A thermosetting epoxy adhesive for photovoltaic 0BB technology and application thereof

Abstract

The application discloses a kind of photovoltaic 0BB technology with thermosetting epoxy glue, including the following mass fraction group: castor oil structure oxabutane 10-20 parts, alicyclic epoxy 30-70 parts, polyester polyol 1-10 parts, hydrogenated rosin resin 1-5 parts, thermal initiator 0.6-3 parts, coupling agent 0.5-1.5 parts, anti-aging agent 0.2-1.0 parts, thixotropic agent 1-7 parts;Photovoltaic 0BB technology with thermosetting epoxy glue prepared by the application has good yellowing resistance, high temperature low volatile fraction, and good high-low temperature impact performance.

Description

Technical fields:

[0001] This invention relates to the field of solar photovoltaic technology, and is applicable to encapsulating adhesives for photovoltaic OBB technology and their preparation methods. Background technology:

[0002] Traditional PERC, new TOPcon cells, and HJT (heterojunction) cells, especially HJT cells, require a high amount of silver paste. Under the premise of energy conservation and cost reduction, reducing the use of silver paste has become one of the important ways for photovoltaic companies to reduce costs.

[0003] Gridless modules, also known as OBB technology, are an innovative photovoltaic (PV) module technology. This technology eliminates the traditional grid of solar cells, instead using solder ribbons to conduct current in the module assembly. Specifically, gridless cells use solder ribbons to collect current through a fine grid and interconnect cells; the width of the solder ribbons is smaller than that of traditional grids. Furthermore, gridless cells typically use copper solder ribbons, completely replacing the original silver electrode grid, thus realizing the function of base metals in place of traditional silver grids. The advantages of OBB are: 1) reduced silver loss; 2) enhanced conductivity; 3) low-temperature encapsulation processes that can accommodate thinner silicon wafers.

[0004] Currently, OBB solder ribbon bonding mainly utilizes UV adhesives, thermosetting epoxy adhesives, and thermosetting silicone adhesives. UV-curable materials have been widely studied and rapidly adopted across various industries due to their numerous advantages, including fast curing speed, environmental friendliness, low energy consumption, and solvent-free evaporation. However, UV-curable adhesives also have their limitations. Conventional UV-curable adhesives have significant limitations in applications requiring resistance to yellowing and small molecule migration, and UV curing can cause some damage to the solar cells. Silicone adhesives offer low bonding strength to solder ribbons; while epoxy adhesives have high adhesion to solder wires, they suffer from significant brittleness and yellowing issues. In OBB encapsulation applications, adhesives need excellent high-temperature yellowing resistance and low small molecule volatile content. The thermosetting encapsulation adhesive of this invention can solve the problems of conventional technologies. Summary of the Invention:

[0005] To address the problem of brittleness and yellowing in existing thermosetting epoxy adhesives, this invention provides an encapsulating adhesive for photovoltaic OBB technology and its preparation method, meeting the high reliability requirements of photovoltaic applications. The technical solution of this invention to solve the above-mentioned technical problems is as follows:

[0006] A thermosetting epoxy adhesive for bonding welding wires in gridless assemblies comprises the following components by mass fraction: 10-20 parts castor oil-based oxobutane, 30-70 parts alicyclic epoxy, 1-10 parts polyester polyol, 1-5 parts hydrogenated rosin resin, 0.6-3 parts thermal initiator, 0.5-1.5 parts coupling agent, 0.2-1.0 parts anti-aging agent, and 1-7 parts thixotropic agent.

[0007] The castor oil-structured oxabutane is synthesized by a substitution reaction between castor oil and 3-ethyl-3-bromomethyloxabutane under potassium hydroxide catalysis, resulting in a trifunctional derivative. When added as a diluent to a cationic epoxy polymerization system, it improves the hydrophobicity of the material, reduces the brittleness of the epoxy, and maintains its heat resistance.

[0008] The method for synthesizing castor oil-structured oxetane is as follows: First, 0.1 mol of castor oil is placed in a three-necked flask equipped with a reflux condenser and a thermometer. Then, 0.3 mol of 3-bromomethyl-3-ethyl-oxetane, 30 ml of toluene, and 0.2 mol of potassium hydroxide are added. The temperature is raised to 100°C, the rotation speed is set to 500 r / min, and the reaction is carried out for 10 h. The reaction solution is then washed three times with distilled water, and the solvent is removed by vacuum distillation to obtain the product. Its chemical reaction formula is as follows:

[0009]

[0010] The alicyclic epoxy resin is one or a mixture of two or more of the following: 3,4-epoxycyclohexylcarboxylic acid-3',4'-epoxycyclohexylmethyl ester, bis((3,4-epoxycyclohexyl)methyl)adipic acid ester, 3,4-epoxycyclohexylmethyl-3',4'-epoxycyclohexylcarboxylic acid ester and caprolactone (1:1).

[0011] The polyester polyols mentioned are mainly polycaprolactone polyols, polycarbonate polyols, and other ester polyols such as caprolactone-modified (meth)acrylates, with ternary polycaprolactone polyols showing particularly good results. Their structures are as follows:

[0012]

[0013] The hydrogenated rosin resin is required to be a rosin resin with a melting point of 85-130 degrees Celsius, such as one of Arakawa KE-604, KE-100, and KE-311.

[0014] The thixotropic agent can be either hydrophobic silica powder or hydrophilic silica. In this experiment, hydrophilic silica was selected, such as Wacker's T40, Evonik's A300, A380, etc.

[0015] The thermal initiator is selected as an amine-blocked hexafluoroantimonate with fast curing speed.

[0016] The coupling agent is selected from 2-(3,4-epoxycyclohexyl)ethyltrimethoxysilane or 2-(3,4-epoxycyclohexyl)ethyltriethoxysilane.

[0017] The anti-aging agent mentioned above must be resistant to both heat aging and light aging. Heat anti-aging agents include 1076, 1035, 1010, BHT, etc., and light anti-aging agents include UV326, UV328, UV123, etc. The present invention selects a compound anti-aging agent, that is, a compound of heat anti-aging agent and light anti-aging agent, with a compounding ratio of 4-8:1-4.

[0018] The thermosetting epoxy adhesive for bonding welding wires in gridless assemblies according to the present invention comprises: weighing 10-20 parts of castor oil-structured oxobutane, 30-70 parts of alicyclic epoxy, 1-10 parts of polyester polyol, 1-5 parts of hydrogenated rosin resin, 0.6-3 parts of thermal initiator, 0.5-1.5 parts of coupling agent, 0.2-1.0 parts of anti-aging agent, and 1-7 parts of thixotropic agent, and adding them sequentially into a mixer. First, stir for 30 minutes, then evacuate to a vacuum degree of -0.08 to -0.05 MPa, stir at 1000-1500 rpm for 0.5 to 2 hours until uniform, allow to air dry to room temperature, and then seal and package.

[0019] The beneficial effects of this invention are as follows: The thermosetting epoxy adhesive for bonding welding wires in gridless modules described in this invention utilizes a castor oil structural unit design to synthesize a novel castor oil-oxybutane. Its structural characteristics determine its excellent water resistance and flexibility, effectively addressing the brittleness issue of epoxy resins while ensuring epoxy strength. The alicyclic epoxy resin ensures rapid curing, heat resistance, and strength. The addition of polyester polyol and hydrogenated rosin enables effective bonding between the resin and the welding wire. The addition of a thixotropic agent ensures a certain adhesive height after printing, achieving the effect of coating the welding wire, especially guaranteeing its light transmittance and printing process characteristics. This experimental design avoids the addition of small molecules, ensuring no small molecule migration. Since the welding wire adhesive is exposed to light and heat, the introduction of a composite anti-aging agent effectively ensures that the photovoltaic adhesive will not yellow after 1500 hours of aging. Detailed Implementation

[0020] The principles and features of the present invention are described below. The examples given are only for explaining the present invention and are not intended to limit the scope of the present invention.

[0021] Example 1

[0022] Weigh out 15 parts of castor oil-based oxabutane, 65 parts of 3,4-epoxycyclohexylcarboxylic acid-3',4'-epoxycyclohexylmethyl ester, 5 parts of ternary polycaprolactone polyol with a molecular weight of 2000, 5 parts of Arakawa KE604 hydrogenated rosin resin, 0.8 parts of thermal initiator amine-blocked hexafluoroantimonate, 11 parts of coupling agent A186, 0.5 parts of aging resistant agent 1076:UV326 = 2:1, and 6 parts of thixotropic agent T40; add them sequentially into a mixer, stir for 30 minutes, then evacuate to a vacuum degree of -0.08 to -0.05 MPa, stir at 1000 to 1500 rpm for 0.5 to 2 hours until homogeneous, allow to air dry to room temperature, and then seal and package.

[0023] Example 2

[0024] Weigh out 10 parts of castor oil-structured oxabutane, 70 parts of bis((3,4-epoxycyclohexyl)methyl)adipate, 10 parts of ternary polycaprolactone polyol with a molecular weight of 2000, 5 parts of Arakawa KE100 hydrogenated rosin resin, 0.8 parts of thermal initiator, 1 part of coupling agent, 0.5 parts of anti-aging agent 1076:UV326 = 2:1, and 6 parts of thixotropic agent T40; add them sequentially into a mixer, stir for 30 minutes, then evacuate to a vacuum degree of -0.08 to -0.05 MPa, stir at 1000 to 1500 rpm for 0.5 to 2 hours until homogeneous, let it air dry to room temperature, and then seal and package.

[0025] Example 3

[0026] Weigh out 10 parts of castor oil-based oxobutane, 70 parts of 3,4-epoxycyclohexylcarboxylic acid-3',4'-epoxycyclohexylmethyl ester, 10 parts of ternary polycaprolactone polyol with a molecular weight of 500, 5 parts of Arakawa 604 hydrogenated rosin resin, 0.8 parts of thermal initiator, 1 part of coupling agent, 0.5 parts of anti-aging agent 1076:UV326 = 2:1, and 6 parts of thixotropic agent A300; add them sequentially into a mixer, stir for 30 minutes, then evacuate to a vacuum degree of -0.08 to -0.05 MPa, stir at 1000 to 1500 rpm for 0.5 to 2 hours until homogeneous, allow to air dry to room temperature, and then seal and package.

[0027] Comparative Example 1

[0028] Weigh out 15 parts of hydroxymethyl methacrylate, 65 parts of 3,4-epoxycyclohexylcarboxylic acid-3',4'-epoxycyclohexylmethyl ester, 5 parts of ternary polycaprolactone polyol with a molecular weight of 2000, 5 parts of Arakawa 604 hydrogenated rosin resin, 0.8 parts of thermal initiator amine-blocked hexafluoroantimonate, 11 parts of coupling agent A186, 0.5 parts of aging resistant agent 1076:UV326 = 2:1, and 6 parts of thixotropic agent 300; add them sequentially into a mixer, stir for 30 minutes, then evacuate to a vacuum degree of -0.08 to -0.05 MPa, stir at 1000 to 1500 rpm for 0.5 to 2 hours until uniform, let it air dry to room temperature, and then seal and package.

[0029] Comparative Example 2

[0030] Weigh out 10 parts of castor oil-based oxabutane, 70 parts of bis((3,4-epoxycyclohexyl)methyl)adipate, 10 parts of binary polycaprolactone polyol with a molecular weight of 2000, 5 parts of hydrogenated rosin resin, 0.8 parts of thermal initiator, 1 part of coupling agent, 0.5 parts of anti-aging agent 1076:UV326 = 2:1, and 6 parts of thixotropic agent T40; add them sequentially into a mixer, stir for 30 minutes, then evacuate to a vacuum degree of -0.08 to -0.05 MPa, stir at 1000 to 1500 rpm for 0.5 to 2 hours until homogeneous, let it air dry to room temperature, and then seal and package.

[0031] Comparative Example 3

[0032] Weigh out 10 parts of castor oil-based oxobutane, 70 parts of 3,4-epoxycyclohexylcarboxylic acid-3',4'-epoxycyclohexylmethyl ester, 10 parts of ternary polycaprolactone polyol with a molecular weight of 500, 5 parts of Arakawa 604 hydrogenated rosin resin, 0.8 parts of thermal initiator, 1 part of coupling agent, 0.5 parts of anti-aging agent 1076:UV326 = 2:1, and 6 parts of Evonik thixotropic agent R9746; add them sequentially into a mixer, stir for 30 minutes, then evacuate to a vacuum degree of -0.08 to -0.05 MPa, stir at 1000 to 1500 rpm for 0.5 to 2 hours until homogeneous, let it air dry to room temperature, and then seal and package.

[0033] Comparative Example 4

[0034] Weigh out 15 parts of castor oil-structured oxobutane, 65 parts of 3,4-epoxycyclohexylcarboxylic acid-3',4'-epoxycyclohexylmethyl ester, 5 parts of ternary polycaprolactone polyol with a molecular weight of 2000, 5 parts of Arakawa KE604 hydrogenated rosin resin, 0.8 parts of thermal initiator amine-blocked hexafluoroantimonate, 11 parts of coupling agent A186, and 6 parts of thixotropic agent T40; add them sequentially to a mixer, stir for 30 minutes, then evacuate to a vacuum degree of -0.08 to -0.05 MPa, stir at 1000 to 1500 rpm for 0.5 to 2 hours until homogeneous, allow to air dry to room temperature, and then seal and package. The performance of this photovoltaic OBB encapsulating adhesive is tested through the following experiments.

[0035] Table 1. Comparative test results of the cured adhesives in the examples and comparative examples.

[0036] Table 1 Performance Indicators

[0037]

[0038]

[0039] As can be seen from the above results, the welding wire adhesive for photovoltaic OBB modules of the present invention has the characteristics of good adhesion to welding ribbons, low molecular volatility, low water absorption, non-yellowing at high temperature, and good printability, which meets the welding ribbon adhesion performance requirements of photovoltaic module OBB technology.

[0040] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A thermosetting epoxy adhesive for photovoltaic OBB technology, characterized in that, The quality percentage group consists of castor oil structure oxetane 10-20 parts, alicyclic epoxy resin 30-70 parts, polyester polyol 1-10 parts, hydrogenated rosin resin 1-5 parts, thermal initiator 0.6-3 parts, coupling agent 0.5-1.5 parts, anti-aging agent 0.2-1.0 parts, thixotropic agent 1-7 parts; The castor oil structure oxetane structure is: ； The polyester polyol is a three-membered polycaprolactone polyol; The thixotropic agent is Wacker T40; the thermal initiator is amine-capped hexafluoroantimonate; The anti-aging agent is a mixture of thermal and light anti-aging agents in a ratio of 4-8:1-4.

2. A photovoltaic OBB technology thermosetting epoxy adhesive according to claim 1, characterized in that, The castor oil structure oxetane is a trifunctional derivative synthesized by substitution reaction of castor oil and 3-ethyl-3-bromomethyl oxetane under potassium hydroxide catalysis; its chemical reaction formula is as follows: 。 3. The thermosetting epoxy adhesive for photovoltaic OBB technology according to claim 1, characterized in that, The alicyclic epoxy resin is one or several of 3,4-epoxycyclohexyl methyl-3',4'-epoxycyclohexyl carboxylate, bis((3,4-epoxycyclohexyl) methyl) adipate, and a polymerization product of 3,4-epoxycyclohexyl methyl-3',4'-epoxycyclohexyl carboxylate and caprolactone in a ratio of 1:

1.

4. The thermosetting epoxy adhesive for photovoltaic OBB technology according to claim 1, characterized in that, The hydrogenated rosin resin is one of Arakawa KE-604, KE-100, and KE-311.

5. The thermosetting epoxy adhesive for photovoltaic OBB technology according to claim 1, characterized in that, The coupling agent is one of 2-(3,4-epoxycyclohexyl) ethyl trimethoxysilane or 2-(3,4-epoxycyclohexyl) ethyl triethoxysilane.

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