A photovoltaic backsheet adhesive, its preparation method, and its application.

Abstract

This invention provides a photovoltaic backsheet adhesive, its preparation method, and its application, relating to the field of photovoltaic module encapsulation composite materials technology. The adhesive comprises, by weight, 60-80 parts of resin component A, 3-8 parts of reactive nanofiller B, 1-5 parts of hydrolysis stabilizer C, 3-12 parts of curing agent D, and 0.5-3 parts of additive E. Resin component A comprises a hydrolysis-resistant polyester resin and an epoxy-modified acrylate resin in a weight ratio of (3-5):1. The photovoltaic backsheet adhesive provided by this invention utilizes a self-made hydrolysis-resistant polyester resin combined with an epoxy-modified acrylate resin, which synergistically provides basic adhesion, flexibility, and reactivity. It employs a self-made reactive nano-montmorillonite with isocyanate reactive groups grafted onto its surface as reactive nanofiller B, and the self-made microcapsules of hydrolysis stabilizer C work synergistically to inhibit hydrolysis reactions that lead to interfacial failure, ensuring that the adhesive strength maintains a very high retention rate even after accelerated aging.

Description

Technical Field

[0001] This invention relates to the field of photovoltaic module encapsulation composite materials technology, specifically to a photovoltaic backsheet adhesive, its preparation method, and its application. Background Technology

[0002] Photovoltaic modules need to operate stably for more than 25 years in harsh outdoor environments. The photovoltaic backsheet, as a crucial barrier protecting the cells from environmental corrosion, requires excellent barrier properties, weather resistance, and reliable interlayer adhesion strength. With the development of high-efficiency cell technologies such as heterojunction and perovskite tandem layers, the sensitivity to moisture has increased dramatically. Even trace amounts of moisture penetration can lead to irreversible degradation of cell performance. This makes the water-blocking reliability of the photovoltaic backsheet a key factor affecting the long-term lifespan of photovoltaic modules.

[0003] Current photovoltaic backsheets are typically composite structures made of fluorinated films such as polyvinylidene fluoride (PVF) or polyvinylidene fluoride (PVDF) and polyethylene terephthalate (PET) base films, bonded together with adhesives. The adhesive layer not only serves as an interlayer bond, but its water-blocking properties and interfacial stability with the film are also key determinants of water vapor permeation rate and backsheet delamination failure. Currently, the adhesives used in the industry to prepare photovoltaic backsheets are generally polyester-based, acrylic-based, or polyurethane-based adhesives. Inorganic nanosheets (such as montmorillonite) are added to physically extend the water vapor permeation path, or the crosslinking density is increased to enhance the water resistance of the substrate.

[0004] However, existing adhesive preparation methods have the following inherent drawbacks: 1. The inorganic filler in physical blends has poor interfacial compatibility with the polymer matrix, i.e., weak bonding pits, and the interface may debond under long-term humid heat stress. Second, although highly cross-linked networks can reduce moisture permeability, they are often accompanied by increased brittleness and are prone to microcracks during thermal cycling. Third, under long-term high temperature and high humidity environment, water molecules will penetrate and preferentially accumulate at the interface between the adhesive and the substrate such as PET and fluorofilm. At this time, the chemical bonds such as ester bonds and urethane bonds at the adhesive interface will undergo hydrolysis and chain breakage under the continuous attack of water molecules, resulting in a slow, hidden and irreversible decrease in interfacial adhesion. Once the interface is weakened, micro-channels are formed, which accelerates the intrusion of more water vapor, forming a vicious cycle of "interfacial hydrolysis - adhesion failure - more water seepage", which eventually leads to backsheet delamination.

[0005] Existing technologies focus on improving the bulk barrier properties of adhesives, neglecting the nature of interfacial hydrolysis. Therefore, it is necessary to develop a photovoltaic backsheet adhesive that can simultaneously achieve high bulk barrier properties, interfacial hydrolysis resistance, and excellent bonding stability under long-term humid and hot conditions. Summary of the Invention

[0006] To address the aforementioned problems, this invention provides a photovoltaic backsheet adhesive, comprising, by weight, 60-80 parts of resin component A, 3-8 parts of reactive nanofiller B, 1-5 parts of hydrolytic stabilizer C, 3-12 parts of curing agent D, and 0.5-3 parts of additive E. The A resin component comprises a hydrolysis-resistant polyester resin and an epoxy-modified acrylate resin in a weight ratio of (3-5):1, wherein the hydrolysis-resistant polyester resin is copolymerized from aromatic diacids, aliphatic diacids, polyols and hydrolysis-resistant monomers. The hydrolysis-resistant monomer is carbodiimide or an oxazoline compound; The epoxy-modified acrylate resin is a bisphenol A type epoxy acrylate, which has high bonding strength and rapid curing characteristics. The B-type reactive nanofiller is a layered silicate with isocyanate reactive groups grafted onto its surface. It can be uniformly dispersed in the adhesive and participate in the cross-linking reaction to form a nanocomposite barrier structure. The C hydrolysis stabilizer is a microcapsule containing a carbodiimide compound encapsulated in a water-soluble polymer as the wall material.

[0007] Furthermore, the aromatic dicarboxylic acid is selected from at least one of terephthalic acid and isophthalic acid; The aliphatic dicarboxylic acid is selected from at least one of sebacic acid and adipic acid; The polyol is selected from at least one of neopentyl glycol, 1,4-butanediol, diethylene glycol, and 1,4-cyclohexanediethanol.

[0008] Furthermore, the preparation method of the B-type reactive nanofiller is as follows: Ammed products are obtained by reacting layered silicates with aminosilane coupling agents. The aminated product is reacted with an excess of polyisocyanate to obtain reactive nano-montmorillonite with isocyanate groups grafted onto its surface, which is B reactive nanofiller. Wherein, the layered silicate is sodium montmorillonite, the aminosilane coupling agent is γ-aminopropyltriethoxysilane, the amination product is aminated montmorillonite, and the polyisocyanate is hexamethylene diisocyanate.

[0009] Furthermore, the water-soluble polymer wall material of the microcapsules is a gelatin-gum arabic composite; The microcapsules have a particle size of 1-30 μm.

[0010] Furthermore, the preparation steps of the microcapsules are as follows: In situ polymerization was used, polycarbodiimide was dissolved in toluene as the oil phase, and gelatin-gum arabic complex was dissolved in water and the pH was adjusted to form the aqueous phase. Under high-speed shearing, the oil phase is added to the aqueous phase to form an emulsion, and the pH of the system is slowly adjusted to the isoelectric point. Reduce the stirring speed to allow the gelatin-gum arabic complex to recombine at the oil droplet interface, forming a capsule wall; The mixture was then cooled and solidified, filtered, washed, and freeze-dried to obtain microcapsules containing carbodiimide compounds encapsulated in the capsule wall.

[0011] Further, the D curing agent includes a multifunctional isocyanate curing agent and a photoinitiator, wherein the weight ratio of the multifunctional isocyanate curing agent to the A resin component is (0.05-0.15):1; The photoinitiator accounts for 0.5-2% of the total weight of the photovoltaic backsheet adhesive.

[0012] Furthermore, the multifunctional isocyanate curing agent is selected from at least one of hexamethylene diisocyanate trimer and isophorone diisocyanate trimer; The photoinitiator is selected from at least one of 2-hydroxy-2-methyl-1-phenyl-1-propanone, 1-hydroxycyclohexylphenyl ketone, and 2,4,6-trimethylbenzoyl-diphenylphosphine oxide.

[0013] Furthermore, the E-additive includes a UV absorber, a leveling agent, and a silane coupling agent; The ultraviolet absorber is a benzotriazole compound; The silane coupling agent is γ-glycidoxypropyltrimethoxysilane.

[0014] Furthermore, a method for preparing a photovoltaic backsheet adhesive includes the following steps: S1. Synthesis of hydrolysis-resistant polyester resin: Under an inert atmosphere, aromatic dicarboxylic acid, aliphatic dicarboxylic acid, polyol, hydrolysis-resistant monomer and catalyst are added to a reaction vessel. First, an esterification and dehydration reaction is carried out at a temperature of 160-200℃ until the acid value reaches the standard. Then, the temperature is increased to 230-260℃ and a polycondensation reaction is carried out under high vacuum to obtain the hydrolysis-resistant polyester resin. S2. Preparation of resin premix: The hydrolysis-resistant polyester resin, epoxy-modified acrylate resin and silane coupling agent in E additive obtained in step S1 are added to a dispersion device and mixed and stirred under controlled temperature to obtain the resin premix. S3. Nanocomposite dispersion: Add the B reactive nanofiller, the ultraviolet absorber and the leveling agent in the E auxiliary agent to the resin premix obtained in step S2. First, perform high-speed shear dispersion at a speed of 2000-4000 rpm for 15-30 min, and then combine it with ultrasonic treatment at a frequency of 20-40 kHz for 20-40 min to obtain nanocomposite prepolymer. S4. Preparation of finished adhesive: Under light-proof and moisture-proof conditions, the nanocomposite prepolymer obtained in step S3 is transferred to a stirring device, and the photoinitiator and hydrolytic stabilizer in curing agent D are added in sequence. After stirring at low speed until uniform, the multifunctional isocyanate curing agent in curing agent D is added, mixed evenly and degassed under vacuum to obtain the finished photovoltaic backsheet adhesive.

[0015] Furthermore, an application of a photovoltaic backsheet adhesive is provided, wherein the photovoltaic backsheet adhesive is used in the preparation of a photovoltaic backsheet, and the prepared photovoltaic backsheet has a structure in which a fluorine film, an adhesive layer, and a PET base film are sequentially composited, wherein the adhesive layer is formed by coating, UV pre-curing, hot-pressing and post-heat curing processes of the photovoltaic backsheet adhesive.

[0016] Compared with the prior art, the beneficial effects of the present invention are: This invention provides a photovoltaic backsheet adhesive that utilizes a self-made hydrolysis-resistant polyester resin combined with an epoxy-modified acrylate resin. These two components synergistically provide basic adhesion, flexibility, and reactivity. A self-made reactive nano-montmorillonite with isocyanate-reactive groups grafted onto its surface serves as a reactive nanofiller (B), and a self-made microcapsule hydrolysis stabilizer (C) works synergistically to inhibit hydrolysis reactions that lead to interfacial failure. Given that the hydrolysis-resistant resin provides a stable bulk network, the reactive nanofiller strengthens the bulk and interface through chemical bonding, and the microencapsulated hydrolysis stabilizer provides long-term, active chemical protection, the adhesive strength maintains a very high retention rate even after accelerated aging. The reactive nanofiller is uniformly dispersed to form a dense physical barrier layer, while the isocyanate-reactive groups grafted onto its surface form strong chemical bonds with the resin, achieving a simultaneous improvement in barrier performance and interfacial adhesion. This overcomes the shortcomings of traditional physical blend fillers that easily lead to interfacial weakening and possesses both process applicability and overall reliability. Detailed Implementation

[0017] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0018] This invention provides a technical solution: a photovoltaic backsheet adhesive, which, by weight, comprises 60-80 parts of resin component A, 3-8 parts of reactive nanofiller B, 1-5 parts of hydrolytic stabilizer C, 3-12 parts of curing agent D, and 0.5-3 parts of additive E. The A resin component comprises a hydrolysis-resistant polyester resin and an epoxy-modified acrylate resin in a weight ratio of (3-5):1, wherein the hydrolysis-resistant polyester resin is copolymerized from aromatic diacids, aliphatic diacids, polyols and hydrolysis-resistant monomers. The hydrolysis-resistant monomer is carbodiimide or an oxazoline compound; The epoxy-modified acrylate resin is a bisphenol A type epoxy acrylate, which has high bonding strength and rapid curing characteristics. The B-type reactive nanofiller is a layered silicate with isocyanate reactive groups grafted onto its surface. It can be uniformly dispersed in the adhesive and participate in the cross-linking reaction to form a nanocomposite barrier structure. The C hydrolysis stabilizer is a microcapsule containing a carbodiimide compound encapsulated in a water-soluble polymer as the wall material.

[0019] In a preferred embodiment, the aromatic dicarboxylic acid is selected from at least one of terephthalic acid and isophthalic acid; The aliphatic dicarboxylic acid is selected from at least one of sebacic acid and adipic acid; The polyol is selected from at least one of neopentyl glycol, 1,4-butanediol, diethylene glycol, and 1,4-cyclohexanediethanol.

[0020] In a preferred embodiment, the preparation method of the B-reactive nanofiller is as follows: Ammed products are obtained by reacting layered silicates with aminosilane coupling agents. The aminated product is reacted with an excess of polyisocyanate to obtain reactive organo-modified montmorillonite with isocyanate groups grafted onto its surface, which is B reactive nanofiller. Wherein, the layered silicate is sodium montmorillonite, the aminosilane coupling agent is γ-aminopropyltriethoxysilane, the amination product is aminated montmorillonite, and the polyisocyanate is hexamethylene diisocyanate.

[0021] In a preferred embodiment, the water-soluble polymer wall material of the microcapsules is selected from a gelatin-gum arabic composite; The microcapsules have a particle size of 1-30 μm.

[0022] In a preferred embodiment, the microcapsules are prepared as follows: In situ polymerization was used, polycarbodiimide was dissolved in toluene as the oil phase, and gelatin-gum arabic complex was dissolved in water and the pH was adjusted to form the aqueous phase. Under high-speed shearing, the oil phase is added to the aqueous phase to form an emulsion, and the pH of the system is slowly adjusted to the isoelectric point. Reduce the stirring speed to allow the gelatin-gum arabic complex to recombine at the oil droplet interface, forming a capsule wall; The mixture was then cooled and solidified, filtered, washed, and freeze-dried to obtain microcapsules containing carbodiimide compounds encapsulated in the capsule wall.

[0023] In a preferred embodiment, the D curing agent comprises a polyfunctional isocyanate curing agent and a photoinitiator, wherein the weight ratio of the polyfunctional isocyanate curing agent to the A resin component is (0.05-0.15):1; The photoinitiator accounts for 0.5-2% of the total weight of the photovoltaic backsheet adhesive.

[0024] In a preferred embodiment, the multifunctional isocyanate curing agent is selected from at least one of hexamethylene diisocyanate trimer and isophorone diisocyanate trimer; The photoinitiator is selected from at least one of 2-hydroxy-2-methyl-1-phenyl-1-propanone, 1-hydroxycyclohexylphenyl ketone, and 2,4,6-trimethylbenzoyl-diphenylphosphine oxide.

[0025] In a preferred embodiment, the E-additive includes a UV absorber, a leveling agent, and a silane coupling agent; The ultraviolet absorber is a benzotriazole compound; The silane coupling agent is γ-glycidoxypropyltrimethoxysilane.

[0026] In a preferred embodiment, a method for preparing a photovoltaic backsheet adhesive includes the following steps: S1. Synthesis of hydrolysis-resistant polyester resin: Under an inert atmosphere, aromatic dicarboxylic acid, aliphatic dicarboxylic acid, polyol, hydrolysis-resistant monomer and catalyst are added to a reaction vessel. First, an esterification and dehydration reaction is carried out at a temperature of 160-200℃ until the acid value reaches the standard. Then, the temperature is increased to 230-260℃ and a polycondensation reaction is carried out under high vacuum to obtain the hydrolysis-resistant polyester resin. S2. Preparation of resin premix: The hydrolysis-resistant polyester resin, epoxy-modified acrylate resin and silane coupling agent in E additive obtained in step S1 are added to a dispersion device and mixed and stirred under controlled temperature to obtain the resin premix. S3. Nanocomposite dispersion: Add the B reactive nanofiller, the ultraviolet absorber and the leveling agent in the E auxiliary agent to the resin premix obtained in step S2. First, perform high-speed shear dispersion at a speed of 2000-4000 rpm for 15-30 min, and then combine it with ultrasonic treatment at a frequency of 20-40 kHz for 20-40 min to obtain nanocomposite prepolymer. S4. Preparation of finished adhesive: Under light-proof and moisture-proof conditions, the nanocomposite prepolymer obtained in step S3 is transferred to a stirring device, and the photoinitiator and hydrolytic stabilizer in curing agent D are added in sequence. After stirring at low speed until uniform, the multifunctional isocyanate curing agent in curing agent D is added, mixed evenly and degassed under vacuum to obtain the finished photovoltaic backsheet adhesive.

[0027] In a preferred embodiment, a photovoltaic backsheet adhesive is used in the preparation of a photovoltaic backsheet, wherein the prepared photovoltaic backsheet has a structure in which a fluorine film, an adhesive layer, and a PET base film are sequentially composited, wherein the adhesive layer is formed by coating, UV pre-curing, hot-pressing and post-heat curing of the photovoltaic backsheet adhesive.

[0028] Example 1 Materials selected: 80 parts of resin component A, 5 parts of reactive nanofiller B, 2 parts of hydrolytic stabilizer C, 9.5 parts of curing agent D, and 1.3 parts of additive E; Resin component A includes hydrolysis-resistant polyester resin and epoxy-modified acrylate resin in a weight ratio of 3.5:1. The hydrolysis-resistant polyester resin is a self-made copolymer of aromatic diacid, aliphatic diacid, polyol and hydrolysis-resistant monomer, and has an acid value of <5mgKOH / g. The epoxy-modified acrylate resin is a commercially available bisphenol A type epoxy acrylate. B-type reactive nanofiller is a reactive nano-montmorillonite made from layered silicate with isocyanate reactive groups grafted onto its surface, with a grafting rate of approximately 1.2 mmol NCO / g; The C hydrolysis stabilizer is self-made, and the wall material is a gelatin-gum arabic complex with a microcapsule particle size of 5-15 μm; The D curing agent comprises 8 parts of commercially available multifunctional isocyanate curing agent and 1.5 parts of photoinitiator, wherein the multifunctional isocyanate curing agent is hexamethylene diisocyanate trimer and the photoinitiator is 1-hydroxycyclohexylphenyl ketone. The E-additive includes 0.5 parts of UV absorber, 0.3 parts of leveling agent and 0.5 parts of silane coupling agent purchased from the market; Preparation process: S1. Synthesis of hydrolysis-resistant polyester resin: Under an inert atmosphere, aromatic diacid, aliphatic diacid, polyol, hydrolysis-resistant monomer and catalyst are added to a reaction vessel. First, an esterification and dehydration reaction is carried out at a temperature of 180°C until the acid value is lower than 10 mg KOH / g. Then, the temperature is increased to 245°C and a high vacuum pressure of less than 100 Pa is applied to carry out a polycondensation reaction to obtain the hydrolysis-resistant polyester resin. S2. Preparation of resin premix: The hydrolysis-resistant polyester resin, epoxy-modified acrylate resin and silane coupling agent in E additive obtained in step S1 are added to a dispersion device and mixed and stirred at a controlled temperature of 60°C to obtain the resin premix. S3. Nanocomposite dispersion: Add the B reactive nanofiller, the ultraviolet absorber and leveling agent in the E auxiliary agent to the resin premix obtained in step S2. First, perform high-speed shear dispersion at a speed of 3000 rpm for 20 min, and then combine it with ultrasonic treatment at a frequency of 30 kHz for 30 min to obtain nanocomposite prepolymer. S4. Preparation of finished adhesive: Under light-proof and moisture-proof conditions, the nanocomposite prepolymer obtained in step S3 is transferred to a stirring device, and the photoinitiator and hydrolytic stabilizer in curing agent D are added in sequence. After stirring at low speed until uniform, the multifunctional isocyanate curing agent in curing agent D is added, mixed evenly and degassed under vacuum to obtain the finished product 1 of the photovoltaic backsheet adhesive.

[0029] Example 2 The difference from Example 1 lies in the selection of materials and the preparation of finished product 2: Resin component A comprises hydrolysis-resistant polyester resin and epoxy-modified acrylate resin in a weight ratio of 2.6:1. 7 parts B reactive nanofiller, 3 parts C hydrolysis stabilizer, 10 parts D curing agent; Example 3 The difference from Example 1 lies in the preparation process and the preparation of finished product 3: First, high-speed shearing and dispersion was performed at a rotation speed of 2500 rpm for 25 min, followed by ultrasonic treatment at a frequency of 25 kHz for 25 min. Comparative Example 1 The difference from Example 1 lies in the selection of materials and the preparation of finished product 4: Use ordinary terephthalic acid-adipic acid-ethylene glycol-based polyester resin, without carbodiimide or oxazoline compounds, to replace hydrolysis-resistant polyester resin in equal amounts.

[0030] Comparative Example 2 The difference from Example 1 lies in the selection of materials and the preparation of finished product 5: Ordinary organic montmorillonite was used, treated only with silane coupling agent, and the surface was not grafted with isocyanate groups, which replaced reactive nano-montmorillonite (B reactive nanofiller).

[0031] Comparative Example 3 The difference from Example 1 lies in the selection of materials and the preparation of finished product 6: Instead of using microcapsules (C hydrolysis stabilizer) that encapsulate carbodiimide compounds with water-soluble polymers as wall materials, an equal amount of carbodiimide powder that is not encapsulated with gelatin-gum arabic composite wall material is directly added.

[0032] In summary, the finished photovoltaic backsheet adhesives 1-6 prepared in Examples-3 and Comparative Examples-3 were coated onto PET films with a coating thickness of approximately 10 μm. They were then pre-cured immediately with UV energy of 300 mJ / cm², and subsequently hot-pressed with PVF fluorine film at 100°C and 0.4 MPa pressure, and cured at 80°C for 24 hours to obtain composite backsheet samples 1-6 with a PET / adhesive / PVF structure.

[0033] The prepared composite backing samples 1-6 were subjected to initial peel strength, damp heat aging resistance (peel strength retention rate after 2000h aging), water vapor transmission rate (WVTR) (WVTR increase after 2000h aging), and interface morphology observation tests. Initial peel strength was measured as the 90° peel strength (N / cm) between the PVF fluoropolymer film and PET. Damp heat aging resistance was tested by placing the composite backing samples 1-6 in a constant temperature and humidity chamber at 85°C and 85% relative humidity for 500h, 1000h, and 2000h of aging, and calculating the peel strength retention rate after 2000h. WVTR was measured as the change in water vapor transmission rate before and after 2000h aging. Interface morphology observation was performed by scanning electron microscopy (SEM) of the peel interface after 2000h aging. The test results are shown in the table below. Test Result Analysis: As can be seen from the test results in the table above, the composite backsheet samples 1-3 manufactured in Examples 1-3 all exhibit excellent initial adhesive strength and long-term durability in terms of initial peel strength, resistance to damp heat aging test, and water vapor transmission rate test indicators. Moreover, the peel strength retention rate after 2000 hours of aging in a high temperature and humid environment exceeds 85%, the increase in WVTR is minimal, and the interface remains intact as observed. This fully verifies the synergistic effectiveness of using hydrolytically resistant polyester resin in resin component A to provide a stable skeleton, reactive nanofiller B to construct a strong and tough barrier network, and hydrolytic stabilizer C to provide long-term chemical protection. As for the composite backplate sample 4 manufactured in Comparative Example 1, it can be seen that only by replacing the hydrolysis-resistant polyester resin with ordinary terephthalic acid-adipic acid-ethylene glycol polyester resin without hydrolysis-resistant monomers, and keeping other components unchanged, the test results show that it degrades rapidly under humid heat and its performance drops sharply after aging, with severe interface damage. Comparative Example 2 shows that the composite backing sample 3, which uses non-reactive common organic montmorillonite as a layered silicate and is only combined with filler prepared by silane coupling agent, has a slightly lower initial strength. After aging, the barrier WVTR growth and adhesion retention rate are significantly lower than those of composite backing sample 1. In addition, there are visible voids at the interface between the filler and the resin matrix, and local detachment occurs. This further confirms that the use of B-reactive nanofiller is the core to achieve strong interfacial bonding and avoid interfacial debonding during long-term application. Conventional physical blending cannot achieve the same effect. Comparative Example 3 shows that the carbodiimide powder encapsulated without the use of gelatin-gum arabic composite as a wall material has a decent initial protective effect, but its performance is significantly lower than that of the composite backing sample 1 after 2000 hours. This is because the powdered stabilizer is consumed in large quantities during the early stages of processing and aging, and cannot provide lasting protection. The microencapsulation method, on the other hand, enables the slow and controllable release of the protectant, thus improving long-term stability. In summary, the photovoltaic backsheet adhesive prepared in this application can solve the technical problem of long-term humid heat aging resistance of photovoltaic backsheet adhesives, while achieving high barrier properties, interface hydrolysis resistance, and bonding stability and reliability under long-term humid heat environment.

[0034] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to the embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A photovoltaic backsheet adhesive, characterized in that, By weight, the raw material composition includes 60-80 parts of resin component A, 3-8 parts of reactive nanofiller B, 1-5 parts of hydrolytic stabilizer C, 3-12 parts of curing agent D, and 0.5-3 parts of additives E. The A resin component comprises a hydrolysis-resistant polyester resin and an epoxy-modified acrylate resin in a weight ratio of (3-5):1, wherein the hydrolysis-resistant polyester resin is copolymerized from aromatic diacids, aliphatic diacids, polyols and hydrolysis-resistant monomers. The hydrolysis-resistant monomer is carbodiimide or an oxazoline compound; The epoxy-modified acrylate resin is a bisphenol A type epoxy acrylate; The B-type reactive nanofiller is a layered silicate with isocyanate reactive groups grafted onto its surface. The C hydrolysis stabilizer is a microcapsule containing a carbodiimide compound encapsulated in a water-soluble polymer as the wall material.

2. The photovoltaic backsheet adhesive according to claim 1, characterized in that, The aromatic dicarboxylic acid is selected from at least one of terephthalic acid and isophthalic acid; The aliphatic dicarboxylic acid is selected from at least one of sebacic acid and adipic acid; The polyol is selected from at least one of neopentyl glycol, 1,4-butanediol, diethylene glycol, and 1,4-cyclohexanediethanol.

3. The photovoltaic backsheet adhesive according to claim 1, characterized in that, The preparation method of the B-type reactive nanofiller is as follows: Ammed products are obtained by reacting layered silicates with aminosilane coupling agents. The aminated product is reacted with an excess of polyisocyanate to obtain reactive nano-montmorillonite with isocyanate groups grafted onto its surface, which is B reactive nanofiller. Wherein, the layered silicate is sodium montmorillonite, the aminosilane coupling agent is γ-aminopropyltriethoxysilane, the amination product is aminated montmorillonite, and the polyisocyanate is hexamethylene diisocyanate.

4. The photovoltaic backsheet adhesive according to claim 1, characterized in that, The water-soluble polymer wall material of the microcapsules is selected from gelatin-gum arabic composite; The microcapsules have a particle size of 1-30 μm.

5. The photovoltaic backsheet adhesive according to claim 4, characterized in that, The preparation steps of the microcapsules are as follows: In situ polymerization was used, polycarbodiimide was dissolved in toluene as the oil phase, and gelatin-gum arabic complex was dissolved in water and the pH was adjusted to form the aqueous phase. Under high-speed shearing, the oil phase is added to the aqueous phase to form an emulsion, and the pH of the system is slowly adjusted to the isoelectric point. Reduce the stirring speed to allow the gelatin-gum arabic complex to recombine at the oil droplet interface, forming a capsule wall; The mixture was then cooled and solidified, filtered, washed, and freeze-dried to obtain microcapsules containing carbodiimide compounds encapsulated in the capsule wall.

6. The photovoltaic backsheet adhesive according to claim 1, characterized in that, The D curing agent comprises a multifunctional isocyanate curing agent and a photoinitiator, wherein the weight ratio of the multifunctional isocyanate curing agent to the A resin component is (0.05-0.15):1; The photoinitiator accounts for 0.5-2% of the total weight of the photovoltaic backsheet adhesive.

7. The photovoltaic backsheet adhesive according to claim 6, characterized in that, The multifunctional isocyanate curing agent is selected from at least one of hexamethylene diisocyanate trimer and isophorone diisocyanate trimer; The photoinitiator is selected from at least one of 2-hydroxy-2-methyl-1-phenyl-1-propanone, 1-hydroxycyclohexylphenyl ketone, and 2,4,6-trimethylbenzoyl-diphenylphosphine oxide.

8. The photovoltaic backsheet adhesive according to claim 1, characterized in that, The E-additive includes ultraviolet absorbers, leveling agents, and silane coupling agents; The ultraviolet absorber is a benzotriazole compound; The silane coupling agent is γ-glycidoxypropyltrimethoxysilane.

9. A method for preparing a photovoltaic backsheet adhesive, wherein the photovoltaic backsheet adhesive according to any one of claims 1-8 is characterized in that, Includes the following steps: S1. Synthesis of hydrolysis-resistant polyester resin: Under an inert atmosphere, aromatic dicarboxylic acid, aliphatic dicarboxylic acid, polyol, hydrolysis-resistant monomer and catalyst are added to a reaction vessel. First, an esterification and dehydration reaction is carried out at a temperature of 160-200℃ until the acid value reaches the standard. Then, the temperature is increased to 230-260℃ and a polycondensation reaction is carried out under high vacuum to obtain the hydrolysis-resistant polyester resin. S2. Preparation of resin premix: The hydrolysis-resistant polyester resin, epoxy-modified acrylate resin and silane coupling agent in E additive obtained in step S1 are added to a dispersion device and mixed and stirred under controlled temperature to obtain the resin premix. S3. Nanocomposite dispersion: Add the B reactive nanofiller, the ultraviolet absorber and the leveling agent in the E auxiliary agent to the resin premix obtained in step S2. First, perform high-speed shear dispersion at a speed of 2000-4000 rpm for 15-30 min, and then combine it with ultrasonic treatment at a frequency of 20-40 kHz for 20-40 min to obtain nanocomposite prepolymer. S4. Preparation of finished adhesive: Under light-proof and moisture-proof conditions, the nanocomposite prepolymer obtained in step S3 is transferred to a stirring device, and the photoinitiator and hydrolytic stabilizer in curing agent D are added in sequence. After stirring at low speed until uniform, the multifunctional isocyanate curing agent in curing agent D is added, mixed evenly and degassed under vacuum to obtain the finished photovoltaic backsheet adhesive.

10. An application of a photovoltaic backsheet adhesive, wherein the photovoltaic backsheet adhesive according to any one of claims 1-8 is prepared by the preparation method of the photovoltaic backsheet adhesive according to any one of claims 9, characterized in that, The photovoltaic backsheet adhesive is used in the preparation of photovoltaic backsheets, and the prepared photovoltaic backsheets are composed of a fluorine film, an adhesive layer, and a PET base film in sequence. The adhesive layer is formed by coating, UV pre-curing, hot-pressing and post-heat curing of the photovoltaic backsheet adhesive.

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