Layered double hydroxides as transesterification catalysts and nanofillers for polyester resin

Abstract

Saturated polyester resins were prepared by reaction of dimethyl terephthalate with alkylene glycols in the presence of layered double hydroxides (hydrotalcites, HT). The effect of HT composition (cation and anion types) on the rate and progress of transesterification was investigated. Itwas found that zinc-aluminum HT intercalated with anionic form of aminolauric acid [HT(ZnAl)ALA] efficiently catalyzes transesterification process, increasing the rate of reaction or lowering its temperature when compared to the reaction with use of conventional organic tin catalyst. The polyester resin obtained in this way is transparent, which along with X-ray diffraction data indicates the delamination of clay layers and formation of nanocomposite. The limitation of using ALA-intercalated HT as an additive for polyesters used in coatings is coloration of the resin with an increase of the reaction temperature above 180 °C. Colorless polyesterwas obtained using more thermally stable hydrotalcite intercalated with ethylenediaminetetra-acetic acid, however, at the expense of significantly longer reaction time. Using HT(ZnAl)ALA catalyst a two-step synthesis of carboxyl polyester resin was performed and the obtained product was used as a component of powder coating formulation.