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
2001-05-18
2002-12-03
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...
C525S274000, C525S301000, C525S236000, C473S371000, C473S372000
Reexamination Certificate
active
06489401
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a one-piece golf ball. More particularly, it relates to a one-piece golf ball having good durability, good shot feel and excellent flight performance.
BACKGROUND OF THE INVENTION
Golf balls are typically classified into two types, that is, golf balls for round games and golf. balls for driving ranges. It is difficult to say that performance, which is required for these two types of golf balls, is the same with each other. The performance required for the golf ball for round games is good shot feel, excellent flight performance, good durability and the like. If the golf balls for round games are used as a golf ball for driving ranges, good shot feel and excellent flight performance are maintained, but the durability is very poor as a golf ball for driving ranges, which is repeatedly hit. Therefore, at driving ranges, the durability is regarded as more important than the shot feel and flight performance, and golf balls having much better durability than that of the golf balls for round games is used.
In the golf balls for driving ranges, there are golf balls having low rebound characteristics, low trajectory and high trajectory, golf balls for using on the water and the like other than a standard ball depending on the extent of the driving ranges, the height of net and the like. There are various golf balls, such as one-piece golf ball, two-piece golf ball and the like, depending on the structure of the golf ball. At present, one-piece solid golf ball, which is standard ball, is mainly used as golf balls for driving ranges.
Recently, since performance as good as golf balls for round games, such as shot feel, has been required for golf balls for driving ranges, good shot feel and excellent flight performance have been required for the one-piece golf ball having excellent durability. However, when softening the golf ball in order to improve the shot feel or improving the flight performance, the durability is degraded. It is very difficult to improve shot feel and flight performance, while maintaining excellent durability.
A one-piece solid golf ball, of which the hardness distribution is adjusted so that an outer portion is hard and an inner portion is soft, is proposed (for example, Japanese Patent Kokai Publication No. 244418/1999 and the like). In Japanese Patent Kokai Publication No. 244418/1999, a one-piece solid golf ball, of which the hardness distribution is adjusted so that an outer portion is hard and an inner portion is soft, and the deformation amount is adjusted to a specific range, is described. However, in the golf ball, the shot feel is improved, but it is problem that excellent durability is not maintained.
Since it is required for the golf ball for driving ranges to be low cost, it is difficult to use expensive materials in order to solve the problem. Therefore one-piece solid golf ball, which is superior in all of durability, shot feel and flight performance, has not been yet obtained.
OBJECTS OF THE INVENTION
A main object of the present invention is to provide a one-piece golf ball having good durability, good shot feel and excellent flight performance.
According to the present invention, the object described above has been accomplished by using two types of polybutadiene having a specific weight average molecular weight and number average molecular weight in a specific weight ratio as a base rubber in a rubber composition comprising a base rubber, co-crosslinking agent, organic peroxide, inorganic filler and the like, thereby providing a one-piece golf ball having good durability, good shot feel and excellent flight performance.
SUMMARY OF THE INVENTION
The present invention provides a one-piece golf ball formed by vulcanizing and press molding a rubber composition comprising a base rubber, co-crosslinking agent, organic peroxide and inorganic filler, wherein
the base rubber comprises
(1) polybutadiene (A) having a weight average molecular weight (Mw) of 55×10
4
to 69×10
4
and a number average molecular weight (Mn) of 10×10
4
to 20×10
4
, and
(2) polybutadiene (B) having a weight average molecular weight (Mw) of 70×10
4
to 120×10
4
and a number average molecular weight (Mn) of 13×10
4
to 25×10
4
, in a weight ratio (A/B) of 3/97 to 70/30.
In order to put the present invention into a more suitable practical application, it is desired that
the polybutadiene (A) have Mw/Mn of 2.0 to 4.0, and the polybutadiene (B) have Mw/Mn of 4.2 to 5.0, and
the golf ball have a center hardness (C) in JIS-C hardness of 55 to 63, a surface hardness (D) in JIS-C hardness of 75 to 88 and a hardness difference (D−C) of 18 to 25.
The one-piece golf ball of the present invention is formed from vulcanized integrally molded article of rubber composition. The rubber composition comprises a base rubber, co-crosslinking agent, organic peroxide, inorganic filler and the like.
It is required for the base rubber used in the present invention to comprise
(1) polybutadiene (A) having a weight average molecular weight (Mw) of 55×10
4
to 69×10
4
and a number average molecular weight (Mn) of 10×10
4
to 20×10
4
, and
(2) polybutadiene (B) having a weight average molecular weight (Mw) of 70×10
4
to 120×10
4
and a number average molecular weight (Mn) of 13×10
4
to 25×10
4
, in a weight ratio (A/B) of 3/97 to 70/30.
It is required for the polybutadiene (A) to have Mw of 55×10
4
to 69×10
4
, preferably 55×10
4
to 65×10
4
, more preferably 57×10
4
to 65×10
4
. When the Mw is smaller than 55×10
4
, the rebound characteristics are degraded. On the other hand, when the Mw is larger than 69×10
4
, the processability is degraded. It is required for the polybutadiene (A) to have Mn of 10×10
4
to 20×10
4
, preferably 12×10
4
to 16×10
4
, more preferably 13×10
4
to 16×10
4
. When the Mn is smaller than 10×10
4
, the rebound characteristics are degraded. On the other hand, when the Mn is larger than 20×10
4
, the processability is degraded. It is desired for the polybutadiene (A) to have Mw/Mn of 2.0 to 4.0. When the Mw/Mn is larger than 4.0, the rebound characteristics are degraded. On the other hand, when the Mw/Mn is smaller than 2.0, the processability is degraded. Therefore the Mw/Mn is within the range of preferably 2.5 to 4.0, more preferably 2.7 to 4.0, most preferably 3.0 to 4.0.
It is required for the polybutadiene (B) to have Mw of 70×10
4
to 120×10
4
, preferably 75×10
4
to 110×10
4
, more preferably 80×10
4
to 110×10
4
. When the Mw is smaller than 70×10
4
, the rebound characteristics are degraded. On the other hand, when the Mw is larger than 120×10
4
, the processability is degraded. It is required for the polybutadiene (A) to have Mn of 13×10
4
to 25×10
4
, preferably 17×10
4
to 25×10
4
, more preferably 17×10
4
to 24×10
4
. When the Mn is smaller than 13×10
4
, the rebound characteristics are degraded. On the other hand, when the Mn is larger than 25×10
4
, the processability is degraded. It is desired for the polybutadiene (A) to have Mw/Mn of 4.2 to 5.0. When the Mw/Mn is larger than 5.0, the rebound characteristics are degraded. On the other hand, when the Mw/Mn is smaller than 4.2, the processability is degraded. Therefore the Mw/Mn is within the range of preferably 4.2 to 4.8, more preferably 4.2 to 4.5, most preferably 4.3 to 4.8.
It is desired for a ratio (Mw
A
/Mw
B
) of the Mw of the polybutadiene (A): (Mw
A
) to the Mw of the polybutadiene (B): (Mw
B
) to be within the range of 0.45 to 0.95, preferably 0.50 to 0.90. When the Mw
A
/Mw
B
is smaller than 0.45, the processability and durability are degraded. On the other hand, when the Mw
A
/Mw
B
is larger than 0.95, the rebound characteristics are degraded. It is desired for a ratio (Mn
A
/Mn
B
) of the Mn of the polybutadiene (A): (Mn
A
). to the Mn of the polybutad
Birch & Stewart Kolasch & Birch, LLP
Buttner David J.
Sumitomo Rubber Industries Ltd.
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