Stearic acid modified degradable waterproof full-biomass mulching film as well as preparation method and application thereof

Abstract

The invention discloses a stearic acid modified degradable waterproof full-biomass mulching film and a preparation method and application thereof, and belongs to the technical field of degradable agricultural mulching films. Stearic acid and hydroxyl groups on the surface of a fiber base material form ester bond crosslinking, hydrogen bond and intermolecular acting force, an alkyl chain compact hydrophobic layer is formed on the surface of a film material, and therefore the degradable waterproof full-biomass mulching film is obtained. The waterproof performance and the mechanical strength of the mulching film are obviously improved; and the mulching film keeps the full-biodegradation characteristic, can be naturally degraded in a field environment, and is free of environmental pollution. The mulching film is simple in preparation process, low in cost and excellent in waterproof and soil moisture preservation effect, can effectively improve the growth index and yield of crops, is suitable for planting various crops such as corn and wheat, solves the technical bottlenecks of pollution of a traditional plastic mulching film and poor waterproofness of an existing fiber-based mulching film, and has a wide application prospect.

Description

A stearic acid-modified biodegradable waterproof biofilm, its preparation method and application Technical Field

[0001] This invention belongs to the field of biodegradable agricultural mulch film technology, and particularly relates to a stearic acid-modified biodegradable waterproof biofilm, its preparation method and application. Background Technology

[0002] Mulching technology is a key means of increasing crop yields in modern agriculture, offering advantages such as heat preservation, moisture retention, and suppression of weed growth. Traditional agricultural mulch films are mostly made of polyethylene (PE film), which, although inexpensive and stable in performance, is difficult to degrade naturally. Long-term use can lead to soil compaction and environmental pollution, seriously threatening sustainable agricultural development.

[0003] To address the pollution problem caused by plastic mulch films, biodegradable fiber-based base membranes have become a research hotspot. Fiber-based base membranes, made from agricultural waste fibers and natural plant fibers, are fully biodegradable, resource-renewable, and inexpensive. However, existing fiber-based base membranes have significant technical drawbacks: the fiber surface is rich in hydrophilic groups such as hydroxyl groups, and the membrane material contains numerous pores, resulting in poor waterproofing, significant capillary absorption, and a sharp decrease in mechanical strength upon contact with water. Furthermore, their water retention capacity is insufficient to meet the moisture retention needs of crops throughout their growth cycle, limiting their large-scale application.

[0004] In existing technologies, physical coating methods using hydrophobic substances such as paraffin and resin are prone to coating peeling, while chemical modification using silane coupling agents is costly, and acetylation modification uses toxic reagents, neither of which meets the environmental protection and low-cost requirements for agricultural applications. Stearic acid, as a natural fatty acid, possesses both hydrophobic long chains and reactive carboxyl groups, is widely available, and has good biocompatibility. However, a mature technical solution has yet to be developed for how to achieve synergistic optimization of waterproof performance, mechanical strength, and degradation performance through precise control of the amount of stearic acid added and the modification process.

[0005] Currently, there are no patents related to stearic acid-modified fiber-based mulch films, either domestically or internationally. Related patents primarily focus on single-fiber modification, using cellulose as a non-primary additive, or mulch film preparation. Examples include Shandong LanHai Crystal Technology Co., Ltd.'s "A High-Strength Degradable Mulch Film and Its Preparation Method (CN118930919A)," Tianjin Yongxu New Materials Co., Ltd.'s "A Controllable Degradable Thermal Insulation and Moisture Retention Mulch Film and Its Preparation Method (CN118271809A)," Wuxi University's "A Cellulose-Reinforced Starch-Based Biodegradable Mulch Film and Its Preparation Method (CN114874503A)," and Shanghai Leyi Plastic Products Co., Ltd.'s "A Degradable Environmentally Friendly Plastic Film, Its Preparation Method and Application (CN113493572A)," none of which involve stearic acid modification. Summary of the Invention

[0006] To address the aforementioned technical problems, this invention proposes a stearic acid-modified biodegradable waterproof biofilm, its preparation method, and its application.

[0007] To achieve the above objectives, the present invention provides the following technical solution: a method for preparing a stearic acid-modified biodegradable waterproof biofilm, comprising the following steps: after hydrolytically disintegrating biomass biodegradable fibers, the fibers are paper-made, hot-pressed, and dried to obtain a basic fiber mulch film blank; stearic acid is heated and melted and uniformly coated on the surface of the basic fiber mulch film blank; the fibers are heated under vacuum conditions for thermal modification; and after the reaction is completed, the fibers are cooled to obtain the stearic acid-modified biodegradable waterproof biofilm.

[0008] Beneficial effects: This invention innovates upon the traditional papermaking process system, enabling modular construction and phased implementation of the modification process. This significantly reduces the technical transformation costs and process adaptation difficulties for traditional papermaking enterprises. It can directly rely on existing production lines to complete upgrades and iterations, providing a convenient and feasible process path for the large-scale production and industrial promotion of the biodegradable, waterproof, and fully biocompatible membrane in this invention. It has significant industrial transformation advantages and application promotion value.

[0009] Preferably, the preparation method of the biomass biodegradable fiber includes the following steps: crushing the biomass raw material, adding water and alkali, cooking, pulping, and then rinsing, drying, and sieving to obtain the biomass biodegradable fiber.

[0010] Beneficial effects: This invention relies on the mature pulping process system of the papermaking industry to carry out biomass raw material processing and fiber preparation. It can be directly adapted to the equipment and technical processes of existing papermaking production lines without the need for large-scale equipment modification. It makes full use of the industry's existing process accumulation and supporting resources, and significantly reduces the preparation threshold and production cost of biodegradable biomass fibers. It has strong process compatibility and good implementation, laying a solid foundation of low-cost and highly adaptable fiber raw materials for the large-scale and industrialized preparation of modified mulch films.

[0011] Preferably, the biomass raw material is corn stalks.

[0012] Beneficial effects: Corn stalks are widely available, readily available, and inexpensive. Using corn stalks as biomass raw materials can simultaneously achieve high-value utilization of agricultural waste biomass, effectively solve the environmental problems caused by the indiscriminate disposal of corn stalks, and have the dual benefits of resource recycling and ecological environmental protection. Moreover, the raw material supply is highly compatible with agricultural production scenarios, which is in line with the industrial orientation of green agricultural development and agricultural-livestock cycle, and provides stable and environmentally friendly raw material support for the sustainable production of biodegradable mulch film.

[0013] Preferably, the alkali is potassium hydroxide.

[0014] Beneficial effects: The present invention uses potassium hydroxide as an effective alkali for delignin removal. The potassium it contains is an essential nutrient for crop growth. After the mulch film degrades, it can release potassium, thereby supplementing the soil potassium nutrition. It has the dual functions of mulch film protection and fertilizer assistance. Potassium is a nutrient for crop growth.

[0015] Preferably, the cooking temperature is 80-120℃, more preferably 100℃, and the cooking time is 1-3 hours, more preferably 2 hours.

[0016] Beneficial effects: This cooking process can effectively accelerate the decomposition of cellulose and lignin components in biomass raw materials and improve pulping efficiency.

[0017] Preferably, the pulping is performed using a Wali pulping machine to homogenize and extract fibers, with a pulping degree of 24°.

[0018] Beneficial effects: The pulping process can effectively extract fibers and achieve uniform fiber dispersion, ensuring uniform fiber quality.

[0019] Preferably, the screening process involves hydraulic screening with a thickness of 0.15 mm. 45mm perforated plate.

[0020] Preferably, the hydraulic dewatering specifically involves mixing the corn stalk fiber with water at a solid-liquid mass ratio of 1:200-1:400, and then hydraulically dewatering the mixture for 1-3 minutes at a dewatering machine speed of 3000 r / min.

[0021] Beneficial effects: Under these optimized parameters, hydraulic dewatering can achieve uniform dispersion of corn stalk fibers and uniform dewatering effect; at the same time, the design of this dewatering process provides a feasible alternative for modularization of raw material fibers and third-party supply.

[0022] More preferably, during the papermaking process, a sheet forming machine is used to form the paper, controlling the basis weight of the paper to be 120-160 g / m³. 2 .

[0023] Preferably, the hot pressing temperature is 100℃, the time is 5-6 minutes, and the pressure is 0.3MPa.

[0024] Beneficial effects: The above process can ensure that the basic fiber mulch film blank is formed in a regular shape and has a certain thickness and mechanical strength; the pressurized hot pressing can make the film blank structure dense and the mechanical properties stable, laying a solid foundation for the substrate of subsequent stearic acid modification and the comprehensive performance of the finished mulch film.

[0025] Preferably, the mass ratio of stearic acid to the base fiber mulch film is (0.1-1):1.

[0026] Beneficial effects: This ratio range can effectively ensure that the fiber mulch film has excellent and stable waterproof performance; and within this ratio range, as the amount of stearic acid added increases, the mechanical properties of the mulch film show a positive upward trend, realizing the synergistic regulation and optimization of the waterproof performance and mechanical properties of the mulch film.

[0027] Preferably, the temperature for thermal modification is 90-100℃ and the time is 3-30 minutes.

[0028] Beneficial effects: During this process, stearic acid undergoes ester bond cross-linking reaction and physical adsorption loading with the hydroxyl groups on the fiber surface, allowing stearic acid to better replace or mask the hydrophilic groups of cellulose.

[0029] A stearic acid-modified biodegradable waterproof biofilm prepared by the method described above.

[0030] Beneficial Effects: The stearic acid-modified biodegradable waterproof fully bio-based mulch membrane of this invention is prepared using the aforementioned process, possessing excellent product performance, outstanding industrial adaptability, and significant ecological benefits. The preparation process of this mulch membrane is highly compatible with traditional papermaking production lines, and the product itself possesses both excellent waterproof properties and controllable biodegradability; its mechanical properties can also be adjusted and optimized as needed. The mulch membrane provided by this invention is composed entirely of bio-based components, leaving no residue or secondary pollution after degradation, making it environmentally friendly and possessing broad application prospects.

[0031] Application of a stearic acid-modified biodegradable waterproof biofilm in crop cultivation.

[0032] More preferably, the crop is one or more of corn, wheat, cotton and sunflower.

[0033] Beneficial effects: The main planting areas of the above-mentioned crops are mostly concentrated production areas of agricultural waste biomass, which can realize the construction of a regional agricultural and livestock circular industrial chain of "agricultural biomass raw materials - biodegradable mulch film - crop planting - biomass recycling", help form a localized closed loop of raw material supply and product application, and further improve the efficiency of industrial circulation and ecological benefits.

[0034] Compared with existing technologies, this invention has the following advantages and technical effects: Stearic acid is used to modify biomass fibers in this invention. Stearic acid forms stable ester crosslinks, intermolecular forces, and hydrogen bonds with the fiber substrate, improving the density and stability of the membrane structure. Simultaneously, the water retention constant and capacity of the mulch film modified with stearic acid in this invention significantly increase with the amount added, effectively locking in soil moisture and preventing crop drought stress caused by rapid water evaporation, meeting the moisture retention needs of crops such as corn and wheat throughout their entire growth cycle. Furthermore, the mulch film obtained after stearic acid modification in this invention can form a dense hydrophobic layer on its surface, completely inhibiting capillary water absorption by the fiber substrate. This is expected to completely solve the core problems of existing fiber-based mulch films, such as easy softening and breakage due to water absorption, achieving a waterproof effect comparable to traditional PE films. Moreover, the modified mulch film in this invention has fully biodegradable characteristics, adapting to agricultural needs. Its degradation rate is precisely matched with the crop growth cycle, allowing it to completely integrate into the soil after crop harvest without any residual pollution. Furthermore, the modified mulch film obtained by this invention possesses both stable heat preservation and long-lasting moisture retention functions, achieving the dual goals of "environmentally friendly degradation" and "increased yield and improved quality." Finally, this invention employs a combined process of "paper forming + melt modification," which is simple and easy to control, requiring no complex equipment or toxic reagents; stearic acid is widely available (a natural fatty acid that can be extracted from animal and vegetable oils), has low cost, and achieves low energy consumption and zero pollution emissions in large-scale production; the process is adaptable to the modification of existing paper mulch film production lines, requiring no large-scale addition of equipment, thus exhibiting high industrialization feasibility and facilitating rapid promotion and application. Attached Figure Description

[0035] The accompanying drawings, which form part of this invention, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an undue limitation of the invention. In the drawings: Figure 1 is a schematic diagram of the preparation process of the stearic acid-modified biodegradable waterproof biofilm of the present invention; Figure 2 shows the effect of stearic acid addition on the tensile stress of the mulch film in Comparative Examples 1-2 and Examples 1-6; wherein, Comparative Example 1, Comparative Example 2, Example 1, Example 2, Example 3, Example 4, Example 5, and Example 6 represent stearic acid addition amounts of 0%, 5%, 10%, 20%, 25%, 50%, 75%, and 100%, respectively.

[0036] Figure 3 shows the effect of stearic acid addition on the water retention performance of the mulch film in Comparative Examples 1-2, 3-4 and 1-6; where Comparative Example 3 and Comparative Example 4 represent the blank control group without film and the control group covered with PE plastic film, respectively.

[0037] Figure 4 shows the effect of stearic acid addition on the waterproof performance of the mulch film in Comparative Examples 1-2 and Examples 1-6; where (a) is Comparative Examples 1-2 and Examples 1-2; (b) is Examples 3-6; Figure 5 shows the waterproof principle of the mulch film preparation; where (a) is a scanning electron microscope image of the surface of the mulch film obtained in Comparative Example 1; (b) is a scanning electron microscope image of the surface of the mulch film obtained in Example 5; (c) is the test result of the weight loss rate of the mulch film obtained in Comparative Examples 1 and Example 5 after pyrolysis; (d) is the test result of the weight change rate of the mulch film obtained in Comparative Examples 1 and Example 5 after pyrolysis; (e) is a schematic diagram of the ester bond, hydrogen bond and intermolecular force between stearic acid and cellulose molecules in the mulch film obtained in Example 5; Figure 6 shows the effect of Comparative Examples 1, 3-4 and Examples 1-6 on the germination of maize seeds; Figure 7 shows the yield results of maize in the mulch film treated plots obtained in Comparative Examples 1, Example 5 and Comparative Examples 3-4.

[0038] Figure 8 shows the degradation effect of the mulch film obtained in Comparative Example 1 and Example 5; Figure 9 shows the degradation kinetics of the mulch film obtained in Comparative Example 1 and Example 5 in a cornfield. Detailed Implementation

[0039] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0040] In related literature (Wang Wanhua, Gu Xunhong, Dong Xinrui, et al. Study on the waterproof and oil-resistant properties of paper-based composites reinforced with lignin-containing cellulose micro / nanofibers modified by stearic acid [J]. China Pulp & Paper, 2025, 44(4):70-78.), micro / nanofibers were prepared by high-pressure homogenization, which greatly changed the width and length of the fibers, and the water retention value of the composites prepared by them was greater than that of the untreated fibers. However, the preparation process mechanism of these methods is significantly different from that of this invention. The process principle of this invention is as follows: after preparing the base fiber base membrane preform using traditional papermaking technology, stearic acid is uniformly coated on the surface of the base fiber base membrane by impregnation or coating. Then, the stearic acid and cellulose are melt-bonded and esterified by vacuum hot pressing (vacuum optional), thus obtaining the stearic acid-modified biodegradable waterproof biofilm.

[0041] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0042] Unless otherwise specified, all raw materials used in the embodiments of this invention were purchased through commercial channels; the corn stalks were collected from the experimental field at No. 44 Weile Avenue, Yuzhong County, Lanzhou City, Gansu Province; unless otherwise specified, room temperature or normal temperature in the embodiments of this invention refers to 25±3℃.

[0043] Example 1-6 A method for preparing a stearic acid-modified biodegradable waterproof biofilm, as shown in Figure 1, includes the following steps: (1) Substrate pretreatment: Corn stalks are crushed into corn stalk segments less than 5 cm in length, then mixed with water at a solid-liquid mass ratio of 1:100. The potassium hydroxide concentration is set at 1 mol / L to remove lignin. After cooking at 100°C for 2 hours, the mixture is pulped and then hydraulically sieved through a 0.15 mol / L filter. Corn stalk fiber was obtained by rinsing a 45mm perforated plate until neutral and then drying it. The fiber particle size was <0.3mm and the length was <60.0mm.

[0044] (2) Preparation of basic fiber mulch film: Weigh 5g of corn stalk fiber obtained in step (1) above, mix it with water at a solid-liquid mass ratio of 1:400, and then use a dewatering machine at 3000r / min for 3min to hydraulically dewater it so that the corn stalk fiber is evenly dispersed in the water. Then, paper is made by paper forming machine, wherein the paper weight is 159g / m²; after vacuum filtration and hot pressing at 100℃ and 0.3MPa for 6min, and then dried, the basic fiber mulch film blank is obtained.

[0045] (3) Stearic acid modification: Stearic acid was heated and melted at 90°C, and then uniformly coated onto the surface of the base fiber mulch film at mass percentages of 10% (Example 1), 20% (Example 2), 25% (Example 3), 50% (Example 4), 75% (Example 5), and 100% (Example 6), respectively. The mixture was then kept at 100°C under vacuum drying for 20 minutes to allow the stearic acid to undergo ester crosslinking and physical adsorption loading with the hydroxyl groups on the fiber surface. After the reaction was completed and cooled, the stearic acid-modified biodegradable waterproof biofilms of Examples 1-6 were obtained.

[0046] Example 7 A method for preparing a stearic acid-modified biodegradable waterproof biofilm, comprising the following steps: (1) Substrate pretreatment: Corn stalks are crushed into corn stalk segments less than 5 cm in length, then mixed with water at a solid-liquid mass ratio of 1:100, and potassium hydroxide concentration is set at 1 mol / L to remove lignin. After cooking at 100°C for 1 hour, the mixture is pulped and then hydraulically sieved through a 0.15 mol / L filter. Corn stalk fiber was obtained by rinsing a 45mm perforated plate until neutral and then drying it. The fiber particle size was <0.3mm and the length was <60.0mm.

[0047] (2) Preparation of basic fiber mulch film: Weigh 5g of corn stalk fiber obtained in step (1) above, mix it with water at a solid-liquid mass ratio of 1:200, and then use a dewatering machine at 3000r / min for 2min to hydraulically dewater it so that the corn stalk fiber is evenly dispersed in the water. Then, paper is made by paper forming machine, wherein the paper weight is 120g / m²; after vacuum filtration and hot pressing at 100℃ and 0.3MPa for 6min, and then dried, the basic fiber mulch film blank is obtained.

[0048] (3) Stearic acid modification: Stearic acid was heated and melted at 90°C, and then uniformly coated on the surface of the base fiber mulch at a mass percentage of 10%. The mixture was then kept at 95°C in a vacuum drying environment for 5 minutes to allow the stearic acid to undergo ester bond crosslinking and physical adsorption loading with the hydroxyl groups on the fiber surface. After the reaction was completed and cooled, the stearic acid-modified biodegradable waterproof biofilm was obtained.

[0049] Example 8 A method for preparing a stearic acid-modified biodegradable waterproof biofilm, comprising the following steps: (1) Substrate pretreatment: Corn stalks are crushed into corn stalk segments less than 5 cm in length, then mixed with water at a solid-liquid mass ratio of 1:100, and potassium hydroxide concentration is set at 1 mol / L to remove lignin. After cooking at 100°C for 5 hours, the mixture is pulped and then hydraulically sieved through a 0.15 mol / L filter. Corn stalk fiber was obtained by rinsing a 45mm perforated plate until neutral and then drying it. The fiber particle size was <0.3mm and the length was <60.0mm.

[0050] (2) Preparation of basic fiber mulch film: Weigh 5g of corn stalk fiber obtained in step (1) above, mix it with water at a solid-liquid mass ratio of 1:300, and then use a dewatering machine at 3000r / min to hydraulically dewater for 1min, so that the corn stalk fiber is evenly dispersed in the water. Then, paper is made by paper forming machine, wherein the paper weight is 160g / m²; after vacuum filtration and hot pressing at 100℃ and 0.3MPa for 5min, and then dried, the basic fiber mulch film blank is obtained.

[0051] (3) Stearic acid modification: Stearic acid was heated and melted at 90°C, and then uniformly coated on the surface of the base fiber mulch at a mass percentage of 10%. The mixture was then kept at 90°C in a vacuum drying environment for 30 minutes to allow the stearic acid to undergo ester bond crosslinking and physical adsorption loading with the hydroxyl groups on the fiber surface. After the reaction was completed and cooled, the stearic acid-modified biodegradable waterproof biofilm was obtained.

[0052] The only difference between Comparative Example 1 and Example 1 is that step (3) is not included, and only the basic fiber mulch film blank is used. The remaining process steps and parameters are the same as those in Example 1.

[0053] The only difference between Comparative Example 2 and Example 1 is that the amount of stearic acid coated in step (3) is 5%. The remaining process steps and parameters are the same as in Example 1.

[0054] Comparative Example 3: Uncoated group.

[0055] Comparative Example 4 used commercially available PE film, model 1 mil thick white mulch film, 1.5 meters wide and 660 meters long.

[0056] Technical effects: 1. Performance tests were conducted on the mulch films obtained in Examples 1-6, Comparative Examples 1-2, and Comparative Examples 3-4.

[0057] Among them, mechanical properties were measured by tensile stress using an electronic tensile tester; water retention properties were measured by the gravimetric method to determine the water retention constant k; waterproof properties were measured by observation, using a pipette to place a 20µL droplet on the membrane surface and observing the capillary phenomenon of the liquid on the biomass membrane; and degradation properties were evaluated by the attenuation of the tensile stress of the mulch film.

[0058] The results are shown in Table 1: Table 1 Figure 2 shows the effect of stearic acid addition on the tensile stress of the mulch film in Comparative Examples 1-2 and Examples 1-6. As can be seen from Figure 2, the overall tensile stress of the mulch film gradually increases with the increase of stearic acid addition.

[0059] Figure 3 shows the effect of stearic acid addition on the water retention performance of the mulch film in Comparative Examples 1-2 and Examples 1-6. As can be seen from Figure 3, the water retention performance of the mulch film gradually improves with the increase of stearic acid addition. When the stearic acid addition reaches 75%, the water retention performance no longer increases with the increase of stearic acid addition.

[0060] Figure 4 shows the effect of stearic acid addition on the waterproof performance of the mulch film in Comparative Examples 1-2 and Examples 1-6. As can be seen from Figure 4, when the stearic acid addition in Comparative Example 1 is 0%, capillary action is very obvious; when the stearic acid addition in Comparative Example 2 is 5%, capillary action is also noticeable. When the stearic acid addition in Examples 1-6 is above 10%, the capillary action disappears, indicating that the waterproof performance of stearic acid has been significantly improved.

[0061] Figure 5 illustrates the waterproofing principle of the mulch films obtained in Comparative Example 1 and Example 5. In Figure 5, parts (a)-(b) show the phenomenon of stearic acid coating on the fiber substrate surface through scanning electron microscopy. In Figure 5, parts (c)-(d) show that approximately 54% of the physically coated or intermolecularly bonded stearic acid decomposes first at 270°C, while the stearic acid cross-linked by ester bonds gradually decomposes at 270-387°C. In Figure 5, part (e) is a schematic diagram of the bonding between stearic acid and the fiber substrate.

[0062] Figure 6 shows the effects of Comparative Examples 1, 3-4, and 1-6 on maize seed germination; it can be seen that the seeds treated in Comparative Example 3 did not germinate. Compared to Comparative Example 4, stearic acid modification in Examples 1-6 significantly promoted seed germination. Compared to Comparative Example 1, the promoting effect in Examples 1-6 increased with the amount of stearic acid added.

[0063] Considering that the water retention performance of the biofilm prepared by stearic acid modification in Example 5 is comparable to that of Example 6 and PE film, Datian chose Example 5 for testing.

[0064] Figure 7 shows the effects of Comparative Example 1, Example 5, and Comparative Example 3 on promoting maize growth and yield. Stearic acid modified fiber-based biofilm can promote an increase in maize yield.

[0065] Figure 8 shows the degradation effect of the mulch film obtained in Comparative Example 1 and Example 5. As can be seen from the figure, as the corn grows, the surface of the modified biofilm gradually becomes covered with bacterial spots and exhibits different degrees of damage and degradation characteristics.

[0066] Figure 9 shows the degradation kinetics of the mulch films obtained in Comparative Example 1 and Example 5. The results show that stearic acid modification can effectively slow down the degradation rate of the mulch film. By adjusting the amount of stearic acid added, the degradation process of the mulch film can be precisely controlled. Based on this, biodegradable mulch films that meet the needs of different agricultural planting scenarios can be developed, greatly expanding the application scenarios and scope of the products.

[0067] As can be seen from Table 1 and Figures 2-9, the modified mulch film obtained by this invention has the following advantages: 1. Improved mechanical properties: Stearic acid forms stable ester crosslinks, intermolecular forces, and hydrogen bonds with the fiber substrate (Figure 5), which improves the density and stability of the film structure; when the amount of stearic acid added is ≥10%, the tensile stress of the mulch film is ≥2.57kN / m, which can meet the stretching and laying requirements during field mulching; 2. Significantly improved water retention performance: After modification with stearic acid, the water retention constant and capacity of the modified mulch film in this invention show a significant increase with the amount added (Figure 3), which is 4.05~8.53 times higher than the water retention constant of the un-mulched film and 1.13~2.37 times higher than the water retention constant of the unmodified film. It can effectively lock in soil moisture, avoid crop drought stress caused by rapid water evaporation, and meet the moisture retention requirements of crops such as corn and wheat throughout their entire growth period.

[0068] 3. Significantly improved waterproof performance: After being modified with stearic acid, the modified mulch film of this invention forms a dense hydrophobic layer on its surface (part (b) in Figure 5), which completely inhibits the capillary water absorption phenomenon of the fiber substrate (Figure 4). Compared with the unmodified mulch film (which has obvious capillary water absorption), it achieves a qualitative leap in waterproof performance and is expected to completely solve the core pain points of existing fiber base mulch films that are easy to soften and break due to water absorption. The waterproof effect is comparable to that of traditional PE film.

[0069] 4. Fully biodegradable characteristics: The modified mulch film obtained by this invention retains its fully biodegradable nature, with a natural degradation rate of ≥88% within 120 days in a field environment (Figures 8 and 9), and a goodness of fit R of the degradation kinetic curve. 2 =0.98 (p<0.01), the degradation process is stable and controllable (Figure 9); the degradation rate is precisely matched with the crop growth cycle, and the crop can be completely integrated into the soil after harvest without any residual pollution. This not only avoids the "white pollution" of PE film, but also solves the problem of unmodified mulch film degrading too quickly (mechanical failure after 60 days).

[0070] 5. Effects on crop growth: Germination tests were conducted on maize hybrid seeds (Dongdan 1331) using stearic acid-modified biodegradable waterproof biofilms obtained in Comparative Examples 1, 3 and Examples 1-5.

[0071] Example 5 (which showed the best water retention) was used to cover the cornfields. Corn yield was measured after harvest, with Comparative Examples 1 and 3 provided as controls. All other field management methods were the same. The corn yield of the different treatments was in the order of Comparative Example 3 (190g / plant) < Comparative Example 1 (234g / plant) < Example 5 (235g / plant), showing an increase compared to both un-mulched and unmodified fields, achieving the dual goals of "environmentally friendly degradation" and "increased yield and improved quality."

[0072] The above are merely preferred embodiments of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A method for preparing a stearic acid-modified biodegradable waterproof biofilm, characterized in that, Includes the following steps: Biodegradable biomass fibers are hydraulically decomposed, then paper-making, hot-pressing, and drying are performed to obtain a basic fiber mulch film blank. Stearic acid is heated and melted and then uniformly coated on the surface of the basic fiber mulch film blank. The film blank is then heated under vacuum conditions for thermal modification. After the reaction is completed, the film is cooled to obtain the stearic acid-modified biodegradable waterproof bio-based mulch film.

2. The method for preparing a stearic acid-modified biodegradable waterproof biofilm according to claim 1, characterized in that, The preparation method of the biodegradable biomass fiber includes the following steps: crushing biomass raw materials, adding water and alkali, cooking, pulping, and then rinsing, drying, and sieving to obtain the biodegradable biomass fiber.

3. The method for preparing a stearic acid-modified biodegradable waterproof biofilm according to claim 2, characterized in that, The cooking temperature is 80-120℃, and the time is 1-3 hours.

4. The method for preparing a stearic acid-modified biodegradable waterproof biofilm according to claim 1, characterized in that, The hydraulic dewatering process specifically involves mixing the corn stalk fiber with water at a solid-liquid mass ratio of 1:200-1:400, and then using a dewatering machine at a speed of 3000 r / min for 1-3 minutes.

5. The method for preparing a stearic acid-modified biodegradable waterproof biofilm according to claim 1, characterized in that, The hot pressing temperature is 100℃, the time is 5-6 minutes, and the pressure is 0.3MPa.

6. The method for preparing a stearic acid-modified biodegradable waterproof biofilm according to claim 1, characterized in that, The mass ratio of stearic acid to the base fiber mulch film is (0.1-1):

1.

7. The method for preparing a stearic acid-modified biodegradable waterproof biofilm according to claim 1, characterized in that, The thermal modification is performed at a temperature of 90-100℃ for 3-30 minutes.

8. The stearic acid-modified biodegradable waterproof biofilm prepared by the preparation method according to any one of claims 1-7.

9. The application of the stearic acid-modified biodegradable waterproof biofilm as described in claim 8 in crop cultivation.

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