Rubber composition and crosslinked rubber molded product

Abstract

To provide a rubber composition from which a molded product crosslinked in a short time and having high hardness can be obtained.SOLUTION: The present disclosure provides a rubber composition containing (a) a base rubber, (b) a co-crosslinking agent, (c) a crosslinking initiator, and (d) a benzothiazole compound. The relationship of {(T2-T1) / (X-18)}≥0.46 is satisfied, where X is an amount of addition (parts by mass) of (b) the co-crosslinking agent with respect to 100 pts.mass of (a) the base rubber, T1 is a torque (N m) at 35 seconds and T2 is a torque (N m) at 45 seconds from a start of measuring the torque of the rubber composition when conducting a crosslinking test at a temperature of 170°C.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present disclosure relates to a rubber composition, and more particularly to a rubber composition that requires a short time for crosslinking. [Background technology]

[0002] As a material for forming the core of a golf ball, a rubber composition containing a base rubber, a co-crosslinking agent, and a crosslinking initiator is widely used because of its good resilience.

[0003] For example, Patent Document 1 describes a golf ball containing a composition including an unsaturated polymer, a crosslinking agent, a peptizer which is a non-metallic salt of an organic sulfur compound, and an accelerator selected from the group consisting of 2-mercaptobenzothiazole and salts of 2-mercaptobenzothiazole (see Patent Document 1 (claims 1, 7, and 11)).

[0004] Patent Document 2 describes a golf ball containing a composition that includes an unsaturated polymer, a crosslinking agent, a mastication accelerator, and a vulcanization accelerator, wherein the vulcanization accelerator is selected from the group consisting of 2-mercaptobenzothiazole and a salt of 2-mercaptobenzothiazole (see Patent Document 2 (Claims 1 and 25)). [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Laid-Open No. 2005-000647 [Patent Document 2] Japanese Patent Application Laid-Open No. 2005-000657 Summary of the Invention [Problem to be solved by the invention]

[0006] Although various rubber compositions have been proposed, conventional rubber compositions have the problem of requiring a long time for crosslinking. Furthermore, in conventional rubber compositions, crosslinking is not efficiently performed, so a large amount of co-crosslinking agent is required to increase the hardness of the cured product. The present disclosure has been made in view of the above circumstances, and an object of the present disclosure is to provide a rubber composition that requires a short time for crosslinking and that can give a molded product having high hardness. [Means for solving the problem]

[0007] A rubber composition according to a first aspect of the present disclosure, which has been able to solve the above problems, comprises (a) a base rubber, (b) a co-crosslinking agent, (c) a crosslinking initiator, and (d) a benzothiazole compound, wherein the (d) benzothiazole compound is at least one selected from the group consisting of compounds represented by formula (1), compounds represented by formula (2), and compounds represented by formula (3), and wherein, when the amount (parts by mass) of the (b) co-crosslinking agent added per 100 parts by mass of the (a) base rubber is X, the torque (N m) 35 seconds after the start of measurement when a crosslinking test of the rubber composition is performed at 170°C is T1, and the torque (N m) 45 seconds after the start of measurement is T2, these satisfy the relationship {(T2 - T1) / (X-18)} ≥ 0.46.

[0008] A rubber composition according to a second aspect of the present disclosure, which has been able to solve the above problems, comprises (a) a base rubber, (b) a co-crosslinking agent, (c) a crosslinking initiator, (d) a benzothiazole compound, and (f) an organic sulfur compound, wherein the (d) benzothiazole compound is at least one selected from the group consisting of compounds represented by formula (1), compounds represented by formula (2), and compounds represented by formula (3), and wherein, when the amount (parts by mass) of the (b) co-crosslinking agent added per 100 parts by mass of the (a) base rubber is X, the torque (N m) 10 seconds after the start of measurement when a crosslinking test is performed on the rubber composition at 170°C is T3, and the torque (N m) 60 seconds after the start of measurement is T4, these satisfy the relationship {(T4 - T3) / (X - 18)}>0.3. [Effects of the Invention]

[0009] By using the rubber composition of the present disclosure, a molded product having high hardness can be obtained in a short crosslinking time. [Brief explanation of the drawings]

[0010] [Figure 1] FIG. 2 is a graph showing the relationship between the crosslinking time and torque of a rubber composition. [Figure 2] FIG. 2 is a graph showing the relationship between the crosslinking time and torque of a rubber composition. [Figure 3] FIG. 2 is a graph showing the relationship between the crosslinking time and torque of a rubber composition. [Figure 4] FIG. 2 is a graph showing the relationship between the crosslinking time and torque of a rubber composition. [Figure 5] FIG. 2 is a graph showing the relationship between the crosslinking time and torque of a rubber composition. DETAILED DESCRIPTION OF THE INVENTION

[0011] [Rubber composition] The rubber composition of the present disclosure contains (a) a base rubber, (b) a co-crosslinking agent, (c) a crosslinking initiator, and a specific (d) benzothiazole compound. The rubber composition of the present disclosure contains the specific (d) benzothiazole compound, and requires a short time for crosslinking.

[0012] The raw materials used in the rubber composition will be described below.

[0013] (a) Base rubber The base rubber (a) can be natural rubber and / or synthetic rubber. Examples of the synthetic rubber include diene rubbers such as polybutadiene rubber (BR), polyisoprene rubber (IR), styrene polybutadiene rubber (SBR), chloroprene rubber (CR), butyl rubber (IIR), and acrylonitrile butadiene rubber (NBR); and non-diene rubbers such as ethylene propylene rubber (EPM), ethylene-propylene-diene rubber (EPDM), urethane rubber, silicone rubber, acrylic rubber, epichlorohydrin rubber, polysulfide rubber, fluororubber, and chlorosulfonated polyethylene rubber. These may be used alone or in combination of two or more.

[0014] The (a) base rubber preferably contains natural rubber and / or diene rubber. The total content of natural rubber and / or diene rubber in the (a) base rubber is preferably 50% by mass or more, more preferably 70% by mass or more, and even more preferably 90% by mass or more. It is also preferable that the (a) base rubber contains only natural rubber and / or diene rubber.

[0015] The base rubber (a) preferably contains polybutadiene rubber. High-cis polybutadiene, which has cis-1,4-bonds advantageous for resilience, is particularly suitable, with a content of 40% by mass or more, preferably 80% by mass or more, and more preferably 90% by mass or more. The content of high-cis polybutadiene in the base rubber (a) is preferably 50% by mass or more, more preferably 70% by mass or more.

[0016] The high-cis polybutadiene preferably has a 1,2-vinyl bond content of 2.0% by mass or less, more preferably 1.7% by mass or less, and even more preferably 1.5% by mass or less. If the 1,2-vinyl bond content is too high, the resilience may decrease.

[0017] The high-cis polybutadiene is preferably synthesized using a rare earth element catalyst, and in particular, the use of a neodymium-based catalyst using a neodymium compound, which is a lanthanum series rare earth element compound, is preferred because it can produce polybutadiene rubber having a high content of 1,4-cis bonds and a low content of 1,2-vinyl bonds with excellent polymerization activity.

[0018] The high-cis polybutadiene preferably has a molecular weight distribution Mw / Mn (Mw: weight-average molecular weight, Mn: number-average molecular weight) of 2.0 or more, more preferably 2.2 or more, even more preferably 2.4 or more, and most preferably 2.6 or more, and preferably 6.0 or less, more preferably 5.0 or less, even more preferably 4.0 or less, and most preferably 3.4 or less. If the molecular weight distribution (Mw / Mn) of the high-cis polybutadiene is too small, workability may decrease, while if it is too large, resilience may decrease. The molecular weight distribution was measured by gel permeation chromatography (manufactured by Tosoh Corporation, "HLC-8120GPC") using a differential refractometer as a detector, a column: GMHHXL (manufactured by Tosoh Corporation), a column temperature: 40°C, and a mobile phase: tetrahydrofuran, and calculated as a value converted into a standard polystyrene.

[0019] The high-cis polybutadiene has a Mooney viscosity (ML 1+4 (100°C)) is preferably 30 or more, more preferably 32 or more, even more preferably 35 or more, and is preferably 140 or less, more preferably 120 or less, even more preferably 100 or less, and most preferably 80 or less. 1+4 (100°C)) is a value measured in accordance with JIS K6300 using an L rotor, with a preheating time of 1 minute, rotor rotation time of 4 minutes, and at 100°C.

[0020] (b) Co-crosslinking agent The (b) co-crosslinking agent has the effect of crosslinking rubber molecules by graft polymerizing with the base rubber molecular chain. As the (b) co-crosslinking agent, an α,β-unsaturated carboxylic acid having 3 to 8 carbon atoms and / or a metal salt thereof is preferred, and a metal salt of an α,β-unsaturated carboxylic acid having 3 to 8 carbon atoms is more preferred. The α,β-unsaturated carboxylic acid used as the (b) co-crosslinking agent preferably has 3 to 8 carbon atoms, more preferably 3 to 6 carbon atoms, and even more preferably 3 or 4 carbon atoms. The α,β-unsaturated carboxylic acid having 3 to 8 carbon atoms and / or a metal salt thereof may be used alone or in combination of two or more types.

[0021] Examples of the α,β-unsaturated carboxylic acid having 3 to 8 carbon atoms include acrylic acid, methacrylic acid, fumaric acid, maleic acid, and crotonic acid. When the rubber composition contains only an α,β-unsaturated carboxylic acid having 3 to 8 carbon atoms as a co-crosslinking agent, the rubber composition preferably further contains (e) a metal compound. This is because, by neutralizing the α,β-unsaturated carboxylic acid having 3 to 8 carbon atoms in the rubber composition with a metal compound, substantially the same effect as when a metal salt of an α,β-unsaturated carboxylic acid having 3 to 8 carbon atoms is used as a co-crosslinking agent can be obtained.

[0022] Examples of metals constituting the metal salt of an α,β-unsaturated carboxylic acid having 3 to 8 carbon atoms include monovalent metal ions such as sodium, potassium, and lithium; divalent metal ions such as magnesium, calcium, zinc, barium, and cadmium; trivalent metal ions such as aluminum; and other ions such as tin and zirconium. The metal components can be used alone or in combination. Among these, divalent metals such as magnesium, calcium, zinc, barium, and cadmium are preferred as the metal component. This is because the use of a divalent metal salt of an α,β-unsaturated carboxylic acid having 3 to 8 carbon atoms facilitates the formation of metal crosslinks between rubber molecules. In particular, the divalent metal salt is preferably a zinc salt of an α,β-unsaturated carboxylic acid having 3 to 8 carbon atoms, and more preferably zinc acrylate, because it enhances the resilience of the resulting golf ball. When an α,β-unsaturated carboxylic acid having 3 to 8 carbon atoms and its metal salt are used in combination as a co-crosslinking agent, a metal compound (e) may be used as an optional component.

[0023] When the metal is a divalent or trivalent metal, (b) the metal salt of an α,β-unsaturated carboxylic acid having 3 to 8 carbon atoms may contain, as the carboxylic acid component, a carboxylic acid other than the α,β-unsaturated carboxylic acid having 3 to 8 carbon atoms. Examples of the other carboxylic acid include saturated carboxylic acids such as caprylic acid, capric acid, lauric acid, myristic acid, palmitic acid, stearic acid, arachidic acid, and behenic acid, and unsaturated carboxylic acids such as palmitoleic acid, oleic acid, linoleic acid, linolenic acid, and arachidonic acid.

[0024] The content of the (b) co-crosslinking agent is preferably more than 18 parts by mass, more preferably 20 parts by mass or more, even more preferably 25 parts by mass or more, particularly preferably 27 parts by mass or more, and is preferably 50 parts by mass or less, more preferably 45 parts by mass or less, and even more preferably 35 parts by mass or less, per 100 parts by mass of the (a) base rubber. If the content of the (b) co-crosslinking agent is more than 18 parts by mass, a small amount of the (c) crosslinking initiator can be used to impart appropriate hardness to a member formed from the rubber composition. On the other hand, if the content of the (b) co-crosslinking agent is 50 parts by mass or less, the member formed from the rubber composition will not be too hard.

[0025] (c) Crosslinking initiator The (c) crosslinking initiator is blended to crosslink the (a) base rubber component. An organic peroxide is suitable as the (c) crosslinking initiator. Specific examples of the organic peroxide include dicumyl peroxide, 1,1-bis(t-butylperoxy)-3,3,5-trimethylcyclohexane, 2,5-dimethyl-2,5-di(t-butylperoxy)hexane, and di-t-butyl peroxide. These organic peroxides may be used alone or in combination of two or more. Among these, dicumyl peroxide is preferably used.

[0026] The one-minute half-life temperature of the (c) crosslinking initiator is preferably 120°C or higher, more preferably 140°C or higher, and even more preferably 150°C or higher, and is preferably 200°C or lower, more preferably 190°C or lower, and even more preferably 180°C or lower.

[0027] The content of the (c) crosslinking initiator is preferably 0.2 parts by mass or more, more preferably 0.5 parts by mass or more, even more preferably 0.7 parts by mass or more, and is preferably 5.0 parts by mass or less, more preferably 2.5 parts by mass or less, even more preferably 2.0 parts by mass or less, and particularly preferably 0.9 parts by mass or less, per 100 parts by mass of the (a) base rubber. If the content is 0.2 parts by mass or more, the crosslinked rubber molded article formed from the rubber composition will not be too soft and will have good resilience, and if it is 5.0 parts by mass or less, the crosslinked rubber molded article formed from the rubber composition will have appropriate hardness and will have good resilience and durability.

[0028] (d) Benzothiazole compounds The (d) benzothiazole compound used in the present disclosure will now be described. The (d) benzothiazole compound includes compounds represented by formula (1), formula (2), and formula (3). By incorporating these (d) benzothiazole compounds, crosslinks can be efficiently formed, shortening the time required for crosslinking. Furthermore, because crosslinks can be efficiently formed, molded articles with high hardness can be obtained even when the amount of (b) co-crosslinking agent incorporated is small.

[0029] [ka] [R 1 represents a hydrogen atom, an alkyl group having 1 to 8 carbon atoms, an aryl group having 4 to 14 carbon atoms, or a metal atom. R 2 ~R 5 are the same or different and represent a hydrogen atom, a halogen atom, an alkyl group having 1 to 8 carbon atoms, an aryl group having 4 to 14 carbon atoms, an alkoxy group having 1 to 8 carbon atoms, or a perfluoroalkyl group having 1 to 8 carbon atoms.

[0030] [ka] [R 11 ~R 14are the same or different and represent a hydrogen atom, a halogen atom, an alkyl group having 1 to 8 carbon atoms, an aryl group having 4 to 14 carbon atoms, an alkoxy group having 1 to 8 carbon atoms, or a perfluoroalkyl group having 1 to 8 carbon atoms. M represents a metal atom. n represents 1 or 2.]

[0031] The compound represented by the formula (3) is more preferably a compound represented by the formula (31).

[0032] [ka] [R 11 ~R 18 are the same or different and represent a hydrogen atom, a halogen atom, an alkyl group having 1 to 8 carbon atoms, an aryl group having 4 to 14 carbon atoms, an alkoxy group having 1 to 8 carbon atoms, or a perfluoroalkyl group having 1 to 8 carbon atoms. X represents a divalent metal atom.

[0033] R in formula (1) or formula (2) 1 Examples of the alkyl group having 1 to 8 carbon atoms represented by the formula (I) include a linear alkyl group, a branched alkyl group, and a cyclic alkyl group. The alkyl group preferably has 1 or more carbon atoms, and 6 or less, and more preferably 4 or less carbon atoms. Examples of the linear alkyl group include a methyl group, an ethyl group, an n-propyl group, an n-butyl group, and an n-pentyl group. Examples of the branched alkyl group include an isopropyl group, an isobutyl group, a s-butyl group, a t-butyl group, and an isopentyl group. Examples of the cyclic alkyl group include a cyclopropyl group, a cyclobutyl group, a cyclopentyl group, and a cyclohexyl group.

[0034] R 1 The number of carbon atoms in the aryl group having 4 to 14 carbon atoms, represented by the following formula, is preferably 12 or less, and more preferably 10 or less. Examples of the aryl group include a phenyl group and a naphthyl group.

[0035] R 1Examples of the metal atom represented by the formula include sodium, potassium, lithium, magnesium, calcium, zinc, barium, and cadmium.

[0036] R 1 is preferably a hydrogen atom or an alkyl group having 1 to 8 carbon atoms, more preferably a hydrogen atom.

[0037] R in formula (1), (2), (3) or (31) 2 ~R 5 , R 11 ~R 18 Examples of the halogen group represented by the formula include a fluoro group (-F), a chloro group (-Cl), and a bromo group (-Br).

[0038] R 2 ~R 5 , R 11 ~R 18 Examples of the alkyl group having 1 to 8 carbon atoms represented by the formula (I) include a linear alkyl group, a branched alkyl group, and a cyclic alkyl group. The alkyl group preferably has 1 or more carbon atoms, and 6 or less, and more preferably 4 or less carbon atoms. Examples of the linear alkyl group include a methyl group, an ethyl group, an n-propyl group, an n-butyl group, and an n-pentyl group. Examples of the branched alkyl group include an isopropyl group, an isobutyl group, a s-butyl group, a t-butyl group, and an isopentyl group. Examples of the cyclic alkyl group include a cyclopropyl group, a cyclobutyl group, a cyclopentyl group, and a cyclohexyl group.

[0039] R 2 ~R 5 , R 11 ~R 18 The number of carbon atoms in the aryl group having 4 to 14 carbon atoms, represented by the following formula, is preferably 12 or less, and more preferably 10 or less. Examples of the aryl group include a phenyl group and a naphthyl group.

[0040] R 2 ~R 5 , R 11 ~R18 The number of carbon atoms in the alkoxy group having 1 to 8 carbon atoms, represented by the following formula, is preferably 6 or less, and more preferably 4 or less. Examples of the alkoxy group include a methoxy group, an ethoxy group, a propoxy group, and a butoxy group.

[0041] R 2 ~R 5 , R 11 ~R 18 The number of carbon atoms in the perfluoroalkyl group having 1 to 8 carbon atoms, represented by the formula (I), is preferably 6 or less, and more preferably 4 or less. Examples of the perfluoroalkyl group include a trifluoromethyl group (-CF3), a pentafluoroethyl group (-C2F5), and a heptafluoropropyl group (-C3F7).

[0042] R 2 ~R 5 , R 11 ~R 18 is preferably a hydrogen atom or an alkyl group having 1 to 8 carbon atoms, more preferably a hydrogen atom.

[0043] Examples of monovalent metal atoms represented by M in formula (3) include sodium, potassium, and lithium, and examples of divalent metal atoms include magnesium, calcium, zinc, barium, and cadmium. Examples of the divalent metal atom represented by X in formula (31) include magnesium, calcium, zinc, barium, and cadmium.

[0044] The amount of the (d) benzothiazole compound is preferably 0.01 part by mass or more, more preferably 0.1 part by mass or more, and even more preferably 0.5 part by mass or more, per 100 parts by mass of the (a) base rubber, and is preferably 20 parts by mass or less, more preferably 10 parts by mass or less, and even more preferably 5 parts by mass or less. If the amount of the (d) benzothiazole compound is 0.01 part by mass or more, the hardness of the obtained crosslinked rubber is further improved, and if it is 20 parts by mass or less, the physical properties of the obtained crosslinked rubber are good.

[0045] (e) Metal compounds The rubber composition may further contain (e) a metal compound. The (e) metal compound is preferably one capable of neutralizing (b) the α,β-unsaturated carboxylic acid having 3 to 8 carbon atoms in the rubber composition. Examples of the (e) metal compound include metal hydroxides such as magnesium hydroxide, zinc hydroxide, calcium hydroxide, sodium hydroxide, lithium hydroxide, potassium hydroxide, and copper hydroxide; metal oxides such as magnesium oxide, calcium oxide, zinc oxide, and copper oxide; and metal carbonates such as magnesium carbonate, zinc carbonate, calcium carbonate, sodium carbonate, lithium carbonate, and potassium carbonate. The (e) metal compound is preferably a divalent metal compound, and more preferably a zinc compound. This is because the divalent metal compound reacts with the α,β-unsaturated carboxylic acid having 3 to 8 carbon atoms to form a metal crosslink. Furthermore, the use of a zinc compound allows for the production of a crosslinked rubber molded product with high resilience. The (e) metal compound may be used alone or in combination of two or more. The content of the (e) metal compound may be appropriately adjusted.

[0046] (f) Organic sulfur compounds The rubber composition may further contain (f) an organic sulfur compound. The (f) organic sulfur compound does not include the (d) benzothiazole compound. Examples of the (f) organic sulfur compound include at least one compound selected from the group consisting of thiophenols, thionaphthols, polysulfides, thiurams, thiocarboxylic acids, dithiocarboxylic acids, sulfenamides, dithiocarbamates, thiazoles, and metal salts thereof. The (f) organic sulfur compound is preferably an organic sulfur compound having a thiol group (-SH) or a metal salt thereof, and more preferably a thiophenol, a thionaphthol, or a metal salt thereof.

[0047] Examples of thiols include thiophenols and thionaphthols. Examples of the thiophenols include thiophenol; thiophenols substituted with a fluoro group, such as 4-fluorothiophenol, 2,5-difluorothiophenol, 2,6-difluorothiophenol, 2,4,5-trifluorothiophenol, 2,4,5,6-tetrafluorothiophenol, and pentafluorothiophenol; 2-chlorothiophenol, 4-chlorothiophenol, 2,4-dichlorothiophenol, 2,5-dichlorothiophenol, 2,6-dichlorothiophenol, 2,4,5-trichlorothiophenol, 2,4,5,6-tetrachlorothiophenol, and pentachlorothiophenol. Thiophenols substituted with a chloro group such as thiophenol; thiophenols substituted with a bromo group such as 4-bromothiophenol, 2,5-dibromothiophenol, 2,6-dibromothiophenol, 2,4,5-tribromothiophenol, 2,4,5,6-tetrabromothiophenol, and pentabromothiophenol; thiophenols substituted with an iodo group such as 4-iodothiophenol, 2,5-diiodothiophenol, 2,6-diiodothiophenol, 2,4,5-triiodothiophenol, 2,4,5,6-tetraiodothiophenol, and pentaiodothiophenol; or metal salts thereof. Zinc salts are preferred as the metal salt.

[0048] Examples of the thionaphthols (naphthalene thiols) include 2-thionaphthol, 1-thionaphthol, 1-chloro-2-thionaphthol, 2-chloro-1-thionaphthol, 1-bromo-2-thionaphthol, 2-bromo-1-thionaphthol, 1-fluoro-2-thionaphthol, 2-fluoro-1-thionaphthol, 1-cyano-2-thionaphthol, 2-cyano-1-thionaphthol, 1-acetyl-2-thionaphthol, 2-acetyl-1-thionaphthol, and metal salts thereof, with 2-thionaphthol and 1-thionaphthol being preferred. The metal salt is preferably a divalent metal salt, more preferably a zinc salt. Specific examples of the metal salt include the zinc salt of 1-thionaphthol and the zinc salt of 2-thionaphthol.

[0049] Polysulfides are organic sulfur compounds having polysulfide bonds, such as disulfides, trisulfides, and tetrasulfides. Diphenyl polysulfides are preferred as the polysulfides.

[0050] Diphenyl polysulfides include, in addition to diphenyl disulfide, bis(4-fluorophenyl) disulfide, bis(2,5-difluorophenyl) disulfide, bis(2,6-difluorophenyl) disulfide, bis(2,4,5-trifluorophenyl) disulfide, bis(2,4,5,6-tetrafluorophenyl) disulfide, bis(pentafluorophenyl) disulfide, bis(4-chloro ... Bis(2,5-dichlorophenyl) disulfide, bis(2,6-dichlorophenyl) disulfide, bis(2,4,5-trichlorophenyl) disulfide, bis(2,4,5,6-tetrachlorophenyl) disulfide, bis(pentachlorophenyl) disulfide, bis(4-bromophenyl) disulfide, bis(2,5-dibromophenyl) disulfide, bis(2,6-dibromophenyl) disulfide, bis(2,4,5-tribromophenyl) disulfide phenyl) disulfide, bis(2,4,5,6-tetrabromophenyl) disulfide, bis(pentabromophenyl) disulfide, bis(4-iodophenyl) disulfide, bis(2,5-diiodophenyl) disulfide, bis(2,6-diiodophenyl) disulfide, bis(2,4,5-triiodophenyl) disulfide, bis(2,4,5,6-tetraiodophenyl) disulfide, bis(pentaiodophenyl) disulfide diphenyl disulfides substituted with a halogen group, such as bis(4-methylphenyl) disulfide, bis(2,4,5-trimethylphenyl) disulfide, bis(pentamethylphenyl) disulfide, bis(4-t-butylphenyl) disulfide, bis(2,4,5-tri-t-butylphenyl) disulfide, and bis(penta-t-butylphenyl) disulfide; and diphenyl disulfides substituted with an alkyl group, such as bis(4-methylphenyl) disulfide, bis(2,4,5-tri-t-butylphenyl) disulfide, and bis(penta-t-butylphenyl) disulfide.

[0051] Examples of thiurams include thiuram monosulfides such as tetramethylthiuram monosulfide, thiuram disulfides such as tetramethylthiuram disulfide, tetraethylthiuram disulfide, and tetrabutylthiuram disulfide, and thiuram tetrasulfides such as dipentamethylenethiuram tetrasulfide. Examples of thiocarboxylic acids include naphthalene thiocarboxylic acid. Examples of dithiocarboxylic acids include naphthalene dithiocarboxylic acid. Examples of sulfenamides include N-cyclohexyl-2-benzothiazole sulfenamide, N-oxydiethylene-2-benzothiazole sulfenamide, and Nt-butyl-2-benzothiazole sulfenamide.

[0052] (f) The organic sulfur compounds can be used alone or in combination. (f) The organic sulfur compounds are preferably thiophenols and / or metal salts thereof, thionaphthols and / or metal salts thereof, diphenyl disulfides, and thiuram disulfides, and more preferably 2,4-dichlorothiophenol, 2,6-difluorothiophenol, 2,6-dichlorothiophenol, 2,6-dibromothiophenol, 2,6-diiodothiophenol, 2,4,5-trichlorothiophenol, pentachlorothiophenol, 1-thionaphthol, 2-thionaphthol, diphenyl disulfide, bis(2,6-difluorophenyl)disulfide, bis(2,6-dichlorophenyl)disulfide, bis(2,6-dibromophenyl)disulfide, bis(2,6-diiodophenyl)disulfide, bis(pentabromophenyl)disulfide, and metal salts thereof.

[0053] If the rubber composition contains an organic sulfur compound (f) other than the benzothiazole compound (d), crosslinking tends to occur more slowly. Therefore, to increase the crosslinking rate, the content of the organic sulfur compound (f) is preferably 5.0 parts by mass or less, more preferably 1.0 part by mass or less, even more preferably 0.05 part by mass or less, and particularly preferably 0.01 part by mass or less, per 100 parts by mass of the base rubber (a). It is also preferable that the rubber composition does not contain any organic sulfur compound (f) other than the benzothiazole compound (d).

[0054] When the rubber composition contains an (f) organic sulfur compound other than the (d) benzothiazole compound, the resilience of the resulting cured product improves, but crosslinking tends to occur more slowly. Therefore, by using the (d) benzothiazole compound in combination with the (f) organic sulfur compound, the resilience of the cured product can be improved while suppressing a decrease in the crosslinking rate. Therefore, to improve resilience, the content of the (f) organic sulfur compound is preferably 0.05 parts by mass or more, more preferably 0.1 parts by mass or more, and preferably 5.0 parts by mass or less, more preferably 2.0 parts by mass or less, per 100 parts by mass of the (a) base rubber. If the content of the (f) organic sulfur compound is less than 0.05 parts by mass, the effect of adding the (f) organic sulfur compound cannot be obtained, and the resilience of the crosslinked rubber molded product may not be improved. Furthermore, if the content of the (f) organic sulfur compound exceeds 5.0 parts by mass, the compressive deformation of the resulting crosslinked rubber molded product increases, potentially resulting in reduced resilience.

[0055] (g) Carboxylic acid and / or its salt The rubber composition may contain (g) a carboxylic acid and / or a salt thereof. By containing the (g) carboxylic acid and / or a salt thereof, the hardness distribution of the resulting crosslinked rubber molded article can be controlled. Examples of the (g) carboxylic acid and / or a salt thereof include aliphatic carboxylic acids, aliphatic carboxylic acid salts, aromatic carboxylic acids, and aromatic carboxylic acid salts. The (g) carboxylic acid and / or a salt thereof can be used alone or as a mixture of two or more. Note that the (g) carboxylic acid and / or a salt thereof does not include the α,β-unsaturated carboxylic acid having 3 to 8 carbon atoms and / or a metal salt thereof used as the (b) co-crosslinking agent.

[0056] The aliphatic carboxylic acid may be either a saturated aliphatic carboxylic acid (hereinafter, sometimes referred to as a "saturated fatty acid") or an unsaturated aliphatic carboxylic acid (hereinafter, sometimes referred to as an "unsaturated fatty acid"). The aliphatic carboxylic acid may have a branched structure or a cyclic structure. The saturated fatty acid preferably has 6 or more carbon atoms, and 24 or less, more preferably 18 or less, and even more preferably 13 or less. The unsaturated fatty acid preferably has 6 or more carbon atoms, more preferably 7 or more, and even more preferably 8 or more, and preferably 24 or less, more preferably 18 or less, and even more preferably 13 or less.

[0057] Examples of the aromatic carboxylic acid include those having a benzene ring in the molecule and those having a heteroaromatic ring in the molecule. The aromatic carboxylic acids may be used alone or in combination of two or more. Examples of the carboxylic acid having a benzene ring include aromatic carboxylic acids in which a carboxyl group is directly bonded to the benzene ring, aromatic-aliphatic carboxylic acids in which an aliphatic carboxylic acid is bonded to the benzene ring, polynuclear aromatic carboxylic acids in which a carboxyl group is directly bonded to a condensed benzene ring, and polynuclear aromatic-aliphatic carboxylic acids in which an aliphatic carboxylic acid is bonded to a condensed benzene ring. Examples of the carboxylic acid having a heteroaromatic ring include those in which a carboxyl group is directly bonded to a heteroaromatic ring.

[0058] The aliphatic carboxylate or aromatic carboxylate salt can be a salt of the above-mentioned aliphatic carboxylic acid or aromatic carboxylic acid. Examples of the cationic components of these salts include metal ions, ammonium ions, and organic cations. The cationic components can be used alone or as a mixture of two or more. Examples of metal ions include monovalent metal ions such as sodium, potassium, lithium, and silver; divalent metal ions such as magnesium, calcium, zinc, barium, cadmium, copper, cobalt, nickel, and manganese; trivalent metal ions such as aluminum and iron; and other ions such as tin, zirconium, and titanium. Among these, divalent metal ions are preferred, with magnesium, zinc, and calcium being more preferred.

[0059] The organic cation is a cation having a carbon chain. The organic cation is not particularly limited, and examples thereof include organic ammonium ions. Examples of the organic ammonium ions include primary ammonium ions such as stearyl ammonium ion, hexyl ammonium ion, octyl ammonium ion, and 2-ethylhexyl ammonium ion; secondary ammonium ions such as dodecyl (lauryl) ammonium ion and octadecyl (stearyl) ammonium ion; tertiary ammonium ions such as trioctyl ammonium ion; and quaternary ammonium ions such as dioctyl dimethyl ammonium ion and distearyl dimethyl ammonium ion. These organic cations may be used alone or in combination of two or more.

[0060] The aliphatic carboxylic acids and / or their salts include saturated fatty acids and / or their salts, and unsaturated fatty acids and / or their salts. The saturated fatty acids and / or their salts are preferred, with caprylic acid (octanoic acid), pelargonic acid (nonanoic acid), capric acid (decanoic acid), lauric acid, myristic acid, palmitic acid, stearic acid, behenic acid, or their potassium salts, magnesium salts, calcium salts, aluminum salts, zinc salts, iron salts, copper salts, nickel salts, and cobalt salts being preferred. The unsaturated fatty acids and / or their salts are preferred, with palmitoleic acid, oleic acid, linoleic acid, or arachidonic acid, or their potassium salts, magnesium salts, calcium salts, aluminum salts, zinc salts, iron salts, copper salts, nickel salts, and cobalt salts being preferred.

[0061] Particularly preferred examples of the aromatic carboxylic acid and / or its salt include benzoic acid, butylbenzoic acid, anisic acid (methoxybenzoic acid), dimethoxybenzoic acid, trimethoxybenzoic acid, dimethylaminobenzoic acid, chlorobenzoic acid, dichlorobenzoic acid, trichlorobenzoic acid, acetoxybenzoic acid, biphenylcarboxylic acid, naphthalenecarboxylic acid, anthracenecarboxylic acid, furancarboxylic acid, and thenoic acid, as well as potassium salts, magnesium salts, calcium salts, aluminum salts, zinc salts, iron salts, copper salts, nickel salts, and cobalt salts thereof.

[0062] The content of the (g) carboxylic acid and / or its salt is, for example, preferably 1 part by mass or more, more preferably 2 parts by mass or more, and even more preferably 3 parts by mass or more, per 100 parts by mass of the (a) base rubber, and is preferably 30 parts by mass or less, more preferably 20 parts by mass or less, and even more preferably 15 parts by mass or less.

[0063] (Other ingredients) The rubber composition may contain additives such as pigments, fillers for adjusting the weight, antioxidants, peptizers, softeners, etc. as needed. The rubber composition may also contain rubber powder obtained by pulverizing the core of a golf ball or scraps generated during the production of the core.

[0064] Examples of pigments that can be compounded into the rubber composition include white pigments, blue pigments, and purple pigments. Titanium oxide is preferably used as the white pigment. The type of titanium oxide is not particularly limited, but rutile-type titanium oxide is preferably used because of its good hiding power. The content of titanium oxide is preferably 0.5 parts by mass or more, more preferably 2 parts by mass or more, and preferably 8 parts by mass or less, more preferably 5 parts by mass or less, per 100 parts by mass of (a) base rubber.

[0065] In another preferred embodiment, the rubber composition contains a white pigment and a blue pigment. The blue pigment is blended to make the white color appear more vivid, and examples of the blue pigment include ultramarine, cobalt blue, and phthalocyanine blue. Examples of the purple pigment include anthraquinone violet, dioxazine violet, and methyl violet.

[0066] The filler used in the rubber composition is blended as a weight adjuster to adjust the mass of the resulting crosslinked rubber molded product, and may be blended as needed. Examples of the filler include inorganic fillers such as zinc oxide, barium sulfate, calcium carbonate, magnesium oxide, tungsten powder, and molybdenum powder.

[0067] The content of the antioxidant is preferably 0.1 part by weight to 1 part by weight per 100 parts by weight of the (a) base rubber, and the content of the peptizing agent is preferably 0.1 part by weight to 5 parts by weight per 100 parts by weight of the (a) base rubber.

[0068] The rubber composition may be exemplified by an embodiment (embodiment 1) in which the (d) benzothiazole compound contains at least one selected from the group consisting of compounds represented by formula (1), compounds represented by formula (2), and compounds represented by formula (3); or an embodiment (embodiment 2) in which the (d) benzothiazole compound contains at least one selected from the group consisting of compounds represented by formula (1), compounds represented by formula (2), and compounds represented by formula (3) and (f) an organic sulfur compound.

[0069] The molar ratio ((d) / (c)) of the molar amount of the (c) crosslinking initiator to the molar amount of the (d) benzothiazole compound in the rubber composition is preferably 0.5 or more, more preferably 1.0 or more, and even more preferably 1.5 or more, and is preferably 10 or less, more preferably 7 or less, and even more preferably 5 or less. If the molar ratio ((d) / (c)) is 0.5 or more, the hardness of the obtained crosslinked rubber is further improved, and if it is 10 or less, the physical properties of the obtained crosslinked rubber are good.

[0070] In the rubber composition of the second embodiment, the mass ratio ((d) / (f)) of the (d) benzothiazole compound to the (f) organic sulfur compound is preferably 0.5 or more, more preferably 1 or more, and even more preferably 1.5 or more, and is preferably 10 or less, more preferably 8 or less, and even more preferably 5 or less. When the mass ratio ((d) / (f)) is 0.5 or more, crosslinking proceeds efficiently, and when it is 10 or less, the physical properties of the resulting crosslinked rubber are good.

[0071] The rubber composition preferably contains (e) a metal compound, more preferably a zinc compound, and particularly preferably zinc oxide.

[0072] When the rubber composition is compounded with a compound represented by formula (1) and / or a compound represented by formula (2) and an (e) metal compound, the ratio (M2 / (M1 × valence)) of the total number of moles M2 of the compound represented by formula (1) and the compound represented by formula (2) to the product of the number of moles M1 of the (e) metal compound and the valence of the contained metal is preferably 0.01 or more, more preferably 0.02 or more, even more preferably 0.04 or more, and is preferably 1.0 or less, more preferably 0.5 or less, even more preferably 0.1 or less.

[0073] When the rubber composition is compounded with a compound represented by formula (3) and an (e) metal compound, the ratio (M21 / {(M1 × valence) + (M22 × valence)} of the number of moles M21 of the structure derived from the compound represented by formula (1) in the compound represented by formula (3) to the sum of the product of the number of moles M1 of the (e) metal compound and the valence of the metal contained therein and the product of the number of moles M22 of the metal component in the compound represented by formula (3) and the valence of the metal is preferably 0.01 or more, more preferably 0.02 or more, even more preferably 0.04 or more, and is preferably 1.0 or less, more preferably 0.5 or less, even more preferably 0.1 or less.

[0074] Preparation of Rubber Composition The rubber composition used in the present disclosure is obtained by mixing and kneading (a) base rubber, (b) co-crosslinking agent, (c) crosslinking initiator, (d) benzothiazole compound, and, if necessary, other additives, etc. The kneading method is not particularly limited, and may be performed using a known kneading machine such as a kneading roll, a Banbury mixer, or a kneader.

[0075] Rubber composition properties The rubber composition of the first embodiment is also characterized in that, when X is the amount (parts by mass) of (b) co-crosslinking agent added relative to 100 parts by mass of (a) base rubber, T1 is the torque (N m) 35 seconds after the start of a crosslinking test of the rubber composition at 170°C, and T2 is the torque (N m) 45 seconds after the start of the test, the ratio {(T2-T1) / (X-18)} falls within a predetermined range. Efficient crosslinking can be achieved when the ratio {(T2-T1) / (X-18)} falls within the predetermined range.

[0076] When the rubber composition of the first aspect contains a compound represented by formula (1) and / or a compound represented by formula (2), the rubber composition has a ratio {(T2-T1) / (X-18)} of preferably 0.46 or greater and more than 0.55, more preferably greater than 0.60, and even more preferably greater than 0.65, and is preferably 3 or less, more preferably 2 or less, and even more preferably 1 or less.

[0077] When the rubber composition of the first aspect contains a compound represented by formula (1) and / or a compound represented by formula (2), the difference (T2-T1) is preferably 6 or more, more preferably 7 or more, and even more preferably 8 or more, and is preferably 20 or less, more preferably 17 or less, and even more preferably 15 or less.

[0078] When the rubber composition of the first aspect contains the compound represented by formula (3), the ratio {(T2-T1) / (X-18)} of the rubber composition is preferably 0.46 or more, more preferably greater than 0.46, even more preferably greater than 0.5, and particularly preferably greater than 0.6, and is preferably 2 or less, more preferably 1.5 or less, and even more preferably 1 or less.

[0079] When the rubber composition of the first aspect contains a compound represented by formula (3), the difference (T2-T1) is preferably 0.3 or more, more preferably 0.4 or more, even more preferably 0.5 or more, and particularly preferably 3 or more, and is preferably 20 or less, more preferably 17 or less, even more preferably 15 or less, and particularly preferably 10 or less.

[0080] The rubber composition of Aspect 2 (when containing (f) an organic sulfur compound) is also characterized in that, when the amount (parts by mass) of (b) co-crosslinking agent added per 100 parts by mass of (a) base rubber is X, the torque (N m) 10 seconds after the start of a crosslinking test of the rubber composition at 170°C is T3, and the torque (N m) 60 seconds after the start of the test is T4, the ratio {(T4 - T3) / (X-18)} falls within a predetermined range. Efficient crosslinking can be achieved when the ratio {(T4 - T3) / (X-18)} falls within the predetermined range.

[0081] In the rubber composition of the second aspect, the ratio {(T4-T3) / (X-18)} is preferably greater than 0.3, more preferably 0.35 or greater, and even more preferably 0.4 or greater, and is preferably 2 or less, more preferably 1.5 or less, and even more preferably 1 or less.

[0082] In the rubber composition of the second aspect, the difference (T4-T3) is preferably 1.5 or more, more preferably 2 or more, and even more preferably 3 or more, and is preferably 8 or less, more preferably 7 or less, and even more preferably 6 or less.

[0083] [Crosslinked rubber molded body] The crosslinked rubber molded article of the present disclosure is characterized by being formed from the rubber composition. The crosslinked rubber molded article can be obtained by molding the kneaded rubber composition in a mold. The molding temperature is preferably 120°C or higher, more preferably 150°C or higher, and preferably 250°C or lower. The molding pressure is preferably 2.9 MPa to 11.8 MPa. The molding time is preferably 10 minutes to 60 minutes.

[0084] Applications of the crosslinked rubber molded article include sporting goods such as golf balls, tennis balls, grips, etc.; industrial goods such as hoses, belts, mats, etc.; shoe soles, tires, resin additives, vibration-proof rubber, fenders, etc. Examples of the golf ball include those having components formed from the rubber composition. [Example]

[0085] The present disclosure will be described in detail below using examples, but the present disclosure is not limited to the following examples, and all modifications and embodiments that do not deviate from the spirit of the present disclosure are included within the scope of the present disclosure.

[0086] [Evaluation method] (1) Slab hardness (Shore C) A sheet approximately 2 mm thick was prepared by heat press molding (170°C, 20 minutes), and the test specimen was stored at a temperature of 23±2°C and a relative humidity of 50±5% for 12 hours or more. Three or more sheets were stacked to avoid interference from the measurement substrate, and the hardness was measured using an automatic hardness tester (DigiTest II, manufactured by H. Burleith). A Shore C detector was used.

[0087] (2) Lubke's rebound resilience (%) The impact resilience test was performed in accordance with JIS K6255 (2013). A sheet approximately 2 mm thick was prepared by hot press molding (170°C, 20 minutes). Six 28 mm diameter circular pieces were punched out from the sheet and stacked to prepare cylindrical test specimens approximately 12 mm thick and 28 mm in diameter. These test specimens were stored at a temperature of 23±2°C and a relative humidity of 50±5% for at least 12 hours. The impact resilience of the prepared test specimens was measured using a Lübke impact resilience tester (manufactured by Ueshima Seisakusho Co., Ltd.). The flat surface of the stacked test specimens was supported by a mechanical fixation method. The measurement conditions were a temperature of 23°C, a relative humidity of 50%, a striking end diameter of 12.50±0.05 mm, a striking mass of 0.35±0.01 kg, and a striking velocity of 1.4±0.01 m / s.

[0088] (3) Cross-linking test After sampling an appropriate amount of each rubber composition, the vulcanization curve was measured at 170°C using a vulcanization tester (Curastometer Model 7, manufactured by JSR Trading Co., Ltd.). According to "9. Die vulcanization test method A" in "Method for determining vulcanization characteristics using a vibration vulcanization tester" of JIS K6300-2 (2001), a low-amplitude sinusoidal vibration was applied to the rubber test piece from the lower die, but not enough to break it, and the torque transmitted from the test piece to the upper die was measured from under-vulcanization to over-vulcanization. The measurement conditions were a torsional vibration frequency of 100 vibrations per minute and an amplitude angle of 1°.

[0089] [Preparation of Rubber Composition] A rubber composition was prepared by kneading the rubber composition having the formulation shown in Table 1 with a kneading roll. The obtained rubber composition was evaluated.

[0090] [Table 1]

[0091] [Table 2]

[0092] [Table 3]

[0093] [Table 4]

[0094] The raw materials used in Tables 1 to 4 are as follows. BR: "BR730" (high cis polybutadiene rubber (cis-1,4-bond content = 96 mass%, 1,2-vinyl bond content = 1.3 mass%, Mooney viscosity (ML 1+4 (100℃)=55, molecular weight distribution (Mw / Mn)=3)) ZN-DA90S: Zinc acrylate (containing 10% zinc stearate by mass), manufactured by Nisshoku Techno Fine Chemical Co., Ltd. ZnO: "Ginrei R" (zinc oxide) manufactured by Toho Zinc Co., Ltd. PBDS: Kawaguchi Chemical Industry Co., Ltd., bis(pentabromophenyl) disulfide PCTP-Zn: Pentachlorothiophenol zinc salt, manufactured by Fujifilm Wako Chemical Co., Ltd. Noccela (registered trademark) EUR: N,N'-diethylthiourea, manufactured by Ouchi Shinko Chemical Industry Co., Ltd. Noccela MP: 2-mercaptobenzothiazole, manufactured by Ouchi Shinko Chemical Industry Co., Ltd. Noccela CZ-G: N-cyclohexyl-2-benzothiazolyl sulfenamide, manufactured by Ouchi Shinko Chemical Industry Co., Ltd. Noccela TBZTB: Tetrabenzyl thiuram disulfide, manufactured by Ouchi Shinko Chemical Industry Co., Ltd. Noccela EZ: Zinc diethyldithiocarbamate, manufactured by Ouchi Shinko Chemical Industry Co., Ltd. Thiazole disulfide: 2,2'-dithiobisbenzothiazole, manufactured by Tokyo Chemical Industry Co., Ltd. Thiazole Zn: 2-mercaptobenzothiazole zinc salt, manufactured by Fujifilm Wako Chemical Co., Ltd. Thiazole Na: 2-mercaptobenzothiazole sodium salt, manufactured by Tokyo Chemical Industry Co., Ltd. DCP: NOF Corporation, "Percumyl (registered trademark) D" (dicumyl peroxide)

[0095] The slab hardness and Lupke rebound resilience of the crosslinked rubber obtained from the rubber composition are shown in Tables 1 to 4. Furthermore, the relationship between the crosslinking time and torque in the crosslinking test is shown in Figures 1 to 5.

[0096] Rubber compositions Nos. 4, 18, and 19 contain a compound represented by formula (1) as the (d) benzothiazole compound, and {(T2-T1) / (X-18)} is 0.46 or greater. Rubber compositions Nos. 24 and 25 contain a compound represented by formula (3) as the (d) benzothiazole compound, and {(T2-T1) / (X-18)} is 0.46 or greater. These rubber compositions Nos. 4, 18, 19, 24, and 25 are crosslinked in a shorter time than rubber compositions Nos. 1, 8 to 11. Furthermore, comparing rubber compositions No. 1 and No. 4, rubber composition No. 4 provides a crosslinked rubber with increased hardness without increasing the amount of co-crosslinking agent used. Furthermore, comparing rubber compositions No. 10 and No. 24, rubber composition No. 24 provides a crosslinked rubber with increased hardness without increasing the amount of co-crosslinking agent used.

[0097] In addition, in the rubber compositions Nos. 3 and 5 to 7 in which compounds other than the (d) benzothiazole compound were compounded, the time required for crosslinking was long, and the hardness of the obtained crosslinked rubber was reduced.

[0098] Furthermore, rubber compositions Nos. 2, 12 to 17, 22, and 23, which contain bis(pentabromophenyl) disulfide, pentachlorothiophenol zinc salt, and thiazole disulfide, have improved impact resilience but require longer times for crosslinking.

[0099] Rubber compositions Nos. 28 to 31 contain a compound represented by formula (1) as a (d) benzothiazole compound and an (f) organic sulfur compound, and {(T4-T3) / (X-18)} is greater than 0.30. Rubber compositions Nos. 32 and 33 contain a compound represented by formula (3) as a (d) benzothiazole compound and an (f) organic sulfur compound, and {(T4-T3) / (X-18)} is greater than 0.30. Rubber compositions Nos. 34 to 37 contain an (f) organic sulfur compound but do not contain a (d) benzothiazole compound. Rubber compositions Nos. 28 to 33 are crosslinked in a shorter time than rubber compositions Nos. 34 to 37. In addition, when comparing rubber compositions Nos. 30 and 33 with No. 35, which contain the same amount of co-crosslinking agent, rubber compositions Nos. 30 and 33 have higher slab hardness than rubber composition No. 35. Therefore, by using the benzothiazole compound (d) represented by formula (1) in combination with the organic sulfur compound (f), it is possible to improve the rebound resilience while suppressing a decrease in hardness.

[0100] The present disclosure (1) is a rubber composition comprising (a) a base rubber, (b) a co-crosslinking agent, (c) a crosslinking initiator, and (d) a benzothiazole compound, wherein the (d) benzothiazole compound is at least one selected from the group consisting of compounds represented by formula (1), compounds represented by formula (2), and compounds represented by formula (3), and wherein, when the amount (parts by mass) of the (b) co-crosslinking agent added per 100 parts by mass of the (a) base rubber is X, the torque (N m) 35 seconds after the start of measurement when a crosslinking test of the rubber composition is performed at 170°C is T1, and the torque (N m) 45 seconds after the start of measurement is T2, these satisfy the relationship {(T2 - T1) / (X-18)} ≥ 0.46.

[0101] [ka] TIFF0007793941000009.tif50161[R 1 represents a hydrogen atom, an alkyl group having 1 to 8 carbon atoms, an aryl group having 1 to 8 carbon atoms, or a metal atom. R 2 ~R 5 are the same or different and represent a hydrogen atom, a halogen atom, an alkyl group having 1 to 8 carbon atoms, an aryl group having 4 to 14 carbon atoms, an alkoxy group having 1 to 8 carbon atoms, or a perfluoroalkyl group having 1 to 8 carbon atoms. R 11 ~R 14are the same or different and represent a hydrogen atom, a halogen atom, an alkyl group having 1 to 8 carbon atoms, an aryl group having 4 to 14 carbon atoms, an alkoxy group having 1 to 8 carbon atoms, or a perfluoroalkyl group having 1 to 8 carbon atoms. M represents a metal atom. n represents 1 or 2.]

[0102] The present disclosure (2) is a rubber composition comprising (a) a base rubber, (b) a co-crosslinking agent, (c) a crosslinking initiator, (d) a benzothiazole compound, and (f) an organic sulfur compound, wherein the (d) benzothiazole compound is at least one selected from the group consisting of compounds represented by formula (1), compounds represented by formula (2), and compounds represented by formula (3), and wherein, when the amount (parts by mass) of the (b) co-crosslinking agent added per 100 parts by mass of the (a) base rubber is X, the torque (N m) 10 seconds after the start of measurement when a crosslinking test of the rubber composition is performed at 170°C is T3, and the torque (N m) 60 seconds after the start of measurement is T4, these satisfy the relationship {(T4 - T3) / (X - 18)}>0.3.

[0103] [ka] TIFF0007793941000011.tif50161[R 1 represents a hydrogen atom, an alkyl group having 1 to 8 carbon atoms, an aryl group having 4 to 14 carbon atoms, or a metal atom. R 2 ~R 5 are the same or different and represent a hydrogen atom, a halogen atom, an alkyl group having 1 to 8 carbon atoms, an aryl group having 4 to 14 carbon atoms, an alkoxy group having 1 to 8 carbon atoms, or a perfluoroalkyl group having 1 to 8 carbon atoms. R 11 ~R 14 are the same or different and represent a hydrogen atom, a halogen atom, an alkyl group having 1 to 8 carbon atoms, an aryl group having 4 to 14 carbon atoms, an alkoxy group having 1 to 8 carbon atoms, or a perfluoroalkyl group having 1 to 8 carbon atoms. M represents a metal atom. n represents 1 or 2.]

[0104] The present disclosure (3) is the rubber composition according to the present disclosure (1) or (2), wherein the content of the (d) benzothiazole compound is 0.01 to 20 parts by mass per 100 parts by mass of the (a) base rubber.

[0105] The present disclosure (4) is a rubber composition according to any one of the present disclosures (1) to (3), in which the (b) co-crosslinking agent is an α,β-unsaturated carboxylic acid having 3 to 8 carbon atoms and / or a metal salt thereof.

[0106] The present disclosure (5) is the rubber composition according to any one of the present disclosures (1) to (4), wherein the content of the (b) co-crosslinking agent is 15 to 50 parts by mass per 100 parts by mass of the (a) base rubber.

[0107] The present disclosure (6) is a crosslinked rubber molded article formed from the rubber composition according to any one of the present disclosures (1) to (5).

[0108] The present disclosure (7) is a golf ball characterized by having a component formed from the rubber composition according to any one of the present disclosures (1) to (5). [Industrial Applicability]

[0109] The rubber composition of the present disclosure can be used to form crosslinks in a short time and to obtain crosslinked rubber molded articles with high hardness. Therefore, the rubber composition of the present disclosure can be used in sports goods such as golf balls, tennis balls, and grips; industrial goods such as hoses, belts, and mats; shoe soles, tires, resin additives, vibration-proof rubber, and fenders.

Claims

1. (a) a base rubber, (b) a co-crosslinking agent, (c) a crosslinking initiator, and (d) a benzothiazole compound, the total content of the natural rubber and / or diene rubber in the (a) base rubber is 90% by mass or more, the (b) co-crosslinking agent is an α,β-unsaturated carboxylic acid having 3 to 8 carbon atoms and / or a metal salt thereof, the one-minute half-life temperature of the (c) crosslinking initiator is 150°C or higher and 180°C or lower; The (d) benzothiazole compound is at least one selected from the group consisting of a compound represented by formula (1), a compound represented by formula (2), and a compound represented by formula (3), and A rubber composition characterized in that, when X is the amount (parts by mass) of the co-crosslinking agent (b) added relative to 100 parts by mass of the base rubber (a), T1 is the torque (N m) 35 seconds after the start of measurement when a crosslinking test is performed on the rubber composition at 170°C, and T2 is the torque (N m) 45 seconds after the start of measurement, these satisfy the relationship {(T2-T1) / (X-18)}≧0.

46. 【Chemistry 1】 【change】 [R 1 represents a hydrogen atom, an alkyl group having 1 to 8 carbon atoms, an aryl group having 6 to 14 carbon atoms, or a metal atom. R 2 ~R 5 are the same or different and represent a hydrogen atom, a halogen atom, an alkyl group having 1 to 8 carbon atoms, an aryl group having 6 to 14 carbon atoms, an alkoxy group having 1 to 8 carbon atoms, or a perfluoroalkyl group having 1 to 8 carbon atoms. R 11 ~R 14 are the same or different and represent a hydrogen atom, a halogen atom, an alkyl group having 1 to 8 carbon atoms, an aryl group having 6 to 14 carbon atoms, an alkoxy group having 1 to 8 carbon atoms, or a perfluoroalkyl group having 1 to 8 carbon atoms; M represents a metal atom; and n represents 1 or 2.

2. (a) a base rubber, (b) a co-crosslinking agent, (c) a crosslinking initiator, (d) a benzothiazole compound, and (f) an organic sulfur compound, the total content of the natural rubber and / or diene rubber in the (a) base rubber is 90% by mass or more, the (b) co-crosslinking agent is an α,β-unsaturated carboxylic acid having 3 to 8 carbon atoms and / or a metal salt thereof, the one-minute half-life temperature of the (c) crosslinking initiator is 150°C or higher and 180°C or lower; The (d) benzothiazole compound is at least one selected from the group consisting of a compound represented by formula (1), a compound represented by formula (2), and a compound represented by formula (3), and A rubber composition characterized in that, when X is the amount (parts by mass) of the co-crosslinking agent (b) added relative to 100 parts by mass of the base rubber (a), T3 is the torque (N m) 10 seconds after the start of measurement when a crosslinking test is performed on the rubber composition at 170°C, and T4 is the torque (N m) 60 seconds after the start of measurement, these satisfy the relationship {(T4 - T3) / (X - 18)} > 0.

3. 【Chemistry 2】 【change】 [R 1 represents a hydrogen atom, an alkyl group having 1 to 8 carbon atoms, an aryl group having 6 to 14 carbon atoms, or a metal atom. R 2 ~R 5 are the same or different and represent a hydrogen atom, a halogen atom, an alkyl group having 1 to 8 carbon atoms, an aryl group having 6 to 14 carbon atoms, an alkoxy group having 1 to 8 carbon atoms, or a perfluoroalkyl group having 1 to 8 carbon atoms. R 11 ~R 14 are the same or different and represent a hydrogen atom, a halogen atom, an alkyl group having 1 to 8 carbon atoms, an aryl group having 6 to 14 carbon atoms, an alkoxy group having 1 to 8 carbon atoms, or a perfluoroalkyl group having 1 to 8 carbon atoms; M represents a metal atom; and n represents 1 or 2.

3. 3. The rubber composition according to claim 1, wherein the amount of the benzothiazole compound (d) is 0.01 to 20 parts by weight per 100 parts by weight of the base rubber (a).

4. A rubber composition described in any one of claims 1 to 3, wherein the molar ratio ((d) / (c)) of the molar amount of (c) the crosslinking initiator to the molar amount of (d) the benzothiazole compound in the rubber composition is 0.5 or more and 10 or less.

5. The rubber composition according to any one of claims 1 to 4, wherein the amount of the (b) co-crosslinking agent is more than 18 parts by mass and not more than 50 parts by mass per 100 parts by mass of the (a) base rubber.

6. A crosslinked rubber molded article formed from the rubber composition according to any one of claims 1 to 5.

7. A golf ball having a component formed from the rubber composition according to any one of claims 1 to 5.

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