Toner polyester resin, method for producing same, and toner

1. A polyester resin, comprising 5 to 30% by mass of a constitutional unit derived from isosorbide, wherein

a storage elastic modulus G′ at 180° C. of said polyester resin is 400 to 1,000 Pa; and

a Tg of said polyester resin is 50 to 65° C.

2. The polyester resin according to claim 1 , further comprising a constitutional unit derived from a tri- or higher polyhydric carboxylic acid.

3. The polyester resin according to claim 2 , comprising 5 to 25 parts by mol of the constitutional unit derived from a tri- or higher polyhydric carboxylic acid based on a total content of acid component in the polyester resin of 100 parts by mol.

4. The polyester resin according to claim 1 , comprising 30% by mass or more of a constitutional unit derived from biomass.

5. The polyester resin according to claim 1 , comprising 9 to 25% by mass of the constitutional unit derived from isosorbide.

6. The polyester resin according to claim 1 , further comprising a constitutional unit derived from 1,3-propanediol.

7. The polyester resin according to claim 6 , wherein the 1,3-propanediol is derived from biomass.

8. A method for producing a polyester resin, comprising polycondensing a mixture comprising 5 to 30% by mass of isosorbide and a polyhydric carboxylic acid at 230° C. or lower, and completing a polycondensation reaction at a softening temperature within a range of 135 to 150° C.,

wherein the polyester resin produced has a storage elastic modulus G′ at 180° C. of 400to 1,000 Pa and a Tg of 50 to 65° C.

9. The method for producing a polyester resin according to claim 8 , wherein the polyhydric carboxylic acid comprises a tri- or higher polyhydric carboxylic acid.

10. The method for producing a polyester resin according to claim 9 , wherein the mixture comprises 5 to 25 parts by mol of the tri- or higher polyhydric carboxylic acid based on a total content of acid component in the mixture of 100 parts by mol.

11. The method for producing a polyester resin according to claim 8 , wherein the mixture comprises 30% by mass or more of a raw material derived from biomass.

12. The method for producing a polyester resin according to claim 8 , which comprises 9 to 25% by mass of the isosorbide in the mixture.

13. The method for producing a polyester resin according to claim 8 , wherein the mixture comprises 1,3-propanediol.

14. The method for producing a polyester resin according to claim 8 , wherein the mixture is polycondensed at 215° C. or higher.

15. A toner comprising the polyester resin according to claim 1 .

16. The polyester resin according to claim 3 , further comprising a constitutional unit derived from 1,3-propanediol.

17. The method according to claim 16 , further comprising a constitutional unit derived from at least one of terephthalic acid and isophthalic acid.

18. A polyester resin, comprising 5 to 30% by mass of a constitutional unit derived from isosorbide and 5 to 25 parts by mol of a constitutional unit derived from a tri- or higher polyhydric carboxylic acid based on a total content of acid component in the polyester resin of 100 parts by mol, wherein a storage elastic modulus G′ at 180° C. of said polyester resin is 400 to 1,000 Pa.

19. A method for producing the polyester resin of claim 18 , comprising polycondensing a mixture comprising 5 to 30% by mass of isosorbide and 5 to 25 parts by mol of a constitutional unit derived from a tri- or higher polyhydric carboxylic acid based on a total content of acid component in the polyester resin of 100 parts by mol, at 230° C. or lower, and completing a polycondensation reaction at a softening temperature within a range of 135 to 150° C.

20. A toner comprising the polyester resin according to claim 18 .