Biodegradable mulching film with high air permeability and heat preservation as well as preparation method and application of biodegradable mulching film

Abstract

The invention discloses a biodegradable mulching film with high air permeability and heat preservation as well as a preparation method and application thereof, and relates to the technical field of agriculture. The biodegradable mulching film comprises a high-air-permeability degradable material and a copper phosphate improved thermal insulation material. Wherein the high-air-permeability degradable material comprises a PBAT / PLA blending system, a compatibilizer, a bio-based plasticizer and pepper stalks; the copper phosphate improved thermal insulation material is obtained by taking copper oxide and ammonium dihydrogen phosphate as precursor materials and mixing the precursor materials with zirconium dioxide. According to the invention, a foaming structure (realizing air permeability) and a copper phosphate thermal insulation material (realizing thermal insulation) are creatively combined, so that the mulching film with high air permeability, biodegradability and thermal insulation is created, the problem that a degradable mulching film is often single in function is solved, and the mulching film is more beneficial to crop growth.

Description

Technical Field

[0001] This invention relates to the field of agricultural technology, and more specifically to a highly breathable, heat-insulating biodegradable mulch film, its preparation method, and its application. Background Technology

[0002] Traditional plastic film only has the function of "moisture retention" and lacks the ability to actively regulate. Whether it is PE film or ordinary biodegradable film, its main function is only to retain water and increase temperature, and it cannot adjust its function according to the needs of crops or changes in the environment.

[0003] How to provide a highly breathable, biodegradable, and heat-insulating mulch film is a problem that needs to be solved by those in the field. Summary of the Invention

[0004] In view of this, the present invention provides a highly breathable and heat-insulating biodegradable mulch film, its preparation method, and its application. As an agricultural mulch film, it has the advantages of high breathability, heat insulation, and biodegradability, and is suitable for most greenhouse horticultural vegetables, helping them to successfully overwinter.

[0005] To achieve the above objectives, the present invention adopts the following technical solution:

[0006] A highly breathable and heat-insulating biodegradable mulch film, comprising the following components in parts by weight: 83-123 parts of highly breathable biodegradable material, 2-8 parts of copper phosphate-modified thermal insulation material; The highly breathable biodegradable material includes: 70-85 parts of PBAT / PLA blend system, 1-3 parts of compatibilizer, 2-10 parts of bio-based plasticizer, and 10-25 parts of chili stems; The copper phosphate modified thermal insulation material is obtained by mixing copper oxide and ammonium dihydrogen phosphate with zirconium dioxide as precursor materials. The mass ratio of copper oxide to ammonium dihydrogen phosphate is 4:1; The mass ratio of the precursor material to zirconium dioxide is 99:1.

[0007] Preferably, the mass ratio of PBAT to PLA in the PBAT / PLA blend system is 60:40.

[0008] Preferably, the compatibilizer comprises an ethylene-methyl acrylate-glycidyl methacrylate terpolymer.

[0009] Preferably, the bio-based plasticizer includes tributyl acetylacetonate.

[0010] Another objective of this invention is to provide a method for preparing a highly breathable and heat-insulating biodegradable mulch film, using a PBAT / PLA blend system as the base material, constructing a highly breathable biodegradable composite material from chili stem fibers using a foaming process, and adding copper phosphate modifier as the heat-insulating material. The method specifically includes the following steps: (1) Cut the chili stems into short sections, crush the pith, obtain fiber bundles by mechanical combing, remove the pith and impurities, and obtain fibers; (2) Treat the fiber with 5% NaOH solution. The ratio of the dry weight of the fiber (g) to the volume of the NaOH solution (mL) is 1:15 to 1:20. Stir mechanically at room temperature for 1 to 3 hours. Filter the treated mixture with a sieve to separate the fiber from the waste alkali solution. Then, repeatedly wash and squeeze the fiber until the wash liquid is neutral. Dry it at 105℃±5℃ to constant weight. Immerse the dried fiber in the prepared silanol solution to ensure that the solution completely submerges the fiber. Stir mechanically at 50℃-60℃ for 60-120 minutes to allow the silane molecules to fully contact and adsorb onto the fiber surface. Filter out the treated fiber and place it in an oven. First, dry it at 80℃-90℃ for 2-4 hours to remove the solvent. Then, heat treat it at 105℃-120℃ for 1-2 hours. Take out the cured fiber and place it in a desiccator to cool to room temperature for later use. (3) The fibers in step (2) are processed by mechanical grinding to form a pumpable suspension, and then homogenized to obtain cellulose nanofibers; (4) Using the PBAT / PLA blend system as the base material, add compatibilizer and bio-based plasticizer as the matrix for later use; (5) Using carbon dioxide dry grade as physical foaming agent, cellulose nanofibers and foaming agent are mixed together into the matrix, and the blended particles are molded into solid sheets of specified size by hot press. (6) Using copper oxide and ammonium dihydrogen phosphate as precursor materials, the precursor materials and zirconium dioxide grinding media are ball-milled and homogenized in ethanol for 20-24 hours, dried at 80-90℃, and then sintered at 1000℃ for 3-4 hours. After cooling, copper phosphate modified material is obtained. (7) Add the mixture of step (5) and step (6) into a high-speed mixer and mix for 1-10 min. Add the mixture into a twin-screw extruder with a feed rate of 100-200 g / min and a screw speed of 100-300 rpm. The resulting resin is melt-blended, cooled and granulated in a pelletizer to obtain composite masterbatch. Add the composite masterbatch to a single-screw extruder for melt extrusion and blow molding into a film.

[0011] Preferably, in step (2), the silanol solution is: a silane coupling agent is mixed with an ethanol-water mixed solvent, the pH of the solution is adjusted to 4-5 with acetic acid, and the solution is magnetically stirred at room temperature for 30-60 minutes to allow it to be fully hydrolyzed and form a clear or microemulsion silanol solution; The silane coupling agent is γ-aminopropyltriethoxysilane; the amount of silane coupling agent used is 1.8% of the fiber mass after drying. The volume ratio of ethanol to water in the ethanol-water mixed solvent is 80:20.

[0012] Preferably, the mechanical grinding in step (3) includes: The fiber from step (2) is fed into the hopper of the high-speed crusher, each time to 1 / 3 to 1 / 2 of the hopper capacity, to ensure full crushing. The operation is carried out intermittently, each time crushing for 5-10 seconds, pausing for 3-5 seconds, and repeating 3-5 times to obtain coarse fibers with a length of approximately 10-20 mm. Then, the initially crushed fiber is transferred to a disc mill for fine grinding. After processing, the fiber length is <5 mm, and the ground fiber is screened using a 5 mm standard sieve.

[0013] Preferably, the homogenization in step (3) specifically includes: pouring the suspension into the feed tank of the homogenizer, initially circulating it 2-3 times at 200-400 bar to initially dissociate the fiber bundles, then gradually increasing the pressure to 600-1500 bar and circulating it 10-30 times. During the grinding process, a circulating cooling system is used to control the temperature of the cellulose nanofibers at <60°C to prevent thermal degradation of cellulose. The gel-like suspension after grinding is diluted with deionized water to a concentration of 0.5%-1.0% to obtain cellulose nanofibers, which are then refrigerated and stored at 4°C for later use.

[0014] Preferably, the co-mixing of the matrix in step (5) is carried out by mixing for 5 hours at a temperature of 70°C and a pressure of 11.7 MPa to ensure that the carbon dioxide is fully dissolved and reaches an equilibrium concentration, and then the temperature is rapidly reduced from 70°C to 58°C.

[0015] Preferably, the hot press molding parameters in step (5) are: First-stage pressure relief: The pressure rapidly drops from 11.7 MPa to 3.45 MPa; Hold at 58℃ and 3.45MPa for 10 min to allow the bubble nuclei to grow to a stable size; Secondary depressurization and cooling: Depressurize to atmospheric pressure and cool to room temperature, and the bubble structure is fixed.

[0016] Preferably, in step (7), the temperature of the seven zones from the feed inlet to the extruder head of the twin-screw extruder is set as: (130-200) / (130-200) / (130-200) / (130-200) / (130-200) / (130-200) / (130-200)℃; The die head temperature of the single screw extruder is set to: (130-200) / (130-200) / (130-200) / (130-200) / (130-200)℃.

[0017] As can be seen from the above technical solution, compared with the prior art, the present invention has the following technical effects: 1. Using agricultural waste such as chili stalks as raw materials turns waste into treasure, reduces raw material costs, and conforms to the concept of circular economy.

[0018] 2. By innovatively combining a foamed structure (for breathability) with copper phosphate insulation material (for insulation), a highly breathable, biodegradable, and heat-insulating mulch film has been created, solving the problem that biodegradable mulch films often have only one function and is more conducive to crop growth. Attached Figure Description

[0019] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the provided drawings without creative effort.

[0020] Figure 1 Soil temperature at -10cm depth after different mulch film treatments. Detailed Implementation

[0021] The technical solutions in the embodiments of the present invention will be clearly and completely described below. 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.

[0022] Example 1 This embodiment provides a method for preparing a highly breathable and heat-insulating biodegradable mulch film. The amounts of each raw material are as follows: 70 parts of PBAT / PLA blend system, appropriate amount of chili stem fiber raw material, 1 part of compatibilizer, 3 parts of bio-based plasticizer, 79.2 parts of copper oxide, 19.8 parts of ammonium dihydrogen phosphate, and 1 part of zirconium dioxide. Specifically, the following steps are included: (1) Cut the chili stems into short sections, crush the pith, and obtain relatively pure fiber bundles by mechanical combing. Remove the pith and impurities to finally obtain fibers with relatively uniform length and diameter. (2) Treat the fiber with 5% NaOH solution. The ratio of the dry weight of the fiber (g) to the volume of the NaOH solution (mL) is 1:15. Stir mechanically at room temperature for 3 hours. Filter the treated mixture with a sieve to separate the fiber from the waste alkali solution. Then, repeatedly wash and squeeze the fiber until the wash liquid is neutral. Then dry it at 105℃ to constant weight. Immerse the dried fiber in the prepared silanol solution to ensure that the solution completely submerges the fiber. Stir mechanically at 60℃ for 60 minutes to allow the silane molecules to fully contact and adsorb onto the fiber surface. Filter out the treated fiber and place it in an oven. First, dry it at 90℃ for 2 hours to remove the solvent. Then, heat treat it at 120℃ for 1 hour. Take out the cured fiber and place it in a desiccator to cool to room temperature for later use. The silanol solution is prepared by mixing a silane coupling agent with an ethanol-water mixed solvent, adjusting the pH of the solution to 5 with acetic acid, and magnetically stirring for 60 minutes at room temperature to allow for complete hydrolysis, forming a clear or microemulsion silanol solution; the silane coupling agent is γ-aminopropyltriethoxysilane; the amount of silane coupling agent used is 1.8% of the mass of the dried fiber; the volume ratio of ethanol to water in the ethanol-water mixed solvent is 80:20. (3) The fiber from step (2) is fed into the hopper of the high-speed pulverizer, each time to 1 / 3 of the hopper capacity, to ensure full crushing. Intermittent operation is carried out, each time crushing for 5-10s, pausing for 3-5s, repeating 5 times to obtain coarse fibers with a length of approximately 10-20mm. Then the initially crushed fiber is transferred to a disc mill for fine grinding. After processing, the fiber length is <5mm. The ground fiber is then screened using a 5mm standard sieve to form a pumpable suspension. The suspension is poured into the feed tank of the homogenizer and initially circulated twice at 400bar to allow the fiber bundles to initially dissociate. Then the pressure is gradually increased to 1500bar and circulated 10 times. During the grinding process, a circulating cooling system is used to control the temperature of the cellulose nanofibers at <60℃ to prevent thermal degradation of cellulose. The ground gel-like suspension is diluted with deionized water to a concentration of 1.0% to obtain cellulose nanofibers, which are then refrigerated at 4℃ for later use. (4) Using PBAT / PLA blend system as the base material, add compatibilizer to improve the interface, add appropriate amount of bio-based plasticizer (citric acid ester) to increase the flexibility and processing fluidity of the matrix, so that the fiber is more evenly dispersed in the matrix; (5) Dry carbon dioxide (99.9% purity) was used as a foaming agent. The treated chili stem fiber CNF was mixed with the foaming agent into the matrix, and the blended particles were molded into solid sheets of specified size (12.7 mm in diameter and 1.5 mm in thickness) using a hot press. (6) At a temperature of 70℃ and a pressure of 11.7MPa for 5 hours, ensure that CO2 is fully dissolved and reaches an equilibrium concentration. Then, rapidly reduce the temperature from 70℃ to 58℃. First-stage depressurization: The pressure is rapidly reduced from 11.7MPa to 3.45MPa. The sudden drop in pressure causes a sharp decrease in gas solubility, triggering homogeneous / heterogeneous nucleation and instantly generating a large number of bubble nuclei. Maintain the pressure at 58℃ and 3.45MPa for 10 minutes to allow the bubble nuclei to grow to a stable size. Second-stage depressurization and cooling: Depressurize to atmospheric pressure and cool to room temperature to allow the bubble structure to stabilize. (7) Using copper oxide and ammonium dihydrogen phosphate (mass ratio 4 / 1) as precursor materials, the precursor materials and zirconium dioxide (mass ratio 99 / 1) grinding media were ball-milled in ethanol for 24 hours to homogenize the mixture, dried at 90°C, and then sintered at 1000°C for 3 hours. After cooling, copper phosphate modified material was obtained.

[0023] (8) Add the mixture of the materials from steps (6) and (7) into a high-speed mixer and mix for 3 minutes. Add the mixture into a twin-screw extruder with a feed rate of 100 g / min and a screw speed of 100 rpm. The resulting resin is melt-blended, cooled, and then granulated in a pelletizer to obtain composite masterbatch. Add the composite masterbatch to a single-screw extruder for melt extrusion and blow molding into a film.

[0024] (9) The temperature of the seven zones from the feed inlet to the extruder head of the twin-screw extruder is set as follows: 130 / 130 / 130 / 130 / 130 / 130 / 130℃.

[0025] (10) The die head temperature of the single screw extruder is set to: 130 / 130 / 130 / 130 / 130℃.

[0026] Example 2 This embodiment provides a method for preparing a highly breathable and heat-insulating biodegradable mulch film. The amount of each raw material is as follows: 80 parts of PBAT / PLA blend system, appropriate amount of chili stem fiber raw material, 4 parts of compatibilizer, 5 parts of bio-based plasticizer, 80 parts of copper oxide, 20 parts of ammonium dihydrogen phosphate, and 1 part of zirconium dioxide. Specifically, the following steps are included: (1) Cut the chili stems into short sections, crush the pith, and obtain relatively pure fiber bundles by mechanical combing. Remove the pith and impurities to finally obtain fibers with relatively uniform length and diameter. (2) Treat the fiber with 5% NaOH solution. The ratio of the dry weight of the fiber (g) to the volume of the NaOH solution (mL) is 1:20. Stir mechanically at room temperature for 1 hour. Filter the treated mixture with a sieve to separate the fiber from the waste alkali solution. Then, repeatedly wash and squeeze the fiber until the wash liquid is neutral. Then dry it at 110°C to constant weight. Immerse the dried fiber in the prepared silanol solution to ensure that the solution completely submerges the fiber. Stir mechanically at 50°C for 120 minutes to allow the silane molecules to fully contact and adsorb onto the fiber surface. Filter out the treated fiber and place it in an oven. First, dry it at 80°C for 4 hours to remove the solvent. Then, heat treat it at 105°C for 1 hour. Take out the cured fiber and place it in a desiccator to cool to room temperature for later use. The silanol solution is prepared by mixing a silane coupling agent with an ethanol-water mixed solvent, adjusting the pH of the solution to 4 with acetic acid, and magnetically stirring at room temperature for 30 minutes to allow for complete hydrolysis, forming a clear or microemulsion silanol solution; the silane coupling agent is γ-aminopropyltriethoxysilane; the amount of silane coupling agent used is 1.8% of the mass of the dried fiber; the volume ratio of ethanol to water in the ethanol-water mixed solvent is 80:20. (3) The fiber from step (2) is fed into the hopper of the high-speed pulverizer, each time to 1 / 2 of the hopper capacity, to ensure full crushing. Intermittent operation is carried out, each time crushing for 5-10s, pausing for 3-5s, repeating 3 times to obtain coarse fibers with a length of approximately 10-20mm. Then the initially crushed fiber is transferred to a disc mill for fine grinding. After processing, the fiber length is <5mm. The ground fiber is then screened using a 5mm standard sieve to form a pumpable suspension. The suspension is poured into the feed tank of the homogenizer and initially circulated 3 times at 200bar to initially dissociate the fiber bundle. Then the pressure is gradually increased to 600bar and circulated 30 times. During the grinding process, a circulating cooling system is used to control the temperature of the cellulose nanofibers at <60℃ to prevent thermal degradation of cellulose. The ground gel-like suspension is diluted with deionized water to a concentration of 0.5% to obtain cellulose nanofibers, which are then refrigerated at 4℃ for later use. (4) Using PBAT / PLA blend system as the base material, add compatibilizer to improve the interface, add appropriate amount of bio-based plasticizer (citric acid ester) to increase the flexibility and processing fluidity of the matrix, so that the fiber is more evenly dispersed in the matrix; (5) Dry carbon dioxide (99.9% purity) was used as a foaming agent. The treated chili stem fiber CNF was mixed with the foaming agent into the matrix, and the blended particles were molded into solid sheets of specified size (12.7 mm in diameter and 1.5 mm in thickness) using a hot press. (6) At a temperature of 70℃ and a pressure of 11.7MPa for 5 hours, ensure that CO2 is fully dissolved and reaches an equilibrium concentration. Then, rapidly reduce the temperature from 70℃ to 58℃. First-stage depressurization: The pressure is rapidly reduced from 11.7MPa to 3.45MPa. The sudden drop in pressure causes a sharp decrease in gas solubility, triggering homogeneous / heterogeneous nucleation and instantly generating a large number of bubble nuclei. Maintain the pressure at 58℃ and 3.45MPa for 10 minutes to allow the bubble nuclei to grow to a stable size. Second-stage depressurization and cooling: Depressurize to atmospheric pressure and cool to room temperature to allow the bubble structure to stabilize. (7) Using copper oxide and ammonium dihydrogen phosphate (mass ratio 4 / 1) as precursor materials, the precursor materials and zirconium dioxide (mass ratio 99 / 1) grinding media were ball-milled in ethanol for 24 hours to homogenize the mixture, dried at 90°C, and then sintered at 1000°C for 4 hours. After cooling, copper phosphate modified material was obtained.

[0027] (8) Add the mixture of the materials from steps (6) and (7) into a high-speed mixer and mix for 5 minutes. Add the mixture into a twin-screw extruder with a feed rate of 150 g / min and a screw speed of 200 rpm. The resulting resin is melt-blended, cooled, and then granulated in a pelletizer to obtain composite masterbatch. Add the composite masterbatch to a single-screw extruder for melt extrusion and blow molding into a film.

[0028] (9) The temperature of the seven zones from the feed inlet to the extruder head of the twin-screw extruder is set as follows: 160 / 160 / 160 / 160 / 160 / 160 / 160℃.

[0029] (10) The die head temperature of the single screw extruder is set to 160 / 160 / 160 / 160 / 160℃.

[0030] Example 3 This embodiment provides a method for preparing a highly breathable and heat-insulating biodegradable mulch film. The amount of each raw material is as follows: 85 parts of PBAT / PLA blend system, appropriate amount of chili stem fiber raw material, 10 parts of compatibilizer, 10 parts of bio-based plasticizer, 396 parts of copper oxide, 99 parts of ammonium dihydrogen phosphate, and 5 parts of zirconium dioxide. Specifically, the following steps are included: (1) Cut the chili stems into short sections, crush the pith, and obtain relatively pure fiber bundles by mechanical combing. Remove the pith and impurities to finally obtain fibers with relatively uniform length and diameter. (2) Treat the fiber with 5% NaOH solution. The ratio of the dry weight of the fiber (g) to the volume of the NaOH solution (mL) is 1:17. Stir mechanically at room temperature for 2 hours. Filter the treated mixture with a sieve to separate the fiber from the waste alkali solution. Then, repeatedly wash and squeeze the fiber until the wash liquid is neutral. Then dry it at 105℃ to constant weight. Immerse the dried fiber in the prepared silanol solution to ensure that the solution completely submerges the fiber. Stir mechanically at 55℃ for 90 minutes to allow the silane molecules to fully contact and adsorb onto the fiber surface. Filter out the treated fiber and place it in an oven. First, dry it at 85℃ for 3 hours to remove the solvent. Then, heat treat it at 110℃ for 2 hours. Take out the cured fiber and place it in a desiccator to cool to room temperature for later use. The silanol solution is prepared by mixing a silane coupling agent with an ethanol-water mixed solvent, adjusting the pH of the solution to 4 with acetic acid, and magnetically stirring at room temperature for 45 minutes to allow for complete hydrolysis, forming a clear or microemulsion silanol solution; the silane coupling agent is γ-aminopropyltriethoxysilane; the amount of silane coupling agent used is 1.8% of the mass of the dried fiber; the volume ratio of ethanol to water in the ethanol-water mixed solvent is 80:20. (3) The fiber from step (2) is fed into the hopper of the high-speed pulverizer, each time to 1 / 3 of the hopper capacity, to ensure full crushing. Intermittent operation is carried out, each time crushing for 5-10s, pausing for 3-5s, repeating 4 times to obtain coarse fibers with a length of approximately 10-20mm. Then the initially crushed fiber is transferred to a disc mill for fine grinding. After processing, the fiber length is <5mm. The ground fiber is then screened using a 5mm standard sieve to form a pumpable suspension. The suspension is poured into the feed tank of the homogenizer and initially circulated twice at 300bar to initially dissociate the fiber bundles. Then the pressure is gradually increased to 1000bar and circulated 20 times. During the grinding process, a circulating cooling system is used to control the temperature of the cellulose nanofibers at <60℃ to prevent thermal degradation of cellulose. The ground gel-like suspension is diluted with deionized water to a concentration of 1.0% to obtain cellulose nanofibers, which are then refrigerated at 4℃ for later use. (4) Using PBAT / PLA blend system as the base material, add compatibilizer to improve the interface, add appropriate amount of bio-based plasticizer (citric acid ester) to increase the flexibility and processing fluidity of the matrix, so that the fiber is more evenly dispersed in the matrix; (5) Dry carbon dioxide (99.9% purity) was used as a foaming agent. The treated chili stem fiber CNF was mixed with the foaming agent into the matrix, and the blended particles were molded into solid sheets of specified size (12.7 mm in diameter and 1.5 mm in thickness) using a hot press. (6) At a temperature of 70℃ and a pressure of 11.7MPa for 5 hours, ensure that CO2 is fully dissolved and reaches an equilibrium concentration. Then, rapidly reduce the temperature from 70℃ to 58℃. First-stage depressurization: The pressure is rapidly reduced from 11.7MPa to 3.45MPa. The sudden drop in pressure causes a sharp decrease in gas solubility, triggering homogeneous / heterogeneous nucleation and instantly generating a large number of bubble nuclei. Maintain the pressure at 58℃ and 3.45MPa for 10 minutes to allow the bubble nuclei to grow to a stable size. Second-stage depressurization and cooling: Depressurize to atmospheric pressure and cool to room temperature to allow the bubble structure to stabilize. (7) Using copper oxide and ammonium dihydrogen phosphate (mass ratio 4 / 1) as precursor materials, the precursor materials and zirconium dioxide (mass ratio 99 / 1) grinding media were ball-milled in ethanol for 24 hours to homogenize the mixture, dried at 90°C, and then sintered at 1000°C for 4 hours. After cooling, copper phosphate modified material was obtained.

[0031] (8) Add the mixture of the materials from steps (6) and (7) into a high-speed mixer and mix for 5 minutes. Add the mixture into a twin-screw extruder with a feed rate of 200 g / min and a screw speed of 300 rpm. The resulting resin is melt-blended, cooled, and then granulated in a pelletizer to obtain composite masterbatch. Add the composite masterbatch to a single-screw extruder for melt extrusion and blow molding into a film.

[0032] (9) The temperature of the seven zones from the feed inlet to the extruder head of the twin-screw extruder is set as follows: 200 / 200 / 200 / 200 / 200 / 200 / 200℃.

[0033] (10) The die head temperature of the single screw extruder is set to 200 / 200 / 200 / 200℃.

[0034] Example 4 Using 'pointed-leaf spinach' as ​​the test material, an open-field overwintering spinach cultivation experiment was conducted in Zhuoqian Village, Wenyang Town, Tai'an City, Shandong Province from November 2024 to March 2025, with biodegradable mulch covering the soil. Example 1 used biodegradable mulch. Ordinary PE mulch was used as a control (CK). Soil temperature at -10cm depth and the degradation characteristics of the mulch were monitored, and the final data were obtained by averaging.

[0035] The specific process was as follows: A flat bed planting pattern of ten rows per bed was adopted, with a row spacing of 18-20cm and a plant spacing of 4-5cm. Four beds were planted per treatment, with one protective bed on each of the east and west sides. After spinach seedlings emerged, holes were manually punched in the PE film, while no holes were punched in the biodegradable mulch film. The mulch film was removed on March 15th. Results showed that the biodegradable mulch film could achieve the purpose of heat preservation. Figure 1The average daily soil temperature at a depth of -10cm was 1.84℃ higher than that under PE film, with no significant difference in spinach yield. The mulch film degrades by over 90% within 30 days. Therefore, this invention saves labor, achieves both heat preservation and ventilation, and enables high-quality and efficient open-field overwintering spinach cultivation.

[0036] The various embodiments in this specification are described in a progressive manner, with each embodiment focusing on its differences from other embodiments. Similar or identical parts between embodiments can be referred to interchangeably. For the apparatus disclosed in the embodiments, since it corresponds to the method disclosed in the embodiments, the description is relatively simple; relevant parts can be referred to in the method section.

[0037] The above description of the disclosed embodiments enables those skilled in the art to make or use the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A highly breathable and heat-insulating biodegradable mulch film, characterized in that, Includes the following ingredients by weight: 83-123 parts of highly breathable biodegradable material, 2-8 parts of copper phosphate-modified thermal insulation material; The highly breathable biodegradable material includes: 70-85 parts of PBAT / PLA blend system, 1-3 parts of compatibilizer, 2-10 parts of bio-based plasticizer, and 10-25 parts of chili stems; The copper phosphate modified thermal insulation material is obtained by mixing copper oxide and ammonium dihydrogen phosphate with zirconium dioxide as precursor materials. The mass ratio of copper oxide to ammonium dihydrogen phosphate is 4:1; The mass ratio of the precursor material to zirconium dioxide is (99-101):

1.

2. The highly breathable and heat-insulating biodegradable mulch film according to claim 1, characterized in that, The mass ratio of PBAT to PLA in the PBAT / PLA blend system is 60:

40. The compatibilizer includes an ethylene-methyl acrylate-glycidyl methacrylate terpolymer; The bio-based plasticizer includes tributyl acetylglucosyl citrate.

3. The method for preparing a highly breathable and heat-insulating biodegradable mulch film as described in claim 2, characterized in that, Includes the following steps: (1) Cut the chili stems into short sections, crush the pith, obtain fiber bundles by mechanical combing, remove the pith and impurities, and obtain fibers; (2) Treat the fiber with 5% NaOH solution. The ratio of the dry weight of the fiber (g) to the volume of the NaOH solution (mL) is 1:15 to 1:

20. Stir mechanically at room temperature for 1 to 3 hours. Filter the treated mixture with a sieve to separate the fiber from the waste alkali solution. Then, repeatedly wash and squeeze the fiber until the wash liquid is neutral. Dry it at 105℃±5℃ to constant weight. Immerse the dried fiber in the prepared silanol solution to ensure that the solution completely submerges the fiber. Stir mechanically at 50℃-60℃ for 60-120 minutes to allow the silane molecules to fully contact and adsorb onto the fiber surface. Filter out the treated fiber and place it in an oven. First, dry it at 80℃-90℃ for 2-4 hours to remove the solvent. Then, heat treat it at 105℃-120℃ for 1-2 hours. Take out the cured fiber and place it in a desiccator to cool to room temperature for later use. (3) The fibers in step (2) are processed by mechanical grinding to form a pumpable suspension, and then homogenized to obtain cellulose nanofibers; (4) Using the PBAT / PLA blend system as the base material, add compatibilizer and bio-based plasticizer as the matrix for later use; (5) Using carbon dioxide dry grade as physical foaming agent, cellulose nanofibers and foaming agent are mixed together into the matrix, and the blended particles are molded into solid sheets of specified size by hot press. (6) Using copper oxide and ammonium dihydrogen phosphate as precursor materials, the precursor materials and zirconium dioxide grinding media are ball-milled and homogenized in ethanol for 20-24 hours, dried at 80-90℃, and then sintered at 1000℃ for 3-4 hours. After cooling, copper phosphate modified material is obtained. (7) Add the mixture of step (5) and step (6) into a high-speed mixer and mix for 1-10 min. Add the mixture into a twin-screw extruder with a feed rate of 100-200 g / min and a screw speed of 100-300 rpm. The resulting resin is melt-blended, cooled and granulated in a pelletizer to obtain composite masterbatch. Add the composite masterbatch to a single-screw extruder for melt extrusion and blow molding into a film.

4. The method for preparing a highly breathable and heat-insulating biodegradable mulch film according to claim 3, characterized in that, In step (2), the silanol solution is prepared by mixing a silane coupling agent with an ethanol-water mixed solvent, adjusting the pH of the solution to 4-5 with acetic acid, and stirring magnetically at room temperature for 30-60 minutes to allow it to fully hydrolyze and form a clear or microemulsion silanol solution. The silane coupling agent is γ-aminopropyltriethoxysilane; the amount of silane coupling agent used is 1.8% of the fiber mass after drying. The volume ratio of ethanol to water in the ethanol-water mixed solvent is 80:

20.

5. The method for preparing a highly breathable and heat-insulating biodegradable mulch film according to claim 4, characterized in that, The mechanical grinding described in step (3) includes: The fiber from step (2) is fed into the hopper of the high-speed crusher, each time to 1 / 3 to 1 / 2 of the hopper capacity, to ensure full crushing. The operation is carried out intermittently, each time crushing for 5-10 seconds, pausing for 3-5 seconds, and repeating 3-5 times to obtain coarse fibers with a length of approximately 10-20 mm. Then, the initially crushed fiber is transferred to a disc mill for fine grinding. After processing, the fiber length is <5 mm, and the ground fiber is screened using a 5 mm standard sieve.

6. The method for preparing a highly breathable and heat-insulating biodegradable mulch film according to claim 5, characterized in that, The homogenization in step (3) specifically includes: pouring the suspension into the feed tank of the homogenizer, initially circulating it 2-3 times at 200-400 bar to initially dissociate the fiber bundles, then gradually increasing the pressure to 600-1500 bar and circulating it 10-30 times. During the grinding process, a circulating cooling system is used to control the temperature of the cellulose nanofibers at <60℃ to prevent thermal degradation of cellulose. The gel-like suspension after grinding is diluted with deionized water to a concentration of 0.5%-1.0% to obtain cellulose nanofibers, which are then refrigerated and stored at 4℃ for later use.

7. The method for preparing a highly breathable and heat-insulating biodegradable mulch film according to claim 6, characterized in that, The co-mixing of the matrix in step (5) is as follows: mix for 5 hours at a temperature of 70°C and a pressure of 11.7 MPa to ensure that the carbon dioxide is fully dissolved and reaches an equilibrium concentration, and then the temperature is rapidly reduced from 70°C to 58°C.

8. The method for preparing a highly breathable and heat-insulating biodegradable mulch film according to claim 7, characterized in that, The hot press molding parameters mentioned in step (5) are: First-stage pressure relief: The pressure rapidly drops from 11.7 MPa to 3.45 MPa; Hold at 58℃ and 3.45MPa for 10 min to allow the bubble nuclei to grow to a stable size; Secondary depressurization and cooling: Depressurize to atmospheric pressure and cool to room temperature, and the bubble structure is fixed.

9. A method for preparing a highly breathable and heat-insulating biodegradable mulch film according to claim 8, characterized in that, In step (7), the temperature of the seven zones from the feed inlet to the extruder head of the twin-screw extruder is set as follows: (130-200) / (130-200) / (130-200) / (130-200) / (130-200) / (130-200) / (130-200)℃; The die head temperature of the single screw extruder is set to: (130-200) / (130-200) / (130-200) / (130-200) / (130-200)℃.

10. The application of the highly breathable and heat-insulating biodegradable mulch film as described in claim 1 in the cultivation of horticultural vegetables.

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