Toner, process for producing toner image forming method and apparatus unit

A process for producing a toner, comprising the steps of:

• melt-kneading a mixture containing at least a binding resin having a glass transition temperature (Tg) of 45 to 75° C. and a coloring agent to obtain a kneaded product;
• cooling the obtained kneaded product and thereafter roughly pulverizing the cooled product with grinding means to obtain a roughly pulverized product;
• introducing a powder raw material of the resulting pulverized product into a first metering feeder and introducing a predetermined quantity of powder raw material from the above described first metering feeder into a mechanical mill, wherein said mechanical mill is provided at least with a rotor mounted on a center rotary shaft, a stator disposed around the rotor with a constant distance from surfaces of said rotor being maintained, a powder introducing orifice for introducing a powder raw material, a spiral chamber at a temperature T1 is not more than 0° C. and is 60 to 75° C. lower than the Tg of said binding resin in communication with the powder introducing orifice and a powder discharging orifice for discharging ground powder and is so configured that an annular space formed by maintaining the distance is in an airtight state;
• finely pulverizing the powder raw material to obtain a finely pulverized product by rotating said rotor of said mechanical mill at high speed;
• discharging the finely pulverized product from the mechanical mill by the powder discharging orifice via a rear chamber of the mechanical mill, wherein a temperature T2 of said rear chamber is 30 to 60° C. and introducing the finely pulverized product into a second metering feeder so that from said metering feeder a predetermined quantity of finely pulverized product is introduced into a multisegment airflow classifier which classifies the powder by utilizing cross airflows and Coanda effect;
• and
• classifying the finely pulverized product into at least fine powder, medium powder and coarse powder inside said multisegment airflow classifier;
• wherein the classified coarse powder is mixed with said powder raw material to be introduced into said mechanical mill in the pulverization step and the toner is produced from the classified medium powder.