A stable and high-solids aqueous dispersion of blocked isocyanates, containing auxiliary solvent, is prepared by (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) and (2) adding water to this solution, with intensive mixing, in an amount which is such as to give a two-phase system comprising a disperse polyisocyanate phase and a continuous, aqueous phase containing auxiliary solvent. In a preferred embodiment of the invention dispersions are prepared which are virtually free from auxiliary solvent, by first adding a portion of water to the solution (1), substantially removing the auxiliary solvent with intensive mixing and then adding a second portion of water with intensive mixing to the mixture comprising the polyisocyanates (A) and (B) and the first portion of water.
一种含有辅助溶剂的稳定的高固体含量的封端
异氰酸酯水分散体是通过以下方法制备的:(1) 在辅助溶剂 (G) 中制备一种多
异氰酸酯混合物溶液,该混合物包括 20-70% (重量百分比)的封端亲
水改性多
异氰酸酯 (A) 和 30-80% (重量百分比)的封端疏
水多
异氰酸酯 (B);(2) 将
水加入到该溶液中,并进行充分搅拌,其加入量应使该溶液成为两相体系、(2) 向该溶液中加
水,并进行充分搅拌,
水的用量应足以形成由分散的多
异氰酸酯相和含 有辅助溶剂的连续
水相组成的两相体系。在本发明的一个优选实施方案中,首先向溶液 (1) 中加入一部分
水,在充分搅拌的情况下基本上除去辅助溶剂,然后在充分搅拌的情况下向包含多
异氰酸酯 (A) 和 (B) 以及第一部分
水的混合物中加入第二部分
水,从而制备出几乎不含辅助溶剂的分散体。