Golf Balls Including A Crosslinked Thermoplastic Polyurethane Cover Layer Having Improved Scuff Resistance

Abstract

This disclosure relates to golf balls having a 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 cover layer may have certain properties, such as a desirable flexural modulus value and a desirable Shore D hardness value, that further contribute to the golf ball having a high degree of scuff resistance.

1 . A golf ball comprising:
 a core, and a cover layer substantially surrounding the core;   wherein the 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   wherein the cover layer has a flexural modulus of from about 200 psi to about 10,000 psi.   
     
     
         2 . The golf ball of  claim 1 , wherein the cover layer further comprises an inner cover layer substantially surrounding the core and an outer cover layer substantially surrounding the inner cover layer; and the outer cover layer comprises the crosslinked thermoplastic polyurethane elastomer having crosslinks located in the hard segments. 
     
     
         3 . The golf ball of  claim 2 , wherein the outer cover layer has a Shore D hardness of from about 40 to about 65 on the golf ball, and the outer cover layer has the flexural modulus of from about 200 psi to about 10,000 psi. 
     
     
         4 . The golf ball of  claim 1 , wherein the cover layer further comprises an inner cover layer substantially surrounding the core and an outer cover layer substantially surrounding the inner cover layer; and the inner cover layer comprises the crosslinked thermoplastic polyurethane elastomer having crosslinks located in the hard segments. 
     
     
         5 . The golf ball of  claim 1 , wherein the crosslinked thermoplastic polyurethane elastomer is the reaction product of a reaction mixture including an unsaturated diol having a pendant side chain that includes a terminal unsaturated bond as a chain extender. 
     
     
         6 . 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, any combination of the above groups, 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. 
     
     
         7 . 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. 
     
     
         8 . The golf ball of  claim 1 , wherein the crosslinked thermoplastic polyurethane elastomer is the reaction product of trimethylolpropane monoallylether as a chain extender. 
     
     
         9 . The golf ball of  claim 1 , wherein the cover layer has a Shore D hardness of between about 40 and about 65 on the golf ball. 
     
     
         10 . The golf ball of  claim 9 , wherein the cover layer has a Shore D hardness of between about 45 and about 60 on the golf ball. 
     
     
         11 . The golf ball of  claim 1 , wherein the cover layer has a flexural modulus of from about 200 psi to about 7,000 psi. 
     
     
         12 . The golf ball of  claim 11 , wherein the cover layer has a flexural modulus of from about 200 psi to about 1,000 psi. 
     
     
         13 . The golf ball of  claim 1 , 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.   
     
     
         14 . The golf ball of  claim 13 , wherein the free radical initiator is selected from the group consisting of peroxides, sulfurs, sulfides, and mixtures thereof. 
     
     
         15 . The golf ball of  claim 13 , wherein the reaction mixture further includes a second chain extender, the second chain extender having at least two reaction sites with isocyanates and having a molecular weight of less than about 450. 
     
     
         16 . A golf ball comprising:
 a core, and a cover layer substantially surrounding the core;   wherein the 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   wherein the crosslinked thermoplastic polyurethane elastomer is the reaction product of an unsaturated diol of formula (1):   
       
         
           
           
               
               
           
         
       
       in which R 1  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, 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, any combination of the above groups, 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. 
     
     
         17 . The golf ball of  claim 16 , wherein the cover layer has a flexural modulus of from about 200 psi and about 10,000 psi. 
     
     
         18 . The golf ball of  claim 16 , wherein the cover layer has a Shore D hardness of from about 40 to about 65 on the golf ball. 
     
     
         19 . 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 having crosslinks located in hard segments, the crosslinks being the reaction product of unsaturated bonds located in the hard segments catalyzed by a free radical initiator; and   the golf ball satisfies the following requirements:
 (1) the outer cover layer has a Shore D hardness from about 40 to about 65 on the golf ball; and 
 (2) the outer cover layer has a flexural modulus of from about 200 psi to about 10,000 psi. 
   
     
     
         20 . The golf ball of  claim 19 , wherein the crosslinked thermoplastic polyurethane elastomer is the reaction product formed from reacting a reaction mixture of:
 (a) trimethylolpropane monoallylether as a first chain extender;   (b) a second chain extender, having at least two reaction sites with isocyantes and having a molecular weight of less than about 450;   (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.