Golf ball having medium positive gradient quotient

Abstract

A golf ball includes a core and a cover. The core has an outer surface, a geometric center, and a soft transition region adjacent to the outer surface. The soft transition region has a thickness of 4 mm or less, includes about 10 to 30% trans-polybutadiene isomer, and has a positive hardness gradient of about 10 Shore C or less. The cover layer has a hardness of about 50 Shore M or greater. The core has a positive hardness gradient of about 10 to 42 Shore C. A secondary gradient quotient, GQ′, from about 2.2 to 9.5, GQ′ being defined by the equation: G ′ + T 10 × COR where G′ is the core positive hardness gradient in Shore C, T is the percent of trans-polybutadiene isomer at the core outer surface, and COR is the coefficient of restitution of the core measured at an incoming velocity of 125 ft/s.

What is claimed is: 
     
         1 . A golf ball comprising:
 a core having an outer surface, a geometric center, and a soft transition region adjacent to the outer surface, the soft transition region having a thickness of about 4 mm or less, comprises about 10 to 30 percent of a trans-polybutadiene isomer, and has a first positive hardness gradient of about 10 Shore C or less; and   an outer cover layer having a hardness of about 50 Shore M or greater;   wherein the core has an outer surface hardness greater than a hardness at the geometric center to define a second positive hardness gradient of about 10 Shore C to 42 Shore C; and a secondary gradient quotient, GQ′, from about 2.2 to 9.5, GQ′ being defined by the equation:   
       
         
           
             
               
                 
                   G 
                   ′ 
                 
                 + 
                 T 
               
               
                 10 
                 × 
                 COR 
               
             
           
         
       
       where G′ is the core positive hardness gradient in Shore C, T is the percent of trans-polybutadiene isomer at the core outer surface, and COR is the coefficient of restitution of the core measured at an incoming velocity of 125 ft/s. 
     
     
         2 . The golf ball of  claim 1 , wherein the second positive hardness gradient is about 12 Shore C to 35 Shore C. 
     
     
         3 . The golf ball of  claim 2 , wherein the second positive hardness gradient is about 13 Shore C to 24 Shore C. 
     
     
         4 . The golf ball of  claim 3 , wherein the second positive hardness gradient is about 14 Shore C to 21 Shore C. 
     
     
         5 . The golf ball of  claim 1 , wherein the core has a COR of about 0.800 or greater. 
     
     
         6 . The golf ball of  claim 5 , wherein the COR is about 0.810 or greater. 
     
     
         7 . The golf ball of  claim 1 , wherein the secondary gradient quotient, GQ′, is about 2.5 to 8.5 and the second positive hardness gradient is about 12 Shore C to about 35 Shore C. 
     
     
         8 . The golf ball of  claim 7 , wherein the secondary gradient quotient, GQ′, is about 2.7 to 6.9 and the second positive hardness gradient is about 13 Shore C to about 24 Shore C. 
     
     
         9 . The golf ball of  claim 8 , wherein the secondary gradient quotient, GQ′, is about 2.9 to 6.5 and the second positive hardness gradient is about 14 Shore C to about 21 Shore C. 
     
     
         10 . The golf ball of  claim 1 , wherein the golf ball comprises an inner cover layer comprising an ionomer. 
     
     
         11 . The golf ball of  claim 10 , wherein the ionomer comprises a lithium ionomer or a sodium ionomer. 
     
     
         12 . The golf ball of  claim 1 , wherein the golf ball comprises an outer core layer disposed about the core. 
     
     
         13 . The golf ball of  claim 1 , wherein the golf ball comprises at least one coating layer disposed about the cover layer. 
     
     
         14 . The golf ball of  claim 13 , wherein the coating layer has a Shore M hardness of about 60 Shore M or less. 
     
     
         15 . The golf ball of  claim 13 , wherein the coating layer has an instrumented hardness of about 1 to 23 MPa. 
     
     
         16 . The golf ball of  claim 13 , wherein the coating layer has a thickness of about 0.001 inches to about 0.003 inches. 
     
     
         17 . The golf ball of  claim 1 , wherein the soft transition region comprises about 10 to 20 percent trans-polybutadiene isomer. 
     
     
         18 . The golf ball of  claim 1 , wherein the soft transition region comprises about 20 to 30 percent trans-polybutadiene isomer. 
     
     
         19 . A golf ball comprising:
 a core having an outer surface, a geometric center, and a soft transition region adjacent to the outer surface, the soft transition region having a thickness of about 4 mm or less, comprises about 10 to 30 percent of a trans-polybutadiene isomer, and has a positive hardness gradient of about 10 Shore C or less; and   an outer cover layer having a hardness of about 50 Shore M or greater;   wherein the core has an outer surface hardness greater than a hardness at the geometric center to define a positive hardness gradient of about 12 Shore C to 24 Shore C; and a secondary gradient quotient, GQ′, from about 7.5 to 9.5, GQ′ being defined by the equation:   
       
         
           
             
               
                 
                   G 
                   ′ 
                 
                 + 
                 T 
               
               
                 10 
                 × 
                 COR 
               
             
           
         
       
       where G′ is the core positive hardness gradient in Shore C, T is the percent of trans-polybutadiene isomer at the core outer surface, and COR is the coefficient of restitution of the core measured at an incoming velocity of 125 ft/s.