KR20140131209A - Porous titanium for biomedical application and manufacturing method thereof - Google Patents

Abstract

There is provided a biomedical medical porous material, wherein the biomedical medical material is titanium and has pores, and a method for producing the same.
According to the present invention, it is possible to provide a porous titanium which can control a desired density and mechanical characteristics and which is harmless to the human body, which can be used instead of the bones of the human body.

Description

TECHNICAL FIELD [0001] The present invention relates to porous biomedical titanium,

TECHNICAL FIELD The present invention relates to porous titanium for biomedical treatment and a method for producing the same.

Titanium has superior nasal, corrosion and biocompatibility than polymers and ceramics used in biomedical materials. It is a medical metal material for dental implants, knee joints, artificial hip joints, and elbow joints that replace the bones of human body. .

Currently, titanium used in biomedical materials is limited to dissolution, casting and forging techniques. However, the biomedical titanium has a modulus of elasticity of about 110 GPa, and when implanted into the affected part of the patient, the surrounding bone of the titanium is degraded due to the difference in elastic modulus between the surrounding human bone having an elastic modulus of 10 to 30 GPa .

Therefore, it is proposed to reduce the difference in elastic modulus between the biomedical material and the human bone by (1) adjusting the ratio of the titanium alloy, (2) by inserting a porous body inside the titanium to make a specific structure, There is a way to reduce the difference in elastic modulus.

The first thing to keep in mind when adjusting the proportions of titanium alloys presented is to use harmless elements. The alloying elements such as Nb, Zr, Ta, Sn, Mo, etc. are confirmed to be safe without inducing toxicity to humans through various cell safety tests. When the alloying elements are added to titanium, the elastic modulus is lowered. The Ti-29Nb-13Ta-4.5Zr combination of beta-titanium alloy has the lowest elastic modulus of about 55 GPa among the biomedical titanium alloys developed so far. However, considering the elastic modulus of the human bone, Five times the difference.

As a second method, there is a method of artificially inserting pores into biomedical titanium to lower the elastic modulus.

Patent Document 1 discloses a powder sintering method using a space holder using a metal powder, a space holder powder, and a binder, and discloses a method of making a porous titanium material by using the method. However, the porous titanium of Patent Document 1 does not reflect characteristics of human bones having different densities between the outside and the inside, and is easily broken when the density of the porous titanium is low.

U.S. Patent No. 7,883,661

One aspect of the present invention is to provide a biomedical porous titanium having sufficient mechanical properties while reflecting the characteristics of human bones having different densities from the outside to the inside, and a method for producing the same.

However, the problems to be solved by the present invention are not limited to the above-mentioned problems, and other problems not mentioned can be clearly understood by those skilled in the art from the following description.

One aspect of the present invention provides porous medical biomedical titanium, wherein the biomedical raw material has a density different from the inside and the outside of the biomedical raw material, and the biomedical raw material is titanium and has pores.

According to another aspect of the present invention, there is provided a method of manufacturing a magnetic recording medium, comprising: preparing a first mixture and a second mixture having different densities by different ratios of titanium powder and space holder powder;

Applying pressure to the first mixture to produce a green compact;

Forming a second mixture layer on the outer periphery of the green compact, applying pressure to the green compact to produce a green compact having different densities between the inside and the outside; And

And dissolving a space holder in the green compact having different densities of the inside and outside, and sintering the green compact. The present invention also provides a method of manufacturing porous titanium for biomedical medical use.

INDUSTRIAL APPLICABILITY According to the present invention, it is possible to provide a porous titanium which is capable of controlling a desired density and mechanical characteristics and is harmless to a human body, which can be used instead of the bones of a human body.

1 is a cross-sectional SEM photograph of porous titanium for biomedical treatment according to an embodiment of the present invention.
2 is a microstructure photograph of porous titanium for biomedical treatment according to an embodiment of the present invention.
3 is a photograph of a mold for producing porous titanium of the present invention.
4 is a schematic diagram of an apparatus for manufacturing porous titanium for biomedical treatment according to an embodiment of the present invention.
FIG. 5 is a graph showing elastic modulus and relative density of porous titanium according to an embodiment of the present invention.
FIG. 6 is a graph showing compression test data measured at different mixing ratios of space holder NaCl according to an embodiment of the present invention.
FIG. 7 is a graph showing compression experiment data measured while varying the mixing ratio of space holder starch according to an embodiment of the present invention.
8 is a graph showing compression test results according to the size and type of the space holder.

Hereinafter, the porous titanium for biomedical treatment of the present invention and the method for producing the same will be described in detail so that those skilled in the art can easily carry out the invention.

Titanium is preferably used as the biomedical material of the present invention, but the present invention is not limited thereto, and a metal powder harmless to the human body may be used.

Nb, Ta, Zr and the like are difficult to make a porous material, ceramics and Ni are heavy, and stainless steel contains Cr and Ni, which is harmful to human body.

The biomedical porous titanium of the present invention is characterized in that the density of the inside and the outside of the material is different and has pores. In other words, similar to the shape of the human bone, the outer density is high, the inner shape is low, or contrary to the shape of the human bone, the outer density is low and the inner density is high. May be provided. In this way, the distribution of density can be adjusted to provide a desired level of density between the outside and the inside, thereby providing biomedical titanium having various density pores.

Biomedical titanium, which has a high external density and a low internal density, improves the mechanical properties and processability by the dense outer surface, while the less dense interior can provide enough room for the cells to grow bone Pores can be present and contribute to lowering the modulus of elasticity due to low density.

When the biomedical material is inserted into the affected part of the human body, the elastic modulus of the biomedical material is higher than the modulus of elasticity of the bone adjacent to the affected part, so that a 'stress shielding phenomenon' occurs. When the surrounding area is subjected to a load due to the movement of the body, most of the load will be limited to the biomaterial. Thus, there is a case where bone around the lesion is degenerated and secondary surgery is inevitable as a result.

Current conventional biomedical materials consist of a combination of external coatings that are inserted around the inside of the load bearing titanium and the lesion to allow organic binding of the body's bone cells. Conventional biomedical medical materials are similar to those of biomedical medical titanium having low density and high internal density, which is one embodiment of the present invention. However, in the case of conventional biomedical materials, stress shielding phenomenon due to high elastic modulus occurs, Re-operation is necessary because of the degeneration of the. However, since the biomedical material of the present invention has a lower elastic modulus than that of conventional biomedical materials, it is advantageous in preventing stress shielding and is superior to the adhesion by coating since it makes the biomedical titanium through the sintering process. It is possible.

As described above, the medical bio-porous titanium having different outer and inner densities according to the present invention is characterized by (1) a dense tissue having almost no pores on the outside and a pore-containing structure on the inside, (2) The inside is dense and the outside is filled with many pores. It has a elastic modulus (30 GPa) close to the elastic modulus (18 GPa) possessed by the bones of the human body, so that the stress shielding phenomenon can be prevented in advance have. In addition, unlike other polymers and ceramics, since they are based on metal materials, mechanical properties such as bones can be realized.

The pore corresponds to the space occupied by the space holder when the space holder mixed with titanium is melted. The size of the pore is 180 to 360 mu m, which is advantageous for compatibility with surrounding bone cells after transplanting the biomedical material into the affected area .

When the average relative density of the bio-medical material is 0.70 to 0.84 as compared to pure Ti, it has a strength of a human bone and a low elastic modulus and is suitable for a human body. In addition, when the elastic modulus of the biomedical material is 33 to 83 GPa, the stress shielding phenomenon can be effectively prevented as compared with the conventional biomedical materials. In addition, the yield strength of the biomedical medical material is preferably 192 to 450 MPa in terms of strength of bone or more.

Hereinafter, a method for producing porous titanium for biomedical treatment of the present invention will be described.

First, a first mixture and a second mixture having different densities are prepared by varying the mixing ratio of the titanium powder and the space holder powder.

It is preferable that the titanium powder has a size of about 45 μm or less because it can sufficiently surround the space holder powder (180 to 360 μm). In addition, the titanium powder has a purity of about 99.9%, and more preferably does not contain remaining Al, Cr, Fe, Ni and unavoidable impurities. Ti is a good reactive material, and if impurities are included, the bio-medical porous titanium finally produced may be contaminated and harmful to the human body.

The powder used as the space holder preferably has a size of 180 to 360 mu m, which is determined to be a sufficient space for the bone cells to grow, but is not limited thereto. In the present invention, a space holder is a material used in combination with a titanium powder. In the case of heat treatment or solution treatment, the titanium powder remains as it is, and only the space holder powder is melted so that pores are formed in the space occupied by the space holder. Of the substance. Therefore, the higher the mixing ratio of the space holder, the more pores are formed in the biomedical material, resulting in a decrease in density. Therefore, the density can be diversified by controlling the mixing ratio of the titanium powder and the space holder.

When space holders are used for biomedical applications, it is common to use harmless substances. As a specific example of the space holder, a material having a low melting point such as magnesium (Mg), aluminum (Al), urea, starch, or the like may be used to melt the material through heat treatment to form pores. At this time, the melting point of the materials may be generally 400 ° C or less, and they can be safely melted through a heat treatment process over a melting point. Or, as an example of the space holder, pores may be formed using a material that reacts with water or an alcohol such as NaCl to melt.

When urea, CO (NH ₂ ) ₂ ) is used as the space holder contained in the first mixture and the second mixture, the content of urea is preferably limited to 0 to 30% by volume. Since the densities of the first mixture and the second mixture are different, when the content of urea of the first mixture is 0 vol%, the content of urea of the second mixture should not be 0 vol%. When the content of the urea is 0 vol% in the porous titanium made of one density which is not different from the inside and the outside, there is no pore corresponding to the size of the urea powder and the environment where the bone cells grow is not formed. It is difficult to make biomedical titanium, and it is difficult to have elastic modulus below bone. Also, when the content of urea exceeds 30% by volume, the elastic modulus of the bone is lower than that of the bone, but it is weaker than the yield strength of the bone.

The shape, size, and distribution of the pores can vary depending on the type of the space holder. That is, urea and starch form round pores, while NaCl form square pores. As shown in FIG. 5, as the type of the space holder is changed, the density and the elastic modulus of the biomedical material do not change greatly. However, as shown in Figs. 6 and 7, the yield strength of the biomedical material may vary greatly depending on the type of the space holder. When the space holder is a starch, it is affected by titanium, which is a matrix existing around the space holder in the sintering process, so that the strength is increased and ductility is lowered, and the pore size is too large It may also be destroyed before the yield strength is reached. That is, the yield strength is influenced by the type, size and distribution of pores

Further, for the sake of human health, it is more preferable that the space holder has a purity of 99% or more and contains substantially no Fe, Al and unavoidable impurities.

It is more preferable to mix the titanium powder and the space holder powder by using a roller, a blend or the like for 6 hours or more.

Subsequently, pressure is applied to the first mixture of the first mixture and the second mixture having different densities to prepare a green compact. The mold for producing the green compact of the mixture has a cylindrical shape as shown in FIG. 3, and a hollow space of a cylindrical bar shape exists inside. For example, the diameter of the cylindrical hollow space may be 8 to 17 mm and the height may be 12 to 15 mm. The first mixture is filled in the mold of the cylindrical bar shape and compressed in a single shaft to produce a green compact to be used as a green compact. A pressure of 120 MPa can be applied at the time of compression. At this time, it is more preferable that one end of the cylinder exists in a wide cylindrical shape so that the force is dispersed when stressed by the pressure device. It is more preferable to compress both sides of the cylinder in order to maintain the density of the green compact uniformly.

When a green compact to be used as an internal compact is manufactured, it is transferred to a mold having a cylindrical bar shape having a larger internal cavity and a second mixture having a different density is filled to form a layer of the second mixture on the periphery of the green compact. Thereafter, the green compact is compressed in one axis to produce a green compact having different internal and external densities. At this time, a small groove may be provided at the lower end of the cylindrical bar so that the green compact to be the inner side can be fitted and fixed to the center of the cylindrical bar. For example, the small groove may have a diameter of 10 mm and a height of 0.5 to 1 mm.

Thereafter, the space holder in the green compact having different internal and external densities is melted and the green compact is sintered.

The method of dissolving the space holder may be heat treatment at a temperature higher than the melting point of the material used as the space holder, or may be dissolved by adding water or alcohol as described above. The green compact may be sintered after the space holder is melted. At this time, sintering may be performed through a high temperature heat treatment, or sintering may be performed in parallel with high temperature heat treatment and pressurization.

For example, the green compact may be heat treated at a pressure of 10 ^-3 torr or less and at a temperature of 1000 ° C for about 12 hours to sinter the titanium powder. It is possible to heat at a temperature higher than or less than that, but the sintering is not easily performed when the temperature is low. When the temperature is high, the overall density of the porous titanium having a different outer and inner densities increases, Density is difficult to obtain. If the heat treatment is performed for more than 12 hours, the economic loss is large, and if the heat treatment is performed for less than 12 hours, it is difficult to obtain the desired sintering property.

FIG. 2 is a cross-sectional photograph of a porous titanium for biomedical treatment according to an example of the present invention finally produced after sintering. In FIG. 2 (a), it can be seen that a relatively large number of pores are formed in the interior, and that the density of the interior is lower than the density of the exterior. Conversely, in the case of FIG. 2 (b), it can be seen that a relatively large number of pores are formed on the outside, and that the density of the outside is lower than the density of the inside.

The proportion of pores formed can be varied by adjusting the amount of space holder to be mixed with the titanium powder.

Hereinafter, the present invention will be described in detail with reference to Examples. However, the following examples are only for illustrating the present invention in more detail and do not limit the scope of the present invention.

( Example  One)

Before describing the cylindrical structure having different densities from the inside to the outside, a cylindrical structure having the same outer and inner densities will be described as follows.

Titanium powder and urea powder are mixed in the rollers at a ratio of 100: 0, 90:10, 80:20, 70:30 for 6 hours or more, on a volume basis basis. At this time, the density of titanium was 4.16 g / cm 3 and the density of urea was 1.32 g / cm 3. A powder mixed in a mold having a diameter of 17 mm shown in Fig. 3 was placed and a green compact having a diameter of 17 mm and a height of 15 mm was produced under the pressure of about 120 MPa upper and lower punches. In order to remove the elements of the green compact, a porous titanium green compact was formed by heat treatment at a temperature of 200 ° C. for 3 hours. The porous titanium green compact was heat-treated at a pressure of 10 ^{-3 to -4} torr at a temperature of 1000 ° C. for 12 hours, The tiatium green compact was sintered.

Then, using the principle of Archimedes, the density thereof was calculated through specific gravity in ethanol, and it is shown in Table 1. At this time, the relative density for 4.516 g / cm < 3 > was calculated. In case of Ti100% -urea0%, the relative density is lower than 1 because the powder does not adhere completely but has micropores.

Kinds Volume ratio Relative density Cylindrical structure with external and internal densities

Ti100% -urea0% 0.84 Ti 90% -urea 10% 0.81 Ti 80% -urea 20% 0.76 Ti 70% -urea 30% 0.70

The cylindrical structure having the same outer and inner densities is shrunk by heat treatment after sintering. Therefore, the compressive yield strength and the elastic modulus were measured by machining a cylindrical specimen having a height of 10 mm and a diameter of 10 mm. The results are shown in Table 2. The compressive yield strength was 0.2% off set.

Kinds Volume ratio Compressive yield strength (MPa) Compression Elastic Modulus (GPa) Cylindrical structure with external and internal densities

Ti100% -urea0% 458 91 Ti 90% -urea 10% 371 73 Ti 80% -urea 20% 302 58 Ti 70% -urea 30% 202 30

From the results shown in Table 2, it can be confirmed that when the content of urea exceeds 30%, it can reach 30 GPa or less close to the elastic modulus of bone.

Based on this, a cylindrical porous body having different densities from the outside to the inside was designed. In this case, the total number of combinations of the densities is 9, and when the outer portion is composed of Ti100% -urea0%, Ti90% -urea10% and Ti80% -urea20%, the inside is Ti90% -urea10%, Ti80% -urea 20%, and Ti 70% -urea 30%.

A green compact having a diameter of 8 mm and a height of 15 mm was manufactured by the upper and lower punch pressures of 120 MPa through the process of FIG. 4 with a mold having a diameter of 8 mm shown in FIG. As shown in Fig. 4, the thus prepared green compact was bonded to grooves having a diameter of 8 mm and a height of 0.5 mm existing in the upper and lower punches having diameters of 17 mm, and then the mixed powder to be fitted into the mold was formed, A cylindrical green compact having a diameter of 17 mm and a height of 17 mm having different densities was manufactured. This was heat treated at 200 ° C for 3 hours to blow off the elements, and then a titanium green compact having different densities of the inside and outside was prepared and then sintered by heat treatment at 1000 ° C for 12 hours.

Table 3 shows the relative densities of the titanium with different densities of the outside and inside. At this time, the relative density for 4.516 g / cm < 3 > was calculated.

Kinds External volume ratio Internal volume ratio Relative density Cylindrical structure with different densities of outside and inside




Ti100% -urea0% Ti 90% -urea 10% 0.83 Ti 80% -urea 20% 0.79 Ti 70% -urea 30% 0.75 Ti 90% -urea 10% Ti100% -urea0% 0.83 Ti 80% -urea 20% 0.77 Ti 70% -urea 30% 0.75 Ti 80% -urea 20% Ti100% -urea0% 0.82 Ti 90% -urea 10% 0.74 Ti 70% -urea 30% 0.72

In Table 3, the relative density is a result of measuring a cylinder having a cylindrical structure having different densities of the inside and the outside, into a cylindrical shape having a diameter of 10 mm and a height of 10 mm. This is because the density of the outside and inside can not be measured in a cylindrical structure having different outer and inner densities, and the result is the result of measuring the overall density after making it into a cylindrical structure.

In the cylindrical structure having the outer and inner densities different from each other, shrinkage occurs due to heat treatment after sintering. Therefore, the compressive yield strength and the elastic modulus were measured by machining with a cylindrical specimen having a diameter of 10 mm and a height of 10 mm. The results are shown in Table 4. The compressive yield strength was 0.2% off set.

Kinds External volume ratio Internal volume ratio Compressive yield strength (MPa) Compression Elastic Modulus (GPa) Cylindrical structure with different densities of outside and inside



Ti100% -urea0% Ti 90% -urea 10% 360 78 Ti 80% -urea 20% 250 66 Ti 70% -urea 30% 192 34 Ti 90% -urea 10% Ti100% -urea0% 450 83 Ti 80% -urea 20% 300 63 Ti 70% -urea 30% 217 34 Ti 80% -urea 20% Ti100% -urea0% 447 80 Ti 90% -urea 10% 308 60 Ti 70% -urea 30% 207 33

As can be seen from Table 4, cylindrical porous titanium having different densities of the inside and outside has a resilience coefficient of 30 GPa similar to bone when the inside is present in a volume ratio of 70% -urea of Ti of 30%, and the compressive yield strength It can be confirmed that it has about 200 MPa.

Fig. 1 is a photograph of a biomedical material made of a cylindrical porous material having an outer portion of Ti 100% - urea of 0% and an inner portion of Ti of 80% - urea of 20%. The structure of the biomedical material is different from that of the naked eye. I will. In addition, it can be confirmed that the sintering is well performed because there is no boundary line or defect even though the inner and outer green compacts are divided before and after sintering.

( Example  2)

On the other hand, when the size of the element is 180 to 360 mu m, the volume ratio of the titanium and the space holder is set to 9: 1, 8: 2, and 10: 1 by using a space holder having an element size of 1 mm or more and a starch of 100 mu m or less. 7: 3 to prepare porous titanium by the method of Example 1 above.

The compressive strength of the porous titanium thus prepared was measured and shown in FIG. Fig. 8 (a) shows a case where the size of the space holder is 180 to 360 m, and excellent strength can be secured in any volume ratio. Fig. 8 (b) shows a case where the size of the space holder is 1 mm or more, (C) shows a case where the space holder is starch, and the size of the produced pores is 100 탆 or less. At this time, it can be confirmed that the compressive strength is very low .

Claims (10)

Wherein the biomedical material has a density different from the inside and the outside of the biomedical material, and the biomedical material is titanium and has pores.
The method according to claim 1,
Wherein the pore size is 180 to 360 mu m.
The method according to claim 1,
Wherein the bio-medical material has an average relative density of 0.72 to 0.83 with respect to pure Ti.
The method according to claim 1,
Wherein the biomedical material has an elastic modulus of 33 to 83 GPa.
The method according to claim 1,
Wherein said biomedical material has a yield strength of 192 to 450 MPa.
Preparing a first mixture and a second mixture having different densities by varying a mixing ratio of the titanium powder and the space holder powder;
Applying pressure to the first mixture to produce a green compact;
Forming a second mixture layer on the outer periphery of the green compact, applying pressure to the green compact to produce a green compact having different densities between the inside and the outside; And
Melting the space holder in the green compact having different internal and external densities and then sintering the green compact
Containing porous titanium.
The method of claim 6,
Wherein the space holder is at least one of magnesium (Mg), aluminum (Al), urea, starch, and NaCl.
The method of claim 6,
Wherein the space holder is heated to a temperature not lower than the melting point of the space holder or dissolved by adding water or ethanol.
The method of claim 6,
Wherein the space holder has a size of 180 to 360 mu m.
The method of claim 6,
Wherein the mixing ratio of the titanium powder to the space holder powder is in a volume fraction of 100: 70: 0 to 30: Titanium: Space Holder.

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