Coating liquid for gas barrier and gas barrier film thereof

Abstract

The invention discloses a coating liquid for gas barrier and a gas barrier film thereof, the coating liquid for gas barrier comprises: a polyvalent metal compound, at least part of the surface of the polyvalent metal compound is provided with a coating layer, the coating layer comprises unsaturated anhydride modified polyvinyl alcohol; a water-soluble resin which has a carboxyl group; and a solvent. The coating liquid disclosed by the invention is good in stability and small in environmental pressure, and a barrier film which can keep excellent gas barrier property under high-temperature and high-humidity conditions can be prepared without repeated coating and drying processes.

Description

Technical Field

[0001] This application relates to the field of materials, and particularly to a coating liquid for gas barrier and its gas barrier film. Background Art

[0002] In the fields of food and drug packaging, packaging materials need to have high gas barrier properties and stability under high temperature and high humidity conditions to meet the requirements of cooking or sterilization processes. However, there are many limitations in the prior art. For example, although PVDC coating liquid has excellent gas barrier performance, it will release toxic gases when incinerated, causing pressure on the environment; the gas barrier performance of PVA coating liquid decreases significantly under high humidity; and traditional cross-linking modification methods require high temperature or long-time curing, with high energy consumption and easy deformation of the substrate. In addition, although the existing patented technologies have improvements, they generally have problems such as complex preparation processes, poor environmental friendliness, insufficient high temperature and high humidity performance, and poor compatibility.

[0003] Therefore, there is an urgent need for a new coating liquid for gas barrier and its gas barrier film, which can simplify the preparation process while providing excellent gas barrier performance and environmental adaptability, and meeting environmental protection requirements at the same time. Summary of the Invention

[0004] This application aims to solve at least one of the technical problems existing in the prior art to some extent. For this purpose, this application provides a coating liquid for gas barrier and its gas barrier film. The coating liquid has good stability, little pressure on the environment, and can prepare a barrier film with excellent gas barrier performance even under high temperature and high humidity conditions without multiple coating and drying processes.

[0005] In the first aspect of this application, this application proposes a coating liquid for gas barrier. According to the embodiments of this application, the coating liquid includes: a polyvalent metal compound, at least part of the surface of the polyvalent metal compound has a coating layer, and the coating layer includes unsaturated anhydride-modified polyvinyl alcohol; a water-soluble resin, the water-soluble resin has a carboxyl group; and a solvent.

[0006] Thus, the polyvalent metal compound can cross-link with the carboxyl group in the water-soluble resin to form ionic bonds or covalent bonds, thereby enhancing the denseness and barrier performance of the coating; using unsaturated anhydride-modified polyvinyl alcohol to coat the metal compound to delay the dissolution of the metal compound into the gas barrier coating liquid, avoiding the rapid reaction of the polyvalent metal compound with the carboxyl group in the water-soluble resin containing carboxyl group, which causes the coating liquid to gel and makes it impossible to coat; using unsaturated anhydride-modified polyvinyl alcohol to coat the metal compound, due to the physical adsorption of the carboxyl group on the metal compound and the chemical cross-linking between unsaturated double bonds, the coating effect is better, and the coated product has good compatibility and stability in the aqueous coating liquid system.

[0007] According to an embodiment of the present application, the coating liquid for gas barrier includes: 0.05 to 10 parts by weight of a polyvalent metal compound, 0.45 to 19 parts by weight of a water-soluble resin, and 80 to 99.5 parts by weight of a solvent.

[0008] According to an embodiment of the present application, the coating layer is obtained by an esterification reaction of an unsaturated acid anhydride and polyvinyl alcohol.

[0009] According to an embodiment of the present application, the unsaturated acid anhydride includes at least one of maleic anhydride, itaconic anhydride, and citraconic anhydride.

[0010] According to an embodiment of the present application, the mass ratio of the unsaturated acid anhydride to polyvinyl alcohol is (1 to 100):1.

[0011] According to an embodiment of the present application, the method for forming the coating layer includes: mixing an unsaturated acid anhydride-modified polyvinyl alcohol with a polyvalent metal compound to obtain a preliminary coating mixture; and subjecting the preliminary coating mixture to a radical polymerization treatment so as to form the coating layer on at least a part of the surface of the polyvalent metal compound.

[0012] According to an embodiment of the present application, the radical polymerization treatment includes at least one of thermal initiation, photoinitiation, and high-energy irradiation initiation.

[0013] According to an embodiment of the present application, the particle size of the polyvalent metal compound is 5 nm to 1 μm.

[0014] According to an embodiment of the present application, the polyvalent metal compound includes at least one of zinc oxide, magnesium oxide, calcium oxide, zinc hydroxide, magnesium hydroxide, calcium hydroxide, zinc carbonate, magnesium carbonate, and calcium carbonate.

[0015] According to an embodiment of the present application, the molecular weight of the water-soluble resin is 5000 to 1000000.

[0016] According to an embodiment of the present application, the water-soluble resin includes at least one of homopolymers and / or copolymers of monomers such as acrylic acid, methacrylic acid, maleic acid, itaconic acid, and crotonic acid.

[0017] According to an embodiment of the present application, the solvent includes at least one of water and an alcohol-water mixture.

[0018] According to an embodiment of the present application, the types of alcohols in the alcohol-water mixture include at least one of methanol, ethanol, isopropanol, and n-propanol.

[0019] According to an embodiment of the present application, the mass ratio of the polyvalent metal compound to the carboxyl group in the water-soluble resin is (0.1 to 1):1.

[0020] According to an embodiment of the present application, the coating liquid for gas barrier further includes a polyol polymer, and the polyol polymer includes at least one of polyvinyl alcohol and ethylene-vinyl alcohol copolymer.

[0021] According to an embodiment of the present application, the mass ratio of the hydroxyl group of the polyol polymer to the carboxyl group of the water-soluble resin is (0.01-10):1.

[0022] According to an embodiment of the present application, the coating liquid for gas barrier further includes a crosslinking agent, and the crosslinking agent includes at least one of amino resin types, isocyanate types, silane coupling agent types, and inorganic nanoparticle types.

[0023] According to an embodiment of the present application, the mass ratio of the water-soluble resin to the crosslinking agent is (10-100):1.

[0024] In a second aspect of the present application, the present application provides a gas barrier film. According to an embodiment of the present application, the gas barrier film includes: a base film layer; a gas barrier layer provided on at least one surface of the base film layer, and the gas barrier layer is formed by using the above-mentioned coating liquid for gas barrier.

[0025] According to an embodiment of the present application, the thickness of the base film layer is 5-300 μm.

[0026] According to an embodiment of the present application, the thickness of the gas barrier layer is 0.1-5 μm.

[0027] According to an embodiment of the present application, the base film layer includes at least one of a polyolefin film, a polyester film, and a polyamide film.

[0028] Additional aspects and advantages of the present application will be given in part in the following description, become apparent in part from the following description, or be learned through the practice of the present application. Detailed Description of Specific Embodiments

[0029] The embodiments of the present application will be described in detail below. The following described embodiments are exemplary and are only used to explain the present application and should not be construed as a limitation to the present application.

[0030] It should be noted that the terms "first" and "second" are only used for descriptive purposes and cannot be construed as indicating or implying relative importance or implicitly specifying the quantity of the indicated technical features. Thus, features defined with "first" and "second" may explicitly or implicitly include one or more of such features. Further, in the description of the present application, unless otherwise stated, the meaning of "a plurality" is two or more.

[0031] The endpoints and any values in the ranges disclosed herein are not limited to the exact ranges or values, and these ranges or values should be understood to include values close to these ranges or values. For numerical ranges, the endpoint values of each range, between the endpoint values of each range and individual point values, and between individual point values can be combined with each other to obtain one or more new numerical ranges, and these numerical ranges should be regarded as specifically disclosed herein.

[0032] In this document, the term "comprising" or "including" is an open expression, that is, it includes the content specified in this application, but does not exclude other aspects of the content.

[0033] In this document, the terms "optionally", "optional" or "option" generally mean that the subsequent events or conditions may but do not necessarily occur, and this description includes the cases where the events or conditions occur and the cases where the events or conditions do not occur.

[0034] Coating liquid for gas barrier

[0035] In the first aspect of the present application, the present application provides a coating liquid for gas barrier. According to an embodiment of the present application, the coating liquid includes: a polyvalent metal compound, at least part of the surface of the polyvalent metal compound has a coating layer, and the coating layer includes unsaturated acid anhydride-modified polyvinyl alcohol; a water-soluble resin, the water-soluble resin has a carboxyl group; and a solvent.

[0036] Thus, the polyvalent metal compound can undergo a crosslinking reaction with the carboxyl group in the water-soluble resin to form an ionic bond or a covalent bond, thereby enhancing the denseness and barrier performance of the coating; using unsaturated acid anhydride-modified polyvinyl alcohol to coat the metal compound to delay the dissolution of the metal compound into the gas barrier coating liquid, avoiding the rapid reaction of the polyvalent metal compound with the carboxyl group in the water-soluble resin containing a carboxyl group, resulting in the gelation of the coating liquid and making it impossible to coat; using unsaturated acid anhydride-modified polyvinyl alcohol to coat the metal compound, due to the physical adsorption effect of the carboxyl group on the metal compound and the chemical crosslinking effect between unsaturated double bonds, the coating effect is better, and the compatibility and stability of the coated product in the aqueous coating liquid system are better.

[0037] According to an embodiment of the present application, the coating liquid for gas barrier comprises: 0.05 to 10 parts by weight of a polyvalent metal compound. For example, it can be 0.05, 0.06, 0.07, 0.08, 0.09, 0.1, 0.2, 0.5, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10; 0.45 to 19 parts by weight of a water-soluble resin. For example, it can be 0.45, 0.46, 0.47, 0.48, 0.49, 0.5, 0.6, 0.7, 0.8, 0.9, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19; 80 to 99.5 parts by weight of a solvent. For example, it can be 80, 81, 82, 83, 84, 85, 86, 87, 88, 89, 90, 91, 92, 93, 94, 95, 96, 97, 98, 99, 99.5. Thus, if the metal compound is too little, the effect of improving gas barrier may not be achieved. If the metal compound is too much, the coating liquid may gel too quickly, resulting in inability to coat. If the content of the water-soluble resin is too low, there will be insufficient crosslinking points and an insufficient network structure cannot be formed, thus reducing the mechanical strength and water resistance of the coating. If the content is too high, the viscosity of the coating liquid will be too large, the drying rate will be too slow, and the flexibility of the coating will be reduced. By controlling the amounts of the polyvalent metal compound and the water-soluble resin within the above ranges in the present application, an optimized crosslinked network structure is formed, which not only improves the gas barrier performance of the coating, but also enhances the mechanical strength, flexibility and water resistance of the coating, enabling it to maintain stable performance under various use conditions.

[0038] According to an embodiment of the present application, the coating layer is obtained by the esterification reaction of an unsaturated acid anhydride and polyvinyl alcohol. Thus, the carboxyl groups of the coating layer can interact with metal ions through ionic bonds or coordination bonds to effectively coat the metal compound, thereby delaying the dissolution of metal ions and preventing the coating liquid from gelling due to rapid crosslinking during storage and processing.

[0039] According to an embodiment of the present application, the unsaturated acid anhydride includes at least one of maleic anhydride, itaconic anhydride and citraconic anhydride, preferably maleic anhydride. Thus, after the esterification reaction of the unsaturated acid anhydride and polyvinyl alcohol, the polyvalent metal compound can be effectively coated, enhancing its dispersibility and stability in the aqueous system.

[0040] According to an embodiment of the present application, the mass ratio of the unsaturated acid anhydride to polyvinyl alcohol is (1 to 100):1, preferably (1 to 10):1. Thus, by adjusting within the mass ratio range of (1 to 100):1, a balance can be achieved among the reaction activity, crosslinking density, water solubility and film-forming property of the coating layer, ensuring the stability of the coating liquid and the high performance of the gas barrier film.

[0041] According to an embodiment of the present application, the method for forming the coating layer includes: mixing an unsaturated anhydride-modified polyvinyl alcohol with a polyvalent metal compound to obtain a preliminary coating mixture; and subjecting the preliminary coating mixture to a radical polymerization treatment so as to form the coating layer on at least a part of the surface of the polyvalent metal compound. Thus, first, the unsaturated anhydride-modified polyvinyl alcohol is mixed with the polyvalent metal compound, and a preliminary coating mixture is formed by the physical adsorption between the carboxyl groups in the modified polyvinyl alcohol and metal ions. This step provides preliminary protection for the metal compound to prevent it from reacting or aggregating rapidly in the coating solution; subsequently, through the radical polymerization treatment, the unsaturated double bonds in the modified polyvinyl alcohol undergo a crosslinking reaction, further enhancing the stability and compactness of the coating layer and forming a more firm coating layer.

[0042] According to an embodiment of the present application, the radical polymerization treatment includes at least one of thermal initiation, photoinitiation, and high-energy irradiation initiation. Thus, free radicals are generated to initiate the crosslinking reaction of the unsaturated double bonds in the unsaturated anhydride-modified polyvinyl alcohol.

[0043] According to an embodiment of the present application, the particle size of the polyvalent metal compound is 5 nm to 1 μm, preferably 5 nm to 100 nm. Thus, if the particle size of the polyvalent metal compound is too small, it is difficult to prepare and store; if the particle size of the metal compound is too large, it will affect the stability of the aqueous coating solution and the gas barrier performance of the formed coating. By controlling the average particle size of the metal compound within the above range in the present application, the gas barrier performance of the coating formed by the coating solution can be improved on the basis of simplifying the processing and storage difficulties.

[0044] According to an embodiment of the present application, the polyvalent metal compound includes at least one of zinc oxide, magnesium oxide, calcium oxide, zinc hydroxide, magnesium hydroxide, calcium hydroxide, zinc carbonate, magnesium carbonate, and calcium carbonate, preferably zinc oxide and magnesium oxide. Thus, the rich polyvalent metal ions in these compounds react with the carboxyl groups in the water-soluble resin to form a dense network structure, significantly improving the gas barrier performance and water resistance of the gas barrier film.

[0045] According to an embodiment of the present application, the molecular weight of the water-soluble resin is 5000 to 1000000. Thus, if the molecular weight is too small, the gas barrier and water resistance of the coating will be reduced; if the molecular weight is too large, the viscosity of the coating solution will be too high, thereby reducing the operability of the coating solution.

[0046] According to an embodiment of the present application, the water-soluble resin includes at least one of homopolymers and / or copolymers of monomers of acrylic acid, methacrylic acid, maleic acid, itaconic acid, and crotonic acid. Thus, the rich carboxyl functional groups in these resins react with the polyvalent metal compound to form a dense and stable network structure, significantly improving the gas barrier performance and water resistance of the gas barrier film.

[0047] According to an embodiment of the present application, the solvent includes at least one of water and an alcohol-water mixture. Thereby, the water-soluble resin can be effectively dissolved and the coated polyvalent metal compound can be dispersed, thereby improving the uniformity and stability of the coating liquid.

[0048] According to an embodiment of the present application, the types of alcohols in the alcohol-water mixture include at least one of methanol, ethanol, isopropanol, and n-propanol. Thereby, the water-soluble resin can be effectively dissolved and the coated polyvalent metal compound can be dispersed, thereby improving the uniformity and stability of the coating liquid.

[0049] According to an embodiment of the present application, the mass ratio of the polyvalent metal compound to the carboxyl group in the water-soluble resin is (0.1-1):1. Thus, if the amount of the metal compound is too small, the effect of improving gas barrier may not be achieved, and if the amount of the metal compound is too large, the coating liquid may gel too quickly, resulting in inability to coat. The present application takes into account the stability of the coating liquid and the gas barrier performance of the coating under high temperature and high humidity conditions by controlling the mass ratio of the polyvalent metal compound to the carboxyl group in the water-soluble resin.

[0050] According to an embodiment of the present application, the gas barrier coating liquid further includes a polyol polymer, and the polyol polymer includes at least one of polyvinyl alcohol and ethylene-vinyl alcohol copolymer. Thereby, the polyol polymer contains multiple hydroxyl functional groups, and the molar percentage content of the hydroxyl functional groups can be not less than 80%. If the content of the hydroxyl functional groups is too low, it is difficult to form a dense packing between the polymer segments, easily resulting in limited oxygen barrier ability of the coating; preferably, the molar percentage content of the hydroxyl functional groups can be not less than 85%, thereby further improving the denseness of the coating and improving the gas barrier ability and effect of the coating.

[0051] According to an embodiment of the present application, the mass ratio of the hydroxyl group of the polyol polymer to the carboxyl group of the water-soluble resin is (0.01-10):1. Thus, if the ratio of the hydroxyl group is lower than the above range, it will have a negative impact on the film-forming property of the coating. If the ratio of the hydroxyl group is higher than the above range, the polyol polymer cannot fully react with the carboxyl group-containing water-soluble resin to form a reorganized cross-linked structure, thereby reducing the gas barrier property of the coating under high temperature and high humidity environment.

[0052] According to an embodiment of the present application, the gas barrier coating liquid further includes a cross-linking agent, and the cross-linking agent includes at least one of amino resin types, isocyanate types, silane coupling agent types, and inorganic nanoparticle types. Thereby, the cross-linking agent can chemically react with the carboxyl group or other functional groups in the water-soluble resin to form a more stable three-dimensional network structure, thereby significantly improving the water resistance, high temperature and high humidity resistance, and adhesion of the coating.

[0053] According to an embodiment of the present application, the mass ratio of the water-soluble resin to the crosslinking agent is (10 to 100):1. Thus, by controlling the mass ratio of the carboxyl-containing water-soluble resin and the crosslinking agent within the above range, the coating has good water resistance, moderate hardness, and good bending resistance, thereby ensuring excellent gas barrier performance of the gas barrier film under high temperature and high humidity conditions.

[0054] According to an embodiment of the present application, the above-mentioned coating solution can be prepared by using a reaction kettle with a stirring device according to a known method. For example, the carboxyl-containing water-soluble resin is dissolved in water to prepare an aqueous solution, and then the polyol polymer and the crosslinking agent are added simultaneously or in batches as required for mixing, and finally the polyvalent metal compound coated with unsaturated acid anhydride-modified polyvinyl alcohol is added for mixing to obtain the coating solution for gas barrier. The preparation method of the coating solution is simple and has good stability, which is suitable for industrial production.

[0055] Gas barrier film

[0056] In a second aspect of the present application, the present application provides a gas barrier film. According to an embodiment of the present application, the gas barrier film includes: a base film layer; and a gas barrier layer provided on at least one surface of the base film layer, and the gas barrier layer is formed by using the above-mentioned coating solution for gas barrier.

[0057] The characteristics and effects described for the above-mentioned coating solution for gas barrier also apply to this gas barrier film, and will not be elaborated here. Compared with the prior art, by laminating a coating layer on the surface of the base film layer at one time, multiple coating and drying processes are avoided, and under high temperature and high humidity conditions, the gas barrier film can still maintain excellent gas barrier performance.

[0058] According to an embodiment of the present application, the thickness of the base film layer is 5 to 300 μm. Thus, if the thickness of the base film layer is too thin, the mechanical strength and barrier performance of the gas barrier film will be reduced, and if it is too thick, the adhesion between the gas barrier layer and the base film will be insufficient. By controlling the thickness of the base film layer within the above range, the mechanical strength, flexibility, cost-effectiveness, and processing efficiency of the gas barrier film are balanced.

[0059] According to an embodiment of the present application, the thickness of the gas barrier layer is 0.1 to 5 μm. Thus, if the thickness of the gas barrier layer is too small, it is difficult to achieve an effective gas barrier effect; if the thickness of the gas barrier layer is too large, the coating uniformity may become poor, and the gas barrier film may be curled as a whole, thereby affecting the gas barrier performance of the gas barrier film and the interlayer adhesion. In the present invention, by limiting the thickness of the gas barrier layer within the above range, various properties such as the gas barrier performance and stress accumulation of the gas barrier layer can be at an optimal level.

[0060] According to an embodiment of the present application, the base film layer includes at least one of a polyolefin film, a polyester film, and a polyamide film. Thus, the diverse requirements for the gas barrier film in different application scenarios are met.

[0061] According to an embodiment of the present application, the gas barrier layer is formed by coating with the above-mentioned gas barrier coating liquid. The gas barrier coating liquid can be directly coated on the base film or on the bottom layer laminated on the surface of the base film, and then immediately subjected to a heat treatment while forming a dry film and performing the heat treatment. Alternatively, after coating the coating material, a dry film can be formed by blowing hot air using a dryer or the like, performing infrared irradiation, etc. to evaporate moisture, etc., and then a heat treatment is performed. Within the limit that does not particularly interfere with the state of the gas barrier layer, gas barrier properties and other physical properties, considering the reduction of processes, it is preferred to perform the heat treatment immediately after coating. The heat treatment method is not particularly limited, and generally, it is considered to perform the heat treatment in a drying atmosphere such as an oven.

[0062] According to an embodiment of the present application, the heat treatment conditions for forming the gas barrier layer are affected by whether other components such as polyol polymers and / or crosslinking agents are further added to the gas barrier coating liquid and the content of the added components, and cannot be generalized. The heating temperature is preferably 100 to 250 °C, more preferably 120 to 200 °C. The heating time is preferably 10 s to 30 min, more preferably 30 s to 5 min. If the treatment temperature is too low or the treatment time is too short, the coating crosslinking reaction cannot proceed sufficiently. If the treatment temperature is too high or the treatment time is too long, the base film may become brittle and the production efficiency may be reduced.

[0063] According to an embodiment of the present application, the coating method for coating the gas barrier coating liquid to form the gas barrier layer is not particularly limited, and those skilled in the art can flexibly select according to the actual situation. For example, one or more of roll coating, gravure coating, knife coating, slot coating, extrusion coating, air knife coating, dip coating, spraying, etc. can be used.

[0064] According to an embodiment of the present application, the bottom layer can be used as needed and is provided between the base film layer and the gas barrier layer, which can effectively cover the surface defects of the base film layer, improve the surface flatness of the base film layer, and thus improve the interlayer adhesion.

[0065] According to an embodiment of the present application, the bottom layer can be either a body layer obtained by activating the surface of the base film layer or a resin layer formed on the surface of the base film layer. Among them, the method of the activation treatment and the selection of the resin are not particularly limited, and those skilled in the art can select according to actual needs. For example, the activation treatment can be obtained by corona and / or plasma treatment of the base film layer, and the resin layer can be formed by using coating liquids such as isocyanate-based, polyurethane-based, polyester-based, polyethyleneimine-based, polybutadiene-based, polyolefin-based, alkyl titanate-based, etc. When considering the effects of the present invention, isocyanate-based, polyurethane-based, and polyester-based tackifying coating liquids are preferred. The bottom layer coating liquid can be coated on the base film layer by the same coating method as the above-mentioned gas barrier coating liquid.

[0066] According to the embodiments of the present application, the thickness of the bottom layer can be 0.005 - 5 μm, preferably 0.01 - 1 μm. If the thickness of the bottom layer is too small, it is difficult to effectively cover the defects on the surface of the base film layer; if the bottom layer is too thick, the planarization function of the base film layer cannot be further increased, but instead, the cost will be increased and there is a risk of cracking.

[0067] According to the embodiments of the present application, the functions of laminating the above-mentioned gas barrier layer on the surface of the base film are as follows: namely, under high-temperature and high-humidity conditions, due to the swelling of the gas barrier layer, the metal cations contained in the gas barrier layer are released to a certain extent, and they perform ionic cross-linking with the carboxyl groups formed by the hydrolysis of the ester groups of the unreacted groups or cross-linked parts in the gas barrier layer, thereby maintaining excellent gas barrier performance. Therefore, the gas barrier coating liquid and the gas barrier film in the present invention can be applied to the food and drug packaging fields that require cooking or high-temperature sterilization treatment and require maintaining high oxygen barrier properties.

[0068] The solutions of the present application will be explained below in conjunction with the embodiments. Those skilled in the art will understand that the following embodiments are only used to illustrate the present application and should not be regarded as limiting the scope of the present application. For those not specified in the embodiments regarding specific technologies or conditions, they shall be carried out according to the technologies or conditions described in the literature in the art or according to the product specifications. For the reagents or instruments not specified regarding the manufacturer, they are all conventional products that can be obtained through commercial purchase.

[0069] General raw materials and preparation methods for the examples and comparative examples:

[0070] (1) Preparation of polyvalent metal compound coated with unsaturated anhydride modified polyvinyl alcohol:

[0071] M1: Through mechanical stirring, nano-magnesium oxide (average particle size 30 nm) was dispersed in water to obtain an aqueous dispersion with a solid content of 10%. According to the mass ratio of nano-magnesium oxide to the aqueous solution of unsaturated anhydride modified polyvinyl alcohol of 50:1, an aqueous solution of unsaturated anhydride modified polyvinyl alcohol with a solid content of 5 wt% was added to the aqueous dispersion, and it was stirred at 80 °C for 30 min. The preliminary powder of nano-magnesium oxide coated with unsaturated anhydride modified polyvinyl alcohol was obtained through the separation methods of suction filtration and vacuum drying. The preliminary powder of nano-magnesium oxide coated with unsaturated anhydride modified polyvinyl alcohol was configured into an aqueous dispersion with a solid content of 10%, and a thermal initiator was added, and it was stirred and reacted at 80 °C for 1.5 h to obtain the final aqueous dispersion of nano-magnesium oxide coated with unsaturated anhydride modified polyvinyl alcohol with a solid content of 10%, denoted as M1.

[0072] M2: Compared with M1, nano-zinc oxide was used instead of nano-magnesium oxide, and finally, an aqueous dispersion of nano-zinc oxide coated with unsaturated anhydride modified polyvinyl alcohol with a solid content of 10% was obtained, denoted as M2.

[0073] (2) Preparation of resin aqueous solution:

[0074] P1: Dissolve polyacrylic acid with a molecular weight of 100,000 in deionized water to prepare an aqueous polyacrylic acid solution with a solid content of 5%, denoted as P1.

[0075] P2: Compared with P1, add an aqueous polyvinyl alcohol solution with a solid content of 5% and an aqueous amino resin solution with a solid content of 10% to the 5% aqueous polyacrylic acid solution in proportion for mixing. The mass ratio of the three aqueous solutions is 1:1:0.5, and the mixed resin aqueous solution is denoted as P2.

[0076] (3) General method for forming a gas barrier film in the examples and comparative examples:

[0077] Coat the coating liquid on a 15-μm-thick polyamide (PA) film and cure it at 120 °C for 3 min to form a gas barrier layer coating with a dry thickness of 500 nm.

[0078] Example 1

[0079] Add M1 to P1 in proportion for mixing to obtain coating liquid T1. Control the mass ratio of the metal compound in M1 to the carboxyl group in P1 to be 1:10, and coat to obtain a gas barrier film using the above general method for preparing a gas barrier film.

[0080] Example 2

[0081] Add M1 to P1 in proportion for mixing to obtain coating liquid T2. Control the mass ratio of the metal compound in M1 to the carboxyl group in P1 to be 1:5, and coat to obtain a gas barrier film using the above general method for preparing a gas barrier film.

[0082] Example 3

[0083] Add M1 to P2 in proportion for mixing to obtain coating liquid T3. Control the mass ratio of the metal compound in M1 to the carboxyl group in P2 to be 1:10, and coat to obtain a gas barrier film using the above general method for preparing a gas barrier film.

[0084] Example 4

[0085] Add M1 to P2 in proportion for mixing to obtain coating liquid T4. Control the mass ratio of the metal compound in M1 to the carboxyl group in P2 to be 1:5, and coat to obtain a gas barrier film using the above general method for preparing a gas barrier film.

[0086] Example 5

[0087] Add M2 to P1 in proportion for mixing to obtain coating liquid T5. Control the mass ratio of the metal compound in M2 to the carboxyl group in P1 to be 1:10, and coat to obtain a gas barrier film using the above general method for preparing a gas barrier film.

[0088] Example 6

[0089] Mix M2 into P1 in proportion to obtain coating solution T6. Control the mass ratio of the metal compound in M2 to the carboxyl group in P1 to be 1:5, and coat to obtain a gas barrier film by using the above general method for preparing a gas barrier film.

[0090] Example 7

[0091] Mix M2 into P2 in proportion to obtain coating solution T7. Control the mass ratio of the metal compound in M2 to the carboxyl group in P2 to be 1:10, and coat to obtain a gas barrier film by using the above general method for preparing a gas barrier film.

[0092] Example 8

[0093] Mix M2 into P2 in proportion to obtain coating solution T8. Control the mass ratio of the metal compound in M2 to the carboxyl group in P2 to be 1:5, and coat to obtain a gas barrier film by using the above general method for preparing a gas barrier film.

[0094] Comparative Example 1

[0095] Add the uncoated magnesium oxide aqueous dispersion into P1 and mix to obtain coating solution T9. Control the mass ratio of magnesium oxide to the carboxyl group in P1 to be 1:10, and coat to obtain a gas barrier film by using the above general method for preparing a gas barrier film.

[0096] Comparative Example 2

[0097] Do not add any metal compound, let P1 be coating solution T10, and coat to obtain a gas barrier film by using the above general method for preparing a gas barrier film.

[0098] Comparative Example 3

[0099] Do not add any metal compound, let P2 be coating solution T11, and coat to obtain a gas barrier film by using the above general method for preparing a gas barrier film.

[0100] Performance test and evaluation:

[0101] Under the same conditions, characterize the gas barrier films prepared in Examples 1-8 and Comparative Examples 1-3 by the following test methods. The characterization contents include: the oxygen transmission rate of the composite film of the gas barrier film before and after cooking. The characterization results are shown in Table 1.

[0102] Test method:

[0103] (1) The gas barrier films prepared in the above Examples 1-8 and Comparative Examples 1-3 were successively laminated with a 15-μm PA film and a 60-μm cast polypropylene film (CPP film) using a high-pressure cooking two-component polyurethane adhesive. Among them, the total thickness of the adhesive was 4 μm. The structure of the prepared packaging composite film was gas barrier film / adhesive layer / PA film / adhesive layer / CPP film, where the gas barrier layer of the gas barrier film faced the adhesive layer. The oxygen transmission rate of each composite film was tested according to GB / T 19789-2005.

[0104] (2) The gas barrier films prepared in the above Examples 1-8 and Comparative Examples 1-3 were subjected to pressurized cooking. The cooking conditions were as follows: The gas barrier films were placed in a high-pressure cooking pot and cooked at 121 °C for 30 min. After cooking, they were balanced in the atmospheric environment for 24 h, and the oxygen transmission rate was tested according to GB / T 19789-2005.

[0105] Table 1. Test results of the composite films before and after cooking in Examples 1-8 and Comparative Examples 1-3

[0106]

[0107]

[0108] As can be seen from Table 1, the gas barrier properties of Examples 1-8 were good before and after cooking, indicating that the gas barrier properties were well maintained under high-temperature and high-humidity conditions. However, in Comparative Examples 2 and 3, due to the absence of the introduction of metal compounds, the oxygen permeability increased after cooking, and the gas barrier properties were not well maintained. Comparative Example 1 showed that the uncoated metal compounds were directly added to the carboxyl-containing resin aqueous solution, which would quickly form a gel, resulting in inability to coat.

[0109] In the description of this specification, the descriptions with reference to the terms "one embodiment", "some embodiments", "example", "specific example", or "some examples" etc. mean that the specific features, structures, materials, or characteristics described in connection with the embodiment or example are included in at least one embodiment or example of the present application. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials, or characteristics described can be combined in a suitable manner in any one or more embodiments or examples. In addition, without contradiction, those skilled in the art can combine and combine the different embodiments or examples described in this specification and the features of different embodiments or examples.

[0110] Although the embodiments of the present application have been shown and described above, it can be understood that the above embodiments are exemplary and should not be construed as limiting the present application. Those of ordinary skill in the art can make changes, modifications, substitutions, and variations to the above embodiments within the scope of the present application.

Claims

1. A gas barrier coating liquid, characterized in that: include: A multivalent metal compound, wherein at least a portion of the surface of the multivalent metal compound has a coating layer, and the coating layer includes unsaturated acid anhydride-modified polyvinyl alcohol; A water-soluble resin having a carboxyl group; as well as Solvent.

2. The gas barrier coating liquid according to claim 1, characterized in that include: 0.05 to 10 parts by weight of a polyvalent metal compound, 0.45 to 19 parts by weight of a water-soluble resin and 80 to 99.5 parts by weight of a solvent.

3. The gas barrier coating liquid according to claim 1, characterized in that The coating layer is obtained by esterification reaction between unsaturated acid anhydride and polyvinyl alcohol; The unsaturated anhydride comprises at least one of maleic anhydride, itaconic anhydride and citraconic anhydride; The mass ratio of the unsaturated acid anhydride to the polyvinyl alcohol is (1-100):

1.

4. The gas barrier coating liquid according to claim 1, characterized in that The method of forming the coating layer comprises: The unsaturated anhydride-modified polyvinyl alcohol and the multivalent metal compound are mixed to obtain a preliminary coating mixture; The preliminary coating mixture is subjected to a free radical polymerization treatment to form the coating layer on at least a portion of the surface of the multivalent metal compound.

5. The gas barrier coating liquid according to claim 4, characterized in that The free radical polymerization process includes at least one of thermal initiation, photoinitiation, and high energy radiation initiation.

6. The gas barrier coating liquid according to claim 1, characterized in that The particle size of the multivalent metal compound is 5 nm to 1 μm; Optionally, the multivalent metal compound includes at least one of zinc oxide, magnesium oxide, calcium oxide, zinc hydroxide, magnesium hydroxide, calcium hydroxide, zinc carbonate, magnesium carbonate, and calcium carbonate.

7. The gas barrier coating liquid according to claim 1, characterized in that The molecular weight of the water-soluble resin is 5000 to 1000000; Optionally, the water-soluble resin comprises at least one of homopolymers and / or copolymers of monomers of acrylic acid, methacrylic acid, maleic acid, itaconic acid and crotonic acid; Optionally, the solvent includes at least one of water and an alcohol-water mixture; Optionally, the type of alcohol in the alcohol-water mixture includes at least one of methanol, ethanol, isopropanol, and n-propanol; Optionally, the mass ratio of the multivalent metal compound to the carboxyl group in the water-soluble resin is (0.1-1):

1.

8. The gas barrier coating liquid according to claim 1, wherein The gas barrier coating liquid further comprises a polyol polymer, wherein the polyol polymer comprises at least one of polyvinyl alcohol and ethylene-vinyl alcohol copolymer; Optionally, the mass ratio of the hydroxyl group of the polyol polymer to the carboxyl group of the water-soluble resin is (0.01-10):1; The gas barrier coating liquid further includes a crosslinking agent, and the crosslinking agent includes at least one of amino resins, isocyanates, silane coupling agents, and inorganic nanoparticles; Optionally, the mass ratio of the water-soluble resin to the cross-linking agent is (10-100):

1.

9. A gas barrier film, characterized in that: include: Basement membrane layer; A gas barrier layer, wherein the gas barrier layer is provided on at least one surface of the base film layer, and the gas barrier layer is formed using the gas barrier coating liquid according to any one of claims 1 to 8.

10. The gas barrier film according to claim 9, characterized in that The base film layer has a thickness of 5 to 300 μm; Optionally, the gas barrier layer has a thickness of 0.1 to 5 μm; Optionally, the base film layer includes at least one of a polyolefin film, a polyester film, and a polyamide film.

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