Highly Neutralized Acid Polymer Compositions having a Low Moisture Vapor Transmission Rate and Their Use in Golf Balls

Abstract

The present invention is directed to a golf ball having at least one layer formed from a moisture resistant composition having a moisture vapor transmission rate of 12.5 g·mil/100 in 2 /day or less, a flexural modulus of from 50 kpsi to 70 kpsi, and comprising a highly neutralized acid polymer, wherein the highly neutralized acid polymer is produced by a process comprising contacting the acid polymer with a sufficient amount of a lithium-based cation source, in the presence of a melt flow modifier, to increase the level of neutralization of the copolymer to at least 70%. Golf balls of the present invention include one-piece, two-piece, multi-layer, and wound golf balls. The composition may be present in any one or more of a core layer, a cover layer, or an intermediate layer.

1 . A golf ball having at least one layer formed from a moisture resistant composition, the moisture resistant composition having a moisture vapor transmission rate (MVTR) of 12.5 g·mil/100 in 2 /day or less, a flexural modulus of from 50 kpsi to 75 kpsi, and comprising a highly neutralized acid polymer, 
 wherein the highly neutralized acid polymer is the salt of a copolymer of from 80 wt % to 90 wt % of an olefin selected from ethylene and propylene; 
 from 10 wt % to 20 wt % of an α,β-ethylenically unsaturated carboxylic acid selected from acrylic acid, methacrylic acid, maleic acid, fumaric acid, and itaconic acid; and  
 from 0 wt % to 10 wt % of a softening monomer selected from methyl acrylate, propyl acrylate, and butyl acrylate;  
 based on the total weight of the copolymer;  
   wherein the highly neutralized acid polymer is produced by a process comprising contacting the copolymer with a sufficient amount of a lithium-based cation source, in the presence of a melt flow modifier, to increase the level of neutralization of the copolymer to at least 70%;    and wherein the moisture resistant composition has a coefficient of restitution (COR) of at least 0.800, as measured on a solid sphere formed from the moisture resistant composition and having a diameter of 1.550 inches.    
   
   
       2 . The golf ball of  claim 1 , wherein the olefin is ethylene.  
   
   
       3 . The golf ball of  claim 2 , wherein the α,β-unsaturated carboxylic acid is (meth) acrylic acid.  
   
   
       4 . The golf ball of  claim 3 , wherein the softening monomer is selected from methyl acrylate and butyl acrylate.  
   
   
       5 . The golf ball of  claim 1 , wherein the copolymer comprises from 13 wt % to 18 wt % of the acid, based on the total weight of the copolymer.  
   
   
       6 . The golf ball of  claim 1 , wherein the copolymer comprises from 15.0 wt % to 15.8 wt % of the acid, based on the total weight of the copolymer.  
   
   
       7 . The golf ball of  claim 1 , wherein the moisture resistant composition has a flexural modulus of from 60 kpsi to 70 kpsi.  
   
   
       8 . The golf ball of  claim 1 , wherein the moisture resistant composition has a COR of at least 0.810.  
   
   
       9 . The golf ball of  claim 1 , wherein the moisture resistant composition has a COR of at least 0.820.  
   
   
       10 . The golf ball of  claim 1 , wherein the moisture resistant composition has an MVTR of 5.0 g mil/100 in 2 /day or less.  
   
   
       11 . The golf ball of  claim 1 , wherein the moisture resistant composition has a melt flow index of at least 0.5 g/10 min.  
   
   
       12 . The golf ball of  claim 1 , wherein the moisture resistant composition has a melt flow index of at least 1.5 g/10 min.  
   
   
       13 . The golf ball of  claim 1 , wherein the moisture resistant composition has a melt flow index of from 1.5 g/10 min to 2.0 g/10 min.  
   
   
       14 . The golf ball of  claim 1 , wherein the ball is a one-piece golf ball formed from the moisture resistant composition.  
   
   
       15 . The golf ball of  claim 1 , wherein the ball is a two-piece golf ball consisting of a core and a cover, and wherein the core is formed from the moisture resistant composition.  
   
   
       16 . The golf ball of  claim 1 , wherein the ball is a two-piece golf ball consisting of a core and a cover, and wherein the cover is formed from the moisture resistant composition.  
   
   
       17 . The golf ball of  claim 1 , wherein the ball comprises an inner core layer, an outer cover layer, and one or more intermediate layer(s) disposed between the inner core layer and the outer cover layer, and wherein at least one of the inner core layer, outer cover layer, and intermediate layer(s) is formed from the moisture resistant composition.  
   
   
       18 . A golf ball having at least one layer formed from a moisture resistant composition, the moisture resistant composition having a moisture vapor transmission rate (MVTR) of 5.0 g-mil/100 in 2 /day or less, a flexural modulus of from 50 kpsi to 75 kpsi, and comprising a highly neutralized acid polymer, 
 wherein the highly neutralized acid polymer is the salt of a copolymer of from 74 wt % to 85 wt % of ethylene; 
 from 15 wt % to 16 wt % of acrylic acid; and  
 from 0 wt % to 10 wt % of a softening monomer selected from methyl acrylate and butyl acrylate;  
 based on the total weight of the copolymer;  
   wherein the highly neutralized acid polymer is produced by a process comprising contacting the copolymer with a sufficient amount of a lithium-based cation source, in the presence of a melt flow modifier, to increase the level of neutralization of the copolymer to 100%;    and wherein the moisture resistant composition has a coefficient of restitution (COR) of at least 0.800, as measured on a solid sphere formed from the moisture resistant composition and having a diameter of 1.550 inches.    
   
   
       19 . The golf ball of  claim 18 , wherein the melt flow modifier is zinc stearate.  
   
   
       20 . The golf ball of  claim 18 , wherein the moisture resistant composition has a COR of at least 0.820.