stabilizing polyoxymethylenen against waermeabbau

摘要

Thermally stable compositions comprise a high molecular weight solid polymer or copolymer with -CH2O-units recurring in the polymeric chain and from 0.001 to 15% by weight of a mono-allophanic ester of a phenol or bisphenol as a stabilizer. The preferred polymers are those obtained from aqueous or anhydrous formaldehyde or trioxan and having an inherent viscosity of at least 0.3. The polymethylenes may be terminally blocked by acyl or ether groups. The formaldehyde may be copolymerized with dimethylketene. Stabilizers specified are phenyl, p-hydroxyphenyl and 2,6-di - t - butyl - 4 - methylphenyl allophanates and the mono-allophanates of 4,41-isopropylidene - bisphenol, 4,41 - butylidene - bis - (6-t-butyl - 3 - methylphenol) and 2,21 - methylene-bis - (4 - methyl - 6 - t - butyl phenol). Known stabilizers may additionally be present, e.g. diphenylamine and 4,41 - butylidene - bis - (6-t - butyl - 3 - methyl - phenol). The compositions may also contain plasticizers and pigments.