Dual core golf ball having a shallow “positive hardness gradient” thermoplastic inner core and a steep “positive hardness gradient” thermoset outer core layer

摘要

A golf ball includes an inner core layer including a thermoplastic highly-neutralized ionomer formed from a copolymer of ethylene and an α,β-unsaturated carboxylic acid, an organic acid or salt thereof, and sufficient cation source to neutralize the acid groups of the copolymer by 80% or greater. The inner core has a geometric center hardness and a surface hardness to define a first hardness gradient having a first slope, S₁. An outer core layer is disposed about the inner core and is formed from a homogenous thermoset composition. The outer core layer has an interior hardness and an outer surface hardness to define a second hardness gradient having a second slope, S₂. An inner cover layer is disposed about outer core layer and an outer cover layer is disposed about the inner cover layer. A ratio of S₂ to S₁ is about 1.0 or greater.