Process for the manufacture of granular oxymethylene polymers
AssigneeHoechst Aktiengesellschaft
InventorsGunter Sextro, Karlheinz Burg, Hans Joachim Leugering, Helmut Schlaf, Alwin Heller
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Abstract
Oxymethylene polymers (POM) are obtained in granular form by cooling a POM solution or dispersion having a temperature above the sintering temperature of the POM in two stages to a temperature just below the said sintering temperature. The solvent or dispersion agent used is a mixture of methanol and water and the cooling agent is a methanol/water mixture which may contain POM suspended therein. The granular POM obtained is suitable as technical material for making shaped articles.
Claims14
A process for making a granular oxymethylene copolymer (POM) containing, in addition to oxymethylene units, from 0.1 to 20% by weight of oxyalkylene units having from 2 to 8 adjacent carbon atoms in the main chain thereof, which process comprises preparing a solution or fine dispersion of POM in a methanol/water mixture at a temperature of 5.degree. to 65.degree. C. above the sintering temperature (T.sub.s) of the POM, preparing a cooling agent which is a suspension of 1 to 25% by weight POM in 99 to 75% by weight of a methanol/water mixture at a temperature below T.sub.s, cooling said POM solution or fine dispersion in a first stage by mixing it with said cooling agent in such proportions as to produce a blend having a temperature of 0.degree. to 10.degree. C. above T.sub.s, thereafter cooling said blend in a second stage to a temperature of 1.degree. to 10.degree. C. below T.sub.s, separating the granular POM from the blend and drying it.
Dependencies are inferred from the claim text.