Preparation method of calcium carbonate micron sheet

Abstract

The invention provides a calcium carbonate micron sheet preparation method, which comprises: S1) crushing a shell raw material, mixing with a sodium hypochlorite solution, and stirring to obtain a turbid liquid; s2) standing and / or centrifuging the turbid liquid to obtain calcium carbonate micron sheets; the shell raw material is selected from a shell pearl layer and / or a calcium hard shell. Compared with the prior art, the preparation method provided by the invention has the advantages that the calcium carbonate micron sheet can be efficiently stripped from the shell, the yield is high, and the preparation process is simple and environment-friendly; secondly, the preparation method provided by the invention can be used for respectively obtaining calcium carbonate micron short sheets with approximate length and width and calcium carbonate micron long sheets with high length-width ratio; in addition, the obtained calcium carbonate micron sheet retains a complete sheet structure in the shell, and can be used as an excellent natural sheet micro-nano material in the fields of preparation of cosmetics, environment-friendly coatings, biological medicines, high-performance micro-nano composite materials and the like.

Description

Technical Field

[0001] The present invention belongs to the technical field of materials, and particularly relates to a method for preparing calcium carbonate microplates. Background Art

[0002] Shellfish represented by abalone shells, as a natural renewable resource, have attracted extensive attention from scientific researchers due to their excellent strength, toughness, beautiful colors, and textures. The nacre is the main component of these shells and is composed of 95 vol% of micron-scale aragonite-phase calcium carbonate flakes and 5 vol% of organic matter stacked orderly in an alternating manner. Therefore, it simultaneously exhibits excellent comprehensive mechanical properties such as high strength, high stiffness, and high fracture toughness.

[0003] Inspired by this unique structure of nacre in shells, researchers have attempted to compound various sheet-like micro-nano ceramic building blocks (aluminum oxide, boron nitride, MXene, glass flakes, clay flakes, etc.) with organic substances and assemble them into a layered structure similar to natural mother-of-pearl through the development of various methods, obtaining a series of lightweight, high-strength, and high-toughness layered-structured nanocomposites (Adv. Mater. 2024, 36, 2313443). However, calcium carbonate microplates, as the main component of these shells, have rarely been developed and used in the preparation of such high-performance materials (Angew. Chem. Int. Ed. 2024, e202405228).

[0004] Currently, the processing and utilization level of abalone shells is relatively low. Only a small amount is processed into ornaments or treated as powders for use in coating additives, traditional Chinese medicines, or livestock and poultry feed additives, etc., while most are piled up as waste around islands and towns, which causes serious resource waste and environmental pollution. In recent years, although there have been individual reports on extracting calcium carbonate microplates from shells, how to improve the utilization rate of shell wastes such as abalone shells and efficiently prepare large-diameter calcium carbonate microplates still faces challenges.

[0005] Currently, the relevant patents on obtaining calcium carbonate powders from shells are: a method for preparing nano-calcium carbonate powders by mechanical force chemistry of shells (Chinese patent with publication number CN104495900A), a method for preparing functional calcium carbonate using mussel shells as raw materials (Chinese patent with publication number CN101920982A), a method for preparing prismatic bio-calcium carbonate (Chinese patent with publication number CN103571235A), and a method for preparing light calcium carbonate using shell powder (Chinese patent with publication number CN107892320A). However, these methods cannot obtain sheet-like calcium carbonate microplates.

[0006] Currently, the relevant patents for obtaining sheet-like calcite-phase calcium carbonate are: A preparation method of sheet-like calcite calcium carbonate crystals (Chinese patent with publication number CN107473252A), A method for preparing sheet-like calcite calcium carbonate crystals (Chinese patent with publication number CN101935866A). However, the particle size of the obtained calcium carbonate tablets is relatively small (2 - 3 μm), and the aspect ratio is also low. Currently, the relevant patents for obtaining nacreous aragonite sheets are: A preparation method of sheet-like aragonite calcium carbonate (Chinese patent with publication number CN102583482A), A method for preparing sheet-like aragonite-structured calcium carbonate powder from shells under hydrothermal conditions (Chinese patent with publication number CN103086415A), and A method for exfoliating nacreous aragonite sheets (Chinese patent with publication number CN108675334A). But these methods have problems such as low yield, complex and time-consuming processes, or reliance on excessive use of harmful chemical reagents. Summary of the Invention

[0007] In view of this, the technical problem to be solved by the present invention is to provide a preparation method of calcium carbonate micro-sheets, which can efficiently obtain relatively complete calcium carbonate micro-sheets from shells such as abalone shells, and has high yield, simple preparation process, and environmental protection.

[0008] The present invention provides a preparation method of calcium carbonate micro-sheets, comprising the following steps:

[0009] S1) After crushing the shell raw material, it is mixed and stirred with a sodium hypochlorite solution to obtain a turbid liquid;

[0010] S2) The turbid liquid is allowed to stand and / or centrifuged to obtain calcium carbonate micro-sheets;

[0011] The shell raw material is selected from nacre and / or calcareous hard shells of shells.

[0012] Preferably, the nacre of the shell is prepared according to the following method:

[0013] The outer surface of the shell is polished and cleaned to obtain the nacre of the shell;

[0014] The calcareous hard shell is selected from the shells of Anomiidae animals.

[0015] Preferably, the mass concentration of sodium hypochlorite in the sodium hypochlorite solution is 0.1% - 10%;

[0016] The mass ratio of the shell raw material to the sodium hypochlorite solution is 1:10 - 50.

[0017] Preferably, the rotation speed of the mixing and stirring is 100 - 1000 revolutions per minute; the mixing and stirring time is 4 - 24 h.

[0018] Preferably, the step S2) is specifically as follows: removing the supernatant by standing the turbid liquid, washing the precipitate, and drying to obtain calcium carbonate microplates; the standing time is 0.5 - 5 h;

[0019] Alternatively, removing the supernatant by centrifuging the turbid liquid, washing the precipitate, and drying to obtain calcium carbonate microplates; the rotation speed of the centrifugation is 500 - 5000 rpm; the centrifugation time is 1 - 10 min.

[0020] Preferably, the drying temperature is 40 - 120 °C; the drying time is 1 - 12 h.

[0021] Preferably, if there are unpeeled fragments in the turbid liquid, take the upper turbid liquid after standing for a moment and then continue to stand and / or centrifuge to obtain calcium carbonate microplates; the standing time for a moment is 1 - 5 min.

[0022] Preferably, the nacre of the shell is selected from nacre of one or more of abalone shell, freshwater mussel, Pinctada martensii, black - lipped pearl oyster, golden - lipped pearl oyster and Hyriopsis schlegelii;

[0023] The calcareous hard shell is selected from Placuna placenta.

[0024] Preferably, the shell raw material is nacre of the shell; the rotation speed of the mixing and stirring is 500 - 1000 revolutions per minute; the mixing and stirring time is 10 - 24 h; the lateral dimension of the calcium carbide microplates is 2 - 9 μm; the thickness of the calcium carbide microplates is 300 - 600 nm.

[0025] Preferably, the shell raw material is calcareous hard shell; the rotation speed of the mixing and stirring is 100 - 500 revolutions per minute; the mixing and stirring time is 4 - 10 h; the width of the calcium carbide microplates is 2 - 14 μm; the length of the calcium carbide microplates is 20 - 140 μm; the thickness of the calcium carbide microplates is 100 - 500 nm.

[0026] The present invention provides a method for preparing calcium carbonate microplates, comprising the following steps: S1) crushing shell raw materials and mixing and stirring them with a sodium hypochlorite solution to obtain a turbid liquid; S2) standing and / or centrifuging the turbid liquid to obtain calcium carbonate microplates; the shell raw materials are selected from nacre and / or calcareous hard shells. Compared with the prior art, the preparation method provided by the present invention can efficiently strip calcium carbonate microplates from shells, and has high yield, simple preparation process and environmental protection; secondly, the preparation method provided by the present invention can respectively obtain calcium carbonate micro-short plates with approximate length and width and calcium carbonate micro-long plates with high aspect ratio; in addition, the obtained calcium carbonate microplates retain their complete sheet structure in the shells and can be used as excellent natural sheet micro-nano materials in the fields of cosmetics, environmental protection coatings, biomedicine and the preparation of high-performance micro-nano composite materials, etc. Description of the Drawings

[0027] Figure 1 It is a photograph of calcium carbonate microplates with approximate length and width obtained in Example 1 of the present invention;

[0028] Figure 2 It is an X-ray diffraction pattern of calcium carbonate microplates with approximate length and width obtained in Example 1 of the present invention;

[0029] Figure 3 It is a scanning electron microscope image (×1000 times) of the flat state of calcium carbonate microplates with approximate length and width obtained in Example 1 of the present invention;

[0030] Figure 4 It is a scanning electron microscope image (×2000 times) of the flat state of calcium carbonate microplates with approximate length and width obtained in Example 1 of the present invention;

[0031] Figure 5 It is a scanning electron microscope image (×8000 times) of the flat state of calcium carbonate microplates with approximate length and width obtained in Example 1 of the present invention;

[0032] Figure 6 It is a scanning electron microscope image (×5000 times) of the upright state of calcium carbonate microplates with approximate length and width obtained in Example 1 of the present invention;

[0033] Figure 7 It is a measurement and statistical result diagram of the size distribution of calcium carbonate microplates with approximate length and width obtained in Example 1 of the present invention;

[0034] Figure 8 It is a scanning electron microscope image (×2000 times) of the flat state of calcium carbonate microplates with approximate length and width obtained in Example 2 of the present invention;

[0035] Figure 9 It is a scanning electron microscope image (×2000 times) of the flat state of calcium carbonate microplates with approximate length and width obtained in Example 3 of the present invention;

[0036] Figure 10 Photograph of the high aspect ratio calcium carbonate microplates obtained in Example 4 of the present invention;

[0037] Figure 11 X-ray diffraction pattern of the high aspect ratio calcium carbonate microplates obtained in Example 4 of the present invention;

[0038] Figure 12 Scanning electron micrograph (×500 magnification) of the high aspect ratio calcium carbonate microplates obtained in Example 4 of the present invention in a flat state;

[0039] Figure 13 Scanning electron micrograph (×1000 magnification) of the high aspect ratio calcium carbonate microplates obtained in Example 4 of the present invention in a flat state;

[0040] Figure 14 Scanning electron micrograph (×2000 magnification) of the high aspect ratio calcium carbonate microplates obtained in Example 4 of the present invention in an upright state;

[0041] Figure 15 Graph of the measurement and statistical results of the size distribution of the high aspect ratio calcium carbonate microplates obtained in Example 4 of the present invention;

[0042] Figure 16 Electron micrograph photograph (×3000 magnification) of the calcium carbonate tablets obtained in Comparative Example 1 of the present invention. Detailed implementation manners

[0043] Next, in combination with the embodiments of the present invention, the technical solutions in the embodiments of the present invention will be clearly and completely described. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

[0044] The present invention provides a method for preparing calcium carbonate microplates, comprising the following steps: S1) Crushing the shell raw material and mixing and stirring it with a sodium hypochlorite solution to obtain a turbid liquid; S2) Standing and / or centrifuging the turbid liquid to obtain calcium carbonate microplates; the shell raw material is selected from nacre and / or calcareous hard shells.

[0045] Among them, the present invention does not have any special restrictions on the sources of all raw materials, and they can be commercially available.

[0046] According to the present invention, the nacre can be the nacre of the shell that can produce nacre well-known to those skilled in the art, without any special restrictions. In the present invention, it is preferably the nacre of one or more of abalone shells, river mussels, Pinctada martensii, black-lip pearl oysters, gold-lip pearl oysters and Hyriopsis schlegelii.

[0047] According to the present invention, the nacre of the shell is preferably prepared by the following method: polishing and cleaning the outer surface of the shell to obtain the nacre of the shell; specifically, removing the non-iridescent part on the surface by polishing, that is, removing the horny layer (periostracum) on the outer layer of the shell and the prismatic layer in the middle layer.

[0048] According to the present invention, the calcareous hard shell is preferably a semi-transparent shell, more preferably the shell of an Anomalodesmata animal, and still more preferably the shell of Placuna placenta.

[0049] After crushing the shell raw material and mixing and stirring it with a sodium hypochlorite solution, a turbid liquid is obtained; the shell raw material is preferably crushed to a particle size of 0.5 - 20 mm; when the shell raw material is nacre of the shell, it is preferably crushed to a particle size of 0.5 - 5 mm; when the shell raw material is a calcareous hard shell, it is preferably crushed to a particle size of 5 - 20 mm; the mass concentration of sodium hypochlorite in the sodium hypochlorite solution is preferably 0.1% - 10%, more preferably 0.5% - 8%, still more preferably 1% - 6%, and most preferably 1% - 5%; in some embodiments provided by the present invention, the mass concentration of sodium hypochlorite in the sodium hypochlorite solution is specifically 1%, 2%, 3%, 4% or 5%; the mass ratio of the nacre of the shell to the sodium hypochlorite solution is preferably 1:10 - 50, more preferably 1:10 - 40, still more preferably 1:10 - 30, still more preferably 1:10 - 20, and most preferably 1:10 - 15; the rotation speed of the mixing and stirring is preferably 100 - 1000 revolutions per minute; optionally, the rotation speed of the mixing and stirring is 100 revolutions per minute, 200 revolutions per minute, 300 revolutions per minute, 400 revolutions per minute, 500 revolutions per minute, 600 revolutions per minute, 700 revolutions per minute, 800 revolutions per minute, 900 revolutions per minute, 1000 revolutions per minute or the range between any two of the above values; the time of the mixing and stirring is preferably 4 - 24 h; optionally, the time of the mixing and stirring is 4 h, 6 h, 10 h, 12 h, 14 h, 16 h, 18 h, 20 h, 22 h, 24 h or the range between any two of the above values.

[0050] In a specific embodiment provided by the present invention, the shell raw material is nacre of the shell; the rotation speed of the mixing and stirring is preferably 500 - 1000 revolutions per minute; optionally, the rotation speed of the mixing and stirring is 500 revolutions per minute, 600 revolutions per minute, 700 revolutions per minute, 800 revolutions per minute, 900 revolutions per minute, 1000 revolutions per minute; the time of the mixing and stirring is preferably 10 - 24 h; optionally, the time of the mixing and stirring is 10 h, 12 h, 14 h, 16 h, 18 h, 20 h, 22 h, 24 h or the range between any two of the above values. By a higher stirring rotation speed and a longer stirring time, calcium carbonate microplates with approximate length and width can be obtained.

[0051] In a specific embodiment provided by the present invention, the shell raw material is a calcareous hard shell; the rotation speed of the mixing and stirring is preferably 100 to 500 revolutions per minute; optionally, the rotation speed of the mixing and stirring is 100 revolutions per minute, 200 revolutions per minute, 300 revolutions per minute, 400 revolutions per minute, 500 revolutions per minute or the range between any two of the above values; the time of the mixing and stirring is preferably 4 to 10 h; optionally, the time of the mixing and stirring is 4 h, 5 h, 6 h, 7 h, 8 h, 9 h, 10 h or the range between any two of the above values. By using a lower stirring speed and a shorter stirring time, the high aspect ratio structure of the calcium carbonate microplate can be avoided from being damaged, and calcium carbonate microplates with a high aspect ratio structure can be obtained.

[0052] Let the turbid liquid stand still and / or be centrifuged; the standing time is preferably 0.5 to 5 h, more preferably 1 to 3 h; the rotation speed of the centrifugation is preferably 2000 to 3000 rpm; optionally, the rotation speed of the centrifugation is 2000 rpm, 2500 rpm, 3000 rpm or the range between any two of the above values; the centrifugation time is preferably 1 to 10 min, more preferably 1 to 8 min, still more preferably 1 to 5 min, and most preferably 1 to 2 min.

[0053] In a specific embodiment provided by the present invention, if there are unpeeled fragments in the turbid liquid, after standing still for a moment, take the upper turbid liquid and continue to stand still or centrifuge to obtain calcium carbonate microplates; the time of standing still for a moment is preferably 1 to 5 min, more preferably 1 to 2 min. The unpeeled fragments can be removed first by a shorter standing time.

[0054] In a specific embodiment provided by the present invention, remove the upper clear liquid from the turbid liquid by standing still, wash the precipitate, and dry it to obtain calcium carbonate microplates; the standing time is preferably 0.5 to 5 h, more preferably 1 to 3 h; in the present invention, it is preferred to wash the precipitate with water, and more preferably to wash the precipitate with pure water; the number of washing times is preferably greater than or equal to three times; the residual sodium hypochlorite is removed by washing; the drying temperature is preferably 40 °C to 120 °C, more preferably 40 °C to 100 °C, still more preferably 50 °C to 90 °C, and most preferably 60 °C to 80 °C; the drying time is preferably 1 to 12 h, more preferably 4 to 12 h, still more preferably 6 to 12 h, still more preferably 8 to 12 h, and most preferably 10 to 12 h.

[0055] In a specific embodiment provided by the present invention, the turbid liquid is centrifuged to remove the supernatant, and the precipitate is washed and dried to obtain calcium carbonate microplates; the rotation speed of the centrifugation is preferably 2000-3000 rpm; optionally, the rotation speed of the centrifugation is 2000 rpm, 2500 rpm, 3000 rpm or the range between any two of the above values; the time of the centrifugation is preferably 1-10 min, more preferably 1-8 min, still more preferably 1-5 min, and most preferably 1-2 min; in the present invention, it is preferred to wash the precipitate with water, and more preferably to wash the precipitate with pure water; the number of washing times is preferably greater than or equal to three; the residual sodium hypochlorite is removed by washing; the drying temperature is preferably 40°C-120°C, more preferably 40°C-100°C, still more preferably 50°C-90°C, and most preferably 60°C-80°C; the drying time is preferably 1-12 h, more preferably 4-12 h, still more preferably 6-12 h, still more preferably 8-12 h, and most preferably 10-12 h.

[0056] According to the present invention, the yield of the calcium carbonate microplates is 75%-85%.

[0057] According to the present invention, two different calcium carbonate microplates can be obtained by the above preparation method, one is a calcium carbonate microplate with approximate length and width, and the other is a calcium carbonate microplate with a high aspect ratio structure.

[0058] In a specific embodiment provided by the present invention, the shell raw material is nacre of shell, and the obtained calcium carbonate microplates are calcium carbonate microplates with approximate length and width. The lateral dimension of the calcium carbonate microplates is preferably 2-9 μm; the thickness of the calcium carbide microplates is preferably 300-600 nm; more specifically, the calcium carbonate microplates with approximate length and width are aragonite phase calcium carbonate.

[0059] In a specific embodiment provided by the present invention, the shell raw material is a calcareous hard shell, and the obtained calcium carbonate microplates have a high aspect ratio structure; the width of the calcium carbonate micro long plates is preferably 2-14 μm; the length of the calcium carbonate micro long plates is preferably 20-140 μm; the thickness of the calcium carbonate microplates is preferably 100-500 nm; more specifically, the calcium carbonate microplates with a high aspect ratio structure are calcite phase calcium carbonate.

[0060] The preparation method provided by the present invention can efficiently strip calcium carbonate microplates from shells, with high yield, simple preparation process and environmental protection. Secondly, calcium carbonate micro-short films with approximate length and width and calcium carbonate micro-long films with high length-width ratio can be obtained by selecting different shell raw materials. In addition, the obtained calcium carbonate microplates retain their complete sheet structure in the shells and can be used as excellent natural sheet micro-nano materials in the fields of cosmetics, environmental protection coatings, biomedicine and the preparation of high-performance micro-nano composite materials, etc.

[0061] In order to further illustrate the present invention, a preparation method of a kind of calcium carbonate microplate provided by the present invention will be described in detail below in conjunction with embodiments.

[0062] The reagents used in the following examples are all commercially available.

[0063] Example 1

[0064] Weigh 10 g of nacre fragments of abalone shells (size 0.5 - 5 mm) and add them to 150 mL of 1% sodium hypochlorite solution, and carry out mechanical stirring at a stirring speed of 600 revolutions per minute. After stirring for 16 h, the solution turns white. Let the solution stand for 3 h to precipitate and layer. The upper layer is a transparent solution, and the lower layer is a white precipitate. Pour out the upper layer solution, wash the lower layer precipitate with pure water for 3 times to remove the residual sodium hypochlorite. Place the white precipitate in an oven at 60 °C and dry it for 12 h to obtain a white powder, which is the calcium carbonate microplate. Its photo is as Figure 1 shown, and its yield is about 85%.

[0065] Through X-ray diffraction characterization of the obtained powder, it shows that its phase is aragonite calcium carbonate, as Figure 2 shown; the obtained powder sample is observed by scanning electron microscopy as a large number of micron-scale sheet units, as Figures 3 - 6 shown. After statistics, the transverse size of the obtained calcium carbonate short films is 2 - 9 μm, and the thickness is 300 - 600 nm ( Figure 7 ).

[0066] Example 2

[0067] Weigh 100 g of nacre fragments of abalone shells (size 0.5 - 5 mm) and add them to 1000 mL of 4% sodium hypochlorite solution, and carry out mechanical stirring at a stirring speed of 800 revolutions per minute. After stirring for 16 h, the solution turns white. Let the solution stand for 3 h to precipitate and layer. The upper layer is a transparent solution, and the lower layer is a white precipitate. Pour out the upper layer solution, wash the lower layer precipitate with pure water for 3 times to remove the residual sodium hypochlorite. Place the white precipitate in an oven at 60 °C and dry it for 12 h to obtain a white powder, which is the calcium carbonate microplate. Its yield is about 80%. The obtained powder sample is observed by scanning electron microscopy as a large number of micron-scale sheet units, as Figure 8 shown.

[0068] Example 3

[0069] Weigh 1 kg of nacre fragments of river mussel shells (size 0.5 - 5 mm) and add them to 10 L of 1% sodium hypochlorite solution. Conduct mechanical stirring at a stirring speed of 800 revolutions per minute. After stirring for 16 h, the solution turns white. Let the solution stand for 3 h to allow precipitation and stratification. The upper layer is a transparent solution, and the lower layer is a white precipitate. Pour out the upper solution, wash the lower precipitate with pure water 3 times to remove the residual sodium hypochlorite. Place the white precipitate in an oven at 60 °C and dry it for 12 h to obtain a white powder, which is calcium carbonate microplates, and its yield is approximately 75%. The obtained powder sample is observed by scanning electron microscopy as a large number of micron-scale flaky units, as Figure 9 shown.

[0070] Example 4

[0071] Weigh 100 g of Pinctada martensii fragments (size 5 - 20 mm) and add them to 1000 mL of 5% sodium hypochlorite solution. Conduct mechanical stirring at a stirring speed of 400 revolutions per minute. After stirring for 6 h, the solution turns white. Let the solution stand for 3 h to allow precipitation and stratification. The upper layer is a transparent solution, and the lower layer is a white precipitate. Pour out the upper solution, wash the lower precipitate with pure water 3 times to remove the residual sodium hypochlorite. Place the white precipitate in an oven at 60 °C and dry it for 12 h to obtain a white powder, which is calcium carbonate microplates, as Figure 10 shown. Its yield is approximately 80%. Through X-ray diffraction characterization of the obtained powder, it is shown that its phase is calcite-phase calcium carbonate, as Figure 11 shown; the obtained powder sample is observed by scanning electron microscopy as a large number of micron-scale long flaky units with a high aspect ratio, as Figures 12 - 14 shown. After statistics, the width of the calcium carbonate micro long plates is 2 - 14 μm, the length is 20 - 140 μm, and the thickness is 100 - 500 nm( Figure 15 ).

[0072] Comparative Example 1

[0073] Weigh 10 g of sodium hydroxide and add it to 100 g of deionized water within 1 minute. Stir until completely dissolved. Then weigh 5 g of urea and add it to the solution within 2 minutes. Stir to dissolve and cool to room temperature to obtain a sodium hydroxide-urea solution.

[0074] Weigh 10 g of nacreous layer fragments of abalone shells (size 0.5 - 5 mm) and add them to 150 mL of sodium hydroxide - urea solution. Conduct mechanical stirring at a stirring speed of 600 revolutions per minute. After stirring for 16 h, the solution turns white. Let the solution stand for 3 h to allow precipitation and stratification. The upper layer is a transparent solution, and the lower layer is a white precipitate. Pour out the upper - layer solution, and wash the lower - layer precipitate with pure water 3 times to remove residual impurities. Place the white precipitate in an oven at 60 °C and dry it for 12 h to obtain white powder, which is calcium carbonate tablets, and the yield is only about 2%.

[0075] Use a scanning electron microscope to analyze the calcium carbonate tablets obtained in Comparative Example 1, and the electron scanning micrograph (×3000 magnification) is as Figure 16 shown. It can be seen from Figure 16 this that the tablet diameter size is significantly smaller than that in Example 1.

[0076] The above - mentioned are only the preferred embodiments 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 can be made, and these improvements and refinements should also be regarded as the protection scope of the present invention.

Claims

1. A method for preparing calcium carbonate micron flakes, characterized in that: The following steps are involved: S1) crushing the shell material and mixing with a sodium hypochlorite solution to obtain a turbid liquid; S2) allowing the turbid liquid to stand and / or centrifuge to obtain calcium carbonate micron flakes; The shell raw material is selected from shell nacre and / or calcareous hard shell.

2. The preparation method according to claim 1, characterized in that: The nacre of the shell is prepared according to the following method: The outer surface of the shell is polished and cleaned to obtain the pearl layer of the shell; The calcareous hard shell is selected from the shells of the family Anisopliae.

3. The preparation method according to claim 1, characterized in that: The mass concentration of sodium hypochlorite in the sodium hypochlorite solution is 0.1% to 10%; The mass ratio of the shell raw material to the sodium hypochlorite solution is 1:10-50.

4. The preparation method according to claim 1, characterized in that: The rotation speed of the mixing and stirring is 100 to 1000 rpm; the time of the mixing and stirring is 4 to 24 hours.

5. The preparation method according to claim 1, characterized in that: The step S2) specifically comprises: removing the supernatant from the turbid liquid by standing, washing the precipitate, and drying to obtain calcium carbonate micron flakes; the standing time is 0.5 to 5 hours; Alternatively, the turbid liquid is centrifuged to remove the supernatant, the precipitate is washed, and dried to obtain calcium carbonate micron sheets; the centrifugal speed is 500 to 5000 rpm; and the centrifugal time is 1 to 10 minutes.

6. The preparation method according to claim 5, characterized in that: The drying temperature is 40 to 120° C.; the drying time is 1 to 12 hours.

7. The preparation method according to claim 1, characterized in that: If there are unpeeled fragments in the turbid liquid, let it stand for a while, take out the upper turbid liquid, and continue to stand and / or centrifuge to obtain calcium carbonate micron sheets; the standing time is 1 to 5 minutes.

8. The preparation method according to claim 1, characterized in that: The shell pearl layer is selected from one or more pearl layers of abalone shells, river clams, Marsh clams, black lip clams, golden lip clams and pond lip clams; The calcareous hard shell is selected from sea moon shells.

9. The preparation method according to claim 1, characterized in that: The shell raw material is shell nacre; the rotation speed of the mixing and stirring is 500 to 1000 rpm; the mixing and stirring time is 10 to 24 hours; the lateral size of the calcium carbide micron sheet is 2 to 9 μm; and the thickness of the calcium carbide micron sheet is 300 to 600 nm.

10. The preparation method according to claim 1, characterized in that: The shell raw material is a calcium hard shell; the mixing rotation speed is 100 to 500 rpm; the mixing time is 4 to 10 hours; the width of the calcium carbide micron sheet is 2 to 14 μm; the length of the calcium carbide micron sheet is 20 to 140 μm; the thickness of the calcium carbide micron sheet is 100 to 500 nm.

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