Investigation And Application Of New Type Of Water-borne Coil Coatings

Coil coating is obviously different from other general industrial coatings. It is usually coated on metal substrates before shaping, which need coil coating has excellent overall performance. The coil coatings should have high hardness in order to prevent abrasion and scratch, and also have good toughness to resist the cracking in the processing of shaping. Today, the main type of coil coating is the solvent-borne coil coating, due to they contain a large amount of volatile organic compounds (VOC), this system does’t comply with the requirements of environmental protection. Therefore, the research of the aqueous coil coating is the key work in the field of the coil coating in the future. In this thesis, water-borne coil coatings were developed, including water-brone primer and water-brone topcoat, to follow up the requirements of environmental protection.In the investigation of the primer system, several water-borne acrylic modified epoxy (PEA) hybrid emulsions were synthesized, and successfully applied to the primer of coil coating. The grafting reaction of the acrylate to epoxy molecular was tested by IR and DSC. The main results were represented as following:In the emulsion system, the dosage of the acrylate monomers about amount40%by epoxy weight was more suitable for the primer. Phosphate-modification was used to enhance adhesion of the primer on metal, the adhesion on metal was enhanced by increasing of the amount of the phosphoric acid.By comparison, the R578urea amino resin was successfully used for curing crosslinking of the above-mentioned modified resins. The coating film obtained from the above system had excellent overall performance.Now, the solvent-based top coil coating based on polyester resins occupy the dominant market in order to balance the hardness, T-bend, weather resistance, and the overall performance. However, the reports of water-borne polyester coil coatings are very rare due to the poor resistnce of the hydrolysis. In this study, a series of water-borne polyesters were synthesized using5-SSIPA, and many influence factors were studied which affected on the properties of the coatings.In this experiment, it found that the polyester resins containing5-SSIPA hydrophilic functional monomer were more hydrophilic prepared by the process of the two-step method than that of by one-step method. The more dosage of5-SSIPA, the more hydrophilic was. However, if the amount of5-SSIPA was too large, the surface of the curing reaction was too fast, which would reduce the performance of the film. End-blocking of the hydroxyl-terminated improved the storage stability of the aqueous polyester resin.Besides, water-borne acrylic resins were used in top coil coatings in order to obtain the coating with excellent storage stability. In this study, El Op was used for modification of acrylic resins. This study showed that the reaction temperature not only affected the free radical polymerization, also affected the El Op epoxy groups grafting onto the macromolecular chains. When the reaction temperature was lower than120℃, the resin had a relative narrow molecular weight distribution and lower acid value, which was benefit to the overall performance of water-based coil coatings. Increasing the amount of E10p can effectively improve the acid and alkali resistance and artificial aging performance of the film.Furthermore, polyurethane was used to modify the polyester to improve the flexibility, which was very important for the solvent-borne top coil coatings. In this study, a new kind of core/shell emusion was prepared by using polyester polyol, isocyanate and acrylate monomers. The property of the coating using this kind of emusion was tested and the depth investigation is still in progress.