Synthetic polymer-free coating formulations containing shellac and related methods

Abstract

When deposited on a base substrate, the coating can impart moisture resistance. A coating formulation free of synthetic polymers can include 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. A thin film coating formed by depositing the coating formulation and removing the aqueous fluid therefrom can be substantially impermeable to water vapor, as determined by the thin film coating having a moisture vapor transmission rate (measured by ASTM F1249 or ASTM E96 at 38°C and 90% relative humidity) of at most about 1200 m 2 / g and / or a Cobb's index (measured by ISO 535, ASTM D3285, or TAPPI T441 over 1800 seconds) of at most about 105 m 2 / g.

Description

Background Technology

[0001] Barrier coatings are used on various substrates to prevent or limit the contact of substances such as water, oxygen or other gases, grease, etc., with the substrate. Industries that use barrier coatings include, for example, food packaging, pharmaceutical manufacturing and packaging, and cosmetic manufacturing and packaging.

[0002] Most barrier coatings are based on synthetic polymer materials that are essentially impermeable to the substances of concern. However, with increasing environmental awareness and government regulations, there is a growing demand for barrier coatings and similar materials that do not contain synthetic polymers. The main issue is that most synthetic polymers are not readily soluble or biodegradable, and therefore can persist in the environment as microplastics for a long time. In fact, the environmental problems associated with microplastics are so impactful that the EU has mandated their phase-out in many industries, and other countries are expected to follow suit in the coming years.

[0003] Another possible type of barrier coating is based on thin-film metal layers. While thin-film metal layers offer robust barrier coating performance in many cases, they are sometimes used in combination with polymers, and the resulting mixed product streams may not be easily compostable or recyclable. Furthermore, thin-film metal layers can lead to higher production costs than polymer-based barrier coatings. Attached Figure Description

[0004] The accompanying drawings are included to illustrate certain aspects of this disclosure and should not be considered as an exclusive configuration. As will be apparent to those skilled in the art who benefit from this disclosure, the disclosed subject matter is capable of considerable modifications, alterations, combinations, and equivalents in form and function.

[0005] Figure 1-4 This is a graph of the Cobb index and MVTR as a function of the amount of wax in the coating formulations of this disclosure. Detailed Implementation

[0006] This disclosure generally relates to coating technology, and more specifically, to coating formulations and barrier coatings formed without the use of synthetic polymers.

[0007] As mentioned above, coating formulations containing synthetic polymers have become less than ideal in many ways, for example, due to their tendency to form microplastics in the environment. As used herein, the term "microplastics" refers to polymer particles having a maximum size of approximately 5 mm in any dimension, wherein the polymer is inherently abiotic (i.e., not naturally occurring), water-insoluble, and non-biodegradable. Because microplastics are a growing environmental problem, polymer coatings based on synthetic polymers that readily form microplastics are currently being phased out.

[0008] This disclosure provides coating formulations and thin-film coatings formed therefrom, which are based on naturally sourced resin materials and contain little or no other types of polymers, particularly synthetic polymers. Due to the natural source of the resin materials, the environmental impact of these coating formulations is significantly lower than that of conventional coating formulations and thin-film coatings based on synthetic polymers. Furthermore, the thin-film coatings produced according to this disclosure exhibit advantageous performance in barrier coating applications.

[0009] Specifically, the coating formulations and film coatings described herein utilize shellac as a naturally derived resin material. Advantageously, the shellac may be at least partially neutralized to promote solubility in aqueous fluids, thereby contributing to the benefits described herein. Once properly dissolved in water or a similar aqueous fluid, the resulting shellac solution can combine with wax particles in a wax emulsion to provide even more robust barrier coating properties. At the very least, the film coatings formed according to this disclosure exhibit robust moisture-proof barrier coating properties. Furthermore, the film coatings exhibit good oil and grease resistance, which is particularly desirable for forming barrier coatings in food packaging. Further details regarding the coating formulations and the film coatings formed therefrom are provided below.

[0010] The coating formulation disclosed herein may comprise: an aqueous fluid, at least partially neutralized shellac dissolved in the aqueous fluid, and a plurality of wax particles emulsified into a solid state in the aqueous fluid. Preferably, the aqueous fluid does not contain synthetic polymers.

[0011] All or some of the components present in the coating formulation are available from natural sources. Shellac is a naturally derived resin that can facilitate the formation of a thin film coating with barrier properties. Further details regarding suitable shellacs are provided below. Additionally, if desired, waxes and other components of the coating formulation may also be of natural origin to provide further environmental benefits.

[0012] The aqueous fluids applicable to this disclosure may contain water or water mixed with a water-miscible organic solvent such as an alcohol or glycol. Sometimes such water-miscible organic solvents may be present to provide antifreeze properties by lowering the freezing point of the aqueous fluid.

[0013] The amount of the aqueous fluid in the coating formulation described herein may be 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%, for example 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 based on the total mass of the coating formulation.

[0014] As used herein, the term "solids" refers to any component of the coating formulation other than the aqueous fluid. Therefore, when calculating based on the mass percentage of total solids, the term "total solids" represents the combined mass of all components (solids, liquids, and / or gases) blended with the aqueous fluid in any form. Depending on the specific component and its solubility in the aqueous fluid, the component may dissolve in the aqueous fluid or remain dispersed as a liquid or solid. For example, the dispersed solids or liquids may exist as an emulsion.

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

[0016] In a non-limiting example, the ratio of dissolved solids to particulate solids in the aqueous emulsion may be 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 based on mass. Therefore, the amount of dissolved solids may be greater than or less than the amount of particulate solids. In this disclosure, the dissolved solids may include at least partially neutralized shellac. The particulate solids may include wax particles and other insoluble materials.

[0017] The term "shellac" refers to a resinous material obtained from the secretions of female lac insects, comprising oligomers of at least aleuritic acid and shellacic acid. Depending on the source and harvest season, the shellac applicable to this disclosure can vary in color and aleuritic acid / shellacic acid ratio. Shellac can be obtained in different grades depending on its degree of purification and dewaxing. Less dewaxed shellac is less soluble in water when at least partially neutralized. Less purified shellac results in a darker color. The degree of dewaxing and purification depends on the acid value and how easily the shellac disperses in water. Golden shellac is a variant of orange shellac, in which many natural shellac dyes are mechanically removed by filtration with activated carbon. While other grades are chemically bleached (e.g., using sodium hypochlorite) and chemically dissolved in caustic solutions (e.g., using sodium carbonate), super golden or extra-gold shellac can be quite light in color and more water-resistant. Button-shaped shellac and granular shellac are other shellac grades commonly encountered and applicable herein. Even shellac, the coarsest grade, can be used in this document. While certain grades of shellac may be preferred depending on the conditions under which the film coating will be exposed, it should be understood that any grade of shellac, whether dewaxed or not, is suitable for the disclosure herein.

[0018] In some embodiments, the shellac used in the coating formulation and the film coating formed therefrom may be at least partially dewaxed shellac, which may include fully dewaxed shellac. For example, at least partially dewaxed shellac is particularly desirable for forming a barrier coating on food containers. To facilitate the dissolution of the at least partially dewaxed shellac, it may be present in a at least partially neutralized form, as discussed further below. Suitable procedures for shellac dewaxing are well known to those skilled in the art.

[0019] The waxy residue obtained after dewaxing shellac (shellac wax) can constitute at least a portion of the wax particles that emulsify into a solid in the aqueous fluid. Other suitable waxes and their amounts are discussed further below.

[0020] Shellac can be added to the aqueous fluid when dissolved in a suitable organic solvent such as methanol or ethanol. The resulting shellac dispersion can then be at least partially neutralized with a suitable base to promote its dissolution. Alternatively, shellac can be at least partially dissolved in the aqueous fluid using a suitable base without initially using an organic solvent. In either case, the at least partially neutralized shellac can become partially or completely soluble in the aqueous fluid by forming one or more ionic charges thereon.

[0021] Preferably, the base used to at least partially neutralize the acid groups of the shellac may comprise ammonia, either alone or in combination with other bases. Other suitable bases that may be used in combination with ammonia or in any combination when ammonia is unavailable may include, for example, amines (e.g., ethanolamine, diethanolamine, triethanolamine, trimethylamine, diethylamine, dimethylethylamine, triethylamine, etc.) or alkali metal bases (e.g., NaOH, KOH, etc.).

[0022] In this disclosure, the shellac may be completely or partially neutralized. Any degree of neutralization that promotes the 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. The aforementioned neutralization amounts may be achieved using a corresponding stoichiometric amount of base, or a stoichiometric excess of base may be used to promote complete neutralization of the shellac.

[0023] Shellac may be present in the coating formulations described herein in amounts up to about 50 wt%, or up to about 40 wt%, or up to about 30 wt%, or up to about 20 wt%, for example, 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 based on total solids measurements. The resulting thin film coating may contain similar amounts of shellac.

[0024] Waxes are hydrophobic organic substances found in petroleum and other oily materials. They are biosynthesized from plants and animals, or obtained through synthesis. Waxes are typically malleable solids at room temperature and may contain one or more higher alkanes (alkanes), particularly ortho- or branched C4 hydrocarbons. 16 -C 100 Alkanes or C 20 -C 50 Alkanes, lipids, and / or oils. Suitable waxes for use in this disclosure may include, but are not limited to, alkane waxes, oxidized alkane waxes, polyolefin waxes, oxidized polyolefin waxes, natural waxes, oxidized natural waxes, and any combination thereof. Furthermore, a waxy component obtained from dewaxed shellac (i.e., shellac wax) may be present as at least a portion of the wax particles in the coating formulation, with or without other waxes. As used herein, a wax is considered “oxidized” if an oxygen-containing functional group, such as an alcohol, carboxylic acid, epoxide, etc., is introduced into the otherwise unsubstituted (alkane) hydrocarbon backbone. The amount of oxygen-containing functional group introduced into a particular wax may be, for example, sufficient to reduce the hydrophobicity of the wax to the degree required to promote the formation of an emulsion-like wax.

[0025] Specific examples of alkane waxes and lipid waxes (including natural waxes) applicable to this disclosure may include, but are not limited to, pine wax, beeswax, hydrogenated lipids, refined waxes, semi-refined waxes, flake waxes, microcrystalline waxes, plant-based waxes such as soybean and palm wax, carnauba wax, rice bran wax, lignite wax, sugarcane wax, sunflower wax, hydrogenated castor oil, poly(3-hydrogenated butyrate-co-3-hydroxyvalerate), synthetic waxes such as oligomer waxes derived from linear α-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 contain at least one natural wax or consist essentially of at least one natural wax. Coating formulations containing at least one natural wax or consisting essentially of at least one natural wax may be particularly advantageous for use in combination with food packaging applications or other applications where synthetic waxes or undesirable waxes may not be used.

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

[0028] Suitable waxes used in the coating formulations of this disclosure may have a melting point of about 50°C or higher, and when emulsified or dispersed in a shellac matrix, have an average diameter as high as about 50,000 nm (50 micrometers), for example, about 400 nm or less, or about 300 nm or less, or about 200 nm or less, or about 100 nm or less, for example, an average diameter of 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 be about 100 nm to about 400 nm.

[0029] The amount of wax present in the coating formulations described herein may be as high as about 60 wt%, or as high as about 50 wt%, or as high as about 40 wt%, or as high as about 30 wt%, for example, 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 based on the total solids in the aqueous emulsion. The resulting thin film coating may contain similar amounts of wax.

[0030] In non-limiting examples, the shellac to wax ratio in this disclosure may be 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 based on a mass meter.

[0031] Other components may be present in the coating formulations disclosed herein, such as one or more of the following: fillers (preferably inorganic fillers, such as inorganic particulates), effect pigments (colorants), dyes, optical brighteners, plasticizers, crosslinking agents, defoamers, antistatic agents, dispersants, thickeners, fillers, biocides, rheology modifiers, flow aids, lubricants, preservatives (e.g., benzisothiazolinone, methylisothiazolinone, methylchloroisothiazolinone, etc.), coalescence aids, buffers, cosolvents, surfactants, and any combination thereof. Such additional components may be present in amounts conventionally useful in the coating formulation. When present, such additional components may be selected independently of each other and in any suitable amount to alter one or more properties of the coating formulation (e.g., promote film formation) or provide suitability for a given application.

[0032] In some instances, the coating formulation and the thin film coating formed therefrom may further comprise inorganic filler materials, such as talc, mica, montmorillonite, kaolin, or any combination thereof.

[0033] When included, the presence of inorganic fillers, such as talc or other inorganic fillers, in the coating formulation may be as high as about 50 wt%, or as high as about 40 wt%, or as high as about 30 wt%, for example, about 5 wt% to about 40 wt%, or about 15 wt% to about 35 wt%, or about 20 wt% to about 30 wt%, based on total solids measurements. The resulting thin film coating may contain similar amounts of filler.

[0034] When forming a coated substrate according to this disclosure, coating formulations containing inorganic fillers are particularly desirable for use as a base coat. Without being bound by theory or mechanism, it is believed that a base coat (pre-coat) containing inorganic fillers can smooth surface roughness, allowing a top coat, which also contains wax particles and shellac, to deposit more effectively on the base coat. Kraft paper is an example of a substrate with high surface roughness, which can be effectively smoothed by using inorganic fillers in the base coat.

[0035] In some instances, the coating formulation may include a suitable plasticizer, which may be biodegradable or non-biodegradable in specific embodiments. There are believed to be no particular limitation on suitable plasticizers, except that they can be dispersed in the aqueous fluid in dissolved or emulsified form and exhibit the ability to promote robust film formation once evaporated on the base substrate. In some cases, a suitable plasticizer may also help transfer flexibility to the film. Some examples of suitable plasticizers may be derived from biological sources. Specific examples of suitable plasticizers may include, but are not limited to, epoxidized soybean oil, epoxidized linseed oil, castor oil, tannic acid, milk protein, polyethylene glycol, or any combination thereof. Other examples of suitable plasticizers still include, for example, epoxidized sunflower oil, cashew nut shells and modified cashew nut shells, glycidyl ether, chlorinated and phosphate / ester-containing plant-based plasticizers, phenanthrene-modified vegetable oils, tung oil esters containing hydroxyl and nitrogen groups, dimethyl oleate-based plasticizers, citrate esters, etc.

[0036] If included, the plasticizer may be present in amounts up to about 10 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%, for example, 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%, based on total solids measurements. The resulting film coating may contain similar amounts of plasticizer. The decision regarding whether to include a plasticizer may be based on the desired properties of the film coating and the conditions under which the film coating will be exposed.

[0037] Surfactants may be present in wax emulsions used in conjunction with coating formulations of this disclosure. The illustrative surfactants believed to be applicable to the coating formulations and film coatings disclosed herein are not particularly limited and may include one or more of cationic surfactants, anionic surfactants, neutral surfactants (nonionic surfactants), zwitterionic surfactants, or any combination thereof. If included (including surfactants introduced through binding with wax particles), the amount of surfactant present in the coating formulations and film coatings may be as high as about 20 wt%, or as high as about 15 wt%, or as high as about 10 wt%, or as high as about 8 wt%, or as high as about 5 wt%, or as high as about 4 wt%, or as high as about 3 wt%, or as high as about 2 wt%, or as high as about 1 wt%, or as high as about 0.5 wt%, based on total solids measurements.

[0038] The illustrative nonionic surfactants applicable to this disclosure include, but are not limited to, alkyl aryl polyether alcohols, alkylphenol ethoxylates, alkyl ethoxylates, poloxamer, fatty acid esters (e.g., fatty acid glycerides, fatty acid dehydrated sorbitol esters, fatty acid sorbitol esters, fatty acid lecithin esters, etc.), polyethylene oxide dehydrated sorbitol fatty acid esters, and any combination thereof. Illustrative cationic surfactants may include quaternary ammonium compounds. Illustrative anionic surfactants applicable to this disclosure include, but are not limited to, alkyl ethoxylate sulfates, alkyl ethoxylate sulfonates, alkylphenol ethoxylate sulfates, alkylphenol ethoxylate sulfonates, alkyl sulfates, alkyl sulfonates, alkyl aryl sulfates, alkyl aryl sulfonates, sulfosuccinates, alkyl carboxylates (e.g., ammonium salts of oleic acid), or any combination thereof. Illustrative zwitterionic surfactants applicable to this disclosure include various betaines and sulfobetaines.

[0039] The coated substrate disclosed herein may comprise a base substrate and a thin film coating formed on the surface of the base substrate. The thin film coating comprises a continuous matrix and a plurality of wax particles dispersed within the continuous matrix, the continuous matrix comprising at least partially neutralized shellac.

[0040] Once the coating formulation is applied to a base substrate and then dried, the thin film coating provides barrier coating properties. Specifically, the moisture vapor transmission rate (MVTR) of the thin film coating described herein can be up to about 1200 μm. 2 / g (measured at 38°C and 90% relative humidity according to ASTM F1249 or ASTM E96) and / or Cobb index may be up to approximately 105 mg / g. 2 / g (measured over 1800 seconds using ISO 535, ASTM D3285, or TAPPI T441). Furthermore, the thin-film coating also exhibits good oil and grease resistance. In some instances, the MVTR of the thin-film coating is approximately 1000 μm. 2 / g or lower, or about 800 m 2 / g or lower, or about 600 m 2 / g or lower, or about 400m 2 / g or lower, or about 300m 2 / g or lower, or about 200m 2 / g or lower, or about 100m 2 / g or lower and / or Cobb index can be around 100m 2 / g or lower, or about 95m 2 / g or lower, or about 90m 2 / g or lower, or about 85m 2 / g or lower, or about 80m 2 / g or lower, or about 75m 2 / g or lower, or about 70m 2 / g or lower, or about 65m 2 / g or lower, or about 60m 2 / g or lower, or about 55m 2 / g or lower, or about 50m 2 / g or lower, or about 45m 2 / g or lower, or about 40m 2 / g or lower, or about 35m 2 / g or lower, or about 30m 2 / g or lower. Therefore, in one or more examples, the MVTR of the thin film coating can be approximately 200 μg. 2 / g or lower, or about 100m 2 / g or lower, and the Cobb index is about 100m 2 / g or lower or about 50m 2 / g or lower, including approximately 50 m 2 / g - approximately 100 m 2 Cobb index / g.

[0041] It is believed that there are no particular limitations on the substrate on which the thin film coating of this disclosure can be formed, provided that there is sufficient adhesion between the thin film coating and the substrate surface. In non-limiting examples, substrates on which the coating formulations of this disclosure can be coated include, but are not limited to, paper, cardboard and other types of packaging, films, wood (e.g., for architectural coatings), metals (e.g., metal cans or metal-lined bags), other polymers (e.g., within food storage containers and polymer-based circuit board assemblies), etc. Similarly, the coating formulations described herein can also be used for coating sizing on fibers.

[0042] The thickness of the thin film coating can be approximately 0.5 mm. m - approximately 5 m, or about 1 m - approximately 400 m, or about 2 m - approximately 300 m, or about 5 m - approximately 200 m, or about 10 m - approximately 100 m, or about 50 m - approximately 300 m, or about 75 m - approximately 225 The coating thickness can be selected based on its suitability for a given application. A suitable coating weight is approximately 5 g / m. 2 - Approximately 25g / m 2 .

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

[0044] Applying the coating formulation to the base substrate can be accomplished using any of a variety of methods, such as dipping, spraying, bar coating or roller coating, tumbling, or by using apparatus such as a sizing press, water tank, doctor blade coater, cast iron coater, bar coater, air knife coater, curtain coater, film press coater, flexographic coater, etc., or any combination thereof. In an advantageous embodiment, the coating formulation can be applied to the base substrate using flexographic coating, gravure coating, bar coating, doctor blade coating, spraying, or any combination thereof. Details regarding the foregoing techniques for applying the coating formulation to the base substrate will be well known to those skilled in the art.

[0045] The coating formulation can be applied directly or indirectly to the base substrate as one or more coatings. When applied directly, the coating formulation can be applied directly to the surface of the base substrate as a primer, which may optionally be topcoated with one or more additional coatings. The composition of the one or more additional coatings may be the same as or different from that of the primer. Preferably, the primer and the one or more additional coatings may each contain partially or fully neutralized shellac. When applied indirectly, the coating formulation can be applied as a topcoat over which the primer is topcoated. The topcoat and primer may have the same or different compositions. Preferably, the topcoat and primer may each contain partially or fully neutralized shellac. In some cases, advantageous performance can be achieved by depositing the coating formulation as multiple coatings, rather than as a single coating with equal weights.

[0046] In some instances, the coating formulation may be a first coating formulation and a second coating formulation with a different composition from the first coating formulation, wherein each coating formulation contains at least partially neutralized shellac and wax particles, and the first coating formulation is applied directly to the base substrate as a base layer, and the second coating formulation is applied to the base layer to form a top layer. In some instances, the first coating formulation of this disclosure containing inorganic fillers may be applied as a base layer to the base substrate, and the second coating formulation of this disclosure without inorganic fillers may be applied as a top layer to the base layer. The top layer may comprise one or more coatings formed by the second coating formulation.

[0047] In some instances, the method of this disclosure may further include heat-treating the thin film coating after removing the aqueous fluid.

[0048] The implementation plan disclosed in this article includes:

[0049] A. A coating formulation. The coating formulation comprises: an aqueous fluid; shellac dissolved in the aqueous fluid and at least partially neutralized; wherein no synthetic polymers are present in the aqueous fluid; and a plurality of wax particles emulsified into a solid in the aqueous fluid.

[0050] B. Coated substrate. The coated substrate comprises: a base substrate; and a thin film coating formed on the surface of the base substrate, and comprising: a continuous matrix containing at least partially neutralized shellac; and a plurality of wax particles dispersed within the continuous matrix; wherein the moisture permeability of the thin film coating is at most about 1200 μm. 2 / g, which is measured by ASTM F1249 or ASTM E96 at 38°C and 90% relative humidity, and / or the Cobb index is at most about 105 m 2 / g, which is measured within 1800 seconds according to ISO 535, ASTM D3285 or TAPPI T441.

[0051] B1. A food container comprising a substrate coated with B.

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

[0053] Each of the implementation schemes AC may have one or more additional elements in any combination of the following:

[0054] Element 1: The coating formulation or film coating further comprises an inorganic filler material.

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

[0056] Element 2: The inorganic filler material therein comprises talc, kaolin, montmorillonite, mica, or any combination thereof.

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

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

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

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

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

[0062] Element 6: The shellac is at least partially neutralized with an alkali containing ammonia.

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

[0064] Element 8: wherein the thin film coating does not contain synthetic polymers, and / or wherein shellac is the only polymer present in the thin film coating.

[0065] Element 9: The basic substrate mentioned therein is paper.

[0066] Element 10: The moisture permeability of the thin film coating is at most about 1200 μm. 2 / g, which is measured by ASTM F1249 or ASTM E96 at 38°C and 90% relative humidity, and / or the Cobb index is at most about 105 m 2 / g, which is measured within 1800 seconds according to ISO 535, ASTM D3285 or TAPPI T441.

[0067] Element 11: The coating formulation is applied to the surface of the base substrate by flexographic coating, gravure coating, bar coating, squeegee coating, spraying, or any combination thereof.

[0068] Element 12: wherein the coating formulation is applied directly to the base substrate as a base layer, and optionally the coating formulation is applied a second time to the base layer to form a top layer.

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

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

[0071] By way of non-limiting example, exemplary combinations applicable to AC 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 implementation methods disclosed herein include:

[0073] Clause 1. A coating formulation comprising:

[0074] Aqueous fluids;

[0075] Shellac dissolved in the aqueous fluid and at least partially neutralized;

[0076] The aqueous fluid in which synthetic polymers are not present; and

[0077] Multiple wax particles that emulsify into a solid in the aqueous fluid.

[0078] Clause 2. The coating formulation of Clause 1 further includes: inorganic filler materials.

[0079] Clause 3. The coating formulation of Clause 2, wherein the inorganic filler material comprises talc, kaolin, montmorillonite, mica or any combination thereof.

[0080] Clause 4. The coating formulation of Clause 2, wherein the coating formulation contains about 0.5 wt% to about 10 wt% of wax particles, about 5 wt% to about 20 wt% of shellac and about 5 wt% to about 40 wt% of inorganic filler, based on total solids.

[0081] Clause 5. The coating formulation of Clause 4, wherein the inorganic filler material comprises talc, kaolin, montmorillonite, mica or any combination thereof.

[0082] Clause 6. The coating formulation of Clause 1, wherein the coating formulation contains about 2 wt% to about 40 wt% wax particles and about 5 wt% to about 25 wt% shellac, based on total solids.

[0083] Clause 7. A coating formulation of any one of Clauses 1-6, wherein shellac is the only polymer present in the coating formulation.

[0084] Clause 8. The coating formulation of any one of Clauses 1-6, wherein the shellac is at least partially neutralized with an alkali containing ammonia.

[0085] 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.

[0086] Clause 10. A coated substrate comprising:

[0087] Basic substrate; and

[0088] A thin film coating formed on the surface of the base substrate, and comprising:

[0089] A continuous matrix containing at least partially neutralized shellac; and

[0090] Multiple wax particles dispersed in the continuous matrix;

[0091] The moisture permeability of the thin film coating is at most about 1200 μm. 2 / g, which is measured by ASTM F1249 or ASTM E96 at 38°C and 90% relative humidity, and / or the Cobb index is at most about 105 m 2 / g, which is measured within 1800 seconds according to ISO535, ASTM D3285 or TAPPI T441.

[0092] Clause 11. The coated substrate of Clause 10, wherein no synthetic polymer is present in the thin film coating.

[0093] Clause 12. The substrate coated in Clause 10, wherein shellac is the only polymer present in the thin film coating.

[0094] Clause 13. The coated substrate of any one of Clauses 10-12 further comprises: an inorganic filler material dispersed within the continuous matrix.

[0095] Clause 14. The coated substrate of Clause 13, wherein the inorganic filler material comprises talc, kaolin, montmorillonite, mica or any combination thereof.

[0096] Clause 15. The coated substrate of Clause 13, wherein the thin film coating contains about 0.5 wt% to about 10 wt% of wax particles, about 5 wt% to about 20 wt% of shellac and about 5 wt% to about 40 wt% of inorganic filler material, based on the total mass of the thin film coating.

[0097] Clause 16. The coated substrate of Clause 15, wherein the filler material comprises talc, kaolin, montmorillonite, mica or any combination thereof.

[0098] Clause 17. A substrate coated according to any one of Clauses 10-12, wherein the thin film coating contains about 2 wt% to about 40 wt% wax particles and about 5 wt% to about 25 wt% shellac, based on the total mass of the thin film coating.

[0099] Clause 18. The coated substrate of any one of Clauses 10-12, wherein the shellac is at least partially neutralized with an alkali containing ammonia.

[0100] Clause 19. The coated substrate of Clause 18, wherein the alkali further comprises one or more of an amine, an alkali metal hydroxide, or any combination thereof.

[0101] Clause 20. The coated substrate of any one of Clauses 10-12, wherein the base substrate is paper.

[0102] Clause 21. A food container comprising a substrate coated with any one of Clauses 10-12.

[0103] Clause 22. A method comprising:

[0104] Provide basic substrates;

[0105] Apply the coating formulation of any one of clauses 1-6 to the surface of the base substrate; and

[0106] The aqueous fluid is removed to form a thin film coating on the surface of the base substrate, the thin film coating comprising a continuous matrix and a plurality of wax particles dispersed in the continuous matrix, the continuous matrix comprising at least partially neutralized shellac.

[0107] Clause 23. The method of Clause 22, wherein the moisture permeability of said thin film coating is at most about 1200 μm. 2 / g, which is measured by ASTM F1249 or ASTM E96 at 38°C and 90% relative humidity, and / or the Cobb index is at most about 105 m 2 / g, which is measured within 1800 seconds according to ISO 535, ASTM D3285 or TAPPI T441.

[0108] Clause 24. The method of Clause 22, wherein shellac is the only polymer present in the coating formulation.

[0109] Clause 25. The method of Clause 22, wherein the shellac is at least partially neutralized with an alkali containing ammonia.

[0110] 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.

[0111] 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 flexographic coating, gravure coating, bar coating, squeegee coating, spraying, or any combination thereof.

[0112] Clause 28. The method of any one of Clauses 21-24, wherein the coating formulation is applied directly to the base substrate as a primer, optionally with a secondary application of the coating formulation to the primer to form a topcoat.

[0113] 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 from the first coating formulation, the first coating formulation being applied directly to the base substrate as a base layer, and the second coating formulation being applied on the base layer to form a top layer.

[0114] The method of any one of Clauses 30.21-24 further comprises: heat-treating the thin film coating after removing the aqueous fluid.

[0115] To facilitate a better understanding of this disclosure, the following examples of different representative embodiments are provided. These examples should not in any way be construed as limiting or restricting the scope of this disclosure.

[0116] Example

[0117] The coating formulation is prepared by combining a 24.7 wt% shellac solution (Stroever GmbH & Co KG, SSBAQUAGOLD) in ammonia water with a beeswax, rice bran wax, or sunflower wax emulsion. Shellac flakes or powder can be used equivalently to reproduce the shellac solution. The beeswax emulsion contains 31.8 wt% solids (Kahlwax 8105 yellow beeswax), the rice bran wax emulsion contains 45 wt% solids (Kahlwax 2811 rice bran wax), and the sunflower wax emulsion contains 50 wt% solids (PrajIndustries Ltc., SUNWAX, sunflower wax). Each wax emulsion contains 3-3.5 wt% oleic acid, 1.2-1.5 wt% propylene glycol, and 1.5-2.5 wt% ammonia water introduced from a commercial 24.5 wt% ammonia solution. Talc was optionally added to some coating formulations (Elementis Minerals BV, C10 grade granules, 90.56% talc solids and balance moisture). The talc was introduced by combining it with a shellac solution and homogenizing it using a high-speed mixer or homogenizer before adding the wax emulsion. The resulting combined mixture was further blended using a high-speed mixer or propeller agitator. Further compositional details of the coating formulations are provided in Table 1 below. The amounts of talc in Table 1 represent the dry weight equivalent of talc added to the mixture. The types of wax used in each entry of Table 1 are specified as follows: BW = beeswax, RB = rice bran wax, and SF = sunflower wax. Theoretical total solids represent the sum of shellac solids and wax solids (each based on the concentration and amount of the solution or emulsion used) and added talc solids (when used). Measured total solids represent the total solids measured using an LMA 200 solids analyzer (Sartorius). ® The measured value.

[0118] Table 1

[0119]

[0120]

[0121] The coating formulation is applied as a single-layer (base coat) or a double-layer (base coat plus top coat) coating via an RDS or Buschman coating bar to a bleached 80 g / m² coating. 2 Paper. The properties of single-layer coatings of the formulations for items 1-25 are shown in Table 2 below. The properties of single-layer and double-layer coatings of the formulations for items 26-34 are shown in Table 3 below. The double-layer coatings in Table 3 are prepared by placing the coating formulation on a paper substrate, drying it, and then applying the coating formulation onto the initially deposited layer. The properties of the double-layer coating formed by a talc-containing undercoat and a talc-free topcoat are shown in Table 4 below. The coating weight of each portion of the double-layer coating is shown in Tables 3 and 4.

[0122] The coating weight was determined according to the following procedure. An A4 sheet of paper (m1) was weighed using an analytical balance and held in a dedicated clamp. Approximately 5 mL of the coating formulation was applied as a line to the top of the A4 sheet, and then spread across the entire surface of the sheet by feeding the RDS or Buschman coating stick from the top to the bottom of the A4 sheet while applying constant pressure. The A4 sheet was then weighed again (m2) to determine the coating weight, and dried in a ventilated oven at 105°C for 1 minute. The coating weight (CW) was calculated according to Equation 1.

[0123] CW(g / m 2 )=( 2- 1)· TS ·16

[0124] Equation 1

[0125] Where TS is the solids content of the formulation, expressed as a decimal percentage. The multiplier "16" in Equation 1 is used to convert the result from being based on per sheet to being based on per meter. There are 16 A4 sheets per square meter.

[0126] The Cobb index was determined according to ISO 535 / ASTM D3285 / TAPPI T441 using a standard Cobb sizing tester (Gurley Precision Instruments, Inc.) with a diameter of 10 cm. The coated paper was initially weighed (m0). Then, a ring was sealed to the paper with a gasket, and 100 ml of distilled water was poured into the ring. After 30 minutes (1800 s), the paper was weighed again (m1). The Cobb index value was calculated by repeating the process on at least two samples according to Equation 2.

[0127] Cobb index (g / m²) = (m1 - m0) · 100

[0128] Equation 2

[0129] The WVTR (MVTR) value is derived from Mocon. ® PERMATRAN-W (now Ametek GmbH) ® The water vapor transmission rate (WVTR) was determined using a Model 3 / 34 system, operating according to ASTM F1249. The instrument's test unit consists of two chambers: a dry chamber with a flowing carrier gas (nitrogen) and a "humid" chamber with controlled relative humidity (nitrogen + water vapor). The coated paper is placed between the two chambers, and water vapor escaping from the humid chamber, passing through the sample, and entering the carrier gas chamber is transported to an infrared sensor, which then measures the amount of moisture and calculates the WVTR value. The test was conducted at 38°C and 90% relative humidity (so-called "tropical conditions"). Each sample was tested at least twice.

[0130] For samples with a WVTR higher than that measurable using the PERMATRAN-W instrument, measurements were performed based on ASTM E96 gravimetric analysis. The method uses a vapometer cup (Thwing Albert model 68-2-3 / 4” depth), in which the coated paper is placed and sealed to the cup opening. A low water vapor pressure environment exists within the test cup, which is achieved by using a calcium chloride desiccant (Carl Roth). ® The cup is filled to produce the effect. The initial weight (m0) of the assembled test system is measured, and then the unit is placed in a container from Memmert. ® The test system was placed in an HPP 260 humid chamber at 38°C and 90% relative humidity (so-called "tropical conditions"). The vapor pressure difference between the inside and outside of the cup caused water molecules to migrate through the permeable material, resulting in an increase in mass. After 24 hours, the test system (m1) was weighed again, and the WVTR value was determined according to Equation 3. At least two replicates were performed for each sample.

[0131] WVTR [g / (m 2 ·day)] =(m1-m0)·316

[0132] Equation 3

[0133] The multiplier "316" in Equation 3 is used to convert the result from being based on each sample to being based on each meter. There are 316 samples per square meter in the test system.

[0134] Oil and grease resistance were determined according to the TAPPI standard test method T 559 using a kit obtained from 3M. The test solution in this standard kit contains castor oil, hexane, and toluene, with increasing amounts of castor oil between solution 12 (minimum amount) and solution 1 (maximum amount). The test solution was applied to a coated paper substrate, and resistance to the test solution was visually determined on a scale of 1-12, where each number corresponds to the number of solutions that would cause coating failure.

[0135] The heat sealing test was performed using the HST-H3 PARAM from Labthink. ® The heat sealing was performed using a heat sealer. The heat sealing conditions were as follows: pressure 200 kPa, 1 second dwell time, and temperature varying depending on the sealing ability of each sample (starting from 120°C). Two different types of seals were tested: coated surface to coated surface (AA) seals and coated surface to uncoated paper (AB) seals. The values ​​HST(AA) and HST(AB) in Table 2-4 below correspond to the temperatures of the heat sealer jaws when the sealed sample exhibits fiber tearing.

[0136] Table 2

[0137]

[0138] Table 3

[0139]

[0140] Table 4

[0141]

[0142] Figure 1-3 This is a graph of the Cobb index and MVTR as a function of the amount of wax in the coating formulations listed in items 1-25. Figure 1 This involves items 1-9 (beeswax). Figure 2 This relates to items 1 and 10-17 (rice bran wax), and Figure 3 This relates to entries 1 and 18-25 (sunflower wax). Figure 4 This is an overlay plot of MVTR as a function of the amounts of all three types of test waxes. Unbound by theory or mechanism, the shape of the plot for sunflower wax is believed to be due to its lower acid value compared to the other two waxes. It should also be noted that... Figure 1-4 The best-fit line in the graph is for readability purposes and does not represent a constrained functional correlation as a function of temperature.

[0143] The data in Table 4 show that mica-containing coating formulations (items 26-34) are particularly effective when applied as a base coat and topcoated with mica-free coating formulations. Two-layer coatings made from the mica-containing coating formulations (Table 3) did not exhibit the same sharp decline in Cobb index and MVTR.

[0144] All references cited herein are incorporated herein by reference for purposes in all jurisdictions that permit such practice, including any priority documents and / or test procedures, provided they are not inconsistent with this document. As is apparent from the foregoing summary and specific embodiments, while the form of this disclosure has been illustrated and described, various modifications may be made without departing from the spirit and scope of this disclosure. Therefore, it is not intended to limit this disclosure. For example, a composition described herein may not contain any component or composition not expressly described or disclosed herein. Any method may omit any step not described or disclosed herein. Similarly, the term “comprising” is considered synonymous with the term “including.” When a method, composition, element, or group of elements precedes the transitional phrase “comprising,” it should be understood that the same composition or group of elements preceding the transitional phrases “substantially constitutes,” “consisting of,” “selected from,” or “is” is also considered, and vice versa.

[0145] Unless otherwise stated, all figures used in this specification and related claims to indicate the amount or properties of components, such as molecular weight, reaction conditions, etc., should be understood to be modified in all cases by the term "about". Therefore, unless stated to the contrary, the numerical parameters listed in the following specification and appended claims are approximate values ​​that may vary depending on the desired properties sought to be obtained according to embodiments of the invention. At the very least, and without attempting to limit the application of the doctrine of equivalents to the scope of the claims, each numerical parameter should be interpreted at least according to the number of significant figures reported and by applying conventional rounding techniques.

[0146] When a numerical range with a lower and upper limit is disclosed, any number falling within that range and any included range are specifically disclosed. In particular, each range of values ​​disclosed herein (in the form of “about a to about b,” or equivalently, “about a to b,” or equivalently, “about ab”) should be understood to describe every number and range encompassed within a wider range of values. Furthermore, unless otherwise explicitly and clearly defined by the patentee, the terms in the claims have their ordinary, common meaning. Additionally, the indefinite articles “a” or “an” used in the claims are defined herein as indicating one or more elements introduced therein.

[0147] This document presents one or more illustrative embodiments. For clarity, not all features of the physical implementation are described or shown in this application. It is understood that in the development of the physical implementations of this disclosure, many implementation-specific decisions must be made to achieve the developer's objectives, such as compliance with system-related, business-related, governmental-related, and other constraints that vary with the implementation and over time. While the developer's efforts may be time-consuming, such efforts will be routine tasks for those skilled in the art who benefit from this disclosure.

[0148] Therefore, this disclosure is well suited to achieving the stated objects and advantages, as well as those inherent therein. The specific embodiments disclosed above are merely illustrative, as this disclosure can be modified and practiced in different but equivalent ways, as will be apparent to those skilled in the art who benefit from the teachings herein. Furthermore, it is not intended to limit itself to the details of the construction or design shown herein, except as set forth in the following claims. Therefore, it is apparent that the specific illustrative embodiments disclosed above may be changed, combined, or modified, and all such changes are considered to be within the scope and spirit of this disclosure. The embodiments of the illustrative disclosure herein may be suitably practiced in the absence of any elements not specifically disclosed herein and / or any optional elements disclosed herein.

Claims

1. A coating formulation comprising: Aqueous fluids; Shellac dissolved in the aqueous fluid and at least partially neutralized; The aqueous fluid in which synthetic polymers are not present; and Multiple wax particles that emulsify into a solid in the aqueous fluid.

2. The coating formulation of claim 1, further comprising: Inorganic filler materials.

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

4. The coating formulation of claim 2, wherein the coating formulation contains 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 filler, based on total solids.

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

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

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

8. The coating formulation of any one of claims 1-6, wherein the shellac is at least partially neutralized with an alkali containing ammonia.

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

10. A coated substrate comprising: Basic substrate; and A thin film coating, formed on the surface of the base substrate, and comprising: A continuous matrix containing at least partially neutralized shellac; and Multiple wax particles dispersed in the continuous matrix; The moisture permeability of the thin film coating is at most about 1200 μm. 2 / g, which is measured by ASTM F1249 or ASTM E96 at 38°C and 90% relative humidity, and / or the Cobb index is at most about 105 m 2 / g, which is measured within 1800 seconds according to ISO 535, ASTM D3285 or TAPPI T441.

11. The coated substrate of claim 10, wherein the thin film coating does not contain synthetic polymers.

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

13. The coated substrate according to any one of claims 10-12, further comprising: Inorganic filler material dispersed in the continuous matrix.

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

15. The coated substrate of claim 13, wherein the thin film coating contains 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 filler, based on the total mass of the thin film coating.

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

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

18. The coated substrate according to any one of claims 10-12, wherein the shellac is at least partially neutralized with an alkali containing ammonia.

19. The coated substrate of claim 18, wherein the alkali further comprises one or more of an amine, 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 according to any one of claims 10-12.

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

23. A method comprising: Provide basic substrates; The coating formulation according to any one of claims 1-6 is applied to the surface of the base substrate; and The aqueous fluid is removed to form a thin film coating on the surface of the base substrate, the thin film coating comprising a continuous matrix and a plurality of wax particles dispersed in the continuous matrix, the continuous matrix comprising at least partially neutralized shellac.

24. The method of claim 23, wherein the moisture permeability of the thin film coating is at most about 1200 μm. 2 / g, which is measured by ASTM F1249 or ASTM E96 at 38°C and 90% relative humidity, and / or the Cobb index is at most about 105m 2 / g, which is measured within 1800 seconds according to ISO 535, ASTM D3285 or TAPPI T441.

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

26. The method of claim 23, wherein the shellac is at least partially neutralized with an alkali containing ammonia.

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

28. The method of claim 23, wherein the coating formulation is applied to the surface of the base substrate by flexographic coating, gravure coating, bar coating, squeegee coating, spraying, or any combination thereof.

29. The method of claim 23, wherein the coating formulation is applied directly to the base substrate as a primer, optionally the coating formulation is applied a second time to the primer to form a topcoat.

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

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

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