Degradable paraffin-bio-based polymer sealing film and preparation method thereof

Abstract

The invention relates to the field of microporous breathable water-blocking sealing films, in particular to a degradable paraffin-bio-based polymer sealing film and a preparation method thereof.The degradable paraffin-bio-based polymer sealing film is prepared from, by mass, 90-100 parts of slurry, 90-100 parts of composite emulsion, 80-90 parts of polylactic resin, 2-4 parts of silicon dioxide and 1-3 parts of bio-based erucyl amide, the full-bio-based sealing film with excellent barrier property and mechanical strength is successfully prepared through an innovative bio-based composite formula and a multi-layer gradient structural design and by adopting a low-temperature emulsification and on-line cross-linking molding technology, and compared with the prior art, the full-bio-based sealing film not only realizes green regeneration of raw materials and complete degradability of the product, but also has the advantages of high barrier property and high mechanical strength. The problem of single performance of a traditional material is solved through optimization of the functional layer, meanwhile, large-scale production is facilitated through mild and efficient technological conditions, and the composite material has wide application prospects in the fields of food preservation, various laboratory utensils and the like.

Description

Technical Field

[0001] This invention relates to the field of microporous breathable and water-blocking sealing films, and more particularly to a biodegradable paraffin-based polymer sealing film and its preparation method. Background Technology

[0002] Biodegradable paraffin-based sealing films primarily utilize bio-based polymers derived from renewable resources (such as plants) blended with bio-based paraffin. They aim to replace traditional petroleum-based plastic films and are widely used in sealing packaging containers for food, pharmaceuticals, and daily necessities to meet increasingly stringent environmental regulations and market demands for green packaging.

[0003] In existing technologies, although single-component bio-based plastics are biodegradable, their inherent brittleness, poor heat-sealing properties, and barrier properties limit their direct application. Therefore, they are often modified by blending with paraffin. However, paraffin has poor compatibility with bio-based polymers, and simple blending can easily lead to phase separation, causing a sharp drop in the mechanical properties of the material. At the same time, the petroleum-based additives introduced to improve compatibility weaken the total bio-based content and the completeness of degradation of the product. In addition, traditional multilayer composite processes often have problems such as high energy consumption, insufficient interlayer bonding, or single function, making it difficult to balance performance, cost, and environmental benefits in the final product.

[0004] Therefore, based on the relevant technologies mentioned above, there is an urgent need to develop a biodegradable paraffin-biobased polymer sealing film and its preparation method. Summary of the Invention

[0005] In view of this, the purpose of this invention is to provide a biodegradable paraffin-based polymer sealing film and its preparation method, so as to solve the problems of poor compatibility, insufficient performance, poor environmental protection and complex process in the prior art.

[0006] To achieve the above objectives, the present invention provides a biodegradable paraffin-based polymer sealing film and its preparation method.

[0007] A biodegradable paraffin-based biopolymer sealing film, characterized in that it is composed of the following components in parts by weight: 90-100 parts of slurry, 90-100 parts of composite emulsion, 80-90 parts of polylactic acid resin, 2-4 parts of silica, and 1-3 parts of bio-based erucamide. The slurry is a modified polyhydroxy fatty acid ester; The modified polyhydroxy fatty acid ester is prepared from polyhydroxy fatty acid ester, acetylglucosyl tributyl citrate and lyophilized nanocellulose powder; The polylactic acid resin is a modified polymeric emulsion; The modified polymeric emulsion is prepared from substances such as soybean wax, alkyl glycosides, maleic anhydride-grafted polylactic acid, polyglycerol ricinoleate, and polylactic acid emulsion.

[0008] Preferably, the preparation steps of the slurry are as follows: Step A1: Add polyhydroxy fatty acid ester to a mixed solvent of ethyl acetate and acetone, heat to 45-55℃, stir at 200-300 rpm for 60-90 min, stir at 120-180 rpm, add acetylacetic acid tributyl ester, stir for 30-40 min, and after stirring is complete, a mixed solution is obtained. Step A2: Add the lyophilized nanocellulose powder to a mixed solvent of ethyl acetate and acetone, and shear at high speed for 8-12 minutes at 2000-3000 rpm. Add the mixed solution, and stir at 100-200 rpm for 8-12 minutes. Transfer to an emulsifier, and shear at 6000-8000 rpm for 15-20 minutes. After shearing, degas under vacuum and filter through a 200-mesh sieve to obtain the slurry.

[0009] Using fully biodegradable polyhydroxy fatty acid esters as the matrix ensures its environmental friendliness. At the same time, the addition of acetylthiol tributyl citrate as a plasticizer effectively improves the brittleness of the material, giving the inner layer excellent flexibility and impact resistance. In addition, the introduction of nanocellulose can enhance the mechanical strength and dimensional stability of the membrane. The optimized dispersion process ensures the uniform distribution of each component and high film quality.

[0010] Preferably, the mass ratio of polyhydroxyalkanoate to tributyl acetylglucosamine in step A1 is 1:0.15-0.25; The mass ratio of the lyophilized nanocellulose powder to the mixed solution in step A2 is 0.02-0.03:1; The volume ratio of ethyl acetate to acetone in steps A1 and A2 is 7:3.

[0011] Preferably, the preparation steps of the composite emulsion are as follows: Step B1: Add soybean wax, alkyl glycoside and maleic anhydride-grafted polylactic acid to polyglycerol ricinoleate, heat to 50-70℃, stir for 20-30 min at 10-20 rpm to obtain the oil phase; Step B2: Add polylactic acid emulsion to deionized water, heat to 55-65℃, stir at 300-400 rpm for 10-20 minutes. After stirring, transfer to an emulsifier, add the oil phase, shear for 5-10 minutes at 2500-3500 rpm, add to a high-pressure homogenizer, heat to 60-70℃, pressurize to 50-80 MPa, and homogenize 3-5 times. After the reaction is complete, cool to 30-40℃ to obtain the primary emulsion. Step B3: Add the citric acid-based waterborne epoxy crosslinking agent to the primary emulsion, heat to 30-40℃, stir for 30-40 minutes at a speed of 400-500 rpm, and after stirring is complete, a composite emulsion is obtained.

[0012] The composite emulsion achieves stable compatibility between bio-based paraffin and polylactic acid by using a fully bio-based emulsifier. At the same time, the addition of compatibilizer strengthens the interfacial bonding and improves the overall mechanical properties, enabling it to form a three-dimensional network during drying. This greatly enhances the water resistance and barrier properties of the coating. In addition, the two-stage emulsification method ensures that the emulsion has a fine and uniform particle size and a dense structure.

[0013] Preferably, the mass ratio of soybean wax, alkyl glycoside, maleic anhydride-grafted polylactic acid and polyglycerol ricinoleate in step B1 is 1:0.07-0.08:0.12-0.13:0.04-0.06.

[0014] Preferably, the mass ratio of polylactic acid emulsion, deionized water and oil phase in step B2 is 0.5-0.7:1.8-2.2:1.

[0015] Preferably, the mass ratio of the citric acid-based aqueous epoxy crosslinking agent to the primary emulsion in step B3 is 0.01-0.012:1.

[0016] A method for preparing a biodegradable paraffin-based polymer sealing film, characterized in that the specific steps of the preparation method are as follows: Step S1: Add polylactic acid resin to a mixed solvent of ethyl acetate and acetone, heat to 45-55℃, stir at 200-300 rpm for 60-90 min, then stir at 120-180 rpm. Add fumed silica and erucamide powder, stir for 20-30 min, transfer to an emulsifier, heat to 50-60℃, stir at 6000-8000 rpm, and shear for 20-30 min. After shearing, degas under vacuum, filter through a 200-mesh sieve to obtain the premixed solution. Step S2: Add the slurry to the coating machine, with a film thickness of 120-150 μm and a speed of 5-10 m / min. Perform primary drying, heating to 60-80℃ and drying for 2-4 min, then cooling to 40-50℃. Add the composite emulsion, with a film thickness of 80-100 μm. Perform secondary drying, heating to 90-100℃ and drying for 3-5 min, then cooling to 40-50℃. Add the premixed solution, with a film thickness of 40-60 μm. Perform tertiary drying, heating to 65-75℃ and drying for 1-2 min, then cooling to 20-30℃. Let stand for 24-48 h to obtain the paraffin-bio-based polymer sealing film.

[0017] Using polylactic acid as the matrix, it provides good heat-sealing performance and high transparency. Fumed silica, as an opening agent, can effectively prevent film adhesion by forming micro-protrusions. At the same time, bio-based erucamide migrates to the surface, which can reduce the coefficient of friction and ensure smooth high-speed packaging. Furthermore, by constructing a gradient structure, the specialization and synergistic effect of each layer's function are achieved. At the same time, the zoned temperature-controlled drying strategy precisely matches the drying and cross-linking requirements of each layer's materials, ensuring the integrity of the reaction and the quality of the film. This enables continuous and efficient production from raw materials to film formation, significantly improving production efficiency, and the final product has stable and reliable performance.

[0018] Preferably, the mass ratio of polylactic acid resin, silica and erucamide powder in step S1 is 1:0.034-0.036:0.022-0.024.

[0019] Preferably, the mass ratio of the slurry, composite emulsion and premixed liquid in step S2 is 1.6-1.7:2-2.1:1.

[0020] The beneficial effects of this invention are: This invention provides a biodegradable paraffin-based biopolymer sealing film and its preparation method. Through an innovative bio-based composite formulation and multi-layer gradient structure design, and employing low-temperature emulsification and online cross-linking molding technology, this invention successfully prepares a fully bio-based sealing film that combines excellent barrier properties and mechanical strength. Compared with existing technologies, this product not only achieves green and renewable raw materials and complete biodegradability, but also solves the problem of single-performance characteristics of traditional materials through functional layer optimization. Furthermore, its mild and efficient processing conditions are more conducive to large-scale production. It has broad application prospects in fields such as scientific research experiments, biochemical experiments, medical experiments, agricultural and veterinary drug water quality testing, tissue culture, microbial culture and fermentation, cosmetic sealing, wine storage, collectible toys, food preservation, and air-permeable and water-resistant sealing of various laboratory utensils. Attached Figure Description

[0021] To more clearly illustrate the technical solutions in this invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only for this invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0022] Figure 1 This is a bar chart showing the mechanical properties of the biodegradable paraffin-biobased polymer sealing film of this invention. Figure 2 This is a bar chart showing the barrier performance and heat-sealing strength tests of the biodegradable paraffin-biobased polymer sealing film in this invention. Figure 3 This is a bar chart showing the biodegradability test results of the biodegradable paraffin-bio-based polymer sealing film of this invention. Detailed Implementation

[0023] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to specific embodiments.

[0024] Example 1: The preparation steps of a slurry are as follows: S1: Add 100g of polyhydroxy fatty acid ester to a mixture of 140mL of ethyl acetate and 60mL of acetone, heat to 45℃, stir at 300rpm for 60min, stir at 180rpm, add 15g of acetylacetic acid tributyl ester, stir for 30min, and after stirring is complete, a mixed solution is obtained. S2: Add 2g of lyophilized nanocellulose powder to a mixture of 7mL ethyl acetate and 3mL acetone, and shear at 2000rpm for 12min. Add 100g of the mixed solution, and stir at 100rpm for 12min. Transfer to an emulsifier, and shear at 6000rpm for 20min. After shearing, degas under vacuum and filter through a 200-mesh sieve to obtain the slurry.

[0025] Example 2: The preparation steps of a slurry are as follows: S1: Add 100g of polyhydroxy fatty acid ester to a mixture of 140mL of ethyl acetate and 60mL of acetone, heat to 50℃, stir at 250rpm for 75min, stir at 150rpm, add 20g of acetylacetic acid tributyl ester, stir for 35min, and after stirring is complete, a mixed solution is obtained. S2: Add 2.5g of lyophilized nanocellulose powder to a mixture of 7mL ethyl acetate and 3mL acetone, and shear at 2500rpm for 10min. Add 100g of the mixed solution, and stir at 150rpm for 10min. Transfer to an emulsifier, and shear at 7000rpm for 18min. After shearing, degas under vacuum and filter through a 200-mesh sieve to obtain the slurry.

[0026] Example 3: The preparation steps of a slurry are as follows: S1: Add 100g of polyhydroxy fatty acid ester to a mixture of 140mL of ethyl acetate and 60mL of acetone, heat to 55℃, stir at 200rpm for 90min, stir at 120rpm, add 25g of acetylacetic acid tributyl ester, stir for 40min, and after stirring is complete, a mixed solution is obtained. S2: Add 3g of lyophilized nanocellulose powder to a mixture of 7mL ethyl acetate and 3mL acetone, and shear at 3000rpm for 8min. Add 100g of the mixed solution, stir at 200rpm for 8min, transfer to an emulsifier, and shear at 8000rpm for 15min. After shearing, degas under vacuum and filter through a 200-mesh sieve to obtain the slurry.

[0027] Example 4: The preparation steps of a composite emulsion are as follows: S1: Add 100g of soybean wax, 7g of alkyl glycoside and 12g of maleic anhydride-grafted polylactic acid to 4g of polyglycerol ricinoleate, heat to 50℃, stir for 30min at 10rpm to obtain the oil phase. S2: Add 50g of polylactic acid emulsion to 180g of deionized water, heat to 55℃, stir at 400rpm for 10min. After stirring, transfer to an emulsifier, add 100g of oil phase, shear for 10min, stir at 2500rpm, add to a high-pressure homogenizer, heat to 70℃, pressurize to 50MPa, homogenize 5 times, after the reaction is complete, cool to 30℃ to obtain the primary emulsion; S3: Add 1g of citric acid-based aqueous epoxy crosslinking agent to 100g of primary emulsion, heat to 30℃, stir for 40min at 400rpm, and after stirring is complete, a composite emulsion is obtained.

[0028] Example 5: The preparation steps of a composite emulsion are as follows: S1: Add 100g of soybean wax, 7.5g of alkyl glycoside and 12.5g of maleic anhydride-grafted polylactic acid to 5g of polyglycerol ricinoleate, heat to 60℃, stir for 25min at 15rpm to obtain the oil phase. S2: Add 60g of polylactic acid emulsion to 200g of deionized water, heat to 60℃, stir at 350rpm for 15min, after stirring is complete, transfer to an emulsifier, add 100g of oil phase, shear for 8min, stir at 3000rpm, add to a high-pressure homogenizer, heat to 65℃, pressurize to 65MPa, cycle homogenize 4 times, after the reaction is complete, cool to 35℃ to obtain the primary emulsion; S3: Add 1.1g of citric acid-based aqueous epoxy crosslinking agent to 100g of primary emulsion, heat to 35℃, stir for 35min at 450rpm, and after stirring is complete, obtain composite emulsion.

[0029] Example 6: The preparation steps of a composite emulsion are as follows: S1: Add 100g of soybean wax, 8g of alkyl glycoside and 13g of maleic anhydride-grafted polylactic acid to 6g of polyglycerol ricinoleate, heat to 70℃, stir for 20min at 20rpm to obtain the oil phase. S2: Add 70g of polylactic acid emulsion to 220g of deionized water, heat to 65℃, stir at 300rpm for 20min. After stirring, transfer to an emulsifier, add 100g of oil phase, shear for 5min, stir at 3500rpm, add to a high-pressure homogenizer, heat to 60℃, pressurize to 80MPa, homogenize 3 times, after the reaction is complete, cool to 40℃ to obtain the primary emulsion; S3: Add 1.2g of citric acid-based waterborne epoxy crosslinking agent to 100g of primary emulsion, heat to 40℃, stir for 30min at 500rpm, and after stirring is complete, obtain composite emulsion.

[0030] Example 7: The preparation steps of a composite emulsion are as follows: S1: Add 100g of soybean wax, 8g of alkyl glycoside and 13g of maleic anhydride-grafted polylactic acid to 6g of polyglycerol ricinoleate, heat to 70℃, stir for 20min at 20rpm to obtain the oil phase. S2: Add 70g of polylactic acid emulsion to 220g of deionized water, heat to 65℃, stir at 300rpm for 20min. After stirring, transfer to an emulsifier, add 100g of oil phase and 3g of organic nano-montmorillonite, shear for 5min, stir at 3500rpm, add to a high-pressure homogenizer, heat to 60℃, pressurize to 80MPa, homogenize 3 times, after the reaction is complete, cool to 40℃ to obtain the primary emulsion; S3: Add 1.2g of citric acid-based waterborne epoxy crosslinking agent to 100g of primary emulsion, heat to 40℃, stir for 30min at 500rpm, and after stirring is complete, obtain composite emulsion.

[0031] Example 8: The preparation steps of a biodegradable paraffin-biobased polymer sealing film are as follows: S1: Add 100g of polylactic acid resin to a mixture of 140mL of ethyl acetate and 60mL of acetone, heat to 45℃, stir at 300rpm for 60min, then stir at 180rpm, add 3.4g of fumed silica and 2.2g of erucamide powder, stir for 20min, transfer to an emulsifier, heat to 60℃, stir at 6000rpm, shear for 30min, after shearing is complete, degas under vacuum, filter through a 200-mesh sieve to obtain the premixed solution; S2: Add 160g of slurry (Example 1) to a coating machine, with a film thickness of 120-150μm and a speed of 5m / min. Perform primary drying, heating to 80℃ and drying for 2min, then cooling to 50℃. Add 200g of composite emulsion (Example 4), with a film thickness of 80-100μm. Perform secondary drying, heating to 90℃ and drying for 5min, then cooling to 40℃. Add 100g of premixed liquid, with a film thickness of 40-60μm. Perform tertiary drying, heating to 75℃ and drying for 1min, then cooling to 30℃ and allowing to stand for 24h to obtain a paraffin-bio-based polymer sealing film.

[0032] Example 9: The preparation steps of a biodegradable paraffin-biobased polymer sealing film are as follows: S1: Add 100g of polylactic acid resin to a mixture of 140mL of ethyl acetate and 60mL of acetone, heat to 50℃, stir at 250rpm for 75min, then stir at 150rpm, add 3.5g of fumed silica and 2.3g of erucamide powder, stir for 25min, transfer to an emulsifier, heat to 55℃, stir at 7000rpm, shear for 25min, after shearing is complete, degas under vacuum, filter through a 200-mesh sieve to obtain the premixed solution; S2: Add 165g of slurry (Example 2) to a coating machine, with a film thickness of 120-150μm and a speed of 8m / min. Perform primary drying, heating to 70℃ and drying for 3min, then cooling to 45℃. Add 205g of composite emulsion (Example 5), with a film thickness of 80-100μm. Perform secondary drying, heating to 95℃ and drying for 4min, then cooling to 45℃. Add 100g of premixed liquid, with a film thickness of 40-60μm. Perform tertiary drying, heating to 70℃ and drying for 1.5min, then cooling to 25℃ and allowing to stand for 36h to obtain a paraffin-bio-based polymer sealing film.

[0033] Example 10: The preparation steps of a biodegradable paraffin-biobased polymer sealing film are as follows: S1: Add 100g of polylactic acid resin to a mixture of 140mL of ethyl acetate and 60mL of acetone, heat to 55℃, stir at 200rpm for 90min, then stir at 120rpm, add 3.6g of fumed silica and 2.4g of erucamide powder, stir for 30min, transfer to an emulsifier, heat to 50℃, stir at 8000rpm, shear for 20min, after shearing is complete, degas under vacuum, filter through a 200-mesh sieve to obtain the premixed solution; S2: Add 170g of slurry (Example 3) to a coating machine, with a film thickness of 120-150μm and a speed of 10m / min. Perform primary drying, heating to 60℃ and drying for 4min, then cooling to 40℃. Add 210g of composite emulsion (Example 6), with a film thickness of 80-100μm. Perform secondary drying, heating to 100℃ and drying for 3min, then cooling to 50℃. Add 100g of premixed liquid, with a film thickness of 40-60μm. Perform tertiary drying, heating to 65℃ and drying for 2min, then cooling to 20℃ and allowing to stand for 48h to obtain a paraffin-bio-based polymer sealing film.

[0034] Example 11: The preparation steps of a biodegradable paraffin-biobased polymer sealing film are as follows: S1: Add 100g of polylactic acid resin to a mixture of 140mL of ethyl acetate and 60mL of acetone, heat to 45℃, stir at 300rpm for 60min, then stir at 180rpm, add 3.4g of fumed silica and 2.2g of erucamide powder, stir for 20min, transfer to an emulsifier, heat to 60℃, stir at 6000rpm, shear for 30min, after shearing is complete, degas under vacuum, filter through a 200-mesh sieve to obtain the premixed solution; S2: Add 160g of slurry (Example 1) to a coating machine, with a film thickness of 120-150μm and a speed of 5m / min. Perform primary drying, heating to 80℃ and drying for 2min, then cooling to 50℃. Add 200g of composite emulsion (Example 7), with a film thickness of 80-100μm. Perform secondary drying, heating to 90℃ and drying for 5min, then cooling to 40℃. Add 100g of premixed liquid, with a film thickness of 40-60μm. Perform tertiary drying, heating to 75℃ and drying for 1min, then cooling to 30℃ and allowing to stand for 24h to obtain a paraffin-bio-based polymer sealing film.

[0035] Example 12: The preparation steps of a biodegradable paraffin-biobased polymer sealing film are as follows: S1: Add 100g of polylactic acid resin to a mixture of 140mL of ethyl acetate and 60mL of acetone, heat to 45℃, stir at 300rpm for 60min, then stir at 180rpm, add 3.4g of fumed silica, 2.2g of erucamide powder and 5g of nano-chitosan powder, stir for 20min, transfer to an emulsifier, heat to 60℃, stir at 6000rpm, shear for 30min, after shearing is complete, degas under vacuum, filter through a 200-mesh sieve to obtain the premixed solution; S2: Add 160g of slurry (Example 1) to a coating machine, with a film thickness of 120-150μm and a speed of 5m / min. Perform primary drying, heating to 80℃ and drying for 2min, then cooling to 50℃. Add 200g of composite emulsion (Example 4), with a film thickness of 80-100μm. Perform secondary drying, heating to 90℃ and drying for 5min, then cooling to 40℃. Add 100g of premixed liquid, with a film thickness of 40-60μm. Perform tertiary drying, heating to 75℃ and drying for 1min, then cooling to 30℃ and allowing to stand for 24h to obtain a paraffin-bio-based polymer sealing film.

[0036] Comparative Example 1: Compared with Example 8, this comparative example did not add a citric acid-based aqueous epoxy crosslinking agent during the preparation of the composite emulsion. All other steps and parameters were the same, and will not be repeated here. The final product was a paraffin-bio-based polymer sealing film.

[0037] Comparative Example 2: This comparative example differs from Example 8 only in that "alkyl glycoside" is replaced with "Span-80". All other steps and parameters are the same, and will not be repeated here. The final product is a paraffin-bio-based polymer sealing film.

[0038] Comparative Example 3: Compared with Example 8, the pressure of high-pressure homogenization in the preparation process of the composite emulsion in this comparative example was adjusted to 20 MPa, and the homogenization was cyclically repeated once. The remaining steps and parameters were the same, and will not be repeated here. The final product was a paraffin-bio-based polymer sealing film.

[0039] Comparative Example 4: Compared with Example 8, this comparative example did not add nano-cellulose freeze-dried powder during the preparation of the slurry. All other steps and parameters were the same, and will not be repeated here. The final product was a paraffin-bio-based polymer sealing film.

[0040] Performance testing: Mechanical property testing The universal testing machine was used in accordance with the GB / T 1040.3-2006 testing standard. 1. Take the sealing films of Examples 8-12 and Comparative Examples 1-4 respectively, and cut them into dumbbell shapes; the total length is 150mm, the narrow part is 60mm long, and the width is 15.0mm. Place them in a universal testing machine and tensile them at a speed of 300mm / min until the sample breaks. 2. Calculation formula: Tensile strength Fm is the maximum tensile force. 3. Elongation at break ΔL is the displacement of the fixture when it breaks, and L0 is the initial gauge length of 50mm.

[0041] Table 1. Mechanical property test results of the examples and comparative examples project σt(MPa) εt(%) Example 8 45.2 35.5 Example 9 47.8 38.2 Example 10 46.5 36.8 Example 11 48.5 37.0 Example 12 49.1 36.5 Comparative Example 1 28.7 15.3 Comparative Example 2 41.3 32.5 Comparative Example 3 35.2 25.4 Comparative Example 4 32.1 12.8 Barrier test According to the GB / T1037-2021 test standard, a water vapor transmission rate tester was used; 1. Take the sealing films of Examples 8-12 and Comparative Examples 1-4 respectively, cut them into circles with a diameter of 100mm, add desiccant, and pre-treat for 24 hours; 2. Add 20g of anhydrous calcium chloride desiccant to the permeation cup, level the surface, cover the mouth of the permeation cup with the sample, tighten the screws evenly with the matching tools, place it on the electronic balance, weigh and record the initial mass M0. 3. Place the initially weighed permeation cup stably in a constant temperature and humidity chamber at a temperature of 38±0.5℃ and a relative humidity of 90±2%. After 24 hours, remove the cup, cool it for 30 minutes, and weigh it again until the mass change stabilizes. Record the data. 4. Calculation formula: , denoted as mass change per unit time, A as the effective test area of ​​the sample, and 24 as the coefficient for converting hours to days.

[0042] Heat seal strength test: According to the GB / T 15171—2025 testing standard, a heat seal tester and a universal testing machine were used; 1. Take the sealing films of Examples 8-12 and Comparative Examples 1-4 respectively, cut them into 100mm×150mm pieces, put them into a heat sealing tester, heat them to 130℃, press them to 0.2MPa, and hold for 1.0s. After heat sealing is completed, let them stand for 16h, and cut them evenly into samples with a width of 15.0mm±0.1mm. 2. Place the sample into the universal testing machine with a clamp spacing of 50 mm and a tensile speed of 300 mm / min. Record the force value during the stable peeling stage and calculate the average value F (N). 3. Calculation formula: 0.015 represents the sample width (m).

[0043] Table 2 Test Results of Examples and Comparative Examples project <![CDATA[WVTR(g / m 3 ·24h)]]> Heat seal strength (N / 15mm) Example 8 5.8 6.5 Example 9 5.5 6.8 Example 10 5.7 6.6 Example 11 4.9 6.9 Example 12 5.2 6.7 Comparative Example 1 15.2 4.1 Comparative Example 2 7.1 6.2 Comparative Example 3 11.5 5.8 Comparative Example 4 6.3 6.4 Biodegradability performance test: Refer to the testing standard GB / T 19277.1-2023; 1. Take 100g of each of the sealing films from Examples 8-12 and Comparative Examples 1-4, cut them into 10mm×10mm fragments, put them in an oven, heat them to 105℃, dry them for 2 hours, take them out and cool them, and weigh them as m0. 2. Pass the fresh compost through a 2mm sieve to achieve a solids content of 50-55% and a pH of 7-9; 3. Test group: Mix the sample with 400g of compost evenly and place it in a reaction bottle; Blank group: Contains only an equal amount of compost inoculum, without any test materials; Control group: Add an equal amount of microcrystalline cellulose to the compost inoculum; 4. Add deionized water to the reaction flask to maintain a water content of 50%, seal it, place it in a constant temperature incubator, raise the temperature to 58±2℃, test for 45 days, and record the amount of carbon dioxide released by the reaction flask. 5. Calculation formula: Theoretical carbon dioxide emissions:

[0044] m0: Dry weight (g) of the test sample; C%: Carbon content in the test sample. : The conversion factor for converting carbon to carbon dioxide.

[0045] Biodegradation rate: CO 2（T） The cumulative carbon dioxide emissions of the test group, CO 2（B） : Cumulative carbon dioxide emissions of the blank group.

[0046] Table 3. Biodegradability test results of the examples and comparative examples project <![CDATA[D t( %)]]> Example 8 78.5 Example 9 80.1 Example 10 79.2 Example 11 75.3 Example 12 76.8 Comparative Example 1 75.8 Comparative Example 2 45.2 Comparative Example 3 76.5 Comparative Example 4 77.9 Data Analysis: As can be seen from Tables 1-3, the biodegradable paraffin-biobased polymer sealing film prepared by this invention has higher mechanical strength, better barrier properties, good heat-sealing strength, and excellent biodegradability. In contrast, Comparative Example 1, lacking the addition of a citric acid-based aqueous epoxy crosslinking agent to the composite emulsion, exhibited a significant decrease in water vapor barrier properties, mechanical properties, and heat-sealing strength. This was because the middle layer lacked crucial covalent crosslinking points, failing to form a stable three-dimensional network structure. This weakened the interfacial bonding between paraffin and the polylactic acid matrix, while insufficient intermolecular forces made the film prone to slippage and damage under stress. Furthermore, the looser structure provided more channels for water vapor molecule penetration, severely impairing the barrier properties. Comparative Example 2 showed a significant decrease in biodegradability and barrier performance due to the use of petroleum-based emulsifier Span-80 instead of alkyl glycosides. The fundamental reason is that the introduction of petroleum-based components disrupted the ester bond structure of the material's molecular chain, making it difficult for microorganisms to recognize and enzymatically degrade it. At the same time, Span-80 has slightly poor compatibility with the bio-based system, which led to the deterioration of emulsion stability and film density, affecting barrier performance. In addition, the residue of non-bio-based components may also have a potential negative impact on the composting environment. Comparative Example 3 suffered from significantly deteriorated barrier and mechanical properties due to the use of lower pressure and fewer cycles during high-pressure homogenization. The core reason was insufficient shear force provided by the emulsification process, which failed to break the paraffin droplets into smaller sizes and make them uniformly distributed. The resulting composite emulsion had large and widely distributed particles. At the same time, the large-sized dispersed phase became stress concentration points after film formation, reducing mechanical strength. In addition, the rough and uneven phase structure could not effectively extend the water vapor permeation path, resulting in poor barrier properties. Comparative Example 4 suffered a significant decrease in mechanical properties, particularly elongation at break, due to the absence of lyophilized nanocellulose powder in the slurry. This was because the inner layer lacked a three-dimensional network scaffold formed by nanocellulose to bear and disperse stress, making the matrix prone to stress concentration and rapid fracture under tension. At the same time, the lack of hydrogen bonding between nanocellulose and polylactic acid molecular chains weakened the interaction forces between molecular chains and reduced the toughness of the material. In addition, the lack of constraint from the nanonetwork in the plasticizing effect of the plasticizer also exacerbated the brittleness of the material. Example 11 shows that the water vapor barrier properties of the composite emulsion are the best among Examples 8-12 due to the introduction of organic nano-montmorillonite into the composite emulsion. This is because the sheet structure of nano-montmorillonite forms a "maze effect" in the system, which can effectively prolong and hinder the diffusion path of water vapor molecules. At the same time, the strong interfacial bonding between its sheets and the polymer matrix plays a significant reinforcing role, further improving the mechanical strength of the film. In addition, the synergistic effect of the nanosheets and the online cross-linking network jointly constructs a more dense and complete barrier layer. Example 12 shows that the introduction of nano-chitosan into the outer premixed liquid resulted in excellent heat-sealing strength and biodegradability. This is because the abundant active groups (such as amino and hydroxyl groups) on the nano-chitosan molecular chain can form a stronger interaction with the polylactic acid molecular chain, thereby improving the bonding force of the heat-sealing interface. At the same time, chitosan itself is a natural biodegradable polysaccharide, and its introduction directly increases the content of biodegradable components in the material. In addition, the excellent biocompatibility of this component with other bio-based materials together ensures that it can be efficiently decomposed by microorganisms in the composting environment.

[0047] Those skilled in the art should understand that the discussion of any of the above embodiments is merely exemplary and is not intended to imply that the scope of the invention is limited to these examples; within the framework of the invention, the technical features of the above embodiments or different embodiments can also be combined, the steps can be implemented in any order, and there are many other variations of the different aspects of the invention as described above, which are not provided in detail for the sake of brevity.

[0048] This invention is intended to cover all such substitutions, modifications, and variations that fall within the broad scope of the appended claims. Therefore, any omissions, modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this invention should be included within the scope of protection of this invention.

Claims

1. A degradable paraffin-bio-based polymer sealant film, characterized by, Composed of the following components by mass: slurry 90-100 parts, composite emulsion 90-100 parts, polylactic acid resin 80-90 parts, silicon dioxide 2-4 parts, and bio-based erucamide 1-3 parts; The slurry is a modified polyhydroxyaliphatic ester; The modified polyhydroxyaliphatic ester is prepared from a polyhydroxyaliphatic ester, acetyl tri-butyl citrate, and nanocellulose freeze-dried powder; The polylactic acid resin is a modified polymer emulsion; The modified polymer emulsion is prepared from soy wax, alkyl glycoside, maleic anhydride grafted polylactic acid, polyglycerol polyricinoleate, and polylactic acid emulsion.

2. The degradable paraffin-bio-based polymer plug seal film according to claim 1, characterized in that, The preparation steps of the slurry are as follows: Step A1: Add polyhydroxyaliphatic ester to a mixed solvent of ethyl acetate and acetone, heat to 45-55℃, stir for 60-90min, reduce the stirring speed, add acetyl tri-butyl citrate, stir for 30-40min, and obtain a mixed solution after stirring is completed; Step A2: Add nanocellulose freeze-dried powder to a mixed solvent of ethyl acetate and acetone, high-speed shear for 8-12min, add the mixed solution, reduce the stirring speed, stir for 8-12min, transfer to an emulsifier, shear for 15-20min, vacuum degassing, filter through a 200-mesh screen, and obtain the slurry.

3. The degradable paraffin-bio-based polymer plug seal film according to claim 2, characterized in that, The mass ratio of the polyhydroxyaliphatic ester to acetyl tri-butyl citrate in step A1 is 1:0.15-0.25; The mass ratio of the nanocellulose freeze-dried powder to the mixed solution in step A2 is 0.02-0.03:1; The volume ratio of ethyl acetate to acetone in steps A1 and A2 is 7:

3.

4. The degradable paraffin-bio-based polymer plug seal film according to claim 1, characterized in that, The preparation steps of the composite emulsion are as follows: Step B1: Add soy wax, alkyl glycoside, and maleic anhydride grafted polylactic acid to polyglycerol polyricinoleate, heat to 50-70℃, stir for 20-30min, and obtain an oil phase; Step B2: Add polylactic acid emulsion to deionized water, heat to 55-65℃, stir for 10-20min, transfer to an emulsifier, add the oil phase, shear for 5-10min, add to a high-pressure homogenizer, heat to 60-70℃, pressurize to 50-80MPa, cycle homogenization for 3-5 times, cool to 30-40℃, and obtain a primary emulsion after reaction is completed; Step B3: Add a citric acid-based waterborne epoxy crosslinking agent to the primary emulsion, heat to 30-40℃, stir for 30-40min, and obtain the composite emulsion after stirring is completed.

5. The degradable paraffin-bio-based polymer plug seal film according to claim 4, characterized in that, The mass ratio of soy wax, alkyl glycoside, maleic anhydride grafted polylactic acid, and polyglycerol polyricinoleate in step B1 is 1:0.07-0.08:0.12-0.13:0.04-0.

06.

6. The degradable paraffin-bio-based polymer plug seal film according to claim 4, characterized in that, The mass ratio of polylactic acid emulsion, deionized water, and oil phase in step B2 is 0.5-0.7:1.8-2.2:

1.

7. The degradable paraffin-bio-based polymer plug seal film according to claim 4, wherein, The mass ratio of the citric acid-based waterborne epoxy crosslinking agent to the primary emulsion in step B3 is 0.01-0.012:

1.

8. A method for preparing a biodegradable paraffin-biobased polymer sealing film according to any one of claims 1-7, characterized in that, The specific steps of the preparation method are as follows: Step S1: add polylactic acid resin into ethyl acetate and acetone mixed solvent, heat to 45-55℃, stir for 60-90min, reduce the speed, add silica and erucic acid amide powder, stir for 20-30min, transfer to emulsifier, heat to 50-60℃, shear for 20-30min, vacuum degassing, filter through 200 mesh screen, get premix; Step S2: add slurry into coating machine, film thickness 120-150μm, speed 5-10m / min, first drying, heat to 60-80℃, dry for 2-4min, cool to 40-50℃, add composite emulsion, film thickness 80-100μm, second drying, heat to 90-100℃, dry for 3-5min, cool to 40-50℃, add premix, film thickness 40-60μm, third drying, heat to 65-75℃, dry for 1-2min, cool to 20-30℃, stand for 24-48h, get paraffin-bio-based polymer sealing film.

9. The method for preparing a biodegradable paraffin-biobased polymer sealing film according to claim 8, characterized in that, The mass ratio of polylactic acid resin, silica and erucic acid amide powder in step S1 is 1:0.034-0.036:0.022-0.

024.

10. The method for preparing a biodegradable paraffin-biobased polymer sealing film according to claim 8, characterized in that, The mass ratio of slurry, composite emulsion and premix in step S2 is 1.6-1.7:2-2.1:1.

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