| 摘要 |
PROBLEM TO BE SOLVED: To obtain a polyoxymethylene having a high molecular weight useful as an industrial material directly from formalin without purifying it by evaporating a formaldehyde-containing aqueous solution and condensing the vapor under specific condensing conditions. SOLUTION: The condensation of the vapor obtained through the evaporation of an aqueous solution containing formaldehyde preferably in an amount of 50 wt.% or more is carried out under conditions satisfying the relation of the equation: 1.4[CH2O]+1.5[CH3OH]<=T<=1.7[CH2O]+3[CH3OH] T is the temperature ( deg.C) of the condensate; [CH2O] is the concentration (wt.%) of the formaldehyde based on three components of formaldehyde, water and methanol in the condensate; CH3OH] is the concentration (wt.%) of the methanol based on the three components} to obtain a polyoxymethylene having a number average molecular weight of 10,000 or more. The above condensation is commonly carried out by passing the vapor through a cooling tube.
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