Ink jet inks containing emulsion polymer additives to improve water-fastness

Abstract: Water-fastness of inks containing pigment and a polymeric dispersant is improved by the addition of core-shell or tetrafluoroethylene emulsion polymers. The printed ink images exhibit improved resistance to smudge or smear when handled or marked with highlight pens.

Description: FIELD OF THE INVENTION This invention relates to aqueous inks for ink jet printers, and more particularly, to aqueous inks containing a tetrafluoroethylene emulsion polymer as an additive to improve water-fastness of the applied ink. BACKGROUND OF THE INVENTION Ink jet printing is a non-impact printing process in which droplets of ink are deposited on a substrate such as paper or transparency film in response to an electronic signal. Low cost and high quality of the output, combined with relatively noise free operation, have made ink jet printers a popular option to other types of printers used with computers. Dyes and pigments are used as colorants in inks adapted for use in ink jet printers. Dyes typically provide superior color properties immediately after printing, but are light sensitive and the printed image will tend to fade. Dyes also remain water-soluble after printing, causing the printed image to smear when contacted with moisture. Pigment colorants offer superior light-fastness and water-fastness, compared to dyes. Polymeric dispersants are employed to form a stable dispersion of the pigment particles in the ink. Representative dispersants proposed for this purpose include polyvinyl alcohol, cellulosic materials, ethylene oxide modified phenols, and ethylene oxide/propylene oxide polymers. More recently, commercial inks have employed a structured polymer dispersant as disclosed in U.S. Patent 5,085,698 to Ma et al. While inks containing pigment colorants generally offer superior water-fastness (compared to inks containing dyes), it is desirable that further improvements be made, particularly for end-use applications wherein the printed image will be exposed to substantial moisture. Water soluble polymeric binders and emulsions have been proposed as additives for this purpose, as in U.S. Patent 5,085,698 to Ma et al. When added at concentrations high enough to form tough protective films, however, it has been found that such additives generally increase the ink viscosity to the extent that the ink will not print in conventional ink jet printers. Accordingly, there is a need for specific additives that will improve water-fastness of inks containing pigment dispersions that are particularly adapted for use in ink jet printers. SUMMARY OF THE INVENTION It has now been found that tetrafluoroethylene emulsion polymers may be added to inks containing insoluble colorants in effective quantities to improve water-fastness of the printed image, without increasing viscosity of the ink to the extent that it compromises performance of an ink jet printer pen. The resulting inks are stable, exhibit excellent print quantity, provide excellent water-fastness, and favorable decap time. The printed images have improved integrity after being marked with a highlighter ("smear"), and after being handled by moist fingers ("smudge). The inks may be used with a variety of ink jet printers (e.g., continuous flow and piezoelectric), and are particularly useful with thermal drop-on-demand printers. The inks also may be used with air brush printing devices. Accordingly the invention provides an ink jet ink comprising: a) an aqueous carrier medium; b) an insoluble colorant; and c) 0.3% to 15% by weight, based on the total weight of the ink composition, tetrafluoroethylene emulsion polymer having pendant side chain groups represented by the formula: wherein R f is F, Cl, or a C 1 to C 10 perfluoroalkyl radical; and W is F, Cl, or OH. DETAILED DESCRIPTION OF THE INVENTION Inks provided by the invention may be used in a variety of printers, but are particularly well suited for use with a thermal drop-on-demand ink jet printer. The ink has an aqueous carrier medium and contains an insoluble colorant, which may be a disperse dye but preferably is a pigment. A dispersant, preferably a structured polymer dispersant is used to form a stable dispersion of the colorant in the aqueous carrier medium. In accordance with the invention, the ink contains a tetrafluoroethylene emulsion polymer in an amount effective to improve image permanence such as water-fastness and/or smear-fastness of images printed with the ink. The inks may be adapted to the requirements of a particular ink jet printer to provide a balance of light stability, viscosity, surface tension, high optical density, and crust resistance. AQUEOUS CARRIER MEDIUM The aqueous carrier medium is water or a mixture of water and one or more water-soluble organic solvent. Selection of the medium depends on requirements of the specific application, such as surface tension and viscosity, the selected colorant, drying time of the ink, and the type of substrate onto which the ink will be printed. Representative solvents that may be selected are disclosed in U.S. Patent 5,085,698. A mixture of water and a polyhydric alcohol, such as diethylene glycol, is preferred. If a mixture of water and a solvent is used, the aqueous carrier medium usually contains from about 30% to about 95% (preferably 60 to 95%) water with the balance being the water-soluble organic solvent. The amount of aqueous carrier medium in the ink is approximately 70 to 99.8% (preferably 94 to 99.8%) based on total weight of the ink when an organic pigment is selected; approximately 25 to 97.5% (preferably 70 to 97.5%) when an inorganic pigment is selected; and 80 to 99.8% when a disperse dye is selected. INSOLUBLE COLORANTS The insoluble colorant preferably is a pigment, but may be a disperse dye. A dispersant is used to assist in forming a stable dispersion of the insoluble colorant in the aqueous carrier medium. Pigment A wide variety of organic and inorganic pigments may be selected, alone or in combination. The pigment particles are sufficiently small to permit free flow of the ink through the ink jet printing device, especially at the ejecting nozzles that usually have a 10 to 50 micron diameter. Particle size also has an influence on the pigment dispersion stability, which is critical throughout the life of the ink. Brownian motion of minute particles will help prevent the particles from settling. It is also desirable to use small particles for maximum color strength. The range of useful particle size is approximately 0.005 micron to 15 micron. Preferably, the pigment particle size is between 0.005 to 5 micron, and most preferably between 0.01 to 0.3 micron. The selected pigment may be used in dry or wet form. For example, pigments are usually manufactured in aqueous media and the resulting pigment is obtained as water wet presscake. In presscake form, the pigment is not aggregated to the extent that it is in dry form. Thus, pigments in water wet presscake form do not require as much deaggregation in the process of preparing the inks from dry pigments. Representative commercial dry and presscake pigments that may be used in practicing the invention are disclosed in U.S. Patent No. 5,085,698. Fine particles of metal or metal oxides also may be used and are included in the term "insoluble colorant" as used herein. For example, metal and metal oxides are suitable for the preparation of magnetic ink jet inks. Fine particle size oxides, such as silica, alumina, titania, and the like, also may be selected. Furthermore, finely divided metal particles, such as copper, iron, steel, aluminum and alloys, may be selected for appropriate applications. In the case of organic pigments, the ink may contain up to approximately 30% pigment by weight, but typically will be in the range of approximately 1 to 15% (preferably 1 to 8%) by weight of the total ink composition for most thermal ink jet printing applications. If an inorganic pigment is selected, the ink will tend to contain higher weight percentages of the pigment than with comparable inks employing organic pigment, and may be as high as 50% because inorganic pigments generally have higher specific gravities than organic pigments. Disperse Dyes The color and amount of disperse dye used in the ink is a matter of choice, being primarily dependent upon the desired color of the print achieved with the ink, the purity of the dye, and its strength Low concentrations of dye may not give adequate color vividness. High concentrations may result in poor printhead performance or unacceptably dark colors. The disperse dye may be present in the amount of 0.01 to 20% by weight, preferably 0.05 to 8% by weight, more preferably 1 to 5% by weight, based on the total weight of the ink. Representative disperse dyes that may be useful in practicing this invention are disclosed in U.S. 5,053,495; U.S. 5,203,912; and U.S. 5,102,448. Dispersant Suitable polymeric dispersants include random polymers and structured polymeric dispersants, such as block copolymers and branched polymers. The polymers may be anionic, cationic, or non-ionic in nature. Random polymers are not as effective in stabilizing pigment dispersions as structured polymers and, therefore, ar.e not preferred. However, a random polymer having both hydrophilic sections for aqueous solubility and hydrophobic sections for interaction with the pigment, and an average molecular weight to contribute to the dispersion stability, can be effectively selected. Such polymeric dispersants are disclosed in U.S. 4,597,794. Block polymers having AB, BAB and ABC type structures are preferred dispersants. A block polymer which has hydrophobic and hydrophilic blocks, and balanced block sizes to contribute to the dispersion stability, may be used to advantage. Functional groups can be built into the hydrophobic (pigment binding) block for stronger specific interactions between the pigment and the polymer dispersant to provide improved dispersion stability. A detailed description of these polymers is found in the aforementioned U.S. Patents 5,085,698; 5,272,201; and 5,519,085 As mentioned in these references, it may be necessary to make salts of functional groups contained in the polymer to render it soluble in the aqueous carrier medium. Salts of the acid monomers can be made with the counter component being selected from organic bases such as mono-, di-, tri-methylamine, morpholine, n-methyl morpholine; alcohol amines such as dimethylethanolamine, methyldiethanolamine, mono-, di-, and tri-ethanolamine; pyridine; ammonium hydroxide; tetra-alkylammonium salts such as tetramethylammonium hydroxide, tetraethyl- ammonium hydroxide; alkali metals such as lithium, sodium and potassium, and the like. Preferred neutralizing agents include dimethylethanolamine and sodium and potassium hydroxides, with potassium hydroxide being particularly preferred for inks adapted for use in thermal ink jet printers. Salts of the amino monomers can be made with the counter component being selected from organic acids such as acetic acid, formic acid, oxalic acid, dimethylol propionic acid, halogens such as chloride, fluoride, and bromide, and other inorganic acids, such as sulfuric acid, nitric acid, phosphoric acid and the like. It is also possible to convert the amino group into a tetra-alkyl ammonium salt. Amphoteric polymers (i.e., a polymer containing both an acid group and an amino group) may be used as is, or can be neutralized with either an acid or base. Alternatively, other polymeric dispersants may be selected, but it will be difficult to formulate inks having the reliable balance of properties that are achieved using the preferred structured polymers. Dispersants such as polyvinyl alcohol, cellulosic materials, ethylene oxide modified phenols, and ethylene oxide/propylene oxide polymers may be selected for some applications. The amount of the polymer depends on the structure, molecular weight and other polymer properties, and on the other components of the ink composition. The block polymers have a number average molecular weight below 20,000; preferably below 10,000; and typically in the range of 1,500 to 6,000. The polymeric dispersant is present in the amount of 0.1 to 25% (preferably 0.1 to 8%) by weight, based on the total weight of the ink composition. If the amount is too high, it will be difficult to maintain the desired ink viscosity. Dispersion stability will be adversely affected if insufficient polymer is present. EMULSION POLYMER ADDITIVE Tetrafluoroethylene Emulsion Polymer The tetrafluoroethylene emulsion polymer has a fluorinated hydrocarbon backbone chain to which are attached pendant side chains which have the functional groups. The pendant side chains contain, groups, wherein R f is F, Cl, or a C 1 to C 10 perfluoroalkyl radical; and W is F, Cl, or OH preferably F. Typically, the functional group in the side chains will be present in terminal groups. Fluorinated polymers of this kind are disclosed in U.S. Pat. Nos. 3,282,875; 3,560,568; and 3,718,627. More specifically, the polymers can be prepared from fluorinated monomers or fluorine substituted vinyl compounds. The polymers are made from at least two monomers. At least one monomer is tetrafluoroethylene or mixtures thereof with vinyl fluoride, hexafluoropropylene vinylidene fluoride, trifluoroetylene chlorotrifluoroethylene or perfluoro (alkyl vinyl ether). In the case of copolymers used in electrolysis of brine, the precursor vinyl monomer desirably will not contain hydrogen. A second monomer is the sulfonyl-containing monomer containing the precursor group wherein R f is as defined above. Illustrative of such sulfonyl fluoride containing comonomers are CF 2 =CFOCF 2 CF 2 SO 2 F, CF 2 =CFCF 2 CF 2 SO 2 F, and The most preferred sulfonyl fluoride containing comonomer is perfluoro (3,6-dioxa-4-methyl-7-octenesulfonyl fluoride), The sulfonyl-containing monomers and their preparation are disclosed in U.S. Patent Nos. 3,282,875; 3,041,317; 3,718,627; and 3,560,568. A preferred class of such polymers has repeating units represented by the formula: wherein: h is 3 to 15; j is 1 to 10; p is 0, 1, or 2; the X's taken together are four fluorines, Y is F or CF 3 ; and R f is F, Cl or a C 1 to C 10 perfluoroalkyl radical. A most preferred copolymer is a copolymer of tetrafluoroethylene and perfluoro (3,6 -dioxa-4-methyl-7-octenesulfonyl fluoride). Such copolymers can be prepared by general polymerization techniques developed for homo- and copolymerizations of fluorinated ethylenes, particularly those employed for tetrafluoroethylene, which are described in the literature. Nonaqueous techniques for preparing the copolymers include that of U.S. Pat. No. 3,041,317, that is, by the polymerization of a mixture of the major monomer therein, such as tetrafluoroethylene, and a fluorinated ethylene containing a sulfonyl fluoride group in the presence of a free radical initiator, preferably a perfluorocarbon peroxide or azo compound, at a temperature in the range 0-200°C. and at pressures in the range of 10 5 to 2 X 10 7 pascals (1-200 Atm.) or higher. The nonaqueous polymerization may, if desired, be carried out in the presence of a fluorinated solvent. Suitable fluorinated solvents are inert, liquid, perfluorinated hydrocarbons, such as perfluoromethylcyclohexane, perfluorodimethl-cyclobutane, perfluorooctane, perfluorobenzene and the like, and inert, liquid chlorofluorocarbons such as 1,1,2-trichloro-1,2-2-trifluoroethane, and the like. Aqueous techniques for preparing the copolymer include contacting the monomers with an aqueous medium containing a free-radical initiator to obtain a slurry of polymer particles in non-water-wet or granular form, as disclosed in U.S. Pat. No. 2,393,967, or contacting the monomers with an aqueous medium containing both a free-radical initiator and a telogenically inactive dispersing agent, to obtain an aqueous colloidal dispersion of polymer particles, and coagulating the dispersion, as disclosed, for example, in U.S. Pat. No. 2,559,752 and U.S. Pat. No. 2,593,583. Other alternate methods may be used to prepare the tetrafluoroethylene emulsion polymers. U.S. Patent 4,433,082 describes a process for making a liquid composition containing a perfluorinated ion exchange polymer of equivalent weight in the range of 1050 to 1500, wherein water is admixed with one or more organic liquids such as lower alcohols and ethers that are completely miscible with water at room temperature. Some suitable fluoropolymer emulsion polymers include tetrafluoroethylene with perfluoro-3,6-dioxa-5-trifluoromethyl-oct-7-enyl sulfonyl fluoride (PSEPVE) wherein sulfonyl fluoride groups have been hydrolyzed to sulfonic acid. The fluoropolymer emulsion polymer additive is present in the amount of 0.3 to 15% by weight, preferably 1 to 7% by weight, based on the total weight of the ink composition. OTHER INGREDIENTS Various types of additives may be used to optimize the properties of the ink compositions for specific applications. Surfactants may be used to alter surface tension, as well as maximize penetration. However, the type of surfactants and the amounts used need to be carefully selected to avoid pigment dispersion destabilization or to negate the benefits of the present inks. Biocides may be used in the ink compositions to inhibit growth of microorganisms. Sequestering agents such as EDTA may also be included to eliminate deleterious effects of heavy metal impurities. Other known additives, such as humectants, viscosity modifiers and other acrylic or non-acrylic polymers made also be added to improve various properties of the ink compositions as desired. INK PROPERTIES AND PREPARATION The ink compositions are prepared in a similar manner as other ink jet inks. The pigment dispersion is first prepared by premixing the selected pigment (s) or disperse dye(s) and polymeric dispersant in the aqueous carrier medium and then dispersing or deflocculating the pigment or disperse dye The dispersing step may be accomplished in a horizontal mini mill, a ball mill, an attritor, or by passing the mixture through nozzles within a liquid jet interaction chamber at a liquid pressure of at least 5000 psi to produce a uniform dispersion of the pigment particles in the aqueous carrier medium. It is generally desirable to make the pigment dispersion in concentrated form, which is subsequently diluted with a suitable liquid to the appropriate concentration for the desired viscosity, color, hue, density and print area coverage for the particular application. The ink drop velocity, drop volume, and stream stability are greatly affected by the surface tension and the viscosity of the ink. Pigmented ink jet inks suitable for use with ink jet printing systems should have a surface tension in the range of about 20 dyne/cm to about 80 dyne/cm and, more preferably, in the range 25 dyne/cm to about 75 dyne/cm at 20°C. Acceptable viscosities are no greater than 20 cP, and preferably in the range of about 1.0 cP to about 10.0 cP, at 20°C. EXAMPLES The invention will now be further illustrated by, but not limited to, the following examples, in which parts and percentages are by weight unless otherwise noted. GLOSSARY PSEPVE - perfluoro-3,6-dioxa-5-trifluoromethyl-oct-7-enyl sulfonyl fluoride TFE - tetrafluoroethylene Triton® X100 surfactant - manufactured by Union Carbide, Industrial Chemicals Division, Danbury, Connecticut. FLUOROPOLYMER PREPARATION 1 : This shows the preparation of (CF 2 CF 2 ) n (CF 2 C(OCF 2 C(CF 2 )F-OCF 2 CF 2 SO 2 H)F) emulsion. Step 1 : Preparation of poly TFE/PSEPVE colloid The polymerization medium was prepared in an enclosed food blender purged with N2, and consisted of: 50 mL deoxygenated water 150 g PSEPVE (DuPont) Vigorous blender stirring suspended the PSEPVE in the water. Then the following ingredients were added: INGREDIENT AMOUNT (GM/ML) nC 7 F 15 CO 2 NH 4 (3M, FC-143) 6 g Distilled Water 5 mL Citric. acid 0.28 g FeSO 4 % 7H 2 O 0.31 g (NH4) 2 S 2 O 8 in 5 mL H 2 O 1.6 g The mixture was stirred cautiously to prevent excessive foaming. The stirred mixture was N2 pressure transferred to a 1 liter stirred autoclave. Just before closing the vessel, a solution of 1.3 g NaHSO 3 in 10 mL H 2 O was added. The closed vessel was stirred and kept under 125 psi TFE pressure for 3 hrs during which time 100 g TFE was consumed. The colorless colloidal suspension weighed 669 g and contained 26.8% solids. Step 2 : Conversion to the free sulfonic acid emulsion The sulfonyl fluoride was hydrolyzed by mixing 100 g of the above colloid with 100 mL concentrated ammonium hydroxide. After 1 week at room temperature, the excess water and ammonia (100 mL) were removed by evaporation. The system was still colloidal. The product was precipitated by pouring into 200 mL hot 1 part concentrated H 2 SO 4 : 2 parts water. The gel-like product was cleaned by repeated suspending in water followed by centrifugation and decantation until the washings were neutral to pH test paper. The final product dispersed in water by simple shaking to give an 8% solids suspension. Triton® X100 surfactant was added to the emulsion as supplied to give 10% surfactant by weight. Potassium hydroxide was added and the suspension was sonicated. The final pH was 10.7. DISPERSANT PREPARATION 1 : An ETEGMA//BZMA//MAA 4//15//12 triblock copolymer was prepared using the following procedure: A 1-liter flask was equipped with a mechanical stirrer, thermometer, N2 inlet, drying tube outlet, and addition funnels. Tetrahydrofuran (THF), 83 g, and mesitylene, 0.1 g, were charged to the flask. The catalyst tetrabutyl ammonium m-chlorobenzoate, 230 µl of a 1.0 M solution in THF, was then added. Initiator, 1,1-bis(trimethylsiloxy)-2-methyl propene, 5.0 g (0.020 mol), was injected. Feed I [tetrabutyl ammonium m-chlorobenzoate, 230 µl of a 1.0 M solution in THF] was started and added over 130 minutes. Feed II [trimethylsilyl methacrylic acid, 40.86 g (0.250 mol)] was started at 0.0 minutes and added over 30 minutes. Thirty minutes after Feed II was completed (over 99% of the monomer had reacted), Feed II [benzyl methacrylate, 56.90 g (0.323 mol)], was started and added over 60 minutes. Ten minutes after Feed III was completed (over 99% monomers had reacted), Feed IV [ethoxytriethylene glycol methacrylate, 21.21 g (0.0862 mol)] was started and added over 30 minutes. At 150 minutes, 12 g of methanol were added. Then 98 g of solvents and trimethylmethoxysilane were stripped out and replaced with 153 g 2-pyrrolidone. This made a ETEGMA//BZMA//MAA 4//15//12 polymer at 40% solids. The above block polymer was neutralized using the following procedure: The ETEGMA//BZMA//MAA block polymer prepared above was neutralized to 80% by adding 45% aqueous potassium hydroxide solution to the block copolymer solution and mixing until a homogeneous solution was obtained. After neutralization the material was reduced to approximately 10% solids with deionized water. INGREDIENT AMOUNT (GMS) Polymer Solution (40% Solids) 100 Potassium Hydroxide (45% Solution in 11 deionized water) Deionized water 289 Total 400 WT% Solids: 10 pH: 8 DISPERSANT PREPARATION 2: The following is an example of how to make an ABC triiblock polymer with an A block of ethoxytriethyleneglycol methacrylate ETEGMA, a B block of benzyl methacrylate BZMA and a C block of methacrylic acid MAA (ETEGMA//BZMA//MAA 4//12//12). A 12-liter flask was equipped with a mechanical stirrer, thermometer, N2 inlet, drying tube outlet, and addition funnels. Tetrahydrofuran THF, 3701 gm, and mesitylene, 13.7 gm, were charged to the flask. The catalyst, tetrabutyl ammonium m-chlorobenzoate, 2.4 ml of a 1.0 M solution in acetonitrile, was then added. Initiator, 1,1-bis(trimethylsiloxy)-2-methyl propene, 180.1 gm (0.776 M) was injected. Feed I [tetrabutyl ammonium m-chlorobenzoate, 2.4 ml of a 1.0 M solution in acetonitrile] was started and added over 185 minutes. Feed II [trimethylsilyl methacrylate, 1471 gm (9.30 M)] was started at 0.0 minutes and added over 45 minutes. One hundred and eighty minutes after Feed II was completed (over 99 % of the monomers had reacted), Feed III [benzyl methacrylate, 1639 gm (9.31 M) was started and added over 30 minutes. Forty minutes after Feed III was completed (over 99 % of the monomers had reacted), Feed IV [ethoxytriethyleneglycol methacrylate, 765 gm (3.10 M) was started and added over 30 minutes. At 400 minutes, 720 gm of methanol was added to the above solution and distillation begun. During the first stage of distillation, 764.0 gm of material were removed. Then more methanol, 304.0 gm, was added and an additional 1992.0 gm of material were distilled out. Finally, I-propanol, 480 gm total, was added. A total of 2756 gms of solvent were removed. It was at 49.7% solids. The polymer had a composition of ETEGMA//BZMA//MAA 4//12//12. It had a molecular weight of Mn = 4,200. DISPERSANT PREPARATION 3: This shows the preparation of a cationic polymer used to disperse the pigments. It is a BzMA//DMAEMA 10//20 diblock polymer. A 12-liter flask was equipped with a mechanical stirrer, thermometer, N2 inlet, drying tube outlet, and addition funnels. Tetrahydrofuran THF, 4002 g, and p-xylene, 7.7 g, were charged to the flask. The catalyst, tetrabutyl ammonium m-chlorobenzoate, 2.0 ml of a 1.0 M solution in acetonitrile, was then added. Initiator, 1-methoxy-1-trimethylsiloxy-2-methyl propene, 155.1 g (0.891 M) was injected. Feed I [2-dimethylaminoethyl methacrylate DMAEMA, 2801 g (17.8 M)] was started at 0.0 minutes and added over 45 minutes. One hundred minutes after Feed I was completed (over 99 % of the monomers had reacted), Feed II [benzylmethacrylate, 1568 g (8.91 M)] was started and added over 30 minutes. At 400 minutes, 310 g of dry methanol were added to the above solution and distillation begun. A total of 1725 g of solvent was removed. I-propanol, 1783 g, was added after completion of the distillation. This made a BZMA//DMAEMA 10//20 diblock polymer at 49.6 % solids with Mn 5000. PREPARATION OF PIGMENT DISPERSION 1: A 1-liter beaker was equipped with a mechanical stirrer. Into the beaker was placed 94 g of the Dispersant 1 and 13 g water. With stirring, 18.7 g FW 18 black pigment (Degussa Corp., Ridgefield Park, NJ) were added in small portions. When the mixture was thoroughly combined, it was passed through a model M-110F Microfluidizer (Microfluidics Corp., Newton, MA) five times. The particle size after microfluidization was 108 nm; and pigment concentration of the dispersion was 15%. PREPARATION OF PIGMENT DISPERSION 2 : This shows the preparation of an anionic cyan pigment dispersion using a ETEGMA/BzMA/MAA 4/12/12 triblock polymer and a 2 roll mill. A cyan pigment dispersion was prepared using the following procedure: The following ingredients were mixed: INGREDIENT AMOUNT (GM) Dispersant Polymer from Preparation 2 (49.7% solids) 402.4 Phthalocyanine pigment 300 Diethylene glycol 45 This mixture was then charged to a 2 roll mill and processed for 30 minutes. This made a pigment dispersion that contained 55% pigment and 36.7% polymer. This 2 roll mill chip was then dissolved using potassium hydroxide as the neutralizing agent to make an aqueous pigment concentrate. An aqueous pigment dispersion concentrate was prepared by mixing the following ingredients with adequate stirring: INGREDIENT AMOUNT (GM) Pigment dispersion 72.7 45.9% solution KOH in water 9 Deionized water 318 This made an aqueous, pigment concentrate that contained 9.55% pigment and had 90 mole% of the acid groups from the polymer neutralized with KOH. PREPARATION OF PIGMENT DISPERSION 3: This shows the preparation of a cationic cyan pigment dispersion using a BzMA//DMAEMA 10//20 diblock polymer and a 2 roll mill. A cyan pigment dispersion was prepared using the following procedure: The following ingredients were mixed: INGREDIENT AMOUNT (g) Polymer from Polymer preparation 3 203.2 Heliogen 7072DD PB15 pigment (from BASF) 150.0 1-propanol 450.0 This mixture was then charged to a 2 roll mill and process for 45 minutes. This made a pigment dispersion chip that contained 60% pigment and 40% polymer. It had a P/D = 1.5/1. This 2 roll mill chip was then dissolved using phosphoric acid as the neutralizing agent to make an aqueous pigment concentrate. An aqueous cyan pigment dispersion concentrate was prepared by mixing the following ingredients with adequate stirring: INGREDIENT AMOUNT (g) Cyan Pigment dispersion 33.3 (from Dispersion Preparation 2) Phosphoric acid (86.0 %) 5.47 Deionized water 161.23 This made an. aqueous, cyan pigment concentrate that contained 10% pigment and had 90 mole % of the amine groups from the polymer neutralized with phosphoric acid. EXAMPLE 1: Inks were made from cyan pigment dispersions. The dispersant was 4//12//12 ETEGMA//BzMA//MAA block terpolymer made by GTP. The pigment was dispersed with this polymer in a two-roll mill. The ink had the following composition: INGREDIENT AMOUNT (% BY WEIGHT) Phthalocyanine pigment 2.5 2-pyrrolidone 6.5 Liponics®EG-1, Lipo Chemicals, Paterson, NJ 5.0 Isopropanol 2.0 Multranol® 4012, Miles, Inc., Pittsburgh, PA 1.5 The example ink contained 4.3% PTFE/PSEPVE emulsion from Fluoropolymer Emulsion Preparation 1. Testing Procedure For Fluoropolymer Emulsion Additive Containing Inks And Control Inks: The inks were tested in modified pens on the Hewlett-Packard 550C printer. The drop weight was measured by firing the pens into a pan on an analytical balance and calculating average drop weight. The volume variation is the variation in drop volume as the firing energy of the pen is varied across its operating range. Waterfastness was measured by dripping water on a series of printed lines and measuring optical density of the run-off after drying. The drip was measured initially after printing and after a 1 hour and 24 hour delay. Highlighter smear was measured by running an acid and base highlighter across a series of printed lines and measuring optical density of the smeared off ink. The rub test was a dry rub done using 30 strokes with a Sutherland ink rub tester. Test were done immediately after printing. Maximum optical density of the rubbed off ink was measured. Sample # Binder Drop Volume (pl) Volume Variation (pl) Rub Test (mOD) Control A none 29.2 2.3 117 Example 1 4.3% PTFE/PSEPVE 30.2 1.7 78 Control B 1% Butyl acrylate emulsion 29.8 2.4 65 Control C 4.2% Butyl acrylate emulsion 26,2 4.8 76 Sample # Waterfastness (mOD) Highlighter (Acid) Highlighter (Base) Init. 1hr 24hrs Init. 1hr 24hrs Init. 1hr 24hrs Control A 195 75 10 96 113 86 215 169 151 Example 1 99 26 19 57 112 48 202 180 105 Control B 375 131 12 46 124 55 171 153 198 Control C 163 62 2 20 49 33 118 96 88 The inks containing the PTFE/PSEPVE emulsion gave improved performance of the pen as measured by drop volume variation. There is less variation as the pen energy. is varied than with no emulsion or with the acrylic emulsion. These inks also gave improved initial waterfastness immediately after the print is made and less smear with the hilighter test and better rub resistance than with no polymer additive.

Claims: An ink jet ink comprising: a) an aqueous carrier medium; b) an insoluble colorant; and c) 0.3% to 15% by weight, based on the total weight of the ink composition, tetrafluoroethylene emulsion polymer having pendant side chain groups represented by the formula: wherein R f is F, Cl, or a C 1 to C 10 perfluoroalkyl radical; and W is F, Cl, or OH. The ink of claim 1, wherein said emulsion polymer additive is present in an amount of from 1 to 7% by weight, based on the total weight of the ink composition. The ink of claim 1 or 2 wherein W in the pendant side chain is F. The ink of claim 3 wherein the tetrafluoroethylene emulsion polymer is prepared by reacting a fluorinated vinyl compound with a monomer containing at least one group having the formula: wherein R f is F, Cl, or a C 1 to C 10 perfluoroalkyl radical. The ink of claim 1, wherein the tetrafluoroethylene emulsion polymer is a copolymer of tetrafluoroethylene with at least one monomer selected from perfluoro-3,6-dioxa-5-trifluoromethyl-oct-7-enyl sulfonyl fluoride; perfluoro-3,6-dioxa-5-trifluoromethyl-oct-7-enyl sulfonyl fluoride acid form; and perfluoro (3,6-dioxa-4-methyl-7-octenesulfonyl fluoride).

Inventors: ANTON WAIFONG LIEW, BEDNAREK MILAN BOHUSLAV, HOWARD EDWARD GEORGE JR, PEARLSTINE KATHRYN AMY, TRONSON SOODABEH, ANTON, WAIFONG LIEW, BEDNAREK, MILAN BOHUSLAV, HOWARD, EDWARD GEORGE, JR., PEARLSTINE, KATHRYN AMY, TRONSON, SOODABEH
Applicants: DU PONT, E.I. DU PONT DE NEMOURS AND COMPANY
Application year: 1997
Main classification: C09D11
IPC codes: B41J2, C09J151, C09D11, C08F265, B41M5