GB1091678A - Improvements relating to making rigid hollow containers from plastics materials - Google Patents

Abstract

Large containers for fluids, e.g. for use in road or rail tankers or in chemical plant for corrosive fluids, milk, granules and powder, are made by coating the interior of a fibre reinforced thermosetting resin shell, e.g. styrene/maleic or other unsaturated organic acid anhydride or epoxy resin reinforced with glass, asbestos, nylon or polyester fibre in matted, woven, or knitted form, with a thermoplastic, e.g. powders of high or low density polyethylene, polymethyl methacrylate, polyoxymethylene copolymers containing ethylene oxide radicals or P.V.C. paste, which is distributed evenly over the surface by rotating the shell about horizontal and vertical axes whilst applying heat to gel the powder or paste which is set upon cooling of the shell. Flanged half shells (3 and 4) are formed by laying up the thermosetting material in moulds (1, 2) (Figs. 1 and 2, not shown) and are joined at the flanges, e.g. by adhesive, riveting or bolting, and may be used directly in the lining operation (Fig. 3, not shown) or may alternatively be supported within the mould halves (1, 2) (Fig. 4, not shown) if the thermosetting material lacks heat resistance. With a split cap (8) placed around the shell flange (when the shell is used as the mould) or with abutting flanges on the metal mould, the shell may be directly flame heated. Gas or air pressure may be supplied to the interior of the shell via pipes 9, 10 (Figs. 7 and 8, not shown) to force the cooling thermoplastic into contact with the shell, and removed via pipes 11, 12; the pipes (10, 12) may entering through tubes (13, 13\sv) forming the axis of rotation. The pipes (9, 10, 11 and 12) may alternatively be employed for internal hot gas heating of the thermoplastic, e.g. when the shell is coated with a layer of foamed polyurethane insulation 7\sv prior to introducing the thermoplastic, followed by internal air or gas cooling. The thermoset half shells may be formed without flanges in half moulds (14, 15) (Fig. 9, not shown). The thermosetting resin shell is preferably cured before application of the thermoplastic lining, e.g. 5 to 10 min. at 100 DEG C followed by 4 hours at 80 DEG C for styrene/maleic anhydride, and thermoplastic powder, e.g. a copolymer of ethylene with a small amount of vinyl acetate or p.v.c. powder, may be applied to the interior surface of the shell before it is cured to provide a key for the thermoplastic lining. With a polyethylene lining, heating for 5 to 10 mins. at 200 DEG C to 250 DEG C is preferred and, with P.V.C. paste, 5 to 10 min. at a temperature above 165 DEG C., e.g. 180 DEG C. A rubbery adhesive may also be applied to the lining surface of the thermoset shell. Polyurethane foam, when introduced between the thermoset shell and the thermoplastic lining, is formed at 30 DEG to 40 DEG C.