Abstract: A method for producing glycolide provided with: step (1) wherein a GAO composition, which preferably contains a high-boiling-point organic solvent or a solubilizing agent, is supplied into a reactor and heated to a temperature at which a depolymerization reaction of the GAO occurs; step (2) wherein the heating is continued to subject the GAO to the depolymerization reaction, thereby producing glycolide; step (3) wherein glycolide is distilled out of the reactor; step (4) wherein the distillate is introduced into a rectifier and is rectified by means of gas-liquid countercurrent contact; and step (5) wherein glycolide is recovered.

Abstract: A method for producing glycolide provided with: step (1) wherein a GAO composition, which preferably contains a high-boiling-point organic solvent or a solubilizing agent, is supplied into a reactor and heated to a temperature at which a depolymerization reaction of the GAO occurs; step (2) wherein the heating is continued to subject the GAO to the depolymerization reaction, thereby producing glycolide; step (3) wherein glycolide is distilled out of the reactor; step (4) wherein the distillate is introduced into a rectifier and is rectified by means of gas-liquid countercurrent contact; and step (5) wherein glycolide is recovered.

Abstract: A method for producing glycolide provided with: step (1) wherein a GAO composition, which preferably contains a high-boiling-point organic solvent or a solubilizing agent, is supplied into a reactor and heated to a temperature at which a depolymerization reaction of the GAO occurs; step (2) wherein the heating is continued to subject the GAO to the depolymerization reaction, thereby producing glycolide; step (3) wherein glycolide is distilled out of the reactor; step (4) wherein the distillate is introduced into a rectifier and is rectified by means of gas-liquid countercurrent contact; and step (5) wherein glycolide is recovered.

Abstract: Disclosed is a process for purifying a hydroxycarboxylic acid, comprising: a crystallization step of subjecting a hydroxycarboxylic acid aqueous solution to crystallization for purification, a separation step of separating a hydroxycarboxylic acid crystal from a mother liquid, and a washing step of washing the hydroxycarboxylic acid crystal for further purification with a washing liquid, wherein the washing liquid is a hydroxycarboxylic acid aqueous solution. The purified or refined hydroxycarboxylic acid obtained through the above process is suitably used as a starting material for production of a polyhydroxycarboxylic acid. The above process is suitably included in a process for producing a cyclic ester and a process for producing a polyhydroxycarboxylic acid.

Abstract: Disclosed is a process for purifying a hydroxycarboxylic acid, comprising: a crystallization step of subjecting a hydroxycarboxylic acid aqueous solution to crystallization for purification, a separation step of separating a hydroxycarboxylic acid crystal from a mother liquid, and a washing step of washing the hydroxycarboxylic acid crystal for further purification with a washing liquid, wherein the washing liquid is a hydroxycarboxylic acid aqueous solution. The purified or refined hydroxycarboxylic acid obtained through the above process is suitably used as a starting material for production of a polyhydroxycarboxylic acid. The above process is suitably included in a process for producing a cyclic ester and a process for producing a polyhydroxycarboxylic acid.

Abstract: A method of refining a crystal of a crude cyclic ester comprises the steps of supplying the crude cyclic ester to a vertically extending cylindrical refiner (1) from an inlet (3) provided at a lower part of the refiner (1), agitating the crude cyclic ester by an agitator provided in the refiner (1) to make the crude cyclic ester flow upwardly, refining the crystals of the crude cyclic ester by counterflow-contact between the upflowing crude cyclic ester and a downflowing melted liquid containing a refined crystal component, and taking out refined crystals of the crude cyclic ester from an outlet (4) provided at an upper part of the refiner (1).

Abstract: A method of refining a crystal of a crude cyclic ester comprises the steps of supplying the crude cyclic ester to a vertically extending cylindrical refiner (1) from an inlet (3) provided at a lower part of the refiner (1), agitating the crude cyclic ester by an agitator provided in the refiner (1) to make the crude cyclic ester flow upwardly, refining the crystals of the crude cyclic ester by counterflow-contact between the upflowing crude cyclic ester and a downflowing melted liquid containing a refined crystal component, and taking out refined crystals of the crude cyclic ester from an outlet (4) provided at an upper part of the refiner (1).