JPS6256336A - Production of crystallized cao-al2o3-p2o5 glass - Google Patents

Abstract

PURPOSE:To produce titled glass adequate as a dental material without having defects such as cracks by subjecting a glassy casting formed by adding F atoms to the compsn of a ternary component system of CaO-Al2O3-P2O5 to multiple stages of crystallization treatments while heating up the casting. CONSTITUTION:F atoms are added to a raw material mixtue of the compsn. composed of 10-60wt% CaO, 5-35wt% Al2O3 and 25-85wt% P2O5 at <=3pts. wt. by 100pts.wt. in total of the above-mentioned compsn. The mixture is melted and cast to produce the glassy casting. The glassy casting is subjected to >=2 stages of the crystallization treatment while the temp. is gradually increased between the softening point thereof and the crystallization temp. of calcium phosphate. The melting of Al2O3 at the lower temp. is made possible by the incorporation of the F atoms into the compsn.; in addition, the cleaning up of the raw material is made easy and the time when the glass is kept melted is shorter; further the formation of crystal nuclei is accelerated in the crystallization stage of the glass. The titled glass having no voids and cracks is obtd. by multiple stages of the crystallization treatments.

Description

Detailed Description of the Invention [Industrial Field of Application] The present invention provides a CaO-Al2O3P20 material containing calcium phosphate crystals, which is most suitable for dental materials, artificial bone materials, etc.
This invention relates to a method for producing B-crystallized glass medical material.

[Conventional technology]

In recent years, the range of applications for ceramics has expanded rapidly, reaching the medical field, and attempts are being made to apply ceramics to medical materials, such as artificial tooth roots, for which metals and plastics have traditionally been used. .

The present inventors searched for a ceramic material that has an affinity for living organisms, and as a result of repeated research into a method for manufacturing high-strength ceramic by freely and highly precisely molding it into any shape, they found that a calcium phosphate-based material was used as a raw material. We have discovered that this is possible by selecting the appropriate method, and have been conducting extensive research on it.

Even with calcium phosphate materials that have these excellent characteristics, once they are vitrified and crystallized, internal defects occur due to the difference in specific gravity between the glass and the crystal, resulting in a decrease in mechanical strength and the intrusion of fine surfaces. It becomes easier.

For example, the atomic ratio of calcium and phosphorus, Ca/P, is 0.
．． The specific gravity of calcium phosphate glass No. 48 is 2.63, and when it is heat-treated and crystallized, CaO.P2O6 is produced. The true specific gravity of this CaO-PzOs crystal is 2.8
5, which is considerably larger than the specific gravity of glass. However, since crystallization proceeds by a surface devitrification mechanism, there is almost no volume reduction accompanying crystallization.

However, an increase in specific gravity due to crystallization means a decrease in volume, and if the overall volume does not change, voids corresponding to the decrease in volume corresponding to the increase in specific gravity will occur inside the crystal, which will cause cracks. or internal defects such as bores. Because of these internal defects, the strength of the crystal is lower than that of a crystal without defects. Furthermore, since the appearance of bores and the like depends on various factors such as the atomic ratio of calcium and phosphorus in the glass, crystallization temperature, and crystallization time, it is inevitable that the mechanical strength will vary widely.

These internal defects are caused by the fact that even when crystallization is carried out by the bulk crystallization mechanism by adding additives or devising the crystallization method, the volume contraction during crystallization is larger than that by the surface devitrification mechanism. Although the degree of occurrence is small, it still occurs in the same way.

In order to eliminate the above-mentioned drawbacks, it is sufficient to eliminate the difference in specific gravity before and after crystallization, and the present inventors have developed a method that does not impair the biocompatibility of calcium phosphate and the characteristics of no volume contraction during crystallization. As a result of various studies on methods that do not cause internal defects, we succeeded in solving the above problem by employing CaO-Al2O3-P205 ternary crystallized glass.

[Problem that the invention seeks to solve]

However, in order to reduce the difference in specific gravity before and after crystallization, a certain amount of Al2O3 is required, but as the amount of Al2O3 increases, the melting point gradually increases, and in order to completely melt the added Al2O3, , it would have to be heated to a fairly high temperature.

However, when the temperature is increased for melting, a disadvantage arises in that the phosphoric acid component is significantly released in the kiln.

Furthermore, when the amount of Al2O3 increases, the softening point of the glass and the crystallization temperature of calcium phosphate also rise, and the Al2O3/P2O5 crystals that should compensate for the difference in specific gravity are not sufficiently formed.
Therefore, a problem arises in that the generation of voids and cracks due to the difference in specific gravity before and after crystallization cannot be prevented.

[Means for solving problems]

The present inventors increased the solubility of Al2O3 by including fluorine atoms in the composition of the CaO-Al2O3P2O15 3-component system, and furthermore, during crystallization, the temperature between the softening point of the glassy casting and the crystallization temperature of calcium phosphate was increased. By performing two or more stages of crystallization treatment while gradually increasing the temperature, the above problems were solved and the present invention was completed.

[Effect]

The feature of the production method according to the present invention is that CaO is 10 to 60% by weight.
, Al2035-35% by weight, P20s 25-8
Composition range of 5% by weight (7) CaO-Al2O3-P2
CaOSAl2O3 and P2O5 in OS-based materials
3 parts by weight or less of F atoms are contained per 100 parts by weight of the total amount of F atoms, and after melting and casting, it is heated in two stages while gradually increasing the temperature between the softening point of the glassy casting and the crystallization temperature of calcium phosphate. The purpose is to perform the above crystallization treatment.

When glass with the above composition is crystallized, the crystals produced are mainly CaO-P20a, 2CaCIPz○6, and Al.
2O3・P2O5. Their true specific gravity is 2 in order
．． 85.3.09, and 2.59, and Al
The specific gravity of 2O3.P20E+ is considerably lower than the other two types of calcium phosphate crystals.

For example, a glass with a composition of 21.8% by weight of Ca, 9.3% by weight of Al2O3, and 68.9% by weight of P20r has a specific gravity of 2.64, and when this glass is crystallized,
If the crystals formed are only the above two types of calcium phosphate, the specific gravity of the crystals is greater than the specific gravity of the glass, causing volumetric contraction and distortion of the external shape, or, if there is no volumetric contraction, there may be holes such as holes inside the crystals. Defects occur. However, since Al2O3 is included in the glass, Al2 has a low specific gravity.
O3 and P2O6 are generated simultaneously. Al2O3・P2O
When enough crystals of 6 are formed, due to their volumetric expansion,
This will compensate for the volumetric contraction caused by calcium phosphate,
The specific gravity after crystallization is 2.65, the difference in specific gravity almost disappears, and all internal defects disappear.

However, depending on the range of the CaO/P2O5 molar ratio, it may be necessary to increase the amount of Al2O3 in order to eliminate the difference in specific gravity before and after crystallization of the glass. However, Al
As the amount of 2O3 increases, the melting point gradually increases, and in order to completely melt the added Al2O3, a considerably high temperature is required. However, when the temperature is raised for melting, the evaporation of the phosphoric acid component becomes significant, which is a disadvantage. So CaO-Al2O3
-P20s When F atoms are included in the three-component material, Al2O3 can be dissolved at lower temperatures. The F atoms contained remain in the glass during crystallization and do not affect the difference in specific gravity before and after crystallization.

Of course, even in a region where the amount of Al2O3 is not so large, it is desirable to contain F atoms since it helps in melting the sample.

In addition, the inclusion of F atoms makes it easier to clarify the molten raw material, shortens the melting time, and also has the effect of promoting the formation of crystal nuclei during glass crystallization, which improves the strength of the product. It also has the advantage of contributing.

On the other hand, the presence of Al2O3 means that CaOHP2O5 and 2
The crystallization temperature of CaO-P2O5 is increased to further increase the difference from the crystallization temperature of Al2O3.P2O5, which was originally present. Therefore, if crystallization is performed near the crystallization temperature of two types of calcium phosphate, two types of calcium phosphate crystals will be mainly formed, and Al2O3・P2O
The crystals of No. 5 do not form much, and the effect of compensating for the difference in specific gravity due to their volumetric expansion is not exhibited.

In order to solve this problem, we first produced crystals of aluminum phosphate by processing at a temperature slightly higher than the softening point of glass and lower than the crystallization temperature of calcium phosphate, and then crystallized calcium phosphate. By employing a method of raising the temperature to complete the crystallization of calcium phosphate, it is possible to fully exhibit the volume compensation effect of aluminum phosphate within the crystal. It is also possible to carry out this crystallization operation in three or more stages while gradually increasing the temperature between the softening point of the glass and the crystallization temperature of calcium phosphate, instead of the above two stages. Furthermore, the temperature may be raised continuously between the softening point of the glass and the crystallization temperature of calcium phosphate.

This multi-step crystallization process eliminates the difference in specific gravity between the glass and the crystal, preventing the formation of defects within the crystal. At the same time, crystallization at low temperatures also generates crystal nuclei inside the crystal, and the surface By weakening the surface devitrification that causes crystals to develop, preventing the occurrence of cracks, and shortening the crystallization time at high temperatures, it also has the effect of reducing softening and deformation of the product.

[Structure of the invention]

The starting materials of the present invention are calcium-containing compounds that produce CaO upon calcination, such as calcium oxide, calcium hydroxide, calcium carbonate, and calcium oxalate, and phosphoric acid, polyphosphoric acid, etc., which produce phosphorus oxides upon calcination. Aluminum-containing compounds and aluminum-containing compounds that become Al2O3 when fired, such as alumina and aluminum hydroxide, are used.Also, calcium phosphate, apatites, aluminum phosphate, calcium aluminate, etc. can be used.Also, as a fluorine source, calcium fluoride is used. , aluminum fluoride, fluorine-containing apatite, etc. can be used, but calcium fluoride, which does not sublimate, is the most suitable.

One or more compounds containing calcium, aluminum, aluminum, and fluorine are selected, and the composition of the glass is set to 10 to 60% by weight of CaO and 35 to 3% of Al2O.
5% by weight, P20s in the range of 25-85% by weight,
Further, the F atom should be 3 parts by weight or less per 1 part by weight of the total amount of CaO, Al2O3, and P2O6.

If CaO is 60% by weight or more or P is less than 20625% by weight, the melting temperature becomes high and vitrification does not occur. Conversely, less than 10% by weight of CaO or 85% by weight of P 20 s
In this case, the melting temperature is lowered and vitrification becomes easier, but the crystallization process becomes difficult and excess phosphoric acid is liberated, resulting in chemical instability, which is not preferable. On the other hand, if the alumina content exceeds 35% by weight, the melting temperature will become high, and if it is less than 5% by weight, Al2O3/P2O5 crystals will not form or will be formed in small amounts (and the generation of internal defects such as bores cannot be prevented). On the other hand, if the F atom content is 3 parts by weight or more, CaF2 crystals will precipitate, and the specific gravity of these crystals will be large, so that the effect of Al2O3 will be lost, which is not preferable.

The calcium phosphate glass of the present invention basically consists of Ca
It is composed of three components: Al and P. However, when using the crystallized glass produced by the method of the present invention as a dental crown material, it is necessary to use the same coloring agent as natural teeth. It is also possible to add other components.If a colorant component is added, Zn, Fe.

Mn, W, Ce, Ti, Ni, Go, Cr
, V oxides are used, and it is particularly preferable to use two or more of them in combination. The amount added is Cab-Altos-P20S3
The amount is 0.01 to 15 parts by weight per 100 parts by weight of the component oxide.

After weighing the raw materials, mix well, place in a container, and heat to 90°C or higher, preferably 1000 to 1700"C to melt. Care must be taken when melting at 1800°C or higher, as the phosphorus component will begin to evaporate. In the case of the present invention, Al2O3 should be sufficiently melted in the above temperature range due to the presence of F atoms.

After the melting is completed, it is cooled and vitrified. Subsequently, it is melted and cast again, but the first melt may be directly cast without being cooled and vitrified. CaO-Al2O3- of the present invention
In the case of P2O5 tricomponent based materials, the lost wax method, which is carried out on metal dental materials, is suitable for casting. The preheating temperature of the casting mold is 8009C or less, preferably 2
The temperature is appropriately selected within the range of 00 to 800°C depending on the material of the casting mold and the composition of the glass.

The casting thus cast is glassy. One of the features of the manufacturing method of the present invention is the crystallization treatment method in which this glassy material is subjected to appropriate heat treatment to produce crystallized glass. The method for crystallizing the three-component crystallized glass according to the present invention is as follows. A molded body formed by a lost wax method or the like is usually heated in a suitable heating device such as an immersion mold or an electric furnace. As for the heating temperature at this time, first, the softening point of the glass and the crystallization temperature of calcium phosphate are determined using differential thermal analysis. First, the glass is crystallized at a temperature slightly higher than the softening point of the glass, and then the temperature is slightly raised and the crystallization process is performed again. In this way, the crystallization process is performed without raising the temperature, and the final process is performed at the crystallization temperature of calcium phosphate. The number of stages of this treatment may be two or more, but from the viewpoint of operability, two to four stages are preferred. Total processing time is 5~
It will be 50 hours.

〔Example〕

Example 1 Calcium carbonate powder, alumina powder, orthophosphoric acid, and calcium fluoride powder with a final composition of 13.6% by weight CaO
, Al20328.0% by weight, P 20 r, 58.
4% by weight, CaO + AlzO3 + P2O6 100 parts by weight, F atoms were weighed so that 1.5 parts by weight were mixed, thoroughly kneaded, melted in a platinum crucible at 1600@C for lhr, and pressure cast into a mold in which the connecting crown was embedded. It was then cooled and vitrified. The obtained glass was kept buried in an electric furnace at 688°C.
2 hours at 690℃, then 10 hours at 700℃
It was treated with r and crystallized.

The obtained crystal was white and translucent, and when the microstructure of the crystal was observed under a microscope, no defects such as bores or clutter were observed. CaO.P2O6 and Al2O3.P2O6 were present.The specific gravity of the glass was 2.64, and the specific gravity of the crystal was 2.65.

Comparative Example 1 An attempt was made to melt the same material as in Example 1 except that it did not contain calcium fluoride, but the raw material did not melt completely at 1600°C, so it finally melted when the temperature was raised to 1850°C, but the melting failed. While heating was continued until the liquid became clear, the phosphoric acid component evaporated and crystals gradually began to precipitate.

Comparative Example 2 Raw materials with exactly the same composition as Example 1 were melted and cast at 700°C.
, crystallized in one step for 10 hr.

The obtained crystallized glass was also white and translucent, but there were few Al2O3/P2O5 crystals in the crystal, the specific gravity of the glass was 2.64, and the specific gravity of the crystal was 2.70, and there was no crystal inside the crystal. A few boas were visible.

〔Effect of the invention〕

As seen in Comparative Example 1, fluorine-free CaO
-In the raw material mixture of only -Al2O3-P2O6, AhO
If 3ffi is too large, melting is impossible, and if fluorine is contained as in Comparative Example 2, melting is possible, but Al2O
Since the amount of 3 is large, if it is crystallized in one step, Al2O3・P
Internal defects occur because 2O5 crystals are not sufficiently produced.

However, as seen in Example 1, the CaO-Al2O3-PzOs-based crystallized glass containing F atoms of the present invention has no internal defects, indicating that it is optimal as a medical material.

Claims (1)

[Claims] To a raw material mixture having a composition of 10 to 60% by weight of CaO, 35 to 35% by weight of Al_2O_, and 525 to 85% by weight of P_2O, 3 parts by weight or less of F atoms are added to 100 parts by weight of the total amount of CaO, Al_2O_3 and P_2O_5, and melted. After casting, a crystallization treatment of CaO-Al_2O_3-P_2O_5 is performed in two or more stages while gradually increasing the temperature between the softening point of the glassy cast body and the crystallization temperature of calcium phosphate. Production method.