Multi-layer core golf ball having thermoset rubber cover
An all rubber golf ball with one or more thermosetting rubber core layers and one or more thermosetting rubber cover layer. At least one of the ball's layers has moisture vapor barrier property, and in one aspect the moisture vapor barrier layer is an intermediate layer. In one embodiment, the thermosetting rubber layers follow a cis- or a trans-polybutadiene gradient from the center of the ball to its cover.
1. A golf ball comprising a core layer, a cover layer, and at least one intermediate layer disposed between the core and the cover, wherein said core layer, said cover layer, and said at least one intermediate layer each comprises a cross-linked thermoset rubber composition having a primary rubber component of polybutadiene having a polydispersity of no greater than about 2 in an amount of greater than about 80% by weight and a crosslinking initiator, the core layer having a cis-1,4-polybutadiene content (δ cr ), the at least one intermediate layer having a cis-1,4-polybutadiene content (δ im ), and the cover layer having a cis-1,4-polybutadiene content (δ cv ) such that δ cr ≧δ im δ cv , wherein the intermediate layer comprises a moisture vapor barrier layer and wherein the overall ball comprises a compression of 60 to 110 and a coefficient of restitution of from 0.750 to 0.850.
2. The golf ball of claim 1 , wherein the thermoset rubber composition further comprises a cis-to-trans catalyst wherein the cis-to-trans catalyst comprises an organosulfur compound, metal-containing organosulfur compound, a substituted or unsubstituted aromatic organic compound that does not contain sulfur or metal, an inorganic sulfide compound, an aromatic organometallic compound, an element from Group VIA, or a combination thereof.
3. The golf ball of claim 2 , wherein the organosulfur compound comprises pentachlorothiolphenol (PCTP) or a metal salt thereof.