Patent ID: 7223815

Claim:
A polylactic acid composition comprising a polylactic acid and a modifier for a polylactic acid, wherein the modifier comprises a block polymer (C) having a polymer block (A) satisfying relationship (1): 7.80≦σ/ρ<8.54 wherein σ represents a solubility parameter value of a polymer block; ρ represents a density value of a polymer block; and the value of σ/ρ is obtained in accordance with σ/ρ=ΣFi/M, wherein Fi represents a molar attraction constant of the chemical group and M represents a molar molecular weight per repeating unit; and a polymer block (B) satisfying relationship (2): 8.54≦σ/ρ<9.20 wherein σ and ρ have the same meanings as described above, wherein each of said polymer (A) and said polymer (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.