GB1345811A - Free-flowing particles of solid tacky synthetic thermoplastics materials and processes for their manufacture - Google Patents

Abstract

1345811 Powder coated plastics particles CHEMISCHE WERKE HULS AG 8 July 1971 [9 July 1970] 32079/71 Heading B5A [Also in Division C3] Particles of synthetic thermoplastic material which are solid but tacky at room temperature are rendered free flowing by coating them with powder. The particles are produced from a hot melt and preferably coated simultaneously with cooling. The particles may, e.g. be atactic polypropylene, atactic polybutene-1, examples relating to this material being given, or plasticized P.V.C. The powder may be inorganic, e.g. talc, asbestos, baryte or whiting; or organic, e.g. cork or plastics especially in the case of the atactic polymer particles which may be powdered with the isotactic form of the same polymer or with the isotactic form of a compatible different polymer. The proportion of powder coating by weight should be from 0À5 to 25%. The particles may be spherical, flat, cylindrical or block-shaped and should be between 1 mm. and 30 mm. across. The powder size should be between 2 Á and 1000 Á. The particles can be produced from a hot melt Fig. 1 and 2, not shown, dripping on to a moving belt covered with a uniform layer of powder by means of metering devices and a weir (and optionally an optical scanner) the imbedded particles then being covered with a further powder layer, the belt cooled, and the powder and particles separated by sieving. Alternatively the forming apparatus may comprise a rotating spray disc discharging into a fluidized bed of powder (Fig. 3 or 4, not shown), or the particles may be extruded, cut, thrown off into a drum sieve together with powder and then separated (Fig. 5, not shown). The extruded ribbon may be pre-powdered on a belt before cutting into particles.