Games using tangible projectile – Golf – Ball
Reexamination Certificate
2000-08-21
2003-06-24
Sewell, Paul T. (Department: 3711)
Games using tangible projectile
Golf
Ball
C473S351000
Reexamination Certificate
active
06582325
ABSTRACT:
BACKGROUND OF THE INVENTION
Professional and skilled golfers favor golf balls using balata rubber as the cover stock because the balata cover offers a soft feel, a desired spin rate and control upon iron shots.
The golf balls using balata rubber, however, are rather difficult to mold and require an increased material cost and manufacturing cost. Because of low resilience, balata rubber is believed unsuitable for combination with solid cores. Another problem of the balata cover balls is that upon iron shots, the cover surface is scraped off by grooves across the iron clubface owing to the frictional force between the clubface and the cover, so that the ball surface is marred or fluffed.
Ionomer resin covers have been proposed. Sullivan, U.S. Pat. No. 4,884,814 or JP-A 308577/1989 discloses to blend an ionomer resin in the form of an ethylene/(meth)acrylic acid copolymer having a certain spectrum of physical properties with a relatively soft ionomer resin in the form of an ethylene/(meth)acrylic acid/(meth)acrylate terpolymer. The soft/hard ionomer blend is used as a golf ball cover. JP-A 277208/1993 discloses a golf ball using a mixture of two or more metal salts of ethylene-unsaturated carboxylic acid-unsaturated carboxylate terpolymers having a low flexural modulus as the cover stock. These are very effective techniques for achieving significant improvements in productivity and cost while maintaining hitting feel and controllability comparable to the balata rubber.
The ionomer resin covers of these patents, however, still suffer from the problem that the ball surface is marred or fluffed by iron shots because the cover surface is scraped off by grooves across the iron clubface. Additionally, on account of low resilience, the ionomer resin covers invite a substantial drop of resilience when combined with solid cores.
Many attempts were made to use thermosetting polyurethane elastomers as a substitute for the balata rubber and ionomer resins because the polyurethane elastomers are relatively inexpensive and offer good feeling and good scuff resistance. See U.S. Pat. Nos. 3,989,568, 4,123,061, and 5,334,673. Despite improvements in the scuff resistance which is the drawback of softened ionomer resin blends, the thermosetting polyurethane elastomers require complex steps of introducing the raw material and then effecting curing reaction, indicating that further efforts must be made for mass-scale production.
Also, U.S. Pat. Nos. 3,395,109, 4,248,432 and 4,442,282 disclose thermoplastic polyurethane elastomers as the cover stock. They do not satisfy all the requirements of moldability, hitting feel, control, resilience, and scuff resistance upon iron shots.
In this regard, we proposed in JP-A 271538/1997 the use of high resilience thermoplastic polyurethane elastomers. A further improvement in scuff resistance upon iron shots is desired.
SUMMARY OF THE INVENTION
An object of the invention is to provide a solid golf ball which is efficiently moldable and meet such requirements as a pleasant feel, ease of control, initial velocity (resilience and flight distance), scuff resistance upon iron shots, and non-discoloration.
The invention pertains to a solid golf ball comprising a solid core and a cover enclosing the core. According to the invention, the reaction product of a thermoplastic polyurethane elastomer with dicyclohexylmethane-4,4″-diisocyanate as an isocyanate compound is used as a main component of a resin composition of which the cover is formed. This resin composition or cover stock is efficient to mold. The resulting solid golf ball meet such requirements as a pleasant feel, ease of control, resilience (initial velocity and flight distance), scuff resistance upon iron shots, and non-discoloration.
More specifically, when a core is enclosed with a cover obtained by subjecting a thermoplastic polyurethane elastomer to crosslinking reaction with dicyclohexylmethane-4,4″-diisocyanate, the ball is significantly improved in scuff resistance upon iron shots. The ball offers a pleasant feel, ease of control, and excellent resilience (initial velocity and flight distance). Moreover, the ball is prevented from discoloring. The crosslinking reaction is effected by adding such an amount of dicyclohexylmethane-4,4″-diisocyanate to a thermoplastic polyurethane elastomer that the thermoplastic polyurethane elastomer remains at a thermoplastic level sufficient to allow injection molding, heating and melting them for reaction to give a batchwise mix, and injection molding the mix. Alternatively, a dry blend of a thermoplastic polyurethane elastomer and dicyclohexylmethane-4,4″-diisocyanate is kneaded and reacted while it is injection molded.
Known in the prior art is a method for preparing a resin molding by causing a polyisocyanate compound to penetrate into a surface layer of polyurethane base resin molding (JP-A 47630/1994). A focus was also placed on polyurethane elastomers having properties comparable to those of thermosetting polyurethane elastomers. In JP-B 2063/1983, a molding is prepared by feeding a batchwise mixture of an isocyanate compound and a compound which is not reactive with isocyanate radicals into a molding machine along with a thermoplastic polyurethane elastomer.
When these prior art methods are applied to the cover of golf balls, the former method requires a prolonged time and a sophisticated technique and is thus impractical. The batchwise mixture of isocyanate compound used in the latter method, at its surface, is unstable in air at room temperature because the isocyanate compound has not been inactivated by chemical reaction. The batchwise mixture must be stored prior to use under conditions capable of avoiding reaction with moisture in air. Additionally, reaction of the batchwise mixture with a thermoplastic polyurethane elastomer is rapid and difficult to control. It is then difficult to produce molded parts of consistent quality on a mass scale. The use in the batchwise mixture of the compound which is not reactive with isocyanate radicals detracts from the physical properties required as the golf ball cover such as resilience and scuff resistance upon iron shots.
DETAILED DESCRIPTION OF THE INVENTION
In the solid golf ball of the invention, the cover is formed of a resin composition primarily comprising the reaction product between (1) a thermoplastic polyurethane elastomer and (2) dicyclohexylmethane-4,4″-diisocyanate.
The thermoplastic polyurethane elastomer (1) has a structure including soft segments of a high molecular weight polyol (or polymeric glycol) and hard segments constructed of a chain extender and a diisocyanate.
The high molecular weight polyol used as one source material may be any of those commonly used in the prior polyurethane elastomer art. Polyester and polyether polyols are generally included. Polyester polyols include polybutylene adipate, polyethylene butylene adipate, polyethylene adipate, polycaprolactone and blends thereof. One exemplary polyether polyol is polyoxytetramethylene glycol. These polyols preferably have an average molecular weight of about 1,000 to about 5,000.
The chain extender used herein may be any of those commonly used in the prior polyurethane elastomer art. Examples include 1,4-butylene glycol, 1,2-ethylene glycol, 1,3-butane diol, 1,6-hexane diol, 2,2-dimethyl-1,3-propane diol, 4,4′-diaminodiphenylmethane, hydrogenated MDA, isophorone diamine, hexamethylenediamine, and hydroquinone diethylol ether. The chain extenders preferably have an average molecular weight of about 200 to about 15,000.
The diisocyanate used herein may be any of those commonly used in the prior polyurethane elastomer art. Examples include aromatic diisocyanates such as 2,4-toluene diisocyanates, 2,6-toluene diisocyanate, mixtures thereof, 4,4′-diphenylmethane diisocyanate, m-phenylene diisocyanate, and 4,4′-biphenyl diisocyanate; aliphatic diisocyanates such as tetramethylene diisocyanate, hexamethylene diisocyanate (HDI), and octamethylene diisocyanate; and alicyclic diisocyanates such as xy
Ichikawa Yasushi
Ishihara Kunitoshi
Kashiwagi Shunichi
Matsumura Nobuhiko
Takesue Rinya
Bridgestone Sports Co. Ltd.
Hunter, Jr. Alvin A.
Sewell Paul T.
Sughrue & Mion, PLLC
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