Thermoplastic elastomers having improved adhesive properties
Adhesive compositions comprising a thermoplastic elastomer and a block copolymer with rigid vinyl aromatic blocks and non-rigid blocks of dienes and vinyl aromatic monomers.
1. An adhesive composition comprising
(a) from 50 to 75 weight percent of a thermoplastic elastomer comprising a blend of a polypropylene and dynamically vulcanized ethylene-propylene-nonconjugated diene terpolymer rubber, and
(b) from 25 to 50 weight percent of a block copolymer comprising rigid blocks of styrene and non-rigid blocks of 1,3-butadiene and styrene containing at least the block structure styrene-1,3-butadiene/styrene-styrene, wherein the 1,3-butadiene content is less than 40 weight percent of the total block copolymer and the non-rigid blocks amount to at least 50 weight percent of the total block copolymer,
based on the total weight of (a)+(b) and wherein the composition exhibits a tensile set according to ASTM D412 of 11% or less.
2. The composition of claim 1 further comprising from about 10 to about 50 weight percent of a thermoplastic polyurethane (c) based on the total weight of (a)+(b)+(c).
3. A method for the preparation of an adhesive composition, comprising the steps of blending
(a) from 50 to 75 weight percent of a thermoplastic elastomer comprising a blend of polypropylene and dynamically vulcanized ethylene-propylene-nonconjugated diene terpolymer rubber with
(b) from 25 to 50 weight percent of a block copolymer comprising rigid blocks of styrene and non-rigid blocks of 1,3-butadiene and styrene containing at least the block structure styrene-1,3-butadiene/styrene-styrene wherein the 1,3-butadiene content is less than 40 weight percent of the total block copolymer and the non-rigid blocks amount to at least 50 weight percent of the total block copolymer,
based on the total weight of (a)+(b) and wherein the composition exhibits a tensile set according to ASTM D412 of 11% or less.