Chemistry of carbon compounds – Miscellaneous organic carbon compounds
Patent
1974-12-20
1976-01-20
Welsh, M. J.
Chemistry of carbon compounds
Miscellaneous organic carbon compounds
260 775AA, 260 75NT, 260 75NE, C08G 1880
Patent
active
039337596
ABSTRACT:
A heat-activatable polyurethane powder is prepared which contains about stoichiometric amounts of both blocked --NCO groups and active hydrogen-containing groups, the distribution of which is determined by the order in which the reactants are brought together. Typically an emulsified polymeric glycol (which may be admixed with more or less low molecular weight diol) reacts with a limited excess of diisocyanate to produce a dispersion of beads of --NCO-terminated polyurethane prepolymer; these in turn are reacted first with enough phenol or other monofunctional blocking agent to tie up about half of the free --NCO groups and secondly with one mole of a diamine or other difunctional active hydrogen compound per equivalent of the other half of the --NCO groups. When the resulting powder is coated upon a substrate and heated, the blocked --NCO groups are regenerated and thereupon they react with the active hydrogens available, resulting in the formation of a high molecular weight polyurethane film.
REFERENCES:
patent: 3236812 (1966-02-01), McElroy
patent: 3770703 (1973-11-01), Gruber et al.
patent: 3787525 (1974-01-01), McGarr
patent: 3846378 (1974-11-01), Greswold
patent: 3857818 (1974-12-01), Frizelle
E. I. du Pont de Nemours & Company
Welsh M. J.
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