Process for producing shaped sintered articles from moldable thermoplastic compositions containing a polyoxymethylene binder

摘要

The process for the producing improved shaped sintered articles by first shaping a) a mixture of a ceramic or metallic powder or mixtures thereof with a moldable thermoplastic composition containing b) a thermoplastic polyoxymethylene binder and c) a second moldable and essentially inert thermoplastic polymer having a melting point between 90 DEG and 220 DEG C., such as a polyether of bisphenol A and an aliphatic diol. The binder is then removed from the shaped article by exposure to a gaseous acid-containing atmosphere, preferably below its softening temperature, while the second inert thermoplastic polymer is retained as a source of elemental carbon in which the ceramic or metallic powder is finely dispersed. This retained polymer is then pyrolyzed under an inert gas at elevated temperatures of at least 600 DEG C. for conversion to a finely dispersed elemental carbon. The resulting pyrolyzed preformed product is then sintered to obtain the desired high density ceramic and/or metallic article as the final product in which elemental carbon is uniformly and finely distributed. The process provides a simpler and more easily controlled method of incorporating elemental carbon into the ceramic/metallic shaped and sintered product while also carefully controlling the initial shaping step to prevent any formaldehyde induced crosslinking in the thermoplastic binder composition.