Four-Piece Golf Balls Including A Crosslinked Thermoplastic Polyurethane Cover Layer

Abstract

This disclosure relates to four-piece golf balls having an outer cover layer made from a crosslinked thermoplastic polyurethane elastomer. The crosslinked thermoplastic polyurethane elastomer includes crosslinks located in the hard segments, where the crosslinks being the reaction product of unsaturated bonds located in the hard segments catalyzed by a free radical initiator. The crosslinks may be formed from an unsaturated diol as a chain extender. The unsaturated diol may be trimethylolpropane monoallylether (TMPME). The four-piece golf ball may include an inner core layer formed from a highly neutralized acid polymer composition. The four-piece golf ball may also include an outer core layer formed from a polybutadiene rubber. The golf ball may exhibit a high degree of scuff resistance.

1 . A golf ball comprising: an inner core layer, an outer core layer substantially surrounding the inner core layer, an inner cover layer substantially surrounding the outer core layer, and an outer cover layer substantially surrounding the inner cover layer;
 wherein the outer cover layer comprises a crosslinked thermoplastic polyurethane elastomer, the crosslinked thermoplastic polyurethane elastomer including hard segments and soft segments;   wherein the crosslinked thermoplastic polyurethane elastomer includes crosslinks located in the hard segments, the crosslinks being the reaction product of unsaturated bonds located in the hard segments catalyzed by a free radical initiator.   
     
     
         2 . The golf ball of  claim 1 , wherein the crosslinked thermoplastic polyurethane elastomer comprises unsaturated diols as chain extenders. 
     
     
         3 . The golf ball of  claim 1 , wherein the crosslinked thermoplastic polyurethane elastomer is the reaction product of an unsaturated diol of formula (1): 
       
         
           
           
               
               
           
         
       
       in which R 1  may be any substituted or unsubstituted alkyl, substituted or unsubstituted aryl, substituted or unsubstituted alkyl-aryl group, substituted or unsubstituted ether group, substituted or unsubstituted ester group, any combination of the above groups, or H, and may optionally include an unsaturated bond in any main chain or side chain of any group; R 2  may be any suitable substituted or unsubstituted alkyl, substituted or unsubstituted aryl, substituted or unsubstituted alkyl-aryl group, substituted or unsubstituted ether group, substituted or unsubstituted ester group, or a continuation of the single bond, and R 2  includes an allyl group; and x and y are integers independently having any value from 1 to 10. 
     
     
         4 . The golf ball of  claim 1 , wherein the crosslinked thermoplastic polyurethane elastomer is the reaction product of an unsaturated diol of formula (2): 
       
         
           
           
               
               
           
         
       
       in which R is a substituted or unsubstituted alkyl group, and x and y are integers independently having any value from 1 to 4. 
     
     
         5 . The golf ball of  claim 4 , wherein the crosslinked thermoplastic polyurethane elastomer is the reaction product of trimethylolpropane monoallylether as a chain extender. 
     
     
         6 . The golf ball of  claim 1 , wherein the golf ball satisfies the following requirements:
 (1) the inner core layer has a compression deformation of from about 3 millimeters to about 5 millimeters under loads of 10 kg and 130 kilograms;   (2) the inner core layer has a coefficient of restitution at 40 meters per second from about 0.785 to about 0.9, the coefficient of restitution of the inner core being higher than that of the golf ball;   (3) the outer core layer has a thickness of from 5 millimeters to 9 millimeters and has a volume which is greater than any other layers of the golf ball;   (4) the inner cover layer has a flexural modulus of from about 60,000 psi to 100,000 psi; and   (5) the outer cover layer has a flexural modulus of from about 200 psi to about 10,000 psi.   
     
     
         7 . A golf ball comprising: an inner core layer, an outer core layer substantially surrounding the inner core layer, an inner cover layer substantially surrounding the outer core layer, and an outer cover layer substantially surrounding the inner cover layer;
 wherein the outer cover layer comprises a crosslinked thermoplastic polyurethane elastomer, the crosslinked thermoplastic polyurethane elastomer including hard segments and soft segments;   wherein the crosslinked thermoplastic polyurethane elastomer includes crosslinks located in the hard segments, the crosslinks being the reaction product of unsaturated bonds located in the hard segments catalyzed by a free radical initiator; and   wherein the inner core layer comprises a highly neutralized acid polymer composition.   
     
     
         8 . The golf ball of  claim 7 , wherein the inner core layer comprises a mixture of at least two highly neutralized acid polymers. 
     
     
         9 . The golf ball of  claim 7 , wherein the highly neutralized acid polymer composition has a Vicat softening temperature of from 50 degrees Celsius to 60 degrees Celsius. 
     
     
         10 . The golf ball of  claim 7 , wherein the inner core layer has a diameter of from about 19 to about 32 millimeters. 
     
     
         11 . The golf ball of  claim 7 , wherein the inner cover layer has a surface Shore D hardness of from about 60 to about 70. 
     
     
         12 . The golf ball of  claim 7 , wherein the inner core layer has a Shore D cross-sectional hardness of from 45 to 55 at any single point on a cross-section obtained by cutting the inner core layer in half, and has a Shore D cross-sectional hardness difference between any two points on the cross-section of within ±6. 
     
     
         13 . The golf ball of  claim 7 , wherein the outer core layer has a thickness of from 5 millimeters to 9 millimeters and has a volume which is greater than any other layers of the golf ball. 
     
     
         14 . The golf ball of  claim 7 , wherein the crosslinked thermoplastic polyurethane elastomer is the reaction product formed from reacting a reaction mixture of:
 (a) an organic isocyanate;   (b) an unsaturated diol first chain extender;   (c) a long chain polyol having a molecular weight of between about 500 and about 4,000; and   (d) a sufficient amount of free radical initiator, so as to be capable of generating free radicals that induce crosslinking structures in the hard segments by free radical initiation.   
     
     
         15 . The golf ball of  claim 14 , wherein the unsaturated diol first chain extender is of formula (1): 
       
         
           
           
               
               
           
         
       
       in which R 1  may be any substituted or unsubstituted alkyl, substituted or unsubstituted aryl, substituted or unsubstituted alkyl-aryl group, substituted or unsubstituted ether group, substituted or unsubstituted ester group, any combination of the above groups, or H, and may optionally include an unsaturated bond in any main chain or side chain of any group; R 2  may be any suitable substituted or unsubstituted alkyl, substituted or unsubstituted aryl, substituted or unsubstituted alkyl-aryl group, substituted or unsubstituted ether group, substituted or unsubstituted ester group, or a continuation of the single bond, and R 2  includes an allyl group; and x and y are integers independently having any value from 1 to 10. 
     
     
         16 . A golf ball comprising: an inner core layer, an outer core layer substantially surrounding the inner core layer, an inner cover layer substantially surrounding the outer core layer, and an outer cover layer substantially surrounding the inner cover layer;
 wherein the outer cover layer comprises a crosslinked thermoplastic polyurethane elastomer, the crosslinked thermoplastic polyurethane elastomer including hard segments and soft segments;   the crosslinked thermoplastic polyurethane elastomer including crosslinks located in the hard segments, the crosslinks being the reaction product of unsaturated bonds located in the hard segments catalyzed by a free radical initiator, and the crosslinked thermoplastic polyurethane elastomer being the reaction product of   (a) an organic isocyanate;   (b) an unsaturated diol first chain extender of formula (1)   
       
         
           
           
               
               
           
         
       
       in which R 1  may be any substituted or unsubstituted alkyl, substituted or unsubstituted aryl, substituted or unsubstituted alkyl-aryl group, substituted or unsubstituted ether group, substituted or unsubstituted ester group, any combination of the above groups, or H, and may optionally include an unsaturated bond in any main chain or side chain of any group; R 2  may be any suitable substituted or unsubstituted alkyl, substituted or unsubstituted aryl, substituted or unsubstituted alkyl-aryl group, substituted or unsubstituted ether group, substituted or unsubstituted ester group, or a continuation of the single bond, and R 2  includes an allyl group; and x and y are integers independently having any value from 1 to 10;
 (c) a long chain polyol having a molecular weight of between about 500 and about 4,000; and 
 (d) a sufficient amount of free radical initiator, so as to be capable of generating free radicals that induce crosslinking structures in the hard segments by free radical initiation; 
 the inner core layer comprises a highly neutralized acid polymer composition that is neutralized to 70% or higher; 
 the outer core layer comprises a polybutadiene rubber, the outer core layer having a thickness of from 5 millimeters to 9 millimeters and a volume which is greater than the volume of any other layer of golf ball; and 
 the inner cover layer comprises a thermoplastic polyurethane having a flexural modulus of from 60,000 psi to 100,000 psi. 
 
     
     
         17 . The golf ball of  claim 16 , wherein the free radical initiator is present in the crosslinked thermoplastic polyurethane elastomer in a weight ratio of free radical initiator to unsaturated diols of from about 0.1:100 to about 100:100. 
     
     
         18 . The golf ball of  claim 16 , wherein a weight ratio of the crosslinked thermoplastic polyurethane elastomer to the unsaturated diols is from about 100:0.1 to about 100:25. 
     
     
         19 . The golf ball of  claim 16 , wherein the free radical initiator is selected from the group consisting of peroxides, sulfurs, sulfides, and mixtures thereof. 
     
     
         20 . The golf ball of  claim 16 , wherein the highly neutralized acid polymer composition has a Vicat softening temperature of from 50 degrees Celsius to 60 degrees Celsius.