This present application describes a coating that imparts anti-glare and texture properties to packaging. Such coating includes water, an acrylic carrier, acrylic particles and other organic particles.
Coatings are used in various industries. For example, U.S. Pat. No. 6,730,388 discloses a high viscosity, cured resin coating applied to a flooring substrate via air knife, roll coater, spray coating, or curtain coating. The cured resin coating is primarily non-aqueous (comprising only minute concentrations or water) and may comprise a flatting agent comprising 5-micron-sized nylon particles and a plurality of texture-producing particles comprising 60-micron-sized nylon particles.
In general, in some industries, coatings may comprise a liquid base, a resin base, an additive or additives, and a reducer/thinner. The liquid base may be water-based or solvent-based. (As used in this context, a water-based liquid base is distinct from a solvent-based liquid base, even though water is chemically considered a solvent.) The resin base may be any one or a combination of various solids-containing materials that impart properties and benefits such as texture, heat resistance, abuse resistance (e.g., scuff and/or abrasion resistance), opacity, gloss, anti-glare, etc. The additive or additives may be liquid or solid and may further contribute to the properties and benefits. The reducer/thinner is a liquid used to adjust the viscosity of the coating to enable efficient application of the coating and may be water-based, solvent-based, or a blend of water-based and solvent-based.
Coatings are used on packaging to impart various properties and benefits to packaging. For example, US Patent Application Publication 2012/0015145 discloses a coating including pigments and a binder to create a matter varnish layer. The pigments may be polyurethane microbeads, and the binder may be based on acrylic.
What is needed is a cost-effective coating that imparts anti-glare and texture properties to packaging without negatively impacting other properties and benefits.
This need is met by the coating described in the present application. A first embodiment describes a coating comprising an emulsion comprising (a) water, (b) a first particle comprising particles having an average particle size of greater than 0 but less than 10 microns and comprising acrylic beads, (c) an acrylic-based carrier, and (d) a second particle comprising particles having an average particle size of from about 10 microns to about 125 microns or from about 25 microns to about 125 microns or from about 80 microns to about 110 microns and comprising polyamide, polyethylene, polypropylene, polytetrafluoroethylene, or combinations of such. The combination of the water, the first particle, and the acrylic-based carrier comprises from about 75% to about 95% or from about 80% to about 90% or from about 82% to about 85% by weight of the coating. The second particle comprises from about 5% to about 25% or from about 10% to about 20% or from about 15% to about 18% by weight of the coating. In some embodiments, the second particle may comprise particles having a first particle size and a second particle size. In some embodiments, the coating may also comprise a coreactant additive in an amount from 0% to about 5% by weight of the coating. The coating may be printable and may create an anti-glare, texture effect on a packaging material in the absence of radiation curing. In some embodiments, the coating may have a viscosity of from about 50 to about 125 centipoise or from about 70 to about 125 centipoise.
In a second embodiment, a packaging material is described comprising a substrate comprising metal, glass, paper, plastic, or thermoplastic and the coating described above. The packaging material may be food packaging. The packaging material may have an anti-glare, texture effect in the absence of radiation curing. In some embodiments of the second embodiment, the substrate may comprise a thermoplastic film or biaxially oriented polyethylene terephthalate. In some embodiments, the coating may be printable and may be flexographic printed or rotogravure printed.
In a third embodiment, a method of rotogravure printing a coating to substrate is described. This method comprises the steps of (a) preparing the coating described above, (b) using a rotogravure press to apply the coating to the substrate described above, and (c) allowing the coated substrate to cure in the absence of radiation curing. In some embodiments, the method may further comprise adding reducer/thinner to the coating as needed to adjust coating viscosity to measure from about 50 centipoise to about 125 centipoise or from about 70 centipoise to about 125 centipoise and/or adding a coreactant additive to the coating in an amount from 0% to about 5% by weight of the coating. In some embodiments, the method may further comprise corona treating the substrate prior to using the rotogravure press to apply the coating to the substrate. In some embodiments, the method may further comprise applying ink to the substrate as either a surface print or reverse print prior to using the rotogravure press to apply the coating to the substrate. If the method includes applying ink, the rotogravure press may then apply the coating on a surface over the ink if surface printed or on a surface without the ink if reverse printed.
With references to the embodiments described in the present application, in some embodiments, the coating may provide the package with the look and feel of traditional butcher paper or Kraft paper. The coating may be applied to various food or non-food packaging materials and substrates including but not limited to metal, glass, paper, plastic, and thermoplastic by means known in the art. In one embodiment, the coating may be “printable” and may be applied to paper or thermoplastic substrates by coating or printing means known in the art. Such means include but are not limited to flexographic coating and printing and rotogravure coating and printing. As used throughout this present application and as known in the art, the term “printable” refers to a coating that can be printed on a substrate, as distinguished from a substrate that is able to be printed with a coating. In some embodiments, the coating or printing means do not require energy curing, such as ultraviolet (UV) radiation or electron beam (e-beam) radiation. As such, thermoplastic webs to be coated or printed may be wider (e.g., greater than about 24 inches (about 61 centimeters)) than those requiring UV curing. As known in the art, UV curing is predominantly done on narrow webs of width less than about 24 inches (about 61 centimeters) As used throughout this present application, the term “thermoplastic” refers to a polymer or polymer mixture that softens when exposed to heat and then returns to its original condition when cooled to room temperature. In general, thermoplastic materials may include natural or synthetic polymers and may be used in flexible, semi-rigid, or rigid packaging, as known in the art.
In some embodiments, the anti-glare, texture coating described in this present application comprises a water-based liquid base, an anti-glare agent resin base, a texture agent additive, an optional coreactant additive, and an optional water-based or water-based and solvent-based blend reducer/thinner.
The anti-glare agent can reduce or eliminate glare. In general, an anti-glare agent addresses external sources of reflection (such as bright sunlight or high ambient lighting conditions) off a surface and the possible impact of the reflection, such as the impact on readability or general aesthetics. Anti-glare agents use diffusion mechanisms to disperse or otherwise break up the reflected light. Such diffusion mechanisms include but are not limited to (1) mechanical or chemical surface texturing and (2) minute particles suspended or otherwise incorporated into a liquid coating.
Non-limiting examples of anti-glare agents with particles (as suspensions or otherwise) include the following;
Further non-limiting examples of anti-glare agents include the Opulux™ Optical Finishes, such as Opulux™ 4903, Opulux™ 5000, and Opulux™ 5001, each available from The Dow Chemical Company (Midland, Mich.). In addition to anti-glare, the Opulux™ Finishes may provide heat resistance and abuse resistance not generally provided by matte coatings or matte varnishes. The Opulux™ Finishes (also referred to as overlacquers) are water-based, acrylic-based (such that they are water-resistant when dry) and include acrylic beads in combination with an acrylic-based carrier technology. As disclosed in the October 2012 Opulux™ Technical Overview from The Dow Chemical Company, the acrylic beads have a particle size of greater than 0 microns but less than 10 microns. As further disclosed in the October 2012 Opulux™ Technical Overview, the Opulux™ Finishes produce a soft, smooth, non-rough, non-textured, luxurious touch and feel for packaging and labels. When used in the coating described in this present application, the water of the Opulux™ Finish comprises the liquid base of the coating and the acrylic beads (also referred to as “first particle”) in combination with the acrylic-based carrier comprise the resin base of the coating. As used throughout this present application, the term “acrylic” refers to thermoplastic polymers or copolymers of acrylic acid, methacrylic acid, esters of these acids, or acrylonitrile, as defined in Hawley's Condensed Chemical Dictionary, 14th Edition, 2001. As known in the art, acrylics (including acrylic beads/particles and acrylic-based carriers) are generally non-water soluble or water insoluble and, as such, form emulsions with water. Furthermore, as known in the art and as used throughout this present application, the term “emulsion” refers to a dispersion of droplets of one substance in another in which it is not soluble or in which it is insoluble.
In general, for the anti-glare, texture coating described in the present application, the combination of the liquid base and the resin base may comprise from about 75% to about 95% by weight of the coating or from about 80% to about 90% by weight of the coating or from about 82% to about 85% by weight of the coating or, more specifically, about 83.5% by weight of the coating.
The anti-glare, texture coating also comprises a texture agent additive (also referred to as “second particle”) and, optionally, a coreactant additive. The texture agent additive may comprise organic compounds, particles or powders such as those comprising polyamide (PA), polyethylene (PE), polypropylene (PP), polytetrafluoroethylene (PTFE), or combinations of such. In some embodiments, the texture agent may consist essentially of organic compounds, particles, or powders, such that it does not comprise any effective amount of inorganic compounds, particles, or powders such as talc (and other inorganic minerals), silica, titanium dioxide, metal, calcium salts such as calcium carbonate and calcium sulfate, sand, clay, diatomaceous earth, or combinations of such. It is believed (without being bound by belief) that softer, compressible organic additives may allow for processing, coating, and printing efficiencies in that they may be easier to wipe and not as harsh on equipment as compared to the traditional hard, coarse, abrasive inorganic additives. Additionally, as known in the art, such organic additives are non-water soluble or water insoluble. Non-limiting examples of organic texture agent additives include the following:
The texture agent additive may comprise particles of from about 10 microns to about 125 microns in size or from about 25 microns to about 125 microns in size or from about 35 microns to about 110 microns in size or from about 50 microns to about 110 microns in size or from about 65 microns to about 110 microns in size or from about 74 microns to about 110 microns in size or from about 80 microns to about 110 microns in size. The texture agent additive may comprise from about 5% to about 25% by weight of the coating or from about 10% to about 20% by weight of the coating of from about 15% to about 18% by weight of the coating or, more specifically about 15% by weight of the coating. Additionally, the texture agent additive may comprise particles of more than one size. As non-limiting examples, the texture agent additive may comprise a combination of about 25% 110-micron size particles and about 75% 80-micron size particles or a combination of about 66.7% 80-micron size particles and about 33.3% 65-micron size particles or a combination of about 66.7% 65-micron size particles and about 33.3% 50-micron size particles or a combination of about 33.3% 50-micron size particles and about 66.7% 35-micron size particles. (In each example above, the percent is a percent by weight of the texture agent additive.)
As described above, the anti-glare, texture coating may also comprise a coreactant additive. The coreactant additive (also known as a hardener, an external crosslinker, a crosslinker, and/or a catalyst) may be added to enable the coating to adhere, dry, cure, and/or solidify and/or to contribute to abuse resistance. A non-limiting example of a coreactant additive is CR 9-101, available from The Dow Chemical Company (Midland, Mich.). In general, a coreactant additive may comprise from 0% to about 5% by weight of the coating or from about 1% to about 3% by weight of the coating or from about 1.5% to about 2.5% by weight of the coating or, more specifically, about 1.5% by weight of the coating.
The anti-glare, texture coating may also comprise a reducer/thinner comprising water only or comprising a water/isopropyl alcohol blend. This reducer/thinner may comprise isopropyl alcohol in any amount from 0% to about 20% (such as, as non-limiting examples, 0% to about 15%, 0% to about 10%, 0% to about 5%, etc.) by weight and water in any amount from about 80% to 100% (such as, as non-limiting examples, about 85% to 100%, about 90% to 100%, about 95% to 100%, etc.) by weight, where the percent is a percent by weight of the blend. As a blend, the reducer/thinner is a blend known in the art that may be added to a coating to adjust the viscosity of the coating to allow for efficient printing or other application. For rotogravure printing of a coating of the present application, the target viscosity may be from about 50 to about 125 centipoise (from about 15 to about 37 seconds on a Shell Cup #4) or from about 70 to about 125 centipoise (from about 21 to about 37 seconds on a Shell Cup #4) or from about 90 to about 107 centipoise (from about 27 to about 32 seconds on a Shell Cup #4).
The anti-glare, texture coating may also comprise additional coating additives. For example, the coating may comprise additives to affect the coefficient of friction (COF) to address sliding or skidding. Such additives may provide anti-skid properties or otherwise prevent sliding. A non-limiting example of an anti-skid additive is HYPOD™ 8501 Polyolefin Dispersion, available from The Dow Chemical Company (Midland, Mich.).
The anti-glare, texture coating may be produced as follows: The anti-glare agent is mixed with the texture agent. The viscosity is then measured. If the viscosity is not within a target range, the reducer/thinner (either water only or a water/isopropyl alcohol blend as described above) is added in an amount known to a person of ordinary skill in the art. The combination is mixed, and the viscosity is again measured. Once the viscosity is within the target range, the combination is trialed as known in the art for the coating or printing application. Adjustments (e.g., further additions of the reducer/thinner) are made as needed based on the quality of the trial. Once the quality of the trial is acceptable as known in the art, the optional coreactant additive may be mixed with the combination to form the coating.
Specific examples of produced coatings (with weight percent of the coating listed) are reported in Table 1.
As described above, the coating may be applied to a thermoplastic film via flexographic printing or coating or rotogravure printing or coating. As known in the art, when viewed under a printer's loop, the edge of a coating applied to a substrate via flexographic printing/coating or flexography has a straight edge and the edge of a coating applied to a substrate via rotogravure printing/coating or gravure has a scalloped edge. With flexographic printing or coating or rotogravure printing or coating, the coating may be pattern-applied or flood coated. A non-limiting example of a thermoplastic film to which the coating may be applied is a monolayer film of 48-gauge biaxially oriented polyethylene terephthalate. Prior to the application of the coating, this film may (or may not) be corona treated as known in the art. In one embodiment, a rotogravure press may apply ink to the optionally corona-treated side (for a surface print) or to the non-treated side (for a reverse print). The press then applies the coating to the optionally corona-treated side either over the ink (if surface printed) or without ink (if reverse printed). As known, in the art, the press may use thermal forced air to dry the coated and optionally printed film. The resulting film may then be laminated (e.g., via adhesive lamination, extrusion lamination or otherwise as known in the art) to another film, such as, as a non-limiting example, a barrier sealant film. A non-limiting example of a barrier sealant film is a 4-mil (102-micron) thick film having the general construction reported in Table 2.
After adhesive lamination, the multilayer film with the anti-glare, texture coating is cured at room temperature for 24 hours. In one embodiment, the film is not subjected to radiation curing in the form of UV radiation or e-beam radiation or otherwise or to any energy curing other than the thermal forced air of the press used to dry the coated and optionally printed film. As the film is not subjected to UV radiation in this embodiment, the coating does not require a photo initiator.
When applied to a film, each of the coatings of Examples 1-5 reported in Table 1 provided heat resistance, abuse resistance, and printability based on tests known in the art. As evidence of heat resistance, each coated film released from a platen without sticking when placed in a heat sealer at 400° F. (204° C.) at 40 psi (275.790 kPA) for one second dwell time. As evidence of abuse resistance, each coated film did not lose any coating when scratched with a fingernail. As evidence of printability, each coated film printed without any known print defects (such as streaks, tails, clouds, etc.) as known in the rotogravure printing arts.
Additionally, various properties of the anti-glare, texture coating may be measured. These properties include but are not limited to gloss level and roughness/texture. Gloss level is a visual impression resulting from surface evaluation. The more direct light that is reflected, the higher the gloss level and vice versa. Gloss level (or specular reflection) may be measured via a glossmeter. The measurement values of a glossmeter relate to the amount of reflected light from a black glass standard with a defined refractive index, not to the amount of incident light. The measurement value for this defined standard is equal to 100 gloss units (calibration). Materials with a higher refractive index, such as uncoated thermoplastic films, may have measurement values above 100 gloss units (GU). As a result, for some applications, the gloss level may be documented as a percent reflection of illuminated light.
To determine a non-limiting example gloss level for an embodiment of the anti-glare, texture coating of the present application, the gloss units for a film having the coating of Example 2 and for the same film not having the coating were measured using a BYK-Gardner Glossmeter. The average reading at 60 degree for a film with the anti-glare, texture coating was 2.4 gloss units, while the average reading at 60 degree for a film without the anti-glare texture coating was 123.6 gloss units, resulting in a gloss level of 1.94%. According to product literature from BYK-Gardner, a material with 2.4 gloss units at 60 degree is considered a low gloss material.
Additional gloss units were measured for further embodiments of the anti-glare, texture coating of the present application. The gloss units for films having the coating of each of Examples 1-5 were measured as described above. The average gloss units at 60 degree is reported in Table 3. (The reported average gloss units for each example is based on 15 readings. Statistically, the high value and low value for each of the 15 readings for each example cross over one another.) Using an average reading of 123.6 gloss units for a film without the anti-glare, texture coating, the gloss level in percentage (%) is also reported in Table 3.
Therefore, a film having the anti-glare, texture coating of the present application may have a gloss level of from 0% to about 15% or from 0% to about 10% or from 0% to about 5% or from about 1.5% to about 3.5% or less than about 5%.
Texture may also be evaluated for the anti-glare, texture coating of the present application. A film having the coating of Example 1 was examined with a first light microscope / scanning electron microscope (SEM) (the “first SEM”). The first SEM is Model 1645 from Amray, Inc. The first SEM uses Semicaps software for analysis.
Additional RA measurements for a film having the coating of Example 1 were obtained using a second scanning electron microscope (SEM) (the “second SEM”). The second SEM is a JSM-6010PLUS/LA Scanning Electron Microscope available from JEOL USA, Inc. (Peabody, Mass.). The second SEM uses Scandium software from Olympus for analysis. With the second SEM, RA was measured at low magnification (e.g., at 100 times magnification). Readings at 0° tilt and 7 ° tilt at 100 times magnification were stacked and combined for a three-dimensional profile to facilitate the determination of RA.
In addition or as an alternative to microscopy, texture/roughness may be measured with a profilometer and/or based on the following “Roughness Parameters” (as reported at http://www.rubert.co.uk/Ra.htm on Feb. 3, 2014):
The Mean Roughness (Roughness Average Ra) is the arithmetic average of the absolute values of the roughness profile ordinates. Ra is one of the most effective surface roughness measures commonly adopted in general engineering practice. It gives a good general description of the height variations in the surface. The units of Ra are micrometres or microinches.
Note: Ra is also called AA and CLA.
Z(x)=profile ordinates of roughness profile
The Root Mean Square (RMS) roughness (Rq) is the root mean square average of the roughness profile ordinates.
Note: Rq is also called RMS.
The Single Roughness Depth (Rzi) is the vertical distance between the highest peak and the deepest valley within a sampling length.
The Mean Roughness Depth (Rz) is the arithmetic mean value of the single roughness depths of consecutive sampling lengths.
The Maximum Roughness Depth (Rmax) is the largest single roughness depth within the evaluation length.
The units of Rz are micrometres or microinches.
The Mean width of profile elements (RSm) is the arithmetic mean value of the widths of the profile elements of the roughness profile, where a profile element is a peak and valley in the roughness profile. The units of Rsm are micrometres or microinches.
The Root Mean Square Slope (Rsq) is the root mean square average of all local profile slopes. Each slope is calculated using a smoothing algorithm to reduce the effect of random noise on the valjue of Rsq.
Each and every document cited in this present application, including any cross-referenced or related patent or application, and any patent application or patent to which this present application claims priority or benefit is incorporated in this present application in its entirety by this reference, unless expressly excluded or otherwise limited. The citation of any document is not an admission that it is prior art with respect to any embodiment disclosed or claimed in this present application or that it alone, or in any combination with any other reference or references, teaches, suggests, or discloses any such embodiment. Further, to the extent that any meaning or definition of a term in this present application conflicts with any meaning or definition of the same term in a document incorporated by reference, the meaning or definition assigned to that term in this present application shall govern.
The above description, examples, and embodiments disclosed are illustrative only and should not be interpreted as limiting. The present invention includes the description, examples, and embodiments disclosed; but it is not limited to such description, examples, or embodiments. Modifications and other embodiments will be apparent to a person of ordinary skill in the art, and all such modifications and other embodiments are intended and deemed to be within the scope of the present invention as defined by the claims.
This present application is a divisional of application Ser. No. 15/115,535 filed Jul. 29, 2016 (the '535 Application). The '535 Application is a national stage application, filed under 35 U.S.C. § 371, of International Patent Application No. PCT/US15/14171 filed Feb. 3, 2015 (the '171 Application). The '171 Application claims the benefit of U.S. Provisional Patent Application No. 61/935,152 filed Feb. 3, 2014 (the '152 Application). Each of the '535 Application, the '171 Application, and the '152 Application is incorporated in its entirety in this present application by this reference.