Shaping of thermoplastic preforms for containers - uses mixt. of two or more polymers some of which are drawn off from accumulation chamber through flow control valve

摘要

Equipment for mfg. a preform for prodn. of cylindrical containers is attached direct to the nozzle of an extruder which supplies a mixture of polymers. The preforming device comprises; i) a chamber forming a melt accumulator connected to the nozzle; ii) a vertically moveable piston in the chamber (4) operated by a cylinder; iii) a core operated vertically along the preform axis by a rod; iv) a control valve mounted at the point of fusion (5) of the melt flow streams to enable a part of the incoming melt to be diverted away from the main flow in the accumulator chamber. USE/ADVANTAGE - For mfg. thermoplastic preforms for subsequent forming of containers, e.g. petrol tanks. Ensures uniform distribution and formation of the diffusion resistant layer at the melt stream fusion zone and around the preform circumference.