JP2527323B2 - Ceramics sintered compact and method for producing the same - Google Patents

Description

TECHNICAL FIELD The present invention relates to a ceramic sintered body that is biocompatible and can be widely used for artificial tooth roots and artificial bones.

[Industrial applications]

Various glass ceramics containing SiO ₂ , P ₂ O ₅ and CaO as basic components are known as artificial tooth roots and artificial bone materials. For example, JP-A-57-191252 discloses at least 90
% Or more is MgO 1 to 7%, CaO 42 to 53%, SiO ₂ 22 to 41% and P
Disclosed is a crystallized glass for artificial bone, which has a composition of 10 to 27% of ₂ O _{5 and} 10% or less of impurities, and has a structure in which a large number of apatite and wollastonite fine crystals are dispersed in the glass. JP-B-51-8970 discloses SiO ₂ , P ₂ O ₅ ,
Glass ceramics containing Na ₂ O, K ₂ O, MgO and CaO as basic components and optionally further containing fluorine are disclosed. And, these compositions contain apatite crystals which are involved in compatibility with living bodies. Since the atomic ratio Ca / P in the apatite crystal is about 1.67, it is desirable that the composition be close to this composition in order to contain many apatite crystals.
However, a conventionally known glass containing SiO ₂ , P ₂ O ₅ , and CaO as a basic component does not vitrify sufficiently when Ca / P is 5.7 or less, so that a uniform composition cannot be obtained. So Ca / P
In order to produce a glass-ceramic having a ratio close to that of an apatite crystal composition, JP-A-57-191252 discloses that MgO should be 1-7.
%, And in Japanese Patent Publication No. 51-8970, MgO 2.9-30% by weight
And Na ₂ O 2.7 to 20 wt% are added, but CaO is MgO and N.
Since it is replaced with a ₂ O, the amount of apatite crystals decreases,
There are problems that the calcium silicate-based crystals that contribute to the strength decrease and the strength decreases, and that addition of Na ₂ O deteriorates the chemical stability of the sintered body.

[Problems to be solved by the invention]

Therefore, it is an object of the present invention to provide a ceramics sintered compact having excellent strength and extremely excellent biocompatibility, and a method for producing the crystal compact.

[Means for solving problems]

In the present invention, since CaO functions as a calcium silicate component (CaO, SiO ₂ ) that contributes to the strength improvement, the atomic ratio Ca / P of Ca / P is set in the range of 1.0 to 5.7, and SiO ₂ , Na ₂ O. , MgO
Since it was made based on the finding that an excellent ceramics sintered body can be obtained when the amount of is in the range, and that a better ceramics sintered compact can be obtained by using the sol-gel method in producing the sintered body. is there.

That is, the present invention has a SiO ₂ content of 20 to 70% by weight, CaO
And P ₂ O ₅ and the atomic ratio Ca / P is 1.0 to 5.7, the total content of SiO ₂ , P ₂ O ₅ and CaO is 70 wt% or more, and the content of Na ₂ O and MgO is A ceramics sintered compact characterized by being less than 2% by weight and less than 0.9% by weight, respectively.

The ceramic sintered compact of the present invention has a SiO ₂ content of 20.
70% by weight (hereinafter abbreviated as%), preferably 30-40
%. That is, if it is less than 20%, the strength of the sintered body will be insufficient, and if it exceeds 70%, the amount of calcium phosphate-based crystals such as apatite will decrease and the amount of crystals derived from SiO ₂ will increase. .

The atomic ratio of Ca and P, Ca / P, is 1.0 to 5.7, preferably 1.5 to
When the ratio is less than 1.0, metaphosphoric acid, calcium and calcium pyrophosphate are produced, and when it exceeds 5.7, the amount of apatite crystals becomes small. In the present invention, the total content of the three components SiO ₂ , CaO, and P ₂ O ₅ is 7
It is 0% or more, preferably 90% or more. The content of CaO and P ₂ O ₅ may be any amount as long as the above conditions are satisfied, but CaO is preferably 10 to 70% and P ₂ O ₅ is 5 to 40%.

In the present invention, it is further preferable that Na ₂ O is less than 2% and MgO is less than 0.9%, and preferably both are not substantially contained. That is, if the amount of Na ₂ O exceeds 2%, the strength of the ceramics sintered compact decreases and the solubility in the living body increases, which is not preferable, and if the amount of MgO exceeds 0.9%, magnesium silicate-based crystals form. It tends to precipitate.

In the present invention, in addition to the above components, Zr is added in an amount of 30% or less.
O ₂ , Al ₂ O ₃ , TiO ₂ , B ₂ O ₃ , Y ₂ O ₃ , SiC, Si ₃ N ₄ , AlN, etc. 1
Seeds or mixtures of two or more can be added. Further, hydrochloric acid, hydrofluoric acid, hydrosilicofluoric acid, halides such as calcium chloride and potassium fluoride, sulfides such as zinc sulfide, and La ₂ O ₃ , CeO ₂ , SnO ₂ , Fe ₂ O ₃ , Li ₂ O. , Sr
Nucleating agents such as O, Nb ₂ O ₅ , Ta ₂ O ₅ , Ag, Au, Pt, Pd and Ph can be added in an amount of 0 to 10%.

The ceramic sintered compact of the present invention has the above composition, but its crystal structure is composed of a crystalline component and an amorphous component. Here, as the crystal component, calcium phosphate-based crystals such as apatite (hydroxyapatite, oxygen apatite, carbonate apatite, fluoroapatite, chlorine apatite) and tricalcium phosphate (TCP) that contribute to compatibility with living organisms are contained and baked. It is preferable to contain wollastonite (CaO · SiO ₂ ) that contributes to the strength of the aggregate. Further, as other crystals, a small amount of SiO ₂ type crystals (cristobalite, quartz, tridymite), calcium pyrophosphate, and calcium metaphosphate may be contained. On the other hand, as the amorphous component, Si such as amorphous calcium phosphate, amorphous calcium silicate, amorphous silica, and amorphous calcium silicate is used.
O _2, including P ₂ O _5, CaO3 independently or in combination with an amorphous component formed by one of the components. In the present invention, it is important to include many apatite crystals among the above various crystals.

The ceramic sintered compact of the present invention can be produced by any method as long as it has the above-mentioned composition, but it is preferably produced by the sol-gel method. That is, conventionally, the glass has
Glass-ceramics produced by VAD (Vaper-Phase Axial Deposition Method) are obtained by crystallizing those glasses, but the sol-gel method makes it possible to synthesize at a low temperature, obtain a high-purity material, and melt it. This is because there is an advantage that the vitrification range is not restricted as in the method.

Specifically, the general formula [I]: (In the formula, R _{1 to} R ₄ are each hydrogen or C _X H _{2x + 1} (OC ₂ H ₄ ) _y
-(Provided that x is 1 to 5 and y is 0 to 10), and not all of R _{1 to} R ₄ are hydrogen. n is 0-20. ) At least one kind of silicic acid ester represented by the formula (3) is gelled in the presence of a phosphorus compound and a calcium compound, and the gel is dried, and then molded and sintered. Is good.

Here, as the silicate represented by the general formula [I], in the formula [I], R _{1 to} R ₄ are CH ₃ , C ₂ H ₅ , and nC.
_{3 H 7, iso-C 3} H 7, n-C 4 H 9, -C 2 H and even preferably at ₄ OCH _3, that is particularly preferred among these R ₁ to R ₄ are identical groups preferable. In the present invention, n = 0 is preferable, but a condensate in which n is 1 to 10 is also preferable. General formula [I]
Specific examples of the silicic acid ester represented by are methyl silicate, ethyl silicate, n-propyl silicate, isopropyl silicate, n-butyl silicate, 2-methoxyethyl silicate, and 2 to 10 amounts thereof. The body etc. are raised. Of these, ethyl silicate Si (OC ₂ H ₅ ) ₄ is ethyl silicate 2
8. Average 5 mol condensate of ethyl silicate: Is readily available from Colcote as ethyl silicate 40.

In the present invention, the concentration of the silicate ester in the mixed solution is arbitrary, but as SiO ₂ , 0.1 to 40% by weight, preferably 2 to 3
It is better to set it to 0%.

The phosphorus compound used in the above-mentioned production method is represented by the general formula [II], [III] or [IV]: (In the formula, R _{5 to} R ₉ are each hydrogen, an alkyl group having 1 to 5 carbon atoms, a phenyl group or an aralkyl group having 7 to 10 carbon atoms, and m is 0 to 10.) Preference is given to using certain compounds. Here, the phosphoric acid ester of the formula [II] has 1 carbon atom as the alkyl group of R _{5 to} R ₇ in the above formula [II].
Preferably, the phenyl group and the benzyl group are also preferred. Further, m is preferably 0 to 4. Any of phosphoric acid esters in which R _{5 to} R ₇ are all alkyl groups, phosphoric acid in which all R _{5 to} R ₇ are hydrogen and its condensates, and partial esters containing both alkyl groups and hydrogen can be used. In addition, the general formula [II
As the phosphite itself and the phosphite represented by I] and [IV], the alkyl group having 1 to 4 carbon atoms is preferable in the formulas [III] and [IV], and the phenyl group and benzyl group are preferable. Groups are also preferred. As a preferred compound,
Specifically, in the general formulas [III] and [IV], R _{5 to} R ₉
Is methyl, ethyl, iso-propyl, n-propyl, n
-Butyl, phenyl and benzyl are preferred.

In the present invention, the formula [I
In the compound of I], at least one of R _{5 to} R ₇ is hydrogen, but a compound in which all are not hydrogen is most preferable.
Specific examples include the following compounds.

1 type or a mixture of 2 or more types. Here in the above formula, R ₅ to R _7, except that except for R ₅ to R ₇ with hydrogen of formula (II) are the same.

The above phosphoric acid ester can be easily prepared by a method of partially hydrolyzing a corresponding phosphoric acid ester, a method of esterifying a corresponding phosphoric acid by adding an alcohol, a method of reacting phosphorus pentoxide with an alcohol and then hydrolyzing the same. Obtainable.

Another essential component of the present invention is calcium ion, and it is preferable to use a calcium salt or an alkoxide thereof as a substance forming the ion.
This is because the addition of Ca is necessary to produce bioactive glass and glass ceramics, and Ca (R ₁₀ ) ₂
(In the formula, R ₁₀ is an alkyl group having 1 to 5 carbon atoms.),
It is preferable to use calcium nitrate, calcium acetate, calcium chloride, calcium hydroxide, calcium hydrogen citrate, calcium citrate, calcium oxalate, or the like.

Of these methods for producing calcium components, water-soluble salts such as calcium nitrate, calcium acetate, calcium chloride and the like are particularly preferable.

Furthermore, in the present invention, in addition to the above-mentioned constituent elements, an element which can be a constituent oxide of the gel can be added. Specifically, it is Al, Zr, Ti, B and the like, and these can be used in the form of a metal alkoxide or a soluble salt like the alkaline earth metal. Of these, Al (OR ₈ ) ₃ and Zr (OR ₈ )
₄ , Ti (OR ₈ ) ₄ and B (OR ₈ ) ₃ are preferable, and these are 0 to 30 in terms of oxides with respect to the total amount of oxides when all the constituent elements of the gel are converted into oxides. It is advisable to use it in an amount of% by weight. In addition, ZrO ₂ , Al was added to the prepared solution before gelation.
Fine particles or whiskers of ₂ O ₃ , mullite, β-wollastonite, hydroxyapatite, SiC, Si ₃ N ₄ , AlN, etc. may be added, and dispersed and then gelled. These fine particles or whiskers are preferably used in an amount of 0 to 30%.

In the present invention, these raw materials are used in an amount such that the finally obtained ceramics sintered compact has a composition within the range described above. Then, the silicate ester is gelled in the presence of a phosphorus compound, a calcium compound or the like. Next, gelation reaction conditions and the like are shown.

PH during gelling reaction The present invention requires that the phosphorus component and the calcium component are compatible with each other, and be performed in an acidic or neutral state that causes uniform gelation,
The pH is preferably 4 or less.

Of the phosphorus component used in the present invention, phosphoric acid, phosphoric acid partial ester, phosphorous acid, phosphorous acid partial ester, since it is an acid, it is not necessary to add a pH adjusting substance again,
To make the pH acidic, it is preferable to use mineral acids such as hydrochloric acid, nitric acid and sulfuric acid and organic acids such as acetic acid, citric acid and lactic acid. or,
It is preferable to add the above-mentioned acidic substance to phosphoric acid ester and phosphorous acid ester. The pH of the liquid may be the same until gelation, or the pH may be increased after the silicate ester is partially hydrolyzed in order to promote gelation. For that purpose, the pH can be raised by adding an alkali such as aqueous ammonia, amines and formamide.

Reaction Solvent Examples of the solvent for dissolving the silicate ester and the phosphorus component and the calcium component include water, alcohols such as methanol and ethanol, and mixtures thereof. It is preferable that the amount of water here is about 1 to 15 times the molar amount of the silicic acid ester, because the hydrolysis proceeds well.

Specific Method for Producing Gel In the present invention, the above-mentioned components are used, and for example, a multi-component gel is produced by the following method.

(I) A phosphorus compound is added to the silicate ester to partially hydrolyze the silicate ester, and then a calcium compound is added to complete gelation.

(Ii) After partially hydrolyzing the silicate ester, the phosphorus compound is added, and then the calcium compound is added to complete gelation.

(Iii) A calcium compound is added to the silicic acid ester to partially hydrolyze the silicic acid ester, and then a phosphorus compound is added to complete gelation.

(Iv) After partially hydrolyzing the silicate ester, a calcium compound is added, and then a phosphorus compound is added to complete gelation.

(V) A silicate ester is added to a solution of a phosphorus compound and a calcium compound to cause gelation.

(Vi) A silicate ester, a phosphorus compound and a calcium compound are simultaneously added to cause gelation.

The gelation by hydrolysis and polycondensation can be performed at room temperature, but may be heated. In the case of heating and when the temperature is not lower than the boiling point of the solvent, an autoclave or the like may be used to carry out hydrolysis and polycondensation under pressure.

Manufacturing of sintered compact As a method of manufacturing glass by the sol-gel method, a method of forming a dry gel that does not crack by drying by controlling the evaporation rate from the gel and firing it as it is generally used for silica glass etc. However, with the multi-component gel of the present invention, it is difficult to make a dry gel without causing cracks in the gel, and it is even more difficult to bake without causing cracking. Therefore, in order to obtain a sintered body, a method in which the dried gel is powdered, heat-treated, and then molded and sintered is preferable.

Drying Dry at 0 to 200 ° C under normal pressure or reduced pressure. The wet gel may be crushed and then dried, or dried and crushed.

Heat treatment In order to remove residual alkoxy groups on Si, P, and Ca atoms, further promote the polycondensation reaction of the gel, and almost complete the reaction between the constituent components, 200 to 1000 ° C, preferably 400 to 800 ° C.
Perform heat treatment at ℃. That is, the treatment at a temperature of less than 200 ° C. is not sufficiently effective, and if it exceeds 1000 ° C., crystallization is promoted and the sinterability deteriorates.

Molding and Sintering The following methods (i) to (iii) can be used.

(I) Heat-treated powder is uniaxially pressed, cold isostatically pressed (CI
P) and then pressureless sintering at 800-1300 ℃.

(Ii) Sinter the heat treated powder by hot pressing at 800 to 1300 ° C.

(Iii) Direct hot isostatic pressing (HI)
P) or sintered under normal pressure and further subjected to hot isostatic pressing.

In the present invention, the apatite crystals are further prevented from decomposing to calcium phosphate (TCP) by heating at a high temperature of 1150 ° C. or higher, and the apatite is not decomposed even if the sintering temperature is increased to increase the sintering density of the apatite, It is advisable to add a halide. Specifically, by adding a halide in the manufacturing process of the raw material powder before sintering, the decomposition of hydroxyapatite is suppressed, and a sintered body having apatite crystals is easily obtained. The halide to be added is particularly preferably a chloride or a fluoride, and specifically, hydrochloric acid, calcium chloride, hydrofluoric acid, hydrosilicofluoric acid, calcium fluoride or the like.

The addition method may be addition to the solution before gelation, impregnation of the gel in a halide solution and drying, or dry powder or heat-treated powder may be re-treated with a halide solution or halide. The amount of addition of is preferably about 0.003 to 3% as halogen ions with respect to the total weight in terms of oxide.

〔The invention's effect〕

According to the present invention, a ceramic sintered body having excellent biocompatibility and high strength is provided.

Therefore, the sintered body of the present invention can be widely used for artificial tooth roots, artificial bones and the like.

Next, the present invention will be described with reference to examples, but the present invention is not limited thereto.

〔Example〕

Example 1 A 10-fold molar amount of water was mixed with a silicate ester, a phosphorus compound and a silicate ester, and the mixture was vigorously stirred at 45 ° C.
After 1 hour, a 50% aqueous solution of calcium nitrate was further added and stirred to obtain a uniform solution. The type of silicate ester and phosphorus compound used and the charging ratio of the three components are converted to oxides and shown in the table.
It is shown in FIG.

Next, the obtained solution was sealed and allowed to stand at 45 ° C. overnight for gelation. Open the lid of the container and let the gel for 1 week, 45
It was dried at ° C. This dry gel is crushed into a powder,
The temperature was raised to 500 ° C. at a rate of 20 ° C./hr, heat treatment was performed at 500 ° C. for 10 hours, and the heat-treated powder was wet pulverized with a ball mill, molded, and sintered with a hot press at 1200 ° C. for 1 hour.

When the composition analysis of the obtained sintered compact was examined by fluorescent X-ray, it coincided with the charged composition, and Na ₂ O and MgO were not detected. Next, a 3 × 4 × 30 mm prism was prepared from the obtained sintered body, and after surface polishing, bending strength was measured by a three-point load method. The results are summarized in Table 1.

As is clear from Table-1, all of the products of the present invention exhibit high bending strength, and all of the materials contain a large amount of apatite crystals that play an important role in forming a chemical bond with bone. I was out.

On the other hand, in the comparative example, almost no apatite crystals were precipitated.

Example 2 Ethyl silicate was used as the silicate ester, and the others are shown in Table-
Gelation and heat treatment were performed in the same manner as in Example 1 except for the conditions shown in 2.

Next, after wet-milling the obtained heat-treated powder with a ball mill,
It was molded by a cold isostatic press and subjected to atmospheric pressure sintering at 1200 ° C. The precipitated crystals are shown in Table-2. Selectivity of the partial ester of phosphoric acid was better than that of orthophosphoric acid as the phosphoric acid compound, and more apatite crystals were deposited.

Example 3 83.3 g of ethyl silicate, 23.6 g of a mixture of monoethyl phosphate and diethyl phosphate (50/50) and water or 95 g of 0.76 mol / hydrochloric acid water were mixed and stirred at room temperature. After 1 hour, 168.7 g of a 50% aqueous solution of calcium nitrate was added and further stirred. The solution was sealed and left to stand at 45 ° C. overnight for gelation. The SiO ₂ / CaO / P ₂ O ₅ weight ratio of these gels is 37/44/1
Is 9. Open these gels for 4 weeks a week
Dried at 5 ° C. Then crush the dried gel powder at 20 ℃ /
Heat treatment was performed by raising the temperature to 800 ° C. for 3 hours and holding it for 3 hours.

Further, the heat-treated powder was wet pulverized with a ball mill, molded with a cold isostatic press, and subjected to normal pressure sintering at 1100 ° C, 1150 ° C and 1200 ° C. The precipitated crystals are shown in Table-3. When water is used, apatite begins to decompose to tricalcium phosphate at around 1150 ° C, whereas when hydrochloric acid water is used, the precipitated crystals are only apatite and wellastonite even at 1.200 ° C. , Degradation of apatite to tricalcium phosphate was hardly observed.

Example 4 The same experiment as in Example 3 was carried out except that water was used as the hydrolyzed water and 2.4 g of a 10% hydrogen fluoride aqueous solution was added to the solution before gelation while cooling. When the heat-treated powder was sintered at 1200 ° C under normal pressure, the only precipitated crystals were apatite and wollastonite, and almost no decomposition of apatite to tricalcium phosphate was observed.

Example 5 Using water as the hydrolyzed water, a heat-treated powder was produced in the same manner as in Example 3, and 0.17 mol / hydrochloric acid water was used in place of the water used for wet grinding with a ball mill. 12 after molding
When pressureless sintering was carried out at 00 ° C, the precipitated crystals were only apatite and wollastonite, and almost no decomposition of apatite into tricalcium phosphate was observed.

Comparative Example 3 30 g of amorphous silica powder, 24.4 g of dibasic calcium phosphate dihydrate and 28.7 g of calcium carbonate (SiO ₂ / CaO / P ₂ O ₅
＝ 46/38/16) is mixed and calcined at 1000 ℃, then calcined powder
When an attempt was made to melt at 1600 ° C. for 1 hour, an insoluble material remained and a uniform melt could not be obtained.

Claims (5)

(57) [Claims] 1. A SiO ₂ content of 20 to 70% by weight, CaO and P ₂ O ₅ are contained, the atomic ratio Ca / P is 1.0 to 5.7, and the total content of SiO ₂ , P ₂ O ₅ and CaO is 70% by weight. %, And the contents of Na ₂ O and MgO are less than 2% by weight and less than 0.9% by weight, respectively, and a ceramic sintered compact. 2. The ceramic sintered compact according to claim 1, which contains apatite crystals. 3. A SiO ₂ content of 20 to 70% by weight, CaO and P ₂ O ₅ are contained, the atomic ratio Ca / P is 1.0 to 5.7, and the total content of SiO ₂ , P ₂ O ₅ and CaO is 70% by weight. % Or more and the content of Na ₂ O and MgO is less than 2% by weight and less than 0.9% by weight, respectively, in order to produce a ceramics sintered compact, the general formula [I]: (In the formula, R _{1 to} R ₄ are each hydrogen or C _X H _{2x + 1} (OC ₂ H ₄ ) _y
-(Provided that x is 1 to 5 and y is 0 to 10), and not all of R _{1 to} R ₄ are hydrogen. n is 0-20. ) At least one kind of silicic acid ester represented by the formula (3) is gelled in the presence of a phosphorus compound and a calcium compound, the gel is dried, and then molded and sintered, which is a method for producing a ceramic sintered compact. 4. A phosphorus compound represented by the general formula [II], [III] or [IV]: (In the formula, R _{5 to} R ₉ are each hydrogen, an alkyl group having 1 to 5 carbon atoms, a phenyl group or an aralkyl group having 7 to 10 carbon atoms, and m is 0 to 10.) The production method according to claim (3), which is a compound of a kind. 5. The calcium compound is represented by a calcium salt or a general formula [V]: Ca (OR ₁₀ ) ₂ ... [V] (wherein R ₁₀ represents an alkyl group having 1 to 5 carbon atoms). The method according to claim (3), wherein the method is at least one compound.