Coatings for golf balls having a thermoplastic polyurethane cover

Abstract

Methods for coatings for golf balls, particularly golf balls having thermoplastic polyurethane covers, and the resulting finished balls are provided. The coating is preferably a topcoat comprising a polyurethane composition containing optical brighteners. The topcoat composition preferably comprises a low concentration of optical brighteners. For example, the concentration of optical brightener can be in the range of 0.01 to about 0.20 weight %. The optical brighteners provide the desired brightness to the golf ball without sacrificing color stability. Multi-piece golf balls having inner cores, outer cores, inner covers, and intermediate layers can be made. The finished ball with the topcoat has many advantageous physical and playing performance properties.

What is claimed is: 
     
         1 . A golf ball comprising a core layer, an outer cover layer, and a polyurethane topcoat, wherein:
 the polyurethane topcoat comprises an optical brightener in a concentration of from about 0.01 wt % to about 0.50 wt %; and   the golf ball has a ΔECMC at 5 hours of less than about 7.00 and a ΔECMC at 40 hours of less than about 15.00.   
     
     
         2 . The golf ball of  claim 1 , wherein the concentration of optical brightener in the polyurethane topcoat is from about 0.01 wt % to about 0.20 wt %. 
     
     
         3 . The golf ball of  claim 1 , wherein the ΔECMC at 5 hours is about 6.56 or less. 
     
     
         4 . The golf ball of  claim 1 , wherein the ΔECMC at 5 hours is about 5.88 or less. 
     
     
         5 . The golf ball of  claim 1 , wherein the ΔECMC at 40 hours is about 14.04 or less. 
     
     
         6 . The golf ball of  claim 1 , wherein the ΔECMC at 40 hours is about 13.30 or less. 
     
     
         7 . The golf ball of  claim 1 , wherein the wet weight of the polyurethane topcoat is from about 0.20 g to about 0.42 g. 
     
     
         8 . The golf ball of  claim 1 , wherein the polyurethane topcoat does not include any light stabilizers. 
     
     
         9 . The golf ball of  claim 1 , wherein the optical brightener is selected from the group consisting of di-, tetra-, and hexa-sulfonated triazine-stilbenes; coumarins; imidazolines; diazoles; triazoles; benzooxazolines; and biphenyl-stilbenes; and mixtures thereof.