Process for preparing a stabilized oxymethylene copolymer
AssigneeHoechst Aktiengesellschaft
InventorsGunter Sextro, Karlheinz Burg, Ernst Wolters
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Abstract
Oxymethylene copolymer having heat and hydrolysis resistant terminal groups is prepared by heating the polymers present in a liquid phase, whereby a thermal degradation of the unstable terminal groups takes place. The degradation is advantageously effected in the presence of a calcium or magnesium salt of an aliphatic carboxylic acid of low molecular weight. The oxymethylene copolymers are suitable as engineering plastic for preparing semi-finished products and finished products.
Claims9
A process for preparing an oxymethylene copolymer having heat and hydrolysis resistant terminal groups by heating a copolymer consisting of from 80 to 99.9% by weight of units derived from cyclic oligomer of formaldehyde and from 20 to 0.1% by weight of units derived from a compound capable of being copolymerized with the said oligomer and forming monomer units having from 2 to 8 adjacent carbon atoms, which comprises heating the copolymer in a liquid phase at a temperature of 130.degree. to 200.degree. C. in the presence of 100 to 2,500 ppm, based on the total weight of said liquid phase, of at least one magnesium or calcium salt of a mono- or dicarboxylic acid having 3, 4 or 5 carbon atoms at a pressure above atmospheric pressure in the absence of oxygen.
Dependencies are inferred from the claim text.