| 摘要 |
This invention relates to a process for the preparation of aqueous emulsions of blocked (poly)isocyanates, this process comprising the steps consisting successively in:a) placing an isocyanate composition containing free isocyanate functions in contact with at least one blocking agent A in the presence of a surfactant B and an aqueous phase, the said isocyanate composition being added gradually to a stock containing at least some of the aqueous phase and at least some of the blocking agent;and optionally,b) subjecting the mixture obtained to a shear (speed gradient) of greater than 1000 s<-1>, preferably greater than 20,000 s<-1 >and less than 1,000,000 s<-1>, preferably less than 200,000 s<-1>, andc) repeating step b), optionally after step a) has been repeated, until a stable emulsion is obtained whose particles have a Sauter diameter of greater than 0.1 mum, preferably 0.2 mum, and less than 5 mum, preferably less than 2 mum, and a dispersion width of less than 5 mum. |
