| 摘要 |
<p>A method for producing a polylactic acid block copolymer constituted by a segment(s) composed of L-lactic acid units and a segment(s) composed of D-lactic acid units, the method comprising the steps of:
obtaining a mixture by mixing poly-L-lactic acid and poly-D-lactic acid one of which has a weight average molecular weight of 60,000 to 300,000 and the other of which has a weight average molecular weight of 10,000 to 50,000, the mixture having a weight average molecular weight of not less than 90,000 and a degree of stereocomplexation (Sc) satisfying the Inequality below: Sc = ”Hh / ”Hl + ”Hh × 100 > 60
(wherein ”Hh represents the heat of fusion of stereocomplex crystals (J/g), and ”H1 represents the heat of fusion of crystals of poly-L-lactic acid alone and crystals of poly-D-lactic acid alone (J/g)); and
subsequently subjecting the mixture to solid-phase polymerization at a temperature lower than the melting point of the mixture. By the production method of the present invention, a polylactic acid block copolymer that forms a polylactic acid stereocomplex having a high molecular weight and a high melting point can be obtained.</p> |
