Polyester-based resin composition, and molded body using the resin composition

1. A polyester-based resin composition comprising a polyester resin (A) that has a dicarboxylic acid unit containing units selected from a sulfophthalic acid unit and a sulfophthalic acid metal salt unit in a total amount of 0.01 to 15.0 mol % based on the dicarboxylic acid unit and a diol unit, a polyester resin (B) having a cyclic acetal structure or an alicyclic hydrocarbon structure, and a polyamide resin (C),

wherein the content of the polyester resin (A) in the resin composition is 87.0 to 99.0% by mass based on the resin composition, the content of the polyester resin (B) in the resin composition is 0.5 to 10.0% by mass based on the resin composition, and the content of the polyamide resin (C) in the resin composition is 0.5 to 3.0% by mass based on the resin composition.

2. The polyester-based resin composition according to claim 1 , wherein the polyester resin (A) has a dicarboxylic acid unit containing units selected from a sulfoisophthalic acid unit and a sulfoisophthalic acid metal salt unit in a total amount of 0.01 to 15.0 mol % based on the dicarboxylic acid unit and a terephthalic acid unit in an amount of 70 mol % or more based on the dicarboxylic acid unit, and a diol unit containing an aliphatic glycol unit having 2 to 24 carbon atoms in an amount of 70 mol % or more based on the diol unit.

3. The polyester-based resin composition according to claim 1 , wherein the polyester resin (A) has a dicarboxylic acid unit containing a sulfoisophthalic acid metal salt unit in an amount of 0.01 to 15.0 mol % based on the dicarboxylic acid unit, an isophthalic acid unit in an amount of 1 to 10 mol % based on the dicarboxylic acid unit and a terephthalic acid unit in an amount of 70 mol % or more based on the dicarboxylic acid unit, and a diol unit containing an aliphatic glycol unit having 2 to 6 carbon atoms in an amount of 70 mol % or more based on the diol unit.

4. The polyester-based resin composition according to claim 1 , wherein the polyester resin (B) is a polyester resin having at least one of a dicarboxylic acid unit having a cyclic acetal structure and a diol unit having a cyclic acetal structure.

5. The polyester-based resin composition according to claim 4 , wherein the diol unit having a cyclic acetal structure is derived from a compound represented by the following formula (1) or (2):

wherein R 1 each independently represents a divalent organic group selected from the group consisting of a divalent aliphatic group having 1 to 10 carbon atoms, a divalent alicyclic group having 3 to 12 carbon atoms, and a divalent aromatic group having 6 to 18 carbon atoms; and R 2 represents a monovalent organic group selected from the group consisting of a monovalent aliphatic group having 1 to 10 carbon atoms, a monovalent alicyclic group having 3 to 12 carbon atoms, and a monovalent aromatic group having 6 to 18 carbon atoms.

6. The polyester-based resin composition according to claim 4 , wherein the dicarboxylic acid unit having a cyclic acetal structure is derived from a compound represented by the following formula (3) or (4):

wherein R 3 each independently represents a divalent organic group selected from the group consisting of a divalent aliphatic group having 1 to 10 carbon atoms, a divalent alicyclic group having 3 to 12 carbon atoms, and a divalent aromatic group having 6 to 18 carbon atoms, R 4 each independently represents a hydrogen atom, a methyl group, an ethyl group, or an isopropyl group; and R 5 represents a monovalent organic group selected from the group consisting of a monovalent aliphatic group having 1 to 10 carbon atoms, a monovalent alicyclic group having 3 to 12 carbon atoms, and a monovalent aromatic group having 6 to 18 carbon atoms.

7. The polyester-based resin composition according to claim 1 , wherein the polyester resin (B) is a polyester resin having at least one of a dicarboxylic acid unit having an alicyclic hydrocarbon structure and a diol unit having an alicyclic hydrocarbon structure.

8. The polyester-based resin composition according to claim 7 , wherein the alicyclic hydrocarbon structure is a cycloalkane structure having 3 to 10 carbon atoms.

9. The polyester-based resin composition according to claim 7 , wherein the diol unit having an alicyclic hydrocarbon structure is derived from a compound represented by the following formula (5):

wherein R 6 each independently represents a divalent aliphatic group having 1 to 10 carbon atoms; R 7 represents a monovalent organic group selected from the group consisting of a monovalent aliphatic group having 1 to 10 carbon atoms, a monovalent alicyclic group having 3 to 12 carbon atoms, and a monovalent aromatic group having 6 to 18 carbon atoms; a indicates 0 or 1, and when a=0, the hydroxyl group directly bonds to the cyclohexane ring; and b indicates an integer of 0 to 4.

10. The polyester-based resin composition according to claim 7 , wherein the dicarboxylic acid unit having an alicyclic hydrocarbon structure is derived from a compound represented by the following formula (6):

wherein R 8 each independently represents a divalent aliphatic group having 1 to 10 carbon atoms; R 9 each independently a hydrogen atom, a methyl group, an ethyl group, or an isopropyl group; R 10 represents a monovalent organic group selected from the group consisting of a monovalent aliphatic group having 1 to 10 carbon atoms, a monovalent alicyclic group having 3 to 12 carbon atoms, and a monovalent aromatic group having 6 to 18 carbon atoms; c indicates 0 or 1, and when c=0, the group —COOR 9 directly bonds to the cyclohexane ring; and d indicates an integer of 0 to 4.

11. The polyester-based resin composition according to claim 1 , wherein the polyamide resin (C) is a polyamide resin (C1) that has a diamine unit containing a metaxylylenediamine unit in an amount of 70 mol % or more based on the diamine unit and a dicarboxylic acid unit containing an α,ω-aliphatic dicarboxylic acid unit in an amount of 70 mol % or more based on the carboxylic acid unit.

12. A molded article having at least one layer formed of the polyester-based resin composition of claim 1 .

13. The molded article according to claim 12 , which is a bottle, a cup, a film or a sheet.

14. The molded article according to claim 12 , wherein the molded article has a portion stretched in a draw ratio of 5 to 20 times.

15. The molded article according to claim 14 , wherein the number average value of the major diameter of the disperse particles of the polyamide resin (C) in the portion stretched by 5 to 20 times is 1.0 to 8.0 μm and the number average value of the minor diameter thereof is 0.01 to 0.50 μm.