Aluminum foil composite film with excellent ink adhesion, preparation method and application of aluminum foil composite film in butter packaging

Abstract

The invention relates to the technical field of aluminum foil composite film research and development, and discloses an aluminum foil composite film with excellent ink adhesive force, a preparation method and application in butter packaging, a bidirectional high-adhesive-force accelerant is prepared, water-soluble acrylic resin is modified through the bidirectional high-adhesive-force accelerant, and a high-adhesive-force acrylic resin primer is prepared; an outer-layer BOPP film of an outer-layer BOPP / Al / inner-layer BOPP base material is subjected to surface coating treatment through a high-adhesion acrylic resin primer, then alcohol-soluble polyurethane ink serves as a raw material, patterns are printed on the outer-layer BOPP film through an overprinting method, finally, the surface of a printing layer is coated with an anti-scraping agent, and the aluminum foil composite film is obtained. The aluminum foil composite film prepared by the invention has excellent ink adhesion, low-temperature bending resistance and scratch resistance, and can be applied to butter packaging.

Description

Technical Field

[0001] This invention relates to the field of aluminum foil composite film research and development technology, and in particular to an aluminum foil composite film with excellent ink adhesion, its preparation method, and its application in butter packaging. Background Technology

[0002] Aluminum foil composite film is a material composed of aluminum foil and biaxially oriented polypropylene (BOPP). The aluminum foil provides excellent barrier properties, effectively blocking moisture, gases, and light, while the BOPP layer is safe and non-toxic, allowing direct contact with food. This makes it an ideal material for packaging high-temperature retortable foods, butter, pharmaceuticals, and lithium battery encapsulation. However, aluminum foil has low mechanical strength and is prone to pinhole formation during packaging and use, reducing its barrier properties. Therefore, it is necessary to compensate for the shortcomings of aluminum foil by using outer films such as BOPP, PET, and PE. Among these, BOPP has become one of the preferred outer composite materials for aluminum foil due to its high mechanical strength, light weight, non-toxicity, odorlessness, and wide range of applications.

[0003] Polypropylene is a non-polar material with low surface energy, a crystallinity of up to 95%, regular molecular arrangement, and low surface tension of only 31 mN / m. When printing on its surface, ink adhesion is poor, ink is easily detached, and the quality of the film is affected. Therefore, improving the adhesion of ink to the outer BOPP film surface has become an urgent problem to be solved in ink printing process.

[0004] Research has found that surface treatment of the outer BOPP film is necessary to improve its surface energy and increase its adhesion. Treatment methods include corona treatment, plasma treatment, and surface coating modification. Among these, surface coating modification effectively improves the surface properties of the BOPP film and increases its adhesion without damaging the internal structure of the outer BOPP film substrate. Furthermore, the process is simple, convenient, and low-cost, making it one of the important methods for surface treatment of outer BOPP films.

[0005] The coating modification method usually involves coating a base coat onto the surface of the outer BOPP film. After film formation, the base coat replaces the original BOPP film surface. Since butter needs to be stored at low temperature (-18℃) and the ink layer is prone to peeling and falling off, it is necessary not only to improve the adhesion between the aluminum foil composite film and the ink, but also to improve the low-temperature bending resistance of the aluminum foil composite film.

[0006] This invention cites the following references:

[0007] The master's thesis from South China University of Technology, "Preparation and Performance Study of Acrylic Emulsion for Polypropylene Coating," discloses that the nonpolar 7,7-dimethylbicycloheptyl group of isoborneol acrylate has a similar molecular structure to polypropylene and exhibits strong intermolecular forces with polypropylene molecules, which can be used to improve the adhesion of emulsions to untreated polypropylene substrates. Summary of the Invention

[0008] This invention utilizes a newly developed bidirectional high adhesion promoter to modify water-soluble acrylic resin and coat it onto the surface of the outer BOPP film of a BOPP / AL / BOPP substrate. Then, using alcohol-soluble polyurethane ink as raw material, a pattern is printed on the outer BOPP film using an overprinting method. Afterward, an anti-scratch agent is coated on the surface of the printed layer to prepare an aluminum foil composite film. This aluminum foil composite film has excellent ink adhesion and can be used in butter packaging.

[0009] To achieve the above objectives, the present invention adopts the following technical solution: a method for preparing an aluminum foil composite film with excellent ink adhesion, comprising the following steps:

[0010] Step 1: Prepare a two-way high adhesion promoter. Modify water-soluble acrylic resin with the two-way high adhesion promoter to obtain a high adhesion acrylic resin primer.

[0011] Step 2: The outer BOPP film of the outer BOPP / Al / inner BOPP substrate is first coated with a high-adhesion acrylic resin primer, and then a pattern is printed on the outer BOPP film using an overprinting method with alcohol-soluble polyurethane ink as the raw material. Finally, an anti-scratch agent is coated on the surface of the printed layer to obtain an aluminum foil composite film.

[0012] Furthermore, the preparation method of the bidirectional high adhesion promoter is as follows:

[0013] Based on the amine-ene reaction mechanism, the α,β-unsaturated alkenyl functional group in isoborneol acrylate reacts with the imino group in iminodiacetic acid to prepare a dicarboxylated monomer.

[0014] Based on the carboxyl-isocyanate reaction mechanism, a bidirectional high adhesion promoter was prepared by reacting the carboxyl group in the dicarboxylated monomer with the isocyanate group in isocyanoethyl methacrylate.

[0015] Furthermore, the preparation method of the high-adhesion acrylic resin primer is as follows: a two-way high-adhesion promoter is grafted onto a water-soluble acrylic resin through a polymerization reaction under the action of an initiator.

[0016] Furthermore, the initiator is one of potassium persulfate, calcium persulfate, and ammonium persulfate.

[0017] Furthermore, the anti-scratch agent is one of water-based acrylic emulsion varnish, epoxy-modified acrylic ester varnish, and modified polyurethane acrylic ester varnish.

[0018] The structure of an aluminum foil composite film with excellent ink adhesion prepared according to the above method is: anti-scratch layer / ink layer / adhesive layer / outer BOPP / Al / inner BOPP.

[0019] The beneficial effects of this invention are as follows:

[0020] This invention designs and synthesizes a novel bidirectional high adhesion promoter, which is used to modify water-soluble acrylic resin to prepare a high-adhesion acrylic resin primer. Then, the high-adhesion acrylic resin primer is coated on the surface of the outer BOPP film of a BOPP / AL / BOPP substrate. Next, using alcohol-soluble polyurethane ink as raw material, a pattern is printed on the outer BOPP film using an overprinting method. Finally, an anti-scratch agent is coated on the surface of the printed layer to prepare an aluminum foil composite film.

[0021] Experiments revealed that the aluminum foil composite film prepared by this invention achieves an adhesion level of 0 at room temperature. After being stored and folded at low temperatures, the ink on the aluminum foil composite film did not peel off. Furthermore, the quality of the film changed very little after a scratch test. In other words, it possesses high adhesion to ink, excellent low-temperature bending resistance, and excellent scratch resistance, making it suitable for use in butter packaging. Detailed Implementation

[0022] To improve the adhesion between the primer and the ink at room temperature, this invention independently developed a bidirectional high adhesion promoter. By modifying the water-soluble acrylic resin with this promoter, the non-polar 7,7-dimethylbicycloheptyl group in its structure is tightly bonded to the surface of the outer BOPP film. At the same time, the amide groups in its structure can form a strong bond with the alcohol-soluble polyurethane ink through hydrogen bonding, which significantly improves the adhesion performance between the primer and the ink layer at room temperature.

[0023] Example 1:

[0024] The preparation of a two-way high adhesion promoter includes the following steps:

[0025] (1) Preparation of isobornyl acrylate functional monomers: The preparation mechanism is as follows: the alkenyl functional group in isobornyl acrylate reacts with the imino group in iminodiacetic acid to prepare isobornyl acrylate functional monomers. The specific experimental steps are as follows: First, 3g of isobornyl acrylate is dissolved in 50mL of acetone and stirred at room temperature until completely dissolved to obtain isobornyl acrylate solution. Then, 1.9g of iminodiacetic acid and 50mL of deionized water are added to a 250mL four-necked flask and stirred with a stirrer to dissolve it. Then, the isobornyl acrylate solution is added to the four-necked flask and stirred at 25℃ for 24h. The acetone is removed by rotary evaporation, filtered, washed, and dried at 80℃ for 8h to prepare isobornyl acrylate functional monomers.

[0026] (2) Preparation of a two-way high adhesion promoter. The preparation mechanism is as follows: the two-way high adhesion promoter is prepared by reacting the carboxyl group in the isoborneol acrylate functional monomer with the isocyanate group in ethyl isocyanate methacrylate. The specific experimental steps are as follows: under a nitrogen atmosphere, 2g of isoborneol acrylate functional monomer is placed in 100mL of N,N-dimethylformamide and ultrasonically dispersed for 20min. Then, 1.8g of ethyl isocyanate methacrylate and 0.02g of butyltin dilaurate are added, mixed, heated to 70℃, reacted for 6h, nitrogen was removed, solvent was removed by rotary evaporation, filtered, the product was collected, and vacuum dried at 60℃ for 6h to prepare the two-way high adhesion promoter.

[0027] The chemical structural formula of the two-way high adhesion promoter is:

[0028] ;

[0029] The 1H NMR spectrum characterization of the two-way high adhesion promoter is as follows:

[0030] 1 H NMR (DMSO-d6, 400MHz) δ: 0.84 (s, 3H), 0.89 (s, 3H), 0.93 (s, 3H), 1.30-1.60 (m, 4H), 1.69-1.76 (m, 2H), 1.87-1.90 (m, 1H), 1.92 (s, 6H), 2.59-2.6 2 (t, 2H), 2.87-2.95 (m, 2H), 3.25-3.31 (m, 4H), 3.38-3.47 (m, 4H), 4.14 -4.21 (m, 4H), 4.63-4.65 (m, 1H), 5.65-5.96 (dd, 4H), 7.87-7.89 (t, 2H).

[0031] Example 2:

[0032] A high-adhesion acrylic resin primer was prepared based on Example 1, including the following steps:

[0033] Add 5g of bidirectional high adhesion promoter to 60g of water-soluble acrylic resin (solid content of 70wt%, hydroxyl content of 3.5%, based on solid content, brand name JE-6132), stir mechanically until uniform, add 0.8g of ammonium persulfate, turn on the heater, control the temperature at 90℃, stir and react for 2h, after the reaction is completed, filter the material through a 200-mesh filter cloth to prepare a high adhesion acrylic resin primer.

[0034] Example 3:

[0035] Based on Example 2, an aluminum foil composite film with excellent ink adhesion was prepared, including the following steps:

[0036] Step 1: A BOPP / AL / BOPP substrate is prepared by sequentially bonding an outer layer of 38μm thick biaxially oriented polypropylene film, an inner layer of 9μm thick aluminum foil, and an inner layer of 38μm thick biaxially oriented polypropylene film together using a high-speed solvent-free lamination process with a polyurethane adhesive (brand name HT8153).

[0037] Step 2: Add 2.7g of isophorone diisocyanate to 10g of high-adhesion acrylic resin primer, stir and disperse evenly, and evenly coat the prepared coating solution on the surface of the outer BOPP film of the BOPP / AL / BOPP substrate. Place the film at 35°C to dry and cure to obtain the tack-enhanced BOPP / AL / BOPP film.

[0038] Step 3: Using an overprinting method, alcohol-soluble polyurethane ink (purchased from Bauhinia Ink (Zhejiang) Co., Ltd.) is used to print the design pattern (e.g., the trademark information of butter products) on the tackifying BOPP / AL / BOPP film. Then, an epoxy-modified acrylic varnish (model R1205) is coated on the surface of the printed layer and vacuum dried at 60°C for 4 hours to obtain an aluminum foil composite film.

[0039] Scratch resistance: Weigh 5g of aluminum foil composite film, scratch the aluminum foil composite film 400 times and then weigh it again to evaluate the scratch resistance of the ink layer. Result: The aluminum foil composite film weighs 5.001g after 400 scratches, indicating that the ink layer does not bleed.

[0040] Bending resistance: The prepared aluminum foil composite film was stored in a refrigerator at -18℃ for 48 hours. After being taken out, it was bent at 90° and the ink was observed to see if it peeled off. Result: No peeling or flaking of the ink layer was observed.

[0041] Comparative Example 1:

[0042] Preparation of ordinary aluminum foil composite film A: Compared with aluminum foil composite film, the only difference is that water-soluble acrylic resin is used instead of high-adhesion acrylic resin primer.

[0043] Comparative Example 2:

[0044] Preparation of ordinary aluminum foil composite film B: Compared with aluminum foil composite film, the only difference is that: high adhesion acrylic resin primer is not used, and alcohol-soluble polyurethane ink is directly printed on the surface of the outer BOPP film of the outer BOPP / Al / inner BOPP substrate by overprinting method. Then, epoxy modified acrylic varnish is coated on the surface of the printed layer.

[0045] Performance testing:

[0046] The aluminum foil composite film with excellent ink adhesion prepared in Example 3 and the ordinary aluminum foil composite film prepared in the comparative example were used as samples. The adhesion of the samples at room temperature was tested according to GB / T 9286-2021 "Paints and Varnishes Cross-cut Test" to evaluate the adhesion between the aluminum foil composite film and the ink. The specific test results are shown in Table 1.

[0047] Table 1 Performance Testing

[0048] Adhesion (Grade) Example 3 0 Comparative Example 1 3 Comparative Example 2 5

[0049] Experiments have shown that: First, the aluminum foil composite film has excellent adhesion at room temperature; second, the ink layer has bending resistance at low temperatures and can be used for butter packaging and frozen storage at -18℃; third, the ink layer does not rub off after 400 scratches.

Claims

1. A method for preparing an aluminum foil composite film with excellent ink adhesion, characterized in that, Includes the following steps: Step 1: Prepare a two-way high adhesion promoter. Modify water-soluble acrylic resin with the two-way high adhesion promoter to obtain a high adhesion acrylic resin primer. Step 2: The outer BOPP film of the outer BOPP / Al / inner BOPP substrate is first coated with a high-adhesion acrylic resin primer, and then a pattern is printed on the outer BOPP film using an overprinting method with alcohol-soluble polyurethane ink as the raw material. Finally, an anti-scratch agent is coated on the surface of the printed layer to obtain an aluminum foil composite film.

2. The method for preparing an aluminum foil composite film with excellent ink adhesion according to claim 1, characterized in that, The chemical structural formula of the bidirectional high adhesion promoter is: 。 3. The method for preparing an aluminum foil composite film with excellent ink adhesion according to claim 1, characterized in that, The preparation method of the bidirectional high adhesion promoter is as follows: Based on the amine-ene reaction mechanism, the α,β-unsaturated alkenyl functional group in isoborneol acrylate reacts with the imino group in iminodiacetic acid to prepare a dicarboxylated monomer. Based on the carboxyl-isocyanate reaction mechanism, a bidirectional high adhesion promoter was prepared by reacting the carboxyl group in the dicarboxylated monomer with the isocyanate group in isocyanoethyl methacrylate.

4. The method for preparing an aluminum foil composite film with excellent ink adhesion according to claim 1, characterized in that, The high-adhesion acrylic resin primer is prepared by grafting a two-way high-adhesion promoter onto a water-soluble acrylic resin through a polymerization reaction under the action of an initiator.

5. The method for preparing an aluminum foil composite film with excellent ink adhesion according to claim 4, characterized in that, The initiator is one of potassium persulfate, calcium persulfate, and ammonium persulfate.

6. The method for preparing an aluminum foil composite film with excellent ink adhesion according to claim 1, characterized in that, The anti-scratch agent is one of water-based acrylic emulsion varnish, epoxy-modified acrylic ester varnish, and modified polyurethane acrylic ester varnish.

7. An aluminum foil composite film with excellent ink adhesion prepared by the method according to any one of claims 1-6, characterized in that, The structure of the aluminum foil composite film is: anti-scratch layer / ink layer / adhesive layer / outer BOPP / Al / inner BOPP.

8. The aluminum foil composite film with excellent ink adhesion according to claim 6, characterized in that, The aluminum foil composite film can be used in butter packaging.

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