Studies on the synthesis of hydroxyl-terminated isophthalate-based oligoesters via transesterification reaction

A series of isophthalate-based oligoesters was synthesized via the transest erification reaction of dimethyl isophthalate (DI) with various aliphatic d iols under different diol(s)/diester molar ratios. The effect of a series o f reaction parameters, such as the diols/diester molar ratio, the molar rat io of the diols in the reaction mixture, the species of the diol, the react ion time, the heating procedure, and the species and the amount of the Lewi s acid catalyst, on the physical state, the polydispersity, the M-n, the vi scosity and the non-volatiles by weight (NVW) of the synthesized oligoester s was studied. A new synthetic procedure fbr the synthesis of high-solids l iquid oligoesters in high yields and high conversions via the transesterifi cation reaction is proposed. The properties of a reference solid oligoester (RefOL) derived from the reaction of DI with the 1,6-hexanediol (HD) (mol ratio DI/HD = 1/1.43), were compared to those of a high-solids liquid oligo ester (L-311) prepared from the transesterification of DI with a mixture of HD and 2-methyl-1,3-propanediol (MP) (mol ratio DI/HD/MP = 1/1.50/1.50). T he new high-solids liquid oligoester (L-311) presented more enhanced physic al properties than its solid counterpart and owing to its improved processa bility is expected to be a very promising candidate when used as a binder f or the preparation of mar-resistant clearcoats or pigmented coatings. (C) 2 000 Elsevier Science Ltd. All rights reserved.