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 from about 21 mm to about 29 mm and a surface hardness H1 of at least about 55 Shore D. The core layer has a thickness of at least about 5 mm and an outer surface hardness H2 of up to about 60 Shore D. The cover has an outer surface hardness H3 of less than about 60 Shore D. H1 is up to about 10 Shore D units higher than H2, and H2 is up to about 10 Shore D units higher than H3. 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 hardness H1 of at least about 55 Shore D;   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 hardness H2 of up to about 60 Shore D, 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 hardness H3 of less than about 60 Shore D;   
       wherein the core center surface hardness H1 is up to about 10 Shore D units higher than the core layer surface hardness H2, the core layer surface hardness H2 is up to about 10 Shore D units higher than the cover surface hardness H3, and the specific gravity of the core layer is at least 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 up to about 70 Shore D. 
     
     
         3 . A golf ball according to  claim 1 , wherein H1 is at least about 60 Shore D. 
     
     
         4 . A golf ball according to  claim 1 , wherein H1 is from about 56 to about 70 Shore D. 
     
     
         5 . A golf ball according to  claim 1 , wherein the core center has a specific gravity of at least about 0.85 g/cm 3 . 
     
     
         6 . A golf ball according to  claim 1 , wherein the core center has a specific gravity of from about 0.85 g/cm 3  to about 1.20 g/cm 3 . 
     
     
         7 . A golf ball according to  claim 1 , wherein H2 is at least about 45 Shore D. 
     
     
         8 . A golf ball according to  claim 1 , wherein H2 is from more than about 45 to about 59 Shore D. 
     
     
         9 . A golf ball according to  claim 1 , wherein the core layer has a specific gravity of at least about 0.95 g/cm 3 . 
     
     
         10 . A golf ball according to  claim 1 , wherein the core layer has a specific gravity of from about 0.95 g/cm 3  to about 1.3 g/cm 3 . 
     
     
         11 . A golf ball according to  claim 1 , wherein the core center has a diameter of from about 23 mm to about 27 mm. 
     
     
         12 . A golf ball according to  claim 1 , wherein the core layer has a thickness of from about 5 mm to about 10 mm. 
     
     
         13 . A golf ball according to  claim 1 , wherein H3 is at least about 35 Shore D. 
     
     
         14 . A golf ball according to  claim 1 , wherein H3 is from about 40 to about 55 Shore D. 
     
     
         15 . A golf ball according to  claim 1 , wherein the golf ball is free from a thermoset rubber layer.