Kneading disc segment and twin-screw extruder

A kneading disc segment mounted on a kneading screw for kneading a material while feeding the material to a downstream side during rotation of the kneading screw, and constituted by a combination of plural kneading discs, said kneading disc segment comprising:

• a plurality of disc sets disposed sequentially and continuously in the axial direction of said kneading screw, said disc sets each comprising two discs and not more than two discs, the two discs of each said set comprising a first kneading disc and a second kneading disc, said second kneading disc being mounted continuously with, and downstream of, said first kneading disc in the direction of feeding the material, wherein the second kneading disc has a phase difference δ of an acute angle relative to said first kneading disc, the phase difference δ being in a direction opposite the direction of rotation of the kneading screw,
• wherein said first kneading discs in each of said plural continuous disc sets have a phase difference of 180° with each other, whereby there is no phase difference in appearance between the first kneading discs in said plural continuous disc sets.