JP3846817B2 - Method for producing calcium phosphate coating - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method for producing a calcium phosphate coating under specific conditions.
[0002]
[Prior art]
2. Description of the Related Art A method for forming a coating film by applying ceramic powder, glass powder, or the like to the surface of a substrate such as metal is conventionally known. In recent years, various methods such as a sol-gel method capable of forming a high-quality film at a low temperature have been studied. Since this sol-gel method is operated at a relatively low temperature, thermal deterioration and oxidation deterioration of the substrate due to heating can be suppressed, and a thin and dense coating film can be obtained.
[0003]
[Problems to be solved by the invention]
Generally, if residual organic matter is contained in the coating film formed on the surface of a substrate such as metal or ceramic, the electrical, magnetic, optical characteristics, etc. inherent to the film itself are hindered. Residual organics are removed. As a removal method, a method of burning while circulating air or oxygen is common. A particular problem in removing residual organics by this method is the case of a coating film having a dense and fine gel structure. In such a dense and fine coating, it is necessary to perform heat treatment for a long time at a high temperature while circulating air or oxygen in order to remove residual organic matter.
[0004]
However, there is a problem when a base material that is easily oxidized and deteriorated is used. When the base material is oxidized by heat treatment at a high temperature for a long time, for example, the strength of the base material itself decreases or the adhesion strength between the base material and the film decreases, and the original purpose is not achieved. There is a need. It is very difficult to suppress the deterioration of the base material and remove the residual organic matter. The heat treatment for a long time at a high temperature cannot sufficiently suppress the base material deterioration. On the other hand, an inert gas such as nitrogen or argon is used. When the heat treatment is performed in an atmosphere, residual organic substances in the film cannot be sufficiently removed. The present inventors tried heat treatment at a high temperature under an argon atmosphere after heat treatment at a low temperature that does not cause deterioration of the base material while circulating air or oxygen. However, residual organic substances can be sufficiently removed. There wasn't. As described above, it is very difficult to suppress oxidative deterioration of a substrate that is easily oxidized and to sufficiently remove residual organic substances in the coating.
[0005]
On the other hand, in the case of a calcium phosphate-based film, a film obtained by a normal alkoxide method tends to crack due to shrinkage caused by heating such as drying or firing, and tends to be a heterogeneous film. The present inventors have found that by using a chelating agent such as ethylenediaminetetraacetic acid, the above problems can be solved, and a single-phase film such as hydroxyapatite that is homogeneous at low temperatures can be obtained, An earlier application was made (Japanese Patent Laid-Open No. 8-91814). However, even in this method, there is no problem of residual organic matter when the base material is an oxide ceramic such as alumina or zirconia, but there is a problem of oxidative deterioration in an easily oxidizable material such as titanium, titanium alloy, stainless steel, etc. Therefore, since heat treatment in the air or oxygen cannot be performed at a high temperature, there has been a problem that the residual organic matter such as residual carbon in the film is not sufficiently removed and the film is colored.
[0007]
The method for producing a calcium phosphate coating according to the first aspect of the present invention includes a solution in which a salt containing calcium, a salt containing phosphorus, and a chelating agent capable of coordinating at least one of calcium ions and phosphorus ions are dissolved. The method for producing a calcium phosphate-based coating by applying to a substrate includes a step of heat treatment at 50 to 500 ° C. in the presence of ozone.
[0008]
Furthermore, the method for producing a calcium phosphate coating according to the third aspect of the invention includes a chelate compound containing calcium and a chelate compound containing phosphorus, a chelate compound containing calcium and a salt containing phosphorus, or a chelate compound containing phosphorus and a salt containing calcium, In a method for producing a calcium phosphate coating by applying a solution in which is dissolved in a substrate, the method comprises a step of heat-treating at 50 to 500 ° C. in the presence of ozone. According to the production methods of the first and third inventions, it is possible to obtain a calcium phosphate coating film in which the base material is prevented from being oxidized and from which residual organic substances, particularly residual carbon, etc. in the coating film are removed.
[0010]
As the “salt containing calcium” and the “salt containing phosphorus” in the first invention, the following various inorganic salts and organic salts can be used. Examples of inorganic salts include nitrates, chlorides, bromides, iodides, chlorates, chlorites, nitrites, sulfites, and the like. As the organic salt, acetate, oxalate, lactate, tartrate, citrate, benzoate, isobutyrate, maleate and the like can be used.
[0011]
Furthermore, as the “chelating agent” capable of coordinating to at least one of calcium ion and phosphorus ion, any of those capable of coordinating to calcium ion and phosphorus ion can be used. Examples thereof include dimethylglyoxime, dithizone, oxine, acetylacetone, glycine, atylenediaminetetraacetic acid (hereinafter referred to as “EDTA”), nitrilotriacetic acid, and the like. As this chelating agent, EDTA having high solubility and excellent reactivity is particularly preferable.
[0012]
Further, in the first invention, the above-described salts and chelating agents are used as starting materials for producing the calcium phosphate compound, but the starting materials described in the third invention can also be used. That is, the "chelate compound containing calcium""chelating compounds containing phosphorus", or salt containing a chelate compound and phosphorus containing calcium, or salts with chelating compound and calcium containing phosphorus, even when combined with the first A homogeneous and transparent solution can be obtained in exactly the same manner as in the invention, and a dense and good-quality calcium phosphate coating can be formed. In these first and third inventions, the solution may be a solution using an organic solvent as a solvent or an aqueous solution.
[0013]
Any organic solvent can be used as long as each component can be easily dissolved. Examples thereof include alcohols such as methanol and ethanol, and ketones such as acetone and methyl ethyl ketone, with alcohols being particularly preferred. These organic solvents have a low surface tension and are easily wetted with a substrate such as metal or ceramics. Therefore, when it is applied to a substrate, a coating having a uniform thickness can be obtained even if the substrate has particularly severe surface irregularities. In general, it has a low boiling point and can be easily vaporized and removed by heating and drying after application to a substrate.
[0014]
Further, when water is used as the solvent, as in the case of the organic solvent, the organometallic compound is easily dissolved, chelated easily, and a stable chelate compound is produced. In addition, the chelate compound used as the starting material dissolves quickly as in the case of the organic solvent.
[0015]
In the first and third inventions, the atomic ratio (Ca / P) between calcium and phosphorus in the solution is preferably 1.40 to 1.75. Hydroxyapatite (HAp; Ca / P = 1.67) can be obtained by carrying out a predetermined heat treatment and firing at an atomic ratio within this range, and when the amount ratio of phosphorus is high, tricalcium phosphate (TCP; Ca /P=1.50) is generated. This atomic ratio of calcium and phosphorus can be easily controlled by the Ca / P ratio of the starting material, and can also be a mixed phase of HAp and TCP.
[0016]
The total molar concentration of calcium and phosphorus in the solution is preferably 0.25 mol / liter or less. When the molar concentration exceeds 0.25 mol / liter, a transparent solution is obtained at the time of preparation, but when concentrated, crystals may precipitate or the surface may become cloudy. This is not preferable because it causes impurity generation in the heat treatment step and the firing step. Such a phenomenon does not occur if the molar concentration is 0.25 mol / liter or less. In the first and third inventions, the total molar concentration of calcium and phosphorus may be even lower, for example, about 0.05 mol / liter, there is no practical problem.
[0017]
In addition, it is preferable to maintain the pH of the above solution at 4 or more. If pH is 4 or more, a stable solution state is maintained. However, when the pH is less than 4, crystals may precipitate from the solution. The crystal to be precipitated is EDTA. However, when the pH is low, it is considered that the crystal is precipitated because the stability of the complex is lowered. The pH of the solution can be easily adjusted by adding aqueous ammonia to the alkaline side and hydrochloric acid to the acidic side.
[0018]
In the first and third inventions, the order of adding each component to the organic solvent or water is not particularly limited. Regardless of the order of addition, the organometallic compound dissolves easily, chelation is easily accomplished, and the chelate compound dissolves quickly. And it becomes a homogeneous and transparent solution without any precipitation such as calcium content. A calcium phosphate-based coating can be formed by applying this solution to a base material such as metal or ceramics and performing a heat treatment.
[0019]
The “application” of the solution to the substrate can be performed by a known method such as casting, spraying, dipping, spinning, brushing, or the like. The obtained solution may be applied as it is, but a liquid concentrated several times, for example, about 5 to 15 times may be applied. When such a concentrated solution is used, the film becomes thick and dense. This concentration can be performed by heating at 100 to 150 ° C. or heating at a relatively low temperature of 40 to 90 ° C. under reduced pressure, and gradually removing the solvent. By concentrating in this way, precipitation does not occur in the solution, the viscosity increases, and a slightly viscous transparent solution is obtained.
[0020]
The most significant feature of the present invention is that after the solution is applied to the substrate, it is “heat treated” at “50 to 500 ° C.” in the presence of ozone. If the temperature of this heat treatment is less than 50 ° C., the residual organic matter is not sufficiently decomposed and removed, and if it exceeds 500 ° C., the residual organic matter is not sufficiently removed. The temperature of this heat treatment is more preferably 100 to 350 ° C., particularly preferably 150 to 350 ° C., and the heat treatment time is not particularly limited, but for example, 30 seconds to 30 minutes, particularly 30 seconds to 15 minutes. preferable. Further, the ozone concentration in the presence of ozone is preferably 1000 ppm or more, particularly preferably 5000 ppm or more.
[0021]
A predetermined calcium phosphate coating can be formed by the heat treatment. However, in order to obtain a denser film, after the heat treatment, it is preferable to “fire” at “600 to 900 ° C.” in “inert atmosphere” as in the fourth invention. The firing temperature is preferably in the range of 700 to 900 ° C., and the firing time is not particularly limited, but is preferably 2 to 30 minutes, particularly preferably 10 to 20 minutes. With this firing temperature and firing time, a dense and good-quality film can be obtained. The inert atmosphere refers to an atmosphere made of an inert gas such as nitrogen, helium, neon, argon, krypton, xenon, or radon. Nitrogen or argon is preferable from the viewpoint of availability and cost. However, when titanium is used as a base material, titanium nitride is generated in a nitrogen atmosphere, and therefore, it is more preferable to fire in an argon atmosphere.
[0022]
In the first and third inventions, the above “base material” can be used as long as it can withstand heat during heat treatment or firing, such as metal and ceramics. In the present invention, in particular, as in the fifth invention, even an easily oxidizable substrate can be formed without oxidative deterioration. The advantage that even this easily oxidizable substrate can be applied without any problem is particularly useful in the case of a calcium phosphate coating.
[0023]
When ceramics such as alumina and zirconia are used as a base material, a calcium phosphate coating without problems such as deterioration or coloring of the base material can be obtained even if a chelating agent such as EDTA is used. However, in the case of using a base material that is susceptible to oxidative degradation such as titanium, titanium alloy, stainless steel, etc., if the heat treatment temperature is lowered in order to suppress this degradation, the residual organic matter is not sufficiently removed and the coating is colored. As described above, the original high-purity calcium phosphate coating cannot be obtained. In the present invention, by performing this heat treatment in the presence of ozone, residual organic substances in the coating can be sufficiently removed even at a low temperature, and there is no oxidative degradation of the base material, and the calcium phosphate is dense and of good quality. A system film can be formed.
[0024]
Therefore, not only ceramics such as alumina, zirconia, silicon carbide, and silicon nitride, but the base material is an easily oxidizable base material such as iron, copper such as titanium, titanium alloy, and stainless steel as in the fifth invention. However, the calcium phosphate coating can be formed without any problem. In particular, it is excellent in bioactivity and strength by forming a calcium phosphate-based film having excellent bioactivity on a base material made of titanium, titanium alloy, etc. that is not toxic to the living body, has excellent corrosion resistance, and has high strength. A large living body hard tissue replacement member can be obtained.
[0025]
In order to obtain a thick film, the coating of the solution and the heat treatment are repeated several times, followed by firing to obtain a film having a predetermined thickness.
[0026]
[Action]
Since the effect of combustion removal by heat treatment in the presence of oxygen is inadequate, it is assumed that it is not a simple thermal effect of ozone and the organic film, but a chemical and thermal reaction.
[0027]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, the present invention will be described in detail by way of examples.
Example 1
3.125 × 10 ⁻² mol of calcium nitrate was dissolved in 1 liter of distilled water. An equimolar amount of EDTA was added to this aqueous solution and stirred for 30 minutes. To this reaction liquid, 1.875 × 10 ⁻² mol of ammonium phosphate was added and stirred until a transparent solution was obtained. Thereafter, the temperature was raised to 120 ° C., the water was gradually removed, the solution was concentrated 10 times, and then the pH was adjusted to 4.4.
[0028]
The concentrated solution was applied to a base material made of a titanium flat plate by dipping. Next, while heating the substrate at 200 ° C., ozone was circulated under a concentration of 10,000 ppm and heat-treated for 10 minutes. Thereafter, the circulation of ozone was stopped, the inside of the thermostatic chamber was changed to an air atmosphere, the temperature was raised to 550 ° C. at a rate of 5 ° C./min, and heat treatment was performed again for 10 minutes. The formed film was white. This coating and heat treatment were repeated to form a film with a predetermined thickness, and then baked at 800 ° C. for 10 minutes in an argon atmosphere to increase the density of the film. The film after baking had a thickness of about 1 μm and a transparent white color. When the constituent crystal phase was identified by the X-ray diffraction method, it was confirmed that this film was a HAp single phase.
[0029]
Example 2
A coating film was formed in the same manner as in Example 1 except that calcium nitrate was changed to 3.00 × 10 ⁻² mol and ammonium phosphate was changed to 2.00 × 10 ⁻² mol. The film after baking had a thickness of about 1 μm and a transparent white color. Moreover, when the constituent crystal phase was identified by the X-ray diffraction method, it was confirmed that this film was a TCP single phase.
[0030]
Reference example 1
A coating film was formed in the same manner as in Example 2 except that the amount of zirconium nitrate was changed to 3.00 × 10 ⁻² mol instead of 2.00 × 10 ⁻² mol of ammonium phosphate. The film after baking had a thickness of about 1 μm and a transparent white color. Moreover, when the constituent crystal phase was identified by the X-ray diffraction method, it was confirmed that this coating was a single phase of calcium zirconate.
Example 3
A film was formed in the same manner as in Example 1 except that the heat treatment temperature in the presence of ozone was 100 ° C. The film after baking had a thickness of about 1 μm and a transparent white color. Further, when the constituent crystal phase was identified by the X-ray diffraction method, it was confirmed that this film was a HAp single phase.
[0031]
Example 4
A film was formed in the same manner as in Example 1 except that the heat treatment temperature in the presence of ozone was 400 ° C. The film after baking had a thickness of about 1 μm and a transparent white color. Further, when the constituent crystal phase was identified by the X-ray diffraction method, it was confirmed that this film was a HAp single phase.
Example 5
A film was formed in the same manner as in Example 1 except that the base material was Ti6A14V. The film after baking had a thickness of about 1 μm and a transparent white color. Further, when the constituent crystal phase was identified by the X-ray diffraction method, it was confirmed that this film was a HAp single phase.
[0032]
Example 6
A film was formed in the same manner as in Example 1 except that the base material was stainless steel. The film after baking had a thickness of about 1 μm and a transparent white color. Further, when the constituent crystal phase was identified by the X-ray diffraction method, it was confirmed that this film was a HAp single phase.
Example 7
A coating film was formed in the same manner as in Example 1 except that a substrate made of a flat plate of titanium was used as a substrate made of a flat plate of transparent quartz glass. The film after baking had a thickness of about 1 μm and a transparent white color. Further, when the constituent crystal phase was identified by the X-ray diffraction method, it was confirmed that this film was a HAp single phase. In Example 7 , since the base material is transparent, it is confirmed more reliably that the coating is not colored by residual organic matter compared to Example 1 in which the influence of the base material made of a titanium flat plate is considered. We were able to.
[0033]
Comparative Example 1
A film was formed in the same manner as in Example 1 except that the heat treatment temperature in the presence of ozone was 600 ° C. The film after firing had a thickness of about 1 μm. Moreover, in this comparative example 1, since the residual organic substance in a film was not fully removed, the film was brown.
Comparative Example 2
A film was formed in the same manner as in Example 1 except that the heat treatment was not performed in the presence of ozone. The film after firing had a thickness of about 1 μm and had a brown color. Thereafter, while heating the substrate at 200 ° C., ozone was circulated at a concentration of 10,000 ppm and heat-treated for 30 minutes, but the coating remained brown.
[0034]
Comparative Example 3
A film was formed in the same manner as in Example 2 except that the substrate was made of a transparent quartz glass plate and the heat treatment temperature in the presence of ozone was 600 ° C. The film after firing had a thickness of about 1 μm. Moreover, in this comparative example 3, since the residual organic substance in a film was not fully removed, the film was brown.
Comparative Example 4
Other than heat treatment in the presence of ozone, pure oxygen was circulated in a constant temperature bath at a flow rate of 8 ml / min, heated to 550 ° C. at a rate of 5 ° C./min, and heat-treated for 10 minutes. A film was formed in the same manner as in Example 1. This film had a brown color. Moreover, the film after baking was about 1 micrometer in thickness, and was exhibiting brown similarly to the film before baking.
[0035]
Comparative Example 5
Heat treatment in the presence of ozone is not performed, and air bubbled in water is circulated at a flow rate of 8 ml / min in a thermostatic bath, and the temperature is raised to 550 ° C. at a rate of 5 ° C./min for 10 minutes. A film was formed in the same manner as in Example 1 except that the heat treatment was performed. This film had a brown color. Moreover, the film after baking was about 1 micrometer in thickness, and was exhibiting brown similarly to the film before baking.
[0036]
【The invention's effect】
According to the method for producing the calcium phosphate coating of the first and third inventions, it is particularly possible to easily produce a uniform, dense, white and excellent bioactive coating.

Claims (5)

  A calcium phosphate-based coating film is produced by applying a solution containing a calcium-containing salt, a phosphorus-containing salt, and a calcium ion and a chelating agent capable of coordinating to at least one of phosphorus ions to a substrate. In the method, the manufacturing method of the calcium-phosphate type coating film provided with the process heat-processed at 50-500 degreeC in presence of ozone. The chelating - method for producing calcium phosphate coatings according to claim 1, wherein bets agent is ethylenediaminetetraacetic acid.   A calcium phosphate-based solution in which a solution in which a chelate compound containing calcium and a chelate compound containing phosphorus, a chelate compound containing calcium and a salt containing phosphorus, or a chelate compound containing phosphorus and a salt containing calcium is dissolved is applied to a base material A method for producing a coating film, comprising the step of heat-treating at 50 to 500 ° C. in the presence of ozone. The manufacturing method of the calcium-phosphate type coating film of any one of Claim 1 thru | or 3 provided with the process baked at 600-900 degreeC in inert atmosphere after the said process to heat-process. The method for producing a calcium phosphate coating according to any one of claims 1 to 4 , wherein the substrate is easily oxidizable.