Adhesive composition for photovoltaic backboard and preparation method of adhesive composition

Abstract

The invention discloses an adhesive composition for a photovoltaic backboard and a preparation method of the adhesive composition, and belongs to the technical field of adhesives. The adhesive composition for the solar photovoltaic backboard comprises the following components in parts by weight: 100 parts of a polyester resin solution, 5-20 parts of a modified urea-formaldehyde resin solution, 3-5 parts of a curing agent, 0.5-3 parts of a plasticizer, 0.1-1 part of a cross-linking agent, 0.5-3 parts of a heat stabilizer, 0.2-2 parts of a light stabilizer, 0.05-1 part of an antioxidant and 1-3 parts of an anti-hydrolysis agent. Through blending of the polyester resin solution and the modified urea-formaldehyde resin solution, the crosslinking density is improved, the prepared backboard has excellent hydrolysis resistance and high interlayer peeling strength, hydrolysis between membrane structures is effectively prevented, the use performance of the backboard glue is effectively enhanced, and the service life of the solar photovoltaic module backboard is prolonged.

Description

Technical Field

[0001] The present invention belongs to the technical field of adhesives, and in particular relates to an adhesive composition for a solar photovoltaic back panel and a preparation method thereof. Background Art

[0002] Photovoltaic backsheets mostly use a three-layer composite structure, which is located on the outermost layer on the back of the module. In outdoor environments, it protects solar cell modules from water vapor erosion, blocks oxygen to prevent oxidation, and has good insulation, aging resistance, and corrosion resistance, thus meeting a service life of more than 25 years. However, since the adhesive is outdoors, it is susceptible to hydrolysis due to the humid climate, which affects its bonding performance.

[0003] Polyester adhesives have good mechanical properties but are not resistant to hydrolysis. This is mainly because polyester adhesives contain ester bonds. The polarity and cohesive energy of ester bonds are large, which makes the adhesives have strong adhesion, high temperature resistance and oil resistance. However, ester bonds are easily hydrolyzed, which makes the adhesives have poor hydrolysis resistance. Existing adhesives for photovoltaic backplanes mostly use carbodiimide to react with the carboxyl groups produced during the hydrolysis process to produce urea to inhibit hydrolysis, thereby playing an anti-hydrolysis role.

[0004] Urea-formaldehyde resin (UF), also known as urea-formaldehyde resin, is produced by urea and formaldehyde under the action of a catalyst. Urea-formaldehyde resin has easy-to-obtain raw materials, low prices, and simple processes, but its hydrolysis resistance and weather resistance are average.

[0005] Patent application CN 104877625 A discloses an adhesive and a preparation method thereof, using hydroxy polyester, hydroxy acrylic resin and a precursor containing PVDF resin as synthetic resins, fluororesin as a modifier, and other auxiliary agents. Fluororesin can significantly improve the aging resistance of polyester or acrylic resin by modifying it. However, due to the presence of solvents, it is easy to hydrolyze in a humid environment, thereby causing the back sheet to delaminate and reducing the peel strength.

[0006] Patent application CN 109233721 A discloses a two-component solvent-free adhesive and a preparation method thereof. The components are formed into a solar backplane glue composition through a simple process and can be industrially produced on a large scale. Through the specific combination of the present invention, it is not necessary to use solvents during use, which is environmentally friendly and energy-saving. However, the combination of cyclic polyester and branched polyester and then the curing of linear polyester obtained by the ring-opening reaction of cyclic polyester is relatively complicated, which may lead to insufficient crosslinking after curing, and the peel strength is not high after aging, and the water resistance is poor.

[0007] Adhesives for photovoltaic backplanes are required to have good adhesion, high temperature resistance, and good hydrolysis resistance. Therefore, more and more attention has been paid to the development of a hydrolysis-resistant adhesive with excellent comprehensive performance suitable for photovoltaic backplanes. Summary of the invention

[0008] The purpose of the present invention is to provide a polyester adhesive composition having excellent hydrolysis resistance, aging resistance and interlayer peeling strength and a preparation method thereof in view of the insufficient comprehensive performance of existing solar photovoltaic backplane adhesives.

[0009] In order to achieve the above object, the technical solution adopted by the present invention is: An adhesive for a solar photovoltaic back sheet, comprising the following raw materials by weight: 100 parts of a polyester resin solution, 5-20 parts of a modified urea-formaldehyde resin solution, 3-5 parts of a curing agent, 0.5-3 parts of a plasticizer, 0.1-1 parts of a cross-linking agent, 0.5-3 parts of a heat stabilizer, 0.2-2 parts of a light stabilizer, 0.05-1 parts of an antioxidant, and 1-3 parts of an anti-hydrolysis agent; The polyester resin solution has a solid content of 40-60%, an acid value of less than 1 mgKOH / g, a hydroxyl value of 17±3 mgKOH / g, and a viscosity of 400-600 mPa.s; The modified urea-formaldehyde resin solution has a viscosity of 1200-1400 mPa.s, a pH of 8.0-8.5, and free formaldehyde less than or equal to 0.5 mg / L.

[0010] Preferably, the modified urea-formaldehyde resin solution of the present invention is prepared by the following steps: dissolving lignin sulfonate to obtain a lignin aqueous solution, adjusting the lignin aqueous solution to be weakly alkaline, adding a quantitative mixed solution of formaldehyde and urea to a reactor for reaction, adjusting the pH value of the reaction solution to 8.0-8.5, the viscosity to 1200-1400mPa.s, controlling the reaction temperature to 45-60°C, and the reaction time to 4-6h, thereby obtaining the modified urea-formaldehyde resin solution.

[0011] More preferably, the mass concentration of the aqueous lignin solution is 20-50%, the molar ratio of formaldehyde to urea is 1.8, and the mass ratio of the mixed solution of formaldehyde and urea to the aqueous lignin solution is (70-90):(10-30).

[0012] Preferably, the polyester resin solution is selected from any one of 50085 or 50087 or a mixture of the two; The curing agent is an isocyanate curing agent, selected from one or a mixture of at least two of toluene diisocyanate, diphenylmethane diisocyanate, isophorone diisocyanate, 1,6-hexamethylene diisocyanate and hexamethylene diisocyanate; The plasticizer is selected from one of dibutyl phthalate (DBP), dioctyl phthalate (DOP), tricresyl phosphate, triphenyl phosphate or dioctyl sebacate, or a mixture of at least two thereof; The cross-linking agent is a soluble aluminum salt; The heat stabilizer is selected from one or a mixture of at least two of stannous octoate, dibutyltin dilaurate or triethylenediamine; The light stabilizer is selected from the group consisting of phenyl salicylate, p-tert-butylphenyl salicylate, 4-[[(methylphenylamine)methylene]amine]benzoic acid acetic acid, 2-cyano-3,3'-ethyl diphenylacrylate, 2,2'-dihydroxy-4-methoxybenzophenone, 2,2',4,4'-tetrahydroxybenzophenone, 2-(2-yl-3',5'-di-tert-butyl)benzotriazole, (2'-hydroxy-3'-tert-butyl-5'-methylphenyl)-5-chlorobenzotriazole, and 2-(2H-benzotriazol-2-yl)-4-tert-butyl-6-sec-butylphenol, or a mixture of at least two thereof; The antioxidant is a hindered amine or a hindered phenol; the antioxidant can inhibit the oxidation process of the backplane adhesive, eliminate the breakage of chemical bonds of organic molecules under the action of heat, light or oxygen, generate active free radicals, prevent the chain reaction, and further delay the aging process of the backplane.

[0013] The anti-hydrolysis agent is selected from at least one of a carbodiimide anti-hydrolysis agent and a polycarbodiimide anti-hydrolysis agent.

[0014] Preferably, the antioxidant of the present invention is selected from any one of antioxidant 1010, antioxidant 1076, antioxidant 1790 or antioxidant BHT, or a mixture of at least two thereof.

[0015] Preferably, the cross-linking agent of the present invention is selected from one of aluminum nitrate, aluminum sulfate, and aluminum phosphate, or a mixture of at least two of them.

[0016] Preferably, the adhesive of the present invention is used for composite solar photovoltaic back panels. When composited, the amount of adhesive applied is 15 g / m 2 -20 g / m 2 , dry film thickness 12~15 um, composite temperature 100~140 ℃, applied pressure 8~15kg / cm 2 ; After compounding, ripen at 70 ℃*72 h.

[0017] A method for preparing an adhesive for a solar photovoltaic back sheet comprises the following steps: (1) Preparation of modified urea-formaldehyde resin solution Dissolving lignin sulfonate to obtain a lignin aqueous solution, adjusting the solution to be weakly alkaline, adding a certain amount of a mixed solution of formaldehyde and urea to a reactor for reaction, adjusting the pH value of the reaction solution to 8.0-8.5, the viscosity to 1200-1400 mPa.s, controlling the temperature to 45-60° C., and the reaction time to 4-6 hours, thereby obtaining the modified urea-formaldehyde resin solution; (2) Preparation of mixed solution Weigh the polyester resin solution and the modified urea-formaldehyde resin solution in proportion, start the stirrer, weigh and add the plasticizer, heat stabilizer, light stabilizer, antioxidant and anti-hydrolysis agent in sequence, stir evenly to obtain a mixed solution, which is milky white; (3) Preparation of adhesive for solar photovoltaic backsheet Slowly add isocyanate curing agent to the mixed solution obtained in step (2), continue stirring to obtain glue solution, then filter the obtained glue solution, ultrasonically degas until there are no bubbles, and let it stand at room temperature to obtain the adhesive for solar photovoltaic backplane.

[0018] Compared with the prior art, the principles and beneficial effects of the present invention are as follows: (1) In addition to improving the hydrolysis resistance of the polyester adhesive by adding a soluble aluminum salt and an anti-hydrolysis agent, the present invention also prepares a light stabilizer to make the adhesive have good resistance to ultraviolet aging.

[0019] (2) The modified urea-formaldehyde resin solution prepared by the present invention has good adhesive properties and excellent heat resistance and hydrolysis resistance. When added to the polyester resin solution, a network cross-linking structure is formed, which improves the adhesive properties of the backplane adhesive, and greatly improves the peel strength and hydrolysis resistance of the composite photovoltaic backplane, thereby solving the problems of the existing solvent-based polyurethane adhesives, such as easy hydrolysis under high humidity, easy aging, easy delamination, and low interlayer peeling strength.

[0020] (3) The present invention provides a polyester adhesive composition specially designed for solar backplane composites. No solvent needs to be added. The crosslinking density is improved by blending a polyester resin solution with a modified urea-formaldehyde resin solution. The prepared backplane has excellent hydrolysis resistance and high interlayer peeling strength. It effectively prevents hydrolysis between film structures, effectively enhances the performance of the backplane adhesive, and increases the life of the solar photovoltaic module backplane.

[0021] (4) The adhesive prepared by the present invention is suitable for the production of solar photovoltaic back panels. The obtained product has been tested and found that under double 85 temperature for 2000 hours, the adhesive layer has no hydrolysis and delamination, no shrinkage, and no yellowing. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1A comprehensive schematic diagram of the initial peel strength of the solar photovoltaic module back sheet of the present invention and the peel strength after aging for 2000 hours with double 85; Figure 2 It is a schematic diagram of the water immersion retention rate of the back plate of the solar photovoltaic module of the present invention. DETAILED DESCRIPTION

[0023] The present invention is described in detail below by way of examples and comparative examples. The following experimental examples can only be used to further illustrate the present invention, and the actual implementation methods are not limited thereto. If a person skilled in the art is inspired by the examples, and does not deviate from the purpose of the invention, a structural method and an embodiment similar to the technical solution can be designed without creativity, and all of them should belong to the protection scope of the present invention.

[0024] The invention discloses an adhesive for a solar photovoltaic back panel, which comprises the following raw materials by weight: 100 parts of a polyester resin solution, 5-20 parts of a modified urea-formaldehyde resin solution, 3-5 parts of a curing agent, 0.5-3 parts of a plasticizer, 0.1-1 parts of a cross-linking agent, 0.5-3 parts of a heat stabilizer, 0.2-2 parts of a light stabilizer, 0.05-1 parts of an antioxidant, and 1-3 parts of an anti-hydrolysis agent.

[0025] In some embodiments of the present invention, the polyester resin is a base resin, liquid, non-hot melt adhesive, solid content 40-60%, acid value less than 1, hydroxyl value 17±3, 400-600 mPa.s. It has a clear and transparent appearance, is a solvent-soluble, linear, thermoplastic polymer polyester, has good leveling, good flexibility, high toughness and high weather resistance, and has good adhesion to PET, PVF / PVDF. It is selected from any one of 50085 or 50087 of Changxing Chemical Industry Co., Ltd. or a mixture of the two.

[0026] In some embodiments of the present invention, the modified urea-formaldehyde resin has a viscosity of 1200-1400 mPa.s, a pH of 8.0-8.5, and free formaldehyde of less than or equal to 0.5 mg / L. The modifier is a lignin solution, the mass concentration of the lignin aqueous solution is 20-50%, the molar ratio of formaldehyde to urea is 1.8, and the mass ratio of the mixed solution of formaldehyde and urea to the lignin aqueous solution is (70-90): (10-30). The urea-formaldehyde resin modified by the lignin aqueous solution has the characteristics of good water resistance, high bonding strength and low formaldehyde release.

[0027] In some embodiments of the present invention, the curing agent is an isocyanate curing agent, selected from one or a mixture of at least two of toluene diisocyanate, diphenylmethane diisocyanate, isophorone diisocyanate, 1,6-hexamethylene diisocyanate, and hexamethylene diisocyanate.

[0028] In some embodiments of the present invention, the plasticizer is selected from one of dibutyl phthalate (DBP), dioctyl phthalate (DOP), tricresyl phosphate, triphenyl phosphate, dioctyl sebacate, or a mixture of at least two thereof.

[0029] Through research, it was found that adding plasticizer components can improve the impact toughness and elongation at break of the polymer, reduce the molding temperature of the polymer, and improve the flexibility and bonding strength of the film.

[0030] In some embodiments of the present invention, the heat stabilizer is selected from one or a mixture of at least two of stannous octoate, dibutyltin dilaurate, and triethylenediamine.

[0031] Through research, it is found that the thermal stabilizer can improve the thermal stability of polyester resin, reduce the activation energy of the reaction, and initiate the cross-linking reaction of the polymer, thereby effectively making the combined system fully react.

[0032] The light stabilizer is selected from one of phenyl salicylate, p-tert-butylphenyl salicylate, 4-[[(methylphenylamine)methylene]amine]benzoic acid acetic acid, 2-cyano-3,3'-diphenylacrylate, 2,2'-dihydroxy-4-methoxybenzophenone, 2,2',4,4'-tetrahydroxybenzophenone, 2-(2-yl-3',5'-di-tert-butyl)benzotriazole, (2'-hydroxy-3'-tert-butyl-5'-methylphenyl)-5-chlorobenzotriazole, and 2-(2H-benzotriazol-2-yl)-4-tert-butyl-6-sec-butylphenol, or a mixture of at least two thereof.

[0033] In some embodiments of the present invention, the antioxidant is a hindered amine or a hindered phenol. Preferably, the antioxidant is any one of antioxidant 1010, antioxidant 1076, antioxidant 1790 or antioxidant BHT, or a mixture of at least two thereof.

[0034] Through research, it is found that the antioxidant can inhibit the oxidation process of the backplane adhesive, eliminate the breakage of chemical bonds of organic molecules under the action of heat, light or oxygen, generate active free radicals, prevent the chain reaction, and further delay the aging process of the backplane.

[0035] In some embodiments of the present invention, the crosslinking agent is selected from one of aluminum nitrate, aluminum sulfate, and aluminum phosphate, or a mixture of at least two thereof. Soluble aluminum salts such as aluminum sulfate and aluminum phosphate can improve the water resistance of urea-formaldehyde resin and enhance its crosslinking reaction.

[0036] In some embodiments of the present invention, the anti-hydrolysis agent is selected from carbodiimide anti-hydrolysis agents, polycarbodiimide anti-hydrolysis agents, or a mixture of at least two of them. Such anti-hydrolysis agents are anti-hydrolysis agents containing carbodiimide functional groups (-N=C=N-), are low-toxic and environmentally friendly, can undergo cross-linking reactions with carboxyl-containing resin systems, improve water resistance, chemical resistance, and wear resistance, and can also enhance adhesion to the substrate.

[0037] The adhesive composition for solar photovoltaic backsheet of the present invention is easy to use, safe, environmentally friendly and non-toxic, and solves the problems of easy hydrolysis under high humidity and low peeling strength of existing solvent-based photovoltaic backsheet adhesives.

[0038] Composite process parameters: coating amount is 15 g / m 2 -20 g / m 2 , dry film thickness 12~15 um, composite temperature 100~140 ℃, applied pressure 8~15kg / cm 2 ; After compounding, ripen at 70 ℃*72 h.

[0039] The adhesive prepared by the present invention can be used for the production of solar photovoltaic back panels. The obtained product has been tested and found that under the double 85 temperature for 2000 hours, the adhesive layer has no hydrolysis and stratification, no shrinkage, and no yellowing. Example 1

[0040] 1) Preparation of modified urea-formaldehyde resin solution: dissolving lignin sulfonate to obtain a lignin aqueous solution, the mass concentration of the lignin aqueous solution is 30%, adjusting the solution to be weakly alkaline, adding a certain amount of a mixed solution of formaldehyde and urea to a reactor for reaction, the molar ratio of formaldehyde to urea is 1.8, the mass ratio of the mixed solution of formaldehyde and urea to the lignin aqueous solution is 7:3, adjusting the pH value of the reaction solution to 8.0-8.5, the viscosity to 1250 mPa.s, controlling the temperature to 45°C, and the reaction time to 6 hours, thereby obtaining the modified urea-formaldehyde resin solution; 2) Weigh 100 parts of 50085 polyester resin solution and 15 parts of modified urea-formaldehyde resin solution in a clean crucible in proportion, slowly start the stirrer, increase the speed to 3 Hz, weigh and add 0.8 parts of tricresyl phosphate, 0.3 parts of aluminum nitrate, 0.6 parts of stannous octoate, 0.1 parts of antioxidant 1076, and 1 part of carbodiimide in sequence, and the mixed solution is transparent. Then slowly and uniformly add 4.5 parts of isophorone diisocyanate curing agent, stir at the original speed for 8 minutes, and then filter the obtained adhesive solution with a 300-mesh filter, ultrasonically degas until there are no bubbles, and let it stand at room temperature to obtain the backplane adhesive.

[0041] The prepared backplane adhesive was coated on the surface of the PET film using a coating rod, and the amount of adhesive was controlled at 15 g / m 2, 100 ℃, after drying for 2 min, the PVDF membrane and the PET coated with glue were laminated together using a laminating machine, and then pressed and flattened using an electric press with a pressure of 8kg / cm 2 ; After compounding, ripen at 70 ℃*72 h.

[0042] The comprehensive evaluation of the initial peel strength of the prepared back sheet after aging was 8.76 N / cm. Example 2

[0043] 1) Preparation of modified urea-formaldehyde resin solution: dissolving lignin sulfonate to obtain a lignin aqueous solution, wherein the mass concentration of the lignin aqueous solution is 45%, adjusting the solution to be weakly alkaline, adding a certain amount of a mixed solution of formaldehyde and urea to a reactor for reaction, wherein the molar ratio of formaldehyde to urea is 1.8, and the mass ratio of the mixed solution of formaldehyde and urea to the lignin aqueous solution is 8:2, adjusting the pH value of the reaction solution to 8.0-8.5, the viscosity to 1400 mPa.s, controlling the temperature to 45°C, and the reaction time to 4 hours, thereby obtaining the modified urea-formaldehyde resin solution; 2) Weigh 100 parts of 50087 polyester resin solution and 12 parts of modified urea-formaldehyde resin in a clean crucible in proportion, slowly start the stirrer, increase the speed to 3 Hz, weigh and add 1 part of tricresyl phosphate, 0.4 parts of aluminum phosphate, 1.2 parts of triethylenediamine, 0.05 parts of antioxidant 1076, and 1 part of polycarbodiimide in sequence, and the mixed solution is transparent. Then slowly and uniformly add 4 parts of isophorone diisocyanate curing agent, stir at the original speed for 8 minutes, and then filter the obtained adhesive solution with a 300-mesh filter, ultrasonically degas until there are no bubbles, and let it stand at room temperature to obtain the backplane adhesive.

[0044] The prepared backplane adhesive was coated on the surface of the PET film using a coating rod, and the amount of adhesive was controlled at 20 g / m 2 , 140 ℃, after drying for 2 min, the PVDF membrane and the PET coated with glue were laminated together by a laminating machine, and then pressed and flattened by an electric press with a pressure of 8kg / cm 2 ; After compounding, ripen at 70 ℃*72 h.

[0045] The initial peel strength of the prepared backsheet after aging was evaluated to be 10.53 N / cm Example 3

[0046] 1) Preparation of modified urea-formaldehyde resin solution: dissolving lignin sulfonate to obtain a lignin aqueous solution, wherein the mass concentration of the lignin aqueous solution is 50%, adjusting the solution to be weakly alkaline, adding a certain amount of a mixed solution of formaldehyde and urea to a reactor for reaction, wherein the molar ratio of formaldehyde to urea is 1.8, and the mass ratio of the mixed solution of formaldehyde and urea to the lignin aqueous solution is 9:1, adjusting the pH value of the reaction solution to 8.0-8.5, the viscosity to 1300 mPa.s, controlling the temperature to 55°C, and the reaction time to 4 hours, thereby obtaining the modified urea-formaldehyde resin solution; 2) Weigh 100 parts of 50085 polyester solution and 10 parts of modified urea-formaldehyde resin in a clean crucible in proportion, slowly start the stirrer, increase the speed to 3 Hz, weigh and add 1.5 parts of dioctyl sebacate, 0.6 parts of aluminum sulfate, 1.3 parts of stannous octoate, 0.2 parts of antioxidant 1076, and 1.5 parts of carbodiimide in sequence, and the mixed solution is transparent. Then slowly and uniformly add 3.5 parts of hexamethylene diisocyanate curing agent, stir at the original speed for 8 minutes, and then filter the obtained adhesive solution with a 300-mesh filter, ultrasonically degas until there are no bubbles, and let it stand at room temperature to obtain the backplane adhesive.

[0047] The prepared backplane adhesive was applied on the surface of the PET film using a coating rod, and the amount of adhesive applied was controlled at 18 g / m 2 , 120 ℃, after drying for 2 min, the PVDF membrane and the PET coated with glue were laminated together by a laminating machine, and then pressed and flattened by an electric press with a pressure of 10kg / cm 2 ; After compounding, ripen at 70 ℃*72 h.

[0048] The comprehensive evaluation of the initial peel strength of the prepared back sheet after aging was 11.12 N / cm. Example 4

[0049] 1) Preparation of modified urea-formaldehyde resin solution: dissolving lignin sulfonate to obtain a lignin aqueous solution, the mass concentration of the lignin aqueous solution is 30%, adjusting the solution to be weakly alkaline, adding a certain amount of a mixed solution of formaldehyde and urea to a reactor for reaction, the molar ratio of formaldehyde to urea is 1.8, the mass ratio of the mixed solution of formaldehyde and urea to the lignin aqueous solution is 7:3, adjusting the pH value of the reaction solution to 8.0-8.5, the viscosity to 1350 mPa.s, controlling the temperature to 60°C, and the reaction time to 5 hours, thereby obtaining the modified urea-formaldehyde resin solution; 2) Weigh 100 parts of 50085 polyester solution and 5 parts of modified urea-formaldehyde resin in a clean crucible in proportion, slowly start the stirrer, increase the speed to 3 Hz, weigh and add 1.8 parts of tricresyl phosphate, 0.7 parts of aluminum phosphate, 2 parts of dibutyltin dilaurate, 0.2 parts of antioxidant 1076, and 1.2 parts of polycarbodiimide in sequence, and the mixed solution is transparent. Then slowly and uniformly add 2.5 parts of hexamethylene diisocyanate curing agent, stir at the original speed for 8 minutes, and then filter the obtained adhesive solution with a 300-mesh filter, ultrasonically degas until there are no bubbles, and let it stand at room temperature to obtain the backplane adhesive.

[0050] The prepared backplane adhesive was applied on the surface of the PET film using a coating rod, and the amount of adhesive applied was controlled at 18 g / m 2 , 120 ℃, after drying for 2 min, the PVDF membrane and the PET coated with glue were laminated together by a laminating machine, and then pressed and flattened by an electric press with a pressure of 10kg / cm 2 ; After compounding, ripen at 70 ℃*72 h.

[0051] The comprehensive evaluation of the initial peel strength of the prepared back sheet after aging was 13.31 N / cm. Example 5

[0052] 1) Preparation of modified urea-formaldehyde resin solution: dissolving lignin sulfonate to obtain a lignin aqueous solution, wherein the mass concentration of the lignin aqueous solution is 20%, adjusting the solution to be weakly alkaline, adding a certain amount of a mixed solution of formaldehyde and urea to a reactor for reaction, wherein the molar ratio of formaldehyde to urea is 1.8, and the mass ratio of the mixed solution of formaldehyde and urea to the lignin aqueous solution is 9:1, adjusting the pH value of the reaction solution to 8.0-8.5, the viscosity to 1200 mPa.s, controlling the temperature to 60°C, and the reaction time to 4 hours, thereby obtaining the modified urea-formaldehyde resin solution; 2) Weigh 100 parts of 50087 polyester solution and 15 parts of modified urea-formaldehyde resin in a clean crucible in proportion, slowly start the stirrer, increase the speed to 3 Hz, weigh and add 1.3 parts of dibutyl phthalate, 0.8 parts of aluminum nitrate, 1.2 parts of stannous octoate, 0.1 parts of antioxidant 1010, and 1.8 parts of carbodiimide in sequence, and the mixed solution is transparent. Then slowly and uniformly add 4 parts of diphenylmethane diisocyanate curing agent, stir at the original speed for 8 minutes, and then filter the obtained adhesive solution with a 300-mesh filter, ultrasonically degas until there are no bubbles, and let it stand at room temperature to obtain the backplane adhesive.

[0053] The prepared backplane adhesive was coated on the surface of the PET film using a coating rod, with the amount of adhesive controlled at 20 g / m2, and dried at 140 °C for 2 min. The PVDF film and the PET coated with glue were laminated together using a laminating machine, and pressed and flattened using an electric press with a pressure of 12 kg / cm2 ; After compounding, ripen at 70 ℃*72 h.

[0054] The prepared back sheet had a comprehensive evaluation of initial peel strength of 7.84 N / cm after aging. Example 6

[0055] Preparation of modified urea-formaldehyde resin solution: dissolving lignin sulfonate to obtain a lignin aqueous solution, adjusting the solution to be weakly alkaline, adding a certain amount of a mixed solution of formaldehyde and urea to a reactor for reaction, wherein the molar ratio of formaldehyde to urea is 1.8, and the mass ratio of the mixed solution of formaldehyde and urea to the lignin aqueous solution is 8:2, adjusting the pH value of the reaction solution to 8.0-8.5, the viscosity to 1350 mPa.s, controlling the temperature to 60°C, and the reaction time to 6 hours, thereby obtaining the modified urea-formaldehyde resin solution; 2) Weigh 100 parts of 50085 polyester solution and 20 parts of modified urea-formaldehyde resin in a clean crucible in proportion, slowly start the stirrer, increase the speed to 3 Hz, weigh and add 2 parts of tricresyl phosphate, 0.5 parts of aluminum sulfate, 1.6 parts of triethylenediamine, 0.1 parts of antioxidant 1076, and 1.5 parts of polycarbodiimide in sequence, and the mixed solution is transparent. Then slowly and uniformly add 3 parts of hexamethylene diisocyanate curing agent, stir at the original speed for 8 minutes, and then filter the obtained adhesive solution with a 300-mesh filter, degas by ultrasonication until there are no bubbles, and let it stand at room temperature to obtain the backplane adhesive.

[0056] The prepared backplane adhesive was coated on the surface of the PET film using a coating rod, with the amount of adhesive controlled at 18 g / m2, and dried at 120 °C for 2 min. The PVDF film and the PET coated with glue were laminated together using a laminating machine, and pressed and flattened using an electric press with a pressure of 10 kg / cm 2 ; After compounding, ripen at 70 ℃*72 h.

[0057] The comprehensive evaluation of the initial peel strength of the prepared back sheet after aging was 6.15 N / cm.

[0058] Comparative Example 1

[0059] This example provides a photovoltaic module backsheet adhesive, and its preparation process is basically the same as that of Example 2, except that the anti-hydrolysis agent polycarbodiimide in the raw material is removed. The prepared backsheet has a comprehensive evaluation of initial peel strength of 4.86 N / cm after aging.

[0060] Comparative Example 2

[0061] This example provides a photovoltaic module backplane adhesive, and its preparation process is basically the same as that of Example 2, except that the homemade modified urea-formaldehyde resin is replaced with a commercially available urea-formaldehyde resin (viscosity 800-1200 mPa.s, pH value 7.0-8.5, free formaldehyde less than or equal to 0.5 mg / L). The prepared backplane has a comprehensive evaluation of initial peel strength of 4.01 N / cm after aging.

[0062] Comparative Example 3

[0063] This example provides a photovoltaic module backplane adhesive, and its preparation process is basically the same as that of Example 2, except that 12 parts of modified urea-formaldehyde resin in the raw material are replaced with epoxy resin. The prepared backplane has a comprehensive evaluation of initial peel strength of 5.48 N / cm after aging.

[0064] Comparative Example 4

[0065] This example provides a photovoltaic module backplane adhesive, and its preparation process is basically the same as that of Example 2, except that the modified urea-formaldehyde resin in the raw material is removed. The prepared backplane has a comprehensive evaluation of initial peel strength of 4.16 N / cm after aging.

[0066] Comparative Example 5

[0067] This example provides a photovoltaic module backplane adhesive, the preparation components of which are basically the same as those in Example 2, except that the ultrasonic degassing in the preparation process is replaced by static room temperature degassing, the rotation speed is increased from 3 Hz to 5 Hz, and the aging condition of 70℃*72h in the backplane composite process is replaced by 45℃*24h. The prepared backplane has a comprehensive evaluation of initial peel strength of 3.21 N / cm after aging.

[0068] Standard or specific method of testing After composite aging, the initial peel strength, peel strength after aging and immersion in water for 168 hours, and backsheet film peeling of each embodiment and control example were tested respectively. The results are shown in Table 1, Table 2, and Table 3: Peel strength test: Refer to GB / T 2790-1995 Adhesive 180° Peel Strength Test Method for testing. Cut the sample into strips with a width of 10.00 mm and a length of 200 mm, and test at a peeling speed of 130 mm / min.

[0069] Constant humidity and heat aging performance: The humidity and heat aging test was carried out according to the GB / T2423.3 test method. Test conditions: 85°C, relative humidity 85%, 2000h. Before and after the test, the peeling force of the sample was measured according to the national standard GB / T 2790-1995 adhesive 180° peel strength test method.

[0070] Water resistance: According to GB / T2791, the specimens were immersed in water for 168 hours, and then the peel strength of the bonded samples was tested on an Instron 4465 universal electronic tensile testing machine at a peeling speed of 100 mm / min to detect the water retention rate.

[0071] Table 1 Peel strength evaluation table

[0072] Table 2 Solar back sheet adhesive performance test results

[0073] Table 3 Backplane appearance evaluation table

[0074] analyze: From Table 1, Table 2, Table 3, Figure 1 and Figure 2 It can be seen that the photovoltaic backsheets described in Examples 1-6 have very good peel strength, excellent hydrolysis resistance and aging resistance, and the comprehensive performance far exceeds the peel strength and national standards of ordinary traditional solar photovoltaic backsheets.

[0075] Through Examples 1-6 and Comparative Examples 1-5, it can be seen that the blending of polyester resin solution and modified urea-formaldehyde resin solution has achieved good results. On the one hand, the modified urea-formaldehyde resin itself has little difference in compatibility with polyester and can be well mixed together; on the other hand, the modified urea-formaldehyde resin has good bonding properties, excellent heat resistance and hydrolysis resistance. When added to the polyester resin, a network cross-linking structure is formed, which improves the bonding properties of the backplane adhesive. Assisted by other additives, the composite photovoltaic backplane has greatly improved peel strength and hydrolysis resistance.

[0076] At the same time, through Comparative Examples 1 and 2, it can be found that the anti-hydrolysis agent used in the present invention and the commercially available urea-formaldehyde resin also have a certain influence on the peel strength and hydrolysis resistance of the system after aging, which also indirectly reflects that the modified urea-formaldehyde resin solution improves its comprehensive performance after being added to the adhesive system.

[0077] From Examples 1-5, we can see that the appearance of the double 85 is still good after 2000h aging, there is no peeling between the adhesive layers, no shrinkage, and no yellowing, indicating that the stability of the backplane is significantly improved.

[0078] The present invention adopts modified urea-formaldehyde resin solution to blend and modify polyester resin solution through the selection of component reagents and the optimization of the proportion of each component. The peel strength, hydrolysis resistance and other properties of the prepared backboard all achieve good expected effects, thereby improving the comprehensive performance of the adhesive for the backboard.

[0079] The above embodiments and comparative examples are only for illustrating the technical concept and features of the present invention, and their purpose is to enable people familiar with the technology to understand the content of the present invention and implement it accordingly, and they cannot limit the protection scope of the present invention. Any equivalent changes or modifications made according to the spirit of the present invention should be included in the protection scope of the present invention.

Claims

1. An adhesive for a solar photovoltaic back sheet, characterized in that: In parts by weight, it includes: 100 parts of polyester resin solution 5-20 parts of modified urea-formaldehyde resin solution 3-5 parts of curing agent Plasticizer 0.5-3 parts Crosslinking agent 0.1-1 part Heat stabilizer 0.5-3 parts Light stabilizer 0.2-2 parts Antioxidant 0.05-1 part 1-3 parts of anti-hydrolysis agent; The polyester resin solution has a solid content of 40-60%, an acid value of less than 1 mgKOH / g, a hydroxyl value of 17±3 mgKOH / g, and a viscosity of 400-600 mPa.s; The modified urea-formaldehyde resin solution has a viscosity of 800-1200 mPa.s, a pH of 8.0-8.5, and free formaldehyde less than or equal to 0.5 mg / L.

2. The adhesive for solar photovoltaic backsheet according to claim 1, characterized in that: The modified urea-formaldehyde resin solution is prepared by the following steps: dissolving lignin sulfonate to obtain a lignin aqueous solution, adjusting the lignin aqueous solution to be weakly alkaline, adding a quantitative mixed solution of formaldehyde and urea to a reaction kettle for reaction, adjusting the pH value of the reaction solution to 8.0-8.5, the viscosity to 1200-1400mPa.s, controlling the reaction temperature to 45-60°C, and the reaction time to 4-6h, thereby obtaining the modified urea-formaldehyde resin solution.

3. The adhesive for solar photovoltaic backsheet according to claim 2, characterized in that: The mass concentration of the lignin aqueous solution is 20-50%, the molar ratio of formaldehyde to urea is 1.8, and the mass ratio of the mixed solution of formaldehyde and urea to the lignin aqueous solution is (70-90): (10-30).

4. The adhesive for solar photovoltaic backsheet according to claim 1, characterized in that: The polyester resin solution is selected from any one of 50085 or 50087 or a mixture of the two; The curing agent is an isocyanate curing agent, selected from one or a mixture of at least two of toluene diisocyanate, diphenylmethane diisocyanate, isophorone diisocyanate, 1,6-hexamethylene diisocyanate and hexamethylene diisocyanate; The plasticizer is selected from one of dibutyl phthalate (DBP), dioctyl phthalate (DOP), tricresyl phosphate, triphenyl phosphate or dioctyl sebacate, or a mixture of at least two thereof; The cross-linking agent is a soluble aluminum salt; The heat stabilizer is selected from one or a mixture of at least two of stannous octoate, dibutyltin dilaurate or triethylenediamine; The light stabilizer is selected from the group consisting of phenyl salicylate, p-tert-butylphenyl salicylate, 4-[[(methylphenylamine)methylene]amine]benzoic acid acetic acid, 2-cyano-3,3'-ethyl diphenylacrylate, 2,2'-dihydroxy-4-methoxybenzophenone, 2,2',4,4'-tetrahydroxybenzophenone, 2-(2-yl-3',5'-di-tert-butyl)benzotriazole, (2'-hydroxy-3'-tert-butyl-5'-methylphenyl)-5-chlorobenzotriazole, and 2-(2H-benzotriazol-2-yl)-4-tert-butyl-6-sec-butylphenol, or a mixture of at least two thereof; The antioxidant is a hindered amine or a hindered phenol; The anti-hydrolysis agent is selected from at least one of a carbodiimide anti-hydrolysis agent and a polycarbodiimide anti-hydrolysis agent.

5. The adhesive for solar photovoltaic backsheet according to claim 4, characterized in that: The antioxidant is selected from any one of antioxidant 1010, antioxidant 1076, antioxidant 1790 or antioxidant BHT, or a mixture of at least two thereof.

6. The adhesive for solar photovoltaic backsheet according to claim 4, characterized in that: The cross-linking agent is selected from one of aluminum nitrate, aluminum sulfate, and aluminum phosphate, or a mixture of at least two of them.

7. The adhesive for solar photovoltaic backsheet according to any one of claims 1 to 6, characterized in that: Used for composite solar photovoltaic back panels. When composited, the coating amount is 15 g / m 2 -20 g / m 2 , dry film thickness 12~15 um, composite temperature 100~140 ℃, applied pressure 8~15kg / cm 2 ; After compounding, ripen at 70 ℃*72 h.

8. A method for preparing the adhesive for solar photovoltaic backsheet as claimed in claim 1, characterized in that: The preparation steps are as follows: (1) Preparation of modified urea-formaldehyde resin solution Dissolving lignin sulfonate to obtain a lignin aqueous solution, adjusting the solution to be weakly alkaline, adding a certain amount of a mixed solution of formaldehyde and urea to a reactor for reaction, adjusting the pH value of the reaction solution to 8.0-8.5, the viscosity to 1200-1400 mPa.s, controlling the temperature to 45-60° C., and the reaction time to 4-6 hours, thereby obtaining the modified urea-formaldehyde resin solution; (2) Preparation of mixed solution Weigh the polyester resin solution and the modified urea-formaldehyde resin solution in proportion, start the stirrer, weigh and add the plasticizer, heat stabilizer, light stabilizer, antioxidant and anti-hydrolysis agent in sequence, stir evenly to obtain a mixed solution, which is milky white; (3) Preparation of adhesive for solar photovoltaic backsheet Slowly add isocyanate curing agent to the mixed solution obtained in step (2), continue stirring to obtain glue solution, then filter the obtained glue solution, ultrasonically degas until there are no bubbles, and let it stand at room temperature to obtain the adhesive for solar photovoltaic backplane.

9. The method according to claim 8, characterized in that: In step 1), the mass concentration of the lignin aqueous solution is 20-50%, the molar ratio of formaldehyde to urea is 1.8, and the mass ratio of the mixed solution of formaldehyde and urea to the lignin aqueous solution is (70-90):(10-30).

10. The method according to claim 8, characterized in that: In step 2), the rotation speed of the stirrer is 3-5 Hz, and the stirring time is 7-10 minutes; in step 3), the stirring time is 3-6 minutes.

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