Patent ID: 8921434

Claim:
A method of producing a polylactic acid composition with an MI value of 0.05 or more and 5 or less, the MI value being measured at 190° C. under a load of 21.6 kg in accordance with JIS K7210 (ISO 1133), comprising: crosslinking a polylactic acid with a polyisocyanate to generate a cross-linked polylactic acid, including a large cross-linked polylactic acid molecule which inhibits foaming, and mechanically grinding the cross-linked polylactic acid, by applying a shear force to decrease a molecular weight of the large cross-linked polylactic acid molecule, the amount of the polyisocyanate combined being 0.4 to 5% by weight based on the polylactic acid, the grinding being conducted in supercritical condition of an inert gas, the shear force being applied in an orifice portion having a slit or a sleeve from which the polylactic acid composition is extruded, by allowing the cross-linked polylactic acid to pass through the orifice portion, the temperature in the orifice portion being from 160 to 180° C., and the pressure in the orifice portion being from 6 to 12 MPa.