Multi-layered cores for golf balls containing polyamide and ionomer layers

Abstract

Multi-piece golf balls having a solid core of at least one layer and cover of at least one layer are provided. At least one of the core layers comprises a thermoplastic ionomer composition, preferably a highly neutralized ethylene acid copolymer. And, at least one of the core layers comprises a thermoplastic polyamide composition. In one embodiment, the polyamide composition is used to form the inner core and the ionomer composition is used to form the outer core layer. Preferably, the polyamide composition has a flex modulus of 90,000 psi or greater; and the ionomer composition has a flex modulus of 80,000 psi or less. The resulting ball has high resiliency and rebounding properties.

We claim: 
     
         1 . A golf ball, comprising:
 a) an inner core layer formed from a polyamide composition having a flex modulus of 90,000 psi or greater,   b) an outer core layer formed from an ionomer composition comprising an ethylene acid copolymer and containing acid groups such that greater than 70% of the acid groups are neutralized, the ionomer composition having a flex modulus of 80,000 psi or less; and   c) a cover having at least one layer.   
     
     
         2 . The golf ball of  claim 1 , wherein the modulus of the polyamide composition is at least 15% greater than the modulus of the ionomer composition. 
     
     
         3 . The golf ball of  claim 1 , wherein the modulus of the polyamide composition is 100,000 psi or greater and the modulus of the ionomer composition is 70,000 psi or less. 
     
     
         4 . The golf ball of  claim 1 , wherein the modulus of the polyamide composition is 120,000 psi or greater and the modulus of the ionomer composition is 50,000 psi or less. 
     
     
         5 . The golf ball of  claim 1 , wherein the center of the inner core and surface of the outer core layer each has a hardness, and the center hardness of the inner core is greater than the surface hardness of the outer core layer. 
     
     
         6 . The golf ball of  claim 5 , wherein the center hardness of the inner core is about 40 Shore D units or greater and the surface hardness of the outer core is about 30 Shore D units or greater. 
     
     
         7 . The golf ball of  claim 1 , wherein the cover is a single layer having a thickness of about 0.015 to about 0.090 inches and is formed from a thermoplastic or thermoset material. 
     
     
         8 . The golf ball of  claim 1 , wherein the cover comprises two or more layers and has an overall thickness of about 0.020 to about 0.210 inches and wherein each cover layer is formed from a thermoplastic or thermoset material. 
     
     
         9 . The golf ball of  claim 8 , wherein the cover comprises an inner cover layer and outer cover layer, the outer cover having a Shore D hardness of less than 65, the hardness of the outer cover being less than the hardness of the inner cover. 
     
     
         10 . The golf ball of  claim 1 , wherein the inner core has a diameter in the range of about 0.050 to about 1.40 inches. 
     
     
         11 . The golf ball of  claim 1 , wherein the inner core has a diameter in the range of about 0.100 to about 0.700 inches. 
     
     
         12 . The golf ball of  claim 1 , wherein the outer core layer has a thickness in the range of about 0.020 to about 0.650 inches. 
     
     
         13 . The golf ball of  claim 1 , wherein the dual-core core has an overall compression in the range of about 50 to about 130. 
     
     
         14 . The golf ball of  claim 13 , wherein the dual-core has an overall compression in the range of about 70 to about 110.