Aluminum foil for high-width high-barrier liquid bag and production process of aluminum foil

Abstract

The invention relates to the technical field of aluminum foils, in particular to a high-width high-barrier aluminum foil for a liquid bag and a production process of the high-width high-barrier aluminum foil. The polyethylene layer, the aluminum foil layer and the polyester layer are sequentially compounded through a modified EVA (Ethylene Vinyl Acetate) adhesive; the preparation process of the modified EVA adhesive comprises the following steps: reacting maleic anhydride grafted EVA with aminated nano titanium dioxide to generate the modified EVA adhesive containing an amido bond structure; the nano TiO2 not only can improve the barrier property of the EVA, but also can effectively improve the heat resistance and weather resistance of the EVA due to the heat resistance and weather resistance of the nano TiO2; the prepared modified EVA adhesive has good heat resistance, weather resistance and barrier property; therefore, the barrier property of the aluminum foil composite film formed by sequentially compounding the polyethylene layer, the aluminum foil layer and the polyester layer through the modified EVA adhesive is further improved.

Description

Technical Field

[0001] The present invention relates to the technical field of aluminum foil, and in particular to a high-width and high-barrier aluminum foil for liquid packaging and a production process thereof. Background Art

[0002] The high-end liquid packaging industry is increasingly demanding material barrier properties, durability, and safety. Aluminum foil composite films, due to their excellent gas and water vapor barrier properties, have become a core material in areas such as aseptic packaging and long-term preservation. Traditional aluminum foil composite films are typically composed of polyethylene (PE), aluminum foil (Al), and polyester (PET) layers bonded together with an adhesive. However, their performance is limited by adhesive selection, aluminum foil pinhole defects, and wide-width production process bottlenecks. Specific issues are as follows: While ethylene-vinyl acetate (EVA) offers advantages such as being solvent-free and environmentally friendly, the barrier properties of EVA film primarily lie in its low gas permeability, resulting in excellent airtightness and barrier properties. EVA film typically has a very low gas permeability, effectively reducing the leakage of substances such as air and water vapor. However, its poor heat resistance (thermal decomposition temperature <250°C), insufficient weather resistance, and limited ability to fill pinholes in aluminum foil during the lamination process make it difficult to achieve breakthrough barrier properties. Summary of the Invention

[0003] The present invention aims to provide a wide-width, high-barrier aluminum foil for liquid packaging and a production process thereof. The present invention addresses the following technical issues: While ethylene-vinyl acetate copolymer (EVA) offers advantages such as being solvent-free and environmentally friendly, it suffers from poor heat resistance (thermal decomposition temperature <250°C), insufficient weather resistance, and limited ability to fill pinholes in the foil during the composite process, making it difficult to achieve improved barrier properties.

[0004] The purpose of the present invention can be achieved through the following technical solutions: A high-width, high-barrier aluminum foil for liquid packaging, comprising a polyethylene layer, an aluminum foil layer, and a polyester layer; the polyethylene layer, the aluminum foil layer, and the polyester layer are sequentially laminated with a modified EVA adhesive; The preparation process of the modified EVA adhesive comprises the following steps: The maleic anhydride grafted EVA reacts with amino-treated nano-titanium dioxide to generate a modified EVA adhesive containing an amide bond structure.

[0005] As a further solution of the present invention: the preparation process of the modified EVA adhesive containing an amide bond structure is as follows: In an ice-water bath, amino-modified nano-titanium dioxide, maleic anhydride-grafted EVA and NN dimethylformamide solvent are mixed, and then a catalyst, p-toluenesulfonic acid, is added; the system is transferred to an oil bath and heated under reflux at 160°C for 4-6 hours to obtain a modified EVA adhesive containing an amide bond structure.

[0006] As a further solution of the present invention, the usage ratio of the amino-treated nano-titanium dioxide, the maleic anhydride-grafted EVA and the NN dimethylformamide solvent is 0.1 mol: 0.1 mol: 1-2 L: 4-8 g.

[0007] As a further solution of the present invention: the preparation process of amination nano titanium dioxide includes: mixing lysine with an aqueous solution of ethylenediamine to obtain a lysine solution; Tetrabutyl titanate and lysine solution are mixed and reacted at 100-120° C. for 10 hours to obtain amino-modified nano-titanium dioxide.

[0008] As a further solution of the present invention: the specific process of preparing the lysine solution is: Anhydrous ethylenediamine was dissolved in distilled water and mixed evenly to form an ethylenediamine solution with a mass fraction of 20%. Lysine was then added to the ethylenediamine solution and mixed evenly to form a lysine solution.

[0009] As a further solution of the present invention: the specific process for preparing amination nano titanium dioxide is: Tetrabutyl titanate and lysine solution were mixed for 30 minutes, and hydrothermally reacted at 100° C. to obtain a precipitate; thus, amino-modified nano-titanium dioxide was obtained.

[0010] As a further solution of the present invention: the mass ratio of anhydrous ethylenediamine, lysine and tetrabutyl titanate is 80-120:5-15:100.

[0011] A production process for high-width, high-barrier aluminum foil for liquid packaging, comprising the following steps: It is composed of a polyethylene layer, an aluminum foil layer, and a polyester layer laminated in sequence through a modified EVA adhesive.

[0012] As a further solution of the present invention: using a gravure coater, the adhesive is evenly coated on the upper and lower surfaces of the aluminum foil, and the upper and lower surfaces are respectively laminated with polyethylene layers and polyester layers; drying; hot pressing and laminating; obtaining a high-width and high-barrier aluminum foil for liquid packaging.

[0013] As a further solution of the present invention: the width of the aluminum foil is 23000 mm.

[0014] Beneficial effects of the present invention: The present invention uses the amide bond reaction of amino-modified nano-titanium dioxide and maleic anhydride-grafted EVA to modify the EVA adhesive, which can effectively fill the pinholes in the aluminum foil and form a dense barrier network, thereby improving the barrier performance of the adhesive layer between the polyethylene layer, the aluminum foil layer, and the polyester layer. The amino groups grafted onto the surface of amination nano-TiO2 react with the carboxyl groups of maleic anhydride to form amide bonds, thereby enhancing interfacial bonding. At the same time, the nanoparticles are evenly dispersed in the EVA matrix, extending the gas permeation path through the "maze effect". The UV shielding properties of TiO2 further enhance the weather resistance of the composite film and delay photooxidative aging. Nano-TiO2 can not only enhance the barrier properties of EVA, but also effectively enhance the heat resistance and weather resistance of EVA due to its heat resistance and weather resistance. This allows the prepared modified EVA adhesive to have excellent heat resistance, weather resistance and barrier properties. This further enhances the barrier properties of the aluminum foil composite film, which is formed by compounding the polyethylene layer, aluminum foil layer and polyester layer in sequence through the modified EVA adhesive. In more detail, the water vapor and oxygen barrier properties are significantly improved: Through the reaction of amino-modified nano-titanium dioxide with the amide bond of maleic anhydride-grafted EVA, the modified EVA adhesive can effectively fill the pinholes in the aluminum foil and form a dense barrier network.

[0015] The amino groups grafted on the surface of amination nano-TiO2 react with the carboxyl groups of maleic anhydride to form amide bonds, which enhances the interfacial bonding strength. At the same time, the nanoparticles are evenly dispersed in the EVA matrix, extending the gas permeation path through the "maze effect".

[0016] High heat resistance and stability: Maleic anhydride grafted EVA forms a three-dimensional network structure through chemical cross-linking, and combined with the heat-resistant enhancement effect of nano-TiO2, the thermal decomposition temperature of the adhesive is increased; The modified EVA adhesive forms a chemical bond with the aluminum foil surface through an amide bond, and at the same time is tightly bonded to the polyester (PET) and polyethylene (PE) layers through polar interactions, thereby improving the peel strength.

[0017] The synergistic filling effect of nano-TiO2 and adhesive can cover the micron-sized pinholes (diameter <5μm) on the surface of aluminum foil, reduce the penetration channels, and improve the overall barrier uniformity. DETAILED DESCRIPTION

[0018] In order to enable those skilled in the art to better understand the solutions of the present invention, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention. Obviously, the embodiments described are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts should fall within the scope of protection of the present invention. Example 1

[0019] The embodiment of the present invention provides a high-width, high-barrier aluminum foil for liquid packaging, comprising a polyethylene layer, an aluminum foil layer, and a polyester layer; and the polyethylene layer, the aluminum foil layer, and the polyester layer are laminated in sequence through a modified EVA adhesive; The preparation process of the modified EVA adhesive comprises the following steps: The maleic anhydride grafted EVA reacts with amino-treated nano-titanium dioxide to generate a modified EVA adhesive containing an amide bond structure; The specific steps are as follows: in an ice-water bath, amino-modified nano-titanium dioxide, maleic anhydride-grafted EVA and NN dimethylformamide solvent are mixed, and then a catalyst, p-toluenesulfonic acid, is added; the system is transferred to an oil bath, heated under reflux at 160°C for a reaction of 4-6 hours, the reaction is stopped, and the reaction solution is poured into deionized water for precipitation, filtered, and dried to obtain a modified EVA adhesive; The ratio of the amount of amino-treated nano-titanium dioxide, maleic anhydride-grafted EVA and NN dimethylformamide solvent is 0.1 mol: 0.1 mol: 1 L: 4 g; More specifically, the preparation process of amination nano titanium dioxide includes: mixing lysine with an aqueous solution of ethylenediamine to obtain a lysine solution; wherein, anhydrous ethylenediamine is dissolved in distilled water and mixed uniformly to form an ethylenediamine solution with a mass fraction of 20%, and then lysine is added to the ethylenediamine solution and mixed uniformly to form a lysine solution; Tetrabutyl titanate and lysine solution were mixed and reacted at 100°C for 10 hours to obtain amino-modified nano-titanium dioxide; Tetrabutyl titanate and lysine solution were mixed for 30 minutes and subjected to a hydrothermal reaction at 100°C to obtain a precipitate. The precipitate was collected by centrifugation, washed with distilled water, anhydrous ethanol, and distilled water in sequence, and dried at 60°C for 10 hours to obtain amino-modified nano-titanium dioxide. The mass ratio of anhydrous ethylenediamine, lysine and tetrabutyl titanate is 80:5:100; The embodiment of the present invention provides a production process of a high-width, high-barrier aluminum foil for liquid packaging, comprising the following steps: Aluminum foil cleaning: Remove surface grease and oxides by plasma cleaning or wiping with ethanol.

[0020] Corona treatment of polyester layer and polyethylene layer: Polyester layer: corona power 8kW, processing speed 20m / min.

[0021] Polyethylene layer: corona power 5kW, use within 48 hours after treatment.

[0022] Film layer lamination: Use a gravure coater to evenly apply the adhesive to the upper and lower surfaces of the aluminum foil, and laminate the polyethylene layer and polyester layer on the upper and lower surfaces respectively, with a coating amount of 3g / m² (dry basis); the width of the aluminum foil is 23000mm.

[0023] Drying: Sectional drying (60℃→80℃→100℃), wind speed 5m / s, time 20 seconds.

[0024] Hot pressing lamination: temperature: 90°C; pressure: 0.3MPa; roller speed: 15m / min; A high-barrier aluminum foil for liquid packaging with high width and width is obtained. Example 2

[0025] The embodiment of the present invention provides a high-width, high-barrier aluminum foil for liquid packaging, comprising a polyethylene layer, an aluminum foil layer, and a polyester layer; and the polyethylene layer, the aluminum foil layer, and the polyester layer are laminated in sequence through a modified EVA adhesive; The preparation process of the modified EVA adhesive comprises the following steps: The maleic anhydride grafted EVA reacts with amino-treated nano-titanium dioxide to generate a modified EVA adhesive containing an amide bond structure; The specific steps are as follows: in an ice-water bath, amino-modified nano-titanium dioxide, maleic anhydride-grafted EVA and NN dimethylformamide solvent are mixed, and then a catalyst, p-toluenesulfonic acid, is added; the system is transferred to an oil bath, heated under reflux at 160°C for 5 hours, the reaction is stopped, and the reaction solution is poured into deionized water for precipitation, filtered, and dried to obtain a modified EVA adhesive; The ratio of the amount of amino-treated nano-titanium dioxide, maleic anhydride-grafted EVA and NN dimethylformamide solvent is 0.1 mol: 0.1 mol: 1.5 L: 6 g; More specifically, the preparation process of amination nano titanium dioxide includes: mixing lysine with an aqueous solution of ethylenediamine to obtain a lysine solution; wherein, anhydrous ethylenediamine is dissolved in distilled water and mixed uniformly to form an ethylenediamine solution with a mass fraction of 20%, and then lysine is added to the ethylenediamine solution and mixed uniformly to form a lysine solution; Tetrabutyl titanate and lysine solution were mixed and reacted at 110°C for 10 hours to obtain amino-modified nano-titanium dioxide; Tetrabutyl titanate and lysine solution were mixed for 30 minutes and subjected to a hydrothermal reaction at 100°C to obtain a precipitate. The precipitate was collected by centrifugation, washed with distilled water, anhydrous ethanol, and distilled water in sequence, and dried at 60°C for 10 hours to obtain amino-modified nano-titanium dioxide. The mass ratio of anhydrous ethylenediamine, lysine and tetrabutyl titanate is 100:10:100; The embodiment of the present invention provides a production process of a high-width, high-barrier aluminum foil for liquid packaging, comprising the following steps: Aluminum foil cleaning: Remove surface grease and oxides by plasma cleaning or wiping with ethanol.

[0026] Corona treatment of polyester layer and polyethylene layer: Polyester layer: corona power 9kW, processing speed 25m / min.

[0027] Polyethylene layer: corona power 6kW, use within 48 hours after treatment.

[0028] Film layer lamination: Use a gravure coater to evenly apply the adhesive to the upper and lower surfaces of the aluminum foil, and laminate the polyethylene layer and polyester layer on the upper and lower surfaces respectively, with a coating amount of 4g / m² (dry basis); the width of the aluminum foil is 23000mm.

[0029] Drying: Sectional drying (60℃→80℃→100℃), wind speed 5m / s, time 25 seconds.

[0030] Hot pressing lamination: temperature: 100°C; pressure: 0.4 MPa; roller speed: 20 m / min; A high-barrier aluminum foil for liquid packaging with high width and width is obtained. Example 3

[0031] The embodiment of the present invention provides a high-width, high-barrier aluminum foil for liquid packaging, comprising a polyethylene layer, an aluminum foil layer, and a polyester layer; and the polyethylene layer, the aluminum foil layer, and the polyester layer are laminated in sequence through a modified EVA adhesive; The preparation process of the modified EVA adhesive comprises the following steps: The maleic anhydride grafted EVA reacts with amino-treated nano-titanium dioxide to generate a modified EVA adhesive containing an amide bond structure; The specific steps are as follows: in an ice-water bath, amino-modified nano-titanium dioxide, maleic anhydride-grafted EVA and NN dimethylformamide solvent are mixed, and then a catalyst, p-toluenesulfonic acid, is added; the system is transferred to an oil bath, heated under reflux at 160°C for 6 hours, the reaction is stopped, and the reaction solution is poured into deionized water for precipitation, filtered, and dried to obtain a modified EVA adhesive; The ratio of the amount of amino-treated nano-titanium dioxide, maleic anhydride-grafted EVA and NN dimethylformamide solvent is 0.1 mol: 0.1 mol: 2 L: 8 g; More specifically, the preparation process of amination nano titanium dioxide includes: mixing lysine with an aqueous solution of ethylenediamine to obtain a lysine solution; wherein, anhydrous ethylenediamine is dissolved in distilled water and mixed uniformly to form an ethylenediamine solution with a mass fraction of 20%, and then lysine is added to the ethylenediamine solution and mixed uniformly to form a lysine solution; Tetrabutyl titanate and lysine solution were mixed and reacted at 120°C for 10 hours to obtain amino-modified nano-titanium dioxide; Tetrabutyl titanate and lysine solution were mixed for 30 minutes and subjected to a hydrothermal reaction at 100°C to obtain a precipitate. The precipitate was collected by centrifugation, washed with distilled water, anhydrous ethanol, and distilled water in sequence, and dried at 60°C for 10 hours to obtain amino-modified nano-titanium dioxide. The mass ratio of anhydrous ethylenediamine, lysine and tetrabutyl titanate is 120:15:100; The embodiment of the present invention provides a production process of a high-width, high-barrier aluminum foil for liquid packaging, comprising the following steps: Aluminum foil cleaning: Remove surface grease and oxides by plasma cleaning or wiping with ethanol.

[0032] Corona treatment of polyester layer and polyethylene layer: Polyester layer: corona power 10kW, processing speed 30m / min.

[0033] Polyethylene layer: corona power 8kW, use within 48 hours after treatment.

[0034] Film layer lamination: Use a gravure coater to evenly apply the adhesive to the upper and lower surfaces of the aluminum foil, and laminate the polyethylene layer and polyester layer on the upper and lower surfaces respectively, with a coating amount of 5g / m² (dry basis); the width of the aluminum foil is 23000mm.

[0035] Drying: Sectional drying (60℃→80℃→100℃), wind speed 5m / s, time 30 seconds.

[0036] Hot pressing lamination: temperature: 110℃; pressure: 0.5MPa; roller speed: 25m / min; A high-barrier aluminum foil for liquid packaging with high width and width is obtained.

[0037] Comparative Example 1 Comparative Example 1 uses the packaging composite film disclosed in Example 1 of Chinese Patent No. CN 116891583 A; The aluminum foils of Examples 1-3 and the composite film of Comparative Example 1 were tested for water vapor and oxygen permeability. Refer to YBB00092003-2015 to test the water vapor transmission rate. The unit of water vapor transmission rate is g / m 224 hours, tested by infrared method; refer to YBB00082003-2015 for oxygen transmission rate, tested by electrical quantity method, the unit of oxygen transmission rate is cm 3 / m 2 24h 0.1MPa; see the results in the table below:

[0038] As can be seen from the above table, the water vapor permeability of the aluminum foil composite films prepared in Examples 1-3 of the present invention is in the range of 0.213-0.217 g / m 2 ·24h, oxygen permeability range is 0.231-0.236cm 3 / m 2 ·24h·0.1MPa, which is higher than the water vapor permeability range of 0.256g / m disclosed in Comparative Example 1 2 24h, oxygen permeability range is 0.281cm 3 / m 2 ·24h·0.1MPa; Therefore, the aluminum foil composite film prepared by the present invention has better barrier properties.

[0039] The above is a detailed description of an embodiment of the present invention. However, the content described is only a preferred embodiment of the present invention and should not be considered to limit the scope of the present invention. All equivalent changes and improvements made within the scope of the present invention should still fall within the scope of the patent coverage of the present invention.

Claims

1. A high-width, high-barrier aluminum foil for liquid packaging, characterized in that: It includes a polyethylene layer, an aluminum foil layer, and a polyester layer; and the polyethylene layer, the aluminum foil layer, and the polyester layer are compounded in sequence through a modified EVA adhesive; The preparation process of the modified EVA adhesive comprises the following steps: The maleic anhydride grafted EVA reacts with amino-treated nano-titanium dioxide to generate a modified EVA adhesive containing an amide bond structure.

2. The high-width, high-barrier aluminum foil for liquid packaging according to claim 1, characterized in that: The preparation process of the modified EVA adhesive containing an amide bond structure is as follows: In an ice-water bath, amino-modified nano-titanium dioxide, maleic anhydride-grafted EVA and NN dimethylformamide solvent are mixed, and then a catalyst, p-toluenesulfonic acid, is added; the system is transferred to an oil bath and heated under reflux at 160°C for 4-6 hours to obtain a modified EVA adhesive containing an amide bond structure.

3. The high-width, high-barrier aluminum foil for liquid packaging according to claim 1, characterized in that: The usage ratio of the amino-modified nano-titanium dioxide, the maleic anhydride-grafted EVA and the NN dimethylformamide solvent is 0.1 mol: 0.1 mol: 1-2 L: 4-8 g.

4. The high-width, high-barrier aluminum foil for liquid packaging according to claim 1, characterized in that: The preparation process of amination nano titanium dioxide includes: mixing lysine with an aqueous solution of ethylenediamine to obtain a lysine solution; Tetrabutyl titanate and lysine solution are mixed and reacted at 100-120° C. for 10 hours to obtain amino-modified nano-titanium dioxide.

5. The high-width and high-barrier aluminum foil for liquid packaging according to claim 1, characterized in that: The specific process of preparing lysine solution is as follows: Anhydrous ethylenediamine was dissolved in distilled water and mixed evenly to form an ethylenediamine solution with a mass fraction of 20%. Lysine was then added to the ethylenediamine solution and mixed evenly to form a lysine solution.

6. The high-width, high-barrier aluminum foil for liquid packaging according to claim 1, characterized in that: The specific process of preparing amination nano titanium dioxide is as follows: Tetrabutyl titanate and lysine solution were mixed for 30 minutes, and hydrothermally reacted at 100° C. to obtain a precipitate; thus, amino-modified nano-titanium dioxide was obtained.

7. The high-width, high-barrier aluminum foil for liquid packaging according to claim 1, characterized in that: The mass ratio of anhydrous ethylenediamine, lysine and tetrabutyl titanate is 80-120:5-15:

100.

8. A production process for high-width, high-barrier aluminum foil for liquid packaging, characterized in that: The production process is used to prepare the high-width and high-barrier aluminum foil for liquid packaging according to any one of claims 1 to 7, and comprises the following steps: It is composed of a polyethylene layer, an aluminum foil layer, and a polyester layer laminated in sequence through a modified EVA adhesive.

9. The production process of a high-width, high-barrier aluminum foil for liquid packaging according to claim 1, characterized in that: The adhesive is evenly coated on the upper and lower surfaces of the aluminum foil using a gravure coater, and the polyethylene layer and the polyester layer are respectively laminated on the upper and lower surfaces; the aluminum foil is dried and hot-pressed to obtain a high-width and high-barrier liquid packaging aluminum foil.

10. The production process of a high-width and high-barrier aluminum foil for liquid packaging according to claim 1, characterized in that: The width of the aluminum foil is 23000mm.

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