PBAT-containing fully biodegradable functional mulching film and preparation method thereof

Abstract

The invention discloses a PBAT-containing fully biodegradable functional mulching film and a preparation method thereof, and belongs to the technical field of biodegradable high polymer materials. The PBAT-containing fully biodegradable functional mulching film comprises the following components in parts by weight: 5%-30% of polylactic acid, 70%-95% of PBAT, 1%-5% of a compatilizer, 0.01%-0.5% of a reaction accelerator, 0.01%-0.1% of an antioxidant, 0.3%-1% of a light stabilizer, 0.1%-0.3% of an anti-ultraviolet absorbent, 0.2%-0.5% of an anti-hydrolysis agent and 2%-5% of carbon black. According to the mulching film, efficient combination of high flexibility of PBAT and high strength of PLA is achieved through dual effects of compatibility improvement and a cross-linking system, the comprehensive mechanical property is far better than that of a traditional PE mulching film, and performance guarantee is provided for achieving the ultra-thin thickness of 5 micrometers. Meanwhile, the hydrolysis speed of the mulching film in a humid environment of a paddy field can be effectively delayed, so that the rupture period and the service life of the mulching film are accurately regulated and controlled.

Description

Technical Field

[0001] This application pertains to biodegradable polymer materials, specifically relating to a fully biodegradable functional mulch film containing PBAT and its preparation method. Background Technology

[0002] With socio-economic development and the improvement of people's living standards, food safety issues have received increasing attention from society. Organic rice cultivation, which does not use pesticides or chemical fertilizers and requires clean water irrigation, has become an important way to protect human health and achieve sustainable agricultural development. However, organic rice cultivation faces the dual challenges of weed control and water management: on the one hand, manual weeding is inefficient and costly; on the other hand, traditional irrigation methods have low water resource utilization rates.

[0003] In existing technologies, black functional mulch films, which suppress weed photosynthesis by shading, have been widely used in agriculture. However, traditional polyethylene (PE) black mulch films are difficult to recycle after use and can remain in the soil for hundreds of years, leading to soil structure damage, difficulty in cultivation, and reduced crop yields. Therefore, they cannot meet the environmental protection requirements for organic rice cultivation.

[0004] Although biodegradable mulch films are stable during use and can completely degrade into carbon dioxide and water in the soil after disposal, avoiding environmental pollution, and also have weed control and moisture retention functions, they are theoretically suitable for organic rice cultivation. However, existing biodegradable mulch films have an inherent drawback: the continuous flooding environment in the field during rice cultivation accelerates the degradation of the mulch film, causing it to be unable to maintain its effective weed control and moisture retention functions throughout the entire growth period. Summary of the Invention

[0005] The purpose of this application is to provide a fully biodegradable functional mulch film containing PBAT and its preparation method, which can solve the problem that biodegradable mulch film degrades rapidly when exposed to water in rice planting environments, affecting its performance, and enable it to be effectively applied to organic rice planting.

[0006] To achieve the above objectives, this application provides a biodegradable functional mulch film containing PBAT, comprising the following components in parts by weight: The ingredients include 5%~30% polylactic acid (PLA), 60%~95% polybutylene terephthalate (PBAT), 1%~5% compatibilizer, 0.01%~0.5% reaction accelerator, 0.01%~0.1% antioxidant, 0.3%~1% light stabilizer, 0.1%~0.3% UV absorber, 0.2%~0.5% hydrolysis inhibitor, and 2%~5% carbon black.

[0007] Furthermore, it includes the following components by weight: 20%~30% polylactic acid, 60%~80% PBAT, 3%~5% compatibilizer, 0.2%~0.3% reaction accelerator, 0.05%~0.1% antioxidant, 0.3%~1% light stabilizer, 0.1%~0.3% UV absorber, 0.2%~0.5% hydrolysis inhibitor, and 2%~5% carbon black.

[0008] Furthermore, it includes the following components by weight: The composition includes 30% polylactic acid, 60.5% PBAT, 5% compatibilizer, 0.25% reaction accelerator, 0.05% antioxidant, 0.6% light stabilizer, 0.1% UV absorber, 0.3% hydrolysis inhibitor, and 3.2% carbon black.

[0009] Furthermore, the polylactic acid has a weight-average molecular weight of 200,000 to 400,000, a molecular weight distribution of 1.15 to 2.0, and a crystallinity of 30% to 60%, and the polylactic acid includes at least one of poly-L-lactic acid, poly-D-lactic acid, and poly-DL-lactic acid.

[0010] Furthermore, the density of the PBAT is 1.1 g / cm³. 3 ~1.35g / cm 3 The weight-average molecular weight is 50,000~80,000, and the melt index at 190℃ is 2g / 10min~4g / 10min.

[0011] Furthermore, the compatibilizer is AX8900 functional polymer toughening agent; The reaction promoter is a combination of nano zinc oxide and zinc stearate; The antioxidant is any one of 1,2-bis(3,5-di-tert-butyl-4-hydroxy-phenylpropionic acid) hydrazine, 4,4-thiobis(6-tert-butyl-3-methylphenol) and tris(3,3-di-tert-butyl-4-hydroxybenzyl) isocyanurate; The light stabilizer is any one of the following: hindered amine light stabilizer, nickel bis(3,5-di-tert-butyl-4-hydroxybenzyl phosphate), succinic acid and a polymer of 4-hydroxy-2,2,6,6-tetramethyl-1-piperidinol; The ultraviolet absorber is any one of 2-phenylbenzimidazole-5-sulfonic acid, 2-(2'-hydroxy-5'-methylphenyl)benzotriazole and 2-hydroxy-4-methoxybenzophenone; The anti-hydrolysis agent is carbodiimide or polycarbodiimide.

[0012] Secondly, a method for preparing a fully biodegradable functional mulch film containing PBAT, as described above, includes the following steps: Polylactic acid and PBAT are mixed, and then the compatibilizer, reaction promoter, antioxidant, light stabilizer, UV absorber, anti-hydrolysis agent and carbon black are added in sequence and stirred until uniform to obtain a mixture. The mixture was extruded and granulated to obtain PLA / PBAT modified particles; The PLA / PBAT modified particles were processed by blown film treatment to obtain the biodegradable functional mulch film containing PBTA.

[0013] Furthermore, the stirring speed is 150 rpm to 300 rpm, and the stirring time is 2 min to 5 min.

[0014] Furthermore, the extruder used for the extrusion granulation process has an length-to-diameter ratio of 50:1 and an extruder barrel temperature of 180℃~200℃.

[0015] Furthermore, the blown film machine used in the blown film processing has a length-to-diameter ratio of 32:1.

[0016] In summary, this application has the following advantages: 1. The PBAT-containing biodegradable functional mulch film of this application uses PLA and PBAT resins as base materials. By adding reactive compatibilizers and reaction promoters, a cross-linking reaction between PLA and PBAT can be effectively promoted. This cross-linking reaction can enhance the bonding force between the two resin molecules, thereby significantly improving the tensile strength and elongation at break of the mulch film. This allows the mulch film thickness to be reduced to 5 micrometers while ensuring performance, thus reducing material usage and meeting the mechanical performance requirements of early rice growth. 2. To achieve precise matching between the degradation time of the mulch film and the growth cycle of early rice, this application scientifically selects the types of antioxidants, light stabilizers, UV absorbers, and carbon black pigments, precisely adjusts their contents, and optimizes the proportion of anti-hydrolysis components to construct a multi-factor synergistic degradation regulation system. Among these, antioxidants can delay the oxidative degradation of the material, light stabilizers and UV absorbers can resist the damage caused by light, carbon black pigments can regulate the absorption and shielding of light by the mulch film, and anti-hydrolysis components can inhibit the accelerated degradation caused by moisture. Through the synergistic effect of these components, the degradation rate of the mulch film can be effectively controlled, ensuring stable performance throughout the early rice growth cycle and timely degradation after harvest, avoiding harm to the soil and environment. This solves a key technical challenge in the application of biodegradable mulch film in rice cultivation. Attached Figure Description

[0017] Figure 1 This is a schematic flowchart illustrating the preparation method of a fully biodegradable functional mulch film containing PBAT, as described in the embodiments of this application. Detailed Implementation

[0018] The principles and features of this application are described below with reference to embodiments. The examples are for illustrative purposes only and are not intended to limit the scope of this application. Unless otherwise specified in the embodiments, conventional conditions or conditions recommended by the manufacturer shall apply. Reagents or instruments whose manufacturers are not specified are all commercially available conventional products.

[0019] In agricultural production, black functional mulch film effectively kills weeds in farmland by blocking sunlight needed for plant photosynthesis, and has been widely used in the cultivation of various crops. However, traditional PE black functional mulch film is difficult to recycle after use, and its residues in farmland can remain for hundreds of years without decomposition, causing difficulties in cultivation and reduced crop yields. This does not meet the environmentally friendly requirements of organic agriculture, and therefore cannot be used in the cultivation of organic rice. Biodegradable mulch film, with its unique molecular structure, maintains stable performance during use, meeting the needs of crops during their growth period. After use, it automatically degrades in the soil, generating carbon dioxide and water, without harming the soil or the environment, thus solving the environmental pollution problem of traditional PE mulch film. Applying biodegradable mulch film to organic rice cultivation can not only reduce the complicated process of weeding but also save farmland water, theoretically showing promising application prospects.

[0020] Currently, research has been conducted on biodegradable mulch films for crops such as potatoes, watermelons, sugar beets, tomatoes, tobacco, and cotton. However, due to the characteristic that biodegradable mulch films degrade more rapidly upon contact with water, their performance in rice cultivation environments is severely affected, preventing their successful application in rice farming. Therefore, how to solve the problem of accelerated degradation of biodegradable mulch films in rice cultivation environments, thus affecting their performance and enabling their effective application in organic rice cultivation, has become a pressing technical challenge in this field.

[0021] Based on this, this application provides a biodegradable functional mulch film containing PBAT, which has functions such as heat preservation, moisture retention, and weed control, and can be completely decomposed into carbon dioxide and water by microorganisms in natural environments (such as soil and composting conditions), thus avoiding white pollution. It specifically comprises the following components by weight: The composition includes 5%~30% polylactic acid (PLA), 60%~95% PBAT, 1%~5% compatibilizer, 0.01%~0.5% reaction accelerator, 0.01%~0.1% antioxidant, 0.3%~1% light stabilizer, 0.1%~0.3% UV absorber, 0.2%~0.5% hydrolysis inhibitor, and 2%~5% carbon black.

[0022] In this application's technical solution, PLA possesses high strength but is brittle, while PBAT exhibits excellent toughness but lower strength. Through the synergistic effect of compatibilizers and reaction promoters, the cross-linking and compatibility between the molecular chains are enhanced. This retains the rigidity of PLA to increase tensile strength while leveraging the flexibility of PBAT to improve elongation at break, enabling the composite substrate to surpass the mechanical properties of polyethylene (PE) even at a thickness of 5 μm. Specifically, anti-hydrolysis agents inhibit hydrolysis reactions in aquatic environments, light stabilizers and UV absorbers jointly resist UV photoaging, and antioxidants delay oxidative degradation. These three components form a multi-layered protective effect against hydrolysis, photoaging, and oxidation, with the degradation cycle precisely controlled through content adjustments. Furthermore, the pigment carbon black not only provides shade and weed control but also assists in absorbing UV light, enhancing the anti-aging effect of the light stabilizer and further stabilizing the degradation cycle.

[0023] In a specific embodiment, the biodegradable functional mulch film of this application, with a thickness of 5μm, achieves a tensile strength of 40MPa~48MPa, a significant improvement compared to traditional 5μm thick PE mulch film (tensile strength of 14MPa~20MPa). The biodegradable functional mulch film of this application, with a thickness of only 5μm, achieves superior tensile strength and elongation at break compared to traditional PE mulch film. While ensuring lightness and material conservation, it possesses stronger mechanical properties, resisting field operation impacts and environmental stresses during rice cultivation. Its hydrolysis resistance and controllable degradation cycle of 90~120 days perfectly match the early rice growth cycle, preventing premature degradation and ensuring complete degradation into harmless substances after harvest, meeting the standards for organic rice cultivation. This application achieves efficient shading and weed control through pigment carbon black, eliminating the need for additional herbicide spraying. With the synergistic effect of various adjuvants, the material maintains stable performance in aquatic environments, while also providing multiple functions such as anti-UV aging and anti-oxidation, significantly improving the environmental adaptability of the mulch film. Furthermore, this application uses PLA and PBAT as base materials, both of which are biodegradable resins. Combined with fully biodegradable additives, it achieves complete biodegradation, solving the residual pollution problem of traditional PE mulch films from the source. The low-thickness design combined with the efficient component ratio reduces the total amount of materials used, thereby reducing production costs and environmental impact.

[0024] Preferably, a biodegradable functional mulch film containing PBAT comprises the following components by weight: 20%~30% polylactic acid, 60%~80% PBAT, 3%~5% compatibilizer, 0.2%~0.3% reaction promoter, 0.05%~0.1% antioxidant, 0.3%~1% light stabilizer, 0.1%~0.3% UV absorber, 0.2%~0.5% anti-hydrolysis agent, and 2%~5% carbon black.

[0025] In a specific embodiment, the following components by weight are included: 30% polylactic acid, 60.5% PBAT, 5% compatibilizer, 0.25% reaction accelerator, 0.05% antioxidant, 0.6% light stabilizer, 0.1% UV absorber, 0.3% hydrolysis inhibitor, and 3.2% carbon black.

[0026] In a specific embodiment, the polylactic acid (PLA) has a weight-average molecular weight of 200,000 to 400,000, a molecular weight distribution of 1.15 to 2.0, and a crystallinity of 30% to 60%. The PLA includes at least one of poly-L-lactic acid, poly-D-lactic acid, and poly-DL-lactic acid. In this application, the weight-average molecular weight of 200,000 to 400,000 falls within the medium-to-high molecular weight range, ensuring sufficient entanglement between PLA molecular chains to provide basic rigidity and tensile strength for the mulch film. Combined with a molecular weight distribution of 1.15 to 2.0 (a relatively narrow distribution), it reduces the weakening of the material's mechanical properties by low molecular weight components, making it easier for PLA and PBAT to form a uniform and stable structure after blending, avoiding fluctuations in mechanical properties caused by molecular weight fluctuations. Furthermore, the addition of compatibilizers and reaction promoters further promotes the interfacial bonding of the two resins, enhancing the stability of the blend system and ensuring the molding and mechanical properties of the 5μm ultrathin mulch film. A crystallinity of 30% to 60% balances the rigidity and processability of the material. If the crystallinity is too high, it will lead to increased brittleness of PLA and decreased melt fluidity during processing. A crystallinity of 30% to 60% can maintain a certain rigidity while retaining appropriate flexibility, which complements the toughness of PBAT and helps to improve the elongation at break of the composite mulch film.

[0027] In a specific embodiment, the density of the PBAT is 1.1 g / cm³. 3 ~1.35g / cm 3 The weight-average molecular weight is 50,000~80,000, the melt index at 190℃ is 2g / 10min~4g / 10min, and the melting point is ≥115℃. In this application, the melt index is of medium fluidity, which ensures that PBAT can be fully melted and mixed with PLA and other additives (compatibilizers, pigments, carbon black, etc.) during processing (such as extrusion, blow molding), while avoiding uneven thickness or tensile breakage during the molding of ultra-thin films (5μm) due to excessive fluidity. The matching of weight-average molecular weight and melt index avoids both insufficient melt strength due to low molecular weight (unable to support ultra-thin film molding) and excessively high melt viscosity due to high molecular weight, which makes it difficult to blend uniformly with PLA, thus providing a foundation for the stable production of ultra-thin films.

[0028] In a specific embodiment, the compatibilizer is AX8900 functional polymer toughening agent, the main component of which is ethylene-methyl acrylate-glycidyl methacrylate terpolymer, purchased from Arkema.

[0029] In a specific embodiment, the reaction promoter is a mixture of nano-zinc oxide and zinc stearate, with a preferred mass ratio of 2:1. The nano-zinc oxide (ZnO, particle size 1nm-100nm) catalyzes the esterification reaction between the hydroxyl groups (-OH) of PLA and the carboxyl groups (-COOH) or ester groups of PBAT through its surface active sites. Simultaneously, it promotes the grafting reaction between the compatibilizer and both resins, accelerating the crosslinking or entanglement of PLA and PBAT molecular chains, thereby reducing the interfacial tension between them (PLA is a polar crystalline polymer, while PBAT is a non-polar flexible polymer with poor interfacial compatibility). Zinc stearate, as an organic acid salt, can, on the one hand, achieve affinity with the non-polar segments of PBAT through its long-chain alkyl groups, and on the other hand, generate weak coordination with the ester groups of PLA through zinc ions, acting as a bridge to further reduce the interfacial resistance between PLA and PBAT. Simultaneously, its lubricity reduces the agglomeration of nano-zinc oxide in the blend system, ensuring uniform dispersion of nano-ZnO at the interface between the two phases and maximizing catalytic efficiency. Therefore, the reaction accelerator compound system of this application optimizes the compatibility of PLA and PBAT, which can make the degradation behavior of the two resins more synchronized (PLA is mainly hydrolyzed, and PBAT is mainly degraded by microorganisms), avoids premature local degradation or residue caused by phase separation, and assists anti-hydrolysis agents and light stabilizers to achieve degradation cycle regulation of 90 days to 120 days.

[0030] In a specific embodiment, the antioxidant is any one of 1,2-bis(3,5-di-tert-butyl-4-hydroxy-phenylpropionic acid) hydrazine (antioxidant B102), 4,4'-thiobis(6-tert-butyl-3-methylphenol) (antioxidant 300), or tris(3,3-di-tert-butyl-4-hydroxybenzyl) isocyanurate (antioxidant 311). The antioxidants in this application all belong to the hindered phenolic class of primary antioxidants (or contain hindered phenolic structures). Their core function is to capture free radicals (such as alkyl free radicals and peroxy free radicals) generated during polymer oxidation through the hydroxyl groups (-OH) in the molecule, terminating the oxidation chain reaction and thus delaying the degradation of PLA and PBAT. In the system of this application, it can effectively inhibit the thermo-oxidative and photo-oxidative aging effects during processing and use, ensuring the mechanical properties and service life of the ultra-thin mulch film; it can also adapt to the high humidity and high temperature environment of paddy fields, working synergistically with other additives, while not interfering with the biodegradability of the material.

[0031] In a specific embodiment, the light stabilizer is any one of the following: hindered amine light stabilizer 944, bis(3,5-di-tert-butyl-4-hydroxybenzyl phosphate monoethyl ester) nickel (light stabilizer 802), and succinic acid and (polymer of 4-hydroxy-2,2,6,6-tetramethyl-1-piperidinol) (light stabilizer 622).

[0032] In a specific embodiment, the UV absorber is any one of 2-phenylbenzimidazole-5-sulfonic acid (UV-T), 2-(2'-hydroxy-5'-methylphenyl)benzotriazole (UV absorber UV-P), and 2-hydroxy-4-methoxybenzophenone (UV absorber UV-9). The UV absorber of this application can significantly slow down the aging rate of the mulch film under sunlight, ensuring that it maintains its complete structure and function during critical rice growth periods (such as seedling and weeding stages). Furthermore, the groups contained in the light stabilizer molecule (such as piperidine rings and hydroxyl groups) have a certain compatibility with the polar parts of PLA and PBAT, allowing for uniform dispersion in the mulch film material and avoiding localized accelerated aging or decreased mechanical properties due to uneven dispersion.

[0033] In a specific implementation, the anti-hydrolysis agent is carbodiimide or polycarbodiimide. Because rice mulch film needs to come into contact with soil moisture, irrigation water, and high humidity environments, the ester bonds in polyester materials such as PLA and PBAT are prone to hydrolytic breakage, leading to material embrittlement and decreased mechanical properties. Carbodiimide compounds (especially polycarbodiimide) can react with the carboxyl groups produced by hydrolysis, blocking the vicious cycle of carboxyl-catalyzed hydrolysis, thus fundamentally slowing down the hydrolytic degradation rate of the material and ensuring that the mulch film maintains its structural integrity throughout the rice growth cycle.

[0034] In this specific embodiment, the carbon black is a commercially available high-grade pigment carbon black. High-grade pigment carbon black has an extremely high specific surface area and light absorption capacity, enabling it to physically shield ultraviolet rays and form a dual protection mechanism with hindered amine light stabilizers. For example, carbon black blocks some ultraviolet rays, while the light stabilizer inhibits degradation reactions caused by ultraviolet rays that have already penetrated the material, further extending the weather resistance of the mulch film.

[0035] The environmental friendliness of biodegradable plastics lies in their ability to gradually decompose into carbon dioxide and water under composting or natural conditions, following a typical pathway of "first hydrolysis, then microbial degradation." Based on this characteristic, and considering the 90-120 day growth cycle of early rice, this application achieves a dynamic match between the lifespan of the mulch film and the crop growth cycle by precisely controlling the degradation process of the material. Specifically: To slow down the hydrolysis process of biodegradable materials in the aquatic environment of rice cultivation (a key factor leading to premature material failure), this application introduces carbodiimide-based anti-hydrolysis agents. These agents react with the carboxyl groups generated during material hydrolysis, inhibiting the continued hydrolysis reaction and effectively delaying the initial degradation of the material. Simultaneously, by synergistically adjusting the content of light stabilizers and anti-hydrolysis agents, a quantifiable degradation cycle control system is constructed. The light stabilizer, by resisting the damage to the material's molecular chains caused by ultraviolet light, further helps maintain the structural stability of the material under natural light conditions; while the anti-hydrolysis agent focuses on inhibiting the hydrolysis process in the aquatic environment. Furthermore, subsequent experimental data show that when the light stabilizer content is controlled within the range of 0.3%–1% and the anti-hydrolysis agent content within the range of 0.2%–0.5%, the service life of the PBAT-containing fully degradable functional mulch film for rice cultivation can be precisely controlled within 90–120 days, fully covering the early rice growth cycle. This application achieves controllable degradation cycle through the selection of specific adjuvants and the adjustment of their content gradients. This ensures that the mulch film maintains its complete physical properties and weeding function during the early rice growth period, and can also initiate the subsequent microbial degradation process after the crop is harvested, ultimately decomposing it completely into harmless substances, which meets the environmental requirements of organic agriculture.

[0036] Secondly, based on the same inventive concept, this application also provides a method for preparing a fully biodegradable functional mulch film containing PBAT, such as... Figure 1 As shown, it includes the following steps: S1. Mix polylactic acid and PBAT, and then add the compatibilizer, reaction promoter, antioxidant, light stabilizer, UV absorber, anti-hydrolysis agent and carbon black in sequence and stir until uniform to obtain a mixture.

[0037] In a specific embodiment, the stirring speed is 150 rpm to 300 rpm, and the stirring time is 2 min to 5 min. Using medium-speed mixing allows for rapid mixing of PLA, PBAT substrates, compatibilizers, reaction accelerators, and other additives through mechanical shear force (avoiding uneven dispersion caused by low speeds), while also avoiding the intense frictional heat generated by high speeds (e.g., ≥300 rpm). This prevents premature thermal degradation of PLA at high temperatures (PLA has poor thermal stability and is prone to chain breakage above 190℃), ensuring that the molecular weight and mechanical properties of the substrate are not affected by the mixing stage.

[0038] S2. The mixture is extruded and granulated to obtain PLA / PBAT modified particles.

[0039] In this specific embodiment, the extruder used for extrusion granulation has an L / D ratio of 50:1 and a barrel temperature of 180°C to 200°C. The 50:1 L / D ratio twin-screw extruder provides a longer material residence time, ensuring sufficient reaction of the compatibilizer and thus eliminating PLA / PBAT interface defects. PLA has a melting point of approximately 150°C to 170°C, while PBAT has a melting point ≥115°C. Setting the extruder barrel temperature to 185°C, higher than both melting points, ensures melt flowability. Simultaneously, it is lower than the thermal degradation temperature of PLA (typically ≥200°C) and the thermo-oxidative aging sensitive temperature of PBAT, reducing molecular chain breakage of the substrate during extrusion (avoiding a decline in mechanical properties) while ensuring the antioxidant functions stably at this temperature.

[0040] S3. The PLA / PBAT modified particles are processed by blown film to obtain the biodegradable functional mulch film containing PBTA.

[0041] In a specific implementation, the blown film machine used for the blown film processing has an aspect ratio of 32:1. The thickness of the mulch film for weed control is typically 5μm to 15μm, requiring extremely high melt flowability and stability. The 32:1 aspect ratio design of the blown film machine balances melt delivery efficiency and plasticization uniformity. It avoids excessive material retention caused by an excessively large aspect ratio (preventing degradation) and ensures the stability of the blown film tubes through a stable melt flow, reducing film thickness deviation and ensuring consistency in the mulch film's light-shielding properties (uniform carbon black distribution) and mechanical properties (tear resistance, puncture resistance).

[0042] The technical solutions described above in this application will be explained in detail below with reference to specific embodiments.

[0043] Example 1 This embodiment provides a biodegradable functional mulch film containing PBAT, which comprises the following components in parts by weight: 10 parts polylactic acid, 84.6 parts PBAT, 1 part compatibilizer, 0.3 parts reaction promoter (obtained by compounding nano zinc oxide and zinc stearate in a mass ratio of 2:1), 0.1 parts antioxidant, 0.5 parts light stabilizer, 0.2 parts UV absorber, 0.3 parts hydrolysis inhibitor, and 3 parts carbon black.

[0044] It is prepared by the following method: (1) PLA (Nature Works 4032D, USA), PBAT (Tunhe 801T), compatibilizer (LOTADERAX 8900, Arkema), reaction promoter (nano zinc oxide and zinc stearate compounded at a mass ratio of 2:1), antioxidant (BASF 1010), light stabilizer (BASF 622), UV absorber (BASF 944), and hydrolysis inhibitor (HyMax) were prepared. ®210 Shanghai Langyi) and pigment carbon black (commercially available) were added to a high-speed mixer and mixed at 200 r / min for 2 min. The raw materials used in the following examples are from the same source as those in this example.

[0045] (2) The mixed material is added to a twin-screw extruder with a length-to-diameter ratio of 60:1, extruded, drawn, cooled and sliced ​​to obtain PLA / PBAT modified particles, wherein the extruder barrel temperature is 175℃ and the die temperature is 180℃.

[0046] (3) The obtained PLA / PBAT modified particles were added to a single screw blown film machine with an aspect ratio of 32:1 for blown film processing to obtain a fully biodegradable mulch film with a thickness of 5μm.

[0047] Example 2 This embodiment provides a biodegradable functional mulch film containing PBAT, comprising the following components by weight: 5 parts polylactic acid, 87.5 parts PBAT, 3 parts compatibilizer, 0.2 parts reaction accelerator, 0.1 parts antioxidant, 0.5 parts light stabilizer, 0.2 parts UV absorber, 0.5 parts anti-hydrolysis agent, and 3 parts carbon black. Except for the different mass ratios, the material selection and preparation method are the same as in Example 1.

[0048] Example 3 This embodiment provides a biodegradable functional mulch film containing PBAT, comprising the following components by weight: 30 parts polylactic acid, 60.5 parts PBAT, 5 parts compatibilizer, 0.25 parts reaction accelerator, 0.05 parts antioxidant, 0.6 parts light stabilizer, 0.1 parts UV absorber, 0.3 parts anti-hydrolysis agent, and 3.2 parts carbon black. Except for the different mass ratios, the material selection and preparation method are the same as in Example 1.

[0049] Comparative Example 1 This embodiment provides a biodegradable functional mulch film containing PBAT, comprising the following components by weight: 10 parts polylactic acid, 84.6 parts PBAT, 1.3 parts compatibilizer, 0.1 parts antioxidant, 0.5 parts light stabilizer, 0.2 parts UV absorber, 0.3 parts anti-hydrolysis agent, and 3 parts carbon black. The preparation method is the same as in Example 1.

[0050] Comparative Example 2 This embodiment provides a biodegradable functional mulch film containing PBAT, comprising the following components by weight: 10 parts polylactic acid, 85.6 parts PBAT, 0.3 parts reaction promoter, 0.1 parts antioxidant, 0.5 parts light stabilizer, 0.2 parts UV absorber, 0.3 parts anti-hydrolysis agent, and 3 parts carbon black. The preparation method is the same as in Example 1.

[0051] Comparative Example 3 This embodiment provides a biodegradable functional mulch film containing PBAT, which comprises the following components by weight: 10 parts polylactic acid, 84.6 parts PBAT, 1 part compatibilizer, 0.3 parts nano zinc oxide, 0.1 parts antioxidant, 0.5 parts light stabilizer, 0.2 parts UV absorber, 0.3 parts hydrolysis inhibitor, and 3 parts carbon black.

[0052] It is prepared by the following method: (1) Add PLA, PBAT, compatibilizer, reaction promoter, antioxidant, light stabilizer, UV absorber, hydrolysis inhibitor and pigment carbon black to a high-speed mixer and mix at 200 r / min for 2 min.

[0053] (2) The mixed material is added to a twin-screw extruder with a length-to-diameter ratio of 60:1, extruded, drawn, cooled and sliced ​​to obtain PLA / PBAT modified particles, wherein the extruder barrel temperature is 175℃ and the die temperature is 180℃.

[0054] Gel formation occurs during granulation, making normal granulation impossible.

[0055] Comparative Example 4 This embodiment provides a biodegradable functional mulch film containing PBAT, comprising the following components by weight: 10 parts polylactic acid, 84.6 parts PBAT, 1 part compatibilizer, 0.3 parts zinc stearate, 0.1 parts antioxidant, 0.5 parts light stabilizer, 0.2 parts UV absorber, 0.3 parts hydrolysis inhibitor, and 3 parts carbon black. The preparation method is the same as in Example 1.

[0056] The mulch films prepared in Examples 1-3 and Comparative Examples 1-4 were tested, and the testing standard was based on the biodegradable mulch film GBT35795-2017. The results are shown in Table 1.

[0057] Table 1

[0058] As shown in Table 1, the longitudinal tensile strength of the mulch films prepared by the schemes in Examples 1-3 of this application ranges from 46 MPa to 48 MPa, the transverse tensile strength from 40.8 MPa to 44.8 MPa, the longitudinal elongation at break from 180% to 220%, and the transverse elongation at break from 268% to 380%. Comparative Example 1, without the addition of a reaction accelerator, exhibits a significant decrease in both tensile strength and elongation at break. Comparative Example 2, without the addition of a compatibilizer, has a longitudinal tensile strength of only 17.8 MPa and a transverse tensile strength of only 14.8 MPa. Comparative Example 4, using only zinc stearate as the reaction accelerator, also shows significantly lower overall performance compared to Examples 1-3. It can be seen that the synergistic effect of the compatibilizer and the reaction accelerator (a combination of nano-zinc oxide and zinc stearate) is key to improving mechanical properties. The compound system of this application can achieve a balance between strength and toughness through deep crosslinking of PLA / PBAT molecular chains. Meanwhile, the changes in tear strength show that the compounded reaction promoter can significantly improve the tear resistance of the ultra-thin mulch film by enhancing intermolecular forces. Table 1 shows that the rupture period of the mulch films in Examples 1-3 is within the range of 110-120 days, which meets the requirements of the rice growth cycle. The rupture period of the comparative example is shortened to 65-80 days; excessively rapid degradation may lead to premature failure of the mulch film. This indicates that the addition of the anti-hydrolysis agent (carbodiimide / polycarbodiimide) can effectively slow down the hydrolysis rate, while the compounded reaction promoter further regulates the degradation rate by optimizing the crosslinking density, thereby achieving controllable degradation. Comparative Example 3, due to the use of only single nano-zinc oxide as the reaction promoter, experienced gelation during granulation, preventing normal production. This indicates that the compounded reaction promoter can avoid the gelation problem caused by excessive reaction of nano-zinc oxide, while the lubricating effect of zinc stearate improves processing fluidity.

[0059] In summary, the poor intermolecular compatibility of PLA and PBAT blends makes it difficult to simultaneously achieve high strength and high toughness, resulting in a mulch film thickness typically exceeding 10 μm to meet application requirements and incurring high costs. To address this issue, this application constructs a highly efficient and synergistic crosslinking regulation system by introducing a reactive compatibilizer and a specific compounding reaction promoter. Specifically, the reactive compatibilizer provides chemical bonding sites for the PLA and PBAT molecular chains, while the catalytic effect of nano-zinc oxide and the interfacial harmonizing effect of zinc stearate synergistically enhance the degree of crosslinking between molecular chains, allowing the advantages of the two resins to complement each other. This retains the high flexibility of PBAT while fully utilizing the high strength properties of PLA.

[0060] Experimental data show that this application can increase the tensile strength of PBAT / PLA alloy mulch film by 2 times (to 48 MPa) and the elongation at break by 1.5 times (up to 600% for the sum of longitudinal and transverse directions) compared to the unoptimized system. Based on the significant improvement in mechanical properties, the mulch film thickness can be reduced from the traditional 10 μm to 5 μm (a reduction of 50%), which not only reduces costs by about 50% by reducing raw material usage, but also breaks through the performance bottleneck of ultra-thin mulch films.

[0061] Meanwhile, this application effectively slows down the hydrolysis rate in aquatic environments through precise formulation of anti-hydrolysis agents; and by combining the synergistic effects of antioxidants, light stabilizers, UV absorbers, and pigment carbon black, a photothermal aging protection system is constructed, achieving a precise match between the mulch film degradation cycle and the rice growth cycle. Ultimately, even at an ultra-thin 5μm specification, the mulch film of this application exhibits significantly superior physical and mechanical properties compared to traditional PE mulch films throughout its entire service life, solving the promotion difficulties caused by insufficient performance and high cost of fully biodegradable mulch films in rice cultivation, and providing key technical support for its large-scale application.

[0062] While specific embodiments of this application have been described in detail, this should not be construed as limiting the scope of protection of this application. Various modifications and variations that can be made by those skilled in the art without inventive effort within the scope described in the claims still fall within the scope of protection of this application.

Claims

1. A biodegradable functional mulch film containing PBAT, characterized in that, Includes the following components by weight: Polylactic acid 5%~30%, PBAT 60%~95%, compatibilizer 1%~5%, reaction accelerator 0.01%~0.5%, antioxidant 0.01%~0.1%, light stabilizer 0.3%~1%, UV absorber 0.1%~0.3%, hydrolysis inhibitor 0.2%~0.5%, and carbon black 2%~5%.

2. The biodegradable functional mulch film containing PBAT according to claim 1, characterized in that, Includes the following components by weight: The composition includes 20%~30% polylactic acid, 60%~80% PBAT, 3%~5% compatibilizer, 0.2%~0.3% reaction accelerator, 0.05%~0.1% antioxidant, 0.3%~1% light stabilizer, 0.1%~0.3% UV absorber, 0.2%~0.5% hydrolysis inhibitor, and 2%~5% carbon black.

3. The biodegradable functional mulch film containing PBAT according to claim 1, characterized in that, Includes the following components by weight: The composition includes 30% polylactic acid, 60.5% PBAT, 5% compatibilizer, 0.25% reaction accelerator, 0.05% antioxidant, 0.6% light stabilizer, 0.1% UV absorber, 0.3% hydrolysis inhibitor, and 3.2% carbon black.

4. The biodegradable functional mulch film containing PBAT according to any one of claims 1 to 3, characterized in that, The polylactic acid has a weight-average molecular weight of 200,000 to 400,000, a molecular weight distribution of 1.15 to 2.0, and a crystallinity of 30% to 60%. The polylactic acid includes at least one of poly-L-lactic acid, poly-D-lactic acid, and poly-DL-lactic acid.

5. The biodegradable functional mulch film containing PBAT according to any one of claims 1 to 3, characterized in that, The density of the PBAT is 1.1 g / cm³. 3 ~1.35g / cm 3 The weight-average molecular weight is 50,000~80,000, and the melt index at 190℃ is 2g / 10min~4g / 10min.

6. The biodegradable functional mulch film containing PBAT according to any one of claims 1 to 3, characterized in that, The compatibilizer is AX8900 functional polymer toughening agent; The reaction promoter is a combination of nano zinc oxide and zinc stearate; The antioxidant is any one of 1,2-bis(3,5-di-tert-butyl-4-hydroxy-phenylpropionic acid) hydrazine, 4,4-thiobis(6-tert-butyl-3-methylphenol) and tris(3,3-di-tert-butyl-4-hydroxybenzyl) isocyanurate; The light stabilizer is any one of hindered amine light stabilizers, nickel bis(3,5-di-tert-butyl-4-hydroxybenzyl phosphate) and polymers of succinic acid and 4-hydroxy-2,2,6,6-tetramethyl-1-piperidinol. The ultraviolet absorber is any one of 2-phenylbenzimidazole-5-sulfonic acid, 2-(2'-hydroxy-5'-methylphenyl)benzotriazole and 2-hydroxy-4-methoxybenzophenone; The anti-hydrolysis agent is carbodiimide or polycarbodiimide.

7. A method for preparing a fully biodegradable functional mulch film containing PBAT according to any one of claims 1 to 6, characterized in that, Includes the following steps: Polylactic acid and PBAT are mixed, and then the compatibilizer, reaction promoter, antioxidant, light stabilizer, UV absorber, anti-hydrolysis agent and carbon black are added in sequence and stirred until uniform to obtain a mixture. The mixture was extruded and granulated to obtain PLA / PBAT modified particles; The PLA / PBAT modified particles were processed by blown film treatment to obtain the biodegradable functional mulch film containing PBTA.

8. The method for preparing a fully biodegradable functional mulch film containing PBTA according to claim 7, characterized in that, The stirring speed is 150 rpm to 300 rpm, and the stirring time is 2 min to 5 min.

9. The method for preparing a fully biodegradable functional mulch film containing PBAT according to claim 7, characterized in that, The extruder used for the extrusion granulation process has an length-to-diameter ratio of 50:1 and a barrel temperature of 180℃~200℃.

10. The method for preparing a fully biodegradable functional mulch film containing PBAT according to claim 7, characterized in that, The blown film machine used in the blown film processing has a length-to-diameter ratio of 32:1.

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