NOVEL COPOLYESTERS CONTAINING NAPHTHALENE STRUCTURE .2. COPOLYESTERS PREPARED FROM 2,6-DIMETHYL NAPHTHALATE, 1,4-DIMETHYL TEREPHTHALATE, AND ETHYLENE-GLYCOL

Copolyesters containing rigid segments (naphthalene and terephthalene) and flexible segments (aliphatic diol) structure were synthesized fro m DMN/DMT/EG (2,6-dimethyl naphthalate/1,4-dimethyl terephthalate/ethy lene glycol) ternary monomers with various mole ratios. Copolyesters h aving intrinsic Viscosities of 0.52-0.65 dL/g were obtained by melt po lycondensation in the presence of metallic catalysts. The effect of re action temperature and time on the formation of the copolyesters was i nvestigated to obtain an optimum condition for copolyester manufacturi ng. The optimum condition for PNT (polyethylene naphthalate terephthal ate) copolyester manufacturing is the transesterification under nitrog en atmosphere for 4 h at a temperature of 185 +/- 2 degrees C followed by polymerization under 2 mm Hg for 2 h at a temperature of 280 degre es C. Most copolyesters have better solubilities than poly(ethylene na phthalate) (PEN) and poly(ethylene terephthalate) (PET) in various sol vents. The effect of the starting mole ratio of DMN, DMT, and EG on th e thermal properties of the resulted copolyesters was also investigate d using differential scanning calorimetry (DSC) and thermal gravimetri c analysis (TGA). Glass transition temperatures of copolyesters were i n the range of 70.7-115.2 degrees C, and 10% weight loss in nitrogen w ere all above 426 degrees C. (C) 1995 John Wiley & Sons, Inc.