Chitosan-based barrier coatings on paper for use as food packaging

Abstract

The present application relates to a coating color for coating paper, which contains chitosan and / or chitosan derivatives having an average molecular weight of 50 kDa or more and at least one solvent. The present application also relates to paper coated with the coating color. The present application further relates to a manufacturing method and packaging made from the coated paper.

Description

[Technical Field]

[0001] The present application relates to a coating color for coating paper, which contains chitosan and / or its derivatives and at least one solvent. [Background technology]

[0002] Packaging accounts for a large portion of global plastic waste pollution, prompting the search for alternatives made from biodegradable materials.

[0003] Food packaging is particularly challenging because it requires good barrier properties against oxygen, water vapor, and microorganisms.Food packaging materials are often made from plastics such as polyethylene terephthalate (PET), polyvinyl chloride (PVC), polyethylene (PE), and polypropylene (PP), which, in addition to their good barrier properties, are also lightweight and have high mechanical stability. Paper-based packaging materials offer many advantages over plastic materials, such as renewable, recyclable and compostable nature, but their applications are limited by their poor gas barrier properties and high sensitivity to moisture.

[0004] To improve barrier properties, paper-based packaging materials can be laminated with aluminum or petroleum-based polymers such as PE, EVOH, and PVC derivatives, but these coatings unnecessarily complicate waste sorting and therefore recycling, and reduce compostability.

[0005] Therefore, from an ecological point of view, the use of barrier layers based on natural bio-based polymers or replacing conventional metal or plastic based layers is highly desirable.

[0006] Examples of natural polymers that have been tested for packaging applications are chitosan, hemicellulose, lignin, microfibrillated cellulose, starch, etc. However, many natural polymers are hydrophilic, and films made from these materials are often hygroscopic, thereby partially losing their barrier properties when humidity levels are high.

[0007] Chitosan is a natural polysaccharide obtained from chitin, a substance found in the shells of crustaceans and insects, and is available in a wide variety of molecular weights and degrees of deacetylation. Economically interesting quantities have already been obtained from fishing waste, mainly during crab and shrimp processing. The barrier properties of chitosan are known in the prior art, as are its film-forming properties. However, chitosan has not been described in detail in many publications and is only proposed due to its properties as a biodegradable polymer.

[0008] However, chitosan has limited applicability due to its maximum solubility of less than 10% by weight, and often even less than 5% by weight, because the viscosity of chitosan coating colors is usually too high even at 5% by weight to be suitable for large-scale industrial paper coating processes. Above 10% by weight, chitosan coating colors known in the prior art become unprocessable.

[0009] When chitosan coating colors are used as a barrier layer for paper against gases such as water vapor or oxygen, the low solids content requires multiple coating steps to obtain a defect-free coating and a coat weight that allows for barrier performance against these gases.

[0010] U.S. Patent Application Publication No. 2013 / 0273353 describes a multilayer film for use as a binding and packaging material. The multilayer film includes at least one biodegradable polymer layer and one or more dense moisture barrier layers connected thereto, either directly or via a primer layer. The film must be at least 90% biodegradable while achieving the desired water vapor transmission properties. Biodegradable polymers include all naturally occurring and synthetically produced (modified) biodegradable polymers. The extensive list of possible polymers includes, among others, PLA, PLA derivatives, polylactic acid / aliphatic polyester copolymers, polyglycolic acid polymers, polyethylene terephthalate copolymers, polyethylene terephthalate cosuccinate, poly(tetramethylene adipate / terephthalate), polyethylene sebacate, polyvinyl alcohol, chitosan, chitosan / cellulose polymers, cellulose acetate-based polymers, starch-based thermoplastic polymers, and modified starch-based polymers. The moisture barrier layer has a moisture vapor transmission rate (MVTR) of approximately 0.5g / 100in per day. 2 (645.2cm 2 ) ~ Approximately 45g / 100in per day 2 The thermoplastic polymer layer is

[0011] U.S. Patent Application Publication No. 2017 / 0016182 describes compositions of chitosan-coated paper and paperboard products and methods for using chitosan as a surface coating or pulp additive to improve the properties of paper and paperboard products. In particular, chitosan coatings having a coating weight of about 1 g / m 2 ~about 10g / m 2By coating a chitosan layer of this type onto a fibrous base sheet, an air permeability of about 20 nm / Pa·s to about 50 nm / Pa·s can be achieved. U.S. Patent Publication No. 2017 / 0016182 further teaches a method for obtaining a unique chitosan composition from chitin- and chitosan-containing fungal biomass. The composition according to U.S. Patent Publication No. 2017 / 0016182 is said to be characterized by a combination of a high degree of deacetylation and a high molecular weight. U.S. Patent Publication No. 2017 / 0016182 does not provide specific examples of the degree of deacetylation and molecular weight. However, degrees of deacetylation greater than about 50%, greater than about 75%, or even greater than about 95% are suggested. Similarly, number-average molar masses greater than 50,000 g / mol, greater than 100,000 g / mol, or even greater than 175,000 g / mol are suggested for the chitosan composition. Furthermore, a range of number average molar mass, or a range of 60,000 g / mol to 90,000 g / mol, is defined.

[0012] Chinese Patent Application Publication No. 109112892 describes a degradable, environmentally friendly lining paper for cigarette packets. The lining paper comprises a raw paper layer, a barrier layer, a chitosan layer, and a microcrystalline wax layer. The barrier layer is disposed on the upper surface of the raw paper layer, the chitosan layer is disposed on the lower surface, and the microcrystalline wax layer is disposed between the raw paper layer and the barrier layer. Chitosan is used because it has good moisture-retaining, film-forming, and antibacterial properties and mechanical strength. However, the chitosan layer is not used as a barrier against gases or moisture. For this purpose, the paper also includes a barrier layer made of a biodegradable polymer such as polylactic acid, starch, polybutylene succinate, or polyhydroxyalkane.

[0013] The problem underlying the present invention is to provide a chitosan-based coating color that can be used as a barrier layer for gases such as oxygen in paper and that can be used for large-scale industrial production of coated paper. Summary of the Invention

[0014] The present invention is based, inter alia, on the surprising realization that, for the first time, it is possible to achieve high chitosan proportions of more than 10% by weight in coating colors in a viscosity range that is suitable for large-scale industrial applications and thus allows the production of paper with a chitosan coating that essentially serves as a gas barrier, using low molecular weight chitosan, in particular chitosan with a number-average molecular weight of less than 50 kDa.

[0015] According to a first aspect, the present application relates to a coating colour for coating paper, comprising chitosan and / or a derivative thereof having an average number average molecular weight of less than or equal to 50 kDa and at least one solvent.

[0016] By further optimizing the type and amount of acid used to dissolve chitosan and adding specific surfactants, plasticizers, clays, or oligochitosan, the paper was given very good oxygen barrier performance (10 cm 3 m -2 d -1 It was possible to produce defect-free single coats of chitosan coating color at application weights providing an OTR of less than 1000 kJ / cm2. Furthermore, depending on the additives, additional barrier properties against oils and fragrances or hexane could be achieved.

[0017] Coated papers produced with this coating color layer have a barrier effect sufficient for use in the food industry, yet are biodegradable and recyclable.Thus, according to a second aspect, the present invention relates to a coated paper comprising a base paper and at least one barrier layer applied directly or indirectly to the base paper, wherein the coating color layer is based on a coating color according to the first aspect.

[0018] The barrier effect of the coating color layer in coated paper, which is important here, is achieved in particular by the method used to produce coated paper according to the invention. Thus, according to a third aspect, the present invention provides a method for producing coated paper according to the second aspect, comprising the following steps: a) preparing a coating color according to the first aspect comprising an acid and a surfactant by introducing the acid and a surfactant into water and adding chitosan in small amounts; b) preparing a base paper; c) applying the coating color to the base paper, preferably by curtain or doctor blade methods; and d) A process of hardening the coating color to obtain a coating color layer. The present invention relates to a method, comprising:

[0019] The coated paper according to the present invention has barrier properties against oxygen, oils, fats and flavourings and is therefore suitable for food packaging. Thus, according to a fourth aspect, the present invention relates to a food packaging comprising the coated paper according to the second aspect. [Brief explanation of the drawings]

[0020] [Figure 1A] 1 is a confocal microscope image of a CT1 coating with a basis weight of 5 g / m2 obtained from a 5 wt% solution of water / acetic acid. [Figure 1B] 1 is a confocal microscope image of a CT1 coating with a basis weight of 5 g / m2 obtained from a 5 wt% solution of water / formic acid. [Figure 1C] 1 is a confocal microscope image of a CT6 coating with a basis weight of 5 g / m2 obtained from a 5 wt% solution of water / acetic acid. [Figure 1D] 1 is a confocal microscope image of a CT6 coating with a basis weight of 5 g / m obtained from a 5 wt % solution of water / formic acid. [Figure 2] Confocal microscopy images of a 5 g / m2 CT6 single chitosan coating obtained from a 7.5 wt% solution in water / acetic acid, with selected magnifications of defective and non-defective areas. [Figure 3A] FIG. 1 shows a chitosan coating pattern of 5 g / m2 in two layers, applied sequentially after oxygen barrier measurement. [Figure 3B] FIG. 1 shows a chitosan coating pattern of 7.5 g / m2 in three layers, applied sequentially after oxygen barrier measurement. [Figure 3C]FIG. 1 shows a chitosan coating pattern of 4 layers of 10 g / m2 applied sequentially after oxygen barrier measurement. [Figure 4] 1 is a graph of oxygen barrier performance (OTR) as a function of total coat weight of a coating color containing CT8, lactic acid, and Tween 20®. [Figure 5] Figure 1 shows the results of optical evaluation of droplets of coating colors containing CT8, lactic acid, and different surfactants. The evaluation is performed by determining the area of ​​the droplet that is occupied by air bubbles out of the total area of ​​the droplet. The surfactants are A) Span 60®, B) Tween 60®, and C) Tween 20®. [Figure 6] Figure 1 shows the results of defect inspection using pigmented biodiesel (pinhole test) of porous papers coated with coating colours according to the invention containing CT8 and lactic acid: A) Coating colour containing CT8, lactic acid and Tween 20; B) Coating colour containing CT8, lactic acid, Tween 20 and kaolin-based inorganic pigment. [Figure 7] FIG. 2 shows the progression of the solids content and viscosity of the coating colours according to the invention as a function of the pigment content. DETAILED DESCRIPTION OF THE INVENTION

[0021] definition According to the present invention, the "degree of deacetylation" of chitosan is the percentage of free amino groups in the molecule, i.e., the percentage of amino groups that do not have an acetyl group, i.e., the percentage of deacetylation (%) = 1-F A = 100 - degree of acetylation.

[0022] Within the scope of this invention, and consistent with common understanding in the papermaking art, the term "coating color" refers to a coating comprising or consisting of binders, additives, and optionally pigments or matrix pigments, which is applied ("coated") to the surface of paper using specialized coating equipment for surface finishing or surface modification of base paper. Paper produced in this manner is called "coated paper."

[0023] Within the scope of the present invention, "coated paper" is understood to mean a base paper provided with one or more layers, i.e., a color coating layer, of which functional layers and structure-forming layers (such as leveling layers for smoothing the surface) are considered as layers of the coated paper substrate.

[0024] According to the present invention, the term "coating color" is used as a general term for all coatable coating materials, formulations and / or solutions in the paper industry for treating, modifying or finishing the surface of paper. By "coating color layer" is understood the coating color that has been applied to the base paper and cured.

[0025] "Paper" is a flat material consisting essentially of fibers of plant origin, which is formed by dewatering a fiber suspension through a sieve. The resulting fibrous nonwoven is then compressed and dried. Within the scope of the present invention, "cardboard" and "paperboard", which are flat materials produced in a similar manner, are also included in the term paper. Paper, cardboard and paperboard are differentiated only by their basis weight, with paperboard having a metric basis weight of 600 g / m². 2 Ultra-thin cardboard with a metric basis weight of 150 g / m 2 Super, 600g / m 2 and the paper has a basis weight of 150 g / m 2 The following is the result.

[0026] The "molar mass" M, or "molar mass" or "molar weight" of a substance is the mass per amount of substance, or in other words the proportionality coefficient m = M n between the mass m and the amount of substance n. The SI unit is kg / mol. The numerical value of the molar mass g / mol is the "relative molecular mass", also called the molecular weight, and is equal to the numerical value of the molecular mass in atomic mass units (u or Daltons). According to the present invention, "molecular weight" usually refers to the relative molecular mass.

[0027] In science and technology, the "molar weight distribution" (MWD), also called molecular weight distribution, describes the frequency distribution of the individual molecular masses within a sample of a polymeric material.

[0028] To statistically represent a sample, various average values ​​are defined, such as viscosity average, mass average, number average of molar mass, etc. The molar mass M of the i-mer i is weighted by the relative number fraction of the polymer. That is, the "number average molar mass" or "number average molecular weight" represents the molar mass of a randomly selected molecule from a sample. In this case, N i corresponds to the number of macromolecules in the sample that have exactly i repeat units.

number

[0029] Coating Color According to a first aspect, the present invention relates to a coating color for coating paper comprising chitosan and / or its derivatives having a low average molecular weight and at least one solvent. According to one embodiment, the average molecular weight is less than 50 kDa.

[0030] Chitosan and chitin are naturally occurring biopolymers similar to cellulose. They differ from glucose in the group attached to the C2 atom. Whereas cellulose has a hydroxyl group, chitosan has an amino or acetamido group. Chitosan and chitin are polyaminosaccharides composed of N-acetylglucosamine monomers (specifically, 2-acetamido-2-deoxy-β-D-glucopyranose residues) and glucosamine monomers linked by β-1,4-glycosidic bonds. Chitosan and chitin can be obtained from crustacean shells and some fungi.

[0031] The ratio of acetamide to amino groups in the chain is an important characteristic and is called the "degree of deacetylation." If the degree of deacetylation is less than 50%, it is called "chitin," and if the degree of deacetylation is more than 50%, it is called "chitosan." To produce chitosan, chitin is deacetylated. This can be done, for example, by enzymatic digestion of chitin with the appropriate deacetylase or by boiling in sodium hydroxide solution.

[0032] According to one embodiment, the chitosan or its derivative has a degree of deacetylation of at least 50%. Generally, as the degree of deacetylation increases, the solubility of the chitosan increases, but so does the viscosity. The degree of deacetylation can be 50%, 53%, 56%, 59%, 60%, 62%, 65%, 68%, 70%, 72%, 75%, 77%, 80%, 82%, 85%, 88%, 90%, 92%, 95%, 98%, or 100%. According to one embodiment, the degree of deacetylation of the chitosan is at least 70%. A deacetylation of at least 70% has the advantage that these chitosans are more soluble than chitosans with the same number-average molecular weight but a lower degree of deacetylation. According to one embodiment, the degree of deacetylation of the chitosan is at least 90%. According to one embodiment, the degree of deacetylation of the chitosan is at least 93%. A degree of deacetylation of at least 93% has the advantage that chitosan is soluble over a wider pH range, especially in acidic media. Increasing the degree of deacetylation increases the solubility, for example, in aqueous lactic acid. Furthermore, the higher the degree of deacetylation, the more acid can be added, which also contributes significantly to the solids content and ultimately improves the barrier properties.

[0033] Chitosans with different combinations of average molecular weight and degree of deacetylation are commercially available, such as Chitosan 90 / 10 / A1 (90% deacetylation, approximately 50 kDa number-average molecular weight) from BioLog Heppe® GmbH, or GP1318 chitosan (5 cps), ultra low molecular weight (approximately 20 kDa number-average molecular weight, more than 90% deacetylation) from Glentham LIFE SCIENCES.

[0034] Chitosan derivatives can also be used instead of chitosan if their physicochemical properties are similar to those of chitosan. The chitosan derivatives can be obtained by modifying chitosan selected from esterification, etherification, carboxylation, alkylation, acylation, acetylation, Schiff base, alkanoylation, sulfonylation, and quaternization. According to one embodiment, the derivatives are selected from hydroxypropyl chitosan, glycol chitosan, methyl glycol chitosan, carboxymethyl chitosan, chitosan hydrochloride, and trimethyl chitosan.

[0035] The manufacturing process can affect not only the degree of deacetylation of chitosan but also its average (number-average) molecular weight. Chitosans with number-average molar masses up to 1,000,000 g / mol can be produced, or chitosans with number-average molecular weights above 1,000 kDa but much lower average number-average molecular weights can be produced. Alternatively, other hydrolysis methods that cause molecular degradation, such as enzymatic hydrolysis, oxidative hydrolysis, microwave hydrolysis, or gamma radiation hydrolysis, can be used. In the prior art, it has been believed that chitosans with particularly high average number-average molecular weights are well suited for layer formation and provide layers with high barrier properties. However, as shown in this application, the opposite is true. Compared to chitosans with high average number-average molecular weights, chitosans with low average number-average molecular weights, especially those with number-average molecular weights below 70 kDa, can dissolve in coating colors at much higher concentrations. Chitosans with higher average number-average molecular weights (80 kDa (CT1) or 100 kDa to 250 kDa (CT7)) already reach viscosities above 1000 mPa·s, making the coating colors unmanageable in large-scale industrial processes, even at concentrations of 1 to 5 wt. In contrast, chitosan CT6 (50 kDa) according to the invention was used to prepare coating color solutions with chitosan concentrations of up to 7.5 wt. % (see Example 1).

[0036] Even better results were obtained with CT8, which uses chitosan with an even lower average number average molecular weight, only 20 kDa (see Example 4 onwards). Concentrations of up to 15 wt % were achievable.

[0037] As a result, the average number average molecular weight of chitosan can be 70 kDa or less. For example, the average number average molecular weight is 10 kDa, 12 kDa, 14 kDa, 16 kDa, 18 kDa, 20 kDa, 22 kDa, 24 kDa, 26 kDa, 28 kDa, 30 kDa, 32 kDa, 34 kDa, 36 kDa, 38 kDa, 40 kDa, 42 kDa, 44 kDa, 46 kDa, 48 kDa, 50 kDa, 52 kDa, 54 kDa, 56 kDa, 58 kDa, 60 kDa, 62 kDa, 64 kDa, 66 kDa, 68 kDa, or 70 kDa. In one embodiment, the average number average molecular weight of chitosan is less than 50 kDa. According to one embodiment, the average number average molecular weight of chitosan is 40 kDa or less. According to one embodiment, the average number average molecular weight of chitosan is 30 kDa or less. According to one embodiment, the average number average molecular weight of chitosan is 20 kDa or less.

[0038] Chitosans with such low average number average molecular weights, or corresponding chitosan derivatives, can be dissolved in concentrations up to 15% by weight. Chitosan and / or its derivatives are present in the coating color at concentrations greater than 5% by weight, based on the total weight of the coating color. Chitosan and / or its derivatives are present in the coating color at concentrations of 5%, 6%, 7%, 8%, 9%, 10%, 11%, 12%, 13%, 14%, 15%, 16%, 17%, 18%, 19%, or 20% by weight. According to one embodiment, chitosan and / or its derivatives are present at concentrations greater than 9% by weight, based on the total weight of the coating color. According to one embodiment, chitosan and / or its derivatives are present at concentrations greater than 11% by weight, based on the total weight of the coating color. According to one embodiment, chitosan and / or its derivatives are present at concentrations greater than 13% by weight, based on the total weight of the coating color. Above 13% by weight, chitosan may reach a viscosity such that the coating color can no longer be well processed process-technically.

[0039] In addition to chitosan or a chitosan derivative, the coating color can also contain oligochitosan. The average molecular weight of the oligochitosan can be in the range of 1 to 10 kDa. For example, the average number-average molecular weight of the oligochitosan can be 1 kDa, 2 kDa, 3 kDa, 4 kDa, 5 kDa, 6 kDa, 7 kDa, 8 kDa, 9 kDa, or 10 kDa. According to one embodiment, the average number-average molecular weight of the oligochitosan is in the range of 2 to 8 kDa. According to one embodiment, the average number-average molecular weight of the oligochitosan is in the range of 4 to 6 kDa. As shown in the examples, the addition of oligochitosan can reduce the viscosity of the coating color by up to one-third without compromising the barrier effect of the chitosan coating color layer. This is achieved when using a 1:3 (25%:75%) ratio of oligochitosan to chitosan. If the ratio is further increased to 1:1, the viscosity will certainly decrease even more significantly. However, this is achieved at the expense of the oxygen barrier effect. A pure oligochitosan layer has no oxygen barrier effect at all. The oligochitosan can be present in a proportion ranging from 5% to 30% by weight based on the total weight of chitosan, i.e., chitosan and / or chitosan derivatives and oligochitosan.

[0040] As shown in the examples, high solids contents can be achieved, particularly when organic acids are used. According to one embodiment, the coating color of the present invention contains at least one organic acid. Examples include alkanoic acids such as acetic acid and formic acid, hydroxycarboxylic acids such as lactic acid, dicarboxylic acids such as malic acid and tartaric acid, tricarboxylic acids such as citric acid, and vinyl carboxylic acids such as ascorbic acid. Surprisingly, it has been shown that the choice of acid not only significantly affects the solubility of chitosan and thus the chitosan content in the coating color, but also the viscosity of the coating color. In particular, the organic acids lactic acid, malic acid, and ascorbic acid not only dissolve high chitosan contents but also maintain viscosity within a range suitable for large-scale industrial papermaking at high solids contents. According to one embodiment, the organic acid is selected from lactic acid, malic acid, and ascorbic acid. As shown in the examples, lactic acid, in particular, can be combined with many different additives, such as surfactants, plasticizers, and inorganic pigments, to produce chitosan coating colors that ensure good processability and high oxygen barrier properties. According to one embodiment, the organic acid is lactic acid.

[0041] In the prior art, 1% acetic acid is typically used to dissolve chitosan. Other sources start by stating that the acid should be used in a 1:1 molar ratio to chitosan. The inventors have discovered that the optimal molar ratio of acid to chitosan corresponds to at least the degree of deacetylation. The starting point is that this amount of acid fully protonates the amine functional groups of chitosan, thereby dissolving the chitosan. The resulting pH value should then be less than about 6.5, which is the pKs value of chitosan. The pH value can be less than 6.5, less than 6.3, or less than 6.0.

[0042] According to one embodiment, the molar ratio of the organic acid corresponds to the degree of deacetylation. Thus, when the degree of deacetylation is 50%, the molar ratio is preferably 0.5, when the degree of deacetylation is 70%, the molar ratio is preferably 0.7, and when the degree of deacetylation is 90%, the molar ratio is preferably 0.9. According to one embodiment of the coating color, the organic acid to chitosan and / or chitosan derivative is present in a molar ratio of at least 0.5 to chitosan and / or chitosan derivative. For example, the molar ratio can be 0.50, 0.52, 0.54, 0.56, 0.58, 0.60, 0.62, 0.64, 0.66, 0.68, 0.70, 0.72, 0.74, 0.76, 0.78, 0.80, 0.82, 0.84, 0.86, 0.88, 0.90, 0.92, 0.94, 0.96, 0.98, or 1.00. According to one embodiment of the coating color, the organic acid relative to the chitosan and / or chitosan derivative is present in a molar ratio relative to the chitosan and / or chitosan derivative of at least 0.7. According to one embodiment of the coating color, the organic acid is present in a molar ratio relative to the chitosan and / or chitosan derivative of at least 0.9, particularly preferably at least 0.9. According to one embodiment of the coating color, the organic acid to chitosan and / or chitosan derivative is present in a molar ratio to chitosan and / or chitosan derivative of at least 0.93.

[0043] Other than the presence of an organic acid in the solution, there are no special requirements for the solvent. Preferably, the solvent should be an aqueous solvent. According to one embodiment, the aqueous solvent is water.

[0044] Further additives can contribute to the properties of the coating color according to the present invention, which functions as an oxygen barrier when applied to paper. For example, the use of nonionic surfactants reduces the OTR. According to one embodiment, the coating color contains at least one nonionic surfactant. As shown in the examples, in particular, sorbitan fatty acid esters, optionally ethoxylated, are suitable as surfactants in chitosan coating colors. In particular, good results were obtained with the ethoxylated sorbitan fatty acid esters sorbitan monolaurate (Span 20®), polyoxyethylene (20) sorbitan monostearate (Tween 60®), and polyoxyethylene (20) sorbitan monolaurate (Tween 20®). According to one embodiment, the coating color contains at least one surfactant selected from the group consisting of sorbitan monolaurate (Span 20®), polyoxyethylene (20) sorbitan monostearate (Tween 60®), and polyoxyethylene (20) sorbitan monolaurate (Tween 20®).

[0045] The surfactant concentration also influences the oxygen transmission rate (OTR) of the coating color layer. The surfactant should be present in the coating color at a concentration of at least 0.1% by weight relative to the chitosan weight. According to the present invention, "chitosan weight" is understood to mean the total weight of all chitosan and chitosan derivatives present in the coating color. For example, the surfactant may be present in the coating color at a concentration of 0.1%, 0.2%, 0.3%, 0.4%, 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, 1.0%, 1.2%, 1.4%, 1.6%, 1.8%, 2.0%, 2.2%, 2.4%, 2.6%, 2.8%, 3.0%, 3.5%, 4.0%, 4.5%, 4.6% by weight relative to the weight of chitosan and / or derivatives. The surfactant may be present in a concentration of 5.0%, 5.5%, 6.0%, 6.5%, 7.0%, 7.5%, 8.0%, 8.5%, 9.0%, 9.5%, 10.0%, 10.5%, 11.0%, 11.5%, 12.0%, 12.5%, 13.0%, 14.0%, 14.5%, 15.0%, 15.5%, or 16.0% by weight. According to one embodiment, the surfactant is present in the coating color at a concentration ranging from 0.4 to 15% by weight relative to the weight of chitosan. According to one embodiment, the surfactant is present in the coating color at a concentration ranging from 0.8 to 12% by weight relative to the weight of chitosan and / or derivatives. According to one embodiment, the surfactant is present in the coating color at a concentration ranging from 1 to 8% by weight relative to the weight of chitosan.

[0046] Furthermore, the coating color according to the present invention can contain a plasticizer. As shown in the examples, hydrophilic plasticizers increase the folding strength of the coating color layer applied to paper without increasing the oxygen transmission rate (OTR). According to one embodiment, the coating color contains at least one hydrophilic plasticizer. In this case, sugar alcohols such as sorbitol, glycerol, xylitol, and mannitol are particularly suitable. According to one embodiment, the coating color contains at least one sugar alcohol. According to one embodiment, the coating color contains a sugar alcohol selected from sorbitol, glycerol, xylitol, and mannitol.

[0047] The plasticizer can be present in the coating color at a concentration ranging from 1 to 40% by weight relative to the weight of chitosan. The plasticizer concentration can be, for example, 1%, 3%, 5%, 7%, 10%, 11%, 13%, 15%, 17%, 20%, 21%, 23%, 25%, 27%, 30%, 31%, 33%, 35%, 37%, or 40% by weight relative to the weight of chitosan. As the plasticizer concentration increases, the flexural strength also increases. For example, at a concentration of 10% by weight, slight cracks are still discernible at the flex points, whereas at a concentration of 30% by weight, these cracks are only detectable under high magnification with a scanning electron microscope. Depending on the choice of plasticizer, concentrations up to 50% by weight still produce good results in terms of flexural strength, but high plasticizer proportions can significantly increase the OTR. According to one embodiment, the concentration of the plasticizer in the coating color ranges from 5 to 35% by weight relative to the weight of chitosan. According to one embodiment, the concentration of the plasticizer in the coating color ranges from 8 to 32% by weight. According to one embodiment, the concentration of the plasticizer in the coating color ranges from 10 to 30% by weight.

[0048] Furthermore, the coating color can contain other additives that impart additional functionality to the coating color. As shown in the examples, inorganic pigments, such as kaolin-based pigments, can be used to create coating colors with higher solids contents but within a manageable viscosity range. Coating colors added in this way have the advantage of imparting oxygen barrier properties to even fairly porous paper. According to one embodiment, the coating color contains at least one inorganic pigment. This pigment can be selected from natural calcium carbonate, precipitated calcium carbonate, aluminum oxide, aluminum hydroxide, silica, particularly precipitated silica and pyrogenic silica, diatomaceous earth, magnesium carbonate, titanium oxide, bentonite, and clays such as kaolinite, montmorillonite, smectite, illite, chlorite, vermiculite, talc, and pyrophyllite. The coating color can also contain several of these pigments, particularly two, three, or four of these pigments. The clay is particularly talc or kaolin. According to one embodiment, the inorganic pigment is a flaky layered silicate. Commercially available silicates are ASP109 and Capim™ NP, among others.

[0049] The inorganic pigment can be present in the coating color at a concentration ranging from 1 to 30% by weight relative to the weight of chitosan. The concentration of the inorganic pigment can be, for example, 1%, 3%, 5%, 7%, 9%, 11%, 13%, 15%, 17%, 20%, 21%, 23%, 25%, 27%, or 30% by weight relative to the weight of chitosan. According to one embodiment, the concentration of the inorganic pigment in the coating color ranges from 10 to 28% by weight relative to the weight of chitosan or a derivative thereof. According to one embodiment, the concentration of the inorganic pigment in the coating color ranges from 20 to 26% by weight. According to one embodiment, the concentration of the inorganic pigment in the coating color ranges from 20 to 25% by weight.

[0050] When inorganic pigments are used, the solids content in the coating color may be greater than 9% by weight, based on the total weight of the coating color. The solids content relative to the total weight may be, for example, 9%, 11%, 13%, 15%, 17%, 20%, 21%, 23%, 25%, 27%, or 30% by weight. According to one embodiment, the solids content is greater than 12% by weight. According to another embodiment, the solids content is greater than 15% by weight. According to another embodiment, the solids content is about 20% by weight.

[0051] The kinematic viscosity of the coating color can range from 80 mPa·s to 2000 mPa·s. The kinematic viscosity can be influenced by the concentration and type of chitosan, by organic acids, and by various additives. For example, the kinematic viscosity of the coating color can be 80 mPa·s, 100 mPa·s, 120 mPa·s, 140 mPa·s, 160 mPa·s, 180 mPa·s, 200 mPa·s, 250 mPa·s, 300 mPa·s, 350 mPa·s, 400 mPa·s, 450 mPa·s, 500 mPa·s, 550 mPa·s, 600 mPa·s, 650 mPa·s, 700 mPa·s, 750 mPa·s, 800 mPa·s, 850 mPa·s, 900 mPa·s, 95 ... According to one embodiment, the kinematic viscosity of the coating color is in the range of 150 mPa·s to 1000 mPa·s. According to one embodiment, the kinematic viscosity of the coating color is in the range of 200 mPa·s to 400 mPa·s.

[0052] Coated paper According to a second aspect, the present invention relates to a coated paper comprising a base paper and at least one barrier layer applied directly or indirectly to the base paper, the coating color layer being based on a coating color according to the first aspect.

[0053] As base paper for the coated paper according to the first or second embodiment, basically any kind of paper is conceivable, i.e., both paperboard and cardboard, or plain paper. Preferably, paper made from hardwood pulp and softwood pulp should be used. The base paper can be kraft paper. Kraft paper is known in the prior art. Kraft paper is the strongest paper variety. It is made from almost 100% cellulose fibers, with only starch, alum, and sizing agents added to create surface effects and increase strength. Low basis weight paper is in high demand for food packaging because it is flexible and material-saving. It is precisely in such paper that the coating color layer according to the present invention significantly improves the barrier performance.

[0054] According to one embodiment of the coated paper according to the first or second aspect, the basis weight of the base paper is 150 g m -2 According to one embodiment of the coated paper according to the first or second aspect, the basis weight of the base paper is 150 g m -2 The basis weight is, for example, 150 g m -2 , 145g·m -2 , 140g·m -2 , 135g·m -2 , 130g·m -2 , 125g·m -2 , 120g·m -2 , 115g·m -2 , 110g·m -2 , 105g·m -2 , 100g·m -2 , 95g·m -2 , 90g·m -2 , 85g·m -2 , 80g·m -2 , 75g·m -2 , 70g·m -2 , 65g·m -2 , 60g·m -2 , 55g·m -2 , 50g·m -2 , 45g·m -2 , 40g·m -2 , 35g·m -2 , 30g·m -2 , 25g·m-2 or 20g·m -2 According to one embodiment, the basis weight is 100 g m -2 According to one embodiment, the basis weight is less than 80 g m -2 According to one embodiment, the basis weight is 40 to 80 g m -2 The range is.

[0055] It is preferred that the paper has a composition in which the long fiber content is 10 to 80%, preferably 20 to 50%, and the short fiber content is 20 to 90% by weight, preferably 50 to 80% by weight.

[0056] Long fibres are understood to be fibres with a fibre length of 2.6 to 4.4 mm, short fibres to be fibres with a fibre length of 0.7 to 2.2 mm.

[0057] The base paper for the coated paper according to the second embodiment can be a base paper coated on one or both sides, or an uncoated base paper. However, the uncoated base paper can also be surface treated, and the coated base paper can be coated with a coating weight of 5 g / m². 2 The composition may contain up to 10 ...

[0058] For use as packaging in the food industry, paper requires a certain tear strength or breaking force. According to one embodiment, the coated paper has a breaking force across the width in the fiber direction of 3.0 to 6.0 kN m -1 The breaking strength in the fiber direction relative to the width is, for example, 3.0 kN m -1 , 3.2 kN m -1 , 3.4 kN m -1 , 3.5 kN m -1 , 3.6 kN m -1 , 3.8 kN m -1 , 4.0 kN m -1 , 4.2 kN m -1 , 4.4 kN m -1 , 4.5 kN m -1 , 4.6 kN m -1 , 4.8 kN m -1 , 5.0 kN m -1 , 5.2 kN m -1 , 5.4 kN m -1 , 5.5 kN m -1 , 5.6 kN m-1 , 5.8 kN m -1 , 6.0 kN m -1 According to one embodiment, the breaking strength in the fiber direction across the width is 3.5 to 5.5 kN·m -1 According to one embodiment, the breaking strength in the fiber direction across the width is in the range of 4.0 to 5.0 kN·m -1 The range is.

[0059] The use of a coated color layer reduces the permeability of the coated paper to at least one gas compared to the base paper, which may be oxygen (O2), nitrogen (N2), carbon dioxide (CO2), methane (CH4), hydrogen (H2), water vapor, or mixtures thereof (e.g., air).

[0060] In particular, the oxygen transfer rate (OTR) is reduced. The OTR can be determined according to ISO 15105-1. Usually, the permeability of the base paper itself is so high that it is not possible to determine the oxygen transfer rate. The OTR of base paper without a color coating is at least 100,000 cm 3 m -2 ·d -1 According to one embodiment, the OTR of the base paper is at least 50,000 cm 3 m -2 ·d -1 According to another embodiment, the OTR of the base paper is at least 10,000 cm 3 m -2 ·d -1 is.

[0061] The coating color layer according to the invention makes it possible to achieve coated papers with high barrier properties, in particular with very low OTR. According to one embodiment, the coating color has a basis weight of 10±1 g m -2 In this case, OTR is 50cm 3 m -2 ·d -1 The following is the result.

[0062] The OTR of the coated paper according to the present invention is, for example, 50 cm 3 m -2 ·d-1 、48cm 3 ·m -2 ·d -1 、46cm 3 ·m -2 ·d -1 、44cm 3 ·m -2 ·d -1 、42cm 3 ·m -2 ·d -1 、40cm 3 ·m -2 ·d -1 、38cm 3 m 2 d -1 、36cm 3 ·m -2 ·d -1 、34cm 3 ·m -2 ·d -1 、32cm 3 ·m -2 ·d -1 、30cm 3 ·m -2 ·d -1 cm 3 、28cm 3 ·m -2 ·d -1 、26cm 3 m 2 d -1 、24cm 3 ·m -2 ·d -1 、22cm 3 ·m -2 ·d -1 、20cm 3 ·m -2 ·d -1 、18cm 3 ·m -2 ·d -1 、16cm 3 ·m -2 ·d -1 、14cm 3 m -2 d -1 、12cm 3 ·m -2 ·d -1 、10cm 3 ·m -2 ·d -1 、8cm 3 ·m-2 ·d -1 , 6cm 3 m -2 ·d -1 , 4cm 3 m -2 ·d -1 , 2cm 3 m -2 ·d -1 , 1cm 3 m -2 ·d -1 By selecting the appropriate components of the coating color, 3 m -2 ·d -1 Less than or equal to 10cm 3 m -2 ·d -1 The following OTR can be achieved:

[0063] The total coating weight of the color layer on coated paper is 2 to 30 g m -2 For example, the basis weight can be in the range of 2 g m -2 , 4g·m -2 , 5g·m -2 , 6g·m -2 , 8g·m -2 , 10g·m -2 , 12g·m -2 , 14g·m -2 , 15g·m -2 , 16g·m -2 , 18g·m -2 , 20g·m -2 , 22g·m -2 , 24g·m -2 , 25g·m -2 , 26g·m -2 , 28g·m -2 , or 30g·m -2 According to one embodiment, the basis weight of the coating color layer is 2 to 15 g m -2 According to one embodiment, the basis weight of the coating color layer is in the range of 4 to 10 g m -2 According to one embodiment, the basis weight of the coating color layer is in the range of 6 to 8 g / m 2 The range is.

[0064] According to one embodiment of the coated paper, the coating color layer is prepared by applying and curing the coating color. As shown in the examples, the chitosan coating color can be applied multiple times, for example, to reduce oxygen permeability and / or to remove possible defects. According to one embodiment, the coating color layer is prepared by applying and curing the coating color at least twice.

[0065] According to one embodiment, the coated paper has a precoat disposed between the base paper and the coated color layer. This precoat contains at least one inorganic pigment and, optionally, a polymer binder. When such a precoat (also called a primer) is applied, it has the advantage of sealing the surface of the paper and allowing a separate barrier layer coated thereon to migrate only slightly into the paper, thereby providing sufficient interlayer adhesion. Furthermore, this precoat reduces the average depth of the base paper's roughness and provides an advantageous "hold-out" characterized by a uniform application and a defined surface energy, so that the coated barrier layer can be optimally formed. Furthermore, the precoat provides interlayer adhesion between the base paper and the barrier layer, which can be important for subsequent sealing applications.

[0066] The term "CCK paper" refers to a base paper in which the base paper is kraft paper and has been coated with a coating, usually consisting of fine clay (kaolin) or other mineral fillers. This coating improves the surface properties of the paper by making it smoother, whiter, and often shinier. "CCK" stands for "Coated Clay Kraft."

[0067] The precoat may be a totally hydrophobic precoat. In another embodiment, the precoat is totally hydrophilic. The precoat preferably contains 1 to 70% by weight, preferably 5 to 50% by weight, and particularly preferably 15 to 30% by weight, of a polymer binder. This amount refers to the amount of dry precoat in the final product. Examples of polymer binders are styrene butadiene latex (SBR), styrene acrylate latex, polyvinyl alcohol (PVA), acrylate copolymers, and starches selected from natural starch, oxidized starch, etherified starch, and esterified starch. According to one embodiment, the binder is SBR. According to one embodiment, the SBR is present in a concentration of 15 to 30% by weight.

[0068] The precoat more preferably contains 50 to 95% by weight, preferably 65 to 90% by weight, and particularly preferably 70 to 80% by weight of inorganic pigment. This amount refers to the amount of dry precoat in the final product. The inorganic pigment can be selected from silicates, especially layered silicates, kaolin (china clay), calcium carbonate, titanium dioxide (TiO), and talc. According to one embodiment, the inorganic pigment is a layered silicate. According to one embodiment, the layered silicate is present in a concentration of 70 to 80% by weight.

[0069] Additionally, the precoat may contain additives such as thickeners, e.g., acrylate-based thickeners, surfactants, and / or rheology modifiers. The use of crosslinking agents is also contemplated. Preferably, the precoat contains a zirconium-based crosslinking agent, which is itself crosslinked by formaldehyde.

[0070] These additives are preferably present in an amount of 0 to 2% by weight each, preferably from greater than 0 to 2% by weight, with the 0% value preferably being excluded. The total amount of additives is preferably 0.5 to 3.0% by weight, particularly preferably 0.8 to 2.0% by weight, and most preferably 1.0 to 1.5% by weight. This amount refers to the amount of dried precoat in the final product. According to one embodiment, the additives are an acrylate-based thickener and a zirconium-based crosslinker. According to one embodiment, the acrylate-based thickener and zirconium-based crosslinker additives are present in a total amount of 1.0 to 1.5% by weight.

[0071] According to one embodiment, the precoat contains 70-80 wt% of layered silicate, 15-30 wt% of SBR, and 1.0-1.5 wt% of additives, acrylate thickener and zirconium crosslinker, preferably in a proportion of 0.05-0.4 wt% of the acrylate thickener and 0.9-1.3 wt% of the zirconium crosslinker.

[0072] Instead of the above precoat, a pure starch precoat can be used. The starch precoat is made of a starch selected from natural starch, cationized starch, oxidized starch, etherified starch, and esterified starch. Cationic starch with a degree of cationization of 0.05 to 0.2 is preferred.

[0073] The amount of precoat applied is preferably 1 to 10 g / m 2 , and particularly preferably 2 to 6 g / m 2 , and particularly preferably 4 to 6 g / m 2 This amount refers to the amount of dry precoat in the final product.

[0074] The materials present in the color coating layer render the coated paper biodegradable. "Biodegradability" refers to the ability of organic chemicals to be broken down biologically, i.e., by living organisms or their enzymes. In an ideal case, this chemical metabolism proceeds completely to mineralization, but it can also stop at transformation products that are stable to degradation. OECD guidelines for the testing of chemicals are generally recognized and are also used within the scope of chemical certification. Tests in OECD Test Series 301 (A-F) demonstrate rapid and complete biodegradation (ready biodegradability) under aerobic conditions. Separate test methods exist for highly soluble, poorly soluble, and volatile substances. Paper that has a biodegradability of at least 40% measured according to OECD 301F or at least 20% measured according to OECD 302C (MITI-II-Test), and therefore has inherent or fundamental degradability, is considered "biodegradable" or "biodegradable" within the meaning of this invention. This corresponds to the limit value of OECD 302C according to the "Revised Introduction to the OECD Guidelines for testing of Chemicals, section 3, Part 1, dated 23 March 2006," which also states that paper is rapidly biodegradable, with at least 60% of the limit value measured according to OECD 301F.

[0075] According to one embodiment of the coated paper according to the second aspect, the coated paper is readily biodegradable according to OECD301.

[0076] Furthermore, the coated paper according to the second embodiment is recyclable. Paper recycling refers to the process of breaking down and recycling waste paper, used cardboard, and paperboard in paper mill facilities, and then producing new paper, cardboard, and paperboard from them. In this case, on a small scale, used waste paper is first converted into waste paper stock, which is then used to produce new paper. Deinking or deinking (from the English word ink = "printing ink" or "ink") is a key process in paper recycling, for removing printing ink from printed waste paper. Recyclability can be assessed, for example, using INGEDE Methode 11. Coated papers according to the invention achieve a deinkability score of more than 50 using INGEDE Methode 11. Preferably, the deinkability score is more than 70.

[0077] Coated papers can be approved for direct or indirect food contact depending on the components used in the barrier layer, and are particularly suitable for approval in accordance with European Food Safety Authority guidelines.

[0078] The coated paper according to the second aspect may comprise further layers in addition to the barrier layer. According to one embodiment, the coated paper comprises a further layer selected from a coating color, an ink, a sealing medium and an adhesive.

[0079] Furthermore, the coated paper according to the invention can be metallized in the nanometer range, for example with Al2O3 or Al. The coated paper according to the invention is further preferably characterized in that a further layer comprising a metal, in particular aluminum and / or a metal oxide, in particular aluminum oxide and / or silicon oxide, is provided on the barrier layer.

[0080] The further layer may in particular reduce the permeability of the coated paper to other gases or form a barrier to liquids or viscous substances such as grease, oils, hydrocarbons, etc.

[0081] Another layer is a) at least one hydrophobic polymer, such as a polyacrylate, a styrene copolymer / butadiene copolymer, and / or a polyolefin-based polymer; b) at least one hydrophilic polymer, such as a polyvinyl alcohol-based polymer; c) at least one inorganic pigment and a binder; d) containing amorphous and crystalline regions; e) comprising or consisting of substances selected from the group consisting of lipophilic substances, paraffins, in particular hard paraffins, waxes, in particular microcrystalline waxes, waxes based on vegetable oils or fats, waxes based on animal oils or fats, vegetable waxes, animal waxes, low molecular weight polyolefins, polyterpenes, and mixtures thereof; f) reducing or preventing the migration of substances, especially hydrophobic substances, such as substances according to item e) above, for example preventing or reducing the migration of substances from the underlying layer into food, especially food containing fats and oils; g) at least heat-sealable or cold-sealable; h) at least one adhesive; i) comprising or consisting of at least one thermoplastic material, in particular as a heat-sealable material; j) at least one natural wax and / or at least one carboxylic acid component and at least one natural resin It is possible.

[0082] Manufacturing method Various manufacturing methods are conceivable for producing coated paper according to the invention. The here important OTR of the color coating layer in the coated paper is achieved in particular by the method for producing coated paper shown in the examples. Thus, according to a fourth aspect, the present invention relates to a method for producing coated paper comprising a base paper and a color coating layer, the method comprising the following steps: a) preparing a coating color according to a first aspect comprising an organic acid and a nonionic surfactant by introducing the organic acid and the nonionic surfactant into water and adding chitosan in small amounts; b) preparing a base paper; c) applying the coating color to the base paper, preferably by curtain or doctor blade methods; and d) A process of hardening the coating color to obtain a coating color layer. Includes:

[0083] According to one embodiment, steps c) and d) are repeated at least once. According to one embodiment, the steps are repeated two, three or four times.

[0084] The method according to the invention can be used to influence the properties of the coated color layer: furthermore, the curing temperature, curing time and curing pressure influence the uniformity and the barrier effect.

[0085] According to one embodiment of the method, the curing temperature is in the range of 20 to 300°C. The curing temperature may be 20°C, 40°C, 60°C, 80°C, 90°C, 100°C, 110°C, 120°C, 130°C, 140°C, 150°C, 160°C, 170°C, 180°C, 190°C, 200°C, 220°C, 240°C, 260°C, 280°C, or 300°C. According to one embodiment of the method, the curing temperature is in the range of 90 to 140°C. According to one embodiment of the method, the curing temperature is in the range of 100 to 110°C.

[0086] According to one embodiment of the method, the curing time ranges from 10 seconds to 15 minutes. The curing time can be, for example, 10 seconds, 20 seconds, 30 seconds, 40 seconds, 50 seconds, 60 seconds, 70 seconds, 80 seconds, 90 seconds, 100 seconds, 110 seconds, 120 seconds, 150 seconds, 3 minutes, 4 minutes, 5 minutes, 6 minutes, 7 minutes, 8 minutes, 9 minutes, 10 minutes, 11 minutes, 12 minutes, 13 minutes, 14 minutes, or 15 minutes. According to one embodiment of the method, the curing time ranges from 1 to 3 minutes.

[0087] According to one embodiment of the method, the curing pressure is in the range of 0.2 bar to 3 bar. According to one embodiment of the method, the curing pressure is in the range of 0.9 bar to 1.1 bar.

[0088] packaging According to a fourth aspect, the present invention relates to packaging comprising a coated paper according to the second aspect. In that case, this may be packaging for tobacco products or consumer goods, for example for use in food, as packaging for electronic components such as silica gel packs, for medical products such as rapid tests, for detergents and cleaning agents, especially in powder or tablet form.

[0089] Furthermore, this may be packaging for dry food, refrigerated food that requires further cooking, packaging containing food in multiple serving sizes, or packaging containing single serving sizes of food sold in several units.

[0090] The packaging may be, for example, a stand-up pouch packaging, a tube-type pouch packaging or a paper wrapper, etc. According to one embodiment, the packaging is a tube-type pouch packaging.

[0091] Example A. Raw materials used The raw materials used in the following examples, their preparation and characteristic properties are shown in Tables 1 to 5 below.

[0092] [Table 1]

[0093] [Table 2]

[0094] [Table 3]

[0095] [Table 4]

[0096] [Table 5]

[0097] B. Carrier Materials Unless otherwise specified, a primed base paper was used as the carrier material in all examples. This primed base paper was composed of 40% long fibers and 60% short fibers and had a precoat / primer coating (coat weight: 5 g / m). 2 ) is composed of 75.9% pigment (layered silicate), 22.8% latex (styrene butadiene latex), and 1.3% rheology modifier (acrylate thickener 0.2%, zirconium crosslinker 1.1%), with a total basis weight of 63 g / m 2 is.

[0098] This primer-bearing base paper is also called clay coated kraft (CCK) paper.

[0099] C. Methods Used C.1 Coating process After the coating color was prepared, it was degassed for 5 minutes using a Hauschild Speedmixer at 30 mbar and 800 rpm. 3-5 ml of this coating color was applied to the precoated side of the base paper at room temperature using a film applicator equipped with a doctor blade (Erichsen). The doctor blade was selected to achieve the specified coating weight. The basis weight indicated refers to the dry layer.

[0100] [Table 6]

[0101] After the color was applied, the paper was attached directly to a commercial paperboard using a magnet (to avoid curling) and dried in a convection oven (Memmert, settings: 50% flap, 50% fan) for 3 minutes at 105° C. The paper was then stored at room temperature under standard laboratory conditions.

[0102] C.2 Determination of oxygen transmission rate (OTR) The oxygen transmission rate (OTR) was measured using a Brugger gas permeability tester. In this case, the gas permeability was quantified using a differential pressure method (manometric method, ISO15105-1) with a pressure sensor. Here, the OTR was 78.4 cm 2 The coated paper was prepared so that the entire measurement area of ​​the sample was covered with the coated surface. In this case, the paper served as a barrier between the low-pressure and high-pressure chambers by sealing with high-vacuum grease. After ensuring proper sample preparation (no leaks, wrinkles, or folds), the low-pressure chamber was evacuated under high vacuum for 1 h. Oxygen was then introduced into the high-pressure chamber at room temperature (1 bar, 50 ml / min). The amount of oxygen permeating the coated paper and entering the low-pressure chamber was recorded by a pressure sensor as the pressure increased. Only after the time-dependent pressure change in the low-pressure chamber reached equilibrium was the oxygen transmission rate (OTR) determined by the instrument's internal software.

[0103] C.3 Determination of oil resistance The oil resistance of the coated papers was determined using a method according to DIN 53116 (Palm Kernel Fat Test).

[0104] C.4 Viscosity measurement The viscosity of the prepared coating colors was determined using a Brookfield DVII+ rotational viscometer at speeds of 10 to 200 revolutions per minute. For this purpose, 10 ml of coating color and a spindle S34 were used at a temperature of 22 °C. The viscosity determination was carried out over a period of 15 minutes.

[0105] C.5 Determination of Barrier Coating Application Weight Barrier coating application weight g / m 2 is determined by the weight difference between coated and uncoated paper.

[0106] Example 1 - Preparation of comparative coating colors and coating colors according to the invention The chitosan with the highest molecular weight (CT2) showed a viscosity exceeding 2000 mPa·s even at low concentrations of 1-2 wt% (dissolved in 1 M acetic acid). Chitosans with relatively low molecular weights (CT1, CT7) also showed a viscosity exceeding 2000 mPa·s at low concentrations of 5 wt% (dissolved in 1 M acetic acid).

[0107] Chitosan was suspended in water and mixed with the required amount of acid depending on the degree of deacetylation (DAC).

[0108] Calculation example: Preparation of 7.5% (w / v) acetic acid aqueous solution (HAC) of CT6:

number

number

[0109] The average molar mass of the chitosan monomer units used in the calculation is determined by a weighted average taking into account the degree of deacetylation and the molar mass of the glucosamine or N-acetylglucosamine units.

number

[0110] When the degree of deacetylation is 0.9, the calculation results are as follows:

number

[0111] 7.5 wt% CT6 solution: 7.5 g of CT6 was suspended in 59.18 ml of distilled water and mixed with 40.82 ml of 1 M acetic acid while stirring. The mixture was stirred overnight at room temperature to ensure complete dissolution.

[0112] The prepared solution was sieved through a sieve bag with a mesh size of 150 μm, and then through a sieve bag with a mesh size of 80 μm to remove impurities and undissolved chitosan / chitin particles.

[0113] 5% by weight CT6 / CT1 solution: 6 g of CT6 was suspended in 87.33 ml of distilled water, and 32.67 ml of 1 M acetic acid was added while stirring. The mixture was stirred overnight at room temperature to ensure complete dissolution.

[0114] The prepared solution was sieved through a sieve bag with a mesh size of 150 μm and then through a sieve bag with a mesh size of 80 μm to remove impurities and undissolved chitosan / chitin particles.

[0115] Example 2 - Barrier paper production by single application and OTR measurement (CT6) 2.1 Preparation and measurement of barrier paper using chitosan CT6 The sieved solution was degassed for 5 minutes at 30 mbar and 800 rpm using a Hauschild Speedmixer before coating. The coating colour was applied to the CCK-coated side of the base paper at room temperature using a film applicator equipped with a doctor blade (Erichsen). The dry coating weight was approximately 5 g / m. 2 In this case, an 80 μm wet film was applied. The squeegee speed was 3 m / min. After the color was applied, the paper was attached directly to a commercial paperboard using a magnet (to avoid curling) and dried in a convection oven (Memmert, settings: 50% flap, 50% fan) at 105 °C for 3 minutes.

[0116] The resulting paper showed defects in the form of scratch marks due to the heavy application of the wet film at low concentrations. Furthermore, confocal microscopy images showed defects due to spontaneous dewetting. Areas with an increased number of defects showed little or no barrier effect against oxygen.

[0117] However, measurements of the selected defect-free area, the "sweet spot" (see Figure 3), show that, in part, 3 m -2 ·d -1 , or about 5 cm more 3 / m2 *d showed very good oxygen barrier effect.

[0118] The prepared solution was sieved through a sieve bag with a mesh size of 150 μm and then through a sieve bag with a mesh size of 80 μm to remove impurities and undissolved chitosan / chitin particles.

[0119] The sieved solution was degassed at 30 mbar and 800 rpm for 5 min before coating. For coating, a doctor blade was used to apply an 80 μm wet film. The squeegee speed was 3 m / min. The chitosan coating was then immediately dried at 105 °C.

[0120] The wet film application required in this case was 100 μm. Figure 1 shows a confocal microscope image of paper coated with the coating colors according to Table 1. However, the heavy wet film application caused water damage to the paper, which was clearly visible on the reverse side of the paper. In addition to the scratch marks, other defects could also be identified in the large-area fluorescent image.

[0121] OTR measurements were then performed on these papers, which revealed that only the chitosan coating consisting of 5 wt% CT6 in water and acetic acid achieved a low but measurable oxygen barrier effect. CT1 showed no barrier effect at all. The lack or low oxygen barrier effect was attributed to defects (see Figure 2). Upon closer inspection, the visible defects were caused by a variety of factors, including undissolved chitosan / chitin particles, dust particles, and spontaneous dewetting.

[0122] 2.2 Manufacturing and measurement of barrier paper using high-density CT6 Next, it was tested whether a higher concentration of CT6, i.e., 7.5 wt. % in acetic acid, would result in a better layer. The layer was applied as described in 2.1. However, again, defects were formed, with a correspondingly very low or even unmeasurable oxygen barrier performance.

[0123] However, the "sweet spot" - the defect-free area - is measured in part at approximately 60 cm 3 / m 2 *d, or approximately 5 cm 3 / m 2 *d, which resulted in a very good oxygen barrier effect.

[0124] Example 3 - Manufacturing of barrier paper with multiple coatings and OTR measurement In this example, a multilayer chitosan layer was prepared and its oxygen barrier properties were determined. Multiple applications were performed to minimize defects discernible from Example 1. For this purpose, a 5% (w / v) solution of CT6 in 1 M aqueous acetic acid was prepared according to Example 1.

[0125] [Table 7]

[0126] Two, three, and four layer barrier coatings were created by applying two, three, or four coats of CT6 coating color at a coating weight of 2.5 g / m² per coat. 2 The results for these multiple coated papers are summarized in Table 7 below. The experimental results show that successive coatings improve the oxygen barrier properties. This is presumably because the multiple coatings fill in any imperfections, resulting in a continuous chitosan film on the paper that provides a good oxygen barrier.

[0127] [Table 8]

[0128] Example 4 - Variation of manufacturing parameters: acid, surfactant amount, and coating weight Preparation of coating colors: Coating colors were prepared by either Variation A or B using chitosan CT8 and acetic acid, lactic acid, ascorbic acid, malic acid as described below.

[0129] Variant A: Chitosan (CT8) was pre-suspended in water with surfactant (CPD mixer, core-pulling precision equipment, at 650 rpm for 5 minutes). Acid was then added with the mixer running until the chitosan was dissolved. A rapid increase in viscosity was observed. The resulting solution was sieved through a 150 μm mesh sieve bag and then through an 80 μm mesh sieve bag to remove impurities and undissolved chitosan / chitin particles.

[0130] Variant B: After the acid and surfactant were added to the water (stirring at 650 rpm for 5 minutes, CPD mixer), chitosan was added in small increments while stirring. This addition sequence allowed chitosan to dissolve without a sudden increase in viscosity or hardening due to impact. The resulting solution was sieved through a 150 μm mesh sieve bag and then through an 80 μm mesh sieve bag to remove impurities and undissolved chitosan / chitin particles.

[0131] CT8 was dissolved in different aqueous acids depending on the degree of deacetylation (93%) and mixed with different amounts of surfactant Tween 20®. The CT8 concentration was 15 wt%. The acids were used depending on the degree of deacetylation (93%) as described in Example 1, and the molar ratio of acid to CT8 was 0.93.

[0132] Next, as in C.1, the coating color is changed to CT8 with a coating weight of 6 g / m 2 or 7.5 g / m 2 Multiple papers were prepared for each coating color composition.

[0133] The resulting papers were first visually inspected, then the OTR was determined according to C.2, and finally the oil resistance test was carried out according to C.4.

[0134] [Table 9]

[0135] Based on OTR values, malic acid, lactic acid and ascorbic acid are particularly suitable for the coating colors according to the invention. The use of all three acids results in an OTR value of 10 cm 3 m -2 ·d -1 Creates an oil-resistant barrier in less than 100g (all pass palm kernel fat test).

[0136] The appropriate dry content could be achieved by adjusting the molar mass. Coatability was also significantly improved with CT8 (separate coating for barrier formation was possible).

[0137] The acid variation was essentially achieved by using acetic acid, ascorbic acid, lactic acid, and malic acid in combination with low molecular weight CT8 (15 wt%) to achieve an OTR value of 10 cm on precoated paper. 3 m -2 ·d -1 It has been shown that a very good oxygen barrier of less than 1000 kJ / cm2 can be produced, and the precoat comprises clay minerals, in particular flaky kaolin. The addition of a surfactant such as Tween 20 is advantageous, as it allows, for example, the avoidance of wetting defects.

[0138] Example 5 - Effect of chitosan concentration on viscosity and OTR To achieve curtain coating, a viscosity range of approximately 200–400 mPa·s must be achieved. However, using 15 wt. % CT8, the viscosity exceeds this range. To ensure flowability, the CT8 content was reduced and the viscosity of the resulting solution was measured.

[0139] [Table 10]

[0140] The results show that a viscosity in the range for curtain coating can be achieved when the chitosan (CT8) concentration is reduced to 11 wt %. For malic acid, a smaller reduction, i.e., 13.5 wt % (relative to CT8), was sufficient to achieve a viscosity in this range, i.e., 400 mPas.

[0141] [Table 11]

[0142] The results show that good to very good OTR values ​​can be achieved even with a low CT8 percentage (11 wt%), especially when using lactic acid and ascorbic acid, to achieve a viscosity range (200-400 mPas). OTR values ​​of 10 cm 3 m -2 ·d -1 In order to achieve a concentration of less than 10 g / m2, when using ascorbic acid, 2 A total application weight of more than 7 g / m is required when using lactic acid. 2 A total coating weight of 10 cm is sufficient. The coated paper still has a coating weight of 10 cm after 4 months of storage at room temperature. 3 m -2 ·d -1 The OTR value was less than 1000kJ / kg.

[0143] Example 6 - Characterization of a coating color system according to the present invention made from CT8 and lactic acid Coating colors were prepared according to the recipes shown in Table 11.

[0144] [Table 12]

[0145] 6.1 Oxygen barrier dependent on coating weight The base paper was coated with coating colors at different coat weights.

[0146] [Table 13]

[0147] 6.2 Oil and fragrance barrier properties The oil and fragrance barrier properties were then tested. Chitosan coating is an effective oil barrier. Single-sided coating with palm kernel fat test doctor blade on CCK-coated base paper as described in Example 4.7. Chitosan coatings are effective fragrance barriers or hexane vapor barriers, i.e., hexane vapor transmission rates (HVTR) <1g / m 2 d (total coating weight approx. 8.8 g / m 2 ) Example 9 - Addition of oligochitosan To address issues related to drying and air entrapment, oligochitosan (O-CT) can be added to further reduce viscosity. For this purpose, oligochitosan (O-CT) was used to replace part of the CT8 in the recipe (100 g preparation) listed in Table 10.

[0148] [Table 14]

[0149] [Table 15]

[0150] In the CT8 lactic acid recipe, some of the CT8 was replaced with O-CT to reduce the viscosity of the coating color. The relatively low viscosity allows for smooth drying, thereby reducing the occurrence of drying defects.

[0151] The addition of O-CT significantly reduced the viscosity, but O-CT alone was unable to form a continuous coating and therefore lacked barrier properties.

[0152] Example 10: Variation of surfactants Surfactants are used in coating colors to improve the coating pattern (Strichbild) and dewetting issues (reducing surface tension). In combination with the CT8 lactic acid-based coating color, various nonionic surfactants have been found to be suitable for creating an effective oxygen barrier.

[0153] [Table 16]

[0154] [Table 17]

[0155] Example 11: Addition of layered silicate In the course of testing various base papers, the addition of flaky layered silicates in the form of a slurry was also investigated. On the one hand, these can close any porous structure of the paper that may be present during drying, but on the other hand, they can increase the solids content and therefore reduce the required drying performance. As carrier materials, either a primed base paper (see B) or a starch-coated paper was used. The starch-coated paper consisted of 40% long and 60% short fibers and had a precoat / primer interface (coat weight: 0.5 g / m). 2 ) is made of cationic starch with a cationization degree of 0.1 and has a total basis weight of 63 g / m 2 is.

[0156] Preparation of coating colors: The coating colors were prepared according to Variant B of Example 4, where the inorganic pigment was presuspended before adding the CT8.

[0157] After the acid and surfactant were introduced into the water, the agitator was turned on (650 rpm, CPD agitator) and the inorganic pigment was added in the form of a slurry. The mixture was stirred for a further 10 minutes before adding the CT8 in small portions to ensure uniform dispersion of the pigment.

[0158] Base paper coating: Same as the previous example. A preliminary evaluation of defects (pinhole test) (see Figure 6) showed a significant reduction in exposed areas of porous starch-coated paper with the addition of flaky layered silicate. Otro percentages: 56.78% CT8, 28.89% lactic acid, 14.19% kaolin-based layered silicate (ASP109), 0.16% Tween 20.

[0159] Various proportions of Capim NP Slurry (TG = 68 wt%) in the CT8 lactic acid recipe were tested to examine their effect on the viscosity and barrier properties of base paper precoated with kaolin-based layered silicates. The results are shown in Figure 7.

[0160] Up to a concentration of approximately 20% by weight (otro) of layered silicate, the viscosity increased only slowly, so that the coating colors remained within the viscosity range for large-scale industrial applications. At concentrations above 20% by weight (otro), a sharp increase in viscosity appeared, suggesting a possible gel effect that could be exploited for film stabilization.

[0161] Up to a proportion of phyllosilicate of about 20% by weight (otro), the thickness of the pre-coated paper after coating and drying is 10 cm 3 m -2 ·d -1 OTR values ​​below 20 wt.% (otro) were measurable, and precoats, especially those containing flaky kaolin, were used. For porous starch-coated paper, OTR values ​​could only be determined above 20 wt.% (otro). As the proportion of layered silicate increased, the OTR also decreased. This indicates that the fiber structure of the base paper is almost completely closed, allowing for stable OTR measurements.

[0162] Example 12: Addition of plasticizer to improve flexural strength To address the brittleness of natural chitosan polymers in the dry state, various plasticizers were added to the CT8 lactic acid recipe in varying proportions. The plasticizers reduce the interactions between the polymer chains, thereby lowering the glass transition temperature and making the material more flexible.

[0163] Preparation of coating colors: The coating color was prepared according to variant B according to example 4, in which the plasticizer was presuspended before the addition of CT8.

[0164] After the acid and surfactant were introduced into the water, the agitator was turned on and the plasticizer was added (650 rpm, CPD agitator). The mixture was stirred for a further 5 minutes before adding the CT8 in portions to ensure uniform dispersion of the plasticizer.

[0165] Base paper coating: Coating was carried out as described in C.1.

[0166] [Table 18]

[0167] Glycerol, sorbitol, mannitol, xylitol, and PEG400 were used as plasticizers at concentrations of 10 to 50% by weight relative to the chitosan mass. As a result, the following proportions were obtained in the coating film.

[0168] [Table 19]

[0169] The results are shown in Table 19. [Table 20]

[0170] The plasticizers sorbitol, glycerol, xylitol (and mannitol) can be used without compromising the oxygen barrier properties (OTR 10cm 3 m -2 ·d -1 It can be added until the ratio of CT8 in the recipe is about 30 to 40% by weight.

[0171] The addition of sugar alcohols (especially xylitol, glycerol, and sorbitol) as plasticizers reduces the interactions between polymer chains as the proportion increases, thereby producing a barrier with improved flexibility.

[0172] With regard to other advantageous embodiments of the device according to the invention, in order to avoid repetition, reference is made to the general part of the description and to the appended claims.

[0173] Finally, it is expressly mentioned that the above-described embodiments of the device according to the invention are used only to illustrate the claimed teaching, and are not limited to these embodiments.

Claims

1. A coating color for coating paper, comprising chitosan and / or a chitosan derivative having an average number average molecular weight of 50 kDa or less and at least one solvent.

2. 2. The coating color according to claim 1, wherein the chitosan and / or chitosan derivative has an average number average molecular weight of 40 kDa or less, preferably 30 kDa or less, particularly preferably 20 kDa or less.

3. 2. The coating color according to claim 1, wherein the chitosan derivative is obtained by modification of the chitosan selected from esterification, etherification, carboxylation, alkylation, acylation, acetylation, Schiff base, alkanolylation, sulfonylation, and quaternization, and is preferably a derivative selected from hydroxypropyl chitosan, glycol chitosan, methyl glycol chitosan, carboxymethyl chitosan, chitosan hydrochloride, and trimethyl chitosan.

4. 10. A coating colour according to any one of the preceding claims, wherein the degree of deacetylation of the chitosan is at least 50%, preferably at least 70%, preferably at least 90%, in particular at least 93%.

5. 10. A coating color according to claim 9, wherein the chitosan and / or chitosan derivative is present in a concentration of more than 7% by weight, preferably more than 9% by weight, particularly preferably more than 11% by weight, in particular more than 13% by weight, based on the total weight of the coating color.

6. 10. A coating color according to any one of the preceding claims, further comprising oligochitosan, preferably having an average number average molecular weight in the range of 1 to 10 kDa, particularly preferably in the range of 2 to 8 kDa, in particular in the range of 4 to 6 kDa.

7. 10. The coating color according to claim 9, further comprising at least one organic acid, preferably selected from acetic acid, formic acid, citric acid, tartaric acid, lactic acid, malic acid and ascorbic acid, particularly preferably selected from lactic acid, malic acid and ascorbic acid, in particular lactic acid.

8. 8. Coating color according to claim 7, wherein the acid is present in a molar ratio to the chitosan and / or chitosan derivative of at least 0.5, preferably at least 0.7, particularly preferably at least 0.9, in particular at least 0.

93.

9. 10. A coating color according to any one of the preceding claims, further comprising at least one non-ionic surfactant, preferably an optionally ethoxylated sorbitan fatty acid ester, particularly preferably selected from sorbitan monolaurate (Span 20), polyoxyethylene (20) sorbitan monostearate (Tween 60), and polyoxyethylene (20) sorbitan monolaurate (Tween 20).

10. 10. Coating color according to claim 9, wherein the surfactant is present in the coating color in a concentration of at least 0.1% by weight, preferably in the range of 0.4 to 15% by weight, particularly preferably in the range of 0.8 to 12% by weight, in particular in the range of 1 to 8% by weight, relative to the weight of the chitosan.

11. 10. A coating color according to any one of the preceding claims, further comprising at least one hydrophilic plasticizer, preferably a sugar alcohol, particularly preferably selected from sorbitol, glycerol, xylitol and mannitol.

12. 12. Coating color according to claim 11, wherein the plasticizer is present in the coating color in a concentration in the range of 1 to 40% by weight, preferably in the range of 5 to 35% by weight, particularly preferably in the range of 8 to 32% by weight, in particular in the range of 10 to 30% by weight, relative to the weight of chitosan.

13. 10. A coating color according to any one of the preceding claims, further comprising at least one inorganic pigment, preferably selected from natural calcium carbonate, aluminium oxide, aluminium hydroxide, silica, in particular precipitated silica and pyrogenic silica, diatomaceous earth, magnesium carbonate, titanium oxide, bentonite and clay, in particular talc or kaolin.

14. 14. Coating colour according to claim 13, wherein the inorganic pigment is present in the coating colour in a concentration in the range of 1 to 30% by weight, preferably in the range of 10 to 28% by weight, particularly preferably in the range of 20 to 26% by weight, in particular in the range of 20 to 25% by weight, based on the weight of chitosan.

15. 10. A coating colour according to any one of the preceding claims, wherein the solvent is selected from aqueous solvents, preferably the solvent is water.

16. 10. A coating color according to claim 9, wherein the solids content of the coating color, based on the total weight of the coating color, is more than 9% by weight, preferably more than 12% by weight, particularly preferably more than 15% by weight, in particular about 20% by weight.

17. 10. A coating color according to any one of the preceding claims, wherein the coating color has a kinematic viscosity in the range of 80 mPa s to 2000 mPa s, preferably in the range of 150 mPa s to 1000 mPa s, particularly preferably in the range of 200 mPa s to 400 mPa s.

18. A coated paper comprising a base paper and at least one coating color layer coated directly or indirectly on the base paper, wherein the coating color layer is based on the coating color according to any one of claims 1 to 17.

19. The total coating weight of the coating color layer is 2 to 15 g / m ２ in the range of 4 to 10 g / m ２ In the range of 6 to 8 g / m ２ 18. The coated paper of claim 17, wherein the viscosity is in the range of

20. The oxygen transmission rate (OTR) of the coated paper is 50 cm ３ ・m －２ ・d －１ Less than 30 cm, preferably ３ ・m －２ ・d －１ Particularly preferably 20 cm or less ３ ・m －２ ・d －１ Below, especially 10 cm ３ ・m －２ ・d －１ 19. The coated paper of claim 17 or claim 18, wherein:

21. The OTR of the base paper without a coated color layer is at least 100,000 cm ３ ・m －２ ・d －１ , preferably at least 50,000 cm ３ ・m －２ ・d －１ , particularly preferably at least 10,000 cm ３ ・m －２ ・d －１ 21. The coated paper of claim 20, wherein

22. 10. A coated paper according to any one of the preceding claims, wherein the coating colour layer is made by applying and curing the coating colour, preferably by applying and curing the coating colour at least twice.

23. 10. Coated paper according to any one of the preceding claims, wherein a precoat comprising at least one inorganic pigment and optionally a polymeric binder is disposed between the base paper and the coated color layer.

24. The coated paper has at least one of the following characteristics: The coated paper is biodegradable, and in particular has ready biodegradability according to OECD 301; - the coated paper is recyclable; and - the coated paper may be permitted for direct or indirect food contact, in particular in accordance with the guidelines of the European Food Safety Authority; The coated paper according to any one of claims 19 to 23, having

25. A method for producing the coated paper of any one of claims 18 to 24, comprising the steps of: a) preparing the coating color according to any one of claims 9 to 17, which contains an organic acid and a nonionic surfactant, by introducing the organic acid and the nonionic surfactant into water and adding chitosan little by little; b) preparing a base paper; c) applying said coating color to the base paper, preferably by curtain or doctor blade method; and d) A step of curing the coating color to obtain a coating color layer. A method comprising:

26. Packaging for consumer goods, food or tobacco products, comprising the coated paper of any one of claims 18 to 24.

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