Method for preparing polyisocyanate containing uretidione group

Abstract

The invention relates to a method for preparing polyisocyanate containing a uretidione group, according to the method, a compound with a oxazaborolidine base structure is used as a catalyst, the oligomerization reaction of isocyanate is catalyzed, a reaction liquid of the polyisocyanate containing the uretidione group can be obtained, and the reaction liquid is separated to obtain the polyisocyanate containing the uretidione group. The polyisocyanate containing the uretidione group prepared with the method is high in the content of the uretidione group, and is low in chroma, and the dependency of the content of the uretidione group on the conversion rate of the isocyanate can be significantly improved.

Description

technical field [0001] The invention relates to a process for the preparation of polyisocyanates having a high content of uretdione groups. Background technique [0002] Polyisocyanates containing uretdione groups have very low viscosity, so they have excellent performance as crosslinking agent components in low-solvent, high-solid content coating compositions. [0003] The key to preparing polyisocyanates with high content of uretdione groups lies in the selection of catalysts, and the catalysts reported in patents mainly include tertiary phosphine compounds, boron trifluoride compounds, and pyridine compounds. [0004] DE 1670720 discloses a process for preparing polyisocyanates containing uretdione groups using at least one aliphatically substituted tertiary phosphine or boron trifluoride compound. The polyisocyanate prepared by this method has a higher uretdione group content, but it is highly dependent on the isocyanate conversion rate, and the polyisocyanate with a hi...

AI Technical Summary

Problems solved by technology

The disadvantage is that the preparation of polyisocyanates containing uretdione groups is highly conversion-dependent, i.e. a polyisocyanate with a high content of uretdione groups must be obtained at a low isocyanate conversion

In addition, tertiary phosphine compounds have the disadvantage of being sensitive to air, which has been greatly restricted in industrial-scale applications.

[0006] US 8134014 discloses a method for preparing polyisocyanates containing uretdione groups by using fused-ring substituted aminopyridine compounds as catalysts. The polyisocyanate prepared has a relatively high content of uretdione groups and has no special requirements for applicable isocyanates. Limitation, but pyridine compounds are easy to cause product coloring

[0007] Existing catalysts have obvious defects in the process of preparing polyisocyanates containing uretdione groups. The use of tertiary phosphine catalysts can only obtain higher urea yields under the premise of lower conversion rates of isocyanate raw materials. Polyisocyanate with diketone group content; tertiary phosphine compounds are unstable in the air, which limits industrial application, and amino-substituted pyridine compounds are easy to cause product coloring

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