Method for producing polyester
View Patent ↗The present invention is aimed to provide a method for producing a polyester with reduced CD content and elution amount, in which even after the production method, a reduction in physical properties of the polyester is small, and furthermore, a polyester having good moldability can be produced, and the present invention is concerned with a method for producing a polyester including an esterification reaction step of allowing an aliphatic diol and an aliphatic dicarboxylic acid to react with each other; a step of pelletizing a polyester obtained through the esterification reaction step; and a contact treatment step of bringing the obtained polyester pellets into contact with a mixed solution containing ethanol and water, wherein the mixed solution contains water in an amount of 10% by mass or more and not more than 99% by mass relative to the whole of the mixed solution.
1. A method for producing a polyester, comprising:
an esterification reaction of allowing an aliphatic diol and an aliphatic dicarboxylic acid to react with each other;
pelletizing a polyester obtained through the esterification reaction; and
a contact treatment of bringing obtained polyester pellets into contact with a mixed solution comprising isopropanol, ethanol and water,
wherein the mixed solution contains water in an amount of 10% by mass or more and not more than 99% by mass relative to the whole of the mixed solution, and
wherein the isopropanol is present in an amount of greater than 0 and not more than 15% by mass relative to the whole amount of the mixed solution.
2. The method for producing a polyester according to claim 1 ,
wherein a temperature at which the polyester pellets are brought into contact with the mixed solution is 25° C. or higher and not higher than a melting point of the polyester.
3. The method for producing a polyester according to claim 1 ,
wherein an oligomer extracted into the mixed solution by the contact of the polyester pellets with the mixed solution is used as a raw material of the polyester.
4. The method for producing a polyester according to claim 1 , comprising:
drying after the contact treatment,
wherein the polyester after the drying contains not more than 1,000 ppm by mass of ethanol.
5. A polyester obtained by the production method according to claim 1 , which has an intrinsic viscosity of 1.4 dL/g or more and not more than 2.8 dL/g and a content of a cyclic dimer of 500 ppm by mass or more and not more than 6,000 ppm by mass.
6. The polyester according to claim 5 , which has a terminal carboxyl group concentration of not more than 80 (equivalents/ton) and 5 (equivalents/ton) or more.
7. The method for producing a polyester according to claim 1 ,
wherein the water is present in an amount of 20% by mass or more relative to the whole of the mixed solution.
8. The method for producing a polyester according to claim 1 ,
wherein the water is present in an amount of 25% by mass or more relative to the whole of the mixed solution.
9. The method for producing a polyester according to claim 1 ,
wherein the water is present in an amount not more than 95% by mass relative to the whole of the mixed solution.
10. The method for producing a polyester according to claim 1 ,
wherein the water is present in an amount not more than 90% by mass relative to the whole of the mixed solution.
11. The method for producing a polyester according to claim 1 ,
wherein the water is present in an amount not more than 85% by mass relative to the whole of the mixed solution.
12. The method for producing a polyester according to claim 1 ,
wherein the isopropanol is present in an amount of not more than 10% by mass relative to the whole amount of the mixed solution.
13. The method for producing a polyester according to claim 1 ,
wherein the isopropanol is present in an amount of from 1.5% by mass to not more than 15% by mass relative to the whole amount of the mixed solution.