GB493541A - Improvements in or relating to methods and apparatus for forming films of synthetic resin - Google Patents

Abstract

Films, sheets, or coatings of thermoplastic synthetic resin are obtained by distributing particles, grains, or flakes of the resin on to a support, heating to render the resin plastic, pressing the resin into a film, cooling, and removing the film from the support. The resin may be applied to two supports which are moved into a position where they are opposite each other and are there pressed to unite the layers of heated resin. The unitary film is then cooled and removed from the support. A <PICT:0493541/IV/1> <PICT:0493541/IV/2> <PICT:0493541/IV/3> fabric or other foundation material may be applied to the heated resin layer or between two layers and united to the resin by the pressing operation. As shown in Fig. 1, powdered synthetic resin, e.g. polystyrol, is applied from hoppers 22 with sieves 23 to endless belts 9. The belts or bands are heated by the heating-devices 29, and the two films are passed between the parallel portions 10 of the belts where they are compressed and united. Fabrics or threads may be united with the films of synthetic resin by passing them between heaters 27 and then between the endless bands carrying the layers of resin. The film or coated material is cooled by means of the cooling-devices 11. Alternative forms of the pressing device are shown at 12 and 13. Device 12 comprises a block in which a cage receives rollers 14 which almost touch each other. The device is adjusted so that the rollers press against the part 10 of the band 9 and are driven along by it. The rollers move in a closed circuit. If desired, the device may be constructed so that the rollers press against an intermediate belt which in turn presses against the belt 9. Device 13 comprises a block adjusted so that its under-face is maintained against the portion 10 of the belt. Ports 15 permit the inflow of oil under pressure, whereby the two belts and the synthetic resin layers between them are pressed closely together. As shown in Fig. 4, the pressing device consists of blocks 33, 34 which pass between rollers 35, 36 with stationary axes. As shown in Fig. 5, one of the belts is replaced by a drum 38 of large diameter. Endless belt 39 moves along drums 40 and winds over a large part of drum 38. The resin is distributed on the portion 41 of the drum and on portion 42 of belt 39, and a fabric 44 may be run between the contacting surfaces. Rollers 43 may be provided for augmenting the pressure between the belt and the drum. The left-hand side of the machine is heated to render the resin plastic, and the other side is cooled. The belts or drums which contact with the synthetic resin may be engraved so as to reproduce patterns, drawings, or writing on the films produced.