GB781171A - Improvements in or relating to moulded plastic articles and processes of making same - Google Patents

Abstract

An anti-static moulded plastic composition comprises a thermoplastic synthetic resin, e.g. polymers and copolymers of methyl methacrylate, vinyl and vinylidene chlorides, ethylene and styrene, 3 to 37 per cent of a finely-divided insoluble sorptive material stable under moulding conditions, and 0.5 to 40 per cent, preferably 5 to 23 per cent, by weight of a liquid organic destaticizing agent having a low vapour pressure and a dielectric constant greater than 25. The sorptive material may be silica gel, wood flour, a -cellulose, a pigment or a thermosetting plastic, or a plastic having a softening-point higher than the synthetic resin, e.g. polyvinyl chloride, and wetting agents such as the sodium salt of sulphated long-chain fatty alcohols or sodium naphthenate may be included. The destaticizing agent is conductive or rendered conductive by the ionization of a dissolved electrolyte, e.g. polyhydric alcohols including higher molecular weight polyethylene glycols, and N-acetylethanolamine or amides, e.g. formamide, nitriles and nitro-compounds and aqueous solutions may contain an ionizable salt and a hydrotropic agent such as sodium xylene sulphonate and toluene sulphonic acid. Lubricants, plasticisers, dyes, pigments and fillers may also be present. The composition may be prepared by mixing the finely-divided ingredients, added separately, or with the sorptive material pretreated with organic liquid destaticizing agent, at a temperature below the softening-point of the plastic material, or as a powder, and applying sufficient heat and pressure to mould the material. The materials may also be incorporated in the monomer or during the polymerization, for example at the liquid stage, after which the polymerization is completed.