Rubber composition, outsole, method for manufacturing the rubber composition, and method for manufacturing a crosslinked rubber sheet

Abstract

To provide a rubber composition improved in abrasion resistance and in strength of the rubber composition after crosslinking without impairing the processability of the rubber composition.SOLUTION: A rubber composition contains (A): a styrene-butadiene copolymer rubber of 5-50 mass% having a mass ratio of styrene block amount to bound styrene amount of 0.02-0.23, a 1,2-vinyl bound amount in a butadiene portion of 10-60 mass%, and a bound styrene amount of 35-55 mass%, and having a Mooney viscosity in a range of 80-110; and (B): a rubber component containing a diene-based rubber having a Mooney viscosity of 20 or more and less than 80 of 50-95 mass% which is at least one selected from a group consisting of a natural rubber, a diene-based synthetic rubber, and a block copolymer of an aromatic vinyl compound and a conjugated diene compound, (C): a filler of 10-50 pts.mass, and (D): a fatty acid and / or a fatty acid derivative of 0.01-1 pts.mass based on 100 pts.mass of the rubber component consisting of (A) and (B).SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a rubber composition, an outsole, a method for producing a rubber composition, and a method for producing a crosslinked rubber sheet. [Background technology]

[0002] Footwear outsoles require not only functional properties such as abrasion resistance, but also fashionability, such as transparency to allow the design and / or color of the midsole (the middle layer of the footwear) to show through. Various rubber compositions have been developed with the aim of manufacturing such footwear outsoles.

[0003] Patent Document 1 discloses a rubber composition with excellent transparency, comprising a two-component rubber polymer having a predetermined refractive index difference and wet silica. Furthermore, Patent Document 2 discloses a rubber composition that combines a low-cis isoprene rubber component (hereinafter also referred to as "IR") that is substantially free of silica with other rubber components. Furthermore, Patent Documents 3 and 4 disclose rubber compositions for footwear soles using block styrene-butadiene rubber (hereinafter also referred to as "SBR") and / or random SBR. [Prior art documents] [Patent Documents]

[0004] [Patent Document 1] Japanese Patent Publication No. 2005-2225 [Patent Document 2] Japanese Patent Publication No. 2017-66423 [Patent Document 3] International Publication No. 2018 / 193555 [Patent Document 4] Japanese Patent Application Laid-Open No. 63-11102 [Overview of the Initiative] [Problems that the invention aims to solve]

[0005] However, the rubber composition described in Patent Document 1 has the problem that its abrasion resistance and / or strength may be insufficient. Furthermore, the rubber composition described in Patent Document 2 uses a combination of rubbers with different refractive indices, such as low-cis isoprene rubber and 1,2-polybutadiene, and is considered to have insufficient transparency as a whole. In addition, the examples in Patent Document 2 only use crosslinked rubber compositions containing rubber components in combinations of low-cis isoprene rubber / 1,2-polybutadiene or low-cis isoprene rubber / butadiene, and combinations of other low-cis isoprene rubber (IR) with styrene-butadiene rubber (SBR), acrylonitrile butadiene rubber (NBR), hydrogenated nitrile rubber (HNBR), urethane rubber (U), ethylene propylene rubber (EPM), ethylene propylene diene rubber (EPDM), or chloroprene rubber (CR) are not disclosed, and no studies have been conducted to improve transparency. Moreover, none of the examples in Patent Document 2 contain fillers, which results in the problem of low strength properties. Furthermore, the rubber compositions for footwear soles described in Patent Documents 3 and 4 also have the problem of insufficient transparency and abrasion resistance.

[0006] In light of the problems with conventionally disclosed technologies as described above, regarding rubber compositions that constitute footwear soles, increasing the molecular weight of the rubber tends to increase the abrasion resistance of the rubber composition, but this also increases viscosity, worsening processability, and furthermore, it becomes difficult to knead the rubber with the filler sufficiently, resulting in a problem where the effect of improving strength and abrasion resistance through the dispersion of the filler in the rubber composition is not realized.

[0007] Therefore, in view of the problems of the prior art described above, the present invention aims to provide a rubber composition that is highly processable and also has excellent strength and abrasion resistance. [Means for solving the problem]

[0008] As a result of diligent research to solve the above problems, the present inventors have found that a rubber composition comprising a predetermined styrene-butadiene copolymer rubber, a predetermined diene rubber, a filler, and a fatty acid and / or a fatty acid derivative exhibits excellent processability and superior abrasion resistance and strength of the crosslinked rubber composition, thus completing the present invention. In other words, the present invention is as follows.

[0009] [1] (A): The mass ratio of styrene block amount to bound styrene amount is 0.02 to 0.23. The amount of 1,2-vinyl bonds in the butadiene portion is 10-60% by mass. The amount of bound styrene is 35-55% by mass. And, Mooney viscosity is in the range of 80-110. 5-50% by mass of styrene-butadiene copolymer rubber, (B): 50 to 95% by mass of a diene rubber selected from the group consisting of natural rubber, diene-based synthetic rubber, and block copolymers of aromatic vinyl compounds and conjugated diene compounds, wherein the Mooney viscosity is 20 or more and less than 80. The rubber components contained therein, With respect to 100 parts by mass of the rubber component consisting of (A) styrene-butadiene copolymer rubber and (B) diene rubber, (C): Filler 10 to 50 parts by mass, (D): 0.01 to 1 part by mass of fatty acids and / or fatty acid derivatives A rubber composition containing the following. [2] The rubber composition according to [1], further containing 0 to 5 parts by mass of (E) liquid diene rubber per 100 parts by mass of the rubber component comprising (A) styrene-butadiene copolymer rubber and (B) diene rubber. [3] The rubber composition according to [1] or [2], wherein the amount of styrene blocks in the (A) styrene-butadiene copolymer rubber is 0.70 to 12% by mass. [4] The refractive index of the (A) styrene-butadiene copolymer rubber is 1.530 to 1.570, the refractive index of the (B) diene rubber is 1.450 to 1.530, and the refractive index of the (C) filler is 1.370 to 1.500, the rubber composition according to any one of the above [1] to [3]. [5] The rubber composition according to any one of the above [1] to [4], wherein the bound styrene amount of the (A) styrene-butadiene copolymer rubber is 40 to 50% by mass. [6] The rubber composition according to any one of the above [1] to [5], wherein the (C) filler is at least one selected from the group consisting of silica, magnesium carbonate, carbon black, and magnesium hydroxide. [7] The rubber composition according to any one of the above [1] to [6], wherein the (D) fatty acid and / or fatty acid derivative has an alkyl group or alkenyl group having 8 to 30 carbon atoms. [8] The (E) liquid diene rubber is butadiene and / or an oligomer of styrene-butadiene or acrylonitrile-butadiene, and the rubber composition according to any one of the above [2] to [7]. [9] The rubber composition according to any one of the above [1] to [8], having a HAZE value of 10 to 40%.

[10] An outsole containing the rubber composition according to any one of the above [1] to [9].

[11] (A) A veil containing 98 to 99.98% by mass of styrene-butadiene copolymer rubber and 0.02 to 2% by mass of (D) fatty acid and / or fatty acid derivative, (B) At least one selected from the group consisting of natural rubber, diene synthetic rubber, and a block copolymer of an aromatic vinyl compound and a conjugated diene compound, and having a Mooney viscosity of 20 or more and less than 80, The above (A) and the above (B) are such that the mass ratio of (A) / (B) is 5 / 95 to 50 / 50, and The process involves kneading 100 parts by mass of rubber components consisting of (A) and (B) with 10 to 50 parts by mass of filler (C), The (A) styrene-butadiene copolymer rubber has a ratio of styrene block amount to bound styrene amount of 0.02 to 0.23, a 1,2-vinyl bond content of the butadiene portion of 10 to 60% by mass, a bound styrene content of 35 to 55% by mass, and a Mooney viscosity of 80 to 110. A method for producing a rubber composition.

[12] A bale containing (A) 98-99.98% by mass of styrene-butadiene copolymer rubber and (D) 0.02-2% by mass of fatty acids and / or fatty acid derivatives, (B) A diene rubber selected from the group consisting of natural rubber, diene-based synthetic rubber, and block copolymers of aromatic vinyl compounds and conjugated diene compounds, wherein the Mooney viscosity is 20 or more and less than 80, The above (A) and the above (B) are such that the mass ratio of (A) / (B) is 5 / 95 to 50 / 50, and A step of kneading 100 parts by mass of rubber components consisting of (A) and (B) with 10 to 50% by mass of (C) filler to obtain a kneaded product, The process involves mixing (G) a crosslinking agent into the aforementioned mixture and then pressurizing and / or heating it, It has, The (A) styrene-butadiene copolymer rubber has a ratio of styrene block amount to bound styrene amount of 0.02 to 0.23, a 1,2-vinyl bond content of the butadiene portion of 10 to 60% by mass, a bound styrene content of 35 to 55% by mass, and a Mooney viscosity of 80 to 110. A method for manufacturing cross-linked rubber sheets. [Effects of the Invention]

[0010] According to the present invention, it is possible to provide a rubber composition that improves the abrasion resistance and strength of the crosslinked rubber composition without impairing the processability of the rubber composition. [Modes for carrying out the invention]

[0011] The following describes in detail embodiments for carrying out the present invention (hereinafter referred to as "these embodiments"). The following embodiments are illustrative for explaining the present invention, and the present invention is not limited to these embodiments. The present invention can be implemented by modifying it as appropriate within the scope of its gist.

[0012] [Rubber composition] The rubber composition of this embodiment is (A): The mass ratio of styrene block amount to bound styrene amount is 0.02 to 0.23. The amount of 1,2-bonds in the butadiene portion is 10-60% by mass. The amount of bound styrene is 35-55% by mass. It contains 5-50% by mass of styrene-butadiene copolymer rubber, with a Mooney viscosity in the range of 80-110. (B): 50 to 95% by mass of a diene rubber selected from the group consisting of natural rubber, diene-based synthetic rubber, and block copolymers of aromatic vinyl compounds and conjugated diene compounds, wherein the Mooney viscosity is 20 or more and less than 80. The rubber components contained therein, With respect to 100 parts by mass of the rubber component consisting of (A) styrene-butadiene copolymer rubber and (B) diene rubber, (C): Filler 10 to 50 parts by mass, (D): 0.01 to 1 part by mass of fatty acids and / or fatty acid derivatives It contains.

[0013] According to this embodiment, it is possible to provide a rubber composition that improves the abrasion resistance and strength of the crosslinked rubber composition without impairing the processability of the rubber composition.

[0014] ((A) Styrene-butadiene copolymer rubber) The rubber composition of this embodiment contains (A) styrene-butadiene copolymer rubber (which may be referred to as component (A) in this specification). Component (A) has a mass ratio of styrene block amount / bonded styrene amount of 0.02 to 0.23, a 1,2-bonded amount of the butadiene portion of 10 to 60% by mass, a bonded styrene amount of 35 to 55% by mass, and a Mooney viscosity at 100°C measured in accordance with JIS K6300-1 of the range of 80 to 110. The inventors have found that a rubber composition containing (A) styrene-butadiene copolymer rubber in a predetermined proportion exhibits excellent abrasion resistance and superior processability (ease of mixing) when processed into molded articles such as outsoles.

[0015] In this specification, styrene-butadiene copolymer rubber means a copolymer of styrene monomer and butadiene monomer. Hereinafter, in styrene-butadiene copolymer rubber, the portion derived from styrene monomer will be referred to as the styrene portion, and the portion derived from butadiene monomer will be referred to as the butadiene portion.

[0016] <Amount of bound styrene> (A) The styrene-butadiene copolymer rubber has a bound styrene content of 35 to 55% by mass. This results in a rubber composition with excellent mechanical properties such as tensile strength and tear strength. From a similar viewpoint, the bound styrene content of component (A) is preferably 38 to 53% by mass, more preferably 40 to 50% by mass. When the amount of bound styrene is 35-55% by mass, the refractive index of (A) styrene-butadiene copolymer rubber is approximately 1.544-1.561. In this specification, "bound styrene content" means the content (mass%) of styrene monomer units in (A) styrene-butadiene copolymer rubber. That is, in (A) styrene-butadiene copolymer rubber, the bound styrene content means the mass ratio of the styrene portion to the total mass of the styrene portion and the butadiene portion, and therefore represents the total amount of styrene monomer units constituting the styrene blocks contained in component (A), and, if component (A) has random blocks, the total amount of styrene monomer units contained in the random blocks. The amount of bound styrene can be calculated by measuring the ultraviolet absorption of the phenyl groups of the styrene portion in (A) styrene-butadiene copolymer rubber. More specifically, it can be measured using the method described in the examples below. The amount of bound styrene can be controlled to the above-mentioned numerical range by adjusting the amount of styrene monomer added during the synthesis of (A) styrene-butadiene copolymer rubber.

[0017] In addition, the butadiene content (mass%) in (A) styrene-butadiene copolymer rubber is the value obtained by subtracting the amount of bound styrene (mass%) from 100% by mass.

[0018] <Mass ratio of styrene block amount / bound styrene amount> (A) The mass ratio of the amount of styrene blocks to the amount of bound styrene in the styrene-butadiene copolymer rubber (hereinafter also referred to as the "mass ratio of styrene block amount / bound styrene amount") is 0.02 to 0.23. This allows the rubber composition to be controlled to the desired physical properties while ensuring excellent abrasion resistance. From a similar viewpoint, the mass ratio of styrene block amount / bound styrene amount is preferably 0.02 to 0.22, and more preferably 0.02 to 0.20. A mass ratio of styrene block amount to bound styrene amount of 0.23 or less provides good abrasion resistance. When designing a transparent molded body, the mass ratio of styrene block amount to bound styrene amount is preferably 0.030 or higher, and more preferably 0.040 or higher.

[0019] In this specification, "styrene block amount" refers to the content (mass%) of the portion in (A) styrene-butadiene copolymer rubber in which styrene monomers are bonded in groups of 8 or more, and can be measured by the method described in the examples below. Therefore, the mass ratio of styrene block amount to bonded styrene amount means the mass ratio of the styrene portion existing as styrene blocks to the total styrene portion in (A) styrene-butadiene copolymer rubber. The amount of styrene block can be measured by a known method in which the copolymer is decomposed by Kolthoff's method (osmium tetroxide decomposition method described in IMKolthoff, et al., J. Polym. Sci. 1, 429 (1946)) and the amount of methanol-insoluble styrene block is analyzed. More specifically, the method described in the examples below can be used. The amount of styrene block can be controlled by adjusting the amount of randomizing agent added during polymerization of (A) styrene-butadiene copolymer rubber, and the styrene block amount / bound styrene amount can be controlled within the above numerical range. Increasing the amount of randomizing agent tends to decrease the amount of styrene block.

[0020] <Wine Blocking Amount> (A) The amount of styrene blocks in component (A) is preferably 0.70% by mass or more and 12% by mass or less, more preferably 0.70% by mass or more and 8% by mass or less, and even more preferably 0.70% by mass or more and 4% by mass or less. (A) The amount of styrene blocks in component (A) is preferably 0.70% by mass or more from the viewpoint of polymer productivity, and preferably 12% by mass or less from the viewpoint of wear resistance. The amount of styrene blocks in component (A) can be controlled to the above numerical range by adjusting the amount of randomizing agent added in the polymerization process, as described above.

[0021] <Amount of 1,2-vinyl bond> The amount of 1,2-vinyl bonds in the butadiene portion affects the glass transition temperature of (A) styrene-butadiene copolymer rubber and influences the abrasion resistance of the rubber composition. Component (A) has a 1,2-vinyl bond content of 10 to 60% by mass in the butadiene portion. This allows for high abrasion resistance while ensuring transparency and strength of the rubber composition. The 1,2-vinyl bond content of the butadiene portion is preferably 13 to 50% by mass, and more preferably 15 to 40% by mass. By setting the 1,2-vinyl bond content of the butadiene portion to 10% by mass or more, it tends to be possible to design a highly transparent product depending on the refractive index settings of other coexisting components. Furthermore, by setting the 1,2-vinyl bond content of the butadiene portion to 60% by mass or less, it tends to be easier to increase the abrasion resistance and strength of the rubber composition.

[0022] Generally, when butadiene monomers polymerize, they can be added to the polymer by 1,2-addition or 1,4-addition. In this specification, "amount of 1,2-vinyl bonds in the butadiene portion" means the ratio (mass%) of the butadiene portion polymerized by 1,2-addition to the total butadiene portion. The butadiene portion polymerized by 1,2-addition exists as a portion having vinyl groups in the styrene-butadiene copolymer rubber before crosslinking, and the butadiene portion polymerized by 1,4-addition exists as a portion having double bonds in the main chain of the styrene-butadiene copolymer rubber before crosslinking. The amount of 1,2-vinyl bond in the butadiene moiety can be measured, for example, by Hampton's method using an infrared spectrophotometer (RR Hampton, Analytical Chemistry, 21, 923 (1949)). More specifically, it can be measured by the method described in the examples below. The amount of 1,2-vinyl bonds in the butadiene portion can be adjusted to the above-mentioned numerical range by adjusting the amount of vinylizing agent added during polymerization of the styrene-butadiene copolymer rubber. Increasing the amount of vinylizing agent tends to increase the amount of 1,2-vinyl bonds in the butadiene portion.

[0023] <Moony viscosity> (A) The styrene-butadiene copolymer rubber has a Mooney viscosity at 100°C measured in accordance with JIS K6300-1 (hereinafter sometimes simply referred to as "Mooney viscosity") of 80 to 110. When the Mooney viscosity of component (A) is 80 or higher, the abrasion resistance and strength of the rubber composition of this embodiment tend to be improved compared to when using styrene-butadiene copolymer rubber with a Mooney viscosity of less than 80. However, when the Mooney viscosity of component (A) is 80 or higher, the processability of the uncrosslinked rubber composition is lower than that of the unvulcanized rubber composition using styrene-butadiene copolymer rubber with a Mooney viscosity of less than 80. However, if the Mooney viscosity is in the range of 80 to 110, excellent processability can be obtained by adding (D) fatty acids and / or fatty acid derivatives, described later, to the rubber composition. The amount of (D) fatty acids and / or fatty acid derivatives added should be determined within a range that does not impair the abrasion resistance and strength of the rubber composition. From the viewpoint of improving the processability of the rubber composition of this embodiment, it is preferable to increase the amount of (D) fatty acids and / or fatty acid derivatives added, or to add (E) liquid diene rubber, described later. However, these may affect the strength of the rubber composition of this embodiment, so it is preferable to set the type and amount of additive according to the physical properties of the crosslinked rubber composition to be used.

[0024] In the rubber composition of this embodiment, it is preferable to add (D) fatty acids and / or fatty acid derivatives in order to ensure processability, but from the viewpoint of strength, it is preferable to set the amount of (D) fatty acids and / or fatty acid derivatives added to a low level. From this viewpoint, the Mooney viscosity of component (A) is preferably 81 to 105, more preferably 83 to 100. In this specification, Mooney viscosity is defined as the torque after 4 minutes of operation using an L-type rotor, preheated at 100°C for 1 minute. (ML) 1+4 Measure (100℃). More specifically, the method described in the examples below can be used.

[0025] The Mooney viscosity of component (A) can be controlled to a value of 80 to 110 by appropriately adjusting the amount of styrene bonded in the (A) styrene-butadiene copolymer rubber, the amount of 1,2-vinyl bonded in the butadiene portion, the amount of styrene blocks, molecular weight, coupling agent, coupling rate, and molecular weight distribution. Specifically, increasing the amount of 1,2-vinyl bonds, styrene block content, molecular weight, and coupling rate leads to an increase in Mooney viscosity. In particular, increasing the amount of styrene block content and increasing the number of branches with a coupling agent significantly increases Mooney viscosity. Furthermore, Mooney viscosity has a high correlation with styrene block content; although it depends on the molecular weight, a styrene block content of around 5% by mass tends to increase Mooney viscosity by about 10. Furthermore, increasing the number of branches in component (A) using a coupling agent tends to increase Mooney viscosity. Generally, as the molecular weight distribution broadens, the Mooney viscosity tends to decrease. For example, when setting the mass-average molecular weight of a styrene-butadiene copolymer to 150,000, the Mooney viscosity can be controlled to 80-110 by increasing the amount of styrene block to about 20% by mass, or by branching component (A) through coupling. However, as long as the Mooney viscosity is within a specified range, this is not intended to limit the above values.

[0026] <Refractive index> (A) The styrene-butadiene copolymer rubber preferably has a refractive index of 1.530 to 1.570. This makes it easier to appropriately set the refractive index of other components to be mixed in, from the viewpoint of transparency of the rubber composition, and tends to improve the transparency of the rubber composition of this embodiment. When the rubber composition of this embodiment is a crosslinked rubber composition, from the viewpoint of obtaining a transparent crosslinked rubber composition, the refractive index of (A) styrene-butadiene copolymer rubber is more preferably 1.535 to 1.570, and even more preferably 1.540 to 1.565. (A) If the refractive index of the styrene-butadiene copolymer rubber is outside the range of 1.530 to 1.570, the transparency of the rubber composition of this embodiment tends to decrease.

[0027] In this specification, the refractive indices of (A) styrene-butadiene copolymer rubber, (B) diene rubber, and (C) filler are measured in accordance with Japanese Industrial Standard JIS K0062. More specifically, they can be measured by the method described in the examples below. (A) The refractive index of the styrene-butadiene copolymer rubber is greatly influenced by the amount of bonded styrene, and can be controlled to the above numerical range by adjusting the amount of bonded styrene. In rubber compositions, transparency is achieved when the refractive indices of the constituent components are similar. For example, if the refractive indices are 1.55 for component (A), 1.51 for component (B), and 1.47 for component (C), component (C) will adhere to component (A), so the average of components (A) and (C) will be close to that of component (B), resulting in high transparency. Here, since the refractive index of component (A) increases with increasing styrene content, the amount of component (C) needs to be increased accordingly.

[0028] It is generally known that changing the refractive index of the components contained in a rubber composition changes the overall transparency of the rubber composition. The inventors have found that the transparency of the entire rubber composition can be improved by controlling the refractive index of (B) diene rubber to a value between the refractive index of (A) styrene-butadiene copolymer rubber and the refractive index of (C) filler. Furthermore, as a result of further diligent investigation, they have found that even when the refractive index of (B) diene rubber is not a value between the refractive index of (A) styrene-butadiene copolymer rubber and the refractive index of (C) filler, the transparency of the entire rubber composition can be improved by keeping the refractive indices of (A) styrene-butadiene copolymer rubber, (C) filler, and (B) diene rubber within a predetermined range. From the above viewpoint, in the rubber composition of this embodiment, (A) the preferred refractive index of the styrene-butadiene copolymer rubber is 1.530 to 1.570, (B) the preferred refractive index of the diene rubber is 1.450 to 1.530, and (C) the preferred refractive index of the filler is 1.370 to 1.500.

[0029] From the above viewpoints, it is preferable that the refractive index of the (B) diene rubber is controlled to be a value between the refractive index of the (A) styrene-butadiene copolymer rubber and the refractive index of the (C) filler. More preferably, the refractive index of the (B) diene rubber is not less than the refractive index of the (C) filler and not more than the refractive index of the (A) styrene-butadiene copolymer rubber. Preferably, the refractive index of the (B) diene rubber is within the range of the mass-weighted average value ± 0.0260 of the refractive index of the (C) filler and the refractive index of the (A) styrene-butadiene copolymer rubber.

[0030] <Peak top molecular weight> (A) The peak top molecular weight of the styrene-butadiene copolymer rubber measured by the GPC measurement method is not particularly limited, but is preferably 5.00×10 4 or more and 90.0×10 4 or less. When coupling is performed using a coupling agent during the synthesis of the (A) styrene-butadiene copolymer rubber, two peaks, a peak derived from the uncoupled copolymer rubber and a peak derived from the coupled copolymer rubber, are observed in the GPC measurement. The peak top molecular weight at the peak derived from the uncoupled copolymer rubber is preferably 10.0×10 4 or more and 50.0×10 4 or less, more preferably 13.0×10 4 or more and 50.0×10 4 or less, and even more preferably 15.0×10 4 or more and 45.0×10 4 or less. When the peak top molecular weight is within the above range, the transparency and strength of the rubber composition of the present embodiment tend to be improved in a well-balanced manner. In this specification, the peak top molecular weight is the molecular weight determined from the position of the apex of the distribution measured by gel permeation chromatography (GPC) measurement using polystyrene as a standard substance. More specifically, the peak top molecular weight can be measured by the method described in the examples below. The peak top molecular weight of (A) styrene-butadiene copolymer rubber can be controlled by adjusting the polymerization conditions and the amount and type of coupling agent added. Specifically, reducing the amount of polymerization initiator relative to the monomer, increasing the polymerization time, or coupling with a coupling agent tends to increase the peak top molecular weight of (A) styrene-butadiene copolymer rubber.

[0031] <Molecular weight distribution> (A) The styrene-butadiene copolymer rubber is not particularly limited in terms of its molecular weight distribution (ratio of mass-average molecular weight to number-average molecular weight), and is, for example, 1.03 to 2.50, preferably 1.10 to 2.00. In this specification, the molecular weight distribution is calculated using the mass-average molecular weight measured by the GPC method and the number-average molecular weight measured by the GPC method. The molecular weight distribution can be controlled by appropriately adjusting the polymerization conditions.

[0032] <Coupling Rate> (A) The styrene-butadiene copolymer rubber may be coupled with a coupling agent (polymerization coupling). The coupling rate when coupled is not particularly limited and may be, for example, 0.10% to 95%, 5.0% to 90%, 10% to 88%, 30% to 85%, or 50% to 83%. The coupling rate can be determined from the peak areas of the peaks originating from uncoupled copolymer rubber and the peaks originating from coupled copolymer rubber, as detected by the GPC measurement method. As a coupling agent, for example, the coupling agent described later can be used.

[0033] <(A) Method for producing styrene-butadiene copolymer rubber> (A) Styrene-butadiene copolymer rubber can be synthesized, for example, by polymerizing styrene monomer and butadiene monomer in a suitable solvent with a suitable polymerization initiator. The styrene monomer and butadiene monomer may be mixed at once or in multiple steps. The polymerization initiation temperature (i.e., the temperature at which the polymerization initiator is added), the polymerization peak temperature (i.e., the highest temperature reached during the polymerization process), and the polymerization time can be appropriately adjusted according to the desired properties of the (A) styrene-butadiene copolymer rubber.

[0034] The polymerization initiation temperature is not particularly limited, and is, for example, 40°C to 80°C, preferably 45°C to 70°C, and more preferably 50°C to 65°C. The polymerization peak temperature is not particularly limited, and is, for example, 50°C to 100°C, preferably 60°C to 95°C, and more preferably 70°C to 90°C. The polymerization time is not particularly limited, but is, for example, 30 seconds to 30 minutes after reaching the polymerization peak temperature, preferably 45 seconds to 15 minutes after reaching the polymerization peak temperature, and more preferably 1.0 minute to 5.0 minutes after reaching the polymerization peak temperature. Polymerization reactions are stopped by adding polymerization inhibitors such as methanol, or coupling agents as described later.

[0035] Any inert hydrocarbon solvent used in the synthesis of conventionally known styrene-butadiene copolymers can be used as the solvent for polymerization. Examples of solvents include, but are not limited to, linear and branched hydrocarbons such as pentane, hexane, heptane, and octane, and their alkyl-substituted derivatives; alicyclic hydrocarbons such as cyclopentane, cyclohexane, and cycloheptane, and their alkyl-substituted derivatives; aromatic hydrocarbons such as benzene, naphthalene, toluene, and xylene, and their alkyl-substituted derivatives; and hydrogenated aromatic hydrocarbons such as tetralin and decalin, and their alkyl-substituted derivatives. These solvents may be used individually or in combination of two or more.

[0036] The polymerization initiator used in polymerization may be any polymerization initiator conventionally used in the synthesis of styrene-butadiene copolymers (e.g., radical polymerization initiators, living polymerization initiators, etc.). It is preferable to use a lithium polymerization initiator because it tends to yield a styrene-butadiene copolymer rubber with less residue and contributes to high transparency. As a lithium polymerization initiator, for example, an organolithium compound can be used, and for example, an organolithium compound that is monosubstituted to tetrasubstituted with a hydrocarbon group having 1 to 20 carbon atoms, preferably a hydrocarbon group having 2 to 8 carbon atoms, can be used. From the viewpoint of improving transparency, emulsion polymerization is undesirable.

[0037] Examples of organolithium compounds include, but are not limited to, alkyllithium (methyllithium, ethyllithium, propyllithium, n-butyllithium, s-butyllithium, and t-butyllithium, etc.), aryllithium (phenyllithium and tolyllithium, etc.), alkenyllithium (vinyllithium and propenyllithium, etc.), and alkylenelithium (tetramethylenelithium and pentamethylenelithium, etc.). Among these, alkyllithium is preferably used as a polymerization initiator, and n-butyllithium is more preferably used. These organolithium compounds may be used individually or in combination of two or more.

[0038] (A) In the polymerization step of the styrene-butadiene copolymer rubber, additives may be added to the reaction system to control the amount of styrene blocks and / or the amount of 1,2-vinyl bonds in the butadiene portion. Examples of such additives include vinylizing agents and randomizing agents. (A) In the polymerization step of the styrene-butadiene copolymer rubber, it is preferable that at least a vinylizing agent is added.

[0039] Examples of vinyling agents include, but are not limited to, diethyl ether, ethylene glycol-dimethyl ether, ethylene glycol-di-n-butyl ether, ethylene glycol-n-butyl-t-butyl ether, ethylene glycol-di-t-butyl ether, diethylene glycol-dimethyl ether, triethylene glycol-dimethyl ether, tetrahydrofuran, α-methoxytetrahydrofuran, 2-methoxymethyltetrahydrofuran, dioxane, 1,2-dimethoxybenzene, triethylamine, N,N,N',N'-tetramethylethylenediamine, and 2,2'-ditetrahydrofurylpropane. These vinyling agents may be used individually or in combination of two or more. Furthermore, when the amount of vinylizing agent added increases, it can not only increase the amount of 1,2-vinyl bonds in the butadiene portion, but also function as a randomizing agent that reduces the amount of styrene block.

[0040] Randomizing agents include, but are not limited to, potassium-t-amyl alkoxide and potassium-t-butyl alkoxide. These randomizing agents tend to reduce the amount of styrene block without affecting the amount of 1,2-vinyl bond in the butadiene moiety.

[0041] When adding a vinyling agent, the amount added is not particularly limited, but the ratio to the amount of polymerization initiator added should be adjusted. The amount of vinyling agent added may be, for example, 0.050 to 1.0 moles per 1.0 mole of polymerization initiator, preferably 0.10 to 0.80 moles, and more preferably 0.12 to 0.70 moles. Furthermore, when a randomizing agent is added, the amount added is not particularly limited, but it can be adjusted in proportion to the amount of polymerization initiator added. The amount of randomizing agent added may be, for example, 0.010 to 0.50 moles per 1.0 mole of polymerization initiator, preferably 0.020 to 0.30 moles, and more preferably 0.030 to 0.10 moles.

[0042] ((B) At least one selected from the group consisting of natural rubber, diene-based synthetic rubber (excluding the above component (A)), and block copolymers of aromatic vinyl compounds and conjugated diene compounds) The rubber composition of this embodiment contains a diene rubber (which may be referred to as (B) diene rubber or (B) component in this specification) selected from the group consisting of natural rubber, diene-based synthetic rubber, and block copolymers of aromatic vinyl compounds and conjugated diene compounds, and having a Mooney viscosity of 20 or more and less than 80.

[0043] In this embodiment, (B) diene rubber can be natural rubber, diene synthetic rubber, or a block copolymer of an aromatic vinyl compound and a conjugated diene compound. "Diene-based rubber" means rubber having at least a portion derived from a diene compound monomer, that is, rubber obtained by polymerizing at least a diene compound monomer. Here, the diene compound monomer constituting the diene-based rubber may be a conjugated diene compound or a non-conjugated diene compound. Component (B) is preferably derived from a conjugated diene compound monomer, such as styrene-butadiene rubber (SBR), butadiene rubber (BR), isoprene rubber (IR), acrylonitrile-butadiene rubber (NBR), and natural rubber of any grade (NR). Furthermore, component (B) may not contain monomer units having aromatic rings and unsaturated bonds such as styrene, and may consist only of portions derived from aliphatic monomers. The butadiene rubber may be 1,2-polybutadiene rubber or 1,4-polybutadiene rubber. In both cases, the Mooney viscosity is 20 or higher and less than 80. (B) Component may be used alone or in combination of two or more types.

[0044] (B) In diene rubbers, stereoisomers of cis and trans may exist, for example, when the main chain contains a double bond. In diene rubbers, the physical properties can change depending on the cis and trans content. The cis content can be measured, for example, by infrared spectroscopy in accordance with Japanese Industrial Standard JIS K6230 (or ISO 4650).

[0045] (B) In diene rubbers, the degree of cis content varies depending on the type of polymer. For example, in the case of polybutadiene, a cis content of about 20-40% is generally called "low cis," a cis content of about 94-99% is called "high cis," and those in between are called "medium cis." Similarly, in the case of polyisoprene, a cis content of about 90-95%, more typically about 90-94%, and even more typically about 90-92% is generally called "low cis," those exceeding about 95%, more typically about 98-99%, are called "high cis," and those in between are called "medium cis."

[0046] From the viewpoint of obtaining a rubber composition with higher transparency or excellent strength and abrasion resistance, it is preferable to use at least one low-cis, medium-cis, or high-cis polybutadiene as component (B). The diene rubber is more preferably 1,4-polybutadiene rubber, even more preferably medium-cis or high-cis 1,4-polybutadiene rubber, and even more preferably high-cis 1,4-polybutadiene rubber.

[0047] <Refractive index> (B) The refractive index of the diene rubber is preferably 1.450 to 1.530. By appropriately selecting the refractive index of the filler (C), the transparency of the rubber composition of this embodiment can be increased. (B) The refractive index of the diene rubber is more preferably 1.470 to 1.530, and even more preferably 1.490 to 1.525. If the refractive index of the diene rubber (B) falls outside the range of 1.450 to 1.530, the rubber composition of this embodiment tends to have poor transparency. The refractive index of component (B) may be appropriately adjusted based on the refractive index of the styrene-butadiene copolymer rubber (A) and the refractive index of the filler (C).

[0048] <Peak top molecular weight, molecular weight distribution> (B) The peak top molecular weight measured by the GPC method for diene rubber is not particularly limited, for example, 10.0 × 10 4 The above 200 x 10 4 The following is preferred: Preferably 20.0 × 10 4 The above 100 x 10 4 More preferably 30.0 × 10 4 The above 70.0 x 10 4 The following applies: When the peak-top molecular weight is within the above range, the transparency, strength, and abrasion resistance of the rubber composition of this embodiment tend to improve in a well-balanced manner. Furthermore, the molecular weight distribution is not particularly limited, and is, for example, 1.100 to 5.500, preferably 1.500 to 4.000.

[0049] The above-mentioned (B) diene-based rubber may be obtained by purchasing a commercially available product, or it may be manufactured by a conventionally known method.

[0050] ((C) Filler) The rubber composition of this embodiment includes (C) a filler (which may be referred to as component (C) in this specification). (C) The filler is preferably at least one selected from the group consisting of silica, magnesium carbonate, carbon black, and magnesium hydroxide. (C) The filler preferably has a refractive index of 1.370 to 1.500. (C) From the viewpoint of improving the transparency of the rubber composition of this embodiment, the refractive index of the filler is preferably 1.380 to 1.500, and more preferably 1.390 to 1.490. (C) If the refractive index of the filler falls outside the range of 1.370 to 1.500, the transparency of the rubber composition tends to decrease.

[0051] In the rubber composition of this embodiment, it is preferable that the (C) filler is sufficiently dispersed. From the viewpoint of improving dispersibility, it is preferable that the particle size of the (C) filler be small. Also, if the affinity between the (C) filler and the rubber component is poor, aggregates of the (C) filler (primary particles), called secondary particles, may be formed in the rubber composition of this embodiment. When such secondary particles are formed and aggregates larger than the wavelength of visible light exist, the rubber composition tends to become opaque due to the difference in refractive index between the region where the (C) filler is not present and the region where it is not. Therefore, by using a (C) filler with a small primary particle size and kneading under appropriate kneading conditions, it is possible to obtain a rubber composition with excellent transparency.

[0052] From the above viewpoint, the average value of the primary particle diameter of the (C) filler is preferably 50 nm or less, more preferably 40 nm, and even more preferably 30 nm or less. The above average value of the primary particle diameter is particularly preferable when the (C) filler is silica. The lower limit of the average value of the primary particle diameter of the (C) filler is not particularly limited and may be, for example, 1.0 nm, 5.0 nm, or 10 nm. The average primary particle size of the (C) filler can be measured by observing the (C) filler before or in the rubber composition using a scanning electron microscope (SEM) and calculating the equivalent circle diameter. The average value is the arithmetic mean obtained by observing 10 or more (C) fillers.

[0053] Alternatively, the specific surface area may be used as an indicator of the small size of the filler (C). The specific surface area of ​​the filler (C) may be, for example, 80.0 m². 2 It is 100m or more / g, preferably 100m 2 It is 1 / g or more. (C) The specific surface area of ​​the filler can be measured by conventionally known methods, for example, by the BET method.

[0054] (C) From the viewpoint of improving the affinity between the filler and the rubber component, it is preferable to add a substance that improves the affinity between the filler and the rubber component, such as a silane coupling agent, to the rubber composition of this embodiment or to the surface of the filler. Details of the silane coupling agent will be described later.

[0055] (C) The fillers are not limited to the following, but particularly preferred examples include silica (dry silica, wet silica, colloidal silica) and synthetic silicate-based white carbon. Surface-hydrophobized silica and mixtures of silica and inorganic fillers other than silica may also be used. The above (C) fillers may be used individually or in combination of two or more. Silica is more preferred as the (C) filler, and dry silica is even more preferred.

[0056] The filler described above (C) may be obtained by purchasing a commercially available product, or it may be manufactured by a conventionally known method.

[0057] (C) When carbon black is used as a filler, the carbon black may be any, but is not limited to the following, such as SRF, GPF, FEF, HAF, 1SAF, SAF, etc., and is preferably a carbon black with an iodine adsorption capacity (IA) of 60 mg / g or more and a dibutyl phthalate oil absorption capacity (DBP) of 80 mL / 100 g or more. By using carbon black, a rubber composition with excellent abrasion resistance can be obtained. HAF, ISAF, and SAF are particularly preferred as carbon blacks.

[0058] (Content of components (A) to (C) that make up the rubber composition) The rubber composition of this embodiment contains 10 to 50 parts by mass of (C) a filler, when the rubber component consisting of (A) styrene-butadiene copolymer rubber and (B) diene rubber is 100 parts by mass. (C) The content of the filler is preferably 15 to 45 parts by mass, more preferably 25 to 40 parts by mass, per 100 parts by mass of the rubber component. (C) A content of 10 parts by mass or more of the filler tends to yield excellent transparency. Furthermore, (C) a content of 50 parts by mass or less tends to yield excellent abrasion resistance and strength properties.

[0059] (Content of components (A) and (B) in a rubber component consisting of component (A) and component (B)) The rubber composition of this embodiment consists of 100% by mass of rubber components comprising component (A) and component (B), with the content of (A) styrene-butadiene copolymer rubber being 5 to 50% by mass and the content of (B) diene rubber being 50 to 95% by mass. By including each component in this blending ratio, the rubber composition of this embodiment exhibits a well-balanced improvement in transparency, abrasion resistance, and strength. (A) The content of the styrene-butadiene copolymer rubber is preferably 15 to 45% by mass, more preferably 25 to 40% by mass, based on 100% by mass of the rubber component. (A) When the content of styrene-butadiene copolymer rubber is 5% by mass or more, excellent transparency tends to be obtained. Also, when the content of styrene-butadiene copolymer rubber is 50% by mass or less, excellent abrasion resistance and strength properties tend to be obtained. (B) The content of diene rubber is preferably 55 to 85% by mass, more preferably 60 to 75% by mass, based on 100% by mass of the rubber component. (B) When the diene rubber content is 95% by mass or less, excellent transparency tends to be obtained. Also, when the diene rubber content is 50% by mass or more, excellent abrasion resistance and strength properties tend to be obtained.

[0060] ((D) Fatty acids and / or fatty acid derivatives) The rubber composition of this embodiment contains (D) fatty acids and / or fatty acid derivatives (which may be referred to as component (D) in this specification). (D) Fatty acids and / or fatty acid derivatives are organic compounds having an alkyl or alkenyl group with 8 to 30 carbon atoms, and examples of fatty acids include, but are not limited to, octanoic acid, nonanoic acid, decanoic acid, lauric acid, myristic acid, palmitic acid, stearic acid, palmitoleic acid, oleic acid, linoleic acid, behenic acid, coconut oil, beef tallow, etc. Among these, lauric acid, myristic acid, palmitic acid, stearic acid, coconut oil, and beef tallow are preferred, with stearic acid being more preferred. The fatty acid derivatives are not limited to the following, but for example, lauric acid amide, palmitic acid amide, and stearic acid amide are preferred, and stearic acid amide is more preferred. (D) Fatty acids and / or fatty acid derivatives may be used alone or in combination of two or more.

[0061] <(D) Content of ingredient> The content of (D) fatty acids and / or fatty acid derivatives in the rubber composition of this embodiment is 0.01 to 1 part by mass per 100 parts by mass of the rubber component consisting of (A) styrene-butadiene copolymer rubber and (B) diene rubber. (D) The content of fatty acids and / or fatty acid derivatives is preferably 0.02 to 0.90 parts by mass, more preferably 0.04 to 0.80 parts by mass, and even more preferably 0.06 to 0.70 parts by mass.

[0062] (A) Styrene-butadiene copolymer rubber is typically distributed in the form of a bale molded body, but (D) fatty acids and / or fatty acid derivatives may be contained in this bale molded body of component (A). This results in the rubber composition of this embodiment containing (D) fatty acids and / or fatty acid derivatives. Including (D) fatty acids and / or fatty acid derivatives in the bale molded body has the advantage of making the bale molded body easier to finish. The content of the fatty acid (D) and / or fatty acid derivative in the veil-formed body of component (A) is preferably 0.04 to 1.80 parts by mass, more preferably 0.08 to 1.6 parts by mass, and even more preferably 0.12 to 1.4 parts by mass, when component (A) is 100 parts by mass.

[0063] (A) Fatty acids and / or fatty acid derivatives may not be incorporated into the bale molded body of styrene-butadiene copolymer rubber, and (D) fatty acids and / or fatty acid derivatives may be added during the kneading process of the rubber composition of this embodiment. In this embodiment, the content of (D) fatty acids and / or fatty acid derivatives in the rubber composition is 0.2 to 1 part by mass per 100 parts by mass of the total of (A) styrene-butadiene copolymer rubber and (B) diene rubber, thereby improving the processability of the rubber composition without affecting abrasion resistance or strength. Furthermore, in terms of the thermal stability of the rubber composition of this embodiment, the content of (D) fatty acids and / or fatty acid derivatives is set to 1 part by mass or less per 100 parts by mass of rubber components in total. Furthermore, if the improvement in the processability of the rubber composition by (D) fatty acids and / or fatty acid derivatives is insufficient, it is preferable to incorporate the above-mentioned (E) liquid diene rubber.

[0064] ((E) Liquid diene rubber) In this embodiment, when the Mooney viscosity of (A) styrene-butadiene copolymer rubber is 100 to 110, it is preferable to use (D) fatty acids and / or fatty acid derivatives and (E) liquid diene rubber in combination, in order to suppress the deterioration of the thermal stability of the rubber composition due to the addition of (D) fatty acids as described above. (A) Styrene-butadiene copolymer rubber and (B) diene rubber can also have structures that fall under the category of diene rubber. However, since Mooney viscosity is measured on solids, liquid diene rubber can be clearly distinguished from component (A) or component (B) by being liquid. (E) Examples of liquid diene rubbers include oligomers of butadiene, styrene-butadiene, and acrylonitrile-butadiene.

[0065] (E) As for the liquid diene rubber, for example, if it is liquid SBR, it is preferable to use one with a refractive index of 1.5300 to 1.5700. The refractive index of the liquid diene rubber (especially liquid SBR) is more preferably 1.5350 to 1.5700, and even more preferably 1.5400 to 1.5650. When the refractive index of the liquid diene rubber is within the above range, the transparency of the rubber composition of this embodiment tends to be maintained at a high level. (E) As for the liquid diene rubber, for example, if it is liquid BR, it is preferable to use one with a refractive index of 1.4500 to 1.5300. The refractive index of the liquid diene rubber is more preferably 1.4700 to 1.5300, and even more preferably 1.4900 to 1.5250. When the refractive index of the liquid diene rubber is within the above range, the transparency of the rubber composition of this embodiment tends to be maintained at a high level.

[0066] (E) When the liquid diene rubber is liquid butadiene rubber (liquid BR), the cis content of the liquid BR is not particularly limited, and it may contain high-cis, medium-cis, or low-cis liquid BR.

[0067] (E) The liquid diene rubber is not particularly limited as long as it is in liquid form, but it is preferable that the peak top molecular weight measured by the GPC method is in the range of 1,000 to 50,000. (E) The peak top molecular weight measured by the GPC method of the liquid diene rubber is more preferably 4,000 to 35,000, and even more preferably 7,000 to 30,000. (E) The processability of the rubber composition of this embodiment is further improved by having the peak top molecular weight of the liquid diene rubber within the above range.

[0068] (E) The content of liquid diene rubber is preferably 5 parts by mass or less per 100 parts by mass of the rubber component consisting of component (A) and component (B). By setting component (E) to 5 parts by mass or less per 100 parts by mass of the rubber component, the rubber composition of this embodiment exhibits excellent mechanical properties such as tensile strength, tear strength, and abrasion resistance.

[0069] In the rubber composition of this embodiment, when using (E) liquid diene rubber, processability is further improved by using (E) liquid diene rubber with a low molecular weight, such as a peak top molecular weight of 4,000 to 10,000. However, from the viewpoint of increasing tensile strength and tear strength, it is preferable to select (E) liquid diene rubber with a high molecular weight, such as a peak top molecular weight of 10,000 to 50,000. (E) Liquid diene rubber may be used alone or in combination of two or more types.

[0070] The content of (E) liquid diene rubber in the rubber composition of this embodiment is more preferably 0.5 parts by mass or more and 4 parts by mass or less, and even more preferably 1 part by mass or more and 3 parts by mass or less, per 100 parts by mass of the rubber component consisting of component (A) and component (B). When (E) liquid diene rubber is used in combination with (D) fatty acids and / or fatty acid derivatives, the total amount of (D) fatty acids and / or fatty acid derivatives and (E) liquid diene rubber is preferably 0.25 to 10 parts by mass, more preferably 0.25 to 8.0 parts by mass, per 100 parts by mass of the rubber component consisting of components (A) and (B).

[0071] ((F) Silane coupling agent) The rubber composition of this embodiment may contain components other than (A) styrene-butadiene copolymer rubber, (B) diene rubber, (C) filler, and (D) fatty acids and / or fatty acid derivatives. For example, the rubber composition of this embodiment preferably contains a silane coupling agent from the viewpoint of improving the affinity between (C) filler and the rubber component. According to this embodiment, the dispersibility of (C) filler and adhesion to the rubber component are improved, and the abrasion resistance, transparency, and strength of the rubber composition of this embodiment tend to be further improved.

[0072] Examples of silane coupling agents include, but are not limited to, tetraethoxysilane, vinyltrimethoxysilane, vinyltris(2-methoxyethoxy)silane, 3-aminopropyltriethoxysilane, 3-glycidoxypropylmethyldimethoxysilane, bis-[3-(triethoxysilyl)-propyl]tetrasulfide, bis-[3-(triethoxysilyl)-propyl]disulfide, and alkoxysilane compounds such as triethoxysilylpropyl-methacrylate-monosulfide. The silane coupling agent is preferably a polysiloxane containing a vinyl group and an alkoxy group, more preferably a polysiloxane containing a vinyl group and an ethoxy group or a methoxy group, and even more preferably vinyltrimethoxysilane or vinyltris(2-methoxyethoxy)silane. The above silane coupling agents may be used individually or in combination of two or more.

[0073] The content of (F) silane coupling agent in the rubber composition of this embodiment is not particularly limited, but is preferably, for example, 0 to 20 parts by mass per 100 parts by mass of the total of (A) styrene-butadiene copolymer rubber and (B) diene rubber. The content of (F) silane coupling agent is more preferably 0.50 to 10 parts by mass within the above range.

[0074] (G) Crosslinking agent The rubber composition of this embodiment contains at least the above-mentioned components (A), (B), (C), and (D) in the above-mentioned amounts, and a crosslinked rubber composition is obtained by crosslinking. The crosslinked rubber composition comprises a structure in which (A) styrene-butadiene copolymer rubber, (B) diene rubber, and (C) filler are crosslinked. Such crosslinking may be performed by (G) a crosslinking agent. The abrasion resistance, strength, and transparency of the rubber composition of this embodiment represent the performance evaluated in the crosslinked state.

[0075] (G) The crosslinking agent is not limited to the following, but may be any conventionally known crosslinking agent used for crosslinking rubber compositions. The crosslinking agent is preferably one or more of a peroxide and a radical crosslinking agent.

[0076] Peroxides include, but are not limited to, dicumyl peroxide, benzoyl peroxide, di-t-hexyl peroxide, t-butylcumyl peroxide, diisobutyryl peroxide, 2,5-dimethyl-2,5-di(t-butylperoxy)hexane, 1,1-bis(t-butylperoxy)-3,5,5-trimethylcyclohexane, di(2-t-butylperoxyisopropyl)benzene, cumyl peroxyneodecanoate, di-n-propyl peroxydicarbonate, diisopropyl peroxydicarbonate, di-sec-butyl peroxydicarbonate, 1,1,3,3-tetramethylbutyl peroxyneodecanoate, di(4-t-butylcyclohexyl)peroxydicarbonate, di(2-ethylhexyl)peroxydicarbonate, t-hexyl peroxyneodecanoate, t-butylperoxyneodecanoate Decanoate, t-butyl peroxyneoheptanoate, t-hexyl peroxypivalate, t-butyl peroxypivalate, di(3,5,5-trimethylhexanoyl) peroxide, dilauroyl peroxide, 1,1,3,3-tetramethylbutyl peroxy-2-ethylhexanoate, disuccinate peroxide, 2,5-dimethyl-2,5-di(2-ethylhexanoyl peroxy)hexane, t-hexyl Peroxy-2-ethylhexanoate, di(4-methylbenzoyl)peroxide, t-butylperoxy-2-ethylhexanoate, di(3-methylbenzoyl)peroxide, benzoyl(3-methylbenzoyl)peroxide, dibenzoylperoxide, 1,1-di(t-butylperoxy)-2-methylcyclohexane, 1,1-di(t-hexylperoxy)-3,5,5-trimethylcyclohexane, 1.1-di(t-hexylperoxy)cyclohexane, 1,1-di(t-butylperoxy)cyclohexane, 2,2-di(4,4-di-(t-butylperoxy)cyclohexyl)propane, t-hexylperoxyisopropyl monocarbonate, t-butylperoxymaleic acid, t-butylperoxy-3,5,5-trimethylhexanoate, t-butylperoxylaurate, t-butylperoxyisopropyl monocarbonate, t-butylperoxy2-ethylhexyl monocarbonate, t-hexylperoxybenzoate, 2,5-dimethyl-2,5-di(benzoylperoxy Examples include hexane, t-butyl peroxyacetate, 2,2-di-(t-butylperoxy)butane, t-butyl peroxybenzoate, n-butyl-4,4-di-(t-butylperoxy)valerate, di(2-t-butylperoxyisopropyl)benzene, di-t-butyl peroxide, p-menthane hydroperoxide, 2,5-dimethyl-2,5-di(t-butylperoxy)hexine-3, diisopropylbenzene hydroperoxide, 1,1,3,3-tetramethylbutyl hydroperoxide, cumene hydroperoxide, and t-butyl hydroperoxide.

[0077] Examples of radical crosslinking agents include, but are not limited to, ethylene glycol methacrylate (EGDMA), trimethylolpropane trimethacrylate, triallyl isocyanurate, triallyl cyanurate, diethylene glycol diacrylate, and neophenylene glycol diacrylate.

[0078] Among these crosslinking agents, peroxides are more preferred from the viewpoint of minimizing contamination of the product. Furthermore, from the viewpoint of minimizing malodor and residue, the crosslinking agents are more preferably dicumyl peroxide, 2,5-dimethyl-2,5-di(t-butylperoxy)hexane, di(2-t-butylperoxyisopropyl)benzene, and 1,1-di(t-butylperoxy)cyclohexane. The above crosslinking agents may be used individually or in combination of two or more.

[0079] The amount of (G) crosslinking agent added to the rubber composition of this embodiment is not particularly limited, and is, for example, 0.10 to 10 parts by mass, preferably 0.20 to 8.0 parts by mass, and more preferably 0.50 to 6.0 parts by mass, per 100 parts by mass of the rubber component consisting of (A) styrene-butadiene copolymer rubber and (B) diene rubber. That is, the rubber composition of this embodiment is manufactured by adding, for example, 0.10 to 10 parts by mass, preferably 0.20 to 8.0 parts by mass, and more preferably 0.50 to 6.0 parts by mass of (G) crosslinking agent to a total of 100 parts by mass of (A) styrene-butadiene copolymer rubber and (B) diene rubber.

[0080] (Other ingredients) The rubber composition of this embodiment may further contain other components other than those described in (A) to (G), as long as they do not significantly impair transparency. Other ingredients include, but are not limited to, antioxidants, colorants, denaturants, processing agents, reducing agents, oxygen absorbers, light stabilizers, pH stabilizers, surface treatment agents, heat stabilizers, colorants, fillers (such as talc and calcium carbonate), surfactants, gelling agents, UV absorbers (such as salicylic acid, benzophenone, benzotriazole, cyanoacrylate, and hindered amines), dusting agents (such as polyolefins like polyethylene, talc, and calcium carbonate powder), and polyphosphates. These other components may be used individually or in combination of two or more.

[0081] Antioxidants include, but are not limited to, monophenol, bisphenol, polyphenol, sulfur, and phosphorus compounds, specifically Nocrac SP (manufactured by Ouchi Shinko Chemical Industry), Irganox 1076 (manufactured by BASF), Irgaphos 168 (manufactured by BASF), and Irganox 1520 (manufactured by BASF). Colorants may be used, for example, when it is desired to give a rubber composition a transparent color such as clear blue, clear red, or clear green, rather than simply transparency. Such colorants may be any known colorants, and are not limited to the following, but include coloring pigments, extender pigments, rust-preventive pigments, and functional pigments (e.g., phthalocyanine green, titanium, Prussian blue, iron oxide, leadous oxide, and zinc sulfide).

[0082] The rubber composition of this embodiment may contain one or more of the following components, with respect to 100 parts by mass of the rubber component consisting of (A) styrene-butadiene copolymer rubber and (B) diene rubber: antioxidant, colorant, modifier, processing agent, reducing agent, oxygen scavenger, light stabilizer, pH stabilizer, surface treatment agent, heat stabilizer, colorant, filler, surfactant, gelling agent, UV absorber, dusting agent, and polyphosphate, in total in the range of, for example, 0 to 15 parts by mass. If these other components are included, the total content of these other components is preferably 0.10 to 10 parts by mass, more preferably 0.20 to 5.0 parts by mass, and even more preferably 0.25 to 2.0 parts by mass.

[0083] [Physical properties of rubber compositions] In this specification, "crosslinked rubber composition" means a rubber composition having a structure in which at least one rubber component is crosslinked. That is, it means a rubber composition obtained by crosslinking a rubber composition containing at least one rubber component. In this specification, a crosslinked rubber composition is a rubber composition having a portion derived from at least one rubber component and a portion derived from at least one crosslinking agent. That is, it is a rubber composition obtained by crosslinking a rubber composition containing at least one rubber component with any crosslinking agent.

[0084] (HAZE value) The rubber composition of this embodiment preferably has a haze value of 10 to 40% from the viewpoint of transparency. In this specification, the transparency of a rubber composition is evaluated by the HAZE value of the crosslinked rubber composition. A lower HAZE value indicates higher transparency, and a rubber composition with a HAZE value above a certain level is referred to in this specification as "opaque" or "translucent." The "haze" value refers to the degree of cloudiness of a transparent material, measured in accordance with the Japanese Industrial Standard JIS K7136 (or ISO 14782). In this specification, the haze value is measured using a 3.00 mm thick sheet as the measurement sample and a test apparatus conforming to the above standard. The HAZE value of the rubber composition of this embodiment, measured in a 3.00 mm thick sheet in accordance with JIS K7136, is not particularly limited, but is preferably 10 to 50%. From the viewpoint of excellent transparency, the HAZE value of the rubber composition is preferably 40% or less, more preferably 38% or less, even more preferably 35% or less, and even more preferably 30% or less within the above range. The lower limit of the HAZE value of the rubber composition is not particularly limited and may be, for example, 15%, 18%, or 20%. The HAZE value of the rubber composition can be controlled, for example, by adjusting the refractive indices of (A) styrene-butadiene copolymer rubber, (B) diene-based rubber, and (C) fillers, as well as their relative magnitudes.

[0085] (hardness) The hardness of the rubber composition in this embodiment shall be evaluated by the hardness of the crosslinked rubber composition. The hardness of the rubber composition in this embodiment is evaluated by the Type A durometer hardness. A higher Type A durometer hardness value indicates a harder material. "Type A Durometer Hardness" (or Hs) or "Shore A" refers to the hardness of a rubber composition measured in accordance with the Japanese Industrial Standard JIS K6253-3. In this specification, the Type A Durometer Hardness or Shore A value is measured using a 6.00 mm thick sheet as the test sample, and is the depth of indentation 3 seconds after pressing a plunger onto the test piece with a constant indentation. The hardness of the rubber composition of this embodiment, measured according to JIS K6253-3 using a durometer type A, is not particularly limited, but is preferably, for example, 50 to 80. From the viewpoint of excellent abrasion resistance and strength, the hardness of the rubber composition according to a durometer type A is preferably 60 to 75, more preferably 63 to 73, and even more preferably 65 to 70 within the above range. When the hardness of the rubber composition according to a durometer type A is 60 or higher, abrasion resistance and strength are further improved, and when it is 75 or lower, tear strength and frictional force tend to be further improved. The hardness of the rubber composition according to durometer type A can be controlled, for example, by adjusting the content of (A) styrene-butadiene copolymer rubber, (B) diene-based rubber, and (C) filler.

[0086] (strength) The strength of the rubber composition in this embodiment shall be evaluated by the strength of the crosslinked rubber composition. The strength of the rubber composition in this embodiment is evaluated by its tensile strength and tear strength. Higher tensile and tear strengths indicate higher strength. "Tensile strength" refers to the tensile strength of a rubber composition as measured in accordance with the Japanese Industrial Standard JIS K6251. In this specification, the tensile strength values ​​are those obtained by using a 2.00 mm thick sheet as the measurement sample, measuring it with a dumbbell-shaped No. 5 test piece, and converting the result to MPa units. "Tear strength" refers to the tear strength of a rubber composition as measured in accordance with the Japanese Industrial Standard JIS K6252-1. In this specification, the tear strength value is the value obtained by converting the measurement of a 2.00 mm thick sheet using an angle-shaped test piece without cuts to N / mm. The strength of the rubber composition can be controlled by adjusting, for example, the content of (A) styrene-butadiene copolymer rubber, (B) diene-based rubber, and (C) filler.

[0087] (Abrasion resistance) The abrasion resistance of the rubber composition in this embodiment shall be evaluated by the strength of the crosslinked rubber composition. The abrasion resistance of the rubber composition in this embodiment is evaluated by the abrasion resistance index of the rubber composition, which is measured in accordance with the Japanese Industrial Standard JIS K6264-2 (or ISO 4649). A higher abrasion resistance index indicates higher abrasion resistance. In this specification, the value of the abrasion resistance index is measured using a DIN abrasion tester conforming to the above standard, in accordance with the above standard. The abrasion resistance of rubber compositions can be controlled by adding fillers (such as carbon or silica) or by blending in diene-based rubbers (BR) which have high abrasion resistance.

[0088] (Refractive index) The refractive index of the rubber composition in this embodiment shall be evaluated by the strength of the crosslinked rubber composition. The refractive index of the rubber composition of this embodiment is not particularly limited, but is preferably, for example, 1.4700 to 1.5500. From the viewpoint of excellent transparency, the refractive index of the rubber composition is preferably 1.5000 to 1.5400, more preferably 1.5050 to 1.5350, even more preferably 1.5100 to 1.5320, and even more preferably 1.5150 to 1.5315. The refractive index of the rubber composition can be controlled by adjusting the refractive index and content of (A) styrene-butadiene copolymer rubber, (B) diene-based rubber, and (C) filler.

[0089] [Method for manufacturing rubber composition] The rubber composition of this embodiment can be produced by adding (A) styrene-butadiene copolymer rubber, (B) diene rubber, (C) filler, (D) fatty acid and / or fatty acid derivative, and (F) silane coupling agent, (G) crosslinking agent, and other components selectively, in a predetermined mixing ratio and kneading. More specifically, for example, the following methods may be used.

[0090] In other words, the method for producing the rubber composition of this embodiment is: A preferred embodiment is one in which a bale containing (A) 98 to 99.98% by mass of styrene-butadiene copolymer rubber and (D) 0.02 to 2% by mass of fatty acids and / or fatty acid derivatives and (B) diene rubber are kneaded together with (C) filler in a mass ratio of (A) component to (B) component of 5 / 95 to 50 / 50, and 100 parts by mass of the rubber component consisting of (A) component and (B) component is kneaded together with (C) filler in a step. Furthermore, it is preferable to blend and knead (E) liquid diene rubber in an amount of 0 to 5 parts by mass with 100 parts by mass of the rubber component. Furthermore, (F) a silane coupling agent and (G) a crosslinking agent may be added in desired amounts. Here, each component (A) to (G) is the same as the corresponding component in the rubber composition described above.

[0091] Furthermore, the method for manufacturing the crosslinked rubber sheet of this embodiment is as follows: A preferred embodiment includes the steps of: kneading a bale containing (A) 98 to 99.98% by mass of styrene-butadiene copolymer rubber and (D) 0.02 to 2% by mass of fatty acids and / or fatty acid derivatives, and (B) diene rubber, with a mass ratio of component (A) to component (B) of 5 / 95 to 50 / 50, and kneading 100 parts by mass of the rubber component consisting of component (A) and component (B) with 10 to 50 parts by mass of (C) filler to obtain a kneaded product; and mixing (G) crosslinking agent into the kneaded product and pressurizing and / or heating it.

[0092] The above mixing process can be carried out using, for example, an open roll, a Banbury mixer, a kneader, a twin-screw extruder, and / or a Laboplast mill. In the mixing process, components (A) to (E) and crosslinking agent (G) may be mixed at once, but it is preferable to mix components (A) to (E) once, then add component (G) crosslinking agent and mix further. The mixing of components (A) to (E) may be carried out at a temperature of, for example, 120 to 160°C, from the viewpoint of uniformly mixing each component. The mixing after adding component (G), the crosslinking agent, may be carried out at a temperature of, for example, 120°C or lower, from the viewpoint of suppressing side reactions, etc. (G) The temperature during kneading after adding the crosslinking agent is preferably 100°C or lower, more preferably 80°C or lower, and even more preferably 0 to 50°C.

[0093] In the above kneading process, components other than components (A) to (E) and (G) may be added as appropriate. Examples of such components include (F) silane coupling agents and antioxidants. It is also preferable that the kneading process further kneads (F) silane coupling agents. The transparency and strength of the rubber composition tend to be further improved by kneading in component (F), a silane coupling agent. It is preferable to knead component (F) together with components (A) to (E). The amount of each component used may be the same as the value described as the content of each component in the description of the rubber composition.

[0094] In the method for producing the rubber composition of this embodiment, a rubber composition of a desired shape can be obtained by a molding step in which the kneaded mixture is formed. The molding process may involve, for example, placing the kneaded material obtained in the kneading process into a press die of a suitable shape, and then applying pressure and heating it. This can result in, for example, obtaining a sheet-like molded body. The molding temperature in the molding process is not particularly limited, but is preferably 140 to 180°C, and more preferably 150 to 170°C. The molding pressure is preferably 140 to 200 kgf, and more preferably 160 to 180 kgf. Furthermore, in the molding process, the kneaded material may be introduced into an injection molding machine and injected to obtain a rubber composition or molded body of the desired shape.

[0095] [Uses of rubber compositions] The rubber composition of this embodiment can be used in any industrial application where transparency is advantageous. Examples of such applications include, but are not limited to, shoe soles, rain gear, toys, vibration damping materials, building materials, wiring insulation materials, packaging materials, and computer protective components.

[0096] In particular, the rubber composition of this embodiment is suitable for use in shoe soles because it allows for the creation of outsoles, tips, ornaments, and other parts that exhibit excellent transparency and a good balance of tensile strength, tear strength, abrasion resistance, and processability. Such transparent shoe soles can enhance fashion appeal and therefore have extremely high commercial value. The above uses are merely examples, and the uses of the rubber composition of this embodiment are not limited to these. [Examples]

[0097] The embodiments will be further described below with reference to examples and comparative examples. However, the present invention is not limited in any way by the following examples and comparative examples.

[0098] 〔material〕 The materials used in the examples and comparative examples are shown below. The refractive index of each material was measured in advance using the method described later.

[0099] (Styrene-butadiene copolymer rubber) • Styrene-butadiene copolymer rubber SBR1~10 produced by the following manufacturing example • Asapren 303 (Asahi Kasei Corporation)

[0100] (Diene-based rubber) BR1208 (LG Chem) (1,4-polybutadiene rubber, high cis, ML: 45, refractive index: 1.5236) • BRU150 (Ube Industries) (1,4-polybutadiene rubber, high cis, ML: 39, refractive index: 1.5224) • IR2200 (Zeon Corporation) (Isoprene rubber, 1,4-vinyl bond content = 98.0%, 3,4-vinyl bond content = 2.0%, ML: 82, refractive index: 1.5203)

[0101] (Filler) • Rheoroseal (Tokuyama Corporation) (wet-processed silica, refractive index: 1.4621) • VN3 (Nipsil) (wet-processed silica, refractive index: 1.4491) ·CB N339 (Carbon Black)

[0102] (Crosslinking agent) • Perkmyl D (Nippon Oil & Fats Co., Ltd.) (Dicumyl peroxide)

[0103] (Silane coupling agent) • Dynasylan6498 (Evonik) (a polysiloxane containing vinyl and ethoxy groups) ·Si69(CHENGUANG)

[0104] (Antioxidant) • Nocrack SP (Ouchi Shinko Chemical Industry Co., Ltd.) (mono(or di, or tri)(α-methylbenzyl)phenol)

[0105] (Liquid diene rubber) • LBR307 (Kuraray Co., Ltd.) (Liquid 1,4-butadiene rubber, peak top molecular weight: 8000, refractive index: 1.5157)

[0106] (Randomizer) • Potassium-t-amyl alkoxide

[0107] (Vinylizing agent) ·2,2'-Ditetrahydrofurylpropane

[0108] (Coupling agent (polymerization coupling agent)) • 1,3-Bis(N,N'-Diglycidylaminomethyl)cyclohexane

[0109] (Polymerization initiator) • n-butyllithium

[0110] (Stabilizer) n-octadecyl-3-(3,5-di-t-butyl-4-hydrooxyphenyl)-propionate

[0111] (fatty acid) • Stearic acid (reagent) • Hexanoic acid (reagent)

[0112] [Material properties] (Measurement of various physical properties of styrene-butadiene copolymer rubber) The physical properties of the styrene-butadiene copolymer rubber were measured as follows.

[0113] (1) Measurement of the amount of bound styrene The absorption spectrum of styrene-butadiene copolymer rubber was measured using a UV spectrophotometer (UV-2450; Shimadzu Corporation) as a sample. The amount of bound styrene was determined from the absorbance of ultraviolet light (around 254 nm) originating from the phenyl group of styrene.

[0114] (2) Measurement of styrene block quantity The amount of styrene block was measured according to the osmium tetroxide decomposition method described in IMKolthoff, et al. J. Polym. Sci. 1,429 (1946). More specifically, 0.050 g of styrene-butadiene copolymer rubber was dissolved in 10 mL of chloroform, and 16 mL of a 69% by mass aqueous solution of tert-butyl hydroperoxide and 4.0 mL of a 0.050% by mass chloroform solution of osmium tetroxide were added. The reaction was carried out under reflux in a 90°C bath for 12 minutes. After the reaction was complete, the reaction solution was cooled, and 200 mL of methanol was added to the reaction solution while stirring to precipitate the styrene block component, which was then filtered off through a 5 μm glass filter. The amount of styrene block was determined by dividing the mass of the obtained material by the total mass of the styrene-butadiene copolymer rubber.

[0115] (3) Ratio of styrene block amount to bound styrene amount This was calculated from the ratio of styrene block amount to bound styrene amount measured above.

[0116] (4) Amount of 1,2-vinyl bonds in the butadiene portion Styrene-butadiene copolymer rubber was dissolved in carbon disulfide to prepare the sample for measurement. The infrared spectrum of each sample was measured using an infrared spectrophotometer (JASCO V-520V). The amount of 1,2-vinyl bond in the butadiene portion was determined from the absorbance at a predetermined wavenumber using the Hampton method (as described in RRHampton, Analytical Chemistry 21,923 (1949)).

[0117] (5) Measurement of Mooney viscosity The Mooney viscometer (SMV-301RT, manufactured by Shimadzu Corporation) conforming to JIS K6300-1 was used for measurement. Using an L-shaped rotor, the sample was preheated to the test temperature (100°C) for 1 minute, then the rotor was rotated at 2 rpm, and the torque after 4 minutes was measured to determine the Mooney viscosity (ML). 1+4 (100℃) was measured. Mooney viscosity was measured for both styrene-butadiene copolymer rubber and diene-based rubber.

[0118] (6) Measurement of peak top molecular weight GPC chromatography was performed (using a Tosoh HLC-8320GPC EcoSEC instrument with three PLgel Column MiniMix-C columns. Tetrahydrofuran was used as the solvent, and the measurement conditions were: temperature 40°C, flow rate 0.4 mL / min, sample concentration 0.1% by mass, and injection volume 50 μL). A calibration curve prepared using commercially available standard monodisperse polystyrene with known molecular weight was used, and the peak top molecular weight of each sample was determined from the obtained GPC chromatogram. When styrene-butadiene copolymer rubber was coupled with a coupling agent, peaks originating from both the uncoupled styrene-butadiene copolymer rubber and the coupled styrene-butadiene copolymer rubber were obtained. In this case, the peak top molecular weight was determined for each peak. The coupling rate was also determined from the ratio of peaks originating from the uncoupled rubber to peaks originating from the coupled rubber.

[0119] (7) Measurement of refractive index The refractive index was measured using an Abbe refractometer (NAR-3T) manufactured by Atago Corporation. Styrene-butadiene copolymer rubber and diene rubber were measured at 23°C in accordance with JIS K0062. Furthermore, the refractive index of the filler was measured as described below. Two liquids with different refractive indices were prepared, and a small amount of filler was added to the liquid with the lower refractive index. At this point, the filler could be visually observed because the refractive indices of the liquid and the filler were different. Then, the liquid with the higher refractive index was gradually added. When the refractive index of the mixture became equal to that of the filler, the filler could no longer be visually observed. The refractive index of the mixture was measured, and this value was taken as the refractive index of the filler. In this embodiment, the refractive index of other materials was also measured in accordance with the method described above.

[0120] The methods for evaluating the properties of the rubber compositions obtained in the examples and comparative examples are shown below. [Evaluation of the processability of rubber compositions before vulcanization] (1) Cohesion The form of the rubber composition extracted after Banbury kneading was scored according to the following criteria, and its cohesiveness was evaluated. There are several chunks of varying sizes. : 1 point There is one large lump and several smaller lumps: 2 points It's almost a large lump: 3 points Beautiful and in large chunks: 4 points

[0121] (2) Wrapping properties The degree to which the rubber composition wrapped around the roll during kneading was evaluated by assigning a score according to the following criteria. Less likely to get tangled in the roll: 1 point Somehow managed to wrap around the roll: 2 points Wrapped around the roll: 3 points Easy to wrap around the roll: 4 points

[0122] (3) Roll processability The state of the rubber composition while it was being kneaded by winding it onto a roll was scored according to the following criteria to evaluate its roll processability. There is a large hole. : 1 point There is a small hole. : 2 points Sometimes holes appear. : 3 points The rubber composition covers the roll surface. : 4 points

[0123] (4) Seat condition The sheet condition of the rubber composition, which was extracted from the roll in sheet form, was evaluated by assigning a score to the sheet surface according to the following criteria. It has large bumps and uneven surfaces. : 1 point There are small bumps and uneven surfaces. : 2 points It is almost perfectly smooth. : 3 points Smooth and glossy. : 4 points

[0124] In evaluating the unvulcanized processability of the aforementioned rubber composition, a higher total score for (1) to (4) indicated superior processability of the unvulcanized rubber composition.

[0125] Furthermore, the Mooney viscosity (ML) of the unvulcanized rubber composition was also used as a criterion for judging processability. Generally, unvulcanized rubber compositions have better processability at lower ML values, and tend to deteriorate significantly above around 170. Therefore, we determined that an ML value lower than 170 is preferable.

[0126] [Evaluation of the physical properties of the rubber composition after vulcanization] (1) Type A durometer hardness Type A durometer hardness was measured using two 3.00 mm thick sheets stacked together (total thickness 6.00 mm) as the sample, in accordance with the Japanese Industrial Standard JIS K6253-3. The depth of indentation after 3 seconds, when a plunger was pressed into the sheet with a constant pressure, was measured as the Type A durometer hardness.

[0127] (2) HAZE value The haze value (%) was measured in accordance with Japanese Industrial Standard JIS K7136 (or ISO 14782). The rubber composition was molded into a 3.00 mm thick sheet and measured using a haze meter (NDH 2000, manufactured by Nippon Denshoku Industries Co., Ltd.). Note that the unit (%) is omitted in the table.

[0128] (3) Abrasion resistance The abrasion was measured using the DIN abrasion test in accordance with JIS K 6264. Specifically, the wear volume of the test specimens for the examples and comparative examples was measured using the DIN wear test, and the wear resistance index was calculated from the wear volume to determine the wear resistance.

[0129] (4) Physical strength (tensile strength and tear strength) Tensile strength was measured in accordance with the Japanese Industrial Standard JIS K6251. Tear strength was measured in accordance with the Japanese Industrial Standard JIS K6252-1. Tensile strength was measured using a 2.00 mm thick sheet as the sample, with a dumbbell-shaped No. 5 test specimen, and the results were converted to MPa units. Tear strength was measured using a 2.00 mm thick sheet as the sample, with the results converted to N / mm using an angle-shaped test specimen without cuts.

[0130] [Manufacturing of styrene-butadiene copolymer rubber] Styrene-butadiene copolymer rubber was synthesized by batch polymerization using a nitrogen-purged 10L autoclave with a stirrer, according to the formulations shown in Tables 1 and 2 below. In each of the following production examples and comparative production examples, the total amount of monomer was 1200 g. Styrene monomer and 1,3-butadiene were copolymerized using n-butyllithium in cyclohexane solvent (550 phm) as a polymerization initiator.

[0131] (Manufacturing Example 1) The butadiene monomer and styrene monomer listed in Table 1 were weighed into an autoclave, and 2,2'-ditetrahydrofurylpropane as a vinyling agent and potassium-t-amyl alkoxide as a randomizing agent were added. Polymerization was started by adding n-butyllithium at a polymerization initiation temperature of 50.2°C. The polymerization reaction peak temperature was 73°C. Two minutes after the temperature peak, methanol was added in an amount equal to 1 molar to n-butyllithium to stop the reaction and obtain styrene-butadiene copolymer rubber SBR-1. The amount of bound styrene was 45.9% by mass, and the amount of styrene blocks was 2.10% by mass. Other physical properties are shown in Table 1 below.

[0132] (Manufacturing example 2) SBR-2 and SBR-3 were prepared according to the method of Production Example 1, with the amount of n-butyllithium polymerization initiator adjusted accordingly. As a result, polymers with different peak-top molecular weights were obtained. In these polymers, the ML value increased as the peak-top molecular weight increased. Table 1 shows the polymerization initiation temperature, reaction peak temperature, amount of bound styrene, amount of styrene blocks, amount of 1,2-vinyl bonds in the butadiene portion, Mooney viscosity, peak top molecular weight, and refractive index of each polymer.

[0133] (Manufacturing Example 3) SBR-4 was manufactured without adding a randomizing agent, and otherwise in the same manner as in Manufacturing Example 1. Table 1 shows the polymerization initiation temperature, reaction peak temperature, amount of bound styrene, amount of styrene blocks, amount of 1,2-vinyl bonds in the butadiene portion, Mooney viscosity, peak top molecular weight, and refractive index of the obtained polymer.

[0134] (Manufacturing example 4) SBR-5 and SBR-6 were manufactured by varying the amount of styrene added and adjusting the amount of randomizing agent added accordingly, with the rest of the process being the same as in Manufacturing Example 1. Table 1 shows the polymerization initiation temperature, reaction peak temperature, amount of bound styrene, amount of styrene blocks, amount of 1,2-vinyl bonds in the butadiene portion, Mooney viscosity, peak top molecular weight, and refractive index of the obtained polymer.

[0135] (Manufacturing example 5) SBR-7 and SBR-8 were manufactured by adjusting the amount of vinylizing agent added according to the desired amount of 1,2-vinyl bonding, and otherwise following the same procedure as in Production Example 1. Table 2 shows the polymerization initiation temperature, reaction peak temperature, amount of bound styrene, amount of styrene blocks, amount of 1,2-vinyl bonds in the butadiene portion, Mooney viscosity, peak top molecular weight, and refractive index of the obtained polymer.

[0136] (Manufacturing example 6) After weighing the butadiene monomers and styrene monomers listed in Table 2 into an autoclave, 2,2'-ditetrahydrofurylpropane was added as a vinyling agent, and potassium-t-amyl alkoxide was added as a randomizing agent. Polymerization was initiated by adding n-butyllithium at a polymerization initiation temperature of 50°C. The polymerization reaction peak temperature was 71°C. Two minutes after the temperature peak, the reaction was stopped by adding methanol in an amount equal to 1 molar to n-butyllithium, yielding styrene-butadiene copolymer rubber SBR-9. The amount of bound styrene was 45.9% by mass, and the amount of styrene blocks was 1.90% by mass. Other physical properties are shown in Table 2.

[0137] (Manufacturing example 7) By adjusting the amount of n-butyllithium, the polymerization initiator, according to the method of Production Example 1, polymers with the peak-top molecular weights shown in Table 2 were obtained for SBR-10. As the peak-top molecular weight increased, the ML value decreased. Table 2 shows the polymer's starting temperature, reaction peak temperature, amount of bound styrene, amount of styrene blocks, amount of 1,2-vinyl bonds in the butadiene portion, Mooney viscosity, peak-top molecular weight, and refractive index.

[0138] In the above manufacturing examples, the styrene conversion rate was 95% or higher and the 1,3-butadiene conversion rate was 99.8% or higher in each polymerization batch 2 minutes after reaching the reaction peak temperature. The above conversion rates were measured using gas chromatography. After the reaction was complete, n-octadecyl-3-(3,5-di-t-butyl-4-hydrooxyphenyl)-propionate was added as a stabilizer to the styrene-butadiene copolymer rubber solution obtained in each production example and comparative production example, in an amount of 0.30 parts by mass per 100 parts by mass of styrene-butadiene copolymer rubber. The solvent was removed using a drum dryer (160°C), and the solution was dried to finish.

[0139] Tables 1 and 2 show the amount of bound styrene, amount of styrene blocks, ratio of styrene blocks to bound styrene, amount of 1,2-vinyl bonds in the butadiene portion, Mooney viscosity, peak-top molecular weight, coupling rate, and refractive index for each styrene-butadiene copolymer rubber.

[0140] [Table 1]

[0141] [Table 2]

[0142] [Manufacturing and evaluation of rubber compositions] (Examples 1-3) The mixture was prepared using the composition shown in Table 3, and consisted of (A) styrene-butadiene copolymer rubber, (B) diene rubber, (C) filler, (D) fatty acid, (F) silane coupling agent, (G) crosslinking agent, and antioxidant. The mixture was kneaded using a 6-inch open roll (manufactured by Kansai Roll, roll temperature 119-121°C, rotation ratio 1:1.25) at a discharge temperature of 120-130°C. Subsequently, a crosslinking agent was added to the mixture, and it was further kneaded using a 6-inch open roll at a temperature of 30-40°C. Examples 1-3 used SBR-1 as component (A), and the "specified amount" of fatty acid (D) in Table 3 followed the formulation amounts shown in Table 4 below.

[0143] Next, this mixture was pressurized using a heated press at 160°C and a pressure of approximately 16 MPa for about 6 minutes to produce vulcanized rubber sheets with a thickness of 2.00 mm and vulcanized rubber sheets with a thickness of 3.00 mm. Furthermore, a cylindrical vulcanized rubber piece with a diameter of 16.0 mm and a thickness of 8.00 mm was prepared in the same manner. Furthermore, a 2.00 mm thick vulcanized rubber sheet was used as a test specimen for measuring tensile strength and tear strength. A 3.00 mm thick vulcanized rubber sheet was used as a test specimen for measuring HAZE value and Type A durometer hardness. Cylindrical vulcanized rubber pieces were used as test specimens for abrasion resistance testing. The same procedure was followed for subsequent tests.

[0144] [Table 3]

[0145] (Example 4) In Example 4, 0.6 parts by mass of fatty acid were added to the SBR-1 used as component (A) during the polymer solution stage, and the dried product was used. When preparing the rubber composition, no fatty acid was added. Otherwise, the vulcanized rubber sheets and vulcanized rubber pieces were prepared under the same conditions as in Example 1.

[0146] [Examples 5, 6, 7, 8, 9] In Examples 5, 6, 7, 8, and 9, the components shown in Table 4 below were used as component (A), and liquid butadiene rubber component (E) was added according to Table 4. The rubber composition was prepared in the same manner as in Example 1, and vulcanized rubber sheets and vulcanized rubber pieces were produced.

[0147] [Examples 10, 11, 12, 13, 14] In Examples 10, 11, 12, 13, and 14, the components shown in Table 5 were used as component (A), and the amount of component (D) was adjusted according to Table 5. The other conditions were the same as in Example 1 to prepare the rubber composition, and vulcanized rubber sheets and vulcanized rubber pieces were produced.

[0148] [Example 15] In Example 15, components (A), (B), and (D) were blended in the amounts shown in Table 5, and the other conditions were the same as in Example 1 to prepare the rubber composition, and vulcanized rubber sheets and vulcanized rubber pieces were produced.

[0149] [Example 16] In Example 16, SBR-1 was used as component (A), BRU150 and IR2200 as component (B), and wet silica VN3 as component (C). These were added according to the proportions shown in Table 5, and the rubber composition was prepared under the same conditions as in Example 1. Vulcanized rubber sheets and vulcanized rubber pieces were then produced.

[0150] [Example 17] In Example 17, SBR-1 was used as component (A) and carbon black (CB N339) was used as component (C). These were added according to the proportions shown in Table 5, and the rubber composition was prepared under the same conditions as in Example 1. A vulcanized rubber sheet and a vulcanized rubber piece were then produced.

[0151] [Comparative Examples 1, 2, 3, 4, 7] Comparative Examples 1, 2, 3, 4, and 7 did not use component (D). Furthermore, the specified components were blended according to Table 6. The rubber compositions were prepared under the same conditions as in Example 1, and vulcanized rubber sheets and vulcanized rubber pieces were produced.

[0152] [Comparative Example 5] Comparative Example 5 was prepared based on the formulation conditions of Comparative Example 4, with hexanoic acid added in the amounts shown in Table 6 below. The rubber composition was prepared under the same conditions as in Example 1, and vulcanized rubber sheets and vulcanized rubber pieces were produced.

[0153] [Comparative Example 6] In Comparative Example 6, liquid butadiene rubber was added as component (E) based on the compounding conditions of Comparative Example 4. The rubber composition was prepared under the same conditions as in Example 1, and vulcanized rubber sheets and vulcanized rubber pieces were produced.

[0154] [Comparative Example 8] In Comparative Example 8, as shown in Table 6, asaprene 303 was used as component (A), BRU150 and IR2200 as component (B), and wet silica VN3 as component (C), according to the blending amounts shown in Table 6. Component (D) was not added. The rubber composition was prepared under the same conditions as in Example 1, and vulcanized rubber sheets and vulcanized rubber pieces were produced.

[0155] [Comparative Example 9] In Comparative Example 9, as shown in Table 6, component (A) was SBR1 and component (C) was carbon black (CB N339). Component (D) was not added. The rubber composition was prepared under the same conditions as in Example 1, and vulcanized rubber sheets and vulcanized rubber pieces were produced.

[0156] Tables 4 to 6 show the measurement results of the physical properties of the rubber compositions of Examples 1 to 17 and Comparative Examples 1 to 9.

[0157] [Table 4]

[0158] [Table 5]

[0159] [Table 6]

[0160] The Type A durometer hardness and haze values ​​are measured values. A lower HAZE value indicates better transparency. For abrasion resistance, tensile strength, and tear strength, the properties of Comparative Example 1 were expressed as an index, with the properties of Comparative Example 1 set to 100. A higher index indicates superior properties.

[0161] Tables 4 to 6 show that in each example, the addition of fatty acids resulted in improvements in processability, abrasion resistance, and tear strength. For example, Examples 1, 2, 3, 16, and 17 demonstrate the effects obtained solely from the addition of fatty acids. Compared to the comparative examples, it was found that processability not obtained in those examples was achieved without compromising the physical properties. Furthermore, it was found that Examples 1, 2, and 3 did not impair transparency in addition to mechanical properties such as abrasion resistance, tensile properties, and tear properties. According to Example 4, it was found that even if the timing of fatty acid addition was changed to the polymer finishing stage, processability improvement was obtained as long as the specified amount was included. Examples 5, 6, 7, and 8 demonstrated further improvements in processability through the combined use of fatty acids and liquid butadiene rubber. In all cases, processability improved, and post-vulcanization physical properties improved. In particular, abrasion resistance was significantly improved. Furthermore, the HAZE value did not decrease significantly. However, when the amount of liquid butadiene rubber was large, as in Example 9, it affected mechanical properties such as abrasion resistance, tensile properties, and tear properties, but this did not pose a practical problem. Furthermore, in Example 8, the timing of fatty acid addition was changed to the finishing stage of the polymer, but there was no difference in processability or physical properties depending on the timing of addition. [Industrial applicability]

[0162] The rubber composition of the present invention has industrial applicability in the fields of various crosslinked rubber sheets and outsole materials for shoes.

Claims

1. (A): The mass ratio of styrene block amount / bound styrene amount is 0.02 to 0.

23. The amount of 1,2-vinyl bonds in the butadiene portion is 10 to 60% by mass. The amount of bound styrene is 35 to 55% by mass. And, Mooney viscosity is in the range of 80 to 110. 5 to 50% by mass of styrene-butadiene copolymer rubber, (B): 50 to 95% by mass of diene rubber, which is at least one selected from the group consisting of natural rubber, diene-based synthetic rubber, and block copolymers of aromatic vinyl compounds and conjugated diene compounds, and which has a Mooney viscosity of 20 or more and less than 80. The rubber component contained therein, With respect to 100 parts by mass of the rubber component consisting of (A) styrene-butadiene copolymer rubber and (B) diene rubber, (C): Filler 10 to 50 parts by mass, (D): 0.01 to 1 part by mass of a fatty acid and / or fatty acid derivative having an alkyl or alkenyl group having 8 to 30 carbon atoms. A rubber composition containing the following.

2. With respect to 100 parts by mass of the rubber component consisting of (A) styrene-butadiene copolymer rubber and (B) diene-based rubber, (E): Further containing 0 to 5 parts by mass of liquid diene rubber, The rubber composition according to claim 1.

3. The amount of styrene blocks in the (A) styrene-butadiene copolymer rubber is 0.70 to 12% by mass. The rubber composition according to claim 1 or 2.

4. The refractive index of the (A) styrene-butadiene copolymer rubber is 1.530 to 1.

570. The refractive index of the aforementioned (B) diene rubber is 1.450 to 1.530, and The refractive index of the filler (C) is 1.370 to 1.

500. The rubber composition according to claim 1 or 2.

5. The amount of bound styrene in the styrene-butadiene copolymer rubber (A) is 40 to 50% by mass. The rubber composition according to claim 1 or 2.

6. The (C) filler is at least one selected from the group consisting of silica, magnesium carbonate, carbon black, and magnesium hydroxide. The rubber composition according to claim 1 or 2.

7. The above (E) liquid diene rubber, Butadiene, and / or an oligomer of styrene-butadiene or acrylonitrile-butadiene, The rubber composition according to claim 2.

8. The haze level is 10-40%. The rubber composition according to claim 1 or 2.

9. An outsole comprising the rubber composition according to claim 1 or 2.

10. A bale containing (A) 98 to 99.98% by mass of styrene-butadiene copolymer rubber and (D) 0.02 to 2% by mass of fatty acids and / or fatty acid derivatives having an alkyl or alkenyl group having 8 to 30 carbon atoms, (B) A diene rubber selected from the group consisting of natural rubber, diene-based synthetic rubber, and block copolymers of aromatic vinyl compounds and conjugated diene compounds, wherein the Mooney viscosity is 20 or more and less than 80, The above (A) and the above (B) are such that the mass ratio of (A) / (B) is 5 / 95 to 50 / 50, and The process involves kneading 100 parts by mass of the rubber component consisting of (A) and (B) with 10 to 50 parts by mass of the filler (C), The (A) styrene-butadiene copolymer rubber has a ratio of styrene block amount to bound styrene amount of 0.02 to 0.23, a 1,2-vinyl bond amount of the butadiene portion of 10 to 60% by mass, a bound styrene amount of 35 to 55% by mass, and a Mooney viscosity of 80 to 110. A method for producing a rubber composition.

11. A bale containing (A) 98 to 99.98% by mass of styrene-butadiene copolymer rubber and (D) 0.02 to 2% by mass of fatty acids and / or fatty acid derivatives having an alkyl or alkenyl group having 8 to 30 carbon atoms, (B) A diene rubber selected from the group consisting of natural rubber, diene-based synthetic rubber, and block copolymers of aromatic vinyl compounds and conjugated diene compounds, wherein the Mooney viscosity is 20 or more and less than 80, The above (A) and the above (B) are such that the mass ratio of (A) / (B) is 5 / 95 to 50 / 50, and A step of kneading 100 parts by mass of the rubber component consisting of (A) and (B) with 10 to 50% by mass of (C) filler to obtain a kneaded product, The process involves mixing (G) a crosslinking agent into the aforementioned kneaded mixture and then pressurizing and / or heating it, It has, The (A) styrene-butadiene copolymer rubber has a ratio of styrene block amount to bound styrene amount of 0.02 to 0.23, a 1,2-vinyl bond amount of the butadiene portion of 10 to 60% by mass, a bound styrene amount of 35 to 55% by mass, and a Mooney viscosity of 80 to 110. A method for manufacturing cross-linked rubber sheets.

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