Mfr. of laminated large blow-mouldings with smooth glossy surface - using a parison comprising at least two layers of plastics with different viscosities

摘要

Mfr. of large, laminated hollow mouldings comprises extruding a thermoplastics parison; sealing one end by pinching; and feeding a compressed gas into the so-sealed parison inside a blow-mould to cause it to hug the walls of the mould cavity. The resulting moulding is removed after cooling. Characteristically, a parison consisting of at least two layers of plastics is extruded. The outer layer completely envelopes the inner one. It comprises a thermoplastics having lower viscosity than the inner layer. Both layers may be of PMMA. Used e.g. in mfr. or barrels, washbasins, and the like. The use of =1 moulding cpds. of same type e.g. PMMA but different grades of viscosity facilitates control of melt flow to ensures that the prod. has even wall thickness and rejects resulting from "necking" of the parison are minimised.