High-adhesion moisture-resistant heat-resistant yellowing-resistant photovoltaic adhesive and preparation method thereof

Abstract

The application discloses a high-adhesion moisture-resistant heat-resistant yellowing-resistant photovoltaic adhesive and a preparation method thereof, and comprises the following raw material components in parts by weight: 40-60 parts of photocuring acrylate, 34-44 parts of active diluent, 0.5-4 parts of photoinitiator, 0.05-3.5 parts of first polymerization inhibitor and 1-6 parts of auxiliary agent; the photocuring acrylate has the following structure: A-(B-C) x Wherein, A is a urea bond-containing heterocyclic compound; B is an alicyclic diisocyanate monomer; C is a hydroxyl-containing acrylic acid derivative, and x is from 1 to 5. The photovoltaic adhesive provided in the application can meet the general requirements of photovoltaic adhesives, has high adhesion, moisture resistance, heat resistance, aging resistance and yellowing resistance, and is matched with low-temperature tin-coated solder strips, so that the solder strips and the battery pieces are doubly fixed, the peeling force between the solder strips and the battery pieces is greatly improved, the traditional infrared heating welding is replaced, the light and thin battery pieces at the component end are provided with realizability, and the cost and energy consumption are reduced.

Description

Technical Field

[0001] This invention relates to the field of adhesive technology, specifically to a photovoltaic adhesive with high adhesion, resistance to damp heat and yellowing, and its preparation method. Background Technology

[0002] With the rapid development of society, economy, and population, people's demand for energy is constantly increasing. Solar energy, as a new energy source, primarily comes from sunlight emitted by the sun; it has vast reserves and is environmentally friendly. Photovoltaic power generation is a technology that converts light energy into electrical energy using the photovoltaic effect at semiconductor interfaces. In industrial applications, solar cells are connected in series or parallel to form modules, which can achieve higher output voltages. Photovoltaic modules are the smallest unit of photovoltaic power generation.

[0003] In the production of photovoltaic (PV) modules, the series or parallel connection of individual solar cells not only affects the photoelectric conversion efficiency of the PV module but also influences the complexity of the manufacturing process. Series connection can increase the voltage of the entire cell array, while parallel connection can increase the current. PV solder ribbon, as a key material for connecting the cells, directly impacts the module's efficiency and lifespan. Using PV solder ribbon connection has long been considered one of the most mature PV module encapsulation methods. To reduce silver loss, increase power, and improve yield, current cell assembly processes have eliminated the main busbar, and the module assembly uses solder ribbon to conduct current. PV solder ribbon dispensing technology is a crucial step in PV module production. This process involves first soldering the solder ribbon onto the cell, then dispensing adhesive to further bond the solder ribbon to the cell, and finally laminating and alloying. This approach differs from adhesive-only lamination because it requires welding. Welding provides initial fixation, while dispensing provides further fixation. Since high temperatures are used during welding, adhesives capable of withstanding high temperatures and possessing high bonding strength are required during dispensing. This ensures that the connection between the solder strip and the battery cell is both strong and reliable.

[0004] Because solar cells are inherently thin, brittle, and prone to oxidation, they are easily and permanently damaged when exposed to air, rain, and other natural environments. Therefore, photovoltaic adhesives, used for connecting and sealing photovoltaic modules, must not only possess good adhesive strength but also excellent resistance to UV exposure, yellowing, damp heat, and aging to meet the requirements of the operating environment. However, currently available photovoltaic adhesives still fall short of these performance requirements. Patent CN117384580A discloses a high-thixotropic, high-temperature resistant, and yellowing-resistant photovoltaic bonding UV adhesive, comprising the following mass fractions: oligomer: 40-60 parts, active monomer: 30-40 parts, modified mixed powder: 1-5 parts, surface photoinitiator: 1-5 parts, and deep photoinitiator: 0.5-1 parts. This UV adhesive formulation incorporates modified mixed powder, utilizing its unique rheological properties to prevent the adhesive from spreading before curing, thus avoiding large-area contamination of the solar cells. The mixed powder contains boron nitride with high thermal transfer efficiency, which can rapidly dissipate heat, preventing the UV adhesive body from overheating and improving its temperature resistance. This ensures the module can withstand high temperatures caused by short circuits for a short time. However, this patent does not disclose the bonding strength and damp heat resistance of the joints.

[0005] Therefore, developing photovoltaic adhesives with high adhesion, resistance to damp heat, aging resistance, and yellowing resistance remains an urgent problem to be solved. Summary of the Invention

[0006] To address the aforementioned issues, this invention provides a photovoltaic adhesive with high adhesion, resistance to damp heat, and resistance to yellowing, along with its preparation method. By changing the type of main resin and using different components in combination, it overcomes the limitations of existing technologies in simultaneously achieving high adhesion, resistance to damp heat, aging resistance, and resistance to yellowing.

[0007] Specifically, the following technical solutions are provided:

[0008] The first aspect of this invention provides a photovoltaic adhesive with high adhesion, resistance to damp heat and yellowing, characterized in that it comprises the following raw material components in parts by weight: 40-60 parts of photocurable acrylate, 34-44 parts of reactive diluent, 0.5-4 parts of photoinitiator, 0.05-3.5 parts of a first polymerization inhibitor, and 1-6 parts of additives; wherein the photocurable acrylate has a structure as shown in general formula (I):

[0009] A-(BC) x (I)

[0010] Wherein, A is a heterocyclic compound containing a urea bond; B is an alicyclic diisocyanate monomer; C is a hydroxyl acrylic acid derivative; and x is from 1 to 5.

[0011] To address the inherent defects of solar cells, such as thinness, brittleness, and susceptibility to oxidation, which easily lead to permanent damage when exposed to air, rain, and other natural environments, and the need for high-temperature resistance in photovoltaic adhesives used for both dispensing and soldering, this invention provides a high-adhesion, moisture- and heat-resistant, and yellowing-resistant photovoltaic adhesive. It uses a self-made photocurable acrylate as the main resin component, with a multifunctional resin structure designed to ensure the adhesive performance and strength of the cured acrylate composition. However, if a heterocyclic compound with urea bonds, providing excessive functionality, is only suitable for modification with acrylic resin, its low molecular weight results in poor toughness and relatively large shrinkage and thermal expansion after curing, thus affecting its moisture- and heat-resistant properties. This invention introduces an alicyclic structure to improve the toughness of the photocurable acrylate and enhance its strength after curing. The modified photocurable acrylate possesses both a urea-bonded heterocyclic structure and an alicyclic structure, resulting in better moisture- and heat resistance and stronger cured strength.

[0012] Furthermore, in the general formula of the photocurable acrylate, A is selected from the following formula:

[0013] One of them,

[0014] Where n ranges from 1 to 4.

[0015] Furthermore, the alicyclic diisocyanate monomer is selected from cyclopentyl-1,3-diisocyanate, cyclohexyl-1,4-diisocyanate, cyclohexyl-1,2-diisocyanate, dicyclohexylmethane diisocyanate (HMDI), 1-isocyano-2-diisocyanomethylcyclopentane, 1-isocyano-3-isocyano-methyl-3,5,5-trimethylcyclohexane (isophorone diisocyanate) Or IPDI), bis-(4-isocyanocyclohexyl)-methane, 2,4-dicyclohexylmethane diisocyanate, 1,3- or 1,4-bis-(isocyanomethyl)-cyclohexane, bis-(4-isocyano-3-methylcyclohexyl)-methane, 1-isocyano-1-methyl-4(3)-isocyanomethylcyclohexane, 2,4- or 2,6-hexahydrotoluene diisocyanate, one or more of these.

[0016] Furthermore, the alicyclic diisocyanate monomer is 1-isocyano-3-isocyano-methyl-3,5,5-trimethylcyclohexane (isophorone diisocyanate or IPDI) or dicyclohexylmethane diisocyanate (HMDI).

[0017] Furthermore, the hydroxyl-containing acrylic acid derivative is selected from one or more of hydroxyethyl acrylate, hydroxyethyl methacrylate, hydroxybutyl acrylate, hydroxyethyl acrylamide, hydroxypropyl methacrylate, and hydroxypropyl acrylate.

[0018] Furthermore, the hydroxyl-containing acrylic derivative is hydroxyethyl acrylate (HEA) or hydroxyethyl methacrylate (HEMA).

[0019] Furthermore, the active diluent is selected from one or more of the following: isobornyl acrylate, isobornyl methacrylate, isooctyl acrylate, isooctyl methacrylate, tetrahydrofuran acrylate, tetrahydrofuran methacrylate, trimethylolpropane triacrylate, 2-phenoxyethyl acrylate, ethoxylated trimethylolpropane triacrylate, 1,6-hexanediol diacrylate, 1,4-butanediol diacrylate, n-butyl acrylate, isodecanyl acrylate, laurate acrylate, cyclohexyl acrylate, 3,3,5-trimethylcyclohexyl acrylate, 4-tert-butylcyclohexyl acrylate, dicyclopentenyl acrylate, pentaerythritol tetraacrylate, and cyclotrimethylolpropane methyl acetal acrylate.

[0020] Furthermore, the active diluent is a combination of isoborneol acrylate and cyclotrimethylolpropane methyl acetal acrylate.

[0021] Furthermore, the photoinitiator is selected from one or more of bis(2,4,6-trimethylbenzoyl)phenylphosphine oxide, 2-methyl-1-[4-(methylthio)phenyl]-2-(4-morpholinyl)-1-propanone, 2-hydroxy-4-(2-hydroxyethoxy)-2-methylphenylpropanone, (2,4,6-trimethylbenzoyl)diphenylphosphine oxide, ethyl 2,4,6-trimethylbenzoylphenylphosphonate, 2-phenylbenzyl-2-dimethylamine-1-(4-morpholinylbenzylphenyl)butanone, 2,2-dimethoxy-2-phenylacetophenone, methyl benzoylformate, isopropylthioxanthraphenone, 2-hydroxy-2-methyl-1-phenyl-1-propanone, and 1-hydroxycyclohexylphenyl methyl ketone.

[0022] Furthermore, the photoinitiator is a combination of (2,4,6-trimethylbenzoyl)diphenylphosphine oxide and 1-hydroxycyclohexylphenyl ketone.

[0023] Furthermore, the additives are selected from one or more of the following: stabilizers, diluents, antioxidants, adhesion promoters, coupling agents, defoamers, leveling agents, wetting agents, homogenizers, toughening agents, flame retardants, pigments, and fillers.

[0024] The second aspect of this invention provides a method for preparing the high-adhesion, moisture-resistant, heat-resistant, and yellowing-resistant photovoltaic adhesive described in the first aspect, characterized by comprising the following steps:

[0025] S1. Under light-protected conditions, diisocyanate monomer, first catalyst, antioxidant, and second polymerization inhibitor are mixed, and hydroxyl-containing acrylic acid derivative is added dropwise at 40-50°C. When the NCO content in the reaction reaches 50% of the initial theoretical value, intermediate product 1 is obtained.

[0026] S2. Under light-protected conditions, the heterocyclic compound containing urea bonds and the second catalyst are mixed, and the temperature is raised to 60-80°C. Intermediate product 1 is added dropwise, and the reaction continues until the mass content of NCO is 0.1%, to obtain the photocurable acrylate.

[0027] S3. Mix the photocurable acrylate, reactive diluent, photoinitiator, first polymerization inhibitor, and additives, and stir for 1 to 5 hours under vacuum conditions of -0.005 MPa to -0.2 MPa and temperature of 20 to 40°C to obtain a photovoltaic adhesive with high adhesion, resistance to damp heat, and resistance to yellowing.

[0028] Furthermore, in step S1, the molar ratio of the diisocyanate monomer to the hydroxyl-containing acrylic acid derivative is 1:(1 to 1.3), such as 1:1, 1:1.1, 1:1.2, 1:1.3, etc., including but not limited to the ratios listed above.

[0029] Furthermore, in step S2, the molar ratio of the alcohol hydroxyl group in the heterocyclic compound containing the urea bond to the intermediate product 1 is (0.8 to 1):1; for example, 0.8:1, 0.85:1, 0.9:1, 0.95:1, 1:1, etc., including but not limited to the ratios listed above.

[0030] Furthermore, the mass ratio of the photocurable acrylate to the diluent is 1:(0.65~0.9); for example, 1:0.65, 1:0.7, 1:0.75, 1:0.8, 1:0.85, 1:0.9, etc., including but not limited to the ratios listed above.

[0031] Furthermore, the first and second catalysts are selected from one or more of organotin, organobismuth, organozinc, organocobalt, and organic base catalysts, respectively.

[0032] Furthermore, both the first and second catalysts are dibutyltin dilaurate.

[0033] Furthermore, the antioxidant is selected from one or more of 2,6-di-tert-butyl-4-methylphenol, 4,4'-thiobis(6-tert-butyl-3-methylphenol), pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate], 2,2'-methylenebis(4-methyl-6-tert-butylphenol), 1,1,3-tris(2-methyl-4-hydroxy-5-tert-butylphenyl)butane, octadecyl 3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate, triphenyl phosphite, and trinonylphenyl phosphite.

[0034] Furthermore, the antioxidant is 2,6-di-tert-butyl-4-methylphenol.

[0035] Furthermore, the first and second polymerization inhibitors are individually selected from one or more of p-hydroxyanisole, p-benzoquinone, hydroquinone, 2-tert-butylhydroquinone, 2,5-di-tert-butylhydroquinone, phenothiazine, and naphthoquinone.

[0036] Furthermore, both the first and second polymerization inhibitors are hydroquinone.

[0037] The beneficial effects of this invention are:

[0038] This invention prepares a photovoltaic adhesive with high adhesion, resistance to damp heat, and resistance to yellowing. Based on photocuring, a urea ring structure is introduced into the structure, providing a multifunctional structural framework for the preparation of the main resin photocurable acrylate in the photovoltaic adhesive formulation. Furthermore, the urea ring structure, due to its structural stability and high urea bond dissociation energy, enhances excellent heat resistance. The presence of numerous amide bonds in the photocurable acrylate improves the adhesion performance of the cured photovoltaic adhesive. The alicyclic ends provide good mechanical strength to the main resin and, unlike benzene rings, do not easily yellow.

[0039] The alicyclic structure forms a tight, rigid molecular structure in the molecule, which improves the mechanical strength, thermal stability, and weather resistance of the cured photovoltaic adhesive. Unlike adhesives containing aromatic ring structures, which are easily oxidized by complex factors such as light and heat in the environment to form a yellowing "quinone" structure at the methyl group substituted by the aromatic ring, the cured photovoltaic adhesive has excellent yellowing resistance.

[0040] Because photocurable acrylates contain a large number of urethane bonds, they can form hydrogen bonds with polymer chains, giving photovoltaic adhesives excellent bonding properties after curing. In addition, the synergistic effect of cyclic urea bonds and alicyclic rings in the structure results in a photovoltaic adhesive with a compact structure, good heat resistance and adhesion, which improves the reliability of photovoltaic modules in humid and hot environments.

[0041] This invention prepares a photovoltaic adhesive with high adhesion, resistance to damp heat and yellowing. After formula screening, it can meet the general requirements of photovoltaic adhesives. It has high adhesion, resistance to damp heat, aging and yellowing. Combined with low-temperature tinned solder ribbon, it can achieve double fixation between the solder ribbon and the solar cell, which greatly improves the peel force between the two. At the same time, it replaces the traditional infrared heating soldering, which makes it possible to make the solar cells at the module end thinner, reduce costs and energy. Detailed Implementation

[0042] The present invention will be further described below with reference to specific embodiments, so that those skilled in the art can better understand and implement the present invention, but the embodiments are not intended to limit the present invention.

[0043] The raw materials used in the following examples and comparative examples, and their sources, are as follows:

[0044] Dibutyltin dilaurate (DBTDL), selected from Maclean's, brand name DBTDL; Isophorone diisocyanate (IPDI), selected from Wanhua Chemical, brand name... IPDI; dicyclohexylmethane diisocyanate (HMDI), selected from Wanhua Chemical, brand name [not specified]. HMDI; Hydroxyethyl acrylate (HEA), selected from Maclean's, brand name HEA; Hydroxyethyl methacrylate (HEMA), selected from Wanhua Chemical, brand name [missing information]. HEMA; 2,6-di-tert-butyl-4-methylphenol, selected from Shanghai Ronghe Chemical; hydroquinone, selected from Eastman Chemical Industries, USA, brand name HQ; tetra(2-hydroxymethyl)glycourea, selected from Shikoku Chemical, brand name TH-G; tris(2-hydroxyethyl)isocyanurate, selected from Titan Chemical, brand name THMP; isobornyl acrylate, selected from Chang Hsing Chemical Industries, Taiwan, brand name EM214; cyclotrimethylolpropane methyl acetal acrylate, selected from Sartoma Chemical Industries, brand name SR351NS; 1-hydroxycyclohexylphenyl ketone, selected from Omnirad 184, brand name IGM; (2, 4,6-Trimethylbenzoyl)diphenylphosphine oxide, selected from Jiuri New Materials, brand name RCure-1108; silane coupling agent, selected from Momentive (USA), brand name SilquestA-187; fumed silica, selected from Wacker Chemie (Germany), brand name H18; polyester acrylate, selected from Sartoma, brand name CN704; epoxy acrylate, selected from Sartoma, brand name CNUVE151; polyether-modified polyurethane acrylate, selected from Chang Hsing (Taiwan), brand name 615-100; fumed silica, selected from Sartoma, brand name CNUVE151.

[0045] Example 1

[0046] (1) Under light-protected conditions, 100g of IPDI, 1g of catalyst DBTDL, 0.01g of di-tert-butyl-4-methylphenol and 0.005g of hydroquinone were added to a three-necked flask equipped with a thermometer. 53g of HEA was added dropwise at 40°C. The concentration of NCO groups was continuously monitored during the reaction. When the concentration reached 50% of the initial theoretical value, the product IPDI-HEA was obtained.

[0047] (2) Under light-protected conditions, add 29g of tetra(2-hydroxymethyl)glycourea and 1g of catalyst DBTDL to a three-necked flask equipped with a thermometer, raise the temperature and maintain it at 60°C, and dropwise add the product IPDI-HEA from step 1. Test the NCO content every 30 minutes. Stop heating when the NCO mass content is 0.1% to obtain the final photocurable acrylate A.

[0048] (3) Add 49 parts by weight of the photocurable acrylate A obtained in step (2), 20 parts of isobornyl acrylate, 20 parts of cyclotrimethylolpropane methyl acetal acrylate, 0.5 parts of 1-hydroxycyclohexylphenyl ketone, 1.5 parts of (2,4,6-trimethylbenzoyl)diphenylphosphine oxide, 1.5 parts of 2,4,6-trimethylbenzoyl-diphenylphosphine oxide, 0.15 parts of hydroquinone, and additives (1.5 parts of silane coupling agent and 2 parts of fumed silica) to the reactor. Stir for 3 hours under vacuum of -0.1 MPa and temperature of 25°C to obtain a photovoltaic adhesive with high adhesion, resistance to damp heat and yellowing.

[0049] Example 2

[0050] The difference between this embodiment and Example 1 lies in the following component contents:

[0051] 42 parts of light-cured acrylate A, 17 parts of isoborneol acrylate, and 17 parts of cyclotrimethylolpropane methyl acetal acrylate are used, with other steps remaining unchanged.

[0052] Example 3

[0053] The difference between this embodiment and Example 1 lies in the following component contents:

[0054] 46 parts of UV-cured acrylate A, 18 parts of isoborneol acrylate, and 18 parts of cyclotrimethylolpropane methyl acetal acrylate are used, with other steps remaining unchanged.

[0055] Example 4

[0056] The difference between this embodiment and Example 1 lies in the following component contents:

[0057] 56 parts of UV-cured acrylate A, 21 parts of isobornyl acrylate, and 21 parts of cyclotrimethylolpropane methyl acetal acrylate are used, with other steps remaining unchanged.

[0058] Example 5

[0059] The difference between this embodiment and Example 1 lies in the following component contents:

[0060] 59 parts of UV-cured acrylate A, 22 parts of isobornyl acrylate, and 22 parts of cyclotrimethylolpropane methyl acetal acrylate are used, with other steps remaining unchanged.

[0061] Example 6

[0062] The difference between this embodiment and Example 1 lies in the following component contents:

[0063] 17 parts of isoborneol acrylate and 18 parts of cyclotrimethylolpropane methyl acetal acrylate, with other steps remaining unchanged.

[0064] Example 7

[0065] The difference between this embodiment and Example 1 lies in the following component contents:

[0066] 23 parts of isobornyl acrylate and 22 parts of cyclotrimethylolpropane methyl acetal acrylate were used, with other steps remaining unchanged.

[0067] Example 8

[0068] (1) Under light-protected conditions, 100g of HMDI, 1g of catalyst DBTDL, 0.01g of di-tert-butyl-4-methylphenol and 0.005g of hydroquinone were added to a three-necked flask equipped with a thermometer. 64g of HEMA was added dropwise at 50°C. The concentration of NCO groups was continuously monitored during the reaction. When the concentration reached 50% of the initial theoretical value, the product HMDI-HEMA was obtained.

[0069] (2) Under light-protected conditions, add 26.6g of tris(2-hydroxyethyl) isocyanurate and 1g of catalyst DBTDL to a three-necked flask equipped with a thermometer, raise the temperature and maintain it at 80°C, add the product HMDI-HEMA from step 1 dropwise, test the NCO content every 30 minutes, and stop heating when the NCO mass content is 0.1% to obtain the final photocurable acrylate B.

[0070] (3) Add 49 parts by weight of the photocurable acrylate B obtained in step (2), 20 parts of isobornyl acrylate, 20 parts of cyclotrimethylolpropane methyl acetal acrylate, 0.5 parts of 1-hydroxycyclohexylphenyl ketone, 1.5 parts of (2,4,6-trimethylbenzoyl)diphenylphosphine oxide, 1.5 parts of 2,4,6-trimethylbenzoyl-diphenylphosphine oxide, 0.15 parts of hydroquinone, and additives (1.5 parts of silane coupling agent and 2 parts of fumed silica) to a reaction vessel and stir for 5 hours under vacuum of -0.2 MPa and temperature of 40°C to obtain a photovoltaic adhesive with high adhesion, resistance to damp heat and yellowing.

[0071] Example 9

[0072] The difference between this embodiment and Example 8 lies in the following component contents:

[0073] 42 parts of light-cured acrylate B, 17 parts of isobornyl acrylate, and 17 parts of cyclotrimethylolpropane methyl acetal acrylate are used, with other steps remaining unchanged.

[0074] Example 10

[0075] The difference between this embodiment and Example 8 lies in the following component contents:

[0076] 46 parts of light-cured acrylate B, 18 parts of isobornyl acrylate, and 18 parts of cyclotrimethylolpropane methyl acetal acrylate are used, with other steps remaining unchanged.

[0077] Example 11

[0078] The difference between this embodiment and Example 8 lies in the following component contents:

[0079] 56 parts of UV-cured acrylate B, 21 parts of isobornyl acrylate, and 21 parts of cyclotrimethylolpropane methyl acetal acrylate are used, with other steps remaining unchanged.

[0080] Example 12

[0081] The difference between this embodiment and Example 8 lies in the following component contents:

[0082] 59 parts of UV-cured acrylate B, 22 parts of isobornyl acrylate, and 22 parts of cyclotrimethylolpropane methyl acetal acrylate are used, with other steps remaining unchanged.

[0083] Comparative Example 1

[0084] 49 parts by weight of polyester acrylate, 20 parts by weight of isobornyl acrylate, 20 parts by weight of cyclotrimethylolpropane methyl acetal acrylate, 0.5 parts by weight of 1-hydroxycyclohexylphenyl ketone, 1.5 parts by weight of (2,4,6-trimethylbenzoyl)diphenylphosphine oxide, 1.5 parts by weight of 2,4,6-trimethylbenzoyl-diphenylphosphine oxide, 0.15 parts by weight of hydroquinone, and 1.5 parts by weight of additives (silane coupling agent and fumed silica) were added to a reaction vessel and stirred for 3 hours under a vacuum of -0.1 MPa and a temperature of 25°C to obtain a photovoltaic adhesive.

[0085] Comparative Example 2

[0086] 49 parts by weight of epoxy acrylate, 20 parts by weight of isobornyl acrylate, 20 parts by weight of cyclotrimethylolpropane methyl acetal acrylate, 0.5 parts by weight of 1-hydroxycyclohexylphenyl ketone, 1.5 parts by weight of (2,4,6-trimethylbenzoyl)diphenylphosphine oxide, 1.5 parts by weight of 2,4,6-trimethylbenzoyl-diphenylphosphine oxide, 0.15 parts by weight of hydroquinone, and 1.5 parts by weight of additives (silane coupling agent and 2 parts by weight of fumed silica) were added to a reaction vessel and stirred for 3 hours under a vacuum of -0.1 MPa and a temperature of 25°C to obtain a photovoltaic adhesive.

[0087] Comparative Example 3

[0088] The following ingredients were added to a reaction vessel according to weight: 49 parts of polyether-modified polyurethane acrylate, 20 parts of isobornyl acrylate, 20 parts of cyclotrimethylolpropane methyl acetal acrylate, 0.5 parts of 1-hydroxycyclohexylphenyl ketone, 1.5 parts of (2,4,6-trimethylbenzoyl)diphenylphosphine oxide, 1.5 parts of 2,4,6-trimethylbenzoyl-diphenylphosphine oxide, 0.15 parts of hydroquinone, and additives (1.5 parts of silane coupling agent and 2 parts of fumed silica). The mixture was stirred for 3 hours under a vacuum of -0.1 MPa and a temperature of 25°C to obtain a photovoltaic adhesive.

[0089] Comparative Example 4

[0090] The difference between this comparative example and Example 1 lies in the following component contents:

[0091] 65 parts of UV-cured acrylate A, 22 parts of isobornyl acrylate, and 22 parts of cyclotrimethylolpropane methyl acetal acrylate are used, with other steps remaining unchanged.

[0092] Comparative Example 5

[0093] The difference between this comparative example and Example 1 lies in the following component contents:

[0094] 33 parts of light-cured acrylate A, 18 parts of isoborneol acrylate, and 18 parts of cyclotrimethylolpropane methyl acetal acrylate are used, with other steps remaining unchanged.

[0095] Comparative Example 6

[0096] The difference between this comparative example and Example 8 lies in the following component contents:

[0097] 65 parts of UV-cured acrylate B, 22 parts of isobornyl acrylate, and 22 parts of cyclotrimethylolpropane methyl acetal acrylate are used, with other steps remaining unchanged.

[0098] Comparative Example 7

[0099] The difference between this comparative example and Example 8 lies in the following component contents:

[0100] The ingredients are: 33 parts of UV-cured acrylate B, 18 parts of isobornyl acrylate, and 18 parts of cyclotrimethylolpropane methyl acetal acrylate, with other steps remaining unchanged.

[0101] Test case

[0102] The shear strength and tensile strength of the products prepared in the examples and comparative examples were tested.

[0103] (1) Tensile shear strength

[0104] Wipe the surfaces of the glass and aluminum substrates with ethanol and allow the ethanol to evaporate completely. Then, attach 0.2mm aluminum foil tape to one end of each substrate. Apply the resin composition obtained in the above examples and comparative examples to one end of the glass substrate, ensuring even application at the bonding area. Next, overlap the two substrates in a staggered manner, clamp them with transparent plastic clips, and place the sample in a UV light source (365nm, 300mW / cm²). 2 After radiation curing for 10 seconds to ensure full curing, remove the product. Tensile shear strength testing was conducted according to GB / T7124-2008 standard on an electronic tensile testing machine at 25℃, with an overlap area of ​​312.5 mm². 2 The test rate was 5 mm / min.

[0105] (2) Tensile shear strength after double 85

[0106] The tensile shear strength samples of UV-cured glass-aluminum substrates were placed in a high-temperature and high-humidity test chamber and subjected to static conditions at 85℃ and 85% relative humidity for 200 hours according to GB / T 5170-2016 standard before testing their tensile shear strength. The tensile shear strength test was conducted according to GB / T 7124-2008 standard on an electronic tensile testing machine at a test temperature of 25℃ and an overlap area of ​​312.5 mm². 2 The test speed was 5 mm / min.

[0107] (3) Tensile shear strength after high temperature aging

[0108] The tensile shear strength samples of the UV-cured glass-aluminum substrate were placed in a high-temperature and high-humidity test chamber and subjected to static treatment at 200℃ for 3 hours according to GB / T 5170.2-2008 standard. The tensile shear strength test was conducted on an electronic tensile testing machine according to GB / T 7124-2008 standard at a test temperature of 25℃ and an overlap area of ​​312.5 mm². 2 The test speed was 5 mm / min.

[0109] (4) The difference in yellowing value before aging and after high-temperature aging

[0110] The resin compositions obtained in the above examples and comparative examples were cast into a transparent plastic mold with a diameter of 5 cm, and then the samples were placed in an ultraviolet light source (365 nm, 300 mW / cm²). 2 After radiation curing for 10 seconds to fully cure, remove the product, demold it, and then let it stand at 200℃ for 3 hours according to GB / T5170.2-2008 standard. Use a color difference tester to test the yellowing value ΔYI before and after the high temperature.

[0111] The performance test results of the products obtained in the examples and comparative examples are shown in Table 1:

[0112] Table 1

[0113]

[0114] Based on the data in Table 1, and by comparing Comparative Example 2 and Examples 1-12, it can be seen that the high-adhesion, moisture-resistant, and yellowing-resistant photovoltaic adhesives prepared in this application can all achieve the initial tensile shear strength, the tensile shear strength after double 85, and the tensile shear strength after high-temperature aging of adhesives prepared from commercially available acrylate resins containing benzene ring structures. However, since the photocurable acrylate structure prepared in this invention does not contain a benzene ring structure, the photovoltaic adhesives protected by this invention have good yellowing resistance while also possessing excellent mechanical properties and high moisture-resistant properties.

[0115] As can be seen from the comparison between Example 1 and Comparative Example 1, when commercially available polyester-based photocurable resins are used as the main resins of photovoltaic adhesives, although they have high initial tensile shear strength and good resistance to yellowing, their resistance to damp heat is poor because ester bonds are easily hydrolyzed. Although polyester-modified polyurethane resins contain more ester bonds and can provide excellent initial tensile shear strength, their weather resistance requirements in the photovoltaic field have always limited their development in this field.

[0116] As can be seen from the comparison between Example 1 and Comparative Example 3, when commercially available polyether-modified polyurethane acrylate is used as the main resin of photovoltaic adhesive, although it has a high initial tensile shear strength, its resistance to damp heat and yellowing is poor. This is because when the polyether segments are exposed to ultraviolet light and high temperature for a long time, the oxidation reaction of the polyether material will be accelerated, making it turn yellow faster; it may even gradually undergo an oxidation reaction to form oxidation products, resulting in yellowing.

[0117] Comparing Examples 4-7 and 8-10 with Comparative Example 4-7, it can be seen that when the content of the prepared photocurable acrylate increases, the excessive urethane bonds due to the increase in the molecular weight of the resin composition will affect the yellowing resistance of the cured product. When the content of the prepared photocurable acrylate decreases, the diluent content increases, and the main resin that can provide strength decreases accordingly, resulting in a decrease in the mechanical properties of the cured product. Excessive small molecule diluent will lead to excessive crosslinking density and reduced adhesion of the cured product.

[0118] Comparing Examples 1-5 and 8-12, it can be seen that the photocurable acrylate A prepared in this application has better properties than the photocurable acrylate B. This is because the cured resin A has more active functional groups, which makes the cross-linking structure of the cured product more compact, and thus has better resistance to damp heat.

[0119] In summary, the use of photocurable acrylate as the main resin in photovoltaic adhesives, along with diluents and appropriate catalysts, polymerization inhibitors, additives, and fillers, can meet the requirements of the photovoltaic adhesive field for high adhesion, resistance to damp heat, aging resistance, and yellowing resistance, thus demonstrating high application value.

[0120] The above-described embodiments are merely preferred embodiments provided to fully illustrate the present invention, and the scope of protection of the present invention is not limited thereto. Equivalent substitutions or modifications made by those skilled in the art based on the present invention are all within the scope of protection of the present invention. The scope of protection of the present invention is defined by the claims.

Claims

1. A photovoltaic adhesive with high adhesion, resistance to damp heat, and resistance to yellowing, characterized in that, The raw material components include the following parts by weight: 40-60 parts of photocurable acrylate, 34-44 parts of reactive diluent, 0.5-4 parts of photoinitiator, 0.05-3.5 parts of primary polymerization inhibitor, and 1-6 parts of additives; the photocurable acrylate has a structure as shown in general formula (I): A-(B-C) x (Ⅰ) Wherein, A is a heterocyclic compound containing a urea bond; B is an alicyclic diisocyanate monomer; C is a hydroxyl acrylic acid derivative; and x is from 1 to 5. In the general formula of the photocurable acrylate, A is selected from the following formula: (II) or (Ⅲ) is one of them, where n is from 1 to 4; The photocurable acrylate comprises the following preparation steps: S1. Under light-protected conditions, alicyclic diisocyanate monomer, first catalyst, antioxidant, and second polymerization inhibitor are mixed, and hydroxyl-containing acrylic acid derivative is added dropwise at 40~50℃. When the NCO content in the reaction reaches 50% of the initial theoretical value, intermediate product 1 is obtained. S2. Under light-protected conditions, the heterocyclic compound containing urea bonds and the second catalyst are mixed, and the temperature is raised to 60~80°C. Intermediate product 1 is added dropwise, and the reaction continues until the mass content of NCO is 0.1%, to obtain the photocurable acrylate. In step S1, the molar ratio of the alicyclic diisocyanate monomer to the hydroxyl-containing acrylic acid derivative is 1:(1~1.3). In step S2, the molar ratio of the alcohol hydroxyl group in the urea-bonded heterocyclic compound to that of the intermediate product is (0.8~1):1; The mass ratio of the photocurable acrylate to the diluent is 1:(0.7~0.9).

2. The photovoltaic adhesive with high adhesion, resistance to damp heat and yellowing as described in claim 1, characterized in that, The alicyclic diisocyanate monomer is selected from one or more of the following: cyclopentyl-1,3-diisocyanate, cyclohexyl-1,4-diisocyanate, cyclohexyl-1,2-diisocyanate, 4,4′-dicyclohexylmethane diisocyanate, 1-isocyano-2-diisocyanomethylcyclopentane, isophorone diisocyanate, 2,4-dicyclohexylmethane diisocyanate, and bis-(4-isocyano-3-methylcyclohexyl)-methane; The hydroxyl-containing acrylic derivative is selected from one or more of hydroxyethyl acrylate, hydroxyethyl methacrylate, hydroxybutyl acrylate, hydroxyethyl acrylamide, hydroxypropyl methacrylate, and hydroxypropyl acrylate.

3. The photovoltaic adhesive with high adhesion, resistance to damp heat and yellowing as described in claim 1, characterized in that, The active diluent is selected from one or more of the following: isobornyl acrylate, isobornyl methacrylate, isooctyl acrylate, tetrahydrofuran acrylate, tetrahydrofuran methacrylate, trimethylolpropane triacrylate, 2-phenoxyethyl acrylate, ethoxylated trimethylolpropane triacrylate, 1,6-hexanediol diacrylate, 1,4-butanediol diacrylate, n-butyl acrylate, isodecanyl acrylate, laurate acrylate, cyclohexyl acrylate, 3,3,5-trimethylcyclohexyl acrylate, 4-tert-butylcyclohexyl acrylate, dicyclopentenyl acrylate, pentaerythritol tetraacrylate, and cyclotrimethylolpropane methyl acetal acrylate.

4. The photovoltaic adhesive with high adhesion, resistance to damp heat and yellowing as described in claim 1, characterized in that, The photoinitiator is selected from one or more of bis(2,4,6-trimethylbenzoyl)phenylphosphine oxide, 2-methyl-1-[4-(methylthio)phenyl]-2-(4-morpholinyl)-1-propanone, 2-hydroxy-4-(2-hydroxyethoxy)-2-methylphenylpropanone, (2,4,6-trimethylbenzoyl)diphenylphosphine oxide, ethyl 2,4,6-trimethylbenzoylphenylphosphonate, 2,2-dimethoxy-2-phenylacetophenone, methyl benzoylformate, isopropylthioxanthonone, 2-hydroxy-2-methyl-1-phenyl-1-propanone, and 1-hydroxycyclohexylphenyl methyl ketone.

5. The photovoltaic adhesive with high adhesion, resistance to damp heat and yellowing as described in claim 1, characterized in that, The additives are selected from one or more of the following: stabilizers, antioxidants, adhesion promoters, coupling agents, defoamers, leveling agents, wetting agents, homogenizers, toughening agents, flame retardants, pigments, and fillers.

6. A method for preparing a photovoltaic adhesive with high adhesion, resistance to damp heat and yellowing as described in any one of claims 1-5, characterized in that, Includes the following steps: The photocurable acrylate, reactive diluent, photoinitiator, first polymerization inhibitor, and additives are mixed and stirred for 1 to 5 hours under vacuum conditions of -0.005 MPa to -0.2 MPa and temperature of 20 to 40°C to obtain a photovoltaic adhesive with high adhesion, resistance to damp heat, and resistance to yellowing.

7. The photovoltaic adhesive with high adhesion, resistance to damp heat and yellowing as described in claim 1, characterized in that, The first and second catalysts are selected from one or more of organotin, organobismuth, organozinc, organocobalt, and organic base catalysts, respectively.

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