Twin screw extruder for use in manufacturing fiber-reinforced resin composition and process for manufacturing fiber-reinforced resin composition

A twin screw extruder comprising:

• a cylinder housing twin screws arranged in parallel;
• a resin feed part configured to feed a molten thermoplastic resin;
• an input port arranged on the cylinder and configured to receive a reinforcing fiber, the reinforcing fiber being fed through the input port into the molten thermoplastic resin located in the resin feed part of the cylinder;
• a discharge-side part arranged at one end of the twin screw extruder;
• a kneading part provided closer to the discharge-side part than a midpoint of the twin screw extruder, and configured to knead the reinforcing fiber and the molten thermoplastic resin to manufacture a fiber-reinforced resin composition;
• a conveying part provided between the input port and the kneading part, and configured to convey the reinforcing fiber and the molten thermoplastic resin to the kneading part;
• and
• a fiber relaxing part configured by a screw element, a minimum outer peripheral length of which has a value smaller than that of the screw element configuring the conveying part, the fiber relaxing part being provided between the conveying part and the kneading part, and adjacent to the conveying part and the kneading part and
• a pin that protrudes into an interior of the cylinder of the twin screw extruder,
• wherein a tip clearance is a distance between one of the twin screws and the cylinder, and a screw clearance is a distance between outer edges of the twin screws in a cross-sectional view perpendicular to rotational axes of the twin screws,
• wherein tip clearances of each of the twin screws arranged in the conveying part are larger than the screw clearance, and
• wherein the reinforcing fiber is conveyed while being stretched over outer peripheries of the twin screws that mesh with each other in the conveying part.