Multifunctional co-extruded film as well as preparation method and application thereof

Abstract

The invention discloses a multifunctional co-extrusion film as well as a preparation method and application thereof, and relates to the field of plastic films. The multifunctional co-extrusion film comprises an anti-UV surface layer, a middle layer and a flame-retardant bottom layer which are formed by co-extrusion, the anti-UV surface layer comprises the following raw materials in parts by weight: 50-60 parts of PE, 10-15 parts of PP and 20-40 parts of an anti-UV complexing agent; the anti-UV complexing agent comprises the following raw materials: nano calcium carbonate with an acrylate group on the surface, an ultraviolet light absorber monomer with an acrylate end group and methyl methacrylate, and the weight ratio of the nano calcium carbonate with the acrylate group on the surface to the ultraviolet light absorber monomer with the acrylate end group to the methyl methacrylate is (30-40): (10-25): (40-55). The multifunctional co-extrusion film provided by the invention integrates UV resistance, moisture permeability, water resistance and flame retardance, and has good comprehensive performance.

Description

Technical Field

[0001] This application relates to the field of plastic film technology, and in particular to a multifunctional co-extruded film, its preparation method, and its application. Background Technology

[0002] Building breathable membranes are building materials that combine waterproofing, moisture permeability (allowing water vapor to escape), and UV protection. They are mainly used for building exterior walls and roofs, providing long-term weather protection while ensuring moisture permeability. Currently, the raw materials for preparing breathable membranes generally include: PE, UV inhibitors, and calcium carbonate pore-forming agents.

[0003] UV absorbers, often small-molecule UV absorbers (such as benzotriazoles), are commonly used as UV stabilizers. During the fabrication of breathable membranes, these small-molecule UV absorbers need to be uniformly dispersed in the substrate to absorb ultraviolet light. However, when UV absorbers are mixed into the substrate, these molecules can occupy or block the micropores originally intended for breathability, reducing the membrane's porosity and causing a sharp decline in moisture permeability. Furthermore, the relatively small molecular weight of small-molecule UV absorbers makes them prone to migration or volatilization from the membrane matrix over time, further degrading UV protection. Conventional breathable membranes struggle to balance moisture permeability and UV protection.

[0004] Some composite membranes are formed by coating the membrane surface with an anti-UV coating. Although the coating itself does not directly block the pores, the micro-uneven structure formed after the coating cures can easily increase airflow resistance and even hinder the passage of micro-airflow, which can also affect the material's moisture permeability to some extent. Moreover, the substrate of the membrane (PE) and the substrate of the anti-UV coating (acrylic or epoxy resin) are usually different materials, making it difficult to form an effective interpenetrating network between them. When exposed to outdoor ultraviolet rays and temperature cycles (alternating hot and cold) for a long time, the anti-UV coating is prone to curling or peeling, affecting the durability of the material. Summary of the Invention

[0005] The main purpose of this application is to propose a multifunctional co-extruded membrane, its preparation method and application, which aims to solve the problems of existing building breathable membranes that are difficult to balance moisture permeability and UV resistance, and have poor material durability.

[0006] In one aspect, this application provides a multifunctional co-extruded film, comprising a co-extruded UV-resistant top layer, an intermediate layer, and a flame-retardant bottom layer; The UV-resistant surface layer comprises the following raw materials in parts by weight: 50-60 parts PE, 10-15 parts PP, and 20-40 parts UV-resistant composite agent; the raw materials for preparing the UV-resistant composite agent include nano-calcium carbonate with acrylate groups on its surface, UV absorber monomer with acrylate end groups, and methyl methacrylate, and the weight ratio of the nano-calcium carbonate with acrylate groups on its surface, the UV absorber monomer with acrylate end groups, and the methyl methacrylate is (30-40):(10-25):(40-55). The intermediate layer comprises the following raw materials in parts by weight: 60-70 parts PE and 30-40 parts calcium carbonate; The flame-retardant base layer comprises the following raw materials in parts by weight: 50-60 parts PE, 10-15 parts PP, 10-12 parts flame-retardant masterbatch, and 18-22 parts modified calcium carbonate.

[0007] By adopting the above technical solution, the substrates of the UV-resistant top layer, intermediate layer, and flame-retardant bottom layer are all PE, with the same substrate. Furthermore, the three layers are co-extruded to form an integral structure, effectively avoiding peeling between adjacent layers and ensuring the material's durability. Each of the flame-retardant bottom layer (inner layer), intermediate layer, and UV-resistant top layer (outer layer) uses a specific amount of calcium carbonate, creating interconnected channels in the three-layer structure from the inside out, i.e., from the flame-retardant bottom layer to the UV-resistant top layer. This facilitates the smooth outward discharge of internal moisture while preventing external rainwater from penetrating, achieving breathable and waterproof performance.

[0008] In the UV-resistant surface layer, the UV absorber is incorporated into the substrate in the form of a UV-resistant composite agent. The raw materials for preparing the UV-resistant composite agent include nano-calcium carbonate with acrylate groups on its surface, UV absorber monomers with acrylate end groups, and methyl methacrylate monomers. Under the initiation of an initiator, the monomers polymerize into polymer chains. Thus, the UV absorber branches to the calcium carbonate surface through the polymer chains, effectively improving the dispersion uniformity of the nano-calcium carbonate. This ensures the formation of pores with suitable pore size and uniform distribution in the UV-resistant surface layer, preventing the UV absorber (UV-resistant component) from clogging the pores and preventing the migration of the UV-resistant component, thereby improving the material's balanced moisture permeability and UV resistance.

[0009] Understandably, when using this material, the flame-retardant base layer should face the building or the structure that needs protection, while the UV-resistant surface layer should face the external environment.

[0010] Preferably, the flame-retardant base layer comprises the following raw materials in parts by weight: 57 parts PE, 13 parts PP, 10 parts flame-retardant masterbatch, and 20 parts modified calcium carbonate.

[0011] More preferably, the flame retardant masterbatch is a flame retardant modified masterbatch, which comprises the following raw materials in parts by weight: 37 parts flame retardant, 2 parts silane coupling KH-550, 4 parts antioxidant, and 57 parts PE.

[0012] By adopting the above technical solution, the flame retardant is added to the substrate in the form of flame retardant masterbatch, which makes the flame retardant more fully dispersed in the substrate and ensures the flame retardant effect of the material.

[0013] Optionally, the preparation method of the UV-resistant composite agent includes the following steps: S1. Add coupling agent KH-570 to the first solvent, adjust the pH to 4~5 to obtain a modified solution, disperse nano-calcium carbonate with an average particle size of 40~60nm in the modified solution, stir and react for 4~8h, and after cooling, filtration, washing and drying, obtain nano-calcium carbonate with acrylate groups on the surface. S2. Mix the ultraviolet absorber, glycidyl methacrylate, catalyst and second solvent, control the temperature at 75~85℃, stir and react for 6~10h, cool, filter, wash and dry to obtain the ultraviolet absorber monomer with acrylate end groups. S3. Disperse the nano-calcium carbonate with acrylate groups on the surface obtained in step S1 in a third solvent, add methyl methacrylate, an initiator and the UV absorber monomer with acrylate end groups obtained in step S2, and stir the reaction for 6 to 10 hours under an inert atmosphere and controlled temperature of 70 to 80°C. After cooling, centrifugation, washing and drying, the UV-resistant composite agent is obtained. In step S1, the weight ratio of nano-calcium carbonate to coupling agent KH-570 is 100:(3~8). In step S2, the weight ratio of the ultraviolet absorber, glycidyl methacrylate, catalyst and first solvent is (33~38):(12~18):(1~3):(300~500).

[0014] By adopting the above technical solution, the surface of the nano-calcium carbonate in the prepared anti-UV composite agent can be stably loaded with ultraviolet absorbers, thus effectively balancing the moisture permeability and anti-UV properties of the material.

[0015] Preferably, in step S1, the weight ratio of nano-calcium carbonate to coupling agent KH-570 is 100:5; In step S2, the weight ratio of the ultraviolet absorber, glycidyl methacrylate, catalyst, and second solvent is 35:15:2:400.

[0016] By adopting the above technical solution and controlling the amount of each raw material, an appropriate amount of ultraviolet absorber is loaded on the surface of the nano-calcium carbonate, thus ensuring the material's moisture permeability and UV resistance.

[0017] Preferably, in the UV-resistant surface layer, the weight ratio of PE, PP and UV-resistant composite agent is (55~60):(10~15):30.

[0018] By adopting the above technical solution and further optimizing the dosage ratio between the anti-UV composite agent and the substrate, the moisture permeability and UV resistance of the material can be further improved.

[0019] Preferably, in the UV-resistant composite agent, the weight ratio of the UV absorber monomer with acrylate end groups to methyl methacrylate is (15~20):(45~50).

[0020] By adopting the above technical solution and further optimizing the ratio of UV absorber monomers with acrylate end groups to methyl methacrylate, an appropriate amount of UV absorber is stably grafted onto nano-calcium carbonate, effectively balancing the material's moisture permeability and UV resistance.

[0021] Optionally, the average particle size of calcium carbonate in the intermediate layer is 40~300nm.

[0022] Optionally, in the intermediate layer, the calcium carbonate includes calcium carbonate with an average particle size of 40-60 nm and calcium carbonate with an average particle size of 200-300 nm, and the weight ratio of the calcium carbonate with an average particle size of 40-60 nm to the calcium carbonate with an average particle size of 200-300 nm is (6-7):(3-4).

[0023] By employing the above technical solution, two types of calcium carbonate with specific particle sizes are mixed in a specific ratio to form a bimodal calcium carbonate distribution. The bimodal calcium carbonate particles construct a continuous network structure in the substrate. Nanoscale particles primarily contribute to the formation of permeable channels, while submicron-sized particles act as physical cross-linking points. By enhancing the material's deformation resistance and interfacial interaction, they improve the overall tensile strength and interlayer bonding, and can also form meandering channels without causing phase separation.

[0024] Preferably, in the intermediate layer, the calcium carbonate includes calcium carbonate with an average particle size of 50 nm and calcium carbonate with an average particle size of 250 nm, and the weight ratio of the calcium carbonate with an average particle size of 50 nm to the calcium carbonate with an average particle size of 250 nm is 6.5:3.5.

[0025] Optionally, the method for preparing the modified calcium carbonate includes the following steps: Calcium carbonate with an average particle size of 0.5~1.0μm is provided, and the calcium carbonate is stirred at 100~110℃ for 10~30min. Then, n-octyltriethoxysilane is added, and the temperature is controlled at 105~120℃. The mixture is stirred at a stirring rate of 1000~1500rpm for 5~20min, and then cooled to obtain modified calcium carbonate.

[0026] Secondly, this application provides a method for preparing a multifunctional co-extruded film as described in any of the above claims, comprising the following steps: The raw materials corresponding to the UV-resistant top layer, intermediate layer and flame-retardant bottom layer are added to each screw extruder of the multi-layer co-extrusion casting equipment, and each melts independently to form the corresponding melt. The melts of each layer are combined and co-extruded through the die head, and after stretching and cooling, the multi-functional co-extruded film is formed. The stretch ratio is 3.0~3.8; based on a total material content of 100v% for the three layers, the material content of the UV-resistant top layer is 33.5~44.7v, the material content of the middle layer is 20~28v, and the material content of the flame-retardant bottom layer is 33.5~44.7v.

[0027] By adopting the above technical solution, the amount of material used in the UV-resistant top layer and flame-retardant bottom layer is relatively high, while the amount of material used in the middle layer is relatively low. This ensures that the resulting material has excellent moisture permeability, waterproofing, UV resistance and durability, while also saving raw material costs.

[0028] It should be noted that "v%" refers to volume percentage.

[0029] Preferably, with a total material content of 100v% for the three layers, the material content of the UV-resistant top layer is 38v, the material content of the middle layer is 24v, and the material content of the flame-retardant bottom layer is 38v.

[0030] Thirdly, this application provides a composite breathable membrane, comprising a protective layer, a support layer, and a multifunctional co-extruded membrane as described in any one of the above; wherein the multifunctional co-extruded membrane is located between the protective layer and the support layer.

[0031] By adopting the above technical solution, a multifunctional co-extruded film is placed between the protective layer and the support layer, making it more suitable for external environments. The protective layer and the support layer can be made from the same raw material, such as a non-woven fabric with flame-retardant properties.

[0032] Optionally, the preparation method of the above-mentioned composite breathable membrane includes the following steps: The protective layer, the multifunctional co-extruded film, and the support layer are stacked together in sequence and composited by hot rolling to form a breathable film; wherein the hot rolling conditions are: upper roll temperature of 150~160℃, lower roll temperature of 170~180℃, hot rolling pressure of 25~35 bar, and rolling speed of 28~35 m / min.

[0033] Fourthly, this application provides the application of a composite breathable membrane as described above in building exterior walls, roofs, and agricultural greenhouses.

[0034] By adopting the above technical solution, the composite breathable membrane provided in this application is particularly suitable for use in the construction industry or agricultural greenhouses. The composite breathable membrane integrates UV resistance, waterproofing, moisture permeability, and flame retardancy, and can be used for applications such as building exterior walls and roofs, providing long-term weather protection. It can also be used in agricultural greenhouses, such as as a covering film or curtain, to regulate humidity and temperature and resist long-term UV aging.

[0035] In summary, this application includes at least one of the following beneficial technical effects: 1. In the technical solution of this application, the substrates of the UV-resistant top layer, the intermediate layer, and the flame-retardant bottom layer are all PE, and the three layers are co-extruded to form an integral structure, effectively avoiding the peeling problem between adjacent layers and ensuring the durability of the material. Furthermore, each of the flame-retardant bottom layer (inner layer), the intermediate layer, and the UV-resistant top layer (outer layer) uses a specific amount of calcium carbonate, so that the three-layer structure forms interconnected channels in the direction from the inside to the outside, i.e., from the flame-retardant bottom layer to the UV-resistant top layer. This facilitates the smooth outward discharge of internal moisture, while preventing external rainwater from penetrating inward, achieving breathable and waterproof performance.

[0036] 2. In the UV-resistant surface layer, the UV absorber is incorporated into the substrate in the form of a UV-resistant composite agent. The raw materials for preparing the UV-resistant composite agent include nano-calcium carbonate with acrylate groups on its surface, UV absorber monomers with acrylate end groups, and methyl methacrylate monomers. Under the initiation of an initiator, the monomers polymerize into polymer chains. Thus, the UV absorber branches to the calcium carbonate surface through the polymer chains, effectively improving the dispersion uniformity of the nano-calcium carbonate. This ensures the formation of pores with suitable pore size and uniform distribution in the UV-resistant surface layer, preventing the UV absorber (UV-resistant component) from clogging the pores and preventing the migration of the UV-resistant component, thereby improving the material's balanced moisture permeability and UV resistance.

[0037] 3. The flame-retardant bottom layer (inner layer), middle layer and UV-resistant top layer (outer layer) are all made of calcium carbonate with a specific particle size. This makes the pore size of the three-layer structure decrease in a gradient from the inside to the outside, i.e. from the flame-retardant bottom layer to the UV-resistant top layer. This allows internal moisture to be discharged smoothly to the outside, while external rainwater cannot penetrate inward, thus achieving excellent moisture permeability and waterproof performance. Detailed Implementation

[0038] The present application will be further described in detail below with reference to the embodiments.

[0039] All raw materials involved in this application are commercially available, including: PP, PP-6001, Dongguan Zhonghao New Materials Co., Ltd.; PE, PE-7042, Dongguan Jinming Plastic Raw Materials Co., Ltd. Preparation Example 1

[0040] A method for preparing an anti-UV composite agent includes the following steps: S1. Add 5 parts by weight of coupling agent KH-570 to 495 parts by weight of ethanol solution (anhydrous ethanol and deionized water mixed at a volume ratio of 19:1), control the temperature at 35℃, stir at a stirring speed of 200 rpm for 20 min, adjust the pH to 4.5 with anhydrous acetic acid to obtain the modified solution; dry 100 parts by weight of nano-calcium carbonate (average particle size of 50 nm) at 120℃ for 2 h, cool to room temperature (25℃), add the cooled nano-calcium carbonate to the modified solution, stir at a stirring speed of 1200 rpm for 30 min, stir at a stirring speed of 200 rpm for 6 h at a temperature of 25℃ and a relative humidity of 55±5%, cool to room temperature (25℃), filter, collect the solid, wash with anhydrous ethanol, and dry under vacuum at 70℃ for 6 h to obtain nano-calcium carbonate with acrylate groups on the surface.

[0041] S2. Add 35 parts by weight of UV absorber UV-234, 15 parts by weight of glycidyl methacrylate, 2 parts by weight of triethylamine and 400 parts by weight of toluene to the reaction vessel. Stir at 200 rpm and control the temperature at 80°C. Maintain the stirring speed at 200 rpm for 8 hours. Then, control the temperature at 3°C ​​and stir at 100 rpm for 1 hour. Filter to obtain a solid. Wash the solid with anhydrous ethanol and dry it under vacuum at 60°C for 8 hours to obtain a UV absorber monomer with acrylate end groups.

[0042] S3. Add 34 parts by weight of the nano-calcium carbonate with acrylate groups on the surface obtained in step S1 to 300 parts by weight of N,N-dimethylformamide, disperse by ultrasonication, then add 15 parts by weight of the UV absorber monomer with acrylate end groups obtained in step S2 and 1 part by weight of azobisisobutyronitrile, stir at 500 rpm for 20 min, stir at 75°C (100 rpm) for 15 min under a nitrogen protective atmosphere, add 50 parts by weight of methyl methacrylate, continue stirring at 75°C (100 rpm) for 6 h, cool to room temperature (25°C), centrifuge to obtain a solid, wash the solid with deionized water and anhydrous ethanol alternately, and dry under vacuum at 70°C for 14 h to obtain the anti-UV composite agent. Preparation Examples 2-4

[0043] Preparation Examples 2-4 are based on Preparation Example 1, with the difference being that in step S3, the total weight of the UV absorber monomer with acrylate end groups and methyl methacrylate remains constant at 65 parts, while the ratio of their amounts is adjusted. The other steps are the same as in Preparation Example 1. Specifically: In Preparation Example 2, the amount of the UV absorber monomer with acrylate end groups was 10 parts by weight, and the amount of methyl methacrylate was 55 parts by weight.

[0044] In Preparation Example 3, the amount of the UV absorber monomer with acrylate end groups was 20 parts by weight, and the amount of methyl methacrylate was 45 parts by weight.

[0045] In Preparation Example 4, the amount of the UV absorber monomer with acrylate end groups was 25 parts by weight, and the amount of methyl methacrylate was 40 parts by weight. Preparation of Comparative Example 1

[0046] A method for preparing an anti-UV composite agent includes the following steps: S1. Add 5 parts by weight of coupling agent KH-570 to 495 parts by weight of ethanol solution (anhydrous ethanol and deionized water mixed at a volume ratio of 19:1), control the temperature at 35℃, stir at a stirring speed of 200 rpm for 20 min, adjust the pH to 4.5 with anhydrous acetic acid to obtain the modified solution; dry 100 parts by weight of nano-calcium carbonate (average particle size of 50 nm) at 120℃ for 2 h, cool to room temperature (25℃), add the cooled nano-calcium carbonate to the modified solution, stir at a stirring speed of 1200 rpm for 30 min, stir at a stirring speed of 200 rpm for 6 h at a temperature of 25℃ and a relative humidity of 55±5%, cool to room temperature (25℃), filter, collect the solid, wash with anhydrous ethanol, and dry under vacuum at 70℃ for 6 h to obtain nano-calcium carbonate with acrylate groups on the surface.

[0047] S2. Add 34 parts by weight of nano-calcium carbonate with acrylate groups on the surface obtained in step S1 to 300 parts by weight of N,N-dimethylformamide, disperse by ultrasonication, then add 15 parts by weight of UV absorber UV-234 and 1 part by weight of azobisisobutyronitrile, stir at 500 rpm for 20 min, stir at 75°C (100 rpm) for 15 min under nitrogen protection, add 50 parts by weight of methyl methacrylate, continue stirring at 75°C (100 rpm) for 6 h, cool to room temperature (25°C), centrifuge to obtain solid, wash the solid with deionized water and anhydrous ethanol alternately, and dry under vacuum at 70°C for 14 h to obtain the anti-UV composite agent. Preparation of Comparative Example 2

[0048] A method for preparing an anti-UV composite agent includes the following steps: S1. Add 35 parts by weight of UV absorber UV-234, 15 parts by weight of glycidyl methacrylate, 2 parts by weight of triethylamine and 400 parts by weight of toluene to the reaction vessel. Stir at 200 rpm and control the temperature at 80°C. Maintain the stirring speed at 200 rpm for 8 hours. Then, control the temperature at 3°C ​​and stir at 100 rpm for 1 hour. Filter to obtain a solid. Wash the solid with anhydrous ethanol and dry it under vacuum at 60°C for 8 hours to obtain a UV absorber monomer with acrylate end groups.

[0049] S2. Add 34 parts by weight of nano-calcium carbonate (average particle size of 50 nm) to 300 parts by weight of N,N-dimethylformamide, disperse by ultrasonication, then add 15 parts by weight of the UV absorber monomer with acrylate end groups obtained in step S1 and 1 part by weight of azobisisobutyronitrile, stir at 500 rpm for 20 min, stir at 75°C (100 rpm) for 15 min under a nitrogen protective atmosphere, add 50 parts by weight of methyl methacrylate, continue stirring at 75°C (100 rpm) for 6 h, cool to room temperature (25°C), centrifuge to obtain solid, wash the solid with deionized water and anhydrous ethanol alternately, and dry under vacuum at 70°C for 14 h to obtain the anti-UV composite agent. Preparation of Comparative Example 3

[0050] This preparation example is based on Preparation Example 1, the difference being that in step S3, the total weight parts of the UV absorber monomer with acrylate end groups and methyl methacrylate remain unchanged at 65 parts, and the ratio of their amounts is adjusted; the other steps are the same as in Preparation Example 1. Specifically: In this preparation example, the weight parts of the ultraviolet absorber monomer with acrylate end groups are 5 parts, and the weight parts of methyl methacrylate are 60 parts. Preparation of Comparative Example 4

[0051] This preparation example is based on Preparation Example 1, except that in step S3, methyl methacrylate is replaced with an equal part by weight of n-butyl methacrylate, while the other steps are the same as in Preparation Example 1. Example 1

[0052] A method for preparing a multifunctional co-extruded film includes the following steps: (1) Mix 30 parts by weight of the UV-resistant composite agent obtained in Preparation Example 1, 10 parts by weight of PP and 60 parts by weight of PE, and stir at a stirring rate of 200 rpm for 30 min to obtain a first mixture. Then, put the first mixture into the first screw extruder of the multilayer co-extrusion casting machine to melt and form a first melt. (2) Mix 65 parts by weight of PE and 35 parts by weight of composite calcium carbonate and stir at a stirring rate of 200 rpm for 20 min to obtain a second mixture. Then, put the second mixture into the second screw extruder of the multi-layer co-extrusion casting machine to melt and form a second melt. The composite calcium carbonate is composed of 70 wt% calcium carbonate with an average particle size of 50 nm and 30 wt% calcium carbonate with an average particle size of 250 nm. (3) Mix 10 parts by weight of flame-retardant modified masterbatch, 20 parts by weight of modified calcium carbonate, 13 parts by weight of PP and 57 parts by weight of PE, and stir at a stirring rate of 200 rpm for 30 min to obtain a third mixture. Then, put the third mixture into the third screw extruder of the multi-layer co-extrusion casting machine to melt and form a third melt. (4) The first melt obtained in step (1), the second melt obtained in step (2), and the third melt obtained in step (3) are combined through the die head of a multi-layer co-extrusion casting machine, co-extruded, stretched, with a stretch ratio of 3.5, cooled and shaped, and post-treated to form a multi-functional co-extruded film consisting of an anti-UV surface layer, an intermediate layer, and a flame-retardant bottom layer from the outside to the inside; wherein, based on a total feed amount of 100v% for the three layers, the feed amount of the first melt is 38v%, the feed amount of the second melt is 24v%, and the feed amount of the third melt is 38v%. The thickness of the multi-functional co-extruded film is measured to be 44±1μm.

[0053] In steps (1) to (3) of this embodiment, the melting temperature in each screw extruder is 190°C.

[0054] In step (3), the preparation method of the flame-retardant modified masterbatch includes the following steps: 25 parts by weight of aluminum hydroxide flame retardant, 12 parts by weight of triphenyl phosphate (flame retardant TPP), 2 parts by weight of silane coupling KH-550, 4 parts by weight of antioxidant 168, and 57 parts by weight of PE were melt-blended in a screw extruder, extruded, and cooled to obtain flame-retardant modified masterbatch. The operating conditions of the screw extruder were as follows: screw speed 300 rpm; temperature of the first zone (feeding section) 155℃, the second zone (melting section) 190℃, the third zone (mixing section) 190℃, and the fourth zone (die head section) 180℃.

[0055] In step (3), the method for preparing modified calcium carbonate includes the following steps: 100 parts by weight of calcium carbonate with an average particle size of 0.8 μm were placed in a high-speed mixer and stirred at 105 °C (500 rpm) for 15 min. Under continuous high-speed stirring (1200 rpm), 4 parts by weight of n-octyltriethoxysilane were added and stirred at 110 °C (1200 rpm) for 10 min. The mixture was then cooled to room temperature (25 °C) to obtain silane-modified calcium carbonate. Examples 2-3

[0056] Examples 2 and 3 are based on Example 1, the difference being that the amount of anti-UV composite agent used in step (1) is different, while the other steps remain the same as in Example 1. Specifically: In Example 2, the amount of the UV-resistant composite agent is 20 parts by weight.

[0057] In Example 3, the amount of the UV-resistant composite agent was 40 parts by weight. Example 4

[0058] This embodiment is based on Embodiment 1, the difference being that the amounts of PP and PE used in step (1) are different, while the other steps remain the same as in Embodiment 1. Specifically: In this embodiment, the weight percentage of PP is 15 parts and the weight percentage of PE is 55 parts. Comparative Example 1

[0059] This comparative example is based on Example 2, the difference being that in step (1), the UV-resistant composite agent obtained from the preparation of Comparative Example 1 is replaced with an equal weight portion of the UV-resistant composite agent obtained from the preparation of Example 1, and the other steps are the same as in Example 2. Comparative Example 2

[0060] This comparative example is based on Example 2, the difference being that in step (1), the UV-resistant composite agent obtained from the preparation of Comparative Example 2 is used in equal parts by weight to replace the UV-resistant composite agent obtained from Preparation Example 1, and the other steps are the same as in Example 2. Comparative Example 3

[0061] This comparative example is based on Example 2, the difference being that in step (1), the UV-resistant composite agent obtained from the preparation of Comparative Example 3 is used in equal parts by weight to replace the UV-resistant composite agent obtained from Preparation Example 1, and the other steps are the same as in Example 2. Comparative Example 4

[0062] This comparative example is based on Example 2, the difference being that in step (1), the UV-resistant composite agent obtained from the preparation of Comparative Example 4 is used in equal parts by weight to replace the UV-resistant composite agent obtained from Preparation Example 1, and the other steps are the same as in Example 2. Comparative Example 5

[0063] This comparative example is based on Example 2, the difference being that in step (3), calcium carbonate with an average particle size of 0.8 μm is used to replace the modified calcium carbonate in equal parts by weight, and the other steps are the same as in Example 2. Application Example 1

[0064] A method for preparing a composite breathable membrane includes the following steps: Step 1: Provide a support layer, the multifunctional co-extruded film obtained in Example 1, and a protective layer. The support layer, multifunctional co-extruded film, and protective layer all have the same length and width. The protective layer and support layer are both flame-retardant nonwoven fabrics (Dongguan Rifu Fiber Technology Co., Ltd.), with a basis weight of 20 g / m². 2 .

[0065] Step 2: Following the bottom-up direction, stack the support layer, multifunctional co-extruded film, and protective layer together in sequence, and form a composite breathable film by hot rolling. The hot rolling conditions are: upper roll temperature 155℃, lower roll temperature 175℃, hot rolling pressure 29 bar, and rolling speed 30 m / min. Application Examples 2-4

[0066] Application Examples 2-4 are based on Application Example 1, with the difference being that the source of the multifunctional co-extruded film in step one is different, while the other steps remain the same as in Application Example 1. Specifically: In Application Example 2, the multifunctional co-extruded film obtained in Example 2 is used.

[0067] In Application Example 3, the multifunctional co-extruded film obtained in Example 3 is used.

[0068] In Application Example 4, the multifunctional co-extruded film obtained in Example 4 is used. Application Comparative Examples 1-5

[0069] Comparative Examples 1-5 are based on Application Example 1, with the difference being that the source of the multifunctional co-extruded film in Step 1 is different, while the other steps remain the same as in Application Example 1. Specifically: In Comparative Example 1, the multifunctional co-extruded film obtained in Comparative Example 1 was used.

[0070] In Comparative Example 2, the multifunctional co-extruded film obtained in Comparative Example 2 was used.

[0071] In Comparative Example 3, the multifunctional co-extruded film obtained in Comparative Example 3 was used.

[0072] In Comparative Example 4, the multifunctional co-extruded film obtained in Comparative Example 4 was used.

[0073] In Comparative Example 5, the multifunctional co-extruded film obtained in Comparative Example 5 was used. Performance Test 1

[0074] The composite breathable membranes obtained from Application Examples 1-4 and Comparative Examples 1-5 were tested for mechanical properties, water tightness, moisture permeability, and durability. The results are shown in Table 1.

[0075] The durability test method is as follows: at a temperature of 60℃, the composite breathable membrane is irradiated with ultraviolet light (with a wavelength of 340nm and a distance of 10cm between the ultraviolet light and the membrane) for 8 hours, followed by 4 hours of dark rest at 50℃, which is counted as the first aging cycle. The same method is used for 39 aging cycles to obtain the composite breathable membrane after 40 aging cycles. The composite breathable membrane after 40 aging cycles is then subjected to mechanical property and moisture permeability tests to obtain the change rate of tensile strength A (%) and the change rate of moisture permeability B (%) after aging.

[0076] Where A = [(A0-A1) / A0] × 100%; B = [(B0-B1) / B0] × 100%.

[0077] In the formula, A0 is the tensile strength of the composite breathable membrane before aging, and A1 is the tensile strength of the composite breathable membrane after aging; B0 is the moisture permeability of the composite breathable membrane before aging, and B1 is the moisture permeability of the composite breathable membrane after aging.

[0078] Table 1 Performance test results of composite breathable membrane

[0079] As shown in Table 1, the composite breathable membrane provided in this application has high moisture permeability, and the rate of change in tensile strength and moisture permeability after aging is low, indicating that the composite breathable membrane provided in this application has excellent moisture permeability, UV resistance, and durability. Application Examples 1-3 investigated the effect of the amount of UV-resistant composite agent on the moisture permeability and UV resistance of the prepared composite breathable membrane, with Application Example 1 being the superior example. Application Example 4, based on Application Example 1, investigated the effect of the amount of PP and PE in the UV-resistant layer on the moisture permeability and UV resistance of the prepared composite breathable membrane.

[0080] Comparative Examples 1 and 2 were used to investigate the effects of acrylate end groups on the UV absorber and silane coupling agents grafted onto nano-calcium carbonate on the moisture permeability and UV resistance of the prepared composite breathable membrane. When the UV absorber lacks acrylate end groups, or when the nano-calcium carbonate is not grafted with silane coupling agents, the pore distribution and stability of the UV absorber are affected, thus impacting the material's mechanical properties, moisture permeability, and UV resistance.

[0081] Comparative Example 3 was used to investigate the effect of the ratio of acrylate-terminated UV absorber monomers to methyl methacrylate on the moisture permeability and UV resistance of the composite breathable membrane. An inappropriate ratio of acrylate-terminated UV absorber monomers to methyl methacrylate can affect the pore distribution of the material and the stability of the UV absorber, leading to a decrease in the moisture permeability and UV resistance of the composite breathable membrane.

[0082] In Comparative Example 4, the use of n-butyl methacrylate instead of methyl methacrylate in the preparation of the UV-resistant composite agent affected the moisture permeability and UV resistance of the resulting composite breathable membrane. This may be because n-butyl methacrylate, with its flexible butyl side chain, exhibits significant steric hindrance, affecting the copolymerization effect and consequently the pore distribution and stability of the UV absorber, leading to a decrease in the moisture permeability and UV resistance of the composite breathable membrane.

[0083] In Comparative Example 5, unmodified calcium carbonate was used as a pore-forming agent in the flame-retardant bottom layer, which affected the pore distribution and the connectivity of the air-permeable channels of the material, and thus affected the moisture permeability of the material to some extent. Example 5

[0084] This embodiment is based on Example 1, the difference being that in step (1), the UV-resistant composite agent obtained in Preparation Example 2 is used in equal parts by weight to replace the UV-resistant composite agent obtained in Preparation Example 1, and the other steps are the same as in Example 1. Example 6

[0085] This embodiment is based on Example 1, the difference being that in step (1), the UV-resistant composite agent obtained in Preparation Example 3 is replaced with an equal weight portion of the UV-resistant composite agent obtained in Preparation Example 1, and the other steps are the same as in Example 1. Example 7

[0086] This embodiment is based on Example 1, the difference being that in step (1), the UV-resistant composite agent obtained in Preparation Example 4 is replaced with an equal weight portion of the UV-resistant composite agent obtained in Preparation Example 1, and the other steps are the same as in Example 1. Application Examples 5-7

[0087] Application Examples 5-7 are based on Application Example 1, with the difference being that the source of the multifunctional co-extruded film in step one is different, while the other steps remain the same as in Application Example 1. Specifically: In Application Example 5, the multifunctional co-extruded film obtained in Example 5 is used.

[0088] In Application Example 6, the multifunctional co-extruded film obtained in Example 6 is used.

[0089] In Application Example 7, the multifunctional co-extruded film obtained in Example 7 is used. Performance Test 2

[0090] Following the method of performance test 1, the composite breathable membranes obtained for test cases 5 to 7 were tested for mechanical properties, moisture permeability, and durability. The results are shown in Table 2.

[0091] Table 2 Performance test results of composite breathable membrane

[0092] As shown in Table 2, the ratio of methyl methacrylate to UV absorber monomers with acrylate end groups has a certain influence on the moisture permeability and UV resistance of the prepared composite breathable membrane. Example 8

[0093] This embodiment is based on Example 6, the difference being that in step (2), the composite calcium carbonate is composed of 60wt% calcium carbonate with an average particle size of 50nm and 40wt% calcium carbonate with an average particle size of 250nm, and the other steps are the same as in Example 6. Example 9

[0094] This embodiment is based on Example 6, the difference being that in step (2), the composite calcium carbonate is composed of 65wt% calcium carbonate with an average particle size of 50nm and 35wt% calcium carbonate with an average particle size of 250nm, and the other steps are the same as in Example 6. Application Examples 8-9

[0095] Application Examples 8 and 9 are based on Application Example 6, with the difference being that the source of the multifunctional co-extruded film in step one is different, while the other steps remain the same as in Application Example 6. Specifically: In Application Example 8, the multifunctional co-extruded film obtained in Example 8 is used.

[0096] In Application Example 9, the multifunctional co-extruded film obtained in Example 9 is used. Performance Test 3

[0097] Following the method of performance test 1, the moisture permeability of the composite breathable membranes obtained in test cases 8-9 was tested, and the results are shown in Table 3.

[0098] Table 3 Performance test results of composite breathable membrane

[0099] As shown in Table 3, the ratio of calcium carbonate with an average particle size of 50 nm to calcium carbonate with an average particle size of 250 nm has a certain influence on the moisture permeability of the prepared composite breathable membrane.

[0100] The embodiments described in this specific implementation are preferred embodiments of this application and are not intended to limit the scope of protection of this application. Therefore, all equivalent changes made in accordance with the principles of this application should be covered within the scope of protection of this application.

Claims

1. A multifunctional co-extruded film, characterized in that, It includes a co-extruded UV-resistant top layer, intermediate layer, and flame-retardant bottom layer; The UV-resistant surface layer comprises the following raw materials in parts by weight: 50-60 parts PE, 10-15 parts PP, and 20-40 parts UV-resistant composite agent; the raw materials for preparing the UV-resistant composite agent include nano-calcium carbonate with acrylate groups on its surface, UV absorber monomer with acrylate end groups, and methyl methacrylate, and the weight ratio of the nano-calcium carbonate with acrylate groups on its surface, the UV absorber monomer with acrylate end groups, and the methyl methacrylate is (30-40):(10-25):(40-55). The intermediate layer comprises the following raw materials in parts by weight: 60-70 parts PE and 30-40 parts calcium carbonate; The flame-retardant base layer comprises the following raw materials in parts by weight: 50-60 parts PE, 10-15 parts PP, 10-12 parts flame-retardant masterbatch, and 18-22 parts modified calcium carbonate.

2. The multifunctional co-extruded film according to claim 1, characterized in that, The preparation method of the UV-resistant composite agent includes the following steps: S1. Add coupling agent KH-570 to the first solvent, adjust the pH to 4~5 to obtain a modified solution, disperse nano-calcium carbonate with an average particle size of 40~60nm in the modified solution, stir and react for 4~8h, and after cooling, filtration, washing and drying, obtain nano-calcium carbonate with acrylate groups on the surface. S2. Mix the ultraviolet absorber, glycidyl methacrylate, catalyst and second solvent, control the temperature at 75~85℃, stir and react for 6~10h, cool, filter, wash and dry to obtain the ultraviolet absorber monomer with acrylate end groups. S3. Disperse the nano-calcium carbonate with acrylate groups on the surface obtained in step S1 in a third solvent, add methyl methacrylate, an initiator and the UV absorber monomer with acrylate end groups obtained in step S2, and stir the reaction for 6 to 10 hours under an inert atmosphere and controlled temperature of 70 to 80°C. After cooling, centrifugation, washing and drying, the UV-resistant composite agent is obtained. In step S1, the weight ratio of nano-calcium carbonate to coupling agent KH-570 is 100:(3~8). In step S2, the weight ratio of the ultraviolet absorber, glycidyl methacrylate, catalyst and first solvent is (33~38):(12~18):(1~3):(300~500).

3. The multifunctional co-extruded film according to claim 1, characterized in that, In the UV-resistant surface layer, the weight ratio of PE, PP and UV-resistant composite agent is (55~60):(10~15):

30.

4. The multifunctional co-extruded film according to claim 1, characterized in that, In the UV-resistant composite agent, the weight ratio of the UV absorber monomer with acrylate end groups to methyl methacrylate is (15~20):(45~50).

5. The multifunctional co-extruded film according to claim 1, characterized in that, In the intermediate layer, the average particle size of calcium carbonate is 40~300nm.

6. The multifunctional co-extruded film according to claim 5, characterized in that, In the intermediate layer, the calcium carbonate includes calcium carbonate with an average particle size of 40-60 nm and calcium carbonate with an average particle size of 200-300 nm, and the weight ratio of the calcium carbonate with an average particle size of 40-60 nm to the calcium carbonate with an average particle size of 200-300 nm is (6-7):(3-4).

7. The multifunctional co-extruded film according to claim 1, characterized in that, The method for preparing the modified calcium carbonate includes the following steps: Calcium carbonate with an average particle size of 0.5~1.0μm is provided, and the calcium carbonate is stirred at 100~110℃ for 10~30min. Then, n-octyltriethoxysilane is added, and the temperature is controlled at 105~120℃. The mixture is stirred at a stirring rate of 1000~1500rpm for 5~20min, and then cooled to obtain modified calcium carbonate.

8. A method for preparing a multifunctional co-extruded film as described in any one of claims 1 to 7, characterized in that, Includes the following steps: The raw materials corresponding to the UV-resistant top layer, intermediate layer and flame-retardant bottom layer are added to each screw extruder of the multi-layer co-extrusion casting equipment, and each melts independently to form the corresponding melt. The melts of each layer are combined and co-extruded through the die head, and after stretching and cooling, the multi-functional co-extruded film is formed. The stretch ratio is 3.0~3.8; based on a total material content of 100v% for the three layers, the material content of the UV-resistant top layer is 33.5~44.7v, the material content of the middle layer is 20~28v, and the material content of the flame-retardant bottom layer is 33.5~44.7v.

9. A composite breathable membrane, characterized in that, It includes a protective layer, a support layer, and a multifunctional co-extruded film as described in any one of claims 1 to 7; wherein the multifunctional co-extruded film is located between the protective layer and the support layer.

10. The application of the composite breathable membrane as described in claim 9 in building exterior walls, roofs, and agricultural greenhouses.

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