Patent ID: 7358023

Claim:
A method for producing a toner comprising: (a) a step of preparing a powder for production of the toner from a raw material containing a resin as a main component, a coloring agent, a crystalline polyester having higher crystallinity than the resin as an accessory component, and an ester-based wax having a softening point of 50 to 100° C. in an amount of 0.5% to 5% by weight, wherein said step of preparing a powder comprises: (i) mixing the raw material; (ii) kneading the raw material at a temperature of 100 to 200° C. using a twin-screw kneading extruder having a head, wherein the head comprises an internal space having a cross sectional area-decreasing section in which the cross sectional area gradually decreases toward an extrusion outlet; (iii) cooling the kneaded product extruded from the head of the kneading extruder while shaping it into a tabular form having an approximately uniform thickness using a belt cooling device, which comprises two sets of rolls and two belts wherein each belt is put around a set of two rolls, and wherein the kneaded product is introduced between the two belts and cooled; and (iv) pulverizing the cooled kneaded product; and (b) a thermal conglobation step of conglobating the powder for production of the toner with heat, wherein (i) the thermal conglobation step is carried out at an atmospheric temperature of from 200 to 400° C., (ii) the content of the resin in the raw material is from 80 to 98% by weight, (iii) the crystalline polyester has a melting point of 50 to 120° C., and (iv) the content of the crystalline polyester in the raw material is from 2 to 15 parts by weight per 100 parts by weight of the resin, wherein the toner has average degree of circularity R, which is represented by the following equation (I): R=L 0 /L 1 (I) wherein L 1 (μm) represents the circumferential length of a projected image of a toner particle to be measured, and L 0 (μm) represents the circumferential length of a complete circle having an area equivalent to that of the projected image of the toner particle to be measured, of 0.92 to 0.978; and wherein the resin as a main component is a polyester having lower crystallinity than the crystalline polyester resin serving as the accessory component.