Counter tapered thermoplastic elastomers

Abstract

A counter tapered thermoplastic elastomer composition comprising: (a) a counter tapered diblock A-[A/B] copolymer with a peak molecular weight from 20,000 to 250,000, which includes a monovinyl aromatic homopolymer block A with a peak molecular weight of at least 8,000 and a counter tapered copolymer block [A/B] with a vinyl content of at least 15 weight percent based on the amount of conjugated diene units in the diblock copolymer; and (b) a block copolymer selected from the group consisting of linear triblock copolymers having a peak molecular weight that is at least about 1.5 times the peak molecular weight of the counter tapered diblock A-[A/B] copolymer described in (a), multiarm coupled block copolymers having a peak molecular weight that is at least about 2.5 times the peak molecular weight of the counter tapered diblock A-[A/B] copolymer described in (a), and mixtures thereof; and (c) wherein the ratio of (a) to (b) in the counter tapered thermoplastic elastomer composition is from about 1:5 to about 5:1. The counter tapered thermoplastic elastomer compositions provide in the applications: i) easy processing such as short dispersion time, low mixing temperature, low viscosity, excellent storage stability; and ii) better reinforcement such as high elastic response, wide range of performance grade, high adherence, higher filler loading capacity, and better compromise between high and low temperature properties; which make them suitable for a broad range of applications such as road paving, roofing, shingles, waterproofing membranes, adhesive tapes and labels, contact and sprayable adhesives, and sealants.