GOLF BALL
20190160343 ยท 2019-05-30
Assignee
Inventors
Cpc classification
B32B1/00
PERFORMING OPERATIONS; TRANSPORTING
B32B25/02
PERFORMING OPERATIONS; TRANSPORTING
B32B27/302
PERFORMING OPERATIONS; TRANSPORTING
A63B37/0076
HUMAN NECESSITIES
A63B37/0021
HUMAN NECESSITIES
B32B25/16
PERFORMING OPERATIONS; TRANSPORTING
B32B2307/718
PERFORMING OPERATIONS; TRANSPORTING
B32B2264/104
PERFORMING OPERATIONS; TRANSPORTING
B32B2274/00
PERFORMING OPERATIONS; TRANSPORTING
B32B3/30
PERFORMING OPERATIONS; TRANSPORTING
B32B27/20
PERFORMING OPERATIONS; TRANSPORTING
International classification
Abstract
A golf ball 2 has a core 4, an inner cover 6, a main cover 8, and an outer cover 10. A product TH2 of a thickness T2 (mm) and a Shore C hardness H2 of the main cover 8 and a product THs of a value of 5% of a radius (mm) of the core 4 and a Shore C hardness Hs at a surface of the core 4 satisfy the following mathematical formula.
15(TH2THs)100
A product TH1 of a thickness T1 (mm) and a Shore C hardness H1 of the inner cover 6, a product TH3 of a thickness T3 (mm) and a Shore C hardness H3 of the outer cover 10, and the product TH2 satisfy the following mathematical formula.
0.25<((TH1+TH3)/2)/TH2<0.65
Claims
1. A golf ball comprising a core, an inner cover positioned outside the core, a main cover positioned outside the inner cover, and an outer cover positioned outside the main cover, wherein a product TH2 of a thickness T2 (mm) and a Shore C hardness H2 of the main cover and a product THs of a value of 5% of a radius (mm) of the core and a Shore C hardness Hs at a surface of the core satisfy the following mathematical formula,
15(TH2THs)100 a product TH1 of a thickness T1 (mm) and a Shore C hardness H1 of the inner cover, a product TH3 of a thickness T3 (mm) and a Shore C hardness H3 of the outer cover, and the product TH2 satisfy the following mathematical formula,
0.25<((TH1+TH3)/2)/TH2<0.65 the golf ball has a plurality of dimples on a surface thereof, a standard deviation Su of areas of all the dimples is not greater than 1.70 mm.sup.2, and a standard deviation Pd of distances L between dimples of all neighboring dimple pairs is less than 0.500 mm.
2. The golf ball according to claim 1, wherein the thickness T2 is equal to or larger than the thickness T1, and the thickness T2 is equal to or larger than the thickness T3.
3. The golf ball according to claim 1, wherein the thickness T2 is not less than 1.00 mm.
4. The golf ball according to claim 1, wherein the thickness T1 is not greater than 1.00 mm, and the thickness T3 is not greater than 1.00 mm.
5. The golf ball according to claim 1, wherein the hardness H2 is not less than 93.
6. The golf ball according to claim 1, wherein the hardness H1 is not greater than 70, and the hardness H3 is not greater than 70.
7. The golf ball according to claim 1, wherein the standard deviation Su is not greater than 1.50 mm.sup.2.
8. The golf ball according to claim 1, wherein the standard deviation Pd is not greater than 0.400 mm.
9. The golf ball according to claim 1, wherein a ratio So of a sum of the areas of the dimples relative to a surface area of a phantom sphere of the golf ball is not less than 78.0%.
10. The golf ball according to claim 1, wherein a sum of volumes of all the dimples is not less than 450 mm.sup.3 and not greater than 750 mm.sup.3.
11. The golf ball according to claim 1, wherein a dimple pattern of each hemisphere of a phantom sphere of the golf ball includes three units that are rotationally symmetrical to each other, and a dimple pattern of each unit includes two small units that are mirror-symmetrical to each other.
Description
BRIEF DESCRIPTION OF THE DRAWINGS
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DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0042] The following will describe in detail the present invention based on preferred embodiments with appropriate reference to the drawings.
[0043] A golf ball 2 shown in
[0044] The golf ball 2 preferably has a diameter of not less than 40 mm and not greater than 45 mm. From the viewpoint of conformity to the rules established by the United States Golf Association (USGA), the diameter is particularly preferably not less than 42.67 mm. In light of suppression of air resistance, the diameter is more preferably not greater than 44 mm and particularly preferably not greater than 42.80 mm.
[0045] The golf ball 2 preferably has a weight of not less than 40 g and not greater than 50 g. In light of attainment of great inertia, the weight is more preferably not less than 44 g and particularly preferably not less than 45.00 g. From the viewpoint of conformity to the rules established by the USGA, the weight is particularly preferably not greater than 45.93 g.
[0046] The core 4 is formed by crosslinking a rubber composition. Examples of preferable base rubbers for use in the rubber composition include polybutadienes, polyisoprenes, styrene-butadiene copolymers, ethylene-propylene-diene copolymers, and natural rubbers. In light of flight distance upon a shot with a driver having a low head speed, polybutadienes are preferable. When a polybutadiene and another rubber are used in combination, it is preferred if the polybutadiene is a principal component. Specifically, the proportion of the polybutadiene to the entire base rubber is preferably not less than 50% by weight and particularly preferably not less than 80% by weight. A polybutadiene in which the proportion of cis-1,4 bonds is not less than 80% is particularly preferable.
[0047] The rubber composition of the core 4 preferably includes a co-crosslinking agent. Preferable co-crosslinking agents in light of durability and resilience performance of the golf ball 2 are monovalent or bivalent metal salts of an ,-unsaturated carboxylic acid having 2 to 8 carbon atoms. Examples of preferable co-crosslinking agents include zinc acrylate, magnesium acrylate, zinc methacrylate, and magnesium methacrylate. In light of durability and resilience performance of the golf ball 2, zinc acrylate and zinc methacrylate are particularly preferable.
[0048] The rubber composition may include a metal oxide and an ,-unsaturated carboxylic acid having 2 to 8 carbon atoms. They both react with each other in the rubber composition to obtain a salt. The salt serves as a co-crosslinking agent. Examples of preferable ,-unsaturated carboxylic acids include acrylic acid and methacrylic acid. Examples of preferable metal oxides include zinc oxide and magnesium oxide.
[0049] The amount of the co-crosslinking agent per 100 parts by weight of the base rubber is preferably not less than 10 parts by weight and not greater than 45 parts by weight. The golf ball 2 in which this amount is not less than 10 parts by weight has excellent resilience performance. From this viewpoint, this amount is more preferably not less than 15 parts by weight and particularly preferably not less than 20 parts by weight. The golf ball 2 in which this amount is not greater than 45 parts by weight has excellent feel at impact. From this viewpoint, this amount is more preferably not greater than 40 parts by weight and particularly preferably not greater than 35 parts by weight.
[0050] Preferably, the rubber composition of the core 4 includes an organic peroxide. The organic peroxide serves as a crosslinking initiator. The organic peroxide contributes to the durability and the resilience performance of the golf ball 2. 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.
[0051] The amount of the organic peroxide per 100 parts by weight of the base rubber is preferably not less than 0.1 parts by weight and not greater than 3.0 parts by weight. The golf ball 2 in which this amount is not less than 0.1 parts by weight has excellent resilience performance. From this viewpoint, this amount is more preferably not less than 0.3 parts by weight and particularly preferably not less than 0.5 parts by weight. The golf ball 2 in which this amount is not greater than 3.0 parts by weight has excellent feel at impact. From this viewpoint, this amount is more preferably not greater than 2.5 parts by weight and particularly preferably not greater than 2.0 parts by weight.
[0052] Preferably, the rubber composition of the core 4 includes an organic sulfur compound. The organic sulfur compound contributes to flight distance upon a shot with a driver. Organic sulfur compounds include naphthalenethiol compounds, benzenethiol compounds, and disulfide compounds.
[0053] Examples of naphthalenethiol 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.
[0054] 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.
[0055] 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.
[0056] In light of resilience performance, the amount of the organic sulfur compound per 100 parts by weight of the base rubber is preferably not less than 0.1 parts by weight, more preferably not less than 0.2 parts by weight, and particularly preferably not less than 0.3 parts by weight. In light of soft feel at impact, the amount is preferably not greater than 1.5 parts by weight, more preferably not greater than 1.0 parts by weight, and particularly preferably not greater than 0.8 parts by weight. Two or more organic sulfur compounds may be used in combination.
[0057] Preferably, the rubber composition of the core 4 includes a carboxylic acid or a carboxylate. The carboxylic acid and the carboxylate can contribute to making the hardness distribution of the core 4 appropriate. An example of preferable carboxylic acids is benzoic acid. Examples of preferable carboxylates include zinc octoate and zinc stearate. The amount of the carboxylic acid and the carboxylate per 100 parts by weight of the base rubber is preferably not less than 0.5 parts by weight, more preferably not less than 0.8 parts by weight, and particularly preferably not less than 1.0 part by weight. This amount is preferably not greater than 20 parts by weight, more preferably not greater than 15 parts by weight, and particularly preferably not greater than 10 parts by weight.
[0058] The rubber composition of the core 4 may include a filler for the purpose of specific gravity adjustment and the like. Examples of suitable fillers include zinc oxide, barium sulfate, calcium carbonate, and magnesium carbonate. The amount of the filler is determined as appropriate so that the intended specific gravity of the core 4 is accomplished.
[0059] The rubber composition of the core 4 may include various additives, such as sulfur, an anti-aging agent, a coloring agent, a plasticizer, a dispersant, and the like, in an adequate amount. The rubber composition may include crosslinked rubber powder or synthetic resin powder.
[0060] The core 4 preferably has a diameter of not less than 35.0 mm and not greater than 40.5 mm. The golf ball 2 that includes the core 4 having a diameter of not less than 35.0 mm has excellent resilience performance. From this viewpoint, the diameter is more preferably not less than 36.0 mm and particularly preferably not less than 36.5 mm. The golf ball 2 that includes the core 4 having a diameter of not greater than 40.5 mm has excellent durability. From this viewpoint, the diameter is more preferably not greater than 39.5 mm and particularly preferably not greater than 39.0 mm.
[0061] A hardness Ho at the central point of the core 4 is preferably not less than 35 and not greater than 70. The golf ball 2 in which the hardness Ho is not less than 35 has excellent resilience performance. From this viewpoint, the hardness Ho is more preferably not less than 40 and particularly preferably not less than 45. The golf ball 2 in which the hardness Ho is not greater than 70 has excellent feel at impact. From this viewpoint, the hardness Ho is more preferably not greater than 65 and particularly preferably not greater than 60.
[0062] The hardness Ho is measured with a Shore C type hardness scale mounted to an automated hardness meter (trade name digi test II manufactured by Heinrich Bareiss Prfgertebau GmbH). The hardness scale is pressed against the central point of the cross-section of a hemisphere obtained by cutting the golf ball 2. The measurement is conducted in an environment of 23 C.
[0063] A hardness Hs at the surface of the core 4 is preferably not less than 55 and not greater than 95. The golf ball 2 in which the hardness Hs is not less than 55 has excellent resilience performance. From this viewpoint, the hardness Hs is more preferably not less than 60 and particularly preferably not less than 65. The golf ball 2 in which the hardness Hs is not greater than 95 has excellent feel at impact. From this viewpoint, the hardness Hs is more preferably not greater than 90 and particularly preferably not greater than 85.
[0064] The hardness Hs is measured with a Shore C type hardness scale mounted to an automated hardness meter (trade name digi test II manufactured by Heinrich Bareiss Prfgertebau GmbH). The hardness scale is pressed against the surface of the core 4. The measurement is conducted in an environment of 23 C.
[0065] A product THs of a value of 5% of the radius (mm) of the core 4 and the Shore C hardness Hs at the surface of the core 4 is preferably not less than 55 and not greater than 90. The golf ball 2 in which the product THs is not less than 55 has excellent resilience performance. From this viewpoint, the product THs is more preferably not less than 60 and particularly preferably not less than 65. The golf ball 2 in which the product THs is not greater than 90 has excellent feel at impact. From this viewpoint, the product THs is more preferably not greater than 85 and particularly preferably not greater than 80.
[0066] The core 4 has a weight of preferably not less than 10 g and not greater than 42 g. The temperature for crosslinking the core 4 is not lower than 140 C. and not higher than 180 C. The time period for crosslinking the core 4 is not shorter than 10 minutes and not longer than 60 minutes.
[0067] The inner cover 6 is positioned outside the core 4. The inner cover 6 is formed from a thermoplastic resin composition. Examples of the base polymer of the resin composition include ionomer resins, thermoplastic polyester elastomers, thermoplastic polyamide elastomers, thermoplastic polyurethane elastomers, thermoplastic polyolefin elastomers, and thermoplastic polystyrene elastomers. Ionomer resins are particularly preferable. Ionomer resins are highly elastic. The golf ball 2 that includes the inner cover 6 including an ionomer resin has excellent resilience performance. The golf ball 2 has excellent flight distance upon a shot with a driver.
[0068] An ionomer resin and another resin may be used in combination. In this case, in light of resilience performance, the ionomer resin is included as the principal component of the base polymer. The proportion of the ionomer resin to the entire base polymer is preferably not less than 50% by weight.
[0069] Examples of preferable ionomer resins include binary copolymers formed with an -olefin and an ,-unsaturated carboxylic acid having 3 to 8 carbon atoms. A preferable binary copolymer includes 80% by weight or more but 90% by weight or less of an -olefin, and 10% by weight or more but 20% by weight or less of an ,-unsaturated carboxylic acid. The binary copolymer has excellent resilience performance. Examples of other preferable ionomer resins include ternary copolymers formed with: an -olefin; an ,-unsaturated carboxylic acid having 3 to 8 carbon atoms; and an ,-unsaturated carboxylate ester having 2 to 22 carbon atoms. A preferable ternary copolymer includes 70% by weight or more but 85% by weight or less of an -olefin, 5% by weight or more but 30% by weight or less of an ,-unsaturated carboxylic acid, and 1% by weight or more but 25% by weight or less of an ,-unsaturated carboxylate ester. The ternary copolymer has excellent resilience performance. For the binary copolymer and the ternary copolymer, preferable -olefins are ethylene and propylene, while preferable ,-unsaturated carboxylic acids are acrylic acid and methacrylic acid. A particularly preferable ionomer resin is a copolymer formed with ethylene and acrylic acid. Another particularly preferable ionomer resin is a copolymer formed with ethylene and methacrylic acid.
[0070] In the binary copolymer and the ternary copolymer, some of the carboxyl groups are neutralized with metal ions. Examples of metal ions for use in 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 types of metal ions. Particularly suitable metal ions in light of resilience performance and durability of the golf ball 2 are sodium ion, zinc ion, lithium ion, and magnesium ion.
[0071] Specific examples of ionomer resins include trade names Himilan 1555, Himilan 1557, Himilan 1605, Himilan 1706, Himilan 1707, Himilan 1856, Himilan 1855, Himilan AM7311, Himilan AM7315, Himilan AM7317, Himilan AM7329, and Himilan AM7337, manufactured by Du Pont-MITSUI POLYCHEMICALS Co., Ltd.; trade names 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, manufactured by E.I. du Pont de Nemours and Company; and trade names IOTEK 7010, IOTEK 7030, IOTEK 7510, IOTEK 7520, IOTEK 8000, and IOTEK 8030, manufactured by ExxonMobil Chemical Corporation. Two or more ionomer resins may be used in combination.
[0072] Preferably, the resin composition of the inner cover 6 includes a styrene block-containing thermoplastic elastomer. The styrene block-containing thermoplastic elastomer includes a polystyrene block as a hard segment, and a soft segment. A typical soft segment is a diene block. Examples of compounds for the diene block include butadiene, isoprene, 1,3-pentadiene, and 2,3-dimethyl-1,3-butadiene. Butadiene and isoprene are preferable. Two or more compounds may be used in combination.
[0073] Examples of styrene block-containing thermoplastic elastomers include styrene-butadiene-styrene block copolymers (SBS), styrene-isoprene-styrene block copolymers (SIS), styrene-isoprene-butadiene-styrene block copolymers (SIBS), hydrogenated SBS, hydrogenated SIS, and hydrogenated SIBS. Examples of hydrogenated SBS include styrene-ethylene-butylene-styrene block copolymers (SEBS). Examples of hydrogenated SIS include styrene-ethylene-propylene-styrene block copolymers (SEPS). Examples of hydrogenated SIBS include styrene-ethylene-ethylene-propylene-styrene block copolymers (SEEPS).
[0074] In light of resilience performance of the golf ball 2, the content of the styrene component in the styrene block-containing thermoplastic elastomer is preferably not less than 10% by weight, more preferably not less than 12% by weight, and particularly preferably not less than 15% by weight. In light of feel at impact of the golf ball 2, the content is preferably not greater than 50% by weight, more preferably not greater than 47% by weight, and particularly preferably not greater than 45% by weight.
[0075] In the present invention, styrene block-containing thermoplastic elastomers include an alloy of an olefin and one or more members selected from the group consisting of SBS, SIS, SIBS, SEBS, SEPS, and SEEPS. The olefin component in the alloy is presumed to contribute to improvement of compatibility with another base polymer. The alloy can contribute to the resilience performance of the golf ball 2. An olefin having 2 to 10 carbon atoms is preferable. Examples of suitable olefins include ethylene, propylene, butene, and pentene. Ethylene and propylene are particularly preferable.
[0076] Specific examples of polymer alloys include trade names RABALON T3221C, RABALON T3339C, RABALON SJ4400N, RABALON SJ5400N, RABALON SJ6400N, RABALON SJ7400N, RABALON SJ8400N, RABALON SJ9400N, and RABALON SR04, manufactured by Mitsubishi Chemical Corporation. Other specific examples of styrene block-containing thermoplastic elastomers include trade name Epofriend A1010 manufactured by Daicel Chemical Industries, Ltd., and trade name SEPTON HG-252 manufactured by Kuraray Co., Ltd.
[0077] In light of feel at impact, the proportion of the styrene block-containing thermoplastic elastomer to the entire base polymer is preferably not less than 10% by weight, more preferably not less than 15% by weight, and particularly preferably not less than 20% by weight. In light of resilience performance, this proportion is preferably not greater than 50% by weight.
[0078] The resin composition of the inner cover 6 may include a coloring agent, a filler, a dispersant, an antioxidant, an ultraviolet absorber, a light stabilizer, a fluorescent material, a fluorescent brightener, and the like in an adequate amount. When the hue of the golf ball 2 is white, a typical coloring agent is titanium dioxide.
[0079] The inner cover 6 preferably has a thickness T1 of not less than 0.50 mm and not greater than 1.30 mm. The golf ball 2 in which the thickness T1 is not less than 0.50 mm has excellent feel at impact. From this viewpoint, the thickness T1 is more preferably not less than 0.70 mm and particularly preferably not less than 0.80 mm. The golf ball 2 in which the thickness T1 is not greater than 1.30 mm has excellent resilience performance. From this viewpoint, the thickness T1 is more preferably not greater than 1.10 mm and particularly preferably not greater than 1.00 mm. The thickness is measured at a position immediately below the land 14.
[0080] The inner cover 6 preferably has a hardness H1 of not less than 45 and not greater than 75. The golf ball 2 in which the hardness H1 is not less than 45 has excellent resilience performance. From this viewpoint, the hardness H1 is more preferably not less than 50 and particularly preferably not less than 55. The golf ball 2 in which the hardness H1 is not greater than 75 has excellent feel at impact. From this viewpoint, the hardness H1 is more preferably not greater than 70 and particularly preferably not greater than 65.
[0081] The hardness H1 of the inner cover 6 is measured according to the standards of ASTM-D 2240-68. The hardness H1 is measured with a Shore C type hardness scale mounted to an automated hardness meter (trade name digi test II manufactured by Heinrich Bareiss Pridfgeratebau GmbH). For the measurement, a sheet that is formed by hot press, is formed from the same material as that of the inner cover 6, and has a thickness of about 2 mm is used. Prior to the measurement, a sheet is kept at 23 C. for two weeks. At the time of measurement, three sheets are stacked.
[0082] A product TH1 of the thickness T1 (mm) and the Shore C hardness H1 of the inner cover 6 is preferably not less than 25 and not greater than 75. The golf ball 2 in which the product TH1 is in this range has excellent resilience performance and feel at impact. From this viewpoint, the product TH1 is more preferably not less than 30 and not greater than 70, and particularly preferably not less than 35 and not greater than 65.
[0083] The main cover 8 is positioned outside the inner cover 6. The main cover 8 is formed from a thermoplastic resin composition. Examples of the base polymer of the resin composition include ionomer resins, thermoplastic polyester elastomers, thermoplastic polyamide elastomers, thermoplastic polyurethane elastomers, thermoplastic polyolefin elastomers, and thermoplastic polystyrene elastomers. Ionomer resins are particularly preferable. Ionomer resins are highly elastic. The golf ball 2 that includes the main cover 8 including an ionomer resin has excellent resilience performance. The golf ball 2 has excellent flight distance upon a shot with a driver. The ionomer resin described above for the inner cover 6 can be used for the main cover 8.
[0084] An ionomer resin and another resin may be used in combination. In this case, in light of resilience performance, the ionomer resin is included as the principal component of the base polymer. The proportion of the ionomer resin to the entire base polymer is preferably not less than 50% by weight, more preferably not less than 70% by weight, and particularly preferably not less than 80% by weight.
[0085] The resin composition of the main cover 8 may include a coloring agent, a filler, a dispersant, an antioxidant, an ultraviolet absorber, a light stabilizer, a fluorescent material, a fluorescent brightener, and the like in an adequate amount. When the hue of the golf ball 2 is white, a typical coloring agent is titanium dioxide.
[0086] The main cover 8 preferably has a thickness T2 of not less than 0.80 mm and not greater than 2.00 mm. The golf ball 2 in which the thickness T2 is not less than 0.80 mm has excellent resilience performance, and spin of the golf ball 2 is suppressed. The golf ball 2 has excellent flight performance. From this viewpoint, the thickness T2 is more preferably not less than 0.90 mm and particularly preferably not less than 1.00 mm. The golf ball 2 in which the thickness T2 is not greater than 2.00 mm has excellent feel at impact. From this viewpoint, the thickness T2 is more preferably not greater than 1.80 mm and particularly preferably not greater than 1.60 mm. The thickness is measured at a position immediately below the land 14.
[0087] The main cover 8 preferably has a hardness H2 of not less than 93 and not greater than 100. The golf ball 2 in which the hardness H2 is not less than 93 has excellent resilience performance, and spin of the golf ball 2 is suppressed. The golf ball 2 has excellent flight performance. From this viewpoint, the hardness H2 is more preferably not less than 95 and particularly preferably not less than 97. The golf ball 2 in which the hardness H2 is not greater than 100 has excellent feel at impact. From this viewpoint, the hardness H2 is more preferably not greater than 99 and particularly preferably not greater than 98.
[0088] The hardness H2 of the main cover 8 is measured according to the standards of ASTM-D 2240-68. The hardness H2 is measured with a Shore C type hardness scale mounted to an automated hardness meter (trade name digi test II manufactured by Heinrich Bareiss Prfgertebau GmbH). For the measurement, a sheet that is formed by hot press, is formed from the same material as that of the main cover 8, and has a thickness of about 2 mm is used. Prior to the measurement, a sheet is kept at 23 C. for two weeks. At the time of measurement, three sheets are stacked.
[0089] A product TH2 of the thickness T2 (mm) and the Shore C hardness H2 of the main cover 8 is preferably not less than 70 and not greater than 180. The golf ball 2 in which the product TH2 is in this range has excellent flight performance and feel at impact. From this viewpoint, the product TH2 is more preferably not less than 80 and not greater than 170, and particularly preferably not less than 90 and not greater than 160.
[0090] The outer cover 10 is the outermost layer except the mark layer and the paint layer. The outer cover 10 is formed from a resin composition. Examples of the base polymer of the resin composition include polyurethanes, ionomer resins, polyesters, polyamides, polyolefins, and polystyrenes. A preferable base polymer in light of feel at impact and spin performance is a polyurethane. When a polyurethane and another resin are used in combination for the outer cover 10, the proportion of the polyurethane to the entire base resin is preferably not less than 50% by weight, more preferably not less than 60% by weight, and particularly preferably not less than 70% by weight.
[0091] The resin composition of the outer cover 10 may include a thermoplastic polyurethane or may include a thermosetting polyurethane. In light of productivity of the golf ball 2, the thermoplastic polyurethane is preferable. The thermoplastic polyurethane includes a polyurethane component as a hard segment, and a polyester component or a polyether component as a soft segment. The thermoplastic polyurethane is flexible. The outer cover 10 in which the polyurethane is used has excellent scuff resistance.
[0092] The thermoplastic polyurethane has a urethane bond within the molecule. The urethane bond can be formed by reacting a polyol with a polyisocyanate. The polyol, as a material for the urethane bond, has a plurality of hydroxyl groups. Low-molecular-weight polyols and high-molecular-weight polyols can be used.
[0093] Examples of low-molecular-weight polyols include diols, triols, tetraols, and hexaols. 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-cyclohexanedimethylol. Aniline diols or bisphenol A diols may be used. Specific examples of triols include glycerin, trimethylol propane, and hexanetriol. Specific examples of tetraols include pentaerythritol and sorbitol.
[0094] Examples of high-molecular-weight polyols include polyether polyols such as polyoxyethylene glycol (PEG), polyoxypropylene glycol (PPG), and polytetramethylene ether glycol (PTMG); condensed polyester polyols such as polyethylene adipate (PEA), polybutylene adipate (PBA), and polyhexamethylene adipate (PHMA); lactone polyester polyols such as poly--caprolactone (PCL); polycarbonate polyols such as polyhexamethylene carbonate; and acrylic polyols. Two or more polyols may be used in combination. In light of feel at impact of the golf ball 2, the high-molecular-weight polyol has a number average molecular weight of preferably not less than 400 and more preferably not less than 1000. The number average molecular weight is preferably not greater than 10000.
[0095] Examples of polyisocyanates, as a material for the urethane bond, include aromatic diisocyanates, alicyclic diisocyanates, and aliphatic diisocyanates. Two or more types of diisocyanates may be used in combination.
[0096] Examples of aromatic diisocyanates include 2,4-toluene diisocyanate, 2,6-toluene diisocyanate, 4,4-diphenylmethane diisocyanate (MDI), 1,5-naphthylene diisocyanate (NDI), 3,3f-bitolylene-4,4-diisocyanate (TODI), xylylene diisocyanate (XDI), tetramethylxylylene diisocyanate (TMXDI), and paraphenylene diisocyanate (PPDI). One example of aliphatic diisocyanates is hexamethylene diisocyanate (HDI). Examples of alicyclic diisocyanates include 4,4-dicyclohexylmethane diisocyanate (H.sub.12MDI), 1,3-bis(isocyanatemethyl)cyclohexane (H.sub.6XDI), isophorone diisocyanate (IPDI), and trans-1,4-cyclohexane diisocyanate (CHDI). 4,4-dicyclohexylmethane diisocyanate is preferable.
[0097] Specific examples of the thermoplastic polyurethane include trade names Elastollan NY80A, Elastollan NY82A, Elastollan NY83A, Elastollan NY84A, Elastollan NY85A, Elastollan NY88A, Elastollan NY90A, Elastollan NY95A, Elastollan NY97A, Elastollan NY585, and Elastollan KP016N, manufactured by BASF Japan Ltd.; and trade names RESAMINE P4585LS and RESAMINE PS62490, manufactured by Dainichiseika Color & Chemicals Mfg. Co., Ltd.
[0098] The resin composition of the outer cover 10 may include a coloring agent, a filler, a dispersant, an antioxidant, an ultraviolet absorber, a light stabilizer, a fluorescent material, a fluorescent brightener, and the like in an adequate amount. When the hue of the golf ball 2 is white, a typical coloring agent is titanium dioxide.
[0099] The outer cover 10 preferably has a thickness T3 of not less than 0.30 mm and not greater than 1.00 mm. The golf ball 2 in which the thickness T3 is not less than 0.30 mm has excellent feel at impact and spin performance. From this viewpoint, the thickness T3 is more preferably not less than 0.40 mm and particularly preferably not less than 0.45 mm. The golf ball 2 in which the thickness T3 is not greater than 1.00 mm has excellent resilience performance. From this viewpoint, the thickness T3 is more preferably not greater than 0.80 mm and particularly preferably not greater than 0.60 mm. The thickness is measured at a position immediately below the land 14.
[0100] The outer cover 10 preferably has a hardness H3 of not less than 50 and not greater than 80. The golf ball 2 in which the hardness H3 is not less than 50 has excellent resilience performance. From this viewpoint, the hardness H3 is more preferably not less than 53 and particularly preferably not less than 55. The golf ball 2 in which the hardness H3 is not greater than 80 has excellent feel at impact and spin performance. From this viewpoint, the hardness H3 is more preferably not greater than 75 and particularly preferably not greater than 70.
[0101] The hardness H3 of the outer cover 10 is measured according to the standards of ASTM-D 2240-68. The hardness H3 is measured with a Shore C type hardness scale mounted to an automated hardness meter (trade name digi test II manufactured by Heinrich Bareiss Prfgertebau GmbH). For the measurement, a sheet that is formed by hot press, is formed from the same material as that of the outer cover 10, and has a thickness of about 2 mm is used. Prior to the measurement, a sheet is kept at 23 C. for two weeks. At the time of measurement, three sheets are stacked.
[0102] A product TH3 of the thickness T3 (mm) and the Shore C hardness H3 of the outer cover 10 is preferably not less than 15 and not greater than 70. The golf ball 2 in which the product TH3 is in this range has excellent flight performance and feel at impact. From this viewpoint, the product TH3 is more preferably not less than 20 and not greater than 60, and particularly preferably not less than 25 and not greater than 55.
[0103] The golf ball 2 may include a reinforcing layer between the main cover 8 and the outer cover 10. The reinforcing layer firmly adheres to the main cover 8 and also to the outer cover 10. The reinforcing layer suppresses separation of the outer cover 10 from the main cover 8. The reinforcing layer is formed from a resin composition. Examples of a preferable base polymer of the reinforcing layer include two-component curing type epoxy resins and two-component curing type urethane resins. The reinforcing layer preferably has a thickness of not less than 5 m and not greater than 30 m.
[0104] Preferably, in the golf ball 2, the thickness T2 of the main cover 8 is equal to or larger than the thickness T1 of the inner cover 6. The difference (T2-T1) therebetween is preferably not less than 0.00 mm and not greater than 0.80 mm. The golf ball 2 in which the difference (T2-T1) is in the above range has excellent flight performance and feel at impact. From this viewpoint, the difference (T2T1) is particularly preferably not less than 0.05 mm and not greater than 0.70 mm.
[0105] Preferably, in the golf ball 2, the hardness H2 of the main cover 8 is greater than the hardness H1 of the inner cover 6. The difference (H2H1) therebetween is preferably not less than 15 and not greater than 55. The golf ball 2 in which the difference (H2H1) is in the above range has excellent flight performance and feel at impact. From this viewpoint, the difference (H2H1) is more preferably not less than 20 and not greater than 50, and particularly preferably not less than 25 and not greater than 45.
[0106] Preferably, in the golf ball 2, the thickness T2 of the main cover 8 is equal to or larger than the thickness T3 of the outer cover 10. The difference (T2T3) therebetween is preferably not less than 0.20 mm and not greater than 2.00 mm. The golf ball 2 in which the difference (T2T3) is in the above range has excellent flight performance and feel at impact. From this viewpoint, the difference (T2T3) is more preferably not less than 0.25 mm and not greater than 1.50 mm, and particularly preferably not less than 0.30 mm and not greater than 1.20 mm.
[0107] Preferably, in the golf ball 2, the hardness H2 of the main cover 8 is greater than the hardness H3 of the outer cover 10. The difference (H2H3) therebetween is preferably not less than 15 and not greater than 55. The golf ball 2 in which the difference (H2H3) is in the above range has excellent flight performance and feel at impact. From this viewpoint, the difference (H2H3) is more preferably not less than 20 and not greater than 50, and particularly preferably not less than 25 and not greater than 45.
[0108] The product TH2 of the thickness T2 and the Shore C hardness H2 of the inner cover 6 and the product THs of the value of 5% of the radius of the core 4 and the Shore C hardness Hs at the surface of the core 4 satisfy the following mathematical formula.
15(TH2THs)100
In other words, the difference (TH2THs) is not less than 15 and not greater than 100. The golf ball 2 in which the difference (TH2THs) is in this range has excellent flight performance and feel at impact. From this viewpoint, the difference (TH2THs) is more preferably not less than 15 and not greater than 90, and particularly preferably not less than 16 and not greater than 85.
[0109] The golf ball 2 satisfies the following mathematical formula.
0.25<((TH1+TH3)/2)/TH2<0.65
In other words, the ratio of the average of the product TH1 in the inner cover 6 and the product TH3 in the outer cover 10 to the product TH2 in the main cover 8 exceeds 0.25 and is less than 0.65. The golf ball 2 in which this ratio is in the above range has excellent flight performance and feel at impact. From this viewpoint, this ratio is more preferably not less than 0.26 and not greater than 0.63, and particularly preferably not less than 0.27 and not greater than 0.60.
[0110] The golf ball 2 preferably has an amount of compressive deformation Sb of not less than 2.5 mm and not greater than 4.0 mm. The golf ball 2 having an amount of compressive deformation Sb of not less than 2.5 mm has excellent feel at impact. From this viewpoint, the amount of compressive deformation Sb is preferably not less than 2.8 mm and particularly preferably not less than 3.2 mm. The golf ball 2 having an amount of compressive deformation Sb of not greater than 4.0 mm has excellent flight performance. From this viewpoint, the amount of compressive deformation Sb is more preferably not greater than 3.8 mm and particularly preferably not greater than 3.6 mm.
[0111] For measurement of the amount of compressive deformation, a YAMADA type compression tester SCH is used. In the tester, the golf ball 2 is placed on a hard plate made of metal. Next, a cylinder made of metal gradually descends toward the golf ball 2. The golf ball 2, squeezed between the bottom face of the cylinder and the hard plate, becomes deformed. A migration distance of the cylinder, starting from the state in which an initial load of 98 N is applied to the golf ball 2 up to the state in which a final load of 1274 N is applied thereto, is measured. A moving speed of the cylinder until the initial load is applied is 0.83 mm/s. A moving speed of the cylinder after the initial load is applied until the final load is applied is 1.67 mm/s.
[0112] As shown in
[0113] The number of the dimples A is 36; the number of the dimples B is 170; the number of the dimples C is 84; the number of the dimples D is 36; and the number of the dimples E is 12. The total number of the dimples 12 is 338. A dimple pattern is formed by these dimples 12 and the land 14.
[0114]
[0115] In
[0116] The diameter Dm of each dimple 12 is preferably not less than 2.0 mm and not greater than 6.0 mm. The dimple 12 having a diameter Dm of not less than 2.0 mm contributes to turbulization. From this viewpoint, the diameter Dm is more preferably not less than 2.5 mm and particularly preferably not less than 2.8 mm. The dimple 12 having a diameter Dm of not greater than 6.0 mm does not impair a fundamental feature of the golf ball 2 being substantially a sphere. From this viewpoint, the diameter Dm is more preferably not greater than 5.5 mm and particularly preferably not greater than 5.0 mm.
[0117] In
[0118] In light of suppression of rising of the golf ball 2 during flight, the first depth Dp1 of each dimple 12 is preferably not less than 0.10 mm, more preferably not less than 0.13 mm, and particularly preferably not less than 0.15 mm. In light of suppression of dropping of the golf ball 2 during flight, the first depth Dp1 is preferably not greater than 0.65 mm, more preferably not greater than 0.60 mm, and particularly preferably not greater than 0.55 mm.
[0119] The area S of the dimple 12 is the area of a region surrounded by the contour line of the dimple 12 when the central point of the golf ball 2 is viewed at infinity. In the case of a circular dimple 12, the area S is calculated by the following mathematical formula.
S=(Dm/2).sup.2*
In the golf ball 2 shown in
[0120] In the present invention, the ratio of the sum of the areas S of all the dimples 12 relative to the surface area of the phantom sphere 16 is referred to as an occupation ratio So. From the viewpoint of achieving sufficient turbulization, the occupation ratio So is preferably not less than 78%, more preferably not less than 80%, and particularly preferably not less than 82%. The occupation ratio So is preferably not greater than 95%. In the golf ball 2 shown in
[0121] The standard deviation Su of the areas of all the dimples 12 is preferably not greater than 1.70 mm.sup.2. The golf ball 2 having a standard deviation Su of not greater than 1.70 mm.sup.2 has excellent flight performance. From this viewpoint, the standard deviation Su is more preferably not greater than 1.62 mm.sup.2 and particularly preferably not greater than 1.50 mm.sup.2. The standard deviation Su is preferably not less than 1.20 mm.sup.2. In the present embodiment, the average of the areas of all the dimples 12 is 14.02 mm.sup.2. Therefore, the standard deviation Su of the areas of these dimples is calculated by the following mathematical formula.
[0122] From the viewpoint of achieving a sufficient occupation ratio So, the total number of the dimples 12 is preferably not less than 250, more preferably not less than 280, and particularly preferably not less than 300. From the viewpoint that each dimple 12 can contribute to turbulization, the total number is preferably not greater than 450, more preferably not greater than 410, and particularly preferably not greater than 390.
[0123] In the present invention, the volume V of the dimple means the volume of a portion surrounded by the surface of the phantom sphere 16 and the surface of the dimple 12. The total volume TV of the dimples 12 is preferably not less than 450 mm.sup.3 and not greater than 750 mm.sup.3. With the golf ball 2 having a total volume TV of not less than 450 mm.sup.3, rising of the golf ball 2 during flight is suppressed. From this viewpoint, the total volume TV is more preferably not less than 480 mm.sup.3 and particularly preferably not less than 500 mm.sup.3. With the golf ball 2 having a total volume TV of not greater than 750 mm.sup.3, dropping of the golf ball 2 during flight is suppressed. From this viewpoint, the total volume TV is more preferably not greater than 730 mm.sup.3 and particularly preferably not greater than 710 mm.sup.3.
[0124] As shown in
[0125] The plan view in
[0126] Of the surface of the golf ball 2 (or the phantom sphere 16), a zone surrounded by the line segment S1, the line segment S2, and the equator Eq (see
[0127] When the dimple pattern of the first spherical triangle T1 is rotated by 120 about a straight line connecting the two poles P, the resultant dimple pattern substantially overlaps the dimple pattern of the second spherical triangle T2. When the dimple pattern of the second spherical triangle T2 is rotated by 120 about the straight line connecting the two poles P, the resultant dimple pattern substantially overlaps the dimple pattern of the third spherical triangle T3. When the dimple pattern of the third spherical triangle T3 is rotated by 120 about the straight line connecting the two poles P, the resultant dimple pattern substantially overlaps the dimple pattern of the first spherical triangle T1. In other words, the dimple pattern of the hemisphere is composed of three units that are rotationally symmetrical to each other.
[0128] A pattern obtained by rotating the dimple pattern of each hemisphere HE by 120 about the straight line connecting the two poles P substantially overlaps the dimple pattern that has not been rotated. The dimple pattern of each hemisphere HE has 120 rotational symmetry.
[0129] A line segment S4 shown in
[0130] A pattern obtained by inverting the dimple pattern of the spherical triangle T1a with respect to a plane containing the line segment S4 and the straight line connecting both poles P substantially overlaps the dimple pattern of the spherical triangle T1b. In other words, the dimple pattern of the first spherical triangle T1 (unit) is composed of two small units that are mirror-symmetrical to each other.
[0131] Although not shown, similar to the first spherical triangle T1, the dimple pattern of the second spherical triangle T2 is also composed of two small units that are mirror-symmetrical to each other. The dimple pattern of the third spherical triangle T3 is also composed of two small units that are mirror-symmetrical to each other. The dimple pattern of the hemisphere HE is composed of the six small units.
[0132] According to the findings by the present inventor, with the golf ball 2 of which the dimple pattern of each hemisphere is composed of three units that are rotationally symmetrical to each other and the dimple pattern of each unit is composed of two small units that are mirror-symmetrical to each other, turbulization is promoted. The golf ball 2 has excellent flight performance.
[0133]
[0134] In
[0135] The surface of the golf ball 2 is a curved surface. The size of each dimple 12 is sufficiently small as compared to the size of the golf ball 2. Thus, in
[0136] The following will describe the definition of neighboring dimples.
[0137] In
[0138] In
[0139] In the present invention, when two dimples 12 satisfy both of conditions (1) and (2) described below, these dimples 12 are referred to as a neighboring dimple pair.
[0140] (1) The straight line that connects the centers of these dimples 12 to each other does not intersect any other dimple 12.
[0141] (2) Each of the two common inscribed lines of these dimples 12 does not intersect any dimple 12.
[0142] When a neighboring dimple pair 18 is present, one dimple 12 of the neighboring dimple pair 18 is a neighboring dimple with respect to the other dimple 12, and the other dimple 12 is a neighboring dimple with respect to the one dimple 12.
[0143] The first dimple 12a and the second dimple 12b shown in
[0144]
[0145]
[0146]
[0147] The line segment that connects the center of the first dimple 12a and the center of the second dimple 12b to each other does not intersect any dimple 12 other than the first dimple 12a and the second dimple 12b. Furthermore, each of the two common inscribed lines of the first dimple 12a and the second dimple 12b does not intersect any dimple 12. The first dimple 12a and the second dimple 12b form a neighboring dimple pair 18.
[0148] The line segment that connects the center of the first dimple 12a and the center of the third dimple 12c to each other does not intersect any dimple 12 other than the first dimple 12a and the third dimple 12c. Furthermore, each of the two common inscribed lines of the first dimple 12a and the third dimple 12c does not intersect any dimple 12. The first dimple 12a and the third dimple 12c form a neighboring dimple pair 18.
[0149] One of the two common inscribed lines of the first dimple 12a and the fourth dimple 12d intersects the second dimple 12b. Therefore, the first dimple 12a and the fourth dimple 12d do not form a neighboring dimple pair 18.
[0150] The line segment that connects the center of the first dimple 12a and the center of the fifth dimple 12e to each other intersects the third dimple 12c. Therefore, the first dimple 12a and the fifth dimple 12e do not form a neighboring dimple pair 18.
[0151] As described above, the first dimple 12a and the second dimple 12b form a neighboring dimple pair 18, and the first dimple 12a and the third dimple 12c also form a neighboring dimple pair 18. In
[0152] As described above, for the first dimple 12a, the second dimple 12b is a neighboring dimple, and the third dimple 12c is also a neighboring dimple. For the first dimple 12a, at least two neighboring dimples are present. Therefore, the first dimple 12a has at least two distances L (see
[0153] The standard deviation Pd of the distances L between the dimples 12 of all the neighboring dimple pairs 18 is preferably less than 0.500 mm. In other words, the standard deviation Pd is preferably small. As described above, in the golf ball 2, the standard deviation Su of the areas of the dimples 12 is small. In the golf ball 2 having a small standard deviation Su and a small standard deviation Pd, the dimples 12, the sizes of which are less varied, are uniformly arranged.
[0154] The vector of the lift force applied to the golf ball 2 on a trajectory after the peak has an upward vertical component and a forward horizontal component. The upward vertical component delays drop of the golf ball 2. In other words, the upward vertical component contributes to long flight duration. The forward horizontal component carries the golf ball 2 forward. With the golf ball 2 to which the lift force on a trajectory after the peak is large, a large flight distance is achieved.
[0155] According to the findings by the present inventor, with the golf ball 2 having a small standard deviation Su and a small standard deviation Pd, the lift force on a trajectory after the peak is large. The golf ball 2 has excellent flight performance. In light of flight performance, the standard deviation Pd is more preferably not greater than 0.458 mm, further preferably not greater than 0.400 mm, and particularly preferably not greater than 0.317 mm.
[0156] The average of the distances L between the dimples 12 of all the neighboring dimple pairs 18 is preferably not greater than 1.0 mm, more preferably not greater than 0.7 mm, and particularly preferably not greater than 0.5 mm. The average is preferably not less than 0.0 mm.
EXAMPLES
Example 1
[0157] A rubber composition I was obtained by kneading 100 parts by weight of a high-cis polybutadiene (trade name BR-730, manufactured by JSR Corporation), 28.5 parts by weight of zinc diacrylate, 12 parts by weight of zinc oxide, an appropriate amount of barium sulfate, 0.5 parts by weight of diphenyl disulfide, 0.9 parts by weight of dicumyl peroxide, and 2 parts by weight of benzoic acid. This rubber composition I was placed into a mold including upper and lower mold halves each having a hemispherical cavity, and heated at 170 C. for 18 minutes to obtain a core with a diameter of 37.80 mm. The amount of barium sulfate was adjusted such that a core having a predetermined weight was obtained.
[0158] A resin composition b was obtained by kneading 26 parts by weight of an ionomer resin (the aforementioned Himilan AM7337), 26 parts by weight of another ionomer resin (the aforementioned Himilan AM7329), 48 parts by weight of a styrene block-containing thermoplastic elastomer (the aforementioned Rabalon T3221C), 4 parts by weight of titanium dioxide, and 0.2 parts by weight of a light stabilizer (trade name JF-90, manufactured by Johoku Chemical Co., Ltd.) with a twin-screw kneading extruder. The core was placed into a mold including upper and lower mold halves each having a hemispherical cavity. The core was covered with the resin composition b by injection molding to form an inner cover. The thickness of the inner cover was 0.950 mm.
[0159] A resin composition f was obtained by kneading 55 parts by weight of an ionomer resin (the aforementioned Himilan AM7329), 45 parts by weight of another ionomer resin (the aforementioned Himilan 1555), 4 parts by weight of titanium dioxide, and 0.2 parts by weight of a light stabilizer (the aforementioned JF-90) with a twin-screw kneading extruder. The sphere consisting of the core and the inner cover was placed into a mold including upper and lower mold halves each having a hemispherical cavity. The sphere was covered with the resin composition f by injection molding to form a main cover. The thickness of the main cover was 1.00 mm.
[0160] A paint composition (trade name POLIN 750LE, manufactured by SHINTO PAINT CO., LTD.) including a two-component curing type epoxy resin as a base polymer was prepared. The base material liquid of this paint composition includes 30 parts by weight of a bisphenol A type epoxy resin and 70 parts by weight of a solvent. The curing agent liquid of this paint composition includes 40 parts by weight of a modified polyamide amine, 55 parts by weight of a solvent, and 5 parts by weight of titanium dioxide. The weight ratio of the base material liquid to the curing agent liquid is 1/1. This paint composition was applied to the surface of the main cover with a spray gun, and kept at 23 C. for 12 hours to obtain a reinforcing layer with a thickness of 10 m.
[0161] A resin composition j was obtained by kneading 30 parts by weight of a thermoplastic polyurethane elastomer (the aforementioned Elastollan NY85A), 70 parts by weight of another thermoplastic polyurethane elastomer (the aforementioned Elastollan NY88A), 0.2 parts by weight of a light stabilizer (trade name TINUVIN 770), 4 parts by weight of titanium dioxide, and 0.04 parts by weight of ultramarine blue with a twin-screw kneading extruder. Half shells were obtained from the resin composition j by compression molding. The sphere consisting of the core, the inner cover, and the main cover was covered with two of these half shells. These half shells and the sphere were placed into a final mold that includes upper and lower mold halves each having a hemispherical cavity and having a large number of pimples on its cavity face, and an outer cover was obtained by compression molding. The thickness of the outer cover was 0.50 mm. Dimples having a shape that is the inverted shape of the pimples were formed on the outer cover.
[0162] A clear paint including a two-component curing type polyurethane as a base material was applied to this outer cover to obtain a golf ball of Example 1 with a diameter of about 42.7 mm and a weight of about 45.6 g. Dimple specifications Dl of the golf ball are shown in detail in Tables 5 and 7 below.
Examples 2 to 5 and Comparative Examples 1 and 2
[0163] Golf balls of Examples 2 to 5 and Comparative Examples 1 and 2 were obtained in the same manner as Example 1, except the specifications of the dimples were as shown in Tables 9 and 10 below. The specifications of the dimples are shown in detail in Tables 5 to 8 below.
Examples 6 to 9 and Comparative Examples 3 to 8
[0164] Golf balls of Examples 6 to 9 and Comparative Examples 3 to 8 were obtained in the same manner as Example 1, except the specifications of the core, the inner cover, the main cover, the outer cover, and the dimples were as shown in Tables 11 and 12 below. The composition of the core is shown in detail in Table 1 below. The composition of the inner cover is shown in detail in Table 2 below. The composition of the main cover is shown in detail in Table 3 below. The composition of the outer cover is shown in detail in Table 4 below. The specifications of the dimples are shown in detail in Tables 5 to 8 below.
[0165] [Flight Test]
[0166] A driver with a head made of a titanium alloy (trade name XXIO 9, manufactured by DUNLOP SPORTS CO. LTD., shaft hardness: R, loft angle: 10.5) was attached to a swing machine manufactured by Golf Laboratories, Inc. A golf ball was hit under a condition of a head speed of 40 m/sec, and the ball speed and the spin rate immediately after the hit, and the flight distance, were measured. The flight distance is the distance from the launch point to the stop point. During the test, the weather was almost windless. The average value of data obtained by 12 measurements is shown in Tables 9 to 12 below.
TABLE-US-00001 TABLE 1 Composition of Core (parts by weight) I II Polybutadiene 100 100 Zinc diacrylate 28.5 24.0 Zinc oxide 12 5 Barium sulfate A.A. A.A. Diphenyl disulfide 0.5 0.5 Pentabromophenyl disulfide 0.3 Dicumyl peroxide 0.9 0.9 Benzoic acid 2 Crosslinking temperature ( C.) 165 165 Crosslinking time (min) 20 20 A.A.: Appropriate amount
TABLE-US-00002 TABLE 2 Composition of Inner Cover (parts by weight a b c d Himilan AM7337 22 26 30 38.5 Himilan AM7329 22 26 30 38.5 Rabalon T3221C 56 48 40 23 Titanium dioxide 4 4 4 4 JF-90 0.2 0.2 0.2 0.2 Hardness H1 50 57 63 76 (Shore C)
TABLE-US-00003 TABLE 3 Composition of Main Cover (parts by weight) e f g h Himilan AM7329 45 55 50 50 Himilan 1605 50 25 Himilan 1555 50 45 Surlyn 8150 25 Rabalon T3221C 5 Titanium dioxide 4 4 4 4 JF-90 0.2 0.2 0.2 0.2 Hardness H2 88 92 96 100 (Shore C)
TABLE-US-00004 TABLE 4 Composition of Outer Cover (parts by weight) i j k l Elastollan NY83A 100 Elastollan NY85A 30 Elastollan NY88A 70 Elastollan NY90A 90 25 Elastollan NY97A 10 75 TINUVIN 770 0.2 0.2 0.2 0.2 Titanium dioxide 4 4 4 4 Ultramarine blue 0.04 0.04 0.04 0.04 Hardness H3 50 57 63 70 (Shore C)
TABLE-US-00005 TABLE 5 Specifications of Dimples Dm Dp2 Dp1 CR S V Number (mm) (mm) (mm) (mm) (mm.sup.2) (mm.sup.3) D1 A 36 4.40 0.135 0.2487 17.99 15.21 1.892 B 170 4.30 0.135 0.2435 17.19 14.52 1.770 D 84 4.20 0.135 0.2385 16.40 13.85 1.654 E 36 4.10 0.135 0.2336 15.63 13.20 1.544 F 12 3.00 0.135 0.1878 8.40 7.07 0.665 D2 A 60 4.40 0.138 0.2517 17.61 15.21 1.915 B 158 4.30 0.137 0.2455 16.94 14.52 1.785 C 72 4.15 0.134 0.2351 16.13 13.53 1.592 D 36 3.90 0.123 0.2122 15.52 11.95 1.269 E 12 3.00 0.122 0.1748 9.28 7.07 0.619 D3 A 314 4.20 0.135 0.2385 16.40 13.85 1.654 B 12 3.90 0.135 0.2242 14.15 11.95 1.341 C 12 3.00 0.135 0.1878 8.40 7.07 0.665 D4 A 102 4.50 0.135 0.2539 18.82 15.90 2.021 B 24 4.40 0.135 0.2487 17.99 15.21 1.892 C 30 4.30 0.135 0.2435 17.19 14.52 1.770 D 54 4.20 0.135 0.2385 16.40 13.85 1.654 E 108 4.00 0.135 0.2289 14.88 12.57 1.440 F 12 3.50 0.135 0.2068 11.41 9.62 0.997
TABLE-US-00006 TABLE 6 Specifications of Dimples Dm Dp2 Dp1 CR S V Number (mm) (mm) (mm) (mm) (mm.sup.2) (mm.sup.3) D5 A 338 4.11 0.120 0.2189 17.61 13.23 1.450 D6 A 30 4.60 0.125 0.2492 21.22 16.62 2.073 B 54 4.50 0.125 0.2439 20.31 15.90 1.941 C 72 4.30 0.125 0.2335 18.55 14.52 1.697 D 54 4.20 0.125 0.2285 17.70 13.85 1.585 E 108 4.00 0.125 0.2189 16.06 12.57 1.377 F 12 2.70 0.125 0.1677 7.35 5.73 0.481 D7 A 16 4.60 0.135 0.2592 19.66 16.62 2.157 B 30 4.50 0.135 0.2539 18.82 15.90 2.021 C 30 4.40 0.135 0.2487 17.99 15.21 1.892 D 150 4.30 0.135 0.2435 17.19 14.52 1.770 E 30 4.20 0.135 0.2385 16.40 13.85 1.654 F 66 4.10 0.135 0.2336 15.63 13.20 1.544 G 10 3.80 0.135 0.2197 13.44 11.34 1.247 H 12 3.40 0.135 0.2028 10.77 9.08 0.922
TABLE-US-00007 TABLE 7 Specifications of Dimples D1 D2 D3 D4 Plan view FIG. 2 FIG. 10 FIG. 12 FIG. 14 Front view FIG. 3 FIG. 11 FIG. 13 FIG. 15 Number of dimples 338 338 338 330 Number of units 3 3 3 3 Number of small 6 6 6 6 units Occupation ratio 82.8 82.0 79.9 81.1 So (%) Total volume TV 571.6 564.6 543.5 561.5 (mm.sup.3) Standard 1.44 1.61 1.29 1.62 deviation Su of S (mm.sup.2) Number of 1,068 1,068 1,068 1,014 neighboring dimple pairs Average of L 0.280 0.295 0.345 0.332 (mm) Standard 0.314 0.302 0.317 0.458 deviation Pd of L (mm)
TABLE-US-00008 TABLE 8 Specifications of Dimples D5 D6 D7 Plan view FIG. 16 FIG. 18 FIG. 20 Front view FIG. 17 FIG. 19 FIG. 21 Number of dimples 338 330 344 Number of units 3 3 Number of small 6 6 units Occupation ratio 78.1 79.9 85.3 So (%) Total volume TV 490.1 529.3 592.5 (mm.sup.3) Standard 0.00 2.10 1.42 deviation Su of S (mm.sup.2) Number of 1,068 1,014 1,038 neighboring dimple pairs Average of L 0.434 0.375 0.190 (mm) Standard 0.502 0.452 0.306 deviation Pd of L (mm)
TABLE-US-00009 TABLE 9 Results of Evaluation Ex. 1 Ex. 2 Ex. 3 Ex. 4 Core I I I I Diameter (mm) 37.80 37.80 37.80 37.80 Ho (Shore C) 48 48 48 48 Hs (Shore C) 80 80 80 80 Inner cover b b b b T1 (mm) 0.95 0.95 0.95 0.95 H1 (Shore C) 57 57 57 57 Main cover h h h h T2 (mm) 1.00 1.00 1.00 1.00 H2 (Shore C) 98 98 98 98 Outer cover j j j J T3 (mm) 0.50 0.50 0.50 0.50 H3 (Shore C) 57 57 57 57 Dimple D1 D2 D3 D4 Deformation Sb (mm) 3.21 3.21 3.21 3.21 THs 76 76 76 76 TH1 54 54 54 54 TH2 98 98 98 98 TH3 29 29 29 29 (TH1 + TH3)/2 41 41 41 41 TH2 THs 22 22 22 22 (TH1 + TH3)/2/TH2 0.42 0.42 0.42 0.42 Ball speed (m/s) 57.61 57.61 57.61 57.61 Spin (rpm) 2390 2390 2390 2390 Flight distance (m) 200.5 199.9 199.5 198.6 Feel at impact A A A A
TABLE-US-00010 TABLE 10 Results of Evaluation Comp. Comp. Ex. 1 Ex. 2 Ex. 5 Core I I I Diameter (mm) 37.80 37.80 37.80 Ho (Shore C) 48 48 48 Hs (Shore C) 80 80 80 Inner cover b b b T1 (mm) 0.95 0.95 0.95 H1 (Shore C) 57 57 57 Main cover h h h T2 (mm) 1.00 1.00 1.00 H2 (Shore C) 98 98 98 Outer cover j j j T3 (mm) 0.50 0.50 0.50 H3 (Shore C) 57 57 57 Dimple D5 D6 D7 Deformation Sb (mm) 3.21 3.21 3.21 THs 76 76 76 TH1 54 54 54 TH2 98 98 98 TH3 29 29 29 (TH1 + TH3)/2 41 41 41 TH2 THs 22 22 22 (TH1 + TH3)/2/TH2 0.42 0.42 0.42 Ball speed (m/s) 57.61 57.61 57.61 Spin (rpm) 2390 2390 2390 Flight distance (m) 193.1 194.0 197.3 Feel at impact A A A
TABLE-US-00011 TABLE 11 Results of Evaluation Comp. Comp. Comp. Ex. 6 Ex. 3 Ex. 4 Ex. 5 Ex. 7 Core I I I I I Diameter (mm) 37.80 37.80 37.80 36.60 37.30 Ho (Shore C) 48 48 48 48 50 Hs (Shore C) 80 80 80 79 80 Inner cover b b b a c T1 (mm) 0.95 0.95 0.95 0.95 0.95 H1 (Shore C) 57 57 57 50 63 Main cover f e e g g T2 (mm) 1.00 1.00 1.00 1.60 1.00 H2 (Shore C) 92 88 88 96 96 Outer cover j j j j l T3 (mm) 0.50 0.50 0.50 0.50 0.75 H3 (Shore C) 57 57 57 57 70 Dimple D1 D2 D6 D5 D1 Deformation Sb (mm) 3.41 3.51 3.51 3.21 3.24 THs 76 76 76 72 75 TH1 54 54 54 48 60 TH2 92 88 88 154 96 TH3 29 29 29 29 53 (TH1 + TH3)/2 41 41 41 38 56 TH2 THs 16 12 12 81 21 (TH1 + TH3)/2/TH2 0.45 0.47 0.47 0.25 0.59 Ball speed (m/s) 57.36 57.27 57.27 57.64 57.65 Spin (rpm) 2490 2502 2502 2615 2537 Flight distance (m) 197.3 196.1 193.8 195.5 198.9 Feel at impact A B B D B
TABLE-US-00012 TABLE 12 Results of Evaluation Comp. Comp. Comp. Ex. 6 Ex. 7 Ex. 8 Ex. 9 Ex. 8 Core II II II II II Diameter (mm) 37.30 35.70 36.60 37.10 37.10 Ho (Shore C) 58 56 56 56 56 Hs (Shore C) 77 74 75 76 76 Inner cover d b b b b T1 (mm) 0.95 0.95 0.95 0.75 0.75 H1 (Shore C) 76 57 57 57 57 Main cover f g g g g T2 (mm) 1.00 1.80 1.60 1.30 1.30 H2 (Shore C) 92 96 96 96 96 Outer cover k j j j j T3 (mm) 0.75 0.75 0.50 0.75 0.75 H3 (Shore C) 63 57 57 57 57 Dimple D3 D6 D2 D3 D5 Deformation Sb (mm) 3.24 3.11 3.16 3.26 3.26 THs 72 66 69 70 70 TH1 72 54 54 43 43 TH2 92 173 154 125 125 TH3 47 43 29 43 43 (TH1 + TH3)/2 60 48 41 43 43 TH2 THs 20 107 85 54 54 (TH1 + TH3)/2/TH2 0.65 0.28 0.27 0.34 0.34 Ball speed (m/s) 57.7 57.83 57.74 57.63 57.63 Spin (rpm) 2742 2658 2602 2564 2564 Flight distance (m) 195.6 195.8 198.2 197.3 195.9 Feel at impact B D C A A
[0167] As shown in Tables 9 to 12, the golf ball of each Example has excellent flight performance and feel at impact. From the evaluation results, advantages of the present invention are clear.
[0168] The golf ball according to the present invention is suitable for, for example, playing golf on golf courses and practicing at driving ranges. The above descriptions are merely illustrative examples, and various modifications can be made without departing from the principles of the present invention.