Rubber composition and crosslinked rubber molded product

Abstract

To provide a rubber composition that can give a crosslinked rubber molding having excellent flexibility and excellent resilience.SOLUTION: A rubber composition contains (a) base rubber, (b) a co-crosslinker, which is a 3-8 α,β-unsaturated carboxylic acid and / or a metal salt thereof, (c) a crosslinking initiator, and (d) a benzothiazole derivative. If, as the (b) co-crosslinker, only a 3-8 α,β-unsaturated carboxylic acid is contained, a (e) metal compound is further added.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present disclosure relates to a rubber composition, and more particularly to a rubber composition that can give a crosslinked rubber molded article having excellent resilience. [Background technology]

[0002] One method for increasing the distance a golf ball can travel on a driver shot is to use a core with high resilience. Increasing the resilience of the core increases the initial velocity of the golf ball, thereby increasing the distance the golf ball can travel. Generally, a rubber composition contains a base rubber, a co-crosslinking agent, and a crosslinking initiator. It is also known to further compound a vulcanization accelerator into the rubber composition.

[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 with enhanced resilience have been proposed, there remains room for improvement in resilience performance. The present disclosure has been made in view of the above circumstances, and aims to provide a rubber composition that can give a crosslinked rubber molded article having good flexibility and excellent resilience performance. [Means for solving the problem]

[0007] The rubber composition of the present disclosure, which has been able to solve the above problems, contains (a) a base rubber, (b) an α,β-unsaturated carboxylic acid having 3 to 8 carbon atoms and / or a metal salt thereof as a co-crosslinking agent, (c) a crosslinking initiator, and (d) a benzothiazole derivative, and when the (b) co-crosslinking agent contains only an α,β-unsaturated carboxylic acid having 3 to 8 carbon atoms, the rubber composition further contains (e) a metal compound, and the (d) benzothiazole derivative is a compound represented by formula (1) and / or a compound represented by formula (2).

[0008] [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 an electron-withdrawing group or a hydrogen atom. 3 ~R 5 At least one of is an electron-withdrawing group. [Effects of the Invention]

[0009] By using the rubber composition of the present disclosure, a crosslinked rubber molded article having good flexibility and excellent resilience can be obtained. [Brief explanation of the drawings]

[0010] [Figure 1] FIG. 2 is a graph showing the relationship between the resilience coefficient and the amount of compressive deformation of a crosslinked rubber composition. DETAILED DESCRIPTION OF THE INVENTION

[0011] [Rubber composition] The rubber composition of the present disclosure contains (a) a base rubber, (b) an α,β-unsaturated carboxylic acid having 3 to 8 carbon atoms and / or a metal salt thereof as a co-crosslinking agent, (c) a crosslinking initiator, and (d) a benzothiazole derivative, and when the (b) co-crosslinking agent contains only an α,β-unsaturated carboxylic acid having 3 to 8 carbon atoms, the rubber composition further contains (e) a metal compound. The (d) benzothiazole derivative is characterized in that it is a compound represented by formula (1) and / or a compound represented by formula (2) described below.

[0012] (d) Benzothiazole derivatives The (d) benzothiazole derivative used in the present disclosure will be explained. Examples of the (d) benzothiazole derivative include compounds represented by formula (1) and compounds represented by formula (2). The (d) benzothiazole derivative may be used alone or in combination of two or more. By blending the (d) benzothiazole derivative with the rubber composition, the crosslinking reaction can be promoted and dense crosslinks can be formed, thereby improving resilience without impairing flexibility.

[0013] [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 an electron-withdrawing group or a hydrogen atom. 3 ~R 5 At least one of is an electron-withdrawing group.

[0014] R in formula (1) or formula (2) 1Examples 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.

[0015] 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.

[0016] R 1 Examples of the metal atom represented by the formula include sodium, potassium, lithium, magnesium, calcium, zinc, barium, and cadmium.

[0017] R 1 is preferably a hydrogen atom or an alkyl group having 1 to 8 carbon atoms, more preferably a hydrogen atom.

[0018] R 2 ~R 5 The electron-withdrawing group represented by the formula (I) is a substituent that has a greater ability to attract electrons from the carbon atom to which it is bonded than a hydrogen atom. 2 ~R 5Examples of the electron-withdrawing group represented by the formula (I) include a halogen group, a perfluoroalkyl group, a halogenated alkyl group, an alkylcarbonyl group, an alkoxycarbonyl group, a pentafluorosulfanyl group (-SF5), a nitro group (-NO2), a cyano group (-CN), a carboxy group (-COOH), an aldehyde group (-CHO), a sulfanyl group (-SH), a sulfo group (-SOH), an alkylsulfonyl group, an alkoxysulfonyl group, and a perfluoroalkylsulfonyl group.

[0019] Examples of the halogen group include a fluoro group (-F), a chloro group (-Cl), and a bromo group (-Br). Examples of the perfluoroalkyl group include a trifluoromethyl group (-CF3), a pentafluoroethyl group (-C2F5), and a heptafluoropropyl group (-C3F7). Examples of the halogenated alkyl group include a trichloromethyl group (-CCl3) and a monochloromethyl group (-CH2Cl). Examples of the alkylcarbonyl group include an acetyl group (-COCH3) and a propionyl group (-COC2H5). Examples of the alkoxycarbonyl group include a methoxycarbonyl group (-COOCH3) and an ethoxycarbonyl group (-COOC2H5). Examples of the alkylsulfonyl group include a methylsulfonyl group (-SO2CH3) and an ethylsulfonyl group (-SO2C2H5). Examples of the alkoxysulfonyl group include a methoxysulfonyl group (-SO2OCH3) and an ethoxysulfonyl group (-SO2OC2H5). Examples of the perfluoroalkylsulfonyl group include a trifluoromethylsulfonyl group (-SO2CF3) and a pentafluoroethylsulfonyl group (-SO2C2F5).

[0020] R 2 ~R 5The electron-withdrawing group represented by the formula (I) is preferably one selected from the group consisting of a halogen group, a perfluoroalkyl group, and a pentafluorosulfanyl group.

[0021] The (d) benzothiazole derivative is preferably a compound represented by formula (3) in which the Mulliken charge of the sulfur atom constituting the thiocarbonyl group is −0.220 or more.

[0022] [ka] [In formula (3), R 2 ~R 5 are the same or different and represent an electron-withdrawing group or a hydrogen atom. 2 ~R 5 At least one of is an electron-withdrawing group.

[0023] The Mulliken charge of the sulfur atom constituting the thiocarbonyl group (>C=S) is preferably -0.220 or more, more preferably -0.215 or more, even more preferably -0.210 or more, and is preferably 0 or less, more preferably -0.01 or less, even more preferably -0.05 or less. When the Mulliken charge is -0.220 or more, high resilience is exhibited. The Mulliken charge of the sulfur atom can be controlled by the type and position of the substituent. The charge on the sulfur of the thiocarbonyl group can also be increased by substituting hydrogen on the benzene ring with multiple electron-withdrawing groups.

[0024] The Mulliken charge of the sulfur atom constituting the thiocarbonyl group was determined by performing a structural optimization calculation and a frequency calculation using Gaussian09 (a quantum chemistry calculation program manufactured by Gaussian) under the conditions of functional: B3LYP and basis function: 6-31G(d), and the Mulliken charge of the sulfur atom constituting the thiocarbonyl group in the obtained optimized structure was determined.

[0025] R in the formula (3) 2 ~R 5The electron-withdrawing group represented by the formula (2) is R 2 ~R 5 In the formula (3), R 2 ~R 5 The electron-withdrawing group represented by the formula (3) is preferably one selected from the group consisting of a halogen group, a perfluoroalkyl group, and a pentafluorosulfanyl group. 2 ~R 5 is R 3 ~R 5 It is preferred that at least one of the groups is an electron-withdrawing group.

[0026] The (d) benzothiazole derivative is more preferably a compound represented by formula (4). 3 If the electron-withdrawing group represented by the formula (I) is at the 5-position, the electronic effect on the thiocarbonyl group will be greater than at other substitution positions.

[0027] [ka] [In formula (4), R 3 represents an electron-withdrawing group.]

[0028] R in the formula (4) 3 The electron-withdrawing group represented by the formula (2) is R 3 In the formula (4), R 3 The electron-withdrawing group represented by the formula (I) is preferably one selected from the group consisting of a halogen group, a perfluoroalkyl group, and a pentafluorosulfanyl group.

[0029] As the (d) benzothiazole derivative, compounds represented by formulae (4-1) to (4-12) are particularly preferred.

[0030] [ka]

[0031] In the (d) benzothiazole derivative, when the bond distance between the sulfur atom and the zinc atom in the compound represented by formula (5) formed from the compound represented by formula (1) and / or the compound represented by formula (2) is X1, and the bond distance between the sulfur atom and the zinc atom in 2-mercaptobenzothiazole zinc (formula (6)) is X2, the ratio (X1 / X2) is preferably less than 1.

[0032] [ka] [In formula (5), R 12 ~R 15 and R 22 ~R 25 are the same or different and represent an electron-withdrawing group or a hydrogen atom. 12 ~R 15 At least one of R is an electron-withdrawing group. 22 ~R 25 At least one of is an electron-withdrawing group.

[0033] [ka]

[0034] The ratio (X1 / X2) is preferably less than 1, and more preferably 0.999 or less. It is believed that the (d) benzothiazole derivative reacts with the (b) metal constituting the metal salt of the α,β-unsaturated carboxylic acid having 3 to 8 carbon atoms or the (e) metal compound in the rubber composition to form a complex. It is believed that the formation of this complex affects the reactivity of the (b) co-crosslinking agent, changing the crosslinking rate. It is believed that when the ratio (X1 / X2) is less than 1, the crosslinking rate is further improved, and the hardness of the resulting cured product is increased. The lower limit of the ratio (X1 / X2) is 0.990.

[0035] In the (d) benzothiazole derivative, when the bond distance between the nitrogen atom and the zinc atom in the compound represented by formula (5) formed from the compound represented by formula (1) and / or the compound represented by formula (2) is Y1 and the bond distance between the nitrogen atom and the zinc atom in 2-mercaptobenzothiazole zinc (formula (6)) is Y2, the ratio (Y1 / Y2) is preferably greater than 1, more preferably 1.0005 or more, and even more preferably 1.0010 or more. The upper limit of the ratio (Y1 / Y2) is 1.0100.

[0036] The bond distances X1, X2, Y1, and Y2 were determined by performing a structural optimization calculation and a frequency calculation using Gaussian09 (a quantum chemistry calculation program manufactured by Gaussian) under the conditions of functional: B3LYP and basis function: 6-31G(d), and the bond distances between the sulfur atom and the zinc atom and the bond distance between the nitrogen atom and the zinc atom in the obtained optimized structure were determined. 12 ~R 15 and R 22 ~R 25 The electron-withdrawing group represented by the formula (1) is 2 ~R 5 In the formula (5), R 12 ~R 15 and R 22 ~R 25 The electron-withdrawing group represented by the formula (5) is preferably one selected from the group consisting of a halogen group, a perfluoroalkyl group, and a pentafluorosulfanyl group. 12 ~R 15 is R 13 ~R 15 It is preferable that at least one of R in the formula (5) is an electron-withdrawing group. 22 ~R 25 is R 23 ~R 25 It is preferred that at least one of the groups is an electron-withdrawing group.

[0037] The amount of the (d) benzothiazole derivative 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 derivative is 0.01 part by mass or more, the resilience is further improved, and if it is 20 parts by mass or less, the flexibility is further improved.

[0038] In the rubber composition, the charge ratio (anion charge / cation charge) between the total charge of the anion component derived from the (d) benzothiazole derivative and the total charge of the cationic component derived from the (b) co-crosslinking agent and the (e) metal compound is preferably 0.01 or more, more preferably 0.02 or more, and preferably 0.10 or less, more preferably 0.05 or less. The total charge of the anion component is equal to the number of moles of the (d) benzothiazole derivative. The total charge of the cationic component is the sum of the product of the number of moles of each metal ion contained in the (b) co-crosslinking agent and the valence of each metal ion, and the product of the number of moles of each metal ion contained in the (e) metal compound and the valence of each metal ion.

[0039] Other raw materials used in the rubber composition will be described below.

[0040] (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.

[0041] 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.

[0042] 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.

[0043] 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.

[0044] 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.

[0045] 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.

[0046] 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.

[0047] (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. The (b) co-crosslinking agent is preferably an α,β-unsaturated carboxylic acid having 3 to 8 carbon atoms and / or a metal salt thereof. 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 kinds.

[0048] 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.

[0049] 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.

[0050] 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.

[0051] The content of the (b) co-crosslinking agent is preferably 15 parts by mass or more, 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. When the content of the (b) co-crosslinking agent is 15 parts by mass or more, a small amount of the (c) crosslinking initiator can be used to impart an appropriate hardness to a member formed from the rubber composition, thereby further improving the resilience of the crosslinked rubber molded product. On the other hand, when the content of the (b) co-crosslinking agent is 50 parts by mass or less, the member formed from the rubber composition does not become too hard.

[0052] (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.

[0053] 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.

[0054] The molar ratio ((d) / (c)) of the molar amount of the (c) crosslinking initiator to the molar amount of the (d) benzothiazole derivative 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.

[0055] (e) Metal compounds When the rubber composition used in the present disclosure contains only an α,β-unsaturated carboxylic acid having 3 to 8 carbon atoms as a co-crosslinking agent, the rubber composition further contains (e) a metal compound as an essential component. The (e) metal compound is not particularly limited as long as it can neutralize (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. Divalent metal compounds are preferred as the (e) metal compound, and zinc compounds are more preferred. This is because divalent metal compounds react with α,β-unsaturated carboxylic acids having 3 to 8 carbon atoms to form metal crosslinks. Furthermore, the use of zinc compounds allows for the production of crosslinked rubber molded articles with high resilience. (e) Metal compounds may be used alone or in combination of two or more. The content of (e) the metal compound may be adjusted appropriately depending on the desired degree of neutralization of (b) the α,β-unsaturated carboxylic acid having 3 to 8 carbon atoms and (d) the unsaturated aliphatic carboxylic acid.

[0056] (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 derivative. 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.

[0057] 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.

[0058] 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.

[0059] Polysulfides are organic sulfur compounds having polysulfide bonds, such as disulfides, trisulfides, and tetrasulfides. Diphenyl polysulfides are preferred as the polysulfides.

[0060] 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.

[0061] 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.

[0062] (f) The above-mentioned 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, and bis(pentabromophenyl)disulfide.

[0063] The content of the (f) organic sulfur compound is preferably at least 0.05 parts by mass, more preferably at least 0.1 parts by mass, and preferably at most 5.0 parts by mass, more preferably at most 2.0 parts by mass, 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 may not be obtained, and the resilience of the crosslinked rubber molded article may not be improved. If the content of the (f) organic sulfur compound is more than 5.0 parts by mass, the compressive deformation of the resulting crosslinked rubber molded article may increase, resulting in a decrease in resilience.

[0064] The mass ratio ((d) / (f)) of the (d) benzothiazole derivative to the (f) organic sulfur compound in the rubber composition 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.

[0065] (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.

[0066] 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.

[0067] 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.

[0068] 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.

[0069] 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.

[0070] 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.

[0071] 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.

[0072] 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.

[0073] (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.

[0074] 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.

[0075] 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.

[0076] 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.

[0077] 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.

[0078] 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 derivative, 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.

[0079] [Crosslinked rubber molding] 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.

[0080] 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]

[0081] 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.

[0082] [Evaluation method] (1) Compression deformation (mm) The deformation in the compression direction (the amount of shrinkage of the spherical molded body in the compression direction) was measured from the state in which an initial load of 98 N was applied to the spherical molded body until a final load of 1275 N was applied.

[0083] (2) Restitution coefficient Each spherical molded product was collided with a 198.4 g metal cylinder at a speed of 40 m / s, the velocities of the cylinder and spherical molded product were measured before and after the collision, and the restitution coefficient of each spherical molded product was calculated from their respective velocities and masses. Measurements were made for 12 spherical molded products, and the average value was taken as the restitution coefficient of each spherical molded product.

[0084] (3) 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.

[0085] [Preparation of spherical molded bodies] A rubber composition having the formulation shown in Table 1 was kneaded with a kneading roll and hot-pressed at 170° C. for 20 minutes in upper and lower molds having hemispherical cavities to obtain spherical molded articles having a diameter of 40.86 mm.

[0086] [Table 1] 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. PCTP-Zn: Pentachlorothiophenol zinc salt, manufactured by Fujifilm Wako Chemical Co., Ltd. 5Me-MBT: 5-methyl-2-mercaptobenzothiazole, manufactured by Cool pharm Ltd. 4Me-MBT: Fluorochem Ltd., 4-methyl-2-mercaptobenzothiazole MBT: 2-mercaptobenzothiazole (Noccela MP), manufactured by Ouchi Shinko Chemical Industry Co., Ltd. 5Cl-MBT: 5-chloro-2-mercaptobenzothiazole, manufactured by Tokyo Chemical Industry Co., Ltd. 5F-MBT: Combi-Blocks, 5-fluoro-2-mercaptobenzothiazole 5CF3-MBT: AA Blocks, 5-trifluoromethyl-2-mercaptobenzothiazole 5Br-MBT: 5-bromo-2-mercaptobenzothiazole, manufactured by Aldrich 6F-MBT:BLD Pharmatech, 6-fluoro-2-mercaptobenzothiazole DCP: NOF Corporation, "Percumyl (registered trademark) D" (dicumyl peroxide)

[0087] Table 1 shows the compressive deformation and resilience coefficient of each spherical molded body. Figure 1 also shows the relationship between the compressive deformation and resilience coefficient of each spherical molded body. As shown in Figure 1, when the raw materials contained in a rubber composition are the same, the greater the content of co-crosslinking agent, the higher the resilience performance and the smaller the compressive deformation. Therefore, it can be said that the closer the line connecting the plots of spherical molded bodies made from the same raw materials is to the upper right of the graph, the higher the flexibility and the better the resilience performance.

[0088] Spherical molded products Nos. 1 to 10 are formed from rubber compositions containing (e) a metal compound and (d) a benzothiazole derivative, which is a compound represented by formula (1) and / or a compound represented by formula (2). Specifically, spherical molded products Nos. 1 to 10 are formed from rubber compositions containing a benzothiazole derivative, which is a compound represented by formula (3), and in which the Mulliken charge of the sulfur atom constituting the thiocarbonyl group is -0.220 or greater. These spherical molded products have higher flexibility and better resilience than spherical molded products Nos. 17 and 18, which do not contain a benzothiazole derivative.

[0089] [Preparation of Rubber Composition] Rubber compositions were prepared by kneading the rubber compositions having the formulations shown in Tables 2 and 3 with a kneading roll. The obtained rubber compositions were evaluated.

[0090] [Table 2]

[0091] [Table 3] 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. PCTP-Zn: Pentachlorothiophenol zinc salt, manufactured by Fujifilm Wako Chemical Co., Ltd. 5Cl-MBT: 5-chloro-2-mercaptobenzothiazole, manufactured by Tokyo Chemical Industry Co., Ltd. 5F-MBT: Combi-Blocks, 5-fluoro-2-mercaptobenzothiazole MBT: 2-mercaptobenzothiazole (Noccela MP), manufactured by Ouchi Shinko Chemical Industry Co., Ltd. 5CF3-MBT: AA Blocks, 5-trifluoromethyl-2-mercaptobenzothiazole 6F-MBT:BLD Pharmatech, 6-fluoro-2-mercaptobenzothiazole 4Me-MBT: Fluorochem Ltd., 4-methyl-2-mercaptobenzothiazole 5Me-MBT: 5-methyl-2-mercaptobenzothiazole, manufactured by Cool pharm Ltd. 4Cl-MBT: 4-chloro-2-mercaptobenzothiazole, manufactured by Fluorochem Ltd. DCP: NOF Corporation, "Percumyl (registered trademark) D" (dicumyl peroxide)

[0092] Spherical molded articles Nos. 19 to 26 are formed from rubber compositions containing (e) a metal compound and (d) a benzothiazole derivative, which is a compound represented by formula (1) and / or a compound represented by formula (2). Specifically, rubber compositions Nos. 19 to 26 contain, as the (d) benzothiazole derivative, a compound in which the ratio (X1 / X2) in the compound represented by formula (5) is less than 1.

[0093] Rubber compositions Nos. 27 to 30 do not contain (d) a benzothiazole derivative. Rubber compositions Nos. 31 to 34 contain unsubstituted mercaptobenzothiazole. Comparing these rubber compositions Nos. 20, 22, 24, 26, 28, and 33, which contain the same amount of co-crosslinking agent, Nos. 20, 22, 24, and 26 have improved slab hardness compared to No. 33.

[0094] Rubber compositions Nos. 35 to 40 contain a benzothiazole derivative that does not have an electron-withdrawing group at the 5th to 7th positions. Comparing these rubber compositions with Nos. 33, 36, 38, and 40, which contain the same amount of co-crosslinking agent, Nos. 36, 38, and 40 had lower slab hardness than No. 33. Although 4Me-MBT has a ratio (X1 / X2) of less than 1, the substituent is not an electron-withdrawing group, so no hardness improvement effect was obtained. [Industrial Applicability]

[0095] The rubber composition of the present disclosure can be used to obtain a crosslinked rubber molded article with excellent resilience, and can therefore 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, anti-vibration rubber, and fenders.

[0096] The present disclosure (1) is a rubber composition comprising (a) a base rubber, (b) an α,β-unsaturated carboxylic acid having 3 to 8 carbon atoms and / or a metal salt thereof as a co-crosslinking agent, (c) a crosslinking initiator, and (d) a benzothiazole derivative, and when the (b) co-crosslinking agent contains only an α,β-unsaturated carboxylic acid having 3 to 8 carbon atoms, the rubber composition further comprises (e) a metal compound, and the (d) benzothiazole derivative is a compound represented by formula (1) and / or a compound represented by formula (2).

[0097] [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 an electron-withdrawing group or a hydrogen atom. 3 ~R 5 At least one of is an electron-withdrawing group.

[0098] This disclosure (2) is 2 ~R 5 The rubber composition according to Disclosure (1)-1, wherein the electron-withdrawing group represented by the formula: is one selected from the group consisting of a halogen group, a perfluoroalkyl group, and a pentafluorosulfanyl group.

[0099] The present disclosure (3) is the rubber composition according to the present disclosure (1) or (2), wherein the content of the (d) benzothiazole derivative is 0.01 to 20 parts by mass per 100 parts by mass of the (a) base rubber.

[0100] The present disclosure (4) is a rubber composition according to any one of the present disclosures (1) to (3), in which the (d) benzothiazole derivative is a compound represented by formula (3), and the Mulliken charge of the sulfur atom constituting the thiocarbonyl group is −0.220 or more.

[0101] [ka] [In formula (1), R 2 ~R 5 are the same or different and represent an electron-withdrawing group or a hydrogen atom. 2 ~R 5 At least one of is an electron-withdrawing group.

[0102] The present disclosure (5) is the rubber composition according to the present disclosure (4), in which the (d) benzothiazole derivative is a compound represented by formula (4).

[0103] [ka] [In formula (4), R 3 represents an electron-withdrawing group.]

[0104] The present disclosure (6) is a rubber composition according to any one of the present disclosures (1) to (3), in which the ratio (X1 / X2) is less than 1, where X1 is the bond distance between a sulfur atom and a zinc atom in the compound represented by formula (5) formed from the compound represented by formula (1) and / or the compound represented by formula (2), and X2 is the bond distance between a sulfur atom and a zinc atom in 2-mercaptobenzothiazole zinc.

[0105] [ka] [In formula (5), R 12 ~R 15 and R 22 ~R 25 are the same or different and represent an electron-withdrawing group or a hydrogen atom. 12 ~R 15 At least one of R is an electron-withdrawing group. 22 ~R 25 At least one of is an electron-withdrawing group.

[0106] The present disclosure (7) is the rubber composition according to any one of the present disclosures (1) to (6), 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 (8) is a crosslinked rubber molded article formed from the rubber composition according to any one of the present disclosures (1) to (7).

[0108] The present disclosure (9) is a golf ball characterized by having a component formed from the rubber composition according to any one of the present disclosures (1) to (7).

Claims

1. The crosslinking composition comprises (a) a base rubber, (b) an α,β-unsaturated carboxylic acid having 3 to 8 carbon atoms and / or a zinc salt thereof as a co-crosslinking agent, (c) a crosslinking initiator, and (d) a benzothiazole derivative, and when the (b) co-crosslinking agent contains only an α,β-unsaturated carboxylic acid having 3 to 8 carbon atoms, the crosslinking composition further comprises (e) a zinc compound, A rubber composition, wherein the (d) benzothiazole derivative is a compound represented by formula (1) and / or a compound represented by formula (2). 【Chemistry 1】 [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 an electron-withdrawing group or a hydrogen atom. 3 ~R 5 At least one of is an electron-withdrawing group.

2. The R 2 ~R 5 2. The rubber composition according to claim 1, wherein the electron-withdrawing group represented by the formula: is one selected from the group consisting of a halogen group, a perfluoroalkyl group, and a pentafluorosulfanyl group.

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

4. The rubber composition according to any one of claims 1 to 3, wherein the (d) benzothiazole derivative is a compound represented by formula (3), and the Mulliken charge of the sulfur atom constituting the thiocarbonyl group is -0.220 or more. 【Chemistry 2】 [In formula (1), R 2 ~R 5 are the same or different and represent an electron-withdrawing group or a hydrogen atom. At least one of R 3 to R 5 is an electron-withdrawing group.]

5. The rubber composition according to claim 4, wherein the benzothiazole derivative (d) is a compound represented by formula (4): 【Transformation 3】 [In formula (4), R 3 represents an electron-withdrawing group.

6. The rubber composition according to any one of claims 1 to 3, wherein the bond distance between a sulfur atom and a zinc atom in the compound represented by formula (5) formed from the compound represented by formula (1) and / or the compound represented by formula (2) is X1, and the bond distance between a sulfur atom and a zinc atom in 2-mercaptobenzothiazole zinc is X2, the ratio (X1 / X2) is less than 1. 【Chemistry 4】 [In formula (5), R 12 ~R 15 and R 22 ~R 25 are the same or different and represent an electron-withdrawing group or a hydrogen atom. At least one of R 13 to R 15 is an electron-withdrawing group. At least one of R 23 to R 25 is an electron-withdrawing group.]

7. 7. The rubber composition according to claim 1, 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.

8. A crosslinked rubber molded article formed from the rubber composition according to any one of claims 1 to 7.

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

Images