KR820000224B1 - Process for preparing crystal whitlockite - Google Patents

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Description

Method for producing crystalline wittrokite

The present invention relates to a process for the preparation of crystalline wittrokite, the equivalent of natural witkite. According to the present invention, the inclusion of a small amount of sulfate ion substantially converts the reactants into the equivalent of wittrakite while substantially no hydroxylatite is obtained. The presence of sulfate ions in the final product has substantially no adverse effect on the crystalline properties of the resulting product and this final product is useful for virtually all purposes, such as antacid fertilizers or animal feed additives, such as natural wittrokite. It can be seen that various uses of wittrokite are described for example in Melk Index. The product as an intermediate may also be calcined to form urine. In recent years, a lot of research has been conducted in the field of biomaterials, which focuses mainly on manufacturing biomaterials suitable for living organisms that can be used as a substitute for bone.

Calcium phosphates, such as wit trokite [Ca ₃ phosphate: Ca ₃ (PO ₄ ) ₂ ], are of particular interest because their chemical composition is biologically similar to hard tissues, and has been adopted as a number of research topics. It is becoming. Although many attempts have been made in the past to produce large whitlockite, it is generally subjected to processes such as powder manufacturing, filling processing and pressure sintering. The preparation thus made is generally porous and lacks the strength properties required for orthopedic surgery. A strong, dense, pore-free, polycrystalline sintered composite made of a mixture of wit trokite and hydroxy latite has been manufactured and used as a dental and surgical graft material. It is manufactured by sintering at 1350 ℃.

In addition, the preparation method is prepared by sedimentation and separation of the witkite produced by rapid mixing in a stoichiometric amount of calcium and phosphate ions.

According to the production method of the present invention, a crystalline wittrokite of a non-commercial company containing about 0.1-2.2% of sulfate ions in the crystal lattice by weight percentage is prepared. That is, calcium ions and phosphate ions are reacted in a liquid medium at a pH of 10-12 at a molar ratio of about 1.2-1.5: 1 to produce a calcium phosphate precipitate having a molar ratio of calcium to phosphorus of about 1.50-1.53: 1 in a gelatinous state. The solution is separated from the solution, washed with water until the soluble salt is removed, and then uniformly suspended and dispersed in about 10-20 ml of 1-3% ammonium sulfate solution per gram of wittrokite. The precipitate is separated from the ammonium sulfate solution, dried and sintered at about 725 ° -900 ° C for about 0.5-4 hours to obtain a product.

To prepare a novel wittrokite according to the present invention, calcium phosphate must be precipitated initially from the liquid medium. The reaction process between phosphate ions and calcium ions in the liquid medium is complex and the reaction mechanism is incompletely identified. Generally, the equilibrium reaction varies according to various reaction rates, and thus different products are produced. As you can guess, the result of this interaction is greatly influenced by stoichiometry, for example, the molar ratio of calcium to phosphorus (Ca / p), reaction time, temperature and pH. The general fact is that calcium ions and phosphate ions initially combine to produce apatite that lacks insoluble calcium content. The ratio of calcium to phosphorus in phosphorite is about 1.5, indicating that the stoichiometry for wittrokite is accurately established.

However, the apatite crystal lattice is the most stable form in the calcium phosphate system. When excess calcium ions are present, the initial precipitate is gradually converted into a hydroxylatpatite having a calcium: phosphate ratio of 1.67. If the ratio of calcium to phosphorus is intermediate, e.g. 1.5-1.67, then the precipitate is heated, it is a mixture of wittrakite and hydroxylatatite. You should keep it at 1.5. Simply reacting with a molar ratio of calcium and phosphate ions to 1.5 produces wittrokite containing impurities, and instead produces a mixture of wittrakite and hydroxylatite, which is not an effective method. In fact, reducing the molar ratio of calcium ions to phosphates to 1.2: 1 produces a mixture of wit trokite and hydroxylatite. If the initial product (precipitate) is separated immediately after reacting calcium and phosphate ions with the stoichiometry of wittrokite, ie Ca / p = 1.5, no further equilibrium will occur. Some have been successfully manufactured. However, this method has been found to be non-reproducible and is not suitable for large scale production.

According to the present invention, the addition of a small amount of sulfate ions to the precipitate of calcium phosphate, which is collected and heated, converts the calcium phosphate completely to wittrakite free of hydroxy lapatite. Moreover, the sintering of the prepared troptrokite thus becomes a high quality urine with excellent physical and mechanical properties, which can be most appropriately used as a biological implant material.

Therefore, calcium ions and phosphate ions are reacted at pH 10-12 to precipitate witkite in the liquid medium.

Compounds containing calcium or phosphates that provide calcium and phosphate ions in the liquid medium can be readily separated from the counter Trokite products, or the ions themselves bind to the Top Trokite crystal lattice. And should not interfere with the sedimentation or segregation of wittrokite.

For example, compounds that provide calcium ions include calcium nitrate, calcium hydroxide, calcium acetate and the like, and compounds that provide phosphate ions include diammonium hydrogen phosphate, ammonium phosphate, and phosphoric acid. In the method of the present invention, calcium nitrate and diammonium hydrogen phosphate are used as sources of calcium ions and phosphate ions, respectively.

First, the molar ratio of calcium nitrate and diammonium hydrogen phosphate is set at about 1.2-1.5: 1 to react at pH 10-12 in a liquid phase to produce a gelatinous precipitate of calcium phosphate. At this time, the reaction temperature is not so important, and precipitation can proceed at about 0 ° -100 ° C, but it is usually performed at room temperature. The gelatinous precipitate is separated from the solution using a suitable method such as centrifugation and supernatant decantation, and the remaining mineral sludge is suspended by distilled water and washed until there is no remaining soluble salt. Separation and decantation. Although not essential to this process, the last separation process can be used to minimize cracks in the sintering process. The washed product is suspended in small amounts of distilled water and left for use in the next process. Dispersion of the mineral sludge in primary homogeneity in a 1 -3% ammonium sulfate solution leads to the conversion to crystalline wittrokite. As a rule, use 10-20 ml of a 1-3% ammonium sulphate solution per gram of wittrokite subcontractor estimate. Solids are separated from the solution by centrifugation and vacuum filtration. The collected gelatinous product contains a large amount of occlusion water. Most of the moisture is pressurized to remove the product, and then the product, such as clay, is cut into a suitable shape or dried by drying, resulting in about 25% of dry shrinkage. Sintering it again shrinks about 25% more.

Important in the chemical process described above is that the ratio of calcium to phosphorus in the dispersed precipitate is approaching the theoretical value for wittrokite, ie Ca / P = 1.50, which results in the content of hydroxylatite in the precipitate. In addition to minimizing the amount of ammonium sulfate required to prepare the pure wittrakite according to the present invention can also be reduced to a minimum. Therefore, when the ratio of calcium to phosphorus in the precipitate exceeds about 1.53, it is not appropriate to contact pure 1-3 chlorite by contacting with 1 to 3% ammonium sulphate, as well as by mixing hirotoprocite and hydroxylatite. Will be. A calcium phosphate precipitate with a calcium and phosphorus ratio of 1.53 or higher can be completely converted to wittrokite using a large amount of ammonium sulfate.

Indeed, pure hydroxylapatite precipitates (Ca / P = 1.67) can be converted to wittrokite using sufficient amounts of ammonium sulfate. However, wittrokite prepared in this way is contaminated by the incorporation of a large amount of calcium sulfate, and also, it is not seen the excellent physical and mechanical properties exhibited by the witkite ceramics produced by the present invention. Therefore, the ratio of calcium to phosphorus should not exceed about 1.53. The molar ratio of calcium and phosphate should be 1.5 or less, or 1 or less, which is preferably 1.2 to 1.4: 1. The calcium phosphate precipitate thus prepared has a calcium to phosphorus ratio of about 1.50 to 1.53, but is treated with 1 to 3% aqueous ammonium sulfate (10-20 ml per g of ant trokite estimate) to obtain pure wittrokite.

As described above, the production of wittrokite in the liquid phase as a gelatinous precipitate is that because the gelatinous material is cohesive, wittrokite can be molded or cast, and then dried and sintered if necessary to make a urine. There is importance. Dry powdery or granular wittrokite cannot be reconstituted into this cohesive gelatin state. For example, if disperse and filter wittrokite powder into water, a cohesive granular filtercake is produced, which simply collapses when dried, and therefore cannot be molded or converted into a ceramics supplier.

According to the process of the present invention, a non-commercial crystalline witrokite containing about 0.1-2.2% of sulfate ions in a weight percentage in the crystal lattice is dried and dried at least 725. The precipitate obtained as the first product in ionicity at the temperature of ℃ is subjected to phase transformation with crystalline wit trokite, which is confirmed by differential thermal analysis and X-ray diffraction. However, below about 1000 ° C., the wit rotites sinter. This is a simple, reliable and economical way to produce substantially pure (eg 97.2-99.9%) wittrokite.

The present invention will be described according to the embodiment (but not limited to the embodiment).

Example 2

To a solution of 0.24 mole diammonium phosphate 0.24 mole (235 ml of 1.02 M solution) was added to 150 ml of ammonia water, adjusted to pH 11, and 600 ml of water was added thereto to dissolve the precipitated ammonium phosphate. To 356 ml of calcium nitrate 1.01M solution (0.36 mol, Ca / P = 1.5) was added 350 ml of water and diluted with dilution. The solution was added dropwise over 30 minutes, and the mixture was continuously stirred by adjusting the pH to 11 using 15 ml of concentrated ammonia water. This suspension is left overnight at room temperature. The reaction mixture is stirred rapidly for about 20 minutes to form a homogeneous suspension. About a quarter of the suspension was centrifuged and decanted to remove 5% (% by weight) of the residue, which was then suspended in 200 ml of ammonium sulfate and centrifuged and the supernatant was decanted again to filter the residue. Then dry overnight at room temperature. The dried material was heat treated at 900 DEG C for 1 hour to obtain the target product. As a result of known X-ray diffraction analysis, 100% -β-toptrokite was confirmed (measured by the present Example and the X-ray diffraction method described below). Percent composition is such that the precision of the diffractometer is in the range of ± 2%).

As a result of confirming the target material by standard element analysis, the ratio of calcium to phosphorus (Ca / P) was 1.53 + 0.03.

As used herein, the term "crystalline" refers to a substance or object having properties that appear in crystals in which the atoms are arranged regularly in the crystal lattice. Thus, "polycrystalline" also refers to a substance or object composed of a plurality of crystals. On the other hand, "single crystal" means a single particle present in one entity, a polycrystalline object. Single crystals can also be defined as microscopic incompletely formed crystals or microscopic objects formed at the initial stage of crystallization.

Claims (1)

The molar ratio of calcium ions to phosphate ions is 1.2-1.5: 1 to react in a liquid medium at a pH of about 10-12 to produce a gelatinous calcium phosphate precipitate having a calcium to phosphorus molar ratio of about 1.50-1.53: 1. Soluble salts were removed by washing with water, and then suspended in about 10-20 ml of 1-3 wt% ammonium sulfate solution per gram of wittrokite. The precipitate was separated, dried and dried. A process for producing crystalline wittrokite of a non-container comprising 0.1-2.2% by weight of sulfate ions in a crystal lattice, consisting of heating at about -4O < 0 > C for about 0.5-4 hours.