Dual purpose electrophotographic magnetic toner and process of making

Claim 1

A method of producing a dual purpose, single component, electronically conductive, magnetically attractable toner comprising the steps of: heating and mixing a mixture of thermoplastic toner resins to form an intimate blend while dispersing therein 50 to 150 phr of finely divided, magnetic pigment and 0 to 15 phr of conductive pigment, said resins consisting essentially of a linear polyester consisting of the condensation product of an aromatic diol with an unsaturated aliphatic, dibasic acid having a softening point from 95° C. to 115° C. and an ethylene-vinyl acetate copolymer containing 5 to 40% vinyl acetate and the ratio of polyester to copolymer being from 1:1 to 5:1; cooling the mixture to a brittle solid; breaking the mixture into large fragments; grinding the fragments to form coarse particles; fine grinding the coarse particles to form fine, fragmentary aspherical, acicular particles having a diameter from 10 to 40 microns by subjecting the particles to jets of inert gas in absence of abrasive such that they fragment by self-impact; dry blending the fine particles with from 0.5 to 2.0 percent by weight of finely divided conductive pigment having a particle diameter in the range of 10-80 milimicrons; and embedding the conductive pigment on the surface of the fine, acicular, aspherical particles without changing the shape thereof by gravity feeding the dry blend into the top of a spray drier and heating the falling particles in a 250°-350° F. gas stream to a temperature just sufficient to soften the thermoplastic resin.

Claim 2

A method of producing a dual purpose, single component, electronically conductive, magnetically attractable toner comprising the steps of: heating and mixing a mixture of thermoplastic toner resins to form an intimate blend while dispersing therein 50 to 150 phr of finely divided, magnetic pigment and 0 to 15 phr of conductive pigment, said resins consisting essentially of a linear polyester consisting of the condensation product of an aromatic diol with an unsaturated aliphatic, dibasic acid having a softening point from 95° C. to 115° C. and an ethylene-vinyl acetate copolymer containing 5 to 40% vinyl acetate and the ratio of polyester to copolymer being from 1:1 to 5:1; cooling the mixture to a brittle solid; breaking the mixture into large fragments; grinding the fragments to form coarse particles; fine grinding the coarse particles to form fine, fragmentary aspherical, acicular particles having a diameter from 10 to 40 microns by subjecting the particles to jets of inert gas in absence of abrasive such that they fragment by self-impact; dry blending the fine particles with from 0.5 to 2.0 percent by weight of finely divided conductive pigment having a particle diameter in the range of 10-80 milimicrons; and embedding the conductive pigment on the surface of the fine, acicular, aspherical particles without changing the shape thereof by gravity feeding the dry blend into the top of a spray drier and heating the falling particles in a 250°-350° F. gas stream to a temperature just sufficient to soften the thermoplastic resin.