JP4761715B2 - Biomaterial, method for manufacturing the same, and artificial joint - Google Patents

Description

  The present invention relates to a biomaterial made of alumina ceramic, a method for producing the same, and an artificial joint.

  Alumina ceramics and zirconia ceramics are biologically inert materials, and are excellent in mechanical strength and wear resistance, and thus are being applied as medical materials such as artificial joints and artificial tooth roots. For example, in artificial hip joints, the combination of alumina or zirconia ceramics / ultra high molecular weight polyethylene is less likely to wear and defects than metal, so ceramic is used for the bone head and ultra high polymer is used for the acetabular socket. Polyethylene has been employed (see Patent Document 1).

  Furthermore, an artificial hip joint having a sliding portion between alumina ceramics has been developed (see Patent Document 2).

  In general, alumina has high wear resistance and corrosion resistance, so its performance can be fully demonstrated when used alone. However, since sinterability itself is poor, sintering aid is necessary to obtain a dense sintered body. Baking is performed by adding a minimum amount of the agent.

  For example, 0.01 to 0.2% by mass of magnesia powder and 0.01 to 0.2% by mass of yttria powder are added to the alumina powder, mixed with polyvinyl alcohol, and mixed with magnesia in the alumina powder. It has been proposed to produce a translucent alumina ceramic by firing at a high temperature of 1600 to 2000 ° C. using a raw material powder in which yttria is uniformly dispersed (see, for example, Patent Document 1).

Further, a molded body containing 0.7 to 3% by mass of chromium oxide powder and 0.05% by mass or less of magnesia powder with respect to the alumina powder was fired at 1280 ° C., and then this sintered body was 1300 to 1310 ° C., A method has been proposed in which HIP treatment is performed under the condition of 1000 to 2000 atm to dissolve chromium oxide and magnesia in a solid solution, thereby producing a light-transmitting ruby free of coarse particles of 4 μm or more.
Japanese Patent Publication No. 06-22572 JP 2000-16836 A Japanese Patent Laying-Open No. 5-43308 Japanese Patent Publication No. 5-83511, claims 1 and 2

  However, although the alumina ceramic produced by the method of Patent Document 3 has an advantage that it has translucency, the magnesium compound easily aggregates, so that there is a problem that Mg is difficult to uniformly disperse in the alumina ceramic.

  In addition, the alumina ceramic described in Patent Document 4 has the advantage that there is no coarse particle of 4 μm or more and translucency is obtained, but the magnesium compound is not uniformly dispersed, and the HIP treatment is performed after firing. However, the defects remained and the strength was low.

  Accordingly, an object of the present invention is to provide an alumina ceramic with improved Mg dispersibility and a method for producing the same.

The biological member of the present invention uses a part of the total amount of alumina powder and the total amount of at least one magnesium compound powder among magnesium hydroxide, magnesium carbonate and magnesium oxide, and the alumina powder is 60 to 99. A step of preparing a first slurry by mixing so that the volume percentage of the magnesium compound powder is 1 to 40 volume%; and adding the remaining amount of the alumina powder to the first slurry a step of the slurry preparation, a process of forming a shaped body from the second slurry, and a step of firing the green body to a living body member obtained by including Manufacturing method, the content of magnesium There Ru der 0.5 mass% or less in terms of oxide.

The magnesium compound powder is preferably magnesium hydroxide powder .

  It is preferable that the average particle diameter of the alumina powder is 0.3 to 0.7 μm.

The magnesium hydroxide powder preferably has an average particle diameter of 0.5 to 10 μm and a BET specific surface area of 10 to 50 m ² / g.

  It is preferable to perform a high-temperature and high-pressure treatment after the firing.

  Examples of the biological member of the present invention using the ceramic sintered body include artificial bones, artificial tooth roots, and the like as artificial materials such as artificial bone heads, which are non-toxic and easily adaptable to living bodies that require high strength and do not cause rejection reactions. is there. In particular, the ceramic sintered body is excellent in ceramic-ceramic wear characteristics in an in vivo environment, and the ceramic sintered body can be used for an artificial joint having a ceramic-ceramic sliding surface.

  In the present invention, when the amount of Mg compound is small with respect to alumina, for example, when it is 0.5% by mass or less, particularly 0.2% by mass or less, the amount of Mg compound is small, so Mg is uniformly dispersed in the slurry. Therefore, it is easy to obtain a slurry in which the Mg compound is aggregated, and the alumina ceramic produced using this slurry forms an aggregated area and a non-aggregated area of Mg, and the aggregated area forms voids. This is based on a novel finding that the adverse effect on wearability tends to occur.

  The present invention also provides a magnesium compound as a sintering aid by mixing a mixed powder having a higher ratio of Mg compound powder to alumina powder and then adding alumina powder to prepare a slurry of the original composition. It becomes easy to uniformly disperse the powder in the alumina powder, and as a result, there is little aggregation area of Mg, and it is possible to produce a high-strength alumina ceramic, especially when a small amount of sintering aid is used. This shows the effect.

The alumina ceramic in the present invention is an alumina ceramic containing Mg, and when the surface of the alumina ceramic is subjected to surface analysis with an electron beam probe microanalyzer, an Mg agglomerated region and a non-aggregated region adjacent to the agglomerated region are present. And C1 / C ₂ ≧ 2, when the Mg concentration in the aggregated region is C ₁ , the Mg concentration in the non-aggregated region is C ₂ , and the diameter when the area of the aggregated region is converted into a circle is R. The number of voids generated by the aggregate coarse particles of the magnesium compound is reduced as a result of the aggregation region satisfying R ≧ 5 μm being 5 or less in the 0.05 mm ² measurement region. It has the effect of improving the properties (bending strength, abrasion resistance).

  Moreover, it is preferable that content of Mg is 0.5 mass% or less in conversion of an oxide. Since the content of the sintering aid is small, the characteristics of alumina itself can be exhibited.

  Moreover, the manufacturing method of the alumina ceramic of this invention prepares the 1st slurry which contains Mg compound powder in the ratio of 1-40 mass% with respect to high purity alumina powder, Then, with respect to this 1st slurry The high-purity alumina powder is added so that the Mg content is lower than the concentration in the first slurry, and this is mixed to prepare a second slurry, and then the second slurry Since the molded body is produced using the sinter and the molded body is fired, the Mg compound powder once dispersed can be dispersed more uniformly without re-aggregation.

Since the Mg compound is Mg (OH) ₂ , there is an effect that no harmful gas is generated during the sintering process as in the case of chlorides, nitrates, sulfates and the like.

  Since the average particle diameter of the alumina powder is 0.3 to 0.7 μm, a dense sintered body having a uniform crystal particle diameter can be formed, and there is an effect that a smooth surface is obtained without removing particles by polishing. .

Since the Mg compound powder has an average particle size of 0.5 to 10 μm and a BET specific surface area of 10 to 50 m ² / g, it has a high specific surface area and eliminates coarse particles by crushing for about 100 hours. There is an effect that uniform dispersion is possible.

  Since high-temperature and high-pressure treatment is performed after the firing, large voids can be reduced, the wear surface can be easily maintained, and the wear amount can be reduced.

  The present invention will be described with reference to the drawings. FIG. 1 shows the results of surface analysis of the surface of an alumina ceramic with an electron beam probe microanalyzer, (a) is a schematic diagram showing the distribution state of Mg in the measurement region, and (b) shows the shape of the aggregation region. FIG. 4 is a schematic diagram showing an agglomerated region in which the area is calculated in terms of a circle and the diameter is calculated and displayed again.

  First, an electron beam probe microanalyzer (EPMA) used in the present invention will be described.

  When an electronic material (sample) is irradiated with an electron beam, various signals such as various X-rays and reflected electrons are generated. The characteristic X-ray generated here is an X-ray having a wavelength unique to the element constituting the substance. By measuring this characteristic X-ray, the constituent elements can be determined, and the existence ratio can be determined from the intensity. EMPA is an application of this principle.

  Specifically, the sample is irradiated with an electron beam, and various signals are excited from the irradiated part. The type and concentration of the element are calculated by selecting X-rays having an arbitrary set wavelength from the excited signal with a spectroscopic crystal and measuring it with a detector.

  For example, a two-dimensional enlarged scan image, that is, an X-ray image is displayed on the CRT based on the X-ray pulse detected by the wavelength dispersion X-ray spectrometer, and the state of the sample surface is recorded. In addition, the electron probe is scanned in the X direction on the sample (corresponding to the horizontal direction on the CRT), and the intensity change of the X-ray generated at that time is defined as a change in the vertical direction of the CRT (amplitude modulation). The waveform, that is, the X-ray line profile is displayed, and the element concentration distribution (on the analysis line) in the line scanned portion is recorded.

In this way, the distribution state of a specific element, that is, the element concentration can be expressed in a map form by representing all analysis regions with an X-ray intensity distribution of a specific wavelength. The probe current (sensitivity) was 1.0 × 10 ⁻⁷ A, the acceleration voltage was 15 kV, and the analysis region was 200 μm × 200 μm.

In the present invention, a JXA-8600 type device manufactured by JEOL Ltd. is used, a 200 μm × 200 μm region of the sample is observed at a measurement magnification of 500 times, and a sintered body is molded at a current value of 3 × 10 ⁻⁷ A. The body was observed at a current value of 1 × 10 ⁻⁷ A.

  When the alumina ceramic containing Mg is subjected to surface analysis by EPMA analysis, the Mg concentration distribution as shown in FIG. 1A is displayed.

According to the present invention, from such a surface analysis result of Mg, an aggregation region 2 in which the Mg concentration in the measurement region 1 is twice or more higher than the surroundings is specified, and the area of the aggregation region 2 is converted into a circle. Aggregation region 2 where diameter is R, Mg concentration in aggregation region 2 is C ₁ , Mg concentration in non-aggregation region 3 adjacent to aggregation region 2 is C ₂ , C ₁ / C ₂ ≧ 2, and R ≧ 5 μm It is important that the number is 5 or less in a measurement area having a measurement area of 0.05 mm ² .

As described above, FIG. 1A showing the Mg distribution on the surface of the alumina ceramic of the present invention shows four agglomeration regions 2 satisfying the above conditions in a measurement region 1 of 0.05 mm ^2. According to the invention, this number is 5 or less and is not limited to 4 in FIG.

  The maximum value of the diameter R of the agglomerated region 2 in terms of a circle is 5 μm or less, particularly 4 μm or less, more preferably 3 μm or less, and more preferably 2 μm or less so as not to cause a large void when used as a sliding member. Is preferred. Thus, even if the aggregation region 2 appears, if the size is small, a smoother surface can be maintained when used as a sliding member.

  Since there are often coarse voids in the Mg agglomerated region 2, reducing the number of agglomerated regions 2 reduces the voids that cause fracture, and as a result, it is possible to prevent a decrease in strength. .

  According to the present invention, the Mg content is 0.5% by mass or less, particularly 0.2% by mass or less, more preferably 0.1% by mass or less in terms of oxide, in order to fully exhibit the characteristics of the alumina ceramic. More preferably, 0.05 mass% is preferable. When the content of Mg, that is, the content of the sintering aid is small, good properties such as mechanical properties, electrical properties, thermal properties, and the like that alumina itself has can be sufficiently expressed. Further, since the Mg compound plays a role as a sintering aid, it is preferably contained in an amount of 0.01% by mass or more, particularly 0.01% by mass or more. When Mg is contained at such a ratio, the sinterability can be improved.

  In addition to Mg, elements such as Ca, Si, Fe, Na, or K and compounds thereof can be included. In particular, the total amount of these elements may be 0.1% by mass or less, particularly 0.05% by mass or less. It is preferable in that abnormal particle growth can be suppressed and void generation can be suppressed.

  Mg may be partly dissolved, or may exist in the crystal grain boundary of alumina as a compound such as spinel, but there is no such compound because it may be a source of destruction. Is most preferred.

  The average crystal grain size of the alumina ceramic is preferably 0.3 to 2 μm, particularly preferably 0.3 to 1.5 μm, and more preferably 0.3 to 1 μm. Alumina crystals are composed of small crystals, and a homogeneous and dense sintered body is formed. Large crystals are crushed by polishing, and the alumina ceramic is damaged by the sized large particles, suppressing abnormal wear resulting in large wear, and a smooth surface. Can be maintained.

  The alumina ceramic of the present invention is a high-purity alumina, uses a uniform and fine particle size, and has a feature that a dense sintered body can be obtained. Therefore, the alumina ceramic is suitable in the field of sliding parts, bearings or mechanical seals. Can be used.

  In the method for producing an alumina ceramic of the present invention, in order to reduce the agglomeration region, a magnesium compound powder is mixed with alumina powder at a high concentration to prepare a first slurry, and then the first slurry is mixed with the first slurry. Alumina powder is added so as to be smaller than the Mg concentration in one slurry, and the magnesium compound powder is uniformly dispersed in the slurry.

  Next, the method for producing an alumina ceramic according to the present invention will be described by taking as an example an example in which magnesium hydroxide is used as an Mg compound that does not generate harmful gas during the sintering process.

First, a high-purity alumina powder having a purity of 99.99%, an average particle size of 0.3 to 0.7 μm, and a BET specific surface area of about 5 to 6 m ² / g is prepared. Using alumina powder with an average particle size in this range, a homogeneous and dense sintered body can be obtained, and a coarse surface can be removed by polishing, resulting in damage to the sintered body and development of abnormal wear. Can be maintained.

Further, magnesium hydroxide powder having a purity of 60% or more and an average particle diameter of 0.5 to 10 μm, particularly 1 to 8 μm, and further 2 to 5 μm is prepared. The specific surface area of Mg _{(OH) 2} is, 10~50m ² / g, especially 15~40m ² / g, more preferably a 20 to 30 m ² / g. By using a powder having such an average particle size and specific surface area, finer and more uniform dispersion can be achieved, and generation of harmful gas can be avoided.

Mg compounds can be used safely because they do not generate harmful gases during the sintering process, as in the case of chlorides, nitrates, sulfates, etc., and damage to the firing furnace is reduced, It is preferable to use Mg (OH) ₂ that can contribute to low cost.

The above raw material powder is prepared in a proportion of 60 to 99% by volume of alumina powder and 1 to 40% by volume of Mg (OH) ₂ , pure water is added, and balls are added and mixed. In order to disperse Mg (OH) ₂ more uniformly, it is particularly preferable that Mg (OH) ₂ is mixed in a proportion of 5 to 35% by volume, more preferably 10 to 30% by volume. By using a high-purity alumina ball of 99% or more, especially 99.9% or more as a ball, mixing of impurities can be suppressed and mixing efficiency can be further increased.

  The mixing method can be performed by a known method such as a rotary mill. Thus, the Mg compound can be effectively mixed by preparing a slurry containing the Mg compound at a high concentration in advance.

  Magnesium compounds easily aggregate, so even if a low concentration magnesium compound of 0.5% by mass or less, particularly 0.2% by mass or less is directly mixed with alumina, for example, for 24 hours, aggregated particles remain, There are coarse aggregated grains. The magnesium compound reacts with alumina during firing to form spinel, causing volume reduction. This volume reduction leads to void formation, which in turn degrades mechanical properties (bending strength, wear resistance).

Next, a high-purity alumina powder is additionally added to the obtained first slurry so as to have a predetermined composition and mixed again to prepare a second slurry. Thus, by mixing in two steps, Mg (OH) ₂ powder, which is a sintering aid, can be uniformly dispersed even with an addition amount of 0.5% by mass or less.

  A molded object is produced using the obtained second slurry. As the molding method, a known method such as a die pressing method, a cold isostatic pressing (CIP) method, a tape molding method such as a doctor blade method, an extrusion method, or an injection molding method can be used.

  Next, the molded body is processed into a predetermined shape as desired, and the molded body is fired. As for the firing conditions, the firing temperature is preferably 1200 to 1700 ° C, particularly preferably 1300 to 1600 ° C.

  Moreover, it is preferable to process the sintered compact obtained by baking at high temperature and high pressure. That is, if high-temperature and high-pressure treatment is performed after firing, densification can be further promoted, large voids can be reduced, and when used as a wear-resistant material, the wear surface can be kept smooth and the wear amount can be further increased. It can be reduced.

  First, a first slurry was prepared. That is, 99.99% of the high-purity alumina powder having the average particle size shown in Table 1 and 60% of the magnesium hydroxide powder having the average particle size and specific surface area S shown in Table 1 are mixed so as to have the primary mixed composition of Table 1. Then, 150% by volume of water was added to the mixed powder, 400% by volume of 99.9% high-purity alumina balls were added, and the mixture was pulverized for 92 hours with a rotary mill to prepare a first slurry.

  Next, the same alumina powder as described above was added so as to have the secondary mixed composition of Table 1, and further mixed for 24 hours to prepare a second slurry.

After the obtained second slurry was dried, it was subjected to a mesh pass using a mesh having a mesh size opening diameter of 74 μm, uniaxially molded at 98 MPa, and fired under the firing conditions shown in Table 1. Then, if desired, HIP treatment was performed for 1 hour in argon gas under the conditions of a pressure of 196 MPa (2000 kg / cm ² ) and a temperature of 1350 ° C.

In addition, Mg dot map analysis was performed on this measurement region with EPMA. At this time, the probe current (sensitivity) of EPMA is 3.0 × 10 ⁻⁷ A.

From the obtained concentration map, the diameter R is calculated by converting the area of each aggregated region into a circle, and C ₁ and C ₂ are measured in each aggregated region and the non-aggregated region adjacent thereto, and C ₁ / C ₂ Was calculated, and the number of aggregated areas satisfying C ₁ / C ₂ ≧ 2 and R ≧ 5 μm was measured. The measurement range was 0.05 mm ² . The results are shown in Table 1.

Sample No. of the present invention. 2 to 8 and 10 to 35 were 5 or less in the measurement region where the number of aggregation regions was 0.05 mm ² .

On the other hand, the amount of Mg compound in the primary mixture composition is as small as 0.5% by volume, and the sample No. No. 1 has a poor dispersion state of the Mg compound, and in the measurement region where the number of aggregation regions is 0.05 mm ² , the dispersion state is bad with 27, and the content of the Mg compound is too small, so the sinterability is poor. There were 55 coarse voids exceeding 5 μm.

Sample No. 1 of the present invention in which the amount of Mg compound in the primary mixed composition is as large as 50% by volume. No. 9 has a dispersion state as bad as 10 in the measurement region where the number of aggregation regions is 0.05 mm ² , and the content of Mg compound is too high and the sinterability is poor, so the number of coarse voids exceeding 5 μm is 22. There were.

Moreover, in the specific abrasion amount implemented based on JIS-T0303, sample No. with many coarse voids. 1 and sample no. 9 exceeded 0.30 × 10 ⁻¹⁰ mm ² / N.

The surface analysis result of the surface of the alumina ceramic with an electron beam probe microanalyzer is shown, (a) is a schematic diagram showing the distribution state of Mg in the measurement region, (b) is the shape of the aggregation region, the area It is a schematic diagram which shows the aggregation area | region which calculated the diameter by circular conversion and redisplayed.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Measurement area | region 2 ... Aggregation area | region 3 ... Non-aggregation area | region C ₁ ... Mg density | concentration C _{2 in} an aggregation area | region ... Mg density | concentration R in a non-aggregation area | region ... Half when converted

Claims (6)

A part of the total amount of alumina powder and the total amount of at least one magnesium compound powder among magnesium hydroxide, magnesium carbonate and magnesium oxide, the alumina powder is 60 to 99% by volume, the magnesium compound powder A step of preparing the first slurry by mixing so that the ratio is 1 to 40% by volume;
Adding the remaining amount of the total amount of the alumina powder to the first slurry to prepare a second slurry;
Producing a molded body from this second slurry;
A biological member obtained by a production method including a step of firing the molded body ,
Biological part material content of magnesium is made of alumina ceramic, characterized in that more than 0.5 wt% in terms of oxide. Biometric member according to claim 1, wherein the magnesium compound powder is a magnesium hydroxide powder. The average particle diameter of the alumina powder, the biological section material according to claim 1 or 2, characterized in that it is 0.3 to 0.7 [mu] m. The average particle size of the magnesium hydroxide powder is 0.5 to 10 [mu] m, and the biological member according to claim 1, a BET specific surface area, characterized in that a 10 to 50 m ² / g . The living body according to any one of claims 1 to 4, wherein a specific wear amount of the alumina ceramic when a wear test is performed according to JIS-T0303 is 0.3 x 10 ^-10 mm ² / N or less. Element. An artificial joint comprising the living body member according to any one of claims 1 to 5 .

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