Preparation And Properties Of Water-Bispersible Polyisocyanate

With the advent of "green chemistry","low-carbon economy","low VOC" and "energysaving and emission reduction", environmental protection has become the maintheme of today's chemical industry development. Water-dispersible polyisocyanates (WDP)play a particular role as crosslinker components for water dilutable two-componentpolyurethane paints. In combination with aqueous polyol dispersions, they allow theformulation of solvent-free paints systems which are curable at room temperature and providehigh-quality coatings which are not inferior to conventional paints with regard to solventresistance. At the same time, polycarbonate diols which are synthesized by regulatedcopolymerization of carbon dioxide and epoxide, have both better mechanical performanceand reducing the "carbon footprint". A serial of new Water-dispersible polyisocyanate weresynthesized and the dispersion properties and films were studied in this research.A water-dispersible polyisocyanate (WDP-PEG-TMP) was prepared by the reactionbetween tolylene-2,4-diisocyanate (TDI), polyethylene glycol (PEG) and1,1,1-trimethylolpropane (TMP). Experimental results indicate that WDP-PEG-TMP can bedispersed in Silicon-modified water-borne acrylic resin (WSA). The coating has goodhardness, but its adhesion, flexibility, water resistance and shock resistance are poor.Synthesis and performance of water-dispersible polyisocyanate (WDP-APC-PEG) werestudied. It was synthesized by the reaction between tolylene-2,4-diisocyanate (TDI),polyethylene glycol (PEG) and aliphatic polycarbonate diols (APC). The experimental resultsshow that with the increase of APC content, the dispersibility of WDP-APC-PEG in WSAdecreases. But the WDP which is synthesized by tolylene-2,4-diisocyanate and polycarbonatediols, has low viscosity and can form a continuous, smooth and flat film after dispersing inWSA. The hardness, impact resistance, flexibility, water resistance and adhesion of the paintare greatly improved by using APC.In order to improve the film properties,1,1,1-trimethylolpropane and aliphaticpolycarbonate diols were selected as a mixture of polyols to prepare the water-dispersible lowcarbon polyisocyanate (WDP-APC-TMP) with tolylene-2,4-diisocyanate through nonionicpolyisocyanates hydrophilically modified method. The branched-chain structure of the WDP-APC-TMP can increase the degree of cross linking and improve the film mechanicalproperties. Experimental results show that with the increase of APC content, the dispersibilityof the WDP-APC-TMP in WSA increases. The paints exhibit high hardness, high impactresistance, excellent flexibility and adhesion. By comparison with the non-ionicpolyether-type polyisocyanate curing agent, WDP-APC-TMP can improve the mechanicalperformance of two-component waterborne polyurethane painting, which indicates thatWDP-APC-TMP is a new perspective water-dispersed non-ionic curing agent.