 35% by mass, the styrene butadiene rubber (B) is 1 to 2 times by mass 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).

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

[0114] Invention [3]: The tire rubber composition according to Invention [1] or [2], wherein the glass transition temperature of the styrene-butadiene rubber (B) is lower than -30°C.

[0115] Invention [4]: ​​The tire rubber composition according to any one of Inventions [1] to [3], wherein the thermoplastic resin is at least one resin selected from the following resins and resins in which at least a portion of the double bonds of these resins are hydrogenated:

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

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

[0118] Invention [5]: The tire rubber composition according to any one of Inventions [1] to [4], further comprising a liquid polymer.

[0119] Invention [6]: A tire having a tread portion made from the rubber composition for a tire according to any one of Inventions [1] to [5].

[0120] Description of the accompanying drawings

[0121] 1. Tread

[0122] 2. Sidewall

[0123] 3 Bead section

[0124] 4 carcass layers

[0125] 5 bead core

[0126] 6 Bead filler

[0127] 7 Lining layer

[0128] 8 belt layer

[0129] 9 belt cover

[0130] 10a tread crown

[0131] 10b tread base

Claims

1. A rubber composition for a tire, characterized in that: 50 to 150 parts by mass of silica and 10 to 80 parts by mass of a thermoplastic resin are mixed with 100 parts by mass of a diene rubber composed of styrene butadiene rubber A, styrene butadiene rubber B and butadiene rubber. In 100% by mass of the diene rubber, the butadiene rubber accounts for 30% by mass or more, the styrene butadiene rubber A accounts for 15 to 35% by mass, the styrene butadiene rubber B is 1 to 2 times by mass 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.

2. The tire rubber composition according to claim 1, wherein 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, wherein: The glass transition temperature of the styrene butadiene rubber B is lower than -30°C.

4. The tire rubber composition according to claim 1 or 2, wherein: The thermoplastic resin is at least one selected from the following resins and resins in which at least a part of the double bonds of these resins are hydrogenated, The resin is terpene, modified terpene, rosin, rosin ester, and a resin composed of at least one selected from a C5 component and a C9 component. The glass transition temperature of the thermoplastic resin is 40 to 120°C.

5. The tire rubber composition according to claim 1 or 2, wherein: Also contains liquid polymer.

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

Images