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US 7,649,108 B2Granted
Process for the distillation of a mixture of isomeric diisocyanatodiphenylmethanes
AssigneeBayer MaterialScience AG
InventorsHans-Peter Schal, Ulrich Wolf, Bernd Thelen
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Abstract
A mixture of isomeric diisocyanatodiphenylmethanes composed of at least 2,2′-diisocyanato-diphenylmethane, 2,4′-diisocyanatodiphenylmethane and 4,4′-diisocyanatodiphenyl-methane is distilled in at least one stage and a divided-wall column is used in at least one distillation stage.
Claims7
A process for the distillation of a mixture of isomeric diisocyanatodiphenylmethanes said mixture comprising 2,2′-diisocyanatodiphenyl-methane, 2,4′-diisocyanatodiphenylmethane and 4,4′-diisocyanato-diphenylmethane in which the distillation is performed in at least one stage using a divided-wall column wherein
- (a) a bottoms product of 4,4′-diisocyanatodiphenylmethane having a purity of at least 98% by weight is obtained in the divided wall column
- and
- (b) a mixture of
- (i) 50-60% by weight of 2,4′-diisocyanatodiphenyl-methane
- and
- (ii) 40-50% by weight of 4,4′-diisocyanatodiphenyl-methane is drawn off in a side stream in the divided wail column.
3 more elements
Dependencies are inferred from the claim text.