MXPA00000900A - Composition and method for improved ink jet printing performance - Google Patents

Abstract

This invention relates to a composition useful for surface treating a sheet substrate for ink jet printing, the composition comprising a salt of a divalent metal, the salt being soluble in an aqueous sizing medium at about pH 7 to about pH 9, the aqueous sizing medium further comprising a carrier agent and a sizing agent. It also includes a method of making an ink jet printing substrate capable of retaining indicia formed by ink jet printing using pigmented ink, the method comprising surface treating the substrate with an aqueous sizing medium containing a divalent metal salt. A method for improving print quality of ink jet printing of pigmented ink on a surface treated substrate made using the composition or method is also disclosed, as is the paper so made, with and without ink jet printed pigmented ink applied thereto. Indicia printed thereon will have improved print quality characteristics.

Description

COMPOSITION AND METHOD FOR ENHANCED PERFORMANCE OF INK-IN PRINTING BACKGROUND OF THE INVENTION The present invention relates to compositions for surface treatments for substrates, such as paper and polymeric plastic material, used for inkjet printing, as well as methods for producing the printing substrates, the treated printing substrate itself, methods to improve the printing of inkjet and printed substrates by inkjet printing. In current, commercial business and office environments, paper is commonly used for multiple purposes, such as reprographic copying, laser printing, inkjet printing, and the like. Special papers have been developed for each type of application, but as a practical matter, a multi-purpose paper suitable for all these uses is convenient. Of the above-mentioned uses, inkjet printing probably has the most stringent requirements, since the ink is printed wet and must provide good print quality and fast drying, properties that are often difficult to achieve together.

Much of the paper intended for inkjet printing, is coated with various types of special layers, typically, a layer of water soluble polymer and silica and other insoluble fillers, which make the paper very expensive, especially considering the desire and tendency by using paper for other general office purposes, such as copying and laser printing. A typical cost per page of this paper is approximately $ 0.10. By comparison, uncoated paper, such as copy paper in general, sells for less than $ 0.01 per page. Inkjet printing has been practiced commercially only in recent years. The desktop inkjet printing is even an even more recent development. Most inkjet printing inks, both black ink and color inks, are dye-based inks. The use of pigmented inks with black in desktop inkjet printing is relatively new, dating from the introduction of the Hewlett Packard DeskJetMP 660C printer in 1994. Desktop inkjet printing, with pigmented inks other than black , for example color inks based on pigment, is still to be commercially available, but it is expected to be commercially available in the near future.

The paper is made with and / or treated superficially with sizing agents, primarily to avoid excessive penetration, absorption by capillarity or dispersion of water or ink. Very different types of non-reactive and reactive sizing agents are well known in the paper production industry. Paper typically made under acidic paper production conditions, referred to as acidic paper, is usually prepared with well-known resin or rosin derivatives (referred to herein as "dispersed rosin resin sizing agents"), an agent of non-reactive sizing. Some papers made under neutral and alkaline paper production conditions can also be treated with dispersed turpentine resin sizing agents. The most common sizing agents for fine paper made under alkaline conditions, referred to as alkaline paper, are alkenyl succinic anhydride (ASA) and alkyl ketene dimer (AKD). Another class of sizing agents useful for sizing fine paper includes ketene dimers and multimers that are liquid at room temperature, such as dimers and multimers of alkenyl ketene. These are reactive sizing agents, since they have functional reactive groups that bind covalently with cellulose fibers in the paper and hydrophobic tails that are oriented away from the fiber. Nature and orientation of these hydrophobic tails causes the fiber to repel water. The increasing popularity of inkjet printers has also focused attention on the sizing requirements for paper intended for this end-use application. The following inkjet printing characteristics relating to print quality have been identified by inkjet printer manufacturers as important for high-quality inkjet printing, many of which are affected by the type and treatment of paper or other substrate to which the ink is applied. OPTICAL DENSITY: The intensity of color as measured by the change in reflectance (OD = log10 (I.,. / Ir (where I and Ir = intensities of incident and reflected light, respectively) where high optical density is desired. PRINT TRANSPARENCY: Intensity of color of an image that is observed from the back side of the sheet, which can be measured by optical density PRINTING TRANSPARENCY STAINED: Often on the back side of a printed image, there is a stained appearance, since that the ink finds its way through bites or areas of poor or poor training.

LINE GROWTH (SCRAPPING) (PLUME): the final printed size characteristics against the initial printed size, which can be seen as lost resolution. It happens so much simple color printing and when printing colors close to and one over another. ROUGH ROUGH (ONLY OCCASIONS PLUMBED): A rough to smooth appearance of the edges as the ink disperses heterogeneously away from the printed area. It occurs in both single-color printing and when colors are printed near one or the other. CAPILLARY ABSORPTION: observed as long spikes of ink that extend from printed areas such as when ink drips on a single fiber on the paper surface. MOTE: heterogeneity of the optical density of printing in a solid printed area. TANNED: an appearance of black printed areas with a bronze glow (reddish tint). COLOR INDEX: the shade or tone of the printed colors or combined colors. In addition, with a black composite print (consisting of light blue, magenta and yellow) there is often a greenish tinge.

DRYING TIME: the time it takes the ink to dry so it does not get dirty or transfer to other surfaces. WATERFALL: low print density lines that occur between print head steps, which are usually observed in some very high size papers. , INSUFFICIENT POINT GAIN: Similar to waterfall but showing a visible white area around ink spots in a solid print area because they have not dispersed enough. The effect is to reduce the optical density. NEBULIZATION: very small spots visible around the edges of printed areas that come from where very small droplets (mist) of ink have been sprayed out of the main print droplet. It has been known to coat paper used as photocopy paper, with materials that increase its conductivity, for example treating the paper in such a way that the paper has a hygroscopic inorganic salt through its body structure as described by Uber et al. US patent No. 3,116,147; when coating with resin-inorganic salt coatings as described by Cheng in US Pat. No. 3,615,403; by surface treatment with a binder such as starch and a sulfate salt as described by Green, Jr. et al. Patent 3,884,685; or by surface treatment with micro encapsulated salts as described by Geer in U.S. Pat. No. 4,020,210. Calcium carbonate is often added to the paper as a dispersed filler. Calcium carbonate has the disadvantage of being a relatively insoluble particulate solid that requires dispersing in aqueous systems. The presence of fillers or fillers such as calcium carbonate can lead to increased wear of the equipment parts during papermaking and end-use applications. Calcium chloride in high concentrations with a reactive sizing agent has been added to the paper as a first of two coatings, the second of which includes calcium carbonate, potassium silicate and carboxy methyl cellulose, to control burning characteristics such as in cigarettes, as described by Kasbo et al. in the US Patent No. 5,170,807, but this paper is not suitable for inkjet printing, and these high concentrations of calcium chloride are not suitable for preparing a paper used for printing.

Aluminum sulfate (alum) is an additive common to many paper machines, usually added at the wet end of a paper production machine. Alum is added to turpentine resin sizing dispersions, used as internal sizing in paper production, and the alum level in the turpentine resin sizing dispersion can be as high as 66% in the solids. Dissolve alum at low pH to give cationic aluminum species. The alum will form non-cationic species in a typical sizing press with a pH of 8. Calcium chloride has been added to paper for applications in milk containers. This paper has a high basis weight, approximately 3 to 5 times larger than normal copy paper and coated with wax. Sizing compositions, particularly for sizing paper used in products with superior liquid storage properties based on aluminum or alkali metal, include a metal salt selected from zirconium, hadmium, titanium and their mixtures, as described in Pandian et al. the US Patent No. 5,472,485. Sizing dispersions containing storage stabilizing amounts of inorganic salts of aluminum or alkali metal soluble in water, are described in International Patent Publication W096 / 35841 of Eka Chemicals AB, useful as internal sizes or surface sizes for paper, cardboard and paperboard. . Paper with relatively high concentrations of 0.5 to 5% deliquescent salt has been treated such that the paper, used as a base material for a resin-coated laminate, has no corrugation at the edges when the paper was coated on both surfaces with films of synthetic resin, as described by Minagawa et al. in the US Patent No. 4,110,155. Suitable paper for inkjet printing with dye-based inks is described by Kuroyama et al. In U.S. Pat. No. 5,522,968, Zuzuki et al. In U.S. Pat. No. 5,620,793 and Zakaki et al. In U.S. Patents. Nos. 5,266,383 and 5,182,175. A method and equipment for inkjet printing with pigmented ink are described by Kashiwazaki et al. In U.S. Pat. No. 5,640,187. As is clear from the descriptions of Kashiwazaki and co-workers, there is a need for quality inkjet printing performance without resorting to the use of coated specialty paper.

The descriptions of all patents, published applications and other publications identified here are incorporated by reference. COMPENDIUM OF THE INVENTION One aspect of this invention relates to a composition useful for surface treatment of a substrate for inkjet printing, the composition comprises a salt of a divalent metal, the salt is soluble in an aqueous sizing medium of about pH 7 to approximately pH 9, the aqueous sizing medium further comprises a carrier agent and a sizing agent. Another aspect of this invention relates to a composition useful for surface treatment of a substrate for inkjet printing with pigmented ink, the composition comprising a carrier agent, a sizing agent and a salt selected from the group consisting of calcium, magnesium chloride, calcium bromide, magnesium bromide, calcium nitrate, magnesium nitrate, calcium acetate and magnesium acetate. Yet another aspect of this invention relates to a method for producing an ink jet printing substrate, capable of retaining signals formed by ink jet printing using pigmented ink, the method comprising (a) surface treatment of the substrate with a composition comprising a divalent metal salt, the salt is soluble in an aqueous sizing medium at about pH 7 to about pH 9, the aqueous sizing medium further comprises a sizing agent; and (b) drying the treated substrate. Yet another aspect of the present invention relates to a method for improving print quality of signals formed by inkjet printing, of pigmented ink on a surface treated substrate comprising surface treatment of the substrate using the metal salt composition. divalent or by using the method of this invention, drying the treated substrate and printing the pigmented ink on the dry treated substrate by ink jet printing to form the signals. Yet another aspect of the invention is a printing substrate made using the divalent metal salt composition or by using the method of this invention, the printing substrate is capable of transporting signals formed from pigmented ink on the dry treated substrate, such that the signals have at least one improved ink jet printing characteristic as compared to a treated printing substrate using the same composition or method as those of this invention but without the salt. DETAILED DESCRIPTION OF THE INVENTION It has been unexpectedly discovered that ink-jet printing quality on a surface-sizing paper or other surface-treated substrate can be improved if the substrate surface is treated with an aqueous sizing medium containing a salt of water. divalent metal which is soluble at about pH 7 to about pH 9. The divalent metal salt is premixed with the aqueous sizing medium, which contains a sizing agent and preferably a carrier agent, to form a composition according to the present invention. invention. The divalent metal salts employed in this invention provide unexpected and surprising improvements in paper inkjet printing thus treated of at least one and preferably several of the inkjet printing quality characteristics, and particularly improved optical density, Reduced transparency of printing of the ink to the back side of the paper and improved print quality with reduced edge roughness and line growth. The benefits are evidenced by the use of pigmented inks that are used in inkjet printing. The benefits of this invention have been demonstrated with print samples that use a Hewlett Packard DeskJet 660C printer ("HP 660C" printer) that uses a pigmented black ink. The same benefits have not been observed with a Hewlett Packard DeskJet 560C printer or an Epson 720 Stylus printer, both of which use dye-based black ink instead of pigmented black ink. The benefits have not yet been observed with color inks based on dye in comparison with pigmented black ink, which will be used with the HP 660C printer. As used herein, the term "pigmented ink" means an ink wherein a black or colored component is insoluble in the ink formulation and the term "dye-based ink" means an ink wherein the black or colored component, It is soluble in the ink formulation. The ink for which the present invention is particularly effective, is an ink containing an anionically charged pigment and does not contain a dye based on nitrogen or a dissolution aid for this dye which is a nitrogen compound that liberates ammonia or ammonium ion during or as a result of printing on the substrate, such that the substrate must contain a material to absorb the ammonia or ammonium ion. Reports in the literature confirm that the inkjet industry is moving towards the use of pigmented ink; see American Ink Maker, 75 (6): June 60 1997). The trend in the industry to pigment-based inkjet inks includes color inks, although pigmented color inks have not yet been marketed for desktop printing applications. The general consensus in the printing industry is that pigment-based inks provide permanence and better performance for printed material exposed to an outdoor environment, such as print advertising or notices on boards or other signs, bus stops, outdoor benches and other Outdoor uses. This invention is extremely beneficial because it provides greatly improved ink jet printing performance on uncoated paper and thus avoids the need to use costly specialty papers for quality inkjet printing performance. Currently, providing paper with superior inkjet printing performance requires that the paper be coated with a layer of water soluble polymer and silica and other fillers or other insoluble fillers. A typical cost per page of this paper is approximately $ 0.10, in comparison, uncoated paper such as copy paper is usually sold for less than $ 0.01 per page. This uncoated paper is typically internally prepared or treated in the paper machine in a sizing press, with a typical sizing agent, together with the usual additives, including emulsifiers, retention aids, optical brighteners and other additives. The present invention includes a composition containing, in addition to water, the soluble divalent metal salt of this invention, a sizing agent and preferably a carrier agent, wherein the components do not result in precipitation or coagulation; and a method for surface treatment of paper or other substrate with an aqueous sizing medium containing a divalent metal salt soluble in water. The invention also includes printed and printable paper with improved inkjet and other substrates as well as an improved ink jet printing method. The invention is also useful for improving ink jet printing on transparency films and non-cellulosic sheet substrates. The metal salt employed in this invention is a divalent metal salt soluble in the amount employed in an aqueous sizing medium, from about pH 7 to about pH 9. The aqueous sizing medium can be in the form of an aqueous solution, emulsion , dispersion or latex or colloidal composition, and the term "emulsion" is used herein, as is usual in the art, to mean already a liquid-in-liquid or solid-in-liquid type dispersion, as well as a latex or colloidal composition. The metal salt of this invention is preferably an organic or mineral acid salt of a divalent cationic metal ion. The salt should be soluble in water at a pH of about 7 to about pH 9, which includes the pH of an aqueous sizing medium generally employed in a sizing press. The relative weight of the divalent cationic metal ion in the metal salt is preferably maximized with respect to the anion in the selected salt, to provide efficiencies improvements based on the total weight of the salt applied. Consequently, for this reason, for example, calcium chloride is preferred over calcium bromide. The water soluble metal salt can include a calcium, magnesium, barium or similar halide, with calcium chloride and magnesium chloride which is particularly preferred. Divalent metal salts which are effective in this invention are without limitation calcium chloride, magnesium chloride, magnesium bromide, calcium bromide, barium chloride, calcium nitrate, magnesium nitrate, barium nitrate, calcium acetate, acetate of magnesium and barium acetate. Calcium chloride and magnesium chloride are preferred, since they provide the greatest improvement in ink printing performance and operate efficiently on a cost-benefit basis. In the present invention, monovalent metal salts such as sodium chloride and potassium chloride are not as effective as equivalent metal salts for improving the print quality of pigmented inks for inkjet. The reason is not fully understood, but it is considered that it may be due to an inefficient load density. The divalent metal salt can be mixed with conventional paper sizing agents, including non-reactive sizing agents and reactive sizing agents, as well as combinations or mixtures of sizing agents. Many non-reactive sizing agents are known in the art. Examples include without limitation, the BASOPLASTMR 335D non-reactive polymer surface sizing emulsion from Basf Corporation (MT Olive, NJ), the emulsion of a copolymer of vinyl acetate and butyl acrylate FLEXBOND1 MR 325 from Air Products and Chemical Inc, (Trexlertown, PA) and PENTAPRINTMR non-reactive sizing agents (described for example in published International Patent Application Publication No. O97 / 45590, published December 4, 1997, corresponding to U.S. Patent Application No. 08 / 861,925 filed May 22, 1997 (from Hercules Incorporated, Wlllmington, Delaware) to name a few. For paper production which is carried out under alkaline pH manufacturing conditions, sizing agents based on alkyl ketene dimers (AKDs) or alkenyl ketene dimers or multimers and alkenyl succinic anhydride sizing agents (ASA) are preferred. Combinations of these and other paper sizing agents can also be employed. Ketene dimers used as paper sizing agents are well known. AKDs, which contain a β-lactone ring, are typically prepared by the dimerization of alkyl ketenes made from two fatty acid chlorides. Commercially available alkyl ketene dimer based sizing agents are often prepared from palmitic and / or stearic fatty acids, for example the sizing agents Hercon ™ and Aquapel ™ both from Hercules Incorporated. The alkyl ketene dimer sizing agents are also commercially available, for example PRECIS ™ sizing agents (from Hercules Incorporated). The patent of the U.S.A. No. 4,017,431 provides a description of non-limiting exemplary AKD sizing agents with wax mixtures and water soluble cationic resins. Ketene multimers containing more than one β-lactone ring can also be used as paper sizing agents. Sizing agents prepared from a mixture of mono- and di-carboxylic acids have been described as sizing agents for paper in Japanese Kokai No. 168991/89 and 168992/89. The publication of the European Patent Application No. 0 629 741 Al discloses mixtures of alkyl ketene dimer and multimer, as paper sizing agents employed in reprographic and high speed conversion machines. The alkyl ketene multimers are made from the reaction of a molar excess of monocarboxylic acid, typically a fatty acid, with a dicarboxylic acid. These multimer compounds are solids at 25 ° C. The publication of European Patent Application No. 0 6"66 368 A2 and U.S. Patent No. 5,685,815 to Bottorff et al. Describe paper for reprographic or high speed operations, which is internally prepared with a dimer sizing agent. and / or alkyl or alkenyl ketene multimer The preferred 2-oxetanone multimers are prepared with proportions of fatty acid to diacid in the range of 1: 1 to 3.5: 1.

Commercial ASA base sizing agents are dispersions or emulsions of materials that can be prepared by reaction of maieic anhydride with an olefin (C14-Cla). Hydrophobic acid anhydrides useful as paper sizing agents include: (i) Turpentine resin anhydride (see U.S. Patent No. 3,582,464, for example); (ii) Anhydrides having the structure (I): wherein each Rb is the same or different hydrocarbon radical; and (iii) cyclic dicarboxylic acid anhydrides which preferably have the structure (II) OR R «R7 O di; \ / Or wherein R7 represents a dimethylene or trimethylene radical and wherein Ra is a hydrocarbon radical. Specific examples of anhydrides of the formula (I) are myristoyl anhydride; palmitoyl anhydride; oleyl anhydride; and stearoyl anhydride. Preferred substituted cyclic dicarboxylic acid anhydrides falling within the above formula (II) are substituted succinic and glutaric anhydrides. Specific examples of anhydrides of the formula (II) are i- and n-octadecenylsuccinic anhydride; n-hexadecenylsuccinic acid anhydride; anhydride of i- and n-tetradocenylsuccinic acid; anhydride of docezylsuccinic acid; anhydride of decenylsuccinic acid; anhydride of ectenylsuccinic acid and heptyl glutaric acid anhydride. Non-reactive sizing agents useful in the present invention include a polymer emulsion comprising a cationic polymer emulsion, an amphoteric polymer emulsion and mixtures thereof. Preferred polymer emulsions are those in which the polymer of the polymer emulsion is made using at least one monomer selected from the group consisting of styrene, α-methyl styrene, acrylate having an ester substituent with 1 to 13 carbon atoms, methacrylate having an ester substituent with 1 to 13 carbon atoms, acrylonitrile, methacrylonitrile, vinyl acetate, ethylene and butadiene; and optionally comprise acrylic acid, methacrylic acid, maieic anhydride, maieic anhydride esters or mixtures thereof, with an acid number of less than about 80. Of these, those in which the polymer is made using at least one monomer selected from the group are more preferred. a group consisting of styrene, acrylate having an ester substituent with 1 to 3 carbon atoms, methacrylate having an ester substituent with 1 to 3 carbon atoms, acrylonitrile and methacrylonitrile. Preferably the polymer emulsion is stabilized by a stabilizer which predominantly comprises degraded starch, such as that described for example in US Patents. Nos. 4,835,212, 4,855,342 and 5,358,998. Also preferably, the emulsion of the polymer has a glass transition temperature of about -15 ° C to about 50 ° C. For traditional acid-pH paper production conditions, non-reactive sizing agents in the form of dispersed rosin resin sizing agents are typically employed. Dispersed rosin resin sizing agents are well known to those skilled in the paper production industry. Non-limiting examples of turpentine resin sizing agents are described in many patents, among them, U.S. Patents. Nos. 3,966,654 and 4,253,182 from Aldrich. The turpentine resin useful for the dispersed rosin resin sizing agents used in the present invention can be any modified or unmodified, dispersible or emulsifiable turpentine resin suitable for paper finishing, including unfortified turpentine resin, fortified turpentine resin and extended resin, as well as turpentine resin esters and their mixtures and compositions thereof. As used herein, the term "rosin resin" means any of these forms of dispersed rosin resin useful in a sizing agent. The rosin in disperse form can be any commercially available type of rosin, such as wood rosin, rubber rosin, talc rosin, and mixtures of any two or more in its raw or refined state . Talol resins and rubber turpentine resins are preferred. Partially hydrogenated turpentine resins and polymerized turpentine resins, as well as turpentine resins that have been treated to inhibit crystallization, such as by heat treatment or reaction with formaldehyde, may also be employed.

A fortified turpentine resin useful in this invention is the reaction product of rosin resin adduct and an acidic compound containing the group and is derived by reacting turpentine resin and the acidic compound at elevated temperatures from about 150 ° C to about 210 ° C. The amount of acidic compound employed will be that amount which provides fortified turpentine resin containing from about 1% to about 16% by weight of acidic adduct compound based on the weight of the fortified turpentine resin. Methods for preparing fortified turpentine resin are well known to those skilled in the art. See, for example, the methods described and illustrated in U.S. Patents. Nos. 2,628,918 and 2,684,300. . Examples of acidic compounds that contain the group • Or that can be used to prepare fortified turpentine resin, include α, β-unsaturated organic acids and their available anhydrides, specific examples of which include fumaric acid, maieic acid, acrylic acid, maieic anhydride, itaconic acid, itaconic anhydride , citraconic acid and citraconic anhydride. Acid mixtures can be used to prepare a fortified turpentine resin, if desired. Thus, for example, a mixture of the acrylic acid adduct of turpentine resin and the fumaric acid adduct can be used to prepare the dispersed rosin resin sizing agents of this invention. Also, fortified turpentine resin that is hydrogenated in substantially complete form after duct formation can be used. Various turpentine resin esters of a type well known to those skilled in the art can also be used in the dispersed rosin resin sizing agents of the present invention. Suitable exemplary turpentine resin esters may be esterified turpentine resin as described in US Pat. Nos. 4,540,635 (Ronge et al.) Or 5,201,944 (Nakata et al.).

The un fortified or fortified turpentine resin or turpentine resin may be extended, if desired, by known extenders thereof such as waxes (particularly paraffin wax and micro crystalline wax); hydrocarbon resins including that is derived from petroleum hydrocarbons and terpenes; and similar. This is achieved by melt-mixing or mixing in solution with the fortified turpentine and rosin resin from about 10% to about 100% by weight, based on the weight of fortified turpentine resin or rosin, of the extender. Also mixtures of fortified turpentine resin and unfortified turpentine resin; and fortified turpentine resin mixtures, unfortified turpentine resin, turpentine resin esters and turpentine resin extender may be employed. Mixtures of fortified and unfortified turpentine resin may comprise for example about 25% to 95% fortified turpentine resin and about 75% to 5% unfortified turpentine resin. Mixtures of fortified turpentine resin and unfortified turpentine resin and turpentine resin extender may comprise for example about 5% to 45% fortified turpentine resin, 0 to 50% turpentine resin and about 5% to 90% strength. turpentine resin extender. Hydrophobic organic isocyanates, for example alkylated isocyanates, are another class of compounds used as paper sizing agents which are well known in the art and which can be used in this invention. Other conventional paper sizing agents suitable for use in this invention include alkyl carbamoyl chlorides, alkylated melamines such as stearylated melamines and styrene acrylates. Mixtures of reactive and non-reactive sizing agents can be used in the present invention. The sizing agent composition containing the divalent metal salt of the present invention can give an additive improvement to the optical density of pigmented inkjet printing versus the performance of salt alone.; In addition, the sizing agent also improves the printing quality of dye-based inkjet inks, by virtue of the sizing agent component of the composition. Thus, the sizing compositions containing the divalent metal salts of the present invention with a sizing agent provide improved inkjet printing quality using dye-based ink and pigmented ink. There is a balance to be achieved when using the sizing agent composition containing the metal salt of the present invention. Too much of any component will not be acceptable. Low concentrations of the metal salt are preferred for surface applications within the concentration ranges specified below. Too much salt in excess of the concentrations noted below can adversely affect conductivity and cause corrosion of paper processing equipment. Calcium chloride, efficient in its performance at relatively low concentrations, is a particularly preferred metal salt. Too much of the sizing agent in excess of the specified ranges can cause cascade formation, can adversely affect the conversion and feed, can increase the cost without improving the performance benefit and can lead to deposits of material in the paper production equipment. The convenient level of sizing agent can be determined by those skilled in the art. The composition of the present invention contains about 0.01% to about 3% of the sizing agent, preferably from about 0.05 to about 3% and more preferably from about 0.1% to about 1%.

All percentages in this description are by weight based on the weight of the solution, mixture, composition or a paper as appropriate, unless otherwise indicated. The concentration of the divalent metal salt in the size composition of this invention is about 0.01 to about 3%, preferably about 0.05% to about 3% and more preferably about 0.1% to about 1%. An important parameter of this invention is the concentration or level of the divalent metal salt in the final dry paper. The amount of the metal salt in the sizing press solution or other coating medium is generally adjusted to provide the desired concentration or weight in the finished dry paper. The amount in the final paper is established by the concentration in the composition and the sizing press solution and the collection of (or amount applied to) the substrate. The concentration of the divalent metal salt in the dry paper should be about .01 to about .4%. The preferred concentration is from about 0.02 to about 0.3% and the most preferred concentration is from about 0.05% to about 0.2%, all based on the total weight of the finished dry paper. The level of addition on paper can typically be for example about 15% salt, about 0.02% and about 0.3% sizing agent and typically about 0.2% to about 10% sizing agent. Because the basis weight of the substrate such as the paper surface treated with the salt can vary, the salt concentration in the dry paper or other substrate is preferably measured as a unit weight of dry salt per unit area. The salt concentration in the substrate, after being surface treated or primed (and dried) should be about .01 g / m 'to about 1 g / m. Preferably, the concentration should be about .02 g / m2 to about .3 g / m2 and more preferably from about .03 g / m2 to about .2 g / m2. The weight ratio of the divalent metal salt, for example calcium chloride or magnesium chloride, to the sizing agent (s) and other additives in the aqueous sizing composition of the present invention is from about 1:20 to about 20. :1. More preferably, the weight ratio is from about 1: 5 to about 5: 1. In particular, the ratio is approximately 1: 3 to approximately 3: 1. The salt-containing sizing composition preferably contains a carrier agent and can also be used with other sizing composition additives conventionally employed, such as sizing press additives, provided there is no resultant precipitation or coagulation of the components of the composition. . The restrictions in the addition of materials with the salt-containing composition are compatibility and performance. Some materials such as solutions of sizing agents based on anionic polymeric styrene anhydride and strongly anionic soluble materials, for example strongly anionic rosin-based soap-based sizing agents, are not compatible with the divalent metal salts of this invention. . Those mixtures that lead to coagulation and precipitation of the aggregate material such that the paper producer can not make more paper, are not suitable. Additives that by themselves improve inkjet printing, preferably are used in combination with the metal salt of this invention because this invention also improves its performance. The sizing compositions containing the divalent metal salts of this invention are suitable for use with a wide variety of additives that preferably include a carrier agent. As used herein a "carrier agent" includes starch or a binding agent such as polyvinyl alcohol, polyvinyl pyrrolidone or polyethylene imine with which the sizing agent and the divalent metal salt and optional additives may be mixed, for application to the substrate. These combinations with one or more additives can be prepared as a pre-mix, to be added for example to a sizing press emulsion or they can be prepared in situ by addition of the individual components to a sizing press emulsion or other coating medium. Preferred pre-mix systems are pre-mixed compositions containing calcium halide and / or magnesium halide, particularly calcium chloride, with reactive preparations such as dimers and multimers of 2-oxetanone with non-reactive dressings or mixtures thereof. The non-reactive sizing agent may for example be a dispersed rosin resin sizing agent or a polymer emulsion including a cationic polymer emulsion, an amphoteric polymer emulsion and mixtures thereof as described above. Any compatible optional surface treatment additives containing the divalent metal salt can be added to the sizing composition, as long as coagulation or precipitation does not occur, and these additives include latex emulsions conventionally employed as paper additives or for other purposes.

The invention is particularly useful with alkali paper sheets prepared with 2-oxetanone dimers (such as AKDs and alkenyl ketene dimers) and 2-oxetanone multimers (such as alkenyl ketene multimers), acid anhydrides such as ASA (and with acid paper sheets treated with dispersed rosin resin sizing agents.Conventional application of other materials for improved inkjet printing, such as high charge levels bound with a water soluble polymer, or polyvinyl alcohol, can lead to rheological problems that are introduced in sizing press, but the present invention is not subject to such problems The sizing press emulsion or other aqueous medium containing the metal salt of this invention can also contain other conventionally used paper additives, used to treat uncoated paper, such as fillers (silica by way of non-limiting example), optical agents icos, defoamers and biocides. The use of the salt of this invention with these additives is convenient in many cases, since the presence of the salt provides improved performance of these additives and improved ink jet printing performance. The level of other optional additives in the size composition in general is from about .01 to about 3% and varies with the type of additive and the amount of suction collected by the paper treatment during the sizing press treatment. The aqueous sizing medium preferably contains a carrier agent, such as an aqueous starch solution, can be made in the conventional manner using the usual components and additives in the conventional amounts, all as is well known to those skilled in the art industry. paper production. When starch is employed as the carrier agent, the components of this invention should be added to the cooked starch (and the starch should be used between pH 7 and 9) and at a temperature of about 50 ° C and about 80 ° C. Retention times, compatibility of additives and other conditions and equipment, can be selected according to conventional practices of those with skill in the specialty. When other additives are employed with the sizing agent and the metal salt, all components are preferably applied to the paper surface concurrently, for example in a single operation, whether the additives are pre-mixed with the agent. sizing and salt composition or add concurrently with this composition.

The surface sizing medium containing the metal salt is applied as a surface treatment to the paper in the method of this invention. The sizing compositions of this invention can be applied to the paper surface or other substrate by any of several different conventional means, well known in the coating and paper production techniques. The sizing composition is usually applied as a surface treatment on both sides of the treated paper, but if desired, surface application can be made to only one side of the paper sheet. As used herein, "surface sizing" or equivalent terms (such as "surface sizing") means applying the sizing agent on or near the sizing press or in a position in a paper production system where the press Sizing otherwise would be present. Typically, a size press is located downstream of a first drying section of a paper production machine. A preferred surface sizing method for application of the composition to a paper substrate in the form of a sheet or web uses a conventional dosed or undosed sizing press in a conventional paper production process. When this technique is employed, the application temperature is at least about 50 ° C and not higher than about 80 ° C, typically about 60 ° C. The invention is not limited to the treatment of paper or other substrate by the sizing press treatment or the temperature typically used in the sizing press., since the substrate can also be surface treated with the composition by other methods. Other surface application methods and equipment may also be employed to apply the composition containing the divalent metal salts to the surface of paper, coated paper, paper film or other sheet substrate, with or without other paper additive components, such as as when using conventional coating equipment (for example with a Mayer rod or a doctor blade) or by spraying techniques. The surface application can also be performed at points other than the sizing press in the paper production process, for example in the calender stack, to obtain paper having the desired ink jet printing characteristics. All types of equipment conventionally used are adequate. The application of material is on or after sizing press is very different from the wet end treatment of paper. The conditions of application and the distribution of materials within the paper will be different. The paper is at least partially dried before the sizing press and subsequently dried by conventional methods after sizing press or another application technique.As noted above, the composition of this invention can preferably be added in The sizing press, for example with starch and other additives currently used with uncoated paper, A sizing press solution suitable for use in this invention can be prepared by conventional techniques.This sizing press solution generally comprises a solution starch, which contains about 2% to about 20% starch, which has been cooked in some form and which remains hot.The temperature of the solution in general is about 60 ° C. The concentration of starch in the starch solution preferably it is about 4% to about 16% and in particular about 6% to about 12%. The carrier agent is a binding agent, as discussed above, the binder is present in the composition such that the composition has a viscosity of not more than about 1000 centipoise (cp) and preferably not more than about 500 cp. The amount of binder employed will depend on the regular characteristics of the particular binder agent selected, as well as the characteristics of the other components of the composition. The paper used in the method of this invention is not critical and can be any grade of paper that requires sizing in its normal end-use application. The paper may include both polymeric and cellulose plastic fibers. Preferably, the paper predominantly contains cellulosic fibers and more preferably the paper contains cellulosic fibers in substantially complete form. All conventional processes known to produce paper are capable of preparing treated paper according to the present invention. The invention works on virtually any type of substrate and can be used on substrates of acidic, alkaline, neutral and unprepared sheets. In this invention, the sheet substrate most often paper, is formed prior to the application of the sizing composition which includes the soluble divalent metal salts of the invention. The present invention is intended primarily but not exclusively for use with alkaline paper. The invention is particularly useful with fine paper handling grades of fine alkaline paper, including without limitation Bond shapes, cut sheet paper, copy paper, envelope paper, add machine roll and the like. The paper of preference is paper in the form of a weft sheet having a basis weight in the range of about 30 g / m2 to about 200 g / m2, more preferably about 4 g / m2 to about 120 g / m2. The paper is suitable for use in this invention includes a paper having a typical basis weight of paper used in inkjet printing or conventional copy paper used in photocopying machines. This printing and writing paper typically has a basis weight of approximately 60 to 100 g / m2. Other types of material include, for example, newsprint with an approximate basis weight of 40 g / m2 to approximately 60 g / m2., Kraft paper, with a basis weight of approximately 50 g / m2 to approximately 120 g / m2, white top liner board with an approximate basis weight of 120 g / m2 to approximately 400 g / m2 and its coated grades. Coated paper is treated with a wide range of fillers and binders on a base sheet which may be light in weight such as about 40 g / rrt or heavier such as about 100 g / m2. Unlike prior art papers intended for use in inkjet inversion, which are typically coated with materials that improve the printing quality of dye-based inkjet printing inks, the paper of the present invention does not require these coatings of the prior art. The paper, therefore, can be produced economically and is competitive with conventional uncoated copy paper that is often used for multiple purposes. The paper used in this invention can be made with or without conventional internal finishes present. It is often preferred to use internal sizing agents that may be present at addition levels of about .02 to 4 g / metric ton of paper, more preferably from about 0.2 to 3 kg / metric ton, and particularly preferably. 5 to 2 kg / metric ton approximately of paper. Conventional internal sizing agents can be used, for example ASA sizing agents and AKD sizing agents, as well as other reactive and non-reactive internal sizing agents. These internal paper sizes can include and be identical to the surface sizing agents, and particularly the active surface sizing agents employed in the present invention. The metal salt of this invention can be used with different paper substrates, for example substrate of polymeric plastic material typically formed by extrusion, casting or other known processes useful in inkjet printing. For example, transparency films and other lamellar polymeric materials, preferably plastics, can be treated according to this invention, with the sizing composition containing the salt of this invention. These transparency sheets can be used to produce inkjet print sheets for use with slide projectors. These polymeric sheet substrate materials can be polyester, polypropylene, polyethylene, acrylic or the like. The application of the metal salts to these substrates is similar to that described above except that the substrate is a plastic sheet material and is subjected to conventional coating methods instead of a paper machine sizing press. The method of this invention can be used of the coated paper treatment by incorporating the sizing agent containing the metal salt into a performance formulation. Coated paper is used in many applications, including dye-based inkjet printing. The addition of the salts from the salt-containing sizing agent composition of this invention improves the performance of these coated sheets for inkjet printing, using pigment-based inks in addition to dye-based inks. The coating can be applied by conventional methods. A typical coating formulation may contain filler, binder and rheology modifier. The coating formulation used in the preparation of coated papers should be selected to be compatible with the metal salts and other components of the sizing compositions of this invention. These compositions can be added either together or in combination with the application of conventional coatings or can be applied after the conventional coating has been applied, dried or cured. Paper for many end-use applications in general becomes a more useful way through operations such as cutting, bending, punching and printing, transport, stacking and winding. Performance in these operations can be affected by paper additives. Conventional additives for improving ink jet printing such as high levels of reactive sizing agents, can cause lower paper friction coefficients and / or paper slippage in high speed equipment. Therefore, the amount of sizing agent component of the compositions of the present invention should be controlled within the concentrations set forth above. Other additives, such as fillers, can nick the cutting knives. As a result, the use of these types of cargo should also be carefully controlled. The performance of inkjet printing is improved by the presence of metal salts of this invention, particularly for inkjet printing using pigmented inks. The present invention provides a high concentration of inks applied by injection near the paper surface and this increases the optical density of the printed image, a convenient result. The invention also limits the undesirable edge roughness of the inks applied and this improves the clarity of the images, likewise, a convenient feature. While not wishing to be bound by any particular theory or mechanism of action, the inventor considers that the metal salts of this invention contained in the paper interact with the pigmented inks to result in these improvements and the sizing component slows the penetration of the ink to the paper. Performance evaluations of the compositions containing the divalent metal salts of this invention, together with other materials, for their effect to improve the optical density, and to reduce the transparency of printing of pigmented ink applied to a base paper by an inkjet printer. ink, are noted below: Calcium chloride (CaCl2) provides excellent results, and magnesium chloride generally works equally or almost equally as calcium chloride on an equivalent weight basis. Calcium bromide also works well, but not as well on an equivalent weight addition basis. Calcium zirconate, zirconium ammonium carbonate and zinc oxide generally do not provide the desired improvement at normal usage levels. Considering the results, it can be assumed (while it should not be bound or limited by any particular theory or mechanism of action) that the preferred salts of CaCl and MgCl2 provide the best performance due to their solubility and their ability to interact strongly with the ink. In general, an increased concentration of metal salt within the indicated range, leads to a superior improvement in inkjet print quality performance, without increasing corrosion or environmental problems and for reasons of economy. Not all metal salts give the same performance as noted above.

It was completely unexpected that metal salts, particularly calcium chloride and magnesium chloride, would perform much better than other salts. It was also unexpected that the metal salts of this invention gave excellent performance, but other salts that were tried were ineffective. Having seen the results, the inventor considers (while not wishing to be bound or limited by any particular theory or mechanism of action) that the successful performance of various metal salts of this invention can be based on two factors: solubility and ionic concentration. Magnesium and calcium salts are preferred because they provide the correct balance of these two factors. EXAMPLES The present invention will now be described in more detail with reference to the following specific non-limiting examples. The procedures employed in the examples are lab scale processes, where efforts are made to limit a paper machine sizing press application. This was achieved by preparing a paper in advance in a separate operation, where the paper was not treated in a sizing press with the surface additive or starch. The paper in the following examples is prepared in a pilot paper machine at Western Michigan University. A representative fine paper raw material is employed with the paper machine of Western Michigan University, to produce a typical alkaline fine paper. The paper (base sheets) was dried and stored. In the examples described below, the paper was passed through a laboratory mix sizing press and the desired treatment was applied. The treated paper was then dried immediately in a drum dryer. The paper was conditioned for a minimum of 24 hours before the inkjet test. In all the examples below, inkjet printing was performed on the Hewlett Packard DeskJet 660C inkjet printer. The print settings were set to "best" (best) and "plain paper" within the software (software) of Hewlett Packard that was supplied with the printer. The printing characteristics of the paper were measured at least one hour after printing. Optical density readings were performed with a Cosar Model 202 densitometer. Printing characteristics were evaluated as previously described using a test pattern with solid color areas, black text printing and printed areas of black-on-yellow and yellow-on -Black. An evaluation method is described in the Hewlett Packard test criteria. The ratings listed on a good, fair and poor scale are based on Hewlett Packard's ratings of good, acceptable and unacceptable. "See Hewlett Packard Paper Acceptance Criteria for HP DeskJet 500C, 550C and 560C Printers, July 1, 1994 (Hewlett Packard Paper Acceptance Criteria for HP DeskJet 500C, 550C and 560C Printers) Hewlett Packard Company, July 1, 1994" . In all cases, the starch was a significant component of the sizing press solution. Starch solutions were prepared by baking the starch in water of about 95 ° C for 30 to 60 minutes and then adjusting the pH to about 8. The additives noted in the examples were mixed into the starch. The mixtures were shaken and the pH was adjusted as noted in the examples below. Within approximately 15 minutes of addition of the materials in the starch mixtures, the mixtures were applied to the paper prepared as described above. The basis weight of the paper used in all cases was approximately that of a normal copy paper or 75 g / rrT. The amounts of salts employed were calculated on a dry salt basis based on the weight of dry paper, before the sizing press treatment (hereinafter "percent dry weight"). In some cases, the water sizing or retention of the paper was measured by the Hercules sizing test (HST = Hercules sizing test). The Hercules sizing test is a well-recognized test for measuring sizing performance and is described by J.P. Casey, Ed. Pulp and Paper Chemistry and Chemical Technology (volume 3 pages 1553-1554 (1981) and in the TAPPI T530 standard. A higher HST number is considered to represent better sizing capacity (less water penetration). EXAMPLE 1 Salt level effect Example 1 demonstrates the effect of the inkjet printing quality on the amount of salt applied on the surface on the dry paper surface treated. A base sheet is made in the pilot paper machine at Western Michigan University with a mixture of hardwood pulp: bleached softwood 70:30 beaten to a Canadian Standard 425 of Freedom (CSF = Canadian Standard Freeness) and containing internally calcium carbonate precipitated at 12% ALBACARM® PO (from Specialty Mineral Inc., Bethlehem, PA) sizing agent at 0.15% HERC0NMp 76 from Hercules Incorporated) and without alum. This base sheet was surface treated with starch alone and with mixtures of starch with various salts as follows: calcium chloride, magnesium chloride, calcium bromide and potassium chloride. The salts were applied in the amounts as illustrated in Table 1 below.

An 8% dry weight solution of GPCMR D-150 oxidized corn starch (from Grain Processing Company), Muscatine, IA) was employed. A sample treated with only the 8% Mayer starch solution GPCMR D-150 is included for comparison. Pre-mixtures of the various salts noted above and FLEXBONDMR 325 cationic copolymer of vinyl acetate and butyl acrylate (from Air Products and Chemicals Inc.), which has a vitreous transition temperature of 15 ° C, an average particle size of 0.3 microns , pH of 4.0 to 6.0, viscosity of 700 to 1200 cps and emulsion of solids of 55%, were added to the starch solution. In all cases except the starch sample alone, 0.15% dry weight solids of FLEXBOND ™ were added to the paper by adding 0.72 g of the emulsion to 55% solids of FLEXB0ND ™ per 100 g of starch solution. The salts were added to the starch solution at one level to give the final paper addition levels illustrated below in Table 1. These starch solutions were adjusted to approximately pH 7.5 and then applied on size press. for surface treatment of paper. The ink-jet printing quality of the resulting paper was evaluated and the results are shown in Table 1.

TABLE 1 Salt% dry weight of OD necrro salt Calcium Chloride 0.15 1.34 Magnesium Chloride 0.13 1.30 Magnesium Chloride 0.15 1.35 Calcium Bromide 0.15 1.24 Calcium Bromide 0.27 1.38 Potassium Chloride 0.15 1.16 Potassium Chloride 0.20 1.15 Starch 0 1.10 OD black optical density (results from injection printing of ink shows that CaCl2 and MgCl2 are more efficient to increase optical density than KCl and on a weight basis, they are more efficient than CaBr2.Bromine ions are much heavier than chlorine ions, so that on an equal weight basis salt, there is less added calcium when CaBr is used against CaCl2, MgCl2 and CaCl2 gave approximately equal results on a weight basis.On an equal molar basis, 0.13 MgCl versus 0.15 CaCl2, the calcium salt gave a superior improvement.

Calcium chloride combined with non-reactive sizing agent in the starch sizing press solution, addition of calcium chloride alone in the starch solution Example 2 was carried out to evaluate the effect on the print quality of injection of ink on paper in a metal salt applied on the surface, used in combination with a non-reactive surface sizing agent, both applied to the paper in the starch sizing press. A base sheet is made in the pilot paper machine at Western Michigan University with a mixture of hardwood pulp: bleached softwood 7:30 beaten to 390 CSF containing internally 20% calcium carbonate filler HYDROCARBMR 65 (from OMIYA Inc., Florence, VT) 0.5% cationic starch HE-CATMR (from Roquette Freres, Lestrem, France), 0.12% sizing agent from AQUAPEL * "3 320 from Hercules Incorporated) and without alum. surface treated with starch sizing press alone, with a mixture of starch with calcium chloride and with a mixture of starch, calcium chloride and BASOPLASTMR 335D polymeric surface sizing, a non-reactive sizing agent. in dry weight of GPCMR D-150, corn starch, is used in the sizing press as in the previous examples.The metal salt and the polymeric sizing agent were added to the starch solution at a level to obtain a level desired end on paper b roasted in the amount of starch solution absorbed by the paper during the sizing press treatment. The pH of the final sizing mixtures was not adjusted after the addition of the sizing agents. The absorption of the salt solution was 34 A% based on the wet weight of the starch solution at the initial weight of the paper. The inkjet printing quality and the sizing properties of the resulting paper were evaluated, and these results are illustrated below in Table 2, where the standard HST ink with a pH of 2 was used. TABLE 2 LEVEL 335D * Mixing pH HST level pH 2 (sec) Black OD CaCl, 0 7.7 0 91 0.93 0 6.9 0.25 52 1 0.1 4.8 0 127 1.03 0. 1 4.5 0.25 141 L55 * percent dry weight The results in Table 2 show that the presence of calcium chloride in paper treated with CaCl2 provides a significant improvement in black optical density, both when CaCl 2 is used alone and when applied in combination with BASOPLAST "335D Non-Reactive Polymeric Surface Sizing The result of sizing performance in the Table confirms that improved black OD performance is not an artifact of an increase in water retention as measured by HST. HST sizing was less than 52 seconds (for the free paper polymeric surface sizing containing the CaCl2 salt than for the same paper without polymeric sizing and CaCl2 (91 seconds) .The HST sizing performance results for the two paper evaluations where A sizing of polymeric surface is presented is similar (127 sec without CACl2 and 141 sec with CaCl2) and this difference in sizing performance HST is not considered significant In addition, the combination of the non-reactive sizing agent and CAC1_ provides an enhanced or synergistic increase in black optical density for surface treated paper, above and above the expected additive increment of the two, separately. The presence of the metal salt therefore provides an unexpected and surprising improvement in inkjet printing quality for surface-sizing paper containing a non-reactive sizing agent. EXAMPLE 3 Pre-mixing of calcium chloride and reactive sizing agent introduced into the sizing press solution Example 3 is carried out to evaluate the effect on ink-jet printing quality resulting from a metal salt applied on the surface, in combination with a reagent surface sizing agent, combine in a pre-mix that is subsequently applied to paper in the starch sizing press. The reagent sizing agent employed in this Example 3 was a paper sizing agent, dichloroquinyl ketene dimer. A base sheet is made in the pilot paper machine at Western Michigan University with a mixture of hardwood pulp: bleached softwood 70:30 beaten at 390 CSF and containing internally 15% precipitated calcium carbonate filler ALBACARMR HO , cationic starch at 0.26% STA-LOKMD (from AE Staley Company Decatur, Illinois) 0.08% alkenyl succinic anhydride and 0.25% alum. This base sheet was surface treated using the laboratory mixing press with: (A) starch alone, (B) starch solution containing a surface reactive emulsion emulsion containing alkenyl ketene dimer (no metal salt present); and (C) starch solution containing a pre-mix of the ketene dimer sizing emulsion and calcium chloride. To prepare the pre-mix, a 50:50 solution of calcium chloride di-hydrated to water is added to the emulsion of dimer ketene, and the premix contains 9.0% by weight of solids of the emulsion of the dimer and 33.8% by weight of calcium chloride based on the weight of the pre-mix.

An 8% dry weight solution of corn starch GPCMR D-150 is used in the sizing press as described in the previous examples. The materials were added to the starch at one level, to provide a desired final level of surface sizing of ketene dimer and / or calcium chloride in the paper (as illustrated below in Table 3) based on the amount of absorption of starch. The inkjet printing quality and the sizing properties of the resulting paper were evaluated, and these results are illustrated below in Table 6, where the standard HST ink with a pH of 2 was used. TABLE 3 LEVEL OF SOLIDS (%) OF DÍMERO SAMPLE KETENE * LEVEL OF CaCl, * HST pH 2 (sec) OD black A 0 0 2 1.10 B 0.025 0 35 1.45 C 0.025 0.094 42 1.59 * percent dry weight The results shown in Table 3 show that the pre-mix contains a combination of CaCl2 with a reactive sizing, when applied as a surface treatment to paper in sizing press, it gave an excellent black OD for the resulting paper, higher than the black OD obtained either without reagent surface sizing present or with the use of reagent surface sizing alone, both without the presence of a metal salt. EXAMPLE 4 Calcium chloride combined with a multimer-based reactive sizing agent Example 4 was carried out to demonstrate that the combination of CaCl1 as the metal salt with another reactive sizing, when both are applied as a surface treatment to the paper in Sizing press, provide excellent inkjet printing quality for the resulting paper. The reagent sizing agent used in this example was a ketene multimer, paper sizing agent described in International Patent Application Publication No. WO97 / 30218 published August 21, 1997, different from the sizing agent used as ketene dimer. in the previous example. The same procedure described for the Example 3. Starch alone solution (A) was tested; (B) Starch solution containing the multimer ketene emulsion is added to the paper as a surface treatment, without a metal salt present; and (C) starch solution and a pre-mix of calcium chloride with the emulsion of multimer ketene, all applied to the paper in sizing press in the same manner as in Example 3. The quality of inkjet printing in the resulting sizing property of the paper was evaluated and these results are shown below in Table 4. TABLE 4 SOLID LEVEL (%) OF MULTIMETER SAMPLE KETTLE * LEVEL OF CaClA OD black A 0 0 1.10 B 0.03 0 1.41 C 0.03 0.15 1.54 * percent dry weight The results shown in Table 4 demonstrate that the pre-mix containing a combination of CaCl2 with a reactive sizing, when applied as a surface treatment to paper in sizing press, gave an excellent black OD for the resulting paper, higher than the black OD that is obtained, either without surface reagent sizing present or with the use of reagent surface sizing only, both without the presence of a metal salt. Examples 1 to 4 demonstrate that the present invention provides improved ink-jet printing quality, as measured by the improved black ink optical density, with a metal salt employed in combination with either a non-surface-sizing agent. reagent or with a reagent surface sizing agent that is applied to the surface treated paper with the metal salt, as compared to the ink jet printing quality that is obtained with the surface sizing agent alone. EXAMPLE 5 Calcium chloride combined with a non-reactive and reactive sizing agent A base sheet made in Western Michigan University with a mixture of hardwood pulp: bleached softwood 75:25 beaten at 425 CSF and containing internally 10% precipitated calcium carbonate ALBACARMR HO, 0.05% alkenyl succinic sizing agent, cationic starch at 0.75% STA- LOKMP 400 and 0.25% alum, is treated with (A) starch solution alone, (B) 8% starch solution dry weight GPCMR of 150; and (C) starch solution with polymer latex PRINTRITEMR 594 (from B.F. Goodrich Company, ÁKRON, OH) (C) starch solution and polymer latex PRINTRITEMR 534 pre-mixed with PRECISMR 2000 reactive sizing dispersion; and (D) PRINTRITEMR polymer latex starch solution pre-mixed with both calcium chloride in PRECIS "'" 2000 reactive sizing dispersion. The ratio in the first pre-mix was 1: 8 of PRECISMR 2000 solids to solids of polymers. The ratio in the second pre-mix was 9: 1: 8 calcium chloride: PRECISMR 2000 solids: polymer solids. The materials were added to a starch solution at 8% dry weight and the final pH is adjusted to approximately pH 8. The solutions were used in sizing press to treat the paper. The levels of materials added to the starch were adjusted based on the amount of starch solution collected or absorbed by the paper. The results are listed in Table 5, where standard HST ink, with a pH of 2, was used. TABLE 5 LEVEL OF SOLID (%) OF PRECIS "" LEVEL OF HST SAMPLE 2000 * OF CaCl. * POLYMER pH2 (sec) OD black A 0 0 0 2 129 B 0 0 0.150 48 135 C 0.017 0 0.133 83 ai D 0.017 0.15 0.133 74 17) * percent dry weight Adding CaCl2 to a polymer emulsion provides improved sizing to inkjet printing. The extra addition of a reagent sizing agent for additional performance reinforcement.

EXAMPLE 6 Calcium chloride combined with. a non-reactive sizing agent and a reagent A base sheet made at Western Michigan University with a mixture of hardwood pulp: bleached softwood 70:30, churned at 390 CSF and internally containing 15% precipitated calcium carbonate 7? LBACARM® HO, 0.11% alkenyl succinic anhydride sizing agents, 0.50% cationic starch STA-LOKMP 400 and 0.25% alum, was treated with (A) starch alone, (B) and mixtures of starch with (B) a pre-mixing an emulsion of a sizing agent PENTAPRINTMP H and calcium chloride, and (C) sizing agent PENTAPRINTMR H pre-mixed with both the alkyl ketene dimer dispersion (HERCONMR 70) and calcium chloride. The ratio in the first pre-mix was 2: 1: from PENTAPRINTMR H solids to calcium chloride. The proportion in the second premix was 2: 1: 0.1 of PENTAPRINTMB H: calcium chloride: HERCONMR 70 solids. The materials were added to an 8% dry weight starch solution and the final pH adjusted to approximately pH 8 The solutions were used in sizing press to treat the paper. The levels of materials added to the starch were adjusted based on the amount of starch solution absorbed by the paper. A sample is treated with 8% dry weight oxidized starch solution GPCMR D150 for comparison. The results are listed in the Table TABLE 6 LEVEL OF SOLID (%) OF HERC0NM LEVEL OF SAMPLE LEVEL 70 * OF CaCl, * PENTAPRINT OD black A 0 0 0 1.14 B 0 0.15 0.30 1.53 C 0.015 0.15 0.30 1.62 * percent by dry weight A pre-mix of CaCl2 to a resin dispersion gave a surface additive that provides improved ink jet printing. The extra addition of a reactive sizing agent to the pre-mix gave additional performance reinforcement.

Pre-mixing of calcium chloride and reactive sizing agent introduced into the sizing press solution Example 7 is carried out to evaluate the effect on ink-jet printing quality on paper resulting from a metal salt applied in surface, used in combination. with a reactive surface sizing agent, both combined in a pre-mix that is subsequently applied to paper in starch sizing press. The reactive sizing agent employed in this Example 7 was paper sizing agent of alkenyl ketene dimer. A base sheet is made in the pilot paper machine at Western Michigan University with a mixture of hardwood pulp: softwood bleached at 75:25 beaten at 425 CSF and containing internally 10% precipitated calcium carbonate filler. ALBACARMR HO, cationic starch at 0.6% STA-LOKMR, 0.05% alginyl succinic anhydride and 0.25% alum. This base sheet was surface treated using a laboratory mix size press with: (A) starch alone, (B) starch solution containing a surface reactive emulsion emulsion containing alkenyl ketene dimer (PRESISMR 2000) and calcium. To prepare the pre-mix, a 50:50 solution of calcium chloride hydrate to water is added to the emulsion of ketene dimer, and the pre-mix contains 13.56% by weight of solids of the dimer emulsion and 20.34% by weight of calcium chloride, based on the weight of the pre-mix. An 8% dry weight solution of corn starch GPCMR D-150 is used in sizing press, as described in the previous examples. The materials were added to the starch at a level to provide a desired final level of surface sizing of ketene dimer and / or calcium chloride in the paper (as illustrated below in Table 7a) based on the amount of starch absorption . The inkjet printing quality and the sizing properties of the resulting paper were evaluated, and these results are illustrated below in Table 7a, where the standard HST ink with a pH of 2 is employed and in Tables 7b and 7c. TABLE 7a SOLID LEVEL (%) OF DÍMERO SAMPLE KETENE * LEVEL OF CaCl, * HST pH (sec) TO 0 0 2 B 0.2 0.18 126 * percent dry weight TABLE 7b Hewlett Packard DeskJet1"660C black print quality: GROWTH ROUGH BLACK OD OF BLACK LINE BLACK EDGE TO 1.25 Regular to Good Regular to Good B 1.60 Regular to Good Good TABLE 7c Print quality of black against yellow from Hewlett Packard DeskJetMD 660C: RUGOSITY GROWTH OF EDGE SAMPLE OD BLUE CELESTE LINE BLACK / YELLOW BLACK / YELLOW TO 0.77 Regular to Good Regular B 0.77 Regular to Good Good Among the unexpected advantages of the invention are the compatibility of the salts with surface additives; the compatibility in pre-mixes of the salts with surface additives; the compatibility of the salts with the sizing press solution; the absence of problems in applying these compositions to paper; the improved performance of the resulting paper for the application of inkjet printing with pigmented inks; and the additive benefits of salts with reactive sizing agents, salts with non-reactive sizing agents and mixtures of salts, reactive sizing agents and non-reactive sizing agents. The present invention particularly improves at least the following print quality characteristics: optical density, print transparency, line growth, runoff, edge roughness, wicking and speckle absorption.

The present invention can be incorporated into other specific forms without departing from the spirit or essential attributes thereof and accordingly the attached claims should be referenced instead of the above specification as indicated by the scope of the invention.

Claims (76)

1. CLAIMS 1. - A composition useful for surface treatment of a substrate for inkjet printing, the composition is characterized in that it comprises a salt of a divalent metal, the salt is soluble in an aqueous sizing medium of about pH 7 to about 9, the The aqueous sizing medium further comprises a carrier agent and a sizing agent. 2. - A composition useful for surface treatment of a substrate for inkjet printing, the composition is characterized in that it comprises a salt of a divalent metal solubilized in a medium of aqueous sizing, from about pH 7 to about pH 9, the The aqueous sizing medium further comprises a carrier agent and a sizing agent. 3. - A composition useful for surface treatment of a substrate for inkjet printing with pigmented ink, the composition is characterized in that it comprises a carrier agent, a sizing agent and a salt selected from calcium chloride, magnesium chloride, calcium bromide, magnesium bromide, calcium nitrate, magnesium nitrate, calcium acetate and magnesium acetate. 4. - The composition according to claim 1 or 2, characterized in that the salt is chosen from calcium chloride, magnesium chloride, calcium bromide, magnesium bromide, calcium nitrate, magnesium nitrate, calcium acetate and acetate of magnesium. 5. The composition according to any of claims 1 to 4, characterized in that the salt is calcium chloride. 6. The composition according to any of claims 1 to 4, characterized in that the salt is magnesium chloride. 7. The composition according to any of claims 1 to 6, characterized in that the carrier agent is starch. 8. The composition according to any of claims 1 to 6, characterized in that the carrier agent is a binder. 9. The composition according to claim 8, characterized in that the binder is chosen from polyvinyl alcohol, polyvinyl pyrrolidone and polyethylene imine. 10. The composition according to any of claims 1 to 9, characterized in that the sizing agent is a reactive sizing agent. 11. The composition according to claim 10, characterized in that the reactive sizing agent is chosen from an alkyl ketene dimer, an alkenyl ketene dimer, an oxetanone dimer, a 2-oxetanone multimer and an anhydride succinic acid sizing agent. . 12. The composition according to claim 9, characterized in that the reactive sizing agent is an alkenyl ketene dimer. 13. The composition according to claim 9, characterized in that the reactive sizing agent is a 2-oxetanone multimer. 14. The composition according to any of claims 1 to 9, characterized in that the sizing agent is a non-reactive sizing agent. 15. The composition according to any of claims 10 to 13, characterized in that it also comprises a non-reactive sizing agent. 16. The composition according to any of claims 14 to 15, characterized in that the non-reactive sizing agent is a polymer emulsion selected from cationic polymer emulsion, an emulsion of amphoteric polymer and mixtures thereof. 17. The composition according to claim 16, characterized in that the polymer of the polymer emulsion is made using at least one monomer selected from styrene, α-methyl styrene, acrylate having an ester substituent with 1 to 13 carbon atoms , methacrylate having an ester substituent with 1 to 13 carbon atoms, acrylonitrile, methacrylonitrile, vinyl acetate, ethylene and butadiene; and optionally comprises acrylic acid, methacrylic acid, maieic anhydride, maieic anhydride esters or mixtures thereof, with an acid number of less than about 80. 18. The composition according to claim 16, characterized in that the polymer is made using at least one monomer selected from styrene, acrylate having an ester substituent with 1 to 13 carbon atoms. carbon, methacrylate having an ester substituent with 1 to 13 carbon atoms, acrylonitrile and methacrylonitrile. 19. The composition according to claim 16, characterized in that the polymer emulsion is stabilized by a stabilizer comprising predominantly degraded starch. 20. The composition according to claim 16, characterized in that the polymer emulsion has a glass transition temperature of about -15 ° C to about 50 ° C. 21. The composition according to any of claims 14 or 15, characterized in that the non-reactive sizing agent is a disperse turpentine resin sizing agent. 22. - Surface of paper prepared with the composition of any of claims 1 to 21. 23. - Surface of polymeric plastic material treated with a composition of any of claims 1 to 21. 24. - Method for producing a substrate for printing Injection ink capable of retaining signals formed by inkjet printing using pigmented ink, the method is characterized in that it comprises: (a) surface treatment of the substrate with a composition comprising a divalent metal salt, the salt is soluble in an aqueous sizing medium of about pH 7 to about pH 8, the aqueous sizing medium further comprises a sizing agent; Y (b) drying the treated substrate. 25. Method for producing a substrate for inkjet printing capable of retaining signals formed by inkjet printing using pigmented ink, the method is characterized in that it comprises: (a) surface treatment of the substrate with a composition comprising a divalent metal salt, the salt is soluble in an aqueous sizing medium of about pH 7 to about pH 9, the aqueous sizing medium further comprises a sizing agent; and (b) drying the treated substrate. 26.- Method for producing a substrate for inkjet printing capable of retaining signals formed by inkjet printing using pigmented ink, the method is characterized in that it comprises: (a) surface treatment of the substrate with a composition comprising a paper enhancing agent, a sizing agent and a salt selected from the group consisting of calcium chloride, magnesium chloride, calcium bromide, magnesium bromide, calcium nitrate, magnesium nitrate, calcium acetate and sodium acetate. magnesium; (b) drying the treated substrate. 27. Method according to claim 24 or 25, characterized in that the salt is chosen from calcium chloride, magnesium chloride, calcium bromide, magnesium bromide, calcium nitrate, magnesium nitrate, calcium acetate and sodium acetate. magnesium. 28. Method according to claim 24 or 25, characterized in that the salt is chosen from calcium halide and magnesium halide. 29. Method according to any of claims 24 to 28, characterized in that the salt is calcium chloride. 30. - Method according to any of claims 24 to 28, characterized in that the salt is calcium chloride. 31. Method according to any of claims 24 to 30, characterized in that the carrier agent is selected from starch and a binder. 32. Method according to claim 31, characterized in that the binder is selected from polyvinyl alcohol, polyvinyl pyrrolidone and polyethylene imine. 33. - Method according to any of claims 24 to 32, characterized in that the sizing agent is a reactive sizing agent. 34. - Method according to claim 33, characterized in that the reactive sizing agent is chosen from an alkyl ketene dimer, an alkenyl ketene dimer, a 2-oxetane -one dimer, a 2-oethanone multimer and an acid anhydride sizing agent. succinic 35. Method according to claim 34, characterized in that the reactive sizing agent is an alkenyl ketene dimer. 36. Method according to claim 34, characterized in that the reactive sizing agent is a 2-oxetanone multimer. 37. - Method according to any of claims 24 to 32, characterized in that the sizing agent is a non-reactive sizing agent. 38. Method according to any of claims 33 to 37, characterized in that the sizing agent further comprises a non-reactive sizing agent. 39. Method according to any of claims 37 or 38, characterized in that the non-reactive sizing agent is a polymer emulsion selected from cationic polymer emulsion, an amphoteric polymer emulsion and mixtures thereof. 40. Method according to claim 39, characterized in that the polymer of the polymer emulsion is made using at least one monomer selected from styrene, α-methyl styrene, acrylate having an ester substituent with 1 to 13 carbon atoms. , methacrylate having an ester substituent with 1 to 13 carbon atoms, acrylonitrile, methacrylonitrile, vinyl acetate, ethylene and butadiene; and optionally comprises acrylic acid, methacrylic acid, maieic anhydride, maieic anhydride esters or mixtures thereof, with an acid number of less than about 80. 41. Method according to claim 39., characterized in that the polymer is made using at least one monomer selected from styrene, acrylate having an ester substituent with 1 to 13 carbon atoms, methacrylate having an ester substituent with 1 to 13 carbon atoms, acrylonitrile and methacrylonitrile. 42. - Method according to claim 39, characterized in that the polymer emulsion is stabilized by a stabilizer comprising predominantly degraded starch. 43. - Method according to claim 39, characterized in that the polymer emulsion has a glass transition temperature of about -15 ° C to about 50 ° C. 44. - Method according to any of claims 37 or 38, characterized in that the non-reactive sizing agent is a disperse turpentine resin sizing agent. 45. - Method of compliance with any of claims 24 to 44, characterized in that the surface treatment is carried out in a sizing press. 46. Method according to any of claims 24 to 45, characterized in that the substrate is chosen from the group consisting of paper and polymeric plastic material. 47. Method according to any of claims 24 to 46, characterized in that the surface treatment is surface sizing using sizing press, and the substrate is paper comprising fibers that are predominantly cellulosic fibers. 48. - "Method of compliance with the claim 47, characterized in that the paper comprises fibers that are cellulosic fibers substantially in their entirety. 49.- Method according to claim 46, characterized in that the substrate is a polymeric plastic material. 50.- Method according to any of claims 24 to 49, characterized in that the salt is present in an amount of about .01% to about .4% based on the weight of the dry treated substrate. 51. Method according to any of claims 24 to 49, characterized in that the salt is present in an amount of about 0.02% to about 0.3% based on the weight of the dry treated substrate. 52. - Method of compliance with any of claims 24 to 49, characterized in that the salt is present in an amount from about 0.05% to about 0.2% based on the weight of the dry treated substrate. 53. - Method according to any of claims 24 to 52, characterized in that the salt is present in the treated substrate in an amount of about 0.01 g / m2 to about 1 g / m2. 54. - Method of compliance with any of claims 24 to 52, characterized in that the salt is present in the treated substrate in an amount of about 0.02 g / m2 to about 0.3 g / m2. 55.- Method according to any of claims 24 to 52, characterized in that the salt is present in the treated substrate in an amount of approximately 0.03 g / m "to approximately 0.2 g / m2. of claims 24 to 55, characterized in that the substrate is writing printing paper having a basis weight of about 60 g / m2 to about 100 g / m2.- Method according to any of claims 24 to 55, characterized in that the substrate is newsprint having a basis weight of about 40 g / m 'to about 60 g / m2 58. Method according to any of claims 24 to 55, characterized in that the substrate is Kraft paper having a basis weight of about 50 g / m2 to about 120 g / pr. 59. - Method according to any of claims 24 to 55, characterized in that the substrate is white top liner paper having a basis weight of about 120 g / m to about 400 g / m. "60.- Paper made according to the The method of any of claims 24 to 48 and 50-59.-Polymeric plastic material made according to the method of any of claims 24 to 46 and 49-55.-A printing substrate made in accordance with the method of any of claims 24 to 61, the printing substrate is capable of transporting signals formed with pigmented ink on the dry treated substrate, such that the signals have at least one improved ink jet printing characteristic in comparison with a printing substrate treated according to the method of any of claims 24 to 61, but without the salt 63. - The printing substrate in accordance with the claim 62, characterized in that the improved ink jet printing feature is at least one group selection consisting of optical density, printing transparency, line growth, runoff, edge roughness, wicking and speckle absorption. 64. - The printing substrate according to claim 63, characterized in that the improved ink jet printing characteristic is optical density. 65.- The printing substrate according to any of claims 62 to 64 the substrate is paper. 66 - The printing substrate according to claim 65, characterized in that the paper comprises fibers that are predominantly cellulosic fibers. 67.- The printing substrate according to claim 66, characterized in that the paper comprises fibers that are cellulosic fibers in substantially total form. 68.- The printing substrate according to any of claims 62 to 64, characterized in that the substrate is polymeric plastic material. 69.- The printing substrate according to any of claims 62 to 68, characterized in that it also comprises signals formed on the substrate from pigmented ink that is applied to the dry treated substrate by ink jet printing. 70.- Method for improving the printing quality of signals formed by inkjet printing of pigmented ink on a substrate treated on the surface, which comprises treating the surface and drying the substrate according to any of claims 24 to 69 and printing the pigmented ink on the dry treated substrate by ink jet printing to form the signals. 71.- Paper printed with ink injection made according to the method of claim 70, characterized in that the substrate is paper. 72. - Printed paper with ink injection made according to the method of claim 70, characterized in that the signals will have at least one improved ink jet printing characteristic compared to paper treated in accordance with the method of claim 70. , but without salt. 73.- The printed paper with ink injection according to claim 72, characterized in that the improved ink jet printing characteristic is at least one selected from the group consisting of optical density, printing transparency, line growth, runoff , edge roughness, capillary and mottled absorption. 74. - The printed paper with ink injection according to claim 73, characterized in that the printing characteristic "improved inkjet is optical density 75. - The paper according to any of claims 22, 60 and 71 74, characterized in that the paper comprises fibers which are predominantly cellulosic fibers 76. The paper according to claim 75, characterized in that the paper comprises cellulosic fibers in substantially total form.