Biodegradable mulching film for soil temperature and moisture conservation and preparation method thereof

Abstract

The application relates to the technical field of agricultural mulching films, in particular to a biodegradable heat-retaining and soil-moisture-preserving mulching film and a preparation method thereof. The biodegradable heat-retaining and soil-moisture-preserving mulching film comprises the following raw materials: a biodegradable base material, a modified polymer material, a heat-retaining agent, a soil-moisture-preserving agent, a film-forming aid, a compatilizer, a plasticizer and an anti-aging agent. The specific preparation method comprises the following steps: in step A, the biodegradable base material and the modified polymer material are added into a high-speed mixer and stirred uniformly, and then the heat-retaining agent, the soil-moisture-preserving agent, the film-forming aid, the compatilizer, the plasticizer and the anti-aging agent are added in sequence to obtain a mixed base material; in step B, the mixed base material is added into a double-screw extruder, extruded after being melt-plasticized to obtain a melt material; and in step C, the melt material is blown into a film shape, and the film is cooled and shaped through cooling air to obtain the biodegradable heat-retaining and soil-moisture-preserving mulching film. The mechanical property of the mulching film meets the use requirement of agricultural mulching; the water vapor permeation amount is moderate, the mulching film has good soil-moisture-preserving property and air permeability, and the comprehensive performance is excellent.

Description

Technical Field

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

[0002] As one of the core production technologies of modern agriculture, plastic film mulching plays an irreplaceable role in heat preservation, moisture retention, quality improvement, yield increase, water conservation, and drought resistance, and has been widely used in the planting of various crops. However, traditional plastic films are mostly made of polyethylene, which has a stable chemical structure and is difficult to degrade in the natural environment. After long-term use, a large amount of residual film accumulates in the soil, damaging the soil structure, hindering crop root growth, and causing soil compaction and nutrient loss, thus restricting the green and sustainable development of agriculture.

[0003] To address the problem of residual film pollution, biodegradable mulch films have gradually become a research hotspot. These films, primarily made from biodegradable polymers such as PBAT and PLA, can be decomposed into carbon dioxide and water by microorganisms in the natural environment, reducing pollution at its source. However, existing biodegradable mulch films still have many technical shortcomings: most products lack sufficient heat and moisture retention properties, making them unsuitable for crop growth in arid and low-temperature regions; some products have poor mechanical properties, are easily damaged, and cannot be adapted to mechanized laying and field operations; and the degradation cycle of some products is uncontrollable, with premature degradation leading to the failure of heat and moisture retention functions, while slow degradation results in residual film. Therefore, developing a biodegradable mulch film with excellent heat and moisture retention properties, stable mechanical properties, and a controllable degradation cycle to solve the pain points of existing technologies and meet the needs of modern green agricultural production has become an urgent technical problem to be solved. Summary of the Invention

[0004] To address the technical problems mentioned in the background section, this application provides a biodegradable thermal insulation and moisture-retaining mulch film and its preparation method.

[0005] Firstly, this application provides a biodegradable thermal insulation and moisture-retaining mulch film, employing the following technical solution: A biodegradable thermal insulation and moisture-retaining mulch film comprises the following raw materials in parts by weight: 50-70 parts of biodegradable substrate, 15-30 parts of modified polymer material, 2-5 parts of thermal insulation agent, 3-6 parts of moisture-retaining agent, 3-5 parts of film-forming aid, 1-5 parts of compatibilizer, 2-8 parts of plasticizer, and 0.5-2 parts of anti-aging agent.

[0006] Preferably, the biodegradable substrate is composed of polybutylene succinate, polybutylene terephthalate, and polybutylene co-succinate in a mass ratio of 3-5:5-8:1-2.

[0007] Preferably, the preparation method of the modified polymer material includes the following steps: Step 1: Disperse nano-silica in anhydrous toluene, add silane coupling agent with epoxy functional group, and reflux at 100-120℃ for 6-8 hours under nitrogen protection. After the reaction is completed, centrifuge, wash and dry to obtain active nano-silica. Step 2: Vacuum-dried polyhydroxyalkanoate, polyethylene oxide, and carboxyl-modified cellulose nanocrystals are respectively subjected to vacuum drying treatment; the vacuum-dried polyhydroxyalkanoate, polyethylene oxide, carboxyl-modified cellulose nanocrystals, and active nano-silica are added to a high-speed mixer, and then a dynamic crosslinking agent containing disulfide bonds and 4-dimethylaminopyridine are added and mixed evenly to obtain a mixture; the mixture is added to a twin-screw extruder for melt reaction, extrusion granulation, and obtaining modified polymer material.

[0008] Preferably, in step 1, the mass ratio of nano-silica, anhydrous toluene, and silane coupling agent with epoxy functional groups is 5-7:100-150:1-2.

[0009] Preferably, the silane coupling agent with epoxy functional group is one or more of γ-glycidoxypropyltrimethoxysilane, γ-glycidoxypropyltriethoxysilane, and β-(3,4-epoxycyclohexyl)ethyltrimethoxysilane.

[0010] Preferably, in step 2, the mass ratio of polyhydroxyalkanoate, polyethylene oxide, carboxyl-modified cellulose nanocrystals, active nano-silica, dynamic crosslinking agent containing disulfide bonds, and 4-dimethylaminopyridine is 40-60:20-30:8-15:5-10:2-5:0.3-0.8.

[0011] Preferably, the dynamic crosslinking agent containing disulfide bonds is one or more of bis(4-hydroxyphenyl) disulfide, dithiodipropionic acid, and dithiodiethanol.

[0012] Preferably, the parameters of the twin-screw extruder are: 140-150℃ for the feeding section, 160-180℃ for the melting section, 170-190℃ for the homogenization section, and a screw speed of 40-60 rpm.

[0013] Preferably, the heat-insulating agent is nano-montmorillonite and / or nano-silica aerogel.

[0014] Preferably, the moisture-retaining agent is sodium carboxymethyl cellulose and / or xanthan gum.

[0015] Preferably, the film-forming aid is dibutyl phthalate and / or dioctyl adipate.

[0016] Preferably, the compatibilizer is maleic anhydride-grafted polylactic acid and / or maleic anhydride-grafted polybutylene succinate.

[0017] Preferably, the plasticizer is one or more of tributyl citrate, acetylated tributyl citrate, and PEG-2000.

[0018] Preferably, the anti-aging agent is one or more of antioxidant 1010, antioxidant 168, and antioxidant 1076.

[0019] Secondly, this application also provides a method for preparing a biodegradable heat-insulating and moisture-retaining mulch film, which adopts the following technical solution: A method for preparing a biodegradable thermal insulation and moisture-retaining mulch film includes the following steps: Step A: Add the biodegradable substrate and modified polymer material to a high-speed mixer and stir evenly. Then add the heat-insulating agent, moisture-retaining agent, film-forming aid, compatibilizer, plasticizer, and anti-aging agent in sequence, and continue mixing for 20-30 minutes to obtain the mixed substrate. Step B: Add the mixed substrate to a twin-screw extruder, and after melting and plasticizing, extrude to obtain the melt material; Step C: The molten material is fed into a blown film machine for blown film forming. It is then cooled and shaped by cooling air to obtain a biodegradable heat-insulating and moisture-retaining mulch film.

[0020] Preferably, the specific conditions for melting and plasticizing in step B are: 130-140°C in the feeding section, 150-170°C in the melting section, 160-180°C in the homogenization section, and a screw speed of 30-50 rpm.

[0021] Preferably, in step C, the die temperature of the blown film machine is 150-170℃, the blow-up ratio is controlled at 2.5-3.5, and the traction speed is 5-8m / min.

[0022] Preferably, the temperature of the cooling air in step C is 20-30℃, and the cooling and setting time is 3-5 minutes.

[0023] In summary, this application has the following beneficial effects: This application utilizes a compound of polybutylene succinate (PBS), polybutylene terephthalate (PBAT), and polybutylene co-butylene terephthalate (PBST) as a biodegradable substrate. This approach balances the degradation rate and mechanical properties of the substrate, enabling the mulch film to completely degrade into harmless substances in the natural environment. This solves the environmental pollution problems caused by traditional non-degradable mulch film residues, such as soil compaction, decreased porosity, and nutrient loss, thus ensuring the integrity of the soil ecosystem. PBS possesses excellent biodegradability and mechanical strength, providing fundamental support for the substrate; PBAT has good flexibility and processability, improving the film-forming toughness of the substrate; and PBST combines the degradability of PBS with the flexibility of PBAT. The ternary compound system used in this application significantly improves compatibility, effectively avoiding problems such as component stratification and film cracking. It not only improves the film-forming properties and toughness of the mulch film but also allows for precise control of the degradation cycle.

[0024] This application optimizes the melt blending parameters of active nano-silica with polyhydroxyalkanoate (PHA), polyethylene oxide (PEO), and carboxyl-modified cellulose nanocrystals (CMCNC) by controlling the modification process of active nano-silica, thereby constructing a multi-component synergistic modification system. This allows the prepared modified polymer material to not only form a stable interfacial bond with the biodegradable substrate but also to compensate for the inherent defects of the substrate at the molecular level, effectively improving the overall performance of the mulch film. Specifically, PHA enhances the biodegradability synergy of the modification system, PEO optimizes the processing fluidity and compatibility of the modification system, and CMCNC strengthens the mechanical strength and moisture retention performance of the mulch film through intermolecular hydrogen bonding. The synergistic effect of these three components with active nano-silica enables the modified polymer material to significantly improve the long-term heat and moisture retention of the mulch film, locking in deep soil moisture and preventing ground temperature loss, while also compensating for the shortcomings of insufficient toughness and poor impact resistance of the biodegradable substrate, achieving a unity of environmental protection, practicality, and long-term effectiveness. Detailed Implementation

[0025] The present application will be further described in detail below with reference to the embodiments.

[0026] The polybutylene succinate used in the embodiments and comparative examples of this application was purchased from Wuhan Shuer Biotechnology Co., Ltd.; polybutylene terephthalate-adipate (brand name: THJS6802) was purchased from Dongguan Guangyu Plastic Raw Materials Co., Ltd.; polybutylene terephthalate-co-butylene succinate (brand name: 778T-BK) was purchased from Dongguan Weicai Plastic Raw Materials Co., Ltd.; nano-montmorillonite (model: DK32B) was purchased from Zhejiang Fenghong New Materials Co., Ltd. Shanghai Branch; maleic anhydride-grafted polylactic acid was purchased from Dongguan Nabaichuan Plastics Co., Ltd.; nano-silica was purchased from Nanjing Tianxing New Materials Co., Ltd.; polyhydroxyalkanoate was purchased from Dongguan Wanwuyuan Plastics Co., Ltd.; polyethylene oxide was purchased from Jiangsu Leien Environmental Protection Technology Co., Ltd.; and carboxyl-modified cellulose nanocrystals (brand name: TL-006) were purchased from Nanjing Tianlu Nanotechnology Co., Ltd.

[0027] Examples 1-3 provide a biodegradable heat-insulating and moisture-retaining mulch film and its preparation method.

[0028] Example 1 A biodegradable thermal insulation and moisture-retaining mulch film comprises the following raw materials in parts by weight: 50 parts of biodegradable substrate, 15 parts of modified polymer material, 2 parts of thermal insulation agent, 3 parts of moisture-retaining agent, 3 parts of film-forming aid, 1 part of compatibilizer, 2 parts of plasticizer, and 0.5 parts of anti-aging agent; wherein, the biodegradable substrate is composed of polybutylene succinate, polybutylene adipate and polybutylene terephthalate in a mass ratio of 3:5:1, the thermal insulation agent is nano-montmorillonite, the moisture-retaining agent is sodium carboxymethyl cellulose, the film-forming aid is dibutyl phthalate, the compatibilizer is maleic anhydride-grafted polylactic acid, the plasticizer is tributyl citrate, and the anti-aging agent is antioxidant 1010.

[0029] The preparation method of the modified polymer material includes the following steps: Step 1: Control the ultrasonic dispersion power to 200W and the ultrasonic frequency to 40kHz, disperse nano-silica in anhydrous toluene, ultrasonically disperse for 30min, add γ-glycidoxypropyltrimethoxysilane, and reflux at 100℃ for 6h under nitrogen protection. After the reaction is completed, centrifuge at 8000rpm for 15min and collect the precipitate; wash the precipitate three times with anhydrous ethanol and dry at 80℃ for 4h to obtain active nano-silica. The mass ratio of nano-silica, anhydrous toluene and γ-glycidoxypropyltrimethoxysilane is 5:100:1. Step 2: Polyhydroxyalkanoate, polyethylene oxide, and carboxyl-modified cellulose nanocrystals were vacuum-dried at 85℃ for 5 hours. The vacuum-dried polyhydroxyalkanoate, polyethylene oxide, carboxyl-modified cellulose nanocrystals, and active nano-silica were then added to a high-speed mixer. Dithiodipropionic acid and 4-dimethylaminopyridine were added, and the high-speed mixer speed was adjusted to 1200 rpm. The mixture was mixed at room temperature for 25 minutes until homogeneous, yielding a homogeneous material. This mixture was then added to a twin-screw extruder for a melt reaction. The temperatures of each section of the twin-screw extruder were controlled as follows: feed section 140℃, melting section 160℃, homogenization section 170℃, screw speed 40 rpm, melt reaction for 20 minutes, extrusion granulation, and the modified polymer material was obtained. The mass ratio of polyhydroxyalkanoate, polyethylene oxide, carboxyl-modified cellulose nanocrystals, active nano-silica, dithiodipropionic acid, and 4-dimethylaminopyridine was 40:20:8:5:2:0.3.

[0030] A method for preparing a biodegradable thermal insulation and moisture-retaining mulch film includes the following preparation steps: Step A: Add the biodegradable substrate and modified polymer material to a high-speed mixer, adjust the speed to 1000 rpm, mix for 10 minutes, then add the heat preservation agent, moisture retention agent, film-forming aid, compatibilizer, plasticizer, and anti-aging agent in sequence, and continue mixing for 20 minutes to obtain the mixed substrate. Step B: Add the mixed base material into a twin-screw extruder and control the extruder parameters as follows: feed section 130℃, melting section 150℃, homogenization section 160℃, screw speed 30rpm. After melting and plasticizing, the material is extruded to obtain the melt material. Step C: Feed the molten material into a blown film machine for blown film forming. Adjust the die temperature of the blown film machine to 150℃, control the blow-up ratio to 2.5, and the traction speed to 5m / min. Cool and shape the film by cooling air at a temperature of 20℃ for 3 minutes to obtain a biodegradable heat-insulating and moisture-retaining mulch film.

[0031] Example 2 A biodegradable thermal insulation and moisture-retaining mulch film comprises the following raw materials in parts by weight: 60 parts of biodegradable substrate, 22 parts of modified polymer material, 4 parts of thermal insulation agent, 4 parts of moisture-retaining agent, 4 parts of film-forming aid, 3 parts of compatibilizer, 5 parts of plasticizer, and 1 part of anti-aging agent; wherein, the biodegradable substrate is composed of polybutylene succinate, polybutylene adipate and polybutylene terephthalate in a mass ratio of 4:7:1.5, the thermal insulation agent is nano-montmorillonite, the moisture-retaining agent is sodium carboxymethyl cellulose, the film-forming aid is dibutyl phthalate, the compatibilizer is maleic anhydride-grafted polylactic acid, the plasticizer is tributyl citrate, and the anti-aging agent is antioxidant 1010.

[0032] The preparation method of the modified polymer material includes the following steps: Step 1: Control the ultrasonic dispersion power to 250W and the ultrasonic frequency to 50kHz. Disperse nano-silica in anhydrous toluene and ultrasonically disperse for 35min. Add γ-glycidoxypropyltrimethoxysilane and reflux at 110℃ for 7h under nitrogen protection. After the reaction is complete, centrifuge at 9000rpm for 18min and collect the precipitate. Wash the precipitate 4 times with anhydrous ethanol and dry at 85℃ for 4.5h to obtain active nano-silica. The mass ratio of nano-silica, anhydrous toluene and γ-glycidoxypropyltrimethoxysilane is 6:130:1.5. Step 2: Polyhydroxyalkanoate, polyethylene oxide, and carboxyl-modified cellulose nanocrystals were vacuum-dried at 90℃ for 5.5 h. The vacuum-dried polyhydroxyalkanoate, polyethylene oxide, carboxyl-modified cellulose nanocrystals, and active nano-silica were then added to a high-speed mixer. Dithiodipropionic acid and 4-dimethylaminopyridine were added, and the high-speed mixer speed was adjusted to 1400 rpm. The mixture was mixed at room temperature for 30 min until homogeneous, yielding a homogeneous material. This mixture was then added to a twin-screw extruder for a melt reaction. The temperatures of each section of the twin-screw extruder were controlled as follows: feed section 145℃, melting section 170℃, homogenization section 180℃, screw speed 50 rpm, melt reaction for 25 min, extrusion granulation, and the modified polymer material was obtained. The mass ratio of polyhydroxyalkanoate, polyethylene oxide, carboxyl-modified cellulose nanocrystals, active nano-silica, dithiodipropionic acid, and 4-dimethylaminopyridine was 50:25:12:8:4:0.5.

[0033] A method for preparing a biodegradable thermal insulation and moisture-retaining mulch film includes the following preparation steps: Step A: Add the biodegradable substrate and modified polymer material to a high-speed mixer, adjust the speed to 1300 rpm, mix for 12 minutes, then add the heat preservation agent, moisture retention agent, film-forming aid, compatibilizer, plasticizer, and anti-aging agent in sequence, and continue mixing for 25 minutes to obtain the mixed substrate. Step B: Add the mixed base material into a twin-screw extruder and control the extruder parameters as follows: feed section 135℃, melting section 160℃, homogenization section 170℃, screw speed 40rpm. After melting and plasticizing, the material is extruded to obtain the melt material. Step C: Feed the molten material into the blown film machine for blown film forming. Adjust the die temperature of the blown film machine to 160℃, control the blow ratio to 3, and the traction speed to 7m / min. Cool and shape the film by cooling air at a temperature of 25℃ for 4 minutes to obtain a biodegradable heat-insulating and moisture-retaining mulch film.

[0034] Example 3 A biodegradable thermal insulation and moisture-retaining mulch film comprises the following raw materials in parts by weight: 70 parts of biodegradable substrate, 30 parts of modified polymer material, 5 parts of thermal insulation agent, 6 parts of moisture-retaining agent, 5 parts of film-forming aid, 5 parts of compatibilizer, 8 parts of plasticizer, and 2 parts of anti-aging agent; wherein, the biodegradable substrate is composed of polybutylene succinate, polybutylene adipate and polybutylene terephthalate in a mass ratio of 5:8:2, the thermal insulation agent is nano-montmorillonite, the moisture-retaining agent is sodium carboxymethyl cellulose, the film-forming aid is dibutyl phthalate, the compatibilizer is maleic anhydride-grafted polylactic acid, the plasticizer is tributyl citrate, and the anti-aging agent is antioxidant 1010.

[0035] The preparation method of the modified polymer material includes the following steps: Step 1: Control the ultrasonic dispersion power to 300W and the ultrasonic frequency to 60kHz, disperse nano-silica in anhydrous toluene, ultrasonically disperse for 40min, add γ-glycidoxypropyltrimethoxysilane, and reflux at 120℃ for 6-8h under nitrogen protection. After the reaction is completed, centrifuge at 10000rpm for 20min and collect the precipitate; wash the precipitate 4 times with anhydrous ethanol and dry at 90℃ for 5h to obtain active nano-silica. The mass ratio of nano-silica, anhydrous toluene and γ-glycidoxypropyltrimethoxysilane is 7:150:2. Step 2: Polyhydroxyalkanoate, polyethylene oxide, and carboxyl-modified cellulose nanocrystals were vacuum-dried at 95℃ for 6 hours. The vacuum-dried polyhydroxyalkanoate, polyethylene oxide, carboxyl-modified cellulose nanocrystals, and active nano-silica were then added to a high-speed mixer. Dithiodipropionic acid and 4-dimethylaminopyridine were added, and the high-speed mixer speed was adjusted to 1600 rpm. The mixture was mixed at room temperature for 35 minutes until homogeneous, yielding a homogeneous material. This mixture was then added to a twin-screw extruder for a melt reaction. The temperatures of each section of the twin-screw extruder were controlled as follows: feed section 150℃, melting section 180℃, homogenization section 190℃, screw speed 60 rpm, melt reaction for 30 minutes, extrusion granulation, and the modified polymer material was obtained. The mass ratio of polyhydroxyalkanoate, polyethylene oxide, carboxyl-modified cellulose nanocrystals, active nano-silica, dithiodipropionic acid, and 4-dimethylaminopyridine was 60:30:15:10:5:0.8.

[0036] A method for preparing a biodegradable thermal insulation and moisture-retaining mulch film includes the following preparation steps: Step A: Add the biodegradable substrate and modified polymer material to a high-speed mixer, adjust the speed to 1500 rpm, mix for 15 minutes, then add the heat preservation agent, moisture retention agent, film-forming aid, compatibilizer, plasticizer, and anti-aging agent in sequence, and continue mixing for 30 minutes to obtain the mixed substrate. Step B: Add the mixed base material into the twin-screw extruder and control the extruder parameters as follows: feed section 140℃, melting section 170℃, homogenization section 180℃, screw speed 50rpm. After melting and plasticizing, the material is extruded to obtain the melt material. Step C: Feed the molten material into a blown film machine for blown film forming. Adjust the die temperature of the blown film machine to 170℃, control the blow-up ratio to 3.5, and the traction speed to 8m / min. Cool and shape the film by cooling air at a temperature of 30℃ for 5 minutes to obtain a biodegradable heat-insulating and moisture-retaining mulch film.

[0037] Comparative Example 1 A biodegradable thermal insulation and moisture-retaining mulch film comprises the following raw materials in parts by weight: 50 parts of biodegradable substrate, 15 parts of modified polymer material, 2 parts of thermal insulation agent, 3 parts of moisture-retaining agent, 3 parts of film-forming aid, 1 part of compatibilizer, 2 parts of plasticizer, and 0.5 parts of anti-aging agent; wherein, the biodegradable substrate is composed of polybutylene succinate and polybutylene terephthalate in a mass ratio of 3:5, the thermal insulation agent is nano-montmorillonite, the moisture-retaining agent is sodium carboxymethyl cellulose, the film-forming aid is dibutyl phthalate, the compatibilizer is maleic anhydride-grafted polylactic acid, the plasticizer is tributyl citrate, and the anti-aging agent is antioxidant 1010.

[0038] The preparation method of the modified polymer material includes the following steps: Step 1: Control the ultrasonic dispersion power to 200W and the ultrasonic frequency to 40kHz, disperse nano-silica in anhydrous toluene, ultrasonically disperse for 30min, add γ-glycidoxypropyltrimethoxysilane, and reflux at 100℃ for 6h under nitrogen protection. After the reaction is completed, centrifuge at 8000rpm for 15min and collect the precipitate; wash the precipitate three times with anhydrous ethanol and dry at 80℃ for 4h to obtain active nano-silica. The mass ratio of nano-silica, anhydrous toluene and γ-glycidoxypropyltrimethoxysilane is 5:100:1. Step 2: Polyhydroxyalkanoate, polyethylene oxide, and carboxyl-modified cellulose nanocrystals were vacuum-dried at 85℃ for 5 hours. The vacuum-dried polyhydroxyalkanoate, polyethylene oxide, carboxyl-modified cellulose nanocrystals, and active nano-silica were then added to a high-speed mixer. Dithiodipropionic acid and 4-dimethylaminopyridine were added, and the high-speed mixer speed was adjusted to 1200 rpm. The mixture was mixed at room temperature for 25 minutes until homogeneous, yielding a homogeneous material. This mixture was then added to a twin-screw extruder for a melt reaction. The temperatures of each section of the twin-screw extruder were controlled as follows: feed section 140℃, melting section 160℃, homogenization section 170℃, screw speed 40 rpm, melt reaction for 20 minutes, extrusion granulation, and the modified polymer material was obtained. The mass ratio of polyhydroxyalkanoate, polyethylene oxide, carboxyl-modified cellulose nanocrystals, active nano-silica, dithiodipropionic acid, and 4-dimethylaminopyridine was 40:20:8:5:2:0.3.

[0039] A method for preparing a biodegradable thermal insulation and moisture-retaining mulch film includes the following preparation steps: Step A: Add the biodegradable substrate and modified polymer material to a high-speed mixer, adjust the speed to 1000 rpm, mix for 10 minutes, then add the heat preservation agent, moisture retention agent, film-forming aid, compatibilizer, plasticizer, and anti-aging agent in sequence, and continue mixing for 20 minutes to obtain the mixed substrate. Step B: Add the mixed base material into a twin-screw extruder and control the extruder parameters as follows: feed section 130℃, melting section 150℃, homogenization section 160℃, screw speed 30rpm. After melting and plasticizing, the material is extruded to obtain the melt material. Step C: Feed the molten material into a blown film machine for blown film forming. Adjust the die temperature of the blown film machine to 150℃, control the blow-up ratio to 2.5, and the traction speed to 5m / min. Cool and shape the film by cooling air at a temperature of 20℃ for 3 minutes to obtain a biodegradable heat-insulating and moisture-retaining mulch film.

[0040] Comparative Example 2 A biodegradable thermal insulation and moisture-retaining mulch film comprises the following raw materials in parts by weight: 50 parts of biodegradable substrate, 15 parts of modified polymer material, 2 parts of thermal insulation agent, 3 parts of moisture-retaining agent, 3 parts of film-forming aid, 1 part of compatibilizer, 2 parts of plasticizer, and 0.5 parts of anti-aging agent; wherein, the biodegradable substrate is composed of polybutylene terephthalate and polybutylene terephthalate in a mass ratio of 5:1, the thermal insulation agent is nano-montmorillonite, the moisture-retaining agent is sodium carboxymethyl cellulose, the film-forming aid is dibutyl phthalate, the compatibilizer is maleic anhydride-grafted polylactic acid, the plasticizer is tributyl citrate, and the anti-aging agent is antioxidant 1010.

[0041] The preparation method of the modified polymer material includes the following steps: Step 1: Control the ultrasonic dispersion power to 200W and the ultrasonic frequency to 40kHz, disperse nano-silica in anhydrous toluene, ultrasonically disperse for 30min, add γ-glycidoxypropyltrimethoxysilane, and reflux at 100℃ for 6h under nitrogen protection. After the reaction is completed, centrifuge at 8000rpm for 15min and collect the precipitate; wash the precipitate three times with anhydrous ethanol and dry at 80℃ for 4h to obtain active nano-silica. The mass ratio of nano-silica, anhydrous toluene and γ-glycidoxypropyltrimethoxysilane is 5:100:1. Step 2: Polyhydroxyalkanoate, polyethylene oxide, and carboxyl-modified cellulose nanocrystals were vacuum-dried at 85℃ for 5 hours. The vacuum-dried polyhydroxyalkanoate, polyethylene oxide, carboxyl-modified cellulose nanocrystals, and active nano-silica were then added to a high-speed mixer. Dithiodipropionic acid and 4-dimethylaminopyridine were added, and the high-speed mixer speed was adjusted to 1200 rpm. The mixture was mixed at room temperature for 25 minutes until homogeneous, yielding a homogeneous material. This mixture was then added to a twin-screw extruder for a melt reaction. The temperatures of each section of the twin-screw extruder were controlled as follows: feed section 140℃, melting section 160℃, homogenization section 170℃, screw speed 40 rpm, melt reaction for 20 minutes, extrusion granulation, and the modified polymer material was obtained. The mass ratio of polyhydroxyalkanoate, polyethylene oxide, carboxyl-modified cellulose nanocrystals, active nano-silica, dithiodipropionic acid, and 4-dimethylaminopyridine was 40:20:8:5:2:0.3.

[0042] A method for preparing a biodegradable thermal insulation and moisture-retaining mulch film includes the following preparation steps: Step A: Add the biodegradable substrate and modified polymer material to a high-speed mixer, adjust the speed to 1000 rpm, mix for 10 minutes, then add the heat preservation agent, moisture retention agent, film-forming aid, compatibilizer, plasticizer, and anti-aging agent in sequence, and continue mixing for 20 minutes to obtain the mixed substrate. Step B: Add the mixed base material into a twin-screw extruder and control the extruder parameters as follows: feed section 130℃, melting section 150℃, homogenization section 160℃, screw speed 30rpm. After melting and plasticizing, the material is extruded to obtain the melt material. Step C: Feed the molten material into a blown film machine for blown film forming. Adjust the die temperature of the blown film machine to 150℃, control the blow-up ratio to 2.5, and the traction speed to 5m / min. Cool and shape the film by cooling air at a temperature of 20℃ for 3 minutes to obtain a biodegradable heat-insulating and moisture-retaining mulch film.

[0043] Comparative Example 3 A biodegradable thermal insulation and moisture-retaining mulch film comprises the following raw materials in parts by weight: 50 parts of biodegradable substrate, 15 parts of modified polymer material, 2 parts of thermal insulation agent, 3 parts of moisture-retaining agent, 3 parts of film-forming aid, 1 part of compatibilizer, 2 parts of plasticizer, and 0.5 parts of anti-aging agent; wherein, the biodegradable substrate is composed of polybutylene succinate and polybutylene terephthalate-co-butylene succinate in a mass ratio of 3:1, the thermal insulation agent is nano-montmorillonite, the moisture-retaining agent is sodium carboxymethyl cellulose, the film-forming aid is dibutyl phthalate, the compatibilizer is maleic anhydride-grafted polylactic acid, the plasticizer is tributyl citrate, and the anti-aging agent is antioxidant 1010.

[0044] The preparation method of the modified polymer material includes the following steps: Step 1: Control the ultrasonic dispersion power to 200W and the ultrasonic frequency to 40kHz, disperse nano-silica in anhydrous toluene, ultrasonically disperse for 30min, add γ-glycidoxypropyltrimethoxysilane, and reflux at 100℃ for 6h under nitrogen protection. After the reaction is completed, centrifuge at 8000rpm for 15min and collect the precipitate; wash the precipitate three times with anhydrous ethanol and dry at 80℃ for 4h to obtain active nano-silica. The mass ratio of nano-silica, anhydrous toluene and γ-glycidoxypropyltrimethoxysilane is 5:100:1. Step 2: Polyhydroxyalkanoate, polyethylene oxide, and carboxyl-modified cellulose nanocrystals were vacuum-dried at 85℃ for 5 hours. The vacuum-dried polyhydroxyalkanoate, polyethylene oxide, carboxyl-modified cellulose nanocrystals, and active nano-silica were then added to a high-speed mixer. Dithiodipropionic acid and 4-dimethylaminopyridine were added, and the high-speed mixer speed was adjusted to 1200 rpm. The mixture was mixed at room temperature for 25 minutes until homogeneous, yielding a homogeneous material. This mixture was then added to a twin-screw extruder for a melt reaction. The temperatures of each section of the twin-screw extruder were controlled as follows: feed section 140℃, melting section 160℃, homogenization section 170℃, screw speed 40 rpm, melt reaction for 20 minutes, extrusion granulation, and the modified polymer material was obtained. The mass ratio of polyhydroxyalkanoate, polyethylene oxide, carboxyl-modified cellulose nanocrystals, active nano-silica, dithiodipropionic acid, and 4-dimethylaminopyridine was 40:20:8:5:2:0.3.

[0045] A method for preparing a biodegradable thermal insulation and moisture-retaining mulch film includes the following preparation steps: Step A: Add the biodegradable substrate and modified polymer material to a high-speed mixer, adjust the speed to 1000 rpm, mix for 10 minutes, then add the heat preservation agent, moisture retention agent, film-forming aid, compatibilizer, plasticizer, and anti-aging agent in sequence, and continue mixing for 20 minutes to obtain the mixed substrate. Step B: Add the mixed base material into a twin-screw extruder and control the extruder parameters as follows: feed section 130℃, melting section 150℃, homogenization section 160℃, screw speed 30rpm. After melting and plasticizing, the material is extruded to obtain the melt material. Step C: Feed the molten material into a blown film machine for blown film forming. Adjust the die temperature of the blown film machine to 150℃, control the blow-up ratio to 2.5, and the traction speed to 5m / min. Cool and shape the film by cooling air at a temperature of 20℃ for 3 minutes to obtain a biodegradable heat-insulating and moisture-retaining mulch film.

[0046] Comparative Example 4 A biodegradable thermal insulation and moisture-retaining mulch film comprises the following raw materials in parts by weight: 50 parts of biodegradable substrate, 15 parts of modified polymer material, 2 parts of thermal insulation agent, 3 parts of moisture-retaining agent, 3 parts of film-forming aid, 1 part of compatibilizer, 2 parts of plasticizer, and 0.5 parts of anti-aging agent; wherein, the biodegradable substrate is composed of polybutylene succinate, polybutylene adipate, and polybutylene terephthalate in a mass ratio of 3:5:1; the thermal insulation agent is nano-montmorillonite; the moisture-retaining agent is sodium carboxymethyl cellulose; the film-forming aid is dibutyl phthalate; the compatibilizer is maleic anhydride-grafted polylactic acid; the plasticizer is tributyl citrate; and the anti-aging agent is antioxidant 1010.

[0047] The preparation method of the modified polymer material includes the following steps: Step 1: Control the ultrasonic dispersion power to 200W and the ultrasonic frequency to 40kHz, disperse nano-silica in anhydrous toluene, ultrasonically disperse for 30min, add γ-glycidoxypropyltrimethoxysilane, and reflux at 100℃ for 6h under nitrogen protection. After the reaction is completed, centrifuge at 8000rpm for 15min and collect the precipitate; wash the precipitate three times with anhydrous ethanol and dry at 80℃ for 4h to obtain active nano-silica. The mass ratio of nano-silica, anhydrous toluene and γ-glycidoxypropyltrimethoxysilane is 5:100:1. Step 2: Polyethylene oxide and carboxyl-modified cellulose nanocrystals were vacuum dried at 85℃ for 5 hours. Then, active nano-silica, vacuum-dried polyethylene oxide, and carboxyl-modified cellulose nanocrystals were added to a high-speed mixer, followed by dithiodipropionic acid and 4-dimethylaminopyridine. The high-speed mixer speed was adjusted to 1200 rpm, and the mixture was stirred at room temperature for 25 minutes until homogeneous, yielding a mixture. This mixture was then added to a twin-screw extruder for a melt reaction. The temperatures of each section of the twin-screw extruder were controlled as follows: feed section 140℃, melting section 160℃, homogenization section 170℃, screw speed 40 rpm, melt reaction for 20 minutes, extrusion granulation, and the modified polymer material was obtained. The mass ratio of polyethylene oxide, carboxyl-modified cellulose nanocrystals, active nano-silica, dithiodipropionic acid, and 4-dimethylaminopyridine was 40:28:5:2:0.3.

[0048] A method for preparing a biodegradable thermal insulation and moisture-retaining mulch film includes the following preparation steps: Step A: Add the biodegradable substrate and modified polymer material to a high-speed mixer, adjust the speed to 1000 rpm, mix for 10 minutes, then add the heat preservation agent, moisture retention agent, film-forming aid, compatibilizer, plasticizer, and anti-aging agent in sequence, and continue mixing for 20 minutes to obtain the mixed substrate. Step B: Add the mixed base material into a twin-screw extruder and control the extruder parameters as follows: feed section 130℃, melting section 150℃, homogenization section 160℃, screw speed 30rpm. After melting and plasticizing, the material is extruded to obtain the melt material. Step C: Feed the molten material into a blown film machine for blown film forming. Adjust the die temperature of the blown film machine to 150℃, control the blow-up ratio to 2.5, and the traction speed to 5m / min. Cool and shape the film by cooling air at a temperature of 20℃ for 3 minutes to obtain a biodegradable heat-insulating and moisture-retaining mulch film.

[0049] Comparative Example 5 A biodegradable thermal insulation and moisture-retaining mulch film comprises the following raw materials in parts by weight: 50 parts of biodegradable substrate, 15 parts of modified polymer material, 2 parts of thermal insulation agent, 3 parts of moisture-retaining agent, 3 parts of film-forming aid, 1 part of compatibilizer, 2 parts of plasticizer, and 0.5 parts of anti-aging agent; wherein, the biodegradable substrate is composed of polybutylene succinate, polybutylene adipate, and polybutylene terephthalate in a mass ratio of 3:5:1; the thermal insulation agent is nano-montmorillonite; the moisture-retaining agent is sodium carboxymethyl cellulose; the film-forming aid is dibutyl phthalate; the compatibilizer is maleic anhydride-grafted polylactic acid; the plasticizer is tributyl citrate; and the anti-aging agent is antioxidant 1010.

[0050] The preparation method of the modified polymer material includes the following steps: Step 1: Control the ultrasonic dispersion power to 200W and the ultrasonic frequency to 40kHz, disperse nano-silica in anhydrous toluene, ultrasonically disperse for 30min, add γ-glycidoxypropyltrimethoxysilane, and reflux at 100℃ for 6h under nitrogen protection. After the reaction is completed, centrifuge at 8000rpm for 15min and collect the precipitate; wash the precipitate three times with anhydrous ethanol and dry at 80℃ for 4h to obtain active nano-silica. The mass ratio of nano-silica, anhydrous toluene and γ-glycidoxypropyltrimethoxysilane is 5:100:1. Step 2: Polyhydroxyalkanoate and carboxyl-modified cellulose nanocrystals were vacuum dried at 85℃ for 5 hours. Then, active nano-silica, the vacuum-dried polyhydroxyalkanoate, and the carboxyl-modified cellulose nanocrystals were added to a high-speed mixer, followed by dithiodipropionic acid and 4-dimethylaminopyridine. The high-speed mixer speed was adjusted to 1200 rpm, and the mixture was stirred at room temperature for 25 minutes until homogeneous, yielding a mixture. This mixture was then added to a twin-screw extruder for a melt reaction. The temperatures of each section of the twin-screw extruder were controlled as follows: feed section 140℃, melting section 160℃, homogenization section 170℃, screw speed 40 rpm, melt reaction for 20 minutes, extrusion granulation, and the modified polymer material was obtained. The mass ratio of polyhydroxyalkanoate, carboxyl-modified cellulose nanocrystals, active nano-silica, dithiodipropionic acid, and 4-dimethylaminopyridine was 50:18:5:2:0.3.

[0051] A method for preparing a biodegradable thermal insulation and moisture-retaining mulch film includes the following preparation steps: Step A: Add the biodegradable substrate and modified polymer material to a high-speed mixer, adjust the speed to 1000 rpm, mix for 10 minutes, then add the heat preservation agent, moisture retention agent, film-forming aid, compatibilizer, plasticizer, and anti-aging agent in sequence, and continue mixing for 20 minutes to obtain the mixed substrate. Step B: Add the mixed base material into a twin-screw extruder and control the extruder parameters as follows: feed section 130℃, melting section 150℃, homogenization section 160℃, screw speed 30rpm. After melting and plasticizing, the material is extruded to obtain the melt material. Step C: Feed the molten material into a blown film machine for blown film forming. Adjust the die temperature of the blown film machine to 150℃, control the blow-up ratio to 2.5, and the traction speed to 5m / min. Cool and shape the film by cooling air at a temperature of 20℃ for 3 minutes to obtain a biodegradable heat-insulating and moisture-retaining mulch film.

[0052] Comparative Example 6 A biodegradable thermal insulation and moisture-retaining mulch film comprises the following raw materials in parts by weight: 50 parts of biodegradable substrate, 15 parts of modified polymer material, 2 parts of thermal insulation agent, 3 parts of moisture-retaining agent, 3 parts of film-forming aid, 1 part of compatibilizer, 2 parts of plasticizer, and 0.5 parts of anti-aging agent; wherein, the biodegradable substrate is composed of polybutylene succinate, polybutylene adipate, and polybutylene terephthalate in a mass ratio of 3:5:1; the thermal insulation agent is nano-montmorillonite; the moisture-retaining agent is sodium carboxymethyl cellulose; the film-forming aid is dibutyl phthalate; the compatibilizer is maleic anhydride-grafted polylactic acid; the plasticizer is tributyl citrate; and the anti-aging agent is antioxidant 1010.

[0053] The preparation method of the modified polymer material includes the following steps: Step 1: Control the ultrasonic dispersion power to 200W, the ultrasonic frequency to 40kHz, and ultrasonic dispersion for 30min. Disperse nano-silica in anhydrous toluene, add γ-glycidoxypropyltrimethoxysilane, and reflux at 100℃ for 6h under nitrogen protection. After the reaction, centrifuge at 8000rpm for 15min and collect the precipitate. Wash the precipitate three times with anhydrous ethanol and dry at 80℃ for 4h to obtain active nano-silica. The mass ratio of nano-silica, anhydrous toluene, and γ-glycidoxypropyltrimethoxysilane is 5:100:1. Step 2: Vacuum-dried polyhydroxyalkanoate and polyethylene oxide were vacuum-dried at 85°C for 5 hours. Then, activated nano-silica, the vacuum-dried polyhydroxyalkanoate, and polyethylene oxide were added to a high-speed mixer, followed by dithiodipropionic acid and 4-dimethylaminopyridine. The high-speed mixer speed was adjusted to 1200 rpm, and the mixture was stirred at room temperature for 25 minutes until homogeneous, yielding a uniform mixture. This mixture was then added to a twin-screw extruder for a melt reaction. The temperatures of each section of the twin-screw extruder were controlled as follows: feed section 140°C, melting section 160°C, homogenization section 170°C, screw speed 40 rpm, and melt reaction for 20 minutes. The mixture was then extruded and granulated to obtain a modified polymer material. The mass ratio of polyhydroxyalkanoate, polyethylene oxide, activated nano-silica, dithiodipropionic acid, and 4-dimethylaminopyridine was 44:24:5:2:0.3.

[0054] A method for preparing a biodegradable thermal insulation and moisture-retaining mulch film includes the following preparation steps: Step A: Add the biodegradable substrate and modified polymer material to a high-speed mixer, adjust the speed to 1000 rpm, mix for 10 minutes, then add the heat preservation agent, moisture retention agent, film-forming aid, compatibilizer, plasticizer, and anti-aging agent in sequence, and continue mixing for 20 minutes to obtain the mixed substrate. Step B: Add the mixed base material into a twin-screw extruder and control the extruder parameters as follows: feed section 130℃, melting section 150℃, homogenization section 160℃, screw speed 30rpm. After melting and plasticizing, the material is extruded to obtain the melt material. Step C: Feed the molten material into a blown film machine for blown film forming. Adjust the die temperature of the blown film machine to 150℃, control the blow-up ratio to 2.5, and the traction speed to 5m / min. Cool and shape the film by cooling air at a temperature of 20℃ for 3 minutes to obtain a biodegradable heat-insulating and moisture-retaining mulch film.

[0055] Performance testing The performance of the biodegradable heat-insulating and moisture-retaining mulch films prepared in Examples 1-3 and Comparative Examples 1-6 was tested, as follows: Tensile strength and elongation at break: In accordance with the national standard GB / T 35795-2017 "Fully biodegradable agricultural ground cover film", the tensile strength and elongation at break of the mulch films prepared in Examples 1-3 and Comparative Examples 1-6 were tested using an electronic universal tensile tester at a tensile rate of 100 mm / min. Barrier properties: Referring to the national standard GB / T 1037-2021 "Determination of water vapor transmission performance of plastic films and sheets - cup method for weight gain and weight loss", the water vapor transmission of the mulch films prepared in Examples 1-3 and Comparative Examples 1-6 was tested using the cup method. The experimental temperature was 38℃ and the relative humidity was set to 90% RH. Weight loss rate: The mulch films prepared in Examples 1-3 and Comparative Examples 1-6 were cut to A4 paper size and their initial mass m0 was recorded. Then, the cut mulch film samples were wrapped with a mesh and buried 15cm deep underground. The mulch film samples were dug out of the soil at 30, 60, 90 and 120 days after mulching, respectively. The mulch film was washed and allowed to dry completely before being weighed again. The mass at this time was recorded as m1. The weight loss rate of the mulch film was calculated according to the formula: mulch film weight loss rate = (m0-m1) / m0×100%; The test results are shown in Table 1.

[0056] Table 1 Performance parameters of biodegradable heat-insulating and moisture-retaining mulch films in Examples 1-3 and Comparative Examples 1-6 As shown in Table 1, the biodegradable thermal insulation and moisture-retaining mulch film prepared in this application exhibits excellent comprehensive performance, with high tensile strength, moderate elongation at break, and mechanical properties that meet the requirements for agricultural mulching. It also has moderate water vapor permeability, combining good moisture retention with good air permeability, effectively reducing soil moisture loss. Furthermore, the degradation behavior of the mulch film under soil burial conditions is controllable, with slow initial degradation and rapid later degradation, enabling environmentally friendly waste disposal and demonstrating strong practicality.

[0057] This specific embodiment is merely an explanation of this application and is not intended to limit it. After reading this specification, those skilled in the art can make modifications to this embodiment without contributing any inventive step, but such modifications are protected by patent law as long as they fall within the scope of the claims of this application.

Claims

1. A biodegradable thermal insulation and moisture-retaining mulch film, characterized in that, The raw materials include the following parts by weight: 50-70 parts of biodegradable substrate, 15-30 parts of modified polymer material, 2-5 parts of heat preservation agent, 3-6 parts of moisture retention agent, 3-5 parts of film-forming aid, 1-5 parts of compatibilizer, 2-8 parts of plasticizer, and 0.5-2 parts of anti-aging agent.

2. The biodegradable heat-insulating and moisture-retaining mulch film according to claim 1, characterized in that, The biodegradable substrate is composed of polybutylene succinate, polybutylene adipate, and polybutylene co-succinate in a mass ratio of 3-5:5-8:1-2.

3. The biodegradable heat-insulating and moisture-retaining mulch film according to claim 1, characterized in that, The preparation method of the modified polymer material includes the following steps: Step 1: Disperse nano-silica in anhydrous toluene, add silane coupling agent with epoxy functional group, and reflux at 100-120℃ for 6-8 hours under nitrogen protection. After the reaction is completed, centrifuge, wash and dry to obtain active nano-silica. Step 2: Vacuum-dried polyhydroxyalkanoate, polyethylene oxide, and carboxyl-modified cellulose nanocrystals are respectively subjected to vacuum drying treatment; the vacuum-dried polyhydroxyalkanoate, polyethylene oxide, carboxyl-modified cellulose nanocrystals, and active nano-silica are added to a high-speed mixer, and then a dynamic crosslinking agent containing disulfide bonds and 4-dimethylaminopyridine are added and mixed evenly to obtain a mixture; the mixture is added to a twin-screw extruder for melt reaction, extrusion granulation, and obtaining modified polymer material.

4. The biodegradable heat-insulating and moisture-retaining mulch film according to claim 3, characterized in that, In step 1, the mass ratio of nano-silica, anhydrous toluene, and silane coupling agent with epoxy functional groups is 5-7:100-150:1-2.

5. The biodegradable heat-insulating and moisture-retaining mulch film according to claim 3, characterized in that, The silane coupling agent with epoxy functional group is one or more of γ-glycidoxypropyltrimethoxysilane, γ-glycidoxypropyltriethoxysilane, and β-(3,4-epoxycyclohexyl)ethyltrimethoxysilane.

6. The biodegradable heat-insulating and moisture-retaining mulch film according to claim 3, characterized in that, In step 2, the mass ratio of polyhydroxyalkanoate, polyethylene oxide, carboxyl-modified cellulose nanocrystals, active nano-silica, dynamic crosslinking agent containing disulfide bonds, and 4-dimethylaminopyridine is 40-60:20-30:8-15:5-10:2-5:0.3-0.

8.

7. The biodegradable heat-insulating and moisture-retaining mulch film according to claim 3, characterized in that, The dynamic crosslinking agent containing disulfide bonds is one or more of bis(4-hydroxyphenyl) disulfide, dithiodipropionic acid, and dithiodiethanol.

8. The biodegradable heat-insulating and moisture-retaining mulch film according to claim 1, characterized in that, The heat-insulating agent is nano-montmorillonite and / or nano-silica aerogel; the moisture-retaining agent is sodium carboxymethyl cellulose and / or xanthan gum; the film-forming aid is dibutyl phthalate and / or dioctyl adipate.

9. A method for preparing a biodegradable thermal insulation and moisture-retaining mulch film as described in any one of claims 1-8, characterized in that, The preparation steps include the following: Step A: Add the biodegradable substrate and modified polymer material to a high-speed mixer and stir evenly. Then add the heat-insulating agent, moisture-retaining agent, film-forming aid, compatibilizer, plasticizer, and anti-aging agent in sequence, and continue mixing for 20-30 minutes to obtain the mixed substrate. Step B: Add the mixed substrate to a twin-screw extruder, and after melting and plasticizing, extrude to obtain the melt material; Step C: The molten material is fed into a blown film machine for blown film forming. It is then cooled and shaped by cooling air to obtain a biodegradable heat-insulating and moisture-retaining mulch film.

10. The method for preparing the biodegradable heat-insulating and moisture-retaining mulch film according to claim 9, characterized in that, The specific conditions for melting and plasticizing in step B are as follows: feeding section 130-140℃, melting section 150-170℃, homogenization section 160-180℃, and screw speed 30-50 rpm; in step C, the die temperature of the blown film machine is 150-170℃, the blow-up ratio is controlled at 2.5-3.5, and the traction speed is 5-8 m / min; in step C, the temperature of the cooling air is 20-30℃, and the cooling and setting time is 3-5 min.

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