JP4572287B2 - Method for producing high strength porous body and high strength porous body - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method for producing a high-strength porous body suitable for use in producing a high-strength porous body of metal as a biomaterial, particularly a porous body having a high porosity.
[0002]
[Prior art]
Conventionally, gold, silver, palladium, nickel chrome alloy, etc. have been used as biomaterials, for example, as dental materials. Recently, titanium materials (titanium or alloys thereof) are also excellent in corrosion resistance and are familiar with living organisms. It has been attracting attention as an artificial bone material such as an artificial hip joint and an artificial knee joint, or as an implant dental material such as an artificial tooth root and an artificial tooth base and other biological materials.
[0003]
This kind of biomaterial is required to have characteristics such as being well adapted to the living body, non-irritating or toxic, not corroding or collapsing, and not being damaged even if a little force is applied. In the case of materials, these required characteristics can be relatively satisfied.
[0004]
By the way, when titanium materials or other metal materials are used as biomaterials as they are, the elastic modulus of these metal materials is orders of magnitude higher than that of artificial bones. A large stress is generated at the interface with the bone or the like, and based on this, there is a possibility that separation or cracking may occur between the biological material such as artificial bone and the biological bone.
[0005]
Therefore, it is conceivable to use this kind of biomaterial as a porous body.
When the biomaterial is configured as a porous body as described above, for example, when this is used as an artificial bone, the living bone tissue enters the void of the porous body, and the biomaterial (artificial bone) and the living bone are It is possible to form a bone tissue that is integrated and very close to the original living bone.
Moreover, by using such a porous material as the biomaterial, it is possible to reduce the weight significantly while using a metal material.
[0006]
By the way, in fields other than biomaterials, the following methods are conventionally known as a method for producing a metal porous body.
The first method is called a casting method. The mold is cast by pouring gypsum into a void of a porous polymer material such as foamed polyurethane, and then the polymer material is burned off by heating and the mold is fired at the same time. In this method, the molten metal is injected into the void of the mold and solidified, and then the mold is crushed and removed.
[0007]
The second method is called a plating method, in which voids in an assembly of fine particles made of resin, etc. are filled with metal by a method such as electroless plating, for example, nickel plating, and then the fine particles are burned off by heating. -What is to be removed, void formation, that is, a porous structure can be obtained by burning off the fine particles.
[0008]
The third method is called a molten metal foaming method, in which a foamed material is mixed in molten metal, and the molten metal is solidified in a state containing a large amount of gas generated by foaming of the foamed material to make it porous. Is.
[0009]
The fourth method is called the space holder method, in which metal powder and spacer material powder that is burned off by heating are mixed and formed into a predetermined shape, and then the spacer material is burned off by heating, and the remaining metal powder is Sintering is performed at a sintering temperature to obtain a porous structure.
[0010]
[Problems to be solved by the invention]
However, in the case of the first method, that is, the method called casting, the mold material such as gypsum is clogged in the void of the metal solidified body after the molten metal is injected and solidified. Although it is necessary to crush and remove the material, this process is difficult, and the mold material remaining in the voids of the porous metal body cannot be easily removed. The actual situation is that only a plate-like material can be produced.
[0011]
On the other hand, in the second method, that is, a method called a plating method, the metal porous body that can be produced is limited to nickel or the like, and the productivity is low so that only the conventional plate-like material can be produced as in the first method. Is the actual situation.
[0012]
Further, in the third method, that is, a method called a molten metal foaming method, a time lag occurs between foaming and solidification, so that it is difficult to produce a uniform porous body, and the high porosity portion is biased toward the solidification start portion. At the end, there is a problem that the process control is extremely difficult, for example, the porosity is remarkably lowered.
[0013]
On the other hand, in the fourth method, that is, the method called the space holder method, both the metal powder and the spacer material powder are conventionally spherical powders, but the spacer material powder is not uniformly dispersed due to the characteristics of the powder mixing. In particular, when the porosity is large, the metal material that should block the gap is likely to be separated and the gaps are connected to each other, and accordingly, the variation in material strength is remarkably increased, and the overall strength is also increased. This creates a problem of lowering.
[0014]
In addition, many sharp points are generated by the separation of the metal material between the gaps. Therefore, when such a porous structure is used as a biomaterial, the sharp parts that occur everywhere are formed. The inconvenience of becoming a stimulation base for a living body arises.
[0015]
FIGS. 3C and 3D schematically show the situation.
(C) shows a state in which the spherical metal powder and the spacer material powder are ideally mixed. In this case, the metal material has a good network structure. It is in a state of being well blocked by the material M, and therefore the metal material M is also well connected in the part between the voids P and P.
[0016]
However, in practice, particularly when the porosity is increased, the metal powder and the spacer material powder are not ideally dispersed and mixed as described above, or the metal material in the portion between the voids is not mixed. Since the thickness of the layer is extremely thin, as shown in FIG. 3 (d), the same part is cut or detached relatively easily, and as a result, many sharp parts are generated.
As a result, the pointed portion becomes a stimulation base for the living body, and this phenomenon also causes a large variation in material strength and a decrease in the overall strength.
[0017]
[Means for Solving the Problems]
The high-strength porous body as a biomaterial according to the present invention and the production method thereof have been devised to solve such problems.
Thus, the first aspect relates to a method for producing a high-strength porous body as a biomaterial, in which a metal powder and an inorganic or organic spacer material powder as a void forming material that is burned down by heating are mixed. After the press molding and then heating to the burning temperature of the spacer material powder to burn off the spacer material, the metal powder is sintered by sintering at a sintering temperature higher than this, and the porosity is 70 When manufacturing a high-strength porous body of metal as a biomaterial of ˜90%, the metal powder is a spherical metal powder that is oriented between the voids to reinforce the metal layer between the voids It uses the thing which added the fiber.
[0018]
According to a second aspect of the present invention, in the first aspect, the spacer material powder is mainly composed of any one of ammonium hydrogen carbonate, urea, polyoxymethylene resin, urea resin, expanded polystyrene resin, and expanded polyurethane resin. It is characterized by.
[0019]
According to a third aspect of the present invention, in any one of the first and second aspects, a volume mixing ratio of the metal powder and the spacer material powder at room temperature is in a range of 1: 1 to 1:10.
[0020]
According to a fourth aspect of the present invention, in any one of the first to third aspects, an average particle size of the spherical metal powder is in a range of 10 to 200 μm.
[0021]
According to a fifth aspect of the present invention, in any one of the first to fourth aspects, the average diameter of the metal fibers is in the range of 50 to 500 μm.
[0022]
According to a sixth aspect of the present invention, in any one of the first to fifth aspects, the ratio of the average length to the average diameter of the metal fibers is in a range of 4 or more.
[0023]
According to a seventh aspect of the present invention, in any one of the first to sixth aspects, a volume ratio of the spherical metal powder and the metal fiber at a normal temperature is in a range of 3: 1 to 10: 1.
[0024]
An eighth aspect is characterized in that in any one of the first to seventh aspects, the spacer material powder is spherical and has an average particle diameter in the range of 200 to 2000 μm.
[0025]
A ninth aspect of the present invention is characterized in that, in any one of the first to seventh aspects, a columnar or fibrous elongated shaped irregular powder is used as the spacer material powder.
[0026]
According to a tenth aspect of the present invention, in the ninth aspect, the spacer material powder is in an average diameter range of 200 to 2000 μm, and an aspect ratio that is an average value of a ratio of a maximum diameter to a minimum diameter of the powder is in a range of 2 or more. It is characterized by being.
[0027]
Claim 11 relates to a high-strength porous body as a biomaterial, which is made of a sintered metal powder and has a porosity of 70 to 90%. And it has the sintered structure containing the metal fiber which has an average diameter in the range of 50-500 micrometers and the ratio of the average length with respect to an average diameter in the range of 4 or more.
[0028]
According to a twelfth aspect of the present invention, in the eleventh aspect, the shape of the void is in the range of 200 to 800 μm in average diameter, and the aspect ratio that is the average value of the ratio of the maximum diameter to the minimum diameter of the void is in the range of 2 or more. It is characterized by being.
[0029]
[Operation and effect of the invention]
As described above, the manufacturing method of the present invention is a method for manufacturing a biomaterial by the above-described fourth method, that is, the space holder method, and using a metal powder in which metal fibers are added to a spherical metal powder. It is characterized by.
When a metal powder added with such metal fibers is used, a porous body is produced with the same porosity as when a conventional spherical metal powder is used alone. As shown in the figure, the network structure made of the metal material is well connected.
That is, the metal fiber F is oriented in a portion between the gap P and the gap P, and the spherical metal powder is sintered together with the metal fiber F around the metal fiber F, and a high-strength joint is formed there. Form.
For this reason, the space | gap P and the space | gap P are interrupted | blocked favorably, and the state which the network structure | tissue which consists of metal materials was connected seamlessly appears.
[0030]
As a result, the frequency of occurrence of pointed parts caused by the separation of the metal material at the part between the gaps is remarkably reduced. Therefore, when this is used as a biomaterial, the pointed part causes the living body to be Inconveniences such as irritation can be avoided.
Furthermore, since the metal material is rarely partly separated, the strength variation is small, and the strength of the porous structure itself is high.
[0031]
The porous structure shown in FIGS. 3 (c) and 3 (d) has an advantageous effect derived from the porous structure itself as compared with a biomaterial made of a metal material having a dense structure. In particular, the porous metal body obtained by the production method of the present invention is particularly suitable as a biomaterial because it has few sharp parts and high strength as described above.
[0032]
In the case of a porous body having a porosity of less than 70%, it is relatively easy to connect the network structure even when a spherical powder is used as the spacer material powder as in the prior art.
Therefore, the present invention is particularly effective when applied to the production of a porous body having a porosity of 70% or more, more desirably a porous body having a porosity of 80% or more. However, when the porosity exceeds 90%, it becomes difficult to produce a porous body satisfactorily. Therefore, the production method of the present invention can be suitably applied to a porous body having a porosity of 90% or less.
[0033]
In the present invention, a single titanium powder or an alloy powder can be suitably used as the metal powder.
[0034]
In addition, as the spacer material powder, a powder mainly composed of any of ammonium hydrogen carbonate, urea, polyoxymethylene resin, urea resin, foamed polystyrene resin, and foamed polyurethane resin can be suitably used.
[0035]
Moreover, the mixing ratio of the metal powder and the spacer material powder at normal temperature can be in the range of 1: 1 to 1:10 in terms of volume mixing ratio.
If the mixing ratio is smaller than 1: 1, that is, if the mixing ratio of the spacer material powder is small, the porosity cannot be increased. Conversely, if the mixing ratio of the spacer material powder is larger than 1:10, the void ratio is increased. It becomes difficult to manufacture a porous structure satisfactorily because the amount of is too large.
[0036]
In the present invention, a spherical metal powder having an average particle diameter in the range of 10 to 200 μm can be preferably used.
In the present invention, the metal fibers having an average diameter in the range of 50 to 500 μm can be used.
[0037]
As the metal fiber, one having a ratio of the average length to the average diameter of 4 or more can be suitably used (Claim 6).
As described above, by using a metal fiber having an average diameter larger than the average particle diameter of the metal powder having a spherical diameter or having a length as described above, a small spherical metal around the metal fiber. By sintering and integrating the powder together, it is possible to effectively increase the strength of the portion where the metal fibers were present.
[0038]
If the metal fiber is too long, it is difficult to exhibit the bridge effect as described above. Therefore, in this sense, the length of the metal fiber is preferably not more than four times the maximum circumference of the spacer material powder.
This metal fiber can set the mixing ratio with respect to the said spherical metal powder to the range of 3 to 1 to 10 to 1 by volume ratio (Claim 7).
[0039]
When the volume ratio of the metal fibers is larger than 3 to 1, the amount of the relatively spherical metal powder is reduced, and it becomes difficult to disperse the metal material between the spacer material powders without a good gap.
On the other hand, if the ratio of metal fibers is less than 10: 1, the original effect of adding metal fibers cannot be sufficiently obtained.
[0040]
In the present invention, a spherical material having an average particle size in the range of 200 to 2000 μm can be suitably used as the spacer material powder.
[0041]
On the other hand, according to the ninth aspect of the present invention, a columnar or fibrous elongated shaped irregular shaped powder is used as the spacer material powder.
For example, when a spherical powder is used alone as a metal powder, when such an elongated shaped powder is used as a spacer material powder, a porous structure with the same porosity as when a conventional spherical spacer powder is used. When the body is manufactured, as shown in the schematic diagram of FIG. 1B, the network structure made of the metal material is well connected.
That is, the metal material existing between the gap P and the gap P is well connected, and the gap P and the gap P are well blocked by the metal material to form an independent gap.
[0042]
In addition, when a metal powder containing metal fibers is used in accordance with the present invention, the porous structure is strengthened and the sharp portion is added by taking into account the above-described metal fiber linking effect and reinforcing effect. Occurrence is also suppressed, and for example, a more suitable biomaterial can be obtained.
[0043]
Here, in the case where an elongated shaped powder is used as the spacer material powder, the spacer material powder has an average diameter in the range of 200 to 2000 μm, and an aspect ratio which is an average value of the ratio of the maximum diameter to the minimum diameter of the powder. Is preferably in the range of 2 or more (claim 10).
[0044]
Particularly desirable is an aspect ratio of 3 or more.
However, when the aspect ratio is excessively large, each void becomes relatively large, and the number of voids decreases when an attempt is made to produce a porous body having the same porosity.
Therefore, it is desirable that the aspect ratio is 10 or less unless a continuous void is actively used.
[0045]
Claims 11 and 12 relate to a porous metal body having a porosity of 70 to 90% as a biomaterial, which has a sintered structure containing metal fibers, or further has a void shape. It has an average diameter of 200 to 800 μm and an aspect ratio of 2 or more, and this is in a state where the network structure made of the metal material is well connected, and therefore has high strength and the metal material is partially detached. There are also few sharp parts which generate | occur | produce by this, and it is suitable as a biomaterial.
[0046]
Embodiment
FIG. 2 shows an example of an embodiment of the present invention.
Here, the raw metal powder and the spacer material powder are stirred and mixed by the stirring and mixing device 12, and the obtained mixture is then press-molded into a predetermined shape by the press molding device 14.
The molded body obtained by this press molding is set in the spacer material removing device 16, and the molded body is heated by the same device to burn off the spacer material.
[0047]
In this example, the spacer material removing device 16 has an evacuation port 18, and the molded material is heated by the heating device 20 while evacuating from the evacuation port 18 to burn out the spacer material.
In the figure, 10a represents an intermediate product from which the spacer material has been removed.
[0048]
Next, the intermediate product 10a from which the spacer material has been removed is set in the sintering device 22, where it is again sintered at a sintering temperature higher than the temperature rising heating in the spacer material removing device.
In addition, the sintering apparatus 22 shown in the figure also has a vacuum exhaust port 18, and the intermediate product 10a is heated by the heating apparatus 20 while being evacuated therefrom, and is sintered.
Here, the porous structure 10 is obtained in which the space after the removal of the spacer material remains as a void.
[0049]
【Example】
Next, examples of the present invention will be described in detail below.
<Example 1>
A spherical Ti powder was prepared by gas atomization method or hydrodehydrogenation method, and then classified to 50 μm or less.
This spherical Ti powder has a diameter of 100 μm, which is 1/5 of the volume of the Ti powder, and a diameter of 300 μm, which is a volume of 5 times the volume of the Ti fiber having a length of 2 mm and the Ti powder material containing the Ti fiber. The spherical spacer material powder made of polyoxymethylene resin was sufficiently mixed at room temperature and molded with a press die.
[0050]
Thereafter, the temperature was raised to 300 ° C. in a vacuum furnace over 5 hours. In this process, the spacer material was burned out, and then heated to 1200 ° C. to perform a sintering process for 2 hours.
The tensile strength of the obtained porous body was measured and found to be 10 MPa. The porosity was 80%.
Here, measurement of tensile strength is performed by a method based on JIS Z 2241 in a test piece based on JIS Z 2550.
[0051]
<Example 2>
A spherical Ti powder was prepared by gas atomization method or hydrodehydrogenation method, and then classified to 50 μm or less.
This spherical Ti powder has a diameter of 100 μm with a volume ratio of 1/5, a 2 mm long Ti fiber, and a diameter of 300 μm, a length of 5 times the volume of the Ti powder material containing the Ti fiber. A columnar spacer material powder made of polyoxymethylene resin of 1.5 mm (aspect ratio 5) was sufficiently mixed at room temperature and molded with a press die.
[0052]
Thereafter, the temperature was raised to 300 ° C. in a vacuum furnace over 5 hours. In this process, the spacer material was burned off, and then further heated to 1200 ° C. to perform a sintering process for 2 hours.
The tensile strength of the obtained porous body was measured and found to be 12 MPa. The porosity was 80%.
[0053]
On the other hand, according to the conventional method, the spherical spacer material powder having a diameter of 300 μm is added to the spherical Ti powder in a volume ratio of 5 times and mixed, and the same treatment as above is performed to produce a porous body. When the strength was measured, it was 5 MPa. The porosity was 80% as described above.
[0054]
Thus, according to the present invention, it is possible to obtain a metal porous body having higher strength than the conventional method.
In addition, the porous body obtained by the Example of this invention has a sintered structure containing the added metal fiber, and the shape of the void is substantially similar to the added spacer material powder, and the network structure There were few sharp parts due to cutting and detachment.
[0055]
That is, when press-molding a mixed powder composed of a spacer material and Ti powder, the metal powder behaves so as to fill in the gaps by the applied pressure. As a result, the spacer material maintains a similar shape, and the metal fibers Sintering seems to have progressed as it is.
[0056]
Although the embodiment of the present invention has been described in detail above, this is merely an example, and the present invention can be implemented in variously modified forms without departing from the gist of the present invention.
[Brief description of the drawings]
FIG. 1 is a diagram schematically showing the structure of a porous body obtained by the method of the present invention.
FIG. 2 is a diagram showing an example of an embodiment of the present invention.
FIG. 3 is a diagram schematically showing the structure of a porous body obtained by a conventional method.

Claims (12)

After mixing the metal powder and the inorganic or organic spacer material powder as a void forming material to be burned down by heating, press forming, and then heating to the burning temperature of the spacer material powder to burn off the spacer material. When the metal powder is sintered by sintering at a higher sintering temperature to produce a high-strength porous body of metal as a biomaterial having a porosity of 70 to 90% ,
A high-strength porous material as a biomaterial, characterized in that a spherical metal powder is added as the metal powder to which metal fibers that are oriented between the voids and reinforce the metal layer between the voids are added. Body manufacturing method.   2. The biomaterial according to claim 1, wherein the spacer material powder is mainly composed of any of ammonium hydrogen carbonate, urea, polyoxymethylene resin, urea resin, expanded polystyrene resin, and expanded polyurethane resin. As a method for producing a high-strength porous body.   The high-strength porous material as a biomaterial according to any one of claims 1 and 2, wherein a volume mixing ratio of the metal powder and the spacer material powder at room temperature is in a range of 1: 1 to 1:10. Body manufacturing method.   The method for producing a high-strength porous body as a biomaterial according to any one of claims 1 to 3, wherein the spherical metal powder has an average particle size in the range of 10 to 200 µm.   The method for producing a high-strength porous body as a biomaterial according to any one of claims 1 to 4, wherein an average diameter of the metal fibers is in a range of 50 to 500 µm.   The method for producing a high-strength porous body as a biomaterial according to any one of claims 1 to 5, wherein a ratio of an average length to an average diameter of the metal fibers is in a range of 4 or more.   The high-strength porous material as a biomaterial according to any one of claims 1 to 6, wherein a volume ratio of the spherical metal powder and the metal fiber at room temperature is in the range of 3: 1 to 10: 1. Body manufacturing method.   The method for producing a high-strength porous body as a biomaterial according to any one of claims 1 to 7, wherein the spacer material powder is spherical and has an average particle diameter in the range of 200 to 2000 µm.   The method for producing a high-strength porous body as a biomaterial according to any one of claims 1 to 7, wherein a columnar or fibrous elongated shaped irregular powder is used as the spacer material powder.   10. The living body according to claim 9, wherein the spacer material powder is in an average diameter range of 200 to 2000 μm, and an aspect ratio that is an average value of a ratio of a maximum diameter to a minimum diameter of the powder is in a range of 2 or more. For producing a high-strength porous body as a material for use. A porous metal body having a porosity of 70 to 90% obtained by sintering metal powder, wherein the average diameter is in the range of 50 to 500 μm, and the ratio of the average length to the average diameter is in the range of 4 or more. A high-strength porous body as a biomaterial characterized by having a sintered structure containing a certain metal fiber.   12. The living body according to claim 11, wherein the shape of the void is in the range of 200 to 800 μm in average diameter, and the aspect ratio that is the average value of the ratio of the maximum diameter to the minimum diameter of the void is in the range of 2 or more. High-strength porous material as a material for use.

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