Golf balls having a center with surrounding foam outer core layer

Abstract

Multi-layered golf balls having a dual-layered core and cover of at least one layer are provided. The dual-core construction includes a non-foamed inner core (center) made of a thermoplastic or thermoset composition such as polybutadiene rubber. An outer core layer comprising a foamed composition, such as polyurethane foam, is disposed about the inner core. In one version, the outer core layer is made of a relatively soft foam composition having low flex modulus and density. A cover may be disposed about the core structure. For example, an inner cover made of ethylene acid copolymer ionomer and outer cover made of polyurethane may be used.

We claim: 
     
         1 . A multi-layered golf ball, comprising:
 i) an inner core layer comprising a non-foamed thermoset or thermoplastic composition, the inner core layer having a diameter in the range of about 0.750 to about 1.500 inches;   ii) an outer core layer comprising a foamed composition, the outer core layer being disposed about the inner core layer and having a thickness in the range of about 0.025 to about 0.800 inches, wherein the inner core has a specific gravity (SG inner ) and flex modulus (FM inner ), and the outer core has a specific gravity (SG outer ) and flex modulus (FM outer ), the SG inner  being greater than the SG outer , and the FM inner  being greater than the FM outer ; and   iii) a cover having at least one layer disposed about the multi-layered core.   
     
     
         2 . The golf ball of  claim 1 , wherein the inner core has a flex modulus in the range of about 5,000 to about 60,000 psi and the outer core has a flex modulus in the range of about 100 to about 10,000 psi. 
     
     
         3 . The golf ball of  claim 1 , wherein the flex modulus of the inner core is at least 20% greater than the flex modulus of the outer core. 
     
     
         4 . The golf ball of  claim 1 , wherein the inner core has a diameter in the range of about 0.90 to about 1.40 inches and specific gravity in the range of about 0.60 to about 2.90 g/cc. 
     
     
         5 . The golf ball of  claim 1 , wherein the inner core layer comprises a thermoset rubber selected from the group consisting of polybutadiene, ethylene-propylene rubber, ethylene-propylene-diene rubber, polyisoprene, styrene-butadiene rubber, polyalkenamers, and butyl rubber, and mixtures thereof. 
     
     
         6 . The golf ball of  claim 5 , wherein the thermoset rubber is polybutadiene rubber. 
     
     
         7 . The golf ball of  claim 1 , wherein the inner core layer comprises a thermoplastic polymer selected from the group consisting of partially-neutralized ionomers; highly-neutralized ionomers;
 polyesters; polyamides; polyamide-ethers, polyamide-esters; polyurethanes, polyureas;   fluoropolymers; polystyrenes; polypropylenes; polyethylenes; polyvinyl chlorides; polyvinyl acetates; polycarbonates; polyvinyl alcohols; polyester-ethers; polyethers; polyimides, polyetherketones, polyamideimides; and mixtures thereof.   
     
     
         8 . The golf ball of  claim 1 , wherein the thermoplastic material is an ionomer composition comprising an O/X/Y-type copolymer, wherein O is α-olefin, X is a C 3 -C 8  α,β-ethylenically unsaturated carboxylic acid present in an amount of 5 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. 
     
     
         9 . The golf ball of  claim 1 , wherein the outer core layer comprises a foamed polyurethane composition. 
     
     
         10 . The golf ball of  claim 9 , wherein the foamed polyurethane composition is prepared by adding water to a mixture of polyisocyanate, polyol, and curing agent compounds, and catalyst, the water being added in a sufficient amount to cause the mixture to foam. 
     
     
         11 . The golf ball of  claim 10 , wherein the composition further comprises mineral filler particulate. 
     
     
         12 . The golf ball of  claim 1 , wherein the outer core layer has a thickness in the range of about 0.050 to about 0.300 inches and specific gravity in the range of about 0.20 to about 0.95 g/cc. 
     
     
         13 . A multi-layered golf ball, comprising:
 i) an inner core layer comprising a non-foamed thermoset or thermoplastic composition, the inner core layer having a diameter in the range of about 0.750 to about 1.500 inches;   ii) an outer core layer comprising a foamed composition, the outer core layer being disposed about the inner core layer and having a thickness in the range of about 0.025 to about 0.800 inches, wherein the inner core has 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 the same or less than the H inner core center  to provide a zero or negative hardness gradient; and the outer core has a specific gravity (SG outer ) and an outer surface hardness (H outer surface of OC ) and a midpoint hardness (H midpoint of OC ), the H outer surface of OC  being greater than the H midpoint of OC , to provide a positive hardness gradient; and the SG inner  is greater than the SG outer ; and   iii) a cover having at least one layer disposed about the multi-layered core.   
     
     
         14 . The golf ball of  claim 13 , wherein the H inner core center  is in the range of about 30 to about 95 Shore C and the H inner core surface  core surface is in the range of about 30 to about 95 Shore C. 
     
     
         15 . The golf ball of  claim 13 , wherein the (H midpoint of OC ) is in the range of about 10 to about 55 Shore C and the H outer surface of OC  is in the range of about 13 to about 60 Shore C. 
     
     
         16 . A multi-layered golf ball, comprising:
 i) an inner core layer comprising a non-foamed thermoset or thermoplastic composition, the inner core layer having a diameter in the range of about 0.750 to about 1.500 inches;   ii) an outer core layer comprising a foamed composition, the outer core layer being disposed about the inner core layer and having a thickness in the range of about 0.025 to about 0.800 inches, wherein the inner core has 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 the outer core has a specific gravity (SG outer ) and an outer surface hardness (H outer surface of OC ) and a midpoint hardness (H midpoint of OC ), the H outer surface of OC  being greater than the (H midpoint of OC ) to provide a positive hardness gradient; and the SG inner  is greater than the SG outer ; and   iii) a cover having at least one layer disposed about the multi-layered core.   
     
     
         17 . The golf ball of  claim 16 , wherein the H inner core center  is in the range of about 30 to about 95 Shore C and the H inner core surface  is in the range of about 33 to about 98 Shore C. 
     
     
         18 . The golf ball of  claim 16 , wherein the H midpoint of OC  is in the range of about 10 to about 55 Shore C and the H outer surface of OC  is in the range of about 13 to about 60 Shore C. 
     
     
         19 . 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. 
     
     
         20 . The golf ball of  claim 1 , wherein the cover comprises an inner cover layer and outer cover layer, each cover having a surface hardness, wherein the surface hardness of the inner cover layer is greater than the surface hardness of the outer cover layer. 
     
     
         21 . The golf ball of  claim 1 , wherein the cover has at least one layer formed from a polyurethane composition. 
     
     
         22 . The golf ball of  claim 1 , wherein the cover has at least one layer formed from an ethylene acid copolymer ionomer composition.