| 摘要 |
PURPOSE:A copolyester excellent in gas barrier property and suitable as a packaging material, obtained by constituting it so that the molar ratio of recurring ethylene isophthalate units to recurring aliphatic hydroxycarboxylic acid component units may fall within a specified range. CONSTITUTION:Esterification is performed among starting materials including isophthalic acid, an aliphatic hydroxycarboxylic acid (e.g., glycolic acid), ethylene glycol, etc. Alternatively transesterification is performed among starting materials including a lower alkyl isophthalate, a lower alkyl aliphatic hydroxycarboxylate, ethylene glycol, etc. The reactants are reacted in such amounts that the molar ratio of recurring ethylene isophthalate units to recurring aliphatic hydroxycarboxylic acid component units falls within the range of 1:99-99:1 and the sum of both units accounts for at least about 50% of the total recurring units. In this way, the purpose copolyester for packaging materials can be obtained.
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