JP2011011088A - Golf ball - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a golf ball 2 which is excellent in flying performance, shot feeling at impact and durability.SOLUTION: A golf ball 2 includes a spherical core 4, an intermediate layer 6 covering the core 4, a reinforcing layer 8 covering the intermediate layer 6 and a cover 10 covering the reinforcing layer 8. Base polymer of the intermediate layer 6 contains a thermoplastic elastomer containing a styrene block and an ionomer resin. The hardness of the intermediate layer 6 measured with a Shore-D type hardness meter is equal to or less than 54. Thickness of the intermediate layer 6 is between 0.5 mm and 1.6 mm. The base polymer of the reinforcing layer 8 is a reaction product of a carboxylic group-containing polyurethane and a polycarbodiimide. Main component of the base polymer of the cover 10 is an ionomer resin. Hardness of the base polymer of the cover 10 measured with the Shore-D type hardness meter is equal to or greater than 55. The thickness of the cover 10 is equal to or less than 1.2 mm.

Description

  The present invention relates to a golf ball. Specifically, the present invention relates to a multi-piece golf ball that includes a core, an intermediate layer, and a cover.

  A golfer's greatest concern with golf balls is flight performance. In particular, golf players place importance on the flight distance of shots with a driver. The feeling of hitting is also important for golf balls. Golfers prefer a soft feel at impact. Furthermore, durability is also important for golf balls. A golf ball that is not damaged by repeated hits is desired.

  From the viewpoints of flight performance and feel at impact, golf balls having various structures have been proposed. Japanese Patent Application Laid-Open No. 2001-585 discloses a golf ball in which an intermediate layer is made of a urethane resin and a cover is made of an ionomer resin. Japanese Patent Application Laid-Open No. 2003-52857 discloses a golf ball whose intermediate layer contains a thermoplastic elastomer and whose cover is made of an ionomer resin.

JP 2001-585 A JP 2003-52857 A

  The ionomer resin is inferior in compatibility with other resins. The ionomer resin is particularly inferior in compatibility with the thermoplastic elastomer. In a golf ball in which an ionomer resin is used for the cover and another resin is used for the intermediate layer, the adhesion between the intermediate layer and the cover is insufficient. In this golf ball, the cover is peeled off from the intermediate layer by repeated hitting. The peeling causes damage to the golf ball. In particular, a golf ball having a thin intermediate layer or cover is likely to be damaged due to insufficient adhesion.

  An object of the present invention is to provide a golf ball having excellent flight performance, feel at impact and durability.

  The golf ball according to the present invention includes a spherical core, an intermediate layer positioned outside the core, a reinforcing layer positioned outside the intermediate layer, and a cover positioned outside the reinforcing layer. The core has a diameter of 39.2 mm or more. The hardness Hm of this intermediate layer measured with a Shore D hardness tester is 54 or less. The main component of the base polymer of this cover is an ionomer resin. The hardness Hc of the cover measured with a Shore D hardness tester is 55 or more. The weight Wc of this cover is 1.5 g or more and 5.7 g or less. The ratio (Wc / Hc) of the mass Wc to the hardness Hc of this cover is 0.080 or less.

  Preferably, the base polymer of the intermediate layer includes 10% by mass or more and 60% by mass or less of a styrene block-containing thermoplastic elastomer and 40% by mass or more and 90% by mass or less of an ionomer resin.

  Preferably, the thickness Tc of the cover is 1.2 mm or less. Preferably, the thickness Tm of the intermediate layer is not less than 0.5 mm and not more than 1.6 mm.

  Preferably, the reinforcing layer is made of an aqueous adhesive. The base polymer of this water-based adhesive is a reaction product of a carboxyl group-containing polyurethane and polycarbodiimide. Preferably, the thickness of the reinforcing layer is 0.003 mm or more and 0.050 mm or less.

  In this golf ball, the intermediate layer and the cover are firmly adhered to each other through the reinforcing layer. In this golf ball, even when a thin intermediate layer or a thin cover is employed, sufficient durability can be obtained by the reinforcing layer. The thin intermediate layer can contribute to the resilience performance of the golf ball. The thin cover can contribute to the feel at impact of the golf ball. The launch angle of the golf ball when hit can be optimized by the thin cover. This golf ball is excellent in flight performance, feel at impact and durability.

FIG. 1 is a partially cutaway sectional view showing a golf ball according to an embodiment of the present invention.

  Hereinafter, the present invention will be described in detail based on preferred embodiments with appropriate reference to the drawings.

  FIG. 1 is a partially cutaway sectional view showing a golf ball 2 according to an embodiment of the present invention. The golf ball 2 includes a spherical core 4, an intermediate layer 6 that covers the core 4, a reinforcing layer 8 that covers the intermediate layer 6, and a cover 10 that covers the reinforcing layer 8. A large number of dimples 12 are formed on the surface of the cover 10. A portion of the surface of the cover 10 other than the dimples 12 is a land 14. The golf ball 2 includes a paint layer and a mark layer outside the cover 10, but these layers are not shown.

  The golf ball 2 has a diameter of 40 mm to 45 mm. The diameter is preferably 42.67 mm or more from the viewpoint that the American Golf Association (USGA) standard is satisfied. In light of suppression of air resistance, the diameter is preferably equal to or less than 44 mm, and more preferably equal to or less than 42.80 mm. The golf ball 2 has a mass of 40 g or more and 50 g or less. From the viewpoint of obtaining a large inertia, the mass is preferably 44 g or more, and more preferably 45.00 g or more. From the viewpoint that the USGA standard is satisfied, the mass is preferably equal to or less than 45.93 g.

  The core 4 is usually obtained by crosslinking a rubber composition. Examples of preferable base rubber include polybutadiene, polyisoprene, styrene-butadiene copolymer, ethylene-propylene-diene copolymer, and natural rubber. From the viewpoint of resilience performance, polybutadiene is preferred. When polybutadiene and other rubber are used in combination, it is preferable that polybutadiene is a main component. Specifically, the proportion of polybutadiene in the total base rubber is preferably 50% by mass or more, particularly 80% by mass or more. Polybutadiene having a cis-1,4 bond ratio of 40% or more, particularly 80% or more is particularly preferred.

  For crosslinking of the core 4, a co-crosslinking agent is usually used. A preferred co-crosslinking agent from the viewpoint of resilience performance is a monovalent or divalent metal salt of an α, β-unsaturated carboxylic acid having 2 to 8 carbon atoms. Specific examples of preferred co-crosslinking agents include zinc acrylate, magnesium acrylate, zinc methacrylate and magnesium methacrylate. Zinc acrylate and zinc methacrylate are particularly preferable because of high resilience performance.

  As a co-crosslinking agent, an α, β-unsaturated carboxylic acid having 2 to 8 carbon atoms and a metal oxide may be blended. Both react in the rubber composition to obtain a salt. This salt contributes to the crosslinking reaction. Preferred α, β-unsaturated carboxylic acids include acrylic acid and methacrylic acid. Preferred metal oxides include zinc oxide and magnesium oxide.

  From the viewpoint of the resilience performance of the golf ball 2, the compounding amount of the co-crosslinking agent is preferably 10 parts by mass or more and more preferably 15 parts by mass or more with respect to 100 parts by mass of the base rubber. From the viewpoint of soft feel at impact, the amount of the co-crosslinking agent is preferably 50 parts by mass or less, more preferably 45 parts by mass or less, relative to 100 parts by mass of the base rubber.

  The rubber composition used for the core 4 is preferably blended with an organic peroxide together with a co-crosslinking agent. The organic peroxide functions as a crosslinking initiator. By blending the organic peroxide, the resilience performance of the golf ball 2 is enhanced. Suitable organic peroxides include dicumyl peroxide, 1,1-bis (t-butylperoxy) -3,3,5-trimethylcyclohexane, 2,5-dimethyl-2,5-di (t- Butyl peroxy) hexane and di-t-butyl peroxide. A particularly versatile organic peroxide is dicumyl peroxide.

  In light of the resilience performance of the golf ball 2, the organic peroxide is preferably blended in an amount of 0.1 part by weight or more, more preferably 0.3 part by weight or more, based on 100 parts by weight of the base rubber, Part by mass or more is particularly preferable. From the viewpoint of a soft feel at impact, the amount of the organic peroxide is preferably 3.0 parts by mass or less, more preferably 2.5 parts by mass or less with respect to 100 parts by mass of the base rubber.

  A filler may be blended in the core 4 for the purpose of adjusting specific gravity and the like. Suitable fillers include zinc oxide, barium sulfate, calcium carbonate and magnesium carbonate. As a filler, a powder made of a high specific gravity metal may be blended. Specific examples of the high specific gravity metal include tungsten and molybdenum. The blending amount of the filler is appropriately determined so that the intended specific gravity of the core 4 is achieved. A particularly preferred filler is zinc oxide. Zinc oxide functions not only as a specific gravity adjuster but also as a crosslinking aid. In the core 4, various additives such as sulfur, a sulfur compound, an anti-aging agent, a colorant, a plasticizer, and a dispersant are blended in appropriate amounts as necessary. The core 4 may be blended with a crosslinked rubber powder or a synthetic resin powder.

  The diameter of the core 4 is preferably 30.0 mm or greater and 41.0 mm or less. By setting the diameter to 30.0 mm or more, sufficient resilience performance of the golf ball 2 can be obtained. From this viewpoint, the diameter is more preferably 32.0 mm or more. By setting the diameter to 41.0 mm or less, the shot feeling by the mid layer 6 and the flight performance by the cover 10 can be exhibited. In this respect, the diameter is more preferably 40.5 mm or less.

  The amount of compressive deformation of the core 4 is preferably 3.0 mm or greater and 6.0 mm or less. The core 4 having a compression deformation amount of 3.0 mm or more contributes to a soft feel at impact. In this respect, the amount of compressive deformation is more preferably equal to or greater than 3.4 mm. The core 4 having a compression deformation amount of 6.0 mm or less contributes to the resilience performance of the golf ball 2. In this respect, the amount of compressive deformation is more preferably equal to or less than 5.5 mm.

  In measuring the amount of compressive deformation, the core 4 is first placed on a metal rigid plate. Next, the metal cylinder gradually descends toward the core 4. The core 4 sandwiched between the bottom surface of the cylinder and the rigid plate is deformed. The moving distance of the cylinder from the state where the initial load of 98 N is applied to the core 4 to the state where the final load of 1274 N is applied is the amount of compressive deformation.

  The mass of the core 4 is preferably 25 g or more and 42 g or less. The crosslinking temperature of the core 4 is usually 140 ° C. or higher and 180 ° C. or lower. The crosslinking time of the core 4 is usually 10 minutes or longer and 60 minutes or shorter. The core 4 may be formed from two or more layers. Another layer made of a resin composition or a rubber composition may be provided between the core 4 and the intermediate layer 6.

  The base polymer of the mid layer 6 includes a styrene block-containing thermoplastic elastomer. The styrene block-containing thermoplastic elastomer contributes to the feel at impact of the golf ball 2. In light of feel at impact, the ratio of the styrene block-containing thermoplastic elastomer to the total amount of the base polymer is preferably 10% by mass or more, and more preferably 25% by mass or more.

  The styrene block-containing thermoplastic elastomer includes styrene-butadiene-styrene block copolymer (SBS), styrene-isoprene-styrene block copolymer (SIS), styrene-isoprene-butadiene-styrene block copolymer (SIBS), SBS hydrogenated, SIS hydrogenated and SIBS hydrogenated are included. Examples of the hydrogenated product of SBS include styrene-ethylene-butylene-styrene block copolymer (SEBS). As a hydrogenated product of SIS, styrene-ethylene-propylene-styrene block copolymer (SEPS) can be mentioned. Examples of the hydrogenated product of SIBS include styrene-ethylene-ethylene-propylene-styrene block copolymer (SEEPS).

  In the present invention, the styrene block-containing thermoplastic elastomer includes an alloy of one or two or more selected from the group consisting of SBS, SIS, SIBS, SEBS, SEPS and SEEPS, and hydrogenated products thereof, and an olefin. included. The olefin component in the alloy is presumed to contribute to the improvement of the compatibility between the thermoplastic elastomer and the ionomer resin. By using this alloy, the resilience performance of the golf ball 2 is improved. Preferably, an olefin having 2 to 10 carbon atoms is used.

  In light of the resilience performance of the golf ball 2, the content of the styrene component in the thermoplastic elastomer is preferably 10% by mass or more, more preferably 12% by mass or more, and particularly preferably 15% by mass or more. In light of feel at impact of the golf ball 2, the content is preferably equal to or less than 50% by mass, more preferably equal to or less than 47% by mass, and particularly preferably equal to or less than 45% by mass.

  Specific examples of the styrene block-containing thermoplastic elastomer include Mitsubishi Chemical's trade names “Lavalon T3339C”, “Lavalon SJ5400N”, “Lavalon SJ6400N”, “Lavalon SJ7400N”, “Lavalon SJ8400N”, “Lavalon SJ9400N” and “Lavalon”. SR04 "; trade name" Epofriend A1010 "by Daicel Chemical Industries, Ltd. and trade name" Septon HG-252 "by Kuraray.

  The base polymer of the mid layer 6 contains an ionomer resin together with a styrene block-containing thermoplastic elastomer. The ionomer resin is highly elastic. The ionomer resin contributes to the resilience performance of the golf ball 2. In light of resilience performance, the ratio of the ionomer resin to the total amount of the base polymer is preferably 40% by mass or more, and more preferably 50% by mass or more.

  A preferable ionomer resin includes a binary copolymer of an α-olefin and an α, β-unsaturated carboxylic acid having 3 to 8 carbon atoms. Other ionomer resins include a ternary copolymer of an α-olefin, an α, β-unsaturated carboxylic acid having 3 to 8 carbon atoms and an α, β-unsaturated carboxylic acid ester having 2 to 22 carbon atoms. A polymer is mentioned. In the binary copolymer and ternary copolymer, preferred α-olefins are ethylene and propylene, and preferred α, β-unsaturated carboxylic acids are acrylic acid and methacrylic acid. In the binary copolymer and ternary copolymer, some of the carboxyl groups are neutralized with metal ions. Examples of the metal ions for neutralization include sodium ions, potassium ions, lithium ions, zinc ions, calcium ions, magnesium ions, aluminum ions, and neodymium ions. Neutralization may be performed with two or more metal ions. Particularly suitable metal ions from the viewpoint of resilience performance and durability of the golf ball 2 are sodium ion, zinc ion, lithium ion and magnesium ion.

  A preferable binary copolymer contains 80% by mass or more and 90% by mass or less α-olefin and 10% by mass or more and 20% by mass or less α, β-unsaturated carboxylic acid. This binary copolymer is excellent in resilience performance. Preferred terpolymers are 70% to 85% by weight α-olefin, 5% to 30% by weight α, β-unsaturated carboxylic acid, and 1% to 25% by weight. α, β-unsaturated carboxylic acid ester. This ternary copolymer is excellent in resilience performance.

  A particularly preferred ionomer resin is a copolymer of ethylene and acrylic acid or methacrylic acid. Preferably, the ionomer resin has a melt index of 3 to 7. This ionomer resin is rich in fluidity. Preferably, the ionomer resin has a bending synthesis rate of 200 MPa or more and 400 MPa or less. This ionomer resin is highly elastic.

  Specific examples of the ionomer resin include Mitsui Dupont Polychemical's trade names “HIMILAN 1555”, “HIMILAN 1557”, “HIMILAN 1605”, “HIMILAN 1706”, “HIMILAN 1707”, “HIMILAN AM7311”, “HIMILAN AM7315”. "High Milan AM 7317", "Hi Milan AM 7318" and "High Milan MK 7320"; DuPont's trade names "Surlin 7930", "Surlin 7940", "Surlin 8140", "Surlin 8940", "Surlin 8945", "Surlin 9120" , "Surlin 9910" and "Surlin 9945"; and Exxon's trade names "IOTEK 7010", "IOTEK 7030", "IOTEK 8000" and "IOTEK 8030". Two or more ionomer resins may be used in combination. An ionomer resin neutralized with a monovalent metal ion and an ionomer resin neutralized with a divalent metal ion may be used in combination.

  Other resins may be used in the mid layer 6 together with the styrene block-containing thermoplastic elastomer and ionomer resin. Examples of the other resins include thermoplastic polyester elastomers, thermoplastic polyamide elastomers, thermoplastic polyurethane elastomers, and thermoplastic polyolefin elastomers.

  A filler may be blended in the resin composition of the mid layer 6 for the purpose of adjusting specific gravity and the like. Suitable fillers include zinc oxide, barium sulfate, calcium carbonate and magnesium carbonate. As a filler, a powder made of a high specific gravity metal may be blended. Specific examples of the high specific gravity metal include tungsten and molybdenum. The blending amount of the filler is appropriately determined so that the intended specific gravity of the mid layer 6 is achieved. The intermediate layer 6 may be blended with a colorant, a crosslinked rubber powder, or a synthetic resin powder.

  The mid layer 6 preferably has a hardness Hm of 54 or less. The mid layer 6 having a hardness Hm of 54 or less can contribute to a soft feel at impact. In this respect, the hardness Hm is more preferably equal to or less than 53, and particularly preferably equal to or less than 52. In light of the resilience performance of the golf ball 2, the hardness Hm is preferably equal to or greater than 30, and more preferably equal to or greater than 33.

  In the present invention, the hardness Hm of the mid layer 6 and the hardness Hc of the cover 10 are measured in accordance with the provisions of “ASTM-D 2240-68”. For the measurement, an automatic rubber hardness tester (trade name “P1” by Kobunshi Keiki Co., Ltd.) to which a spring type hardness tester Shore D type is attached is used. For the measurement, a sheet made of the same material as that of the intermediate layer 6 (or the cover 10) and having a thickness of about 2 mm is used. Prior to measurement, the sheet is stored at a temperature of 23 ° C. for 2 weeks. At the time of measurement, three sheets are overlaid.

  The thickness Tm of the mid layer 6 is preferably 0.5 mm or greater and 1.6 mm or less. The mid layer 6 having a thickness Tm of 0.5 mm or more can contribute to a soft feel at impact. In this respect, the thickness Tm is more preferably equal to or greater than 0.6 mm. By setting the thickness Tm to 1.6 mm or less, the adverse effect of the intermediate layer 6 on the resilience performance is suppressed. In this respect, the thickness Tm is more preferably equal to or less than 1.5 mm, and particularly preferably equal to or less than 1.2 mm.

  The surface of the intermediate layer 6 may be subjected to a treatment such as brushing or polishing. This treatment increases the surface roughness. The large roughness increases the adhesion between the intermediate layer 6 and the reinforcing layer 8 or the cover 10.

  The reinforcing layer 8 is interposed between the intermediate layer 6 and the cover 10. The reinforcing layer 8 is firmly attached to the intermediate layer 6 and is also firmly attached to the cover 10. As described above, the mid layer 6 of the golf ball 2 is thin. As will be described later, the cover 10 of the golf ball 2 is extremely thin. Since the cover 10 is firmly adhered to the intermediate layer 6 through the reinforcing layer 8, the intermediate layer 6 and the cover 10 are hardly damaged even though the intermediate layer 6 and the cover 10 are thin. This golf ball 2 is excellent in durability. In other words, the presence of the reinforcing layer 8 allows the thin intermediate layer 6 and the thin cover 10.

  Preferably, the reinforcing layer 8 is made of an aqueous adhesive. The water-based adhesive is excellent in workability and has no adverse effect on the environment. Particularly preferred is a reaction product of an aqueous carboxyl group-containing polyurethane and an aqueous polycarbodiimide. A solution obtained by mixing an aqueous solution or aqueous dispersion of a carboxyl group-containing polyurethane and an aqueous solution or aqueous dispersion of a polycarbodiimide is applied to the intermediate layer 6, and the carboxyl group-containing polyurethane and the polycarbodiimide react to reinforce. Layer 8 is obtained. This reinforcing layer 8 has a three-dimensional structure and is excellent in strength. The reinforcing layer 8 is excellent in adhesion with the intermediate layer 6 and adhesion with the cover 10.

  Anionic and nonionic type carboxyl group-containing polyurethane liquids can be used. In the anionic carboxyl group-containing polyurethane liquid, the polyurethane is dissolved or dispersed in water by neutralizing the carboxyl group with a base. In the nonionic type carboxyl group-containing polyurethane liquid, polyurethane is forcibly dispersed in water with high shear force in the presence of a nonionic emulsifier.

The polyisocyanate component in the carboxyl group-containing polyurethane has a plurality of isocyanate groups. Specific examples of the polyisocyanate include 2,4-toluene diisocyanate, 2,6-toluene diisocyanate, a mixture of 2,4-toluene diisocyanate and 2,6-toluene diisocyanate (TDI), and 4,4′-diphenylmethane diisocyanate (MDI). ), 1,5-naphthylene diisocyanate (NDI), 3,3′-vitrylene-4,4′-diisocyanate (TODI), xylylene diisocyanate (XDI), tetramethylxylylene diisocyanate (TMXDI) and paraphenylene diisocyanate ( Aromatic polyisocyanates such as PPDI); 4,4′-dicyclohexylmethane diisocyanate (H ₁₂ MDI), hydrogenated xylylene diisocyanate (H ₆ XDI), hexamethylene diisocyanate (HDI) ) And cycloaliphatic polyisocyanates such as isophorone diisocyanate (IPDI); and aliphatic polyisocyanates. Two or more polyisocyanates may be used in combination. From the viewpoint of weather resistance, TMXDI, XDI, HDI, H ₆ XDI, IPDI and H ₁₂ MDI are preferred.

  The polyol component in the carboxyl group-containing polyurethane has a plurality of hydroxyl groups. A low molecular weight polyol having a molecular weight of less than 500 and a high molecular weight polyol having a molecular weight of 500 or more can be used. Examples of the low molecular weight polyol include diol and triol. Specific examples of the diol include ethylene glycol, diethylene glycol, triethylene glycol, 1,3-butanediol, 1,4-butanediol, neopentyl glycol and 1,6-hexanediol. Specific examples of the triol include glycerin, trimethylolpropane, and hexanetriol. High molecular weight polyols include polyether polyols such as polyoxyethylene glycol (PEG), polyoxypropylene glycol (PPG) and polyoxytetramethylene glycol (PTMG); polyethylene adipate (PEA), polybutylene adipate (PBA) ) And polyhexamethylene adipate (PHMA); lactone polyester polyols such as poly-ε-caprolactone (PCL); polycarbonate polyols such as polyhexamethylene carbonate; and acrylic polyols. Two or more polyols may be used in combination. A polyol having a weight average molecular weight of 50 or more and 2000 or less, particularly 100 or more and 1000 or less is particularly preferable.

  The carboxyl group-containing polyurethane may contain a polyamine component. Polyamine components include: aliphatic polyamines such as ethylenediamine, propylenediamine and hexamethylenediamine; aromatic polyamines such as tolylenediamine, xylylenediamine and diaminodiphenylmethane; alicyclic rings such as diaminocyclohexylmethane, piperazine and isophoronediamine And polyhydramines; and hydrazines such as hydrazine, succinic dihydrazide, adipic dihydrazide and phthalic dihydrazide. Alkanolamines such as diethanolamine and monoethanolamine may be used.

  The aqueous polycarbodiimide has two or more carbodiimide groups in the molecule, and is water-soluble or water-dispersible. Preferably, a polycarbodiimide resin having a structure represented by the following formula (I) is used.

  In the above formula (I), S1 and S2 represent hydrophilic segments, R represents a residue obtained by removing an isocyanate group from diisocyanate, K represents a bond formed by a reaction between an isocyanate group and a hydrophilic segment, n represents an average degree of polymerization. n is an integer of 2 or more and 100 or less. Examples of the hydrophilic segment include a nonionic segment containing an ethylene oxide chain; an anionic segment containing a sulfonate, a sulfate, and the like; and a cationic segment containing a quaternary ammonium salt. Specific examples of the polycarbodiimide resin represented by the above formula (I) include tetramethylxylylene carbodiimide and dicyclohexylmethane carbodiimide.

  The carbodiimide equivalent in the aqueous polycarbodiimide is preferably from 100 to 500. By setting the carbodiimide equivalent to 100 or more, the reinforcing layer 8 having a high crosslinking density can be obtained. The reinforcing layer 8 contributes to the close contact between the intermediate layer 6 and the cover 10. In this respect, the carbodiimide equivalent is more preferably equal to or greater than 150, and particularly preferably equal to or greater than 250. By using a polycarbodiimide having a carbodiimide equivalent of 500 or less, the reaction with the carboxyl group-containing polyurethane is completed in a short time. From this viewpoint, the carbodiimide equivalent is more preferably 450 or less, and particularly preferably 400 or less. The carbodiimide equivalent is the chemical formula amount of polycarbodiimide per 1 mol of carbodiimide group.

  20 mass% or more is preferable and, as for the solid content in the aqueous solution or aqueous dispersion of polycarbodiimide, 30 mass% or more is more preferable. The solid content is preferably 80% by mass or less, and more preferably 70% by mass or less. Examples of preferable polycarbodiimide aqueous solution include trade names “Carbodilite E-01”, “Carbodilite E-02” and “Carbodilite E-03A” of Nisshinbo Co., Ltd.

  The blending amount of the polycarbodiimide is preferably 5 parts by mass or more and 25 parts by mass or less with respect to 100 parts by mass of the carboxyl group-containing polyurethane. By setting the blending amount to 5 parts by mass or more, the reinforcing layer 8 having a high crosslinking density can be obtained. The reinforcing layer 8 contributes to the close contact between the intermediate layer 6 and the cover 10. In this respect, the amount is more preferably equal to or greater than 6 parts by weight, and particularly preferably equal to or greater than 7 parts by weight. By setting the blending amount to 25 parts by mass or less, the reaction with the carboxyl group-containing polyurethane is completed in a short time. In this respect, the amount is more preferably equal to or less than 23 parts by weight, and particularly preferably equal to or less than 20 parts by weight.

  The reinforcing layer 8 may be made of an oil-based adhesive. As the base polymer of the reinforcing layer 8, a two-component curable thermosetting resin is typically used. Specific examples of the two-component curable thermosetting resin include an epoxy resin, a urethane resin, an acrylic resin, a polyester resin, and a cellulose resin. From the viewpoint of mechanical properties (for example, breaking strength) and durability of the reinforcing layer 8, a two-component curable epoxy resin and a two-component curable urethane resin are preferable.

  The two-component curable epoxy resin is obtained by curing the epoxy resin with a polyamide curing agent. Examples of the epoxy resin used in the two-component curable epoxy resin include bisphenol A type epoxy resin, bisphenol F type epoxy resin, and bisphenol AD type epoxy resin. The bisphenol A type epoxy resin is obtained by a reaction between bisphenol A and an epoxy group-containing compound such as epichlorohydrin. The bisphenol F type epoxy resin is obtained by a reaction between bisphenol F and an epoxy group-containing compound. The bisphenol AD type epoxy resin is obtained by a reaction between bisphenol AD and an epoxy group-containing compound. From the viewpoint of the balance of flexibility, chemical resistance, heat resistance and toughness, bisphenol A type epoxy resin is preferable.

  The polyamide-based curing agent has a plurality of amino groups and one or more amide groups. This amino group can react with an epoxy group. Specific examples of the polyamide curing agent include a polyamide amine curing agent and a modified product thereof. The polyamidoamine curing agent is obtained by a condensation reaction between a polymerized fatty acid and a polyamine. Typical polymerized fatty acids can be obtained by synthesizing natural fatty acids containing a large amount of unsaturated fatty acids such as linoleic acid and linolenic acid by heating in the presence of a catalyst. Specific examples of unsaturated fatty acids include tall oil, soybean oil, linseed oil and fish oil. A polymerized fatty acid having a dimer content of 90% by mass or more, a trimer content of 10% by mass or less, and hydrogenated is preferable. Preferred polyamines include polyethylene diamine, polyoxyalkylene diamine and derivatives thereof.

  In the mixing of the epoxy resin and the polyamide curing agent, the ratio of the epoxy equivalent of the epoxy resin and the amine active hydrogen equivalent of the polyamide curing agent is 1.0 / 1.4 or more and 1.0 / 1.0 or less. Is preferred.

  The two-component curable urethane resin is obtained by a reaction between the main agent and the curing agent. A two-component curable urethane resin obtained by a reaction between a main component containing a polyol component and a curing agent containing a polyisocyanate or a derivative thereof, a main component containing an isocyanate group-terminated urethane prepolymer, and a curing agent having active hydrogen. A two-component curable urethane resin obtained by reaction may be used. In particular, a two-component curable urethane resin obtained by a reaction between a main component containing a polyol component and a curing agent containing polyisocyanate or a derivative thereof is preferable.

  It is preferable that urethane polyol is used as the polyol component of the main agent. The urethane polyol has a urethane bond and at least two hydroxyl groups. Preferably, the urethane polyol has a hydroxyl group at its terminal. The urethane polyol can be obtained by reacting the polyol and the polyisocyanate at a ratio such that the hydroxyl group of the polyol component is excessive in molar ratio with respect to the isocyanate group of the polyisocyanate.

  The polyol used for the production of the urethane polyol has a plurality of hydroxyl groups. A polyol having a weight average molecular weight of 50 to 2,000, particularly 100 to 1,000 is preferred. Examples of the low molecular weight polyol include diol and triol. Specific examples of the diol include ethylene glycol, diethylene glycol, triethylene glycol, 1,3-butanediol, 1,4-butanediol, neopentyl glycol and 1,6-hexanediol. Specific examples of the triol include trimethylolpropane and hexanetriol. High molecular weight polyols include polyether polyols such as polyoxyethylene glycol (PEG), polyoxypropylene glycol (PPG) and polyoxytetramethylene glycol (PTMG); polyethylene adipate (PEA), polybutylene adipate (PBA) ) And polyhexamethylene adipate (PHMA); lactone polyester polyols such as poly-ε-caprolactone (PCL); polycarbonate polyols such as polyhexamethylene carbonate; and acrylic polyols. Two or more polyols may be used in combination.

The polyisocyanate used for the production of the urethane polyol has a plurality of isocyanate groups. Specific examples of the polyisocyanate include 2,4-toluene diisocyanate, 2,6-toluene diisocyanate, a mixture of 2,4-toluene diisocyanate and 2,6-toluene diisocyanate (TDI), and 4,4′-diphenylmethane diisocyanate (MDI). ), 1,5-naphthylene diisocyanate (NDI), 3,3′-vitrylene-4,4′-diisocyanate (TODI), xylylene diisocyanate (XDI), tetramethylxylylene diisocyanate (TMXDI) and paraphenylene diisocyanate ( Aromatic polyisocyanates such as PPDI); 4,4′-dicyclohexylmethane diisocyanate (H ₁₂ MDI), hydrogenated xylylene diisocyanate (H ₆ XDI), hexamethylene diisocyanate (HDI) ) And cycloaliphatic polyisocyanates such as isophorone diisocyanate (IPDI); and aliphatic polyisocyanates. Two or more polyisocyanates may be used in combination. From the viewpoint of weather resistance, TMXDI, XDI, HDI, H ₆ XDI, IPDI and H ₁₂ MDI are preferred.

  A known catalyst can be used in the reaction of the polyol and the polyisocyanate for producing the urethane polyol. A typical catalyst is dibutyltin dilaurate.

  From the viewpoint of the strength of the reinforcing layer 8, the ratio of the urethane bond contained in the urethane polyol is preferably 0.1 mmol / g or more. From the viewpoint of followability of the reinforcing layer 8 to the cover 10, the ratio of urethane bonds contained in the urethane polyol is preferably 5 mmol / g or less. The ratio of the urethane bond can be adjusted by adjusting the molecular weight of the polyol as a raw material and adjusting the blending ratio of the polyol and the polyisocyanate.

  From the viewpoint that the time required for the reaction between the main agent and the curing agent is short, the weight average molecular weight of the urethane polyol is preferably 4000 or more, and more preferably 4500 or more. From the viewpoint of adhesion of the reinforcing layer 8, the weight average molecular weight of the urethane polyol is preferably 10,000 or less, and more preferably 9000 or less.

  From the viewpoint of adhesion of the reinforcing layer 8, the hydroxyl value (mgKOH / g) of the urethane polyol is preferably 15 or more, and more preferably 73 or more. From the viewpoint that the time required for the reaction between the main agent and the curing agent is short, the hydroxyl value of the urethane polyol is preferably 130 or less, more preferably 120 or less.

  The main agent may contain a polyol having no urethane bond together with the urethane polyol. The aforementioned polyol, which is a raw material for urethane polyol, can be used as the main agent. Polyols that are compatible with urethane polyols are preferred. From the viewpoint that the time required for the reaction between the main agent and the curing agent is short, the ratio of the urethane polyol in the main agent is preferably 50% by mass or more and more preferably 80% by mass or more in terms of solid content. Ideally this ratio is 100% by weight.

  The curing agent contains polyisocyanate or a derivative thereof. The aforementioned polyisocyanate, which is a raw material of urethane polyol, can be used as a curing agent.

  The reinforcing layer 8 made of a two-component curable thermosetting resin is obtained by applying a liquid in which the main agent and the curing agent are dissolved or dispersed in a solvent to the surface of the intermediate layer 6. From the viewpoint of workability, application with a spray gun is preferred. After application, the solvent volatilizes and the main agent and the curing agent react to form the reinforcing layer 8. Preferred solvents include toluene, isopropyl alcohol, xylene, methyl ethyl ketone, methyl isobutyl ketone, ethylene glycol monomethyl ether, ethylbenzene, propylene glycol monomethyl ether, isobutyl alcohol and ethyl acetate.

  From the viewpoint of the durability of the golf ball 2, the thickness of the reinforcing layer 8 is preferably 0.003 mm or more, and more preferably 0.005 mm or more. From the viewpoint that the reinforcing layer 8 is easily formed, the thickness is preferably 0.05 mm or less, and more preferably 0.02 mm or less. The thickness is measured by observing a cross section of the golf ball 2 with a microscope. When the surface of the intermediate layer 6 is provided with irregularities by the roughening treatment, the thickness is measured immediately above the convex portions.

  The main component of the base polymer of the cover 10 is an ionomer resin. The aforementioned binary copolymer ionomer resin and ternary copolymer ionomer resin can be used for the cover 10. The ionomer resin is highly elastic. By using an ionomer resin for the cover 10, the golf ball 2 having excellent resilience performance can be obtained.

  As described above, the intermediate layer 6 includes a styrene block-containing thermoplastic elastomer. When the intermediate layer 6 and the cover 10 made of an ionomer resin are directly joined, there is a possibility that the adhesion between the two becomes insufficient. In this golf ball 2, since the reinforcing layer 8 is interposed between the mid layer 6 and the cover 10, the mid layer 6 and the cover 10 are firmly adhered to each other through the reinforcing layer 8.

  Other resins may be used for the cover 10 together with the ionomer resin. Examples of other resins include styrene block-containing thermoplastic elastomers, thermoplastic polyurethane elastomers, thermoplastic polyester elastomers, thermoplastic polyamide elastomers, and thermoplastic polyolefin elastomers. When the ionomer resin and another resin are used in combination, the ratio of the ionomer resin to the total amount of the base polymer is preferably 50% by mass or more, more preferably 70% by mass or more, and particularly preferably 90% by mass or more.

  If necessary, the cover 10 includes a colorant such as titanium dioxide, a filler such as barium sulfate, a dispersant, an antioxidant, an ultraviolet absorber, a light stabilizer, a fluorescent agent, a fluorescent whitening agent, and the like. Appropriate amount is blended. For the purpose of adjusting the specific gravity, the cover 10 may be mixed with a powder of a high specific gravity metal such as tungsten or molybdenum.

  The cover 10 has a hardness Hc of 55 or more. The cover 10 having a hardness Hc of 55 or more contributes to resilience performance. In this respect, the hardness Hc is more preferably equal to or greater than 56, and particularly preferably equal to or greater than 57. From the viewpoint of soft feel at impact, the hardness Hc is preferably 65 or less, and more preferably 64 or less.

  The cover 10 has a thickness Tc of 1.2 mm or less. This cover 10 is very thin. By adopting the thin cover 10, a large launch angle can be obtained when hit with a golf club. A large launch angle contributes to a large flight distance. Furthermore, by adopting the thin cover 10, the adverse effect of the cover 10 on the feel at impact is suppressed. In this respect, the thickness Tc is more preferably equal to or less than 1.0 mm, further preferably equal to or less than 0.8 mm, and particularly preferably equal to or less than 0.5 mm. Although the thin cover 10 is easily damaged by repeated hits, the reinforcing layer 8 suppresses the damage in the golf ball 2. This golf ball 2 is excellent in flight performance, feel at impact and durability. In light of ease of manufacture, the thickness Tc of the cover 10 is preferably equal to or greater than 0.1 mm, and more preferably equal to or greater than 0.3 mm. The thickness Tc is measured directly under the land 14 while avoiding the dimple 12.

  The mass Wc of the cover 10 is 5.7 g or less. A large launch angle can be obtained by setting the mass Wc to 5.7 g or less. A large launch angle contributes to a large flight distance. Furthermore, when the mass Wc is set to 5.7 g or less, the adverse effect of the cover 10 on the feel at impact is suppressed. In this respect, the mass Wc is more preferably equal to or less than 5.3 g, and particularly preferably equal to or less than 4.8 g. From the viewpoint of easy manufacture, the cover 10 has a mass Wc of preferably 1.5 g or more, more preferably 1.7 g or more, and particularly preferably 1.9 g or more.

  The ratio (Wc / Hc) of the mass Wc to the hardness Hc in the cover 10 is 0.080 or less. By setting the ratio (Wc / Hc) to 0.080 or less, both a large launch angle and a large coefficient of restitution can be achieved. In this respect, the ratio (Wc / Hc) is more preferably equal to or less than 0.078, and particularly preferably equal to or less than 0.075. The ratio (Wc / Hc) is preferably 0.030 or more. By setting the ratio (Wc / Hc) to be equal to or greater than 0.030, both productivity and feel at impact can be achieved. The ratio (Wc / Hc) is an index representing the contribution angle of the cover 10 to the launch angle, the coefficient of restitution, the productivity, and the feel at impact of the golf ball 2.

  The amount of compressive deformation of the golf ball 2 is preferably 2.0 mm or greater and 4.5 mm or less. The golf ball 2 having a compression deformation amount of 2.0 mm or more is excellent in feel at impact. In this respect, the amount of compressive deformation is more preferably equal to or greater than 2.2 mm, and particularly preferably equal to or greater than 2.3 mm. The golf ball 2 having a compression deformation amount of 4.5 mm or less is excellent in resilience performance. In this respect, the amount of compressive deformation is more preferably equal to or less than 4.3 mm, and particularly preferably equal to or less than 4.0 mm. The amount of compressive deformation of the golf ball 2 is measured according to the method for measuring the amount of compressive deformation of the core 4 described above.

  Hereinafter, the effects of the present invention will be clarified by examples. However, the present invention should not be construed in a limited manner based on the description of the examples.

[Example 1]
100 parts by mass of high-cis polybutadiene (trade name “BR-730” from JSR), 25 parts by mass of zinc acrylate, 10 parts by mass of zinc oxide, an appropriate amount of barium sulfate, 0.5 parts by mass of diphenyl disulfide (Sumitomo Seimitsu Co., Ltd.) and 0.8 part by mass of dicumyl peroxide (Nippon Yushi Co., Ltd.) were kneaded to obtain a type x rubber composition. This rubber composition was put into a mold composed of an upper mold and a lower mold each having a hemispherical cavity, and heated at a temperature of 170 ° C. for 20 minutes to obtain a core having a diameter of 39.2 mm.

  A resin composition of type b shown in Table 1 below was obtained using a twin screw extruder having a screw diameter of 45 mm, a screw rotation speed of 200 rpm, and an L / D of 35. The temperature in the die of the resin composition at the time of extrusion was 180 ° C. to 230 ° C. This resin composition was coated around the core by an injection molding method to obtain an intermediate layer. The intermediate layer had a thickness Tm of 1.0 mm and a hardness Hm of 42.

  100 parts by mass of a carboxyl group-containing polyurethane aqueous solution (trade name “W-615” manufactured by Mitsui Takeda Chemical Co., Ltd.) and 10 parts by mass of a polycarbodiimide aqueous dispersion (the above-mentioned product name “carbodilite E-03A”) were mixed. . In this carboxyl group-containing polyurethane aqueous solution, the acid value is 9 mgKOH / g, and the solid content is 35% by mass. The carbodiimide equivalent in this polycarbodiimide aqueous dispersion is 365, and the solid content is 40% by mass. This mixed solution was applied to the intermediate layer with a spray gun to obtain a reinforcing layer having a thickness of 0.008 mm.

  With the above twin screw extruder, a resin composition of type e shown in Table 2 below was obtained. A half shell was obtained from this resin composition by compression molding. The two half shells cover the sphere consisting of the core, intermediate layer, and reinforcing layer, and both are put into a mold consisting of an upper die and a lower die having a hemispherical cavity, and a cover is obtained by compression molding. It was. The cover thickness Tc was 0.8 mm. A paint layer was formed around the cover to obtain a golf ball of Example 1. The golf ball had a diameter of 42.8 mm.

[Examples 3 to 4]
Golf balls of Examples 3 to 4 were obtained in the same manner as in Example 1 except that the diameter of the core and the thickness of the intermediate layer were as shown in Table 3 below.

[Examples 2, 5 and 6 and Comparative Example 1]
Golf balls of Examples 2, 5 and 6 and Comparative Example 1 were obtained in the same manner as in Example 1 except that the resin composition type of the intermediate layer was as shown in Table 3 below. Details of the resin composition are shown in Table 2 below.

[Comparative Example 2]
A golf ball of Comparative Example 2 was obtained in the same manner as in Example 1 except that the type of the resin composition of the cover was as shown in Table 4 below. Details of the resin composition are shown in Table 2 below.

[Examples 7 to 8 and Comparative Example 3]
Golf balls of Examples 7 to 8 were obtained in the same manner as in Example 1 except that the diameter of the core and the thickness of the cover were as shown in Table 4 below. A golf ball of Comparative Example 3 was obtained in the same manner as in Example 1 except that the type and diameter of the core rubber composition and the thickness of the cover were as shown in Table 4 below. Details of the rubber composition are shown in Table 1 below.

[Example 9]
Example 9 Got a golf ball. This coating composition was prepared by mixing 100 parts by weight of the main agent and 100 parts by weight of the curing agent. The main agent contains 30% by mass of a bisphenol A type epoxy resin and 70% by mass of a solvent. The curing agent contains 40% by weight modified polyamidoamine, 5% by weight titanium dioxide, and 55% by weight solvent.

[Comparative Example 4]
A golf ball of Comparative Example 4 was obtained in the same manner as in Example 1 except that the reinforcing layer was not provided.

[Examples 10 to 11]
Golf balls of Examples 10 to 11 were obtained in the same manner as in Example 1 except that the specifications of the core, intermediate layer and cover were as shown in Table 4 below.

[Measurement of compression deformation]
The amount of compressive deformation of the golf ball was measured by the same method as that for measuring the amount of compressive deformation of the core. The results are shown in Tables 3 and 4 below.

[Durability evaluation]
A driver with a metal head was attached to a swing machine manufactured by Tsurtemper. Set the machine conditions so that the head speed is 45 m / sec, hit the golf ball,
It collided with the collision plate. The number of hits until the golf ball was destroyed was counted, and an average value for six golf balls was calculated. The results are shown in Tables 3 and 4 below as indices when the value of Comparative Example 4 is 100.

[Measurement of flight distance]
A driver with a metal head was attached to the swing machine. The machine conditions were set so that the head speed was 45 m / sec, a golf ball was hit, and the distance from the launch point to the rest point was measured. The average values of 10 measurements are shown in Tables 3 and 4 below.

[Evaluation of feel at impact]
The golfer was hit with a golf ball with a driver, and the hit feeling was graded from “A” to “D”.
A: Extremely good B: Good C: Somewhat bad D: Bad This result is shown in Table 3 and Table 4 below.

  As is apparent from Tables 3 and 4, the golf balls of the examples are excellent in all of durability, flight performance, and feel at impact. From this evaluation result, the superiority of the present invention is clear.

  The golf ball according to the present invention can be used for playing on a golf course or practice in a driving range.

2 ... Golf ball 4 ... Core 6 ... Intermediate layer 8 ... Reinforcement layer 10 ... Cover 12 ... Dimple 14 ... Land

Claims (8)

A spherical core, an intermediate layer located outside the core, a reinforcing layer located outside the intermediate layer, and a cover located outside the reinforcing layer,
The diameter of this core is 39.2 mm or more,
The intermediate layer has a hardness Hm measured with a Shore D hardness tester of 54 or less,
The main component of the base polymer of this cover is an ionomer resin,
The cover has a hardness Hc measured by a Shore D hardness tester of 55 or more,
The weight Wc of this cover is 1.5 g or more and 5.7 g or less,
A golf ball having a ratio of a mass Wc to a hardness Hc (Wc / Hc) of the cover of 0.080 or less.   2. The golf ball according to claim 1, wherein the base layer polymer of the intermediate layer includes 10% by mass or more and 60% by mass or less of a styrene block-containing thermoplastic elastomer and 40% by mass or more and 90% by mass or less of an ionomer resin. .   The golf ball according to claim 1, wherein the base polymer of the cover includes a styrene block-containing thermoplastic elastomer.   The golf ball according to claim 1, wherein the cover has a thickness Tc of 1.2 mm or less.   The golf ball according to claim 1, wherein a thickness Tm of the intermediate layer is not less than 0.5 mm and not more than 1.6 mm.   The golf ball according to claim 1, wherein the reinforcing layer is made of a water-based adhesive.   The golf ball according to claim 6, wherein the base polymer of the aqueous adhesive is a reaction product of a carboxyl group-containing polyurethane and polycarbodiimide.   The golf ball according to claim 1, wherein the reinforcing layer has a thickness of 0.003 mm or more and 0.050 mm or less.

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