The Continuous And Efficient Preparation Of Acrylic Prepolymer And The Performance Of UV-curable Coating Film

Bisphenol A epoxy acrylate(BA-EA)and polyurethane acrylate(PUA)are two important prepolymers of UV-curable coatings.Their productions involve highly exothermic heterogeneous reaction process."Thus one of the raw materials is ordinarily dropwisly added to the reaction system to guarantee the safety of the production process,and reactions must be cooled by a large number of circulating medium and vigorously stirred by mechanical agitators to reinforce the efficiency of heat and mass transfer.However,problews of low reaction period,low security,bad quality of productions and high energy consumption always plague their industrial productions.Microstructured reactors have such capabilities as efficient heat and mass transfer,enabling the reaction to proceed safely,efficiently and continuously.In this study,BA-EA and PUA prepolymers had been prepared by microstructured reactors.Two prepolymers were used as the main resin to the coatings formulation,the performance of coatings after UV curing had been tested and characterized.The main work were as follows:BA-EA was prepared from bisphenol A epoxy resin(BA-EP)and acrylic acid by esterification reaction in microstructured reactors.The effects of reaction temperature,flow rate,residence time,the type and amount of catalyst and diameter of tube on reaction were investigated.The optimum reaction conditions were as follows:the reaction temperature of 140 ℃ the flow rate of 3.05 mL/min,residence time of 4 min,triphenylphosphine as catalyst with contents of BA-EP 2 wt%and the diameter of 1 mm.The conversion of acrylic acid and epoxy group could reach 99.1%and 96.3%,respectively.FTIR spectum analysis indicated that the product was consistent with the target product.The prepolymer BA-EA was mixed with photoinitiator and leveling agents to prepare coating films.The condition of UV-curing was investigated,and the properties of the coating films were tested.The appropriate UV-curing conditions were as follows:UV-irradiation distance was 10 cm,and curing time was 66 s;using IR184 as photoinitiator and the dosage was 3 wt%of the formula;using Tego410 as leveling agent and the dosage was 0.5 wt%of the formula.The appearance of the cured film was smooth and light yellow.The performance tests showed that the cured film had superior properties such as hardness,adhesion,abrasion resistance,leveling,chemical erode resisitance and thermal stability which conformed with the industrial requirements.PUA was prepared from two-step reaction using isophorone diisocyanate,polyethylene(400)and 2-hydroxyethyl acrylate.The optimum reaction conditions of the first step were as follows:the reaction temperature 60 ℃,residence time 80 s and 1 wt%dibutyltin dilaurate(DBTDL).The optimum reaction conditions of the second step were 70℃,residence time 90 s,1.25 wt%DBTDL and 0.5 wt%hydroquinone.FTIR spectum analysis indicated that the product was consistent with the target product.The prepolymer PUA was mixed with photoinitiator,active diluent and auxiliaries to prepare coating films.The condition of UV-curing was investigated,and the properties of the coating films were tested.The appropriate UV-curing conditions were as follows:UV-irradiation distance was 20 cm,using IR184 as photoinitiator and the dosage was 4 wt%of the formula,the UV-curing time of coating was shorter;using trimethylol propane triacrylate(TMPTA)as active diluent and the dosage was 25 wt%of the formula,the coatings held good integrated performance.Tego Glide432 showed better performance,which needed 0.5 wt%-l wt%.Leveling 810 was more appropriate,which needed 0.5 wt%～1 wt%.The appearance of the cured film was smooth and light yellow,the performance tests showed that the cured film had superior properties.