Golf balls having particle-based foam center

Abstract

Multi-layered, golf balls having a core made of a particle-based polyurethane foam composition are provided. The ball includes a dual-layered core having a foam inner core (center) and surrounding outer core layer. The surrounding outer core layer may be made from a non-foamed thermoset material such as polybutadiene rubber. In one embodiment, pre-expanded thermoplastic polyurethane foam beads containing a blowing agent are used to form the foam center. In another embodiment, pre-formed polyurethane foam particles are used. The foam cores have good resiliency, thermal stability, and durability over a wide temperature range. The ball further includes a cover that may be multi-layered.

We claim: 
     
         1 . A core assembly for a golf ball, comprising:
 i) an inner core layer comprising a particle-based polyurethane foam composition, the inner core layer having a diameter in the range of about 0.100 to about 1.100 inches and a specific gravity (SG inner ) and a center hardness (H inner core center ); and   ii) an outer core layer comprising a non-foamed thermoset or thermoplastic material, the outer core layer being disposed about the intermediate core layer and having a thickness in the range of about 0.100 to about 0.750 inches, and a specific gravity (SG outer ) and an outer surface hardness (H outer surface of OC ), wherein the SG outer , is greater than the SG inner , and the H inner core center  is in the range of about 10 to about 60 Shore C and the H outer surface of OC  is in the range of about 65 to about 96 Shore C to provide a positive hardness gradient across the core assembly.   
     
     
         2 . The core assembly of  claim 1 , wherein the particle-based thermoplastic polyurethane foam composition is prepared from pre-expanded polyurethane foam beads. 
     
     
         3 . The core assembly of  claim 2 , wherein the pre-expanded polyurethane foam beads contain an aliphatic hydrocarbon blowing agent. 
     
     
         4 . The core assembly of  claim 2 , wherein the composition is prepared from pre-expanded thermoplastic polyurethane foam beads that are heat-treated. 
     
     
         5 . The core assembly of  claim 1 , wherein the particle-based polyurethane foam composition is prepared from pre-formed foam particles. 
     
     
         6 . The core assembly of  claim 5 , wherein the pre-formed foam particles have a mean diameter size in the range of about 0.001 to about 0.250 inches. 
     
     
         7 . The core assembly of  claim 5 , wherein the foam particles are coated with a binder and heat-pressed together. 
     
     
         8 . The core assembly of  claim 7 , wherein the binder is selected from the group consisting of acrylic resins such as acrylate resins, polyacrylate resins, acrylate-styrene copolymer resins, acrylate-vinyl acetate copolymer resins; polyvinyl alcohols, polyacrylamides, polyvinyl chloride resins, urethane resins, vinyl acetate resins, butadiene resins, epoxy resins, alkyd resins, melamine resins, and chloroprene rubbers, and mixtures thereof. 
     
     
         9 . The core assembly of  claim 1 , wherein the outer core layer comprises a thermoset polybutadiene rubber composition. 
     
     
         10 . The core assembly of  claim 1 , wherein the outer core layer comprises a thermoplastic highly neutralized ionomer composition. 
     
     
         11 . The golf ball of  claim 9 , wherein the highly-neutralized ionomer composition comprises an E/X/Y-type copolymer, wherein E is ethylene, X is a C 3 -C 8  α,β-ethylenically unsaturated carboxylic acid present in an amount of 10 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. 
     
     
         12 . A core assembly for a golf ball, comprising:
 i) an inner core layer comprising a particle-based polyurethane foam composition, the inner core layer having a diameter in the range of about 0.100 to about 1.100 inches and a specific gravity (SG inner ) and a center hardness (H inner core center ); and   ii) an outer core layer comprising a foamed thermoset or thermoplastic material, the outer core layer being disposed about the intermediate core layer and having a thickness in the range of about 0.100 to about 0.750 inches, and a specific gravity (SG outer ) and an outer surface hardness (H outer surface of OC ), wherein the SG outer , is greater than the SG inner , and the H inner core center  is in the range of about 10 to about 60 Shore C and the H outer surface of OC  is in the range of about 45 to about 96 Shore C to provide a positive hardness gradient across the core assembly.   
     
     
         13 . The golf ball of  claim 12 , wherein the outer core layer comprises a second particle-based polyurethane foam composition. 
     
     
         14 . The golf ball of  claim 12 , wherein the outer core layer comprises a foamed thermoplastic highly neutralized ionomer composition. 
     
     
         15 . The golf ball of  claim 1 , wherein the inner core layer has a diameter in the range of about 0.100 to about 0.900 inches and a specific gravity in the range of about 0.25 to about 1.25 g/cc. 
     
     
         16 . The golf ball of  claim 1 , wherein the inner core layer has a diameter in the range of about 0.400 to about 0.800 inches and a specific gravity in the range of about 0.30 to about 0.95 g/cc. 
     
     
         17 . The golf ball of  claim 1 , wherein the outer core layer has a thickness in the range of about 0.250 to about 0.750 inches and a specific gravity in the range of about 0.60 to about 2.90 g/cc. 
     
     
         18 . The golf ball of  claim 1 , wherein the inner core layer has 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 layer has 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. 
     
     
         19 . The golf ball of  claim 18 , wherein the H inner core center  is in the range of about 10 to about 48 Shore C and the H inner core surface  is in the range of about 24 to about 55 Shore C. 
     
     
         20 . The golf ball of  claim 18 , wherein the H inner core center  is in the range of about 15 to about 80 Shore A and the H inner core surface  is in the range of about 20 to about 95 Shore A. 
     
     
         21 . The golf ball of  claim 18 , wherein the H midpoint of OC  is in the range of about 40 to about 87 Shore C and the H outer surface of OC  is in the range of about 72 to about 95 Shore C. 
     
     
         22 . The golf ball of  claim 1 , wherein the inner core layer has 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 layer has 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. 
     
     
         23 . The golf ball of  claim 22 , wherein the H inner core center  is in the range of about 10 to about 60 Shore C and the H inner core surface  is in the range of about 10 to about 55 Shore C. 
     
     
         24 . The golf ball of  claim 22 , wherein the H inner core center  is in the range of about 15 to about 80 Shore A and the H inner core surface  is in the range of about 10 to about 75 Shore A. 
     
     
         25 . The golf ball of  claim 22 , wherein the H midpoint of OC  is in the range of about 45 to about 85 Shore C and the H outer surface of OC  is in the range of about 72 to about 95 Shore C.