Chitin blended reinforced degradable mulch film and its preparation method

Abstract

This invention discloses a chitin-reinforced biodegradable mulch film and its preparation method, belonging to the field of biodegradable agricultural mulch film technology. The biodegradable mulch film is prepared from the following raw material components in parts by weight: 70-90 parts polybutylene terephthalate (PBAT), 10-20 parts chitin, 0.5-2 parts compatibilizer, 0.2-1 parts glycerol, and 0.5-2 parts additives. This invention overcomes the shortcomings of existing technologies. By optimizing the formula and preparation process, the compatibility between chitin and the PBAT matrix is ​​significantly improved, fully utilizing the natural functional properties of chitin. The resulting biodegradable mulch film possesses excellent mechanical properties, controllable degradation, and antibacterial and pest-resistant functions, which is of great significance for the sustainable development of agricultural production.

Description

Technical Field

[0001] This invention relates to the field of biodegradable agricultural mulch film technology, specifically a chitin-reinforced biodegradable mulch film and its preparation method. Background Technology

[0002] Mulching technology, as an important cultivation method in modern agriculture, can effectively increase soil temperature, retain soil moisture, suppress weed growth, reduce pest and disease attacks, and significantly improve crop yield and quality. However, traditional polyethylene mulch film is difficult to degrade naturally, and its residues in the soil after large-scale use can damage soil structure, hinder crop root growth, and cause soil pollution and ecological damage, which has become a prominent problem restricting the sustainable development of agriculture.

[0003] To address the aforementioned issues, how to gradually replace traditional plastic mulch films with biodegradable mulch films has become a research hotspot. Currently, biodegradable mulch films primarily use biodegradable materials such as polylactic acid (PLA) and polybutylene terephthalate (PBAT) as substrates. However, these films still have some limitations in application, such as insufficient mechanical properties, poor matching between degradation rate and crop growth cycle, high production costs, and a general lack of antibacterial and pest-preventing functions, failing to effectively inhibit the growth and reproduction of harmful microorganisms and insect eggs in the soil, easily leading to crop diseases and pests.

[0004] Chitin is a natural polymer compound found abundantly in the exoskeletons of crustaceans such as shrimp and crabs, as well as in the cell walls of insects and fungi. It is widely available, relatively inexpensive, and completely biodegradable. Furthermore, the chitin molecule is rich in active groups such as hydroxyl and amino groups, exhibiting excellent antibacterial, antiviral, and biodegradable properties. Incorporating chitin into biodegradable substrates holds promise for improving the mechanical properties of mulch films, regulating degradation rates, and endowing them with antibacterial and pest-repellent functions. However, chitin suffers from poor compatibility with biodegradable substrates; direct mixing easily leads to agglomeration and weak interfacial bonding, making it difficult to achieve satisfactory mechanical properties and thus limiting the application of chitin in the field of biodegradable mulch films.

[0005] Therefore, how to effectively improve the compatibility between chitin and biodegradable substrates, give full play to the natural functional properties of chitin, and prepare biodegradable mulch films with both good mechanical and antibacterial properties has become a key technical problem that urgently needs to be solved in the field of biodegradable agricultural mulch film technology. Summary of the Invention

[0006] Therefore, the present invention provides a chitin-reinforced biodegradable mulch film and its preparation method, which can overcome the shortcomings of the prior art, effectively improve the compatibility between chitin and polybutylene terephthalate matrix, give full play to the natural functional properties of chitin, and obtain a biodegradable mulch film with excellent mechanical properties, controllable degradation and antibacterial and pest-preventing functions.

[0007] To achieve the above objectives, the present invention provides the following technical solution:

[0008] A chitin-reinforced biodegradable mulch film is prepared from the following raw material components by weight: 70-90 parts of polybutylene terephthalate (PBAT), 10-20 parts of chitin, 0.5-2 parts of compatibilizer, 0.2-1 parts of glycerin, and 0.5-2 parts of additives.

[0009] In the above technical solution, the compatibilizer is key to solving the compatibility problem between chitosan and PBAT. Its role is to act at the interface between the two phases, effectively reducing interfacial tension, promoting the uniform dispersion of chitosan in the PBAT matrix, and enhancing the interfacial bonding between the two. Glycerin, as a plasticizer and processing aid, can improve the processing flowability of the blend and has a certain plasticizing effect on chitosan, which helps its dispersion during processing. Through the combined action of the compatibilizer and glycerin, the performance of chitosan in the PBAT matrix blending process can be enhanced, improving film-forming properties and toughness while achieving higher mechanical strength and antibacterial properties. Simultaneously, chitosan has broad-spectrum antibacterial and antifungal activity, effectively inhibiting microbial attack on the film material. By adjusting the amount of chitosan added, the distribution sites of degradation "weak points" can be controlled, thereby regulating the overall degradation rate of the mulch film to match the growth cycle of the target crop, achieving good degradation controllability.

[0010] Furthermore, the chitin-reinforced biodegradable mulch film is prepared by weight from the following raw material components: 80 parts of polybutylene terephthalate (PBAT), 18 parts of chitin, 0.7 parts of compatibilizer, 0.6 parts of glycerin, and 0.7 parts of additives.

[0011] In the above technical solution, this formula enables the PBAT matrix and chitosan to achieve ultimate interfacial compatibility and mechanical enhancement under the combined action of compatibilizer and glycerin, while giving the mulch film good antibacterial and pest-resistant properties.

[0012] Furthermore, the additive is one or a combination of two or more of the following: lubricant, antioxidant, light stabilizer, and ultraviolet absorber.

[0013] In the above technical solutions, lubricants can improve processing fluidity, prevent materials from adhering in the extruder and mold, and improve the surface properties of the final mulch film; antioxidants can prevent the polymer from undergoing thermo-oxidative degradation and photo-oxidative degradation during processing (high-temperature shearing) and use, thereby maintaining the stability of the mechanical properties of the mulch film; light stabilizers and ultraviolet absorbers can effectively protect the mulch film used in the open air, ensuring the stability of the mechanical properties and degradation cycle of the mulch film.

[0014] Furthermore, the lubricant is one or a combination of two of ethylene bis-stearamide and pentylenetetrastearate.

[0015] In the above technical solution, both ethylene bis-stearamide and pentylene tetrastearate can play a role in both internal and external lubrication. More importantly, both of them contain polar groups and non-polar long carbon chains in their molecular structure. This structure has a certain compatibility and migration ability between the two phases of PBAT (non-polar / weakly polar) and chitin (strongly polar), thereby reducing the interfacial tension between the two phases to a certain extent, improving the compatibility problem caused by polarity mismatch, and helping chitin to be more uniformly dispersed in the PBAT matrix.

[0016] Furthermore, the antioxidant is a combination of hindered phenolic antioxidant and antioxidant 168, wherein the hindered phenolic antioxidant is one or a combination of two of antioxidant 1010 and antioxidant 1076.

[0017] In the above technical solution, hindered phenolic antioxidants can transform free radicals in the early stages of polymer oxidation into stable compounds, while antioxidant 168 can decompose hydroperoxides generated during oxidation, cutting off the source of free radical regeneration. The combined use of antioxidant 168 and hindered phenolic antioxidants can effectively inhibit the thermal oxidative degradation of PBAT and chitin during extrusion granulation and blown film processes, ensuring processing stability and providing long-term protection for the stable service of the mulch film.

[0018] Furthermore, the ultraviolet absorber is one or a combination of two of UV234 and UV326.

[0019] In the above technical solutions, UV-234 and UV-326, due to their benzotriazole structure and high heat resistance, have good compatibility with PBAT matrix materials and can withstand the temperature during material processing. They can improve the weather resistance of the mulch film when used outdoors, delay premature aging, embrittlement and loss of physical properties caused by ultraviolet radiation, and achieve stable service of the mulch film.

[0020] Furthermore, the light stabilizer is one or a combination of GW-622 and GW-944.

[0021] In the above technical solutions, GW-622 and GW-944 have low volatility and excellent resistance to migration and extraction, which can effectively prevent the polymer chain from breaking under light conditions, thereby ensuring the mechanical properties and integrity of the mulch film during its service life.

[0022] Furthermore, the compatibilizer is a composite of bamboo charcoal powder and ethylene-vinyl acetate copolymer (EVA).

[0023] In the above technical solution, the molecular chain of EVA contains both nonpolar ethylene segments and polar vinyl acetate segments. This amphiphilic structure enables it to interact with substances of different polarities simultaneously. The nonpolar ethylene segments of EVA have good compatibility with PBAT, while the polar vinyl acetate segments of EVA interact with strongly polar groups such as hydroxyl (-OH) and amino (-NH2) groups on chitin molecules. This allows EVA to act as a molecular bridge, effectively reducing the interfacial tension between the PBAT and chitin phases, promoting the dispersion of chitin in the PBAT matrix, and enhancing interfacial adhesion. The bamboo charcoal powder is made from high-temperature activated bamboo charcoal and has a high specific surface area and a unique honeycomb microporous structure. It can strongly adsorb chitin particles through physical adsorption, preventing chitin from agglomerating during processing due to its own hydrogen bonding. This allows it to be pre-fixed on the surface or in the pores of the bamboo charcoal powder and uniformly dispersed into the PBAT matrix during subsequent melt blending. Meanwhile, bamboo charcoal powder itself has the property of absorbing odors and harmful substances, which can complement the antibacterial function of chitosan. As a rigid particle, bamboo charcoal powder can also have a certain reinforcing effect on composite materials.

[0024] Furthermore, the compatibilizer is prepared as follows:

[0025] A1. Add bamboo charcoal powder to a hydrogen peroxide solution with a mass fraction of 20-40%, disperse it by ultrasonication, and then reflux for 2-4 hours. Separate, wash, and dry the product to obtain functionalized powder.

[0026] A2. Add ethylene-vinyl acetate copolymer (EVA) to dichloroethane to prepare an EVA solution with a mass fraction of 3-10% for later use; add functionalized powder to ethyl acetate and ultrasonically disperse to obtain bamboo charcoal powder dispersion.

[0027] A3. Under stirring conditions, EVA solution is added to bamboo charcoal powder dispersion, heated and stirred for 20-40 minutes, then filtered and dried to obtain compatibilizer.

[0028] In the above technical solution, high-concentration hydrogen peroxide, under heating and reflux conditions, can undergo an oxidation reaction with the carbon atoms on the surface of bamboo charcoal powder, introducing a large number of active groups, such as carboxyl (-COOH), hydroxyl (-OH), and carbonyl (C=O) oxygen-containing functional groups, onto the surface of the bamboo charcoal powder. Under high-temperature stirring conditions, the dissolved EVA molecular chains spontaneously adsorb, entangle, and coat the surface of the bamboo charcoal powder particles due to the strong interaction between their polar parts (vinyl acetate segments) and the polar groups on the surface of the functionalized bamboo charcoal powder. This causes the non-polar ethylene segments to face outward, forming a hydrophobic shell, resulting in a compatibilizer with bamboo charcoal powder as the core and EVA as the shell. Under the plasticizing effect of melt blending and glycerol, functionalized bamboo charcoal powder exhibits strong migration ability and good binding performance. It can generate strong physical adsorption and chemical interactions (such as hydrogen bonds) with active groups such as hydroxyl and amino groups on chitin molecules. Simultaneously, due to the good compatibility between the EVA shell (non-polar ethylene segments) and the PBAT matrix, the compatibilizer acts as an intermediary bridge, constructing a uniformly distributed core-shell network node between chitin and the PBAT matrix, forming a robust three-dimensional network structure. This three-dimensional network structure not only effectively transfers stress, significantly improving the tensile strength, toughness, and other mechanical properties of the mulch film, but also firmly fixes the chitin, preventing its migration or aggregation, ensuring the durability and uniformity of its antibacterial function. Furthermore, the abundant carboxyl and hydroxyl functional groups on the surface of oxidized bamboo charcoal powder can form a local hydrogen bond network in the glycerol plasticizing environment. This dynamic and reversible interaction can dissipate energy through the breaking and recombination of hydrogen bonds, allowing the compatibilizer and chitin to achieve better dispersion performance, further improving the mechanical properties and antibacterial ability of the mulch film.

[0029] This invention also provides a method for preparing a chitin-reinforced biodegradable mulch film, which includes the following steps:

[0030] S1. Add PBAT, compatibilizer and glycerin to a high-speed mixing tank and stir for 4-6 minutes. Then add chitosan and adjuvants and continue stirring for 3-8 minutes to obtain a premix.

[0031] S2. Feed the premixed material into a twin-screw extruder, with an extrusion temperature range of 90-160℃, and granulate it by extrusion. After air cooling, obtain biodegradable mulch film masterbatch.

[0032] S3. The biodegradable mulch film masterbatch is fed into a blown film machine. The temperature range of the blown film machine cylinder is 100-160℃. The machine is then subjected to melt extrusion, blow-up traction and cooling shaping in sequence. The film thickness is controlled to be 0.01-0.04 mm, thus obtaining a biodegradable mulch film reinforced with chitin blend.

[0033] In the above technical solution, the mixing method is not a simple single mixing, but a two-step mixing process. The compatibilizer and glycerin are first fully contacted and wetted with PBAT resin, and then chitin and additives are added. This can achieve uniform mixing and effective fusion of raw material components, thereby obtaining biodegradable mulch film masterbatch with uniform composition, ensuring the smooth progress of subsequent blown film process and the consistency of final mulch film quality.

[0034] The technical solution of the present invention achieves the following beneficial technical effects:

[0035] 1. The raw materials used in this invention are widely available. Chitosan can be extracted from waste materials such as shrimp and crab shells, realizing resource recycling. Through the combined action of compatibilizer and glycerol, chitosan is uniformly dispersed and the interface is enhanced in the PBAT matrix, significantly improving the overall performance of the biodegradable mulch film. In addition, the preparation method of this invention is mature and can be scaled up using conventional twin-screw extrusion and blown film equipment. The product quality is highly stable, providing a practical and feasible technical solution for the industrial application of biodegradable agricultural mulch film.

[0036] 2. This invention can effectively improve the compatibility between chitin and polybutylene terephthalate (PET) matrix. The chitin-blended biodegradable mulch film provided has excellent mechanical properties, controllable degradation, and antibacterial and pest-preventing functions. In terms of mechanical properties, a three-dimensional network structure with compatibilizers as network nodes was constructed, which can effectively transfer stress, enabling the tensile strength of the mulch film to reach over 18 MPa and the elongation at break to exceed 400%. In terms of antibacterial and pest control functions, the synergistic effect of chitosan and bamboo charcoal powder endows the mulch film with broad-spectrum antibacterial activity, with an inhibition rate of over 78% against soil-borne pathogens (Fusarium oxysporum), and a significant repellent effect against underground pests (such as grubs and cutworms), which can effectively reduce the amount of pesticides used. In terms of degradation controllability, the introduction of chitosan provides a "weak point" for degradation of the mulch film. By adjusting the chitosan content, the degradation cycle can be controlled, which can be precisely matched according to the growth cycle of different crops, avoiding premature degradation leading to loss of heat preservation and moisture retention functions, or soil residue problems caused by slow degradation. Attached Figure Description

[0037] Figure 1 The blown film machine (left) and the winding equipment (right) used in this invention;

[0038] Figure 2 A physical image of the chitin-reinforced biodegradable mulch film prepared according to this invention. Detailed Implementation

[0039] Example 1

[0040] A chitin-reinforced biodegradable mulch film is prepared from the following raw material components: 4 kg polybutylene terephthalate (PBAT), 0.9 kg chitin, 35 g compatibilizer, 30 g glycerin and 35 g additives, wherein the additives include 15 g lubricant, 10 g antioxidant, 5 g UV absorber and 5 g light stabilizer;

[0041] The lubricant is ethylene bis-stearamide; the antioxidant is a mixture of 5 g antioxidant 1010 and 5 g antioxidant 168; the ultraviolet absorber is UV234; and the light stabilizer is GW-622.

[0042] The compatibilizer is prepared as follows:

[0043] A1. Add 20 g of bamboo charcoal powder to 500 mL of 30% hydrogen peroxide solution, disperse by ultrasonication, and reflux for 3 h. Separate, wash and dry the product to obtain functionalized powder.

[0044] A2. Add 100 g of EVA to 1.9 kg of dichloroethane to obtain an EVA solution for later use; add the functionalized powder to 500 g of ethyl acetate and disperse it by ultrasonication to obtain a bamboo charcoal powder dispersion.

[0045] A3. Under stirring conditions, EVA solution is added to bamboo charcoal powder dispersion, heated and stirred for 30 min, then filtered and dried to obtain compatibilizer;

[0046] The above-mentioned chitin-reinforced biodegradable mulch film is prepared by the following steps:

[0047] S1. Add PBAT, compatibilizer and glycerin to a high-speed mixing tank and stir at 20 Hz for 5 minutes. Then add chitosan and adjuvants and continue stirring at 25 Hz for 5 minutes to obtain a premix.

[0048] S2. The premixed material is fed into a twin-screw extruder, with the feeding section at 120°C, the melting section at 150°C, and the die head section at 145°C, for extrusion granulation. After air cooling, biodegradable mulch film masterbatch is obtained.

[0049] S3. The biodegradable mulch film masterbatch is fed into a blown film machine. The temperatures of zones one to four are 145 ℃, 155 ℃, 155 ℃, and 155 ℃, respectively. The temperature of the three-way valve is 155 ℃, the temperature of the die head is 152 ℃, the blow-up ratio is 3.0, and the traction speed is 5 m / min. The process is carried out in sequence: melt extrusion, blow-up traction, cooling and shaping, and winding, to obtain a biodegradable mulch film reinforced with chitin blend with a film thickness of 0.025 mm.

[0050] Example 2

[0051] A chitin-reinforced biodegradable mulch film is prepared from the following raw material components: 4.1 kg polybutylene terephthalate (PBAT), 0.75 kg chitin, 50 g compatibilizer, 25 g glycerin and 75 g additives, wherein the additives include 40 g lubricant, 15 g antioxidant, 10 g light stabilizer and 10 g ultraviolet absorber;

[0052] The lubricant is pentylenetetrastearate; the antioxidant is a mixture of 10 g antioxidant 1076 and 5 g antioxidant 168; the ultraviolet absorber is UV326; and the light stabilizer is GW-944.

[0053] The compatibilizer is prepared as follows:

[0054] A1. Add 16 g of bamboo charcoal powder to 500 mL of 30% hydrogen peroxide solution, disperse by ultrasonication, and reflux for 3 h. Separate, wash and dry the product to obtain functionalized powder.

[0055] A2. Add 100 g of EVA to 1.2 kg of dichloroethane to obtain an EVA solution for later use; add the functionalized powder to 500 g of ethyl acetate and disperse it by ultrasonication to obtain a bamboo charcoal powder dispersion.

[0056] A3. Under stirring conditions, EVA solution is added to bamboo charcoal powder dispersion, heated and stirred for 30 min, then filtered and dried to obtain compatibilizer;

[0057] The above-mentioned chitin-reinforced biodegradable mulch film is prepared by the following steps:

[0058] S1. Add PBAT, compatibilizer and glycerin to a high-speed mixing tank and stir at 20 Hz for 5 minutes. Then add chitosan and adjuvants and continue stirring at 25 Hz for 5 minutes to obtain a premix.

[0059] S2. The premixed material is fed into a twin-screw extruder, with the feeding section at 120°C, the melting section at 150°C, and the die head section at 145°C, for extrusion granulation. After air cooling, biodegradable mulch film masterbatch is obtained.

[0060] S3. The biodegradable mulch film masterbatch is fed into a blown film machine. The temperatures of zones one to four are 145 ℃, 155 ℃, 155 ℃, and 155 ℃, respectively. The temperature of the three-way valve is 155 ℃, the temperature of the die head is 152 ℃, the blow-up ratio is 3.0, and the traction speed is 5 m / min. The process is carried out in sequence: melt extrusion, blow-up traction, cooling and shaping, and winding, to obtain a biodegradable mulch film reinforced with chitin blend with a film thickness of 0.025 mm.

[0061] Example 3

[0062] A biodegradable mulch film reinforced with chitin blend is prepared from the following raw material components: 3.75 kg polybutylene terephthalate (PBAT), 1 kg chitin, 100 g compatibilizer, 50 g glycerin, and 100 g additives; the additives include 50 g lubricant, 20 g antioxidant, 10 g light stabilizer, and 20 g UV absorber;

[0063] The lubricant is ethylene bis-stearamide; the antioxidant is a mixture of 10 g antioxidant 1010 and 10 g antioxidant 168; the ultraviolet absorber is UV234; and the light stabilizer is GW-622.

[0064] The compatibilizer is prepared as follows:

[0065] A1. Add 24 g of bamboo charcoal powder to 500 mL of 30% hydrogen peroxide solution, disperse by ultrasonication, and reflux for 3 h. Separate, wash and dry the product to obtain functionalized powder.

[0066] A2. Add 100 g of EVA to 2 kg of dichloroethane to prepare an EVA solution with a mass fraction of 3-10%; add the functionalized powder to 500 g of ethyl acetate and disperse it by ultrasonication to obtain a bamboo charcoal powder dispersion.

[0067] A3. Under stirring conditions, EVA solution is added to bamboo charcoal powder dispersion, heated and stirred for 30 min, then filtered and dried to obtain compatibilizer;

[0068] The above-mentioned chitin-reinforced biodegradable mulch film is prepared by the following steps:

[0069] S1. Add PBAT, compatibilizer and glycerin to a high-speed mixing tank and stir at 20 Hz for 5 minutes. Then add chitosan and adjuvants and continue stirring at 25 Hz for 5 minutes to obtain a premix.

[0070] S2. The premixed material is fed into a twin-screw extruder, with the feeding section at 120°C, the melting section at 150°C, and the die head section at 145°C, for extrusion granulation. After air cooling, biodegradable mulch film masterbatch is obtained.

[0071] S3. The biodegradable mulch film masterbatch is fed into a blown film machine. The temperatures of zones one to four are 145 ℃, 155 ℃, 155 ℃, and 155 ℃, respectively. The temperature of the three-way valve is 155 ℃, the temperature of the die head is 152 ℃, the blow-up ratio is 3.0, and the traction speed is 5 m / min. The process is carried out in sequence: melt extrusion, blow-up traction, cooling and shaping, and winding, to obtain a biodegradable mulch film reinforced with chitin blend with a film thickness of 0.025 mm.

[0072] Example 4

[0073] The only difference between this embodiment and Example 1 is that the bamboo charcoal powder was not functionalized during the preparation of the compatibilizer. The specific preparation method is as follows:

[0074] A1. Add 20 g of bamboo charcoal powder to 500 g of ethyl acetate and disperse by ultrasonication to obtain a bamboo charcoal powder dispersion.

[0075] A2. Add 100 g of EVA to 1.9 kg of dichloroethane to obtain an EVA solution;

[0076] A3. Under stirring conditions, EVA solution is added to bamboo charcoal powder dispersion, heated and stirred for 30 min, then filtered and dried to obtain compatibilizer.

[0077] Comparative Example 1

[0078] The only difference between this comparative example and Example 1 is that glycerol was not added to the raw material components of the chitosan-reinforced biodegradable mulch film, as detailed below:

[0079] A chitin-reinforced biodegradable mulch film is prepared from the following raw material components: 4 kg polybutylene terephthalate (PBAT), 0.9 kg chitin, 35 g compatibilizer and 35 g additives, wherein the additives include 15 g lubricant, 10 g antioxidant, 5 g UV absorber and 5 g light stabilizer.

[0080] The lubricant is ethylene bis-stearamide; the antioxidant is a mixture of 5 g antioxidant 1010 and 5 g antioxidant 168; the ultraviolet absorber is UV234; and the light stabilizer is GW-622.

[0081] The compatibilizer is prepared as follows:

[0082] A1. Add 20 g of bamboo charcoal powder to 500 mL of 30% hydrogen peroxide solution, disperse by ultrasonication, and reflux for 3 h. Separate, wash and dry the product to obtain functionalized powder.

[0083] A2. Add 100 g of EVA to 1.9 kg of dichloroethane to obtain an EVA solution for later use; add the functionalized powder to 500 g of ethyl acetate and disperse it by ultrasonication to obtain a bamboo charcoal powder dispersion.

[0084] A3. Under stirring conditions, EVA solution is added to bamboo charcoal powder dispersion, heated and stirred for 30 min, then filtered and dried to obtain compatibilizer;

[0085] The above-mentioned chitin-reinforced biodegradable mulch film is prepared by the following steps:

[0086] S1. Add PBAT and compatibilizer to a high-speed mixing vessel and stir at 20Hz for 5 minutes. Then add chitosan and additives and continue stirring at 25Hz for 5 minutes to obtain a premix.

[0087] S2. The premixed material is fed into a twin-screw extruder, with the feeding section at 120°C, the melting section at 150°C, and the die head section at 145°C, for extrusion granulation. After air cooling, biodegradable mulch film masterbatch is obtained.

[0088] S3. The biodegradable mulch film masterbatch is fed into a blown film machine. The temperatures of zones one to four are 145 ℃, 155 ℃, 155 ℃, and 155 ℃, respectively. The temperature of the three-way valve is 155 ℃, the temperature of the die head is 152 ℃, the blow-up ratio is 3.0, and the traction speed is 5 m / min. The process is carried out in sequence: melt extrusion, blow-up traction, cooling and shaping, and winding, to obtain a biodegradable mulch film reinforced with chitin blend with a film thickness of 0.025 mm.

[0089] Comparative Example 2

[0090] The difference between this comparative example and Example 1 is that glycerol was not added to the raw material components of the chitosan-reinforced biodegradable mulch film, and the bamboo charcoal powder was not functionalized during the preparation of the compatibilizer, as detailed below:

[0091] A chitin-reinforced biodegradable mulch film is prepared from the following raw material components: 4 kg polybutylene terephthalate (PBAT), 0.9 kg chitin, 35 g compatibilizer and 35 g additives, wherein the additives include 15 g lubricant, 10 g antioxidant, 5 g UV absorber and 5 g light stabilizer.

[0092] The lubricant is ethylene bis-stearamide; the antioxidant is a mixture of 5 g antioxidant 1010 and 5 g antioxidant 168; the ultraviolet absorber is UV234; and the light stabilizer is GW-622.

[0093] The compatibilizer is prepared as follows:

[0094] A1. Add 20 g of bamboo charcoal powder to 500 g of ethyl acetate and disperse by ultrasonication to obtain a bamboo charcoal powder dispersion.

[0095] A2. Add 100 g of EVA to 1.9 kg of dichloroethane to obtain an EVA solution;

[0096] A3. Under stirring conditions, EVA solution is added to bamboo charcoal powder dispersion, heated and stirred for 30 min, then filtered and dried to obtain compatibilizer;

[0097] The above-mentioned chitin-reinforced biodegradable mulch film is prepared by the following steps:

[0098] S1. Add PBAT and compatibilizer to a high-speed mixing vessel and stir at 20Hz for 5 minutes. Then add chitosan and additives and continue stirring at 25Hz for 5 minutes to obtain a premix.

[0099] S2. The premixed material is fed into a twin-screw extruder, with the feeding section at 120°C, the melting section at 150°C, and the die head section at 145°C, for extrusion granulation. After air cooling, biodegradable mulch film masterbatch is obtained.

[0100] S3. The biodegradable mulch film masterbatch is fed into a blown film machine. The temperatures of zones one to four are 145 ℃, 155 ℃, 155 ℃, and 155 ℃, respectively. The temperature of the three-way valve is 155 ℃, the temperature of the die head is 152 ℃, the blow-up ratio is 3.0, and the traction speed is 5 m / min. The process is carried out in sequence: melt extrusion, blow-up traction, cooling and shaping, and winding, to obtain a biodegradable mulch film reinforced with chitin blend with a film thickness of 0.025 mm.

[0101] Proof of effectiveness

[0102] The chitin-reinforced biodegradable mulch films prepared in Examples 1-4 and Comparative Examples 1-2 were used to make mulch film samples, and their mechanical and antibacterial properties were tested. The specific test results are shown in Table 1.

[0103] I. Mechanical properties: The tensile strength and elongation at break of each group of mulch film samples were tested according to GB / T 1040 standard.

[0104] II. Antibacterial properties: The antibacterial rate of each group of mulch film samples against Fusarium oxysporum was tested according to GB / T 37206-2018 standard.

[0105] Table 1

[0106] Group Tensile strength / MPa Elongation at break / % Antibacterial rate / % Example 1 22.6 458.2 92.1 Example 2 22.2 436.4 91.7 Example 3 22.5 449.7 93.2 Example 4 20.7 441.1 89.8 Comparative Example 1 19.2 345.9 81.1 Comparative Example 2 17.7 328.3 80.3

[0107] As can be seen from Examples 1-4 and Comparative Examples 1-2, and in conjunction with the data in Table 1, the mulch film samples prepared in Examples 1-4 have a tensile strength of over 20.7 MPa, an elongation at break of over 441.1%, and an antibacterial rate of over 89.8%. Their overall performance is significantly better than that of the comparative examples, indicating that the chitin-reinforced biodegradable mulch film provided by this invention has both excellent mechanical properties and antibacterial effects.

[0108] Obviously, the above embodiments are merely illustrative examples for clear explanation and are not intended to limit the implementation. Those skilled in the art will recognize that other variations or modifications can be made based on the above description. It is neither necessary nor possible to exhaustively list all possible implementations here. However, obvious variations or modifications derived therefrom are still within the scope of protection of the claims of this patent application.

Claims

1. A biodegradable mulch film reinforced with chitin blend, characterized in that, It is prepared by weight from the following raw material components: 70-90 parts of polybutylene terephthalate-adipate, 10-20 parts of chitosan, 0.5-2 parts of compatibilizer, 0.2-1 parts of glycerin and 0.5-2 parts of additives.

2. The chitin-reinforced biodegradable mulch film according to claim 1, characterized in that, The product is prepared by weight from the following raw material components: 80 parts of polybutylene terephthalate-adipate, 18 parts of chitosan, 0.7 parts of compatibilizer, 0.6 parts of glycerin, and 0.7 parts of additives.

3. The chitin-reinforced biodegradable mulch film according to claim 1, characterized in that, The additive is one or a combination of two or more of the following: lubricant, antioxidant, light stabilizer and ultraviolet absorber.

4. The chitin-reinforced biodegradable mulch film according to claim 3, characterized in that, The lubricant is one or a combination of two of ethylene bis-stearamide and pentylenetetrastearate.

5. The chitin-blended and reinforced biodegradable mulch film according to claim 3, characterized in that, The antioxidant is a combination of hindered phenolic antioxidant and antioxidant 168, wherein the hindered phenolic antioxidant is one or a combination of two of antioxidant 1010 and antioxidant 1076.

6. The chitin-blended and reinforced biodegradable mulch film according to claim 3, characterized in that, The ultraviolet absorber is one or a combination of two of UV234 and UV326.

7. The chitin-blended and reinforced biodegradable mulch film according to claim 3, characterized in that, The light stabilizer is one or a combination of GW-622 and GW-944.

8. The chitin-reinforced biodegradable mulch film according to claim 1, characterized in that, The compatibilizer is a composite of bamboo charcoal powder and ethylene-vinyl acetate copolymer.

9. The chitin-reinforced biodegradable mulch film according to claim 1, characterized in that, The compatibilizer is prepared as follows: A1. Add bamboo charcoal powder to a hydrogen peroxide solution with a mass fraction of 20-40%, disperse it by ultrasonication, and then reflux for 2-4 hours. Separate, wash, and dry the product to obtain functionalized powder. A2. Add ethylene-vinyl acetate copolymer to dichloroethane to prepare an ethylene-vinyl acetate copolymer solution with a mass fraction of 3-10% for later use; add functionalized powder to ethyl acetate and ultrasonically disperse to obtain bamboo charcoal powder dispersion. A3. Under stirring conditions, the ethylene-vinyl acetate copolymer solution is added to the bamboo charcoal powder dispersion, heated and stirred for 20-40 minutes, then filtered and dried to obtain the compatibilizer.

10. A method for preparing a chitin-reinforced biodegradable mulch film, used to prepare the chitin-reinforced biodegradable mulch film according to any one of claims 1-9, characterized in that, Includes the following steps: S1. Add PBAT, compatibilizer and glycerin to a high-speed mixing tank and stir for 4-6 minutes. Then add chitosan and adjuvants and continue stirring for 3-8 minutes to obtain a premix. S2. Feed the premixed material into a twin-screw extruder, with an extrusion temperature range of 90-160℃, and granulate it by extrusion. After air cooling, obtain biodegradable mulch film masterbatch. S3. The biodegradable mulch film masterbatch is fed into a blown film machine. The temperature range of the blown film machine cylinder is 100-160℃. The machine is then subjected to melt extrusion, blow-up traction and cooling shaping in sequence. The film thickness is controlled to be 0.01-0.04 mm, thus obtaining a biodegradable mulch film reinforced with chitin blend.

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