Лако-красочные материалы — производство

Ketones (Figure 4.3), compounds having a carbonyl group bonded to two carbon atoms or alkyl groups in the molecule, are highly polar solvents with outstanding solvency. They have the ability to form strong hydrogen bonds with polar resins containing active hydrogen atoms. Acetone, methyl ethyl ketone, methyl isobutyl ketone, diiso­butyl ketone, cyclohexanone and isophorone are typical examples of solvents of this class. They are versatile solvents with powerful solvency for a wide range of synthetic binders and act as an active solvent in most cases. Ketones have a wide range of evaporation rates, from very fast evaporating acetone or methyl ethyl ketone, to moderately fast evaporating methyl isobutyl ketone, to slow eva­porating isophorone. They have a strong, characteristic odor. The polarity of ketones is highest for lower ketones and progressively decreases from the lower to higher ketones. Acetone is completely miscible with water, while other ketones have varying degrees of water solubility depending upon the size of the alkyl group. The lower ketones are good solvents for polar resins, while the higher ketones are good solvents for non-polar polymers and copolymers. Due to their high solvency and hence viscosity reduction capability, they are frequently used in high-solid coatings. Although they are relatively chemically stable, their use should be avoided in systems containing free amine groups (such as amine hardeners in two — component epoxy coating systems), as they have a tendency to react with primary amines during storage.

Figure 4.3: Examples of ketone solvents