Solar cell packaging adhesive film based on polycarbonate type polyurethane and preparation method of solar cell packaging adhesive film

Abstract

The invention discloses a solar cell packaging adhesive film based on polycarbonate type polyurethane and a preparation method of the solar cell packaging adhesive film. The polyurethane elastomer is prepared from the following components in percentage by mass: 50-75% of polycarbonate polyol, 0-20% of polyether polyol, 10-30% of diisocyanate, 1-4% of a chain extender and 0.1-0.3% of a catalyst. The polycarbonate type polyurethane adhesive film has high tensile strength, high elongation at break, high bonding strength and high light transmittance, shows excellent bonding performance, mechanical strength and optical performance, and can be used for packaging the solar cell on the premise of ensuring high photoelectric conversion efficiency of the solar cell. The adhesive film does not need to be crosslinked and can be directly applied to packaging of solar cells, compared with an EVA adhesive film, the packaging process time required by the adhesive film is greatly shortened, and the cost is reduced. The carbon dioxide is used as a raw material for synthesis, so that the environment is protected. The obtained adhesive film is resistant to hydrolysis and yellowing and long in service life. And the material can be completely degraded at a high temperature, thereby facilitating the recycling of solar cells.

Description

Technical Field

[0001] The invention belongs to the technical field of polyurethane materials, and in particular relates to a solar cell encapsulation adhesive film based on polycarbonate polyurethane and a preparation method thereof. Background Art

[0002] Solar cell modules are the core and most important part of solar power generation systems. They are products that convert solar energy into electrical energy. They include high-efficiency single-crystal / polycrystalline solar cells, low-iron ultra-white velvet tempered glass, encapsulation film, functional backplane, interconnection strips, bus bars, junction boxes and aluminum alloy frames. Figure 1 This is a schematic diagram of the basic structure of a common solar cell module.

[0003] For solar cell modules, encapsulation films play a very important role in overall impact resistance, optical properties, etc. Common encapsulation films include: polyvinyl butyral (PVB) film, ethylene-vinyl acetate copolymer (EVA) film, ionotropic interlayer (SGP), XIR interlayer and thermoplastic polyurethane elastomer (TPU) film, etc.

[0004] At present, EVA is the most widely used solar cell encapsulation film material. Although EVA film can meet the basic requirements of solar cell encapsulation, it still has many shortcomings: (1) In the actual use environment of solar cell modules, EVA film will turn yellow over time under the combined effects of light, heat and oxygen. This will further cause the light transmittance of the EVA film to decrease, resulting in a decrease in the photoelectric conversion efficiency of the solar cell module; (2) When water vapor enters the module, EVA decomposes into acetic acid when it meets water, and acetic acid reacts with alkali to produce sodium ions. Under the action of an external electric field, the sodium ions move to the surface of the battery and gather in the anti-reflection layer on the surface of the battery, resulting in a decrease in the power of the module; (3) EVA material undergoes cross-linking during the vacuum lamination process, so it cannot be recycled and reused, which increases costs; (4) The EVA cross-linking process takes a long time, which seriously affects the encapsulation efficiency of solar cells. Since EVA has many problems in the actual production and use process, finding an encapsulation film material that can replace EVA has become a research hotspot. CN112852311A discloses a method of grafting modification on SEBS resin to improve the adhesion of SEBS resin to glass, battery cells, and backplane materials. The obtained encapsulation film has a high refractive index, excellent light transmission and refractive properties, and can significantly improve the utilization rate of light by photovoltaic modules. However, SEBS materials have problems such as difficulty in grinding powder size and difficulty in plasticizing large particles during processing. CN115595072A discloses a method for preparing a high-strength anti-PID type EVA film by adding polar resin, a compatibilizing chelating agent, and a nucleating permeability enhancer to EVA. However, a large amount of time is still required for crosslinking during the vacuum lamination process, and the production efficiency is low. CN108102065A discloses a fiber-reinforced thermoplastic polyurethane for bulletproof glass, comprising the following components: 20-35 parts of aliphatic diisocyanate, 50-55 parts of polytetrahydrofuran ethylene oxide copolyether with an average molecular weight of 2000-4000, 6-12 parts of 1,4-butanediol, 5-15 parts of glass fiber modified by γ-aminopropyltriethoxysilane, and an appropriate amount of dibutyltin dilaurate. The TPU film is reinforced by glass fiber, but the overall mechanical properties and bonding properties of the material are still low, which makes it difficult to meet the needs of solar cell encapsulation film.

[0005] Therefore, developing an adhesive film material with excellent mechanical properties, optical properties and adhesive properties to meet the application requirements of encapsulation films in solar cell modules is an urgent problem to be solved in this field. Summary of the invention

[0006] In view of the deficiencies in the prior art, the object of the present invention is to provide a solar cell encapsulation film based on polycarbonate polyurethane and a preparation method thereof. The polyurethane film has excellent water resistance, oxygen barrier, adhesion, mechanical strength, flexibility, optical properties and yellowing resistance through the screening and compounding of components, especially the selection of diisocyanate types, and is particularly suitable for encapsulation film materials for solar cell modules.

[0007] To achieve this object, the present invention adopts the following technical solutions: A solar cell encapsulation adhesive film based on polycarbonate polyurethane is prepared from the following components in percentage by mass: 50-75% of polycarbonate polyol, 0-20% of polyether polyol, 10-30% of diisocyanate, 1-4% of chain extender and 0.1-0.3% of catalyst.

[0008] In the present invention, the polycarbonate polyol is 50-75%, for example, 50%, 52%, 56%, 58%, 60%, 62%, 66%, 70% or 72%, and specific values ​​between the above points. Due to space limitations and for the sake of simplicity, the present invention no longer exhaustively lists the specific points included in the range.

[0009] In the present invention, the polyether polyol is 1% to 20%, for example, 1%, 3%, 5%, 8%, 10%, 13%, 15% or 20%, as well as specific values ​​between the above values. Due to space limitations and for the sake of simplicity, the present invention no longer exhaustively lists the specific values ​​included in the range.

[0010] The diisocyanate is 10-25%, for example, it can be 10%, 13%, 15%, 17%, 19%, 21%, 23% or 25%, as well as specific point values ​​between the above point values. Due to space limitations and for the sake of simplicity, the present invention no longer exhaustively lists the specific point values ​​included in the range.

[0011] The chain extender is 1-4%, for example, 1%, 2%, 3%, or 4%, as well as specific values ​​between the above values. Due to space limitations and for the sake of simplicity, the present invention no longer exhaustively lists the specific values ​​included in the range.

[0012] The catalyst is 0.1-0.3%, for example, 0.10%, 0.15%, 0.20%, 0.25% or 0.30%, and specific values ​​between the above values. Due to space limitations and for simplicity, the present invention does not exhaustively list the specific values ​​included in the range. The catalyst is any one of dibutyltin dilaurate, di-n-octyltin dilaurate, stannous octoate or tin methyl mercaptan, or a combination of at least two thereof.

[0013] In the present invention, the “raw materials for preparation include by weight percentage” refers to the weight percentage of the polycarbonate polyol, polyether polyol, diisocyanate, chain extender and catalyst, excluding the solvent, based on the solid content of the raw materials for preparation being 100%.

[0014] In the present invention, through the reaction of specific contents of polycarbonate polyol, polyether polyol, diisocyanate, chain extender and catalyst, especially the selection of the type and content of polyol, the polycarbonate polyurethane film (PPC-T) has high tensile strength, high elongation at break, high bonding strength and high light transmittance, and exhibits excellent water resistance, oxygen barrier, bonding performance, mechanical strength, flexibility, optical properties and yellowing resistance, and can fully meet the performance requirements of the encapsulation film of solar cell modules.

[0015] Preferably, the polycarbonate polyol is synthesized by one-step polymerization of carbon dioxide, propylene oxide or ethylene oxide and a polyhydroxyl-containing chain transfer agent under the catalysis of a non-metallic catalyst. It includes oligomeric propylene carbonate di(poly)ols, oligomeric ethyl carbonate di(poly)ols and mixtures thereof. Its number average molecular weight is 1000 to 4000 g / mol. Its structure is as follows:

[0016] Preferably, the polyether polyol is any one of polyethylene glycol and polypropylene glycol or a combination of at least two thereof; the number average molecular weight of the polyether diol is 600-4000 g / mol.

[0017] Due to space limitations and for simplicity, the present invention no longer exhaustively lists the specific point values ​​included in the range, and more preferably 1500~2500 g / mol. In the present invention, the diisocyanate further includes any one of dicyclohexylmethane diisocyanate, toluene diisocyanate, hexamethylene diisocyanate, isophorone diisocyanate, and naphthalene diisocyanate, or a combination of at least two thereof.

[0018] Preferably, the chain extender is a diol chain extender, and the chain extender is selected from any one of propylene glycol, butanediol, pentanediol or hexanediol, or a combination of at least two thereof.

[0019] A method for preparing a solar cell encapsulation film based on polycarbonate polyurethane comprises the following steps: (1) Polycarbonate polyol, polyether polyol, diisocyanate and catalyst react to obtain a prepolymer; (2) the prepolymer obtained in step (1) is subjected to a chain extension reaction with a chain extender to obtain a polycarbonate polyurethane elastomer; (3) Casting the polycarbonate polyurethane elastomer obtained in step (2) into a film to obtain a solar cell encapsulation film based on polycarbonate polyurethane.

[0020] Preferably, the reaction temperature in step (1) is 60-90° C., and the reaction time is 2-4 h.

[0021] Preferably, the temperature of the chain extension reaction in step (2) is 70-90° C., and the time of the chain extension reaction is 1.5-3 h. The film-forming step in step (3) further includes a drying step, and the drying temperature is 60-80° C. The polyether polyol is a polyether polyol that has been treated with dehydration.

[0022] Preferably, the reaction in steps (1) and (2) is carried out in the presence of a solvent, and the solvent is N,N-dimethylformamide or N,N-dimethylacetamide.

[0023] Compared with the prior art, the present invention has the following beneficial effects: (1) Polycarbonate polyurethane film (PPC-T) has high tensile strength, high elongation at break, high bonding strength and high light transmittance, showing excellent bonding performance, mechanical strength and optical properties, and can encapsulate solar cells while ensuring their high photoelectric conversion efficiency.

[0024] (2) Polycarbonate polyurethane film (PPC-T) does not require cross-linking and can be directly used for solar cell encapsulation. Compared with the encapsulation process time required for EVA film, it greatly shortens the cost.

[0025] (3) The polycarbonate diol (polyol) used in the present invention is synthesized using carbon dioxide as a raw material, which is beneficial to environmental protection.

[0026] (4) The polycarbonate polyurethane film (PPC-T) prepared by the present invention is resistant to hydrolysis and yellowing, and has a long service life in outdoor use scenarios.

[0027] (5) The polycarbonate polyurethane film (PPC-T) prepared by the present invention can be completely degraded at high temperature, which is beneficial to the recycling and reuse of solar cells. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 A schematic diagram of the structure of a solar cell module. DETAILED DESCRIPTION Embodiment 1:

[0029] 45g of polycarbonate diol (structural formula shown in Formula 1 below) and 5g of polyethylene glycol were added to a three-necked flask equipped with a nitrogen dehydration device, a mechanical stirrer and a condenser, and vacuum dehydrated at 110°C for 3h. After completion, the temperature was lowered to 50°C under the protection of a nitrogen atmosphere, and 15.3g of dicyclohexylmethane-4,4'-diisocyanate and 3mg of stannous octoate catalyst were slowly added. After reacting for 3h, 1.3g of 1,4-butanediol was added. After reacting for 2h, the mixture was poured into a mold, the mold was closed and placed on a 140°C flat vulcanizer for molding for 10min, and then the mold was removed. After cooling, a colorless and transparent thermoplastic polycarbonate polyurethane elastomer (PPC-T 1) with a hard segment content of 25% was obtained. According to national standards GB / T 1865-1997, HG / T 3839-2006, GB / T 2790-1995 and IEC612152-2:2016, the light transmittance, tensile elongation at break, yellowing resistance, bonding strength and barrier properties of the thermoplastic polycarbonate polyurethane film are tested. Figure 1 The schematic diagram of the structure of the solar cell module is shown in Figure 2. Figure 1 It can be seen that the encapsulation film of the present invention is used in solar cell modules.

[0030]

[0031] Example 2 40g of polycarbonate diol (structural formula as shown in Formula 1) and 10g of polyethylene glycol were added to a three-necked flask equipped with a nitrogen dehydration device, a mechanical stirrer and a condenser, and vacuum dehydrated at 110°C for 3h. After the end, the temperature was lowered to 50°C under the protection of a nitrogen atmosphere, and 15.7g of diphenylmethane diisocyanate and 3mg of stannous octoate catalyst were slowly added. After reacting for 3h, 0.6g of 1,4-butanediol was added. After reacting for 2h, the mixture was poured into a mold, the mold was closed and placed on a 140°C flat vulcanizer for molding for 10min, and then the mold was removed. After cooling, a colorless and transparent thermoplastic polycarbonate polyurethane elastomer (PPC-T 2) with a hard segment content of 25% was obtained. According to national standards GB / T 1865-1997, HG / T 3839-2006, GB / T 2790-1995 and IEC 612152-2:2016, the light transmittance, tensile elongation at break, yellowing resistance, bonding strength and barrier properties of the thermoplastic polycarbonate polyurethane film were tested.

[0032] Example 3 40g of polycarbonate diol (structural formula as shown in Formula 1) and 10g of polypropylene glycol were added into a three-necked flask equipped with a nitrogen dehydration device, a mechanical stirrer and a condenser, and vacuum-dehydrated at 110°C for 3h. After completion, the temperature was lowered to 50°C under the protection of a nitrogen atmosphere, and 11.7g of dicyclohexylmethane-4,4'-diisocyanate and 3mg of stannous octoate catalyst were slowly added. After reacting for 3h, 0.8g of 1,4-butanediol was added. After reacting for 2h, the mixture was poured into a mold, the mold was closed and placed on a 140°C flat vulcanizer for molding for 10 min, and then the mold was removed. After cooling, a colorless and transparent thermoplastic polycarbonate polyurethane elastomer (PPC-T3) with a hard segment content of 20% was obtained. According to national standards GB / T 1865-1997, HG / T 3839-2006, GB / T 2790-1995 and IEC612152-2:2016, the light transmittance, tensile elongation at break, yellowing resistance, bonding strength and barrier properties of the thermoplastic polycarbonate polyurethane film are tested.

[0033] Example 4 35g of polycarbonate diol (structural formula shown in Formula 2 below) and 15g of polyethylene glycol were added to a three-necked flask equipped with a nitrogen dehydration device, a mechanical stirrer and a condenser, and vacuum dehydrated at 110°C for 3h. After the dehydration, the temperature was lowered to 50°C under the protection of a nitrogen atmosphere, and 17.4g of dicyclohexylmethane-4,4'-diisocyanate and 3mg of stannous octoate catalyst were slowly added. After reacting for 3h, 4.1g of 1,3-propylene glycol was added. After reacting for 2h, the mixture was poured into a mold, the mold was closed and placed on a 140°C flat vulcanizer for molding for 10min, and then the mold was removed. After cooling, a colorless and transparent thermoplastic polycarbonate polyurethane elastomer (PPC-T 4) with a hard segment content of 30% was obtained. According to national standards GB / T 1865-1997, HG / T 3839-2006, GB / T 2790-1995 and IEC 612152-2:2016, the light transmittance, tensile elongation at break, yellowing resistance, bonding strength and barrier properties of the thermoplastic polycarbonate polyurethane film were tested.

[0034]

[0035] Example 5 45g of polycarbonate diol (structural formula as shown in Formula 1) and 5g of polypropylene glycol were added into a three-necked flask equipped with a nitrogen dehydration device, a mechanical stirrer and a condenser, and vacuum-dehydrated at 110°C for 3h. After completion, the temperature was lowered to 50°C under the protection of a nitrogen atmosphere, and 15.3g of dicyclohexylmethane-4,4'-diisocyanate and 3mg of stannous octoate catalyst were slowly added. After reacting for 3h, 1.3g of 1,4-butanediol was added. After reacting for 2h, the mixture was poured into a mold, the mold was closed and placed on a 140°C flat vulcanizer for molding for 10 min, and then the mold was removed. After cooling, a colorless and transparent thermoplastic polycarbonate polyurethane elastomer (PPC-T5) with a hard segment content of 30% was obtained. According to national standards GB / T 1865-1997, HG / T 3839-2006, GB / T 2790-1995 and IEC612152-2:2016, the light transmittance, tensile elongation at break, yellowing resistance, bonding strength and barrier properties of the thermoplastic polycarbonate polyurethane film are tested.

[0036] Example 6 40g of polycarbonate diol (structural formula as shown in Formula 1) and 10g of polypropylene glycol were added to a three-necked flask equipped with a nitrogen dehydration device, a mechanical stirrer and a condenser, and vacuum dehydrated at 110°C for 3h. After the end, the temperature was lowered to 50°C under the protection of a nitrogen atmosphere, and 19.3g of dicyclohexylmethane-4,4'-diisocyanate and 3mg of dibutyltin dilaurate catalyst were slowly added. After reacting for 3h, 2.1g of 1,4-butanediol was added. After reacting for 2h, the mixture was poured into a mold, the mold was closed and placed on a 140°C flat vulcanizer for molding for 10 min, and then the mold was removed. After cooling, a colorless and transparent thermoplastic polycarbonate polyurethane elastomer (PPC-T 6) with a hard segment content of 30% was obtained. According to national standards GB / T 1865-1997, HG / T 3839-2006, GB / T 2790-1995 and IEC 612152-2:2016, the light transmittance, tensile elongation at break, yellowing resistance, bonding strength and barrier properties of the thermoplastic polycarbonate polyurethane film were tested.

[0037] Example 7 40g of polycarbonate diol (structural formula as shown in Formula 1), 5g of polyethylene glycol and 5g of polypropylene glycol were added to a three-necked flask equipped with a nitrogen dehydration device, a mechanical stirrer and a condenser, and vacuum dehydrated at 110°C for 3h. After the end, the temperature was lowered to 50°C under the protection of a nitrogen atmosphere, and 15.3g of dicyclohexylmethane-4,4'-diisocyanate and 3mg of stannous octoate catalyst were slowly added. After reacting for 3h, 1.3g of 1,4-butanediol was added. After reacting for 2h, the mixture was poured into a mold, the mold was closed and placed on a 140°C flat vulcanizer for molding for 10 min, and then the mold was removed. After cooling, a colorless and transparent thermoplastic polycarbonate polyurethane elastomer (PPC-T 7) with a hard segment content of 30% was obtained. According to national standards GB / T 1865-1997, HG / T 3839-2006, GB / T 2790-1995 and IEC 612152-2:2016, the light transmittance, tensile elongation at break, yellowing resistance, bonding strength and barrier properties of the thermoplastic polycarbonate polyurethane film were tested.

[0038] Example 8 35g of polycarbonate diol (the structural formula is shown in Formula 3 below) and 15g of polyethylene glycol were added to a three-necked flask equipped with a nitrogen dehydration device, a mechanical stirrer and a condenser, and vacuum dehydrated at 110°C for 3 hours. After the end, the temperature was lowered to 50°C under the protection of a nitrogen atmosphere, and 17.4g of dicyclohexylmethane-4,4'-diisocyanate and 3 mg of stannous octoate catalyst were slowly added. After reacting for 3 hours, 4.1g of 1,3-propylene glycol was added. After reacting for 2 hours, the mixture was poured into a mold, the mold was closed and placed on a 140°C flat vulcanizer for molding for 10 minutes, and then the mold was removed. After cooling, a colorless and transparent thermoplastic polycarbonate polyurethane elastomer (PPC-T 8) with a hard segment content of 30% was obtained. According to national standards GB / T 1865-1997, HG / T 3839-2006, GB / T 2790-1995 and IEC 612152-2:2016, the light transmittance, tensile elongation at break, yellowing resistance, bonding strength and barrier properties of the thermoplastic polycarbonate polyurethane film were tested.

[0039]

[0040] Comparative Example 1 The properties of the commercial EVA films were tested and compared with the thermoplastic polycarbonate PPC-T films prepared in Examples 1-6 of the present invention. The obtained data are listed in Table 1.

[0041]

[0042] As can be seen from Table 1, the yellowing resistance and bonding performance of the prepared thermoplastic polycarbonate polyurethane PPC-T film are better than those of commercial EVA film. The tensile strength of the thermoplastic polycarbonate polyurethane PPC-T film can reach up to 33MPa, and the elongation at break can reach more than 1000%, which is significantly improved compared with the traditional EVA film. The light transmittance of the thermoplastic polycarbonate polyurethane PPC-T film also meets the use requirements of solar cells.

Claims

1. A solar cell encapsulation film based on polycarbonate polyurethane, characterized in that The invention is prepared from the following components in percentage by mass: 50-75% of polycarbonate polyol, 0-20% of polyether polyol, 10-30% of diisocyanate, 1-4% of chain extender and 0.1-0.3% of catalyst.

2. The polycarbonate polyurethane-based solar cell encapsulation film according to claim 1, characterized in that: The polycarbonate polyol is synthesized by one-step polymerization of carbon dioxide, propylene oxide or ethylene oxide and a polyhydroxyl-containing chain transfer agent under the catalysis of a non-metallic catalyst, and has a number average molecular weight of 1000 to 4000 g / mol. Its structure is as follows: 。 3. The polycarbonate polyurethane-based solar cell encapsulation adhesive film according to claim 1, characterized in that: The diisocyanate is any one of dicyclohexylmethane diisocyanate, toluene diisocyanate, hexamethylene diisocyanate, isophorone diisocyanate, and naphthalene diisocyanate, or a combination of at least two of them.

4. The polycarbonate polyurethane-based solar cell encapsulation film according to claim 1, characterized in that: The polyether polyol is any one of polyethylene glycol and polypropylene glycol or a combination of at least two of them.

5. The polycarbonate polyurethane-based solar cell encapsulation adhesive film according to claim 1, characterized in that: The chain extender is any one of propylene glycol, butylene glycol, pentanediol or hexanediol, or a combination of at least two of them.

6. The polycarbonate polyurethane-based solar cell encapsulation adhesive film according to claim 1, characterized in that: The catalyst is any one of dibutyltin dilaurate, di-n-octyltin dilaurate, stannous octoate or tin methyl mercaptan, or a combination of at least two thereof.

7. A method for preparing a solar cell encapsulation film based on polycarbonate polyurethane according to any one of claims 1 to 6, characterized in that The steps include: (1) reacting polycarbonate polyol, polyether polyol, diisocyanate and a catalyst to obtain a prepolymer; (2) the prepolymer obtained in step (1) is subjected to a chain extension reaction with a chain extender to obtain a polycarbonate polyurethane elastomer; (3) Casting the polycarbonate polyurethane elastomer obtained in step (2) into a film to obtain a polycarbonate polyurethane-based solar cell encapsulation film.

8. The method for preparing a solar cell encapsulation film based on polycarbonate polyurethane according to claim 7, characterized in that: The reaction temperature of step (1) is 60-90° C., and the reaction time is 2-4 h.

9. The method for preparing a solar cell encapsulation film based on polycarbonate polyurethane according to claim 7, characterized in that: The temperature of the chain extension reaction in step (2) is 70-90° C., and the time of the chain extension reaction is 1.5-3 hours; the step (3) further comprises a drying step after the film-casting, and the drying temperature is 60-80° C.; the polyether polyol is a polyether polyol that has been treated with dehydration.

10. The method for preparing a solar cell encapsulation film based on polycarbonate polyurethane according to claim 7, characterized in that The reactions in steps (1) and (2) are carried out in the presence of a solvent, which is N,N-dimethylformamide or N,N-dimethylacetamide.

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