Appeal No. 2005-1116 Page 5
Application No. 10/077,148
producing a golf ball having excellent flight stability and go-straight stability upon putting.
The cover outer layer's specific gravity is properly selected in accordance with the
specific gravity of the core and cover inner layer although it is preferred that the cover
outer layer is formed to a specific gravity of at least 1.10, especially 1.10 to 1.25 and the
difference of specific gravity between the cover outer layer and the core is 0.01 to 0.15.
Yamagishi's cover inner layer 2 has a specific gravity of 0.9 to 1.2. The cover outer
layer is preferably formed to a Shore D hardness of 40 to 68, more preferably 43 to 65.
A Shore D hardness of less than 40 would lead to low restitution whereas a Shore D
hardness of more than 68 would blunt the hitting feel.
Yamagishi's cover outer layer 3 may be formed of conventional cover stocks,
preferably thermoplastic resins. The thermoplastic resins that may be used include
thermoplastic polyurethane elastomers, ionomer resins, polyester elastomers,
polyamide elastomers, propylene-butadiene copolymers, 1,2-polybutadiene, and
styrene-butadiene copolymers. These resins may be used alone or in admixture of two
or more. Yamagishi prefers to use thermoplastic polyurethane elastomers as a base.
To satisfy the cover's specific gravity defined above, various fillers such as barium
sulfate, titanium oxide and magnesium stearate may be blended in the thermoplastic
resin. In Table 4, Yamagishi teaches that the inner cover layer can be made from either
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Last modified: November 3, 2007