| 摘要 |
UREA AND BIURET PREPOLYMERS OF MDI Disclosed herein is a liquid isocyanate prepolymer having an isocyanate group content of from 10 to 30% by weight, prepared by reacting: i) a polyfunctional secondary amine group containing material of the general formula: wherein R represents alkyl, alkenyl, cycloalkyl, aralkyl or aryl radical: A represents an organic radical having a molecular weight between 28 and 6000 and having a functionality of m and m represents an integer from 2 to 6; with ii) an isocyanate mixture comprising: a) from 50 to 100% by weight of diphenylmethane diisocyanate of which from 2 to 50% by weight consist of 2,2'- and 2,4'-isomers; and b) the balance being polyphenylpolymethylene polyisocyanates.
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