Hoechst Aktiengesellschaft

Eberhard Fischer

Karlheinz Burg

Karl-Friedrich Muck

Gunter Sextro

Siegfried Schiessler

Helmold Von Plessen

Helmut Strametz

Gunter Mayer

Continuous process for removing unstable components from crude oxymethylene copolymer, which still contains catalysts, monomeric starting materials and unstable components, by treating the copolymer with deactivators, optionally in the presence of auxiliaries, in a pressure zone, and subsequently removing volatile components in a pressure-release zone in the presence or absence of stabilizers, in which process the crude polymer is fully melted in the absence of the deactivators and auxiliaries immediately after completion of the polymerization step, and the deactivators are subsequently incorporated, alone or together with auxiliaries, under pressure into the resultant polymer melt in at least one pressure zone. By this process, degradation is avoided and significantly better properties are obtained.

Continuous process for removing unstable components from crude

During the recovery of the unreacted propylene from the mother liquor obtained in the polymerization of liquid propylene, the major part of the propylene is evaporated in a first evaporation step at a low temperature and the remaining part is evaporated in a second evaporator at a high temperature. In this way an early agglomerization of the atactic and/or low-molecular weight polymer dissolved in the mother liquor and fouling of the heat exchanger tubes and/or of the column trays is avoided.

Process for recovering and purifying unreacted propylene during mass

Contaminated sulfuric acid which may contain water, organic compounds and inorganic salts is converted to almost pure concentrated sulfuric acid by passing the acid through a Pauling plant and distilling the concentrated contaminated acid. Addition of nitric acid improves the decomposition of organic compounds and ammonium salts of the contaminated acid.

Process for the regeneration of sulfuric acid

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Kelkheim, Germany

Eberhard Fischer