US Patent 7323283 Method of producing an electrostatic charge image developing toner

A pulverized starting material is supplied quantitatively from a quantitative feeder 1 to a first mechanical pulverizer 2 where the material is pulverized moderately, the resulting moderately pulverized material is supplied quantitatively from a quantitative feeder 3 to a second mechanical pulverizer 4 where the material is finely pulverized, and the resulting finely pulverized material is introduced into a coarse-powder classifier 5 to classify coarse powder not smaller than a predetermined particle diameter. The finely pulverized material from which the coarse powder was removed by classification is further classified fine powder not larger than a predetermined size by a fine-powder classifier 7 to produce a classified product, while the separated classified coarse powder is introduced into a returning-powder feeder 6. The classified coarse powder introduced into the returning-powder feeder 6 is again supplied quantitatively to the second mechanical pulverizer 4, upon which when it is detected that the weight of the coarse powder stored in the returning-powder feeder 6 is deviated from a predetermined range, the amount of the returning powder supplied to the second mechanical pulverizer 4 is changed and regulated such that the powder is supplied in the above changed amount. The pulverization conditions in the first and second mechanical pulverizers are established such that the volume-average particle diameter D1 (μm) of the moderately pulverized material obtained by the first mechanical pulverizer 2 and the volume-average particle diameter D2 (μm) of the finely pulverized material obtained by the second mechanical pulverizer satisfy: 3 μm≦D1−D2 ≦6 μm.