Preparation method of nano calcium carbonate for electronic adhesive

Abstract

The application provides a preparation method of nano calcium carbonate for electronic glue, and the steps are as follows: S1, diluting calcium hydroxide slurry with deionized water to obtain lime milk diluent, and adjusting the pH to 11.5-12.5; S2, pumping the lime milk diluent into a carbonization kettle, adding a composite crystal type regulating dispersant, and performing two-stage carbonization under stirring to obtain nano calcium carbonate slurry; S3, dehydrating, drying, crushing and grading the nano calcium carbonate slurry to obtain nano calcium carbonate dry powder; S4, performing radio frequency plasma surface activation modification treatment on the nano calcium carbonate dry powder; S5, dispersing the activated nano calcium carbonate dry powder in deionized water, adding zinc stearate, gamma-aminopropyl triethoxysilane and a reactive hyperbranched modifier to perform surface modification; and S6, dehydrating, drying, crushing and grading the modified slurry to obtain a finished product. The nano calcium carbonate for electronic glue provided by the application has good dispersion stability, and can effectively improve the mechanical properties, dielectric properties and storage stability of electronic glue.

Description

Technical Field

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

[0002] Nano-calcium carbonate, as a core reinforcing inorganic filler in silicone sealants and potting compounds for electronic appliances, directly determines the mechanical properties, dielectric properties, and long-term storage reliability of electronic adhesives due to its particle size uniformity, crystal regularity, surface activity, and dispersion stability in organosilicon matrices. In the field of non-metallic mineral product manufacturing, electronic-grade inorganic powders such as barium carbonate and barium titanate are widely used in the manufacture of electronic components such as ceramic capacitors and thermistors. Downstream applications place stringent requirements on their purity, particle size, and surface characteristics, providing a technical reference for the high-performance preparation of nano-calcium carbonate specifically for electronic adhesives.

[0003] Current methods for preparing nano-calcium carbonate often employ a single crystal form control agent combined with conventional surface modification processes. This approach struggles to simultaneously achieve precise crystal form control and long-term dispersion stability. Insufficient control precision in lime slurry pretreatment and poor matching of carbonation processes can lead to uneven powder particle size and severe agglomeration. Furthermore, traditional surface modification methods suffer from weak interfacial bonding and insufficient coating effects. These methods fail to meet the requirements of electronic adhesives for high dispersion, high stability, and high interfacial compatibility of fillers. Consequently, fillers tend to settle and stratify in colloidal systems, resulting in decreased high-temperature storage performance and difficulty in synergistically improving mechanical properties. Summary of the Invention

[0004] To address the shortcomings of existing technologies, this invention provides a method for preparing nano-calcium carbonate for electronic adhesives.

[0005] To achieve the above objectives, the present invention provides the following technical solution: This invention provides a method for preparing nano-calcium carbonate for electronic adhesives, comprising the following steps: S1. Dilute the calcium hydroxide slurry with a mass concentration of 15-18% with deionized water, and sieve it through a 200-mesh nylon sieve to remove impurities, to obtain a lime milk dilution with a calcium hydroxide mass concentration of 8-10%. Adjust the pH to 11.5-12.5 with a sodium hydroxide aqueous solution with a mass concentration of 10-20%, heat it to 28-32℃ and keep it at a constant temperature for later use. S2. Pump the diluted lime slurry into the carbonization reactor, maintaining the pressure inside the reactor at 0.05~0.15MPa. Add a composite crystal form regulating dispersant and carry out two-stage carbonization under stirring: In the first stage, carbon dioxide gas with a purity ≥99.9% is introduced at a flow rate of 0.3~0.4m. 3 At a constant temperature of 28-32℃, the aeration rate is increased to 0.5-0.7 m / h until the slurry pH drops to 8.5-9.0. In the second stage, the aeration rate is further increased to 0.5-0.7 m / h. 3 / h, cool down to 22~26℃, continue carbonation until the pH of the slurry drops to 6.5~7.0, stop aeration and continue constant temperature aging for 20~30min to obtain nano calcium carbonate slurry; S3. Dehydrate, dry, pulverize, and classify the nano-calcium carbonate slurry to obtain nano-calcium carbonate dry powder. S4. Place the nano-calcium carbonate dry powder in a radio frequency plasma processing device for radio frequency plasma surface activation modification treatment. S5. Disperse the activated nano-calcium carbonate dry powder in deionized water, and add zinc stearate, γ-aminopropyltriethoxysilane (KH-550) and reactive hyperbranching modifier stepwise for surface modification. S6. The modified slurry is dehydrated, dried, pulverized, and classified to obtain the nano-calcium carbonate for electronic adhesive.

[0006] Using the above technical solution, a stable reaction system is provided for the carbonation reaction by diluting, sieving to remove impurities, and adjusting the pH of the calcium hydroxide slurry. The two-stage carbonation process combined with a composite crystal form regulating dispersant can obtain a nano-calcium carbonate slurry with uniform particle size. After dehydration, drying, pulverization and classification to obtain nano-calcium carbonate dry powder, radio frequency plasma surface activation treatment can enhance its surface activity. Then, by adding zinc stearate, KH-550 and reactive hyperbranching modifier in steps for surface modification, combined with subsequent dehydration, drying, pulverization and classification treatment, the final nano-calcium carbonate for electronic adhesives has excellent dispersion stability and can significantly improve the mechanical strength, dielectric stability and long-term high-temperature storage stability of electronic adhesives.

[0007] Preferably, the raw materials for preparing the composite crystal form regulating dispersant, by weight, include: 20-30 parts of L-aspartic acid, 15-25 parts of trisodium citrate dihydrate, 20-30 parts of dodecyl dimethyl betaine, and 350-450 parts of deionized water.

[0008] Using the above technical solution, L-aspartic acid can selectively adsorb onto specific crystal faces of calcium carbonate through coordination with calcium ions via its carboxyl group, inducing directional crystal growth; trisodium citrate dihydrate can regulate the crystal growth rate by chelating calcium ions with carboxylate groups; dodecyl dimethyl betaine can inhibit crystal nucleus collision and aggregation through electrostatic repulsion and steric hindrance; deionized water, as a dispersion medium, can ensure uniform mixing of all components and allow them to fully exert their effects. The synergistic effect of the above components can achieve effective control of the crystal form of nano-calcium carbonate and improve dispersion stability.

[0009] Preferably, the preparation method of the composite crystal form regulating dispersant is as follows: deionized water is heated to 50~60℃, L-aspartic acid and trisodium citrate dihydrate are added under nitrogen protection, and the mixture is stirred at a speed of 250~350 r / min for 20~30 min; the temperature is maintained at 50~60℃, dodecyl dimethyl betaine is added, and the mixture is stirred at a speed of 500~600 r / min for 30~40 min to obtain the composite crystal form regulating dispersant.

[0010] Using the above technical solution, L-aspartic acid and trisodium citrate dihydrate form a homogeneous chelate solution under nitrogen protection and at 50-60℃, which can guide the subsequent growth of calcium carbonate crystals. Maintaining this temperature and adding dodecyl dimethyl betaine while stirring can reduce particle agglomeration through electrostatic repulsion and steric hindrance. The synergistic effect of the components makes the prepared composite crystal form regulating dispersant have the dual functions of crystal form regulation and particle dispersion stability, which can meet the requirements of the subsequent carbonization reaction of nano-calcium carbonate.

[0011] Preferably, the raw materials for preparing the reactive hyperbranching modifier, by weight, include: 40-50 parts of terminal amino hyperbranched polysiloxane, 15-20 parts of maleic anhydride, 12-18 parts of 3,3,3-trifluoropropyltrimethoxysilane, 0.2-0.5 parts of dibutyltin dilaurate, and 80-100 parts of anhydrous ethanol; the terminal amino hyperbranched polysiloxane has a number average molecular weight of 2000-3000 g / mol and a degree of branching of 0.50-0.60.

[0012] Using the above technical solution, the terminal amino hyperbranched polysiloxane can provide three-dimensional steric hindrance to reduce nanoparticle aggregation; maleic anhydride can undergo an amidation reaction with the terminal amino group of the terminal amino hyperbranched polysiloxane to generate an intermediate containing an amide acid structure; 3,3,3-trifluoropropyltrimethoxysilane can react with the intermediate to achieve grafting and introduce fluorine-containing segments; dibutyltin dilaurate can act as a catalyst to promote the reaction; anhydrous ethanol can act as a solvent to dissolve the raw materials and ensure uniform reaction; the synergistic effect of the raw materials can prepare a reactive hyperbranched modifier that combines hydrophobicity, temperature resistance and interfacial reactivity.

[0013] Preferably, the preparation method of the reactive hyperbranching modifier includes the following steps: (1) Under nitrogen protection, the terminal amino hyperbranched polysiloxane was dissolved in anhydrous ethanol, heated to 60~70℃, and stirred at 200~300r / min until completely dissolved. Then maleic anhydride was added, the system temperature was maintained at 60~70℃, and the reaction was stirred for 2~3h. (2) Add 3,3,3-trifluoropropyltrimethoxysilane and dibutyltin dilaurate to the reaction solution obtained in step (1), heat to 75~85℃, and reflux for 4~6h; after the reaction is completed, remove ethanol by vacuum distillation at 50~60℃ and vacuum degree -0.085~-0.095MPa until no ethanol flows out of the system, and obtain the reactive hyperbranching modifier.

[0014] Using the above technical solution, the terminal amino hyperbranched polysiloxane can be dissolved in anhydrous ethanol and react with maleic anhydride to generate an intermediate containing ammonium acid groups; dibutyltin dilaurate can catalyze the reaction of 3,3,3-trifluoropropyltrimethoxysilane with this intermediate, so that the fluorinated segments are grafted to the ends of the hyperbranched polymer molecular chains; the reflux reaction at 75~85℃ can ensure that the grafting reaction is fully carried out, and the anhydrous ethanol in the system can be removed by vacuum distillation, finally obtaining the reactive hyperbranched modifier.

[0015] Preferably, in step S2, the amount of the composite crystal form regulating dispersant added is 1.2~1.8% of the dry weight of calcium hydroxide in the lime slurry dilution; the stirring speed in the two-stage carbonization process is 400~500 r / min; and the aeration time in the first stage carbonization is 25~35 min.

[0016] Using the above technical solution, the composite crystal form regulating dispersant is added at 1.2-1.8% of the dry weight of calcium hydroxide in the lime slurry dilution. This fully utilizes its crystal form regulating and dispersing stabilizing effects, inducing the directional growth of calcium carbonate crystals and inhibiting crystal nucleus aggregation. The stirring speed of 400-500 r / min during the two-stage carbonization process ensures that the lime slurry dilution, composite crystal form regulating dispersant, and carbon dioxide gas are fully mixed, ensuring that the carbonization reaction proceeds uniformly and stably. The aeration time of 25-35 min during the first stage of carbonization allows carbon dioxide to fully react with calcium hydroxide to form regular crystal nuclei, providing a guarantee for the grain growth during the second stage of carbonization.

[0017] Preferably, in step S3, dewatering is performed using a plate and frame filter press with a pressure of 0.5~0.7MPa to obtain a filter cake with a moisture content of ≤40%; drying is performed using a flash dryer with an inlet temperature of 260~300℃, an outlet temperature of ≤105℃, and a drying time of 20~30s; pulverization is performed using an air jet mill with a classifying wheel speed of 2000~2500r / min.

[0018] The above technical solution can quickly remove moisture from the filter cake while avoiding changes in the crystal form of nano-calcium carbonate. By using an air jet mill to pulverize the dried powder at a classifier speed of 2000~2500 r / min, the powder can be refined to the required particle size range, resulting in nano-calcium carbonate dry powder with uniform particle size and a moisture content of ≤0.5%, ensuring the stable implementation of subsequent surface modification processes.

[0019] Preferably, in step S4, the frequency of the radio frequency plasma surface activation modification treatment is 13.56MHz, the power is 150~250W, a mixture of nitrogen and oxygen is introduced, the volume ratio of the mixture is nitrogen:oxygen = (85~95):(15~5), the cavity pressure is controlled at 50~100Pa, and the treatment time is 8~12min.

[0020] Using the above technical solution, radio frequency plasma can enhance the activity of hydroxyl groups on the powder surface, increase the number of surface active sites, weaken soft agglomeration between particles, enhance the grafting activity of modifiers, increase the number of surface active sites, improve the grafting efficiency of subsequent modifiers, and enhance the tightness of the binding between the modifier and the calcium carbonate surface, providing a reaction basis for the subsequent stepwise coating process. At the same time, it can regulate the surface chemical properties of calcium carbonate, which is beneficial to improving its interfacial compatibility with the organosilicon matrix of electronic adhesive.

[0021] Preferably, in step S5, the stepwise surface modification includes: The plasma-activated nano-calcium carbonate powder was dispersed in deionized water to prepare a slurry with a solid content of 15-20%, and then heated to 60-70℃. First coating: Add 1.5~2.5% zinc stearate by dry weight of nano calcium carbonate, and stir at 500~600 r / min for 40~60 min; Second coating: Add 0.5~1.0% KH-550 by dry weight of nano-calcium carbonate, and stir at 400~500 r / min for 20~30 min; then add 2.0~3.0% reactive hyperbranching modifier by dry weight of nano-calcium carbonate, heat to 70~80℃, and stir at 600~800 r / min for 60~90 min, while simultaneously evacuating to -0.06~-0.08 MPa; The reactive hyperbranching modifier is pre-dissolved in a mixed solvent of ethanol and water in a volume ratio of 1:1, and then slowly added dropwise to prepare a solution with a mass fraction of 15-20%.

[0022] Using the above technical solution, plasma-activated nano-calcium carbonate powder is dispersed in deionized water to prepare a slurry with a specific solid content, and the temperature is controlled for two coating processes. In the first coating, zinc stearate forms a hydrophobic coating layer on the surface of nano-calcium carbonate, reducing the surface energy of the particles. In the second coating, KH-550 first reacts with the hydroxyl groups on the surface of nano-calcium carbonate. The reactive hyperbranching modifier is added after pre-dissolving and, under specific temperature, rotation speed, and vacuum conditions, combines with the surface of nano-calcium carbonate and the reacted KH-550, improving the hydrophobic properties and interfacial reactivity of the nano-calcium carbonate surface. The stepwise coating process allows for the orderly adsorption and reaction of each modifier, forming a uniform and dense coating layer on the surface of calcium carbonate, improving its dispersibility and interfacial bonding stability in the organosilicon matrix.

[0023] Preferably, the dehydration, drying, pulverizing, and classification conditions of the modified slurry in step S6 are the same as those described in step S3; the average particle size of the nano-calcium carbonate used in the electronic adhesive is 40~60nm, and the specific surface area is 26~32m². 2 / g, purity ≥99.0%.

[0024] By adopting the above technical solution, the modified nano-calcium carbonate powder can maintain a uniform particle size distribution and good dispersion, ensuring that the nano-calcium carbonate has the basic performance to meet the requirements of electronic adhesives for filler particle size, specific surface area and purity.

[0025] The beneficial effects of this invention are as follows: By diluting, sieving to remove impurities, and adjusting the pH of the calcium hydroxide slurry, a stable reaction system is provided for the carbonation reaction. The two-stage carbonation process, combined with a composite crystal form regulating dispersant, yields a nano-calcium carbonate slurry with uniform particle size. After dehydration, drying, pulverization, and classification to obtain nano-calcium carbonate dry powder, radio frequency plasma surface activation treatment can enhance its surface activity. Then, by adding zinc stearate, KH-550, and a reactive hyperbranching modifier in steps for surface modification, combined with subsequent dehydration, drying, pulverization, and classification treatment, the final nano-calcium carbonate for electronic adhesives has excellent dispersion stability and can significantly improve the mechanical strength, dielectric stability, and long-term high-temperature storage stability of electronic adhesives. Detailed Implementation

[0026] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0027] The specific information on the raw materials used in the embodiments of the present invention is shown in Table 1.

[0028] Table 1

[0029] Example 1: This embodiment provides a method for preparing nano-calcium carbonate for electronic adhesives, including the following steps: S1. Dilute the 15% calcium hydroxide slurry with deionized water, sieve it through a 200-mesh nylon sieve to remove impurities, and obtain a lime milk dilution with a calcium hydroxide concentration of 8%. Adjust the pH to 11.5 with a 10% sodium hydroxide aqueous solution, heat it to 28℃ and keep it at a constant temperature for later use. S2. Pump the diluted lime slurry into the carbonization reactor, maintaining the pressure inside the reactor at 0.05 MPa. Add a composite crystal form regulating dispersant, the amount of which is 1.2% of the dry weight of calcium hydroxide in the diluted lime slurry. Perform two-stage carbonization under stirring at 400 r / min: the first stage introduces carbon dioxide gas with a purity ≥99.9% at a flow rate of 0.3 m / s. 3 The ventilation rate was set at 28°C for 25 minutes per hour until the slurry pH dropped to 8.5; in the second stage, the ventilation rate was increased to 0.5 m / s. 3 / h, cool down to 22℃, continue carbonation until the pH of the slurry drops to 6.5, stop aeration and continue constant temperature aging for 20min to obtain nano calcium carbonate slurry; S3. The nano-calcium carbonate slurry is dehydrated by plate and frame filter press at a pressure of 0.5 MPa to obtain a filter cake with a moisture content of ≤40%. The filter cake is then dried in a flash dryer at an inlet temperature of 260℃ and an outlet temperature of ≤105℃ for 20 seconds. The powder is then pulverized using an air jet mill at a classifier speed of 2000 r / min to obtain nano-calcium carbonate dry powder with an average particle size of 40 nm and a moisture content of ≤0.5%. S4. Place the nano-calcium carbonate dry powder in a radio frequency plasma treatment device for radio frequency plasma surface activation modification treatment. The treatment frequency is 13.56MHz, the power is 150W, and a mixture of nitrogen and oxygen is introduced. The volume ratio of the mixed gas is nitrogen:oxygen = 85:15. The chamber pressure is controlled at 50Pa and the treatment time is 8min. S5. Disperse the activated nano-calcium carbonate dry powder in deionized water to prepare a slurry with a solid content of 15%, and heat it to 60℃. First coating: Add 1.5% zinc stearate by dry weight of nano calcium carbonate, and stir at 500 r / min for 40 min. Second coating: Add 0.5% KH-550 by dry weight of nano-calcium carbonate and stir at 400 r / min for 20 min; then add 2.0% reactive hyperbranching modifier by dry weight of nano-calcium carbonate, heat to 70℃, stir at 600 r / min for 60 min, and simultaneously evacuate to -0.06 MPa. The reactive hyperbranching modifier is pre-dissolved in a mixed solvent of ethanol and water in a volume ratio of 1:1, and then slowly added dropwise to prepare a 15% mass fraction solution. S6. Under the same conditions as S3, the modified slurry was sequentially dehydrated, dried, pulverized, and classified to obtain an average particle size of 40 nm and a specific surface area of ​​26.8 m². 2 / g, nano calcium carbonate for electronic adhesives with a purity ≥99.0%.

[0030] The raw materials for preparing the composite crystal form regulating dispersant, by weight, include: 20 parts L-aspartic acid, 15 parts trisodium citrate dihydrate, 20 parts dodecyl dimethyl betaine, and 350 parts deionized water.

[0031] The preparation method of the composite crystal form regulating dispersant is as follows: Deionized water is heated to 50°C, and L-aspartic acid and trisodium citrate dihydrate are added under nitrogen protection. The mixture is stirred at 250 r / min for 20 min. The temperature is maintained at 50°C, and dodecyl dimethyl betaine is added. The mixture is stirred at 500 r / min for 30 min to obtain the composite crystal form regulating dispersant.

[0032] The raw materials for preparing the reactive hyperbranching modifier, by weight, include: 40 parts of amino-terminated hyperbranched polysiloxane, 15 parts of maleic anhydride, 12 parts of 3,3,3-trifluoropropyltrimethoxysilane, 0.2 parts of dibutyltin dilaurate, and 80 parts of anhydrous ethanol; the number average molecular weight of the amino-terminated hyperbranched polysiloxane is 2000 g / mol, and the degree of branching is 0.50.

[0033] The preparation method of reactive hyperbranching modifier includes the following steps: (1) Under nitrogen protection, the terminal amino hyperbranched polysiloxane was dissolved in anhydrous ethanol, heated to 60°C, and stirred at 200 r / min until completely dissolved. Then maleic anhydride was added, the system temperature was maintained at 60°C, and the reaction was stirred for 2 h. (2) Add 3,3,3-trifluoropropyltrimethoxysilane and dibutyltin dilaurate to the reaction solution obtained in step (1), heat to 75°C, and reflux for 4 hours; after the reaction is completed, remove ethanol by vacuum distillation at 50°C and vacuum degree -0.085MPa until no ethanol flows out of the system, and obtain the reactive hyperbranching modifier.

[0034] Example 2: This embodiment provides a method for preparing nano-calcium carbonate for electronic adhesives, including the following steps: S1. Dilute the 18% calcium hydroxide slurry with deionized water, sieve it through a 200-mesh nylon sieve to remove impurities, and obtain a lime milk dilution with a calcium hydroxide concentration of 10%. Adjust the pH to 12.5 with a 20% sodium hydroxide aqueous solution, heat it to 32℃ and keep it at a constant temperature for later use. S2. Pump the diluted lime slurry into the carbonization reactor, maintaining the pressure inside the reactor at 0.15 MPa. Add a composite crystal form regulating dispersant, the amount of which is 1.8% of the dry weight of calcium hydroxide in the diluted lime slurry. Perform two-stage carbonization under stirring at 500 r / min: the first stage introduces carbon dioxide gas with a purity ≥99.9% at a flow rate of 0.4 m / s. 3 The ventilation rate was set at 32℃ for 35 minutes per hour until the slurry pH dropped to 9.0; in the second stage, the ventilation rate was increased to 0.7 m / s. 3 / h, cool down to 26℃, continue carbonation until the pH of the slurry drops to 7.0, stop aeration and continue constant temperature aging for 30 minutes to obtain nano calcium carbonate slurry; S3. The nano-calcium carbonate slurry is dehydrated by plate and frame filter press at a pressure of 0.7 MPa to obtain a filter cake with a moisture content of ≤40%. The filter cake is then dried in a flash dryer at an inlet temperature of 300℃ and an outlet temperature of ≤105℃ for 30 seconds. The powder is then pulverized using an air jet mill at a classifier speed of 2500 r / min to obtain nano-calcium carbonate dry powder with an average particle size of 60 nm and a moisture content of ≤0.5%. S4. Place the nano-calcium carbonate dry powder in a radio frequency plasma treatment device for radio frequency plasma surface activation modification treatment. The treatment frequency is 13.56MHz, the power is 250W, a mixture of nitrogen and oxygen is introduced, the volume ratio of the mixture is nitrogen:oxygen = 95:5, the chamber pressure is controlled at 100Pa, and the treatment time is 12min. S5. Disperse the activated nano-calcium carbonate dry powder in deionized water to prepare a slurry with a solid content of 20%, and heat it to 70℃. First coating: Add 2.5% zinc stearate by dry weight of nano calcium carbonate, and stir at 600 r / min for 60 min. Second coating: Add 1.0% by weight of KH-550 of nano-calcium carbonate dry basis, and stir at 500 r / min for 30 min; then add 3.0% by weight of reactive hyperbranching modifier of nano-calcium carbonate dry basis, heat to 80℃, stir at 800 r / min for 90 min, and simultaneously evacuate to -0.08 MPa; The reactive hyperbranching modifier is pre-dissolved in a mixed solvent of ethanol and water in a volume ratio of 1:1, and then slowly added dropwise to prepare a 20% mass fraction solution. S6. Under the same conditions as S3, the modified slurry was sequentially dehydrated, dried, pulverized, and classified to obtain an average particle size of 60 nm and a specific surface area of ​​29.2 m². 2 / g, nano calcium carbonate for electronic adhesives with a purity ≥99.0%.

[0035] The raw materials for preparing the composite crystal form regulating dispersant, by weight, include: 30 parts L-aspartic acid, 25 parts trisodium citrate dihydrate, 30 parts dodecyl dimethyl betaine, and 450 parts deionized water.

[0036] The preparation method of the composite crystal form regulating dispersant is as follows: Deionized water is heated to 60℃, and L-aspartic acid and trisodium citrate dihydrate are added under nitrogen protection. The mixture is stirred at 350 r / min for 30 min. The temperature is maintained at 60℃, and dodecyl dimethyl betaine is added. The mixture is stirred at 600 r / min for 40 min to obtain the composite crystal form regulating dispersant.

[0037] The raw materials for preparing the reactive hyperbranching modifier, by weight, include: 50 parts of amino-terminated hyperbranched polysiloxane, 20 parts of maleic anhydride, 18 parts of 3,3,3-trifluoropropyltrimethoxysilane, 0.5 parts of dibutyltin dilaurate, and 100 parts of anhydrous ethanol; the number average molecular weight of the amino-terminated hyperbranched polysiloxane is 3000 g / mol, and the degree of branching is 0.60.

[0038] The preparation method of reactive hyperbranching modifier includes the following steps: (1) Under nitrogen protection, the terminal amino hyperbranched polysiloxane was dissolved in anhydrous ethanol, heated to 70°C, and stirred at 300 r / min until completely dissolved. Then maleic anhydride was added, the system temperature was maintained at 70°C, and the reaction was stirred for 3 h. (2) Add 3,3,3-trifluoropropyltrimethoxysilane and dibutyltin dilaurate to the reaction solution obtained in step (1), heat to 85°C, and reflux for 6 hours; after the reaction is completed, remove ethanol by vacuum distillation at 60°C and vacuum degree -0.095MPa until no ethanol flows out of the system, and obtain the reactive hyperbranching modifier.

[0039] Example 3: This embodiment provides a method for preparing nano-calcium carbonate for electronic adhesives, including the following steps: S1. Dilute the 16% calcium hydroxide slurry with deionized water, sieve it through a 200-mesh nylon sieve to remove impurities, and obtain a lime milk dilution with a calcium hydroxide concentration of 9%. Adjust the pH to 12.0 with a 15% sodium hydroxide aqueous solution, heat it to 30℃ and keep it at a constant temperature for later use. S2. Pump the diluted lime slurry into the carbonization reactor, maintaining the pressure inside the reactor at 0.1 MPa. Add a composite crystal form regulating dispersant, the amount of which is 1.5% of the dry weight of calcium hydroxide in the diluted lime slurry. Perform two-stage carbonization under stirring at 450 r / min: the first stage introduces carbon dioxide gas with a purity ≥99.9% at a flow rate of 0.35 m / s. 3 The ventilation rate is maintained at 30℃ for 30 minutes per hour until the slurry pH drops to 8.8; in the second stage, the ventilation rate is increased to 0.6 m / s. 3 / h, cool down to 24℃, continue carbonation until the pH of the slurry drops to 6.8, stop aeration and continue constant temperature aging for 25min to obtain nano calcium carbonate slurry; S3. The nano-calcium carbonate slurry is dehydrated by plate and frame filter press at a pressure of 0.6 MPa to obtain a filter cake with a moisture content of ≤40%. The filter cake is then dried in a flash dryer at an inlet temperature of 280℃ and an outlet temperature of ≤105℃ for 25 seconds. The powder is then pulverized using an air jet mill at a classifier speed of 2300 r / min to obtain nano-calcium carbonate dry powder with an average particle size of 55 nm and a moisture content of ≤0.5%. S4. Place the nano-calcium carbonate dry powder in a radio frequency plasma treatment device for radio frequency plasma surface activation modification treatment. The treatment frequency is 13.56MHz, the power is 200W, and a mixture of nitrogen and oxygen is introduced. The volume ratio of the mixed gas is nitrogen:oxygen = 90:10. The chamber pressure is controlled at 70Pa and the treatment time is 10min. S5. Disperse the activated nano-calcium carbonate dry powder in deionized water to prepare a slurry with a solid content of 17%, and heat it to 65℃. First coating: Add 2.0% zinc stearate by dry weight of nano calcium carbonate, and stir at 550 r / min for 50 min. Second coating: Add 0.8% KH-550 by dry weight of nano-calcium carbonate and stir at 450 r / min for 25 min; then add 2.5% reactive hyperbranching modifier by dry weight of nano-calcium carbonate, heat to 75℃, stir at 700 r / min for 75 min, and simultaneously evacuate to -0.07 MPa. The reactive hyperbranching modifier is pre-dissolved in a mixed solvent of ethanol and water in a volume ratio of 1:1, and then slowly added dropwise to prepare a solution with a mass fraction of 17%. S6. Under the same conditions as S3, the modified slurry was sequentially dehydrated, dried, pulverized, and classified to obtain an average particle size of 50 nm and a specific surface area of ​​31.5 m². 2 / g, nano calcium carbonate for electronic adhesives with a purity ≥99.0%.

[0040] The raw materials for preparing the composite crystal form regulating dispersant, by weight, include: 25 parts L-aspartic acid, 20 parts trisodium citrate dihydrate, 25 parts dodecyl dimethyl betaine, and 400 parts deionized water.

[0041] The preparation method of the composite crystal form regulating dispersant is as follows: Deionized water is heated to 55℃, and L-aspartic acid and trisodium citrate dihydrate are added under nitrogen protection. The mixture is stirred at 300 r / min for 25 min. The temperature is maintained at 55℃, and dodecyl dimethyl betaine is added. The mixture is stirred at 550 r / min for 35 min to obtain the composite crystal form regulating dispersant.

[0042] The raw materials for preparing the reactive hyperbranching modifier, by weight, include: 45 parts of amino-terminated hyperbranched polysiloxane, 18 parts of maleic anhydride, 15 parts of 3,3,3-trifluoropropyltrimethoxysilane, 0.3 parts of dibutyltin dilaurate, and 90 parts of anhydrous ethanol; the number average molecular weight of the amino-terminated hyperbranched polysiloxane is 2500 g / mol, and the degree of branching is 0.55.

[0043] The preparation method of reactive hyperbranching modifier includes the following steps: (1) Under nitrogen protection, the terminal amino hyperbranched polysiloxane was dissolved in anhydrous ethanol, heated to 65°C, and stirred at 250 r / min until completely dissolved. Then maleic anhydride was added, the system temperature was maintained at 65°C, and the reaction was stirred for 2.5 h. (2) Add 3,3,3-trifluoropropyltrimethoxysilane and dibutyltin dilaurate to the reaction solution obtained in step (1), heat to 80°C, and reflux for 5 hours; after the reaction is completed, remove ethanol by vacuum distillation at 55°C and vacuum degree -0.09MPa until no ethanol flows out of the system, and obtain the reactive hyperbranching modifier.

[0044] Comparative Example 1: A method for preparing nano-calcium carbonate for electronic adhesives, which differs from Example 3 only in that the composite crystal form regulating dispersant is replaced with an equal mass of aspartic acid.

[0045] Comparative Example 2: A method for preparing nano-calcium carbonate for electronic adhesives, which differs from Example 3 only in that no reactive hyperbranching modifier is added.

[0046] Comparative Example 3: A method for preparing nano-calcium carbonate for electronic adhesives differs from Example 3 only in that the reactive hyperbranching modifier is replaced with an equal mass of KH-550.

[0047] Comparative Example 4: A method for preparing nano-calcium carbonate for electronic adhesives, which differs from Example 3 only in that zinc stearate is not added.

[0048] Comparative Example 5: A method for preparing nano-calcium carbonate for electronic adhesives differs from Example 3 only in that the two coatings are replaced with a single coating. Specifically, in step S5, the plasma-activated nano-calcium carbonate dry powder is redispersed in deionized water to prepare a slurry with a solid content of 17%, and heated to 65°C. Simultaneously, 2.0% by weight of zinc stearate, 0.8% of KH-550, and 2.5% of reactive hyperbranching modifier (pre-dissolved in a 1:1 volume ratio of ethanol and water to prepare a 17% solution) of nano-calcium carbonate dry weight are added. The mixture is stirred at 700 r / min for 75 min, while a vacuum is drawn to -0.07 MPa to allow the three modifiers to react simultaneously with the surface of the calcium carbonate.

[0049] Comparative Example 6: A method for preparing nano-calcium carbonate for electronic adhesives differs from Example 3 only in that plasma treatment is not performed before surface modification, i.e., step S4 is omitted.

[0050] Comparative Example 7: A method for preparing nano-calcium carbonate for electronic adhesives differs from Example 3 only in that: no trisodium citrate dihydrate is added during the preparation of the composite crystal form regulating dispersant, and only L-aspartic acid and dodecyl dimethyl betaine are contained.

[0051] The nano-calcium carbonate obtained in Examples 1-3 and Comparative Examples 1-7 were subjected to performance testing, and their application performance in electronic silicone adhesives was also tested. Specific testing items and methods are as follows: (I) Performance Testing of Nano-Calcium Carbonate Particle size and distribution: Referring to the "Analytical Methods for Calcium Carbonate" (GB / T 19281-2014), the particle size D corresponding to the cumulative particle size distribution of 50% and 97% was determined using a laser particle size analyzer (Malvin Mastersizer 3000). 50 D 97 .

[0052] Specific surface area: According to the "Determination of Specific Surface Area of ​​Solid Substances by Gas Adsorption BET Method" (GB / T 19587-2017), the nitrogen adsorption method was adopted and the specific surface area and pore size were determined using a McMurray Ticco ASAP 2460 fully automated specific surface area and pore size analyzer.

[0053] Crystal form: Phase analysis was performed using an X-ray diffractometer (Brook D8 Advance), and the proportion of cubic crystal forms in the calcite phase was calculated using the Rietveld full-spectrum fitting method.

[0054] Oil absorption value: determined by the dibutyl phthalate absorption method according to the "Analytical Methods for Calcium Carbonate" (GB / T 19281-2014), with units of g / 100g.

[0055] Activity level: Determined by aqueous sedimentation method according to the "Analytical Methods for Calcium Carbonate" (GB / T 19281-2014).

[0056] pH value: According to the "Analytical Methods for Calcium Carbonate" (GB / T 19281-2014), a 10% aqueous suspension was prepared and the pH value was measured using a pH meter.

[0057] Moisture content: determined by constant weight method at 105℃, referring to the "Analytical Methods for Calcium Carbonate" (GB / T 19281-2014).

[0058] (II) Performance testing of electronic adhesive applications Nano-calcium carbonate was added to an electronic silicone adhesive formulation at a ratio of 75 parts (based on 100 parts α-hydro-ω-hydroxy-polydimethylsiloxane) to prepare the electronic adhesive, and its performance was tested. The electronic silicone adhesive formulation was as follows: 100 parts α-hydro-ω-hydroxy-polydimethylsiloxane, 15 parts dimethyl silicone oil, 75 parts nano-calcium carbonate, 2 parts KH-550, 8 parts methyl tributanone oxime silane, and 0.6 parts dibutyltin dilaurate. The preparation method was as follows: α-hydro-ω-hydroxy-polydimethylsiloxane, dimethyl silicone oil, and nano-calcium carbonate were added to a planetary mixer and dehydrated at 120℃ and a vacuum degree of -0.095MPa for 2 hours; the temperature was then lowered to below 40℃, and a crosslinking agent, coupling agent, and catalyst were added. The mixture was then stirred under vacuum for 30 minutes and discharged.

[0059] Dispersibility: The prepared electronic adhesive was observed under an optical microscope and scored according to the uniformity of dispersion, with 10 points being the best and 0 points being the worst.

[0060] Thixotropic index: Refer to "Determination of viscosity of adhesives" (GB / T 2794-2013), use a rotational viscometer (Brookfield DV2T) to measure the viscosity of the adhesive at 6 r / min and 60 r / min, and calculate the ratio of the two, which is the thixotropic index.

[0061] Tensile strength and elongation at break: Referring to the "Determination of tensile stress-strain properties of vulcanized rubber or thermoplastic rubber" (GB / T 528-2009), the rubber compound was made into a type I dumbbell-shaped specimen and tested at a tensile rate of 500 mm / min.

[0062] Shear strength: Refer to "Determination of tensile shear strength of adhesives (rigid material to rigid material)" (GB / T7124-2008), aluminum-aluminum lap joint specimens were used. After curing for 7 days under standard conditions, tensile shear tests were conducted at a test rate of 100 mm / min.

[0063] High temperature resistance: Refer to "Organic silicone sealant for electrical appliances" (HG / T 5379-2018), place the cured tensile test specimen in an oven at 200℃ for 500h, take it out and cool it, test the tensile strength, and calculate the tensile strength retention rate after aging. The calculation formula is: retention rate = (tensile strength after aging / tensile strength before aging) × 100%.

[0064] Storage stability: The prepared sealant was sealed in a polyethylene plastic tube and placed in an oven at 70°C for accelerated aging for 7 days. The viscosity before and after aging was measured using a rotational viscometer, and the viscosity change rate was calculated. The calculation formula is: Change rate = (viscosity after aging - viscosity before aging) / viscosity before aging × 100%.

[0065] The results are shown in Tables 2 and 3.

[0066] Table 2. Test results of bulk properties of nano-calcium carbonate

[0067] Table 3. Performance test results of electronic adhesive application

[0068] Using Example 3 as the control group, the performance differences and causes of Comparative Examples 1-7 are analyzed as follows: Comparative Example 1 replaced the complex crystal form regulating dispersant with a single L-aspartic acid, D 50 It is 72nm (a 50.0% increase compared to Example 3), D 97The nanometer diameter was 135 nm (an increase of 58.8%), the proportion of cubic crystal form decreased to 85% (a decrease of 12.4%), the oil absorption value was 28.5 g / 100 g (an increase of 21.3%), and the activation degree decreased to 89.5% (a decrease of 9.1%). In terms of application performance, the dispersibility score was 7.0, the thixotropic index decreased to 3.6 (a decrease of 34.5%), the tensile strength decreased to 1.55 MPa (a decrease of 33.2%), the elongation at break decreased to 355% (a decrease of 32.4%), the shear strength decreased to 1.78 MPa (a decrease of 27.3%), and the viscosity change rate increased to 19.5% (an increase of 236.2%). Although L-aspartic acid alone has a certain crystal form regulation effect, it lacks the synergistic chelation of trisodium citrate dihydrate and the electrostatic-steric dual stability of dodecyl dimethyl betaine, which leads to a wider particle size distribution and a decrease in crystal form regularity, thus affecting its application performance. This proves that the ternary compound of composite crystal form regulating dispersants is irreplaceable.

[0069] Comparative Example 2, without the addition of reactive hyperbranching modifier, showed an increase in oil absorption value from 23.5 g / 100 g to 30.5 g / 100 g (an increase of 29.8%), a decrease in activation degree to 86.8% (a decrease of 11.9%), a dispersibility score of 7.8, a decrease in thixotropic index to 3.4 (a decrease of 38.2%), a decrease in tensile strength to 1.75 MPa (a decrease of 24.6%), a decrease in elongation at break to 395% (a decrease of 24.8%), a decrease in shear strength to 1.88 MPa (a decrease of 23.3%), a decrease in high-temperature strength retention to 73.5% (a decrease of 19.7%), and an increase in viscosity change rate to 18.5% (an increase of 219.0%). This demonstrates that the lack of dense coating of hyperbranched structures and chemical bonding of reactive groups leads to incomplete hydrophobic modification of the filler surface, susceptibility to secondary agglomeration in silicone oil, a significant decrease in interfacial bonding at high temperatures, and severely deteriorated storage stability.

[0070] In Comparative Example 3, the reactive hyperbranching modifier was replaced with an equal mass of KH-550. The oil absorption value increased to 28.2 g / 100 g (an increase of 20.0%), the dispersibility score decreased to 8.2, the thixotropic index decreased to 4.0 (a decrease of 27.3%), the tensile strength decreased to 1.98 MPa (a decrease of 14.7%), the elongation at break decreased to 445% (a decrease of 15.2%), the shear strength decreased to 2.08 MPa (a decrease of 15.1%), the high-temperature strength retention decreased to 80.5% (a decrease of 12.0%), and the viscosity change rate increased to 13.5% (an increase of 132.8%). The linear silane coupling agent exhibited weak interfacial bonding and lacked the steric hindrance of a hyperbranched structure and the hydrophobic effect of the fluorinated segments, failing to form a dense protective layer. This resulted in poor dispersion stability and anti-settling properties of the filler in the rubber compound, leading to significantly inferior application performance compared to Example 3.

[0071] Comparative Example 4, without the addition of zinc stearate, showed a significant increase in oil absorption value from 23.5 g / 100 g to 29.5 g / 100 g (an increase of 25.5%), while the activation degree decreased to 76.5% (a decrease of 22.3%). 50 Increased to 51nm (6.3% increase), D 97 The particle size increased to 90 nm (an increase of 5.9%), resulting in a decrease in dispersibility score to 6.5, thixotropic index to 2.8 (a decrease of 49.1%), tensile strength to 1.45 MPa (a decrease of 37.5%), elongation at break to 335% (a decrease of 36.2%), shear strength to 1.58 MPa (a decrease of 35.5%), and viscosity change rate to 20.5% (an increase of 253.4%). The absence of zinc stearate prevented the formation of a basic hydrophobic layer. When subsequent modifiers reacted directly with inorganic surfaces with excessively high surface energy, the modification effect was significantly reduced, filler agglomeration occurred severely, and both mechanical properties and storage stability deteriorated significantly.

[0072] Comparative Example 5 changed the two-layer coating to a single-layer coating, D 50 Increased to 56nm (an increase of 16.7%), D 97 The size was increased to 102 nm (an increase of 20.0%), while the BET specific surface area decreased to 28.6 μm. 2 / g (a decrease of 9.2%), oil absorption value increased to 26.8g / 100g (an increase of 14.0%), dispersibility score decreased to 8.0, thixotropic index decreased to 3.8 (a decrease of 30.9%), tensile strength decreased to 1.88MPa (a decrease of 19.0%), elongation at break decreased to 425% (a decrease of 19.0%), shear strength decreased to 2.02MPa (a decrease of 17.6%), and viscosity change rate increased to 10.5% (an increase of 81.0%). The simultaneous addition of various modifiers leads to competitive adsorption, affecting the uniformity and density of the coating layer, resulting in a wider particle size distribution and decreased interfacial bonding force, demonstrating the necessity of stepwise coating for constructing an ordered multilayer structure.

[0073] Comparative Example 6, without plasma treatment before surface modification, showed an increase in oil absorption value to 27.5 g / 100 g (an increase of 17.0%), a decrease in dispersibility score to 8.6, a decrease in thixotropic index to 4.6 (a decrease of 16.4%), a decrease in tensile strength to 2.05 MPa (a decrease of 11.6%), a decrease in elongation at break to 465% (a decrease of 11.4%), a decrease in shear strength to 2.18 MPa (a decrease of 11.0%), and an increase in viscosity change rate to 9.5% (an increase of 63.8%). Due to insufficient density of active sites on the particle surface, the grafting rate of the modifier decreased, and the density of the coating layer decreased, leading to a decrease in interfacial bonding and storage stability. Meanwhile, D... 50The particle size is 49 nm, which is basically the same as in Example 3. Plasma is a surface physicochemical modification that does not change the primary particle size of calcium carbonate. It mainly breaks up soft agglomerates and enhances the activity of surface hydroxyl groups, making the apparent particle size of the powder more uniform.

[0074] Comparative Example 7: No trisodium citrate dihydrate was added during the preparation of the composite crystal form regulating dispersant. 50 Increased to 65nm (an increase of 35.4%), D 97 The nanometer diameter was increased to 125 nm (an increase of 47.1%), the proportion of cubic crystal form decreased to 85% (a decrease of 12.4%), and the BET specific surface area decreased to 25.5 μm. 2 / g (decrease of 19.0%), dispersibility score decreased to 8.2, thixotropic index decreased to 4.2 (decrease of 23.6%), tensile strength decreased to 1.82 MPa (decrease of 21.6%), elongation at break decreased to 405% (decrease of 22.9%), shear strength decreased to 1.98 MPa (decrease of 19.2%), and viscosity change rate increased to 10.2% (increase of 75.9%). Due to the lack of chelation regulation of calcium ions by trisodium citrate dihydrate, calcium carbonate crystal nuclei grew disorderedly, the proportion of cubic crystals decreased significantly, the particle size distribution widened significantly, and application performance declined markedly.

[0075] The above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit it. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for preparing nano-calcium carbonate for electronic adhesives, characterized in that, Includes the following steps: S1. Dilute the calcium hydroxide slurry with deionized water to obtain a lime milk dilution with a calcium hydroxide mass concentration of 8-10%. Adjust the pH to 11.5-12.5, raise the temperature to 28-32℃ and keep it at that temperature. S2. Pump the diluted lime slurry into the carbonization kettle, add a composite crystal form regulating dispersant, and carry out two-stage carbonization under stirring: the first stage introduces high-purity carbon dioxide gas at a flow rate of 0.3~0.4 m / s. 3 At a constant temperature of 28-32℃, the aeration rate is increased to 0.5-0.7 m / h until the slurry pH drops to 8.5-9.

0. In the second stage, the aeration rate is further increased to 0.5-0.7 m / h. 3 / h, cool down to 22~26℃, continue carbonation until the pH of the slurry drops to 6.5~7.0, stop aeration and continue constant temperature aging for 20~30min to obtain nano calcium carbonate slurry; S3. Dehydrate, dry, pulverize, and classify the nano-calcium carbonate slurry to obtain nano-calcium carbonate dry powder. S4. The nano-calcium carbonate dry powder is subjected to radio frequency plasma surface activation modification treatment. S5. Disperse the activated nano-calcium carbonate dry powder in deionized water, and add zinc stearate, γ-aminopropyltriethoxysilane and reactive hyperbranching modifier step by step for surface modification. S6. The modified slurry is dehydrated, dried, pulverized, and classified to obtain the nano-calcium carbonate for electronic adhesive.

2. The method for preparing nano-calcium carbonate for electronic adhesives according to claim 1, characterized in that, The raw materials for preparing the composite crystal form regulating dispersant, by weight, include: 20-30 parts of L-aspartic acid, 15-25 parts of trisodium citrate dihydrate, 20-30 parts of dodecyl dimethyl betaine, and 350-450 parts of deionized water.

3. The method for preparing nano-calcium carbonate for electronic adhesives according to claim 2, characterized in that, The preparation method of the composite crystal form regulating dispersant is as follows: Deionized water is heated to 50~60℃, L-aspartic acid and trisodium citrate dihydrate are added under nitrogen protection, and the mixture is stirred at a speed of 250~350 r / min for 20~30 min; the temperature is maintained at 50~60℃, dodecyl dimethyl betaine is added, and the mixture is stirred at a speed of 500~600 r / min for 30~40 min to obtain the composite crystal form regulating dispersant.

4. The method for preparing nano-calcium carbonate for electronic adhesives according to claim 1, characterized in that, The raw materials for preparing the reactive hyperbranching modifier, by weight, include: 40-50 parts of amino-terminated hyperbranched polysiloxane, 15-20 parts of maleic anhydride, 12-18 parts of 3,3,3-trifluoropropyltrimethoxysilane, 0.2-0.5 parts of dibutyltin dilaurate, and 80-100 parts of anhydrous ethanol.

5. The method for preparing nano-calcium carbonate for electronic adhesives according to claim 4, characterized in that, The preparation method of the reactive hyperbranching modifier includes the following steps: (1) Under nitrogen protection, the terminal amino hyperbranched polysiloxane was dissolved in anhydrous ethanol, heated to 60~70℃, and stirred at 200~300r / min until completely dissolved. Then maleic anhydride was added, the system temperature was maintained at 60~70℃, and the reaction was stirred for 2~3h. (2) Add 3,3,3-trifluoropropyltrimethoxysilane and dibutyltin dilaurate to the reaction solution obtained in step (1), heat to 75~85℃, and reflux for 4~6h; after the reaction is completed, remove ethanol by vacuum distillation at 50~60℃ and vacuum degree -0.085~-0.095MPa to obtain reactive hyperbranching modifier.

6. The method for preparing nano-calcium carbonate for electronic adhesives according to claim 1, characterized in that, In step S2, the amount of the composite crystal form regulating dispersant added is 1.2~1.8% of the dry weight of calcium hydroxide in the lime slurry dilution; the stirring speed in the two-stage carbonization process is 400~500 r / min; and the aeration time in the first stage carbonization is 25~35 min.

7. The method for preparing nano-calcium carbonate for electronic adhesives according to claim 1, characterized in that, In step S3, dewatering is performed using a plate and frame filter press at a pressure of 0.5~0.7MPa to obtain a filter cake with a moisture content of ≤40%; drying is performed using a flash dryer with an inlet temperature of 260~300℃, an outlet temperature of ≤105℃, and a drying time of 20~30s; pulverization is performed using an air jet mill with a classifying wheel speed of 2000~2500r / min.

8. The method for preparing nano-calcium carbonate for electronic adhesives according to claim 1, characterized in that, In step S4, the frequency of the radio frequency plasma surface activation modification treatment is 13.56MHz, the power is 150~250W, a mixture of nitrogen and oxygen is introduced, the volume ratio of the mixture is nitrogen:oxygen = (85~95):(15~5), the cavity pressure is controlled at 50~100Pa, and the treatment time is 8~12min.

9. The method for preparing nano-calcium carbonate for electronic adhesives according to claim 1, characterized in that, In step S5, the stepwise surface modification includes: The plasma-activated nano-calcium carbonate powder was dispersed in deionized water to prepare a slurry with a solid content of 15-20%, and then heated to 60-70℃. First coating: Add 1.5~2.5% zinc stearate by dry weight of nano calcium carbonate, and stir at 500~600 r / min for 40~60 min; Second coating: Add 0.5-1.0% (by dry weight) of γ-aminopropyltriethoxysilane to nano-calcium carbonate and stir at 400-500 r / min for 20-30 min; then add 2.0-3.0% (by dry weight) of reactive hyperbranching modifier to nano-calcium carbonate, heat to 70-80℃, stir at 600-800 r / min for 60-90 min, and simultaneously apply vacuum to -0.06 to -0.08 MPa; The reactive hyperbranching modifier is pre-dissolved in a mixed solvent of ethanol and water in a volume ratio of 1:1, and then slowly added dropwise to prepare a solution with a mass fraction of 15-20%.

10. The method for preparing nano-calcium carbonate for electronic adhesives according to claim 7, characterized in that, The dehydration, drying, pulverization, and classification conditions of the modified slurry in step S6 are the same as those described in step S3; the average particle size of the nano-calcium carbonate used in the electronic adhesive is 40~60nm, and the specific surface area is 26~32m². 2 / g, purity ≥99.0%.

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