Procedure for the simultaneous preparation of a pure 4,4-difenylmethane diisocyanate and a mixture of folifenylpolimethylene-polyisocianate. (Machine-translation by Google Translate, not legally binding)

摘要

Process for the simultaneous preparation of a pure 4,4'-diphenylmethane diisocyanate and a mixture of polyphenyl-polymethylene-polyisocyanate, from a mixture of polyisocyanates such as that obtained by aniline-formaldehyde condensation and subsequent phosgenation of the product of condensation, characterized in that the polyisocyanate mixture is separated by fractional distillation into a fraction a consisting mainly of diphenylmethane diisocyanates isomers and a fraction b which, in addition to isomeric diphenylmethane diisocyanates, also contains polyisocyanates of more than two aromatic rings, is separated then fraction a by fractional distillation in a c fraction consisting of 2,2'-, 2,4'- and 4,4'-diphenylmethane diisocyanates and a d fraction consisting of at least 98% diisocyanate 4,4'-diphenylmethane as well as a corresponding residue e formed by thermal polymerization and finally mixtures are prepared go from fractions c and b and eventually from residue e. (Machine-translation by Google Translate, not legally binding)