Mitsui Chemicals, Inc.

Yasuhiro Mutou

Seiji Ota

Junji Tan

Toyoaki Sasaki

There is provided by the present invention a polyester resin composition containing a copolyester having hydroxy carboxylic acid units as constituent units or a polyoxycarboxylic acid, wherein hydroxy carboxylic acid units of 5 or less carbon atoms are contained in amounts of 2 to 75% by mol based on 100% by mol of all the constituent units contained in the composition, and a molar ratio Sof hydroxy carboxylic acid units both of whose neighboring units are hydroxy carboxylic acid units to all the hydroxy carboxylic acid units contained and a molar ratio Sof hydroxy carboxylic acid units neither of whose neighboring units is a hydroxy carboxylic acid unit to all the hydroxy carboxylic acid units contained satisfy the following formula:0.03&#x3c;&#x3c;30. In the present invention, the amount (% by mol) of the hydroxy carboxylic acid contained in the polymer is in the specific range, and a molar ratio S/Sof continuously bonded hydroxy carboxylic acid units to isolated hydroxy carboxylic acid units is in the specific range, and hence, a resin composition having excellent gas barrier properties and a good balance among mechanical properties, heat resistance, transparency and hue can be provided. The resin composition can be favorably used for packaging materials requiring gas barrier properties, for example, food packaging materials, such as films and blown contains, and electronic part packaging materials.

Polyester resin composition

The present invention provides a polyester resin which comprises (a-1) 45 to 99% by mole of an oxycarboxylic acid unit having 5 carbon atoms or less, (a-2) 0.5 to 27.5% by mole of an aromatic dicarboxylic acid unit, and (a-3) 0.5 to 27.5% by mole of an aliphatic diol unit having 4 carbon atoms or less, and containing (a-1) to (a-3) in a total amount of 95% by mole or greater, wherein the relationship between the content of the oxycarboxylic acid, expressed as M % by mole, and the density &#x3c1; (kg/m) of the polyester resin, satisfies the formula &#x3c1;&#x2267;1349+M&#xd7;0.85.

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Sodegaura, Japan

Yasuhiro Mutou