Biodegradable barrier antibacterial moisture absorption film

Abstract

The invention relates to a biodegradable barrier antibacterial moisture absorption film which is composed of two layers, one layer is a quaternary ammonium salt chitosan / hydroxyethyl cellulose composite layer, the other layer is a methacrylic acid esterified gelatin / methacrylated carboxymethyl chitosan composite layer, and the two layers are combined through tape casting and two-way stretching hot pressing treatment. The two layers are tightly combined through reaction; the composite film has good tensile strength, ductility and tear resistance, has good oxygen and carbon dioxide barrier property under a dry condition, also has a good moisture absorption effect, and can be applied to the packaging field with barrier, moisture absorption and antibacterial property requirements.

Description

Technical Field

[0001] The present invention relates to a barrier antibacterial moisture-absorbing film, and particularly to a film material prepared from biomass as a raw material, which has high strength and toughness, gas barrier property, antibacterial property and can absorb moisture to a certain extent. Background Art

[0002] Film materials are extremely widely used and play an important role in fields such as packaging, functional devices, biomedicine, etc. At present, plastic films still occupy an absolute dominant position. Plastic films are prepared from petroleum-based synthetic raw materials, have strong processability, diverse physical property selections, and can adapt to various application scenarios with different requirements. In terms of mechanical properties and barrier properties, plastic film materials represented by PP, PE, PS, BOPP, PVA, PA, EVOH, etc. achieve excellent mechanical properties and water and gas barrier characteristics through the adjustment of formulation, crystallinity, and orientation. Based on the excellent combined processability of plastics, various multilayer composite and multilayer coextruded films have been developed to further broaden their application scope. In food and drug packaging, it is required that the film has good flexibility and mechanical properties, and also has good gas barrier property to ensure the long-term preservation of its contents, which can often be achieved through special materials or multilayer composites in plastic materials. However, due to the non-degradability of plastic materials and the complexity of recycling and reuse, their large-scale use and random disposal often have a certain impact on the environment. Therefore, people hope to use degradable materials for substitution. Biomass materials are the main category of degradable materials, but due to their complex molecular structure and interactions, it is difficult to achieve regular arrangement, and it is often impossible to obtain film products with uniform structure and good barrier property. It is also very difficult to achieve the coordination of various properties by relying on a single biomass material to form a film. For example, polylactic acid films have high strength but poor toughness; although the polybutylene adipate / terephthalate / polylactic acid composite film has good comprehensive mechanical properties, its barrier property cannot meet the requirements.

[0003] According to the natural properties of biomass, some biomass materials can provide strong hydrogen bond interactions and thus produce close binding. If this property can be utilized, the compactness between the molecular structures of the film can be improved, and thus a good barrier effect can be produced. In view of the above idea, the present invention adopts a special double-layer film composite technology. One layer is a fiber-based film layer dissolved and precipitated to provide barrier property and strength, and the other layer is a cross-linked flexible layer to provide toughness. Through the construction of a double-layer degradable layer, combined with multi-dimensional cross-linking and dynamic binding between the two layers, the coordination of the properties between the films is achieved. The orientation of the molecular structure in the film is also promoted through a stretching process, so as to achieve the purpose of good mechanical properties, gas barrier property and antibacterial property. This film can be used in special packaging fields, such as the outer packaging of foods and drugs that require antibacterial and barrier properties. Summary of the Invention

[0004] The object of the present invention is to overcome the defect that biomass film materials are difficult to be compatible with mechanical properties, barrier properties and hygroscopicity, to develop a composite film material mainly composed of degradable materials, to achieve good barrier properties under high strength and toughness under dry conditions, and to provide antibacterial and water absorption functions.

[0005] The object of the present invention is achieved by the following technical solutions:

[0006] A biodegradable barrier antibacterial and moisture-absorbing film is formed by double-layer casting. It includes a surface layer made of a quaternary ammonium salt chitosan / hydroxyethyl cellulose composite layer and a inner layer made of a methacrylated gelatin / methacryloylated carboxymethyl chitosan composite layer. The substances and compositions of the two layers are 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 / methacryloylated carboxymethyl chitosan composite layer: Methacrylated gelatin: 100 Methacryloylated carboxymethyl chitosan: 20 - 60 Double bond crosslinking agent: 3 - 6 Macromolecular aldehyde crosslinking agent: 4 - 8 Water-soluble photoinitiator: 0.2 - 0.4.

[0007] Furthermore, the preparation process of the composite film is as follows: I: Preparation of the surface layer casting solution: Quaternary ammonium salt chitosan, hydroxyethyl cellulose, and polyethylene glycol borate are put into pure water according to the mass ratio, dissolved and stirred evenly at 50 - 70 °C to form a uniform solution, which is used as the surface layer casting solution and reserved; among them, the mass concentration of the aqueous solution is between 8 - 12%; II: Preparation of the inner layer casting solution: Methacrylated gelatin, methacryloylated carboxymethyl chitosan, double bond crosslinking agent, macromolecular aldehyde crosslinking agent, and photoinitiator are dissolved in water at 40 - 60 °C and stirred evenly at room temperature to form a solution as the inner layer casting solution and reserved; among them, the mass fraction of methacrylated gelatin is between 4 - 8%; III: Casting process: The surface layer casting solution is cast on a casting plate at 80 - 90 °C at a speed of 2 - 4 m / min until a film is formed; after heat drying, it is introduced into a second casting device as a casting bottom film. A misty weak acid solution is sprayed on the upper surface of the bottom film until it is wetted, and then the inner layer casting solution is cast on it. Casting is carried out at a speed of 2 - 5 m / min and a temperature of 70 - 90 °C, and ultraviolet light with a specific wavelength is continuously irradiated until the inner layer film is formed and fully dried; IV: Place the dried film into a stretching device, heat it to a temperature between 40 - 65 °C, stretch it to 1.1 - 1.3 times its original width in the horizontal axis direction and 1.2 - 1.4 times its original length in the vertical axis direction, then introduce it into a hot roll press. Set the roll gap to be between 0.01 - 0.03 mm less than the film thickness, set the temperature to 140 - 180 °C, and after roll pressing, export it to obtain the final composite film.

[0008] Furthermore, the roll pressing can be carried out in a single roll pressing, double roll pressing or triple roll pressing manner as required.

[0009] Furthermore, the weak acid solution can be an oxalic acid solution or a hydrochloric acid solution, and the mass concentration of the acid in the acid solution is between 3 - 6%.

[0010] Furthermore, the ultraviolet light irradiation duration for the casting of the inner layer film should be between 10 - 25 minutes.

[0011] Furthermore, the purpose of spraying the atomized weak acid solution on the surface is to slightly dissolve the chitosan in the surface layer film and promote its Schiff base reaction with the aldehyde cross-linking agent in the inner layer casting solution.

[0012] Furthermore, the thickness of the quaternary ammonium chitosan / hydroxyethyl cellulose composite layer is between 0.1 - 0.2 mm, and the thickness of the methacrylated gelatin / methacryloylated carboxymethyl chitosan composite layer is between 0.05 - 0.15 mm.

[0013] Furthermore, the degree of substitution of the hydroxyethyl cellulose, calculated based on the proportion of hydroxyl groups in cellulose, is between 45 - 80%.

[0014] Furthermore, the degree of substitution of the quaternary ammonium chitosan, calculated based on the proportion of hydroxyl groups in chitosan, is between 50 - 80%.

[0015] Furthermore, the degree of substitution of the methacrylated gelatin, calculated based on the proportion of hydroxyl groups in the substituted gelatin, is between 50 - 70%; the degree of substitution of carboxymethyl in the methacryloylated carboxymethyl chitosan, calculated based on the proportion of hydroxyl groups in chitosan, is between 30 - 50%, and the degree of substitution of methacryloyl, calculated based on the proportion of amino groups in chitosan, is between 20 - 40%.

[0016] Furthermore, the molecular structural formula of the methacryloylated carboxymethyl chitosan is as follows:

[0017] Furthermore, the molecular weight of the polyethylene glycol borate is between 2000 - 5000, and its molecular structural formula is as follows:

[0018] Furthermore, the polyethylene glycol borate ester not only acts as a lubricant and stabilizer during the film-forming process to improve the film quality, but also can strengthen the strength and barrier properties of the film through the binding of B-O bonds.

[0019] Furthermore, the double bond crosslinking agent is one of N,N-methylenebisacrylamide and polyethylene glycol diacrylate.

[0020] Furthermore, the macromolecular aldehyde crosslinking agent is multi-arm polyethylene glycol aldehyde, including di-arm, tetra-arm, hexa-arm, and octa-arm polyethylene glycol aldehyde, with a molecular weight between 2000 and 6000, and its molecular structural formula is as follows:

[0021] n is the degree of polymerization of ethylene glycol; x = 2, 4, 6, 8 Furthermore, the macromolecular aldehyde crosslinking agent can react with amino groups to strengthen the binding within and between the films.

[0022] Furthermore, the double bond crosslinking agent is one of N,N-methylenebisacrylamide and polyethylene glycol diacrylate.

[0023] Furthermore, the water-soluble photoinitiator can be photoinitiator 2959 with a maximum absorption wavelength of 328 nm; or LAP photoinitiator with a maximum absorption wavelength of 365 nm.

[0024] Furthermore, when the film is used as a packaging film, generally, the quaternary ammonium salt chitosan / hydroxyethyl cellulose composite layer is used as the contact layer for packaging the contents.

[0025] Furthermore, the film material can be sealed by heat sealing.

[0026] Furthermore, the beneficial effects of the present invention are as follows: The synergy of double-layer biomass composite is adopted. The surface quaternary ammonium salt chitosan / hydroxyethyl cellulose composite layer has good mechanical properties, antibacterial properties, and water absorption; the inner layer methacrylated gelatin / methacryloylated carboxymethyl chitosan composite layer has good strength and barrier properties, and the double layers synergistically strengthen the above properties; A special processing technology is adopted. Spraying a weakly acidic solution on the surface quaternary ammonium salt chitosan / hydroxyethyl cellulose composite layer before casting the inner layer can promote the reaction between aldehyde group substances and amino group substances in the inner layer to strengthen crosslinking and improve strength; at the same time, it can also promote the reaction between aldehyde group substances and the amino groups of chitosan in the surface layer to strengthen the binding between the double layers, thereby realizing performance synergy; The double stretching combined with hot roll pressing technology after film formation is adopted, which is beneficial to the bidirectional orientation of biomass molecules and promotes the formation of hydrogen bonds during this process, which is beneficial to the optimization of various properties.

[0027] Furthermore, the performance of the membrane material is tested as follows: The tensile strength and elongation at break of the membrane are tested according to the standard of GB / T 1040.3-2006 "Plastics - Determination of tensile properties - Part 3: Test conditions for films and sheets". The tear strength of the membrane is tested according to the standard of GB / T 16578.1-2008 "Plastics - Films and sheets - Determination of tear resistance". The impact strength of the membrane is tested according to the standard of GB / T 9639.1-2008 "Plastics - Films and sheets - Determination of impact resistance - Free-falling dart method - Part 1: Staircase method". The carbon dioxide and oxygen barrier properties of the membrane are tested according to GB / T 1038-2000 "Plastics - Films and sheets - Determination of gas permeability - Manometry method". The hygroscopicity of the membrane: Fix the methacrylated gelatin / methacryloylated carboxymethyl chitosan composite layer of the membrane and the flat material such as the target in place, with the quaternary ammonium salt chitosan / hydroxyethyl cellulose composite layer blank facing the space. Control the humidity in the space at 50%, and calculate the change in weight over different times. (Real-time weight - dry film weight) / dry film weight = water absorption rate calculated by weight (%).

[0028] The antibacterial property of the membrane: Test with Escherichia coli. Culture Escherichia coli at a concentration of 10 4 CFU / mL on both surfaces of the prepared membrane. After 1 week, observe the change in the area of the Escherichia coli flora. The antibacterial property is defined as the reduction ratio of the flora area compared to the original area, which can be determined by processing with Image J software. The surface of the quaternary ammonium salt chitosan / hydroxyethyl cellulose composite layer is defined as side A, and the methacrylated gelatin / methacryloylated carboxymethyl chitosan is defined as side B.

[0029] Furthermore, the performance range of the membrane material is as follows: Tensile strength (MPa): 21 - 28; Elongation at break (%): 185 - 350; Transverse tear strength (kN / m): 200 - 300; Longitudinal tear strength (kN / m): 200 - 300; O 2 Transmittance (cm 3 / (m 3 ·24hr·MPa)): 50 - 150; CO 2 Transmittance (cm 3 / (m 3 ·24hr·MPa)): 40 - 100; Water absorption rate at 12h / 24h (%): 0.21 - 0.44 / 0.49 - 0.87; Antibacterial property (A / B side) (%): 67 - 92; 46 - 75. Description of the Drawings

[0030] Figure 1 SEM cross-sectional interface diagram of the film prepared in Example 1; Figure 2 SEM cross-sectional interface diagram of the film prepared in Example 2.

[0031] The exemplary implementation methods of the present invention will be described in detail below. However, these implementation methods are for illustrative purposes only, and the present invention is not limited thereto. Example 1

[0032] A biodegradable barrier antibacterial moisture-absorbing film, which is composed of a double layer composite, as Figure 1 shown, including a quaternary ammonium salt chitosan / hydroxyethyl cellulose composite layer 1 and a methacrylated gelatin / methacryloylated carboxymethyl chitosan composite layer 2. The substances and compositions of the two layers are as follows: Quaternary ammonium salt chitosan / hydroxyethyl cellulose composite layer: Quaternary ammonium salt chitosan: 100 Hydroxyethyl cellulose: 22 Polyethylene glycol borate: 6.5 Methacrylated gelatin / methacryloylated carboxymethyl chitosan composite layer: Methacrylated gelatin: 100 Methacryloylated carboxymethyl chitosan: 45.3 N,N-methylenebisacrylamide: 4.5 Four-arm polyethylene glycol aldehyde group: 7.5 Photoinitiator 2959: 0.25.

[0033] The preparation process of the composite film is as follows: I: Preparation of the surface casting solution: Quaternary ammonium salt chitosan, hydroxyethyl cellulose, and polyethylene glycol borate are added to pure water according to the mass ratio, dissolved and stirred evenly at 65°C to form a homogeneous solution, which is used as the surface casting solution and reserved; among them, the mass concentration of the aqueous solution is 8.5%; II: Preparation of the inner layer casting solution: Methacrylated gelatin, methacryloylated carboxymethyl chitosan, N,N-methylenebisacrylamide, four-arm polyethylene glycol aldehyde group, and photoinitiator 2959 are dissolved in water at 55°C and stirred evenly at room temperature to form a solution as the inner layer casting solution and reserved; among them, the mass fraction of methacrylated gelatin is 5.5%; III: Casting process: Cast the surface casting solution on a casting plate at 85°C at a speed of 2.5 m / min until a film is formed; after heat drying, it is introduced into the second casting device as the casting bottom film. The upper surface of the bottom film is sprayed with an atomized hydrochloric acid solution with a mass concentration of 4% until it is wetted, and then the inner layer casting solution is cast on it. Casting is carried out at 85°C at a speed of 3.2 m / min, and it is continuously irradiated with ultraviolet light at a wavelength of 328 nm for 15 min until the inner layer film is formed and fully dried; IV: Place the dried film into a stretching device, heat it to 55°C, stretch it to 1.15 times the original width in the horizontal axis direction and 1.25 times the original length in the vertical axis direction, introduce it into hot roll pressing, set the roller spacing to less than 0.02 mm of the film thickness, set the temperature to 160°C, and export it after roll pressing to obtain the final composite film.

[0034] The thickness of the quaternary ammonium salt chitosan / hydroxyethyl cellulose composite layer is 0.16 mm, and the thickness of the methacrylated gelatin / methacryloylated carboxymethyl chitosan composite layer is 0.12 mm.

[0035] The degree of substitution of the hydroxyethyl cellulose is 64% calculated according to the proportion of hydroxyl groups in cellulose; The degree of substitution of the quaternary ammonium salt chitosan is 72% calculated according to the proportion of hydroxyl groups in chitosan; The degree of substitution of the methacrylated gelatin is 55% calculated according to the proportion of hydroxyl groups in the substituted gelatin; The degree of substitution of carboxymethyl in the methacryloylated carboxymethyl chitosan is 42% calculated according to the proportion of hydroxyl groups in chitosan, and the degree of substitution of methacryloyl is 28% calculated according to the proportion of amino groups in chitosan.

[0036] The molecular weight of the polyethylene glycol borate is 4200.

[0037] The molecular weight of the four-arm polyethylene glycol aldehyde is 4000.

[0038] From Figure 1 It can be seen that due to the addition of more four-arm polyethylene glycol aldehyde, the reaction between the two layers increases, and the interface between the two layers is very blurred.

[0039] The performance of the prepared film is shown in Table 1.

[0040] Example 2 A biodegradable barrier antibacterial and moisture-absorbing film is composed of a double layer composite, as Figure 2 shown, including a quaternary ammonium salt chitosan / hydroxyethyl cellulose composite layer 1' and a methacrylated gelatin / methacryloylated carboxymethyl chitosan composite layer 2'. The substances and compositions of the two layers are as follows: Quaternary ammonium salt chitosan / hydroxyethyl cellulose composite layer: Quaternary ammonium chitosan: 100 Hydroxyethyl cellulose: 28 Polyethylene glycol borate: 4.2 Methacrylated gelatin / methacryloylated carboxymethyl chitosan composite layer: Methacrylated gelatin: 100 Methacryloylated carboxymethyl chitosan: 28.6 N,N - methylenebisacrylamide: 5.8 Six - armed polyethylene glycol aldehyde: 4.2 Photoinitiator 2959: 0.2 The preparation process of the composite film is as follows: I: Preparation of the surface casting solution: Quaternary ammonium chitosan, hydroxyethyl cellulose, and polyethylene glycol borate are put into pure water according to the mass ratio, dissolved at 60 °C, and stirred evenly to form a uniform solution, which is used as the surface casting solution and reserved; among them, the mass concentration of the aqueous solution is 10.5%; II: Preparation of the inner - layer casting solution: Methacrylated gelatin, methacryloylated carboxymethyl chitosan, N,N - methylenebisacrylamide, six - armed polyethylene glycol aldehyde, and photoinitiator 2959 are dissolved in water at 50 °C and stirred evenly at room temperature to form a solution as the inner - layer casting solution and reserved; among them, the mass fraction of methacrylated gelatin is 6.5%; III: Casting process: The surface casting solution is cast on an 88 °C casting plate 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. An atomized oxalic acid solution with a mass concentration of 5% is sprayed on the upper surface of the base film until it is wetted, and then the inner - layer casting solution is cast on it. It is cast at a speed of 4.4 m / min at 75 °C and continuously irradiated with ultraviolet light at a wavelength of 328 nm for 20 min until the inner - layer film is formed and fully dried; IV: The dried film is placed in a stretching device, heated to 50 °C, stretched to 1.25 times the original width in the horizontal axis direction and 1.3 times the original length in the vertical axis direction, introduced into a hot roll - pressing process, the roller spacing is set to be less than 0.025 mm of the film thickness, the temperature is set to 170 °C, and the final composite film is obtained after roll - pressing and exporting.

[0041] The thickness of the quaternary ammonium chitosan / hydroxyethyl cellulose composite layer is 0.18 mm, and the thickness of the methacrylated gelatin / methacryloylated carboxymethyl chitosan composite layer is 0.09 mm.

[0042] The degree of substitution of the hydroxyethyl cellulose is 68% calculated according to the proportion of hydroxyl groups in cellulose.

[0043] The degree of substitution of the quaternary ammonium chitosan is 55% calculated according to the proportion of hydroxyl groups in chitosan.

[0044] The degree of substitution of the methacrylated gelatin is 64% calculated according to the proportion of hydroxyl groups in the substituted gelatin; The degree of substitution of carboxymethyl in the methacryloylated carboxymethyl chitosan is 36% calculated according to the proportion of hydroxyl groups in chitosan, and the degree of substitution of methacryloyl group is 32% calculated according to the proportion of amino groups in chitosan.

[0045] The molecular weight of the polyethylene glycol borate is 3200.

[0046] The molecular weight of the six-armed polyethylene glycol aldehyde group is 5000.

[0047] From Figure 2 It can be seen that due to the addition of a small amount of six-armed polyethylene glycol aldehyde group, the reaction between the two layers is less, and the interface between the two layers is clear.

[0048] The properties of the prepared membrane are shown in Table 1.

[0049] Example 3 A biodegradable barrier antibacterial and moisture-absorbing membrane is composed of a double layer, including a quaternary ammonium chitosan / hydroxyethyl cellulose composite layer and a methacrylated gelatin / methacryloylated carboxymethyl chitosan composite layer. The substances and compositions of the two layers are as follows: Quaternary ammonium chitosan / hydroxyethyl cellulose composite layer: Quaternary ammonium chitosan: 100 Hydroxyethyl cellulose: 16.5 Polyethylene glycol borate: 5.3 Methacrylated gelatin / methacryloylated carboxymethyl chitosan composite layer: Methacrylated gelatin: 100 Methacryloylated carboxymethyl chitosan: 33.7 Polyethylene glycol diacrylate: 4.8 Four-armed polyethylene glycol aldehyde group: 5.7 Photoinitiator LAP: 0.3 The preparation process of the composite membrane is as follows: I: Preparation of the surface casting solution: Put quaternary ammonium chitosan, hydroxyethyl cellulose, and polyethylene glycol borate into pure water according to the mass ratio, dissolve and stir evenly at 55 °C to form a uniform solution as the surface casting solution for standby; among them, the mass concentration of the aqueous solution is 9.5%; II: Preparation of the inner casting solution: Dissolve methacrylated gelatin, methacryloylated carboxymethyl chitosan, polyethylene glycol diacrylate, tetra-arm polyethylene glycol aldehyde group, and photoinitiator LAP in water at 45 °C, and stir evenly at room temperature to form a solution as the inner casting solution for standby; among them, the mass fraction of methacrylated gelatin is 7.5%; III: Casting process: Cast the surface casting solution on an 82 °C casting plate 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. Spray atomized oxalic acid solution with a mass concentration of 4% on the upper surface of the base film until it is wetted, and then cast the inner casting solution on it. Cast at a speed of 3.8 m / min at 88 °C, and continuously irradiate with ultraviolet light at a wavelength of 365 nm for 16 min until the inner layer film is formed and fully dried; IV: Place the dried film into a stretching device, heat it to 60 °C, stretch it to 1.22 times the original width in the horizontal axis direction and 1.35 times the original length in the vertical axis direction, introduce it into hot rolling, set the roller spacing to less than 0.02 mm of the film thickness, set the temperature to 175 °C, and export it after rolling to obtain the final composite film.

[0050] The thickness of the quaternary ammonium salt chitosan / hydroxyethyl cellulose composite layer is 0.14 mm, and the thickness of the methacrylated gelatin / methacryloylated carboxymethyl chitosan composite layer is 0.12 mm.

[0051] The degree of substitution of the hydroxyethyl cellulose is 56% calculated according to the proportion of hydroxyl groups in cellulose; The degree of substitution of the quaternary ammonium salt chitosan is 63% calculated according to the proportion of hydroxyl groups in chitosan; The degree of substitution of the methacrylated gelatin is 58% calculated according to the proportion of hydroxyl groups in the substituted gelatin; The degree of substitution of carboxymethyl in the methacryloylated carboxymethyl chitosan is 42% calculated according to the proportion of hydroxyl groups in chitosan, and the degree of substitution of methacryloyl group is 35% calculated according to the proportion of amino groups in chitosan.

[0052] The molecular weight of the polyethylene glycol borate is 3600.

[0053] The molecular weight of the tetra-arm polyethylene glycol aldehyde group is 5500.

[0054] The performance of the prepared film is shown in Table 1.

[0055] Example 4 A biodegradable barrier antibacterial and moisture-absorbing film is composed of a double layer composite, including a quaternary ammonium salt chitosan / hydroxyethyl cellulose composite layer and a methacrylated gelatin / methacryloylated carboxymethyl chitosan composite layer. The substances and compositions of the two layers are as follows: Quaternary ammonium chitosan / hydroxyethyl cellulose composite layer: Quaternary ammonium chitosan: 100 Hydroxyethyl cellulose: 28.5 Polyethylene glycol borate: 7.6 Methacrylated gelatin / methacryloylated carboxymethyl chitosan composite layer: Methacrylated gelatin: 100 Methacryloylated carboxymethyl chitosan: 55.2 Polyethylene glycol diacrylate: 5.2 Octa-arm polyethylene glycol aldehyde group: 7.2 Photoinitiator LAP: 0.35 The preparation process of the composite film is as follows: I: Preparation of the surface casting solution: Quaternary ammonium chitosan, hydroxyethyl cellulose, and polyethylene glycol borate are put into pure water according to the mass ratio, dissolved at 65 °C, and stirred evenly to form a homogeneous solution, which is used as the surface casting solution and reserved; among them, the mass concentration of the aqueous solution is 11.5%; II: Preparation of the inner layer casting solution: Methacrylated gelatin, methacryloylated carboxymethyl chitosan, polyethylene glycol diacrylate, octa-arm polyethylene glycol aldehyde group, and photoinitiator LAP are dissolved in water at 50 °C and stirred evenly at room temperature to form a solution as the inner layer casting solution and reserved; among them, the mass fraction of methacrylated gelatin is 7.0%; III: Casting process: The surface casting solution is cast on an 86 °C casting plate 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 bottom film. The upper surface of the bottom film is sprayed with an atomized acetic acid solution with a mass concentration of 5% until it is wetted, and then the inner layer casting solution is cast on it. It is cast at a speed of 2.6 m / min at 84 °C and continuously irradiated with ultraviolet light with a wavelength of 365 nm for 18 min until the inner layer film is formed and fully dried; IV: The dried film is placed in a stretching device, heated to 45 °C, stretched to 1.14 times the original width in the horizontal axis direction and 1.25 times the original length in the vertical axis direction, introduced into a hot roll press, the roll shaft spacing is set to be less than 0.025 mm of the film thickness, the temperature is set to 175 °C, and the final composite film is obtained after roll pressing and exporting.

[0056] The thickness of the quaternary ammonium chitosan / hydroxyethyl cellulose composite layer is 0.15 mm, and the thickness of the methacrylated gelatin / methacryloylated carboxymethyl chitosan composite layer is 0.14 mm.

[0057] The degree of substitution of the hydroxyethyl cellulose is calculated as 72% according to the proportion of hydroxyl groups in cellulose; The degree of substitution of the quaternary ammonium chitosan is 56% calculated based on the proportion of hydroxyl groups in chitosan; The degree of substitution of the methacrylated gelatin is 66% calculated based on the proportion of hydroxyl groups in the substituted gelatin; The degree of substitution of carboxymethyl in the methacryloylated carboxymethyl chitosan is 32% calculated based on the proportion of hydroxyl groups in chitosan, and the degree of substitution of methacryloyl group is 36% calculated based on the proportion of amino groups in chitosan.

[0058] The molecular weight of the polyethylene glycol borate is 4600.

[0059] The molecular weight of the octa-arm polyethylene glycol aldehyde is 4000.

[0060] The properties of the prepared membrane are shown in Table 1.

[0061] Table 1. Properties of the membrane materials prepared in the examples and comparative examples 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[O 2 Transmittance / cm 3 / (m 3 ·24hr·MPa)]]> 83.5 66.4 106.4 79.3 <![CDATA[CO 2 Transmittance / 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 property (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 hygroscopic film, which is formed by a double-layer cast composite, including a quaternary ammonium salt chitosan / hydroxyethyl cellulose composite layer as a surface layer, and a methacrylated gelatin / methacrylylated carboxymethyl chitosan composite layer as an inner layer, and the materials and composition of the two layers are 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 Methacryloyl carboxymethyl chitosan: 20-60 Double bond crosslinker: 3-6 Macromolecular aldehyde crosslinker: 4-8 Water-soluble photoinitiator: 0.2-0.

4.

2. The biodegradable barrier antibacterial film according to claim 1, characterized in that: The preparation process is as follows: I: Preparation of surface casting liquid: put quaternary ammonium salt chitosan, hydroxyethyl cellulose and polyethylene glycol borate into pure water according to the mass ratio, dissolve and stir at 50-70°C to form a uniform solution, which is used as the surface casting liquid for standby use; wherein the mass concentration of the aqueous solution is between 8-12%; II: Preparation of inner layer casting liquid: dissolve methacrylated gelatin, methacrylated carboxymethyl chitosan, double bond crosslinker, macromolecular aldehyde crosslinker and photoinitiator in water at 40-60°C, stir evenly at room temperature to form a solution as inner layer casting liquid for standby use; wherein the mass fraction of methacrylated gelatin is between 4-8%; III: Casting process: Cast the surface casting liquid on a casting plate at 80-90℃ at a speed of 2-4m / min until a film is formed; after thermal drying, introduce the second casting device as a casting bottom film, spray atomized weak acid solution on the upper surface of the bottom film until it is wet, and then cast the inner layer casting liquid on it at a speed of 2-5m / min and a temperature of 70-90℃, and continue to irradiate with ultraviolet light of a specific wavelength until the inner layer film is formed and fully dried; IV: Place the dried double-layer film in a stretching device, heat it to 40-65°C, stretch it in the transverse direction to 1.1-1.3 times of the original width, stretch it in the longitudinal direction to 1.2-1.4 of the original length, and introduce it into hot rolling. The roller spacing is set to be less than 0.01-0.03mm of the film thickness, the temperature is set to 140-180°C, and the final composite film is obtained after rolling.

3. The biodegradable barrier antibacterial film according to claim 1, characterized in that: 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 / methacrylylated carboxymethyl chitosan composite layer is between 0.05-0.15 mm.

4. The biodegradable barrier antibacterial film according to claim 1, characterized in that: The degree of substitution of the hydroxyethyl cellulose is between 45% and 80% calculated based on the proportion of hydroxyl groups in cellulose.

5. The biodegradable barrier antibacterial film according to claim 1, characterized in that: The degree of substitution of the quaternary ammonium salt chitosan is between 50-80% calculated based on the proportion of hydroxyl groups in the chitosan.

6. The biodegradable barrier antibacterial film according to claim 1, characterized in that: The degree of substitution of the methacrylated gelatin is between 50-70% calculated based on the proportion of hydroxyl groups in the substituted gelatin; the degree of substitution of the carboxyl group in the methacryloyl carboxymethyl chitosan is between 30-50% calculated based on the proportion of hydroxyl groups in the chitosan, and the degree of substitution of the methacryloyl group is between 20-40% calculated based on the proportion of amino groups in the chitosan.

7. The biodegradable barrier antibacterial film according to claim 1, characterized in that: The molecular weight of the polyethylene glycol borate is between 2000-5000.

8. The biodegradable barrier antibacterial film according to claim 1, characterized in that: The double bond cross-linking agent is one of N,N-methylenebisacrylamide and polyethylene glycol diacrylate.

9. The biodegradable barrier antibacterial film according to claim 1, characterized in that: The macromolecular aldehyde cross-linking agent is a multi-arm polyethylene glycol aldehyde, including two-arm, four-arm, six-arm and eight-arm polyethylene glycol aldehydes, and the molecular weight thereof is between 2000-6000.

Images