Preparation method of low-viscosity calcium carbonate

Abstract

The invention belongs to the technical field of calcium carbonate preparation, and particularly provides a preparation method of low-viscosity calcium carbonate, which comprises the following steps: S1, carbonization and crystal face regulation and control: adding alkylphenol ethoxylates and dimethylformamide into calcium hydroxide slurry as a composite crystal form control agent, controlling the pH value in a weak alkali environment, carrying out primary carbonization, and carrying out secondary carbonization; then carrying out aging-secondary carbonization until the pH value is stabilized at 7.0-7.5; s2, wet grafting modification: adding a multifunctional group monomer into the slurry subjected to secondary carbonization, reacting for 1.5-2.5 hours at 60-65 DEG C to obtain modified slurry, adding itaconic acid and an initiator, keeping the temperature at 70-85 DEG C, and reacting for 3.5-4.5 hours in an inert gas atmosphere; s3, microwave-ultrasonic wave synergistic drying: dehydrating the modified slurry through a centrifugal machine until the solid content is 40%-50%, and drying under the synergistic effect of microwave frequency 2.45 GHz and ultrasonic frequency 20kHz to obtain a dried product; and S4, crushing and grading the dried product, and carrying out surface secondary modification to obtain a calcium carbonate finished product which is very low in viscosity and oil absorbency.

Description

Technical Field

[0001] The present invention relates to the technical field of calcium carbonate preparation, and specifically relates to a method for preparing low-viscosity calcium carbonate. Background Art

[0002] As an important inorganic chemical product, calcium carbonate is widely used in industries such as rubber, plastics, papermaking, coatings, and inks. It can significantly improve the heat resistance, wear resistance, dimensional stability, and rigidity of products, while effectively reducing the production cost of products. However, calcium carbonate prepared by traditional processes often has a high viscosity, which increases the difficulty of material processing and reduces product performance. Moreover, high-viscosity slurries are prone to sedimentation and caking, requiring frequent stirring or the addition of anti-settling agents, increasing the reserve management cost. Summary of the Invention

[0003] Aiming at the defect of high viscosity of calcium carbonate in the prior art, the present invention provides a method for preparing low-viscosity calcium carbonate, which realizes the dual reduction of oil absorption value and viscosity through multi-step coordinated regulation.

[0004] To achieve the above object, the present invention provides the following technical solution: A method for preparing low-viscosity calcium carbonate, comprising the following steps: S1: Carbonization and crystal plane regulation: Add octylphenol polyoxyethylene ether and dimethylformamide as a composite crystal form control agent to the calcium hydroxide slurry, and adjust the pH to a weak alkaline environment of 8.5±0.2. Subsequently, introduce CO2 for primary carbonization, and terminate the reaction when the conductivity of the calcium hydroxide slurry drops to 10%-15% of the initial value. Then, carry out aging-secondary carbonization, let the slurry stand at a certain temperature for a period of time, and then introduce CO2 for the second time until the pH stabilizes at 7.0-7.5; S2: Wet graft modification, add a multi-functional monomer to the slurry after secondary carbonization, and react at 60-65°C for 1.5-2.5 hours to obtain a modified slurry. Then, add itaconic acid and an initiator, maintain the temperature at 70-85°C under an argon or nitrogen atmosphere, and the reaction time is 3.5h-4.5h; S3: Microwave-ultrasonic synergistic drying: After dehydrating the modified slurry by a centrifuge to a solid content of 40%-50%, use the synergistic action of a microwave frequency of 2.45 GHz and an ultrasonic frequency of 20 kHz for drying to obtain a dried product; S4: Crush and classify the dried product, and perform surface secondary modification to obtain the final low-viscosity calcium carbonate product.

[0005] As a further improvement of the present invention, in S1, the octylphenol polyoxyethylene ether is octylphenyl polyoxyethylene ether, and its addition amount is 0.03%-0.08% of the dry basis mass of calcium hydroxide. In S1, the addition amount of dimethylformamide is 0.1%-0.5% of the dry basis mass of calcium hydroxide.

[0006] As a further improvement of the present invention, the rate of the first CO₂ introduction in S1 is 0.5 - 1.0 L / min, and the rate of the second CO₂ introduction in S1 is 0.2 - 0.5 L / min.

[0007] As a further improvement of the present invention, during the aging - secondary carbonization in S1, the temperature is maintained at 40 - 50 °C, and the standing time is 30 - 60 minutes.

[0008] As a further improvement of the present invention, the multifunctional monomer added in step S2 is acryloxypropyltrimethoxysilane, and its addition amount is 1.5% - 2.5% of the dry basis mass of calcium hydroxide; the addition amount of itaconic acid in S2 is 2% - 4% of the dry basis mass of calcium hydroxide, and the addition amount of the initiator is 0.02% - 0.08% of the dry basis mass of calcium hydroxide. The initiator is ammonium persulfate or potassium persulfate.

[0009] As a further improvement of the present invention, before adding acryloxypropyltrimethoxysilane to the carbonized slurry, it is pre - hydrolyzed with acetic acid as a catalyst in a mixed solution of water and ethanol with a mass ratio of 1:1 for 30 minutes.

[0010] As a further improvement of the present invention, in step S3, the microwave power density is 3 - 5 W / m 2 , the ultrasonic power density is 0.5 - 1.2 W / cm², and the energy input ratio of microwave to ultrasonic wave is 2.5 - 3.5:1.

[0011] As a further improvement of the present invention, the drying process in step S3 adopts dynamic coupling control, specifically: The first stage: the microwave power is 4 - 5 W / g, the ultrasonic power density is 1.0 - 1.2 W / cm², lasting for 10 - 15 minutes; The second stage: the microwave power is 3 - 4 W / g, the ultrasonic power density is 0.5 - 0.8 W / cm², lasting for 20 - 25 minutes.

[0012] As a further improvement of the present invention, in S4, a jet mill is used for pulverization, the rotational speed of the classification wheel is 2000 - 3000 rpm, and the particle diameter of the obtained low - viscosity calcium carbonate finished product is controlled at 1.8 - 5.5 μm.

[0013] As a further improvement of the present invention, the surface secondary modification in step S4 is specifically as follows: the product obtained by classification is placed in a mixer, and a 10% ethanol solution of cyclodextrin - grafted modified poly - malic acid is sprayed for rolling mixing. The mixing temperature is 70 - 80 °C, the mixing time is 25 - 35 minutes, and the spraying amount of the ethanol solution of cyclodextrin - grafted modified poly - malic acid is 0.1% - 0.6% of the mass of the product obtained by classification.

[0014] Advantages of the present invention: 1. By using alkylphenol polyoxyethylene ether, the formation of high-energy crystal planes can be promoted, and itaconic acid can be grafted through acryloxypropyltrimethoxysilane. After grafting, itaconic acid has a certain chain length and volume, weakening the interaction force between particles, reducing the friction and cohesion between particles, and enabling the free movement of particles to achieve overall viscosity reduction. At the same time, through the synergistic effect of microwave heating and ultrasonic oscillation in the drying stage, microwave selectively heats the internal moisture of particles, and ultrasonic waves break the surface hard shell, improving the coating effect and reducing the oil absorption value, thereby reducing viscosity.

[0015] 2. The cavity of cyclodextrin can encapsulate solvent molecules to form a hydration layer, reducing the internal frictional resistance of particles in the solvent; in addition, the carboxyl groups of poly(malic acid) disperse particles through electrostatic repulsion and steric hindrance. Specific embodiments

[0016] In order to make the objectives, technical solutions and advantages of the present invention more clear and understandable, the present invention will be further described in detail below with reference to embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0017] The present invention provides a method for preparing low-viscosity calcium carbonate, comprising the following steps: S1: Carbonization and crystal plane regulation: Add alkylphenol polyoxyethylene ether (preferably octylphenyl polyoxyethylene ether, with an addition amount of 0.03%-0.08% of the dry basis mass of calcium hydroxide) and dimethylformamide (with an addition amount of 0.1%-0.5% of the dry basis mass of calcium hydroxide) as a composite crystal form control agent to the calcium hydroxide slurry, and control the pH to be 8.3-8.7. Pass CO2 for primary carbonization (rate 0.5-1.0 L / min), and determine the reaction end point when the conductivity drops to 10%-15% of the initial value. Subsequently, aging-secondary carbonization is carried out. Aging stage: Let the slurry stand for 30-60 minutes, and maintain the temperature at 40-50°C to promote the directional growth of crystal nuclei; secondary carbonization: Pass CO2 again (rate 0.2-0.5 L / min) until the pH stabilizes at 7.0-7.5 to form a uniform crystal form.

[0018] As a further explanation of this embodiment, by using alkylphenol polyoxyethylene ether and dimethylformamide to synergistically inhibit the growth of calcium hydroxide crystals on the 0001 crystal plane and the 1010 crystal plane, the formation and exposure of other crystal planes are promoted, so that the proportion of high-energy crystal planes reaches more than 60%. By regulating the crystal plane energy of calcium carbonate with alkylphenol polyoxyethylene ether, by selectively adsorbing specific crystal planes, the charge distribution of the crystal plane is changed to inhibit disordered growth, forming a regular structure and morphology with low oil absorption. Secondary carbonization can promote the directional growth of crystal planes and optimize the particle density.

[0019] S2: Wet grafting modification Add a multifunctional monomer to the carbonized slurry for grafting modification. The multifunctional monomer is preferably acryloxypropyltrimethoxysilane, and its addition amount is 1.5%-2.5% of the dry basis mass of calcium hydroxide. Before addition, the multifunctional monomer needs to be pretreated: dissolve it in a mixed solution of water and ethanol (mass ratio 1:1), add a small amount of acetic acid (0.5% of the mass of acryloxypropyltrimethoxysilane) as a catalyst, make it fully hydrolyze, and then filter out impurities to obtain a clear solution. The modification reaction is carried out at 60-65°C for 1.5-2.5 hours to obtain a modified slurry. The mass ratio of the mixed solution to the multifunctional monomer is 6:1.

[0020] Then add itaconic acid (monomer) and initiators (such as ammonium persulfate, potassium persulfate), maintain the temperature at 70-85°C and carry out the reaction under an argon or nitrogen atmosphere for 3.5h-4.5h. The addition amount of itaconic acid is 2%-4% of the dry basis mass of calcium hydroxide, and the addition amount of the initiator is 0.02% - 0.08% of the dry basis mass of calcium hydroxide.

[0021] As a further explanation of this embodiment, the high-energy crystal planes promoted by alkylphenol polyoxyethylene ether in S1 are grafted with itaconic acid through acryloxypropyltrimethoxysilane. The grafted itaconic acid forms a long-chain structure with it, and by virtue of its unique spatial dimension, weakens the interactions such as van der Waals forces and electrostatic forces between particles, reduces the frictional resistance and cohesion effect generated when particles come into contact, enables the particles to slide and decompose freely, and effectively reduces the overall viscosity of the system.

[0022] S3: Microwave-ultrasonic synergistic drying After dehydrating the modified slurry by a centrifuge to a solid content of 40%-50%, use the synergistic action of microwave and ultrasonic for drying. The microwave frequency is 2.45 GHz, the ultrasonic frequency is 20 kHz, the microwave power density is 3-5 W / g, the ultrasonic power density is 0.5-1.2 W / cm², and the energy input ratio of microwave to ultrasonic is (2.5-3.5):1. The drying process adopts dynamic coupling control, specifically divided into two stages: The first stage: microwave power 4-5W / g, ultrasonic power density 0.8-1.2 W / cm², lasting for 10-15 minutes; The second stage: microwave power 3-4W / g, ultrasonic power density 0.5-0.8 W / cm², lasting for 20-25 minutes.

[0023] As a further explanation of this embodiment, by adopting the synergistic effect of microwave heating and ultrasonic oscillation in the drying stage, the moisture inside the particles is selectively heated by microwave, and the surface hard shell is broken by ultrasonic wave, so as to improve the coating effect, reduce the oil absorption value, and thus reduce the viscosity.

[0024] S4: Crushing, classifying and surface secondary modification The dried product is crushed and classified by a jet mill, the rotational speed of the classification wheel is 2000 - 3000 rpm, and the particle size of the finished product is controlled to be 1.8 - 5.5 μm. Then surface secondary modification is carried out: the classified product is placed in a mixer, and an ethanol solution of cyclodextrin grafted modified poly(malic acid) with a mass concentration of 10% is sprayed (the spraying amount is 0.1% - 0.6% of the mass of the dried product), and it is rolled and mixed at 70°C - 80°C for 25 - 35 minutes to obtain the final low-viscosity calcium carbonate finished product.

[0025] As a further explanation of this embodiment, the cyclodextrin cavity can include solvent molecules to form a hydration layer, reducing the internal frictional resistance of the particles in the solvent; in addition, the carboxylic acid groups of poly(malic acid) disperse the particles through electrostatic repulsion and steric hindrance.

[0026] Example 1 S1: Take a calcium hydroxide slurry with a concentration of 15% (w / w), add octylphenol polyoxyethylene ether with a mass of 0.03% of the calcium hydroxide dry basis and dimethylformamide with a mass of 0.1% of the calcium hydroxide dry basis into it, control the pH to be maintained at 8.3, and introduce CO2 at a rate of 0.5 L / min for primary carbonization. When the conductivity drops to 10% of the initial value, stop introducing CO2 and pH regulation.

[0027] Then the slurry is allowed to stand for 30 min, the temperature is maintained at 40°C, and then CO2 is introduced again at a rate of 0.2 L / min until the pH stabilizes at 7.5.

[0028] S2: Add 1.5% of acryloxypropyltrimethoxysilane based on the mass of the calcium hydroxide dry basis to the slurry after secondary carbonization in S1. Before adding, acryloxypropyltrimethoxysilane is hydrolyzed in a mixed solution of water and ethanol (mass ratio of 1:1) with acetic acid as a catalyst for 30 minutes, and the ratio of the mixed solution to acryloxypropyltrimethoxysilane is 6:1. After adding, the reaction is carried out at 60°C for 1.5 hours to obtain a modified slurry; Then itaconic acid (monomer) and ammonium persulfate are added, and the reaction is carried out at 70°C under a nitrogen atmosphere for 3.5 h. The addition amount of itaconic acid is 2% of the calcium hydroxide dry basis, and the addition amount of the initiator is 0.02% of the calcium hydroxide dry basis.

[0029] S3: After centrifugally dehydrating the modified slurry to a solid content of 50%, it is dried using microwaves with a frequency of 2.45 GHz and ultrasonic waves with a frequency of 20 kHz. First stage: microwave power is 4 W / g, ultrasonic power density is 0.8 W / cm², for 10 minutes. Second stage: microwave power is 3 W / g, ultrasonic power is 0.5 W / cm², for 20 minutes. The dried product is obtained.

[0030] S4: The dried product is pulverized and classified using a jet mill with a classifier wheel rotation speed of 2000 rpm, controlling the finished product particle size to be 1.8 - 5.5 μm. Subsequently, surface secondary modification is carried out: The classified product is placed in a mixer, and a 10% ethanol solution of cyclodextrin-grafted poly(malic acid) with a concentration of 0.1% of the mass of the dried product is sprayed, and it is rolled and mixed at 70°C for 25 minutes to obtain the final low-viscosity calcium carbonate finished product.

[0031] Example 2 S1: Take a calcium hydroxide slurry with a concentration of 15% (w / w), add octylphenol polyoxyethylene ether with a mass of 0.05% of the calcium hydroxide dry basis and dimethylformamide with a mass of 0.3% of the calcium hydroxide dry basis into it, control the pH to be maintained at 8.5, and introduce CO2 at a rate of 0.7 L / min for primary carbonization. When the conductivity drops to 13% of the initial value, stop introducing CO2 and pH regulation.

[0032] Then let the slurry stand for 45 minutes, maintain the temperature at 45°C, and then introduce CO2 again at a rate of 0.3 L / min until the pH stabilizes at 7.3.

[0033] S2: Add 2.0% of acryloxypropyltrimethoxysilane based on the mass of the calcium hydroxide dry basis to the slurry after secondary carbonization in S1. Before adding, hydrolyze acryloxypropyltrimethoxysilane in a mixed solution of water and ethanol (mass ratio 1:1) using acetic acid as a catalyst for 30 minutes, and the ratio of the mixed solution to acryloxypropyltrimethoxysilane is 6:1. After adding, carry out the reaction at 60°C for 2 hours to obtain the modified slurry; Then add itaconic acid (monomer) and ammonium persulfate, and carry out the reaction at 78°C under a nitrogen atmosphere for 4 hours. The addition amount of itaconic acid is 3% of the mass of the calcium hydroxide dry basis, and the addition amount of the initiator is 0.05% of the mass of the calcium hydroxide dry basis.

[0034] S3: After centrifugally dewatering the modified slurry to a solid content of 45%, it is dried using microwaves with a frequency of 2.45 GHz and ultrasound with a frequency of 20 kHz. First stage: microwave power is 4 W / g, ultrasound power density is 1.0 W / cm², for 13 minutes. Second stage: microwave power is 4 W / g, ultrasound power is 0.7 W / cm², for 23 minutes. The dried product is obtained.

[0035] S4: The dried product is pulverized and classified using a jet mill with a classifier wheel rotation speed of 2500 rpm, controlling the finished product particle size to be 1.8 - 5.5 μm. Subsequently, surface secondary modification is carried out: The classified product is placed in a mixer, and a 0.4% ethanol solution of cyclodextrin grafted modified poly(malic acid) with a concentration of 10% based on the mass of the dried product is sprayed, and it is rolled and mixed at 75°C for 30 minutes to obtain the final low-viscosity calcium carbonate finished product.

[0036] Example 3 S1: Take a calcium hydroxide slurry with a concentration of 15% (w / w), add octylphenol polyoxyethylene ether with a mass of 0.08% of the calcium hydroxide dry basis and dimethylformamide with a mass of 0.5% of the calcium hydroxide dry basis into it, control the pH to be maintained at 8.7, and introduce CO2 at a rate of 1.0 L / min for primary carbonization. When the conductivity drops to 15% of the initial value, stop introducing CO2 and pH regulation.

[0037] Then the slurry is left standing for 60 minutes at a temperature maintained at 50°C, and then CO2 is introduced again at a rate of 0.5 L / min until the pH stabilizes at 7.0.

[0038] S2: Add 2.5% of acryloxypropyltrimethoxysilane based on the mass of the calcium hydroxide dry basis to the slurry after secondary carbonization in S1. Before addition, acryloxypropyltrimethoxysilane is hydrolyzed in a mixture of water and ethanol (mass ratio 1:1) with acetic acid as a catalyst for 30 minutes, and the ratio of the mixture to acryloxypropyltrimethoxysilane is 6:1. After addition, the reaction is carried out at 65°C for 2.5 hours to obtain the modified slurry; Then itaconic acid (monomer) and ammonium persulfate are added, and the reaction is carried out at 85°C under a nitrogen atmosphere for 4.5 h. The addition amount of itaconic acid is 4% of the calcium hydroxide dry basis, and the addition amount of the initiator is 0.08% of the calcium hydroxide dry basis.

[0039] S3: After centrifugally dehydrating the modified slurry to a solid content of 40%, it is dried using microwaves with a frequency of 2.45 GHz and ultrasonic waves with a frequency of 20 kHz. First stage: The microwave power is 5 W / g, and the ultrasonic power density is 1.2 W / cm², lasting for 10 minutes. Second stage: The microwave power is 4 W / g, and the ultrasonic power is 0.8 W / cm², lasting for 20 minutes. The dried product is obtained.

[0040] S4: The dried product is crushed and classified using a jet mill with a classifier wheel speed of 3000 rpm, and the finished product particle size is controlled to be 1.8 - 5.5 μm. Subsequently, surface secondary modification is carried out: The classified product is placed in a mixer, and a 10% ethanol solution of cyclodextrin-grafted poly(malic acid) with a concentration of 0.6% of the mass of the dried product is sprayed, and it is rolled and mixed at 80°C for 35 minutes to obtain the final low-viscosity calcium carbonate finished product.

[0041] Comparative Example 1: This comparative example is based on Example 2, with the difference that in step S1, the addition of octylphenol polyoxyethylene ether is omitted.

[0042] Comparative Example 2: This comparative example is based on Example 2, with the difference that in step S1, the addition of dimethylformamide is omitted.

[0043] Comparative Example 3: This comparative example is based on Example 2, with the difference that in step S1, the aging-secondary carbonization process is omitted.

[0044] Comparative Example 4: This comparative example is based on Example 2, with the difference that the graft modification process in step S2 is omitted.

[0045] Comparative Example 5: This comparative example is based on Example 2, with the difference that hot air drying (80°C, 6 hours) is used to replace microwave-ultrasonic synergistic drying in step S3.

[0046] Comparative Example 6: This comparative example is based on Example 2, with the difference that in step S4, the step of the ethanol solution of cyclodextrin-grafted poly(malic acid) is omitted.

[0047] The calcium carbonate finished products obtained from Examples 1 - 3 and Comparative Examples 1 - 6 are subjected to experimental determination: Oil absorption measurement: According to GB / T 19281-2014, the DOP titration method is used; Viscosity measurement: In accordance with GB / T 10247-2008, using a rotational viscometer (Brookfield DV2T), the shear rate was 250 s⁻¹, and the measurement was carried out at a temperature of 25 ± 0.5 °C. The measurement results of each example and comparative example are shown in the following comparison table:

[0048] As can be seen from the above table, through the synergistic effect of the composite crystal form control agent octyl phenyl polyoxyethylene ether, dimethylformamide, and aging-secondary carbonization, graft modification, microwave-ultrasonic drying, and surface modification, the present application realizes the dual optimization of the oil absorption and viscosity of calcium carbonate, which is significantly superior to the calcium carbonate prepared by traditional processes.

[0049] The above is only the preferred embodiment of the present invention, and the protection scope of the present invention is not limited to the above-mentioned implementation measures. All technical solutions falling within the idea of the present invention belong to the protection scope of the present invention. It should be pointed out that for those of ordinary skill in the art, without departing from the principle of the present invention, several improvements and refinements should also be regarded as the protection scope of the present invention.

Claims

1. A preparation method of low-viscosity calcium carbonate, characterized in that, It includes the following steps: S1: Carbonization and crystal plane regulation. Add alkylphenol polyoxyethylene ether and dimethylformamide as a composite crystal form control agent to the calcium hydroxide slurry, control the pH value in a weak alkaline environment of 8.5±0.2, and introduce CO2 for primary carbonization. The reaction end point is determined by the conductivity of the calcium hydroxide slurry dropping to 10%-15% of the initial value. Subsequently, aging-secondary carbonization is carried out. The slurry is left standing at a certain temperature for a period of time, and then CO2 is introduced for the second time until the pH stabilizes at 7.0-7.5; S2: Wet grafting modification. Add a multi-functional monomer to the slurry after secondary carbonization and react at 60-65°C for 1.5-2.5 hours to obtain a modified slurry. Then add itaconic acid and an initiator, and maintain the temperature at 70-85°C under an argon or nitrogen atmosphere. The reaction time is 3.5h-4.5h; S3: Microwave-ultrasonic synergistic drying. After dehydrating the modified slurry by a centrifuge to a solid content of 40%-50%, use the synergistic effect of a microwave frequency of 2.45 GHz and an ultrasonic frequency of 20 kHz for drying to obtain a dried product; S4: Crush and classify the dried product, and perform surface secondary modification to obtain the final low-viscosity calcium carbonate finished product.

2. The preparation method of the low-viscosity calcium carbonate according to claim 1, characterized in that, In the above S1, the alkylphenol polyoxyethylene ether is octylphenyl polyoxyethylene ether, and its addition amount is 0.03%-0.08% of the dry basis mass of calcium hydroxide. In the above S1, the addition amount of dimethylformamide is 0.1%-0.5% of the dry basis mass of calcium hydroxide.

3. The preparation method of the low-viscosity calcium carbonate according to claim 1, wherein In the above S1, the rate of introducing CO2 for the first time is 0.5-1.0 L / min, and the rate of introducing CO2 for the second time is 0.2-0.5 L / min.

4. The preparation method of the low-viscosity calcium carbonate according to claim 1, characterized in that, In the above S1 for aging-secondary carbonization, the standing time is 30-60 minutes, and the temperature is maintained at 40-50°C.

5. The preparation method of the low-viscosity calcium carbonate according to claim 1, characterized in that, In the above step S2, the multi-functional monomer added is acryloxypropyltrimethoxysilane, and its addition amount is 1.5%-2.5% of the dry basis mass of calcium hydroxide; the addition amount of itaconic acid in the above S2 is 2%-4% of the dry basis mass of calcium hydroxide, and the addition amount of the initiator is 0.02%~0.08% of the dry basis mass of calcium hydroxide. The initiator is ammonium persulfate or potassium persulfate.

6. The preparation method of the low-viscosity calcium carbonate according to claim 5, wherein Before adding acryloxypropyltrimethoxysilane to the slurry after carbonization, it is pre-hydrolyzed with acetic acid as a catalyst in a mixed solution with a mass ratio of water to ethanol of 1:1 for 30 minutes.

7. The preparation method of the low-viscosity calcium carbonate according to claim 1, characterized in that, In the above step S3, the microwave power density is 3-5 W / g, the ultrasonic power density is 0.5-1.2 W / cm², and the energy input ratio of microwave to ultrasonic is 2.5-3.5:

1.

8. The preparation method of the low-viscosity calcium carbonate according to claim 7, wherein, In step S3, the drying process adopts dynamic coupling control, specifically: The first stage: microwave power 4-5 W / g, ultrasonic power density 1.0-1.2 W / cm², lasting for 10-15 minutes; The second stage: microwave power 3-4 W / g, ultrasonic power density 0.5-0.8 W / cm², lasting for 20-25 minutes.

9. The preparation method of the low-viscosity calcium carbonate according to claim 1, wherein In S4, airflow pulverizer is used for pulverization, the rotational speed of the classification wheel is 2000 - 3000 rpm, and the particle diameter of the obtained low-viscosity calcium carbonate finished product is controlled at 1.8 - 5.5 μm.

10. The preparation method of the low-viscosity calcium carbonate according to claim 1, wherein, The specific surface secondary modification in step S4 is as follows: The product obtained by classification is placed in a mixer, and a 10% ethanol solution of cyclodextrin grafted modified poly(malic acid) is sprayed for rolling mixing. The mixing temperature is 70 - 80 °C, the mixing time is 25 - 35 minutes, and the spraying amount of the ethanol solution of cyclodextrin grafted modified poly(malic acid) is 0.1% - 0.6% of the mass of the product obtained by classification.

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