HETEROGENEOUS MELT STABILIZATION HYDROLYSIS OF OXYMETHYLENE COPOLYMERS

摘要

1407145 Stabilization of oxymethylene copolymers CELANESE CORP 25 April 1973 [26 April 1972] 19589/73 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, with 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 from the copolymer and from 2 to 25 weight per cent, based on the copolymer, of a reactant which is water, an alcohol, or a mixture thereof, a heterogeneous system consisting essentially of molten copolymer and vaporous reactant in a reaction zone by maintaining the reaction zone 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 system under the above conditions of temperature and pressure for from 0À1 to 15 minutes to remove unstable oxymethylene units from the terminal portions of the copolymer molecules so that at least 90% of the terminal chains of the resulting poymer are terminated by the stable -OR- units, the stabilization reaction being conducted in the presence of from 0À05 to 10À0 weight per cent (based on copolymer weight) of a stabilizer comprising an acid scavenger or an acid scavenger and an antioxidant. In the examples a trioxane-ethylene oxide copolymer is treated with water, calcium ricinoleate, 2,21-methylene bis-(4-methyl-6-t-butyl phenol), ethylene bisstearamide, cyanoguanidine and melamine in a single screw extruder and a co-rotating, intermeshed twin-screw extruder.