Design method and application of multilayer composite film with barrier, hydrophobic and antibacterial functions

Abstract

The invention discloses a design method and application of a multilayer composite film with barrier, hydrophobic and antibacterial functions. An alkyl ketene dimer (AKD) modified polyvinyl alcohol (PVA) coating and an orange peel essential oil active layer are constructed on the surface of a rice straw fiber base material to prepare the multilayer composite film with barrier, hydrophobic and antibacterial functions, and the multilayer composite film is applied to the field of green food packaging such as strawberry packaging. According to the AKD modified PVA / orange peel essential oil loaded rice straw fiber-based composite film, the barrier property, the hydrophobicity and the antibacterial stability are improved, meanwhile, the shelf life of fruits is remarkably prolonged, good food packaging application potential is shown, and a practical path is provided for high-value utilization of agricultural and forestry residues and development of green packaging materials.

Description

Technical Field

[0001] This invention relates to the field of composite preservation film preparation technology, and more specifically to a design method and application of a multilayer composite film with barrier, hydrophobic and antibacterial functions. Background Technology

[0002] Traditional petroleum-based plastic films, due to their stable hydrocarbon polymer structure, exhibit extremely high durability in the natural environment, with degradation cycles reaching hundreds of years and being irreversible, leading to the continuous accumulation of white pollution. The global plastic pollution problem is becoming increasingly severe; in 2023, my country's daily plastic product output reached 82 million tons. Data from the United Nations Environment Programme shows that more than 400 million tons of plastic waste are generated globally each year, but the effective recycling rate is less than 10%, resulting in microplastics flowing into the ocean, soil, and atmosphere, forming trans-sphere pollution and seriously threatening food safety and human health. In the agricultural sector, residual plastic film leads to soil compaction, fertility decline, and microbial community imbalance. Long-term accumulation can even trigger secondary salinization and exacerbate the enrichment of organic pollutants such as phthalates. This production model of exchanging long-term soil degradation for short-term agricultural benefits is unsustainable, and there is an urgent need to develop environmentally friendly and biodegradable materials as alternatives to traditional plastic-based films.

[0003] Driven by both policy and market forces, the global biodegradable materials industry is entering a period of rapid development, gradually replacing traditional plastic-based films in food packaging, express delivery, and agricultural mulch films. Among these, the demand growth in the food packaging sector is the most significant; data shows that China's food delivery industry alone consumes over 20 billion disposable tableware items annually. Among various biomass raw materials, crop straw fiber has attracted considerable attention due to its unique advantages. Its significant cost-effectiveness (processing costs are 30-40% lower than other biomass raw materials), high renewability, and complete biodegradability (degradation rate ≥90% within 180 days) have made it an ideal raw material for developing high-performance biodegradable films. Current research focuses on converting agricultural waste such as rice straw, corn straw, and wheat husks into high-performance biomass materials. By optimizing extraction processes, these cellulose-rich agricultural byproducts can be processed into functional membrane materials with good mechanical properties and controllable degradation cycles. The resource utilization model of agricultural waste has dual environmental benefits: it can transform traditional incineration methods into the production of high-value-added materials; and it effectively reduces plastic pollution. Therefore, in-depth research on the preparation process, performance regulation, and application scenario expansion of rice straw fiber-based membranes is of great strategic significance for promoting the advancement of bio-based materials technology and the development of the agricultural circular economy.

[0004] my country's annual crop straw production is approximately 900 million tons, including rice straw, rice husks, corn straw, wheat husks, and wheat straw, with rice straw accounting for 5.8%. However, its comprehensive utilization rate is less than 65%. The burning of rice straw reaches 80 million tons, generating 120 million tons of carbon emissions. Driven by carbon neutrality and circular economy strategies, research on the high-value transformation of agricultural waste focuses on the structural characteristics and functional applications of fibrous materials. Rice straw fiber, produced through a mechanical crushing-steam explosion synergistic process, contains 35-45% cellulose, 20-30% hemicellulose, and 10-15% lignin. Its aspect ratio is approximately 50:1, tensile strength is superior to wheat straw, and elongation at break is superior to corn straw, making it an ideal raw material for preparing bio-based materials. The application of steam explosion-enzyme decoupling technology has significantly improved fiber extraction efficiency, promoting its large-scale application in food tray packaging, biodegradable straws, and seedling pots. Previous studies have shown that rice straw fiber can partially replace wood fiber, while the composite membrane still maintains excellent mechanical properties. Its abundant hydroxyl groups, high specific surface area, and excellent biocompatibility provide a foundation for constructing composite membrane systems that enhance barrier properties and functional characteristics. At the same time, it can effectively extend the shelf life of fruits and vegetables, inhibit moisture loss and microbial contamination, and further expand its application prospects. Summary of the Invention

[0005] In view of this, the present invention provides a design method and application of a multilayer composite membrane with barrier, hydrophobic and antibacterial functions. The present invention prepares a multilayer composite membrane with barrier, hydrophobic and antibacterial functions by constructing an alkyl ketene dimer (AKD) modified polyvinyl alcohol (PVA) coating and an orange peel essential oil active layer on the surface of a rice straw fiber substrate, which can be applied in the field of green food packaging such as strawberry packaging. First, an orange peel essential oil antibacterial coating is prepared, and then a rice straw fiber base layer and an AKD modified PVA hydrophobic layer are prepared separately. Then, the AKD modified PVA coating is transferred to the surface of the base layer, and orange peel essential oil is introduced into the membrane surface by a coating method to obtain an AKD modified PVA / orange peel essential oil-loaded rice straw fiber-based composite membrane.

[0006] To achieve the above objectives, the present invention adopts the following technical solution:

[0007] A design method for a multilayer composite membrane with barrier, hydrophobic, and antibacterial functions includes the following steps:

[0008] (1) Extraction of orange peel essential oil

[0009] Select commercially available fresh oranges, clean them to obtain the peel, cut the peel into pieces, mix the orange peel pieces with water to ensure the orange peel is completely submerged, transfer to a container, heat to the boiling point, maintain a gentle boil, the water vapor carrying the essential oil will be condensed to achieve phase separation, let the distillate stand, after the oil and water have fully separated, use a separatory funnel to separate the upper orange-yellow oil layer, which is the crude orange peel essential oil, remove the water from the crude orange peel essential oil, filter through filter paper to obtain the clear essential oil, for later use;

[0010] (2) Preparation of rice straw fiber base membrane

[0011] After soaking, KP pulp board and rice straw fiber were pulped separately to 40-50°SR and then mixed to obtain a mixed pulp. Then, water was added to dilute it. Next, rice straw fiber base film samples were prepared using a sheet forming machine. After drying, the samples were left to stand at room temperature for a period of time for later use.

[0012] (3) Preparation of AKD-modified PVA solution

[0013] An AKD-modified PVA solution was prepared by adding a 20% AKD emulsion to a PVA solution and controlling the mass ratio of AKD to PVA to be 5%-20% and mechanically stirring at room temperature.

[0014] (4) Preparation of AKD-modified PVA / orange peel essential oil-loaded rice straw fiber-based composite membrane

[0015] AKD-modified PVA solution was coated on one side of the rice straw fiber base membrane, then dried in an oven, and then transferred to a constant temperature and humidity chamber for standing. After standing, the prepared orange peel essential oil was loaded onto the other side of the rice straw fiber base membrane by rod coating. After coating, the composite membrane was obtained by drying.

[0016] Preferably, the mixed slurry in step (2) consists of 70% rice straw fiber and 30% KP fiber.

[0017] Preferably, the dilution with water in step (2) is to dilute to 0.2%.

[0018] Preferably, the rice straw fiber base film sample in step (2) is quantified as 80 g / m2.

[0019] Preferably, the drying in step (2) is performed by drying at 105°C using a plate dryer for 15 minutes.

[0020] Preferably, the PVA solution in step (3) is prepared by the following method: PVA with a degree of alcoholysis of 98.0 mol%-99.0 mol% and a molecular weight of 190,000 is selected as raw material, PVA particles are dissolved in deionized water, and stirred for 1 hour at 90°C and 800 rpm using a heated magnetic stirrer. After the solution is cooled to room temperature, a PVA solution with a concentration of 3%-10% is prepared for use.

[0021] Preferably, the mechanical stirring in step (3) is stirring at 1000 rpm for 1 hour.

[0022] Preferably, the drying in the oven in step (4) is performed at 105°C for 10 minutes; the standing in the constant temperature and humidity chamber is performed at 22-24°C and 48-58%RH.

[0023] Preferably, the loading of orange peel essential oil in step (4) is 0.4%-2.0%, and after coating, it is dried at 60°C for 10 minutes.

[0024] Another objective of this invention is to provide the application of the composite film prepared by the above-mentioned design method of multilayer composite film with barrier, hydrophobic and antibacterial functions in strawberry preservation.

[0025] As can be seen from the above technical solution, compared with the prior art, the present invention has the following beneficial effects:

[0026] This invention effectively optimizes the performance of biomass-based membrane materials in terms of antibacterial properties, hydrophobicity, and barrier properties by constructing an AKD-modified polyvinyl alcohol (PVA) coating on the surface of a rice straw fiber-based membrane and loading it with orange peel essential oil. Specifically, it offers the following beneficial technical effects:

[0027] Significantly improves hydrophobic properties

[0028] By introducing 15 wt% alkyl ketene dimer (AKD) into the PVA coating, the water contact angle of the composite membrane prepared by this invention is increased from 35.08° of the unmodified membrane to 107.14°, which significantly enhances the hydrophobicity of the membrane surface, inhibits water penetration, delays hygroscopic expansion, and improves the water resistance and morphological stability of the membrane.

[0029] Significantly improves barrier performance

[0030] The water vapor transmission rate (WVTR) of the multilayer composite membrane is 3281 g / m³. 2 ·day decreased to 81.98g / m 2The air permeability decreased from 21.51 μm / (Pa·s) to 0.45 μm / (Pa·s) over the day, representing a reduction of 97.5% and 97.9% respectively compared to the uncoated film. This significantly improved the barrier ability against small molecules such as water vapor and oxygen, effectively extending the shelf life of packaged foods.

[0031] It imparts excellent antibacterial properties.

[0032] By coating the membrane surface with orange peel essential oil in a gradient manner (0.4%–2.0%), the optimal addition amount of 1.6% showed inhibition zone diameters of 30.04 mm and 10.42 mm against Staphylococcus aureus and Escherichia coli, respectively. The MIC and MBC against Staphylococcus aureus were 0.625 mg / mL and 1.250 mg / mL, respectively, indicating that it has a significant inhibitory and bactericidal effect on Gram-positive bacteria.

[0033] Regulating the slow-release behavior of orange peel essential oil

[0034] The composite coating effectively reduces the diffusion rate of orange peel essential oil in the first 24 hours, decreasing the diffusion constant by 44.6%, significantly alleviating its initial "burst release effect," prolonging the antibacterial activity period, and improving the utilization efficiency of the essential oil.

[0035] Improve the mechanical properties and structural density of the membrane.

[0036] The composite coating and the cellulose substrate form a stable interface through hydrogen bonding and mechanical interlocking, which enhances the adhesion of the film layer and improves the uniformity and integrity of the overall structure; at the same time, it can still maintain good structural stability under high humidity conditions.

[0037] Improve the preservation effect of fruits and vegetables

[0038] Actual strawberry preservation tests show that, compared with PE film packaging, the composite film of this invention can reduce fruit weight loss by 49.7% and slow down the decrease in firmness by 24.0% during a 7-day storage period, stabilize TSS and pH levels, and significantly extend the shelf life of fruits and vegetables.

[0039] AKD-modified PVA / orange peel oil-loaded rice straw fiber-based composite film significantly extends the shelf life of fruits while improving barrier properties, hydrophobicity, and antibacterial stability, demonstrating good potential for food packaging applications and providing a practical path for the high-value utilization of agricultural and forestry waste and the development of green packaging materials. Attached Figure Description

[0040] To more clearly illustrate the technical solutions in the embodiments of the present 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 embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the provided drawings without creative effort.

[0041] Figure 1 The process flow diagram provided for this invention;

[0042] Figure 2 Total ion current chromatogram (TIC) of orange peel essential oil;

[0043] Figure 3 The results of MBC assays for Escherichia coli and Staphylococcus aureus using orange peel essential oil;

[0044] Figure 4 The effect of different amounts of orange peel essential oil added on the diameter of the antibacterial zone generated by the composite film;

[0045] Figure 5 The air permeability of rice straw fiber-based membranes and their coating modification systems;

[0046] Figure 6 The effect of AKD content on the hydrophobic properties of AKD-modified PVA composite coated rice straw fiber base membrane;

[0047] Figure 7 A comparison of OPEO release curves in different membrane structures;

[0048] Figure 8 A comparison chart of changes in weight loss rate during strawberry storage;

[0049] Figure 9 A comparison chart showing the changes in hardness of strawberries during storage;

[0050] Figure 10 This is a graph showing the changing trends of TSS and pH during strawberry storage. Detailed Implementation

[0051] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0052] Example 1

[0053] This embodiment provides a design method for a multilayer composite membrane with barrier, hydrophobic, and antibacterial functions, including the following steps:

[0054] (1) Extraction of orange peel essential oil

[0055] Select commercially available fresh oranges, clean them to obtain the peel, cut the peel into 1cm×1cm pieces, mix 150g of orange peel pieces with 300mL of water, ensuring the orange peel is completely submerged, transfer to a container, heat to boiling point, maintain a gentle boil, the water vapor carrying the essential oil will be condensed to achieve phase separation, let the distillate stand, after the oil and water have fully separated, use a separatory funnel to separate the upper orange-yellow oil layer, which is the crude orange peel essential oil, remove the water from the crude orange peel essential oil, filter through filter paper to obtain the clear essential oil, for later use;

[0056] (2) Preparation of rice straw fiber base membrane

[0057] After soaking for 8 hours, KP pulp board and rice straw fiber were separately beaten to 45°SR and then mixed (the freeness was measured using an AT-DT pulp freeness tester according to GB / T3332-2004) to obtain a mixed pulp composed of 70% rice straw fiber and 30% KP fiber. Then, water was added to dilute it to 0.2%. Rice straw fiber base film samples were then prepared using a sheet forming machine. After drying, the samples were left to stand at room temperature for a period of time for later use.

[0058] (3) Preparation of AKD-modified PVA solution

[0059] PVA with a degree of alcoholysis of 99.0 mol% and a molecular weight of 190,000 was selected as the raw material. The PVA particles were dissolved in deionized water and stirred for 1 hour at 90°C and 800 rpm using a heated magnetic stirrer. After the solution was cooled to room temperature, a PVA solution with a concentration of 3%-10% was prepared for later use.

[0060] An AKD-modified PVA solution was prepared by adding 20% ​​AKD emulsion to a PVA solution and controlling the mass ratio of AKD to PVA to be 15%. The solution was mechanically stirred at 1000 rpm for 1 hour at room temperature.

[0061] (4) Preparation of AKD-modified PVA / orange peel essential oil-loaded rice straw fiber-based composite membrane

[0062] AKD-modified PVA solution was coated on one side of a rice straw fiber base membrane, and then dried in an oven at 105℃ for 10 minutes. After drying, it was transferred to a constant temperature and humidity chamber at 23±1℃ and 50±2%RH for standing. After standing, the prepared orange peel essential oil was loaded onto the other side of the rice straw fiber base membrane by rod coating at a loading of 1.6%. After coating, it was dried at 60℃ for 10 minutes to obtain the composite membrane.

[0063] Performance testing:

[0064] Figure 2 The total ion current spectrum of orange peel essential oil obtained by GC-MS analysis identified 62 chemical components. The main active components included γ-terpinene (28.62%), limonene (19.89%), and myrcene (11.00%), which provided a chemical basis for the broad-spectrum antibacterial properties of orange peel essential oil.

[0065] Figure 3 The effects of orange peel essential oil at the minimum bactericidal concentration (MBC) against two bacterial strains were demonstrated. The results showed that its antibacterial effect against Staphylococcus aureus (MBC = 1.250 mg / mL) was significantly stronger than that against Escherichia coli, verifying its excellent antibacterial properties.

[0066] Figure 4 This image shows the difference in the size of the inhibition zones formed on two strains of bacteria after loading different concentrations of orange peel essential oil onto rice straw fiber base membranes. The optimal concentration (1.6%) showed an inhibition zone diameter of 30.04 mm against Staphylococcus aureus.

[0067] Figure 5 The study demonstrated the effect of different coating structures in the composite membrane system on suppressing air permeability. By applying PVA and AKD synergistically to construct a dense coating, the air permeability was significantly reduced from 21.51 μm / (Pa·s) to 0.45 μm / (Pa·s), indicating that this structure can effectively suppress the diffusion of gas molecules such as oxygen.

[0068] Figure 6 The surface water contact angle values ​​of different membrane structures are shown. The results indicate that with the synergistic effect of orange peel essential oil and AKD, the hydrophobicity of the membrane is continuously enhanced, and the contact angle increases from 35.08° to 107.14°, indicating that the material has excellent waterproof performance.

[0069] Figure 7 The study demonstrates the comparison of OPEO diffusion behavior between uncoated and AKD-PVA composite films over 24 hours using a Higuchi model. Data shows that the diffusion coefficient of the composite film is reduced by 44.6%, significantly suppressing the initial "burst release" phenomenon and achieving a controlled-release effect.

[0070] Unwrapped strawberries served as the control group, while strawberries packaged in AKD-modified PVA / orange peel oil-loaded rice straw fiber-based composite film and polyethylene film served as the experimental group. Strawberries were stored at 23℃ and 50% relative humidity for 7 days, with performance indicators tested daily.

[0071] Figure 8The changes in weight loss rate of strawberries during a 7-day storage period were demonstrated using the composite film of this invention, a traditional PE film, and a control group. The results showed that the film of this invention effectively inhibited fruit moisture loss, reducing the weight loss rate by 49.7% compared to the control group.

[0072] Figure 9 This study demonstrates a comparison of the ability of different packaging films to maintain strawberry firmness under the same storage conditions. Samples treated with the composite film of this invention maintained a higher firmness value at the end of storage, with a firmness decrease of only 24.0%.

[0073] Figure 10 This study reflects changes in total soluble solids (TSS) and pH value in strawberry samples during storage. Results show that the membrane of this invention can effectively delay TSS decline and maintain pH stability around 3.80, thus helping to preserve the flavor and quality of fruits and vegetables.

[0074] The various embodiments in this specification are described in a progressive manner, with each embodiment focusing on its differences from other embodiments. Similar or identical parts between embodiments can be referred to interchangeably. For the apparatus disclosed in the embodiments, since it corresponds to the method disclosed in the embodiments, the description is relatively simple; relevant parts can be referred to the method section.

[0075] The above description of the disclosed embodiments enables those skilled in the art to make or use the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A design method for a multilayer composite membrane with barrier, hydrophobic, and antibacterial functions, characterized in that, Includes the following steps: (1) Extraction of orange peel essential oil Select commercially available fresh oranges, clean them to obtain the peel, cut the peel into pieces, mix the orange peel pieces with water to ensure the orange peel is completely submerged, transfer to a container, heat to the boiling point, maintain a gentle boil, the water vapor carrying the essential oil will be condensed to achieve phase separation, let the distillate stand, after the oil and water have fully separated, use a separatory funnel to separate the upper orange-yellow oil layer, which is the crude orange peel essential oil, remove the water from the crude orange peel essential oil, filter through filter paper to obtain the clear essential oil, for later use; (2) Preparation of rice straw fiber base membrane After soaking, KP pulp board and rice straw fiber were pulped separately to 40-50°SR and then mixed to obtain a mixed pulp. Then, water was added to dilute it. Next, rice straw fiber base film samples were prepared using a sheet forming machine. After drying, the samples were left to stand at room temperature for a period of time for later use. (3) Preparation of AKD-modified PVA solution An AKD-modified PVA solution was prepared by adding a 20% AKD emulsion to a PVA solution and controlling the mass ratio of AKD to PVA to be 5%-20% and mechanically stirring at room temperature. (4) Preparation of AKD-modified PVA / orange peel essential oil-loaded rice straw fiber-based composite membrane AKD-modified PVA solution was coated on one side of the rice straw fiber base membrane, then dried in an oven, and then transferred to a constant temperature and humidity chamber for standing. After standing, the prepared orange peel essential oil was loaded onto the other side of the rice straw fiber base membrane by rod coating. After coating, the composite membrane was obtained by drying.

2. The design method of a multilayer composite membrane with barrier, hydrophobic and antibacterial functions according to claim 1, characterized in that, The mixed slurry described in step (2) consists of 70% rice straw fiber and 30% KP fiber.

3. The design method of a multilayer composite membrane with barrier, hydrophobic and antibacterial functions according to claim 1, characterized in that, The dilution with water in step (2) is to dilute to a solid content of 0.2%.

4. The design method of a multilayer composite membrane with barrier, hydrophobic and antibacterial functions according to claim 1, characterized in that, The quantitative sample of rice straw fiber base membrane in step (2) is 80 g / m³. 2 .

5. The design method of a multilayer composite membrane with barrier, hydrophobic and antibacterial functions according to claim 1, characterized in that, The drying process described in step (2) involves drying at 105°C using a plate dryer for 15 minutes.

6. The design method of a multilayer composite membrane with barrier, hydrophobic and antibacterial functions according to claim 1, characterized in that, The PVA solution mentioned in step (3) is prepared by the following method: PVA with a degree of alcoholysis of 98.0 mol%-99.0 mol% and a molecular weight of 190,000 is selected as raw material. PVA particles are dissolved in deionized water and stirred for 1 hour at 90°C and 800 rpm using a heated magnetic stirrer. After the solution is cooled to room temperature, a PVA solution with a concentration of 3%-10% is prepared for use.

7. The design method of a multilayer composite membrane with barrier, hydrophobic and antibacterial functions according to claim 1, characterized in that, The mechanical stirring in step (3) is stirring at 1000 rpm for 1 hour.

8. The design method of a multilayer composite membrane with barrier, hydrophobic and antibacterial functions according to claim 1, characterized in that, The drying in the oven in step (4) is to dry at 105℃ for 10 minutes; the standing in the constant temperature and humidity chamber is to stand at 22-24℃ and 48-58%RH.

9. The design method of a multilayer composite membrane with barrier, hydrophobic and antibacterial functions according to claim 1, characterized in that, In step (4), the loading of orange peel essential oil is 0.4%-2.0%, and after coating, it is dried at 60℃ for 10 minutes.

10. The application of the composite film prepared by the design method of the multilayer composite film with barrier, hydrophobic and antibacterial functions as described in any one of claims 1-9 in the preservation of strawberries.

Images