RECORDING MEDIUM

Info

Publication number: 20140238625
Type: Application
Filed: Oct 5, 2011
Publication Date: Aug 28, 2014
Applicant: HEWLETT-PACKARD DEVELOPMENT COMPANY, L.P. (Houston, TX)
Inventors: Manoj K. Bhattacharyya (Palo Alto, CA), Hou T. Ng (Campbell, CA)
Application Number: 14/347,130

Abstract

A recording medium includes a substrate, and a deinking agent incorporated in the substrate, on the substrate in a layer, or both in the substrate and on the substrate in a layer. The deinking agent is chosen from an unsaturated fatty acid having from 19 to 23 carbon atoms and combinations of these unsaturated fatty acids. The deinking agent interacts with an ink having been printed on the recording medium to remove the ink during a deinking process.

Description

Description

BACKGROUND

The present disclosure relates generally to recording mediums.

Recycling processes may be used to regenerate usable cellulose fibers from waste papers. Some recycling processes involve a deinking method, where ink is removed from waste paper pulp. In some cases, the deinking method includes applying deinking chemicals to waste paper, which interact with and remove ink particles from the paper. Such deinking processes may, in some instances, pose a challenge for the recycling of some digitally inked papers.

BRIEF DESCRIPTION OF THE DRAWINGS

Features and advantages of examples of the present disclosure will become apparent by reference to the following detailed description and drawings, in which like reference numerals correspond to similar, though perhaps not identical, components. For the sake of brevity, reference numerals or features having a previously described function may or may not be described in connection with other drawings in which they appear.

FIG. 1 schematically depicts an example of a recording medium;

FIG. 2 schematically depicts another example of a recording medium;

FIG. 3 schematically depicts yet another example of a recording medium;

FIG. 4 is a flow diagram depicting an example of a deinking process;

FIGS. 5A and 5B are schematic representations of handsheets made from un-deinked pulps (FIG. 5A) and deinked pulps (FIG. 5B), where the pulps were from a liquid electrophotographic (LEP) print medium and oleic acid was used as a deinking chemical during pulping;

FIGS. 6A and 6B are schematic representations of handsheets made from un-deinked pulps (FIG. 6A) and deinked pulps (FIG. 6B), where the pulps were from an LEP print medium and erucic acid was used as a deinking chemical during pulping;

FIGS. 7A and 7B are schematic representations of handsheets made from un-deinked pulps (FIG. 7A) and deinked pulps (FIG. 7B), where the pulps were from a dye-based ink print medium and oleic acid was used as a deinking chemical during pulping, and FIG. 7C is a schematic representation of a membrane filter showing the presence of dissolved ink left in a flotation tank after pulping and flotation;

FIGS. 8A and 8B are schematic representations of handsheets made from un-deinked pulps (FIG. 8A) and deinked pulps (FIG. 8B), where the pulps were from a dye-based ink print medium and erucic acid was used as a deinking chemical during pulping, and FIG. 8C is a schematic representation of a membrane filter showing the presence of dissolved ink left in a flotation tank after pulping and flotation;

FIGS. 9A and 9B are schematic representations of handsheets made from un-deinked pulps (FIG. 9A) and deinked pulps (FIG. 9B), where the pulps were from a pigment-based ink print medium and oleic acid was used as a deinking chemical during pulping, and FIG. 9C is a schematic representation of a membrane filter showing the presence of dissolved ink left in a flotation tank after pulping and flotation;

FIGS. 10A and 10B are schematic representations of handsheets made from un-deinked pulps (FIG. 10A) and deinked pulps (FIG. 10B), where the pulps were from a pigment-based ink print medium and erucic acid was used as a deinking chemical during pulping, and FIG. 10C is a schematic representation of a membrane filter showing the presence of dissolved ink left in a flotation tank after pulping and flotation;

FIGS. 11A and 11B are schematic representations of handsheets made from un-deinked pulps (FIG. 11A) and deinked pulps (FIG. 11B), where the pulps were from an offset print medium and oleic acid was used as a deinking chemical during pulping; and

FIGS. 12A and 12B are schematic representations of handsheets made from un-deinked pulps (FIG. 12A) and deinked pulps (FIG. 12B), where the pulps were from an offset print medium and erucic acid was used as a deinking chemical during pulping.

DETAILED DESCRIPTION

Processes for recycling printed waste papers, in some instances, involve converting the waste paper into a pulp, and then contacting the pulp with deinking chemicals. The deinking chemicals interact with the ink, and then separate the ink from the waste paper. This recycling process has suitably been used for waste papers printed using offset inks, but some challenges may exist for separating and removing digital inks (e.g., liquid electrophotographic (LEP) or other digitally printed inks) from waste papers. For instance, traditional deinking involves removing ink particulates falling within a size range of about 10 microns to about 100 microns. Some challenges with removing digital ink, particularly digital pigment-based inkjet inks or digital dye-based inkjet inks, include finding a solution to aggregate the pigment particles or the dye molecules into a desired size range, and changing the particles/molecules physical properties from being too hydrophilic to more hydrophobic. It has been found that some existing deinking chemicals do not, in some instances, efficiently separate the ink from fibers of a waste paper. It is believed that the challenge(s) is/are due, at least in part, to the material composition and/or properties of the digital ink, which may, in some instances, adversely interact, or not at all, with the deinking chemicals used by the recycling mill. In many cases, the digital ink cannot be separated and removed from the waste paper to an extent required for adequate waste paper recycling.

The inventors of the present disclosure have found that digital inks may suitably and successfully be separated from waste papers by selecting a proper deinking agent. As used herein, a deinking agent is a component of a substrate or of a layer that is deposited on the substrate, whereas a deinking chemical is a component that is added during the pulping stage of a deinking process. It is to be understood that examples of the deinking chemicals disclosed herein may also be used as examples of the deinking agent. Certain fatty acids (such as those having a carbon chain length of 18 carbons or less (e.g., oleic acid) or those having a carbon chain length of 24 carbons or more (e.g., nervonic acid)) have been successfully used as a deinking chemical for alkaline deinking of offset prints. It has been found, however, that these fatty acids are not as effective for the deinking of other selected digital prints, such as, e.g., deinking of LEP prints and/or thermal inkjet prints. In contrast, it has also been found that erucic acid (which has a carbon chain length of 22 carbon atoms) effectively deinks LEP digital prints, as well as other prints, such as digital pigment-based inkjet inks or digital dye-based inkjet inks and non-digital prints.

It is believed that unsaturated fatty acids having from 19 to 23 carbon atoms or combinations of these unsaturated fatty acids may be successfully incorporated into and/or on a substrate as a deinking agent. Examples of such unsaturated fatty acids include 18-nonadecenoic acid, arachidonic acid, eicosapentaenoic acid, docosahexaenoic acid, erucic acid, and docos-21-enoic acid. When the unsaturated fatty acid has the chemical formula of C₂₂H₄₂O₂, it is believed that the double bond may be present at any position along the carbon chain. For example, the C₂₂H₄₂O₂acid may be erucic acid or docos-21-enoic acid.

Based, at least in part upon the results disclosed herein, it is believed that a erucic acid deinking agent may be incorporated into the substrate (e.g., between the cellulose fibers of the paper, or as part of a coating layer formed on the paper), and the inventors of the present disclosure believe that the erucic acid, when included as part of the substrate, may be effective as a non-liquid deinking agent. As a component of the substrate, it is believed that the 19 to 23 carbon atom unsaturated fatty acid deinking agent (e.g., the erucic acid deinking agent) is within close proximity of the ink during the pulping and flotation stages of a deinking process. This is believed to advantageously improve deinking of the ink from the underlying substrate for digital prints, as well as for non-digital prints including, e.g., offset inks. In particular regarding erucic acid, since erucic acid emulsifies with water, it is believed that the incorporation of a minimal amount of the erucic acid into the substrate does not pose any difficulties during paper manufacturing. It is believed that this is due, at least in part, to the fact that erucic acid forms a workable emulsion in water, and this emulsion may be easily incorporated into the slurry making up the paper base or the coating formed on the paper base. It is also believed that erucic acid, or any of the 19 to 23 carbon atom unsaturated fatty acids, does not deleteriously affect the integrity of the substrate.

Referring now to the figures, one example of the recording medium 10 of the present disclosure is schematically shown in FIG. 1. In this example, the recording medium 10 includes a substrate 12 and a deinking agent DA, 14 incorporated into the substrate 12.

The substrate 12 for the medium 10 may be chosen from any raw base containing any type of pulp fibers, and may be referred to herein as a pulp-based substrate or a cellulose fiber-based substrate. The substrate 12 may be made from pulp fibers derived from wood, such as from hardwood trees (e.g., deciduous trees (angiosperms) such as birch, oak, beech, maple, and eucalyptus) and/or softwood trees (e.g., coniferous trees (gymnosperms) such as varieties of fir, spruce, and pine, as for example loblolly pine, slash pine, Colorado spruce, balsam fir and Douglas fir), and these pulp fibers may be prepared via any known pulping process. The substrate 12 may also be made from fibers derived from non-wood (such as bagasse, straw, and bamboo) or from recycled fibers. The raw base for the substrate 12 may be made with wood containing fibers, such as thermomechanical pulp (TMP) fibers, chemithermomechanical pulp (CTMP) fibers, refiner mechanical pulp fibers (RMP), ground wood (GW) pulp fibers, and/or the like. Further, the raw base may include one or more fillers and/or binders to control the physical properties of the substrate 12. Examples of fillers include carbonates (e.g., ground calcium carbonate and precipitated calcium carbonate), titanium dioxide, clays (e.g., kaolin clay), silicates, oxides, zeolites, talc, and combinations thereof. An example of a binder is styrene-butadiene rubber (SBR). The filler and/or binder may be added to the fiber structure of the raw base, or may be added inside a size/film press.

In an example, the substrate 12 may include some additives, examples of which include internal sizing agents, dry strengthening agents, wet strengthening agents, fixers, pH adjusters, and/or coloring agents. Examples of internal sizing agents include fatty acids, metal salts of fatty acids, alkyl ketene dimmer emulsification products, epoxidized higher fatty acid amides, alkenyl acid anhydride emulsification products and rosin derivatives, alkylsuccinic acid anhydride emulsification products and rosin derivatives, and/or combinations thereof. Examples of dry strengthening agents that may be used include anionic polyacrylamides, cationic polyacrylamides, amphoteric polyacrylamides, polyvinyl alcohol, cationized starch, vegetable galactomannan, and/or combinations thereof. Wet strengthening agents may, for example, include polyaminepolyamide epichlorohydrin resins, and fixers may, for example, include water-soluble aluminum salts, aluminum chloride, and/or aluminum sulfate. Further, examples of the pH adjuster include sodium hydroxide, sodium carbonate, and/or sulfuric acid, and examples of coloring agents include pigments, coloring dyes, and/or fluorescent brighteners.

The deinking agent DA, 14 is any unsaturated fatty acid having from 19 to 23 carbon atoms or combinations of these unsaturated fatty acids. When the selected unsaturated acid has the chemical formula of C₂₂H₄₂O₂, it is believed that the double bond may be present at any position along the carbon chain. In an example, the deinking agent DA, 14 is erucic acid. In the example shown in FIG. 1, the deinking agent DA, 14 is incorporated into the substrate 12 material. The deinking agent DA, 14 may be incorporated into the substrate 12 during paper manufacturing, and when incorporated, is distributed throughout the bulk of the formed paper. For instance, the substrate 12 may be manufactured by forming a paper base by chemically and/or mechanically treating wood pulp (e.g., via a conventional paper manufacturing process), and then adding the deinking agent DA, 14 to the paper base. In instances where the substrate 12 includes fillers, the deinking agent DA, 14 may be added to the paper base at the same time the fillers are added, or the deinking agent DA, 14 may be added in a separate step. In instances where the substrate 12 does not include fillers, the deinking agent DA, 14 may be added by itself once the paper base is formed.

In an example, the amount of deinking agent DA, 14 present in the substrate 12 ranges from about 0.2 wt % to about 0.8 wt % of the total wt % of the substrate 12. This range suitably covers most, if not all waste paper supplies. It is believed that more than 0.8 wt % of the deinking agent DA, 14 may be present in the substrate 12, up to about 2 wt % of the total wt % of the substrate 12. The higher amount of deinking agent DA, 14 may be used, for example, for graphic-grade papers, where high ink coverage (e.g., more than 50% of the paper is covered with ink) may occur. It has been found that a minimal amount of deinking agent DA, 14 present in the substrate 12 (e.g., from about 0.2 wt % to about 2 wt %) is enough deinking agent to effectively interact with an ink having been printed on the medium 10 (i.e., a print) to remove the ink during deinking. Further, it is believed that the minimal amount of deinking agent DA, 14 may also be incorporated into the substrate 12 without deleteriously affecting the paper manufacturing process. If higher amounts of the deinking agent DA, 14 were used, for example, it is believed that the excess deinking agent DA, 14 may aggregate into larger particulates, and remain in the slurry during paper manufacturing.

In an example, the substrate 12 has incorporated therein the deinking agent DA, 14 and at least one other deinking agent (not shown). It is believed that the presence of the other deinking agent further enhances the deinking process (e.g., may render the deinking process more efficient, at least in terms of the amount of time for deinking to take place. The other deinking agent(s) are selected from another fatty acid, such as a saturated fatty acid, another unsaturated fatty acid, or combinations thereof. Examples of the saturated fatty acid that may be used as the other deinking agent include acetic acid, propionic acid, butyric acid, valeric acid, caproic acid, enanthic acid, caprylic acid, pelargonic acid, capric acid, undecylic acid, lauric acid, tridecylic acid, myristic acid, pentadecanoic acid, palmitic acid, margaric acid, stearic acid, nonadecylic acid, arachidic acid, heneicosylic acid, behenic acid, tricosylic acid, lignoceric acid, pentacosylic acid, cerotic acid, heptacosylic acid, montanic acid, nonacosylic acid, melissic acid, hentriacontylic acid, lacceroic acid, psyllic acid, geddic acid, ceroplastic acid, hexatriacontylic acid, and combinations thereof. Examples of other unsaturated fatty acids that may be used as the other deinking agent include α-linolenic acid, stearidonic acid, eicosapentaenoic acid, docosahexaenoic acid, linoleic acid, γ-linolenic acid, dihomo-γ-linolenic acid, arachidonic acid, oleic acid, eicosenoic acid, nervonic acid, mead acid, and combinations thereof. In an example, the other fatty acid that is used in combination with the deinking agent DA, 14 may be chosen from oleic acid (an unsaturated fatty acid) and/or arachidic acid (a saturated fatty acid). It is to be understood that the other deinking agent may be selected from a single deinking agent (one saturated fatty acid or one unsaturated fatty acid), a combination of two or more saturated fatty acids, a combination of two or more unsaturated fatty acids, or a combination of one or more saturated fatty acids and one or more unsaturated fatty acids.

In an example, the amount of the other deinking agent present in the substrate 12 ranges from about 0.2 wt % to about 2 wt % of the total wt % of the substrate 12, and in another example, the amount of the other deinking agent ranges from about 0.2 wt % to about 0.6 wt % of the total wt % of the substrate 12.

Another example of the recording medium 10′ is schematically depicted in FIG. 2. The medium 10′ includes a substrate 12′, and a layer 16 formed on the substrate 12′. It is to be understood that, as used herein, the terms “formed on”, “disposed on”, “deposited on”, “established on”, and the like are broadly defined to encompass a variety of divergent layering arrangements and assembly techniques. These arrangements and techniques include i) the direct attachment of the layer 16 to another layer (e.g., the substrate 12′) with no intervening layers therebetween, ii) the attachment of the layer 16 to another layer (e.g., substrate 12′) with one or more layers therebetween, and iii) the attachment of a layer (other than layer 16) to the substrate 12 (shown in FIG. 1) with one or more layers therebetween, provided that the one layer being “formed on”, “disposed on”, “deposited on”, or “established on” the other layer is somehow supported by the other layer (notwithstanding the presence of one or more additional material layers therebetween). The other layer(s) (i.e., not layer 16) may include, for example, a first coarse coating layer for plain papers, or a top smooth coating for graphics papers. In some instances, an adhesive layer may be applied between layers, such as between the layer 16 and the substrate 12′ or between a smooth coating and substrate 12. Further, the phrases “formed directly on”, “disposed directly on”, “deposited directly on”, “established directly on” and/or the like are broadly defined herein to encompass a situation (s) wherein a given layer (e.g., layer 16) is secured to another layer (e.g., substrate 12′) without any intervening layers therebetween. Any statement used herein which indicates that one layer is on another layer is to be understood as involving a situation wherein the particular layer that is “on” the other layer in question is the outermost of the two layers relative to incoming ink materials being delivered by the printing system of interest. It is to be understood that the characterizations recited above are to be effective regardless of the orientation of the recording medium materials under consideration.

In an example, the substrate 12′ may be the pulp-based or fiber-based substrate material described above. In this example, the substrate 12′ has coating layer 16 formed thereon. As such, the recording medium 10′ may be referred to as a coated substrate.

The coating layer 16 may include inorganic pigments/fillers (e.g., calcium carbonate, kaolin clay, etc.), natural or synthetic binders (e.g., styrene butadiene rubber (SBR), polyvinyl alcohol, starches, polyethylene imine, polyamide resins, polyesters, polyurethane aqueous dispersions, polyethylene acrylic acid, or the like, or combinations thereof), and possibly other additives (e.g., a whitening agent such as zinc oxide, titanium oxide, and aluminum oxide).

In an example, the layer 16 has the deinking agent DA, 14 incorporated therein. In another example, the layer 16 has the deinking agent DA, 14 and one or more other deinking agents incorporated therein. The one or more other deinking agents is/are selected from saturated fatty acids, unsaturated fatty acids, or combinations thereof, and examples of these other deinking agents are provided above.

The medium 10′ may be formed by adding the deinking agent DA, 14 to a combination of the pigment(s)/filler(s) and binder(s) to form a relatively dilute coating layer composition (e.g., the coating layer composition may contain from about 2 wt % to about 5 wt % solids in an aqueous mixture). This coating layer composition may then be applied onto a surface of the substrate 12′ to form the layer 16. In an example, the composition is applied to a single surface (e.g., S₁) of the substrate 12′, or is applied to both surfaces (e.g., opposed surfaces S₁, S₂) of the substrate 12′. The composition may be applied to the substrate 12′ to form the coating layer 16 utilizing a metered-size press, a puddle-size press, roll-coating, conventional slot-die processing, blade coating, slot-die cascade coating, curtain coating, rod coating, and/or gravure air knife coating. In an example, the coating layer composition is applied on the base substrate 12′ via a coating machine, which utilizes a sponge and metering blade combination, followed by heating and/or drying. In some instances, spray-coating, immersion-coating, and/or cast coating techniques may also be used.

In the example medium 10′ shown in FIG. 2, the substrate 12′ does not include the deinking agent DA, 14 therein. In yet another example, as shown in FIG. 3, the medium 10″ includes a substrate 12 that has the deinking agent DA, 14 incorporated therein, and a layer 16 formed on the substrate 12. In this example, the layer 16 also has the deinking agent DA, 14 incorporated therein. The example medium 10″ shown in FIG. 3 may be made by incorporating the deinking agent DA, 14 into the substrate 12 during manufacturing as described above, and then the substrate 12 may be coated with the coating layer composition as described above to form the layer 16.

The medium 10, 10′, 10″ may be printed on using any suitable ink and any suitable printing system.

Fibers of the medium 10, 10′, 10″ upon which an ink may be deposited to form a printed medium (or print) may be recycled using a conventional paper recycling process. For example, the printed medium may be placed inside a recycling mill, and then the colorant of the ink that was deposited on the printed medium may be detached from the fibers of the medium 10, 10′, 10″ to form a deinked pulp. The detaching of the colorant from the medium 10, 10′, 10″ may be referred to herein as a deinking process, and an example of the deinking process is diagrammatically shown in FIG. 4. This deinking process includes pulping the printed medium having the ink printed on a surface thereof in the presence of a deinking liquid to form a slurry, as shown by reference numeral 100. Pulping may be accomplished by introducing the printed medium into a pulper of the recycling mill, and then chopping the printed medium up into smaller pieces. In a neutral or near-neutral deinking process, pulping takes place in the presence of neutral or near-neutral deinking chemicals (e.g., those chemicals having a pH within the range of about 7 to about 8). In an alkaline-based deinking process, pulping takes place in the presence of alkaline-based deinking chemicals, such as NaOH (an alkalinity modifier), a Na₂SiO₃solution (an alkalinity buffering agent), oleic acid or another suitable acid, and H₂O₂(a bleaching agent). It is believed that some deinking chemicals (e.g., oleic acid) may not be utilized during pulping due, at least in part, to the required specifications (e.g., as dictated by the deinking method used) of the recovered pulps for certain final paper products (e.g., tissue paper). It is to be understood that during either the neutral/near-neutral deinking process or the alkaline-based deinking process, water may be added inside the pulper while the printed medium is chopped, thereby converting the printed medium into a slurry of pulp and ink.

During the pulping process, the deinking agent DA, 14 in and/or on the medium 10, 10′, 10″ interacts with the ink that was printed on the medium 10, 10′, 10″. During this interaction, the ink breaks into smaller particles that are removable during a flotation process, described below. The inks that may be removed from a printed medium via the deinking process described herein include LEP inks, pigment-based inkjet inks, dye-based inkjet inks, and inks for offset printing such as water-based inks for aqueous flexo offset printing, oil-based inks for sheet-fed offset printing, and solvent-based inks (e.g., those including toluene) for roto-gravure offset printing.

Regardless of the deinking process used to make the slurry, upon making the slurry, examples of the method include performing a flotation process, as shown by reference numeral 102 in FIG. 4. The flotation process is used to separate the ink from the slurry.

When a neutral or near-neutral deinking process is used, the slurry is introduced into a froth flotation cell, and then a collector (e.g., a frother) is introduced into the slurry. One example of a suitable frother is sodium dodecyl sulfate. The frother facilitates formation of foam which allows the removal of the detached ink particles from the fibers. More particularly, since the frother has an affinity to the now-detached colorant particles, the colorant particles attach to the frother foam. The foam has a sufficient yield strength to carry a large distribution of colorant particles to the top of the froth flotation cell. In an example, air may also be blown into the slurry. The air bubbles lift the colorant particles to the surface of the flotation cell as a thick froth, which may be removed from the cell.

When an alkaline-based deinking process is used, the slurry is introduced into a froth flotation cell. The flotation process of this example may take place in the presence or the absence of a frother.

In some instances, the pulp slurry is screened to remove any materials that may be denser than the pulp, such as contaminants or other foreign matter. In an example, coarse and fine screening may be accomplished, for example, by passing the slurry over or through a screen with varying slot opening sizes to separate such materials from the slurry, and these materials may be caught using another mesh screen.

To further illustrate the present disclosure, examples are given herein. It is to be understood that these examples are provided for illustrative purposes and are not to be construed as limiting the scope of the disclosed example(s).

EXAMPLES Example 1

Some saturated fatty acids, mono-unsaturated fatty acids, and poly-unsaturated fatty acids were tested for deinking LEP inks. Print samples were formed by printing an LEP ink on different cellulose-based papers, where each paper was deinked with a different fatty acid. The amount of fatty acid utilized ranged from about 0.2% per unit paper weight to about 2.0% per unit paper weight. Printing was accomplished using an HP® Indigo 5500 digital press, and the prints were deinked utilizing a lab-scale deinking set up that applied deinking chemicals during the pulping step. The deinking chemicals included the selected fatty acid, about 0.6 wt % sodium hydroxide, about 1.8 wt % sodium silicate, and about 0.7 wt % hydrogen peroxide, the wt % of which is with respect to the weight of the paper products.

Tables 1 and 2 set forth below provide ink/dirt specks (A, measured in terms of the area of specks per unit area) of deinked pulp (DP) for both ink/dirt specks of 50 microns or higher (A₅₀) and ink/dirt specks for 250 microns or higher (A₂₅₀), where A₅₀and A₂₅₀are each expressed in mm²/m². The ink/dirt specks were determined by analyzing handsheets using image analysis algorithm(s) run by a processor, and the algorithm(s) produced a distribution of speck diameters for the handsheets analyzed.

TABLE 1 Ink/dirt specks for non-deinked or un-deinked pulps (UP), i.e., those that did not undergo flotation, and deinked pulps (DP), i.e., those that underwent pulping and flotation, where saturated fatty acids were used as deinking agents UP DP A₅₀ A₂₅₀ A₅₀ A₂₅₀ Fatty Acid Formula (mm²/m²) (mm²/m²) (mm²/m²) (mm²/m²) Succinic Acid (C₄H₆O₄₎ 2 × 10⁴ 1.8 × 10⁴ 2.2 × 10⁴ 2.1 × 10⁴ Lauric Acid (C₁₂H₂₄O₂) 1.75 × 10⁴ 1.5 × 10⁴ 3.22 × 10⁴ 2.7 × 10⁴ Palmitic acid (C₁₆H₃₂O₂) 2.3 × 10⁴ 2.2 × 10⁴ 5.4 × 10³ 4.9 × 10³ Stearic Acid (C₁₈H₃₆O₂) 2.1 × 10⁴ 2 × 10⁴ 3.9 × 10³ 3.4 × 10³ Arachidic Acid (C₂₀H₄₀O₂) 2 × 10⁴ 1.9 × 10⁴ 4.35 × 10³ 3.95 × 10³ Behenic Acid (C₂₂H₄₄O₂) 2.1 × 10⁴ 1.9 × 10⁴ 4.4 × 10³ 4.2 × 10³ Lignoceric Acid (C₂₄H₄₈O₂) 2.16 × 10⁴ 2.0 × 10⁴ 5.5 × 10³ 4.9 × 10³

TABLE 2 Ink/dirt specks for non-deinked or un-deinked pulps (UP), i.e., those that did not undergo flotation, and deinked pulps (DP), i.e., those that underwent pulping and flotation, where unsaturated fatty acids were used as deinking agents UP DP A₅₀ A₂₅₀ A₅₀ A₂₅₀ Fatty Acid Formula (mm²/m²) (mm²/m²) (mm²/m²) (mm²/m²) Oleic Acid (C₁₈H₃₄O₂) 8.7 × 10³ 6.6 × 10³ 4.4 × 10³ 3.2 × 10³ Erucic Acid (C₂₂H₄₂O₂) 3.8 × 10³ 2.2 × 10³ 186 84 Nervonic acid (C₂₄H₄₆O₂) 9.4 × 10⁴ 8.5 × 10⁴ 2.69 × 10³ 2.4 × 10³

As shown in Table 1 above, as the length of the alkyl chain of the saturated fatty acids increased from 12 carbons to 20 carbons, the ink/dirt specks (i.e., the area of specks per unit area) decreased. Fatty acid having 22 and 24 carbon chain lengths had relatively high ink/dirt specks that were not consistent with the decreasing trend exhibited by the other fatty acids. Based on this data, it is believed that the saturated fatty acids used as deinking agents in and/or on the paper may suitably be used for neutral or near-neutral deinking of non-digital inks; but the saturated acids may not be suitable for deinking LEP inks.

Further, as shown in Table 2 above, some of the mono-unsaturated fatty acids were found to be very effective for deinking. The ink/dirt specks of oleic acid (which has 18 carbon atoms) were too high (i.e., ink/dirt specks (A₅₀) were larger than about 4000 mm²/m²after deinking (i.e., deinked pulps DP)), and there was no noticeable change in the speck count from un-deinked pulps (UP) to deinked pulps (DP). As such, it is believed that oleic acid may be unsuitable as a substrate/paper component to achieve effective deinking of LEP inks. The ink/dirt specks of nervonic acid (which has 24 carbon atoms) were too high (i.e., ink/dirt specks (A₅₀) were larger than about 2000 mm²/m²after deinking (i.e., deinked pulps DP)), even though a noticeable change in the speck count from un-deinked pulps (UP) to deinked pulps (DP) was observed. As such, it is believed that nervonic acid may be unsuitable as a substrate/paper component to achieve effective deinking of LEP inks. However, erucic acid (which has 22 carbon atoms) was found to be particularly effective for removing LEP ink/dirt specks. This is true, at least in part, because of the noticeable change (which is at least a magnitude lower) in the ink/dirt specks (A₅₀) from un-deinked pulps (UP) to deinked pulps (DP). Further, after deinking, the ink/dirt specks (A₅₀) for erucic acid was determined to be 186 mm²/m², which is significantly lower than the 600 mm²/m²threshold value (which is set forth on the European Recycling Paper Council Deinking Scorecard's Parameters). These results indicate that erucic acid may be included in and/or on the substrate/paper to achieve effective deinking of LEP inks.

In examples 2-5, it is noted that the wt % values are with respect to the weight of the comparative paper sample or the paper sample, whichever is being discussed.

Example 2

FIGS. 5A and 5B are schematic representations of handsheets made from un-deinked pulps (i.e., those that did not undergo flotation) and deinked pulps, respectively, of a comparative LEP print medium sample, where the ink was Hewlett Packard EI 4.5 ink and the medium was STERLING® ultra Digital™ paper (available from Newpage Corp., Miamisburg, Ohio). For the comparative LEP print medium sample, oleic acid was used as a deinking chemical. FIGS. 6A and 6B are schematic representations of handsheets made from un-deinked pulps and deinked pulps, respectively, of an LEP print medium sample, where the ink was Hewlett Packard EI 4.5 ink and the medium was STERLING® ultra Digital™ paper (available from Newpage Corp., Miamisburg, Ohio). For the LEP print medium sample, erucic acid was used as a deinking chemical.

An alkaline-based deinking process was used for the comparative sample and the sample, respectively. The alkaline-based deinking processes followed the protocol as outlined in INGEDE (International Association of the Deinking Industry) Method 11p. The deinking processes were accomplished with deinking chemicals, including about 0.3 wt % sodium hydroxide and 0.9 wt % sodium silicate. Further, as mentioned above, oleic acid was used as a deinking chemical during the pulping of the comparative LEP print medium sample and erucic acid was used as a deinking chemical during the pulping of the LEP print medium sample. In the respective deinking processes, each of the acids was used in an amount of about 0.8 wt %.

The results obtained for the comparative LEP print medium sample illustrated that poor deinkability of LEP prints occurred when oleic acid was used as a deinking chemical. As shown in FIG. 5B, the comparative deinked pulp (DP) ink/dirt specks (A₅₀) was 4403 mm²/m²which was representative of the fact that a significant amount of ink was still left in the pulp after deinking. The results obtained for the LEP print medium sample illustrated that good deinkability of LEP prints occurred when erucic acid was used as a deinking chemical. As shown in FIG. 6B, the deinked pulp (DP) ink/dirt specks (A₅₀) was measured to be about 186 mm²/m², and the deinked pulp (DP) ink/dirt specks (A₂₅₀) was measured to be about 24 mm²/m². This was a significant change from the un-deinked pulp (UP) shown in FIG. 6A, demonstrating that a significant amount of the LEP ink was removed from the pulp during deinking. In fact, so few LEP ink particles were left after deinking, the average diameter (d_avg) could not be measured.

These results further support the conclusion that oleic acid may be an unsuitable paper component to achieve effective deinking of LEP inks and that erucic acid may be a suitable paper component to achieve effective deinking of LEP inks.

Example 3

FIGS. 7A and 7B are schematic representations of handsheets made from un-deinked pulps (i.e., those that did not undergo flotation) and deinked pulps, respectively, of a comparative dye-based inkjet print medium sample, where the medium was COLORLOK® paper (Hewlett-Packard, Co., Houston, Tex.). For the comparative dye-based inkjet print medium sample, oleic acid was used as a deinking chemical. FIGS. 8A and 8B are schematic representations of handsheets made from un-deinked pulps and deinked pulps, respectively, of a dye-based inkjet print medium sample, where the medium was COLORLOK® paper (Hewlett-Packard, Co., Houston, Tex.). For the sample dye-based inkjet print medium sample, erucic acid was used as a deinking chemical. The handsheets in FIGS. 7A-8B were formed from prints produced using dye-based cyan, magenta, and/or yellow ink and/or a black ink including carbon black nanoparticles.

An alkaline-based deinking process was used for the comparative dye-based inkjet print medium sample and the dye-based inkjet print medium sample. The respective alkaline-based deinking processes followed the protocol as outlined in INGEDE (International Association of the Deinking Industry) Method 11p. The deinking processes were accomplished with deinking chemicals, including about 0.3 wt % sodium hydroxide, 0.9 wt % sodium silicate, and 0.7 wt % hydrogen peroxide. As mentioned above, oleic acid was used as a deinking chemical during the pulping of the comparative dye-based inkjet print medium sample and erucic acid was used as a deinking chemical during the pulping of the dye-based inkjet print medium sample. In the respective deinking processes, each of the acids was used in an amount of about 0.8 wt %.

The brightness (Y) of the water in the flotation tank both after pulping and after pulping and flotation was measured for both the comparative samples and the samples. This was accomplished by taking an optical measurement of the filter pad made from the un-deinked pulp and deinked pulp utilizing an industry standard process called INGEDE (International Association of the Deinking Industry) Method 2, entitled “Measurement of Optical Characteristics of Pulps and Filtrates from Deinking Processes”. The ink elimination (1E) of the comparative deinked sample the deinked sample was also measured utilizing the same process, namely INGEDE Method 2.

A comparison between the comparative sample and the sample was made with respect to ink elimination (IE) and brightness difference (ΔY). The results show that the sample deinked with erucic acid had a higher IE (which was about 43.8% of ink particles removed) than the comparative sample that was deinked with oleic acid (where the IE was about 40.3% of ink particles removed). Further, a much larger brightness difference (ΔY) was observed for the comparative sample deinked with oleic acid (i.e., a ΔY of about 31.7) compared with the sample that was deinked with erucic acid (i.e., a ΔY of about 11.7, which was lower than the threshold value of 18). Based upon these results, it can be concluded that erucic acid is more effective than oleic acid as a deinking chemical for dye-based inkjet inks. In turn, it is believed that erucic acid may be incorporated into or onto a paper substrate as an effective deinking agent for the deinking of dye-based inkjet inks printed on such a paper substrate.

FIGS. 7C and 8C, respectively, are representations of a membrane filter made using the process water obtained i) after deinking of the comparative dye-based inkjet print medium sample where oleic acid was used as a deinking chemical and ii) after deinking of the dye-based inkjet print medium sample where erucic acid was used as a deinking chemical. The membrane filter is representative of the quality of the process water that is left in the tank after pulping and flotation. More specifically, about a one liter sample including deinked pulp was collected from the flotation tank after the flotation cycle was completed. The liquid was then passed through a Watman grade 41 intermediate pore filter paper using a Buchner Filter. About 100 mL of the filtrate from the Buchner filter was collected, and was completely drained in a vacuum filtration unit with a cellulose nitrate membrane filter (i.e. the membrane filter). The membrane filter was then dried, and was used as a measure of the dissolved ink in the flotation tank. The darker color shown in the membrane filter (MF) for the comparative print sample including oleic acid (FIG. 7C) illustrates that too much color (i.e., the presence of the ink particles) was left in the water after deinking, and thus the water could not be reused for another deinking process. In contrast, the membrane filter for the print sample that used the erucic acid deinking chemical was substantially clear (see FIG. 8C), indicating that the water did not have as much ink remaining and was reusable.

Example 4

FIGS. 9A and 9B are schematic representations of handsheets made from un-deinked pulps (i.e., those that did not undergo flotation) and deinked pulps, respectively, of a comparative pigment-based inkjet print medium sample, where the medium was COLORLOK® paper (Hewlett-Packard, Co., Houston, Tex.). For the comparative pigment-based inkjet print medium sample, oleic acid was used as a deinking chemical. FIGS. 10A and 10B are schematic representations of handsheets made from un-deinked pulps and deinked pulps, respectively, of pigment-based inkjet print medium samples, where the medium was COLORLOK® paper (Hewlett-Packard, Co., Houston, Tex.). For the pigment-based inkjet print medium sample, erucic acid was used as a deinking chemical. The handsheets in FIGS. 9A-10B were formed from prints utilizing pigment-based inks for the HP® Edgeline printer (available from Hewlett-Packard Co., Houston, Tex.).

An alkaline-based deinking process was used for the comparative pigment-based inkjet print medium sample and the pigment-based inkjet print medium sample, respectively. The respective alkaline-based deinking processes followed the protocol as outlined in INGEDE (International Association of the Deinking Industry) Method 11p. The deinking processes were accomplished with deinking chemicals, including about 0.3 wt % sodium hydroxide, 0.9 wt % sodium silicate, and 0.7 wt % hydrogen peroxide. Further, as mentioned above, oleic acid was used as a deinking chemical during pulping of the comparative pigment-based inkjet print medium sample and erucic acid was used as a deinking chemical during pulping of the pigment-based inkjet print medium sample. In the respective deinking processes, each of the acids was used in an amount of about 0.8 wt %.

The brightness (Y) of the water in the flotation tank both after pulping and after pulping and flotation was measured for both the comparative pigment-based inkjet print medium sample and the pigment-based inkjet print medium sample. The brightness (Y) was measured utilizing INGEDE method 2 mentioned above. The ink elimination (IE) of the comparative deinked sample the deinked sample was also measured utilizing INGEDE method 2.

A comparison between the comparative pigment-based inkjet print medium sample and the pigment-based inkjet print medium sample was made with respect to ink elimination (IE) and brightness difference (ΔY). The results show that the sample deinked using erucic acid as a deinking chemical had a higher ink elimination (which was about 71.5% of ink particles removed) than the comparative sample that was deinked using oleic acid as a deinking chemical (where the IE was about 43.4% of ink particles removed). Further, a much larger brightness difference (ΔY) was observed for the comparative pigment-based inkjet print medium sample that was deinked with oleic acid (i.e., a ΔY of about 35) compared with the pigment-based inkjet print medium sample that was deinked with erucic acid (i.e., a ΔY of about 9.9, which again was lower than the threshold value of 18). Based upon these results, it can be concluded that erucic acid is more effective than oleic acid as a deinking chemical for pigment-based inkjet inks. In turn, it is believed that erucic acid may be incorporated into or onto a paper substrate as an effective deinking agent for the deinking of pigment-based inkjet inks printed on such a paper substrate.

FIGS. 9C and 10C, respectively, are representations of a membrane filter made using the process water from i) the deinking of the comparative pigment-based inkjet print medium sample using oleic acid as a deinking chemical and ii) the deinking of the pigment-based inkjet print medium sample using erucic acid as a deinking chemical. These membrane filters were formed and treated in the same manner as the membrane filters described in Example 3. The darker color shown in the membrane filter for the comparative pigment-based inkjet print medium sample deinked using oleic acid (FIG. 9C) illustrates that too much color (i.e., ink particles) was left in the water after deinking, and thus the water could not be reused for another deinking process. In contrast, the membrane filter for the pigment-based inkjet print medium sample deinked using erucic acid was substantially clear (see FIG. 10C), indicating that the water did not have as much ink remaining and was reusable.

Example 5

FIGS. 11A and 11B are schematic representations of handsheets made from un-deinked pulps (i.e., those that did not undergo flotation) and deinked pulps, respectively, of comparative coldset web offset matte paper samples, where the medium was matte coated paper. For this comparative sample, oleic acid was used as a deinking chemical. FIGS. 12A and 12B are schematic representations of handsheets made from un-deinked pulps and deinked pulps, respectively, of coldset web offset matte paper samples, where the medium was matte coated paper. For this sample, deinking was accomplished using erucic acid as a deinking chemical. The handsheets in FIGS. 11A-12B were formed from prints utilizing offset inks.

An alkaline-based deinking process was performed for the comparative coldset web offset matte print medium sample and the coldset web offset matte print medium sample. The alkaline-based deinking processes followed the protocol as outlined in INGEDE (International Association of the Deinking Industry) Method 11p. The respective deinking processes were accomplished with deinking chemicals, including about 0.3 wt % sodium hydroxide, 0.9 wt % sodium silicate, and 0.7 wt % hydrogen peroxide. Further, as mentioned above, oleic acid was used as a deinking chemical during the pulping of the comparative coldset web offset matte print medium sample and erucic acid was used as a deinking chemical during the pulping of the coldset web offset matte print medium sample. In the respective deinking processes, each of the acids was present in an amount of about 0.8 wt %.

The results obtained for the comparative coldset web offset matte print medium sample and the coldset web offset matte print medium sample illustrate adequate deinkability of offset prints when either oleic acid or erucic acid was used as a deinking chemical during deinking. This is shown in both FIGS. 11B and 12B for oleic acid and erucic acid deinked samples, respectively.

From Examples 2 through 5 above, it was found that erucic acid may be used as a suitable deinking chemical during pulping for the removal of LEP inks, dye-based inks, pigment-based inks, and offset inks from various papers. Based on these results, it is believed that the erucic acid will also perform in the same way when the fatty acid is introduced into and/or onto the paper as a deinking agent. Erucic acid will be closer in proximity to the inks when incorporated into and/or onto the paper, and thus it is believed that the deinking results for these examples may be even better than the deinking results reported herein.

Example 6

Table 3 shows the European Recycling Paper Council's deinking score card results for the comparative deinked samples and deinked samples of each of Examples 2-5. The first section of Table 3 illustrates the European Recycling Paper Council's deinking score card parameters; and the subsequent sections of Table 3 illustrate the scores for the various Examples 2-5.

TABLE 3 European Recycling Paper Council Deinking Scorecard Results of Comparative Samples and Samples in Examples 2-5 Color Ink Filtrate Optical Shade, Dirt, A₅₀ Dirt, A₂₅₀ Elimination, Darkening, Total Brightness, Y a* (mm²/m²) (mm²/m²) IE (%) ΔY Score European Recycling Paper Council Deinking Scorecard's Parameters Threshold 47 −3/+2 2000 600 40 18 100 Target 90 −2/+1 600 180 80 6 Max 35 20 15 10 10 10 Score Comparative Examples with Oleic Acid Example # 2 33 20 −15 −10 10 10 Fail 3 26 20 15 10 1 −10 Fail 4 17 20 15 10 1 −1 Fail 5 35 20 15 10 10 10 100 Examples with Erucic Acid 2 35 20 15 10 10 10 100 3 17 20 15 10 1 5 68 4 35 19 15 10 10 7 96 5 35 20 15 10 10 10 100

It is to be understood that a total score of 70 on the European Recycling Paper Council's deinking score card is considered to be good deinkability.

In Table 3, any print sample that failed any category (e.g., A₅₀, ΔY, etc.) (which is shown by the term “fail” in the total score in the table) means that the print sample could not be properly deinked utilizing the INGEDE Method 11p deinking method, and is considered to be unsuitable for deinking. As shown in Table 3, deinking may be accomplished for all four of the papers utilizing the erucic acid deinking agent in the paper, whereas it was found that for comparative examples 2-4, incorporation of oleic acid into the paper does not meet passing standards stipulated for the INGEDE method 11p. In fact, it was found that of all of the comparative examples, only the offset paper (comparative example 5) may be properly deinked utilizing the oleic acid deinking agent as a component of the paper.

It is to be understood that the ranges provided herein include the stated range and any value or sub-range within the stated range. For example, a range from about 0.2 wt % to about 2 wt % should be interpreted to include not only the explicitly recited limits of about 0.2 wt % to about 2 wt %, but also to include individual values, such as 0.2 wt %, 0.7 wt %, 1 wt %, etc., and sub-ranges, such as from about 0.5 wt % to about 1 wt %, from about 0.75 wt % to about 1.6 wt %, etc. Furthermore, when “about” is utilized to describe a value, this is meant to encompass minor variations (up to +/−10%) from the stated value.

While several examples have been described in detail, it will be apparent to those skilled in the art that the disclosed examples may be modified. Therefore, the foregoing description is to be considered non-limiting.

Claims

1. A recording medium, comprising:

a substrate; and

a deinking agent incorporated: i) in the substrate; ii) on the substrate in a layer; or iii) both i and ii, the deinking agent being chosen from an unsaturated fatty acid having from 19 to 23 carbon atoms and combinations of these unsaturated fatty acids;

wherein the deinking agent is to interact with an ink having been printed on the recording medium to remove the ink during a deinking process.

2. The recording medium as defined in claim 1 wherein the unsaturated fatty acid has a chemical formula of C22H42O2, and wherein a double bond of the C22H42O2 is present at any position along its carbon chain.

3. The recording medium as defined in claim 2 wherein the unsaturated fatty acid is erucic acid.

4. The recording medium as defined in claim 1 wherein the unsaturated fatty acid is present in an amount ranging from about 0.2 wt % to about 2 wt % per unit weight of the substrate.

5. The recording medium as defined in claim 1, further comprising an other deinking agent chosen from a saturated fatty acid, an other unsaturated fatty acid, and combinations thereof.

6. The recording medium as defined in claim 5 wherein:

the saturated fatty acid is chosen from acetic acid, propionic acid, butyric acid, valeric acid, caproic acid, enanthic acid, caprylic acid, pelargonic acid, capric acid, undecylic acid, lauric acid, tridecylic acid, myristic acid, pentadecanoic acid, palmitic acid, margaric acid, stearic acid, nonadecylic acid, arachidic acid, heneicosylic acid, behenic acid, tricosylic acid, lignoceric acid, pentacosylic acid, cerotic acid, heptacosylic acid, montanic acid, nonacosylic acid, melissic acid, hentriacontylic acid, lacceroic acid, psyllic acid, geddic acid, ceroplastic acid, and hexatriacontylic acid; and

the other unsaturated fatty acid is chosen from α-linolenic acid, stearidonic acid, eicosapentaenoic acid, docosahexaenoic acid, linoleic acid, γ-linolenic acid, dihomo-γ-linolenic acid, arachidonic acid, oleic acid, eicosenoic acid, nervonic acid, and mead acid.

7. The recording medium as defined in claim 1 wherein the recording medium includes the layer, which has the deinking agent incorporated therein.

8. The recording medium as defined in claim 7 wherein the layer further has an other deinking agent therein, the other deinking agent chosen from a saturated fatty acid, an other unsaturated fatty acid, or combinations thereof.

9. The recording medium as defined in claim 1 wherein the substrate is chosen from a base paper including cellulose fibers.

10. A method for forming the recording medium as defined in claim 1, comprising incorporating the deinking agent into the substrate by:

forming a paper base by any of chemically or mechanically treating wood pulp; and

adding the deinking agent to the paper base.

11. A method for forming the recording medium as defined in claim 1, comprising:

adding the deinking agent to a combination of a pigment and a binder to form a coating layer composition; and

applying the coating layer composition onto a surface of the substrate to form the layer.

12. A deinking process, comprising:

pulping a medium having an ink printed on a surface thereof in the presence of a deinking chemical to form a slurry, the medium having a deinking agent that is: i) incorporated into the medium; ii) incorporated into a layer formed on a surface of the medium; or iii) both i and ii, the deinking agent being chosen from an unsaturated fatty acid having from 19 to 23 carbon atoms and combinations of these unsaturated fatty acids; and

performing a flotation process using the slurry and a frother.

13. The deinking process as defined in claim 12 wherein the deinking agent, upon interacting with the ink during the pulping process, breaks the ink into smaller particles that are removable during the flotation process, and wherein the ink is chosen from liquid electrophotographic (LEP) inks, pigment-based inkjet inks, dye-based inkjet inks, and inks for offset printing.

14. The deinking process as defined in claim 12 wherein the medium further includes an other deinking agent in combination with the deinking agent, the other deinking agent chosen from a saturated fatty acid, an other unsaturated fatty acids, and combinations thereof.

15. The deinking process as defined in claim 12 wherein the deinking chemical is a mixture of sodium hydroxide, sodium silicate, and hydrogen peroxide.