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 is preferably made from a foamed composition. In one embodiment, pre-expanded thermoplastic polyurethane foam beads containing a blowing agent are used to form the foam center and outer core. In another embodiment, pre-formed polyurethane foam particles are used in both core layers. 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 method for producing a core assembly for a golf ball, comprising the steps of:
 i) providing a foam polyurethane material;   ii) forming foam polyurethane particles from the foam polyurethane material, the particles having a mean diameter size in the range of about 0.001 to about 0.250 inches;   iii) heat-pressing the foam polyurethane particles together to form a spherical inner core, the inner core having a diameter in the range of about 0.100 to about 1.100 inches and a specific gravity (SG inner ) of at least 1.10 and a center hardness (H inner core center ); and   ii) forming an outer core layer comprising a foamed thermoset or thermoplastic composition, the outer core layer being disposed about the inner core 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.   
     
     
         2 . The method of  claim 1 , wherein the foam polyurethane material is in the form of a sheet and the foam polyurethane particles are cut from the sheet. 
     
     
         3 . The method of  claim 1 , wherein the foam polyurethane particles are cross-linked when the particles are heat-pressed to form the inner core. 
     
     
         4 . The method of  claim 1 , wherein the foam polyurethane particles have a specific gravity of less than about 0.95 g/cc. 
     
     
         5 . The method of  claim 1 , wherein the foam particles are non-spherically shaped. 
     
     
         6 . The method of  claim 1 , wherein the foam polyurethane particles are coated with a binder prior to heat-pressing the particles together. 
     
     
         7 . The method of  claim 1 , wherein the foam polyurethane material is coated with a binder prior to forming the foam polyurethane particles from the material. 
     
     
         8 . The method of  claim 7 , wherein the binder is selected from the group consisting of acrylic resins, acrylate resins, polyvinyl alcohols, polyacrylamides, polyvinyl chloride resins, urethane resins, urea resins, vinyl acetate resins, butadiene resins, epoxy resins, alkyd resins, melamine resins, and chloroprene rubbers, and mixtures thereof. 
     
     
         9 . The method of  claim 1 , wherein the outer core layer comprises a non-foamed thermoset rubber composition. 
     
     
         10 . The method of  claim 1 , wherein the outer core layer comprises a non-foamed thermoplastic ethylene acid copolymer ionomer composition. 
     
     
         11 . The method of  claim 1 , wherein the outer core layer comprises a foamed thermoplastic highly neutralized ionomer composition.