Лако-красочные материалы — производство

Like many other resins, high-solid polyesters are an increasingly important class of polyester resins due to the increasing regulatory
pressure for reducing VOC emissions. Achieving the low-viscosity polyester resins required for high-solid coatings can be accomplished by considering many factors. Low number average MW and a narrow MW distribution are two important parameters required for high-solid polyester resins. To maintain the final properties of the coating, the lower MW must be compensated by a higher hydroxyl number and hence higher cross-link density. However, a high hydroxyl number generally results in higher resin viscosity due to the effect of inter­molecular hydrogen bonding through hydroxyl groups. Therefore, to obtain lower viscosity by minimizing the associative effect of hydrogen bonding, hydrogen-bond acceptor solvents (such as ketones) are fre­quently used. Structural modifications that reduce hydrogen bonding interactions can also help in reducing the viscosity. The glass transition temperature, T of the resin also controls the viscosity of the polyester solution at a given non-volatile content. Lowering of Tg can be achieved by using acyclic polyol and aliphatic diacids.