A preparation method of hydroxyapatite powder with high purity and different strengths

Abstract

This application relates to the field of new materials, and particularly to a method for preparing hydroxyapatite powder with high purity and controllable hardness, comprising the following steps: making calcium hydroxide suspension by adding water to calcium oxide and heating the calcium hydroxide suspension; heating, concentrating and dehydrating phosphoric acid; stirring the heated calcium hydroxide suspension and the phosphoric acid with increased polymerization degree under alkaline conditions and mixing them evenly; subjecting the mixture after the reaction to high-speed shear emulsification; aging the mixture after the shear emulsification; filtering the mixture after aging by pressure filtration and drying the filter cake; subjecting the dried solid to segmented calcination to obtain hydroxyapatite in different shapes. The process involved in the present invention is simple and easy to operate, the raw materials are cheap and easy to obtain, the cost is low, and the cost performance is high. It is very suitable for large-scale industrial production and is an improvement and enhancement of the chemical precipitation method for making hydroxyapatite.

Description

Technical Field

[0001] This application relates to the field of new materials (ceramics), and particularly to a method for preparing hydroxyapatite powder with high purity and different strengths. Background Art

[0002] Hydroxyapatite is a newly recognized ceramic material with good biocompatibility and osteoconductivity, that is, biocompatible. It is the main component of human and animal bones, teeth, and dental enamel. With the progress of science and technology and the continuous improvement of people's understanding, many research results show that hydroxyapatite is a bioactive material with non-toxic, non-carcinogenic, and no side effects and good biocompatibility. People also found that hydroxyapatite has solid base properties and strong polymer exchange capabilities. Therefore, it has been widely used in catalytic carriers and the polymer field (for defluorination of industrial water and domestic water), and at the same time, it can also have ion and temperature and humidity sensitivity effects, and passivate heavy metal cadmium ions in soil improvement. Therefore, it is also a green, environmentally friendly, degradable material and intelligent material. It has better lipophilicity, hydrophilicity, and is an adsorbent for proteins. It is also used in different polymer plastic composites to resist high temperature, shear, and increase mechanical strength. With the expansion of the application field, the requirements for its performance and product purity are also getting higher and higher.

[0003] Hydroxyapatite is not a natural mineral and is mainly synthesized artificially. Currently, the synthesis methods of hydroxyapatite powder are generally divided into two types: wet method and dry method cooperation. In addition, it can also be extracted from animal bones. The hydroxyapatite obtained by these methods has low product purity first, which in turn affects the biocompatibility and product strength of hydroxyapatite, and its performance cannot meet the requirements of the application market. In the process field, to better exert the product performance of hydroxyapatite, it cannot provide guarantee for product upgrading. And in order to obtain a purer product in these production methods, a large amount of water washing, acid washing, alcohol washing and other processes are saved during the process. This will lead to a large amount of waste water and waste residue, which is contrary to the current national environmental requirements. Either the production conditions are harsh, and the process needs to meet high temperature and high pressure conditions, increasing the risk factor. These conditions increase the production cost, the process equipment is complex, difficult to control, and not suitable for industrial production. Summary of the Invention

[0004] This application provides a method for preparing hydroxyapatite powder with high purity and different strengths to solve the technical problems in the prior art.

[0005] In the first aspect, this application provides a method for preparing hydroxyapatite powder with high purity and controllable hardness, including the following steps:

[0006] S1. Make calcium hydroxide suspension by adding water to calcium oxide, and heat the calcium hydroxide suspension; Heat, concentrate, and dehydrate phosphoric acid.

[0007] S2. Stir the heated calcium hydroxide suspension and the phosphoric acid with improved polymerization degree under alkaline conditions to mix them evenly.

[0008] S3. Subject the mixture after the reaction to high-speed shear emulsification.

[0009] S4. Age the mixture after the shear emulsification for 4 - 8 h.

[0010] S5. Filter-press the mixture after aging, and dry the filter cake.

[0011] S6. Calcinate the dried solid in stages to obtain hydroxyapatite in different shapes.

[0012] Optionally, the concentration of the calcium hydroxide suspension is 8% - 12%, and it is heated to 60 - 70 °C.

[0013] Optionally, the concentration of the phosphoric acid is 85%, and the polymerization degree is increased to 8 - 10 after treatment.

[0014] Optionally, the mass ratio of the phosphoric acid to the calcium hydroxide suspension is 1:3.

[0015] Optionally, after the reaction, a phosphorus-containing pH alkaline stabilizer is added to the reaction system.

[0016] Optionally, the drying temperature is 100 °C, and the drying time is 0.5 - 1 h.

[0017] Optionally, the staged calcination includes the following steps:

[0018] Control the temperature range at 100 - 200 °C and calcinate for 2 h to obtain amorphous needle-like hydroxyapatite;

[0019] Control the temperature range at 200 - 600 °C and calcinate for 4 h to obtain cylindrical hydroxyapatite;

[0020] Control the temperature range at 600 - 1250 °C and calcinate for 6 h to obtain spherical hydroxyapatite.

[0021] Optionally, the Mohs hardness of the calcined hydroxyapatite is 5.8 - 6.8.

[0022] The above technical solutions provided by the embodiments of the present application have the following advantages compared with the prior art:

[0023] 1. The raw materials used in the present invention are cheap and easily available, the preparation process is simple, and the process parameters are simple and easy to control. There is no need to add too many auxiliary agents and a large amount of water washing, acid washing, and alcohol washing processes, which is environmentally friendly and saves water, achieving the recycling of water, and is both economical and environmentally friendly.

[0024] 2. The ratio of the raw materials formulated in the present invention is adjusted, and the parameters of each process flow are strictly controlled, avoiding incomplete reactions and the formation of other calcium phosphates, thereby ensuring the high purity of hydroxyapatite.

[0025] 3. Through calcination at different temperatures in the present invention, different crystal forms of hydroxyapatite are formed at different temperatures, thereby changing the mechanical properties of hydroxyapatite, different hardnesses and crystal shapes, and also increasing the hardness of the product to reach 5.8 - 6.8 (Mohs hardness).

[0026] 4. Using the technical solution of the present invention, 10,000 tons of hydroxyapatite can be produced annually, having good economic benefits. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] The drawings herein are incorporated into the specification and form a part of this specification, showing embodiments in accordance with the present invention and, together with the specification, are used to explain the principles of the present invention.

[0028] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or in the prior art, the following will briefly introduce the drawings required for use in the description of the embodiments or the prior art. Obviously, for those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative efforts.

[0029] Figure 1 is the process flow chart of the present invention;

[0030] Figure 2 is the X-ray diffraction pattern of hydroxyapatite;

[0031] Figure 3 is the electron microscope image of spherical hydroxyapatite;

[0032] Figure 4 is the electron microscope image of needle-shaped hydroxyapatite;

[0033] Figure 5 is the electron microscope image of rod-shaped hydroxyapatite;

[0034] Figure 6 is the SEM photograph of the microscopic morphology of hydroxyapatite powder;

[0035] Figure 7 is the surface EDS composition plane scan photograph of hydroxyapatite powder;

[0036] Figure 8 is the surface EDS element percentage curve of hydroxyapatite powder;

[0037] Figure 9 is the chemical element selection diagram of hydroxyapatite powder;

[0038] Figure 10 XRD diffraction pattern comparison diagram of hydroxyapatite powder and theoretical PDF card;

[0039] Figure 11 XRD phase structure analysis diagram of hydroxyapatite powder;

[0040] Figure 12 Wear resistance test comparison diagram. Specific implementation manners

[0041] To make the objectives, technical solutions and advantages of the embodiments of the present application clearer, the technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present application. Obviously, the described embodiments are some but not all of the embodiments of the present application. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present application without creative efforts shall fall within the scope of protection of the present application.

[0042] In one embodiment of the present application, a preparation method of high-purity hydroxyapatite powder with controllable hardness includes the following steps:

[0043] S1. Prepare a calcium hydroxide suspension by adding water to calcium oxide, and heat the calcium hydroxide suspension; heat, concentrate and dehydrate phosphoric acid in a heating dehydration tank;

[0044] S2. In a heat-preserving reaction kettle, stir the heated calcium hydroxide suspension and the phosphoric acid with increased polymerization degree under alkaline conditions, and mix them evenly;

[0045] S3. Perform high-speed shear emulsification on the mixture after the reaction in a high-speed shear emulsification device;

[0046] S4. Age the mixture after shear emulsification in an aging tank for 4 to 8 hours;

[0047] S5. Filter the mixture after aging through a fully automatic hydraulic press to achieve solid-liquid separation, dry the filter cake, and the mother liquor enters the circulating water use system for the treatment of calcium oxide;

[0048] S6. Perform segmented calcination on the dried solid to obtain hydroxyapatite with different shapes and different hardnesses.

[0049] In this application, lime / calcium oxide and phosphoric acid are used as raw materials. Without adjusting the pH value and related aging time, and without ion water washing, acid washing, or alcohol washing, after calcium hydroxide slurry is made from calcium oxide / limestone, it is then titrated and neutralized with a certain concentration of phosphoric acid, and then dehydrated, dried, and calcined to obtain micron-sized hydroxyapatite powder. The entire process is simple and easy to control, does not cause environmental pollution, is economical and environmentally friendly, and is suitable for large-scale industrial production. It is an improvement and enhancement of the chemical precipitation method for making hydroxyapatite.

[0050] As an optional embodiment, the concentration of the calcium hydroxide suspension is 8% - 12%, and it is heated to 60 - 70 °C.

[0051] In this application, the concentration of the calcium hydroxide suspension is regulated and heated to prevent the formation of by-products such as other calcium phosphate salts.

[0052] As an optional embodiment, the concentration of the phosphoric acid is 85%, and after treatment, the degree of polymerization is increased to 8 - 10.

[0053] In this application, 85% phosphoric acid is dehydrated to make its degree of polymerization reach 8 - 10, reducing the hydrolysis reaction rate and further avoiding the formation of by-products such as dicalcium hydrogen phosphate and calcium dihydrogen phosphate.

[0054] As an optional embodiment, the mass ratio of the phosphoric acid to the calcium hydroxide suspension is 1:3.

[0055] In this application, the mass ratio of the phosphoric acid to the calcium hydroxide suspension is limited, and they react according to the following reaction equation: 10Ca 2+ +6PO4 3- +2OH - →Ca 10 (Po4)5(OH)2, reducing the formation of by-products.

[0056] As an optional embodiment, after the reaction, a phosphorus-containing pH alkaline stabilizer is added to the reaction system.

[0057] In this application, the pH of the reaction system is stabilized within a certain range to avoid the formation of other dicalcium hydrogen phosphate and calcium dihydrogen phosphate.

[0058] As an optional embodiment, the staged calcination includes the following steps:

[0059] Controlling the temperature range at 100 - 200 °C and calcining for 2 h to obtain amorphous needle-like hydroxyapatite;

[0060] Controlling the temperature range at 200 - 600 °C and calcining for 4 h to obtain cylindrical hydroxyapatite;

[0061] Calcine at a temperature range of 600 to 1250 °C for 6 h to obtain spherical hydroxyapatite.

[0062] In this application, when the hydroxyapatite is used for different purposes, the calcination temperature and time are controlled so that the shapes of the product particles are three different shapes: amorphous needle-like, cylindrical, and spherical. The products with different shapes have different strength application performances and are applied in different industrial fields.

[0063] As an optional embodiment, the Mohs hardness of the calcined hydroxyapatite is 5.8 to 6.8.

[0064] In this application, the Mohs hardness of the prepared hydroxyapatite is 5.8 to 6.8, and it has relatively wide application performances. When it is applied to coatings, the wear resistance of the coatings can be greatly improved.

[0065] Example 1

[0066] A preparation method of high-purity and hardness-controllable hydroxyapatite powder, comprising the following steps:

[0067] S1. Add water to calcium oxide to make a calcium hydroxide suspension with a concentration of 8% to 12%, and heat the calcium hydroxide suspension to 60 to 70 °C; heat, concentrate, and dehydrate phosphoric acid with a concentration of 85% to increase its polymerization degree to 8 to 10.

[0068] S2. Add the heated calcium hydroxide suspension and the phosphoric acid with increased polymerization degree to a heat-insulated reaction kettle at a mass ratio of 3:1, stir under alkaline conditions, mix evenly, and after obtaining the required pH value, add a phosphorus-containing pH alkaline stabilizer.

[0069] S3. Perform high-speed shear emulsification on the mixture after the reaction ends.

[0070] S4. Age the mixture after shear emulsification for 4 to 8 h.

[0071] S5. Filter press the mixture after aging, and dry the filter cake at 100 °C for 0.5 to 1 h.

[0072] S6. Perform staged calcination on the dried solid.

[0073] Calcine at a temperature range of 100 to 200 °C for 2 h to obtain amorphous needle-like hydroxyapatite;

[0074] Calcine at a temperature range of 200 to 600 °C for 4 h to obtain cylindrical hydroxyapatite;

[0075] Calcine at a temperature range of 600 to 1250 °C for 6 h to obtain spherical hydroxyapatite;

[0076] The Mohs hardness of the calcined hydroxyapatite is 5.8 to 6.8.

[0077] The hydroxyapatite prepared by the present invention was detected by a D / Max-2550pc multi-crystal X-ray diffractometer. The detection was based on the general rules of the rotating anode multi-crystal X-ray diffraction method JY / T009-1996. The detection results are as Figure 1 . From Figure 1 it can be seen that the composition of the hydroxyapatite prepared by the present invention is Ca5(PO4)3(OH), the structure is a hexagonal crystal, and the space group is P63 / m(176 # )

[0078] From Figure 6 it can be seen that the hydroxyapatite produced by the present invention is in the form of particle clusters (a-b) or amorphous structure (see Figures c-f) in terms of morphology, and the diameter of a single cluster is about 5-8 μm.

[0079] From Figures 7 - 8 it can be seen that the main components of the hydroxyapatite produced by the present invention are composed of C, O, P, Ca, Na, and Si elements. Among them, the Ca content accounts for 39.95 wt.%, the P content accounts for 17.25 wt.%, and the O content accounts for 42.23 wt.%; the trace Na and Si elements account for 0.17 wt.% and 0.32 wt.% respectively. According to the elemental composition of the above energy spectrum and the basic elements that the sample may involve, the chemical elements H, C, N, O, Na, Si, P, and Ca were selected for this sample. Secondly, when selecting the PDF card library and selecting "Minerals", it can be automatically analyzed by S / M matching that, in principle, the best option is preliminarily determined according to the smaller FOM value and the one-to-one correspondence of the three strongest peaks; but when comparing the four theoretical PDF cards in Figure 10 , it can be seen that for the theoretical cards Ca5(PO 4)3 F and the theoretical cards Ca5(PO4)3OH, Ca5(PO4)3OH in the diffraction angle range of 10° to 90°, the three strongest peaks of the two are basically corresponding to the diffraction peaks of the test sample. However, it can be found through careful comparison and observation that the degree of coincidence between the diffraction peaks of the theoretical card Ca3(PO4)3OH and the test sample is the highest; combined with the fact that no F element was detected in the composition analysis of the energy spectrum EDS; therefore, through comprehensive analysis, it can be determined that the test sample is Ca5(PO4)3OH in terms of the phase structure.

[0080] Quartz sand and the hydroxyapatite prepared in this application were used for sample preparation and comparison tests on the abrasion resistance of the paint film. The designed formula is shown in Table 1.

[0081] resin 50 auxiliary agent 2 solvent 30 quartz sand / hydroxyapatite 18 total 100

[0082] It is carried out in accordance with the provisions of GB / T 1768. The test is conducted using a TABER abrasion tester, a rubber grinding wheel CS-17, a paint film thickness of 40 microns, and 750 g / 500 r. The test results are shown in Figure 12 , indicating that the Mohs hardness of hydroxyapatite is relatively high. When added to the coating, it can significantly improve the wear resistance of the coating and can be used as a wear-resistant functional filler.

[0083] It should be noted that in this article, relational terms such as "first" and "second" are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Moreover, the terms "include", "comprise" or any other variant thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements not only includes those elements, but also includes other elements not expressly listed, or also includes elements inherent to such process, method, article or device. Without further limitation, an element defined by the statement "including a..." does not exclude the existence of additional identical elements in the process, method, article or device including the said element.

[0084] The above are only specific embodiments of the present invention, enabling those skilled in the art to understand or implement the present invention. Various modifications to these embodiments will be obvious to those skilled in the art. The general principles defined herein can be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention will not be limited to these embodiments shown herein, but rather to the broadest scope consistent with the principles and novel features claimed herein.

Claims

1. A method for preparing high-purity hydroxyapatite powder with controllable hardness, characterized in that: The following steps are involved: S1, adding water to calcium oxide to prepare a calcium hydroxide suspension, and heating the calcium hydroxide suspension; heating, concentrating and dehydrating phosphoric acid; S2, stirring the heated calcium hydroxide suspension and the phosphoric acid with increased polymerization degree under alkaline conditions to fully mix them; S3, subjecting the mixture after the reaction to high-speed shear emulsification; S4, aging the mixture after shear emulsification for 4 to 8 hours; S5, filtering the mixture after aging, and drying the filter cake; S6, calcining the dried solid in stages to obtain hydroxyapatite of different shapes; The concentration of the calcium hydroxide suspension is 8% to 12%, and it is heated to 60 to 70°C; The concentration of the phosphoric acid is 85%, and the degree of polymerization is increased to 8-10 after the treatment.

2. The method for preparing a high-purity hydroxyapatite powder with controllable hardness according to claim 1, characterized in that: The mass ratio of the phosphoric acid to the calcium hydroxide suspension is 1:

3.

3. The method for preparing a high-purity hydroxyapatite powder with controllable hardness according to claim 1, characterized in that: After the reaction is completed, a phosphorus-containing pH alkaline stabilizer is added to the reaction system.

4. The method for preparing a high-purity hydroxyapatite powder with controllable hardness according to claim 1, characterized in that: The drying temperature is 100°C and the drying time is 0.5 to 1 hour.

5. The method for preparing a high-purity hydroxyapatite powder with controllable hardness according to claim 1, characterized in that: The staged calcination includes the following steps: The temperature range is controlled at 100-200°C and calcined for 2 hours to obtain amorphous needle-shaped hydroxyapatite; The temperature range is controlled at 200-600°C and calcined for 4 hours to obtain cylindrical hydroxyapatite; The temperature range is controlled at 600-1250°C and calcined for 6 hours to obtain spherical hydroxyapatite.

6. The method for preparing a high-purity hydroxyapatite powder with controllable hardness according to claim 5, characterized in that: The Mohs hardness of the calcined hydroxyapatite is 5.8-6.8.

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