Multifunctional full-degradable mulching film with water taking, slow release and soil improvement functions and preparation method of multifunctional full-degradable mulching film

Abstract

The invention discloses a multifunctional fully-degradable mulching film with water taking, slow release and soil improvement functions and a preparation method thereof, and belongs to the technical field of agricultural mulching films. The method comprises the following steps: preparing a PVA aqueous solution; the preparation method comprises the following steps: extracting a 3-8wt% nano cellulose solution from plant fibers by a two-step DES method; preparing a silicon source dispersion liquid; adding 10 parts of a nanocellulose solution, 1.25 parts of a silicon source dispersion liquid and 20 parts of glycerol into 100 parts of a PVA aqueous solution to obtain a film coating liquid; adding humic acid and an ion-based fertilizer into the film coating liquid, uniformly mixing, and carrying out curtain coating and drying to form a base film; the preparation method comprises the following steps: preparing 8-12wt% of a hydrophobic degradable material solution, and performing electrostatic spinning on a base film by using the solution to form a Janus structure, thereby obtaining the multifunctional full-degradable mulching film which can realize water extraction from air. The device has a function of taking water from air and a fertilizer slow release function, can release different fertilizers in a gradient manner, and meets the requirements of plants in different growth cycles. After being used, the soil conditioner can be directly turned into soil, the rest part directly acts with the soil, and PVA and humic acid synergistically improve the soil environment.

Description

Technical Field

[0001] The present invention belongs to the technical field of agricultural mulch films, and in particular relates to a multifunctional fully degradable mulch film with water intake, slow release and soil improvement functions and a preparation method thereof. Background Art

[0002] The functions of existing agricultural mulch films (including traditional PE films and early degradable films) are limited to physical covering and cannot meet the needs of efficient production in modern agriculture: in terms of water management, moisture conservation is achieved only by blocking the surface. The soil moisture evaporation rate in arid and semi-arid areas (accounting for 38% of my country's arable land) is still as high as 60%, and there is a lack of active water replenishment capacity. The additional irrigation required during the crop growth period accounts for 40%-50% of the water demand, resulting in serious waste of water resources; in terms of nutrient supply, artificial topdressing after mulch film covering requires breaking the film, which increases the cost by 80-120 yuan per mu, and the loss rate of chemical fertilizers through the gaps under the film exceeds 30%, and the utilization rate is only 35%-40%, resulting in aggravated soil salinization (electrical conductivity increased by 20%-30%), forming a vicious cycle of "high investment and low efficiency". Summary of the Invention

[0003] The present invention aims to address the aforementioned problems of the prior art by providing a multifunctional, fully biodegradable mulch film with the functions of water collection, slow release, and soil improvement, and a method for preparing the same. The mulch film combines the functions of collecting water from the atmosphere and slow-releasing fertilizer, is fully biodegradable, pollution-free, and improves soil.

[0004] To achieve the above object, the technical solution adopted by the present invention is as follows:

[0005] A method for preparing a multifunctional fully degradable mulch film with water intake, slow release and soil improvement functions, the method comprising:

[0006] Step 1: Prepare 8-12 wt% PVA aqueous solution;

[0007] Step 2: Extracting 3-8 wt% nanocellulose from plant fibers by a two-step DES method;

[0008] Step 3: preparing a 1-4 wt% ultrasonically dispersed silicon source dispersion;

[0009] Step 4: adding 10 parts of the solution from step 2, 1.25 parts of the solution from step 3, and 20 parts of glycerin to 100 parts of the solution from step 1, and then obtaining a coating solution under certain conditions;

[0010] Step 5: Add a certain amount of humic acid and ion-based fertilizer to the coating solution obtained in step 4, mix well, and then cast and dry on a polytetrafluoroethylene mold to form a base film; the mass ratio of humic acid to PVA is 30-45:100; the mass ratio of ion-based fertilizer to humic acid is 1:2; the ion-based fertilizer is a common nitrogen, phosphorus, and potassium water-soluble fertilizer, and a specific ratio can be set according to the needs of a certain plant, but a general compound fertilizer ratio will do;

[0011] Step 6: preparing 8-12 wt% hydrophobic degradable material solution;

[0012] Step 7: Use the solution from step 6 to electrospin on the base film obtained in step 5 to form a Janus structure, thereby obtaining a multifunctional and fully degradable ground film that can realize water extraction from air.

[0013] Furthermore, in step 2, the plant fiber comes from any crop straw such as corn, wheat, rice, sorghum, etc.

[0014] Furthermore, the step 2 is specifically as follows:

[0015] (1) The pretreated straw (washed, dried, and crushed to 40 mesh) was added to the DES-1 solution at a solid-liquid ratio of 1 g:10 mL, and then microwaved at 80 °C for 1 h. The solid phase was retained by filtration to obtain filter cake 1;

[0016] (2) Filter cake 1 was added to DES-2 solution at a solid-liquid ratio of 1 g:10 mL, microwaved at 80 °C for 45 min, and then filtered to obtain filter cake 2;

[0017] (3) The filter cake 2 was then dispersed in water at a mass fraction of 0.5%, ultrasonicated at 800W and 20KHz for 30 min, and then evaporated under reduced pressure to obtain 2.5-10wt% nanocellulose.

[0018] Furthermore, in step 2, the DES-1 solution consists of component 1 and component 2; component 1 is choline chloride, component 2 is one of glycerol, urea or ethylene glycol, and the molar ratio of component 1 to component 2 is 1:2; the DES-2 solution consists of component 3 and component 4; component 3 is choline chloride, component 4 is one of citric acid, lactic acid, oxalic acid or acetic acid, and the molar ratio of component 3 to component 4 is 1:2.

[0019] Furthermore, in step three, the silicon source is one or more of nano-silicon dioxide, calcium silicate, ethyl orthosilicate or methyl orthosilicate.

[0020] Furthermore, in step 4, the certain conditions refer to 80° C. water bath for 4 hours or 80° C. microwave water bath for 45 minutes.

[0021] Furthermore, in step six, the hydrophobic degradable material is one or more of polybutylene terephthalate-adipate (PBAT), polylactic acid (PLA) or polyurethane (PU).

[0022] Furthermore, in step six, the solvent of the solution is N,N-dimethylformamide DMF: dichloromethane DCM = 2:3.

[0023] Furthermore, in step seven, the electrospinning parameters are 15-20 KV voltage, roller receiving, roller distance of 15 cm from the needle tip, 45% ± 5% air humidity, 30° C., and a controlled propulsion rate of 1.5 ml / h.

[0024] A multifunctional fully degradable mulch film with water intake, slow release and soil improvement functions prepared by the above preparation method.

[0025] The beneficial effects of the present invention compared to the prior art are:

[0026] (1) Using Janus structure design to realize active air water extraction

[0027] This invention constructs a Janus structure with asymmetric wettability. The outer layer utilizes a hydrophobic PBAT electrospun fiber membrane, leveraging its high porosity and surface roughness to efficiently capture droplets and promote condensation. The droplets are then directed to the inner hydrophilic PVA / CNF membrane, enabling air-to-water extraction without external energy input. This achieves an integrated "moisture conservation and water replenishment" approach, alleviating crop water stress.

[0028] (2) Using humic acid loading to achieve synergy between slow-release fertilization and soil improvement

[0029] Humic acid is rich in active functional groups such as carboxyl and phenolic hydroxyl groups. When loaded into a PVA-based membrane, it can adsorb nitrogen, phosphorus, potassium, and trace elements (such as Fe and Zn) through ion exchange and chelation. Humic acid responds to moisture and microbial activity, slowly releasing nutrients and reducing leaching. At the same time, humic acid can regulate the acid-base balance of the soil to alleviate salinization and promote the reproduction of beneficial microorganisms to enhance soil biological activity. This synergistic "fertilizer supply-soil improvement" model not only meets the long-term nutritional needs of crops, but also improves soil health and achieves the sustainability of agricultural production.

[0030] In summary, the present invention has the function of extracting water from air with an efficiency of 254 ml·m -2 ·day -1 It also has a slow-release fertilizer function, which can release different fertilizers in a gradient to meet the needs of plants at different growth cycles. After use, it can be directly turned into the soil. The remaining part directly interacts with the soil, and PVA and humic acid synergistically improve the soil environment. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1This is a schematic diagram of the multifunctional degradable ground film of the present invention.

[0032] Figure 2 This is a diagram showing the slow-release effect of the fertilizer using the mulch film of the present invention.

[0033] Figure 3 This is a picture of a biodegradable mulch film product.

[0034] Figure 4 Comparison of tensile strength of membranes with different nanocellulose contents.

[0035] Figure 5 This is the Fourier infrared spectrum.

[0036] Figure 6 This is the SEM image of the PBAT layer.

[0037] Figure 7 This is a graph showing plant growth tests using different mulch films at different times. The horizontal lines represent time, which are 5, 10, 15, 20, and 25 days, while the vertical lines represent conditions, which from top to bottom are multifunctional mulch film, ordinary PE mulch film, and no mulch film.

[0038] Figure 8 Schematic diagram of the initial water contact angle of the PBAT layer.

[0039] Figure 9 Schematic diagram of the 2s water contact angle of the PBAT layer.

[0040] Figure 10 Schematic diagram of the 4s water contact angle of the PBAT layer.

[0041] Figure 11 Schematic diagram of the 6s water contact angle of the PBAT layer.

[0042] Figure 12 Schematic diagram of the 8s water contact angle of the PBAT layer.

[0043] Figure 13 Schematic diagram of the 12s water contact angle of the PBAT layer.

[0044] Figure 14 Schematic diagram of the initial water contact angle of the hydrophilic layer.

[0045] Figure 15 Schematic diagram of the 2s water contact angle of the hydrophilic layer.

[0046] Figure 16 Schematic diagram of the 4s water contact angle of the hydrophilic layer.

[0047] Figure 17 Schematic diagram of the 6s water contact angle of the hydrophilic layer.

[0048] Figure 18 Schematic diagram of the 8s water contact angle of the hydrophilic layer.

[0049] Figure 19 Schematic diagram of the 12s water contact angle of the hydrophilic layer. DETAILED DESCRIPTION

[0050] The technical solution of the present invention is further described below with reference to the accompanying drawings and embodiments, but is not limited thereto. Any modification or equivalent replacement of the technical solution of the present invention that does not depart from the spirit and scope of the technical solution of the present invention should be included in the scope of protection of the present invention.

[0051] Example 1:

[0052] A method for preparing a multifunctional fully degradable mulch film with water intake, slow release and soil improvement functions, the method comprising:

[0053] Step 1: prepare a 10 wt% PVA aqueous solution;

[0054] Step 2: The pretreated (washed, dried, and crushed to 40 mesh) corn straw was added to DES-1 (ChCl:Gly (urea / ethylene glycol) molar ratio of 1:2) at a solid-liquid ratio of 1 g:10 mL, followed by microwave treatment at 80°C for 1 h. The solid phase was retained by filtration to obtain filter cake 1;

[0055] Step 3: Filter cake 1 was added to DES-2 (ChCl: citric acid (acetic acid / lactic acid / oxalic acid) molar ratio of 1:2) at a solid-liquid ratio of 1 g:10 mL, microwave-treated at 80°C for 45 min, and then filtered to obtain filter cake 2;

[0056] Step 4: The filter cake 2 was then dispersed in water at a mass fraction of 0.5%, ultrasonicated at 800W and 20KHz for 30min, and then evaporated under reduced pressure to obtain 5wt% nanocellulose;

[0057] Step 5: preparing a 2 wt% ultrasonically dispersed nano-silica dispersion;

[0058] Step 6: Add 10 parts of the solution from step 4, 1.25 parts of the solution from step 5, and 20 parts of glycerol to 100 parts of the solution from step 1, and then incubate under certain conditions (80°C water bath for 4 hours or 80°C microwave water bath for 45 minutes) to obtain a coating solution;

[0059] Step 7: Add a certain amount of humic acid and ion-based fertilizer to the coating solution obtained in step 6, mix well, and then cast and dry on a polytetrafluoroethylene mold to form a film; the mass ratio of humic acid to PVA is 30-45:100; the mass ratio of the ion-based fertilizer to humic acid is 1:2; the ion-based fertilizer is a common nitrogen, phosphorus, and potassium water-soluble fertilizer, and a specific ratio can be set according to the needs of a certain plant, but a general compound fertilizer ratio will do;

[0060] Step 8: Prepare a 10 wt% poly (butylene terephthalate adipate) PBAT solution, the solvent being N,N-dimethylformamide (DMF) and dichloromethane (DCM) = 2:3;

[0061] Step 9: The base film obtained in Step 7 was electrospun with the solution from Step 8 to form a Janus structure, achieving air-water extraction. The electrospinning parameters were 18 kV, a roller receiving device 15 cm from the needle tip, 45% ± 5% humidity, 30°C, and a controlled feed rate of 1.5 ml / h.

[0062] The present invention has the function of extracting water from air, with an efficiency of 254ml·m -2 ·day -1 , and also has the function of slow release of fertilizer. Humic acid forms a hydrogen bond network with PVA hydroxyl group through carboxyl group, realizing water-responsive controlled release, reducing irrigation demand in arid areas by 30%-40%. 20-day fertilizer release rate, taking ammonium chloride and sodium phosphate as an example, Figure 2 As shown, fertilizer utilization rate increased from 30% to over 50%. All film components (PVA, CNF, HA, PBAT) completely degrade in the soil within 60-90 days, leaving no microplastics. The degradation products are converted into humus, increasing the soil organic matter content by 0.5%-1.2%, forming an ecological closed loop of "film waste into fertilizer."

[0063] like Figure 5 As shown in the figure, it is a Fourier infrared spectrum, which can prove the successful introduction of nanocellulose, silicon source and humic acid. Figure 6 As shown in the SEM image of the PBAT layer, it can be seen that there is a porous fiber structure. Figure 7 As shown in the figure, the horizontal direction of the corn planting represents the time, which is 5, 10, 15, 20, and 25 days respectively, and the vertical direction represents the conditions, which are multifunctional mulch film, ordinary PE mulch film, and no mulch film covering from top to bottom, which proves that it can indeed promote plant growth. Figures 8 to 13 and Figures 14-19 , respectively, are water contact angle photos of the PBAT layer and the hydrophilic layer at 0.246812s, which can prove that they have unidirectional conductivity to water.

[0064] Example 2:

[0065] This embodiment differs from Example 1 in that, in step 4, the final mass fraction of nanocellulose is 2.5%.

[0066] Example 3:

[0067] This embodiment differs from Example 1 in that, in step 4, the final mass fraction of nanocellulose is 7.5%.

[0068] Example 4:

[0069] This embodiment differs from Example 1 in that, in step 4, the final mass fraction of nanocellulose is 10%.

[0070] like Figure 4 Shown is a comparison chart of the tensile strength of membranes with different nanocellulose contents in Examples 1 to 4.

Claims

1. A method for preparing a multifunctional fully degradable mulch film with water intake, slow release, and soil improvement functions, characterized by: The method is: Step 1: Prepare 8-12 wt% PVA aqueous solution; Step 2: Extracting 3-8 wt% nanocellulose from plant fibers by a two-step DES method; Step 3: preparing a 1-4 wt% ultrasonically dispersed silicon source dispersion; Step 4: adding 10 parts of the solution from step 2, 1.25 parts of the solution from step 3, and 20 parts of glycerol to 100 parts of the solution from step 1, and then obtaining a coating solution under certain conditions; Step 5: adding a certain amount of humic acid and ion-based fertilizer to the coating solution obtained in step 4, mixing evenly, and then casting and drying on a polytetrafluoroethylene mold to form a base film; the mass ratio of the humic acid to PVA is 30-45:100; the mass ratio of the ion-based fertilizer to humic acid is 1:2; Step 6: preparing 8-12 wt% hydrophobic degradable material solution; Step 7: Use the solution from step 6 to electrospin on the base film obtained in step 5 to form a Janus structure, thereby obtaining a multifunctional and fully degradable ground film.

2. The method for preparing a multifunctional fully degradable mulch film with water intake, slow release and soil improvement functions according to claim 1, characterized in that: In step 2, the plant fiber comes from any crop straw such as corn, wheat, rice, sorghum, etc.

3. The method for preparing a multifunctional fully degradable mulch film with water intake, slow release and soil improvement functions according to claim 1 or 2, characterized in that: The step 2 is specifically as follows: (1) The pretreated straw (washed, dried, and crushed to 40 mesh) was added to the DES-1 solution at a solid-liquid ratio of 1 g:10 mL, and then microwaved at 80 °C for 1 h. The solid phase was retained by filtration to obtain filter cake 1; (2) Filter cake 1 was added to DES-2 solution at a solid-liquid ratio of 1 g:10 mL, microwaved at 80 °C for 45 min, and then filtered to obtain filter cake 2; (3) The filter cake 2 was then dispersed in water at a mass fraction of 0.5%, ultrasonicated at 800W and 20KHz for 30 minutes, and then evaporated under reduced pressure to obtain 2.5-10wt% nanocellulose.

4. The method for preparing a corn straw nanocellulose reinforced water-resistant and fully degradable mulch film according to claim 3, characterized in that: In step 2, the DES-1 solution consists of component 1 and component 2; component 1 is choline chloride, component 2 is one of glycerol, urea or ethylene glycol, and the molar ratio of component 1 to component 2 is 1:2; the DES-2 solution consists of component 3 and component 4; component 3 is choline chloride, component 4 is one of citric acid, lactic acid, oxalic acid or acetic acid, and the molar ratio of component 3 to component 4 is 1:

2.

5. The method for preparing a multifunctional fully degradable mulch film with water intake, slow release and soil improvement functions according to claim 1, characterized in that: In step 3, the silicon source is one or more of nano-silicon dioxide, calcium silicate, ethyl orthosilicate or methyl orthosilicate.

6. The method for preparing a multifunctional fully degradable mulch film with water intake, slow release and soil improvement functions according to claim 1, characterized in that: In step 4, the certain conditions refer to 80° C. water bath for 4 h or 80° C. microwave water bath for 45 min.

7. The method for preparing a multifunctional fully degradable mulch film with water intake, slow release and soil improvement functions according to claim 1, characterized in that: In step six, the hydrophobic degradable material is one or more of polybutylene terephthalate-adipate (PBAT), polylactic acid (PLA) or polyurethane (PU).

8. The method for preparing a multifunctional fully degradable mulch film with water intake, slow release and soil improvement functions according to claim 1, characterized in that: In step 6, the solvent of the solution is N,N-dimethylformamide (DMF):dichloromethane (DCM)=2:

3.

9. The method for preparing a multifunctional fully degradable mulch film with water intake, slow release and soil improvement functions according to claim 1, characterized in that: In step seven, the electrospinning parameters are 15-20 kV voltage, roller receiving, roller distance of 15 cm from the needle tip, 45% ± 5% air humidity, 30° C., and a controlled propulsion rate of 1.5 ml / h.

10. A multifunctional fully degradable mulch film with water intake, slow release and soil improvement functions, prepared by the preparation method according to any one of claims 1 to 9.

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