Bayer Materialscience Ag

Covestro Deutschland Ag

Ulrich Wolf

Hans-Peter Schal

Walter Meckel

Hans-Georg Pirkl

Matthias Wintermantel

Bernd Thelen

Jeffrey Bolton

Jochen Mahrenholtz

The invention relates to a distillation unit () which is designed for a continuous distillation process and to a method for a continuous operation for separating a liquid substance mixture () into two to six liquid product flows (, . . . ) with different compositions and into a gaseous product flow (). For this purpose, an evaporation unit () is provided consisting of multiple evaporation devices (--, . . . ), wherein each evaporation device has a circuit device (--, . . . ) for recirculating a sub-quantity of each of the liquid sump flows (, . . . ) of an evaporation device into the respective evaporation device, and each of the circuit devices additionally has a discharge device (--, . . . ) for providing one of the liquid product flows (, . . . ).

Distillation unit and method for separating a liquid substance mixture into two to six liquid product flows with different compositions

A mixture of isomeric diisocyanatodiphenylmethanes composed of at least 2,2'-diisocyanato-diphenylmethane, 2,4&#x2032;-diisocyanatodiphenylmethane and 4,4&#x2032;-diisocyanatodiphenyl-methane is distilled in at least one stage and a divided-wall column is used in at least one distillation stage.

Process for the distillation of a mixture of isomeric diisocyanatodiphenylmethanes

2,4'-MDI which contains very little 2,2&#x2032;-MDI is prepared by distilling an isomeric starting mixture of diisocyanatodiphenylmethanes which includes 2,2&#x2032;-diisocyanato-diphenylmethane, 2,4&#x2032;-diisocyanatodiphenylmethane and 4,4&#x2032;-diisocyanatodiphenyl-methane in at least one stage in a separating wall column. This distillation produces at least one mixture which contains 85 to 99 wt. % of 2,4&#x2032;-diisocyanatodiphenylmethane, up to 15 wt. % of 4,4&#x2032;-diisocyanatodiphenyl-methane and no more than 0.2 wt. % of 2,2&#x2032;-diisocyanatodiphenylmethane.

Process for the distillation of a mixture of isomeric diisocyanatodiphenyl-methanes

The present invention relates to a process for the production of MDI fractions containing 2,4'-MDI, and in which the 2,2&#x2032;-MDI component from the MDA production is largely removed from the isomer mixture. Highly reactive monomeric MDI products can be produced in this way. These MDI products are characterised in their processing by significantly reduced emissions of MDI monomers.

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Kerken, Germany

Ulrich Wolf