SYNTHESIS OF POLYISOCYANATES OF DIPHENYLMETHANE FAMILY Russian patent published in 2011 - IPC C07C263/10 C07C263/20 C07C265/14 C08G18/76 

FIELD: chemistry.

SUBSTANCE: present invention relates to a method of preparing mixtures which contain diphenylmethane diisocyanates and polyphenyl polymethylene polyisocyanates, used in preparing polyurethane compositions for producing plastics, insulation materials, adhesives, coatings etc. The method involves a step for reacting corresponding mixtures of diphenylmethane diamines and polyphenyl polymethylene polyamines with phosgene in the presence of at least one solvent in several steps. At the first step, corresponding carbomoyl chlorides and amine hydrochlorides are formed, and at the next step residual carbamoyl chlorides are dissociated to corresponding polyisocyanates and hydrogen chloride, and the amine hydrochlorides undergo phosgenation to form corresponding polyisocyanates in the end. At the step for removing excess phosgene, the remaining unreacted amount of solid amine hydrochlorides, which lies between 10 and 5000 parts per million, is monitored.

EFFECT: cheap method of producing polyisocyanate mixtures, having a brighter colour, usually having colour index L in HunterLab coordinates higher than 10, without addition of extra reagents which reduce brightening and/or use of additional equipment.

9 cl, 1 ex, 1 dwg