Patent ID: 11944875
Assignee: ACUSHNET COMPANY
Field: Furniture, games (Other fields)
Classification: CPC A | IPC A

Claim 5:
6. A golf ball, comprising:
a dual core comprising an outer core layer disposed over an inner core layer,
wherein the outer core layer is formed of a first rubber composition cured under heat, the first rubber composition comprising:
a base rubber comprising a mixture of polybutadiene rubber and styrene butadiene rubber,
an organic peroxide, and
zinc diacrylate,

wherein the inner core layer is formed of a second rubber composition cured under heat, the second rubber composition comprising:
a base rubber comprising polybutadiene rubber,
an organic peroxide,
zinc diacrylate, and
calcium sulfate dihydrate in an amount of about 1 phr to about 3.75 phr,

wherein the inner core layer has a geometric center and an outer surface, each having a hardness, the hardness of the geometric center ranging from about 40 Shore C to about 70 Shore C and the hardness of the outer surface ranging from about 75 Shore C to about 105 Shore C, and 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
     ≤
     
      
       
        WRA
        C
       
       *
       
        WRA
        WOH
       
      
      
       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 dual core, wherein the inner cover layer is formed of an ionomer; and
an outer cover layer disposed about the inner cover layer, wherein the outer cover layer is formed of a polymer selected from the group consisting of polyurethanes, polyureas, polyurethane-urea hybrids, and copolymers and blends thereof.