Thermoplastic multi-layer golf ball

Abstract

A thermoplastic multi-layer golf ball has a thermoplastic core center, a thermoplastic core layer, and an inner cover layer and outer cover layer each including a thermoplastic polyurethane. The core center has a diameter of about 5-20 mm and a first flexural modulus of ≦about 8,000 psi. The core layer has a diameter of about 28-40 mm, a thickness of about 4-10 mm, a second flexural modulus of ≦about 15,000 psi and greater than the first flexural modulus, a 10-130 kg compression deformation of about 2.6-4.0 mm, and a surface hardness greater than the core center's surface hardness. The outer cover layer has a 10-130 kg compression deformation of about 2.3-3.2 mm and a surface hardness that is less than that of the inner cover layer. The difference between the core center's specific gravity and the core layer's specific gravity is ≦about 0.1 g/cm 3 .

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 5 mm to about 20 mm, a first flexural modulus of up to about 8,000 psi, and a surface hardness;   a core layer comprising a second thermoplastic material disposed radially outward from the core center, wherein the core layer has a diameter of from about 28 mm to about 40 mm, a thickness of from about 4 mm to about 10 mm, a second flexural modulus of up to about 15,000 psi that is greater than the first flexural modulus, a 10-130 kg compression deformation of from about 2.6 mm to about 4.0 mm, and a surface hardness that is greater than the surface hardness of the core center;   an inner cover layer disposed radially outward from the core layer, wherein the inner cover layer comprises a thermoplastic polyurethane and has a surface hardness; and   an outer cover layer on the surface of the golf ball having a 10-130 kg compression deformation of from about 2.3 mm to about 3.2 mm, comprising a thermoplastic polyurethane that may be the same as or different from the thermoplastic polyurethane of the inner cover layer, and having a surface hardness that is less than the surface hardness of the inner cover layer, wherein the difference between the specific gravity of the core center and the specific gravity of the core layer is not more than about 0.1 g/cm 3 .   
     
     
         2 . A golf ball according to  claim 1 , wherein one of the first thermoplastic material and the second thermoplastic material comprises an ionomer resin. 
     
     
         3 . A golf ball according to  claim 2 , wherein the ionomer resin comprises a monomeric organic acid or salt thereof and wherein the ionomer resin is neutralized from at least about 40% to about 100%. 
     
     
         4 . A golf ball according to  claim 3 , wherein the ionomer resin is neutralized from at least about 90% to about 100%. 
     
     
         5 . A golf ball according to  claim 1 , wherein each of the first thermoplastic material and the second thermoplastic material independently comprises an ionomer resin. 
     
     
         6 . A golf ball according to  claim 5 , wherein each ionomer resin comprises a monomeric organic acid or salt thereof and wherein each ionomer resin is independently neutralized from at least about 40% to 100%. 
     
     
         7 . A golf ball according to  claim 6 , wherein each ionomer resin is independently neutralized from at least about 90% to 100%. 
     
     
         8 . A golf ball according to  claim 1 , wherein the core center has a diameter of from about 8 mm to about 19 mm. 
     
     
         9 . A golf ball according to  claim 1 , wherein the first flexural modulus is from about 2800 psi to about 7400 psi. 
     
     
         10 . A golf ball according to  claim 1 , wherein the second flexural modulus is from about 7000 psi to about 13,000 psi. 
     
     
         11 . A golf ball according to  claim 1 , wherein the second flexural modulus is from about 3000 psi to about 6000 psi greater than the first flexural modulus. 
     
     
         12 . A golf ball according to  claim 1 , wherein the core layer has a diameter of from about 30 mm to about 38 mm or has a thickness of from about 5 mm to about 8 mm. 
     
     
         13 . A golf ball according to  claim 1 , wherein the core layer has a 10-130 kg compression deformation of from about 3.3 mm to about 3.8 mm. 
     
     
         14 . A golf ball according to  claim 1 , wherein the surface hardness of the core layer is from about 4 to about 15 Shore D hardness units greater than the surface hardness of the core center. 
     
     
         15 . A golf ball according to  claim 1 , wherein the inner cover layer has a thickness of from about 0.6 mm to about 2.0 mm and the outer cover layer has a thickness of from about 0.6 mm to about 2.0 mm. 
     
     
         16 . A golf ball according to  claim 1 , wherein the outer cover layer has a 10-130 kg compression deformation of from about 2.4 mm to about 3.0 mm. 
     
     
         17 . A golf ball according to  claim 1 , wherein the surface hardness of the inner cover layer is from about 8 to about 20 Shore D hardness units greater than the surface hardness of the outer cover layer. 
     
     
         18 . A golf ball according to  claim 1 , wherein the specific gravity of each of the core center and the core layer is at least about 1.01 g/cm 3 . 
     
     
         19 . A golf ball according to  claim 1 , wherein the first flexural modulus is from about 3000 to about 7200 psi and the second flexural modulus is from about 7200 to about 12,000 psi. 
     
     
         20 . A golf ball according to  claim 1 , wherein each of the inner cover layer and the outer cover layer independently has a thickness of from about 0.6 mm to about 2.0 mm.