Golf ball

Abstract

To provide a golf ball 2 which is excellent in all of flight performance at a shot with a middle iron, spin performance at a shot with a short iron, hitting feeling at a shot with the middle iron, 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). (Fa / Fan)≤0.90 (1) (Fa / Fan)2 / (Fp / Fpn)≤0.90 (2) In the mathematical formulas, Fa represents the maximum vertical force of the golf ball 2 measured under a first condition, Fan 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] The concerns of golf players regarding golf balls are flight performance. Golf players prefer golf balls that can achieve a long flight distance. Golf players also value the control performance of golf balls. The control performance correlates with the spin performance. Furthermore, golf players value the feel of hitting the golf ball. Generally, players prefer a soft feel of hitting.

[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 Unexamined Patent Application Publication 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 middle iron as well as in a shot with a driver.

[0006] Golf players value the spin performance when a golf ball in the rough is struck with a short iron.

[0007] Golf players value the feel of hitting in a shot with a short iron. Players further value the feel of hitting in putting.

[0008] What the applicant intends is to provide a golf ball that excels in all of flight performance in shots with middle irons, spin performance in shots with short irons, feel at impact in shots with short irons, and feel at impact in putting.

Means for Solving the Problems

[0009] 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 formulas (1) and (2). (Fa / Fan) ≦ 0.90 (1) (Fa / Fan) 2 / (Fp / Fpn) ≦ 0.90 (2) In these formulas, Fa represents the maximum vertical force of the golf ball measured under the first condition, Fan 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.

Advantages of the Invention

[0010] This golf ball excels in all of flight performance in shots with middle irons, spin performance in shots with short irons, feel at impact in shots with short irons, and feel at impact in putting.

Brief Description of the Drawings

[0011]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

DETAILED DESCRIPTION OF THE INVENTION

[0012] Hereinafter, preferred embodiments will be described in detail while appropriately referring to the drawings.

[0013] 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 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.

[0014] The diameter of this golf ball 2 is preferably 40 mm or more and 45 mm or less. From the viewpoint of meeting 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.

[0015] 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 meeting the USGA standards, the mass is particularly preferably 45.93 g or less.

[0016] The core 4 is formed by crosslinking the rubber composition. Preferred base rubbers include polybutadiene, polyisoprene, styrene-butadiene copolymer, ethylene-propylene-diene copolymer, and natural rubber. From the perspective 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 with a cis-1,4 bond ratio of 80% or more is particularly preferred.

[0017] The rubber composition of the core 4 preferably contains a co-crosslinking agent. Preferred co-crosslinking agents from the perspectives of the durability and resilience performance of the golf ball 2 are monovalent or divalent metal salts of α,β-unsaturated carboxylic acids having 2 to 8 carbon atoms. Preferred co-crosslinking agents include zinc acrylate, magnesium acrylate, zinc methacrylate, and magnesium methacrylate. From the perspective of the resilience performance of the core 4, zinc acrylate and zinc methacrylate are particularly preferred.

[0018] The rubber composition may contain an α,β-unsaturated carboxylic acid having 2 to 8 carbon atoms and a metal oxide. The two 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.

[0019] The amount of the co-crosslinking agent is preferably 10 parts by mass or more and 45 parts by mass or less based on 100 parts by mass of the base rubber. The golf ball 2 with this amount of 10 parts by mass or more has excellent resilience performance. From this perspective, this amount is more preferably 15 parts by mass or more, and particularly preferably 20 parts by mass or more. The golf ball 2 with this amount of 45 parts by mass or less has excellent hitting feel. From this perspective, this amount is more preferably 40 parts by mass or less, and particularly preferably 35 parts by mass or less.

[0020] 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. A particularly versatile organic peroxide is dicumyl peroxide.

[0021] 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 has excellent 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 has excellent 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.

[0022] 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.

[0023] Examples of the naphthalenethiol-based compounds 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.

[0024] Examples of benzenethiol compounds 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.

[0025] 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.

[0026] From the viewpoint of the 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.

[0027] 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.

[0028] The rubber composition of the core 4 may contain a filler for the purpose of adjusting the specific gravity or the like. 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 core 4 is achieved.

[0029] The rubber composition of the core 4 may contain appropriate amounts of various additives such as sulfur, an antioxidant, a colorant, a plasticizer, and a dispersant. This rubber composition may contain crosslinked rubber powder or synthetic resin powder.

[0030] The diameter D1 of the core 4 is preferably 35.0 mm or more and 40.7 mm or less. The golf ball 2 having the core 4 with the 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 the core 4 with the 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.

[0031] The core hardness H1o of core 4 is preferably 45 or more and 70 or less. The golf ball 2 having a core 4 with a core hardness H1o of 45 or more has excellent resilience performance. From this perspective, the core hardness H1o is more preferably 48 or more, and particularly preferably 50 or more. The golf ball 2 having a core 4 with a core hardness H1o of 70 or less has excellent hitting feeling. From this perspective, the core hardness H1o is more preferably 67 or less, and particularly preferably 65 or less.

[0032] The core hardness H1o is measured by a Shore C hardness meter attached to an automatic hardness tester (trade name "Digitest II" of H. Barreis). 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 of 23°C.

[0033] The hardness H1 of the core 4 at a point where the distance from the center is 10 mm (10) is preferably 55 or more and 85 or less. This hardness H1 (10) The golf ball 2 having a core 4 with this 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 this 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.

[0034] Hardness H1 (10) is measured by a Shore C hardness meter attached to an automatic hardness tester (trade name "Digitest II" of H. Barreis). 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.

[0035] The surface hardness H1s of the core 4 is preferably 70 or more and 90 or less. The golf ball 2 having the core 4 with the surface hardness H1s of 70 or more is excellent in repulsion performance. From this viewpoint, the surface hardness H1s is more preferably 73 or more, and particularly preferably 75 or more. The golf ball 2 having the core 4 with the surface hardness H1s of 90 or less is excellent in hitting feeling. From this viewpoint, the surface hardness H1s is more preferably 87 or less, and particularly preferably 85 or less.

[0036] 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.

[0037] The difference (H1s - H1o) between the surface hardness H1s and the core hardness H1o is preferably 14 or more. The golf ball 2 having the core 4 with the difference (H1s - H1o) of 14 or more is excellent in flight performance in a shot with a middle iron. This golf ball 2 is further excellent in hitting feeling in a shot with a short iron and putting. From these viewpoints, the difference (H1s - H1o) is more preferably 16 or more, and particularly preferably 18 or more. From the viewpoint of the durability of the golf ball 2, the difference (H1s - H1o) is preferably 30 or less.

[0038] The difference (H1s - H1 (10) between the surface hardness H1s and the hardness H1 at a point 10 mm away from the center (10) ) is preferably 7 or more. The golf ball 2 having the core 4 with the difference (H1s - H1 (10) ) of 7 or more has a small spin in a shot with a driver, and thus is excellent in flight performance. This golf ball 2 is further excellent in hitting feeling in an approach shot and putting. From these viewpoints, the difference (H1s - H1 (10) ) is more preferably 8 or more, and particularly preferably 9 or more. From the viewpoint of the durability of the golf ball 2, the difference (H1s - H1 (10) ) is preferably 15 or less.

[0039] 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.

[0040] The intermediate layer 6 is located outside the core 4. The intermediate layer 6 is formed from a thermoplastic resin composition. Examples of the base polymer of this resin composition include ionomer resin, thermoplastic polyester elastomer, thermoplastic polyamide elastomer, thermoplastic polyurethane elastomer, thermoplastic polyolefin elastomer, and thermoplastic polystyrene elastomer. In particular, ionomer resin is preferred. The ionomer resin has high elasticity. The golf ball 2 having the intermediate layer 6 containing the ionomer resin has excellent resilience performance. This golf ball 2 has excellent flight performance.

[0041] The ionomer resin and other resins may be used in combination. When used in combination, from the viewpoint of resilience performance, the ionomer resin is the main component of the base polymer. The ratio of the ionomer resin to all the base polymers is preferably 50% by mass or more.

[0042] Preferred ionomer resins include binary copolymers of an α-olefin and an α,β-unsaturated carboxylic acid having 3 to 8 carbon atoms. Preferred binary copolymers contain 80% by mass or more and 90% by mass or less of an α-olefin and 10% by mass or more and 20% by mass or less of an α,β-unsaturated carboxylic acid. This binary copolymer has excellent resilience performance. Other preferred ionomer resins include terpolymers 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. Preferred terpolymers contain 70% by mass or more and 85% by mass or less of an α-olefin, 5% by mass or more and 30% by mass or less of an α,β-unsaturated carboxylic acid, and 1% by mass or more and 25% by mass or less of an α,β-unsaturated carboxylic acid ester. This terpolymer has excellent resilience 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.

[0043] In the binary copolymer and the terpolymer, a part of the carboxyl groups is neutralized with metal ions. Examples of metal ions for neutralization include sodium ion, potassium ion, lithium ion, zinc ion, calcium ion, magnesium ion, aluminum ion, and neodymium ion. The neutralization may be carried out with two or more kinds of metal ions. Metal ions particularly suitable from the viewpoints of the resilience performance and durability of the golf ball 2 are sodium ion, zinc ion, lithium ion, and magnesium ion.

[0044] 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.

[0045] The resin composition of the intermediate layer 6 may contain an appropriate amount of a colorant, a filler, a dispersant, an antioxidant, an ultraviolet absorber, a light stabilizer, a fluorescent agent, a fluorescent brightening agent, etc. When the hue of the golf ball 2 is white, a typical colorant is titanium dioxide.

[0046] 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.

[0047] 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.

[0048] 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 that 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 together.

[0049] 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.

[0050] 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.

[0051] The 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 the 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.

[0052] The resin composition of the cover 8 may contain thermoplastic polyurethane or may contain thermosetting polyurethane. From the viewpoint of the productivity of the golf ball 2, thermoplastic polyurethane is preferable. The thermoplastic polyurethane contains a polyurethane component as a hard segment and a polyester component or a polyether component as a soft segment. The thermoplastic polyurethane is soft. The cover 8 using this polyurethane is excellent in scratch resistance.

[0053] The 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.

[0054] 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 also be used. Specific examples of triols include glycerin, trimethylolpropane and hexanetriol. Specific examples of tetraols include pentaerythritol and sorbitol.

[0055] 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 perspective 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 10,000 or less.

[0056] 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.

[0057] 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.

[0058] Specific examples of thermoplastic polyurethanes include "Elastollan NY80A", "Elastollan NY82A", "Elastollan NY83A", "Elastollan NY84A", "Elastollan NY85A", "Elastollan NY88A", "Elastollan NY90A", "Elastollan NY95A", "Elastollan NY97A", "Elastollan NY585", and "Elastollan KP016N" with the trade names of BASF Japan Ltd.; and "Resamin P4585LS" and "Resamin PS62490" with the trade names of Dainichi Kasei Kogyo Co., Ltd.

[0059] 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.

[0060] 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.

[0061] 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.

[0062] 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.

[0063] 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.

[0064] 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 the sphere composed of the core 4, the intermediate layer 6, and the cover 8. The measurement is made in an environment of 23°C.

[0065] 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.

[0066] 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 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.

[0067] 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 middle iron. This golf ball 2 further has excellent hitting feeling in shots with a middle iron and 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.

[0068] 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 excels in flight performance in a shot with a middle iron. This golf ball 2 excels in spin performance in a shot with a middle iron. This golf ball 2 further excels in the feel of hitting the ball in a shot with a middle iron 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.

[0069] 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, and the like. 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.

[0070] 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, and the like. 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.

[0071] 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).

[0072] 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.

[0073] 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. Examples of 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 polyether polyols include polyoxyethylene glycol (PEG), polyoxypropylene glycol (PPG) and polyoxytetramethylene glycol (PTMG). Examples of polyester polyols include polyethylene adipate diol, polybutylene adipate diol and polyhexamethylene adipate diol. Examples of polycaprolactone polyols include poly - ε - caprolactone diol. Examples of polycarbonate polyols include polyhexamethylene carbonate diol.

[0074] 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.

[0075] 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, biuret, isocyanurate, and adduct forms of diisocyanate. The polyisocyanate composition (B) may contain two or more polyisocyanate compounds.

[0076] 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 is excellent in spin performance in shots with short irons. This golf ball 2 is further excellent in the feel of hitting the ball in shots with short irons 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.

[0077] 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 a nanoindenter is applied to the cross-section of the outer paint layer 12 and pressed in a direction perpendicular to the cross-section. By the 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)

[0078] The compression deformation amount CD of the golf ball 2 is preferably 3.00 mm or more. The golf ball 2 with a compression deformation amount CD of 3.00 mm or more is excellent in spin performance in shots with short irons. This golf ball 2 is further excellent in the hitting feeling in shots with short irons and putting. From this viewpoint, 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 middle irons, the compression deformation amount CD is preferably 4.00 mm or less.

[0079] 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 until the final load is applied is 1.67 mm / s.

[0080] In this specification, the maximum vertical force of the golf ball 2 is measured under the first condition and the second condition. In this specification, the maximum vertical force of the standard ball is also measured under the first condition and the second condition.

[0081] 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 Pushing-in depth: 971 nm Compression deformation amount CDn: 3.12 mm

[0082] 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.

[0083] Under the first condition, the golf ball 2 or the standard ball is struck with the sand wedge 18 (product name "RTX-3" of Cleveland Golf shown in FIGS. 2 and 3). FIGS. 2 and 3 also show the fixture 19 and the acceleration sensor 20 (product name "356A01" of Tokuyo Technica). This sand wedge 18 has a head 22, a shaft 24, and a grip 26. The loft angle of the head 22 is 58°, the brand of the shaft 24 is "DG-S200" of True Temper, and the flex of this shaft 24 is S200. The acceleration sensor 20 is fixed to this shaft 24 via the fixture 19. The acceleration sensor 20 and the grip 26 are 10 mm apart. This acceleration sensor 20 has an X-axis, a Y-axis, and a Z-axis. The X-axis coincides with the length direction of the shaft 24. The Z-axis is orthogonal to the X-axis and parallel to the hitting direction of the golf ball 2. The Y-axis is orthogonal to the X-axis and the Z-axis.

[0084] This sand wedge 18 is mounted on a swing machine (Golf Laboratories). Under the condition that the head speed is 16 m / s, the golf ball 2 or the standard ball is struck with the sand wedge 18. The hitting point in this strike is the sweet spot of the head 22. The acceleration in the Z-axis direction at the time of this strike is measured by the acceleration sensor 20. The product of the total mass of the head 22, the shaft 24, 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.

[0085] In the second condition, the golf ball 2 or the standard ball is struck with the putter 28 (trade name of Cleveland "Huntington Beach Soft Putter #4") shown in FIGS. 4 and 5. FIGS. 4 and 5 also show the aforementioned acceleration sensor 20 (trade name of Tokuyo Technica "356A01"). This putter 28 has a head 30 and a shaft 32. The head 30 includes a face 34 and a sole 35. The face 34 has a toe-side end point 36, a heel-side end point 38, and a bottom edge line 40. In FIGS. 4 and 5, the symbol CP represents the center point of the face 34. The center point CP is on the center line CL. The distance from the center line CL to the heel-side end point 38 is equal to the distance from the center line CL to the toe-side end point 36. The distance from the bottom edge line 40 to the center point CP is 20 mm. On the back side of the center point CP, the acceleration sensor 20 is fixed to the head 30.

[0086] This putter 28 is mounted on a swing machine (Golf Laboratories). The golf ball 2 or the standard ball is struck with the putter 28 under the condition that the rolling distance is 15 m on a green where the horizontal speed measured by a stimpmeter is 10.0 m. 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 30 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.

[0087] The golf ball 2 according to the present embodiment satisfies the following mathematical formulas (1) and (2). (Fa / Fan) ≦ 0.90 (1) (Fa / Fan) 2 / (Fp / Fpn) ≦ 0.90 (2) Fa: The maximum vertical force of the golf ball 2 measured under the first condition Fan: 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 the standard ball measured under the second condition

[0088] When the golf ball 2 in the rough is struck by a golf club, turf is sandwiched between the golf ball 2 and the head 22. This turf induces slipping of the golf ball 2. This slip reduces the spin speed and carries the golf ball 2 to a position unintended by the golfer. In a shot with a short iron of the golf ball 2 that satisfies the above formula (1), even if turf is sandwiched between the golf ball 2 and the head 22, slipping is suppressed. This golf ball 2 is excellent in spin performance in a shot with a short iron. Further, in a shot with a short iron of the golf ball 2 that satisfies the above formula (1), a soft hitting feeling is achieved. In the golf ball 2 that satisfies the above formula (2), the soft hitting feeling in a shot with a short iron and the soft hitting feeling in putting are compatible. In this golf ball 2, the flight performance in a shot with a middle iron is not inhibited.

[0089] In the golf ball 2 that satisfies the above formula (1), the ratio (Fa / Fan) is 0.90 or less. From the viewpoints of spin performance and hitting feeling in a shot with a short iron, the ratio (Fa / Fan) is more preferably 0.86 or less, and particularly preferably 0.84 or less. The ratio (Fa / Fan) is preferably 0.75 or more.

[0090] In the golf ball 2 that satisfies the above formula (2), the ratio ((Fa / Fan) 2 / (Fp / Fpn)) is 0.90 or less. From the viewpoint of hitting feeling in a shot with a short iron and putting, the ratio ((Fa / Fan) 2 / (Fp / Fpn)) is more preferably 0.80 or less, and particularly preferably 0.77 or less. The ratio ((Fa / Fan) 2 / (Fp / Fpn)) is preferably 0.70 or more.

[0091] As means for achieving the above formulas (1) and (2), (a) Set the difference in hardness of core 4 (H1s - H1o) to be large. (b) Set the difference in hardness of core 4 (H1s - H1 (10) ) to be large. (c) Set the ratio of the hardness H2 of intermediate layer 6 to the hardness H3 of cover 8 (H2 / H3) to be large. (d) Set the ratio of the sum of the thickness T2 of intermediate layer 6 and the thickness T3 of cover 8 (T2 + T3) to the diameter D1 of core 4 to be small. Etc. are exemplified.

[0092] Preferably, golf ball 2 satisfies the following mathematical 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.

[0093] Preferably, golf ball 2 satisfies the following mathematical formula (4). (Tp / Tpn) ≧ 1.01 (4) Tp: Contact time of golf ball 2 measured under the second condition Tpn: Contact time of a 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.

[0094] Preferably, golf ball 2 satisfies the following mathematical 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.

Examples

[0095] Hereinafter, the effects of the golf ball according to the examples will be clarified, but the scope disclosed in this specification based on the description of this example should not be construed in a limited manner.

[0096] [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 consisting of an upper mold and a lower mold each having a hemispherical cavity and heated to obtain a core with a diameter of 39.7 mm.

[0097] 50 parts by mass of an ionomer resin (the aforementioned "Himilan 1605"), 50 parts by mass of another ionomer resin (the aforementioned "Himilan AM7329"), 4 parts by mass of titanium dioxide, and 9 parts by mass of barium sulfate were kneaded with a twin - screw kneading extruder to obtain a resin composition. The core was put 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.

[0098] A paint composition (product name "Polin 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 in an atmosphere of 23°C for 12 hours to obtain a reinforcing layer. The thickness of this reinforcing layer was 10 μm.

[0099] 100 parts by mass of a thermoplastic polyurethane elastomer (the aforementioned "Estane NY84A"), 2 parts by mass of a lubricant (product 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 (product name "JF-90" of Johoku Chemical Industry Co., Ltd.) were kneaded with 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 put into a final mold composed 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.

[0100] 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 having a diameter of about 42.7 mm and a mass of about 45.3 g was obtained.

[0101] [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, the intermediate layer, and the cover were as shown in Tables 1 and 2 below.

[0102] [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.

[0103] [Flight Test, I#7] A 7-iron club (product name "XXIO 11" of Sumitomo Rubber Industries, Ltd., shaft part number: MP1100, shaft hardness: S, loft angle: 28°) was attached to the swing machine of Golf Laboratories, Inc. The golf ball was hit under the condition that the head speed was 33 m / sec, and the spin speed and the flight distance were measured. The flight distance is the distance from the hitting point to the point where the golf ball came to rest. Twelve measurements were made, and the average value of the obtained data was calculated. Further, 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.

[0104] [Control Performance] A sand wedge (product name "RTX-3" of Cleveland Golf Company, loft angle: 58°) was attached to the swing machine of Golf Laboratories, Inc. Two blades of wild grass were attached to the surface of the golf ball with adhesive tape. The golf ball was set such that wild grass was interposed between the golf ball and the head, and the groove of the head was at a position orthogonal to the longitudinal direction of the wild grass. The golf ball was hit under the condition that the head speed was 16 m / s, and the spin speed was measured. Twelve measurements were made, and the average value of the obtained data was calculated. Further, based on this average value, the following grading was performed. A: 3500 rpm or more B: 3000 rpm or more and less than 3500 rpm C: Less than 3000 rpm This result is shown in Table 3 below.

[0105] [Feeling of hitting the ball, wedge] The tester hit the golf ball with a wedge and gave points 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 of 50 testers were calculated and the following grading was carried out. A: 340 points or more B: 310 points or more and less than 340 points C: Less than 310 points This result is shown in Table 3 below.

[0106] [Feeling of hitting the ball, putter] The testers were made to hit the golf ball with the 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 of 50 testers were calculated and the following grading was carried out. 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.

[0107]

Table 1

[0108]

Table 2

[0109]

Table 3

[0110] As shown in Table 3, the golf balls of each example are excellent in all of the flight performance in a shot with a middle iron, the spin performance in a shot with a short iron, the hitting feeling in a shot with a short iron, and the hitting feeling in putting. From these evaluation results, the superiority of this golf ball is clear.

[0111] [Disclosed Items] Each of the following items is a disclosure of a preferred embodiment.

[0112] [Item 1] A golf ball comprising a core, an intermediate layer located outside the core, and a cover located outside the intermediate layer, A golf ball satisfying the following formulas (1) and (2). (Fa / Fan) ≦ 0.90 (1) (Fa / Fan) 2 / (Fp / Fpn) ≦ 0.90 (2) (In these formulas, Fa represents the maximum vertical force of the golf ball measured under the first condition, Fan 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.)

[0113] [Item 2] The golf ball according to Item 1, satisfying the following formula (3). (Fp / Fpn) ≦ 0.98 (3)

[0114] [Item 3] The golf ball according to Item 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.)

[0115] [Item 4] The golf ball according to item 3 that satisfies the following formula (5). (Fp / Fpn) / (Tp / Tpn) ≦ 0.98 (5)

[0116] [Item 5] The golf ball according to any one of items 1 to 4, 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.

[0117] [Item 6] The golf ball according to any one of items 1 to 5, 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.

[0118] [Item 7] The golf ball according to any one of items 1 to 6, 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.

[0119] [Item 8] The golf ball according to any one of items 1 to 7, 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.

[0120] [Item 9] The golf ball according to any one of items 1 to 8, 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.

[0121] [Item 10] Further comprising one or more paint layers located outside the cover, The golf ball according to any one of items 1 to 9, 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]

[0122] The golf ball described above is suitable for play on a golf course, practice at a driving range, and the like.

Explanation of Signs

[0123] 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). (Fa / Fan) ≤ 0.90 (1) (Fa / Fan) ２ / (Fp / Fpn) ≤ 0.90 (2) (In these formulas, Fa represents the maximum vertical force of the golf ball measured under the first condition, Fan 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 16 m / s, using the sweet spot of the face of a sand wedge as the hitting point, the golf ball and the standard ball are hit. Under the second condition, on a horizontal green where the speed measured by a stimpmeter is 10.0 m and the rolling distance is 15 m, using the center point of the face of a putter as the hitting point, the golf ball and the standard ball are hit. The maximum vertical force under the first condition 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, shaft, and this acceleration sensor. The maximum vertical force under the second condition 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 a penetration 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, wherein the compression deformation amount CD measured under the conditions that the initial load is 98 N and the final load is 1275 N is 3.00 mm or more.

6. The golf ball according to any one of claims 1 to 5, 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.

7. The golf ball according to any one of claims 1 to 6, 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.

8. The golf ball according to any one of claims 1 to 7, 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.

9. The golf ball according to any one of claims 1 to 8, 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.

10. The golf ball further comprises one or more paint layers located outside the cover, The golf ball according to any one of claims 1 to 9, 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.

Images