JP4572286B2 - 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. 1 (a) and 1 (b) schematically show the situation.
(A) shows a state in which spherical metal powder and 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 portion between the voids P and P.
[0016]
In practice, however, especially when the porosity is high, the metal powder and the spacer material powder are ideally not dispersed and mixed, or the layer of the metal material in the portion between the voids. Since the thickness of Ma is extremely thin, as shown in FIG. 1 (b), the same part is cut or detached relatively easily, and 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 manufacturing method of a high-strength porous body as a biomaterial of the present invention and the high-strength porous body have been devised to solve such problems.
Thus, claim 1 relates to a method for producing a high-strength porous metal body as a biomaterial. The metal powder is mixed with an inorganic or organic spacer material powder as a void forming material that is burned off by heating. After forming, 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 higher sintering temperature than this, and the porosity is 70- When producing a high-strength porous metal body as a 90% biomaterial, the spacer material powder has an average diameter in the range of 200 to 2000 μm, and an average value of the ratio of the maximum diameter to the minimum diameter of the powder A columnar or fibrous elongated shaped irregular powder having an aspect ratio of 2 or more is used.
[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, the average particle size of the metal powder is in the range of 10 to 200 μm .
[0021]
請 Motomeko 5 relates strength porous body of metal as biomaterials, the metal powder a porosity formed by sintering 70 to 90% of the metal porous body, the shape of the gap is the average The diameter is in the range of 200 to 800 μm, and the aspect ratio that is the average value of the ratio of the maximum diameter to the minimum diameter of the voids is in the range of 2 or more.
[0022]
[Operation and effect of the invention]
As described above, the manufacturing method of the present invention is to manufacture a biomaterial by the fourth method, that is, the space holder method, and a columnar or fibrous elongated shaped powder is used as the spacer material powder. It is characterized by.
When such a long and narrow shaped irregular shaped powder is used as the spacer material powder, a porous structure is produced with the same porosity as when a conventional spherical spacer powder is used. As shown, the network structure made of the metal material is well connected.
In other words, the metal material existing between the gap P and the gap P is in a well-connected state, and the gap P and the gap P are well blocked by the metal material to form an independent gap. .
[0023]
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.
[0024]
The porous structure shown in FIGS. 1 (a) and 1 (b) has an advantageous effect derived from the porous structure itself as compared with the biomaterial made of a metal material having a dense structure. However, the metal porous body obtained by the production method of the present invention is particularly suitable as a biomaterial since it has few sharp parts and has high strength as described above.
[0025]
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.
In the present invention, it is preferable to use a spacer material powder having an average diameter in the range of 200 to 2000 μm and an aspect ratio of 2 or more. More desirable is an aspect ratio of 3 or more.
However, if the aspect ratio is excessively large, each void becomes relatively large, and when trying to produce a porous body having the same porosity, the number of voids decreases and the network structure becomes coarse. Therefore, it is desirable that the aspect ratio is 10 or less unless a continuous void is actively used.
[0026]
In the present invention, a single titanium powder or an alloy powder can be suitably used as the metal powder.
[0027]
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.
[0028]
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.
[0029]
In the present invention, a metal powder having an average particle size in the range of 10 to 200 μm can be preferably used .
[0030]
請 Motomeko 5 relates to a porous body of metal as biomaterials, 200～800Myuemu shape of the gap is the average diameter, which aspect ratio is in the 2 or more ranges, from the ones metal material The network structure is in a well-connected state, and therefore has high strength, and there are few sharp portions generated by partial separation of the metal material, which is suitable as a biomaterial.
[0031]
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.
[0032]
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.
[0033]
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.
[0034]
【Example】
Next, examples of the present invention will be described in detail below.
After producing Ti powder by gas atomization method or hydrodehydrogenation method, it was classified to 50 μm or less.
To this Ti powder, a columnar spacer material powder made of polyoxymethylene resin having a diameter of 300 μm and a length of 1.5 mm (aspect ratio: 5) is added in an amount of about 5 times at room temperature, and sufficiently stirred and mixed, and then pressed. Molded with a mold.
[0035]
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%.
[0036]
Here, measurement of tensile strength is performed by a method based on JIS Z 2241 in a test piece based on JIS Z 2550.
[0037]
When the obtained porous body 10 was examined, the shape of the voids was almost similar to the added spacer material powder.
In other words, when press-molding a mixed powder composed of a spacer material and Ti powder, the metal powder behaves so as to fill the gaps by the applied pressure. As a result, the spacer material retains a similar shape and is sintered as it is. The result seems to have advanced.
In addition, a porous material was manufactured according to the same procedure using a spacer material having the same diameter as described above and an aspect ratio of 3 (mixing ratio is the same as above), and the tensile strength was measured. (The porosity is 80%).
[0038]
Next, a spacer material powder having a diameter substantially the same as the above and an aspect ratio of 30 was mixed with the Ti powder (the mixing ratio was the same as above), and a porous body was manufactured according to the above procedure. The tensile strength of the porous body was 7 MPa. The porosity was 80%.
[0039]
Thus, when the aspect ratio of the spacer material powder added to and mixed with the Ti powder is increased, the tensile strength is increased. When is increased, it was confirmed that the tensile strength gradually decreases because the size of the test piece is fixed.
[0040]
On the other hand, according to a conventional method, the spherical spacer material powder having a diameter of 300 μm is added to the Ti powder in a volume ratio of 5 times and mixed, and the same treatment as above is performed to produce a porous body. Was 5 MPa. The porosity was 80% as described above.
[0041]
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 and configured in various 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 together with a comparative example.
FIG. 2 is a diagram showing an example of an embodiment of the present invention.

Claims (5)

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% ,
The spacer material powder has a columnar or fibrous elongated shape with an average diameter in the range of 200 to 2000 μm and an aspect ratio that is an average value of the ratio of the maximum diameter to the minimum diameter of the powder in the range of 2 or more. A method for producing a high-strength porous body as a biomaterial, characterized by using a powder.   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 an average particle diameter of the metal powder is in a range of 10 to 200 µm. A porous metal body having a porosity of 70 to 90% formed by sintering metal powder, wherein the void shape has an average diameter in the range of 200 to 800 μm, and the ratio of the maximum diameter to the minimum diameter of the void A metal high-strength porous body as a biomaterial characterized by having an average aspect ratio in a range of 2 or more.

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