Crosslinked ETFE composite film with gradient ultraviolet shielding function and preparation method and application thereof

Abstract

The invention discloses a cross-linked ETFE composite film with a 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 a surface layer, a middle layer and a bottom layer; the surface layer material comprises ETFE resin and carbon fluoride quantum dots; the material of the middle layer comprises ETFE resin, an allyl-containing comonomer A and a phenyl-containing comonomer B; the bottom layer material comprises ETFE resin and a CeO2 nanowire; the particle size of the carbon fluoride quantum dot is 3-5nm, and the carbon fluoride quantum dot comprises a-C4F9 structure; the comonomer A is a fluoroolefin monomer containing allyl; the comonomer B is organic fluoride containing phenyl. Through the synergistic effect of the self-migration carbon fluoride quantum dots on the surface layer, copolymerization modification on the middle layer and the CeO2 nanowires on the bottom layer, high light transmittance, full-band ultraviolet shielding and long-term weather resistance are achieved.

Description

Technical Field

[0001] The present invention belongs to the technical field of ETFE film preparation, and in particular relates to a cross-linked ETFE composite film with a gradient ultraviolet shielding function, a preparation method thereof, and an application thereof. Background Art

[0002] Ethylene-tetrafluoroethylene (ETFE) is a polymer compound formed by the copolymerization of ethylene and tetrafluoroethylene. It exhibits excellent weather resistance, antifouling, and self-cleaning properties. However, ETFE film lacks UV protection, resulting in the underlying material being susceptible to UV degradation, limiting its application in photovoltaic modules. Therefore, developing an ETFE film with excellent UV resistance and its preparation method are crucial for improving the service life and performance of photovoltaic modules.

[0003] The UV protection of existing ETFE films mainly relies on physically blended UV absorbers (such as benzotriazoles and benzophenones). By evenly dispersing compounds that can absorb UV rays in the ETFE matrix, the UV rays are captured by the absorber when passing through the film, thereby reducing the amount of UV rays reaching the underlying material and achieving the protection purpose.

[0004] CN119529414A discloses a UV-blocking ETFE film for photovoltaic modules. The ETFE film comprises the following components based on 100 parts by weight: an ethylene-tetrafluoroethylene copolymer as a substrate; a stabilizing agent in the range of 0.5-1.5 parts by weight; an antioxidant in the range of 0.5-1.5 parts by weight; and an anti-ultraviolet agent in the range of 0.4-1.6 parts by weight. The invention is characterized in that 2,2'-methylenebis(6-(2H-benzotriazole-2-yl)-4-(1,1,3,3-tetramethylbutyl)phenol and C 27 H27N3O2 significantly improves the UV blocking rate of the film. However, the 2,2'-methylenebis(6-(2H-benzotriazole-2-yl)-4-(1,1,3,3-tetramethylbutyl)phenol used in this invention degrades after high-temperature processing or long-term light exposure, causing the film to yellow (yellowing index > 5).

[0005] CN114591558A discloses an ETFE film with UV-blocking properties. The film comprises ETFE resin, TiO2@polydopamine composite particles, and a UV absorber. The UV absorber can be any combination of salicylate, acetone, or triazine. TiO2 is modified with dopamine and coated with polydopamine (PDA) to produce PDA-coated TiO2 (TiO2@PDA) composite particles with light-absorbing properties. The TiO2@PDA absorbs UV frequencies that are easily absorbed by the human body. This invention can block over 98% of UV rays with wavelengths between 290nm and 400nm. However, the uneven dispersion of the nanoparticles (e.g., TiO2 and ZnO) in this invention increases the haze of the ETFE film (haze > 10%) and significantly reduces its light transmittance.

[0006] In summary, the existing ETFE film with anti-ultraviolet performance has problems such as severe yellowing and reduced transmittance. Therefore, it is very necessary to provide an ETFE film with anti-yellowing and anti-transmittance and UV blocking function. Summary of the Invention

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

[0008] In order to achieve the above object, the present invention adopts the following technical solutions: In a first aspect, the present invention provides a cross-linked ETFE composite film with gradient UV shielding function, which is composed of a three-layer structure of a surface layer, an intermediate layer and a bottom layer. The surface materials include ETFE resin and fluorinated carbon quantum dots (F-CQDs); The intermediate layer material includes ETFE resin, allyl-containing comonomer A and phenyl-containing comonomer B; The underlying materials include ETFE resin and CeO2 nanowires.

[0009] This invention utilizes F-CQDs in the surface layer to shield UAB (280-315nm), CeO2 nanowires in the bottom layer to scatter UVA (315-400nm), and the benzene ring structure in the middle layer to supplement absorption, achieving full-band UV shielding. Furthermore, the F-CQDs spontaneously accumulate on the surface layer due to the surface energy gradient, while the allyl structure in the middle layer provides radiation crosslinking sites. Under electron beam irradiation, the F-CQDs are fixed in position and the phenyl-containing comonomer B is crosslinked to the ETFE backbone, addressing the degradation issue of small-molecule UV absorbers.

[0010] In some embodiments, the particle size of the carbon fluoride quantum dots is 3-5 nm and comprises a -C4F9 structure. Preferably, the carbon fluoride quantum dots account for 0.05%-0.2% of the weight of the surface material.

[0011] In some embodiments, the comonomer A is an allyl-containing fluoroolefin monomer, and the comonomer B is an organic fluoride containing a phenyl group. Preferably, the comonomer A accounts for 1% to 3% of the total molar amount of the intermediate layer material, and the comonomer B accounts for 2% to 5% of the total molar amount of the intermediate layer material.

[0012] In some embodiments, the CeO2 nanowires are 0.01% to 0.1% by weight of the underlying material.

[0013] In some embodiments, the CeO2 nanowires are CeO2 nanowires modified with a silane coupling agent; preferably, the silane coupling agent is at least one of KH-570, KH550, tridecafluorooctyltriethoxysilane, and heptadecafluorodecyltrimethoxysilane; more preferably KH-570.

[0014] In some embodiments, the preparation method of the silane coupling agent-modified CeO2 nanowires is as follows: dispersing the CeO2 nanowires in a nitric acid solution, ultrasonically treating the surface of the CeO2 nanowires for hydroxylation, washing the solution by centrifugation until neutral, and then drying to obtain hydroxylated CeO2 nanowires; mixing the silane coupling agent with anhydrous ethanol and deionized water, adjusting the pH to 4-5 with acetic acid, and stirring to hydrolyze the methoxy groups into silanols to obtain a hydrolyzate; adding the hydroxylated CeO2 nanowires to the hydrolyzate, ultrasonically dispersing the solution, and refluxing the solution under nitrogen protection for reaction; after the reaction is complete, centrifuging the solution, washing the solution with anhydrous ethanol to remove physically adsorbed silane, and drying the solution.

[0015] Preferably, the diameter of the CeO2 nanowire is 10-50 nm, and the aspect ratio is greater than 20.

[0016] Preferably, the concentration of the nitric acid solution is 2.7-3.3M.

[0017] Preferably, the ultrasonic treatment time is 0.5-1.5 h.

[0018] Preferably, the volume ratio of the silane coupling agent to anhydrous ethanol and deionized water is 3-7:90:3-7.

[0019] Preferably, the reflux reaction is carried out at 75-85° C. for 4-8 hours.

[0020] In some embodiments, the surface layer is 5%-20% of the thickness of the cross-linked ETFE composite film; the middle layer is 70%-85% of the thickness of the cross-linked ETFE composite film; and the bottom layer is 5%-10% of the thickness of the cross-linked ETFE composite film.

[0021] Preferably, the surface layer is 15%-20% of the thickness of the cross-linked ETFE composite film.

[0022] Preferably, the intermediate layer is 80%-85% of the thickness of the cross-linked ETFE composite film.

[0023] In some embodiments, the cross-linked ETFE composite film has a thickness of 15-250 μm, preferably 25-100 μm.

[0024] In a second aspect, the present invention provides a method for preparing the cross-linked ETFE composite membrane, comprising the steps of: (1) After the components of the surface layer material, the middle layer material and the bottom layer material are mixed evenly, they are granulated separately to obtain the surface layer forming material, the middle layer forming material and the bottom layer forming material; (2) The surface layer forming material, the middle layer forming material and the bottom layer forming material are co-extruded and cast to obtain a composite film; (3) The composite film is obtained by irradiation cross-linking, traction cooling, testing, slitting and winding.

[0025] In some embodiments, the irradiation in step (3) is electron beam irradiation, preferably, the irradiation dose is 15-25 kGy, and the ambient gas is nitrogen. Further preferably, the oxygen content in the nitrogen is less than 50 ppm.

[0026] In a third aspect, the present invention provides the use of the cross-linked ETFE composite film or the cross-linked ETFE composite film prepared by the above preparation method in the preparation of photovoltaic modules, architectural membrane structures or aerospace light-transmitting materials.

[0027] In a fourth aspect, the present invention provides a photovoltaic module, using the cross-linked ETFE composite film or the cross-linked ETFE composite film prepared by the above preparation method as a photovoltaic backsheet.

[0028] In a fifth aspect, the present invention provides a double-glass component, wherein the cross-linked ETFE composite film or the cross-linked ETFE composite film prepared by the above preparation method is used as the packaging material of the double-glass component.

[0029] The beneficial effects of the present invention are: (1) The present invention utilizes the F-CQDs of the surface material to shield UAB (280-315nm), utilizes the CeO2 nanowires of the bottom material to scatter UVA (315-400nm), and utilizes the benzene ring structure of the intermediate material to supplement absorption, thereby achieving full-band UV shielding. Simultaneously, the F-CQDs can spontaneously accumulate on the surface due to the surface energy gradient, and the allyl structure of the intermediate material provides radiation cross-linking sites. Under electron beam irradiation, the position of the F-CQDs is fixed, and the phenyl-containing comonomer B is cross-linked to the ETFE main chain, thus solving the problem of degradation of small molecule UV absorbers.

[0030] (2) The present invention achieves high light transmittance (>92%), full-band UV shielding (>99%) and long-term weather resistance (QUV3000h, ΔYI <1.0) through the synergistic effect of surface self-migrating fluorinated carbon quantum dots (F-CQDs), intermediate layer copolymerization modification and bottom layer CeO2 nanowires. DETAILED DESCRIPTION

[0031] The following examples are only intended to help understand the methods of the present invention and their core concepts. It should be noted that, for those skilled in the art, without departing from the principles of the present invention, several improvements and modifications may be made to the present invention, and these improvements and modifications also fall within the scope of protection of the claims of the present invention. The following description of the disclosed embodiments enables professionals in this field to implement or use the present invention. Various modifications to these embodiments will be apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention will not be limited to the embodiments shown herein, but may be applied to a wider range consistent with the principles and novel features disclosed herein. Although any methods and materials similar or equivalent to those described in the present invention may be used in the practice or testing of the present invention, preferred methods and materials are listed herein.

[0032] Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs.

[0033] The raw materials used in the present invention are all conventional commercial products, so the present invention does not limit the source of the raw materials. For example, the ETFE resin is purchased from Dongyue Future Hydrogen Energy with the product number ET825LMJ; the F-CQDs is CH2=CH-CH2-O-CO-(CQD)-NH-CO-C4F9, and the preparation method is referred to Example 1 of CN118156436A; 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-(trifluoroethyleneoxy)phenyl]hexafluoropropane, purchased from Shanghai Enfujia Technology Co., Ltd., and the structural formula is shown below.

[0034]

[0035] The CeO2 nanowires are CeO2 nanowires modified with a silane coupling agent, and the specific preparation method is as follows: CeO2 nanowires (diameter 10-50nm, aspect ratio > 20) were dispersed in 3M nitric acid solution and ultrasonically treated for 1h (power 300W) for surface hydroxylation. After centrifugal washing until neutral, the mixture was vacuum dried at 80℃ for 12h to obtain hydroxylated CeO2 nanowires. The silane coupling agent KH-570 was mixed with anhydrous ethanol and deionized water in a volume ratio of 5:90:5, and the pH was adjusted to 4-5 with acetic acid. The mixture was magnetically stirred for 30min to hydrolyze the methoxy group into silanol to obtain a hydrolyzate. The hydroxylated CeO2 nanowires were added to the hydrolyzate, ultrasonically dispersed for 30min, and then transferred to a three-necked flask. The mixture was refluxed at 80℃ under nitrogen protection for 6h. After the reaction was completed, the mixture was centrifuged (8000rpm, 10min) and washed with anhydrous ethanol three times to remove physically adsorbed silane. The mixture was vacuum dried at 60℃ for 24h.

[0036] Example 1-Example 3 The cross-linked ETFE composite film was prepared according to the formula in Table 1 and the following preparation method.

[0037] Table 1

[0038] Note: The "%" of F-CQDs in the table is the weight percentage of F-CQDs in the total weight of the surface layer material; the "%" of comonomer A is the molar percentage of comonomer A in the total molar amount of the intermediate layer material; the "%" of comonomer B is the molar percentage of comonomer B in the total molar amount of the intermediate layer material; the "%" of CeO2 nanowires is the weight percentage of CeO2 nanowires modified with silane coupling agent in the total weight of the bottom layer material.

[0039] The preparation method comprises the following steps: (1) Dry the ETFE resin in vacuum at 100°C for 6 hours to remove moisture and control the moisture content to ≤0.02%; The surface material is made of fluorinated carbon quantum dots (F-CQDs, particle size 3-5 nm) and ETFE resin melt-blended and granulated at 260-280°C through a twin-screw extruder; The middle layer material is a premix of ETFE resin, allyl-containing comonomer A, and phenyl-containing comonomer B; The bottom layer material is a premix of CeO2 nanowires (diameter 25 nm, aspect ratio 25) modified with silane coupling agent KH-570 and ETFE resin; (2) Three co-rotating twin-screw extruders (L / D = 40:1) were fed with independent temperature gradients: the surface layer extruder was set at a feeding section of 270 °C, a melting section of 290 °C, and a homogenizing section of 300 °C, with a screw speed of 80 rpm; the middle layer extruder was set at 275-295-305 °C, 120 rpm; the bottom layer extruder was set at 270-290-300 °C, 100 rpm; the melt was converged and formed by a specially designed three-layer hanger-type co-extrusion die head, and the die head temperature zones were precisely controlled to be 260 °C for the surface layer, 290 °C for the middle layer, and 270 °C for the bottom layer. The F-CQDs spontaneously migrated to the surface layer by inducing the temperature difference, and the melt was cast onto a 50 °C mirror cooling roller at a speed of 5 m / min to obtain a composite film; (3) The composite film is then irradiated (20 kGy) by a 1.5 MeV electron accelerator 2 meters away from the die outlet. The oxygen content in the nitrogen atmosphere is controlled to <50 ppm to prevent oxidation. The irradiated film is solidified by the cooling system. The thickness is adjusted to 25 ± 1 μm in real time using a β-ray online thickness gauge (accuracy ± 0.5 μm), and finally wound by a tension control system.

[0040] Comparative Example 1 The difference between this comparative example and Example 3 is that the raw materials are the same, but no separation is performed, and the specific preparation methods are different.

[0041] Specifically, the preparation method of Comparative Example 1 comprises the following steps: (1) The ETFE resin was vacuum dried at 100°C for 4 hours to remove moisture, and the moisture content was controlled to ≤0.02%; The surface material is made of fluorinated carbon quantum dots (F-CQDs, particle size 3-5 nm) and ETFE resin melt-blended and granulated at 260-280°C through a twin-screw extruder; The middle layer material is a premix of ETFE resin, allyl-containing comonomer A, and phenyl-containing comonomer B; The bottom layer material is a premix of CeO2 nanowires (diameter 25 nm, aspect ratio 25) modified with silane coupling agent KH-570 and ETFE resin; (2) The surface layer material, the middle layer material and the bottom layer material were added to a high-speed mixer and premixed for 30 minutes to obtain a total premix. The total premix was fed into a single screw extruder (L / D=30:1) for melt blending. The temperature was set to 260°C in the feeding section, 280°C in the melting section, and 270°C in the homogenizing section. The screw speed was set to 100 rpm. The melt was extruded through the die head (270°C) at a speed of 5 m / min and then cast onto a 50°C mirror cooling roller. It was then irradiated (20 kGy) by a 1.5 MeV electron accelerator 2 meters away from the die head outlet. The nitrogen atmosphere controlled the oxygen content to <50 ppm to prevent oxidation. The irradiated film material was solidified and shaped by the cooling system. The thickness was adjusted to 25±1 μm in real time using a β-ray online thickness gauge (accuracy ±0.5 μm). Finally, it was wound up by a tension control system.

[0042] The properties of the cross-linked ETFE composite films prepared in different embodiments and comparative examples were tested, and the results are shown in Table 2.

[0043] Table 2

[0044] The results show that the cross-linked ETFE composite films prepared in Examples 1 to 3 of the present invention have good performance in terms of UV shielding, visible light transmittance, clarity, tensile strength, color stability, interlayer adhesion and hydrophobicity.

[0045] Comparing Comparative Example 1 and Example 3, it can be seen that the preparation method has different degrees of influence on the properties of the cross-linked ETFE composite film, such as UV shielding, visible light transmittance, clarity, tensile strength, color stability, interlayer adhesion and hydrophobicity, especially clarity, color stability and interlayer adhesion.

[0046] Example 4-Example 6 Cross-linked ETFE composite films of different thicknesses were prepared according to the formula in Table 3 and the following preparation method.

[0047] Table 3

[0048] Note: The "%" of F-CQDs in the table is the weight percentage of F-CQDs in the total weight of the surface layer material; the "%" of comonomer A is the molar percentage of comonomer A in the total molar amount of the intermediate layer material; the "%" of comonomer B is the molar percentage of comonomer B in the total molar amount of the intermediate layer material; the "%" of CeO2 nanowires is the weight percentage of CeO2 nanowires modified with silane coupling agent in the total weight of the bottom layer material.

[0049] The preparation method is the same as that of Example 1.

[0050] The properties of the cross-linked ETFE composite films prepared in different embodiments were tested, and the results are shown in Table 4.

[0051] Table 4

[0052] Note: The tensile strength 45 / 42 in the table means longitudinal tensile strength / transverse tensile strength.

[0053] The results show that the cross-linked ETFE composite films of different thicknesses prepared in Examples 4 to 6 of the present invention have good performance in terms of UV shielding, visible light transmittance, clarity, tensile strength, color stability, interlayer adhesion and hydrophobicity.

[0054] Example 7-Example 8 and Comparative Examples 2-3 The cross-linked ETFE composite film was prepared according to the formula in Table 5 and the following preparation method.

[0055] Table 5

[0056] Note: The “%” of F-CQDs in the table is the weight percentage of F-CQDs in the total weight of the surface layer material; the “%” of comonomer A is the molar percentage of comonomer A in the total molar amount of the intermediate layer material; the “%” of comonomer B is the molar percentage of comonomer B in the total molar amount of the intermediate layer material; the “%” of CeO2 nanowires is the weight percentage of CeO2 nanowires modified with silane coupling agent in the total weight of the bottom layer material; “*” indicates that the CeO2 nanowires are CeO2 nanowires that have not been modified with silane coupling agent.

[0057] The preparation method is the same as that of Example 1.

[0058] The properties of the cross-linked ETFE composite films prepared in different embodiments and comparative examples were tested, and the results are shown in Table 6.

[0059] Table 6

[0060] The results show that the cross-linked ETFE composite films prepared in Examples 7 and 8 of the present invention have good performance in terms of UV shielding, visible light transmittance, clarity, tensile strength, color stability, interlayer adhesion and hydrophobicity.

[0061] The cross-linked ETFE composite films prepared in Comparative Examples 2 and 3 have excellent UV shielding, tensile strength, interlayer adhesion and hydrophobicity, but cannot achieve the same performance in terms of visible light transmission, clarity or color stability.

[0062] The above further describes the present invention in conjunction with specific embodiments. However, these embodiments are merely exemplary and do not constitute any limitation on the scope of the present invention. It should be understood by those skilled in the art that the details and forms of the technical solutions of the present invention may be modified or replaced without departing from the spirit and scope of the present invention, and such modifications and replacements shall fall within the scope of protection of the present invention.

Claims

1. A cross-linked ETFE composite film with gradient UV shielding function, characterized in that: It consists of three layers: surface layer, middle layer and bottom layer; The surface material includes ETFE resin and fluorinated carbon quantum dots; The intermediate layer material includes ETFE resin, allyl-containing comonomer A and phenyl-containing comonomer B; The underlying materials include ETFE resin and CeO2 nanowires; The particle size of the carbon fluoride quantum dots is 3-5 nm and contains a -C4F9 structure; The comonomer A is an allyl-containing fluoroolefin monomer; The comonomer B is an organic fluoride containing a phenyl group.

2. cross-linked ETFE composite membrane according to claim 1, characterized in that, The carbon fluoride quantum dots account for 0.05-0.2% of the total weight of the surface layer material; the comonomer A accounts for 1%-3% of the total molar weight of the intermediate layer material; the comonomer B accounts for 2%-5% of the total molar weight of the intermediate layer material; and the CeO2 nanowires account for 0.01%-0.1% of the total weight of the bottom layer material.

3. cross-linked ETFE composite membrane according to claim 1, characterized in that, 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. cross-linked ETFE composite membrane according to claim 1, characterized in that, The surface layer is 5%-20% of the total thickness of the cross-linked ETFE composite film; the middle layer is 70%-85% of the total thickness of the cross-linked ETFE composite film; and the bottom layer is 5%-10% of the total thickness of the cross-linked ETFE composite film.

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

6. The cross-linked ETFE composite membrane according to claim 1, wherein The surface layer is 15%-20% of the total thickness of the cross-linked ETFE composite film.

7. The cross-linked ETFE composite membrane according to claim 1, wherein The middle layer accounts for 80%-85% of the total thickness of the cross-linked ETFE composite film.

8. The method for preparing the cross-linked ETFE composite membrane according to any one of claims 1 to 7, wherein: The steps include: (1) After the components of the surface layer material, the middle layer material and the bottom layer material are mixed evenly, they are granulated separately to obtain the surface layer forming material, the middle layer forming material and the bottom layer forming material; (2) The surface layer forming material, the middle layer forming material and the bottom layer forming material are co-extruded and cast to obtain a composite film; The composite film is obtained through irradiation cross-linking, traction cooling, testing, slitting and winding; The irradiation in step (2) is electron beam irradiation; the irradiation dose is 15-25 kGy, and the ambient gas is nitrogen.

9. Use of the cross-linked ETFE composite film according to any one of claims 1 to 7 or the cross-linked ETFE composite film prepared by the preparation method according to claim 8 in preparing photovoltaic modules, architectural membrane structures or aerospace light-transmitting materials.

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

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