Golf balls having foam inner core and themoplastic outer core
View Patent ↗Multi-piece golf balls containing a dual-core structure are provided. The core structure includes an inner core (center) comprising a foam composition, preferably foamed polyurethane. The outer core layer is preferably formed from a non-foamed thermoplastic composition such as ethylene acid copolymer ionomer. Preferably, the specific gravity (density) of the foam inner core is less than the density of the outer core layer. The ball further includes a cover of at least one layer and may include at least one casing layer. The core structure and resulting ball have relatively good resiliency.
1. A golf ball, comprising:
i) an inner core layer comprising a foamed composition, the inner core layer having a diameter in the range of about 0.100 to about 1.100 inches, a specific gravity (SG inner ), and an outer surface hardness (H inner core surface ) and a center hardness (H inner core center ), the H inner core surface being greater than the H inner core center to provide a positive hardness gradient; and
ii) an outer core layer comprising a thermoplastic material, the outer core layer being disposed about the inner core and having a thickness in the range of about 0.100 to about 0.750 inches, a specific gravity (SG outer ), and an outer surface hardness (H outer surface of OC ) and an inner surface hardness (H inner surface of OC ), the H outer surface of OC being the same or less than the H inner surface of OC to provide a zero or negative hardness gradient, wherein the SG outer , is greater than the SG inner .
2. The golf ball of claim 1 , wherein the inner core comprises a foamed polyurethane composition.
3. The golf ball of claim 1 , wherein the thermoplastic material is a highly-neutralized ionomer composition comprising an E/X/Y-type copolymer, wherein E is ethylene, X is a C 3 -C 8 α,β-ethylenically unsaturated carboxylic acid present in an amount of 10 to 20 wt. %, based on total weight of the copolymer, and Y is an acrylate selected from alkyl acrylates and aryl acrylates present in an amount of 0 to 50 wt. %, based on total weight of the copolymer, wherein greater than 70% of the acid groups present in the composition are neutralized with a metal ion.
4. The golf ball of claim 1 , wherein the H inner core center is in the range of about 10 Shore C to about 50 Shore C and the H inner core surface is in the range of about 13 Shore C to about 60 Shore C.
5. The golf ball of claim 1 , wherein the H inner surface of OC is in the range of about 42 Shore C to about 90 Shore C and the H outer surface of OC is in the range of about 40 Shore C to about 88 Shore C.
6. The golf ball of claim 5 , wherein the H inner surface of OC is in the range of about 52 Shore C to about 80 Shore C and the H outer surface of OC is in the range of about 50 Shore C to about 78 Shore C.