Patent ID: 11938379
Assignee: ACUSHNET COMPANY
Field: Furniture, games (Other fields)
Classification: CPC A | IPC A

Claim 5:
6. A golf ball, comprising:
a solid core having an outer surface and a geometric center, wherein the solid core is formed from a rubber composition cured under heat, the rubber composition comprising:
a base rubber comprising a mixture of two or more polybutadiene rubbers and ethylene-propylene-diene rubber,
an organic peroxide,
a cross-linking co-agent comprising zinc diacrylate,
calcium sulfate dihydrate present in the rubber composition in an amount of about 1 phr to about 3.9 phr,

wherein the geometric center and the outer surface each has a hardness and the hardness of the geometric center ranges from about 40 Shore C to about 70 Shore C and the hardness of the outer surface ranges from about 75 Shore C to about 105 Shore C,
wherein the hardness of the outer surface is greater than the hardness of the geometric center to define a positive hardness gradient of 30 Shore C units to 50 Shore C units,
wherein the amount of calcium sulfate dihydrate and the number of waters of hydration are related to the positive hardness gradient, according to equation (I):, 2
     ≤
     
      
       W
       ⁢
       R
       ⁢
       
        A
        C
       
       *
       W
       ⁢
       R
       ⁢
       
        A
        
         W
         ⁢
         O
         ⁢
         H
        
       
      
      
       1
       -
       
        1
        
         H
         Gr
        
       
      
     
     ≤
     
      1
      ⁢
      5
     
    
   
   
    
     (
     I
     ), where WRAC represents the amount of calcium sulfate dihydrate in parts per hundred; HGr represents the positive hardness gradient (Shore C); and WRAWOH represents the number of waters of hydration in the calcium sulfate dihydrate;
an inner cover layer surrounding the core; and
an outer cover layer disposed about the inner cover layer.