Dual-stretch polybutylene adipate-terephthalate biodegradable mulch film

Abstract

This disclosure provides a bistretched polybutylene adipate terephthalate (PBAT) biodegradable mulch film, belonging to the field of polymer materials technology. The mulch film comprises: an inner layer, a core layer, and an outer layer arranged sequentially; by mass percentage, the inner and outer layers each comprise 54.5-94.5% PBAT, 5-44.5% biodegradable material, 0.1-0.5% antioxidant, 0.1-0.5% slip agent, 0.1-0.5% compatibilizer, 0.1-0.5% heat stabilizer, and 0.1-0.5% UV absorber, totaling 100%; the core layer is an intermediate layer... By weight percentage, the core layer comprises 54.5-94.5% polybutylene adipate terephthalate, 5-44.5% biodegradable material, 0.1-0.5% chain extender, 0.1-0.5% antioxidant, 0.1-0.5% compatibilizer, 0.1-0.5% heat stabilizer, and 0.1-0.5% UV absorber, totaling 100%; wherein the biodegradable material is selected from any one of polylactic acid and polycaprolactone; the compatibilizer is selected from at least one of glycidyl methacrylate and maleic anhydride; and the chain extender is selected from at least one compound of polyurethane, polyol, azo, and epoxy.

Description

Technical Field

[0001] This disclosure belongs to the technical field of polymer materials and biodegradable membrane materials, specifically relating to a bistretched polybutylene adipate terephthalate biodegradable mulch film. Background Technology

[0002] In agricultural production, mulch film, as an important ground cover material, plays a crucial role in maintaining soil temperature and humidity, preventing rainwater erosion and crust formation, facilitating fertilizer decomposition and improving soil fertility, and resulting in significant yield and income increases. However, with increasing environmental awareness and higher requirements for sustainable development, the non-degradability of traditional polyethylene mulch film and its environmental pollution problems are becoming increasingly prominent. Therefore, finding a membrane material that is both environmentally friendly and possesses excellent performance has become a current research hotspot.

[0003] Polybutylene adipate terephthalate (PBAT), as a biodegradable material, is considered an ideal alternative due to its large production capacity and physical properties similar to polyethylene. However, PBAT mulch films currently on the market, prepared using blown film and cast film methods, exhibit a problem of excessively rapid degradation when applied in Xinjiang. The films reach their induction period within 2-3 months and begin to crack, resulting in a short lifespan and hindering their long-term warming and water-retaining functions, severely impacting crop growth and yield.

[0004] Furthermore, while PBAT mulch films prepared using the bi-stretch process improve the mechanical and optical properties of mulch films to some extent, they contain a high amount of easily degradable PBAT, resulting in a faster degradation rate, shorter lifespan, and lower water retention. Moreover, they still exhibit problems such as poor UV resistance and high water permeability during application. Especially in Xinjiang, due to strong ultraviolet radiation, long hours of sunshine, and harsh climatic conditions, existing PBAT mulch film technology cannot yet meet the performance requirements of mulch films for crop cultivation in the region.

[0005] Therefore, how to provide a new type of mulch film material that can improve the warming and water retention effect while maintaining moderate degradation performance and durability, and has excellent weather resistance, so as to meet the usage requirements under different environmental conditions, has become an urgent technical problem to be solved. Summary of the Invention

[0006] In view of this, in order to solve at least one technical problem in the related art and other aspects, this disclosure provides a bistretched polybutylene adipate terephthalate biodegradable mulch film, comprising: an inner layer, a core layer and an outer layer arranged sequentially;

[0007] By weight percentage, the inner and outer layers each comprise 54.5-94.5% polybutylene adipate terephthalate, 5-44.5% biodegradable material, 0.1-0.5% antioxidant, 0.1-0.5% slip agent, 0.1-0.5% compatibilizer, 0.1-0.5% heat stabilizer, and 0.1-0.5% UV absorber, totaling 100%.

[0008] The core layer is an intermediate layer, and by mass percentage, it comprises 54.5-94.5% polybutylene adipate terephthalate, 5-44.5% biodegradable material, 0.1-0.5% chain extender, 0.1-0.5% antioxidant, 0.1-0.5% compatibilizer, 0.1-0.5% heat stabilizer, and 0.1-0.5% UV absorber, totaling 100%.

[0009] The biodegradable material is selected from any one of polylactic acid and polycaprolactone; the compatibilizer is selected from at least one of glycidyl methacrylate and maleic anhydride; and the chain extender is selected from at least one compound of polyurethane, polyol, azo, and epoxy.

[0010] According to embodiments of this disclosure, the thickness ratio of the inner layer, core layer, and outer layer is 1-3:4-8:1-3;

[0011] The thickness of the mulch film is 3-10 μm.

[0012] According to embodiments of this disclosure, the antioxidant is selected from antioxidant 1010 or antioxidant 168;

[0013] The slip agent is selected from at least one of ethylene bis-stearamide, erucamide, and zinc stearate;

[0014] The heat stabilizer is selected from organotin heat stabilizers;

[0015] The ultraviolet absorber is selected from any one of the following ultraviolet absorbers: salicylates, benzophenones, benzotriazoles, triazines, and substituted acrylonitriles.

[0016] According to embodiments of this disclosure, in the inner layer, core layer and outer layer, polybutylene adipate terephthalate accounts for 89%-94% by weight, and biodegradable material accounts for 5%-10%.

[0017] According to embodiments of this disclosure, the induction period of the membrane is 120-180 days, and the water vapor permeability of the mulch film is 85-200 g / m³. 2 24h.

[0018] According to embodiments of this disclosure, the mulch film is obtained through the following steps:

[0019] The raw materials for the inner layer, core layer and outer layer are added to different extruders for extrusion casting, and after cooling, a composite casting sheet is obtained.

[0020] The composite casting sheet is first stretched longitudinally, then stretched laterally, and then heat-set to obtain the mulch film.

[0021] According to embodiments of this disclosure, the extrusion temperature of the inner layer, core layer, and outer layer is 160-180°C, and the cooling temperature is 5-10°C.

[0022] The longitudinal stretching ratio is 3-5, and the longitudinal stretching temperature is 80-100℃;

[0023] The stretching ratio for transverse stretching is 7-9 times, and the transverse stretching temperature is 90-120℃.

[0024] The thermally stable temperature range is 110-140℃.

[0025] According to embodiments of this disclosure, the light transmittance of the mulch film is greater than 85%.

[0026] According to embodiments of this disclosure, the longitudinal tensile strength of the mulch film is greater than 50 MPa, and the transverse tensile strength is greater than 100 MPa.

[0027] Based on the above technical solution, the bistretched polybutylene adipate terephthalate biodegradable mulch film provided in this disclosure has at least the following beneficial effects:

[0028] (1) The bistretched polybutylene adipate terephthalate biodegradable mulch film provided in this embodiment of the present disclosure can improve the water resistance rate of the bistretched mulch film and effectively reduce the evaporation of water by introducing biodegradable materials to replace part of the PBAT, thereby achieving the effect of optimizing the temperature increase and water retention.

[0029] (2) In the embodiments of this disclosure, an ultraviolet absorber is added to the mulch film to enhance its UV resistance, thereby extending its service life. This results in a biaxially oriented poly(butylene adipate-terephthalate) biodegradable mulch film that possesses both excellent water retention and weather resistance, further extending its service life. Simultaneously, a compatibilizer is used to ensure uniform blending between PBAT and the biodegradable material, giving the biaxially oriented PBAT mulch film of this application good mechanical and optical properties. Detailed Implementation

[0030] To make the objectives, technical solutions, and advantages of this disclosure clearer, the following detailed description is provided in conjunction with specific embodiments.

[0031] The endpoints and any values ​​of the ranges disclosed in this disclosure are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed in this disclosure.

[0032] The terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit this disclosure. The terms “comprising,” “including,” etc., as used herein indicate the presence of the stated features, steps, operations, and / or components, but do not exclude the presence or addition of one or more other features, steps, operations, or components.

[0033] Currently, polybutylene adipate terephthalate (PBAT) mulch films prepared using blow molding and casting methods still have many problems. For example, PBAT films prepared by blow molding are difficult to achieve their intended warming effect when used as mulch films due to their poor optical properties and slow heating rate. While PBAT films prepared using the bistretching process have higher optical and mechanical properties compared to blown films, they are not resistant to ultraviolet radiation and degrade more rapidly. This is especially true in Xinjiang, where long hours of sunshine and high UV content significantly shorten the induction period, typically leading to cracking and degradation within 2-3 months, thus significantly reducing the mulch film's lifespan. Furthermore, PBAT material is easily absorbent and degraded. The higher PBAT content in bistretched mulch films accelerates this degradation process, hindering their ability to effectively perform warming and water-retention functions and extend their lifespan, a problem particularly pronounced in the arid environment of Xinjiang. These problems severely restrict the practical application of PBAT mulch film in Xinjiang.

[0034] In the process of developing this disclosure, it was discovered that by introducing biodegradable materials to replace part of PBAT (reducing PBAT content), the water resistance of the mulch film can be effectively improved, and water evaporation reduced. Simultaneously, adding ultraviolet absorbers to the mulch film enhances its UV resistance, thereby extending its service life. This results in a biaxially oriented poly(butylene adipate-terephthalate) biodegradable mulch film exhibiting slow degradation, long durability, and warming and water-retaining properties. Furthermore, by combining it with the biaxial stretching process, the prepared mulch film also possesses high light transmittance (>85%) and mechanical strength (longitudinal tensile strength >50 MPa, transverse tensile strength >100 MPa), facilitating mulch film laying and enabling rapid warming of the laid mulch film. Considering the arid and sun-intensive climate of Xinjiang, the biodegradable mulch film provided in this disclosure is particularly suitable for this region, making a positive contribution to the sustainable development of agricultural production.

[0035] This disclosure provides a bistretched polybutylene adipate terephthalate biodegradable mulch film, comprising: an inner layer, a core layer, and an outer layer arranged sequentially.

[0036] By weight percentage, the inner and outer layers each comprise 54.5-94.5% polybutylene adipate terephthalate, 5-44.5% biodegradable material, 0.1-0.5% antioxidant, 0.1-0.5% slip agent, 0.1-0.5% compatibilizer, 0.1-0.5% heat stabilizer, and 0.1-0.5% UV absorber, totaling 100%.

[0037] The core layer is an intermediate layer, and by mass percentage, it comprises 54.5-94.5% polybutylene adipate terephthalate, 5-44.5% biodegradable material, 0.1-0.5% chain extender, 0.1-0.5% antioxidant, 0.1-0.5% compatibilizer, 0.1-0.5% heat stabilizer, and 0.1-0.5% UV absorber, totaling 100%.

[0038] The biodegradable material is selected from either polylactic acid or polycaprolactone.

[0039] The compatibilizer is selected from at least one of glycidyl methacrylate and maleic anhydride; the chain extender is selected from at least one compound of polyurethane, polyol, azo, and epoxy.

[0040] According to embodiments of this disclosure, by adding a biodegradable material with relatively low water absorption to replace part of the polybutylene adipate terephthalate (PBAT), the overall water-blocking effect of the mulch film is improved. This reduces the evaporation of moisture inside the mulch film while maintaining high light transmittance, achieving the purpose of warming and moisturizing. By adding a UV absorber, ultraviolet energy is absorbed and converted, thereby enhancing the UV resistance of the mulch film and effectively extending its service life. The addition of a compatibilizer allows biodegradable materials such as polycaprolactone (PCL) and PBAT to be uniformly blended, further increasing the water-blocking capacity of PCL and other biodegradable materials on the biaxially stretched PBAT mulch film.

[0041] According to embodiments of this disclosure, both polylactic acid and polycaprolactone can reduce water vapor transmission rate, with polycaprolactone exhibiting better water-blocking effect.

[0042] In some specific embodiments, polybutylene adipate terephthalate comprises 89%-94% by weight in the inner layer, core layer, and outer layer, and biodegradable material comprises 5%-10%.

[0043] According to embodiments of this disclosure, the antioxidant is selected from antioxidant 1010 or antioxidant 168. Adding antioxidants prevents aging of the mulch film and extends its service life. The slip agent is selected from at least one of ethylene bis-stearamide, erucamide, and zinc stearate. Adding slip agents makes the surface of the mulch film smoother and also prevents adhesion during the preparation of the biaxially stretched PBAT mulch film. The heat stabilizer is selected from organotin heat stabilizers, such as di-n-octyltin dimercaptoacetate or dimethyl dimercaptoacetate isooctyltin. Adding heat stabilizers improves the heat resistance and stability of the mulch film and extends its degradation time. The ultraviolet absorber is selected from salicylates, benzophenones, and benzotriazoles. Specifically, the ultraviolet absorber can be any one of phenyl benzoate, 2-hydroxy-4-n-octyloxybenzophenone, 2-hydroxy-4-methoxybenzophenone, 2,4-dihydroxybenzophenone, or 2-(2'-hydroxy-3',5'-di-tert-phenyl)-5-chlorobenzotriazole. By adding the ultraviolet absorber, the mulch film is protected from ultraviolet damage, thereby extending its service life and enhancing its weather resistance.

[0044] According to embodiments of this disclosure, the chain extender is selected from any one of 1,4-cyclohexanediol, ADR4468, and ADR4368.

[0045] According to embodiments of this disclosure, the thickness ratio of the inner layer, core layer, and outer layer is 1-3:4-8:1-3, for example, it can be 1:4:4, 2:5:2, 2:6:2, 3:7:2, 3:8:3, etc. The thickness of the mulch film is 3-10 μm, for example, it can be 3 μm, 5 μm, 7 μm, 9 μm, 10 μm, etc. A thinner mulch film can further improve its light transmittance and reduce production costs, but an excessively thin mulch film is easily damaged.

[0046] According to embodiments of this disclosure, the induction period of the mulch film is 120-180 days, for example, 120 days, 140 days, 160 days, 180 days, etc., and it can remain stable for more than 4 months in Xinjiang. The water vapor permeability of the mulch film is 85-200 g / m². 2 0.24h, for example, can be 85g / m 2 24h, 100g / m 2 24h, 150g / m 2 24h, 160g / m 2 24h, 180g / m 2 24h, 200g / m 2 With a low water vapor transmission rate of 0.24h, good water retention can be achieved.

[0047] According to embodiments of this disclosure, the light transmittance of the mulch film is greater than 85%, and the high light transmittance can achieve the effect of rapid warming.

[0048] According to embodiments of this disclosure, the longitudinal tensile (MD) strength of the mulch film is greater than 50 MPa, and the transverse tensile (TD) strength is greater than 100 MPa. The high tensile strength in both directions not only facilitates the film laying operation, but also meets the high-efficiency operation requirements of machine film laying. Furthermore, due to its good mechanical properties, the thickness of the mulch film can be effectively reduced while being easy to spread.

[0049] According to embodiments of this disclosure, the mulch film is obtained through the following steps: the raw materials for the inner layer, core layer and outer layer are respectively added to different extruders for extrusion casting, and after cooling, a composite casting sheet is obtained; the composite casting sheet is first stretched longitudinally, then stretched transversely, and after heat setting, the mulch film is obtained.

[0050] According to embodiments of this disclosure, the biaxial stretching technique transforms the crystal structure of the mulch film during the stretching process, forming a highly oriented network structure, which makes the internal structure of the mulch film more stable. Furthermore, by adjusting the biaxial stretching process, the light transmittance of the mulch film is increased (>85%), making its optical properties flexibly adjustable.

[0051] According to embodiments of this disclosure, the extrusion temperature of the inner layer, core layer, and outer layer is 160-180°C, for example, 160°C, 170°C, 180°C, etc.; the cooling temperature is 5-10°C, for example, 5°C, 7°C, 9°C, 10°C, etc.; the longitudinal stretching ratio is 3-5 times, for example, 3 times, 4 times, 5 times, etc.; the longitudinal stretching temperature is 80-100°C, for example, 80°C, 90°C, 100°C, etc.; the transverse stretching ratio is 7-9 times, for example, 7 times, 8 times, 9 times, etc.; the transverse stretching temperature is 90-120°C, for example, 90°C, 100°C, 110°C, 120°C, etc.; the thermal stability temperature is 110-140°C, for example, 110°C, 120°C, 130°C, 140°C, etc.

[0052] To make the objectives, technical solutions, and advantages of this disclosure clearer, the following detailed description is provided in conjunction with specific embodiments.

[0053] Example 1:

[0054] A bistretched polybutylene adipate terephthalate biodegradable mulch film, comprising an inner layer, a core layer, and an outer layer from the inside out;

[0055] By weight percentage, the inner layer raw materials include: polybutylene adipate terephthalate: 94%, polycaprolactone: 5%, antioxidant 1010: 0.1%, erucamide (i.e., slip agent): 0.3%, maleic anhydride (i.e., compatibilizer): 0.2%, dioctyl tin dithiocarbamate (i.e., heat stabilizer): 0.2%, and 2-hydroxy-4-n-octyloxybenzophenone (i.e., ultraviolet absorber): 0.2%.

[0056] By weight percentage, the core layer raw materials include: polybutylene adipate terephthalate: 94%, polycaprolactone: 5%, ADR4368 (i.e., chain extender): 0.1%, antioxidant 1010: 0.3%, maleic anhydride (i.e., compatibilizer): 0.2%, dioctyl tin dithiocarbamate (i.e., heat stabilizer): 0.2%, and 2-hydroxy-4-n-octyloxybenzophenone (i.e., ultraviolet absorber): 0.2%.

[0057] By weight percentage, the outer layer materials include: polybutylene adipate terephthalate: 94%, polycaprolactone: 5%, antioxidant 1010: 0.1%, erucamide (i.e., slip agent): 0.3%, compatibilizer: 0.2%, dioctyl tin dithiocarbamate (i.e., heat stabilizer): 0.2%, and 2-hydroxy-4-n-octyloxybenzophenone (i.e., UV absorber): 0.2%.

[0058] The polybutylene adipate terephthalate in the inner, outer, and core layers is Lanshan Tunhe TH801T, with a weight-average molecular weight of 120,000-150,000 g / mol, a melt flow rate of 3.9 g / 10 min at 2.16 kg and 190 °C, and a melting point of 119 °C.

[0059] In Example 1, the thickness of the mulch film is 10 μm, and the thickness ratio of the inner layer, core layer and outer layer is 2:6:2.

[0060] The preparation method of the bistretched polybutylene adipate terephthalate biodegradable mulch film in Example 1 includes the following steps:

[0061] The raw materials for the inner layer, core layer, and outer layer are added to different extruders and extruded and cast at 170°C. After cooling at 10°C, a composite casting is obtained. The composite casting is first stretched longitudinally by 3 times at a stretching temperature of 90°C, then stretched transversely by 8 times at a stretching temperature of 100°C, and finally heat-set at 120°C to obtain a bi-stretched poly(butylene adipate-terephthalate) biodegradable mulch film.

[0062] Example 2:

[0063] Compared with Example 1, the raw materials and their mass percentages in the inner layer, core layer, and outer layer of this example are as follows:

[0064] By weight percentage, the inner layer materials include: polybutylene adipate terephthalate: 89%, polycaprolactone: 10%, antioxidant 1010: 0.1%, erucamide (i.e., slip agent): 0.3%, maleic anhydride (i.e., compatibilizer): 0.2%, dioctyl tin dithiocarbamate (i.e., heat stabilizer): 0.2%, and 2-hydroxy-4-n-octyloxybenzophenone (i.e., ultraviolet absorber): 0.2%.

[0065] By weight percentage, the core layer raw materials include: polybutylene adipate terephthalate: 89%, polycaprolactone: 10%, ADR4368 (i.e., chain extender): 0.1%, antioxidant 1010: 0.3%, maleic anhydride (i.e., compatibilizer): 0.2%, dioctyl tin dithiocarbamate (i.e., heat stabilizer): 0.2%, and 2-hydroxy-4-n-octyloxybenzophenone (i.e., ultraviolet absorber): 0.2%.

[0066] By weight percentage, the outer layer materials include: polybutylene adipate terephthalate: 89%, polycaprolactone: 10%, antioxidant 1010: 0.1%, erucamide: 0.3%, maleic anhydride: 0.2%, isooctyl thioglycolate di-n-octyltin: 0.2%, and 2-hydroxy-4-n-octyloxybenzophenone: 0.2%.

[0067] In Example 2, the other preparation processes of the biaxially stretched PBAT mulch film were the same as in Example 1, and a biaxially stretched polybutylene adipate-terephthalate biodegradable mulch film was prepared.

[0068] Example 3:

[0069] Compared with Example 1, the raw materials and their mass percentages in the inner layer, core layer, and outer layer of this example are as follows:

[0070] By weight percentage, the inner layer raw materials include: polybutylene adipate terephthalate: 54.5%, polycaprolactone: 44.5%, antioxidant 1010: 0.1%, erucamide (i.e., slip agent): 0.3%, maleic anhydride (i.e., compatibilizer): 0.2%, dioctyl tin dithiocarbamate (i.e., heat stabilizer): 0.2%, and 2-hydroxy-4-n-octyloxybenzophenone (i.e., ultraviolet absorber): 0.2%.

[0071] By weight percentage, the core layer raw materials include: polybutylene adipate terephthalate: 54.5%, polycaprolactone: 44.5%, ADR4368 (i.e., chain extender): 0.1%, antioxidant 1010: 0.3%, maleic anhydride (i.e., compatibilizer): 0.2%, dioctyl tin dithiocarbamate (i.e., heat stabilizer): 0.2%, and 2-hydroxy-4-octyloxybenzophenone (i.e., ultraviolet absorber): 0.2%.

[0072] By weight percentage, the outer layer materials include: polybutylene adipate terephthalate: 54.5%, polycaprolactone: 44.5%, antioxidant 1010: 0.1%, erucamide: 0.3%, maleic anhydride: 0.2%, isooctyl thioglycolate di-n-octyltin: 0.2%, and 2-hydroxy-4-n-octyloxybenzophenone: 0.2%.

[0073] In Example 3, the other preparation processes of the biaxially stretched PBAT mulch film were the same as in Example 1, and a biaxially stretched polybutylene adipate-terephthalate biodegradable mulch film was prepared.

[0074] Comparative Example 1:

[0075] A bistretched polybutylene adipate terephthalate biodegradable mulch film, comprising an inner layer (heat-sealing layer), a core layer, and an outer layer (corona layer) from the inside out;

[0076] By weight percentage, the inner layer materials include: polybutylene adipate terephthalate A: 98%, antioxidant 1010: 2%;

[0077] By weight percentage, the core layer raw materials include: polybutylene adipate terephthalate B: 97.2%, chain extender BASF ADR4468: 0.8%, and antioxidant 1010: 2%.

[0078] By weight percentage, the outer layer materials include: polybutylene adipate terephthalate B: 90%, corn starch: 5%, bis-tert-butylperoxyisopropylbenzene: 1%, sorbitol: 2%, and ethylene bis-stearamide: 2%.

[0079] Among them, polybutylene adipate terephthalate A is Lanshan Tunhe TH803S, with a weight-average molecular weight of 70,000-120,000 g / mol, a melt flow rate of 10-16 g / 10 min at 2.16 kg and 190 °C, and a melting point of 113 °C.

[0080] Polybutylene adipate terephthalate B is Lanshan Tunhe TH801T, with a weight-average molecular weight of 120,000-150,000 g / mol, a melt flow rate of 3.9 g / 10 min at 2.16 kg and 190 °C, and a melting point of 119 °C.

[0081] The thickness of the mulch film in Comparative Example 1 is 25 μm, and the thickness ratio of the inner layer, core layer and outer layer is 1.5:6.5:2.

[0082] The preparation method of the bistretched polybutylene adipate terephthalate biodegradable mulch film in Comparative Example 1 includes the following steps:

[0083] The inner layer material was added to extruder A and extruded at 140°C. The core layer material was added to a twin-screw extruder and extruded at 160°C. The outer layer material was added to another twin-screw extruder and extruded at 150°C. After cooling at 30°C, a composite casting was obtained. Subsequently, the composite casting was first stretched longitudinally by 3 times at a stretching temperature of 110°C, then stretched transversely by 8 times at a stretching temperature of 115°C, and finally heat-set at 122°C to obtain a bi-stretched poly(butylene adipate-terephthalate) biodegradable mulch film.

[0084] Comparative Example 2:

[0085] Commercially available blown film is polybutylene adipate terephthalate (PEG) mulch film.

[0086] The performance of the polybutylene adipate terephthalate (PEG) mulch films prepared in Examples 1-3 and Comparative Examples 1-2 was tested. Tensile strength was tested according to GB / T 1040.3, haze and light transmittance according to GB / T 2410, water vapor transmission rate according to GB / T 1037-1988, and the induction period met the Class II requirements of GB / T 35795-2017. The relevant test results of Examples 1-3 and Comparative Examples 1-2 are recorded in Table 1.

[0087] Table 1

[0088]

[0089] As can be seen from the test data in Table 1, the mulch films prepared in Examples 1-3 of this disclosure have good mechanical properties, with longitudinal tensile strength all greater than 50 MPa and transverse tensile strength all greater than 100 MPa. Compared with mulch film materials in the prior art, the mulch films prepared in Examples 1-3 have a longer induction period, reaching more than 4 months, requiring a longer time to begin the degradation process and extending their service life. Simultaneously, the mulch films in Examples 1-3 have a light transmittance greater than 85%, achieving rapid temperature increase, and the water vapor transmission is significantly reduced compared to mulch film materials in the prior art, achieving good water retention.

[0090] The above specific embodiments further illustrate the purpose, technical solutions and beneficial effects of this disclosure. It should be understood that the above are only specific embodiments of this disclosure and are not intended to limit this disclosure. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this disclosure should be included within the protection scope of this disclosure.

Claims

1. A biaxially oriented polybutylene adipate-terephthalate biodegradable mulch film suitable for Xinjiang region, comprising: The inner layer, core layer, and outer layer are arranged sequentially. By weight percentage, the inner and outer layers each comprise 89-94% polybutylene adipate terephthalate, 5-10% biodegradable material, 0.1-0.5% antioxidant, 0.1-0.5% slip agent, 0.1-0.5% compatibilizer, 0.1-0.5% heat stabilizer, and 0.1-0.5% UV absorber, totaling 100%. The core layer is an intermediate layer, and by mass percentage, the core layer comprises 89-94% polybutylene adipate terephthalate, 5-10% biodegradable material, 0.1-0.5% chain extender, 0.1-0.5% antioxidant, 0.1-0.5% compatibilizer, 0.1-0.5% heat stabilizer, and 0.1-0.5% UV absorber, totaling 100%. The biodegradable material is selected from polylactic acid and polycaprolactone; the compatibilizer is selected from at least one of glycidyl methacrylate and maleic anhydride; and the chain extender is selected from at least one compound of polyurethane, polyol, azo, and epoxy. The slip agent is selected from at least one of ethylene bis-stearamide, erucamide, and zinc stearate; the heat stabilizer is selected from organotin heat stabilizers; and the ultraviolet absorber is selected from any one of salicylates, benzophenones, and substituted acrylonitrile ultraviolet absorbers. The polybutylene adipate terephthalate has a weight-average molecular weight of 120,000-150,000 g / mol, a melt flow rate of 3.9 g / 10 min at 2.16 kg and 190 °C, and a melting point of 119 °C. The thickness ratio of the inner layer, core layer and outer layer is 1-3:4-8:1-3; The induction period of the mulch film is 120-180 days, and the water vapor permeability of the mulch film is 150-200 g / m². 2 24h; The plastic film is obtained through the following steps: The raw materials for the inner layer, core layer and outer layer are respectively added to different extruders for extrusion casting, and after cooling, a composite casting sheet is obtained. The composite casting sheet is first stretched longitudinally, then stretched transversely, and then heat-set to obtain the mulch film. The extrusion temperature of the inner layer, core layer, and outer layer is 160-180℃, and the cooling temperature is 5-10℃. The longitudinal stretching ratio is 3-5, and the longitudinal stretching temperature is 80-100℃. The transverse stretching ratio is 7-9 times, and the transverse stretching temperature is 90-120℃. The heat-setting temperature is 110-140℃.

2. The mulch film according to claim 1, wherein: The thickness of the mulch film is 3-10 μm.

3. The mulch film according to claim 1, wherein: The antioxidant is selected from antioxidant 1010 or antioxidant 168.

4. The mulch film according to claim 1, wherein: The light transmittance of the mulch film is greater than 85%.

5. The mulch film according to claim 1, wherein: The longitudinal tensile strength of the mulch film is greater than 50 MPa, and the transverse tensile strength is greater than 100 MPa.

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