Aluminum foil cover film with high stripping force and high acid resistance and production process thereof

Abstract

The invention belongs to the technical field of packaging materials, and particularly relates to an aluminum foil cover film with high stripping force and high acid resistance and a production process of the aluminum foil cover film. The aluminum foil cover film is formed by sequentially compounding a PET layer, an aluminum foil layer and a film blowing PE layer in a dry mode, the film blowing PE layer is composed of a layer A, a layer B and a layer C which are sequentially connected, and the aluminum foil layer is connected with the layer A through an adhesive; the layer A consists of first linear low-density polyethylene and second linear low-density polyethylene; the layer B is prepared from first linear low-density polyethylene, second linear low-density polyethylene and high-density polyethylene; and the layer C consists of first linear low-density polyethylene, third linear low-density polyethylene and an anti-blocking agent. The aluminum foil cover film prepared by the invention has relatively high stripping force, can effectively prevent layering and bag breaking when being used in a high-temperature and high-humidity environment, and has excellent acid resistance.

Description

Technical Field

[0001] This invention relates to the field of packaging materials technology, and in particular to an aluminum foil cover film with high peel strength and high acid resistance, and its manufacturing process. Background Technology

[0002] With economic development and improved living standards, people have higher demands for product packaging. The market offers a dazzling array of packaging materials of various materials and structures. However, a good product not only needs eye-catching printed designs, but more importantly, the packaging material itself must ensure the contents remain fresh and undamaged, thus extending the product's shelf life. Currently, aluminum foil cap film packaging materials are widely used in yogurt, jelly-like foods, oral liquid medicines, and lithium battery packaging due to their excellent barrier properties, good sealing performance, and low processing costs. When packaging acidic contents (such as juice drinks, pickles, and acidic medicines), the acid resistance and sealing strength of the aluminum foil cap film are extremely important. Furthermore, if the aluminum foil cap film needs to undergo high-temperature and high-humidity sterilization during the packaging process, this poses an even greater challenge to its peelability.

[0003] Traditional aluminum foil capping film, after being soaked in a pH 2.5 solution for 30 days, exhibits a 40% decrease in peel strength and a 15% decrease in acid resistance. This makes it unsuitable for the stable use of products requiring long-term storage. Furthermore, the physical properties of traditional aluminum foil capping film deteriorate even more significantly after being boiled in high-temperature, high-humidity water.

[0004] Most of the aluminum foil cap film packaging materials for liquid milk on the market have a two- or three-layer structure: PET / AL / PE or PET / AL / CPP, AL / PE or AL / CPP (AL printing must be coated).

[0005] The main drawbacks are: 1. Insufficient peel strength: Traditional adhesives are prone to aging in high temperature and high humidity environments, resulting in a decrease in peel strength (usually <10N / 15mm), which leads to sealing failure during transportation or sterilization.

[0006] 2. Poor acid resistance: Acidic environments easily corrode the aluminum layer and the bonding interface, causing film delamination, aluminum layer perforation, and even deterioration of the contents.

[0007] 3. Complex process: Existing technology requires multiple coating layers (such as primer + adhesive layer + protective layer), resulting in high production costs and low yield.

[0008] 4. Low success rate of inserting straw into the capping film: The capping film is tough, making it difficult for consumers to insert straws. Summary of the Invention

[0009] To solve the above-mentioned technical problems, the present invention provides an aluminum foil cover film with high peel strength and high acid resistance and its manufacturing process. The aluminum foil cover film has high peel strength, good acid resistance, simple processing technology, and easy insertion of straws.

[0010] To achieve one of the objectives of this invention, the following technical solution is adopted: An aluminum foil cover film with high peel strength and high acid resistance is provided. The aluminum foil cover film is formed by dry lamination of a PET layer, an aluminum foil layer and a blown PE layer in sequence. The blown PE layer is composed of layers A, B and C connected in sequence. The aluminum foil layer is connected to layer A by an adhesive. Layer A is composed of a first linear low-density polyethylene and a second linear low-density polyethylene. Layer B is composed of a first linear low-density polyethylene, a second linear low-density polyethylene and a high-density polyethylene. Layer C is composed of a first linear low-density polyethylene, a third linear low-density polyethylene and an opening agent.

[0011] Preferably, layer A comprises 65-70 parts by weight of first linear low-density polyethylene and 30-35 parts by weight of second linear low-density polyethylene; layer B comprises 30-35 parts by weight of first linear low-density polyethylene, 30-35 parts by weight of second linear low-density polyethylene and 30-35 parts by weight of high-density polyethylene; and layer C comprises 30-35 parts by weight of first linear low-density polyethylene, 64-68 parts by weight of third linear low-density polyethylene and 1-2 parts by weight of opening agent.

[0012] Preferably, the first linear low-density polyethylene is 2010MA manufactured by ExxonMobil, Inc.; the second linear low-density polyethylene is 5538G manufactured by DowDuPont, Inc.; the high-density polyethylene is 5960G1 manufactured by Dow Chemical, Inc.; the third linear low-density polyethylene is 5401GT manufactured by Dow Chemical, Inc.; and the opening agent is AB-20LD manufactured by Beijing Yalen Company.

[0013] Preferably, layer A comprises 67 parts by mass of first linear low-density polyethylene and 33 parts by mass of second linear low-density polyethylene; layer B comprises 33 parts by mass of first linear low-density polyethylene, 34 parts by mass of second linear low-density polyethylene and 33 parts by mass of high-density polyethylene; and layer C comprises 33 parts by mass of first linear low-density polyethylene, 65.5 parts by mass of third linear low-density polyethylene and 1.5 parts by mass of opening agent.

[0014] Preferably, the adhesive is prepared by mixing the main agent and the curing agent in a mass ratio of 20:3.5, the main agent is grade SY-3004 and the curing agent is grade 3004H.

[0015] Preferably, the thickness of layer A is 15μm, the thickness of layer B is 34μm, the thickness of layer C is 21μm, the thickness of PET layer is 12μm, and the thickness of aluminum foil layer is 30μm.

[0016] Preferably, the aluminum foil used for the aluminum foil layer is grade 8011-O; the PET layer uses PET film produced by Sanfangxiang Company.

[0017] To achieve the second objective of this invention, this invention provides a manufacturing process for an aluminum foil cover film with high peel strength and high acid resistance, comprising the following steps: S1. First, print on the PET film, then dry-laminate the non-printed side of the PET film with aluminum foil to obtain a PET / AL composite film. S2. Weigh out the raw material particles of layer A, layer B and layer C in parts by mass, add them into the corresponding material cylinder of the blown film machine, and obtain PE film, i.e. blown PE layer, through the blown film process. S3. The aluminum foil layer of the PE film and the PET / AL composite film are dry-laminated with an adhesive to obtain an aluminum foil cover film.

[0018] The advantages of this invention compared to the prior art are as follows: 1) The aluminum foil cover film prepared by this invention has high peel strength, which can effectively prevent delamination and packaging breakage when used in high temperature and high humidity environments. It also has excellent acid resistance, is stable for a long time in an environment with a pH value of 2-5, and can resist corrosion well, which can improve the storage period of the packaged contents. The production process does not require coating, the preparation is very simple, and the straw insertion success rate is high, which improves consumer satisfaction.

[0019] 2) The PE film of this invention is easy to apply when laminated with aluminum foil, and exhibits better adhesion to the aluminum foil. Adding 33% high-density polyethylene (HDPE) particles 5960G1 to the B layer of the PE film has the following advantages: ① Improved the overall heat resistance of PE film, making it more suitable for the harsh conditions of high-temperature treatment after downstream filling; ② The overall stiffness and rigidity of the PE film are increased, resulting in a slight decrease in its puncture resistance. This makes it easier to insert straws during use, increasing the success rate of single straw insertion and greatly improving the customer experience. Furthermore, compared to conventional PE, its haze is reduced by 5%, its temperature resistance is improved by 10%, and it does not delaminate after high-temperature sterilization when used with water-resistant adhesives.

[0020] 3) Aluminum foil cap films for beverage packaging require rigorous high-temperature spray sterilization after filling. This step is crucial for determining the film's quality. The interlayer peel strength between AL and PE directly determines whether the film can be used normally. When the AL / PE peel strength is low (<9N / 15mm), delamination and demolding generally occur, leading to leakage and increasing the product defect rate. This invention, through a unique PE film formulation design and the use of specific adhesives (main agent SY-3004 / curing agent 3004H) during lamination, can significantly improve the AL / PE interlayer peel strength of the aluminum foil cap film.

[0021] 4) This invention uses 8011-O aluminum foil, which possesses high mechanical strength, excellent toughness, and superior ductility, and exhibits excellent processing performance, thus solving the problem of excessive debris during capping. Aluminum foil produced using 8011-O foil ensures smooth capping, preventing blockages and jamming, and eliminating debris generation. Furthermore, by thinning the inner PE film (70μm→65μm), the debris problem during capping is further reduced.

[0022] 5) The adhesive used in the composite process of this invention is the main agent SY-3004 / curing agent 3004H from Seyia Corporation. This adhesive has excellent processing characteristics and is suitable for high-temperature sterilization packaging with aluminum foil structures, better meeting the high-temperature and high-humidity sterilization environment required for subsequent filling. Its main component is a hydroxyl-containing polyurethane prepolymer, and the curing agent mainly consists of polyisocyanate, UV absorbers, antioxidants, and other additives. Furthermore, the packaging structure composited using this adhesive shows significantly improved peel strength after boiling compared to before boiling, and no delamination occurs, greatly reducing the defect rate.

[0023] 6) This invention innovatively designs a blown PE layer specifically for the cap film by selecting appropriate aluminum foil type and adhesive, and through a special composite process, prepares an aluminum foil cap film with high peel strength and high acid resistance. This solves the problems of low peel strength and poor acid resistance of aluminum foil cap films for yogurt products, and also overcomes the defect of easy delamination after boiling. At the same time, using this cap film can significantly increase the shelf life of the packaged contents. The product preparation process is simple and the processing technology is convenient, which can greatly reduce production costs. Through this innovative process, it can be greatly extended to other bottled beverage products.

[0024] 7) This invention relates to a novel aluminum foil cap film with high peel strength that significantly increases after boiling without diminishing. It also facilitates capping during subsequent packaging processes, prevents delamination during high-temperature sterilization, and ensures easy demolding. By selecting suitable 8011-O type aluminum foil, a self-developed inner blown PE layer, and employing a special composite processing technology, a high-peel-strength, highly acid-resistant aluminum foil cap film was prepared. This cap film provides excellent sealing and strong barrier properties after sealing with the bottle, allowing it to withstand prolonged corrosion from acidic contents without affecting its physical properties, thus extending product shelf life. Therefore, it is widely applicable for packaging acidic dairy beverages. Attached Figure Description

[0025] Figure 1 This is a flowchart of the present invention. Detailed Implementation

[0026] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without creative effort are within the scope of protection of this invention.

[0027] Example 1 A manufacturing process for an aluminum foil cover film with high peel strength and high acid resistance includes the following steps: S1. First, print on the PET film, then dry-laminate the non-printed side of the PET film with aluminum foil to obtain a PET / AL composite film. S2. Weigh out the raw material particles of layer A, layer B and layer C in parts by mass, add them into the corresponding material cylinder of the blown film machine, and obtain PE film through blown film process; S3. The PE film and the aluminum foil layer of the PET / AL composite film are dry-laminated with an adhesive to obtain the aluminum foil cover film 1.

[0028] The process sheet for PE film is shown in Table 1 below: Table 1 .

[0029] Comparative Example 1 The structure of the aluminum foil cover film packaging material is: PET / AL / PE, wherein the A and B layers of the PE layer of the cover film are composed of low-density polyethylene and linear low-density polyethylene, and the C layer is composed of metallocene polyethylene and low-density polyethylene, thus producing aluminum foil cover film 2.

[0030] The performance of aluminum foil cover film 1 and aluminum foil cover film 2 was tested, and the results are shown in Table 2 below: Table 2 ; As shown in Table 2 above, compared to room temperature conditions, the aluminum foil cover film 1 prepared in Example 1 exhibits a significant increase in AL / PE interlayer peel strength after high-temperature boiling (95℃ / 1h) (13N / 15mm→19N / 15mm), which is significantly higher than that of the aluminum foil cover film prepared in Comparative Example 1. This fully meets the customer's processing requirements, improves production efficiency, and expands economic benefits. Furthermore, its excellent acid resistance greatly extends the shelf life of the packaged contents, and makes it easier to insert a straw during use.

Claims

1. An aluminum foil cover film with high peel strength and high acid resistance, characterized in that: The aluminum foil cover film is formed by dry lamination of a PET layer, an aluminum foil layer, and a blown PE layer. The blown PE layer consists of layers A, B, and C connected in sequence. The aluminum foil layer is connected to layer A by an adhesive. Layer A consists of a first linear low-density polyethylene and a second linear low-density polyethylene. Layer B consists of a first linear low-density polyethylene, a second linear low-density polyethylene, and a high-density polyethylene. Layer C consists of a first linear low-density polyethylene, a third linear low-density polyethylene, and an opening agent.

2. The aluminum foil cover film with high peel strength and high acid resistance according to claim 1, characterized in that: Layer A comprises 65-70 parts by weight of first linear low-density polyethylene and 30-35 parts by weight of second linear low-density polyethylene; Layer B comprises 30-35 parts by weight of first linear low-density polyethylene, 30-35 parts by weight of second linear low-density polyethylene and 30-35 parts by weight of high-density polyethylene; Layer C comprises 30-35 parts by weight of first linear low-density polyethylene, 64-68 parts by weight of third linear low-density polyethylene and 1-2 parts by weight of opening agent.

3. The aluminum foil cover film with high peel strength and high acid resistance according to claim 1, characterized in that: The first linear low-density polyethylene is 2010MA manufactured by ExxonMobil, Inc.; the second linear low-density polyethylene is 5538G manufactured by DowDuPont, Inc.; the high-density polyethylene is 5960G1 manufactured by Dow Chemical, Inc.; the third linear low-density polyethylene is 5401GT manufactured by Dow Chemical, Inc.; and the opening agent is AB-20LD manufactured by Beijing Yalen Company.

4. An aluminum foil cover film with high peel strength and high acid resistance according to claim 1 or 2, characterized in that: Layer A comprises 67 parts by mass of first linear low-density polyethylene and 33 parts by mass of second linear low-density polyethylene; Layer B comprises 33 parts by mass of first linear low-density polyethylene, 34 parts by mass of second linear low-density polyethylene and 33 parts by mass of high-density polyethylene; Layer C comprises 33 parts by mass of first linear low-density polyethylene, 65.5 parts by mass of third linear low-density polyethylene and 1.5 parts by mass of opening agent.

5. The aluminum foil cover film with high peel strength and high acid resistance according to claim 1, characterized in that: The adhesive is formulated from a main agent and a curing agent in a mass ratio of 20:3.

5. The main agent is designated as SY-3004 and the curing agent is designated as 3004H.

6. The aluminum foil cover film with high peel strength and high acid resistance according to claim 1, characterized in that: The thickness of layer A is 15 μm, the thickness of layer B is 34 μm, and the thickness of layer C is 21 μm; The PET layer has a thickness of 12 μm, and the aluminum foil layer has a thickness of 30 μm.

7. The aluminum foil cover film with high peel strength and high acid resistance according to claim 1, characterized in that: The aluminum foil used in the aluminum foil layer is grade 8011-O; the PET layer uses PET film produced by Sanfangxiang Company.

8. A manufacturing process for an aluminum foil cover film with high peel strength and high acid resistance as described in any one of claims 1-7, characterized in that, Includes the following steps: S1. First, print on the PET film, then dry-laminate the non-printed side of the PET film with aluminum foil to obtain a PET / AL composite film. S2. Weigh out the raw material particles of layer A, layer B and layer C in parts by mass, add them into the corresponding material cylinder of the blown film machine, and obtain PE film through blown film process; S3. The aluminum foil layer of the PE film and the PET / AL composite film are dry-laminated with an adhesive to obtain an aluminum foil cover film.

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