GB1407144A - Heterogeneous melt hydrolysis of oxymethylene copolymers - Google Patents

Abstract

1407144 Stabilization of oxymethylene copolymers CELANESE CORP 25 April 1973 [26 April 1972] 19588/73 Heading C3P An oxymethylene copolymer having a melting point above 150‹ C., the molecules of the copolymer containing from 60 to 99À6 mol per cent of comparatively unstable oxymethylene units interspersed with comparatively stable -OR- units wherein R is a divalent radical containing at least two carbon atoms directly linked to each other, any substituents on the R radical being inert and each -OR- unit being positioned between two oxymethylene units, at least part of the terminal portions of the molecules comprising the unstable units, is stabilized by forming a heterogeneous system consisting essentially of molten copolymer and from 2 to 25 weight per cent, based on the copolymer, of a vaporous reactant selected from water, alcohols and mixtures thereof in a reaction zone maintained at a temperature above the melting point of the copolymer and at a pressure sufficient to maintain the copolymer in a molten state and the reactant in a vaporous state, and reacting the molten copolymer with the reactant under the above conditions of temperature and pressure for 0À1 to 15 minutes to remove unstable oxymethylene units from the terminal portion of the copolymer molecules so that at least 90% of the terminal chains of the resulting polymer are terminated by the stable -OR- units. In the examples a trioxane-ethylene oxide copolymer is treated with water and triethylamine in a single screw extruder and a co-rotating intermeshed twinscrew extruder.