Low compression golf ball

Abstract

A golf ball ( 20 ) in accordance with the principles of the present invention has a core ( 22 ) with a low compression, but has at least two additional layers ( 24, 26 ) that provide for increased durability and control. The core ( 22 ) is formed of a polybutadiene compound that produces a zero (or less) compression. The mantle ( 24 ) is molded around the core ( 22 ) using terpolymers, which are comprised of ethylene, acrylic acid and n-butyl acrylate, with 100% of the acrylic acid groups neutralized with metal ions. The mantle ( 24 ), when molded, yields a deflection of greater than 0.170 inches under an applied static load of 200 lb. This correlates to a PGA compression of between about −20 and 15. The cover ( 26 ) is molded using conventional ionomers and “very low modulus” ionomers (V.L.M.I.), and has a hardness of between about 50 and 75 on a Shore D scale.

What is claimed is:  
     
         1 . A golf ball core comprising: 
 a polybutadiene rubber;    a co-crosslinking agent; and    a free radical initiator;    wherein the golf ball core has an Atti compression of less than about zero.    
     
     
         2 . The golf ball core of  claim 1 , wherein the polybutadiene has a high-cis isomer content.  
     
     
         3 . The golf ball core of  claim 2 , wherein the cis-isomer content of the polybutadiene is at least about 94%.  
     
     
         4 . The golf ball core of  claim 1 , wherein the polybutadiene is synthesized using at least one catalyst chosen from the group consisting of nickel, cobalt, neodymium and combinations thereof.  
     
     
         5 . The golf ball core of  claim 1 , wherein the at least one catalyst comprises neodymium.  
     
     
         6 . The golf ball core of  claim 1 , wherein the co-crosslinking agent comprises a zinc salt of an unsaturated acrylate ester.  
     
     
         7 . The golf ball core of  claim 6 , wherein the zinc salt of an unsaturated acrylate ester comprises zinc diacrylate.  
     
     
         8 . The golf ball of  claim 7 , wherein the co-crosslinking agent further comprises less than about 7% to about 12% by weight of a fatty acid salt.  
     
     
         9 . The golf ball core of  claim 1 , wherein the free radical initiator comprises a peroxide.  
     
     
         10 . The golf ball core of  claim 9 , wherein the peroxide is chosen from the group consisting of dicumyl peroxide, tert-butyl peroxybenzoate, butyl 4,4′-di-(tert-butylperoxy) valerate, 1,1-di-(tert-butylperoxy)-3,3,5-trimethylcyclohexane, and combinations thereof.  
     
     
         11 . The golf ball core of  claim 1  further comprising a filler.  
     
     
         12 . A golf ball comprising: 
 at least a first layer, a second layer, and a third layer, the first layer comprising a low compression core, the second layer being disposed over the first layer and the third layer being disposed over the second layer;    wherein the golf ball has a deflection of greater than about 0.170 inches under an applied static load of 200 lb.    
     
     
         13 . The golf ball of  claim 12 , wherein the low compression core comprises: 
 a polybutadiene rubber;    a co-crosslinking agent; and    a free radical initiator.    
     
     
         14 . The golf ball of  claim 13 , wherein the polybutadiene has a high-cis isomer content of at least about 94%.  
     
     
         15 . The golf ball of  claim 13. , wherein the polybutadiene is synthesized using at least one catalyst chosen from the group consisting of nickel, cobalt, neodymium and combinations thereof.  
     
     
         16 . The golf ball of  claim 13 , wherein the co-crosslinking agent comprises a zinc salt of an unsaturated acrylate ester.  
     
     
         17 . The golf ball of  claim 13 , wherein the free radical initiator comprises a peroxide.  
     
     
         18 . The golf ball of  claim 12  further comprising a filler.  
     
     
         19 . The golf ball of  claim 18 , wherein the filler is chose from the group consisting of zinc oxide, barium sulfate, titanium dioxide, and combinations thereof.  
     
     
         20 . The golf ball of  claim 12 , wherein the second layer comprises from about 60% to about 80% by weight ethylene, from about 8% to about 20% by weight of the α, β-unsaturated carboxylic acid, and from about 0% to about 25% by weight of the n-alkyl acrylate.  
     
     
         21 . The golf ball of  claim 20 , wherein the carboxylic acid is neutralized with Magnesium ions.  
     
     
         22 . The golf ball of  claim 20 , wherein the second layer further comprises greater than five parts per hundred weight of a magnesium fatty acid salt.  
     
     
         23 . The golf ball of  claim 22 , wherein the fatty acid salt is selected from the group consisting of magnesium stearate, magnesium oleate, and mixtures thereof.  
     
     
         24 . The golf ball of  claim 12 , wherein the third layer comprises a blend of high acid ionomers comprising about 80% to about 82% by weight of ethylene and about 18% to about 20% by weight of an α, β-unsaturated carboxylic acid.  
     
     
         25 . The golf ball of  claim 24 , wherein about 40% to about 70% of the carboxylic acid groups are neutralized with metal ions.  
     
     
         26 . The golf ball of  claim 12 , wherein the cover layer has a shore D hardness within the range of 50 to 75.  
     
     
         27 . The golf ball of  claim 12 , wherein the cover layer has a shore D hardness within the range of 68 to 73.  
     
     
         28 . The golf ball of  claim 12 , wherein the cover layer has a shore D hardness within the range of 58 to 64.  
     
     
         29 . The golf ball of  claim 12 , wherein the golf ball, when struck by a driver club at a club head velocity of about 160 ft/s, has an initial velocity off the club head of greater than about 231 ft/s.  
     
     
         30 . A golf ball comprising: 
 a center having a deflection, under an applied static load of 200 lb., of greater than about 0.160 inches;    at least one intermediate layer; and    a cover.    
     
     
         31 . The golf ball of  claim 30 , wherein the golf ball, when struck by a driver club at a club head velocity of about 160 ft/s, has an initial velocity off the club head of greater than about 231 ft/s.  
     
     
         32 . The golf ball of  claim 30 , wherein the center has a diameter of less than about 1.375 inches.  
     
     
         33 . The ball of  claim 30 , wherein the center, the at least one intermediate layer, and the cover have approximately the same specific gravity.  
     
     
         34 . The golf ball of  claim 30 , wherein the golf ball has a deflection, under an applied static load of 200 lb., of greater than about 0.080 inches.  
     
     
         35 . The golf ball of  claim 30 , wherein the cover has a shore D hardness within the range of 50 to 75.  
     
     
         36 . The golf ball of  claim 3 , wherein the cover has a shore D hardness within the range of 68 to 73.  
     
     
         37 . The golf ball of  claim 30 , wherein the cover has a shore D hardness within the range of 58 to 64.  
     
     
         38 . A golf ball comprising: 
 a low compression core formed of a first composition;    an intermediate layer formed of a second composition; and    a cover layer formed of a third composition,    the core, the intermediate layer, and the cover layer each having a generally equal specific gravity.    
     
     
         39 . The golf ball of  claim 38 , wherein the low compression core has a deflection, under an applied static load of 200 lb., of greater than about 0.160 inches.  
     
     
         40 . The golf ball of  claim 38 , wherein the specific gravity is within the range of about 1.118 and about 1.132.  
     
     
         41 . The golf ball of  claim 38 , wherein the specific gravity is about 1.125.  
     
     
         42 . The golf ball of  claim 38  further comprising fillers.  
     
     
         43 . The golf ball of  claim 38 , wherein the low compression core comprises a polybutadiene with a high-cis isomer content of at least about 94%, a co-crosslinking agent, and a free radical initiator and wherein the polybutadiene is synthesized using at least one catalyst chosen from the group consisting of nickel, cobalt, neodymium and combinations thereof  
     
     
         44 . The golf ball of  claim 43 , wherein the free-radical initiator further comprises a peroxide.  
     
     
         45 . The golf ball of  claim 38 , wherein the golf ball, when struck by a driver club at a club head velocity of about 160 ft/s, has an initial velocity off the club head of greater than about 231 ft/s.  
     
     
         46 . The golf ball of  claim 38 , wherein the cover layer has a shore D hardness within the range of 50 to 75.  
     
     
         47 . The golf ball of  claim 38 , wherein the cover layer has a shore D hardness within the range of 68 to 73.  
     
     
         48 . The golf ball of  claim 38 , wherein the cover layer has a shore D hardness within the range of 58 to 64.  
     
     
         49 . A golf ball comprising: 
 a core comprising a high cis-content polybutadiene rubber, a co-crosslinking agent, and a free radical initiator;    an inner layer comprising about 60% to about 80% ethylene, from about 8% to about 20% by weight of an α, β-unsaturated carboxylic acid and from about 5% to about 25% of an n-alkyl acrylate; and    a cover layer comprising about 80% to about 82% by weight of ethylene and about 18% to 20% of weight of an α, β-unsaturated carboxylic acid.    
     
     
         50 . The golf ball of  claim 49 , wherein about 40% to about 70% of carboxylic acid groups of the inner layer are neutralized with metal ions.  
     
     
         51 . The golf ball of  claim 50 , wherein the metal ion is chosen from the group consisting of sodium, magnesium, lithium, and zinc.  
     
     
         52 . The golf ball of  claim 49 , wherein about 100% of the carboxylic acid groups of the inner layer are neutralized with metal ions.  
     
     
         53 . The golf ball of  claim 49 , wherein the inner layer comprises about 75% to about 80% ethylene, from about 8% to about 12% by weight of an α, β-unsaturated carboxylic acid, and from about 8% to about 17% of an n-alkyl acrylate.  
     
     
         54 . The golf ball of  claim 49 , wherein about 100% of the carboxylic acid groups of the cover layer are neutralized with metal ions.  
     
     
         55 . The golf ball of  claim 49  further wherein the core, the inner layer, and the cover layer all have substantially the same specific gravity.  
     
     
         56 . The golf ball of  claim 49  further wherein the core, the inner layer, and the cover layer all have a specific gravity of about 1.118 to about 1.132.  
     
     
         57 . The golf ball of  claim 49 , wherein the cover layer has a shore D hardness within the range of 50 to 75.  
     
     
         58 . The golf ball of  claim 49 , wherein the cover layer has a shore D hardness within the range of 68 to 73.  
     
     
         59 . The golf ball of  claim 49 , wherein the cover layer has a shore D hardness within the range of 58 to 64.  
     
     
         60 . The golf ball of  claim 49 , wherein the golf ball, when struck by a driver club at a club head velocity of about 160 ft/s, has an initial velocity off the club head of greater than about 231 ft/s.  
     
     
         61 . A golf ball comprising: 
 a core comprising a high cis-content polybutadiene rubber, a co-crosslinking agent, and a free radical initiator;    an inner layer comprising about 60% to about 80% ethylene, from about 8% to about 20% by weight of an α, β-unsaturated carboxylic acid and from about 5% to about 25% of an n-alkyl acrylate; and    a cover layer comprising a terpolymer comprising about 80% to about 82% by weight of ethylene and about 18% to about 20% of weight of an α, β-unsaturated carboxylic acid, the cover layer further comprising a very low modulus ionomer comprising from about 67% to about 70% by weight of ethylene, about 10% by weight of an α, β-unsaturated carboxylic acid, and from about 20% to about 23% by weight of an n-alkyl acrylate.    
     
     
         62 . The golf ball of  claim 61 , wherein the golf ball, when struck by a driver club at a club head velocity of about 160 ft/s, has an initial velocity off the club head of greater than about 231 ft/s.  
     
     
         63 . The golf ball of  claim 61 , wherein the core, the inner layer, and the cover layer all have substantially the same specific gravity.  
     
     
         64 . The golf ball of  claim 61 , wherein about 40% to about 70% of the carboxylic acid groups of the terpolymer are neutralized with a metal ion and further wherein about 70% of the carboxylic acid groups of the very low modulus ionomer are neutralized with a metal ion.  
     
     
         65 . The golf ball of  claim 61 , wherein the carboxylic acid groups of the terpolymer are neutralized by a mono-valent metal ion and further wherein the carboxylic acid groups of the very low modulus ionomer are neutralized using a di-valent ionomer.  
     
     
         66 . The golf ball of  claim 61 , wherein the cover layer has a shore D hardness within the range of 50 to 75.  
     
     
         67 . The golf ball of  claim 61 , wherein the cover layer has a shore D hardness within the range of 68 to 73.  
     
     
         68 . The golf ball of  claim 61 , wherein the cover layer has a shore D hardness within the range of 58 to 64.