Cationic toner processes

Abstract: A process for the preparation of toner comprising (I) preparing, or providing a cationic emulsion resin latex comprised of at least one olefinic nonpolar monomer, a cationic olefinic monomer, a cationic free radical initiator, and optionally a chain transfer agent in an aqueous mixture comprised of a nonionic surfactant and a cationic surfactant, and which mixture is heated at a temperature of from about 60°C to about 95°C; (ii) adjusting the pH of said cationic latex to from about 10 to about 14 by the addition of a base; (iii) preparing, or providing a pigment dispersion, which dispersion is comprised of a pigment and an anionic surfactant, and optionally a charge control agent; (iv) shearing said pigment dispersion with the pH adjusted latex of (ii) and heating below about the resin Tg to form electrostatically bound toner size aggregates, and optionally adding a cationic surfactant to stabilize the size of the toner aggregates; and (v) heating said electrostatically bound toner size aggregates above about the Tg of the resin to form coalesced toner particles; followed by optionally filtering, washing and drying the toner obtained.

Description: The present invention is generally directed to toner processes, and more specifically, to aggregation and coalescence processes for the preparation of toner compositions. In embodiments, the present invention is directed to the economical in situ chemical preparation of toners without the utilization of the known pulverization and/or classification methods. The resulting toners can be selected for known electrophotographic imaging and printing processes, including color processes, and lithography. A number of advantages are associated with the processes of the present invention including enabling the generation of positively charging stable toners, such as from about 5 to about 30 microcoulombs per gram as measured by the Faraday Triboelectric Cage. In a number of prior art patents, the emulsion-aggregation process is primarily directed to anionic latexes and anionic initiators in acidic pH to enable the preparation of negative charging toners. With the present invention, positive charging toners are prepared by an emulsion aggregation process involving cationic latexes, and more importantly utilizing cationic initiators, and wherein the process is accomplished in basic pH range of from about 10 to about 14, preferably from about 10 to about 12. It is an object of the present invention to provide simple and economical processes for the direct preparation of black and stable colored toner compositions with, for example, excellent pigment dispersion and narrow GSD, and wherein rejection or pigment, especially yellow pigment, destabilization is avoided or minimized. It is another object of the present invention to provide emulsion/aggregation/coalescence processes wherein pigment destabilization, especially of yellow pigments, is avoided or minimized. According to one aspect of the present invention there is provided a process for the preparation of toner comprising (i) preparing, or providing a cationic emulsion resin latex comprised of at least one nonpolar olefinic monomer, a cationic olefinic monomer, a cationic free radical initiator, and optionally a chain transfer agent in an aqueous mixture comprised of a nonionic surfactant and a cationic surfactant, and which mixture is heated at a temperature of from 60°C to 95°C; (ii) adjusting the pH of said cationic latex to from 10 to 14 by the addition of a base; (iii) preparing, or providing a colorant dispersion, which dispersion is comprised of a colorant and an anionic surfactant, and optionally a charge control agent; (iv) shearing said colorant dispersion with the pH adjusted latex of (ii) and heating below about the resin Tg to form electrostatically bound toner size aggregates, and optionally adding a cationic surfactant to stabilize the size of the toner aggregates; and (v) heating said electrostatically bound toner size aggregates above the Tg of the resin to form coalesced toner particles; followed by optionally filtering, washing and drying the toner obtained. A preferred embodiment of the present invention is a process for the preparation of toner comprising (i) preparing, or providing a cationic latex generated by the emulsion free radical process of at least one olefinic monomer, such as styrene, butylacrylate, butadiene and mixtures thereof, at least one cationic monomer such as vinylpyridine, a cationic free radical initiator, such as 2,2'-azobis(N,N'-dimethylene isobutyramidine) dihydrochloride, a cationic surfactant such as benzyltrialkyl ammonium chloride, a nonionic surfactant such as polyethyleneoxidephenylnonylether, and optionally a chain transfer agent, such as dodecanethiol and carbon tetrabromide, in water at a temperature of from 60 to 75°C for a duration of from 3 to 9 hours; (ii) adjusting the pH of the latex to 10 to 14 by the addition of a base such as an alkali metal carbonate like sodium carbonate or an alkali metal hydroxide like sodium hydroxide; (iii) preparing, or providing a pigment dispersion, which dispersion is comprised of a pigment, an anionic surfactant such as sodium dodecylbenzene sulfonate, and optionally a charge control agent; (iv) shearing the pigment dispersion with the pH adjusted latex resulting to form aggregates, especially electrostatically bound toner size aggregates, and optionally adding a cationic surfactant primarily to stabilize the size of the aggregates; heating below or at the resin Tg; followed by (v) heating the aggregates above or at the Tg of the resin to form coalesced toner particles; followed by filtering, washing and drying the toner product, and which toner is comprised of resin and pigment, and optional charge control additive or agent. The present invention in another preferred embodiment relates to a process for the preparation of toner comprising (i) providing a cationic emulsion resin latex comprised of at least one olefinic nonpolar monomer, a cationic olefinic monomer, a cationic free radical initiator, and optionally a chain transfer agent in an aqueous mixture comprised of a nonionic surfactant and a cationic surfactant, and which mixture is heated at a temperature of from 60 to 95°C for a duration of from 3 to 9 hours; (ii) adjusting the pH of said cationic latex to from 10 to 14, and preferably to 12 by the addition of a base; (iii) providing a pigment dispersion, which dispersion is comprised of a pigment, and an anionic surfactant, and optionally a charge control agent; (iv) shearing the pigment dispersion with the pH adjusted latex of (ii) to form electrostatically bound toner size aggregates, optionally and preferably adding a cationic surfactant to stabilize the size of the toner aggregates; heating below the resin Tg; (v) heating the electrostatically bound toner size aggregates above the Tg of the resin to form coalesced toner particles; followed by optionally filtering, washing and drying the toner obtained. A further preferred process comprises shearing a pigment dispersion comprised of a pigment, and an anionic surfactant, and optionally a charge control agent with a latex dispersion at a pH of from 10 to 14 and preferably 12, wherein the latex dispersion is comprised of a cationic emulsion latex comprised of at least one olefinic nonpolar monomer, at least one cationic olefinic monomer, a cationic free radical initiator, and optionally a chain transfer agent in an aqueous mixture comprised of a nonionic surfactant and cationic surfactant, and which mixture is heated; and heating above the Tg of the resin to form coalesced toner particles. The process sequence can be in the order as illustrated herein, such as (i) to (v), however, other sequences can be selected in embodiments, for example the pigment dispersion can be added to and/or mixed with the latex, the latex can be added to and/or mixed with the pigment dispersion, the latex and pigment dispersion can be prepared, the latex and the pigment dispersion can be provided, and the like. In embodiments, the present invention is directed to processes for the preparation of toner compositions, which processes comprise initially attaining or generating a cationic emulsion latex comprised of a resin derived from the free-radical polymerization in water of an olefinic monomer, such as styrene, butyl acrylate, butadiene, mixtures thereof and the like, and at least one cationic monomer component, such as vinylpyridine, in an aqueous surfactant mixture containing a cationic surfactant, a nonionic surfactant and a cationic initiator, such as a water soluble azo component, and optionally at least one chain transfer, such as a thiol or halogenated carbon, to result in a latex; heating the mixture to generate an emulsion latex mixture comprised of polymeric particles in water wherein the particle diameter size of the suspended resin mixture is, for example, from 0.01 to 0.5 µm (micron). The cationic latex is then treated with base, such as sodium hydroxide, to adjust the pH to 10 to 14. Thereafter, a pigment dispersion is prepared, for example, by dispersing an aqueous mixture of a pigment or pigments, such as carbon black like REGAL 330®, phthalocyanine, quinacridone or RHODAMINE B™ type with an anionic surfactant, such as sodium dodecylbenzene sulfonate, by utilizing a high shearing device, such as a Brinkmann Polytron, and thereafter, shearing this mixture with the prepared cationic latex by utilizing a high shearing device, such as a Brinkmann Polytron, a sonicator or microfluidizer, and thereafter, heating below the resin Tg resulting in a flocculation, or heterocoagulation of the polymer or resin with the pigment particles caused primarily by the neutralization of anionic surfactant absorbed on the resin particles with the oppositely charged cationic surfactant absorbed on the pigment particle; and further stirring the mixture using a mechanical stirrer at 250 to 500 rpm while heating below the resin Tg, for example from 5 to 15°C, and allowing the formation of electrostatically stabilized aggregates ranging in size of from 0.5 µm (micron) to 10 µm (microns) in volume average diameter; followed by heating above the resin Tg, for example from 5 to 50°C, to cause coalescence of the latex, and pigment particles, followed by washing with, for example, hot water at 40 to 70°C to remove, for example, surfactants, and drying, such as by use of an Aeromatic fluid bed dryer, freeze dryer, or spray dryer, whereby toner particles comprised of resin, pigment, and optional charge control additive with various particle size diameters can be obtained, such as from 1 to 10 µm (microns) in volume average particle diameter as measured by the Coulter Counter. Illustrative examples of specific resin particles, resins or polymers selected for the latex in the process of the present invention, and resulting from the nonpolar olefinic monomer, and the cationic olefinic monomer include polymers, such as terpoly-(styrene-butadiene-vinylpyridine), terpoly-(styrene-butylacrylate-vinylpyridine), terpoly-(butylacrylate-butadiene-vinylpyridine), terpoly-(styrene-butylmethacrylate-vinylpyridine), terpoly-(styrene-ethylacrylate-vinylpyridine), terpoly-(propylacrylate-butadiene-vinylpyridine), terpoly-(styrene-2-ethylhexylmethacrylate-vinylpyridine), terpoly-(styrene-butadiene-acrylamide), terpoly-(styrene-butylacrylate-acrylamide), terpoly-(butylacrylate-butadiene-acrylamide), terpoly-(styrene-butylmethacrylate-acrylamide), terpoly-(styrene-ethylacrylate-acrylamide), terpoly-(propylacrylate-butadiene-acrylamide), terpoly-(styrene-butadiene-methacrylamide), terpoly-(styrene-butylacrylate-methacrylamide), terpoly-(butylacrylate-butadiene-methacrylamide), terpoly-(styrene-butylmethacrylate-methacrylamide), terpoly-(styrene-ethylacrylate-acrylamide), terpoly-(propylacrylate-butadiene-acrylamide), terpoly-(styrene-2-ethylhexylmethacrylate-acrylamide), and mixtures thereof. The resin selected can be present in various effective amounts, such as from 85 weight percent to 98 weight percent of the toner. The olefinic monomer selected for the process of the present invention includes in embodiments, for example, styrene, methylstyrene, butadiene, isoprene, methyl acrylate, ethyl acrylate, propyl acrylate, butyl acrylate, pentyl acrylate, hexyl acrylate, 2-ethyl acrylate, octyl acrylate, decyl acrylate, lauryl acrylate, stearyl acrylate, methyl methacrylate, ethyl methacrylate, propyl methacrylate, butyl methacrylate, pentyl methacrylate, hexyl methacrylate, 2-ethyl methacrylate, octyl methacrylate, decyl methacrylate, lauryl methacrylate, stearyl methacrylate, mixtures thereof, and this monomer is selected in various effective amounts, such as for example from 80 to 95 percent of the cationic emulsion resin. The cationic monomer selected for the process of the present invention includes basic olefinic monomers, such as 2-vinylpyridine, 3-vinylpyridine, 4-vinylpyridine, acrylamide, methacrylamide, vinylpyrrolidone, vinyl-N-methylpyridinium chloride, 3-methacryloxy-2-hydroxypropyltrimethyl ammonium chloride salt, acryloxy-2-ethyl-tetralkyl ammonium chloride, acryloxy-3-propyl-tetralkyl ammonium chloride, methacryloxy-2-ethyl-tetralkyl ammonium chloride, methacryloxy-3-propyl-tetralkyl ammonium chloride, mixtures thereof and the like, and wherein the alkyl group contains, for example, from 1 to 25 carbon atoms, such as methyl, ethyl, propyl, butyl, pentyl, hexyl, octyl, and wherein the cationic monomer is selected in various effective amounts, such as from 1 to 20, and from 5 to 10 percent of the emulsion resin. Examples of cationic initiators selected for the process of the present invention include azo derivitized water soluble initiators, such as 2,2'-azobis(N,N'-dimethylene isobutyramidine) dihydrochloride, 2,2'-azobis(2-amidinepropane) dihydrochloride, 2,2'-azobis-2-methyl-N-[1,1-bis-(hydroxymethyl)-2-hydroxyethyl] propion-amide, 2,2'-azobis-2-methyl-N-[1,1-bis-(hydroxymethyl)-ethyl] propion-amide, 2,2'-azobis(isobutyramide) dihydrate, mixtures thereof, and which initiator is selected in various effective amounts, such as from 0.5 to 5 percent of the emulsion resin. These and similar initiators are available from Wako Chemical Inc. as VA-080, VA-082, VA-086 and VA-088. Examples of chain transfer agents selected for the process of the present invention include methanethiol, ethanethiol, propanethiol, butanethiol, pentanethiol, hexanethiol, decanethiol, dodecanethiol, carbon tetrabromide, carbon tetrachloride, bromoform, chloroform mixtures thereof, and which agents are selected in various effective amounts, for example from 0.01 to 1 percent of the emulsion resin. Surfactants in amounts of, for example, 0.1 to 25 weight selected in embodiments include, for example, nonionic surfactants such as dialkylphenoxypoly(ethyleneoxy) ethanol, available from Rhone-Poulenac as IGEPAL CA-210™, IGEPAL CA-520™, IGEPAL CA-720™, IGEPAL CO-890™, IGEPAL CO-720™, IGEPAL CO-290™, IGEPAL CA-210™, ANTAROX 890™ and ANTAROX 897™. An effective concentration of the nonionic surfactant is in embodiments, for example, from 0.01 to 10 percent by weight, and preferably from 0.1 to 5 percent by weight of monomer, or monomers selected to prepare the copolymer resin of the emulsion or latex blend. Examples of ionic surfactants include sodium dodecylsulfate (SDS), sodium dodecylbenzene sulfonate, sodium dodecylnaphthalene sulfate, dialkyl benzenealkyl, sulfates and sulfonates, abitic acid, available from Aldrich, NEOGEN R™, NEOGEN SC™ obtained from Kao. 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 or monomer used to prepare the copolymer resin particles of the emulsion or latex blend. Examples of anionic surfactants that can be selected in various effective amounts, such as from 1 to 10 weight percent, include sodium dodecylbenzene sulfonate, sodium dodecylnaphthalene sulfate, dialkyl benzenealkyl, sulfates and sulfonates, abitic acid, available from Aldrich, NEOGEN R™, NEOGEN SC™ obtained from Kao. They can also be selected from nonionic surfactants, such as 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, dialkylphenoxy poly(ethyleneoxy) ethanol, available from Rhone-Poulenac as IGEPAL CA-210™, IGEPAL CA-520™, IGEPAL CA-720™, IGEPAL CO-890™, IGEPAL CO-720™, IGEPAL CO-290™, IGEPAL CA-210™, ANTAROX 890™ and ANTAROX 897™. In embodiments, known cationic surfactants can be selected for the emulsion resin blend, such as an alkylbenzalkanium halide, especially the chloride, reference U.S. Patent 5,370,964, especially column 22, lines 21 to 40. An effective amount of cationic surfactant is selected, for example the amount can be from 0. 01 to 10, and more specifically, from 0.1 to 5 weight percent of the components present in the emulsion resin latex. Various known colorants or pigments present in the toner in an effective amount of, for example, from 1 to 25 percent by weight of the toner, and preferably in an amount of from 1 to 10 weight percent that can be selected include carbon black like REGAL 330®; magnetites, such as Mobay magnetites MO8029™, MO8060™; Columbian magnetites; MAPICO BLACK™ and surface treated magnetites; and the like. As colored pigments, there can be selected cyan, magenta, yellow, red, green, brown, blue or mixtures thereof. Generally, colored pigments that can be selected are cyan, magenta, or yellow pigments, and mixtures thereof. The toner may also include known charge additives in effective amounts of, for example, from 0.1 to 5 weight percent such as alkyl pyridinium halides, bisulfates, the charge control additives of U.S. Patents 3,944,493; 4,007,293; 4,079,014; 4,394,430 and 4,560,635, which illustrates a toner with a distearyl dimethyl ammonium methyl sulfate charge additive, negative charge enhancing additives like aluminum complexes. Surface additives that can be added to the toner compositions after washing or drying are known and include, for example, metal salts, metal salts of fatty acids, colloidal silicas, mixtures thereof and the like, which additives are usually present in an amount of from 0.1 to 2 weight percent, reference U.S. Patents 3,590,000; 3,720,617; 3,655,374 and 3,983,045. Preferred additives include zinc stearate and AEROSIL R972® available from Degussa in amounts of from 0.1 to 2 percent which can be added during the aggregation process or blended into the formed toner product. Developer compositions can be prepared by mixing the toners obtained with the processes of the present invention with known carriers or carrier particles, including coated carriers, such as steel, ferrites, and the like, reference U.S. Patents 4,937,166 and 4,935,326, for example from 2 percent toner concentration to 8 percent toner concentration. Imaging methods are also envisioned with the toners of the present invention, reference for example a number of the patents mentioned herein, and U.S. Patent 4,265,660. At least one in embodiments refers, for example, to 1 to 10, and more specifically, from 1 to 5, preferably from 1 to 3, and at least one includes one. Examples of components, such as surfactants, selected for the processes of the present invention are illustrated in a number of patents mentioned herein, such as 5,346,797. COMPARATIVE EXAMPLE I Preparation of a latex comprised of 30 percent resin particles in water containing 1.7 percent nonionic surfactant (ANTAROX™) and 1.8 percent of cationic surfactant (SANIZOL B™), and wherein the resin is derived from styrene, butyl acrylate, and 3-methacryloxy-2-hydroxypropyltrimethyl ammonium chloride, dodecanethiol, carbon tetrabromide and an anionic initiator (ammonium persulfate). A 1 liter Buchi reactor equipped with a mechanical stirrer was charged with styrene (328 grams), butyl acrylate (72 grams), dodecanethiol (12 grams), carbon tetrabromide (4 grams), 3-methacryloxy-2-hydroxypropyltrimethyl ammonium chloride (16 grams), water (500 grams), ANTAROX™ (8.6 grams), SANIZOL B™ (9 grams) and ammonium persulfate (4 grams). The mixture resulting was heated to 70°C under nitrogen atmosphere for a duration of 6 hours. A 10 gram sample of this resin mixture was then freeze dried and evaluated with the following results: a resin number average molecular weight of 10,088 and a resin weight average molecular weight of 75,291, as measured by gel permeation chromatography using polystyrene as the standard. The glass transition of the resin was found to be 56°C using the DuPont differential scanning calorimeter. COMPARATIVE EXAMPLE II Attempt to prepare a cyan toner comprised of 5 percent by weight of PV FAST BLUE™, and 95 percent by weight of terpoly(styrene-butylacrylate-3-methacryloxy-2-hydroxypropyltrimethyl ammonium chloride) of Comparative Example I follows. In a 1 liter flask equipped with a mechanical stirrer were added 300 grams of the latex of Comparative Example I. To this stirred mixture, was then added dropwise a 1 percent aqueous solution of potassium hydroxide until the pH was about 10, as measured using Litmus pH paper. The mixture was left stirring at 25°C for a duration of three hours. In a separate 300 milliliter metal beaker was prepared a pigment dispersion by adding 15 grams of PV FAST BLUE™, 1.2 grams of NEOGEN R™ (anionic surfactant) and 100 grams of water, and which mixture was dispersed using a polytron at 8,000 revolutions per minute for a duration of 5 minutes. The pigment dispersion was then added to the 1 liter flask containing the latex followed by the addition of 100 grams of water. Particle aggregation did not occur. The mixture was then heated to about 60°C during a 1 hour interval, and no aggregation was observed. The above latex comprised of a cationic resin derived with an anionic initiator, such as ammonium persulfate, did not result in the aggregation or flocculation of resin particles and pigment. Adjusting the pH of the mixture to a pH of 2, 4, 7 or 12 also resulted in no particle aggregation. EXAMPLE III Preparation of a latex comprised of 30 percent resin particles in water containing 1.7 percent nonionic surfactant (ANTAROX™) and 1.8 percent of cationic surfactant (SANIZOL B™), dodecanethiol, carbon tetrabromide and a cationic initiator (2,2'-azobis(N,N'-dimethylene isobutyramidine) dihydrochloride), and wherein the resin is derived from styrene and butyl acrylate, and 3-methacryloxy-2-hydroxypropyltrimethyl ammonium chloride. A 1 liter Buchi reactor equipped with a mechanical stirrer was charged with styrene (328 grams), butyl acrylate (72 grams), dodecanethiol (12 grams), carbon tetrabromide (4 grams), 3-methacryloxy-2-hydroxypropyltrimethyl ammonium chloride (16 grams), water (500 grams), ANTAROX™ (8.6 grams), SANIZOL B™ (9 grams) and 2,2'-azobis(N,N'-dimethylene isobutyramidine) dihydrochloride (13.5 grams). The resulting mixture was heated to 70°C under a nitrogen atmosphere for a duration of 6 hours. A 10 gram sample was then freeze dried and evaluated with the following results: a number average molecular weight of 9,390 and a weight average molecular weight of 70,291 for the resin, as measured by gel permeation chromatography using polystyrene as standard. The glass transition of the resin was found to be 60°C using the DuPont differential scanning calorimeter. EXAMPLE IV A 7.2 µm (micron) cyan toner comprised of 5 percent by weight of PV FAST BLUE™, and 95 percent by weight of terpoly(styrene-butylacrylate-3-methacryloxy-2-hydroxypropyltrimethyl ammonium chloride) of Example III was prepared as follows: In a 1 liter flask equipped with a mechanical stirrer were added 300 grams of the latex of Example III. To this stirred mixture was then added dropwise a 1 percent aqueous solution of potassium hydroxide until the pH was about 10, as measured using Litmus pH paper. The mixture was left stirring at 25°C for a duration of three hours. In a separate 300 milliliter metal beaker was prepared a pigment dispersion by adding 15 grams of PV FAST BLUE™, 1.2 grams of NEOGEN R™ (anionic surfactant) and 100 grams of water, and which pigment was dispersed using a polytron at 8,000 revolution per minute for a duration of 5 minutes. The pigment dispersion was then added to the 1 liter flask containing the latex followed by the addition of 100 grams of water. Particle aggregation occurred and the flask mixture was homogenized at 2,000 revolutions per minute for a duration of 2 minutes at 25°C. The mixture was then heated to about 60°C over a 1 hour period, followed by the addition of 0.5 gram of SANIZOL B™ in 25 grams of water. The mixture was then heated to 96°C over a 2 hour period, followed by maintaining heating for an additional 3 hours, after which the mixture was cooled to room temperature, about 25°C, filtered off, washed excessively with water (about 16 liters), and dried by freeze drying. The toner particle size was then measured to be 7.2 µm (microns) with a geometric distribution of 1.32, as measured by the Coulter Counter. It is believed in the context of the present invention that the latex particle resin is to be derived with a cationic initiator and the other components of (i) to enable effective aggregation, coalescence, and the preparation of toners. EXAMPLE V Preparation of a latex comprised of 30 percent resin particles in water containing 1.7 percent nonionic surfactant (ANTAROX™) and 1.8 percent of cationic surfactant (SANIZOL B™), dodecanethiol, carbon tetrabromide and the cationic initiator (2,2'-azobis(N,N'-dimethylene isobutyramidine) dihydrochloride), and wherein the resin is derived from styrene, butyl acrylate, vinylpyridine, was prepared as follows: A 1 liter Buchi reactor equipped with a mechanical stirrer was charged with styrene (264 grams), butadiene (36 grams), dodecanethiol (1.12 grams), carbon tetrabromide (3.75 grams), vinylpyridine (15 grams), water (500 grams), ANTAROX™ (10 grams), SANIZOL B™ (9 grams) and 2,2'-azobis(N,N'-dimethylene isobutyramidine) dihydrochloride (6.0 grams). The mixture was heated to 70°C under nitrogen atmosphere for a duration of 6 hours. A 10 gram sample of the resin resulting was then freeze dried and was evaluated with the following results: a number average molecular weight of 6,697 and a weight average molecular weight of 24,498, as measured by gel permeation chromatography using polystyrene as standard. The glass transition of the resin was found to be 56°C using the DuPont differential scanning calorimeter. EXAMPLES VI to IX Using the procedure of Example IV, a series of toners comprised of 95 percent by weight of resin and 5 percent by weight of pigment were prepared and are listed in Table 1. Example Pigment Particle Size µm GSD Example VI PV FAST BLUE 5.4 (microns) 1.35 Example VII FANAL PINK 6.5 (microns) 1.32 Example VIII REGAL 330 8.4 (microns) 1.28 Example IX Pigment Yellow 14 9.1 (microns) 1.30 The triboelectric properties of the above prepared toners and the toner of Example IV were evaluated by roll milling 3 percent by weight of the toner with 97 percent by weight of carrier, about 90 µm (microns) in diameter, comprised of a steel core with a polymer mixture thereover of 60 percent of polyvinylidene fluoride (KYNAR®) and 40 percent of polymethylmethacrylate. The triboelectric charge was then evaluated with a Faraday Cage at 2 relative humidity zones (both 20 and 80 percent RH). The results are shown in Table 2 that follows. TONER Triboelectric Charge 20 RH 80 RH Example IV 50 30 Example VI 25 15 Example VII 45 20 Example VIII 60 28 Example IX 12 6

Claims: A process for the preparation of cationic toner comprising (i) preparing, or providing a cationic emulsion resin latex comprised of at least one nonpolar olefinic monomer, a cationic olefinic monomer, a cationic free radical initiator, and optionally a chain transfer agent in an aqueous mixture comprised of a nonionic surfactant and a cationic surfactant, and which mixture is heated at a temperature of from 60°C to 95°C; (ii) adjusting the pH of said cationic latex to from 10 to 14 by the addition of a base; (iii) preparing, or providing a colorant dispersion, which dispersion is comprised of a colorant and an anionic surfactant, and optionally a charge control agent; (iv) shearing said colorant dispersion with the pH adjusted latex of (ii) and heating below the resin Tg to form electrostatically bound toner size aggregates, and optionally adding a cationic surfactant to stabilize the size of the toner aggregates; and (v) heating said electrostatically bound toner size aggregates above the Tg of the resin to form coalesced toner particles; followed by optionally filtering, washing and drying the toner obtained. A process in accordance with claim 1 wherein said base of (ii) is an alkali metal hydroxide, preferably selected from the group consisting of sodium hydroxide, potassium hydroxide, magnesium hydroxide, barium hydroxide, cesium hydroxide, lithium hydroxide, calcium hydroxide, ammonium hydroxide, aluminum hydroxide, and mixtures thereof. A process in accordance with either of claims 1 or 2 wherein the nonpolar olefinic monomer is selected from the group consisting of styrene, methylstyrene, butadiene, isoprene, methyl acrylate, ethyl acrylate, propyl acrylate, butyl acrylate, pentyl acrylate, hexyl acrylate, 2-ethyl acrylate, octyl acrylate, decyl acrylate, lauryl acrylate, stearyl acrylate, methyl methacrylate, ethyl methacrylate, propyl methacrylate, butyl methacrylate, pentyl methacrylate, hexyl methacrylate, 2-ethyl methacrylate, octyl methacrylate, decyl methacrylate, lauryl methacrylate, stearyl methacrylate, and mixtures thereof. A process in accordance with any of claims 1 to 3 wherein the cationic olefinic monomer is selected from the group consisting of 2-vinylpyridine, 3-vinylpyridine, 4-vinylpyridine, acrylamide, methacrylamide, vinylpyrrolidone, vinyl-N-methylpyridinium chloride, 3-methacryloxy-2-hydroxypropyltrimethyl ammonium chloride salt, acryloxy-2-ethyl-tetralkyl ammonium chloride, acryloxy-3-propyl-tetralkyl ammonium chloride, methacryloxy-2-ethyl-tetralkyl ammonium chloride, methacryloxy-3-propyl-tetralkyl ammonium chloride, and mixtures thereof. A process in accordance with any of claims 1 to 4 wherein the cationic emulsion resin latex of (i) is selected from the group consisting of terpoly-(styrene-butadiene-vinylpyridine), terpoly-(styrene-butylacrylate-vinylpyridine), terpoly-(butylacrylate-butadiene-vinylpyridine), terpoly-(styrene-butylmethacrylate-vinylpyridine), terpoly-(styrene-ethylacrylate-vinylpyridine), terpoly-(propylacrylate-butadiene-vinylpyridine), terpoly-(styrene-2-ethylhexylmethacrylate-vinylpyridine), terpoly-(styrene-butadiene-acrylamide), terpoly-(styrene-butylacrylate-acrylamide), terpoly-(butylacrylate-butadiene-acrylamide), terpoly-(styrene-butylmethacrylate-acrylamide), terpoly-(styrene-ethylacrylate-acrylamide), terpoly-(propylacrylate-butadiene-acrylamide), terpoly-(styrene-butadiene-methacrylamide), terpoly-(styrene-butylacrylate-methacrylamide), terpoly-(butylacrylate-butadiene-methacrylamide), terpoly-(styrene-butylmethacrylate-methacrylamide), terpoly-(styrene-ethylacrylate-acrylamide), terpoly-(propylacrylate-butadiene-acrylamide), terpoly-(styrene-2-ethylhexylmethacrylate-acrylamide), and mixtures thereof. A process in accordance with any of claims 1 to 5 wherein the cationic initiator is a cationic water soluble initiator selected from the group consisting of 2,2'-azobis(N,N'-dimethylene isobutyramidine) dihydrochloride, 2,2'-azobis(2-amidinopropane) dihydrochloride, 2,2'-azobis(N,N'-dimethylene isobutyramidine), 2,2'-azobis-2-methyl-N-[I,I -bis(hydroxymethyl)2-hydroxyethyl] propionamide, 2,2'-azobis-2-methyl-N[1,1-bis(hydroxymethyl)ethyl] propionamide, and 2,2'-azobis(isobutyramide)dihydrate. A process in accordance with any of claims 1 to 6 wherein the nonpolar olefinic monomer is present in an amount of from 85 to 98 percent by weight of the resin present in the latex, the cationic olefinic monomer is present in an amount of from 2 to 15 percent by weight of the resin present in the latex, the optional chain transfer agent is present in an amount of from 0.5 to 3 percent by weight of the resin present in the latex, and the cationic initiator is present in an amount of from 0.5 to 5 percent by weight of the resin present in the latex. A process in accordance with any of claims 1 to 7 wherein the nonionic surfactant is selected from the group consisting of polyvinyl alcohol, 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, and dialkylphenoxy poly(ethyleneoxy)ethanol, and wherein the anionic surfactant is selected from the group consisting of sodium dodecyl sulfate, sodium dodecylbenzene sulfate, sodium dodecylnaphthalene sulfate and mixtures thereof. A process in accordance with claim 1 wherein said colorant is a pigment, preferably selected from carbon black, magnetite, cyan, yellow, magenta, and mixtures thereof. A process in accordance with any of claims 1 to 9 wherein the cationic surfactant is an alkylbenzalkonium chloride selected in an amount of from 0.01 to 10 weight percent.

Inventors: KEDIAN MAUREEN M, MYCHAJLOWSKIJ WALTER, ONG BENG S, PATEL RAJ D, SACRIPANTE GUERIONO G, KEDIAN, MAUREEN M., MYCHAJLOWSKIJ, WALTER, ONG, BENG S., PATEL, RAJ D., SACRIPANTE, GUERIONO G.
Applicants: XEROX CORP, XEROX CORPORATION
Application year: 1997
Main classification: G03G9
IPC codes: G03G9