A method for manufacturing a multifunctional paper-like cold foil and packaging bag

Abstract

This invention relates to a method for manufacturing a multifunctional paper-like cold-stamping film and packaging bags, belonging to the technical field of packaging bag materials. The multifunctional paper-like cold-stamping film is obtained by curing a polyvinyl alcohol (PVA) coating. The PVA coating comprises the following raw materials: PVA, crosslinking agent, EDC, modified mica, antioxidant, and deionized water. This invention increases the compatibility and binding force of mica in the system through organic modification, thereby improving the mechanical and barrier properties of the PVA coating. By forming an alumina coating layer on a BOPE polyethylene film substrate and then coating it with the PVA coating and curing it, the resulting packaging bag can extend the shelf life of the packaged goods.

Description

Technical Field

[0001] This invention belongs to the technical field of packaging bag materials, and relates to a multifunctional paper-like cold foil and a method for manufacturing packaging bags. Background Technology

[0002] With the rapid growth of the social economy and the gradual improvement of people's living standards, packaging bags, due to their rich and varied colors, multifunctionality, and diverse shapes, have become indispensable items in daily life. Generally speaking, flexible packaging bags can be divided into three main categories: paper packaging bags, plastic packaging bags, and paper-plastic composite packaging bags.

[0003] While paper packaging bags offer the advantage of recyclability, their poor water resistance makes the food inside susceptible to moisture absorption and spoilage. Furthermore, the pulp production process consumes significant amounts of forest resources and leaves chemical residues in the paper, potentially posing food safety risks. Plastic packaging bags, on the other hand, offer better toughness and are oil and water resistant, but their less appealing feel leads consumers to perceive them as lower-end.

[0004] In recent years, paper-plastic composite packaging bags have become the most popular packaging products. They cleverly combine the advantages of paper and plastic packaging bags, possessing not only the oil and water resistance of plastic bags but also the recyclability of paper bags, greatly enhancing the practicality and environmental friendliness of packaging. Polyvinyl alcohol-based materials have numerous advantages, including being green and biodegradable. Among methods to improve the barrier properties of materials, surface coating is relatively easy to achieve, with a simple process and relatively low production costs.

[0005] Mica powder is a non-metallic mineral containing various components, the main component of which is SiO2, with a content of about 49%, and Al2O3, with a content of about 30%. Its structure is a layered complex aluminosilicate composed of aluminum-oxygen octahedron pairs, which has high heat resistance and acid and alkali corrosion resistance. Its layered structure can improve the barrier properties of membrane materials against oxygen and water vapor. However, as an inorganic filler, it has poor compatibility with polyvinyl alcohol coatings, which affects its application in membrane materials. Summary of the Invention

[0006] The purpose of this invention is to provide a method for manufacturing a multifunctional paper-like cold-stamping film and packaging bags. This invention uses cinnamaldehyde grafted with oleic acid, a natural material, as a modifier to modify mica powder and chitosan composites. This reduces the hydrophilicity of mica while introducing organic groups, increasing its reactivity and compatibility with polyvinyl alcohol (PVA) coating systems, and improving its mechanical properties, water resistance, and gas barrier properties. Finally, an alumina coating layer is formed on a BOPE polyethylene film substrate, followed by coating with PVA and curing. The resulting packaging bags extend the shelf life of packaged products.

[0007] The objective of this invention can be achieved through the following technical solutions:

[0008] A multifunctional paper-like cold foil is obtained by curing a polyvinyl alcohol coating. The polyvinyl alcohol coating comprises the following components by weight: 38-44 parts polyvinyl alcohol, 1.8-2.1 parts crosslinking agent, 0.1-0.2 parts EDC, 7-10 parts modified mica, 0.06-0.09 parts antioxidant, and 34-40 parts deionized water.

[0009] As a preferred embodiment of the present invention, the crosslinking agent is one or more of glutaraldehyde, vanillin, and citral.

[0010] As a preferred embodiment of the present invention, the antioxidant is a mixture of antioxidant 168 and antioxidant 1010 in a mass ratio of 1:2.

[0011] As a preferred embodiment of the present invention, the EDC is 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide.

[0012] This invention discloses the preparation of the modified mica comprising the following steps:

[0013] Step S1: After stirring and mixing cinnamaldehyde and initiator, preheat the mixture. Under a nitrogen atmosphere, add oleic acid dropwise and stir until mixed. Then, keep the mixture at the same temperature to obtain the modifier.

[0014] Step S2: Place the chitosan solution and mica powder in a container and stir to mix. Add anhydrous ethanol and modifier, heat and stir to mix. After removing the solvent by rotary evaporation, wash and place in an oven to dry to obtain modified mica.

[0015] As a preferred technical solution of the present invention, mica powder, due to its unique sheet-like stacked structure, can effectively increase the barrier properties of the material as well as the water resistance and impermeability of the film.

[0016] As a preferred embodiment of the present invention, in step S1, the mass ratio of cinnamaldehyde, initiator and oleic acid is 20-23:30-36:1.0-1.2.

[0017] As a preferred embodiment of the present invention, in step S1, the preheating is heating to a temperature of 70-75°C; the heat preservation treatment is heat preservation treatment at a temperature of 70-75°C for 4-6 hours.

[0018] As a preferred embodiment of the present invention, in step S1, the initiator is one or more of azobisisobutyronitrile, azobisisovalerate, azobisisoheptanenitrile, diethyl azodicarbonate, benzoyl peroxide, and tert-butyl peroxide.

[0019] As a preferred technical solution of the present invention, in step S2, the stirring and mixing is carried out at a temperature of 30-36°C for 30-45 minutes.

[0020] As a preferred technical solution of the present invention, in step S2, the heating and stirring mixture is heated to 60-70°C and stirred for 6-8 hours.

[0021] As a preferred embodiment of the present invention, in step S2, the washing is performed by washing three times with anhydrous ethanol; the drying is performed by drying at 80°C to constant weight.

[0022] As a preferred embodiment of the present invention, in step S2, the mass ratio of the chitosan solution, mica powder, anhydrous ethanol and modifier is 10-12:5-7:15-20:0.6-1.0.

[0023] As a preferred embodiment of the present invention, in step S2, the chitosan solution is prepared by stirring and mixing chitosan and an aqueous acetic acid solution at a ratio of 0.10-0.13g:4mL, wherein the mass fraction of the aqueous acetic acid solution is 2%.

[0024] As a preferred technical solution of the present invention, the multifunctional paper-like cold foil is obtained by curing polyvinyl alcohol coating. The preparation method of the polyvinyl alcohol coating includes the following steps: after mixing polyvinyl alcohol and deionized water, heating to 65°C, adding modified mica, EDC and crosslinking agent, and stirring for 30-45 minutes, the polyvinyl alcohol coating is obtained.

[0025] This invention discloses a method for preparing a packaging bag using a multifunctional paper-like cold foil, the method comprising the following steps:

[0026] Using the electron beam gun of an electron beam coating equipment, high-purity aluminum material and high-purity oxygen reactants are vapor-deposited onto a BOPE polyethylene film substrate in a high-temperature environment of 1400-1600℃ and under vacuum to form an aluminum oxide coating layer. Then, a polyvinyl alcohol water-based coating is applied to the aluminum oxide coating layer and cured. After cutting, folding, and heat-sealing, a packaging bag is formed.

[0027] The beneficial effects of this invention are:

[0028] This invention uses cinnamaldehyde grafted with oleic acid, a natural material, as a modifier to modify mica powder and chitosan composites. This reduces the hydrophilicity of mica while introducing organic groups, increasing its reactivity and compatibility with polyvinyl alcohol (PVA) coating systems, and improving its mechanical properties, water resistance, and gas barrier properties. This allows for the formation of an alumina coating layer on a BOPE polyethylene film substrate, followed by coating with PVA and curing, ultimately resulting in packaging bags that extend the shelf life of packaged products. Detailed Implementation

[0029] To further illustrate the technical means and effects of the present invention in achieving its intended purpose, the following detailed description of the specific implementation methods, structures, features, and effects of the present invention, in conjunction with embodiments, is provided below.

[0030] A method for preparing a packaging bag made of multifunctional paper-like cold foil includes the following steps:

[0031] Using the electron beam gun of an electron beam coating equipment, high-purity aluminum material and high-purity oxygen reactants are vapor-deposited onto a BOPE polyethylene film substrate in a high-temperature environment of 1400-1600℃ and under vacuum to form an aluminum oxide coating layer. Then, a polyvinyl alcohol water-based coating is coated on the aluminum oxide coating layer and cured to form a multifunctional paper-like cold foil film. After cutting, folding and heat-sealing, it forms a packaging bag.

[0032] Example 1

[0033] A multifunctional paper-like cold-stamping film is obtained by curing a polyvinyl alcohol coating. The polyvinyl alcohol coating comprises the following components by weight: 38 parts polyvinyl alcohol, 1.8 parts crosslinking agent, 0.1 parts EDC, 7 parts modified mica, 0.06 parts antioxidant, and 34 parts deionized water. The crosslinking agent is a mixture of glutaraldehyde and citral in a mass ratio of 2:1. The antioxidant is a mixture of antioxidant 168 and antioxidant 1010 in a mass ratio of 1:2.

[0034] The preparation of the modified mica includes the following steps:

[0035] Step S1: Cinnamaldehyde and initiator are stirred and mixed, then preheated. Under a nitrogen atmosphere, oleic acid is added dropwise and stirred until mixed, followed by heat treatment to obtain the modifier. The mass ratio of cinnamaldehyde, initiator, and oleic acid is 20:30:1.0. The preheating is to heat to 70°C. The heat treatment is to maintain the temperature at 70°C for 4 hours. The initiator is azobisisobutyronitrile (AIB).

[0036] Step S2: Chitosan solution and mica powder are placed in a container and stirred. Anhydrous ethanol and modifier are added, and the mixture is heated and stirred. The solvent is removed by rotary evaporation, and the mixture is washed and dried in an oven to obtain modified mica. The stirring is performed at 30°C for 30 minutes; the heating and stirring is performed at 60°C for 6 hours; the washing is performed three times with anhydrous ethanol; and the drying is performed at 80°C to constant weight. The mass ratio of chitosan solution, mica powder, anhydrous ethanol, and modifier is 10:5:15:0.6. The chitosan solution is prepared by stirring and mixing chitosan and acetic acid aqueous solution at a ratio of 0.10 g:4 mL, where the mass fraction of the acetic acid aqueous solution is 2%.

[0037] The preparation method of the polyvinyl alcohol coating includes the following steps: after mixing polyvinyl alcohol and deionized water, heating to 65°C, adding modified mica, EDC, antioxidant and crosslinking agent, and stirring for 30 minutes, a polyvinyl alcohol coating is obtained.

[0038] Example 2

[0039] A multifunctional paper-like cold-stamping film is obtained by curing a polyvinyl alcohol coating. The polyvinyl alcohol coating comprises the following components by weight: 40 parts polyvinyl alcohol, 1.9 parts crosslinking agent, 0.13 parts EDC, 8 parts modified mica, 0.07 parts antioxidant, and 36 parts deionized water. The crosslinking agent is a mixture of glutaraldehyde and citral in a mass ratio of 2:1. The antioxidant is a mixture of antioxidant 168 and antioxidant 1010 in a mass ratio of 1:2.

[0040] The preparation of the modified mica includes the following steps:

[0041] Step S1: Cinnamaldehyde and initiator are stirred and mixed, then preheated. Under a nitrogen atmosphere, oleic acid is added dropwise and stirred until mixed, followed by heat treatment to obtain the modifier. The mass ratio of cinnamaldehyde, initiator, and oleic acid is 21:32:1.07. The preheating is to heat to 72°C. The heat treatment is to maintain the temperature at 72°C for 4.5 hours. The initiator is azobisisobutyronitrile (AIB).

[0042] Step S2: Chitosan solution and mica powder are placed in a container and stirred. Anhydrous ethanol and modifier are added, and the mixture is heated and stirred. The solvent is removed by rotary evaporation, and the mixture is washed and dried in an oven to obtain modified mica. The stirring is performed at 32°C for 35 minutes; the heating and stirring is performed at 63°C for 6.7 hours; the washing is performed three times with anhydrous ethanol; and the drying is performed at 80°C to constant weight. The mass ratio of chitosan solution, mica powder, anhydrous ethanol, and modifier is 10.7:5.7:17:0.7. The chitosan solution is prepared by stirring and mixing chitosan and acetic acid aqueous solution at a ratio of 0.11 g:4 mL, where the mass fraction of the acetic acid aqueous solution is 2%.

[0043] The preparation method of the polyvinyl alcohol coating includes the following steps: after mixing polyvinyl alcohol and deionized water, heating to 65°C, adding modified mica, EDC, antioxidant and crosslinking agent, and stirring for 35 minutes, a polyvinyl alcohol coating is obtained.

[0044] Example 3

[0045] A multifunctional paper-like cold-stamping film is obtained by curing a polyvinyl alcohol coating. The polyvinyl alcohol coating comprises the following components by weight: 42 parts polyvinyl alcohol, 2 parts crosslinking agent, 0.17 parts EDC, 9 parts modified mica, 0.08 parts antioxidant, and 38 parts deionized water. The crosslinking agent is a mixture of glutaraldehyde and citral in a mass ratio of 2:1. The antioxidant is a mixture of antioxidant 168 and antioxidant 1010 in a mass ratio of 1:2.

[0046] The preparation of the modified mica includes the following steps:

[0047] Step S1: Cinnamaldehyde and initiator are stirred and mixed, then preheated. Under a nitrogen atmosphere, oleic acid is added dropwise and stirred until mixed, followed by heat treatment to obtain the modifier. The mass ratio of cinnamaldehyde, initiator, and oleic acid is 22:34:1.13. The preheating is performed at 73°C. The heat treatment is performed at 73°C for 5.5 hours. The initiator is azobisisobutyronitrile (AIB).

[0048] Step S2: Chitosan solution and mica powder are placed in a container and stirred. Anhydrous ethanol and modifier are added, and the mixture is heated and stirred. The solvent is removed by rotary evaporation, and the mixture is washed and dried in an oven to obtain modified mica. The stirring is performed at 34°C for 40 minutes; the heating and stirring is performed at 67°C for 7.5 hours; the washing is performed three times with anhydrous ethanol; and the drying is performed at 80°C to constant weight. The mass ratio of chitosan solution, mica powder, anhydrous ethanol, and modifier is 11.3:6.3:18:0.9. The chitosan solution is prepared by stirring and mixing chitosan and acetic acid aqueous solution at a ratio of 0.12 g:4 mL, where the mass fraction of the acetic acid aqueous solution is 2%.

[0049] The preparation method of the polyvinyl alcohol coating includes the following steps: after mixing polyvinyl alcohol and deionized water, heating to 65°C, adding modified mica, EDC, antioxidant and crosslinking agent, and stirring for 40 minutes, a polyvinyl alcohol coating is obtained.

[0050] Example 4

[0051] A multifunctional paper-like cold-stamping film is obtained by curing a polyvinyl alcohol coating. The polyvinyl alcohol coating comprises the following components by weight: 44 parts polyvinyl alcohol, 2.1 parts crosslinking agent, 0.2 parts EDC, 10 parts modified mica, 0.09 parts antioxidant, and 40 parts deionized water. The crosslinking agent is a mixture of glutaraldehyde and citral in a mass ratio of 2:1. The antioxidant is a mixture of antioxidant 168 and antioxidant 1010 in a mass ratio of 1:2.

[0052] The preparation of the modified mica includes the following steps:

[0053] Step S1: Cinnamaldehyde and initiator are stirred and mixed, then preheated. Under a nitrogen atmosphere, oleic acid is added dropwise and stirred until mixed, followed by heat treatment to obtain the modifier. The mass ratio of cinnamaldehyde, initiator, and oleic acid is 23:36:1.2. The preheating is to heat to 75°C. The heat treatment is to keep the mixture at 75°C for 6 hours. The initiator is azobisisobutyronitrile.

[0054] Step S2: Chitosan solution and mica powder are placed in a container and stirred. Anhydrous ethanol and modifier are added, and the mixture is heated and stirred. The solvent is removed by rotary evaporation, and the mixture is washed and dried in an oven to obtain modified mica. The stirring and mixing are carried out at 36°C for 45 min; the heating and stirring are carried out at 70°C for 8 h; the washing is carried out by washing three times with anhydrous ethanol; and the drying is carried out at 80°C to constant weight. The mass ratio of chitosan solution, mica powder, anhydrous ethanol and modifier is 12:7:20:1.0. The chitosan solution is prepared by stirring and mixing chitosan and acetic acid aqueous solution at a ratio of 0.13 g:4 mL, and the mass fraction of the acetic acid aqueous solution is 2%.

[0055] The preparation method of the polyvinyl alcohol coating includes the following steps: after mixing polyvinyl alcohol and deionized water, heating to 65°C, adding modified mica, EDC, antioxidant and crosslinking agent, and stirring for 45 minutes, a polyvinyl alcohol coating is obtained.

[0056] Comparative Example 1

[0057] Compared with Example 3, Comparative Example 1 differs in that cinnamaldehyde is not used, while the other components, preparation steps and parameters are the same.

[0058] Comparative Example 2

[0059] Compared with Example 3, Comparative Example 2 differs in that oleic acid is not used, while the other components, preparation steps and parameters are the same.

[0060] Comparative Example 3

[0061] Compared with Example 3, Comparative Example 3 differs in that chitosan is not used, while the other components, preparation steps and parameters are the same.

[0062] Comparative Example 4

[0063] Compared with Example 3, Comparative Example 4 differs in that mica powder is used instead of modified mica, while the other components, preparation steps and parameters are the same.

[0064] Comparative Example 5

[0065] Compared with Example 3, Comparative Example 5 differs in that EDC is not used, while the other components, preparation steps and parameters are the same.

[0066] The polyvinyl alcohol coatings prepared in Examples 1-4 and Comparative Examples 1-5 were tested as follows, and the test results are shown in Table 1.

[0067] Oxygen barrier performance test: According to GB / T1038-2000; the oxygen barrier performance of the membrane is tested using an air permeability tester. The sample membrane is cut into a circle with a diameter of 8.5cm using a standard sample cutter. Three samples are measured for each type of sample, and the average value is taken.

[0068] Water vapor barrier performance test: According to GB / T 1037-88, the film was cut into circles with an area of ​​50cm2 and tested using a water vapor transmission rate tester.

[0069] Table 1. Test results of oxygen barrier performance and water vapor barrier performance

[0070]

[0071] As shown in Table 1, the oxygen barrier and water vapor barrier properties of the membrane materials prepared by this invention are significantly better than those of Comparative Examples 1-5 compared to Examples 1-5. This is because this invention uses cinnamaldehyde grafted with oleic acid as a modifier, a natural material, and utilizes the hydrogen bonding between mica powder and chitosan to allow chitosan to enter the interlayer structure of mica powder, introducing amino groups. These amino groups are then chemically bonded to the aldehyde groups of the modifier, reducing the hydrophilicity of mica while grafting imine-containing organic groups onto the mica powder as an inorganic filler. This increases its reactivity and compatibility with the polyvinyl alcohol coating system. The modifier, containing long carbon chains and benzene ring structures, can also act as a plasticizer, adjusting the flowability of the polyvinyl alcohol coating, improving its mechanical properties and water resistance, thereby enhancing the gas barrier properties of the polyvinyl alcohol coating under high humidity conditions. Furthermore, this invention utilizes an aldehyde-containing compound as a crosslinking agent to undergo an acetalization crosslinking reaction with the hydroxyl groups of polyvinyl alcohol, forming a three-dimensional crosslinked network structure. Mica is modified with a modifier to introduce active functional groups, increasing the compatibility of mica in the polyvinyl alcohol coating system. Then, the carboxyl groups on the modified mica are activated using EDC to further increase its bonding force with the polyvinyl alcohol coating, forming a denser crosslinked network structure, which significantly improves the mechanical properties and barrier properties of the polyvinyl alcohol coating.

[0072] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. Although the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art can make some modifications or alterations to the above-disclosed technical content to create equivalent embodiments without departing from the scope of the present invention. Any simple modifications, equivalent changes and alterations made to the above embodiments based on the technical essence of the present invention without departing from the scope of the present invention shall still fall within the scope of the present invention.

Claims

1. A multifunctional paper-like cold foil, characterized in that, The multifunctional paper-like cold foil is obtained by curing polyvinyl alcohol coating. The polyvinyl alcohol coating comprises the following components by weight: 38-44 parts polyvinyl alcohol, 1.8-2.1 parts crosslinking agent, 0.1-0.2 parts EDC, 7-10 parts modified mica, 0.06-0.09 parts antioxidant, and 34-40 parts deionized water. The preparation of the modified mica includes the following steps: Step S1: After stirring and mixing cinnamaldehyde and initiator, preheat the mixture. Under a nitrogen atmosphere, add oleic acid dropwise and stir until mixed. Then, keep the mixture at the same temperature to obtain the modifier. Step S2: Place the chitosan solution and mica powder in a container and stir to mix. Add anhydrous ethanol and modifier, heat and stir to mix. After removing the solvent by rotary evaporation, wash and place in an oven to dry to obtain modified mica. In step S1, the mass ratio of cinnamaldehyde, initiator, and oleic acid is 20-23:30-36:1.0-1.2; In step S2, the mass ratio of the chitosan solution, mica powder, anhydrous ethanol and modifier is 10-12:5-7:15-20:0.6-1.

0.

2. The multifunctional paper-like cold foil according to claim 1, characterized in that: The crosslinking agent is one or more of glutaraldehyde, vanillin, and citral; the antioxidant is a mixture of antioxidant 168 and antioxidant 1010 in a mass ratio of 1:

2.

3. The multifunctional paper-like cold foil according to claim 1, characterized in that: In step S1, the preheating is heating to a temperature of 70-75℃; the heat preservation treatment is heat preservation treatment at a temperature of 70-75℃ for 4-6 hours.

4. The multifunctional paper-like cold foil according to claim 1, characterized in that: In step S1, the initiator is one or more of azobisisobutyronitrile, azobisisovalerate, azobisisoheptanenitrile, diethyl azodicarbonate, benzoyl peroxide, and tert-butyl peroxide.

5. The multifunctional paper-like cold foil according to claim 1, characterized in that: In step S2, the stirring and mixing is carried out at a temperature of 30-36℃ for 30-45 minutes; the heating and stirring is carried out at a temperature of 60-70℃ for 6-8 hours; the washing is carried out by washing three times with anhydrous ethanol; and the drying is carried out at a temperature of 80℃ to constant weight.

6. The multifunctional paper-like cold foil according to claim 1, characterized in that: In step S2, the chitosan solution is prepared by mixing chitosan and an aqueous acetic acid solution at a ratio of 0.10-0.13g:4mL, wherein the aqueous acetic acid solution has a mass fraction of 2%.

7. The multifunctional paper-like cold foil according to claim 1, characterized in that, The multifunctional paper-like cold foil is obtained by curing polyvinyl alcohol coating. The preparation method of the polyvinyl alcohol coating includes the following steps: after mixing polyvinyl alcohol and deionized water, heating to 65°C, adding modified mica, EDC and crosslinking agent, and stirring for 30-45 minutes, the polyvinyl alcohol coating is obtained.

8. A method for preparing a packaging bag using the multifunctional paper-like cold-stamping film according to any one of claims 1 to 7, characterized in that, The method for preparing the packaging bag includes the following steps: Using the electron beam gun of an electron beam coating equipment, high-purity aluminum material and high-purity oxygen reactants are vapor-deposited onto a BOPE polyethylene film substrate in a high-temperature environment of 1400-1600℃ and under vacuum to form an aluminum oxide coating layer. Then, a polyvinyl alcohol water-based coating is applied to the aluminum oxide coating layer and cured. After cutting, folding, and heat-sealing, a packaging bag is formed.

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