Preparation method of ETFE composite film for high-strength greenhouse

Abstract

The invention relates to the technical field of agricultural greenhouse covering materials, in particular to a preparation method of a high-strength ETFE composite film for greenhouses, which comprises the following steps: preparing a support layer, mixing ETFE resin, PFA resin and silicon dioxide filler as raw materials according to a mass ratio of 7: 2: 1, and adding carbon powder for pretreatment modification; preparing a functional layer, taking ETFE resin as a base material, and adding a fiber component and rare earth metal powder; preparing a hydrophobic anti-dripping layer, taking pure ETFE resin as a raw material, and optimizing the surface performance through PTFE emulsion coating; and finally, combining the three layers of films. The tear resistance and puncture resistance of the prepared greenhouse film reach the engineering level, the designed service life exceeds 15 years, the crop yield can be increased, plant diseases and insect pests are reduced, the consumption of pesticides and the greenhouse film is reduced, waste films can be recycled, and the greenhouse film has long-term effectiveness and environmental friendliness and is suitable for various agricultural greenhouse scenes.

Description

Technical Field

[0001] This invention relates to the field of agricultural greenhouse covering materials technology, specifically to a method for preparing a high-strength ETFE composite film for greenhouses. Background Technology

[0002] As a crucial facility in modern agricultural production, the performance of the covering materials used in agricultural greenhouses directly impacts crop growth, yield, and production efficiency. Currently, traditional agricultural greenhouse films are mainly made of materials such as polyethylene (PE), polyvinyl chloride (PVC), or ethylene-vinyl acetate (EVA). However, these films have the following inherent defects: First, they lack mechanical strength, exhibiting poor tensile strength, tear strength, and puncture resistance, making them prone to damage under extreme weather conditions such as hail and strong winds, resulting in a short service life and frequent replacements. Second, they have limited weather resistance, easily aging, yellowing, and becoming brittle when exposed to ultraviolet radiation, high temperature, and high humidity for extended periods. Third, although some functions can be achieved by adding additives such as anti-drip agents and heat-insulating agents, these additives are prone to migration and loss, resulting in a short effective period and failing to meet the long-term, stable needs of agricultural production.

[0003] To address the aforementioned issues, existing technologies utilize ETFE materials to prepare greenhouse films. While ETFE possesses excellent weather resistance, light transmittance, and chemical stability, its application in agriculture still faces significant challenges: First, its high cost limits large-scale application; second, although pure ETFE films are stronger than traditional film materials such as PE and PVC, their tear and puncture resistance is still insufficient to completely withstand extreme weather conditions; third, ETFE has low surface energy, making it difficult to adhere to functional coatings such as anti-drip agents, and its natural hydrophobicity prevents condensation droplets from spreading inside the greenhouse, creating a "lens effect" that can easily scorch crop leaves and affect the uniform transmission of light.

[0004] Therefore, there is an urgent need for a method to prepare a high-strength ETFE composite film for greenhouses to solve the above problems. Summary of the Invention

[0005] To achieve the above objectives, this application employs the following technical solution: A method for preparing a high-strength ETFE composite film for greenhouses includes the following steps: Step 100: Prepare the support layer by mixing ETFE resin, PFA resin and silica filler in a mass ratio of 7:2:1, adding carbon powder for pretreatment modification, preparing a special masterbatch by a twin-screw granulator, extruding the masterbatch into a film in an extruder, and then curing it in a 50°C curing chamber for 96 hours to obtain the finished support layer film. Step 200: Prepare the functional layer by adding fiber components and rare earth metal powder to ETFE resin as the base material. The amount of rare earth metal powder added shall not exceed 5% of the total mass. After pretreatment and modification, functional masterbatch is obtained and extruded into a film by an extruder to obtain the finished functional layer film. Step 300: Prepare a hydrophobic anti-drip layer by extruding pure ETFE resin into a film using an extruder, and then uniformly coating the film surface with a PTFE emulsion with a solid content of 60% to obtain the finished hydrophobic anti-drip layer film. Step 400, composite molding: The three-layer film obtained in steps 100, 200 and 300 are coated with a special primer, and then placed in a curing room at 60°C for 96 hours to cure. A special adhesive is used to composite the cured three-layer film in the order of support layer, functional layer and hydrophobic anti-drip layer. After pressure curing, a high-strength ETFE film for greenhouses is obtained.

[0006] Furthermore, in step 100, the amount of carbon powder added is 0.5-2% of the total mass of the finished support layer film.

[0007] Furthermore, in step 200, the rare earth metal powder is one or a mixture of two of cerium powder and neodymium powder.

[0008] Further, in step 200, the fiber component is one or more of glass fiber, carbon fiber or aramid fiber, and the amount added is 3-8% of the total mass of the finished functional layer membrane.

[0009] Furthermore, in step 400, the special primer is a polyurethane primer, and the coating amount is 5-10 g / m2.

[0010] Further, in step 400, the special adhesive is a fluoropolymer adhesive, the bonding temperature is 80-100℃, and the pressure is 0.3-0.5MPa.

[0011] Further, in step 100 or 200, the pretreatment modification includes high-speed mixing, drying, and twin-screw melt blending, wherein the high-speed mixing speed is 800-1200 r / min, the mixing time is 15-30 min, the drying temperature is 80-100℃, and the drying time is 4-6 hours.

[0012] Compared with the prior art, the beneficial effects of this application are: 1. The technical solution in this application, through the synergistic design of a three-layer structure—a support layer, a functional layer, and a hydrophobic anti-drip layer—changes the current situation where traditional single-layer membranes or simple composite membranes emphasize a single function and struggle to achieve multiple performance characteristics simultaneously. The support layer provides a solid mechanical foundation, the functional layer imparts agricultural efficiency-enhancing properties, and the hydrophobic anti-drip layer optimizes surface protection. These three elements form an organic whole, enabling the membrane material to simultaneously possess engineering-grade mechanical strength, significant agricultural yield-increasing and pest-repellent effects, and stable surface protection performance. This solves the difficulty of existing membrane materials in simultaneously meeting multiple requirements such as extreme weather resistance, crop growth promotion, and light transmission stability. 2. The technical solution of this application can extend the service life, greatly reduce the frequency of greenhouse film replacement, and reduce the total consumption of greenhouse film. At the same time, the waste film can be recycled and reused, and the pest and disease control effect brought by rare earth metals can reduce the amount of pesticides used, forming a green and environmentally friendly closed loop of less replacement, recycling, and reduced pesticides, effectively reducing the impact of agricultural production on the environment.

[0013] 3. This application, through the scientific formulation of low-cost components such as PFA, silica, and fiber, controls the total cost of membrane materials while ensuring performance, solving the problem that ETFE membranes are difficult to apply on a large scale due to their high cost. It achieves an organic balance between environmental and economic benefits, which is in line with the development trend of green, efficient, and low-cost modern agriculture. Detailed Implementation

[0014] The present application will be further described in conjunction with specific embodiments. It should be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of the invention. Furthermore, it should be understood that after reading the teachings of this application, those skilled in the art can make various alterations or modifications to this application, and these equivalent forms also fall within the scope defined by this application.

[0015] A method for preparing a high-strength ETFE film for greenhouses includes the following steps: Step 100: Prepare the support layer by mixing ETFE resin, PFA resin, and silica filler in a mass ratio of 7:2:1. Then, add 0.5-2% carbon powder (by weight of the finished support layer film) for pretreatment modification. Prepare a special masterbatch using a twin-screw granulator and extrude the masterbatch into a film using an extruder. The screw temperature of the extruder is 200-230℃, the die temperature is 210-240℃, and the extrusion speed is 1-3m / min. After winding, place the film in a 50℃ curing chamber for 96 hours to eliminate internal stress and improve dimensional stability. Finally, the finished support layer film is obtained. The pretreatment modification includes high-speed mixing, drying, and twin-screw melt blending, wherein the high-speed mixing speed is 800-1200 r / min, the mixing time is 15-30 min, the drying temperature is 80-100℃, and the drying time is 4-6 hours.

[0016] Step 200: Prepare a functional layer to achieve selective sunlight transmission, increase crop yield, and suppress pests and diseases. Using ETFE resin as the base material, fiber components and rare earth metal powder are added. The amount of rare earth metal powder added is less than 5% of the total mass of the finished functional layer film. After pretreatment and modification, a functional masterbatch is obtained. This masterbatch is then extruded into a film using an extruder. The screw temperature of the extruder is 200-230℃, the die temperature is 210-240℃, and the extrusion speed is 1-3 m / min, resulting in the finished functional layer film.

[0017] The fiber component is one or more of glass fiber, carbon fiber or aramid fiber, and the amount added is 3-8% of the total mass of the finished functional layer membrane.

[0018] The rare earth metal powder is one or a mixture of cerium powder and neodymium powder. Cerium can optimize the light spectrum, promote crop photosynthesis, and increase yield, while neodymium can inhibit the reproduction of some pathogens and reduce the occurrence of diseases and pests.

[0019] The pretreatment modification includes high-speed mixing, drying, and twin-screw melt blending, wherein the high-speed mixing speed is 800-1200 r / min, the mixing time is 15-30 min, the drying temperature is 80-100℃, and the drying time is 4-6 hours.

[0020] Step 300: Prepare a hydrophobic anti-drip layer to optimize the hydrophobic properties of the membrane surface, eliminate condensation residue and lens effect, and ensure uniform light transmission. Using pure ETFE resin as raw material, the film is extruded through an extruder. The screw temperature of the extruder is 200-230℃, the die temperature is 210-240℃, and the extrusion speed is 1-3 m / min. A PTFE emulsion with a solid content of 60% is uniformly coated on the membrane surface. PTFE and ETFE have good compatibility, and after coating, the contact angle between the membrane surface and water can be significantly increased, allowing water droplets to slide off quickly and avoiding fog residue. Finally, a hydrophobic anti-drip membrane is obtained. Simultaneously, the synergistic hydrophobic design of the PTFE emulsion coating and the support layer can completely solve the problems of condensation residue and lens effect, ensuring uniform and stable crop photosynthesis.

[0021] Step 400: Composite molding. The three-layer membranes obtained in steps 100, 200, and 300 are coated with a special primer. The primer enhances the surface energy of the membrane and strengthens its adhesion to the adhesive. The membranes are then placed in a 60°C curing chamber for 96 hours to further stabilize the membrane structure. A special adhesive is used to bond the cured three-layer membranes in the order of support layer, functional layer, and hydrophobic anti-drip layer. After pressure curing, a high-strength ETFE membrane for greenhouses is obtained. The three-layer composite structure and precise modification design enable the membrane material to achieve engineering material-level tear resistance, puncture resistance, and impact toughness. It can withstand extreme weather such as hail and strong winds, with a designed service life exceeding 15 years, more than 5 times that of traditional membrane materials, significantly reducing replacement frequency and costs.

[0022] In some preferred embodiments of this application, the specially formulated primer is a polyurethane primer, and the coating amount is 5-10 g / m². 2 The polyurethane primer, by weight, comprises 70 parts aliphatic polyether polyurethane prepolymer, 25 parts ethyl acetate, 3 parts γ-aminopropyltriethoxysilane, 1.2 parts polyether-modified polydimethylsiloxane, 0.3 parts dibutyltin dilaurate, and 0.5 parts deionized water. The preparation method is as follows: A measured amount of aliphatic polyether polyurethane prepolymer is added to a sealed stirred tank. Under low-speed stirring conditions of 350 r / min at 26℃, ethyl acetate is slowly added and stirred for 13 min until the system is uniform and transparent. While maintaining the stirring speed, γ-aminopropyltriethoxysilane and polyether-modified polydimethylsiloxane are added sequentially, and stirring continues for 16 min to ensure uniform dispersion of the additives. Finally, dibutyltin dilaurate is added, and the mixture is stirred at low speed for 7 min. After thorough mixing, the mixture is filtered through a 200-mesh filter to obtain the finished polyurethane primer. Meanwhile, the polyurethane primers described in this application can also be purchased directly from chemical raw material suppliers and must be aliphatic polyether type polyurethane prepolymer base primers.

[0023] In some preferred embodiments of this application, the special adhesive is a fluoropolymer adhesive, with a bonding temperature of 80-100℃ and a pressure of 0.3-0.5 MPa. Specifically, by weight, the fluoropolymer adhesive comprises 43 parts polyvinylidene fluoride, 25 parts ethylene-tetrafluoroethylene copolymer, 6 parts fluororubber powder, 25 parts methyl isobutyl ketone, 0.5 parts pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate], and 0.5 parts nano-silica. The preparation method is as follows: Polyvinylidene fluoride and ethylene-tetrafluoroethylene copolymer are added to a high-speed mixer and mixed for 13 minutes at 45°C and 550 r / min to obtain a mixed resin powder; methyl isobutyl ketone is added to a sealed stirring vessel with a heating jacket, the temperature is raised to 60°C, and the above mixed resin powder is slowly added under stirring at 470 r / min, and stirred for 36 minutes until the resin is completely dissolved to form a uniform resin solution; the vessel temperature is lowered to 33°C, and fluororubber powder, pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate], and nano silica are added in sequence, and stirring is continued for 28 minutes to ensure that the filler and additives are uniformly dispersed; after uniform mixing, the mixture is filtered through a 300-mesh filter to remove undissolved particles and impurities, thus obtaining the finished fluororesin adhesive. The fluororesin adhesive used in this application can be directly purchased from chemical raw material suppliers and must be a thermosetting fluororesin adhesive.

[0024] Example 1 A method for preparing a high-strength ETFE film for greenhouses includes the following steps: Step 100: Prepare the support layer by mixing ETFE resin, PFA resin, and silica filler in a mass ratio of 7:2:1. Then, add 1% carbon powder (by weight of the total mass of the finished support layer film) for pretreatment modification. The high-speed mixing speed is 1000 r / min, the mixing time is 20 min, the drying temperature is 80℃, and the drying time is 5 hours. The film is extruded through an extruder at a speed of 2 m / min, and after winding, it is cured at 50℃ for 96 hours to obtain the finished support layer film.

[0025] Step 200: Prepare the functional layer by using ETFE resin as the base material, adding 5% glass fiber and 3% cerium powder, pre-treating and modifying it, mixing at a high speed of 900 r / min for 25 min, drying at 90℃ for 4 hours, and extruding it into a film to obtain the finished functional layer film.

[0026] Step 300: Prepare a hydrophobic antidrip layer by extruding pure ETFE resin into a film using an extruder, uniformly coating the film surface with a PTFE emulsion with a solid content of 60%, and finally obtaining the finished hydrophobic antidrip layer film.

[0027] Step 400: Composite molding, coating the three-layer films obtained in steps 100, 200, and 300 with 8 g / m² of film. 2 A polyurethane primer was cured at 60°C for 96 hours, and a fluoropolymer adhesive was used. The mixture was then composited and pressure-cured at 90°C and 0.4MPa to obtain a high-strength ETFE film for greenhouses.

[0028] The finished film obtained in this embodiment exhibits excellent mechanical properties, with a tensile strength of not less than 50 MPa, a tear strength of not less than 25 kN / m, and a puncture resistance of not less than 30 N. It also demonstrates excellent light transmittance, with an initial transmittance of 92% and maintaining 88% transmittance even after 5000 hours of UV aging. Furthermore, it leaves no condensation residue and does not produce a lens effect.

[0029] Example 2 A method for preparing a high-strength ETFE film for greenhouses includes the following steps: Step 100: Prepare the support layer by mixing ETFE resin, PFA resin, and silica filler in a mass ratio of 7:2:1. Then, add 1.5% carbon powder (by mass of the finished support layer film) for pretreatment modification. The high-speed mixing speed is 1100 r / min, the mixing time is 18 min, the drying temperature is 85℃, and the drying time is 4.5 hours. The film is extruded through an extruder at a speed of 1.8 m / min, and after winding, it is cured at 50℃ for 96 hours to obtain the finished support layer film.

[0030] Step 200: Prepare the functional layer by adding 6% carbon fiber, 2% cerium powder, and 1% neodymium powder to ETFE resin as the base material. After pretreatment and modification, the high-speed mixing speed is 1000 r / min, the mixing time is 22 min, the drying temperature is 95℃, and the drying time is 4 hours. The film is then extruded through an extruder to obtain the finished functional layer film.

[0031] Step 300: Prepare a hydrophobic antidrip layer by extruding pure ETFE resin into a film using an extruder, uniformly coating the film surface with a PTFE emulsion with a solid content of 60%, and finally obtaining the finished hydrophobic antidrip layer film.

[0032] Step 400: Composite molding, coating the three-layer films obtained in steps 100, 200, and 300 with 7 g / m² of film. 2 A polyurethane primer was cured at 60°C for 96 hours, and a fluoropolymer adhesive was used. The mixture was then composited and pressure-cured at 95°C and 0.35MPa to obtain a high-strength ETFE film for greenhouses.

[0033] The finished film prepared in this embodiment exhibits excellent mechanical properties, with a tensile strength of not less than 53 MPa, a tear strength of not less than 28 kN / m, and a puncture resistance of not less than 33 N. It also demonstrates excellent light transmittance, with an initial transmittance of 91% and maintaining 87% transmittance even after 5000 hours of UV aging. Furthermore, it leaves no condensation residue and does not produce a lens effect.

[0034] Example 3 A method for preparing a high-strength ETFE film for greenhouses includes the following steps: Step 100: Prepare the support layer by mixing ETFE resin, PFA resin, and silica filler in a mass ratio of 7:2:1. Then, add 0.8% carbon powder (based on the total mass of the finished support layer film) for pretreatment modification. The high-speed mixing speed is 900 r / min, the mixing time is 25 min, the drying temperature is 80℃, and the drying time is 5 hours. The film is then extruded through an extruder at a speed of 2.2 m / min, wound up, and cured at 50℃ for 96 hours to obtain the finished support layer film.

[0035] Step 200: Prepare the functional layer by adding 8% aramid fiber and 4% neodymium powder to ETFE resin as the base material. After pretreatment and modification, the high-speed mixing speed is 1100 r / min, the mixing time is 20 min, the drying temperature is 100℃, and the drying time is 4 hours. The film is then extruded through an extruder to obtain the finished functional layer film.

[0036] Step 300: Prepare a hydrophobic antidrip layer by extruding pure ETFE resin into a film using an extruder, uniformly coating the film surface with a PTFE emulsion with a solid content of 60%, and finally obtaining the finished hydrophobic antidrip layer film.

[0037] Step 400: Composite molding, coating the three-layer films obtained in steps 100, 200, and 300 with 10 g / m² of film. 2 The polyurethane primer was cured at 60℃ for 96 hours, and then bonded with fluororesin adhesive under pressure at 100℃ and 0.45MPa to obtain a high-strength ETFE film for greenhouses.

[0038] The finished film prepared in this embodiment exhibits excellent mechanical properties, with a tensile strength of not less than 55 MPa, a tear strength of not less than 30 kN / m, and a puncture resistance of not less than 35 N. It also demonstrates excellent light transmittance, with an initial transmittance of 90% and maintaining 86% transmittance after 5000 hours of UV aging. Furthermore, it leaves no condensation residue and does not produce a lens effect.

[0039] Comparative Example 1 The ETFE membrane preparation method of this comparative example is as follows: pure ETFE is used as the substrate, 10% silica filler is added, high-speed mixing is carried out at a speed of 800 r / min for 25 min, and then dried at 80℃ for 5 hours. Finally, it is granulated by twin screw extruder and extruded into a film. After winding, it is cured at 50℃ for 96 hours to obtain a single-layer ETFE membrane.

[0040] The single-layer ETFE membrane in this comparative example has poor mechanical properties, with a tensile strength of only 38 MPa, a tear strength of 18 kN / m, and a puncture resistance of 20 N. It is significantly different from the three-layer composite membrane material in Examples 1-3 of this invention. Its light transmittance is also poor, with an initial transmittance of only 88%, which decreases significantly to 75% after 5000 hours of ultraviolet aging. The condensation residue is prominent, and a lens effect appears in some areas.

[0041] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of this application, and are not intended to limit them. Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of this application.

Claims

1. A method for preparing a high-strength ETFE composite film for greenhouses, characterized in that: Includes the following steps: Step 100: Prepare the support layer by mixing ETFE resin, PFA resin and silica filler in a mass ratio of 7:2:1, adding carbon powder for pretreatment modification, preparing a special masterbatch by a twin-screw granulator, extruding the masterbatch into a film in an extruder, and then curing it in a 50°C curing chamber for 96 hours to obtain the finished support layer film. Step 200: Prepare the functional layer by adding fiber components and rare earth metal powder to ETFE resin as the base material. The amount of rare earth metal powder added shall not exceed 5% of the total mass. After pretreatment and modification, functional masterbatch is obtained and extruded into a film by an extruder to obtain the finished functional layer film. Step 300: Prepare a hydrophobic anti-drip layer by extruding pure ETFE resin into a film using an extruder, and then uniformly coating the film surface with a PTFE emulsion with a solid content of 60% to obtain the finished hydrophobic anti-drip layer film. Step 400, composite molding: The three-layer film obtained in steps 100, 200 and 300 are coated with a special primer, and then placed in a curing room at 60°C for 96 hours to cure. A special adhesive is used to composite the cured three-layer film in the order of support layer, functional layer and hydrophobic anti-drip layer. After pressure curing, a high-strength ETFE film for greenhouses is obtained.

2. The method for preparing a high-strength ETFE composite film for greenhouses according to claim 1, characterized in that: In step 100, the amount of carbon powder added is 0.5-2% of the total mass of the finished support layer film.

3. The method for preparing a high-strength ETFE composite film for greenhouses according to claim 1, characterized in that: In step 200, the rare earth metal powder is one or a mixture of two of cerium powder and neodymium powder.

4. The method for preparing a high-strength ETFE composite film for greenhouses according to claim 1, characterized in that: In step 200, the fiber component is one or more of glass fiber, carbon fiber or aramid fiber, and the amount added is 3-8% of the total mass of the finished functional layer membrane.

5. The method for preparing a high-strength ETFE composite film for greenhouses according to claim 1, characterized in that: In step 400, the specially formulated primer is a polyurethane primer, and the coating amount is 5-10 g / m². 2 .

6. The method for preparing a high-strength ETFE composite film for greenhouses according to claim 1, characterized in that: In step 400, the special adhesive is a fluoropolymer adhesive, the bonding temperature is 80-100℃, and the pressure is 0.3-0.5MPa.

7. The method for preparing a high-strength ETFE composite film for greenhouses according to claim 1, characterized in that: In step 100 or 200, the pretreatment modification includes high-speed mixing, drying, and twin-screw melt blending, wherein the high-speed mixing speed is 800-1200 r / min, the mixing time is 15-30 min, the drying temperature is 80-100℃, and the drying time is 4-6 hours.