French company launches MDI purification process

Zulze Chemical Technology of France has recently developed a compounding process to purify diphenylmethane diisocyanate (MDI), which can reduce investment costs and reduce operating costs and energy consumption. MDI is a raw material for producing polyurethane, which is prepared by reacting diphenylmethanediamine with phosgene. In the preparation process, the reaction produces MDI monomer and its isomers and high molecular mass products. A complex process developed by Zulzer Chemical Technologies can separate MDI monomers from the mixture of reactants. The composite process includes distillation and melt crystallization and other operating steps. The pressure drop of the crude MDI distillation process is very small, and the distilled product is condensed to the storage temperature for storage or sent directly to the isopipeline distillation column. The separation of MDI isomers can be completed in this distillation column. The distillation column usually consists of three or more beds with sufficient structured packing. The distillation capacity of a single column can meet the needs of the 160,000 t/a unit. After distilling, the pre-concentrated diphenylmethane-4,4-diisocyanate undergoes melt crystallization, and then the purified diphenylmethane-4,4-diisocyanate product is obtained through repeated heating and cooling operations. 99% of diphenylmethane-4,4-diisocyanate compounds can be obtained with this composite process. Zulze Chemical Technology believes that this process will play an important role in the world MDI market in the future.