Preparation Of Polyacrylate Modified Water-Borne Polyurethane Coatings In Wooden Furniture

With the strong demand for protecting environment, water-borne coatings of low VOC are being studied in the coatings industry. But water-borne polyurethane used to wooden furniture has some shortcomings of its film in hardness and water resistance. In order to improve the hardness and water resistance, a number of experiments are done by studying on prescription of water-borne polyurethane and content of its composition.In home, due to the shortage of polyester glycol, one of raw materials of preparing water-borne polyurethane, aromatic polyester glycols having designed molecular weight of 600,1000 and 2000 are synthesized in lab. The preferred aromatic diacids are phthalic anhydride, o-phthalic acid and p-phthalic acid. The preferred diols are ethylene glycol, 1,3-propanediol, neopenthyl glycol and so on. Influence factors, such as molar excess content of glycol, high vacuum time, are mainly studied in the synthesis of polyester glycol. Polyester glycols having molecular weight of 600 and 1000 are synthesized on condition that molar excess content of glycol is 14~15%, and high vacuum time is 8h. Polyester glycols having molecular weight of 2000 are synthesized on condition that molar excess content should not exceed 8%, and high vacuum time should be not lower than 12h.Through the experiment, we find film's hardness of water-borne polyurethane can be increased to H on condition that aromatic polyester glycols having molecular weight of 2000 acts as a component of high molecular weight glycol, 1,4 -butylene glycol acts as chain extender and its content is about 15%, content of DMBA is about 7%, and NCO/OH ratio is 1.2 :1. But it is no obvious improvement in water resistance of water-borne polyurethane.Polyacrylate modified water-borne polyurethane is studied based on the above prescription in this paper in order to improve the water resistance of water-borne polyurethane. Polyacrylate modified water-borne polyurethane emulsion with hardness of H and water resistance for 24h can be prepared by studying its influence factors on condition that PA/PU ratio is 50 : 50~60 : 40,and polyacrylate includes emulsifying agent of 2.0% and its Tg is 40℃. In addition, content of auxiliary of forming film affecting the form of mixture emulsion is studied. At the lower room temperature in winter, the dosage of auxiliary resulting from the experiment is about 10%.Water-borne polyurethane has high hardness of H and good water resistance by modifying polyacrylate, which overcomes difficulties of low hardness and bad water resistance of water-borne coatings in wooden furniture.