Practice golf ball

Abstract

A practice golf ball has a core and a cover. The core is made of a rubber composition which includes a base rubber, a co-crosslinking agent, a crosslinking initiator and a metal oxide. The base rubber is a mixture of polybutadiene with styrene-butadiene rubber and / or isoprene rubber, and the co-crosslinking agent is methacrylic acid. The core has a specific deflection under a specific load, and the ball has a specific initial velocity. The dimples on the surface of the ball have a volume ratio VR of from 0.95 to 1.7.

Description

CROSS-REFERENCE TO RELATED APPLICATION[0001]This non-provisional application claims priority under 35 U.S.C. §119(a) on Patent Application No. 2011-099969 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 which 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 the ability to maintain a stable feel on impact and a stable flight performance over a long period of time, and which, moreover, by further limiting the flight of the ball, has a controlled distance for use at very small driving ranges.[0004]2. Prior Art[0005]In terms of the performance sought in a practice g...

AI Technical Summary

Benefits of technology

[0013]We have discovered that, in the production of practice golf balls having a core made of a rubber composition and a cover encasing the core, by using a mixture of polybutadiene with styrene-butadiene rubber and / or isoprene rubber as the base rubber, by using methacrylic acid as a co-crosslinking agent in the rubber composition and also including a given amount of a crosslinking initiator per 100 parts by weight of the base rubber, and moreover by optimizing the core deflection under a specific load, the initial velocity of the finished ball and the dimple volume ratio VR, owing to the synergistic effects of these features, 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 a practice golf ball which, even with long-term use, retains a good appearance and a good flight performance, has a good feel on impact and, by further limiting the flight of the ball, has a controlled distance.

[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 rubber composition, the ball can be made much more durable to cracking than a game ball. In addition, by having the cover material formed primarily of polyurethane, a practice golf ball endowed with excellent durability to cracking and durability to abrasion can be obtained. Moreover, 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, the ability to maintain a stable feel on impact and a stable flight performance over a long period of time, and also, by further limiting the flight of the ball, a controlled distance for use at very small driving ranges.

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, drawbacks of such golf balls include a hard cover, a large decrease in ball flight following abrasion of the ball surface, and poor durability of markings (“markings” referring here to, for example, a brand name or player number printed on the surface of the ball at the time of manufacture).

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