The Study On Structure And Properties Of Water Dispersible Hydroxyl Acrylate

Since the German Bayer company developed water-borne polyurethane coating for leather in 1972, polyurethane has caused wide public concern around the world. In the early 1990s, Jacobs successfully dispersed polyisocyanate curing agent in water so that the research of two-component waterborne polyurethane coatings was developed rapidly. Due to its performance is equivalent to the solvent-based polyurethane, low toxic and environmentally sound two-component water-borne polyurethane instead of the traditional polyurethane is going to be an imperative. Therefore, the water-borne polyurethane with two-component has been a hotspot in the past ten years.Currently, water-borne polyurethane has lower solid content, slow evaporation of water, and side effects of curing agent consumption. Structure and properties of two-component water-borne polyurethane depends on hydroxyl composition. In order to alleviate the above problems, this article is to improve the solid content and make resin have both high hydroxyl value and low viscosity through hydroxyl composition. Our research aims to balance the high solid content and hydroxyl value of the contradictory relationship between the low viscosity by controlling the structure of hydroxyl composition, and obtain better performance of polyurethane coating via cross-linking with the polyisocyanate.The water-borne hydroxyl acrylate has been prepared with low-acid, high-hydroxyl via solution radical polymerization, and AIBN, mercaptoethanol and propylene glycol monomethyl ether as initiator, chain transfer agent, solvent respectively, and use semi-continuous reaction by way of dropping. According to the relationship of kinetics of radical polymerization among polymerization temperature, initiator, chain transfer agent concentration and polymer molecular weight, we prepared a series of hydroxyl acrylate by changed the polymerization temperature, initiator and chain transfer agent. In accordance with the results of GPC and the test of the viscosity, viscosity decreases with more initiator, polymerization and temperature of chain transfer agent concentration increases. The factors that affect the order of molecular weight distribution of resin:chain transfer agent concentration> initiator concentration> polymerization temperature; The factors that affect the order of molecular weight of resin:chain transfer agent concentration> polymerization temperature>initiator concentration. The glass transition temperature has significant effect on the viscosity of hydroxyl acrylate; we obtained a series of different glass transition temperature of the resin by changing the ratio of hard and soft monomers. Experimental results showed that the glass transition temperature decreased 10℃, the viscosity decreased over 10%. By selecting the optimal reaction conditions, which prepared hydroxyl value 125 mgKOH/g, solid content of 70% water dispersible hydroxyl acrylate, the Mn is 1500～3000, the molecular weight distribution is about 2.2, and the viscosity is 4200 mPa·s. Hydroxyl acrylic water dispersion with the appearance is translucent and pan-blue light, and has good performance of freeze-thaw stability, storage stability and thermal stability. Although the polar hydroxyl and carboxyl groups on the polymer chain have good hydrophilicity, studies of hydroxyl-acrylic water dispersion have shown that the water dispersion of resin depends on the content of carboxyl, and hydroxyl on the resin aqueous dispersion is just as assistance role.The two-component waterborne polyurethane coatings which are prepared by hydroxyl acrylic resin and Bayer's Desmodur (?) N 3390 hydrophobic polyisocyanates HDI tripolymer shows a good film performance:Adhesion level is 2, pencil hardness is H～2H, impact resistance is 50Kg·cm, and good water resistance.