METHODS FOR MAKING GOLF BALLS HAVING HETEROGENEOUS LAYERS AND RESULTING BALLS
Methods for making multi-piece golf balls having an outer cover, intermediate, or other layer comprising a heterogeneous composition are provided. The heterogeneous composition comprises a mixture of Compounds A and B. For example, the compounds can be different polyurethanes, ethylene acid copolymer ionomers, polyesters, polyamides, or any other suitable materials for making golf ball layers. Compounds having different hardness levels can be used. For example, the composition can comprise a mixture of hard and soft materials. The invention also encompasses golf balls made from such methods. The golf balls have good resiliency and impact durability along with other optimum playing performance properties.
1 . A method for making a multi-piece golf ball, comprising the steps of:
a) introducing a first composition comprising Compound A into upper and lower mold members, the upper and lower mold members defining a mold cavity with a dimple pattern;
b) introducing a second composition comprising Compound B into the upper and lower mold members so that the first and second compositions are mixed together to form a heterogeneous composition comprising Compounds A and B;
c) placing a spherical core into the mold cavity;
d) applying heat and pressure to the mold members so the heterogeneous composition encapsulates the core and forms an outer cover having a dimpled pattern, and e) removing the multi-piece golf ball from the mold.
2 . The method of claim 1 , wherein Compound A is an aliphatic polyurethane and Compound B is an aromatic polyurethane.
3 . The method of claim 1 , wherein Compound A and Compound B are O/X-type copolymers, wherein O is selected from the group consisting of ethylene and propylene, and X is an acid group selected from the group consisting of methacrylic acid, acrylic acid, ethacrylic acid, crotonic acid, maleic acid, fumaric acid, and itaconic acid, and wherein at least 70% of the acid groups in Compound A are neutralized, and greater than 70% of the acid groups in Compound B are neutralized.
4 . The method of claim 3 , wherein the O of the O/X-type acid copolymer is ethylene and the X is methacrylic acid or acrylic acid.
5 . The method of claim 1 , wherein Compound A and Compound B are O/X/Y-type copolymers, wherein O is selected from the group consisting of ethylene and propylene, and X is an acid group selected from the group consisting of methacrylic acid, acrylic acid, ethacrylic acid, crotonic acid, maleic acid, fumaric acid, and itaconic acid, and Y is a (meth) acrylate or alkyl (meth) acrylate wherein the alkyl groups have from 1 to 8 carbon atoms, and wherein at least 70% of the acid groups in Compound A are neutralized, and greater than 70% of the acid groups in Compound B are neutralized.
6 . The method of claim 1 , wherein the outer cover layer formed from the heterogeneous composition has a midpoint hardness and outer hardness surface, the hardness of the outer surface being greater than the hardness of the midpoint to define a positive hardness gradient.
7 . The method of claim 1 , wherein the hardness of the outer surface is in the range of about 35 to about 90 Shore D and the hardness of the midpoint is in the range of about 30 to about 80 Shore D.
8 . The golf ball of claim 1 , wherein the outer cover layer formed from the heterogeneous composition has a midpoint hardness and outer hardness surface, the hardness of the outer surface being the same or greater than the hardness of the midpoint to define a zero or negative hardness gradient.
9 . The method of claim 8 , wherein the hardness of the midpoint is in the range of about 40 to about 75 Shore D and the hardness of the outer surface is in the range of about 35 to about 70 Shore D.
10 . The method of claim 1 , wherein the core is single-layered, the core being formed from a rubber composition.
11 . The method of claim 1 , wherein the core is dual-layered, the core comprising an inner core and surrounding outer core layer, at least one of the core layers being formed from a rubber composition.
12 . A method for making a multi-piece golf ball, comprising the steps of:
a) introducing a first composition comprising Compound A into upper and lower mold members, the upper and lower mold members defining a mold cavity;
b) introducing a second composition comprising Compound B into the upper and lower mold members so that the first and second compositions are mixed together to form a heterogeneous composition comprising Compounds A and B;
c) placing a spherical core into the mold cavity;
d) applying heat and pressure to the mold members so the heterogeneous composition encapsulates the core and forms an intermediate layer the core and surrounding intermediate layer comprising a ball subassembly;
e) removing the ball subassembly from the mold; and
f) forming a cover having at least one layer over the subassembly to form a multi-piece golf ball.