Game balls with cover containing post crosslinkable thermoplastic polyurethane and method of making same

Abstract

A game ball having a cover formed from a crosslinkable thermoplastic polyurethane is disclosed. By selective exposure to radiation, the thermoplastic polyurethane cover is crosslinked and its hardness is increased. Typically, increases in hardness values of at least 2 units on the Shore D scale are realized upon exposure to 3.5 Mrads of gamma radiation.

1 . A game ball, comprising: 
 a core, and    a cover layer formed over said core, said cover layer comprising a crosslinkable thermoplastic polyurethane and a saturated co-agent capable of crosslinking said crosslinkable thermoplastic polyurethane via free radical initiation.    
   
   
       2 . The game ball according to  claim 1 , wherein said crosslinkable thermoplastic polyurethane is a post crosslinkable thermoplastic polyurethane.  
   
   
       3 . The game ball according to  claim 1 , wherein said saturated co-agent is a short chain diene.  
   
   
       4 . The game ball according to  claim 1 , wherein said crosslinkable thermoplastic polyurethane has a Shore D hardness of from about 35 to about 72 before crosslinking and undergoes an increase in Shore D hardness of at least 2 units upon exposure to gamma radiation at a dosage of 3.5 Mrads.  
   
   
       5 . The game ball according to  claim 1 , wherein said crosslinkable thermoplastic polyurethane has a Shore D hardness of from about 35 to about 72 before crosslinking and experiences an increase in Shore D hardness of at least 5 units upon exposure to gamma radiation at a dosage of 3.5 Mrads.  
   
   
       6 . The game ball according to  claim 1 , wherein said crosslinkable thermoplastic polyurethane comprises at least one of a polyether based polyurethane and a polyester based polyurethane.  
   
   
       7 . The game ball according to  claim 1 , wherein said core is at least one member selected from the group consisting of solid cores, wound cores and liquid filled cores.  
   
   
       8 . The game ball according to  claim 1  wherein the game ball is selected from the group consisting of golf ball, baseball, basketball, football, soccer ball, softball, volleyball, lacrosse ball, or tennis ball.  
   
   
       9 . A game ball comprising: 
 a core; and    a cover layer disposed about said core, said cover comprising a thermoplastic polyurethane capable of undergoing crosslinking upon exposure to about 3.5 Mrads of radiation, and thereby increasing in hardness by at least 2 units on the Shore D hardness scale, wherein said cover layer further comprises a saturated co-agent capable of crosslinking said thermoplastic polyurethane.    
   
   
       10 . The game ball according to  claim 9  wherein said saturated co-agent is a short chain diene.  
   
   
       11 . The game ball according to  claim 9  wherein said cover layer comprises at least an inner cover layer and an outer cover layer.  
   
   
       12 . The game ball according to  claim 9  wherein the game ball is selected from the group consisting of golf ball, baseball, basketball, football, soccer ball, softball, volleyball, lacrosse ball, or tennis ball.  
   
   
       13 . A game ball, comprising: 
 a core;    an inner cover layer disposed over the core; and    a cover layer formed over said core, said cover layer comprising a crosslinkable thermoplastic polyurethane and a saturated co-agent capable of crosslinking said crosslinkable thermoplastic polyurethane via free radical initiation.    
   
   
       14 . The game ball according to  claim 13  wherein the core is a dual core.  
   
   
       15 . The game ball according to  claim 13  wherein the game ball is selected from the group consisting of golf ball, baseball, basketball, football, soccer ball, softball, volleyball, lacrosse ball, or tennis ball.