Patent ID: 6096805
Filing Date: 2000-08-01
Classification: C07C,C08G,C09D

Abstract:
A process for preparing stable and high-solids aqueous dispersions of blocked isocyanates, containing auxiliary solvent, which comprises:(1) preparing a solution of a polyisocyanate mixture of from 20-70% by weight of a blocked, hydrophilically modified polyisocyanate (A) and from 30-80% by weight of a blocked, hydrophobic polyisocyanate (B) in an auxiliary solvent (G);(2) adding to this solution, with intensive mixing, an amount of water which is such as to give a two-phase system comprising a disperse polyisocyanate phase and a continuous, aqueous phase containing auxiliary solvent;(3) adding a first portion of the total amount of water used in the preparation of the dispersion to the solution of stage (1);(4) substantially removing the auxiliary solvent (G) from the aqueous mixture that is formed, containing auxiliary solvent, with intensive mixing; and(5) adding a second portion of water to the remaining mixture comprising the blocked polyisocyanates (A) and (B) and the first portion of water, with the provisos that (i) the first portion of water added is of an amount such that the polyisocyanates (A) and (B) form the continuous phase in the mixture which remains after the substantial removal of the auxiliary solvent (G), and (ii) the addition of the second portion of water takes place with intensive mixing, at least up until the point of phase inversion.