Method for producing rubber composition

Abstract

To provide a method for producing a rubber composition which satisfies both rubber hardness and low heat generating property, and has excellent tensile breaking strength, tensile breaking elongation and high temperature property thereof.SOLUTION: A method for producing a rubber composition in which at least one compounding agent selected from zinc oxide, sulfur, vulcanization accelerator, and vulcanization retarder is compounded into a rubber component containing isoprene-based rubber by 10 mass% or more and hydrogenated aromatic vinyl-conjugated diene copolymer by 10 mass% or more, where the method has a step of using a master batch for rubber in which 40 to 500 pts.mass of at least a part of the compounding agent is compounded into 100 pts.mass of diene-based rubber containing the hydrogenated aromatic vinyl-conjugated diene copolymer, and compounding the master batch for rubber, the isoprene-based rubber, the hydrogenated aromatic vinyl-conjugated diene copolymer and the remainder of the compounding agent, and the content of A mass% of the hydrogenated aromatic vinyl-conjugated diene copolymer in the diene-based rubber is larger than the content of B mass% of the hydrogenated aromatic vinyl-conjugated diene copolymer in the rubber component.SELECTED DRAWING: None

Description

[Technical field]

[0001] The present invention relates to a method for producing a rubber composition which has both high rubber hardness and low heat build-up, and is excellent in tensile strength at break, tensile elongation at break, and their high-temperature properties. [Background technology]

[0002] In order to reduce the environmental load, there is a particular demand for lighter tires and lower heat generation. For example, a method is known in which a rubber component with a low glass transition temperature (Tg) is compounded to change the behavior of the loss tangent (tan δ) of the rubber (see, for example, Patent Documents 1 and 2). These methods are mainly used for tread rubber, but there is a limit to how much lower heat generation and lighter weight a tire can be achieved by only reducing tan δ (60°C). For example, for components such as undertreads, sidewalls and / or rim cushions that use high-hardness rubber compositions to improve the steering stability of tires, technology that achieves both high rubber hardness and low heat generation has not yet been fully developed.

[0003] The inventors have been studying rubber compositions containing hydrogenated aromatic vinyl-conjugated diene copolymers in order to achieve both low heat buildup and rubber hardness, but the tensile strength at break, tensile elongation at break, and these high-temperature properties tend to be lower than in the past. However, in recent years, there has been an increasing demand for achieving both rubber hardness and low heat buildup to reduce the weight of tires, and there is a strong demand for solving these problems while maintaining and improving the tensile strength at break, tensile elongation, and these high-temperature properties. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Patent Publication No. 2021-035801 [Patent Document 2] Patent Publication No. 2021-066371 Summary of the Invention [Problem to be solved by the invention]

[0005] An object of the present invention is to provide a method for producing a rubber composition which maintains and improves tensile strength at break, tensile elongation at break, and these high-temperature properties while simultaneously achieving both rubber hardness and low heat build-up. [Means for solving the problem]

[0006] The method for producing a rubber composition according to the present invention for achieving the above object is a method for producing a rubber composition, which comprises blending at least one compounding agent selected from the group consisting of zinc oxide, sulfur, a vulcanization accelerator, and a vulcanization retarder with a rubber component containing 10% by mass or more of an isoprene-based rubber and 10% by mass or more of a hydrogenated aromatic vinyl-conjugated diene copolymer, and the method comprises the steps of using a rubber master batch in which 40 to 500 parts by mass of at least a part of the compounding agent is blended with 100 parts by mass of a diene-based rubber containing the hydrogenated aromatic vinyl-conjugated diene copolymer, and blending the rubber master batch with the isoprene-based rubber, the hydrogenated aromatic vinyl-conjugated diene copolymer, and the remainder of the compounding agents, wherein the content A (mass%) of the hydrogenated aromatic vinyl-conjugated diene copolymer in 100% by mass of the diene-based rubber in the rubber master batch is greater than the content B (mass%) of the hydrogenated aromatic vinyl-conjugated diene copolymer in 100% by mass of the rubber component in the rubber composition.

[0007] The rubber masterbatch of the present invention for achieving the above object is characterized in that 100 parts by mass of a diene-based rubber containing a hydrogenated aromatic vinyl-conjugated diene copolymer is blended with 40 to 500 parts by mass of at least one compounding agent selected from the group consisting of zinc oxide, sulfur, a vulcanization accelerator, and a vulcanization retarder. Effect of the Invention

[0008] The method for producing a rubber composition of the present invention uses a rubber masterbatch having a high content (A mass %) of hydrogenated aromatic vinyl-conjugated diene copolymer, and therefore the compounding ingredients consisting of zinc oxide, sulfur, vulcanization accelerator, and vulcanization retarder are present in a larger amount in the hydrogenated aromatic vinyl-conjugated diene copolymer phase, thereby obtaining a rubber composition that has both rubber hardness and low heat build-up, and maintains and improves the room temperature properties and high temperature properties of tensile strength at break and tensile elongation at break.

[0009] The rubber composition to be produced may preferably contain zinc oxide in the rubber master batch, and may achieve excellent rubber hardness and low heat build-up, and may achieve an even higher level of effects of improving room temperature and high temperature properties of tensile strength at break and tensile elongation at break. The hydrogenated aromatic vinyl-conjugated diene copolymer may preferably have a weight average molecular weight of 200,000 or more, a glass transition temperature of -40°C or less, and a hydrogenation rate of 60% or more. The rubber composition to be produced may further comprise a rubber master batch containing zinc oxide and a CTAB specific surface area of ​​60 to 120 m per 100 parts by mass of the rubber component. 2 It is preferable to mix 10 parts by mass or more of silica having a silica content of 10 parts by mass / g.

[0010] A tire manufactured by using the rubber composition obtained by the above-mentioned manufacturing method in the undertread, sidewall and / or rim cushion achieves both weight reduction and fuel efficiency while maintaining and improving the room temperature and high temperature properties of tensile breaking strength and tensile breaking elongation, and therefore has excellent external damage resistance, high speed durability and load durability.

[0011] The rubber masterbatch of the present invention has a high content of hydrogenated aromatic vinyl-conjugated diene copolymer and can be suitably used in a method for producing a rubber composition containing the hydrogenated aromatic vinyl-conjugated diene copolymer, and the rubber composition can have both high rubber hardness and low heat build-up, and can maintain and improve the room temperature properties and high temperature properties of tensile strength at break and tensile elongation at break. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0012] In this specification, the diene rubber contained in the rubber masterbatch is referred to as "diene rubber", and the diene rubber contained in the rubber composition is referred to as "rubber component". The rubber component contained in the rubber composition is the total of the diene rubber blended during production and the diene rubber contained in the rubber masterbatch. The vulcanization compounding agent contained in the rubber composition is the total of the vulcanization compounding agent blended during production and the vulcanization compounding agent contained in the rubber masterbatch. The vulcanization compounding agent refers to at least one compounding agent selected from the group consisting of zinc oxide, sulfur, vulcanization accelerator, and vulcanization retarder.

[0013] The method for producing a rubber composition of the present invention is a method for producing a rubber composition using a rubber master batch. The rubber master batch is a premixture obtained by compounding 40 to 500 parts by mass of at least one compounding agent selected from the group consisting of zinc oxide, sulfur, vulcanization accelerators, and vulcanization retarders with 100 parts by mass of diene rubber containing a hydrogenated aromatic vinyl-conjugated diene copolymer. The rubber master batch may be produced in one step in the method for producing a rubber composition, or may be produced in a separate step and stored. In addition, an appropriate one may be prepared from commercially available products, or one compounded in the production process of the raw material polymer may be used.

[0014] The hydrogenated aromatic vinyl-conjugated diene copolymer is blended into the rubber master batch and the rubber composition so that the content A% by mass in 100% by mass of the diene rubber in the rubber master batch is greater than the content B% by mass in 100% by mass of the rubber component in the rubber composition. A rubber master batch is prepared so that the content A% by mass of the hydrogenated aromatic vinyl-conjugated diene copolymer in the rubber master batch is greater than the content B% by mass in 100% by mass of the rubber component in the rubber composition, and blended into the rubber composition, so that the vulcanization compounding agent is present in a greater amount in the phase of the hydrogenated aromatic vinyl-conjugated diene copolymer, and the vulcanization of the hydrogenated aromatic vinyl-conjugated diene copolymer with a small amount of carbon-carbon double bonds can be promoted. This makes it possible to maintain and improve the room temperature and high temperature properties of the tensile strength at break and the tensile elongation at break of the rubber composition. The content A (mass%) of the hydrogenated aromatic vinyl-conjugated diene copolymer in 100 mass% of diene rubber in the rubber masterbatch is not particularly limited as long as the above-mentioned conditions are satisfied, but is preferably 40 mass% or more, more preferably 50 mass% or more, even more preferably 50 to 100 mass%, even more preferably 65 to 100 mass%, and particularly preferably 80 to 100 mass%.

[0015] The hydrogenated aromatic vinyl-conjugated diene copolymer in the rubber masterbatch may be the same as or different from the hydrogenated aromatic vinyl-conjugated diene copolymer contained in the rubber composition to which the rubber masterbatch is compounded. The hydrogenated aromatic vinyl-conjugated diene copolymer will be described later.

[0016] The diene rubber of the rubber masterbatch may contain other diene rubbers other than the hydrogenated aromatic vinyl-conjugated diene copolymer. Examples of other diene rubbers include natural rubber, isoprene rubber, etc., non-hydrogenated aromatic vinyl-conjugated diene copolymers (styrene butadiene rubber, etc.), butadiene rubber, butyl rubber, halogenated butyl rubber, acrylonitrile-butadiene rubber, etc. These other diene rubbers may be modified diene rubbers having functional groups, and may be used alone or in any blend. As the other diene rubber, isoprene rubber is preferred, and the content of the other diene rubber, which can improve the cohesion of the rubber masterbatch containing a large amount of vulcanization compounding agents, is preferably 50 mass% or less, more preferably 0 to 50 mass%, even more preferably 0 to 35 mass%, and even more preferably 0 to 20 mass% in 100 mass% of the diene rubber.

[0017] The rubber master batch is prepared by compounding 40 to 500 parts by mass of a vulcanization compounding agent with 100 parts by mass of diene rubber containing A% by mass of hydrogenated aromatic vinyl-conjugated diene copolymer. The vulcanization compounding agent is at least one selected from the group consisting of zinc oxide, sulfur, vulcanization accelerators, and vulcanization retarders. One rubber master batch may contain one or more types of vulcanization compounding agents. Zinc oxide is a preferred vulcanization compounding agent. A plurality of vulcanization compounding agents can be freely combined. When the rubber master batch contains a plurality of types of vulcanization compounding agents, the total amount of the vulcanization compounding agents is 40 to 500 parts by mass. The vulcanization compounding agent is preferably 80 parts by mass or more, more preferably 120 parts by mass or more, and even more preferably 160 parts by mass or more, relative to 100 parts by mass of the diene rubber of the rubber master batch. The amount of the vulcanization compounding agent is preferably 440 parts by mass or less, more preferably 360 parts by mass or less, and further preferably 280 parts by mass or less.

[0018] The method for producing the rubber masterbatch can use a known rubber kneading machine, such as a Banbury mixer or kneader, to mix and knead at a temperature lower than the temperature at which the vulcanization compounding agents function. The temperature for producing the rubber masterbatch is preferably 70°C to 140°C, more preferably 90°C to 130°C.

[0019] The method for producing a rubber composition of the present invention uses one or more of the above-mentioned rubber masterbatches. For example, one type of rubber masterbatch containing zinc oxide may be used, or two types of rubber masterbatch containing zinc oxide and sulfur may be used. Furthermore, four types of rubber masterbatches may be used, including two types of rubber masterbatches containing different vulcanization accelerators, a rubber masterbatch containing zinc oxide, and a rubber masterbatch containing sulfur. Although multiple rubber masterbatches can be freely combined, it is preferable to use a rubber masterbatch containing zinc oxide.

[0020] The composition of the rubber composition produced by the production method of the present invention is determined as the sum of the composition of one or more rubber masterbatches and the composition of the rubber components and vulcanization compounding agents to be compounded. The production method of the rubber composition has a step of compounding one or more rubber masterbatches with the isoprene-based rubber, the hydrogenated aromatic vinyl-conjugated diene copolymer, and the remaining vulcanization compounding agents, taking into account the final composition of the rubber composition.

[0021] The content A% by mass of hydrogenated aromatic vinyl-conjugated diene copolymer in 100% by mass of diene rubber in the rubber master batch is set to be greater than the content B% by mass of hydrogenated aromatic vinyl-conjugated diene copolymer in 100% by mass of rubber component in the final composition of the rubber composition. The content A% by mass of hydrogenated aromatic vinyl-conjugated diene copolymer in the rubber master batch is set to be greater than the content B% by mass of hydrogenated aromatic vinyl-conjugated diene copolymer in the final composition, so that the vulcanization compounding agent is present in a greater amount in the phase of hydrogenated aromatic vinyl-conjugated diene copolymer in the final composition, and vulcanization of the hydrogenated aromatic vinyl-conjugated diene copolymer with a small amount of carbon-carbon double bonds can be promoted. This makes it possible to obtain a rubber composition that has both rubber hardness and low heat generation, and maintains and improves the room temperature properties and high temperature properties of tensile strength at break and tensile elongation at break.

[0022] When a plurality of rubber masterbatches are used in a rubber composition, it is preferable that the content A (mass%) of the hydrogenated aromatic vinyl-conjugated diene copolymer in each rubber masterbatch is greater than the content B (mass%) of the hydrogenated aromatic vinyl-conjugated diene copolymer in the final composition. In addition, the total content of the hydrogenated aromatic vinyl-conjugated diene copolymer derived from the plurality of rubber masterbatches is preferably 16 parts by mass or less, more preferably 12 parts by mass or less, and even more preferably 8 parts by mass or less, per 100 parts by mass of the rubber component in the final composition.

[0023] The method for producing the rubber composition can be mixed and kneaded using a known rubber kneading machine, such as a Banbury mixer or kneader. The method for producing the rubber composition has a so-called non-process kneading step in which compounding ingredients other than sulfur, vulcanization accelerator, vulcanization retarder, etc. are kneaded, and a so-called final kneading step in which sulfur, vulcanization accelerator, vulcanization retarder, etc. are added to the kneaded product obtained in the non-process kneading step and mixed at a relatively low temperature. In the production method of the present invention, the rubber master batch containing zinc oxide is kneaded together with a rubber component and inorganic fillers such as silica and carbon black in the non-process kneading step, and the rubber master batch containing at least one of sulfur, vulcanization accelerator, and vulcanization retarder is mixed and kneaded in the final kneading step. It is also possible to use zinc oxide, sulfur, vulcanization accelerator, vulcanization retarder, etc. other than the rubber master batch.

[0024] The final composition of the rubber composition produced by the production method of the present invention (hereinafter, sometimes simply referred to as "rubber composition") will be described below. The rubber composition contains an isoprene-based rubber and a hydrogenated aromatic vinyl-conjugated diene copolymer as rubber components. By containing an isoprene-based rubber, a rubber composition having an excellent balance between the processability and physical properties of the unvulcanized rubber can be obtained. Examples of the isoprene-based rubber include natural rubber and isoprene rubber. The content of the isoprene-based rubber is 10% by mass or more, preferably 20 to 70% by mass, more preferably 25 to 65% by mass, and even more preferably 30 to 60% by mass, based on 100% by mass of the rubber component. If the isoprene-based rubber is less than 10% by mass, the effect of improving the processability and physical properties cannot be sufficiently obtained. Also, if it exceeds 90% by mass, the effect of the hydrogenated aromatic vinyl-conjugated diene copolymer cannot be sufficiently obtained.

[0025] The rubber composition contains a hydrogenated aromatic vinyl-conjugated diene copolymer, and while ensuring fatigue resistance equivalent to that of butadiene rubber, the rubber composition can achieve both rubber hardness and low heat buildup, and can also achieve ozone resistance and heat aging resistance that are superior to conventional levels. The hydrogenated aromatic vinyl-conjugated diene copolymer is contained in an amount of 10% by mass or more, preferably 20 to 80% by mass, more preferably 30 to 75% by mass, and even more preferably 40 to 70% by mass, based on 100% by mass of the rubber component. If the hydrogenated aromatic vinyl-conjugated diene copolymer is less than 10% by mass, the effect of achieving both rubber hardness and low heat buildup, and of improving fatigue resistance, ozone resistance, and heat aging resistance, is not sufficiently obtained. In addition, the effect of increasing the tensile breaking strength is not sufficiently obtained. On the other hand, if it exceeds 90% by mass, the effect of the isoprene-based rubber is not sufficiently obtained.

[0026] In this specification, the hydrogenated aromatic vinyl-conjugated diene copolymer is a rubber component obtained by hydrogenating an aromatic vinyl-conjugated diene copolymer. The aromatic vinyl-conjugated diene copolymer is a copolymer of aromatic vinyl and conjugated diene, and is preferably a random copolymer. Examples of aromatic vinyl compounds constituting the aromatic vinyl-conjugated diene copolymer include styrene, methylstyrene, ethylstyrene, t-butylstyrene, α-methylstyrene, α-methyl-p-methylstyrene, chlorostyrene, bromostyrene, methoxystyrene, dimethylaminomethylstyrene, dimethylaminoethylstyrene, diethylaminomethylstyrene, diethylaminoethylstyrene, cyanoethylstyrene, and vinylnaphthalene. Among these, styrene is preferred. Examples of conjugated diene compounds constituting the aromatic vinyl-conjugated diene copolymer include 1,3-butadiene, isoprene (2-methyl-1,3-butadiene), 2,3-dimethyl-1,3-butadiene, 2-chloro-1,3-butadiene, and 1,3-pentadiene. Examples of aromatic vinyl-conjugated diene copolymers include styrene-butadiene copolymer rubber (SBR) and styrene-isoprene copolymer rubber. In addition to the aromatic vinyl compound and the conjugated diene compound, the aromatic vinyl-conjugated diene copolymer may contain any other copolymerizable monomer. The polymerization method for the aromatic vinyl-conjugated diene copolymer may be any of solution polymerization, gas phase polymerization, and bulk polymerization, but the solution polymerization method is preferred. In addition, the polymerization method may be any of batch and continuous.

[0027] The method and conditions for the reaction of hydrogenating (hydrogenating) an aromatic vinyl-conjugated diene polymer are not particularly limited. Examples of the method for hydrogenating an aromatic vinyl-conjugated diene polymer include a method using a catalyst mainly composed of an organometallic compound of titanium as a hydrogenation catalyst, a method using a catalyst composed of an organic compound of iron, nickel, or cobalt and an organometallic compound such as alkylaluminum, a method using an organic complex of an organometallic compound such as ruthenium or rhodium, and a method using a catalyst in which a metal such as palladium, platinum, ruthenium, cobalt, or nickel is supported on a carrier such as carbon, silica, or alumina.

[0028] The hydrogenated aromatic vinyl-conjugated diene copolymer preferably has a weight average molecular weight of 200,000 or more, a glass transition temperature of -40°C or less, and a hydrogenation rate of 60% or more. The weight average molecular weight of the hydrogenated aromatic vinyl-conjugated diene copolymer is more preferably 200,000 to 700,000, and even more preferably 250,000 to 600,000. When the weight average molecular weight of the hydrogenated aromatic vinyl-conjugated diene copolymer is 200,000 or more, the rubber hardness and tensile strength at break of the rubber composition can be increased. In addition, when the weight average molecular weight is 700,000 or less, the viscosity increase of the rubber composition is suppressed, and both processability and strength are achieved, which is preferable. In this specification, the weight average molecular weight of the hydrogenated aromatic vinyl-conjugated diene copolymer can be a polystyrene-equivalent value measured by gel permeation chromatography (GPC).

[0029] The hydrogenated aromatic vinyl-conjugated diene copolymer preferably has a glass transition temperature of -40°C or lower, more preferably -80°C to -40°C, and even more preferably -75°C to -40°C. When the hydrogenated aromatic vinyl-conjugated diene copolymer has a glass transition temperature of -40°C or lower, it is preferable that the copolymer can ensure sufficient flexibility even when used in cold regions. In addition, when the glass transition temperature is -80°C or higher, it is preferable that a tire rubber composition having an excellent balance between hardness and flexibility can be obtained. In this specification, the glass transition temperature can be determined as the midpoint temperature of the transition region measured by differential scanning calorimetry (DSC) at a temperature rise rate of 20°C / min.

[0030] The hydrogenated aromatic vinyl-conjugated diene copolymer preferably has a hydrogenation rate (hydrogenation rate) of 60% or more, more preferably 60 to 90%, and even more preferably 60 to 80%. If the hydrogenation rate is less than 60%, the ozone resistance is deteriorated. In addition, it is not possible to improve fatigue resistance and heat aging resistance while simultaneously achieving rubber hardness and low heat buildup. Furthermore, sufficient tensile strength at break is not obtained. By setting the hydrogenation rate to less than 100%, crosslinkability can be imparted to the hydrogenated aromatic vinyl-conjugated diene copolymer. In this specification, the hydrogenation rate refers to the percentage (%) of hydrogenated carbon-carbon bonds in the conjugated diene portion of the aromatic vinyl-conjugated diene copolymer relative to the total of carbon-carbon double bonds before hydrogenation (100%). A hydrogenation rate of 100% means that the carbon-carbon double bonds in the conjugated diene portion have been completely hydrogenated. The hydrogenation rate is 1 It can be calculated from the spectral reduction rate of the unsaturated bond in the conjugated diene portion of the spectrum obtained by measuring H-NMR.

[0031] The rubber composition may contain other diene rubbers other than the isoprene rubber and the hydrogenated aromatic vinyl-conjugated diene copolymer. Examples of other diene rubbers include non-hydrogenated aromatic vinyl-conjugated diene copolymers (such as styrene butadiene rubber), butadiene rubber, butyl rubber, halogenated butyl rubber, acrylonitrile-butadiene rubber, and the like. These other diene rubbers may be modified diene rubbers having functional groups, and may be used alone or as any blend. The content of the other diene rubber is preferably 0 to 40% by mass, more preferably 0 to 30% by mass, based on 100% by mass of the diene rubber.

[0032] The rubber composition is preferably a rubber having a CTAB specific surface area of ​​60 to 170 m, and 100 parts by mass of the diene rubber. 2 The silica having a specific surface area of ​​65 to 120 m is preferably blended in an amount of 10 parts by mass or more. 2 / g, more preferably 70 to 90m 2 / g. The CTAB specific surface area of ​​silica is preferably 60m 2 When the tensile strength is 170m / g or more, the rubber strength and rubber hardness of the rubber composition can be maintained and improved. 2 When the CTAB specific surface area is set to 1 / g or less, the fatigue resistance can be improved and the heat buildup can be reduced. In this specification, the CTAB specific surface area of ​​silica can be measured in accordance with JIS K6217-3.

[0033] CTAB specific surface area is 60~120m 2 The amount of silica having a molecular weight of 100 to 1000 parts by mass of the diene rubber is preferably 10 parts by mass or more, more preferably 10 to 180 parts by mass, further preferably 15 to 130 parts by mass, and even more preferably 20 to 90 parts by mass. When the amount of silica is 10 parts by mass or more, the fatigue resistance, low heat build-up property, and ozone resistance can be maintained or improved to levels equal to or higher than those of the conventional level.

[0034] As the silica, silica normally used in rubber compositions, such as wet-process silica, dry-process silica, or surface-treated silica, can be used. In addition, it is preferable to compound a silane coupling agent together with the silica, which can improve the dispersibility of the silica and further increase the reinforcing property with the diene rubber. The silane coupling agent is preferably compounded in an amount of 3 to 20 mass%, more preferably 4 to 15 mass%, based on the amount of silica. If the amount of the silane coupling agent is less than 3 mass% of the silica weight, the effect of improving the dispersibility of the silica may not be sufficiently obtained. In addition, if the amount of the silane coupling agent is more than 20 mass%, the silane coupling agents may condense with each other, and the desired effect may not be obtained.

[0035] The rubber composition may contain inorganic fillers other than the specific silica. The rubber composition may contain 10 to 200 parts by mass of an inorganic filler containing preferably 10% by mass or more of the specific silica in 100 parts by mass of diene rubber. The mass ratio of silica in 100% by mass of the inorganic filler is more preferably 20 to 90% by mass, further preferably 30 to 80% by mass, and further more preferably 40 to 70% by mass. By containing 10% by mass or more of the specific silica, fatigue resistance can be improved, heat build-up can be reduced, and ozone resistance can be improved.

[0036] The inorganic filler containing specific silica is preferably blended in an amount of 10 to 200 parts by mass, more preferably 15 to 150 parts by mass, even more preferably 20 to 120 parts by mass, and even more preferably 25 to 100 parts by mass, per 100 parts by mass of diene rubber. If the inorganic filler is less than 10 parts by mass, the rubber strength and rubber hardness of the rubber composition are insufficient, and the steering stability and external damage resistance of the tire may not be sufficiently obtained. If the inorganic filler is more than 200 parts by mass, heat generation may not be sufficiently suppressed.

[0037] Other examples of inorganic fillers include carbon black, clay, calcium carbonate, mica, talc, aluminum hydroxide, aluminum oxide, titanium oxide, barium sulfate, etc. Of these, carbon black is preferred.

[0038] It is preferable to compound carbon black in the rubber composition because it is possible to increase the rubber strength and rubber hardness of the rubber composition. The nitrogen adsorption specific surface area of ​​carbon black is preferably 30 to 120 m 2 / g, more preferably 30 to 100m 2 / g, more preferably 40 to 90m 2 / g. The nitrogen adsorption specific surface area of ​​carbon black is 30 m 2 When the carbon black has a nitrogen adsorption specific surface area of ​​120 m / g or more, the rubber strength and hardness of the rubber composition can be ensured, which is preferable. 2By setting the nitrogen adsorption specific surface area of ​​carbon black to be not more than 1 / g, heat buildup can be reduced, which is preferable. In this specification, the nitrogen adsorption specific surface area of ​​carbon black can be measured in accordance with JIS K6217-2.

[0039] Carbon black may be blended with furnace black, acetylene black, thermal black, channel black, graphite, etc. Among these, furnace black is preferred. Carbon black may be used alone or in combination of two or more kinds. Surface-treated carbon black obtained by chemically modifying carbon black with various acid compounds or the like may also be used.

[0040] In addition to the above components, various compounding agents generally used in rubber compositions, such as vulcanizing or crosslinking agents, vulcanization accelerators, antiaging agents, processing aids, plasticizers, liquid polymers, thermosetting resins, and thermoplastic resins, can be compounded in the rubber composition in a conventional manner. Such compounding agents can be kneaded in a conventional manner to prepare a rubber composition, which can then be used for vulcanization or crosslinking. The compounding amounts of these compounding agents can be conventional amounts as long as they do not go against the object of the present invention.

[0041] The rubber composition obtained by the manufacturing method of the present invention is suitable for forming the undertread, sidewall and / or rim cushion of a tire. A tire having an undertread, sidewall and / or rim cushion formed from the above-mentioned rubber composition has excellent fatigue resistance, ozone resistance and heat aging resistance beyond conventional levels while simultaneously achieving both weight reduction and low fuel consumption performance, and also maintains and improves the room temperature and high temperature properties of tensile strength at break and tensile elongation at break, resulting in excellent external damage resistance, high speed durability and load durability.

[0042] The present invention will be further described below with reference to examples, but the scope of the present invention is not limited to these examples. EXAMPLES

[0043] In preparing the rubber masterbatches (ZnO-MB1-4) shown in Table 1, the rubber components, stearic acid, and zinc oxide were weighed, mixed in a 1.7-liter closed Banbury mixer for 5 minutes until the temperature reached approximately 130°C, and then the mixture was discharged from the mixer. The mixture was air-cooled to room temperature to obtain the rubber masterbatches (ZnO-MB1-4). In preparing the rubber masterbatches (S-MB, Ac-MB1-4, and Re-MB) shown in Table 1, the rubber components, stearic acid, sulfur, vulcanization accelerator, and vulcanization retarder were weighed, mixed in a 1.7-liter closed Banbury mixer for 5 minutes until the temperature reached approximately 110°C, and then the mixture was discharged from the mixer. The mixture was air-cooled to room temperature to obtain the rubber masterbatches (S-MB, Ac-MB1-4, and Re-MB).

[0044] [Table 1]

[0045] The types of raw materials used in Table 1 are shown below. NR: Natural rubber, TSR20 Stearic acid: Stearic acid beads manufactured by NOF CORPORATION Hydrogenated SBR: Hydrogenated aromatic vinyl-conjugated diene copolymer obtained by the polymerization method described below, with a styrene content of 2% by mass, a vinyl content of 25% by mass, a hydrogenation rate of 75%, a weight average molecular weight of 400,000, and a glass transition temperature of -65°C. Zinc oxide: Three types of zinc oxide manufactured by Seido Chemical Industry Co., Ltd. Soluble sulfur: Tsurumi Chemical Industry Co., Ltd. Kinkaji oil-filled fine sulfur Vulcanization accelerator-1: Noccela CZ-G manufactured by Ouchi Shinko Chemical Co., Ltd. Vulcanization accelerator-2: Sancerer DG (DPG) manufactured by Sanshin Chemical Industry Co., Ltd. Vulcanization accelerator-3: Sancerer TBzTD manufactured by Sanshin Chemical Industry Co., Ltd. Vulcanization accelerator-4: Bayer Vulcren KA9188, 1,6-bis(N,N'-dibenzylthiocarbamoyldithio)hexane · Vulcanization retarder: Toray Fine Chemical Co., Ltd. Retarder CTP (PVI)

[0046] Polymerization method for hydrogenated SBR (hydrogenated aromatic vinyl-conjugated diene copolymer) In a nitrogen-purged 10L autoclave reactor, 4200g of cyclohexane, styrene (15g, 0.144mol), butadiene (585g, 10.85mol), tetrahydrofuran (0.433g, 6.0mmol) and 2,2-di(2-tetrahydrofuryl)propane (0.037g, 0.20mmol) were charged and stirring was started. After the temperature of the contents in the reaction vessel was raised to 50°C, a hexane solution of n-butyllithium (3.03ml at a concentration of 1.55mol / L, 4.69mmol of n-butyllithium) was added. After the polymerization conversion rate reached almost 100%, 2,2-dimethoxy-1-(3-trimethoxysilylpropyl)-1-aza-2-silacyclopentane (0.254g, 0.82mmol) was added and reacted for 30 minutes. After the reaction, methanol (80.1 mg, 2.5 mmol) was added to stop the reaction, and a portion was extracted and dried for analysis. The styrene content was 2 mass%, the vinyl content was 25 mass% in butadiene, the weight average molecular weight was 400,000, and the glass transition temperature was -65°C. The reaction solution was heated to 80°C or higher and hydrogen was introduced into the system. Next, 0.70 g of a catalyst mainly composed of titanocene dichloride, 1.2 g of diethylaluminum chloride, and 0.30 g of n-butyllithium were added, and the reaction was carried out while maintaining a hydrogen pressure of 1.0 MPa. After reaching a predetermined cumulative hydrogen flow rate, the reaction solution was returned to room temperature and pressure and extracted from the reaction vessel to obtain a polymerization solution. After neutralization, solid rubber was recovered by steam stripping. The obtained solid rubber was dehydrated by rolls and dried in a dryer to obtain hydrogenated SBR. The hydrogenation rate was 75%.

[0047] In preparing the rubber compositions (Examples 1 to 6, Comparative Examples 1 to 3) having the common compounding formulation shown in Table 3 and composed of the formulation shown in Table 2, the components other than sulfur, vulcanization accelerator, vulcanization retarder, and rubber master batch containing sulfur, vulcanization accelerator, and vulcanization retarder were weighed and kneaded for 5 minutes in a 1.7-liter closed Banbury mixer, and then the kneaded product was discharged outside the mixer and cooled at room temperature. This kneaded product was fed to the same Banbury mixer, and sulfur, vulcanization accelerator, vulcanization retarder, and rubber master batch containing sulfur, vulcanization accelerator, and vulcanization retarder were added and mixed to produce a rubber composition. The compounding formulations in Table 3 are listed in parts by mass relative to 100 parts by mass of the rubber components listed in Table 2.

[0048] The rubber compositions obtained above were vulcanized in a mold of a predetermined shape at 160°C for 20 minutes to prepare evaluation samples. Using the obtained evaluation samples, the rubber hardness at 23°C, dynamic viscoelasticity (loss tangent tanδ), tensile strength at break at 23°C and 100°C, and tensile elongation at break were measured by the following methods.

[0049] Rubber hardness at 23℃ (lightweight tires) Using the obtained evaluation sample of the rubber composition, the rubber hardness was measured at a temperature of 23°C with a type A durometer in accordance with JIS K6253. The obtained results were recorded in the "rubber hardness" column as an index with the value of Comparative Example 1 being 100. A higher index means that the tire can be made lighter.

[0050] Dynamic viscoelasticity (loss tangent tanδ) The dynamic viscoelasticity of the evaluation sample of the obtained rubber composition was measured using a viscoelasticity spectrometer manufactured by Iwamoto Seisakusho Co., Ltd. under conditions of an elongation deformation strain rate of 10±2%, a vibration frequency of 20 Hz, and a temperature of 60°C, and tan δ(60°C) was calculated. The obtained tan δ(60°C) value was recorded in the column "tan δ(60°C)" as an index with the value of Comparative Example 1 being 100. The smaller this index, the smaller the heat buildup and the lower the rolling resistance.

[0051] Tensile strength and elongation at break at 23℃ and 100℃ Using the obtained rubber composition evaluation sample, a No. 3 dumbbell-shaped test piece was cut out in accordance with JIS K6251. In accordance with JIS K6251, the tensile breaking strength and tensile breaking elongation at 23 ° C. and the tensile breaking strength and tensile breaking elongation at 100 ° C. were measured, and the ratio of the tensile breaking strength at 100 ° C. to the tensile breaking strength at 23 ° C. and the ratio of the tensile breaking elongation at 100 ° C. to the tensile breaking strength at 23 ° C. were calculated. The obtained tensile breaking strength and tensile breaking elongation values ​​at 23 ° C. were listed in the "tensile breaking strength" and "tensile breaking elongation" columns as indexes with the value of Comparative Example 1 set to 100. The larger the "tensile breaking strength" and "tensile breaking elongation", the lighter the tire can be, and the more excellent the flex fatigue resistance and external damage resistance are. In addition, the value of the ratio of the tensile breaking strength at 100 ° C. to the tensile breaking strength at 23 ° C. was listed in the "high temperature breaking strength ratio" column as an index with the value of the ratio of Comparative Example 1 set to 100. Furthermore, the ratio of the tensile breaking elongation at 100°C to the tensile breaking elongation at 23°C is shown in the "High temperature breaking elongation ratio" column as an index with the ratio value of Comparative Example 1 being 100. The larger the "high temperature breaking strength ratio" and the "high temperature breaking elongation ratio", the more excellent the high speed durability properties and the load durability properties are.

[0052] [Table 2]

[0053] The types of raw materials used in Table 2 are shown below. Hydrogenated SBR: Hydrogenated aromatic vinyl-conjugated diene copolymer obtained by the above-mentioned polymerization method, with a styrene content of 2% by mass, a vinyl content of 25% by mass, a hydrogenation rate of 75%, a weight average molecular weight of 400,000, and a glass transition temperature of -65°C. NR: Natural rubber, TSR20 ZnO-MB1-4: Masterbatches for rubber containing zinc oxide listed in Table 1 S-MB: Masterbatch for rubber containing soluble sulfur as listed in Table 1 Ac-MB1-4: Masterbatches for rubber containing the vulcanization accelerators listed in Table 1 Re-MB: Masterbatch for rubber containing the vulcanization retarders listed in Table 1 Zinc oxide: Three types of zinc oxide manufactured by Seido Chemical Industry Co., Ltd. Stearic acid: Stearic acid beads manufactured by NOF CORPORATION Soluble sulfur: Tsurumi Chemical Industry Co., Ltd. Kinkaji oil-filled fine sulfur Vulcanization accelerator-1: Noccela CZ-G manufactured by Ouchi Shinko Chemical Co., Ltd. Vulcanization accelerator-2: Sancerer DG (DPG) manufactured by Sanshin Chemical Industry Co., Ltd. · Vulcanization retarder: Toray Fine Chemical Co., Ltd. Retarder CTP (PVI)

[0054] [Table 3]

[0055] The types of raw materials used in Table 3 are shown below. Carbon black: Tokai Carbon Co., Ltd.'s Seast F, nitrogen adsorption specific surface area is 41m 2 / g Silica: Solvay Zeosil 1085GR, CTAB specific surface area 85m 2 / g Coupling agent: Silane coupling agent, Si69 manufactured by Evonik Degussa Japan Anti-aging agent: SANTOFLEX 6PPD manufactured by Solutia Europe Wax: Ozoace 0015A made by Nippon Seiro Co., Ltd. Aroma oil: Idemitsu Kosan Diana Process NH-70S

[0056] As is clear from Table 2, the rubber compositions of Examples 1 to 6 were confirmed to be excellent in rubber hardness at 23°C, dynamic viscoelasticity (tan δ at 60°C), tensile strength at break and tensile elongation at break at 23°C, as well as the ratio of tensile strength at break at 100°C to tensile strength at 23°C and the ratio of tensile elongation at break at 100°C to tensile elongation at 23°C. In the rubber composition of Comparative Example 2, since the rubber master batch ZnO-MB3 does not contain hydrogenated SBR, the rubber hardness at 23°C is small, the tan δ (60°C) is large, and the tensile break strength and tensile break elongation at 23°C, the ratio of the tensile break strength at 100°C to the tensile break strength at 23°C, and the ratio of the tensile break elongation at 100°C to the tensile break elongation at 23°C are poor. In the rubber composition of Comparative Example 3, since the rubber master batch ZnO-MB4 contains less than 40 parts by mass of a vulcanization accelerator (zinc oxide), the rubber hardness at 23°C is small, tan δ (60°C) is large, and the tensile breaking strength and tensile breaking elongation at 23°C, as well as the ratio of the tensile breaking strength at 100°C to the tensile breaking strength at 23°C and the ratio of the tensile breaking elongation at 100°C to the tensile breaking elongation at 23°C are poor.

[0057] The present invention includes the following inventions. Invention [1] A method for producing a rubber composition comprising a rubber component containing 10% by mass or more of an isoprene-based rubber and 10% by mass or more of a hydrogenated aromatic vinyl-conjugated diene copolymer, and at least one compounding agent selected from the group consisting of zinc oxide, sulfur, a vulcanization accelerator, and a vulcanization retarder, the method comprising the steps of using a rubber master batch in which 40 to 500 parts by mass of at least a portion of the compounding agent is compounded with 100 parts by mass of a diene-based rubber containing the hydrogenated aromatic vinyl-conjugated diene copolymer, and compounding the rubber master batch, the isoprene-based rubber, the hydrogenated aromatic vinyl-conjugated diene copolymer, and the remainder of the compounding agents, wherein the content A (mass%) of the hydrogenated aromatic vinyl-conjugated diene copolymer in 100% by mass of the diene-based rubber in the rubber master batch is greater than the content B (mass%) of the hydrogenated aromatic vinyl-conjugated diene copolymer in 100% by mass of the rubber component in the rubber composition. Invention [2] The method for producing a rubber composition according to invention [1], wherein the rubber masterbatch contains 40 mass% or more of the hydrogenated aromatic vinyl-conjugated diene copolymer based on 100 mass% of the diene rubber. Invention [3] The method for producing a rubber composition according to invention [1] or [2], characterized in that the rubber masterbatch contains zinc oxide. Invention [4] The method for producing a rubber composition according to any one of inventions [1] to [3], characterized in that the hydrogenated aromatic vinyl-conjugated diene copolymer has a weight average molecular weight of 200,000 or more, a glass transition temperature of -40°C or less, and a hydrogenation rate of 60% or more. Invention [5] The rubber component is mixed with 100 parts by mass of a rubber having a CTAB specific surface area of ​​60 to 100 m 2 10 parts by mass or more of silica having a molecular weight of 100 / g are blended in the rubber composition. Invention [6] A method for producing a tire, characterized in that a rubber composition obtained by the production method according to any one of Inventions [1] to [5] is used in an undertread, a sidewall and / or a rim cushion. Invention [7] A masterbatch for rubber, comprising 100 parts by mass of a diene rubber containing a hydrogenated aromatic vinyl-conjugated diene copolymer, and 40 to 500 parts by mass of at least one compounding agent selected from the group consisting of zinc oxide, sulfur, a vulcanization accelerator, and a vulcanization retarder. Invention [8] The rubber masterbatch according to invention [7], comprising 40 mass% or more of the hydrogenated aromatic vinyl-conjugated diene copolymer based on 100 mass% of the diene rubber. Invention [9] The rubber masterbatch according to invention [7] or [8], characterized in that it contains zinc oxide.

Claims

1. A method for producing a rubber composition comprising blending a rubber component containing 10% by mass or more of an isoprene-based rubber and 10% by mass or more of a hydrogenated aromatic vinyl-conjugated diene copolymer with at least one compounding agent selected from the group consisting of zinc oxide, sulfur, a vulcanization accelerator and a vulcanization retarder, the method comprising the steps of using a rubber master batch in which 40 to 500 parts by mass of at least a portion of the compounding agents are blended with 100 parts by mass of a diene-based rubber containing the hydrogenated aromatic vinyl-conjugated diene copolymer, and blending the rubber master batch with the isoprene-based rubber, the hydrogenated aromatic vinyl-conjugated diene copolymer and the remainder of the compounding agents, wherein a content A (mass %) of the hydrogenated aromatic vinyl-conjugated diene copolymer in 100% by mass of the diene-based rubber in the rubber master batch is greater than a content B (mass %) of the hydrogenated aromatic vinyl-conjugated diene copolymer in 100% by mass of the rubber component in the rubber composition.

2. 2. The method for producing a rubber composition according to claim 1, wherein the rubber master batch contains 40% by mass or more of the hydrogenated aromatic vinyl-conjugated diene copolymer based on 100% by mass of the diene rubber.

3. 3. The method for producing a rubber composition according to claim 1, wherein the rubber master batch contains zinc oxide.

4. The method for producing a rubber composition according to claim 1 or 2, characterized in that the hydrogenated aromatic vinyl-conjugated diene copolymer has a weight average molecular weight of 200,000 or more, a glass transition temperature of -40°C or less, and a hydrogenation rate of 60% or more.

5. 100 parts by mass of the rubber component has a CTAB specific surface area of ​​60 to 100 m ２ 3. The method for producing a rubber composition according to claim 1, wherein 10 parts by mass or more of silica having a molecular weight of 1 / g are blended.

6. A method for producing a tire, comprising using a rubber composition obtained by the method according to claim 1 or 2 for an undertread, a sidewall and / or a rim cushion.

7. A rubber master batch comprising 100 parts by mass of a diene rubber containing a hydrogenated aromatic vinyl-conjugated diene copolymer and 40 to 500 parts by mass of at least one compounding agent selected from the group consisting of zinc oxide, sulfur, a vulcanization accelerator, and a vulcanization retarder.

8. The rubber master batch according to claim 7, characterized in that the hydrogenated aromatic vinyl-conjugated diene copolymer is contained in an amount of 40 mass% or more based on 100 mass% of the diene rubber.

9. 9. The rubber masterbatch according to claim 7 or 8, further comprising zinc oxide.

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