Multi-layer flexible packaging material

Abstract

The invention relates to the field of multi-layer flexible packaging materials, in particular to a multi-layer flexible packaging material which sequentially comprises a first blocking layer, a first bonding layer, a reinforcing layer, a second bonding layer, a second blocking 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 which is a non-polar polymer; the reinforcing layer is made of a polar polymer, the prepared multi-layer flexible packaging material has good appearance, the problem of delamination of the multi-layer flexible packaging material is effectively solved, the service life of the multi-layer flexible packaging material is prolonged, and effective killing of gram-positive bacteria and gram-negative bacteria is achieved.

Description

Technical Field

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

[0002] With the development of the times, higher requirements are put forward for multi-layer packaging products in the fields of food and medicine packaging. In the prior art, generally, a multi-layer co-extrusion process technology is adopted to compound a barrier material and a general-purpose plastic, and then a multi-layer packaging product with good barrier performance is produced. However, the barrier substrate and the general-purpose plastic often have different polarities, and their affinity is poor. The existing adhesives also have an unsatisfactory bonding effect between the two, and it is easy to delaminate after direct bonding and compounding, which affects the service life and cannot meet the use requirements. In addition, most of the existing multi-layer packaging products do not have antibacterial effects, which makes the shelf life of food and medicine shorter and easily causes waste. Therefore, more requirements are put forward for the structure and performance of multi-layer packaging products. Summary of the Invention

[0003] Object of the Invention: Aiming at the above technical problems, the present invention provides a multi-layer flexible packaging material.

[0004] The technical solution adopted is as follows: A multi-layer flexible packaging material sequentially includes a first barrier layer, a first bonding layer, a reinforcing layer, a second bonding 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 reinforcing layer is made of a polar polymer; The first bonding layer and the second bonding layer are made of the same material, and are both made of the following raw materials 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.

[0005] "Non-polar polymer" refers to a polymer with a dipole moment of zero, mainly polyolefin compounds (such as polyethylene, polystyrene, etc.), specifically manifested as no polar groups on the polymer molecular chain; "Polar polymer" generally refers to a polymer with a non-zero total dipole moment, 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.

[0006] Furthermore, the preparation method of the maleimide-functionalized high-density polyethylene is as follows: Mix high-density polyethylene, maleimide monomer, and peroxide initiator evenly and then add them 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, the screw speed is 200 - 300 rpm. The extrudate is cooled by water and pelletized, and then vacuum dried.

[0007] Further, the mass ratio of the high-density polyethylene to the maleimide monomer is 100:1 - 10.

[0008] Further, the preparation method of the polyisobutylene maleic anhydride grafted polyvinyl alcohol is as follows: Under nitrogen protection, add polyisobutylene maleic anhydride, polyvinyl alcohol, N,N'-dicyclohexylcarbodiimide, and 4-dimethylaminopyridine to dimethyl sulfoxide, heat to 100 - 120 °C and keep the temperature for reaction for 12 - 48 h. After the reaction is completed, cool to room temperature, add water to precipitate the product, collect the product and vacuum dry it, and then extract with dichloromethane to remove the unreacted raw materials to obtain polyisobutylene maleic anhydride grafted polyvinyl alcohol.

[0009] Further, the mass ratio of the polyisobutylene maleic anhydride to the polyvinyl alcohol is 100:1 - 5.

[0010] Further, the non-polar polymer is any one or any combination of two or more of high-density polyethylene, low-density polyethylene, and linear low-density polyethylene.

[0011] Further, the polar polymer is nylon.

[0012] Further, the antibacterial film layer is composed of polyvinyl alcohol, haloamine-modified chitosan, and nano-titanium dioxide.

[0013] Further, the mass ratio of the polyvinyl alcohol, haloamine-modified chitosan, and nano-titanium dioxide is 100:10 - 20:1 - 5.

[0014] Further, the preparation method of the haloamine-modified chitosan is as follows: Dissolve chitosan powder in acetic acid solution to obtain a chitosan solution. Under the water bath condition of 40 - 60 °C, add N,N-methylenebisacrylamide to the chitosan solution to obtain a reaction solution, then adjust the pH of the reaction solution to 10 - 11 with sodium hydroxide solution, keep the temperature for reaction for 5 - 10 h and then return to room temperature. Dropwise add sodium hypochlorite solution to the reaction solution, and at the same time adjust the pH of the reaction solution to 7 - 8 with an acid solution, stir and react for 1 - 5 h, and then remove small molecules by vacuum distillation.

[0015] The beneficial effects of the present invention: The present invention provides a multi-layer flexible packaging material. The reinforcing layer can not only prevent oxygen and moisture from penetrating and causing deterioration of food and drugs, greatly improving the barrier effect, but also improve the mechanical strength of the multi-layer flexible packaging material, and enhance its anti-tearing, anti-puncturing, and anti-chemical corrosion properties during transportation and storage; The first adhesive layer and the second adhesive layer can achieve strong bonding between the barrier layer and the reinforcing layer, effectively solve the delamination problem of the multi-layer flexible packaging material, extend the service life of the multi-layer flexible packaging material. Through the physical entanglement of the maleimide polar group and the non-polar polyethylene long chain of maleimide-functionalized high-density polyethylene, a "polar-non-polar bifunctional" compatibilizing interface is formed, enhancing the bonding effect of the adhesive layer between the barrier layer and the reinforcing layer. Polyisobutylene maleic anhydride grafted polyvinyl alcohol has both the non-polar segment of polyisobutylene and the polar group of maleic anhydride. At the same time, the anhydride group may also ring-open and react with the imino group in maleimide at high temperature melting to achieve multi-scale interface compatibilization, further improving the bonding strength between the barrier layer and the reinforcing layer; In the antibacterial film layer, halogenamine groups are introduced into chitosan molecules through chemical modification, endowing it with more efficient oxidative bactericidal ability. The positive charge of chitosan adsorbs and destroys the cell membrane, providing a channel for the active halogen of the halogenamine group to penetrate, accelerating the oxidation reaction. The halogenamine group further expands the membrane damage, forming a "membrane-breaking-oxidation" double blow to effectively kill 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

[0016] Figure 1 It is a schematic structural diagram of the multi-layer flexible packaging material prepared in Example 1, and the labels in the figure represent respectively: 1 - First barrier layer, 2 - First adhesive layer, 3 - Reinforcing layer, 4 - Second adhesive layer, 5 - Second barrier layer, 6 - Acrylate adhesive layer, 7 - Antibacterial film layer. Detailed Embodiments

[0017] For those not specified in the embodiments, they are carried out according to conventional conditions or the conditions recommended by the manufacturer. For the reagents or instruments whose manufacturers are not specified, they are all conventional products that can be obtained through commercial purchase. The technologies not mentioned in the present invention refer to the prior art. Unless otherwise specified, the following examples and comparative examples are parallel tests and adopt the same treatment steps and parameters.

[0018] Example 1: This example provides a multi-layer flexible packaging material, and the specific structure is shown in Figure 1, successively including a first barrier layer 1 with a thickness of 30 μm, a first adhesive layer 2 with a thickness of 20 μm, a reinforcing 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; Among them, the first barrier layer 1 and the second barrier layer 5 are made of the same material, both being linear low-density polyethylene; The material of the reinforcing layer 3 is nylon 6; The first adhesive layer 2 and the second adhesive layer 4 are made of the same material, and are both made from the following raw materials in parts by weight: 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, 0.4 part of antioxidant 1010.

[0019] Among them, the preparation method of maleimide-functionalized high-density polyethylene is as follows: Mix high-density polyethylene, maleimide monomer, and dibenzoyl peroxide with a mass ratio of 100:5:0.01 evenly, then add them 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, the screw speed is 250 rpm, the extrudate is cooled by water and pelletized, and then vacuum dried.

[0020] The preparation method of polyisobutylene maleic anhydride-grafted polyvinyl alcohol is as follows: Under nitrogen protection, add polyisobutylene maleic anhydride, 1799 type polyvinyl alcohol, N,N'-dicyclohexylcarbodiimide, and 4-dimethylaminopyridine with a mass ratio of 100:5:0.15:0.01 to an appropriate amount of dimethyl sulfoxide, heat up to 110 °C and keep the temperature for reaction for 24 h. After the reaction is completed, cool to room temperature, drop 20 times the volume of deionized water into the reaction solution to precipitate the product, collect the product and vacuum dry it, and then extract with dichloromethane to remove the unreacted raw materials to obtain polyisobutylene maleic anhydride-grafted polyvinyl alcohol.

[0021] The antibacterial film layer 7 is composed of polyvinyl alcohol, haloamine-modified chitosan, and nano-titanium dioxide with a mass ratio of 100:15:5. The preparation method of haloamine-modified chitosan is as follows: Dissolve 2 g of chitosan powder in 50 ml of acetic acid solution with a mass fraction of 5% to obtain a chitosan solution. Under the condition of a 60 °C water bath, add 0.05 g of N,N - methylenebisacrylamide to the chitosan solution to obtain a reaction solution. Then, adjust the pH of the reaction solution to 11 with 0.01 mol / L sodium hydroxide solution, keep the temperature for reaction for 10 h, and then restore to room temperature. Add 0.8 ml of sodium hypochlorite solution with a mass fraction of 5% dropwise to the reaction solution, and at the same time adjust the pH of the reaction solution to 7 - 8 with dilute sulfuric acid. Stir and react for 5 h, and then remove small molecules by vacuum distillation.

[0022] The preparation method of the above - mentioned antibacterial film layer 7 is as follows: Add polyvinyl alcohol of type 1799, halogen - amine - modified chitosan, and nano - titanium dioxide to N,N - dimethylformamide at a solid - to - liquid mass ratio of 1:8, and ultrasonically oscillate for 30 min under the condition of a 60 °C water bath to obtain a homogeneous solution. Pour the solution into a mold, let it level naturally, and then heat to evaporate the solvent.

[0023] The preparation method of the above - mentioned multi - layer flexible packaging material is as follows: Use a multi - layer co - extrusion casting film - forming process to prepare the first barrier layer 1, the first adhesive layer 2, the reinforcing layer 3, the second adhesive layer 4, and the second barrier layer 5. Finally, coat a commercially available acrylate adhesive on one side surface of the antibacterial film layer 7, and adhere it to the second barrier layer 5 through the acrylate adhesive layer 6.

[0024] Staphylococcus aureus is a representative of Gram - positive bacteria, while Escherichia coli is a representative of Gram - negative bacteria. These two kinds of bacteria are relatively common in testing antibacterial effects. In this example, Escherichia coli and Staphylococcus aureus are used to evaluate the antibacterial effect of the antibacterial film layer 7. First, revive the frozen bacteria and perform sub - culture in phosphate - buffered saline with a pH between 7.2 and 7.4. After sub - culturing for 18 h, take a certain amount of the bacterial solution and wash it by centrifugation with phosphate - buffered solution. After washing, add an equal volume of phosphate - buffered solution and vortex to disperse the bacteria. Then, use phosphate - buffered solution to prepare Escherichia coli and Staphylococcus aureus with a bacterial concentration of 1×10 7 cfu / ml. Secondly, cut 1 g of the antibacterial film layer 7 and add it to a conical flask containing 75 ml of the above - mentioned bacterial solution. Then, place the conical flask in a constant - temperature oscillating water bath at 37 °C for 1 min, and then add 0.50 ml of the upper - layer bacterial suspension to a conical flask containing 4 ml of sterile phosphate - buffered saline and 0.5 ml of sterile 0.1 mol / L Na 2 S 2 O 3In a sterile test tube. Then, vortex the mixed solution and dilute it to a certain multiple. Finally, take 100 μl of the diluted bacterial solution and place it on the plate medium, and count the number of colonies on the plate medium after incubating at 37 °C for 24 h. The killing rates of both Staphylococcus aureus and Escherichia coli are 100%.

[0025] Example 2: Basically the same as Example 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: 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, 0.5 part of antioxidant 1010.

[0026] Example 3: Basically the same as Example 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: 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, 0.1 part of antioxidant 1010.

[0027] Comparative Example 1: Basically the same as Example 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: 45 parts of high-density polyethylene, 8 parts of polyisobutylene maleic anhydride-grafted polyvinyl alcohol, 3 parts of ethylene-vinyl acetate copolymer, 0.4 part of antioxidant 1010.

[0028] Comparative Example 2: Basically the same as Example 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: 45 parts of high-density polyethylene, 18 parts of maleimide-functionalized high-density polyethylene, 3 parts of ethylene-vinyl acetate copolymer, 0.4 part of antioxidant 1010.

[0029] Comparative Example 3: Basically the same as Example 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: 45 parts of high-density polyethylene, 3 parts of ethylene-vinyl acetate copolymer, 0.4 part of antioxidant 1010.

[0030] Comparative Example 4: Basically the same as Example 1, except that the antimicrobial film layer 7 does not contain haloamine-modified chitosan.

[0031] In this comparative example, in this example, 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, the killing rate of Staphylococcus aureus was 65.2%, and the killing rate of Escherichia coli was 50.9%.

[0032] Comparative Example 5: It was basically the same as Example 1, except that chitosan was directly added to the antibacterial film layer 7 without undergoing haloamine modification.

[0033] In this comparative example, in this example, 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, the killing rate of Staphylococcus aureus was 72.8%, and the killing rate of Escherichia coli was 66.4%.

[0034] Performance test: The fish eyes on the multi-layer flexible packaging materials prepared in Examples 1-3 and Comparative Examples 1-3 were measured according to the method specified in the national standard GB / T 11115-2009 "Polyethylene (PE) Resin". The peel strength of the first adhesive layer 2 between the first barrier layer 1 and the reinforcing layer 3 in Examples 1-3 and Comparative Examples 1-3 was implemented according to the method specified in the national standard GB / T 2791-1995 "Test Method for T Peel Strength of Adhesives - Flexible Material to Flexible Material".

[0035] The test results are shown in Table 1 below:

[0036] It can be seen from the comparison of Examples 1-3 in Table 1 above that the multi-layer flexible packaging material prepared by the present invention has a good appearance, and the bonding performance between the first barrier layer 1, the second barrier layer 5 and the reinforcing layer 3 is excellent, 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.

[0037] It can be seen from the comparison of Example 1 with Comparative Examples 1-3 in Table 1 above that the addition of maleimide-functionalized high-density polyethylene and polyisobutylene maleic anhydride-grafted polyvinyl alcohol has played a positive role in improving the surface morphology of the multi-layer flexible packaging material and realizing the strong bonding between the barrier layer and the reinforcing layer.

[0038] The above examples are only used to illustrate the technical solutions of the present invention, rather than to limit it; although the present invention has been described in detail with reference to the foregoing examples, those of ordinary skill in the art should understand that: they can still modify the technical solutions recorded in the foregoing examples, or perform equivalent replacements on some of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate 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: It includes 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 in sequence; The first barrier layer and the second barrier layer are made of the same material, both of which are non-polar polymers; The material of the reinforcement layer is 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.

2. The multilayer flexible packaging material according to claim 1, characterized in that 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, the screw speed is 200-300 rpm, the extrudate is water-cooled, pelletized and vacuum dried.

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

4. The multilayer flexible packaging material according to claim 1, characterized in that: 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 kept for 12-48 hours. After the reaction is completed, it 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.

5. The multilayer flexible packaging material according to claim 4, characterized in that The mass ratio of the polyisobutylene maleic anhydride to the polyvinyl alcohol is 100:1-5.

6. The multi-layer flexible packaging material according to claim 1, characterized in that: 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.

7. The multilayer flexible packaging material according to claim 1, characterized in that: The polar polymer is nylon.

8. The multi-layer flexible packaging material according to claim 1, characterized in that: The antibacterial film layer consists of polyvinyl alcohol, halogenamine-modified chitosan and nano titanium dioxide.

9. The multilayer flexible packaging material according to claim 8, characterized in that The mass ratio of the polyvinyl alcohol, the halogenamine-modified chitosan and the nano-titanium dioxide is 100:10-20:1-5.

10. The multilayer flexible packaging material according to claim 9, characterized in that The preparation method of the halamine-modified chitosan is as follows: The chitosan powder is dissolved in an 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. After the reaction is kept warm for 5-10 hours, the reaction solution is restored to room temperature. A 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. After stirring the reaction for 1-5 hours, the small molecules can be removed by distillation under reduced pressure.

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