Method for preparing compositey sealed polyisocyanates coating

The invention discloses a method for preparing a compositely sealed polyisocyanates coating. The method comprises the following steps: heating and stirring polyether polyol and 4,4-diphenylmethane diisocyanate, reacting to obtain a 4,4-diphenylmethane diisocyanate-polyether polyol prepolymer, performing composite sealing on the 4,4-diphenylmethane diisocyanate-polyether polyol prepolymer by using malonic acid diethyl ester, ethyl acetoacetate and 3,5-lutidine so as to obtain a polyisocyanates curing agent, and finally adding an amino chain expanding agent and a powder filling material into the compositely sealed polyisocyanates curing agent, thereby obtaining the compositely sealed polyisocyanates coating. When heated, the compositely sealed polyisocyanates coating prepared by using the method can be gradually unsealed and cured in different periods, the phenomenon of edge curtain coating of conventional singly sealed polyisocyanates in the baking process because of too high unsealing temperature is avoided, the filming property of the compositely sealed polyisocyanates coating is improved, a prepared film is relatively high in cross-linking degree, and thus good mechanical property is achieved.