KR102490787B1 - Coating agent and barrier film comprising the same - Google Patents

Abstract

The present invention relates to a coating agent capable of realizing a barrier film having excellent mechanical properties while having low oxygen permeability and water permeability, and the barrier film comprising the same. The coating agent of the present invention includes a crosslinked protein containing a crosslinked link between an amide group site of glutamine and an amino group site of lysine by a transglutaminase crosslinking agent.

Description

Coating agent and barrier film containing the same {COATING AGENT AND BARRIER FILM COMPRISING THE SAME}

The present invention relates to a coating agent and a barrier film including the coating agent.

In general, food is decomposed into low-molecular substances by the action of microorganisms, light, oxygen, chemicals, etc., and as a result, the original quality of taste, smell, color, appearance, etc. is lost, which is called deterioration or deterioration. In order to suppress this phenomenon, contamination of microorganisms and chemicals must be minimized through a hygienic manufacturing process, and the key is to minimize contact of the contents from deterioration factors (light, moisture, oxygen, etc.) that affect food contents during distribution. to be.

In particular, the moisture content of the contents and the oxygen concentration inside the package directly affect the growth of microorganisms and the rancidity of the contents, so the selection and application of packaging materials with appropriate moisture and oxygen barrier properties for the stable storage and distribution of food contents are essential. It is a very important factor in the development of processed foods.

Currently, synthetic resin films commonly used in the food packaging field are mainly general-purpose materials such as polyethylene (PE), polypropylene (PP), polyvinyl chloride (PVC), polystyrene (PS), and polyacrylonitrile (PAN). After manufacturing polymers such as polyvinyl alcohol (PVA), polyvinylidene chloride (PVDC), ethylene vinyl alcohol (EVOH), and polyamide (PA) as a solvent-based coating agent, thin film coating is applied on the above-mentioned substrate for final packaging Films are manufactured, and finally, various composite film types are manufactured with a multi-layer structure such as PP/EVOH/Nylon, PP/Nylon/Al foil/PET, etc., to give barrier properties suitable for product characteristics.

However, polymers such as EVOH and PVDC, which are currently mainly used as coating liquids, are mostly solvent-type coatings containing a high content of organic solvents due to their low solubility. And it is causing continuous problems in terms of health and safety of composite film manufacturing workers. Accordingly, there is a very high need for development of an eco-friendly and safe water-based coating agent and a composite film using the same. Accordingly, research on replacing existing plastic films using biopolymers derived from natural products is being actively conducted. Carbohydrates, proteins, lipids, etc. are used as coating agents using biopolymers derived from natural products.

However, natural-based proteins conventionally applied to coatings have a low molecular weight, and thus there is a problem in that the mechanical properties of the produced film are deteriorated and it is vulnerable to moisture.

The problem to be solved by the present invention is to provide a coating agent capable of realizing a barrier film having physical properties suitable for food packaging materials and a barrier film including the same.

However, the problem to be solved by the present invention is not limited to the above-mentioned problem, and other problems not mentioned will be clearly understood by those skilled in the art from the following description.

One embodiment of the present invention provides a coating agent comprising a cross-linked protein containing a cross-linking of the amide group site of glutamine and the amino group site of lysine by an enzymatic cross-linking agent.

In addition, an exemplary embodiment of the present invention, a substrate; and a barrier layer provided on at least one surface of the substrate and including the coating agent.

The coating agent according to one embodiment of the present invention can effectively implement a barrier layer having low oxygen permeation and water permeability properties.

The coating agent according to one embodiment of the present invention can effectively implement a barrier layer having excellent mechanical properties such as strength and durability.

The barrier film according to an exemplary embodiment of the present invention may have low oxygen permeation and water permeability and excellent mechanical properties.

Effects of the present invention are not limited to the above-mentioned effects, and effects not mentioned will be clearly understood by those skilled in the art from the present specification and accompanying drawings.

1 is a diagram schematically illustrating cross-linking between an amide group site of glutamine and an amino group site of lysine through an enzymatic cross-linking agent according to an exemplary embodiment of the present invention.
Figure 2a shows the result of measuring the IR spectrum of the barrier layer prepared in Example 1, Figure 2b shows the result of measuring the IR spectrum of the barrier layer prepared in Comparative Example 1.
Figure 3a is a view showing the oxygen permeability according to the oxygen barrier property evaluation time of the barrier film prepared in Example 1, Figure 3b is a view showing the oxygen permeability according to the oxygen barrier property evaluation time of the barrier film prepared in Example 2 3c is a view showing the oxygen permeability according to the oxygen barrier property evaluation time of the barrier film prepared in Comparative Example 1, and FIG. 3d is the oxygen permeability according to the oxygen barrier property evaluation time of the barrier film prepared in Comparative Example 2 is the drawing shown.

Throughout the present specification, when a certain component is said to "include", it means that it may further include other components without excluding other components unless otherwise stated.

Throughout the present specification, when a member is said to be located “on” another member, this includes not only a case where a member is in contact with another member, but also a case where another member exists between the two members.

Throughout the present specification, the unit "parts by weight" may mean the ratio of the weight of each component.

Throughout this specification, “layer” represents a broad concept including “film, stretched sheet, unstretched sheet, or similar form”.

Throughout the present specification, “coating agent” is capable of forming a coating layer (barrier layer), and may also be referred to as a coating composition.

Hereinafter, the present invention will be described in more detail.

One embodiment of the present invention provides a coating agent comprising a cross-linked protein containing a cross-linking of the amide group site of glutamine and the amino group site of lysine by an enzymatic cross-linking agent.

The coating agent according to one embodiment of the present invention can effectively implement a barrier layer having low oxygen permeation and water permeability properties. The coating agent according to one embodiment of the present invention can effectively implement a barrier layer having excellent mechanical properties such as strength and durability.

Protein is a complex molecule made up of relatively simple molecules called amino acids. There are about 20 types of amino acids that make up proteins, and these amino acids are connected to each other through chemical bonds called peptide bonds to make polypeptides. A peptide bond (-O=C-NH-) is a chemical bond formed by the reaction between a carboxyl group and an amino group, and contains an amine group site.

The amine group site is a hydrophilic part capable of hydrogen bonding, and the coating agent containing the protein in which the amine group site exists as it is decreases the moisture barrier property, and the boiling point (B.P) of the coating agent increases when dried after application. There is a problem that drying is slow and productivity is lowered.

According to an exemplary embodiment of the present invention, the cross-linked protein may be one in which an amide group site of glutamine and an amino group site of lysine contained in a raw protein to be described later form an isopeptide bond through the enzyme cross-linking agent and cross-link it. That is, in the case of proteins included in the coating agent, the oxygen barrier properties and moisture barrier properties of the coating agent can be effectively improved by minimizing the amine group site present in the raw protein.

1 is a diagram schematically illustrating cross-linking between an amide group site of glutamine and an amino group site of lysine through an enzymatic cross-linking agent according to an exemplary embodiment of the present invention.

According to an exemplary embodiment of the present invention, the enzyme cross-linking agent may include at least transglutaminase. Specifically, the enzyme cross-linking agent may be transglutaminase. In particular, as an enzyme crosslinking agent, transglutaminase can effectively and stably crosslink the amide group site of glutamine and the amino group site of lysine. Referring to FIG. 1, transglutaminase (TG), an enzyme cross-linking agent, is composed of a γ-carboxamide group (-(C=O)NH ₂ ) and lysine (Lys) of glutamine (Gln) contained in raw protein. By forming an isopeptide bond between the ε-amino groups (-NH ₂ ) of, raw proteins can be cross-linked.

In the protein cross-linked through the enzymatic cross-linking agent, exposed amine groups are reduced through cross-linking, so that the hydrophilic portion of the protein can be relatively hydrophobic. Through this, the water permeability and oxygen permeability of the coating agent including the cross-linked protein can be effectively reduced. Furthermore, there are advantages in that rapid drying is possible after application of the coating agent, thereby increasing productivity of the barrier film, and improving processability by facilitating dispersion of the crosslinked protein even in a solvent with a low boiling point. Furthermore, the barrier layer prepared using the coating agent may have improved interlayer strength with respect to the film.

According to one embodiment of the present invention, the cross-linked protein may include a reaction product of a mixture of an enzyme cross-linking agent dispersion containing the enzyme cross-linking agent and a protein solution containing the raw protein. Specifically, the coating agent may include a reaction product of a mixture of an enzyme crosslinking agent dispersion and a protein solution. More specifically, the cross-linked protein may be obtained by cross-linking the source protein through the enzyme cross-linking agent. In order to form the cross-linked protein, the mixture may be reacted for a time of 1 hour or more and 3 hours or less under mild conditions of 40 ° C. or more and 60 ° C. or less. Under the above conditions, the enzymatic cross-linking reaction of the mixture is activated to effectively obtain the cross-linked protein.

According to one embodiment of the present invention, the raw protein is whey protein isolate (9410 WPI), whey protein concentrate (8000 WPC), soy protein isolate (SPI), rice protein isolate (RPI), Among oat protein isolate (OPI), pea protein isolate (PPI), casein, sodium caseinate, corn zein, gelatin and wheat protein (Gluten) may contain at least one.

The protein is a natural product-derived protein and has advantages of being environmentally friendly and having high stability. Therefore, it has high suitability to be used as a packaging film coating agent for products directly related to consumer safety, such as food, medicine, and household goods.

According to one embodiment of the present invention, based on 100 parts by weight of the protein solution, the content of the raw protein is 1 part by weight or more and 15 parts by weight or less, 5 parts by weight or more and 15 parts by weight or less, or 7 parts by weight or more 10 parts by weight. may be below. When the content of the raw protein contained in the protein solution is within the above range, the water barrier performance and oxygen barrier performance of the coating agent containing the cross-linked protein can be effectively improved. In addition, it is possible to suppress deterioration of mechanical properties such as durability and strength of the barrier layer prepared using the coating agent. Furthermore, the barrier layer prepared using the coating agent may have improved interlayer strength with respect to the film.

According to an exemplary embodiment of the present invention, based on 100 parts by weight of the enzyme crosslinking agent dispersion, the content of the enzyme crosslinking agent is 0.1 part by weight or more and 10 parts by weight or less, 0.5 parts by weight or more and 5 parts by weight or less, or 1 part by weight or more 3 parts by weight. may be less than When the content of the enzyme cross-linking agent included in the dispersion of the enzyme cross-linking agent is within the above-mentioned range, the cross-linking reaction of the raw protein can be stably and sufficiently proceeded. Through this, the hydrophobicity of the cross-linked protein is sufficiently supplemented, so that the water permeability and oxygen permeability of the coating agent can be effectively lowered, and mechanical properties of the coating agent can be improved. Furthermore, the barrier layer prepared using the coating agent may have improved interlayer strength with respect to the film.

According to an exemplary embodiment of the present invention, the weight ratio of the raw protein and the enzyme cross-linking agent included in the mixture may be 100:0.1 to 100:10. Specifically, the weight ratio of the raw material protein and the enzyme cross-linking agent, which are solids, in the mixture is 100:0.1 to 100:10, 100:0.1 to 100:5, 100:0.1 to 100:3, or 100:0.1 to 100:1. can be By adjusting the weight ratio of the raw protein and the enzymatic crosslinking agent included in the mixture within the above-mentioned range, the crosslinking reaction of the raw protein can be stably and sufficiently proceeded, and the moisture barrier performance of the coating agent containing the crosslinked protein and The oxygen barrier performance can be effectively improved. In addition, the barrier layer prepared using the coating agent may have improved interlayer strength with respect to the film.

According to an exemplary embodiment of the present invention, the mixture may further include a plasticizer. As the plasticizer, those used in the art may be used without limitation. For example, the plasticizer may include sorbitol, fructose, sucrose, mannitol, propylene glycol, glycerol, and polyethylene glycol (PEG200, PEG400). , PEG600, etc.).

According to an exemplary embodiment of the present invention, the content of the plasticizer may be 20 parts by weight or more and 130 parts by weight or less, 50 parts by weight or more and 120 parts by weight or less, or 80 parts by weight or more and 110 parts by weight or less, based on 100 parts by weight of the raw protein. there is. When the content of the plasticizer is within the above range, the coatability of the coating agent may be improved, and the appearance, mechanical properties, and oxygen barrier performance of the barrier layer prepared using the coating agent may be further improved.

According to an exemplary embodiment of the present invention, the coating agent may further include an additive including at least one of a wax and a fatty acid. Specifically, the mixture may further include the additive. The wax and fatty acids are hydrophobic substances and may play a role of supplementing the hydrophobicity of the coating agent.

The wax may be a natural wax, and specific examples include beeswax, carnauba wax, rice bran wax, and candelilla wax, but are not limited thereto. Specific examples of the fatty acids include, but are not limited to, palmitic acid, stearic acid, and lauric acid.

According to an exemplary embodiment of the present invention, the content of the additive included in the mixture is 0.01 part by weight or more and 100 parts by weight or less, 0.1 part by weight or more and 50 parts by weight or less, based on 100 parts by weight of the protein solution, or It may be 0.1 parts by weight or more and 20 parts by weight or less. When the amount of the wax or fatty acid added is within the above-mentioned range, hydrophobicity is sufficiently imparted to the coating agent to improve moisture barrier performance and suppress deterioration in liquid phase stability.

According to an exemplary embodiment of the present invention, the coating agent may be a barrier coating agent. The barrier coating refers to a coating agent having barrier properties, and the barrier properties may mean barrier properties against oxygen and moisture.

An exemplary embodiment of the present invention is a substrate; and a barrier layer provided on at least one surface of the substrate and including the coating agent.

The barrier film according to an exemplary embodiment of the present invention may have low oxygen permeation and water permeability and excellent mechanical properties.

According to an exemplary embodiment of the present invention, the substrate may have a thickness of 10 μm or more and 60 μm or less, and the barrier layer may have a thickness of 0.5 μm or more and 5 μm or less. When the thicknesses of the substrate and the barrier layer in the barrier film are within the aforementioned range, the barrier film may have low oxygen permeation and moisture permeability and excellent mechanical properties.

According to an exemplary embodiment of the present invention, the substrate is polyethylene terephthalate, low density polyethylene, polypropylene, polycarbonate, polymethyl methacrylate, polyimide, stretched polypropylene, unstretched polypropylene, biaxially stretched polypropylene, polyethylene 2 ,6-dicarboxylnaphthalate, polyethersulfone, polyester, polystyrene, nylon, polycaprolactone, polyhydroxyalkanoate, polybutylene adipate terephthalate, polylactic acid, and paper. .

According to one embodiment of the present invention, the barrier layer may be provided in direct contact with the substrate or provided on the substrate through an adhesive or an adhesive film. For example, the coating agent may be applied on the substrate and dried to form the barrier layer on the substrate.

As a coating method for applying the coating agent, spray coating, spin coating, dip coating, gravure coating, micro gravure coating, die coating coating), comma coating, knife coating, direct coating, bar coating, etc. may be used, but is not limited thereto.

In addition, the coating agent can be applied using an applicator, and the thinner the coating film thickness within the above thickness range showing oxygen and moisture barrier properties, the more advantageous it is in terms of economy and work process.

Thereafter, the substrate coated with the coating agent may be dried for 3 to 10 minutes at 100 ° C. or higher and 120 ° C. or lower using a hot air dryer, and specifically, at 110 ° C. or higher and 120 ° C. for 3 to 5 minutes. there is.

According to an exemplary embodiment of the present invention, the oxygen permeability of the barrier film is 0.4 cc/m ² *day or less, 0.35 cc/m ² *day or less, 0.3 cc/m ² *day or less, 0.2 cc/m ² *day or less, or 0.1 cc/m ² *day or less. In addition, the oxygen permeability of the barrier film may be 0.1 cc/m ² *day or more, 0.2 cc/m ² *day or more, or 0.3 cc/m ² *day or more. The barrier film having an oxygen permeability within the aforementioned range may have excellent oxygen barrier performance.

According to an exemplary embodiment of the present invention, the water permeability of the barrier film is 5 g/m ² *day or less, 4 g/m ² *day or less, 3.5 g/m ² *day or less, 3 g/m ² *day or less or less, or 2.5 g/m ² *day or less. In addition, the water permeability of the barrier film may be 2 g/m ² *day or more, 2.5 g/m ² *day or more, or 3 g/m ² *day or more. The barrier film having a moisture permeability within the aforementioned range may have excellent moisture barrier performance.

According to an exemplary embodiment of the present invention, the barrier film can be used as a packaging film for foods, medicines, and household items that must block oxygen and moisture, and can be commercialized as a single-layer film due to its excellent oxygen barrier and moisture barrier properties. Do.

Hereinafter, examples will be described in detail to explain the present invention in detail. However, embodiments according to the present invention can be modified in many different forms, and the scope of the present invention is not construed as being limited to the embodiments described below. The embodiments herein are provided to more completely explain the present invention to those skilled in the art.

Example

Example 1: Preparation of coating agent and barrier film

As an enzyme cross-linking agent, 1 g of transglutaminase was added to 99 g of distilled water and stirred for 10 minutes to prepare an enzyme cross-linking agent dispersion.

8 g of whey protein as raw protein was slowly added to 92 g of distilled water while stirring to prepare a protein solution. Then, 8 g of sorbitol as a plasticizer was added to the protein solution.

Thereafter, 8 g of the prepared enzyme cross-linking agent dispersion was added to the protein solution to which the plasticizer was added to prepare a mixture. The prepared mixture was stirred at 300 rpm using a mechanical stirrer, heated to 50 °C and reacted for 2 hours to activate the enzyme crosslinking reaction. After the enzymatic crosslinking reaction, the mixture was heated to 90° C. for 30 minutes to denature proteins and inhibit enzyme activity, and then cooled to finally prepare a coating agent.

A polyethylene terephthalate (PET) film having a thickness of 12 μm was prepared as a substrate. Thereafter, after applying the coating agent on the PET film with an applicator (YBA-5), the PET film coated with the coating agent was put in a hot air dryer and dried at 120 ° C. for 3 minutes to obtain a barrier layer having a thickness of 1 μm. A barrier film was prepared.

Example 2

In Example 1, a coating agent and a barrier film were prepared in the same manner as in Example 1, except that soybean protein was used instead of whey protein as a raw material protein.

Example 3

In Example 1, a coating agent and a barrier film were prepared in the same manner as in Example 1, except that sodium caseinate was used instead of whey protein as a raw material protein.

Example 4

In Example 1, a coating agent and a barrier film were prepared in the same manner as in Example 1, except that corn protein was used instead of whey protein as a raw protein and ethanol (90% concentration) was used instead of distilled water.

Example 5

In Example 1, a coating agent and a barrier film were prepared in the same manner as in Example 1, except that gelatin was used instead of whey protein as a raw protein.

Comparative Example 1 (without using an enzyme cross-linking agent)

In Example 1, a coating agent and a barrier film were prepared in the same manner as in Example 1, except that the enzyme crosslinking agent dispersion was not added during the preparation of the mixture.

Comparative Example 2 (using an organic acid as a crosslinking agent)

As a cross-linking agent, 1 g of citric acid, an organic acid, was added to 99 g of distilled water and stirred for 10 minutes to prepare an organic acid cross-linking agent dispersion.

Thereafter, a coating agent and a barrier film were prepared in the same manner as in Example 1, except that an organic acid crosslinking agent dispersion was used instead of the enzyme crosslinking agent dispersion in Example 1.

Experimental example

Experimental Example 1: IR spectrum analysis

IR spectra were measured for the film provided with a barrier layer prepared in Example 1 and the film provided with a barrier layer prepared in Comparative Example 1 to confirm crosslinking. The results are shown in Figures 2a and 2b, respectively.

Figure 2a shows the result of measuring the IR spectrum of the barrier layer prepared in Example 1, Figure 2b shows the result of measuring the IR spectrum of the barrier layer prepared in Comparative Example 1.

Referring to Figures 2a and 2b, the barrier layer (coating agent) of Example 1 is compared to the barrier layer (coating agent) of Comparative Example 1, the amide group site and lysine of glutamine contained in whey protein by transglutaminase It was confirmed that a new amide (-CO-NH-) bond was created by cross-linking of the amino group site, and the peak corresponding to the amide appeared relatively large.

Through this, it can be seen that the barrier layer (coating agent) of Example 1 is effectively cross-linked proteins.

Experimental Example 2: Evaluation of oxygen barrier properties (barrier properties) and moisture barrier properties (barrier properties)

With respect to the barrier films prepared in Examples 1 to 5 and Comparative Example 1 and Comparative Example 2, oxygen permeability and moisture permeability were measured through the following methods. The measured results are shown in Table 1 below.

Oxygen permeability evaluation method: Oxygen permeability was measured using an OXTRAN 2/21 oxygen permeability tester manufactured by MOCON, and the result was evaluated. The oxygen permeability indicates the amount of oxygen passing through the barrier film for 24 hours under conditions of a temperature of 23±1 °C, humidity (relative humidity) of 0% and 50%, and O ₂ concentration of 100%.

Water permeability evaluation method: The water permeability was evaluated using a PERMATRAN-W 3/34G permeability tester manufactured by MOCON. The water permeability indicates the amount of water that has passed through the barrier film per unit time under conditions of a temperature of 38 ± 1 °C and a humidity of 100%.

Figure 3a is a view showing the oxygen permeability according to the oxygen barrier property evaluation time of the barrier film prepared in Example 1, Figure 3b is a view showing the oxygen permeability according to the oxygen barrier property evaluation time of the barrier film prepared in Example 2 3c is a view showing the oxygen permeability according to the oxygen barrier property evaluation time of the barrier film prepared in Comparative Example 1, and FIG. 3d is the oxygen permeability according to the oxygen barrier property evaluation time of the barrier film prepared in Comparative Example 2 is the drawing shown.

Experimental Example 3: Interlayer strength evaluation

With respect to the barrier films prepared in Examples 1 to 5, Comparative Example 1 and Comparative Example 2, interlayer strength was measured through the following method. The measured results are shown in Table 1 below.

Interlayer strength evaluation method: Prior to interlayer strength evaluation, an adhesive is applied to the upper surface (barrier layer) of the barrier film coated with a coating agent (barrier layer) to make an evaluation sample, and then LDPE, which is mainly used on the inner surface of the packaging material, is laminated to the adhesive did After lamination, the film was aged in an oven at 40 °C for 72 hours to improve adhesion. Interlayer strength was measured using a universal testing machine (Ametek Inc. LS1 model) at a distance between grips of 30 mm and a test speed of 254 mm/min, and the specimen was cut to a width of 15 mm and a height of 100 mm. After pretreatment for 24 hours by dipping in ethyl acetate to a point of 5 cm at the end of the specimen, it was prepared by peeling about 40 mm.

Raw protein/crosslinking agent oxygen permeability
(cc/(m ² *day)) moisture permeability
(g/(m ² *day)) interfloor strength
(kgf/15mm) Example 1 Whey Protein / TG 0.10 2.96 243.21 Example 2 Soy Protein / TG 0.20 3.15 257.38 Example 3 Sodium Caseinate / TG 0.26 3.64 255.46 Example 4 Corn Protein / TG 0.32 2.31 282.06 Example 5 Gelatin/TG 0.30 3.47 246.88 Comparative Example 1 Whey Protein / TG Free 0.60 6.80 188.13 Comparative Example 2 Use of whey protein / organic acid 0.42 5.93 238.90

In Table 1, TG means transglutaminase.

Referring to Table 1 and FIGS. 3A to 3D, the barrier films prepared in Examples 1 to 5 have significantly lower oxygen permeability and moisture permeability than the barrier films prepared in Comparative Examples 1 and 2. confirmed that

In addition, referring to Table 1, it was confirmed that the barrier films prepared in Examples 1 to 5 had very excellent interlayer strength compared to the barrier films prepared in Comparative Examples 1 and 2.

From this, it can be seen that the coating agent according to an exemplary embodiment of the present invention can easily implement a barrier film having excellent oxygen and moisture barrier performance and excellent mechanical properties such as interlayer strength.

The foregoing detailed description is intended to illustrate and explain the present invention. In addition, the foregoing merely represents and describes preferred embodiments of the present invention, and as described above, the present invention can be used in various other combinations, modifications, and environments, and the scope of the inventive concept disclosed herein, the writings Changes or modifications are possible within the scope equivalent to the disclosure and / or within the scope of skill or knowledge in the art. Accordingly, the above detailed description of the invention is not intended to limit the invention to the disclosed embodiments. Also, the appended claims should be construed to cover other embodiments as well.

Claims (10)

A coating agent comprising a cross-linked protein containing a cross-linked link between an amide group site of glutamine and an amino group site of lysine by a transglutaminase enzyme cross-linking agent,
The cross-linked protein includes a reaction product of a mixture of an enzyme cross-linking agent dispersion containing the enzyme cross-linking agent and a protein solution containing the raw protein,
The content of the enzyme cross-linking agent is 1 part by weight or more and 3 parts by weight or less based on 100 parts by weight of the enzyme cross-linking agent dispersion,
The content of the raw protein is 7 parts by weight or more and 10 parts by weight or less based on 100 parts by weight of the protein solution,
The weight ratio of the raw protein and the enzyme crosslinking agent is 100: 0.1 to 100: 1 coating agent. delete delete delete delete According to claim 1,
The raw protein,
A coating agent comprising at least one of whey protein isolate, whey protein concentrate, soybean protein, rice protein, oat protein, pea protein, casein, sodium caseinate, corn protein, gelatin, and wheat protein. delete According to claim 1,
The mixture further contains a plasticizer,
The content of the plasticizer is 20 parts by weight or more and 130 parts by weight or less based on 100 parts by weight of the raw protein. write; and
A barrier film including a barrier layer provided on at least one surface of the substrate and containing the coating agent according to claim 1 .
According to claim 9,
The above description is
Polyethylene terephthalate, low-density polyethylene, polypropylene, polycarbonate, polymethyl methacrylate, polyimide, stretched polypropylene, unstretched polypropylene, biaxially stretched polypropylene, polyethylene 2,6-dicarboxynaphthalate, polyethersulfone A barrier film of any one of polyester, polystyrene, nylon, polycaprolactone, polyhydroxyalkanoate, polybutylene adipate terephthalate, polylactic acid, and paper.

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