| abstract |
An electrostatic image developing toner having goodncharge properties, low-temperature fixing properties,noffset resistance and blocking resistance as well as goodnresistance against sticking to a heated roll and waxndispersibility employs a particular urethane-modifiednpolyester resin. n The said urethane-modified polyester resin has a totalnacid value not greater than 10 KOH mg/g and is obtainablenby kneading, in a molten state, a base polyester resin (A)nhaving an acid value of 5 to 20 KOH mg/g and a hydroxylnvalue of 40 to 70 KOH mg/g, with a low-molecular-weightnpolyester resin (B) having an acid value not greater thann5 KOH mg/g a hydroxyl value not greater than 10 KOH mg/gnand a weight-average molecular weight of 3,000 to 5,000,ntogether with a polyisocyanate compound. Components (A)nand (B) are present at a weight ratio of 3 to 5 : 7 to 5nand the polyisocyanate compound is present in an amount ofn0.2 to 1.2 equivalent, in terms of an isocyanate group pernequivalent, of the total hydroxyl groups of all the resins.nThe urethane-modified polyester resin is used as a bindernresin for the toner, in the preparation of which the resinnis mixed and kneaded e.g. with a colorant, magneticnpowders, charge control agents in a molten state, followednby cooling and pulverization. |