METHOD OF PRODUCING BLOCKED ISOCYANATES Russian patent published in 2013 - IPC C07C263/18 C07C265/12 C07C265/14 C08G18/80 

FIELD: chemistry.

SUBSTANCE: invention relates to a method of producing blocked isocyanates which are used as a curing agent for epoxy resins, involving reaction of aromatic di- and triisocyanates with compounds which contain an active hydrogen atom, where the isocyanate component used is polyisocyanate, which is a liquid mixture of 4,4'-2,2' and 4,2'-diphenylmethane diisocyanate isomers and tri- and tetraisocyanate homologues thereof, the aromatic rings of which are linked by methylene bridges, and the blocking agent used is a mixture which consists of ε-caprolactam (A), methylpyrazole (B) and benzyl alcohol (C) in ratio A:B:C ranging from 90:9:1 to 10:80:10, wherein blocking is carried out by mixing a molten reaction mass at temperature of 60-140°C for 40-180 minutes with ratio of the isocyanate to the blocking component ranging from 76:24 to 60:40.

EFFECT: simple process of producing blocked isocyanates, avoiding the need to pass nitrogen through the reaction mixture.

5 ex, 2 tbl