Abstract: A modifier for a polylactic acid comprising a block polymer (C) having a polymer block (A) satisfying relationship (1): 7.80??/?<8.54 wherein ? represents a solubility parameter value of a polymer block; and ? represents a density value of a polymer block, and a polymer block (B) satisfying relationship (2): 8.54??/?<9.20 wherein ? and ? have the same meanings as described above, wherein each of the aforementioned polymer block (A) and the aforementioned polymer block (B) is independently a polymer block selected from the group consisting of a polyester block, a polyether block, and a polyhydroxycarboxylic acid block, and said block polymer (C) has a glass transition temperature of 0° C. or lower, can enhance impact resistance, flexibility, and tensile strain, while biodegradability of the polylactic acids and thermal resistance are maintained, and in addition, is free from bleed-out from the moldings formed from a polylactic acid composition.

Abstract: A modifier for a polylactic acid comprising a block polymer (C) having a polymer block (A) satisfying relationship (i) 7.80??/?<8.54 wherein ? represents a solubility parameter value of a polymer block; and ? represents a density value of a polymer block, and a polymer block (B) satisfying relationship (2): 8.54??/?<9.20 wherein ? and ? have the same meanings as described above, wherein each of the aforementioned polymer block (A) and the aforementioned polymer block (B) is independently a polymer block selected from the group consisting of a polyester block, a polyether block, and a polyhydroxycarboxylic acid block, and said block polymer (C) has a glass transition temperature of 0° C. or lower, can enhance impact resistance, flexibility, and tensile strain, while biodegradability of the polylactic acids and thermal resistance are maintained, and in addition, is free from bleed-out from the moldings formed from a polylactic acid composition.

Abstract: A process for producing a lactic acid-based copolyester by the ring-opening copolymerization and transesterification of a lactide (A) with an aromatic polyester (B) and/or an aliphatic polyester (C) in the presence of a ring-opening polymerization catalyst (D), and a packaging material comprising the lactic acid-based copolyester obtained by the process are disclosed. According to the present invention, a lactic acid-based degradable copolyester which has a sufficiently high molecular weight and satisfactory toughness and also has suitable rigidity, pliability, and transparency according to applications can be produced. Further, a general-purpose packaging material, e.g., a sheet or film, which comprises the lactic acid-based copolyester produced by the process and is excellent in formability, degradability, and transparency can also be produced.