Multi-Core Golf Ball Having Increased Initial Velocity

Abstract

A golf ball having certain relationships and values of its initial velocities at various club head speeds is provided. The golf ball may achieve an initial velocity of at least about 173 mph at a club head speed of about 125 mph, therefore achieving an increased total shot distance. The golf ball has multiple layers making up its core, and the golf ball may be a four piece golf ball.

What is claimed is: 
     
         1 . A golf ball comprising:
 an inner core, the inner core being formed primarily of at least one thermoplastic highly neutralized polymer, and the inner core has a diameter of from about 20 mm to about 26 mm;   an outer core layer, the outer core substantially surrounding the inner core and being made primarily of a thermoset rubber, and the outer core layer has a thickness of from about 5 mm to about 9 mm;   an inner cover layer, the inner cover layer substantially surrounding the outer core layer; and   an outer cover layer, the outer cover layer substantially surrounding the inner cover layer;   wherein the inner core has a compression deformation of from about 3.5 mm to about 4.1 mm, the outer core layer has a compression deformation of from about 2.7 mm to about 3.3 mm, and a ratio of the compression deformation of the inner core to the compression deformation of the outer core layer is from about 1.1 to about 1.3;   the inner core having a first COR, the outer core having a second COR, the second COR being greater than the first COR and having a value of at least 0.8; and   wherein the golf ball has an initial velocity measured at a club head speed of about 125 mph of at least about 174 mph.   
     
     
         2 . The golf ball of  claim 1 , wherein the golf ball has an initial velocity measured at a club head speed of about 80 mph of at least about 88 mph. 
     
     
         3 . The golf ball of  claim 1 , wherein
 the inner cover layer is formed primarily of a thermoplastic material, has a surface Shore D hardness of at least 60, and has a thickness of less than 1 mm; and   the outer cover layer comprises a thermoplastic material, has a surface Shore D hardness of from 50 to 60, and has a thickness that is greater than the thickness of the inner cover layer.   
     
     
         4 . The golf ball of  claim 1 , wherein the outer cover layer comprises a crosslinked thermoplastic polyurethane that is the reaction product of unsaturated bonds located in hard segments of the polyurethane polymer, as catalyzed by a free radical initiator; the unsaturated bonds being present in an unsaturated diol of formula (2): 
       
         
           
           
               
               
           
         
         in which R is a substituted or unsubstituted alkyl group, and x and y are integers independently having values of 1 to 4. In particular embodiments, x and y may both have values of 1, 2, 3 or 4. In other embodiments, x and y may each have different values from 1 to 4. 
       
     
     
         5 . The golf ball of  claim 4 , wherein the unsaturated diol is trimethylolpropane monoallylether. 
     
     
         6 . The golf ball of  claim 1 , wherein the golf ball has a COR of about 0.80 or less. 
     
     
         7 . A golf ball comprising:
 an inner core, the inner core consisting essentially of at least one highly neutralized polymer;   an outer core layer, the outer core substantially surrounding the inner core and being made primarily of a thermoset rubber; and   an inner cover layer, the inner cover layer substantially surrounding the outer core layer; and   an outer cover layer, the outer cover layer substantially surrounding the inner cover layer;   wherein the golf ball has an initial velocity measured at a club head speed of about 125 mph of at least about 174 mph.   
     
     
         8 . The golf ball of  claim 7 , wherein the golf ball has an initial velocity measured at a club head speed of about 80 mph of at least 88 mph, and the difference between the initial velocity at a club head speed of about 125 mph and the initial velocity at the club head speed of about 80 mph is at least about 86. 
     
     
         9 . The golf ball of  claim 7 , wherein the inner core consists essentially of a mixture of two highly neutralized polymers. 
     
     
         10 . The golf ball of  claim 7 , wherein
 the inner core has a diameter of from about 20 mm to about 26 mm;   the outer core layer has a thickness of from about 5 mm to about 9 mm;   the inner cover layer has a thickness of less than 1 mm; and   the outer cover layer has a thickness that is greater than the thickness of the inner cover layer.   
     
     
         11 . The golf ball of  claim 7 , wherein
 the inner core has a first COR;   the outer core layer has a second COR;   the second COR being greater than the first COR, the second COR being 0.80 or more; and   the first COR being greater than the golf ball COR.   
     
     
         12 . The golf ball of  claim 11 , wherein the golf ball has a COR of about 0.80 or less. 
     
     
         13 . The golf ball of  claim 7 , wherein
 the inner core has a surface Shore D hardness of at least about 60;   the outer core layer has a surface Shore D hardness of from about 50 to about 60;   the inner cover layer has a surface Shore D hardness of at least 60; and   the outer cover layer has a surface Shore D hardness of from about 50 to about 60.