| Coil coating is unique because it is usually coated on substrates before shaping,which require coil coating has good adhesion and stability to the substrate.It can meet the performance requirements of fast curing in high temperature and later mechanical processing.Currently,the solvent-borne polyester with excellent comprehensive performance has occupied the absolute position of coil coating.However,facing the increasingly tough environmental situation and collection of VOC sewage charges in our country,water-borne coil coating with high performance has become a new hot spot in the field of coating.Because of the advantages of low VOC,light color,weather resistance and solvent resistance,water-borne acrylic resin can be a good research object to develop new type of water-borne coil coating.However,the film of conventional water-borne acrylic is lack of flexibility,which makes the coil coating can’t withstand deep processing.Therefore,in order to obtain the water-borne top coil coating with good flexibility,a new preparation method of water-borne acrylic resin modified by Butyl Glycidyl ether(BGE)was explored.BGE is a compound with active epoxy group,which is able to react with the carboxyl group of AA.The alkyl side chain with steric hindrance grafting onto the macromolecular chains could reduce the viscosity of resin and improve the flexibility of paint film at the same time.A series of water-borne acrylic resin was prepared by using BGE、MMA、BA、AA and other materials as raw materials.The study showed that the size distribution of water-borne acrylic resin prepared by one-step polymerization process was much narrower,and furthermore the amount of organic solvent could be reduced,which meant that the steps of solvent extraction in the later stage would be omitted.The dosage of catalyst TBAI not only affected the reaction degree of BGE and carboxyl groups but also influenced the distribution of BGE grafted onto the macromolecular chains.The viscosity of resin decreased and the flexibility of film enhanced as the dosage of amount of BGE increased.In addition,the content of hydroxyl,functional monomers,the amount of acrylic acid and neutralizing agent would have a significant effect on the properties of the resin.The results indicated that water-borne acrylic resin could obtain the solid content of 40% and viscosity of 2403 mPa·s when the dosage of mixed solvent was 30% of the total mass of monomers,the dosage of initiator TBPB was 3%,the amount of BGE was 25%,the dosage of catalyst TBAI was 1%,the amount of AA was 12%,the content of hydroxyl was 2.5% and the neutralization degree was 90%.The resin could obtain good appearance and solubility in water.The FT-IR demonstrated that the epoxy group of BGE had reacted with the carboxyl group of acrylic acid and the synthetic water dispersion had the characteristic absorption peaks of acrylic resin.Furthermore,DSC,TGA and Laser Particle Size Analyzer were applied to characterize the properties of water-borne acrylic resin and its curing film.In addition,a kind of water-borne top coil coating with satisfactory performance was prepared by using self-made water-borne acrylic resin as the base material,with a pigment(titanium dioxide),a curing agent(Cytec 303 amino resin)and various auxiliaries.As the formula and process constantly optimizing and improving,the main conclusions were as follows: PVC would affect the performance of the paint film,its optimal values was from 32% to 35%.The best curing time was 70 seconds at 250℃.The amount of acid catalyst(Kings X49-110)was 0.8%.Three kinds of Adhesion accelerator(601-75 epoxy resin,Tego 1300 and ADP),wetting dispersant(Tego 270),leveling agent(Glide 450)were also necessary.Finally,the film of top coil coating had good flexibility,solvent wiping resistance and other properties.It had practical value to some degree. |
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