METHOD FOR THE PURIFICATION OF A POLYOXYMETHYLENE HONO- OR COPOLYMER

摘要

1377083 Purification of polyoxymethylene polymers EBAUCHES SA 9 Nov 1971 [24 Nov 1970] 52046/71 Heading C3P Polyoxymethylene (POM) homo- or copolymers having terminal ester, ether or urethane groups are purified by subjecting them whilst in solution or in the form of a homogeneous gel to a heat treatment to destroy unstable residual components in the polymer which do not contain said terminal groups, converting the gel to a solution, if a gel is heat treated, effecting controlled cooling of the solution to induce crystallization of the polymer and thermostatically filtering the crystallized mixture so as to separate substantially pure POM homo- or copolymer having said terminal groups from short length polymer chains and impurities. A crystalline material (e.g. POM powder or a di- or polyurethane obtained by reaction of a diol with a mono-, di- or polyisocyanate) may be added to the solution to induce crystallization and a non solvent for the POM polymer may be added to the solution during cooling to facilitate crystallization. In the examples POM having terminal urethane or acetyl end groups is dissolved in γ butyrolactone, dimethylsulphoxide or a mixture of ethylene glycol and cyclohexanol, the solution is heated, then slowly cooled with and without the addition of POM crystallization seeds and thermostatically filtered.