# US 2010/0168446 A1 · Method for purification of cyclic ester

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- Number: US 2010/0168446 A1
- Document ID: US20100168446A1
- Status: Published application
- Kind: A1
- Application number: 12/449,669
- Filed: 2008-01-28
- Published: 2010-07-01
- Earliest claimed: 2007-02-20
- Assignees: Kureha Corporation
- Inventors: Kazuyuki Yamane; Tomohiro Hoshi; Tomoyuki Ogawa
- Web page: https://patentgrep.com/patent/US20100168446A1

## CPC

- C07D 319/12: not condensed with other rings
- C07D: HETEROCYCLIC COMPOUNDS (macromolecular compounds C08)

## Abstract

A method of purifying a cyclic ester, comprising: mixing a co-distillated liquid comprising a cyclic ester produced by heating depolymerization of a hydroxycarboxylic acid oligomer in the presence of a depolymerization solvent and the depolymerization solvent with an organic solvent for washing which is mutually soluble with the depolymerization solvent and has a lower boiling point than the cyclic ester; subjecting the resultant mixture liquid to liquid-liquid separation into an organic solvent phase containing the depolymerization solvent and a cyclic ester phase containing the organic solvent; and then evaporating the organic solvent from the cyclic ester phase containing the organic solvent to recover the cyclic ester containing a reduced amount of the depolymerization solvent. As a result, purified cyclic ester is recovered at high heat efficiency, purification efficiency and operation efficiency, from the co-distillate liquid containing the depolymerization solvent and the cyclic ester from the depolymerization system for thermal decomposition of the hydroxycarboxylic acid oligomer in the presence of the depolymerization solvent.

## Claims

### Claim 1

A method of purifying a cyclic ester, comprising: subjecting a co-distillated liquid comprising a cyclic ester produced by heating depolymerization of a hydroxycarboxylic acid oligomer in the presence of a depolymerization solvent and the depolymerization solvent to a liquid-liquid separation step of separating the co-distillated liquid into a depolymerization solvent phase and a cyclic ester phase containing the depolymerization solvent; then mixing the resultant cyclic ester phase containing the depolymerization solvent with an organic solvent for washing which is mutually soluble with the depolymerization solvent and has a lower boiling point than the cyclic ester; subjecting the resultant mixture liquid to liquid-liquid separation into an organic solvent phase containing the depolymerization solvent and a cyclic ester phase containing the organic solvent; and then evaporating the organic solvent from the cyclic ester phase containing the organic solvent to recover the cyclic ester containing a reduced amount of the depolymerization solvent.

### Claim 2

(canceled)

### Claim 3 (depends on 1)

A purification method according to claim 1, wherein the depolymerization solvent is a polyalkylene glycol ether.

### Claim 4 (depends on 3)

A purification method according to claim 3, wherein the polyalkylene glycol ether has a number of repeating alkylene-oxy group of 2-8 and includes ether oxygen-bonded groups at both ends each comprising an alkyl group having totally 3-21 carbon atoms.

### Claim 5 (depends on 4)

A purification method according to claim 4, wherein the polyalkylene glycol ether has a boiling point (under normal pressure) of 230-450° C.

### Claim 6 (depends on 1)

A purification method according to any of claim 1, wherein the organic solvent for washing has a boiling point (under normal pressure) of at most 90° C.

### Claim 7 (depends on 6)

A purification method according to claim 6, wherein the organic solvent for washing is hexane.

### Claim 8 (depends on 1)

A purification method according to any of claim 1, wherein the co-distillate is washed with the organic solvent for washing at 85-150° C.

### Claim 9 (depends on 1)

A purification method according to any of claim 1, including a step of subjecting the recovered cyclic ester with a reduced content of the depolymerization solvent to crystallization, and after solid liquid separation, a step of washing the crystal with a molten liquid of refined cyclic ester.

### Claim 10 (depends on 1)

A purification method according to any of claim 1, wherein the cyclic ester is glycolide.