Thermoplastic multi-layer golf ball

Abstract

A thermoplastic multi-layer golf ball has a core center including a first thermoplastic material, a core layer including a second thermoplastic material, and a cover including a third thermoplastic material. The core center has a diameter of 21-29 mm and a surface Shore D hardness H1 less than about 55. The core layer is at least about 5 mm thick with and an outer surface Shore D hardness H2 of more than about 50. The cover has an outer surface Shore D hardness H3 of more than about 50. H2 is up to about 10 Shore D units higher than H3, and H3 is up to about 20 Shore D units higher than H1. The core layer has a specific gravity that is at least 0.1 g/cm 3 greater than the specific gravity of the core center.

What is claimed is: 
     
         1 . A golf ball, comprising:
 a core center comprising a first thermoplastic material, wherein the core center has a diameter of from about 21 mm to about 29 mm and a surface Shore D hardness H1 of less than about 55;   a core layer disposed radially outward from the core center, wherein the core layer has a thickness of at least about 5 mm, a surface Shore D hardness H2 of more than about 50, and comprises a second thermoplastic material;   a cover disposed radially outward of the core layer, wherein the cover comprises a third thermoplastic material and has a surface Shore D hardness H3 of more than about 50; wherein the core layer surface hardness H2 is up to about 10 Shore D units higher than the cover surface hardness H3, the cover surface hardness H3 is up to about 20 Shore D units higher than the core center surface hardness H1, and the specific gravity of the core layer is at least about 0.1 g/cm 3  higher than the specific gravity of the core center.   
     
     
         2 . A golf ball according to  claim 1 , wherein H1 is from about 10 to about 53 Shore D. 
     
     
         3 . A golf ball according to  claim 1 , wherein H1 is at least about 30 Shore D. 
     
     
         4 . A golf ball according to  claim 1 , wherein the core center specific gravity is at least about 0.85 g/cm 3 . 
     
     
         5 . A golf ball according to  claim 1 , wherein the core center specific gravity is up to about 1.20 g/cm 3 . 
     
     
         6 . A golf ball according to  claim 1 , wherein H2 is from more than about 50 to about 85 Shore D. 
     
     
         7 . A golf ball according to  claim 1 , wherein H2 is at least about 55 Shore D. 
     
     
         8 . A golf ball according to  claim 1 , wherein the core layer specific gravity is at least about 0.95 g/cm 3 . 
     
     
         9 . A golf ball according to  claim 1 , wherein the core layer specific gravity is up to about 1.3 g/cm 3 . 
     
     
         10 . A golf ball according to  claim 1 , wherein the core center has a diameter of from about 23 mm to about 27 mm. 
     
     
         11 . A golf ball according to  claim 1 , wherein the core layer has a thickness of from about 5 mm to about 10 mm. 
     
     
         12 . A golf ball according to  claim 1 , wherein H3 of at least about 55 Shore D. 
     
     
         13 . A golf ball according to  claim 1 , wherein H3 is less than about 75 Shore D. 
     
     
         14 . A golf ball according to  claim 1 , wherein the golf ball is free from a thermoset rubber layer.