Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Mixing of two or more solid polymers; mixing of solid...
Reexamination Certificate
2002-12-23
2004-11-16
Buttner, David J. (Department: 1712)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Mixing of two or more solid polymers; mixing of solid...
C525S101000, C473S371000, C473S374000, C473S378000, C473S385000
Reexamination Certificate
active
06818701
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a golf ball having a good durability against repetitive hitting and a good resilience even in a low temperature, and particularly to a golf ball with the reduced dependency of a hitting head speed on the flight distance (resilience) of the ball.
In conventional two-piece golf balls, cores have been typically formed from rubbers obtained by thermally crosslinking materials mainly containing highly resilient polybutadiene rubber by using peroxides and co-crosslinking agents such as methacrylic acid, and covers have been typically formed from ionomer resins being excellent in impact resistance and cut resistance and commercially available, for example, under the trade names of Surlyn and Himilan.
The two-piece golf balls produced by using the above-described materials are excellent in flight characteristic and durability; however, they must generally sacrifice a soft feel, which is very important to golf players.
To cope with such an inconvenience, efforts have been made to develop two-piece golf balls capable of giving a soft feel by making the core softer and the cover harder. These golf balls, however, tend to give rise to other problems associated with poor durability against repetitive hitting, insufficient resilience, and/or poor low-temperature performance.
In view of the foregoing, various examinations have been recently made to improve two-piece golf balls, and golf balls, each including a core and a cover, at least one of which is of a two-layer structure having one layer for enhancing resilience and the other layer for giving a soft feel, have been put into markets.
With respect to the above two-layer structure of a cover or a core of a two-piece golf ball, there occurs an inconvenience that the resilience of each of an ionomer resin used as the cover material and crosslinked polybutadiene used as the core material can be kept as desirable at a high hardness; however, the resilience tends to be reduced as the hardness becomes low. In addition, a polyurethane based elastomer, a polyamide based elastomer, a polyester based elastomer, and the like used for forming an intermediate layer for the cover, of a golf ball for giving a pleasant feel of hitting the ball have been required to be further improved in resilience and to be further reduced in dependency of temperature on hardness.
To further improve the resilience and reduce the dependency of temperature on hardness, an attempt has been made to blend millable type silicone rubber in polybutadiene rubber, followed by crosslinking the resultant rubber by using peroxide, as disclosed in Japanese Patent Laid-open No. Sho 60-258236.
The above-described material, however, has a problem associated with dispersion of silicone rubber in polybutadiene rubber and non-uniform reactivity therebetween, which leads to the reduced durability against hitting. Accordingly, it is very difficult to stably obtain a rubber material having excellent characteristic by blending silicone rubber in polybutadiene rubber.
Another attempt has been made to blend millable type silicone rubber in a core-forming rubber or a cover-forming resin, followed by dynamic crosslinking, as disclosed in Japanese Patent Laid-open Nos. Hei 8-243191, Hei 9-220296, and Hei 9-225066. These blends, however, have problems associated with the extremely reduced flowability to the extent that injection molding thereof becomes difficult, the non-uniformity of crosslinking reaction and particle size, and the difficulty of uniform dispersion, resulting in insufficient characteristics, for example, durability against hitting. A further attempt has been made to blend crosslinked silicone powder in a golf ball member, as disclosed in Japanese Patent Laid-open No. Hei 2001-170213. The golf ball member disclosed in this document, however, has a problem that since the silicone powder blended in the golf ball member is an ultra fine powder having an average particle size in a range of 0.5 to 50 &mgr;m, adhesiveness of a coating film tends to become insufficient.
To give the above-described various characteristics to a golf ball, it is essential to develop a new golf ball material, and recently, it is increasingly expected to develop a golf ball material capable of enhancing the resilience in a wide hitting head speed range so as to realize a further improved flight performance, and exhibiting stable ball characteristics in a wide temperature range.
SUMMARY OF THE INVENTION
An object of the present invention is to provide a golf ball formed from a material which is easy for molding, and which has a high resilience in a wide hitting head speed range, a high flexibility and a high durability against repetitive hitting in a wide temperature range, and an excellent adhesiveness of a coating film.
To achieve the above object, the present inventors have made studies, and found that by blending an appropriate amount of a powder having a polysiloxane structure, such as crosslinked silicone rubber powder or a crosslinked silicone resin powder which has a relatively large average particle size, in a golf ball-forming composition, it is possible to obtain a golf ball excellent in flight performance, durability against repetitive hitting, and adhesiveness of a coating film, as compared with the above-described related art golf ball in which an appropriate amount of a fine powder having a polysiloxane structure, such as a crosslinked silicone rubber powder or a crosslinked silicone resin powder which has a relatively small average particle size, is blended.
The present inventors have further found that by blending at least one kind selected from a crosslinked silicone rubber powder and a crosslinked silicone resin powder in the above-described golf ball-forming composition (used as a material for forming a center ball, a core, a cover, a cover layer, a one-piece (1P) golf ball, or the like), preferably, in an amount of 0.5 to 30% by weight, the golf ball formed by using such a material can exhibit excellent resilience, low-temperature characteristic, flight performance, durability against repetitive hitting, and adhesiveness of a coating film. On the basis of such knowledge, the present invention has been accomplished.
Accordingly, to achieve the above-described object, according to an aspect of the present invention, there is provided a golf ball including: a portion formed from a golf ball-forming composition containing at least one kind selected from a crosslinked silicone rubber powder and a crosslinked silicone resin powder; wherein each of the crosslinked silicone rubber powder and the crosslinked silicone resin powder has an average particle size in a range of 60 to 500 &mgr;m.
The crosslinked silicone rubber powder is preferably a powder obtained by crosslinking dimethyl polysiloxane and/or methylphenyl polysiloxane.
The crosslinked silicone resin powder is preferably a powder of hardened polyorgano silsesquioxanes.
The golf ball-forming composition preferably contains the crosslinked silicone rubber powder and/or the crosslinked silicone resin powder in an amount of 0.5 to 30% by weight.
Each of the crosslinked silicone rubber powder and the crosslinked silicone resin powder preferably has functional groups.
The golf ball-forming composition is preferably used as at least one kind of material selected from a group consisting of a one-piece golf ball material, a core material and a cover material for a two-piece golf ball, a core material, an intermediate layer material, and a cover material for a multi-piece golf ball having three pieces or more.
The golf ball-forming composition preferably mainly contains at least one kind selected from the group consisting of an ethylene based ionomer resin, a polyester based elastomer, a polyurethane based elastomer, a polyolefin based elastomer, a polyamide based elastomer, a polyolefin resin, and a styrene block copolymer.
DESCRIPTION OF THE PREFERRED EMBODIMENT
The present invention will be more fully described below. The golf ball of the invention is characterized in that at least one k
Ichikawa Yasushi
Takehana Eiji
Takesue Rinya
Bridgestone Sports Co. Ltd.
Buttner David J.
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