Golf ball

Abstract

To provide a golf ball 2 which is excellent in all of flight performance at a shot with a driver, flight performance at a shot with a middle iron, hitting feeling at a shot with the driver, and hitting feeling with a putter.SOLUTION: A golf ball 2 includes a core 4, a middle layer 6, and a cover 8. The golf ball 2 satisfies the following mathematical formulas (1) and (2). (Fw / Fwn)≤0.98 (1) (Fw / Fwn)2 / (Fp / Fpn)≤0.98 (2) In the mathematical formulas, Fw represents the maximum vertical force of the golf ball 2 measured under a first condition, Fwn represents the maximum vertical force of a standard ball measured under the first condition, Fp represents the maximum vertical force of the golf ball 2 measured under a second condition, and Fpn represents the maximum vertical force of the standard ball measured under the second condition.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] This specification discloses a golf ball having a core, an intermediate layer, and a cover.

Background Art

[0002] What concerns golf players about a golf ball is flight performance. Golf players prefer a golf ball that can achieve a long flight distance. Golf players also value the feel of hitting the ball. Generally, players prefer a soft feel of hitting the ball.

[0003] Typical golf balls have a core, an intermediate layer, and a cover. Devices related to the core, the intermediate layer, and the cover are disclosed in Japanese Patent Application Laid-Open No. 2020-171623.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] Golf players value the flight distance in a shot with a driver. Players also value the flight distance in a shot with a middle iron.

[0006] Golf players value the feel of hitting the ball in a shot with a driver. Players also value the feel of hitting the ball in putting.

[0007] What the applicant intends is to provide a golf ball that is excellent in all of the flight performance in a shot with a driver, the flight performance in a shot with a middle iron, the feel of hitting the ball in a shot with a driver, and the feel of hitting the ball in putting.

Means for Solving the Problems

[0008] A preferred golf ball includes a core, an intermediate layer positioned outside the core, and a cover positioned outside the intermediate layer, and satisfies the following mathematical formulas (1) and (2). (Fw / Fwn) ≦ 0.98 (1) (Fw / Fwn) 2 / (Fp / Fpn) ≦ 0.98 (2) In these formulas, Fw represents the maximum vertical force of the golf ball measured under the first condition described later, Fwn represents the maximum vertical force of the standard ball measured under this first condition, Fp represents the maximum vertical force of the golf ball measured under the second condition described later, and Fpn represents the maximum vertical force of the standard ball measured under this second condition.

Advantages of the Invention

[0009] This golf ball is excellent in all of the flight performance in a shot with a driver, the flight performance in a shot with a middle iron, the feel of hitting the ball in a shot with a driver, and the feel of hitting the ball in putting.

Brief Description of the Drawings

[0010]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Modes for Carrying Out the Invention

[0011] Hereinafter, preferred embodiments will be described in detail while appropriately referring to the drawings.

[0012] The golf ball 2 shown in FIG. 1 has a spherical core 4, an intermediate layer 6 located outside the core 4, a cover 8 located outside the intermediate layer 6, an inner paint layer 10 located outside the cover 8, and an outer paint layer 12 located outside the inner paint layer 10. The number of paint layers is 2. The outer paint layer 12 is the outermost paint layer. The number of paint layers may be 1 or may be 3 or more. This golf ball 2 has a plurality of dimples 14 on its surface. The portion of the surface of the golf ball 2 other than the dimples 14 is the land 16. This golf ball 2 has a mark layer (not shown) outside the cover 8.

[0013] The diameter of this golf ball 2 is preferably 40 mm or more and 45 mm or less. From the viewpoint of satisfying the standards of the United States Golf Association (USGA), the diameter is particularly preferably 42.67 mm or more. From the viewpoint of suppressing air resistance, the diameter is more preferably 44 mm or less, and particularly preferably 42.80 mm or less.

[0014] The mass of this golf ball 2 is preferably 40 g or more and 50 g or less. From the viewpoint of obtaining a large inertia, the mass is more preferably 44 g or more, and particularly preferably 45.00 g or more. From the viewpoint of satisfying the USGA standards, the mass is particularly preferably 45.93 g or less.

[0015] The core 4 is formed by crosslinking a rubber composition. Preferred base rubbers include polybutadiene, polyisoprene, styrene-butadiene copolymer, ethylene-propylene-diene copolymer, and natural rubber. From the viewpoint of the resilience performance of the core 4, polybutadiene is preferred. When polybutadiene is used in combination with other rubbers, it is preferably the main component. Specifically, the ratio of polybutadiene to all base rubbers is preferably 50% by mass or more, and particularly preferably 80% by mass or more. Polybutadiene having a cis-1,4 bond ratio of 80% or more is particularly preferred.

[0016] The rubber composition of the core 4 preferably contains a co-crosslinking agent. From the viewpoints of the durability and the resilience performance of the golf ball 2, a preferable co-crosslinking agent is a monovalent or divalent metal salt of an α,β-unsaturated carboxylic acid having 2 to 8 carbon atoms. Examples of the preferable co-crosslinking agent include zinc acrylate, magnesium acrylate, zinc methacrylate, and magnesium methacrylate. From the viewpoint of the resilience performance of the core 4, zinc acrylate and zinc methacrylate are particularly preferable.

[0017] The rubber composition may contain an α,β-unsaturated carboxylic acid having 2 to 8 carbon atoms and a metal oxide. Both react in the rubber composition to obtain a salt. This salt functions as a co-crosslinking agent. Examples of the preferable α,β-unsaturated carboxylic acid include acrylic acid and methacrylic acid. Examples of the preferable metal oxide include zinc oxide and magnesium oxide.

[0018] The amount of the co-crosslinking agent is preferably 10 parts by mass or more and 45 parts by mass or less with respect to 100 parts by mass of the base rubber. The golf ball 2 in which this amount is 10 parts by mass or more is excellent in resilience performance. From this viewpoint, this amount is more preferably 15 parts by mass or more, and particularly preferably 20 parts by mass or more. The golf ball 2 in which this amount is 45 parts by mass or less is excellent in hitting feeling. From this viewpoint, this amount is more preferably 40 parts by mass or less, and particularly preferably 35 parts by mass or less.

[0019] Preferably, the rubber composition of the core 4 contains an organic peroxide. The organic peroxide functions as a crosslinking initiator. The organic peroxide contributes to the resilience performance of the core 4. Examples of suitable organic peroxides include dicumyl peroxide, 1,1-bis(t-butylperoxy)-3,3,5-trimethylcyclohexane, 2,5-dimethyl-2,5-di(t-butylperoxy)hexane, and di-t-butyl peroxide. An organic peroxide with particularly high versatility is dicumyl peroxide.

[0020] The amount of the organic peroxide is preferably 0.1 part by mass or more and 3.0 parts by mass or less with respect to 100 parts by mass of the base rubber. The golf ball 2 in which this amount is 0.1 part by mass or more is excellent in resilience performance. From this viewpoint, this amount is more preferably 0.3 part by mass or more, and particularly preferably 0.5 part by mass or more. The golf ball 2 in which this amount is 3.0 parts by mass or less is excellent in hitting feeling. From this viewpoint, this amount is more preferably 2.5 parts by mass or less, and particularly preferably 2.0 parts by mass or less.

[0021] Preferably, the rubber composition of the core 4 contains an organic sulfur compound. The organic sulfur compound contributes to the resilience performance of the core 4. The organic sulfur compound includes naphthalenethiol-based compounds, benzenethiol-based compounds, and disulfide-based compounds.

[0022] Examples of the naphthalenethiol-based compound include 1-naphthalenethiol, 2-naphthalenethiol, 4-chloro-1-naphthalenethiol, 4-bromo-1-naphthalenethiol, 1-chloro-2-naphthalenethiol, 1-bromo-2-naphthalenethiol, 1-fluoro-2-naphthalenethiol, 1-cyano-2-naphthalenethiol, and 1-acetyl-2-naphthalenethiol.

[0023] Examples of the benzenethiol-based compound include benzenethiol, 4-chlorobenzenethiol, 3-chlorobenzenethiol, 4-bromobenzenethiol, 3-bromobenzenethiol, 4-fluorobenzenethiol, 4-iodobenzenethiol, 2,5-dichlorobenzenethiol, 3,5-dichlorobenzenethiol, 2,6-dichlorobenzenethiol, 2,5-dibromobenzenethiol, 3,5-dibromobenzenethiol, 2-chloro-5-bromobenzenethiol, 2,4,6-trichlorobenzenethiol, 2,3,4,5,6-pentachlorobenzenethiol, 2,3,4,5,6-pentafluorobenzenethiol, 4-cyanobenzenethiol, 2-cyanobenzenethiol, 4-nitrobenzenethiol, and 2-nitrobenzenethiol.

[0024] Examples of disulfide compounds include diphenyl disulfide, bis(4-chlorophenyl) disulfide, bis(3-chlorophenyl) disulfide, bis(4-bromophenyl) disulfide, bis(3-bromophenyl) disulfide, bis(4-fluorophenyl) disulfide, bis(4-iodophenyl) disulfide, 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, bis(2-cyano-5-bromophenyl) disulfide, bis(2,4,6-trichlorophenyl) disulfide, bis(2-cyano-4-chloro-6-bromophenyl) disulfide, bis(2,3,5,6-tetrachlorophenyl) disulfide, bis(2,3,4,5,6-pentachlorophenyl) disulfide, and bis(2,3,4,5,6-pentabromophenyl) disulfide.

[0025] From the viewpoint of repulsion performance, the amount of the organic sulfur compound is preferably 0.1 part by mass or more, more preferably 0.2 part by mass or more, and particularly preferably 0.3 part by mass or more with respect to 100 parts by mass of the base rubber. From the viewpoint of a soft hitting feeling, this amount is preferably 1.5 parts by mass or less, more preferably 1.0 part by mass or less, and particularly preferably 0.8 part by mass or less. Two or more organic sulfur compounds may be used in combination.

[0026] The rubber composition of the core 4 may contain a carboxylic acid or a carboxylate. The carboxylic acid and the carboxylate can contribute to the optimization of the hardness distribution of the core 4. Preferred carboxylic acids include benzoic acid. Preferred carboxylates include zinc octanoate and zinc stearate.

[0027] The rubber composition of core 4 may contain fillers for the purpose of specific gravity adjustment and the like. Preferred 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 core 4 is achieved.

[0028] The rubber composition of core 4 may contain appropriate amounts of various additives such as sulfur, anti-aging agents, coloring agents, plasticizers, and dispersants. This rubber composition may contain crosslinked rubber powder or synthetic resin powder.

[0029] The diameter D1 of core 4 is preferably 35.0 mm or more and 40.7 mm or less. The golf ball 2 having core 4 with a diameter D1 of 35.0 mm or more is excellent in repulsion performance. From this viewpoint, the diameter D1 is more preferably 37.0 mm or more, and particularly preferably 38.0 mm or more. The golf ball 2 having core 4 with a diameter D1 of 40.7 mm or less is excellent in durability. From this viewpoint, the diameter D1 is more preferably 40.3 mm or less, and particularly preferably 40.0 mm or less.

[0030] The core hardness H1o of core 4 is preferably 45 or more and 70 or less. The golf ball 2 having core 4 with a core hardness H1o of 45 or more is excellent in repulsion performance. From this viewpoint, the core hardness H1o is more preferably 48 or more, and particularly preferably 50 or more. The golf ball 2 having core 4 with a core hardness H1o of 70 or less is excellent in hitting feeling. From this viewpoint, the core hardness H1o is more preferably 67 or less, and particularly preferably 65 or less.

[0031] The core hardness H1o is measured by a Shore C-type hardness meter attached to an automatic hardness meter (trade name "Digitest II" of H. Barreis Co., Ltd.). This hardness meter is pressed against the center of the cross section of the hemisphere obtained by cutting the golf ball 2. The measurement is made in an environment at 23°C.

[0032] The hardness H1 of core 4 at a point 10 mm away from the center (10) is preferably 55 or more and 85 or less. This hardness H1 (10)The golf ball 2 having a core 4 with a hardness H1 of 55 or more has excellent resilience performance. From this perspective, this hardness H1 (10) is more preferably 58 or more, and particularly preferably 60 or more. This hardness H1 (10) The golf ball 2 having a core 4 with a hardness H1 of 85 or less has excellent hitting feeling. From this perspective, this hardness H1 (10) is more preferably 82 or less, and particularly preferably 80 or less.

[0033] Hardness H1 (10) is measured by a Shore C-type hardness meter attached to an automatic hardness meter (trade name "Digitest II" of H. Barreis Co., Ltd.). This hardness meter is pressed against a position 10 mm away from the center of the cross-section of the hemisphere obtained by cutting the golf ball 2. The measurement is made in an environment of 23°C.

[0034] The surface hardness H1s of the core 4 is preferably 70 or more and 90 or less. The golf ball 2 having a core 4 with a surface hardness H1s of 70 or more has excellent resilience performance. From this perspective, the surface hardness H1s is more preferably 73 or more, and particularly preferably 75 or more. The golf ball 2 having a core 4 with a surface hardness H1s of 90 or less has excellent hitting feeling. From this perspective, the surface hardness H1s is more preferably 87 or less, and particularly preferably 85 or less.

[0035] The surface hardness H1s is measured by a Shore C-type hardness meter attached to an automatic hardness meter (trade name "Digitest II" of H. Barreis Co., Ltd.). This hardness meter is pressed against the surface of the core 4. The measurement is made in an environment of 23°C.

[0036] The difference (H1s-H1o) between the surface hardness H1s and the center hardness H1o is preferably 14 or greater. A golf ball 2 having a core 4 with a difference (H1s-H1o) of 14 or greater is excellent in flight performance in driver and middle iron shots. This golf ball 2 is further excellent in shot feel in driver shots and putting. From these viewpoints, the difference (H1s-H1o) is more preferably 16 or greater, and particularly preferably 18 or greater. From the viewpoint of durability of the golf ball 2, the difference (H1s-H1o) is preferably 30 or less.

[0037] Surface hardness H1s and hardness H1 at a distance of 10 mm from the center (10) Difference between H1s and H1 (10) ) is preferably 7 or more. The difference (H1s-H1 (10) A golf ball 2 having a core 4 with a difference (H1s-H1) of 7 or more has a small spin rate upon shots with a driver, and therefore has excellent flight performance. This golf ball 2 also has an excellent shot feeling upon driver shots and putting. From these viewpoints, (10) ) is more preferably 8 or greater, and particularly preferably 9 or greater. In light of the durability of the golf ball 2, the difference (H1s-H1 (10) ) is preferably 15 or less.

[0038] The mass of the core 4 is preferably 10 g or more and 42 g or less. The crosslinking temperature of the core 4 is typically 140° C. or more and 180° C. or less. The crosslinking time of the core 4 is typically 10 minutes or more and 60 minutes or less.

[0039] The intermediate layer 6 is located outside the core 4. The intermediate layer 6 is formed from a thermoplastic resin composition. Examples of base polymers of this resin composition include ionomer resins, thermoplastic polyester elastomers, thermoplastic polyamide elastomers, thermoplastic polyurethane elastomers, thermoplastic polyolefin elastomers, and thermoplastic polystyrene elastomers. In particular, ionomer resins are preferred. Ionomer resins have high elasticity. A golf ball 2 having an intermediate layer 6 containing an ionomer resin has excellent resilience performance. This golf ball 2 has excellent flight performance.

[0040] The ionomer resin and other resins may be used in combination. When used in combination, from the viewpoint of the repulsion performance, the ionomer resin is used as the main component of the base polymer. The ratio of the ionomer resin to the total base polymer is preferably 50% by mass or more.

[0041] Preferred ionomer resins include binary copolymers of α-olefins and α,β-unsaturated carboxylic acids having 3 to 8 carbon atoms. Preferred binary copolymers contain 80% by mass or more and 90% by mass or less of α-olefins and 10% by mass or more and 20% by mass or less of α,β-unsaturated carboxylic acids. This binary copolymer is excellent in repulsion performance. Preferred other ionomer resins include terpolymers of α-olefins, α,β-unsaturated carboxylic acids having 3 to 8 carbon atoms, and α,β-unsaturated carboxylic acid esters having 2 to 22 carbon atoms. Preferred terpolymers contain 70% by mass or more and 85% by mass or less of α-olefins, 5% by mass or more and 30% by mass or less of α,β-unsaturated carboxylic acids, and 1% by mass or more and 25% by mass or less of α,β-unsaturated carboxylic acid esters. This terpolymer is excellent in repulsion performance. In the binary copolymer and the terpolymer, preferred α-olefins are ethylene and propylene, and preferred α,β-unsaturated carboxylic acids are acrylic acid and methacrylic acid. Particularly preferred ionomer resins are copolymers of ethylene and acrylic acid. Particularly preferred other ionomer resins are copolymers of ethylene and methacrylic acid.

[0042] In the binary copolymer and the terpolymer, a part of the carboxyl groups is 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. The neutralization may be carried out with two or more kinds of metal ions. Particularly preferred metal ions from the viewpoints of the repulsion performance and durability of the golf ball 2 are sodium ions, zinc ions, lithium ions, and magnesium ions.

[0043] Specific examples of the ionomer resin include "Hymilan 1555", "Hymilan 1557", "Hymilan 1605", "Hymilan 1706", "Hymilan 1707", "Hymilan 1856", "Hymilan 1855", "Hymilan AM7311", "Hymilan AM7315", "Hymilan AM7317", "Hymilan AM7329", and "Hymilan AM7337" under the trade names of Mitsui DuPont Polychemicals Co., Ltd.; "Surlyn 6120", "Surlyn 6910", "Surlyn 7930", "Surlyn 7940", "Surlyn 8140", "Surlyn 8150", "Surlyn 8940", "Surlyn 8945", "Surlyn 9120", "Surlyn 9150", "Surlyn 9910", "Surlyn 9945", "Surlyn AD8546", "HPF1000", and "HPF2000" under the trade names of DuPont; and "Iotek 7010", "Iotek 7030", "Iotek 7510", "Iotek 7520", "Iotek 8000", and "Iotek 8030" under the trade names of ExxonMobil Chemical Company. Two or more ionomer resins may be used in combination.

[0044] The resin composition of the intermediate layer 6 may contain an appropriate amount of a colorant, filler, dispersant, antioxidant, ultraviolet absorber, light stabilizer, fluorescent agent, fluorescent brightening agent, etc. When the hue of the golf ball 2 is white, a typical colorant is titanium dioxide.

[0045] The thickness T2 of the intermediate layer 6 is preferably 0.5 mm or more and 2.0 mm or less. The golf ball 2 with a thickness T2 of 0.5 mm or more has excellent resilience performance. From this perspective, the thickness T2 is more preferably 0.7 mm or more, and particularly preferably 0.9 mm or more. The golf ball 2 with a thickness T2 of 2.0 mm or less has excellent hitting feeling. From this perspective, the thickness T2 is preferably 1.7 mm or less, and particularly preferably 1.5 mm or less. The thickness T2 is measured directly below the land 16.

[0046] The material hardness H2 of the intermediate layer 6 is preferably 55 or more and 75 or less. The golf ball 2 with a hardness H2 of 55 or more has excellent resilience performance. From this perspective, the hardness H2 is more preferably 58 or more, and particularly preferably 60 or more. The golf ball 2 with a hardness H2 of 75 or less has excellent hitting feeling. From this perspective, the hardness H2 is more preferably 72 or less, and particularly preferably 70 or less.

[0047] The hardness H2 of the intermediate layer 6 is measured in accordance with the provisions of "ASTM-D 2240-68". The hardness H2 is measured by a Shore D type hardness meter attached to an automatic hardness tester (trade name "Digitest II" of H. Barreis Co., Ltd.). For the measurement, a sheet made of the same material as the material of the intermediate layer 6, which is formed by hot pressing and has a thickness of about 2 mm, is used. Prior to the measurement, the sheet is stored at a temperature of 23 °C for 2 weeks. At the time of measurement, three sheets are stacked.

[0048] The surface hardness H2s of the intermediate layer 6 is preferably 85 or more and 100 or less. The golf ball 2 with a surface hardness H2s of 85 or more has excellent resilience performance. From this perspective, the surface hardness H2s is more preferably 88 or more, and particularly preferably 90 or more. The golf ball 2 with a surface hardness H2s of 100 or less has excellent hitting feeling. From this perspective, the surface hardness H2s is more preferably 98 or less, and particularly preferably 96 or less.

[0049] The surface hardness H2s is measured by a Shore C type hardness meter attached to an automatic hardness tester (trade name "Digitest II" of H. Barreis Co., Ltd.). This hardness meter is pressed against the surface of the ball composed of the core 4 and the intermediate layer 6. The measurement is made in an environment of 23 °C.

[0050] Cover 8 is formed from a resin composition. Examples of the base polymer of this resin composition include polyurethane, ionomer resin, polyester, polyamide, polyolefin, and polystyrene. From the viewpoints of hitting feeling and spin performance, a preferable base polymer is polyurethane. When polyurethane and another resin are used in combination for cover 8, the ratio of polyurethane to the total base resin is preferably 50% by mass or more, more preferably 60% by mass or more, and particularly preferably 70% by mass or more.

[0051] The resin composition of cover 8 may contain thermoplastic polyurethane or may contain thermosetting polyurethane. From the viewpoint of the productivity of golf ball 2, thermoplastic polyurethane is preferable. Thermoplastic polyurethane contains a polyurethane component as a hard segment and a polyester component or a polyether component as a soft segment. Thermoplastic polyurethane is soft. Cover 8 using this polyurethane is excellent in scratch resistance.

[0052] Thermoplastic polyurethane has a urethane bond in the molecule. This urethane bond can be formed by the reaction of a polyol and a polyisocyanate. The polyol, which is a raw material of the urethane bond, has a plurality of hydroxyl groups. Low molecular weight polyol and high molecular weight polyol can be used.

[0053] Examples of low molecular weight polyols include diols, triols, tetraols and hexols. Specific examples of diols include ethylene glycol, diethylene glycol, triethylene glycol, 1,2-propanediol, 1,3-propanediol, 2-methyl-1,3-propanediol, dipropylene glycol, 1,2-butanediol, 1,3-butanediol, 1,4-butanediol, 2,3-butanediol, 2,3-dimethyl-2,3-butanediol, neopentyl glycol, pentanediol, hexanediol, heptanediol, octanediol and 1,6-cyclohexanedimethanol. Aniline-based diols or bisphenol A-based diols may be used. Specific examples of triols include glycerin, trimethylolpropane and hexanetriol. Specific examples of tetraols include pentaerythritol and sorbitol.

[0054] Examples of high molecular weight polyols include polyether polyols such as polyoxyethylene glycol (PEG), polyoxypropylene glycol (PPG) and polytetramethylene ether glycol (PTMG); condensation polyester polyols such as 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. From the viewpoint of the hitting feeling of the golf ball 2, the number average molecular weight of the high molecular weight polyol is preferably 400 or more, more preferably 1000 or more. The number average molecular weight is preferably 10000 or less.

[0055] Examples of the polyisocyanate which is a raw material of the urethane bond include aromatic diisocyanates, alicyclic diisocyanates and aliphatic diisocyanates. Two or more diisocyanates may be used in combination.

[0056] Examples of aromatic diisocyanates include 2,4-toluene diisocyanate, 2,6-toluene diisocyanate, 4,4'-diphenylmethane diisocyanate (MDI), 1,5-naphthylene diisocyanate (NDI), 3,3'-bitolylene-4,4'-diisocyanate (TODI), xylylene diisocyanate (XDI), tetramethylxylylene diisocyanate (TMXDI), and paraphenylene diisocyanate (PPDI). An example of an aliphatic diisocyanate is hexamethylene diisocyanate (HDI). Examples of alicyclic diisocyanates include 4,4'-dicyclohexylmethane diisocyanate (H 12 MDI), 1,3-bis(isocyanatomethyl)cyclohexane (H 6 XDI), isophorone diisocyanate (IPDI), and trans-1,4-cyclohexane diisocyanate (CHDI). 4,4'-Dicyclohexylmethane diisocyanate is preferred.

[0057] Specific examples of thermoplastic polyurethanes include the product names "Estane NY80A", "Estane NY82A", "Estane NY83A", "Estane NY84A", "Estane NY85A", "Estane NY88A", "Estane NY90A", "Estane NY95A", "Estane NY97A", "Estane NY585", and "Estane KP016N" of BASF Japan Ltd.; and the product names "Resamin P4585LS" and "Resamin PS62490" of Dainichi Kasei Kogyo Co., Ltd.

[0058] The resin composition of the cover 8 may contain an appropriate amount of a colorant, filler, dispersant, antioxidant, ultraviolet absorber, light stabilizer, fluorescent agent, fluorescent brightener, lubricant, etc. When the hue of the golf ball 2 is white, a typical colorant is titanium dioxide.

[0059] The thickness T3 of the cover 8 is preferably 0.3 mm or more and 1.5 mm or less. The golf ball 2 with a thickness T3 of 0.3 mm or more is excellent in control performance and hitting feeling. From this viewpoint, the thickness T3 is more preferably 0.4 mm or more, and particularly preferably 0.5 mm or more. The golf ball 2 with a thickness T3 of 1.5 mm or less is excellent in resilience performance. From this viewpoint, the thickness T3 is more preferably 1.0 mm or less, and particularly preferably 0.8 mm or less. The thickness T3 is measured directly below the land 16.

[0060] The material hardness H3 of the cover 8 is preferably 20 or more and 45 or less. The golf ball 2 with a hardness H3 of 20 or more is excellent in durability. From this viewpoint, the hardness H3 is more preferably 25 or more, and particularly preferably 28 or more. The golf ball 2 with a hardness H3 of 45 or less is excellent in control performance and hitting feeling. From this viewpoint, the hardness H3 is more preferably 40 or less, and particularly preferably 35 or less.

[0061] The hardness H3 of the cover 8 is measured in accordance with the provisions of "ASTM-D 2240-68". The hardness H3 is measured by a Shore D hardness meter attached to an automatic hardness tester (trade name "Digitest II" of H. Barreis Co., Ltd.). For the measurement, a sheet made of the same material as the material of the cover 8, which is formed by hot pressing and has a thickness of about 2 mm, is used. Prior to the measurement, the sheet is stored at a temperature of 23°C for 2 weeks. At the time of measurement, three sheets are stacked.

[0062] The surface hardness H3s of the cover 8 is preferably 70 or more and 95 or less. The golf ball 2 with a surface hardness H3s of 70 or more is excellent in resilience performance. From this viewpoint, the surface hardness H3s is more preferably 75 or more, and particularly preferably 80 or more. The golf ball 2 with a surface hardness H3s of 95 or less is excellent in hitting feeling. From this viewpoint, the surface hardness H3s is more preferably 92 or less, and particularly preferably 90 or less.

[0063] The surface hardness H3s is measured by a Shore C-type hardness meter attached to an automatic hardness meter (trade name "Digitest II" by H. Barleys). This hardness meter is pressed against the surface of a sphere composed of a core 4, an intermediate layer 6, and a cover 8. The measurement is made in an environment of 23°C.

[0064] The golf ball 2 may be provided with a reinforcing layer between the intermediate layer 6 and the cover 8. The reinforcing layer adheres firmly to the intermediate layer 6 and also adheres firmly to the cover 8. The reinforcing layer suppresses the peeling of the cover 8 from the intermediate layer 6. The reinforcing layer is formed from a resin composition. Examples of preferred base polymers for the reinforcing layer include two-component curable epoxy resins and two-component curable urethane resins. The thickness of the reinforcing layer is preferably 5 μm or more and 30 μm or less.

[0065] The ratio ((T2 + T3) / D1) of the sum (T2 + T3) of the thickness T2 of the intermediate layer 6 and the thickness T3 of the cover 8 to the diameter D1 of the core 4 is preferably 0.042 or less. The golf ball 2 with this ratio of 0.042 or less has excellent flight performance in shots with a driver and a middle iron. From this perspective, this ratio ((T2 + T3) / D1) is more preferably 0.040 or less, and particularly preferably 0.038 or less. From the perspective of the durability of the golf ball 2, this ratio ((T2 + T3) / D1) is preferably 0.032 or more.

[0066] The ratio (H2 / H3) of the hardness H2 of the intermediate layer 6 to the hardness H3 of the cover 8 is preferably 1.80 or more. The golf ball 2 with this ratio (H2 / H3) of 1.80 or more has excellent flight performance in shots with a driver and a middle iron. This golf ball 2 further has excellent hitting feeling in putting. From these perspectives, this ratio (H2 / H3) is more preferably 2.00 or more, and particularly preferably 2.10 or more. This ratio (H2 / H3) is preferably 3.00 or less.

[0067] Preferably, the surface hardness H2s of the intermediate layer 6 is greater than the surface hardness H1s of the core 4 and greater than the surface hardness H3s of the cover 8. This golf ball 2 has excellent flight performance in shots with a driver and a middle iron. This golf ball 2 further has excellent hitting feelings in driver shots and putting. From these viewpoints, the difference (H2s - H1s) is preferably 6 or more, more preferably 9 or more, and particularly preferably 11 or more. The difference (H2s - H1s) is preferably 20 or less. The difference (H2s - H3s) is preferably 3 or more, more preferably 5 or more, and particularly preferably 7 or more. The difference (H2s - H3s) is preferably 15 or less.

[0068] The inner paint layer 10 is formed from a resin composition. Examples of the base resin of this resin composition include urethane resin, epoxy resin, acrylic resin, vinyl acetate resin, polyester resin, etc. A particularly preferred base resin is urethane resin. The thickness of the inner paint layer 10 is preferably 5 μm or more and 20 μm or less.

[0069] The outer paint layer 12 is formed from a resin composition. Examples of the base resin of this resin composition include urethane resin, epoxy resin, acrylic resin, vinyl acetate resin, polyester resin, etc. A particularly preferred base resin is urethane resin. The thickness of the outer paint layer 12 is preferably 5 μm or more and 20 μm or less.

[0070] Typically, the inner paint layer 10 is formed from a polyurethane paint, and the outer paint layer 12 is formed from another polyurethane paint. A preferred polyurethane paint has a main agent and a curing agent. The main agent is a polyol composition (A), and the curing agent is a polyisocyanate composition (B).

[0071] The polyol composition (A) contains a polyol compound. The polyol compound has two or more hydroxyl groups in the molecule. It may be a polyol compound (a1) having a hydroxyl group at the end of the molecular chain, or it may be a polyol compound (a2) having a hydroxyl group other than at the end of the molecular chain. The polyol composition (A) may have two or more polyol compounds.

[0072] Examples of the polyol compound (a1) having a hydroxyl group at the end of the molecular chain include diols such as ethylene glycol, diethylene glycol, triethylene glycol, 1,3 - butanediol, 1,4 - butanediol, neopentyl glycol and 1,6 - hexanediol; and triols such as glycerin, trimethylolpropane and hexanetriol. Other polyol compounds (a1) having a hydroxyl group at the end of the molecular chain include polyether polyols, polyester polyols, polycaprolactone polyols, polycarbonate polyols, urethane polyols and acrylic polyols. Examples of the polyether polyol include polyoxyethylene glycol (PEG), polyoxypropylene glycol (PPG) and polyoxytetramethylene glycol (PTMG). Examples of the polyester polyol include polyethylene adipate diol, polybutylene adipate diol and polyhexamethylene adipate diol. Examples of the polycaprolactone polyol include poly - ε - caprolactone diol. Examples of the polycarbonate polyol include polyhexamethylene carbonate diol.

[0073] Examples of the polyol compound (a2) having a hydroxyl group other than at the end of the molecule include modified polyrotaxane having a hydroxyl group and a hydroxyl - modified vinyl chloride - vinyl acetate copolymer.

[0074] The polyisocyanate composition (B) contains a polyisocyanate compound. The polyisocyanate compound has two or more isocyanate groups. Examples of the polyisocyanate compound include aromatic diisocyanates such as 2,4-toluene diisocyanate, 2,6-toluene diisocyanate, a mixture of 2,4-toluene diisocyanate and 2,6-toluene diisocyanate (TDI), 4,4'-diphenylmethane diisocyanate (MDI), 1,5-naphthylene diisocyanate (NDI), 3,3'-bitolylene-4,4'-diisocyanate (TODI), xylylene diisocyanate (XDI), tetramethylxylylene diisocyanate (TMXDI), and paraphenylene diisocyanate (PPDI); alicyclic or aliphatic diisocyanates such as 4,4'-dicyclohexylmethane diisocyanate (H 12 MDI), hydrogenated xylylene diisocyanate (H 6 XDI), hexamethylene diisocyanate (HDI), isophorone diisocyanate (IPDI), and norbornene diisocyanate (NBDI); and triisocyanates such as allophanate bodies, burette bodies, isocyanurate bodies, and adduct bodies of diisocyanates. The polyisocyanate composition (B) may contain two or more polyisocyanate compounds.

[0075] The indentation depth of the outer paint layer 12 is preferably 300 nm or more. The golf ball 2 having the outer paint layer 12 with an indentation depth of 300 nm or more is excellent in hitting feeling in driver shots and putting. From this viewpoint, the indentation depth is more preferably 500 nm or more, and particularly preferably 700 nm or more. From the viewpoint of the durability of the outer paint layer 12, the indentation depth is preferably 3000 nm or less.

[0076] In the measurement of the indentation depth, the golf ball 2 is broken to obtain a hemisphere. In this hemisphere, a cross-section passing through the center of the golf ball 2 is exposed. This cross-section includes the cross-section of the outer paint layer 12. The cross-section of this hemisphere is made horizontal by a cryomicrotome. The indenter of the nanoindenter is applied to the cross-section of the outer paint layer 12 and pressed in a direction perpendicular to the cross-section. By pressing, the indenter advances. The pressing is continued until the load of the indenter reaches 50 mgf. The advancing distance of the indenter when the load is 30 mgf is measured as the indentation depth. The measurement conditions are as follows. Nanoindenter: "ENT-2100" of Elionix, Inc. Temperature: 30 °C Indenter: Berkovich indenter (65.03° As(h)=26.43h2) Number of divisions: 500 steps Step interval: 20 msec (100 mgf)

[0077] The compression deformation amount CD of the golf ball 2 is preferably 3.00 mm or more. A golf ball 2 with a compression deformation amount CD of 3.00 mm or more has excellent hitting feeling in driver shots and putting. From this point of view, the compression deformation amount CD is more preferably 3.15 mm or more, and particularly preferably 3.25 mm or more. From the viewpoint of flight performance in shots with a driver and a middle iron, the compression deformation amount CD is preferably 4.00 mm or less.

[0078] The compression deformation amount CD is measured by the YAMADA type compression tester "SCH". In the measurement, the golf ball 2 is placed on a metal steel plate. A metal cylinder gradually descends toward this golf ball 2. The golf ball 2 sandwiched between the bottom surface of this cylinder and the steel plate deforms. The moving distance of the cylinder from the state where an initial load of 98 N is applied to the golf ball 2 to the state where a final load of 1275 N is applied is measured. The moving speed of the cylinder until the initial load is applied is 0.83 mm / s. The moving speed of the cylinder from when the initial load is applied to when the final load is applied is 1.67 mm / s.

[0079] In this specification, under the first condition and the second condition, the maximum vertical force of the golf ball 2 is measured. In this specification, under the first condition and the second condition, the maximum vertical force of the standard ball is also measured.

[0080] The specifications of this standard ball are as follows. Core Diameter: 39.0 mm Center hardness: 62 (Shore C) Hardness at a point 10 mm from the center: 71 (Shore C) Surface hardness: 78 (Shore C) Intermediate layer Thickness: 1.4 mm Material hardness: 71 (Shore D) Surface hardness: 97 (Shore C) Cover Thickness: 0.5 mm Material hardness: 40 (Shore D) Surface hardness: 87 (Shore C) Paint layer Thickness: 10 μm Indentation depth: 971 nm Compression deformation amount CDn: 3.12 mm

[0081] In the production of this standard ball, 100 parts by mass of high cis-polybutadiene (trade name "BR-60" of JSR), 24.3 parts by mass of zinc acrylate, 5.0 parts by mass of zinc oxide, 12.4 parts by mass of barium sulfate, and 0.6 parts by mass of dicumyl peroxide (DCP) are kneaded to obtain a rubber composition. This rubber composition is put into a mold consisting of an upper mold and a lower mold both having hemispherical cavities and heated to obtain a core with a diameter of 39.0 mm. 50 parts by mass of an ionomer resin (the aforementioned "Surlyn 8150"), 50 parts by mass of another ionomer resin (the aforementioned "Surlyn 9150"), 4 parts by mass of titanium dioxide, and 9 parts by mass of barium sulfate are kneaded by a twin-screw kneading extruder to obtain a resin composition. The core is put into a mold consisting of an upper mold and a lower mold both having hemispherical cavities. The resin composition is coated around the core by an injection molding method to form an intermediate layer. The thickness of this intermediate layer is 1.4 mm. The aforementioned PTMG and TDI are kneaded at a ratio at which a shore D hardness of 40 can be achieved to obtain a resin composition. A final mold consisting of an upper mold and a lower mold having hemispherical cavities and having a large number of pimples on the cavity surface is heated to 80°C or higher and 100°C or lower. The resin composition is put into this final mold, and further a ball having a core and an intermediate layer is put in, and a cover is formed by a compression molding method. The thickness of this cover is 0.5 mm. Dimples having a shape in which the shape of the pimples is inverted are formed on this cover. A clear paint based on a two-component curable polyurethane is applied around this cover. This paint is dried to obtain a standard golf ball.

[0082] Under the first condition, the golf ball 2 or the standard ball is struck with the driver 18 (W#1, trade name of Sumitomo Rubber Industries, Ltd. "XXIO 11") shown in FIGS. 2 and 3. FIG. 3 also shows the acceleration sensor 20 (trade name of B&K "#4393"). This driver 18 has a head 22 and a shaft 24. The loft angle of the head 22 is 10.5°, the hardness of the shaft 24 is S, and the part number of the shaft 24 is MP1100. The head 22 includes a face 26, a crown 28, and a sole 30. The face 26 has a toe-side end point 32, a heel-side end point 34, a top edge line 36, and a bottom edge line 38. In FIGS. 2 and 3, the symbol CP represents the center point of the face 26. The center point CP is on the center line CL. The distance from the center line CL to the heel-side end point 34 is equal to the distance from the center line CL to the toe-side end point 32. The distance from the center point CP to the intersection of the center line CL and the bottom edge line 38 is equal to the distance from the center point CP to the intersection of the center line CL and the top edge line 36. The virtual line L1 shown in FIG. 3 passes through the center point CP and is perpendicular to the face 26. The acceleration sensor 20 is fixed to the sole 30 at the intersection of this virtual line L1 and the outer surface of the sole 30.

[0083] This driver 18 is mounted on a swing machine (Golf Laboratories, Inc.). Under the condition that the head speed is 40 m / s, the golf ball 2 or the standard ball is struck with the driver 18. The hitting point in this strike is the center point CP. The acceleration in the hitting direction at the time of this strike is measured by the acceleration sensor 20. The product of the total mass of the head 22 and the acceleration sensor 20 and the acceleration is the vertical force. The time from the point when the vertical force is generated to the point when the vertical force disappears is the contact time. The maximum value of the vertical force during the contact time is the maximum vertical force. The average value of the data obtained from 12 strikes is calculated.

[0084] Under the second condition, the golf ball 2 or the standard ball is struck with the putter 40 (trade name "Huntington Beach Soft Putter #4" of Cleveland Golf) shown in FIGS. 4 and 5. FIGS. 4 and 5 also show an acceleration sensor 42 (trade name "356A01" of Toyo Technica). This putter 40 has a head 44 and a shaft 46. The head 44 includes a face 48 and a sole 50. The face 48 has a toe-side end point 52, a heel-side end point 54, and a bottom edge line 56. In FIGS. 4 and 5, the symbol CP represents the center point of the face 48. The center point CP is on the center line CL. The distance from the center line CL to the heel-side end point 54 is equal to the distance from the center line CL to the toe-side end point 52. The distance from the bottom edge line 56 to the center point CP is 20 mm. On the back side of the center point CP, the acceleration sensor 42 is fixed to the head 44.

[0085] This putter 40 is attached to a swing machine (Golf Laboratories). On the green where the horizontal speed measured by a stimpmeter is 10.0 m and the rolling distance is 15 m, the golf ball 2 or the standard ball is struck with the putter 40. The hitting point in this strike is the center point CP. The acceleration in the hitting direction at the time of this strike is measured by the acceleration sensor 42. The product of the total mass of the head 44 and the acceleration sensor 42 and the acceleration is the vertical force. The time from the point when the vertical force is generated to the point when the vertical force disappears is the contact time. The maximum value of the vertical force during the contact time is the maximum vertical force. The average value of the data obtained from 12 strikes is calculated.

[0086] The golf ball 2 according to the present embodiment satisfies the following mathematical formulas (1) and (2). (Fw / Fwn) ≦ 0.98 (1) (Fw / Fwn) 2 / (Fp / Fpn) ≦ 0.98 (2) Fw: The maximum vertical force of the golf ball 2 measured under the first condition Fwn: The maximum vertical force of the standard ball measured under the first condition Fp: Maximum vertical force of golf ball 2 measured under the second condition Fpn: Maximum vertical force of a standard ball measured under the second condition

[0087] In the driver shot of golf ball 2 that satisfies the above formula (1), a soft hitting feeling is achieved. In golf ball 2 that satisfies the above formula (2), the soft hitting feeling in the driver shot and the soft hitting feeling in putting are compatible. In this golf ball 2, the flight performance in shots with driver 18 and middle iron is not inhibited.

[0088] In golf ball 2 that satisfies the above formula (1), the ratio (Fw / Fwn) is 0.98 or less. From the viewpoint of the hitting feeling in the driver shot, the ratio (Fw / Fwn) is more preferably 0.96 or less, and particularly preferably 0.94 or less. The ratio (Fw / Fwn) is preferably 0.85 or more.

[0089] In golf ball 2 that satisfies the above formula (2), the ratio ((Fw / Fwn) 2 / (Fp / Fpn)) is 0.98 or less. From the viewpoint of the hitting feeling in the driver shot and putting, the ratio ((Fw / Fwn) 2 / (Fp / Fpn)) is more preferably 0.96 or less, and particularly preferably 0.95 or less. The ratio ((Fw / Fwn) 2 / (Fp / Fpn)) is preferably 0.85 or more.

[0090] As means for achieving the above formulas (1) and (2), (a) Set the difference in hardness (H1s - H1o) of core 4 to be large. (b) Set the difference in hardness (H1s - H1 (10) ) to be large. (c) Set the ratio (H2 / H3) of the hardness H2 of intermediate layer 6 and the hardness H3 of cover 8 to be large. (d) Set the ratio of the sum (T2 + T3) of the thickness T2 of intermediate layer 6 and the thickness T3 of cover 8 to the diameter D1 of core 4 to be small. And the like are exemplified.

[0091] Preferably, the golf ball 2 satisfies the following formula (3). (Fp / Fpn) ≦ 0.98 (3) In other words, the ratio (Fp / Fpn) is 0.98 or less. This golf ball 2 achieves both a soft hitting feeling and a firm feeling in putting. From this perspective, the ratio (Fp / Fpn) is more preferably 0.96 or less, and particularly preferably 0.95 or less. The ratio (Fp / Fpn) is preferably 0.80 or more.

[0092] Preferably, the golf ball 2 satisfies the following formula (4). (Tp / Tpn) ≧ 1.01 (4) Tp: Contact time of the golf ball 2 measured under the second condition Tpn: Contact time of the standard ball measured under the second condition In other words, the ratio (Tp / Tpn) is 1.01 or more. This golf ball 2 achieves both a soft hitting feeling and a firm feeling in putting. From this perspective, the ratio (Tp / Tpn) is more preferably 1.02 or more, and particularly preferably 1.03 or more. The ratio (Tp / Tpn) is preferably 1.15 or less.

[0093] Preferably, the golf ball 2 satisfies the following formula (5). (Fp / Fpn) / (Tp / Tpn) ≦ 0.98 (5) In other words, the ratio ((Fp / Fpn) / (Tp / Tpn)) is 0.98 or less. This golf ball 2 achieves both a soft hitting feeling and a firm feeling in putting. From this perspective, the ratio ((Fp / Fpn) / (Tp / Tpn)) is more preferably 0.95 or less, and particularly preferably 0.92 or less. The ratio ((Fp / Fpn) / (Tp / Tpn)) is preferably 0.75 or more.

[0094] Preferably, the golf ball 2 satisfies the following formula (6). (Tw / Twn) ≧ 1.01 (6) Tw: Contact time of the golf ball 2 measured under the first condition Twn: Contact time of the standard ball measured under the first condition In other words, the ratio (Tw / Twn) is 1.01 or more. This golf ball 2 achieves both a soft hitting feeling and a biting feeling in a driver shot. From this perspective, the ratio (Tw / Twn) is particularly preferably 1.02 or more. The ratio (Tw / Twn) is preferably 1.20 or less.

[0095] Preferably, the golf ball 2 satisfies the mathematical formula (7). (Fw / Fwn) / (Tw / Twn) ≦ 0.98 (7) In other words, the ratio ((Fw / Fwn) / (Tw / Twn)) is 0.98 or less. This golf ball 2 achieves both a soft hitting feeling and a biting feeling in a driver shot. From this perspective, the ratio ((Fw / Fwn) / (Tw / Twn)) is more preferably 0.95 or less, and particularly preferably 0.92 or less. The ratio ((Fw / Fwn) / (Tw / Twn)) is preferably 0.75 or more.

Example

[0096] Hereinafter, the effects of the golf balls according to the examples will be clarified, but the scope disclosed in this specification should not be construed in a limited manner based on the description of this example.

[0097] [Example 1] 100 parts by mass of high cis-polybutadiene (trade name “BR-60” of JSR), 25.3 parts by mass of zinc acrylate, 5.0 parts by mass of zinc oxide, 12.0 parts by mass of barium sulfate, 0.3 parts by mass of pentabromodiphenyldisulfide (PBDS) and 0.7 parts by mass of dicumyl peroxide (DCP) were kneaded to obtain a 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 to obtain a core having a diameter of 39.7 mm.

[0098] 50 parts by mass of an ionomer resin (the aforementioned "Hy-Milan 1605"), 50 parts by mass of another ionomer resin (the aforementioned "Hy-Milan AM7329"), 4 parts by mass of titanium dioxide, and 9 parts by mass of barium sulfate were kneaded using a twin-screw kneading extruder to obtain a resin composition. A core was placed into a mold consisting of an upper mold and a lower mold, each having a hemispherical cavity. The resin composition was coated around the core by an injection molding method to form an intermediate layer. The thickness of this intermediate layer was 1.0 mm.

[0099] A paint composition (trade name "Polyene 750LE" of Shinto Paint Co., Ltd.) using a two-component curable epoxy resin as a base polymer was prepared. The main agent liquid of this paint composition contains 30 parts by mass of bisphenol A type epoxy resin and 70 parts by mass of a solvent. The curing agent liquid of this paint composition contains 40 parts by mass of a modified polyamide amine, 55 parts by mass of a solvent, and 5 parts by mass of titanium dioxide. The mass ratio of the main agent liquid to the curing agent liquid is 1 / 1. This paint composition was applied to the surface of the intermediate layer with a spray gun and held for 12 hours in an atmosphere at 23°C to obtain a reinforcing layer. The thickness of this reinforcing layer was 10 μm.

[0100] 100 parts by mass of a thermoplastic polyurethane elastomer (the aforementioned "Estane NY84A"), 2 parts by mass of a lubricant (trade name "Wax Master VD" of BASF Japan Ltd.), 4 parts by mass of titanium dioxide, and 0.2 parts by mass of a light stabilizer (trade name "JF-90" of Johoku Chemical Industry Co., Ltd.) were kneaded using a twin-screw kneading extruder to obtain a resin composition. From this resin composition, a half shell was obtained by a compression molding method. A sphere including a core, an intermediate layer, and a reinforcing layer was covered with two of these half shells. These half shells and the sphere were placed into a final mold consisting of an upper mold and a lower mold, each having a hemispherical cavity and a large number of pimples on the cavity surface, and a cover was obtained by a compression molding method. The thickness of this cover was 0.5 mm. Dimples having a shape in which the shape of the pimples was reversed were formed on this cover.

[0101] A clear paint based on a two-component curable polyurethane was applied around this cover to form an inner paint layer. Another clear paint based on a two-component curable polyurethane was applied around this inner paint layer to form an outer paint layer. Thus, a golf ball of Example 1 with a diameter of about 42.7 mm and a mass of about 45.3 g was obtained.

[0102] [Example 2] A golf ball of Example 2 was obtained in the same manner as in Example 1, except that the specifications of the core, intermediate layer, and cover were as shown in Tables 1 and 2 below.

[0103] [Comparative Examples 1 and 2] As Comparative Example 1, a commercially available golf ball was prepared. As Comparative Example 2, another commercially available golf ball was prepared.

[0104] [Flight Test, W#1] A driver (product name "XXIO 11" of Sumitomo Rubber Industries, shaft part number: MP1100, shaft hardness: S, loft angle: 10.5°) was attached to a swing machine of Golf Laboratories, Inc. The golf ball was hit under the condition that the head speed was 40 m / sec, and the spin speed and flight distance were measured. The flight distance is the distance from the hitting point to the point where the golf ball stopped. Twelve measurements were made, and the average value of the obtained data was calculated. Further, the following grading was performed based on the average value of the flight distance. A: 215.5 yards or more B: Less than 215.5 yards This result is shown in Table 3 below.

[0105] [Flight Test, I#7] A 7-iron club (product name of Sumitomo Rubber Industries, Ltd. "XXIO 11", shaft part number: MP1100, shaft hardness: S, loft angle: 28.0°) was attached to the swing machine of Golf Laboratory Co., Ltd. A golf ball was hit under the condition that the head speed was 33 m / sec, and the spin speed and flight distance were measured. Twelve measurements were made, and the average value of the obtained data was calculated. Furthermore, based on the average value of the flight distance, the following grading was performed. A: 148.0 yards or more B: 145.0 yards or more and less than 148.0 yards C: Less than 145.0 yards This result is shown in Table 3 below.

[0106] [Feeling at impact, W#1] The tester was made to hit a golf ball with a driver, and points were given according to the following criteria. 0 points: Hard 2 points: Slightly hard 5 points: Normal 8 points: Slightly soft 10 points: Soft The total points given by 50 testers were calculated, and the following grading was performed. A: 310 points or more B: 300 points or more and less than 310 points C: Less than 300 points This result is shown in Table 3 below.

[0107] [Feeling at impact, putter] The tester was made to hit a golf ball with a putter, and points were given according to the following criteria. 0 points: Hard 2 points: Slightly hard 5 points: Normal 8 points: Slightly soft 10 points: Soft The total points given by 50 testers were calculated, and the following grading was performed. A: 330 points or more B: 300 points or more and less than 330 points C: Less than 300 points This result is shown in Table 3 below.

[0108]

Table 1

[0109]

Table 2

[0110]

Table 3

[0111] As shown in Table 3, the golf balls of each example are excellent in all of the flight performance in a shot with a driver, the flight performance in a shot with a middle iron, the hitting feeling in a shot with a driver, and the hitting feeling in putting. From this evaluation result, the superiority of this golf ball is clear.

[0112] [Disclosed Items] Each of the following items is a disclosure of a preferred embodiment.

[0113] [Item 1] A golf ball comprising a core, an intermediate layer located outside the core, and a cover located outside the intermediate layer, and satisfying the following formulas (1) and (2). (Fw / Fwn) ≦ 0.98 (1) (Fw / Fwn) 2 / (Fp / Fpn) ≦ 0.98 (2) (In these formulas, Fw represents the maximum vertical force of the above golf ball measured under the first condition, Fwn represents the maximum vertical force of the standard ball measured under the first condition, Fp represents the maximum vertical force of the above golf ball measured under the second condition, and Fpn represents the maximum vertical force of the above standard ball measured under the second condition.)

[0114] [Item 2] The golf ball according to Item 1 that satisfies the following formula (3). (Fp / Fpn) ≦ 0.98 (3)

[0115] [Item 3] The golf ball according to Item 1 or 2 that satisfies the following formula (4). (Tp / Tpn) ≧ 1.01 (4) (In this formula, Tp represents the contact time of the golf ball measured under the second condition, and Tpn represents the contact time of the standard ball measured under the second condition.)

[0116] [Item 4] The golf ball according to Item 3 that satisfies the following formula (5). (Fp / Fpn) / (Tp / Tpn) ≦ 0.98 (5)

[0117] [Item 5] The golf ball according to any one of Items 1 to 4 that satisfies the following formula (6). (Tw / Twn) ≧ 1.01 (6) (In this formula, Tw represents the contact time of the golf ball measured under the first condition, and Twn represents the contact time of the standard ball measured under the first condition.)

[0118] [Item 6] The golf ball according to Item 5 that satisfies the following formula (7). (Fw / Fwn) / (Tw / Twn) ≦ 0.98 (7)

[0119] [Item 7] The golf ball according to any one of Items 1 to 6, wherein the compression deformation amount CD measured under the condition that the initial load is 98 N and the final load is 1274 N is 3.00 mm or more.

[0120] [Item 8] The golf ball according to any one of Items 1 to 7, wherein the surface hardness H2s (Shore C) of the intermediate layer is greater than the surface hardness H1s (Shore C) of the core and greater than the surface hardness H3s (Shore C) of the cover.

[0121] [Item 9] The golf ball according to any one of Items 1 to 8, wherein the difference (H1s - H1o) between the surface hardness H1s (Shore C) and the core hardness H1o (Shore C) in the core is 14 or more.

[0122] [Item 10] The golf ball according to any one of Items 1 to 9, wherein the ratio of the sum (T2 + T3) of the thickness T2 of the intermediate layer and the thickness T3 of the cover to the diameter D1 of the core is 0.042 or less.

[0123] [Item 11] The golf ball according to any one of Items 1 to 10, wherein the ratio (H2 / H3) of the hardness H2 (Shore D) of the intermediate layer to the hardness H3 (Shore D) of the cover is 1.80 or more.

[0124] [Item 12] The golf ball further includes one or more paint layers located outside the cover, The golf ball according to any one of Items 1 to 11, wherein the indentation depth when the load of the outermost paint layer is 30 mgf is 300 nm or more and 3000 nm or less. [Industrial Applicability]

[0125] The above-mentioned golf ball is suitable for play on a golf course, practice at a driving range, etc. [Explanation of Signs]

[0126] 2 ··· Golf ball 4 ··· Core 6 ··· Intermediate layer 8 ··· Cover 10 ··· Inner paint layer 12... Outer paint layer 14... Dimple 16... Land

Claims

1. A golf ball comprising a core, an intermediate layer positioned outside the core, and a cover positioned outside the intermediate layer, satisfying the following formulas (1) and (2). (Fw / Fwn) ≤ 0.98 (1) (Fw / Fwn) ２ / (Fp / Fpn) ≤ 0.98 (2) (In these formulas, Fw represents the maximum vertical force of the golf ball measured under the first condition, Fwn represents the maximum vertical force of the standard ball measured under the first condition, Fp represents the maximum vertical force of the golf ball measured under the second condition, and Fpn represents the maximum vertical force of the standard ball measured under the second condition. Under the first condition, with a head speed of 40 m / s, using the center point of the face of the driver as the hitting point, the golf ball and the standard ball are hit. Under the second condition, on a green where the horizontal speed measured by a stimpmeter is 10.0 m and the rolling distance is 15 m, using the center point of the face of the putter as the hitting point, the golf ball and the standard ball are hit. The maximum vertical force is the maximum value of the vertical force, which is the product of the acceleration in the hitting direction measured by an acceleration sensor and the total mass of the head and this acceleration sensor. The standard ball has a core with a diameter of 39.0 mm, a center hardness of 62 (Shore C), a hardness of 71 (Shore C) at a point 10 mm from the center, and a surface hardness of 78 (Shore C), an intermediate layer with a thickness of 1.4 mm, a material hardness of 71 (Shore D), and a surface hardness of 97 (Shore C), a cover with a thickness of 0.5 mm, a material hardness of 40 (Shore D), and a surface hardness of 87 (Shore C), and a paint layer with a thickness of 10 μm and an indentation depth of 971 nm, and its compression deformation amount CDn is 3.12 mm.)

2. The golf ball according to claim 1, satisfying the following formula (3). (Fp / Fpn) ≤ 0.98 (3)

3. The golf ball according to claim 1 or 2, satisfying the following formula (4). (Tp / Tpn) ≥ 1.01 (4) (In this formula, Tp represents the contact time of the golf ball measured under the second condition, and Tpn represents the contact time of the standard ball measured under the second condition.)

4. The golf ball according to claim 3, satisfying the following formula (5). (Fp / Fpn) / (Tp / Tpn) ≤ 0.98 (5)

5. The golf ball according to any one of claims 1 to 4, which satisfies the following formula (6). (Tw / Twn) ≧ 1.01 (6) (In this formula, Tw represents the contact time of the golf ball measured under the first condition, and Twn represents the contact time of the standard ball measured under the first condition.) (Claim 6) The golf ball according to claim 5, which satisfies the following formula (7). (Fw / Fwn) / (Tw / Twn) ≦ 0.98 (7) (Claim 7) The golf ball according to any one of claims 1 to 6, wherein the compression deformation amount CD measured under the condition that the initial load is 98 N and the final load is 1275 N is 3.00 mm or more. (Claim 8) The golf ball according to any one of claims 1 to 7, wherein the surface hardness H2s (Shore C) of the intermediate layer is greater than the surface hardness H1s (Shore C) of the core and greater than the surface hardness H3s (Shore C) of the cover. (Claim 9) The golf ball according to any one of claims 1 to 8, wherein the difference (H1s - H1o) between the surface hardness H1s (Shore C) and the core hardness H1o (Shore C) in the core is 14 or more. (Claim 10) The golf ball according to any one of claims 1 to 9, wherein the ratio of the sum (T2 + T3) of the thickness T2 of the intermediate layer and the thickness T3 of the cover to the diameter D1 of the core is 0.042 or less. (Claim 11) The golf ball according to any one of claims 1 to 10, wherein the ratio (H2 / H3) of the hardness H2 (Shore D) of the intermediate layer to the hardness H3 (Shore D) of the cover is 1.80 or more. (Claim 12) The golf ball further includes one or more paint layers located outside the cover, The golf ball according to any one of claims 1 to 11, wherein the indentation depth when the load of the outermost paint layer is 30 mgf is 300 nm or more and 3000 nm or less.

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