RUBBER COMPOSITION FOR TIRES

Abstract

A rubber compound is provided for a tire that offers excellent wear resistance and wet performance, as well as excellent formability.The rubber composition for a tire contains 50 to 150 parts by mass of silica and 10 to 80 parts by mass of a thermoplastic resin, which per 100 parts by mass of a diene rubber consisting of a styrene-butadiene rubber (A), a styrene-butadiene rubber (B), and a butadiene rubber, wherein, in 100% by mass of the diene rubber, the butadiene rubber is present in an amount of 30% by mass or more, the styrene-butadiene rubber (A) is present in an amount of 15 to 35% by mass, and the styrene-butadiene rubber (B) is present in an amount one to two times the mass of the styrene-butadiene rubber (A), wherein the styrene-butadiene rubber (A) has a glass transition temperature of -75°C to -50°C and the Styrene-butadiene rubber (B) has a weight-averaged molecular weight that is two or more times that of the weight-averaged molecular weight of styrene-butadiene rubber (A).

Description

Technical area

[0001] The present invention relates to a rubber composition for a tire, the rubber composition having excellent wear resistance, excellent wet performance and excellent moldability. State of the art

[0002] Tires for the North American market must provide a high degree of wear resistance and wet performance in a compatible manner. Attempting to improve wet performance by using a high-glass-transition-temperature diene rubber in a rubber composition to form a tread results in reduced wear resistance, making it difficult to obtain a tire that provides both properties in a compatible manner. Furthermore, attempting to improve wear resistance by using a high-molecular-weight diene rubber results in increased viscosity of the rubber composition and impaired moldability. In contrast, attempting to reduce viscosity by using a low-molecular-weight diene rubber leads to the problem of reduced wear resistance.

[0003] In order to ensure good wet skid resistance, low rolling resistance, and good wear properties, Patent Document 1 proposes a pneumatic tire whose tread has a vulcanizable rubber composition containing: (A) about 20 to about 100 phr of a 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 a 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 has not necessarily achieved a sufficient effect in providing a high degree of wear resistance and wet performance in a compatible manner and ensuring excellent formability. Literature listPatent documents

[0005] Patent Document 1: JP 2021-021070 A Brief description of the inventionTechnical problem

[0006] An object of the present invention is to provide a rubber composition for a tire, the rubber composition compatibly providing a high level of wear resistance and wet performance and having low viscosity and good moldability. Solution to the problem

[0007] A rubber composition for a tire according to the present invention which achieves the object may contain 50 to 150 parts by mass of silica and 10 to 80 parts by mass of a thermoplastic resin blended per 100 parts by mass of a diene rubber consisting of a styrene-butadiene rubber (A), a styrene-butadiene rubber (B) and a butadiene rubber, wherein, in 100 mass% of the diene rubber, the butadiene rubber is present in an amount of 30 mass% or more, the styrene-butadiene rubber (A) is present in an amount of 15 to 35 mass%, the styrene-butadiene rubber (B) is present in an amount one to two times the mass of the styrene-butadiene rubber (A), the styrene-butadiene rubber (A) has a glass transition temperature of -75 °C to -50 °C, and wherein the styrene-butadiene rubber (B) has a weight-average molecular weight,which is at least twice the weight-average molecular weight of the styrene-butadiene rubber (A). Advantageous effects of the invention

[0008] The rubber composition for a tire according to an embodiment of the present invention has the above composition and thus can compatibly provide a high level of wear resistance and wet performance and has a low viscosity and good moldability.

[0009] Preferably, the weight-average molecular weight of the styrene-butadiene rubber (A) is 300,000 to 600,000. Preferably, the styrene-butadiene rubber (B) has a glass transition temperature of less than -30°C.

[0010] The thermoplastic resin preferably has a glass transition temperature of 40°C to 120°C and is at least one selected from the group consisting of a resin composed of at least one selected from a terpene, a modified terpene, a rosin, a rosin ester, a C5 component, and a C9 component, and a resin in which at least some of the double bonds of this resin are hydrogenated.

[0011] Preferably, the rubber composition for a tire further contains a liquid polymer.

[0012] A tire comprising a tread portion made of the above-described rubber composition for a tire has a compatible high level of wear resistance and wet performance, and high-quality tires with good formability can be reliably produced. Brief description of the drawings Fig. 1 is a cross-sectional view in a tire meridian direction illustrating an example of an embodiment of a tire formed using a rubber composition for a tire according to an embodiment of the present invention. Description of embodiments

[0013] The rubber composition for a tire according to one embodiment of the present invention can be suitably used in a tread portion and / or a sidewall portion of a tire. The tire may be a pneumatic tire or an airless tire. Fig. Figure 1 is a cross-sectional view illustrating an example of an embodiment of a pneumatic tire. The pneumatic tire includes a tread portion 1, a side portion 2, and a bead portion 3.

[0014] In Fig.1, two carcass layers 4 extend between the left and right parts of a bead portion 3. In the two carcass layers 4, reinforcing cords extending in the tire radial direction are arranged at a predetermined pitch in the tire circumferential direction and embedded in a rubber layer. Both end portions of the two carcass layers 4 are folded back from the inside to the outside in the tire axial direction around a bead core 5 embedded in the bead portion 3 so as to sandwich a bead filler 6. An inner liner layer 7 is arranged on the inside of the carcass layers 4. Two belt layers 8 are arranged on the outer circumferential side of the carcass layers 4 of the tread portion 1.In the belt layers 8, reinforcing inclined cords extending in the tire radial direction are arranged at a predetermined pitch in the tire axial direction and embedded in the rubber layer. The reinforcing cords of the two belt layers 8 are arranged in opposite directions to each other and intersect between the layers with the inclination directions relative to the tire circumferential direction, i.e., the cord directions. Belt cover layers 9 are arranged on the outer peripheral side of the belt layers 8. The belt cover layers 9 can be of the "full cover" type, which covers the entire belt layer, or of the "edge cover" type, which covers an end portion of the belt layer in the tire width direction, or both types can be combined. The tread portion 1 is arranged on the outer peripheral side of the belt cover layers 9.The tread portion 1 includes a breaker tread 10a and an undertread 10b. The rubber composition for a tire according to an embodiment of the present invention is preferably used in the tread portion 1 and / or the side portion 2, and more preferably in the breaker tread 10a and / or the undertread 10b.

[0015] In the rubber composition for a tire according to one embodiment of the present invention, a diene rubber consists of a styrene-butadiene rubber (A), a styrene-butadiene rubber (B), and a butadiene rubber. The styrene-butadiene rubber (A) has a glass transition temperature of -75°C to -50°C and a lower weight-average molecular weight than the styrene-butadiene rubber (B). The diene rubber including the styrene-butadiene rubber (A) reduces the viscosity of the rubber composition and can provide good moldability.

[0016] The glass transition temperature (hereinafter referred to as "Tg") of the styrene-butadiene rubber (A) is preferably from -75°C to -50°C, and more preferably from -70°C to -55°C. In the present specification, Tg can be measured as the temperature in the center of the transition region on a thermogram obtained by differential scanning calorimetry (DSC) under conditions of a heating rate of 20°C / minute. Furthermore, when the diene rubber is an oil-extended product, the Tg of the diene rubber is determined in a state where it does not contain an oil-extending ingredient (oil).

[0017] The weight-average molecular weight of the styrene-butadiene rubber preferably ranges from 300,000 to 600,000, and more preferably from 320,000 to 580,000. The styrene-butadiene rubber (A) having a weight-average molecular weight within such a range further reduces the viscosity of the rubber composition and can provide good moldability. In the present specification, the weight-average molecular weight may be a value obtained by measurement using gel permeation chromatography (GPC) and calibration with polystyrene.

[0018] The styrene-butadiene rubber (A) has a styrene content of preferably 3 to 35 mass%, and more preferably 5 to 30 mass%. With a styrene content of less than 3 mass%, wet performance may be reduced, and with a styrene content of more than 35 mass%, wear resistance may be reduced, both of which are not preferred. In the present specification, the styrene content is a value measured by 1 H-NMR.

[0019] The styrene-butadiene rubber (A) has a vinyl content of preferably 5 to 60%, and more preferably 10 to 55%. With a vinyl content of less than 5%, wet performance may be reduced, and with a vinyl content of more than 60%, wear resistance may be reduced, both of which are not preferred. In the present specification, the vinyl content is a value measured by 1 H-NMR.

[0020] The styrene-butadiene rubber (A) can be either an unmodified styrene-butadiene rubber or a modified styrene-butadiene rubber. In the styrene-butadiene rubber, at least one terminal is preferably modified with a functional group. Examples of the functional group include an epoxy group, a carboxyl group, an amino group, a hydroxy group, an alkoxy group, a silyl group, an alkoxysilyl group, an amide group, an oxysilyl group, a silanol group, an isocyanate group, an isothiocyanate group, a carbonyl group, and an aldehyde group. Among these, a functional group having a polyorganosiloxane structure or an aminosilane structure is preferred. The functional group having a polyorganosiloxane structure or an aminosilane structure provides good dispersibility for silica and can provide excellent wear resistance and wet performance.

[0021] The styrene-butadiene rubber (A) is present in an amount of 15 to 35 mass%, preferably 17 to 33 mass%, and more preferably 22 to 28 mass%, in 100 mass% of the diene rubber. A content of less than 15 mass% of the styrene-butadiene rubber (A) would not provide a sufficient effect of improving moldability by reducing the viscosity of the rubber composition. Furthermore, if the styrene-butadiene rubber (A) exceeds 35 mass%, the balance of the styrene-butadiene rubber (B) and the butadiene rubber would not provide a sufficient effect of improving moldability by reducing the viscosity of the rubber composition.

[0022] The styrene-butadiene rubber (B) contained in the rubber composition for a tire has a weight-average molecular weight at least twice that of the styrene-butadiene rubber (A). The presence of styrene-butadiene rubber (B) can improve the wear resistance of the rubber composition. Furthermore, the Tg of the styrene-butadiene rubber (B) is higher than that of the styrene-butadiene rubber (A), which can improve wet performance.

[0023] The weight-average molecular weight of the styrene-butadiene rubber (B) is twice or more than the weight-average molecular weight of the styrene-butadiene rubber (A), and is preferably 600,000 or more, more preferably 700,000 to 1,600,000, and even more preferably 800,000 to 1,500,000. The styrene-butadiene rubber (B) having a weight-average molecular weight in such a range can further improve the wear resistance of the rubber composition.

[0024] The Tg of the styrene-butadiene rubber (B) is preferably below -30°C, more preferably between -70°C and -31°C, and even more preferably between -60°C and -32°C. However, the Tg of the styrene-butadiene rubber (B) is preferably higher than the Tg of the styrene-butadiene rubber (A). The styrene-butadiene rubber (B) having a Tg in such a range can improve the wet performance of the rubber composition and is preferred.

[0025] The styrene-butadiene rubber (B) has a styrene content of preferably 5 to 50 mass%, and more preferably 10 to 45 mass%. A styrene content of less than 5 mass% may reduce wet performance, and a styrene content of more than 50 mass% may reduce wear resistance, both of which are not preferred.

[0026] The styrene-butadiene rubber (B) has a vinyl content of preferably 5 to 70%, and 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.

[0027] The content of the styrene-butadiene rubber (B) is one to two times the mass content of the styrene-butadiene rubber (A), and is preferably 15 to 70 mass%, more preferably 25 to 60 mass%, further preferably 30 to 55 mass%, or even more preferably 34 to 66 mass%, and especially 44 to 56 mass%, based on 100 mass% of the diene rubber. A lower content of the styrene-butadiene rubber (B) than that of the styrene-butadiene rubber (A) would not provide a sufficient effect on improving the wear resistance of the rubber composition. In addition, a content of styrene-butadiene rubber (B) of more than twice the mass of styrene-butadiene rubber (A) would not provide a sufficient effect in improving the moldability by reducing the viscosity of the rubber composition.

[0028] The rubber composition for a tire contains the butadiene rubber in an amount of 30 mass% or more, preferably from 33 to 50 mass%, and more preferably from 35 to 45 mass%, based on 100 mass% of the diene rubber. A butadiene rubber content of less than 30 mass% would reduce wear resistance. Furthermore, a butadiene rubber content of 50 mass% or less facilitates good silica dispersibility and can ensure good wet performance. The type of butadiene rubber is not particularly limited, and a butadiene rubber commonly used in a rubber composition for tires can be used.

[0029] The rubber composition for a tire preferably does not contain natural rubber. The rubber composition that does not contain natural rubber tends to have improved wet performance and is preferred. "Does not contain natural rubber" means that natural rubber is not actively blended into the rubber composition for a tire. For example, the rubber composition for a tire may contain a small amount of natural rubber because, during the production of the rubber composition for a tire, waste material or the like is blended with another rubber composition containing natural rubber for reuse, that is, for in-process recycling. In the above case, the content of the natural rubber is preferably from 0 to 5 mass%, and more preferably from 0 to 4 mass%, based on 100 mass% of the diene rubber.

[0030] In the rubber composition for a tire, silica is blended in an amount of 50 to 150 parts by mass, preferably 60 to 140 parts by mass, and more preferably 70 to 130 parts by mass, per 100 parts by mass of the diene rubber. Blending silica can provide improved wet performance. Blending silica in an amount of less than 50 parts by mass would not provide sufficient effect in improving wet performance. Furthermore, blending silica in an amount exceeding 150 parts by mass would reduce moldability.

[0031] The silica used is preferably silica commonly used in a rubber composition for a tire. For example, wet silica, dry silica, carbon silica in which the silica is supported on a carbon black surface (two-phase filler), or silica whose surface has been treated with a compound that is reactive or miscible with both silica and rubber, such as a silane coupling agent or polysiloxane, can be used. Of these, wet silica, which contains hydrous silicic acid as a main component, is preferred.

[0032] Furthermore, blending a silane coupling agent with silica improves the dispersibility of the silica and further enhances wet performance, making it preferred. There are no particular restrictions on the type of silane coupling agent, but a sulfur-containing silane coupling agent is preferred. Examples thereof may include bis(3-triethoxysilylpropyl)tetrasulfide, bis(3-triethoxysilylpropyl)trisulfide, bis(3-triethoxysilylpropyl)disulfide, bis(2-triethoxysilylethyl)tetrasulfide, bis(3-trimethoxysilylpropyl)tetrasulfide, bis(2-triethoxysilylethyl)tetrasulfide, mercaptan compounds exemplified in JP 2006-249069 A such as 3-mercaptopropyltrimethoxysilane, 3-mercaptopropyldimethoxymethylsilane, 3-mercaptopropyldimethylmethoxysilane, 2-mercaptoethyltriethoxysilane, 3-mercaptopropyltriethoxysilane, and VP Si363 available from Evonik Co., 3-Trimethoxysilylpropylbenzothiazoltetrasulfid, 3-Triethoxysilylpropylbenzothiazolyltetrasulfid, 3-Triethoxysilylpropylmethacrylatmonosulfid, 3-Trimethoxysilylpropylmethacrylatmonosulfid, 3-Triethoxysilylpropyl-N,N-dimethylthiocarbamoyltetrasulfid, 3-Trimethoxysilylpropyl-N,N-dimethylthiocarbamoyltetrasulfid, 2-Triethoxysilylethyl-N,N-dimethylthiocarbamoyltetrasulfid, Bis(3-diethoxymethylsilylpropyl)tetrasulfid, Dimethoxymethylsilylpropyl-N,N-dimethylthiocarbamoyltetrasulfid, Dimethylmethylsilylpropylbenzothiazolyltetrasulfid, 3-Octanoylthiopropyltriethoxysilan, 3-Propionylthiopropyltrimethoxysilan, Vinyltrimethoxysilan, Vinyltriethoxysilan, Vinyltris(2-methoxyethoxy)silan, 3-Glycidoxypropyltrimethoxysilan, 3-Glycidoxypropylmethyldimethoxysilan, β-(3,4-Epoxycyclohexyl)ethyltrimethoxysilan, 3-Aminopropyltrimethoxysilan, N-(β-Aminoethyl)-γ-Aminopropyltrimethoxysilan und N-(β-Aminoethyl)-γ-Aminopropylmethyldimethoxysilan einschließen.

[0033] The silane coupling agent is preferably blended in an amount of 3 to 20 mass%, and more preferably 5 to 15 mass%, based on the silica mass. Blending the silane coupling agent in an amount of less than 3 mass% of the silica mass would not provide a sufficient effect in improving the dispersibility of the silica. Furthermore, blending the silane coupling agent in an amount exceeding 20 mass% would tend to facilitate gelation of the diene rubber component and thus not provide the desired effect.

[0034] Incorporating an additional filler besides silica into the rubber composition for a tire increases the strength of the rubber composition and can ensure the durability of the tire. Examples of the additional filler may include an inorganic filler such as carbon black, calcium carbonate, magnesium carbonate, talc, clay, alumina, aluminum hydroxide, titanium oxide, calcium sulfate, mica, and barium sulfate; and an organic filler such as cellulose, lecithin, lignin, and dendrimer.

[0035] Among them, the incorporation of carbon black imparts excellent strength to the rubber composition and can improve wear resistance. As the carbon black, a carbon black such as furnace black, acetylene black, thermal black, channel black, and graphite can be incorporated. Among them, 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 alone or in combination with two or more types. In addition, a surface-treated carbon black obtained by chemically modifying one of these carbon blacks with various acid compounds can also be used.

[0036] In the rubber composition for a tire, a thermoplastic resin is blended in an amount of 10 to 80 parts by mass, preferably 12 to 78 parts by mass, and more preferably 15 to 75 parts by mass, per 100 parts by mass of the diene rubber. By blending the thermoplastic resin, wear resistance can be improved and a decrease in wear resistance can be prevented even when the styrene-butadiene rubber (A) has a low weight-average molecular weight. In addition, the thermoplastic resin functions as a plasticizer, thus improving the moldability, the Tg of the rubber composition, and the wet performance. Blending the thermoplastic resin in an amount of less than 10 parts by mass would not provide a sufficient effect on improving wear resistance.Blending the thermoplastic resin in an amount of more than 80 parts by mass would tend to reduce the effect of improving wear resistance.

[0037] The thermoplastic resin is a resin commonly blended with a tire rubber composition, has a molecular weight of approximately several hundred to several thousand, and functions to impart adhesion to the tire rubber composition. The thermoplastic resin is preferably at least one selected from the group consisting of a resin composed of at least one selected from a terpene, a modified terpene, a rosin, a rosin ester, a C5 component, and a C9 component, and a resin in which at least some of the double bonds of the resin are hydrogenated.Examples of the resin include a natural resin such as a terpene resin, a modified terpene resin, a rosin resin, and a rosin ester resin; and a synthetic resin such as petroleum resins consisting of a C5 component and / or a C9 component, a carbon resin, a phenolic resin, and a xylene-based resin.

[0038] Examples of terpene resin include α-pinene resin, β-pinene resin, limonene resin, hydrogenated limonene resin, dipentene resin, terpene-phenolic resin, terpene-styrene resin, an aromatic modified terpene resin, and a hydrogenated terpene resin. Examples of rosin resin include a modified rosin such as gum rosin, tall oil resin, wood rosin, hydrogenated rosin, disproportionated rosin, polymerized rosin, maleated rosin, and fumarated rosin; an ester derivative of these rosins such as a glycerol ester, a pentaerythritol ester, a methyl ester, and a triethylene glycol ester; and a rosin-modified phenolic resin.

[0039] Examples of the petroleum resin include an aromatic hydrocarbon resin or, alternatively, a saturated or unsaturated aliphatic hydrocarbon resin. Examples include a C5 petroleum resin (an aliphatic petroleum resin obtained by polymerizing fractions of isoprene, 1,3-pentadiene, cyclopentadiene, methylbutene, pentene, and / or the like), a C9 petroleum resin (an aromatic petroleum resin obtained by polymerizing fractions of α-methylstyrene, o-vinyltoluene, m-vinyltoluene, p-vinyltoluene, and / or the like), and a C5C9 copolymerized petroleum resin.

[0040] The thermoplastic resin has a glass transition temperature of preferably 40°C to 120°C, more preferably 45°C to 115°C, and even more preferably 50°C to 110°C. The thermoplastic resin with a glass transition temperature of 40°C or higher improves dry grip performance and is preferred. Furthermore, the thermoplastic resin with a glass transition temperature of 120°C or lower improves wear resistance and is preferred. The glass transition temperature of the thermoplastic resin can be measured by the method described above.

[0041] The rubber composition for a tire preferably contains a liquid polymer. By blending a liquid polymer, wear resistance is improved. The liquid polymer is blended in an amount preferably from 0 to 30 parts by mass, and more preferably from 3 to 25 parts by mass, per 100 parts by mass of the diene rubber. Blending the liquid polymer in an amount exceeding 30 parts by mass would reduce wet performance. Examples of the liquid polymer may include, but are not limited to, liquid polybutene, liquid polyisobutene, liquid polyisoprene, liquid polybutadiene, liquid poly(α-olefin), liquid ethylene-propylene copolymer, and liquid ethylene-butylene copolymer.

[0042] Various compounding agents commonly used in a rubber composition for a tire can be blended in addition to the above components of the rubber composition for a tire by a conventional method. The compounding agents include a vulcanizing or crosslinking agent, a vulcanization accelerator, an aging retarder, a processing aid, a plasticizer, and a thermosetting resin. Such a compounding agent can be kneaded into a rubber composition by conventional methods and used for vulcanization or crosslinking. The blended amount of the compounding agent may be a conventional blended amount known in the art, as long as the objects of the present invention are not hindered.The rubber composition for a tire can be prepared by mixing the above-mentioned components using a known rubber kneading device such as a Banbury mixer, a kneader or a roll mill.

[0043] The rubber composition for a tire is suitable for forming a tread portion and / or a sidewall portion of a tire, and is particularly suitable for forming a tread portion of a high-performance tire. The resulting tire exhibits a compatible high degree of wear resistance and wet performance, and high-quality tires with good formability can be reliably produced.

[0044] The present invention will be described in more detail below using examples. However, the scope of the present invention is not limited to these examples. Examples

[0045] To prepare 33 types of tire rubber compositions (Standard Example, Examples 1 to 20, and Comparative Examples 1 to 12) containing the common additive formulation shown in Table 6 and having the compositions shown in Tables 1 to 5, the components except sulfur and vulcanization accelerator were weighed and kneaded for 5 minutes in a 1.7-liter sealed Banbury mixer. A masterbatch was then removed from the mixer and cooled to room temperature. This masterbatch was added to the same Banbury mixer, sulfur and vulcanization accelerator were added and mixed, and a tire rubber composition was obtained.In the tables, SBR (B)-1 and SBR (B)-2 are oil-extended products containing 37.5 parts by mass of an oil extender. Thus, the blended amount without the oil extender is given in parentheses in the bottom row. Furthermore, the additive formulation is described in Table 6 as a value in parts by mass per 100 parts by mass of the diene rubbers from Tables 1 to 5.

[0046] The Mooney viscosity of the rubber compositions obtained above was measured using the following method. Furthermore, the rubber compositions were each vulcanized for one tire at 160 °C for 20 minutes in a mold of a predetermined shape, and evaluation samples were prepared. Using the resulting evaluation samples, the dynamic viscoelasticity (loss factor tan δ at 0 °C) and wear resistance were measured using the following methods. Mooney viscosity (ML 1+4 )

[0047] The Mooney viscosity of each of the rubber compositions obtained for a tire was measured in accordance with JIS K 6300 using an L-shaped rotor (diameter: 38.1 mm, thickness: 5.5 mm) in a Mooney viscometer under the conditions of a preheating time of 1 minute, a rotor running time of 4 minutes, at 100 °C, and 2 rpm. The results obtained are presented as index values ​​in the "Formability (Viscosity)" rows of Tables 1 to 5, with the value of the standard example set to 100. A smaller value of this index value indicates lower viscosity and better processability. Dynamic viscoelasticity (loss factor tan δ at 0 °C)

[0048] The dynamic viscoelasticity of the evaluation samples of the rubber compositions for a tire was measured using a viscoelasticity spectrometer from Iwamoto Seisakusho Co., Ltd. under the conditions of a tensile strain of 10 ± 2%, a vibration frequency of 20 Hz, and a temperature of 0 °C, and the loss tangent tan δ at 0 °C was determined. The obtained results are presented in the "Wet Performance" rows of Tables 1 to 5 as index values, with the value of the standard example set at 100. A larger value of this index indicates a larger tan δ at 0 °C and thus superior wet performance. Abrasion resistance

[0049] The wear extent of the resulting evaluation samples of the rubber compositions for a tire was measured according to JIS K6264 using a Lambourn abrasion tester (available from Iwamoto Seisakusho, Co., Ltd.) under conditions of a load of 15.0 kg (147.1 N) and a slip rate of 25%. For each of the obtained results, a reciprocal value was calculated and reported as an index value in the "Abrasion Resistance" row in Tables 1 to 5, with "100" assigned to the reciprocal of the abrasion degree of the standard example. A larger index value indicates a lower abrasion degree and superior abrasion resistance. [Table 1] Standard example Example 1 Example 2 Example 3 Example 4 Example 5 Example 6 SBR (A)-1 Mass-produced parts 30 30 17 22 28 33 30 SBR (B)-1 Mass-produced parts 41,3 (30) 41,3 (30) 45,4 (33) 52,3 (38) 44 (32) 48,1 (35) 41,3 (30) BR Mass-produced parts 40 40 50 40 40 32 40 CB Mass-produced parts 10 10 10 10 10 10 10 Silica Mass-produced parts 100 100 100 100 100 100 53 Thermoplastic resin-1 Mass-produced parts 5 25 25 25 25 25 25 Aroma oil Mass-produced parts 80 60 60 60 60 60 60 Adhesion promoter Mass-produced parts 10 10 10 10 10 10 5,3 Ratio SBR (B) / SBR (A) (-) 1,0 1,0 1,9 1,7 1,1 1,1 1,0 Formability (viscosity) Index value 100 95 92 93 93 97 82 Wear resistance performance Index value 100 120 130 125 122 118 118 Wet performance Index value 100 110 105 110 108 115 104 [Table 2] Example 7 Example 8 Example 9 Example 10 Example 11 Example 12 Example 13 SBR (A)-1 Mass-produced parts 30 30 30 30 30 30 30 SBR (B)-1 Mass-produced parts 41,3 (30) 41,3 (30) 41,3 (30) 41,3 (30) 41,3 (30) 41,3 (30) 41,3 (30) BR Mass-produced parts 40 40 40 40 40 40 40 CB Mass-produced parts 10 10 10 10 10 10 10 Silica Mass-produced parts 80 120 147 100 100 100 100 Thermoplastic resin-1 Mass-produced parts 25 25 25 11 20 40 60 Aroma oil Mass-produced parts 60 60 60 74 65 45 25 Adhesion promoter Mass-produced parts 8 12 14,7 10 10 10 10 Ratio SBR (B) / SBR (A) (-) 1,0 1,0 1,0 1,0 1,0 1,0 1,0 Formability (viscosity) Index value 87 92 98 98 96 97 98 Wear resistance performance Index value 123 119 115 103 110 123 128 Wet performance Index value 106 109 111 103 109 112 115 [Table 3] Example 14 Example 15 Example 16 Example 17 Example 18 Example 19 Example 20 SBR (A)-1 Mass-produced parts 30 30 30 30 30 SBR (A)-2 Mass-produced parts 30 SBR (A)-3 Mass-produced parts 30 SBR (B)-1 Mass-produced parts 41,3 (30) 41,3 (30) 41,3 (30) 41,3 (30) 41,3 (30) 41,3 (30) SBR (B)-2 Mass-produced parts 41,3 (30) BR Mass-produced parts 40 40 40 40 40 40 40 CB Mass-produced parts 10 10 10 10 10 10 10 Silica Mass-produced parts 100 100 100 100 100 100 100 Thermoplastic resin-1 Mass-produced parts 79 25 25 25 Thermoplastic Resin-2 Mass-produced parts 25 Thermoplastic Resin-3 Mass-produced parts 25 Thermoplastic Resin-4 Mass-produced parts 25 Aroma oil Mass-produced parts 6 60 60 60 60 85 85 Adhesion promoter Mass-produced parts 10 10 10 10 10 10 10 Ratio SBR (B) / SBR (A) (-) 1,0 1,0 1,0 1,0 1,0 1,0 1,0 Formability (viscosity) Index value 99 95 96 95 98 95 95 Wear resistance performance Index value 130 120 125 102 102 120 119 Wet performance Index value 116 120 105 105 112 107 112 [Table 4] Comparison example 1 Comparison example 2 Comparison example 3 Comparison example 4 Comparison example 5 Comparison example 6 SBR (A)-1 Mass-produced parts 13 36 30 30 30 30 SBR (B)-1 Mass-produced parts 48,1 (35) 50,9 (37) 41,3 (30) 41,3 (30) 41,3 (30) 41,3 (30) BR Mass-produced parts 52 27 40 40 40 40 CB Mass-produced parts 10 10 10 10 10 10 Silica Mass-produced parts 100 100 48 152 100 100 Thermoplastic resin-1 Mass-produced parts 25 25 25 25 8 82 Aroma oil Mass-produced parts 58 57 60 60 77 3 Adhesion promoter Mass-produced parts 10 10 4,8 15,2 10 10 Ratio SBR (B) / SBR (A) (-) 2,7 1,0 1,0 1,0 1,0 1,0 Formability (viscosity) Index value 102 105 80 101 100 102 Wear resistance performance Index value 131 103 108 105 105 126 Wet performance Index value 95 112 99 112 103 117 [Table 5] Comparison example 7 Comparison example 8 Comparison example 9 Comparison example 10 Comparison example 11 Comparison example 12 SBR (A)-1 Mass-produced parts 13 25 30 34 20 SBR (A)-2 Mass-produced parts 30 SBR (B)-1 Mass-produced parts 35,8 (26) 66 (48) 41,3 (30) 41,3 (30) 61,9 (45) SBR (B)-2 Mass-produced parts 41,3 (30) BR Mass-produced parts 61 27 40 40 36 35 CB Mass-produced parts 10 10 10 10 10 10 Silica Mass-produced parts 100 100 100 100 100 100 Thermoplastic resin-1 Mass-produced parts 25 25 25 25 25 25 Aroma oil Mass-produced parts 62 53 71 60 60 54 Adhesion promoter Mass-produced parts 10 10 10 10 10 10 Ratio SBR (B) / SBR (A) (-) 2,0 1,9 - - 0,9 2,3 Formability (viscosity) Index value 98 105 90 120 98 105 Wear resistance performance Index value 131 95 93 103 98 104 Wet performance Index value 80 112 75 115 102 102

[0050] The raw material types used in Tables 1 to 5 are listed below. • SBR (A)-1: terminal-modified styrene-butadiene rubber with polyorganosiloxane structure, NS612 available from ZEON CORPORATION, glass transition temperature -61 °C, weight average molecular weight 450,000, styrene content 15 mass%, vinyl content 30%, non-oil extended product. • SBR (A)-2: terminal-modified styrene-butadiene rubber with polyorganosiloxane structure obtained by the following polymerization process, glass transition temperature -70 °C, weight-average molecular weight 450,000, styrene content 18 mass%, vinyl content 13%, non-oil-extended product. • SBR (A)-3: styrene-butadiene rubber, Tufdene 1000, available from Asahi Kasei Corporation, glass transition temperature -73 °C, weight average molecular weight 290,000, styrene content 18 mass%, vinyl content 12%, non-oil extended product. • SBR (B)-1: modified styrene-butadiene rubber, Tufdene E581, available from Asahi Kasei Corporation, glass transition temperature -34 °C, weight average molecular weight 1,260,000, styrene content 36 mass%, vinyl content 42%, oil extended product containing 37.5 parts by mass of an oil extender. • SBR (B)-2: modified styrene-butadiene rubber, Tufdene E680, available from Asahi Kasei Corporation, glass transition temperature -25 °C, weight average molecular weight 1470000, styrene content 36 mass%, vinyl content 57%, oil extended product containing 37.5 parts by mass of an oil extender. • BR: Butadiene rubber, Nipol BR1220, available from ZEON CORPORATION, glass transition temperature -105 °C, weight average molecular weight 460,000. • Carbon black: DASHBLACK N220, available from OCI Company Ltd. • Silica: ZEOSIL 1165MP, available from Solvay • Thermoplastic Resin-1: aromatic modified terpene resin, YS Resin TO-125, available from Yasuhara Chemical Co., Ltd., glass transition temperature 79 °C • Thermoplastic Resin-2: aromatic modified terpene resin, YS Resin TO-105, available from Yasuhara Chemical Co., Ltd., glass transition temperature 57 °C • Resin-3: C9 resin, Neopolymer S100, available from ENEOSE Corporation, glass transition temperature 58 °C • Resin-4: C5C9 resin, Neopolymer 170S, available from ENEOSE Corporation, glass transition temperature 105 °C • Oil: Extract No. 4S, available from Shell Lubricants Japan KK • Adhesion promoter: Silane adhesion promoter, Si69, available from Evonik Degussa Corporation Polymerization process of SBR (A)-2

[0051] 70.0 g of cyclohexane and 0.77 mmol of tetramethylethylenediamine were added to a nitrogen-purged 800-ml ampoule, 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 allowed to react in the ampoule for 120 minutes at a temperature of 50°C, forming a polymer block with an active end.

[0052] 4000 g of cyclohexane, 1.50 mmol of tetramethylethylenediamine, 445 g of 1,3-butadiene, and 155 g of styrene were added to an autoclave equipped with a stirrer under a nitrogen atmosphere. Subsequently, the entire amount of the active-end polymer block obtained above was added, and polymerization was initiated at 50 °C. Ten minutes after polymerization was initiated, 355 g of 1,3-butadiene and 40 g of styrene were continuously added 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. After confirming that the polymer conversion rate had reached a range of 95% to 100%, 2.44 g of polyorganosiloxane represented by the following formula (I) was added in the form of a xylene solution having a concentration of 40 mass%, and the mixture was allowed to react for 30 minutes.Subsequently, methanol was added as a polymerization terminator in an amount equivalent to twice the number of moles of n-butyllithium used, and a solution containing conjugated diene rubber was obtained. Irganox 1520L (available from BASF) was added to this solution as an anti-aging agent in an amount of 0.15 parts per 100 parts of the conjugated diene rubber, and the solvent was then removed by steam stripping. The remaining mixture was dried under vacuum at 60°C for 24 hours, and a solid conjugated diene rubber (SBR (A)-2) was obtained.

[0053] In the above formula (I), m is 80, k is 120, X 1 , X 4 , R 1 to R 3 and R 5 to R 8 are methyl groups, and X 2 is a group represented by the following formula (II) (where * represents a bonding position). [Table 6] Common additive formulation Anti-aging agents 3,0 Mass-produced parts wax 1,0 Mass part zinc oxide 2,0 Mass-produced parts Stearic acid 1,0 Mass part Vulcanization accelerator-1 2,0 Mass-produced parts Vulcanization accelerator-2 1,0 Mass part sulfur 1,5 Mass-produced parts

[0054] The raw material types used in Table 6 are listed below. • Anti-aging agent: VULANOX 4020, available from LANXESS AG • Wax: OZOACE-0015A, available from NIPPON SEIRO Co., Ltd. • Zinc oxide: Zinc oxide III, available from Seido Chemical Industry Co., Ltd. • Stearic acid: Stearic acid beads, available from NOF Corporation • Vulcanization accelerator-1: NOCCELER CZ-G, available from Ouchi Shinko Chemical Industrial Co., Ltd. • Vulcanization accelerator-2: Soxinol DG, available from Sumitomo Chemical Co., Ltd. • Sulfur: SULFAX 5, available from Tsurumi Chemical Industry Co., Ltd.

[0055] As can be seen from Tables 1 to 3, it was confirmed that the rubber compositions for a tire in Examples 1 to 20 have excellent wear resistance and wet performance, and also have excellent moldability (Mooney viscosity).

[0056] As can be seen from Table 4, the rubber composition for a tire in Comparative Example 1 contains less than 15 parts by mass of SBR (A) with an SBR (B) / SBR (A) mass ratio of over 2, resulting in poor wet performance and an inability to improve moldability (Mooney viscosity). The rubber composition for a tire in Comparative Example 2 contains more than 35 parts by mass of SBR (A) and therefore cannot improve the moldability (Mooney viscosity). The rubber composition for a tire in Comparative Example 3 contains less than 50 parts by mass of silica and therefore cannot improve the wet performance. The rubber composition for a tire in Comparative Example 4 contains more than 150 parts by mass of silica and therefore cannot improve the moldability (Mooney viscosity). The rubber composition for a tire in Comparative Example 5 contains less than 10 parts by mass of the thermoplastic resin and therefore cannot improve the moldability (Mooney viscosity). The rubber composition for a tire in Comparative Example 6 contains more than 80 parts by mass of the thermoplastic resin and therefore cannot improve the moldability (Mooney viscosity).

[0057] As can be seen from Table 5, the rubber composition for a tire in Comparative Example 7 contains less than 15 parts by mass of SBR (A) and thus cannot improve the wear resistance. The rubber composition for a tire in Comparative Example 8 contains less than 30 parts by mass of butadiene rubber and therefore cannot improve the moldability (Mooney viscosity) and wear resistance. The rubber composition for a tire in Comparative Example 9 does not contain SBR (B) and therefore cannot improve the wear resistance and wet performance. The rubber composition for a tire in Comparative Example 10 does not contain SBR (A) and thus deteriorates the moldability (Mooney viscosity). The rubber composition for a tire in Comparative Example 11 has a mass ratio of SBR (B) / SBR (A) of less than 1 and therefore cannot improve the wear resistance. The rubber composition for a tire in Comparative Example 12 has a mass ratio of SBR (B) / SBR (A) of over 2 and therefore cannot improve the moldability (Mooney viscosity).

[0058] The present disclosure includes the following embodiments of the invention. Invention [1] A rubber composition for a tire, wherein the rubber composition contains 50 to 150 parts by mass of silica and 10 to 80 parts by mass of a thermoplastic resin blended per 100 parts by mass of a diene rubber consisting of a styrene-butadiene rubber (A), a styrene-butadiene rubber (B) and a butadiene rubber, where, in 100 mass% of the diene rubber, the butadiene rubber is present in an amount of 30% by mass or more, the styrene-butadiene rubber (A) is present in an amount of 15 to 35 mass% and the styrene-butadiene rubber (B) is present in an amount which is one to two times the mass of the styrene-butadiene rubber (A), wherein the styrene-butadiene rubber (A) has a glass transition temperature of -75 °C to -50 °C, and wherein the styrene-butadiene rubber (B) has a weight-average molecular weight that is at least twice as high as the weight-average molecular weight of the styrene-butadiene rubber (A). Invention [2] The rubber composition for a tire according to invention [1], wherein the styrene-butadiene rubber (A) has a weight-average molecular weight of 300,000 to 600,000. Invention [3] The rubber composition for a tire according to invention [1] or [2], wherein the styrene-butadiene rubber (B) has a glass transition temperature of less than -30 °C.

[0059] Invention [4] The rubber composition for a tire according to any one of inventions [1] to [3], wherein the thermoplastic resin is at least one selected from the group consisting of a resin composed of at least one selected from a terpene, a modified terpene, a rosin, a rosin ester, a C5 component and a C9 component, and a resin in which at least some of the double bonds of this resin are hydrogenated, and the thermoplastic resin has a glass transition temperature of 40 °C to 120 °C. Invention [5] The rubber composition for a tire according to any one of inventions [1] to [4], which further contains a liquid polymer.

[0060] Invention [6] A tire comprising a tread portion made of the rubber composition for a tire according to any one of inventions [1] to [5]. List of reference symbols 1 tread section 2 page section 3 bead section 4 carcass layers 5 Bead core 6 bead fillers 7 inner soul layer 8 Belt layer 9 Belt cover layer 10a Protector tread 10b Underflow area QUOTES CONTAINED IN THE DESCRIPTION

[0000] This list of documents submitted by the applicant was generated automatically and is included solely for the convenience of the reader. This list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions. Cited patent literature

[0000] JP 2021-021070 A

[0005] JP 2006-249069 A

[0032]

Claims

[1] A rubber composition for a tire, wherein the rubber composition comprises 50 to 150 parts by mass of silica and 10 to 80 parts by mass of a thermoplastic resin blended per 100 parts by mass of a diene rubber consisting of a styrene-butadiene rubber (A), a styrene-butadiene rubber (B) and a butadiene rubber, where, in 100 mass% of the diene rubber, the butadiene rubber is present in an amount of 30% by mass or more, the styrene-butadiene rubber (A) is present in an amount of 15 to 35 mass% and the styrene-butadiene rubber (B) is present in an amount which is one to two times the mass of the styrene-butadiene rubber (A), wherein the styrene-butadiene rubber (A) has a glass transition temperature of -75 °C to -50 °C, and wherein the styrene-butadiene rubber (B) has a weight-average molecular weight that is at least twice as high as the weight-average molecular weight of the styrene-butadiene rubber (A). [2] The rubber composition for a tire according to claim 1, wherein the styrene-butadiene rubber (A) has a weight-average molecular weight of 300,000 to 600,000. [3] A rubber composition for a tire according to claim 1 or 2, wherein the styrene-butadiene rubber has a glass transition temperature of below -30°C. [4] The rubber composition for a tire according to claim 1 or 2, wherein the thermoplastic resin is at least one selected from the group consisting of a resin consisting of at least one selected from a terpene, a modified terpene, a rosin, a rosin ester, a C5 component and a C9 component, and a resin in which at least some of the double bonds of this resin are hydrogenated, and the thermoplastic resin has a glass transition temperature of 40°C to 120°C. [5] A rubber composition for a tire according to claim 1 or 2, further comprising a liquid polymer. [6] A tire comprising a tread portion made of the rubber composition for a tire according to claim 1 or 2.

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