MXPA96006340A - It compositions - Google Patents

Abstract

The present invention relates to an aqueous ink composition suitable for use in ink jet printers, characterized in that it comprises: a) from about 1% to about 10% of a pigment, b) from about 0.1% to about 10% of a a polymeric dispersant for the pigment, c) from about 50% to about 93% of an aqueous carrier, and d) from about 5% to about 40% of a mixture of co-solvent comprising: (1) 1,3-propanediol , 4-butanediol, and 2) a material selected from the group consisting of: i) mixed polyethylene glycols and poly (ethylene) (propylene) glycols, having a molecular weight of from about 200 to about 600; ii) a polyol / condensate polyalkylene oxide having the formula: wherein X is HóCH 3, R is H, C 1 -C 4 alkyl or CH 2 O (CH 2 CH 2 O) e H, b is O 1, a + d + f (c + e) from about 2 to about 100, and f ranges from approximately 1 to approximately 6, and iii) mixtures thereof, wherein the weight ratio (1) :( 2) ranges from about 70:30 to about 30:

Description

INK COMPOSITIONS TECHNICAL FIELD The present invention relates to ink compositions used in inkjet printers.

BACKGROUND OF THE INVENTION Ink jet printing is effected by ejecting ink from a nozzle into the paper or other printing medium. The ink can be propelled into the medium in a variety of ways. For example, in electrostatic printing, ink is propelled from a nozzle into a medium by an electrostatic field. Another method of ink jet printing, known as a compression tube, employs a piezoelectric element in the ink nozzle. The electrically caused distortions of the piezoelectric element pump the ink through the nozzle and into the printing medium. In another ink jet printing process, known as thermal or bubble ink jet printing, the ink is propelled from the nozzle into the printing medium by forming a vapor phase bubble that expands in the nozzle. These 'various printing methods are described in "Output P1362 / 96MX Hard Copy Devices, "edited by Durbeck and Sherr, Academic Press, 1988 (see particularly chapter 13, entitled" In jet Printing "). Ink compositions used in inkjet printers generally comprise deionized water, a water-soluble or water-miscible organic solvent or a dye Generally, the dye is a soluble dye Unfortunately, inks containing soluble dyes can exhibit many problems, such as poor water resistance, poor light resistance, clogging Jet emission channels as a result of solvent evaporation and changes in dye solubility, dye crystallization, poor print quality including ink shift and granulation, poor thermal stability, chemical instability and easy oxidation. These problems can be overcome by replacing the soluble dyes, used in the ink formulations, with inso pigments. In general, the pigments have superior properties when compared to dyes, particularly in terms of water resistance, light resistance, thermal stability, oxidation stability and compatibility with both coated / treated and simple papers. However, because the pigments are insoluble in the composition P1362 / 96MX ink and should, therefore, be included as a dispersion, a new set of problems arises. Ink stability is critical, both in terms of maintaining the uniformity of properties and ensuring that the pigment does not obstruct the ink jets during inactivity spaces. Ideally, both for reasons of stability and for reasons of cost, it would of course be to use the minimum amount of pigment needed in the ink composition. However, decreasing the amount of pigment in the ink compositions can lead to images having poor optical densities. In addition, due to the balance of composition required to ensure the necessary stability, it is also important to ensure that the composition has an appropriate viscosity for use in an ink jet printer, as well as good printing properties, for example good water resistance, good light resistance and minimum bleed and granulation when applied to paper. It has been very difficult to develop an ink formulation that optimizes all these properties. The general approach has been to adjust the dispersants and solvent systems of the ink compositions in an attempt to balance and optimize these properties that often compete. However, prior to the present invention, a formulation that optimizes was not achieved P1362 / 96MX all these properties without requiring the use of specific polymeric dispersants. United States Patent No. 5, 180,425, Matrick, et al., Issued January 19, 1993, discloses inkjet ink compositions that include an aqueous carrier medium, a pigment dispersion and a polyol / alkylene oxide co-solvent. It is taught that these inks provide a long functional life to inkjet printers and that they resist film formation. Liponic EG-1 is one of the preferred co-solvents presented. Other optional solvents that may be used in the disclosed invention include polyethylene glycol. U.S. Patent No. 5,302,197, to Wickramanayke, issued April 12, 1994, discloses aqueous inkjet ink compositions comprising a pigment dispersion, an aqueous carrier medium and a co-solvent mixture including a polyol / alkylene oxide condensate together with a cyclic amide derivative. It is taught that Liponic EG-1 is useful as a component of the polyol / alkylene oxide condensate. European Patent Application No. 603,469, by Chan, et al., Published on June 29, 1994, discloses inkjet inks comprising an aqueous carrier medium, with alkyl polyol ether solvents P1362 / 96MX specifically defined and a pigment dispersion (pigment particles stabilized by a dispersant). It is taught that these inks provide a good balance of viscosity, surface tension, resistance to clogging of the nozzle, print quality, light stability and resistance to bending or staining by carving and water resistance. Solvents that can be used in the presented invention include 1,2,3-butanetriol. U.S. Patent No. 4,597,794, Ohta, et al. granted on July 1, 1986, describes an ink formulation used in inkjet printing processes that is said to form a clear image and has good physical properties. Solvents presented specifically for use in the ink include polyethylene glycol and 1,2,6-hexanetriol. It has now been discovered that the use of a very specific co-solvent mixture containing 1,3-propanediol or 1,4-butanediol together with either (a) a low molecular weight polyethylene glycol or a related compound or, (b) a condensate of a polyol / alkylene oxide in an aqueous ink composition containing a dispersion of an insoluble pigment, provides a unique blend of optimized properties. Specifically, these compositions provide excellent properties in P1362 / 96MX terms of stability, optical density (even when using low levels of pigment), viscosity, printing characteristic (water resistance, light resistance, minimal granulation, minimum ink shift on the printed page), and problems with printer maintenance (ie, minimal clogging or clogging of the printer's jets during idle spaces of the printer). None of the patents mentioned above describe or suggest the specific co-solvent combinations of the present invention. Therefore, an object of the present invention is to provide an improved pigmented ink composition for inkjet printers comprising a very specific co-solvent system. Other objects and advantages of the present invention will be apparent from the following discussion.

SUMMARY OF THE INVENTION In a first aspect, the present invention relates to an aqueous ink composition suitable for use in inkjet printers, comprising: (a) from about 1% to about 10% of a pigment; P1362 / 96MX (b) from about 0.1% to about 10% of a polymeric dispersant for the pigment; (c) from about 50% to about 93% of an aqueous carrier; and (d) from about 5% to about 40% of a co-solvent mixture comprising (1) 1,3-propanediol or 1,4-butanediol, and (2) a material selected from the group consisting of: (i) ) polyethylene glycols and poly (ethylene) (propylene) glycols, having a molecular weight of from about 200 to about 3,400; (ii) an alkylene oxide polyol / condensate having the formula CH2? (CH2CHXO) aH rRC (CH2) bO (CH2CHXO) cH f CH2? (CH2CHXO) dH where X is H or CH3, R is H, alkyl of -04 or CH20 (CH2CH20) TH, b is 0 or 1, a + d + f (c + e) ranges from about 2 to about 100, and f is from about 1 to about 6; and (iii) mixtures thereof; wherein the weight ratio (1): (2) is from about 70:30 to about 30:70. In a second aspect, the present invention is directed to a co-solvent mixture as described in (d). All percentages and relationships used herein are "by weight" unless otherwise specified. All molecular weights, used herein, are number average molecular weights unless otherwise specified.

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to aqueous ink compositions suitable for use in inkjet printers. These compositions contain an insoluble pigment, a polymeric dispersant for the pigment (the pigment and the dispersant are present in the composition as a dispersion), an aqueous carrier and a specifically defined co-solvent mixture. Each of these required components, as well as some optional components, will be described in detail below. The polymeric dispersant is included in the compositions of the present invention in an amount from about 0.1% up to P1362 / 96MX about 10%, preferably from about 0.25% to about 5%, more preferably from about 0.5% to about 4% of the final composition. Polymeric dispersants suitable for use in the present invention include any of the anionic, cationic or nonionic polymers known in the art, so long as they are suitable for use as dispersants in inkjet ink preparations. Examples of these materials are described in U.S. Patent No. 5,310,778, Short, et al., Issued May 10, 1994, incorporated herein by reference. These polymeric dispersants may be homopolymers, copolymers, branched polymers or embedded polymers. They can be random or block polymers. The interpolymer blocks AB, BAB and ABC represent a type of polymeric dispersants useful in the present invention. The preferred interpolymer blocks are AB, BAB and ABC derived from at least one alkyl acrylic or methacrylic acid ether and substituted amino or acrylic methacrylic ester monomers. Preferred interpolymer blocks AB and BAB and their preparation processes are described in U.S. Patent No. 5,085,698, Ma, et al., Issued February 4, 1992, incorporated herein by reference.

P1362 / 96MX reference. The polymeric dispersants useful in the present invention generally include both hydrophobic and hydrophilic polymer segments, the hydrophobic segments tend to bind with the pigment particles in the ink compositions and the hydrophilic segments tend to be solvated by the liquid ink medium thereby serving to stabilize the dispersion by steric and / or ionic mechanisms. A preferred class of polymeric stabilizers for use in the present invention include block or inserted copolymers comprising a hydrophilic polymeric segment and a hydrophobic polymeric segment that includes a hydrolytically stable siloxyl substituent. A particularly preferred subgroup of these dispersants are inserted copolymers comprising a hydrophilic polymeric segment (particularly an acrylate or methacrylate copolymer) together with a hydrophobic polymeric segment derived from the macromer having the formula: P1362 / 96MX wherein n ranges from 2 to 16 and each R is independently lower alkyl (Ci-Ce) or siloxyl. These materials are presented in U.S. Patent Application Serial No. 08 / 360,199, Beach, et al., Filed December 21, 1994, and incorporated herein by reference. Another class of preferred polymeric dispersants include embedded copolymers, having a molecular weight of from about 1,500 to about 20,000, comprising: (a) a hydrophilic polymeric segment; (b) a hydrophobic polymeric segment, having a molecular weight of from about 400 to about 3,000 incorporating and substituting hydrolytically stable siloxyl; and (c) a stabilizing segment having a molecular weight of from about 200 to about 2,000, selected from the group consisting of reactive surfactant macromers, protective colloid macromers, and non-siloxyl hydrophobic monomers. The preferred monomer ratio (a): (b) ranges from about 10: 1 to about 100: 1, while the preferred monomer ratio (b): (c) ranges from about 1: 0.5 to about 1: 5 . The P1362 / 96MX preferred hydrophilic polymer segments include a carboxy substituent and more preferably are acrylate or methacrylate polymer materials. The preferred hydrophobic polycarboxylic segment containing siloxane is an acryloyl acryloxy acryloyl or methacryloyl-terminated polydialkylsiloxane acrymer. The most preferred hydrophobic segments have a molecular weight of from about 400 to about 2,000 and incorporate a di-polydysolysiloxy group. Preferred stabilizing segments include stearyl acrylate, stearyl methacrylate, lauryl acrylate, lauryl methacrylate, nonylphenol acrylate, nonylphenol methacrylate, nonylphenoxy poly (ethyleneoxy) n methacrylate, wherein n ranges from about 1 to about 40.; nonylphenoxy poly (ethyleneoxy) n acrylate, wherein n ranges from about 1 to about 40; methoxy poly (ethyleneoxy) n methacrylate, wherein n ranges from about 5 to about 40; methoxypoly (ethyleneoxy) n acrylate, wherein n ranges from about 5 to about 40; stearyl oxypoly (ethyleneoxy) n methacrylate, wherein n ranges from about 1 to about 20; stearyl oxypoly (ethyleneoxy) n acrylate, wherein n ranges from about 1 to about 20; C C-C ?β fluorinated alkyl methacrylate; fluorinated Ci-Ciß alkyl acrylate; methyl ether P1362 / 96 X poly (propylene glycol) methacrylate; methyl ether poly (propylene glycol) acrylate; methyl ether poly (propylene glycol) methacrylate; 4-nonylphenyl ether; poly (propylene glycol) 4-nonylphenyl ether acrylate; polyethylene oxide terminated by methacryloxytrimethylsiloxy; polyethylene oxide terminated in acryloxytrimethylsiloxy; and mixtures thereof, The most preferred polymeric dispersant of this class comprises, in its main chain, the structural formula OR CH3 If CH (CH2) d CH3 P1362 / 96MX where x ranges from about 5 to about 100, preferably from about 15 to about 50; and ranges from about 1 to about 2, preferably about 1; z ranges from about 1 to about 5, preferably about 1; a ranges from about 3 to about 45, preferably about 9; b ranges from about 3 to about 29, preferably from about 15 to about 17; c ranges from about 2 to about 8, preferably about 3; and d is from 0 to about 7, preferably from about 3. However, it will also be noted that this is within the scope of this invention for all the structural units represented by X, y, and z in the present to be randomly dispersed throughout the polymer main chain. These polymeric dispersants are presented in a co-pending US Patent Application entitled "Polymeric Dispersants for Pigmented Ink", Beach, et al., Incorporated herein by reference. In the present it will be noted that the end groups in the dispersants of this invention are not limited. For illustrative purposes, they may include thiosubstituted hydrocarbons as well as hydrogen. P1362 / 96MX Another group of preferred polymeric dispersants are those described in U.S. Patent Application Serial No. 08 / 360,200, to Beach, et al., Filed December 21, 1994, incorporated herein by reference. These materials are grafted polymers comprising a hydrophilic polyacrylic acid backbone with a weight average molecular weight of between about 1,000 and about 5,000 and hydrophobic segment side chains, preferably with a side chain attached to the backbone. Preferred polymers of this class are those which comprise in their main chain one of the following structural formulas: R wherein x + y ranges from about 20 to about 200, z ranges from about 1 to about 10, and R is C6-C36 alkyl or Rx wherein R is a C-C20 alkyl; or P1362 / 96MX CH2 S CH O HC OR2 H wherein x + y ranges from about 20 to about 200, z ranges from about 1 to about 10, and n goes from about 2 to about 40, and R is alkyl or aryl, preferably butyl; or P1362 / 96MX - < CH2CH (CH2CHr (CH2CH) y: O = O OH N-H OH CH-CH3 CH2 R3 wherein x + y ranges from about 20 to about 200, z ranges from about 1 to about 10, and R3 is H or CH3, R4 is H, CH3 or 0CH3, and n ranges from about 10 to about 60; or those that have the formula P1362 / 96MX O O o (HOCCH2CH2C) - - CH2CH2N) - (CH2CH2N) y- CH2CH2N - (C-CH2CH2C-OH) 2 I I 2 c = o C = 0 R.5 CH2 CH2 = 0 OH wherein and ranges from about 6 to about 20, x ranges from about 1 to about 5, and R5 is a C5-C30 alkyl. The graft copolymer dispersants of the present invention require a relatively low molecular weight in order to achieve particle stability and a low viscosity required for use in stable inks for ink jet printing. This may result in the selection of a polar solvent polymerization process to make the copolymers. This process controls the molecular weight and the uniformity of the copolymers, maintaining the solubility of all the raw materials (initiator of free radical, hydrophobic and hydrophilic monomers and chain transfer agents), as well as the copolymer Resulting P1362 / 96MX. Since the synthesized copolymer needs to be suspended in an aqueous medium in order to be formulated for ink jet printing, it is necessary to recover the polymer of the polar organic solvent in the reaction mixture and dissolve it in water. A typical polar polymerization solvent copolymer recovery process comprises the following steps: 1. adding the copolymer solution to a non-solvent, such as hexane, in order to precipitate the copolymer from the solution, thereby purifying it; 2. vacuum filtering the precipitate; and 3. drying the precipitated copolymer. The copolymer powder could then be dissolved in an aqueous base and used in the preparation of the ink for jet printing. This process can be costly and unnecessarily complicated. Preferred processes for recovering the polar organic polymerization solvent copolymer dispersant mean not only the recovery of the copolymer dispersant, but also result in improved printing qualities for inkjet inks made from these dispersants in which the tendency of inks to form satellites and splashes is reduced. Specifically, these preferred processes are: 1. solvent extraction followed by base dissolution P1362 / 96MX aqueous; e 2. solvent exchange. In the process of solvent extraction and dissolution, the polar solvent is first extracted from the copolymer by a standard process that can convert the copolymer solution into a dry powder, such as vacuum tray drying, rotary evaporator drying, drum drying , vacuum drying in rotating cylinder, or spray drying. The dry copolymer powder is then dissolved in the aqueous base so that it can be used in the preparation of pigmented inkjet inks. In the solvent exchange process, from about 35% to about 60% (preferably about 50%) of the polar solvent in the polymerization reactor is distilled and deionized water and the aqueous base (for example KOH solution) are added to adjust the pH from about 4.5 to about 6.5, preferably about 5. For a polar solvent with a lower boiling point than water, the temperature of this mixture is slowly increased to distill the solvent until the temperature reaches about 100 ° C at which time all the polar organic solvent is removed or removed, (this process can not be used where the polar solvent P1362 / 96MX has a higher boiling point than water. An additional aqueous base (for example a KOH solution) is added to the solution to increase the pH from about 7 to about 8.5, preferably about 7.5. The solution is then ready to be used in the formulation of a pigmented inkjet ink. The second component of the ink composition of the present invention is the pigment, an insoluble dye. The pigment is present in the compositions of the present invention in from about 0.1% to about 10%, preferably from about 0.25% to about 5%, more preferably from about 0.5% to about 4% of the final composition. Of course, one of the important advantages of the present invention is that it allows the formulation of ink having low levels of pigment (for example between 0.5% to about 4%) while still providing high quality and excellent printing optical density. The pigments useful in the present invention are any of the conventional pigments known in the art, such as those presented in US Pat. No. 5,085,698, to Ma et.al., issued on February 4, 1992, and incorporated therein.

P1362 / 96MX herein for reference. The pigments can be used individually or in combination. The pigment particles must be small enough to allow free flow of the ink through the ink jet printing device, especially in the ejector nozzles that usually have a diameter that varies from approximately 10 microns to approximately 50 microns. The particle size also has an influence on the stability of the pigment dispersion, which is critical throughout the life of the ink. Broian movement of small particles will help prevent particles from flocculating, thus providing a more stable product. The range of useful particle size ranges from about 0.05 microns to about 15 microns. Preferably, the particle size of the pigment ranges from about 0.05 microns to about 5 microns, and more preferably from about 0.5 microns to about 1 micron. The pigments can be used in dry or wet form. For example, the pigments are usually manufactured in aqueous medium and the resulting pigment is obtained as a press filter cake wet with water. In the form of press filter cake, the pigment is not agglomerated to the extent that it is in P1362 / 96MX dry form. In this way, the pigments in the form of filter cake press wet with water do not require as much deflocculation during the preparation process as the dry pigments require. Fine particles of metals or metal oxides can also be used to practice the present invention. For example, metals or metal oxides are suitable for the preparation of magnetic inks for inkjet. Oxides with fine particle size such as silica, alumina, titania, and the like, can also be used. Additionally, finely divided metal particles, such as copper, and iron, steel, aluminum and alloys can be selected for appropriate applications. Examples of pigments that can be used in the present invention include azo pigments, such as azo lacquers, fused azo pigments and azo chelate pigments; polycyclic pigments, such as phthalocyanine pigments, perylene pigments, anthraquinone pigments, quinoacridone pigments, dioxacin pigments, thioindigo pigments, isoindolinone pigments and quinophthalone pigments; dye lacquers, such as basic dye lacquers and acid dye lacquers; organic pigments ,. such as nitrated pigments, nitrous pigments, aniline black and fluorescent pigments to the P1362 / 96MX daylight; and inorganic pigments, such as titanium oxide, iron oxide and carbon black. Preferred pigments for use in the present invention include titanium oxide, iron oxide and carbon black. Examples of commercially available pigments that can be used in the present invention include the following: Heliogen® Blue L 6091F (BASF), Heliogen® Blue NBD 7010 (BASF), Heliogen® Blue K 7090F (BASF), Heucophthal® Blue G XBT-583D (Heubach), Irgalite® Rubine 4BL (Ciba-Geigy), Quiñdo® Magenta (Mobay), Indofast® Brillant Scarlet (Mobay), Hostaperm® Scarlet GO (Hoechst), Permanent Rubine F6B (Hoechst), Monastral® Scarlet (Ciba- Geigy), Raven® 1170 (Col. Chem.), Special Black 4A (Degussa), Black FW18 (Degussa), Sterling® NS Black (Cabot), Sterling® NSX 76 (Cabot), Monarch® 880 (Cabot), Tipure ® R-101 (DuPont), Mogul L (Cabot), BK 8200 (Paul Uhlich), Heliogen® Green K 8683 (BASF), Heliogen® Green L 9140 (BASF), Monastral® Red B (Ciba-Geigy), Monastral ® Violet R (Ciba-Geigy), Hostaperm Orange GR (Hoechst), Paliogen® Orange (BASF), L75-2377 Yellow (Sun Chem), L74-1357 Yellow (Sun Chem.), Hostaperm® Yellow H4G (Hoechst), Irgazin® Yellow 5GT (Ciba-Geigy), Permanent Yellow G3R-01 (Hoechst), Novoperm® Yellow FGL (Hoechst), Chromophthal® Yellow 3G (Ciba-Geigy) Hansa Yellow X (Hoechst), Dalamar® Yellow YT-858-D (Heubach) , and Hansa Brillant Yellow 5GX-02 (Hoechst). P1362 / 96MX The third component in the composition in the ink of the present invention is the aqueous carrier. This component comprises water (preferably deionized water) or a mixture of water with at least one water-soluble organic solvent. The aqueous carrier component is present in from about 50% to about 93%, preferably from about 70% to about 80%, of the compositions of the present invention. The selection of a suitable mixture depends on the specific ink requirements that are being formulated, such as the desired surface tension and viscosity, the pigment that will be used, the drying time required for the pigmented ink and the type of paper in the which ink will be printed. Representative examples of water-soluble organic solvents that may be selected include (1) alcohols, such as methyl alcohol, ethyl alcohol, n-propyl alcohol, iso-propyl alcohol, n-butyl alcohol, sec-butyl alcohol, t-butyl alcohol, iso-butyl alcohol, n-furfuryl alcohol and tetrahydrofurfuryl alcohol; (2) ketones or keto alcohols, such as acetone, methyl ethyl ketone and diacetone alcohol; (3) ethers such as tetrafuran and dioxane; (4) ethers, such as ethyl acetate, ethyl lactate, ethylene carbonate and propylene carbonate; (5) polyhydric alcohols, such as ethylene glycol, P1362 / 96MX diethylene glycol, glycerol, 2-methyl-2,4-pentanediol, 1,2,6-hexanetriol and thiodiglycol; (6) lower alkyl monoethers or diethers derived from alkylene glycols, such as ethylene glycol monomethyl (or monoethyl) ether, diethylene glycol monomethyl (or monoethyl) ether, propylene glycol monomethyl (or monoethyl) ether, triethylene glycol monomethyl (or monoethyl) ether and diethylene glycol dimethyl (or diethyl) ether; (7) nitrogen-containing cyclic compounds, such as pyrrolidone, N-methyl-2-pyrrolidone, and 1,3-dimethyl-2-imidazolidinone; and (8) sulfur-containing compounds, such as dimethyl sulfoxide and tetraethylsulfone. Other useful solvents include lactones and lacta as. When mixtures of water and an organic solvent are used as the carrier medium of the present invention, the medium typically contains from about 25% water / 75% organic solvent to about 99.9% water / 0.1% organic solvent. Preferred proportions are from about 50% water / 50% organic solvent to about 99.9% water / 0.1% organic solvent. These percentages are based on the total weight of the aqueous carrier medium. It will be understood that, as used herein, the term "organic solvent", which may be used in the aqueous carrier medium, is not intended to include the specified materials that are used in the carrier component.

P1362 / 96MX solvent of the present invention. Preferred organic solvents for use in the aqueous carrier medium component of the present invention include polyhydric alcohols, such as "ethylene glycol, 1,2,6-hexanediol, thiodiglycol, hexylene glycol and diethylene glycol; diols such as pentanediol, hexanediol and homologous diols; glycol ethers, such as propylene glycol laureate, glycerol, and lower alkyl ethers of polyhydric alcohols, such as ethylene glycol monomethyl (or monoethyl) ether, diethylene glycol methyl (or ethyl) ether and triethylene glycol monomethyl (or monoethyl) ether; alcohols, such as methanol, ethanol, propanol and butanol, ketones such as acetone, ethers such as tetrahydrofuran and dihexane, ethers, such as ethyl acetate, sulfoianes, N-methylpyrrolidone, lactones such as β-butyrolactone, lactams such as 2- pyrrolidone, l-methyl-2-pyrrolidone Although organic solvents can impart useful properties, such as a faster drying time, a Reduced orientation and increased penetration to the ink compositions, generally (in contrast to the co-solvent materials defined herein) do not improve the optical density, the stability of the composition or the print quality. Particularly, preferred organic solvents include 1,5-pentanediol, 1,6-hexanediol, 1,7-heptanediol, P1362 / 96MX n-propanol and mixtures thereof. The final component required for use in the compositions of the present invention is the cosolvent mixture comprising from about 5% to about 40%, preferably, from about 5% to about 30%, more preferably from about 10% to about 20%, of the final composition. This co-solvent mixture contains a first component which is 1,3-propanediol, 1,4-butanediol, or a mixture of these materials. 1,3-propanediol is preferred. In addition, it also contains a second component which is a compound of the polyethylene glycol type, a polyol / alkylene oxide condensate or a mixture of these compounds. The second component used in this co-solvent mixture may be a polyethylene glycol or a mixed poly (ethylene) (propylene) glycol, having a molecular weight of from about 200 to about 600. Polyethylene glycols (PEG) are preferred, particularly it prefers a polyethylene glycol having a molecular weight of about 400. The second component in the co-solvent may also be a polyol / alkylene oxide condensate having the formula: P1362 / 96MX CH2O (CH2CHXO) aH [~ RC (CH2) bO (CH2CHXO) cH | f CH2? (CH2CHXO) dH where x is H or CH3, R is H, C1-C4 alkyl or -CH20 (CH2CH20) eH, b is 0 or 1, a + d + f (c + e) ranges from about 2%, to about 100% and, f ranges from about 1 to about 6%. The condensed polyol / alkylene oxide compounds useful in the present invention are reaction products of a polyol and an alkylene oxide. These are described in U.S. Patent 5,180,425, to Matrick, et al., Issued January 19, 1993, and incorporated herein by reference. These compounds generally have a solubility in water of at least about 4.5% (ie, 4.5 parts in 100 parts of water) at 25 ° C. The alkylene oxide used in these compounds is either ethylene oxide or propylene oxide or combinations of both oxides. The reaction with a single alkylene oxide can produce mixtures of compounds with varying degrees of oxyalkylation, so that the structures illustrated are based on average compositions that can contain a range of oxide units.

P1362 / 96MX alkylene. Random polymer and block chains of propylene and ethylene oxide can be used. The polyol reacted with the alkylene oxide may contain three or more hydroxyl groups. Useful triols are glycerol, trimethylol propane and trimethylol ethane. Other such as 1,2,4-butanetriol and 1,2,6-hexanetriol may also be used. Useful tetroles include pentaperitritol, di- (trimethylol propane), and methyl glucosides. Glucose, which is a pentole, can be used. Sorbitol is a useful hexol. Other useful hexoles include dipentaerythritol and inositol. Diols are generally not suitable for use in the present invention, because their alkylene oxide condensates are generally not compatible with pigment dispersions. An exception may be the alkylene oxide condensates of neopentyl glycol. Some examples of polyol / alkylene oxide condensates are the following: P1362 / 96MX a + d + f Product R (c + e) b f Liponic ® EG-11 -H 26 0 1 Liponic ® SO-201 -H 20 0 4 Photonol ® PHO-71492 -C2HS 2.7 Photonol ® PHO-71552 -C2H5 7.4 Voranol ® 230-6603 -CHj 3.0 Voranol ® 234-6303 -C2H $ 3.0 Fomrez ® T-2794 -CjH5 3.1 Fomrez ® T-3154 -Q? 4.1 1 Lipo Chemicals Co., Paterson, N.J. Hen el Corp., Ambler, PA 3 Dow Chemical Co., Midland, MI 4 Witco Corp., Organic Division, New York, NY A particularly preferred alkylene oxide polyol / condensate for use in the present invention is Liponic EG-1, described above. This material, which has the CTFA name of glycereth-26, is the ethylene oxide adduct of 26 moles of glycerin and is commercially available from Lipo Chemicals, Inc. Paterson, New Jersey. The first and second components of the co-solvent mixture are present in a dry ratio (first component: second component) of from about 70:30 to about 30:70. When the co-solvent mixture contains a compound of the polyethylene glycol (PEG) type and either 1,3-propanediol or 1,4-butanediol, the optimum weight ratio of PEG: diol goes P1362 / 96MX from approximately 50:50 to approximately 70:30. When the co-solvent mixture contains a polyol / alkylene oxide condensate compound together with 1,3-propanediol or 1,4-butanediol, the optimum condensate: diol ratio ranges from about 30:70 to about 50:50. In general, the most preferred proportion of co-solvent component is about 50:50. The ink composition of the present invention can be prepared by any method known in the art for making the compositions. The key aspect of the composition is that the pigment and the polymeric dispersant form a stable dispersion of the aqueous carrier / co-solvent mixture. In one method, the segment and the polymeric dispersant are mixed first. The resulting mill base is then ground in a harvester to reduce the particle size to an acceptable level. This material is then mixed with the other components of the ink and with water to produce the desired concentration of ink. Optionally, a surfactant can be added to improve the pigment dispersion and to modify the surface tension of the ink to control its penetration into the paper. Suitable surfactants include non-ionic, amphoteric and ionic surfactants. Other additives, such as biocides, humectants, agents P1362 / 96MX viscosity modifiers and chelators can be added to the ink compositions at their levels established in the art to achieve their benefits known in the art. The process for preparing pigmented inkjet ink typically prefers that its particles be reduced in size using a grinding mill. It is desired that the inks have a shelf life stability of two years or more and that the only limitation, considering the particle size of the pigment, is of the selected size is one that is capable of producing the above-described shelf stability. This particle size requirement is achieved by subjecting the pigment particles to shear by using a small grinding medium. The typical medium used in the preparation of pigmented tapes includes spherical particles made of stainless steel, zirconium silicate, zirconium oxide and glass. The particulate medium of high surface area used in this grinding process sometimes wears out and remains in the ink dispersion, contaminating the final formulation. Pollution, depending on the type and amount, can adversely affect the performance of the ink. For example, contamination can result in discoloration of color pigment formulations (particularly, P1362 / 96MX light colors such as yellow) alteration of the pH as a result of the reaction of the medium with the unique compounds of the formulation, a difficult filtration of the ink and a decrease in the functional stability of the ink during the life of the print cartridge . The preferred grinding medium is ceramic spherical particles having a very smooth and uniform outer surface, a high density and high hardness. A particularly preferred grinding medium for use in the preparation of the tapes of the present invention is the material commercially available under the name YTZ Cera ic Beads, commercially available from S.E. Firestone Associates, Philadelphia, Pa. And, manufactured by Nippon Kagaku Togyo. This material is in the form of spherical ceramic particles that have a core of high purity zirconium oxide treated with yttrium to make the spheres highly resistant to wear. The particles are perfect spheres having a very smooth and uniform outer surface, a density of 6.0 grams per cubic centimeter and a hardness of 91. Examples of processes for manufacturing these materials are described in Japanese Published Application 57-191234, published on November 25, 1982, and Japanese Published Application 56-145118, published November 11, 1981, both incorporated herein by reference.

P1362 / 96MX The following examples are detailed descriptions of methods of preparing and using the ink compositions of the present invention. The detailed descriptions fall within the scope of the more general description set forth above and serve to exemplify it. The examples are presented for illustrative purposes only and are not intended to be a restriction on the scope of the invention.

EXAMPLE 1 An ink composition of the present invention, which uses the polymeric dispersant having the following general formula (hereinafter referred to as terpolymer L): P1362 / 96MX O CH3 If CH (CH2) d I CH3 Terpolymer L is prepared as follows: a solution of 22.8 g of methacrylic acid (265 mmol), 7.84 g of polydimethylsiloxane terminated with onometacryloxypropyl (PDMS-A) (8.7 mmol, MW 900), 2.95 g of stearyl methacrylate (8.7 g) mmol), 2.06 g of dodecanethiol (9.9 mmol), 0.64 g of dimethyl 2,2'-azobiisobutyrate (2.84 mmol) and 100 L of isopropyl alcohol which was degassed with argon (effected by repeated partial evacuation followed by refilling with argon using a Valve P1362 / 96MX Firestone), then heated to 70 ° C for 16 hours. The mixture was allowed to cool to room temperature and then slowly added to 1.0 L of rapidly stirred hexane. The resulting solid was asylated by vacuum filtration and dried in vacuo overnight at 80 ° C. The yield of the reaction is about 85%. The copolymer was characterized by proton NMR and GPC. A stock solution of the dispersant was prepared as follows: a 400 L beaker containing 40 g of DI water, was placed on a hot plate with a magnetic stirrer. To the beaker was added 12 g of terpolymer L, while stirring, then 18 g of 20% KOH was added to the system. The mixture was heated at 50 ° C for 2 hours. The pH was adjusted to 7.5 and was necessary, by the addition of 20% KOH. DI water was then added to bring the weight of the stock solution to 100 g (12% terpolymer L).

Preparing the base for mill A Components Quantity Smoke Black (Cabot Corp., Monarch 880) 26.0 g Terpolymer stock solution L 54.0 g Water DI 100.0 g P1362 / 96MX Base preparation for mill B Components Quantity Smoke Black (Degussa Corp., Special Black 4A) 26.0 g Terpolymer stock solution L 54.0 g Water DI 100.0 g The base preparations for mill A and B are prepared as follows. The components are pre-mixed by mechanical agitation until there are no visible lumps. The mixture is dispersed by a process of atriculator using a standard Szegvari model 01 strut with 10-12 mesh zirconium silicate pellets at a speed of 700 rpm. The attrition process is usually carried out for a minimum of one hour, however, longer times at controlled temperature can also be used. The resulting ground mill base was removed from the harvester and diluted by the addition of deionized water to a final solids percentage of 12%. Using the dispersion described in the preparation of the base for mill A, an ink composition was prepared having the following components: 4% (by weight) of carbon black 1% terpolymer L 10% polyethylene glycol (MW = 400) 10% 1,3-propanediol 75% DI water P1362 / 96MX The ink composition was prepared using the following procedure: (1) Mix DI, PEG and 1,3-propanedil water for 20 minutes. (2) Add the base for ground mill (Base Preparation for Mill A) to the mixture while stirring. Continue stirring for 20 minutes. (3) Adjust the pH of the composition in 8.3 by the addition of 20% KOH. (4) Filter at 1.2 μm. This ink, when used in an inkjet printer, exhibited good maintenance characteristics, good optical density and highly desirable printing characteristics when tested on six different representative types of paper.

EXAMPLE 2 Using the base preparation for mill B, and the preparation method described in Example 1, an ink composition was prepared having the following components: 3% carbon black 0.75% terpolymer L 14% polyethylene glycol ( MW = 400) P1362 / 96MX 6% 1, 3-propanediol 76.25% DI water This ink, when used in an inkjet printer, exhibited good optical density, has good maintenance characteristics and exhibits highly desirable printing characteristics when tested in six representative types of paper.

EXAMPLE 3 Using the base preparation for mill A, and the preparation method described in Example 1, an ink composition having the following components was prepared: 3% carbon black 0.75% terpolymer L 10% polyethylene glycol (MW = 400) 10% 1, 3-propanediol 76.25% DI water This ink, when used in a conventional inkjet printer, exhibits good maintenance characteristics, provides a printed product that exhibits a set of printing characteristics highly desirable, including a good optical density.

P1362 / 96MX EXAMPLE 4 Using the base preparation for mill B, and the preparation method described in Example 1, an ink composition was prepared having the components described below: 3% carbon black 1% terpolymer L 10 Liponic% EG-1 10% 1,3-propanediol 76% DI water This ink, when used in a conventional ink jet printer, exhibits good maintenance characteristics and has excellent printing characteristics (including good optical density) ) when used in 6 representative samples of papers.

EXAMPLE 5 Using the base preparation for mill B, and the preparation method described in Example 1, an ink composition was prepared having the components described below: 3% carbon black 0.75% terpolymer L 10% 1, 3-propanediol 10% polyethylene glycol (mw = 400) 76.25% DI water P1362 / 96MX This ink, when used in a conventional ink jet printer, exhibits good maintenance characteristics and has good optical density when tested on six types of paper reagents.

EXAMPLE 6 Using the procedures described in Example 1, an ink composition having the following components was prepared: 3% carbon black (FW18, Degussa Corp., Ridgefield Park, NJ) 0.75% Terpolymer L 10% 1, 3-propanediol 10% polyethylene glycol (mw = 400) 76.25% DI water This ink, when used in a conventional ink jet printer, exhibits good maintenance characteristics and has a good optical density when tested in six types of representative of paper.

EXAMPLE 7 Using the procedures described in Example 1, an ink composition having the following components was prepared: P1362 / 96MX 3% carbon black (FW18) 0.75% terpolymer L 10% 1,3-propanediol 10% Liponic EG-1 0.15% Kathon® PFM (biocide - Rohm &Haas) 76.10% DI water This ink , when used in a conventional ink jet printer, exhibits good maintenance characteristics and has a good optical density when tested on six types of paper reagents.

EXAMPLE 8 Using the procedures described in Example 1, an ink composition having the following components was prepared: 3% carbon black (Special Black 4A) 0.75% terpolymer L 10% 1,4-butanediol 10% polyethylene glycol ( mw-600) 0.2% n-propanediol 75% DI water This ink, when used in a conventional ink jet printer, exhibits good maintenance characteristics and has a good optical density when tested on six types of paper reagents .

P1362 / 96MX

Claims (18)

1. NOVELTY OF THE INVENTION Having described the present invention, it is considered as a novelty and, therefore, the content of the following CLAIMS is claimed as property: 1. An aqueous ink composition suitable for use in inkjet printers, characterized because it comprises: (a) from about 1% to about 10% of a pigment; (b) from about 0.1% to about 10% of a polymeric dispersant for the pigment; (c) from about 50% to about 93% of an aqueous carrier; and (d) from about 5% to about 40% of a co-solvent mixture comprising; (1) 1,3-propanediol or 1,4-butanediol, and (2) a material selected from the group consisting of: (i) polyethylene glycols and mixed poly (ethylene) (propylene) glycols, having a molecular weight of from about 200 to about 3,400; (ii) a polyol / polyalkylene oxide condensate having the formula
2. P1362 / 96MX CH2? (CH2CHXO) aH [~ RC (CH2) bO (CH2CHXO) cH | f CH2? (CH2CHXO) dH wherein X is H or CH3, R is H, Ci-C4 alkyl or CH20 (CH2CH20) eH, b is 0 or 1, a + d + f (c + e) from about 2 to about 100, and f from about 1 to about 6; and (iii) mixtures thereof; wherein the weight ratio (1): (2) ranges from about 70:30 to about 30:70. 2. An ink composition according to claim 1, characterized in that the solvent mixture comprises (1) 1,3-propanediol or 1,4-butanediol, and (2) a material selected from the group consisting of: (i) polyethylene glycol having a molecular weight of from about 200 to about 3,400; (ii) the polyol / alkylene oxide condensate wherein X is hydrogen, R is hydrogen, b
3. P1362 / 96MX is O, f is 1, and a + d + f (c + e) 26; and (iii) mixtures thereof. 3. An ink composition according to claim 2, characterized in that it contains from about 10% to about 20% of the co-solvent mixture. 4. An ink composition according to claim 3, characterized in that in the cosolvent mixture, the polyethylene glycol component (i) is polyethylene glycol having a molecular weight of about 400. 5. An ink composition according to claim 4, characterized in that the cosolvent mixture, is a mixture of 1,3-propanediol and polyethylene glycol having a molecular weight of about 400. 6. An ink composition according to claim 4, characterized in that the weight ratio (1): (2) is approximately 50. :fifty. 7. An ink composition according to claim 1, characterized in that the polymeric dispersant comprises in its main chain structural units selected from the group consisting of
4. P1362 / 96MX (a) - (CH2CH) -? (CH2CHÍ2 (CH2CH) y- O O
5. OH H-N OH wherein x + y ranges from about 20 to about 200, z ranges from about 1 to about 10, and R is C6-C36 alkyl or Ri where Ri is a C4-C2Q alkyl; or (b) - (
6. P1362 / 96MX wherein x + y ranges from about 20 to about 200, z ranges from about 1 to about 10, and n goes from about 2 to about 40, and R2 is alkyl or aryl; (c) - < CH2
7. R3 wherein x + y ranges from about 20 to about 200, z ranges from about 1 to about 10, and R3 is H or CH3, R4 is H, CH3 or OCH3, and n ranges from about 10 to about 60; or those that have the formula
8. P1362 / 96MX () wherein and ranges from about 6 to about 20, x ranges from about 1 to about 5, and R5 is a C6-C30 alkyl. 8. An ink composition according to claim 7, characterized in that the aqueous carrier is water or a mixture of water and an organic solvent consisting of ethylene glycol, 1,2,6-hexanediol, thiodiglycol, hexylene glycol, diethylene glycol, pentanediol, hexanediol, laureate. of propylene glycol, glycerol, monomethyl (or monoethyl) ether of ethylene glycol, methyl (or ethyl) ether of diethylene glycol, monomenthyl (or monoethyl) ether of triethylene glycol, methanol, ethanol, propanol, butanol, acetone, tetrahydrofuran and dihexane, ethyl acetate, sulfolanes, N-methylpyrrolidone,? -butyrolactone, 2-
9. P1362 / 96MX pyrrolidone, l-methyl-2-pyrrolidone l- (2-hydroxyethyl) -2-pyrrolidone and mixtures thereof 9. An ink composition according to claim 8, characterized in that the pigment is selected from the group consisting of carbon black, titanium dioxide, iron oxide and color pigments. 10. An ink composition according to claim 9, characterized in that it contains from about 0.5% to about 4% of the insoluble pigment. 11. An ink composition according to claim 9, characterized in that the polymeric dispersant is an inserted copolymer, having a molecular weight of about 1,500 to about 20,000, comprising: (a) a hydrophilic polymeric segment; (b) a hydrophobic polymeric segment having a molecular weight of about 400 to about 3,000, which incorporates a hydrolytically stable siloxyl substituent; (c) a stabilizing segment having a molecular weight of from about 200 to about 2,000, selected from the group consisting of surfactant macromers
10. P1362 / 96MX protective colloidal macromers and non-siloxyl hydrophobic monomers. 12. An ink composition according to claim 11, characterized in that the polymeric dispersant comprises, in its chain, the formula
11. CH3 If CH
12. (CH2) d
13. CH3 wherein x ranges from about 5 to about 100, and ranges from about 1 to about 2, z ranges from about 1 to about 5, to
14. P1362 / 96MX from about 3 to about 45, b ranges from about 3 to about 29, c from about 2 to about 8, d goes from 0 to about 7. 13. An ink composition according to claim 11, characterized in that the The cosolvent mixture comprises: (1) 1,3-propanediol or 1,4-butanediol, and (2) a material selected from the group consisting of: (i) polyethylene glycol having a molecular weight of from about 200 to about 3,400; (ii) the polyol / alkylene oxide condensate wherein X is hydrogen, R is hydrogen, b is 0, f is 1, and a + d + f (c + e) 26; and (iii) mixtures thereof. 14. An ink composition according to claim 13, characterized in that it contains from about 10% to about 20% of the co-solvent mixture. 15. An ink composition according to claim 14, characterized in that the cosolvent mixture comprises (1) 1,3-propanediol or 1,4-butanediol, and
15. P1362 / 96MX (2) a material selected from the group consisting of: (i) polyethylene glycol having a molecular weight of about 400; (ii) the polyol / alkylene oxide condensate wherein X is hydrogen, R is hydrogen, b is 0, f is 1, and a + d + f (c + e) 26; and (iii) mixtures thereof.
16. 16. An ink composition according to claim 15, characterized in that the weight ratio (1): (2) is approximately 50:50.
17. 17. An ink composition according to claim 16, characterized in that the aqueous carrier is water or a mixture of water with n organic solvent selected from the group consisting of 1,5-pentanediol, 1,6-hexanediol, 1,7-heptanediol. , n-propanol and mixtures thereof, wherein the aqueous carrier comprises from about 50% water / 50% organic solvent to about 99.9% water / 0.1% organic solvent.
18. 18. A co-solvent mixture characterized in that it comprises: (1) 1,3-propanediol or 1,4-butanediol, and (2) a material selected from the group consisting of: (i) polyethylene glycols and poly (ethylene) P1362 / 96MX (propylene) mixed glycols, having a molecular weight of from about 200 to about 3,400; (ii) a polyol / polyalkylene oxide condensate having the formula CH2? (CH2CHXO) aH? ~ RC (CH2) bO (CH2CHXO) cH] f CH2O (CH2CHXO) dH where X is H or CH 3, R is H, alkyl C! -C4 or CH20 (CH2CH20) eH, b is 0 or 1, a + d + f (c + e) ranges from about 2 to about 100, and f goes from about 1 to about 6; and (iii) mixtures thereof; wherein the weight ratio (1): (2) ranges from about 70:30 to about 30:70.