Лако-красочные материалы — производство

Powder coatings are an important technology that offers 100 % solid products with practically zero volatile emissions. Polyester resins for powder coating are friable solids with a relatively high Tg (50 to 60 °C) to avoid sintering of particles during storage. They are commonly prepared from terephthalic acid and neopentyl glycol as the principal monomers, […]

As discussed in the section on water-reducible alkyd resins (Sec­tion 2.3.8), water-reducible polyesters can also be prepared by the classical approach of formulating an acid-rich resin (acid value 35 to 60 mg KOH/g), which upon neutralization with a tertiary amine, forms an anionic salt. Water is then added to produce reasonably stable dispersions of polyester […]

Like many other resins, high-solid polyesters are an increasingly important class of polyester resins due to the increasing regulatorypressure 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 […]

Safe preparation of polyester resins from polyfunctional monomers (Fn > 2) without gelation requires careful optimization of average functionality and calculation of the degree of polymerization at the gel point (Pgel). Wallace Carother and P. J. Flory have made significant contributions in this area; however, a detailed discussion is outside the scope of this book. […]

Direct esterification is one of the most important routes for for­ming saturated polyesters, and involves condensation of polybasic acids and polyols with removal of water of the reaction. Another important reaction of this type is self-condensation of polyfunc­tional monomers having both hydroxyl and carboxylic acid group. Transesterification between polyols (generally diols) and dialkyl esters of […]

As the name indicates, saturated polyesters are polymers with ester linkages in their backbone. They are the condensation products of polyols and polybasic acids. The early development of saturated polyesters traces back to preparation of glyptal resins, formed from glycerol and phthalic anhydride, which are also the foundation for development of alkyd resins, as mentioned […]

One of the recent advancements and interests in alkyd resin tech­nology is hyperbranched alkyd resins, which, due to their unique highly branched polymer architecture, have low viscosities at higher MWs. An important characteristic of these alkyds is rapid drying. Generally they are prepared by reacting hyperbranched polyes­ter polyols with fatty acids. The main limitation of […]

Alkyd emulsions are among the major developments in alkyd resins in the past few decades. Water-reducible alkyds contain considerable amounts of co-solvents that contribute to VOCs in the final compo­sitions, while alkyd emulsions are aqueous alkyd resins with little, if any, VOCs. They are prepared by emulsification of alkyd resins in water using emulsifiers (surfactants) […]

Waterbased binders are increasingly used in low VOC coatings, and like all other binders, demand for waterborne alkyds is continuously growing. Waterborne alkyd resins can be broadly categorized into two groups: water-reducible alkyds and alkyd emulsions. 2.3.8.1 Water-reducible alkyds Water-reducible alkyds, in general, are prepared by formulating alkyds with an acid value in the range […]

In order to meet environmental regulations pertaining to VOCs, high- solid alkyd resins have been developed with about 80 % by weight or more of the vehicle solids at acceptable viscosity. In high-solid resins, low viscosities are typically achieved by decreasing the MW of the polymers. The reduction in MW has a consequence of relatively […]