A recyclable high-barrier packaging film material and its preparation method

Abstract

This application relates to the technical field of packaging materials, and specifically discloses a recyclable high-barrier packaging film material and a preparation method thereof. A recyclable high-barrier packaging film material and a preparation method thereof include an upper layer, a middle layer, and a lower layer. The upper layer includes the following raw materials in parts by weight: 40-55 parts of linear polyethylene particles, 35-45 parts of metallocene polyethylene; the middle layer includes the following raw materials in parts by weight: 40-50 parts of linear polyethylene particles, 5-8 parts of polyolefin elastomer, 1.2-1.8 parts of composite barrier agent; the lower layer includes the following raw materials in parts by weight: 45-60 parts of linear polyethylene particles, 10-18 parts of metallocene polyethylene; in addition, the preparation method of this application has the advantages of improving the barrier performance and recyclability of the packaging film material.

Description

Technical Field

[0001] This application relates to the technical field of packaging materials. More specifically, it relates to a recyclable high-barrier packaging film material and a preparation method thereof. Background Art

[0002] Packaging film materials are a means to reduce the oxidation and contamination of the packaged goods. They can wrap the packaged goods, isolate the packaged goods from the outside world, reduce the contact between the packaged goods and oxygen and moisture, thereby improving the storage resistance and storability of the packaged goods. Most packaging film materials are plastic products, which have good processing performance and low cost, and are widely used in various fields.

[0003] However, plastic film materials are not easily degraded by the environment. If plastic film materials are not recycled, they will cause great pollution to the environment. At the same time, commonly used plastic film materials on the market often do not have sufficient barrier properties and cannot meet the long-term preservation requirements of some special products, especially in the food and pharmaceutical fields. Although there are various means to improve the barrier properties of the film materials, the barrier properties and recyclability of the film materials cannot be both achieved. Summary of the Invention

[0004] In order to improve the barrier properties and recyclability of packaging film materials, this application provides a recyclable high-barrier packaging film material and a preparation method thereof.

[0005] In the first aspect, this application provides a recyclable high-barrier packaging film material, adopting the following technical scheme:

[0006] A recyclable high-barrier packaging film material includes an upper layer, a middle layer and a lower layer. The upper layer includes the following raw materials in parts by weight: 40 - 55 parts of linear polyethylene particles, 35 - 45 parts of metallocene polyethylene; the middle layer includes the following raw materials in parts by weight: 40 - 50 parts of linear polyethylene particles, 5 - 8 parts of polyolefin elastomer, 1.2 - 1.8 parts of composite barrier agent; the lower layer includes the following raw materials in parts by weight: 45 - 60 parts of linear polyethylene particles, 10 - 18 parts of metallocene polyethylene.

[0007] By adopting the above technical scheme, the upper layer, the middle layer and the lower layer are mainly composed of linear polyethylene particles, so that the polyethylene content of the film material ≥ 95%, meeting the requirements of recycling. At the same time, the upper layer and the lower layer compound linear polyethylene and metallocene polyethylene. Metallocene polyethylene has good blendability and can effectively improve the tensile resistance of the film material, ensuring the strength of the film material. The middle layer is added with polyolefin elastomer, which can effectively improve the kneading resistance of the film material, facilitating the extension of the service life of the film material. At the same time, the composite barrier agent can enhance the barrier properties of the middle layer of the film material, thereby improving the barrier properties of the film material.

[0008] Preferably, the composite barrier agent comprises modified montmorillonite and microfibrillated cellulose with a mass ratio of (1.95 - 2.13):(0.45 - 0.62).

[0009] By adopting the above technical solution, the modified montmorillonite has a relatively high specific surface area, which can block oxygen, making the diffusion path of oxygen complex and the diffusion rate decrease. The microfibrillated cellulose can be compounded with the modified montmorillonite to form an intercalated structure, further enhancing the barrier effect of the composite barrier agent.

[0010] Preferably, the preparation method of the modified montmorillonite comprises the following steps: mixing absolute ethanol, water and a silane coupling agent, adjusting the pH to 4 - 5 with acetic acid, reacting at 50 °C for 3 h, adding sodium-based montmorillonite, stirring for 12 h, ultrasonic dispersing for 1 h, reacting at 80 °C for 5 h, cooling, centrifuging, washing and drying to obtain the modified montmorillonite.

[0011] By adopting the above technical solution, modifying the sodium-based montmorillonite with a silane coupling agent can effectively reduce the hydroxyl content on the surface of the modified montmorillonite, which is beneficial to improving the dispersibility of the modified montmorillonite, and thus improving the barrier performance of the film material.

[0012] Preferably, the mass ratio of the silane coupling agent to the sodium-based montmorillonite is (2.98 - 3.24):(3.89 - 4.51).

[0013] By adopting the above technical solution, controlling the mass ratio of the silane coupling agent to the sodium-based montmorillonite is beneficial to improving the modification effect of the silane coupling agent on the sodium-based montmorillonite, enabling epoxy modification on the surface of the sodium-based montmorillonite and improving its dispersibility.

[0014] Preferably, acetic acid lignin is also added to the middle layer, and the addition amount of acetic acid lignin is 1.38 - 2.61 wt% of the linear polyethylene particles in the middle layer.

[0015] By adopting the above technical solution, acetic acid lignin has good antioxidant activity. Adding acetic acid lignin to the middle layer can effectively reduce the oxygen permeability of the middle layer, and at the same time can scavenge free radicals, improving the antioxidant performance and oxygen barrier performance of the film material.

[0016] Preferably, the preparation method of the acetic acid lignin comprises the following steps: crushing and drying bamboo shoots shells, dispersing them in water, after water bath extraction at 95 °C for 2 h, adding them to an acetic acid solution and adding a hydrochloric acid solution, reacting in an oil bath at 114 °C for 80 min, vacuum filtering, washing with acetic acid, washing with water, precipitating, centrifuging, separating, and freeze-drying to obtain acetic acid lignin.

[0017] By adopting the above technical solution, lignin in bamboo shoot husks can be extracted to obtain acetic acid lignin, with a relatively high extraction efficiency, and the obtained acetic acid lignin has good antioxidant properties.

[0018] Preferably, the addition amount of the bamboo shoot husks is 4.02 - 4.35 wt% of the acetic acid solution.

[0019] By adopting the above technical solution, controlling the amounts of the acetic acid solution and lignin increases the extraction amount of acetic acid lignin, and at the same time prevents the separation of lignin and fibers, effectively improving the extraction rate of acetic acid lignin.

[0020] In a second aspect, the present application provides a preparation method for a recyclable high-barrier packaging film material, adopting the following technical solution:

[0021] A preparation method for a recyclable high-barrier packaging film material includes the following steps: separately mixing the raw materials for the upper layer, middle layer, and lower layer, and then performing three-layer coextrusion to obtain the film material.

[0022] By adopting the above technical solution, the obtained film material has good barrier properties and antioxidant properties, which is beneficial to the long-term storage of the objects inside the film material.

[0023] In summary, the present application has the following beneficial effects:

[0024] 1. Since the upper layer, middle layer, and lower layer in the present application are mainly composed of linear polyethylene particles, the polyethylene content of the film material is ≥95%, meeting the requirements for recycling. At the same time, the upper layer and the lower layer use linear polyethylene and metallocene polyethylene in combination. Metallocene polyethylene has good blendability, which can effectively improve the tensile resistance of the film material and ensure the strength of the film material. The middle layer is added with polyolefin elastomer, which can effectively improve the rub resistance of the film material, facilitating the extension of the service life of the film material. At the same time, the composite barrier agent can enhance the barrier properties of the middle layer of the film material, thereby improving the barrier properties of the film material.

[0025] 2. The modified montmorillonite in the present application has a relatively high specific surface area, which can block oxygen, making the diffusion path of oxygen complex and the diffusion rate decrease. Microfibrillated cellulose can be compounded with the modified montmorillonite to form an intercalated structure, further increasing the barrier effect of the composite barrier agent.

[0026] 3. The acetic acid lignin in the present application has good antioxidant activity. Adding acetic acid lignin to the middle layer can effectively reduce the oxygen transmission rate of the middle layer, and at the same time can scavenge free radicals, improving the antioxidant properties and oxygen barrier properties of the film material. Specific Embodiments

[0027] The following further elaborates on the present application in conjunction with embodiments.

[0028] Preparation Examples 1-4 of Modified Montmorillonite

[0029] Preparation Example 1

[0030] The preparation method of modified montmorillonite includes the following steps: Mix 75 mL of absolute ethanol, 8 mL of water and 3 mL of silane coupling agent KH-560, adjust the pH to 4 with 10 wt% acetic acid, react at 50 °C for 3 h, add sodium-based montmorillonite, and the mass ratio of the silane coupling agent to sodium-based montmorillonite is 2.98:3.89. Stir for 12 h, perform ultrasonic dispersion for 1 h, react at 80 °C for 5 h, cool, centrifuge, wash, and dry to obtain modified montmorillonite.

[0031] Preparation Example 2

[0032] The preparation method of modified montmorillonite includes the following steps: Mix 80 mL of absolute ethanol, 10 mL of water and 3.2 mL of silane coupling agent KH-560, adjust the pH to 5 with 10 wt% acetic acid, react at 50 °C for 3 h, add sodium-based montmorillonite, and the mass ratio of the silane coupling agent to sodium-based montmorillonite is 3.24:4.51. Stir for 12 h, perform ultrasonic dispersion for 1 h, react at 80 °C for 5 h, cool, centrifuge, wash, and dry to obtain modified montmorillonite.

[0033] Preparation Example 3

[0034] The difference between Preparation Example 3 and Preparation Example 1 is that the mass ratio of the silane coupling agent to sodium-based montmorillonite is 2.98:2.21.

[0035] Preparation Example 4

[0036] The difference between Preparation Example 4 and Preparation Example 1 is that the mass ratio of the silane coupling agent to sodium-based montmorillonite is 2.98:5.68.

[0037] Preparation Examples 5-8 of Lignin Acetate

[0038] Preparation Example 5

[0039] The preparation method of lignin acetate includes the following steps: Crush and dry bamboo shoot shells, disperse them in water, after extracting in a water bath at 95 °C for 2 h, add them to an 87 wt% acetic acid solution, the addition amount of bamboo shoot shells is 4.02 wt% of the acetic acid solution, and add a 4 wt% hydrochloric acid solution, the addition amount of HCl is 6%. React in an oil bath at 114 °C for 80 min, perform vacuum filtration, wash with acetic acid, wash with water, precipitate, centrifuge, separate, and freeze-dry to obtain lignin acetate.

[0040] Preparation Example 6

[0041] Preparation method of acetic acid lignin, comprising the following steps: crushing and drying bamboo shoots husk, dispersing it in water, extracting it in a water bath at 95°C for 2 h, then adding it to a 90 wt% acetic acid solution, the addition amount of bamboo shoots husk being 4.35 wt% of the acetic acid solution, and adding a 5 wt% hydrochloric acid solution, the addition amount of HCl being 6%, reacting at 114°C in an oil bath for 80 min, performing vacuum filtration, washing with acetic acid, washing with water, precipitating, centrifuging, separating, and freeze-drying to obtain acetic acid lignin.

[0042] Preparation Example 7

[0043] The difference between Preparation Example 7 and Preparation Example 5 lies in that the addition amount of bamboo shoots husk is 3.21 wt% of the acetic acid solution.

[0044] Preparation Example 8

[0045] The difference between Preparation Example 8 and Preparation Example 5 lies in that the addition amount of bamboo shoots husk is 5.98 wt% of the acetic acid solution.

[0046] In this embodiment, linear polyethylene particles are selected as LLDPE XP 7021ML, metallocene polyethylene is selected as M8470, and polyolefin elastomer is selected as Engage 8842.

[0047] Example 1

[0048] A recyclable high-barrier packaging film material, comprising an upper layer, a middle layer, and a lower layer. The upper layer comprises the following raw materials in parts by weight: 40 kg of linear polyethylene particles, 35 kg of metallocene polyethylene; the middle layer comprises the following raw materials in parts by weight: 40 kg of linear polyethylene particles, 5 kg of polyolefin elastomer, 1.2 kg of composite barrier agent, and the composite barrier agent comprises modified montmorillonite and microfibrillated cellulose with a mass ratio of 1.95:0.45, and the modified montmorillonite is the modified montmorillonite prepared in Preparation Example 1; the lower layer comprises the following raw materials in parts by weight: 45 kg of linear polyethylene particles, 10 kg of metallocene polyethylene.

[0049] The preparation method of the above-mentioned recyclable high-barrier packaging film material comprises the following steps: mixing the raw materials of the upper layer, the middle layer, and the lower layer separately, and then performing three-layer coextrusion to obtain the film material.

[0050] Example 2

[0051] A recyclable high-barrier packaging film material, comprising an upper layer, a middle layer and a lower layer. The upper layer comprises the following raw materials in parts by weight: 55 kg of linear polyethylene particles, 45 kg of metallocene polyethylene; the middle layer comprises the following raw materials in parts by weight: 50 kg of linear polyethylene particles, 8 kg of polyolefin elastomer, 1.8 kg of composite barrier agent, and the composite barrier agent comprises modified montmorillonite and microfibrillated cellulose with a mass ratio of 2.13:0.62. The modified montmorillonite is the modified montmorillonite prepared in Preparation Example 1; the lower layer comprises the following raw materials in parts by weight: 60 kg of linear polyethylene particles, 18 kg of metallocene polyethylene.

[0052] The preparation method of the above-mentioned recyclable high-barrier packaging film material comprises the following steps: After separately mixing the raw materials of the upper layer, the middle layer and the lower layer, perform three-layer coextrusion to obtain the film material.

[0053] Example 3

[0054] The difference between Example 3 and Example 1 is that the composite barrier agent comprises modified montmorillonite and microfibrillated cellulose with a mass ratio of 1.95:0.23.

[0055] Example 4

[0056] The difference between Example 4 and Example 1 is that the composite barrier agent comprises modified montmorillonite and microfibrillated cellulose with a mass ratio of 1.95:0.89.

[0057] Example 5

[0058] The difference between Example 5 and Example 1 is that the modified montmorillonite is the modified montmorillonite prepared in Preparation Example 3.

[0059] Example 6

[0060] The difference between Example 6 and Example 1 is that the modified montmorillonite is the modified montmorillonite prepared in Preparation Example 4.

[0061] Example 7

[0062] The difference between Example 7 and Example 1 is that the middle layer further adds lignin acetate, and the addition amount of lignin acetate is 1.38 wt% of the linear polyethylene particles in the middle layer. The lignin acetate is the lignin acetate prepared in Preparation Example 5.

[0063] Example 8

[0064] The difference between Example 8 and Example 1 is that the middle layer further adds lignin acetate, and the addition amount of lignin acetate is 2.61 wt% of the linear polyethylene particles in the middle layer. The lignin acetate is the lignin acetate prepared in Preparation Example 6.

[0065] Example 9

[0066] Example 9 is different from Example 7 in that the addition amount of acetic acid lignin is 0.25 wt% of the middle-layer linear polyethylene particles.

[0067] Example 10

[0068] Example 10 is different from Example 7 in that the addition amount of acetic acid lignin is 3.98 wt% of the middle-layer linear polyethylene particles.

[0069] Example 11

[0070] Example 11 is different from Example 7 in that the acetic acid lignin selected is the acetic acid lignin prepared in Preparation Example 7.

[0071] Example 12

[0072] Example 12 is different from Example 7 in that the acetic acid lignin selected is the acetic acid lignin prepared in Preparation Example 8.

[0073] Comparative Example 1

[0074] Comparative Example 1 is different from Example 1 in that no polyolefin elastomer is added to the middle layer.

[0075] Comparative Example 2

[0076] Comparative Example 2 is different from Example 1 in that no composite barrier agent is added to the middle layer.

[0077] Comparative Example 3

[0078] Comparative Example 3 is different from Example 1 in that an equal amount of modified montmorillonite is used to replace the composite barrier agent.

[0079] Comparative Example 4

[0080] Comparative Example 4 is different from Example 1 in that an equal amount of microfibrillated cellulose is used to replace the composite barrier agent.

[0081] Detection method

[0082] According to the raw materials and preparation methods of Examples 1-12 and Comparative Examples 1-4, film materials were prepared. Using a GDP-C gas permeation instrument, according to GB / T 1038-2000 "Test Method for Gas Permeability of Plastic Films and Sheets - Differential Pressure Method", the temperature was set at 23 °C and the relative humidity was 50%. Three parallel samples of the film were cut into appropriate sizes for testing, and the average value was calculated and recorded in Table 1. Using the test method for the rubbing resistance of flexible packaging materials GB / T41347-2022, the number of pinholes after 8100 rubs was recorded and recorded in Table 1.

[0083] Table 1 Oxygen Permeability and Rubbing Resistance of Film Materials

[0084] Project Oxygen permeability rate / cm³ / (m²·d·pa) Number of pinholes / piece Example 1 0.43 2 Example 2 0.42 2 Example 3 0.65 2 Example 4 0.62 2 Example 5 0.49 2 Example 6 0.48 2 Example 7 0.37 2 Example 8 0.36 2 Example 9 0.47 2 Example 10 0.49 2 Example 11 0.51 2 Example 12 0.50 2 Comparative Example 1 0.43 3 Comparative Example 2 0.95 2 Comparative Example 3 0.68 2 Comparative Example 4 0.67 2

[0085] According to Examples 1-2, Table 1 and Comparative Examples 1-2, it can be seen that the film materials prepared in Examples 1-2 not only have a low oxygen permeability rate, but also have good anti-rubbing performance. The linear polyethylene and metallocene polyethylene are used in combination in the upper and lower layers. Metallocene polyethylene has good blendability, making the texture of the upper and lower layers uniform. At the same time, metallocene polyethylene has good tensile resistance, which can effectively improve the strength of the upper and lower layers, and thus improve the strength of the film material. The middle layer is added with polyolefin elastomer, which can improve the flexibility and elasticity of the middle layer, thereby improving the anti-rubbing performance of the film material. The composite barrier agent formed by the composite of modified montmorillonite and microfibrillated cellulose has a good barrier effect on oxygen, which can reduce the oxygen permeability rate of the film material, thereby improving the barrier performance of the film material.

[0086] Compared with Examples 1-2, the oxygen permeability rate of the film materials in Examples 3-4 and Comparative Examples 3-4 increases, indicating that the barrier performance of the film materials prepared in Examples 3-4 and Comparative Examples 3-4 decreases. In Examples 3-4, the mass ratio of modified montmorillonite to microfibrillated cellulose is changed. In Comparative Example 3, only modified montmorillonite is added, and in Comparative Example 4, only microfibrillated cellulose is added. This shows that the composite barrier agent formed by the composite of modified montmorillonite and microfibrillated cellulose has higher barrier performance, and the effect is better than that of using modified montmorillonite or microfibrillated cellulose alone. Modified montmorillonite has a high specific surface area, which can block oxygen, making the diffusion path of oxygen complex and the diffusion rate decrease. Microfibrillated cellulose can be combined with modified montmorillonite to form an intercalated structure, further increasing the barrier effect of the composite barrier agent. The two are compounded according to the mass ratio to fully exert the synergistic effect, thereby effectively improving the barrier performance of the film material.

[0087] Compared with Examples 1-2, the oxygen permeability rate of the film materials in Examples 5-6 increases, indicating that the barrier performance of the film materials prepared in Examples 5-6 decreases. When the modified montmorillonite used in Examples 5-6 is prepared, the mass ratio of silane coupling agent to sodium montmorillonite is changed. The mass ratio of silane coupling agent to sodium montmorillonite affects the number of hydroxyl groups on the surface of sodium montmorillonite. The treatment with silane coupling agent can make the surface of sodium montmorillonite undergo epoxy modification, which is beneficial to improving its dispersion performance. The change in the mass ratio reduces the modification effect of the silane coupling agent on the surface of sodium montmorillonite, thereby reducing the dispersion of modified montmorillonite and the barrier effect of the composite barrier agent.

[0088] Compared with Examples 1-2, the oxygen permeability of the film material in Examples 7-8 decreased, indicating that the barrier performance of the film material prepared in Examples 7-8 was improved. In Examples 7-8, lignin acetate was added to the middle layer. Lignin acetate has good antioxidant activity. Adding lignin acetate to the middle layer can effectively reduce the oxygen permeability of the middle layer, and at the same time can scavenge free radicals, improving the antioxidant and oxygen barrier properties of the film material. The addition of lignin acetate can effectively improve the antioxidant and oxygen barrier properties of the middle layer, thereby improving the barrier performance of the film material.

[0089] Compared with Examples 7-8, the oxygen permeability of the film material in Examples 9-10 increased, indicating that the barrier performance of the film material prepared in Examples 9-10 decreased. In Examples 9-10, the addition amount of lignin acetate was changed. The decrease in the addition amount of lignin acetate weakened the enhancement of the barrier performance of the film material by lignin acetate, resulting in a decrease in the barrier performance of the film material. When the addition amount of lignin acetate increased, lignin acetate was prone to agglomeration and uneven distribution, thus reducing the barrier performance of the film material.

[0090] Compared with Examples 7-8, the oxygen permeability of the film material in Examples 11-12 increased, indicating that the barrier performance of the film material prepared in Examples 11-12 decreased. When preparing lignin acetate in Examples 11-12, the addition amount of bamboo shoot shells was changed. An increase in the addition amount of bamboo shoot shells led to a decrease in the extracted lignin acetate, while a decrease in the addition amount of bamboo shoot shells resulted in excessive acetic acid and the separation of lignin from fibers, also reducing the extraction rate of lignin acetate.

[0091] This specific embodiment is only an interpretation of the present application and does not limit the present application. After reading this specification, those skilled in the art can make modifications to this embodiment without creative contributions as needed, but as long as it is within the scope of the claims of the present application, it is protected by the patent law.

Claims

1. A recyclable high-barrier packaging film material, characterized in that: It includes an upper layer, a middle layer and a lower layer. The upper layer comprises raw materials in the following parts by weight: 40 - 55 parts of linear polyethylene particles, 35 - 45 parts of metallocene polyethylene; the middle layer comprises raw materials in the following parts by weight: 40 - 50 parts of linear polyethylene particles, 5 - 8 parts of polyolefin elastomer, 1.2 - 1.8 parts of composite barrier agent. The composite barrier agent comprises modified montmorillonite and microfibrillated cellulose with a mass ratio of (1.95 - 2.13):(0.45 - 0.62). The modified montmorillonite and microfibrillated cellulose are compounded to form an intercalated structure. Lignin acetate is also added to the middle layer, and the addition amount of lignin acetate is 1.38 - 2.61 wt% of the linear polyethylene particles in the middle layer; the lower layer comprises raw materials in the following parts by weight: 45 - 60 parts of linear polyethylene particles, 10 - 18 parts of metallocene polyethylene. The preparation method of the modified montmorillonite comprises the following steps: Mix absolute ethanol, water and silane coupling agent, adjust the pH to 4 - 5 with acetic acid, react at 50 °C for 3 h, add sodium montmorillonite, stir for 12 h, ultrasonically disperse for 1 h, react at 80 °C for 5 h, cool, centrifuge, wash and dry to obtain the modified montmorillonite.

2. The recyclable high-barrier packaging film material according to claim 1, wherein: The mass ratio of the silane coupling agent to the sodium montmorillonite is (2.98 - 3.24):(3.89 - 4.51).

3. The recyclable high-barrier packaging film material according to claim 1, characterized in that: The preparation method of the lignin acetate comprises the following steps: Crush and dry bamboo shoots shells, disperse them in water, after extracting in a water bath at 95 °C for 2 h, add them to an acetic acid solution, and add a hydrochloric acid solution, react in an oil bath at 114 °C for 80 min, carry out vacuum filtration, wash with acetic acid, wash with water, precipitate, centrifuge and separate, and freeze-dry to obtain the lignin acetate.

4. The recyclable high-barrier packaging film material according to claim 3, characterized in that: The addition amount of the bamboo shoots shells is 4.02 - 4.35 wt% of the acetic acid solution.

5. The preparation method of the recyclable high-barrier packaging film material according to any one of claims 1-4, characterized in that: Comprises the following steps: After separately mixing the raw materials of the upper layer, the middle layer and the lower layer, carry out three-layer coextrusion to obtain the film material.