Rice straw-based liquid mulch emulsion, and preparation method and application thereof

Abstract

The application discloses a rice straw-based liquid mulch emulsion and a preparation method and application thereof. The preparation method comprises the following steps: adding pretreated rice straw into a sodium hydroxide solution for alkali treatment, so as to obtain rice straw fibers and a silicon-containing black liquor; washing and bleaching the rice straw fibers, so as to obtain bleached rice straw fibers; first standing the silicon-containing black liquor, then adjusting the pH value, and continuing to stand, so as to obtain a silicon-containing dispersion liquid; mixing the bleached rice straw fibers with an alkaline alcohol solution and activating, then adding chloroacetic acid for etherification reaction, so as to obtain carboxymethyl cellulose; mixing a polyvinyl alcohol solution and the carboxymethyl cellulose solution, and adding the silicon-containing dispersion liquid under stirring, and then supplementing water, so as to obtain the rice straw-based liquid mulch emulsion. The rice straw-based liquid mulch emulsion prepared by the application can be applied to the covering of cultivation soil, has the advantages of excellent film forming strength, toughness, light shielding and soil covering adaptability, and the like, and has the advantages of wide raw material sources, simple preparation process and suitability for large-scale popularization.

Description

Technical Field

[0001] This invention relates to the field of agricultural waste resource utilization, specifically to a rice straw-based liquid mulch film emulsion, its preparation method, and its application. Background Technology

[0002] Mulching technology, as an important agronomic measure, has been widely used in agricultural production in my country, and has the functions of heat preservation and moisture retention, weed suppression and yield increase, and improved fertilizer utilization efficiency. Although the petroleum-based plastic mulch films such as polyethylene (PE) commonly used in agricultural production are low in cost and have good covering effect, they are difficult to completely recycle in the field. The residual film left in the soil for a long time can easily lead to soil compaction, reduced aeration, and damage to the topsoil structure.

[0003] In recent years, bio-based biodegradable mulch films have attracted attention. Liquid mulch films can be applied to the soil surface by spraying or pouring to form a continuous film layer, which is convenient to construct and does not require recycling. However, existing liquid mulch films are mostly made from industrial starch, commercial cellulose, or synthetic polymers as raw materials, which have problems such as high raw material costs, reliance on industrial systems for resource sources, and low coupling with agricultural production. At the same time, some products have insufficient film strength, poor water resistance, and limited coverage period. Therefore, there is an urgent need to develop new liquid mulch films to meet the needs of modern agriculture for green, low-carbon, and sustainable development. Summary of the Invention

[0004] The technical problem to be solved by the present invention is to overcome the shortcomings of the prior art, especially the problems of insufficient film-forming strength, poor durability, weak synergy of covering functions and low utilization of straw resources of existing liquid mulch films. The present invention provides a rice straw-based liquid mulch emulsion with excellent film-forming strength, toughness, light-blocking performance and soil covering adaptability, as well as its preparation method and application.

[0005] To solve the above-mentioned technical problems, the present invention adopts the following technical solution.

[0006] A method for preparing a rice straw-based liquid mulch film emulsion includes the following steps:

[0007] (1) The rice straw is dried, crushed and sieved to obtain pretreated rice straw;

[0008] (2) The pretreated rice straw is added to sodium hydroxide solution and treated with alkali at 15℃~35℃. After filtration and separation, rice straw fiber and silicon-containing black liquor are obtained. The rice straw fiber is washed until the pH value is 7~8. The washed rice straw fiber is added to hydrogen peroxide solution for bleaching to obtain bleached rice straw fiber.

[0009] (3) The silicon-containing black liquor obtained in step (2) is first allowed to stand, and then the pH value is adjusted to 8-9 so that the silicon is stably dispersed in colloidal form. After standing, a silicon-containing dispersion is obtained. The silicon-containing dispersion contains 35mg / L-70mg / L of silicon, 2.0g / L-5.0g / L of cellulose, 10.0g / L-25.0g / L of hemicellulose, and 25.0g / L-50.0g / L of lignin. The bleached rice straw fiber obtained in step (2) is mixed with an alkaline alcohol solution and stirred at 30℃-40℃ for activation. Then chloroacetic acid is added and etherification reaction is carried out at 30℃-40℃. After the reaction is completed, the pH value is adjusted to 7-8. The precipitate obtained after filtration is washed with ethanol solution and dried to obtain carboxymethyl cellulose.

[0010] (4) Add polyvinyl alcohol to water and heat to dissolve it to obtain a polyvinyl alcohol solution. Add the carboxymethyl cellulose obtained in step (3) to water and heat to dissolve it to obtain a carboxymethyl cellulose solution. Mix the polyvinyl alcohol solution with the carboxymethyl cellulose solution and add the silicon-containing dispersion obtained in step (3) under stirring to obtain rice straw-based liquid mulch film emulsion.

[0011] In the preferred embodiment of the above-mentioned method for preparing rice straw-based liquid mulch film emulsion, in step (2), the solid-liquid ratio of the pretreated rice straw and the sodium hydroxide solution is 1g:8mL~15mL, and the mass fraction of sodium hydroxide in the sodium hydroxide solution is 3%~8%; the solid-liquid ratio of the washed rice straw fiber and the hydrogen peroxide solution is 1g:10mL~15mL, and the mass fraction of hydrogen peroxide in the hydrogen peroxide solution is 2%~5%.

[0012] In the preferred method for preparing the above-mentioned rice straw-based liquid mulch emulsion, in step (3), the addition ratio of the bleached rice straw fiber, alkaline alcohol solution, and chloroacetic acid is 1g:10mL~20mL:0.5g~1.5g. The alkaline alcohol solution is an ethanol solution containing sodium hydroxide. In the ethanol solution containing sodium hydroxide, the mass fraction of sodium hydroxide is 5%~15%, and the volume fraction of ethanol solution is 70%~90%. The stirring activation time is 50min~90min, and the etherification reaction time is 2h~4h.

[0013] In the above-mentioned method for preparing rice straw-based liquid mulch film emulsion, preferably, in step (4), the ratio of polyvinyl alcohol, carboxymethyl cellulose, and silicon-containing dispersion is 1g~4g∶2g~4g∶20mL~40mL, and the sum of the mass fractions of polyvinyl alcohol and carboxymethyl cellulose in the rice straw-based liquid mulch film emulsion is controlled to be 3%~6%, and the control method includes water replenishment adjustment.

[0014] In the above-mentioned method for preparing rice straw-based liquid mulch film emulsion, preferably, in step (1), the drying temperature is 50℃~70℃, the drying time is 6h~24h, and the sieving is 2mm sieve.

[0015] In the above-mentioned method for preparing rice straw-based liquid mulch film emulsion, preferably, in step (2), the alkali treatment time is 2h to 5h, the rice straw fiber is washed with water, and the bleaching time is 0.5h to 2h.

[0016] In the above-mentioned method for preparing rice straw-based liquid mulch film emulsion, preferably, in step (3), the standing time is 12h to 24h, the pH value is adjusted by an acidic regulator, the acidic regulator is an acetic acid solution, the standing time is 6h to 24h, and the volume fraction of the ethanol solution used for washing is 70% to 95%.

[0017] In the above-mentioned method for preparing rice straw-based liquid mulch emulsion, preferably, in step (4), the temperature at which the polyvinyl alcohol is added to water and heated to dissolve is 60℃~90℃, and the temperature at which the carboxymethyl cellulose is added to water and heated to dissolve is 30℃~40℃.

[0018] As a general technical concept, the present invention also provides a rice straw-based liquid mulch film emulsion prepared by the above-mentioned method.

[0019] As a general technical concept, the present invention also provides the application of the above-mentioned rice straw-based liquid mulch emulsion in cultivation soil.

[0020] The preferred application described above includes spraying or pouring the rice straw-based liquid mulch emulsion onto the soil surface, followed by air drying to form a rice straw-based liquid mulch.

[0021] In this invention, during the alkali treatment process in step (2), some amorphous silicon components in the pretreated rice straw can react with sodium hydroxide to generate soluble sodium silicate, allowing the silicon components to enter the liquid phase black liquor. The main conversion process is as follows:

[0022] Equation (1)

[0023] After adjusting the pH value in step (3), the silicate is further converted into a large amount of silicic acid and a small amount of silanol. The silanol Si(OH)4 is H4SiO4. The conversion process is as follows:

[0024] Equation (2)

[0025] The generated silanols can further condense to form a silicon-oxygen-silicon structure:

[0026] Equation (3)

[0027] Compared with the prior art, the advantages of the present invention are as follows:

[0028] This invention provides a method for preparing a rice straw-based liquid mulch film emulsion. Using rice straw as the main raw material, it achieves high-value utilization of straw resources through an integrated approach involving alkali treatment separation, pH adjustment of silicon-containing black liquor, carboxymethylation modification of cellulose, and film formation by compounding polyvinyl alcohol / carboxymethyl cellulose / silicon-containing dispersion. Compared to existing liquid mulches, which often use industrial starch, commercial cellulose, or synthetic polymers as main materials, resulting in high raw material costs and issues such as insufficient film strength, poor water resistance, and limited coverage duration in some products, this invention uses straw-derived cellulose derivatives as the film-forming framework and introduces silicon-containing components from straw for synergistic enhancement. This approach balances emulsion stability, film-forming performance, and coverage duration, reducing reliance on purchased commercial raw materials.

[0029] In this invention, the silicon-containing black liquor obtained through alkali treatment and separation is pH-adjusted to form a stable silicon-containing dispersion, which participates in the compounding as an inorganic functional component. The silicic acid, silanol, and siloxane structures in this silicon-containing dispersion can form a synergistic reinforcing network with components such as carboxymethyl cellulose, hemicellulose, and lignin through hydrogen bonding, physical entanglement, and interfacial filling. This is beneficial for improving the dispersion stability of the emulsion system and enhancing the density, continuity, and durability of the film after formation. Compared with film formation solely relying on organic polymers, the introduction of silicon-containing components enhances the skeletal support of the film, reduces the risk of cracking after drying, and improves its resistance to wind erosion, scour, and water and heat retention. Simultaneously, this process fully utilizes the silicon resources naturally present in rice straw, reducing the need for external inorganic fillers or commercial additives, thus improving the resource utilization rate of agricultural waste and reducing preparation costs.

[0030] In this invention, alkali-treated rice straw fibers are bleached and then modified with carboxymethyl cellulose. Carboxymethyl cellulose serves as a film-forming thickener and skeleton component, and, in combination with polyvinyl alcohol, further enhances the emulsion stability and film strength. This allows the resulting emulsion to be sprayed or poured onto the soil surface and air-dried at room temperature to form a film. Since the main components, such as carboxymethyl cellulose, hemicellulose, and lignin, are all derived from rice straw, they possess good biodegradability. After fulfilling its water-retention, heat-preserving, and slow-release functions, the film layer can gradually break down, degrade, and return to the soil system under the influence of soil microorganisms, moisture, and the natural environment. This reduces the need for manual removal, recycling, and centralized disposal of traditional plastic mulch films. This method not only reduces the risk of residual film pollution but also reduces field operations and labor costs. It also avoids problems such as soil structure damage, decreased aeration, and limited growth of subsequent crops caused by residual film, meeting the application requirements of green, low-carbon, and sustainable agricultural development. Attached Figure Description

[0031] Figure 1 The Fourier transform infrared spectra of the PVA@CMC@Si film of Example 1, the PVA@CMC film of Comparative Example 1, and the PVA film of Comparative Example 2 are shown.

[0032] Figure 2 The UV-Vis transmittance curves are for the PVA@CMC@Si film of Example 1, the PVA@CMC film of Comparative Example 1, and the PVA film of Comparative Example 2 of this invention.

[0033] Figure 3 The tensile stress-strain curves are of the PVA@CMC@Si film of Example 1, the PVA@CMC film of Comparative Example 1, and the PVA film of Comparative Example 2 of the present invention.

[0034] Figure 4 The graph shows the test results of oxygen transmission rate, water vapor transmission rate, and carbon dioxide transmission rate of the PVA@CMC@Si membrane of Example 1, the PVA@CMC membrane of Comparative Example 1, and the PVA membrane of Comparative Example 2 of this invention. Figure 4 (a) is a graph showing the test results for oxygen permeability. Figure 4 (b) is a graph showing the test results for water vapor transmission rate. Figure 4 (c) is a graph showing the test results of carbon dioxide transmission rate.

[0035] Figure 5 The degradation diagrams of the PVA@CMC@Si membrane of Example 1, the PVA@CMC membrane of Comparative Example 1, and the PVA membrane of Comparative Example 2 on the soil surface are shown. Detailed Implementation

[0036] The present invention will be further described below with reference to the accompanying drawings and specific preferred embodiments, but this does not limit the scope of protection of the present invention. All materials and instruments used in the following embodiments are commercially available.

[0037] Example 1

[0038] A method for preparing a rice straw-based liquid mulch film emulsion according to the present invention includes the following steps:

[0039] (1) Dry the rice straw at 65℃ for 8 hours, crush it, and pass it through a 2mm sieve to obtain pretreated rice straw.

[0040] (2) Add the pretreated rice straw to a 5% sodium hydroxide solution. The solid-liquid ratio of the pretreated rice straw to the sodium hydroxide solution is 1g:10mL. Treat with alkali at 30℃ for 3.5h. After filtration and separation, rice straw fiber and silicon-containing black liquor are obtained. Wash the rice straw fiber with water until the pH value is 7 (neutral). Add the washed rice straw fiber to a 3% hydrogen peroxide solution. The solid-liquid ratio of the washed rice straw fiber to the hydrogen peroxide solution is 1g:12mL. After bleaching for 1h, bleached rice straw fiber is obtained.

[0041] (3) The silicon-containing black liquor obtained in step (2) was first allowed to stand for 12 hours, and then the pH value was adjusted to 8.5 with a 95% acetic acid solution to make the silicon stably dispersed in colloidal form. It was allowed to stand for another 12 hours until a milky white silicon-containing dispersion was formed. The silicon content in the silicon-containing dispersion was 43 mg / L, the cellulose content was 3.6 g / L, the hemicellulose content was 15.4 g / L, and the lignin content was 34.6 g / L. The bleached rice straw fiber obtained in step (2) was added to an alkaline alcohol solution and stirred and activated at 35°C for 70 minutes. Chloroacetic acid was then added. The etherification reaction was carried out at 35℃ for 3 hours. The ratio of bleached rice straw fiber, alkaline alcohol solution, and chloroacetic acid was 1g:15mL:1g. The alkaline alcohol solution was an ethanol solution containing sodium hydroxide, in which the mass fraction of sodium hydroxide was 10% and the volume fraction of ethanol solution (i.e., aqueous solution of ethanol) was 85%. After the reaction was completed, the pH was adjusted to 7. The precipitate obtained after filtration was washed with a 95% volume fraction ethanol solution and dried to obtain carboxymethyl cellulose (CMC, also known as rice straw-based carboxymethyl cellulose).

[0042] (4) Add 4.0g of polyvinyl alcohol (PVA) to 60mL of deionized water and heat at 85℃ to dissolve, obtaining a polyvinyl alcohol solution. Add 2.0g of carboxymethyl cellulose obtained in step (3) to 40mL of deionized water and heat at 40℃ to dissolve, obtaining a carboxymethyl cellulose solution. Mix the polyvinyl alcohol solution and the carboxymethyl cellulose solution, and add 20mL of the silicon-containing dispersion obtained in step (3) while stirring. Add water to a total volume of 150mL to obtain a rice straw-based liquid mulch film emulsion, namely PVA@CMC@Si liquid mulch film emulsion. The final mass fraction of polyvinyl alcohol and carboxymethyl cellulose in the obtained mulch film emulsion is 4%.

[0043] The application of the rice straw-based liquid mulch emulsion prepared in this embodiment in cultivated soil (especially vegetable cultivation soil) includes the following process:

[0044] The rice straw-based liquid mulch emulsion prepared in this embodiment is evenly sprayed onto the prepared soil surface using a sprayer, ideally forming a continuous moist film layer on the soil surface. This soil can be used to cultivate water spinach. After natural air drying, a rice straw-based liquid mulch film (covering layer) is formed, denoted as PVA@CMC@Si film. During the mulching period, appropriate re-spraying can be carried out according to rainfall and irrigation conditions.

[0045] Example 2

[0046] A method for preparing a rice straw-based liquid mulch film emulsion according to the present invention includes the following steps:

[0047] (1) Dry the rice straw at 65℃ for 8 hours, crush it, and pass it through a 2mm sieve to obtain pretreated rice straw.

[0048] (2) Add the pretreated rice straw to a 6% sodium hydroxide solution. The solid-liquid ratio of the pretreated rice straw to the sodium hydroxide solution is 1g:12mL. The rice straw is treated with alkali at 25℃ for 3h. After filtration and separation, rice straw fiber and silicon-containing black liquor are obtained. The rice straw fiber is washed with water until the pH value is 7 (neutral). The washed rice straw fiber is added to a 2% hydrogen peroxide solution. The solid-liquid ratio of the washed rice straw fiber to the hydrogen peroxide solution is 1g:15mL. After bleaching for 1.5h, bleached rice straw fiber is obtained.

[0049] (3) The silicon-containing black liquor obtained in step (2) was first allowed to stand for 12 hours, and then the pH value was adjusted to 8.5 with acetic acid solution with a mass fraction of 95% to make the silicon stably dispersed in colloidal form. It was allowed to stand for another 12 hours until a milky white silicon-containing dispersion was formed in the system. The silicon content in the silicon-containing dispersion was 45 mg / L, the cellulose content was 3.3 g / L, the hemicellulose content was 20.1 g / L, and the lignin content was 35.7 g / L. The bleached rice straw fiber obtained in step (2) was added to an alkaline alcohol solution and stirred at 35°C for 7 hours to activate it. At 0 min, chloroacetic acid was added, and the etherification reaction was carried out at 35℃ for 3 h. The ratio of bleached rice straw fiber, alkaline alcohol solution, and chloroacetic acid was 1 g: 14 mL: 1 g. The alkaline alcohol solution was an ethanol solution containing sodium hydroxide, in which the mass fraction of sodium hydroxide was 8% and the volume fraction of ethanol solution (i.e., aqueous solution of ethanol) was 85%. After the reaction was completed, the pH was adjusted to 7, and the precipitate obtained after filtration was washed with a 90% volume fraction ethanol solution and dried to obtain carboxymethyl cellulose.

[0050] (4) Add 3.5g of polyvinyl alcohol to 60mL of deionized water and heat at 85℃ to dissolve, obtaining a polyvinyl alcohol solution. Add 2.5g of carboxymethyl cellulose obtained in step (3) to 40mL of deionized water and heat at 40℃ to dissolve, obtaining a carboxymethyl cellulose solution. Mix the polyvinyl alcohol solution and the carboxymethyl cellulose solution, and add 40mL of the silicon-containing dispersion obtained in step (3) while stirring. Add water to make a total volume of 150mL to obtain a rice straw-based liquid mulch film emulsion. The sum of the mass fractions of polyvinyl alcohol and carboxymethyl cellulose in the obtained mulch film emulsion is 4%.

[0051] The application of the rice straw-based liquid mulch film emulsion prepared in this embodiment in cultivation soil includes the following process:

[0052] The rice straw-based liquid mulch emulsion prepared in this embodiment is evenly sprayed onto the prepared soil surface using a sprayer, ideally forming a continuous moist film layer on the soil surface. After natural air drying, a rice straw-based liquid mulch is formed. During the mulching period, additional spraying can be applied as needed based on rainfall and irrigation conditions. The resulting mulch layer reduces soil moisture evaporation, alleviates surface temperature fluctuations, and improves the heat and moisture retention effects of soils used in greenhouse vegetable cultivation (such as those in plastic tunnels, polytunnels, and arched sheds).

[0053] Comparative Example 1

[0054] A method for preparing a rice straw-based liquid mulch film emulsion is basically the same as that in Example 1, except that: in step (4), no silicon-containing dispersion is added, and an equal volume of deionized water is used to replace the silicon-containing dispersion to obtain a PVA@CMC liquid mulch film emulsion without silicon-containing dispersion.

[0055] Comparative Example 2

[0056] Add 4.0 g of commercially available polyvinyl alcohol (model PVA-1788) to 150 mL of deionized water and heat at 65°C to dissolve until a homogeneous and transparent solution is formed, thus obtaining a PVA solution.

[0057] The PVA@CMC@Si liquid mulch film emulsion prepared in Example 1, the PVA@CMC liquid mulch film emulsion prepared in Comparative Example 1, and the PVA solution prepared in Comparative Example 2 were dried under the same conditions to obtain PVA@CMC@Si film, PVA@CMC film, and PVA film. Figures 1 to 5 All results are characterization results of dried film samples. To ensure the comparability of the characterization results, all film samples were prepared using the same amount of film-forming agent, film-forming area, and drying conditions, and the film thickness after drying was kept to be basically consistent.

[0058] like Figure 1As shown, the FTIR spectra of the PVA@CMC@Si film of Example 1, the PVA@CMC film of Comparative Example 1, and the PVA film of Comparative Example 2 exhibit significant differences, which can be used to verify the introduction and interaction of components. The pure PVA film shows a FTIR spectrum at 3430 cm⁻¹. -1 A broad -OH stretching vibration absorption band is observed nearby, reflecting its abundant hydroxyl groups and hydrogen bonding interactions. Compared to pure PVA films, PVA@CMC and PVA@CMC@Si films exhibit absorption bands at 1580 cm⁻¹. -1 With 1430cm -1 The enhanced characteristic absorption peaks appear at these locations, which are attributed to carboxylate groups (-COO). - The asymmetric and symmetric stretching vibrations of ) were observed. In Comparative Example 1 and Example 1, step (3) used rice straw fiber as raw material, which was alkalized, activated and etherified to introduce carboxymethyl substituents. At the same time, the product obtained in step (3) had added or enhanced characteristic peaks of carboxylate groups compared with unmodified rice straw fiber, indicating that the carboxymethylation modification reaction had occurred and the product obtained was rice straw-based carboxymethyl cellulose. This rice straw-based carboxymethyl cellulose was not only successfully introduced into the PVA membrane system, but also formed stronger hydrogen bonding with the -OH of PVA, which further broadened the -OH peak. After further introducing Si, the PVA@CMC@Si membrane at 1080 cm⁻¹ -1 A more pronounced absorption band appears at 925 cm⁻¹, and at the same time... -1 And 650cm -1 600cm -1 The presence of enhanced absorption nearby indicates that the silicon-oxygen network structure has been successfully loaded into the composite system. These results demonstrate that both CMC and Si components have been effectively incorporated into the PVA matrix, and a more stable composite structure has been constructed through interfacial interactions.

[0059] Figure 2 The transmittance variations of the PVA@CMC@Si film of Example 1, the PVA@CMC film of Comparative Example 1, and the PVA film of Comparative Example 2 in the range of 200–800 nm are shown. The pure PVA film exhibits high transmittance in both the ultraviolet and visible light regions, indicating strong transparency but limited blocking ability against ultraviolet radiation. Compared to the pure PVA film, the transmittance of the PVA@CMC film is significantly reduced, indicating that the introduction of rice straw-based carboxymethyl cellulose can enhance the light-shielding performance of the film to a certain extent. This may be related to the blocking effect of the CMC molecular chain and its carboxymethyl structure on light propagation. The transmittance of the PVA@CMC@Si film remains at an even lower level in the ultraviolet region and is still significantly suppressed in the 400–500 nm range, indicating that the addition of Si further enhances the light-shielding and UV-resistant capabilities of the film. This enhancement can be attributed to the blocking effect brought by the silicon-oxygen structure and the perturbation of the light propagation path by the microstructure of the composite system, thereby effectively reducing ultraviolet light transmission.

[0060] like Figure 3 As shown, the tensile stress-strain curves of the three samples—the PVA@CMC@Si film of Example 1, the PVA@CMC film of Comparative Example 1, and the PVA film of Comparative Example 2—show that the mechanical properties of the materials are significantly improved with the introduction of CMC and Si. The pure PVA film has the lowest maximum tensile stress and fracture strain, which are 5.8 MPa and 34%, respectively. After adding CMC, these values ​​increase to approximately 10.1 MPa and 38%, respectively. With the further introduction of Si, the maximum tensile stress and fracture strain of the PVA@CMC@Si film reach approximately 13.8 MPa and 80%, respectively, exhibiting the highest strength and ductility. At the same time, its area under the curve is the largest, indicating that its toughness is also the best. This shows that the synergistic effect of CMC and the silicon-containing dispersion effectively enhances the structural stability, stress transmission capacity, and energy dissipation capacity of the PVA@CMC@Si film, thereby significantly improving the overall mechanical properties of the material.

[0061] The PVA@CMC@Si film of Example 1, the PVA@CMC film of Comparative Example 1, and the PVA film of Comparative Example 2 were cut into sample sizes that met the requirements for barrier performance testing and placed in a standard environment with a temperature of 23±2℃ and a relative humidity of 50±5% for 24 h for equilibration. After equilibration, the gas and water vapor barrier performance of each film was measured. Oxygen permeability was measured according to the differential pressure method specified in GB / T 1038, carbon dioxide permeability was measured according to the infrared sensor method specified in GB / T 31354, and water vapor permeability was measured according to the cup method specified in GB / T 1037. The test conditions were a temperature of 38℃ and a relative humidity of 90%. Measurements were taken continuously for 8 h, with permeability data recorded every h. Three parallel samples were set up for each type of film for testing, and the average value of the test results at each time point within 8 h was used as the barrier performance index of the corresponding film.

[0062] Figure 4 The barrier performance test results of the PVA@CMC@Si film of Example 1, the PVA@CMC film of Comparative Example 1, and the PVA film of Comparative Example 2 are shown. Figure 4 (a) Figure 4 (b) Figure 4(c) As can be seen, the PVA@CMC@Si membrane prepared by this invention has lower oxygen translucency (OTR), water vapor translucency (WVTR), and carbon dioxide translucency (CO2TR) than both PVA membrane and PVA@CMC membrane, indicating that the composite membrane system constructed by this invention can significantly improve the membrane material's ability to block gases and water vapor. Compared with a single PVA membrane, the barrier performance of the membrane has been significantly improved after the introduction of CMC. Further introduction of Si-containing components further reduces the three permeability indicators of the resulting membrane, indicating that the synergistic effect of the Si-containing components and the PVA / CMC system can further optimize the membrane structure and improve the overall barrier performance. Therefore, the rice straw-based liquid mulch film emulsion of this invention is more suitable for applications with high requirements for oxygen barrier, moisture protection, and gas exchange isolation.

[0063] Figure 5 This diagram shows the degradation of the PVA@CMC@Si membrane of Example 1, the PVA@CMC membrane of Comparative Example 1, and the PVA membrane of Comparative Example 2 on the soil surface. Day 0 represents the initial state of the membrane before seed germination, characterizing its integrity and structural stability during the initial stage of use. Day 30 represents the state of the membrane in the soil surface environment 30 days after completing its function of assisting seed germination and early seedling growth, characterizing its degradation after fulfilling its functional purpose. As shown in the diagram, the PVA membrane, PVA@CMC membrane, and PVA@CMC@Si membrane all maintained a complete and continuous membrane structure at day 0, indicating that they could maintain their basic shape and perform their functions of moisture retention, air permeability, and barrier protection during the early stages of seed germination, preventing premature damage or degradation that could affect seed water absorption, germination, and seedling growth. Once the seeds have completed germination and entered the seedling growth stage, the membrane's auxiliary function gradually decreases. At this point, the membrane can gradually undergo structural damage and degradation under the combined influence of soil moisture, microorganisms, and environmental factors. After 30 days of soil burial treatment, varying degrees of roughening, wrinkling, and damage appeared on the surfaces of the membranes, indicating that the membrane materials can gradually degrade after completing their seed germination assisting function. Among them, the PVA@CMC@Si membrane showed more obvious degradation characteristics after 30 days, with the membrane structure gradually becoming looser. This indicates that the membrane prepared by this invention has good structural stability during the effective seed germination period, and can enter the degradation process after completing its germination assisting function, thus possessing both functional stability during the germination stage and environmental degradability in the later stage.

[0064] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. Although the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art can make many possible variations and modifications to the technical solutions of the present invention using the methods and techniques disclosed above, or modify them into equivalent embodiments with equivalent changes, without departing from the spirit and technical essence of the present invention. Therefore, any simple modifications, equivalent substitutions, equivalent changes, and modifications made to the above embodiments based on the technical essence of the present invention without departing from the content of the technical solutions of the present invention shall still fall within the protection scope of the technical solutions of the present invention.

Claims

1. A method of preparing a rice straw-based liquid mulch emulsion, characterized by, Includes the following steps: (1) The rice straw is dried, crushed and sieved to obtain pretreated rice straw; (2) The pretreated rice straw is added to sodium hydroxide solution and treated with alkali at 15℃~35℃. After filtration and separation, rice straw fiber and silicon-containing black liquor are obtained. The rice straw fiber is washed until the pH value is 7~8. The washed rice straw fiber is added to hydrogen peroxide solution for bleaching to obtain bleached rice straw fiber. (3) The silicon-containing black liquor obtained in step (2) is first allowed to stand, and then the pH value is adjusted to 8-9 so that the silicon is stably dispersed in colloidal form. After standing, a silicon-containing dispersion is obtained. The silicon-containing dispersion contains 35mg / L-70mg / L of silicon, 2.0g / L-5.0g / L of cellulose, 10.0g / L-25.0g / L of hemicellulose, and 25.0g / L-50.0g / L of lignin. The bleached rice straw fiber obtained in step (2) is mixed with an alkaline alcohol solution and stirred at 30℃-40℃ for activation. Then chloroacetic acid is added and etherification reaction is carried out at 30℃-40℃. After the reaction is completed, the pH value is adjusted to 7-8. The precipitate obtained after filtration is washed with ethanol solution and dried to obtain carboxymethyl cellulose. (4) Add polyvinyl alcohol to water and heat to dissolve to obtain a polyvinyl alcohol solution. Add the carboxymethyl cellulose obtained in step (3) to water and heat to dissolve to obtain a carboxymethyl cellulose solution. Mix the polyvinyl alcohol solution and the carboxymethyl cellulose solution. Add the silicon-containing dispersion obtained in step (3) under stirring to obtain rice straw-based liquid mulch film emulsion. In step (4), the ratio of polyvinyl alcohol, carboxymethyl cellulose, and silicon-containing dispersion is 1g~4g∶2g~4g∶20mL~40mL, and the sum of the mass fractions of polyvinyl alcohol and carboxymethyl cellulose in the rice straw-based liquid mulch film emulsion is controlled to be 3%~6%. The control method includes water replenishment adjustment.

2. The method for preparing rice straw-based liquid mulch emulsion according to claim 1, characterized in that, In step (2), the solid-liquid ratio of the pretreated rice straw and the sodium hydroxide solution is 1g:8mL to 15mL, and the mass fraction of sodium hydroxide in the sodium hydroxide solution is 3% to 8%; the solid-liquid ratio of the washed rice straw fiber and the hydrogen peroxide solution is 1g:10mL to 15mL, and the mass fraction of hydrogen peroxide in the hydrogen peroxide solution is 2% to 5%.

3. The method for preparing rice straw-based liquid mulch emulsion according to claim 1, characterized in that, In step (3), the addition ratio of bleached rice straw fiber, alkaline alcohol solution, and chloroacetic acid is 1g:10mL~20mL:0.5g~1.5g. The alkaline alcohol solution is an ethanol solution containing sodium hydroxide. In the ethanol solution containing sodium hydroxide, the mass fraction of sodium hydroxide is 5%~15%, and the volume fraction of ethanol solution is 70%~90%. The stirring activation time is 50min~90min, and the etherification reaction time is 2h~4h.

4. The method for preparing rice straw-based liquid mulch emulsion according to any one of claims 1 to 3, characterized in that, In step (1), the drying temperature is 50℃~70℃, the drying time is 6h~24h, and the sieving is through a 2mm sieve; in step (2), the alkali treatment time is 2h~5h, the rice straw fiber is washed with water, and the bleaching time is 0.5h~2h.

5. The method for preparing rice straw-based liquid mulch emulsion according to any one of claims 1 to 3, characterized in that, In step (3), the standing time is 12h to 24h, the pH value is adjusted by an acidic regulator, the acidic regulator is an acetic acid solution, the standing time is 6h to 24h, and the volume fraction of the ethanol solution used for washing is 70% to 95%.

6. The method for preparing rice straw-based liquid mulch emulsion according to any one of claims 1 to 3, characterized in that, In step (4), the polyvinyl alcohol is added to water and heated to dissolve at a temperature of 60°C to 90°C, and the carboxymethyl cellulose is added to water and heated to dissolve at a temperature of 30°C to 40°C.

7. A rice straw-based liquid mulch film emulsion prepared by the method described in any one of claims 1 to 6.

8. The application of the rice straw-based liquid mulch emulsion as described in claim 7 in cultivation soil.

9. The application according to claim 8, characterized in that, The application includes spraying or pouring the rice straw-based liquid mulch emulsion onto the soil surface, and after air drying, forming a rice straw-based liquid mulch.

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