Rubber outer covers for golf balls based on ethylene-propylene diene copolymers

Abstract

A multi-piece golf ball comprising at least one component made of an ethylene-propylene diene copolymer (EPDM) rubber is provided. The multi-piece golf ball includes a cover, preferably a dual-cover having inner and outer cover layers. The outer cover is preferably made of the EPDM rubber material. The golf ball further includes an inner core, preferably a dual-core containing a center and surrounding outer core layer. The center may be made of a polybutadiene rubber composition and the outer core layer may be made of an EPDM rubber composition. The resulting golf ball has high resiliency, a soft feel, and good weatherability.

1 . A multi-layered golf ball, comprising:
 a solid core of at least one layer; and   a cover disposed about the core, the cover comprising an inner layer and outer layer, the outer layer being formed from a first rubber composition comprising ethylene-propylene-diene copolymer rubber; a polymerization initiator; and a reactive cross-linking co-agent, wherein the rubber composition is subjected to a cross-linking reaction.   
     
     
         2 . The golf ball of  claim 1 , wherein the outer layer is formed from a thermoset liquid rubber composition comprising liquid ethylene-propylene-diene copolymer rubber. 
     
     
         3 . The golf ball of  claim 1 , wherein the polymerization initiator is a peroxide. 
     
     
         4 . The golf ball of  claim 1 , wherein the cross-linking co-agent is a metal salt of an α,β unsaturated carboxylic acid. 
     
     
         5 . The golf ball of  claim 1 , wherein the rubber composition further comprises a filler selected from the group consisting of polymeric, metal, and mineral fillers and mixtures thereof. 
     
     
         6 . The golf ball of  claim 1 , wherein the core is single-layered, the core being formed from a second rubber composition comprising polybutadiene rubber. 
     
     
         7 . The golf ball of  claim 1 , wherein the core is dual-layered, the core comprising an inner core and outer core layer, the inner core being formed from a second rubber composition comprising polybutadiene rubber, and the outer core layer being formed from a third rubber composition comprising ethylene-propylene-diene copolymer rubber. 
     
     
         8 . The golf ball of  claim 6 , wherein the core has a diameter of about 1.45 to about 1.59 inches. 
     
     
         9 . The golf ball of  claim 7 , wherein the inner core has a diameter of about 0.40 to about 1.55 inches. 
     
     
         10 . The golf ball of  claim 7 , wherein the outer core has a thickness of about 0.020 to about 0.150 inches. 
     
     
         11 . The golf ball of  claim 7 , wherein the dual core has an overall diameter of about 1.51 to about 1.62 inches 
     
     
         12 . The golf ball of  claim 1 , wherein the first rubber composition further comprises an elastomer selected from the group consisting of polybutadiene, ethylene-propylene rubber, polyisoprene, styrene-butadiene rubber, polyalkenamers, butyl rubber, halobutyl rubber, polystyrene elastomers, polyethylene elastomers, polyurethane elastomers, polyurea elastomers, metallocene-catalyzed elastomers and plastomers, copolymers of isobutylene and p-alkylstyrene, halogenated copolymers of isobutylene and p-alkylstyrene, copolymers of butadiene with acrylonitrile, polychloroprene, alkyl acrylate rubber, chlorinated isoprene rubber, acrylonitrile chlorinated isoprene rubber, and mixtures thereof. 
     
     
         13 . The golf ball of  claim 1 , wherein the inner cover layer is formed from an ionomeric resin comprising a copolymer of α-olefin, C 3  to C 8  α,β-ethylenically unsaturated mono- or dicarboxylic acid, and optional softening monomer. 
     
     
         14 . The golf ball of  claim 13 , wherein the ionomeric resin contains greater than 16 weight percent acid groups. 
     
     
         15 . The golf ball of  claim 13 , wherein the ionomeric resin contains less than 16 weight percent acid groups. 
     
     
         16 . The golf ball of  claim 1 , wherein the inner cover layer has a material hardness of 60 Shore D or greater. 
     
     
         17 . The golf ball of  claim 1 , wherein the outer cover layer has a thickness in the range of about 0.010 to about 0.080 inches. 
     
     
         18 . The golf ball of  claim 1 , wherein the outer cover layer has a material hardness of 60 Shore D or less. 
     
     
         19 . The golf ball of  claim 1 , wherein the inner cover is formed from a second rubber composition comprising EPDM copolymer rubber, a polymerization initiator, and a reactive cross-linking agent. 
     
     
         20 . The golf ball of claim  27 , wherein the inner cover has a hardness of 55 Shore D or greater and the outer cover has a hardness of 55 Shore D or less.