MEDICAL BIODEGRADABLE ZN-CU ALLOY AND ITS PREPARATION METHOD AS WELL AS APPLICATIONS

Abstract

The present invention relates to the preparation methods and applications of biodegradable zinc-copper alloys, which can be applied to medical implant materials. The alloy of present invention is mainly composed of copper (1-10 wt. %), the balance of zinc and trace impurity elements. As-cast alloy ingot is homogenized and then hot processed to refine microstructure. The mechanical properties of the alloys are improved due to the refined microstructure. The alloys are capable of being further fabricated into micro-tubes, wires and plates. There are many advantages of these Zn alloys such as excellent mechanical properties, easy to process, appropriate corrosion resistance, good biocompatibility and so on, which correspondingly can be applied to many kinds of biodegradable medical implant devices. With excellent mechanical properties, good biocompatibility and degrading completely in 6-18 months, the Zn alloys meet the requirements of implant materials for mechanical properties and biosafety.

Claims

1. Biodegradable Zn—Cu alloys for medical application, wherein the alloys are composed of copper, zinc and unavoidable impurity elements, of which the content of copper is 1-10 wt. % and the content of impurity elements is no more than 0.1 wt. %.

2. The Biodegradable Zn—Cu alloys for medical application as claimed in claim 1, wherein the preferably content of copper is 1-4 wt. %.

3. A preparation method of biodegradable Zn—Cu alloys for medical application as claimed in claim 1, wherein the Zn—Cu ingot is prepared by using pure zinc and brass or by using pure zinc and pure copper.

4. The preparation method as claimed in claim 3, wherein the method comprises the following steps: At first, brass or pure copper is added when pure zinc is heated and melted completely. When brass or pure copper is melted completely, the melt of the patent alloy is obtained. The second, after stirring the melt, removing slag, standing for several minutes, casting, the as-cast alloy ingot is obtained. The third, after the as-cast alloy is homogenized at about 360-380° C. for 8-10 hours, the hot extrusion is performed at 200˜350° C. Followed by drawing or rolling, rods, wires, tubes and plates can be obtained.

5. The preparation method as claimed in claim 4, wherein the biodegradable Zn—Cu alloys for medical application are characterized by the characteristic that the extrusion ratio of the hot extrusion process described above is controlled between 9 and 50.

6. The preparation method as claimed in claim 4, wherein the biodegradable Zn—Cu alloys for medical application are characterized by the characteristic that the amount of deformation of the rolling process is controlled between 5 and 20%.

7. The applications of biodegradable Zn—Cu alloys for medical application as claimed in claim 1, wherein the biodegradable Zn—Cu alloys are used in medical application. The applications as claimed in claim 7, wherein the biodegradable Zn—Cu alloys are used in medical devices including tube-type devices and one of the devices of bone implants.

8. The applications as claimed in claim 8, wherein the tube-type devices include vascular stent, bile duct stent or tracheal stent and one of the devices of bone implants include bone plates or bone screws.

Description

BRIEF DESCRIPTION OF DRAWINGS

[0024] Other features, objects, and advantages of the present invention will become more apparent by reading and referring the detailed description of nonrestrictive embodiment in following figures.

[0025] FIG. 1 shows the microstructures of four as-cast alloys described in embodiment one;

[0026] FIG. 2 shows the microstructures of four as-extruded alloys described in embodiment two.

DESCRIPTION OF EMBODIMENT

[0027] Next, present invention is illustrated in detail combined with specific embodiments. The following embodiments will assist one skilled in this technology to further understand the invention, but not to limit the invention in any way. It should be noted that several modifications and improvements can be made by one skilled in this technology without deviating from the conception of present invention. All these are within the scope of present invention.

[0028] The biodegradable medical Zn—Cu alloys of present invention contain Cu of 1˜4 wt. % and the balance of Zn.

[0029] Properties of material depend on the microstructure of it. Thus, the microstructure of material can be modified according to application requirements. For example, microstructure of alloys can be modified to improve the properties of alloys by modifying the composition of the alloys within the composition range described above, homogenizing the alloys, processing the alloys (e.g. rolling and extrusion).

Embodiment 1

[0030] Zn—Cu alloy ingots are obtained by using current traditional melting and casting process of electric resistance furnace. Brass or pure copper is added and melting is kept at 550° C. for one hour until brass or pure copper is melted completely after pure zinc is heated and melted completely in electric resistance furnace. After stirring the melt for 10˜15 minutes, removing slag, standing for 10˜30 minutes, and casting, as-cast Zn—Cu binary alloy ingots are then obtained. Microstructure of four representative Zn-xCu (x=1, 2, 3, 4 wt. %) alloys is shown in FIG. 1.Raw materials are pure zinc (99.995%) and brass (Cu-38wt. %Zn) or pure copper (99.99%). The secondary phase of four binary alloys described above is CuZn.sub.5 phase (white dendritic secondary phase), as shown in FIG. 1. Biocompatibility test indicates that all the four Zn—Cu binary alloys described above exhibit good biocompatibility without obvious cytotoxicity.

Embodiment 2

[0031] Four representative Zn-xCu (x=1, 2, 3, 4 wt. %) alloys described in embodiment one are homogenized at 360° C.˜380° C. for 8 hours. And then the alloys are extruded at 280° C. with extrusion ratio of 9:1, as a result of which more uniform and finer microstructure of as-extruded rods or plates can be obtained. In this way, the properties of the alloys are improved. Microstructure of as-extruded alloys is shown in FIG. 2. After extrusion, the secondary phase is crushed, lengthened and distributes along the extrusion direction. Grain size of as-extruded alloys is refined of 1˜10 μm. The results of tensile test in room temperature are shown in Table 1. The yield strength (YS), ultimate tensile strength (UTS) and elongation values of the Zn—Cu binary alloys can reach 150˜230 MPa, 187˜271 MPa and 22˜55%, respectively. The corrosion rate of Zn—Cu binary alloys measured in hank's solution at 37° C. is about 0.02˜0.2 mm year.sup.−1. These properties meet the requirements of biodegradable medical materials for clinical application and Zn—Cu binary alloys are proper for fabricating biodegradable medical implants including wires, vascular stents, bile duct stents, tracheal stents, bone plates, bone screws, bone tissue engineering scaffolds and so on.

[0032] The mechanical properties of the Zn-xCu (x=1, 2, 3, 4 wt. %) alloys described in this embodiment are shown in Table 1.

TABLE-US-00001 TABLE 1 Mechanical properties of as-extruded alloys alloys UTS (MPa) YS (MPa) Elongation (%) Zn-1 wt. % Cu 187 150 22.2 Zn-2 wt. % Cu 241 204 47.4 Zn-3 wt. % Cu 258 215 49.1 Zn-4 wt. % Cu 271 230 52.3

Embodiment 3

[0033] Zn-1Cu alloy described in embodiment one is machined into plate of 10 mm in thickness and then rolled at 350° C., of which the amount of deformation of each rolling pass is about 10%. At last, plate of 2 mm in thickness can be obtained. The UTS, YS and elongation values of plates along rolling direction are 210 MPa, 160 MPa and 19.8%, respectively. The corrosion rate of this plate measured in hank's solution at 37° C. is about 0.18 mm year.sup.−1. These properties meet the requirements of biodegradable medical materials for clinical application and Zn-1Cu binary alloys are proper for fabricating bone implants like bone plates.

Embodiment 4

[0034] As-extruded rods of Zn-2Cu alloy described in embodiment two are machined into tubes of 20 mm in diameter and 13 mm in height. After being extruded at 300° C., seamless tube of 8mm in outer diameter and 0.8 mm in thickness of wall can be obtained. The seamless tubes are drawn or rolled in room temperature. After annealing treatment of 300° C. for 30 min is performed during each rolling or drawing pass, micro-tube of 3 mm in outer diameter and 0.185 mm in thickness of wall. The UTS, YS and elongation values of the tubes are 240 MPa, 200 MPa and 40.3%, respectively. The corrosion rate of this plate measured in hank's solution at 37° C. is about 0.12 mm year.sup.−1. These properties meet the requirements of biodegradable medical stents for clinical application and Zn-2Cu binary alloys are proper for fabricating vascular stents, bile duct stents and tracheal stents.

Embodiment 5

[0035] As-extruded rods of Zn-2Cu alloy described in embodiment two are machined into cylinder of 20 mm in diameter and 30 mm in height. After being extruded at 330° C., wires of 1.5 mm in diameter can be obtained. The UTS, YS and elongation values of the wires are 270 MPa, 220 MPa and 52%, respectively. The seamless tubes are drawn in room temperature for many passes. After annealing treatment of 350° C. for 30 min is performed during each drawing pass, micro-wires of 500 mm-50 μm in diameter can be obtained. The typical UTS, YS and elongation values of the wires are 255 MPa, 216 MPa and 44.6%, respectively. The corrosion rate of the wires measured in hank's solution at 37° C. is about 0.08 mm year.sup.−1. Biodegradable catheters weaved by these wires can be applied to stents for implantation including vascular stents, bile duct stents, tracheal stents and so on.

[0036] The specific embodiments of the present invention have been described above. It should be noted that the invention is not limited to the specific embodiments described above and various changes or modifications may be made by one skilled in this technology within the scope of the claims but this does not affect the substantial content of present invention.