VERFAHREN ZUR HERSTELLUNG EINES MAGNETISCHEN AUFZEICHNUNGSTRAEGERS.

摘要

In the prodn. of a magnetic recording medium, consisting of a film base and magnetisable coating(s) contg. finely-divided magnetic pigment and a crosslinked polymeric matrix as binder, the novelty is that the binder is crosslinked by polyureas and/or oligo- and/or polyurethanes (I) contg. oxadiazintrione rings. Crosslinking is carried out in the presence of OH and/or aliphatic amino gps. (I) are reaction prods. of polyisocyanates with a functionality of 1.95-2.05, pref. 1.99-2.01, 5-100 mole-% of which are polyisocyanates contg. oxadiazintrione rings, and OH and/or amino cpds. with mainly 2 Zerewitinoff-active H atoms, using an NCO:active H ratio of 0.75-1.1:1. The components used for the matrix pref. consist of 0-99 wt.% polymers contg. OH and/or amino gps. and free from oxadiazintrione and 100-1 wt.% (I). (a) 25-100 or (b) 5-25 mole-% of the polyisocyanates used in (I) contain oxadiazintrione rings and form (a) 1-60 or (b) 30-100 wt.% of the total polymer matrix. Aliphatic and/or cycloaliphatic polyamines (II) with mol.wt. under 2000 are added to (I) to give an amino gp.:oxadiazintrione ring ratio of 5:1 to 1:4, pref. 3:1 to 1:2. Cure is carried out in the presence of catalytic amts. of tert. amines (III), esp. bicyclic amidines.