Golf balls having multi-layered covers based on aromatic and aliphatic polyurethanes

1. A method for molding a multi-layered golf ball, comprising the steps of:

a) dispensing a first liquid mixture comprising a first reactive polyurethane prepolymer and chain-extender, the polyurethane prepolymer being formed from the reaction of an aliphatic diisocyante and polyol, into lower and upper mold cavities and allowing the mixture to react and coat the interior surfaces of each mold cavity, whereby the coating produced from the first liquid mixture forms an outer cover layer having a thickness in the range of 0.004 to 0.020 inches;

b) dispensing a second liquid mixture comprising a second reactive polyurethane prepolymer and chain-extender, the polyurethane prepolymer being formed from the reaction of an aromatic diisocyante and polyol, into the coated lower and upper mold cavities to form a coating over the coating produced in step a), whereby the coating produced from the second liquid mixture forms an intermediate cover layer having a thickness in the range of 0.010 to 0.040 inches, the thickness of the intermediate coating layer being greater than thickness of the outer cover layer;

c) placing an intermediate golf ball comprising at least a core and inner cover layer into the lower or upper mold cavity containing the reactive liquid mixture comprising the second reactive polyurethane prepolymer;

d) bringing the lower and upper mold cavities together under sufficient pressure so the liquid mixture reacts and forms a multi-layered cover; and

e) removing the molded, multi-layered cover golf ball from the mold cavities.

2. The method of claim 1 , wherein the aliphatic diisocyanate used to form the first polyurethane prepolymer is selected from the group consisting of isophorone diisocyanate (IPDI), 1,6-hexamethylene diisocyanate (HDI), 4,4′-dicyclohexylmethane diisocyanate (“H 12 MDI”), meta-tetramethylxylyene diisocyanate (TMXDI), trans-cyclohexane diisocyanate (CHDI), and homopolymers and copolymers and blends thereof.

3. The method of claim 2 , wherein the chain extender used to form the first polyurethane prepolymer is 1,4-butanediol.

4. The method of claim 1 , wherein the mold cavities are pre-heated to a temperature within the range of about 125° to about 300° F.

5. The method of claim 1 , wherein the aromatic diisocyanate used to form the second polyurethane prepolymer is selected from the group consisting of toluene 2,4-diisocyanate (TDI), toluene 2,6-diisocyanate (TDI), 4,4′-methylene diphenyl diisocyanate (MDI), 2,4′-methylene diphenyl diisocyanate (MDI), polymeric methylene diphenyl diisocyanate (PMDI), p-phenylene diisocyanate (PPDI), m-phenylene diisocyanate (PDI), naphthalene 1,5-diisocynate (NDI), naphthalene 2,4-diisocyanate (NDI), p-xylene diisocyanate (XDI), and homopolymers and copolymers and blends thereof. isophorone diisocyanate (IPDI), 1,6-hexamethylene diisocyanate (HDI), 4,4′-dicyclohexylmethane diisocyanate (“H 12 MDI”), meta-tetramethylxylyene diisocyanate (TMXDI), trans-cyclohexane diisocyanate (CHDI), and homopolymers and copolymers and blends thereof.

6. The method of claim 5 , wherein the chain extender used to form the second polyurethane prepolymer is 1,4-butanediol.

7. The method of claim 1 , wherein the core comprises an inner core layer and surrounding outer core layer.

8. The method of claim 1 , wherein the inner cover layer comprises an ionomer composition containing ethylene acid copolymer having acid groups such that at least 30% of the acid groups are neutralized.