New process for manufacturing maleimides

It has been well-known that the heat distortion temperature of resin is eff ectively enhanced by the incorporation of a maleimide unit. However, an eco nomical industrial production method for maleimide was not yet established. We have established a new industrial production method of maleimides based on a reaction model which was revealed by analyzing the reactions occurrin g in the dehydration of maleamic acid. Especially, we have developed a new re-usable catalyst which has high performance without corrosion problems an d a new process having superior productivity of maleimide with a high yield . This method contains the following two features: (1) a new catalyst, supp orted orthophosphoric acid and its amine salt mixture; (2) employment of a reaction to change the by-product to maleimide.