Polyester-based thermoplastic elastomers containing plasticizers for making golf balls
Multi-layered golf balls having at least one layer made of a polyester composition containing a polyester thermoplastic elastomer and plasticizer are provided. The plasticizers help reduce the glass transition temperature (Tg) of the composition and various plasticizers may be used. For example, the composition may include alkyl oleate plasticizers such as ethyl oleate and octyl oleate. Polyester-ether block copolymers are particularly preferred. The golf ball includes a core having at least one layer and a cover having at least one layer. The polyester composition may be used to form any core, cover, or other layer in the golf ball.
1. A golf ball, comprising:
a) dual core comprising an inner core and outer core layer, the inner core having an outer surface and geometric center and, the outer core layer having an outer surface and midpoint; the inner core comprising a rubber composition and the outer core layer comprising a polyester-based thermoplastic elastomer composition, the polyester-based composition comprising;
i) about 40 to about 99% by weight polyester thermoplastic elastomer; and
ii) about 1 to about 60% by weight of an alkyl oleate plasticizer selected from the group consisting of methyl oleate, ethyl oleate, propyl oleate, butyl oleate, and octyl oleate, and mixtures thereof
wherein the midpoint and outer surface of the outer core layer each has a hardness, and the outer surface hardness is greater than the midpoint hardness to provide a positive hardness gradient in the outer core layer; and
b) cover having at least one layer disposed about the core.
2. The golf ball of claim 1 , wherein the midpoint hardness of the outer core layer is in the range of about 40 to about 80 Shore C and the outer surface hardness of the outer core layer is in the range of about 48 to about 88 Shore C.
3. The golf ball of claim 1 , wherein the outer surface hardness of the outer core layer is greater than midpoint hardness of the outer core layer by at least 5 Shore C units.
4. The golf ball of claim 1 , wherein the center of the inner core and outer surface of the outer core layer each has a hardness, and the outer surface hardness of the outer core layer is greater than the center hardness of the inner core.
5. The golf bail of claim 1 , wherein the center and outer surface of the inner core each has a hardness, and the outer surface hardness is greater than the center hardness to provide a positive hardness gradient in the inner core.
6. The golf ball of claim 1 , wherein the polyester thermoplastic elastomer is a polyester-polyether block copolymer.
7. The golf hall of claim 1 , wherein the polyester-based thermoplastic elastomer composition further comprises an acid copolymer of ethylene and an α,β-unsaturated carboxylic acid, optionally including a softening monomer selected from the group consisting of alkyl acrylates and methacrylates; and a cation source present in an amount sufficient to neutralize from about 0 to about 100% of all acid groups present in the composition.
8. The golf hall of claim 7 , wherein the acid copolymer of ethylene contains acid groups and greater than 70% of the acid groups ate neutralized.
9. The golf ball of claim 1 , wherein the polyester-based composition comprises about 10 to about 30% by weight plasticizer.