Polyoxymethylene molding composition containing melamine formaldehyde polycondensate

In a molding composition comprising a polyoxymethylene, a melamine formaldehyde polycondensate as thermal stabilizer and an antioxidation agent, the improvement wherein said melamine formaldehyde polycondensate is a finely divided, cross-linked substantially water insoluble polycondensate comprising the precipitation product obtained by reacting formaldehyde, melamine and at least one other substance that can react to form a part of said polycondensate wherein the molar ratio of formaldehyde to melamine plus said other substance is between 1.2:1 and 10.0:1;

• up to 20 mole percent of said melamine being replaced with said at least one other substance that can react to form a part of said polycondensate;
• and said polycondensate is in an amount of about 0.001 to about 30 percent by weight, related to the total weight of said composition, said polyoxymethylene has a crystallite melting point of about 140.degree. C. to about 180.degree. C., a density of about 1.38 to about 1.45 g/ml (DIN 53 479), and a viscosity of at least about 30 ml/g when measured at 135.degree. C. with a solution of 0.5 g polyoxymethylene in 100 ml dimethylformamide containing 2% by weight diphenylamine;
• said polycondensate has a primary particle size less than about 1 .mu.m, and a specific surface up to about 250 m.sup.2 /g.