A cross-linked ETFE composite film with gradient ultraviolet shielding function and a preparation method and application thereof

Abstract

The application discloses a cross-linked ETFE composite film with gradient ultraviolet shielding function and a preparation method and application thereof, and belongs to the technical field of ETFE film preparation. The cross-linked ETFE composite film is composed of three layers of a surface layer, a middle layer and a bottom layer. The surface layer material comprises ETFE resin and fluorinated carbon quantum dots; the middle layer material comprises ETFE resin, allyl-containing comonomer A and phenyl-containing comonomer B; and the bottom layer material comprises ETFE resin and CeO2 nanowires. The fluorinated carbon quantum dots have a particle size of 3-5 nm and contain a -C4F9 structure. The comonomer A is an allyl-containing fluorine olefin monomer, and the comonomer B is a phenyl-containing organic fluorinated compound. Through the synergistic effect of the surface layer self-migration fluorinated carbon quantum dots, the middle layer copolymerization modification and the bottom layer CeO2 nanowires, high light transmittance, full-waveband ultraviolet shielding and long-term weather resistance are achieved.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of ETFE film preparation, and particularly relates to a cross-linked ETFE composite film with gradient ultraviolet shielding function and a preparation method and application thereof. BACKGROUND

[0002] Ethylene-tetrafluoroethylene copolymer (ETFE) is a high molecular compound copolymerized by ethylene and tetrafluoroethylene, which has excellent weather resistance, antifouling property and self-cleaning property. However, ETFE film does not have the function of blocking ultraviolet rays, which leads to easy aging of the underlying material under ultraviolet rays, limiting its application in photovoltaic modules. Therefore, developing an ETFE film with excellent ultraviolet resistance and a preparation method thereof is of great significance to improve the service life and performance of photovoltaic modules.

[0003] The existing ultraviolet protection of ETFE film mainly relies on physical blending of ultraviolet absorbers (such as benzotriazole and benzophenone), which can uniformly disperse compounds capable of absorbing ultraviolet rays in the ETFE matrix, so that the ultraviolet rays are captured by the absorbers when they pass through the film, thereby reducing the amount of ultraviolet rays reaching the underlying material and achieving the purpose of protection.

[0004] CN119529414A discloses an ultraviolet-resistant ETFE film for photovoltaic modules, which includes the following components by weight: ethylene-tetrafluoroethylene copolymer as a base material; stabilizing aids in an amount of 0.5-1.5 parts by weight; antioxidants in an amount of 0.5-1.5 parts by weight; and ultraviolet-resistant agents in an amount of 0.4-1.6 parts by weight. The application significantly improves the ultraviolet blocking rate of the film by adding 2,2'-methylene bis 6-(2H-benzotriazole-2-yl)-4-(1,1,3,3-tetramethylbutyl) phenol and C 27 H27N3O2. However, the 2,2'-methylene bis 6-(2H-benzotriazole-2-yl)-4-(1,1,3,3-tetramethylbutyl) phenol used in the application degrades after high-temperature processing or long-term light exposure, causing the film to turn yellow (yellowing index > 5).

[0005] CN114591558A discloses an ETFE film with ultraviolet blocking function, which comprises ETFE resin, TiO2@polydopamine composite particles and ultraviolet absorber. The ultraviolet absorber comprises any one or a combination of salicylate ultraviolet absorber, acetone ultraviolet absorber or triazine ultraviolet absorber. Dopamine is used to modify TiO2, and PDA is coated on the surface of TiO2 to prepare PDA-coated TiO2(TiO2@PDA) composite particles with light absorption function. The TiO2@PDA can absorb the part of ultraviolet light with frequency easy to be absorbed by human body. The invention can block more than 98% of ultraviolet light with a wavelength of 290-400 nm. However, the nanometer ions (such as TiO2 and ZnO) are not uniformly dispersed, which leads to the increase of haze of ETFE film (haze > 10%) and the significant decrease of light transmittance.

[0006] In summary, the existing ETFE film with anti-ultraviolet performance has the problems of serious yellowing and decrease of light transmittance. Therefore, it is necessary to provide an ETFE film with ultraviolet blocking function which is resistant to yellowing and can prevent the decrease of light transmittance. SUMMARY

[0007] In order to solve the above technical problems, the present application provides a cross-linked ETFE composite film with gradient ultraviolet shielding function and its preparation method and application.

[0008] In order to achieve the above purpose, the present application adopts the following technical scheme:

[0009] In the first aspect, the present application provides a cross-linked ETFE composite film with gradient ultraviolet shielding function, which is composed of three layers of surface layer, middle layer and bottom layer,

[0010] The surface layer material comprises ETFE resin and fluorinated carbon quantum dots (F-CQDs);

[0011] The middle layer material comprises ETFE resin, allyl-containing comonomer A and phenyl-containing comonomer B;

[0012] The bottom layer material comprises ETFE resin and CeO2 nanowires.

[0013] The present application uses F-CQDs of the surface layer material to shield UAB (280-315 nm), uses CeO2 nanowires of the bottom layer material to scatter UVA (315-400 nm), and uses the benzene ring structure of the intermediate layer material to supplement absorption, thereby achieving full-band ultraviolet shielding. Meanwhile, F-CQDs can spontaneously accumulate on the surface layer due to surface energy gradient, the allyl structure of the intermediate layer material provides irradiation crosslinking sites, the position of F-CQDs is fixed under electron beam irradiation, and the copolymerization monomer B containing phenyl is crosslinked to the ETFE main chain, thereby solving the degradation problem of small molecule ultraviolet absorbers.

[0014] In some embodiments, the fluorinated carbon quantum dots have a particle size of 3-5 nm and contain a -C4F9 structure. Preferably, the fluorinated carbon quantum dots are 0.05%-0.2% of the weight of the surface layer material.

[0015] In some embodiments, the copolymerization monomer A is an allyl-containing fluorine olefin monomer, and the copolymerization monomer B is a phenyl-containing organic fluorine compound. Preferably, the copolymerization monomer A is 1%-3% of the total moles of the intermediate layer material, and the copolymerization monomer B is 2%-5% of the total moles of the intermediate layer material.

[0016] In some embodiments, the CeO2 nanowires are 0.01%-0.1% of the weight of the bottom layer material.

[0017] In some embodiments, the CeO2 nanowires are silane coupling agent modified CeO2 nanowires; preferably, the silane coupling agent is at least one of KH-570, KH550, tridecafluorooctyltriethoxysilane, and heptadecafluorodecyltrimethoxysilane; and further preferably, KH-570.

[0018] In some embodiments, the preparation method of the silane coupling agent modified CeO2 nanowires is as follows: CeO2 nanowires are dispersed in a nitric acid solution and subjected to ultrasonic treatment for surface hydroxylation, centrifuged and washed to neutral, and then dried to obtain hydroxylated CeO2 nanowires; a silane coupling agent is mixed with anhydrous ethanol and deionized water, and acetic acid is used to adjust the pH to 4-5, and stirring is performed to hydrolyze methoxyl groups into silanol groups to obtain a hydrolysis solution; the hydroxylated CeO2 nanowires are added to the hydrolysis solution, ultrasonic dispersion is performed, and reflux reaction is performed under nitrogen protection, after the reaction is completed, centrifugation is performed and anhydrous ethanol is used to wash and remove physically adsorbed silane, and then drying is performed.

[0019] Preferably, the diameter of the CeO2 nanowires is 10-50 nm, and the aspect ratio is >20.

[0020] Preferably, the concentration of the nitric acid solution is 2.7-3.3 M.

[0021] Preferably, the ultrasonic treatment time is 0.5-1.5 h.

[0022] Preferably, the volume ratio of the silane coupling agent, anhydrous ethanol and deionized water is 3-7:90:3-7.

[0023] Preferably, the conditions of the reflux reaction are refluxing at 75-85℃ for 4-8h.

[0024] In some embodiments, the surface layer is 5%-20% of the thickness of the crosslinked ETFE composite film; the intermediate layer is 70%-85% of the thickness of the crosslinked ETFE composite film; and the bottom layer is 5%-10% of the thickness of the crosslinked ETFE composite film.

[0025] Preferably, the surface layer is 15%-20% of the thickness of the crosslinked ETFE composite film.

[0026] Preferably, the intermediate layer is 80%-85% of the thickness of the crosslinked ETFE composite film.

[0027] In some embodiments, the thickness of the crosslinked ETFE composite film is 15-250μm, preferably 25-100μm.

[0028] In the second aspect, the present application provides a preparation method of the above crosslinked ETFE composite film, comprising the following steps:

[0029] (1) each component in the surface layer material, the intermediate layer material and the bottom layer material is mixed uniformly respectively, and then granulated to obtain a surface layer forming material, an intermediate layer forming material and a bottom layer forming material;

[0030] (2) the surface layer forming material, the intermediate layer forming material and the bottom layer forming material are subjected to three-layer co-extrusion and cast molding to obtain a composite film;

[0031] (3) the composite film is subjected to irradiation crosslinking, traction cooling, detection, slitting and winding to obtain the crosslinked ETFE composite film.

[0032] In some embodiments, the irradiation in step (3) is electron beam irradiation, preferably, the dose of the irradiation is 15-25kGy, and the environmental gas is nitrogen. Further preferably, the oxygen content in the nitrogen is less than 50ppm.

[0033] In the third aspect, the present application provides the use of the above crosslinked ETFE composite film or the crosslinked ETFE composite film prepared by the above preparation method in the preparation of photovoltaic modules, building membrane structures or space transparent materials.

[0034] In the fourth aspect, the present application provides a photovoltaic module, wherein the above crosslinked ETFE composite film or the crosslinked ETFE composite film prepared by the above preparation method is used as a photovoltaic backboard.

[0035] In a fifth aspect, the present application provides a double glass assembly, wherein the crosslinked ETFE composite film prepared by the aforementioned method or the aforementioned crosslinked ETFE composite film is used as the encapsulating material of the double glass assembly.

[0036] The present application has the following advantages:

[0037] (1) The present application uses F-CQDs of the surface layer material to shield UAB (280-315 nm), uses CeO2 nanowires of the bottom layer material to scatter UVA (315-400 nm), and uses the benzene ring structure of the intermediate layer material to supplement absorption, thereby achieving full-band ultraviolet shielding. At the same time, F-CQDs can spontaneously accumulate on the surface layer due to the surface energy gradient, the allyl structure of the intermediate layer material provides irradiation crosslinking sites, and the position of F-CQDs is fixed under electron beam irradiation, and the copolymerized monomer B containing a benzene group is crosslinked to the ETFE main chain, thereby solving the problem of degradation of small molecule ultraviolet absorbers.

[0038] (2) The present application realizes high light transmittance (>92%), full-band ultraviolet shielding (>99%), and long-term weather resistance (QUV 3000 h, ΔYI <1.0) through the synergistic effect of the surface layer self-migration fluorocarbon quantum dots (F-CQDs), the intermediate layer copolymerization modification, and the bottom layer CeO2 nanowires. DETAILED DESCRIPTION

[0039] The following description of the embodiments is merely exemplary in nature and is in no way intended to limit the scope of the application, its application, or its interpretation. Since those skilled in the art are well aware that any changes in form and details can be made to the embodiments described herein without departing from the spirit and scope of the application, it should be understood that all such changes and modifications are intended to be included within the scope of the application. Various modifications to the embodiments disclosed herein will be readily apparent to those skilled in the art, and generic principles defined herein can be applied to other embodiments without departing from the spirit or scope of the application. Thus, the present application is not to be limited to the embodiments shown herein but is to be accorded the full scope consistent with the patent laws. Although any methods and materials similar or equivalent to those described herein can be used in the practice or testing of the present application, the preferred methods and materials are described herein.

[0040] Unless otherwise defined, all technical and scientific terms used in the application have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs.

[0041] The raw materials used in the present application are all conventional commercially available products, therefore the present application does not limit the source of the raw materials, for example, the ETFE resin is purchased from Dongyue Future Hydrogen Energy, with the item number ET825LMJ; the F-CQDs are CH2=CH-CH2-O-CO-(CQD)-NH-CO-C4F9, and the preparation method is referred to CN118156436A embodiment 1; the comonomer A is CF2=CF-O-CH2-CH=CH2, purchased from Zibo Hangyu Biotechnology Development Co., Ltd.; the comonomer B is 2,2-bis[4-(trifluorovinyloxy)phenyl]hexafluoropropane, purchased from Shanghai Enfluor Technology Co., Ltd., and the structural formula is shown as follows.

[0042]

[0043] The CeO2 nanometer is a silane coupling agent modified CeO2 nanowire, and the specific preparation method is as follows:

[0044] The CeO2 nanowire (diameter 10-50 nm, aspect ratio > 20) is dispersed in 3M nitric acid solution and ultrasonically treated for 1h (power 300W) to perform surface hydroxylation, centrifuged and washed to neutral, and then vacuum dried at 80℃ for 12h to obtain hydroxylated CeO2 nanowire; the silane coupling agent KH-570 is mixed with anhydrous ethanol and deionized water in a volume ratio of 5:90:5, and the pH is adjusted to 4-5 with acetic acid, and the methoxy group is hydrolyzed to silanol by magnetic stirring for 30min to obtain a hydrolysis solution; the hydroxylated CeO2 nanowire is taken and added to the hydrolysis solution, ultrasonically dispersed for 30min, and then transferred to a three-necked flask, and refluxed at 80℃ under nitrogen protection for 6h, and then centrifuged (8000rpm, 10min) and washed with anhydrous ethanol for 3 times to remove the physically adsorbed silane, and then vacuum dried at 60℃ for 24h.

[0045] Examples 1-3

[0046] The crosslinked ETFE composite film is prepared according to the following preparation method according to the formula in Table 1.

[0047] Table 1

[0048]

[0049] Note: In the table, the "%" of F-CQDs is the weight percentage of F-CQDs in the total weight of the surface layer material; the "%" of comonomer A is the mole percentage of comonomer A in the total moles of the intermediate layer material; the "%" of comonomer B is the mole percentage of comonomer B in the total moles of the intermediate layer material; the "%" of the silane coupling agent modified CeO2 nanowire is the weight percentage of the silane coupling agent modified CeO2 nanowire in the total weight of the bottom layer material.

[0050] The preparation method has the following steps:

[0051] (1) The ETFE resin is vacuum dried at 100°C for 6 hours to remove moisture, and the moisture content is controlled to be ≤0.02%;

[0052] The surface layer material is prepared by melt blending fluorocarbon quantum dots (F-CQDs, particle size 3-5 nm) and ETFE resin through a double-screw extruder at 260-280°C;

[0053] The intermediate layer material is a premix of ETFE resin, allyl-containing comonomer A, and phenyl-containing comonomer B;

[0054] The bottom layer material is a premix of silane coupling agent KH-570 modified CeO2 nanowires (diameter 25 nm, aspect ratio 25) and ETFE resin;

[0055] (2) Three co-rotating twin-screw extruders (L / D = 40:1) are fed with independent temperature gradients: the surface layer extruder is set to 270°C for feeding, 290°C for melting, and 300°C for homogenization, with a screw speed of 80 rpm; the intermediate layer extruder is set to 275-295-305°C, with a screw speed of 120 rpm; the bottom layer extruder is set to 270-290-300°C, with a screw speed of 100 rpm; the melt is converged into a three-layer clothes hanger type co-extrusion die through special design, with the die temperature zones accurately controlled to be 260°C for the surface layer, 290°C for the intermediate layer, and 270°C for the bottom layer; F-CQDs spontaneously migrate to the surface layer through temperature difference induction, and the melt is cast onto a 50°C mirror surface cooling roller at a speed of 5 m / min, obtaining a composite film;

[0056] (3) The composite film is immediately irradiated by a 1.5 MeV electron accelerator (20 kGy) at a distance of 2 meters from the die outlet, with a nitrogen atmosphere to control the oxygen content to be <50 ppm to prevent oxidation; the irradiated film material is solidified and shaped by a cooling system, the thickness is adjusted to 25±1 μm in real time by a β-ray online thickness gauge (accuracy ±0.5 μm), and finally wound up by a tension control system.

[0057] Comparative Example 1

[0058] The difference between this comparative example and Example 3 is that the raw materials are the same, but not layered, and the specific preparation method is different.

[0059] Specifically, the preparation method of Comparative Example 1 is as follows:

[0060] (1) The ETFE resin is vacuum dried at 100°C for 4 hours to remove moisture, and the moisture content is controlled to be ≤0.02%;

[0061] The surface layer material is prepared by melt blending fluorocarbon quantum dots (F-CQDs, particle size 3-5 nm) and ETFE resin through a double-screw extruder at 260-280°C;

[0062] The intermediate layer material is a premix of ETFE resin and allyl-containing comonomer A and phenyl-containing comonomer B;

[0063] The bottom layer material is a premix of CeO2 nanowires (diameter 25 nm, aspect ratio 25) modified by silane coupling agent KH-570 and ETFE resin;

[0064] (2) The surface layer material, the intermediate layer material and the bottom layer material are added into a high-speed mixer and premixed for 30 minutes to obtain a total premix, and the total premix is put into a single-screw extruder (L / D = 30:1) for melt blending, the temperature is set to 260℃ for the feeding section, 280℃ for the melting section and 270℃ for the homogenizing section, the screw rotation speed is set to 100 rpm, the melt is extruded through a die (270℃) at a speed of 5 m / min and then cast onto a 50℃ mirror surface cooling roller, and then irradiated by a 1.5 MeV electron accelerator (20 kGy) at a distance of 2 meters from the die outlet, the oxygen content is controlled to be less than 50 ppm in a nitrogen atmosphere to prevent oxidation, the irradiated film material is solidified and shaped by a cooling system, the thickness is adjusted to 25±1 μm in real time by a β-ray online thickness gauge (accuracy ±0.5 μm), and finally wound up by a tension control system.

[0065] The properties of the crosslinked ETFE composite film prepared in different examples and comparative examples are detected, and the results are shown in Table 2.

[0066] Table 2

[0067]

[0068] The results show that the crosslinked ETFE composite film prepared in Examples 1-3 of the application has good performance in terms of ultraviolet shielding, visible light transmission, clarity, tensile strength, color stability, interlayer adhesion and hydrophobicity.

[0069] Comparing Comparative Example 1 and Example 3, it can be seen that the preparation method has different degrees of influence on the performance of the crosslinked ETFE composite film, such as ultraviolet shielding, visible light transmission, clarity, tensile strength, color stability, interlayer adhesion and hydrophobicity, especially clarity, color stability and interlayer adhesion.

[0070] Examples 4-6

[0071] The crosslinked ETFE composite film is prepared according to the following preparation method and the formula in Table 3 to obtain crosslinked ETFE composite films with different thicknesses.

[0072] Table 3

[0073]

[0074] Note: In the table, the "%" of F-CQDs is the weight percentage of F-CQDs in the total weight of the surface layer material; the "%" of comonomer A is the mole percentage of comonomer A in the total moles of the intermediate layer material; the "%" of comonomer B is the mole percentage of comonomer B in the total moles of the intermediate layer material; the "%" of CeO2 nanowires is the weight percentage of silane coupling agent modified CeO2 nanowires in the total weight of the bottom layer material.

[0075] The preparation method is the same as that in Example 1.

[0076] The properties of the crosslinked ETFE composite films prepared in different examples were detected, and the results are shown in Table 4.

[0077] Table 4

[0078]

[0079] Note: In the table, the tensile strength 45 / 42 represents the longitudinal tensile strength / the transverse tensile strength.

[0080] The results show that the crosslinked ETFE composite films prepared in Examples 4-6 of the present application have good properties in terms of ultraviolet shielding, visible light transmission, clarity, tensile strength, color stability, interlayer adhesion and hydrophobicity.

[0081] Examples 7-8 and Comparative Examples 2-3

[0082] The crosslinked ETFE composite films were prepared according to the following preparation method according to the formulations in Table 5.

[0083] Table 5

[0084]

[0085] Note: In the table, the "%" of F-CQDs is the weight percentage of F-CQDs in the total weight of the surface layer material; the "%" of comonomer A is the mole percentage of comonomer A in the total moles of the intermediate layer material; the "%" of comonomer B is the mole percentage of comonomer B in the total moles of the intermediate layer material; the "%" of CeO2 nanowires is the weight percentage of silane coupling agent modified CeO2 nanowires in the total weight of the bottom layer material; "*" indicates that the CeO2 nanowires are CeO2 nanowires that have not been modified by a silane coupling agent.

[0086] The preparation method is the same as that in Example 1.

[0087] The properties of the crosslinked ETFE composite films prepared in different examples and comparative examples were detected, and the results are shown in Table 6.

[0088] Table 6

[0089]

[0090] The results show that the crosslinked ETFE composite film prepared in Example 7-Example 8 has good performance in ultraviolet shielding, visible light transmission, clarity, tensile strength, color stability, interlayer adhesion and hydrophobicity.

[0091] The crosslinked ETFE composite film prepared in Comparative Example 2 and Comparative Example 3 has good performance in ultraviolet shielding, tensile strength, interlayer adhesion and hydrophobicity, but cannot simultaneously have good performance in visible light transmission, clarity or color stability.

[0092] The above is a further description of the present application in combination with specific examples, but these examples are only exemplary and do not constitute any limitation on the scope of the present application. Those skilled in the art should understand that the details and forms of the technical solutions of the present application can be modified or replaced without departing from the spirit and scope of the present application, and such modifications and replacements all fall within the protection scope of the present application.

Claims

1. A crosslinked ETFE composite film having a gradient ultraviolet shielding function, characterized by, The cross-linked ETFE composite film is composed of a surface layer, an intermediate layer and a bottom layer; The surface layer material comprises ETFE resin and carbon fluoride quantum dots; The intermediate layer material comprises ETFE resin, allyl-containing comonomer A and phenyl-containing comonomer B; The bottom layer material comprises ETFE resin and CeO2 nanowires; The carbon fluoride quantum dots have a particle size of 3-5 nm and contain a -C4F9 structure; The comonomer A is an allyl-containing fluoroolefin monomer; The comonomer B is a phenyl-containing organic fluorine compound; The carbon fluoride quantum dots account for 0.05-0.2% of the total weight of the surface layer material; The CeO2 nanowires account for 0.01-0.1% of the total weight of the bottom layer material.

2. The crosslinked ETFE composite film according to claim 1, wherein, The comonomer A accounts for 1-3% of the total moles of the intermediate layer material; and the comonomer B accounts for 2-5% of the total moles of the intermediate layer material.

3. The crosslinked ETFE composite film according to claim 1, wherein, The CeO2 nanowires are modified by a silane coupling agent; the silane coupling agent is at least one of KH-570, KH550, tridecafluorooctyltriethoxysilane and heptadecafluorodecyltrimethoxysilane.

4. The crosslinked ETFE composite film according to claim 1, wherein, The surface layer accounts for 5-20% of the total thickness of the cross-linked ETFE composite film; the intermediate layer accounts for 70-85% of the total thickness of the cross-linked ETFE composite film; and the bottom layer accounts for 5-10% of the total thickness of the cross-linked ETFE composite film.

5. The crosslinked ETFE composite film of claim 1, wherein The thickness of the cross-linked ETFE composite film is 15-250 μm.

6. The crosslinked ETFE composite film of claim 1, wherein The surface layer accounts for 15-20% of the total thickness of the cross-linked ETFE composite film.

7. The crosslinked ETFE composite film of claim 1, wherein The intermediate layer accounts for 80-85% of the total thickness of the cross-linked ETFE composite film.

8. The method for producing the crosslinked-ETFE composite film according to any one of claims 1 to 7, characterized by, The method comprises the following steps: (1) Each component in the surface layer material, the intermediate layer material and the bottom layer material is uniformly mixed and then granulated to obtain surface layer forming material, intermediate layer forming material and bottom layer forming material; (2) The surface layer forming material, the intermediate layer forming material and the bottom layer forming material are subjected to three-layer co-extrusion and flow casting to obtain a composite film; The composite film is subjected to irradiation cross-linking, traction cooling, detection and slitting and winding to obtain the cross-linked ETFE composite film. In step (2), the irradiation is electron beam irradiation; the dose of the irradiation is 15-25 kGy; and the environmental gas is nitrogen.

9. Use of the cross-linked ETFE composite film according to any one of claims 1-7 or prepared by the preparation method of claim 8 in the preparation of photovoltaic components, building membrane structures or space transparent materials.

10. A photovoltaic module, characterized by, The cross-linked ETFE composite film according to any one of claims 1-7 or prepared by the preparation method of claim 8 is used as an encapsulating material for photovoltaic back plates or double-glass components.

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