Easily degradable modified agricultural mulching film and preparation method thereof

Abstract

The invention discloses an easily degradable modified agricultural mulching film and a preparation method thereof, and relates to the field of high polymer materials. When the easily degradable modified agricultural mulching film is prepared, oyster shell powder sequentially reacts with 3-bromopropyltrimethoxysilane, 4-methylpyridine, 5-(7-bromobenzo [C] [1, 2, 5] thiadiazole-4-yl) thiophene-2-formaldehyde and 4-(diphenylamine) phenylboronic acid pinacol ester, and functionalized oyster shell powder is prepared; and reacting urea with formaldehyde, reacting with monopotassium phosphate and chitosan, mixing with the functionalized oyster shell powder, performing injection molding, and drying to obtain the easily degradable modified agricultural mulching film. The easily-degradable modified agricultural mulching film prepared by the invention has good mechanical properties and capabilities of resisting bacteria, performing photocatalytic degradation, adjusting the pH value of soil and degrading the soil into fertilizers.

Description

Technical Field

[0001] The invention relates to the field of polymer materials, in particular to an easily degradable modified agricultural mulch film and a preparation method thereof. Background Art

[0002] Agricultural mulch film has the effect of retaining moisture and keeping the soil warm, bringing increased production and harvest to agriculture. Since my country is located in the monsoon zone, most of the arable land is subject to obstacles such as drought, low-lying, and saline-alkali. Soil erosion, soil desertification, soil salinization and soil pollution are serious, especially in the northwest and northeast regions. Conditioning and improvement are needed, and the demand for mulch film is very high. Mud film has become an important measure to increase crop yields and save water in my country's arid, semi-arid, low-lying, and saline-alkali areas.

[0003] However, while the film mulching cultivation technology has brought huge economic benefits to agricultural production and income, the many years of use of ordinary film cannot be recycled and reused. As the film is used for a longer time, the residual film accumulates and increases in the soil tillage layer, causing the soil aggregate structure to be destroyed. The infiltration of soil capillary water and natural water is seriously blocked, affecting soil cultivation and harvest, reducing soil fertility, causing a serious reduction in crop yields, and causing serious environmental pollution. Therefore, this article introduces a biodegradable modified agricultural film and its preparation method. Summary of the invention

[0004] The object of the present invention is to provide a degradable modified agricultural mulch film and a preparation method thereof, so as to solve the problems existing in the prior art.

[0005] A degradable modified agricultural mulch film, which is prepared by reacting urea and formaldehyde, reacting with potassium dihydrogen phosphate and chitosan, mixing with functionalized oyster shell powder, injection molding, and drying;

[0006] The functionalized oyster shell powder is prepared by sequentially reacting the oyster shell powder with 3-bromopropyltrimethoxysilane, 4-methylpyridine, 5-(7-bromobenzo[C][1,2,5]thiadiazol-4-yl)thiophene-2-carboxaldehyde and 4-(diphenylamine)phenylboronic acid pinacol ester.

[0007] A method for preparing a degradable modified agricultural mulch film, the method for preparing the degradable modified agricultural mulch film mainly comprises the following preparation steps:

[0008] (1) Mix oyster shell powder, 3-bromopropyltrimethoxysilane and isopropanol in a mass ratio of 6-8:1:30-50, stir at 85-95°C and 200-300 r / min for 5-7 h, filter, wash with deionized water for 3-5 times, and dry at 90-100°C for 2-4 h to obtain pre-modified oyster shell powder; mix the pre-modified oyster shell powder with 4-methylpyridine in a mass ratio of 1:1, stir at 700-900 r / min for 100-140 s, heat to 105-115°C, stir at 1100-1300 r / min for 100-140 min, cool to room temperature, filter, wash with deionized water for 3-5 times, and dry at -10-0°C for 22-26 h to obtain modified oyster shell powder;

[0009] (2) 5-(7-bromobenzo[C][1,2,5]thiadiazol-4-yl)thiophene-2-carboxaldehyde, modified oyster shell powder, ethanol and piperidine were mixed in a mass ratio of 1:3-5:10-14:4-6, reacted at 200-300 r / min, 78-82°C, under nitrogen protection for 22-26 hours, filtered, washed with ethanol 3-5 times, and dried at -10-0°C for 22-26 hours to obtain a functionalized oyster shell powder precursor; 4- (Diphenylamine) phenylboronic acid pinacol ester, functionalized oyster shell powder precursor, tetrahydrofuran, potassium carbonate aqueous solution, tetrakis(triphenylphosphine) palladium are mixed in a mass ratio of 1:3-5:10-14:2.5-3.5:0.16-0.2, reacted at 200-300 r / min, 68-72°C, under nitrogen protection for 70-74h, filtered, washed with ethanol 3-5 times, and dried at -10-0°C for 22-26h to obtain functionalized oyster shell powder;

[0010] (3) Urea and formaldehyde were mixed in a molar ratio of 1.5 to 1.7:1, the pH was adjusted to 7.9 to 8.1 with a potassium hydroxide aqueous solution, the mixture was reacted at 25 to 35°C and 200 to 300 r / min for 75 to 85 min, the mixture was heated to 45 to 55°C, the stirring was continued for 25 to 35 min, chitosan solution with a mass of 95 to 105 times that of urea and potassium dihydrogen phosphate with a mass of 0.1 to 0.2 times that of urea were added, the mixture was heated to 65 to 75°C, the stirring was continued for 2 to 3 h, functionalized oyster shell powder with a mass of 1.8 to 2.2 times that of urea was added, the mixture was stirred at 200 to 300 r / min for 8 to 12 min, the mixture was evenly poured into a polystyrene mold, dried at 55 to 65°C for 24 to 28 h, and scraped off to obtain an agricultural mulch film.

[0011] As an optimization, the oyster shell powder in step (1) is obtained by drying the oyster shell at 75-85° C. for 9-11 hours and grinding it to 420-460 meshes using a ball mill.

[0012] As an optimization, the potassium carbonate aqueous solution in step (2) is a 1.8-2.2 mol / L potassium carbonate aqueous solution.

[0013] As an optimization, the potassium hydroxide aqueous solution in step (3) is a 0.1 mol / L potassium hydroxide aqueous solution.

[0014] As an optimization, the chitosan solution in step (3) is prepared by uniformly mixing chitosan and 0.4% acetic acid aqueous solution in a mass ratio of 1:8-11.

[0015] As an optimization, the chitosan in step (3) is food grade chitosan.

[0016] Compared with the prior art, the beneficial effects achieved by the present invention are:

[0017] When preparing the easily degradable modified agricultural mulch film, the present invention sequentially reacts oyster shell powder with 3-bromopropyltrimethoxysilane, 4-methylpyridine, 5-(7-bromobenzo[C][1,2,5]thiadiazol-4-yl)thiophene-2-carboxaldehyde and 4-(diphenylamine)phenylboronic acid pinacol ester to obtain functionalized oyster shell powder; urea and formaldehyde are reacted, and then reacted with potassium dihydrogen phosphate and chitosan, mixed with the functionalized oyster shell powder, injection molded, and dried to obtain the easily degradable modified agricultural mulch film.

[0018] Firstly, oyster shell powder was reacted with 3-bromopropyltrimethoxysilane, 4-methylpyridine, 5-(7-bromobenzo[C][1,2,5]thiadiazol-4-yl)thiophene-2-carboxaldehyde and 4-(diphenylamine)phenylboronic acid pinacol to obtain functionalized oyster shell powder. Oyster shell has the ability to adjust the pH of acidic soil, and oyster shell powder can be dispersed in the matrix. When subjected to external force, it can share the load, reduce the damage to the matrix, and improve the mechanical strength of the material. Pyridine was grafted on the surface of oyster shell. Pyridine is a commonly used fungicide that can destroy the cell membrane and cell wall of bacteria, causing bacterial death and achieving an antibacterial effect. The modified oyster shell powder is reacted with 5-(7-bromobenzo[C][1,2,5]thiadiazol-4-yl)thiophene-2-carboxaldehyde and 4-(diphenylamine)phenylboronic acid pinacol ester to form an organic photosensitizer on the surface of the oyster shell powder, which can destroy the internal and external structures of bacteria, thereby causing bacterial death and achieving an antibacterial effect. The photosensitive structure can better degrade chitosan under photocatalytic conditions.

[0019] Secondly, urea and formaldehyde are reacted, and then reacted with potassium dihydrogen phosphate and chitosan, mixed with functionalized oyster shell powder, injection molded, and dried to obtain a biodegradable modified agricultural mulch film; urea, formaldehyde, potassium dihydrogen phosphate and the amino group of chitosan are reacted to form a cross-linked structure, which enhances the mechanical strength of the material and increases the tensile strength of the material. After the chitosan is degraded, the N and P contained therein will be released as nutrients to improve soil fertility. DETAILED DESCRIPTION

[0020] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0021] Embodiment 1:

[0022] A method for preparing a biodegradable modified agricultural mulch film mainly comprises the following preparation steps:

[0023] (1) The oyster shell was dried at 75 ° C for 9 hours, and ground into 420 mesh with a ball mill to obtain oyster shell powder; the oyster shell powder, 3-bromopropyltrimethoxysilane and isopropanol were mixed in a mass ratio of 6:1:30, stirred at 85 ° C and 200 r / min for 5 hours, filtered, washed with deionized water for 3 times, and dried at 90 ° C for 2 hours to obtain pre-modified oyster shell powder; the pre-modified oyster shell powder and 4-methylpyridine were mixed in a mass ratio of 1:1, stirred at 700 r / min for 100 seconds, heated to 105 ° C, stirred at 1100 r / min for 100 minutes, cooled to room temperature, filtered, washed with deionized water for 3 times, and dried at -10 ° C for 22 hours to obtain modified oyster shell powder;

[0024] (2) 5-(7-bromobenzo[C][1,2,5]thiadiazol-4-yl)thiophene-2-carboxaldehyde, modified oyster shell powder, ethanol and piperidine were mixed in a mass ratio of 1:3:10:4, reacted at 200 r / min, 78°C, under nitrogen protection for 22 hours, filtered, washed with ethanol three times, and dried at -10°C for 22 hours to obtain a functionalized oyster shell powder precursor; 4-(diphenylamine)phenylboronic acid pinacol ester, functionalized oyster shell powder precursor, tetrahydrofuran, 1.8 mol / L potassium carbonate aqueous solution, and tetrakis(triphenylphosphine)palladium were mixed in a mass ratio of 1:3:10:2.5:0.16, reacted at 200 r / min, 68°C, under nitrogen protection for 70 hours, filtered, washed with ethanol three times, and dried at -10°C for 22 hours to obtain a functionalized oyster shell powder;

[0025] (3) Chitosan was mixed with 0.4% acetic acid aqueous solution in a mass ratio of 1:8 to obtain a chitosan solution; urea and formaldehyde were mixed in a molar ratio of 1.5:1, the pH was adjusted to 7.9 with 0.1 mol / L potassium hydroxide aqueous solution, the reaction was carried out at 25°C and 200 r / min for 75 min, the temperature was raised to 45°C, stirring was continued for 25 min, 95 times the mass of chitosan solution of urea and 0.1 times the mass of potassium dihydrogen phosphate of urea were added, the temperature was raised to 65°C, stirring was continued for 2 h, 1.8 times the mass of urea functionalized oyster shell powder was added, stirring was carried out at 200 r / min for 8 min, the mixture was evenly poured into a polystyrene mold, dried at 55°C for 24 h, and scraped off to obtain an agricultural mulch film.

[0026] Embodiment 2:

[0027] A method for preparing a biodegradable modified agricultural mulch film mainly comprises the following preparation steps:

[0028] (1) The oyster shell was dried at 80 ° C for 10 h, and ground to 440 mesh with a ball mill to obtain oyster shell powder; the oyster shell powder, 3-bromopropyltrimethoxysilane and isopropanol were mixed evenly in a mass ratio of 7:1:40, stirred at 90 ° C and 250 r / min for 6 h, filtered, washed with deionized water 4 times, and dried at 95 ° C for 3 h to obtain pre-modified oyster shell powder; the pre-modified oyster shell powder and 4-methylpyridine were mixed in a mass ratio of 1:1, stirred at 800 r / min for 120 s, heated to 110 ° C, stirred at 1200 r / min for 120 min, cooled to room temperature, filtered, washed with deionized water 4 times, and dried at -5 ° C for 24 h to obtain modified oyster shell powder;

[0029] (2) 5-(7-bromobenzo[C][1,2,5]thiadiazol-4-yl)thiophene-2-carboxaldehyde, modified oyster shell powder, ethanol and piperidine were mixed in a mass ratio of 1:4:12:5, reacted at 250 r / min, 80°C, under nitrogen protection for 24 hours, filtered, washed with ethanol 4 times, and dried at -5°C for 24 hours to obtain a functionalized oyster shell powder precursor; 4-(diphenylamine)phenylboronic acid pinacol ester, functionalized oyster shell powder precursor, tetrahydrofuran, 2 mol / L potassium carbonate aqueous solution, tetrakis(triphenylphosphine)palladium were mixed in a mass ratio of 1:4:12:3:0.18, reacted at 250 r / min, 70°C, under nitrogen protection for 72 hours, filtered, washed with ethanol 4 times, and dried at -5°C for 24 hours to obtain a functionalized oyster shell powder;

[0030] (3) Chitosan was mixed with 0.4% acetic acid aqueous solution at a mass ratio of 1:10 to obtain a chitosan solution; urea and formaldehyde were mixed at a molar ratio of 1.6:1, the pH was adjusted to 8 with 0.1 mol / L potassium hydroxide aqueous solution, the mixture was reacted at 30°C and 250 r / min for 80 min, the temperature was raised to 50°C, stirring was continued for 30 min, chitosan solution with a mass of 100 times that of urea and potassium dihydrogen phosphate with a mass of 0.15 times that of urea were added, the temperature was raised to 70°C, stirring was continued for 2.5 h, functionalized oyster shell powder with a mass of 2 times that of urea was added, stirring was continued at 250 r / min for 10 min, the mixture was evenly poured into a polystyrene mold, dried at 60°C for 26 h, and scraped off to obtain an agricultural mulch film.

[0031] Embodiment 3:

[0032] A method for preparing a biodegradable modified agricultural mulch film mainly comprises the following preparation steps:

[0033] (1) The oyster shell was dried at 85 ° C for 11 hours, and ground to 460 mesh with a ball mill to obtain oyster shell powder; the oyster shell powder, 3-bromopropyltrimethoxysilane and isopropanol were mixed in a mass ratio of 8:1:50, stirred at 95 ° C and 300 r / min for 7 hours, filtered, washed with deionized water 5 times, and dried at 100 ° C for 4 hours to obtain pre-modified oyster shell powder; the pre-modified oyster shell powder and 4-methylpyridine were mixed in a mass ratio of 1:1, stirred at 900 r / min for 140 seconds, heated to 115 ° C, stirred at 1300 r / min for 140 minutes, cooled to room temperature, filtered, washed with deionized water 5 times, and dried at 0 ° C for 26 hours to obtain modified oyster shell powder;

[0034] (2) 5-(7-bromobenzo[C][1,2,5]thiadiazol-4-yl)thiophene-2-carboxaldehyde, modified oyster shell powder, ethanol and piperidine were mixed in a mass ratio of 1:5:14:6, reacted at 300 r / min, 82°C, under nitrogen protection for 26 hours, filtered, washed with ethanol 5 times, and dried at 0°C for 26 hours to obtain a functionalized oyster shell powder precursor; 4-(diphenylamine)phenylboronic acid pinacol ester, functionalized oyster shell powder precursor, tetrahydrofuran, 2.2 mol / L potassium carbonate aqueous solution, and tetrakis(triphenylphosphine)palladium were mixed in a mass ratio of 1:5:14:3.5:0.2, reacted at 300 r / min, 72°C, under nitrogen protection for 74 hours, filtered, washed with ethanol 5 times, and dried at 0°C for 26 hours to obtain a functionalized oyster shell powder;

[0035] (3) Chitosan was mixed with 0.4% acetic acid aqueous solution in a mass ratio of 1:11 to obtain a chitosan solution; urea and formaldehyde were mixed in a molar ratio of 1.7:1, the pH was adjusted to 8.1 with 0.1 mol / L potassium hydroxide aqueous solution, the reaction was carried out at 35°C and 300 r / min for 85 min, the temperature was raised to 55°C, stirring was continued for 35 min, 105 times the mass of chitosan solution and 0.2 times the mass of potassium dihydrogen phosphate of urea were added, the temperature was raised to 75°C, stirring was continued for 3 h, 2.2 times the mass of urea functionalized oyster shell powder was added, stirring was carried out at 300 r / min for 12 min, the mixture was evenly poured into a polystyrene mold, dried at 65°C for 28 h, and scraped off to obtain an agricultural mulch film.

[0036] Comparative Example 1:

[0037] A method for preparing a biodegradable modified agricultural mulch film mainly comprises the following preparation steps:

[0038] (1) The oyster shell was dried at 80 ° C for 10 h, and ground to 440 mesh with a ball mill to obtain oyster shell powder; the oyster shell powder, 3-bromopropyltrimethoxysilane and isopropanol were mixed evenly in a mass ratio of 7:1:40, stirred at 90 ° C and 250 r / min for 6 h, filtered, washed with deionized water 4 times, and dried at 95 ° C for 3 h to obtain pre-modified oyster shell powder; the pre-modified oyster shell powder and 4-methylpyridine were mixed in a mass ratio of 1:1, stirred at 800 r / min for 120 s, heated to 110 ° C, stirred at 1200 r / min for 120 min, cooled to room temperature, filtered, washed with deionized water 4 times, and dried at -5 ° C for 24 h to obtain modified oyster shell powder;

[0039] (2) Chitosan and 0.4% acetic acid aqueous solution were mixed uniformly in a mass ratio of 1:10 to obtain a chitosan solution; urea and formaldehyde were mixed in a molar ratio of 1.6:1, the pH was adjusted to 8 with a 0.1 mol / L potassium hydroxide aqueous solution, the mixture was reacted at 30°C and 250 r / min for 80 min, the temperature was raised to 50°C, stirring was continued for 30 min, chitosan solution with a mass of 100 times that of urea and potassium dihydrogen phosphate with a mass of 0.15 times that of urea were added, the temperature was raised to 70°C, stirring was continued for 2.5 h, modified oyster shell powder with a mass of 2 times that of urea was added, stirring was continued at 250 r / min for 10 min, the mixture was uniformly poured into a polystyrene mold, dried at 60°C for 26 h, and scraped off to obtain an agricultural mulch film.

[0040] Comparative Example 2:

[0041] A method for preparing a biodegradable modified agricultural mulch film mainly comprises the following preparation steps:

[0042] (1) Dry the oyster shell at 80°C for 10 h, grind it to 440 mesh with a ball mill to obtain oyster shell powder; mix chitosan with 0.4% acetic acid aqueous solution at a mass ratio of 1:10 to obtain chitosan solution; mix urea and formaldehyde at a molar ratio of 1.6:1, adjust the pH to 8 with 0.1 mol / L potassium hydroxide aqueous solution, react at 30°C and 250 r / min for 80 min, heat to 50°C, continue stirring for 30 min, add chitosan solution with 100 times the mass of urea and potassium dihydrogen phosphate with 0.15 times the mass of urea, heat to 70°C, continue stirring for 2.5 h, add oyster shell powder with 2 times the mass of urea, stir at 250 r / min for 10 min, pour evenly into a polystyrene mold, dry at 60°C for 26 h, scrape off, and obtain agricultural mulch film.

[0043] Comparative Example 3:

[0044] A method for preparing a biodegradable modified agricultural mulch film mainly comprises the following preparation steps:

[0045] (1) Chitosan and 0.4% acetic acid aqueous solution are mixed uniformly in a mass ratio of 1:10 to obtain a chitosan solution; urea and formaldehyde are mixed in a molar ratio of 1.6:1, the pH is adjusted to 8 with a 0.1 mol / L potassium hydroxide aqueous solution, the mixture is reacted at 30°C and 250 r / min for 80 min, the mixture is heated to 50°C, stirred for 30 min, a chitosan solution with a mass of 100 times that of urea and potassium dihydrogen phosphate with a mass of 0.15 times that of urea are added, the mixture is heated to 70°C, stirred for 2.5 h, and evenly poured into a polystyrene mold, dried at 60°C for 26 h, and scraped to obtain an agricultural mulch film.

[0046] Comparative Example 4:

[0047] A method for preparing a biodegradable modified agricultural mulch film mainly comprises the following preparation steps:

[0048] (1) The oyster shell was dried at 80 ° C for 10 h, and ground to 440 mesh with a ball mill to obtain oyster shell powder; the oyster shell powder, 3-bromopropyltrimethoxysilane and isopropanol were mixed evenly in a mass ratio of 7:1:40, stirred at 90 ° C and 250 r / min for 6 h, filtered, washed with deionized water 4 times, and dried at 95 ° C for 3 h to obtain pre-modified oyster shell powder; the pre-modified oyster shell powder and 4-methylpyridine were mixed in a mass ratio of 1:1, stirred at 800 r / min for 120 s, heated to 110 ° C, stirred at 1200 r / min for 120 min, cooled to room temperature, filtered, washed with deionized water 4 times, and dried at -5 ° C for 24 h to obtain modified oyster shell powder;

[0049] (2) 5-(7-bromobenzo[C][1,2,5]thiadiazol-4-yl)thiophene-2-carboxaldehyde, modified oyster shell powder, ethanol and piperidine were mixed in a mass ratio of 1:4:12:5, reacted at 250 r / min, 80°C, under nitrogen protection for 24 hours, filtered, washed with ethanol 4 times, and dried at -5°C for 24 hours to obtain a functionalized oyster shell powder precursor; 4-(diphenylamine)phenylboronic acid pinacol ester, functionalized oyster shell powder precursor, tetrahydrofuran, 2 mol / L potassium carbonate aqueous solution, tetrakis(triphenylphosphine)palladium were mixed in a mass ratio of 1:4:12:3:0.18, reacted at 250 r / min, 70°C, under nitrogen protection for 72 hours, filtered, washed with ethanol 4 times, and dried at -5°C for 24 hours to obtain a functionalized oyster shell powder;

[0050] (3) Chitosan and 0.4% acetic acid aqueous solution were mixed in a mass ratio of 1:10 to obtain a chitosan solution; the chitosan solution and functionalized oyster shell powder were mixed in a mass ratio of 50:1, stirred at 250 r / min for 10 min, poured evenly into a polystyrene mold, dried at 60°C for 26 h, and scraped off to obtain an agricultural mulch film.

[0051] Test Example 1:

[0052] Antimicrobial testing

[0053] According to QB / T2591, the selected bacteria were Staphylococcus aureus and Escherichia coli. The results are shown in Table 1.

[0054] Table 1

[0055]

[0056] From the comparison of the experimental data in Table 1, it can be found that the easily degradable modified agricultural mulch film prepared by the present invention has good antibacterial ability.

[0057] From the comparison of the experimental data of Examples 1, 2, 3 and Comparative Example 1 in Table 1, it can be found that the antibacterial rates of Examples 1, 2, and 3 are higher than those of Comparative Example 1, indicating that the organic photosensitizer formed on the surface of oyster shell powder can destroy the internal and external structures of bacteria, thereby causing the death of bacteria and achieving an antibacterial effect;

[0058] From the comparison of the experimental data of Examples 1, 2, 3 and Comparative Example 2, it can be found that the antibacterial rates of Examples 1, 2, 3 are higher than those of Comparative Example 2, indicating that pyridine is a commonly used bactericide, and its mechanism of action is to destroy the cell membrane and cell wall of bacteria, thereby causing the death of bacteria and achieving an antibacterial effect.

[0059] Test Example 2:

[0060] Mechanical properties test

[0061] The mechanical properties of the film were tested according to the national standard GB1040-79. The ground films prepared in the embodiments and comparative examples were made into sample blocks with a length of 150 mm, a width of 20 mm, and a thickness of 120 μm. The sample blocks were placed in an incubator with a relative humidity of 75% for 3 days and placed on a tensile testing machine with a tensile speed of 3 cm·min. -1 , record the tensile strength. The results are shown in Table 2.

[0062] Table 2

[0063] Tensile Strength Example 1 7.05MPa Example 2 7.08MPa Example 3 7.06MPa Comparative Example 1 7.04MPa Comparative Example 2 6.98MPa Comparative Example 3 6.75MPa Comparative Example 4 5.95MPa

[0064] From the comparison of the experimental data in Table 2, it can be found that the easily degradable modified agricultural mulch film prepared by the present invention has good mechanical properties.

[0065] From the comparison of the experimental data of Examples 1, 2, 3 and Comparative Example 3 in Table 2, it can be found that the tensile strength of Examples 1, 2, and 3 is greater than that of Comparative Example 3, which shows that the oyster shell powder can be dispersed in the matrix, can share the load when subjected to external force, reduce the damage to the matrix, improve the mechanical strength of the material, and increase the tensile strength of the material;

[0066] From the comparison of the experimental data of Examples 1, 2, 3 and Comparative Example 4, it can be found that the tensile strength of Examples 1, 2, 3 is greater than that of Comparative Example 4, which illustrates that urea, formaldehyde, potassium dihydrogen phosphate and the amino group of chitosan are reacted to form a cross-linked structure, thereby enhancing the mechanical strength of the material and increasing the tensile strength of the material.

[0067] Test Example 3:

[0068] Photodegradation test

[0069] Each embodiment and comparative example was made into a sample block with a length of 150 mm, a width of 20 mm, and a thickness of 120 μm, mixed with 100 ml of deionized water, turned on the power of the photocatalytic device for 120 minutes, and the sample block was taken out and dried at -5°C for 24 hours. The mass loss rate was tested by comparing with the initial mass, and the Kjeldahl nitrogen determination method and the vanadium molybdenum yellow colorimetric method were used to detect whether the degradation solution contained P and N. The mass loss rate = (initial mass - mass after ultraviolet light irradiation) / initial mass * 100%. The results are shown in Table 3.

[0070] Table 3

[0071] Quality loss rate Does it contain P? Whether it contains N Example 1 9.6％ yes yes Example 2 9.8％ yes yes Example 3 9.7％ yes yes Comparative Example 1 3.7％ yes yes Comparative Example 2 3.9％ yes yes Comparative Example 3 3.8％ yes yes Comparative Example 4 9.0％ no yes

[0072] From the comparison of the experimental data in Table 3, it can be found that the easily degradable modified agricultural mulch film prepared by the present invention has good photocatalytic degradation ability and the ability to release N and P fertilizers.

[0073] From the comparison of the experimental data of Examples 1, 2, 3 and Comparative Example 1 in Table 3, it can be found that the mass loss rate of Examples 1, 2, 3 is greater than that of Comparative Example 1, indicating that the photosensitive structure formed on the surface of the oyster shell powder can better degrade chitosan under photocatalytic conditions;

[0074] From the comparison of the experimental data of Examples 1, 2, 3 and Comparative Example 4 in Table 3, it can be found that Examples 1, 2, 3 do not release P compared to Comparative Example 4, which shows that adding organic matter containing N and P nutrients to the mulch can release them and improve soil fertility.

[0075] Test Example 4:

[0076] Soil pH Adjustment Test:

[0077] Each example and comparative example was made into a sample block with a length of 150 mm, a width of 20 mm, and a thickness of 120 μm, and mixed with soil with a pH of 5.3 at a mass ratio of 1:20, and then placed in a ceramic pot for cultivation. During the cultivation period, deionized water was added once every 3 days, and the soil moisture content was maintained at 20% by weighing method. The soil pH value was tested after 21 days. The results are shown in Table 4.

[0078] Table 4

[0079] pH Example 1 6.75 Example 2 6.76 Example 3 6.73 Comparative Example 1 6.71 Comparative Example 2 6.74 Comparative Example 3 6.72 Comparative Example 4 5.93

[0080] From the comparison of the experimental data in Table 4, it can be found that the easily degradable modified agricultural mulch film prepared by the present invention has a good ability to regulate soil pH.

[0081] From the comparison of the experimental data of Examples 1, 2, 3 and Comparative Example 4 in Table 4, it can be found that the pH of Examples 1, 2, 3 is closer to neutral than that of Comparative Example 4, which shows that oyster shells have the ability to adjust the pH of acidic soil.

[0082] The specific implementation methods described above further illustrate the objectives, technical solutions and beneficial effects of the present invention in detail. It should be understood that the above description is only a specific implementation method of the present invention and is not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A degradable modified agricultural mulch film, characterized in that: The easily degradable modified agricultural mulch film is prepared by reacting urea and formaldehyde, reacting with potassium dihydrogen phosphate and chitosan, mixing with functionalized oyster shell powder, injection molding, and drying. The functionalized oyster shell powder is prepared by sequentially reacting the oyster shell powder with 3-bromopropyltrimethoxysilane, 4-methylpyridine, 5-(7-bromobenzo[C][1,2,5]thiadiazol-4-yl)thiophene-2-carboxaldehyde and 4-(diphenylamine)phenylboronic acid pinacol ester.

2. A method for preparing a biodegradable modified agricultural mulch film, characterized in that: The preparation method of the easily degradable modified agricultural mulch film mainly includes the following preparation steps: (1) Mix oyster shell powder, 3-bromopropyltrimethoxysilane and isopropanol in a mass ratio of 6-8:1:30-50, stir at 85-95°C and 200-300 r / min for 5-7 h, filter, wash with deionized water for 3-5 times, and dry at 90-100°C for 2-4 h to obtain pre-modified oyster shell powder; mix the pre-modified oyster shell powder with 4-methylpyridine in a mass ratio of 1:1, stir at 700-900 r / min for 100-140 s, heat to 105-115°C, stir at 1100-1300 r / min for 100-140 min, cool to room temperature, filter, wash with deionized water for 3-5 times, and dry at -10-0°C for 22-26 h to obtain modified oyster shell powder; (2) 5-(7-bromobenzo[C][1,2,5]thiadiazol-4-yl)thiophene-2-carboxaldehyde, modified oyster shell powder, ethanol and piperidine were mixed in a mass ratio of 1:3-5:10-14:4-6, reacted at 200-300 r / min, 78-82°C, under nitrogen protection for 22-26 hours, filtered, washed with ethanol 3-5 times, and dried at -10-0°C for 22-26 hours to obtain a functionalized oyster shell powder precursor; 4- (Diphenylamine) phenylboronic acid pinacol ester, functionalized oyster shell powder precursor, tetrahydrofuran, potassium carbonate aqueous solution, tetrakis(triphenylphosphine) palladium are mixed in a mass ratio of 1:3-5:10-14:2.5-3.5:0.16-0.2, reacted at 200-300 r / min, 68-72°C, under nitrogen protection for 70-74h, filtered, washed with ethanol 3-5 times, and dried at -10-0°C for 22-26h to obtain functionalized oyster shell powder; (3) Urea and formaldehyde were mixed in a molar ratio of 1.5 to 1.7:1, the pH was adjusted to 7.9 to 8.1 with a potassium hydroxide aqueous solution, the mixture was reacted at 25 to 35°C and 200 to 300 r / min for 75 to 85 min, the mixture was heated to 45 to 55°C, the stirring was continued for 25 to 35 min, chitosan solution with a mass of 95 to 105 times that of urea and potassium dihydrogen phosphate with a mass of 0.1 to 0.2 times that of urea were added, the mixture was heated to 65 to 75°C, the stirring was continued for 2 to 3 h, functionalized oyster shell powder with a mass of 1.8 to 2.2 times that of urea was added, the mixture was stirred at 200 to 300 r / min for 8 to 12 min, the mixture was evenly poured into a polystyrene mold, dried at 55 to 65°C for 24 to 28 h, and scraped off to obtain an agricultural mulch film.

3. The method for preparing a degradable modified agricultural mulch film according to claim 2, characterized in that: The oyster shell powder in step (1) is obtained by drying the oyster shell at 75-85° C. for 9-11 hours and grinding it to 420-460 meshes using a ball mill.

4. The method for preparing a degradable modified agricultural mulch film according to claim 2, characterized in that: The potassium carbonate aqueous solution in step (2) is a 1.8-2.2 mol / L potassium carbonate aqueous solution.

5. The method for preparing a degradable modified agricultural mulch film according to claim 2, characterized in that: The potassium hydroxide aqueous solution in step (3) is a 0.1 mol / L potassium hydroxide aqueous solution.

6. The method for preparing a degradable modified agricultural mulch film according to claim 2, characterized in that: The chitosan solution in step (3) is prepared by uniformly mixing chitosan and 0.4% acetic acid aqueous solution in a mass ratio of 1:8-11.

7. The method for preparing a degradable modified agricultural mulch film according to claim 2, characterized in that: The chitosan in step (3) is food grade chitosan.

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