Preparation method of nano calcium carbonate for solar photovoltaic glue

Abstract

This invention discloses a method for preparing nano-calcium carbonate for solar photovoltaic adhesives. The steps include: adding sucrose to lime milk, cooling the lime milk to 6-10°C, and introducing a high-carbon dioxide concentration mixed gas to carry out a carbonation reaction, obtaining a calcium carbonate suspension #1; then adding hot water to dilute the suspension, introducing a low-carbon dioxide concentration mixed gas to carry out a carbonation reaction, and simultaneously adding lime milk to the suspension to carry out a calcium carbonate reaction, obtaining a calcium carbonate suspension #2; then adding sodium stearate for surface treatment, adding a soluble inorganic metal salt, and finally adding phosphoric acid triamine and phosphate ester for surface treatment respectively; dehydrating, drying, and pulverizing using a filter press to obtain nano-calcium carbonate. This invention uses a unique carbonation process to prepare nano-calcium carbonate with controllable particle size and more regular morphology, which can endow nano-calcium carbonate with superior mechanical properties; special surface treatment further improves the aging resistance of nano-calcium carbonate-filled photovoltaic adhesives.

Description

Technical Field

[0001] This invention relates to the field of calcium carbonate preparation technology, specifically a method for preparing nano-calcium carbonate for solar photovoltaic adhesives. Background Technology

[0002] Solar photovoltaic adhesive is an essential auxiliary material for solar photovoltaic modules. Its main function is to bond and seal the gaps in the frame of the photovoltaic module, the power junction box, and the photovoltaic glass, preventing air and moisture from entering and damaging the photovoltaic devices, maintaining the photoelectric conversion efficiency of the silicon cell wafers, and extending their service life. Since solar photovoltaic power generation devices must withstand harsh climatic environments such as sun and rain for extended periods during operation, the photovoltaic adhesive must possess not only excellent mechanical properties but also good aging resistance.

[0003] Nano-calcium carbonate is an essential raw material in photovoltaic adhesives, typically comprising more than 40% (by mass). It plays a crucial role in reinforcing the performance of photovoltaic adhesives. For nano-calcium carbonate, particle size, morphological regularity, and surface treatment formulation are key factors influencing its mechanical properties in photovoltaic adhesives. Currently, controlling crystal particle size and ensuring morphological regularity during the crystallization process of nano-calcium carbonate remains a critical technological challenge and a key differentiator in the technological advancement of various nano-calcium carbonate manufacturers. Surface treatment formulation not only affects the mechanical properties of nano-calcium carbonate-filled photovoltaic adhesives but also significantly impacts their aging resistance. Research indicates that the most common fatty acid-based nano-calcium carbonate treatment agents are the primary cause of decreased high-temperature and humid-heat resistance in photovoltaic adhesives. Therefore, selecting a suitable surface treatment agent is the best method to improve the aging resistance of nano-calcium carbonate.

[0004] Currently, under the global goal of carbon neutrality, the world is vigorously developing new energy sources, especially the photovoltaic industry, which is developing rapidly. With the development of the photovoltaic industry, the requirements for upstream products are constantly increasing, and this is also true for nano-calcium carbonate used in solar photovoltaic adhesives. However, some nano-calcium carbonate products on the market still have some shortcomings and cannot meet the higher requirements.

[0005] Patent CN 105778568 discloses a surface treatment method for nano-calcium carbonate specifically for photovoltaic adhesives. This invention uses a saponification of stearic acid and polyethylene stearate as the surface treatment agent. Although the introduction of polyethylene stearate modification can improve the resistance to damp heat aging of photovoltaic adhesives, the large amount of sodium stearate modification limits further improvement in damp heat resistance and fails to solve the problem of poor high-temperature resistance.

[0006] Patent CN 106700657 discloses a surface treatment method for nano-calcium carbonate used in high-temperature resistant silicone adhesives. This invention uses sodium fatty acid and polyfluoroalkylsiloxane as surface treatment agents. Although secondary dry modification with polyfluoroalkylsiloxane can significantly improve the high-temperature resistance of nano-calcium carbonate, a large portion of the sodium fatty acid modification remains. Due to the water solubility of sodium fatty acid, the humid heat resistance of calcium carbonate is severely reduced, making it unsuitable for photovoltaic adhesives.

[0007] Patent CN 116282115 discloses a method for preparing nano-calcium carbonate for photovoltaic sealants. This invention improves product stability through grinding calcium hydroxide, and then uses high-melting-point fatty acid salts, PEG-polydimethylsiloxane, and water-soluble silane coupling agents as surface treatment agents. Although the compounded treatment agents avoid the use of sodium fatty acid salts and can impart certain aging resistance to nano-calcium carbonate, the high-melting-point fatty acid salts mentioned in the invention exist as solids in the calcium carbonate suspension system due to their poor water solubility and high melting point, making it difficult to coat the calcium carbonate surface. This results in poor surface modification and fails to effectively utilize the reinforcing properties of nano-calcium carbonate.

[0008] In conclusion, it is necessary to develop a nano-calcium carbonate that can impart superior mechanical properties and better and more comprehensive resistance to damp heat and high-temperature aging to photovoltaic adhesives. Summary of the Invention

[0009] The purpose of this invention is to provide a method for preparing nano-calcium carbonate for solar photovoltaic adhesives that meets higher requirements. This invention employs a unique carbonation process to prepare nano-calcium carbonate with controllable particle size and more regular morphology, which imparts superior mechanical properties to the nano-calcium carbonate-filled photovoltaic adhesive. Furthermore, in-situ coating technology with stearic acid metal soap provides even better resistance to damp heat and high temperatures. Simultaneously, surface modification with phosphate esters and phosphoric acid triamine introduces phosphate and amine groups to delay the aging of the photovoltaic adhesive, further improving the aging resistance of the nano-calcium carbonate-filled photovoltaic adhesive.

[0010] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0011] A method for preparing nano-calcium carbonate for solar photovoltaic adhesive includes the following steps:

[0012] (1) Calcining limestone at 1000-1100℃ to obtain quick-burning lime, then digesting quick-burning lime with tap water to obtain lime milk, letting it stand, aging, removing waste residue through a 100-mesh sieve, adjusting the solid content of lime milk to 15-20%, and keeping it for later use.

[0013] (2) Place the lime milk from step (1) into a small carbonation reaction tower with a high stirring rate, add sucrose, cool the lime milk to 6-10°C, and introduce a mixed gas with a high carbon dioxide concentration to carry out the carbonation reaction. Use the conductivity of the reaction suspension to determine the carbonation endpoint. Stop the reaction when the conductivity drops to the lowest value to obtain calcium carbonate suspension #1.

[0014] (3) Transfer the No. 1 calcium carbonate suspension to a large carbonation reaction tower with high stirring speed and heat preservation function, add 3-6 times the mass of No. 1 calcium carbonate suspension with hot water to dilute the suspension, then heat the suspension to 85-95℃, and then introduce a mixed gas with low carbon dioxide concentration to carry out the carbonation reaction. At the same time, add 3-6 times the mass of lime milk in step (1) to the suspension. When the lime milk is added, stop the gas introduction immediately when the pH of the suspension is 7.5 after carbonation to terminate the carbonation reaction, and finally obtain No. 2 calcium carbonate suspension.

[0015] (4) Transfer the No. 2 calcium carbonate suspension to the treatment tank, ensuring that the temperature of the suspension is not lower than 60°C during the transfer process. First, add sodium stearate to the suspension and stir for surface treatment. After a delay of 1-3 minutes, add the corresponding mass of soluble inorganic metal salt to the suspension. Finally, add phosphoric acid triamine and phosphate ester respectively for stirring and surface treatment.

[0016] (5) The surface-treated calcium carbonate slurry is dehydrated by a filter press, dried, and pulverized to obtain nano-calcium carbonate finished powder.

[0017] As a preferred technical solution of the present invention: the amount of sucrose used in step (2) is 0.2~0.5% of the mass of lime milk.

[0018] As a preferred technical solution of the present invention: the volume concentration of carbon dioxide in the high carbon dioxide concentration mixed gas in step (2) is 85-95%.

[0019] As a preferred technical solution of the present invention: the volume concentration of carbon dioxide in the low carbon dioxide concentration mixed gas in step (3) is 7-15%.

[0020] As a preferred technical solution of the present invention: step (3) is to add an equal amount of lime milk to the suspension at regular intervals of 40-120 minutes.

[0021] As a preferred technical solution of the present invention: step (4) is to add an equal amount of sodium stearate (calcium carbonate dry weight) to the suspension at 10-20 min for 10-20 min and stir for surface treatment.

[0022] As a preferred technical solution of the present invention: step (4) is to add an equal amount of soluble inorganic metal salt to the suspension at 10-20 min time. The amount of metal salt added is calculated based on the complete reaction with sodium stearate to form the corresponding stearic acid metal soap.

[0023] As a preferred technical solution of the present invention, the metal salt is one or a combination of two of aluminum sulfate, barium chloride, lead nitrate, strontium chloride, cadmium sulfate, zinc sulfate and lithium chloride.

[0024] As a preferred embodiment of the present invention, the amounts of phosphoric acid triamine and phosphate ester added are 0.1-0.3% and 0.4-0.8% of the dry weight of calcium carbonate, respectively.

[0025] As a preferred technical solution of the present invention: the phosphate ester is one or a combination of hexadecyl phosphate ester and octadecyl phosphate ester; the phosphoric acid triamine is one or a combination of hexamethylphosphoric acid triamine and hexaethylphosphoric acid triamine.

[0026] Compared with the prior art, the advantages and beneficial effects of the present invention include:

[0027] 1. This invention uses a specific carbonation process to prepare small-particle-size nano-calcium carbonate seed crystals, and then grows calcium carbonate crystals at high temperature. This not only ensures that the crystal morphology of nano-calcium carbonate is regular and gives nano-calcium carbonate better mechanical properties when used to fill photovoltaic adhesives, but also allows the size of nano-calcium carbonate crystal particles to be freely controlled by the amount of lime milk added.

[0028] 2. This invention uses sodium stearate to react with metal salts to form metal stearate soap for in-situ modification. Compared with traditional sodium stearate modifiers, the high melting point of metal stearate soap can give nano-calcium carbonate-filled photovoltaic adhesives better high-temperature resistance. At the same time, the water insolubility of metal stearate soap reduces the migration of nano-calcium carbonate treatment agents in hydrothermal conditions, thereby improving the humid heat resistance of nano-calcium carbonate-filled photovoltaic adhesives.

[0029] 3. This invention uses hexadecyl / octadecyl phosphate as a surface modifier. Hexadecyl / octadecyl phosphate not only retains some of the characteristics of hexadecyl / octadecyl acid, but also has a stronger binding force between the phosphate group and calcium carbonate, and its surface adsorption force is stronger. The treatment agent is not easy to migrate in the adhesive system. In addition, the thermal stabilizing effect of the phosphate group and the synergistic effect with stearic acid metal soap are more conducive to improving the high temperature resistance and damp heat resistance of nano calcium carbonate filled photovoltaic adhesive.

[0030] 4. The present invention uses a small amount of phosphoric acid triamine as a compound surface modifier, which can improve the aging resistance of nano-calcium carbonate filled photovoltaic adhesive under sunlight irradiation. Attached Figure Description

[0031] Figure 1 This is a SEM image of nano-calcium carbonate from Example 1 of this invention;

[0032] Figure 2 This is a SEM image of the precipitated calcium carbonate of Comparative Example 1 described in this invention;

[0033] Figure 3 This is a SEM image of the comparative example 2 nanometer calcium carbonate described in this invention;

[0034] Figure 4 This is a SEM image of the comparative example 3-nanometer calcium carbonate described in this invention. Implementation

[0035] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention. Example

[0036] A method for preparing nano-calcium carbonate for solar photovoltaic adhesive includes the following steps:

[0037] (1) Take limestone with a size of 2-3cm and calcine it at 1000℃ for 400min to obtain quick-burned lime. Then mix the lime with tap water at a ratio of 1 / 3 and stir for 30min to prepare lime milk. Let the lime milk stand and age for 24h. After removing the waste residue through a 100-mesh sieve, add tap water to adjust the solid content of the lime milk to 15%.

[0038] (2) Take 2 kg of lime milk and put it into a 3 L high-stirring carbonization tower. Use a chiller to lower the temperature of the lime milk to 10 °C, then add 0.5% sucrose. Adjust the stirring speed of the carbonization tower to 1400 r / min, and start introducing a mixed gas with a carbon dioxide concentration of 95% to carry out the carbonation reaction. Control the flow rate of the mixed gas to 2 m³ / min. 3 / h, when the conductivity of the reaction system drops to the minimum value, the gas mixture is stopped to obtain calcium carbonate suspension No. 1;

[0039] (3) Transfer the No. 1 calcium carbonate suspension to a 25L high-stirring carbonation tower with a heat insulation jacket, then add 3 times the mass of the No. 1 calcium carbonate suspension with 90℃ tap water for dilution, then heat the suspension to 85℃, adjust the stirring speed of the carbonation tower to 1300r / min, start to introduce a mixed gas with a 7% carbon dioxide concentration, control the flow rate of the mixed gas to 2m3 / h, and at the same time add 12kg of lime milk to the suspension at 120min intervals to carry out the carbonation reaction. When the pH value of the reaction system is 7.5, stop introducing the mixed gas immediately to obtain the No. 2 calcium carbonate suspension.

[0040] (4) Transfer the No. 2 calcium carbonate suspension to the treatment tank and ensure that the temperature of the suspension is 65-70℃. First, add an equal amount of 3.0% sodium stearate (calcium carbonate dry basis mass) for 15 minutes and stir for surface treatment. After a 2-minute delay, add an equal amount of aluminum sulfate for in-situ coating for 15 minutes. After adding aluminum sulfate, add 0.2% hexamethylphosphoric acid triamine and 0.6% octadecyl phosphate respectively and stir for 10 minutes to continue surface treatment.

[0041] (5) The surface-treated slurry is dewatered by a plate and frame filter press, and then the pressed material is dried at 120°C and finally pulverized to obtain a specific surface area of ​​23.20 m². 2 / g of nano calcium carbonate. Example

[0042] A method for preparing nano-calcium carbonate for solar photovoltaic adhesive includes the following steps:

[0043] (1) Take limestone with a size of 2-3cm and calcine it at 1000℃ for 400min to obtain quick-burning lime. Then mix the lime with tap water at a ratio of 1 / 3 and stir for 30min to prepare lime milk. Let the lime milk stand and age for 24h. After removing the waste residue through a 100-mesh sieve, add tap water to adjust the solid content of the lime milk to 20%.

[0044] (2) Take 2 kg of lime milk and put it into a 3L high-stirring carbonization tower. Use a chiller to lower the temperature of the lime milk to 6℃, then add 0.2% sucrose, adjust the stirring speed of the carbonization tower to 1400 r / min, and start to introduce a mixed gas with a carbon dioxide concentration of 90% for carbonation reaction. Control the flow rate of the mixed gas to 2 m3 / h. When the conductivity of the reaction system drops to the minimum value, stop introducing the mixed gas to obtain 1# calcium carbonate suspension.

[0045] (3) Transfer the No. 1 calcium carbonate suspension to a 25L high-stirring carbonation tower with an insulation jacket, then add 6 times its mass (of the No. 1 calcium carbonate suspension) of 90℃ tap water for dilution. Next, heat the suspension to 95℃, adjust the stirring speed of the carbonation tower to 1300r / min, and start introducing a mixed gas with a 15% carbon dioxide concentration, controlling the flow rate of the mixed gas to 2m³ / min. 3 / h, and at the same time, 6kg of lime milk is added to the suspension at 40min intervals to carry out the carbonation reaction. When the pH value of the reaction system is 7.5, the mixed gas is stopped immediately to obtain calcium carbonate suspension No. 2.

[0046] (4) Transfer the No. 2 calcium carbonate suspension to the treatment tank and ensure that the temperature of the suspension is 65-70℃. First, add an equal amount of 2.5% sodium stearate (calcium carbonate dry basis mass) for 10 minutes and stir for surface treatment. After a delay of 2 minutes, add an equal amount of zinc sulfate / strontium chloride = 3 / 1 for in-situ coating for 10 minutes. After adding the inorganic salt, add 0.2% hexamethylphosphoric acid triamine and 0.6% octadecyl phosphate respectively and stir for 10 minutes to continue surface treatment.

[0047] (5) The surface-treated slurry is dewatered by a plate and frame filter press, and then the pressed material is dried at 120°C and finally crushed to obtain a specific surface area of ​​22.76 m². 2 / g of nano calcium carbonate. Example

[0048] A method for preparing nano-calcium carbonate for solar photovoltaic adhesive includes the following steps:

[0049] (1) Take limestone with a size of 2-3cm and calcine it at 1000℃ for 400min to obtain quick-burned lime. Then mix lime with tap water at a ratio of 1 / 3 and stir for 30min to prepare lime milk. Let the lime milk stand and age for 24h. After removing the waste residue through a 100-mesh sieve, add tap water to adjust the solid content of the lime milk to 18%.

[0050] (2) Take 2 kg of lime slurry and put it into a 3 L high-stirring carbonization tower. Use a chiller to lower the temperature of the lime slurry to 8 °C, then add 0.5% sucrose. Adjust the stirring speed of the carbonization tower to 1400 r / min, and start introducing a mixed gas with a carbon dioxide concentration of 85% to carry out the carbonation reaction. Control the flow rate of the mixed gas to 2 m³ / min. 3 / h, when the conductivity of the reaction system drops to the minimum value, the gas mixture is stopped to obtain calcium carbonate suspension No. 1;

[0051] (3) Transfer the No. 1 calcium carbonate suspension to a 25L high-stirring carbonation tower with an insulation jacket, then add 6 times its mass (of the No. 1 calcium carbonate suspension) of 90℃ tap water for dilution. Next, heat the suspension to 85℃, adjust the stirring speed of the carbonation tower to 1300r / min, and start introducing a mixed gas with a 10% carbon dioxide concentration, controlling the flow rate of the mixed gas to 2m³ / min. 3 / h, and at the same time, 6kg of lime milk is added to the suspension at 40min intervals to carry out the carbonation reaction. When the pH value of the reaction system is 7.5, the mixed gas is stopped immediately to obtain calcium carbonate suspension No. 2.

[0052] (4) Transfer the No. 2 calcium carbonate suspension to the treatment tank and ensure that the temperature of the suspension is 65-70℃. First, add an equal amount of 3.5% sodium stearate (calcium carbonate dry basis mass) for 20 minutes and stir for surface treatment. After a 2-minute delay, add an equal amount of barium chloride for in-situ coating for 20 minutes. After adding barium chloride, add 0.3% hexaethylphosphoric acid triamine and 0.8% hexadecyl phosphate respectively and stir for 10 minutes to continue surface treatment.

[0053] (5) The surface-treated slurry is dewatered by a plate and frame filter press, and then the pressed material is dried at 120°C and finally pulverized to obtain a specific surface area of ​​26.30 m². 2 / g of nano calcium carbonate. Example

[0054] A method for preparing nano-calcium carbonate for solar photovoltaic adhesive includes the following steps:

[0055] (1) Take limestone with a size of 2-3cm and calcine it at 1000℃ for 400min to obtain quick-burning lime. Then mix the lime with tap water at a ratio of 1 / 3 and stir for 30min to prepare lime milk. Let the lime milk stand and age for 24h. After removing the waste residue through a 100-mesh sieve, add tap water to adjust the solid content of the lime milk to 20%.

[0056] (2) Take 2 kg of lime milk and put it into a 3L high-stirring carbonization tower. Use a chiller to lower the temperature of the lime milk to 10℃, then add 0.5% sucrose. Adjust the stirring speed of the carbonization tower to 1400 r / min, and start to introduce a mixed gas with a carbon dioxide concentration of 95% for carbonation reaction. Control the flow rate of the mixed gas to 2 m3 / h. When the conductivity of the reaction system drops to the minimum value, stop introducing the mixed gas to obtain 1# calcium carbonate suspension.

[0057] (3) Transfer the No. 1 calcium carbonate suspension to a 25L high-stirring carbonation tower with a heat insulation jacket, then add 3 times the mass of the No. 1 calcium carbonate suspension with 90℃ tap water for dilution, then heat the suspension to 95℃, adjust the stirring speed of the carbonation tower to 1300r / min, start to introduce a mixed gas with a 7% carbon dioxide concentration, control the flow rate of the mixed gas to 2m3 / h, and at the same time add 12kg of lime milk to the suspension at 120min intervals to carry out the carbonation reaction. When the pH value of the reaction system is 7.5, stop introducing the mixed gas immediately to obtain the No. 2 calcium carbonate suspension.

[0058] (4) Transfer the No. 2 calcium carbonate suspension to the treatment tank and ensure that the temperature of the suspension is 65-70℃. First, add an equal amount of 2.5% sodium stearate (calcium carbonate dry basis mass) for 10 minutes and stir for surface treatment. After a delay of 2 minutes, add an equal amount of lead nitrate / lithium chloride = 3 / 1 for in-situ coating for 10 minutes. After adding the inorganic salt, add 0.1% hexamethylphosphoric acid triamine / hexaethylphosphoric acid triamine = 1 / 1 and 0.4% hexadecyl phosphate / octadecyl phosphate = 1 / 1 respectively and stir for 10 minutes to continue surface treatment.

[0059] (5) The surface-treated slurry is dewatered by a plate and frame filter press, and then the pressed material is dried at 120°C and finally pulverized to obtain a specific surface area of ​​16.76 m². 2 / g of nano calcium carbonate.

[0060] (1) Take limestone with a size of 2-3cm and calcine it at 1000℃ for 400min to obtain quick-burned lime. Then mix the lime with tap water at a ratio of 1 / 3 and stir for 30min to prepare lime milk. Let the lime milk stand and age for 24h. After removing the waste residue through a 100-mesh sieve, add tap water to adjust the solid content of the lime milk to 15%.

[0061] (2) Take 2 kg of lime milk and put it into a 3L high-stirring carbonization tower. Use a chiller to lower the temperature of the lime milk to 25℃, then add 0.5% sucrose, adjust the stirring speed of the carbonization tower to 1400 r / min, and start to introduce a mixed gas with a carbon dioxide concentration of 33% for carbonation reaction. Control the flow rate of the mixed gas to 2 m3 / h. When the conductivity of the reaction system drops to the minimum value, stop introducing the mixed gas to obtain 1# calcium carbonate suspension.

[0062] (3) Transfer the No. 1 calcium carbonate suspension to a 25L high-stirring carbonation tower with a heat insulation jacket, then add 3 times the mass of the No. 1 calcium carbonate suspension with 90℃ tap water for dilution, then heat the suspension to 85℃, adjust the stirring speed of the carbonation tower to 1300r / min, start to introduce a mixed gas with a 7% carbon dioxide concentration, control the flow rate of the mixed gas to 2m3 / h, and at the same time add 12kg of lime milk to the suspension at 120min intervals to carry out the carbonation reaction. When the pH value of the reaction system is 7.5, stop introducing the mixed gas immediately to obtain the No. 2 calcium carbonate suspension.

[0063] (4) Transfer the No. 2 calcium carbonate suspension to the treatment tank and ensure that the temperature of the suspension is 65-70℃. First, add an equal amount of 3.0% sodium stearate (calcium carbonate dry basis mass) for 15 minutes and stir for surface treatment. After a delay of 2 minutes, add an equal amount of aluminum sulfate for in-situ coating for 15 minutes. After adding the inorganic salt, add 0.2% hexamethylphosphoric acid triamine and 0.6% octadecyl phosphate respectively and stir for 10 minutes to continue surface treatment.

[0064] (5) The surface-treated slurry is dehydrated by a plate and frame filter press, and then the pressed material is dried at 120°C and finally crushed to obtain nano-calcium carbonate with a specific surface area of ​​4.32 m2 / g.

[0065] (1) Take limestone with a size of 2-3cm and calcine it at 1000℃ for 400min to obtain quick-burned lime. Then mix the lime with tap water at a ratio of 1 / 3 and stir for 30min to prepare lime milk. Let the lime milk stand and age for 24h. After removing the waste residue through a 100-mesh sieve, add tap water to adjust the solid content of the lime milk to 15%.

[0066] (2) Take 2 kg of lime milk and put it into a 3 L high-stirring carbonization tower. Use a chiller to lower the temperature of the lime milk to 10 °C, then add 0.5% sucrose. Adjust the stirring speed of the carbonization tower to 1400 r / min, and start introducing a mixed gas with a carbon dioxide concentration of 95% to carry out the carbonation reaction. Control the flow rate of the mixed gas to 2 m³ / min. 3 / h, when the conductivity of the reaction system drops to the minimum value, the gas mixture is stopped to obtain calcium carbonate suspension No. 1;

[0067] (3) Transfer the No. 1 calcium carbonate suspension to a 25L high-stirring carbonation tower with an insulation jacket, then add 3 times the mass of room temperature tap water for dilution. Adjust the stirring speed of the carbonation tower to 1300 r / min, and start introducing a mixed gas with a 7% carbon dioxide concentration, controlling the flow rate of the mixed gas to 2 m³ / min. 3 / h, and at the same time, 12kg of lime milk is added to the suspension at 120min intervals to carry out the carbonation reaction. When the pH value of the reaction system is 7.5, the mixed gas is stopped immediately to obtain calcium carbonate suspension No. 2.

[0068] (4) Transfer the No. 2 calcium carbonate suspension to the treatment tank and ensure that the temperature of the suspension is 65-70℃. First, add an equal amount of 3.0% sodium stearate (calcium carbonate dry basis mass) for 15 minutes and stir for surface treatment. After a delay of 2 minutes, add an equal amount of aluminum sulfate for in-situ coating for 15 minutes. After adding the inorganic salt, add 0.2% hexamethylphosphoric acid triamine and 0.6% octadecyl phosphate respectively and stir for 10 minutes to continue surface treatment.

[0069] (5) The surface-treated slurry is dewatered by a plate and frame filter press, and then the pressed material is dried at 120°C and finally crushed to obtain a specific surface area of ​​24.30 m². 2 / g of nano calcium carbonate.

[0070] (1) Take limestone with a size of 2-3cm and calcine it at 1000℃ for 400min to obtain quick-burned lime. Then mix the lime with tap water at a ratio of 1 / 3 and stir for 30min to prepare lime milk. Let the lime milk stand and age for 24h. After removing the waste residue through a 100-mesh sieve, add tap water to adjust the solid content of the lime milk to 10%.

[0071] (2) Take 20 kg of lime slurry and put it into a 25 L high-stirring carbonization tower. Use a chiller to lower the temperature of the lime slurry to 21 °C, then add 0.1% sucrose. Adjust the stirring speed of the carbonization tower to 1400 r / min, and start introducing a mixed gas with a carbon dioxide concentration of 33% to carry out the carbonation reaction. Control the flow rate of the mixed gas to 2 m³ / min. 3 / h, when the pH of the reaction system reaches 7.5, immediately stop the flow of mixed gas to obtain a calcium carbonate suspension;

[0072] (3) Transfer the calcium carbonate suspension to the treatment tank and ensure that the temperature of the suspension is 65-70℃. First, add an equal amount of 3.0% sodium stearate (calcium carbonate dry basis mass) for 15 minutes and stir for surface treatment. After a delay of 2 minutes, add an equal amount of aluminum sulfate for in-situ coating for 15 minutes. After adding the inorganic salt, add 0.2% hexamethylphosphoric acid triamine and 0.6% octadecyl phosphate respectively and stir for 10 minutes to continue surface treatment.

[0073] (4) The surface-treated slurry is dewatered by a plate and frame filter press, and then the pressed material is dried at 120°C and finally crushed to obtain a specific surface area of ​​22.40 m². 2 / g of nano calcium carbonate.

[0074] (1) Take limestone with a size of 2-3cm and calcine it at 1000℃ for 400min to obtain quick-burned lime. Then mix the lime with tap water at a ratio of 1 / 3 and stir for 30min to prepare lime milk. Let the lime milk stand and age for 24h. After removing the waste residue through a 100-mesh sieve, add tap water to adjust the solid content of the lime milk to 15%.

[0075] (2) Take 2 kg of lime milk and put it into a 3 L high-stirring carbonization tower. Use a chiller to lower the temperature of the lime milk to 10 °C, then add 0.5% sucrose. Adjust the stirring speed of the carbonization tower to 1400 r / min, and start introducing a mixed gas with a carbon dioxide concentration of 95% to carry out the carbonation reaction. Control the flow rate of the mixed gas to 2 m³ / min. 3 / h, when the conductivity of the reaction system drops to the minimum value, the gas mixture is stopped to obtain calcium carbonate suspension No. 1;

[0076] (3) Transfer the No. 1 calcium carbonate suspension to a 25L high-stirring carbonation tower with an insulation jacket, then add 3 times its mass (of the No. 1 calcium carbonate suspension) of 90℃ tap water for dilution. Next, heat the suspension to 85℃, adjust the stirring speed of the carbonation tower to 1300r / min, and start introducing a mixed gas with a 7% carbon dioxide concentration, controlling the flow rate of the mixed gas to 2m³ / min. 3 / h, and at the same time, 12kg of lime milk is added to the suspension at 120min intervals to carry out the carbonation reaction. When the pH value of the reaction system is 7.5, the mixed gas is stopped immediately to obtain calcium carbonate suspension No. 2.

[0077] (4) Transfer the No. 2 calcium carbonate suspension to the treatment tank, ensure that the temperature of the suspension is 65-70℃, add 3.8% sodium stearate (calcium carbonate dry basis mass) and stir for surface treatment;

[0078] (5) The surface-treated slurry is dewatered by a plate and frame filter press, and then the pressed material is dried at 120°C and finally pulverized to obtain a specific surface area of ​​23.06 m². 2 / g of nano calcium carbonate.

[0079] (1) Take limestone with a size of 2-3cm and calcine it at 1000℃ for 400min to obtain quick-burned lime. Then mix the lime with tap water at a ratio of 1 / 3 and stir for 30min to prepare lime milk. Let the lime milk stand and age for 24h. After removing the waste residue through a 100-mesh sieve, add tap water to adjust the solid content of the lime milk to 15%.

[0080] (2) Take 2 kg of lime milk and put it into a 3 L high-stirring carbonization tower. Use a chiller to lower the temperature of the lime milk to 10 °C, then add 0.5% sucrose. Adjust the stirring speed of the carbonization tower to 1400 r / min, and start introducing a mixed gas with a carbon dioxide concentration of 95% to carry out the carbonation reaction. Control the flow rate of the mixed gas to 2 m³ / min. 3 / h, when the conductivity of the reaction system drops to the minimum value, the gas mixture is stopped to obtain calcium carbonate suspension No. 1;

[0081] (3) Transfer the No. 1 calcium carbonate suspension to a 25L high-stirring carbonation tower with an insulation jacket, then add 3 times its mass (of the No. 1 calcium carbonate suspension) of 90℃ tap water for dilution. Next, heat the suspension to 85℃, adjust the stirring speed of the carbonation tower to 1300r / min, and start introducing a mixed gas with a 7% carbon dioxide concentration, controlling the flow rate of the mixed gas to 2m³ / min. 3 / h, and at the same time, 12kg of lime milk is added to the suspension at 120min intervals to carry out the carbonation reaction. When the pH value of the reaction system is 7.5, the mixed gas is stopped immediately to obtain calcium carbonate suspension No. 2.

[0082] (4) Transfer the No. 2 calcium carbonate suspension to the treatment tank and ensure that the temperature of the suspension is 65-70℃. First, add an equal amount of 3.8% sodium stearate (calcium carbonate dry basis mass) for stirring and surface treatment at 15 minutes. After a 2-minute delay, add an equal amount of aluminum sulfate for in-situ coating at 15 minutes.

[0083] (5) The surface-treated slurry is dewatered by a plate and frame filter press, and then the pressed material is dried at 120°C and finally pulverized to obtain a specific surface area of ​​22.75 m². 2 / g of nano calcium carbonate.

[0084] The calcium carbonate obtained in Examples 1-4 and Comparative Examples 1-5 were applied to solar photovoltaic adhesives. According to the formula, 107 adhesive, calcium carbonate, and silicone oil were weighed and added to a power mixer, heated at 120°C, and then vacuum-stirred and dehydrated for 2 hours. After the material temperature cooled to 45°C, a crosslinking agent, coupling agent, and catalyst were added sequentially, and the mixture was stirred evenly under vacuum to obtain the photovoltaic adhesive, which was then bottled. Table 1 shows the solar photovoltaic adhesive formula.

[0085] The prepared solar photovoltaic adhesive was subjected to application tests. The tensile strength and elongation were tested according to GB / T 528-2009 "Determination of tensile stress-strain properties of vulcanized rubber or thermoplastic rubber". The test results are shown in Table 2.

[0086] Table 1: Solar Photovoltaic Adhesive Formulation

[0087]

[0088] Table 2: Test Results of Solar Photovoltaic Adhesive

[0089]

[0090] The test results above show that the present invention uses a specific carbonation process to prepare small-particle-size nano-calcium carbonate seeds, and then grows calcium carbonate crystals at high temperature. This not only ensures that the crystal morphology of nano-calcium carbonate is regular and gives nano-calcium carbonate better mechanical properties when used to fill photovoltaic adhesives, but also allows the size of nano-calcium carbonate crystal particles to be freely controlled by the amount of lime milk added. The results from Comparative Example 1 show that carbonation using a low-temperature + high-concentration carbon dioxide mixed gas promotes the formation of a large number of small-diameter seed crystals, which is beneficial to the subsequent formation of nano-calcium carbonate. Otherwise, micron-sized calcium carbonate will be produced, and the conventional mechanical properties will be significantly reduced. Comparative Example 2 shows that non-high-temperature carbonation leads to the formation of chain-like calcium carbonate and clusters, which is detrimental to conventional mechanical properties. Comparative Example 3 shows that, compared with conventional carbonation processes, the nano-calcium carbonate produced by the specific carbonation process of this invention has a more regular morphology and superior conventional mechanical properties. Comparative Example 4 shows that, compared with conventional sodium stearate modification, the surface modification formula of this invention can significantly improve high-temperature resistance and damp heat resistance. Comparative Example 5 shows that phosphate esters and phosphoryltriamine have a good synergistic effect with stearic acid metal soap, which can further improve high-temperature resistance and damp heat resistance.

[0091] The above description, in conjunction with specific / preferred embodiments, provides a further detailed explanation of the present invention. It should not be construed that the specific implementation of the present invention is limited to these descriptions. For those skilled in the art, various substitutions or modifications can be made to these described embodiments without departing from the inventive concept, and all such substitutions or modifications should be considered within the scope of protection of the present invention.

Claims

1. A method for preparing nano-calcium carbonate for solar photovoltaic adhesives, characterized in that: Includes the following steps: (1) Calcining limestone at 1000-1100℃ to obtain quick-burning lime, then digesting quick-burning lime with tap water to obtain lime milk, letting it stand, aging, removing waste residue through a 100-mesh sieve, adjusting the solid content of lime milk to 15-20%, and keeping it for later use. (2) Place the lime milk from step (1) into a small carbonation reaction tower with a high stirring rate, add sucrose, cool the lime milk to 6-10°C, and introduce a mixed gas with a high carbon dioxide concentration to carry out the carbonation reaction. Use the conductivity of the reaction suspension to determine the carbonation endpoint. Stop the reaction when the conductivity drops to the lowest value to obtain calcium carbonate suspension #1. (3) Transfer the No. 1 calcium carbonate suspension to a large carbonation reaction tower with high stirring speed and heat preservation function, add 3-6 times the mass of No. 1 calcium carbonate suspension with hot water to dilute the suspension, then heat the suspension to 85-95℃, and then introduce a mixed gas with low carbon dioxide concentration to carry out the carbonation reaction. At the same time, add 3-6 times the mass of lime milk in step (1) to the suspension. When the lime milk is added, stop the gas introduction immediately when the pH of the suspension is 7.5 after carbonation to terminate the carbonation reaction, and finally obtain No. 2 calcium carbonate suspension. (4) Transfer the No. 2 calcium carbonate suspension to the treatment tank, ensuring that the temperature of the suspension is not lower than 60°C during the transfer process. First, add sodium stearate to the suspension and stir for surface treatment. After a delay of 1-3 minutes, add the corresponding mass of soluble inorganic metal salt to the suspension. Finally, add phosphoric acid triamine and phosphate ester respectively for stirring and surface treatment. (5) The surface-treated calcium carbonate slurry is dehydrated by a filter press, dried, and pulverized to obtain nano-calcium carbonate finished powder.

2. The method for preparing nano-calcium carbonate for solar photovoltaic adhesive according to claim 1, characterized in that: The amount of sucrose used in step (2) is 0.2-0.5% of the mass of lime milk.

3. The method for preparing nano-calcium carbonate for solar photovoltaic adhesive according to claim 1, characterized in that: The volume concentration of carbon dioxide in the high carbon dioxide concentration mixed gas in step (2) is 85-95%.

4. The method for preparing nano-calcium carbonate for solar photovoltaic adhesive according to claim 1, characterized in that: The carbon dioxide volume concentration of the low carbon dioxide concentration mixed gas in step (3) is 7-15%.

5. The method for preparing nano-calcium carbonate for solar photovoltaic adhesive according to claim 1, characterized in that: Step (3) involves adding an equal amount of lime slurry to the suspension at regular intervals of 40-120 minutes.

6. The method for preparing nano-calcium carbonate for solar photovoltaic adhesive according to claim 1, characterized in that: Step (4) involves adding an equal amount of sodium stearate (2.5-3.5% by dry weight of calcium carbonate) to the suspension at 10-20 min intervals and stirring for surface treatment.

7. The method for preparing nano-calcium carbonate for solar photovoltaic adhesive according to claim 6, characterized in that: Step (4) involves adding an equal amount of soluble inorganic metal salt to the suspension at 10-20 min intervals. The amount of metal salt added is calculated based on the complete reaction with sodium stearate to form the corresponding stearic acid metal soap.

8. The method for preparing nano-calcium carbonate for solar photovoltaic adhesive according to claim 7, characterized in that: The metal salt is one or a combination of two of aluminum sulfate, barium chloride, lead nitrate, strontium chloride, cadmium sulfate, zinc sulfate, and lithium chloride.

9. The method for preparing nano-calcium carbonate for solar photovoltaic adhesive according to claim 1, characterized in that: The amounts of phosphoric acid triamine and phosphate ester added are 0.1-0.3% and 0.4-0.8% of the dry weight of calcium carbonate, respectively.

10. The method for preparing nano-calcium carbonate for solar photovoltaic adhesive according to claim 9, characterized in that: The phosphate ester is one or a combination of hexadecyl phosphate and octadecyl phosphate; the phosphoric acid triamine is one or a combination of hexamethylphosphoric acid triamine and hexaethylphosphoric acid triamine.

Images