Thermoplastic elastomer polyurethane as well as preparation method and application thereof in photovoltaic packaging material

Abstract

The invention relates to the technical field of synthesis of photovoltaic module packaging high polymer materials, in particular to thermoplastic elastomer polyurethane, a preparation method of the thermoplastic elastomer polyurethane and application of the thermoplastic elastomer polyurethane in photovoltaic packaging materials, and a soft segment structure of the polyurethane material is composed of low-molecular-weight polycarbonate diol with the molecular weight of 1000-5000 and low-molecular-weight polyether diol with the molecular weight of 600-3000. The hard segment part is composed of diisocyanate and a micromolecular polyol chain extender, a solution method is used for two-step polymerization in the preparation process, the prepared thermoplastic polyurethane elastomer material has the advantages of low Young modulus, good optical permeability, hydrolysis resistance, ultraviolet aging resistance, high cohesiveness and the like, a crosslinking process is not needed, the processing temperature is low, and the thermoplastic polyurethane elastomer material is suitable for industrial production. The method is not only suitable for the packaging of silicon-based photovoltaic modules, but also suitable for the packaging of novel perovskite photovoltaic and organic photovoltaic modules.

Description

Technical Field

[0001] The invention relates to the technical field of photovoltaic module encapsulation polymer material synthesis, and in particular to a thermoplastic elastomer polyurethane and a preparation method thereof and application thereof in photovoltaic encapsulation materials. Background Art

[0002] The photovoltaic industry is a technology industry that uses the photovoltaic effect to directly convert light energy into electrical energy. It has the advantages of sufficiency, safety, extensiveness, and cleanliness. Since the output power of a single solar cell itself is low and insufficient to meet traditional electricity needs, solar cells need to be packaged into modules to increase their output capacity. Different types of photovoltaic modules are similar in overall architecture and can be more personalized according to the solar cells and installation environment. Generally speaking, photovoltaic encapsulation materials cover the upper and lower surfaces of the cell, combining the cell with photovoltaic glass or backplane. Although the encapsulation layer is inconspicuous compared to other core components such as the cell, the encapsulation material is an important protective layer that protects the cell from external damage and has good light transmittance. It is an indispensable core auxiliary material to ensure that the photovoltaic module has a service life of 25 years.

[0003] EVA materials, which currently account for more than half of the market share of photovoltaic packaging materials, have the characteristics of high transparency and strong adhesion, but their anti-aging, hydrolysis resistance and delamination performance are relatively insufficient. In addition, the EVA molecular chain contains a vinyl acetate structure, which produces acetic acid molecules during aging, oxidation, degradation, etc., causing damage to solar panels. Moreover, it needs to be cross-linked in the packaging process, and the processing temperature is relatively high, which is no longer the optimal solution for new solar cells and their packaging systems. Summary of the invention

[0004] In view of the deficiencies of the above-mentioned prior art, the object of the present invention is to provide a thermoplastic elastomer polyurethane and a preparation method thereof and application in photovoltaic packaging materials. The thermoplastic polyurethane elastomer material prepared by the present invention has the advantages of low Young's modulus, good optical transmittance, hydrolysis resistance, UV aging resistance and strong adhesion, and does not require a cross-linking process and has a low processing temperature. It is not only suitable for the packaging of silicon-based photovoltaic modules, but also suitable for the packaging of new perovskite photovoltaic and organic photovoltaic modules.

[0005] In order to solve the above technical problems, the present invention adopts the following technical solutions: A thermoplastic elastomer polyurethane, which is obtained by prepolymerization of the following raw materials, calculated by weight: 100 parts of polycarbonate diol with a number average molecular weight of 1000-5000, 8 parts to 15 parts of polyether diol with a number average molecular weight of 600-3000, 10 parts to 20 parts of polyisocyanate and 1 part to 8 parts of polyol, wherein the polycarbonate diol is an aliphatic polycarbonate diol.

[0006] The soft segment structure of the polyurethane material of the invention is composed of low molecular weight polycarbonate diol with a molecular weight of 1000-5000 and low molecular weight polyether diol with a molecular weight of 600-3000, and the hard segment part is composed of diisocyanate and small molecular weight polyol chain extender. Polycarbonate and polyether are used as flexible segments, and the material has a lower glass transition temperature and a larger glass transition range. The photovoltaic panel encapsulated by the material can also maintain good working performance in winter or in a relatively low temperature environment. The polyether structure is mainly used to increase the softness and reduce the brittleness of the polycarbonate, and is an auxiliary segment of the polycarbonate as the main segment. The aliphatic polycarbonate diol molecular segment has a high content of carbonate bonds, carbon oxygen ester bonds and carbon oxygen ether bonds and a high density. The polyurethane molecular structure synthesized by the polycarbonate contains newly formed carbamate bonds, and a large number of intramolecular and intermolecular hydrogen bonds can be formed between the molecular segments. These molecular structures enable the polyurethane material to have strong light transmittance, aging resistance, hydrolysis resistance and adhesion.

[0007] In a preferred embodiment of the present invention, the polycarbonate diol is a carbon dioxide-based polycarbonate diol obtained by copolymerization of carbon dioxide and propylene oxide. The carbon dioxide-based polycarbonate diol belongs to an aliphatic polycarbonate diol, and the structural formula of the polycarbonate diol is as follows: .

[0008] In a preferred embodiment of the present invention, the mass percentage of polycarbonate in the carbon dioxide-based polycarbonate diol is 95% to 99.9%.

[0009] In a preferred embodiment of the present invention, the polyether diol having a number average molecular weight of 600 to 3000 is polyethylene glycol, polypropylene glycol or polytetramethylene glycol, and the structural formulas of polyethylene glycol, polypropylene glycol and polytetramethylene glycol are as follows: .

[0010] In a preferred embodiment of the present invention, the polyisocyanate is 4,4′-diisocyanatodicyclohexylmethane, hexamethylene diisocyanate, 1,3,3-trimethyl-5-isocyanato-1-isocyanatomethylcyclohexane, 4,4′-methylenebis(phenylisocyanate) or triphenylmethane triisocyanate.

[0011] In a preferred embodiment of the present invention, the polyol is 1,3-propylene glycol, 1,4-butylene glycol, 1,6-hexanediol, glycerol or trimethylolpropane.

[0012] Another object of the present invention is to provide a method for preparing the thermoplastic elastomer polyurethane described in any one of the above, comprising the following steps: The following raw materials are weighed in parts by mass: 100 parts of polycarbonate diol with a number average molecular weight of 1000-5000, 8 parts to 15 parts of polyether diol with a number average molecular weight of 600-3000, 10 parts to 20 parts of polyisocyanate and 1 part to 8 parts of polyol.

[0013] A polycarbonate diol having a number average molecular weight of 1000 to 5000 and a polyether diol having a number average molecular weight of 600 to 3000 are dissolved in an organic solvent, and then washed and dried.

[0014] The treated polycarbonate diol with a number average molecular weight of 1000-5000 and the polyether diol with a number average molecular weight of 600-3000 are heated to 60°C-85°C under a nitrogen atmosphere, a solvent is added, and after stirring evenly, polyisocyanate and a catalyst are added to carry out a prepolymerization reaction, and then a polyol chain extender is added, and the reaction is maintained for 2 h-4 h.

[0015] After the reaction is completed, the reaction solution is precipitated and the product is dried to obtain a colorless and transparent thermoplastic elastomer polyurethane.

[0016] In a preferred embodiment of the present invention, the catalyst is dibutyltin dilaurate or stannous octoate.

[0017] In a preferred embodiment of the present invention, the prepolymerization time is 2 h to 4 h.

[0018] The third object of the present invention is to provide a use of the thermoplastic elastomer polyurethane described in any one of the above items in photovoltaic packaging materials.

[0019] Compared with the prior art, the present invention has the following beneficial effects: 1. The thermoplastic elastomer polyurethane of the present invention comprises, by weight, 100 parts of polycarbonate diol with a number average molecular weight of 1000-5000, 8 parts-15 parts of polyether diol with a number average molecular weight of 600-3000, 10 parts-20 parts of polyisocyanate and 1 part-8 parts of polyol. The soft segment structure of the polyurethane material is composed of low molecular weight polycarbonate diol with a molecular weight of 1000-5000 and low molecular weight polyether diol with a molecular weight of 600-3000, the hard segment is composed of polyisocyanate and small molecule polyol chain extender, polycarbonate and polyether are used as flexible segments, and has a lower glass transition temperature and a larger glass transition range. Photovoltaic panels encapsulated with the material can also maintain good working performance in winter or in a relatively low temperature environment; in the present invention, the polycarbonate diol is 100 parts and the polyether diol is 8 parts to 15 parts. The polyether structure is mainly used to increase the softness and reduce the brittleness of the polycarbonate. It is an auxiliary segment of the main segment of the polycarbonate. The aliphatic polycarbonate diol molecular segment has a high content of carbonate bonds, carbon-oxygen ester bonds and carbon-oxygen ether bonds and a high density. The polyurethane molecular structure synthesized in this way contains newly formed carbamate bonds, and a large number of intramolecular and intermolecular hydrogen bonds can be formed between the molecular segments. These molecular structures enable the polyurethane material to have strong light transmittance, aging resistance, hydrolysis resistance and adhesion.

[0020] 2. The material synthesized in the present invention is a thermoplastic elastomer material, which does not require heating and cross-linking during photovoltaic encapsulation, and the encapsulation process does not require high-temperature lamination above 100°C.

[0021] 3. Compared with other types of photovoltaic packaging materials, the polyurethane material of the present invention has a lower thermal decomposition temperature. During the photovoltaic panel recycling stage, the problem of silicon wafer recycling can be solved by heating it to about 250°C. DETAILED DESCRIPTION

[0022] The following is a detailed description of the preferred embodiments of the present invention, and the technical solutions in the embodiments of the present invention are clearly and completely described. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0023] It should be noted that all professional terms used in the present invention are only for the purpose of describing specific embodiments and are not intended to limit the scope of protection of the present invention. Unless otherwise specifically stated, various raw materials, reagents, instruments and equipment used in the following embodiments of the present invention can be purchased from the market or prepared by existing methods.

[0024] Example 1 A method for preparing thermoplastic elastomer polyurethane comprises the following steps: (1) A carbon dioxide-based polycarbonate diol with a number average molecular weight of 2000 and a polyethylene glycol with a number average molecular weight of 2000 were dissolved in dichloromethane, washed with deionized water for more than 3 times, and placed in a forced air drying oven at 60°C for 24 h and a vacuum drying oven at 80°C for 24 h for drying, and the water content of the low molecular weight diol after the treatment was controlled to be below 100 ppm.

[0025] (2) 10 g of carbon dioxide-based polycarbonate diol and 1 g of polyethylene glycol were placed in a three-necked flask, and the temperature was raised to 60 °C under nitrogen protection. The solvent dimethylformamide was added, and after stirring evenly, 1.59 g of hexamethylene diisocyanate and 3.0 mg of dibutyltin dilaurate as a catalyst were added. The reaction was carried out for 2 h for prepolymerization. During the reaction, samples were taken for NCO titration to determine the end of prepolymerization. Subsequently, 0.35 g of 1,4-butanediol was added to the reaction system as a chain extender, and the reaction was maintained for 2 h.

[0026] (3) After the reaction is completed, the reaction solution is precipitated in ethanol, and the flocculent white product is taken out, placed in a mold, and transferred to an 80°C oven for drying. After cooling, a colorless and transparent elastomeric polyurethane is obtained, which is recorded as TPU-1.

[0027] Example 2 A method for preparing thermoplastic elastomer polyurethane comprises the following steps: (1) A carbon dioxide-based polycarbonate diol with a number average molecular weight of 2000 and a polyethylene glycol with a number average molecular weight of 1000 were dissolved in dichloromethane, washed with deionized water for more than 3 times, and placed in a forced air drying oven at 60°C for 24 h or a vacuum drying oven at 80°C for 24 h for drying, and the water content of the low molecular weight diol after treatment was controlled to be below 100 ppm.

[0028] (2) 10 g of carbon dioxide-based polycarbonate diol and 1 g of polyethylene glycol were placed in a three-necked flask, and the temperature was raised to 60 °C under nitrogen protection. The solvent dimethylformamide was added, and after stirring evenly, 1.84 g of 4,4′-diisocyanate dicyclohexylmethane and 3.0 mg of catalyst dibutyltin dilaurate were added. The prepolymerization process was carried out for 2 h. During the reaction, samples were taken for NCO titration to determine the end of the prepolymerization. Subsequently, 0.10 g of propylene glycol was added to the reaction system as a chain extender, and the reaction was maintained for 2 h.

[0029] (3) After the reaction is completed, the reaction solution is precipitated in ethanol, and the flocculent white product is taken out, placed in a mold, and transferred to an 80°C oven for drying. After cooling, a colorless and transparent elastomeric polyurethane is obtained, which is recorded as TPU-2.

[0030] Example 3 A method for preparing thermoplastic elastomer polyurethane comprises the following steps: (1) A carbon dioxide-based polycarbonate diol with a number average molecular weight of 3000 and a polyethylene glycol with a number average molecular weight of 2000 were dissolved in dichloromethane, washed with deionized water for more than 3 times, and placed in a forced air drying oven at 60°C for 24 h and a vacuum drying oven at 80°C for 24 h for drying, and the water content of the low molecular weight diol after treatment was controlled to be below 100 ppm.

[0031] (2) 10 g of carbon dioxide-based polycarbonate diol and 1 g of polyethylene glycol were placed in a three-necked flask, and the temperature was raised to 60 °C under nitrogen protection. The solvent dimethylformamide was added, and after stirring evenly, 1.70 g of 4,4′-diisocyanate dicyclohexylmethane and 3.0 mg of catalyst dibutyltin dilaurate were added. The prepolymerization process was carried out for 2 h. During the reaction, samples were taken for NCO titration to determine the completion of the prepolymerization. Subsequently, 0.24 g of 1,4-butanediol was added to the reaction system as a chain extender, and the reaction was maintained for 2 h.

[0032] (3) After the reaction is completed, the reaction solution is precipitated in ethanol, and the flocculent white product is taken out, placed in a mold, and transferred to an 80°C oven for drying. After cooling, a colorless and transparent elastomeric polyurethane is obtained, which is recorded as TPU-3.

[0033] Example 4 A method for preparing thermoplastic elastomer polyurethane comprises the following steps: (1) A carbon dioxide-based polycarbonate diol with a number average molecular weight of 3000 and a polyethylene glycol with a number average molecular weight of 2000 were dissolved in dichloromethane, washed with deionized water for more than 3 times, and placed in a forced air drying oven at 60°C for 24 h and a vacuum drying oven at 80°C for 24 h for drying, and the water content of the low molecular weight diol after treatment was controlled to be below 100 ppm.

[0034] (2) 10 g of carbon dioxide-based polycarbonate diol and 1 g of polyethylene glycol were placed in a three-necked flask, and the temperature was raised to 60 °C under nitrogen protection. The solvent dimethylformamide was added, and after stirring evenly, 2.05 g of 4,4′-diisocyanate dicyclohexylmethane and 3.0 mg of catalyst dibutyltin dilaurate were added. The prepolymerization process was carried out for 2 h. During the reaction, samples were taken for NCO titration to determine the completion of the prepolymerization. Subsequently, 0.36 g of 1,4-butanediol was added to the reaction system as a chain extender, and the reaction was maintained for 2 h.

[0035] (3) After the reaction is completed, the reaction solution is precipitated in ethanol, and the flocculent white product is taken out, placed in a mold, and transferred to an 80°C oven for drying. After cooling, a colorless and transparent elastomeric polyurethane is obtained, which is recorded as TPU-4.

[0036] Example 5 A method for preparing thermoplastic elastomer polyurethane comprises the following steps: (1) A carbon dioxide-based polycarbonate diol with a number average molecular weight of 1000 and a polyethylene glycol with a number average molecular weight of 600 were dissolved in dichloromethane, washed with deionized water for more than 3 times, and placed in a forced air drying oven at 60°C for 24 h or a vacuum drying oven at 80°C for 24 h for drying, and the water content of the low molecular weight diol after treatment was controlled to be below 100 ppm.

[0037] (2) 10 g of carbon dioxide-based polycarbonate diol and 0.8 g of polyethylene glycol were placed in a three-necked flask, and the temperature was raised to 80 °C under nitrogen protection. The solvent dimethylformamide was added, and after stirring evenly, 1 g of 4,4′-diisocyanate dicyclohexylmethane and 3.0 mg of catalyst dibutyltin dilaurate were added. The prepolymerization process was carried out for 2 h. During the reaction, samples were taken for NCO titration to determine the end of the prepolymerization. Subsequently, 0.10 g of propylene glycol was added to the reaction system as a chain extender, and the reaction was maintained for 3 h.

[0038] (3) After the reaction is completed, the reaction solution is precipitated in ethanol, and the flocculent white product is taken out, placed in a mold, and transferred to an 80°C oven for drying. After cooling, a colorless and transparent elastomeric polyurethane is obtained.

[0039] Example 6 A method for preparing thermoplastic elastomer polyurethane comprises the following steps: (1) A carbon dioxide-based polycarbonate diol with a number average molecular weight of 5000 and a polyethylene glycol with a number average molecular weight of 3000 were dissolved in dichloromethane, washed with deionized water for more than 3 times, and placed in a forced air drying oven at 60°C for 24 h or a vacuum drying oven at 80°C for 24 h for drying. The water content of the low molecular weight diol after treatment was controlled to be below 100 ppm.

[0040] (2) 10 g of carbon dioxide-based polycarbonate diol and 1.5 g of polyethylene glycol were placed in a three-necked flask, and the temperature was raised to 85 °C under nitrogen protection. The solvent dimethylformamide was added, and after stirring evenly, 2 g of 4,4′-diisocyanate dicyclohexylmethane and 3.0 mg of catalyst dibutyltin dilaurate were added. The prepolymerization process was carried out for 2 h. During the reaction, samples were taken for NCO titration to determine the end of the prepolymerization. Subsequently, 0.80 g of propylene glycol was added to the reaction system as a chain extender, and the reaction was maintained for 4 h.

[0041] (3) After the reaction is completed, the reaction solution is precipitated in ethanol, and the flocculent white product is taken out, placed in a mold, and transferred to an 80°C oven for drying. After cooling, a colorless and transparent elastomeric polyurethane is obtained.

[0042] The properties of the elastomeric polyurethane materials prepared in Examples 1 to 4 are shown in Table 1.

[0043] Table 1 Properties of elastomeric polyurethane materials prepared in Examples 1 to 4 Comparative Example 1 Commercially purchased EVA raw material particles (VA content 32%, Mitsui Chemicals, Japan) were used for tableting and performance testing.

[0044] Some performance comparison results of Examples 1 to 4 and Comparative Example 1 are shown in Table 2.

[0045] Table 2 Comparison of some performances of Examples 1 to 4 and Comparative Example 1 As can be seen from the data in Tables 1 and 2, the polyurethane photovoltaic encapsulation material prepared by the present invention using carbon dioxide-based polycarbonate diol has a lower glass transition temperature, and shows similar and better light transmittance, mechanical properties, peel strength with glass, etc. compared with traditional EVA materials, and its shrinkage rate is significantly reduced. Due to the carbonate bond, carbon oxygen ester bond, carbon oxygen ether bond and carbamate bond in the molecular chain segment of the polyurethane material prepared by the present invention, a large number of hydrogen bonds are formed within and between molecules, showing excellent mechanical strength and performance. In addition, the polyurethane material prepared by the present invention has flexible hardness, molecular weight, glass transition temperature, strength and toughness controllability, can be customized according to the actual conditions such as the type of photovoltaic cell and the installation environment, and has diversified applications and development prospects.

[0046] It should be noted that when the present invention involves a numerical range, it should be understood that the two endpoints of each numerical range and any value between the two endpoints can be selected. Since the steps and methods used are the same as those in the embodiments, in order to avoid redundancy, the present invention describes a preferred embodiment. 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 know the basic creative concept. Therefore, the attached claims are intended to be interpreted as including the preferred embodiments and all changes and modifications that fall within the scope of the present invention.

[0047] Obviously, those skilled in the art can make various changes and modifications to the present invention without departing from the spirit and scope of the present invention. Thus, if these modifications and variations of the present invention fall within the scope of the claims of the present invention and their equivalents, the present invention is also intended to include these modifications and variations.

Claims

1. A thermoplastic elastomer polyurethane, characterized in that: The thermoplastic elastomer polyurethane is obtained by prepolymerization of the following raw materials, which include, by weight: 100 parts of polycarbonate diol with a number average molecular weight of 1000-5000, 8 parts to 15 parts of polyether diol with a number average molecular weight of 600-3000, 10 parts to 20 parts of polyisocyanate and 1 part to 8 parts of polyol; The polycarbonate diol is an aliphatic polycarbonate diol.

2. The thermoplastic elastomer polyurethane according to claim 1, characterized in that The aliphatic polycarbonate diol is a carbon dioxide-based polycarbonate diol.

3. The thermoplastic elastomer polyurethane according to claim 2, characterized in that The mass percentage of polycarbonate in the carbon dioxide-based polycarbonate diol is 95% to 99.9%.

4. The thermoplastic elastomer polyurethane according to claim 1, characterized in that The polyether diol with a number average molecular weight of 600 to 3000 is polyethylene glycol, polypropylene glycol or polytetramethylene glycol.

5. The thermoplastic elastomer polyurethane according to claim 1, characterized in that The polyisocyanate is 4,4′-diisocyanatodicyclohexylmethane, hexamethylene diisocyanate, 1,3,3-trimethyl-5-isocyanato-1-isocyanatomethylcyclohexane, 4,4′-methylenebis(phenylisocyanate) or triphenylmethane triisocyanate.

6. The thermoplastic elastomer polyurethane according to claim 1, characterized in that The polyol is 1,3-propylene glycol, 1,4-butylene glycol, 1,6-hexanediol, glycerol or trimethylolpropane.

7. A method for preparing the thermoplastic elastomer polyurethane according to any one of claims 1 to 6, characterized in that: The following steps are involved: Weigh the following raw materials in parts by mass: 100 parts of polycarbonate diol with a number average molecular weight of 1000-5000, 8 parts to 15 parts of polyether diol with a number average molecular weight of 600-3000, 10 parts to 20 parts of polyisocyanate and 1 part to 8 parts of polyol; Dissolving a polycarbonate diol having a number average molecular weight of 1000 to 5000 and a polyether diol having a number average molecular weight of 600 to 3000 in an organic solvent, and then washing and drying the mixture; The treated polycarbonate diol with a number average molecular weight of 1000-5000 and the polyether diol with a number average molecular weight of 600-3000 are heated to 60°C-85°C under a nitrogen atmosphere, a solvent is added, and after being stirred evenly, polyisocyanate and a catalyst are added to perform a prepolymerization reaction, and then a polyol chain extender is added, and the reaction is maintained for 2 h-4 h; After the reaction is completed, the reaction solution is precipitated and the product is dried to obtain a colorless and transparent thermoplastic elastomer polyurethane.

8. The method for preparing thermoplastic elastomer polyurethane according to claim 7, characterized in that: The catalyst is dibutyltin dilaurate or stannous octoate.

9. The method for preparing thermoplastic elastomer polyurethane according to claim 7, characterized in that: The prepolymerization time is 2 h~4 h.

10. Use of the thermoplastic elastomer polyurethane according to any one of claims 1 to 6 in photovoltaic encapsulation materials.

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