A biodegradable barrier antibacterial moisture-absorbing membrane

Abstract

This invention relates to a biodegradable barrier antibacterial moisture-absorbing film, which consists of two layers: a quaternary ammonium salt chitosan / hydroxyethyl cellulose composite layer and a methacrylated gelatin / methacrylated carboxymethyl chitosan composite layer. The two layers are bonded together by casting, biaxial stretching, and hot pressing, and a reaction is achieved between them to achieve a tight bond. The composite film has good tensile strength, ductility, and tear resistance. Under dry conditions, the film has good oxygen and carbon dioxide barrier properties, and also has good moisture absorption. This film can be used in packaging applications requiring barrier, moisture absorption, and antibacterial properties.

Description

Technical Field

[0001] This invention relates to a barrier, antibacterial, and moisture-absorbing membrane, and more particularly to a membrane material prepared from biomass that has high strength and toughness, gas barrier properties, antibacterial properties, and a certain degree of moisture absorption. Background Technology

[0002] Membrane materials have extremely wide applications, playing a vital role in packaging, functional devices, and biomedicine. Currently, plastic films still hold a dominant position. Plastic films are made from petroleum-based synthetic raw materials, offering strong processability, diverse physical properties, and adaptability to various application scenarios. In terms of mechanical and barrier properties, plastic film materials such as PP, PE, PS, BOPP, PVA, PA, and EVOH achieve differentiated excellent mechanical properties and water and gas barrier characteristics through adjustments to formulation, crystallinity, and orientation. Based on the excellent processability of plastics, various multilayer composite and multilayer co-extruded films have been developed to further broaden their application range. In food and pharmaceutical packaging, films are required to possess both good flexibility and mechanical properties, as well as excellent gas barrier properties to ensure the long-term preservation of their contents. In plastic materials, this is often achieved through special materials or multilayer composites. However, because plastic materials are non-degradable and complex to recycle, their large-scale use and indiscriminate disposal often have a certain impact on the environment. Therefore, people hope to use biodegradable materials as alternatives. Biomass materials are the most important category of biodegradable materials. However, due to their complex molecular structure and interactions, biomass materials are difficult to arrange in a regular pattern, often resulting in thin film products with uniform structure and good barrier properties. Relying solely on biomass materials to form films also makes it difficult to achieve synergistic performance across various properties. For example, polylactic acid (PLA) films have high strength but poor toughness; while poly(adipate fatty acid) / butylene terephthalate (butylene terephthalate) / PLA composite films have good overall mechanical properties, their barrier properties fail to meet requirements.

[0003] Based on the natural properties of biomass, some biomass materials can provide strong hydrogen bonding, resulting in tight bonds. Utilizing this characteristic can enhance the compactness of membrane molecular structures, thereby producing excellent barrier effects. To address this, this invention employs a special bilayer membrane composite technology. One layer, a fibrous base membrane layer leached from dissolved material, provides barrier properties and strength; the other layer, a cross-linked flexible layer, provides toughness. Through the construction of these two biodegradable layers, combined with multi-dimensional cross-linking and dynamic bonding between the two layers, synergistic performance between the membranes is achieved. Furthermore, a stretching process promotes the orientation of the membrane's molecular structure, thereby achieving excellent mechanical properties, gas barrier properties, and antibacterial properties. This membrane can be used in specialized packaging applications, such as food and pharmaceutical packaging requiring antibacterial and barrier properties. Summary of the Invention

[0004] The purpose of this invention is to overcome the shortcomings of biomass membrane materials in terms of compatibility in terms of mechanical properties, barrier properties, and hygroscopic properties, and to develop a composite membrane material based on biodegradable materials that achieves good barrier properties under high strength and toughness under dry conditions, while also providing antibacterial and water-absorbing functions.

[0005] The objective of this invention is achieved through the following technical solution:

[0006] A biodegradable barrier antibacterial moisture-absorbing membrane is composed of a double-layer cast composite, comprising a surface layer of quaternary ammonium salt chitosan / hydroxyethyl cellulose composite layer and an inner layer of methacrylated gelatin / methacrylated carboxymethyl chitosan composite layer. The materials and composition of the two layers are as follows:

[0007] Quaternary ammonium salt chitosan / hydroxyethyl cellulose composite layer:

[0008] Quaternary ammonium salt chitosan: 100

[0009] Hydroxyethyl cellulose: 15-30

[0010] Polyethylene glycol borate: 3.5-8

[0011] Methacrylated gelatin / methacrylated carboxymethyl chitosan composite layer:

[0012] Methacrylated gelatin: 100

[0013] Methacrylamide carboxymethyl chitosan: 20-60

[0014] Double bond crosslinking agent: 3-6

[0015] Macromolecular aldehyde crosslinking agent: 4-8

[0016] Water-soluble photoinitiator: 0.2-0.4.

[0017] Furthermore, the preparation process of the composite membrane is as follows:

[0018] I: Preparation of surface casting solution: Quaternary ammonium salt chitosan, hydroxyethyl cellulose, and polyethylene glycol borate are added to pure water in a certain mass ratio, dissolved and stirred at 50-70℃ to form a homogeneous solution, which is used as the surface casting solution for later use; wherein, the mass concentration of the aqueous solution is between 8-12%.

[0019] II: Preparation of the inner layer casting solution: Dissolve methacrylated gelatin, methacrylamide carboxymethyl chitosan, double bond crosslinking agent, macromolecular aldehyde crosslinking agent, and photoinitiator in water at 40-60℃, and stir evenly at room temperature to form a solution as the inner layer casting solution for later use; wherein, the mass fraction of methacrylated gelatin is between 4-8%.

[0020] III: Casting process: The surface casting solution is cast on a casting plate at 80-90℃ at a speed of 2-4 m / min until a film is formed; after heat drying, it is introduced into the second casting device as the casting base film. Atomized weak acid solution is sprayed onto the surface of the base film until it is wetted, and then the inner layer casting solution is cast on it at a speed of 2-5 m / min and a temperature of 70-90℃, and is continuously irradiated with ultraviolet light of a specific wavelength until the inner layer film is formed and fully dried;

[0021] IV: Place the dried film into a stretching device and heat it to between 40-65℃. Stretch it in the transverse direction to between 1.1-1.3 times the original width and in the longitudinal direction to between 1.2-1.4 times the original length. Then, introduce it into a hot roller press. Set the roller spacing to be less than 0.01-0.03mm of the film thickness and set the temperature to 140-180℃. After roller pressing, export the final composite film.

[0022] Furthermore, the rolling process can be carried out using single-roller, double-roller, or triple-roller methods as needed.

[0023] Furthermore, the weak acid solution may be an oxalic acid solution or a hydrochloric acid solution, and the mass concentration of the acid in the acid solution is between 3% and 6%.

[0024] Furthermore, the ultraviolet light irradiation time for the inner layer film casting should be between 10 and 25 minutes.

[0025] Furthermore, the purpose of spraying atomized weak acid solution onto the surface is to dissolve chitosan in the surface film in small amounts and promote its Schiff base reaction with the aldehyde crosslinking agent in the inner casting liquid.

[0026] Furthermore, the thickness of the quaternary ammonium salt chitosan / hydroxyethyl cellulose composite layer is between 0.1-0.2 mm, and the thickness of the methacrylated gelatin / methacrylated carboxymethyl chitosan composite layer is between 0.05-0.15 mm.

[0027] Furthermore, the degree of substitution of the hydroxyethyl cellulose is between 45% and 80% based on the proportion of hydroxyl groups in the cellulose.

[0028] Furthermore, the degree of substitution of the quaternary ammonium salt chitosan, calculated based on the proportion of hydroxyl groups in the chitosan, is between 50% and 80%.

[0029] Furthermore, the degree of substitution of the methacrylated gelatin is between 50-70% based on the proportion of hydroxyl groups in the substituted gelatin; the degree of substitution of carboxymethyl groups in the methacrylated carboxymethyl chitosan is between 30-50% based on the proportion of hydroxyl groups in the chitosan, and the degree of substitution of methacryloyl groups is between 20-40% based on the proportion of amino groups in the chitosan.

[0030] Furthermore, the molecular structural formula of the methacrylamide carboxymethyl chitosan is as follows:

[0031]

[0032] Furthermore, the molecular weight of the polyethylene glycol borate is between 2000 and 5000, and its molecular structure is as follows:

[0033]

[0034] Furthermore, the polyethylene glycol borate acts as a lubricant and stabilizer during film formation to improve film quality, and can also enhance the strength and barrier properties of the film through the bonding of BO bonds.

[0035] Furthermore, the double bond crosslinking agent is one of N,N-methylenebisacrylamide and polyethylene glycol diacrylate.

[0036] Furthermore, the macromolecular aldehyde crosslinking agent is a multi-arm polyethylene glycol aldehyde group, including two-arm, four-arm, six-arm, and eight-arm polyethylene glycol aldehyde groups, with a molecular weight between 2000 and 6000, and its molecular structure is as follows:

[0037] n is the degree of polymerization of ethylene glycol; x = 2, 4, 6, 8

[0038] Furthermore, the macromolecular aldehyde crosslinking agent can react with amino groups, thereby strengthening the intra- and inter-membrane bonding.

[0039] Furthermore, the double bond crosslinking agent is one of N,N-methylenebisacrylamide and polyethylene glycol diacrylate.

[0040] Furthermore, the water-soluble photoinitiator may be initiator 2959 with a maximum absorption wavelength of 328 nm; or LAP photoinitiator with a maximum absorption wavelength of 365 nm.

[0041] Furthermore, when the membrane is used as a packaging film, a quaternary ammonium salt chitosan / hydroxyethyl cellulose composite layer is generally used as the contact layer for the packaging contents.

[0042] Furthermore, the membrane material can be sealed by heat sealing.

[0043] Furthermore, the beneficial effects of the present invention are as follows:

[0044] The product employs a synergistic dual-layer biomass composite. The outer quaternary ammonium salt chitosan / hydroxyethyl cellulose composite layer exhibits excellent mechanical properties, antibacterial properties, and water absorption. The inner methacrylated gelatin / methacryloyl carboxymethyl chitosan composite layer possesses excellent strength and barrier properties. The dual-layer synergy enhances these properties.

[0045] A special processing technique is adopted. Before the inner layer is cast, a weakly acidic solution is sprayed on the surface quaternary ammonium salt chitosan / hydroxyethyl cellulose composite layer. This can promote the reaction of aldehydes and amino groups in the inner layer to strengthen cross-linking and improve strength. At the same time, it can also promote the reaction between aldehydes and amino groups of chitosan in the surface layer to strengthen the bond between the two layers, thereby achieving synergistic performance.

[0046] The use of bi-stretching combined with hot rolling technology after film formation is beneficial for the bidirectional orientation of biomass molecules and promotes hydrogen bonding in the process, which is conducive to the optimization of various properties.

[0047] Furthermore, the performance testing method for the membrane material is as follows:

[0048] The tensile strength and elongation at break of the film were tested according to GB / T 1040.3-2006 "Determination of tensile properties of plastics - Part 3: Test conditions for films and sheets";

[0049] The tear strength of the film was tested according to GB / T 16578.1-2008 "Determination of tear resistance of plastic films and sheets";

[0050] The impact strength of the membrane was tested according to GB / T 9639.1-2008 "Test methods for impact resistance of plastic films and sheets - free-falling dart method - Part 1: step method";

[0051] The carbon dioxide and oxygen barrier properties of the membrane were tested according to GB / T 1038-2000 "Test Method for Gas Permeability of Plastic Films and Sheets - Differential Pressure Method";

[0052] Moisture absorption of the membrane: The methacrylated gelatin / methacrylated carboxymethyl chitosan composite layer of the membrane and the flat material are attached and fixed to the target. The quaternary ammonium salt chitosan / hydroxyethyl cellulose composite layer is placed with the blank facing the space. The humidity in the space is controlled at 50%. The weight change over different time periods is calculated. (Real-time weight - dry film weight) / dry film weight = water absorption rate (%) calculated by weight.

[0053] The membrane's antibacterial properties were tested using E. coli. 10 4 CFU / mL Escherichia coli was cultured on both surfaces of the prepared membrane. After one week, the change in the area of ​​the E. coli colony was observed. Antibacterial activity was defined as the percentage reduction in the colony area compared to the original area, which could be determined using ImageJ software. The surface of the quaternary ammonium salt chitosan / hydroxyethyl cellulose composite layer was defined as surface A, and the surface of the methacrylated gelatin / methacrylated carboxymethyl chitosan was defined as surface B.

[0054] Furthermore, the performance range of the membrane material is as follows:

[0055] Tensile strength (MPa): 21-28;

[0056] Elongation at break (%): 185-350;

[0057] Transverse tear strength (kN / m): 200-300; Longitudinal tear strength (kN / m): 200-300;

[0058] O2 transmittance (cm) 3 / (m 3 ·24hr·MPa)): 50-150;

[0059] CO2 transmission rate (cm) 3 / (m 3 ·24hr·MPa)): 40-100;

[0060] 12h / 24h water absorption rate (%): 0.21-0.44 / 0.49-0.87;

[0061] Antibacterial activity (A / B side) (%): 67-92; 46-75. Attached Figure Description

[0062] Figure 1 This is a cross-sectional SEM image of the membrane prepared in Example 1;

[0063] Figure 2 This is a cross-sectional SEM image of the membrane prepared in Example 2.

[0064] Exemplary embodiments of the present invention will be described in detail below. However, these embodiments are for illustrative purposes only, and the present invention is not limited thereto.

[0065] Example 1

[0066] A biodegradable barrier antibacterial moisture-absorbing membrane, composed of a double-layer composite, such as Figure 1 As shown, the composite material includes a quaternary ammonium salt chitosan / hydroxyethyl cellulose composite layer 1 and a methacrylated gelatin / methacrylated carboxymethyl chitosan composite layer 2. The materials and compositions of the two layers are as follows:

[0067] Quaternary ammonium salt chitosan / hydroxyethyl cellulose composite layer:

[0068] Quaternary ammonium salt chitosan: 100

[0069] Hydroxyethyl cellulose: 22

[0070] Polyethylene glycol borate: 6.5

[0071] Methacrylated gelatin / methacrylated carboxymethyl chitosan composite layer:

[0072] Methacrylated gelatin: 100

[0073] Methacrylamide carboxymethyl chitosan: 45.3

[0074] N,N-Methylenebisacrylamide: 4.5

[0075] Four-arm polyethylene glycol aldehyde group: 7.5

[0076] Photoinitiator 2959: 0.25.

[0077] The preparation process of the composite membrane is as follows:

[0078] I: Preparation of the surface casting solution: Quaternary ammonium salt chitosan, hydroxyethyl cellulose, and polyethylene glycol borate are added to pure water in a certain mass ratio, dissolved at 65°C, and stirred until homogeneous to form a uniform solution, which is used as the surface casting solution for later use; wherein, the mass concentration of the aqueous solution is 8.5%;

[0079] II: Preparation of the inner layer casting solution: Methacrylated gelatin, methacrylamide carboxymethyl chitosan, N,N-methylenebisacrylamide, tetra-arm polyethylene glycol aldehyde, and photoinitiator 2959 are dissolved in water at 55°C and stirred evenly at room temperature to form a solution for use as the inner layer casting solution; wherein, the mass fraction of methacrylated gelatin is 5.5%;

[0080] III: Casting process: The surface casting solution is cast on an 85°C casting plate at a speed of 2.5 m / min until a film is formed; after heat drying, it is introduced into a second casting device as the casting base film. Atomized hydrochloric acid solution with a mass concentration of 4% is sprayed onto the surface of the base film until it is wetted. Then, the inner layer casting solution is cast on it at a speed of 3.2 m / min at 85°C, and continuously irradiated with 328 nm wavelength ultraviolet light for 15 min until the inner layer film is formed and fully dried.

[0081] IV: Place the dried film into a stretching device, heat it to 55°C, stretch it in the horizontal direction to 1.15 times the original width and in the vertical direction to 1.25 times the original length, and then introduce it into a hot roller press. The roller spacing is set to be less than 0.02 mm of the film thickness, and the temperature is set to 160°C. After roller pressing, the final composite film is obtained.

[0082] The thickness of the quaternary ammonium salt chitosan / hydroxyethyl cellulose composite layer is 0.16 mm, and the thickness of the methacrylated gelatin / methacrylated carboxymethyl chitosan composite layer is 0.12 mm.

[0083] The degree of substitution of the hydroxyethyl cellulose is 64% based on the proportion of hydroxyl groups in the cellulose.

[0084] The degree of substitution of the quaternary ammonium salt chitosan is 72% based on the proportion of hydroxyl groups in the chitosan;

[0085] The degree of substitution of the methacrylated gelatin is calculated as 55% based on the proportion of hydroxyl groups in the substituted gelatin;

[0086] The degree of substitution of carboxyl groups in the methacrylamide carboxymethyl chitosan is 42% based on the proportion of hydroxyl groups in the chitosan, and the degree of substitution of methacryloyl groups is 28% based on the proportion of amino groups in the chitosan.

[0087] The molecular weight of the polyethylene glycol borate is 4200.

[0088] The molecular weight of the four-armed polyethylene glycol aldehyde group is 4000.

[0089] Depend on Figure 1 It is evident that the addition of more four-arm polyethylene glycol aldehyde groups leads to increased reactions between the two layers, resulting in a very blurred interface between them.

[0090] The properties of the prepared membrane are shown in Table 1.

[0091] Example 2

[0092] A biodegradable barrier antibacterial moisture-absorbing membrane, composed of a double-layer composite, such as Figure 2 As shown, the composite material includes a quaternary ammonium salt chitosan / hydroxyethyl cellulose composite layer 1' and a methacrylated gelatin / methacrylated carboxymethyl chitosan composite layer 2'. The materials and compositions of the two layers are as follows:

[0093] Quaternary ammonium salt chitosan / hydroxyethyl cellulose composite layer:

[0094] Quaternary ammonium salt chitosan: 100

[0095] Hydroxyethyl cellulose: 28

[0096] Polyethylene glycol borate: 4.2

[0097] Methacrylated gelatin / methacrylated carboxymethyl chitosan composite layer:

[0098] Methacrylated gelatin: 100

[0099] Methacrylamide carboxymethyl chitosan: 28.6

[0100] N,N-Methylenebisacrylamide: 5.8

[0101] Six-arm polyethylene glycol aldehyde: 4.2

[0102] Photoinitiator 2959: 0.2

[0103] The preparation process of the composite membrane is as follows:

[0104] I: Preparation of the surface casting solution: Quaternary ammonium salt chitosan, hydroxyethyl cellulose, and polyethylene glycol borate are added to pure water in a certain mass ratio, dissolved at 60°C, and stirred until homogeneous to form a uniform solution, which is used as the surface casting solution for later use; wherein, the mass concentration of the aqueous solution is 10.5%;

[0105] II: Preparation of the inner layer casting solution: Methacrylated gelatin, methacrylamide carboxymethyl chitosan,

[0106] N,N-methylenebisacrylamide, hexagonal polyethylene glycol aldehyde, and photoinitiator 2959 were dissolved in water at 50°C and stirred evenly at room temperature to form a solution for use as the inner layer casting liquid; wherein, the mass fraction of methacrylated gelatin was 6.5%;

[0107] III: Casting process: The surface casting solution is cast on a casting plate at 88°C at a speed of 3.0 m / min until a film is formed; after heat drying, it is introduced into the second casting device as the casting base film. Atomized oxalic acid solution with a mass concentration of 5% is sprayed onto the surface of the base film until it is wetted. Then, the inner layer casting solution is cast on it at a speed of 4.4 m / min at 75°C, and continuously irradiated with 328 nm wavelength ultraviolet light for 20 min until the inner layer film is formed and fully dried.

[0108] IV: Place the dried film into a stretching device, heat it to 50°C, stretch it in the horizontal direction to 1.25 times the original width and in the vertical direction to 1.3 times the original length, and then introduce it into a hot roller press. The roller spacing is set to be less than 0.025 mm of the film thickness, and the temperature is set to 170°C. After roller pressing, the final composite film is obtained.

[0109] The thickness of the quaternary ammonium salt chitosan / hydroxyethyl cellulose composite layer is 0.18 mm, and the thickness of the methacrylated gelatin / methacrylated carboxymethyl chitosan composite layer is 0.09 mm.

[0110] The degree of substitution of the hydroxyethyl cellulose is 68% based on the proportion of hydroxyl groups in the cellulose.

[0111] The degree of substitution of the quaternary ammonium salt chitosan is calculated as 55% based on the proportion of hydroxyl groups in the chitosan.

[0112] The degree of substitution of the methacrylated gelatin is 64% based on the proportion of hydroxyl groups in the substituted gelatin.

[0113] The degree of substitution of carboxyl groups in the methacrylamide carboxymethyl chitosan is 36% based on the proportion of hydroxyl groups in the chitosan, and the degree of substitution of methacryloyl groups is 32% based on the proportion of amino groups in the chitosan.

[0114] The molecular weight of the polyethylene glycol borate is 3200.

[0115] The molecular weight of the six-armed polyethylene glycol aldehyde group is 5000.

[0116] Depend on Figure 2 It is evident that the addition of fewer six-arm polyethylene glycol aldehyde groups resulted in less reaction between the bilayers, leading to a clearer interface between them.

[0117] The properties of the prepared membrane are shown in Table 1.

[0118] Example 3

[0119] A biodegradable barrier antibacterial moisture-absorbing membrane is composed of a two-layer composite, comprising a quaternary ammonium salt chitosan / hydroxyethyl cellulose composite layer and a methacrylated gelatin / methacrylated carboxymethyl chitosan composite layer. The materials and compositions of the two layers are as follows:

[0120] Quaternary ammonium salt chitosan / hydroxyethyl cellulose composite layer:

[0121] Quaternary ammonium salt chitosan: 100

[0122] Hydroxyethyl cellulose: 16.5

[0123] Polyethylene glycol borate: 5.3

[0124] Methacrylated gelatin / methacrylated carboxymethyl chitosan composite layer:

[0125] Methacrylated gelatin: 100

[0126] Methacrylamide carboxymethyl chitosan: 33.7

[0127] Polyethylene glycol diacrylate: 4.8

[0128] Four-arm polyethylene glycol aldehyde group: 5.7

[0129] Photoinitiator LAP: 0.3

[0130] The preparation process of the composite membrane is as follows:

[0131] I: Preparation of the surface casting solution: Quaternary ammonium salt chitosan, hydroxyethyl cellulose, and polyethylene glycol borate are added to pure water in a certain mass ratio, dissolved at 55°C, and stirred until homogeneous to form a uniform solution, which is used as the surface casting solution for later use; wherein, the mass concentration of the aqueous solution is 9.5%;

[0132] II: Preparation of the inner layer casting solution: Methacrylated gelatin, methacrylamide carboxymethyl chitosan, polyethylene glycol diacrylate, four-arm polyethylene glycol aldehyde, and photoinitiator LAP are dissolved in water at 45°C and stirred evenly at room temperature to form a solution for use as the inner layer casting solution; wherein, the mass fraction of methacrylated gelatin is 7.5%;

[0133] III: Casting process: The surface casting solution is cast on a casting plate at 82°C at a speed of 2.2 m / min until a film is formed; after heat drying, it is introduced into the second casting device as the casting base film. Atomized oxalic acid solution with a mass concentration of 4% is sprayed onto the surface of the base film until it is wetted. Then, the inner layer casting solution is cast on it at a speed of 3.8 m / min at 88°C, and continuously irradiated with 365 nm wavelength ultraviolet light for 16 min until the inner layer film is formed and fully dried.

[0134] IV: Place the dried film into a stretching device, heat it to 60°C, stretch it in the horizontal direction to 1.22 times the original width and in the vertical direction to 1.35 times the original length, and then introduce it into a hot roller press. The roller spacing is set to be less than 0.02 mm of the film thickness, and the temperature is set to 175°C. After roller pressing, the final composite film is obtained.

[0135] The thickness of the quaternary ammonium salt chitosan / hydroxyethyl cellulose composite layer is 0.14 mm, and the thickness of the methacrylated gelatin / methacrylated carboxymethyl chitosan composite layer is 0.12 mm.

[0136] The degree of substitution of the hydroxyethyl cellulose is 56% based on the proportion of hydroxyl groups in the cellulose.

[0137] The degree of substitution of the quaternary ammonium salt chitosan is calculated as 63% based on the proportion of hydroxyl groups in the chitosan;

[0138] The degree of substitution of the methacrylated gelatin is calculated as 58% based on the proportion of hydroxyl groups in the substituted gelatin;

[0139] The degree of substitution of carboxyl groups in the methacrylamide carboxymethyl chitosan is 42% based on the proportion of hydroxyl groups in the chitosan, and the degree of substitution of methacryloyl groups is 35% based on the proportion of amino groups in the chitosan.

[0140] The molecular weight of the polyethylene glycol borate is 3600.

[0141] The molecular weight of the four-armed polyethylene glycol aldehyde group is 5500.

[0142] The properties of the prepared membrane are shown in Table 1.

[0143] Example 4

[0144] A biodegradable barrier antibacterial moisture-absorbing membrane is composed of a two-layer composite, comprising a quaternary ammonium salt chitosan / hydroxyethyl cellulose composite layer and a methacrylated gelatin / methacrylated carboxymethyl chitosan composite layer. The materials and compositions of the two layers are as follows:

[0145] Quaternary ammonium salt chitosan / hydroxyethyl cellulose composite layer:

[0146] Quaternary ammonium salt chitosan: 100

[0147] Hydroxyethyl cellulose: 28.5

[0148] Polyethylene glycol borate: 7.6

[0149] Methacrylated gelatin / methacrylated carboxymethyl chitosan composite layer:

[0150] Methacrylated gelatin: 100

[0151] Methacrylamide carboxymethyl chitosan: 55.2

[0152] Polyethylene glycol diacrylate: 5.2

[0153] Eight-arm polyethylene glycol aldehyde: 7.2

[0154] Photoinitiator LAP: 0.35

[0155] The preparation process of the composite membrane is as follows:

[0156] I: Preparation of the surface casting solution: Quaternary ammonium salt chitosan, hydroxyethyl cellulose, and polyethylene glycol borate are added to pure water in a certain mass ratio, dissolved at 65°C, and stirred until homogeneous to form a uniform solution, which is used as the surface casting solution for later use; wherein, the mass concentration of the aqueous solution is 11.5%;

[0157] II: Preparation of the inner layer casting solution: Methacrylated gelatin, methacrylamide carboxymethyl chitosan, polyethylene glycol diacrylate, octa-arm polyethylene glycol aldehyde, and photoinitiator LAP are dissolved in water at 50°C and stirred evenly at room temperature to form a solution for use as the inner layer casting solution; wherein, the mass fraction of methacrylated gelatin is 7.0%;

[0158] III: Casting process: The surface casting solution is cast on a casting plate at 86℃ at a speed of 2.8 m / min until a film is formed; after heat drying, it is introduced into the second casting device as the casting base film. Atomized acetic acid solution with a mass concentration of 5% is sprayed onto the surface of the base film until it is wetted. Then, the inner layer casting solution is cast on it at a speed of 2.6 m / min at 84℃, and continuously irradiated with 365nm wavelength ultraviolet light for 18 min until the inner layer film is formed and fully dried.

[0159] IV: Place the dried film into a stretching device, heat it to 45°C, stretch it in the horizontal direction to 1.14 times the original width and in the vertical direction to 1.25 times the original length, and then introduce it into a hot roller press. The roller spacing is set to be less than 0.025 mm of the film thickness, and the temperature is set to 175°C. After roller pressing, the final composite film is obtained.

[0160] The thickness of the quaternary ammonium salt chitosan / hydroxyethyl cellulose composite layer is 0.15 mm, and the thickness of the methacrylated gelatin / methacrylated carboxymethyl chitosan composite layer is 0.14 mm.

[0161] The degree of substitution of the hydroxyethyl cellulose is 72% based on the proportion of hydroxyl groups in the cellulose.

[0162] The degree of substitution of the quaternary ammonium salt chitosan is calculated as 56% based on the proportion of hydroxyl groups in the chitosan;

[0163] The degree of substitution of the methacrylated gelatin is 66% based on the proportion of hydroxyl groups in the substituted gelatin;

[0164] The degree of substitution of carboxymethyl groups in the methacrylamide carboxymethyl chitosan is 32% based on the proportion of hydroxyl groups in the chitosan, and the degree of substitution of methacryloyl groups is 36% based on the proportion of amino groups in the chitosan.

[0165] The molecular weight of the polyethylene glycol borate is 4600.

[0166] The molecular weight of the eight-arm polyethylene glycol aldehyde group is 4000.

[0167] The properties of the prepared membrane are shown in Table 1.

[0168] Table 1. Performance of membrane materials prepared in the examples and comparative examples

[0169] Example 1 Example 2 Example 3 Example 4 Thickness / mm 0.28 0.27 0.26 0.29 Tensile strength / MPa 23.6 21.1 20.6 24.2 Elongation at break / % 286.7 234.2 317.6 203.5 Tear strength (longitudinal / transverse) / MPa 192.7 / 158.3 268.4 / 188.1 156.4 / 129.5 238.6 / 195.2 <![CDATA[O2 permeation rate / cm 3 / (m 3 · 24 hr · MPa)]]> 83.5 66.4 106.4 79.3 <![CDATA[CO2 transmission rate / cm 3 / (m 3 ·24hr·MPa)]]> 54.6 82.7 62.3 78.6 Water absorption rate (12h / 24h) / % 0.28 / 0.53 0.31 / 0.64 0.34 / 0.62 0.24 / 0.64 Antibacterial properties (A / B side) / % 82.5 / 54.6 78.4 / 51.3 89.3 / 54.3 73.6 / 49.7

Claims

1. A biodegradable barrier antibacterial moisture-absorbing membrane, comprising a double-layer cast composite, including a surface layer of quaternary ammonium salt chitosan / hydroxyethyl cellulose composite layer and an inner layer of methacrylated gelatin / methacrylated carboxymethyl chitosan composite layer, the two layers being composed as follows: Quaternary ammonium salt chitosan / hydroxyethyl cellulose composite layer: Quaternary ammonium salt chitosan: 100 Hydroxyethyl cellulose: 15-30 Polyethylene glycol borate: 3.5-8 Methacrylated gelatin / methacrylated carboxymethyl chitosan composite layer: Methacrylated gelatin: 100 Methacrylamide carboxymethyl chitosan: 20-60 Double bond crosslinking agent: 3-6 Macromolecular aldehyde crosslinking agent: 4-8 Water-soluble photoinitiator: 0.2-0.4; Its characteristics also lie in, Its preparation process is as follows: I: Preparation of surface casting solution: Quaternary ammonium salt chitosan, hydroxyethyl cellulose, and polyethylene glycol borate are added to pure water in a certain mass ratio, dissolved and stirred at 50-70℃ to form a homogeneous solution, which is used as the surface casting solution for later use; wherein, the mass concentration of the aqueous solution is between 8-12%. II: Preparation of the inner layer casting solution: Dissolve methacrylated gelatin, methacrylamide carboxymethyl chitosan, double bond crosslinking agent, macromolecular aldehyde crosslinking agent, and photoinitiator in water at 40-60℃, and stir evenly at room temperature to form a solution as the inner layer casting solution for later use; wherein, the mass fraction of methacrylated gelatin is between 4-8%. III: The surface casting solution is cast on a casting plate at 80-90℃ at a speed of 2-4 m / min until a surface film is formed; after the surface film is heat-dried, it is introduced into a second casting device as a casting base film. Atomized weak acid solution is sprayed onto the surface of the casting base film until it is wetted, and then the inner layer casting solution is cast on it at a speed of 2-5 m / min and a temperature of 70-90℃, and continuously irradiated with ultraviolet light of a specific wavelength until the inner layer film is formed and fully dried; IV: Place the dried double-layer film into a stretching device and heat it to between 40-65℃. Stretch it in the transverse direction to between 1.1-1.3 times the original width and in the longitudinal direction to between 1.2-1.4 times the original length. Then, introduce the film into a hot roller press. The roller spacing in the roller press is set to be 0.01-0.03mm smaller than the film thickness, and the temperature is set to 140-180℃. After roller pressing, the final composite film is obtained.

2. The biodegradable barrier antibacterial moisture-absorbing membrane as described in claim 1, characterized in that, The thickness of the quaternary ammonium salt chitosan / hydroxyethyl cellulose composite layer is between 0.1 and 0.2 mm, and the thickness of the methacrylated gelatin / methacrylated carboxymethyl chitosan composite layer is between 0.05 and 0.15 mm.

3. The biodegradable barrier antibacterial moisture-absorbing membrane as described in claim 1, characterized in that, The degree of substitution of the hydroxyethyl cellulose is calculated based on the proportion of hydroxyl groups in the cellulose and ranges from 45% to 80%.

4. The biodegradable barrier antibacterial moisture-absorbing membrane as described in claim 1, characterized in that, The degree of substitution of the quaternary ammonium salt chitosan is calculated based on the proportion of hydroxyl groups in the chitosan and is between 50% and 80%.

5. The biodegradable barrier antibacterial moisture-absorbing membrane as described in claim 1, characterized in that, The degree of substitution of the methacrylated gelatin is calculated based on the proportion of hydroxyl groups in the substituted gelatin, and is between 50% and 70%; the degree of substitution of carboxymethyl groups in the methacryloylated carboxymethyl chitosan is calculated based on the proportion of hydroxyl groups in the chitosan, and is between 30% and 50%; the degree of substitution of methacryloyl groups is calculated based on the proportion of amino groups in the chitosan, and is between 20% and 40%.

6. The biodegradable barrier antibacterial moisture-absorbing membrane as described in claim 1, characterized in that, The molecular weight of the polyethylene glycol borate is between 2000 and 5000.

7. The biodegradable barrier antibacterial moisture-absorbing membrane as described in claim 1, characterized in that, The double bond crosslinking agent is one of N,N-methylenebisacrylamide and polyethylene glycol diacrylate.

8. The biodegradable barrier antibacterial moisture-absorbing membrane as described in claim 1, characterized in that, The macromolecular aldehyde crosslinking agent is a multi-arm polyethylene glycol aldehyde group, including two-arm, four-arm, six-arm, and eight-arm polyethylene glycol aldehyde groups, with a molecular weight between 2000 and 6000.

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