Лако-красочные материалы — производство

Type II waterborne epoxy systems are based on solid epoxy resins in the form of uniform aqueous dispersions containing co-solvents and stabilized by emulsifiers. These systems can be prepared by direct emulsification involving dispersion of epoxy resin (a solution in co-solvent) in water using an emulsifying agent (surfactant). These systems can also be prepared by an inversion process, in which water is added to a liquid resin to form first a water-in-oil emulsion that subsequently is inverted to an oil-in-water emul­sion upon addition of a further quantity of water. The inversion technique is preferred, as it gives a more stable emulsion with a small particle size and narrow particle size distribution. Just prior to application, hardener is added and emulsified into the resin emulsion. The pot life is longer than type I due to the high epoxy equivalent weight and difficulty of hardener diffusion into the par­ticles. After application, as dispersion particles coalesce, resin and hardeners interdiffuse and curing takes place. However, there is a greater tendency for such films to develop a heterogeneous morpho­logy (due to improper diffusion of hardener) with epoxy-rich and amine-rich domains.