Patent Publication Number: US-2016237626-A1

Title: Packaging material having moisture barrier and methods for preparing same

Description:
FIELD OF THE INVENTION 
     The present invention broadly relates to a recyclable packaging material comprising a paper substrate; a print-receptive layer which is positioned over the outer surface of the paper substrate; and a moisture barrier layer which comprises one or more energy-cured polymers and which is positioned over the print-receptive layer. The present invention also broadly relates to a method for preparing these recyclable packaging materials by applying an energy-curable coating comprising one or more energy-curable monomers over the calendered print-receptive layer; and curing the energy-curable monomers to form a moisture barrier layer positioned over the calendered print-receptive layer and comprising one or more energy-cured polymers. The present invention further broadly relates to a method for preparing printed packaging materials by providing a printable material having a print-receptive layer; depositing print colorant on the print-receptive to form one or more printed areas; applying the energy-curable coating comprising one or more energy-curable monomers over the print-receptive layer of the printed material to provide a coated printed material; and curing the energy-curable monomers to form a moisture barrier layer comprising one or more energy-cured polymers and positioned over the print-receptive layer of the printed material to provide a printed packaging material, wherein the printing, applying and curing steps are carried out as a single pass operation, and without reeling up: the printed material prior to the applying step; and the coated printed material prior to the curing step. 
     BACKGROUND 
     Polyethylene films, which may be laminated or coated on paper, are widely used in packaging applications to protect products from moisture and provide water or grease resistance. Conventional ream wraps may be a multi-ply product having a ply of polyethylene adjacent at least one surface of a paper substrate, or having a center ply of polyethylene in between two other plys of a paper substrate. The polyethylene ply may be used in ream wraps to provide an effective barrier to water vapor (humidity). This water vapor (humidity) may cause the wrapped paper to curl, resulting in misfeeds and jams in copy machines or printing presses. Other paper coatings which comprise wax have also been used. For example, U.S. Pat. No. 4,117,199 (Gotoh et al.), issued Sep. 26, 1978, discloses a repulpable coated paper containing a synthetic rubber latex and a wax emulsion. Coatings such as Vapo-Stop, manufactured by Cham-Tenero Paper Mills, Inc., Cham, Switzerland, include a styrene-butadiene polymer, wax and acrylic polymer components which may provide moisture resistance to coated paper substrates. 
     SUMMARY 
     According to a first broad aspect of the present invention, there is provided an article comprising a recyclable packaging material comprising:
         a paper substrate comprising at least about 40% recyclable paper fibers and having an inner surface and an outer surface;   a print-receptive layer having an inner surface and an outer surface, wherein the print-receptive layer inner surface is positioned over the paper substrate outer surface and wherein the print-receptive layer outer surface has a Parker Print Smoothness value of about 1.5 or less; and   a moisture barrier layer comprising one or more energy-cured polymers positioned over the print-receptive layer outer surface, wherein the packaging material has a water vapor transportation rate of about 500 g/m 2 /day or less.       

     According to a second broad aspect of the present invention, there is provided a method comprising the following steps:
         (a) providing a calendared printable material comprising:
           a paper substrate comprising at least about 40% recyclable paper fibers and having an outer surface and inner surface; and   a print-receptive layer having an inner surface and a calendered outer surface, wherein the print-receptive layer inner surface is positioned over the paper substrate outer surface and wherein the calendered print-receptive layer outer surface has a Parker Print Smoothness value of about 1.5 or less;   
           (b) applying an energy-curable coating comprising one or more energy-curable monomers over the calendered print-receptive layer outer surface; and   (c) curing the energy-curable monomers to form a moisture barrier layer comprising one or more recyclable energy-cured polymers positioned over the calendered print-receptive layer outer surface to provide a recyclable packaging material having a water vapor transportation rate of about 500 g/m 2 /day or less.       

     According to a third broad aspect of the present invention, there is provided a method comprising the following steps:
         (a) providing an unreeled printable material comprising:
           a paper substrate having an outer surface and inner surface; and   a print-receptive layer having an inner surface and an outer surface, wherein the print-receptive layer inner surface is positioned over the paper substrate outer surface and wherein the print-receptive layer outer surface has a Parker Print Smoothness value of about 1.5 or less;   
           (b) depositing print colorant on the print-receptive layer outer surface to form one or more printed areas to provide a printed material;   (c) applying to the printed material an energy-curable coating comprising one or more energy-curable monomers over the print-receptive layer outer surface, including the printed areas, to provide a coated printed material; and   (d) curing the energy-curable monomers to form a moisture barrier layer comprising one or more energy-cured polymers positioned over the print-receptive layer outer surface to provide a printed packaging material having a water vapor transportation rate of about 500 g/m 2 /day or less;   wherein steps (a) through (d) are carried out as a single pass operation, and without reeling up: the printed material of step (b) prior to carrying step (c); and the coated printed material of step (c) prior to carrying out step (d).       

    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The invention will be described in conjunction with the accompanying drawings, in which: 
         FIG. 1  is a side sectional view of an embodiment of a recyclable printable packaging material of the present invention; and 
         FIG. 2  is a flowchart to illustrate various embodiments of a method for preparing a (recyclable) printed packaging material according to embodiments of the present invention. 
     
    
    
     DETAILED DESCRIPTION 
     It is advantageous to define several terms before describing the invention. It should be appreciated that the following definitions are used throughout this application. 
     DEFINITIONS 
     Where the definition of terms departs from the commonly used meaning of the term, applicant intends to utilize the definitions provided below, unless specifically indicated. 
     For the purposes of the present invention, directional terms such as “outer,” “inner,” “upper,” “lower,” “top”, “bottom”, “side,” “front,” “frontal,” “forward,” “rear,” “rearward,” “back,” “trailing,” “above”, “below”, “left”, “right”, “horizontal”, “vertical”, “upward”, “downward”, etc. are merely used for convenience in describing the various embodiments of the present invention. For example, the embodiments of the present invention illustrated in  FIGS. 1 and 2 , may be oriented in various ways. 
     For the purposes of the present invention, the term “packaging material” refers to materials for forming packages for protecting, carrying, distributing, etc., products, such as a ream of paper, paper rolls, foods, beverages, etc. Packaging material may include, for example, ream wrap, roll wrap, envelopes, containers (e.g., for foods or beverages), boxes, etc. 
     For the purposes of the present invention, the term “ream wrap” refers to packaging material used to protect, carry, distribute, etc., a ream of paper. 
     For the purposes of the present invention, the term “roll wrap” refers to packaging material used to protect, carry, distribute, etc., one or more rolls of paper. 
     For the purposes of the present invention, the term “ream of paper” refers to the conventional sense of the term as providing a quantity of paper (e.g., packaged quantity of paper) in the range of, for example, from about 480 to about 516 sheets (e.g., 480, 500 or 516 sheets). 
     For the purposes of the present invention, the term “paper substrate” refers to a fibrous web that may be formed, created, produced, etc., from a mixture, furnish, etc., comprising paper fibers, etc., plus any other optional papermaking additives such as, for example, internal and/or external paper sizing agents, fillers, wet-strength agents, optical brightening agents, etc. The paper substrate may be in the form of a continuous roll, a discrete sheet, etc. 
     For the purposes of the present invention, the term “softwood fibers” refers to fibrous pulps derived from the woody substance of coniferous trees (gymnosperms) such as varieties of fir, spruce, pine, etc., for example, loblolly pine, slash pine, Colorado spruce, balsam fir, Douglas fir, jack pine, radiata pine, white spruce, lodgepole pine, redwood, etc. North American southern softwoods and northern softwoods may be used to provide softwood fibers, as well as softwoods from other regions of the world. 
     For the purposes of the present invention, the term “hardwood fibers” refers to fibrous pulps derived from the woody substance of deciduous trees (angiosperms) such as birch, oak, beech, maple, eucalyptus, poplars, etc. 
     For the purposes of the present invention, the term “paper substrate filler” refers to mineral products (e.g., calcium carbonate, kaolin clay, etc.), as well as nonmineral products (e.g., plastic pigments), which may be used in paper making to reduce materials cost per unit mass of the paper, increase opacity, increase smoothness, etc. The mineral products may be finely divided, for example, the size range of from about 0.5 to about 5 microns. 
     For the purposes of the present invention, the term “calendered material” refers to a material which has been subjected to calendering to, for example, smooth out the material for enabling printing on the material, to increase the gloss on the material surface, etc. For example, calendering may involve a process of using pressure (and optionally temperature and moisture) for embossing a smooth surface on the still rough material surface. Calendering may be carried out on a calendar which may comprise a series of calendar rolls at the end of, for example, a papermaking machine (on-line), or separate from the papermaking machine (off-line). Calendering may include supercalendering, hot-soft calendering, moisture-gradient calendering, extended nit calendering, belt calendering, etc. See G. A. Smook, Handbook for Pulp and Paper Technologists (2 nd  Edition, 1992), pages 273-78, the entire contents and disclosure of which is herein incorporated by reference, for a general description of calendering, as well as devices for carrying out calendering, that may be useful herein. 
     For the purposes of the present invention, the term “supercalendered material” refers to a material which has been processed (calendered) through an alternating series of harder surface (e.g., steel, etc.) and softer surface (e.g., fiber-covered, polymer covered, etc.) calender rolls. See G. A. Smook, Handbook for Pulp and Paper Technologists (2 nd  Edition, 1992), pages 296-98, the entire contents and disclosure of which is herein incorporated by reference, for a general description of supercalendering, as well as devices for carrying out supercalendering, that may be useful herein. 
     For the purposes of the present invention, the term “energy-curable coating” refers to those coatings, which comprise, at minimum, one or more energy-cured polymers, one more energy-curable monomers for forming the energy-cured polymers, etc. These energy-curable coatings (or energy-curable coating compositions used to provide such coatings) may also include other optional additives, such as, for example, solvents, diluents, rheology modifiers, dispersants, surfactants, etc. The energy-curable coating compositions may be formulated as an aqueous solution, an aqueous slurry, a colloidal suspension, a liquid mixture, a thixotropic mixture, etc. 
     For the purposes of the present invention, the term “solids basis” refers to the weight percentage of each of the respective solid materials (e.g., energy-cured polymers, energy-curable monomers, etc.) present in the coating, coating composition, etc., in the absence of any liquids (e.g., water, other solvents, etc.). Unless otherwise specified, all percentages given herein for the solid materials are on a solids basis. 
     For the purposes of the present invention, the term “solids content” refers to the percentage of non-volatile, non-liquid components (by weight) that are present in the coating, composition, etc. 
     For the purposes of the present invention, the term “substrate pigment” refers to a material (e.g., a finely divided particulate matter) which may be used or may be intended to be used to affect optical properties of a paper substrate. Substrate pigments may include calcium carbonate pigments, absorptive plastic pigments, clay pigments, kaolin pigments, calcined clay pigments, talc pigments, titanium dioxide pigments, barium sulfate pigments, silica pigments, zeolite pigments, etc. Substrate pigments may also be platy mineral pigments, non-platy mineral pigments, etc. 
     For the purposes of the present invention, the term “platy mineral pigment” refers to substrate pigments which are plate-like in structure and consist of thin, ill formed, sheet-like particles of high aspect ratio (width to thickness of the particles) of greater than about 2, for example, greater than about 5, such as in the range of from about 10 to about 60 (e.g., from about 20 to about 40). Platy mineral pigments may include one or more of: delaminated clays, kaolin, talc, montmorillonite, halloysite, attapulgite, illite, natural and synthetic micas, such as muscovite, phlogopite, biotite, barium disilic, etc. See commonly-assigned U.S. Pat. No. 7,320,825 (Morabito), issued Jan. 22, 2008, the entire contents and disclosure of which is herein incorporated by reference, for description of platy mineral pigments, and the difference from non-platy mineral pigments. 
     For the purposes of the present invention, the term “calcium carbonate” refers various calcium carbonates which may be used as substrate pigments, such as precipitated calcium carbonate (PCC), ground calcium carbonate (GCC), modified PCC and/or GCC, etc. 
     For the purposes of the present invention, the term “precipitated calcium carbonate (PCC)” refers to a calcium carbonate which may be manufactured by a precipitation reaction and which may used as a substrate pigment. PCC may comprise almost entirely of the calcite crystal form of CaCO 3 . The calcite crystal may have several different macroscopic shapes depending on the conditions of production. Precipitated calcium carbonates may be prepared by the carbonation, with carbon dioxide (CO 2 ) gas, of an aqueous slurry of calcium hydroxide (“milk of lime”). The starting material for obtaining PCC may comprise limestone, but may also be calcined (i.e., heated to drive off CO 2 ), thus producing burnt lime, CaO. Water may added to “slake” the lime, with the resulting “milk of lime,” a suspension of Ca(OH) 2 , being then exposed to bubbles of CO 2  gas. Cool temperatures during addition of the CO 2  tend to produce rhombohedral (blocky) PCC particles. Warmer temperatures during addition of the CO 2  tend to produce scalenohedral (rosette-shaped) PCC particles. In either case, the end the reaction occurs at an optimum pH where the milk of lime has been effectively converted to CaCO 3 , and before the concentration of CO 2  becomes high enough to acidify the suspension and cause some of it to redissolve. In cases where the PCC is not continuously agitated or stored for many days, it may be necessary to add more than a trace of such anionic dispersants as polyphosphates. Wet PCC may have a weak cationic colloidal charge. By contrast, dried PCC may be similar to most ground CaCO 3  products in having a negative charge, depending on whether dispersants have been used. The calcium carbonate may be precipitated from an aqueous solution in three different crystal forms: the vaterite form which is thermodynamically unstable, the calcite form which is the most stable and the most abundant in nature, and the aragonite form which is metastable under normal ambient conditions of temperature and pressure, but which may convert to calcite at elevated temperatures. The aragonite form has an orthorhombic shape that crystallizes as long, thin needles that may be either aggregated or unaggregated. The calcite form may exist in several different shapes of which the most commonly found are the rhombohedral shape having crystals that may be either aggregated or unaggregated and the scalenohedral shape having crystals that are generally unaggregated. 
     For the purposes of the present invention, the term “substrate pigment binder” refers to a binder agent for paper substrates which may be used to improve the substrate pigment binding strength of the coating composition, coating, etc. Substrate pigment binders may be hydrophilic. Suitable substrate pigment binders may include synthetic or naturally occurring polymers (or a combination of different polymers), for example, a polyvinyl alcohol (PVOH), starch binders, proteinaceous adhesives such as, for example, casein or soy proteins, etc.; polymer latexes such as styrene butadiene rubber latexes, acrylic polymer latexes, polyvinyl acetate latexes, styrene acrylic copolymer latexes, etc., or a combination thereof. 
     For the purposes of the present invention, the term “starch binder” refers to a binder agent for substrate pigments and/or paper substrates which comprises starch, a starch derivative, etc., or a combination thereof. Suitable starch binders may be derived from a natural starch, e.g., natural starch obtained from a known plant source, for example, wheat, maize, potato, tapioca, etc. The starch binder may be modified (i.e., a modified starch) by one or more chemical treatments known in the paper starch binder art, for example, by oxidation to convert some of —CH. 2 OH groups to —COOH groups, etc. In some cases the starch binder may have a small proportion of acetyl groups. Alternatively, the starch binder may be chemically treated to render it cationic (i.e., a cationic starch) or amphoteric (i.e., an amphoteric starch), i.e., with both cationic and anionic charges. The starch binder may also be a starch converted to a starch ether, or a hydroxyalkylated starch by replacing some —OH groups with, for example, —OCH 2 CH 2 OH groups, —OCH2CH 3  groups, —OCH 2 CH 2 CH 2 OH groups, etc. A further class of chemically treated starch binders which may be used are known as the starch phosphates. Alternatively, raw starch may be hydrolyzed by means of a dilute acid, an enzyme, etc., to produce a starch binder in the form of a gum of the dextrin type. 
     For the purpose of the present invention, the term “applying” with reference to the coatings, and compositions used to provide such coatings, may include adding, depositing, spraying, daubing, spreading, wiping, dabbing, dipping, printing, etc. 
     For the purposes of the present invention, the term “surface coverage” refers to amount of a coating, or composition used to provide such coatings, present on a given side or surface of the paper substrate or layer being coated. Surface coverage may be defined in terms of grams (of solids) of composition per square meter of paper substrate or layer (hereinafter referred to as “gsm”). 
     For the purposes of the present invention, the term “coater” refers to a device, equipment, machine, etc., which may be used to apply, print, etc., the coating, or composition used to provide such coatings, to one or more surfaces of a paper substrate or layer. Coaters may include air-knife coaters, rod coaters, blade coaters, size presses, flexographic printers, other printers, etc. See G. A. Smook, Handbook for Pulp and Paper Technologists (2 nd  Edition, 1992), pages 289-92, the entire contents and disclosure of which is herein incorporated by reference, for a general description of coaters that may be useful herein. Size presses may include a puddle size press, a metering size press, etc. See G. A. Smook, Handbook for Pulp and Paper Technologists (2 nd  Edition, 1992), pages 283-85, the entire contents and disclosure of which is herein incorporated by reference, for a general description of size presses that may be useful herein. 
     For the purposes of the present invention, the term “opacity” refers to the ability of a paper substrate to hide things such as print images on subsequent sheets or printed on the back, e.g., to minimize, prevent, etc., show-through, etc. As used herein, opacity of the paper substrate may be measured by, for example, in terms of TAPPI opacity and show-through. TAPPI opacity may be measured by T425 om-91. 
     For the purposes of the present invention, the term “Parker Print Smoothness” refers to the extent to which the paper surface deviates from a planar or substantially planar surface, as affected by the depth of the paper, paper width, numbers of departure from that planar surface, etc., as measured by TAPPI test method T555 om-99 at a clamping pressure of 10 kgf/cm 2 . Parker Print Smoothness values reflect the degree of “microroughness” of the substrate or coating surface. The higher the Parker Print Smoothness value, the rougher the substrate, layer, or coating surface. Conversely, the lower Parker Print Smoothness value, the smoother the substrate, layer, or coating surface. 
     For the purposes of the present invention, the term “gloss” refers to the ability of paper to reflect some portion of the incident light at the mirror angle. Gloss may be based on a measurement of the quantity of light specularly reflected from the surface of a paper specimen at a set angle, for example, at 75 degrees, such as in the case of 75 degree gloss (and as measured by TAPPI test method T 480 om-92). 
     For the purposes of the present invention, the term “print gloss” refers to a gloss measurement made on a printed paper substrate. 
     For the purposes of the present invention, the term “digital printing” refers to reproducing, forming, creating, providing, etc., digital images on a printable material, such as paper substrate having a print-receptive layer. Digital printing may include laser printing, ink jet printing, etc. 
     For the purposes of the present invention, the term “laser printing” refers to a digital printing technology, method, device, etc., that may use a laser beam to create, form produce, etc., a latent image on, for example, photoconductor drum. The light of laser beam may later create charge on the drum which may then pick up toner which carries an opposite charge. This toner may then be transferred to the printable material, such as paper substrate having a print-receptive layer, and the resulting print image created, formed, produced, etc., fused to the printable material through, for example, a fuser. 
     For the purposes of the present invention, the term “electrophotographic recording process” refers to a process which records images on a printable material, such as paper substrate having a print-receptive layer, by xerography or electrophotography. In an electrophotographic process, the image is often formed on of the c by toner particles which are deposited one surface or side of the printable substrate, and are then thermally fixed and/or fused to that one surface or side of the printable material, for example, by heating. 
     For the purposes of the present invention, the term “ink jet printing” refers to a digital printing technology, method, device, etc., that may form images on a printable material, such as paper substrate having a print-receptive layer, by spraying, jetting, etc., tiny droplets of liquid inks onto the printable material through the printer nozzles. The size (e.g., smaller size), precise placement, etc., of the ink droplets may be provide higher quality inkjet prints. Ink jet printing may include continuous ink jet printing, drop-on-demand ink jet printing, etc. 
     For the purposes of the present invention, the term “liquid” refers to a non-gaseous fluid composition, compound, material, etc., which may be readily flowable at the temperature of use (e.g., room temperature) with little or no tendency to disperse and with a relatively high compressibility. 
     For the purposes of the present invention, the term “viscosity,” with reference to energy-curable coatings applied by, for example, flexographic printing, refers to a viscosity measured by the Zahn cup test, using a #2 Zahn cup. To determine the viscosity of a liquid substance by the Zahn cup test, the Zahn cup is dipped and completely filled with the substance. After lifting the Zahn cup out of the substance, the time (in seconds) until the liquid streaming out of cup breaks up is measured (referred to as the “efflux time”). 
     For the purpose of the present invention, the term “printer” refers to any device which prints an image on a printable material, such as a paper substrate having a print-receptive layer, including laser printers, inkjet printers, flexographic printers, electrophotographic recording devices (e.g., copiers), scanners, fax machines, etc. 
     For the purpose of the present invention, the term “print colorant” refers to any material which may form, create, etc., print images. Print colorants may include ink (as used by, for example, an inkjet printer, flexographic printer, etc.), toner (as used by, for example, a laser printer, electrographic recording device, etc.), etc. 
     For the purpose of the present invention, the term “ink” refers to printer colorant as used by ink jet printers, flexographic printers, etc. The term ink may include dye-based inks and/or pigment-based inks. Dye-based inks comprise a dye which may be an organic molecule which is soluble in the ink medium. Dye-based inks may be classified by their usage, such as acid dyes, basic dyes, or direct dyes, or by their chemical structure, such as azo dyes, which are based on the based on an —N═N— azo structure; diazonium dyes, based on diazonium salts; quinone-imine dyes, which are derivates of quinine, etc. Pigment-based dyes comprise a pigment, which is a solid colored particle suspended in the ink medium. The particle may comprise a colored mineral, a precipitated dye, a precipitated dye which is attached to a carrier particle, etc. Inks are often dispensed, deposited, sprayed, etc., on a printable material (e.g., ink-receptive layer) in the form of droplets which then dry on the printable material to form the printed image(s). 
     For the purpose of the present invention, the term “toner” refers to printer pigment as used by laser printers. Toner is often dispensed, deposited, etc., on the printable material, such as paper substrate having a print-receptive layer, in the form of particles, with the particles then being fused on the printable material to form the image. 
     For the purposes of the present invention, the term “room temperature” refers to the commonly accepted meaning of room temperature, i.e., an ambient temperature of 20° to 25° C. 
     For the purpose of the present invention, the term “print-receptive layer” refers to a layer which is able to absorb, imbibe, take up, accept, etc., deposited print colorant to form one or more printed images. Print-receptive layers may include ink-receptive layers (e.g., those layers able to receive, absorb, imbibe, take up, accept, etc., deposited ink) and toner-receptive layers (e.g. those layers able to receive, accept, etc., deposited toner). The print-receptive layer may comprise, for example, one or more substrate pigments (e.g., clay, titanium dioxide, calcium carbonate, calcined clay, etc.), starch binder, latex binder, a lubricant (e.g., calcium stearate), optical brightening agents, fluorocarbon-containing compounds, etc. See commonly-assigned U.S. Published Appln. No. 20090239020 (Schultz et al.), published Sep. 24, 2009, the entire contents and disclosure of which is herein incorporated by reference, which describes a coating layer 3 which may be used as an embodiment of the print-receptive layer. See also commonly-assigned U.S. Published Appln. No. 20070020462 (Rudolph et al.), published Jan. 25, 2007, the entire contents and disclosure of which is herein incorporated by reference, which describes coating layer which may optionally contain a fluorocarbon-containing compound which may also be used as an embodiment of the print-receptive layer. 
     For the purposes of the present invention, the term “printed area” refers to any area of the print-receptive layer comprising one or more printed images created as a result of print colorant being deposited on the print-receptive layer. 
     For the purposes of the present invention, the term “moisture barrier layer” refers to a layer that is protective against environmental moisture, i.e., has a relatively low water vapor transmission rate, especially in environments having a relatively high relative humidity (RH) (e.g., about 65% or greater, more typically about 80% or greater), and may comprise one or more layers. 
     For the purposes of the present invention, the term “relative humidity” (RH) refers to the percentage relation between the actual amount of water vapor in a given volume of air at a definite temperature and the maximum amount of water vapor that would be present if the air environment were saturated with water vapor at that temperature. RH is typically measured herein at temperatures of about 90° F. 
     For the purposes of the present invention, the term “water vapor transmission rate” (WVTR) refers to the rate at which water vapor or moisture passes through or is transmitted through a material, layer, substrate, etc., in units of g/m 2 /day. One method that is used herein to define WVTR is by TAPPI method T464 om-90 (but measured at 90° F. and 80% RH). 
     For the purposes of the present invention, the terms “flexography” and “flexographic” (also referred to as “flexo”) refer to a form, technique, method, etc., of printing that uses a flexible relief plate. Flexographic methods also use a specially designed or engraved roller (anilox roller) having a surface containing a plurality of recessed dimples or cells for receiving and transferring the printable material to the printed substrate. Flexographic methods may use highly fluid printable materials (e.g., water-based inks), specially designed polymer relief printing plates, and light pressure in the printing nip area. See G. A. Smook, Handbook for Pulp and Paper Technologists (2 nd  Edition, 1992), page 354, the entire contents and disclosure of which is herein incorporated by reference, for a general description of flexographic printing and machines/components for carrying out flexographic printing. 
     For the purposes of the present invention, the term “energy-curable” refers to compositions, compounds, substances, materials, etc., which may be curable (e.g., polymerizable, crosslinkable, etc.) to a solid or near-solid by exposure to energy from a radiant or thermal energy source, such as thermally-curable, electron beam-curable (i.e., by exposure to high energy electrons from an electron beam source), photoinitiated-curable (e.g., by exposure to UV radiation, actinic radiation, etc.), etc. 
     For the purposes of the present invention, the term “energy-curable monomers” refers monomers, oligomers, etc., which are energy-curable (e.g., polymerizable, crosslinkable, etc.) to provide (recyclable) energy-cured polymers. Energy-curable monomers may include, for example, one or more of: dipropylene glycol diacrylate; tripropylene glycol diacrylate; butanediol diacrylate; hexanediol diacrylate; alkoxylated hexanediol diacrylate; trimethyol propane triacrylate; alkoxylated trimethylol propane triacrylate; di(trimethylol propane triacrylate); glycerolpropoxy triacrylate; pentaerythritrol triacrylate; alkoxylated pentaerythritrol triacrylate; di(pentaerythritrol triacrylate); neopentaglycol diacrylate; alkoxylated neopentaglycol diacrylate; dipropylene glycol dimethacrylate; tripropylene glycol dimethacrylate; butanediol dimethacrylate; hexanediol dimethacrylate; alkoxylated hexanediol dimethacrylate; trimethyol propane trimethacrylate; alkoxylated trimethylol propane trimethacrylate; di(trimethylol propane methtriacrylate); glycerolpropoxy trimethacrylate; pentaerythritrol trimethacrylate; alkoxylated pentaerythritrol trimethacrylate; di(pentaerythritrol trimethacrylate); neopentaglycol dimethacrylate; alkoxylated neopentaglycoldimethacrylate; acrylated epoxy resins; bis acrylic esters of bisphenol A (such as di-(3-methacryloxy-2-hydroxypropyl ether of bisphenol-A; di(2-methacryloxyethyl ether of bisphenol-A; di-(3-acryloxy-2-hydroxypropyl ether of bisphenol-A; di(2-acryloxyethyl ether of bisphenol-A, etc.); acrylated polyurethanes; acrylated polyesters; acrylated polyethers, etc, disclosed in, for example, U.S. Pat. No. 7,479,511 (Laksin et al.), issued Jan. 20, 2009; U.S. Pat. No. 7,612,122 (Herlihy), issued Nov. 3, 2009, the entire contents and disclosure of which are herein incorporated by reference. Energy-curable monomers may also include, for example, one or more of: urethane acrylates, aliphatic urethane acrylates, aliphatic urethane triacrylate/monomer blends, aliphatic urethane triacrylates blended with 1,6-hexanediol acrylates, hexafunctional urethane acrylates, siliconized urethane acrylates, aliphatic siliconized urethane acrylates, polyether acrylates, trimethylolpropane triacrylates, 2-phenoxyethyl acrylates, isobornyl acrylates, propoxylated glyceryl triacrylates, acrylate ester derivatives, methacrylate ester derivatives, acrylate ester derivatives, tripropylene glycol diacrylate, etc., disclosed in U.S. Published Appln. No. 20050234152 (Ramsey), published Oct. 20, 2005; U.S. Published Appln. No. 20080027154 (Ramsey), published Jan. 31, 2008; U.S. Published Appln. No. 20080254303 (Ramsey), published Oct. 16, 2008, the entire contents and disclosure of which are herein incorporated by reference. 
     For the purposes of the present invention, the term “energy-cured polymers” refers to polymers (other than polyethylene) obtained by curing (e.g., polymerizing, crosslinking, etc.) energy-curable monomers. See, for example, U.S. Pat. No. 7,479,511 (Laksin et al.), issued Jan. 20, 2009; U.S. Pat. No. 7,612,122 (Herlihy), issued Nov. 3, 2009; U.S. Published Appln. No. 20050234152 (Ramsey), published Oct. 20, 2005; U.S. Published Appln. No. 20080027154 (Ramsey), published Jan. 31, 2008; U.S. Published Appln. No. 20080254303 (Ramsey), published Oct. 16, 2008, the entire contents and disclosure of which are herein incorporated by reference, which describe illustrative methods for converting energy-curable monomers to energy-cured polymers. In some embodiments of the recyclable packaging materials, these energy-cured polymers, even if not themselves recyclable, should be compatible with the recyclability of these packaging materials, i.e., do not impede, inhibit, obstruct, block, hamper, hinder, decrease, prevent, etc., the recyclability (e.g., repulpability) of these packaging materials. 
     For the purposes of the present invention, the term “recyclable” refers to refers to compositions, compounds, substances, materials, paper substrates, etc., which may be reused as is or after reprocessing (e.g., composting, other chemical processing, etc.) in preparing new compositions, compounds, substances, materials, paper substrates, etc. The term “recyclable” includes the term “repulpable.” 
     For the purposes of the present invention, the term “repulpable” refers to compositions, compounds, substances, materials, paper substrates, etc., (e.g., paper fibers, etc.) which may be reused as is or after reprocessing (e.g., composting, other chemical processing, etc.) in papermaking. 
     For the purposes of the present invention, the term “brightness gain per yield loss” refers to a method for evaluating how effectively and efficiently compositions, compounds, substances, materials, paper substrates, etc., may be repulped and processed for recovery of, for example, paper fibers, in terms of increasing the brightness of the repulped material (e.g., paper fibers), versus the mass (yield) loss of the repulped/recovered material. This method, which uses a “flotation test” to evaluate the increased brightness of the repulped/recovered material, versus the yield loss of the repulped/recovered material. See Procedure for Determining Brightness Gain Per Yield Loss for Repulped/Recovered Materials (Flotation Test) section below for how to carry out a “flotation test” for determining the efficiency and effectiveness of repulped/recovered materials in terms of brightness gain per yield loss. A brightness gain per yield loss value of at least about 0.3, such as at least about 0.5, is considered herein to indicate materials which may be efficiently and effectively repulped and recovered. 
     For the purposes of the present invention, the term “basis weight” refers to the grammage of a sheet, roll, etc., of material comprising the paper substrate, with or without layers or coatings, as determined by TAPPI test T410. See G. A. Smook, Handbook for Pulp and Paper Technologists (2 nd  Edition, 1992), page 342, Table 22-11, the entire contents and disclosure of which is herein incorporated by reference, which describes the physical test for measuring basis weight. 
     For the purposes of the present invention, the term “caliper,” refers to the thickness of a sheet, web, etc., of a material, for example, a material comprising the paper substrate, with or without layers or coatings, before or after calendaring, in mils, as determined by measuring the distance between smooth, flat plates at a defined pressure. 
     For the purposes of the present invention, the term “mil(s)” is used in the conventional sense of referring to thousandths of an inch. 
     For the purposes of the present invention, the term “reeling” refers to the process of rolling up, winding, collecting, etc., a material into a rolled (wound) form. Conversely, the term “unreeling” refers to unrolling, unwinding, dispensing, etc., a material into an unrolled (unwound) form. See G. A. Smook, Handbook for Pulp and Paper Technologists (2 nd  Edition, 1992), pages 278-82, the entire contents and disclosure of which is herein incorporated by reference, for a general description of reeling/winding materials (e.g., paper), as well as devices for carrying out reeling/winding of materials. 
     For the purposes of the present invention, the term “single pass operation” refers to an operation (in some embodiments of the method of the present invention) wherein at least the step of providing an unreeled printable material through at least the step of curing the energy-curable monomers to form a moisture barrier layer to provide a printed packaging material, are carried out continuously in one pass through the operation (i.e., through the machinery, apparatus, devices, etc., used to carry out these steps), as opposed to multiple passes (i.e., two or more passes) through the operation, and without reeling up/unreeling: the printed material prior to the step of applying the energy-curable coating; and the coated printed material prior to step of curing the energy-curable monomers. If specified in certain embodiments of the method of the present invention, a single step operation may also include other steps, for example, reeling up of the printed packaging material into a rolled (wound) form. 
     DESCRIPTION 
     Polyethylene films and some wax coatings used in packaging materials may not degrade if the package is composted. Recycling of packaging materials containing polyethylene films and wax coatings may also be limited and costly because of special equipment which may be necessary for repulping, as well as the various process steps which may be required prior to reintroducing such a slurry into a recycling stream along with, for example, office waste paper. Multilayered plastic film ream wraps having a center ply of polyethylene in between two other plys of paper may be particularly difficult to recycle (e.g., repulp) because of the polyethylene ply. Wax paper coating systems may contain such a high loading of wax as to be unacceptable for recycling and for repulping for papermaking, including for paper substrates used in packaging materials such as ream wrap. 
     Embodiments of the printed (and unprinted) packaging material (e.g., ream wrap) of the present invention provide adequate moisture/vapor barrier protection for products (e.g., paper) contained within the packaging material, but may also be recyclable (e.g., repulpable). Embodiments of the printed (and unprinted) packaging material (e.g., ream wrap) of the present invention may comprise: a paper substrate having an outer surface and inner surface; a print-receptive layer having an inner and an outer surface, wherein the print-receptive layer is positioned over the paper substrate outer surface and having a Parker Print Smoothness value of about 1.5 or less (such as about 1 or less); and a moisture barrier layer comprising one or more energy-cured polymers positioned over the print-receptive layer outer surface (e.g., the entire print-receptive layer outer surface), wherein the packing material has a water vapor transportation rate of about 500 g/m 2 /day or less, such as about 310 g/m 2 /day or less (e.g., about 155 g/m 2 /day or less). In some embodiments, the print-receptive layer comprises one or more printed areas, with the moisture barrier layer being positioned over the print-receptive layer so as to include the printed areas, i.e., providing a printed packaging material. 
     An embodiment of a recyclable printed packaging material of the present invention is further illustrated in  FIG. 1 . Referring to  FIG. 1 , the packaging material is referred to generally as  100 . Packaging material  100  comprises a base paper substrate, indicated as  104 , having an inner surface  108  and an outer surface  112 . Paper substrate  104  comprises at least about 40% recyclable pulp fibers, such as at least about 60% recyclable pulp fibers. The pulp fibers may comprise softwood fibers, hardwood fibers, or a mixture of softwood and hardwood fibers. For example, the paper substrate  104  may comprise from about 5 to about 95% (such as from about 25 to about 75%) softwood fibers and from about 5 to about 95% (such as from about 25 to about 75%) hardwood fibers. Paper substrate  104  may also have, for example, a basis weight of from about 30 to about 100 lbs/3300 sq. ft. (such as from about 45 to about 75 lbs/3300 sq. ft.), and a caliper (thickness) of from about 2 to about 5 mils (such as from about 3 to about 4 mils). 
     As shown in  FIG. 1 , packaging material  100  may also be provided with an optional inner surface paper sizing layer, indicated as  116 , positioned, disposed, etc., adjacent inner surface  108  is. As further shown in  FIG. 1 , packaging material  100  may also be provided with an optional outer surface paper sizing layer, indicated as  120 , positioned, disposed, etc., adjacent outer surface  108 . Sizing layers  116  and  120  may comprise paper sizing starch, other paper sizing agents, etc., and are provided to decrease, reduce, minimize, etc., the penetration, wicking, spreading, etc., of water or ink into paper substrate  104 . Sizing layers  116  and  120  may provide a coat weight of, for example, from about 0.5 to about 4 gsm, such as from about from about 1 to about 3 gsm. 
     As shown in  FIG. 1 , packaging material  100  may also be provided with an inner curl control layer (also referred to as a “backwash” or “wash” layer), indicated as  124 , adjacent to and positioned underneath inner surface paper sizing. Curl control layer  124  may comprise, for example, starch, clay, starch crosslinkers (e.g., glyoxal, borax, zirconium carbonate, etc.), as well as optional components such as latexes, platy mineral pigments, etc., to further improve (decrease) the moisture vapor transport rate (MVTR). See commonly-assigned U.S. Published Appln. No. 20070020462 (Rudolph et al.), published Jan. 25, 2007, the entire contents and disclosure of which is herein incorporated by reference, which describes the composition and components of “backwash”/“wash” layers which may be used as an embodiment of curl control layer  124 . Curl control layer  124  is normally adjacent the packaged product (e.g., ream of paper) and provides, for example, control against curling of the packaged paper (due to absorbed moisture). Curl control layer  124  may provide a coat weight of, for example, from about 0.25 to about 10 lbs./3300 sq. ft., such as from about from about 2 to about 6 lbs./3300 sq. ft. 
     As shown in  FIG. 1 , disposed, positioned, etc., over outer surface paper sizing layer  120  (as well as paper substrate  104 ) is a print-receptive layer, indicated as  128 . Print-receptive layer  128  has an inner surface, indicated as  132 , which is adjacent to outer surface paper sizing layer  120 , as well as an outer surface, indicated as  136 . Outer surface  136  has a Parker Print Smoothness value of about 1.5 or less, such as about 1 or less, which tends to make outer surface  136  less porous. Print-receptive layer  128  may comprise substrate pigments (e.g., clay, calcium carbonate, etc.) in amounts of, for example, from about 10 to about 90 parts (e.g., from about 35 to about 90 parts) clay based on print-receptive layer  128 , from about 10 to about 30 parts (e.g., from about 15 to about 25 parts) calcium carbonate based on print-receptive layer  128 , starch in amounts of, for example, from about 0.25 to about 10 parts (e.g., from about 0.5 to about 3 parts) based on print-receptive layer  128 , latex in amounts of, for example, from about 10 to about 40 parts (e.g., from about 20 to about 30 parts) based on print-receptive layer  128 , crosslinker such as dialdehydes (e.g., glyoxal, polyethoxylated dialdehydes, etc.) in amounts of, for example, from about 0.01 to about 1 parts (e.g., from about 0.02 to about 0.04 parts) based on print-receptive layer  128 , and may be provided in a coat weight of, for example, from about 3 to about 15 lbs./3300 sq. ft. (such as from about 4 to about 12 lbs./3300 sq. ft., e.g., from about 9 to about 10 lbs./3300 sq. ft.). 
     When print colorant (e.g., ink) is deposited on print-receptive layer  128  (e.g., to print label or other descriptive information on packaging material  100 ) to create one or more printed images, print-receptive layer  128  becomes a printed layer. In some embodiments, deposition of printer colorant may be omitted, i.e., print-receptive layer  128  is an imprinted layer. In addition to providing a layer for receiving print colorant, print-receptive layer  128  may provide additional benefits. One such additional benefit is reducing the penetration of, and thus keeping on outer surface  136 , the subsequently applied energy-curable coating because of the reduced porosity of outer surface  136  (due to the components in print-receptive layer  128 , as well as the lower Parker Print Smoothness value of outer surface  136 ). Another benefit of print-receptive layer  128  is additionally improving (decreasing) the water vapor transmission rate (WVTR) of packaging material  104 , again due to the reduced (moisture/vapor) porosity of print-receptive layer  128 , and especially outer surface  136 . 
     As shown in  FIG. 1 , print-receptive layer  128  comprises a printed area, indicated generally as  140 . Printed area  140  is formed from the depositing of print colorant (e.g., ink) on outer surface  136  of print-receptive layer  128 . As further shown in  FIG. 1 , disposed, positioned, etc., over print-receptive layer  128  (including printed area  140 ), and adjacent outer surface  136  is a moisture barrier layer, indicated as  144 . Initially, moisture barrier layer  144  comprises an energy-curable coating (comprising one or more energy-curable monomers disposed, positioned, etc., on or over outer surface  136  (e.g., the entire outer surface  136 ) of print-receptive layer  128 . One benefit of using energy-curable coatings to form moisture barrier layer is the ability to increase the amount of solids present in the coating, and thus decrease amount the penetration of the coating into and through print-receptive layer  128 , i.e., keeping more coating solids on outer surface  136 . Upon curing (e.g., polymerization, crosslinking, etc.), the energy-curable coating is converted into one or more energy-cured polymers to create moisture barrier layer  144 . Moisture barrier layer  144  may be provided in a coat weight of, for example, from about 2 to about 10 gsm, such as from about 3 to about 7 gsm, (e.g., from about 3.5 to about 5 gsm). Moisture barrier layer  144  provides additional moisture/vapor barrier protection for products (e.g., paper) contained within the packaging material  104  (e.g., ream wrap). After moisture barrier layer  144  is formed, packaging material  104  has (provides) a water vapor transportation rate (WVTR) of about 500 g/m 2 /day or less, for example, about 310 g/m 2 /day or less, such as about 155 g/m 2 /day or less. 
     Various embodiments of a method for preparing a (recyclable) packaging material of the present invention according to embodiments of the present invention are also described herein. One embodiment of a method for preparing a recyclable packaging material comprises the following steps: (a) providing a printable material comprising: a paper substrate comprising at least about 40% recyclable paper fibers and having an outer surface and inner surface; and a print-receptive layer having an inner surface and a calendered outer surface, wherein the print-receptive layer inner surface is disposed, positioned, etc., over the paper substrate outer surface and wherein the calendered print-receptive layer outer surface has a Parker Print Smoothness value of about 1.5 or less; (b) applying an energy-curable coating comprising one or more energy-curable monomers over the calendered print-receptive layer outer surface (e.g., the entire print-receptive layer outer surface), including at least the printed areas; and (c) curing the energy-curable monomers to form a moisture barrier layer comprising one or more energy-cured polymers positioned over the calendered print-receptive layer outer surface to provide a recyclable packaging material having a water vapor transportation rate of about 500 g/m 2 /day or less, for example, about 310 g/m 2 /day or less, such as about 155 g/m 2 /day or less. In some embodiments, a printed packaging material may be formed by including the following additional step: (d) prior to applying the energy-curable coating in step (b), depositing a print colorant on the calendered print-receptive layer outer surface to form one or more printed areas. 
     Another embodiment of a method for preparing a printed packaging material (which may include recyclable printed packaging materials) provided with a moisture barrier layer in a “single pass operation,” and without repeated winding/unwinding of the material during the method, comprises the following steps: (a) providing an unreeled printable material comprising: a paper substrate having an outer surface and inner surface; and a print-receptive layer having an inner surface and an outer surface, wherein the print-receptive layer inner surface is positioned over the paper substrate outer surface and wherein the print-receptive layer outer surface has a Parker Print Smoothness value of about 1.5 or less; (b) depositing print colorant on the print-receptive layer outer surface to form one or more printed areas to provide a printed material; (c) applying to the printed material an energy-curable coating comprising one or more energy-curable monomers over the print-receptive layer outer surface (e.g., the entire print-receptive layer outer surface), including the printed areas, to provide a coated printed material; and (d) curing the energy-curable monomers to form a moisture barrier layer comprising one or more energy-cured polymers positioned over the print-receptive layer outer surface to provide a printed packaging material having a water vapor transportation rate of about 500 g/m 2 /day or less, for example, about 310 g/m 2 /day or less, such as about 155 g/m 2 /day or less. In this embodiment of the method of the present invention, steps (a) through (d) are carried out as a single pass operation and without reeling up (e.g., rolling up, winding): the printed material of step (b) prior to carrying step (c); and the coated printed material of step (c) prior to carrying out step (d). 
       FIG. 2  is a flowchart to illustrate various embodiments of a method for preparing a (recyclable) printed packaging material according to embodiments of the present invention, and which is indicated generally as  200 . In method  200 , a Paper Substrate, indicated as  202  (corresponding to paper substrate  104  in  FIG. 1 ), is provided, as indicated by arrow  204 , with a print-pigment receptive layer (see Print-Receptive Layer, as indicated by step  206 ) on the outer surface (see surface  108  in  FIG. 1 ) of Paper Substrate  202 . 
     Alternatively, as indicated by arrow  208  in  FIG. 2 , Paper Substrate  202  may optionally be provided with an inner surface paper sizing layer and/or an outer surface paper surface sizing layer (collectively referred to as Sizing Layer, as indicated by step  210 , and corresponding to surface sizing layers  116  and  120  in  FIG. 1 ), before being provided with Print-Receptive Layer  206 , as indicated by step  212 . Sizing Layer step  212  may be carried by using any conventional size press to apply an inner and/or outer surface paper sizing layer to Paper Substrate  202 . Also alternatively, as indicated by arrow  214  in  FIG. 2 , the inner surface paper sizing layer  116  may be optionally provided with a Curl Control Layer (corresponding to curl control layer  124  in  FIG. 1 ), as indicated by step  216  in  FIG. 2 , before being provided with Print-Receptive Layer  206 , as indicated by step  218 . 
     As indicated by arrow  220  in  FIG. 2 , Print-Receptive Layer  206 , which may have, for example, an initial Parker Print Smoothness value of at least about 2.5 (e.g., in the range from about 2.5 to about 5), may be calendered (e.g., supercalendered), as indicated by Calendering step  222 , to a lower Parker Print Smoothness value of about 1.5 or less, such as about 1 or less (e.g., to reduce the porosity of outer surface  136 /print-receptive layer  128  in  FIG. 1 ). In some embodiments, Calendered material  222  may be optionally reeled, wound, rolled up, etc., before carrying out any further steps in method  200 . 
     As further shown in  FIG. 2 , and as indicated by arrow  224 , print colorant may be deposited on the print-receptive layer of the Calendered material  222  (see Deposit Print Colorant in  FIG. 2 , as indicated by step  226 ) to form one or more printed areas (e.g., corresponding to printed area  140  in  FIG. 1 ). (In some embodiments where the Calendered material  222  is reeled up, wound, rolled up, etc., Calendered material  222  will need to be unreeled, unwound, unrolled, etc., before carrying out Deposit Print Colorant step  226 .) In one embodiment, Deposit Print Colorant step  226  may be carried out by using flexographic printing to form one or more printed areas (e.g., corresponding to printed area  140  in  FIG. 1 ). In some embodiments where unprinted packaging materials are prepared by process  200 , Deposit Print Colorant step  226  may be omitted. 
     After carrying out Deposit Print Colorant step  226 , and as indicated arrow  228 , an energy-curable coating may be applied (see Apply Coating in  FIG. 2 , indicated by step  230 ) over at least a portion the printed print-receptive layer (e.g., part of the print-receptive layer, including the printed areas, or the entire print-receptive layer) of the printed material from step  226 . Apply Coating step  230  may be carried out in a variety ways, including by rod coating, metering roll coating, gravure printing, Dahlgren application, etc. In one embodiment, Apply Coating step  230  may be carried out by using flexographic printing, for example, when Deposit Print Colorant step  226  is carried out by using flexographic printing. When the Apply Coating step  230  is carried out using flexographic printing, the energy-curable coating may have a relatively fluid viscosity of, for example, from about 10 to about 60 seconds (as measured by the Zahn cup test), such as a viscosity in the range of from about 20 to about 60 seconds. 
     As indicated by arrow  232 , after carrying out Apply Coating step  230 , the energy-curable coating may then be cured to form the moisture barrier layer (see Cure Coating in  FIG. 2 , indicated by step  234 ), which corresponds to moisture barrier layer  144  in  FIG. 1 . As indicated by arrow  236 , after carrying out Cure Coating step  234 , the printed packaging material with the cured moisture barrier layer may be reeled, rolled, or wound up (see Wind in  FIG. 2 , indicated by step  238 ). As indicated by arrow  240 , after carrying out Wind step  238 , a roll of printed packaging material (see Packaging Material in  FIG. 2 , indicated as oval  242 ) is provided which may be used to provide, for example, ream wrap, roll wrap, containers, boxes, etc. In some embodiments of method  200 , at least steps  226 ,  230 ,  234 , (and optionally  238 ) are carried out as a “single pass operation” and without winding/unwinding after step  226  and before step  238 . 
     Procedure for Determining Brightness Gain Per Yield Loss for Repulped/Recovered Materials (Flotation Test) 
     The material to be tested is cut into approximately 1 in.×1 in. pieces. The pieces are soaked overnight in tap water. 
     Water is pre-heated in a laboratory pulper (Adirondack Hydrapulper with four 3-inch tall vanes at right angles to each other) and the material to be tested is added to the pulper. Pulper conditions used are as follows:
         Target Pulper Consistency: 12% solids   Target Pulper Temperature: 50° C.   Pulper Speed: 330 rpm   Time in Pulper: 12-15 minutes       

     The pulped material is diluted to a consistency of less than 2% solids content and is screened using a vibrating screen containing 0.010 in. slots. The screen pressure is limited to approximately 4 inches of water head. The screen rejects (i.e., material not passing through the screen) are collected, dried, and expressed (calculated) as a mass percentage of the total material which is screened. The screen accepts (material which passes through the screen) are centrifuged at a speed of at least 2100 rpm to a target solids content of 30% to 40% (moisture content is measured and recorded). A Hobart low speed, low-shear industrial kitchen mixer is then used to break up the centrifuged screen accepts into loose clumps ranging from approximately 3 to 15 mm in diameter. The screen accepts are then used as feedstock to a Readco Model RK1-CP Continuous Processor (which uses helical paddles designed both for conveying and mixing) operating at a speed of 300 rpm with the restrictor plate fully open. The pulp is kneaded by this Processor and contaminants are reduced in size. 
     The kneaded pulp is then subjected to further processing in a flotation cell. The pulp is diluted to approximately a 1.3% solids consistency to be within the operating limits of the lab flotation cell. Dilution is carried out in two steps to ensure that the kneaded pulp is de-nitted, since kneaded pulp may contains many fiber bundles (referred to as “nits”) which otherwise tend to float out during the test. First, each sample is repulped in a Hobart-Kitchenaid Mixer at 12% consistency using 110° F. tap water for dilution. Surfactant (Lexair LA-S-105 at 1 lb ton) is added at the start of this step. The Hobart mixer is run for 5 minutes at speed setting 1 and then a further 5 minutes at speed setting 2. The pulp is then diluted to 4% consistency, again using 110° F. tap water, and allowed to rest for 30 minutes. 
     The diluted pulp is further diluted with tap water to give 6 liters at approximately a 1.3% solids consistency and is then floated in the lab flotation cell. The lab flotation cell is a modified Wemco lab cell and is run at 900 rpm impeller speed with a metered air addition of 3 liters per minute. The lab system recirculates pulp from a heated, temperature-controlled reservoir through the Wemco cell using a Masterflex peristaltic pump. The cell level is maintained with a simple weir for vat level control. The stock circulation flow is 3 1 pm; the total pulp capacity of the lab system is 6 liters. 
     The flotation stock temperature is brought to 110° F. before the flotation run is carried out. The stock is circulated in the system without added air for a half-hour to ensure stable temperature conditions. Air addition is then begun and flotation is continued until 240 grams of foam is collected (approximately 12 minutes). Pulp samples from the flotation cell are collected at the start and the end of the flotation run. Foam volume and consistency are converted to yield loss. Pulp samples are also made into small pads for brightness analysis. Yield Loss (YL) (%)=100*{(Foam Consistency)*(Foam Mass)}/{(Starting Consistency)*(Starting Mass)}. Pad brightness is read on a Technidyne Brightness Meter (model ERIC-950). Brightness Gain (BG)=Brightness (End)−Brightness (Start). The brightness gain per yield loss for the repulped/recovered material is then calculated as BG/YL. 
     EXAMPLES 
     The preparation of an embodiment of recyclable ream wrap is described below: 
     A paper substrate comprising 25-75% softwood fibers and 25-75% hardwood fibers is used. The paper substrate has a basis weight of 45-75 lbs/3300 sq. ft. and a caliper of 3-4 mils. 
     A surface paper sizing agent comprising paper sizing starch is optionally applied to either or both surfaces of the paper substrate using a size press. Each of the sizing layers formed provides a coat weight of 1-3 gsm. 
     A print-receptive layer is prepared from the following ingredients: 
     
       
         
           
               
             
               
                 TABLE 1 
               
             
            
               
                   
               
               
                 Pigment 
               
            
           
           
               
               
               
               
            
               
                   
                 Pigment Type 
                 Product Name 
                 Parts 
               
               
                   
                   
               
               
                   
                 Clay 
                 Astracote 
                 85 
               
               
                   
                 Calcium Carbonate 
                 Covercarb HP 
                 15 
               
               
                   
                   
               
            
           
         
       
     
     
       
         
           
               
             
               
                 TABLE 2 
               
             
            
               
                   
               
               
                 Other Ingredients 
               
            
           
           
               
               
               
               
            
               
                   
                 Type 
                 Product Name 
                 Parts 
               
               
                   
                   
               
            
           
           
               
               
               
               
            
               
                   
                 Starch 
                 Ethylex 2040 
                 1 
               
               
                   
                 Latex 
                 Dow 30985.50 
                 25 
               
               
                   
                 Crosslinker 
                 Sequarez 765 
                 0.035 
               
               
                   
                 Viscosity 
                 Admiral 3089 
                 0.30 
               
               
                   
                 Modifier 
               
               
                   
                   
               
            
           
         
       
     
     The ingredients in Tables 1 and 2 are combined and mixed together. After the ingredients in Tables 1 and 2 are combined and mixed together, the mixture is applied to the outer surface of the paper substrate (surface sized or unsized) with a commercial scale blade coater to provide a coat weight of 9-10 lbs/3300 sq. ft., and dried to form the print-receptive layer. 
     A curl control/“backwash” layer is prepared from the following ingredients: 
     
       
         
           
               
             
               
                 TABLE 3 
               
             
            
               
                   
               
               
                 Curl Control Layer Ingredients 
               
            
           
           
               
               
               
               
            
               
                   
                 Type 
                 Product Name 
                 Parts 
               
               
                   
                   
               
               
                   
                 Starch 
                 Ethylex 2040 
                 171 
               
               
                   
                 Clay 
                 Astracote 
                 100 
               
               
                   
                 Starch 
                 Earth Works Linkup Plus 
                 5% on dry starch 
               
               
                   
                 Crosslinker 
                 (Glyoxal) 
               
               
                   
                   
               
            
           
         
       
     
     The ingredients in Table 3 are combined and mixed together. After the ingredients in Table are combined and mixed together, the mixture is applied to the inner surface of the paper substrate (surface sized or unsized) with a size press to provide a coat weight of 3-4 lbs./3300 sq. ft., and dried to form the curl control layer. 
     After the print-receptive layer and curl control layer are applied to the paper substrate, the resulting material is calendered using a commercial scale supercalender to a Parker Print Smoothness value of about 1 or less. The basis weight and caliper of the calendered material is approximately 60 lbs/3300 sq. ft. and 3 mils, respectively. The calendered material is printed on using six-color flexography using a commercial flexographic printer. Immediately after the six-color printing by flexography, an energy-curable coating (SunBeam FF 9503-T, made by SunChemical of Carlstadt, N.J., comprising 40-70% trimethylolpropane ethoxy triacrylate, 25-40% epoxy acrylate oligomers, and tripropylene glycol diacrylate) is also applied using flexography, and the coating is then cured using electron-beam irradiation to provide a printed ream wrap. 
     The properties of the resulting printed ream wrap are as follows: 
     
       
         
           
               
             
               
                 TABLE 4 
               
             
            
               
                   
               
               
                 Printed Ream Wrap Properties 
               
            
           
           
               
               
               
            
               
                   
                 Property 
                 Units 
               
               
                   
                   
               
            
           
           
               
               
               
               
            
               
                   
                 WVTR 
                 117 
                 g/m 2 /day 
               
               
                   
                 Caliper 
                 3.3 
                 mils 
               
            
           
           
               
               
               
            
               
                   
                 Basis Weight 
                 63 lbs/3300 sq. ft. 
               
            
           
           
               
               
               
               
            
               
                   
                 Burst Strength 
                 38 
                 psi 
               
            
           
           
               
               
               
            
               
                   
                 Static Coefficient of Friction (Machine 
                 0.41 
               
               
                   
                 Direction, barrier against barrier 
               
               
                   
                 Brightness Gain Per Yield Loss 
                 at least 0.3 
               
               
                   
                   
               
            
           
         
       
     
     All documents, patents, journal articles and other materials cited in the present application are hereby incorporated by reference. 
     Although the present invention has been fully described in conjunction with several embodiments thereof with reference to the accompanying drawings, it is to be understood that various changes and modifications may be apparent to those skilled in the art. Such changes and modifications are to be understood as included within the scope of the present invention as defined by the appended claims, unless they depart therefrom.