# US 2005/0233237 A1 · Toner for electrostatic image development > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 2005/0233237 A1 - Document ID: US20050233237A1 - Status: Published application - Kind: A1 - Application number: 11/102,719 - Filed: 2005-04-11 - Published: 2005-10-20 - Earliest claimed: 2004-04-15 - Assignees: Kao Corporation - Inventors: Akihiro Eida; Jun Shimizu - Web page: https://patentgrep.com/patent/US20050233237A1 ## CPC - G03G 9/09716: {treated with organic compounds} - G03G 9/081: {by mixing the toner components in a liquefied state; melt kneading; reactive mixing} - G03G 9/0819: {characterised by the dimensions of the particles} - G03G 9/0823: {Electric parameters} - G03G 9/09708: {Inorganic compounds} - G03G 9/09725: {Silicon-oxides; Silicates} - G03G: ELECTROGRAPHY; ELECTROPHOTOGRAPHY; MAGNETOGRAPHY ## Abstract The present invention relates to a toner for electrostatic image development, obtainable by a process including the steps of: (I) melt-kneading a raw material mixture containing a resin binder, a releasing agent, and a colorant, cooling the melt-kneaded mixture, and pulverizing the cooled mixture; and (II) further pulverizing a pulverized product obtained in the step (I) in the presence of an external additive containing a negatively chargeable inorganic oxide subjected to hydrophobic treatment and a positively chargeable inorganic oxide subjected to hydrophobic treatment, and classifying the pulverized product; and a process for preparing the toner. ## Claims ### Claim 1 A toner for electrostatic image development, obtainable by a process comprising the steps of: (I) melt-kneading a raw material mixture comprising a resin binder, a releasing agent, and a colorant, cooling the melt-kneaded mixture, and pulverizing the cooled mixture; and (II) further pulverizing a pulverized product obtained in the step (I) in the presence of an external additive comprising a negatively chargeable inorganic oxide subjected to hydrophobic treatment and a positively chargeable inorganic oxide subjected to hydrophobic treatment, and classifying the pulverized product. ### Claim 2 (depends on 1) The toner according to claim 1, wherein the step (II) comprises mixing the roughly pulverized product obtained in the step (I) with the external additive, further pulverizing the resulting mixture, and classifying the pulverized product. ### Claim 3 (depends on 1) The toner according to claim 1, wherein a triboelectric charge of the negatively chargeable inorganic oxide is from −10 to −500 μC/g, and wherein a triboelectric charge of the positively chargeable inorganic oxide is from 10 to 500 μC/g. ### Claim 4 (depends on 1) The toner according to claim 1, wherein at least one of the negatively chargeable inorganic oxide and the positively chargeable inorganic oxide is a hydrophobic silica. ### Claim 5 (depends on 1) The toner according to claim 1, wherein each of the negatively chargeable inorganic oxide and the positively chargeable inorganic oxide has an average particle size of from 6 to 20 nm. ### Claim 6 (depends on 1) The toner according to claim 1, obtainable by a method further comprising, subsequent to the step (II), the step of: (III) mixing the product obtained in the step (II) with an inorganic oxide having an average particle size of from 25 to 100 nm. ### Claim 7 (depends on 1) The toner according to claim 1, wherein the melt-kneading of the raw material mixture in the step (I) is carried out with an open-roller type kneader. ### Claim 8 (depends on 1) The toner according to claim 1, wherein the toner has a volume-average particle size (D50) of from 3.5 to 9 μm. ### Claim 9 (depends on 1) The toner according to claim 1, wherein the negatively chargeable inorganic oxide and the positively chargeable inorganic oxide are uniformly dispersed on and adhered to a surface of the toner. ### Claim 10 A process for preparing a toner for electrostatic image development, comprising the steps of: (I) melt-kneading a raw material mixture comprising a resin binder, a releasing agent, and a colorant, cooling the melt-kneaded mixture, and pulverizing the cooled mixture; and (II) further pulverizing a pulverized product obtained in the step (I) in the presence of an external additive comprising a negatively chargeable inorganic oxide subjected to hydrophobic treatment and a positively chargeable inorganic oxide subjected to hydrophobic treatment, and classifying the pulverized product. ### Claim 11 (depends on 10) The process according to claim 10, wherein the step (II) comprises mixing the pulverized product obtained in the step (I) with the external additive, further pulverizing the resulting mixture, and classifying the pulverized product. ### Claim 12 (depends on 10) The process according to claim 10, wherein the pulverizing step in the step (II) is carried out with a jet mill having an air pressure during pulverization of from 0.2 to 1 MPa. ### Claim 13 (depends on 10) The process according to claim 10, wherein the melt-kneading of the raw material mixture in the step (I) is carried out with an open-roller type kneader. ### Claim 14 (depends on 10) The process according to claim 10, wherein a triboelectric charge of the negatively chargeable inorganic oxide is from −10 to −500 μC/g, and wherein a triboelectric charge of the positively chargeable inorganic oxide is from 10 to 500 μC/g. ### Claim 15 (depends on 10) The process according to claim 10, wherein at least one of the negatively chargeable inorganic oxide and the positively chargeable inorganic oxide is a hydrophobic silica. ### Claim 16 (depends on 10) The process according to claim 10, wherein each of the negatively chargeable inorganic oxide and the positively chargeable inorganic oxide has an average particle size of from 6 to 20 nm. ### Claim 17 (depends on 10) The process according to claim 10, further comprising, subsequent to the step (II), the step of: (III) mixing the product obtained in the step (II) with an inorganic oxide having an average particle size of from 25 to 100 nm. ### Claim 18 (depends on 10) The process according to claim 10, wherein the toner has a volume-average particle size (D50) of from 3.5 to 9 μm. ### Claim 19 (depends on 10) The process according to claim 10, wherein the negatively chargeable inorganic oxide and the positively chargeable inorganic oxide are uniformly dispersed on and adhered to a surface of the toner. ### Claim 20 (depends on 10) The process according to claim 10, wherein the pulverized product obtained in the step (I) has an average particle size of from 0.03 to 4 mm.