Ultrathin high-strength two-way stretching biodegradable mulching film and preparation method thereof

Abstract

The invention belongs to the field of polymeric membranes. The invention relates to an ultrathin high-strength two-way stretching biodegradable mulching film and a preparation method thereof.The film is designed according to a formula, PBAT and PPC-P serve as matrix resin, a rigid-tough combination is formed, and self-made modified talcum powder and other auxiliaries are adopted; extruding, and performing high-magnification two-way stretching to prepare; the mulching film can effectively overcome the defects that in the prior art, a mulching film prepared through film blowing is high in thickness and poor in mechanical property, meanwhile, the used main raw materials are degradable materials, and great application potential is achieved.

Description

Technical Field

[0001] The present invention relates to an ultra-thin high-strength biaxially stretched biodegradable ground film and a preparation method thereof, and belongs to the field of polymer films. Background Art

[0002] Biodegradable mulch is widely recognized as the best solution to the problem of soil plasticization. However, because current biodegradable mulch primarily uses PBAT and PLA, it lacks water retention and strength after forming. To address this issue, the common approach is to thicken the film, typically requiring a thickness of at least 8μm to qualify. This results in high cost and low light transmittance. Furthermore, for crops like garlic and peanuts, excessively thick films can severely hinder seedling emergence and rooting, resulting in reduced yields.

[0003] Currently, the primary material used in the production of biodegradable mulch films is still polybutylene terephthalate (PBAT). Although PBAT offers excellent flexibility, its strength and stiffness are low, and its water barrier properties are poor, making it unsuitable for practical applications. Modifying PBAT with polylactic acid (PLA) can further improve the strength and stiffness of biodegradable mulch films, but the resulting films still suffer from high water permeability, limiting their use in arid areas. Modifying PBAT with propylene phthalate / propylene carbonate copolymer (PPCP) has successfully improved the water barrier properties of biodegradable mulch films, while also providing good strength and stiffness. However, PPCP itself has a low elongation at break and exhibits some phase separation. Using PBAT to modify PBAT not only results in a slight reduction in transparency, but also limits the thickness of the blown film, which must be around 10 μm. This approach also presents the problem of excessive film thickness, which can affect crop emergence and rooting.

[0004] Furthermore, the traditional method for preparing mulch film involves melt-extruding the blend through a twin-screw extruder at a specific temperature and pressure, vacuuming the system to remove moisture and forming granules. The granules are then blown through a film-blowing machine at a specific temperature and speed to form a film. The film-blowing process also consists of two steps: melt conveying and inflation and cooling. The material produced by this method is not oriented, and its performance advantages are not fully exploited. This results in a lack of significant improvement in mechanical strength, rapid degradation, and the film thickness remains relatively high, resulting in high costs and hindering the further promotion and use of biodegradable materials. Summary of the Invention

[0005] The present invention aims to address the shortcomings of existing blown film-made mulch films, which suffer from high thickness and poor mechanical properties, by providing a method for preparing an ultra-thin, high-strength, biaxially oriented biodegradable mulch film. First, the mulch film material is designed with PBAT and PPC-P as the main resins to form a rigid-tough composite. Functional additives are then added based on the formulation design. The film is then extruded and subjected to high-ratio biaxial stretching before being prepared. The technical solutions employed by the present invention to solve the technical problems are as follows: The present invention provides an ultra-thin high-strength biaxially oriented biodegradable ground film, comprising the following raw materials in parts by weight: PBAT 65-75 parts; PPC-P 25-35 copies; 5.0-7.0 parts of modified talc; 0.4-0.6 parts of carbodiimide; Chain extender 0.2-0.4 parts; 0.2-0.4 parts of antioxidant; Antiaging agent 0.3-0.5 parts; 0.1-0.3 parts of lubricant; Wherein, the total weight of the PBAT and PPC-P is 100 parts.

[0006] Furthermore, The modified talc powder is prepared in the following steps: S11, performing a coupling reaction between talc powder and a mercaptosilane coupling agent; S12, click reaction of the product of S11 with an unsaturated alcohol; S13, polycondensing the product of S12, adipic acid, fluorinated terephthalic acid, hydroxy terephthalic acid, and butanediol, and capping with phenol; S14, subjecting the product of S13 to a nucleophilic addition reaction with an asymmetric diisocyanate; S15, subjecting the product of S14 to a nucleophilic addition reaction with p-phenylenediamine to obtain an amino-terminated modified structure, i.e., the target product.

[0007] Furthermore, the particle size of the talc powder is 2500-5000 mesh.

[0008] Furthermore, the molar ratio of adipic acid, fluorinated terephthalic acid, and hydroxyterephthalic acid is 1:0.4-0.7:0.3-0.6.

[0009] Furthermore, the degree of polymerization of the product of the condensation reaction is 20-35.

[0010] Furthermore, the chain extender is an epoxy structure.

[0011] Furthermore, the antioxidant is a compound of hindered phenols and phosphites.

[0012] Furthermore, the antioxidant is a compound of a light stabilizer and an ultraviolet absorber.

[0013] Another object of the present invention is to provide a method for preparing an ultra-thin high-strength biaxially oriented biodegradable mulch film, comprising the following steps: S21, mixing and plasticizing, i.e. Mix all the raw materials evenly according to the formula and put them into the extruder for plasticization; S22, casting, cooling, i.e. The melt plasticized in S21 is extruded through a die head and attached to the surface of a casting roll for cooling to obtain a cast sheet; S23, preheating, biaxial stretching, heat setting, i.e. Preheating the cast sheet in S22, biaxially stretching it, and then heat-setting it to obtain a biaxially stretched film; and S24, pulling and winding, i.e. The biaxially oriented film in S23 is drawn, trimmed, and finally rolled up to obtain an ultra-thin high-strength biaxially oriented biodegradable ground film.

[0014] Furthermore, The die temperature is 180-190°C; The biaxial stretching has a transverse stretching ratio of 6.5-7.5 and a stretching temperature of 95-105° C.; and The longitudinal stretching ratio of the biaxial stretching is 7.5-8.5; the stretching temperature is 100-110°C.

[0015] Beneficial effects of the present invention: (1) The present invention provides an ultra-thin, high-strength, biaxially oriented biodegradable mulch film with PBAT and PPC-P as the main resins. While having excellent degradability, it forms a complementary system of rigidity and toughness. While having excellent toughness and processability, it also has excellent rigidity and barrier properties.

[0016] (2) The present invention provides an ultra-thin, high-strength, biaxially stretched biodegradable mulch film, the formula of which is added with a certain amount of modified talc powder, which is a polyester structure with end-amino side chains embedding talc powder; wherein the polyester structure is a low-molecular-weight PBAT structure and contains fluorine. First, the talc powder embedded with organic chains has an excellent dispersion effect, improving performance; second, the long-chain structure of polyester and the end-amino side chain structure are conducive to the orientation of the mulch film at a high stretching ratio, improving performance; third, the end-amino structure can undergo an amine ester exchange reaction with the ester structure in PBAT and PPC-P, improving compatibility while performing a chain extension reaction, thereby improving the mechanical properties of the mulch film at a high stretching ratio; fourth, the lamellar talc powder structure can easily form a planar oriented arrangement under the traction of the organic chain during the biaxial stretching orientation process, which can further improve the barrier performance; fifth, the fluorine-containing structure can improve the hydrophobic effect of the mulch film surface, avoiding condensation due to the large temperature difference between day and night, which leads to the "burning seedling" phenomenon.

[0017] (3) The present invention provides a method for preparing an ultra-thin, high-strength, biaxially stretched biodegradable mulch film. The method uses a high-ratio biaxial stretching process to effectively improve the crystallinity of the mulch film, thereby providing mechanical properties, barrier properties, etc., thereby improving the water and moisture retention capacity. The mulch film is thinner and has a high cost-effectiveness. DETAILED DESCRIPTION

[0018] The present invention will be described in detail below with reference to the following examples. However, it should be understood that the following examples are merely illustrative of the embodiments of the present invention and are not intended to limit the scope of the present invention.

[0019] The purpose of this invention is to develop an ultra-thin, high-strength, biaxially oriented biodegradable mulch film. The design concept addresses the high thickness and poor mechanical strength of existing biodegradable mulch films produced by blown film. First, a biaxially oriented process was selected to replace the blown film process. Biaxially oriented film production promotes material crystallization, improves mechanical strength, and can also reduce film thickness. However, issues such as material compatibility and inconsistent processing temperatures must be addressed. Regarding the compatibility of materials, mainly PBAT and PPCP, and PPCP having a faster degradation cycle, chain extenders are added to increase the volume through chemical modification, and modified talc is used to further increase the volume and improve performance, so the talc is modified and designed: specifically, the talc is modified with an organic chain containing a side-terminated amino main chain with a polyester structure (a low-polymerization PBAT structure); wherein, the polyester main chain structure provides compatibility with the PBAT matrix; the side-terminated amino structure can undergo an amine ester exchange reaction with the ester structure, which has a chain extension effect; and during high-ratio biaxial stretching, the molecular chain entanglement provides physical crosslinking and chemical crosslinking to pull the lamellar talc structure into a large-scale planar directional arrangement, thereby improving the crystallinity, enhancing the mechanical properties, and extending the degradation cycle while improving the barrier properties. In addition, in response to the condensation phenomenon existing in the ground film, the surface properties of the ground film can be improved by involving a fluorine-containing structure in the modified talc. The embodiments of the present invention are as follows: An embodiment of the present invention provides an ultra-thin high-strength biaxially oriented biodegradable ground film, comprising the following raw materials in parts by weight: PBAT 65-75 parts; PPC-P 25-35 copies; 5.0-7.0 parts of modified talc; 0.4-0.6 parts of carbodiimide; Chain extender 0.2-0.4 parts; 0.2-0.4 parts of antioxidant; Antiaging agent 0.3-0.5 parts; 0.1-0.3 parts of lubricant; Wherein, the total weight of the PBAT and PPC-P is 100 parts.

[0020] The modified talc powder is prepared in the following steps: S11, adding talc powder and mercaptosilane coupling agent to alcohol solvent, ultrasonically oscillating for 0.5 h, standing at room temperature for 2 h, reacting at 50-70° C. for 4-10 h, filtering, taking insoluble matter, drying at 60° C. for 12 h; and setting aside.

[0021] The usage ratio of the talc powder, the mercaptosilane coupling agent and the alcohol solvent is 30g:0.8-1.5g:80mL.

[0022] The particle size of the talc powder is 2500-5000 mesh; the particle size can be customized as needed and is purchased from Shanghai Yuanjiang Chemical Co., Ltd.; and the preferred particle size is 4000 mesh.

[0023] The mercaptosilane coupling agent may be silane coupling agent KH580, silane coupling agent KH590, etc., and preferably silane coupling agent KH580.

[0024] The alcohol solvent may be anhydrous methanol, anhydrous ethanol, anhydrous isopropanol, etc., and anhydrous ethanol is preferred.

[0025] S12, add the product of S11, unsaturated alcohol, and photoinitiator to anhydrous N,N-dimethylformamide, stir, and place under UV device for UV curing for 5-120 minutes; remove the reaction device, continue stirring for 1 hour, distill under reduced pressure, and vacuum dry at 40°C for 12 hours; set aside.

[0026] The S11 product and the unsaturated alcohol are added at a molar ratio of thiol to carbon-carbon double bond of 1:1; The usage ratio of the S11 product to anhydrous N,N-dimethylformamide is 1 g:20 mL.

[0027] The unsaturated alcohol is an alcohol containing a carbon-carbon double bond; it may be allyl alcohol, crotyl alcohol, 3-butene-1-ol, 3-methyl-3-butene-1-ol, leaf alcohol, 4-pentene-1-ol, 5-hexene-1-ol, etc.; and crotyl alcohol is preferred.

[0028] The amount of the photoinitiator is 0-2.0% of the total mass of the reactants; when the amount of the photoinitiator is 0, no photoinitiator is added; The photoinitiator may be photoinitiator 184, photoinitiator 1173, photoinitiator 2959, photoinitiator TPO, etc.; and photoinitiator 184 is preferred.

[0029] The radiation energy intensity of the UV device can be 300-500 mW / cm 2 ; Specifically, it can be 300mW / cm 2 、350mW / cm 2 , 400mW / cm 2 , 450mW / cm 2 , 500mW / cm 2 , or a range of values ​​consisting of any two values. In addition, the radiation energy intensity of the UV device described in the following embodiments of the present invention is 400mW / cm 2 .

[0030] S13, N2 protection, add S12 product, adipic acid, fluorinated terephthalic acid, hydroxyterephthalic acid, 1,4-butanediol, catalyst, and xylene into the reactor, heat to 155-165°C for reaction for 2 hours, continue to heat to 170-180°C for condensation reaction for 4-6 hours, observe the water quality to determine the reaction endpoint; add excess phenol dropwise, continue stirring for 1-2 hours; cool, filter, and take insoluble matter; rinse with N,N-dimethylformamide 3 times, and vacuum dry at 40°C for 12 hours; set aside.

[0031] The adipic acid, fluorinated terephthalic acid, hydroxy terephthalic acid, S12 product, and 1,4-butanediol are added at a molar ratio of carboxyl to hydroxyl of 1.025:1; The molar ratio of adipic acid, fluorinated terephthalic acid, and hydroxyterephthalic acid is 1:0.4-0.7:0.3-0.6; The usage ratio of the S12 product to xylene and N,N-dimethylformamide is 1 g:100 mL:50 mL.

[0032] The fluorinated terephthalic acid is 2-fluoroterephthalic acid, 2,3,5,6-tetrafluoroterephthalic acid, etc.; and preferably 2,3,5,6-tetrafluoroterephthalic acid; The hydroxyterephthalic acid is 2-hydroxyterephthalic acid.

[0033] The amount of the catalyst used is 0.5% of the total mass of the reactants; The catalyst is a mixture of stannous octoate and p-toluenesulfonic acid in a mass ratio of 2:1.

[0034] The condensation reaction has a product polymerization degree of 20-35. The polymerization degree is the average polymerization degree of the molecular chains in the product. Since the esterification polymerization of dibasic acid and diol belongs to a dehydration condensation reaction, the molecular weight and polymerization degree of the polyester can be theoretically controlled by the number of moles of the added raw materials and the mass of the separated water. Since the S12 product is added to the reaction raw materials, it has a polyhydroxy structure, so the average polymer of the molecular chains in the product can be obtained by calculating the mass of the separated water. When the average polymerization degree is less than 20, the molecular weight is low and the degree of chain entanglement is not high, which affects the compatibility and thus has adverse consequences on the stretching ratio; when the average polymerization degree is greater than 35, the molecular chain is longer, which affects the processing performance and affects the subsequent reaction activity.

[0035] S14, N2 protection, dissolve the product of S13, dibutyltin dilaurate, and asymmetric diisocyanate in N,N-dimethylformamide in a reaction vessel, heat to 80-100°C, stir for 6-12h, cool to room temperature, and let stand for use.

[0036] The S13 product and the asymmetric diisocyanate are added at a molar ratio of hydroxyl group to isocyanate group of 1:2; The ratio of the diisocyanate to N,N-dimethylformamide is 0.1 mol:50 mL; The diisocyanate is an asymmetric diisocyanate; it can be toluene diisocyanate or isophorone diisocyanate; The toluene diisocyanate has an asymmetric structure, and the two isocyanate groups have a certain difference in activity. When one of the highly active isocyanate groups reacts, the activity of the other isocyanate group decreases rapidly due to the certain molecular weight of the S13 product. However, the two isocyanate groups of isophorone diisocyanate itself have a large difference in activity. Therefore, the use of an asymmetric diisocyanate can obtain a structure with an isocyanate group capped at one end. In addition, isophorone diisocyanate is preferred.

[0037] The amount of dibutyltin dilaurate used is 1 wt % of the total mass of the reactants.

[0038] S15, adding the reaction solution of the product of S14 dropwise to N,N-dimethylformamide A containing p-phenylenediamine via a peristaltic pump, raising the temperature to 80-100°C, and continuing stirring for 1-2 hours after the addition is completed; cooling, filtering, and collecting insoluble matter; rinsing with N,N-dimethylformamide B three times, and vacuum drying at 40°C for 12 hours; obtaining a terminal amino-modified structure, i.e., the target product.

[0039] The S14 product and p-phenylenediamine are added at a molar ratio of hydroxyl to amino of 1:2; The usage ratio of the p-phenylenediamine to N,N-dimethylformamide A and N,N-dimethylformamide B is 0.1 mol:50 mL:40 mL.

[0040] The PBAT has a melt index of 4.2 g / 10 min (190° C., 2.16 kg), is model TH801T, and was purchased from Xinjiang Lanshan Tunhe Polyester Co., Ltd.

[0041] The PPC-P has a molecular weight of 52.5 kg / mol and a glass transition temperature (Tg) of 47° C. and was purchased from Guangdong Tianxin New Material Technology Co., Ltd.

[0042] The carbodiimide is bis(2,6-diisopropylbenzene)carbodiimide, model number HyMax1010, purchased from Shanghai Langyi Functional Materials Co., Ltd.

[0043] The chain extender is an epoxy structure; specifically Joncryl® ADR 4468, purchased from BASF, Germany.

[0044] The antioxidant is a compound of hindered phenols and phosphites. The hindered phenol antioxidant may be antioxidant 1010, antioxidant 1076, antioxidant 264, antioxidant 2246, or the like; preferably antioxidant 1010. The phosphite antioxidant may be antioxidant 168, antioxidant 242, antioxidant TPP, or the like; preferably antioxidant 168. In the following examples and comparative examples of the present invention, the antioxidants are antioxidant 1010 and antioxidant 168 added in a mass ratio of 1 / 2.

[0045] The antioxidant is a combination of a light stabilizer and a UV absorber. The light stabilizer may be UV-292, UV-770, or GW540, with UV-292 being preferred. The UV absorber may be UV-326, UV-327, or UV-531, with UV-531 being preferred. In the following examples and comparative examples of the present invention, the light stabilizer is UV-292 and UV-531 added in a mass ratio of 1 / 2.

[0046] The lubricant is erucamide, oleamide, ethylene bisstearamide, etc.; and, the lubricant in the following examples and comparative examples of the present invention is erucamide and ethylene bisstearamide mixed and added in a mass ratio of 2 / 1.

[0047] Another object of the present invention is to provide a method for preparing an ultra-thin, high-strength, biaxially oriented biodegradable mulch film, comprising the following steps: S21, mixing, plasticizing, extrusion, i.e. Mix all the raw materials in a mixer at 40°C according to the formula, and then plasticize and extrude them in a twin-screw extruder. The twin-screw extruder is set to a temperature of 140-180°C in each zone; wherein, Twin-screw extruder with a screw diameter of 25 cm and an aspect ratio of 40:1.

[0048] S22, casting, cooling, i.e. The melt plasticized in S21 is extruded through a die head and attached to the surface of a casting roll for cooling to obtain a cast sheet; The die temperature is 180-190°C.

[0049] S23, preheating, biaxial stretching, heat setting, i.e. The cast sheet in S22 is preheated, biaxially stretched, and then heat-set to obtain a biaxially stretched film; The biaxial stretching has a transverse stretching ratio of 6.5-7.5 and a stretching temperature of 95-105° C.; and The longitudinal stretching ratio of the biaxial stretching is 7.5-8.5; the stretching temperature is 100-110°C.

[0050] The stretching rate is 100-200 mm / s.

[0051] The heat setting is a heat treatment at 80-90° C. for 15-25 minutes.

[0052] S24, pulling and winding, i.e. The biaxially oriented film in S23 is drawn, trimmed, and finally rolled up to obtain an ultra-thin high-strength biaxially oriented biodegradable mulch film (with a total thickness of 5.5±0.5 μm).

[0053] The ultra-thin high-strength biaxially oriented biodegradable mulch film of the present invention has a transverse and longitudinal tensile strength greater than 80 MPa, a transverse and longitudinal elongation at break greater than 300%, and a water vapor permeability less than 300 g / m after material modification design and high-ratio biaxially oriented process design. 2 *24h, the degradation cycle can be extended by about 50% compared with the biodegradable mulch film prepared by traditional blown film; compared with the mulch film prepared by traditional blown film (the thickness is generally 8-12μm), the barrier property is better, the water and moisture retention capacity is stronger, the degradation cycle is longer, and the cost is lower after the material is thinned. All test indicators meet GB / T 35795. The mulch film of the present invention has a higher cost-effectiveness.

[0054] In order to further understand the present invention, an ultra-thin high-strength biaxially oriented biodegradable mulch provided by the present invention is described in detail below with reference to specific embodiments. The protection scope of the present invention is not limited by the following embodiments.

[0055] Example 1 This embodiment provides an ultra-thin high-strength biaxially oriented biodegradable ground film, comprising the following raw materials in parts by weight: PBAT 70 parts; PPC-P 30 copies; 6.0 parts of modified talc; 0.5 parts of carbodiimide; 0.3 parts of chain extender; 0.3 parts of antioxidant; 0.4 parts of antioxidant; 0.2 parts of lubricant.

[0056] The modified talc powder is prepared in the following steps: S11, talc powder and silane coupling agent KH580 were added to anhydrous ethanol, ultrasonically vibrated for 0.5 h, allowed to stand at room temperature for 2 h, reacted at 60° C. for 6 h, filtered, and the insoluble matter was collected and dried at 60° C. for 12 h; set aside.

[0057] The usage ratio of the talc powder, the silane coupling agent KH580 and the anhydrous ethanol is 30 g:1.1 g:80 mL.

[0058] The particle size of the talcum powder is 4000 mesh.

[0059] Its infrared data are as follows: 3415cm -1 :-OH exists and weakens; 2550 cm -1 :-SH exists; 1109 cm -1 、801cm -1 :-Si-O- exists; 621cm -1 :-Mg-O- exists.

[0060] S12, add the product of S11, crotyl alcohol, and photoinitiator 184 to anhydrous N,N-dimethylformamide, stir, and place under UV device for UV curing for 20 minutes; remove the reaction device, continue stirring for 1 hour, distill under reduced pressure, and vacuum dry at 40°C for 12 hours; set aside.

[0061] The S11 product and crotyl alcohol are added at a molar ratio of thiol to carbon-carbon double bond of 1:1; The usage ratio of the S11 product to anhydrous N,N-dimethylformamide is 1 g:20 mL.

[0062] The amount of the photoinitiator 184 used is 1.0% of the total mass of the reactants.

[0063] Its infrared data is as follows: 3489cm -1 :-OH exists; 2550 cm -1 :-SH does not exist; 1109 cm -1 、801cm -1 :-Si-O- exists; 621cm -1 :-Mg-O- exists.

[0064] S13, N2 protection, add S12 product, adipic acid, 2,3,5,6-tetrafluoroterephthalic acid, 2-hydroxyterephthalic acid, 1,4-butanediol, catalyst, and xylene into the reactor, heat to 160°C for reaction for 2 hours, continue to heat to 175°C for condensation reaction for 5 hours, observe the water quality to determine the reaction end point; add excess phenol dropwise, continue stirring for 1.5 hours, cool, filter, and take insoluble matter; rinse with N,N-dimethylformamide 3 times, and vacuum dry at 40°C for 12 hours; set aside.

[0065] The adipic acid, 2,3,5,6-tetrafluoroterephthalic acid, 2-hydroxyterephthalic acid, S12 product and 1,4-butanediol are added at a molar ratio of carboxyl to hydroxyl of 1.025:1; The molar ratio of adipic acid, 2,3,5,6-tetrafluoroterephthalic acid and 2-hydroxyterephthalic acid is 1:0.55:0.45; The usage ratio of the S12 product to xylene and N,N-dimethylformamide is 1 g:100 mL:50 mL.

[0066] The amount of the catalyst used is 0.5% of the total mass of the reactants; The catalyst is a mixture of stannous octoate and p-toluenesulfonic acid in a mass ratio of 2:1.

[0067] The condensation reaction has a product polymerization degree of 29.2.

[0068] Its infrared data are as follows: 3514cm -1 :-OH exists; 3011cm -1 、1595cm -1 、1498cm -1 : benzene ring exists; 1735cm -1 、1720cm -1 :-C=O exists; 1222cm -1 :-CF exists; 1109 cm -1 、801cm -1 :-Si-O- exists; 621cm -1 :-Mg-O- exists.

[0069] S14, N2 protection, dissolve the product of S13, dibutyltin dilaurate, and isophorone diisocyanate in N,N-dimethylformamide and place in a reaction vessel, heat to 90°C and stir for 7.5h, cool to room temperature, and let stand for use.

[0070] The S13 product and isophorone diisocyanate are added at a molar ratio of hydroxyl group to isocyanate group of 1:2; The usage ratio of isophorone diisocyanate to N,N-dimethylformamide is 0.1 mol:50 mL; The amount of dibutyltin dilaurate used is 1 wt % of the total mass of the reactants.

[0071] Its infrared data are as follows: 3514cm -1 :-OH does not exist; 3415cm -1 :-OH exists; 3011cm -1 、1595cm -1 、1498cm -1 : benzene ring exists; 2250cm -1 : Isocyanate exists; 1735cm -1 、1720cm -1 :-C=O (ester group) exists; 1692cm -1 :-C=O (amide) exists; 1222cm -1:-CF exists; 1109 cm -1 、801cm -1 :-Si-O- exists; 621cm -1 :-Mg-O- exists.

[0072] S15, add the reaction solution of the product of S14 dropwise to N,N-dimethylformamide A containing p-phenylenediamine via a peristaltic pump, raise the temperature to 90°C, and continue stirring for 1.5 hours after the addition is completed; cool down, filter, and collect the insoluble matter; rinse with N,N-dimethylformamide B three times, and vacuum dry at 40°C for 12 hours to obtain a terminal amino-modified structure, i.e., the target product.

[0073] The S14 product and p-phenylenediamine are added at a molar ratio of hydroxyl to amino of 1:2; The usage ratio of the p-phenylenediamine to N,N-dimethylformamide A and N,N-dimethylformamide B is 0.1 mol:50 mL:40 mL.

[0074] Its infrared data are as follows: 3415cm -1 :-OH exists; 3328cm -1 : -NH exists; 3011cm -1 、1595cm -1 、1498cm -1 : benzene ring is enhanced; 2250cm -1 :Isocyanate does not exist; 1735cm -1 、1720cm -1 :-C=O (ester group) exists; 1692cm -1 :-C=O (amide) exists; 1656cm -1 :-C=O (amide) exists; 1222cm -1 :-CF exists; 1109 cm -1 、801cm -1 :-Si-O- exists; 621cm -1 :-Mg-O- exists.

[0075] Another object of this embodiment is to provide a method for preparing an ultra-thin, high-strength, biaxially oriented biodegradable mulch film, comprising the following steps: S21, mixing, plasticizing, extrusion, i.e. Mix all the raw materials in a mixer at 40°C according to the formula, and then plasticize and extrude them in a twin-screw extruder. The twin-screw extruder has temperature zones set at 144°C, 154°C, 162°C, 170°C, 175°C, 178°C, 180°C, and 180°C, respectively.

[0076] S22, casting, cooling, i.e. The melt plasticized in S21 is extruded through a die head and attached to the surface of a casting roll for cooling to obtain a cast sheet; The die temperature was 185°C.

[0077] S23, preheating, biaxial stretching, heat setting, i.e. The cast sheet in S22 is preheated, biaxially stretched, and then heat-set to obtain a biaxially stretched film; The biaxial stretching has a transverse stretching ratio of 7.0 and a stretching temperature of 100° C.; and The longitudinal stretching ratio of the biaxial stretching is 8.0; and the stretching temperature is 105°C.

[0078] The stretching rate is 150 mm / s.

[0079] The heat setting is a heat treatment at 85° C. for 20 minutes.

[0080] S24, pulling and winding, i.e. The biaxially oriented film in S23 is drawn, trimmed, and finally rolled up to obtain an ultra-thin high-strength biaxially oriented biodegradable ground film.

[0081] Example 2 This embodiment provides an ultra-thin high-strength biaxially oriented biodegradable ground film, comprising the following raw materials in parts by weight: PBAT 65 parts; PPC-P 35 copies; 5.0 parts of modified talc; 0.6 parts of carbodiimide; 0.4 parts of chain extender; 0.2 parts of antioxidant; 0.5 parts of antioxidant; 0.3 parts of lubricant.

[0082] The modified talc powder is prepared in the following steps: S11, talc powder and silane coupling agent KH580 were added to anhydrous ethanol, ultrasonically vibrated for 0.5 h, allowed to stand at room temperature for 2 h, reacted at 50° C. for 10 h, filtered, and the insoluble matter was collected and dried at 60° C. for 12 h; set aside.

[0083] The usage ratio of the talc powder, the silane coupling agent KH580 and the anhydrous ethanol is 30 g:1.5 g:80 mL.

[0084] The particle size of the talcum powder is 2500 meshes.

[0085] S12, add the product of S11, crotyl alcohol, and photoinitiator 184 to anhydrous N,N-dimethylformamide, stir, and place under UV device for UV curing for 5 minutes; remove the reaction device, continue stirring for 1 hour, distill under reduced pressure, and vacuum dry at 40°C for 12 hours; set aside.

[0086] The S11 product and crotyl alcohol are added at a molar ratio of thiol to carbon-carbon double bond of 1:1; The usage ratio of the S11 product to anhydrous N,N-dimethylformamide is 1 g:20 mL.

[0087] The amount of the photoinitiator 184 used is 2.0% of the total mass of the reactants.

[0088] S13, N2 protection, add S12 product, adipic acid, 2,3,5,6-tetrafluoroterephthalic acid, 2-hydroxyterephthalic acid, 1,4-butanediol, catalyst, and xylene into the reactor, heat to 155°C for reaction for 2 hours, continue to heat to 170°C for condensation reaction for 6 hours, observe the water quality to determine the reaction end point; add excess phenol dropwise, continue stirring for 2 hours; cool, filter, and take insoluble matter; rinse with N,N-dimethylformamide 3 times, vacuum dry at 40°C for 12 hours; set aside.

[0089] The adipic acid, 2,3,5,6-tetrafluoroterephthalic acid, 2-hydroxyterephthalic acid, S12 product and 1,4-butanediol are added at a molar ratio of carboxyl to hydroxyl of 1.025:1; The molar ratio of adipic acid, 2,3,5,6-tetrafluoroterephthalic acid and 2-hydroxyterephthalic acid is 1:0.55:0.45; The usage ratio of the S12 product to xylene and N,N-dimethylformamide is 1 g:100 mL:50 mL.

[0090] The amount of the catalyst used is 0.5% of the total mass of the reactants; The catalyst is a mixture of stannous octoate and p-toluenesulfonic acid in a mass ratio of 2:1.

[0091] The condensation reaction has a product polymerization degree of 20.6.

[0092] S14, N2 protection, dissolve the product of S13, dibutyltin dilaurate, and isophorone diisocyanate in N,N-dimethylformamide and place in a reaction vessel, heat to 80°C and stir for 12 hours, cool to room temperature, and let stand for use.

[0093] The S13 product and isophorone diisocyanate are added at a molar ratio of hydroxyl group to isocyanate group of 1:2; The usage ratio of isophorone diisocyanate to N,N-dimethylformamide is 0.1 mol:50 mL; The amount of dibutyltin dilaurate used is 1 wt % of the total mass of the reactants.

[0094] S15, add the reaction solution of the product of S14 dropwise to N,N-dimethylformamide A containing p-phenylenediamine via a peristaltic pump, raise the temperature to 80°C, and continue stirring for 1 hour after the addition is completed; cool down, filter, and collect the insoluble matter; rinse with N,N-dimethylformamide B three times, and vacuum dry at 40°C for 12 hours to obtain a terminal amino-modified structure, i.e., the target product.

[0095] The S14 product and p-phenylenediamine are added at a molar ratio of hydroxyl to amino of 1:2; The usage ratio of the p-phenylenediamine to N,N-dimethylformamide A and N,N-dimethylformamide B is 0.1 mol:50 mL:40 mL.

[0096] Another object of this embodiment is to provide a method for preparing an ultra-thin, high-strength, biaxially oriented biodegradable mulch film, comprising the following steps: S21, mixing, plasticizing, extrusion, i.e. Mix all the raw materials in a mixer at 40°C according to the formula, and then plasticize and extrude them in a twin-screw extruder. The twin-screw extruder has temperature zones set at 145°C, 155°C, 164°C, 171°C, 177°C, 177°C, 180°C, and 180°C, respectively.

[0097] S22, casting, cooling, i.e. The melt plasticized in S21 is extruded through a die head and attached to the surface of a casting roll for cooling to obtain a cast sheet; The die temperature was 190°C.

[0098] S23, preheating, biaxial stretching, heat setting, i.e. The cast sheet in S22 is preheated, biaxially stretched, and then heat-set to obtain a biaxially stretched film; The biaxial stretching has a transverse stretching ratio of 7.5 and a stretching temperature of 105° C.; and The longitudinal stretching ratio of the biaxial stretching is 7.5; the stretching temperature is 100°C.

[0099] The stretching rate is 200 mm / s.

[0100] The heat setting is a heat treatment at 90° C. for 15 minutes.

[0101] S24, pulling and winding, i.e. The biaxially oriented film in S23 is drawn, trimmed, and finally rolled up to obtain an ultra-thin high-strength biaxially oriented biodegradable ground film.

[0102] Example 3 This embodiment provides an ultra-thin high-strength biaxially oriented biodegradable ground film, comprising the following raw materials in parts by weight: PBAT 75 parts; PPC-P 25 copies; 7.0 parts of modified talc; 0.4 parts of carbodiimide; 0.2 parts of chain extender; 0.4 parts of antioxidant; 0.3 parts of antioxidant; 0.1 parts of lubricant.

[0103] The modified talc powder is prepared in the following steps: S11, talc powder and silane coupling agent KH580 were added to anhydrous ethanol, ultrasonically vibrated for 0.5 h, allowed to stand at room temperature for 2 h, reacted at 70° C. for 4 h, filtered, and the insoluble matter was collected and dried at 60° C. for 12 h; set aside.

[0104] The usage ratio of the talc powder, the silane coupling agent KH580 and the anhydrous ethanol is 30 g:0.8 g:80 mL.

[0105] The particle size of the talcum powder is 5000 mesh.

[0106] S12, add the product of S11, crotyl alcohol, and photoinitiator 184 to anhydrous N,N-dimethylformamide, stir, and place under UV device for UV curing for 120 minutes; remove the reaction device, continue stirring for 1 hour, distill under reduced pressure, and vacuum dry at 40°C for 12 hours; set aside.

[0107] The S11 product and crotyl alcohol are added at a molar ratio of thiol to carbon-carbon double bond of 1:1; The usage ratio of the S11 product to anhydrous N,N-dimethylformamide is 1 g:20 mL.

[0108] The amount of the photoinitiator 184 used is 0% of the total mass of the reactants, that is, no photoinitiator is added.

[0109] S13, N2 protection, add S12 product, adipic acid, 2,3,5,6-tetrafluoroterephthalic acid, 2-hydroxyterephthalic acid, 1,4-butanediol, catalyst, and xylene into the reactor, heat to 165°C for reaction for 2 hours, continue to heat to 180°C for condensation reaction for 4 hours, observe the water quality to determine the reaction end point; add excess phenol dropwise, continue stirring for 1 hour, cool, filter, and take insoluble matter; rinse with N,N-dimethylformamide 3 times, vacuum dry at 40°C for 12 hours, and set aside.

[0110] The adipic acid, 2,3,5,6-tetrafluoroterephthalic acid, 2-hydroxyterephthalic acid, S12 product and 1,4-butanediol are added at a molar ratio of carboxyl to hydroxyl of 1.025:1; The molar ratio of adipic acid, 2,3,5,6-tetrafluoroterephthalic acid and 2-hydroxyterephthalic acid is 1:0.55:0.45; The usage ratio of the S12 product to xylene and N,N-dimethylformamide is 1 g:100 mL:50 mL.

[0111] The amount of the catalyst used is 0.5% of the total mass of the reactants; The catalyst is a mixture of stannous octoate and p-toluenesulfonic acid in a mass ratio of 2:1.

[0112] The condensation reaction has a product polymerization degree of 34.8.

[0113] S14, N2 protection, dissolve the product of S13, dibutyltin dilaurate, and isophorone diisocyanate in N,N-dimethylformamide and place in a reaction vessel, heat to 100°C and stir for 6 hours, cool to room temperature, and let stand for use.

[0114] The S13 product and isophorone diisocyanate are added at a molar ratio of hydroxyl group to isocyanate group of 1:2; The usage ratio of isophorone diisocyanate to N,N-dimethylformamide is 0.1 mol:50 mL; The amount of dibutyltin dilaurate used is 1 wt % of the total mass of the reactants.

[0115] S15. Add the reaction solution of the product of S14 dropwise to N,N-dimethylformamide A containing p-phenylenediamine via a peristaltic pump, raise the temperature to 100°C, and continue stirring for 2 hours after the addition is completed; cool down, filter, and collect the insoluble matter; rinse with N,N-dimethylformamide B three times, and vacuum dry at 40°C for 12 hours to obtain a terminal amino-modified structure, i.e., the target product.

[0116] The S14 product and p-phenylenediamine are added at a molar ratio of hydroxyl to amino of 1:2; The usage ratio of the p-phenylenediamine to N,N-dimethylformamide A and N,N-dimethylformamide B is 0.1 mol:50 mL:40 mL.

[0117] Another object of this embodiment is to provide a method for preparing an ultra-thin, high-strength, biaxially oriented biodegradable mulch film, comprising the following steps: S21, mixing, plasticizing, extrusion, i.e. Mix all the raw materials in a mixer at 40°C according to the formula, and then plasticize and extrude them in a twin-screw extruder. The twin-screw extruder has temperature zones set at 140°C, 151°C, 160°C, 168°C, 175°C, 175°C, 178°C, and 178°C, respectively.

[0118] S22, casting, cooling, i.e. The melt plasticized in S21 is extruded through a die head and attached to the surface of a casting roll for cooling to obtain a cast sheet; The die temperature was 180°C.

[0119] S23, preheating, biaxial stretching, heat setting, i.e. The cast sheet in S22 is preheated, biaxially stretched, and then heat-set to obtain a biaxially stretched film; The biaxial stretching has a transverse stretching ratio of 6.5 and a stretching temperature of 95° C.; and The longitudinal stretching ratio of the biaxial stretching is 8.5, and the stretching temperature is 110°C.

[0120] The stretching rate is 100 mm / s.

[0121] The heat setting is a heat treatment at 80° C. for 25 minutes.

[0122] S24, pulling and winding, i.e. The biaxially oriented film in S23 is drawn, trimmed, and finally rolled up to obtain an ultra-thin high-strength biaxially oriented biodegradable ground film.

[0123] Example 4 The rest is the same as in Example 1, except that: An ultra-thin, high-strength, biaxially oriented biodegradable mulch film. The modified talc powder, in the preparation step S13, The molar ratio of the adipic acid, 2,3,5,6-tetrafluoroterephthalic acid and 2-hydroxyterephthalic acid is 1:0.4:0.6.

[0124] Example 5 The rest is the same as in Example 1, except that: An ultra-thin, high-strength, biaxially oriented biodegradable ground film. The modified talc powder, in the preparation step S13, The molar ratio of the adipic acid, 2,3,5,6-tetrafluoroterephthalic acid and 2-hydroxyterephthalic acid is 1:0.7:0.3.

[0125] Example 6 The rest is the same as in Example 1, except that: An ultra-thin, high-strength, biaxially oriented biodegradable ground film. The modified talc powder, in the preparation step S13, The condensation reaction has a product polymerization degree of 20.2.

[0126] Example 7 The rest is the same as in Example 1, except that: An ultra-thin, high-strength, biaxially oriented biodegradable ground film. The modified talc powder, in the preparation step S13, The condensation reaction has a product polymerization degree of 34.7.

[0127] The following comparative examples are compared with specific embodiment 1: Comparative Example 1 The rest is the same as in Example 1, except that: An ultra-thin, high-strength, biaxially oriented biodegradable mulch film is formulated without adding PPC-P.

[0128] Comparative Example 2 The rest is the same as in Example 1, except that: The invention discloses an ultra-thin high-strength biaxially oriented biodegradable ground film without adding modified talc powder.

[0129] Comparative Example 3 The rest is the same as in Example 1, except that: An ultra-thin, high-strength, biaxially oriented biodegradable ground film. The modified talc powder, in the preparation step S11, Replace talc with calcium carbonate.

[0130] Comparative Example 4 The rest is the same as in Example 1, except that: An ultra-thin, high-strength, biaxially oriented biodegradable ground film. The modified talc was replaced with the corresponding talc.

[0131] Comparative Example 5 The rest is the same as in Example 1, except that: An ultra-thin, high-strength, biaxially oriented biodegradable ground film. The modified talc powder, in the preparation step S11, The particle size of the talcum powder is 1250 mesh.

[0132] Comparative Example 6 The rest is the same as in Example 1, except that: An ultra-thin, high-strength, biaxially oriented biodegradable ground film. The modified talc powder, in the preparation step S11, The particle size of the talcum powder is 8000 mesh.

[0133] Comparative Example 7 The rest is the same as in Example 1, except that: An ultra-thin, high-strength, biaxially oriented biodegradable ground film. The modified talc powder, in the preparation step S13, The molar ratio of adipic acid, 2,3,5,6-tetrafluoroterephthalic acid, and 2-hydroxyterephthalic acid is 1:1.0:0; that is, no 2-hydroxyterephthalic acid is added.

[0134] Comparative Example 8 The rest is the same as in Example 1, except that: An ultra-thin, high-strength, biaxially oriented biodegradable ground film. The modified talc powder, in the preparation step S13, The molar ratio of adipic acid, 2,3,5,6-tetrafluoroterephthalic acid, and 2-hydroxyterephthalic acid is 1:0:1.0; that is, no 2,3,5,6-tetrafluoroterephthalic acid is added.

[0135] Comparative Example 9 The rest is the same as in Example 1, except that: An ultra-thin, high-strength, biaxially oriented biodegradable ground film. The modified talc powder, in the preparation step S13, The molar ratio of adipic acid, 2,3,5,6-tetrafluoroterephthalic acid, and 2-hydroxyterephthalic acid is 0:0.7:0.3; that is, no adipic acid is added.

[0136] Comparative Example 10 The rest is the same as in Example 1, except that: An ultra-thin, high-strength, biaxially oriented biodegradable ground film. The modified talc powder, in the preparation step S13, The condensation reaction has a product polymerization degree of 18.5.

[0137] Comparative Example 11 The rest is the same as in Example 1, except that: An ultra-thin, high-strength, biaxially oriented biodegradable ground film. The modified talc powder, in the preparation step S13, The condensation reaction has a product polymerization degree of 37.7.

[0138] Comparative Example 12 The rest is the same as in Example 1, except that: An ultra-thin, high-strength, biaxially oriented biodegradable ground film. The modified talc powder, in the preparation step S15, Replace p-phenylenediamine with aniline.

[0139] Comparative Example 13 The rest is the same as in Example 1, except that: An ultra-thin, high-strength, biaxially oriented biodegradable ground film. The epoxy chain extender was replaced with a maleic anhydride compatibilizer (purchased from Yuanxiang Chemical).

[0140] Comparative Example 14 The rest is the same as in Example 1, except that: In a method for preparing an ultra-thin high-strength biaxially stretched biodegradable mulch film, The longitudinal stretching ratio of the biaxial stretching is 6.0.

[0141] Comparative Example 15 The rest is the same as in Example 1, except that: In a method for preparing an ultra-thin high-strength biaxially stretched biodegradable mulch film, The transverse stretching ratio of the biaxial stretching is 5.0.

[0142] Comparative Example 16 The rest is the same as in Example 1, except that: In the preparation method of the ultra-thin high-strength biaxially oriented biodegradable ground film, the film is not subjected to biaxially oriented process and is prepared by conventional film blowing process after co-extrusion.

[0143] Table 1 shows the results of measuring the physical properties of the ultra-thin high-strength biaxially oriented biodegradable mulch films in the embodiments of the present invention and the comparative examples.

[0144] Table 1 Physical test performance of each embodiment First, it can be concluded from Examples 1-7 in Table 1 that the ultra-thin high-strength biaxially oriented biodegradable mulch film of the present invention has excellent mechanical properties and water vapor barrier properties.

[0145] Second, it can be observed from Example 1 and Comparative Example 1 that the PPC-P in the ultra-thin high-strength biaxially oriented biodegradable mulch film of the present invention has the function of improving mechanical strength and basic water vapor barrier; Second, from Example 1 and Comparative Examples 2-6, it can be observed that the ultra-thin, high-strength, biaxially oriented biodegradable mulch film of the present invention, using modified talc, has a significant effect on improving mechanical properties, etc.; from Example 1 and Comparative Examples 2-4, it can be observed that the lamellar structure of talc has a significant effect on improving water vapor barrier properties; from Example 1 and Comparative Examples 5-6, suitable small-particle talc used as a nucleating agent has a positive effect on crystallinity; and from Example 1 and Comparative Examples 4-5, it can be observed that talc of different particle sizes has different emphases on improving mechanical strength and barrier properties. From Example 1 and Comparative Examples 7-11, it can be observed that in the ultra-thin, high-strength, biaxially oriented biodegradable mulch film of the present invention, the structure of the organic chain in the homemade modified talc has a positive effect on improving mechanical properties, barrier properties, and hydrophobicity; that is, the fluorine-containing structure has an excellent hydrophobic effect, which can effectively reduce condensation and avoid burning seedlings; the hydroxyl structure provides an active site for the next reaction, thereby having a chain extension effect to improve mechanical properties; the flexible structure of adipic acid also has a positive effect on mechanical properties; in addition, the degree of polymerization of the organic chain structure also has an impact on mechanical properties, and a too small molecular weight affects mechanical properties; a too large molecular weight effectively encapsulates the talc, which affects barrier properties; From Example 1 and Comparative Examples 12-13, it can be observed that the ultra-thin high-strength biaxially oriented biodegradable mulch film of the present invention has an aniline structure in the homemade modified talc powder that can undergo a chain extension reaction to improve mechanical properties; and can also synergistically improve performance with an epoxy chain extender. It can be observed from Example 1 and Comparative Examples 14-15 that the ultra-thin high-strength biaxially stretched biodegradable mulch film of the present invention has significant comprehensive properties such as mechanical strength and barrier properties after high-ratio biaxial stretching; It can be observed from Example 1 and Comparative Example 16 that the ultra-thin high-strength biaxially oriented biodegradable mulch film of the present invention has significantly improved tensile strength and degradation cycle at a thinner thickness, and significantly reduced material cost, compared to the traditional blown film preparation process.

[0146] In summary, the present invention provides an ultra-thin, high-strength, biaxially oriented biodegradable mulch film. The ultra-thin, high-strength, biaxially oriented biodegradable mulch film has the advantages of excellent mechanical properties, barrier properties, hydrophobic properties, low cost, etc.; and the main raw materials used have the advantage of being completely degradable and have a wide range of applications.

[0147] The test method is as follows: (1) Thickness: GB / T 6672 2001 standard test is used, and the average value is obtained by measuring 10 points evenly.

[0148] (2) Mechanical properties: Tested according to the method described in GB / T 1040.3-2006.

[0149] (3) Water vapor transmission rate: Test according to the method described in GB / T 1037.

[0150] (4) Water contact angle: Tested according to the method described in ASTM D 5725 1999 (R2008).

[0151] (5) Surface condensation: The main condensation area of ​​water droplets is in the middle area of ​​the arched ground film. The particle size, shape and quantity are observed around 11-12 o'clock in the morning. The number of water droplets is the largest and the particle size is the largest. It is observed and recorded with the naked eye.

[0152] (6) Degradation period: According to the experimental design, starting from the date of laying in May, the degradation of the ground film was observed every day until it was completely degraded, and the time was recorded.

[0153] With the above-described preferred embodiments of the present invention as a guide, and with reference to the above description, relevant personnel are fully capable of making various changes and modifications without departing from the technical scope of this invention. The technical scope of this invention is not limited to the contents of the specification and must be determined according to the scope of the claims.

Claims

1. An ultra-thin high-strength biaxially oriented biodegradable mulch film, characterized in that: The invention comprises the following raw materials in parts by weight: PBAT 65-75 parts; PPC-P 25-35 copies; 5.0-7.0 parts of modified talc; 0.4-0.6 parts of carbodiimide; Chain extender 0.2-0.4 parts; 0.2-0.4 parts of antioxidant; Antiaging agent 0.3-0.5 parts; 0.1-0.3 parts of lubricant; Wherein, the total weight of the PBAT and PPC-P is 100 parts.

2. The ultra-thin high-strength biaxially oriented biodegradable mulch film according to claim 1, characterized in that: The modified talc powder is prepared in the following steps: S11, performing a coupling reaction between talc powder and a mercaptosilane coupling agent; S12, click reaction of the product of S11 with an unsaturated alcohol; S13, polycondensing the product of S12, adipic acid, fluorinated terephthalic acid, hydroxy terephthalic acid, and butanediol, and capping with phenol; S14, subjecting the product of S13 to a nucleophilic addition reaction with an asymmetric diisocyanate; S15, subjecting the product of S14 to a nucleophilic addition reaction with p-phenylenediamine to obtain an amino-terminated modified structure, i.e., the target product.

3. The ultra-thin high-strength biaxially oriented biodegradable mulch film according to claim 2, characterized in that: The particle size of the talc powder is 2500-5000 mesh.

4. The ultra-thin high-strength biaxially oriented biodegradable mulch film according to claim 2, characterized in that: The molar ratio of the adipic acid, the fluorinated terephthalic acid and the hydroxy terephthalic acid is 1:0.4-0.7:0.3-0.

6.

5. The ultra-thin high-strength biaxially oriented biodegradable mulch film according to claim 2, characterized in that: The condensation reaction has a product polymerization degree of 20-35.

6. The ultra-thin high-strength biaxially oriented biodegradable mulch film according to claim 1, characterized in that: The chain extender is an epoxy structure.

7. The ultra-thin high-strength biaxially oriented biodegradable mulch film according to claim 1, characterized in that: The antioxidant is a compound of hindered phenols and phosphites.

8. The ultra-thin high-strength biaxially oriented biodegradable mulch film according to claim 1, characterized in that: The antioxidant is a compound of a light stabilizer and an ultraviolet absorber.

9. A method for preparing an ultra-thin high-strength biaxially oriented biodegradable mulch film, characterized in that: The steps include: S21, mixing and plasticizing, i.e. Mix all the raw materials evenly according to the formula and put them into the extruder for plasticization; S22, casting, cooling, i.e. The melt plasticized in S21 is extruded through a die head and attached to the surface of a casting roll for cooling to obtain a cast sheet; S23, preheating, biaxial stretching, heat setting, i.e. The cast sheet in S22 is preheated, biaxially stretched, and then heat-set to obtain a biaxially stretched film; as well as S24, pulling and winding, i.e. The biaxially oriented film in S23 is drawn, trimmed, and finally rolled up to obtain an ultra-thin high-strength biaxially oriented biodegradable ground film.

10. The method for preparing the ultra-thin high-strength biaxially oriented biodegradable mulch film according to claim 9, characterized in that: The die temperature is 180-190°C; The biaxial stretching has a transverse stretching ratio of 6.5-7.5 and a stretching temperature of 95-105° C.; and The longitudinal stretching ratio of the biaxial stretching is 7.5-8.5; the stretching temperature is 100-110°C.

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