(19)
(11)EP 2 716 777 B1

(12)EUROPEAN PATENT SPECIFICATION

(45)Mention of the grant of the patent:
26.06.2019 Bulletin 2019/26

(21)Application number: 12790246.8

(22)Date of filing:  08.05.2012
(51)International Patent Classification (IPC): 
A61C 7/20(2006.01)
A61L 31/14(2006.01)
C22C 1/10(2006.01)
A61L 31/12(2006.01)
B22F 3/20(2006.01)
C22C 32/00(2006.01)
(86)International application number:
PCT/JP2012/061712
(87)International publication number:
WO 2012/160956 (29.11.2012 Gazette  2012/48)

(54)

COMPOSITE MATERIAL FOR MEDICAL DEVICES

VERBUNDMATERIAL FÜR MEDIZINISCHE VORRICHTUNGEN

MATÉRIAU COMPOSITE POUR DISPOSITIFS MÉDICAUX


(84)Designated Contracting States:
AL AT BE BG CH CY CZ DE DK EE ES FI FR GB GR HR HU IE IS IT LI LT LU LV MC MK MT NL NO PL PT RO RS SE SI SK SM TR

(30)Priority: 26.05.2011 JP 2011118434

(43)Date of publication of application:
09.04.2014 Bulletin 2014/15

(73)Proprietor: Terumo Kabushiki Kaisha
Tokyo 151-0072 (JP)

(72)Inventor:
  • SOBA, Ryoichi
    Fujinomiya-shi Shizuoka 418-0015 (JP)

(74)Representative: Dossmann, Gérard 
Casalonga & Partners Bayerstrasse 71-73
80335 München
80335 München (DE)


(56)References cited: : 
WO-A1-2010/051515
CN-A- 101 440 439
JP-A- 63 190 130
US-A- 4 389 250
WO-A1-2010/051515
JP-A- 9 118 967
JP-A- 2002 105 561
US-A1- 2006 228 536
  
      
    Note: Within nine months from the publication of the mention of the grant of the European patent, any person may give notice to the European Patent Office of opposition to the European patent granted. Notice of opposition shall be filed in a written reasoned statement. It shall not be deemed to have been filed until the opposition fee has been paid. (Art. 99(1) European Patent Convention).


    Description

    Technical Field



    [0001] The present invention relates to a composite material which is used for medical devices such as stents, guide wires, embolization coils, inferior vena cava filters, and wires for orthodontics, and particularly relates to a composite material for medical devices utilizing a superelastic shape memory alloy as a matrix and a method of manufacturing the same.

    Background Art



    [0002] As a material for medical devices such as stents and guide wires, various kinds of alloys have been used. For example, JP-A-2003-325655 (Patent Document 1) discloses a stent consisting of NiTi shape memory alloys and JP-A-9-182799 (Patent Document 2) discloses a guide wire consisting of NiTi-based alloys, CuZnAl-based alloys, CuAlNi-based alloys, or the like.

    [0003] NiTi-based alloys, FeMnSi-based alloys, CuAlNi-based alloys, CuZnAl-based alloys, or the like are generally called a shape memory alloy, and among these, there is an alloy showing superelasticity at human body temperature (around 37°C). The superelastic shape memory alloys have a crystal structure in which stress-induced type martensitic transformation is generated and have characteristics of returning to their original shape after releasing the stress. The term, "superelasticity" herein means that even if the material is deformed (bent, stretched, compressed, and twisted) at service temperature to the region in which ordinary metals undergo plastic deformation, releasing the deformation stress results in recovery to nearly the original shape before deformation without heating. The superelastic shape memory alloys having such characteristics can be used with advantage in stents, guide wires, or the like which are used in the living body.

    [0004] Document WO2010/051515 discloses a medical device including a wire made of Ni-Ti shape memory material. The material is superelastic and can contain an oxide phase. Document JP63190130 also discloses a shape memory alloy. The material is a NiTi alloy, to which 10-30 vol.-% alumina or SiC powder is added. Document US 2006/228536 also discloses a shape memory alloy. The material is a porous NiTi alloy, which contains metal oxide distributed throughout its structure. The amount of oxygen is at least 0.4 atom% for the TiNi matrix. Document CN101440439 discloses a sintered body containing a shape memory alloy made of NiTi based alloy and 5-15 wt% of alumina particles.

    Citation List


    Patent Literature



    [0005] 

    [Patent Document 1] JP-A-2003-325655

    [Patent Document 2] JP-A-9-182799


    Summary of Invention


    Technical Problem



    [0006] Since the superelastic shape memory alloys are generally a "soft" alloy, there were some cases where the stress value in the plateau region (the region in which the stress value shows nearly constant value with respect to an increase of strain in the stress-strain curve) is insufficient depending on the application. In particular, in medical devices such as stents and guide wires which are arranged or used in the living body, more reduction in size is desired. However, when the stress value in the plateau region (the strength) is insufficient, it is difficult to promote a reduction in size such as a reduction in wall thickness and a reduction in diameter.

    [0007] An object of the invention is to improve the stress value in the plateau region in a composite material for medical devices utilizing a superelastic shape memory alloy as a matrix.

    Solution to Problem



    [0008] A composite material for medical devices according to the invention includes a superelastic shape memory alloy which configures a matrix, and a metal oxide which is dispersed in the matrix.

    [0009] Description will be given later with reference to Examples. However, the stress value in the plateau region is improved by containing the proper dose of the metal oxide in the matrix.

    [0010] In order to contain the proper dose of the metal oxide in the matrix, the composite material for medical devices is preferably obtained by sintering to be subjected to extrusion processing after the superelastic shape memory alloy powder and the metal oxide particles are mixed. Even if the metal oxide particles are added into the dissolved superelastic shape memory alloys, it is difficult to remain the proper dose of the metal oxide in the matrix. In contrast, if the metal oxide particles are added into and mixed with the superelastic shape memory alloy powder, it is possible to remain the proper dose of the metal oxide in the matrix.

    [0011] The additive amount of the metal oxide particles to the superelastic shape memory alloy powder is from 0.10% by volume to 1.0% by volume. When the additive amount is less than 0.10% by volume, an improvement of the stress value in the plateau region is insufficient. When the additive amount is over 1.0% by volume, while the stress value in the plateau region is improved, it does not become appropriate for the application as medical devices used in the living body since a decrease in stretching becomes prominent.

    [0012] Furthermore, "the additive amount of the metal oxide to the superelastic shape memory alloy powder" defined by % by volume is part by volume of the additive amount of the metal oxide to 100 part by volume of the superelastic shape memory alloy powder.

    [0013] The superelastic shape memory alloy powder is TiNi-based alloy powder. As a material for medical devices such as stents and guide wires, TiNi-based alloys which have excellent biocompatibility are particularly preferable. TiNi-based alloys have excellent corrosion resistance in the blood, and there is no risk that the alloy constituents are eluted into the blood since the surface is stable. The metal oxide particles are one kind of oxide particles selected from a group consisting of TiO2 and Al2O3.

    [0014] The superelastic shape memory alloy powder is TiNi-based alloy powder, and the metal oxide particles and the additive amount thereof are any one of 0.10% by volume to 1.0 % by volume of TiO2 and 0.1% by volume to 1.0 % by volume of Al2O3.

    [0015] A method of manufacturing a composite material for medical devices according to the invention includes the following steps.
    1. a) A step of producing an ingot consisting of a superelastic shape memory alloy by a dissolution method.
    2. b) A step of making the superelastic shape memory alloy ingot into a superelastic shape memory alloy powder by crushing or cutting the superelastic shape memory alloy ingot.
    3. c) A step of mixing the superelastic shape memory alloy powder and metal oxide particles.
    4. d) A step of sintering a mixture of the superelastic shape memory alloy powder and the metal oxide particles to be subjected to extrusion processing.


    [0016] In the method described above, the superelastic shape memory alloys are TiNi-based alloys, and the metal oxide and the additive amount thereof are any one of 0.10% by volume to 1.0 % by volume of TiO2 and 0.1% by volume to 1.0 % by volume of Al2O3.

    Advantageous Effects of Invention



    [0017] According to the invention, in a composite material for medical devices utilizing a superelastic shape memory alloy as a matrix, it is possible to improve the stress value in the plateau region in the stress-strain curve by containing a metal oxide which is dispersed in the matrix. As a result, it is possible to realize a reduction in wall thickness and a reduction in diameter, of medical devices such as stents and guide wires.

    Brief Description of Drawings



    [0018] 

    Fig. 1 is a figure illustrating the results of tensile tests for an extruded product of TiNi-based alloys to which a metal oxide is not added (Sample 1), an extruded product of TiNi-based alloys to which 0.5% by volume (0.33 wt%) of TiO2 particles are added (Sample 2), and an extruded product of TiNi-based alloys to which 1.0% by volume (0.66 wt%) of TiO2 particles are added (Sample 3).

    Fig. 2 is a figure illustrating the results of tensile tests for an extruded product of TiNi-based alloys to which a metal oxide is not added (Sample 1), an extruded product of TiNi-based alloys to which 0.2% by volume of Al2O3 particles are added (Sample 4), and an extruded product of TiNi-based alloys to which 1.0% by volume of Al2O3 particles are added (Sample 5).

    Fig. 3 is a figure illustrating the result of hysteresis test for Sample 2.

    Fig. 4 is a figure illustrating the result of hysteresis test for Sample 3.

    Fig. 5 is a figure illustrating the results of tensile tests for an extruded product of TiNi-based alloys to which 0.15% by volume (0.1 wt%) of TiO2 particles are added (Sample 6), and an extruded product of TiNi-based alloys to which 0.38% by volume (0.25 wt%) of TiO2 particles are added (Sample 7).

    Fig. 6 is a figure illustrating the result of hysteresis test for Sample 6

    Fig. 7 is a figure illustrating the result of hysteresis test for Sample 7.


    Description of Embodiments



    [0019] A composite material according to the invention is used for medical devices such as stents, guide wires, embolization coils, inferior vena cava filters, and wires for orthodontics, and contains a metal oxide which is dispersed in the matrix, utilizing a superelastic shape memory alloy as a matrix.

    [0020] Superelastic shape memory alloys have the alloy constituents which can exhibit superelastic shape memory characteristics, such as TiNi-based alloys, Cu-based alloys, Fe-based alloys and Ti-based alloys. In a case of TiNi-based alloys, TiNi-based alloys contain 43% by mass to 57% by mass of Ni and the residue consists of Ti and unavoidable impurities. A small amount of other metals, for example, cobalt, iron, palladium, platinum, boron, aluminum, silicon, vanadium, niobium, copper, or the like may be added to such TiNi-based alloys.

    [0021]  As Cu-based alloys, for example, CuAlNi alloys, CuZn alloys, CuZnAl alloys, and the like can be included. As Fe-based alloys, for example, FeNi alloys, FeMnSi alloys, FePd alloys, FePt alloys, and the like can be included. As Ti-based alloys, for example, TiNb alloys, TiMo alloys, and the like can be included.

    [0022] Among various kinds of the superelastic shape memory alloys described above, the superelastic shape memory alloys which are particularly appropriate as a composite material for medical devices are TiNi-based alloys in which the strain recovery is large and which have excellent biocompatibility. An example of TiNi-based alloys is TiNi-based alloys, for example, in which TiNi-based alloys contain 54.5% by mass to 57% by mass of Ni and the residue consists of Ti and unavoidable impurities. As unavoidable impurities, 0.050% by mass or less of Co, 0.010% by mass or less of Cu, 0.010% by mass or less of Cr, 0.005% by mass or less of H, 0.050% by mass or less of Fe, or 0.050% by mass or less of Nb may be contained.

    [0023] In order to improve the stress value in the plateau region in the stress-strain curve, it is important to disperse the metal oxide in the matrix of the superelastic shape memory alloys. The metal oxide is any one of TiO2 and Al2O3. When the proper dose of the metal oxide is contained in the matrix, even if the metal oxide particles such as TiO2 and Al2O3 are added into the dissolved superelastic shape memory alloy, it is difficult to remain the proper dose of the metal oxide in the matrix.

    [0024] Whereat, the composite material according to the invention is manufactured through the following steps. Description will be given of an example of a case where the superelastic shape memory alloys are TiNi-based alloys.

    (A) Production of an ingot



    [0025] An ingot consisting of TiNi-based alloys is produced by a dissolution method. As other method, it is considered that a sintered body of TiNi-based alloy is obtained by a powder metallurgy method in which Ti powder and Ni powder are mixed to be sintered.

    (B) Production of TiNi-based alloy powder



    [0026] TiNi-based alloy powder is obtained by crushing or cutting a TiNi-based alloy ingot.

    (C) Addition of a metal oxide



    [0027] Metal oxide particles such as TiO2 and Al2O3 are added to TiNi-based alloy powder to mix so that metal oxide particles are uniformly dispersed. The additive amount of metal oxide particles to TiNi-based alloy powder is 0.10% by volume to 1.0% by volume. If the additive amount is less than 0.10% by volume, an improvement of the stress value in the plateau region is insufficient in the stress-strain curve in the composite material which is finally obtained. When the additive amount is over 1.0% by volume, while the stress value in the plateau region is improved, it does not become appropriate for the application as medical devices used in the living body, since a decrease in stretching becomes prominent. Particularly, in a case of stents being arranged at a bending part of the blood vessel, the characteristic of stretching becomes an important factor, since a cyclic bending load acts.

    (D) Sintering and extrusion processing



    [0028] A mixture of TiNi-based alloy powder and metal oxide particles is sintered to be subjected to extrusion processing. Sintering is preferably performed in a vacuum atmosphere or an inert gas atmosphere, and more preferably performed in a vacuum atmosphere. The sintering temperature is not particularly limited. However, for example, 700°C to 1,200°C is preferable, and 800°C to 1,100°C is more preferable. In addition, extrusion processing is preferably hot extrusion processing.

    [0029]  After steps described above, the composite material for medical devices according to the invention is obtained. In the composite material which is finally obtained, for example, by dispersing Al2O3 as particles in the matrix of TiNi-based alloys, the strength of the composite material is enhanced. In this manner, if Al2O3 particles are added, it is possible to improve the stress value in the plateau region of the composite material which is finally obtained, by strengthening particle dispersion. However, there is a possibility that a particle dispersion strengthening type composite material is not appropriate for the application like a cyclic bending load acts. For example, in a case of manufacturing stents being arranged at a bending part of the blood vessel using a particle dispersion type composite material, by particles which are dispersed in the matrix being received the cyclic load for is likely to be the starting point of fatigue failure.

    [0030] In a case of the application described above, it is preferable that TiO2 particles be used as metal oxide particles . In a case where metal oxide particles which are added are TiO2, TiO2 are not finally present as particles but by decomposing, oxygen is dissolved in a parent phase to try the solid solution strengthening and the strength of the composite material for medical devices is improved. Particularly, by adding Tio2 particles not by a melting method (a dissolution method), but by a powder metallurgy method, it is possible to dissolve more oxygen content. Since oxygen which is dissolved does not become the starting point of fatigue failure, an oxygen solid solution strengthening type composite material is appropriate for the application in which a cyclic load is applied.

    [0031] As a metal oxide where the solid solution strengthening of oxygen can be expected, CeO2, MgO, CaO, ZrO2, and the like in which it is considered that it is more difficult to decompose than TiO2, from an oxide standard production free energy diagram, can be included. In these metal oxides, without oxygen which has been decomposed once reacting to a metal element to generate a metal oxide again, oxygen is dissolved in a parent phase.

    [0032] The applications of the composite material of the invention are medical devices such as stents, guide wires, embolization coils, inferior vena cava filters, and wires for orthodontics. While being described in Examples later, in a case of TiNi-based alloy composite material to which 0.5% by volume (0.33 wt%) of TiO2 particles are added, the stress value (the strength) in the plateau region increases form 600 MPa (no addition of TiO2) to 800 MPa. Therefore, the application for stents of the conventional board thickness of 0.2 mm is considered, the board thickness can be reduced to approximately three-quarter (about 1.5 mm) if the same degree of the strength is maintained. A merit of reducing the board thickness is that the amount of the used alloys is decreased and as a result, it is possible to reduce elution of alloy constituents since it is possible to support a film of the blood vessel by a thin beam. In addition, when delivering to the blood vessel, it is possible to fold stents into more smaller diameter.

    [0033] Considering that the stress value (the strength) in the plateau region increases form 600 MPa to 800 MPa, when the application for guide wires is considered, the outer diameter of 0.50 mm of the conventional wires can be reduce to 0.45 mm if the same degree of the strength is maintained. A merit of this reduction in diameter is that it is possible to achieve the reduction in diameter of the inner and outer diameter of other medical devices which can be laid along wires.

    Examples


    [Preparation of a mixture]



    [0034] The following mixtures were prepared.

    Sample 1: TiNi-based alloy powder (Comparative Example)

    Sample 2: 0.5% by volume (0.33 wt%) of TiO2 particles are added to TiNi-based alloy powder (Example of the invention)

    Sample 3: 1.0% by volume (0.66 wt%) of TiO2 particles are added to TiNi-based alloy powder (Example of the invention)

    Sample 4: 0.2% by volume of Al2O3 particles are added to TiNi-based alloy powder (Example of the invention)

    Sample 5: 1.0% by volume of Al2O3 particles are added to TiNi-based alloy powder (Example of the invention)

    Sample 6: 0.15% by volume (0.10 wt%) of TiO2 particles are added to TiNi-based alloy powder (Example of the invention)

    Sample 7: 0.38% by volume (0.25 wt%) of TiO2 particles are added to TiNi-based alloy powder (Example of the invention)


    [Sintering]



    [0035] Each sample described above was sintered according to the following conditions to obtain a sintered body.

    Temperature: 900°C

    Retention time: 30 minutes

    Atmosphere: Vacuum

    Pressure: 40 MPa

    Rate of temperature elevation: 20°C/min


    [Hot extrusion processing]



    [0036] The sintered body obtained was subjected to hot extrusion processing according to the following conditions to obtain an extruded product.

    Preheating temperature: 1,050°C

    Pre-overheating time: 10 minutes

    Extrusion ratio: 6

    Extrusion ram speed: 6 mm/sec


    [Tensile Test]



    [0037] Tensile tests of the extruded products of Samples 1 to 7 were performed at ambient temperature under the following conditions (N=2).

    Shape of test piece: Round bar

    Diameter of test piece: 3.5 mm

    Length of test piece: 20 mm

    Tension speed: Strain rate 5×10-4s-1



    [0038] Figs. 1, 2 and 5 illustrate the test results of Sample 1, Sample 2 and Sample 3, the test results of Sample 1, Sample 4 and Sample 5, and the test results of Sample 6 and Sample 7, respectively.

    [0039] It is recognized from the graph illustrated in Fig. 1 that in Sample 2 to which 0.5% by volume (0.33 wt%) of TiO2 was added and Sample 3 to which 1.0% by volume (0.66 wt%) of TiO2 was added, the stress values in the plateau region in the stress-strain curve are improved as compared to Sample 1 to which TiO2 was not added. In addition, as the additive amount of TiO2 is bigger, it is recognized that the breaking strengths is also improved. On the other hand, regarding elongation characteristics, it is recognized that Sample 3 to which 1.0% by volume of TiO2 was added is deteriorated as compared to Sample 1 and Sample 2.

    [0040] Considering the application for medical devices such as stents and guide wires, since deteriorating elongation characteristics very much is not desired, the preferred upper limit value of the additive amount of TiO2 is 1.0% by volume.

    [0041] The stress value of Sample 1 to which TiO2 was not added in the plateau region is about 600 MPa, whereas the stress value of Sample 2 to which 0.5% by volume (0.33 wt%) of TiO2 was added in the plateau region is about 800 MPa. Regarding elongation characteristics, big difference between Sample 1 and Sample 2 is not recognized.

    [0042] From the graph illustrated in Fig. 5, the stress value of Sample 6 to which 0.15% by volume (0.10 wt%) of TiO2 was added in the plateau region is about 720 MPa, the stress value of Sample 7 to which 0.38% by volume (0.25 wt%) of TiO2 was added in the plateau region is about 770 MPa, and the stress values are significantly improved as compared to Sample 1 to which TiO2 was not added. Regarding elongation characteristics, big difference among Sample 1, Sample 6 and Sample 7 is not recognized.

    [0043] It is recognized that the preferred additive amount of TiO2 is from approximately 0.15% by volume (0.10 wt%) to 0.5% by volume (0.33 wt%), from the viewpoint of improving the stress value in the plateau region without deteriorating elongation characteristics. Considering that the stress value in the plateau region increases by about 120 MPa when the additive amount of TiO2 is 0.15% by volume (0.10 wt%), an increase in the stress value by about 100 MPa is expected even if 0.10% by volume is added. Therefore, the preferred lower limit value of the additive amount of TiO2 is 0.10% by volume.

    [0044] It is recognized from the graph illustrated in Fig. 2 that in Sample 4 to which 0.2% by volume of Al2O3 was added and Sample 5 to which 1.0% by volume of Al2O3 was added, the stress values and the breaking strength in the plateau region in the stress-strain curve are improved as compared to Sample 1 to which Al2O3 was not added. The stress values and the breaking strengths in the plateau region increase in proportion to the additive amount of Al2O3. On the other hand, regarding elongation characteristics, it is recognized that Sample 5 to which 1.0% by volume of Al2O3 was added is deteriorated as compared to Sample 1 and Sample 4.

    [0045] Considering the application for medical devices, since deteriorating elongation characteristics very much is not desired, the upper limit value of the additive amount of Al2O3 is 1.0% by volume.

    [0046] The stress value of Sample 1 to which Al2O3 was not added in the plateau region is about 600 MPa, whereas the stress value of Sample 4 to which 0.2% by volume of Al2O3 was added in the plateau region is about 750 MPa. Regarding elongation characteristics, big difference between Sample 1 and Sample 4 is not recognized. It is recognized that the preferred additive amount of Al2O3 is approximately 0.2% by volume, from the viewpoint of improving the stress value in the plateau region without deteriorating elongation characteristics. Considering that the stress value in the plateau region increases by about 150 MPa when the additive amount of Al2O3 is 0.2% by volume, an increase in the stress value by about 100 MPa is expected even 0.1% by volume is added. Therefore, the lower limit value of Al2O3 is 0.1% by volume.

    [Hysteresis test]



    [0047] By setting tensile test in which the stress is released after imparting a constant strain by stretching the extruded products of Sample 2, Sample 3, Sample 6 and Sample 7, as a cycle, hysteresis test in which three cycles are performed by changing the strain imparted was performed according to the following conditions. The strain amount of Sample 2 is set to 3% at cycle 1, 7% at cycle 2, and 15% at cycle 3. The strain amount of Sample 3 is set to 3% at cycle 1, 5% at cycle 2, and 10% at cycle 3. The strain amount of Sample 6 and Sample 7 is set to 4% at cycle 1, 10% at cycle 2, and 15% at cycle 3.

    Shape of test piece: Round bar

    Diameter of test piece: 3.5 mm

    Length of test piece: 20 mm

    Tension speed: Strain rate 5×10-4s-1



    [0048] The result of Sample 2 is illustrated in Fig. 3, the result of Sample 3 is illustrated in Fig. 4, the result of Sample 6 is illustrated in Fig. 6, and the result of Sample 7 is illustrated in Fig. 7. From these Figs, it is recognized that after releasing the stress, the strain deformation returns to some extent in Sample 2, Sample 3, Sample 6, and Sample 7 to which TiO2 was added.

    Industrial Applicability



    [0049] A composite material according to the invention can be used with advantage as a material for medical devices such as stents and guide wires.


    Claims

    1. A composite material for medical devices, comprising:

    - a superelastic shape memory alloy powder which configures a matrix; and

    - metal oxide particles which are dispersed in the matrix,

    wherein the superelastic shape memory alloy powder is TiNi-based alloy powder, and the metal oxide particles and the additive amount thereof are any one of 0.10% by volume to 1.0 % by volume of TiO2 and 0.1% by volume to 1.0 % by volume of Al2O3.
     
    2. The composite material for medical devices according to claim 1, wherein the additive amount thereof are any one of 0.10% by volume to 0.5 % by volume of TiO2 and 0.1% by volume to 0.2 % by volume of Al2O3.
     


    Ansprüche

    1. Verbundmaterial für medizinische Vorrichtungen, umfassend:

    - ein Pulver aus einer superelastischen Formgedächtnislegierung, das eine Matrix bildet; und

    - Metalloxidpartikel, die in der Matrix dispergiert sind,

    wobei das Pulver aus einer superelastischen Formgedächtnislegierung ein Legierungspulver auf TiNi-Basis ist und die Metalloxidpartikel und deren Zugabemenge eines von 0,10 Vol.-% bis 1,0 Vol.-% TiO2 und 0,1 Vol.-% bis 1,0 Vol.-% Al2O3 sind.
     
    2. Verbundmaterial für medizinische Vorrichtungen nach Anspruch 1, wobei die Zugabemenge eines von 0,10 Vol.-% bis 0,5 Vol.-% TiO2 und 0,1 Vol.-% bis 0,2 Vol.-% Al2O3 ist.
     


    Revendications

    1. Matériau composite pour dispositifs médicaux, comprenant :

    - une poudre d'un alliage super-élastique à mémoire de forme, qui forme une matrice,

    - et des particules d'un oxyde de métal, qui sont dispersées dans la matrice,

    dans lequel matériau la poudre d'alliage super-élastique à mémoire de forme est une poudre d'un alliage à base de titane et de nickel, et les particules d'oxyde de métal, et la proportion en laquelle elles sont ajoutées, sont des particules de TiO2, en une proportion qui vaut de 0,10 % en volume à 1,0 % en volume, ou des particules de Al2O3, en une proportion qui vaut de 0,1 % en volume à 1,0 % en volume.
     
    2. Matériau composite pour dispositifs médicaux, conforme à la revendication 1, dans lequel la proportion en laquelle les particules sont ajoutées vaut de 0,10 % en volume à 0,5 % en volume pour des particules de TiO2, et de 0,1 % en volume à 0,2 % en volume pour des particules de Al2O3.
     




    Drawing

















    Cited references

    REFERENCES CITED IN THE DESCRIPTION



    This list of references cited by the applicant is for the reader's convenience only. It does not form part of the European patent document. Even though great care has been taken in compiling the references, errors or omissions cannot be excluded and the EPO disclaims all liability in this regard.

    Patent documents cited in the description