Preparation method of snowflake-shaped micro-nano calcium carbonate

Abstract

The invention belongs to the field of calcium carbonate preparation, and particularly relates to a preparation method of snowflake-shaped micro-nano calcium carbonate. The method comprises the following steps: 1) preparation of a reversed-phase microemulsion: uniformly mixing N235 and alcohol, then adding an oil phase, and then adding a calcium salt solution to obtain the reversed-phase microemulsion; 2) preparation of snowflake-shaped micro-nano calcium carbonate: in a stirring state, introducing a mixed gas of carbon dioxide and nitrogen into the reversed-phase micro-emulsion in the step 1) to react until no precipitate is generated, then stopping introducing the carbon dioxide gas and the nitrogen, ending stirring, standing at room temperature, aging, and performing centrifugal separation to obtain snowflake-shaped micro-nano calcium carbonate; and drying the obtained precipitate to obtain the snowflake-shaped micro-nano calcium carbonate. The method disclosed by the invention is high in safety performance, simple and reasonable, low in energy consumption, easily available in raw materials and low in price, and the snowflake-shaped micro-nano calcium carbonate belongs to light calcium carbonate, has good particle size distribution and stability and good dispersity, and can be used as a filler of rubber, plastic, papermaking, coating, printing ink and the like.

Description

Technical Field

[0001] The invention belongs to the field of calcium carbonate preparation, and particularly relates to a method for preparing snowflake-shaped micro-nano calcium carbonate. Background Art

[0002] Calcium carbonate is an important inorganic chemical product, widely used in rubber, plastic, ink, coating, papermaking and other industries. In particular, micron calcium carbonate can be used in rubber, papermaking, plastics, etc. to make the surface of the products bright, with high tensile strength, high tension resistance, good bending resistance and crack resistance. It has good gloss, transparency, stability, quick drying and other characteristics in advanced inks. In the coating industry, it is mainly used in synthetic resin coatings, automotive paints, etc. to improve the thixotropy of the system, which can significantly improve the adhesion, scrub resistance, stain resistance of the coating, and has a good anti-settling effect; it has many excellent functions when added to automobile chassis paint, such as strong adhesion, impact resistance, scratch resistance, and durability. In the sealing and bonding material industry, it can accelerate the cross-linking reaction of the glue, enhance the stability of the glue, improve the mechanical properties of the glue, achieve the dual effects of filling and reinforcement, and make the surface of the rubber bright and delicate. In the production of micron calcium carbonate, the size, crystal shape, particle size distribution and dispersion performance of calcium carbonate crystals are its important performance indicators. Products with small particle size, uniform distribution and good dispersibility have higher economic utilization value and broader market prospects.

[0003] The reverse microemulsion method is an oil-in-water dispersion system composed of an oil phase, an aqueous phase, a surfactant, etc. As a new preparation method, it has simple equipment and process, can provide a nano-scale microreactor, can accurately control the size and morphology of particles, and well avoid the agglomeration and oxidation of micron particles that may be caused in other preparation methods. In addition, the prepared nanoparticles have the advantages of small particle size, good dispersibility, and no impurities. However, this method of preparing calcium carbonate generally mixes calcium salt microemulsion with carbonate microemulsion or a microemulsion with an aqueous solution. At this time, the carbonate ion concentration in the solution is large, the supersaturation is relatively large, and the ion diffusion rate is fast, which accelerates the nucleation and growth kinetics of calcium carbonate particles, but the crystal form of the particles is not well controlled. By introducing CO2 gas into the reverse CaCl2 microemulsion, the solubility of the gas in the liquid is relatively low, and the concentration of carbonate is relatively low, which can reduce the process of nucleation and growth of nano calcium carbonate. In addition, the reaction involves a three-phase reaction of gas, liquid, and solid, with large resistance and a long reaction time. It is easier to control the crystal form of nano calcium carbonate and the accumulation mode of the crystal nucleus, affecting the morphology. Summary of the invention

[0004] The purpose of the present invention is to provide a method for preparing snowflake-shaped micro-nano calcium carbonate. The method has high safety performance, is simple and reasonable, has low energy consumption, and the raw materials are easily available and inexpensive. The snowflake-shaped micro-nano calcium carbonate has good particle size distribution and stability, good dispersion, and has broad application prospects.

[0005] In order to achieve the above object, the technical solution adopted by the present invention is as follows:

[0006] A method for preparing snowflake-shaped micro-nano calcium carbonate comprises the following steps:

[0007] 1) Preparation of reverse microemulsion: N235 and alcohol are mixed evenly, then the oil phase is added, and then the calcium salt solution is added to obtain a reverse microemulsion;

[0008] 2) Preparation of snowflake-shaped micro-nano calcium carbonate: Under stirring, a mixture of carbon dioxide and nitrogen is introduced into the reverse microemulsion of step 1) to react until no precipitation is generated, then the introduction of carbon dioxide and nitrogen is stopped, stirring is terminated, the mixture is allowed to stand at room temperature, aged, and then centrifuged, and the obtained precipitate is dried to obtain the snowflake-shaped micro-nano calcium carbonate.

[0009] Furthermore, in step 1), the reverse microemulsion is composed of the following components in parts by weight: 18-75 parts of N235, 15-72 parts of alcohol, 10 parts of oil phase, and 2-4 parts of calcium salt solution.

[0010] Furthermore, in step 1), the alcohol is one of isopropanol, n-hexanol and sec-octanol.

[0011] Furthermore, in step 1), the oil phase is one of kerosene, dodecane and petroleum ether.

[0012] Furthermore, in step 1), the calcium salt solution is one of calcium chloride, calcium nitrate and calcium acetate solution, the concentration of the calcium salt solution is 0.5-2 mol / L, and the pH is 10-12.

[0013] Furthermore, in the step 2), the mixed gas of carbon dioxide and nitrogen is introduced into the reverse microemulsion of step 1) for a reaction time of 10 minutes, a stirring speed of 500-1200 rpm, and a volume ratio of carbon dioxide to nitrogen of 1:3-5.

[0014] Furthermore, in step 2), the aging time is 24 to 48 hours.

[0015] Furthermore, in step 2), the drying is carried out in an oven at 80° C. for 24 hours.

[0016] In summary, due to the adoption of the above technical solution, the beneficial effects of the present invention are:

[0017] (1) The present invention controls the morphology of the prepared calcium carbonate by introducing nitrogen and carbon dioxide into the reverse microemulsion and continuously stirring during the process of passing the gas, thereby obtaining snowflake-shaped micro-nano calcium carbonate. After the introduction of the carbon dioxide and nitrogen mixed gas, the micro-water pools (also called droplets) in the microemulsion gather around the carbon dioxide bubbles, and the carbon dioxide that penetrates into the micro-water pools combines with the Ca2+ in the micro-water pools to form nano-calcium carbonate, the size of which is similar to the droplet size. As the carbon dioxide and nitrogen mixed gas is continuously introduced, it continuously reacts with the surrounding micro-water pools to form layers of nano-calcium carbonate piled together, and then due to the influence of other factors such as stirring rate, viscosity, temperature, and carbon dioxide introduction rate, snowflake-shaped micro-nano calcium carbonate is finally formed. Stirring is conducive to the dispersion of the water phase in the oil phase, thereby facilitating the maintenance of the microemulsion, making it easy for the calcium carbonate to form smaller nano-scale particles in the micro-water pools. These nano-calcium carbonates gather together, so that more micro-nano composite calcium carbonate is formed in the system.

[0018] (2) The preparation method of the snowflake-shaped micro-nano calcium carbonate of the present invention has high safety performance, is simple and reasonable, has low energy consumption, and the raw materials are easily available and inexpensive. The snowflake-shaped micro-nano calcium carbonate has good particle size distribution and stability, good dispersion, and has broad application prospects. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 This is a SEM image of the snowflake-shaped micro-nano calcium carbonate prepared in Example 1;

[0020] Figure 2 This is a SEM image of the snowflake-shaped micro-nano calcium carbonate prepared in Example 2;

[0021] Figure 3 This is a SEM image of the snowflake-shaped micro-nano calcium carbonate prepared in Example 3;

[0022] Figure 4 This is the SEM image of the micro-nano calcium carbonate prepared in Comparative Example 1. DETAILED DESCRIPTION

[0023] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0024] Example 1

[0025] 1) Preparation of calcium chloride aqueous solution: Take 11.099g calcium chloride and 5ml ammonia water with a mass concentration of 25% in a beaker, add water to dissolve, transfer to a 100ml volumetric flask and make up to volume after complete dissolution to obtain a 1mol / L calcium chloride aqueous solution with a pH of 12, which is set aside;

[0026] 2) Preparation of reverse microemulsion: 37.5 g N235, 7.5 g isopropanol, 5 g kerosene and 1 g of the calcium chloride aqueous solution of step 1) were measured respectively, N235 and isopropanol were mixed evenly, kerosene was added, and then the calcium chloride aqueous solution was added to prepare a reverse microemulsion;

[0027] 3) Preparation of snowflake-shaped micro-nano calcium carbonate: placing the beaker containing the reverse microemulsion prepared in step 2) on a magnetic stirrer and stirring at a speed of 800 rpm, while introducing a mixed gas of carbon dioxide and nitrogen in a volume ratio of 1:3 into the reverse microemulsion, reacting for 10 minutes, at which time no precipitation is generated; then stopping the introduction of carbon dioxide and nitrogen, ending the stirring, standing and aging at room temperature for 24 hours, and then centrifuging, and drying the resulting precipitate at 80° C. for 24 hours to obtain the snowflake-shaped micro-nano calcium carbonate.

[0028] The samples obtained were Figure 1 Show, from Figure 1 It can be observed that the micronized calcium carbonate prepared in this example is shaped like snowflakes, has a particle size of 3 to 5 μm, and has a uniform morphology and good dispersion.

[0029] Example 2

[0030] 1) Preparation of calcium nitrate aqueous solution: Take 8.2045 calcium nitrate and 0.5 ml of 25% ammonia water in a beaker, add water to dissolve, transfer to a 100 ml volumetric flask after complete dissolution, and make up to volume to obtain a 0.5 mol / L calcium nitrate aqueous solution with a pH of 10, which is set aside;

[0031] 2) Preparation of reverse microemulsion: 36 g of isopropanol, 9 g of N235, 5 g of kerosene and 2 g of the calcium nitrate aqueous solution of step 1) were measured respectively, N235 and isopropanol were mixed evenly, kerosene was added, and then the calcium nitrate aqueous solution was added to prepare a reverse microemulsion;

[0032] 3) Preparation of snowflake-shaped micro-nano calcium carbonate: placing the beaker containing the reverse microemulsion prepared in step 2) on a magnetic stirrer and stirring at a speed of 500 rpm, while introducing a mixed gas of carbon dioxide and nitrogen in a volume ratio of 1:4 into the reverse microemulsion, reacting for 10 minutes, at which time a precipitate is generated; then the introduction of carbon dioxide and nitrogen is stopped, the stirring is terminated, the mixture is allowed to stand and age at room temperature for 32 hours, and then centrifuged, and the resulting precipitate is dried at 80° C. for 24 hours to obtain the snowflake-shaped micro-nano calcium carbonate.

[0033] The samples obtained were Figure 2 Show, from Figure 2 It can be observed that the micronized calcium carbonate prepared in this example is shaped like snowflakes, has a particle size of 3 to 5 μm, and has a uniform morphology and good dispersion.

[0034] Example 3

[0035] 1) Preparation of calcium acetate aqueous solution: 15.871 g of calcium acetate and 1 ml of 25% ammonia water were placed in a beaker, and water was added to dissolve the mixture. After the mixture was completely dissolved, the mixture was transferred to a 100 ml volumetric flask and the volume was fixed to obtain a 1 mol / L calcium acetate aqueous solution with a pH of 11, which was set aside;

[0036] 2) Preparation of reverse microemulsion: 11.25 g N235, 33.75 g isopropanol, 5 g kerosene and 1 g of the calcium acetate aqueous solution of step 1) were respectively measured, N235 and isopropanol were mixed evenly, kerosene was added, and then the calcium acetate aqueous solution was added to prepare a reverse microemulsion;

[0037] 3) Preparation of snowflake-shaped micro-nano calcium carbonate: placing the beaker containing the reverse microemulsion prepared in step 2) on a magnetic stirrer and stirring at a stirring speed of 1100 rpm, while introducing a mixed gas of carbon dioxide and nitrogen in a volume ratio of 1:5 into the reverse microemulsion, reacting for 10 minutes, at which time no precipitation is generated; then stopping the introduction of carbon dioxide and nitrogen, ending the stirring, standing and aging at room temperature for 48 hours, and then centrifuging, and drying the resulting precipitate at 80° C. for 24 hours to obtain the snowflake-shaped micro-nano calcium carbonate.

[0038] The samples obtained were Figure 3 Show, from Figure 3 It can be observed that the micronized calcium carbonate prepared in this example is shaped like snowflakes, has a particle size of 3 to 5 μm, and has a uniform morphology and good dispersion.

[0039] In order to illustrate the technical effect of the present invention, the inventors conducted the following comparative examples.

[0040] Comparative Example 1

[0041] The difference between Comparative Example 1 and Example 1 is that in step 2) of Comparative Example 1, pure carbon dioxide is used instead of the mixed gas of carbon dioxide and nitrogen, as follows:

[0042] 1) Preparation of calcium chloride aqueous solution: Take 11.099g calcium chloride and 5ml ammonia water with a mass concentration of 25% in a beaker, add water to dissolve, transfer to a 100ml volumetric flask and make up to volume after complete dissolution to obtain a 1mol / L calcium chloride aqueous solution with a pH of 12, which is set aside;

[0043] 2) Preparation of reverse microemulsion: 37.5 g N235, 7.5 g isopropanol, 5 g kerosene and 1 g of the calcium chloride aqueous solution of step 1) were measured respectively, N235 and isopropanol were mixed evenly, kerosene was added, and then the calcium chloride aqueous solution was added to prepare a reverse microemulsion;

[0044] 3) Preparation of micro-nano calcium carbonate: The beaker containing the reverse microemulsion prepared in step 2) is placed on a magnetic stirrer and stirred at a stirring speed of 800 rpm. At the same time, carbon dioxide is introduced into the reverse microemulsion and reacted for 10 min until no precipitation is generated. Then, the introduction of carbon dioxide is stopped and the stirring is terminated. The mixture is allowed to stand at room temperature for 24 h and then centrifuged. The obtained precipitate is dried at 80° C. for 24 h to obtain micro-nano calcium carbonate. The obtained sample is as follows: Figure 4 shown.

[0045] like Figure 4 It can be observed that the micron calcium carbonate prepared in Comparative Example 1 has an irregular shape.

[0046] From Comparative Example 1, it can be seen that the introduction of gases of different compositions into the reverse microemulsion to prepare micronized calcium carbonate has a great influence on the morphology of the particles. It may be that the introduction of the mixed gas of carbon dioxide and nitrogen can relatively slow down the reaction rate of carbon dioxide and calcium salt solution, making the formation of calcium carbonate more uniform, which is conducive to the formation of snowflake-like micro-nano structures. If the reaction rate is too fast, the generated calcium carbonate particles will be of different sizes and irregular shapes.

[0047] The above description is a detailed description of the preferred feasible embodiments of the present invention, but the embodiments are not intended to limit the scope of the patent application of the present invention. All equivalent changes or modified changes completed under the technical spirit suggested by the present invention should fall within the patent scope covered by the present invention.

Claims

1. A method for preparing snowflake-shaped micro-nano calcium carbonate, characterized in that: The following steps are involved: 1) Preparation of reverse microemulsion: N235 and alcohol are mixed evenly, then the oil phase is added, and then the calcium salt solution is added to obtain a reverse microemulsion; 2) Preparation of snowflake-shaped micro-nano calcium carbonate: Under stirring, a mixture of carbon dioxide and nitrogen is introduced into the reverse microemulsion of step 1) to react until no precipitation is generated, then the introduction of carbon dioxide and nitrogen is stopped, stirring is terminated, the mixture is allowed to stand at room temperature, aged, and then centrifuged, and the obtained precipitate is dried to obtain the snowflake-shaped micro-nano calcium carbonate.

2. The method for preparing snowflake-shaped micro-nano calcium carbonate according to claim 1, wherein In step 1), the reverse microemulsion is composed of the following components in parts by weight: 18-75 parts of N235, 15-72 parts of alcohol, 10 parts of oil phase, and 2-4 parts of calcium salt solution.

3. The preparation method of snowflake-shaped micro-nano calcium carbonate according to claim 1, characterized in that, In step 1), the alcohol is one of isopropanol, n-hexanol and sec-octanol.

4. The method for preparing snowflake-shaped micro-nano calcium carbonate according to claim 1, characterized in that: In step 1), the oil phase is one of kerosene, dodecane and petroleum ether.

5. The method for preparing snowflake-shaped micro-nano calcium carbonate according to claim 1, characterized in that: In step 1), the calcium salt solution is one of calcium chloride, calcium nitrate and calcium acetate solution, the concentration of the calcium salt solution is 0.5-2 mol / L, and the pH is 10-12.

6. The method for preparing snowflake-shaped micro-nano calcium carbonate according to claim 1, characterized in that: In the step 2), the mixed gas of carbon dioxide and nitrogen is introduced into the reverse microemulsion of step 1) for a reaction time of 10 minutes, a stirring speed of 500-1200 rpm, and a volume ratio of carbon dioxide to nitrogen of 1:3-5.

7. The method for preparing snowflake-shaped micro-nano calcium carbonate according to claim 1, characterized in that: In step 2), the aging time is 24 to 48 hours.

8. The method for preparing snowflake-shaped micro-nano calcium carbonate according to claim 1, characterized in that: In step 2), the drying is carried out in an oven at 80° C. for 24 hours.

Images