| 摘要 |
<p>In prepn. of polyisocyanates with biuret structure by reacting an excess of an aliphatic diisocyanate with a biuretting agent at raised temp. and opt. raised pressure, opt. in a water-miscible solvent, opt. with removal after the reaction of excess amts. of unconverted diisocyanate, solvent and volatiles by distn. and/or extn., the biuretting agent is (a) an alpha, alpha, alpha-tri-substd. acetic acid with no NCO-reactive gps. except COOH, and opt. (b) water. The molar ratio of (a):(b) is 1:0-2.5. - Pref. the diisocyanate is 1,6-diisocyanatohexane. The substd. acetic acid is R1R2R3C-COOH. R1, R2, R3 = alkyl, alkoxy or alkoxyalkyl gps., or 2 of the R gps. may form a cycloaliphatic ring with the C atom. The pref. acid is trimethylacetic acid (pivalic acid).</p> |
