Compositions and methods for improving adhesion of images to treated substrates

Abstract

In general, the present disclosure relates to compositions and methods for treating a substrate and for improving the adhesion of an image to the treated substrate, and more particularly to systems and methods for treating a substrate and for improving the adhesion of an electrophotographic image to the treated substrate utilizing a combination of a polyteramide, colloidal silica, and optionally a polymeric adhesive.

Description

[0001] This application claims the benefit of U.S. Provisional Application No. 63 / 043,803, filed June 25, 2020, the entire contents of which are incorporated herein by reference. TECHNICAL FIELD

[0002] In general, the present disclosure relates to compositions and methods for treating a substrate and for improving the adhesion (adherence) of an image to the treated substrate, and more particularly to systems and methods for treating a substrate and improving the adhesion of electrophotographic images to the treated substrate utilizing a combination of polyteramide and colloidal silica. BACKGROUND

[0003] Liquid electrophotographic (LEP) printing uses liquid inks to print on a substrate rather than using dry toner. A common example of a LEP printer is the HP Indigo digital press. The toner particles in the liquid inks used in LEP printing are small enough that the LEP printed image cannot mask the roughness / glossiness of the underlying surface of the paper substrate, for example. The liquid inks used in LEP printing (also referred to herein as “inks,” “liquid toners,” or “LEP inks”) are suspensions of small pigment particles in the range of about 1 to 2 microns in a non-aqueous liquid. EVOQUE® is a liquid ink commonly used for liquid electrophotographic printing. LEP printing is believed to be able to provide some of the best digital printing quality images at relatively fast speeds.

[0004] LEP printed images do not adhere to the substrate as do images printed using the electrostatic copying printing method using dry toner processes. While conventional compositions have been applied to substrates in an attempt to improve the adhesion of images formed from liquid toners, further improvements are needed due to (1) inconsistencies in adhesion performance depending on the grade of paper used as the substrate and (2) the difficulty in obtaining near perfect (100%) adhesion of printed images by LEP printing tested by standard procedures. Near perfect (100%) adhesion of printed images by LEP printing tested by standard procedures still requires further improvements.

[0005] In a typical paper size-press treatment, a starch solution and additives are applied to the surface of the paper after initial drying. The treatment occurs in the size-press section of the paper machine. The formed and once or partially dried paper is treated with a formulation containing primarily a water-based polymer solution or dispersion plus a sizing agent such as starch. This is called a size-press treatment. Alternatively, the modified and dried paper is treated with a composition containing an adhesion-promoting polymer solution or dispersion. This is sometimes called a primer treatment. The treatment can be performed days or minutes or seconds before the printing process and can be performed on a coater that is not part of the printing press or a coater that is part of the printing press. Drying occurs between the application of the composition and the printing. The primer treatment is applicable to a variety of substrates from paper to plastic. In a typical manufacture of so-called "coated paper" in the paper industry, a coating formulation containing primarily a filler such as clay and a sizing agent such as starch is applied to the dried paper. For the current method, the composition containing the tertiary polyamide and colloidal silica can be applied as part of the size-press formulation, or as a primer treatment or part of a primer treatment, or as part of a paper coating formulation.

[0006] For many years, several different additives have been applied to the surface of paper with starch or as a primer to provide a variety of properties from improved sizing (water resistance) to improved print quality to adhesion of electrostatically copied printed images to surface strength. However, the combined use of a polytertiary amide such as polyethyl oxazoline (PEOx) and colloidal silica for size-press, primer, or coated paper treatment is not previously known and the benefit of adhesion of liquid toners is unexpected. Colloidal silica by itself does not provide the same benefit. In the present invention, the combination of polytertiary amide and colloidal silica replaces the use of polytertiary amide without colloidal silica.

[0007] One solution for improving the adhesion of HP Indigo digital press images is to treat the paper with polyvinyl / acrylic acid. However, polyvinyl / acrylic acid was found to be inefficient, resulting in deposits during the coating process and reducing the paper surface friction. In many cases, treatment with polytertiary amides such as polyethyl oxazoline and polyvinyl pyrrolidone was more effective and did not produce deposits or reduce friction. However, they were found to have less benefit for substrates or base sheets with open or more porous structures compared to base sheets with more closed or less porous structures. It was subsequently found that the addition of an aluminum salt overcame the efficiency loss.

[0008] However, the addition of aluminum salts significantly reduces the pH of the solution and in some cases causes deposit problems with paper size-press formulations and in some cases interferes with the performance of anionic optical brighteners. Therefore, other formulations are needed that do not severely reduce the pH of the paper machine size-press formulation and do not interfere with the addition of anionic optical brighteners.

[0009] Current research has shown that the addition of colloidal silica and polyethyloxazoline (PEOx) or other polytertiary amide at the size press will improve the performance of the open substrate, thus providing an option to replace the formulations currently used in the industry. Also, it has been found that the combination of PEOx or other polytertiary amide (PTA) with colloidal silica enhances the adhesion of LEP printed images to the substrate more than PEOx or PTA or colloidal silica alone. Current research has also shown that colloidal silica does not provide any benefit when used without PEOx or PTA.

[0010] Accordingly, it is desirable to provide systems and methods for treating a substrate and for improving the adhesion of an image to the treated substrate. Moreover, in view of the foregoing discussion, it will be appreciated that other desirable features and characteristics will become apparent in connection with the subsequent Summary and Detailed Description, and the appended Claims. SUMMARY

[0011] The present disclosure provides a water-based composition for treating a substrate. The water-based composition comprises a stick promoting polymer; colloidal silica; and optionally a polymeric adhesive, the stick promoting polymer comprising a polymer comprising one or more repeat units, wherein the one or more repeat units include a tertiary amide group, wherein the tertiary amide group is about 70 mole percent to about 100 mole percent of the stick promoting polymer.

[0012] A method for forming an image on a treated substrate is also provided. The method comprises providing a substrate and applying a water-based composition to the substrate to form a treated substrate. The water-based composition comprises a stick promoting polymer; colloidal silica; and optionally a polymeric adhesive, the stick promoting polymer comprising one or more repeat units, wherein the one or more repeat units include a tertiary amide group.

[0013] In another non-limiting embodiment, a method for improving the adhesion of an image to a treated substrate is provided herein. The method comprises providing a substrate having a composition applied thereto. The method further comprises, but is not limited to, applying the composition to the substrate to form a treated substrate. The method further comprises, but is not limited to, applying a liquid toner to the treated substrate to form an image on the treated substrate.

[0014] In another non-limiting embodiment, a printed material exhibiting improved adhesion of an image to a treated substrate is provided herein. The printed material comprises, but is not limited to, a treated substrate. The treated substrate comprises, but is not limited to, a substrate and a coating disposed on the substrate and formed from the composition. The printed material further comprises, but is not limited to, an image disposed on the treated substrate and formed from a liquid toner. DETAILED DESCRIPTION

[0015] The following detailed description is merely exemplary in nature and is not intended to limit the disclosure or the application and uses of it. Furthermore, there is no intention to be bound by any theory of operation described herein or suggested by the following detailed description.

[0016] Provided herein are compositions and methods for treating a substrate and / or improving the adhesion of a liquid toner to a substrate. In some embodiments, provided herein is a method for improving the adhesion of an image formed from a liquid toner using liquid electrophotographic printing (LEP printing). As used herein, "liquid electrophotographic printing" can be used interchangeably with "LEP printing," "xerographic printing using liquid toner particles," or "xerographic using liquid toner particles"; all of these encompass, for example, HP Indigo digital printers and processes. Further, as used herein, liquid electrophotographic printing does not mean or encompass a flexographic type printing process known as lithography and discussed in more detail in Alex Glassman, Printing Fundamentals, TAPPI Press, 1985, which is incorporated herein in its entirety.

[0017] The composition applied to the substrate is a water-based composition comprising a coadhesive polymer, colloidal silica, and optionally a polymeric adhesive. The method comprises the steps of providing a substrate, applying the water-based composition to the substrate to form a treated substrate, and applying a liquid toner to the treated substrate to form an image on the treated substrate.

[0018] In some aspects, the liquid toner comprises a pigment or a suspension of pigment-containing particles in a non-aqueous liquid. The liquid toner is applied to the treated substrate using liquid electrophotographic printing.

[0019] The coadhesive polymer can comprise at least one repeat unit. Unless otherwise specified herein, the term "polymer" as used herein refers to a polymer comprising one or more different monomeric units, which can include, for example, copolymers and terpolymers.

[0020] In some aspects of the coadhesive polymer, the repeat unit has a strong locally negative dipole (e.g., carbonyl) without a strong positive dipole. As used herein, "strong locally negative dipole" refers to the presence of a functional group such as a carboxyl group in the structure of the repeat unit and "strong" is defined herein as having a local dipole moment greater than 2 Debye, where a carbonyl group is known to have a dipole moment of about 2.4 Debye, and a local dipole is caused by the difference in electronegativity of the atoms bonded together. Here, "without a strong positive dipole" refers to the absence of a local dipole of a dipole greater than 0.8 Debye (e.g., from a hydroxyl group). The repeat unit can include, but is not limited to, a carbonyl group.

[0021] In other aspects of the adhesion promoting polymer, the at least one repeat unit includes a tertiary amide group. At least one of the carbon atoms bonded to the nitrogen atom of the tertiary amide group can have two or three hydrogen atoms bonded thereto, and the carbonyl of the tertiary amide group can be bonded to a -CH, -CH2, or -CH3 group.

[0022] In other aspects of the adhesion promoting polymer, the at least one repeat unit is formed from a monomer selected from the group consisting of vinylpyrrolidinone, oxazoline- containing monomers, N-vinylpiperidinone, N-vinylcaprolactam, N,N-dimethylacrylamide, and combinations thereof. Preferably, the at least one repeat unit of the adhesion promoting polymer is formed from a monomer selected from the group consisting of 2-ethyl-2-oxazoline, 2-methyl-2-oxazoline, and combinations thereof.

[0023] In some aspects, the adhesion promoting polymer can be a homopolymer. In other aspects, the adhesion promoting polymer can include poly(2-ethyl-2-oxazoline), poly(2-methyl-2-oxazoline), or combinations thereof. Preferably, the adhesion promoting polymer can include polyvinylpyrrolidinone.

[0024] In other aspects, the adhesion promoting polymer can additionally be formed from one or more non-ionic monomers. For example, the adhesion promoting polymer can be formed from (i) one or more monomers selected from the group consisting of vinylpyrrolidinone, oxazoline-containing monomers, N-vinylpiperidinone, N-vinylcaprolactam, N,N-dimethylacrylamide, or combinations thereof, and (ii) one or more non-ionic monomers. As used herein, the term "non-ionic monomer" is a monomer that does not have an anionic or cationic functional group under the conditions of use.

[0025] Small amounts, such as less than about 5 mole percent, of ionic monomers can be added. In some aspects, the anionic or cationic functional group is from an acrylic acid. In other cases, the ionic functional group is from an amine, or is based on ethyleneimine.

[0026] The adhesion promoting polymer can additionally be formed from one or more monomers that do not strongly lead to hydrogen bonding with itself, either within the same polymer chain or between polymer chains. In other words, the adhesion promoting polymer can be substantially free of monomers that are capable of leading to a strong degree of self-association of the adhesion promoting polymer. With respect to monomers that are capable of leading to a strong degree of self-association, the term "substantially free" as used herein means that the adhesion promoting polymer is formed from less than about 5% and less than about 1% by weight of monomers that are capable of leading to a strong degree of self-association when polymerized. The term "strong degree of self-association" as used herein means significant hydrogen bonding of the adhesion promoting polymer with itself or a high degree of dipole-dipole interaction of the adhesion promoting polymer with itself. For a discussion of the interactions between monomer units in a polymer and between one polymer and another polymer or with a solvent, see Chapter 12 of the classic text by Paul Flory, Principles of Polymer Chemistry, first published in 1953 by Cornell Press. Paul Flory defined an interaction parameter that is a measure of the "free energy of first-neighbor interactions." Since Flory's work, others have greatly expanded upon this concept. Those familiar with the concept will recognize that the point being made here is that the polymer additives of this disclosure have the property of having little self-association relative to other polymers and, more importantly, although not meant to be limited to theory, they are polymers that interact with the polymers of the liquid toner at the molecular level more strongly than they interact with themselves.

[0027] In some aspects, the adhesion promoting polymer can be water dispersible or water soluble. The adhesion promoting polymer can be water soluble. Water solubility can be defined in a number of ways. In this application, water soluble means that the material is at least about 80% soluble in water at room temperature, although heating can be used to aid in the dissolution of the polymer. Water soluble can also mean that the polymer dissolves in water to a concentration of at least about 5%. Water soluble can also be defined as a degree of hydrophobicity. Solubility also implies that the material is not crosslinked to the extent that the molecular chains are prevented from separating in water.

[0028] The adhesion promoting polymer of the composition can have a weight average molecular weight of greater than about 40,000 Daltons, or greater than about 80,000 Daltons, or greater than about 190,000 Daltons, or greater than about 450,000 Daltons, where the upper limit is the average molecular weight that will prevent the formation of a solution comprising the adhesion promoting polymer.

[0029] In some aspects of the present composition, the composition is water-based and has solids of about 2% to about 50% by weight solids, can be about 3% solids to about 30% solids by weight, can be about 4% solids to about 25% solids by weight, and can be about 5% solids to about 20% solids by weight.

[0030] The solids (amount) depends on the amount of material to be applied to the substrate and viscosity limitations based on the method of application. The solids portion comprises the "adhesion promoting polymer" and colloidal silica. The levels of each component will vary depending on the amount of composition that can and is applied to the substrate and the desired end performance required of each component to impart improved electronic copy image adhesion. It has been found that the levels of "adhesion promoting polymer" and colloidal silica on the substrate and the ratio of these two ingredients greatly affect performance. It should be understood that the composition can include more than one type of "adhesion promoting polymer" and more than one type of "colloidal silica".

[0031] In some aspects of the composition, the solids of the composition are greater than about 3% by weight and the viscosity is less than about 1000 centipoise (cps), can have solids greater than about 4% by weight and a viscosity less than about 500 cps, and can have solids greater than about 5% by weight and a viscosity less than about 200 cps.

[0032] In some aspects, the composition is for use on a sized press treated paper. The level of adhesion promoting polymer can be from about 0.1% to about 1% of the dry weight of the paper, can be from about 0.15% to about 0.7% of the dry weight of the paper; and the level of colloidal silica can be from about 0.1% to about 1% of the dry weight of the paper, and can be from about 0.15% to about 0.7% of the dry weight of the paper, in percentage relative to the dry weight of the paper. The ratio of "adhesion promoting polymer" to silica is from about 1 : 1 to about 1 :0.2, can be from about 1 : 1 to about 1 :0.5, or can be from about 1 :0.7 to about 1 :0.5.

[0033] In other aspects, the level of treatment agent as part of a coating formulation to treat paper to form a coated paper should be from 2% to 10% by weight of the coating formulation or from 3% to 5% by weight of the coating formulation, in percentage relative to the dry weight of the paper coating. In various non-limiting embodiments, all values and value ranges, including all of the above-mentioned values and all integers and fractions between the above-mentioned values, are hereby expressly considered for use herein.

[0034] In some aspects of treating a substrate, the composition remains primarily at the surface, such as greater than 50% of the solids portion of the composition penetrates less than 10 microns into the substrate. In this regard, the amount of adhesion promoting polymer applied to the substrate on each side of the treated substrate can be from about 0.0075 gsm to about 0.375 gsm by dry weight, or from 0.0115 gsm to about 0.165 gsm by dry weight, or from about 0.015 gsm to about 0.095 gsm, or from about 0.015 gsm to about 0.04 gsm. The level of colloidal silica can be from about 0.02 gsm to about 1.3 gsm. These amounts are based on the total amount of adhesion promoting polymer and colloidal silica applied to the substrate and not the total composition applied. The ratio of adhesion promoting polymer to colloidal silica can be from about 1 :2 to about 1 :0.2, or from about 1 : 1 to about 1 :0.5, or from about 1 :0.7 to about 1 :0.5. In various non-limiting embodiments, all values and ranges of values, including all of the above values and all integers and fractions between the above values, are hereby expressly considered for use herein.

[0035] In some aspects of the composition, the colloidal silica can have a surface charge that is cationic or anionic.

[0036] In other aspects of the composition, the colloidal silica has an average particle size that is less than about 150 nanometers, can be less than about 100 nanometers, and can be less than about 25 nanometers.

[0037] In other aspects, the average particle size of the colloidal silica is between about 0.4 and 120 nanometers, and can be between about 1 nanometer and 100 nanometers.

[0038] In other aspects of the composition, the colloidal silica has a surface area that can be greater than about 50 m 2 / g, can be greater than about 100 m 2 / g, can be greater than about 200 m 2 / g and the surface area can have greater than about 220 m 2 / g. In various non-limiting embodiments, all values and ranges of values, including all of the above values and all integers and fractions between the above values, are hereby expressly considered for use herein.

[0039] In other aspects of the composition, the colloidal silica particles are basic.

[0040] In other aspects of the composition, the colloidal silica surface is a reaction product of an aluminum chlorohydrate compound with the surface of the colloidal silica.

[0041] The inclusion of colloidal silica in the composition provides unexpected improvements in the adhesion of the liquid toner to the substrate compared to compositions that do not contain colloidal silica. The colloidal silica affects the efficacy of the adhesion promoting polymer providing unexpected results. When the colloidal silica is used without the adhesion promoting polymer, no improvement in the adhesion of the liquid toner image is found.

[0042] In other aspects of the composition, the composition optionally includes a polymeric adhesive such as a water soluble hydroxyl functional polymer. The adhesive can include polyvinyl alcohol, starch such as oxidized starch, cationized starch, ethylated starch, esterified starch, and enzymatically modified starch, gelatin, casein, proteins such as soy protein, carboxymethyl cellulose, hydroxyethyl cellulose. The adhesive can also be a polymer such as an acrylic emulsion, a vinyl acetate emulsion, a vinylidene chloride emulsion, a polyester emulsion, a styrene-butadiene emulsion, an acrylonitrile-butadiene latex, or combinations thereof. The adhesive can be an acrylamide based polymer such as an acrylamide-acrylic acid copolymer. The adhesive can be an organic adhesive.

[0043] In some aspects, the optional adhesive is a starch selected from the group consisting of oxidized starch, cationized starch, ethylated starch, esterified starch, enzymatically modified starch, and combinations thereof.

[0044] The composition can include the optional adhesive in an amount of from 0 to about 98% by weight of the total composition, can be from about 5% by weight to about 90% by weight of the total composition, and can be from about 10% by weight to about 80% by weight of the total composition. However, the viscosity of the composition plays an important role and must be suitable for application by the method chosen, and the viscosity provides the level of application of the composition desired. Further, the ratio of the adhesion promoting polymer and the colloidal silica can also play a major role in the efficacy of the composition.

[0045] The viscosity required for the composition will depend on the method used to apply the composition to the substrate. It will also depend on the concentration of the components of the composition and the desired final level of the composition. The viscosity required depends on the specific size-press equipment and other factors such as the speed of the paper machine or coater, and can be adjusted according to the machine.

[0046] In some aspects, the composition can also include additional additives for improving the adhesion of the liquid toner printed on the substrate via LEP printing. Non-limiting examples of additional additives include poly(ethylene acrylic acid) and polyethylene imine and polymers based on or containing these materials. The amount of carboxylic acid containing polymer and the amount of colloidal silica must be such that the composition remains homogeneous. It is well known that multivalent salts can coagulate dispersions, especially those containing carboxylic acid containing polymers, and can also precipitate solutions containing carboxylic acid containing polymers.

[0047] In other aspects of the composition, the composition can further include additional additives known in the art, including but not limited to fillers, defoamers, waxes, pigments, dyes, paper sizing agents, biocides, rheology modifiers, rosin derivatives, surfactants, solvents, plasticizers, or combinations thereof. Rheology modifiers that can be used can include virtually any known material that alters the rheology of water-based solutions, such as cellulose-based thickeners like carboxymethylcellulose or hydrophobically modified hydroxyethylcellulose or alginate-based thickeners or starch-based thickeners or high molecular weight polymers, pectin, associative thickeners, and the like. The rheology modifier can be a solution or can be a dispersion such as modified starch, for example, Ecosphere materials from Ecosynthetix. The dispersion can act on the paper surface to close the porous nature of the paper, thereby retaining the active adhesion-enhancing additive at the paper surface. The rheology of the coating and treatment solution can also be altered by combinations of materials that can form hydrogen bonds or ionic complexes. Limitations of the rheology modifier depend on the ability of the composition to be applied to the substrate in a consistent manner. For example, there are viscosity limitations for sizing press compositions to be used in a paper machine sizing press. The modifier or additional additives should not detract from the purpose of the composition such that the adhesion of the printed image is greatly reduced.

[0048] In some aspects, the order in which the adhesion-promoting polymer, colloidal silica, and optional adhesive are added to form the composition can affect the performance of the composition. To this end, when an adhesive is used in the composition, the various materials can be added to the adhesive all at once while mixing is occurring. For example, the process can begin with a starch solution to which an adhesion-promoting polymer is added, followed by the separate addition of colloidal silica. These materials can be added as aqueous solutions or water-based dispersions to aid in mixing, shorten the mixing time, and reduce the occurrence of adverse interactions of concentrated solutions.

[0049] As introduced above, a method for treating a substrate is provided herein. The method includes the steps of providing a substrate and applying a composition to the substrate to form a treated substrate. In one embodiment, the step of applying the composition to the substrate includes the step of transferring the composition as a water-based solution or dispersion or both to a sizing press of a paper machine where the paper substrate is treated. In another embodiment, the step of applying the composition to the substrate includes the steps of providing an applicator roll, applying the composition to the applicator roll, and contacting the substrate and the applicator roll to form a treated substrate. It will be appreciated that the composition can be applied to the substrate using any suitable method known to one of ordinary skill in the art so long as the method results in a substantially uniform treatment on the surface of the substrate. Such methods include, for example, but are not limited to, the use of sizing press equipment typically used with paper machines, spray coating, foam coating, curtain coating, roll coating, printing, transfer coating from a substrate, or combinations thereof.

[0050] The treatment of the substrate can be at least a portion of at least one surface of the substrate. Coating can refer to a treatment of paper at a size press or some other machine as just described. For uncoated paper as defined in the paper industry, the size press treatment of paper is commonly referred to as a size press treatment. Coating in the paper industry can refer to materials and processes classically defined in the paper industry for making "coated paper" and the term "coated" as used herein can refer to a treatment of paper or woven or nonwoven substrates that are referred to as coated paper and can include at least one composition comprising a sizing agent, a coadhesive polymer, and colloidal silica. It can also include one or more components known to those of ordinary skill in the art that are beneficial to coat a substrate (e.g., a paper substrate) to improve the print quality of the substrate and / or an image printed thereon. For example, "coated paper" is generally paper having a particulate inorganic filler such as calcium carbonate or a clay layer held on the surface by a sizing agent. Thus, coated paper is a class of paper that has a filler in a "coating" held on the surface by a sizing agent. The term is well known in the art relating to the paper industry and printing presses. See David Saltman et al., Pulp & Paper Primer, 2nd Ed., TAPPI Press (1998), for example, but not limited to, pages 24-25, which is incorporated by reference herein in its entirety. The treatment of the substrate by the composition can also occur after the substrate is formed and dried, or in the case of plastics, surface modified by means such as corona treatment, for example, when making paper, dried or coated to make "coated paper." Such application to the final substrate can be as a last step before printing and can be referred to as a primer treatment. For example, the substrate can be passed through an anilox roll coater to apply the composition, then dried, then printed within days, hours, or even seconds after printing.

[0051] The substrate can be selected from a paper product, a woven fibrous material, a nonwoven fibrous material, or a nonwoven non-fibrous substrate such as a plastic film, and combinations thereof. However, it should be understood that any substrate known in the art to be compatible with LEP printing can be used. The three main types of substrates printed with LEP printers are well known and include: 1) uncoated paper; 2) coated paper; and polymeric substrates. Uncoated paper and coated paper are well defined terms in the paper industry, although there can be differences in these substrates and other paper surfaces that can be LEP printed. In certain embodiments, the substrate is a paper product and the paper product is uncoated.

[0052] The paper product can be in any orientation known to those of ordinary skill in the art, such as one or more rolls, cut sheets, and / or various shapes and configurations capable of being printed by a digital LEP printer. The substrate can be uncoated paper, such as paper commonly used in offices for xerographic printing. The substrate can be coated paper, such as used in higher quality printing. The substrate can be various grades of paper used for packaging, and these grades can be uncoated or coated. The substrate can be a woven or nonwoven substrate and those can be cellulose-based materials, other natural products or processed products. The substrate can also be any other substrate known to those of ordinary skill in the art to be compatible with the LEP printing process. However, the formulation of each type of substrate can vary as an adhesive can or can not be used, and if used, the adhesive can vary significantly. How the composition penetrates into the substrate is important as it will affect the required levels of adhesive, adhesion promoting polymer, and colloidal silica, as well as possibly other components such as rheology modifiers. For example, for very porous substrates, the composition can need higher levels of colloidal silica than for non-porous substrates, and can need greater viscosity of the composition.

[0053] The properties of the substrate can also affect the step of applying the composition to the substrate. In addition, any treatment of the substrate prior to applying the composition can have an effect on the method of applying the composition, the amount of composition, and / or the ratio of adhesion promoting polymer to colloidal silica. For example, if the substrate is porous, such as uncoated untreated paper, the composition can soak into the substrate completely but at least partially, and the amount of composition can need to be increased as more of the material soaks into the paper. That is, the amount of composition, particularly the amount of adhesion promoting polymer and colloidal silica, applied to the substrate to produce the desired increase in adhesion can depend on the properties of the substrate. In addition, the properties of the adhesive and other additives of the composition, as well as the viscosity of the composition, can also affect the amount of composition that can penetrate into the substrate. Even with uncoated paper, a viscous composition can penetrate the paper minimally. For treatment of non-porous coated substrates, the composition can be part of a coating composition that includes filler or pigment particles, and the coating composition can be applied to the surface of the paper to form a layer on the substrate. For coated paper, the composition can also be applied to the surface of the paper after the paper has been treated to reduce its porosity. Regardless of the properties of the substrate, the composition can form an ink-receiving layer with which the ink will come into contact during the printing process, and the image of the ink can adhere to the ink-receiving layer.

[0054] The method of applying the composition to the substrate affects the distribution and amount of the composition needed to achieve the desired image adhesion improvement. Where the composition substantially penetrates the substrate, the amount of composition applied to the substrate is typically described as a percentage of the weight of the substrate. However, for substrates such as relatively non-porous substrates or where the paper surface is a relatively closed structure in which the composition substantially remains at the surface of the substrate, such as in embodiments including coated paper where the composition does not substantially penetrate the substrate, the amount of composition applied to the substrate is typically described as the weight of the composition per unit of surface area treated (e.g., grams per square meter) and the amount of composition applied to the surface of the substrate.

[0055] In one aspect, the substrate is a paper product and the amount of adhesion promoting polymer can be from about 0.1% to about 1% of the dry weight of the paper, can be from about 0.15% to about 0.7% of the dry weight of the paper; and the amount of colloidal silica can be from about 0.1% to about 1% of the dry weight of the paper, and can be from about 0.15% to about 0.7% of the dry weight of the paper. The ratio of adhesion promoting polymer to silica is from about 1 : 1 to about 1 :0.2, can be from about 1 : 1 to about 1 :0.5, and can be from about 1 :0.7 to about 1 :0.5.

[0056] In other aspects, the substrate can be a relatively non-porous substrate or a paper having a closed surface and the amount of composition includes an adhesion promoting polymer and colloidal silica. In the case of a relatively non-porous substrate, the amount of adhesion promoting polymer added is from about 0.0075 gsm to about 0.375 gsm on a dry weight basis, can be from about 0.0115 gsm to about 0.165 gsm, can be from about 0.015 gsm to about 0.095 gsm, and can be from about 0.015 gsm to about 0.04 gsm. The amount of colloidal silica applied to the paper product can be from about 0.004 gsm to about 0.2 gsm on a dry weight basis based on the total weight of the substrate, and can be from about 0.005 gsm to about 0.15 gsm.

[0057] In some aspects of the method, the ratio of adhesion promoting polymer to colloidal silica of the composition to be applied to the substrate is from about 1 :2 to about 1 :0.2, or from about 1 : 1 to about 1 :0.5, or from about 1 :0.7 to about 1 :0.5. In various non-limiting embodiments, all values and ranges of values, including all of the above values and all integers and fractions between the above values, are hereby expressly considered for use herein.

[0058] In another aspect, there is also provided herein a printed material exhibiting improved adhesion of an image to a treated substrate. The printed material includes a treated substrate and an image disposed on the treated substrate and formed from a liquid toner. The treated substrate includes a substrate and a coating layer. The coating layer is disposed on the substrate and formed from the composition.

[0059] In some aspects of the method, the image applied to the treated substrate, such as a 100% black image or a 290% composite black image (as used in the adhesion retention of greater than about 80%, can be greater than about 85%, can be greater than about 90%, can be greater than 95%. The tape pull test is a test developed by the Rochester Institute of Technology (RIT) for use with HP Indigo 7000 series digital presses using the standard HP procedure. The test currently calls for the use of 3M 232 masking tape. It replaces the use of 3M 230 tape and has a program correction built in for changing tape types. In another embodiment, the adhesion is greater than 95% as reported by RIT.

[0060] In another aspect, the image formed from a 290% black liquid toner has an adhesion retention of greater than 80% to the treated substrate as determined by the test method described above, in some cases greater than 90%, in other cases the adhesion retention is greater than 95% as determined by RIT.

[0061] Examples

[0062] The following test is conducted by the Rochester Institute of Technology (North American test site for determining if an Indigo printed paper treatment is qualified) following the standard test procedure developed by HP for testing the adhesion of ink applied using one of the Indigo digital presses.

[0063] Test method for measuring adhesion

[0064] The test method used in the following examples is a standard method for determining the adhesion of a HP Indigo digitally printed image to a substrate where a black rectangular image of 100% black liquid toner is printed using a HP Indigo 7000 series digital press using standard temperature settings in 4 shot mode to provide a test pattern. A black rectangular image is also printed using the same press and settings but the black liquid toner is composed of 52 parts yellow, 66 parts magenta, 72 parts cyan and 100 parts black toner which is commonly referred to as a 290% photo image. The latter test is a more rigorous test.

[0065] After printing the above images for ten minutes, the images were tested by the Rochester Institute of Technology (RIT) using standard HP test and Indigo 7000 series digital press, using 3M™ 230 or 232 tape and a 2 kilogram (kg) roller to apply even and consistent pressure and pass the tape test to determine adhesion to the substrate. The percentage of the image that did not remove with the tape was measured. In any embodiment, in any example, only one of the tapes (3M™ 230 or 232 tape) was used, RIT used only one of the standard procedures reported in this patent. The adhesion values reported in this patent are the RIT reported adhesion values. The tests were also performed 60 minutes after printing. Adhesion generally improves with longer times before testing.

[0066] Example 1: Image Adhesion

[0067] Example 1: Image Adhesion

[0068] Uncoated good paper rolls suitable for offset printing or LEP printing were prepped and used as the base substrate. This base paper was manufactured on a commercial paper machine and was not treated with a size press. The paper used in the current example had an internal size from alkyl succinic anhydride and contained about 25% precipitated calcium carbonate filler. The paper was fed through a Dixon coater in a puddle size press mode so that both sides of the paper were treated with the starch solution. During this process, the paper continued through the Dixon coater for drying and was wound onto a spool.

[0069] The results for the various formulations can be seen in Table 1. In the current example, the imPress® 0.3% (6# / ton) of starch with 40# / ton starch had a 32% improvement in image adhesion compared to the starch alone (sample 1). The results show that when the PerForm® 0.2% (4# / ton) of starch was added to the imPress® 0.3% (6# / ton) of starch, there was a 48% improvement in image adhesion compared to the starch alone (sample 1). TM ID-115 (Solenis, LLC, a polyethyl oxazoline based polymer) (sample 2) had a 32% improvement in image adhesion compared to the starch alone (sample 1). The results show that when the PerForm® 0.2% (4# / ton) of starch was added to the imPress® 0.3% (6# / ton) of starch, there was a 48% improvement in image adhesion compared to the starch alone (sample 1). TM ​PB9007 (Sample 3) (a polyaluminum chloride (PAC)) added to the imPress ID-115 and starch formulation of Sample 2, the image adhesion was improved by 49% over Sample 1 (starch only). When PerForm TM PB9007 was replaced with Ludox TM CL colloidal silica and Ludox TM AM-30 both (see Samples 4-6) similar improvements were seen. All Ludox TM Products were obtained from W.R. Grace Company. The results show that the addition of colloidal silica to the formulation can enhance the adhesion properties.

[0070] Table 1 - Unadjusted % Ink Adhesion

[0071]

[0072] Example 2: Unadjusted % Ink Adhesion

[0073] The process and conditions used in Example 1 were used for the following examples. The level of imPress TM ID-115 (a poly based on polyethyl oxazoline) was kept constant at 6# / ton, with the exception of Sample 1 which was a control sample containing only starch and no imPress TM ID-115. Comparisons were made here using the 10 minute adhesion of the 290% ink coverage test used in Example 1. As stated above, all testing was run at RIT. The results shown in Table 2 show the unadjusted % ink adhesion.

[0074] Table 2 - Unadjusted % Ink Adhesion

[0075] Sample Additive Unadjusted % ink adhesion 1 Starch 66 2 imPress TM ID-115 / starch control 79 3 0.2% PAC 87 4 0.1% Ludox TM CL 79 5 0.2% Ludox TM CL 88 6 0.2% Ludox TM AM 86 7 0.2% Ludox TM TM40 84 8 0.2% Ludox TM LS 86 9 0.2% Ludox TM TMA 83 10 0.2% Ludox TM AS-40 88 11 imPress TM ID-115 control 79

[0076] The results of this study show that a level of colloidal silica higher than 0.1% (3# / ton) is needed to improve image adhesion. At a level of 0.2% (4# / ton), multiple colloidal silica materials improved adhesion. Ludox TM Colloidal silica is a product of WR Grace Company. The improved adhesion was unexpected.

[0077] Example 3

[0078] A formulation containing ethylated starch, imPress TMID-115 (polyethyl oxazoline) and colloidal silica formulations (samples 3-7) were used to treat the surface of a commercially available paper. In addition, a sodium chloride solution and an optical brightening agent were added to each formulation. The level of NaCl and optical brightening agent (OBA) addition was to a certain weight percent of the final dry paper. The level of ethylated starch addition was to a certain weight percent of the final dry paper. Table 3 provides the level of PEOx, the type of silica, and the level of silica. The samples were tested to determine the adhesion of images printed using an Indigo 7000 series press in so-called 4-color mode, in which each of the four colors was printed in the order of 52 parts yellow, 66 parts magenta, 72 parts cyan, and 100 parts black toner. As in the previous examples, the total ink coverage was 290% and the image adhesion was tested as instructed by HP. Adhesion was determined by the same tape test as in Examples 1 and 2 after 10 and 60 minutes.

[0079] Table 3

[0080]

[0081] imPress AS-450 and AS-452 are colloidal silica products from Solenis, LLC.

[0082] PW-50EC is a larger particle colloidal silica provided by W. R. Grace Company.

[0083] Silica particle size and surface area are reported by the manufacturer of the silica product, and their values are recorded in the file. Particle size is typically determined by light scattering from a dilute solution using equipment such as described in: Nanomaterials (Basel). 2018 Jul; 8(7): 454. Published online 2018 Jun 21. doi: 10.3390 / nano8070454, Effects of Sample Preparation on Particle Size Distributions of Different Types of Silica in Suspensions Rodrigo R. Retamal Marín, 1,* Frank Babick, 1 Gottlieb-Georg Lindner, 2 Martin Wiemann, 3 and Michael Stintz1. Surface area is typically determined by methods such as ASTM D 5604-96.

[0084] Considering the 10 minutes and 60 minutes adhesion, the results show that the addition of colloidal silica to the formulation (samples 3 and 4) exhibits an improvement in adhesion compared to the control (sample 2). From sample 6, it can be seen that non-colloidal silica with a particle size of 0.4 nm does not show an improvement in adhesion compared to the control. Finally, the results show that microporous silica aluminate (sample 7) does not provide an improvement in adhesion, which is clearly seen in the 60 minutes test.

[0085] While at least one example embodiment has been presented in the foregoing detailed description, it should be appreciated that a multitude of modifications can be made. It should also be appreciated that the example embodiment is only an example and is not intended to limit the scope, applicability, or configuration of the disclosure in any way. Rather, the foregoing detailed description will provide those skilled in the art with a convenient road map for implementing an example embodiment of the disclosure. It should be understood that various changes can be made in the function and arrangement of elements described in the example embodiment without departing from the scope of the disclosure as set forth in the appended claims.

Claims

1. A water-based composition for treating a substrate, wherein the water-based composition comprises: a stick promoting polymer; colloidal silica; and a polymeric adhesive; wherein the amount of colloidal silica is 0.1% to 1% of the dry weight of the substrate; the polymeric adhesive is selected from the group consisting of polyvinyl alcohol, starch, gelatin, casein, protein, carboxymethyl cellulose, hydroxyethyl cellulose, and combinations thereof; the stick promoting polymer comprises one or more repeating units comprising a tertiary amide group, and wherein the repeating units comprising a tertiary amide group are 70 mole % to 100 mole % of the stick promoting polymer, wherein the weight ratio of the stick promoting polymer to colloidal silica is 1 : 1 to 1 : 0.

2.

2. The water-based composition of claim 1, wherein the water-based composition has greater than 3% by weight solids and a viscosity of less than 1000 cps.

3. The composition of claim 1, wherein the one or more repeating units of the stick promoting polymer are formed from monomers selected from the group consisting of vinyl pyrrolidone, oxazoline containing monomers, N-vinyl piperidone, N-vinyl caprolactam, N,N-dimethyl acrylamide, and combinations thereof.

4. The composition of claim 3, wherein the one or more repeating units of the stick promoting polymer are formed from monomers selected from the group consisting of 2-ethyl-2-oxazoline, 2-methyl-2-oxazoline, and combinations thereof.

5. The composition of any one of claims 1-4, wherein the stick promoting polymer is a homopolymer.

6. The composition of any one of claims 1-4, wherein the stick promoting polymer is a polyethyl oxazoline.

7. The composition of any one of claims 1-4, wherein the colloidal silica has a surface charge that is cationic or anionic.

8. The composition of any one of claims 1-4, wherein the colloidal silica has an average particle size of less than 150 nanometers.

9. The composition of any one of claims 1-4, wherein the colloidal silica has an average particle size of 0.4 to 120 nanometers.

10. The composition of any one of claims 1-4, wherein the colloidal silicon dioxide has a surface area of greater than 50 m 2 / g.

11. The composition of any one of claims 1-4, wherein the colloidal silica particles are basic.

12. The composition of any one of claims 1-4, wherein the colloidal silica surface is a reaction product from an aluminum chlorohydrate compound with the colloidal silica surface.

13. The composition of any one of claims 1-4, wherein the polymeric adhesive comprises 0 to 98% by weight of the total composition.

14. A method for treating a substrate to improve image adhesion comprising: a) providing a substrate; b) applying a water-based composition to a substrate to form a treated substrate, the composition comprising: a cohesiveness promoting polymer containing one or more repeat units comprising a tertiary amide group, and repeat units comprising a tertiary amide group are 70 mole % to 100 mole % of the cohesiveness promoting polymer; colloidal silica in an amount of 0.1 % to 1 % by dry weight of the substrate; and a polymeric adhesive selected from the group consisting of polyvinyl alcohol, starch, gelatin, casein, protein, carboxymethyl cellulose, hydroxyethyl cellulose, and combinations thereof; wherein the weight ratio of the cohesiveness promoting polymer to colloidal silica is 1 : 1 to 1 :0.2; c) drying the treated substrate; and d) applying a liquid toner to the treated substrate to form an image on the treated substrate.

15. The method of claim 14, wherein the substrate is a paper product having a relatively non-porous surface, and wherein the amount of cohesiveness promoting polymer applied to the surface of the substrate is 0.0075 gsm to 0.375 gsm by dry weight based on the total weight of the substrate; and the amount of colloidal silica applied to the surface of the substrate is 0.004 gsm to 0.2 gsm by dry weight based on the total weight of the substrate.

16. The method of claim 14, wherein the substrate is selected from the group consisting of paper products, fibrous felts, woven fibrous materials, nonwoven fibrous materials, plastic films, and combinations thereof.

17. The method of claim 15, wherein the substrate is selected from the group consisting of paper products, fibrous felts, woven fibrous materials, nonwoven fibrous materials, plastic films, and combinations thereof.

18. The method of any one of claims 14-17, wherein the substrate is a paper product and the paper product is uncoated prior to applying the water-based composition thereto.

19. The method of any one of claims 16-17, wherein the substrate is a fibrous felt.

20. The method of any one of claims 14-17, wherein the composition is applied at a size press of a paper machine, wherein: a) the cohesiveness promoting polymer is applied to the substrate in an amount of a certain percentage of the dry weight of the paper, the amount being 0.1 % to 1 % of the dry weight of the paper; b) the colloidal silica is applied to the substrate in an amount of 0.1 % to 1 % of the dry weight of the paper.

21. The method of any one of claims 14-17, wherein less than 50% of the solids of the composition applied to the surface of the substrate penetrate more than 10 microns into the substrate.

22. A method for improving the adhesion of electrophotographic images to a treated substrate, comprising: providing a substrate; applying a composition to the substrate to form a treated substrate, the composition comprising a cohesiveness promoting polymer and colloidal silica, the cohesiveness promoting polymer containing one or more repeat units comprising a tertiary amide group, and wherein repeat units comprising a tertiary amide group are 70 mole % to 100 mole % of the cohesiveness promoting polymer; the colloidal silica being in an amount of 0.1 % to 1 % by dry weight of the substrate; and wherein the weight ratio of the cohesiveness promoting polymer to colloidal silica is 1 : 1 to 1 :0.2; applying a liquid toner to the treated substrate to form an electrophotographic image on the treated substrate.

23. The method of claim 22, wherein the image formed on the treated substrate retains greater than 80% of its adhesion to the treated substrate.

Images