Rubber composition for grips and golf club grips

Abstract

The present invention provides a rubber composition for grips that yields crosslinked rubber with a high coefficient of friction. [Solution] The grip rubber composition is a grip rubber composition containing a base rubber and a vulcanizing agent, wherein the base rubber contains a solid rubber that is solid at 25°C and a liquid rubber that is liquid at 25°C, and the ratio of the loss coefficient (tanδ) to the complex modulus of elasticity (E*) (MPa) (tanδ / E*) at 25°C, measured using a dynamic viscoelastic device under measurement conditions of an excitation frequency of 10 Hz, a strain amplitude of 0.05%, and a tensile mode, is 0.030 to 0.045.

Description

[Technical Field]

[0001] This invention relates to a rubber composition for grips used in the manufacture of grips. [Background technology]

[0002] Rubber grips are widely used as grips (anti-slip components) attached to sports equipment and other items. 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 from a surface rubber composition 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, phenolic resin, xylene resin, and styrene resin (see Patent Document 1 (Claim 1, paragraphs 0013, 0019)). [Prior art documents] [Patent Documents]

[0004] [Patent Document 1] Japanese Patent Publication No. 2017-113388 [Overview of the project] [Problems that the invention aims to solve]

[0005] Grips used on sports equipment and other items require excellent anti-slip properties. While the anti-slip properties of a grip can be improved by forming a groove pattern on its surface, it is preferable that the cross-linked rubber that makes up the grip itself has a high coefficient of friction. Here, as a method to increase the coefficient of friction of cross-linked rubber, there is a method of adding tackifying low molecular weight components such as rosin or coumarone resin, or liquid softeners, to the rubber composition, as described in Reference 1. However, when the amount of low molecular weight tackifying components or softeners added was large, there was a tendency for bleeding to occur after curing.

[0006] This invention has been made in view of the above circumstances, and aims to provide a rubber composition for grips that can obtain crosslinked rubber having a high coefficient of friction. [Means for solving the problem]

[0007] The present invention, which has been able to solve the above problems, is a grip rubber composition containing a base rubber and a vulcanizing agent, wherein the base rubber contains a solid rubber that is solid at 25°C and a liquid rubber that is liquid at 25°C, and the ratio of the loss coefficient (tanδ) to the complex modulus of elasticity (E*) (MPa) (tanδ / E*) at 25°C, measured using a dynamic viscoelastic device under measurement conditions of an excitation frequency of 10 Hz, a strain amplitude of 0.05%, and a tensile mode, is 0.030 to 0.045.

[0008] By using both solid and liquid rubber as the base rubber, the resulting cured product (crosslinked rubber) exhibits increased hysteresis loss during deformation and a higher coefficient of friction. Furthermore, the liquid rubber crosslinks with the solid rubber during the curing process, preventing bleeding after curing. [Effects of the Invention]

[0009] The rubber composition for grips of the present invention yields a crosslinked rubber having a high coefficient of friction. Therefore, according to the present invention, a grip can be obtained in which the crosslinked rubber constituting the grip itself has a high coefficient of friction. [Brief explanation of the drawing]

[0010] [Figure 1] This is a perspective view showing an example of a golf club grip according to the present invention. [Figure 2] It is a perspective view showing an example of a golf club provided with a grip for a golf club of the present invention.

Embodiments for Carrying Out the Invention

[0011] [Rubber Composition] The rubber composition for a grip of the present invention (hereinafter, may be simply referred to as "rubber composition") is used for molding a grip. The rubber composition contains a base rubber and a vulcanizing agent, and the base rubber contains a solid rubber that is solid at 25°C and a liquid rubber that is liquid at 25°C. Furthermore, for the cured product of the rubber composition for a grip, the ratio (tanδ / E*) of the loss factor (tanδ) and the complex elastic modulus (E*) (MPa) 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 0.030 to 0.045.

[0012] By using a solid rubber and a liquid rubber in combination as the base rubber, the cured product (crosslinked rubber) obtained has a large hysteresis loss during deformation and a high friction coefficient. In addition, the liquid rubber does not cause a bleeding phenomenon after curing by crosslinking with the solid rubber when the rubber composition cures.

[0013] And, the larger the loss tangent (tanδ) of the crosslinked rubber at 25°C, the greater the energy lost during deformation, so the hysteresis friction becomes larger. Also, the higher the complex elastic modulus (E * )(MPa) of the crosslinked rubber (the harder the crosslinked rubber), the more disadvantageously it acts on friction. Therefore, if this ratio (tanδ / E * ) is 0.030 or more, the hysteresis loss becomes large and the friction coefficient of the crosslinked rubber is improved, and if it is 0.045 or less, the occurrence of poor dispersion is prevented and the friction coefficient of the crosslinked rubber is considered to be improved.

[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, and more preferably 55% by mass or more.

[0015] The base rubber contains solid rubber, which is solid at 25°C, and liquid rubber, which is liquid at 25°C.

[0016] (Solid rubber) Examples of the solid rubber include diene rubbers such as natural rubber (NR), ethylene-propylene-diene rubber (EPDM), acrylonitrile-butadiene rubber (NBR), hydrogenated acrylonitrile-butadiene rubber (HNBR), carboxy-modified acrylonitrile-butadiene rubber (XNBR), hydrogenated carboxy-modified acrylonitrile-butadiene rubber (HXNBR), butadiene rubber (BR), styrene-butadiene rubber (SBR), isoprene rubber (IR), and chloroprene rubber (CR); and non-diene rubbers such as butyl rubber (IIR), ethylene-propylene rubber (EPM), and urethane rubber (PU). These solid rubbers may be used individually or in combination of two or more types.

[0017] The solid rubber is preferably a diene-based rubber, and more preferably an acrylonitrile-butadiene-based rubber. The solid rubber is even more preferably to contain at least one selected from the group consisting of carboxy-modified acrylonitrile-butadiene rubber (XNBR), hydrogenated acrylonitrile-butadiene rubber (HNBR), and hydrogenated carboxy-modified acrylonitrile-butadiene rubber (HXNBR). XNBR is a copolymer of a monomer having a carboxyl group, acrylonitrile, and butadiene. HNBR is a hydrogenated product of acrylonitrile-butadiene rubber. HXNBR is a hydrogenated product of a copolymer of a monomer having a carboxyl group, acrylonitrile, and butadiene.

[0018] The content of acrylonitrile-butadiene rubber in the solid 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 base rubber contains only acrylonitrile-butadiene rubber as the solid rubber.

[0019] In the aforementioned NBR, XNBR, HNBR, and HXNBR, the acrylonitrile content is preferably 15% by mass or more, more preferably 18% by mass or more, even more preferably 21% by mass or more, preferably 50% by mass or less, more preferably 45% by mass or less, and even more preferably 40% by mass or less. If the acrylonitrile content is 15% by mass or more, the abrasion resistance will be good, and if it is 50% by mass or less, the grip will feel good in cold regions or in winter.

[0020] In the HNBR and HXNBR mentioned above, the double bond content 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, and even more preferably 1.5 mmol / g or less. If the double bond content is 0.09 mmol / g or more, vulcanization during molding becomes easier, further improving the tensile strength of the grip, and if it is 2.5 mmol / g or less, the durability (weather resistance) and tensile strength of the grip are better. The double bond content can be adjusted by the butadiene content in the copolymer and the amount of hydrogenation added to the copolymer.

[0021] In the XNBR and HXNBR mentioned above, examples of monomers having a carboxyl group include acrylic acid, methacrylic acid, fumaric acid, and maleic acid. In the XNBR and HXNBR mentioned above, the content of monomers containing a carboxyl group is preferably 1.0% by mass or more, more preferably 2.0% by mass or more, even more preferably 3.5% by mass or more, preferably 30% by mass or less, more preferably 25% by mass or less, and even more preferably 20% by mass or less. If the content of monomers containing a carboxyl group is 1.0% by mass or more, the abrasion resistance will be better, and if it is 30% by mass or less, the grip will feel better in cold regions or in winter.

[0022] In the XNBR and HXNBR mentioned above, the carboxyl group content is preferably 1.0% by mass or more, more preferably 2.0% by mass or more, even more preferably 3.5% by mass or more, preferably 30% by mass or less, more preferably 25% by mass or less, and even more preferably 20% by mass or less. If the carboxyl group content is 1.0% by mass or more, the abrasion resistance is better, and if it is 30% by mass or less, the grip feel in cold regions or winter is better.

[0023] Mooney viscosity (ML) of the aforementioned HXNBR 1+4 The Mooney viscosity (ML) is preferably 60 or higher, more preferably 64 or higher, even more preferably 68 or higher, preferably 95 or lower, more preferably 90 or lower, and even more preferably 85 or lower. 1+4 If the Mooney viscosity (ML) (at 100°C) is 60 or higher, the wear resistance of the grip is improved, and if it is 95 or lower, the processability of the rubber composition is good. Note that in this invention, Mooney viscosity (ML) 1+4 (100℃)) refers to the value measured in accordance with JIS K6300, using an L rotor, with a preheating time of 1 minute, a rotor rotation time of 4 minutes, and under conditions of 100℃.

[0024] (Liquid rubber) The liquid rubber is not particularly limited as long as it is liquid at 25°C. By incorporating the liquid rubber, the coefficient of friction of the resulting cured product increases.

[0025] Examples of the liquid rubber include liquid isoprene rubber, carboxy-modified liquid isoprene rubber, liquid farnesene rubber, liquid farnesene-butadiene copolymer, liquid styrene-butadiene rubber, hydrogenated liquid isoprene rubber, liquid butadiene rubber, liquid isoprene-butadiene copolymer, and other liquid diene rubbers; and liquid non-diene rubbers such as liquid butyl rubber. These liquid rubbers may be used individually or in combination of two or more types.

[0026] The liquid rubber is preferably a rubber having carbon-carbon unsaturated bonds. Liquid rubber having carbon-carbon unsaturated bonds can co-crosslink with solid rubber during curing, which further suppresses bleeding.

[0027] The liquid rubber is preferably a liquid diene-based rubber, and more preferably at least one selected from the group consisting of liquid isoprene rubber, carboxy-modified liquid isoprene rubber, liquid farnesene rubber, liquid farnesene-butadiene copolymer, liquid styrene-butadiene rubber, and hydrogenated liquid isoprene rubber.

[0028] The liquid farnesene rubber and the liquid farnesene-butadiene copolymer have structural units derived from farnesene, which may be derived from α-farnesene or β-farnesene. It is also preferable that all of the farnesene-derived structural units are derived from β-farnesene.

[0029] The number-average molecular weight of the liquid rubber is preferably 20,000 or more, more preferably 25,000 or more, even more preferably 30,000 or more, preferably 150,000 or less, more preferably 140,000 or less, and even more preferably 135,000 or less. If the number-average molecular weight of the liquid rubber is within the above range, it can be easily kneaded with solid rubber. The number-average molecular weight of the liquid rubber is the number-average molecular weight on a polystyrene basis, measured by gel permeation chromatography (GPC).

[0030] The viscosity of the liquid rubber is preferably 10 Pa·s or more, more preferably 50 Pa·s or more, even more preferably 100 Pa·s or more, preferably 700 Pa·s or less, more preferably 600 Pa·s or less, and even more preferably 500 Pa·s or less. If the viscosity of the liquid rubber is within the above range, it can be easily mixed with solid rubber. The viscosity of the liquid rubber was measured using a Brookfield viscometer after heating the liquid rubber to 38°C.

[0031] The glass transition temperature of the liquid rubber is preferably 0°C or lower, more preferably -10°C or lower, and even more preferably -20°C or lower. If the glass transition temperature of the liquid rubber is 0°C or lower, flexibility can be imparted to the rubber composition under general usage conditions. The glass transition temperature of the liquid rubber is measured by differential scanning calorimetry. The lower limit of the glass transition temperature of the liquid rubber is not particularly limited, but is -90°C.

[0032] The liquid rubber content is preferably 5 parts by mass or more, more preferably 10 parts by mass or more, even more preferably 12 parts by mass or more, particularly preferably 14 parts by mass or more, preferably 35 parts by mass or less, more preferably 30 parts by mass or less, even more preferably 28 parts by mass or less, and particularly preferably 26 parts by mass or less, per 100 parts by mass of solid rubber. If the liquid rubber content is 5 parts by mass or more, the flexibility of the rubber composition can be improved, and if it is 35 parts by mass or less, a significant decrease in the strength of the rubber composition can be prevented.

[0033] (Vulcanizing agent) As the vulcanizing agent, sulfur-based vulcanizing agents and organic peroxides can be used. The vulcanizing agent may be used alone or in combination of two or more types.

[0034] Examples of the sulfur-based vulcanizing agent include elemental sulfur and sulfur donor compounds. Examples of elemental sulfur include powdered sulfur, precipitated sulfur, colloidal sulfur, and insoluble sulfur. Examples of sulfur donor compounds include 4,4'-dithiobismorpholine. Examples of the aforementioned organic peroxides include dicumyl peroxide, α,α'-bis(t-butylperoxy-m-diisopropyl)benzene, 2,5-dimethyl-2,5-di(t-butylperoxy)hexane, and 1,1-bis(t-butylperoxy)3,3,5-trimethylcyclohexane.

[0035] As the vulcanizing agent, a sulfur-based vulcanizing agent is preferred, and elemental sulfur is more preferred. Using a sulfur-based vulcanizing agent tends to improve the mechanical strength of the resulting crosslinked rubber. Furthermore, using a sulfur-based vulcanizing agent does not increase the bonding energy between rubber chains, resulting in a larger hysteresis loss during deformation and an improved coefficient of friction.

[0036] The content of the vulcanizing agent is preferably 0.2 parts by mass or more, more preferably 0.4 parts by mass or more, even more preferably 0.6 parts by mass or more, preferably 4.0 parts by mass or less, more preferably 3.5 parts by mass or less, and even more preferably 3.0 parts by mass or less, per 100 parts by mass of solid rubber. If the content of the vulcanizing agent is 0.2 parts by mass or more, vulcanization will proceed more easily, and if it is 4.0 parts by mass or less, the occurrence of scorching can be reduced.

[0037] (Vulcanization accelerator) The rubber composition may contain a vulcanization accelerator. The vulcanization accelerator may be used alone or in combination of two or more types.

[0038] The total content of the vulcanization accelerator in the rubber composition is preferably 4.4 parts by mass or more, more preferably 5.4 parts by mass or more, even more preferably 6.4 parts by mass or more, preferably 12.5 parts by mass or less, more preferably 10.5 parts by mass or less, and even more preferably 8.5 parts by mass or less, per 100 parts by mass of the solid rubber. If the total content of the vulcanization accelerator is within the above range, the occurrence of bloom and the like can be further suppressed.

[0039] Examples of the aforementioned vulcanization accelerators include thiram-based vulcanization accelerators, sulfenamide-based vulcanization accelerators, thiourea-based vulcanization accelerators, thiazole-based vulcanization accelerators, guanidine-based vulcanization accelerators, and dithiocarbamate-based vulcanization accelerators.

[0040] Thiuram-based vulcanization accelerator Examples of the thiram-based vulcanization accelerators include tetramethylthiram disulfide (TMTD), tetrabenzylthiram disulfide (TBzTD), tetramethylthiram monosulfide (TMTM), dipentamethylenethiram tetrasulfide, and tetrakis(2-ethylhexyl)thiram disulfide. While the thiram-based vulcanization accelerators may be used individually, it is preferable to use two or more in combination from the viewpoint of preventing blooming.

[0041] The content of the thiram-based vulcanization accelerator is preferably 4 parts by mass or more, more preferably 5 parts by mass or more, even more preferably 6 parts by mass or more, preferably 9 parts by mass or less, more preferably 8 parts by mass or less, and even more preferably 7 parts by mass or less, per 100 parts by mass of the solid rubber. If the content of the thiram-based vulcanization accelerator is within the above range, even faster vulcanization can be achieved while maintaining scorch resistance, even in base rubber with a small amount of double bonds.

[0042] Sulfenamide-based vulcanization accelerator Examples of the sulfenamide-based vulcanization accelerators include N-cyclohexyl-2-benzothiazolyl sulfenamide (CBS) and N-(tert-butyl)-2-benzothiazo-lsulfenamide (BBS). The sulfenamide-based vulcanization accelerators may be used alone or in combination of two or more types.

[0043] The content of the sulfenamide-based vulcanization accelerator is preferably 0.3 parts by mass or more, more preferably 0.5 parts by mass or more, even more preferably 0.7 parts by mass or more, preferably 2.5 parts by mass or less, more preferably 2.0 parts by mass or less, and even more preferably 1.5 parts by mass or less, per 100 parts by mass of the solid rubber. If the content of the sulfenamide-based vulcanization accelerator is within the above range, the occurrence of bloom can be further reduced.

[0044] Thiourea-based vulcanization accelerators Examples of the thiourea-based vulcanization accelerators include trimethylthiourea and N,N'-diethylthiourea. These thiourea-based vulcanization accelerators may be used alone or in combination of two or more types.

[0045] The content of the thiourea-based vulcanization accelerator is preferably 0.1 parts by mass or more, more preferably 0.2 parts by mass or more, even more preferably 0.3 parts by mass or more, preferably 1.0 part by mass or less, more preferably 0.8 parts by mass or less, and even more preferably 0.6 parts by mass or less, per 100 parts by mass of the solid rubber. If the content of the thiourea-based vulcanization accelerator is within the above range, the thiram-based vulcanization accelerator can be activated and the vulcanization time can be further shortened.

[0046] Examples of the thiazole-based vulcanization accelerators include mercaptobenzothiazole (MBT) and benzothiazole disulfide. Examples of the guanidine-based vulcanization accelerator include diphenylguanidine (DPG). Examples of the dithiocarbamate-based vulcanization accelerators include zinc dimethyldithiocarbamate (ZnPDC) and zinc dibutyldithiocarbamate.

[0047] The rubber composition preferably contains a thiram-based vulcanization accelerator and a sulfenamide-based vulcanization accelerator as vulcanization accelerators. By including a thiram-based vulcanization accelerator and a sulfenamide-based vulcanization accelerator, a crosslinked rubber with excellent mechanical strength can be obtained even when vulcanization is performed at high temperatures.

[0048] The total content of the thiram-based vulcanization accelerator and the sulfenamide-based vulcanization accelerator in the rubber composition is preferably 4.5 parts by mass or more, more preferably 5.5 parts by mass or more, even more preferably 6.5 parts by mass or more, preferably 11.5 parts by mass or less, more preferably 10.0 parts by mass or less, and even more preferably 8.5 parts by mass or less, per 100 parts by mass of the solid rubber. If the total content is 4.5 parts by mass or more, the vulcanization rate can be increased even in solid rubber with a small amount of double bonds, and if it is 11.5 parts by mass or less, the scorch resistance is improved in rubber with a small amount of double bonds.

[0049] The mass ratio (thiuram-based vulcanization accelerator / sulfenamide-based vulcanization accelerator) of the thiuram-based vulcanization accelerator in the rubber composition is preferably 1.5 or higher, more preferably 3.0 or higher, even more preferably 4.5 or higher, preferably 30 or lower, more preferably 20 or lower, and even more preferably 10 or lower. If the mass ratio (thiuram-based vulcanization accelerator / sulfenamide-based vulcanization accelerator) is 1.5 or higher, the vulcanization rate can be increased even with solid rubber that has a small amount of double bonds, and if it is 30 or lower, the decrease in strength of the crosslinked rubber obtained during vulcanization at high temperature and high speed can be further suppressed.

[0050] The rubber composition preferably contains a thiram-based vulcanization accelerator, a sulfenamide-based vulcanization accelerator, and a thiourea-based vulcanization accelerator as vulcanization accelerators. By including the thiourea-based vulcanization accelerator, the thiram-based vulcanization accelerator is activated, and the vulcanization time can be further shortened.

[0051] The total content of the thiram-based vulcanization accelerator, sulfenamide-based vulcanization accelerator, and thiourea-based vulcanization accelerator in the rubber composition is preferably 4.4 parts by mass or more, more preferably 5.4 parts by mass or more, even more preferably 6.4 parts by mass or more, preferably 12.5 parts by mass or less, more preferably 10.5 parts by mass or less, and even more preferably 9.5 parts by mass or less, per 100 parts by mass of the solid rubber. If the total content is 4.4 parts by mass or more, the vulcanization rate can be increased even in solid rubber with a small amount of double bonds, and if it is 12.5 parts by mass or less, the scorch resistance is improved in rubber with a small amount of double bonds.

[0052] The mass ratio (thiuram-based vulcanization accelerator / thiourea-based vulcanization accelerator) of the thiuram-based vulcanization accelerator in the rubber composition is preferably 4 or more, more preferably 6 or more, even more preferably 8 or more, preferably 20 or less, more preferably 18 or less, and even more preferably 16 or less. If the mass ratio (thiuram-based vulcanization accelerator / thiourea-based vulcanization accelerator) is 4 or more, the strength of the resulting crosslinked rubber is further improved, and if it is 20 or less, the activation of the thiuram-based accelerator by the thiourea-based accelerator is further improved.

[0053] (Vulcanizing activator) The rubber composition may further contain a vulcanizing activator. Examples of the vulcanizing activators include metal oxides, metal peroxides, and fatty acids. Examples of the metal oxides include zinc oxide, magnesium oxide, and lead oxide. Examples of the metal peroxides include zinc peroxide, chromium peroxide, magnesium peroxide, and calcium peroxide. Examples of the fatty acids include stearic acid, oleic acid, and palmitic acid. These vulcanizing activators may be used individually or in combination of two or more.

[0054] The total amount of the vulcanizing activator used is preferably 0.5 parts by mass or more, more preferably 0.6 parts by mass or more, even more preferably 0.7 parts by mass or more, preferably 10.0 parts by mass or less, more preferably 9.5 parts by mass or less, and even more preferably 9.0 parts by mass or less, per 100 parts by mass of solid rubber.

[0055] (thermoplastic resin) The rubber composition may contain a thermoplastic resin (excluding a tackifier). The inclusion of the thermoplastic resin makes it possible to control the viscoelastic properties of the cured rubber composition, thereby improving the feel. The thermoplastic resin may be used alone or in combination of two or more types.

[0056] If 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, even more preferably 9 parts by mass or more, preferably 40 parts by mass or less, more preferably 38 parts by mass or less, and even more preferably 36 parts by mass or less, per 100 parts by mass of solid rubber. If the content of the thermoplastic resin is 5 parts by mass or more, the coefficient of friction of the resulting grip is further improved, and if it is 40 parts by mass or less, the decrease in strength of the cured product of the rubber composition is suppressed.

[0057] Examples of the thermoplastic resin include ethylene-vinyl acetate copolymers and styrene-based elastomers.

[0058] The vinyl acetate content of the ethylene-vinyl acetate copolymer is preferably 10% by mass or more, more preferably 12% by mass or more, even more preferably 15% by mass or more, preferably 80% by mass or less, more preferably 75% by mass or less, and even more preferably 70% by mass or less. If the vinyl acetate content is 10% by mass or more, the grip feel is improved, and if it is 80% by mass or less, the wear resistance of the grip is further improved.

[0059] Mooney viscosity (ML) of the ethylene-vinyl acetate copolymer 1+4(100 °C)) 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.

[0060] 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.

[0061] (Reinforcing material) The rubber composition may contain a reinforcing material. Examples of the reinforcing material include carbon black, silica, calcium carbonate, and the like. Also, 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.

[0062] When the rubber composition contains a reinforcing material, the content of the reinforcing material is preferably ⑨ mass parts or more, more preferably 14 mass parts or more, still more preferably 19 mass parts or more, and preferably 36 mass parts or less, more preferably 30 mass parts or less, still more preferably 24 mass parts or less, per 100 mass parts of the solid rubber. If 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.

[0063] (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.

[0064] Examples of the aforementioned tackifiers include rosin esters, coumarone resins, phenolic resins, terpene resins, terpene-phenolic resins, and styrene-based resins.

[0065] The rosin ester is an ester compound obtained by reacting the rosin with alcohols. Rosin is a natural resin containing abietic acid, neoabietic acid, palastic acid, pimaric acid, isopimaric acid, and dehydroabietic acid. 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 of dihydric or higher hydrity are preferred, and glycerin is more preferred.

[0066] The rosin esters mentioned above include hydrogenated rosin esters and disproportionated rosin esters. The hydrogenated rosin esters and disproportionated rosin esters are so-called stabilized rosin esters.

[0067] The hydrogenated rosin ester is an ester compound in which at least a portion of the rosin-derived portion of a rosiene ester is hydrogenated. The hydrogenated rosin ester can be obtained by hydrogenating rosin and then reacting the hydrogenated rosin with an alcohol, or by reacting rosin with an alcohol and then hydrogenating the resulting rosin ester.

[0068] The disproportionated rosin ester is an ester compound in which at least a portion of the rosin-derived portion of the rosin ester is disproportionated. Disproportionated rosin esters can be obtained by disproportionating rosin and then reacting the disproportionated rosin with alcohols, or by reacting rosin with alcohols and then disproportionating the resulting rosin ester.

[0069] The coumarone resin is a resin containing coumarones as monomer components. Coumarone-indene resin is preferred as the coumarone resin. The coumarone-indene resin is a copolymer containing coumarones and indenes as monomer components, with a total content of coumarones and indenes of 50% by mass or more in the total monomer components. Examples of coumarones include coumarone and methylcoumarone. The content of coumarones in the total monomer components is preferably 1% to 20% by mass. Examples of indenes include indene and methylindene. The content of indenes in the total monomer components is preferably 40% to 95% by mass. The coumarone-indene resin may also contain other monomer components besides coumarones and indenes. Examples of other monomer components include styrene, vinyltoluene, and dicyclopentadiene.

[0070] Examples of the phenolic resin include condensates of phenols and formaldehyde. Examples of phenols include phenol and m-cresol. The phenolic resin also includes resol, which is obtained by an addition reaction of phenols and formaldehyde with an alkaline catalyst; and novolac, which is obtained by a condensation reaction with an acid catalyst. Furthermore, the phenolic resin also includes rosinphenol resin, which is obtained by adding phenols to rosin with an acid catalyst and then thermal polymerization.

[0071] If the rubber composition contains a tackifier, the tackifier content is preferably 5 parts by mass or more, more preferably 6 parts by mass or more, even more preferably 7 parts by mass or more, preferably 20 parts by mass or less, more preferably 19 parts by mass or less, and even more preferably 18 parts by mass or less, per 100 parts by mass of solid rubber. If the resin content is 5 parts by mass or more, the resulting grip feel will be better, and if it is 20 parts by mass or less, the decrease in the mechanical strength of the cured product of the rubber composition will be suppressed.

[0072] (Processing aid) The rubber composition may also preferably contain processing aids. Examples of processing aids include internal lubricants and external lubricants. Examples of the internal lubricant include mineral oil and plasticizer. Examples of the mineral oil include paraffin oil, naphthenic oil, and aromatic oil. Examples of the plasticizer include dioctyl phthalate, dibutyl phthalate, dioctyl separator, 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 including a phosphate ester compound as an external lubricant, adhesion inside the equipment during kneading can be prevented even with a small amount of addition, and a homogeneous rubber composition can be obtained.

[0073] If the rubber composition contains an external lubricant, the content of the external lubricant is preferably 0.1 parts by mass or more, more preferably 0.15 parts by mass or more, even more preferably 0.25 parts by mass or more, preferably 1.0 part by mass or less, more preferably 0.75 parts by mass or less, and even more preferably 0.5 parts by mass or less, per 100 parts by mass of solid rubber. If the content of the external lubricant is within the above range, the lubricant effect is high and the occurrence of bloom can be suppressed.

[0074] The rubber composition may further contain, if necessary, an anti-aging agent, an anti-scorching agent, a coloring agent, and the like.

[0075] Examples of the aforementioned anti-aging agents include imidazoles, amines, phenols, and thioureas. Examples of the imidazoles include nickel dibutyldithiocarbamate (NDIBC), 2-mercaptobenzimidazole, and zinc salt of 2-mercaptobenzimidazole. Examples of amines include phenyl-α-naphthylamine. Examples of phenols include 2,2'-methylenebis(4-methyl-6-t-butylphenol) (MBMBP) and 2,6-di-tert-butyl-4-methylphenol. Examples of thioureas include tributylthiourea and 1,3-bis(dimethylaminopropyl)-2-thiourea. These anti-aging agents may be used individually or in combination of two or more.

[0076] If the rubber composition contains an anti-aging agent, the amount of the anti-aging agent is preferably 0.2 parts by mass or more, more preferably 0.3 parts by mass or more, even more preferably 0.4 parts by mass or more, preferably 5.0 parts by mass or less, more preferably 4.8 parts by mass or less, and even more preferably 4.6 parts by mass or less, per 100 parts by mass of solid rubber.

[0077] Examples of the scorching inhibitor include organic acids and nitroso compounds. Examples of the organic acids include phthalic anhydride, pyromellitic anhydride, trimellitic anhydride, benzoic acid, salicylic acid, and malic acid. Examples of the nitroso compounds include N-nitroso-diphenylamine, N-(cyclohexylthio)phthalimide, sulfonamide derivatives, diphenylurea, bis(tridecyl)pentaerythulol diphosphite, and 2-mercaptobenzimidazole.

[0078] Examples of the coloring agent include inorganic pigments and organic pigments. Examples of the inorganic pigment include titanium dioxide, with rutile-type titanium dioxide being particularly preferred due to its high opacity. Examples of the organic pigment include azo pigments and phthalocyanine pigments.

[0079] The rubber composition may contain microballoons. By incorporating microballoons into the rubber composition, a porous grip structure can be obtained. Either organic or inorganic microballoons can be used as the microballoons. Examples of organic microballoons include hollow particles made of thermoplastic resin and resin capsules in which low-boiling point hydrocarbons are encapsulated in a thermoplastic resin shell.

[0080] The rubber composition can be prepared by conventionally known methods. For example, it can be prepared by kneading the raw materials using a kneader such as a Banbury mixer, kneader, or open roll. If the rubber composition contains microballoons, it is preferable to knead the components other than the microballoons beforehand, and then knead this mixture with the microballoons. When kneading the mixture with the microballoons, it is preferable to set the material temperature below the temperature at which the microballoons begin to expand.

[0081] (Vulcanization properties) The rubber composition preferably has a 90% vulcanization time (t90) of 5 min or less in the vulcanization curve measured at a vulcanization temperature of 185°C, more preferably 4.5 min or less, and even more preferably 4 min or less. A 90% vulcanization time of 5 min or less results in higher productivity. The lower limit of the 90% vulcanization time is not particularly limited, but is usually 3 min.

[0082] The aforementioned 90% vulcanization time is determined from the vulcanization curve measured at a vulcanization temperature of 185°C. Specifically, when the minimum torque in the vulcanization curve is defined as ML, the maximum torque as MH, and the difference between them as ME, the time required for the torque to become ML + 90%ME was defined as the 90% vulcanization time.

[0083] (Cross-linked rubber) Preferably, the cured product (crosslinked rubber) of the rubber composition has the physical properties described later. The vulcanization conditions for the rubber composition were a vulcanization temperature of 185°C and a vulcanization time of 2 minutes added to the 90% vulcanization time (t90) on the vulcanization curve.

[0084] The loss coefficient (tanδ) and complex modulus (E) at 25°C were measured for the cured product of the aforementioned rubber composition using a dynamic viscoelastic apparatus under the following measurement conditions: excitation frequency of 10 Hz, strain amplitude of 0.05%, and tensile mode. * The ratio of (MPa) (tanδ / E * The ratio is 0.030 or higher, preferably 0.032 or higher, more preferably 0.034 or higher, and 0.045 or lower, preferably 0.044 or lower, more preferably 0.043 or lower.

[0085] The cured product of the rubber composition preferably has a loss tangent (tanδ) of 0.10 or higher at 25°C, more preferably 0.12 or higher, and even more preferably 0.14 or higher, measured using a dynamic viscoelastic apparatus under the conditions of an excitation frequency of 10 Hz, a strain amplitude of 0.05%, and tensile mode. A loss tangent (tanδ) of 0.10 or higher results in better anti-slip performance of the resulting grip. The upper limit of the loss tangent (tanδ) is not particularly limited, but it 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, excessive deflection of the cured rubber composition can be suppressed.

[0086] The cured product of the rubber composition was measured using a dynamic viscoelastic apparatus under the following conditions: excitation frequency of 10 Hz, strain amplitude of 0.05%, and tensile mode. The complex modulus of elasticity (E) at 25°C was then determined. * The complex modulus (E) is preferably 8.00 MPa or less, more preferably 7.90 MPa or less, and even more preferably 7.80 MPa or less. * If the pressure is 8.00 MPa or less, it is possible to prevent the hardening agent of the rubber composition from becoming too hard. The complex modulus (E * The lower limit of the complex modulus (E) is not particularly limited, but is preferably 3.00 MPa or higher, more preferably 3.20 MPa or higher, and even more preferably 3.40 MPa or higher. * If the pressure is 3.00 MPa or higher, the hardness of the cured rubber composition will be more suitable for the desired grip hardness.

[0087] The cured product of the aforementioned rubber composition has a density of 1.05 g / cm³. 3 Preferably, it is 1.06 g / cm³ or more, and more preferably 1.06 g / cm³. 3 More preferably 1.07 g / cm³ 3 The above is 1.10 g / cm³. 3 The following is preferred, and more preferably, 1.09 g / cm³. 3 More preferably, 1.08 g / cm³ 3 The following applies: If the density is within the above range, the weight of the single-layer grip formed from the rubber composition will be about the same as that of a conventional grip, and it can be replaced without any problems.

[0088] The hardness of the cured product of the rubber composition is preferably 50 or higher on the Shore A hardness scale, more preferably 51 or higher, even more preferably 52 or higher, preferably 60 or lower, more preferably 59 or lower, and even more preferably 58 or lower. If the hardness of the cured product is 50 or higher on the Shore A hardness scale, the mechanical strength of the grip is further improved, and if it is 60 or lower, the grip does not become too hard, resulting in a better feel when gripped.

[0089] The cured product of the rubber composition preferably has a tensile strength (Tb) at break of 9 MPa or more, more preferably 11 MPa or more, and even more preferably 13 MPa or more. A tensile strength at break of 9 MPa or more results in better abrasion resistance of the grip. There is no particular upper limit to the tensile strength at break of the cured product of the rubber composition, but it is preferably 40 MPa or less, more preferably 38 MPa or less, and even more preferably 26 MPa or less.

[0090] The cured product of the rubber composition preferably has an elongation at break (Eb) of 300% or more, more preferably 320% or more, and even more preferably 340% or more. An elongation at break of 300% or more can further suppress problems such as grip breakage when inserting a shaft into the grip. There is no particular upper limit to the elongation at break of the cured product of the rubber composition, but it is usually 800%.

[0091] The rubber composition for grips of the present invention is used for molding grips. Because the rubber composition for grips has an excellent coefficient of friction after curing, it is suitable for use in golf club grips.

[0092] [Golf club grips] The golf club grip of the present invention is characterized by having a cylindrical portion, and at least a part of the cylindrical portion being formed from the rubber grip composition. That is, at least a part of the cylindrical portion is made of cross-linked rubber obtained by vulcanizing the rubber grip composition.

[0093] The golf club grip has a cylindrical portion into which the shaft is inserted. The cylindrical portion can be constructed as a single layer, a two-layer structure, a three-layer structure, or the like. When the cylindrical portion has a single layer structure, the entire cylindrical portion is made of the rubber composition. When the cylindrical portion has a multilayer structure, at least one layer is made of the rubber composition. When the cylindrical portion has a multilayer structure, it is preferable that at least the outermost layer is made of the rubber composition.

[0094] The cylindrical portion of the golf club grip is preferably a single-layer structure. Since the rubber composition for the grip can be vulcanized at high temperatures, even thick members can be molded in a short time. Therefore, if a single-layer cylindrical portion is manufactured using the rubber composition for the grip, the structure is simple and the vulcanization time is shortened, further improving the productivity of the grip. Furthermore, the density of the crosslinked rubber formed from the rubber composition is 1.05 g / cm³. 3 ~1.10g / cm 3 Therefore, the weight of the single-layer grip formed from the aforementioned rubber composition will be about the same as that of a conventional grip, and it can be replaced without any problems.

[0095] The cylindrical portion may be a solid structure or a porous structure. If the cylindrical portion is a solid structure, the mechanical strength of the grip will be increased, and if the cylindrical portion is a porous structure, the weight of the grip can be reduced.

[0096] Golf club grips are obtained by molding the rubber composition in a mold. Molding methods include press molding and injection molding. Furthermore, a golf club grip having an inner layer and an outer layer can be obtained, for example, by press molding a laminate of an unvulcanized rubber sheet formed from the outer layer rubber composition and an unvulcanized rubber sheet formed from the inner layer rubber composition in a mold.

[0097] [Golf clubs] The present invention also includes a golf club using the golf club grip described above. The golf club comprises a shaft, a head attached to one end of the shaft, and a grip attached to the other end of the shaft, wherein the grip is the golf club grip. The shaft can be made of stainless steel or carbon fiber reinforced resin. The head can be a wood type, a utility type, or an iron type. The material constituting the head is not particularly limited and can be titanium, titanium alloy, carbon fiber reinforced plastic, stainless steel, maraging steel, soft iron, etc.

[0098] The following describes the golf club grip and golf club with reference to the drawings. Figure 1 is a perspective view showing an example of a golf club grip. The grip 1 has a cylindrical portion 2 into which the shaft is inserted, and a cap portion 3 integrally formed to cover the opening at the rear end of the cylindrical portion. The cylindrical portion 2 has a single-layer structure. The thickness of the cylindrical portion 2 is formed to gradually increase from the front end to the rear end. In the grip 1 shown in Figure 1, the cap portion 3 is formed from the same rubber composition as the cylindrical portion 2.

[0099] Figure 2 is a perspective view showing an example of a golf club equipped with the golf club grip of the present invention. The golf club 4 comprises 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. [Examples]

[0100] The present invention will be described in detail below with reference to examples, but the present invention is not limited to the following examples, and any modifications and embodiments that do not depart from the spirit of the present invention are all included within the scope of the present invention.

[0101] [Evaluation Method] (1) Acrylonitrile content The acrylonitrile content was measured in acrylonitrile-butadiene rubber before hydrogenation according to ISO 24698-1 (2008).

[0102] (2) Double bond content (mmol / g) The double bond content was calculated from the butadiene content (mass%) and the amount of remaining double bonds (%) in the copolymer. The amount of remaining double bonds is the mass ratio of the double bonds in the copolymer before hydrogenation to the double bonds in the copolymer after hydrogenation (amount of double bonds after hydrogenation / amount of double bonds before hydrogenation), and can be measured by infrared spectroscopy. If the acrylonitrile-butadiene rubber is an acrylonitrile-butadiene binary copolymer, the butadiene content in the copolymer can be determined by subtracting the acrylonitrile content (mass%) from 100. Double bond amount = {butadiene content / 54} × remaining double bond amount × 10

[0103] (3) Content of monomers containing carboxyl groups 1 g of hydrogenated carboxylated acrylonitrile-butadiene rubber was weighed out and dissolved in 50 mL of chloroform, to which thymol blue indicator was added dropwise. While stirring this solution, a 0.05 mol / L methanol solution of sodium hydroxide was added dropwise, and the volume (V mL) until the first color change occurred was recorded. As a blank, 50 mL of chloroform without hydrogenated carboxylated acrylonitrile-butadiene rubber was also prepared, and a 0.05 mol / L methanol solution of sodium hydroxide was added dropwise using thymol blue as an indicator, and the volume (B mL) until the first color change occurred was recorded. The carboxyl group content was calculated using the following formula. Carboxylic group monomer content = {0.05 × (VB) × PM} / (10 × X) (In the formula, V: volume of sodium hydroxide solution dropped as the test solution (mL), B: volume of sodium hydroxide solution dropped as the blank (mL), PM: molecular weight of the carboxyl group-containing monomer, X: valence of the carboxyl group-containing monomer)

[0104] (4) Vulcanization test The rubber compositions were subjected to vulcanization tests using a vulcanization tester (Curlastometer® Type 7, manufactured by JSR Trading Co., Ltd.) at the vulcanization temperatures listed in Table 2. Following "Method A of Die Vulcanization Test" in JIS K6300-2 (2001), "Method for Determining Vulcanization Characteristics Using a Vibration-Type Vulcanization Tester," a low-amplitude sinusoidal vibration, not damaging 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 unvulcanized to overvulcanized. 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 curves, the minimum (ML) and maximum (MH) torque values, as well as the 90% vulcanization time (t90), were determined.

[0105] (5) Hardness (Shore A hardness) A 2 mm thick sheet was prepared by vulcanizing the rubber composition under the conditions described in Table 2. This sheet was stored at 23°C for two weeks, and its hardness was measured using an automated hardness tester (H. Barleys, DigiTest II) with three sheets stacked together to avoid interference from the measurement substrate. The "Shore A" detector was used.

[0106] (6) Density (g / cm 3 ) Using the rubber composition, a 13 cm square, 2 mm thick sheet was prepared by vulcanization under the conditions described in Table 2. Test specimens were prepared by punching out 2 cm squares from this sheet. The density of the obtained test specimens was measured using an automatic hydrometer (MSTEC Corporation, SP-GR1, Archimedes' principle).

[0107] (7) Tensile strength at break (MPa), elongation at break (%) The tensile strength and elongation at break were measured in accordance with JIS K 6251 (2017). Specifically, a 1 mm thick sheet was prepared by vulcanizing the rubber composition under the conditions described in Table 2, and this sheet was punched out into a dumbbell shape (Dumbbell Type 3) to prepare test specimens. The physical properties were measured using a tensile testing device (Shimadzu Corporation, Autograph® AGS-D) (measurement temperature 23°C, tensile speed 500 mm / min). The tensile strength at break was calculated by dividing the tensile force recorded when the test specimen broke by the cross-sectional area of ​​the test specimen before testing.

[0108] (8) Viscoelasticity Loss tangent (tanδ), complex modulus of elasticity (E * The viscoelasticity was measured using a dynamic viscoelasticity measuring device (Rheogel-E4000, manufactured by UBM). The test specimens were prepared by slicing the grip in the thickness direction to a thickness of 1.6 mm and punching them out to the specified size. The measurement conditions were: temperature; -100°C to 100°C, heating rate; 3°C / min, measurement interval; 3°C, frequency; 10 Hz, strain amplitude; 10%, jig; tensile, specimen shape; width 4 mm, thickness 2 mm, length 40 mm. The loss tangent (tanδ) and complex modulus (E) at 25°C were obtained from the viscoelastic spectrum obtained by dynamic viscoelastic measurement. * ) was sought.

[0109] (9) Coefficient of friction The coefficient of friction was measured using a static and dynamic friction measuring instrument (Trinity Labs, Tribomaster). The test specimen was prepared by slicing the grip to a thickness of 1.6 mm in the thickness direction, removing the groove pattern, and punching it out to a width of 10 mm and a length of 20 mm, which was then fixed to the flat contact of the device. In addition, natural leather cut from the palm of a golf glove (Sumitomo Rubber Industries, XXIO® Golf Glove (GGG-X008)) was fixed to the movable table. The measurement conditions were a load of 25g, a travel speed of 1mm / sec, and a travel distance of 10mm. The average value of the kinetic friction coefficient was calculated from 2000ms to 6000ms from the start of the measurement. The coefficient of friction is shown as an indexed value, with the coefficient of friction of cross-linked rubber No. 10 set to 100.

[0110] [Preparation of rubber composition] The rubber composition was prepared by kneading each raw material according to the formulations shown in Table 1. All raw materials were kneaded in a closed-type kneader.

[0111] [Table 1]

[0112] The materials used in Table 1 are as follows: HXNBR: Hydrogenated carboxylated acrylonitrile-butadiene rubber (manufactured by ARANXEO, Thermal XT VPKA 8889 (residual double bond content 3.5%, acrylonitrile content 33.0% by mass, double bond content 0.40 mmol / g, carboxyl group monomer content 5.0% by mass)) Liquid IR: Kuraray Co., Ltd., "LIR-50" (Liquid isoprene rubber, isoprene homopolymer, molecular weight: 54,000, viscosity: 500 Pa·s (38℃), glass transition temperature: -63℃) Carboxylated Liquid Isoprene Rubber: Kuraray Co., Ltd., "LIR-410" (Carboxylated Liquid Isoprene Rubber, Molecular Weight: 30,000, Viscosity: 430 Pa·s (38°C), Glass Transition Temperature: -59°C, Number of Functional Groups per Molecular Weight: 10) Liquid farnesene: Kuraray Co., Ltd., "L-FR-107L" (liquid farnesene rubber, farnesene homopolymer, molecular weight: 130,000, viscosity: 69 Pa·s (38℃), glass transition temperature: -70℃) Liquid farnesene-butadiene copolymer: Manufactured by Kuraray Co., Ltd., "L-FBR-746" (liquid farnesene-butadiene random copolymer, molecular weight: 100,000, viscosity: 603 Pa·s (38℃), glass transition temperature: -78℃) Sulfur: Tsurumi Chemical Industry Co., Ltd., Kinka brand 5% oil-containing fine sulfur powder (200 mesh) Zinc peroxide: Struktol ZP 1014 (29% by mass zinc peroxide content), manufactured by Struktol. Thiuram-based accelerator 1: Sanshin Chemical Industry Co., Ltd., "Sunceller (registered trademark) TBzTD" (tetrabenzyl thiuram disulfide) Thiuram-based accelerator 2: "Noxellar (registered trademark) TOT-N" (tetrakis(2-ethylhexyl) thiuram disulfide), manufactured by Ouchi Shinko Chemical Industry Co., Ltd. Thiourea-based accelerator: "Noxellar EUR" (N,N'-diethylthiourea), manufactured by Ouchi Shinko Chemical Industry Co., Ltd. Sulfenamide-based accelerator: "Sunceller NS-G" (N-(tert-butyl)-2-benzothiazole sulfenamide), manufactured by Sanshin Chemical Industry Co., Ltd. EVA: Ethylene-vinyl acetate copolymer (manufactured by ARANXEO, Levapren 500 (vinyl acetate content 50% by mass, Mooney viscosity (ML)) 1+4 (100℃) 27) Solid tackifier: Eastman Chemical Company, "Staybelite Ester 10-E" (partially hydrogenated rosin ester) Liquid tackifier: Arizona Chemical, "SYLVATAC RE-5S" (rosin ester (melting point below 25°C)) Carbon Black: Manufactured by Tokai Carbon Co., Ltd., SEAST (registered trademark) 3 (specific surface area 79 m²) 2 / g) Silica: Manufactured by Tosoh Corporation, NipSeal (registered trademark) VN3 (specific surface area 180-230 m²) 2 / g) Calcium carbonate: Manufactured by Shiraishi Calcium Co., Ltd., Softon 3200 (specific surface area 3.2 m²) 2 / g) Rutile-type titanium dioxide: Manufactured by Ishihara Sangyo Co., Ltd., CR60 vanfre VAM: Polyoxyethylene-octadecyl ether-phosphate, manufactured by Vanderbilt Chemicals.

[0113] [Making the grip] The rubber composition was placed in a mold with a groove pattern on the cavity surface. The rubber was then vulcanized under the conditions described in Table 2 to induce a crosslinking reaction, yielding a golf club grip. The viscoelastic properties and friction coefficient of the grip were evaluated, and the results are shown in Table 2.

[0114] [Table 2]

[0115] Rubber compositions No. G to O contain a base rubber which is solid at 25°C and a liquid rubber which is liquid at 25°C. The crosslinked rubbers No. 1 to 9, which are cured products of these rubber compositions No. G to O, have a ratio (tanδ / E*) of 0.030 to 0.045 between the loss coefficient (tanδ) and the complex modulus of elasticity (E*) (MPa) at 25°C. Grips made using these rubber compositions No. G to O had a high coefficient of friction.

[0116] Rubber compositions No. A to F do not contain liquid rubber, which is a liquid at 25°C, as the base rubber. Furthermore, crosslinked rubbers No. 10 to 15, which are cured products of these rubber compositions No. B to F, have a ratio (tanδ / E*) of the loss coefficient (tanδ) to the complex modulus of elasticity (E*) (MPa) at 25°C of less than 0.030 or greater than 0.045. Grips made using these rubber compositions No. A to F had a low coefficient of friction.

[0117] The present invention (1) is a grip rubber composition containing a base rubber and a vulcanizing agent, wherein the base rubber contains a solid rubber that is solid at 25°C and a liquid rubber that is liquid at 25°C, and the ratio of the loss coefficient (tanδ) to the complex modulus of elasticity (E*) (MPa) (tanδ / E*) at 25°C, measured using a dynamic viscoelastic device under measurement conditions of an excitation frequency of 10 Hz, a strain amplitude of 0.05%, and a tensile mode, is 0.030 to 0.045.

[0118] The present invention (2) is a grip rubber composition according to the present invention (1), wherein the tensile strength at break of the cured grip rubber composition is 9 MPa or more.

[0119] The present invention (3) is a grip rubber composition according to the present invention (1) or (2), wherein the solid rubber contains at least one selected from the group consisting of carboxy-modified acrylonitrile-butadiene rubber, hydrogenated acrylonitrile-butadiene rubber, and hydrogenated carboxy-modified acrylonitrile-butadiene rubber.

[0120] The present invention (4) is a rubber composition for gripping according to any one of the present inventions (1) to (3), wherein the liquid rubber is a rubber having carbon-carbon unsaturated bonds.

[0121] The present invention (5) relates to a case in which the density of the cured product of the rubber composition for grip is 1.05 g / cm³. 3 ~1.10g / cm 3 This is a rubber composition for grips according to any one of the present invention (1) to (4).

[0122] The present invention (6) is a grip rubber composition according to any one of the present inventions (1) to (5), wherein the hardness of the cured product of the grip rubber composition is 50 to 60 on the Shore A hardness scale.

[0123] The present invention (7) is a golf club grip having a cylindrical portion, wherein at least a part of the cylindrical portion is formed from a rubber grip composition described in any one of the present inventions (1) to (6). [Explanation of Symbols]

[0124] 1: Grip, 2: Cylindrical part, 3: Cap part, 4: Golf club, 5: Shaft, 6: Head

Claims

1. A rubber composition for grips containing a base rubber and a vulcanizing agent, The aforementioned base rubber contains solid rubber, which is solid at 25°C, and liquid rubber, which is liquid at 25°C. A grip rubber composition characterized in that, for the cured product of the grip rubber composition, the ratio of the loss coefficient (tanδ) to the complex modulus of elasticity (E*) (MPa) (tanδ / E*) at 25°C, measured using a dynamic viscoelastic device under measurement conditions of an excitation frequency of 10 Hz, a strain amplitude of 0.05%, and tensile mode, is 0.030 to 0.

045.

2. The grip rubber composition according to claim 1, wherein the tensile strength at break of the cured product of the grip rubber composition is 9 MPa or more.

3. The rubber composition for grip according to claim 1, wherein the solid rubber contains at least one selected from the group consisting of carboxylated acrylonitrile-butadiene rubber, hydrogenated acrylonitrile-butadiene rubber, and hydrogenated carboxylated acrylonitrile-butadiene rubber.

4. The rubber composition for gripping according to claim 1, wherein the liquid rubber is a rubber having carbon-carbon unsaturated bonds.

5. The density of the cured product of the aforementioned rubber composition for grips is 1.05 g / cm³. 3 ~1.10 g / cm 3 The rubber composition for grip according to claim 1.

6. The grip rubber composition according to claim 1, wherein the hardness of the cured product of the grip rubber composition is 50 to 60 on the Shore A hardness scale.

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

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