Polyester resin for photovoltaic backboard fluorocarbon coating as well as preparation method and application of polyester resin

Abstract

The invention belongs to the technical field of polyester resin preparation, and provides polyester resin for a photovoltaic backboard fluorocarbon coating as well as a preparation method and application of the polyester resin. The preparation method comprises the following steps: preparing and melting the quantitative component A and component B; the component A comprises quantitative 1, 2-cyclohexanedicarboxylic acid or anhydride thereof and other acids or anhydrides (at least one of maleic acid, maleic anhydride, succinic acid, fumaric acid and fumaric anhydride); the component B comprises quantitative 1, 6-hexanediol and other alcohols (which comprise quantitative neopentyl glycol and 2-ethyl-2-(hydroxymethyl)-1, 3-propanediol), and the component B comprises quantitative 1, 6-hexanediol and other alcohols (which comprise quantitative neopentyl glycol and 2-ethyl-2-(hydroxymethyl)-1, 3-propanediol); adding a catalyst, heating, and carrying out esterification reaction; and reducing the pressure, raising the temperature and carrying out polycondensation reaction to obtain the polyester resin. The polyester resin is added into the fluorocarbon coating for the photovoltaic back plate, so that the fluorocarbon coating has better anti-aging adhesion performance, anti-aging peel strength, anti-aging yellowing performance, acid and alkali resistance and solvent resistance.

Description

Technical Field

[0001] The invention relates to the technical field of polyester resin preparation, and in particular to a polyester resin for photovoltaic backplane fluorocarbon coating, and a preparation method and application thereof. Background Art

[0002] In recent years, with the improvement of environmental awareness and the increasing importance of renewable energy, solar photovoltaic power generation has received widespread attention and application. As we all know, solar photovoltaic modules are made of photovoltaic front panels, photovoltaic cells, encapsulation films, photovoltaic back panels and photovoltaic frames. Among them, the photovoltaic back panel is bonded to the back of the photovoltaic cell through the encapsulation film, and the photovoltaic back panel is connected to the connector to insulate and protect the photovoltaic cell. With the continuous improvement of the market's requirements for battery power generation efficiency, it has gradually become a trend to use photovoltaic back panels with excellent performance to improve the power generation efficiency of the back of photovoltaic cells. Fluorocarbon coatings are coatings with fluorocarbon resin as the main film-forming material, which are widely used in construction, chemical industry, aerospace industry, household products and other fields. Compared with silicone coatings, polyurethane coatings, etc., fluorocarbon coatings have excellent properties such as corrosion resistance, weather resistance, and stain resistance. Therefore, fluorocarbon coatings are widely used in photovoltaic back panels.

[0003] Fluorocarbon coatings used in photovoltaic backplanes disclosed in the prior art (such as CN116218296A, CN116333274A) are usually added with polyester resins. Although the proportion of polyester resins in fluorocarbon coatings for photovoltaic backplanes is not high, it plays a pivotal role in its adhesion, bonding and other properties. However, the aging-resistant bonding between the coating formed by the fluorocarbon coatings added with polyester resins disclosed in the prior art (such as CN116218296A, CN116333274A) and the photovoltaic backplane (such as PET photovoltaic backplane) and the encapsulation film (such as EVA film) is low; and the diluent of the solvent-based fluorocarbon coating will swell the plastic photovoltaic backplane substrate (such as PVC base film, TPU base film), resulting in poor aging-resistant adhesion between the coating and the photovoltaic backplane substrate, which will have an adverse effect on the comprehensive performance of the photovoltaic backplane. In addition, in order to further improve the comprehensive performance of photovoltaic backsheets, the aging and yellowing resistance, acid and alkali resistance, and solvent resistance of existing fluorocarbon coatings with added polyester resins need to be further improved. Therefore, it is necessary to prepare a high-performance polyester resin suitable for photovoltaic backsheet fluorocarbon coatings. Summary of the invention

[0004] The purpose of the present invention is to provide a polyester resin for photovoltaic backplane fluorocarbon coating and a preparation method and application thereof in view of the deficiencies in the prior art.

[0005] Based on this, the present invention discloses a method for preparing a polyester resin for photovoltaic backplane fluorocarbon coating, comprising the following steps: Step 1, melt the reaction raw materials prepared with component A and component B in a molar ratio of 0.8-1:1 until the solution is clear and transparent; Wherein, the component A comprises, by mole percentage, 80-90% mol of 1,2-cyclohexanedicarboxylic acid or its anhydride and 10-20% mol of other acids or anhydrides; the other acids or anhydrides comprise at least one of maleic acid, maleic anhydride, succinic acid, fumaric acid, and fumaric anhydride; Wherein, the B component, in terms of molar percentage, includes 60-70% mol of 1,6-hexanediol and 30-40% mol of other alcohols; the other alcohols include neopentyl glycol and 2-ethyl-2-(hydroxymethyl)-1,3-propanediol in a molar ratio of 3:1-2; Step 2, adding a catalyst to the solution of step 1, heating to 170-190° C. to carry out esterification reaction until the yield of byproduct water reaches more than 95%; Step 3: reduce the pressure of the reaction system in step 2 to minus 0.03-0.01 MPa, raise the temperature to 200-230° C. to carry out polycondensation reaction, and obtain the polyester resin for photovoltaic backplane fluorocarbon coating.

[0006] Preferably, in step 1, the reaction raw materials, measured by molar proportions, include: 0.30-0.33 parts of 1,2-cyclohexanedicarboxylic anhydride, 0.04-0.07 parts of maleic acid, 0.23-0.26 parts of 1,6-hexanediol, 0.09 parts of neopentyl glycol and 0.03-0.06 parts of 2-ethyl-2-(hydroxymethyl)-1,3-propanediol.

[0007] Further preferably, in step 1, the molar ratio of component A to component B is 0.37:0.38.

[0008] The polyester resin in the present invention is mainly used in fluorocarbon coatings for photovoltaic backsheets. The reaction principle of the polyester resin for fluorocarbon coatings for photovoltaic backsheets of the present invention is as follows:

[0009] During the experiment, it was found that compared with dibasic acids and diols with straight-chain structures, the polyester resin synthesized by reacting dibasic acids and diols containing benzene rings will give the resin rigidity and chemical resistance, greatly improving the hardness of the polyester resin; adding this polyester resin to fluorocarbon coatings for photovoltaic backplanes can significantly increase the adhesion of the fluorocarbon coatings to the photovoltaic backplanes; however, polyester resins containing benzene rings often have a larger dry heat yellowing, so cycloalkanes such as 1,2-cyclohexanedicarboxylic anhydride are used instead.

[0010] Among them, 1. By introducing 1,2-cyclohexanedicarboxylic anhydride, the ring structure is increased to give the polyester resin rigidity and chemical resistance, greatly improving the hardness of the polyester resin; moreover, 1,2-cyclohexanedicarboxylic anhydride as a saturated anhydride can effectively adjust the double bond density, improve the expansion rate of the polyester resin after curing, play a role of plasticization, reduce the number of unsaturated bonds in the polyester resin, and reduce aging and yellowing. 2. 1,6-hexanediol and neopentyl glycol are used as saturated diols to effectively reduce the double bond density of the polyester resin, improve the expansion rate of the polyester resin after curing, play a role of plasticization, and help reduce yellowing. 3. 2-ethyl-2-(hydroxymethyl)-1,3-propanediol is selected. Due to its structural asymmetry, non-crystalline polyester resin can be prepared. The remaining hydroxyl group after the reaction can increase the hydroxyl value of the polyester resin. It is used in fluorocarbon coatings for photovoltaic backplanes, which can effectively improve the aging resistance between fluorocarbon coatings and photovoltaic backplanes, and between fluorocarbon coatings and encapsulation films. 4. When synthesizing polyester resin for photovoltaic backplane fluorocarbon coating, maleic acid and fumaric acid are commonly used unsaturated acids, which can provide unsaturated double bonds. The introduction of unsaturated bonds can improve the adhesion with the packaging film.

[0011] Preferably, in step 1, the reaction raw materials are melted at 90-120°C for 0.5-1.5h (preferably 0.5-1.0h) in an inert atmosphere (such as a nitrogen atmosphere) to make the solution clear and transparent. The ester group, hydroxyl group, carboxyl group, double bond, hydrogenated aromatic ring and other groups in the polyester resin molecular chain can be thermally oxidized and degraded in an oxygen atmosphere, making the polyester resin yellow in color. Therefore, nitrogen or other inert gas protection is required during the synthesis process to prevent oxidation and discoloration.

[0012] Preferably, in step 2, the catalyst is at least one of tetrabutyl titanate, tetraisopropyl titanate, monobutyl tin oxide, dibutyl tin oxide, dibutyl tin dilaurate, dibutyl tin diacetate, dibutyl tin dichloride, ethylene glycol titanium, lithium acetate, potassium acetate, calcium acetate, magnesium acetate, barium acetate, and toluenesulfonic acid; The amount of the catalyst used is 0.1-0.3 wt % of the total mass of the A component and the B component.

[0013] Further preferably, the catalyst is tetrabutyl titanate, and the amount of the catalyst used is 0.2 wt % of the total mass of the A component and the B component.

[0014] Preferably, in step 2, the reaction temperature of the esterification reaction is 180-190°C, the reaction time is 1.0-3.0h (preferably 1.5-2.5h), until the yield of by-product water reaches more than 95%. In step 2, in order to ensure that the esterification reaction is basically completed, the yield of by-product water needs to reach more than 95%. The degree of esterification reaction is usually estimated by the percentage of collected by-product water to the theoretical amount of generated water in polyester synthesis.

[0015] Preferably, in step 3, the reaction temperature of the polycondensation reaction is 220-230°C, the reaction time is 2.0-3.0h (preferably 1.5-2.5h), until the acid value is less than or equal to 8mgKOH / g, the temperature is lowered, and propylene glycol methyl ether acetate is added to dilute to a solid content of 60-68% (preferably 65%) to obtain the polyester resin for photovoltaic backplane fluorocarbon coating.

[0016] The present invention also discloses a polyester resin for photovoltaic backplane fluorocarbon coating, which is prepared by the preparation method of the polyester resin for photovoltaic backplane fluorocarbon coating described above in the present invention; The polyester resin for photovoltaic backplane fluorocarbon coating is an unsaturated polyester resin, whose acid value is less than or equal to 8 mgKOH / g (preferably 5-8 mgKOH / g), whose hydroxyl value is 50-80 mgKOH / g (preferably 55-70 mgKOH / g), and whose weight average molecular weight is 5000-30000 (preferably 8600-9500).

[0017] The present invention also discloses an application of a polyester resin for photovoltaic backplane fluorocarbon coating, wherein the polyester resin for photovoltaic backplane fluorocarbon coating described in the present invention is added to the fluorocarbon coating for photovoltaic backplane; The fluorocarbon coating comprises a component C and a component D; in parts by weight, the component C comprises 0.5 to 30 parts of a curing agent, and the component D comprises 10 to 70 parts of a fluorocarbon resin, 0.1 to 10 parts of a polyester resin (a polyester resin for a photovoltaic backplane fluorocarbon coating as described above in the present invention), 0.5 to 25 parts of an acrylic oligomer with a molecular weight of 500 to 1500, 0.1 to 40 parts of an auxiliary agent, and 20 to 70 parts of a diluent.

[0018] Preferably, the curing agent is N3390 from Covestro; the fluorocarbon resin is GK570 from Daikin; the acrylic oligomer is 6145-100 from Changxing Chemical Co., Ltd. in Taiwan, China; the auxiliary agent includes an ultraviolet absorber and a leveling agent added in a ratio of 1:1, the ultraviolet absorber is preferably UV400 from BASF, and the leveling agent is preferably BYK333 from BYK Chemical; the diluent is preferably propylene glycol methyl ether acetate.

[0019] Compared with the prior art, the present invention has at least the following beneficial effects: In the process of preparing the polyester resin, the structure of the polyester resin is adjusted by adjusting the molar content of each reaction raw material. After adding the polyester resin to the fluorocarbon coating, it is helpful to improve the aging-resistant adhesion between the fluorocarbon coating and the photovoltaic backboard (such as the PET photovoltaic backboard), and between the fluorocarbon coating and the encapsulation film (such as the EVA film); at the same time, in the fluorocarbon coating, only a small amount of the polyester resin needs to be added to improve the aging-resistant adhesion between the fluorocarbon coating and the photovoltaic backboard, and can improve the aging-resistant yellowing performance, acid and alkali resistance and solvent resistance of the fluorocarbon coating for the photovoltaic backboard, and can reduce the production cost. The polyester resin can be applied to a variety of fluorocarbon coating formula systems for photovoltaic backboards, which helps to improve the comprehensive performance of the photovoltaic backboard. DETAILED DESCRIPTION

[0020] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, the present invention is further described in detail below in conjunction with specific implementation methods.

[0021] Example 1 A method for preparing a polyester resin for a photovoltaic backsheet fluorocarbon coating in this embodiment includes the following preparation steps: Step S1, adding the following reaction raw materials into a reaction system connected to a heating device, a stirring device, a water separation and condensation device, and a nitrogen protection device: 0.33 mol of 1,2-cyclohexanedicarboxylic anhydride, 0.04 mol of maleic acid, 0.26 mol of 1,6-hexanediol, 0.09 mol of neopentyl glycol and 0.03 mol of 2-ethyl-2-(hydroxymethyl)-1,3-propanediol.

[0022] Step S2: In a high-purity nitrogen atmosphere, the reaction system was heated to 90° C. to completely dissolve the reaction raw materials into a clear and transparent state, and the temperature was maintained for 0.5 h.

[0023] Step S3, adding 0.2% of tetrabutyl titanate based on the total mass of the reaction raw materials, slowly heating the reaction system to 190°C for esterification reaction, maintaining it at normal pressure for 2.0 hours, and the amount of byproduct water collected by the water separator accounts for 95% of the theoretical amount of water generated.

[0024] Step S4, vacuum the reaction system to reduce the pressure to -0.01MPa, gradually raise the temperature to 230°C and maintain for 2.0h for polycondensation reaction, and terminate the reaction when the acid value of the reaction system is not more than 8mgKOH / g; that is, when the temperature of the reaction system drops to 180°C, discharge the material, add propylene glycol methyl ether acetate to dilute to a solid content of 65%, and obtain the polyester resin for photovoltaic backplane fluorocarbon coating of this embodiment.

[0025] Example 2 A method for preparing a polyester resin for a photovoltaic backsheet fluorocarbon coating in this embodiment includes the following preparation steps: Step S1, adding the following reaction raw materials into a reaction system connected to a heating device, a stirring device, a water separation and condensation device, and a nitrogen protection device: 0.30 mol of 1,2-cyclohexanedicarboxylic anhydride, 0.07 mol of maleic acid, 0.26 mol of 1,6-hexanediol, 0.09 mol of neopentyl glycol and 0.03 mol of 2-ethyl-2-(hydroxymethyl)-1,3-propanediol.

[0026] The subsequent preparation steps of this embodiment are all referred to steps S2-S4 of Example 1 to obtain the polyester resin for photovoltaic backplane fluorocarbon coating of this embodiment.

[0027] Example 3 A method for preparing a polyester resin for a photovoltaic backsheet fluorocarbon coating in this embodiment includes the following preparation steps: Step S1, adding the following reaction raw materials into a reaction system connected to a heating device, a stirring device, a water separation and condensation device, and a nitrogen protection device: 0.33 mol of 1,2-cyclohexanedicarboxylic anhydride, 0.04 mol of maleic acid, 0.23 mol of 1,6-hexanediol, 0.09 mol of neopentyl glycol and 0.06 mol of 2-ethyl-2-(hydroxymethyl)-1,3-propanediol.

[0028] The subsequent preparation steps of this embodiment are all referred to steps S2-S4 of Example 1 to obtain the polyester resin for photovoltaic backplane fluorocarbon coating of this embodiment.

[0029] Comparative Example 1 The preparation method of a polyester resin for photovoltaic backplane fluorocarbon coating in this comparative example comprises the following preparation steps: Step S1, adding the following reaction raw materials into a reaction system connected to a heating device, a stirring device, a water separation and condensation device, and a nitrogen protection device: 0.23 mol of 1,2-cyclohexanedicarboxylic anhydride, 0.14 mol of maleic acid, 0.26 mol of 1,6-hexanediol, 0.09 mol of neopentyl glycol and 0.03 mol of 2-ethyl-2-(hydroxymethyl)-1,3-propanediol.

[0030] The subsequent preparation steps of this comparative example all refer to steps S2-S4 of Example 1 to obtain the polyester resin for photovoltaic backplane fluorocarbon coating of this comparative example.

[0031] Comparative Example 2 The preparation method of a polyester resin for photovoltaic backplane fluorocarbon coating in this comparative example comprises the following preparation steps: Step S1, adding the following reaction raw materials into a reaction system connected to a heating device, a stirring device, a water separation and condensation device, and a nitrogen protection device: 0.33 mol of 1,2-cyclohexanedicarboxylic anhydride, 0.04 mol of maleic acid, 0.20 mol of 1,6-hexanediol, 0.09 mol of neopentyl glycol and 0.09 mol of 2-ethyl-2-(hydroxymethyl)-1,3-propanediol.

[0032] The subsequent preparation steps of this comparative example all refer to steps S2-S4 of Example 1 to obtain the polyester resin for photovoltaic backplane fluorocarbon coating of this comparative example.

[0033] Comparative Example 3 The preparation method of a polyester resin for photovoltaic backplane fluorocarbon coating in this comparative example comprises the following preparation steps: Step S1, adding the following reaction raw materials into a reaction system connected to a heating device, a stirring device, a water separation and condensation device, and a nitrogen protection device: 0.37 mol of 1,2-cyclohexanedicarboxylic anhydride, 0.26 mol of 1,6-hexanediol, 0.09 mol of neopentyl glycol and 0.03 mol of 2-ethyl-2-(hydroxymethyl)-1,3-propanediol.

[0034] The subsequent preparation steps of this comparative example all refer to steps S2-S4 of Example 1 to obtain the polyester resin for photovoltaic backplane fluorocarbon coating of this comparative example.

[0035] Comparative Example 4 The preparation method of a polyester resin for photovoltaic backplane fluorocarbon coating in this comparative example comprises the following preparation steps: Step S1, adding the following reaction raw materials into a reaction system connected with a heating device, a stirring device, a water separation and condensation device, and a nitrogen protection device: 0.33 mol of 1,2-cyclohexanedicarboxylic anhydride, 0.04 mol of maleic acid, 0.29 mol of 1,6-hexanediol and 0.09 mol of neopentyl glycol.

[0036] The subsequent preparation steps of this comparative example all refer to steps S2-S4 of Example 1 to obtain the polyester resin for photovoltaic backplane fluorocarbon coating of this comparative example.

[0037] Performance Testing 1. The performance of the polyester resins for photovoltaic backsheet fluorocarbon coatings prepared in Examples 1 to 3 and Comparative Examples 1 to 4 was tested respectively. The test results are shown in Table 1 below.

[0038] Table 1

[0039] 2. To test the performance of the fluorocarbon coating for photovoltaic backplane added with polyester resin, the polyester resins of Examples 1 to 3 and Comparative Examples 1 to 4 were added to a fluorocarbon coating for photovoltaic backplane. The raw materials of the fluorocarbon coating are divided into component C and component D. By weight, component C is 10 parts of curing agent; component D is 40 parts of fluorocarbon resin, 8 parts of polyester resin, 10 parts of acrylic oligomer, 4 parts of auxiliary agent, and 28 parts of diluent. Among them, the curing agent is N3390 from Covestro; the fluorocarbon resin is GK570 from Daikin; the acrylic oligomer is 6145-100 from Changxing Company of Taiwan, China; the auxiliary agent includes an ultraviolet absorber and a leveling agent added in a ratio of 1:1, the ultraviolet absorber is UV400 from BASF, the leveling agent is BYK333 from BYK Chemical; the diluent is propylene glycol methyl ether acetate. The performance of the fluorocarbon coatings to which the polyester resins of Examples 1 to 3 and Comparative Examples 1 to 4 were added was tested, and the performance of the fluorocarbon coatings without the polyester resin added was tested. The test results are shown in Table 2 below (the thickness of the fluorocarbon coating used in the test in Table 2 is 8 microns).

[0040] The test method is as follows: (1) Adhesion: Referring to the standard GB / T 9286-2021, 10*10 small grids of 1 mm*1 mm were drawn on the surface of the sample to test the adhesion between the fluorocarbon coating added with polyester resin and the PET photovoltaic backsheet.

[0041] (2) Aging resistance (high-pressure accelerated aging test): Refer to standard JESD 22-A102-C, temperature 121°C, pressure 205KPa, humidity 100%, test time 48h, to test the aging resistance of fluorocarbon coatings.

[0042] (3) Interlayer peeling strength: Referring to the standard GB / T 2790-1995, the sample size is 200 mm long, 10 ± 1 mm wide, and the peeling speed is 100 mm / min. The peeling strength between the fluorocarbon coating added with polyester resin and the EVA film is tested.

[0043] (4) Solvent resistance (butanone resistance) of coating: refer to standard GB / T 17748-2016, sample size 100*430mm, wiping solvent is butanone, load 10N, wiping frequency 100 times / min, test the solvent resistance (butanone) of fluorocarbon coating with polyester resin added.

[0044] (5) Hydrochloric acid / alkali resistance: With reference to the standard GB / T 17748-2016, use 5% HCl (volume fraction) and 5% NaOH (mass fraction), liquid level 20 mm ± 2 mm, test time 24 h, and test the hydrochloric acid / alkali resistance of fluorocarbon coatings added with polyester resin.

[0045] Table 2

[0046] Combining Table 1-2, we can see that: (1) Compared with the fluorocarbon coating without polyester resin, the aging resistance adhesion performance between the fluorocarbon coating with polyester resin added in Examples 1-3 and the PET photovoltaic backsheet is significantly improved, and the peel strength between the fluorocarbon coating with polyester resin added in Examples 1-3 and the EVA film is also significantly improved. At the same time, the polyester resin in Examples 1-3 also makes the formed fluorocarbon coating have better hardness. The fluorocarbon coating of Examples 1-3 has better acid and alkali resistance, and the solvent resistance (butanone resistance) of the fluorocarbon coating of Examples 1-3 is also greatly improved.

[0047] (2) Compared with Example 1 (in the process of preparing the polyester resin in Example 1, the molar content of maleic acid is 0.04 mol and the molar content of 1,2-cyclohexanedicarboxylic anhydride is 0.33 mol), the aging resistance peel strength between the fluorocarbon coating and the EVA film added with the polyester resin of Comparative Example 3 (in the process of preparing the polyester resin in Comparative Example 3, maleic acid is not added and the molar content of 1,2-cyclohexanedicarboxylic anhydride is increased by 0.37 mol) is significantly reduced, and the solvent resistance is also significantly reduced.

[0048] Compared with Example 1, the aging-resistant peel strength between the fluorocarbon coating and the EVA film to which the polyester resin of Example 2 is added (in the process of preparing the polyester resin in Example 2, the molar content of maleic acid is increased to 0.07 mol, and the molar content of 1,2-cyclohexanedicarboxylic anhydride is reduced to 0.30 mol) is improved, but its aging-resistant yellowing performance and solvent resistance are poor.

[0049] Compared with Example 1, the aging-resistant peel strength between the fluorocarbon coating and the EVA film is further improved by adding the polyester resin of Comparative Example 1 (in the process of preparing the polyester resin in Comparative Example 1, the molar content of maleic acid is increased to 0.14 mol, and the molar content of 1,2-cyclohexanedicarboxylic anhydride is reduced to 0.23 mol). However, the aging-resistant peel strength between the fluorocarbon coating and the EVA film is not the greater the better. If the aging-resistant peel strength between the fluorocarbon coating and the EVA film is too large, it will have an adverse effect on the adhesion performance between the fluorocarbon coating and the PET photovoltaic backplane. Moreover, the aging-resistant yellowing performance and solvent resistance of the fluorocarbon coating of Comparative Example 1 are significantly deteriorated. Therefore, the fluorocarbon coating added with the polyester resin of Comparative Example 1 is difficult to extend the long-term outdoor life of the photovoltaic backplane, and is not suitable for application in photovoltaic backplanes.

[0050] Therefore, in order to ensure that the fluorocarbon coating for photovoltaic backplane has good aging-resistant peeling strength, aging-resistant yellowing performance and solvent resistance, in the process of preparing the polyester resin for photovoltaic backplane fluorocarbon coating, the molar content of maleic acid should not be too much or too little, and the molar ratio of maleic acid to 1,2-cyclohexanedicarboxylic anhydride should be moderate.

[0051] (3) Compared with Example 1 (in the process of preparing the polyester resin in Example 1, the molar content of 2-ethyl-2-(hydroxymethyl)-1,3-propanediol is 0.03 mol and the molar content of 1,6-hexanediol is 0.26 mol), the fluorocarbon coating to which the polyester resin of Comparative Example 4 is added (in the process of preparing the polyester resin in Comparative Example 4, 2-ethyl-2-(hydroxymethyl)-1,3-propanediol is not added and the molar content of 1,6-hexanediol is increased to 0.29 mol) has significantly decreased aging resistance adhesion performance, aging resistance peel strength, acid and alkali resistance and solvent resistance.

[0052] Compared with Example 1, the fluorocarbon coating added with the polyester resin of Example 3 (in the process of preparing the polyester resin in Example 3, the molar content of 2-ethyl-2-(hydroxymethyl)-1,3-propanediol is increased to 0.06 mol, and the molar content of 1,6-hexanediol is reduced to 0.23 mol) helps to improve the aging-resistant adhesion between the coating and the PET photovoltaic backplane; however, in the process of preparing the polyester resin, if the molar content of 2-ethyl-2-(hydroxymethyl)-1,3-propanediol is relatively high, it is easy to quickly polycondense and cross-link, which will lead to a decrease in the aging-resistant peel strength between the fluorocarbon coating added with the polyester resin and the EVA film.

[0053] Compared with Example 1, the polyester resin of Comparative Example 2 (in the process of preparing the polyester resin in Comparative Example 2, the molar content of 2-ethyl-2-(hydroxymethyl)-1,3-propanediol is increased to 0.09 mol, and the molar content of 1,6-hexanediol is reduced to 0.20 mol) has too high intrinsic viscosity and is prone to explosion; moreover, the fluorocarbon coating to which the polyester resin of Comparative Example 2 is added has poor aging resistance adhesion performance, aging resistance peel strength, acid and alkali resistance, and solvent resistance.

[0054] Therefore, when preparing polyester resin for photovoltaic backplane fluorocarbon coating, the molar content of 2-ethyl-2-(hydroxymethyl)-1,3-propanediol should not be too much or too little, and the molar ratio of 2-ethyl-2-(hydroxymethyl)-1,3-propanediol to 1,6-hexanediol should be moderate to avoid explosion and affect the aging resistance adhesion, aging resistance peel strength, acid and alkali resistance and solvent resistance of the fluorocarbon coating.

[0055] In summary, compared with comparative examples 1-4, in the process of preparing the polyester resin, Examples 1-3 adjust the structure of the polyester resin by adjusting the molar content of each reaction raw material in step S1, and make the prepared polyester resin cooperate with the effective components in the fluorocarbon coating, which is helpful to improve the cross-linking strength of the fluorocarbon coating system for photovoltaic backplanes, and further promote the fluorocarbon coating to be more firmly bonded to the surface of the PET photovoltaic backplane, so that the fluorocarbon coating added with the polyester resin of Examples 1-3 has better aging adhesion resistance, aging peel strength, aging yellowing resistance, acid and alkali resistance and solvent resistance, so that a fluorocarbon coating with good aging adhesion resistance, strong aging bonding resistance, high hardness, good thermal aging resistance, small aging yellowing resistance, good acid and alkali resistance and good solvent resistance can be obtained, which helps to improve the comprehensive performance of the photovoltaic backplane.

[0056] Although the preferred embodiments of the present invention have been described, those skilled in the art may make additional changes and modifications to these embodiments once they have learned the basic creative concept. Therefore, the appended claims are intended to be interpreted as including the preferred embodiments and all changes and modifications that fall within the scope of the embodiments of the present invention.

[0057] The technical solution provided by the present invention is introduced in detail above. Specific examples are used in this article to illustrate the principle and implementation mode of the present invention. The description of the above embodiments is only used to help understand the method of the present invention and its core idea. At the same time, for those skilled in the art, according to the idea of ​​the present invention, there will be changes in the specific implementation mode and application scope. In summary, the content of this specification should not be understood as limiting the present invention.

Claims

1. A method for preparing a polyester resin for photovoltaic backplane fluorocarbon coating, characterized in that: The steps include: Step 1, melt the reaction raw materials prepared with component A and component B in a molar ratio of 0.8-1:1 until the solution is clear and transparent; Wherein, the component A comprises, by mole percentage, 80-90% mol of 1,2-cyclohexanedicarboxylic acid or its anhydride and 10-20% mol of other acids or anhydrides; the other acids or anhydrides comprise at least one of maleic acid, maleic anhydride, succinic acid, fumaric acid, and fumaric anhydride; Wherein, the B component, in terms of molar percentage, includes 60-70% mol of 1,6-hexanediol and 30-40% mol of other alcohols; the other alcohols include neopentyl glycol and 2-ethyl-2-(hydroxymethyl)-1,3-propanediol in a molar ratio of 3:1-2; Step 2, adding a catalyst to the solution of step 1, heating to 170-190° C. to carry out esterification reaction until the yield of byproduct water reaches more than 95%; Step 3: reduce the pressure of the reaction system in step 2 to minus 0.03-0.01 MPa, raise the temperature to 200-230° C. to carry out polycondensation reaction, and obtain the polyester resin for photovoltaic backplane fluorocarbon coating.

2. The method for preparing a polyester resin for photovoltaic backsheet fluorocarbon coating according to claim 1, characterized in that: In step 1, the reaction raw materials, by mole, include: 0.30-0.33 parts of 1,2-cyclohexanedicarboxylic anhydride, 0.04-0.07 parts of maleic acid, 0.23-0.26 parts of 1,6-hexanediol, 0.09 parts of neopentyl glycol and 0.03-0.06 parts of 2-ethyl-2-(hydroxymethyl)-1,3-propanediol.

3. The method for preparing a polyester resin for photovoltaic backsheet fluorocarbon coating according to claim 2, characterized in that: In step 1, the molar ratio of component A to component B is 0.37:0.

38.

4. The method for preparing a polyester resin for photovoltaic backsheet fluorocarbon coating according to claim 1, characterized in that: In step 1, in an inert atmosphere, the reaction raw materials are melted at 90-120° C. for 0.5-1.5 h to make the solution clear and transparent.

5. The method for preparing a polyester resin for photovoltaic backsheet fluorocarbon coating according to claim 1, characterized in that: In step 2, the catalyst is at least one of tetrabutyl titanate, tetraisopropyl titanate, monobutyl tin oxide, dibutyl tin oxide, dibutyl tin dilaurate, dibutyl tin diacetate, dibutyl tin dichloride, ethylene glycol titanium, lithium acetate, potassium acetate, calcium acetate, magnesium acetate, barium acetate, and toluenesulfonic acid; The amount of the catalyst used is 0.1-0.3 wt % of the total mass of the A component and the B component.

6. The method for preparing a polyester resin for photovoltaic backsheet fluorocarbon coating according to claim 5, characterized in that: The catalyst is tetrabutyl titanate, and the amount of the catalyst used is 0.2 wt % of the total mass of the A component and the B component.

7. The method for preparing a polyester resin for photovoltaic backsheet fluorocarbon coating according to claim 1, characterized in that: In step 2, the reaction temperature of the esterification reaction is 180-190° C., and the reaction time is 1.0-3.0 h, until the yield of the by-product water reaches more than 95%.

8. The method for preparing a polyester resin for photovoltaic backsheet fluorocarbon coating according to claim 1, characterized in that: In step 3, the reaction temperature of the polycondensation reaction is 220-230° C., the reaction time is 2.0-3.0 h, until the acid value is less than or equal to 8 mgKOH / g, the temperature is lowered, and propylene glycol methyl ether acetate is added to dilute to a solid content of 60-68% to obtain the polyester resin for photovoltaic backplane fluorocarbon coating.

9. A polyester resin for photovoltaic backsheet fluorocarbon coating, characterized in that: It is prepared by the method for preparing a polyester resin for photovoltaic backsheet fluorocarbon coating according to any one of claims 1 to 8; The polyester resin for photovoltaic backplane fluorocarbon coating is an unsaturated polyester resin, the acid value of which is less than or equal to 8 mgKOH / g, the hydroxyl value of which is 50-80 mgKOH / g, and the weight average molecular weight of which is 5000-30000.

10. An application of polyester resin for photovoltaic backplane fluorocarbon coating, characterized in that: Adding the polyester resin for photovoltaic backsheet fluorocarbon coating according to claim 9 to the fluorocarbon coating for photovoltaic backsheet; The fluorocarbon coating comprises a component C and a component D; in parts by weight, the component C comprises 0.5 to 30 parts of a curing agent, and the component D comprises 10 to 70 parts of a fluorocarbon resin, 0.1 to 10 parts of a polyester resin, 0.5 to 25 parts of an acrylic oligomer with a molecular weight of 500 to 1500, 0.1 to 40 parts of an auxiliary agent, and 20 to 70 parts of a diluent.

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