| abstract |
The present invention provides a method and apparatus for preparing a methylene diphenyl diisocyanate (MDI) isomer mixture having a low 2,2'-MDI isomer content and a high 2,4'-MDI isomer content. The resulting mixture has increased reactivity and may be acceptable for food grade applications due to the reduction of primary aromatic amines formed during the curing process. In addition, the methods and apparatus of the present invention include controlling the amount of 4,4'-MDI, which is the most reactive isomer in the mixture, to be used for a wide range of applications. |