GB1397513A - Process for the production of hollow plastics articles - Google Patents

Abstract

1397513 Blow-moulding MESSER GRIESHEIM GmbH 3 May 1973 [15 May 1972] 21081/73 Heading B5A In a blow moulding process, a preform is expanded and cooled by a low boiling point liquefied gas flowing thereinto through a single pipe having a valve and a blowing mandrel, the liquefied gas at the beginning of the inflow phase evaporating on passing through the pipe, valve and blow mandrel, subsequently any partially evaporating as a result of cooling the pipe, valve and mandrel and at the end of the inflow phase entering the preform in the liquid state. As shown in Fig. 5, a hollow article 1 is blow-moulded in mould 2, liquid nitrogen reservoir 7 provides blowing and cooling fluid through pipe 6, valve 5, past heater 8, through pipe 4 and mandrel 3. Pipe 4 has a high heat capacity which may be supplemented by heater 8 so that the nitrogen is initially evaporated thereby to provide gaseous nitrogen for blowing. As the pipe is now cooled as a result of the evaporation, final expansion and cooling is effected by a gas/liquid mixture. During final cooling, pressure on the article may be released, e.g. by raising the mandrel, so that the nitrogen is atomized finely. During initial blowing, the nitrogen preferably comes out of the nozzle as about the speed of sound. The medium may alternatively be argon or fluorinated hydrocarbon. The nozzle may be a naval nozzle. An outlet valve 9 enables the scavenging, e.g. with nitrgen and cooling to operating temperatre on starting up the machine.