Hyperbranched aliphatic polycarbonate for photovoltaic module encapsulation film and preparation method thereof

Abstract

The present invention discloses a hyperbranched aliphatic polycarbonate for use in a photovoltaic module encapsulation film and a preparation method thereof. The soft segment is a carbon dioxide-based polycarbonate diol (polyol), and the hard segment is composed of a diisocyanate (polyisocyanate) and a small molecule diol chain extender through a one-step polymerization reaction. The polycarbonate diol (polyol) is obtained by the direct reaction of carbon dioxide, an epoxide, and a chain transfer agent in the presence of a non-metallic catalyst. The thermoplastic polycarbonate-type polyurethane adhesive obtained by the preparation method of the present invention can avoid yellowing during use while ensuring water resistance, good bonding properties, and mechanical strength. The excellent water vapor and oxygen barrier properties prevent corrosion from acidic molecules to increase the life of photovoltaic cells. Hyperbranched aliphatic polycarbonate (PPC‑T) can replace traditional EVA films for the encapsulation of photovoltaic cells, providing a new and practical film material for the field of photovoltaic module encapsulation.

Description

Technical Field

[0001] The present invention relates to the field of photovoltaic module packaging, and in particular to a hyperbranched aliphatic polycarbonate for photovoltaic module packaging film and a preparation method thereof. Background Art

[0002] Improving the efficiency of photovoltaic cells and using lower-cost materials are important factors in reducing the cost of solar energy. The quality of cell packaging directly affects the power generation efficiency and service life of photovoltaic modules, so the selection of film materials is crucial. In the existing technology, the order of laying packaging materials used in the packaging structure of crystalline silicon modules is as follows: Figure 1 As shown, from the light-receiving surface, the order is: glass / top film / cell / back film / backboard. Glass-EVA (ethylene-vinyl acetate copolymer) is generally used as the packaging material. Although this packaging mode can meet the basic requirements of solar photovoltaic cell packaging, it has many shortcomings: (1) EVA film has poor anti-aging performance and tends to turn yellow during use, which greatly reduces the service life and photoelectric conversion efficiency of solar photovoltaic cells. (2) When moisture enters the component, EVA decomposes with water to produce acetic acid, which reacts with alkali to produce sodium ions. Under the action of the external electric field, the sodium ions move to the surface of the cell and gather in the anti-reflection layer on the surface of the cell, resulting in a decrease in the power of the component. (3) After heating, the EVA material undergoes a chemical reaction and cross-links once, which can only be used once, which is not conducive to the rework process of photovoltaic components. (4) The light transmittance of the EVA material is relatively low, and it is difficult to absorb natural light near the ultraviolet wavelength.

[0003] In order to solve the above problems, Patent Publication No. 105542671 reported the addition of benzocrown ether derivatives to complex the harmful metal ions Na in photovoltaic modules. + , Ca 2+ However, the high toxicity of benzocrown ether derivatives is detrimental to the concept of green chemistry. Patent Publication No. 102676069 uses phenolic or phosphite antioxidants, hindered amine light stabilizers, and silane adhesion promoters to prepare aging-resistant and yellowing-resistant EVA films. However, the complex preparation process and difficulty in uniform mixing pose challenges to industrial production. Summary of the Invention

[0004] The present invention aims to overcome the shortcomings of traditional EVA films and provides a hyperbranched aliphatic polycarbonate (PPC-T) film that can be used as a photovoltaic module encapsulation film. The PPC-T film exhibits high light transmittance, yellowing resistance, UV aging resistance, hydrolysis resistance, high barrier properties to water vapor and oxygen, and high bond strength.

[0005] A hyperbranched aliphatic polycarbonate (PPC-T) for photovoltaic module encapsulation film is prepared by a one-step polymerization reaction using a carbon dioxide-based polycarbonate di(poly)ol as a soft segment and a di(poly)isocyanate and a small molecule diol chain extender as a hard segment.

[0006] Preferably, in the above-mentioned hyperbranched aliphatic polycarbonate, the carbon dioxide-based polycarbonate diol (polyol) includes oligopropylene carbonate diol (polyol), oligoethylene carbonate diol (polyol) or a mixture thereof, and its structure is as follows:

[0007]

[0008]

[0009] Preferably, in the above-mentioned hyperbranched aliphatic polycarbonate, the number average molecular weight of the carbon dioxide-based polycarbonate diol (polyol) is 600 to 6000 g / mol.

[0010] Preferably, in the above-mentioned hyperbranched aliphatic polycarbonate, the carbon dioxide-based polycarbonate diol (polyol) is synthesized by one-step polymerization of carbon dioxide, epoxide and a polyhydroxyl-containing chain transfer agent under the catalysis of a non-metallic catalyst; the molar feed ratio of epoxide and non-metallic catalyst is 200-800, and the molar feed ratio of epoxide and polyhydroxyl-containing chain transfer agent is 20-80; after the carbon dioxide is introduced into the reactor, the internal pressure range is 0.5-3.0 MPa, the reaction temperature is 40-70°C, and the reaction time is 12-36 hours.

[0011] Preferably, in the above-mentioned hyperbranched aliphatic polycarbonate, the epoxide is propylene oxide or ethylene oxide, and the non-metallic catalyst is a borane / organic amine two-component catalyst.

[0012] Preferably, in the above-mentioned hyperbranched aliphatic polycarbonate, the borane catalyst is triethylboron (TEB), triphenylboron (TPB), or tributylboron (TBB); the organic amine is triethylamine (TEA), N,N-diisopropylethylamine (DIPEA), N,N-dimethylcyclohexylamine (DMCHA), bis(triphenylphosphorano)ammonium chloride, tetra-n-butylammonium chloride, tetra-n-butylammonium bromide, or 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU).

[0013] Preferably, in the above-mentioned hyperbranched aliphatic polycarbonate, the polyhydroxy-containing chain transfer agent is ethylene glycol, diethylene glycol, triethylene glycol, propylene glycol, dipropylene glycol, tripropylene glycol, neopentyl glycol, 1,3-propylene glycol, 1,4-butanediol, 1,2-butanediol, 1,3-butanediol, 2,3-butanediol, 1,6-hexanediol, water, glycerol, trimethylolpropane, trimethylolethane, pentaerythritol, α-methyl glucoside, sorbitol, mannitol, hydroxymethyl glucoside, hydroxypropyl glucoside, sucrose, 1,4-cyclohexanediol, cyclohexanedimethanol, hydroquinone or resorcinol.

[0014] Preferably, in the above-mentioned hyperbranched aliphatic polycarbonate, the di(poly)isocyanate is isophorone diisocyanate (IPDI), 4,4'-dicyclohexylmethane diisocyanate (HMDI), hexamethylene diisocyanate (HDI), toluene diisocyanate (TDI), diphenylmethane diisocyanate (MDI), lysine diisocyanate (LDI), 1,4-butanediisocyanate (BDI) or triphenylmethane triisocyanate.

[0015] Preferably, in the above-mentioned hyperbranched aliphatic polycarbonate, the alcohol chain extender is 1,2-ethylene glycol, 1,4-butanediol, 1,6-hexanediol, 1,3-propylene glycol, 1,5-pentanediol, 1,4-cyclohexanedimethanol or diethylene glycol.

[0016] The preparation method of the hyperbranched aliphatic polycarbonate comprises the following steps:

[0017] A carbon dioxide-based polycarbonate diol (polyol) and an alcohol chain extender are added to a dried three-necked round-bottom flask and vacuum-dehydrated at 110-120°C for 2-3 hours. The flask is then cooled to 60-70°C under a nitrogen atmosphere. Isocyanate and a catalyst are then added, and the mixture is mechanically stirred and injected into a mold. The mold is closed and placed on a 160°C flat-plate vulcanizer for molding. The mold is then removed and cooled to obtain a colorless, transparent, and elastic hyperbranched aliphatic polycarbonate (PPC-T). The catalyst is tin isooctanoate, dibutyltin dilaurate, stannous octoate, stannous oleate, triethylenediamine, and bisdimethylaminoethyl ether.

[0018] Compared with the prior art, the present invention has the following beneficial effects:

[0019] (1) The present invention uses hyperbranched aliphatic polycarbonate (PPC-T) to replace traditional EVA as an encapsulation film. Hyperbranched aliphatic polycarbonate not only has excellent mechanical properties and wear resistance, but also has excellent water vapor and oxygen barrier properties, high light transmittance and aging resistance, as well as good glass and silicon wafer adhesion. It is the preferred material for high-efficiency and high-reliability photovoltaic module encapsulation film that can replace EVA. It can avoid yellowing during use. Due to its excellent water vapor and oxygen barrier properties, it can avoid corrosion by acidic molecules and thus increase the life of photovoltaic cells. It provides a new and practical thin film material for the field of photovoltaic module encapsulation to realize lightweight solar cells.

[0020] (2) The carbon dioxide-based polycarbonate diol (polyol) used in the present invention is obtained by a one-pot polymerization of epoxide, carbon dioxide and a chain transfer agent in the presence of a non-metallic catalyst. The preparation method is simple and safe, has low cost, and can avoid the residue of metal catalyst in the product.

[0021] (3) The carbon dioxide-based polycarbonate diol (polyol) used in the present invention has a high carbonate content (≥95%) and an easily controllable molecular weight (600 to 6000 g / mol). BRIEF DESCRIPTION OF THE DRAWINGS

[0022] The accompanying drawings are intended to further clearly illustrate and explain the technical solutions and embodiments of the present invention and do not constitute a limitation of the present invention. In the accompanying drawings:

[0023] Figure 1 Schematic diagram of the structure of a photovoltaic module.

[0024] Figure 2 These are the infrared spectra of the carbon dioxide-based polycarbonate diol synthesized in Example 3 and the hyperbranched aliphatic polycarbonate synthesized in Example 5. DETAILED DESCRIPTION

[0025] Example 1

[0026] In an anhydrous and oxygen-free environment, 50 g of propylene oxide, 39.8 μL of triethylamine, 2.3 ml of 1,4-butanediol, and 3.4 mL of triethylboron solution were sequentially added to an autoclave, filled with 1 MPa of carbon dioxide, and reacted in a 50°C oil bath for 24 h. After the reaction, the temperature was cooled to room temperature and the carbon dioxide pressure was released. The reaction was quenched with dilute hydrochloric acid solution, and then poured into deionized water with stirring to remove residual catalyst. The polymer solution was separated and vacuum-dried for molecular weight testing, nuclear magnetic resonance analysis, hydroxyl value titration, and thermal performance analysis. The specific data are listed in Table 1. The structure of the synthesized carbon dioxide-based polycarbonate diol is shown below.

[0027]

[0028] Example 2

[0029] In an anhydrous and oxygen-free environment, 50 g of propylene oxide, 39.8 μL of triethylamine, 2.5 mL of 1-3-propylene glycol, and 3.4 mL of triethylboron solution were sequentially added to an autoclave, filled with 1 MPa of carbon dioxide, and reacted in a 50°C oil bath for 36 h. After the reaction, the temperature was cooled to room temperature and the carbon dioxide pressure was released. The reaction was quenched with dilute hydrochloric acid solution, and then poured into deionized water with stirring to remove residual catalyst. The polymer solution was separated and vacuum-dried, and then subjected to molecular weight measurement, nuclear magnetic resonance analysis, hydroxyl value titration, and thermal performance analysis. The specific data are listed in Table 1. The structure of the synthesized carbon dioxide-based polycarbonate diol is shown below.

[0030]

[0031] Example 3

[0032] In an anhydrous and oxygen-free environment, 50g of ethylene oxide, 155mg of bis(triphenylphosphorane)ammonium chloride, 0.8mL of propylene glycol, and 0.8g of triphenylboron were added to a high-pressure reactor in sequence, filled with 2MPa of carbon dioxide, and reacted in a 50°C oil bath for 36h. After the reaction, the temperature was lowered to room temperature and the carbon dioxide pressure was released. The reaction was quenched with a dilute hydrochloric acid solution, and then poured into deionized water with stirring to remove the residual catalyst. The polymer solution was separated and vacuum dried for molecular weight test, nuclear magnetic resonance analysis, hydroxyl value titration and thermal performance analysis. The specific data are listed in Table 1. The structure of the synthesized carbon dioxide-based polycarbonate polyol is shown below, and the infrared spectrum is shown below. Figure 2 shown.

[0033]

[0034] Example 4

[0035] In an anhydrous and oxygen-free environment, 50 g of ethylene oxide, 32 mg of 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU), 3.0 g of pentaerythritol, and 3.4 mL of tributylboron solution were sequentially added to an autoclave, filled with 1.5 MPa of carbon dioxide, and reacted in a 50°C oil bath for 36 h. After the reaction, the temperature was cooled to room temperature and the carbon dioxide pressure was released. The reaction was quenched with dilute hydrochloric acid solution, and then poured into deionized water with stirring to remove residual catalyst. The polymer solution was separated and vacuum-dried for molecular weight measurement, nuclear magnetic resonance analysis, hydroxyl value titration, and thermal performance analysis. The specific data are listed in Table 1. The structure of the synthesized carbon dioxide-based polycarbonate diol is shown below.

[0036]

[0037] Table 1. Molecular weight, composition, and glass transition temperature of polycarbonate diols (polyols).

[0038]

[0039]

[0040] In Table 1, PPC% is the molar percentage of polycarbonate units obtained by copolymerization of epoxide and carbon dioxide; PPO% is the molar percentage of polyether units obtained by self-polymerization of epoxy monomer.

[0041] Example 5

[0042] 15g of the polycarbonate diol (polyol) synthesized in Example 1 and 0.95g of 1-4-butanediol were added to a three-necked round-bottom flask equipped with a nitrogen dehydration device, a mechanical stirrer, and a condenser, and vacuum dehydrated at 120°C for 2 hours. After the reaction, the substrate was cooled to 70°C under the protection of a nitrogen atmosphere, 5.6g of MDI and 6mg of dibutyltin dilaurate catalyst were slowly added, and after mechanical stirring for 5 minutes, the mixture was poured into a mold, the mold was closed, and the mixture was placed on a 160°C flat plate vulcanizer for molding for 30 minutes. The mold was then removed and cooled to obtain a colorless, transparent, elastic hyperbranched aliphatic polycarbonate (PPC-T 1) with a hard segment content of 30%. The infrared spectrum of the synthesized hyperbranched aliphatic polycarbonate is shown as follows: Figure 2 shown.

[0043] Example 6

[0044] 15 g of the polycarbonate diol (polyol) synthesized in Example 2 and 0.6 g of ethylene glycol were added to a three-necked round-bottom flask equipped with a nitrogen dehydration device, a mechanical stirrer, and a condenser, and the mixture was vacuum-dehydrated at 120° C. for 2 h. After the reaction, the substrate was cooled to 70° C. under a nitrogen atmosphere, 3.36 g of HMDI and 5 mg of stannous oleate catalyst were slowly added, and after mechanical stirring for 5 min, the mixture was poured into a mold. The mold was closed and pressed on a flat-plate vulcanizer at 160° C. for 30 min. The mold was then removed and cooled to obtain a colorless, transparent, elastic hyperbranched aliphatic polycarbonate (PPC-T 2) having a hard segment content of 21%.

[0045] Example 7

[0046] 15 g of the polycarbonate diol (polyol) synthesized in Example 3 and 0.6 g of 1,6-hexanediol were added to a 250 mL three-necked round-bottom flask equipped with a nitrogen dehydration device, a mechanical stirrer, and a condenser, and the mixture was vacuum-dehydrated at 120° C. for 2 h. After the reaction, the substrate was cooled to 70° C. under the protection of a nitrogen atmosphere, 6.1 g of HDI and 5 mg of tin isooctanoate catalyst were slowly added, and after mechanical stirring for 5 min, the mixture was poured into a mold. The mold was closed and placed on a flat vulcanizer at 160° C. for molding for 30 min. The mold was then removed and cooled, and the mold was opened to obtain a colorless, transparent, elastic hyperbranched aliphatic polycarbonate (PPC-T 3) having a hard segment content of 30%.

[0047] Example 8

[0048] 15 g of the polycarbonate diol (polyol) synthesized in Example 4 and 1.0 g of 1,5-pentanediol were added to a 250 mL three-necked round-bottom flask equipped with a nitrogen dehydration device, a mechanical stirrer, and a condenser, and the mixture was vacuum-dehydrated at 115° C. for 2 h. After the reaction substrate was cooled to 70° C. under the protection of a nitrogen atmosphere, 5.9 g of IPDI and 10 mg of triethylenediamine catalyst were slowly added, and after mechanical stirring for 5 min, the mixture was poured into a mold. The mold was closed and placed on a flat plate vulcanizer at 160° C. for molding for 30 min. The mold was then removed and cooled to obtain a colorless, transparent, elastic hyperbranched aliphatic polycarbonate (PPC-T 4) having a hard segment content of 31%.

[0049] Comparative Example 1

[0050] Commercial EVA films were tested and compared with the hyperbranched aliphatic polycarbonate of the present invention. The obtained data are listed in Table 2.

[0051] Table 2. Comparison of related properties of hyperbranched aliphatic polycarbonate PPC-T and EVA film

[0052]

[0053] The hyperbranched aliphatic polycarbonate prepared by the present invention exhibits excellent mechanical properties, UV aging resistance, high peel strength, and high light transmittance. It can replace traditional EVA films in photovoltaic modules, overcoming the generation of acidic molecules and extending the service life of photovoltaic cells. Different polycarbonate polyols can be adjusted according to actual needs, thereby expanding their application in the polyurethane field and showing considerable application prospects.

Claims

1. A hyperbranched aliphatic polycarbonate for photovoltaic module encapsulation film, characterized by a one-step polymerization reaction of a carbon dioxide-based polycarbonate polyol as a soft segment and a hard segment consisting of a diisocyanate or polyisocyanate and a small molecule diol chain extender; The carbon dioxide-based polycarbonate polyol includes oligopropylene carbonate polyol, oligoethylene carbonate polyol or a mixture thereof, and its structure is as follows: The number average molecular weight of the carbon dioxide-based polycarbonate polyol is 600 to 6000 g / mol.

2. The hyperbranched aliphatic polycarbonate according to claim 1, wherein The carbon dioxide-based polycarbonate polyol is synthesized by one-step polymerization of carbon dioxide, epoxide and a polyhydroxyl-containing chain transfer agent under the catalysis of a non-metallic catalyst; the molar feed ratio of the epoxide to the non-metallic catalyst is 200-800, and the molar feed ratio of the epoxide to the polyhydroxyl-containing chain transfer agent is 20-80; after the carbon dioxide is introduced into the reactor, the internal pressure ranges from 0.5 to 3.0 MPa, the reaction temperature is 40 to 70° C., and the reaction time is 12 to 36 hours.

3. The hyperbranched aliphatic polycarbonate according to claim 2, wherein The epoxide is propylene oxide or ethylene oxide, and the non-metallic catalyst is a borane / organic amine two-component catalyst.

4. The hyperbranched aliphatic polycarbonate according to claim 3, wherein The borane catalyst is triethylboron, triphenylboron, or tributylboron; and the organic amine is triethylamine, N,N-diisopropylethylamine, N,N-dimethylcyclohexylamine, bis(triphenylphosphoranyl)ammonium chloride, tetra-n-butylammonium chloride, tetra-n-butylammonium bromide, or 1,8-diazabicyclo[5.4.0]undec-7-ene.

5. The hyperbranched aliphatic polycarbonate according to claim 2, wherein The polyhydroxyl chain transfer agent is ethylene glycol, diethylene glycol, triethylene glycol, dipropylene glycol, tripropylene glycol, neopentyl glycol, 1,3-propylene glycol, 1,4-butanediol, 1,2-butanediol, 1,3-butanediol, 2,3-butanediol, 1,6-hexanediol, glycerol, trimethylolpropane, trimethylolethane, pentaerythritol, α-methyl glucoside, sorbitol, mannitol, hydroxymethyl glucoside, hydroxypropyl glucoside, sucrose, 1,4-cyclohexanediol, cyclohexanedimethanol, hydroquinone or resorcinol.

6. The hyperbranched aliphatic polycarbonate according to claim 1, wherein The diisocyanate or polyisocyanate is isophorone diisocyanate, 4,4'-dicyclohexylmethane diisocyanate, hexamethylene diisocyanate, toluene diisocyanate, diphenylmethane diisocyanate, lysine diisocyanate, 1,4-butanediisocyanate or triphenylmethane triisocyanate.

7. The hyperbranched aliphatic polycarbonate according to claim 1, wherein The small molecule diol chain extender is 1,4-butanediol, 1,6-hexanediol, 1,3-propylene glycol, 1,5-pentanediol, 1,4-cyclohexanedimethanol or diethylene glycol.

8. The method for preparing the hyperbranched aliphatic polycarbonate according to claim 1, characterized in that The steps include: A carbon dioxide-based polycarbonate polyol and a small molecule diol chain extender are added to a dried three-necked round-bottom flask and vacuum-dehydrated at 110-120°C for 2-3 hours. The flask is then cooled to 60-70°C under the protection of a nitrogen atmosphere. Subsequently, a diisocyanate or polyisocyanate and a catalyst are added. After mechanical stirring, the flask is injected into a mold. The mold is closed and placed on a 160°C flat-plate vulcanizer for molding. The mold is then removed and cooled to obtain a colorless, transparent, and elastic hyperbranched aliphatic polycarbonate. The catalyst is tin isooctanoate, dibutyltin dilaurate, stannous octoate, stannous oleate, triethylenediamine, and bisdimethylaminoethyl ether.

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