Rubber composition for grips and golf club grip

Abstract

To provide a rubber composition including a hydrogenated carboxy-modified acrylonitrile-butadiene rubber as a base rubber, the rubber composition being capable of affording a cross-linked rubber having excellent mechanical strength even at high-temperature vulcanization and a high friction coefficient.SOLUTION: A rubber composition for grips includes a base rubber, a vulcanizer and a vulcanization accelerator. The base rubber includes a hydrogenated carboxy-modified acrylonitrile-butadiene rubber and further includes, based on 100 pts.mass of the base rubber, 4 pts.mass or more of a thiuram-based vulcanization accelerator, 0.3 pt.mass or more of a sulfenamide-based vulcanization accelerator, and 0.1 pt.mass or more of a thiourea-based vulcanization accelerator. A ratio (tanδ / E*) of a loss factor (tanδ) to a complex elastic modulus (E*)(MPa) at 25°C is 0.027 to 0.052 as measured by subjecting a cross-linked rubber, obtained by curing the rubber composition at a vulcanization temperature of 185°C, to a measurement using a dynamic viscoelastometer (oscillation frequency 10 Hz, strain amplitude 0.05%, and tensile mode).SELECTED DRAWING: None

Description

Technical Field

[0001] The present invention relates to a rubber composition for grips used in the production of grips.

Background Art

[0002] As a grip (anti-slip member) attached to sports equipment and the like, rubber grips are frequently used. In such grips, it has been proposed to use hydrogenated carboxy-modified acrylonitrile-butadiene rubber as the base rubber.

[0003] For example, Patent Document 1 describes a grip for sports equipment characterized in that the outermost layer is formed of a rubber composition for the surface layer containing (A) a base rubber and (B) a resin having a softening point of 5°C to 120°C, wherein the (A) base rubber contains acrylonitrile-butadiene rubber, and the (B) resin is at least one selected from the group consisting of hydrogenated rosin ester, disproportionated rosin ester, ethylene-vinyl acetate copolymer, coumarone resin, phenol resin, xylene resin, and styrene resin (see Patent Document 1 (Claim 1, Paragraphs 0013, 0019)).

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] Although hydrogenated carboxy-modified acrylonitrile-butadiene rubber exhibits properties such as weather resistance and ozone resistance due to its low unsaturated bond content, on the other hand, due to its low unsaturated bond content, there are problems such as a slow vulcanization rate and poor productivity of crosslinked rubber. Here, as a method for accelerating the vulcanization rate of the rubber composition, it is common to increase the vulcanization temperature. However, vulcanization at a high temperature tends to reduce the mechanical strength of the resulting crosslinked rubber. In addition, excellent anti-slip performance is required for grips attached to sports equipment and the like. The anti-slip performance of the grip can be enhanced by forming a groove pattern on the surface, but it is preferable that the rubber composition itself used for forming the grip has a high coefficient of friction. The present invention has been made in view of the above circumstances, and provides a rubber composition containing a hydrogenated carboxy-modified acrylonitrile-butadiene rubber as a base rubber, which can obtain a crosslinked rubber having excellent mechanical strength and a high coefficient of friction even in high-temperature vulcanization.

Means for Solving the Problems

[0006] The rubber composition for a grip of the present invention that can solve the above problems contains a base rubber, a vulcanizing agent, and a vulcanization accelerator. The base rubber contains a hydrogenated carboxy-modified acrylonitrile-butadiene rubber. The vulcanization accelerator contains a thiuram-based vulcanization accelerator, a sulfenamide-based vulcanization accelerator, and a thiourea-based vulcanization accelerator. The content of the thiuram-based vulcanization accelerator is 4 parts by mass or more with respect to 100 parts by mass of the base rubber. The content of the sulfenamide-based vulcanization accelerator is 0.3 parts by mass or more with respect to 100 parts by mass of the base rubber. The content of the thiourea-based vulcanization accelerator is 0.1 parts by mass or more with respect to 100 parts by mass of the base rubber. For the crosslinked rubber obtained by curing the rubber composition for a grip at a vulcanization temperature of 185°C, using a dynamic viscoelasticity apparatus, measured under the measurement conditions of a vibration frequency of 10 Hz, a strain amplitude of 0.05%, and a tensile mode, the loss factor (tanδ) and the complex elastic modulus (E * )(MPa) ratio (tanδ / E * ) is 0.027 to 0.052.

[0007] The rubber composition for grips of the present invention can obtain a crosslinked rubber that is excellent in mechanical strength and has a high coefficient of friction even under high-temperature vulcanization. Therefore, the vulcanization temperature during grip molding can be set high and the vulcanization time can be shortened, improving the productivity of grips.

Advantages of the Invention

[0008] By using the rubber composition for grips of the present invention, a grip excellent in mechanical strength and anti-slip performance can be obtained, and the productivity of the grip can also be improved.

Brief Description of the Drawings

[0009]

Figure 1

Figure 2

Embodiments for Carrying Out the Invention

[0010] [Rubber Composition] The rubber composition for grips of the present invention (hereinafter, may be simply referred to as "rubber composition") is used for molding grips. The rubber composition contains a base rubber, a vulcanizing agent, and a vulcanization accelerator. The base rubber contains a hydrogenated carboxy-modified acrylonitrile-butadiene rubber. The vulcanization accelerator contains a thiuram-based vulcanization accelerator, a sulfenamide-based vulcanization accelerator, and a thiourea-based vulcanization accelerator. The content of the thiuram-based vulcanization accelerator is 4 parts by mass or more with respect to 100 parts by mass of the base rubber. The content of the sulfenamide-based vulcanization accelerator is 0.3 parts by mass or more with respect to 100 parts by mass of the base rubber. The content of the thiourea-based vulcanization accelerator is 0.1 parts by mass or more with respect to 100 parts by mass of the base rubber. Furthermore, for the crosslinked rubber cured at a vulcanization temperature of 185°C, the loss coefficient (tanδ) and complex elastic modulus (E * )(MPa) ratio (tanδ / E * ) at 25°C, measured under the measurement conditions of a vibration frequency of 10 Hz, a strain amplitude of 0.05%, and a tensile mode using a dynamic viscoelasticity apparatus, is 0.027 to 0.052.

[0011] In a rubber composition containing hydrogenated carboxy-modified acrylonitrile-butadiene rubber as a base rubber, by blending a predetermined amount of a thiuram-based vulcanization accelerator, a sulfenamide-based vulcanization accelerator, and a thiourea-based vulcanization accelerator as vulcanization accelerators, it is possible to obtain a crosslinked rubber having excellent mechanical strength even when vulcanized at a high temperature.

[0012] The reason why the mechanical strength of the crosslinked rubber obtained even by high-temperature vulcanization does not decrease is not necessarily clear, but it is considered as follows. When vulcanizing hydrogenated carboxy-modified acrylonitrile-butadiene rubber with a low amount of unsaturated bonds, when the vulcanization temperature is increased, intramolecular crosslinking and the so-called pendants that do not become crosslinking points remain hanging on the rubber chain increase. Therefore, it is considered that the crosslinking density decreases and the strength of the crosslinked rubber decreases. In the rubber composition for grips of the present invention, by using a thiuram-based vulcanization accelerator, a sulfenamide-based vulcanization accelerator, and a thiourea-based vulcanization accelerator in combination, these vulcanization accelerators activate each other, and the vulcanization rate is increased. As a result, it is considered that even under high-temperature vulcanization, intramolecular crosslinking and pendant formation, which cause a decrease in crosslinking density and strength, can be reduced, and a decrease in mechanical strength accompanying a decrease in crosslinking density can be prevented.

[0013] And, the larger the loss tangent (tanδ) of the crosslinked rubber at 25°C, the greater the energy lost during deformation, and thus the greater the hysteresis friction. Also, the higher the complex elastic modulus (E * )(MPa) of the crosslinked rubber at 25°C (the harder the crosslinked rubber), the more disadvantageously it acts on friction. Therefore, the ratio of these (tanδ / E *) If it is 0.027 or more, the hysteresis loss becomes large and the friction coefficient of the crosslinked rubber improves. If it is 0.052 or less, the occurrence of poor dispersion is prevented, and it is considered that the friction coefficient of the crosslinked rubber improves.

[0014] (Base rubber) The rubber composition contains a base rubber. The content of the base rubber in the rubber composition is preferably 50% by mass or more, more preferably 55% by mass or more.

[0015] The base rubber contains a hydrogenated carboxy-modified acrylonitrile-butadiene rubber (hereinafter sometimes referred to as "HXNBR"). The HXNBR is a hydrogenated product of a copolymer of a monomer having a carboxy group, acrylonitrile, and butadiene. Note that the HXNBR may be used alone or in combination of two or more.

[0016] The acrylonitrile content of the HXNBR is preferably 15% by mass or more, more preferably 18% by mass or more, still more preferably 21% by mass or more, and preferably 50% by mass or less, more preferably 45% by mass or less, still more preferably 40% by mass or less. If the acrylonitrile content is 15% by mass or more, the wear resistance of the grip is good, and if it is 50% by mass or less, the touch feeling of the grip in cold regions or in winter is good.

[0017] In the HXNBR, examples of the monomer having a carboxy group include acrylic acid, methacrylic acid, fumaric acid, maleic acid, etc. In the HXNBR, the content of the monomer containing a carboxy group is preferably 1.0% by mass or more, more preferably 2.0% by mass or more, still more preferably 3.5% by mass or more, and preferably 30% by mass or less, more preferably 25% by mass or less, still more preferably 20% by mass or less. If the content of the monomer containing a carboxy group is 1.0% by mass or more, the wear resistance of the grip becomes better, and if it is 30% by mass or less, the touch feeling of the grip in cold regions or in winter is good.

[0018] In the above-mentioned HXNBR, the carboxyl group content is preferably 1.0% by mass or more, more preferably 2.0% by mass or more, still more preferably 3.5% by mass or more, and preferably 30% by mass or less, more preferably 25% by mass or less, still more preferably 20% by mass or less. If the carboxyl group content is 1.0% by mass or more, the wear resistance of the grip becomes better, and if it is 30% by mass or less, the touch feeling of the grip in cold regions or in winter becomes better.

[0019] The double bond content of the above-mentioned HXNBR is preferably 0.09 mmol / g or more, more preferably 0.2 mmol / g or more, preferably 2.5 mmol / g or less, more preferably 2.0 mmol / g or less, still more preferably 1.5 mmol / g or less. If the double bond content is 0.09 mmol / g or more, it becomes easier to vulcanize during molding and the tensile strength of the grip is further improved, and if it is 2.5 mmol / g or less, the durability (weather resistance) and tensile strength of the grip become better. The double bond content can be adjusted by the butadiene content in the copolymer and the amount of hydrogenation of the copolymer.

[0020] The content of HXNBR in the base rubber is preferably 50% by mass or more, more preferably 70% by mass or more, still more preferably 90% by mass or more. It is also preferable that the rubber composition contains only HXNBR as the base rubber. The higher the content of HXNBR in the base rubber, the better the wear resistance, durability (weather resistance) and tensile strength of the resulting grip.

[0021] The base rubber may contain other rubber components other than HXNBR to such an extent that the effects of the present invention are not impaired. Examples of the other rubber components include natural rubber (NR), ethylene-propylene-diene rubber (EPDM), butyl rubber (IIR), acrylonitrile-butadiene rubber (NBR), hydrogenated acrylonitrile-butadiene rubber (HNBR), carboxy-modified acrylonitrile-butadiene rubber (XNBR), butadiene rubber (BR), styrene-butadiene rubber (SBR), polyurethane rubber (PU), isoprene rubber (IR), chloroprene rubber (CR), ethylene-propylene rubber (EPM), and the like. These base rubbers may be used alone or in combination of two or more.

[0022] (Vulcanizing agent) As the vulcanizing agent, a sulfur-based vulcanizing agent or an organic peroxide can be used. The vulcanizing agent may be used alone or in combination of two or more.

[0023] Examples of the sulfur-based vulcanizing agent include elemental sulfur and sulfur donor-type compounds. Examples of the elemental sulfur include powdered sulfur, precipitated sulfur, colloidal sulfur, and insoluble sulfur. Examples of the sulfur donor-type compounds include 4,4'-dithiobismorpholine and the like. Examples of the organic peroxide include dicumyl peroxide, α,α'-bis(t-butylperoxy-m-diisopropyl)benzene, 2,5-dimethyl-2,5-di(t-butylperoxy)hexane, 1,1-bis(t-butylperoxy)3,3,5-trimethylcyclohexane, and the like.

[0024] As the vulcanizing agent, a sulfur-based vulcanizing agent is preferable, and elemental sulfur is more preferable. By using a sulfur-based vulcanizing agent as the vulcanizing agent, the mechanical strength of the obtained crosslinked rubber tends to be improved. Further, when a sulfur-based vulcanizing agent is used, the binding energy between rubber chains does not increase, the hysteresis loss during deformation increases, and the friction coefficient is improved.

[0025] The content of the vulcanizing agent is preferably 0.2 parts by mass or more, more preferably 0.4 parts by mass or more, still more preferably 0.6 parts by mass or more, and preferably 4.0 parts by mass or less, more preferably 3.5 parts by mass or less, still more preferably 3.0 parts by mass or less, based on 100 parts by mass of the base rubber. If the content of the vulcanizing agent is 0.2 parts by mass or more, vulcanization proceeds more easily, and if it is 4.0 parts by mass or less, the occurrence of scorch can be reduced.

[0026] (Vulcanization accelerator) The rubber composition contains a predetermined amount of a thiuram-based vulcanization accelerator, a sulfenamide-based vulcanization accelerator, and a thiourea-based vulcanization accelerator as vulcanization accelerators. By using a thiuram-based vulcanization accelerator and a sulfenamide-based vulcanization accelerator in combination, a crosslinked rubber excellent in mechanical strength can be obtained even when vulcanization is carried out at a high temperature.

[0027] Thiuram-based vulcanization accelerator Examples of the thiuram-based vulcanization accelerator include tetramethylthiuram disulfide (TMTD), tetrabenzylthiuram disulfide (TBzTD), tetramethylthiuram monosulfide (TMTM), dipentamethylene thiuram tetrasulfide, and tetrakis(2-ethylhexyl)thiuram disulfide. The thiuram-based vulcanization accelerator may be used alone, but it is preferably used in combination of two or more from the viewpoint of preventing bloom.

[0028] The content of the thiuram-based vulcanization accelerator is preferably 4 parts by mass or more, more preferably 5 parts by mass or more, still more preferably 6 parts by mass or more, and preferably 9 parts by mass or less, more preferably 8 parts by mass or less, still more preferably 7 parts by mass or less, based on 100 parts by mass of the base rubber. If the content of the thiuram-based vulcanization accelerator is within the above range, even in a base rubber with a small amount of double bonds, it is possible to achieve further high-speed vulcanization while maintaining scorch resistance.

[0029] Sulfenamide-based vulcanization accelerator Examples of the sulfenamide vulcanization accelerator include N-cyclohexyl-2-benzothiazolyl sulfenamide (CBS), N-(tert-butyl)-2-benzothiazolyl sulfenamide (BBS), and the like. The sulfenamide vulcanization accelerator may be used alone or in combination of two or more.

[0030] The content of the sulfenamide vulcanization accelerator is preferably 0.3 parts by mass or more, more preferably 0.5 parts by mass or more, still more preferably 0.7 parts by mass or more, and preferably 2.5 parts by mass or less, more preferably 2.0 parts by mass or less, still more preferably 1.5 parts by mass or less, based on 100 parts by mass of the base rubber. If the content of the sulfenamide vulcanization accelerator is within the above range, the occurrence of bloom can be further reduced.

[0031] Thiourea vulcanization accelerator Examples of the thiourea vulcanization accelerator include trimethylthiourea, N,N'-diethylthiourea, and the like. The thiourea vulcanization accelerator may be used alone or in combination of two or more.

[0032] The content of the thiourea vulcanization accelerator is preferably 0.1 parts by mass or more, more preferably 0.2 parts by mass or more, still more preferably 0.3 parts by mass or more, and preferably 1.0 parts by mass or less, more preferably 0.8 parts by mass or less, still more preferably 0.6 parts by mass or less, based on 100 parts by mass of the base rubber. If the content of the thiourea vulcanization accelerator is within the above range, the thiuram vulcanization accelerator can be activated and the vulcanization time can be further shortened.

[0033] The total content of thiuram vulcanization accelerators, sulfenamide vulcanization accelerators and thiourea vulcanization accelerators in the rubber composition is preferably 4.4 parts by mass or more, more preferably 5.4 parts by mass or more, still more preferably 6.4 parts by mass or more, and preferably 12.5 parts by mass or less, more preferably 10.5 parts by mass or less, still more preferably 9.5 parts by mass or less, based on 100 parts by mass of the base rubber. If the total content is 4.4 parts by mass or more, the vulcanization rate can be further increased even for a base rubber with a small amount of double bonds. If it is 12.5 parts by mass or less, the scorch resistance is better in rubbers with a small amount of double bonds.

[0034] The mass ratio of the thiuram vulcanization accelerator to the sulfenamide vulcanization accelerator in the rubber composition (thiuram vulcanization accelerator / sulfenamide vulcanization accelerator) is preferably 1.5 or more, more preferably 3.0 or more, still more preferably 4.5 or more, and preferably 30 or less, more preferably 20 or less, still more preferably 10 or less. If the mass ratio (thiuram vulcanization accelerator / sulfenamide vulcanization accelerator) is 1.5 or more, the vulcanization rate can be further increased even for a base rubber with a small amount of double bonds. If it is 30 or less, the decrease in the strength of the crosslinked rubber obtained in vulcanization at high temperature and high speed can be more suppressed.

[0035] The mass ratio of the thiuram vulcanization accelerator to the thiourea vulcanization accelerator in the rubber composition (thiuram vulcanization accelerator / thiourea vulcanization accelerator) is preferably 4 or more, more preferably 6 or more, still more preferably 8 or more, and preferably 20 or less, more preferably 18 or less, still more preferably 16 or less. If the mass ratio (thiuram vulcanization accelerator / thiourea vulcanization accelerator) is 4 or more, the strength of the obtained crosslinked rubber is further improved. If it is 20 or less, the activation of the thiuram vulcanization accelerator by the thiourea vulcanization accelerator is further improved.

[0036] The rubber composition may contain other vulcanization accelerators to such an extent that the effects of the present invention are not impaired. Examples of other vulcanization accelerators include thiazole-based ones such as mercaptobenzothiazole (MBT) and benzothiazole disulfide; guanidine-based ones such as diphenylguanidine (DPG); dithiocarbamate-based ones such as zinc dimethyldithiocarbamate (ZnPDC) and zinc dibutyldithiocarbamate, etc.

[0037] The total content of the vulcanization accelerator in the base rubber is preferably 4.4 parts by mass or more, more preferably 5.4 parts by mass or more, still more preferably 6.4 parts by mass or more, and preferably 12.5 parts by mass or less, more preferably 10.5 parts by mass or less, still more preferably 8.5 parts by mass or less, based on 100 parts by mass of the base rubber. If the total content of the vulcanization accelerator is within the above range, the occurrence of bloom, etc. can be more suppressed.

[0038] (Vulcanization activator) The rubber composition may further contain a vulcanization activator. Examples of the vulcanization activator include metal oxides, metal peroxides, fatty acids, etc. Examples of the metal oxides include zinc oxide, magnesium oxide, lead oxide, etc. Examples of the metal peroxides include zinc peroxide, chromium peroxide, magnesium peroxide, calcium peroxide, etc. Examples of the fatty acids include stearic acid, oleic acid, palmitic acid, etc. These vulcanization activators may be used alone or in combination of two or more.

[0039] The total amount of the vulcanization activator used is preferably 0.5 parts by mass or more, more preferably 0.6 parts by mass or more, still more preferably 0.7 parts by mass or more, and preferably 10.0 parts by mass or less, more preferably 9.5 parts by mass or less, still more preferably 9.0 parts by mass or less, based on 100 parts by mass of the base rubber.

[0040] (Thermoplastic resin) The rubber composition may further contain a thermoplastic resin (excluding tackifiers). By containing the thermoplastic resin, it becomes possible to control the viscoelastic properties of the cured product of the rubber composition, and the feeling can be improved.

[0041] When the rubber composition contains the thermoplastic resin, the content of the thermoplastic resin is preferably 5 parts by mass or more, more preferably 7 parts by mass or more, still more preferably 9 parts by mass or more, and preferably 40 parts by mass or less, more preferably 38 parts by mass or less, still more preferably 36 parts by mass or less, based on 100 parts by mass of the base rubber. If the content of the thermoplastic resin is 5 parts by mass or more, the friction coefficient of the resulting grip is further improved, and if it is 40 parts by mass or less, a decrease in the strength of the cured product of the rubber composition is suppressed.

[0042] Examples of the thermoplastic resin include ethylene-vinyl acetate copolymer, styrene-based elastomer, and the like.

[0043] The vinyl acetate content of the ethylene-vinyl acetate copolymer is preferably 10% by mass or more, more preferably 12% by mass or more, still more preferably 15% by mass or more, and preferably 80% by mass or less, more preferably 75% by mass or less, still more preferably 70% by mass or less. If the vinyl acetate content is 10% by mass or more, the feeling of the grip becomes better, and if it is 80% by mass or less, the abrasion resistance of the grip is further improved.

[0044] The Mooney viscosity (ML 1+4 (100 °C)) of the ethylene-vinyl acetate copolymer is preferably 20 or more, more preferably 22 or more, still more preferably 24 or more, and preferably 40 or less, more preferably 38 or less, still more preferably 36 or less. In this specification, the Mooney viscosity (ML 1+4 (100 °C)) is a value measured under the conditions of using an L rotor, a preheating time of 1 minute, a rotor rotation time of 4 minutes, and 100 °C in accordance with ISO289.

[0045] Examples of the styrenic elastomer include styrene-butadiene-styrene block copolymer (SBS), styrene-isobutylene-styrene block copolymer (SIBS), styrene-ethylene-butylene-styrene block copolymer (SEBS), and the like.

[0046] (Reinforcing material) Examples of the reinforcing material include carbon black, silica, calcium carbonate, and the like. Further, by blending the reinforcing material, the density of the crosslinked rubber can be adjusted, and the mass of the grip formed from the rubber composition can be adjusted. The specific surface area of the reinforcing material is preferably 1 m 2 / g to 300 m 2 / g. When the rubber composition contains a reinforcing material, the content of the reinforcing material is preferably 9 parts by mass or more, more preferably 14 parts by mass or more, still more preferably 19 parts by mass or more, and preferably 36 parts by mass or less, more preferably 30 parts by mass or less, still more preferably 24 parts by mass or less, based on 100 parts by mass of the base rubber. When the content of the reinforcing material is within the above range, it becomes easier to control the mass of the obtained grip within a desired range.

[0047] (Tackifier) The rubber composition may further contain a tackifier. When the content of the reinforcing material in the rubber composition increases for adjusting the density of the crosslinked rubber, the ratio (tanδ / E * ) of the crosslinked rubber tends to increase. However, by blending a tackifier, the ratio (tanδ / E * ) can be reduced. Note that when the tackifier is blended, the time required for vulcanization of the rubber composition tends to be long. However, in the rubber composition of the present invention, since a predetermined amount of thiuram-based vulcanization accelerator, sulfenamide-based vulcanization accelerator, and thiourea-based vulcanization accelerator are contained as vulcanization accelerators, vulcanization can be performed in a short time even when a tackifier is blended.

[0048] Examples of the tackifier include rosin esters, coumarone resins, phenolic resins, terpene resins, terpene phenol resins, styrenic resins, and the like.

[0049] The rosin ester is an ester compound obtained by reacting the rosin with alcohols. Rosin is a natural resin containing abietic acid, neoabietic acid, palustric acid, pimaric acid, isopimaric acid, and dehydroabietic acid. Examples of the alcohols include monohydric alcohols such as n-octyl alcohol, 2-ethylhexyl alcohol, decyl alcohol, lauryl alcohol, and stearyl alcohol; dihydric alcohols such as ethylene glycol, diethylene glycol, polyethylene glycol, propylene glycol, dipropylene glycol, polypropylene glycol, and neopentyl glycol; trihydric alcohols such as glycerin and trimethylolpropane; tetrahydric alcohols such as pentaerythritol and diglycerin; and hexahydric alcohols such as dipentaerythritol and sorbitol. Among these, polyhydric alcohols having two or more hydroxyl groups are preferred, and glycerin is more preferred.

[0050] The rosin ester includes hydrogenated rosin ester and disproportionated rosin ester. The hydrogenated rosin ester and disproportionated rosin ester are so-called stabilized rosin esters.

[0051] The hydrogenated rosin ester is an ester compound in which at least a part of the moiety derived from the rosin of the rosin ester is hydrogenated. The hydrogenated rosin ester can be obtained by hydrogenating rosin and then reacting the hydrogenated rosin with alcohols, or by reacting rosin with alcohols and then hydrogenating the obtained rosin ester.

[0052] The disproportionated rosin ester is an ester compound in which at least a part of the portion derived from rosin of the rosin ester is disproportionated. The disproportionated rosin ester can be obtained by reacting the disproportionated rosin with alcohols after disproportionating rosin, or by disproportionating the obtained rosin ester after reacting rosin with alcohols.

[0053] The coumarone resin is a resin containing coumarones as monomer components. As the coumarone resin, a coumarone-indene resin is preferred. The coumarone-indene resin contains coumarones and indenes as monomer components, and is a copolymer in which the total content of coumarones and indenes in all monomer components is 50% by mass or more. Examples of the coumarones include coumarone and methylcoumarone. The content of coumarones in all monomer components is preferably 1% by mass to 20% by mass. Examples of the indenes include indene and methylindene. The content of indenes in all monomer components is preferably 40% by mass to 95% by mass. The coumarone-indene resin may contain other monomer components other than coumarones and indenes. Examples of the other monomer components include styrene, vinyltoluene, and dicyclopentadiene.

[0054] Examples of the phenolic resin include condensates of phenols and formaldehyde. Examples of the phenols include phenol and m-cresol. The phenolic resin also includes resol obtained by subjecting phenols and formaldehyde to an addition reaction with an alkali catalyst; novolac obtained by subjecting them to a condensation reaction with an acid catalyst, etc. Furthermore, the phenolic resin also includes rosin phenolic resin obtained by adding phenols to rosin with an acid catalyst and subjecting it to thermal polymerization, etc.

[0055] When the rubber composition contains a tackifier, the content of the tackifier is preferably 5 parts by mass or more, more preferably 6 parts by mass or more, still more preferably 7 parts by mass or more, and preferably 20 parts by mass or less, more preferably 19 parts by mass or less, still more preferably 18 parts by mass or less, based on 100 parts by mass of the base rubber. If the content of the resin is 5 parts by mass or more, the feel of the grip obtained is better, and if it is 20 parts by mass or less, a decrease in the mechanical strength of the cured product of the rubber composition is suppressed.

[0056] (Processing aid) The rubber composition preferably contains a processing aid. Examples of the processing aid include internal lubricants and external lubricants. Examples of the internal lubricant include mineral oil and plasticizer. Examples of the mineral oil include paraffin oil, naphthene oil, and aromatic oil. Examples of the plasticizer include dioctyl phthalate, dibutyl phthalate, dioctyl sebacate, and dioctyl adipate. Examples of the external lubricant include phosphate ester compounds and long-chain alkylamine compounds. The rubber composition preferably contains a phosphate ester compound as an external lubricant. By containing a phosphate ester compound as an external lubricant, it is possible to prevent adhesion inside the apparatus during kneading even with a small addition amount, and a homogeneous rubber composition can be obtained.

[0057] When the rubber composition contains an external lubricant, the content of the external lubricant is preferably 0.1 part by mass or more, more preferably 0.15 part by mass or more, still more preferably 0.25 part by mass or more, and preferably 1.0 part by mass or less, more preferably 0.75 part by mass or less, still more preferably 0.5 part by mass or less, based on 100 parts by mass of the base rubber. If the content of the external lubricant is within the above range, the effect as a lubricant is high and the occurrence of bloom can be suppressed.

[0058] The rubber composition may further contain an antioxidant, a scorch inhibitor, a coloring material, etc., as required.

[0059] Examples of the anti-aging agent include imidazoles, amines, phenols, thioureas, etc. Examples of the imidazoles include nickel dibutyldithiocarbamate (NDIBC), 2-mercaptobenzimidazole, zinc salt of 2-mercaptobenzimidazole, etc. Examples of the amines include phenyl-α-naphthylamine, etc. Examples of the phenols include 2,2'-methylenebis(4-methyl-6-t-butylphenol) (MBMBP), 2,6-di-tert-butyl-4-methylphenol, etc. Examples of the thioureas include tributylthiourea, 1,3-bis(dimethylaminopropyl)-2-thiourea, etc. These anti-aging agents may be used alone or in combination of two or more.

[0060] When the rubber composition contains an anti-aging agent, the content of the anti-aging agent is preferably 0.2 parts by mass or more, more preferably 0.3 parts by mass or more, still more preferably 0.4 parts by mass or more, with respect to 100 parts by mass of the base rubber, and preferably 5.0 parts by mass or less, more preferably 4.8 parts by mass or less, still more preferably 4.6 parts by mass or less.

[0061] Examples of the scorch inhibitor include organic acids, nitroso compounds, etc. Examples of the organic acids include phthalic anhydride, pyromellitic anhydride, trimellitic anhydride, benzoic acid, salicylic acid, malic acid, etc. Examples of the nitroso compounds include N-nitroso-diphenylamine, N-(cyclohexylthio)phthalimide, sulfonamide derivatives, diphenylurea, bis(tridecyl)pentaerythritol diphosphite, 2-mercaptobenzimidazole, etc.

[0062] Examples of the coloring material include, for example, inorganic pigments, organic pigments, etc. Examples of the inorganic pigments include, for example, titanium oxide, and rutile-type titanium oxide is preferred particularly from the viewpoint of high hiding power. Examples of the organic pigments include azo pigments, phthalocyanine pigments, etc.

[0063] The rubber composition may contain microballoons. By blending microballoons into the rubber composition, a grip with a porous structure can be obtained. As the microballoons, either organic microballoons or inorganic microballoons can be used. Examples of the organic microballoons include hollow particles made of a thermoplastic resin, and resin capsules in which a low-boiling hydrocarbon is encapsulated in the shell of a thermoplastic resin.

[0064] The rubber composition can be prepared by a conventionally known method. For example, it can be prepared by kneading each raw material using a kneader such as a Banbury mixer, a kneader, or an open roll. When the rubber composition contains microballoons, it is preferable to knead the components other than the microballoons in advance and then knead this kneaded product with the microballoons. The material temperature when kneading the kneaded product and the microballoons is preferably set to a temperature lower than the expansion start temperature of the microballoons.

[0065] (Vulcanization characteristics) The rubber composition preferably has a 90% vulcanization time (t90) in the vulcanization curve measured at a vulcanization temperature of 185°C of 5 minutes or less, more preferably 4.5 minutes or less, and even more preferably 4 minutes or less. If the 90% vulcanization time is 5 minutes or less, grips can be produced in the same cycle as a base rubber having many unsaturated bonds such as natural rubber, and the productivity is increased. The lower limit of the 90% vulcanization time is not particularly limited, but is usually 3 minutes.

[0066] The 90% vulcanization time is determined from the vulcanization curve measured at a vulcanization temperature of 185°C. Specifically, when the minimum value of the torque in the vulcanization curve is ML, the maximum value is MH, and the difference is ME, the time required for the torque to reach ML + 90%ME is defined as the 90% vulcanization time.

[0067] (Vulcanized rubber) It is preferable that the crosslinked rubber obtained by curing the rubber composition at a vulcanization temperature of 185°C has the physical properties described below. The vulcanization time when vulcanizing the rubber composition was set as the time obtained by adding 2 minutes to the 90% vulcanization time (t90) in the vulcanization curve.

[0068] Regarding the crosslinked rubber obtained by curing the rubber composition at a vulcanization temperature of 185°C, using a dynamic viscoelasticity apparatus, the loss coefficient (tanδ) and complex elastic modulus (E * )(MPa) ratio (tanδ / E * ) measured under the measurement conditions of a vibration frequency of 10 Hz, a strain amplitude of 0.05%, and a tensile mode at 25°C is 0.027 or more, preferably 0.030 or more, more preferably 0.033 or more, and 0.052 or less, preferably 0.050 or less, more preferably 0.048 or less.

[0069] The crosslinked rubber obtained by curing the rubber composition at a vulcanization temperature of 185°C preferably has a loss tangent (tanδ) at 25°C, measured using a dynamic viscoelasticity apparatus under the measurement conditions of a vibration frequency of 10 Hz, a strain amplitude of 0.05%, and a tensile mode, of 0.10 or more, more preferably 0.12 or more, and even more preferably 0.14 or more. If the loss tangent (tanδ) is 0.10 or more, the anti-slip performance of the obtained grip will be better. The upper limit of the loss tangent (tanδ) is not particularly limited, but is preferably 0.26 or less, more preferably 0.24 or less, and even more preferably 0.23 or less. If the loss tangent (tanδ) is 0.26 or less, it is possible to suppress excessive deflection of the cured product of the rubber composition.

[0070] The crosslinked rubber obtained by curing the rubber composition at a vulcanization temperature of 185°C preferably has a complex elastic modulus (E * ) at 25°C, measured using a dynamic viscoelasticity apparatus under the measurement conditions of a vibration frequency of 10 Hz, a strain amplitude of 0.05%, and a tensile mode, of 8.00 MPa or less, more preferably 7.90 MPa or less, and even more preferably 7.80 MPa or less. If the complex elastic modulus (E * ) is 8.00 MPa or less, it is possible to suppress the hardening agent of the rubber composition from becoming too hard. The lower limit of the complex elastic modulus (E * ) is not particularly limited, but is preferably 3.00 MPa or more, more preferably 3.20 MPa or more, and even more preferably 3.40 MPa or more. If the complex elastic modulus (E * ) is 3.00 MPa or more, the hardness of the cured product of the rubber composition will be more suitable for the hardness of the grip.

[0071] The crosslinked rubber obtained by curing the rubber composition at a vulcanization temperature of 185°C preferably has a density of 1.05 g / cm 3 or more, more preferably 1.06 g / cm 3 or more, and even more preferably 1.07 g / cm 3 or more, and preferably 1.10 g / cm 3 or less, more preferably 1.09 g / cm 3 or less, and even more preferably 1.08 g / cm 3 or less. If the density is within the above range, the weight of the single-layer grip formed from the rubber composition will be comparable to that of the conventional grip, and it can be replaced with the conventional product without problems.

[0072] The hardness (Shore A hardness) of the crosslinked rubber is preferably 52 or more, more preferably 53 or more, and even more preferably 54 or more, and preferably 62 or less, more preferably 61 or less, and even more preferably 60 or less. If the hardness (Shore A hardness) of the crosslinked rubber is 52 or more, the mechanical strength of the grip will be further improved, and if it is 62 or less, the grip will not become too hard, and the feeling when gripping will be better.

[0073] The crosslinked rubber obtained by curing the rubber composition at a vulcanization temperature of 185°C preferably has a tensile strength at break (Tb) of 23 MPa or more, more preferably 24 MPa or more, and even more preferably 25 MPa or more. If the tensile strength at break is 23 MPa or more, the wear resistance of the grip will be better. The upper limit of the tensile strength at break of the crosslinked rubber obtained by curing the rubber composition at a vulcanization temperature of 185°C is not particularly limited, but is usually 40 MPa.

[0074] The crosslinked rubber obtained by curing the rubber composition at a vulcanization temperature of 185°C preferably has an elongation at break (Eb) of 300% or more, more preferably 320% or more, and even more preferably 340% or more. If the elongation at break is 300% or more, problems such as breakage of the grip during insertion of the shaft into the grip can be more effectively suppressed. The upper limit of the elongation at break of the crosslinked rubber obtained by curing the rubber composition at a vulcanization temperature of 185°C is not particularly limited, but is usually 800%.

[0075] The rubber composition for a grip of the present invention is used for molding a grip. Since the rubber composition for a grip has excellent abrasion resistance, tensile strength, and coefficient of friction after curing, it can be suitably used for a golf club grip.

[0076] [Golf Club Grip] The golf club grip of the present invention is characterized by having a cylindrical portion, and at least a part thereof is formed from the rubber composition for a grip. That is, at least a part of the cylindrical portion is composed of crosslinked rubber obtained by vulcanizing the rubber composition for a grip.

[0077] The golf club grip has a cylindrical portion into which a shaft is inserted. Examples of the configuration of the cylindrical portion include a single-layer structure, a two-layer structure, and a three-layer structure. When the cylindrical portion has a single-layer structure, the entire cylindrical portion is formed from the rubber composition. When the cylindrical portion has a multilayer structure, at least one layer is formed from the rubber composition. When the cylindrical portion has a multilayer structure, it is preferable that at least the outermost layer is formed from the rubber composition.

[0078] The cylindrical portion of the golf club grip preferably has a single-layer structure. Since the rubber composition for a grip can be vulcanized at a high temperature, even a thick member can be molded in a short time. Therefore, if a cylindrical portion having a single-layer structure is manufactured using the rubber composition for a grip, the structure is simple and the vulcanization time can be shortened, further improving the productivity of the grip. Also, the density of the crosslinked rubber formed from the rubber composition is 1.05 g / cm 3 ~1.10 g / cm 3If so, the weight of the single-layer grip formed from the rubber composition is comparable to that of the conventional grip, and it can be replaced with the conventional product without any problem.

[0079] The cylindrical portion may have a solid structure or a porous structure. If the cylindrical portion has a solid structure, the mechanical strength of the grip is increased, and if the cylindrical portion has a porous structure, the weight of the grip can be reduced.

[0080] The golf club grip is obtained by molding the rubber composition in a mold. Examples of the molding method include press molding and injection molding. Further, a golf club grip having an inner layer and an outer layer is obtained, for example, by press molding a laminate of an unvulcanized rubber sheet formed from the rubber composition for the outer layer and an unvulcanized rubber sheet formed from the rubber composition for the inner layer in a mold.

[0081] [Golf Club] The present invention also includes a golf club using the golf club grip. The golf club includes a shaft, a head attached to one end of the shaft, and a grip attached to the other end of the shaft, and the grip is the golf club grip. As the shaft, stainless steel or carbon fiber reinforced resin can be used. Examples of the head include a wood type, a utility type, and an iron type. The material constituting the head is not particularly limited, and examples thereof include titanium, titanium alloy, carbon fiber reinforced plastic, stainless steel, maraging steel, and soft iron.

[0082] Hereinafter, the golf club grip and the golf club will be described with reference to the drawings. FIG. 1 is a perspective view showing an example of the golf club grip. The grip 1 has a cylindrical portion 2 into which the shaft is inserted, and a cap portion 3 integrally formed so as to cover the opening at the rear end of the cylindrical portion. The cylindrical portion 2 has a single-layer structure. And the thickness of the said cylindrical part 2 is formed so that it may become thick gradually from the front-end part toward the rear-end part. In the grip 1 shown in FIG. 1, the cap portion 3 is formed of the same rubber composition as the cylindrical portion 2.

[0083] Figure 2 is a perspective view showing an example of a golf club provided with the golf club grip of the present invention. The golf club 4 includes a shaft 5, a head 6 attached to one end of the shaft 5, and a grip 1 attached to the other end of the shaft 4. The rear end of the shaft 5 is fitted into the cylindrical portion 2 of the grip 1.

Example

[0084] Hereinafter, the present invention will be described in detail by way of examples. However, the present invention is not limited to the following examples, and any modifications and embodiments within the scope not departing from the gist of the present invention are all included in the scope of the present invention.

[0085] [Evaluation Method] (1) Acrylonitrile content The acrylonitrile content was measured for acrylonitrile-butadiene rubber before hydrogenation in accordance with ISO 24698-1 (2008).

[0086] (2) Double bond content (mmol / g) The double bond content was calculated from the butadiene content (%) and the residual double bond amount (%) in the copolymer. The residual double bond amount is the mass ratio of the double bonds in the copolymer before hydrogenation to the double bonds in the copolymer after hydrogenation (double bond amount after hydrogenation / double bond amount before hydrogenation), and can be measured by infrared spectroscopy. When acrylonitrile-butadiene rubber is an acrylonitrile-butadiene binary copolymer, the butadiene content in the copolymer is obtained by subtracting the acrylonitrile content (%) from 100. Double bond amount = {butadiene content / 54} × residual double bond amount × 10

[0087] (3) Content of monomer containing carboxyl group Weighed 1 g of hydrogenated acrylonitrile-butadiene rubber, dissolved it in 50 mL of chloroform, and added thymol blue indicator dropwise thereto. While stirring this solution, a 0.05 mol / L methanol solution of sodium hydroxide was added dropwise, and the amount of the solution added dropwise (V mL) until the first color change was recorded. As a blank, for 50 mL of chloroform not containing hydrogenated acrylonitrile-butadiene rubber, a 0.05 mol / L methanol solution of sodium hydroxide was added dropwise using thymol blue as the indicator, and the amount of the solution added dropwise (B mL) until the first color change was recorded. The carboxyl group content was calculated by the following formula. Content of carboxyl group-containing monomer = {0.05×(V - B)×PM} / (10×X) (In the formula, V: amount of sodium hydroxide solution added dropwise to the test solution (mL), B: amount of sodium hydroxide solution added dropwise to the blank (mL), PM: molecular weight of the carboxyl group-containing monomer, X: valence of the carboxyl group-containing monomer)

[0088] (4) Vulcanization test For the rubber composition, a vulcanization test was carried out at the vulcanization temperatures described in Tables 3 and 4 using a vulcanization tester (manufactured by JSR Trading Co., Ltd., Curastometer (registered trademark) Model 7). According to "9. Die vulcanization test A method" of "Method for determining vulcanization characteristics by vibrating vulcanization tester" in JIS K6300-2 (2001), a low-amplitude sine wave vibration that does not break the rubber test piece was applied from the lower die, and the torque transmitted from the test piece to the upper die was measured from the unvulcanized state to the overvulcanized state. The measurement conditions were a torsional vibration frequency of 100 times per minute, an amplitude angle of 1°, and a measurement time of 30 minutes. From the obtained vulcanization curve, the minimum value (ML) and maximum value (MH) of the torque, as well as the 90% vulcanization time (t90) were determined.

[0089] (5) Hardness (Shore A hardness) Using the rubber composition, it was vulcanized under the conditions described in Tables 3 and 4 to produce a sheet with a thickness of 2 mm. This sheet was stored at 23°C for 2 weeks, and the hardness was measured using an automatic hardness tester (manufactured by H. Bareiss, Digitest II) in a state where 3 sheets were stacked so as not to be affected by the measurement substrate or the like. The detector used was "Shore A".

[0090] (6) Density (g / cm 3 ) Using the rubber composition, vulcanization was carried out under the conditions described in Tables 3 and 4 to produce a sheet with a size of 13 cm square and a thickness of 2 mm. Test pieces were prepared by punching out 2 cm square pieces from this sheet. The density of the obtained test pieces was measured using an automatic specific gravity meter (manufactured by MS Tech Co., Ltd., SP-GR1, based on the Archimedes principle).

[0091] (7) Tensile strength at break (MPa), elongation at break (%) The tensile strength at break and the elongation at break were measured in accordance with JIS K 6251 (2017). Specifically, using the rubber composition, vulcanization was carried out under the conditions described in Tables 3 and 4 to produce a sheet with a thickness of 1 mm. This sheet was punched into a dumbbell shape (dumbbell shape No. 3) to prepare test pieces. The physical properties were measured using a tensile test measuring device (manufactured by Shimadzu Corporation, Autograph (registered trademark) AGS-D) (measurement temperature: 23°C, tensile speed: 500 mm / min). Also, the tensile strength at break was calculated by dividing the tensile force recorded when the test piece was cut by the cross-sectional area of the test piece before the test.

[0092] (8) Viscoelasticity Loss tangent (tanδ), complex elastic modulus (E * ) were measured using a dynamic viscoelasticity measuring device (manufactured by UBM Co., Ltd., Rheogel-E4000). The test sample was prepared by slicing the grip to a thickness of 1.6 mm in the thickness direction and punching it into a predetermined size. The measurement conditions were as follows: temperature: -100°C to 100°C, heating rate: 3°C / min, measurement interval: 3°C, frequency: 10 Hz, strain amplitude: 10%, jig: tension, sample shape: width 4 mm, thickness 2 mm, length 40 mm. The loss tangent (tanδ) and the complex elastic modulus (E * ) at 25°C were determined from the viscoelasticity spectrum obtained by dynamic viscoelasticity measurement.

[0093] (9) Coefficient of friction The coefficient of friction was measured using a static / dynamic friction measuring machine (manufactured by Trinity Lab Co., Ltd., TriboMaster). The test sample was prepared by slicing the grip in the thickness direction to a thickness of 1.6 mm to remove the groove pattern, punching it into a width of 10 mm and a length of 20 mm, and fixing it to the planar contactor of the device. Also, natural leather cut from the palm of a golf glove (manufactured by Sumitomo Rubber Industries, XXIO (registered trademark) golf glove (GGG-X008)) was fixed to the moving table. The measurement conditions were a load of 25 g, a moving speed of 1 mm / sec, and a moving distance of 10 mm, and the average value of the coefficient of kinetic friction from 2000 ms to 6000 ms from the start of measurement was calculated. The coefficient of friction was shown as an exponentiated value with the coefficient of friction of crosslinked rubber No. 6 taken as 100.

[0094] [Preparation of Rubber Composition] Each raw material was kneaded with the formulation shown in Tables 1 and 2 to prepare a rubber composition. All the raw materials of the rubber composition were kneaded with a closed kneader.

[0095]

Table 1

[0096]

Table 2

[0097] The materials used in Tables 1 and 2 are as follows. HXNBR: Hydrogenated carboxy-modified acrylonitrile-butadiene rubber (manufactured by ARANXEO, Therban XT VPKA 8889 (residual double bond content 3.5%, acrylonitrile content 33.0% by mass, double bond content 0.40 mmol / g, carboxy group-containing monomer content 5.0% by mass)) Sulfur: Manufactured by Tsurumi Chemical Industry Co., Ltd., 5% oil-in microfine sulfur (200 mesh) Santocure (registered trademark) TBzTD: Manufactured by Sanshin Chemical Industry Co., Ltd., tetrabenzylthiuram disulfide Nocceler (registered trademark) TOT-N: Manufactured by Ouchi Shinko Chemical Industry Co., Ltd., tetrakis(2-ethylhexyl)thiuram disulfide Suncellar NS: Manufactured by Sanshin Chemical Industry Co., Ltd., N-(tert-butyl)-2-benzothiazolesulfenamide Noceller EUR: Manufactured by Ouchi Shinko Chemical Industry Co., Ltd., N,N’-diethylthiourea Zinc peroxide: Manufactured by Struktol, Struktol ZP 1014 (zinc peroxide content 29% by mass) EVA: Ethylene-vinyl acetate copolymer (manufactured by ARANXEO, Levapren 500 (vinyl acetate content 50% by mass, Mooney viscosity (ML 1+4 (100 °C)) 27) Staybelite Ester 10-E: Manufactured by Eastman Chemical Company, partially hydrogenated rosin ester SYLVATAC RE-5S: Manufactured by Arizona Chemical, rosin ester (melting point 25 °C or lower) Carbon black: Manufactured by Tokai Carbon Co., Ltd., Seast (SEAST) (registered trademark) 3 (specific surface area 79 m 2 / g) Silica: Manufactured by Tosoh Corporation, Nipsil (registered trademark) VN3 (specific surface area 180 - 230 m 2 / g) Calcium carbonate: Manufactured by Shiraishi Calcium Co., Ltd., Softon 3200 (specific surface area 3.2 m 2 / g) Rutile titanium oxide: Manufactured by Ishihara Sangyo Co., Ltd., CR60 vanfre VAM: Manufactured by Vanderbilt Chemicals, polyoxyethylene-octadecyl ether-phosphoric acid

[0098] [Manufacture of grip] The rubber composition was put into a mold with a groove pattern on the cavity surface. Then, it was vulcanized under the conditions shown in Table 2 to cause a crosslinking reaction in the rubber, and a grip for a golf club was obtained. The viscoelastic properties and coefficient of friction of the grip were evaluated, and the results are shown in Tables 3 and 4.

[0099]

Table 3

[0100]

Table 4

[0101] Crosslinked rubbers No.1 to 6 and 9 to 15 were formed using rubber compositions No.A to F and H to N. Rubber compositions No.A to F and H to N each contain a predetermined amount of a thiuram-based vulcanization accelerator, a sulfenamide-based vulcanization accelerator, and a thiourea-based vulcanization accelerator as vulcanization accelerators. These rubber compositions No.A to F and H to N have a 90% vulcanization time of 3.6 minutes or less at a vulcanization temperature of 185°C, indicating a fast vulcanization rate. Further, crosslinked rubbers No.1 to 6 and 9 to 15 vulcanized from these rubber compositions No.A to F and H to N at a vulcanization temperature of 185°C had a tensile strength at break of 24 MPa or more and excellent mechanical properties.

[0102] Furthermore, rubber compositions No.B to E and K to N have a ratio (tanδ / E * )(MPa) of the loss factor (tanδ) to the complex elastic modulus (E * ) of the grip (crosslinked rubber) cured at a vulcanization temperature of 185°C at 25°C in the range of 0.027 to 0.052, indicating excellent friction coefficient.

[0103] On the other hand, rubber compositions No.A and F have a ratio (tanδ / E * )(MPa) of the loss factor (tanδ) to the complex elastic modulus (E * ) of the grip (crosslinked rubber) cured at a vulcanization temperature of 185°C at 25°C exceeding 0.052. The grips formed from these rubber compositions No.A and F had inferior friction coefficients.

[0104] Also, rubber compositions No.H to J have a ratio (tanδ / E * )(MPa) of the loss factor (tanδ) to the complex elastic modulus (E * ) of the grip (crosslinked rubber) cured at a vulcanization temperature of 185°C at 25°C less than 0.027. The grips formed from these rubber compositions No.H to J had inferior friction coefficients.

[0105] Bridged rubbers No. 7 and 8 are formed using rubber composition No. G. Rubber composition No. G contains a thiuram-based vulcanization accelerator and a sulfenamide-based vulcanization accelerator as vulcanization accelerators and does not contain a thiourea-based vulcanization accelerator. When this rubber composition No. G is used, the bridged rubber No. 7 vulcanized at a vulcanization temperature of 165°C has a tensile strength at break of 27 MPa or more and excellent mechanical properties. However, the 90% vulcanization time at a vulcanization temperature of 165°C is 11 minutes, and the vulcanization takes a long time. Also, for this rubber composition No. G, the 90% vulcanization time at a vulcanization temperature of 185°C is 3.5 minutes, and the vulcanization rate is fast. However, the bridged rubber No. 8 vulcanized from rubber composition No. G at a vulcanization temperature of 185°C had a tensile strength at break of 21 MPa and inferior mechanical properties.

[0106] The present invention (1) is a rubber composition for grips containing a base rubber, a vulcanizing agent, and a vulcanization accelerator, wherein the base rubber contains a hydrogenated carboxy-modified acrylonitrile-butadiene rubber, the vulcanization accelerator contains a thiuram-based vulcanization accelerator, a sulfenamide-based vulcanization accelerator, and a thiourea-based vulcanization accelerator, the content of the thiuram-based vulcanization accelerator is 4 parts by mass or more with respect to 100 parts by mass of the base rubber, the content of the sulfenamide-based vulcanization accelerator is 0.3 parts by mass or more with respect to 100 parts by mass of the base rubber, the content of the thiourea-based vulcanization accelerator is 0.1 parts by mass or more with respect to 100 parts by mass of the base rubber, and for the bridged rubber obtained by curing the rubber composition for grips at a vulcanization temperature of 185°C, measured using a dynamic viscoelasticity apparatus under the measurement conditions of a vibration frequency of 10 Hz, a strain amplitude of 0.05%, and a tensile mode, the ratio of the loss factor (tanδ) to the complex elastic modulus (E * )(MPa) (tanδ / E * ) is 0.027 to 0.052.

[0107] The present invention (2) is the rubber composition for grips according to the present invention (1), wherein the 90% vulcanization time (t90) in the vulcanization curve measured at a vulcanization temperature of 185°C is 5 minutes or less.

[0108] The present invention (3) is the rubber composition for grips according to the present invention (1) or (2), wherein the tensile strength at break of the crosslinked rubber obtained by curing the rubber composition for grips at a vulcanization temperature of 185°C is 23 MPa or more.

[0109] The present invention (4) is the rubber composition for grips according to any one of the present inventions (1) to (3), wherein the density of the crosslinked rubber obtained by curing the rubber composition for grips at a vulcanization temperature of 185°C is 1.05 g / cm 3 ~1.10 g / cm 3 The present invention (5) is the rubber composition for grips according to any one of the present inventions (1) to (4), wherein the hardness of the crosslinked rubber obtained by curing the rubber composition for grips at a vulcanization temperature of 185°C is 52 to 62 in Shore A hardness.

[0110] The present invention (6) is a golf club grip characterized by having a cylindrical portion, and at least a part of the cylindrical portion being formed from the rubber composition for grips according to any one of the present inventions (1) to (5).

[0111] The present invention (6) is a golf club grip characterized by having a cylindrical portion, and at least a part of the cylindrical portion being formed from the rubber composition for grips according to any one of the present inventions (1) to (5).

Explanation of reference numerals

[0112] 1: Grip, 2: Cylindrical portion, 3: Cap portion, 4: Golf club, 5: Shaft, 6: Head

Claims

1. A rubber composition for a grip containing a base rubber, a vulcanizing agent, and an accelerator, wherein the base rubber contains a hydrogenated carboxy-modified acrylonitrile-butadiene rubber, the accelerator contains a thiuram-based accelerator, a sulfenamide-based accelerator, and a thiourea-based accelerator, the content of the thiuram-based accelerator is 4 parts by mass or more with respect to 100 parts by mass of the base rubber, the content of the sulfenamide-based accelerator is 0.3 parts by mass or more with respect to 100 parts by mass of the base rubber, the content of the thiourea-based accelerator is 0.1 parts by mass or more with respect to 100 parts by mass of the base rubber, The crosslinked rubber obtained by curing the rubber composition for grips at a vulcanization temperature of 185°C was measured for loss factor (tan δ) and complex modulus (E) at 25°C using a dynamic viscoelasticity device under the measurement conditions of an excitation frequency of 10 Hz, a strain amplitude of 0.05%, and a tensile mode. * ) (MPa) ratio (tan δ / E * ) is 0.027 to 0.

052.

2. The rubber composition for a grip according to claim 1, wherein the 90% vulcanization time (t90) in the vulcanization curve measured at a vulcanization temperature of 185°C is 5 minutes or less.

3. The rubber composition for a grip according to claim 1, wherein the tensile strength at break of the crosslinked rubber obtained by curing the rubber composition for a grip at a vulcanization temperature of 185°C is 23 MPa or more.

4. The density of the crosslinked rubber obtained by curing the rubber composition for grips at a vulcanization temperature of 185°C is 1.05 g / cm 3 to 1.10 g / cm 3 The rubber composition for grips according to claim 1, wherein the density is as described above.

5. The rubber composition for a grip according to claim 1, wherein the hardness of the crosslinked rubber obtained by curing the rubber composition for a grip at a vulcanization temperature of 185°C is 52 to 62 in Shore A hardness.

6. A golf club grip having a cylindrical portion, wherein at least a part of the cylindrical portion is formed from the rubber composition for a grip according to any one of claims 1 to 5.

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