| 摘要 |
Method for synthesizing masked polyisocyanates in emulsion comprises a step involving contacting an isocyanate composition, having free isocyanate functions, with at least a masking agent, A, in the presence of a surfactant, B, and an aqueous phase. Method for synthesizing masked polyisocyanates in solution comprises:- (1) Contacting an isocyanate composition, having free isocyanate functions, with at least a masking agent, A, in the presence of a surfactant, B, and an aqueous phase; said composition being gradually added on a heel solution comprising at least part of the aqueous phase and at least part of the masking agent; (2) Subjecting the resulting mixture to shearing (shear rate) higher than 1000s<-1>, preferably higher than 20000s<-1> and less than 1000000s<-1>, preferably less than 200000s<-1>; and (3) Repeating step (2), optionally after repeating step (3), until a stable emulsion is obtained in which particles have Sauter diameter greater than 0.1 mu m, preferably 0.2 mu m and less than 5 mu m, preferably less than 2 mu m and dispersion width less than 5 mu m. Independent claims are also included for:- (a) Use of the surfactant in blocking isocyanate functions; (b) An installation for carrying out the method; (c) A composition containing masked polyisocyanates and its use in making coatings. |
