Highly flexible 2-phase thermoplastic elastomer

摘要

A 2-phase thermoplastic material (I) consists of a microdispersion of silane-crosslinked polyethylene (PE) (B) in a continuous, fluid polypropylene (PP) matrix (A). Component (B) comprises VLDPE with a density of 0.88-0.91 g/cm<3> and/or ULDPE with a density of 0.85-0.88 g/cm<3>, and the amts. of (A) and (B) in material (I) are less than 65 wt.% and at least 35 wt.% respectively. Also claimed is a process for the prodn. of (I) (see below). Component (B) has a mol.wt. distribution (Mw/Mn) of 1.5-3.0, pref. about 2.0, a gel content of 30-95 (pref. 60-90) wt.% and a mean particle size of 0.2-2 microns. (B) is silane-grafted by the addn. of radical sources, pref. organic peroxides, and organosilanes, pref. vinyl-trimethoxy-silane (VTMOS) or vinyl-triethoxy-silane. (A) is a PP homopolymer, PP block copolymer and/or random PP copolymer. The polymer component in (I) contains more than 20 wt.% (A) and up to 80 (pref. 40-75) wt.% (B). (I) may also contain pigments, fillers, colouring agents, fire retardants, stabilisers, metal and deactivators, processing aids and opt. plasticisers, etc.. The silane-grafted (B) is dynamically crosslinked by adding crosslinker (D) during the mixing process with (A), which is carried out in a mixer suitable for the dispersion of the crosslinking structure of (B). Pref. (D) contains the water required for hydrolysis of the silane gps., and opt. additives such as high-boiling alcohols, etc.