Лако-красочные материалы — производство

The key properties of alkyd resins controlled by type and content of fatty acid or oil are drying time, hardness and yellowing properties. The degree of unsaturation and presence of conjugated unsaturation in fatty acids increases the curing rate and improves their drying time. Oils with a high content of linoleic acid produce non-yellowing films, while those with high linolenic acid or conjugated fatty acids cause yellowing of the film upon aging. Oil imparts flexibility to the films, and hence, hardness of alkyd films is proportional to the oil length. For a given oil content in an alkyd resin, the hardness of the film it forms is proportional to the polyunsaturated acid content. Also, as oil length decreases, solubility in aliphatic hydrocarbon solvents (mineral spirit) decreases. Thus, selection of fatty acids and their content is very impor­tant in formulating alkyd resins for specific end uses.