WO2012124661A1 - Titanium-magnesium material having high strength and low elasticity - Google Patents

Abstract

Provided is a titanium biomaterial which has higher strength than human bones and a low elastic modulus similar to human bones, and which is effective as a bone substitute material or a bone reinforcing material. A Ti-Mg biomaterial in which Mg is evenly dispersed within Ti, and which is obtained by sintering a mixture obtained by subjecting titanium powder and magnesium powder to mechanical alloying.

Description

Titanium-magnesium material with high strength and low elasticity

The present invention relates to a titanium-magnesium biomaterial having high strength, low elasticity, and excellent suitability as a bone substitute material.

In Japan, which has reached a super-aging society, research and development of biomaterials are actively conducted with the aim of maintaining and improving the quality of life (life). Titanium alloys are biomaterials, high specific strength, high corrosion resistance, and environmental cleanliness, and thus are the most frequently applied to living organisms among metal biomaterials. However, when embedded in the human bone, the difference in Young's modulus between the human bone (20 to 40 GPa) and the titanium alloy (100 GPa) is large. It is difficult to say that it performs a sufficient function as a biomaterial.

Against this background, research has also been conducted on lowering the modulus of elasticity so that the modulus of elasticity approximates that of human bones by elements added to titanium alloys and heat treatment. However, domestic and overseas metal biomaterial manufacturing processes are being researched and developed based on conventional melting and casting methods, which dramatically improve the mechanical properties and biocompatibility of titanium biomaterials. It is almost impossible to do so, and only minor characteristics are improved (Patent Documents 1 and 2).

On the other hand, the elastic modulus of magnesium is about 45 GPa, which is closer to the elastic modulus of human bone. In addition, pure magnesium has been attracting attention as a bioabsorbable material for medical use in recent years because it is highly safe even when decomposed in the body. However, when pure magnesium or a magnesium alloy is used as an osteosynthesis material, the decomposition rate in the body is extremely fast, so that it decomposes in 1/3 to 1/4 of the period required for fracture treatment. Therefore, magnesium and magnesium alloys are not suitable for bone-bonding materials.

JP-A-5-49656 JP 2004-277873 A

An object of the present invention is to provide a titanium-based biomaterial that has a higher elasticity than a human bone and has a low elastic modulus close to that of a human bone and is useful as a bone substitute material or a bone reinforcing material.

Therefore, the present inventor has made various studies in order to reduce the elastic modulus of the titanium-based material. Since the melting point of titanium is 1668 ° C., while the boiling point of magnesium is 1090 ° C., it is theoretically impossible for titanium and magnesium to form an alloy by the melt casting method. Therefore, further investigation revealed that, surprisingly, if a mixture obtained by mechanically alloying titanium and magnesium powder was sintered, magnesium was uniformly dispersed in the titanium and had high strength. The present inventors have found that a biocompatible Ti—Mg material having a reduced elastic modulus can be obtained.

That is, the present invention provides a Ti—Mg biomaterial in which Mg is uniformly dispersed in Ti obtained by sintering a mixture obtained by mechanically alloying titanium and magnesium powder. is there.
The present invention also provides a method for producing a Ti—Mg biomaterial in which Mg is uniformly dispersed in Ti, wherein a mixture obtained by mechanically alloying titanium and magnesium powder is sintered. It is to provide.

The Ti—Mg biomaterial of the present invention is a molded body in which magnesium is uniformly dispersed in titanium. Therefore, the Ti—Mg biomaterial has a high strength and a lower elastic modulus than titanium, and the elasticity of human bones. Since it is close to the rate, it is useful as a bone substitute material, bone reinforcing material, artificial joint, orthodontic wire, implant material and the like. In addition, Mg uniformly dispersed in the biomaterial of the present invention not only contributes to lowering the elastic modulus, but also gradually decomposes in the body, thereby increasing the surface area of Ti, and cortical bone in the body. It is thought that the bond becomes stronger.

The SEM image of the powder before and behind mechanical alloying is shown. (A) pure titanium before mechanical alloying, (b) pure magnesium before mechanical alloying, (c) mechanical alloying 4 hours Ti-20Mg, (d) mechanical alloying 8 hours Ti-30Mg. The X-ray-diffraction result of the powder after 4 hours mechanical alloying is shown. From the top, Ti-30Mg, Ti-20Mg, Ti-10Mg, Pure Ti. It is a figure which shows the relationship between the mechanical alloying time with respect to magnesium addition amount, and the hardness of each powder. The X-ray-diffraction result of the sintered compact obtained from the Ti-10Mg mechanical alloying 4 hour powder is shown. From above, sintering temperature is 873K, 773K, 673K. The hardness of the sintered body [Ti—xMg (x = 0, 10, 20, 30, 40, 50 mass%)] produced with different mechanical alloying times is shown.

The Ti—Mg biomaterial of the present invention can be obtained by sintering a mixture obtained by mechanically alloying titanium and magnesium powder.

Titanium as a raw material may be metal titanium, but it is preferable in terms of biocompatibility to use titanium having a purity of 98% or more, particularly titanium having a purity of 99% or more. Further, the particle diameter of titanium to be used is preferably 100 μm or less, and more preferably 50 μm or less from the viewpoint of obtaining a desired material by mechanical alloying and sintering.
On the other hand, magnesium may be metallic magnesium, but it is preferable in terms of biocompatibility to use magnesium having a purity of 98% or more, particularly magnesium having a purity of 99% or more. Further, the particle diameter of magnesium used is preferably 100 μm or less, and more preferably 50 μm or less, from the viewpoint of obtaining a desired material by mechanical alloying and sintering.

The mixing ratio of titanium and magnesium may be changed according to the target elastic modulus, and the mixing mass of magnesium with respect to 100 parts by mass of titanium is preferably 20 to 75 parts by mass, more preferably 25 to 60 parts by mass, Further, 30 to 60 parts by mass is particularly preferable. The elastic modulus of the obtained biomaterial can be controlled by the mixing mass of magnesium, and the elastic modulus decreases as the mixing amount of magnesium increases. However, an excessively large amount of magnesium is not preferable from the viewpoint of degradability in living organisms.

The mechanical alloying treatment of the mixture is not particularly limited as long as it is a method of mixing while imparting mechanical energy, and examples thereof include a ball mill, a turbo mill, a mechano-fusion, a disk mill, and the like. In particular, a vibration type ball mill and a planetary ball mill are preferable.

The mechanical alloying conditions may be any conditions in which titanium and magnesium are uniformly dispersed, but it is preferable to add an alloying aid. As the alloying aid, an organic compound that disappears by sintering, for example, an organic wax, a fatty acid, or the like is used. Of these, hydrocarbons and C ₆ -C ₂₄ fatty acids are preferred, and stearic acid is more preferred. The amount of alloying aid used is preferably 0.5 to 5 parts by mass with respect to 100 parts by mass of the total amount of titanium and magnesium. When a ball mill is employed, steel and ceramics are used as the ball, but steel is preferred. The amount used is preferably about 100 to 5000 parts by mass with respect to 100 parts by mass of the total amount of titanium and magnesium. The rotation speed is preferably 200 to 800 rpm, and the treatment time is preferably 1 hour to 50 hours. The atmosphere is preferably an inert gas atmosphere such as a nitrogen gas or argon gas atmosphere.

The obtained mechanical alloying mixture is sintered. Examples of the sintering means include pressureless sintering, hot pressing, hot isostatic pressing, high frequency induction heating, and discharge plasma sintering (SPS), with discharge plasma sintering being particularly preferred. As a spark plasma sintering method, a graphite die is installed in a discharge plasma apparatus, and a direct current obtained by applying a pulse direct current or a short wave to a graphite die in a vacuum or an inert gas (nitrogen, argon, etc.) atmosphere, or First, a pulse direct current is applied, and then a direct current with a short wave added is applied. As the discharge plasma conditions, the raw material is preferably held at 700 to 1200 ° C. and a pressure of 20 to 80 MPa for 60 to 600 seconds.
Moreover, the shape of the biomaterial obtained can be adjusted with the apparatus used for sintering.

The Ti—Mg material obtained by mechanical alloying and sintering described above exhibits uniform properties as a whole because Mg is uniformly dispersed in Ti. There is also a trace amount of TiC.

The Ti—Mg biomaterial of the present invention is high in strength and has a lower elastic modulus than that of pure titanium, and is close to the elastic modulus of human bone. Moreover, it is formed of Ti and Mg and has good biocompatibility. Therefore, the Ti—Mg biomaterial of the present invention is useful as a bone substitute material, a bone reinforcing material, an artificial joint, a correction wire, an implant material, and the like.

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

Example 1
(1) Method The purity of the used pure titanium powder is 99.5%, and the particle diameter is 44 μm or less (rare metallic). On the other hand, the pure magnesium powder used had a purity of 99.8% and a particle size of 276 μm or less.
Table 1 shows the composition and material symbols. Weighed using a precision balance so that the total amount of each composition was 10 g. Further, stearic acid was used as an alloying aid (PCA), and the amount added was constant 0.25 g. These powders and 70 g of tool steel balls were charged in a tool steel container in an argon gas atmosphere. A vibration type ball mill was used for the mechanical alloying (MA) treatment, and the treatment time was set to two conditions of 4 hours and 8 hours.

The prepared MA powder was evaluated by X-ray diffraction, micro Vickers hardness test, and scanning electron microscope observation.
A spark plasma sintering (SPS) apparatus was used for the sintering of the MA powder. Using a φ20 graphite die, the temperature was increased to 873 K at a temperature increase rate of 1.67 K / s, and then the mold was held at a pressure of 49 MPa for 0.18 ks.
The produced SPS material was evaluated by X-ray diffraction, Vickers hardness test, and SEM observation.

(2) Results (a) The SEM image of the powder obtained by changing the addition amount of pure magnesium powder with respect to pure titanium and treating for MA 4 hours or 8 hours is shown in FIG. As shown in FIG. 1, it can be seen that a fine powder in which magnesium was uniformly dispersed in titanium was obtained by the MA treatment.

(B) FIG. 2 shows the X-ray diffraction results of the powder obtained by keeping the MA treatment constant for 4 hours and changing the magnesium addition amount. As can be seen from the results of FIG. 2, magnesium is uniformly dispersed in titanium (α-Ti). A trace amount of TiH ₂ was generated.
Moreover, the result of having measured the hardness of the powder is shown in FIG. As shown in FIG. 3, it can be seen that the Vickers hardness decreases as the amount of magnesium added is increased.

(C) The X-ray diffraction result of the SPS material obtained by plasma sintering after MA treatment is shown in FIG. As can be seen from FIG. 4, the obtained SPS material is a sintered body in which Mg is uniformly dispersed in titanium (α-Ti). Small amounts of TiH ₂ , TiC and MgO are present.
The measurement result of the Vickers hardness of the obtained SPS material is shown in FIG. FIG. 5 shows that the obtained sintered body has lower Vickers hardness as the amount of magnesium added increases. This Vickers hardness is lower than Ti but higher than Mg, and is close to a human bone. Note that there is a proportional relationship between Vickers hardness, strength, and elastic modulus, and a decrease in Vickers hardness means that these characteristics also decrease. In particular, it is also known that about three times the Vickers hardness is equal to the strength (MPa). The strength of the sintered body is sufficient as a bone material.

Claims (6)

1. Ti-Mg biomaterial in which Mg is uniformly dispersed in Ti, obtained by sintering a mixture obtained by mechanically alloying titanium and magnesium powder.
2. The Ti-Mg biomaterial according to claim 1, wherein the mixed mass of magnesium is 20 to 75 parts by mass with respect to 100 parts by mass of titanium.
3. 3. The Ti—Mg biomaterial according to claim 1, wherein the mechanical alloying process is a ball mill process.
4. The Ti-Mg biomaterial according to any one of claims 1 to 3, wherein the sintering is spark plasma sintering.
5. The Ti-Mg biomaterial according to any one of claims 1 to 4, which is a bone substitute material or a bone reinforcing material.
6. A method for producing a Ti—Mg biomaterial in which Mg is uniformly dispersed in Ti, wherein a mixture obtained by mechanically alloying titanium and magnesium powder is sintered.

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