MANUFACTURE OF POLYISOCYANATE

摘要

Polyisocyanates are produced by reacting a polyamide solution with a phosgene solution. After the product polyisocyanate has been recovered, the solvent or a portion of the solvent employed is treated with crosslinked polymers insoluble in the solvent which polymers contain primary and/or secondary alcoholic hydroxyl groups and/or primary and/or secondary amino groups. After treatment, the polymer and any reaction products are removed. The solvent may then be reused. Preferred solvents are chlorobenzene and o-dichlorobenzene. The preferred polymers are bead polymers or bead copolymers of (meth)acrylic acid or styrene/divinyl benzene copolymer.