| abstract |
A pipe-insulating process comprises extruding onto the pipe an insulating layer of rigid polyurethane (PU) foam and opt. an outer covering layer by using the rotational casting method. The PU foam is obtd. by reacting (a) an aromatic polyisocyanate with (b) a cpd. of mol.wt. 92-1000 contg. at least 3 NCO-reactive H atoms and (c) an aliphatic, cycloaliphatic or aromatic polyamine and/or polyimine crosslinker with a mol.wt. of 32-1000, in the presence of (d) a blowing agent and opt. (e) known additives, etc., with addn. of (f) cpds. of formula (I) with a mol.wt. of 32-1000 as additional crosslinkers. n = 2-9, pref. 2 or 3; R1 = H, 1-9C alkyl or -(CR3R4)n-OH; R2 = H; R3, R4 = H or Me. |