Screw pair and co-rotating intermeshing twin-screw extruder provided with screw pair

A screw pair comprising:

• first and second screws for a co-rotating intermeshing type twin-screw extruder, the first and second screws having an outer circumferential surface on which a groove is spirally formed,
• wherein the first and second screws are configured to rotate about an axis center of each screw in a state where the first and second screws mesh with each other and to transport a thermoplastic synthetic resin raw material containing a liquid component in a predetermined direction along the axis center and to remove the liquid component from said raw material, and
• wherein an inner surface of the groove of each of the first and second screws comprises a first surface, which faces in the predetermined direction, and a second surface, which faces in a direction opposite to the predetermined direction,
• wherein the first surfaces of the first and second screws are formed to coincide with the outer circumferential surfaces of second and first screws without a gap therebetween, respectively, in the state where the first and second screws mesh with each other;
• and
• wherein the second surfaces of the first and second screws form a gap between the outer circumferential surfaces of the second and first screws, respectively, in the state where the first and second screws mesh with each other.