Golf balls having a foam center

Abstract

Large diameter golf balls having a foam core are provided.

What is claimed is: 
     
         1 . A golf ball having a diameter of 1.70 inches or greater and comprising:
 an inner core layer having a diameter of 1.60 inches or greater and formed from a foamed polyurethane composition, the inner core layer having an outer surface hardness (H inner core surface ) and a center hardness (H inner core center ), the H inner core surface  being the same or less than the H inner core center  to provide a zero or negative hardness gradient; and   a cover layer formed from a composition comprising:
 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; 
 an organic acid or salt thereof; 
 a cation source present in an amount sufficient to neutralize greater than 80% of all acid groups present in the composition; and 
 optionally a non-acid polymer selected from the group consisting of polyolefins, polyamides, polyesters, polyethers, polyurethanes, metallocene-catalyzed polymers, single-site catalyst polymerized polymers, ethylene propylene rubber, ethylene propylene diene rubber, styrenic block copolymer rubbers, alkyl acrylate rubbers, and functionalized derivatives thereof. 
   
     
     
         2 . The golf ball of  claim 1 , wherein the golf ball has a diameter of 1.80 inches or greater. 
     
     
         3 . The golf ball of  claim 1 , wherein the golf ball has a diameter of 2.00 inches or greater. 
     
     
         4 . A golf ball having a diameter of greater than 1.70 inches and comprising:
 an inner core layer having a diameter of 1.30 inches or greater and formed from a foamed polyurethane composition, the inner core layer having 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   an outer core layer having a thickness of 0.20 inches or greater and formed from a thermoset composition, the outer core layer having 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; and   a cover layer.   
     
     
         5 . The golf ball of  claim 4 , wherein the golf ball has a diameter of 1.80 inches or greater. 
     
     
         6 . A golf ball having a diameter of greater than 1.70 inches and comprising:
 an inner core layer having a diameter of 1.30 inches or greater and formed from a foamed polyurethane composition, the inner core layer having an outer surface hardness (H inner core surface ) and a center hardness (H inner core center ), the H inner core surface  being the same or less than the H inner core center  to provide a zero or negative hardness gradient; and   an outer core layer having a thickness of 0.20 inches or greater and formed from a thermoset composition, the outer core layer having 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 greater than the H inner surface of OC  to provide a positive hardness gradient; and   a cover layer.   
     
     
         7 . The golf ball of  claim 6 , wherein the golf ball has a diameter of 1.80 inches or greater. 
     
     
         8 . A golf ball having a diameter of greater than 1.70 inches and comprising:
 an inner core layer having a diameter of 1.30 inches or greater and formed from a foamed polyurethane composition, the inner core layer having an outer surface hardness (H inner core surface ) and a center hardness (H inner core center ), the H inner core surface  being the same or less than the H inner core center  to provide a zero or negative hardness gradient; and   an outer core layer having a thickness of 0.20 inches or greater and formed from a thermoset composition, the outer core layer having 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; and   a cover layer.   
     
     
         9 . The golf ball of  claim 8 , wherein the golf ball has a diameter of 1.80 inches or greater.