GB567012A - Improvements in or relating to the production of hollow moulded articles from polythene compositions - Google Patents

Abstract

<PICT:0567012/IV/1> <PICT:0567012/IV/2> A mould containing molten polythene is cooled, or allowed to cool, whereby part of the polythene solidifies to form a hollow shell on the inside of the mould, the remaining unsolidified polythene is removed from the mould, and finally the solid hollow shell of polythene is removed from the mould. The polythene may be melted in the mould, and may include 25 per cent of paraffin wax (to give a resilient composition), or may include polyisobutylene, dyes, pigments, fillers, &c. To prevent the polythene sticking to the mould, the latter may be coated with sodium silicate. The mould may be cooled with water, mineral oil or methanol. Jars, bowls, dishes and stoppers for bottles and carboys may be made. Figs. 1 and 3 show apparatus for making tapered hollow plugs open at the narrow end and suitable for use as stoppers, comprising truncated cones 1 fixed on a shaft 12 and connected at their wider ends to a flat plate 5 having apertures coinciding with the wider ends. In use, a bottom plate 10 is clipped to the plate 5, the moulds are half filled with polythene in chip form, and the polythene is melted by heating the apparatus on an electric hot-plate. The apparatus is then inverted over a similar apparatus, as shown in Fig. 3, and a cold wet cloth 32 is placed on the plate 10. Polythene drains from the upper moulds into the lower moulds, leaving a solid shell on the inside of each of the upper moulds, which shells are removed when the moulds have cooled. The lower apparatus, with, if necessary, more polythene chips, is ready for a similar cycle of operations in conjunction with a third apparatus. A modified apparatus is described for making bottles. In a modified procedure (example 1), a temporary projection is formed on the moulded body, to facilitate removal of the body from the mould.