Haze removal coating and method of use

Abstract

A method for enhancing the transparency of a substrate, particularly paper having a certain degree of translucency, using an aqueous coating containing a polysaccharide resin. The present invention also relates to a method for heat-sealing the substrate using the aqueous polysaccharide resin.

Description

[Technical Field]

[0001] The present invention relates to a method and use of an aqueous polysaccharide coating for enhancing the transparency of transparent or translucent paper or plastic substrates. The present invention also relates to a method and use of the aqueous polysaccharide coating for heat sealing the substrates. [Background technology]

[0002] Plastic (film) substrates are commonly used as part of both packaging products that do not come into direct contact with food and those that do, where visibility of the contents inside the sealed packaging is required. These thin-layer substrates are often used, for example, as windows or lids in gift boxes or fruit baskets. However, even when these plastics are derived from sustainable and / or biorenewable resources, the use of plastic films in food packaging and other packaging applications presents challenges.

[0003] Many plastics are not biodegradable (or compostable), and laminated plastics in particular can be difficult to recycle. Especially since the recycling industry is currently focused on recycling plastics derived from fossil fuels, even plastics derived from bio-renewable resources may be difficult to recycle. Furthermore, the use of such plastics can lead to the accumulation of microplastics in soil, oceans, and air, contributing to adverse ecological and human health impacts, particularly if these microplastics enter the food chain. This is a real concern, given that at least 10 million tons of plastic waste currently flow into the world's oceans each year.

[0004] As a result, there is a growing demand for paper and cardboard substrates that offer a more sustainable approach to food packaging with less environmental impact. Most of these substrates are opaque in appearance due to the air cavities present in the cellulose matrix, but translucent paper and cellophane are available from the paper industry and could potentially be used in the aforementioned applications. However, the processing of cellophane is large-scale, and achieving its transparency requires the use of harmful chemicals such as carbon disulfide.

[0005] Translucent paper can be produced using less stringent methods, but these papers lack sufficient optical transparency and vary in the degree of haze related to density and thickness. Translucent paper, in particular, is well known in the packaging industry and may be called vellum paper. Since trapped air in paper contributes to its opacity, translucency is achieved by removing most of this trapped air. Such vellum paper has some degree of translucency, but it is not transparent enough to allow sufficient visibility of the contents of the packaged item, especially perishable foods.

[0006] Cellulose films may possess several surface resistance properties, but to further enhance these properties, which can affect whether these films can be used in applications where they come into direct contact with food and / or whether they are sustainable, they often have thin-film coatings or treatments. Furthermore, these thin cellulose / paper substrates also lack heat-sealing ability when used alone. This means that polymer adhesives may be required to bond them together to form box / basket-type packaging with a viewing window, which can lead to extra processing and potentially affect the overall biodegradability of the final engineered product.

[0007] This invention addresses these problems in the art and provides an environmentally friendly alternative to plastic packaging. In particular, the invention enhances the transparency of the substrate (e.g., vellum paper) to a degree that the packaged article is easily visible.

[0008] Background document: WO2022003472A1 refers to barrier coatings containing anionic polysaccharides. US20140230691 refers to a method by which thermoplastic coatings may be prepared from fatty acid-modified hemicellulose. WO2021 / 019468, US7427643B2, and US8557033B2 refer to oxygen barrier coatings containing hemicellulose and a secondary plasticizer or hydrophobic agent, which may also be used in the present invention.

[0009] US10934448B2, US9878839B2, US6066368B2, and US8734959B2 relate to starch-containing barrier coatings. Various additional components, including hydrophobic agents, plasticizers, and clays, may be used to further enhance barrier performance. WO2018200783 refers to heat-sealable coatings based on styrene-acrylic polymers and waxes, representing the cutting edge of coatings based on petrochemical-derived raw materials.

[0010] DE102021125162 refers to a flat fibrous packaging material comprising at least one fibrous layer, wherein fibrous gaps are formed between the fibers of the at least one fibrous layer, and the packaging material stretches in a minimum dimension in the thickness direction and in two principal elongation directions that are perpendicular to each other and perpendicular to the thickness direction.

[0011] None of these references describe how a coating containing polysaccharides having a refractive index (RI) matching that of a substrate (e.g., paper, particularly vellum paper) can be used to enhance the optical transparency (i.e., clarity) of the substrate, e.g., paper. Furthermore, further use of these coatings in heat sealing is not disclosed in the prior art, particularly at temperatures below 150°C. Hundreds of references exist regarding the use of polysaccharides in barrier coatings for paper. However, there are no examples of the use of these coatings in heat sealing applications where the optical transparency of the substrate (e.g., paper packaging) is also to be enhanced.

Prior Art Documents

Patent Documents

[0012]

Patent Document 1

Patent Document 2

Patent Document 3

Patent Document 4

[0014] The present invention also provides a method for increasing the transparency of a substrate, which comprises a) applying an aqueous polysaccharide coating to a paper or plastic substrate, for example, a paper substrate, to form a coated substrate, wherein the refractive index of the dried coating is within 10% of that of the substrate, and the uncoated substrate has a total visible light transmittance of at least 70%, for example, at least 80% or at least 90%.

[0015] The present invention further provides the use of an aqueous polysaccharide coating for enhancing the transparency of a substrate, wherein the substrate is a paper or plastic substrate, for example, a paper substrate, and the refractive index of the dried aqueous polysaccharide coating is within 10% of the refractive index of the substrate, the use comprising a) applying the aqueous polysaccharide coating to the substrate to form a coated substrate, the uncoated substrate having a total visible light transmittance of at least 70%, for example, at least 80% or at least 90%.

[0016] The present invention further provides a method for heat-sealing a transparent or translucent paper or plastic substrate, the method comprising: a) applying an aqueous polysaccharide coating to the substrate to form a coated substrate, wherein the refractive index of the dried aqueous polysaccharide coating is within 10% of the refractive index of the substrate; b) forming an adhesive region by bringing the coated substrate into contact with itself or with a second substrate; and c) applying heat and pressure to the adhesive region to seal, optionally forming an airtight seal, wherein the heating temperature is 60°C to 200°C.

[0017] The present invention further provides the use of an aqueous polysaccharide coating for heat sealing a substrate, wherein the substrate is a transparent or translucent paper or plastic substrate, and the use includes: a) applying the aqueous polysaccharide coating to the substrate to form a coated substrate, wherein the refractive index of the dried aqueous polysaccharide coating is within 10% of the refractive index of the substrate; b) forming an adhesive region by bringing the coated substrate into contact with itself or with a second substrate; and c) sealing the adhesive region by applying heat and pressure to optionally form an airtight seal, wherein the heating temperature is between 60°C and 200°C.

[0018] The present invention further provides a method for heat-sealing a paper or plastic substrate, for example, a paper substrate, wherein the uncoated substrate has a total visible light transmittance of at least 70%, for example, at least 80% or at least 90%, and the method comprises: a) applying an aqueous polysaccharide coating to the substrate to form a coated substrate, wherein the refractive index of the dried aqueous polysaccharide coating is within 10% of the refractive index of the substrate; b) forming an adhesive region by bringing the coated substrate into contact with itself or with a second substrate; and c) applying heat and pressure to the adhesive region to seal, optionally forming an airtight seal, wherein the heating temperature is 60°C to 200°C.

[0019] The present invention further provides the use of an aqueous polysaccharide coating for heat sealing a substrate, wherein the substrate is a paper or plastic substrate, for example, a paper substrate, and the uncoated substrate has a total visible light transmittance of at least 70%, for example, at least 80% or at least 90%, and the use includes a) applying the aqueous polysaccharide coating to the substrate to form a coated substrate, wherein the refractive index of the dried aqueous polysaccharide coating is within 10% of the refractive index of the substrate; b) forming an adhesive region by bringing the coated substrate into contact with itself or with a second substrate; and c) sealing the adhesive region by applying heat and pressure to optionally form an airtight seal, wherein the heating temperature is 60°C to 200°C. [Brief explanation of the drawing]

[0020] [Figure 1] Display a diagram of polysaccharides, including subgroups based on the number of sugar units. [Figure 2] These photographs demonstrate the increased transparency and reduced haze provided by the present invention. They show how low the visibility of packaged contents (e.g., fresh produce - see left photograph) is when the contents are covered with an uncoated paper substrate (center photograph, top = 32 g / m2 paper, bottom = 50 g / m2 paper), and how much the visibility improves when that substrate is replaced with a coated substrate obtained from the present invention (right photograph, top = 32 g / m2 paper with the coating used in the present invention, bottom = 50 g / m2 paper with the coating used in the present invention). OPV = overprint varnish, i.e., a coating layer obtained from the coating used in the present invention. [Modes for carrying out the invention]

[0021] definition Increased transparency = an increase of at least 2%, more preferably at least 3%, at least 5%, or at least 10% in the total visible light transmittance through the substrate.

[0022] Transparent substrate = a substrate having a total visible light transmittance of at least 80%. The total visible light transmittance is measured according to the method described in the examples.

[0023] A translucent substrate allows light to pass through, but because the light is diffused, the image seen through the substrate is not clearly visible.

[0024] MAP = Modulated Atmosphere Packaging. A widely used technology in the packaging industry that involves introducing a gas into food packaging to extend the shelf life of packaged agricultural products.

[0025] Fumaric acid resin = A rosin-derived resin that has been modified with fumaric acid and partially esterified with glycerin.

[0026] Non-chemically modified = Naturally derived material that has not undergone chemical modification.

[0027] Nanoclay = Nanoparticles of layered metal silicate salts

[0028] Cellophane is a thin, transparent sheet made from regenerated cellulose. Cellulose derived from wood, cotton, hemp, or other resources is dissolved in alkali and carbon disulfide to create a solution called viscose, which is then extruded through a slit into a bath of dilute sulfuric acid and sodium sulfate to convert the viscose back into cellulose. The film is then passed through several baths: one for removing sulfur, one for bleaching the film, and one for adding a softening material, such as glycerin to prevent the film from becoming brittle.

[0029] Room temperature = 25℃.

[0030] (w / w) = the mass of the component as a percentage of the total mass of the composition.

[0031] Directly food-contacting (DFC) inks and coatings (including OPVs) are compositions intended to come into direct physical contact with food, for example, in food packaging. Therefore, DFC inks and coatings can be used on the inside of food packaging. In DFC applications, due to the short diffusion pathway between the ink or coating and the food, DFC inks or coatings are more likely to migrate into food compared to non-directly food-contacting (non-DFC) inks used on non-food-contacting surfaces of food packaging or other articles. The term "non-directly food-contacting" is also used for "indirectly food-contacting" materials, describing materials that have a functional barrier layer between the material (e.g., ink or coating) and the food substance, and where the material is less likely to come into contact with food. Examples of indirectly food-contacting inks are those applied to the outside of food packaging or to the middle layer of food packaging. Migration from non-DFC inks is possible, but the risk is lower than that from DFC inks and coatings.

[0032] Heat sealability = the ability of a packaging film to form a seal, such as an airtight seal, on a molded package when exposed to heat and pressure.

[0033] Airtight seal = Any type of seal that makes a given object airtight.

[0034] Water solubility = the amount of compound or composition that can be completely dissolved in 100g of water at ambient temperature (20°C). Therefore, a water solubility of 5% is equivalent to 5g of the compound or composition being completely dissolved in 100g of water at 20°C.

[0035] Completely dissolved = when the mixture of water and the compound or composition is clear after 30 minutes of stirring at 20°C.

[0036] A transparent solution is defined as a solution through which text on a printed sheet of paper can be read (from any angle).

[0037] A-to-A heat seal = When both substrates to be bonded to each other to form a heat seal have an adhesive coating before heat seal formation.

[0038] Self-crosslinking polymers are polymers that contain self-reactive functional groups and therefore do not require the use of separate co-reacting agents. Self-crosslinking polymers are usually in the form of aqueous dispersions or emulsions and are typically the product of at least two monomers that react with each other. For example, such polymers may contain both carbonyl and amine functional groups. There are several mechanisms by which polymers can self-crosslink. Alternatively or further, self-crosslinking polymer emulsions may contain crosslinkable functional groups bonded to the polymer backbone in addition to a crosslinking agent (i.e., a polyfunctional species that reacts with the crosslinkable functional group). Typically, in the chemistry of self-crosslinking polymers, polymers containing ketone groups crosslink at room temperature when mixed with a bifunctional or polyfunctional compound that is reactive to carbonyl. One example of these reactive compounds is bishydrazides. Such self-crosslinking PUDs are supplied as a one-component product.

[0039] Self-crosslinking reactions can also be initiated by evaporation of water during drying, changes in the pH of the medium, or curing at high temperatures, which may cause the crosslinking reaction to proceed more rapidly or deblock the reactive groups. In preferred embodiments, the self-crosslinking polymers used in the present invention self-crosslink at room temperature (e.g., 25°C). In other words, self-crosslinking polymers and polymer emulsions are species that crosslink if initiated by one of the methods described above, but otherwise can be stored stably for long periods without significant crosslinking. Self-crosslinking polymers and polymer emulsions do not require mixing with a crosslinking agent to crosslink.

[0040] Tortuosity = the length of the diffusion pathway through the coating. Dispersed (and detached) clay or other plate-like mineral materials can increase the length of the diffusion pathway through the coating, thereby reducing the diffusivity of penetrating gases and improving barrier performance.

[0041] Chitin / chitosan is a naturally derived crosslinking agent containing amine functional groups that have the ability to crosslink starch and polysaccharides.

[0042] Vellum paper is made from cellulose fibers, which are beaten and processed to remove air, resulting in a high-density, translucent sheet.

[0043] This invention This specification describes a method for improving the transparency of a substrate (e.g., paper), particularly a substrate having a certain degree of translucency, using an aqueous polysaccharide coating, such as a corn / rice-derived polysaccharide resin, more specifically, maltodextrin. Similarly, it describes a heat sealing of the substrate using the same aqueous polysaccharide coating.

[0044] To the best of our knowledge, this is the first reported example of a coating primarily based on raw materials derived from sustainable bio-renewable resources, which may improve the light transmittance and heat sealability of paper packaging. Both of these features of the present invention are highly advantageous for the preparation of sustainable, biodegradable, or recyclable paper-based packaging. It is envisioned that the present invention may be used as a substitute for a considerable amount of various plastic packaging.

[0045] Furthermore, the coating substrates obtained from the present invention can provide a barrier against gases, particularly oxygen, and impart oil and grease resistance. The improvement in optical transparency, especially in vellum paper, is particularly advantageous. The aforementioned features of the substrates obtained from the present invention (e.g., paper packaging) offer a significant technological advantage over the prior art. Moreover, the paper packaging obtained from the present invention facilitates the replacement of widely used plastic packaging in the industry.

[0046] Advantages associated with the present invention Reduced haze, increased transparency, bio-renewable material content The coating used in this invention has an RI close to (i.e., within 10%) that of the substrate (e.g., cellulose fibers in paper). The inventors have found that by matching the RI of the polysaccharide coating to that of the substrate (e.g., paper), the transparency of the coated substrate (e.g., coated paper) is improved and haze is reduced. These advantages are quantified by haze and transmittance tests, where haze may decrease by 20-40%, and total visible light transmittance may increase by at least 2%, for example, at least 3%. In some cases, an increase of at least 10% in total visible light transmittance may be possible. The percentage changes in haze and total visible light transmittance are given as absolute values, i.e., the difference between the actual haze percentage value and the transmittance percentage value measured for the coated and uncoated substrates, respectively.

[0047] Those skilled in the art will understand that an increase in the transparency of a substrate can be achieved by applying the coating used in the present invention to one side of the substrate. In this case, the visible light used in the transmittance test is incident on the surface of the substrate containing the coating. Alternatively, an increase in the transparency of a substrate can preferably be achieved by applying the coating used in the present invention to both sides of the substrate. In this case, the visible light used in the transmittance test may be incident on both sides of the substrate.

[0048] The inventors have also found that the chemistry, rheology, and application method of the coating used in the present invention can contribute to a reduction in the overall haze and an increase in the light transmittance of the final product. Improvements to the substrate for reducing haze (e.g., paper packaging, particularly those obtained from translucent vellum paper) are highly desirable to improve the transparency of the finished product by simply using a fully recyclable / compostable coating.

[0049] The present invention can also bring significant environmental benefits by reducing reliance on plastic packaging and decreasing the amount of plastic waste that enters and pollutes the environment. Furthermore, the coated substrates obtained from the present invention (e.g., paper packaging) may be recyclable as paper or treated as biodegradable packaging. Another further advantage is that all the raw materials used in the coating techniques described herein may be non-chemically modified and therefore excluded from the scope of the SUPD (Single-Use Plastics Directive) and its associated controls and restrictions.

[0050] Heat sealable, oil and grease resistant, CO2 / O2 barrier, recoatable. The inventors have surprisingly discovered that the coating used in the present invention possesses heat-sealing ability, oil and grease resistance, oxygen barrier properties, and recoating capabilities. All of these are advantageous for use in engineered sustainable food packaging. These further functional attributes mean that the substrates obtained from the present invention (e.g., paper-based packaging) are a viable alternative to the petrochemical-derived plastic packaging prevalent in the packaging industry.

[0051] The heat-sealability of the coating used in this invention is a particularly advantageous feature, allowing the coated substrate (e.g., paper) to form a seal, such as an airtight sealed package. The coating used in this invention also has barrier capabilities against oils and gases, particularly oxygen and carbon dioxide. These properties are advantageous for the production of food packaging pouches, sealed trays, and the like.

[0052] Therefore, the use of the present invention for paper or plastic substrates used in the method of the present invention and for heat sealing of the substrates may substantially not include conventional adhesives. For example, the paper or plastic substrate may contain 10% by mass or less of a conventional adhesive, for example, 5% by mass or less, or 1% by mass or less, or 0.1% by mass or less, based on the mass of the substrate. Examples of conventional adhesives include acrylic emulsions, polyvinyl acetate, polyvinyl alcohol, combinations of polyvinyl acetate and acrylic emulsion, and combinations thereof.

[0053] Furthermore, the barrier properties of the substrate obtained from the present invention enable its use in Modulated Atmosphere Packaging (MAP), where a gas is circulated through the food packaging to extend the shelf life of the packaged agricultural products. Typically, the circulated gas is a mixture of nitrogen and carbon dioxide, which removes most of the oxygen from the packaging and also utilizes the bactericidal activity of carbon dioxide. For dry foods, the barrier performance of the coating used in the present invention is clearly advantageous. In addition, the good oil resistance of the coating used in the present invention is useful for packaging cooked foods, such as fresh sandwiches.

[0054] The coatings used in this invention provide aqueous direct food contact coatings that can be based solely on naturally derived materials. In particular, by selecting polysaccharides that closely match the radioisotopes (RI) of cellulose fibers distributed in translucent paper (as a substrate), or the RI of the translucent paper (as a substrate) itself, these substrates and coatings can be obtained solely from naturally derived materials, i.e., the BRC can be at least 95%, for example, 100%.

[0055] The heat-seal properties of this novel coating technology provide a viable alternative to the primarily synthetic heat-sealable coating technologies used in the art. The combination of the aforementioned barrier properties and this heat-seal property means that the coatings used herein are multifunctional. Because the raw materials incorporated into the coatings used herein are natural and safe, the compositions used in the present invention can be used for both indirect and DFC packaging coatings. These multifunctional coating compositions used in the present invention are highly advantageous because they can simplify the preparation of paper packaging by eliminating processing steps that typically require several different coatings and / or adhesives.

[0056] Another advantage provided by the coating prepared according to the present invention is its oil resistance, with the surface repelling oily substances, particularly in both folded and flat coated areas, for more than eight hours. This further advantage serves as a preventative measure against oily or grease-containing foods causing visible defects on paper packaging, or against fingerprints adhering to the surface when touched during application.

[0057] Method / Use of the present invention Increased transparency and reduced haze The method and use of the present invention enhance the transparency of transparent or translucent paper or plastic substrates. For the purposes of the present invention, enhancing the transparency of a substrate means an increase of at least 2% in total visible light transmittance. Preferably, the increase in total visible light transmittance is at least 3%, for example, at least 3.4%. In some cases, the total visible light transmittance may increase by at least 10%.

[0058] The method and use of the present invention also reduces the haze of transparent or translucent paper or plastic substrates. For the purposes of the present invention, reducing the haze of a substrate means a reduction of at least 20% of the haze. Preferably, the reduction of the haze is at least 25%, for example, at least 28%.

[0059] Coating method The coatings of the present invention can be applied by any suitable coating or printing method, including but not limited to flexographic printing, gravure printing, offset printing, spray, inkjet, and roller coating methods.

[0060] The film thickness of the coating on the substrate may be 0.1 to 20 μm. Preferably, the film thickness of the coating on the substrate is 0.5 to 10 μm, for example, 1 to 6 μm.

[0061] The coating is applied at a rate of 1 to 20 g / m² relative to the substrate. 2 It can be applied in a basis weight of 3 to 17 g / m² relative to the substrate. Preferably, the coating is applied in an amount of 3 to 17 g / m² relative to the substrate. 2 More comfortably, 5-15 g / m 2 Furthermore, more comfortably, 5-10 g / m 2 It is applied using the given weight.

[0062] The coating may be applied to one or both sides of the substrate. Preferably, the coating is applied to both sides of the substrate.

[0063] Multiple coats A substrate (e.g., paper) coated with the coating used in the present invention can then be overcoated with further materials. These materials include inks, including water-based inks, such as flexographic printing inks. The coated substrate obtained from the present invention has a viscosity of at least 35 J / m². 2 For example, at least 40 J / m 2 It may have a surface energy (SE) of 35 mJ / m². 2 The following coating substrates are typically extremely difficult to recoat, and corona treatment is necessary to facilitate recoating.

[0064] The coated substrate (e.g., paper) obtained from the present invention may be subjected to further coating processes, including the application of overcoating adhesives, further oxygen or water vapor barrier coatings, and / or adhesive layers, whether or not it is printed. The coated substrate (e.g., paper) may also be laminated onto further paper or plastic layers.

[0065] The present invention may further include the step of overlaying the coating with a further layer selected from the group consisting of inks, further coatings, adhesives, and combinations thereof. A substrate obtained from the present invention may be overlaid with a subsequent ink and / or coating layer, such as a pigment ink to give decorative or graphic features, or a barrier coating to further enhance barrier resistance. Advantageously, these subsequently applied inks and / or coatings may also have a high BRC, be biodegradable, and / or be compostable. The inks, further coatings, adhesives, and combinations thereof used in the overlaying step preferably have a BRC of at least 50%, for example, at least 70%, or at least 90%.

[0066] The coatings used in the present invention provide excellent overcoating properties, particularly with water-based inks, and especially with water-based inks containing a significant content derived from sustainable or biorenewable resources, such as the water-based inks provided in US11352522B2 incorporated herein by reference.

[0067] Heat seal The substrates containing the coating used in this invention (e.g., paper packaging) have surprisingly been found to be heat-sealable. Heat-sealability is a well-understood term in the art and refers to the ability of a packaging film to form a seal, such as an airtight seal, on molded packaging when exposed to heat and pressure. Typically, sealing temperatures exceeding 150°C are used.

[0068] The inventors have found that a substrate obtained from the present invention (e.g., paper) can be heat-sealed at a temperature of about 60°C, for example, 80°C. Heat-sealing packaging at temperatures below 150°C is advantageous because it is less likely to be harmful to the substrate and requires less energy.

[0069] Accordingly, the present invention may further include using the aqueous polysaccharide coating to heat-seal a substrate to itself or to a second substrate, which includes a) applying the aqueous polysaccharide coating to the substrate; b) forming an adhesive region by bringing the coated substrate into contact with itself or to a second substrate; and c) applying heat and pressure to the adhesive region to seal, optionally forming an airtight seal, wherein the heating temperature is 60°C to 200°C, for example, 60°C to 145°C.

[0070] Heat sealing may be performed at a temperature of 60°C to 170°C, for example, 60°C to 150°C or 100°C to 150°C, preferably 60°C to 145°C, for example, 80°C to 140°C, more preferably 80°C to 130°C, for example, 90°C to 120°C. Heat sealing may be performed at a pressure of 100 to 10,000 kPa, for example, 300 to 7,000 kPa.

[0071] The substrates obtained from the present invention can be used for lid applications as an alternative to laminated plastics, for example, as lids for cooked meat. An example of heat-sealable packaging is laminated PET-PE (polyester-polyethylene) used for lid applications, where the laminated film is heat-sealed to trays, usually made of polyester, via a PE film. The coated (e.g., paper) substrates obtained from the present invention can also be used to prepare airtight seal barrier pouch packaging in which the packaging is made solely of the coated paper. In the case of the aforementioned lid applications, the coated (e.g., paper) substrates obtained from the present invention are readily recyclable or compostable, whereas laminated PET-PE (and other laminated plastics), especially those of the mixed plastic type, are difficult to recycle and in most cases end up in landfills, which is undesirable.

[0072] The inventors have found that the heat seals formed according to the present invention have an adhesive strength of at least 0.5 N / 25 mm, preferably at least 1.0 N / 25 mm, as measured according to the T peel test (see Examples for details).

[0073] If the second substrate used to create the heat-seal adhesive region is a paper substrate, it can also be coated with the coating for use according to the present invention (thus constituting what is known as an "A-to-A heat seal"). In the latter case, pouches, sealed bags, flow packs, etc., formed from the coated paper of the present invention are most advantageously used to form airtight sealed packaging.

[0074] Coatings used in the present invention Refractive index (RI) The coating used in the present invention comprises a water-soluble polysaccharide resin having an RI close to (i.e., within 10%) that of the substrate to which it is applied. This RI is the RI of the dried coating obtained from the aqueous polysaccharide coating. Preferably, the RI of the dried coating obtained from the aqueous polysaccharide coating is within 5% of the RI of the substrate. For example, if the RI of the substrate is 1.5, the dried coating obtained from the aqueous polysaccharide coating used in the present invention will have an RI of 1.35 to 1.65 (i.e., ±10% of the RI value of the substrate).

[0075] For example, if the substrate is translucent (vellum) paper containing cellulose fibers, the aqueous polysaccharide coating used in the present invention has an RI closer to that of the substrate than many other bio-renewable and synthetic coatings. Preferably, the RI is in the range of 1.45 to 1.60 for both the coating and the substrate (e.g., paper).

[0076] Before the aqueous polysaccharide coating is applied to the substrate, the method of the present invention may further include the step of identifying the aqueous polysaccharide to be used in the present invention by identifying its radioisotope (RI). The step of identifying the aqueous polysaccharide coating may include performing an analytical test (i.e., the method described in the Examples) to identify its RI. Alternatively, or further, the step of identifying the aqueous polysaccharide coating may include consulting relevant technical data sheets (or equivalent sources) to identify its RI. Only coating compositions having an RI of 10% or less of the substrate to which the coating is applied are used in the present invention.

[0077] Other characteristics The coating used in the present invention preferably has a low viscosity. For example, the viscosity of the coating used in the present invention is preferably 10 to 200 cps at a shear rate of 10 to 15 sec (DIN#4) or 1000 1 / sec, for example, preferably 10 to 100, more preferably 10 to 15 cps at a shear rate of 1000 1 / sec. The inventors have found that a coating having this viscosity has optimal coating penetration into the paper substrate and further improves performance in both haze reduction and light transmittance.

[0078] The coating used in the present invention preferably has a pH of 5 to 8. The solid content of the coating used in the present invention may be 5 to 80% by mass (w / w), preferably 20 to 70% by mass, and more preferably 30 to 60% by mass. Most preferably, the coating used in the present invention has a solid content of 40 to 50% by mass.

[0079] The unexpected heat-seal properties of these coatings further enhance their use in packaging (e.g., paper-based), overcoming the problems associated with synthetic adhesives and potentially providing fully functional paper-based packaging with transparency, barrier properties, and heat-sealability. Further possible applications of the (e.g., paper) packaging films obtained from the present invention include lid applications as an alternative to laminated plastics, such as lids for cooked meat.

[0080] The coating used in this invention, when applied to a paper packaging substrate, provides a barrier against oxygen and oils. Preferably, the coating also imparts water vapor resistance to the substrate.

[0081] component The coating used in the present invention contains a polysaccharide. The polysaccharide is preferably obtained from rice and / or corn, and more preferably from corn. The polysaccharide may be in the form of a polysaccharide composition comprising two or more different polysaccharides. The polysaccharide composition is preferably rich in maltodextrin. In other words, the polysaccharide composition used in the present invention preferably contains at least 50% by mass of maltodextrin relative to the total amount of polysaccharides.

[0082] The coating used in the present invention preferably comprises 30 to 60% by mass of a polysaccharide solid, the polysaccharide solid derived from rice and / or corn, 1 to 8% by mass of an organic solvent, such as alcohol, and 20 to 60% by mass of water.

[0083] The coating used in the present invention more preferably contains 40-50% by mass of a polysaccharide solid, for example, about 48% by mass of a solid derived from corn and containing maltodextrin, 2-5% by mass of alcohol, for example, isopropanol, and 30-50% by mass of water.

[0084] The maltodextrin may contain D-allose monomer units linked mainly by α-1,4-glucosidic bonds. The polymer chain mainly contains 3 to 20 monomer units, which are further crosslinked.

[0085] The mass-average molecular weight (M) of the high molecular weight fraction of the polysaccharide composition used in this invention. w) can be 50,000 to 5,000,000 Da, or 10,000 to 250,000 Da. Maltodextrin usually contains a significant proportion of oligosaccharides with a mass average molecular weight of 300 to 5,000 Da. Without wishing to be bound by theory, the inventors assume that the low molecular weight components of maltodextrin, for example, components derived from rice and corn, promote the plasticization of the coating used in the present invention, thereby improving the heat sealability.

[0086] The glass transition temperature (T g ) of the polysaccharide used in the present invention is preferably 100 to 200 °C, or more preferably 120 to 180 °C.

[0087] Examples of alternative polysaccharides to the maltodextrin (3 to 20 glucose units) used in the present invention include starch (300 to 1,000 glucose units). The polysaccharide composition used in the present invention may also contain a moderate, moderately high, or high amylose content (Table 1). In other words, the polysaccharide composition used in the present invention may contain at least 16% by mass of amylose, for example, 16% to 60% by mass, or 16% to 40% by mass, based on the total amount of polysaccharide.

Table 1

[0088] Figure 1 defines common sugars and particularly polysaccharides.

[0089] Water solubility The polysaccharide used in the present invention is water-dispersible. Preferably, the polysaccharide used in the present invention is water-soluble, and in the latter case, it is advantageous that the water solubility at 25 °C is at least 5% (w / w) based on the dry mass of the polysaccharide.

[0090] Water content The coating composition used in the present invention may have a water content of 30 to 80% by mass, for example, 40 to 60% by mass, or about 43% by mass, based on the total mass of the coating composition. This includes both the water present in the polysaccharide resin (e.g., Sunresin 20100) and any additional water added.

[0091] Any additives The additive incorporated into the coating used in the present invention preferably contains at least 50%, for example, at least 70%, and more preferably at least 90% BRC.

[0092] Crosslinking agent The coating used in the present invention may contain a crosslinking agent. Examples of crosslinking agents used in the present invention include those containing the following reactive species: carbodiimides, oxazolines, aziridines, epoxys, amino resins (e.g., melamine-formaldehyde), metal complexes (including titanates and zirconates organometallic, e.g., zirconium ammonium carbonate), isocyanates (including blocked isocyanates), epoxys, polyaldehydes, sodium tripropylphosphate, calcium chloride, borax and boric acid, chitin / chitosan, and combinations thereof. Preferably, the crosslinking agent is selected from the group consisting of sodium tripolyphosphate, calcium chloride, and combinations thereof.

[0093] The crosslinking agent can be incorporated into the composition in an amount of 1 to 20% by mass, preferably 1 to 10% by mass, more preferably 1 to 8% by mass, even more preferably 2 to 4% by mass, and most preferably 3 to 4% by mass. The inventors have found that incorporating the crosslinking agent into the composition used in the present invention can advantageously increase the hydrophobicity of the resulting coated substrate, as demonstrated by the reduction in the amount of water that can be absorbed (see Table 5).

[0094] Further resin The coating used in the present invention may also contain, in addition to the polysaccharide, further water-soluble, alkali-soluble, and / or water-dispersible resins.

[0095] The further resins include both resins derived from renewable resources and resins derived from petrochemical products, and in particular, polyurethane dispersions, self-crosslinked polyurethane dispersions, alkali-soluble acrylic resins, acrylic dispersions, self-crosslinked acrylic dispersions, polyester dispersions, dispersions of poly(vinyl acetate) and vinyl acetate copolymers, poly(vinyl alcohol), poly(vinylpyrrolidone), rosin ester resins, and combinations thereof.

[0096] Other resins and materials can be used in the coatings used in the present invention, and particularly preferred are alternative resins and materials that have a high BRC (for example, at least 70%, preferably 100% BRC) and do not lack the basic properties of the coating (e.g., haze removal, heat sealability, etc.).

[0097] Water-soluble organic cosolvent The coatings used in the present invention may include water-soluble organic cosolvents. Volatile solvents, such as ethanol, propanol, and isopropanol, may be used. Glycol ether solvents, including polyols, alkylene glycols, alkylene glycol ethers, or ether acetate types, may also be included.

[0098] Non-limiting examples include 4-hydroxy-4-methyl-2-pentanone, diethylene glycol, diethylene glycol butyl ether, diethylene glycol ethyl ether, diethylene glycol methyl ether, diethylene glycol monoethyl ether acetate, diethylene glycol monopropyl ether, dipropylene glycol, dipropylene glycol ethyl ether, dipropylene glycol methyl ether, ethylene glycol butyl ether, ethylene glycol ethyl ether, ethylene glycol isopropyl ether, ethylene glycol methyl ether, ethylene glycol propyl ether, glycerin carbonate, N-methyl 2-pyrrolidone, glycerol, propylene glycol, propylene glycol ethyl ether, propylene glycol ethyl ether acetate, propylene glycol methyl ether, propylene glycol n-propyl ether, triethylene glycol, triethylene glycol butyl ether, triethylene glycol methyl ether, tripropylene glycol, tripropylene glycol methyl ether, N-methylpyrrolidone, urea, and combinations thereof.

[0099] At least 0.5% by mass of an organic cosolvent is incorporated into the coating used in the present invention, more preferably at least 1% by mass, for example 1 to 10% by mass, and even more preferably at least 2% by mass of an organic cosolvent, for example 2 to 8% by mass. The organic cosolvent used in the present invention is preferably an alcohol, for example ethanol, propanol, and isopropanol, and more preferably isopropanol. The coating used in the present invention preferably contains 1 to 10% by mass, for example 1 to 8% by mass or 2 to 5% by mass, or about 2% by mass of isopropanol.

[0100] While we do not wish to be bound by theory, the inventors assume that the presence of the organic co-solvent (e.g., alcohol) further increases the penetration of the coating into the substrate, particularly paper substrates, thus further improving transparency and further reducing haze. The increased penetration of the coating composition containing the organic co-solvent is assumed to be due to improved wetting. This is observed from a comparison of the surface tension of the coating composition, and as described in the examples, increasing the amount of the organic co-solvent (e.g., alcohol) reduces the surface tension.

[0101] When cosolvents are incorporated, it is preferable that they constitute less than 40% (w / w) of the coating composition, preferably less than 30% (w / w), more preferably less than 20% (w / w), and most preferably less than 10% (w / w).

[0102] Biocides and / or mold inhibitors The coating used in the present invention is aqueous. Therefore, it is preferable to include a biocide and / or a fungicide. Suitable examples include products based on the following biocide structural types: benzoisothiazolinone, bromonitropropanediol, isothiazolinone, ethylenedioxydimethanol, iodopropynyl butylcarbamate, and combinations thereof.

[0103] Commercial grades include those sold under the trade names Intercide (Akcros Chemicals) or Nipacide (Clariant). Other biocides that may be used include sodium dehydroacetate (Geogard 111S, Lonza), sodium benzoate (Vancide 51, RTVANDERBILT), sodium pyridinethiol-1-oxide (Sodium Omadine, Arch Chemicals), sodium salt of O-phenylphenol (Dowicide A, DOW Chemical), and ethyl p-hydroxybenzoate (Nipastat Sodium, Aako).

[0104] The biocide and / or fungicide is preferably incorporated into the coating used in the present invention in an amount of 0.01 to 1.00% by mass of the coating (e.g., ink) composition.

[0105] defoaming agent An antifoaming agent is optionally included in the coating used in this invention. The antifoaming agent prevents the formation of bubbles during the manufacturing and spraying of the coating / ink. The antifoaming agent is particularly important in circulating printheads.

[0106] Examples of suitable defoamers include, but are not limited to, Evonik's TEGO FOAMEX N, FOAMEX 1488, 1495, 3062, 7447, 800, 8030, 805, 8050, 810, 815N, 822, 825, 830, 831, 835, 840, 842, 843, 845, 855, 860, and 883, TEGO FOAMEX K3, TEGO FOAMEX K7 / K8, and TEGO TWIN 4000. Available from BYK are BYK-066N, 088, 055, 057, 1790, 020, BYK-A 530, 067A, and BYK 354. Additives DC62, DC65, DC68, DC71, and DC74 are available from Dow Corning. Agitan 120, 150, 160, 271, 290, 298, 299, 350, 351, 731, 760, 761, and 777 are available from Munzing. Surfynol 104PA, AD01, DF-110, DF-58, DF-62, DF-66, DF-695, DF-70, and MD-20 are available from Air Products.

[0107] Surface conditioning additives The coating used in the present invention may include surface conditioning additives. Surface conditioning additives are often added to the ink to adjust the surface tension required to regulate the wetting of the printhead face and to provide the desired wetting to the substrate on which the ink is printed. Surface conditioning additives may also be used to adjust the level of slip and scratch resistance of the coating used in the present invention.

[0108] Examples of surface conditioning additives used in the present invention include polyacrylates, polyethersiloxane copolymers, siloxane-based gemini surfactants, silicones, wax dispersions, and combinations thereof.

[0109] Examples of suitable surface conditioning additives include, but are not limited to, TEGO FLOW 300, 370, and 425, TEGO GLIDE 100, 110, 130, 406, 410, 411, 415, 420, 432, 435, 440, 482, A115, and B1484, all available from Evonik, TEGO GLIDE ZG 400, TEGO TWIN 4000, and 4100, TEGO WET 240, 250, 260, 265, 270, 280, 500, 505, and 510, and TEGO WET KL245. Available from BYK are BYK 333 and 337, BYK 378, 347 and 361, CERAFLOUR 998 and 996, NANOBYK 3601, 3610 and 3650, and CERMAT 258. Surfynol 104, 420, 440, 465, 485, 61, 82, and 2502 are available from Air Products. Multiwet BD, EF, SU, SO, and VE are available from Croda. Capstone FS-30, 31, 34, 35, 50, 51, 60, 61, 63, 64, 65, and 3100 are available from DuPont.

[0110] Coloring agents The present invention primarily relates to clear coating compositions. However, the coating compositions used in the present invention may further include colorants that provide further decoration to the substrate, for example, packaging paper.

[0111] Examples of colorants include those derived from petrochemical products. Preferably, the colorants used in the present invention are derived from renewable resources and / or bioresources.

[0112] The coatings used in the present invention may contain one or more colorants, including pigments and / or dyes. Suitable examples of organic or inorganic pigments used in the present invention include carbon black, zinc oxide, titanium dioxide, phthalocyanine, anthraquinone, perylene, carbazole, monoazo and disazobenzimidazole, rhodamine, indigoid, quinacridone, diazopyrantrone, dinitroaniline, pyrazole, diazopyrantrone, pyrazole, dianisidine, pyrantrone, tetrachloroisoindoline, dioxazine, monoazoacrylide, anthrapyrimidine, and mixtures thereof. Examples of dyes used in the present invention include, but are not limited to, azo dyes, anthraquinone dyes, xanthene dyes, azine dyes, and combinations thereof. Food-derived dyes are also included in the present invention.

[0113] Nanoclay The coating used in the present invention provides an oxygen barrier to a substrate, such as a paper packaging substrate. To further enhance this property, the coating may optionally further include nanoclay that improves the oxygen barrier performance by increasing the "twist" of the coating to the diffusion of oxygen (and any other gases, including water vapor, nitrogen, and carbon dioxide).

[0114] The nanoclays that may be included in the coatings used in the present invention include, but are not limited to, natural nanoclays such as bentonite, heclite, kaolin, and vermiculite, or synthetic nanoclays such as laponite. Therefore, by incorporating nanoparticles into the coatings used in the present invention, improved barrier performance can be obtained. For example, the coatings used in the present invention can withstand temperatures of 100 cm² per 1 μm dry coating layer at 25°C and 50% relative humidity (RM). 3 m -2 day -1 It may have an oxygen permeability (OTR) of less than 1.

[0115] The coating used in this invention preferably also improves the water vapor barrier performance of the substrate, for example, paper packaging. The coating used in this invention is applied at 25°C and 50% RM, with 100 gm per 1 μm dry coating layer. -2 day -1 It can provide the coated substrate with a water vapor barrier performance of less than 1.

[0116] To further improve barrier properties, nanoclay can be incorporated into the composition used in the present invention. When incorporated, the nanoclay is used in an amount of 0.1 to 20% by mass, preferably 1 to 10% by mass, relative to the total coating composition.

[0117] plasticizer The coating used in this invention may also contain a plasticizer. The plasticizer may enhance the heat sealability of the coating, as well as its water vapor barrier performance. While we do not wish to be bound by theory, the inventors hypothesize that the plasticizer may also help to make the heat seal more effective by assisting the flexibility of the coating after it has dried by evaporation, thereby ensuring that the polysaccharide-based coating is sufficiently thermoplastic.

[0118] When a substrate obtained from the present invention (e.g., paper) is used for heat sealing applications, the adhesive strength of the heat-seal joint is preferably at least 0.5 N / 25 mm and more preferably at least 1.0 N / 25 mm in a T peel test, as is known to those skilled in the art and as described in the examples. The heat seals formed by the coated substrates used in the present invention include both plastic and paper substrates.

[0119] The plasticizer may be selected from any of the following non-limiting examples: glycerol, propylene glycol, triethylene glycol, poly(ethylene glycol), sorbitol, xylitol (and other sugars), urea, and combinations thereof.

[0120] WO2021 / 019468, US7427643B2, US8557033B2, US10934448B2, US9878839B2, US6066368B2, and US8734959B2 are incorporated herein by reference as a whole and disclose plasticizers, hydrophobic agents, and clays that can be incorporated into coatings used in the present invention.

[0121] wax The coatings used in this invention may comprise any blend of wax emulsions or dispersions. To maintain a high BRC of the coating, waxes derived from natural sources, such as carnauba, beeswax, candelilla, rice bran wax, and vegetable oil-derived waxes, are preferred. However, waxes derived from petrochemical resources may also be used, including paraffin, polyethylene, polypropylene, polyamide, and montan wax.

[0122] Preferably, each of the above additives is derived from renewable and sustainable resources. For example, with respect to wetting aids and surfactants, those derived from bio-based ethoxylated natural fatty alcohols and sorbitan esters may be used. Suitable wetting aids include oligosaccharides, glucitol, polyhydroxyamides, sulfosuccinates, and combinations thereof.

[0123] Biorenewable material ratio (BRC) The coating used in the present invention preferably has a biorenewable material content (BRC) of at least 90%, more preferably at least 95%, and even more preferably 100%. The solid content of the coating used in the present invention preferably contains at least 80%, for example, at least 90%, of materials derived from sustainable or biorenewable resources. That is, the solid preferably has at least 80%, for example, at least 90% BRC. The BRC content of the coating of the present invention was tested by an independent laboratory and found to be 100% biocarbon (as a percentage of total carbon). In this case, biocarbon refers to carbon from "renewable" (biomass or animal-derived components) resources in contrast to petroleum (or fossil) resources.

[0124] The coating used in the present invention is preferably a water-soluble polysaccharide resin derived from corn, based on 100% BRC Sunresin 20100, which is blended with water. The resin is preferably unchemically modified.

[0125] Base material The substrate used in this invention is a transparent or translucent paper or plastic substrate. A transparent substrate means that the total visible light transmittance of the substrate is at least 80%.

[0126] The uncoated substrate used in the present invention may have a total visible light transmittance of at least 70%, for example, at least 80%, or at least 90%. The uncoated substrate used in the present invention may have a haze of up to 100%.

[0127] The substrate used in this invention is paper, preferably translucent vellum paper.

[0128] The paper substrate used in this invention (i.e., before coating) has a paper weight of 10 to 400 g / m². 2 (gsm), preferably 20-200 g / m² 2 , comfortably, 30-150g / m 2 More preferably, 30-70 g / m 2 It is possible.

[0129] The substrate used in the present invention may have a thickness of 1 to 200 μm, preferably 10 to 150 μm, for example, 10 to 100 μm, more preferably 20 to 80 μm, and even more preferably 30 to 55 μm. The thickness is measured using micrometers in accordance with ASTM F2251-13 (2018).

[0130] The substrate used in the present invention preferably contains less than 20% by mass of cellophane, more preferably less than 10% by mass of cellophane, and even more preferably substantially cellophane-free.

[0131] The base material used in the present invention preferably contains at least 50% by mass of BRC, for example, at least 60% by mass.

[0132] The substrate used in the present invention may have a benthocene roughness of 0 to 1000 ml / min, preferably 30 to 800 ml / min, more preferably 100 to 700 ml / min, and even more preferably 140 to 600 ml / min. The benthocene roughness of the surfaces of the substrate used in the present invention may differ. Therefore, one surface of the substrate used in the present invention may be rougher than the other surface. In particular, one surface of the substrate used in the present invention may have a benthocene roughness of 30 to 1000 ml / min, preferably 100 to 700 ml / min, and more preferably 250 to 600 ml / min. The other surface of the substrate used in the present invention may have a benthocene roughness of 0 to 400 ml / min, preferably 20 to 300 ml / min, and more preferably 100 to 200 ml / min.

[0133] The base material used in this invention has a density of 0.6 to 2 g / cm³. 3 Preferably, 0.7 to 1.5 g / cm³ 3 More preferably, 0.9 to 1.4 g / cm³ 3 More preferably, 1.0 to 1.25 g / cm³ 3 This may be the case. The base material used in this invention has a density of 1.0 to 1.1 g / cm³. 3 It is possible.

[0134] While we do not wish to be bound by theory, the inventors assume that the surface roughness and density of the substrate may affect the degree of penetration of the coating into the substrate, and consequently, the amount of increased transparency and reduced haze achieved by the present invention.

[0135] packaging The methods and uses of the present invention may also provide airtight seal packaging, such as pouches, sealed bags, flow packs, etc.

[0136] Test method T g (Glass transition temperature): The glass transition temperature can be determined using differential scanning calorimetry (DSC) according to the process defined in ASTM E1356-08. The sample was maintained in a dry nitrogen atmosphere during scanning. A flow rate of 20 ml / min and an Al pan were used. The sample (5 mg) was heated from 20°C to 350°C at 20°C / min. As described in ASTM E1356-08, T g The value was identified as the extrapolated onset temperature of the glass transition (heat flow rate (W / g) relative to temperature (°C)) observed in the DSC scan.

[0137] viscosity Viscosity is measured at 32°C using a TA Instruments AR1500ex rheometer at a shear rate of 1000 1 / s.

[0138] Biorenewable material ratio (BRC) BRC is calculated by taking the percentage of renewable materials in each ingredient used. Therefore, the percentage of bio-renewable materials = divide the molecular weight of the natural fraction by the total molecular weight and multiply by 100.

[0139] The carbon-14 method is used to calculate the BRC of both individual components and the final composition. The carbon-14 method accurately measures the carbon content derived from renewable resources such as plants. This test is conducted in accordance with the international standard ASTM D6866. By measuring the carbon-14 content, ASTM D6866 makes it possible to distinguish between carbon from modern carbon resources such as biomass (biocarbon) and carbon from petroleum derivatives. Biomass contains known amounts of carbon-14, while petroleum-derived materials contain none. For the coating of the present invention, the measured carbon-14 content was determined using ASTM D6866-18 method B (AMS).

[0140] molecular weight Molecular weight of nonpolymer or oligomeric compounds The molecular weight of a nonpolymer or oligomeric compound is defined and calculated by the molecular structure of the compound. This is usually provided in the technical data sheet provided by the supplier of the compound or can be found on the European Chemicals Agency (ECHA) website.

[0141] Molecular weight of polymers and oligomer compounds - GPC This was determined by size exclusion chromatography, particularly gel permeation chromatography (GPC), using monodisperse polystyrene-based molecular weight calibration standards and GPC columns (manufactured by PSS (Polymer Standards Service-USA, Inc.)), with applicable column combinations: SDV 5μm 1000Å, SDV 5μm 500Å, SDV 5μm 100Å). The column flow rate was 1.0 ml / min, the eluent was tetrahydrofuran, the column temperature was 40°C, and a differential refractive index detector (RI) and a UV detector (254 nm) were used. Dispersibility DISP=(Mw / Mn) is the quotient of the mass average and number average of the molecules, and was calculated from the measurement results. Unless otherwise specified, the molecular weights of polymers and oligomer compounds are number average molecular weights.

[0142] compostability This refers to the ability of a material to naturally biodegrade within a specified timeframe under controlled conditions. Compostable materials conform to ASTM D6400, subsection 6.2 and / or ASTM D6868, subsection 6.2.

[0143] biodegradable This refers to the conversion of organic carbon present in a sample to carbon dioxide under controlled conditions, in accordance with ASTM D6400 and / or ASTM D6868, subsection 6.3. When biodegradability is defined in units of a percentage, it is the percentage of material remaining after the test outlined in one of the aforementioned standards.

[0144] Oxygen transmission rate (OTR) OTR was measured using a Systech Oxysense 8101 analyzer in accordance with ASTM D3985, and the results were obtained in cc / m2 Recorded daily. In this case, the test was conducted at 25°C and 50% relative humidity. A foil mask with a 5cm opening was also used to reduce the effect of oxygen penetration at the edges of the paper.

[0145] Refractive index test The refractive indices of the final coatings, pure polysaccharide resins, and other bio-renewable / synthetic resin options were measured in their dry state using an RFM900-T refractometer (589.63 nm - ASTM D2140). To ensure accurate readings and sufficient contact with the glass prism, the coating / resin options were added to the machine in a wet state and dried in situ. To do this, the instrument temperature was set to 50°C until all moisture was removed, and then reduced to 20°C for measurement.

[0146] Haze and transmittance testing (i.e., transparency) The transparency of the coated paper was quantified using a Byk Gardner Haze Guard Dual, and the visible light transmittance was measured according to ISO 13468 1:2019(E). Haze was also measured using a Byk Gardner Haze Guard Dual, according to ISO 14782:2021. For completeness, ISO 14782:2021 states that it is applicable to haze values ​​less than 40%, but it can also be used to evaluate haze values ​​greater than 40%, albeit with reduced accuracy. To mitigate this loss of accuracy, at least four measurements were taken from each sample, and the average value was calculated.

[0147] Samples were prepared by coating both sides of paper with two layers using a k-bar (from RK Print) at a wet basis weight of 4–6 microns per layer. Each layer was force-dried at a temperature of 60–80°C for 10–20 seconds. All uncoated and coated papers were held properly against the COM port and haze port, and haze and transmittance values ​​were read out as percentages.

[0148] Heat seal test: Paper samples were prepared using the same methods as described above for haze and transmittance testing. Furthermore, 100 g / m² was used. 2 Kraft paper exceeding this weight was also used as a representative body for packaging in complete engineering products. This kraft board was applied in 6 μm increments, weighing approximately 3-6 g / m² in dry condition. 2 The coated translucent paper was then sealed against itself, unused kraft paper, and kraft paper coated with a single layer of coating to evaluate its heat-sealing ability in various packaging situations.

[0149] The tests were performed using a C632B hot stack tester (e.g., Labthink) with the ASTM F1921-1921M-12 method. The parameters used were a sample width of 25 mm, a pressure of 40 psi, a jaw clamp time of 0.2 seconds, and a speed of 1500 mm / min. Various temperatures were evaluated to create heat seal curves. A dwell time of 0.5 seconds (sample cooling) was used to replicate hot tack conditions, and 180 seconds was used for standard heat seals. Results were reported as N / 25 mm sample width.

[0150] Oil and grease resistance test As described in the "Haze and Permeability Test" section above, the sample was coated on both sides to prepare a 10x20cm sample piece. Next, one area of ​​this sample was folded 180° using a folding tool and returned to a flat position. Then, the sample was taped flat to a non-porous, uncontaminated surface, sealing all edges to prevent unwanted penetration caused by the spreading of oil. Next, 2-3 drops of olive oil were applied in a line to the flat and folded areas of the substrate. Each drop of oil was treated as a double test. The sample was then evaluated based on observation of the area of ​​penetration over selected time periods (24, 72, and 168 hours).

[0151] A second oil and grease test, known as the “kit test,” was performed according to TAPPI T559. This method describes a procedure for determining the degree of wicking and / or anti-wicking properties of paper or cardboard treated with a fluorinated sizing agent. The test involves placing a series of numbered reagents (with different surface tensions and viscosities or “invasiveness”) onto the surface of the sample. These solutions are numbered from 1 (least invasive) to 12 (most invasive). The highest number that does not stain the surface is reported as the “kit grade.”

[0152] Surface roughness The surface roughness of the substrate was measured using a ventometer in accordance with ISO 8791-2.

[0153] Surface energy The surface energy of the (coated) substrate was measured according to ASTM D7490-13(2022).

[0154] The dynamic surface tension of the coating composition was measured at 25°C and 2.7Hz using a SITA bubble tensile meter, and the static surface temperature was measured at 25°C and a bubble frequency of 0.025Hz using a SITA bubble tensile meter.

[0155] Cobb test for crosslinking research: Wet samples were coated using the "Haze and Permeability Test" section above, and water absorption was examined using the Tappi T441 method. The cobbling used in this example was 25 cm. 2 The improvement in the Cobb value shown in Table 5 demonstrates the advantages of using a crosslinking agent.

[0156] Layering method To demonstrate its suitability for overcoating, translucent paper was coated and dried with the coating of Example 1 (as described in the "Haze and Transmittance Test" section above), and then overcoated with DFC cyan-based ink (Aquasafe DFC Reflex Blue GAQS-50002, Sun Chemical) using #350 (6cc anilox). This ink was force-dried at 40-60°C for 10-20 seconds. The ink showed no trace of a mesh pattern, demonstrating good overcoating and laydown properties.

[0157] To further demonstrate the recoating properties, the surface energy of the coating surface of Example 1 was measured using deionized water as the medium, and it was found to be 56.7 mJ / m 2 The value obtained was 35 mJ / m 2 The following surface energies (SE) make overcoating extremely difficult, and often require corona treatment: 35-40 J / m 2 SE is printable, but in terms of overcoating properties, it is 40 J / m 2 A higher surface tension is desirable. This is more relevant to water-based / ink-based systems, as the surface tension of the liquid applied to the surface is naturally higher. [Examples]

[0158] Substrate used in the examples [Table 2]

[0159] Preparation and testing of coating examples: Example 1 Example 1 was prepared by mixing 50% (w / w) water-soluble polysaccharide resin (corn-derived Sunresin 20100) with 50% water and mixing in a low-shear stirrer for approximately 15 minutes. This product was left to stand for at least 30 minutes before coating to allow trapped air to dissipate. Other coating examples are shown in Table 3. Sunresin 20100 has a water content of 30-50% by mass, for example, about 40% by mass.

[0160] The resulting low-viscosity coating was applied using the protocol described in the haze and transmittance test sections above.

[0161] The penetration of the first layer is crucial for improving transparency. Water acts as a carrier, helping to sufficiently reduce the viscosity of the coating to penetrate through the pores of the paper. Next, this resin is deposited in the air cavities within the paper, which remain there as the water particles are blown away during drying. The purpose of any second or subsequent coating application is to further fill the pores and provide a smooth surface. Wetting aids can be added to the coating to facilitate the penetration of the coating into the paper pores.

[0162] The oil and grease resistance of Example 1 of the invention was determined. [Table 3]

[0163] Table 2 clearly shows the excellent oil and grease resistance provided by the coating of the present invention. [Table 4]

[0164] As shown in Table 3, coatings (Comparative Example 4) that fall outside the RI range of 1.45 to 1.60 (i.e., within 10% of the RI of a substrate with an RI of 1.525 (1.45 to 1.6)) do not result in the same degree of haze % reduction and transmittance % increase as those within the RI range of 1.45 to 1.60. The coatings used in Comparative Examples 2 and 3 have an Ri within 10% of the RI of the substrate. However, since these coating compositions are made from acrylic dispersions, they are not aqueous polysaccharide coatings and do not possess advantageous properties, such as high BRC.

[0165] To further demonstrate the performance of the composition relating to the invention of Example 1, the coating was applied using the protocol described in the "Haze and Transmittance Test" section above. The papers used were "Sylvicta," manufactured by Arjowiggins, and "SP Crystalal," manufactured by Ahlstrom-Munksjo. [Table 5]

[0166] The results in Table 4 support the claim that the coating prepared according to the present invention can increase the transmittance and reduce haze of translucent paper useful in the food packaging industry.

[0167] As those skilled in the art will understand, the degree of increase in transparency and / or reduction in haze also depends on the unique characteristics of the substrate. For example, variations in the roughness and density of the substrate can affect the penetration of the coating into the substrate. Thus, substrates with lower density and higher roughness may promote increased coating penetration than fir (FIR) substrates with higher density and lower roughness. Therefore, a greater increase in transparency / reduction in haze can be achieved with substrates that are low in density and high in roughness.

[0168] Furthermore, 42g / m 2 Analysis of the Sylvicta substrate confirmed that the OTR is improved by applying the coating used in the present invention. Uncoated substrate = 112 cc / m 2 / day Substrate coated with the coating in the example = 18.9 cc / m² 2 / day. Therefore, the addition of nanoclay can further improve the OTR.

[0169] Heat sealing performance of the coating used in this invention The heat-sealing ability of paper coated with the composition of the invention was evaluated according to the procedure described above. Heat-sealing ability was evident in a variety of conditions, including coated paper to coated paper and coated paper to unused (kraft) paper. Sealing ability was detected at a low temperature of 60°C, and the optimal sealing window is in the range of 100°C to 150°C. The ability to seal in this manner offers opportunities for various packaging designs, including lids, pouches, flow packs, sealed bags, and laminates. In the case of laminates, this includes paper-to-paper laminates and paper-to-plastic film laminates. Another significant advantage of the current technology is that the optimal sealing temperature is relatively low, at 100 to 150°C.

[0170] Table 5 shows the heat sealability according to the tear strength grade of the fibers. Here, the printed material is Ahlstrom 40g / m². 2 The coating was prepared by applying two layers of the coating from Example 1 to both sides of a sheet of Cristal paper and drying it at 100°C for 10 seconds. The total dry basis weight was 10 g / m². 2 The apparatus used was a Specac blocking tester with clamp test parameters of 0.2 seconds clamping and 275 kPa pressure. Grade 3 or higher was considered acceptable, with 5 being considered ideal. These examples also demonstrated acceptable adhesive strength. [Table 6]

[0171] Use of crosslinking agents to improve the resistance of coatings Crosslinking chemistry can be used to enhance the aesthetic properties and water resistance of the final dry system. Salts such as sodium tripolyphosphate (STPP) and calcium chloride have been studied as methods for ion crosslinking to achieve further improvements within these performance ranges. Evidence shows that levels of 3-4% by mass of STPP can improve hydrophobicity by up to 15% for coatings and 30% compared to uncoated substrates. In the examples in Table 4, STPP was used as a crosslinking agent, but other crosslinking agents known in the art, such as calcium chloride and boric acid, can also be used. Table 5 shows data indicating how much crosslinking 2-4% by mass of STPP incorporated, reducing the amount of water that can be absorbed by the coated substrate. [Table 7]

[0172] Measurement of the surface tension of the coating used in the present invention The compositions were prepared as shown in Table 6, and their surface tension was measured using a SITA bubble tensile strength meter. These compositions were also applied to a substrate (Sylvicta 42gsm), and their transmittance and haze were measured. [Table 8]

[0173] As can be seen in Table 6, the surface tension of the coating composition decreased as the amount of IPA in the coating composition increased. As a result, the coating compositions containing IPA (i.e., compositions 2 and 3) provided a coated substrate with lower haze compared to the coating composition without IPA (i.e., composition 1). The inventors hypothesize that the reduction in haze is greater because the reduced surface tension allows the coating composition to penetrate the substrate more easily.

[0174] Paragraphs numbered according to the Invention which form part of this specification The present invention is further described by the following numbered paragraphs: 1. A method for increasing the transparency of a substrate, The method comprising applying an aqueous polysaccharide coating to a transparent or translucent paper or plastic substrate, wherein the refractive index of the dried coating is within 10% of that of the substrate.

[0175] 2. The method according to paragraph 1, wherein the refractive index of the dried coating is within 5% of that of the substrate.

[0176] 3. The method according to paragraph 1 or 2, wherein the refractive index of both the dried coating and the substrate is 1.45 to 1.60.

[0177] 4. The method according to paragraph 1 or 2, wherein the substrate is translucent vellum paper.

[0178] 5. The method according to any of the preceding paragraphs, wherein the polysaccharide is maltodextrin derived from maize or rice.

[0179] 6. The method according to any of the preceding paragraphs, wherein the polysaccharide has a water solubility at 25°C of at least 5% (w / w) based on the dry mass of the polysaccharide.

[0180] 7. The method according to any of the preceding paragraphs, wherein the coating is based on 80% or more BRC material, or 90% or more BRC material, 95% or more BRC material, 98% or more BRC material, or 100% BRC material.

[0181] 8. The method according to any of the preceding paragraphs, wherein the coating is compostable.

[0182] 9. The method according to any of the preceding paragraphs, wherein the coating is recyclable.

[0183] 10. The method according to any of the preceding paragraphs, wherein the coating is suitable for applications in which it comes into direct contact with food.

[0184] 11. The method according to any of the preceding paragraphs, wherein the coating has a low viscosity printing viscosity, for example, in the range of 5 to 15 seconds (DIN #4) or 5 to 20 cps (shear of 1000 1 / second).

[0185] 12. The method according to any of the preceding paragraphs, wherein the coating is heat-sealable at a temperature of 80 to 200°C.

[0186] 13. The coating is exposed to oxygen at 25°C and 50% relative humidity, at 100 cm². 3 / m 2 The method according to any of the preceding paragraphs, which provides a barrier of less than / 24 hours / μm.

[0187] 14. The method according to any of the preceding paragraphs, further comprising one or more wetting additives.

[0188] 15. Furthermore, the method according to any of the preceding paragraphs, comprising a crosslinking agent.

[0189] 16. The method according to any of the preceding paragraphs, wherein the coating is applied by a method selected from the group consisting of flexographic printing, gravure printing, offset printing, spray, inkjet, and roller coating.

[0190] 17. The coating according to any of the preceding paragraphs, wherein the solids content is 5-80% (w / w), or 10-70%, or 15-60%.

[0191] 18. The method according to any of the preceding paragraphs, wherein the glass transition temperature of the polysaccharide is 100-200°C or 120-180°C.

[0192] 19. A printed product comprising one or more layers of the coatings described in paragraphs 1 to 18 on a substrate.

[0193] 20. The product according to paragraph 19, wherein the substrate is a transparent or translucent paper or plastic substrate.

[0194] 21. The product described in paragraph 19 or 20, wherein the haze value is less than 70%.

[0195] 22. Products described in one or more of paragraphs 19-21, having a light transmittance of 80% or more, or 85% or more, or 90% or more.

[0196] 23. The product described in one or more of paragraphs 19 to 22, wherein the product is a food packaging product.

[0197] The present invention has been described in detail, including various embodiments thereof. However, those skilled in the art will understand that, taking into consideration this disclosure, modifications and / or improvements can be made to the present invention within the scope and spirit of the invention.

Claims

1. A method for increasing the transparency of a substrate, a) The process includes applying an aqueous polysaccharide coating to a transparent or translucent paper or plastic substrate to form a coated substrate, A method wherein the refractive index of the aqueous polysaccharide coating (after drying) is within 10% of that of the substrate.

2. The method according to claim 1, further comprising the step of identifying the aqueous polysaccharide coating by specifying its refractive index, prior to step a).

3. The use of an aqueous polysaccharide coating to enhance the transparency of the substrate, The substrate is a transparent or translucent paper or plastic substrate. The aqueous polysaccharide coating (after drying) is characterized in that its refractive index is within 10% of the refractive index of the substrate. a) Applying the aqueous polysaccharide coating to the substrate to form a coated substrate. Includes, use.

4. The aqueous polysaccharide coating is heat-sealable by applying heat and pressure in a heat-sealing process (for example, the coated substrate can be heat-sealed to itself or to a second substrate), The heat sealing process described above is i) Forming an adhesive region by bringing the coated substrate into contact with itself or with the second substrate, and ii) Applying heat and pressure to the adhesive area to form a seal, which may optionally be an airtight seal. The method or use according to any one of claims 1 to 3, including

5. A method for heat-sealing a transparent or translucent paper or plastic substrate, a) A step of applying an aqueous polysaccharide coating to the substrate to form a coated substrate, wherein the refractive index of the aqueous polysaccharide coating (after drying) is within 10% of the refractive index of the substrate. b) The step of forming an adhesive region by bringing the coated substrate into contact with itself or with a second substrate, c) A step of applying heat and pressure to the bonding area to form a seal, which may optionally be an airtight seal, wherein the heating temperature is 60°C to 200°C. Methods that include...

6. The use of an aqueous polysaccharide coating for heat sealing a substrate, The substrate is a transparent or translucent paper or plastic substrate. a) Forming a coated substrate by applying an aqueous polysaccharide coating to the substrate, wherein the refractive index of the aqueous polysaccharide coating (after drying) is within 10% of the refractive index of the substrate. b) Forming an adhesive region by bringing the coated substrate into contact with itself or with a second substrate. c) Applying heat and pressure to the adhesive area to seal it, optionally forming an airtight seal, wherein the heating temperature is between 60°C and 200°C. Includes, use.

7. The method according to claim 5 or the use according to claim 6, further comprising the step of identifying the aqueous polysaccharide coating by specifying its refractive index, prior to step a).

8. The method or use according to claim 4, wherein the heating temperature is 60°C to 200°C, or the method or use according to any one of claims 4 to 7, wherein the heating temperature is 60°C to 160°C, 60°C to 145°C, 80°C to 140°C, or 100°C to 130°C.

9. The method or use according to any one of claims 4 to 8, wherein the seal obtained from the method or use has an adhesive strength of at least 0.5 N / 25 mm or at least 1.0 N / 25 mm.

10. The method or use according to any one of claims 1 to 9, wherein the refractive index of the aqueous polysaccharide coating (after drying) is within 5% of that of the substrate.

11. The method or use according to any one of claims 1 to 10, wherein the refractive index of both the aqueous polysaccharide coating (after drying) and the substrate is 1.45 to 1.

60.

12. The method or use according to any one of claims 1 to 11, wherein the substrate is paper, and optionally the paper substrate may be translucent vellum paper.

13. The method or use according to any one of claims 1 to 12, wherein the substrate before coating has a total visible light transmittance of at least 80%.

14. The method or use according to any one of claims 1 to 13, wherein the polysaccharide is maltodextrin derived from corn and / or rice, and optionally the polysaccharide may be maltodextrin derived from corn.

15. The method or use according to any one of claims 1 to 14, wherein the aqueous polysaccharide coating comprises 30 to 60% by mass of a polysaccharide solid derived from rice and / or corn, 1 to 8% by mass of an organic solvent (e.g., alcohol), and 20 to 60% by mass of water.

16. The method or use according to any one of claims 1 to 15, wherein the polysaccharide has a water solubility at 25°C of at least 5% (w / w) based on the dry mass of the polysaccharide.

17. The method or use according to any one of claims 1 to 16, wherein the aqueous polysaccharide coating has at least 80% BRC, at least 90% BRC, at least 95% BRC, at least 98% BRC, or 100% BRC.

18. The method or use according to any one of claims 1 to 17, wherein the aqueous polysaccharide coating is compostable, and optionally the substrate may be compostable.

19. The method or use according to any one of claims 1 to 18, wherein the aqueous polysaccharide coating is recyclable, and optionally the substrate may be recyclable.

20. The method or use according to any one of claims 1 to 19, wherein the aqueous polysaccharide coating is suitable for applications in which it comes into direct contact with food.

21. The method or use according to any one of claims 1 to 20, wherein the aqueous polysaccharide coating has a printing viscosity in the range of 5 to 15 seconds (DIN #4) or 5 to 20 cps at a shear rate of 1000 1 / second.

22. The method or use according to any one of claims 1 to 21, wherein the aqueous polysaccharide coating is applied to both sides of the substrate.

23. The aqueous polysaccharide coating was subjected to a temperature of 25°C and 50% relative humidity at 100 cm². ３ / m ２ The method or use according to any one of claims 1 to 22, which provides a barrier against oxygen of 24 hours / μm or less.

24. The method or use according to any one of claims 1 to 23, wherein the aqueous polysaccharide coating further comprises one or more wetting additives.

25. The method or use according to any one of claims 1 to 24, wherein the aqueous polysaccharide coating further comprises a crosslinking agent.

26. The method or use according to claim 25, wherein the crosslinking agent is selected from the group consisting of sodium tripolyphosphate, calcium chloride, and combinations thereof.

27. The method or use according to claim 25 or 26, wherein the crosslinking agent is present in an amount of 1 to 10% by mass, 1 to 8% by mass, or 2 to 4% by mass.

28. The method or use according to any one of claims 1 to 27, wherein the composition further comprises nanoclay, which optionally may be present in an amount of 1 to 10% by mass.

29. The method or use according to any one of claims 1 to 28, wherein the aqueous polysaccharide coating further comprises a plasticizer.

30. The method or use according to any one of claims 1 to 29, wherein the aqueous polysaccharide coating is applied by a method selected from flexographic printing, gravure printing, offset printing, spray printing, inkjet printing, and roller coating.

31. The method or use according to any one of claims 1 to 30, wherein the aqueous polysaccharide coating has a solid content of 5 to 80% (w / w), 10 to 70% (w / w), or 15 to 60% (w / w).

32. The method or use according to any one of claims 1 to 31, wherein the aqueous polysaccharide coating comprises an organic cosolvent, and optionally the organic cosolvent may be an alcohol selected from the group consisting of methanol, ethanol, isopropanol, butanol, pentanol, hexanol, and combinations thereof.

33. The method or use according to claim 32, wherein the organic cosolvent is isopropanol.

34. The method or use according to claim 32 or 33, wherein the organic cosolvent is incorporated into the aqueous polysaccharide coating in an amount of 1 to 10% by mass, 1 to 5% by mass, 1 to 3% by mass, or about 2% by mass.

35. The method or use according to any one of claims 1 to 34, wherein the glass transition temperature of the polysaccharide is 100 to 200°C, and optionally 120 to 180°C.

36. The method or use according to any one of claims 1 to 35, wherein the aqueous polysaccharide coating is applied to the substrate with a film thickness of 0.1 to 20 μm, optionally 0.5 to 10 μm, or 1 to 6 μm.

37. The method or use according to any one of claims 1 to 36, further comprising applying a material selected from the group consisting of ink, additional coatings, adhesives, and combinations thereof to the aqueous polysaccharide coating.

38. The method or use according to claim 37, wherein the material is an aqueous flexographic printing ink.

39. The method or use according to claim 37, wherein the material is an additional coating that enhances the oxygen barrier properties and / or moisture barrier properties of the substrate.

40. The method or use according to any one of claims 37 to 39, wherein the ink, the additional coating, the adhesive, and any combination thereof have a BRC of at least 50%, optionally at least 70%, or at least 90%.

41. The method or use according to any one of claims 1 to 41, wherein the substrate contains less than 20% by mass of cellophane, and optionally may contain less than 10% by mass of cellophane, or the substrate is substantially free of cellophane.

42. A printed product obtained by the method or use according to any one of claims 1 to 41, comprising one or more coatings on the substrate.

43. The product according to claim 42, wherein the base material is paper.

44. The product according to claim 42 or 43, wherein the haze value is less than 70%.

45. The product according to any one of claims 42 to 44, wherein the light transmittance is at least 80%, at least 85%, or at least 90%.

46. The product according to any one of claims 42 to 45, wherein the product is a food packaging product.

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