Continuous twin-screw mixer and mixing method

A continuous mixer for continuously mixing a material, comprising:

• a barrel with a hollow interior;
• a hopper positioned to feed a material to be mixed to the interior of the barrel;
• and
• a pair of mixing rotors which are housed in the barrel and rotate in mutually different directions, each of the mixing rotors including a feeding portion which is an upstream part in an axial direction, the feeding portion including a first screw flight shaped to feed the material supplied from the hopper to the downstream side through the barrel, a mixing portion which is an intermediate part in the axial direction, the mixing portion including a plurality of mixing flights shaped to mix the material fed from the feeding portion, the mixing flights being formed about an axial center of the mixing rotor and projecting radially outward, and a discharging portion which is a downstream part in the axial direction, the discharging portion including a second screw flight shaped to feed the material mixed by the mixing portion to the downstream side, wherein:
• each of the mixing flights is shaped differently from each of the first screw flight and the second screw flight;
• the mixing flights each have a tip, a spacing between the tip of one mixing flight of the pair of mixing rotors and the other mixing flight of the pair of mixing rotors comprising an inter-rotor clearance which is a smallest clearance between the mixing portions in a cross section perpendicular to axial directions of both of the mixing rotors at each rotation phase of the mixing rotors, the rotations of the pair of mixing rotors in the mutually different directions causing respective surfaces of the mixing rotors to move in the same direction on the both sides of the inter-rotor clearance;
• both of the mixing rotors are arranged so as to make a center distance therebetween smaller than a rotation outer diameter of each of the mixing flights;
• and
• the inter-rotor clearance at each rotation phase of the mixing portions of the mixing rotors has a size equal to or smaller than 0.1-fold of an inner diameter of the barrel over a rotation region of 59% or more of one rotation of each of the mixing rotors.

A continuous mixer for continuously mixing a material, comprising:

• a barrel with a hollow interior;
• a hopper positioned to feed a material to be mixed to the interior of the barrel;
• and
• a pair of mixing rotors which are housed in the barrel and rotate in mutually different directions, each of the mixing rotors including a feeding portion which is an upstream part in an axial direction, the feeding portion including a first screw flight shaped to feed the material supplied from the hopper to the downstream side through the barrel, a mixing portion which is an intermediate part in the axial direction, the mixing portion including a plurality of mixing flights shaped to mix the material fed from the feeding portion, the mixing flights being formed about an axial center of the mixing rotor and projecting radially outward, and a discharging portion which is a downstream part in the axial direction, the discharging portion including a second screw flight shaped to feed the material mixed by the mixing portion to the downstream side, wherein:
• each of the mixing flights is shaped differently from each of the first screw flight and the second screw flight;
• the mixing flights each have a tip, a spacing between the tip of one mixing flight of the pair of mixing rotors and the other mixing flight of the pair of mixing rotors comprising an inter-rotor clearance which is a smallest clearance between the mixing portions in a cross section perpendicular to axial directions of both of the mixing rotors at each rotation phase of the mixing rotors, the rotations of the pair of mixing rotors in the mutually different directions causing respective surfaces of the mixing rotors to move in the same direction on the both sides of the inter-rotor clearance;
• both of the mixing rotors are arranged so as to make a center distance therebetween smaller than a rotation outer diameter of each of the mixing flights;
• and
• the inter-rotor clearance at each rotation phase of the mixing portions of the mixing rotors has a size smaller than 0.07-fold of an inner diameter of the barrel over a rotation region of 34% or more of one rotation of each of the mixing rotors.