| abstract |
1488631 Uretdione derivatives BAYER AG 21 Jan 1976 [24 Jan 1975] 02295/76 Heading C2C [Also in Division C3] Organic compounds containing uretdione groups and blocked isocyanate end groups are prepared by converting an organic polyisocyanate into an intermediate product containing uretdione groups and free isocyanate groups and reacting this intermediate product with a blocking agent which is monofunctional towards isocyanates. The intermediate product is suitably prepared by dimerizing an organic diisocyanate in the presence of a tertiary phosphine as catalyst. Suitable blocking agents are secondary or tertiary alcohols, oximes, lactams, phenols, N - alkylamides, imides, imidazole or alkali metal bisulphites. In a typical Example (1) tolylene-2,4-diisocyanate is dimerized in the presence of tri-nbutylphosphine and the dimer is then reacted with #-caprolactam. The organic compounds may be used in the preparation of polyurethanes (see Division C3). |