Method for preparing compositey sealed polyisocyanates coating

Abstract

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.

Description

technical field [0001] The invention belongs to the preparation of a blocked isocyanate curing agent, in particular to a method for preparing a composite blocked polyisocyanate coating suitable for vehicle bottom coatings. Background technique [0002] Cars are vulnerable to friction and impact from hard objects such as gravel, gravel, and muddy water during driving, resulting in peeling, damage, or cracks on the bottom of the car. In order to protect the automobile chassis and prolong its service life, a layer of protective paint is usually applied to the automobile chassis. In recent years, the research on polyurethane underbody coatings has been very active, and its coating has become a new favorite of underbody protective coatings because of its excellent elasticity, wear resistance, damping and anti-corrosion properties. Blocked isocyanate is the main raw material for synthesizing polyurethane. The structure of the blocked group has a great influence on the unblocking ...

AI Technical Summary

Problems solved by technology

[0003] Patent CN102936210A discloses a blocked toluene-2,4-diisocyanate and its preparation method and application. The preparation method is to add toluene-2,4-diisocyanate into the phenol cyanobenzoate solution at 40-95°C The product is obtained by distilling the solution from the reaction, which has a low unblocking temperature. The disadvantage is that the environmental pollution is relatively large during the unblocking process, and the storage stability and thermal stability of the unblocked product are poor.

Patent CN102391469B has announced highly closed 4,4-diphenylmethane diisocyanate-TMP type polyurethane prepolymer, through 4,4-diphenylmethane diisocyanate (4,4-diphenylmethane diisocyanate) and TMP (trimethylol propane) reaction to obtain 4,4-diphenylmethane diisocyanate-TMP prepolymer, and then blocked with sodium bisulfite or phenol, with sodium sulfite as accelerator, the product is environmentally friendly, low toxicity, but the product stability is poor , the scope of application is limited