Wet surface modification preparation method of active superfine calcium carbonate

Abstract

The invention relates to a wet surface modification preparation method of active superfine calcium carbonate, which comprises the following steps: preparing slurry: mixing calcium carbonate powder with water to obtain the slurry; pre-dispersion treatment: adding a pH regulator, adjusting the pH of the slurry system to 7-9, adding a dispersing agent, and stirring and mixing to obtain a uniform emulsion; surface modification: controlling the temperature of the emulsion to be 20-100 DEG C, adding an activating agent, and stirring for 20-90 minutes to obtain a modified substance; and post-treatment: filtering the modified substance, and drying to obtain the active superfine calcium carbonate product. The method has the effect of improving the quality and dispersity of the calcium carbonate product.

Description

Technical Field

[0001] This application relates to the field of calcium carbonate, and in particular to a wet surface modification method for preparing active ultrafine calcium carbonate. Background Technology

[0002] Calcium carbonate is a widely used inorganic non-metallic material. In particular, ultrafine calcium carbonate products are widely used in various fields such as rubber, plastics, coatings, inks, papermaking, food, and medicine due to their easy availability of raw materials, low price, high whiteness, excellent performance, low pollution during production, and good filling and processing properties. The development and utilization of various functional active ultrafine calcium carbonate products is currently a hot topic in the calcium carbonate industry.

[0003] In the wet modification of ultrafine calcium carbonate, due to the small particle size, large specific surface area, and high surface energy of calcium carbonate, the calcium carbonate particles easily agglomerate and agglomerate into large particles in the slurry. If calcium carbonate particles adsorb and agglomerate in the slurry, the strong mutual adsorption forces between the agglomerated particles make it difficult to separate them in subsequent processing. As a result, the prepared activated ultrafine calcium carbonate product will contain agglomerated pseudo-large particles. Under the same conditions, the higher the slurry concentration, the more obvious the agglomeration phenomenon. The smaller the prepared calcium carbonate particles, the more serious the agglomeration phenomenon. The presence of agglomerated particles not only damages the properties of the ultrafine calcium carbonate product, but also makes subsequent processing difficult, especially adversely affecting the activation and modification of ultrafine calcium carbonate.

[0004] Currently, the production technology of ultrafine calcium carbonate is developing rapidly, and the variety and output of activated ultrafine calcium carbonate products are constantly increasing. In particular, various activated nano calcium carbonate products have been and are being developed and utilized. However, many activated ultrafine calcium carbonate products, especially activated nano calcium carbonate products, have more or less agglomeration, which seriously affects the quality of the products, their compatibility in organic matrices, and their application performance. Summary of the Invention

[0005] To improve the agglomeration phenomenon of activated ultrafine calcium carbonate, this application provides a wet surface modification preparation method for activated ultrafine calcium carbonate.

[0006] The wet surface modification method for preparing active ultrafine calcium carbonate provided in this application adopts the following technical solution: A wet surface modification method for preparing activated ultrafine calcium carbonate includes the following steps: Preparation of slurry: Mix calcium carbonate powder with water to obtain slurry; Pre-dispersion treatment: Add pH adjuster to adjust the pH of the slurry system to 7-9, then add dispersant and stir to obtain a uniform emulsion; Surface modification: Control the emulsion temperature to 20-100℃, add activator and stir for 20-90 min to obtain the modified product; Post-processing: The modified material is filtered and dried to obtain the active ultrafine calcium carbonate product.

[0007] By adopting the above technical solution, calcium carbonate powder is modified using organic and inorganic dispersants. The organic dispersant adsorbs onto the surface of calcium carbonate through polar groups in its molecules, while the non-polar groups extend into the medium, forming a steric hindrance or electrostatic repulsion effect. The adsorption layer of the organic dispersant can form a "physical barrier" between particles, reducing the binding of particles after collision and enabling the particles to be uniformly dispersed in the medium. The original surface of calcium carbonate is usually weakly negatively charged, and the inorganic dispersant can increase the surface negative charge density, making it difficult for particles to agglomerate due to electrostatic repulsion. This reduces the hydrogen bonding between calcium carbonate particles, making the particles easier to disperse under stirring or shearing forces, and improving the stability of the system after dispersion. The original surface of calcium carbonate is hydrophilic, and the hydrophobic groups of the activator can replace the surface hydroxyl groups, making the surface of calcium carbonate hydrophobic, improving its compatibility with the organic phase, and resulting in more uniform dispersion. The treated nano-calcium carbonate can be uniformly dispersed in the system, reducing the occurrence of agglomeration, thereby improving product quality.

[0008] Preferably, in the pre-dispersion process, the linear velocity during stirring and mixing is 8-12 m / s.

[0009] By adopting the above technical solution, and preferably in the pre-dispersion treatment, the linear velocity during stirring and mixing is within the above range, which can further improve the dispersion performance and compatibility of the prepared calcium carbonate powder product.

[0010] Preferably, the calcium carbonate powder has a particle size ≤100nm, the slurry has a weight concentration of 5-40%, the pH adjuster includes any one of tartaric acid, oxalic acid, or phosphoric acid, the inorganic dispersant includes any one or a mixture of sodium aluminate, sodium phosphate, and sodium pyrophosphate, the organic dispersant includes any one of sodium polyacrylate or sodium hexadecyl diphenyl ether disulfonate, and the modifying activator includes any one or a mixture of lauric acid, rosin acid, and stearic acid.

[0011] By adopting the above technical solutions and using tartaric acid, oxalic acid, or phosphoric acid as pH adjusters, not only can the reaction environment be optimized by regulating the acidity and alkalinity of the system, but it can also have a specific interaction with the surface of calcium carbonate, thereby improving its surface properties, dispersibility, and compatibility with subsequent modifiers. The above-mentioned inorganic dispersants adjust the charge and form a protective layer on the surface of calcium carbonate by adsorbing onto it, reducing agglomeration and improving dispersibility. The organic dispersants improve the dispersibility of calcium carbonate in aqueous systems through the electrostatic adsorption of anionic groups, thereby improving the flowability, uniformity, and processing performance of calcium carbonate in slurries, coatings, plastics, and other systems. The modifiers and activators improve the dispersibility of calcium carbonate in organic systems through hydrophobic modification.

[0012] Preferably, the inorganic dispersant is used at 0.5-12% of the weight of the calcium carbonate powder, the organic dispersant is used at 11-13% of the weight of the calcium carbonate powder, and the modifying activator is used at 1-8% of the weight of the calcium carbonate powder.

[0013] By adopting the above technical solution, and preferably within the above-defined ranges for the addition of inorganic dispersant, organic dispersant, and modified activator, the stability of the prepared active calcium carbonate can be further improved.

[0014] Preferably, the raw materials for preparing the nano-calcium carbonate include saponification liquid, isopropanol, kerosene, calcium chloride, and calcium carbonate.

[0015] By adopting the above technical solution and using the above materials as a ternary system to prepare nano-calcium carbonate, the stability of nano-calcium carbonate can be further improved. The prepared calcium carbonate also has a large specific surface area. When it is subsequently combined with organic and inorganic dispersants, the grafting effect can be further improved, thereby enhancing the dispersion performance of active calcium carbonate.

[0016] Preferably, the nano-calcium carbonate is prepared by the following method: After mixing saponification solution, isopropanol, kerosene and calcium chloride, a microemulsion was obtained by stirring. After removing the oil phase, sodium carbonate solution was added to obtain a complex. The mixture was stirred and reacted. After standing, the emulsion was broken with ethanol, washed and dried to obtain nano-calcium carbonate powder.

[0017] By adopting the above technical solution, using the reverse microemulsion method, with saponification liquid as the surfactant, isopropanol as the co-surfactant, kerosene as the oil phase, and calcium chloride solution and calcium carbonate solution as the aqueous phase, nano-calcium carbonate is prepared, which has good specific surface area, thin thickness and mechanical properties.

[0018] Preferably, the saponification liquid is prepared by the following method: 2-Ethylhexyl phosphate mono-2-ethylhexyl ester was mixed with sodium hydroxide to obtain a saponified solution.

[0019] By adopting the above technical solution, 2-ethylhexyl phosphate mono-2-ethylhexyl ester after the saponification process has the properties of anionic surfactant.

[0020] Preferably, the volume ratio of the saponification liquid to isopropanol is (1.5-1.7):1.

[0021] By adopting the above technical solution, and preferably within the above-mentioned range the volume ratio between the saponification liquid and isopropanol, the prepared calcium carbonate has good binding performance, thereby further improving the overall stability of the prepared nano-calcium carbonate.

[0022] Preferably, the concentration of calcium chloride in the complex is 0.42-0.44 mol / L, and the concentration of sodium carbonate in the complex is 0.42-0.44 mol / L.

[0023] By adopting the above technical solution, and preferably with the concentrations of calcium chloride and calcium carbonate in the system within the above range, the prepared nano-calcium carbonate has a uniform particle size, thereby improving the overall stability of the nano-calcium carbonate.

[0024] Preferably, the stirring speed of the composite is 1200-1400 r / min.

[0025] By adopting the above technical solution, the stirring speed of the preferred composite is within the above range, so that the prepared calcium carbonate has a clear outline and is uniformly dispersed, which effectively improves the stability of nano-calcium carbonate.

[0026] In summary, this application includes at least one of the following beneficial technical effects: 1. Calcium carbonate powder is modified using organic and inorganic dispersants. The organic dispersant adsorbs onto the calcium carbonate surface through polar groups in its molecules, while the non-polar groups extend into the medium, forming steric hindrance or electrostatic repulsion. The adsorption layer of the organic dispersant can form a "physical barrier" between particles, reducing the binding of particles after collision and allowing the particles to be uniformly dispersed in the medium. The original surface of calcium carbonate is usually weakly negatively charged, and the inorganic dispersant can increase the surface negative charge density, making it difficult for particles to agglomerate due to electrostatic repulsion. This reduces the hydrogen bonding between calcium carbonate particles, making the particles easier to disperse under stirring or shearing forces, and improving the stability of the system after dispersion. The original surface of calcium carbonate is hydrophilic, and the hydrophobic groups of the activator can replace the surface hydroxyl groups, making the calcium carbonate surface hydrophobic, improving its compatibility with the organic phase, and resulting in more uniform dispersion. The treated nano-calcium carbonate can be uniformly dispersed in the system, reducing the occurrence of agglomeration and thus improving product quality. 2. Using tartaric acid, oxalic acid, or phosphoric acid as pH adjusters can not only optimize the reaction environment by regulating the acidity and alkalinity of the system, but also have a specific effect on the surface of calcium carbonate, thereby improving its surface properties, dispersibility, and compatibility with subsequent modifiers. The above-mentioned inorganic dispersants adjust the charge and form a protective layer on the surface of calcium carbonate by adsorbing onto it, reducing agglomeration and improving dispersibility. Organic dispersants improve the dispersibility of calcium carbonate in aqueous systems through the electrostatic adsorption of anionic groups, thereby improving the flowability, uniformity, and processing performance of calcium carbonate in slurries, coatings, plastics, and other systems. Modifying activators enhance the dispersibility of calcium carbonate in organic systems through hydrophobic modification. 3. Nano-sized calcium carbonate was prepared using a reverse microemulsion method, with a saponification liquid made from 2-ethylhexyl phosphate mono-2-ethylhexyl ester and sodium hydroxide as the surfactant, isopropanol as the co-surfactant, kerosene as the oil phase, and calcium chloride solution and calcium carbonate solution as the aqueous phase. The prepared calcium carbonate has a large specific surface area, which can further enhance the grafting effect when combined with organic and inorganic dispersants in the subsequent process, thereby improving the dispersion performance of activated calcium carbonate and resulting in calcium carbonate products with good thickness and mechanical properties. Detailed Implementation

[0027] The present application will be further described in detail below with reference to the embodiments: Raw material description: All raw materials used in the examples are commercially available; Example 1 Preparation of slurry: Mix calcium carbonate powder with water to obtain slurry with a weight concentration of 5%; Pre-dispersion treatment: Add tartaric acid (CAS No.: 526-83-0) as a pH adjuster to adjust the pH of the slurry system to 7, then add sodium aluminate (CAS No.: 1302-42-7) as an inorganic dispersant and sodium polyacrylate (CAS No.: 9003-04-7) as an organic dispersant, stir and mix to obtain a uniform emulsion. The amount of inorganic dispersant added is 0.5% of the weight of calcium carbonate powder, and the amount of organic dispersant added is 11% of the weight of calcium carbonate powder. The stirring linear speed is 8 m / s. Surface modification: Control the emulsion temperature to 20℃, add lauric acid (CAS No.: 143-07-7) as an activator and stir for 90 min to obtain the modified product, wherein the amount of activator added is 1% of the weight of calcium carbonate powder; Post-processing: The modified material was filtered and dried at 120℃ to obtain the active ultrafine calcium carbonate product.

[0028] The calcium carbonate powder is a commercially available nano-calcium carbonate powder with a particle size of 100nm.

[0029] Example 2 Preparation of slurry: Mix calcium carbonate powder with water to obtain slurry with a weight concentration of 40%; Pre-dispersion treatment: Add oxalic acid (CAS No.: 144-62-7) as a pH adjuster to adjust the pH of the slurry system to 9. Then add sodium phosphate (CAS No.: 7601-54-9) as an inorganic dispersant and sodium hexadecyl diphenyl ether disulfonate (CAS No.: 65143-89-7) as an organic dispersant. Stir and mix to obtain a uniform emulsion. The amount of inorganic dispersant added is 12% of the weight of calcium carbonate powder, and the amount of organic dispersant added is 13% of the weight of calcium carbonate powder. The stirring linear speed is 12 m / s. Surface modification: Control the emulsion temperature to 100℃, add activator rosin acid (CAS No.: 514-10-3) and stir for 20 min to obtain the modified product, wherein the amount of activator added is 8% of the weight of calcium carbonate powder; Post-processing: The modified material was filtered and dried at 145℃ to obtain the active ultrafine calcium carbonate product.

[0030] The calcium carbonate powder is a commercially available nano-calcium carbonate powder with a particle size of 100nm.

[0031] Example 3 Preparation of calcium carbonate powder: 2-Ethylhexyl phosphate mono-2-ethylhexyl ester (CAS No.: 14802-03-0) was mixed with sodium hydroxide and heated to 60℃ to obtain a saponification solution. The saponification solution, isopropanol (CAS No.: 67-63-0), kerosene (CAS No.: 8008-20-6), and calcium chloride were mixed and stirred to obtain a microemulsion. After removing the oil phase, sodium carbonate solution was added to obtain a complex. The reaction was stirred at 1200 r / min and allowed to stand for 60 min. The microemulsion was broken with ethanol, washed, and dried to obtain nano-calcium carbonate powder. The mass ratio of saponification solution to kerosene was 1:1, the volume ratio of saponification solution to isopropanol was 1.5:1, the concentration of calcium chloride in the complex was 0.42 mol / L, and the concentration of sodium carbonate in the complex was 0.42 mol / L.

[0032] Preparation of slurry: Mix calcium carbonate powder with water to obtain slurry with a weight concentration of 25%; Pre-dispersion treatment: Add oxalic acid as a pH adjuster to adjust the pH of the slurry system to 8, then add sodium pyrophosphate (CAS No.: 7722-88-5) as an inorganic dispersant and sodium hexadecyl diphenyl ether disulfonate as an organic dispersant, stir and mix to obtain a uniform emulsion, wherein the amount of inorganic dispersant added is 6% of the weight of calcium carbonate powder, the amount of organic dispersant added is 12% of the weight of calcium carbonate powder, and the stirring linear speed is 10m / s; Surface modification: Control the emulsion temperature to 60℃, add activator stearic acid (CAS No.: 57-11-4) and stir for 55 min to obtain the modified product, wherein the amount of activator added is 5% of the weight of calcium carbonate powder; Post-processing: The modified material was filtered and dried at 135℃ to obtain the active ultrafine calcium carbonate product.

[0033] Example 4 Preparation of calcium carbonate powder: 2-Ethylhexyl phosphate mono-2-ethylhexyl ester was mixed with sodium hydroxide and heated to 60°C to obtain a saponification solution. The saponification solution, isopropanol, kerosene, and calcium chloride were mixed and stirred to obtain a microemulsion. After removing the oil phase, sodium carbonate solution was added to obtain a complex. The reaction was stirred at 1400 r / min and allowed to stand for 60 min. The microemulsion was broken with ethanol, washed, and dried to obtain nano-calcium carbonate powder. The mass ratio of saponification solution to kerosene was 1:1, the volume ratio of saponification solution to isopropanol was 1.7:1, the concentration of calcium chloride in the complex was 0.44 mol / L, and the concentration of sodium carbonate in the complex was 0.44 mol / L.

[0034] Preparation of slurry: Mix calcium carbonate powder with water to obtain slurry with a weight concentration of 25%; Pre-dispersion treatment: Add oxalic acid as a pH adjuster to adjust the pH of the slurry system to 8, then add sodium pyrophosphate as an inorganic dispersant and sodium hexadecyl diphenyl ether disulfonate as an organic dispersant, stir and mix to obtain a uniform emulsion, wherein the amount of inorganic dispersant added is 6% of the weight of calcium carbonate powder, the amount of organic dispersant added is 12% of the weight of calcium carbonate powder, and the stirring linear speed is 10m / s. Surface modification: Control the emulsion temperature to 60℃, add rosin acid as an activator and stir for 55 min to obtain the modified product, wherein the amount of activator added is 5% of the weight of calcium carbonate powder; Post-processing: The modified material was filtered and dried at 135℃ to obtain the active ultrafine calcium carbonate product.

[0035] Example 5 Preparation of calcium carbonate powder: 2-Ethylhexyl phosphate mono-2-ethylhexyl ester was mixed with sodium hydroxide and heated to 60°C to obtain a saponification solution. The saponification solution, isopropanol, kerosene, and calcium chloride were mixed and stirred to obtain a microemulsion. After removing the oil phase, sodium carbonate solution was added to obtain a complex. The reaction was stirred at 1300 r / min and allowed to stand for 60 min. The microemulsion was broken with ethanol, washed, and dried to obtain nano-calcium carbonate powder. The mass ratio of saponification solution to kerosene was 1:1, the volume ratio of saponification solution to isopropanol was 1.6:1, the concentration of calcium chloride in the complex was 0.43 mol / L, and the concentration of sodium carbonate in the complex was 0.43 mol / L.

[0036] Preparation of slurry: Mix calcium carbonate powder with water to obtain slurry with a weight concentration of 25%; Pre-dispersion treatment: Add oxalic acid as a pH adjuster to adjust the pH of the slurry system to 8, then add sodium pyrophosphate as an inorganic dispersant and sodium hexadecyl diphenyl ether disulfonate as an organic dispersant, stir and mix to obtain a uniform emulsion, wherein the amount of inorganic dispersant added is 6% of the weight of calcium carbonate powder, the amount of organic dispersant added is 12% of the weight of calcium carbonate powder, and the stirring linear speed is 10m / s. Surface modification: Control the emulsion temperature to 60℃, add rosin acid as an activator and stir for 55 min to obtain the modified product, wherein the amount of activator added is 5% of the weight of calcium carbonate powder; Post-processing: The modified material was filtered and dried at 135℃ to obtain the active ultrafine calcium carbonate product.

[0037] Example 6 Example 6 is based on Example 5. In Example 6, when preparing calcium carbonate powder, the mass ratio between the saponification liquid and isopropanol is 1.2:1.

[0038] Example 7 Example 7 is based on Example 5. In Example 7, the mass ratio between the saponification liquid and isopropanol is 2:1 when preparing calcium carbonate powder.

[0039] Example 8 Example 8 is based on Example 5. In Example 8, when preparing calcium carbonate powder, the concentration of calcium chloride is 0.37 mol / L and the concentration of calcium carbonate is 0.37 mol / L.

[0040] Example 9 Example 9 is based on Example 5. In Example 9, when preparing calcium carbonate powder, the concentration of calcium chloride is 0.48 mol / L and the concentration of calcium carbonate is 0.48 mol / L.

[0041] Example 10 Example 10 is based on Example 5. In Example 10, the stirring rate of the complex during the stirring reaction was 900 r / min when preparing calcium carbonate powder.

[0042] Example 11 Example 11 is based on Example 5. In Example 11, the stirring rate of the complex during the stirring reaction was 1700 r / min when preparing calcium carbonate powder.

[0043] Example 12 Example 12 is based on Example 5. In Example 12, the stirring linear speed of the pre-dispersion treatment during the surface modification of calcium carbonate powder is 5 m / s.

[0044] Example 13 Example 13 is based on Example 5. In Example 13, the stirring linear speed of the pre-dispersion treatment during the surface modification of calcium carbonate powder is 15 m / s.

[0045] Comparative Example 1 Comparative Example 1 is based on Example 5. In Comparative Example 1, no inorganic dispersant was added when modifying the surface of calcium carbonate powder.

[0046] Comparative Example 2 Comparative Example 2 is based on Example 5. In Comparative Example 2, no organic dispersant was added when modifying the surface of calcium carbonate powder.

[0047] Comparative Example 3 Comparative Example 3 is based on Example 5. In Comparative Example 3, no modifying activator was added when modifying the surface of calcium carbonate powder.

[0048] Performance testing The following performance tests were performed on the samples of Examples 1-13 and Comparative Examples 1-3: (1) Oil absorption value Using GB / T 19281-2014 as the testing reference, the oil absorption value of the samples was tested. Each sample was tested 3 times, and the average value was taken. The test results were filled in Table 1. (2) Activation Using HG / T 3249.2-2013 as the testing reference, the activation degree of the samples was tested. Each sample was tested 3 times, and the average value was taken. The test results were filled in Table 1.

[0049] Table 1 Performance test results of Examples 1-13 and Comparative Examples 1-3 As shown in Table 1, the oil absorption values ​​of Examples 1-2 are all above 30.5 mL, indicating that the surface-modified active ultrafine calcium carbonate powder prepared in this application has good mechanical properties. The activation values ​​of Examples 1-2 are all above 97.8%, indicating that the surface-modified active ultrafine calcium carbonate powder prepared in this application has good compatibility and dispersibility. The oil absorption values ​​of Examples 3-5 are all above 33.2 mL, and the activation values ​​are all above 99.2%, indicating that the performance of the modified calcium carbonate powder can be further improved after surface modification of the calcium carbonate powder prepared in this application.

[0050] In Examples 6 and 7, the mass ratio between the saponification liquid and isopropanol during the preparation of calcium carbonate powder was outside the range specified in this application. When the amount of saponification liquid added was too small, it was difficult to form a sufficient number of nucleation sites, resulting in decreased stability and particle size uniformity of the prepared calcium carbonate powder, making it difficult to further improve the surface area and affecting subsequent surface activity modification. When the amount of saponification liquid added was too large, the calcium carbonate powder formed by the supersaturated system was too concentrated, and the calcium carbonate powder agglomerated, affecting the subsequent modification effect. Therefore, the performance of Examples 6 and 7 was reduced.

[0051] In Examples 8 and 9, the concentrations of calcium chloride and calcium carbonate during the preparation of calcium carbonate powder were not within the ranges specified in this application. When the concentrations of calcium chloride and calcium carbonate were too low, homogeneous nucleation was difficult to dominate, and the generated calcium carbonate powder agglomerated together, producing particles locally, which affected the particle size and stability of the prepared calcium carbonate. When the concentrations of calcium chloride and calcium carbonate were too high, the generated calcium carbonate stacked together and agglomerated, affecting the overall stability of the system. Therefore, the performance of Examples 8 and 9 was affected.

[0052] In Examples 10 and 11, the stirring rates during the preparation of calcium carbonate powder were not within the range specified in this application. When the stirring rate was too low, the calcium carbonate nanoparticles were difficult to fuse further, resulting in incomplete structures and affecting the overall stability of the prepared calcium carbonate powder. When the stirring rate was too high, the stable structure on the surface of the system was destroyed, and the prepared calcium carbonate powder was damaged, thus affecting the overall stability of the system. Therefore, the performance of Examples 10 and 11 was reduced.

[0053] In Examples 12 and 13, the stirring speed during the pre-dispersion treatment of calcium carbonate powder was not within the range specified in this application. When the stirring speed during the pre-dispersion treatment was too low, the dispersant and activator in the system could not fully contact the calcium carbonate powder, which reduced the effect of the calcium carbonate surface activation treatment and affected the performance of the system. When the stirring speed during the pre-dispersion treatment was too high, it resulted in local unevenness rather than better mixing, making it difficult to further improve the overall performance of the modified calcium carbonate.

[0054] In Comparative Example 1, no inorganic dispersant was added when modifying the calcium carbonate powder, making it difficult to form steric hindrance or electrostatic repulsion effects. This caused the calcium carbonate powder to agglomerate during subsequent use, affecting product performance, and both mechanical and compatibility properties were affected.

[0055] In Comparative Example 2, no organic dispersant was added when modifying calcium carbonate powder, making it difficult to further reduce the bonding after particle collision. This resulted in a decrease in the uniform dispersion performance of particles in the medium and the occurrence of agglomeration, which affected the overall performance of the system.

[0056] In Comparative Example 3, no modifying activator was added when modifying calcium carbonate powder, which reduced the binding effect between calcium carbonate powder and organic and inorganic dispersants, affecting the overall stability of the system.

[0057] This specific embodiment is merely an explanation of this application and is not intended to limit it. Based on the above description, those skilled in the art can make various changes and modifications without departing from the technical concept of this application. The technical scope of this application is not limited to the contents of the specification but must be determined according to the scope of the claims.

Claims

1. A wet surface modification method for preparing activated ultrafine calcium carbonate, characterized in that: Includes the following steps: Preparation of slurry: Mix calcium carbonate powder with water to obtain slurry; Pre-dispersion treatment: Add pH adjuster to adjust the pH of the slurry system to 7-9, then add dispersant and stir to mix to obtain a uniform emulsion; Surface modification: Control the emulsion temperature to 20-100℃, add activator and stir for 20-90 min to obtain the modified product; Post-processing: The modified material is filtered and dried to obtain the active ultrafine calcium carbonate product.

2. The wet surface modification preparation method of activated ultrafine calcium carbonate according to claim 1, characterized in that: In the pre-dispersion process described above, the linear velocity during stirring and mixing is 8-12 m / s.

3. The wet surface modification preparation method of activated ultrafine calcium carbonate according to claim 1, characterized in that: The calcium carbonate powder has a particle size ≤100nm, the slurry has a weight concentration of 5-40%, the pH adjuster includes any one of tartaric acid, oxalic acid, or phosphoric acid, the inorganic dispersant includes any one or a mixture of sodium aluminate, sodium phosphate, and sodium pyrophosphate, the organic dispersant includes any one of sodium polyacrylate or sodium hexadecyl diphenyl ether disulfonate, and the modified activator includes any one or a mixture of lauric acid, rosin acid, and stearic acid.

4. The wet surface modification preparation method of activated ultrafine calcium carbonate according to claim 1, characterized in that: The amount of the inorganic dispersant is 0.5-12% of the weight of the calcium carbonate powder, the amount of the organic dispersant is 11-13% of the weight of the calcium carbonate powder, and the amount of the modifying activator is 1-8% of the weight of the calcium carbonate powder.

5. The wet surface modification preparation method of activated ultrafine calcium carbonate according to claim 1, characterized in that: The raw materials for preparing nano-calcium carbonate include saponification liquid, isopropanol, kerosene, calcium chloride, and calcium carbonate.

6. The wet surface modification preparation method of activated ultrafine calcium carbonate according to claim 5, characterized in that: The nano-calcium carbonate was prepared by the following method: After mixing saponification solution, isopropanol, kerosene and calcium chloride, a microemulsion was obtained by stirring. After removing the oil phase, sodium carbonate solution was added to obtain a complex. The mixture was stirred and reacted. After standing, the emulsion was broken with ethanol, washed and dried to obtain nano-calcium carbonate powder.

7. The wet surface modification preparation method of activated ultrafine calcium carbonate according to claim 5, characterized in that: The saponification liquid is prepared by the following method: 2-Ethylhexyl phosphate mono-2-ethylhexyl ester was mixed with sodium hydroxide to obtain a saponified solution.

8. The wet surface modification preparation method of activated ultrafine calcium carbonate according to claim 6, characterized in that: The volume ratio between the saponification liquid and isopropanol is (1.5-1.7):

1.

9. The wet surface modification preparation method of activated ultrafine calcium carbonate according to claim 6, characterized in that: The concentration of calcium chloride in the complex is 0.42-0.44 mol / L, and the concentration of sodium carbonate in the complex is 0.42-0.44 mol / L.

10. The wet surface modification preparation method of active ultrafine calcium carbonate according to claim 6, characterized in that: The stirring speed of the composite is 1200-1400 r / min.

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