反应详情

A 90 wt % aqueous solution of L-lactic acid (50 g) and 50 g of hydroxybutyric acid were put into a reaction vessel equipped with a stirrer and a nitrogen-introducing tube. After substitution of nitrogen gas was carried out three times, the mixture was concentrated at 120° C. for 5 hours with stirring in a stream of nitrogen to give 65 g of lactic acid-hydroxybutyric acid oligomer. To the obtained oligomer was added 1.3 g of Baylith 5A with which sodium elution (381 ppm) had been observed. Then, the temperature was raised to 200° C., and the pressure was reduced gradually to 20 mmHg over 30 minutes. The mixture was stirred at 195±5° C. for 3 hours. After the pressure was reduced gradually to 1 mmHg over 30 minutes, the mixture was stirred at 195±5° C. for 7 hours to give lactic acid-hydroxybutyric acid copolymer in the molten state. The product was cooled to room temperature to give 28.15 g of lactic acid-hydroxybutyric acid copolymer as a light brown solid. The weight-average molecular weight of this copolymer was 58,000.

1. customequipped with a stirrer
2. additiona nitrogen-introducing tube
3. concentrationthe mixture was concentrated at 120° C. for 5 hours