Practice golf ball

Abstract

A practice golf ball has a core made of a rubber composition which includes a base rubber, a co-crosslinking agent, a crosslinking initiator and a metal oxide, and has a cover which encases the core and is made of a resin material. The co-crosslinking agent is methacrylic acid. The resin material has a breaking strength of 20 to 80 MPa and an elongation of 150 to 600%. The ball is endowed with the properties required of practice balls intended for long-term use, including better durability to cracking and durability of appearance than ordinary game balls, and also better durability to ball surface loss than the one-piece golf balls which are commonly used as practice balls.

Description

CROSS-REFERENCE TO RELATED APPLICATION[0001]This non-provisional application claims priority under 35 U.S.C. §119(a) on Patent Application No. 2011-099853 filed in Japan on Apr. 27, 2011, the entire contents of which are hereby incorporated by reference.BACKGROUND OF THE INVENTION[0002]1. Field of the Invention[0003]The present invention relates to a practice golf ball which is suitable for use at such places as driving ranges. More specifically, the invention relates to a practice golf ball endowed with the properties required of practice balls intended for long-term use, including better durability to cracking and durability of appearance than ordinary game balls, and also better durability to ball surface loss than the one-piece golf balls which are commonly used as practice balls.[0004]2. Prior Art[0005]In terms of the performance sought in a practice golf ball, it is generally desirable to obtain ball characteristics which are no different from those of golf balls used to play ...

AI Technical Summary

Benefits of technology

[0013]We have discovered that, in the production of practice golf balls having a core and a cover, by using methacrylic acid as a co-crosslinking agent for the base rubber in the core-forming rubber composition and by using a resin material having a breaking strength of from 20 MPa to 80 MPa and an elongation of from 150% to 600% as the cover material, owing to the synergistic effects of these materials, the resulting balls have better durability to cracking and durability to abrasion than anticipated by golf ball designers. This discovery has made it possible to obtain practice golf balls which, even with long-term use, retain a good appearance and a good flight performance, and moreover have better durability to ball surface loss than the one-piece golf balls which are commonly used as practice balls.

[0014]That is, in the present invention, by using methacrylic acid as a co-crosslinking agent in the core-forming rubber composition and by optimizing the amounts of methacrylic acid and crosslinking initiator included in the composition, the ball can be made much more durable to cracking than a game ball. In addition, by selecting a resin material which has a high strength and good elongation and using this resin material to form the cover, a practice golf ball endowed with excellent durability to cracking, durability to surface loss and durability to abrasion can be obtained. Moreover, in the invention, by optimizing the cross-sectional shape of the dimples formed on the ball surface, a practice golf ball having excellent durability to markings (e.g., a brand name or player number printed on the surface of the ball at the time of manufacture) in long-term use can be obtained. Furthermore, by optimizing the internal hardness profile of the core, a golf ball having a good feel on impact can be obtained.

[0030]The practice golf ball of the invention is endowed with the properties required of practice balls intended for long-term use, including better durability to cracking and durability of appearance than ordinary game balls, and also better durability to ball surface loss than the one-piece golf balls which are commonly used as practice balls.

Problems solved by technology

If, for example, a practice ball has a feel on impact or a flight performance which differs from that of a game ball, when the time comes to play an actual round, the golfer will be unable to take full advantage of the skills acquired through practice.

However, when zinc methacrylate is used in this way in a core-forming rubber composition, achieving good ball durability in long-term use at a golf driving range has been difficult.

However, here too, when zinc acrylate is used in the rubber-forming rubber composition, achieving good ball durability in long-term use at a driving range has been difficult.

However, this prior-art golf ball lacks a satisfactory durability to surface loss when hit with the sharp portion of a clubhead, such as the leading edge of an iron.

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