Toner production system

A process for producing a toner, comprising:

• melt-kneading a mixture comprising at least a binder resin and a colorant to form a kneaded product, cooling the kneaded product, coarsely crushing the cooled kneaded product to provide a crushed product, and pulverizing the crushed product by means of a mechanical pulverizer to provide a toner having a weight-average particle size of 3 to 12 μm, wherein
• the mechanical pulverizer includes an inlet port for introducing the crushed product into a pulverization zone to form a pulverizate, a cooling means for cooling the pulverization zone, a discharge port for discharging the pulverizate out of the pulverization zone, a rotor rotatably supported about a rotation axis and having an outer wall, a stator surrounding the rotor and having an inner wall spaced apart from the outer wall of the rotor so as to form the pulverization zone between the inner wall of the stator and the outer wall of the rotor where the crushed product is pulverized into the pulverizate,
• each of the outer wall of the rotor and the inner wall of the stator is provided with a plurality of grooves which extend generally in parallel with the rotation axis of the rotor and are formed of a wave-shaped plurality of projections and intervening recesses, so that the recesses of at least one of the outer wall of the rotor and the inner wall of the stator have flat-faced bottoms, and
• in case where the outer wall of the rotor has the recesses having flat-faced bottoms, each recess of the outer wall has a corner (A) at a rear edge of the flat-faced bottom with respect to the rotation direction of the rotor and adjacent to a rising slope which forms an angle (α1) of at least 10 deg. and below 80 deg. in a direction opposite to the rotation direction with respect to a reference line connecting the rotation axis and the corner (A), and
• in case where the inner wall of the stator has the recesses having flat-faced bottoms, each recess of the inner wall has a corner (A′) at a forward edge of the flat-faced bottom with respect to the rotation direction of the rotor and adjacent to a rising slope which forms an angle (β1) of at least 10 deg. and below 80 deg. in the rotation direction with respect to a reference line connecting the rotation axis of the rotor and the corner (A′).