Лако-красочные материалы — производство

One-component baking types of coatings in which resins such as alkyd, polyester, hydroxyl func­tional acrylic or epoxy esters are cross-linked with amino resins are typically catalyzed by acid catalysts. Strong acid catalysts such as sulfonic acid and phos-

phoric acid are generally used. Even though less reactive hexame- thoxymethyl melamine resins are used in coatings, the curing rate can be accelerated significantly by use of a strong acid catalyst. Different types of acid catalysts varying in their acid strength are commercially available. The type and amount of catalyst is deter­mined by the curing conditions of the coating, such as specific sto — ving temperature and time. High acid strength and high addition levels negatively impact their storage stability. The storage stabi­lity of coatings with a strong acid may be improved by blocking the acid group with amines to form a salt. At higher temperature curing, the amine evaporates and acid is released, triggering its catalytic effect. Some important examples of such a catalyst are shown in Figure 5.14.