Application of a seven-layer coextruded agricultural film in the field of pesticide resistance and its production process

Abstract

The present invention provides an application of a seven-layer co-extruded agricultural film in the field of pesticide resistance and its production process, belonging to the technical field of agricultural film preparation. The agricultural film of the present invention includes outer layer 1, transition layer 1, heat preservation layer 1, barrier core layer, heat preservation layer 2, transition layer 2, and outer layer 2; the raw materials of outer layer 1 include polylactic acid, metallocene linear low-density polyethylene, compatibilizer, toughening agent, heat insulation masterbatch, and anti-aging masterbatch; the raw materials of outer layer 2 include polylactic acid, metallocene linear low-density polyethylene, compatibilizer, heat insulation masterbatch, and anti-aging masterbatch; the raw materials of transition layer 1 and transition layer 2 include low-density polyethylene, metallocene linear low-density polyethylene, anti-aging masterbatch, and heat insulation masterbatch; the raw materials of heat preservation layer 1 and heat preservation layer 2 include ethylene-vinyl acetate copolymer resin, anti-aging masterbatch, and heat insulation masterbatch; the raw materials of the barrier core layer include ethylene-vinyl alcohol copolymer, modified organic montmorillonite, and anti-aging masterbatch. The agricultural film of the present invention has properties such as high barrier, pesticide resistance, and degradability.

Description

Technical Field

[0001] The present invention relates to the technical field of agricultural film preparation, and specifically relates to the application of a seven-layer co-extruded agricultural film in the field of pesticide resistance and its production process. Background Art

[0002] Under the background of the accelerating global agricultural modernization process, polyolefin agricultural films have become essential important materials for modern agricultural production due to their excellent properties. The polyolefin agricultural film industry in China is large in scale, and its annual output and consumption have long ranked among the top in the world. Some regions with developed vegetable and fruit planting industries have gradually become concentrated consumption areas for polyolefin agricultural films.

[0003] Traditional polyethylene agricultural films have obvious shortcomings in terms of strength, weather resistance, functionality, and environmental protection. With the increasing demand for agricultural modernization, they are gradually developing towards multi-functional compounding (such as anti-aging, anti-fogging, heat preservation, degradable) and greening to meet the needs of efficient and sustainable agriculture.

[0004] The prior art with the publication number CN119489608A discloses a coated polyolefin seven-layer co-extruded light conversion, dust-proof, high heat-preserving, pesticide-resistant, long-acting drip-eliminating and fog-eliminating greenhouse film and its preparation method. The greenhouse film consists of an inner 1 layer of dust-proof and anti-aging layer, an inner 2 layer of heat-preserving, anti-aging and dust-proof reserve layer, an inner 3 layer of high heat-preserving and anti-aging layer, a middle layer of light conversion layer, an outer 3 layer of high heat-preserving and anti-aging layer, an outer 2 layer of heat-preserving and anti-aging layer, an outer 1 layer of modified bonding and anti-aging layer, and a coating layer of long-acting drip-eliminating and fog-eliminating layer. First, the above-mentioned agricultural film achieves the pesticide resistance effect by adding an anti-aging masterbatch containing an acid-resistant light stabilizer, but it cannot specifically block different types of pesticides, and there may be risks such as the decline of the light stabilizer activity and the attenuation of pesticide resistance performance after long-term use. Second, there are certain environmental protection problems. Although long-term use is achieved, the core material is still polyolefin, which is difficult to degrade naturally after being discarded. The technology does not involve a degradable modification scheme or a recycling treatment technology, which does not meet the current requirements of agricultural green development.

[0005] At present, although biodegradable mulch films can replace traditional polyethylene agricultural films to reduce environmental pollution and the pressure on the environment in agricultural production. However, the biodegradable films in the prior art generally have the following problems: insufficient mechanical properties such as tensile strength and tear resistance; shortfalls in functional properties such as barrier properties and heat preservation properties.

[0006] Therefore, there is an urgent need to develop an agricultural film with good mechanical properties, high barrier properties, good heat preservation properties, pesticide resistance, and degradability. Summary of the Invention

[0007] To solve the above problems existing in the prior art, the present invention provides an application of a seven-layer coextruded agricultural film in the field of pesticide resistance and its production process, achieving the following invention purposes: preparing an agricultural film with excellent properties such as high barrier, high heat preservation, pesticide resistance, and degradability.

[0008] To achieve the above invention purposes, the technical solution adopted by the present invention is:

[0009] An application of a seven-layer coextruded agricultural film in the field of pesticide resistance, wherein the agricultural film is composed of outer layer one, transition layer one, heat preservation layer one, barrier core layer, heat preservation layer two, transition layer two, and outer layer two.

[0010] The raw material components of outer layer one include: 40-50 parts of polylactic acid, 40-50 parts of metallocene linear low-density polyethylene, 3-4 parts of compatibilizer, 2-4 parts of toughening agent, 3-5 parts of heat insulation masterbatch, and 2-4 parts of anti-aging masterbatch;

[0011] The compositions of transition layer one and transition layer two are the same, and the raw material components include: 35-45 parts of low-density polyethylene, 40-50 parts of metallocene linear low-density polyethylene, 7-10 parts of anti-aging masterbatch, and 5-8 parts of heat insulation masterbatch;

[0012] The compositions of heat preservation layer one and heat preservation layer two are the same, and the raw material components include: 80-85 parts of ethylene-vinyl acetate copolymer resin, 5-10 parts of anti-aging masterbatch, and 8-12 parts of heat insulation masterbatch;

[0013] The raw material components of outer layer two include: 40-55 parts of polylactic acid, 35-45 parts of metallocene linear low-density polyethylene, 3-5 parts of compatibilizer, 3-5 parts of heat insulation masterbatch, and 2-4 parts of anti-aging masterbatch;

[0014] The raw material components of the barrier core layer include: 80-90 parts of ethylene-vinyl alcohol copolymer, 6-10 parts of modified organic montmorillonite, and 3-10 parts of anti-aging masterbatch. The organic montmorillonite is quaternary ammonium salt modified montmorillonite.

[0015] Among them, the anti-aging masterbatch is prepared from the following raw material components in the following ratio: 90-94 parts of low-density polyethylene, 4-6 parts of light stabilizer, and 2-4 parts of antioxidant;

[0016] The heat insulation masterbatch is prepared from the following raw material components in the following ratio: 45-55 parts of low-density polyethylene, 40-50 parts of nano kaolin, 1-3 parts of silane coupling agent, and 2-4 parts of dispersant.

[0017] All the above parts are in parts by weight.

[0018] The density of the polylactic acid is 1.22-1.26 g / cm³.

[0019] The density of the metallocene linear low-density polyethylene is 0.914 - 0.922 g / cm³.

[0020] The density of the low-density polyethylene is 0.917 - 0.925 g / cm 3 .

[0021] The compatibilizer is maleic anhydride grafted polyethylene.

[0022] The toughening agent is a polyolefin elastomer.

[0023] The light stabilizer is a hindered amine light stabilizer.

[0024] The dispersant is polyethylene wax.

[0025] The antioxidant is a compound antioxidant of hindered phenols and phosphites.

[0026] A production process of a seven-layer co-extruded agricultural film applied in the anti-pesticide field, including the preparation of anti-aging masterbatch, the preparation of heat-insulating masterbatch, the modification of organic montmorillonite, the premixing of barrier core layer raw materials and the co-extrusion molding step;

[0027] The preparation of the anti-aging masterbatch: Mix the light stabilizer and the antioxidant, add low-density polyethylene, and after mixing, melt and extrude through an extruder; The control parameters of the extruder: the feeding section temperature is set at 120 - 130 °C, the melting section temperature is 140 - 160 °C, the mixing section temperature is 150 - 170 °C, and the die head temperature is 160 - 180 °C.

[0028] The preparation of the heat-insulating masterbatch: Mix the nano kaolin and the silane coupling agent solution evenly, and mix with low-density polyethylene and the dispersant; Melt and extrude through a twin-screw extruder, the feeding section temperature is set at 120 - 130 °C, the melting section temperature is 140 - 160 °C, the mixing section temperature is 150 - 170 °C, and the die head temperature is 160 - 180 °C.

[0029] The modification of the organic montmorillonite: Add the organic montmorillonite into anhydrous N,N-dimethylformamide to form a suspension; Add polymethylene diphenyl diisocyanate into the suspension, add a catalyst, stir and heat up to 50 - 70 °C, react for 2 - 4 hours to obtain modified organic montmorillonite; The mass ratio of the organic montmorillonite to N,N-dimethylformamide is 1:(10 - 15). The mass ratio of the polymethylene diphenyl diisocyanate to the organic montmorillonite is 1:(5 - 10). The catalyst is dibutyltin dilaurate, and the mass of the catalyst is 0.5% - 1% of the mass of the polymethylene diphenyl diisocyanate. The organic montmorillonite is quaternary ammonium salt modified montmorillonite.

[0030] Pre - mixing of the raw materials for the barrier core layer: The modified organic montmorillonite and ethylene - vinyl alcohol copolymer are melt - extruded. The temperature of the feeding section of the extruder is 160 - 170 °C, the melting section is 190 - 210 °C, the mixing section is 200 - 220 °C, the head temperature is 180 - 190 °C. After extrusion, it is pelletized and mixed with the anti - aging masterbatch to obtain the pre - mixed material for the barrier core layer.

[0031] Co - extrusion molding: The seven - layer raw materials are pre - mixed respectively and then extruded through an extruder. The feeding section is 115 - 190 °C, the compression section is 150 - 200 °C, the melting section is 180 - 220 °C, the homogenization section is 180 - 220 °C, the connector is 180 - 210 °C, the transition section is 190 - 210 °C, the distributor is 205 - 215 °C, and the die head outlet is 205 - 215 °C.

[0032] The seven - layer co - extruded agricultural film: The thickness ratio of outer layer 1, transition layer 1, heat - preservation layer 1, barrier core layer, heat - preservation layer 2, transition layer 2, and outer layer 2 is 1.25:1:1.25:1.5:1.25:1:1.1.

[0033] The present invention has the following beneficial effects:

[0034] (1) In the application of the seven - layer co - extruded agricultural film of the present invention in the field of anti - pesticides, the thickness of the agricultural film is 0.10 mm ± 5%. The light transmittance is above 89%, the haze is below 13%, and the infrared barrier rate is above 81%, significantly improving the optical properties of the film. In terms of mechanical properties, the transverse tensile strength is above 39 MPa, the longitudinal tensile strength is above 41 MPa, and the right - angle tear strength is above 124 N / mm, effectively improving the tear - resistance ability and the ability to resist external impacts.

[0035] (2) In the application of the seven - layer co - extruded agricultural film of the present invention in the field of anti - pesticides, the agricultural film can achieve more than 55% degradation within 6 months. With the increase of the PLA addition amount, the degradation efficiency is higher. The degradation rate of the film can be controllably adjusted by controlling the PLA addition amount.

[0036] (3) In the application of the seven - layer co - extruded agricultural film of the present invention in the field of anti - pesticides, the barrier efficiency of the agricultural film for organophosphorus pesticides, pyrethroid pesticides, and triazole pesticides has been significantly enhanced, reaching a barrier rate of above 94%, showing excellent performance in pesticide barrier. Specific embodiments

[0037] To make the purpose, technical solutions, and advantages of the present invention clearer, the following will further describe the embodiments of the present invention in detail. It should be understood that the specific embodiments described here are only for explaining and understanding the present invention, and do not limit the present invention.

[0038] Example 1 Application of a Seven-Layer Coextruded Agricultural Film in the Field of Pesticide Resistance and Its Production Process

[0039] A seven-layer coextruded agricultural film applied in the field of pesticide resistance is composed of outer layer 1, transition layer 1, thermal insulation layer 1, barrier core layer, thermal insulation layer 2, transition layer 2, and outer layer 2.

[0040] The raw material components of outer layer 1 include: 50 parts of polylactic acid, 40 parts of metallocene linear low-density polyethylene, 3 parts of compatibilizer, 4 parts of toughening agent, 3 parts of heat-insulating masterbatch, and 4 parts of anti-aging masterbatch; the compatibilizer is maleic anhydride grafted polyethylene; the toughening agent is polyolefin elastomer.

[0041] The compositions of transition layer 1 and transition layer 2 are the same, and the raw material components include: 35 parts of low-density polyethylene, 50 parts of metallocene linear low-density polyethylene, 7 parts of anti-aging masterbatch, and 8 parts of heat-insulating masterbatch.

[0042] The compositions of thermal insulation layer 1 and thermal insulation layer 2 are the same, and the raw material components include: 80 parts of ethylene-vinyl acetate copolymer resin, 10 parts of anti-aging masterbatch, and 8 parts of heat-insulating masterbatch.

[0043] The raw material components of the barrier core layer include: 90 parts of ethylene-vinyl alcohol copolymer, 10 parts of modified organic montmorillonite, and 3 parts of anti-aging masterbatch; the organic montmorillonite is quaternary ammonium salt modified montmorillonite, and the specific model is Nanomer® I.44P produced by American nanomer company.

[0044] The raw material components of outer layer 2 include: 55 parts of polylactic acid, 35 parts of metallocene linear low-density polyethylene, 3 parts of compatibilizer, 5 parts of heat-insulating masterbatch, and 2 parts of anti-aging masterbatch; the compatibilizer is maleic anhydride grafted polyethylene.

[0045] Among them, the raw material components of the anti-aging masterbatch include: 90 parts of low-density polyethylene, 6 parts of light stabilizer, and 4 parts of antioxidant; the light stabilizer is a hindered amine light stabilizer NOR356. The antioxidant is a composite antioxidant of hindered phenols and phosphites, and the model is B225.

[0046] The raw material components of the heat-insulating masterbatch include: 45 parts of low-density polyethylene, 50 parts of nano kaolin, 1 part of silane coupling agent, and 4 parts of dispersant. The model of the silane coupling agent is KH550. The model of the nano kaolin is KCR-66. The model of dibutyltin dilaurate is Evonik T12. The dispersant is polyethylene wax.

[0047] All the above parts are in parts by weight.

[0048] The production process of a seven-layer coextruded agricultural film applied in the field of pesticide resistance includes the following steps:

[0049] Step 1: Preparation of the anti-aging masterbatch

[0050] Add a light stabilizer and an antioxidant to a high-speed mixer and mix them evenly. Add low-density polyethylene and stir to mix evenly to form a premix. Add the premix to a twin-screw extruder, set the temperature parameters of the extruder, set the feeding section temperature at 120 °C, the melting section temperature at 140 °C, the mixing section temperature at 150 °C, and the head temperature at 160 °C. Let the premix be fully melted and kneaded in the extruder, and the molten material extruded from the extruder is air-cooled, and the air ring cooling temperature is 20 °C. The cooled strip material enters a granulator for granulation to produce granular anti-aging masterbatch.

[0051] Step Two: Preparation of heat-insulating masterbatch

[0052] Mix the nano kaolin and the silane coupling agent solution evenly, and add them to a high-speed mixer together with low-density polyethylene and polyethylene wax, and mix evenly. The silane coupling agent solution is an ethanol solution of the silane coupling agent, and the content of the silane coupling agent is 20% (mass percentage).

[0053] Add the mixed material to a twin-screw extruder for melt extrusion. The temperature of the extruder is set to gradually increase from the feeding section to the head, the feeding section temperature is set at 120 °C, the melting section temperature is 140 °C, the mixing section temperature is 150 °C, and the head temperature is 160 °C. The strip material extruded from the head is air-cooled, the air ring cooling temperature is 20 °C, and the cooled material enters a granulator for granulation to produce granular heat-insulating masterbatch.

[0054] Step Three: Modification of organophilic montmorillonite

[0055] Add organophilic montmorillonite to anhydrous N,N-dimethylformamide and stir evenly to form a suspension. The mass ratio of organophilic montmorillonite to N,N-dimethylformamide is 1:10. Slowly add polymethylene diphenyl diisocyanate to the suspension. The mass ratio of polymethylene diphenyl diisocyanate to organophilic montmorillonite is usually 1:5. Add the catalyst dibutyltin dilaurate, and the mass of the catalyst is 1% of the mass of polymethylene diphenyl diisocyanate. Stir at room temperature for 30 minutes, then raise the temperature to 50 °C, react for 2 hours, then filter, and then vacuum dry at 60 °C for 12 hours to obtain modified organophilic montmorillonite.

[0056] Step Four: Premixing of barrier core layer raw materials

[0057] Add the modified organophilic montmorillonite and ethylene-vinyl alcohol copolymer to a twin-screw extruder for melt extrusion. The feeding section temperature of the extruder is 160 °C, the melting section temperature is 190 °C, the mixing section temperature is 200 °C, and the head temperature is 180 °C. The strip material extruded from the head is air-cooled, the air ring cooling temperature is 20 °C, and the cooled material enters a granulator for granulation. After granulation, it is mixed evenly with the anti-aging masterbatch to obtain a barrier core layer premix for standby.

[0058] The dosage of each raw material in the barrier core layer premix is as shown in the content of the raw material components in the formula.

[0059] Step Five: Coextrusion Molding

[0060] Mix the raw materials of the first outer layer, the first transition layer, the first insulation layer, the second insulation layer, the second transition layer, and the second outer layer according to the formula respectively to form the premixes for each layer.

[0061] Add the premixes of the seven layers (the first outer layer, the first transition layer, the first insulation layer, the barrier core layer, the second insulation layer, the second transition layer, and the second outer layer) into a seven-layer coextrusion extruder respectively. The temperature process conditions of each zone in the extruder are shown in Table 1 in detail. After extrusion from the die head, blow molding, cooling, corona treatment, and drying are carried out, and finally a seven-layer coextruded agricultural film applied in the anti-pesticide field is obtained. The blow molding adopted: the blow-up ratio is 3.0, and the traction speed is 15 m / min; Cooling: the cooling temperature of the air ring is 20 °C; Corona treatment: the corona treatment power is 10 kW, and the treatment speed is 15 m / min; Drying: the drying temperature is 60 °C. The thickness of the obtained product is 0.10 mm ± 5%, and the thickness ratio of the first outer layer, the first transition layer, the first insulation layer, the barrier core layer, the second insulation layer, the second transition layer, and the second outer layer is 1.25:1:1.25:1.5:1.25:1:1.1.

[0062] Table 1 Temperature process conditions of each zone in the extruder

[0063] The seven-layer coextruded anti-pesticide high-barrier agricultural film prepared in this example is suitable for the planting of leafy vegetables and multi-crop planting crops.

[0064] Example 2 Application of a seven-layer coextruded agricultural film in the anti-pesticide field and its production process

[0065] A seven-layer coextruded agricultural film applied in the anti-pesticide field is composed of the first outer layer, the first transition layer, the first insulation layer, the barrier core layer, the second insulation layer, the second transition layer, and the second outer layer.

[0066] The raw material components of the first outer layer include: 45 parts of polylactic acid, 45 parts of metallocene linear low-density polyethylene, 4 parts of compatibilizer, 3 parts of toughening agent, 4 parts of heat insulation masterbatch, and 3 parts of anti-aging masterbatch; The compatibilizer is maleic anhydride grafted polyethylene; The toughening agent is polyolefin elastomer.

[0067] The first transition layer and the second transition layer have the same composition, and the raw material components include: 40 parts of low-density polyethylene, 45 parts of metallocene linear low-density polyethylene, 8 parts of anti-aging masterbatch, and 7 parts of heat insulation masterbatch.

[0068] The components of Insulation Layer 1 and Insulation Layer 2 are the same. The raw material components include: 83 parts of ethylene-vinyl acetate copolymer resin, 7 parts of anti-aging masterbatch, and 10 parts of heat-insulating masterbatch.

[0069] The raw material components of the barrier core layer include: 85 parts of ethylene-vinyl alcohol copolymer, 8 parts of modified organic montmorillonite, and 7 parts of anti-aging masterbatch; the organic montmorillonite is quaternary ammonium salt modified montmorillonite, and the specific model is Nanomer® I.44P produced by American nanomer company.

[0070] The raw material components of Outer Layer 2 include: 48 parts of polylactic acid, 40 parts of metallocene linear low-density polyethylene, 4 parts of compatibilizer, 4 parts of heat-insulating masterbatch, and 3 parts of anti-aging masterbatch. The compatibilizer is maleic anhydride grafted polyethylene.

[0071] Among them, the raw material components of the anti-aging masterbatch include: 92 parts of low-density polyethylene, 5 parts of light stabilizer, and 3 parts of antioxidant; the light stabilizer is a hindered amine light stabilizer NOR356. The antioxidant is a compound antioxidant of hindered phenols and phosphites, and the model is B225.

[0072] The raw material components of the heat-insulating masterbatch include: 50 parts of low-density polyethylene, 45 parts of nano kaolin, 2 parts of silane coupling agent, and 3 parts of dispersant. The model of the silane coupling agent is KH550. The model of the nano kaolin is KCR-66. The model of dibutyltin dilaurate is Evonik T12. The dispersant is polyethylene wax.

[0073] All the above parts are in parts by weight.

[0074] A production process of a seven-layer co-extruded agricultural film applied in the anti-pesticide field includes the following steps:

[0075] Step 1: Preparation of anti-aging masterbatch

[0076] Add the light stabilizer and antioxidant into a high-speed mixer and mix evenly. Then add low-density polyethylene and stir to mix evenly to form a premix. Add the premix into a twin-screw extruder, set the temperature parameters of the extruder, the feeding section temperature is set at 125 °C, the melting section temperature is 150 °C, the mixing section temperature is 160 °C, and the head temperature is 170 °C. Make the premix fully melt and knead in the extruder, and the molten material extruded from the extruder is air-cooled, and the air ring cooling temperature is 20 °C. The cooled strip enters a granulator for granulation to make granular anti-aging masterbatch.

[0077] Step 2: Preparation of heat-insulating masterbatch

[0078] Mix the nano kaolin evenly with the silane coupling agent solution, and add it together with low-density polyethylene and polyethylene wax into a high-speed mixer and mix evenly. The silane coupling agent solution is an ethanol solution of the silane coupling agent, and the content of the silane coupling agent is 20% (mass percentage).

[0079] Add the mixed material into a twin-screw extruder for melt extrusion. The temperature of the extruder is set to gradually increase from the feeding section to the die head. The temperature of the feeding section is set at 125 °C, the melting section is 150 °C, the mixing section is 160 °C, and the die head is 170 °C. The strip-shaped material extruded from the die head is air-cooled, the air ring cooling temperature is 20 °C, and the cooled material enters a granulator for granulation to produce granular heat-insulating masterbatch.

[0080] Step Three: Modification of Organophilic Montmorillonite

[0081] Add the organophilic montmorillonite into anhydrous N,N-dimethylformamide, stir evenly to form a suspension, and the mass ratio of the organophilic montmorillonite to N,N-dimethylformamide is 1:13. Slowly add polymethylene polyphenyl isocyanate into the suspension, and the mass ratio of polymethylene polyphenyl isocyanate to the organophilic montmorillonite is usually 1:8. Add the catalyst dibutyltin dilaurate, and the mass of the catalyst is 0.8% of the mass of polymethylene polyphenyl isocyanate. Stir at room temperature for 30 minutes, then raise the temperature to 60 °C, react for 3 hours, then filter, and then vacuum dry at 60 °C for 12 hours to obtain modified organophilic montmorillonite.

[0082] Step Four: Premixing of Barrier Core Layer Raw Materials

[0083] Add the modified organophilic montmorillonite and ethylene-vinyl alcohol copolymer into a twin-screw extruder for melt extrusion. The temperature of the feeding section of the extruder is 165 °C, the melting section is 200 °C, the mixing section is 210 °C, and the die head is 185 °C. The strip-shaped material extruded from the die head is air-cooled, the air ring cooling temperature is 20 °C, and the cooled material enters a granulator for granulation. After granulation, it is mixed evenly with the anti-aging masterbatch to obtain the barrier core layer premix for standby.

[0084] The dosage of each raw material in the barrier core layer premix is as shown in the content of the raw material components in the formula.

[0085] Step Five: Coextrusion Molding

[0086] Mix the raw materials of the first outer layer, the first transition layer, the first insulation layer, the second insulation layer, the second transition layer, and the second outer layer respectively according to the formula to form the premix of each layer;

[0087] Add the seven-layer (outer layer 1, transition layer 1, insulation layer 1, barrier core layer, insulation layer 2, transition layer 2, outer layer 2) premix into a seven-layer co-extrusion extruder respectively. The temperature process conditions in each zone of the extruder are shown in Table 2 in detail. After extrusion from the die head, blow molding, cooling, corona treatment, and drying are carried out, and finally a seven-layer co-extruded agricultural film applied in the anti-pesticide field is obtained. The blow molding adopted: the blow-up ratio is 3.0, and the traction speed is 15 m / min; cooling: the cooling temperature of the air ring is 20 °C; corona treatment: the corona treatment power is 10 kW, and the treatment speed is 15 m / min; drying: the drying temperature is 60 °C.

[0088] The thickness of the obtained product is 0.10 mm ± 5%, and the thickness ratio of outer layer 1, transition layer 1, insulation layer 1, barrier core layer, insulation layer 2, transition layer 2, and outer layer 2 is 1.25:1:1.25:1.5:1.25:1:1.1.

[0089] Table 2 Temperature process conditions in each zone of the extruder

[0090] The agricultural film prepared in this example is suitable for the planting of solanaceous crops such as tomatoes and peppers, as well as the use in organic certified farms.

[0091] Example 3 Application of a seven-layer co-extruded agricultural film in the anti-pesticide field and its production process

[0092] A seven-layer co-extruded agricultural film applied in the anti-pesticide field is composed of outer layer 1, transition layer 1, insulation layer 1, barrier core layer, insulation layer 2, transition layer 2, and outer layer 2.

[0093] The raw material components of outer layer 1 include: 40 parts of polylactic acid, 50 parts of metallocene linear low-density polyethylene, 4 parts of compatibilizer, 2 parts of toughening agent, 5 parts of heat insulation masterbatch, and 2 parts of anti-aging masterbatch; the compatibilizer is maleic anhydride grafted polyethylene; the toughening agent is polyolefin elastomer.

[0094] The compositions of transition layer 1 and transition layer 2 are the same, and the raw material components include: 45 parts of low-density polyethylene, 40 parts of metallocene linear low-density polyethylene, 10 parts of anti-aging masterbatch, and 5 parts of heat insulation masterbatch.

[0095] The compositions of insulation layer 1 and insulation layer 2 are the same, and the raw material components include: 85 parts of ethylene-vinyl acetate copolymer resin, 5 parts of anti-aging masterbatch, and 12 parts of heat insulation masterbatch.

[0096] The raw material components of the barrier core layer include: 80 parts of ethylene-vinyl alcohol copolymer, 6 parts of modified organic montmorillonite, and 10 parts of anti-aging masterbatch; the organic montmorillonite is quaternary ammonium salt modified montmorillonite, and the specific model is Nanomer® I.44P produced by American nanomer company.

[0097] The raw material components of the outer layer II include: 40 parts of polylactic acid, 45 parts of metallocene linear low density polyethylene, 5 parts of compatibilizer, 3 parts of heat insulation masterbatch, and 4 parts of anti-aging masterbatch. The compatibilizer is maleic anhydride grafted polyethylene.

[0098] Among them, the raw material components of the anti-aging masterbatch include: 94 parts of low density polyethylene, 4 parts of light stabilizer, and 2 parts of antioxidant; the light stabilizer is the hindered amine light stabilizer NOR356. The antioxidant is a compound antioxidant of hindered phenol type and phosphite type, with the model B225.

[0099] The raw material components of the heat insulation masterbatch include: 55 parts of low density polyethylene, 40 parts of nano kaolin, 3 parts of silane coupling agent, and 2 parts of dispersant. The model of the silane coupling agent is KH550. The model of the nano kaolin is KCR-66. The model of dibutyltin dilaurate is Evonik T12. The dispersant is polyethylene wax.

[0100] All the above parts are in parts by weight.

[0101] A production process of a seven-layer co-extruded agricultural film applied in the anti-pesticide field includes the following steps:

[0102] Step 1: Preparation of the anti-aging masterbatch

[0103] Add the light stabilizer and antioxidant into a high-speed mixer and mix evenly. Then add the low density polyethylene and stir to mix evenly to form a premix. Add the premix into a twin-screw extruder, set the temperature parameters of the extruder, the feeding section temperature is set at 130 °C, the melting section temperature is 160 °C, the mixing section temperature is 170 °C, and the head temperature is 180 °C. Make the premix fully melt and knead in the extruder, and the molten material extruded from the extruder is air-cooled, and the air ring cooling temperature is 20 °C. The cooled strip material enters a granulator for granulation to make granular anti-aging masterbatch.

[0104] Step 2: Preparation of the heat insulation masterbatch

[0105] Mix the nano kaolin and the silane coupling agent solution evenly, and add them into a high-speed mixer together with the low density polyethylene and polyethylene wax, and mix evenly. The silane coupling agent solution is an ethanol solution of the silane coupling agent, and the content of the silane coupling agent is 20% (mass percentage).

[0106] Add the mixed material into a twin-screw extruder for melt extrusion. The temperature of the extruder is set to gradually increase from the feeding section to the head, the feeding section temperature is set at 130 °C, the melting section temperature is 160 °C, the mixing section temperature is 170 °C, and the head temperature is 180 °C. The strip material extruded from the head is air-cooled, the air ring cooling temperature is 20 °C, and the cooled material enters a granulator for granulation to make granular heat insulation masterbatch.

[0107] Step 3. Modification with organophilic montmorillonite

[0108] Add the organophilic montmorillonite into anhydrous N,N-dimethylformamide and stir evenly to form a suspension. The mass ratio of the organophilic montmorillonite to N,N-dimethylformamide is 1:15. Slowly add polymethylene polyphenyl isocyanate into the suspension. The mass ratio of the polymethylene polyphenyl isocyanate to the organophilic montmorillonite is usually 1:10. Add the catalyst dibutyltin dilaurate. The mass of the catalyst is 0.5% of the mass of the polymethylene polyphenyl isocyanate. Stir at room temperature for 30 minutes, then raise the temperature to 70°C and react for 4 hours, followed by filtration and then vacuum drying at 60°C for 12 hours to obtain the modified organophilic montmorillonite.

[0109] Step 4. Premixing of the raw materials for the barrier core layer

[0110] Add the modified organophilic montmorillonite and ethylene-vinyl alcohol copolymer into a twin-screw extruder for melt extrusion. The temperature of the feeding section of the extruder is 170°C, the temperature of the melting section is 210°C, the temperature of the mixing section is 220°C, and the temperature of the die head is 190°C. The strip-shaped material extruded from the die head is air-cooled. The cooling temperature of the air ring is 20°C. The cooled material enters a granulator for granulation. After granulation, it is mixed evenly with the anti-aging masterbatch to obtain the premixed material for the barrier core layer, which is reserved for use.

[0111] The dosages of the raw materials in the premixed material for the barrier core layer are as shown in the content of the raw material components in the formula.

[0112] Step 5. Coextrusion molding

[0113] Mix the raw materials of the first outer layer, the first transition layer, the first insulation layer, the second insulation layer, the second transition layer, and the second outer layer respectively according to the formula to form the premixed materials for each layer;

[0114] Add the premixed materials of the seven layers (the first outer layer, the first transition layer, the first insulation layer, the barrier core layer, the second insulation layer, the second transition layer, and the second outer layer) into a seven-layer coextrusion extruder respectively. The temperature process conditions of each zone in the extruder are shown in Table 3 in detail. After extrusion from the die head, blow molding, cooling, corona treatment, and drying are carried out, and finally a seven-layer coextruded agricultural film applied in the anti-pesticide field is obtained. The blow molding adopted: the blow-up ratio is 3.0, and the traction speed is 15 m / min; cooling: the cooling temperature of the air ring is 20°C; corona treatment: the power of the corona treatment is 10 kW, and the treatment speed is 15 m / min; drying: the drying temperature is 60°C. The thickness of the obtained product is 0.10 mm ± 5%, and the thickness ratio of the first outer layer, the first transition layer, the first insulation layer, the barrier core layer, the second insulation layer, the second transition layer, and the second outer layer is 1.25:1:1.25:1.5:1.25:1:1.1.

[0115] Table 3 Temperature process conditions of each zone in the extruder

[0116] The agricultural film prepared in this embodiment is suitable for the cultivation of leafy vegetables, multi-crop cultivation, or solanaceous crops such as tomatoes and peppers.

[0117] Comparative example

[0118] A seven-layer co-extruded agricultural film is composed of outer layer 1, transition layer 1, thermal insulation layer 1, barrier core layer, thermal insulation layer 2, transition layer 2, and outer layer 2.

[0119] The raw material components of outer layer 1 include: 90 parts of metallocene linear low-density polyethylene, 4 parts of compatibilizer, 3 parts of toughening agent, 4 parts of heat insulation masterbatch, and 3 parts of anti-aging masterbatch.

[0120] The compositions of transition layer 1 and transition layer 2 are the same, and the raw material components include: 40 parts of low-density polyethylene, 45 parts of metallocene linear low-density polyethylene, 8 parts of anti-aging masterbatch, and 7 parts of heat insulation masterbatch.

[0121] The compositions of thermal insulation layer 1 and thermal insulation layer 2 are the same, and the raw material components include: 83 parts of ethylene-vinyl acetate copolymer resin, 7 parts of anti-aging masterbatch, and 10 parts of heat insulation masterbatch.

[0122] The raw material components of the barrier core layer include: 85 parts of ethylene-vinyl alcohol copolymer, 8 parts of organic montmorillonite, and 7 parts of anti-aging masterbatch; the organic montmorillonite is quaternary ammonium salt modified montmorillonite.

[0123] The raw material components of outer layer 2 include: 88 parts of metallocene linear low-density polyethylene, 4 parts of compatibilizer, 4 parts of heat insulation masterbatch, and 3 parts of anti-aging masterbatch.

[0124] Among them, the raw material components of the anti-aging masterbatch include: 92 parts of low-density polyethylene, 5 parts of light stabilizer, and 3 parts of antioxidant;

[0125] The raw material components of the heat insulation masterbatch include: 50 parts of low-density polyethylene, 45 parts of nano kaolin, 2 parts of silane coupling agent, and 3 parts of dispersant.

[0126] The above parts are all in parts by weight. The compatibilizer, toughening agent, light stabilizer, antioxidant, silane coupling agent, and dispersant used are the same as the corresponding raw materials in Example 2.

[0127] Preparation process:

[0128] Step 1. Preparation of the anti-aging masterbatch

[0129] The same as the "Preparation of the anti-aging masterbatch" step in Example 2.

[0130] Step 2. Preparation of the heat insulation masterbatch

[0131] The same as the "preparation of heat insulation masterbatch" step in Example 2.

[0132] Step 4. Coextrusion molding

[0133] Mix the raw materials of the first outer layer, the first transition layer, the first insulation layer, the barrier core layer, the second insulation layer, the second transition layer, and the second outer layer according to the formula respectively to form the premixed materials for each layer.

[0134] Add the premixed materials of the seven layers (the first outer layer, the first transition layer, the first insulation layer, the barrier core layer, the second insulation layer, the second transition layer, and the second outer layer) into a seven-layer coextrusion extruder respectively. The temperature process conditions in each zone of the extruder are the same as those controlled by the extruder in the "coextrusion molding" step of Example 2. The control conditions during the processes of film blowing, cooling, corona treatment, and drying after die head extrusion are the same as those in Example 2.

[0135] Example 4 Performance test

[0136] Perform optical property and mechanical property tests on the products prepared in Examples 1-3 and the comparative example. The test results are shown in Table 4 and Table 5.

[0137] Table 4 Optical property test results

[0138] From the test results in Table 4, it can be seen that Examples 1-3 all have good optical properties. The light transmittance reaches 89.7-91.1%, the haze reaches 10.4-12.6%, and the infrared barrier rate reaches 81.7-85.8%. The relatively high light transmittance and infrared barrier rate and the relatively low haze mean that the optical properties of the film are better, the light transmission is more uniform, it can ensure more stable lighting conditions for crops, is conducive to the photosynthesis of crops, can effectively block infrared rays, reduce the heat loss through infrared radiation, play a better heat preservation effect, and promote the growth of crops.

[0139] Table 5 Mechanical property test results

[0140] From the test results in Table 5, it can be seen that Examples 1-3 all have good mechanical properties. The transverse tensile strength reaches 39-44.2 MPa, the longitudinal tensile strength reaches 41.5-45.4 MPa, the right-angle tear strength reaches 124-138 N / mm, the dart impact strength reaches 480-557 g, and the puncture strength reaches 44.2-48.7 N. The relatively high tensile strength means a stronger ability to resist tensile failure, and can effectively prevent the film from being torn during use. The higher the right-angle tear strength, dart impact strength, and puncture strength, the stronger the tear resistance and the ability to resist external impacts of the film.

[0141] The products prepared in Examples 1-3 and Comparative Examples were subjected to degradation tests. Referring to ISO 14855-1:2012 and GB / T 20197-2006, degradation was simulated in laboratory soil. The test results are shown in Table 6. Test conditions: temperature was set at 25°C, humidity was set at 60±5%RH, the soil matrix was a standard reference soil, and the test period was 6 months. Samples were taken monthly to measure the weight loss rate and surface morphology (SEM) of the samples.

[0142] Table 6 Laboratory accelerated degradation test results

[0143] From the experimental data in Table 6, it can be seen that the weight loss rate of the product in Example 1 reached 73.5% after 6 months, and the surface morphology was a honeycomb structure, indicating the fastest degradation rate and achieving 73.5% degradation within 6 months; the degradation rate of Example 2 was moderate, which could maintain certain performance and achieve good degradation within a certain time; the degradation rate of Example 3 was slower, but it also ensured that it retained certain mechanical strength and functional integrity for a long time; while the degradation degree of the comparative example was the lowest, with almost no degradation in a short time. Therefore, the degradation rate of the film can be controllably adjusted by controlling the addition amount of PLA.

[0144] The products prepared in Examples 1-3 and Comparative Examples were subjected to pesticide barrier performance tests. Referring to GB / T 23243-2009, the barrier efficiencies of various pesticides were measured respectively. The specific measurement results are shown in Table 7.

[0145] Table 7 Pesticide barrier performance measurement results

[0146] From the experimental data in Table 7, it can be seen that the barrier rates of Examples 1-3 against chlorpyrifos reached 96.2-98.7%, the barrier rates against cypermethrin reached 97.8-99.2%, and the barrier rates against tebuconazole reached 94.5-97.5%. Compared with the comparative example, the barrier efficiencies of Examples 1-3 against organophosphorus pesticides, pyrethroid pesticides, and triazole pesticides were significantly enhanced, showing excellent performance in pesticide barrier.

[0147] In summary, from the test analysis of optical properties, mechanical properties, degradability, and pesticide barrier properties, it can be seen that the agricultural film of the present invention meets the actual use standards and has high optical properties, mechanical properties, degradability, and pesticide barrier properties. It is particularly suitable for use in leafy vegetables or multi-crop planting, for the planting of solanaceous crops such as tomatoes and peppers, and for the planting in organically certified farms.

[0148] The specific parameters of the raw materials used in the present invention are as follows:

[0149] The VA content of the ethylene-vinyl acetate copolymer resin is 12.0 - 14.0%, and the melt index is 0.3 - 0.65 g / 10min.

[0150] The density of polylactic acid is 1.22 - 1.26 g / cm³, the melting point is 155 - 170 °C, and the melt index is 5 - 15 g / 10min.

[0151] The density of metallocene linear low-density polyethylene is 0.914 - 0.922 g / cm³, the melting point is 110 °C - 130 °C, and the melt index is 0.5 - 1.0 g / 10min.

[0152] The density of low-density polyethylene is 0.917 - 0.925 g / cm 3 , the melting point is 110 - 115 °C, and the melt index is 1.5 - 2.5 g / 10min.

[0153] Maleic anhydride grafted polyethylene: The density is 0.925 - 0.935 g / cm³, the melt index is 0.15 - 0.30 g / 10min, and the grafting rate is 0.8 - 1.5%.

[0154] Polyolefin elastomer: The density is 0.872 - 0.885 g / cm³, and the melt index is 0.8 - 1.2 g / 10min.

[0155] The ethylene content of ethylene-vinyl alcohol copolymer is 32 - 44 mol%, the melt index is 2.5 - 3.5 g / 10min, and the density is 1.0 - 1.5 g / cm³.

[0156] The isocyanate group content of polymethylene polyphenyl isocyanate is 30.5% - 32.0%, and the viscosity is 150 - 250 mPa・s.

[0157] Unless otherwise specified, the percentages described in the present invention are all mass percentages, and the ratios are all mass ratios.

[0158] Obviously, there are many specific implementation methods that can be changed under the concept of the present invention. Here, it should be stated that any changes made under the inventive concept of the present invention will fall within the protection scope of the present invention.

Claims

1. Application of a seven-layer coextruded agricultural film in the field of pesticide resistance, characterized in that: The agricultural film described above includes outer layer 1, transition layer 1, thermal insulation layer 1, barrier core layer, thermal insulation layer 2, transition layer 2, and outer layer 2; the raw material components of the outer layer 1 include polylactic acid, metallocene linear low density polyethylene, compatibilizer, toughening agent, heat insulation masterbatch, and anti-aging masterbatch; The raw material components of the outer layer 2 include polylactic acid, metallocene linear low density polyethylene, compatibilizer, heat insulation masterbatch, and anti-aging masterbatch; The raw material components of the transition layer 1 and the transition layer 2 include low density polyethylene, metallocene linear low density polyethylene, anti-aging masterbatch, and heat insulation masterbatch; The raw material components of the thermal insulation layer 1 and the thermal insulation layer 2 include ethylene-vinyl acetate copolymer resin, anti-aging masterbatch, and heat insulation masterbatch; The barrier core layer: in terms of parts by weight, the raw material components include 80-90 parts of ethylene-vinyl alcohol copolymer, 6-10 parts of modified organic montmorillonite, and 3-10 parts of anti-aging masterbatch; the modified organic montmorillonite is prepared from organic montmorillonite, N,N-dimethylformamide, polymethylene diphenyl diisocyanate, and dibutyltin dilaurate; The preparation method of the modified organic montmorillonite is: adding organic montmorillonite into anhydrous N,N-dimethylformamide to form a suspension; adding polymethylene diphenyl diisocyanate into the suspension, adding dibutyltin dilaurate, the reaction temperature is 50-70 °C, and the reaction time is 2-4 hours; the organic montmorillonite is quaternary ammonium salt modified montmorillonite; The anti-aging masterbatch is prepared from low density polyethylene, light stabilizer, and antioxidant; The heat insulation masterbatch is prepared from low density polyethylene, nano kaolin, silane coupling agent, and dispersant.

2. Use of a seven-layer coextruded agricultural film according to claim 1 in the field of pesticide resistance, characterized in that: The compatibilizer is maleic anhydride grafted polyethylene; the toughening agent is polyolefin elastomer; the light stabilizer is a hindered amine light stabilizer; the antioxidant is a compound antioxidant of hindered phenols and phosphites; the dispersant is polyethylene wax.

3. Use of a seven-layer coextruded agricultural film according to claim 1 in the field of pesticide resistance, characterized in that: The mass ratio of the organic montmorillonite to N,N-dimethylformamide is 1:(10-15); the mass ratio of the polymethylene diphenyl diisocyanate to the organic montmorillonite is 1:(5-10); the mass of the dibutyltin dilaurate is 0.5%-1% of the mass of the polymethylene diphenyl diisocyanate.

4. Use of a seven-layer coextruded agricultural film according to claim 1 in the field of pesticide resistance, characterized in that: The raw material component ratio of the anti-aging masterbatch is 90-94 parts of low density polyethylene, 4-6 parts of light stabilizer, and 2-4 parts of antioxidant; the raw material component ratio of the heat insulation masterbatch is 45-55 parts of low density polyethylene, 40-50 parts of nano kaolin, 1-3 parts of silane coupling agent, and 2-4 parts of dispersant; the parts are all parts by weight.

5. Use of a seven-layer coextruded agricultural film according to claim 1 in the field of pesticide resistance, characterized in that: The ratio of the raw material components of the outer layer 1 is 40-50 parts of polylactic acid, 40-50 parts of metallocene linear low density polyethylene, 3-4 parts of compatibilizer, 2-4 parts of toughening agent, 3-5 parts of heat insulation masterbatch, and 2-4 parts of anti-aging masterbatch; The transition layer 1 and the transition layer 2 have the same composition, and the ratio of the raw material components is 35-45 parts of low density polyethylene, 40-50 parts of metallocene linear low density polyethylene, 7-10 parts of anti-aging masterbatch, and 5-8 parts of heat insulation masterbatch; The compositions of the first thermal insulation layer and the second thermal insulation layer are the same, and the ratio of the raw material components is 80-85 parts of ethylene-vinyl acetate copolymer resin, 5-10 parts of anti-aging masterbatch, and 8-12 parts of heat insulation masterbatch; The ratio of the raw material components of the second outer layer is 40-55 parts of polylactic acid, 35-45 parts of metallocene linear low-density polyethylene, 3-5 parts of compatibilizer, 3-5 parts of heat insulation masterbatch, and 2-4 parts of anti-aging masterbatch.

6. The production process of the seven-layer co-extruded agricultural film in the application according to any one of claims 1-5, characterized in that: It includes the preparation of anti-aging masterbatch, the preparation of heat insulation masterbatch, the modification of organic montmorillonite, the premixing of the raw materials of the barrier core layer, and the co-extrusion molding step; for the co-extrusion molding: the seven-layer raw materials are respectively premixed and then extruded through an extruder. The feeding section is at 115-190 °C, the compression section is at 150-200 °C, the melting section is at 180-220 °C, the homogenization section is at 180-220 °C, the connector is at 180-210 °C, the transition section is at 190-210 °C, the distributor is at 205-215 °C, and the die head outlet is at 205-215 °C.

7. The production process of the seven-layer co-extruded agricultural film according to claim 6, characterized in that: The preparation of the anti-aging masterbatch: mix the light stabilizer and antioxidant, add low-density polyethylene, and after mixing, melt and extrude through an extruder; the control parameters of the extruder: the temperature of the feeding section is set at 120-130 °C, the temperature of the melting section is 140-160 °C, the temperature of the mixing section is 150-170 °C, and the temperature of the head is 160-180 °C.

8. The production process of the seven-layer co-extruded agricultural film according to claim 6, characterized in that: The preparation of the heat insulation masterbatch: mix the nano kaolin and the silane coupling agent solution evenly, and mix with low-density polyethylene and dispersant; melt and extrude through a twin-screw extruder. The temperature of the feeding section is set at 120-130 °C, the temperature of the melting section is 140-160 °C, the temperature of the mixing section is 150-170 °C, and the temperature of the head is 160-180 °C.

9. The production process of the seven-layer co-extruded agricultural film according to claim 6, characterized in that: The premixing of the raw materials of the barrier core layer: melt and extrude the modified organic montmorillonite and ethylene-vinyl alcohol copolymer. The temperature of the feeding section of the extruder is 160-170 °C, the temperature of the melting section is 190-210 °C, the temperature of the mixing section is 200-220 °C, the temperature of the head is 180-190 °C. After extrusion, pelletize and mix with the anti-aging masterbatch.

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