Golf balls having foam, hollow, or metal center and plasticized thermoplastic core layer

A golf ball, comprising a core assembly and cover having at least one layer, the core assembly comprising:

• i) an inner core layer comprising a metal material, the inner core having an outer surface hardness (Hinner core surface) and a center hardness (Hinner core center), the Hinner core surface being greater than the Hinner core center to provide a positive hardness gradient, the inner core having a diameter in the range of about 0.100 to about 1.100 inches;
• and
• ii) an outer core layer formed from a plasticized 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;
• and
• 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;
• the outer core layer being disposed about the inner core layer and having a thickness in the range of about 0.200 to about 1.200 inches and having an outer surface hardness (Houter surface of OC) and a midpoint hardness (Hmidpoint of OC), the Houter surface of OC being greater than the Hmidpoint of OC to provide a positive hardness gradient,
• wherein the diameter of the inner core is less than the thickness of the outer core layer and the center hardness of the inner core (Hinner core center) is in the range of about 30 Shore C to about 65 Shore C and the outer surface hardness of the outer core layer (Houter surface of OC) is in the range of about 40 Shore C to about 85 Shore C to provide a positive hardness gradient across the core assembly.

A golf ball, comprising a core assembly and cover having at least one layer, the core assembly comprising:

• i) an spherical inner core shell layer formed from a thermoset or thermoplastic composition, the shell layer having an outer surface, an inner surface, and an inner diameter to define a hollow center, the shell layer having a diameter in the range of about 0.100 to about 1.100 inches;
• and
• ii) an outer core layer formed from a plasticized 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;
• and
• 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;
• the outer core layer being disposed about the inner core layer, wherein the difference in Shore C hardness between the outer surface of the shell layer and inner surface of the shell layer is in the range of about 3 to about 25 Shore C.