Patent ID: 8791192

Claim:
A method for producing a resin composition which has a retention of viscosity average molecular weight of at least 60% comprising the steps of (I) preparing a polylactic acid (component B) produced by melt-kneading only a component B-2 and a component B-5 in a weight ratio (component B-2/component B-5) of 10/90 to 90/10 at a temperature of 270 to 300° C., wherein the component B-2 is a polylactic acid comprising 90 to 99 mol % of the L-lactic acid unit and 1 to 10 mol % of the D-lactic acid unit and/or units other than lactic acid, wherein the component B-5 is a polylactic acid comprising 90 to 99 mol % of the D-lactic acid unit and 1 to 10 mol % of the L-lactic acid unit and/or units other than lactic acid, wherein the component B shows a proportion of melt peaks at 195° C. or higher to all melt peaks in a temperature rising process in measurement by a differential scanning calorimeter (DSC) of at least 80%, and (II) melt-kneading 100 parts by weight of thermoplastic resin (component A) and 10 to 190 parts by weight of the polylactic acid (component B).