Лако-красочные материалы — производство

All the major ingredients, including resins, of powder coatings are solid powders. The ingredients are mixed and then homogenized in a heated extruder (a process called melt kneading). The extruded product is cooled, crushed and milled, sieved and classified. The resin must melt at a predetermined temperature to effect proper mixing and pigment dispersion. In the case of thermoset powder coatings, there should not be any cross-linking during this extru­sion process or the product will be rendered useless. Thus, resins for power coatings must meet a number of critical specifications per­taining to their Tg, melting temperature, and functionality type and amount. Hydroxyl functional and carboxylic acid functional acrylic resins are very commonly used in commercial applications. These are prepared to predetermined Tg and functional group content by solution polymerization. The process solvent is then removed by distillation, polymer melt is discharged onto cooling conveyer belts and is then crushed to the desired particle size. Depending upon the type of functional groups and end-use requirements, different cross-linker types are used in the formulation.