sacrificial coating compositions comprising polyvinyl alcohol and wax starch

Abstract

Sacrificial coating composition comprising: at least one polyvinyl alcohol having a degree of hydrolysis of at least about 95%; at least one waxy maize starch; at least one hygroscopic agent; at least one surfactant; and water, wherein the weight ratio of the at least one waxy maize starch to the at least one polyvinyl alcohol is at least two to one.

Description

In indirect printing with aqueous ink, an aqueous ink is sprayed onto an intermediate imaging surface, which may be in the form of a cloth. The ink may be dried or partially dried prior to transfixing the image to a media substrate such as a sheet of paper on the cloth. In order to ensure excellent print quality, it is desirable that the ink droplets sprayed onto the cloth spread and converge well before drying. Otherwise, the ink images may appear granular and / or have erasures. Lack of distribution may also result in a failure of ink jets in the printheads becoming much more pronounced, producing wider stripes in the ink image. The distribution of aqueous ink may be made possible by materials having high surface energy, and thus it may be desirable to use a cloth having high surface energy to improve ink distribution.To enable transfer of the ink image from the cloth to the media substrate after the ink on the intermediate imaging surface has been dried or partially dried, a cloth having a surface with a relatively low surface energy is preferred. Rather than providing the desired ink distribution, low surface energy materials promote drop formation ("wetting") of individual ink drops on the image receiving surface.Thus, an optimal wipe for an indirect image transfer process should address all challenges regarding the quality of the wet image, including the desired distribution and coalescence of the wet ink, as well as the image transfer of the dried or partially dried ink. With respect to the first challenge - wet image quality - a high surface energy wipe is preferred which causes the aqueous ink to disperse and wet the surface. With respect to the second challenge - image transfer - a low surface energy wipe is preferred so that the ink has minimal attractive force to the wipe surface after drying and can be transferred to the media substrate. These two conflicting requirements can make the entire process of wetting, dispensing and transfer in indirect printing processes very problematic.In addition to indirect inkjet printing, offset lithography is a common printing method today and is contemplated for the processes and compositions disclosed herein, although it has similar challenges. In a typical lithographic process, a printing plate, which may be a flat plate, the surface of a cylinder or belt, etc., is formed to have "image areas" formed of hydrophobic and oleophilic material and "non-image areas" formed of a hydrophilic material. The image areas are areas corresponding to the areas on the final print (i.e., the target substrate) filled in by a printing or marking material such as ink, whereas the non-image areas are those areas corresponding to the areas on the final print that are not filled in by the marking material. The hydrophilic regions receive a water-based fluid, commonly referred to as a fountain solution (comprising, for example, water and a small amount of alcohol, as well as other surface tension reducing additives and / or surfactants), and are readily wetted thereby. The hydrophobic regions will take away fountain solution and take up ink, whereas the fountain solution formed over the hydrophilic regions will form a fluid "release layer" for ink rejection. Thus, the hydrophilic areas of the printing plate correspond to the non-printed areas or "non-image areas" of the final print.The ink may be transferred directly to a substrate such as paper or may be applied to an intermediate surface such as an offset (or cloth) cylinder in an offset printing system. The offset cylinder may be covered with an adjustable coating or sleeve having a surface that can conform to the texture of the substrate, which may have a surface roughness depth that is slightly greater than the surface roughness depth of the imaging plate. Further, the surface roughness of the offset blanket cylinder contributes to providing a more uniform printing material layer free from defects such as turbidity to the substrate. Sufficient pressure is applied to transfer the image from the offset cylinder to the substrate. Compressing the substrate between the offset cylinder and a printing cylinder may provide this pressure.The above-described ink jet and lithographic printing techniques may have certain disadvantages. For example, one drawback encountered in attempting to modify conventional variable printing lithographic systems is relatively low transfer efficiency of the inks from the imaging plate or belt. For example, in some cases, about half of the ink applied to the "reimageable" surface is actually transferred to the image receiving media substrate so that the other half of the ink must be cleaned and removed from the surface of the plate or belt. This relatively low efficiency presents a cleaning problem in that a substantial amount of cleaning is required to completely decolor the surface of the plate or belt so as to avoid the formation of ghost images ("ghosting") from one image to another in variable data printing by means of a modification of conventional lithographic techniques.Further, the effective cost of the ink is increased as far as the ink cannot be recycled without contamination. Conventionally, however, it is very difficult to recycle the high viscosity ink, so that the effective cost of printing is increased and the cost associated with ink disposal is increased. The proposed systems do not meet the expectation of providing sufficiently high transfer ratios to reduce ink waste and associated costs. Therefore, a means of composition of the ink must be found to provide optimum distribution on a plate or belt surface, including adequate separation between print and non-print areas and increased transfer ability to a substrate.Various approaches have been studied to provide potential solutions to the above mentioned challenges. These approaches include, for example, cloth material selection, ink design, and auxiliary fluid methods. With regard to cloth material selection, materials known to provide optimum dispensing properties include the classes of silicone, fluorosilicone, a fluoropolymer such as Teflon® Viton® and certain blend materials. These materials, while having relatively low surface energy, may provide poor wetting. Alternatively, polyurethane and polyimide have been used to improve wetting, but at the expense of ink release properties. Improving ink compositions to address these challenges has proven to be very difficult because the main performance characteristic of the ink is performance in the printhead. For example, if the ink surface tension is too high, the jet ejection may be improper. However, if the ink surface tension is too low, it leaks out from the face plate of the print head.One solution that has been proposed is to apply a wetting enhancing sacrificial coating, such as a sacrificial coating composition, to the cloth. The sacrificial coating composition can be applied to the transfer intermediate (wipe) where it dries to form a dried or semi-dried film. The coating may have a higher surface energy or be more hydrophilic than the base transfer intermediate. Ink droplets can be ejected in an image-like pattern onto the sacrificial coating composition and thereafter the ink can be at least partially dried to form an ink pattern on the blanket. Finally, the ink pattern and sacrificial coating composition can be transferred from the cloth to a substrate such as paper.Polyvinyl alcohol and starches are used as film formers which are particularly useful in adhesive formulations. They can also be used in sacrificial coating compositions if appropriate conditions are met in the selection of the most suitable polyvinyl alcohols and / or starches, the aim being to minimize or eliminate adverse effects on the printing process associated with their use. For example, the sacrificial coating compositions comprising polyvinyl alcohols and / or starches can have an undesirably high release force when coated onto a cloth. This high release force can result in paper jams and / or printing of the ink during the printing process, as the polyvinyl alcohol and / or starch-based sacrificial coating composition can adhere to the cloth. However, the release force can be reduced by selecting starches and polyvinyl alcohols having very specific properties such as molecular weight, molecular weight distribution and / or degree of hydrolysis for the formulation of sacrificial coating compositions.The use of only starch in a sacrificial coating composition may have several disadvantages. First, the physical robustness of the starch film may be deficient. Therefore, there is a potential contamination problem after transferring the starch film to the prints. Secondly, the durability of the starch can be short. The starch solution decomposes rapidly and can decompose after a few days. Even using biocide, the life of the starch solution can be as short as a few weeks. As a result, sacrificial coating solutions based only on starch may have limited applicability and short durability, leading to poor printability and / or higher running costs. It is therefore desirable to develop and identify novel polymers or resins and mixtures thereof that can be used to formulate, develop and identify sacrificial coating compositions for indirect printing processes.To implement a polyvinyl alcohol or starch-based sacrificial coating composition that does not undesirably adhere to the cloth, it may be desirable to reduce the high release force observed in such sacrificial coating compositions while maintaining their advantageous properties such as good ink wetting and distribution.A further prior art is the document WO 99 / 56 682 A1. The document describes a method for cold transfer of images without using additional heat in the course of image transfer to a variety of substrates. The method comprises printing an image on an image transfer sheet having a coating of water receptive adhesive. The transfer sheet is then applied to the substrate to transfer only the portions of the adhesive carrying the image to the substrate while the remainder of the adhesive remains adhered to the sheet. Disclosed herein are sacrificial coating compositions comprising at least one polyvinyl alcohol; at least one waxy starch such as waxy maize starch; at least one hygroscopic agent; at least one surfactant; and water, wherein the weight ratio of the at least one waxy starch to the at least one polyvinyl alcohol is at least two to one.In certain embodiments, the at least one polyvinyl alcohol has a weight average molecular weight (weight average) of about 85,000 to about 186,000. In certain embodiments, the at least one polyvinyl alcohol has a degree of hydrolysis of at least about 95%, such as at least about 98%, at least about 98.8%, at least about 99.3%, or in the range of at least about 95% to about 99.9%. The viscosity of the polyvinyl alcohol solution in a deionized water solution at 20° C. is, for example, at least about 30 cP, such as at least about 45 cP, or at least about 60 cP, or is in the range of about 30 cP to about 80 cP, wherein the solution may contain about 4 wt % polyvinyl alcohol, based on the total weight of polyvinyl alcohol and deionized water in the solution.In other embodiments, the weight ratio of the at least one waxy starch, such as waxy maize starch, to the at least one polyvinyl alcohol is at least three to one, such as at least four to one, or is in the range of about two to one to about four to one.In certain embodiments disclosed herein, the at least one hygroscopic agent is selected from glycerol, glycols, sorbitol and mixtures thereof. In certain embodiments, the at least one surfactant is selected from anionic surfactants such as sodium lauryl sulfate or nonionic surfactants having an HLB value in the range of 4 to 14, or a mixture of at least one anionic surfactant and at least one nonionic surfactant.Also disclosed herein are methods of making a sacrificial coating composition comprising mixing at least one polyvinyl alcohol having a degree of hydrolysis of at least about 95%, at least one waxy maize starch, and at least one hygroscopic agent in water; heating to a temperature of at least about 90°C; and maintaining the temperature for at least about 15 minutes; wherein the weight ratio of the at least one waxy maize starch to the at least one polyvinyl alcohol in the sacrificial coating composition is at least two to one. In certain exemplary methods disclosed herein, the at least one polyvinyl alcohol may have a degree of hydrolysis of at least about 95%, such as at least about 98%, at least about 98.8%, at least about 99.3%, or range from at least about 95% to about 99.9%. In certain embodiments, the at least one hygroscopic agent may be glycerin, and in certain embodiments, the weight ratio of the at least one waxy maize starch to the at least one polyvinyl alcohol may be in the range of at least three to one to at least four to one. In certain exemplary methods disclosed herein, the mixture may further comprise at least one surfactant, such as at least one surfactant selected from anionic surfactants, such as sodium lauryl sulfate, and nonionic surfactants having an HLB value in the range of 4 to 14.Further disclosed herein are methods of making a sacrificial coating composition comprising mixing at least one polyvinyl alcohol having a degree of hydrolysis of at least about 95% and water at a temperature of about 20° C. to form a first solution; heating the first solution to a first temperature of at least about 90° C. and maintaining the first solution at the first temperature for at least about 15 minutes; mixing at least one waxy maize starch and water at about 20° C. to form a second solution; heating the second solution to a second temperature of at least about 90° C. and maintaining the second solution at the second temperature for at least about 15 minutes; and combining the first solution and the second solution to form a sacrificial coating composition, wherein the weight ratio of the at least one waxy maize starch and the at least one polyvinyl alcohol in the sacrificial coating composition is in the range of at least two to one to at least four to one.In certain methods disclosed herein, the first solution may further comprise at least one hygroscopic agent, the second solution may further comprise at least one hygroscopic agent, or both the first solution and the second solution may further comprise at least one hygroscopic agent. In certain exemplary methods disclosed herein, the at least one polyvinyl alcohol may have a degree of hydrolysis of at least about 95%, such as at least about 98%, at least about 98.8%, at least about 99.3%, or range from at least about 95% to about 99.9%, wherein the at least one polyvinyl alcohol may have a weight average molecular weight (weight average) in the range from about 85,000 to about 186,000. In certain exemplary methods disclosed herein, the sacrificial coating composition may further comprise at least one surfactant, such as at least one surfactant selected from anionic surfactants, such as sodium lauryl sulfate, and nonionic surfactants having an HLB value in the range of 4 to 14.In certain embodiments of the methods disclosed herein, the viscosity of the at least one polyvinyl alcohol in a deionized water solution at 20° C. is in the range of about 30 centipoise to about 80 centipoise, the solution containing about 4 wt % polyvinyl alcohol relative to the total weight of polyvinyl alcohol and deionized water in the solution. In other exemplary methods disclosed herein, the sacrificial coating composition may further comprise at least one solvent selected from isopropanol, methyl ethyl ketone, 2-pyrollidinone, terpineol, dimethyl sulfoxide, N-methylpyrrolidone, 1,3-dimethyl-2-imidazolidinone, 1,3-dimethyl-3,4,5,6-tetrahydro-2-pyrimidinone, dimethylpropyleneurea, and mixtures thereof.It is to be understood that both the foregoing general summary and the following detailed description are exemplary and explanatory only and do not limit the invention as claimed.The accompanying drawings, which are incorporated in and constitute a part of the specification, illustrate embodiments of the present teachings and together with the description serve to explain the principles of the present teachings. FIG. 1 is a schematic drawing of an aqueous indirect inkjet printer that prints sheet media, according to an embodiment of the present disclosure. FIG. 2 is a graph illustrating transfer performance at various drying capacities for a standard sacrificial coating composition and a sacrificial coating composition prepared according to Example 1B.It should be understood that some details of the figures are simplified and drawn to make the embodiments easier to understand and not to achieve strict structural precision, details, and scale.Disclosed herein are sacrificial coating compositions comprising at least one polyvinyl alcohol; at least one waxy starch, such as at least one waxy maize starch; at least one hygroscopic agent; at least one surfactant; and water, wherein the weight ratio of the at least one waxy starch to the at least one polyvinyl alcohol is at least two to one.Reference will now be made in detail to embodiments of the present teachings, examples of which are illustrated in the accompanying drawings. In the drawings, like reference numerals have been used throughout to designate like or identical elements. In the following description, reference is made to the accompanying drawings, which form a part hereof, and in which is shown by way of example a specific embodiment in which the present teachings may be practiced. The following description is therefore merely exemplary.As used herein, the terms "printer", "printing device", or "imaging device" generally refer to a device that produces an image on aqueous ink print media, and may include any device such as a digital copier, book making machine, facsimile machine, multifunction device, or the like that can produce printed images for any purpose. Image data generally includes information in electronic form that is calculated, output, and used to actuate the ink jet ejectors to form an ink ink image on the print media. This data may include text, graphics, images, and the like. The operation of forming images with colorants on print media, for example graphics, texts, photographs, and the like, is generally referred to herein as printing or marking. Aqueous ink jet printers use inks having a high water content with respect to the amount of colorant and / or solvent in the ink.The term "printhead" as used herein refers to a component in the printer that is configured with ink jet ejectors for ejecting ink droplets onto an image receiving surface. A typical printhead includes a plurality of inkjet ejectors that eject ink droplets of one or more inks onto the image receiving surface in response to trigger signals that actuate actuators in the inkjet ejectors. The ink jets are arranged in an array of one or more rows and columns. In some embodiments, the inkjets are arranged in staggered diagonal rows across a surface of the printhead. Various printer embodiments include one or more printheads that form ink images on an image capture surface. Some printer embodiments include multiple printheads arranged in a print region. An imaging surface, such as an intermediate imaging surface, moves beyond the printheads in a processing direction through the print region. The ink jets in the printheads eject ink droplets in rows in a processing transverse direction that is perpendicular to the processing direction across the imaging surface.As used herein, the term "aqueous ink" includes liquid inks in which colorant is present in a solution, suspension, or dispersion with a liquid solvent comprising water and / or one or more liquid solvents. The terms "liquid solvent" or simply "solvent" are used broadly and include compounds that can dissolve colorants in a solution or that can be a liquid that holds colorant particles in a suspension or dispersion without dissolving the colorant.As used herein, the term "hydrophilic" refers to any composition or compound that attracts water molecules or other solvents used in aqueous ink. As used herein, reference to a hydrophilic composition refers to a liquid carrier bearing a hydrophilic agent. Examples of liquid carriers include, but are not limited to, a liquid such as water or alcohol carrying a dispersion, suspension or solution.As used herein, reference to a dried layer or coating refers to an arrangement of a hydrophilic compound after all or a substantial portion of the liquid carrier has been removed from the composition by a drying process. As described in more detail below, an indirect inkjet printer forms a layer of a hydrophilic composition on a surface of a transfer intermediate using a liquid carrier such as water to apply a layer of the hydrophilic composition. The liquid carrier is used as a mechanism for conveying the hydrophilic composition onto an image receiving surface to form a uniform layer of the hydrophilic composition on the image receiving surface.Embodiments of the present disclosure relate to a sacrificial coating formed on an intermediate transfer member of an indirect printing apparatus. The sacrificial coating composition comprises at least one polyvinyl alcohol; at least one waxy maize starch; at least one hygroscopic material; at least one surfactant; and water.As is known, polyvinyl alcohol can be prepared by hydrolyzing polyvinyl acetate in, for example, partially hydrolyzed forms 87-89%), intermediate hydrolyzed forms (91-95%), fully hydrolyzed forms (98-98.8%), and superhydrolysed forms (greater than 99.3%). In one embodiment, the polyvinyl alcohol employed in the compositions of the present disclosure has a degree of hydrolysis of at least about 95%. In certain embodiments, the at least one polyvinyl alcohol may have a degree of hydrolysis of at least about 95%, at least about 98%, at least about 98.8%, at least about 98.9%, or at least about 99.3%.In one embodiment, the polyvinyl alcohol may have a viscosity suitable for forming a sacrificial coating on an intermediate transfer member. For example, 4 wt % polyvinyl alcohol in a solution of deionized water at about 20° C. may have a viscosity in the range of about 30 cP to about 80 cP, such as about 35 cP to about 75 cP, about 40 cP to about 70 cP, or about 50 to about 60 cP, where the weight percent is based on the total weight of polyvinyl alcohol and water.The at least one polyvinyl alcohol disclosed herein may have any suitable molecular weight. For polyvinyl alcohols, molecular weight can be expressed in terms of solution viscosity. Generally, the higher the viscosity of the polyvinyl alcohol solution, the higher the molecular weight of the polyvinyl alcohol. In certain embodiments disclosed herein, the average molecular weight (weight average) may range from about 85,000 to about 186,000, such as from about 85,000 to about 124,000, or from about 146,000 to about 186,000.Polyvinyl alcohol is a hydrophilic polymer having a good water retention property and an excellent film forming property. As a hydrophilic polymer, a sacrificial coating composition formed of polyvinyl alcohol may have good water retention properties that can aid in ink distribution to the cloth. Because of their excellent strength, the coatings formulated with polyvinyl alcohol can achieve a significant reduction in the overall solids content. This can provide substantial cost savings while still providing significant improvement in coating film performance.A polyvinyl alcohol and starch-based sacrificial coating composition may have much better wettability on a wipe and may easily form a continuous uniform thin film when dried or partially dried compared to other known sacrificial coating compositions. The sacrificial coating compositions disclosed herein may also more uniformly control ink distribution, thus resulting in improved image quality (such as improved drop uniformity, line sharpness, etc.). Moreover, polyvinyl alcohol and starch-based sacrificial coating compositions can have improved mechanical properties and provide improved printability, such as improved ink skin transfer properties, for example for long printing runs, as compared to other known sacrificial coating compositions. Moreover, polyvinyl alcohol and starch are considered environmentally friendly for use in sacrificial coating compositions.In certain embodiments disclosed herein, higher molecular weight and higher hydrolyzed polyvinyl alcohols for use in the sacrificial coating compositions disclosed herein may be selected to improve image quality and transfer efficiency. Higher molecular weight polyvinyl alcohols can aid in the formation of much stronger sacrificial films after drying, contributing to improved transfer efficiency. Higher hydrolysis of the polyvinyl alcohol may also contribute to the reduction of the adhesion of the sacrificial film to the cloth, thus improving the discharge properties. However, to achieve improved coating rheology for the coating processes disclosed herein, as well as to achieve improved coating solution stability in certain embodiments disclosed herein, the proportion of the at least one polyvinyl alcohol in the sacrificial coating composition may be less than about 30%, such as less than about 20%, less than about 15%, less than about 10%, or about 10%. In certain embodiments disclosed herein, the proportion of the at least one polyvinyl alcohol may be greater than about 30%, such as about 45% or less than about 45%.In certain embodiments, it is contemplated that polyvinyl alcohols having higher viscosity grades such as polyvinyl alcohols Sekisui® Selvol® 125, 165, 325, 350, 825, and 443 may be used. Table 1 below lists certain exemplary polyvinyl alcohols that can be used in accordance with certain embodiments of the sacrificial coating compositions disclosed herein. Table 1 Table 1Selvol® 12599,3+28-32Selvol® 16599,3+62-72Selvol® 32598,0-98,828-32Selvol® 35098,0-98,962-72Selvol® 82598,0-98,828-32Selvol® 44392,0-94,053-63The chemical structure of the at least one polyvinyl alcohol-containing coating composition can be customized to match the wettability and the release characteristics of the sacrificial coating from the underlying surface of the transfer intermediate. This may be achieved, for example, by the use of one or more hygroscopic materials and / or one or more surfactants in the coating composition, as explained below.In certain embodiments, the sacrificial coating compositions disclosed herein may comprise, in addition to the at least one polyvinyl alcohol, at least one additional binder selected from starches; at least one surfactant; at least one hygroscopic material; and water. In certain embodiments, the starch may be waxy starch such as waxy maize starch, waxy rice starch, waxy cassava starch, waxy potato starch, waxy wheat starch, or waxy barley starch. In certain embodiments, the waxy starch may comprise at least 90% amylopectin. The viscosity of the at least one waxy starch, such as a waxy maize starch, may be less than about 1000 cP at about 25° C. with a solids concentration of starch of about 4%, such as less than about 500 cP.In certain embodiments disclosed herein, the at least one waxy starch may be gelled. Starch gelation is a process that decomposes the intermolecular bonds of starch molecules in the presence of water and heat so that the hydrogen bonding sites (the hydroxyl hydrogen and oxygen) can bind more water. Therefore, heating the at least one waxy maize starch in the presence of water irreversibly dissolves the starch grain. As discussed further below, in certain embodiments, the at least one waxy starch such as waxy maize starch may be gelled together with the at least one polyvinyl alcohol to produce a sacrificial coating composition, or in certain embodiments, the at least one waxy starch such as waxy maize starch and the at least one polyvinyl alcohol may be separately heated before being combined to form a sacrificial coating composition.The sacrificial coating compositions disclosed herein may further comprise at least one hygroscopic agent. Any suitable hygroscopic agent may be employed. Hygroscopic agents may contain substances capable of absorbing water from their environment, such as humectants. In one embodiment, the hygroscopic agent may be a compound that is also functionalized as a plasticizer. Accordingly, the term "hygroscopic plasticizer" as used herein refers to a hygroscopic agent that has been functionalized and can be characterized as a plasticizer. In certain embodiments, the at least one hygroscopic agent may be a hygroscopic plasticizer selected from glycerol / glycerol, sorbitol, xylitol, maltitol, polymeric polyols such as polydextrose, glyceryl triacetate, vinyl alcohol, glycols such as propylene glycol, hexylene glycol, butylene glycol, urea and alpha hydroxy acids (AHA). In certain embodiments disclosed herein, the at least one hygroscopic agent may be selected from the group consisting of glycerol, glycerol, sorbitol, glycols such as polyethylene glycol, and mixtures thereof. In certain embodiments disclosed herein, the at least one hygroscopic agent is glycerol. A single hygroscopic agent may be used. Alternatively, multiple hygroscopic agents such as two, three or more hygroscopic agents may be used.The sacrificial coating compositions disclosed herein may further comprise at least one surfactant. Any suitable hygroscopic surfactant may be used. Examples of suitable surfactants include anionic surfactants, cationic surfactants, nonionic surfactants, and mixtures thereof. The nonionic surfactants can have an HLB value in the range of about 4 to about 14. A single surfactant may be used. Alternatively, multiple surfactants such as two, three or more surfactants may be used. For example, a mixture of a low HLB nonionic surfactant having a value of about 4 to about 8 and a nonionic surfactant having a value of about 10 to about 14 has good wettability and can be used.In certain embodiments, at least one anionic surfactant such as sodium lauryl sulfate (SLS), Dextrol OC-40, Strodex tredox PK 90, ammonium lauryl sulfate, potassium lauryl sulfate, sodium myreth sulfate, and sodium dioctylsulfosuccinate may be used. As disclosed herein, the at least one surfactant may be selected from secondary alcohol ethoxylate and branched secondary alcohol ethoxylate. In certain embodiments, at least one nonionic surfactant such as Surfynol 104 series, Surfynol 400 series, Dynol 604, Dynol 810, Envirogem® 360, secondary alcohol ethoxylate series such as Tergitol® 15-s-7 (having an HLB value of about 12), Tergitol® 15-s-9, TMN-6 (having an HLB value of about 13), TMN-100x, and Tergitol® NP-9, and Triton X-100, etc. may be used. In certain embodiments, cationic surfactants such as Chemguard S-106A, Chemguard S-208M, and Chemguard S-216M may be used. Fluorinated silicone surfactants can be used in certain embodiments, such as PolyFox® TMPF-136A, 156A and 151N, Chemguard S-761p and S-764p, Silsurf® A008, Siltec C-408, BYK 345, 346, 347, 348 and 349, and polyether siloxane copolymers such as TEGO Wet-260, 270 and 500, etc. Some amphoteric fluorinated surfactants are also contemplated in certain embodiments, such as alkyl betaine fluorosurfactants and alkyl amine oxyfluorosurfactants such as Chemguard S-500 and Chemguard S-111.The embodiments disclosed herein have good wettability and distribution properties and good printed image quality as well as further improved transfer properties.In certain embodiments disclosed herein, the sacrificial coating composition may be prepared by mixing the ingredients comprising at least one polyvinyl alcohol; at least one waxy starch such as waxy maize starch; at least one hygroscopic agent; at least one surfactant; and water. In certain embodiments, the components may be at room temperature when mixed. As used herein, room temperature is defined at about 20°C. In certain embodiments, the at least one polyvinyl alcohol and the at least one waxy starch may be separately heated and then combined. For example, in certain embodiments, the at least one polyvinyl alcohol may be mixed with water and heated for a sufficient period of time, such as a period of time ranging from about 15 minutes to about 90 minutes, about 30 minutes to about 60 minutes, or about 60 minutes. In certain embodiments, the at least one polyvinyl alcohol and water may be heated at a temperature in the range of about 90° C. to about 100° C., such as about 93° C. to about 98° C., or about 93° C + / - 1° C. In certain embodiments, the at least one polyvinyl alcohol may be mixed with water and optionally at least one hygroscopic agent such as glycerol and heated for a sufficient period of time such as a period of time ranging from about 15 minutes to about 90 minutes. In certain embodiments, the mixture of at least one polyvinyl alcohol, optionally at least one hygroscopic agent, and water may be heated at a temperature in the range of about 90° C. to about 100° C., such as about 93° C. to about 98° C., or about 93° C.+ / - 1° C. In certain embodiments, the at least one waxy maize starch may be mixed with water and heated for a sufficient period of time, such as a period of time ranging from about 10 minutes to about 60 minutes, about 15 minutes to about 30 minutes, or about 15 minutes. In certain embodiments, the at least one waxy maize starch and water may be heated at a temperature in the range of about 90° C. to about 100° C., such as about 93° C. to about 98° C., or about 93° C + / - 1° C. In certain embodiments, the at least one waxy maize starch may be mixed with a hygroscopic agent such as glycerol and water and heated for a sufficient period of time such as a period of time ranging from about 10 minutes to about 60 minutes, about 15 minutes to about 30 minutes, or about 15 minutes. In certain embodiments, the mixture of at least one waxy maize starch, the at least one hygroscopic agent, and water may be heated at a temperature in the range of about 90° C. to about 100° C., such as about 93° C. to about 98° C., or about 93° C + / - 1° C. After the at least one polyvinyl alcohol or waxy maize starch has been gelled for the appropriate periods of time, they may be combined to form a sacrificial coating composition.In other embodiments, the at least one polyvinyl alcohol and the at least one waxy maize starch may be gelled together. In such embodiments, the at least one hygroscopic agent may be added to water first. Thereafter, the at least one polyvinyl alcohol and the at least one waxy maize starch may be added to the hygroscopic agent-water solution with stirring to produce a mixture. The mixture comprising at least one polyvinyl alcohol and at least one waxy maize starch may then be gelled for a sufficient period of time, such as a period of time ranging from about 15 minutes to about 90 minutes, about 30 minutes to about 60 minutes, or about 60 minutes. In certain embodiments, the mixture may be heated at a temperature in the range of about 90° C. to about 100° C., such as about 93° C. to about 96° C., or about 93° C + / - 1° C.Further disclosed herein are processes for coating a wipe with a sacrificial coating composition comprising at least one polyvinyl alcohol; at least one waxy starch; at least one hygroscopic agent; at least one surfactant; and water, wherein the weight ratio of the at least one waxy starch to the at least one polyvinyl alcohol is at least two to one, such as transfix printing processes using a wipe. In certain embodiments, the preparation of sacrificial coating compositions as disclosed herein includes at least two steps, namely preparing the sacrificial coating composition and coating the sacrificial coating composition onto a blanket such as a fluorosilicone blanket.First, the sacrificial coating composition may be applied to an intermediate transfer member where it is dried or semi-dried to form a film. The formed film may have a higher surface energy or be more hydrophilic than the base transfer intermediate, which is typically a low surface energy material such as a polysiloxane such as polydimethylsiloxane or other silicone rubber material, fluorosilicone, Teflon® polyimide, or combinations thereof.The drying process may increase the viscosity of the aqueous ink such that the consistency of the aqueous ink is changed from a low viscosity liquid to a higher viscosity tacky material. The drying process may also reduce the thickness of the ink. In certain embodiments, the drying process may remove sufficient water such that the ink contains less than about 5 wt % water or another solvent, such as less than about 2 wt % water, or even less than about 1 wt % water or another solvent, based on the weight of the ink.In addition to the ingredients discussed above, the sacrificial coating compositions disclosed herein may comprise other ingredients such as solvents and biocides. Exemplary biocides may include ActiveIdes ® CT, ActiveIdes ® LA 1209, and ActiveIdes ® MBS in any suitable concentration, such as from about 0.1 weight percent to about 2 weight percent. Examples of suitable solvents include water, isopropanol, MEK (methyl ethyl ketone), 2-pyrollidinone, terpineol, dimethyl sulfoxide, N-methylpyrrolidone, 1,3-dimethyl-2-imidazolidinone, 1,3-dimethyl-3,4,5,6-tetrahydro-2-pyrimidinone, dimethylpropyleneurea, and mixtures thereof.The ingredients may be mixed in any suitable amount. For example, the at least one polyvinyl alcohol may be added in an amount ranging from about 0.1% to about 5% by weight, such as from about 0.5% to about 4% by weight, or from about 1% to about 3% by weight, based on the total weight of the coating mixture. The at least one surfactant may be added in an amount ranging from about 0.1 wt % to about 4 wt %, or from about 0.3 wt % to about 2 wt %, or from about 0.5 wt % to about 1 wt %, based on the total weight of the coating mixture. The at least one hygroscopic agent may be added in an amount ranging from about 0.5 wt % to about 30 wt %, or from about 5 wt % to about 20 wt %, or from about 10 wt % to about 15 wt %, based on the total weight of the coating mixture. The at least one waxy maize starch may be added in an amount ranging from about 1% to about 10% by weight, such as from about 2% to about 8% by weight, or from about 5% to about 7% by weight, based on the total weight of the coating mixture.In certain embodiments disclosed herein, the weight ratio of the at least one waxy maize starch to the at least one polyvinyl alcohol in the sacrificial coating composition is greater than one to one, such as at least two to one, at least three to one, or at least four to one. It is believed that a weight ratio of one to one may result in a composition that does not have sufficient stability for use as a sacrificial coating composition according to the embodiments disclosed herein.The compositions of the present disclosure may be used to form a sacrificial coating over any suitable substrate. Any suitable coating method may be employed including, but not limited to, gravure, dip, spray, spin, flow, emboss, die extrusion, flexo or gravure, and / or knife techniques. In embodiments, suitable methods for coating the sacrificial liquid coating composition onto a transfer intermediate member such as by means of a screen roller; or an air atomizing device such as an airbrush or an automated air / liquid sprayer may be used for spray coating. In another example, to perform flow coating, a programmable dispenser may be used to apply the coating material.In certain embodiments disclosed herein, the sacrificial coating composition may first be applied or disposed as a wet coating on the intermediate transfer member. In certain embodiments, depending on the material or process used, the wet coating may be heated at a suitable temperature for drying and curing. For example, the wet coating may be heated to a temperature in the range of about 30° C. to about 180° C. for about 0.01 seconds to about 10 seconds, such as from about 0.05 seconds to about 5 seconds.In certain embodiments, the sacrificial coating after the drying and curing process may have a thickness in the range of about 0.01 micrometers to about 10 micrometers, such as from about 0.02 micrometers to about 5 micrometers, or from about 0.05 micrometers to about 1 micrometer.In an embodiment, the sacrificial coating may cover a portion of a major surface of the transfer intermediate member. The outer major surface of the transfer intermediate member may comprise, for example, polysiloxanes, fluorosilicones, fluoropolymers such as Viton ®, Teflon ® and the like.Figure 1 shows a high speed aqueous ink imaging machine or printer 10. As shown, the printer 10 is an indirect printer that forms an ink image on a surface of a blanket 21 that is mounted around a rotary interposer 12 and thereafter transfers the ink image to media passing through a nip 18 formed between the blanket 21 and the transfix roller 19. Surface 14 of the blanket 21 is referred to as the image receiving surface of the blanket 21 and the rotational member 12 because surface 14 receives a hydrophilic composition and the aqueous ink images that are transfixed to print media during a printing process. A printing cycle will be described below with reference to the printer 10. As used herein, "print cycle" refers to the operations of a printer to prepare an imaging surface for printing, the ejection of ink onto the prepared surface, the treatment of ink on the imaging surface to stabilize and prepare the image for transfer to media, and the transfer of the image from the imaging surface to the media.The printer 10 includes a frame 11 which directly or indirectly supports operating subsystems and components described below. The printer 10 includes a transfer intermediate member illustrated as an imaging rotating drum 12 in FIG. 1, but may have other suitable configurations such as that of a supported endless belt. The imaging drum 12 includes an outer cloth 21 attached around the periphery of the drum 12. The cloth moves in a direction 16 as the member 12 rotates. A transfix roller 19 rotatable in the direction 17 is biased against the surface 21 of the blanket 21 to form a transfix nip 18 in which ink images formed on the surface of the blanket 21 are transfixed to a print medium 49. In some embodiments, a heating element in the drum 12 (not shown) or elsewhere in the printer heats the image receiving surface 14 on the blanket 21 to a temperature in a range from about 50°C to about 70°C, for example. The elevated temperature promotes partial drying of the liquid carrier used to deposit the hydrophilic composition and the water in the aqueous ink droplets deposited on the image receiving surface 14.The blanket is formed of a material having a relatively low surface energy to allow the transfer of the ink image from the surface of the blanket 21 to the media sheet 49 in the nip 18. Such materials include polysiloxanes, fluorosilicones, fluoropolymers such as VITON® or Teflon® and the like. A surface maintenance unit (SMU) 92 removes residual ink left on the surface of the blanket 21 after the ink images are transferred to the print medium 49. The low energy surface of the cloth need not necessarily be designed to aid in the formation of high quality ink images, as such surfaces do not at least spread ink droplets, as well as high energy surfaces.The SMU 92 deposits the sacrificial coating composition on the image receiving surface 14. After a drying process, the dried sacrificial coating substantially covers the image receiving surface 14 before the printer ejects ink drops during a printing process. The SMU 92 may be operatively connected to a controller 80, described in more detail below, for causing the controller to actuate the dispensing roller as well as a metering blade and a cleaning blade, which may also function to deposit and distribute the coating material onto the surface of the blanket and to remove untransferred ink and any sacrificial coating debris from the surface of the blanket 21.The printer 10 includes a dryer 96 which gives off heat and optionally directs an air flow to the sacrificial coating composition which is applied to the image receiving surface 14. The dryer 96 allows at least a portion of the liquid carrier to be evaporated from the sacrificial coating composition to leave a dried layer on the image receiving surface 14 before the transfer intermediate passes the printhead modules 34A-34D to receive the aqueous printed image.The printer 10 may include an optical sensor 94A, also known as an image-on-drum (IODO) sensor, configured to detect light reflected from the tissue surface 14 and the sacrificial coating applied to the tissue surface as the member 12 rotates past the sensor. The optical sensor 94A comprises a linear array of individual optical detectors arranged across the cloth 21 transversely of the processing direction. The optical sensor 94A generates digital image data corresponding to light reflected from the cloth surface 14 and the sacrificial coating. The optical sensor 94A generates a series of series of image data, referred to as "scanlines" (scanlines), as the intermediate transfer member 12 rotates the blanket 21 in the direction 16 past the optical sensor 94A. In one embodiment, each optical detector in the optical sensor 94A further includes three sensing elements sensitive to wavelengths of light corresponding to the red, green, and blue (RGB) reflected light colors. Alternatively, the optical sensor 94A has illumination sources that emit red, green, and blue light, or in another embodiment, the sensor 94A has an illumination source that emits white light onto the surface of the cloth 21, using white light detectors. The optical sensor 94A radiates complementary colors of light onto the image receiving surface to enable detection of different colors of ink by the photodetectors. The image data generated by the optical sensor 94A is analyzed by the controller 80 or other processor in the printer 10 to identify the thickness of the sacrificial coating on the blanket and the surface coverage. The thickness and coverage can be identified from either specular or diffuse light reflection from the cloth surface and / or coating. Other optical sensors such as 94B, 94C, and 94D are similarly configured and may be located at various locations around the blanket 21 to identify other parameters in the printing process such as missing or disabled ink jets and pre-image-drying ink imaging (94B), image transfer ink image treatment (94C), and ink image transfer efficiency (94D). Alternatively, some embodiments may include an optical sensor to generate additional data that may be used to evaluate the image quality on the media (94E).The printer 10 includes an airflow management system 100 that generates and controls airflow through the print area. The airflow management system 100 includes a printhead air supply 104 and a printhead air return 108. The printhead air supply 104 and return 108 are operatively connected to the controller 80 or other processor in the printer 10 to allow the controller to regulate the air flowing through the print area. This regulation of the air flow may be across the entire print area or around one or more print head assemblies. The regulation of the air flow helps prevent condensation of evaporated solvents and water in the ink on the printhead and helps to reduce the attenuation of heat in the print area to reduce the likelihood that ink will dry in the ink jet nozzles, which can clog the ink jet nozzles. The airflow management system 100 may also include sensors for sensing humidity and temperature in the pressure range to enable more precise control of the temperature, flow, and humidity of the air supply 104 and recirculation 108 to ensure optimal conditions in the pressure range. The controller 80 or other processor in the printer 10 may also enable control of the system 100 with respect to ink coverage in an image area or even to time the operation of the system 100 so that air flows through the print area only when no image is being printed.The high speed aqueous ink printer 10 includes an aqueous ink supply and delivery subsystem 20 that includes at least one source 22 of aqueous ink. For example, because the illustrated printer 10 is a multicolor imaging machine, the ink delivery system 20 includes four (4) sources 22, 24, 26, 28 representing four (4) different colors CYMK (cyan, yellow, magenta, black) of aqueous inks. In the embodiment of Fig. 1, the printhead system 30 includes a printhead support 32 that supports a plurality of printhead modules, also referred to as "printbox" units 34A-34D. Each printhead module 34A-34D, in fact, extends across the width of the blanket and ejects ink droplets onto the surface 14 of the blanket 21. A printhead module may include a single printhead or multiple printheads arranged in a staggered arrangement. Each printhead module is operatively connected to a frame (not shown) and is oriented to eject the ink droplets such that an ink image is formed on the coating of the blanket surface 14. The printhead modules 34A- 34D may include associated electronics, ink reservoirs, and ink conduits for supplying ink to the one or more printheads. In the illustrated embodiment, conduits (not shown) operatively connect the sources 22, 24, 26, and 28 to the printhead modules 34A-34D to provide ink supply to the one or more printheads in the modules. As is well known, each of the one or more printheads in a printhead module may eject a single ink. In other embodiments, the printheads may be configured to eject two or more inks. For example, printheads in modules 34A and 34B may eject cyan and magenta ink, while printheads in modules 34C and 34D may eject yellow and black ink. The printheads in the illustrated modules are arranged in two arrays that are offset or staggered from each other to increase the resolution of each color separation printed by one module. Such an arrangement enables printing at an increased resolution as compared to a printing system having only a single array of printheads that eject only one ink. Although the printer 10 has four printhead modules 34A-34D, each having two arrays of printheads, alternative configurations include a different number of printhead modules or arrays in a module.After the printed image on the surface 14 leaves the print area, the image is passed under an image dryer 130. The image dryer 130 includes a heating element such as an infrared or near infrared and / or hot air forced convection heating element 134, a dryer 136 shown as a heated air source 136, and air returns 138A and 138B. The infrared heater 134 applies infrared heat to the printed image on the surface 14 of the blanket 21 to evaporate water or solvent in the ink. The heated air source 136 directs heated air across the ink to aid in the evaporation of the water or solvent from the ink. In one embodiment, the dryer 136 is a heated air source having the same configuration as the dryer 96. while the dryer 96 is positioned along the processing direction to dry the hydrophilic composition, the dryer 136 is positioned along the processing direction after the printhead modules 34A-34D to at least partially dry the aqueous ink on the image receiving surface 14. The air is then collected and discharged through the air recirculations 138A and 138B to reduce interference with the air flow with other components in the pressure range.As further illustrated, the printer 10 includes a print media supply and handling system 40 that stores, for example, one or more stacks of different sized paper print media. The print media supply and handling system 40 includes, for example, sheet or substrate supply sources 42, 44, 46, and 48. In the embodiment of the printer 10, the supply source 48 is a high capacity paper supply or feeder for storing and supplying image receiving substrates in the form of, for example, cut print media 49. the print media supply and handling system 40 also includes a substrate handling and transport system 50 that includes a media preconditioner assembly 52 and a media post-conditioning assembly 54. The printer 10 includes an optional fuser 60 for applying additional heat and pressure to the print medium after the print medium has passed through the transfix nip 18. In the embodiment of Fig. 1, printer 10 includes an original document feeder 70 which includes a document holding tray 72, document sheet feeding and removing devices 74, and a document exposure and scanning system 76.Operation and control of the various subsystems, components, and functions of the machine or printer 10 is via a controller or electronic subsystem (ESS) 80. The ESS or controller 80 is operatively connected to, for example, the transfer interposer 12, the printhead modules 34A- 34D (and thus the printheads), the substrate feed and handling system 40, the substrate handling and transport system 50, and in some embodiments, the one or more optical sensors 94A- 94E. The ESS or controller 80 is, for example, an independent dedicated minicomputer having a central processing unit (CPU) 82 with an electronic memory 84 and a display or user interface (UI) 86. the ESS or controller 80 includes, for example, a sensor input and control circuit 88 and a pixel placement and control circuit 89. In addition, CPU 82 reads, captures, prepares, and manages the flow of image data between image input sources such as scan system 76 or online or workstation connection 90 and printhead modules 34A-34D. Accordingly, the ESS or controller 80 is the most important multi-tasking processor for operating and controlling all other machine subsystems and functions, including the printing process discussed below.The controller 80 may be implemented with general or special purpose programmable processors executing programmed instructions. The instructions and data required to perform the programmed functions may be stored in memory associated with the processors or controllers. The processors, their memories, and interface circuits configure the controllers to perform the operations described below. These components may be provided on a printed circuit board or provided as a circuit in an application specific integrated circuit (ASIC). Each of the circuits may be implemented with a separate processor or multiple circuits may be implemented on the same processor. Alternatively, the circuits may be implemented with discrete components or circuits provided in very large scale integrated (VLSI) circuits. Further, the circuits described herein may be implemented with a combination of processors, ASICs, discrete components, or VLSI circuits.Although the printer 10 is described in Figure 1 with a cloth 21 mounted around a rotating intermediate member 12, other configurations of image receiving surface may be used. For example, the rotating interposer may have a surface that is integral with its periphery and allows an aqueous ink image to be formed on the surface. Alternatively, a cloth is configured as an endless rotating belt to form an aqueous image. Other variations of these structures may be configured for this purpose. As used herein, the term "imaging interface" includes these various configurations.After forming an image or images on the cloth and coating under the control of the controller 80, the illustrated inkjet printer 10 operates components in the printer to perform a process for transferring and fixing the image or images from the cloth surface 14 to media. In the printer 10, the controller 80 actuates actuators to drive one or more of the rollers 64 in the media transport system 50 to move the print medium 49 in the processing direction P to a position adjacent the transfix roller 19 and then through the transfix nip 18 between the transfix roller 19 and the blanket 21. The transfix roller 19 applies pressure against the back side of the print medium 49 to press the front side of the print medium 49 against the cloth 21. Although the transfix roller 19 can also be heated, in the embodiment of Fig. 1, the transfix roller 19 is not heated. Instead, the preheater assembly 52 is provided for the print medium 49 in the media path leading to the nip. Preconditioner assembly 52 conditions print medium 49 to a predetermined temperature that helps transfer the image to the media, thus simplifying the design of the transfix roller. The pressure generated by the transfix roller 19 on the back side of the heated print medium 49 allows the image from the intermediate transfer member 12 to be transfixed (transferred and fixed) to the print medium 49, and the rotation or rolling of both the intermediate transfer member 12 and the transfix roller 19 not only transfixes the images to the print medium 49, but also assists in the transport of the print medium 49 through the nip. The intermediate transfer member 12 continues to rotate to cause the printing process to be repeated.After the intermediate transfer member 12 passes through the transfix nip 18, the image receiving surface passes a cleaning unit which removes residual portions of the sacrificial coating and small amounts of ink residues from the image receiving surface 14. In the printer 10, the cleaning unit is configured as a cleaning blade 95 that engages the image pickup surface 14. The squeegee 95 is formed of a material that wipes the image pickup surface 14 without causing damage to the cloth 21. For example, the cleaning blade 95 is formed of a flexible polymer material in the printer 10. As shown below in Figure 1, another embodiment includes a cleaning unit that includes a roller or other element that applies a mixture of water and detergent to remove residual material from the image receiving surface 14 after the image receiving element moves through the transfix nip 18. As used herein, the term "detergent" or cleaning agent refers to any surfactant, solvent or other chemical compound suitable for removing sacrificial coating and ink residue that may remain on the image receiving surface from the image receiving surface. An example of a suitable detergent is sodium stearate, which is a compound commonly used in soap. Another example is IPA, which is a commercially available solvent that is highly effective for removing ink residue from the image receiving surface. In one embodiment, after transfer of the ink and sacrificial layer, no residue of the sacrificial coating layer remains on the ITM, in which case cleaning the ITM to remove sacrificial coating residues is unproblematic.As disclosed herein, certain advantages over prior art processes can be achieved by embodiments disclosed herein. For example, the exemplary sacrificial coating compositions disclosed herein may provide a wide range of formulations while still imparting desirable properties such as improved transmission efficiency and image quality. Additionally, the sacrificial coating compositions disclosed herein can have a wide transfer bandwidth, such that uniform image transfer is possible under many different conditions and in many different fields. The methods disclosed herein for making sacrificial coating compositions may also result in a more robust composition that enables both improved image quality and transfer efficiency.Unless otherwise indicated, all numbers used in the specification and claims are in all cases to be understood as modified by the term "about" whether or not so indicated. It is also to be understood that the exact numerical values used in the specification and claims, as well as all ranges and sub-ranges within specified endpoints, form additional embodiments of the disclosure. Efforts have been made to ensure the accuracy of the numerical values disclosed in the examples. However, each measured numerical value may inherently contain certain errors resulting from the standard deviation occurring in its respective metrology.As used herein, the use of the terms "the," "the," or "an," "an" refers to "at least one / one," and is not to be limited to "only one / one," unless expressly stated to the contrary. As used herein, the term "one / one or more" refers to a listing of, for example, items A and B only A, only B, or A and B. The term "at least one / one" is intended to refer to one or more of the listed items.It is to be understood that both the foregoing description and the following examples are merely exemplary and explanatory and are not intended to be limiting. It should also be noted that where steps are disclosed, the steps need not be performed in the order indicated, unless expressly stated.The accompanying figures, which are incorporated in and constitute a part of this specification, are not intended to be limiting, but to explain embodiments of the disclosure.Other embodiments will be apparent to those skilled in the art in view of the specification and practice of the disclosure.EXAMPLESThe following examples are not intended to limit the disclosure.Example 1Example 1A - Preparation of a Polyvinyl Alcohol-Starch Binder SolutionA solution was prepared according to the following steps. First, 20 g of glycerol was charged into 74 g of water. Thereafter, 4.5 g of waxy maize starch powder Cargill Caliber 180 was combined with 1.5 g of powder SEKISUI Selvol® polyvinyl alcohol 125 and mixed. The mixture of starch and polyvinyl alcohol was loaded into the glycerol-water liquid and then heated at 93°C + / - 1°C for 60 minutes. Thereafter, a 6% solid concentrated binder (polyvinyl alcohol and starch) solution was ready for the preparation of a sacrificial coating solution.Example 1B - Preparation of Sacrificial Coating CompositionThe polyvinyl alcohol and starch binder solution prepared in Example 1A above was made to have a solids content of 2% with distilled water, after which 0.1% sodium lauryl sulfate (SLS) surfactant was added. The ratio of starch to polyvinyl alcohol was 75% to 25% (i.e., three to one). The sacrificial coating composition was stable without phase separation after a few days.Comparative Example 2A 10% solution of SEKISUI Selvol® polyvinyl alcohol 125 was boiled at a temperature of 93°C for 60 minutes. A 10% strength waxy maize starch Cargill Caliber 180 was cooked at a temperature of 93° C. for 15 minutes. The following were then mixed: 10 grams of cooked 10% SEKISUI Selvol® polyvinyl alcohol 125; 10 grams of gelled 10% waxy maize starch Caliser 180; 6.7 grams of glycerol; and 73.3 grams of deionized water.The ratio of starch to polyvinyl alcohol was 50% to 50% (i.e., one to one). The solution was not stable. After one day, phase separation was observed. While there is no desire to be bound by theory, it is believed that the higher the charge of superhydrolysed SEKISUI Selvol® polyvinyl alcohol 125, the less stable the solution. It was found that cooking polyvinyl alcohol or starch together with the hygroscopic material glycerol produced a sacrificial coating solution that was more stable to phase separation and that had improved rheological properties. The stability of the sacrificial coating solution was thus further improved by selecting the manufacturing method disclosed in Example 1 herein.Comparative Example 3A standard control formulation was prepared with 2% waxy maize starch Cargill Calibrator 180, 6.7% glycerol, 0.1% sodium lauryl sulfate and 91.2% distilled water.Example 4A 10% solution of SEKISUI Selvol® polyvinyl alcohol 825 was boiled at a temperature of 93°C + / - 1°C for 60 minutes and maintained at that temperature. A 10% waxy maize starch Cargill Caliber 180 was gelled at a temperature of 93°C + / - 1°C for 15 minutes and held at that temperature for 15 minutes.16 g of a gelled 10% waxy maize starch solution Cargill Caliber 180 and 4 g of the 10% cooked solution of SEKISUI Selvol® polyvinyl alcohol were then mixed with 6.7 g glycerol and 0.1 g sodium lauryl sulfate (SLS) surfactant to produce a sacrificial coating composition. The ratio of starch to polyvinyl alcohol was 80% to 20% (i.e., four to one). After a few days, the sacrificial coating composition was stable without phase separation.Example 5A solution was prepared by boiling a 10% solution of SEKISUI Selvol® polyvinyl alcohol 825 at a temperature of 93°C + / - 1°C and held at that temperature for 60 minutes. A 10% waxy maize starch Cargill Caliber 180 was gelled at a temperature of 93°C + / - 1°C for 15 minutes and held at that temperature for 15 minutes.Thereafter, a sacrificial coating solution was prepared by mixing in a flask the following: 48 g of 10% Cargill Caliber 180 waxy maize starch; 12 g of 10% solution of SEKISUI Selvol® 10% polyvinyl alcohol 825; 15 g glycerol; 1 g sodium lauryl sulfate surfactant; and 24 g distilled water.The ratio of starch to polyvinyl alcohol was 80% to 20% (i.e., four to one). The sacrificial coating skin solution had a high solids content and was stable without phase separation after several days.Example 6 - Transmission EfficiencyA performance evaluation of the sacrificial coating composition prepared in Example 1B was made. The skin was applied to the cloth by skin solution deposition and then dried. This formed a strong and robust film layer on the top surface of the cloth having a thickness of about 0.2 to 0.5 microns. Ink was then ejected onto the top of the skin and semidried before the entire layer of ink and skin was transferred to the substrate. Drying conditions were varied to check the system bandwidth, and the images were examined to evaluate system performance. As compared to the control formulation described in Comparative Example 3 and containing only waxy maize starch without polyvinyl alcohol, the formulation of Example 1B showed the same performance in terms of wet image quality and considerably better performance in terms of transfer, as discussed below.The transfer performance was evaluated by ink residue on the intermediate cloth under various ink drying conditions (varying percentages of full dryer performance). The residue was evaluated by a visual rating scale called a standard image reference (SIR). The SIR of various prints was evaluated on a scale of 0 to 5, where it was considered that the smaller the number, the better the transmission efficiency. Accordingly, a rating of 0 was considered to be the best possible result that indicated excellent transmission performance. An SIR rating of 5 was considered a very poor result. SIR intermediate evaluations from 1 to 4 had decreasing transmit power values. In addition to a low SIR, good transmission performance with lower drying performance may be preferred.Figure 2 is a graph showing the transfer power SIR vs. the drying power percentage setting for two sacrificial coating compositions: the composition prepared in Example 1B and the control coating composition prepared in Comparative Example 3. The vertical axis is the SIR rating and the horizontal axis is the percent drying capacity. As seen in Figure 2, the sacrificial coating composition prepared in Example 1B had better transfer performance and required lower drying performance than the control formulation.

Claims

A sacrificial coating composition comprising: at least one polyvinyl alcohol having a degree of hydrolysis of at least about 95%; at least one waxy maize starch; at least one hygroscopic agent; at least one surfactant; and water, wherein the weight ratio of the at least one waxy maize starch to the at least one polyvinyl alcohol is at least two to one.The sacrificial coating composition of claim 1, wherein the at least one polyvinyl alcohol has a weight average molecular weight (weight average) of about 85,000 to about 186,000.The sacrificial coating composition of claim 1, wherein the at least one polyvinyl alcohol has a degree of hydrolysis in the range of about 95% to about 99.9%.The sacrificial coating composition of claim 1, wherein the viscosity of the at least one polyvinyl alcohol in a deionized water solution at 20°C is in the range of about 30 centipoise to about 80 centipoise, and wherein the solution contains about 4 wt% polyvinyl alcohol, based on the total weight of polyvinyl alcohol and deionized water in the solution.The sacrificial coating composition of claim 1, wherein the weight ratio of the at least one waxy maize starch to the at least one polyvinyl alcohol is in the range of about two to one to about four to one.A method of making a sacrificial coating composition comprising: mixing at least one polyvinyl alcohol having a degree of hydrolysis of at least about 95%, at least one waxy maize starch, and at least one hygroscopic agent in water to form a mixture; heating the mixture to a temperature of at least about 90°C; and maintaining the mixture at the temperature for at least about 15 minutes, wherein the weight ratio of the at least one waxy maize starch to the at least one polyvinyl alcohol in the mixture is at least two to one.The method of claim 6, wherein the at least one polyvinyl alcohol has a degree of hydrolysis in the range of about 95% to about 99.9%.The method of claim 6, wherein the weight ratio of the at least one waxy maize starch to the at least one polyvinyl alcohol is in the range of at least about two to one to at least four to one.A method of making a sacrificial coating composition comprising: mixing at least one polyvinyl alcohol having a degree of hydrolysis of at least about 95% and water at about 20°C to form a first mixture; heating the first mixture to a first temperature of at least about 90°C; maintaining the first mixture at the first temperature for at least about 15 minutes; mixing at least one waxy maize starch and water at about 20°C to form a second mixture; heating the second mixture to a second temperature of at least about 90°C; maintaining the second mixture at the second temperature for at least about 15 minutes; and combining the first mixture and the second mixture to form a sacrificial coating composition, wherein the weight ratio of the at least one waxy maize starch and the at least one polyvinyl alcohol in the sacrificial coating composition is in the range of at least about two to one to at least four to one.The method of claim 9, wherein the first mixture further comprises at least one hygroscopic agent.

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