A method for preparing a biodegradable film doped with a photosensitizer

Abstract

The present application relates to mulching film preparation technical field, specifically to a kind of preparation method of biodegradable film doped with photosensitizer, the structure of the biodegradable film includes base film, titanium dioxide layer and chitosan layer, the component of the biodegradable film includes polyethylene, sodium glutamate, iron phthalocyanine, titanium dioxide, silver phosphate, chitosan, toughening agent and reinforcing agent.Compared with prior art, the present application improves the interfacial adhesion of sodium glutamate, iron phthalocyanine and modified polyethylene matrix by modifying polyethylene, promotes effective stress transfer, realizes the improvement of tensile strength, and adds iron phthalocyanine and silver phosphate in the component of biodegradable film base film to improve the speed of thin film photo-oxygen degradation, the base film in biodegradable film adds sodium glutamate and chitosan layer as biodegradation initiator, promotes field microorganism to accelerate the degradation of film, and the combination of photodegradation and microbial degradation accelerates the degradation of mulching film.

Description

Technical Field

[0001] This invention relates to the field of mulch film preparation technology, and more specifically to a method for preparing a biodegradable film doped with a photosensitizer. Background Technology

[0002] Ordinary polyethylene mulch film is difficult to degrade and recycle. Currently, the recycling rate of waste mulch film is less than 30%. The mulch film remaining in the topsoil layer accumulates more and more, forming serious "white pollution." Studies have shown that crop mulching for 7-10 years can cause serious farmland pollution, leading to a 10%-23% reduction in cotton yield, a 10%-15% reduction in peanut yield, a 10%-21% reduction in corn yield, a 15%-30% reduction in potato yield, and a 15%-59% reduction in vegetable yield, causing serious damage to soil structure and crop growth and development.

[0003] To address the environmental pollution and crop yield impact of ordinary polyethylene film, a number of biodegradable films have been developed. However, existing biodegradable films have insufficient mechanical properties, particularly poor tensile strength and puncture resistance, which are insufficient to meet the requirements of mechanized laying and field operations. Summary of the Invention

[0004] This invention provides a method for preparing a biodegradable film doped with a photosensitizer, aiming to solve the problems of poor tensile strength and puncture resistance, and the limited degradation mode of existing biodegradable films.

[0005] To achieve the above objectives, the present invention provides a biodegradable film doped with a photosensitizer. The structure of the biodegradable film includes a base film, a titanium dioxide layer, and a chitosan layer. The components of the biodegradable film include polyethylene, monosodium glutamate, iron phthalocyanine, titanium dioxide, silver phosphate, chitosan, dispersant, reinforcing agent, and toughening agent.

[0006] Preferably, in the above technical solution, the weight ratio of polyethylene to monosodium glutamate is 80:20.

[0007] Preferably, in the above technical solution, the amount of phthalocyanine iron added is 0.5-1% of the total amount of base film raw materials, the amount of silver phosphate added is 0.3-0.8% of the total amount of base film raw materials, and the amount of dispersant added is 0.5-0.8% of the total amount of base film raw materials.

[0008] According to the above technical solution, silver phosphate and iron phthalocyanine form an "organic-inorganic" synergistic effect, which broadens the spectral response range and improves the degradation efficiency.

[0009] A method for preparing a biodegradable thin film doped with a photosensitizer, characterized in that the preparation method comprises: S1, the composite masterbatch and polyethylene particles are mixed in a weight ratio and blow-molded, cooled and shaped, and then rolled up to obtain a base film. One side of the base film is treated with a roll-to-roll corona treatment machine to obtain a corona-treated base film. S2, TiO2 powder is dissolved in Tris buffer to prepare a suspension, 3-aminopropyltriethoxysilane is added to prepare a mixture, dopamine hydrochloride is dissolved in Tris buffer to obtain a dopamine solution, and the mixture and the dopamine solution are mixed to obtain an impregnation solution. S3, the impregnation solution is dipped onto the treated surface of the base film after corona treatment by dip coating, the film is taken out and rinsed with a large amount of deionized water, and dried for 2-4 hours; S4. Chitosan powder is slowly added to a 1% acetic acid solution and continuously magnetically stirred at room temperature until a clear and transparent viscous solution is formed. The viscous solution is then coated onto the surface of the film, dried, rinsed with deionized water, and dried again to obtain a biodegradable film.

[0010] Preferably, in the above technical solution, the modification method of the modified polyethylene particles is as follows: maleic anhydride and initiator are dissolved in a small amount of acetone to obtain a modifier, the modifier is mixed with polyethylene particles at high speed, the screw speed of the twin-screw extruder is 150-200 rpm, the extruded strip is cooled in a water tank, and then the modified polyethylene particles are produced by a pelletizer.

[0011] According to the above technical solution, by grafting maleic anhydride onto polyethylene, the modified polyethylene matrix is ​​more uniformly dispersed in the phthalocyanine iron-based film, thus solving the problem of decreased film physical properties such as tensile strength and puncture resistance caused by the agglomeration of existing fillers or components.

[0012] Preferably, in the above technical solution, the amount of maleic anhydride is 1-5% of the mass of polyethylene particles, and the amount of initiator is 5-10% of the mass of maleic anhydride.

[0013] Preferably, in the above technical solution, the preparation method of the composite masterbatch is as follows: modified polyethylene particles, reinforcing agent, toughening agent, dispersant, monosodium glutamate powder, ferrophthalocyanine, and silver phosphate are melt-blended by a twin-screw extruder, wherein the screw speed of the twin-screw extruder is 150-200 rpm, and the extruded strip is cooled in a water tank and then pelletized by a pelletizer into composite masterbatch.

[0014] Preferably, in the above technical solution, the weight ratio of the modified polyethylene particles to the sodium glutamate powder is 80:20.

[0015] Preferably, in the above technical solution, the amount of phthalocyanine iron added is 0.5-1% of the total amount of base film raw materials, the amount of silver phosphate added is 0.3-0.8% of the total amount of base film raw materials, and the amount of dispersant added is 0.5-0.8% of the total amount of base film raw materials.

[0016] Preferably, in the above technical solution, the blow-inflation ratio of the blow molding is 2.5-3.0.

[0017] Preferably, in the above technical solution, the composite masterbatch and polyethylene particles are in a weight ratio of 15-20:85.

[0018] Preferably, in the above technical solution, the thickness of the base film is controlled at 35±5μm.

[0019] Compared with the prior art, the beneficial effects of the present invention are as follows: (1) Adding sodium glutamate, iron phthalocyanine and silver phosphate to the base film, under natural light irradiation, the base film absorbs light and has the ability to oxidize and decompose, which accelerates the photo-oxidative degradation of the film. Sodium glutamate is a high-quality carbon and nitrogen source, and it is a biodegradation initiator in the base film, which promotes the accelerated biodegradation of the base film. Chitosan coating is used as a biodegradation initiator to promote the accelerated degradation of the film by microorganisms. (2) By using maleic anhydride grafting to modify polyethylene, the interfacial bonding force between sodium glutamate, iron phthalocyanine and polyethylene matrix is ​​improved, stress is effectively transferred, and tensile strength is improved, thus solving the defects of poor tensile strength and puncture resistance of existing biodegradable films and ordinary polyethylene films. (3) During the blow molding process, bidirectional stretching is used to straighten the randomly curled molecules and make them oriented, which improves the performance of the base film. At the same time, the surface of the stretched film is smoother and more uniform, which makes the corona treatment effect better. Attached Figure Description

[0020] The realization of the objective, functional features and advantages of the present invention will be further explained in conjunction with the embodiments and with reference to the accompanying drawings.

[0021] Figure 1 This is a graph showing the effect of the toughening agent and reinforcing agent of the base film on the tensile strength of the base film in this invention; Figure 2 This is a graph showing the effect of toughening agents and reinforcing agents on the elongation at break of the base film; Figure 3 This is a graph showing the relationship between the thickness of the present invention and the oxygen permeability. Figure 4 This is a picture showing the field application of the film of this invention in a high-sugar sugarcane base in Xingbin District, Laibin City; Figure 5 This is a diagram showing the molecular arrangement of the present invention before and after biaxial stretching. Detailed Implementation

[0022] The technical solutions in the embodiments of this invention are clearly and completely described. Obviously, the described embodiments are only a part of the embodiments of this invention, and not all of them. Based on the embodiments of this invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this invention.

[0023] To investigate the effects of toughening agents and reinforcing agents on the tensile strength of the base film, the following addition configurations of toughening agents and reinforcing agents were designed: A —— —— B 1.05 kg of 3% polyolefin elastomer —— C 1.05 kg of 3% polyolefin elastomer 1.05 kg of 3% talc D 1.75 kg of 5% polyolefin elastomer 1.05 kg of 3% talc F 3.5 kg of 10% polyolefin elastomer 1.75 kg of 5% talc The base film is prepared as follows: 4 kg of modified polyethylene granules, toughening agent, reinforcing agent, 1 kg of monosodium glutamate powder, 175 g of phthalocyanine iron, 105 g of silver phosphate, and 175 g of ethylene bis-stearamide are melt-blended using a twin-screw extruder with a screw speed of 150-200 rpm. The extruded strip is cooled in a water bath and then pelletized into composite masterbatch by a pelletizer. 5.2 kg of the composite masterbatch is mixed with 29.8 kg of low-density polyethylene granules and blow-molded at a blow-up ratio of 2.5-3.0. After cooling and setting, the mixture is wound up to obtain the base film. The modification method of the modified polyethylene granules is as follows: 50g of maleic anhydride and 2.5g of benzoyl peroxide are dissolved in 200mL of acetone to obtain a modifier. The modifier is mixed with 5kg of polyethylene granules by high-speed stirring. The extruded strip is cooled in a water tank and then pelletized into modified polyethylene granules by a pelletizer.

[0024] The base films corresponding to A, B, C, D, and F are base film 1, base film 2, base film 3, base film 4, and base film 5, respectively. The tensile strength of these five base films was tested according to the method in GB / T 1040.3-2006, and the results are as follows: Figure 1 As shown.

[0025] The tensile strength of base film 5 is the best. The reason why the tensile strength of base film 2 is lower than that of base film 1 may be that the addition of polyolefin elastomer will form a soft "island structure" in the PE matrix, which will greatly improve the impact toughness, but will lead to a decrease in tensile strength.

[0026] Compared to base film 2, the reason why the tensile strength of base film 3 is improved by adding talc may be that the structure of talc forms physical cross-linking points with the PE matrix, which hinders the movement of molecular chains, overcomes the negative effect of polyolefin elastomer on tensile strength, and thus improves tensile strength.

[0027] The tensile strength of base film 4 decreased compared to base film 3, which may be due to the amount of reinforcing agent affecting the tensile strength.

[0028] The base films corresponding to A, B, C, D, and F are base film 1, base film 2, base film 3, base film 4, and base film 5, respectively. The elongation at break results for these five base films are as follows: Figure 2 As shown.

[0029] Combination Figure 1 and Figure 2 The base film prepared with 3-5% polyolefin elastomer and 3% talc has the most suitable toughening and strengthening effect, which is the preparation for obtaining a base film of a certain thickness.

[0030] To investigate the relationship between base film thickness and oxygen permeability, the base film was prepared as follows: 4 kg of modified polyethylene granules, 1.75 kg of polyolefin elastomer, 1.05 kg of talc, 1 kg of monosodium glutamate powder, 17.5 g of phthalocyanine iron, and 15 g of silver phosphate were melt-blended using a twin-screw extruder with a screw speed of 150-200 rpm. The extruded strip was cooled in a water bath and then pelletized into composite masterbatch by a pelletizer. 5.3 kg of the composite masterbatch was mixed with 29.8 kg of low-density polyethylene granules and blow-molded at a blow-up ratio of 2.5-3.0, controlling the base film thickness within a preset range. After cooling and setting, the film was wound up to obtain the base film. The modification method of the modified polyethylene granules is as follows: 50g of maleic anhydride and 2.5g of benzoyl peroxide are dissolved in 200mL of acetone to obtain a modifier. The modifier is then mixed with 5kg of polyethylene granules by high-speed stirring. The screw speed of the twin-screw extruder is 150-200rpm. After the extruded strip is cooled in a water tank, it is pelletized into modified polyethylene granules by a pelletizer.

[0031] By adjusting the traction speed to control the thickness of the base film, base films with thicknesses of 20μm, 22μm, 25μm, and 35μm were obtained. These four base films were then tested using a VAC-V2 differential pressure gas permeation meter according to GB / T1038-2000, the test method for gas permeability of thin films (differential pressure method). The results are shown in Table 1 and... Figure 2 As shown.

[0032] Table 1. Trend of the relationship between base film thickness and oxygen permeability <![CDATA[Oxygen permeability (cm 3 / (m 2 ·24 h·0.1 MPa)]]> 927.603 813.071 701.184 657.825 483.639 The experimental results show that as the thickness of the base film increases, the oxygen permeability of the base film decreases significantly. When the thickness is around 35 μm, the oxygen permeability is slightly high, which may result in a lower heat preservation effect than the base film with a thickness of 40 μm or 50 μm. Therefore, this application adds a titanium dioxide layer and a chitosan layer on the basis of the base film to reduce the oxygen permeability and enhance its heat preservation effect. Example 1

[0033] A method for preparing a biodegradable thin film doped with a photosensitizer, the method comprising: S1, modified polyethylene granules, toughening agent, reinforcing agent, monosodium glutamate powder, dispersant, phthalocyanine iron, and silver phosphate are melt-blended using a twin-screw extruder. The screw speed of the twin-screw extruder is 150-200 rpm. The weight ratio of modified polyethylene granules to monosodium glutamate powder is 80:20. The amount of phthalocyanine iron added is 0.5-1% of the total amount of base film raw materials, the amount of silver phosphate added is 0.3-0.8% of the total amount of base film raw materials, and the amount of dispersant added is 0% of the total amount of base film raw materials. 5-0.8% of the extruded strip is cooled in a water tank and then pelletized into composite masterbatch by a pelletizer. The composite masterbatch is mixed with low-density polyethylene granules at a weight ratio of 15:85 and blow-molded with a blow-up ratio of 2.5-3.0, controlling the base film thickness at 35±5μm. After cooling and setting, it is wound up to obtain the base film. One side of the base film is treated with a roll-to-roll corona treatment machine to obtain a corona-treated base film. The corona treatment promotes the bonding of silver particles and titanium dioxide in the impregnation solution to the surface of the base film. The modification method of the modified polyethylene particles is as follows: maleic anhydride (1-5% of the mass of the polyethylene particles) and initiator (5-10% of the mass of the maleic anhydride) are dissolved in a small amount of acetone to obtain a modifier. The modifier is then mixed with the polyethylene particles by high-speed stirring. The screw speed of the twin-screw extruder is 150-200 rpm. After the extruded strip is cooled in a water tank, it is pelletized into modified polyethylene particles by a pelletizer. S2, 20g TiO2 powder was added to 500mL Tris buffer and ultrasonically dispersed for 30 minutes under ice-water bath conditions until a uniform suspension was formed. 5.0mL 3-aminopropyltriethoxysilane was added and magnetic stirring was continued for 30 minutes to obtain a mixture. 2.0g dopamine hydrochloride was dissolved in the remaining 500mL Tris buffer to obtain a dopamine solution. The mixture and the dopamine solution were mixed to obtain an impregnation solution. S3, the impregnation solution is dipped onto the treated surface of the base film after corona treatment by dip coating, the film is taken out and rinsed with a large amount of deionized water, and then dried at 60±2℃ for 2-4 hours; S4. Slowly add 10.0g of chitosan powder to 1000mL of 1% acetic acid solution and continuously stir magnetically at room temperature until a clear and transparent viscous solution is formed. Coat the viscous solution onto the surface of the film, dry at 40-50℃, rinse with deionized water, and dry to obtain a biodegradable film. Example 2

[0034] A method for preparing a biodegradable thin film doped with a photosensitizer, the method comprising: S1, 8 kg of modified polyethylene granules, 3.5 kg of polyolefin elastomer, 2.1 kg of talc powder, 2 kg of monosodium glutamate powder, 350 g of phthalocyanine iron, 210 g of silver phosphate, and 350 g of ethylene bis-stearamide are melt-blended using a twin-screw extruder with a screw speed of 150-200 rpm. The extruded strip is cooled in a water bath and then pelletized into composite masterbatch by a pelletizer. 10.5 kg of the composite masterbatch is mixed with 59.5 kg of low-density polyethylene granules and blow-molded at a blow-up ratio of 2.5-3.0, controlling the base film thickness at 35±5 μm. After cooling and setting, the film is wound up to obtain a base film. One side of the base film is treated with a roll-to-roll corona treatment machine to obtain a corona-treated base film. The modification method of the modified polyethylene particles is as follows: 100g of maleic anhydride and 5g of benzoyl peroxide are dissolved in 500mL of acetone to obtain a modifier. The modifier is mixed with 10kg of polyethylene particles at high speed. The screw speed of the twin-screw extruder is 150-200rpm. After the extruded strip is cooled in a water tank, it is pelletized into modified polyethylene particles by a pelletizer. S2, 20g TiO2 powder was added to 500mL Tris buffer and ultrasonically dispersed for 30 minutes under ice-water bath conditions until a uniform suspension was formed. 5.0mL 3-aminopropyltriethoxysilane was added and magnetic stirring was continued for 30 minutes to obtain a mixture. 2.0g dopamine hydrochloride was dissolved in the remaining 500mL Tris buffer to obtain a dopamine solution. The mixture and the dopamine solution were mixed to obtain an impregnation solution. S3, the impregnation solution is dipped onto the treated surface of the base film after corona treatment by dip coating, the film is taken out and rinsed with a large amount of deionized water, and then dried at 60±2℃ until it is dry; S4. 10.0 g of chitosan powder was slowly added to 1000 mL of 1% acetic acid solution and continuously stirred magnetically at room temperature until a clear and transparent viscous solution was formed. The viscous solution was coated on the surface of the film, dried at 50±5℃, rinsed with deionized water, and dried to obtain biodegradable film 1.

[0035] Comparative Example 1 A method for preparing a biodegradable thin film doped with a photosensitizer, the method comprising: S1, mix 7kg of low-density polyethylene granules and blow mold them with a blow-up ratio of 2.5-3.0, control the thickness of the base film at 35±5μm, cool and set it, and then roll it up to obtain the base film. Use a roll-to-roll corona treatment machine to treat one side of the base film to obtain the corona-treated base film. S2, add 2g TiO2 powder to 50mL Tris buffer, and sonicate for 30 minutes under ice-water bath conditions until a uniform suspension is formed. Add 0.5mL 3-aminopropyltriethoxysilane and continue magnetic stirring for 30 minutes to obtain a mixture. Dissolve 0.2g dopamine hydrochloride in the remaining 50mL Tris buffer to obtain a dopamine solution. Mix the mixture with the dopamine solution to obtain an impregnation solution. S3, the impregnation solution is dipped onto the treated surface of the base film after corona treatment by dip coating, the film is taken out and rinsed with a large amount of deionized water, and then dried at 60±2℃; S4. Slowly add 1g of chitosan powder to 100mL of 1% acetic acid solution and continuously stir magnetically at room temperature until a clear and transparent viscous solution is formed. Coat the viscous solution onto the surface of the film, dry at 505℃, rinse with deionized water, and dry to obtain film 1.

[0036] Comparative Example 2 A method for preparing a biodegradable thin film doped with a photosensitizer, the method comprising: S1, take 0.2g of nano titanium dioxide, 21g of nano silver phosphate, 0.35kg of polyolefin elastomer and 0.2kg of talc powder and mix them. Add 35g of phthalocyanine iron and 100g of sodium glutamate and mix thoroughly to obtain an inorganic mixture. Put the inorganic mixture into a ball mill and perform thorough physical grinding to obtain inorganic powder. S2, inorganic powder, 800g low-density polyethylene granules and 100g sodium glutamate are mixed and melt-extruded through a twin-screw extruder. The screw speed of the twin-screw extruder is 150-200 rpm. After the extruded strip is cooled in a water tank, it is pelletized by a pelletizer to produce composite masterbatch. S3, mix 1.05kg of composite masterbatch with 5.95kg of polyethylene resin and blow mold it with a blow-up ratio of 2.5-3.0, control the thickness of the base film at 35±5μm, cool and set it, and then roll it up to obtain the base film; S4. Slowly add 1g of chitosan powder to 100mL of 1% acetic acid solution and continuously stir magnetically at room temperature until a clear and transparent viscous solution is formed. Coat the viscous solution onto the surface of the film, dry at 45±5℃, rinse with deionized water, and dry to obtain film 2.

[0037] Comparative Example 3 A method for preparing a biodegradable thin film doped with a photosensitizer, the method comprising: S1. 8 kg of modified polyethylene granules, 3.5 kg of polyolefin elastomer, 2.1 kg of talc, 2 kg of monosodium glutamate powder, 350 g of phthalocyanine iron, 210 g of silver phosphate, and 350 g of ethylene bis-stearamide are melt-blended using a twin-screw extruder with a screw speed of 150-200 rpm. The extruded strip is cooled in a water bath and then pelletized into composite masterbatch by a pelletizer. 10.5 kg of the composite masterbatch is mixed with 59.5 kg of low-density polyethylene granules and blow-molded at a blow-up ratio of 2.5-3.0, controlling the base film thickness at 35±5 μm. After cooling and setting, the film is wound up to obtain a base film. One side of the base film is treated with a roll-to-roll corona treatment machine to obtain a corona-treated base film. S2, 20g TiO2 powder was added to 500mL Tris buffer and ultrasonically dispersed for 30 minutes under ice-water bath conditions until a uniform suspension was formed. 5.0mL 3-aminopropyltriethoxysilane was added and magnetic stirring was continued for 30 minutes to obtain a mixture. 2.0g dopamine hydrochloride was dissolved in the remaining 500mL Tris buffer to obtain a dopamine solution. The mixture and the dopamine solution were mixed to obtain an impregnation solution. S3, the impregnation solution is dipped onto the treated surface of the base film after corona treatment by dip coating, the film is taken out and rinsed with a large amount of deionized water, and then dried at 60±2℃ for 4 hours; S4. 10.0 g of chitosan powder was slowly added to 1000 mL of 1% acetic acid solution and continuously stirred magnetically at room temperature until a clear and transparent viscous solution was formed. The viscous solution was coated on the surface of the film, dried at 50 °C, rinsed with deionized water, and dried to obtain biodegradable film 2.

[0038] The biaxial tensile strength of the above-mentioned biodegradable film 1, film 1, film 2, biodegradable film 2 and ordinary polyethylene film were tested according to GB / T1040.3-2006, the oxygen permeability of the film was tested according to GB / T1038-2000 gas permeability test method (differential pressure method), and the puncture resistance was tested according to GB / T 37841-2019, with a puncture speed of 50±5 mm / min.

[0039] Table 2. Biaxial tensile strength and oxygen permeability of the film. Biodegradable film 1 23.1 455.625 19.3 Film 1 13.9 464.528 11.3 Film 2 19.7 469.371 13.1 Biodegradable film 2 20.6 458.413 15.5 Ordinary polyethylene film 13.1 720.287 ___ It should be noted that because this biodegradable membrane has a low oxygen permeability, it can be physically perforated during use according to the season and crop needs to promote crop growth.

[0040] Degradation experiments were conducted on biodegradable film 1, film 1, film 2, biodegradable film 2, and ordinary polyethylene film. Specifically, test samples of the same mass were cut from the film or mulch film. Three test samples were taken from each type of mulch film, weighed, and marked. They were then placed in the field and fixed to prevent movement without soil covering. After 80 days, 100 days, and 120 days of fixing, one test sample was taken out, weighed, and the weight loss rate was calculated. The weight loss rate was calculated as (original mass - treated mass) / original mass * 100%. The above method was repeated three times, and the average value was taken.

[0041] Table 3. Weight loss rate of membranes after 80, 100, or 120 days of degradation experiments. Biodegradable film 1 27.4 43.5 54.8 Film 1 12.1 18.7 24.2 Film 2 20.7 32.4 50.8 Biodegradable film 2 26.2 42.8 54.1 Ordinary polyethylene film 0.6 0.9 1.3 The degradation test shows that the biodegradability of ordinary polyethylene film is extremely poor, while the degradation of biodegradable film 1 and biodegradable film 2 is far better than that of ordinary polyethylene film, and better than film 1 and film 2.

[0042] An embedding experiment was conducted on biodegradable film 1, film 1, film 2, biodegradable film 2, and ordinary polyethylene film. Specifically, test samples of the same mass were cut from the film or mulch film. Three test samples of each type of mulch film were taken, weighed, and marked, and then buried in a 10cm deep soil layer. After 80d, 100d, and 120d, one of the test samples was taken out, weighed, and the weight loss rate was calculated. The weight loss rate was calculated as (original mass - treated mass) / original mass * 100%. The test was repeated three times according to the above method, and the average value was taken.

[0043] Table 4. Weight loss rate of membranes after 80, 100, or 120 days of embedding experiments. Biodegradable film 1 6.4 11.7 19.3 Film 1 6.1 7.5 8.1 Film 2 6.3 13.8 21.8 Biodegradable film 2 6.7 11.6 19.9 Ordinary polyethylene film 0.5 0.7 0.8 The results of the embedding test show that the degradation of the above-mentioned films after being embedded in soil at a depth of 10 cm was actually worse than that of film 2, indicating that light promoted the accelerated degradation of biodegradable films 1 and 2. The weight loss rates of biodegradable films 1, 2, and 2 were similar at 60 days, suggesting that the chitosan layer may have degraded during this stage. The lower weight loss rate of film 1 at 100-120 days indicates that monosodium glutamate (MSG) can improve the biodegradability of the film. The lower weight loss rate of film 1 at 100-120 days compared to film 2 suggests that the use of modified polyethylene in the composite masterbatch may have prolonged the biodegradation time, leading to a decrease in the biodegradability rate.

[0044] This invention can be implemented in various ways and is not limited to the embodiments described. Those skilled in the art will understand that the invention can be implemented in other specific ways without changing the technical concept or essential features. Therefore, it should be understood that the embodiments described above are exemplary and not intended to limit the invention.

Claims

1. A biodegradable film doped with a photosensitizer, characterized in that, The structure of the biodegradable film includes a base film, a titanium dioxide layer, and a chitosan layer. The components of the biodegradable film include polyethylene, monosodium glutamate, iron phthalocyanine, titanium dioxide, silver phosphate, chitosan, dispersant, reinforcing agent, and toughening agent.

2. The biodegradable film doped with a photosensitizer of claim 1, wherein, The polyethylene and monosodium glutamate are in a weight ratio of 80:20, the amount of iron phthalocyanine added is 0.5-1% of the total amount of base film raw materials, the amount of silver phosphate added is 0.3-0.8% of the total amount of base film raw materials, and the amount of dispersant added is 0.5-0.8% of the total amount of base film raw materials.

3. A method of making a biodegradable film doped with a photosensitizer, characterized in that, The preparation method includes: S1, the composite masterbatch and polyethylene particles are mixed in a weight ratio and blow-molded, cooled and shaped, and then rolled up to obtain a base film. One side of the base film is treated with a roll-to-roll corona treatment machine to obtain a corona-treated base film. S2, TiO2 powder is dissolved in Tris buffer to prepare a suspension, 3-aminopropyltriethoxysilane is added to prepare a mixture, dopamine hydrochloride is dissolved in Tris buffer to obtain a dopamine solution, and the mixture and the dopamine solution are mixed to obtain an impregnation solution. S3, the impregnation solution is dipped onto the treated surface of the base film after corona treatment by dip coating, the film is taken out and rinsed with a large amount of deionized water, and dried for 2-4 hours; S4. Chitosan powder is slowly added to a 1% acetic acid solution and continuously magnetically stirred at room temperature until a clear and transparent viscous solution is formed. The viscous solution is then coated onto the surface of the film, dried, rinsed with deionized water, and dried again to obtain a biodegradable film.

4. The method for preparing a biodegradable thin film doped with a photosensitizer as described in claim 3, characterized in that, The modification method of the modified polyethylene particles is as follows: maleic anhydride and initiator are dissolved in a small amount of acetone to obtain a modifier, the modifier is mixed with polyethylene particles at high speed, the screw speed of the twin-screw extruder is 150-200 rpm, the extruded strip is cooled in a water tank and then pelletized into modified polyethylene particles by a pelletizer.

5. The method for preparing a biodegradable thin film doped with a photosensitizer as described in claim 3, characterized in that, The amount of maleic anhydride used is 1-5% of the mass of the polyethylene particles, and the amount of initiator used is 5-10% of the mass of the maleic anhydride.

6. The method for preparing a biodegradable thin film doped with a photosensitizer as described in claim 3, characterized in that, The method for preparing the composite masterbatch is as follows: modified polyethylene particles, reinforcing agent, toughening agent, dispersant sodium glutamate powder, phthalocyanine iron, and silver phosphate are melt-blended using a twin-screw extruder with a screw speed of 150-200 rpm. After the extruded strip is cooled in a water tank, it is pelletized into composite masterbatch by a pelletizer.

7. The method for preparing a biodegradable thin film doped with a photosensitizer as described in claim 6, characterized in that, The amount of phthalocyanine iron added is 0.5-1% of the total amount of the base film raw materials, the amount of silver phosphate added is 0.3-0.8% of the total amount of the base film raw materials, and the amount of dispersant added is 0.5-0.8% of the total amount of the base film raw materials.

8. The method for preparing a biodegradable thin film doped with a photosensitizer as described in claim 3, characterized in that, The blow-inflation ratio of the blow molding process is 2.5-3.

0.

9. The method for preparing a biodegradable thin film doped with a photosensitizer as described in claim 3, characterized in that, The composite masterbatch and modified polyethylene particles are in a weight ratio of 15-20:

85.

10. The method for preparing a biodegradable thin film doped with a photosensitizer as described in claim 3, characterized in that, The thickness of the base film is controlled at 35±5μm.

Images