Patent ID: 8378144

Claim:
A process for preparing polyoxymethylene homopolymers or copolymers ( 7 ) by homopolymerization or copolymerization of trioxane, starting from methanol ( 1 ), in which methanol ( 1 ) is oxidized in a first reactor in a first production plant (A) to give an aqueous formaldehyde-comprising stream ( 2 ) which is fed to a second production plant (B) in which the formaldehyde is trimerized in the presence of an acid catalyst in a second reactor (R) to form trioxane and from which a trioxane/formaldehyde/water mixture ( 3 ) is taken off, the trioxane/formaldehyde/water mixture ( 3 ) is fractionally distilled in a first column (K 1 ) to give crude trioxane as overhead stream ( 4 ) and the overhead stream ( 4 ) is condensed in a condenser (W) at the top of the column to give a condensate, a substream ( 4 a ) of the condensate is returned to the first column (K 1 ) and the remaining substream ( 4 b ) is passed to further work-up in one or more further process stages to give pure trioxane ( 6 ), with one of these further process stages comprising removal of low boilers ( 5 ) selected from the group consisting of methyl formate, methylal, bis(methoxymethyl) ether and methanol by distillation in a low boiler removal column (K 2 ), and the pure trioxane ( 6 ) is fed to a third production plant (C) in which it is homopolymerized or copolymerized to form polyoxymethylene homopolymers or copolymers ( 7 ), wherein the low boiler stream ( 5 ) from the low boiler removal column (K 2 ) is recycled to the feed stream into the first reactor in the first production plant (A), wherein the low boiler stream has the following main components: methanol up to 50% by weight, methyl formate up to 40% by weight, methylal up to 30% by weight and trioxane less than 10% by weight.