| abstract |
Reactive blocked polyisocyanates comprise the reaction prod. of epsilon-caprolactam with adducts of isophorone diisocyanate and polyols contg. 3.3-8 NCO equiv. per OH equiv. The blocked adduct is highly reactive and can be used to form thermosetting polyurethane powder coating compsns. for electrostatic spraying which harden at low temps. The polyol is pref. (di)ethylene-, propylene- a neopentyl glycol, (4-di-(hydroxymethyl)-cyclohexane, 3(4), 8(a)-dihydroxymethyl- tricyclo -(5.2.1.0(2,6))-decane, neopentyl ester of hydroxypivalic acid, 1-hydroxy-3-aminomethyl-3,5,5-trimethyl cyclohexane, trimethylol ethane or - propane, tris (hydroxyethyl)-isocyanurate, triethanolamine or pentaerythritol. The blocked polyisocyanate pref. was a Tg of 30-150 esp. 35-90 deg.C and a softening temp. of 65-150 pref. 70-120 deg.C. |