Patent GB-1481227-A (GB)
Title: Plastics products and methods of producing them
IPC: B29C48/09
Filed: 1974-09-04
Abstract: 1481227 Extruded protective detachable coating BELLAPLAST GmbH 4 Sept 1974 38728/74 Heading B5A An extruded thermoplastics material section, e.g. a strip, sheet, or tube, of 0À2 to 10 mm. wall thickness, is coated with an unbonded and detachable protective surface film of a different material, of a thickness of 50 to 200 microns and which is simultaneously extruded from the same extrusion die orifice as the section. The section material may comprise polymethacrylate, or polymethylmethacrylate, or acrylonitrile-butadiene-styrene, and the detachable film may comprise polyethylene, polypropylene, polycarbonate, or a copolymer of acrylonitrilestyrene, or ethylene vinylacetate. The film protects the section during extrusion through the die and during and after subsequent forming, e.g. into domestic and kitchen furniture, refrigerators, light fittings, and light transmitting sheets. The protection is afforded against irregularities in the die shaping surface, mechanical damage, and localized cooling, and heating degradation during the subsequent forming. The film may be coloured or loaded with dye or pigment to protect against radiation or bacteria. In the Fig. 1 embodiment (not shown) a strip or sheet section is extruded from polymethacrylate or polymethylmethacrylate with a film of polyethylene, polypropylene, or polycarbonate either completely enveloping the section, or being on its upper and lower surfaces, the section material being delivered as a stream to the extrusion die along a passage into which the skin material is delivered, from an annular chamber, as a surrounding layer which is progressively thinner towards opposed sides, Fig. 4 (not shown), at which the layer may be interrupted and which correspond to the edges of the section which issues from the die. In the Fig. 2 and 6 embodiment, an extruded strip or sheet 17 comprises a section extruded from an inner stream 9a of impact resistant polystyrene, and surrounding layers of bonding material 9b and polymethylmethacrylate 9c, and of polyolefin or polycarbonate film material 5. The strip or sheet of the Fig. 1 or Fig. 2 embodiments may be delivered directly to further intermittently acting forming apparatus 24, Fig. 3, via a cooling means 21 which renders the section half supporting, by cooling the film and optionally the surfaces of the section, whilst the interior of the section remains plastically deformable. The continuous delivery from the die 3 is converted to an intermittent delivery by means 22, downstream of which the section 11 passes through a station 23 conditioning its temperature for the forming apparatus 24, at which the section is either stretched or blown by compressed air into contact with a cooled forming tool, or is pressed between two cooled forming surfaces. The further formed section passes through a station 25 at which shapes 26 are punched out of the section, and the remaining section then passes through a cutting station 27 where the surface films 15 are peeled off, to each pass through recovery means 29, 28, for recycling to extruders 6, 1, feeding the die 3. Alternatively, Fig. 5 (not shown) the extruded section of the Fig. 1 or Fig. 2 embodiment may pass through a cooling means and cooling calender rolls to be found on to a storage roll, from which it is subsequently unwound to pass through an infra-red heating means, to be further formed Fig. 7 (not shown), as in the Fig. 3 embodiment. In the Fig. 8 embodiment (not shown), a tube 32, Fig. 9, is extruded, comprising an inner layer 33 of impact polystyrene, an intermediate layer 34 of acrylonitrile-butadiene-styrene, and an outer layer 35 of polyethylene film material, the extruded tube 32 being inflated on issuing from the die, and changed to the Fig. 10 square configuration in continuous passage through a vacuum, or hydraulic sizing device. The tube may be used to manufacture plastics furniture, whereafter the protective film 46 is removed.