Process for the preparation of spherical calcium carbonate

Abstract

The application discloses a preparation method of spherical calcium carbonate. The method comprises the following steps: (1) dissolving xanthan gum and guar gum in water to obtain a mixed gum solution; (2) dissolving water-soluble carbonate and water-soluble calcium salt in the mixed gum solution respectively to obtain a carbonate mixed gum solution and a calcium salt mixed gum solution; (3) slowly adding the calcium salt mixed gum solution into the carbonate mixed gum solution under stirring, and aging after the addition is completed to obtain the spherical calcium carbonate. Compared with the prior art, the preparation method has the advantages of simple operation and easily available raw materials, the prepared spherical calcium carbonate is uniform in morphology and good in dispersity, and is suitable for mass production of micron-sized spherical calcium carbonate.

Description

Technical Field

[0001] This invention belongs to the field of calcium carbonate preparation, and specifically relates to a method for preparing spherical calcium carbonate. Background Technology

[0002] Micron- and nano-sized ultrafine calcium carbonate exhibits superior properties compared to conventional materials in terms of magnetism, photothermal resistance, catalytic activity, and melting point due to its ultrafine size. When used in rubber, papermaking, and plastics, it imparts a glossy surface, high tensile strength, high tensile strength, good bending resistance, and excellent crack resistance, making it an excellent white reinforcing filler. Furthermore, it can be used as a functional filler in electronic ceramic products, such as PTC thermistors, MLCC chip capacitors, semiconductor ceramic capacitors, and ceramic substrates.

[0003] Ultrafine calcium carbonate particles commonly take the forms of cubic, needle-like, chain-like, spindle-shaped, and spherical shapes. These different shapes determine the material's physical and chemical properties and its applicability. For example, as a reinforcing material, cubic calcium carbonate particles are widely used in industries such as papermaking and paint manufacturing because they easily align in a regular pattern, producing high smoothness and excellent gloss. Needle-like particles and whiskers can improve the tensile strength, impact strength, and glass transition temperature of plastics and rubber. Spherical calcium carbonate particles have excellent dispersibility and abrasion resistance, making them suitable for ink production, improving viscosity, stability, and drying speed. Furthermore, due to their unique properties, such as high surface area and chemical stability, spherical nanoscale calcium carbonate particles are also used in drug delivery, ceramics, and orthopedics, and their application prospects in electronic ceramics are also noteworthy. Since the size and shape of CaCO3 crystals largely determine their properties and applications, researchers are dedicated to finding methods to reliably control the morphology, form, and size of CaCO3 particles.

[0004] In terms of the preparation of spherical calcium carbonate, Ma et al. [1] prepared spherical calcium carbonate for drug delivery research by using different mixing strategies such as mechanical stirring, homogenization and ultrasound. The calcium carbonate obtained was spherical with irregular surface. Guo et al. [2] injected a small amount of calcium chloride solution into the polymer and allowed it to react slowly in the air to prepare spherical calcium carbonate, but its biggest drawback was that it could not be prepared on a large scale.

[0005] Guar gum is a galactomannan extracted from the endosperm of guar bean seeds. This polysaccharide is composed of galactose and mannose molecules. The backbone is a chain of (1-4)b-d-mannose units, with single (1-6)a-galactose units attached to the backbone. Xanthan gum is a biopolymer synthesized by Xanthomonas sp14 and is used as a thickener in many industries, such as pharmaceuticals, cosmetics, and food. The structure of xanthan gum in solution changes with solution temperature. At low solubility temperatures, below 40°C, xanthan gum exhibits an ordered conformation, while at higher temperatures, it transforms into a disordered structure. When xanthan gum is mixed with guar gum, the intermolecular interactions [3-5] and synergistic effects between the two gums result in a three-dimensional network structure, significantly increasing viscosity [3,6-8].

[0006] References:

[0007] [1]Jia J, Liu Q, Yang T, Wang L, Ma G. Facile fabrication ofvarisized calcium carbonate microspheres as vaccine adjuvants. Journal ofMaterials Chemistry B. 2017;5(8):1611-1623.

[0008] [2]Guo XH, Yu SH, Cai GB. Crystallization in a Mixture of Solvents byUsing a Crystal Modifier: Morphology Control in the Synthesis of HighlyMonodisperse CaCO3 Microspheres. Angew Chem Int Ed. 2006;45(24):3977-3981.

[0009] [3]Bresolin TMB, Milas M, Rinaudo M and Ganter JLMS, Xanthan-galactomannan interactions as related to xanthan conformations. Int J BiolMacromol 23:263–275 (1998).

[0010] [4]Kovacs P, Useful incompatibility of xanthan gum with galactomannans. Food Technol 27:26–30 (1973).

[0011] [5]Tako M, Asato A and Nakamura S, Rheological aspects of the intermolecular interaction between xanthan and locust bean gum in aqueousmedia. Agric Biol Chem 12:2995–3000 (1984).

[0012] [6]Schorsch C, Garnier C and Doublier JL, Viscoelastic properties of xanthan / galactomannan mixtures: comparison of guar gum with locust bean gum. Carbohydr Polym 34:165–175 (1997).

[0013] [7]Hoppe CA and Goswami A, Unique properties of high viscosity guargums. Polym Prep 39:690 (1998).

[0014] [8]Chaisawang M, Suphantharika M. Pasting and rheological properties of native and anionic tapioca starches as modified by guar gum and xanthangum. Food Hydrocolloids. 2006;20(5):641-649. Summary of the Invention

[0015] Given the shortcomings of existing methods for preparing spherical calcium carbonate, the purpose of this invention is to provide a simple and mass-production-friendly method for preparing spherical calcium carbonate, which produces spherical calcium carbonate with uniform morphology.

[0016] A method for preparing spherical calcium carbonate, comprising:

[0017] (1) Dissolve xanthan gum and guar gum in water to obtain a mixed gum solution;

[0018] (2) Dissolve the water-soluble carbonate and the water-soluble calcium salt in the mixed gel solution respectively to obtain the carbonate mixed gel solution and the calcium salt mixed gel solution;

[0019] (3) While stirring, the calcium salt mixed solution is slowly added to the carbonate mixed solution. After the addition is complete, the mixture is aged to obtain spherical calcium carbonate.

[0020] During the reaction of calcium salts and carbonates to form calcium carbonate, the three-dimensional network structure formed by the interaction of xanthan gum and guar gum in the mixed solution restricts and separates the growth process of calcium carbonate.

[0021] Preferably, the water-soluble carbonate is sodium carbonate, potassium carbonate, or ammonium carbonate.

[0022] Preferably, the water-soluble calcium salt is calcium chloride, calcium nitrate, or calcium acetate.

[0023] Preferably, the mass ratio of xanthan gum to guar gum is 1:2 to 2:1.

[0024] Preferably, in the reaction system of step (3), the total amount of xanthan gum and guar gum is 3wt% to 50wt% of the theoretical yield of calcium carbonate. Within this range, regular spherical calcium carbonate can be obtained. However, the larger the total amount of xanthan gum and guar gum, the higher the viscosity of the system, which makes stirring inconvenient and increases the cost of raw materials. More preferably, the total amount of xanthan gum and guar gum is 3wt% to 20wt% of the theoretical yield of calcium carbonate, and most preferably 4wt% to 10wt%.

[0025] Preferably, the concentration of calcium ions in the calcium salt mixed solution is 1 to 10 times the concentration of carbonate ions in the carbonate mixed solution.

[0026] In this reaction system, the concentrations of carbonate ions and calcium ions have little effect on the shape of calcium carbonate. Preferably, the concentration of carbonate ions in the carbonate mixed solution is controlled at 0.1~1 mol / L, and the concentration of calcium ions in the calcium salt mixed solution is controlled at 0.1~1 mol / L. Within this concentration range, regular spherical calcium carbonate can be obtained by reacting the two in appropriate excess or equimolar amounts of carbonate ions.

[0027] The mixing of the salt-mixed colloidal solution and the carbonate-mixed colloidal solution can be carried out at an equimolar ratio of carbonate ions to calcium ions, or with a slight excess of carbonate ions. Preferably, the calcium salt-mixed colloidal solution is slowly added to the carbonate-mixed colloidal solution at a molar ratio of calcium ions to carbonate ions of 1:1.

[0028] Preferably, in step (3), the aging time is more than 10 hours.

[0029] Preferably, in step (3), a homogenizer is used for stirring.

[0030] Preferably, in step (3), the stirring speed is above 2000 rpm.

[0031] The beneficial effects of this invention are:

[0032] (1) The preparation method of the present invention is simple to operate, the raw materials are readily available, and the prepared spherical calcium carbonate has a uniform morphology and good dispersion, which is suitable for mass production of micron-sized spherical calcium carbonate.

[0033] (2) The micron-sized spherical calcium carbonate prepared by the present invention is a spherical body formed by the aggregation of nano-sized calcium carbonate. It has a high specific surface area and is a good carrier. Since calcium carbonate is non-toxic, harmless and has no side effects, and xanthan gum and guar gum are also common food additives, the post-processing of this product is relatively simple when used for drug transportation. Attached Figure Description

[0034] Figure 1 This is a scanning electron microscope image of the spherical calcium carbonate product prepared in Example 1, wherein... Figure 1 -A is a magnification of 1000. The inset is an image of a single spherical calcium carbonate at a magnification of 20000. Figure 1 -B has a magnification of 5000.

[0035] Figure 2 This is a scanning electron microscope image of the spherical calcium carbonate product prepared in Comparative Example 1, in which... Figure 2 The magnification of -A is 1000. Figure 2 -B has a magnification of 5000.

[0036] Figure 3 The image shows a scanning electron microscope (SEM) image of the spherical calcium carbonate product prepared in Comparative Example 2. Figure 3 The magnification of -A is 1000. Figure 3 -B has a magnification of 5000.

[0037] Figure 4 This is a scanning electron microscope image of the spherical calcium carbonate product prepared in Example 2, wherein... Figure 4 The magnification of -A is 1000. Figure 4 -B has a magnification of 5000. Detailed Implementation

[0038] The technical solution of the present invention will be further described in detail below with reference to the embodiments.

[0039] Example 1

[0040] A method for preparing spherical calcium carbonate includes the following steps:

[0041] Taking the reaction of equimolar amounts of Na2CO3 (5.3g, 0.05mol) and CaCl2 (5.55g, 0.05mol) to produce a theoretical yield of 5g of calcium carbonate as an example.

[0042] (1) Preparation of a mixed solution of xanthan gum and guar gum:

[0043] The total amount of xanthan gum and guar gum (2:1) is weighed as 9% of the theoretical yield of calcium carbonate, that is, 0.3g xanthan gum and 0.15g guar gum are weighed, and then the xanthan gum and guar gum are mixed and dissolved in 550ml of distilled water. The resulting mixed gum solution is ready for use.

[0044] (2) Preparation of Na2CO3 mixed gel solution and CaCl2 mixed gel solution:

[0045] Weigh 5.3g of Na2CO3 and dissolve it in 500ml of the above mixed gel solution to obtain a Na2CO3 mixed gel solution with a concentration of 0.1mol / L;

[0046] Weigh 5.55g of CaCl2 and dissolve it in 50ml of the above mixed gel solution to obtain a CaCl2 mixed gel solution with a concentration of 1mol / L.

[0047] (3) Double decomposition reaction of Na2CO3 and CaCl2:

[0048] The prepared Na₂CO₃ mixed gel solution was placed in an 800 ml beaker and stirred in a homogenizer (2000 rpm). Then, the prepared CaCl₂ mixed gel solution was slowly added using a constant pressure dropping funnel (addition rate 1 drop / s). After stirring for 15 min, the mixture was aged for 12 h, centrifuged, washed, and dried to obtain spherical calcium carbonate. The scanning electron microscope image of the product (white powder) is shown below. Figure 1 As shown. From Figure 1 -A and Figure 1 -B indicates that calcium carbonate has a regular spherical morphology.

[0049] Figure 1 The inset in -A is a scanning electron microscope image (SEM) of a single spherical calcium carbonate crystal (magnification 20,000), combined with a magnified SEM image of a single spherical calcium carbonate crystal and the fracture surface of a very small number of spherical calcium carbonate crystals after they broke (see...). Figure 1 -B (indicated by the arrow) shows that a single spherical calcium carbonate is formed by the aggregation of countless calcium carbonate nanoparticles.

[0050] Comparative Examples 1 and 2 investigated the calcium carbonate prepared using xanthan gum and guar gum alone.

[0051] Comparative Example 1

[0052] (1) Preparation of xanthan gum solution:

[0053] Weigh 0.45g of xanthan gum, then dissolve the xanthan gum in 550ml of distilled water. Set aside the xanthan gum solution.

[0054] (2) Preparation of Na2CO3 solution and CaCl2 solution:

[0055] Weigh 5.3g of Na2CO3 and dissolve it in 500ml of the above xanthan gum solution to obtain a Na2CO3 solution with a concentration of 0.1mol / L;

[0056] Weigh 5.55g of CaCl2 and dissolve it in 50ml of the above xanthan gum solution to obtain a CaCl2 solution with a concentration of 1mol / L.

[0057] (3) Double decomposition reaction of Na2CO3 and CaCl2:

[0058] The prepared Na2CO3 solution was placed in an 800ml beaker and stirred in a homogenizer (2000 rpm). Then, the prepared CaCl2 solution was slowly added using a constant pressure dropping funnel (1 drop / s). After stirring for 15 minutes, the mixture was aged for 12 hours, centrifuged, washed, and dried to obtain calcium carbonate.

[0059] Figure 2 These are scanning electron microscope images of calcium carbonate obtained in this comparative example at different magnifications. Under these conditions, the vast majority of calcium carbonate is twinned spherical (see...). Figure 2 -B is indicated by the arrow.

[0060] Comparative Example 2

[0061] (1) Preparation of guar gum solution:

[0062] Weigh 0.45g of guar gum, then dissolve the guar gum in 550ml of distilled water. Set aside the guar gum solution.

[0063] (2) Preparation of Na2CO3 solution and CaCl2 solution:

[0064] Weigh 5.3g of Na2CO3 and dissolve it in 500ml of the above guar gum solution to obtain a Na2CO3 solution with a concentration of 0.1mol / L;

[0065] Weigh 5.55g of CaCl2 and dissolve it in 50ml of the above guar gum solution to obtain a CaCl2 solution with a concentration of 1mol / L.

[0066] (3) Double decomposition reaction of Na2CO3 and CaCl2:

[0067] The prepared Na2CO3 solution was placed in an 800ml beaker and stirred in a homogenizer (2000 rpm). Then, the prepared CaCl2 solution was slowly added using a constant pressure dropping funnel (1 drop / s). After stirring for 15 minutes, the mixture was aged for 12 hours, centrifuged, washed, and dried to obtain calcium carbonate.

[0068] Figure 3 These are scanning electron microscope images of calcium carbonate obtained in this comparative example at different magnifications. Under these conditions, the vast majority of calcium carbonate is also twinned spherical (see...). Figure 3 -B is indicated by the arrow.

[0069] As can be seen from Example 1 and Comparative Examples 1-2, when xanthan gum and guar gum are used alone, calcium carbonate forms a twin spherical shape. However, in Example 1, the interaction and synergistic effect between xanthan gum and guar gum can form a three-dimensional network structure. This three-dimensional network structure restricts and separates the process of calcium carbonate, thereby promoting the formation of a uniform and regular spherical shape.

[0070] Example 2

[0071] The preparation process and conditions in this embodiment are the same as in Example 1, except that the total amount of xanthan gum and guar gum (2:1) is weighed as 4.5% of the theoretical yield of calcium carbonate. The scanning electron microscope image of the prepared spherical calcium carbonate product is shown below. Figure 4 As shown.

[0072] The products mentioned above contain trace amounts of square calcium carbonate, which is introduced by the calcium chloride raw material. This is because the calcium chloride raw material readily absorbs water and reacts with carbon dioxide in the air to form calcium carbonate. The square calcium carbonate mixed in with the calcium chloride raw material can be removed by adding a small amount of acid after the calcium chloride solution is prepared.

[0073] Finally, it should be noted that the above descriptions are merely preferred embodiments of the present invention and are not intended to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for preparing spherical calcium carbonate, comprising: (1) Dissolve xanthan gum and guar gum in water to obtain a mixed gum solution; (2) Dissolve the water-soluble carbonate and the water-soluble calcium salt in the mixed gel solution respectively to obtain the carbonate mixed gel solution and the calcium salt mixed gel solution; (3) While stirring, the calcium salt mixed solution is slowly added to the carbonate mixed solution. After the addition is complete, the mixture is aged to obtain spherical calcium carbonate.

2. The preparation method according to claim 1, characterized in that: Water-soluble carbonates are sodium carbonate, potassium carbonate, or ammonium carbonate.

3. The preparation method according to claim 1, characterized in that: Water-soluble calcium salts are calcium chloride, calcium nitrate, or calcium acetate.

4. The preparation method according to claim 1, characterized in that: The mass ratio of xanthan gum to guar gum is 1:2 to 2:

1.

5. The preparation method according to claim 1 or 4, characterized in that: In the reaction system of step (3), the total amount of xanthan gum and guar gum used is 3wt%~50wt% of the theoretical yield of calcium carbonate.

6. The preparation method according to claim 5, characterized in that: The total amount of xanthan gum and guar gum used is 3 wt% to 20 wt% of the theoretical calcium carbonate yield.

7. The preparation method according to claim 6, characterized in that: The total amount of xanthan gum and guar gum used is 4 wt% to 10 wt% of the theoretical calcium carbonate yield.

8. The preparation method according to claim 1, characterized in that: The concentration of calcium ions in calcium salt mixed gel solutions is 1 to 10 times that of carbonate ions in carbonate mixed gel solutions.

9. The preparation method according to claim 1 or 8, characterized in that: The concentration of carbonate ions in the carbonate mixed gel solution is 0.1~1 mol / L, and the concentration of calcium ions in the calcium salt mixed gel solution is 0.1~1 mol / L.

10. The preparation method according to claim 1 or 8, characterized in that: The calcium salt mixed solution was slowly added to the carbonate mixed solution at a molar ratio of 1:1 for calcium ions and carbonate ions.

11. The preparation method according to claim 1, characterized in that: In step (3), the aging time is more than 10 hours.

12. The preparation method according to claim 1, characterized in that: In step (3), a homogenizer is used for stirring.

13. The preparation method according to claim 1 or 12, characterized in that: In step (3), the stirring speed is above 2000 rpm.

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