Method of removing impurities from polymeric synthetic plastics

Details Method of removing impurities from polymeric synthetic plastics Method of removing impurities from polymeric synthetic plastics

1989-11-21

1992-01-14

Thurlow, Jeffery

Plastic and nonmetallic article shaping or treating: processes

Vacuum treatment of work

159 22, 210634, 264141, 425203, 425204, 425205, B29C 4776

Patent

active

050808451

ABSTRACT:
The removal of impurities, for example monomeric low-molecular substances, solvents or the like, from polymeric synthetic plastics materials takes place by the admixture of extraction gas in a first extruder in a supercritical state. The mixture is transferred to a second extruder where, in a first separating zone, and by a counter-current method, it is cleansed of the major part of the extraction gas containing the impurities, this being passed through a discharge orifice. Separation of any residue takes place in a vacuum zone on the downstream side. The high pressure in the first extruder is maintained by a counter-pressure valve in the connecting pipe between the first and second extruders. By the separation of contaminated extraction gas from molten synthetic plastics material in a closed space, namely the second extruder, it is possible to achieve an ordered dissipation of extraction gas on the one hand and molten synthetic plastics material on the other hand.

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Anders, "Plastverarbeiter", 32nd vol. 1981, No. 7, pp. 811-818.

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