Patent GB-1443194-A (GB)
Title: Method of and apparatus for producing a shaped material made of wood and thermoplastic plastic
IPC: B27N7/00
Filed: 1973-09-19
Abstract: 1443194 Extruding wood filled thermoplastics; laminates therefrom H BRAUNING 19 Sept 1973 [19 Sept 1972. 26 June 1973] 44033/73 Headings B5A and B5N [Also in Division E1] A section which is extruded, and then subjected to compression between opposed press platens downstream of the extrusion outlet, comprises an extruded mixture of 50-90% by weight, e.g. 68%, of wood particles, e.g. fibres, wood flour and particularly beech chips, and 50 to 10% by weight of thermoplastics e.g. 32%, of a rigid P.V.C., the section being coated with a rigid or flexible P.V.C., either by extrusion or by the application of a thermoplastics adhesive retained pre-formed film of rigid P.V.C. The particles comprise average sizes of not more than 3 mm. for wood, and 0À02 to 10 for the plastics. The section may comprise a skirting or cill for a room, and having a smooth surface and a ribbed opposite surface for directing towards the room, and at its upper and lower edges it may terminate at a lip, Fig. 5, respectively for abutting the wall and conforming to the floor. Alternatively, Fig. 4 (not shown), one surface of the section may be ribbed, and an opposite surface may be planar with an adhesive retained film thereon and a central area embossed with a pattern moulded by the press. In the Fig. 1 embodiment, the P.V.C. and wood particles are delivered to the extruder respectively from hoppers 1, 2, via metering gates 3, pre-drier 4 and a mixer 5. Within the extruder barrel, the wood/P.V.C. mixture is heated to 100C /min. to 200 C., which temperature is maintained by fans 11, 12 controlled, together with barrel heaters, by barrel thermocouples. The mixture is subjected to progressively increasing compression along an initial screw portion 8 comprising a decreasing volume double start thread, and an unthreaded compression zone 14. The mixture is subjected to decompression in a following screw zone, 15 having a thread of constant pitch and in which volatiles are removed by a suction device 18, via barrel openings 16 and a steam on vapour separator 19 removing condensed water. The die 20 is heated to 180 C., and the section is drawn therefrom by rolls 37, located downstream of the platen press 22, drying chambers 30, 36 through which air is blown, and a further extruder 31 which applies a coating of flexible P.V.C. Cooling and cutting devices are provided downstream of rolls 37. Adhesive may be applied to the extruding material, prior to the application of a film thereto, but in the Fig. 2 embodiment (not shown), the extruder 31 and chamber 36 are omitted, and a pre-formed film, coated with thermoplastic adhesive, is applied to the extrusion upstream of the press (22), via guiding and stretching rollers (52), and a final deflecting roller (53) which is cooled. The press, Fig. 3, comprises a carriage 23 provided with platens through which cooling medium circulates and the lower platen 25 of which is fixed, and the upper 26 of which is vertically displaceable by cylinders 27 and may carry a die 55 for embossing the extrusion with a pattern 56. The carriage 23 is mounted for reciprocation of the press towards and away from the extrusion die, by a cable 24, to effect sequential compression along the length of the extrusion which is also supported by the cable 24. The moulded wood/P.V.C. mixture part of the section is slightly porous.