Synthetic polymer-free coating formulations containing shellac and methods associated therewith

Abstract

Coatings may convey moisture resistance when deposited upon a base substrate. Coating formulations containing no synthetic polymers may comprise: an aqueous fluid, at least partially neutralized shellac dissolved in the aqueous fluid, and a plurality of wax particles emulsified as solids in the aqueous fluid. Thin-film coatings formed by depositing the coating formulations and removing the aqueous fluid therefrom may be significantly impermeable to water, as determined by the thin-film coating having a moisture vapor transmission rate of at most about 1200 m2 / g, as measured at 38°C and 90% relative humidity by ASTM F1249 or ASTM E96, and / or a Cobb index of at most about 105 m2 / g, as measured over 1800 s by ISO 535, ASTM D3285, or TAPPI T441.

Description

SYNTHETIC POLYMER-FREE COATING FORMULATIONS CONTAINING SHELLAC AND METHODS ASSOCIATED THEREWITH BACKGROUND

[0001] Barrier coatings are used on a variety of substrates to prevent or limit contact of substances such as water, oxygen or other gases, grease, or the like with the substrate. Among the industries where barrier coatings are utilized include, for example, food packaging, pharmaceutical manufacturing and packaging, cosmetic manufacturing and packaging, and the like.

[0002] Most barrier coatings are based upon synthetic polymer materials that are substantially impermeable to a substance of interest. However, with increasing environmental awareness and growing government regulations, there is a drive toward barrier coatings and similar materials that do not contain synthetic polymers. A leading issue is that most synthetic polymers are not readily dissolvable or biodegradable and thus may persist as microplastics in the environment for extended periods of time. Indeed, the environmental issues associated with microplastics are so impactful, the European Union has mandated their phase-out in many industries, and it is expected that other countries may follow suit in the coming years.

[0003] Another possible type of barrier coating is based upon thin-film metal layers. Although thin-film metal layers may afford robust barrier coating performance in many cases, they are sometimes used in combination with polymers, and the resulting mixed product streams may not be readily compostable or recyclable. In addition, thin-film metal layers may result in higher production costs than do polymer-based barrier coatings. BRIEF DESCRIPTION OF THE DRAWINGS

[0004] The following figures are included to illustrate certain aspects of the disclosure, and should not be viewed as exclusive configurations. The subject matter disclosed is capable of considerable modifications, alterations, combinations, and equivalents in form and function, as will occur to one having ordinary skill in the art and having the benefit of this disclosure.

[0005] FIGS. 1-4 are plots of Cobb Index and MVTR as a function of the amount of wax in coating formulations of the present disclosure. DETAILED DESCRIPTION

[0006] The present disclosure generally relates to coating technologies and, more specifically, coating formulations and barrier coatings formed without using synthetic polymers.

[0007] As discussed above, coating formulations containing synthetic polymers are becoming less desirable in many respects, such as due to their propensity to form microplastics in the environment. As used herein, the term “microplastics” refers to polymer particles having a maximumsize of about 5 mm in any dimension, wherein the polymer is non-biopolymer in nature (i.e., not naturally occurring), water-insoluble and non-biodegradable. Because microplastics are a growing environmental concern, polymer coatings based upon synthetic polymers that are prone toward forming microplastics are currently being phased out.

[0008] The present disclosure provides coating formulations and thin-film coatings formed therefrom that are based on naturally sourced resin materials and are free or substantially free of other types of polymers, particularly synthetic polymers. Because of the natural origin of the resin material, the environmental burden of the coating formulations is much lower than traditional coating formulations and thin-film coatings based upon synthetic polymers. In addition, the thin-film coatings produced according to the disclosure herein may exhibit advantageous performance in barrier coating applications.

[0009] In particular, the coating formulations and thin-film coatings described herein utilize shellac as the naturally sourced resin material. Advantageously, the shellac may be at least partially neutralized to promote solubility in aqueous fluids to aid in realizing the benefits described herein. Once suitably solubilized in water or a similar aqueous fluid, the resulting shellac solution may be combined with wax particles in a wax emulsion to afford even more robust barrier coating performance. At the very least, thin-film coatings formed according to the present disclosure may display robust barrier coating performance against moisture. In addition, the thin-film coatings may exhibit good oil and grease resistance, which may be particularly desirable for forming barrier coatings upon food packaging. Additional details regarding the coating formulations and the thin-film coatings formed therefrom are provided hereinafter.

[0010] Coating formulations of the present disclosure may comprise: an aqueous fluid, at least partially neutralized shellac dissolved in the aqueous fluid, and a plurality of wax particles emulsified as solids in the aqueous fluid. Preferably, no synthetic polymers are present in the aqueous fluid.

[0011] All or a portion of the components present in the coating formulations may be obtained from natural sources. Shellac is a naturally sourced resin that may be advantageous for forming thin-film coatings having barrier properties. Additional details regarding suitable shellacs are provided hereinbelow. In addition, the wax and other components of the coating formulations may be naturally sourced as well, if desired, to provide further environmental favorability.

[0012] Aqueous fluids suitable for use in the present disclosure may comprise water or water admixed with a water-miscible organic solvent, such as an alcohol or a glycol. Such water-miscible organic solvents may sometimes be present to provide anti-freeze performance by lowering thefreezing point of the aqueous fluid.

[0013] The aqueous fluid may be present in the coating formulations described herein in an amount up to about 90 wt. %, or up to about 80 wt. %, or up to about 70 wt. %, or up to about 60 wt. %, or up to about 50 wt. %, or up to about 40 wt. %, or up to about 30 wt. %, or up to about 20 wt. %, or up to about 15 wt. %, such as about 5 wt. % to about 20 wt. %, or about 10 wt. % to about 25 wt. %, or about 10 wt. % to about 30 wt. %, or about 15 wt. % to about 25 wt. %, or about 50 wt. % to about 80 wt. %, each as measured based on total mass of the coating formulations.

[0014] As used herein, the term “solids” refers to any component of the coating formulations other than the aqueous fluid. Thus, when calculating mass percentages based on total solids, the term “total solids” represents the combined mass of all components (solid, liquid, and / or gas) blended with the aqueous fluid in any form. Depending on the particular component and its solubility properties in the aqueous fluid, the component may undergo dissolution in the aqueous fluid, or remain dispersed as a liquid or solid in the aqueous fluid. Dispersed solids or liquids may be present as an emulsion, for instance.

[0015] In non-limiting examples, the coating formulations described herein may contain about 5 wt. % to about 60 wt. % total solids, or about 10 wt. % to about 60 wt. % total solids, or about 15 wt. % to about 55 wt. % total solids, or about 20 wt. % to about 50 wt. % total solids, or about 35 wt. % to about 55 wt. % total solids, based on total mass of the aqueous emulsion (total solids plus aqueous fluid). Solids present in particulate form (emulsified or dispersed solids) may be present in the coating formulations in particle sizes ranging from about 50 nm to about 5 ^m in size or about 100 nm to about 5 ^m in size, for example.

[0016] In non-limiting examples, the ratio of dissolved solids to particulate solids in the aqueous emulsions may range from about 15:1 to about 1:5, or about 15:1 to about 1:1, or about 10:1 to about 1:1, or about 5:1 to about 1:1, or about 1:1 to about 1:5, or about 1:1 to about 1:3, each on a mass basis. Accordingly, dissolved solids may be present in a greater amount than particulate solids, or dissolved solids may be present in a lesser amount than particulate solids. In the present disclosure, dissolved solids may include at least shellac that has been at least partially neutralized. Particulate solids may include the wax particles and other insoluble materials.

[0017] The term “shellac” refers to a resinous material obtained from secretions of the female lac bug and comprising oligomers of at least aleuritic acid and shellolic acid. Shellacs suitable for use in the present disclosure may, depending on source and the season of harvest, vary in color and aleuritic acid / shellolic acid ratio. Shellac is available in various grades depending on how purified it is and how dewaxed it is. Less dewaxed shellac may be more difficult to dissolve in water when atleast partially neutralized. Less purified shellac can result in a darker color. The degree of dewaxing versus purification comes down to acid value and how easily the shellac is dispersed in water. Blonde is a variant of orange shellac with much of the natural shellac dye removed mechanically by filtering with activated carbon. While other grades are bleached chemically (e.g., using sodium hypochlorite) and chemically dissolved in caustic solution (e.g., using sodium carbonate), super-blonde or ultra- blonde shellac can be quite light colored and more water-resistant. Button lac and seed lac are additional shellac grades of shellac that are commonly encountered and may be used herein. Even stick lac, the crudest grade of shellac, may be utilized herein. Though there may be preference for certain grades of shellac depending on the conditions to which the thin-film coatings will be exposed, it is to be appreciated that any grade of shellac in dewaxed or non-dewaxed form may be suitable for use in the disclosure herein.

[0018] In some embodiments, the shellac utilized in the coating formulations and thin-film coatings formed therefrom may be an at least partially dewaxed shellac, which may include a fully dewaxed shellac. At least partially dewaxed shellac may be particularly desirable for forming barrier coatings upon food containers, for example. To promote dissolution of the at least partially dewaxed shellac, the at least partially dewaxed shellac may be present in at least partially neutralized form, as discussed further below. Suitable procedures for dewaxing shellac will be familiar to persons having ordinary skill in the art.

[0019] The waxy residue obtained following dewaxing of shellac (shellac wax) may constitute at least a portion of the wax particles emulsified as solids in the aqueous fluid. Additional suitable waxes and amounts thereof are discussed further below.

[0020] Shellacs may be added to the aqueous fluid when dissolved in a suitable organic solvent, such as methanol or ethanol. The resulting shellac dispersion may then be at least partially neutralized with a suitable base to promote dissolution thereof. Alternately, the shellac may be at least partially dissolved in the aqueous fluid using a suitable base without using an organic solvent initially. In either case, the at least partially neutralized shellac may become partially or fully soluble in the aqueous fluid upon formation of one or more ionic charges thereon.

[0021] Preferably, the base used to at least partially neutralize the acid groups of the shellac may comprise aqueous ammonia, either alone or in combination with other bases. Other suitable bases that may be used in combination with aqueous ammonia or in any combination without aqueous ammonia may include, for example, an amine (e.g., ethanolamine, diethanolamine, triethanolamine, trimethylamine, diethylamine, dimethylethylamine, triethylamine, and the like) or an alkali metal base (e.g., NaOH, KOH, or the like).

[0022] The shellac may be fully or partially neutralized in the disclosure herein. Any extent of neutralization that promotes solubility of the shellac in the aqueous fluid may be used. In non- limiting examples, the shellac is at least about 50% neutralized, or at least about 60% neutralized, or at least about 70% neutralized, or at least about 80% neutralized, or at least about 90% neutralized, or at least about 95% neutralized, or at least about 99% neutralized. A corresponding stoichiometric base may be utilized to achieve the foregoing amounts of neutralization, or a stoichiometric excess of base may be utilized to promote full neutralization of the shellac.

[0023] Shellac may be present in the coating formulations described herein in an amount up to about 50 wt. %, or up to about 40 wt. %, or up to about 30 wt. %, or up to about 20 wt. %, such as about 5 wt. % to about 50 wt. %, or about 5 wt. % to about 30 wt. %, or about 10 wt. % to about 40 wt. %, or about 15 wt. % to about 30 wt. %, each as measured based on total solids. The resulting thin-film coatings may contain a similar amount of shellac.

[0024] Waxes are hydrophobic organic substances that occur in petroleum and other oleaginous materials, are biosynthesized by plants and animals, or are obtained synthetically. Waxes are usually malleable solids at room temperature and may comprise one or more higher alkanes (paraffins), particularly normal or branched C16-C100 alkanes or C20-C50 alkanes, lipids and / or oils. Suitable waxes for use in the disclosure herein may include, but are not limited to, paraffin waxes, oxidized paraffin waxes, polyolefin waxes, oxidized polyolefin waxes, natural waxes, oxidized natural waxes, and any combination thereof. In addition, waxy components obtained from de-waxed shellac (i.e., shellac wax) may be present as at least a portion of the wax particles in the coating formulations, either with or without other waxes being present. As used herein, a wax is considered “oxidized” if oxygenated functional groups such as alcohols, carboxylic acids, epoxides or the like are introduced to an otherwise unsubstituted (paraffinic) hydrocarbon backbone. The amount of oxygenated functional groups introduced to a particular wax may, for example, be sufficient to lower the hydrophobicity of the wax to an extent necessary to facilitate formation of an emulsified form of the wax.

[0025] Specific examples of paraffin waxes and lipidic waxes, including natural waxes, suitable for use in the disclosure herein may include, but are not limited to, slack wax, beeswax, hydrogenated lipids, refined wax, semi-refined wax, scale wax, microcrystalline wax, vegetable-based waxes such as soy and palm waxes, carnauba wax, rice bran wax, montan ester wax, sugar cane wax, sunflower wax, hydrogenated castor oil, poly(3-hydrobuyrate-co-3-hydroxyvalerate), synthetic waxes such as oligomer waxes derived from linear alpha olefins or copolymers thereof, Fischer-Tropsch waxes, polyolefin waxes (e.g., polyethylene wax or polypropylene wax), and any combination thereof.

[0026] Advantageous coating formulations may comprise or consist essentially of at least onenatural wax. Coating formulations comprising or consisting essentially of at least one natural wax may be particularly advantageous for use in conjunction with food packaging applications or other applications in which synthetic waxes or undesirable waxes or may not be used.

[0027] Suitable waxes may be sourced as a wax emulsion in an aqueous fluid, which may then be further combined with at least partially neutralized shellac to form the coating formulations described herein. Examples of wax emulsions that may be suitable for use in the disclosure herein include, but are not limited to, MICHEM® emulsions such as ME62330, ME93335, ME61335, ME52137, and ME24414 (Michelman). Particularly suitable waxes for use in the disclosure herein may be obtained from a biological (natural) source, such as any plant- or animal-based wax listed above. Thus, in particular embodiments, the wax may comprise at least one natural wax in the disclosure herein. Examples of natural wax emulsions may include, for example, ML160PFP (anionic carnauba wax emulsion, Michelman).

[0028] Suitable waxes for use in the coating formulations of the present disclosure may have a melting point of about 50°C or above and an average diameter, when emulsified or dispersed within a shellac matrix, ranging up to about 50,000 nm (50 microns) in size, such as about 400 nm or less, or about 300 nm or less, or about 200 nm or less, or about 100 nm or less, such as an average diameter ranging from about 10 nm to about 100 nm, or about 25 nm to about 50 nm, or about 50 nm to about 90 nm, or about 20 nm to about 75 nm. In other examples, the average diameter may range from about 100 nm to about 400 nm.

[0029] Waxes may be present in the coating formulations described herein in an amount up to about 60 wt. %, or up to about 50 wt. %, or up to about 40 wt. %, or up to about 30 wt. %, such as about 5 wt. % to about 50 wt. %, or about 5 wt. % to about 40 wt. %, or about 10 wt. % to about 45 wt. %, or about 15 wt. % to about 35 wt. %, each as measured based on total solids within the aqueous emulsions. The resulting thin-film coatings may contain a similar amount of wax.

[0030] In non-limiting examples, the ratio of shellac to wax in the disclosure may range from about 15:1 to about 1:5, or about 10:1 to about 1:1, or about 5:1 to about 1:1, or about 15:1 to about 1:1, or about 1:1 to about 1:5, or about 1:1 to about 1:3, each on a mass basis.

[0031] Additional components may be present in the coating formulations disclosed herein such as one or more of, for example, fill materials (preferably inorganic fill materials, such as inorganic particulates), effect pigments (colorants), dyes, optical brighteners, plasticizers, crosslinking agents, defoamers, anti-static agents, dispersants, thickeners, fillers, biocides, rheology modifiers, fluency aids, lubricants, preservatives (e.g., benzoisothiazolinones, methylisothiazolinones, methylchloroisothaizolinones, and the like), coalescent aids, buffers, co-solvents, surfactants, and anycombination thereof. Such additional components may be present in amounts conventionally useful in coating formulations. When present, such additional components may be selected independently from one another and in any suitable amount to modify one or more properties of the coating formulations (e.g., to promote formation of a thin film) or to provide suitability for a given application.

[0032] In some examples, the coating formulations and thin-film coatings formed therefrom may further comprise an inorganic fill material, such as talc, mica, montmorillonite, kaolin, or any combination thereof.

[0033] When included, inorganic fill materials, such as talc or other inorganic fillers, may be present in the coating formulations in an amount up to about 50 wt. %, or up to about 40 wt. %, or up to about 30 wt. %, such as about 5 wt. % to about 40 wt. %, or about 15 wt. % to about 35 wt. %, or about 20 wt. % to about 30 wt. %, as measured based on total solids. The resulting thin-film coatings may contain a similar amount of fill material.

[0034] Coating formulations containing inorganic fill materials may be particularly desirable for application as a base coat when forming coated substrates according to the present disclosure. Without being bound by theory or mechanism, it is believed that a base coat (pre-coat) containing an inorganic fill material may smooth surface roughness to allow a top coat, also containing wax particles and shellac, to be more effectively deposited upon the base coat. Kraft paper is an example of a substrate having high surface roughness that may be effectively smoothed by employing an inorganic filler in the base coat.

[0035] In some examples, the coating formulations may include a suitable plasticizer, which may be biodegradable or non-biodegradable in particular embodiments. Suitable plasticizers are not believed to be particularly limited, other than being dispersible in the aqueous fluid, either in dissolved or emulsified form, and exhibiting capability of promoting robust thin-film formation once evaporated onto a base substrate. A suitable plasticizer may also aid in conveying flexibility to the thin-film in some cases. Some examples of suitable plasticizers may be derived from a biological source. Specific examples of suitable plasticizers may include, but are not limited to, epoxidized soybean oil, epoxidized linseed oil, castor oil, tannic acid, milk proteins, polyethylene glycol, or any combination thereof. Still other examples of plasticizers that may be suitable include, for example, epoxidized sunflower oil, cardanol and modified cardanol, glycidol, chlorine- and phosphate-containing vegetable-based plasticizers, phosphaphenanthrene-modified vegetable oils, hydroxyl- and nitrogen- group-containing tung oil esters, dimethyl oleate-based plasticizers, citric acid esters, and the like.

[0036] If included, the plasticizer may be present in the coating formulations and thin-film coatings described herein in an amount up to about 10 wt. %, or up to about 5 wt. %, or up to about4 wt. %, or up to about 3 wt. %, or up to about 2 wt. %, or up to about 1 wt. %, such as about 0.1 wt. % to about 1.5 wt. %, or about 0.5 wt. % to about 2 wt. %, or about 0.7 wt. % to about 1.7 wt. %, or about 0.8 wt. % to about 2 wt. %, as measured based on total solids. The resulting thin-film coatings may contain a similar amount of plasticizer. The decision as to whether a plasticizer needs to be included may be based upon desired performance of the thin-film coating and the conditions to which the thin-film coating will be exposed.

[0037] Surfactants may be present in wax emulsions used in conjunction with forming the coating formulations of the present disclosure. Illustrative surfactants that may be suitable for use in the coating formulations and thin-film coatings disclosed herein are not believed to be particularly limited and may include one or more of, cationic surfactants, anionic surfactants, neutral surfactants (non-ionic surfactants), zwitterionic surfactants, or any combination thereof. If included (including surfactants introduced in conjunction with the wax particles), surfactants may be present in the coating formulations and thin-film coatings in an amount up to about 20 wt. %, or up to about 15 wt. %, or up to about 10 wt. %, or up to about 8 wt. %, or up to about 5 wt. %, or up to about 4 wt. %, or up to about 3 wt. %, or up to about 2 wt. %, or up to about 1 wt. %, or up to about 0.5 wt. %, as measured based upon total solids.

[0038] Illustrative non-ionic surfactants that may be suitable for use in the disclosure herein include, but are not limited to, alkylaryl polyether alcohols, alkylphenol ethoxylates, alkyl ethoxylates, polyoxamers, fatty acid esters (e.g., fatty acid glycerol esters, fatty acid sorbitan esters, fatty acid sorbitol esters, fatty acid lecithin esters, and the like), polyethylene oxide sorbitan fatty acid esters, and any combination thereof. Illustrative cationic surfactants may include quaternary ammonium compounds. Illustrative anionic surfactants that may be suitable for use in the disclosure herein include, but are not limited to, alkyl ethoxylate sulfates, alkyl ethoxylate sulfonates, alkylphenol ethoxylate sulfates, alkylphenol ethoxylate sulfonates, alkylsulfates, alkylsulfonates, alkylarylsulfates, alkylarylsulfonates, sulfosuccinates, alkyl carboxylates (e.g., an ammonium salt of oleic acid), or any combination thereof. Illustrative zwitterionic surfactants that may be suitable for use in the disclosure herein include various betaines and sultaines.

[0039] Coated substrates of the present disclosure may comprise a base substrate, and a thin-film coating formed upon a surface of the base substrate. The thin-film coating comprises a continuous matrix comprising at least partially neutralized shellac, and a plurality of wax particles dispersed within the continuous matrix.

[0040] Once the coating formulation is disposed upon the base substrate and then dried, the thin-film coatings may afford barrier coating performance. In particular, the thin-film coatingsdescribed herein may have a moisture vapor transmission rate (MVTR) of at most about about 1200 m2 / g, as measured at 38°C and 90% relative humidity by ASTM F1249 or ASTM E96, and / or a Cobb index of at most about 105 m2 / g, as measured over 1800 seconds (s) by ISO 535, ASTM D3285, or TAPPI T441. In addition, the thin-film coatings may exhibit good resistance against oil and grease as well. In some examples, the thin-film coatings may have a MVTR of about 1000 m2 / g or below, or about 800 m2 / g or below, or about 600 m2 / g or below, or about 400 m2 / g or below, or about 300 m2 / g or below, or about 200 m2 / g or below, or about 100 m2 / g or below and / or have a Cobb Index of about 100 m2 / g or below, or about 95 m2 / g or below, or about 90 m2 / g or below, or about 85 m2 / g or below, or about 80 m2 / g or below, or about 75 m2 / g or below, or about 70 m2 / g or below, or about 65 m2 / g or below, or about 60 m2 / g or below, or about 55 m2 / g or below, or about 50 m2 / g or below, or about 45 m2 / g or below, or about 40 m2 / g or below, or about 35 m2 / g or below, or about 30 m2 / g or below. Accordingly, in one or more examples, the thin-film coatings may have a MVTR of about 200 m2 / g or below, or about 100 m2 / g or below, and a Cobb Index of about 100 m2 / g or below or about 50 m2 / g or below, including a Cobb Index within a range of about 50 m2 / g to about 100 m2 / g.

[0041] Base substrates upon which thin-film coatings of the present disclosure may be formed are not believed to be particularly limited, provided that there is adequate adhesion between the thin-film coating and the surface of the substrate. In non-limiting examples, base substrates that may be coated using the coating formulations of the present disclosure include, but are not limited to, paper, cardboard and other types of packaging, films, wood (e.g., for architectural coatings), metal (e.g., a metal can or metal-lined pouch), other polymers (e.g., within polymer-based circuit board assemblies and food storage containers), and the like. Similarly, the coating formulations described herein may be used to coat sizing upon fibers as well.

[0042] The thin-film coatings may have a thickness of about 0.5 ^m to about 5 ^m, or about 1 ^m to about 400 ^m, or about 2 ^m to about 300 ^m, or about 5 ^m to about 200 ^m, or about 10 ^m to about 100 ^m, or about 50 ^m to about 300 ^m, or about 75 ^m to about 225 ^m. Coating thicknesses may be selected based on their suitability for a given application. Suitable coating weights may range from about 5 g / m2to about 25 g / m2.

[0043] Methods for forming a thin-film coating of the present disclosure may comprise applying a coating formulation of the present disclosure upon a surface of a base substrate, and removing aqueous fluid from the coating formulation (e.g., by evaporation) while upon the base substrate to produce a thin-film coating disposed upon a surface of the base substrate. The thin-film coating comprises a continuous matrix comprising at least partially neutralized shellac, and a plurality of wax particles dispersed within the continuous matrix.

[0044] Application of the coating formulations to the base substrate may be achieved using any of a variety of methods such as, for example, immersion, spraying, rod or roller coating, tumbling, or through using equipment such as a size press, water box, blade coater, cast coater, rod coater, air knife coater, curtain coater, film press coater, flexo coater, the like, or any combination thereof. In advantaged embodiments, the coating formulation may be applied to the base substrate using flexo coating, gravure coating, rod coating, blade coating, spray coating, or any combination thereof. Details regarding the foregoing techniques for applying the coating formulations to the base substrate will be familiar to one having ordinary skill in the art.

[0045] The coating formulations may be applied to the base substrate as one or more coating layers, either directly or indirectly. When applied directly, the coating formulations may be applied directly to the surface of the base substrate as a base coat, which may be optionally overcoated with one or more additional coating layers. The composition of the one or more additional coating layers may be the same as or different than that of the base coat. Preferably, the base coat and the one or more additional coating layers may each comprise partially or fully neutralized shellac. When applied indirectly, the coating formulations may be applied as a top coat overcoating a base coat. The top coat and the base coat may have the same or different compositions. Preferably, the top coat and base coat may each comprise partially or fully neutralized shellac. In some instances, advantaged performance may be realized by depositing the coating formulations as multiple coating layers, rather than as a single coating layer having an equivalent coating weight.

[0046] In some examples, the coating formulation may be a first coating formulation and a second coating formulation having a different composition than the first coating formulation, wherein each coating formulation comprises at least partially neutralized shellac and wax particles, and the first coating formulation is applied directly to the base substrate as a base coat and the second coating formulation is applied upon the base coat to form a top coat. In some examples, a first coating formulation of the present disclosure comprising an inorganic filler may be applied as a base coat to a base substrate, and a second coating formulation of the present disclosure lacking an inorganic filler may be applied upon the base coat as a top coat. The top coat may comprise one or more coating layers formed from the second coating formulation.

[0047] In some examples, methods of the present disclosure may further comprise heat treating the thin-film coating after removing the aqueous fluid.

[0048] Embodiments disclosed herein include:

[0049] A. Coating formulations. The coating formulations comprise: an aqueous fluid; at least partially neutralized shellac dissolved in the aqueous fluid; wherein no synthetic polymers are present in the aqueous fluid; and a plurality of wax particles emulsified as solids in the aqueous fluid.

[0050] B. Coated substrates. The coated substrates comprise: a base substrate; and a thin- film coating formed upon a surface of the base substrate and comprising: a continuous matrix comprising at least partially neutralized shellac; and a plurality of wax particles dispersed within the continuous matrix; wherein the thin-film coating has a moisture vapor transmission rate of at most about 1200 m2 / g, as measured at 38°C and 90% relative humidity by ASTM F1249 or ASTM E96, and / or a Cobb index of at most about 105 m2 / g, as measured over 1800 s by ISO 535, ASTM D3285, or TAPPI T441.

[0051] B1. A food container comprising the coated substrate of B.

[0052] C. Coating methods. The coating methods comprise: providing a base substrate; applying the coating formulation of A to a surface of the base substrate; and removing the aqueous fluid to produce a thin-film coating upon the surface of the base substrate, the thin-film coating comprising a continuous matrix comprising at least partially neutralized shellac, and a plurality of wax particles dispersed within the continuous matrix.

[0053] Each of embodiments A-C may have one or more of the following additional elements in any combination:

[0054] Element 1: wherein the coating formulation or thin-film coating further comprises an inorganic fill material.

[0055] Element 1A: wherein the coated substrate further comprises an inorganic fill material dispersed within the continuous matrix.

[0056] Element 2: wherein the inorganic fill material comprises talc, kaolin, montmorillonite, mica, or any combination thereof.

[0057] Element 3: wherein the coating formulation contains, based on total solids, about 0.5 wt. % to about 10 wt. % wax particles, about 5 wt. % to about 20 wt. % shellac, and about 5 wt. % to about 40 wt. % inorganic fill material.

[0058] Element 3A: wherein the thin-film coating contains, based on total mass of the thin- film coating, about 0.5 wt. % to about 10 wt. % wax particles, about 5 wt. % to about 20 wt. % shellac, and about 5 wt. % to about 40 wt. % inorganic fill material.

[0059] Element 4: wherein the coating formulation contains, based on total solids, about 2 wt. % to about 40 wt. % wax particles, and about 5 wt. % to about 25 wt. % shellac.

[0060] Element 4A: wherein the thin-film coating contains, based on total mass of the thin- film coating, about 2 wt. % to about 40 wt. % wax particles, and about 5 wt. % to about 25 wt. % shellac.

[0061] Element 5: wherein shellac is the only polymer present in the coating formulation.

[0062] Element 6: wherein the shellac is at least partially neutralized with a base comprising ammonia.

[0063] Element 7: wherein the base further comprises one or more of an amine, an alkali metal hydroxide, or any combination thereof.

[0064] Element 8: wherein no synthetic polymers are present in the thin-film coating, and / or wherein shellac is the only polymer present in the thin-film coating.

[0065] Element 9: wherein the base substrate is paper.

[0066] Element 10: wherein the thin-film coating has a moisture vapor transmission rate of at most about 1200 m2 / g, as measured at 38°C and 90% relative humidity by ASTM F1249 or ASTM E96, and / or a Cobb index of at most about 105 m2 / g, as measured over 1800 s by ISO 535, ASTM D3285, or TAPPI T441.

[0067] Element 11: wherein the coating formulation is applied to the surface of the base substrate by flexo coating, gravure coating, rod coating, blade coating, spray coating, or any combination thereof.

[0068] Element 12: wherein the coating formulation is applied directly to the base substrate as a base coat, optionally with a second application of the coating formulation being applied upon the base coat to form a top coat.

[0069] Element 13: wherein the coating formulation is a first coating formulation and a second coating formulation having a different composition than the first coating formulation, the first coating formulation being applied directly to the base substrate as a base coat, and the second coating formulation being applied upon the base coat to form a top coat.

[0070] Element 14: wherein the method further comprises heat treating the thin-film coating after removing the aqueous fluid.

[0071] By way of non-limiting example, exemplary combinations applicable to A-C include, but are not limited to, 1 or 1A, and 3 or 3A; 1 or 1A, 3 or 3A, and 4; 1 or 1A, and 5; 1 or 1A, and 6; 1 or 1A, 6, and 7; 4 or 4A, and 5; 4 or 4A, and 6; 4 or 4A, 6 and 7; 5 and 6; 5-7; 9 and 10; 9 and 11; 9 and 12; 9 and 13; 10 and 11; 10 and 12; 10 and 13; 11 and 12; and 11 and 13.

[0072] Additional embodiments disclosed herein include:

[0073] Clause 1. A coating formulation comprising:an aqueous fluid; at least partially neutralized shellac dissolved in the aqueous fluid; wherein no synthetic polymers are present in the aqueous fluid; and a plurality of wax particles emulsified as solids in the aqueous fluid.

[0074] Clause 2. The coating formulation of clause 1, further comprising: an inorganic fill material.

[0075] Clause 3. The coating formulation of clause 2, wherein the inorganic fill material comprises talc, kaolin, montmorillonite, mica, or any combination thereof.

[0076] Clause 4. The coating formulation of clause 2, wherein the coating formulation contains, based on total solids, about 0.5 wt. % to about 10 wt. % wax particles, about 5 wt. % to about 20 wt. % shellac, and about 5 wt. % to about 40 wt. % inorganic fill material.

[0077] Clause 5. The coating formulation of clause 4, wherein the inorganic fill material comprises talc, kaolin, montmorillonite, mica, or any combination thereof.

[0078] Clause 6. The coating formulation of clause 1, wherein the coating formulation contains, based on total solids, about 2 wt. % to about 40 wt. % wax particles, and about 5 wt. % to about 25 wt. % shellac.

[0079] Clause 7. The coating formulation of any one of clauses 1-6, wherein shellac is the only polymer present in the coating formulation.

[0080] Clause 8. The coating formulation of any one of clauses 1-6, wherein the shellac is at least partially neutralized with a base comprising ammonia.

[0081] Clause 9. The coating formulation of clause 8, wherein the base further comprises one or more of an amine, an alkali metal hydroxide, or any combination thereof.

[0082] Clause 10. A coated substrate comprising: a base substrate; and a thin-film coating formed upon a surface of the base substrate and comprising: a continuous matrix comprising at least partially neutralized shellac; and a plurality of wax particles dispersed within the continuous matrix; wherein the thin-film coating has a moisture vapor transmission rate of at most about 1200 m2 / g, as measured at 38°C and 90% relative humidity by ASTM F1249 or ASTM E96, and / or a Cobb index of at most about 105 m2 / g, as measured over 1800 s by ISO 535, ASTM D3285, or TAPPI T441.

[0083] Clause 11. The coated substrate of clause 10, wherein no synthetic polymers are present in the thin-film coating.

[0084] Clause 12. The coated substrate of clause 10, wherein shellac is the only polymer present in the thin-film coating.

[0085] Clause 13. The coated substrate of any one of clauses 10-12, further comprising: an inorganic fill material dispersed within the continuous matrix.

[0086] Clause 14. The coated substrate of clause 13, wherein the inorganic fill material comprises talc, kaolin, montmorillonite, mica, or any combination thereof.

[0087] Clause 15. The coated substrate of clause 13, wherein the thin-film coating contains, based on total mass of the thin-film coating, about 0.5 wt. % to about 10 wt. % wax particles, about 5 wt. % to about 20 wt. % shellac, and about 5 wt. % to about 40 wt. % inorganic fill material.

[0088] Clause 16. The coated substrate of clause 15, wherein the fill material comprises talc, kaolin, montmorillonite, mica, or any combination thereof.

[0089] Clause 17. The coated substrate of any one of clauses 10-12, wherein the thin- film coating contains, based on total mass of the thin-film coating, about 2 wt. % to about 40 wt. % wax particles, and about 5 wt. % to about 25 wt. % shellac.

[0090] Clause 18. The coated substrate of any one of clauses 10-12, wherein the shellac is at least partially neutralized with a base comprising ammonia.

[0091] Clause 19. The coated substrate of clause 18, wherein the base further comprises one or more of an amine, an alkali metal hydroxide, or any combination thereof.

[0092] Clause 20. The coated substrate of any one of clauses 10-12, wherein the base substrate is paper.

[0093] Clause 21. A food container comprising the coated substrate of any one of clauses 10-12.

[0094] Clause 22. A method comprising: providing a base substrate; applying the coating formulation of any one of clauses 1-6 to a surface of the base substrate; and removing the aqueous fluid to produce a thin-film coating upon the surface of the base substrate, the thin-film coating comprising a continuous matrix comprising at least partially neutralized shellac, and a plurality of wax particles dispersed within the continuous matrix.

[0095] Clause 23. The method of clause 22, wherein the thin-film coating has a moisture vapor transmission rate of at most about 1200 m2 / g, as measured at 38°C and 90% relative humidity by ASTM F1249 or ASTM E96, and / or a Cobb index of at most about 105 m2 / g, as measured over 1800 s by ISO 535, ASTM D3285, or TAPPI T441.

[0096] Clause 24. The method of clause 22, wherein shellac is the only polymer present in the coating formulation.

[0097] Clause 25. The method of clause 22, wherein the shellac is at least partially neutralized with a base comprising ammonia.

[0098] Clause 26. The method of clause 25, wherein the base further comprises one or more of an amine, an alkali metal hydroxide, or any combination thereof.

[0099] Clause 27. The method of any one of clauses 21-24, wherein the coating formulation is applied to the surface of the base substrate by flexo coating, gravure coating, rod coating, blade coating, spray coating, or any combination thereof.

[0100] Clause 28. The method of any one of clauses 21-24, wherein the coating formulation is applied directly to the base substrate as a base coat, optionally with a second application of the coating formulation being applied upon the base coat to form a top coat.

[0101] Clause 29. The method of any one of clauses 21-24, wherein the coating formulation is a first coating formulation and a second coating formulation having a different composition than the first coating formulation, the first coating formulation being applied directly to the base substrate as a base coat, and the second coating formulation being applied upon the base coat to form a top coat.

[0102] Clause 30. The method of any one of clauses 21-24, further comprising: heat treating the thin-film coating after removing the aqueous fluid.

[0103] To facilitate a better understanding of the disclosure herein, the following examples of various representative embodiments are given. In no way should the following examples be read to limit, or to define, the scope of the present disclosure. EXAMPLES

[0104] Coating formulations were prepared by combining a 24.7 wt. % shellac solution in aqueous ammonia (Stroever GmbH & Co KG, SSB AQUAGOLD) with a beeswax, rice bran wax, or sunflower wax emulsion. Shellac flakes or powders could be used equivalently to produce the shellac solution de novo. The beeswax emulsion contained 31.8 wt. % solids (Kahlwax 8105 Yellow Beeswax), the rice bran wax emulsion contained 45 wt. % solids (Kahlwax 2811 rice bran wax), and the sunflower wax emulsion contained 50 wt. % solids (Praj Industries Ltc., SUNWAX, sunflower wax). Each wax emulsion contained 3-3.5 wt. % oleic acid, 1.2-1.5 wt. % propylene glycol, and 1.5-2.5 wt. % aqueous ammonia introduced from a commercial 24.5 wt. % ammonia solution. Talc was optionally added to some of the coating formulations (Elementis Minerals B.V., grade C10 granules, 90.56 talc solids and balance moisture). Talc was introduced by combining the talc with the shellac solution andhomogenized with a speed mixer or homogenizer before adding the wax emulsion thereto. The resulting combined mixture was further blended with a speed mixer or propeller stirrer. Further composition details of the coating formulations are provided in Table 1 below. The talc amounts in Table 1 represent the dry-weight equivalent of talc added to the mixture. The type of wax used in each entry in Table 1 is designated as follows: BW=beeswax, RB=rice bran wax, and SF=sunflower wax. Theoretical total solids represents the sum of shellac solids and wax solids (each based on the concentration and amount of solution or emulsion used) and added talc solids (when used). Measured total solids represents the value determined using a LMA200 solids tester (Sartorius®). Table 1 Entry Shellac Wt. % Wax Wt. % Wax Wt. % Theoretical Total Measured Total of on)al of on) orBuschman coating rods, either as a single-layer (base coat) coating or as a double-layer coating (base coat plus top coat). Properties of the single-layer coatings for the formulations of Entries 1-25 are shown in Table 2 below. Properties of single-layer and double-layer coatings for the formulations for Entries 26-34 are shown in Table 3 below. The double-layer coatings in Table 3 were prepared by disposing the coating formulation on the paper substrate, drying, and then applying the coating formulation upon the initially deposited layer. Properties of double-layer coatings formed from a talc- containing base coat and a talc-free top coat are shown in Table 4 below. Coating weights for each portion of the double-layer coatings are shown in Tables 3 and 4.

[0106] Coating weights were determined according to the following procedure. An A4 sheet of paper was weighed (m1) using an analytical scale and fixed in a special holder. About 5 mL of coating formulation was applied as a line at the top of the A4 sheet and then spread over the whole sheet surface by passing the RDS or Buschman coating rod from top to the bottom of the A4 sheet, applying constant pressure while doing so. After that, the A4 sheet was weighed again (m2) to determine the coating weight and dried for 1 minute in a ventilated oven at 105°C. The coating weight (CW) was calculated according to Equation 1, CW (g / m2) = (^2 - ^1) · TS · 16 Equation 1 where TS is the solid content of the formulation expressed as a decimal percentage. The multiplier ‘16’ in Equation 1 is used to convert the result from a per sheet basis to a per meter basis. There are 16 sheets of A4 paper per square meter.

[0107] Cobb Indices were determined according to ISO 535 / ASTM D3285 / TAPPI T441 method using standard Cobb sizing testers with a diameter of 10 cm (Gurley Precision Instruments, Inc.). The coated paper was initially weighed (m0). Afterward, the ring was sealed onto the paper with a gasket and 100 mL of distilled water was poured inside the ring. After 30 minutes (1800 s), the paper was weighed again (m1). The Cobb index value was calculated according to Equation 2 over at least two sample replicates. Cobb index (g / m²) = (m1-m0) · 100 Equation 2

[0108] WVTR (MVTR) values were determined with a PERMATRAN-W®Model 3 / 34 Water Vapor Transmission Rate system from Mocon®(now Ametek GmbH), which operates according to ASTM F1249. The test cell of this instrument consists of two chambers: one dry chamber with flowing carrier gas (Nitrogen), and one “humid” chamber with controlled relative humidity (nitrogen+water vapor). The coated paper was placed between the two chambers and the water vapor escaping fromthe humidity chamber through the sample into the carrier gas chamber is carried to an infrared sensor which then measures the amount of moisture and calculates the WVTR value. Tests were performed at 38°C and 90% relative humidity (so-called “tropical conditions”). At least two replicates were made for each sample.

[0109] For samples having a WVTR higher than measurable using the PERMATRAN-W instrument, measurements were performed gravimetrically based on ASTM E96. The method uses a vapometer cup (Thwing Albert Model 68-2 - 3 / 4" deep), where the coated paper under test was placed and sealed to the cup opening. Inside the test cup, there is an environment of low water vapor pressure, created by filling the cup with calcium chloride desiccant (Carl Roth®). An initial weight of the assembled test system was determined (m0), and the cell was then placed in a HPP260 humidity chamber from Memmert®at 38°C and 90% relative humidity (so-called “tropical conditions”). The vapor pressure difference between the inside and the outside of the cup causes water molecules to migrate through the permeable material to result in a mass gain. After 24 hours, the test system was weighed again (m1) and the WVTR value was determined as according to Equation 3. At least two replicates were made for each sample. WVTR [g / (m²·day)] = (m1-m0) · 316 Equation 3 The multiplier ‘316’ in Equation 3 is used to convert the result from a per sample basis to a per meter basis. There are 316 samples per square meter in the test system.

[0110] Oil and grease resistance was determined according to TAPPI Standard Test Method T 559 using a kit available from 3M. The standard kit test solutions contain castor oil, hexane, and toluene, having increasing amounts of castor oil between solution 12 (lowest amount) and solution 1 (highest amount). The test solutions were applied onto a coated paper substrate, and resistance to the test solution was determined visually on a scale of 1 to 12, the number corresponding to the number of solution resulting in coating failure.

[0111] Heat sealing tests were performed using a HST-H3 PARAM®heat sealer from Labthink. The heat sealing conditions were as follows: pressure 200 kPa, 1 second dwell time and varying temperatures depending on the sealing ability of each sample (starting from 120°C). Two different types of sealing were tested: the coated face to coated face (A-A) sealing and the coated face to uncoated paper (A-B) sealing. The values HS T (A-A) and HS T (A-B) in the Tables 2-4 below correspond to the temperature of the heat sealer jaws at which the sample presents fiber tear after sealing.Table 2 E t ti bb I d MVTR H T H T RTable 3 E t ti bb I d MVTR H T H T RTable 4 Entry Entry Coating Cobb MVTR HS T HS T OGR. - p the coating formulations of Entries 1-25. FIG.1 is directed to Entries 1-9 (beeswax), FIG.2 is directed to Entries 1 and 10-17 (rice bran wax), and FIG.3 is directed to Entries 1 and 18-25 (sunflower wax). FIG. 4 is an overlay plot of MVTR as a function of the amount of all three types of tested wax. Without being bound by theory or mechanism, the shape of the plot for sunflower wax is believed to arise from the lower acid value of this wax in comparison to the other two waxes. It should be further noted that the best-fit lines in the plots of FIGS. 1-4 are for ease of readability and do not imply a defined functional correlation as a function of temperature.

[0113] The data in Table 4 demonstrates that the mica-containing coating formulations (Entries 26-34) are particularly effective when applied as a base coat and overcoated with a coating formulation lacking mica. Double-layer coatings made from the mica-containing coating formulations (Table 3) did not demonstrate the same type of sharp decrease in Cobb Index and MVTR.

[0114] All documents described herein are incorporated by reference herein for purposes of all jurisdictions where such practice is allowed, including any priority documents and / or testing procedures to the extent they are not inconsistent with this text. As is apparent from the foregoinggeneral description and the specific embodiments, while forms of the disclosure have been illustrated and described, various modifications can be made without departing from the spirit and scope of the disclosure. Accordingly, it is not intended that the disclosure be limited thereby. For example, the compositions described herein may be free of any component, or composition not expressly recited or disclosed herein. Any method may lack any step not recited or disclosed herein. Likewise, the term “comprising” is considered synonymous with the term “including.” Whenever a method, composition, element or group of elements is preceded with the transitional phrase “comprising,” it is understood that we also contemplate the same composition or group of elements with transitional phrases “consisting essentially of,” “consisting of,” “selected from the group of consisting of,” or “is” preceding the recitation of the composition, element, or elements and vice versa.

[0115] Unless otherwise indicated, all numbers expressing quantities of ingredients, properties such as molecular weight, reaction conditions, and so forth used in the present specification and associated claims are to be understood as being modified in all instances by the term “about.” Accordingly, unless indicated to the contrary, the numerical parameters set forth in the following specification and attached claims are approximations that may vary depending upon the desired properties sought to be obtained by the embodiments of the present invention. At the very least, and not as an attempt to limit the application of the doctrine of equivalents to the scope of the claim, each numerical parameter should at least be construed in light of the number of reported significant digits and by applying ordinary rounding techniques.

[0116] Whenever a numerical range with a lower limit and an upper limit is disclosed, any number and any included range falling within the range is specifically disclosed. In particular, every range of values (of the form, “from about a to about b,” or, equivalently, “from approximately a to b,” or, equivalently, “from approximately a-b”) disclosed herein is to be understood to set forth every number and range encompassed within the broader range of values. Also, the terms in the claims have their plain, ordinary meaning unless otherwise explicitly and clearly defined by the patentee. Moreover, the indefinite articles “a” or “an,” as used in the claims, are defined herein to mean one or more than one of the elements that it introduces.

[0117] One or more illustrative embodiments are presented herein. Not all features of a physical implementation are described or shown in this application for the sake of clarity. It is understood that in the development of a physical embodiment of the present disclosure, numerous implementation-specific decisions must be made to achieve the developer’s goals, such as compliance with system-related, business-related, government-related and other constraints, which vary by implementation and from time to time. While a developer’s efforts might be time-consuming, suchefforts would be, nevertheless, a routine undertaking for one of ordinary skill in the art and having benefit of this disclosure.

[0118] Therefore, the present disclosure is well adapted to attain the ends and advantages mentioned as well as those that are inherent therein. The particular embodiments disclosed above are illustrative only, as the present disclosure may be modified and practiced in different but equivalent manners apparent to one having ordinary skill in the art and having the benefit of the teachings herein. Furthermore, no limitations are intended to the details of construction or design herein shown, other than as described in the claims below. It is therefore evident that the particular illustrative embodiments disclosed above may be altered, combined, or modified and all such variations are considered within the scope and spirit of the present disclosure. The embodiments illustratively disclosed herein suitably may be practiced in the absence of any element that is not specifically disclosed herein and / or any optional element disclosed herein.

Claims

CLAIMS What is claimed is the following:

1. A coating formulation comprising:an aqueous fluid; at least partially neutralized shellac dissolved in the aqueous fluid; wherein no synthetic polymers are present in the aqueous fluid; and a plurality of wax particles emulsified as solids in the aqueous fluid.

2. The coating formulation of claim 1, further comprising:an inorganic fill material.

3. The coating formulation of claim 2, wherein the inorganic fill material comprises talc, kaolin,montmorillonite, mica, or any combination thereof.

4. The coating formulation of claim 2, wherein the coating formulation contains, based on totalsolids, about 0.5 wt. % to about 10 wt. % wax particles, about 5 wt. % to about 20 wt. % shellac, and about 5 wt. % to about 40 wt. % inorganic fill material.

5. The coating formulation of claim 4, wherein the inorganic fill material comprises talc, kaolin,montmorillonite, mica, or any combination thereof.

6. The coating formulation of claim 1, wherein the coating formulation contains, based on totalsolids, about 2 wt. % to about 40 wt. % wax particles, and about 5 wt. % to about 25 wt. % shellac.

7. The coating formulation of any one of claims 1-6, wherein shellac is the only polymerpresent in the coating formulation.

8. The coating formulation of any one of claims 1-6, wherein the shellac is at least partiallyneutralized with a base comprising ammonia.

9. The coating formulation of claim 8, wherein the base further comprises one or more of anamine, an alkali metal hydroxide, or any combination thereof.

10. A coated substrate comprising:a base substrate; and a thin-film coating formed upon a surface of the base substrate and comprising: a continuous matrix comprising at least partially neutralized shellac; and a plurality of wax particles dispersed within the continuous matrix; wherein the thin-film coating has a moisture vapor transmission rateof at most about 1200 m2 / g, as measured at 38°C and 90% relative humidity by ASTM F1249 or ASTM E96, and / or a Cobb index of at most about 105 m2 / g, as measured over 1800 s by ISO 535, ASTM D3285, or TAPPI T441.

11. The coated substrate of claim 10, wherein no synthetic polymers are present in the thin-filmcoating.

12. The coated substrate of claim 10, wherein shellac is the only polymer present in the thin-filmcoating.

13. The coated substrate of any one of claims 10-12, further comprising:an inorganic fill material dispersed within the continuous matrix.

14. The coated substrate of claim 13, wherein the inorganic fill material comprises talc, kaolin,montmorillonite, mica, or any combination thereof.

15. The coated substrate of claim 13, wherein the thin-film coating contains, based on totalmass of the thin-film coating, about 0.5 wt. % to about 10 wt. % wax particles, about 5 wt. % to about 20 wt. % shellac, and about 5 wt. % to about 40 wt. % inorganic fill material.

16. The coated substrate of claim 15, wherein the fill material comprises talc, kaolin,montmorillonite, mica, or any combination thereof.

17. The coated substrate of any one of claims 10-12, wherein the thin-film coating contains,based on total mass of the thin-film coating, about 2 wt. % to about 40 wt. % wax particles, and about 5 wt. % to about 25 wt. % shellac.

18. The coated substrate of any one of claims 10-12, wherein the shellac is at least partiallyneutralized with a base comprising ammonia.

19. The coated substrate of claim 18, wherein the base further comprises one or more of anamine, an alkali metal hydroxide, or any combination thereof.

20. The coated substrate of any one of claims 10-12, wherein the base substrate is paper.

21. A food container comprising the coated substrate of any one of claims 10-12.

22. The food container of claim 21, wherein the base substrate is paper.

23. A method comprising:providing a base substrate; applying the coating formulation of any one of claims 1-6 to a surface of the base substrate; and removing the aqueous fluid to produce a thin-film coating upon the surface of the base substrate, the thin-film coating comprising a continuous matrix comprising at least partially neutralized shellac, and a plurality of wax particles dispersed within the continuousmatrix.

24. The method of claim 23, wherein the thin-film coating has a moisture vapor transmissionrate of at most about 1200 m2 / g, as measured at 38°C and 90% relative humidity by ASTM F1249 or ASTM E96, and / or a Cobb index of at most about 105 m2 / g, as measured over 1800 s by ISO 535, ASTM D3285, or TAPPI T441.

25. The method of claim 23, wherein shellac is the only polymer present in the coatingformulation.

26. The method of claim 23, wherein the shellac is at least partially neutralized with a basecomprising ammonia.

27. The method of claim 26, wherein the base further comprises one or more of an amine, analkali metal hydroxide, or any combination thereof.

28. The method of claim 23, wherein the coating formulation is applied to the surface of thebase substrate by flexo coating, gravure coating, rod coating, blade coating, spray coating, or any combination thereof.

29. The method of claim 23, wherein the coating formulation is applied directly to the basesubstrate as a base coat, optionally with a second application of the coating formulation being applied upon the base coat to form a top coat.

30. The method of claim 23, wherein the coating formulation is a first coating formulation and asecond coating formulation having a different composition than the first coating formulation, the first coating formulation being applied directly to the base substrate as a base coat, and the second coating formulation being applied upon the base coat to form a top coat.

31. The method of claim 23, further comprising:heat treating the thin-film coating after removing the aqueous fluid.

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