Classifications

• • A—HUMAN NECESSITIES
  • A63—SPORTS; GAMES; AMUSEMENTS
  • A63B—APPARATUS FOR PHYSICAL TRAINING, GYMNASTICS, SWIMMING, CLIMBING, OR FENCING; BALL GAMES; TRAINING EQUIPMENT
  • A63B37/00—Solid balls; Rigid hollow balls; Marbles
  • A63B37/0003—Golf balls
• • A—HUMAN NECESSITIES
  • A63—SPORTS; GAMES; AMUSEMENTS
  • A63B—APPARATUS FOR PHYSICAL TRAINING, GYMNASTICS, SWIMMING, CLIMBING, OR FENCING; BALL GAMES; TRAINING EQUIPMENT
  • A63B37/00—Solid balls; Rigid hollow balls; Marbles
  • A63B37/0003—Golf balls
  • A63B37/0023—Covers
  • A63B37/0029—Physical properties
  • A63B37/0031—Hardness
• • A—HUMAN NECESSITIES
  • A63—SPORTS; GAMES; AMUSEMENTS
  • A63B—APPARATUS FOR PHYSICAL TRAINING, GYMNASTICS, SWIMMING, CLIMBING, OR FENCING; BALL GAMES; TRAINING EQUIPMENT
  • A63B37/00—Solid balls; Rigid hollow balls; Marbles
  • A63B37/0003—Golf balls
  • A63B37/0023—Covers
  • A63B37/0029—Physical properties
  • A63B37/0035—Density; Specific gravity
• • A—HUMAN NECESSITIES
  • A63—SPORTS; GAMES; AMUSEMENTS
  • A63B—APPARATUS FOR PHYSICAL TRAINING, GYMNASTICS, SWIMMING, CLIMBING, OR FENCING; BALL GAMES; TRAINING EQUIPMENT
  • A63B37/00—Solid balls; Rigid hollow balls; Marbles
  • A63B37/0003—Golf balls
  • A63B37/005—Cores
  • A63B37/006—Physical properties
  • A63B37/0066—Density; Specific gravity

Definitions

• This invention relates to a multi-piece solid golf ball comprising a solid core enclosed with a cover having an inner and an outer layer.
• a multi-piece solid golf ball comprising a solid core and a cover of two inner and outer layers surrounding the core that the solid core is formed relatively soft, the inner cover layer is formed mainly of a thermoplastic polyester elastomer, the outer cover layer is formed mainly of a thermoplastic polyurethane elastomer, the inner cover layer has a Shore D hardness of 28 to 58, and the outer cover layer has a Shore D hardness of 30 to 55.
• the present invention provides:
• the golf ball of the invention features an increased flight distance, superior control upon iron shots, good feeling upon shots with any club of wood, iron and putter, high resistance to scraping upon control shots with an iron, and good durability.
• the multi-piece solid golf ball of the invention has a solid core and a cover surrounding the core of a two-layer structure of inner and outer cover layers.
• the solid core used herein is formed mainly of a rubber base.
• Natural rubber and/or synthetic rubber which is used in conventional solid golf balls can be used as the rubber base although 1,4-polybutadiene having at least 40% of a cis structure is especially preferred in the practice of the invention.
• natural rubber, polyisoprene rubber, styrene-butadiene rubber or the like may be blended with the polybutadiene rubber if desired.
• the solid core of the golf ball according to the invention is obtained in conventional ways by adjusting vulcanizing conditions and blending ratio.
• the solid core composition contains a base rubber, a crosslinking agent, a co-crosslinking agent, an inert filler, etc.
• the base rubber used may be the above-mentioned natural rubber and/or synthetic rubber.
• the crosslinking agent is exemplified by organic peroxides such as dicumyl peroxide and di-t-butyl peroxide, with the dicumyl peroxide being especially preferred.
• the amount of the crosslinking agent blended is usually 0.5 to 2.0 parts by weight per 100 parts by weight of the base rubber.
• the co-crosslinking agent is not critical and exemplified by metal salts of unsaturated fatty acids, especially zinc and magnesium salts of unsaturated fatty acids having 3 to 8 carbon atoms (e.g., acrylic acid and methacrylic acid), with zinc acrylate being especially preferred.
• the amount of the co-crosslinking agent blended is 10 to 50 parts by weight, preferably 20 to 48 parts by weight per 100 parts by weight of the base rubber.
• the inert filler examples include zinc oxide, barium sulfate, silica, calcium carbonate, and zinc carbonate, with zinc oxide and barium sulfate being commonly used.
• the amount of the filler blended is governed by the specific gravity of the core and the cover, the weight specification of the ball, etc. and not critical although it is usually 1 to 30 parts by weight per 100 parts by weight of the base rubber. It is understood that in the practice of the invention, the solid core is given an optimum hardness by properly adjusting the amount of zinc oxide and barium sulfate blended.
• a solid core composition is prepared by kneading the above-mentioned components in a conventional mixer such as a Banbury mixer and roll mill, and it is compression or injection molded in a core mold. The molding is then cured into a solid core by heating at a sufficient temperature for the crosslinking agent and co-crosslinking agent to function (for example, about 130 to 170°C when dicumyl peroxide and zinc acrylate are used as the crosslinking agent and the co-crosslinking agent, respectively).
• the solid core should have a distortion or deformation of at least 2.7 mm, preferably 2.8 to 6.0 mm, more preferably 2.9 to 5.0 mm under an applied load of 100 kg.
• a distortion of less than 2.7 mm under an applied load of 100 kg (hard core) would give disadvantages such as a hard hitting feel.
• a too much distortion (too soft core) would sometimes result in poor restitution.
• the solid core preferably has a specific gravity of 0.9 to 1.2, especially 1.01 to 1.18.
• the solid core preferably has a diameter of 30 to 40 mm, especially 33 to 39 mm.
• the solid core may be of multi-layer structure insofar as it satisfies the above-defined distortion under an applied load of 100 kg.
• the inner cover layer is formed mainly of a thermoplastic polyester elastomer.
• thermoplastic polyester elastomer used herein includes polyether ester type multi-block copolymers synthesized from terephthalic acid, 1,4-butane diol, and polytetramethylene glycol (PTMG) or polypropylene glycol (PPG) wherein polybutylene terephthalate (PBT) portions become hard segments and polytetramethylene glycol (PTMG) or polypropylene glycol (PPG) portions become soft segments, for example, Hytrel 4047, G3548W, 4767, and 5577 (by Toray duPont K.K.).
• PBT polytetramethylene glycol
• PPG polypropylene glycol
• thermoplastic polyester elastomer To the thermoplastic polyester elastomer, another polymer such as another elastomer and ionomer resin may be added if necessary.
• the amount of the other polymer added is less than 70 parts by weight, especially less than 50 parts by weight per 100 parts by weight of the thermoplastic polyester elastomer.
• the inner cover layer composed mainly of the thermoplastic polyester elastomer may contain 0 to about 30% by weight of an inorganic filler such as zinc oxide, barium sulfate, and titanium dioxide.
• the inner cover layer should have a Shore D hardness of 28 to 58, especially 30 to 56. A Shore D hardness of less than 28 would detract from restitution whereas hitting feel would be exacerbated above 58.
• the inner cover layer should preferably have a specific gravity of 1.05 to 1.4, especially 1.1 to 1.3.
• the inner cover layer preferably has a gage of 0.5 to 3.0 mm, especially 0.9 to 2.5 mm.
• the outer cover layer is formed of a thermoplastic polyurethane elastomer.
• thermoplastic polyurethane elastomer used herein has a molecular structure consisting of a high molecular weight polyol compound constituting a soft segment, a monomolecular chain extender constituting a hard segment, and a diisocyanate.
• the high molecular weight polyol compound is not critical and may be any of polyester polyols, polyether polyols, copolyester polyols, and polycarbonate polyols.
• Exemplary polyester polyols include polycaprolactone glycol, poly(ethylene-1,4-adipate) glycol, and poly(butylene-1,4-adipate) glycol; an exemplary copolyester polyol is poly(diethylene glycol adipate) glycol; an exemplary polycarbonate polyol is (hexanediol-1,6-carbonate) glycol; and an exemplary polyether polyol is polyoxytetramethylene glycol.
• Their number average molecular weight is about 600 to 5,000, preferably 1,000 to 3,000.
• diisocyanate aliphatic diisocyanates are preferably used in consideration of the yellowing resistance of the cover. Examples include hexamethylene diisocyanate (HDI), 2,2,4- or 2,4,4-trimethylhexamethylene diisocyanate (TMDI), and lysine diisocyanate (LDI). HDI is especially preferred for its compatibility with another resin upon blending.
• the monomolecular chain extender is not critical and may be selected from conventional polyhydric alcohols and amines. Examples include 1,4-butylene glycol, 1,2-ethylene glycol, 1,3-propylene glycol, 1,6-hexylene glycol, 1,3-butylene glycol, dicyclohexylmethylmethanediamine (hydrogenated MDA), and isophoronediamine (IPDA).
• 1,4-butylene glycol 1,2-ethylene glycol, 1,3-propylene glycol, 1,6-hexylene glycol, 1,3-butylene glycol, dicyclohexylmethylmethanediamine (hydrogenated MDA), and isophoronediamine (IPDA).
• thermoplastic polyurethane elastomers those having a tan ⁇ peak temperature of lower than -15°C, especially -16°C to -50°C as determined by viscoelasticity measurement are preferred in view of softness and resiliency.
• thermoplastic polyurethane elastomer there may be used commercially available ones whose diisocyanate component is aliphatic, for example, Pandex T7298 (-20°C), T7295 (-26°C), and T7890 (-30°C) (by Dai-Nihon Ink Chemical Industry K.K.). Note that the numerals in parentheses each represent a tan ⁇ peak temperature.
• thermoplastic polyurethane elastomer may be added to the thermoplastic polyurethane elastomer in an amount of 0 to 60 parts by weight, especially 0 to 50 parts by weight per 100 parts by weight of the thermoplastic polyurethane elastomer.
• outer cover layer composed mainly of the thermoplastic polyurethane elastomer may contain less than 30% by weight, especially 1 to 25% by weight of an inorganic filler such as zinc oxide, barium sulfate, and titanium dioxide.
• the outer cover layer should have a Shore D hardness of 30 to 55, preferably 32 to 54, more preferably 33 to 53. A Shore D hardness of less than 30 would detract from restitution whereas hitting feel would be exacerbated above 55.
• the outer cover layer should preferably have a specific gravity of 1.05 to 1.4, especially 1.07 to 1.35.
• the outer cover layer preferably has a gage of 0.5 to 2.5 mm, especially 0.9 to 2.4 mm. Durability would become poor below 0.5 mm whereas restitution and hitting feel would become poor above 2.5 mm.
• the inner and outer cover layers preferably have a total gage (overall cover gage) of 1.0 to 5.5 mm, especially 1.5 to 5.0 mm.
• the inner and outer cover layers may be formed by well-known techniques such as injection molding and compression molding using half shells.
• the multi-piece solid golf ball thus obtained should preferably have an inertia moment of at least 83 g-cm 2 , especially 84 to 90 g-cm 2 as measured by the method described later.
• An inertia moment of less than 83 g-cm 2 would lead to the disadvantage that the ball rolling upon putting becomes unsustained and loses straightness.
• the outer cover layer is formed with dimples in a conventional manner.
• the golf ball of the invention is constructed in accordance with the Rules of Golf to a diameter of not less than 42.67 mm and a weight of not greater than 45.93 grams.
• Solid cores of the composition shown in Table 1 were prepared.
• Solid core composition (pbw) Example Comparative Example 1 2 3 4 1 2 3 4 5 6
• Polybutadiene 100 100 100 100 100 100 100 100 100 100 100 100 100 100 100 100 100 100 100 100 100 100 100 100 Dicumyl peroxide 1.2 1.2 1.2 1.2 1.2 1.2 1.2 1.2 1.2 1.2 1.2 1.2 1.2 1.2 1.2 1.2 Barium sulfate 3.7 3.8 0 0 19 21.2 12.9 20.7 10
• Zinc oxide 5 5 1.5 4.2 3.8 5 5 5 5 5
• compositions d, e, f in Table 2 and D, E, F, G in Table 3 are not according to the invention and were tested for comparative purposes only.
• the golf balls were examined for inertia moment, flight distance, spin rate, feeling, scraping resistance, and consecutive durability by the following tests.
• the results are shown in Tables 4, in accordance with the invention, and 5 showing the comparative examples.
• the inertia moment is a value calculated from the diameters (gages) and specific gravities of the respective layers and it can be determined from the following equation on the assumption that the ball is spherical.
• the specific gravity of the outer cover layer is lower than the specific gravity of the outer cover-forming resin itself because the dimples are present on the actual ball.
• the specific gravity of the outer cover layer is herein designated a phantom outer cover layer specific gravity, which is used for the calculation of an inertia moment M.
• M ( ⁇ /5880000) ⁇ (r1-r2) ⁇ D1 5 + (r2-r3) ⁇ D2 5 + r3 ⁇ D3 5 ⁇
• the ball was hit with a driver (#W1, head speed 45 m/sec.) to measure a carry and total distance.
• a spin rate was calculated from photographic analysis by photographing the behavior of the ball immediately after impact with #W1 and a sand wedge (#SW, head speed 20 m/sec.).
• the ball was hit at two points with a sand wedge (#SW, head speed 38 m/sec.). The ball at the hit points was visually examined.
• the ball was repeatedly hit at a head speed of 38 m/sec.
• the ball was evaluated in terms of the number of hits repeated until the ball was broken.

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• Health & Medical Sciences (AREA)
• General Health & Medical Sciences (AREA)
• Physical Education & Sports Medicine (AREA)
• Compositions Of Macromolecular Compounds (AREA)

Applications Claiming Priority (6)

Publications (2)

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• 1997
  • 1997-10-22 JP JP30796997A patent/JP3516123B2/ja not_active Expired - Fee Related
• 1998
  • 1998-08-07 DE DE1998619975 patent/DE69819975T2/de not_active Expired - Lifetime
  • 1998-08-07 EP EP19980306356 patent/EP0895794B1/en not_active Expired - Lifetime

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