Non-conforming golf balls made from plasticized thermoplastic materials
Golf balls having a single or dual-layered solid core are provided. In one embodiment, the golf ball has dimensions and properties that do not conform to the rules of the United States Golf Association (USGA). For example, the ball weight; ball size; ball spherical symmetry; ball initial velocity; and/or ball overall distance may fall outside of the USGA standards. The dual-layered core can have an inner core comprising a thermoplastic composition and surrounding outer core comprising a thermoset composition. In another embodiment, the dual-layered core has an inner core comprising a thermoplastic composition and outer core comprising a thermoset composition. The thermoplastic composition preferably comprises an ethylene acid copolymer ionomer and plasticizer. The thermoset composition preferably comprises polybutadiene rubber. The ball further includes a cover of at least one layer.
1. A golf ball comprising:
i) an inner core comprising a thermoset rubber composition, the inner core having an outer surface hardness (H core surface ) and a center hardness (H core center ), the H core surface being greater than the H core center to provide a positive hardness gradient;
ii) an outer core comprising a thermoplastic composition, the thermoplastic composition comprising;
a) an acid copolymer of ethylene and an α,β-unsaturated carboxylic acid, optionally including a softening monomer selected from the group consisting of alkyl acrylates and methacrylates;
b) a plasticizer;
c) a cation source present in an amount sufficient to neutralize from about 0 to about 100% of all acid groups present in the composition, wherein the overall diameter of the inner core/outer core structure is in the range of about 1.30 to about 1.66 inches; and
d) a non-acid polymer, wherein the non-acid polymer is an alkyl acrylate rubber selected from ethylene-alkyl acrylates and ethylene-alkyl methacrylates and is present in an amount of greater than 50 wt. %, based on the combined weight of the acid copolymer and the non-acid polymer;
iii) a cover disposed about the core, wherein the golf ball has at least one non-conforming property selected from the group consisting of a golf ball weight of greater than 1.62 ounces and a golf ball size of less than 1.68 inches.
2. The golf ball of claim 1 , wherein the positive hardness gradient of the inner core is from 2 Shore C units to 40 Shore C units.
3. The golf ball of claim 1 , wherein the positive hardness gradient of the inner core is from 10 Shore C units to 25 Shore C units.
4. The golf ball of claim 2 , wherein the outer core has an inner surface and an outer surface, wherein the outer surface is harder than the inner surface to produce a positive hardness gradient of from 2 Shore C units to 20 Shore C units.
5. The golf ball of claim 2 , wherein the outer core has an inner surface and an outer surface, wherein the outer surface is harder than the inner surface to produce a positive hardness gradient of from 3 Shore C units to 10 Shore C units.
6. The golf ball of claim 1 , wherein the (H core center ) is from 10 Shore C to 60 Shore C and the outer core has an outer surface hardness (H outer surface of OC ) of 65 Shore C to 96 Shore C.
7. The golf ball of claim 1 , wherein the (H core center ) is from 13 Shore C to 55 Shore C and the outer core has an outer surface hardness (H outer surface of OC ) of 75 Shore C to 93 Shore C.