JP5620261B2 - Golf ball - Google Patents

Description

  The present invention relates to a golf ball. Specifically, the present invention relates to a multi-piece golf ball having a center, an envelope layer, an intermediate layer, and a cover.

  A golfer's greatest demand for a golf ball is flight performance. Golfers place importance on flight performance in shots with drivers and long irons. The flight performance correlates with the resilience performance of the golf ball. When a golf ball excellent in resilience performance is hit, it flies at a high speed and a large flight distance is achieved.

In order to achieve a large flight distance, an appropriate ballistic height is required. The ballistic height depends on the spin speed and launch angle. A golf ball that achieves a high trajectory with a high spin rate has insufficient flight distance. A golf ball that achieves a high trajectory with a large launch angle can provide a large flight distance. By adopting an outer-hard / inner-soft core,
Small spin speeds and large launch angles can be achieved.

  From the viewpoint of achieving various performances, golf balls having a multilayer structure have been proposed. Japanese Patent Application Laid-Open No. 9-56848 discloses a golf ball including a core, an inner cover, and an outer cover. This core consists of a core and an envelope layer.

  Japanese Patent Application Laid-Open No. 10-328326 discloses a golf ball having an inner core, an envelope layer, an inner cover and an outer cover.

  Japanese Patent Application Laid-Open No. 2001-17575 discloses a golf ball including a core, an envelope layer, an intermediate layer, and a cover.

  Japanese Patent Laid-Open No. 2002-272880 discloses a golf ball having a core and a cover. This core consists of a center and an outer core layer. The cover includes an inner cover layer and an outer cover layer.

  Japanese Patent Application Laid-Open No. 2003-205052 discloses a golf ball including a center, an intermediate layer, and a cover.

  Japanese Patent Application Laid-Open No. 2004-130072 discloses a golf ball having a core and a cover. This core has a three-layer structure.

  Japanese Patent Application Laid-Open No. 2006-289065 discloses a golf ball having a core and a cover. This core consists of an inner layer and an outer layer.

JP-A-9-56848 Japanese Patent Laid-Open No. 10-328326 JP 2001-17575 A JP 2002-272880 A JP 2003-205052 A Japanese Patent Laid-Open No. 2004-130072 JP 2006-289065 A

  Middle iron shots are primarily intended to carry golf balls on the putting green. Even in this middle iron shot, a golf ball having a large flight distance is advantageous, like a driver shot and a long iron shot.

  The loft angle of the middle iron is larger than that of the long iron. Middle iron shots have a higher spin rate than long iron shots. The middle iron shot has a high trajectory. The middle iron shot trajectory is susceptible to wind. In particular, in the case of headwind, the flight distance is greatly impaired. A golf ball that is less susceptible to wind in middle iron shots is desired.

  Golfers also place importance on the spin performance of golf balls. If the backspin rate is high, the run is small. For golfers, a golf ball that is subject to backspin is likely to be stationary at a target point. When the side spin rate is high, the golf ball tends to bend. For golfers, golf balls that are susceptible to side spin tend to bend intentionally. A golf ball that is easily spun has excellent control performance. Advanced golfers place particular importance on control performance in shots with short irons.

  An object of the present invention is to provide a golf ball having excellent flight performance when hit with a middle iron. A further object of the present invention is to provide a golf ball having excellent control performance when hit with a short iron.

  The golf ball according to the present invention includes a core, an intermediate layer located outside the core, and a cover located outside the intermediate layer. The core has a center and an envelope layer located outside the center. The ratio of the core volume Ve to the volume of the phantom sphere of the golf ball is 76% or more. The ratio (Co / Do) of the center compressive deformation amount Co measured under the condition that the initial load is 98 N and the final load is 294 N, and the diameter Do of the center is 0.085 or more and 0.130 or less. . The ratio (Ce / De) of the core compressive deformation amount Ce measured under the conditions that the initial load is 98 N and the final load is 294 N is 0.015 or more and 0.020 or less. .

  Preferably, the JIS-C hardness Hc of the cover is smaller than the JIS-C hardness Ho of the center of the center.

  Preferably, the ratio (Vo / Ve) between the center volume Vo and the core volume Ve is 0.01 or more and 0.13 or less.

  Preferably, the cover has a JIS-C hardness Hc of 65 or less. Preferably, the cover has a thickness of 0.8 mm or less.

  Preferably, the intermediate layer has a JIS-C hardness Hm of 90 or more. Preferably, the thickness of the intermediate layer is 1.5 mm or less.

The cover may be made of a resin composition. Preferably, the shear loss elastic modulus G ″ of this resin composition measured under conditions where the excitation frequency is 10 Hz and the temperature is 0 ° C. is 1.95 × 10 ⁷ Pa or less. The ratio (E ″ / G ″) of the tensile loss elastic modulus E ″ of the resin composition measured under the conditions where the vibration frequency is 10 Hz and the temperature is 0 ° C. to the shear loss elastic modulus G ″ is 1 .76 or more.

  The cover may be made of a resin composition. Preferably, the main component of the base material of this resin composition is thermoplastic polyurethane. Preferably, the polyol component of the thermoplastic polyurethane is polytetramethylene ether glycol having a number average molecular weight of 1500 or less.

  The golf ball according to the present invention has a large ratio (Co / Do) and a small ratio (Ce / De), so that spin is suppressed in a middle iron shot. Energy loss occurs in a core having a large ratio (Co / Do) and a small ratio (Ce / De). The golf ball according to the present invention has a large diameter. The large diameter of the core compensates for energy loss. This golf ball is excellent in flight performance in a middle iron shot. This golf ball is difficult to hop on a middle iron shot under a headwind condition. This golf ball has excellent flight performance under headwind conditions. Since this golf ball has a small JIS-C hardness Hc of the cover, even if the ratio (Co / Do) is large and the ratio (Ce / De) is small, sufficient spin is generated in a short iron shot. This golf ball is excellent in control performance in a short iron shot.

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.

  The golf ball 2 shown in FIG. 1 includes a spherical core 4, an intermediate layer 6 located outside the core 4, and a cover 8 located outside the intermediate layer 6. The core 4 includes a spherical center 10 and an envelope layer 12 positioned outside the center 10. A large number of dimples 14 are formed on the surface of the cover 8. A portion of the surface of the golf ball 2 other than the dimples 14 is a land 16. The golf ball 2 includes a paint layer and a mark layer on the outside of the cover 8, but these layers are not shown.

  The golf ball 2 preferably has a diameter of 40 mm or greater and 45 mm or less. 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 preferably 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.

  Preferably, the center 10 is obtained by crosslinking the 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 ratio of the amount of polybutadiene to the total amount of the base rubber is preferably 50% by mass or more, and more preferably 80% by mass or more. The ratio of cis-1,4 bonds in the polybutadiene is preferably 40% or more, and more preferably 80% or more.

  The rubber composition of the center 10 includes a co-crosslinking agent. High repulsion of the center 10 is achieved by the co-crosslinking agent. 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. From the viewpoint of the resilience performance of the golf ball 2, zinc acrylate and zinc methacrylate are preferable.

  In light of resilience performance and durability of the golf ball 2, the amount of the co-crosslinking agent is preferably 10 parts by mass or more, more preferably 13 parts by mass or more, and particularly preferably 15 parts by mass or more with respect to 100 parts by mass of the base rubber. preferable. This amount is preferably 30 parts by mass or less, more preferably 25 parts by mass or less, and particularly preferably 22 parts by mass or less from the viewpoint of spin suppression in the middle iron shot.

  An α, β-unsaturated carboxylic acid having 2 to 8 carbon atoms and a metal oxide may be blended with the rubber composition. Both react in the rubber composition to obtain a salt. This salt functions as a co-crosslinking agent. 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 releasability, magnesium oxide is particularly preferable.

  Preferably, the rubber composition of the center 10 includes an organic peroxide together with a co-crosslinking agent. The organic peroxide functions as a crosslinking initiator. The organic peroxide contributes to the resilience performance of the golf ball 2. 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. From the viewpoint of versatility, dicumyl peroxide is preferable.

  In light of resilience performance and durability of the golf ball 2, the amount of the organic peroxide is preferably 0.1 parts by mass or more, more preferably 0.2 parts by mass or more, based on 100 parts by mass of the base rubber. .3 parts by mass or more is particularly preferable. From the viewpoint of spin suppression in the middle iron shot, the amount of the organic peroxide is preferably 1.5 parts by mass or less, more preferably 1.0 part by mass or less, based on 100 parts by mass of the base rubber, 0.8 Part by mass or less is particularly preferable.

  The rubber composition of the center 10 may contain an organic sulfur compound. Preferred organic sulfur compounds include diphenyl disulfide, bis (4-chlorophenyl) disulfide, bis (3-chlorophenyl) disulfide, bis (4-bromophenyl) disulfide, bis (3-bromophenyl) disulfide, and bis (4-fluorophenyl). Monosubstituted compounds such as disulfide, bis (4-iodophenyl) disulfide and bis (4-cyanophenyl) disulfide; bis (2,5-dichlorophenyl) disulfide, bis (3,5-dichlorophenyl) disulfide, bis (2, 6-dichlorophenyl) disulfide, bis (2,5-dibromophenyl) disulfide, bis (3,5-dibromophenyl) disulfide, bis (2-chloro-5-bromophenyl) disulfide and bis (2-cyano-5-bromide) Disubstituted compounds such as phenyl) disulfide; trisubstituted compounds such as bis (2,4,6-trichlorophenyl) disulfide and bis (2-cyano-4-chloro-6-bromophenyl) disulfide; Tetra substituents such as 3,5,6-tetrachlorophenyl) disulfide; and bis (2,3,4,5,6-pentachlorophenyl) disulfide and bis (2,3,4,5,6-pentabromophenyl) ) Examples of penta-substituted compounds such as disulfides. Organic sulfur compounds contribute to resilience performance. Particularly preferred organic sulfur compounds are diphenyl disulfide and bis (pentabromophenyl) disulfide.

  In light of resilience performance and durability of the golf ball 2, the amount of the organic sulfur compound is preferably equal to or greater than 0.1 parts by weight and more preferably equal to or greater than 0.2 parts by weight with respect to 100 parts by weight of the base rubber. From the viewpoint of spin suppression in the middle iron shot, the amount of the organic sulfur compound is preferably 1.5 parts by mass or less, more preferably 1.0 part by mass or less, and 100 parts by mass with respect to 100 parts by mass of the base rubber. Part or less is particularly preferable.

  The center 10 may be blended with a filler for the purpose of adjusting specific gravity and the like. Examples of suitable fillers include zinc oxide, barium sulfate, calcium carbonate, and magnesium carbonate. The amount of the filler is appropriately determined so that the intended specific gravity of the center 10 is achieved. A particularly preferred filler is zinc oxide. Zinc oxide functions not only as a specific gravity adjusting role but also as a crosslinking aid.

  An anti-aging agent, a colorant, a plasticizer, a dispersant, sulfur, a vulcanization accelerator, and the like are added to the rubber composition of the center 10 as necessary. Crosslinked rubber powder or synthetic resin powder may be dispersed in the rubber composition.

  In light of resilience performance, the center 10 has a center hardness Ho of preferably 40 or greater, more preferably 50 or greater, and particularly preferably 55 or greater. From the viewpoint of spin suppression, the center hardness Ho is preferably 80 or less, more preferably 75 or less, and particularly preferably 70 or less. The center hardness Ho is measured by pressing a JIS-C type hardness meter against the center point of the cut surface of the hemisphere obtained by cutting the golf ball 2. For the measurement, an automatic rubber hardness measuring machine (trade name “P1” by Kobunshi Keiki Co., Ltd.) equipped with this hardness meter is used.

  The hardness of the center 10 gradually increases from the center point toward the surface. The surface hardness of the center 10 is greater than the center hardness Ho.

  The diameter Do of the center 10 is preferably 10 mm or greater and 23 mm or less. The center 10 having a diameter Do of 10 mm or more can suppress spin in the middle iron shot. In this respect, the diameter Do is more preferably 12 mm or more, and particularly preferably 13 mm or more. The envelope layer 12 having a sufficiently large thickness can be formed by the center 10 having a diameter Do of 23 mm or less. In this respect, the diameter Do is more preferably 21 mm or less, and particularly preferably 20 mm or less.

The volume Vo of the center 10 is preferably 524 mm ³ or more and 6371 mm ³ or less. The center 10 having a volume Vo of 524 mm ³ or more can suppress spin in the middle iron shot. In this respect, the volume Vo is more preferably 905 mm ³ or more, and particularly preferably 1150 mm ³ or more. The envelope layer 12 having a sufficiently large thickness can be formed by the center 10 having a volume Vo of 6371 mm ³ or less. In this respect, the volume Vo is more preferably 4849Mm ³ or less, 4189Mm ³ or less is particularly preferred.

  The amount of compressive deformation Co of the center 10 is preferably 1.2 mm or greater and 2.4 mm or less. An excellent feel at impact can be achieved by the center 10 having the amount of compressive deformation Co of 1.2 mm or more. The center 10 further suppresses the spin on the middle iron shot. From these viewpoints, the amount of compressive deformation Co is more preferably 1.3 mm or more, and particularly preferably 1.4 mm or more. Excellent resilience performance can be achieved by the center 10 having a compression deformation amount Co of 2.4 mm or less. In this respect, the amount of compressive deformation Co is more preferably equal to or less than 2.3 mm, and particularly preferably equal to or less than 2.2 mm.

  In measurement of the amount of compressive deformation, a sphere (center 10, core 4, golf ball 2, etc.) to be measured is placed on a metal rigid plate. A metal cylinder descends toward this sphere. The sphere sandwiched between the bottom surface of the cylinder and the rigid plate is deformed. The moving distance of the cylinder from the state in which the initial load of 98N is applied to the sphere to the state in which the final load of 294N is applied is measured.

  The envelope layer 12 is obtained by crosslinking the 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 ratio of the amount of polybutadiene to the total amount of the base rubber is preferably 50% by mass or more, and more preferably 80% by mass or more. The ratio of cis-1,4 bonds in the polybutadiene is preferably 40% or more, and more preferably 80% or more.

  For crosslinking of the envelope layer 12, a co-crosslinking agent is preferably 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. From the viewpoint of resilience performance, zinc acrylate and zinc methacrylate are particularly preferred.

  In light of the resilience performance of the golf ball 2, the amount of the co-crosslinking agent is preferably 20 parts by mass or more and particularly preferably 25 parts by mass or more with respect to 100 parts by mass of the base rubber. In light of soft feel at impact, the amount of the co-crosslinking agent is preferably 60 parts by mass or less, more preferably 50 parts by mass or less, and particularly preferably 45 parts by mass or less with respect to 100 parts by mass of the base rubber.

  Preferably, the rubber composition of the envelope layer 12 includes an organic peroxide together with a co-crosslinking agent. The organic peroxide functions as a crosslinking initiator. The organic peroxide contributes to the resilience performance of the golf ball 2. 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. From the viewpoint of versatility, dicumyl peroxide is preferable.

  In light of the resilience performance of the golf ball 2, the amount of the organic peroxide is preferably equal to or greater than 0.1 parts by weight, more preferably equal to or greater than 0.3 parts by weight, based on 100 parts by weight of the base rubber. Part or more is particularly preferable. From the viewpoint of soft feel at impact, the amount of the organic peroxide is preferably 2.0 parts by mass or less, more preferably 1.5 parts by mass or less, and 1.0 part by mass or less with respect to 100 parts by mass of the base rubber. Is particularly preferred.

  Preferably, the rubber composition of the envelope layer 12 includes an organic sulfur compound. The organic sulfur compounds described above with respect to the center 10 can be used for the envelope layer 12. In light of the resilience performance of the golf ball 2, the amount of the organic sulfur compound is preferably equal to or greater than 0.1 parts by weight and more preferably equal to or greater than 0.2 parts by weight with respect to 100 parts by weight of the base rubber. From the viewpoint of soft feel at impact, the amount of the organic sulfur compound is preferably 1.5 parts by mass or less, more preferably 1.0 part by mass or less, and 0.8 part by mass or less with respect to 100 parts by mass of the base rubber. Particularly preferred.

  A filler may be added to the envelope layer 12 for the purpose of adjusting specific gravity and the like. Examples of 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 amount of the filler is appropriately determined so that the intended specific gravity of the envelope layer 12 is achieved. A particularly preferred filler is zinc oxide. Zinc oxide functions not only as a specific gravity adjusting role but also as a crosslinking aid. In the envelope layer 12, various additives such as sulfur, an anti-aging agent, a colorant, a plasticizer, and a dispersant are blended in appropriate amounts as necessary. The envelope layer 12 may be blended with a crosslinked rubber powder or a synthetic resin powder.

  In forming the envelope layer 12, the center 10 is covered with two half shells in an uncrosslinked state or a semi-crosslinked state. This half shell is pressurized and heated. A crosslinking reaction occurs by heating, and the envelope layer 12 is completed. The crosslinking temperature is usually 140 ° C. or higher and 180 ° C. or lower. The crosslinking time of the envelope layer 12 is usually 10 minutes or more and 60 minutes or less.

  In the envelope layer 12, the hardness gradually increases from the innermost to the surface. In light of resilience performance, the hardness He of the surface of the envelope layer 12 (that is, the surface of the core 4) is preferably 70 or greater, more preferably 80 or greater, and particularly preferably 84 or greater. In light of feel at impact, the hardness He is preferably equal to or less than 95, more preferably equal to or less than 90, and particularly preferably equal to or less than 88. The hardness He is measured by pressing a JIS-C type hardness meter against the surface of the core 4. For the measurement, an automatic rubber hardness measuring machine (trade name “P1” by Kobunshi Keiki Co., Ltd.) equipped with this hardness meter is used.

  The thickness of the envelope layer 12 is preferably 8 mm or greater and 18 mm or less. The envelope layer 12 having a thickness of 8 mm or more can contribute to the resilience performance of the golf ball 2. In this respect, the thickness is more preferably equal to or greater than 9 mm, and particularly preferably equal to or greater than 10 mm. A center 10 having a large diameter can be formed by the envelope layer 12 having a thickness of 18 mm or less. The center 10 having a large diameter can suppress spin in the middle iron shot. In this respect, the thickness is more preferably equal to or less than 16 mm, and particularly preferably equal to or less than 15 mm.

  The outer diameter De of the core 4 is preferably 38.0 mm or more and 41.0 mm. The core 4 having an outer diameter De of 38.0 mm or more can contribute to the resilience performance of the golf ball 2. In this respect, the outer diameter De is particularly preferably 39.0 mm or more. The core 4 having the outer diameter De of 41.0 mm or more can form the intermediate layer 6 and the cover 8 having a sufficiently large thickness. In this respect, the outer diameter De is particularly preferably 40.5 mm or less.

The volume Ve of the core 4 is preferably 28700 mm ³ or more and 36100 mm ³ or less. The core 4 having a volume Ve of 28700 mm ³ or more can contribute to the resilience performance of the golf ball 2. In this respect, the volume Ve is particularly preferably 31100 mm ³ or more. The core 4 having a volume Ve of 36100 mm ³ or less can form the intermediate layer 6 and the cover 8 having a sufficiently large thickness. In this respect, the volume Ve is particularly preferably equal to or less than 34700 mm ³ .

  The ratio Pv of the volume Ve of the core 4 to the volume Vc of the phantom sphere of the golf ball 2 is preferably 76% or more. This core 4 is large. With the core 4, the excellent resilience performance of the golf ball 2 can be achieved. From this viewpoint, the ratio Pv is more preferably 79% or more, and particularly preferably 80% or more. The ratio Pv is preferably 85% or less. The surface of the phantom sphere is the surface of the golf ball 2 when it is assumed that the dimple 14 does not exist.

  The amount of compressive deformation Ce of the core 4 is preferably 0.4 mm or greater and 1.0 mm or less. An excellent shot feeling of the golf ball 2 can be achieved by the core 4 having the compression deformation amount Ce of 0.4 mm or more. In this respect, the amount of compressive deformation Ce is more preferably equal to or greater than 0.5 mm, and particularly preferably equal to or greater than 0.6 mm. Due to the center 10 having the amount of compressive deformation Ce of 1.0 mm or less, the excellent resilience performance of the golf ball 2 can be achieved. In this respect, the amount of compressive deformation Ce is more preferably equal to or less than 0.9 mm, and particularly preferably equal to or less than 0.8 mm.

  From the viewpoint of suppressing spin in the middle iron shot, the difference (He−Ho) between the surface hardness He of the core 4 and the center hardness Ho of the center 10 is preferably 15 or more, more preferably 18 or more, and particularly preferably 20 or more. . From the viewpoint of easy production and the resilience performance of the core 4, the difference (He-Ho) is preferably 30 or less, particularly preferably 26 or less.

  The ratio (Vo / Ve) between the volume Vo of the center 10 and the volume Ve of the core 4 is preferably 0.01 or more and 0.13 or less. In the golf ball 2 having the ratio (Vo / Ve) of 0.01 or more, the spin on the middle iron shot is suppressed. In this respect, the ratio (Vo / Ve) is more preferably equal to or greater than 0.03 and particularly preferably equal to or greater than 0.06. The golf ball 2 having a ratio (Vo / Ve) of 0.13 or less is excellent in resilience performance and durability. From this viewpoint, the ratio (Vo / Ve) is particularly preferably 0.10 or less.

  The ratio (Co / Do) between the compression deformation amount Co of the center 10 and the diameter Do of the center 10 measured under the condition that the initial load is 98 N and the final load is 294 N is 0.085 or more and 0.130 or less. It is. This ratio (Co / Do) is large. The ratio (Ce / De) between the compression deformation amount Ce of the core 4 and the diameter De of the core 4 measured under the conditions that the initial load is 98 N and the final load is 294 N is 0.015 or more and 0.020 or less. It is. This ratio (Ce / De) is small. In the golf ball 2 having a large ratio (Co / Do) and a small ratio (Ce / De), spin on a middle iron shot is suppressed. From the viewpoint of spin suppression, the ratio (Co / Do) is more preferably 0.086 or more, and particularly preferably 0.087 or more. In light of resilience performance and durability, the ratio (Co / Do) is more preferably equal to or less than 0.129, and particularly preferably equal to or less than 0.128. In light of feel at impact, the ratio (Ce / De) is particularly preferably equal to or greater than 0.016. In light of resilience performance and durability, the ratio (Ce / De) is particularly preferably equal to or less than 0.019.

  A resin composition is suitably used for the mid layer 6. Examples of the base polymer of the resin composition include ionomer resins, styrene block-containing thermoplastic elastomers, thermoplastic polyester elastomers, thermoplastic polyamide elastomers, and thermoplastic polyolefin elastomers.

  A particularly preferred base polymer is an ionomer resin. The ionomer resin is highly elastic. As will be described later, the cover 8 of the golf ball 2 is thin and soft. Therefore, when the golf ball 2 is hit with a driver, the mid layer 6 is greatly deformed. The intermediate layer 6 containing an ionomer resin contributes to resilience performance on driver shots. An ionomer resin and another resin may be used in combination. When used together, from the viewpoint of resilience performance, the ratio of the amount of 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 85% 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. 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. As another preferable ionomer resin, 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 is used. A polymer is mentioned. 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. 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. A particularly preferred ionomer resin is a copolymer of ethylene and acrylic acid or 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.

  As specific examples of the ionomer resin, trade names “Hi-Milan 1555”, “Hi-Milan 1557”, “Hi-Milan 1605”, “Hi-Milan 1706”, “Hi-Milan 1856”, “Hi-Milan 1856”, “Hi-Milan 1855” “High Milan AM7311”, “High Milan AM7315”, “High Milan AM7317”, “High Milan AM7318”, “High Milan AM7320”, “High Milan AM7329” and “High Milan AM7337”; DuPont's trade names “Surlin 6120”, “Surlin 6910”, “Surling 7930”, “Surling 7940”, “Surling 8140”, “Surling 8150”, “Surling 8940”, “Surling 8945”, “Surling 9120”, “Surling 9150” , “Surlin 9910”, “Surlin 9945”, “Surlin AD8546”, “HPF1000” and “HPF2000”; And “IOTEK8030”.

  Two or more ionomer resins may be used in combination with the mid layer 6. An ionomer resin neutralized with a monovalent metal ion and an ionomer resin neutralized with a divalent metal ion may be used in combination.

  The intermediate layer 6 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 brightening agent, and the like as necessary. An appropriate amount is blended. For the formation of the intermediate layer 6, known methods such as injection molding and compression molding can be employed.

  The mid layer 6 preferably has a hardness Hm of 90 or more. Due to the mid layer 6 having a hardness Hm of 90 or more, the excellent resilience performance of the golf ball 2 is achieved. With the intermediate layer 6 having a hardness Hm of 90 or more, an outer-hard / inner-soft structure of a sphere including the core 4 and the intermediate layer 6 can be achieved. A sphere having an outer-hard / inner-soft structure suppresses spin on a middle iron shot. From these viewpoints, the hardness Hm is particularly preferably 92 or more. In light of feel at impact, the hardness Hm is preferably equal to or less than 98, and particularly preferably equal to or less than 97. From the viewpoint of spin suppression, it is preferable that the hardness Hm of the intermediate layer 6 is larger than the surface hardness He of the core 4 and the surface hardness He of the core 4 is larger than the surface hardness of the center 10.

  The hardness Hm is measured by a JIS-C spring type hardness meter attached to an automatic rubber hardness measuring device (trade name “P1” of Kobunshi Keiki Co., Ltd.). For the measurement, a slab having a thickness of about 2 mm formed by hot pressing is used. A slab stored for 2 weeks at a temperature of 23 ° C. is used for the measurement. At the time of measurement, three slabs are overlaid. A slab made of the same resin composition as that of the mid layer 6 is used for the measurement.

  In light of the resilience performance of the golf ball 2, the mid layer 6 has a thickness Tm of preferably 0.3 mm or greater and particularly preferably 0.5 mm or greater. In light of feel at impact, the thickness is preferably equal to or less than 1.5 mm, more preferably equal to or less than 1.2 mm, and particularly preferably equal to or less than 1.0 mm.

  In light of the feel at impact of the golf ball 2, the amount of compressive deformation Cm of the sphere including the core 4 and the mid layer 6 is preferably equal to or greater than 0.3 mm, and particularly preferably equal to or greater than 0.5 mm. In light of the resilience performance of the golf ball 2, the amount of compressive deformation Cm is preferably equal to or less than 1.2 mm, and particularly preferably equal to or less than 0.9 mm.

  The cover 8 is made of a resin composition. Examples of the base polymer of this resin composition include polyurethane, polyester, polyamide, polyolefin, polystyrene, and ionomer resin. In particular, polyurethane is preferred. Polyurethane is soft. When the golf ball 2 having the cover 8 made of polyurethane is hit with a short iron, the spin rate is high. The cover 8 made of polyurethane contributes to control performance in a shot with a short iron. The polyurethane also contributes to the scratch resistance performance of the cover 8.

  When this golf ball 2 is hit with a driver, a long iron or a middle iron, the head speed is high, so that the sphere composed of the core 4 and the mid layer 6 is greatly distorted. Since this sphere has an outer-hard / inner-soft structure, the spin rate is suppressed. A large flight distance is achieved by suppressing the spin speed. When the golf ball 2 is hit with a short iron, since the head speed is low, the distortion of the ball is small. The behavior of the golf ball 2 when hit with a short iron mainly depends on the cover 8. Since the cover 8 containing polyurethane is soft, a large spin speed can be obtained. Excellent control performance is achieved due to the high spin rate. In the golf ball 2, the flight performance in a shot with a driver, a long iron and a middle iron and the control performance in a shot with a short iron are compatible.

  When the golf ball 2 is hit, the cover 8 containing polyurethane absorbs the impact. This absorption achieves a soft feel at impact. In particular, when hit with a short iron or a putter, an excellent shot feeling is achieved by the cover 8.

  The cover 8 at the time of hitting is subjected to compressive stress due to the progression of the head of the golf club. Since the face of the golf club has a loft angle, the cover 8 at the time of hitting is also subjected to shear stress. The head speed of the short iron is low, and the loft angle of the short iron is large. Therefore, when the golf ball 2 is hit with a short iron, the shear stress greatly affects the deformation behavior of the cover 8. The driver's head speed is high and the driver's loft angle is small. Therefore, when the golf ball 2 is hit with a driver, the compressive stress greatly affects the deformation behavior of the cover 8.

The shear loss elastic modulus G ″ of the cover 8 is preferably 1.95 × 10 ⁷ Pa or less. As described above, the deformation behavior of the cover 8 when hit with a short iron is strongly influenced by the shear stress. The spin speed when hit with an iron correlates with the shear loss modulus G ″. When the golf ball 2 provided with the cover 8 having the shear loss elastic modulus G ″ of 1.95 × 10 ⁷ Pa or less is hit with a short iron, the spin speed is high. In this respect, the shear loss elastic modulus G ″ is particularly preferably 1.83 × 10 ⁷ Pa or less. From the viewpoint of easy molding of the cover 8, the shear loss elastic modulus G ″ is preferably 1.00 × 10 ⁶ Pa or more, and particularly preferably 1.10 × 10 ⁶ Pa or more.

  The ratio (E ″ / G ″) of the tensile loss elastic modulus E ″ of the cover 8 to the shear loss elastic modulus G ″ is preferably 1.76 or more. As described above, the deformation behavior of the cover 8 when hit with a driver is strongly influenced by the compressive stress. The spin speed when hit with a driver correlates with the tensile loss elastic modulus E ″. The golf ball 2 provided with the cover 8 having a ratio (E ″ / G ″) of 1.76 or more was hit with the driver. The spin rate is low, and the spin rate is high when the golf ball 2 is hit with a short iron.From this viewpoint, the ratio (E ″ / G ″) is more preferably 1.86 or more. The ratio (E ″ / G ″) is preferably 6.0 or less and particularly preferably 5.5 or less from the viewpoint of easy molding of the cover 8.

The tensile loss elastic modulus E ″ is preferably 2.00 × 10 ⁷ Pa or higher, more preferably 2.20 × 10 ⁷ Pa or higher, particularly preferably 2.40 × 10 ⁷ Pa or higher. The tensile loss elastic modulus E ″ is 1.00 × 10 ⁸ Pa or less is preferable.

  The shear loss elastic modulus G ″ and the tensile loss elastic modulus E ″ can be controlled by adjusting the molecular weight of the polyol, the molecular weight of the polyisocyanate, the ratio (NCO / OH), and the like.

For the measurement of the shear loss elastic modulus G ″, a sheet having a thickness of 2 mm is obtained by press molding from a resin composition equivalent to the resin composition of the cover 8. From this sheet, a sheet having a width of 10 mm and a clamp is obtained. A sample piece having a distance of 10 mm is punched. With this test piece, the shear loss elastic modulus G ″ is measured. The measurement conditions are as follows.
Equipment: “Rheometer ARES” from TA Instruments
Measurement mode: twist (shear)
Measurement temperature: 0 ° C
Excitation frequency: 10Hz
Measurement strain: 0.1%

In order to measure the tensile loss elastic modulus E ″, a sheet having a thickness of 2 mm is obtained by press molding from a resin composition equivalent to the resin composition of the cover 8. From this sheet, a sheet having a width of 4 mm and a clamp is obtained. A sample piece having a distance of 20 mm is punched. With this test piece, the tensile loss elastic modulus E ″ is measured. The measurement conditions are as follows.
Apparatus: UBM's dynamic viscoelasticity measuring device "Rheogel-E4000"
Measurement mode: Tensile Measurement temperature: 0 ° C
Excitation frequency: 10Hz
Measurement strain: 0.1%

  The contact time between the golf ball 2 and the club is several hundred microseconds. Therefore, the frequency of deformation of the golf ball 2 at the time of hitting is several thousand Hz. On average, the golf ball 2 is hit at a temperature of approximately normal temperature (25 ° C.). Based on a general time conversion rule for polyurethane, a deformation with a frequency of several thousand Hz under an environment where the temperature is 25 ° C. corresponds to a deformation with a frequency of 10 Hz under an environment where the temperature is 0 ° C. Therefore, in the present invention, the shear loss elastic modulus G ″ and the tensile loss elastic modulus E ″ are measured under conditions where the excitation frequency is 10 Hz and the temperature is 0 ° C.

  The cover 8 may be used in combination with polyurethane and other resins. When used in combination, polyurethane is the main component of the base polymer from the viewpoint of spin performance and feel at impact. The ratio of the amount of polyurethane 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 85% by mass or more.

  For the cover 8, thermoplastic polyurethane and thermosetting polyurethane can be used. From the viewpoint of productivity, thermoplastic polyurethane is preferred. The thermoplastic polyurethane includes a polyurethane component as a hard segment and a polyester component or a polyether component as a soft segment.

  The polyurethane contains a polyol component. Polymer polyols are preferred. Specific examples of polymer polyols include polyether polyols such as polyoxyethylene glycol (PEG), polyoxypropylene glycol (PPG) and polytetramethylene ether glycol (PTMG); polyethylene adipate (PEA), polybutylene adipate Condensed polyester polyols such as (PBA) and polyhexamethylene adipate (PHMA); Lactone polyester polyols such as poly-ε-caprolactone (PCL); Polycarbonate polyols such as polyhexamethylene carbonate; and acrylic polyols It is done. Two or more polyols may be used in combination.

  In particular, polytetramethylene ether glycol is preferable. The spin speed when the golf ball 2 is hit with a short iron has a large correlation with the content of polytetramethylene ether glycol. On the other hand, the spin rate when the golf ball 2 is hit with a driver, a long iron or a middle iron has a small correlation with the content of polytetramethylene ether glycol. The golf ball 2 in which polyurethane contains an appropriate amount of polytetramethylene ether glycol is excellent in both flight performance when hit with a driver, long iron or middle iron, and control performance when hit with a short iron. .

  From the viewpoint of control performance, the number average molecular weight of the polyol is preferably 200 or more, more preferably 400 or more, and particularly preferably 650 or more. From the viewpoint of suppression of spin, this molecular weight is preferably 1500 or less, more preferably 1200 or less, and particularly preferably 850 or less.

The number average molecular weight is measured by gel permeation chromatography. The measurement conditions are as follows.
Equipment: HLC-8120GPC (Tosoh Corporation)
Eluent: Tetrahydrofuran Concentration: 0.2% by mass
Temperature: 40 ° C
Column: TSKgel SuperHM-M (Tosoh Corporation)
Sample volume: 5 microliters Flow rate: 0.5 milliliters / min
Reference material: Polystyrene (“PStQuick Kit-H” from Tosoh Corporation)

  The hydroxyl value of the polymer polyol component is preferably 94 mgKOH / g or more, particularly preferably 112 mgKOH / g or more. The hydroxyl value is preferably 561 mgKOH / g or less, particularly preferably 173 mgKOH / g or less.

As isocyanate component in polyurethane, 2,4-toluene diisocyanate, 2,6-toluene diisocyanate, mixture of 2,4-toluene diisocyanate and 2,6-toluene diisocyanate (TDI), 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 (PPDI) Aromatic polyisocyanates such as 4,4′-dicyclohexylmethane diisocyanate (H ₁₂ MDI), hydrogenated xylylene diisocyanate (H ₆ XDI) and isophorone diisocyanate (I) Alicyclic polyisocyanates such as PDI); and aliphatic polyisocyanates such as hexamethylene diisocyanate (HDI). 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, and H ₁₂ MDI is particularly preferred.

  The polyurethane may contain a chain extender as its component. Examples of chain extenders include low molecular weight polyols and low molecular weight polyamines.

  Low molecular weight polyols include diols, triols, tetraols and hexaols. Specific examples of the diol include ethylene glycol, diethylene glycol, propanediol, dipropylene glycol, butanediol, neopentyl glycol, pentanediol, hexanediol, heptanediol and octanediol. Specific examples of triols include glycerin, trimethylolpropane, and hexanetriol. Specific examples of tetraol include pentaerythritol and sorbitol. 1,4-butanediol is preferred.

  Low molecular weight polyamines include aliphatic polyamines, monocyclic aromatic polyamines and polycyclic aromatic polyamines. Specific examples of the aliphatic polyamine include ethylenediamine, propylenediamine, butylenediamine and hexamethylenediamine. Specific examples of the monocyclic aromatic polyamine include phenylenediamine, toluenediamine, dimethyltoluenediamine, dimethylthiotoluenediamine, and xylylenediamine.

  The number average molecular weight of the chain extender is preferably 30 or more, more preferably 40 or more, and particularly preferably 45 or more. The molecular weight is preferably 400 or less, more preferably 350 or less, and particularly preferably 200 or less. Low molecular weight polyols and low molecular weight polyamines used as chain extenders are low molecular weight compounds with little molecular weight distribution. Therefore, the low molecular weight polyol and the low molecular weight polyamine can be distinguished from the polymer polyol.

  The cover 8 may be formed from a composition containing a thermoplastic polyurethane and an isocyanate compound. At the time of molding of the cover 8 or after molding, the polyurethane is crosslinked by this isocyanate compound.

  If necessary, the cover 8 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.

  The cover 8 has a JIS-C hardness Hc of 65 or less. By adopting the soft cover 8, good control performance in a shot with a short iron can be achieved. In light of control performance, the hardness Hc is more preferably equal to or less than 60, still more preferably equal to or less than 55, and particularly preferably equal to or less than 50. If the hardness is too low, the flight performance on a shot with a driver is insufficient. In this respect, the hardness is preferably 20 or greater, more preferably 25 or greater, and particularly preferably 35 or greater. For the measurement of the hardness Hc, a slab made of the same resin composition as the resin composition of the cover 8 is used. The measuring method is the same as the measuring method of the hardness Hm of the mid layer 6.

  The cover 8 has a hardness Hc smaller than the center hardness Ho of the core 4. This golf ball 2 is excellent in control performance with a short iron. From the viewpoint of control performance, the difference (Ho−Hc) is preferably 5 or more, more preferably 10 or more, and particularly preferably 15 or more. The difference (Ho−Hc) is preferably 40 or less, more preferably 35 or less, and particularly preferably 30 or less.

  From the viewpoint of flight performance in a shot with a driver, the thickness of the cover 8 is preferably 0.8 mm or less, more preferably 0.6 mm or less, further preferably 0.5 mm or less, and particularly preferably 0.4 mm or less. From the viewpoint of control performance in a shot with a short iron, the thickness is preferably 0.10 mm or more, and particularly preferably 0.15 mm or more.

  For forming the cover 8, a known method such as an injection molding method or a compression molding method may be employed. When the cover 8 is molded, dimples 14 are formed by pimples formed on the cavity surface of the mold.

  In light of feel at impact, the amount of compressive deformation of the golf ball 2 is preferably equal to or greater than 0.3 mm, and particularly preferably equal to or greater than 0.5 mm. In light of resilience performance, the amount of compressive deformation is preferably 0.9 mm or less, and particularly preferably 0.7 mm or less.

  When the cover 8 is directly laminated on the intermediate layer 6, the cover 8 does not firmly adhere to the intermediate layer 6 because the material of the cover 8 is different from the material of the intermediate layer 6. The golf ball 2 preferably has an adhesive layer between the mid layer 6 and the cover 8. This adhesive layer is firmly attached to the intermediate layer 6 and is also firmly attached to the cover 8. By this adhesive layer, peeling of the cover 8 from the intermediate layer 6 is suppressed. As described above, the cover 8 of the golf ball 2 is thin. When the golf ball 2 is hit with the edge of the club face, wrinkles are likely to occur. Wrinkles are suppressed by the adhesive layer. Furthermore, the golf ball 2 is not easily damaged even if hit repeatedly. In this golf ball 2, loss of energy transmission when hit with a golf club is small. Therefore, this golf ball 2 is excellent in resilience performance.

  The adhesive layer is formed by applying an adhesive to the surface of the intermediate layer 6 and drying the adhesive. The base polymer of this adhesive is a two-component curable epoxy resin. A preferable two-pack curable epoxy resin is obtained by curing a bisphenol A type epoxy resin with a curing agent containing a polyamine compound. Since this two-pack curable epoxy resin uses a bisphenol A type epoxy resin, it is excellent in flexibility, chemical resistance, heat resistance and toughness.

  The adhesive is obtained by mixing a main agent containing a bisphenol A type epoxy resin and a solvent and a curing agent containing a polyamine compound and a solvent. Examples of the solvent in the main agent and the curing agent include organic solvents such as xylene and toluene, and water.

  Specific examples of the polyamine compound include polyamidoamine and modified products thereof. The polyamidoamine has a plurality of amino groups and one or more amide groups. This amino group can react with an epoxy group. Polyamidoamine 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 examples of the polyamine include polyethylene diamine and polyoxyalkylene diamine and derivatives thereof.

  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 weight of high-cis polybutadiene (trade name “BR-730” from JSR), 18 parts by weight of zinc acrylate, 5 parts by weight of zinc oxide, an appropriate amount of barium sulfate, 0.5 parts by weight of diphenyl disulfide and 0 parts 7 parts by mass of dicumyl peroxide was kneaded to obtain a rubber composition (3). This rubber composition (3) 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 15 minutes to obtain a center having a diameter of 18 mm.

  100 parts by weight of high-cis polybutadiene (previously referred to as “BR-730”), 35 parts by weight of zinc acrylate, 5 parts by weight of zinc oxide, appropriate amount of barium sulfate, 0.3 part by weight of bis (pentabromophenyl) disulfide And 0.9 mass part dicumyl peroxide was knead | mixed and the rubber composition (8) was obtained. A half shell was molded from this rubber composition (8). The center was covered with two half shells. The center and the half shell were both put into a mold composed of an upper mold and a lower mold each having a hemispherical cavity, and heated at a temperature of 150 ° C. for 20 minutes to obtain a core having a diameter of 40.1 mm. . An envelope layer was formed from the rubber composition (8). The amount of barium sulfate was adjusted so that the specific gravity of the envelope layer coincided with the specific gravity of the center and the ball mass was 45.4 g.

  50 parts by mass of an ionomer resin (the above-mentioned “Surlin 8945”) and 50 parts by mass of another ionomer resin (the above-mentioned “Himilan AM7329”) were kneaded by a twin-screw kneading extruder to obtain a resin composition. The core was put into a mold composed of an upper mold and a lower mold each having a hemispherical cavity. The resin composition was injected around the core by an injection molding method to form an intermediate layer. The thickness of this intermediate layer was 1.0 mm.

  An adhesive containing a main agent and a curing agent was prepared. This main agent is a water-based epoxy composition of Shinto Paint Co., Ltd. This main ingredient contains 36 parts by mass of bisphenol A type epoxy resin and 64 parts by mass of water. The epoxy equivalent of this main agent is 1405 g / eq. The curing agent is a water-based amine composition of Shinto Paint Co., Ltd. This curing agent contains 44 parts by weight of modified polyamidoamine, 50 parts by weight of water, 1 part by weight of propylene glycol and 5 parts by weight of titanium dioxide. The active hydrogen equivalent of this curing agent is 348 g / eq. This adhesive was applied to the surface of the intermediate layer with a spray gun and held at 23 ° C. for 12 hours to obtain an adhesive layer. The thickness of this adhesive layer was 0.003 mm.

  100 parts by mass of thermoplastic polyurethane elastomer and 4 parts by mass of titanium dioxide were kneaded with a biaxial kneading extruder to obtain a resin composition (A). A half shell was obtained from the resin composition (A) by compression molding. Two half shells covered a sphere composed of a core, an intermediate layer and a reinforcing layer. Both the sphere and the half shell were put into a final mold which was composed of an upper mold and a lower mold each provided with a hemispherical cavity, and had many pimples on the cavity surface. A cover was obtained by compression molding. The thickness of this cover was 0.3 mm. A dimple having a shape obtained by inverting the shape of the pimple was formed on the cover. A clear paint based on a two-component curable polyurethane was applied around the cover to obtain a golf ball of Example 1 having a diameter of 42.7 mm.

[Examples 2 to 8 and Comparative Examples 1 to 6]
Golf balls of Examples 2 to 8 and Comparative Examples 1 to 6 were obtained in the same manner as in Example 1 except that the specifications of the center, envelope layer, intermediate layer and cover were as shown in Tables 4 to 7 below. It was. Details of the rubber composition of the center are shown in Table 1 below. Details of the rubber composition of the envelope layer are shown in Table 2 below. Details of the resin composition of the cover are shown in Table 3 below.

[Shot with No. 5 Iron (I # 5)]
A No. 5 iron (trade name “SRIXON Z-TX (steel shaft)” by SRI Sports Co., Ltd.) was mounted on a golf laboratory swing machine. The golf ball was hit under the condition that the head speed was 41 m / sec. The ball speed and spin speed immediately after hitting, and the distance from the launch point to the rest point were measured. The average value (flight distance I) of the data obtained by 12 measurements is shown in Tables 4 to 7 below. During the measurement, there was almost no wind. In addition, under the same machine conditions, the distance from the launch point to the rest point was measured under headwind conditions. Average values (flight distance II) of data obtained by 12 measurements are shown in Tables 4 to 7 below.

[Shot with short iron (SW)]
A sand wedge (trade name “CG15 chrome wedge, loft angle: 58 °” by SRI Sports Co., Ltd.) was attached to the swing machine. A golf ball was hit under the condition that the head speed was 21 m / sec, and the spin speed immediately after hitting was measured. The average values of the data obtained by 12 measurements are shown in Tables 4 to 7 below. Further, the golf ball was hit with water attached to the club face and the ball, and the spin speed immediately after hitting was measured. The average values of the data obtained by 12 measurements are shown in Tables 4 to 7 below.

[Hit feel]
Ten golfers hit golf balls with sand wedges and heard the feel of the ball. The rating was based on the number of golfers who answered “good shot feel”.
A: 8 or more B: 6-7 people C: 4-5 people D: 3 or less The results are shown in Tables 4 to 7 below.

Details of the polyurethane in Table 3 are as follows.
Polyurethane # 1
BASF Japan's brand name "Elastolan XNY97A"
Polyol component: polytetramethylene ether glycol Number average molecular weight of the polyol component: 1800
Polyurethane # 2
Thermoplastic polyurethane elastomer Polyol component: Polytetramethylene ether glycol Number average molecular weight of polyol component: 1500

  As shown in Tables 4 to 7, the golf balls according to the examples are excellent in various performances. From this evaluation result, the superiority of the present invention is clear.

  The golf ball according to the present invention can be used for golf play and practice in a driving range.

2 ... Golf ball 4 ... Core 6 ... Intermediate layer 8 ... Cover 10 ... Center 12 ... Enveloping layer 14 ... Dimple 16 ... Land

Claims (10)

A core, an intermediate layer located outside the core, and a cover located outside the intermediate layer, the core having a center and an envelope layer located outside the center. A golf ball
The ratio of the volume Ve of the core to the volume of the phantom sphere of the golf ball is 76% or more,

The ratio (Co / Do) between the compression deformation amount Co of the center and the diameter Do of the center measured under the condition that the initial load is 98 N and the final load is 294 N is 0.085 or more and 0.130 or less. Yes,
The ratio (Ce / De) of the core compressive deformation amount Ce measured under the conditions that the initial load is 98 N and the final load is 294 N is 0.015 or more and 0.020 or less. A golf ball.   The golf ball according to claim 1, wherein the cover has a JIS-C hardness Hc smaller than a JIS-C hardness Ho at the center of the center.   The golf ball according to claim 2, wherein a ratio (Vo / Ve) between the center volume Vo and the core volume Ve is 0.01 to 0.13.   4. The golf ball according to claim 1, wherein the cover has a JIS-C hardness Hc of 65 or less.   The golf ball according to claim 1, wherein the cover has a thickness of 0.8 mm or less.   The golf ball according to claim 1, wherein the intermediate layer has a JIS-C hardness Hm of 90 or more.   The golf ball according to claim 1, wherein the intermediate layer has a thickness of 1.5 mm or less. The cover is made of a resin composition, the shear loss elastic modulus G ″ of the resin composition measured under the conditions where the excitation frequency is 10 Hz and the temperature is 0 ° C. is 1.95 × 10 ⁷ Pa or less. Yes,
The ratio (E ″ / G ″) of the tensile loss elastic modulus E ″ of the resin composition, measured under the conditions where the excitation frequency is 10 Hz and the temperature is 0 ° C., to the shear loss elastic modulus G ″, The golf ball according to claim 1, which is 1.76 or more.   The golf ball according to claim 1, wherein the cover is made of a resin composition, and a main component of a base material of the resin composition is thermoplastic polyurethane.   The golf ball according to claim 9, wherein the polyol component of the thermoplastic polyurethane is polytetramethylene ether glycol having a number average molecular weight of 1500 or less.

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