Elementary Study On Solvent Based Acrylic Acid Coating Spraying Using Supercritical CO₂ As Quick Volatile Solvent

Traditional solvent based coating needs a lot of quick volatile organic solvent which is volatile into the atmosphere as spraying,so it pollutes environment badly.Because supercritical CO₂ has particular solvent capability and can swell polymer,it can take place of quick volatile organic solvent to reduce the coating viscosity in order to decrease the environmental pollution as spraying.Entrusted by Fujian Donghai Coating Company we exploit supercritical CO₂ spraying of acrylic acid coating.The text is elementary study of this problem. The research headway of supercritical CO₂ application in extraction,polymer swell and preparation of microparticles which are directly correlative with our study was summed up ,the advantage of coating spraying technique which quick volatile solvent is replaced by supercritical CO₂ was also summarized and discussed . The influence of supercritical CO₂ on the character of coating film substance was studied with IR,gas chromatograghy ,etc.The experimental results indicated that through the action of supercritical CO₂ the character of coating film substance did not change basically,compared with traditional spraying supercritical CO₂ spraying can not change the quality of coating film.The partial mole volume of n-butyl acetate in supercritical CO₂ was also measured,the experimental results indicated that it was minus which could heighten the swell capability of supercritical CO₂ in polymer.The phase behavior of CO₂-solvent-acrylic acid resin was studied which could be based on by the composing of spraying solution.The influence of nozzle,s length and diameter on the effect of atomization was investigated,which show that fibre appeared when the nozzle was long and microparticles appeared when the diameter of nozzle was small.The desorption mechanism of CO₂ from spraying solution was studied ,the experimental results show that the desorption of CO₂ were entire when atomization particles were small.The influences of temperature,pressure and CO2 content on the magnitude of atomization particles and spraying angle were investigated by using L9(34) orthogonal experiments,the results indicated that the atomization particles were smaller and the spraying angle was bigger along with the higher temperature ,pressure and CO2 content. The influencing order of factors on the magnitude of atomization particles was:pressure > CO2 content > temperature;on the spraying angle was:CO2 content > pressure > temperature.Under the condition of 20MPa,80℃,CO2 35%,the average diameter of atomization particles was 32μm,spraying angle was 61.24°,the diameter of atomization particles in spraying sector region was different,it was bigger when it was nearer the center of nozzle,the measured results of obtained test slice were that the test of carving pane was in the second grade,the diameter of flex axis in flex test was 2mm,which were all accorded with the standard of the state.