Grip for a golf club and golf club

Abstract

To provide a golf club grip having high tensile strength in an outer layer and little entrainment of air between the outer layer and an inner layer.SOLUTION: A golf club grip includes a cylindrical portion constituted of a cylindrical inner layer and a cylindrical outer layer covering the inner layer. In the outer layer, a ratio (E'23 / E'60) of a storage elastic modulus (E'23) at 23°C to a storage elastic modulus (E'60) at 60°C, while measuring with a dynamic viscoelasticity measuring apparatus under measuring conditions of an oscillation frequency of 10 Hz, a strain amplitude of 0.05%, and a tensile mode, ranges from 1.20 to 1.32.SELECTED DRAWING: None

Description

Technical Field

[0001] The present invention relates to a grip for a golf club.

Background Art

[0002] As a grip attached to a golf club, a rubber grip is frequently used. As such a rubber grip, a golf club grip using acrylonitrile-butadiene rubber as a base rubber and having improved tensile strength and wear resistance has also been proposed. Such a grip is described in, for example, Patent Document 1 and Patent Document 2.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0004] It has been proposed to use a material having excellent tensile strength for the outer layer (surface layer) of a golf grip. However, when a material having excellent tensile strength is blended into a rubber composition, the shrinkage rate of an uncrosslinked molded product tends to increase. Therefore, when an uncrosslinked rubber composition is formed into a sheet shape, there arises a problem that the surface easily becomes uneven. And when an outer layer of a grip is produced using such a rubber composition blended with a material having excellent tensile strength, when the outer layer and the inner layer are bonded together, air biting occurs, and there occurs a problem that molding defects and initial fractures of the resulting grip occur. The present invention has been made in view of the above circumstances, and an object thereof is to provide a golf club grip having a high tensile strength of the outer layer and little air biting between the outer layer and the inner layer.

Means for Solving the Problems

[0005] The grip for a golf club of the present invention that has solved the above problems has a cylindrical portion composed of a cylindrical inner layer and a cylindrical outer layer that covers the inner layer. The outer layer is 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 storage elastic modulus (E’ 23 ) at 23°C and the storage elastic modulus (E’ 60 ) at 60°C have a ratio (E’ 23 / E’ 60 ) of 1.20 to 1.32. The ratio (E’ 23 / E’ 60 ) being 1.20 to 1.32 can reduce the shrinkage rate of the uncrosslinked molded product. Therefore, when bonding the outer layer and the inner layer together, air entrapment can be suppressed, and the occurrence of molding defects and initial fractures in the resulting grip can be suppressed.

Effect of the Invention

[0006] According to the present invention, a grip for a golf club with a high tensile strength of the outer layer and little air entrapment between the outer layer and the inner layer can be obtained.

Brief Description of the Drawings

[0007]

Figure 1

Figure 2

Figure 3

Modes for Carrying Out the Invention

[0008] The grip for a golf club of the present invention has a cylindrical portion composed of a cylindrical inner layer and a cylindrical outer layer that covers the inner layer. And the outer layer is 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 storage elastic modulus (E’ 23 ) at 23°C and the storage elastic modulus (E’60 ) ratio (E’ 23 / E’ 60 ) is characterized by being 1.20 to 1.32.

[0009] The 23°C, which is the measurement temperature of the storage elastic modulus, is the temperature condition when the molded product is stored, and 60°C is the temperature condition when the rubber composition is processed into a sheet. Therefore, by controlling the ratio (E’ 23 ) of the storage elastic modulus at 23°C to the storage elastic modulus (E’ 60 ) at 60°C (E’ 23 / E’ 60 ) to 1.20 to 1.32, the shrinkage rate after processing can be reduced. If the ratio (E’ 23 / E’ 60 ) is 1.20 or more, the processability of the rubber composition is improved, and the residual stress during processing can be reduced, so the deformation after processing can be reduced. Also, if the ratio (E’ 23 / E’ 60 ) is 1.32 or less, the amount of change from the storage elastic modulus at the processing temperature of the rubber composition to the storage elastic modulus at room temperature is small, so the deformation after processing can be reduced.

[0010] The golf club grip has a cylindrical portion composed of a cylindrical inner layer and a cylindrical outer layer covering the inner layer. The cylindrical portion may have a two-layer structure consisting of one layer of inner layer and one layer of outer layer, or may have a three-layer structure having two layers of inner layer and one layer of outer layer.

[0011] The outer layer has a ratio (E’ 23 ) of the storage elastic modulus (E’ 60 ) at 23°C to the storage elastic modulus (E’ 23 / E’ 60 ) 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, which is 1.20 or more, preferably 1.23 or more, more preferably 1.25 or more, and 1.32 or less, preferably 1.30 or less, more preferably 1.28 or less. The ratio (E’ 23 / E’ 60) is 1.23 or more, the rubber is more easily deformed at 60°C, and the residual stress can be further reduced. If it is 1.30 or less, the stress change when cooled to room temperature (23°C) after processing can be further suppressed.

[0012] The outer layer is 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. The storage modulus (E’ 23 ) at 23°C is preferably 2.0 MPa or more, more preferably 2.5 MPa or more, still more preferably 3.0 MPa or more, and preferably 4.2 MPa or less, more preferably 3.7 MPa or less, still more preferably 3.4 MPa or less. The storage modulus (E’ 23 ) is 2.0 MPa or more, the processability of the rubber composition is further improved. If it is 4.2 MPa or less, the stress generated during deformation in the molded product after processing becomes smaller.

[0013] The outer layer is 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. The storage modulus (E’ 60 ) at 60°C is preferably 1.5 MPa or more, more preferably 1.8 MPa or more, still more preferably 2.0 MPa or more, and preferably 3.7 MPa or less, more preferably 3.5 MPa or less, still more preferably 3.2 MPa or less. The storage modulus (E’ 60 ) is 1.5 MPa or more, the processability of the rubber composition is further improved. If it is 3.7 MPa or less, the stress generated during deformation in the molded product after processing becomes smaller.

[0014] The outer layer is 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. The loss tangent (tanδ) at 60°C is preferably 0.138 or more, more preferably 0.142 or more, still more preferably 0.146 or more. If the loss tangent (tanδ) is 0.138 or more, the stress generated during deformation in the molded product after processing becomes smaller.

[0015] The tensile strength at break (Tb) of the outer layer is preferably 20 MPa or more, more preferably 21 MPa or more, still more preferably 22 MPa or more, and preferably 30 MPa or less, more preferably 29 MPa or less, still more preferably 28 MPa or less. If the tensile strength at break is 20 MPa or more, the wear resistance of the grip is further improved, and if it is 30 MPa or less, the feeling of the grip becomes better.

[0016] In all parts of the outer layer, the ratio (E’ 23 / E’ 60 ) is preferably within the range of the above numerical values, but it may have a portion where the ratio (E’ 23 / E’ 60 ) is outside the above range. In this case, in 100% of the area of the outer layer, the area ratio of the portion where the ratio (E’ 23 / E’ 60 ) is within the above numerical range is preferably 50% or more, more preferably 70% or more, still more preferably 90% or more.

[0017] The physical properties of the outer layer can be controlled by adjusting the raw materials and compounding amounts of the rubber composition constituting the outer layer. Examples of the rubber composition for the outer layer constituting the outer layer include a rubber composition containing (A) a base rubber, (B) a thermoplastic resin, and (C) a crosslinking agent.

[0018] (A) Base rubber The content rate of the (A) base rubber in the rubber composition for the outer layer is preferably 50% by mass or more, more preferably 55% by mass or more, still more preferably 60% by mass or more. Examples of the (A) base rubber 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), etc. These base rubbers may be used alone or in combination of two or more.

[0019] The (A) base rubber preferably contains acrylonitrile-butadiene rubber. Examples of the acrylonitrile-butadiene rubber include at least one selected from the group consisting of acrylonitrile-butadiene rubber (NBR), carboxy-modified acrylonitrile-butadiene rubber (XNBR), hydrogenated acrylonitrile-butadiene rubber (HNBR), and carboxy-modified hydrogenated acrylonitrile-butadiene rubber (HXNBR). The XNBR is a copolymer of a monomer having a carboxy group, acrylonitrile, and butadiene. The HNBR is a hydrogenated product of acrylonitrile-butadiene rubber. The HXNBR is a hydrogenated product of a copolymer of a monomer having a carboxy group, acrylonitrile, and butadiene.

[0020] The content rate of the acrylonitrile-butadiene rubber in the (A) base rubber is preferably 50% by mass or more, more preferably 60% by mass or more, still more preferably 70% by mass or more. It is also preferable that the rubber composition contains only acrylonitrile-butadiene rubber as the (A) base rubber.

[0021] In the NBR, XNBR, HNBR, and HXNBR, the acrylonitrile content 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 is good, and if it is 50% by mass or less, the grip feel in cold regions or in winter is good.

[0022] In the HNBR and HXNBR, the double bond content is preferably 0.09 mmol / g or more, more preferably 0.2 mmol / g or more, and 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 are better. The double bond content can be adjusted by the butadiene content in the copolymer and the amount of hydrogen added to the copolymer.

[0023] In the XNBR and HXNBR, examples of the monomer having a carboxy group include acrylic acid, methacrylic acid, fumaric acid, maleic acid, and the like. In the XNBR and 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 is better, and if it is 30% by mass or less, the grip feel in cold regions or in winter is good.

[0024] In the above XNBR and HXNBR, the carboxy 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 carboxy group content is 1.0% by mass or more, the abrasion resistance will be better, and if it is 30% by mass or less, the touch feeling of the grip in cold regions or in winter will be good.

[0025] The above-mentioned (A) base rubber is preferably at least one selected from the group consisting of XNBR, HNBR, and HXNBR, and particularly preferably HXNBR. That is, it is preferable that the outer layer contains at least one selected from the group consisting of carboxy-modified acrylonitrile-butadiene rubber (XNBR), hydrogenated acrylonitrile-butadiene rubber (HNBR), and carboxy-modified hydrogenated acrylonitrile-butadiene rubber (HXNBR), and more preferably contains HXNBR. By containing these rubbers as the base rubber in the outer layer, the abrasion resistance and weather resistance of the grip are improved.

[0026] The Mooney viscosity (ML 1+4 (100 °C)) of the above-mentioned HXNBR is preferably 60 or more, more preferably 64 or more, still more preferably 68 or more, and preferably 95 or less, more preferably 90 or less, still more preferably 85 or less. If the Mooney viscosity (ML 1+4 (100 °C)) is 60 or more, the abrasion resistance of the grip is improved, and if it is 95 or less, the processability of the rubber composition is good.

[0027] (B) Resin The above-mentioned (B) resin is a component that reduces the Mooney viscosity of the outer layer rubber composition. Examples of the (B) resin include rosin ester, ethylene-vinyl acetate copolymer, coumarone resin, and phenol resin.

[0028] The compounding amount of the said (B) resin is preferably 5 parts by mass or more, more preferably 8 parts by mass or more, still more preferably 12 parts by mass or more, with respect to 100 parts by mass of the (A) base rubber, and preferably 45 parts by mass or less, more preferably 42 parts by mass or less, still more preferably 40 parts by mass or less. If the compounding amount of the (B) resin is 5 parts by mass or more, the feel of the grip becomes better, and if it is 45 parts by mass or less, the abrasion resistance of the grip is further improved.

[0029] The outer layer rubber composition preferably contains (B1) ethylene-vinyl acetate copolymer and (B2) rosin ester as the said (B) resin. By containing these (B1) ethylene-vinyl acetate copolymer and (B2) rosin ester, they melt during processing, the rubber composition becomes soft, and the stress during deformation can be reduced.

[0030] The vinyl acetate content of the said (B1) 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 feel of the grip becomes better, and if it is 80% by mass or less, the abrasion resistance of the grip is further improved.

[0031] The Mooney viscosity (ML 1+4 (100 °C)) of the said (B1) ethylene-vinyl acetate copolymer is preferably 20 or more, more preferably 23 or more, still more preferably 25 or more, and preferably 50 or less, more preferably 45 or less, still more preferably 40 or less. If the Mooney viscosity (ML 1+4 (100 °C)) is 20 or more, the processability of the rubber composition becomes better, and if it is 50 or less, the feel of the grip is good.

[0032] The blending amount of the (B1) ethylene-vinyl acetate copolymer is preferably 3 parts by mass or more, more preferably 5 parts by mass or more, still more preferably 8 parts by mass or more, and preferably 40 parts by mass or less, more preferably 35 parts by mass or less, still more preferably 30 parts by mass or less, based on 100 parts by mass of the (A) base rubber. When the blending amount of the (B1) ethylene-vinyl acetate copolymer is 3 parts by mass or more, the grip feeling becomes better, and when it is 40 parts by mass or less, the abrasion resistance of the grip is further improved.

[0033] The above-mentioned (B2) rosin ester is an ester compound obtained by reacting the above-mentioned 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 2 or more valences are preferred, and glycerin is more preferred.

[0034] The above-mentioned rosin ester includes hydrogenated rosin ester and disproportionated rosin ester. The above-mentioned hydrogenated rosin ester and disproportionated rosin ester are so-called stabilized rosin esters.

[0035] The above-mentioned hydrogenated rosin ester is an ester compound in which the part 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.

[0036] The disproportionated rosin ester is an ester compound in which the part derived from the rosin of the rosin ester is disproportionated. The disproportionated rosin ester can be obtained by disproportionating rosin and then reacting the disproportionated rosin with alcohols, or by reacting rosin with alcohols and then disproportionating the obtained rosin ester.

[0037] The acid value of the rosin ester is preferably 2 mgKOH / g or more, more preferably 4 mgKOH / g or more, still more preferably 6 mgKOH / g or more, and preferably 200 mgKOH / g or less, more preferably 180 mgKOH / g or less, still more preferably 160 mgKOH / g or less. If the acid value is 2 mgKOH / g or more, the compatibility with acrylonitrile-butadiene rubber is good, and if it is 200 mgKOH / g or less, the carboxyl groups of the rosin ester hardly affect the vulcanization reaction of the base rubber.

[0038] The blending amount of the (B2) rosin ester is preferably 2 parts by mass or more, more preferably 5 parts by mass or more, still more preferably 7 parts by mass or more, and preferably 15 parts by mass or less, more preferably 12 parts by mass or less, still more preferably 10 parts by mass or less, based on 100 parts by mass of the (A) base rubber. If the blending amount of the (B2) rosin ester is 2 parts by mass or more, the rubber composition becomes softer, and if it is 15 parts by mass or less, the processability of the rubber composition becomes better.

[0039] When the outer layer rubber composition contains the (B1) ethylene-vinyl acetate copolymer and the (B2) rosin ester, the mass ratio (B1 / B2) of the (B1) ethylene-vinyl acetate copolymer to the (B2) rosin ester is preferably 0.8 or more, more preferably 1.0 or more, still more preferably 1.2 or more, particularly preferably 1.5 or more, and preferably 5.0 or less, more preferably 4.8 or less, still more preferably 4.5 or less.

[0040] When the rubber composition for the outer layer contains (B1) ethylene-vinyl acetate copolymer and (B2) rosin ester, the total content (B1 + B2) of the (B1) ethylene-vinyl acetate copolymer and the (B2) rosin ester is preferably 5 parts by mass or more, more preferably 8 parts by mass or more, still more preferably 12 parts by mass or more, and preferably 45 parts by mass or less, more preferably 42 parts by mass or less, still more preferably 40 parts by mass or less.

[0041] The coumarone resin is a resin containing coumarones as monomer components. As the coumarone resin, a coumarone-indene resin is preferable. The coumarone-indene resin contains coumarones and indenes as monomer components and is a copolymer in which the total content rate of coumarones and indenes in all monomer components is 50% by mass or more. Examples of the coumarones include coumarone and methylcoumarone. The content rate 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 rate 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.

[0042] Examples of the phenol resin include condensates of phenols and formaldehyde. Examples of the phenols include phenol and m-cresol. Further, the phenol resin 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 phenol resin also includes rosin-phenol resin obtained by adding phenols to rosin with an acid catalyst and subjecting it to thermal polymerization, etc.

[0043] (C) Crosslinking agent As the crosslinking agent, a sulfur-based crosslinking agent or an organic peroxide can be used. Examples of the sulfur-based crosslinking 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'-dithiobis(morpholine). 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. The crosslinking agent may be used alone or in combination of two or more. As the crosslinking agent, a sulfur-based crosslinking agent is preferred, and elemental sulfur is more preferred.

[0044] The amount of the (C) crosslinking agent used 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 (A) base rubber.

[0045] The rubber composition for the outer layer preferably further contains a vulcanization accelerator and a vulcanization activator.

[0046] (Vulcanization accelerator) Examples of the vulcanization accelerator include thiuram-based ones such as tetramethylthiuram disulfide (TMTD), tetrabenzylthiuram disulfide (TBzTD), tetramethylthiuram monosulfide (TMTM), dipentamethylenethiuram tetrasulfide, and tetrakis(2-ethylhexyl)thiuram disulfide; guanidine-based ones such as diphenylguanidine (DPG); dithiocarbamate-based ones such as zinc dimethyldithiocarbamate (ZnPDC) and zinc dibutyldithiocarbamate; thiourea-based ones such as trimethylthiourea and N,N'-diethylthiourea; thiazole-based ones such as mercaptobenzothiazole (MBT) and benzothiazole disulfide; sulfenamide-based ones such as N-cyclohexyl-2-benzothiazolylsulfenamide (CBS) and N-t-butyl-2-benzothiazolylsulfenamide (BBS); and the like. These vulcanization accelerators may be used alone or in combination of two or more.

[0047] The total amount of the vulcanization accelerator used is preferably 0.4 part by mass or more, more preferably 0.8 part by mass or more, still more preferably 1.2 part by mass or more, and preferably 9.0 parts by mass or less, more preferably 8.0 parts by mass or less, still more preferably 7.0 parts by mass or less, based on 100 parts by mass of the base rubber (A).

[0048] (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.

[0049] 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 (A).

[0050] The rubber composition for the outer layer may further contain a reinforcing material, an antioxidant, a softening agent, a scorch inhibitor, a coloring agent, etc., as required.

[0051] Examples of the reinforcing material include carbon black and silica. The amount of the reinforcing material used is preferably 2.0 parts by mass or more, more preferably 3.0 parts by mass or more, still more preferably 4.0 parts by mass or more, and preferably 50 parts by mass or less, more preferably 45 parts by mass or less, still more preferably 40 parts by mass or less, based on 100 parts by mass of the base rubber (A).

[0052] Examples of the antioxidant include imidazoles, amines, phenols, thioureas, etc. Examples of the imidazoles include nickel dibutyldithiocarbamate (NDIBC), 2-mercaptobenzimidazole, and zinc salt of 2-mercaptobenzimidazole. Examples of the amines include phenyl-α-naphthylamine. Examples of the phenols include 2,2'-methylenebis(4-methyl-6-t-butylphenol) (MBMBP), 2,6-di-tert-butyl-4-methylphenol. Examples of the thioureas include tributylthiourea, 1,3-bis(dimethylaminopropyl)-2-thiourea. These antioxidants may be used alone or in combination of two or more.

[0053] The amount of the antioxidant used 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, 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, based on 100 parts by mass of the base rubber (A).

[0054] Examples of the softening agent 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.

[0055] Examples of the scorch inhibitor include organic acid and nitroso compound. Examples of the organic acid include phthalic anhydride, pyromellitic anhydride, trimellitic anhydride, benzoic acid, salicylic acid, and malic acid. Examples of the nitroso compound include N-nitroso-diphenylamine, N-(cyclohexylthio)phthalimide, sulfonamide derivative, diphenylurea, bis(tridecyl)pentaerythritol diphosphite, and 2-mercaptobenzimidazole.

[0056] The rubber composition for the outer layer 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 for the outer layer contains the microballoon described later, it is preferable to knead the components other than the microballoon in advance and then knead this kneaded product with the microballoon. The material temperature when kneading the kneaded product and the microballoon is preferably set to a temperature lower than the expansion start temperature of the microballoon.

[0057] The outer layer may be a solid layer or a porous layer. If the outer layer is a porous layer, the weight of the grip for the golf club can be reduced. The porous layer is a layer in which a large number of pores (voids) are formed in the rubber serving as the base material. Due to the formation of a large number of pores, the apparent density of the layer becomes small, and weight reduction can be achieved.

[0058] Examples of methods for producing a porous layer include the balloon foaming method, chemical foaming method, supercritical carbon dioxide injection molding method, salt extraction method, solvent removal method, etc. In the balloon foaming method, microballoons are contained in a rubber composition, and the microballoons are expanded by heating to cause foaming. In addition, expanded microballoons may be blended into the rubber composition and molded. In the chemical foaming method, a rubber composition contains a foaming agent (such as azodicarbonamide, azobisisobutyronitrile, N,N-dinitrosopentamethylenetetramine, p-toluenesulfonyl hydrazide, p-oxybis(benzenesulfohydrazide), etc.) and a foaming aid, and a gas (such as carbon dioxide gas, nitrogen gas, etc.) is generated by a chemical reaction to cause foaming. In the supercritical carbon dioxide injection molding, carbon dioxide in a supercritical state under high pressure is impregnated into a rubber composition, and this rubber composition is injected under normal pressure to vaporize the carbon dioxide to cause foaming. In the salt extraction method, a rubber composition contains an easily soluble salt (such as boric acid, calcium chloride, etc.), and after molding, the salt is dissolved and extracted to form pores. In the solvent removal method, a rubber composition contains a solvent, and after molding, the solvent is removed to form pores.

[0059] When the outer layer is a porous layer, a foamed layer formed from an outer layer rubber composition containing a foaming agent is preferred. In particular, it is preferably a foamed layer produced by the balloon foaming method. That is, as the outer layer, a foamed layer formed from an outer layer rubber composition containing microballoons is preferred. By using microballoons, weight reduction can be achieved while maintaining the mechanical strength of the outer layer.

[0060] As the microballoons, either organic microballoons or inorganic microballoons can be used. Examples of 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. Specific examples of the resin capsules include Expancel manufactured by Akzo Nobel and Matsumoto Microsphere (registered trademark) manufactured by Matsumoto Yushi Seiyaku Co., Ltd. Examples of inorganic microballoons include hollow glass particles (such as silica balloons, alumina balloons, etc.) and hollow ceramic particles.

[0061] The volume average particle diameter of the resin capsules (before expansion) is preferably 5 μm or more, more preferably 6 μm or more, still more preferably 9 μm or more, and preferably 90 μm or less, more preferably 70 μm or less, still more preferably 60 μm or less.

[0062] When the outermost layer is produced by the balloon foaming method, the content of microballoons in the rubber composition for the outer layer is preferably 1.0 part by mass or more, more preferably 1.2 part by mass or more, still more preferably 1.5 part by mass or more, and preferably 10 parts by mass or less, more preferably 8 parts by mass or less, still more preferably 6 parts by mass or less, based on 100 parts by mass of the base rubber. If the content of the microballoons is 1.0 part by mass or more, the foaming when forming the porous layer becomes more uniform, and if it is 10 parts by mass or less, both weight reduction and mechanical strength of the porous layer can be achieved.

[0063] The material hardness (Shore A hardness) of the rubber composition for the outer layer is preferably 25 or more, more preferably 28 or more, still more preferably 30 or more, and preferably 60 or less, more preferably 55 or less, still more preferably 50 or less. If the material hardness (Shore A hardness) of the rubber composition for the outer layer is 25 or more, the mechanical strength of the outer layer is further improved, and if it is 60 or less, the outer layer does not become too hard and the grip feeling when grasped is better.

[0064] The Mooney viscosity (ML 1+4 (100 °C)) of the rubber composition for the outer layer is preferably 35 or more, more preferably 37 or more, still more preferably 39 or more, and preferably 55 or less, more preferably 53 or less, still more preferably 50 or less. If the Mooney viscosity (ML 1+4 (100 °C)) is 35 or more, the wear resistance of the grip is further improved, and if it is 55 or less, the processability of the rubber composition is better.

[0065] For the golf club grip, the material of other parts than the outer layer is not particularly limited. Examples of the material for forming the inner layer include a rubber composition for the inner layer and a resin composition.

[0066] As the rubber composition for the inner layer, it is preferable to contain a base rubber and a crosslinking agent. Examples of the base rubber 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), carboxy-modified hydrogenated acrylonitrile-butadiene rubber (HXNBR), butadiene rubber (BR), styrene-butadiene rubber (SBR), polyurethane rubber (PU), isoprene rubber (IR), chloroprene rubber (CR), ethylene-propylene rubber (EPM), etc. Among these, as the base rubber, NR, EPDM, IIR, NBR, HNBR, XNBR, HXNBR, BR, SBR, PU are preferable.

[0067] Examples of the crosslinking agent for the rubber composition for the inner layer include the same ones as those used in the rubber composition for the outer layer, and elemental sulfur is preferable. The rubber composition for the inner layer preferably further contains a vulcanization accelerator and a vulcanization activator. Examples of these vulcanization accelerator and vulcanization activator include the same ones as those used in the rubber composition for the outer layer. As the vulcanization accelerator, N-t-butyl-2-benzothiazolylsulfenamide and tetrabenzylthiuram disulfide are preferable. As the vulcanization activator, zinc oxide and stearic acid are preferable.

[0068] The rubber composition for the inner layer may further be blended with a reinforcing material, an antioxidant, a softening agent, a coloring agent, a scorch inhibitor, etc. as necessary. Examples of these reinforcing material, antioxidant, and coloring agent include the same ones as those used in the rubber composition for the outer layer. As the reinforcing material, carbon black and silica are preferable. As the antioxidant, 2,2'-methylenebis(4-methyl-6-t-butylphenol) is preferable.

[0069] The rubber composition for the inner layer 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. The temperature (material temperature) during kneading is preferably 70°C to 160°C. When the rubber composition for the inner layer contains microballoons, it is preferably kneaded at a temperature below the expansion start temperature of the microballoons.

[0070] The resin composition contains a base resin. Examples of the base resin include polyurethane resin, polystyrene resin, polyethylene resin, polypropylene resin, ethylene vinyl acetate copolymer resin, and polyethylene terephthalate resin.

[0071] As the material for forming the inner layer, a rubber composition for the inner layer is preferred, and it is preferably contains natural rubber (NR), ethylene-propylene-diene rubber (EPDM), and butyl rubber (IIR) as the base rubber. Further, when the rubber composition for the outer layer contains acrylonitrile-butadiene rubber as the (A) base rubber, it is also preferred that the rubber composition for the inner layer contains acrylonitrile-butadiene rubber as the base rubber. By containing acrylonitrile-butadiene rubber in the rubber composition for the inner layer, the adhesion to the outer layer formed from the rubber compositions for the inner and outer layers is improved.

[0072] The inner layer may be solid or porous. When the inner layer is porous, a foamed structure formed from a rubber composition for the inner layer containing microballoons is preferred. By using microballoons, weight reduction can be achieved while maintaining the mechanical strength of the formed part. Examples of the microballoons include those used in the rubber composition for the outer layer, and resin capsules in which a low-boiling hydrocarbon is encapsulated in a shell of a thermoplastic resin are preferred.

[0073] The thickness of the cylindrical portion is preferably 0.5 mm or more, more preferably 1.0 mm or more, still more preferably 1.5 mm or more, and preferably 17.0 mm or less, more preferably 10.0 mm or less, still more preferably 8.0 mm or less. The thickness of the cylindrical portion may be formed to be constant in the axial direction, or may be formed to gradually increase from the tip end portion toward the rear end portion.

[0074] The thickness of the outer layer and the thickness of the inner layer may be uniform or may vary. For example, it may be formed to gradually increase from one end to the other end in the axial direction of the cylindrical grip. The thickness of the outer layer is preferably uniform.

[0075] When the thickness of the cylindrical portion is 0.5 mm to 17.0 mm, the thickness of the outer layer is preferably 0.5 mm or more, more preferably 0.6 mm or more, still more preferably 0.7 mm or more, and preferably 2.5 mm or less, more preferably 2.3 mm or less, still more preferably 2.1 mm or less. If the thickness of the outer layer is 0.5 mm or more, the reinforcing effect by the outer layer material becomes greater, and if it is 2.5 mm or less, the inner layer can be made relatively thicker, and the effect of weight reduction of the grip becomes greater.

[0076] The percentage of the thickness of the outer layer with respect to the thickness of the cylindrical portion ((outer layer thickness / cylindrical portion thickness) × 100) is preferably 0.5% or more, more preferably 1.0% or more, still more preferably 1.5% or more, and preferably 99.0% or less, more preferably 98.0% or less, still more preferably 97.0% or less. If the percentage is 0.5% or more, the reinforcing effect by the outer layer material becomes greater, and if it is 99.0% or less, the inner layer can be made relatively thicker, and the effect of weight reduction of the grip becomes greater.

[0077] The material hardness (Shore A hardness) of the rubber composition for the inner layer is preferably 30 or more, more preferably 35 or more, still more preferably 40 or more, and preferably 60 or less, more preferably 55 or less, still more preferably 50 or less. If the material hardness (Shore A hardness) of the rubber composition for the inner layer is 30 or more, the inner layer will not become too soft, and a firm fixing feeling can be obtained when grasped. If it is 60 or less, the inner layer will not become too hard, and the grip feeling when grasped will be better.

[0078] Examples of the combination of the outer layer and the inner layer include a solid outer layer and a solid inner layer, a solid outer layer and a porous inner layer, and a porous outer layer and a porous inner layer. Among these, the combinations of a solid outer layer and a porous inner layer, and a porous outer layer and a porous inner layer are preferred. By making the inner layer porous, the weight of the grip can be reduced, but the mechanical strength of the inner layer decreases. However, since the rubber composition for the outer layer is excellent in mechanical strength, the mechanical strength of the grip can be maintained even if the inner layer is porous.

[0079] The inner layer is preferably a porous layer, and more preferably a foamed layer produced by the balloon foaming method. When producing the inner layer by the balloon foaming method, the content of microballoons in the composition for the inner layer is preferably 5 parts by mass or more, more preferably 8 parts by mass or more, still more preferably 12 parts by mass or more, and preferably 20 parts by mass or less, more preferably 18 parts by mass or less, still more preferably 15 parts by mass or less, based on 100 parts by mass of the base material (base rubber or base resin). If the content of the microballoons is 5 parts by mass or more, the effect of reducing the weight of the grip becomes greater, and if it is 20 parts by mass or less, a decrease in the mechanical strength of the inner layer can be suppressed.

[0080] Also, the foaming ratio of the inner layer produced by the balloon foaming method is preferably 1.2 or more, more preferably 1.5 or more, still more preferably 1.8 or more, and preferably 5.0 or less, more preferably 4.5 or less, still more preferably 4.0 or less. If the foaming ratio is 1.2 or more, the effect of reducing the weight of the grip becomes greater, and if it is 5.0 or less, a decrease in the mechanical strength of the inner layer can be suppressed.

[0081] The golf club grip is obtained by molding the rubber composition for the outer layer 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 can be 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. When adopting press molding, the mold temperature is preferably 140°C to 200°C, the molding time is preferably 5 minutes to 40 minutes, and the molding pressure is preferably 0.1 MPa to 100 MPa.

[0082] Examples of the shape of the golf club grip include a shape having a cylindrical portion into which a shaft is inserted and a cap portion integrally formed so as to cover the opening at the rear end of the cylindrical portion. And the cylindrical portion has a laminated structure of an inner layer and an outer layer.

[0083] The thickness of the cylindrical portion may be formed to be constant in the axial direction, or may be formed to gradually increase from the front end portion toward the rear end portion. Also, the thickness of the cylindrical portion may be formed to be constant in the radial direction, or a rib portion (so-called back line) may be provided in part. Further, grooves may be provided on the surface of the cylindrical portion. The grooves suppress the formation of a water film between the golfer's hand and the grip, and the grip performance in a wet state is further improved. Furthermore, from the viewpoints of the anti-slip performance and wear resistance of the grip, a reinforcing cord may be disposed in the grip.

[0084] The mass of the golf club grip is preferably 16 g or more, more preferably 18 g or more, still more preferably 20 g or more, and preferably 35 g or less, more preferably 32 g or less, still more preferably 30 g or less.

[0085] [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, wherein the grip is the golf club grip. The shaft can be made of stainless steel or carbon fiber reinforced resin. 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.

[0086] Hereinafter, with reference to the drawings, a golf club grip and a golf club will be described. FIG. 1 is a perspective view showing an example of a golf club grip. The grip 1 has a cylindrical portion 2 into which a shaft is inserted, and a cap portion 3 integrally formed so as to cover the opening at the rear end of the cylindrical portion.

[0087] FIG. 2 is a schematic cross-sectional view showing an example of a golf club grip. The cylindrical portion 2 is composed of an inner layer 2a and an outer layer 2b. The outer layer 2b is formed with a uniform thickness from the tip end to the rear end. The thickness of the inner layer 2a is formed to gradually increase from the tip end to the rear end. In the grip 1 shown in FIG. 2, the cap portion 3 is formed from the same rubber composition as the outer layer 2b.

[0088] FIG. 3 is a perspective view showing an example of the golf club 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.

Examples

[0089] Hereinafter, the present invention will be described in detail by way of examples. However, the present invention is not limited by the following examples, and any changes and embodiments within the scope not departing from the spirit of the present invention are all included in the scope of the present invention.

[0090] [Evaluation method] (1) Acrylonitrile content The acrylonitrile content was measured for acrylonitrile-butadiene rubber before hydrogenation in accordance with ISO 24698-1 (2008).

[0091] (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 the acrylonitrile-butadiene rubber is an acrylonitrile-butadiene binary copolymer, the butadiene content in the copolymer can be obtained by subtracting the acrylonitrile content (%) from 100. Double bond amount = {butadiene content / 54} × residual double bond amount × 10

[0092] (3) Content of monomer containing carboxyl group 1 g of hydrogenated acrylonitrile-butadiene rubber was weighed and dissolved in 50 ml of chloroform, and thymol blue indicator was added dropwise thereto. While stirring this solution, a 0.05 mol / L methanol solution of sodium hydroxide was added dropwise, and the dropping amount (V ml) until the first color change was recorded. For 50 ml of chloroform not containing hydrogenated acrylonitrile-butadiene rubber as a blank, a 0.05 mol / L methanol solution of sodium hydroxide was added dropwise using thymol blue as an indicator, and the dropping amount (B ml) until the first color change was recorded. The carboxyl group content was calculated by the following formula. Carboxyl group-containing monomer content = {0.05 × (V - B) × PM} / (10 × X) (In the formula, V: dropping amount of sodium hydroxide solution in the test solution (ml), B: dropping amount of sodium hydroxide solution in the blank (ml), PM: molecular weight of the carboxyl group-containing monomer, X: valence of the carboxyl group-containing monomer)

[0093] (4) Mooney viscosity (ML 1+4 (at 100 °C)) The Mooney viscosity of the rubber composition was measured in accordance with JIS K6300-1 (2013). The measurement was carried out using an L-shaped rotor.

[0094] (5) Material hardness (Shore A hardness) Using the rubber composition, it was pressed at 160 °C for 8 to 20 minutes to produce a sheet with a thickness of 2 mm. When the rubber composition contains microballoons, the microballoons were inflated to achieve the same expansion ratio as when forming the grip to produce the sheet. 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) with three sheets stacked together to avoid the influence of the measurement substrate. The detector used was "Shore A".

[0095] (6) Tensile strength at break (Tb) The tensile strength at break was measured in accordance with JIS K 6251 (2017). Specifically, a sheet with a thickness of 1 mm was produced using the rubber composition, and this was punched into a dumbbell shape (dumbbell shape No. 3) to produce test pieces. The physical properties were measured using a tensile test measuring device (manufactured by Shimadzu Corporation, Autograph AGS-D) (measurement temperature 23 °C, tensile speed 500 mm / min). Then, 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.

[0096] (7) Viscoelastic properties Loss tangent (tanδ), storage modulus (E ’) was measured using a dynamic viscoelasticity measuring device (manufactured by UBM, Rheogel-E4000). The test sample was prepared by pressing an outer layer rubber composition at 160 °C to form a rubber sheet, and then punching out the rubber sheet 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: 0.05%, jig: tension, sample shape: width 4 mm, thickness 1 mm, length 40 mm. E’ at 23 °C, tanδ and E’ at 60 °C were determined from the viscoelastic spectrum obtained by dynamic viscoelasticity measurement.

[0097] (8) Shrinkage rate Using a calendar roll, the outer layer rubber composition was sheeted out to a thickness of 0.80 mm. For this rubber sheet, the thickness immediately after sheeting out (D1) and the thickness one week after sheeting out (D2) were measured, and the shrinkage rate was calculated by the following formula. Also, visual observation was performed on the surface of the rubber sheet one week after sheeting out, and when there were no noticeable irregularities, it was evaluated as "〇", when irregularities occurred but it was possible to bond with the inner layer, it was evaluated as "△", and when irregularities occurred and it was difficult to bond with the inner layer, it was evaluated as "×". Shrinkage rate (%) = {(D2 - D1) / D1} × 100

[0098] (9) Grip appearance evaluation The appearance of the grip after production was visually observed and evaluated according to the following criteria. 〇: Immediately after taking out from the mold, there was no swelling of the outer layer due to air entrapment. △: Immediately after taking out from the mold, there was swelling of the outer layer in the appearance, but after cooling, the swelling of the outer layer could not be confirmed. ×: Immediately after taking out from the mold and after cooling, there was swelling of the outer layer in the appearance.

[0099] [Manufacture of grip] The respective raw materials were kneaded with the formulations shown in Tables 1 and 2 to prepare an outer layer rubber composition and an inner layer rubber composition. For the outer layer rubber composition, all the raw materials were kneaded using a Banbury mixer. For the inner layer rubber composition, the raw materials other than the microballoons were kneaded using a Banbury mixer, and then the microballoons were compounded using rolls. The material temperature during kneading with the Banbury mixer for the inner layer rubber composition and the material temperature when compounding the microballoons using rolls were set to be lower than the expansion start temperature of the microballoons.

[0100]

Table 1

[0101]

Table 2

[0102] 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, Mooney viscosity (ML 1+4 (100 °C)) 77)) HNBR: Hydrogenated acrylonitrile-butadiene rubber (manufactured by ARANXEO, Therban 3446 (residual double bond content 4.0%, acrylonitrile content 34.0% 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) sylvatac RE 5S: Manufactured by Arizona Chemical, rosin ester SEAST (SEAST) (registered trademark) 3: Manufactured by Tokai Carbon Co., Ltd., carbon black Zinc peroxide: manufactured by Struktol, Struktol ZP 1014 (zinc peroxide content 29% by mass) Zinc oxide: manufactured by PT. INDO LYSAGHT, White Seal 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 Nocceler EUR: manufactured by Ouchi Shinko Chemical Industry Co., Ltd., N,N'-diethylthiourea Microballoon: manufactured by Akzo Nobel, "Expancel (registered trademark) 909-80DU" (resin capsule with low-boiling hydrocarbon encapsulated in a thermoplastic resin shell, volume average particle diameter 18 μm to 24 μm, expansion start temperature 120 °C to 130 °C)

[0103] Using the outer layer rubber composition, a frustum-shaped unvulcanized rubber sheet and a cap member were produced. The outer layer rubber sheet was molded to have a constant thickness. Using the inner layer rubber composition, a rectangular unvulcanized rubber sheet was produced. The inner layer rubber sheet was formed to gradually thicken from one end to the other end. The inner layer rubber sheet was wound around a mandrel, and the outer layer rubber sheet was overlaid and wound on top of it. The mandrel and the cap member around which these rubber sheets were wound were placed in a mold having a groove pattern on the cavity surface. Then, heat treatment was performed at a mold temperature of 160 °C for 15 minutes to obtain a golf club grip. The thickness of the cylindrical portion of the obtained golf club grip was 1.5 mm at the thinnest part (head side end) and 6.7 mm at the thickest part (grip end side end). Also, the surface of the obtained grip was buffed with abrasive paper (#80).

[0104]

Table 3

[0105] The ratios (E’ 23 / E’ 60 ) of Grips No. 1 to 3 are 1.20 to 1.32. These grips have a low shrinkage rate of the outer layer material, and there is no swelling of the outer layer due to air biting in the produced grips

Explanation of Symbols

[0106] 1: Grip, 2: Cylindrical portion, 2a: Inner layer, 2b: Outer layer, 3: Cap portion, 4: Golf club, 5: Shaft, 6: Head

Claims

1. It has a cylindrical part composed of a cylindrical inner layer and a cylindrical outer layer covering the inner layer. The outer layer is 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, and the storage elastic modulus (E' 23 ) at 23°C and the storage elastic modulus (E' 60 ) at 60°C, and the ratio (E' 23 / E' 60 ) is 1.21 to 1.

29. A grip for a golf club characterized by this.

2. The golf club grip according to claim 1, wherein the tensile strength at break of the outer layer is 20 MPa to 30 MPa.

3. The rubber composition forming the outer layer has a Mooney viscosity (ML 1+4 (100 °C)) of 35 to 55. The golf club grip according to claim 1 or 2.

4. The golf club grip according to any one of claims 1 to 3, wherein the outer layer has a loss tangent (tan δ) at 60°C of 0.138 or more, 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.

5. The golf club grip according to any one of claims 1 to 4, wherein the outer layer contains at least one selected from the group consisting of carboxyl-modified acrylonitrile-butadiene rubber, hydrogenated acrylonitrile-butadiene rubber, and carboxyl-modified hydrogenated acrylonitrile-butadiene rubber.

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