A method for preparing micron-sized monodisperse spherical calcium carbonate powder

Abstract

This invention discloses a method for preparing micron-sized monodisperse spherical calcium carbonate powder. The method involves adding an additive, at least one of hypozinotriacetic acid or triethylenetetramine, to an aqueous calcium chloride solution under stirring; continuing stirring to obtain a calcium chloride mixture; heating the carbonate aqueous solution and the calcium chloride mixture separately; mixing and stirring them at this temperature; maintaining the temperature and continuing stirring after mixing; allowing the mixture to stand for aging; separating the solid and liquid phases; washing the solid; and drying to obtain micron-sized monodisperse spherical calcium carbonate powder. The calcium carbonate powder prepared by this invention is spherical, with a calcite crystal form and monodisperse particles; the average particle size is 0.8–9 μm. The preparation method of this invention is simple, low-cost, and easy for industrial production.

Description

Technical Field

[0001] This invention relates to the field of crystallization technology, specifically to a method for preparing micron-sized monodisperse spherical calcium carbonate powder. Background Technology

[0002] Calcium carbonate, a commonly used inorganic material, has wide applications in numerous fields such as food ingredients, rubber, papermaking, coatings, lubricants, ceramics, and electronic components. In electronic ceramic applications, such as multilayer ceramic capacitors and thermistors, calcium carbonate, as a crucial component, faces stringent requirements regarding morphology and crystal form. Specifically, it is often required to have a size between 1-5 micrometers, the most stable calcite crystal form, and monodisperse spherical particles. However, the preparation of spherical calcium carbonate particles with a calcite structure is difficult to control. Morphology and crystal form control are often mutually exclusive; sometimes spherical particles are obtained, but the crystal form is not calcite; sometimes calcite particles are obtained, but the morphology is blocky; sometimes spherical calcite-type calcium carbonate is obtained, but the particle size distribution is wide and it is not monodisperse. Furthermore, many published methods for preparing spherical calcium carbonate powder often suffer from drawbacks such as complex processes, high costs, and limitations to small-scale laboratory trials, making industrial production difficult. Currently, there are relatively few reports on monodisperse calcite-type calcium carbonate, while there are more reports on monodisperse spheroidal calcium carbonate. Examples include patent application CN202111091049.9, which discloses a method for preparing stable spheroidal spheroidal phase calcium carbonate in an organic medium, and patent application TW080104299, which discloses monodisperse vaterite-type calcium carbonate, its preparation method, and methods for controlling particle growth and morphology. However, the electronic ceramics field requires the use of calcite-type calcium carbonate because it is the most stable crystalline phase of calcium carbonate. In the manufacturing process of components such as multilayer ceramic capacitors, calcite-type calcium carbonate does not undergo crystal transformation due to heat, thus ensuring the quality of ceramic components. In contrast, other crystalline phases of calcium carbonate, because they are not the most stable crystalline phases, undergo crystal transformation upon heating, which can lead to performance degradation of electronic ceramic components. Therefore, calcite-type calcium carbonate is the preferred choice for use in the field of electronic ceramics. However, existing calcite-type calcium carbonates have poor dispersibility and are prone to agglomeration, such as the method for preparing cubic precipitated calcium carbonate with controllable particle size disclosed in patent application number CN202111291794.8; some calcite-type calcium carbonates also have too wide a particle size distribution, such as the method for preparing large and small cubic dispersed precipitated calcium carbonate disclosed in patent application number CN202111664054.4. In general, calcium carbonate used in the field of electronic ceramics needs to have several characteristics, including calcite-type, non-agglomeration, and narrow particle size distribution.

[0003] Therefore, based on the actual situation of industrial production, it is an important task for the calcium carbonate materials industry to explore a simple, low-cost method for preparing calcium carbonate powder that can simultaneously control crystal form, morphology and particle size, so as to meet the requirements of electronic grade calcium carbonate. Summary of the Invention

[0004] In view of the above-mentioned prior art, the purpose of this invention is to provide a method for preparing micron-sized monodisperse spherical calcium carbonate powder. This powder consists of micron-sized monodisperse spherical particles with a calcite crystal form and a concentrated particle size distribution. The preparation method of this invention is simple, low-cost, and easy to industrialize.

[0005] To achieve the above objectives, the present invention adopts the following technical solution:

[0006] In a first aspect, the present invention provides a method for preparing micron-sized monodisperse spherical calcium carbonate powder, characterized by comprising the following steps:

[0007] (1) Add additives to calcium chloride aqueous solution while stirring, and continue stirring to obtain calcium chloride mixture;

[0008] (2) Heat the carbonate aqueous solution and the calcium chloride mixture separately, mix and stir them under the heat, keep warm and continue stirring after mixing, then let stand and age, wash the solid after solid-liquid separation, and dry to obtain micron-sized monodisperse spherical calcium carbonate powder.

[0009] Preferably, in step (1), the concentration of calcium ions in the calcium chloride mixture is 0.2 to 1.2 mol / L, and the concentration of the additive is 0.1 to 0.5 mol / L.

[0010] Preferably, the additive is at least one of nitrotriacetic acid or triethylenetetramine.

[0011] Preferably, the additive consists of hyponitrotriacetic acid and triethylenetetramine in a 1:1 molar ratio.

[0012] Preferably, in step (2), the molar ratio of calcium ions in the calcium chloride mixture to carbonate ions in the carbonate aqueous solution is 1:(1-1.1); the concentration of carbonate ions in the carbonate aqueous solution is 0.3-1.0 mol / L; and the carbonate in the carbonate aqueous solution is at least one of sodium carbonate, sodium bicarbonate, potassium carbonate, potassium bicarbonate, ammonium carbonate, and ammonium bicarbonate.

[0013] More preferably, the carbonate aqueous solution is a mixed solution of potassium carbonate and potassium bicarbonate.

[0014] Preferably, in step (2), the heating temperature is 35-45°C; the mixing is spray mixing, and the mixing time is 10-100 min.

[0015] Preferably, in step (2), the stirring speed is 300-1300 rpm; the heat preservation time is 10-120 min; and the settling and aging time is 20-120 min.

[0016] Preferably, the washing involves washing the solid 2-4 times with deionized water or anhydrous ethanol, or first with deionized water and then with anhydrous ethanol.

[0017] Preferably, the drying is carried out at 50-120°C for 1-3 hours.

[0018] In a second aspect, the present invention provides micron-sized monodisperse spherical calcium carbonate powder obtained by the above preparation method.

[0019] Preferably, the calcium carbonate powder is spherical, has a calcite crystal form, and the particles are monodisperse; the average particle size of the calcium carbonate powder is 0.8–9 μm.

[0020] A third aspect of this invention provides the application of micron-sized monodisperse spherical calcium carbonate powder in the fabrication of electronic ceramic devices. Furthermore, micron-sized monodisperse spherical calcium carbonate powder can also be used in various fields such as food ingredients and rubber fillers.

[0021] The beneficial effects of this invention are:

[0022] (1) The raw materials used in this invention are readily available, the process is simple, and it is easy to industrialize.

[0023] (2) The present invention uses medium temperature synthesis, which can effectively control the nucleation and crystal growth of calcium carbonate while the additives are introduced; the crystal form and morphology of the final calcium carbonate particles can be controlled through the particle maturation process during the heat preservation and aging stage.

[0024] (3) The calcium carbonate particles prepared by this invention are spherical, with a calcite crystal form and a size that can be controlled within the range of 0.8 to 9 μm. The particles are monodisperse and fully meet the high standard requirements of electronic grade calcium carbonate. Attached Figure Description

[0025] Figure 1 Transmission electron microscope (TEM) images of calcium carbonate powder samples prepared in Examples 1-3 and Comparative Examples 1-2, wherein (a) is a TEM image of calcium carbonate powder prepared in Example 1, (b) is a TEM image of calcium carbonate powder prepared in Example 2, (c) is a TEM image of calcium carbonate powder prepared in Example 3, (d) is a TEM image of calcium carbonate powder prepared in Comparative Example 1, and (e) is a TEM image of calcium carbonate powder prepared in Comparative Example 2.

[0026] Figure 2 A scanning electron microscope (SEM) image of the calcium carbonate powder sample prepared in Example 1;

[0027] Figure 3 The image shows the powder X-ray diffraction (XRD) pattern of the calcium carbonate powder sample prepared in Example 1. Detailed Implementation

[0028] It should be noted that the following detailed descriptions are illustrative and intended to provide further explanation of this application. Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains.

[0029] As introduced in the background section, the preparation of micron-sized monodisperse spherical calcium carbonate powder suitable for the field of electronic ceramics is currently challenging, especially in terms of meeting several high requirements for electronic-grade calcium carbonate, such as spherical shape, calcite crystal form, concentrated particle size, and non-agglomerated particle dispersion, while achieving low-cost industrial production.

[0030] Based on this, the purpose of this invention is to provide a method for preparing micron-sized monodisperse spherical calcium carbonate powder. This invention, through research on additives, uses hyponitrotriacetic acid and triethylenetetramine as additives and controls a specific crystallization temperature to effectively control the nucleation and growth of calcium carbonate. The resulting calcium carbonate crystals are not only calcite-type and non-agglomerated, but also have a concentrated particle size distribution, meeting the requirements for electronic-grade calcium carbonate.

[0031] To enable those skilled in the art to better understand the technical solution of this application, the technical solution of this application will be described in detail below with reference to specific embodiments.

[0032] The test materials used in the embodiments of this invention are all conventional test materials in the art and can be purchased through commercial channels.

[0033] Example 1:

[0034] (1) Mix triethylenetetramine and hypotriacetic acid in an equal molar ratio to obtain an additive. Prepare 20 L of 0.5 mol / L calcium chloride aqueous solution at room temperature. Add the additive to the calcium chloride aqueous solution while stirring so that the concentrations of triethylenetetramine and hypotriacetic acid are both 0.2 mol / L. Continue stirring for 40 min to obtain solution A.

[0035] (2) Prepare a mixed solution of potassium carbonate and potassium bicarbonate at room temperature, so that the concentrations of potassium carbonate and potassium bicarbonate in the mixed solution are 0.25 mol / L, to obtain solution B;

[0036] (3) First heat solution A and solution B to 40°C, take 20.0L of solution A and solution B respectively, spray them into the reactor at the same speed using a spray method, and stir at a speed of 500rpm. Complete the spray feeding within 20min. After feeding, continue stirring at 40°C for 60min, and then let it stand at 40°C for 100min.

[0037] (4) The system obtained in step (3) after standing and aging is separated into solid and liquid by centrifugation. The filter cake is first washed with deionized water 3 times and then washed with anhydrous ethanol once.

[0038] (5) The solid obtained in step (4) is dried at 100°C for 2 hours to obtain micron-sized spherical calcium carbonate powder.

[0039] The obtained calcium carbonate powder has the following characteristics: Figure 1 As shown in (a), the particles are spherical; the crystal form is calcite type; D 10 It is 1.3μm, D 50 It is 2.9 μm, D 90 It has a particle size of 4.6 μm and a narrow particle size distribution. (From...) Figure 2 The scanning electron microscope (SEM) images show that the calcium carbonate powder prepared in Example 1 has a basically uniform particle size, exhibits no agglomeration, and is in a monodisperse state. Figure 3 The XRD pattern shows that the calcium carbonate powder prepared in Example 1 has a calcite crystal form.

[0040] Example 2

[0041] The difference from Example 1 is that in step (1), only triethylenetetramine is used as an additive. 20L of 0.5mol / L calcium chloride aqueous solution is prepared at room temperature. The additive (the amount added is the same as the mass of the additive in Example 1) is added to the calcium chloride aqueous solution while stirring. Stirring is continued for 40min to obtain solution A.

[0042] The final calcium carbonate powder has the following characteristics: Figure 1 As shown in (b), the particles are spherical; the crystal form is calcite type; D 10 It is 0.7μm, D 50 It is 2.5μm, D 90 It has a particle size of 5.2 μm and a narrow particle size distribution.

[0043] Example 3

[0044] The difference from Example 1 is that in step (1), only nitrotriacetic acid is used as an additive. 20L of 0.5mol / L calcium chloride aqueous solution is prepared at room temperature. The additive (the amount added is the same as the mass of the additive in Example 1) is added to the calcium chloride aqueous solution while stirring. Stirring is continued for 40min to obtain solution A.

[0045] The final calcium carbonate powder has the following characteristics: Figure 1 As shown in (c), the particles are spherical; the crystal form is calcite type; D 10 It is 1.1 μm, D 50 It is 4.5μm, D 90 It has a particle size of 8.0 μm and a narrow particle size distribution.

[0046] Example 4

[0047] (1) Mix triethylenetetramine and hypotriacetic acid in an equal molar ratio to obtain an additive. Prepare 20.0 L of 1.2 mol / L calcium chloride aqueous solution at room temperature. Add the additive to the calcium chloride aqueous solution while stirring, so that the concentrations of triethylenetetramine and hypotriacetic acid are both 0.1 mol / L. Continue stirring for 40 min to obtain solution A.

[0048] (2) Prepare a mixed solution of potassium carbonate and potassium bicarbonate at room temperature, so that the concentrations of potassium carbonate and potassium bicarbonate in the mixed solution are 0.6 mol / L, to obtain solution B;

[0049] (3) First heat solution A and solution B to 40°C, take 20.0L of solution A and solution B respectively, spray them into the reactor at the same speed using a spray method, and stir at a speed of 500rpm. Complete the spray feeding within 60min. After feeding, continue stirring at 40°C for 60min, and then let it stand at 40°C for 100min.

[0050] (4) The system obtained in step (3) after standing and aging is separated into solid and liquid by centrifugation. The filter cake is first washed with deionized water 3 times and then washed with anhydrous ethanol once.

[0051] (5) The solid obtained in step (4) is dried at 100°C for 2 hours to obtain micron-sized spherical calcium carbonate powder.

[0052] The final calcium carbonate powder has the following characteristics: spherical particles; calcite crystal form; D 10 It is 1.8μm, D 50 It is 5.6 μm, D 90 It has a particle size of 8.3 μm and a narrow particle size distribution.

[0053] Example 5

[0054] (1) Mix triethylenetetramine and hypotriacetic acid in an equal molar ratio to obtain an additive. Prepare 20 L of 0.3 mol / L calcium chloride aqueous solution at room temperature. Add the additive to the calcium chloride aqueous solution while stirring, so that the concentrations of triethylenetetramine and hypotriacetic acid are both 0.1 mol / L. Continue stirring for 100 min to obtain solution A.

[0055] (2) Prepare a mixed solution of potassium carbonate and potassium bicarbonate at room temperature, so that the concentrations of potassium carbonate and potassium bicarbonate in the mixed solution are 0.15 mol / L, to obtain solution B;

[0056] (3) First heat solution A and solution B to 35°C, take 20L of solution A and solution B respectively, spray them into the reactor at the same speed using a spray method, and stir at a speed of 1300rpm. Complete the spray feeding within 10min. After feeding, continue stirring at 35°C for 100min, and then let it stand and age at 35°C for 100min.

[0057] (4) The system obtained in step (3) after standing and aging is separated into solid and liquid by centrifugation. The filter cake is first washed with deionized water 3 times and then washed with anhydrous ethanol once.

[0058] (5) The solid obtained in step (4) is dried at 100°C for 2 hours to obtain micron-sized spherical calcium carbonate powder.

[0059] The final calcium carbonate powder has the following characteristics: spherical particles; calcite crystal form; D 10 It is 2.8μm, D 50 It is 7.8 μm, D 90 It has a particle size of 11.5 μm and a narrow particle size distribution.

[0060] Comparative Example 1

[0061] The difference from Example 1 is that no additives are added. The final calcium carbonate powder has the following characteristics: Figure 1 As shown in (d), the particles are blocky hexahedrons of varying sizes; the crystal form is calcite type; the size is about 2 to 8 μm; the particle size distribution is uneven.

[0062] Comparative Example 2

[0063] Calcium carbonate was prepared according to the method described in "Synthesis Mechanism of Electronic Grade Calcium Carbonate" (Journal of East China University of Science and Technology (Natural Science Edition), Vol.45 NO.5, 2019-10):

[0064] Tartaric acid was added as an additive at a mass fraction of 1.0% to a purified calcium chloride aqueous solution. Then, ammonia and ammonium bicarbonate in a molar ratio of 1:1 were added. The reaction temperature was set at 30°C, and the mixture was stirred continuously for 1 hour. The mixture was washed with deionized water and anhydrous ethanol until the conductivity was 0. After drying at 400°C, the product calcium carbonate was obtained.

[0065] The final calcium carbonate powder has the following characteristics: Figure 1 As shown in (e), the particles are nearly spherical; the crystal form is calcite type; D 10 It is 0.6μm, D 50It is 2.6μm, D 90 It has a particle size of 5.1 μm and a relatively narrow particle size distribution.

[0066] The particle size distribution of Examples 1-5 and Comparative Examples 1-2 was calculated, and the results are shown in Table 1.

[0067] Where ΔD represents the particle size distribution, ΔD = (D 90 -D 10 ) / D 50 .

[0068] Table 1

[0069]

[0070] The calcium carbonate particles in Examples 1, 4, and 5 have the smallest particle size distribution ΔD, indicating that their particle size distribution is the most concentrated. Therefore, the calcium carbonate particles prepared by the method of the present invention have a concentrated particle size distribution, which meets the requirements of electronic grade calcium carbonate.

[0071] The above description is merely a preferred embodiment of this application and is not intended to limit this application. Various modifications and variations can be made to this application by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the protection scope of this application.

Claims

1. A method for preparing micron-sized monodisperse spherical calcium carbonate powder, characterized in that, Includes the following steps: (1) Add the additive to the calcium chloride aqueous solution under stirring, and continue stirring to obtain a calcium chloride mixture; the concentration of calcium ions in the calcium chloride mixture is 0.2~1.2 mol / L, and the concentration of the additive is 0.1~0.5 mol / L; the additive is at least one of hypozinotriacetic acid or triethylenetetramine; (2) The carbonate aqueous solution and the calcium chloride mixture are heated separately, and the two are mixed and stirred under the heat. After the mixing is completed, the mixture is kept warm and stirred. Then it is allowed to stand for aging. After solid-liquid separation, the solid is washed and dried to obtain micron-sized monodisperse spherical calcium carbonate powder. The heating temperature is 35~45℃. The mixing is spray feeding and the mixing time is 10~100min.

2. The preparation method according to claim 1, characterized in that, The additive is composed of hyponitrotriacetic acid and triethylenetetramine in a 1:1 molar ratio.

3. The preparation method according to claim 1, characterized in that, In step (2), the molar ratio of calcium ions in the calcium chloride mixture to carbonate ions in the carbonate aqueous solution is 1:(1~1.1); the concentration of carbonate ions in the carbonate aqueous solution is 0.3~1.0 mol / L; the carbonate in the carbonate aqueous solution is at least one of sodium carbonate, sodium bicarbonate, potassium carbonate, potassium bicarbonate, ammonium carbonate, and ammonium bicarbonate.

4. The preparation method according to claim 1, characterized in that, In step (2), the stirring speed is 300~1300 rpm; the heat preservation time is 10~120 min; and the settling and aging time is 20~120 min.

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