Method for forming polyurethane covers for golf balls using foam compositions
The present invention provides methods for producing molded golf balls and the resultant balls. The methods of this invention involve producing foamed polyurethane covers and these methods help reduce dimple distortions and other surface imperfections. These golf balls contain an inner core and outer foamed polyurethane cover. One or more intermediate layers can be disposed between the core and cover. In one embodiment, a castable liquid polyurethane composition containing a foaming agent is dispensed into mold cavities, which are then pressed together to form a foam cover for the ball.
1. A golf ball formed by a method, the method comprising:
providing a spherical core having at least one layer;
providing an upper and lower mold cavity, each mold cavity having an arcuate inner surface defining an inverted dimple pattern;
introducing a polyurethane composition comprising a foaming agent into at least one mold cavity and loading the core into a mold cavity, wherein the foaming agent is present in an amount of from 0.25 wt % to 3.25 wt % based on the weight of the polyurethane composition;
joining the mold cavities together under compressive force and heating the polyurethane composition so that the foaming agent is activated and foaming of the composition is initiated and a spherical foamed polyurethane cover layer is formed over the core; and
detaching the mold cavities and removing the golf ball, the foamed polyurethane cover layer of the golf ball having a thickness of 0.008 inches or less, a specific gravity of from about 0.90 to about 1.20 and a Shear Durability Rating of 4.00 or greater.
2. The golf ball of claim 1 , wherein the specific gravity of the foamed polyurethane cover layer is from about 0.95 to about 1.15.