Preparation of isocyanate virtual ‘core-shell’ and its application in wood adhesive

Abstract

Isocyanates have gradually attracted attention due to their extremely high chemical activity, but they are too active and have poor water dispersibility, which limits the use of isocyanates. In this study, salicylic acid (SA) was reacted with polyethylene glycol monomethyl ether (MPEG) by acyl chloride to prepare MPEG-SA, and the prepared MPEG-SA was introduced into isocyanate (PAPI) as a virtual ‘shell’ through phenolic hydroxyl groups to build a virtual ‘core (PAPI)-shell (MPEG-SA)’ structure to improve the stability of isocyanate and water dispersibility. Then the prepared MPEG-SA-PAPI was applied to wood adhesive to prepare plywood. The chemical structure, activity content stability and water dispersibility of the prepared MPEG-SA and MPEG-SA-PAPI were analyzed by means of Fourier transform infrared spectroscopy, Nuclear magnetic resonance, chemical titration analysis, and Laser particle size analyzer. The results show that the prepared MPEG-SA-PAPI was the preset molecular structure. The particle size of the prepared MPEG-SA-PAPI emulsion is about 5 μm, and the content of active groups after storage for 8 h was about 15%, indicating that the ‘core-shell’ structure improved the stability and water dispersibility of isocyanate. When the prepared MPEG-SA-PAPI was applied to the plywood, the MPEG-SA-PAPI could significantly improve the water resistance of the plywood, making its working life reach nearly 5 h.