Synthesis And Properties Of Two Component Waterborne Polyurethane Matt Curing Agent

With the increasingly stringent environmental protection regulations,water dispersion polyurethane curing agent(WDP)has been developed rapidly.The present WDP has some defects including high viscosity,poor storage stability,and there is a lack of matt WDP technology.In view of this,this paper prepared a matt WDP with long pot life,and studied the effects of precursors,hydrophilic modifier and stabilizer on the storage stability of WDP,the pot life of 2K-WPU and the gloss of the film,the main contents are as follows:The matte WDP was prepared by reaction of CAPS and HDI trimer with N,Ndimethylcyclohexamine as a neutralizer.The contents of HDI trimer of N3390,N3600,HT-600 and HT-100 were 87.64%,82.32%,74.63%,66.56% respectively,which were tested by GPC.The effect of the content of trimer in the precursor on the properties of WDP was studied and found that the higher the content of trimer in the starting material,the lower the viscosity of WDP,the better compatibility between WDP and hydroxy resin,and the gloss of 2K-WPU film prepared with WDP was better;The lower the content of trimer,the worse the compatibility with hydroxyl resin,the lower the gloss of their film.Among the four starting materials,HT-600 and HT100 are suitable for the preparation of matte WDP,and the viscosity of WDP prepared by HT-600 is as low as 1500 c P,the pot life of 2K WPU coating is 3h,and the gloss of its film is as low as 30%.The other coating properties are equivalent to Bayhydur 2547.The effect of stabilizers on the storage stability of WDP was studied,and at same time,the molecular weight and distribution of WDP storage process were also analyzed by GPC.It was found that stabilizer A could effectively inhibit the self polymerization reaction and improve the storage stability of WDP,and the optimum addition was 0.4%.WDP was modified by hydrophilic polyether MPEG in two ways: First,MPEG-IPDI/TDI hydrophilic long chain compound was synthesized and added to WDP to make a new waterbased curing agent.Second,HT-600 was modified with MPEG and CAPS to increase the pot life of WDP.The products were characterized by FT-IR,GPC and NMR.The effects of MPEG and MPEG-IPDI/TDI on the properties of WDP and its film were studied.It was found that the long chain of hydrophilic polyether can form the wrapping effect on polyisocyanate,thus delaying the reaction between isocyanate and water,and prolonging the pot life of 2K-WPU coating.The larger the molecular weight of MPEG,the longer the pot life of the 2K-WPU.In addition,the introduction of MPEG can reduce the compatibility between WDP and hydroxyl resin,and the higher the molecular weight or addition amount of MPEG,the lower the gloss of2K-WPU film.It is also found that the WDP prepared by MPEG-750 has a longer pot life and a lower gloss.When the addition amount is 1.5%,the pot life of the 2K-WPU is high up to 4h,and the gloss of the film as low as 23%.DSC-Tg was used to test the thermal stability of the film.It was found that the thermal stability of the cured film with WDP carried MPEGIPDI/TDI was better.The WDP prepared in this paper exhibit obvious advantages over bayhydur 2547 in the pot life of 2K-WPU and the alkali resistance of its film.