Fluorine-free high-weather-resistant coating composition for high-barrier aluminum-containing photovoltaic back plate

Abstract

The invention provides a fluorine-free high-weather-resistant coating composition for a high-barrier aluminum-containing photovoltaic back plate. The coating composition is composed of a main agent and a curing agent, wherein the main agent does not contain fluorine and comprises matrix resin, pigment, inorganic filler, an auxiliary agent and an anhydrous diluent; wherein the matrix resin comprises organic silicon modified acrylic resin, polyester resin, polyvinyl alcohol resin copolymer and epoxy resin. By introducing the specially designed organic silicon modified acrylic resin, the adhesive force and weather resistance of the coating composition to an aluminum foil and a polyester base film are improved, and the water vapor transmittance is reduced; the polyester resin with a high hydroxyl value is introduced, so that the overall flexibility of the coating is improved, the brittleness is reduced, and meanwhile, the adhesion to a substrate and the weather resistance are further improved; meanwhile, the polyvinyl alcohol resin copolymer is also introduced, so that the water vapor transmittance is further reduced. The coating composition disclosed by the invention does not contain fluorine elements, so that the environmental protection problem caused by an existing backboard fluorocarbon coating system is solved.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of coatings, and relates to a fluorine-free high-weather-resistant coating composition for a high-barrier aluminum-containing photovoltaic backsheet. BACKGROUND

[0002] The photovoltaic backsheet, as the encapsulating material on the back of the photovoltaic module, is a key raw material for ensuring the mechanical strength of the solar panel and the service life of the photovoltaic module. It not only needs to play a sealing and insulating protection role to prevent water vapor from penetrating into the sealing layer and affecting the service life and power generation efficiency of the cell sheet. In addition, it also needs to have good environmental erosion resistance, moisture heat aging resistance, high temperature resistance, and ultraviolet radiation resistance. Therefore, in actual use, the weather resistance of the backsheet is required to be more stringent.

[0003] In recent years, photovoltaic power generation has shown a significant growth trend in China. In photovoltaic power generation, crystalline silicon cells have always dominated the photovoltaic technology. With the continuous development and progress of crystalline silicon solar cell technology, the production cost is continuously reduced, and the conversion efficiency is continuously improved. Emerging cell technologies such as N-type TOPCon and HJT cell technologies, and even advanced cell technologies such as perovskite have gradually become mainstream technology routes. However, in practical applications, although these iterative cell technologies have higher efficiency, due to the particularity of the cell structure and the materials used, these modules are more sensitive to water vapor, and high water vapor content in the module can significantly reduce the power generation efficiency. Therefore, higher requirements are placed on the packaging materials. At present, most of these photovoltaic modules use a double-glass packaging structure without a backsheet, i.e., glass is used as the packaging material on both the front and back surfaces of the module. Double-glass modules have the advantages of high water vapor barrier rate and double-sided power generation. However, the packaging method of double-glass is significantly heavier than the traditional packaging method of photovoltaic modules with front glass and back backsheet, which limits the application scenarios of new photovoltaic modules. In recent years, with the rapid development of distributed photovoltaic and photovoltaic building integration, double-glass modules have load-bearing problems in many buildings. At the same time, under the background of the gradual increase in the size of the module, in order to reduce the weight of the module, the front and back glasses used in double-glass packaging are thinner than those in single-glass modules (with a backsheet). During production, transportation, installation, and normal operation, the glass is prone to cracking when subjected to temperature changes or external impacts, and there are more and more cases of broken pieces. In addition, the double-glass front surface has poorer resistance to hail and impact than the single-glass front surface. Furthermore, the appearance color of the double-glass module is single, which cannot meet the needs of some customers for color diversity of the module.

[0004] Based on other technical defects existing in the existing double glass packaging, the lower water vapor transmission rate is particularly important for the backboard. The lower the permeability, the better the barrier performance. If the backboard has poor water vapor barrier performance, moisture will penetrate the backboard into the inside of the battery plate, which will also affect the bonding performance of EVA, causing the backboard and EVA to separate, and then more moisture directly contacts the battery plate and causes the battery plate to be oxidized. Therefore, higher water vapor transmission rate has gradually become one of the important indicators for measuring the barrier performance of the backboard. However, at present, the mainstream photovoltaic backboard in the industry, whether it is a composite TPO / TPC / KPO / KPC type of fluorine material structure or a coated CPC type of double-sided coated fluorine-containing material structure, the main water vapor barrier comes from the PET in the middle layer, and the water vapor barrier rate of PET can only be 2.0-4.0 g / m 2 / day. This level of water vapor barrier rate cannot meet the requirements of high-efficiency cells such as N-type TopCon and HJT. It is necessary to develop a high-water-resistance photovoltaic backboard with low water vapor transmission rate to improve the overall water vapor barrier property of the module for single-glass module packaging.

[0005] At present, in the design of backboard to improve the barrier property of the material and reduce the water vapor transmission rate, there are two main schemes. One is to use a technology of depositing or vacuum plating an inorganic barrier layer such as aluminum oxide, silicon oxide, and silicon nitride on the PET substrate. This method can achieve a very high water vapor barrier purpose, but its defect is that the adhesion between the plating layer and the base layer is relatively poor, and it is easy to fall off from the substrate during peeling, especially after humid heat aging, which is prone to delamination. In addition, the inorganic barrier material itself is relatively brittle, and the increase in thickness will increase the risk of cracking, and it is impossible to greatly improve the barrier performance by continuously increasing the thickness. The photovoltaic backboard and its preparation method disclosed in application numbers CN201721476719.8 and CN202111104922.3 are both prepared by vacuum plating to obtain a low-water-vapor-transmission-rate plating layer, which ensures that the water vapor transmission rate of the photovoltaic backboard is <0.2 g / m 2 / day. According to the IEC standard, the photovoltaic cell backboard must pass the ultraviolet light aging, double 85, PCT, and other aging tests. The above-mentioned application improves the adhesion between the plating layer and the plating base layer by plasma treatment. In actual application, in addition to the decrease in peeling force between the plating layer and the adhesive layer, water vapor can also damage the packaging system through other interfaces. Especially after severe aging tests, the plating layer will separate from the plating base layer, which will greatly reduce the water vapor barrier performance of the backboard and shorten its service life. Therefore, the above-mentioned method of depositing an inorganic barrier layer has a great risk in actual use and is not mature.

[0006] The other is to add a metal layer as a water barrier layer in the conventional backboard, using a composite aluminum foil as the main technical route. Aluminum foil, zinc foil, nickel foil, copper foil, etc. have high density and moderate hardness, which can achieve good water barrier effect. The backboard material added to the existing technology can reduce stable cracking and power decay, and compared with the plating scheme, it has the advantages of convenient construction, and can pass through severe double 85, PCT, DH, DH+UV aging test. But the difficulty of this scheme lies in the insulation treatment of aluminum foil and its preparation method. At the same time, as described in patent CN201520923522.9, the water vapor transmission rate of the water barrier backboard is still relatively high, and the water barrier effect is not ideal enough, and needs to be further improved. Like the conventional backboard, the aluminum foil needs to be protected and preserved by other materials. For the problem of aluminum foil insulation, there are many solutions (CN202410607677.5) to solve it. Therefore, the current aluminum-containing backboard scheme is a relatively mature and reliable scheme to solve the water vapor barrier problem of backboard. For such aluminum-containing backboard scheme, the aluminum foil is generally close to the air side weather protection layer. Using fluorine film material to composite aluminum foil not only has high manufacturing cost, but also has poor adhesion between fluorine film and EVA. In high humidity and heat environment, aging and peeling problems are easy to occur. The scheme of using paint to coat aluminum foil meets the requirements of conventional backboard for moisture resistance and ultraviolet resistance according to the existing most backboard technology patents (CN201410411372.3, CN202310057508.4, CN202310489946.8, etc.), but it performs poorly on aluminum foil substrate. There are still risks of backboard delamination, poor adhesion, poor weather resistance and ultraviolet resistance, etc. during use. At the same time, it does not help to further reduce the water vapor transmission rate of aluminum-containing backboard, and even has the opposite effect. In addition, the above-mentioned current backboard paint uses a large amount of fluorocarbon resin, and the fluorine-containing photovoltaic backboard will cause negative impact on the environment during the preparation of the industry chain. More importantly, it brings new difficulties to the recycling of photovoltaic modules and component accident handling. The backboard recycling industry generally adopts the treatment method of burning, cracking and landfilling fluorides, which are highly toxic. If treated by burning or component fire, toxic gases such as hydrogen fluoride will be produced, which will cause harm to the human body and the environment. Therefore, the destructive nature of fluorine-containing backboard to the environment and the harm to the human body are indisputable, and the application of non-fluorine materials in backboard is imperative. SUMMARY

[0007] In view of the defects in the prior art, the present application provides a fluorine-free high-weather-resistant coating composition for high-barrier aluminum-containing photovoltaic backsheet, which can simultaneously meet the performance requirements of high adhesion, ultraviolet resistance, moisture resistance, corrosion resistance and other weather resistance of the PET and aluminum foil surfaces of the aluminum-containing backsheet, and further reduce the water vapor transmission rate of the entire backsheet based on the original aluminum-containing backsheet, providing a more reliable and cost-effective weather-resistant coating solution for high-water-vapor-barrier backsheet. In addition, the coating composition designed in the present application does not contain fluororesin or fluorine element, reducing the dependence of the backsheet coating on fluororesin, which is more cost-effective; it helps to reduce environmental pollution caused by the production of fluororesin; provides convenience for harmless treatment of component material recycling and degradation, in line with the concept of green development.

[0008] The purpose of the present application is achieved by the following technical solutions:

[0009] In a first aspect, the present application provides a fluorine-free high-weather-resistant coating composition for high-barrier aluminum-containing photovoltaic backsheet, which comprises a main agent and a curing agent, and the mass ratio of the main agent and the curing agent is 100:10-100:30.

[0010] The main agent comprises the following components by weight:

[0011] 10-30 parts of silicone-modified acrylic resin,

[0012] 10-30 parts of polyvinyl alcohol copolymer,

[0013] 10-30 parts of polyester resin,

[0014] 0.5-10 parts of epoxy resin,

[0015] 10-40 parts of pigment,

[0016] 0.5-15 parts of inorganic filler,

[0017] 0.1-5 parts of auxiliary agent,

[0018] 80-120 parts of anhydrous diluent.

[0019] As an embodiment of the present application, the curing agent comprises one or more of 1,5-pentamethylene diisocyanate, 1,6-hexamethylene diisocyanate, isophorone diisocyanate, 4,4-dicyclohexyl methane diisocyanate, isophorone diisocyanate trimer, 1,5-pentamethylene diisocyanate trimer, 1,6-hexamethylene diisocyanate trimer, 1,5-pentamethylene diisocyanate biuret, 1,6-hexamethylene diisocyanate biuret.

[0020] Preferably, the curing agent is (solid content 100%) 1,5-pentamethylene diisocyanate (PDI trimer). More preferably, Covestro N7300.

[0021] As an embodiment of the present application, the composition of the silicone-modified acrylic resin comprises alkyl ester segment monomers, hydroxyl-containing ester segment monomers, and siloxane segment monomers.

[0022] Further, the alkyl ester segment monomers comprise one or more of methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, n-butyl (meth)acrylate, sec-butyl (meth)acrylate, isobutyl (meth)acrylate, t-butyl (meth)acrylate, cyclohexyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, n-octyl (meth)acrylate, isooctyl (meth)acrylate, dodecyl (meth)acrylate, tridecyl (meth)acrylate, cetyl (meth)acrylate, isobornyl (meth)acrylate, (meth)acrylate, glycidyl (meth)acrylate; the hydroxyl-containing ester segment monomers comprise one or more of 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 2-hydroxybutyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate; and the siloxane segment monomers comprise one or more of vinyltrimethoxysilane, vinyltriethoxysilane, vinyltriisopropoxysilane, γ-methacryloyloxypropyltrimethoxysilane, 3-(methacryloyloxy)propyltrimethoxysilane, 3-(methacryloyloxy)propyltriethoxysilane, 3-(methacryloyloxy)propylmethyldimethoxysilane, 3-butenetriethoxysilane, tris(isopropoxy)vinylsilane, and (4-vinylphenyl)trimethoxysilane, 3-glycidyloxypropyltrimethoxysilane.

[0023] Further, the method for preparing the silicone-modified acrylic resin comprises mixing the alkyl ester segment monomers with the hydroxyl-containing ester segment monomers to form mixed monomers, stirring and dissolving the mixed monomers, adding an initiator and the siloxane segment monomers, and then heating and evaporating the solvent to obtain the silicone-modified acrylic resin.

[0024] Compared with the preparation method of the traditional silicone-modified acrylic resin, the siloxane chain segment monomer is first hydrolyzed and condensed, the silane is hydrolyzed into silicon hydroxyl, the adjacent silicon hydroxyl is dehydrated and condensed into siloxane to form an oligomer, and then the oligomer is reacted with a hydroxyl ester chain segment monomer and an alkyl ester chain segment monomer to obtain the silicone-modified acrylic resin. First, the silicone-modified acrylic resin prepared by this method is not compatible with other coating resin components due to its own crosslinking, and the reactivity is reduced, which leads to the reduction of the crosslinking network density of the final coating, and the phase separation is easy to occur. And because of its strong cohesive energy, it is easy to migrate to the surface of the coating, which leads to poor adhesion with the packaging material (EVA) and easy delamination after aging, thereby resulting in low adhesion of the coating to the packaging material, polyester-based film and aluminum foil substrate. Secondly, due to the hydrolysis and condensation of the siloxane chain segment monomer, the ability of the siloxane chain segment monomer to react with other components in the coating is reduced, thereby preventing the formation of a dense multi-layer network structure inside the coating, which leads to a decrease in water resistance. Finally, due to the hydrolysis and condensation of the siloxane chain segment monomer to form an oligomer, the oligomer is further hydrolyzed and condensed to form a network structure of sol, which leads to high hardness, which is not conducive to the subsequent lamination process of preparing solar modules. The preparation method of the silicone-modified acrylic resin is optimized, and the hydrolysis and condensation treatment of the siloxane chain segment monomer is avoided, thereby improving the adhesion of the coating to the packaging material, polyester-based film and aluminum foil substrate and the water resistance effect, and facilitating the subsequent lamination process.

[0025] Further, the initiator includes one or more of azobisisobutyronitrile, azobisisopentyl nitrile, azobisisoheptyl nitrile, dibenzoyl peroxide, tert-butyl peroxyacetate, tert-amyl peroxyacetate, tert-butyl peroxy-2-ethylhexanoate, tert-amyl peroxy-2-ethylhexanoate, tert-butyl peroxy-3,5,5-trimethylhexanoate, tert-butyl peroxybenzoate, tert-amyl peroxybenzoate, dicumyl peroxide, di-tert-butyl peroxide, di-tert-amyl peroxide, and isopropyl peroxide.

[0026] Further, the stirring temperature is 100-120 DEG C, and the temperature for the heat preservation is 110-130 DEG C for 2-6 h.

[0027] As an embodiment of the present application, the polyvinyl alcohol resin copolymer includes a polyethylene-vinyl alcohol copolymer.

[0028] Further, the average molecular weight of the polyvinyl alcohol resin copolymer is 30-130 thousand, the polymerization degree is 500-3000, and the high alcoholysis degree is 87-98%.

[0029] As an embodiment of the present application, the polyester resin is a saturated and unsaturated aliphatic polyester resin containing terminal hydroxyl functional groups, having a hydroxyl value of 40-60 mgKOH / g and an acid value of 1-6 mgKOH / g.

[0030] As an embodiment of the present application, the polyester resin is obtained by polycondensation polymerization of aliphatic acid monomers, aliphatic alcohol monomers and unsaturated monomers; the aliphatic acid monomers include one or more of 1,6-hexanedioic acid, 1,9-nonanedioic acid, 1,10-decanedioic acid, dimer acid, hexahydrophthalic anhydride, 1,4-cyclohexanedicarboxylic acid, 1,3-cyclohexanedicarboxylic acid, 1,2,4-cyclohexanetricarboxylic anhydride, 1,2,4,5-cyclohexanetetracarboxylic dianhydride; the aliphatic alcohol monomers include one or more of ethylene glycol, diethylene glycol, 1,2-propanediol, 1,3-propanediol, 1,3-butanediol, 1,4-butanediol, 1,5-pentanediol, neopentyl glycol, 1,6-hexanediol, 1,7-heptanediol, 1,3-heptanediol, 1,2-octanediol, 1,8-octanediol, 2-methyl-2,4-pentanediol, 3-methyl-1,5-pentanediol, 2,2,4-trimethyl-1,3-pentanediol, 3-hydroxy-2,2-dimethylpropyl, glycerol, sorbitol; the unsaturated monomers include one or more of cis-anhydride, trans-butenedioic acid, trimethylolpropane monoallyl ether, trimethylolpropane monoallyl ether, hydroxyl-modified polybutadiene, hydroxyl-modified polybutadiene acrylonitrile, hydroxyl-modified polyacetylenic resin.

[0031] The polyester resin composition used in the present application is a special multifunctional branched aliphatic saturated and unsaturated polyester containing terminal hydroxyl groups and having no aromatic ring structure.

[0032] As an embodiment of the present application, the epoxy resin includes one or more of bisphenol A epoxy resin, bisphenol F epoxy resin, phenolic epoxy resin, hydrogenated epoxy resin, glycidyl ester type epoxy resin. Preferably, bisphenol A epoxy resin, hydrogenated epoxy resin.

[0033] As an embodiment of the present application, the pigment includes one or more of white pigment, black pigment; the white pigment is titanium white; the black pigment includes one or more of silicone rubber carbon black, iron oxide black, iron-chromium black, copper-chromium black, iron-manganese black, nickel-chromium black, titanium-iron black, black pearl powder, perylene black, phthalocyanine, anthraquinone, indigo, sulfur indigo, quinacridone, fluoran, aniline. Preferably, carbon black, perylene black.

[0034] As an embodiment of the present application, the inorganic filler includes one or more of titanium dioxide, barium sulfate, calcium carbonate, silicon dioxide, talc, kaolin, barium sulfate, montmorillonite, mica powder, glass powder, white carbon, zinc oxide, aluminum oxide. Preferably, silicon dioxide, aluminum oxide.

[0035] As an embodiment of the present application, the auxiliary agent includes the following components in weight parts: wet dispersant 0.8-2.5 parts, catalyst 0.05-0.5 parts, anti-hydrolysis agent 0.1-2 parts, antioxidant 0.05-1, silane coupling agent 0.1-8 parts.

[0036] Further, the auxiliary agent further includes at least one of leveling agent 0-0.5 parts, defoaming agent 0-0.5 parts, ultraviolet absorber 0-5 parts, light stabilizer 0-2.5 parts.

[0037] Further, the wet dispersant includes one or more of acid group-containing copolymer solution, acrylic block copolymer, hydroxyl functional carboxylate, highly branched structure polyester, block copolymer solution of polyamine.

[0038] Further, the catalyst is a metal compound catalyst, and the metal compound catalyst includes one or more of stannous octoate, dibutyltin dilaurate, dioctyltin dilaurate, monobutyltin triisooctoate, zinc isooctoate. Preferably, dibutyltin dilaurate.

[0039] Further, the leveling agent includes one or more of silicone leveling agent, fluorocarbon-modified leveling agent, acrylic resin leveling agent, polyester leveling agent, polyether-modified polysiloxane leveling agent, polyester-modified polysiloxane leveling agent.

[0040] Further, the defoaming agent includes one or more of silicone-based defoaming agent, polyether-based defoaming agent, fatty acid and fatty acid ester-based defoaming agent, mineral oil-based defoaming agent, amide-based defoaming agent, phosphate-based defoaming agent, polyether-modified silicone-type defoaming agent.

[0041] Further, the anti-hydrolysis agent includes one or more of carbodiimide, polycarbodiimide compound.

[0042] Furthermore, the antioxidant includes one or more of 2,2'-methylene-bis-(4-methyl-6-tert-butyl)phenol, 2,2'-methylene-bis-(4-ethyl-6-tert-butyl)phenol, 1,3,5-tris(4-tert-butyl-3-hydroxy-2,6-dimethylbenzyl)-1,3,5-triazine-2,4,6-(1H,3H,5H)-trione, 3,5-di-tert-butyl-4-hydroxy-benzoic acid hexadecyl ester, distearyl pentaerythritol diphosphite, tris(2,4-tert-butylphenyl)phosphite, and tris(1,2,2,6-pentamethyl-4-piperidinyl)phosphite.

[0043] Furthermore, the ultraviolet absorber includes one or more of benzophenones, benzotriazoles, substituted acrylonitriles, salicylates or triazines.

[0044] Furthermore, the light stabilizer is a hindered amine light stabilizer.

[0045] Furthermore, the silane coupling agent includes vinyl triethoxysilane, ethylene triethoxysilane, 2-(3,4-epoxycyclohexyl) ethyl trimethoxysilane, 3-glycidyloxypropyl methyl dimethoxysilane, 3-glycidyloxypropyl trimethoxysilane, 3-glycidyloxypropyl methyl diethoxysilane, 3-glycidyloxypropyl triethoxysilane, 3-methacryloxypropyl methyl dimethoxysilane, 3-methacryloxypropyl trimethoxysilane, 3-methacryloxypropyl methyl One or more of 1,2-dimethoxysilane, 3-methacryloyloxypropyltriethoxysilane, 3-propyltrimethoxysilane, N-2-(aminoethyl)-3-aminopropylmethyldimethoxysilane, N-2-(aminoethyl)-3-aminopropyltrimethoxysilane, 3-aminopropyltrimethoxysilane, 3-aminopropyltriethoxysilane, N-phenyl-3-aminopropyltrimethoxysilane, N-(ethylbenzyl)-2-oxyethyl-3-aminopropyltrimethoxysilane hydrochloride, and 3-propyltrimethoxysilane.

[0046] The auxiliary agents in the present invention include leveling agent, defoaming agent, ultraviolet absorber and light stabilizer according to the backsheet type and application process.

[0047] As an embodiment of the present invention, the anhydrous diluent includes one or more of toluene, xylene, n-butyl acetate, ethyl acetate, butanone, cyclohexanone, methyl ethyl ketone, cyclohexane, and propylene glycol methyl ether acetate.

[0048] In a second aspect, the present invention provides a method for preparing the coating composition, comprising the following steps:

[0049] S1, stirring and mixing the silicone-modified acrylic resin, polyvinyl alcohol resin copolymer, polyester resin, epoxy resin, and anhydrous diluent to obtain a resin mixture;

[0050] S2, stirring and mixing the pigment, wetting dispersant and part of the resin mixture in the auxiliary agent, and grinding and filtering to obtain a color paste mixture;

[0051] S3, stirring and mixing the remaining resin mixture, color paste mixture, remaining auxiliary agent, and inorganic filler, and filtering to obtain a main agent;

[0052] S4, stirring and mixing the main agent with the curing agent, and defoaming to obtain the coating composition.

[0053] As an embodiment of the present application, the stirring speed is 1000-1500 rpm, and the time is 20 min-3 h.

[0054] As an embodiment of the present application, in step S2, the mass percentage of the part of the resin mixture in the resin mixture is 20-40%.

[0055] As an embodiment of the present application, in step S2, the grinding speed is 800-1200 r / min, and the time is 30-40 min, until the particle size is less than 2-4 μm; the mesh number used for filtering is 300 mesh. In some embodiments, the instrument used for grinding is a sand mill.

[0056] As an embodiment of the present application, in step S3, the mesh number used for filtering is 3000 mesh (filter bag). The purpose is to remove impurities.

[0057] As an embodiment of the present application, in step S3, the solid content of the main agent is 40-60%.

[0058] As an embodiment of the present application, in step S4, the defoaming time is 2-10 min.

[0059] In a third aspect, the present application provides a use of the coating composition in preparing a solar energy component.

[0060] As an embodiment of the present application, the solar energy component is prepared by laminating the polyester-based film side of the high water-resistance aluminum-containing structural backboard with the battery component through the encapsulating material.

[0061] Further, the preparation process of the high water-resistance aluminum-containing structural backboard comprises: coating the coating composition on the polyester-based film and the aluminum foil-based film respectively, and bonding the polyester-based film and the aluminum foil-based film using backboard adhesive, and obtaining after curing.

[0062] Further, the polyester-based film comprises polyethylene terephthalate (PET), the average thickness of the polyester-based film is 150-300 mu m, the average thickness of the aluminum foil is 10-80 mu m, and the encapsulating material comprises one or more of ethylene-vinyl acetate copolymer (EVA) and polyolefin thermoplastic elastomer (POE).

[0063] Further, the coating method comprises any one of roll coating, spray coating, dip coating and brush coating, and the dry coating thickness is 4-30 mu m.

[0064] Further, the curing temperature is 150-180 DEG C, and the curing time is 20-40 min, or the low temperature is 40-80 DEG C, and the curing time is 12-48 h.

[0065] Further, the polyester-based film is a polyester-based film after surface treatment, and the surface treatment method comprises any one of flame treatment, atmospheric pressure plasma treatment, corona treatment, low pressure plasma treatment and ultraviolet treatment.

[0066] Compared with the prior art, the present application has the following beneficial effects:

[0067] 1. The present application provides a high weather resistance high barrier coating for photovoltaic aluminum-containing coated backboard, which is used as a protective coating composition for the polyester-based film battery surface and the aluminum foil air surface.

[0068] 2. The present application improves the overall flexibility of the coating, reduces brittleness, improves the adhesion to the substrate, and improves the ultraviolet aging resistance of the finished backboard by simultaneously adding a high-hydroxyl-value multifunctional branched saturated or unsaturated aliphatic polyester resin to the coating composition.

[0069] 3、The polyvinyl alcohol resin copolymer with a special structure in the coating can form a dense multi-layer network structure with the silicone-modified acrylic resin, silane coupling agent, curing agent and the like, the high molecular chain of the polyvinyl alcohol copolymer has both strong intermolecular interaction force and chemical bond crosslinking between other molecules, so that a high molecular network structure which is difficult to penetrate and resistant to hydrolysis is formed, water penetration into the backboard is effectively prevented, and the barrier property of the backboard is greatly improved.

[0070] 4、The prepared coating in the application can balance the adhesion and weather resistance of the polyester-based film and the aluminum foil material, has high peel strength when laminated with the adhesive film, high long-term wet heat aging retention rate, and excellent comprehensive weather resistance. The selection and formula design of various resins with special structures without fluorine elements further reduce the dependence of the coating on fluororesin, reduce the cost of backboard manufacturing materials, and also avoid a series of environmental problems that may be caused by fluorine-containing coatings. BRIEF DESCRIPTION OF DRAWINGS

[0071] Other features, objects and advantages of the present application will become more apparent from the following detailed description of non-limiting embodiments, made with reference to the following drawings:

[0072] Figure 1 A schematic diagram of the multi-layer network structure formed by the polyvinyl alcohol resin copolymer and the silicone-modified acrylic resin, silane coupling agent, curing agent and the like in the coating composition of the application. DETAILED DESCRIPTION

[0073] The application will be described in detail below with reference to specific embodiments. The following examples are implemented under the premise of the technical solutions of the application, provide detailed implementation modes and specific operation processes, which will help those skilled in the art to further understand the application. It should be pointed out that the protection scope of the application is not limited to the following examples, and several adjustments and improvements made under the premise of the concept of the application also belong to the protection scope of the application.

[0074] The main agent in the application can be prepared by the following method: weigh the anhydrous diluent, and then add the silicone-modified acrylic resin, polyvinyl alcohol resin copolymer, polyester resin and epoxy resin in sequence, stir at 1200 rpm for 2 h to mix, to obtain a resin mixture; after the pigment, wetting dispersant and part of the resin mixture (30 wt.%) are uniformly dispersed at 1200 rpm for 1 h, pour them into a sand mill (grind at 1000 r / min for 30-40 minutes), mill to a particle fineness of 1-3 μm, and filter through a 300 mesh sieve to obtain a color paste mixture; after the remaining resin mixture, color paste mixture, other additives and fillers are mixed at 1200 rpm for 2 h, impurities are removed by filtering through a 3000 mesh filter bag to obtain the main agent, and then add anhydrous diluent to a solid content of 50%, uniformly disperse and mix at high speed, filter, and seal and fill in a dry container.

[0075] The specific use of the high-barrier fluorine-free high-weatherability coating composition for an aluminum-containing photovoltaic backsheet of the present application on a solar backsheet is as follows: the adhesive coating main agent and the curing agent (100:10), anhydrous diluent are mixed in a specified ratio for 60 minutes to be uniform (the amount of diluent depends on the predetermined coating thickness), and then respectively coated on a polyester-based film (polyethylene terephthalate (PET) or an aluminum foil-based film. After drying, the PET and the aluminum foil coated with the coating are bonded using a two-component polyurethane backsheet adhesive, and a high-water-barrier aluminum-containing structural backsheet is prepared after curing. The prepared high-adhesion backsheet PET side is laminated with a battery assembly through an encapsulating material. The average thickness of the polyester-based film is 300 μm, the aluminum foil is a single zero pure aluminum foil with an average thickness of 80 μm, and the encapsulating material is mainly ethylene-vinyl acetate copolymer (EVA).

[0076] The polyester-based film needs to be surface treated before being coated with the adhesive coating, and the surface treatment can be selected from flame treatment, atmospheric pressure plasma treatment, corona treatment, low-pressure plasma treatment, ultraviolet treatment, etc. In this embodiment or the comparative examples, the surface treatment is corona treatment, and the treatment time is 10 s. The coating method is roll coating, the coating dry thickness is 30 μm, the curing temperature is 150°C, and the curing time is 40 min.

[0077] Examples 1-8

[0078] Embodiments 1-8 provide a high-barrier fluorine-free high-weatherability coating composition for an aluminum-containing photovoltaic backsheet, which includes a main agent and a curing agent. The specific formulation is shown in Table 1.

[0079] Comparative Examples 1-6

[0080] Comparative examples 1-6 provide a high-barrier fluorine-free high-weatherability coating composition for an aluminum-containing photovoltaic backsheet, which includes a main agent and a curing agent. The specific formulation is shown in Table 1.

[0081] Table 1 Formulation table of examples and comparative examples

[0082]

[0083] Among them, the polyvinyl alcohol resin copolymer is selected from KOLARAY POVAL T 105-88KX S, the polyester resin is selected from WINGATE DKS LH748-02, the epoxy resin is selected from BALIN CYD300, the inorganic filler is selected from SYLOID ED30 silicon dioxide, the titanium white powder is selected from DUPONT 902 titanium white powder, the carbon black is selected from DKS carbon black HIBLACK 50L, the wetting dispersant is BYK-111, the catalyst is dibutyl tin dilaurate, the antioxidant is LINGRUI CHEMICAL 1010, and the anti-hydrolysis agent is LANGYI 1010, the silane coupling agent is Shin-Etsu KBM403, the UV absorber is BASF Tinuvin 400, the light stabilizer is Tinuvin UV292, the curing agent is Covestro Desmodur N7300, and the solvent is butyl acetate.

[0084] The specific synthesis method of the silicone-modified acrylic resin is as follows: alkyl ester segment monomers (methyl methacrylate, n-butyl methacrylate, isooctyl acrylate, dodecyl methacrylate, tridecyl methacrylate) and hydroxyl ester segment monomers (2-hydroxyethyl methacrylate, 2-hydroxyethyl acrylate) are mixed to form a mixed monomer. Then, 50% of the solvent (xylene) and a portion of the mixed monomer are added to a reactor, which is stirred and heated to 110°C under nitrogen. The remaining mixed monomer and solvent are then added dropwise, along with a portion of the initiator (azobisisobutyronitrile). The addition is completed within 2 hours, and the temperature is maintained at 120°C for 2 hours. Subsequently, silane-containing monomers (vinyltriethoxysilane, 3-(methacryloyloxy)propyltriethoxysilane) and a small amount of initiator are added dropwise, and the temperature is maintained at 120°C for 2 hours. The solvent was evaporated and the mixture was cooled to room temperature to obtain an organosilicon-modified acrylic resin; wherein the molar ratio of methyl methacrylate, n-butyl methacrylate, isooctyl acrylate, dodecyl methacrylate, tridecyl methacrylate, 2-hydroxyethyl methacrylate, 2-hydroxyethyl acrylate, vinyltriethoxysilane, and 3-(methacryloyloxy)propyltriethoxysilane was 0.8:0.25:0.25:0.1:0.1:0.3:0.1:0.06:0.06.

[0085] Performance Testing

[0086] The test method is as follows:

[0087] 1. Peel strength between back sheet and EVA film

[0088] The test was carried out in accordance with the national standard GB / T2790-1995 and the peel strength value was recorded.

[0089] 2. Water vapor transmission rate, heat and humidity resistance and UV resistance:

[0090] Photovoltaic cell backsheet performance testing was conducted according to the GB / T2423.3 test method and GB / T 31034-2014 standard for insulating backsheets for crystalline silicon solar cell modules. Adhesion of the samples was tested before and after the experiment according to ISO-2409-2007; the yellowing index (△YI) of the samples was measured according to the national standard GB2409-80.

[0091] Table 2 Performance test results of various embodiments and comparative examples

[0092]

[0093]

[0094] Comparing the data in Table 2, the high weather-resistant coating provided by the present application has high peel strength of the prepared coated high-barrier aluminum-containing photovoltaic backsheet with the packaging material, and after DH high-temperature and humidity aging for 2000h, the peel strength and adhesion between the layers can still remain high compared with the comparative example. After UV 300 kwh / m 2 illumination, the adhesion is good, and the yellowing index of backsheet of various colors is less than 2. And more severe UV+DH 120 kwh / m 2 After testing, the yellowing index of backsheet of various colors is not more than 3 and the adhesion is excellent. In addition, the high weather-resistant coating provided by the present application can further reduce the water vapor transmission rate of the aluminum-containing backsheet (each example is less than 15 mg / m 2 / d, and the water vapor transmission rate of the PET and aluminum foil composite film without coating is about 50-100 mg / m 2 / d).

[0095] In summary, the present application applies a kind of high weather-resistant, high-barrier coating composition without fluorine to the photovoltaic aluminum-containing backsheet structure, which improves the adhesion and moisture resistance of the coating to the packaging material, and also improves the adhesion and weather resistance of the coating to the aluminum foil, and has high ultraviolet aging resistance. The aluminum foil layer of the aluminum-containing backsheet has excellent moisture resistance and corrosion protection. In addition, the present coating can form a high molecular network structure (such as Figure 1 shown) that is difficult to penetrate and resistant to hydrolysis, effectively preventing water from penetrating into the backsheet, further toughening and water-blocking the existing aluminum-containing backsheet, forming high water vapor barrier, and solving the technical defects of the existing fluorocarbon coating system applied to high-barrier aluminum-containing photovoltaic backsheet.

[0096] The specific embodiments of the present application are described above. It should be understood that the present application is not limited to the above specific embodiments, and those skilled in the art can make various modifications or changes within the scope of the claims, which does not affect the essential content of the present application.

Claims

1. A fluorine-free and highly weather-resistant coating composition for a high-barrier aluminum-containing photovoltaic backsheet, characterized in that: The coating composition comprises a main agent and a curing agent, wherein the mass ratio of the main agent to the curing agent is 100:10-100:30; The main agent includes the following components in parts by weight: 10-30 parts of silicone modified acrylic resin, 10-30 parts of polyvinyl alcohol resin copolymer, 10-30 parts of polyester resin, 0.5-10 parts of epoxy resin, 10-40 parts of pigment, 0.5-15 parts of inorganic filler, 0.1-5 parts of additives, 80-120 parts of anhydrous diluent.

2. The coating composition according to claim 1, wherein The composition of the organosilicon-modified acrylic resin includes an alkyl ester segment monomer, a hydroxyl-containing ester segment monomer, and a siloxane segment monomer; The alkyl ester segment monomers include one or more of methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, n-butyl (meth)acrylate, sec-butyl (meth)acrylate, isobutyl (meth)acrylate, tert-butyl (meth)acrylate, cyclohexyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, n-octyl (meth)acrylate, isooctyl (meth)acrylate, dodecyl (meth)acrylate, tridecyl (meth)acrylate, hexadecyl (meth)acrylate, isobornyl (meth)acrylate, (meth)acrylate, and glycidyl (meth)acrylate; The hydroxyl ester segment monomer includes one or more of 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 2-hydroxybutyl (meth)acrylate, and 4-hydroxybutyl (meth)acrylate; The siloxane segment-containing monomer includes one or more of vinyltrimethoxysilane, vinyltriethoxysilane, vinyltriisopropoxysilane, γ-methacryloxypropyltrimethoxysilane, 3-(methacryloxy)propyltrimethoxysilane, 3-(methacryloxy)propyltriethoxysilane, 3-(methacryloxy)propylmethyldimethoxysilane, 3-butenetriethoxysilane, tri(isopropoxy)vinylsilane, (4-vinylphenyl)trimethoxysilane, and 3-glycidoxypropyltrimethoxysilane.

3. The coating composition according to claim 2, characterized in that The preparation method of the organosilicon-modified acrylic resin comprises: mixing an alkyl ester segment monomer and a hydroxyl ester segment monomer to form a mixed monomer, stirring and dissolving the mixed monomer, adding an initiator and a siloxane segment monomer, keeping the mixture warm, and evaporating the solvent to obtain the organosilicon-modified acrylic resin; The initiator comprises one or more of azobisisobutyronitrile, azobisisovaleronitrile, azobisisoheptonitrile, dibenzoyl peroxide, tert-butyl peroxyacetate, tert-amyl peroxyacetate, tert-butyl peroxy-2-ethylhexyl acid ester, tert-amyl peroxy-2-ethylhexyl acid ester, tert-butyl peroxy-3,5,5-trimethylhexanoate, tert-butyl peroxybenzoate, tert-amyl peroxybenzoate, dicumyl peroxide, di-tert-butyl peroxide, di-tert-amyl peroxide and isopropyl peroxide; The stirring temperature is 100-120° C.; the insulation temperature is 110-130° C., and the insulation time is 2-6 hours.

4. The coating composition according to claim 1, wherein The polyvinyl alcohol resin copolymer comprises polyethylene-vinyl alcohol copolymer; the polyvinyl alcohol resin copolymer has an average molecular weight of 30,000-130,000, a polymerization degree of 500-3000, and a high alcoholysis degree of 87-98%.

5. The coating composition according to claim 1, wherein The polyester resin is a saturated and unsaturated aliphatic polyester resin containing terminal hydroxyl functional groups, with a hydroxyl value of 40-60 mgKOH / g and an acid value of 1-6 mgKOH / g.

6. The coating composition according to claim 1, wherein Include at least one of the following technical features: The curing agent includes one or more of 1,5-pentamethylene diisocyanate, 1,6-hexamethylene diisocyanate, isophorone diisocyanate, 4,4-dicyclohexylmethane diisocyanate, isophorone diisocyanate trimer, 1,5-pentamethylene diisocyanate trimer, 1,6-hexamethylene diisocyanate trimer, 1,5-pentamethylene diisocyanate biuret, and 1,6-hexamethylene diisocyanate biuret; The epoxy resin includes one or more of bisphenol A epoxy resin, bisphenol F epoxy resin, novolac epoxy resin, hydrogenated epoxy resin, and glycidyl ester epoxy resin; The pigment includes one or more of white and black pigments; the white pigment is titanium dioxide; the black pigment includes one or more of silicone rubber carbon black, iron oxide black, iron chrome black, copper chrome black, iron manganese black, nickel chrome black, titanium iron black, black pearl powder, perylene black, phthalocyanine, anthraquinone, indigo, thioindigo, quinacridone, cyanine, and aniline; The inorganic filler includes one or more of titanium dioxide, barium sulfate, calcium carbonate, silicon dioxide, talc, kaolin, barium sulfate, montmorillonite, mica powder, glass powder, white carbon black, zinc oxide, and aluminum oxide; The auxiliary agent includes the following components in parts by weight: 0.8-2.5 parts of a wetting and dispersing agent, 0.05-0.5 parts of a catalyst, 0.1-2 parts of an anti-hydrolysis agent, 0.05-1 parts of an antioxidant, and 0.1-8 parts of a silane coupling agent; The anhydrous diluent includes one or more of toluene, xylene, n-butyl acetate, ethyl acetate, butanone, cyclohexanone, methyl ethyl ketone, cyclohexane, and propylene glycol methyl ether acetate.

7. The coating composition according to claim 6, characterized in that The wetting and dispersing agent includes one or more of a copolymer solution containing an acidic group, an acrylic block copolymer, a hydroxyl functional carboxylic acid ester, a highly branched polyester, and a block copolymer solution of a polyamine; The catalyst is a metal compound catalyst, including one or more of stannous octoate, dibutyltin dilaurate, dioctyltin dilaurate, monobutyltin triisooctoate, and zinc isooctanoate; The anti-hydrolysis agent includes one or more of carbodiimide and polycarbodiimide compounds; The antioxidant includes one or more of 2,2'-methylene-bis-(4-methyl-6-tert-butyl)phenol, 2,2'-methylene-bis-(4-ethyl-6-tert-butyl)phenol, 1,3,5-tris(4-tert-butyl-3-hydroxy-2,6-dimethylbenzyl)-1,3,5-triazine-2,4,6-(1H,3H,5H)-trione, 3,5-di-tert-butyl-4-hydroxy-benzoic acid hexadecyl ester, distearyl pentaerythritol diphosphite, tris(2,4-tert-butylphenyl)phosphite, and tris(1,2,2,6-pentamethyl-4-piperidinyl)phosphite; The silane coupling agent includes vinyl triethoxysilane, ethylene triethoxysilane, 2-(3,4-epoxycyclohexyl) ethyl trimethoxysilane, 3-glycidoxypropyl methyl dimethoxysilane, 3-glycidoxypropyl trimethoxysilane, 3-glycidoxypropyl methyl diethoxysilane, 3-glycidoxypropyl triethoxysilane, 3-methacryloxypropyl methyl dimethoxysilane, 3-methacryloxypropyl trimethoxysilane, 3-methacryloxypropyl methyl dimethoxysilane, One or more of ethoxysilane, 3-methacryloyloxypropyltriethoxysilane, 3-propyltrimethoxysilane, N-2-(aminoethyl)-3-aminopropylmethyldimethoxysilane, N-2-(aminoethyl)-3-aminopropyltrimethoxysilane, 3-aminopropyltrimethoxysilane, 3-aminopropyltriethoxysilane, N-phenyl-3-aminopropyltrimethoxysilane, N-(ethylbenzyl)-2-oxyethyl-3-aminopropyltrimethoxysilane hydrochloride, and 3-propyltrimethoxysilane.

8. A method for preparing the coating composition according to any one of claims 1 to 7, characterized in that: The following steps are involved: S1, stirring and mixing an organosilicon-modified acrylic resin, a polyvinyl alcohol resin copolymer, a polyester resin, an epoxy resin, and an anhydrous diluent to obtain a resin mixture; S2, stirring and mixing the pigment, the wetting and dispersing agent in the additives and part of the resin mixture, grinding and filtering to obtain a color paste mixture; S3, stirring and mixing the remaining resin mixture, the color paste mixture, the remaining additives, and the inorganic filler, and filtering to obtain the main agent; S4. The main agent and the curing agent are stirred and mixed, and the coating composition is obtained after degassing.

9. The preparation method according to claim 8, characterized in that In step S2, the mass percentage of the partial resin mixture to the total mass of the resin mixture is 20-40%.

10. Use of the coating composition according to any one of claims 1 to 7, or the coating composition obtained by the preparation method according to claim 8 or 9, in the preparation of a solar module.

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