Multilayer golf ball containing at least three core layers, at least one intermediate barrier layer, and at least one cover layer
View Patent ↗The present invention is directed to multi-layer golf balls having at least three core layers, at least one cover layer, and at least one intermediate layer between the core and the cover layer that acts as a vapor barrier. Advantageously, the at least three core layers have a hardness gradient that increases toward the at least one intermediate vapor barrier layer.
1. A multilayer golf ball comprising:
at least three core layers comprising a center, an inner core layer, and an outer core layer;
at least one cover layer; and
at least one vapor barrier layer intermediate between the outer core layer and the at least one cover layer and exhibiting a moisture vapor transmission rate less than that of the cover layer;
wherein the center, the inner core layer, and the outer core layer exhibit a hardness gradient that increases toward the moisture barrier layer; and
wherein two core layers have specific gravities that are within about 5% of each other and one core layer has a specific gravity that differs from the specific gravities of the two core layers by greater than about 5%.
2. The multilayer golf ball of claim 1 , wherein:
the center hardness is no greater than about 50 Shore C;
the inner core hardness is greater than about 50 Shore C;
the outer core hardness is greater than about 65 Shore C; or
a combination thereof.
3. The multilayer golf ball of claim 1 , wherein the vapor barrier layer comprises a moisture vapor transmission rate of less than about 0.6 grams·mm/m 2 ·day.
4. The multilayer golf ball of claim 1 , wherein the vapor barrier layer comprises a thickness of not more than 0.020 inch.
5. The multilayer golf ball of claim 1 , wherein the vapor barrier layer comprises a thermoplastic elastomeric binder and a particulate material wherein the ratio of binder to particulate is from about 0.8:1.2 to about 1.2:0.80.
6. The multilayer golf ball of claim 1 , wherein the cover comprises a thermoset polyurethane having a hardness of from about 25 Shore D to about 65 Shore D and a flexural modulus of at least about 2,000 psi.
7. The multilayer golf ball of claim 1 , wherein the cover comprises a thermoplastic polyurethane having a hardness of from about 25 Shore D to about 65 Shore D and a flexural modulus of at least about 2,000 psi.