Golf Ball with Scuff-Resistant Cover

Abstract

Scuff-resistant golf ball covers and methods of manufacturing golf balls are described. The cover is made of a thermoplastic polymeric portion including at least one first, high molecular weight copolymer of ethylene/5-12 percent by weight acrylic or methacrylic acid or both/5-40 percent by weight alkyl acrylate or methacrylate or both; optionally at least one second, low molecular weight copolymer of ethylene/3-25 percent by weight acrylic or methacrylic acid or both; and a high molecular weight dipolymer of ethylene/acrylic acid that has a molar fraction of the acrylic acid monomer units within ±about 10% of a molar fraction of the α,β-ethylenically unsaturated carboxylic acid monomer units of the at least one first copolymer. The acid groups of all acid monomer units are neutralized 30% to about 75% on a molar basis by magnesium cations, calcium cations, zinc cations, or a combination of these cations.

1 . A golf ball having a core and a cover, wherein the cover comprises a thermoplastic polymeric portion consisting essentially of
 (a) (i) at least one first copolymer that has a weight average molecular weight of from about 80,000 to about 500,000 daltons and that consists of ethylene monomer units, from about 5 to about 12 percent by weight of α,β-ethylenically unsaturated carboxylic acid monomer units selected from the group consisting of acrylic acid monomer units, methacrylic acid monomer units, and combinations thereof, and from about 5 to about 40 percent by weight of at least one member selected from the group consisting of alkyl acrylate monomer units, alkyl methacrylate monomer units, and combinations thereof;
 (ii) at least one second copolymer that has a weight average molecular weight of from about 2000 to about 30,000 daltons and that consists of ethylene monomer units and from about 3 to about 25 percent by weight of α,β-ethylenically unsaturated carboxylic acid monomer units selected from the group consisting of acrylic acid monomer units, methacrylic acid monomer units, and combinations thereof, 
   wherein (a)(i) is from about 80 to 100 percent by weight of the sum of the weights of (a)(i) and (a)(ii) and (a)(ii) is from 0 to about 20 percent by weight of the sum of the weights of (a)(i) and (a)(ii); and   (b) at least one dipolymer that has a weight average molecular weight of from about 80,000 to about 500,000 daltons and that consists of ethylene monomer units and acrylic acid monomer units, wherein the at least one dipolymer has a molar fraction of the acrylic acid monomer units that is within ±about 10% of a molar fraction of the α,β-ethylenically unsaturated carboxylic acid monomer units of the at least one first copolymer (a)(i);   wherein (b) is from about 10 to about 90 percent by weight of a combined weight of (a) and (b), and   wherein from about 30% to about 75% on a molar basis of total acid groups of (a) and (b) are neutralized with cations selected from the group consisting of magnesium cations, calcium cations, zinc cations, and combinations thereof.   
     
     
         2 . A golf ball according to  claim 1 , wherein the at least one first copolymer (a)(i) has from about 8 to about 12 percent by weight of α,β-ethylenically unsaturated carboxylic acid monomer units. 
     
     
         3 . A golf ball according to  claim 1 , wherein the at least one dipolymer (b) has a molar fraction of acrylic acid monomer units within ±about 5% of the molar fraction of α,β-ethylenically unsaturated carboxylic acid monomer units of the at least one first copolymer (a)(i). 
     
     
         4 . A golf ball according to  claim 1 , wherein the at least one dipolymer (b) has a molar fraction of acrylic acid monomer units within ±about 3% of the molar fraction of α,β-ethylenically unsaturated carboxylic acid monomer units of the at least one first copolymer (a)(i). 
     
     
         5 . A golf ball according to  claim 1 , wherein the weight average molecular weight of the at least one first copolymer (a)(i) is from about 200,000 to about 400,000 daltons and the weight average molecular weight of the at least one dipolymer (b) is from about 200,000 to about 400,000 daltons. 
     
     
         6 . A golf ball according to  claim 1 , wherein from about 50% to about 100% on a molar basis of the neutralizing cations are selected from the group consisting of magnesium cations, calcium cations, and combinations thereof. 
     
     
         7 . A golf ball according to  claim 1 , wherein the at least one member of (a)(i) comprises n-butyl acrylate monomer units. 
     
     
         8 . A golf ball according to  claim 1 , wherein the α,β-ethylenically unsaturated carboxylic acid monomer units of the at least one first copolymer (a)(i) are acrylic acid monomer units. 
     
     
         9 . A golf ball according to  claim 1 , wherein the α,β-ethylenically unsaturated carboxylic acid monomer units of the at least one second copolymer (a)(ii) are acrylic acid monomer units. 
     
     
         10 . A golf ball according to  claim 1 , wherein (a)(i) is 100 percent by weight and (a)(ii) is 0 percent by weight of the sum of the weights of (a)(i) and (a)(ii). 
     
     
         11 . A golf ball according to  claim 1 , wherein from about 50% to about 100% on a molar basis of the neutralizing cations are calcium cations. 
     
     
         12 . A golf ball according to  claim 11 , wherein 100% on a molar basis of the neutralizing cations are calcium cations. 
     
     
         13 . A golf ball according to  claim 1 , wherein the cover has a thickness of from about 1 mm to about 3 mm. 
     
     
         14 . A method of manufacturing a golf ball having a core and a cover, comprising:
 forming the cover around the core from a thermoplastic polymeric portion consisting essentially of   (a) (i) at least one first copolymer that has a weight average molecular weight of from about 80,000 to about 500,000 daltons and that consists of ethylene monomer units, from about 5 to about 12 percent by weight of α,β-ethylenically unsaturated carboxylic acid monomer units selected from the group consisting of acrylic acid monomer units, methacrylic acid monomer units, and combinations thereof, and from about 5 to about 40 percent by weight of at least one member selected from the group consisting of alkyl acrylate monomer units, alkyl methacrylate monomer units, and combinations thereof;
 (ii) at least one second copolymer that has a weight average molecular weight of from about 2000 to about 30,000 daltons and that consists of ethylene monomer units and from about 3 to about 25 percent by weight of α,β-ethylenically unsaturated carboxylic acid monomer units selected from the group consisting of acrylic acid monomer units, methacrylic acid monomer units, and combinations thereof, 
   wherein (a)(i) is from about 80 to 100 percent by weight of the sum of the weights of (a)(i) and (a)(ii) and (a)(ii) is from 0 to about 20 percent by weight of the sum of the weights of (a)(i) and (a)(ii); and   (b) at least one dipolymer that has a weight average molecular weight of from about 80,000 to about 500,000 daltons and that consists of ethylene monomer units and acrylic acid monomer units, wherein the at least one dipolymer has a molar fraction of the acrylic acid monomer units that is within ±about 10% of a molar fraction of the α,β-ethylenically unsaturated carboxylic acid monomer units of the at least one first copolymer (a)(i);   wherein (b) is from about 10 to about 90 percent by weight of a combined weight of (a) and (b), and   wherein from about 30% to about 75% on a molar basis of total acid groups of (a) and (b) are neutralized with cations selected from the group consisting of magnesium cations, calcium cations, zinc cations, and combinations thereof.   
     
     
         15 . A method according to  claim 14 , wherein the step of forming the cover comprises forming the cover to have a thickness of from about 1 mm to about 3 mm.