The heat stabilisation of trioxan copolymers (based on 80-99.5% trioxan and 0.5 to 20% comonomer) by the thermal degradation of the unstable oxymethylene termina

摘要

The heat stabilisation of trioxan copolymers (based on 80-99.5% trioxan and 0.5 to 20% comonomer) by the thermal degradation of the unstable oxymethylene terminal portions of the molecular chains is accomplished by heating the polymers in aqueous solutions of alkaline or alkaline earth fluorides at 120 deg.-200 deg.C, especially 140 deg.-190 deg.C. Sodium or potassium fluoride are the preferred salts and the concentration of the solution is generally 0.01-5%, especially 0.1-3%. Acid (in particular sulphuric, phosphoric or formic acid is added to the solution to bring the pH to 4.5-6.7, especially 5.2-6.4.