The Synthesis Of Water-Dispersible Polyisocyanate And Its Study On Coating Performance

With the national laws and regulations for the constraints of environmental protection and the importance of people's health,waterborne coating has become an inevitable trend of development.Water-dispersible polyisocyanate is a component of two-component waterborne polyurethane,and determines transparency,gloss,hardness and other properties of the coating.At present,technology and market of water-dispersible polyisocyanate have been monopolized by foreign companies.This paper aims to develop a water-dispersible polyisocyanate,the impact of hydrophilic modifier on the water dispersion of the sample,the experimental formula,operation process and product performance were discussed.The specific work is as follows:The effects of the amount of hydrophilic modifier,the amount of catalyst and the reaction temperature on the properties of hydrophilic modified samples were investigated by the following formula.The result showed that: the water-dispersible polyisocyanate can be prepared by using 2-3wt% 3-cyclohexylaminopropane sulfonic acid at 90?with amount of 110% N,N-dimethylcyclohexylamine as catalyst.In order to further obtain the water-dispersible polyisocyanate which is water dispersible,excellent storage and performance of coating film,it is further modified with a nonionic hydrophilic modifier.The results show that the water dispersibility of polyisocyanate can be improved effectively by using 5-7wt% polyethylene glycol monomethyl ether 400 at 60?,and percentage of mass 3-Cyclohexylaminopropanesulfonic acid and polyethylene glycol monoether 400 is 40%,and the emulsion after water dispersion was stable.Water-dispersible polyisocyanate was obtained with solid content of 100wt%,-NCO content of 20.10wt%,viscosity of 4500 cp,and water dispersion of 164 nm.It is suitable for the two-component waterborne polyurethane coating.Index,storage stability and performances were compared between self-made and other kinds of water-dispersible polyisocyanates.The results showed that the self-made water-dispersible polyisocyanate had better storage stability,6 months storage at room temperature and 4 weeks storage at 50?,the index of-NCO content and viscosity had small changes.The water-dispersible polyisocyanate and acrylic emulsion were mixed at different molar ratios of-NCO and-OH to prepare two-component water-borne polyurethane coating.The surface dry speed,dry speed was correlated with the molar ratios of-NCO and –OH,and hardness of coating film,gloss index was positively correlated with the molar ratios of-NCO and –OH.Compared with commercially available curing agent of the same quality,pot life of the coating is more than 3 hours,and it has good transparency and thermal stability,and meets the requirements of waterborne wood coatings.