GOLF BALL COVERS MADE FROM PLASTICIZED THERMOPLASTIC MATERIALS
Multi-layered golf balls containing a two or three-layered cover assembly are provided. In one embodiment, the cover assembly includes a relatively hard inner cover and relatively soft outer cover. Alternatively, the cover assembly may include a relatively soft inner cover with a relatively hard outer cover. Three-layered covers comprising an inner cover, intermediate cover, and outer cover layer also may be prepared. Preferably, at least one of the layers is formed from a thermoplastic composition that comprises: a) ethylene acid copolymer, b) plasticizer, and c) cation source. A sulfonamide, alkyl diacid ester, or organophosphate or organosulfur compound is preferably used as the plasticizer. The cover assembly has good impact durability and helps provide the ball with relatively high resiliency at given compressions.
1 . A golf ball, comprising:
i) a core having at least one layer;
ii) an inner cover layer comprising a first thermoplastic material, the inner cover layer being disposed about the core and having a Shore D midpoint hardness in the range of about 55 to about 75;
iii) an outer cover layer comprising a second thermoplastic material, the outer cover layer being disposed about the inner cover layer and having a Shore D outer surface hardness in the range of about 15 to about 60, wherein the outer surface hardness of the outer cover layer is less than the midpoint hardness of the inner cover layer, the first and second thermoplastic materials comprising:
a) an acid copolymer of ethylene and an α,β-unsaturated carboxylic acid, optionally including a softening monomer selected from the group consisting of alkyl acrylates and methacrylates;
b) a plasticizer in an amount from about 3 to about 50% by weight; and
c) a cation source present in an amount sufficient to neutralize from about 0 to about 100% of all acid groups present in the material.
2 . The golf ball of claim 1 , wherein the plasticizer is a sulfonamide compound.
3 . The golf ball of claim 1 , wherein the plasticizer is an alkyl diacid ester compound.
4 . The golf ball of claim 1 , wherein the plasticizer is selected from the group consisting of organophosphate and organosulfur compounds.
5 . The golf ball of claim 1 , wherein the golf ball further comprises an intermediate cover layer, the intermediate cover layer being disposed between the inner cover layer and outer cover layer.
6 . The golf ball of claim 5 , wherein the intermediate cover layer has a midpoint hardness and the midpoint hardness of the inner cover layer is greater than the midpoint hardness of the intermediate cover layer.
7 . The golf ball of claim 6 , wherein the intermediate cover layer has a midpoint hardness in the range of about 25 to about 65 Shore D.
8 . The golf ball of claim 5 , wherein the intermediate cover layer has a midpoint hardness and the midpoint hardness of the inner cover layer is less than the midpoint hardness of the intermediate cover layer, and the midpoint hardness of the intermediate cover layer is greater than the outer surface hardness of the outer cover layer.