Abstract: The present invention provides a kneading method for a fiber-reinforced thermoplastic resin with which dispersibility of reinforcement fibers is enhanced and sufficient reinforcement fibers having a proper fiber length remain, and a fiber-reinforced thermoplastic resin plasticizing device and an extruding machine for carrying out the method. The kneading method comprises supplying a thermoplastic resin and reinforcement fibers into a cylinder of a plasticizing device, and rotating a screw to obtain a fiber-reinforced thermoplastic resin, wherein the size of a clearance between the bore of the cylinder and the screw is made different between an upstream side in the vicinity of a reinforcement fiber loading port and a downstream side, so that the clearance becomes larger from the vicinity of the reinforcement fiber loading port toward the downstream side compared with the upstream side.

Abstract: A process for producing polylactic acid includes the steps of polycondensing lactic acid to a lactic acid prepolymer having a weight-average molecular weight of 10,000-50,000 in a batch-type polymerization reactor, and polycondensing the lactic acid prepolymer to lactic acid polymer having a weight-average molecular weight of at least 100,000 by means of a screw-type extruder.