Blocked isocyanate and preparation method thereof

Abstract

The preparation method for closure isocyanate in fine chemical industry comprises: adding the NaHSO3 solution and auxiliary solvent into the reaction kettle at given temperature to stir and then dripping the solvent and PAPI into kettle for closure reaction. Compared with prior art, this invention overcomes the current defect, sets temperature within 60-100Deg for removing closure with maximal rate more than 92% at 80Deg, and has no limit to NCO content and viscosity.

Description

technical field [0001] The invention relates to a blocked isocyanate and a method for blocking the isocyanate. Background technique [0002] The blocking of isocyanate groups is to combine isocyanate or prepolymers containing free isocyanate groups with certain active hydrogen-containing substances or substances that can react with isocyanate groups, and by virtue of their reaction with isocyanate groups or some effect, free isocyanate groups The acid group is not active at normal temperature, that is to realize the blocking of the isocyanate group. This blocking reaction is a reversible reaction under certain conditions or makes the blocked isocyanate group play a role again. Due to the difference in the structure of the original isocyanate and the difference in the properties of the blocked isocyanate, the uses of different blocked isocyanates are different. One of the main factors determining its application is the unblocking temperature and unblocking efficiency of the b...

AI Technical Summary

Problems solved by technology

For example, the initial unblocking temperature of isocyanates blocked with phenols is 130°C, the unblocked temperature of isocyanates blocked with oximes is also about 140°C, and the unblocked temperature of isocyanates blocked with lactams is 160°C (Song Congmei, Luo Zhenyang The blocking and unblocking reaction of PAPI [Polyurethane Industry, 2000, 15 (1) has been reported: the initial unblocking temperature of the product of blocking isocyanate with phenols is 130 ° C, and the unblocking temperature of isocyanate blocked by oxime is also At about 140°C, it was reported in Zeno W.Wicks, Blocked isocyanates, Progress in Organic Coating, 1975, 3:73-99, that the deblocking temperature of isocyanates blocked by lactams is 160°C]), which leads to the blocking of isocyanates application has certain limitations

It is pointed out in JP3898197 that sodium bisulfite can be used to block isocyanate, but its blocking method has the following limitations: sodium bisulfite can only block aliphatic isocyanate, and isocyanate must first be prepared into a prepolymer. The content is generally not higher than 10%, and a certain modifier must be added to the obtained closed product, otherwise the stability is extremely poor

Images