Highly-filled fire-resistant cpds. - by melt-compounding mixt. of polyolefin, fire-retardant, additives, stabilisers and special processing cpd. in twin-screw extruder

摘要

The prodn. of highly-filled compounds (I) contg. polyolefins (II), fire retardants (III), additives and stabilisers (IV), and processing cpd. (V), by melt-compounding in continuous homogenisers at below 463 K; the process involves introducing (II), (III) (which liberate water from 473 K upwards), (IV) and 0.2-3.5 wt.% (V) from a feed hopper into the inlet zone of a twin-screw extruder which has a screw with a box profile of length = 2-4D (with D = screw dia.) in the inlet zone and compressionless outlet zone of length 3-5D; (V) is a mixt. of 75 wt.% Ca stearate, 12 wt% triethylene glycol stearate, 7 wt.% stearic acid, 5 wt.% glyceric acid partial ester and 1 wt.% Zn 2-ethylhexanoate. Pref. (II) is EVA copolymer with vinyl acetate (VA) content 10-35 wt.% and/or a partial post-hydrolysis prod. thereof with degree of hydrolysis below 85%; (III) is Al(OH)3 with particle size below 2 microns (50-65 wt.%) and hydrated silica contg. 8-11 wt.% bound water (1-5 wt.%); (IV) consists of up to 10 wt.% Zn borate or MgO with particle size below 3 microns, and 0.2-1 wt.% of a stabiliser mixt. comprising antioxidant and metal deactivator; (V) is introduced into the inlet zone as a dry powder or a liq., or premixed with (III). USE/ADVANTAGE - The process enables the prodn. of highly-filled, halogen-free, fire-resistant cpds. (I) with excellent mechanical and electrical properties, useful e.g. for cable and wire insulation, esp. in ships, energy installations and computers; (I) are low-smoking, self-extinguishing and non-dripping, and can contain up to 70 wt.% fire retardant without loss of other desirable prop