| 摘要 |
1513518 Polyoxymethylene moulding compositions DEUTSCHE GOLD-UND SILBERSCHEIDEANSTALT 24 June 1976 [10 Sept 1975] 26270/76 Headings C3K C3M and C3R Moulding compositions comprise (1) a polyoxymethylene, (2) 0À001-2% of an antioxidant and (3) 0À001 to 30% of finely divided crosslinked water-insoluble precipitation polycondensate of formaldehyde and melamine in molar ratio 1À2 : 1 to 10 : 1, wherein up to 20 mole per cent of the melamine may be replaced by other co-condensible substances. The polycondensate may be prepared by reacting formaldehyde with melamine and optionally a co-condensable substance, e.g. dicyanodiamide, 2,5 - diamino - 1,3,4 - triazole, urea, amides, ethanolamines, aromatic amines, phenols, hydrazines and hydrazides, in aqueous alkaline medium which may contain a protective colloid, the resulting precondensate being crosslinked and precipitated by acidifying the medium. The antioxidant may be a hindered phenol, and the compositions may also contain heat and light stabilizers, fillers, processing aids, nucleating agents, pigments, acid acceptors and flameproofing agents. Examples describe compositions comprising a copolymer derived from trioxane, 1,3-dioxepane and butylal and polycondensates derived from melamine, formaldehyde and optionally ethanolamine. |
