Swellable clay-containing aqueous barrier coating, and method for producing the same.

Abstract

Aqueous barrier coatings for paper products may contain chemically unmodified swellable clay dispersed in a binder, the swellable clay being dispersed under high shear conditions such that it exists in a tactoid form.

Description

[Technical Field]

[0001] Cross-reference of related applications The benefit of priority to U.S. Provisional Patent Application No. 63 / 454,558, filed on 24 March 2023, is claimed herein, and its disclosure is incorporated herein by reference in its entirety.

[0002] This disclosure relates to a water-based barrier coating and a method for producing a water-based barrier coating containing swellable clay. [Background technology]

[0003] Paper-based packaging materials are used worldwide. Currently, barrier coatings for paper and packaging applications rely primarily on petroleum-based materials and synthetic polymers such as waxes, polyvinyl alcohol, and polyolefins (Gironi & Piemonte, 2011). These materials are cost-effective, readily available, and provide significant barriers against water vapor, oil / grease, and oxygen for packaging applications. However, these materials have major drawbacks, such as the poor recyclability and non-biodegradability of coated paper, which can have adverse environmental impacts. Ideal packaging materials in the context of food packaging need to have good barriers against oxygen, water vapor, and oil / grease while being bio-based, recyclable, compostable, and / or derived from otherwise environmentally friendly sources. The need for barrier properties can vary depending on the coating application and the end-use of the paper product.

[0004] Nanoclay is used in a variety of applications and is generally found to be advantageous due to its ability to swell in water. Sun et al. reported on nanoclay / latex composites for improving barrier properties in coatings. See Sun et al., Comps Science Tech 67(2007)1823-1829. Consistent with conventional expectations and intended uses of nanoclay, Sun et al. teach that the nanoclay must be completely exfoliated in the coating and that cationic surface modification of the clay and / or the use of dispersants are necessary. Specifically, Sun concludes that the barrier properties of polymer / clay nanocomposites are strongly dependent on the degree of exfoliation of the nanoclay layer, and that complete exfoliation is necessary to obtain good barrier performance. [Overview of the Initiative]

[0005] According to this disclosure, a process for preparing an aqueous barrier coating for a paper substrate may include mixing a dry powder of chemically unmodified swellable clay with a binder, and subjecting the mixture to high-shear mixing under conditions such that the swellable clay is dispersed in the binder and at least a portion of the swellable clay maintains a tactoid shape, thereby forming a barrier coating. The binder may be aqueous or water-soluble.

[0006] According to this disclosure, a process for preparing an aqueous barrier coating for a paper substrate may include mixing a dry powder of chemically unmodified swellable clay with a polymer latex binder, and subjecting the mixture to high-shear mixing under conditions such that the swellable clay is dispersed in the polymer latex and at least a portion of the swellable clay maintains a tactoid shape, thereby forming a barrier coating.

[0007] The process described herein may further include coating a paper substrate with a barrier coating.

[0008] According to this disclosure, the aqueous barrier coating may include chemically unmodified swellable clay dispersed in a binder, the swellable clay being dispersed under high shear conditions such that the swellable clay exists in a tactoid shape.

[0009] The coating may not contain a dispersant. [Brief explanation of the drawing]

[0010] [Figure 1] This is a scanning electron microscope image of the coating according to this disclosure, showing the sodium bentonite tactoid present in the coating. [Figure 2] This graph shows the water vapor transmission performance of the coating described herein and a conventional coating formed as a single layer, tested under tropical conditions. [Figure 3] This graph shows the water vapor transmission performance of the coating described herein and a conventional coating formed as a two-layer coating, tested under tropical conditions. [Modes for carrying out the invention]

[0011] The aqueous coatings according to this disclosure include chemically unmodified swellable clay dispersed in a binder to provide an aqueous-based barrier coating. It has been advantageously found that barrier coating properties can be achieved through the incorporation of dry swellable clay. The swellable clay used in the coating as an untreated starting material can be in its naturally unexfoliated state. Exfoliation of the swellable clay can be performed under high-shear mixing conditions used to disperse sodium bentonite in the binder when preparing the coatings of this disclosure. Advantageously, no pretreatment of the swellable clay is required before dispersion in the binder.

[0012] The coatings of this disclosure include chemically unmodified swelling clay dispersed in a binder using high-shear mixing conditions such that at least a portion of the swelling clay is present in the coating in a tactoid shape. The coatings of this disclosure can be aqueous-based barrier coatings. Figure 1 is an SEM image of a coating according to this disclosure, having sodium bentonite as the swelling clay showing the presence of tactoids.

[0013] A method for producing an aqueous-based barrier coating according to this disclosure may include mixing a dry powder of chemically unmodified swellable clay with a binder, and subjecting the mixture to high-shear mixing under conditions such that the swellable clay is dispersed in the binder and at least a portion of the swellable clay maintains a tactoid shape.

[0014] Examples of swellable clays include, but are not limited to, smectite, nontronite, bentonite, montmorillonite, bydelite, and vermiculite, and may include one or more clay minerals. The swellable clay may be chemically unmodified and optionally mechanically unmodified. As used herein, “mechanically unmodified swellable clay” means swellable clay that has not been subjected to mechanical shearing, such as delamination, before being incorporated into a coating, and retains its natural hydrophilic state. As used herein, “chemically unmodified swellable clay” means swellable clay that has not been subjected to chemical modification, such as the use of organic modifiers. In some coatings of this disclosure, the swellable clay mixed with the binder is chemically and mechanically unmodified and optionally delaminates during dispersion of the swellable clay in the binder, thereby modifying the clay present in the final coating by mechanical shearing. In some coatings of this disclosure, the swellable clay mixed with the binder is chemically unmodified. In some of the coatings of this disclosure, the swelling clay present in the coating is chemically unmodified.

[0015] The swelling clay used in the coatings and methods of the present disclosure can have less than about 12% moisture. The swelling clay is incorporated into the coating binder in dry particle or powder form without pre-swelling or exfoliating and is dispersed in the binder using high-shear mixing. The high-shear mixing conditions can be selected and adjusted to provide exfoliation of the swelling clay while dispersing the sodium bentonite in the binder. By using exfoliated swelling clay during dispersion, high aspect ratio swelling clay is present in the final coating. As used herein, high aspect ratio refers to an aspect ratio greater than 4, measured by the ratio of the Horiba d 50 measured by static light scattering to the Zave particle size measured by dynamic light scattering. Exfoliation during dispersion in the binder can increase the aspect ratio of the swelling clay while allowing some of the swelling clay to remain in the tactoid shape.

[0016] Referring to FIG. 1, it was observed that at least a portion of the swelling clay was maintained in the tactoid shape in the coatings of the present disclosure. Surprisingly, it has been found that improved barrier coating properties were achieved not by complete exfoliation of the swelling clay, but rather by maintaining at least a portion of the tactoid shape of the swelling clay. By using the dry powder form of the swelling clay in combination with the high-shear mixing used to disperse the swelling clay in the binder, it was observed that it was possible to incorporate the swelling clay into the coating such that tactoids were present and dispersed in the binder.

[0017] It has been observed that the coatings of the present disclosure achieve improved barrier properties compared to conventional talc and kaolin-containing coatings. The coatings of the present disclosure can achieve equivalent barrier coating properties, even if not improved, with a significantly reduced loading level of swelling clay compared to talc or kaolin-containing coatings. In addition, the coatings of the present disclosure can be formed without the need for additional dispersants.

[0018] The swellable clay is dispersed in a binder using high-shear mixing conditions to achieve a coating in which at least a portion of the swellable clay exists in a tactoid shape. Such high-shear mixing can be achieved, for example, by mixing at a tip speed of about 655 feet / min to about 3300 feet / min (200 m / min to 1010 m / min). High-shear mixing can be carried out using any known method or combination of methods, including but not limited to the use of a Cowles mixer, sonication, and rotor-stator mixing. High-shear mixing can include, for example, sonication for at least 1 minute. The sonication time can be about 1 minute to about 40 minutes, about 10 minutes to about 30 minutes, or about 5 minutes to about 25 minutes. Other suitable times include approximately 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, and 40 minutes, as well as values ​​between them, and the ranges defined by those values. High shear can be carried out, for example, under conditions that reduce or prevent overheating. For example, ultrasonic treatment can be carried out using a jacketed vessel with water circulation and a pulse method to prevent overheating.

[0019] The coating can include any suitable aqueous binder. For example, the binder can be an aqueous polymer latex. For example, non-latex binders can also be used. For example, the binder can be styrene butadiene, polyolefin, styrene acrylate, ethylene acrylic acid copolymer, ethylene vinyl alcohol copolymer, polyurethane, epoxy resin, polyester, polyolefin, carboxylated styrene-butadiene latex, carboxylated styrene acrylate latex, polyvinylidene chloride, polyvinyl chloride, starch, styrene-acrylic copolymer, styrene-maleic anhydride, polyvinyl alcohol, polyvinyl acetate, carboxymethyl cellulose, silicone, wax, neoprene, polyhydroxy ether, lacquer, polylactic acid, a copolymer of polylactic acid, a polymer containing fluorine atoms, a copolymer of acrylonitrile, and one or more of anionic polymer latexes such as carboxylated styrene-butadiene acrylonitrile copolymer.

[0020] Swelling clay can be added to the binder in amounts of about 1% to about 20% by weight, about 1% to about 5% by weight, about 3% to about 15% by weight, or about 10% to about 20% by weight, based on the total weight of the coating on a dry weight basis. Other preferred amounts include about 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, and 20% by weight, based on the total weight of the coating on a dry weight basis, as well as any value between them, and any range defined by such values. Unless otherwise specified, references to the presence (%) of swelling clay in a coating in this disclosure refer to a weight percentage based on the total weight of the coating on a dry weight basis. The level of filling with swelling clay can be significantly lower than the level required with talc or kaolin in conventional coatings, while maintaining or even exhibiting improved barrier properties. For example, the amount of swellable clay filling in the coatings of this disclosure can be 2 to 60 times lower than that required in other plate-like mineral-based barrier coatings such as talc or kaolin coatings.

[0021] The coatings of this disclosure are intended for use in coating porous substrates such as paper and cardboard. For suitability in such applications, the coatings of this disclosure may have solids content of about 5% to about 55%, about 15% to about 55%, about 20% to about 40%, about 30% to about 50%, or about 10% to about 25%. Other suitable solids content includes about 5%, 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, 50%, 55%, and any value in between, as well as the ranges defined by such values.

[0022] Coatings prepared by the dry addition of swellable clay can, advantageously, have a solids content greater than or equal to that of the binder. In contrast, coatings prepared by the wet addition of swellable clay have a solids content lower than that of the binder, as a result of the liquid present in the sodium bentonite slurry.

[0023] The coatings of the present disclosure can be coated by conventional paper coating methods such as drawdown coating, blade coating, curtain coating, rotary gravure coating (gravure coating), machine roll-to-roll coating, size press, reverse roll coating, hot melt coating, flex bar coating / flexo coating, film transfer coating, die slot coating, wet film applicator coating, coating film casting using filtration and evaporation, dip coater, or extrusion coating. The substrate can be coated, for example, with any desired coating weight and / or number of coating layers. For example, the coating can be coated at a coating weight of about 1 g / m 2 to about 35 g / m 2 about 1 g / m 2 to about 25 g / m 2 about 5 g / m 2 to about 15 g / m 2 The coating can be coated at a coating weight of. For example, the coating weight can be about 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, or 35 g / m 2 and any value between them, or a range defined by such values.

[0024] The coatings of the present disclosure can be single-layer coatings, less than 10 g / m 2 for example, about 2 g / m 2 to less than 10 g / m 2 or about 4 g / m 2 to about 8 g / m 2 and can have a coating weight of. Other suitable single-layer coat weights include about 1, 2, 3, 4, 5, 6, 7, 8, and 9 g / m 2, as well as any values ​​between them, and the range defined by such values ​​can be cited. The beneficial effect of the coatings of the present disclosure, as opposed to kaolin or talc, has been observed to be advantageous in that they can enable the use of single-layer coatings while achieving desired barrier properties. This is advantageous because two-layer or multi-layer coatings may not be practical in many applications, especially when using multi-functional layers / coatings. In single-layer coat weight, the coatings of the present disclosure demonstrated a 31% improvement in barrier properties with a 3% dry addition of sodium bentonite in the coating compared to pure latex. The coatings of the present disclosure with a 3% dry addition of sodium bentonite also demonstrated a 39% improvement over the competing product Barrisurf® LX containing 40% kaolin clay. The dry addition of sodium bentonite in the coating demonstrated an improvement of over 30% in barrier properties compared to wet addition.

[0025] Porous substrates used with the coatings of this disclosure generally include any paper or cardboard product to which a barrier coating is desired. Paper substrates that can be coated with the coatings of this disclosure include, but are not limited to, solid bleached sulfuric acid (SBS) paper, folded cardboard (FBB), white topliner (WTL), low basis weight paper such as fast food packaging paper, copy paper, coated and uncoated paper, coated and uncoated cardboard, coated unbleached kraft (CUK) paper, and coated recycled cardboard.

[0026] The coatings of this disclosure can be adjusted to provide water vapor permeability or other barrier properties based on the intended use of the paper substrate. For example, the barrier coating may be 40 g / m² under tropical conditions (38°C and 90% RH). 2 Water vapor transmission rate (WVTR) less than / d, and / or 1 g / m 2 It can provide less than 60 minutes of water COBB. For ultra-high barrier applications in tropical conditions, the WVTR is 10 g / m². 2The value is less than / d, and for high barrier applications, 100g / m 2 The value is less than / d, and for medium barrier applications, it is 100-400 g / m². 2 The low barrier is 400 g / m². 2 It is generally understood in the art that the value is greater than / d. The barrier coatings according to this disclosure can be adapted for any of the aforementioned applications. [Examples]

[0027] The following examples demonstrate the performance of coatings according to this disclosure using sodium bentonite as the swelling smectite clay. The results demonstrated herein are considered applicable to other swelling clays, as they exhibit similar performance with respect to swelling when exposed to water and delaminate under high-shear mixing conditions, while maintaining a portion of the clay in a tactoid shape.

[0028] Example 1: Determination of shape factor and its effect on the mixing conditions Chemically unmodified, untreated sodium bentonite with a moisture content of 8%, containing at least 99.00% dry particles finer than 200 mesh (74 microns) and at least 99.75% wet particles finer than 200 mesh (74 microns). The particle size of the dispersed sodium bentonite was determined using a Horiba LA950 static light scattering instrument. A 1.0% bentonite suspension was prepared by adding 0.5 gm of bentonite powder to 50 ml of a deionized aqueous solution with a dispersant concentration of 0.005% DAXAD® 30. The resulting suspension was dispersed by sonication for 8 minutes at a setting of 1.5 using a 0.5-inch horn. The dispersed suspension was dropped into a Horiba LA950 cell to achieve a red laser % transmittance of 89-91%, and the particle size was determined using the standard setting and refractive index of calcium carbonate. This method measures the particle size related to the larger basal surface dimensions of the bentonite.

[0029] Undispersed sodium bentonite samples were also tested. Aqueous suspensions of sodium bentonite with any solid content of approximately 1-10% can be prepared, and varying degrees of shearing can be applied using any type of mixing or sonicating equipment. This suspension is added to a Horiba LA950 cell, and the particle size is measured as described above. [Table 1]

[0030] The particle size of sodium bentonite was also determined by dynamic light scattering (DLS) technique using a Malven Zetasizer 1000 instrument. Either a dispersed or non-dispersed suspension could be used. The suspension was diluted to 0.1% solids using deionized water. The diluted suspension was transferred to an instrument cuvette (1 cm × 1 cm plastic with all sides transparent), and the cuvette was placed in the instrument measurement chamber. Using standard software settings, the size was measured using water as the solvent and the refractive index of sodium bentonite (1.503). The obtained Zave value (hydrodynamic diameter) is reported. This instrument is designed to measure nanoparticles, and therefore, the inventors used this technique to provide values ​​related to the dimensions of thinner sodium bentonite plates, although the values ​​were much thicker than those of thinner plates. The measured Zave values ​​of sodium bentonite varied from 500 to 1500 nm.

[0031] The shape factor (SF) of bentonite was determined to be calculated as a ratio of two particle size methods, using the ratio of the diameter from static light scattering (Horiba LA-950) to the diameter from dynamic light scattering (DLS). It was observed that the sedimentation method could not be used for bentonite due to its extremely long sedimentation time. The shape factor (SF) was calculated by taking the ratio of the median particle size (d50) determined by Horiba light scattering to the Zave particle size (microns) determined using Malvern Zetasizer 1000DLS. The resulting SF values ​​for sodium bentonite can vary from 3.5 to 7, with higher values ​​indicating higher delamination and higher particle aspect ratios.

[0032] Two samples, one with high SF and the other with low SF, were prepared as follows. Low SF: A 5% solids sodium bentonite slurry in deionized water was prepared by adding 27.8 g / m³ of dry sodium bentonite with 10% moisture to 472.2 g / m³ of water. The suspension was then stirred for 5 minutes at a tip speed of 2000 rpm or 1310 ft / min using a Premier Model 2500HV Cowles mixer with a 2.5-inch (6.35 cm) diameter blade. The solids content of this aqueous sodium bentonite slurry was determined to be 5% using the oven drying method. High SF: Another 500 mL of 5% solids starting slurry was sonicated in a water-cooled beaker for a total of 20 minutes while being constantly mixed with a propeller stirrer. To avoid overheating, the sonication was switched on and off in 10-second on / 20-second off cycles for a total of 20 minutes on schedule. [Table 2]

[0033] This demonstrates that the mixing method used to disperse sodium bentonite within the binder can be selected to produce a final composition having sodium bentonite with high or low shape moduli present therein. High shear mixing methods, such as sonication, have been observed to result in materials with high shape moduli.

[0034] Example 2: Barrier performance test Coatings according to the Disclosure were prepared using sodium bentonite with high and low shape coefficients, as well as with dry and wet additions of sodium bentonite. The chemically unmodified sodium bentonite described in Example 1 was used as the starting material in the coatings of the Disclosure. Each coating according to the Disclosure contained 3% by weight of sodium bentonite based on the total weight of the composition on a dry weight basis. The barrier performance of these coatings was compared not only with each other, but also with coatings containing Tykote® 1004 (pure latex) and coatings containing Barrisurf® LX (kaolin).

[0035] A coating according to this disclosure having a low shape factor and a 3% dry sodium bentonite additive was prepared by combining 150 g of Tykote® 1004 with 2.6 g of dry sodium bentonite powder. To create a low shape factor formulation, this mixture was stirred for 5 minutes at 2000 RPM using a 2.5-inch diameter Cowles blade. The formulation was diluted to 47% by adding deionized water. After holding the formulation overnight, viscosity, pH, and solids content were measured.

[0036] A coating according to this disclosure, having a 3% dry sodium bentonite additive with a high shape factor, was prepared by combining 150 g of Tykote® 1004 with 2.6 g of dry sodium bentonite powder. For the high shape factor formulation, the mixture was stirred at 2000 RPM for 5 minutes, followed by 20 minutes of sonication with a pulse function, alternating between 30 seconds on and 30 seconds off. The pulse function was used to prevent overheating. The formulation was diluted to 47% by adding deionized water. After holding the formulation overnight, viscosity, pH, and solids content were measured.

[0037] Coatings according to this disclosure, having a 3% sodium bentonite wetting addition with a low shape factor, were prepared by first forming a sodium bentonite slurry. To prepare the sodium bentonite slurry with a low shape factor, the slurry described in Example 1 was prepared. Specifically, 25 g of dry sodium bentonite powder was mixed with 475 g of water and sheared for 5 minutes at 2000 RPM using a 2.5-inch Cowles blade to obtain a final bentonite slurry with a solid content of 5%. Subsequently, 150 g of Tykote® 1004 was combined with 48.2 g of the wet 5% sodium bentonite slurry. Then, the Tykote® 1004 latex and sodium bentonite slurry were mixed for 15 minutes at 800 RPM using a propeller-type overhead mixer. After holding the mixture overnight, the viscosity, pH, and solid content were measured.

[0038] Coatings according to this disclosure, having a high shape factor and a 3% sodium bentonite wetting addition, were prepared by first forming a sodium bentonite slurry. To prepare a sodium bentonite slurry with a high shape factor, the slurry described in Example 1 was prepared. Specifically, 25 g of dry sodium bentonite powder was mixed with 475 g of water and sheared for 5 minutes at 2000 RPM using a 2.5-inch Cowles blade. Furthermore, to obtain a high shape factor, the same formulation was sonicated for 20 minutes using a pulse function, alternating between 10 seconds on and 20 seconds off. The pulse function was used to prevent overheating. The final solids content of the sodium bentonite slurry was 5%. 150 g of Tykote® 1004 was combined with 48.2 g of a 5% wetting sodium bentonite slurry. The Tykote® 1004 latex and sodium bentonite slurry were then mixed for 15 minutes at 800 RPM using a propeller-type overhead mixer. After holding this mixture overnight, its viscosity, pH, and solids content were measured.

[0039] A comparative coating of Barrisurf® LX (kaolin) was prepared as a 40% Barrisurf® LX-Tykote® 1004 formulation. 150 g of Tykote® 1004 was combined with 84.4 g of Barrisurf® LX slurry. The Barrisurf® LX slurry had a solids content of 61.6%. The mixture was then blended at 800 RPM for 15 minutes using a propeller-type overhead mixer. After holding the formulation overnight, the viscosity, pH, and solids content were measured.

[0040] For each coating compound, the coating was applied at a rate of 40 m / min using an automatic drawdown coater at a rate of 175 g / m². 2The coating was applied to a white top liner. The coating was dried in an oven at 103°C for 10 minutes, followed by conditioning in a CTH chamber for 24 hours. Both single and double-layer coatings were applied. For single-layer coatings, the target coat weight was 5.8 ± 0.4 g / m². 2 However, in the case of a two-layer coating, the target coating weight is 10.8 ± 0.3 g / m². 2 Next, a circular section with a diameter of 7.62 cm was cut out and used for WVTR testing under tropical conditions.

[0041] Table 3 provides the viscosity, pH, and solids content of the prepared coating formulations. [Table 3]

[0042] Water vapor transmission rate (WVTR) was tested under tropical conditions using TAPPI T 464. Referring to Figure 7, the single-layer coatings of this disclosure demonstrated significant improvement in water vapor transmission characteristics compared to Tykote®-1004 alone and Barrisurf® LX (kaolin)-containing coatings. In addition, improvement in water vapor transmission performance was observed with dry addition of sodium bentonite in the coatings of this disclosure compared to wet addition. Finally, improvement in water vapor transmission performance was also observed when using a coating formulation process that resulted in high shape factor sodium bentonite present in the coating. In particular, quantitative improvements were observed in the following performance aspects: Compared to pure latex, a 3% dry addition to high aspect ratio WVTR resulted in a 31% reduction. Compared to high-aspect-ratio wet addition, the WVTR of high-aspect-ratio dry addition was reduced by 36%. Compared to wet addition with a low aspect ratio, dry addition with a low aspect ratio resulted in a 32% reduction in WVTR. Compared to Barrisurf® LX, the WVTR at high aspect ratio with 3% dry additive is reduced by 39%.

[0043] Referring to Figure 3, the significance of the reduction in WVTR between the coating of this disclosure and comparative coatings of Tykote® 1004 and Barrisurf® LX (kaolin) is not so pronounced when using a two-layer coating. A reduction in water vapor transmission rate is still observed, particularly with regard to the dry addition of sodium bentonite. Furthermore, it was surprisingly and beneficially observed that, when formed as a single-layer coating, the coating of this disclosure with the dry addition of sodium bentonite having a high shape factor can provide similar or even improved water vapor transmission rate performance compared to two-layer coatings of Tykote® 1004 and Barrisurf® coatings. Therefore, the coating of this disclosure can avoid the need for a two-layer coating, which can be complex and impractical in some applications, while maintaining at least the same level of barrier performance as a two-layer coating of conventional kaolin coatings.

[0044] The foregoing explanation is provided solely for the purpose of clarifying understanding, and no unnecessary limitations should be inferred therefrom, as modifications within the scope of this disclosure may be obvious to those skilled in the art.

[0045] All patents, patent applications, government publications, government regulations, and references cited herein are incorporated herein by reference in their entirety. In the event of any conflict, this description, including definitions, shall prevail.

[0046] Throughout this specification, where a compound, composition, method, and / or process is described as including components, steps, or materials, unless otherwise specified, the compound, composition, method, and / or process is intended to also essentially consist of, or may consist of, any combination of the listed components or materials. Component concentrations may be expressed in units of weight concentration unless otherwise specifically indicated. Combinations of components are intended to include homogeneous and / or heterogeneous mixtures, as will be understood by those skilled in the art in light of the foregoing disclosures.

Claims

1. A process for preparing an aqueous barrier coating for paper substrates, The process involves mixing a dry powder of chemically unmodified swellable clay with a binder, A process comprising subjecting an admixture to high-shear mixing under conditions such that the swellable clay is dispersed in the binder, at least a portion of the swellable clay maintains a tactoid shape, thereby forming the barrier coating, wherein the binder is aqueous or water-soluble.

2. The process according to claim 1, wherein the binder comprises a polymer latex.

3. The process according to claim 2, wherein the polymer latex is an anionic polymer latex.

4. The process according to claim 3, wherein the anionic polymer latex comprises one or more of styrene-butadiene, polyolefin, styrene acrylate, ethylene acrylic acid copolymer, ethylene vinyl alcohol copolymer, polyurethane, epoxy resin, polyester, polyolefin, and carboxylated styrene-butadiene.

5. The process according to any one of the prior claims, wherein the binder comprises one or more of the following: carboxylated styrene acrylic latex, polyvinylidene chloride, polyvinyl chloride, starch, styrene-acrylic copolymer, styrene-maleic anhydride, polyvinyl alcohol, polyvinyl acetate, carboxymethylcellulose, silicone, wax, neoprene, polyhydroxyether, lacquer, polylactic acid, copolymer of polylactic acid, polymer containing a fluorine atom, copolymer of acrylonitrile, and carboxylated styrene-butadiene acrylonitrile copolymer.

6. A process for preparing an aqueous barrier coating for paper substrates, The process involves mixing a dry powder of chemically unmodified swellable clay with an aqueous polymer latex binder, A process comprising subjecting the admixture to high-shear mixing under conditions such that the swellable clay is dispersed in the polymer latex, at least a portion of the swellable clay maintains a tactoid shape, thereby forming the barrier coating.

7. The process according to claim 6, wherein the polymer latex is an anionic polymer latex.

8. The process according to claim 7, wherein the anionic polymer latex comprises one or more of styrene-butadiene, polyolefin, styrene acrylate, ethylene acrylic acid copolymer, ethylene vinyl alcohol copolymer, polyurethane, epoxy resin, polyester, polyolefin, and carboxylated styrene-butadiene.

9. The process according to any one of the prior claims, wherein the aqueous barrier coating has a solid content of about 5% to about 55%.

10. The process according to any one of the prior claims, wherein high-shear mixing is carried out at a tip speed of approximately 655 feet / min to approximately 3300 feet / min (200 m / min to 1010 m / min).

11. The process according to any one of the prior claims, wherein the dry powder of chemically unmodified swellable clay contains less than 12% moisture.

12. The process according to any one of the prior claims, wherein high-shear mixing is performed using a Coules mixer, an ultrasonic device, or a rotor-stator mixer.

13. The process according to claim 12, wherein high-shear mixing is carried out using an ultrasonic device.

14. The process according to claim 13, comprising ultrasonic treatment for approximately 1 minute to approximately 40 minutes.

15. The high-shear mixing is carried out under conditions that disperse the swelling clay while dispersing it in the binder, and as a result the swelling clay present in the coating is measured by static light scattering relative to the Zave particle size measured by dynamic light scattering. ５０ The process according to any one of the prior claims, having a shape factor greater than 4, as measured by the ratio of .

16. The process according to any one of the prior claims, wherein the dry powder of chemically unmodified swellable clay is added to the binder in an amount of about 1% to about 20% by weight, based on the total weight of the admixture on a dry weight basis.

17. The process according to any one of the prior claims, wherein the admixture does not contain a dispersant.

18. The process according to any one of the prior claims, wherein the chemically unmodified swelling clay is a chemically and mechanically unmodified swelling clay.

19. A process for preparing a barrier coating for a paper substrate, The process involves mixing a dry powder of chemically unmodified swellable clay with a binder, The admixture is subjected to high-shear mixing under conditions such that the swellable clay is dispersed in the binder, at least a portion of the swellable clay maintains a tactoid shape, thereby forming the barrier coating. Approximately 1.5 g / m² of the aforementioned paper substrate ２ ~Approx. 25g / m ２ The process includes coating with the barrier coating having a coating weight of, A process wherein the binder is aqueous or water-soluble.

20. The aforementioned coating weight is 10 g / m ２ The process according to claim 19, wherein the process is less than [amount missing].

21. The process according to claim 19 or 20, wherein the paper substrate is solid bleached sulfuric acid (SBS) paper, folded cardboard (FBB), white top liner (WTL), low basis weight paper packaging paper, copy paper, coated paper or uncoated paper and coated or uncoated cardboard, coated unbleached kraft paper (CUK), or coated recycled cardboard.

22. The process according to any one of claims 19 to 21, wherein the binder comprises a polymer latex.

23. The process according to claim 22, wherein the polymer latex is an anionic polymer latex.

24. The process according to claim 23, wherein the anionic polymer latex comprises one or more of styrene-butadiene, polyolefin, styrene acrylate, ethylene acrylic acid copolymer, ethylene vinyl alcohol copolymer, polyurethane, epoxy resin, polyester, polyolefin, and carboxylated styrene-butadiene.

25. The process according to any one of claims 19 to 24, wherein the binder comprises one or more of the following: carboxylated styrene acrylic latex, polyvinylidene chloride, polyvinyl chloride, starch, styrene-acrylic copolymer, styrene-maleic anhydride, polyvinyl alcohol, polyvinyl acetate, carboxymethylcellulose, silicone, wax, neoprene, polyhydroxyether, lacquer, polylactic acid, polylactic acid copolymer, polymer containing a fluorine atom, acrylonitrile copolymer, and carboxylated styrene-butadiene acrylonitrile copolymer.

26. The process according to any one of claims 19 to 25, wherein the aqueous barrier coating has a solid content of about 5% to about 55%.

27. The process according to any one of claims 19 to 26, wherein high-shear mixing is carried out at a tip speed of approximately 655 feet / min to approximately 3300 feet / min (200 m / min to 1010 m / min).

28. The process according to any one of claims 19 to 27, wherein the dried powder of chemically unmodified swellable clay contains less than 12% moisture.

29. The process according to any one of claims 19 to 28, wherein high-shear mixing is performed using a Coules mixer, an ultrasonic device, or a rotor-stator mixer.

30. The process according to claim 29, wherein high-shear mixing is carried out using an ultrasonic device.

31. The process according to claim 30, comprising ultrasonic treatment for approximately 1 minute to approximately 40 minutes.

32. The high-shear mixing is carried out under conditions that disperse the swelling clay while dispersing it in the binder, and as a result the swelling clay present in the coating is measured by static light scattering relative to the Zave particle size measured by dynamic light scattering. ５０ The process according to any one of claims 19 to 31, having a shape factor greater than 4, as measured by the ratio of .

33. The process according to any one of claims 19 to 32, wherein the dry powder of chemically unmodified swellable clay is added to the binder in an amount of about 1% to about 20% by weight, based on the total weight of the admixture on a dry weight basis.

34. The process according to any one of claims 19 to 33, wherein the admixture does not contain a dispersant.

35. The process according to any one of claims 19 to 34, wherein the chemically unmodified swelling clay is a chemically and mechanically unmodified swelling clay.

36. A water-based barrier coating, An aqueous barrier coating comprising chemically unmodified swellable clay dispersed in a binder, wherein the swellable clay is dispersed under high shear conditions such that at least a portion of the swellable clay exists in a tactoid shape, and the binder is aqueous or water-soluble.

37. The aforementioned swelling clay is measured by static light scattering relative to the Zave particle size measured by dynamic light scattering. ５０ The coating according to claim 36, having a shape factor greater than 4, as measured by the ratio of .

38. The coating according to claim 36 or 37, wherein the binder comprises a polymer latex.

39. The coating according to claim 38, wherein the polymer latex is an anionic polymer latex.

40. The coating according to claim 39, wherein the anionic polymer latex comprises one or more of styrene-butadiene, polyolefin, styrene acrylate, ethylene acrylic acid copolymer, ethylene vinyl alcohol copolymer, polyurethane, epoxy resin, polyester, polyolefin, and carboxylated styrene-butadiene.

41. The coating according to any one of claims 36 to 40, wherein the binder comprises one or more of the following: carboxylated styrene acrylic latex, polyvinylidene chloride, polyvinyl chloride, starch, styrene-acrylic copolymer, styrene-maleic anhydride, polyvinyl alcohol, polyvinyl acetate, carboxymethylcellulose, silicone, wax, neoprene, polyhydroxyether, lacquer, polylactic acid, polylactic acid copolymer, polymer containing a fluorine atom, acrylonitrile copolymer, and carboxylated styrene-butadiene acrylonitrile copolymer.

42. The coating according to any one of claims 36 to 41, wherein the aqueous barrier coating has a solid content of about 5% to about 55%.

43. The coating according to any one of claims 36 to 42, wherein the swelling clay is present in the coating in an amount of about 1% to about 20% by weight, based on the total weight of the coating on a dry weight basis.

44. The coating according to any one of claims 36 to 43, wherein the coating does not contain a dispersant.

45. The coating according to any one of claims 36 to 44, wherein the coating has a solid content equal to or greater than the solid content of the binder.

46. A barrier-coated paper substrate comprising a paper substrate coated with the coating described in any one of claims 36 to 45.

47. The barrier-coated paper substrate according to claim 46, wherein the paper substrate is solid bleached sulfuric acid (SBS) paper, folded cardboard (FBB), white top liner (WTL), low basis weight paper packaging paper, copy paper, coated paper or uncoated paper and coated or uncoated cardboard, coated unbleached kraft paper (CUK), or coated recycled cardboard.

48. The coating is 10 g / m ２ Coating weight less than 400 g / m² ２ A barrier-coated paper substrate according to claim 46 or 47, having a water permeability of less than / d.

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