Nano calcium carbonate with high humidity and heat performance for photovoltaic adhesive as well as preparation method and application of nano calcium carbonate

Abstract

The invention discloses nano calcium carbonate for a photovoltaic adhesive with high humidity and heat performance, and a preparation method and application thereof, and belongs to the technical field of inorganic nano material modification. The method comprises the following steps: preparing a calcium carbonate suspension by taking sucrose as a crystal form control agent, treating the calcium carbonate suspension with ammonium oxalate to form a calcium oxalate coated calcium carbonate suspension, and then sequentially carrying out long-chain fatty acid wet modification and aluminum-zirconium coupling agent dry treatment. A multi-layer composite protection structure is constructed on the surfaces of the particles through the working procedures, so that the physical water blocking, hydrophobic and interface enhancing effects are synchronously realized. The photovoltaic adhesive prepared by the invention shows excellent tensile strength, elongation at break and bonding strength retention rate in a high-temperature and high-humidity aging environment, and the damp-heat aging resistance of the photovoltaic adhesive is remarkably improved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of inorganic nanomaterial modification, and particularly relates to a nano calcium carbonate prepared through multi-step coating and synergistic modification, and application of the nano calcium carbonate as a functional filler in the fields of sealant, paint, high-performance composite material and the like. BACKGROUND

[0002] As a kind of inorganic filler with low price and easy to obtain, nano calcium carbonate is often applied in photovoltaic glue to improve its mechanical properties and reduce cost. However, the surface of unmodified nano calcium carbonate presents hydrophilic and oleophobic characteristics, and it is prone to agglomeration in the polymer matrix, and has poor compatibility with the organic phase; in a high humidity and heat environment, water molecules can easily invade, thereby causing interface adhesion to decrease, mechanical properties to decrease and other aging phenomena, which seriously affect the service life of the photovoltaic glue.

[0003] Therefore, in order to improve the compatibility between calcium carbonate and polymer, it is necessary to modify the surface of calcium carbonate. The existing single modification method, such as stearic acid modification or coupling agent modification, can improve the dispersibility of nano calcium carbonate to a certain extent, but it is prone to hydrolysis reaction under high humidity and heat conditions, which causes the modified layer to be hydrolyzed and detached, and the interface bonding force to decrease.

[0004] Chinese patent CN116282115 A discloses a preparation method of nano calcium carbonate for photovoltaic sealant. The invention prepares nano calcium carbonate by adding dispersants and crystal form control agents, and then modifies the calcium carbonate using a compounded surface treatment agent. The calcium carbonate prepared by the method is cheap and easy to obtain, has low cost and simple process; it is easy to process, has low viscosity and good dispersibility in photovoltaic glue application, but it still has deficiencies in reinforcement performance.

[0005] Chinese patent CN119799034 A discloses a surface treatment method of anti-aging nano calcium carbonate for photovoltaic sealant. The invention uses monostearin, 2,4,6-tris(4-carboxyphenyl)-1,3,5-triazine and sodium phosphite to treat the surface of calcium carbonate. The nano calcium carbonate treated by the method has high activity and good dispersibility, and has good resistance to humid heat aging and ultraviolet aging in photovoltaic glue application, thereby improving the aging and yellowing problems existing in the current photovoltaic glue.

[0006] Chinese patent CN105778568A discloses a surface treatment method of special nano calcium carbonate for photovoltaic glue. The invention obtains modified nano calcium carbonate by heating and stirring nano calcium carbonate slurry and then adding a compounded surface treatment agent for surface treatment. The nano calcium carbonate product can be obtained by pressure filtration, dehydration and drying. The nano calcium carbonate treated by this method has good dispersibility, high activity and strong hydrophobicity. When applied to filling photovoltaic glue, it not only ensures excellent processing performance and mechanical properties of the glue, but also has good viscosity, thixotropy, high tensile strength and moisture and heat aging resistance.

[0007] Chinese patent application CN108864763A discloses a surface treatment method of nano calcium carbonate for photovoltaic component silicone sealant. The invention obtains modified nano calcium carbonate product by adding beef tallow and ammonium polyphosphate for first surface treatment, and then using carboxyl-terminated polyester and phosphite for second surface treatment. The nano calcium carbonate obtained by this method has high dispersibility and low hygroscopicity. The modified nano calcium carbonate also has moisture and heat resistance, high temperature resistance and oxidation resistance. When applied to photovoltaic glue filling, it can improve the mechanical properties of photovoltaic glue and enhance the moisture and heat resistance and high temperature resistance of photovoltaic glue.

[0008] Chinese patent application CN117467285A discloses a preparation method of nano calcium carbonate that can improve the aging resistance of photovoltaic sealant. The invention obtains nano calcium carbonate by using a compound of octyl decanol polyoxyethylene ether phosphate and sodium stearate to modify the surface of nano calcium carbonate suspension, and then using tridecafluorooctyltrimethoxysilane for second surface modification after ultrasonic dispersion treatment. The nano calcium carbonate applied in photovoltaic glue can significantly improve the aging resistance and comprehensive performance.

[0009] Through comprehensive and detailed analysis of the above patents, it is found that the conventional surface treatment agent of nano calcium carbonate can basically meet the application requirements of photovoltaic glue in the current actual situation. These conventional surface treatment agents to some extent guarantee the role of nano calcium carbonate in photovoltaic glue, so that photovoltaic glue can maintain relatively stable performance in normal use. However, when the focus is on the aging adhesion performance of photovoltaic glue, it is found that there are still some deficiencies in the current situation. Although the conventional surface treatment agent performs well in other aspects, its ability to maintain adhesion performance when dealing with the aging problem of photovoltaic sealant over time cannot achieve more ideal results.

[0010] Therefore, it is of great significance to develop a modified nano calcium carbonate that can fundamentally block the invasion of water vapor and strengthen the interface bonding of fillers and matrix, for improving the moisture and heat aging resistance of photovoltaic glue and prolonging the service life of photovoltaic modules. SUMMARY

[0011] The application provides a nano calcium carbonate with high moisture and heat performance for photovoltaic glue, a preparation method and application thereof, so as to solve the problems of the prior art.

[0012] In order to achieve the above technical purposes, the application adopts the following technical scheme:

[0013] A preparation method of a nano calcium carbonate with high moisture and heat performance for photovoltaic glue, comprising the following steps:

[0014] (1) calcining limestone at a high temperature of 900-1100 DEG C to obtain quicklime, and then performing a digestion reaction on the quicklime with tap water to obtain lime milk, filtering the lime milk through a 150-mesh screen to remove impurities, and obtaining refined lime milk;

[0015] (2) mixing the refined lime milk obtained in step (1) with a crystal form control agent, placing the mixture in a jacketed reaction kettle, adjusting the initial temperature of the slurry to 21-25 DEG C, starting to stir and carbonize the slurry by introducing carbon dioxide, stopping the reaction when the pH value reaches 7.0, and obtaining a calcium carbonate suspension;

[0016] (3) reducing the temperature to 50 DEG C, slowly adding a compound containing oxalate ions to the slurry at a mass of 0.25-0.75% of the dry weight of the calcium carbonate, slowly adding dilute ammonia water and continuously stirring, maintaining the pH value at 7.0-9.0, and placing the slurry for 60-90 min after the addition is completed; after the end, introducing carbon dioxide to adjust the pH value to 7.0, and obtaining a calcium oxalate-coated calcium carbonate suspension;

[0017] (4) heating the calcium oxalate-coated calcium carbonate suspension obtained in step (3) to 70-90 DEG C in a water bath, stirring and adding 3-3.5% of long-chain fatty acids based on the dry weight of the calcium carbonate to perform wet modification, and reacting for 30-40 min;

[0018] (5) filtering, washing, drying and crushing the slurry after the reaction in step (4) to obtain pre-modified calcium carbonate;

[0019] (6) adding the pre-modified calcium carbonate obtained in step (5) into a high-speed mixer, heating to 60-75 DEG C, slowly adding a coupling agent at a mass of 0.5-1.0% of the dry weight of the calcium carbonate under high-speed stirring at 900-1000 rpm, discharging after 10-20 min, and obtaining the nano calcium carbonate for photovoltaic glue with high moisture and heat performance.

[0020] Preferably, the crystal form control agent is sucrose, and the mass of the sucrose is 0.1-0.2% of the dry weight of the calcium carbonate.

[0021] Preferably, the oxalate ion-containing compound is one of oxalic acid and ammonium oxalate.

[0022] Preferably, the ammonium oxalate is added in the form of a 0.1 mol / L aqueous solution.

[0023] Preferably, the long-chain fatty acid is one of stearic acid, oleic acid and palmitic acid having a carbon atom number of 12-22, and more preferably stearic acid.

[0024] Preferably, the stearic acid is slowly added dropwise to the slurry after being configured into a solution with a mass fraction of 5-10%.

[0025] Preferably, the coupling agent is an aluminum-zirconium coupling agent, and the general molecular structure thereof is as follows:

[0026]

[0027] The core function of the aluminum-zirconium coupling agent is determined by the organic coordination group (R-COO - ). Al and Zr represent the metal centers of aluminum and zirconium, which are connected to each other by μ2-O (oxygen bridge) to form an inorganic skeleton, and each metal center is simultaneously coordinated with a hydrolyzable alkoxy group (OR') and an organic carboxylate group (R-COO - ) containing a long-chain alkyl group at one end. The alkoxy group can be hydrolyzed during the modification process and reacts with the active groups on the surface of the nano calcium carbonate to form a chemical bond; the long-chain alkyl group has good compatibility with the polymer matrix, thereby constructing a firm interface bridging layer between the inorganic filler and the organic polymer.

[0028] Preferably, the aluminum-zirconium coupling agent needs to be diluted to a concentration of 50% with anhydrous ethanol when used.

[0029] The present application is based on the following principles:

[0030] The core innovation of the present application lies in the three-step synergistic modification strategy of "calcium oxalate barrier layer + stearic acid hydrophobic layer + aluminum-zirconium coupling outer enhancement layer", which constructs a dense, hydrophobic and strong interface bonding composite coating structure on the surface of nano calcium carbonate particles, and the technical principle is as follows:

[0031] (1) Inner layer (physical barrier layer): first, a layer of calcium oxalate (CaC2O4) coating is formed on the surface of nano calcium carbonate by in-situ reaction with ammonium oxalate as a precursor. This layer has high chemical stability and low solubility, and can effectively block the penetration and erosion of water molecules to the calcium carbonate body, providing a solid physical barrier for the entire modification system and laying the foundation for structural stability.

[0032] (2) Middle layer (hydrophobic and bridging layer): Secondly, the calcium oxalate coated calcium carbonate is modified by wet method. The carboxyl group of stearic acid is chemically bonded with the calcium ion on the surface of the particles, and the long alkyl chain is arranged outward, which gives the powder excellent hydrophobicity and initial compatibility with organic polymers.

[0033] (3) Outer layer (interface enhancement layer): Finally, the aluminum zirconium coupling agent is used for dry modification. The alkoxyl group at one end of the coupling agent molecule can be firmly combined with the stearic acid layer of the middle layer or the calcium oxalate surface of the inner layer through chemical reaction or hydrogen bonding, and the other end of the organic long chain can form strong chemical bonds or physical entanglement with the polymer matrix of the photovoltaic glue, which significantly enhances the interfacial bonding force between the filler and the matrix, preventing interfacial debonding under humid heat conditions.

[0034] In order to achieve the above purposes, the technical scheme adopted by the present application is as follows:

[0035] Compared with the prior art, the present application has the following advantages:

[0036] (1) The present application uses a three-step composite process sequence of "wet-wet-dry", each step is closely connected, the utilization efficiency of the modifier is high, the production process is stable, and it is suitable for large-scale industrial production.

[0037] (2) The present application constructs a three-layer coating structure with clear functions through three-step modification. The inner layer is a physical and chemical barrier of calcium oxalate, which effectively blocks the invasion of water vapor; the middle layer is a hydrophobic layer of stearic acid, and the outer layer is an aluminum zirconate interface enhancement layer, which enhances the interfacial bonding force between the filler and the matrix; the three layers work together to form a hydrolysis-resistant and strongly bonded interface region, achieving all-round protection from water vapor blocking to interface strengthening.

[0038] (3) The photovoltaic glue filled with the modified nano calcium carbonate of the present application has a significantly higher retention rate of tensile strength, elongation at break and adhesive strength than the products filled with ordinary modified calcium carbonate or single modified calcium carbonate after severe aging test at 85℃ / 85% relative humidity.

[0039] (4) The product of the present application is mainly aimed at the field of photovoltaic glue, but its excellent moisture resistance and interface enhancement effect also show wide application potential in the fields of sealant, paint, high-performance composite materials, etc. DETAILED DESCRIPTION

[0040] In order to better understand the present application, the following examples are used for illustration, which belong to the protection scope of the present application, but do not limit the protection scope of the present application.

[0041] Example 1

[0042] A method for preparing a kind of nano calcium carbonate with high moisture resistance and heat resistance for photovoltaic glue, comprising the following steps:

[0043] (1) Take 1-1.5 cm of limestone and calcine at 1000℃ for 450 min to obtain quicklime. Digest the quicklime with tap water at a lime-water mass ratio of 1:4 to obtain lime milk. After standing for 24 h, sieve the lime milk with a 150-mesh sieve to obtain refined lime milk. Adjust the solid content of the refined lime milk to 15%.

[0044] (2) Mix the refined lime milk obtained in (1) with 0.1% sucrose, and place the mixture in a jacketed reactor. Circulate water through the jacket to control the initial temperature at 23℃. Adjust the stirring speed to 300 r / min. While stirring, introduce carbon dioxide to perform carbonation. Stop the reaction when the pH value reaches 7.0 to obtain a nano calcium carbonate suspension.

[0045] (3) Place the nano calcium carbonate suspension obtained in (2) in a temperature-controllable reactor. Reduce the temperature to 50℃, and slowly add 0.5% of a 0.1 mol / L ammonium oxalate solution to the reactor. At the same time, continuously add dilute ammonia water and maintain the pH value at 8.0. After the addition is complete, stand for 75 min. After the reaction is complete, introduce carbon dioxide to adjust the pH value to 7.0. Thus, a calcium oxalate-coated calcium carbonate suspension is obtained.

[0046] (4) Heat the calcium oxalate-coated calcium carbonate suspension obtained in (3) in a water bath to 80℃. While stirring, slowly add 3.2% of a 5% stearic acid solution. React for 35 min. Dehydrate the obtained slurry with a filter press, and then dry at 110℃. Crush and sieve the product through a 400-mesh sieve to obtain a pre-modified calcium carbonate.

[0047] (5) Add the pre-modified calcium carbonate obtained in (4) to a high-speed mixer. Heat the mixture to 70℃. While stirring at 950 rpm, slowly add 0.75% of a 50% aluminum-zirconium coupling agent ethanol solution to perform surface dry treatment. After 15 min, discharge the product. Thus, a nano calcium carbonate product for a photovoltaic adhesive with high moisture and heat resistance is obtained. The product is a regular cubic nano calcium carbonate product with a specific surface area of 20.93 m 2 / g.

[0048] Example 2

[0049] A method for preparing a nano calcium carbonate product for a photovoltaic adhesive with high moisture and heat resistance includes the following steps:

[0050] (1) Take 1-1.5 cm of limestone and calcine at 950℃ for 600 min to obtain quicklime. Digest the quicklime with tap water at a lime-water mass ratio of 1:4 to obtain lime milk. After standing for 24 h, sieve the lime milk with a 150-mesh sieve to obtain refined lime milk. Adjust the solid content of the refined lime milk to 15%.

[0051] (2) The refined milk of lime prepared in (1) is mixed with 0.15% sucrose uniformly, and then is placed in a jacketed reaction kettle. Circulating water is introduced into the jacket to control the initial temperature at 21°C. The stirring speed is adjusted to 300 r / min. Carbon dioxide is introduced for carbonation reaction while stirring. The reaction is stopped when the pH value reaches 7.0, and a nano calcium carbonate suspension is obtained.

[0052] (3) The nano calcium carbonate suspension obtained in (2) is placed in a temperature-controllable reaction kettle. The temperature is reduced to 50°C. 0.25% of 0.1 mol / L ammonium oxalate solution is slowly added into the reaction kettle. Dilute ammonia water is also added dropwise while stirring is maintained. The pH value is maintained at 7.0. After the addition is completed, the mixture is allowed to stand for 60 min. After the end of the reaction, carbon dioxide is introduced to adjust the pH value to 7.0. A calcium oxalate-coated calcium carbonate suspension is obtained.

[0053] (4) The calcium oxalate-coated calcium carbonate suspension obtained in (3) is heated in a water bath to 70°C. While stirring, 3.0% of 5% stearic acid solution is added dropwise. The reaction is carried out for 30 min. The obtained slurry is dewatered by a filter press, and then is dried at 110°C. After being pulverized, the product is passed through a 400-mesh sieve to obtain a pre-modified calcium carbonate.

[0054] (5) The pre-modified calcium carbonate obtained in (4) is added into a high-speed mixer. The temperature is raised to 65°C. While stirring at 900 rpm, 0.5% of 50% aluminum-zirconium coupling agent ethanol solution is slowly added dropwise for surface dry treatment. After 10 min, the product is discharged. Thus, a nano calcium carbonate product for a photovoltaic adhesive with high moisture and heat resistance is obtained. The product is a regular cubic nano calcium carbonate product with a specific surface area of 21.24 m 2 / g.

[0055] Example 3

[0056] A method for preparing a nano calcium carbonate product for a photovoltaic adhesive with high moisture and heat resistance comprises the following steps:

[0057] (1) Limestone with a size of 1-1.5 cm is calcined at 1100°C for 200 min to obtain quicklime. The quicklime is subjected to digestion reaction with tap water at a lime-water mass ratio of 1:4 to obtain lime milk. The lime milk is allowed to stand for 24 h, and then is passed through a 150-mesh sieve to obtain refined lime milk. The solid content of the refined lime milk is adjusted to 15%.

[0058] (2) The refined lime milk prepared in (1) is mixed with 0.2% sucrose uniformly, and then is placed in a jacketed reaction kettle. Circulating water is introduced into the jacket to control the initial temperature at 25°C. The stirring speed is adjusted to 300 r / min. Carbon dioxide is introduced for carbonation reaction while stirring. The reaction is stopped when the pH value reaches 7.0, and a nano calcium carbonate suspension is obtained.

[0059] (3) Put the nano calcium carbonate suspension obtained in (2) into a controllable temperature reaction kettle, reduce the temperature to 50°C, slowly add 0.75% of 0.1 mol / L ammonium oxalate solution into it, and at the same time, add dilute ammonia water continuously while stirring, maintain the pH value at 9.0, after the addition is completed, stand for 90 min, after the end, pass in carbon dioxide to adjust the pH value to 7.0, after the reaction is completed, obtain the calcium oxalate coated calcium carbonate suspension.

[0060] (4) Heat the calcium oxalate coated calcium carbonate suspension obtained in (3) in a water bath to 90°C, slowly add 3.5% of 5% stearic acid solution while stirring, react for 40 min, dehydrate the obtained slurry through a filter press, then dry at 110°C, crush, pass through a 400 mesh screen, and obtain the pre-modified calcium carbonate.

[0061] (5) Put the pre-modified calcium carbonate obtained in (4) into a high-speed mixer, heat to 90°C, slowly add 1.0% of 50% aluminum zirconium coupling agent ethanol solution for surface dry treatment under high-speed stirring at 1000 rpm, after 20 min, discharge, and the nano calcium carbonate product for photovoltaic adhesive with high moisture and heat resistance is obtained, which is a regular cubic nano calcium carbonate product with a specific surface area of 22.29 m 2 / g.

[0062] Example 4

[0063] A method for preparing a nano calcium carbonate for photovoltaic adhesive with high moisture and heat resistance, comprising the following steps:

[0064] (1) Take 1-1.5 cm of limestone, calcine at 1000°C for 450 min, and obtain quicklime. Digest the quicklime with tap water at a lime water mass ratio of 1:4 to obtain lime milk, stand for 24 h, pass through a 150 mesh screen, and obtain refined lime milk. Adjust the solid content of the obtained lime milk to 15%.

[0065] (2) Mix the refined lime milk prepared in (1) with 0.1% of sucrose uniformly, and place in a jacketed reaction kettle. Control the initial temperature to be 23°C by circulating water through the jacket, and adjust the stirring speed to be 300 r / min. Carbonize by passing in carbon dioxide while stirring. Stop the reaction when the pH value reaches 7.0, and obtain a nano calcium carbonate suspension.

[0066] (3) Put the nano calcium carbonate suspension obtained in (2) into a controllable temperature reaction kettle, reduce the temperature to 50°C, slowly add 0.75% of 0.1 mol / L ammonium oxalate solution into it, and at the same time, add dilute ammonia water continuously while stirring, maintain the pH value at 9.0, after the addition is completed, stand for 90 min, after the end, pass in carbon dioxide to adjust the pH value to 7.0, after the reaction is completed, obtain the calcium oxalate coated calcium carbonate suspension.

[0067] (4) The calcium oxalate-coated calcium carbonate suspension obtained in (3) is heated to 80°C in a water bath, and 3.2% of a 5% stearic acid solution is added dropwise while stirring, and the reaction is carried out for 35 min. The obtained slurry is dewatered by a filter press, and then dried at 110°C. After crushing and sieving through a 400-mesh sieve, a pre-modified calcium carbonate is obtained.

[0068] (5) The pre-modified calcium carbonate obtained in (4) is added to a high-speed mixer, heated to 70°C, and 0.75% of a 50% aluminum-zirconium coupling agent ethanol solution is slowly added dropwise under high-speed stirring at 950 rpm for surface dry treatment. After 15 min of treatment, the product is discharged, and a nano calcium carbonate product for a moisture-resistant and heat-resistant photovoltaic adhesive is obtained. The product is a regular cubic nano calcium carbonate product with a specific surface area of 22.79 m 2 / g.

[0069] Comparative Example 1

[0070] A method for preparing a nano calcium carbonate includes the following steps:

[0071] (1) Limestone with a size of 1-1.5 cm is calcined at 1000°C for 450 min to obtain quicklime. The quicklime is subjected to a digestion reaction with tap water at a lime-water mass ratio of 1:4 to obtain lime milk. After standing for 24 h, the lime milk is sieved through a 150-mesh sieve to obtain refined lime milk. The solid content of the refined lime milk is adjusted to 15%.

[0072] (2) The refined lime milk obtained in (1) is placed in a jacketed reaction kettle, and circulating water is introduced through the jacket to control the initial temperature to 23°C. The stirring speed is adjusted to 300 r / min, and carbon dioxide is introduced while stirring to carry out a carbonation reaction. When the pH value reaches 7.0, the reaction is stopped, and a nano calcium carbonate suspension is obtained.

[0073] (3) The nano calcium carbonate suspension obtained in (2) is placed in a controllable temperature reaction kettle, and the temperature is reduced to 50°C. 0.5% of a 0.1 mol / L ammonium oxalate solution is slowly added dropwise, and dilute ammonia water is added dropwise while stirring. The pH value is maintained at 8.0. After the addition is completed, the mixture is left to stand for 75 min. After the reaction is completed, carbon dioxide is introduced to adjust the pH value to 7.0, and a calcium oxalate-coated calcium carbonate suspension is obtained.

[0074] (4) The calcium oxalate-coated calcium carbonate suspension obtained in (3) is heated to 80°C in a water bath, and 3.2% of a 5% stearic acid solution is added dropwise while stirring, and the reaction is carried out for 35 min. The obtained slurry is dewatered by a filter press, and then dried at 110°C. After crushing and sieving through a 400-mesh sieve, a pre-modified calcium carbonate is obtained.

[0075] (5) The pre-modified calcium carbonate obtained in (4) is added into a high-speed mixer, heated to 70°C, and 0.75% of a 50% aluminum-zirconium coupling agent ethanol solution is slowly added dropwise under high-speed stirring at 950 rpm for surface dry treatment. After treatment for 15 min, the modified nano calcium carbonate product is obtained, which is nano calcium carbonate with a specific surface area of 26.53 m 2 / g.

[0076] Comparative Example 2

[0077] A method for preparing nano calcium carbonate, comprising the following steps:

[0078] (1) Limestone of 1-1.5 cm is calcined at 1000°C for 450 min to obtain quicklime. The quicklime is subjected to digestion reaction with tap water at a lime-water mass ratio of 1:4 to obtain lime milk. After standing for 24 h, the lime milk is sieved with a 150-mesh sieve to obtain refined lime milk. The solid content of the refined lime milk is adjusted to 15%.

[0079] (2) The refined lime milk obtained in (1) is uniformly mixed with 0.1% sucrose, and then placed in a jacketed reactor. Circulating water is introduced into the jacket to control the initial temperature at 23°C. The stirring speed is adjusted to 300 r / min. Carbon dioxide is introduced while stirring to perform carbonation reaction. When the pH value reaches 7.0, the reaction is stopped to obtain a nano calcium carbonate suspension.

[0080] (3) The calcium carbonate suspension obtained in (2) is heated to 80°C in a water bath. While stirring, 3.2% of a 5% stearic acid solution is added dropwise. The reaction is performed for 35 min. The obtained slurry is dewatered by a filter press, and then dried at 110°C. After being pulverized and sieved through a 400-mesh sieve, a modified nano calcium carbonate product is obtained, which is cubic nano calcium carbonate with a specific surface area of 20.84 m 2 / g.

[0081] Comparative Example 3

[0082] A method for preparing nano calcium carbonate, comprising the following steps:

[0083] (1) Limestone of 1-1.5 cm is calcined at 1000°C for 450 min to obtain quicklime. The quicklime is subjected to digestion reaction with tap water at a lime-water mass ratio of 1:4 to obtain lime milk. After standing for 24 h, the lime milk is sieved with a 150-mesh sieve to obtain refined lime milk. The solid content of the refined lime milk is adjusted to 15%.

[0084] (2) The refined milk of lime prepared in (1) is mixed with 0.1% sucrose uniformly, and then is placed in a jacketed reaction kettle. Circulating water is introduced into the jacket to control the initial temperature at 23°C. The stirring speed is adjusted to 300 r / min. Carbon dioxide is introduced for carbonation reaction while stirring. The reaction is stopped when the pH value reaches 7.0, and a nano calcium carbonate suspension is obtained.

[0085] (3) The calcium carbonate suspension obtained in (2) is heated to 80°C in a water bath. While stirring, 3.2% of a 5% stearic acid solution is added dropwise. The reaction is carried out for 35 min. The obtained slurry is dewatered by a filter press, and then is dried at 110°C. After being crushed and sieved through a 400-mesh sieve, a stearic acid modified calcium carbonate is obtained.

[0086] (4) The stearic acid modified calcium carbonate obtained in (3) is added into a high-speed mixer, and is heated to 70°C. While stirring at 950 rpm, 0.75% of a 50% aluminum-zirconium coupling agent ethanol solution is added dropwise for surface dry treatment. After treatment for 15 min, the product, a modified nano calcium carbonate, is obtained. The modified nano calcium carbonate is cubic nano calcium carbonate with a specific surface area of 21.37 m 2 / g.

[0087] Comparative Example 4

[0088] A method for preparing nano calcium carbonate comprises the following steps:

[0089] (1) Limestone with a size of 1-1.5 cm is calcined at 1000°C for 450 min to obtain quicklime. The quicklime is subjected to digestion reaction with tap water at a lime water mass ratio of 1:4 to obtain lime milk. The lime milk is allowed to stand for 24 h, and then is sieved through a 150-mesh sieve to obtain refined lime milk. The solid content of the refined lime milk is adjusted to 15%.

[0090] (2) The refined lime milk prepared in (1) is mixed with 0.1% sucrose uniformly, and then is placed in a jacketed reaction kettle. Circulating water is introduced into the jacket to control the initial temperature at 23°C. The stirring speed is adjusted to 300 r / min. Carbon dioxide is introduced for carbonation reaction while stirring. The reaction is stopped when the pH value reaches 7.0, and a nano calcium carbonate suspension is obtained.

[0091] (3) The nano calcium carbonate suspension obtained in (2) is placed in a controllable temperature reaction kettle. The temperature is reduced to 50°C. 0.5% of a 0.1 mol / L ammonium oxalate solution is slowly added into the reaction kettle. At the same time, dilute ammonia water is added dropwise and stirring is continuously carried out. The pH value is maintained at 8.0. After the addition is completed, the mixture is allowed to stand for 75 min. After the reaction is completed, carbon dioxide is introduced to adjust the pH value to 7.0. A calcium oxalate coated calcium carbonate suspension is obtained.

[0092] (4) The calcium oxalate-coated calcium carbonate suspension obtained in (3) is heated in a water bath to 80°C, and 3.2% of a 5% stearic acid solution is added dropwise while stirring, and the reaction is carried out for 35 min. The obtained slurry is dewatered by a filter press, and then dried at 110°C, crushed, and sieved through a 400-mesh sieve to obtain a modified nano calcium carbonate product, which is a cubic nano calcium carbonate product with a specific surface area of 21.71 m 2 / g.

[0093] The nano calcium carbonate products obtained in Examples 1-4 and Comparative Examples 1-4 above are applied to photovoltaic glue respectively. The photovoltaic glue is prepared by weighing 107 glue, calcium carbonate, and 1500-mesh heavy calcium according to the formula, and then adding them into a dynamic mixer, heating, vacuumizing, and stirring for 2 h at 120°C. When the material is cooled to below 45°C, a crosslinking agent, a coupling agent, and a catalyst are added in sequence, and then stirred uniformly in vacuum to obtain the photovoltaic glue. Table 1 is the formula of the photovoltaic glue.

[0094] The prepared photovoltaic glue is subjected to application test, and the tensile strength and elongation rate test is carried out according to the standard of GB / T528-2009 "Determination of Tensile Stress-Strain Properties of Vulcanized or Thermoplastic Rubber", and the adhesion performance test is carried out according to CB / T13477 "Test Methods for Building Sealing Materials". The test results are shown in Table 2. Table 2 double 85 1000h refers to the condition of aging for 1000 h at 85°C / 85% relative humidity.

[0095]

[0096]

[0097] It can be seen from the test results in Table 2 that the regular cubic nano calcium carbonate with a specific surface area of 20-23 is prepared by adding the crystal form control agent in the present application, which indicates that the crystal form control agent (sucrose) effectively controls the growth of the particles, and provides a substrate for the subsequent coated and modified calcium carbonate. It can be known from the results of Comparative Example 1 that the particle morphology is irregular and the specific surface area is too large due to the absence of the crystal form control agent, which leads to uneven coating effect and the most obvious decline in the moisture and heat resistance, thereby verifying the importance of the nano calcium carbonate prepared by adding the crystal form control agent (sucrose) for the subsequent coated and modified calcium carbonate. It can be known from the results of Comparative Example 2 that the calcium carbonate is modified by only using a single stearic acid, which is hydrophobic on the surface, but lacks a barrier layer and a coupling layer, leading to a significant decline in the performance after moisture and heat aging, which indicates that the single stearic acid modification cannot meet the demand of the high moisture and heat environment. It can be known from the results of Comparative Example 3 that the calcium carbonate is directly treated by stearic acid + coupling agent without calcium oxalate coating, although the coupling layer can enhance the interface bonding, but the water molecules can still invade the calcium carbonate bulk, and the aging performance retention rate is obviously lower than that of the present application. It can be known from the results of Comparative Example 4 that the coupling agent modification is not carried out, although it has a barrier layer and a hydrophobic layer, but the interface bonding force between the filler and the matrix is insufficient, leading to the complete debonding of the test piece after aging, which indicates that the coupling layer is indispensable for the interface strengthening.

[0098] The three-layer coating structure constructed by the application forms a synergistic protection system of "physical barrier-hydrophobic protection-interface enhancement", and the structure still has relatively high mechanical properties and bonding properties after high humidity and heat aging, which is significantly better than each proportion, proving the significant effect of the application in the high humidity and heat aging performance of photovoltaic glue.

[0099] The above content cannot be regarded as a limitation of the specific implementation of the application to these descriptions. For ordinary skilled persons in the technical field to which the application belongs, without departing from the concept of the application, a number of simple deductions or substitutions can be made, which should be regarded as belonging to the patent protection range determined by the submitted claims.

Claims

1. A method for preparing nano calcium carbonate for photovoltaic glue with high hygrothermal performance, characterized in that, The method comprises the following steps: (1) calcining limestone at 900-1100℃ to obtain quicklime, and then digesting the quicklime with water to obtain lime milk, which is filtered through a screen to remove impurities and obtain refined lime milk; (2) mixing the refined lime milk obtained in step (1) with a crystal form control agent, and then placing the mixture in a jacketed reactor, adjusting the initial temperature of the slurry to 21-25℃, and then starting to carbonize the slurry by stirring and introducing carbon dioxide, to obtain a calcium carbonate suspension; (3) reducing the temperature to below 50℃, slowly adding a compound containing oxalate ions to the slurry, the compound having a mass of 0.25-0.75% of the dry weight of the calcium carbonate, and simultaneously adding dilute ammonia water and continuously stirring, and maintaining the pH value at 7.0-9.0, and then standing for 60-90min after the addition is completed; and then introducing carbon dioxide to adjust the pH value, to obtain a calcium oxalate-coated calcium carbonate suspension; (4) heating the calcium oxalate-coated calcium carbonate suspension obtained in step (3) in a water bath to 70-90℃, and then adding a long-chain fatty acid to the slurry by stirring, the long-chain fatty acid having a mass of 3-3.5% of the dry weight of the calcium carbonate, and then reacting for 30-40min; (5) filtering, washing, drying, and crushing the slurry after the reaction in step (4), to obtain pre-modified calcium carbonate; (6) adding the pre-modified calcium carbonate obtained in step (5) to a high-speed mixer, heating to 60-75℃, and then adding a coupling agent to the slurry by dripping, the coupling agent having a mass of 0.5-1.0% of the dry weight of the calcium carbonate, and then discharging after 10-20min, to obtain nano calcium carbonate for photovoltaic adhesive with high moisture and heat resistance.

2. A process for the preparation of nano calcium carbonate for high moisture and heat performance photovoltaic paste as claimed in claim 1, wherein, The crystal form control agent in step (2) is sucrose, and the mass of the sucrose is 0.1-0.2% of the dry weight of the calcium carbonate.

3. A process for the preparation of nano calcium carbonate for high moisture and heat performance photovoltaic paste as claimed in claim 1, wherein, The compound containing oxalate ions in step (3) is one or more of oxalic acid and ammonium oxalate.

4. The process for the preparation of nano calcium carbonate for high moisture and heat performance photovoltaic paste as claimed in claim 3, wherein, The ammonium oxalate is added in the form of a 0.1mol / L aqueous solution.

5. The process for the preparation of nano calcium carbonate for high moisture and heat performance photovoltaic paste as claimed in claim 1, wherein, The long-chain fatty acid in step (4) is one or more of stearic acid, oleic acid, and palmitic acid having 12-22 carbon atoms.

6. The process for the preparation of nano calcium carbonate for high moisture and heat performance photovoltaic paste as claimed in claim 5, wherein, The stearic acid is configured into a solution having a mass fraction of 5-10%, and then added to the slurry by dripping.

7. The process for the preparation of nano calcium carbonate for high moisture and heat performance photovoltaic paste as claimed in claim 1, wherein, The coupling agent in step (5) is an aluminum-zirconium coupling agent.

8. The process for the preparation of nano calcium carbonate for high moisture and heat performance photovoltaic paste as claimed in claim 7, wherein, The aluminum-zirconium coupling agent needs to be diluted with anhydrous ethanol to a concentration of 50% when used.

9. Nano calcium carbonate for photovoltaic adhesive with high moisture and heat resistance, which is prepared by the method according to any one of claims 1-8.

10. Use of the nano calcium carbonate for high-hygrothermal performance photovoltaic glue according to claim 9, characterized in that, The nano calcium carbonate is applied in the fields of sealant, paint, and high-performance composite material.

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