Patent Application
20070292800
In accordance with the present invention a dispersion of a polymeric, a UV curable material, a UV photoinitiator, a solvent and optionally a charge control agent and a pigment dispersion are combined to form an organic phase. This mixture is permitted to stir overnight and then dispersed in an aqueous phase comprising a particulate stabilizer and optionally a promoter.
The resultant mixture is then subjected to mixing and homogenization. The flocculating agent is added to the aqueous phase either before or after mixing/homogenization. In this process, the particulate stabilizer forms an interface between the organic globules in the organic phase. Due to the high surface area associated with small particles, the coverage by the particulate stabilizer is not complete. Coalescence continues until the surface is completely covered by particulate stabilizer. Thereafter, no further growth of the particles occurs. Accordingly, the amount of the particulate stabilizer is inversely proportional to the size of the toner obtained. The relationship between the aqueous phase and the organic phase, by volume may range from 1:1 to approximately 9:1. This indicates that the organic phase is typically present in an amount from about 10% to 50% of the total homogenized volume.
Following the homogenization treatment, the solvent present is removed by evaporation or boiling, optionally under vacuum, and the resultant product washed and dried.
The solvents chosen for use in the organic phase steps may be selected from among any of the well-known solvents capable of dissolving polymers. Typical of the solvents chosen for this purpose are chloromethane, dichloromethane, ethyl acetate, vinyl chloride, n-propyl acetate, iso-propyl acetate, trichloromethane, carbon tetrachloride, ethylene chloride, trichloroethane, toluene, xylene, cyclohexanone, 2-nitropropane, and the like.
The particulate stabilizer selected for use herein may be selected from among highly crosslinked polymeric latex materials of the type described in U.S. Pat. No. 4,965,131 to Nair et al., or silicon dioxide. Silicon dioxide is preferred. It is generally used in an amount ranging from 1 to 15 parts, by weight, based on 100 parts of the total solids in the toner. The size and concentration of these stabilizers control and predetermine the size of the final toner particles. In other words, the smaller the size and/or the higher the concentration of such particles, the smaller the size of the final toner particles.
Any suitable promoter that is water soluble and affects the hydrophilic/hydrophobic balance of the solid dispersing agent in the aqueous solution may be employed in order to drive the solid dispersing agent, that is, the particulate stabilizer, to the polymer/solvent droplet-water interface. Typical of such promoters are sulfonated polystyrenes, alginates, carboxyl methylcellulose, tetramethyl ammonium hydroxide or chloride, diethylaminoethylmethacrylate, water-soluble complex resinous amine condensation products of ethylene oxide, urea and formaldehyde and polyethyleneimine. Also effective for this purpose are gelatin, casein, albumin, gluten and the like or non-ionic materials such as methoxycellulose. The promoter is generally used in an amount from about 0.2 to about 0.6 parts per 100 parts of aqueous solution by weight.
Various additives generally present in electrostatographic toner may be added to the polymer prior to dissolution in the solvent or in the dissolution step itself, such as charge control agents, waxes and lubricants. Suitable charge control agents are disclosed, for example, in U.S. Pat. Nos. 3,893,935 and 4,323,634 to Jadwin et al., U.S. Pat. No. 4,079,014 to Burness et al. and British Patent No. 1,420,839 to Eastman Kodak. Charge control agents are generally employed in small quantities such as from about 0 to 10 parts per hundred based upon the weight of the total solids content (weight of the toner) and preferably from about 0.2 to about 3.0 parts per hundred.
The present invention is applicable to the preparation of polymeric toner particles from any type of polymer that is capable of being dissolved in a solvent that is immiscible with water and includes compositions such as, for example, olefin homopolymers and copolymers, such as, polyethylene, polypropylene, polyisobutylene and polyisopentylene; polytrifluoroolefins; polytetrafluoroethylene and polytrifluorochloroethylene; polyamides, such as polyhexamethylene adipamide, polyhexamethylene sebacamide, and polycaprolactam; acrylic resins, such as polymethylmethacrylate, polymethylacrylate, polyethylmethacrylate and styrene-methylmethacrylate; ethylene-methylacrylate copolymers, ethylene-ethyl acrylate copolymers, ethylene-ethyl methacrylate copolymers, polystyrene and copolymers of styrene with unsaturated monomers such as butyl acrylate-styrene copolymer, cellulose derivatives, polyesters, polyvinyl resins and ethylene-vinyl alcohol copolymers and the like. Preferably, the polymer material is polyester or butyl acrylate-styrene copolymer. Optionally, the polymer material also may contain UV curable functional groups, such as ethylenic unsaturated groups or epoxide groups, to be polymerized upon exposure to a UV radiation source.
The UV curable toner embodiment of the invention comprise UV curable components containing mono-, di-, or polyfunctional ethylenic unsaturated groups or multi-functional epoxide groups. The UV curable components may be in liquid or solid forms. Examples of ethylenic unsaturated compounds include styrenic derivatives, vinyl ether, vinyl ester, allyl ether, allyl ester, N-vinyl caprolactam, N-vinyl caprolacton, acrylate, or methacrylate monomers. The examples of such compounds may also include oligomers of epoxy acrylates, urethane acryaltes, unsaturated polyesters, polyester acrylates, polyether acrylates, vinyl acrylates and polyene/thiol systems. The most commonly used UV curable components contain the acrylate unsaturation groups. The backbone structures of acrylate compounds include aliphatic, cycloaliphatic, aromatic, alkosylated, polyols, polyester, polyether, silicone, and polyurethane. The UV curable ethylenic unsaturated components may be polymerized via free radical polymerization initiated by a photoinitiator upon exposure to radiation source, e.g. UV radiation. The ethylenic unsaturated groups are consumed during the polymerization process and the degree of unsaturated groups conversion is a measure of the degree of cure. The multi-functional epoxide compounds can be polymerized via cationic polymerization initiated by a photogenerated active species upon exposure to radiation source, e.g. UV radiation. However, cationic UV curing is not restricted to epoxide. The radiation-curable components typically have a weight average molecular weight ranging from 100 to 10,000, and preferably in a range from 400 to 4,000. The degree of unsaturation or epoxy group ranges from 2 to 30% by weight. Depending on specific application and final cured image properties, the weight ratio of UV curable components to non-reactive polymer binders in toner formulations may range from 0.1 to 100 percent.
One embodiment of the invention comprises a photoinitiator and/or a co-initiator that is chosen from those commonly used for radiation curing purposes. The appropriate photoinitiators which can be used in the present invention are direct cleavage (Norrish Type I or II) photoinitiators including benzoin and its derivatives, benzil ketals and its derivatives, acetophenone and its derivatives, hydrogen abstraction photoinitiators including benzophenone and its alkylated or halogenated derivatives, anthraquinone and its derivatives, thioxanthone and its derivatives, and Michler's ketone. Examples of photoinitators which may be suitable for the present invention are benxophenone, chlorobenzophenone, 4-benzoyl-4′-methyldiphenyl sulphide, acrylated bensophenone, 4-phenyl benzophenone, 2-chlorothioxanthone, isopropyl thioxanthone, 2,4-dimethyl thioxanthone, 2,4 dichlorothioxantlhone, 3,3′-dimthyl-4-methoxybenzophenone, 2,4-diethylthixanthone, 2,2-diethoxyacetophenone, a,a-dichloroaceto,p-phenoxyphenone, 1-hydroxycyclohexyl actecophenone, a,a-dimethyl,a-hydroxy acetophenone, benzion, benzoin ethers, benzyl ketals, 4,4′-dimethyl amino-benzophenone, 1-phenyl-1,2-propane dione-2 (O-ethoxy carbonyl) oxime, acylphosphine oxide, 9,10-phenantrene quinine, and the like. It may optionally be beneficial to use photosensitizers in combination with a radical generating initiator, wherein the sensitizer absorbs light energy and transfers it to the initiator. Examples of photsensitizers include thioxanthone derivatives and tertiary amines, such as tirethanolamine, methyl diethanolamine, ethyl 4-dimethyl aminobenzoate, 2(n-butoxy)ethyl 4-dimethylamino benzoate, 2-ethyl hexyl p-dimethyl-aminobenzoate, amyl p-dimethyl-aminobenzoate and tri-isopropanolamine. Photoinitiated cationic polymerization uses salts of complex organic molecules to initiate cationic chain polymerization in oligomers or monomers containing epoxides. Cationic photoinitiators include, but are not limited to diaryliodonium and triarylsulfonium salts with non-nucleophilic complex metal halide anions. Examples of cationic photoinitiators are aryldiazonium salts of the general formula Ar—N2+X−, wherein Ar is an aromatic ring such as butyl benzene, nitrobenzene, dinitrobenzene, or the like and X is BF4, PF6, AsF6, SbF6, CF3SO3, or the like; diaryliodonium salts of the general formula Ar2 I+ X−, wherein Ar is an aromatic ring such as methoxy benzene, butyl benzene, butoxy benzene, octyl benzene, didecyl benzene, or the like, and X is an ion of low nucleophilicity, such as BF4, PF6, AsF6, SbF6, CF3SO3, and the like; triarylsulfonium salts of the general formula Ar3 S+ X−, wherein Ar is an aromatic ring such as hydroxy benzene, methoxy benzene, butyl benzene, butoxy benzene, octyl benzene, dodecyl benzene, or the like and X is an ion of low nucleophilicity, such as BF4, PF6, AsF6, SbF6, CF3SO3, or the like. The toner compositions may contain 0.1-20% by weight of photoinitiators, and preferably contain 1 to 10% by weight. UV curing technology via radical polymerization and cationic polymerization are well known. The UV curing materials and processes are reviewed in, for example, “UV & EB Curing Technology & Equipment Volume I” by R. Mehnert, A. Pincus, I. Janorsky, R. Stowe and A. Berejka, disclosure of which is totally incorporated herein by reference.
Optionally, pigments can be dispersed in the polymer, insoluble in water and yield strong permanent color. Typical of such pigments are the organic pigments such as phthalocyanines, lithols and the like and inorganic pigments such as TiO2, carbon black, and the like. Typical of the phthalocyanine pigments are copper phthalocyanine, a mono-chloro copper phthalocyanine, and hexadecachloro copper phthalocyanine. Other organic pigments suitable for use herein include anthraquinone vat pigments such as vat yellow 6GLCL1127, quinone yellow 18-1, indanthrone CL1106, pyranthrone CL1096, brominated pyranthrones such as dibromopyranthrone, vat brilliant orange RK, anthramide brown CL1151, dibenzanthrone green CL1101, flavanthrone yellow CL1118; azo pigments such as toluidine red C169 and hansa yellow; and metallized pigments such as azo yellow and permanent red. The carbon black may be any of the known types such as channel black, furnace black, acetylene black, thermal black, lamp black, and aniline black. The pigments are employed in an amount sufficient to give a content thereof in the toner from about 1% to 40%, by weight, based upon the weight of the toner, and preferably within the range of 4% to 20%, by weight.
Flocculating agents are listed in detail in the book “The Chemistry of Silica” by R. K. Iler (John Wiley & Sons, 1979, pp. 384-396). Preferred flocculating agents suitable for use in the present invention include cationic surfactants, basic metal salts, cationic polymers and inorganic colloids. The flocculating agent may comprise 0.0001-50% by weight of the total solids present in the organic phase.
Preferred inorganic colloids are colloidal alumina and any colloidal silica with opposite charge of colloidal silica used as a stabilizer in the present invention such as positively charged LUDOX CL® silica or negatively charged NALCOAG 1060® silica.
A spherical particle is well known and is defined as a three dimensional object which has all points on the surface essentially equidistant from a central point. A non-spherical particle is defined as a three dimensional object in which individual points on the surface have varying distances from a central point. This will be seen as irregular, or oblong, or wrinkled shapes and surfaces. The toner particles prepared by the present invention have a particle size of from 3 to 20 microns, preferably 4 to 12 microns.
The invention will be more fully understood by reference to the following exemplary embodiment, which is set forth solely for purposes of exposition and is not to be construed as limiting. Unless otherwise indicated all percentages are by weight.
The invention is demonstrated by the following examples.
An aqueous mixture was prepared by mixing about 240 ml of distilled water, 10 grams of Nalcoag TM1060 (50% solid), which is a sodium stabilized silica suspension by the Nalco Chemical Company, 2.2 ml of a 10 percent solution of poly(adipic acid-co-methylaminoethanol) and 1.5 grams of potassium phthalate. An organic solution was made by mixing 100 grams of ethyl acetate, 30 grams of a 70% solution of phenoxy modified epoxy diacrylate resin in ethyl acetate, which is called UV-93 from InChem Corporation, 2 grams of CN 968 and 2 grams of SR1130, both from Sartomer Company. The organic solution and aqueous phase were then mixed together and sheared by using a Silverson mixer followed by a Microfluidizer unit sold from Microfluidics operating at 275 kPa. The white emulsion was then heated to 40° C. under vacuum for about 30 minutes, during which the organic solvent, ethyl acetate evaporated from the mixture and the organic emulsion then became solid particles. The solid particles were washed with water and then stirred for 3 hours in a 1.0N sodium hydroxide solution to remove the silica particles from their surfaces. The particles were then filtered, washed with water and dried in a vacuum oven at 40° C. overnight. The collected toner particles are spherical with number average diameter of 6.8 micron and volume average diameter of 7.4 micron.
The toner particles of Example 1 were developed through electrophotographic process and applied on the surface of substrates, and then fused through fusing rollers at about 130° C. The fused images were cured under microwave-powered UV lamp from Fusion UV Systems, Inc. The energy of the UV curing is set to be about 250 mJ/cm2 from H-type UV lamp and belt speed around 60 f/m. The organic solvent resistance, e.g. ethyl acetate, acetone, of the UV cured images is significantly better than the non-cured images based on the same Example 1 toner.
The UV cured images were put into a 65° C. and 95% RH environmental control oven. The image remained in the oven overnight with face-to-face contact to another image and predetermined pressure equal to 500 sheets of stacked paper. The UV cured images showed no sign of change or block problem after they are removed from the oven. In comparison, the non-UV cured images from Example 1 were fused together and surface images were totally damaged.
The procedure of Example 1 was repeated except that the organic phase was prepared from 100 grams of ethyl acetate, 18.4 grams of P3125 and 4.6 grams of P3307, both from DSM, in addition to 2 grams of CN 968 and 2 grams of SR1130, both from Sartomer Company. The obtained toner particles from the evaporative limited coalescence process are spherical with number average diameter of 6.0 micron and volume average diameter of 8.2 micron.
The toner particles of Example 2 were developed through electrophotographic process and applied on the surface of substrates, and then fused through fusing rollers at about 130° C. The fused images were cured at about 250 mJ/cm2 with H-type UV lamp and belt speed around 60 f/m. The organic solvent resistance, e.g. ethyl acetate, acetone, of the UV cured images is significantly better than the non-cured images based on the same Example 2 toner. The UV cured images were put into a 65° C. and 95% RH environmental control oven. The image remained in the oven overnight with face-to-face contact to another image and predetermined pressure equal to 500 sheets of stacked paper. The UV cured images showed no sign of change or block problem after they are removed from the oven. In comparison, the non-UV cured images from Example 2 were fused together and surface images were totally damaged.
The procedure of Example 1 was repeated except that the organic phase was prepared from 100 grams of ethyl acetate, 24 grams of FPESL-2, low molecular weight polyester from Kao Corporation, 0.1 grams of CN968 from Sartomer Company, 0.05 grams of Bontron E84 from Orient Chemicals Company, 1 gram of ESACURE ONE from Sartomer. After ethyl acetate was removed from the white emulsion, the toner particles were washed with water and enough 1N sodium hydroxide solution was added dropwise to raise the pH of white suspension to 12. After stirred for 1 minute, the particles were then filtered, washed with water and dried in a vacuum oven at 40° C. overnight. The collected toner particles are spherical with number average diameter of 7.4 micron and volume average diameter of 7.9 micron.
The toner particles of Example 3 were developed through electrophotographic process and applied on the surface of substrates, and then fused through fusing rollers at about 130° C. The fused images were cured at about 250 mJ/cm2 with H-type UV lamp and belt speed around 60 f/m. The organic solvent resistance, e.g. ethyl acetate, acetone, of the UV cured images is significantly better than the non-cured images based on the same Example 2 toner. The UV cured images were put into a 60° C. and 95% RH environmental control oven. The image remained in the oven overnight with face-to-face contact to another image and predetermined pressure equal to 500 sheets of stacked paper. The UV cured images showed no sign of change or block problem after they are removed from the oven. In comparison, the images from Example 3 but without UV curing were fused together and surface images were totally damaged.
The procedure of Example 1 was repeated except that the organic phase was prepared from 110 grams of ethyl acetate, 24 grams of Pro7403 and 0.1 grams of CN968 from Sartomer, 0.36 grams of diphenyl sulfone from Sigma-Aldrich and 1 gram of Irgacure 184 from Ciba Specialty Chemicals. The organic solution and aqueous phase were then mixed together and sheared by using a Silverson mixer followed by a Microfluidizer unit sold from Microfluidics operating at 275 kPa. While homogenized by microfluidizer, the obtained emulsion was simultaneously added 4 g of 1% aqueous solution of poly((adipic acid-co-(methylaminoethanol)90-co-(N-methyl-N-benzyl-diethanolammonium chloride)10) dropwise. The white emulsion was then heated to 40° C. under vacuum for about 30 minutes, during which the organic solvent, ethyl acetate evaporated from the mixture and the organic emulsion then became solid particles. The toner particles were washed with water and enough 1N sodium hydroxide solution was added dropwise to raise the pH of white suspension to 12. After stirred for 1 minute, the particles were then filtered, washed with water and dried in a vacuum oven at 40° C. overnight. The collected toner particles are irregular and potato-like with number average diameter of 6.9 micron and volume average diameter of 8.7 micron.
The toner particles of Example 4 were developed through electrophotographic process and applied on the surface of substrates, and then fused through fusing rollers at about 130° C. The fused images were cured at about 250 mJ/cm2 with H-type UV lamp and belt speed around 60 f/m. The organic solvent resistance, e.g. ethyl acetate, acetone, of the UV cured images is significantly better than the non-cured images based on the same Example 2 toner. The UV cured images were put into a 60° C. and 95% RH environmental control oven. The image remained in the oven overnight with face-to-face contact to another image and predetermined pressure equal to 500 sheets of stacked paper. The UV cured images showed no sign of change or block problem after they are removed from the oven. In comparison, the non-UV cured images from Example 4 were fused together and surface images were totally damaged.
The procedure and formulation of Example 3 was repeated except that no photoinitiator, ESACURE ONE from Sartomer, was added to the organic phase. The collected toner particles are spherical with number average diameter of 7.2 micron and volume average diameter of 8.7 micron.
The toner particles of Comparative Example 1 were developed through electrophotographic process and applied on the surface of substrates, and then fused through fusing rollers at about 130° C. The fused images were cured at about 250 mJ/cm2 with H-type UV lamp and belt speed around 60 f/m. The UV cured images were put into a 60° C. and 95% RH environmental control oven. The image remained in the oven overnight with face-to-face contact to another image and predetermined pressure equal to 500 sheets of stacked paper. However, due to lack of photoinitiator in the toner formulation, the cured images were fused together and showed no difference from those images without UV curing.
The invention has been described in detail with particular reference to certain preferred embodiments thereof, but it will be understood that variations and modifications can be effected within the spirit and scope of the invention.
