Process for producing toner, and apparatus for modifying surfaces of toner particles

A process for producing a toner containing toner particles, comprising:

• a kneading step of melt-kneading a composition containing at least a binder resin and a colorant;
• a cooling step of cooling the kneaded product obtained;
• a pulverization step of finely pulverizing the resultant cooled and solidified product to obtain a finely pulverized product;
• and
• a step of simultaneously carrying out a surface modification step for making surface modification of particles contained in the finely pulverized product obtained and a classification step of carrying out classification for removing fine powder and ultrafine powder contained in the finely pulverized product obtained, to obtain toner particles;
• wherein:
• the step of simultaneously carrying out the surface modification step and the classification step is carried out using a batch-wise surface modifying apparatus;
• the surface modifying apparatus has at least:
• a cylindrical main-body casing;
• a worktop provided open-close operably at a top of the main-body casing;
• an introduction area through which the finely pulverized product is introduced into the main-body casing;
• a classifying means having a classifying rotor which rotates in a stated direction in order that fine powder and ultrafine powder having particle diameter not larger than stated particle diameter are continuously removed out of the apparatus from the finely pulverized product having been introduced into the main-body casing;
• a fine-powder discharge area through which the fine powder and ultrafine powder having been removed by the classifying means are discharged out of the main-body casing;
• a surface modifying means having a dispersing rotor which rotates in the same direction as the rotational direction of the classifying rotor and a liner which is stationarily disposed, in order that particles contained in the finely pulverized product from which the fine powder and ultrafine powder have been removed are subjected to surface modification treatment using a mechanical impact force;
• a cylindrical guide means for forming a first space and a second space in the main-body casing;
• and
• a toner particle discharge area through which the toner particles having been subjected to surface modification treatment by means of the dispersing rotor are discharged out of the main-body casing;
• the first space, which is provided between the inner wall of the main-body casing and the outer wall of the cylindrical guide means, is a space through which the finely pulverized product and the particles having been surface-modified are guided to the classifying rotor;
• the second space is a space in which the finely pulverized product from which the fine powder and ultrafine powder have been removed and the particles having been surface-modified are treated by the dispersing rotor;
• in the surface modifying apparatus, the finely pulverized product having been introduced into the main-body casing through the introduction area is led into the first space, the fine powder and ultrafine powder having particle diameter not larger than the stated particle diameter are removed by the classifying means and continuously discharged out of the apparatus, during which the finely pulverized product from which the fine powder and ultrafine powder have been removed are moved to the second space, and treated by the dispersing rotor to carry out the surface modification treatment of the particles contained in the finely pulverized product, and the finely pulverized product containing the particles having been surface-modified are again circulated to the first space and the second space to repeat the classification and the surface modification treatment, to thereby obtain toner particles from which the fine powder and ultrafine powder having particle diameter not larger than stated particle diameter have been removed to be in a quantity not more than stated quantity and which have been surface-modified;
• the dispersing rotor has an outer diameter of 120 mm or more;
• the minimum gap between the dispersing rotor and the liner is from 1.0 mm to 3.0 mm;
• and
• the dispersing rotor has a plurality of rectangular disks,
• wherein number n of the rectangular disks provided at a top surface of the dispersing rotor and external diameter D of the dispersing rotor satisfy a relationship of expression (1):
• π×D/n≦95.0 (mm) (1).