| 摘要 |
<PICT:0602575/IV(a)/1> Perforated sheets of organic thermoplastic material are produced by covering a heated metal surface engraved with intersecting grooves with a molten hot-melt thermoplastic material, removing excess material not in the grooves, and cooling the surface to solidify the material. Hot-melt thermoplastic material is liquid above 100 DEG C. and of a certain viscosity. Molten material such as polythene is fed from a nozzle 7 and a heated trough 8 on to a rotating roller 1 having the engraved surface. A heated spreader bar 9 forces the material into the grooves and a heated doctor knife 10 removes excess material. Running water 3 in the cylinder and a cooled roller 11 solidify the material which is removed on the roller 11. The roller 1 is supported and rotated by the rollers 2, 11 and is heated by infra-red lamps 6. The surface of the roller 1 is polished and coated with a film of a separating aid, such as high melting point grease, aluminium or zinc stearate, a glazing material such as sodium silicate or a detergent. The roller is of stainless steel, mild steel, brass or aluminium. Specification 516,807 is referred to. |
