Golf ball and method of manufacture

DETAILED DESCRIPTION OF THE INVENTION The golf balls of the invention are produced using standard choices for the core composition.
As a non-limiting example, the core may comprise a rubber composition including a polybutadiene polymer having at least 40% of cis -1.
4 bonds, as a principal ingredient, a crosslinking agent such as zinc diacrylate late, an inorganic filler such as zinc oxide, and a peroxide curing agent.
The core is molded to a diameter in the order of 1.
36 to 1.
50 inches, preferably about 1.
40 to 1.
45 inches.
The intermediate and outer layers are formed over the core to achieve a final ball diameter between 1.
68 and 1.
72 inches.
The final ball diameter is maintained at the lower dimension by virtue of USGA regulations and the higher dimension is the maximum employed commercially.
The intermediate layer comprises a two-component mixture with the first component comprising a blend of n-butyl acrylate and ethylene methacrylic acid copolymer.
These ingredients are not crosslinked, that is, a cross linking agent such as methacrylic acid is not used in combination with this blend.
The ingredients of the blend without the crosslinking agent are sold commercially under the brand name Nucrel by du Pont.
Specifically ly, Nucrel RX9-1 comprises a suitable n-butyl acrylate and Nucrel 925 or 960 comprise suitable ethylene methacrylic acid copolymer.
The second component comprises a vulcanizate of a polybutadiene polymer and a peroxide vulcanizing agent.
Zinc diacrylate or methacrylate and/or zinc oxide may be included as part of the second component.
In the formation of the intermediate layer, the Nucrel components are typically supplied in pellet form.
The pellets are introduced to a conventional Banburymixer and roll mill which results in formation of a thin film of material.
The vulcanizate is reduced to powder form, 20-40 mesh, before addition to the Nucrel blend, and the equipment disperses the powder uniformly throughout the Nucrel blend.
The mill discharges a sheet of material which is adapted to be pelletized, molten and then fed to injection molding equipment for formation about the core