Methods for applying polyurethane coatings to golf balls having a thermoplastic polyurethane cover
Golf balls having covers made of thermoplastic polyurethane compositions are provided. Multi-piece golf balls can be made. Polyurethane primer coatings and polyurethane top-coatings are applied to the thermoplastic polyurethane cover. Different coating methods can be used. Isocyanate-rich and polyol-rich polyurethane coatings can be applied. In one embodiment, the golf ball can be treated with a multi-functional isocyanate prior to applying the coatings. The polyurethane cover composition and surface coatings can further include catalysts, ultraviolet (UV)—light stabilizers, and other additives. Heat is used to cure the coatings. The coating methods have many benefits and the finished balls have good physical properties.
1. A coated golf ball formed by a method, the method comprising the steps of:
providing a golf ball comprising at least one core layer and an outer cover layer, wherein the outer cover layer is formed from a thermoplastic polyurethane composition;
applying a first polyurethane coating comprising unreacted isocyanate groups and having an isocyanate index of at least about 115 to the outer cover layer;
treating the golf ball with heat; and
applying a second polyurethane coating having an isocyanate index of less than 96 to the outer cover of the golf ball to form a coated golf ball.
2. The golf ball of claim 1 , wherein at least one of the first and second polyurethane coatings further comprises a catalyst.
3. The golf ball of claim 1 , wherein the thermoplastic polyurethane composition further comprises a catalyst.
4. The golf ball of claim 1 , wherein the outer cover layer has a thickness in the range of about 0.010 to about 0.050 inches.
5. The golf ball of claim 1 , wherein the outer cover layer has hardness in the range of about 20 to about 59 Shore D.
6. The golf ball of claim 1 , wherein the golf ball comprises an inner core and outer core layer.
7. The golf ball of claim 1 , wherein the golf ball further comprises an inner cover layer.
8. The golf ball of claim 1 , wherein the first and second polyurethane coatings are applied by spray-coating.
9. The golf ball of claim 1 , wherein an outer surface of the golf ball is heated with a source of infrared heat.
10. The golf ball of claim 9 , wherein the outer surface of the golf ball is heated to a surface temperature of about 120° to about 150° F.