Method to prepare charge to produce bioceramics

FIELD: construction.

SUBSTANCE: method to prepare charge to produce bioceramics includes dosing of initial components and their grinding in a planetary mill. Initial components are hydroxyapatite and sodium dihydrophosphate at the mass ratio of "hydroxyapatite/sodium dihydrophosphate" in the range of 20/80 - 85/15.

EFFECT: method makes it possible to prepare charge for bioceramics of new generation, capable of resorption and stimulating new bone tissue.

1 tbl, 1 ex

 

The invention relates to the field of materials for bone implants, namely, for use in traumatology and orthopedics, maxillofacial surgery and dental surgery, can be used for the manufacture of bioceramics for the treatment of bone defects. During preparation of the initial charge in the technology of ceramics is almost always used high-energy equipment for disaggregation, grinding or conduct of mechanochemical synthesis. Mechanochemical processing of powder mixtures is considered as a convenient method of soft chemistry for activation of various chemical processes and production of powders of multicomponent oxide compounds, including calcium phosphates [1]. Mechanochemical synthesis is attributed to ecological processes ("green processes"), which allows to save energy and implement unique synthesis at room temperature [2]. The literature describes different ways to obtain hydroxyapatite by mechanochemical method of brushite CaHPO 4 *2H 2 O and calcium oxide [3] or oxide and calcium hydroxide [4], brushite CaHPO 4 *2H 2 O and calcium carbonate [5], from calcium hydroxide and phosphoric acid [1, 6], dihydrophosphate calcium and calcium oxide [7], oxide of phosphorus and calcium hydroxide or oxide of phosphorus and a mixture of oxide and hydroxide of phosphorus [8]. The mixture of the initial components in a ratio of Ca/P=1.67 or other value in the interval 1-2 [1] is subjected to processing in a planetary mill for a sufficient for reaction time. Thus, the method of preparation of the charge for bioceramics includes dosing source components and mechanochemical synthesis in a planetary mill. The closest method of preparation of the mixture can be considered, for example, the method described in [1]. Obtained by mechanochemical method, a mixture consisting mainly of hydroxyapatite, is used for bioceramics. If the ratio Ca/P is less than or greater than the ratio Ca/P=1,67, as in method [1], in powder mixtures are present unreacted components CaO or H 3 PO 4 , which is undesirable. Hydroxyapatite has excellent biocompatibility and surface bioactivity. However, the materials based on hydroxyapatite virtually no rezorbiruetsa (not dissolved) during implantation. Materials based on hydroxyapatite may not be applied in the methods of treatment that uses regenerative approach. Regenerative approach requires the use of new generation materials, resorbable in a short time and stimulating the formation of new bone. The new generation materials contain resorbable phase, such as calcium pyrophosphate, polyphosphates or double phosphates of calcium - alkali metals. The aim of the present invention was to develop a method of preparation of the charge for bioceramics new generation, capable of rezorbiruetsa and to stimulate the formation of new bone. The goal has been achieved by the present invention, in which the preparation of the charge for bioceramics is in the process of mechanochemical synthesis when milling in the planetary mill. The method of preparation of the charge for bioceramics, including the dosing of the components and their milling in the planetary mill, in which according to the invention as starting components used hydroxyapatite and hydrated sodium dihydrophosphate when the mass ratio of hydroxyapatite/hydrated sodium dihydrophosphate" in the range of 85/15-20/80. Hydroxyapatite should be synthesized in accordance with reaction (1) from aqueous solutions by co-deposition. The coprecipitation from solutions allows to obtain powders consisting of aggregates of nanoparticles. The small particle size and huge specific surface provide high reactivity of nano-powders. where X=NO 3 - , Cl - , CH 3 COO - , and Z=NH 4 + , Na + , K + . Stoichiometric hydroxyapatite - thermodynamically stable phase, and when grinding or roasting is not degradable. Hydrated sodium dihydrophosphate NaH 2 PO 4 *2H 2 O prolonged grinding in acetone loses a certain amount of hydrated water and is converted, for example, NaH 2 PO 4 *H 2 O, and when heated it loses water and is subjected to polycondensation with the formation of polyphosphate sodium - biosovmestimost substances [9]. The biological role of polyphosphates in the early stages of evolution as analogues of ATP, including sodium polyphosphate, described Kulaeva [10, 11]. Under normal mixing and subsequent long-term storage of a mixture of hydrated sodium dihydrophosphate NaH 2 PO 4 *2H 2 O with hydroxyapatite chemical interaction between the components there. Source components (hydroxyapatite and hydrated sodium dihydrophosphate) at a ratio of hydroxyapatite/gidratirovannyi sodium dihydrophosphate in the range of 85/15-20/80 placed in the drum Zirconia and add grinding media (balls of zirconium dioxide and acetone as the medium dispersion and reaction. The mixture is subjected to grinding for 10-30 minutes in a planetary mill. When such processing is mechanochemical synthesis in accordance with reaction (2), (3) or with a large excess of hydrated sodium dihydrophosphate in accordance with reaction (4) When excess hydroxyapatite reactions 2 and 3 will be held until the end, and in the mixture after grinding will be the brushite or monetite, sodium phosphate and hydroxyapatite (table, line 1). In that case, if the components are taken in quantities calculated by the reaction of 2 or 3, is formed of monetite (reaction 2) or brushite (reaction 3) and sodium hydrogen phosphate (table, line 2). With an excess of hydrated sodium dihydrophosphate possible reactions 2, 3 or 4. According to reactions 2 and 3 in the composition of the charge along with brushite or moneycom and sodium phosphate is unreacted sodium dihydrophosphate. And by the reaction of 4 in the composition of the mixture additionally includes dihydrophosphate calcium (table, line 3). When heated at the stage of firing the brushite and monetite will form phase calcium pyrophosphate (reactions 5 and 6), sodium phosphate will form phase pyrophosphate sodium (reaction 7), and dihydrophosphate calcium and unreacted sodium dihydrophosphate will form polyphosphates in accordance with the reactions 8-10. Hydroxyapatite reacts with pyrophosphate, forming tricalcium phosphate (reaction 11). Formed components come when heated in the reaction with each other, forming a double ortho - or pyrophosphates (reaction 12-24). When heated powder mixture, which contains unreacted during mechanochemical synthesis of hydroxyapatite and acidic phosphates of sodium, or the products of their thermal condensation is the formation of double orthophosphate sodium-calcium: Ca 10 Na(PO 4 ) 7 (reaction 12, 14, 16) or β-renania NaCaPO 4 (reaction 13, 15, 18), and double pyrophosphates Na 2 CaP 2 O 7 (14, 15, 17, 19). If the ratio of hydroxyapatite/gidratirovannyi dihydrophosphate more than 85/15, after heat treatment of the material will remain hydroxyapatite, and the material will not be fully biodegradiruemym. With decreasing content of hydroxyapatite in the mixture in the composition of the material after heat treatment may include calcium pyrophosphate and double ortho-, pyro - and polyphosphates sodium-calcium, which are biocompatible and biodegradable. When the ratio of hydroxyapatite/gidratirovannyi dihydrophosphate, equal 45/55 by weight, in the mixture after mechanochemical synthesis reactions proceed 2 and 3, and in the blend there is no unreacted component (hydroxyapatite or hydrated dihydrophosphate). Further decrease in the ratio of hydroxyapatite/gidratirovannyi dihydrophosphate leads to the fact that after mechanochemical synthesis mixture contains unreacted sodium dihydrophosphate, which when heated tends to polycondensation and the formation of sodium polyphosphate or polyphosphate sodium calcium. The polyphosphates of sodium and sodium calcium are biocompatible and biodegradable. When the ratio of hydroxyapatite/gidratirovannyi dihydrophosphate, less than 20/80, extrusion billets from the obtained mixture is difficult: the samples do not retain their shape. The decrease in the ratio of hydroxyapatite/gidratirovannyi dihydrophosphate in the range of 85/15-20/80 leads to an increase in the rate of biodegradation, since the solubility of phosphates in the ranks of CA 3 (PO 4 ) 4 →NaCa 10 (PO 4 ) 7 →NaCaPO 4 ; Ca 2 P 2 O 7 →Na 2 CaP 2 O 7 ; CA(PO 3 ) 2 →NaCa(PO 3 ) 3 →NaPO 3 increases. When the duration of grinding is less than 10 min reactions 2, 3 and 4 occur not until the end, and duration more than 30 minutes is excessive. Obtained after grinding the mixture is pressed in the form of beams or drives, and then calcined in the range of 1000-1200°C. Calcination at temperatures below 1000°C does not ensure the completeness of the reactions between the components of the mixture. Calcination at temperatures above 1200°C leads to the formation of significant amounts of melt and abnormal grain growth. Thus, the experimental data show that the use of the claimed method allows to prepare the mixture to obtain bioceramics with a complex phase composition, which determines the ability of a material to biodegradation using. Example To obtain the charge for bioceramics 4.5 g of hydroxyapatite, 5.5 g of hydrated sodium dihydrophosphate, 25 ml of acetone and 50 g of grinding media (balls Zirconia) is placed in a container of Zirconia. A closed tank containing a source of salt, acetone and the grinding body, fixed ball mill. After grinding for 20 min, the suspension is separated from the acetone and air-dried. The resulting powder consisting of brushite/monetite and hydrogen phosphate sodium, pressed into the form of beams or disks and then fired at 1100°C. the Phase composition of the material after firing presents resorbable phases: calcium pyrophosphate and double phosphates of calcium, sodium. The method of preparation of the mixture to obtain bioceramics, including the dosage of the source components and the milling in the planetary mill, characterized in that the starting components used hydroxyapatite and sodium dihydrophosphate when the mass ratio of hydroxyapatite/sodium dihydrophosphate in the range of 20/80-85/15.

 

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2 cl, 3 ex, 1 tbl

FIELD: chemistry.

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4 ex

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1 ex, 2 tbl, 1 dwg

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1 tbl, 4 ex

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1 tbl, 1 ex

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3 cl, 7 dwg, 1 tbl

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