EP1808733B1

EP1808733B1 - Toner processes

Info

Publication number: EP1808733B1
Application number: EP20060100387
Authority: EP
Inventors: Raj D. Patel; Allan K. Chen; Cuong Vong
Original assignee: Xerox Corp
Current assignee: Xerox Corp
Priority date: 2006-01-16
Filing date: 2006-01-16
Publication date: 2009-11-11
Anticipated expiration: 2026-01-16
Also published as: DE602006010318D1; EP1808733A1

Description

Illustrated herein are toner processes, and more specifically, aggregation and coalescence processes. More specifically, the present invention relates in embodiments to methods for the preparation of toner compositions by a chemical process, such as emulsion/aggregation/coalescence, wherein latex particles are aggregated with a wax and a crosslinked gel wherein the gel or crosslinking value is, for example, from 20 to 55 percent as measured gravimetrically; colorants, and a magnetite in the presence of a coagulant like a polymetal halide, or alternatively a mixture of coagulants or flocculating agents; thereafter stabilizing the aggregates with an organic complexing agent or a chelating agent, such as ethylenediaminetetraacetic acid (EDTA) dissolved in a base, such as sodium hydroxide, and thereafter coalescing or fusing by heating the mixture above the resin Tg to provide toner size particles which when developed by an electrographic process generates documents suitable for magnetic image character. In embodiments illustrated herein the chelating agent or compound allows the toner aggregates formed comprised, for example, of magnetite and metal coagulant ions like aluminum, for the formation of water soluble complexes which prevents or minimizes undesired interaction of magnetite or iron particles. By utilizing complexing or chelating compounds, the point of zero change Pzc of magnetic can be altered and thereby also minimize the generation of charges which may interfere in the toner emulsion aggregation process.
A number of advantages are associated with the present invention in embodiments thereof including, for example, excellent toner hot offset, for example above 210°C, and more specifically, from 210°C to 230°C; a toner fusing latitude of from 20°C to 40°C wherein fusing latitude refers to a temperature in which, when a developed image is fused, evidences substantially no offset either to the substrate that the image is fused on, referred to as "Cold" offset or an offset on the fuser roll referred to as the "Hot" offset; a minimum fixing temperature of, for example, 170°C to 195°C; and extended photoreceptor life since the toner fusing temperature can be below 195°C, such as from 175°C to 190°C; stable, controllable and substantially predictable PCZ, (point of zero charge), and wherein the charge on the magnetite particles can be either positive or negative depending, for example, on the pH of the medium, that is when the pH is acidic there results a positive charge; when the pH is basic there results negative charge, such as lowering the point of zero charge, for example from a value of 5.4 to about 3.5 of the complexed magnetite thereby enabling, for example, coalescence of the aggregates; and also in embodiments a process that enables a means of identifying how a toner was fabricated by, for example, analyzing for aluminum and organic complexing compound content.
Disclosed in U.S. Patent 4,128,202 is a device for transporting a document that has been mutilated or erroneously encoded, and wherein there is provided a predetermined area for the receipt of correctly encoded magnetic image character recognition information (MICR). As indicated in this patent, the information is referred to as MICR characters, which characters can appear, for example, at the bottom of personal checks as printed numbers and symbols. These checks have been printed in an ink containing magnetizable particles therein, and when the information contained on the document is to be read, the document is passed through a sorter/reader which first magnetizes the magnetizable particles, and subsequently detects a magnetic field of the symbols resulting from the magnetic retentivity of the ink. The characters and symbols involved, according to the '202 patent, are generally segregated into three separate fields, the first field being termed a transient field, which contains the appropriate symbols and characters to identify the bank, bank branch, or the issuing source.
US-A-2004/0265729 discloses a method for the preparation of a toner for use in a Magnetic Ink Character Recognition (MICR) process, said method comprising the step of heating a mixture of a magnetite dispersion, a colorant dispersion, a wax dispersion, a first latex containing a crosslinked resin, a second latex containing a resin free of crosslinking, a coagulant, and a silica. The silica may be introduced in the form of a silicate salt dissolved in a base.
US-A-2002/0187415 discloses a process for the preparation of pigmented toner particles in with certain coagulants such as polyaluminum chloride are used. This publication teaches that an organic complexing compound is added, which reacts with the coagulant, thereby preventing or minimizing the formation of cationic species such as aluminum ions, which would act as a coagulant, thereby initiating further undesirable growth in toner particle size.
In applications requiring MICR capabilities, the toners selected usually contain magnetites having specific properties, an important one of which is a high enough level of remanence or retentivity. Retentivity is a measure of the magnetism left when the magnetite is removed from the magnetic field, that is, the residual magnetism. Also of value are toners with a high enough retentivity, such that when the characters are read, the magnetites produce a signal strength of equal to greater than about 100 percent. The signal level can vary in proportion to the amount of toner deposited on the document being generated, and signal strength of a toner composition can be measured by using known devices, including the MICR-Mate 1, manufactured by Checkmate Electronics, Inc.
The present invention provides :

(1) A toner process comprised of heating a mixture of an acicular magnetite dispersion, a colorant dispersion, a wax dispersion, a first latex containing a crosslinked resin, and a second latex containing a resin free of crosslinking in the presence of a coagulant to provide aggregates, stabilizing the aggregates with an organic complexing compound or salt thereof dissolved in a base, and further heating said aggregates to provide coalesced toner particles.
(2) A process in accordance with (1) wherein said complexing compound is selected in an amount of from 0.5 to 2 percent by weight of toner.
(3) A process in accordance with (1) wherein said coagulant is selected from the group consisting of polyaluminum chloride, polyaluminum sulfosilicate, aluminum sulfate, zinc sulfate, and magnesium sulfate, and optionally wherein from 80 to 90 percent of said coagulant metal ion is retained in said toner.
(4) A process in accordance with (1) wherein said colorant is carbon black, and wherein said carbon black dispersion comprises carbon black particles of from 0.01 to 0.2 µm (micron) diameter dispersed in water and an anionic surfactant, and wherein said colorant is present in an amount of from 4 to 10 weight percent, and optionally wherein the amount of acicular magnetite selected is from 20 to 40 percent by weight of toner, said colorant is carbon black present in the amount of from 4 to 8 percent by weight of toner, and said wax is present in the amount of 4 to 12 percent by weight of toner; said crosslinked resin is present in the amount of 5 to 10 percent by weight; said uncrosslinked resin is present in an amount of 55 to 65 percent by weight of toner; and said coagulant is comprised of polymetal halide present in an amount of 0.02 to 2 percent by weight of toner.
(5) A process in accordance with (1) wherein said wax dispersion contains a polyethylene wax, a polypropylene wax or mixtures thereof, water, and an anionic surfactant; and wherein said wax is selected in an amount of from 5 to 20 weight percent.
(6) A process in accordance with (1) wherein said first latex contains a crosslinked resin in an amount of from 2 to 25 weight percent; and wherein said crosslinked resin possesses a molecular weight M_w of from 100,000 to 1,000,000, and an onset glass transition (Tg) temperature of 48°C to 58°C, and optionally wherein said crosslinked resin is poly(styrene butylacrylate, beta carboxy ethyl acrylate divinyl benzene).
(7) A toner process comprised of heating a mixture of an acicular magnetite dispersion, a colorant dispersion, a first latex containing a crosslinked resin, and a second latex containing a resin free of crosslinking in the presence of a coagulant; adding an organic complexing compound salt dissolved in a base, and further heating said aggregates to provide coalesced toner particles.
(8) A process comprising heating a mixture of magnetite, colorant, a first latex, and a second latex wherein the first latex contains a crosslinked polymer and the second latex is substantially free of a crosslinked polymer, and which heating is accomplished in the presence of a coagulant and an organic complexing compound salt base mixture, and wherein said heating comprises a first and second heating, which second heating is at a higher temperature than said first heating, and wherein said first heating is below the glass transition temperature Tg of said resin free of crosslinking, and said second heating is above the Tg of said resin free of crosslinking.

Aspects of the present invention relate to a process wherein the reaction between the complexing agent, such as EDTA, and the magnetite particle changes the Pzc of from 5.4 to 3.5 (complexed magnetite particles); the preparation of MICR toners wherein the toner comprises magnetite, resin wax, an organic complexing compound and crosslinked gel particles wherein a complexing compound is introduced in the form of a complexing compound dissolved in sodium hydroxide, and which solution possesses a pH of about 12, and wherein a complexing compound binds or coats the magnetite or the aggregate particles containing the magnetite thereby allowing the pH during coalescence to be lowered below the Point of Zero Charge of the uncoated magnetite, for example equal to or less than 5.4; a process wherein the coating of a complexing compound on the magnetite particles lowers the Pzc from a value of about 5.4 to about 3.5 enabling the pH during coalescence to be reduced to 4 to 5 without any toner size increase, thereby providing a broader process latitude and more rapid coalescence, which coalescence can be reduced by about 40 percent; a toner process wherein there is selected an organic complexing or chelating compound in the form of a complexing compound salt, such as magnesium, iron, manganese, copper, cobalt, zinc, nickel, cadmium, chromium, and aluminum which exhibit dual charge capabilities depending on the pH of the surrounding media, allowing these particles to function as coagulating/flocculating agents for an anionic or a cationic process, and wherein the addition of the complexing compound forms a coating of this compound on the magnetite aggregates thereby reducing or lowering the Pzc, a toner process wherein the toner formed can be of various shapes, such as a potato like shape to spherical shape by, for example, reducing the pH during coalescence below a pH of 5; a MICR toner containing a complexing compound and prepared by emulsion aggregation processes wherein the magnetite is in the form of needle shape or acicular magnetite particles, which are of a size diameter of, for example, from 450 nanometers to 700 nanometers;
a process for the preparation of a MICR toner composition, which when analyzed for aluminum and a complexing compound contents contains 70 to 95 percent of both thereby providing a means of detection of how the toner was fabricated; a process wherein the magnetite dispersion contains an anionic surfactant and a nonionic surfactant wherever the dispersion possesses a pH of from 6.5 to 6.8; a process wherein the carbon black dispersion comprises particles dispersed in water and an anionic surfactant, and which dispersion possesses a pH of 6.3 to 6.8; a process wherein the wax dispersion comprises particles dispersed in water and an ionic surfactant; a process wherein the acicular magnetite is present in an amount of from 20 to 35 percent by weight of toner, and preferably in an amount of from 23 to 32 percent by weight of toner; a process wherein the acicular magnetite utilized exhibits a coercivity of from 19.9 to 55.7 KA/m (250 to 700 Oe); a process wherein the acicular magnetite has a particle size of about 0.6 µm (micron) in length by 0.1 µm (micron) in diameter, and is comprised of about 21 percent FeO and about 79 percent Fe₂O₃; a process wherein the toner exhibits a magnetic signal of from 90 to 150 percent of the nominal signal;
a process wherein the carbon black dispersion is present in an amount of 4 to 8 percent by weight of toner; a process wherein the latex resin particles are from 0.15 to 0.3 µm (micron) in volume average diameter; a process wherein the magnetite is of a size of 0.6 µm (micron) to 0.1 µm (micron), and the carbon black is of a size of 0.01 to 0.2 µm (micron) in average volume diameter; a process wherein the acid is selected from the group consisting of nitric, sulfuric, hydrochloric, citric and acetic acid; a process wherein the base is selected from the group consisting of sodium hydroxide, potassium hydroxide and ammonium hydroxide; a process wherein the addition of the organic complexing compound in the form of a salt of sodium, potassium or calcium is dissolved in the base which is added to the toner size aggregates, which provides a coating of a complexing compound on the aggregates containing the magnetite or the iron oxide particles, rendering it substantially nonreactive, and stabilizes the toner size aggregates from further growth during coalescence, or when the temperature of the aggregate mixture is raised above the resin Tg; a process wherein there is added to the formed toner size aggregates a latex comprised of noncrosslinked submicron resin particles suspended in an aqueous phase containing an anionic surfactant, and wherein the noncrosslinked latex is selected in an amount of from 10 to 40 percent by weight of the initial latex to form a shell on the formed aggregates, and which shell is of a thickness of, for example, 0.2 to 0.8 µm (micron);
a process wherein the time of coalescence or fusion is from 5 to 10 hours, and wherein there are provided toner particles with a smooth morphology; a process wherein the latex contains a resin or polymer selected from the group consisting of poly(styrene-alkyl acrylate), poly(styrene-1,3-diene), poly(styrene-alkyl methacrylate), poly(styrene-alkyl acrylate-acrylic acid), poly(styrene-1,3-diene-acrylic acid), poly(styrene-alkyl methacrylate-acrylic acid), poly(alkyl methacrylate-alkyl acrylate), poly(alkyl methacrylate-aryl acrylate), poly(aryl methacrylate-alkyl acrylate), poly(alkyl methacrylate-acrylic acid), poly(styrene-alkyl acrylate-acrylonitrile-acrylic acid), poly(styrene-1,3-diene-acrylonitrile-acrylic acid), and poly(alkyl acrylate-acrylonitrile-acrylic acid); a process wherein the latex contains a resin selected from the group consisting of poly(styrene-butadiene), poly(methylstyrene-butadiene), poly(methyl methacrylate-butadiene), poly(ethyl methacrylate-butadiene), poly(propyl methacrylate-butadiene), poly(butyl methacrylate-butadiene), poly(methyl acrylate-butadiene), poly(ethyl acrylate-butadiene), poly(propyl acrylate-butadiene), poly(butyl acrylate-butadiene), poly(styrene-isoprene), poly(methylstyrene-isoprene), poly(methyl methacrylate-isoprene), poly(ethyl methacrylate-isoprene), poly(propyl methacrylate-isoprene), poly(butyl methacrylate-isoprene), poly(methyl acrylate-isoprene), poly(ethyl acrylate-isoprene), poly(propyl acrylate-isoprene), poly(butyl acrylate-isoprene), poly(styrene-propyl acrylate), poly(styrene-butyl acrylate), polystyrene-butyl-acrylate beta carboxy ethyl acrylate, poly(styrene-butadiene-acrylic acid), poly(styrene-butadiene-methacrylic acid), poly(styrene-butadiene-acrylonitrile-acrylic acid), poly(styrene-butyl acrylate-acrylic acid), poly(styrene-butyl acrylate-methacrylic acid), poly(styrene-butyl acrylate-acrylononitrile), poly(styrene butyl acrylate (beta CEA), poly(styrene butadiene beta CEA), poly(styrene isoprene beta CEA), poly(styrene butyl acrylate, acrylonitrile beta CEA), poly(styrene butyl acrylate, divinylbenzene beta CEA), and poly(styrene-butyl acrylate-acrylononitrile-acrylic acid), and more specifically, poly(styrene butyl acrylate beta CEA), and poly(styrene butyl acrylate, divinylbenzene beta CEA), and yet more specifically, poly(styrene butyl acrylate beta CEA);
a process wherein the magnetite dispersion is obtained by ball milling, attrition, polytroning or media milling with an anionic surfactant resulting in magnetite particles suspended in water containing the anionic surfactant; a process wherein the colorant is carbon black, and the amount of the carbon black dispersion is from 3 to 10 percent by weight of toner; a process wherein the crosslinked resin contains resin particles of from 0.15 to 0.4 µm (micron) in volume average diameter, and a second latex contains a resin free of crosslinking; a process wherein the magnetite size is from µm (0.6 micron) to 0.1 µm (micron) in average volume diameter, and the colorant is carbon black, and the carbon black is from 0.01 to 0.2 µm (micron) in average volume diameter;
a process wherein the crosslinked resin is selected in an amount of from 1 to 40 weight percent; a process wherein the crosslinked resin is selected in an amount of from 2 to 25 weight percent; a process wherein the crosslinked resin is poly(styrene butylacrylate, beta carboxy ethyl acrylate divinyl benzene); a process wherein the resin free from crosslinking possesses a molecular weight M_w of 20,000 to 500,000, and an onset glass transition (Tg) temperature of from 45°C to 70°C; a process wherein the crosslinked latex resin possesses a molecular weight M_w of 100,000 to 1,000,000, and an onset glass transition (Tg) temperature of 48°C to 58°C; a process wherein the crosslinked resin latex is selected in an amount of from 2 to 15 weight percent, the latex free of a crosslinked resin is selected in an amount of from 40 65 weight percent, the magnetite is selected in an amount of from 20 to 35 weight percent, the wax is selected in an amount of from 5 to 15 weight percent, and wherein the total thereof is about 100 percent based on the toner; a process wherein the resulting toner possesses a shape factor of from 110 to 148; a process wherein the colorant dispersion contains colorant and an anionic surfactant; a process wherein colorant dispersion is comprised of carbon black particles dispersed in water and an anionic surfactant; a process wherein the amount of acicular magnetite selected is from 15 to 40 percent by weight of toner, and the coagulant is a polymetal halide present in an amount of 0.02 to 0.4 percent by weight of toner; a process where the coagulant is a cationic surfactant present in the amount of 0.1 to 2 percent by weight of toner; a process wherein the coagulant is comprised of a mixture of a polymetal halide and a cationic surfactant; a process wherein the amount of acicular magnetite selected is from 23 to 32 percent by weight of toner, and the amount of coagulant, which coagulant is a polymetal halide, is present in an amount of 0.05 to 0.13 percent by weight of toner, and the optional cationic surfactant coagulant is present in an amount of 0.15 to 1.5 percent by weight of toner; a process wherein the noncrosslinked resin or polymer has a glass transition temperature (Tg) of 45°C to 70°C; a process wherein the noncrosslinked resin possesses a weight average molecular weight of 20,000 to 90,000; a process wherein the crosslinked latex contains a polymer, wherein the crosslinking percentage or value is, for example, from 20 to 75 percent, or 25 to 55 of poly(styrene-alkyl acrylate), poly(styrene-1,3-diene), poly(styrene-alkyl methacrylate), poly(alkyl methacrylate-alkyl acrylate), poly(alkyl methacrylate-aryl acrylate), poly(aryl methacrylate-alkyl acrylate), poly(alkyl methacrylate), poly(styrene-alkyl acrylate-acrylonitrile), poly(styrene-1,3-diene-acrylonitrile), poly(alkyl acrylate-acrylonitrile), poly(styrene-butadiene), poly(methylstyrene-butadiene), poly(methyl methacrylate-butadiene), poly(ethyl methacrylate-butadiene), poly(propyl methacrylate-butadiene), poly(butyl methacrylate-butadiene), poly(methyl acrylate-butadiene), poly(ethyl acrylate-butadiene), poly(propyl acrylate-butadiene), poly(butyl acrylate-butadiene), poly(styrene-isoprene), poly(methylstyrene-isoprene), poly(methyl methacrylate-isoprene), poly(ethyl methacrylate-isoprene), poly(propyl methacrylate-isoprene), poly(butyl methacrylate-isoprene), poly(methyl acrylate-isoprene), poly(ethyl acrylate-isoprene), poly(propyl acrylate-isoprene), poly(butyl acrylate-isoprene); poly(styrene-propyl acrylate), poly(styrene-butyl acrylate), poly(styrene-butadiene-acrylonitrile), and poly(styrene-butyl acrylate-acrylononitrile), and wherein the polymer in addition contains a crosslinking component, such as divinyl benzene (DVB), to enable the crosslinked resin or polymer, and wherein the crosslinking component can be selected in an amount of from 0.1 to 15 weight percent; a process wherein the polymer, in addition to DVB, can contain a carboxylic acid, and which carboxylic acid is, for example, selected from the group comprised of acrylic acid, methacrylic acid, itaconic acid, beta carboxy ethyl acrylate; and wherein the carboxylic acid is present in an amount of from 0.5 to 10 weight percent;
and a process for preparing a MICR toner composition by emulsion aggregation, which toner possesses a smooth shape and feel, and contains from 20 to 40 weight percent of an acicular magnetite, wax, crosslinked resin, and colorant, and with a toner particle size distribution of 1.20 to 1.26, and which toner provides a MICR signal of 90 to 140 percent and a bulk remanence of about 26 A m²/kg (emu/gram) wherein the remanence can be measured on a tapped powder magnetite sample in a cell of 1 centimeter X 1 centimeter X about 4 centimeters. The sample is magnetized between two magnetic pole faces with a saturating magnetic field of 2,000 Gauss, such that the induced magnetic field is perpendicular to one of the 1 X 4 centimeter faces of the cell. The sample is removed from the saturating magnetic field, and the remanence is measured perpendicular to the above 1 centimeter wide face using a Hall-Effect device or a gaussmeter, such as the F.W. Bell, Inc. Model 615 gaussmeter.
Colorants include dyes, pigments, and mixtures thereof, colorant examples include known colorants like black, cyan, red, blue, magenta, green, brown, yellow, and mixtures thereof.
Various known colorants, such as pigments, selected for the processes of the present invention and present in the toner in an effective amount of, for example, from 1 to 25 percent by weight of toner, and more specifically, in an amount of from 3 to 10 percent by weight include, for example, carbon black like REGAL 330^®; REGAL 660^®; phthalocyanine Pigment Blue 15, Pigment Blue 15.1, Pigment Blue 15.3, Pigment Green 7, Pigment Green 36, Pigment Orange 5, Pigment Orange 13, Pigment Orange 16, Pigment Orange 36, Pigment Red 122, Pigment Red 53.1, Pigment Red 48.1, and Pigment Red 48.2.
Crosslinked resin examples with crosslinking values as illustrated herein, and yet more specifically, of, for example, from 25 to 80, and more specifically, from 30 to 65 percent, and which resins are selected in various amounts, such as from 1 to 20, and more specifically, from 5 to 10 weight percent based on the weight percentages of the remaining toner components, include the resins illustrated herein, which resins are crosslinked by known crosslinking compounds, such as divinyl benzene. Specific crosslinked resin examples are poly(styrene divinyl benzene beta CEA), poly(styrene butyl acrylate divinyl benzene beta CEA), poly(styrene divinyl benzene acrylic acid) and , poly(styrene butyl acrylate divinyl benzene acrylic acid).
Examples of anionic surfactants that can be selected for the processes illustrated herein include, for example, sodium dodecylsulfate (SDS), sodium dodecylbenzene sulfonate, sodium dodecylnaphthalene sulfate, dialkyl benzenealkyl, sulfates and sulfonates, abitic acid, available from Aldrich, NEOGEN RK™, NEOGEN SC™ from Kao, DOWFAX™ obtained from Dow Chemicals, and ABEX™ obtained from Rhodia. An effective concentration of the anionic surfactant generally employed is, for example, from 0.01 to 10 percent by weight, and preferably from 0.1 to 5 percent by weight of monomers used to prepare the toner polymer resin.
Examples of nonionic surfactants that can be selected for the processes illustrated herein and that may be, for example, included in the resin latex dispersion are, for example, polyvinyl alcohol, polyacrylic acid, methalose, methyl cellulose, ethyl cellulose, propyl cellulose, hydroxy ethyl cellulose, carboxy methyl cellulose, polyoxyethylene cetyl ether, polyoxyethylene lauryl ether, polyoxyethylene octyl ether, polyoxyethylene octylphenyl ether, polyoxyethylene oleyl ether, polyoxyethylene sorbitan monolaurate, polyoxyethylene stearyl ether, polyoxyethylene nonylphenyl ether, dialkylphenoxypoly(ethyleneoxy) ethanol, available from Rhodia as IGEPAL CA-210^®. A suitable concentration of the nonionic surfactant is, for example, from 0.01 to 10 percent by weight, and more specifically, from 0.1 to 5 percent by weight of monomers used to prepare the toner polymer resin.
Examples of cationic surfactants, which are usually positively charged, selected for the toners and processes of the present invention include, for example, alkylbenzyl dimethyl ammonium chloride dialkyl benzenealkyl ammonium chloride, lauryl trimethyl ammonium chloride, alkylbenzyl methyl ammonium chloride, alkyl benzyl dimethyl ammonium bromide, benzalkonium chloride, cetyl pyridinium bromide, C₁₂, C₁₅, C₁₇ trimethyl ammonium bromides, halide salts of quaternized polyoxyethylalkylamines, dodecylbenzyl triethyl ammonium chloride, MIRAPOL™ and ALKAQUAT™, available from Alkaril Chemical Company, Aldrich Chemicals SANIZOL™ (benzalkonium chloride), available from Kao Chemicals, and mixtures thereof. A suitable amount of cationic surfactant can be selected, such as from 0.2 to 5 percent by weight of the toner components.
Examples of a complexing compound that can be selected are those that are suitable, such as ethylenediamine tetraacetic acid; diethylenetriamine pentacetic acid; nitrilotriacetic acid; the corresponding salts of the aforementioned, such as the alkali metal salts like sodium, potassium, calcium, and which complexing compound can be mixed with soap, water.. Also, in embodiments, biodegradable compounds of the complexing compounds illustrated can also be selected. Specific examples of organic complexing compounds or agents include ethylene diamine tetraacetic acid (EDTA), gluconal, sodium gluconate, potassium and sodium citrate, nitrotriacetate (NTA) salt, GLDA (commercially available L-glutamic acid N,N diacetic acid) humic and fulvic acids, maltol and ethyl-maltol, peta-acetic and tetraacetic acids; the corresponding salts of the aforementioned, such as the alkali metal salts like sodium, potassium, calcium.
Counterionic coagulants selected for the processes illustrated herein can be comprised of organic, or inorganic components. For example, in embodiments the ionic surfactant of the resin latex dispersion can be an anionic surfactant, and the counterionic coagulant can be a polymetal halide or a polymetal disulfo compound (PASS). Coagulants that can be included in amounts of, for example, from 0.05 to 10 weight percent include polymetal halides, polymetal disulfo compounds, and divalent or multivalent salts optionally in combination with cationic surfactants. Inorganic cationic coagulants include, for example, polyaluminum chloride (PAC), polyaluminum sulfates (PASS), aluminum sulfate, zinc sulfate, or magnesium sulfate.
The coagulant is in embodiments present in an aqueous medium in an amount of from, for example, 0.05 to 10 percent by weight, and more specifically, in an amount of from 0.075 to 2 percent by weight. The coagulant may also contain minor amounts of other components, such as for example nitric acid. The coagulant is usually added slowly while continuously subjecting the mixture resulting to high shear, for example, by stirring with a blade at 3,000 to 10,000 rpm, and preferably about 5,000 rpm, for 1 to 120 minutes. A high shearing device, for example an intense homogenization device, such as the in-line IKA SD-41, may be used to ensure that the coagulant is homogeneous and uniformly dispersed.
Examples of waxes include polypropylenes and polyethylenes commercially available from Allied Chemical and Petrolite Corporation, wax emulsions available from Michaelman Inc. and the Daniels Products Company, EPOLENE N-15™ commercially available from Eastman Chemical Products, Inc., and VISCOL 550-P™ , a low weight average molecular weight polypropylene available from Sanyo Kasei K.K.. The commercially available polyethylenes selected possess, it is believed, a molecular weight M_w of from 500 to 15,000, while the commercially available polypropylenes are believed to have a molecular weight of from 3,000 to 7,000. Examples of functionalized waxes are amines, amides, for example AQUA SUPERSLIP 6550™, SUPERSLIP 6530™ available from Micro Powder Inc., fluorinated waxes, for example POLYFLUO 190™, POLYFLUO 200™, POLYFLUO 523XF™, AQUA POLYFLUO 411™, AQUA POLYSILK 19™, POLYSILK 14™ available from Micro Powder Inc., mixed fluorinated, amide waxes, for example MICROSPERSION 19™ also available from Micro Powder Inc., imides, esters, quaternary amines, carboxylic acids or acrylic polymer emulsions, for example JONCRYL 74™, 89™, 130™, 537™, and 538™, all available from SC Johnson Wax; chlorinated polypropylenes and polyethylenes available from Allied Chemical and Petrolite Corporation and SC Johnson Wax. The amounts of the wax selected in embodiments is, for example, from 3.5 to 15 percent by weight of toner.
During coalescence, the pH is increased, for example, from 2 to 3 to 7 to 8; from 2 to 2.8 to 7 to 7.5 by the addition of a suitable pH agent of, for example, sodium hydroxide to provide for the stabilization of the aggregated particles and to prevent/minimize the toner size growth and loss of GSD during further heating, for example, raising the temperature 10°C to 50°C above the resin Tg. Also, the complexing compound provides for a coating thereof on the magnetite particles thereby lowering the Pzc of the magnetite such that during the coalescence where the pH of the mixture reduced to below 5 and preferably 4.5, the fusion of the aggregates can be accomplished by using an acid. Examples of pH reducing agents include, for example, nitric acid, citric acid, sulfuric acid or hydrochloric acid.
In embodiments, the toner particles formed by processes illustrated herein possess, for example, an average volume diameter of from 0.5 to 25, and more specifically, from 1 to 10 µm (microns), and narrow GSD characteristics of, for example, from 1.05 to 1.25, or from 1.15 to 1.25 as measured by a Coulter Counter. The toner particles also possess an excellent shape factor, for example, of 135 or less wherein the shape factor refers, for example, to the measure of toner smoothness and toner roundness where a shape factor of about 100 is considered spherical and smooth without any surface protrusions, while a shape factor of about 150 is considered to be rough in surface morphology and the shape is like a potato.
The toner particles illustrated herein may also include known charge additives in effective amounts of, for example, from 0.1 to 5 weight percent, such as alkyl pyridinium halides and bisulfates. Surface additives that can be added to the toner compositions after washing or drying include, for example, metal salts, metal salts of fatty acids, colloidal silica, metal oxides, and mixtures thereof, which additives are usually present in an amount of from 0.1 to 2 weight percent. Specific additives include zinc stearate and AEROSIL R972^® available from Degussa Chemical, and each present in an amount of from 0.1 to 2 percent, which can be added during the aggregation process or blended into the formed toner product, calcium stearate.
Developer compositions can be prepared by mixing the toners obtained with the process of the present invention with known carrier particles, including coated carriers, such as steel or ferrites, for example from 2 percent toner concentration to 8 percent toner concentration.
The following Examples are provided. Parts and percentages are by weight unless otherwise indicated, and temperatures are in degrees Centigrade.

EXAMPLES

Preparation of Noncrosslinked Latex A:

A latex emulsion (i) comprised of polymer particles generated from the emulsion polymerization of styrene, butyl acrylate and beta carboxy ethyl acrylate (Beta CEA) was prepared as follows. A surfactant solution of 434 grams of DOWFAX 2A1™ (anionic emulsifier -55 percent active ingredients) and 387 kilograms of deionized water was prepared by mixing these components for 10 minutes in a stainless steel holding tank. The holding tank was then purged with nitrogen for 5 minutes before transferring the mixture into a reactor. The reactor was then continuously purged with nitrogen while being stirred at 100 RPM. The reactor was then heated to 80°C.
Separately, 6.11 kilograms of ammonium persulfate initiator were dissolved in 30.2 kilograms of deionized water. Also, separately a monomer emulsion A was prepared in the following manner. 315.7 Kilograms of styrene, 91.66 kilograms of butyl acrylate, 12.21 kilograms of beta-CEA, 7.3 kilograms of 1-dodecanethiol, 1.42 kilograms of decanediol diacrylate (ADOD), 8.24 kilograms of DOWFAX™ (anionic surfactant), and 193 kilograms of deionized water were mixed to form an emulsion. Five percent of the above emulsion was then slowly fed into the reactor containing the aqueous surfactant phase at 80°C to form seeds wherein "seeds" refer, for example, to the initial emulsion latex added to the reactor prior to the addition of the initiator solution while being purged with nitrogen. The above initiator solution was then slowly charged into the reactor forming 5 to 12 nanometers of latex "seed" particles. After 10 minutes, the remainder of the emulsion was continuously fed using metering pumps.
After the above monomer emulsion was charged into the main reactor, the temperature was maintained at 80°C for an additional 2 hours to complete the reaction. The reactor contents were then cooled down to about 25°C. The resulting isolated product was comprised of 40 weight percent of submicron, 0.5 µm (micron) diameter resin particles of styrene/butylacrylate/beta CEA suspended in an aqueous phase containing the above surfactant. The molecular properties resulting for the resin latex were M_w (weight average molecular weight) of 35,000, M_n of 10,600 as measured by a Gel Permeation Chromatograph, and a midpoint Tg of 55.8°C, as measured by a Differential Scanning Calorimeter where the midpoint Tg is the halfway point between the onset and the offset Tg of the polymer.

Preparation of the Crosslinked Latex B (50 nanometers):

A crosslinked latex emulsion comprised of polymer particles generated from the emulsion polymerization of styrene, butyl acrylate and beta carboxy ethyl acrylate (p) CEA was prepared as follows. A surfactant solution of 4.08 kilograms of NEOGEN™ RK (anionic emulsifier) and 78.73 kilograms of deionized water was prepared by mixing these components for 10 minutes in a stainless steel holding tank. The holding tank was then purged with nitrogen for 5 minutes before transferring the resulting mixture into the above reactor. The reactor was then continuously purged with nitrogen while the contents were being stirred at 100 RPM. The reactor was then heated up to 76°C, and held there for a period of 1 hour.
Separately, 1.24 kilograms of ammonium persulfate initiator were dissolved in 13.12 kilograms of deionized water.
Also separately, monomer emulsion was prepared in the following manner. 47.39 Kilograms of styrene, 25.52 kilograms of butyl acrylate, 2.19 kilograms of β-CEA, 0.729 kilogram of divinyl benzene (DVB) crosslinking agent, 1.75 kilograms of NEOGEN™ RK (anionic surfactant), and 145.8 kilograms of deionized water were mixed to form an emulsion. One (1) percent of the emulsion was then slowly fed into the reactor while the reactor was being purged with nitrogen containing the aqueous surfactant phase at 76°C to form "seeds". The initiator solution was then slowly charged into the reactor and after 40 minutes the remainder of the emulsion was continuously fed in using metering pumps over a period of 3 hours.
Once all the monomer emulsion was charged into the above main reactor, the temperature was held at 76°C for an additional 4 hours to complete the reaction. Cooling was then accomplished and the reactor temperature was reduced to 35°C. The product was collected into a holding tank. After drying, the resin latex onset Tg was 53.5°C. The resulting latex was comprised of 25 percent crosslinked resin, 72.5 percent water and 2.5 percent anionic surfactant. The resin had a ratio of 65:35:3 pph:1 pph of styrene:butyl acrylate:β-CEA:DVB. The mean particle size of the gel latex was 50 nanometers as measured on disc centrifuge, and the resin in the latex possessed a crosslinking value of 25 percent as measured by known gravimetric methods.

Wax and Pigment Dispersions:

The aqueous wax dispersion utilized in the following Examples was generated using waxes available from Baker-Petrolite (1) P725 polyethylene wax with a low molecular weight M_w of 725, and a melting point of 104°C, or (2) P850 wax with a low molecular weight of 850 and a melting point of 107°C and NEOGEN RK™ as an anionic surfactant/dispersant. The wax particle diameter size was determined to be approximately 200 nanometers, and the wax slurry was a solid loading of 30 percent (weight percent throughout).
The pigment dispersion, obtained from Sun Chemicals, was an aqueous dispersion containing carbon black (REGAL 330^®), an anionic surfactant, 2 percent, and 79 percent water.

EXAMPLE I

Toner Preparation - PAC (0.1 pph) - with 50 Nanometer Gel, 1 pph of EDTA:

79 Grams of MAGNOX B2550™ acicular magnetite composed of 21 percent FeO and 79 percent Fe₂O₃ having a particle size of about 0.6 µm (micron) X 0.1 µm (micron) was added to 600 grams of water containing 1.3 grams of a 20 percent aqueous anionic surfactant (NEOGEN RK™) to which 85 grams of an 18 percent carbon black REGAL 330^® solution were added. The resultant mixture was then polytroned or homogenized at a speed of 5,000 rpm, for 3 minutes, to provide a pigment dispersion. To the resulting pigment dispersion was added 90 grams of a dispersion of submicron polyethylene P 850 wax particles (30 percent solids) followed by the addition of 320 grams of the above prepared anionic latex A comprised of submicron latex particles (40 percent solids) of styrene/butylacrylate/beta CEA, and 64 grams of the cross linked latex B of styrene/butylacrylate/divinyl benzene beta CEA (25.5 percent solids) while polytroned at a speed of 5,000 rpm for a period of 5 minutes 300 grams of water were added to reduce the viscosity of the resulting blend to which then was added an aqueous PAC (polyaluminum chloride) solution comprised of 3.1 grams of a 10 percent solids placed in 25 grams of 0.3M nitric acid.
The resulting blend was then heated to a temperature of 50°C while stirring for a period of 100 minutes to obtain a particle size of 5.3 µm (micron) with a GSD of 1.20. 140 Grams of the above prepared noncrosslinked latex (Latex A) were then added to the aggregate mixture, and followed by stirring at 50°C for 130 minutes to provide a particle size of 5.9 µm (microns) and a GSD of 1.20. The aggregate mixture was then stabilized from further growth by introducing 10.5 grams of a basic mixture of EDTA powder dissolved in sodium hydroxide and containing 30 percent solids thereby changing the pH of the mixture from a value of 2.6 to 4.5, followed by adding 4 percent of sodium hydroxide to arrive at a pH of about 7. The mixture was then heated to 93°C during which the pH decreased to 6.5. After 10 minutes at 93°C the particle size measure was 6.2 with a GSD of 1.20. After 60 minutes the pH was reduced to 4.7. The particle size measure was 6.4 with a GSD of 1.22. The mixture was then further heated for a period of 600 minutes at a pH of 4.7 and the particle size obtained was 6.4 µm (microns) with a GSD of 1.20. The resultant mixture was cooled and the toner obtained was washed 4 times with water and dried on the freeze dryer. The resulting toner was comprised of 25 percent magnetite, 57.1 percent noncrosslinked resin, 5 percent crosslinked resin, 4.4 percent carbon black, and 8.5 percent wax. The charge of the toner was 19.8 microC/g as measured against the FC076 carrier, similar to the control or the comparative toner. The development of the resulting toner as a function of development voltage under various throughput conditions illustrated that the toner performance was stable to aging under various throughputs of printing. The target MICR signal of 120 percent of the nominal (nominal being 100 percent) was achieved at a development voltage of 250. The toner was then evaluated in a Xerox Corporation DC 265 engine and toner development as a function of voltage did not change at different throughputs conditions, for example the development at time zero, and that after 1,000 prints including under zero throughput conditions (xerographic stress case) at a given voltage indicated little toner aging.
The above toner when fused in a Xerox Corporation DC 265 xerographic engine possessed a MFT (melt fusing temperature) of 187°C and a HOT offset temperature greater than about 210°C, (for example, about an estimated 214°C) the optimum temperature that could be measured by the temperature detector used. The shape factor of the toner was 125 where a SF of 100 is considered very smooth and spherical in shape; a SF of 145 is considered irregular in shape with a rough morphology; and a SF of 125 is considered a potato shape with a smooth surface.

Toner Preparation - PAC (0.1 pph) - with 50 nanometer gel; 1.25 pph of EDTA

79 Grams of MAGNOX B2550™ acicular magnetite composed of 21 percent FeO and 79 percent Fe₂O₃ having a particle size of about µm (0.6 micron) X 0.1 µm (micron) was added to 600 grams of water containing 1.3 grams of 20 percent aqueous anionic surfactant (NEOGEN RK™) to which 85 grams of an 18 percent carbon black REGAL 330^® solution were added. The resultant mixture was then polytroned or homogenized at a speed of 5,000 rpm for 3 minutes to provide a pigment dispersion. To the resulting pigment dispersion were added 90 grams of a dispersion of submicron polyethylene P 850 wax particles 30 percent solids followed by the addition of 320 grams of the anionic Latex A comprised of submicron latex particles (40 percent solids) of styrene/butylacrylate/beta CEA, and 64 grams of the crosslinked Latex B of styrene/butylacrylate/divinyl benzene beta CEA (25.5 percent solids) while polytroned at a speed of 5,000 rpm for a period of 5 minutes 300 grams of water were added to reduce the viscosity of the resulting blend to which was then added an aqueous PAC solution comprised 3.1 grams of 10 percent solids placed in 25 grams of 0.3M nitric acid.
The resulting blend was then heated to a temperature of 50°C while stirring for a period of 100 minutes to obtain a particle size of 5.5 µm (microns) with a GSD of 1.21. 140 Grams of the above noncrosslinked latex (Latex A) were then added to the aggregate mixture and stirred at 50°C for 120 minutes to provide a particle size of 6 µm (microns) and a GSD of 1.20. The aggregate mixture was then stabilized from further growth by introducing 13.4 grams of a basic mixture of EDTA powder dissolved in sodium hydroxide containing 30 percent solids to change the pH of the mixture from value of 2.6 to 4.9, followed by adding 4 percent sodium hydroxide resulting in a pH of about 70. The mixture was then heated to 93°C during which the pH decreased to 6.5. After 10 minutes at 93°C, the particle size measured was 6.1 with a GSD of 1.20. After 60 minutes, the pH was reduced to 4.6 by adding 4 percent nitric acid. The particle size measured was 6.3 with a GSD of 1.21. The mixture was then further heated for a period of 600 minutes at a pH of 4.6 and the particle size obtained was 6.4 µm (microns) with a GSD of 1.20. The resultant mixture was cooled and the toner obtained was washed 4 times with water and dried on the freeze dryer. The resulting toner was comprised of 25 percent magnetite, 57.1 percent noncrosslinked resin, 5 percent crosslinked resin, 4.4 percent carbon black, and 8.5 percent wax. The shape factor of this toner was 126. The charge of the toner was -17 microC/g measured against a carrier comprised of a ferrite carrier coated with a polymer mixture of butylmethylmethacrylate/methylmethylacrylate or preferably the carrier of the Xerox Corporation Docutech 2240 machine.

Toner Preparation- PAC (0.1 pph)- with 50 Nanometers Gel; 1.50 pph of EDTA:

79 Grams of MAGNOX B2550™ acicular magnetite composed of 21 percent FeO and 79 percent Fe₂O₃ having a particle size of about 0.6 µm (micron) X 0.1 µm (micron) were added to 600 grams of water containing 1.3 grams of 20 percent aqueous anionic surfactant (NEOGEN RK™) to which 85 grams of an 18 percent carbon black REGAL 330^® solution were added. The resultant mixture was then polytroned or homogenized at a speed of 5,000 rpm for 3 minutes to provide a pigment dispersion. To the resulting pigment dispersion were added 90 grams of a dispersion of submicron polyethylene P 850 wax particles (30 percent solids) followed by the addition of 320 grams of the anionic Latex A comprised of submicron latex particles (40 percent solids) of styrene/ butylacrylate/beta CEA, and 64 grams of the crosslinked Latex B of styrene/butylacrylate/divinyl benzene beta CEA (25.5 percent solids) while polytroned at a speed of 5,000 rpm for a period of 5 minutes. 300 Grams of water were added to reduce the viscosity of the resulting blend to which was then added an aqueous PAC solution comprised of 3.1 grams of 10 percent solids placed in 25 grams of 0.3M nitric acid.
The resulting blend was then heated to a temperature of 50°C while stirring for a period of 100 minutes to obtain a particle size of 5.4 µm (microns) with a GSD of 1.19. 140 Grams of the above noncrosslinked latex (Latex A) were then added to the aggregate mixture and stirred at 50°C for 120 minutes to provide a particle size of 5.8 µm (microns) and a GSD of 1.20. The aggregate mixture was then stabilized from further growth by introducing 16 grams of a basic mixture of EDTA powder dissolved in sodium hydroxide containing 30 percent solids to change the pH of the mixture from a value of 2.6 to 4.5, followed by adding 4 percent sodium hydroxide resulting in a pH of about 7. The mixture was then heated to 93°C during which the pH decreased to 6.3. After 10 minutes at 93°C the particle size measure was 6.3 with a GSD of 1.20. After 60 minutes, the pH was reduced to 4.5 by adding 4 percent nitric acid. The particle size measured was 6.3 with a GSD of 1.21. The mixture was then further heated for a period of 600 minutes at a pH of 4.5 and the particle size obtained was 6.4 µm (microns) with a GSD of 1.20. The resultant mixture was cooled and the toner obtained was washed 4 times with water and dried on the freeze dryer. The resulting toner was comprised of 25 percent magnetite, 57.1 percent noncrosslinked resin, 5 percent crosslinked resin, 4.4 percent carbon black, and 8.5 percent wax. The shape factor for this toner was 124. The dry toner charge triboelectric was -16.4 microC/g as measured against a carrier comprised of a ferrite carrier coated with a polymer mixture of butylmethylmethacrylate/methylmethylacrylate or preferably the carrier of the Xerox Corporation Docutech 2240 machine.

COMPARATIVE EXAMPLE

A comparative toner (T 2239) was prepared in a similar manner as the above Examples and where sodium hydroxide was used as a stabilizer instead of EDTA resulting in a particle size of 6.8 µm (microns) with a GSD of 1.23. The pH of the mixture was allowed to drift to below 6.8 during the ramping of the temperature to 93°C. The coalesce pH was reduced to a pH of 5.8 in stages over a period of 2 hours and the mixture resulting heated for a period of 10 hours. The resulting particle size was 7.6 µm (microns) with a GSD of 1.27. The charge of this toner against the carrier was 15.1 microC/g.

Claims

A toner process comprised of heating a mixture of an acicular magnetite dispersion, a colorant dispersion, a wax dispersion, a first latex containing a crosslinked resin, and a second latex containing a resin free of crosslinking in the presence of a coagulant to provide aggregates, stabilizing the aggregates with an organic complexing compound or salt thereof dissolved in a base, and further heating said aggregates to provide coalesced toner particles.
A process in accordance with claim 1 wherein said complexing compound is selected in an amount of from 0.5 to 2 percent by weight of toner.
A process in accordance with claim 1 wherein said coagulant is selected from the group consisting of polyaluminum chloride, polyaluminum sulfosilicate, aluminum sulfate, zinc sulfate, and magnesium sulfate, and optionally wherein from 80 to 90 percent of said coagulant metal ion is retained in said toner.
A process in accordance with claim 1 wherein said colorant is carbon black, and wherein said carbon black dispersion comprises carbon black particles of from 0.01 to 0.2 µm (micron) diameter dispersed in water and an anionic surfactant, and wherein said colorant is present in an amount of from 4 to 10 weight percent, and optionally wherein the amount of acicular magnetite selected is from 20 to 40 percent by weight of toner, said colorant is carbon black present in the amount of from 4 to 8 percent by weight of toner, and said wax is present in the amount of 4 to 12 percent by weight of toner; said crosslinked resin is present in the amount of 5 to 10 percent by weight; said uncrosslinked resin is present in an amount of 55 to 65 percent by weight of toner; and said coagulant is comprised of polymetal halide present in an amount of 0.02 to 2 percent by weight of toner.
A process in accordance with claim 1 wherein said wax dispersion contains a polyethylene wax, a polypropylene wax or mixtures thereof, water, and an anionic surfactant; and wherein said wax is selected in an amount of from 5 to 20 weight percent.
A process in accordance with claim 1 wherein said first latex contains a crosslinked resin in an amount of from 2 to 25 weight percent; and wherein said crosslinked resin possesses a molecular weight M_w of from 100,000 to 1,000,000, and an onset glass transition (Tg) temperature of 48°C to 58°C, and optionally wherein said crosslinked resin is poly(styrene butylacrylate, beta carboxy ethyl acrylate divinyl benzene).
A toner process comprised of heating a mixture of an acicular magnetite dispersion, a colorant dispersion, a first latex containing a crosslinked resin, and a second latex containing a resin free of crosslinking in the presence of a coagulant; adding an organic complexing compound salt dissolved in a base, and further heating said aggregates to provide coalesced toner particles.
A process comprising heating a mixture of magnetite, colorant, a first latex, and a second latex wherein the first latex contains a crosslinked polymer and the second latex is substantially free of a crosslinked polymer, and which heating is accomplished in the presence of a coagulant and an organic complexing compound salt base mixture, and wherein said heating comprises a first and second heating, which second heating is at a higher temperature than said first heating, and wherein said first heating is below the glass transition temperature Tg of said resin free of crosslinking, and said second heating is above the Tg of said resin free of crosslinking.