Verfahren zur Herstellung von Formteilen mit Zellstruktur aus Oxymethylenpolymeren

摘要

Producing shaped oxymethylene polymer articles by preparing an intimate mixture of an oxymethylene polymer resistant to degradation at an elevated temperature by aqueous and/or alcoholic liquids under non-acid conditions and another oxymethylene polymer not so resistant, forming a shaped article from the polymer mixture under heat and pressure and thereafter subjecting the article to treatment with a non-acid aqueous and/or alcoholic liquid to destroy the oxymethylene polymer not resistant to degradation and endowing the article with a cellular structure. The preferred degradable polymers are hydroxy-methyl terminated homopolymers of formaldehyde or trioxan which may be end-capped by esterification of the terminal hydroxy groups. The degradation resistant polymers may be homopolymers of the above type which have been end-capped by etherification of the terminal hydroxy groups or copolymers of trioxan and ethylene oxide or dioxolane which contain oxyalkylene groups having carbon to carbon single bonds dispersed in the chains of oxymethylene groups. The mixture of polymers is formed by conventional dry or wet mixing methods and stabilizers, anti-oxidants or compounds to inhibit chain scission may be included. The desired shaped article is formed in known manner. Degradation may be effected with water or specified alcohols containing less than 20 carbon atoms preferably mixed with water optionally in the presence of specified inorganic or organic bases at a temperature typically in the range 100-140 DEG C. The product may be in the form of bearings, gaskets or filters and may be impregnated with specified lubricants.ALSO:Filters are formed from oxymethylene polymers by preparing an intimate mixture of an oxymethylene polymer resistant to degradation at an elevated temperature by aqueous and/or alcoholic liquids under non-acid conditions and another oxymethylene polymer not so resistant, moulding a shaped article from the polymer mixture under heat and pressure and thereafter subjecting the article to treatment with a non-acid aqueous and/or alcoholic liquid to destroy the oxymethylene polymer not resistant to degradation and endow the article with a cellular structure. The filter may be in the form of a film plate or cartridge or cup and only a portion of the moulded article need be rendered porous. The filter maybe strengthened by sintering.