Multilayer flexible packaging material

Abstract

The present invention relates to the field of multi-layer flexible packaging materials, specifically a multi-layer flexible packaging material, which comprises, in sequence, a first barrier layer, a first adhesive layer, a reinforcing layer, a second adhesive layer, a second barrier layer, an acrylate adhesive layer and an antibacterial film layer; the first barrier layer and the second barrier layer are made of the same material, both being non-polar polymers; the reinforcing layer is made of a polar polymer. The multi-layer flexible packaging material prepared by the present invention has a good appearance and morphology, effectively solves the delamination problem of the multi-layer flexible packaging material, extends the service life of the multi-layer flexible packaging material, and effectively kills Gram-positive bacteria and Gram-negative bacteria.

Description

Technical Field

[0001] The present invention relates to the field of multi-layer flexible packaging materials, in particular to a multi-layer flexible packaging material. Background Art

[0002] With the advancement of technology, higher requirements are being placed on multilayer packaging products in the food and pharmaceutical packaging sectors. Existing technologies typically utilize multilayer co-extrusion processes to laminate barrier materials and general-purpose plastics, producing multilayer packaging products with excellent barrier properties. However, barrier substrates and general-purpose plastics often have different polarities and poor compatibility. Existing adhesives also exhibit poor bonding performance between the two. Direct bonding and lamination can lead to delamination, shortening product life and failing to meet demanding requirements. Furthermore, most existing multilayer packaging products lack antibacterial properties, shortening the shelf life of food and pharmaceuticals and potentially leading to waste. Consequently, additional requirements are being placed on the structure and performance of multilayer packaging products. Summary of the Invention

[0003] Purpose of the invention: In response to the above technical problems, the present invention proposes a multi-layer flexible packaging material.

[0004] The technical solutions adopted are as follows:

[0005] A multi-layer flexible packaging material comprises, in sequence, a first barrier layer, a first adhesive layer, a reinforcement layer, a second adhesive layer, a second barrier layer, an acrylate adhesive layer, and an antibacterial film layer;

[0006] The first barrier layer and the second barrier layer are made of the same material, both being non-polar polymers;

[0007] The material of the reinforcement layer is a polar polymer;

[0008] The first adhesive layer and the second adhesive layer are made of the same material, and are both made of the following raw materials in parts by weight:

[0009] 40-50 parts of high-density polyethylene, 15-20 parts of maleimide functionalized high-density polyethylene, 5-10 parts of polyisobutylene maleic anhydride grafted polyvinyl alcohol, 1-5 parts of ethylene-vinyl acetate copolymer, and 0.1-0.5 parts of antioxidant.

[0010] "Non-polar polymer" refers to a polymer with zero dipole moment, mainly polyolefin compounds (polyethylene, polystyrene, etc.), which is specifically reflected in the absence of polar groups on the polymer molecular chain;

[0011] "Polar polymer" generally refers to a polymer with a non-zero total dipole, and can also be interpreted as a polymer with strong polar bonds or polar groups (such as amide groups, nitrile groups, ester groups, halogens, etc.) in the molecule.

[0012] Furthermore, the preparation method of the maleimide functionalized high-density polyethylene is as follows:

[0013] High-density polyethylene, maleimide monomer, and peroxide initiator are mixed evenly and added to a twin-screw extruder for melt extrusion. The temperature of the first zone of the twin-screw extruder is 160-170°C, the temperature of the second zone is 180-190°C, the temperature of the third zone is 190-200°C, the temperature of the fourth zone is 180-185°C, and the screw speed is 200-300 rpm. The extrudate is water-cooled, pelletized, and vacuum-dried.

[0014] Furthermore, the mass ratio of the high-density polyethylene to the maleimide monomer is 100:1-10.

[0015] Furthermore, the preparation method of the polyisobutylene maleic anhydride grafted polyvinyl alcohol is as follows:

[0016] Under nitrogen protection, polyisobutylene maleic anhydride, polyvinyl alcohol, N,N'-dicyclohexylcarbodiimide and 4-dimethylaminopyridine are added to dimethyl sulfoxide, the temperature is raised to 100-120°C and the reaction is maintained for 12-48 hours. After the reaction is completed, the mixture is cooled to room temperature, water is added to precipitate the product, the product is collected and vacuum-dried, and then extracted with dichloromethane to remove the unreacted raw materials to obtain polyisobutylene maleic anhydride grafted polyvinyl alcohol.

[0017] Furthermore, the mass ratio of the polyisobutylene maleic anhydride to the polyvinyl alcohol is 100:1-5.

[0018] Furthermore, the non-polar polymer is any one of high-density polyethylene, low-density polyethylene and linear low-density polyethylene, or a combination of any two or more thereof.

[0019] Furthermore, the polar polymer is nylon.

[0020] Furthermore, the antibacterial film layer is composed of polyvinyl alcohol, halogenamine-modified chitosan and nano-titanium dioxide.

[0021] Furthermore, the mass ratio of the polyvinyl alcohol, halamine-modified chitosan and nano-titanium dioxide is 100:10-20:1-5.

[0022] Furthermore, the preparation method of the halamine-modified chitosan is as follows:

[0023] Chitosan powder is dissolved in acetic acid solution to obtain a chitosan solution. N,N-methylenebisacrylamide is added to the chitosan solution in a water bath at 40-60°C to obtain a reaction solution. The pH of the reaction solution is adjusted to 10-11 with a sodium hydroxide solution. The reaction is kept warm for 5-10 hours and then returned to room temperature. Sodium hypochlorite solution is added dropwise to the reaction solution. At the same time, the pH of the reaction solution is adjusted to 7-8 with an acid solution. The reaction is stirred for 1-5 hours and then the small molecules are removed by distillation under reduced pressure.

[0024] Beneficial effects of the present invention:

[0025] The present invention provides a multi-layer flexible packaging material. The reinforcement layer can not only prevent oxygen and moisture from penetrating and causing deterioration of food and medicine, thereby significantly improving the barrier effect, but also improve the mechanical strength of the multi-layer flexible packaging material, thereby improving its tear resistance, puncture resistance, and chemical corrosion resistance during transportation and storage.

[0026] The first and second adhesive layers can achieve strong bonding between the barrier layer and the reinforcement layer, effectively solving the delamination problem of multi-layer flexible packaging materials and extending the service life of multi-layer flexible packaging materials. Maleimide-functionalized high-density polyethylene forms a "polar-nonpolar dual-functional" compatibilization interface through the physical entanglement of maleimide polar groups with non-polar polyethylene long chains, enhancing the bonding effect of the adhesive layer between the barrier layer and the reinforcement layer. Polyisobutylene maleic anhydride grafted polyvinyl alcohol combines the non-polar chain segments of polyisobutylene with the polar groups of maleic anhydride. At the same time, the anhydride groups can open the ring when melted at high temperature and react with the imine groups in maleimide to achieve multi-scale interface compatibilization, further improving the bond strength between the barrier layer and the reinforcement layer.

[0027] In the antibacterial film layer, halamine groups are introduced into the chitosan molecules through chemical modification, giving it more efficient oxidative bactericidal ability. The positive charge adsorption of chitosan destroys the cell membrane, providing a channel for the penetration of active halogens in the halamine groups, accelerating the oxidation reaction. The halamine groups further expand the membrane damage, forming a "membrane rupture-oxidation" double attack, achieving effective killing of Gram-positive bacteria and Gram-negative bacteria. The addition of nano-titanium dioxide can inhibit the growth of microorganisms and improve the mechanical strength of the antibacterial film layer. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 This is a schematic diagram of the structure of the multilayer flexible packaging material prepared in Example 1, where the reference numerals represent:

[0029] 1-first barrier layer, 2-first adhesive layer, 3-reinforcement layer, 4-second adhesive layer, 5-second barrier layer, 6-acrylate adhesive layer, 7-antibacterial film layer. DETAILED DESCRIPTION

[0030] Unless otherwise specified, the following examples and comparative examples were conducted in parallel, using the same processing steps and parameters.

[0031] Example 1:

[0032] This embodiment provides a multi-layer flexible packaging material. Figure 1 , comprising in sequence a first barrier layer 1 with a thickness of 30 μm, a first adhesive layer 2 with a thickness of 20 μm, a reinforcement layer 3 with a thickness of 50 μm, a second adhesive layer 4 with a thickness of 20 μm, a second barrier layer 5 with a thickness of 30 μm, an acrylate adhesive layer 6 with a thickness of 20 μm, and an antibacterial film layer 7 with a thickness of 20 μm;

[0033] The first barrier layer 1 and the second barrier layer 5 are made of the same material, which is linear low-density polyethylene.

[0034] The material of the reinforcement layer 3 is nylon 6;

[0035] The first adhesive layer 2 and the second adhesive layer 4 are made of the same material, and are both made of the following raw materials in parts by weight:

[0036] 45 parts of high-density polyethylene, 18 parts of maleimide-functionalized high-density polyethylene, 8 parts of polyisobutylene maleic anhydride grafted polyvinyl alcohol, 3 parts of ethylene-vinyl acetate copolymer, and 0.4 parts of antioxidant 1010.

[0037] The preparation method of maleimide functionalized high-density polyethylene is as follows:

[0038] High-density polyethylene, maleimide monomer, and dibenzoyl peroxide in a mass ratio of 100:5:0.01 are mixed evenly and added to a twin-screw extruder for melt extrusion. The temperature of the first zone of the twin-screw extruder is 160-170°C, the temperature of the second zone is 180-190°C, the temperature of the third zone is 190-200°C, the temperature of the fourth zone is 180-185°C, and the screw speed is 250 rpm. The extrudate is water-cooled, pelletized, and vacuum-dried.

[0039] The preparation method of polyisobutylene maleic anhydride grafted polyvinyl alcohol is as follows:

[0040] Under nitrogen protection, polyisobutylene maleic anhydride, 1799 type polyvinyl alcohol, N,N'-dicyclohexylcarbodiimide and 4-dimethylaminopyridine in a mass ratio of 100:5:0.15:0.01 were added to an appropriate amount of dimethyl sulfoxide, the temperature was raised to 110°C and the reaction was maintained for 24 hours. After the reaction was completed, it was cooled to room temperature, and 20 times the volume of deionized water was added dropwise to the reaction solution to precipitate the product. The product was collected and vacuum-dried, and then extracted with dichloromethane to remove the unreacted raw materials to obtain polyisobutylene maleic anhydride grafted polyvinyl alcohol.

[0041] The antibacterial film layer 7 is composed of polyvinyl alcohol, halogenamine-modified chitosan, and nano-titanium dioxide in a mass ratio of 100:15:5. The preparation method of the halogenamine-modified chitosan is as follows:

[0042] Dissolve 2 g of chitosan powder in 50 ml of 5% acetic acid solution to obtain a chitosan solution. Add 0.05 g of N,N-methylenebisacrylamide to the chitosan solution in a 60°C water bath to obtain a reaction solution. Adjust the pH of the reaction solution to 11 with 0.01 mol / L sodium hydroxide solution. Keep the reaction warm for 10 hours and then return to room temperature. Add 0.8 ml of 5% sodium hypochlorite solution dropwise to the reaction solution. Adjust the pH of the reaction solution to 7-8 with dilute sulfuric acid. Stir the reaction for 5 hours and then remove small molecules by vacuum distillation.

[0043] The preparation method of the antibacterial film layer 7 is as follows:

[0044] Add 1799 type polyvinyl alcohol, halamine modified chitosan and nano titanium dioxide at a solid-liquid mass ratio of 1:8 to N,N-dimethylformamide, and ultrasonically oscillate for 30 minutes in a 60°C water bath to obtain a uniform solution. Pour the solution into a mold, let it level naturally, and then heat to evaporate the solvent.

[0045] The preparation method of the multilayer flexible packaging material is as follows:

[0046] A multi-layer co-extrusion cast film process is used to prepare the first barrier layer 1, the first adhesive layer 2, the reinforcement layer 3, the second adhesive layer 4 and the second barrier layer 5. Finally, a commercially available acrylic adhesive is coated on one side of the antibacterial film layer 7, and it is adhered to the second barrier layer 5 through the acrylic adhesive layer 6.

[0047] Staphylococcus aureus is a representative of Gram-positive bacteria, while Escherichia coli is a representative of Gram-negative bacteria. These two bacteria are relatively common in testing antibacterial effects. In this embodiment, Escherichia coli and Staphylococcus aureus were used to evaluate the antibacterial effect of the antibacterial film layer 7. First, the frozen bacteria were revived and subcultured in a phosphate buffer with a pH between 7.2 and 7.4. After 18 hours of subculture, a certain amount of bacterial solution was taken and washed by centrifugation with a phosphate buffer solution. After washing, an equal volume of phosphate buffer solution was added and vortexed to disperse the bacteria. The phosphate buffer solution was then used to prepare a bacterial concentration of 1×10 7 cfu / ml of Escherichia coli and Staphylococcus aureus. Secondly, cut 1g of antibacterial film layer 7 and add it to a conical flask containing 75ml of the above bacterial solution. Then, place the conical flask in a constant temperature shaking water tank at 37°C for 1min, and then add 0.50ml of the upper bacterial suspension to a sterile test tube containing 4ml of sterile phosphate buffer and 0.5ml of sterile 0.1mol / L Na2S2O3. Then, vortex the mixed solution and dilute it to a certain multiple. Finally, take 100μl of the diluted bacterial solution and place it on a plate culture medium, and count the number of colonies on the plate culture medium after incubation at 37°C for 24h. The killing rate of Staphylococcus aureus and Escherichia coli is 100%.

[0048] Example 2:

[0049] The embodiment is basically the same as the embodiment 1, except that the first adhesive layer 2 and the second adhesive layer 4 are both made of the following raw materials in parts by weight:

[0050] 50 parts of high-density polyethylene, 20 parts of maleimide-functionalized high-density polyethylene, 10 parts of polyisobutylene maleic anhydride grafted polyvinyl alcohol, 5 parts of ethylene-vinyl acetate copolymer, and 0.5 parts of antioxidant 1010.

[0051] Example 3:

[0052] The embodiment is basically the same as the embodiment 1, except that the first adhesive layer 2 and the second adhesive layer 4 are both made of the following raw materials in parts by weight:

[0053] 40 parts of high-density polyethylene, 15 parts of maleimide-functionalized high-density polyethylene, 5 parts of polyisobutylene maleic anhydride grafted polyvinyl alcohol, 3 parts of ethylene-vinyl acetate copolymer, and 0.1 part of antioxidant 1010.

[0054] Comparative Example 1:

[0055] The embodiment is basically the same as the embodiment 1, except that the first adhesive layer 2 and the second adhesive layer 4 are both made of the following raw materials in parts by weight:

[0056] 45 parts of high-density polyethylene, 8 parts of polyisobutylene maleic anhydride grafted polyvinyl alcohol, 3 parts of ethylene-vinyl acetate copolymer, and 0.4 parts of antioxidant 1010.

[0057] Comparative Example 2:

[0058] The embodiment is basically the same as the embodiment 1, except that the first adhesive layer 2 and the second adhesive layer 4 are both made of the following raw materials in parts by weight:

[0059] 45 parts of high-density polyethylene, 18 parts of maleimide functionalized high-density polyethylene, 3 parts of ethylene-vinyl acetate copolymer, and 0.4 parts of antioxidant 1010.

[0060] Comparative Example 3:

[0061] The embodiment is basically the same as the embodiment 1, except that the first adhesive layer 2 and the second adhesive layer 4 are both made of the following raw materials in parts by weight:

[0062] 45 parts of high-density polyethylene, 3 parts of ethylene-vinyl acetate copolymer, and 0.4 parts of antioxidant 1010.

[0063] Comparative Example 4:

[0064] The method is basically the same as Example 1, except that the antibacterial film layer 7 does not contain halamine-modified chitosan.

[0065] In this comparative example, in this embodiment, Escherichia coli and Staphylococcus aureus were used to evaluate the antibacterial effect of the antibacterial film layer 7. The specific method was the same as that in Example 1. Finally, it was found that the killing rate against Staphylococcus aureus was 65.2%, and the killing rate against Escherichia coli was 50.9%.

[0066] Comparative Example 5:

[0067] The method is basically the same as Example 1, except that chitosan is directly added to the antibacterial film layer 7 without being modified by halamine.

[0068] In this comparative example, in this embodiment, Escherichia coli and Staphylococcus aureus were used to evaluate the antibacterial effect of the antibacterial film layer 7. The specific method was the same as that in Example 1. Finally, it was found that the killing rate against Staphylococcus aureus was 72.8%, and the killing rate against Escherichia coli was 66.4%.

[0069] Performance testing:

[0070] The fisheyes on the multilayer flexible packaging materials prepared in Examples 1-3 and Comparative Examples 1-3 were measured according to the method specified in GB / T 11115-2009 "Polyethylene (PE) Resin";

[0071] The peel strength of the first adhesive layer 2 between the first barrier layer 1 and the reinforcement layer 3 in Examples 1-3 and Comparative Examples 1-3 was measured according to the national standard GB / T 2791-1995 "Test method for T-peel strength of adhesives - Flexible material to flexible material".

[0072] The test results are shown in Table 1 below:

[0073]

[0074] As can be seen from the comparison of Examples 1-3 in Table 1 above, the multi-layer flexible packaging material prepared by the present invention has a good appearance and morphology, and the first barrier layer 1, the second barrier layer 5 and the reinforcing layer 3 have excellent bonding properties, which can effectively solve the delamination problem of the multi-layer flexible packaging material and extend the service life of the multi-layer flexible packaging material.

[0075] As can be seen from the comparison of Example 1 with Comparative Examples 1-3 in Table 1 above, the addition of maleimide-functionalized high-density polyethylene and polyisobutylene maleic anhydride grafted polyvinyl alcohol plays a positive role in improving the surface morphology of the multilayer flexible packaging material and achieving strong adhesion between the barrier layer and the reinforcement layer.

[0076] The above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit the same. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the various embodiments of the present invention.

Claims

1. A multi-layer flexible packaging material, characterized in that: The invention comprises in sequence a first barrier layer, a first adhesive layer, a reinforcement layer, a second adhesive layer, a second barrier layer, an acrylate adhesive layer and an antibacterial film layer; The first barrier layer and the second barrier layer are made of the same material, both of which are non-polar polymers; the reinforcement layer is made of a polar polymer; The first adhesive layer and the second adhesive layer are made of the same material, and are both made of the following raw materials in parts by weight: 40-50 parts of high-density polyethylene, 15-20 parts of maleimide-functionalized high-density polyethylene, 5-10 parts of polyisobutylene maleic anhydride grafted polyvinyl alcohol, 1-5 parts of ethylene-vinyl acetate copolymer, and 0.1-0.5 parts of antioxidant; The preparation method of the maleimide functionalized high-density polyethylene is as follows: High-density polyethylene, maleimide monomer, and peroxide initiator are mixed evenly and added into a twin-screw extruder for melt extrusion. The temperature of the first zone of the twin-screw extruder is 160-170°C, the temperature of the second zone is 180-190°C, the temperature of the third zone is 190-200°C, the temperature of the fourth zone is 180-185°C, and the screw speed is 200-300 rpm. The extrudate is water-cooled, pelletized, and vacuum-dried. The preparation method of the polyisobutylene maleic anhydride grafted polyvinyl alcohol is as follows: Under nitrogen protection, polyisobutylene maleic anhydride, polyvinyl alcohol, N,N'-dicyclohexylcarbodiimide and 4-dimethylaminopyridine are added to dimethyl sulfoxide, the temperature is raised to 100-120°C and the reaction is maintained for 12-48 hours. After the reaction is completed, the mixture is cooled to room temperature, water is added to precipitate the product, the product is collected and vacuum-dried, and then extracted with dichloromethane to remove the unreacted raw materials to obtain polyisobutylene maleic anhydride grafted polyvinyl alcohol.

2. The multilayer flexible packaging material according to claim 1, wherein The mass ratio of the high-density polyethylene to the maleimide monomer is 100:1-10.

3. The multilayer flexible packaging material according to claim 1, wherein The mass ratio of the polyisobutylene maleic anhydride to the polyvinyl alcohol is 100:1-5.

4. The multilayer flexible packaging material according to claim 1, wherein The non-polar polymer is any one of high-density polyethylene, low-density polyethylene and linear low-density polyethylene, or a combination of any two or more thereof.

5. The multi-layer flexible packaging material according to claim 1, wherein The polar polymer is nylon.

6. The multi-layer flexible packaging material according to claim 1, wherein The antibacterial film layer consists of polyvinyl alcohol, halogenamine-modified chitosan and nano-titanium dioxide.

7. The multilayer flexible packaging material according to claim 6, wherein The mass ratio of the polyvinyl alcohol, halamine-modified chitosan and nano-titanium dioxide is 100:10-20:1-5.

8. The multi-layer flexible packaging material according to claim 6, wherein The preparation method of the halamine-modified chitosan is as follows: Chitosan powder is dissolved in acetic acid solution to obtain a chitosan solution. N,N-methylenebisacrylamide is added to the chitosan solution in a water bath at 40-60°C to obtain a reaction solution. The pH of the reaction solution is adjusted to 10-11 with a sodium hydroxide solution. The reaction is kept warm for 5-10 hours and then returned to room temperature. Sodium hypochlorite solution is added dropwise to the reaction solution. At the same time, the pH of the reaction solution is adjusted to 7-8 with an acid solution. The reaction is stirred for 1-5 hours and then the small molecules are removed by distillation under reduced pressure.

Images