Highly corrosion-resistant biodegradable magnesium alloy for stent and method for manufacturing microtube using same

Abstract

The present application provides a highly corrosion-resistant biodegradable magnesium alloy for a stent and a method for manufacturing a microtube using same. More specifically, the present application provides a highly corrosion-resistant biodegradable magnesium alloy for a stent, a highly corrosion-resistant biodegradable microtube for a stent, the microtube being made of the magnesium alloy and having an improved hydrogen generation rate, yield strength, and tensile strength, and a method for manufacturing the microtube.

Description

Highly corrosion-resistant biodegradable magnesium alloy for stents and method for manufacturing microtubes using the same

[0001] The present invention relates to a highly corrosion-resistant biodegradable magnesium alloy for stents and a method for manufacturing a microtube using the same.

[0002] Biodegradable orthopedic implants and materials for treating vascular diseases are among the core technologies for future bio-implantable medical devices. Currently, materials used for vascular stents include stainless steel, Co-Cr, or nitinol alloys that remain permanently in the body, but these materials pose problems such as potential side effects like thrombosis and persistent inflammation. To address these issues, biodegradable stents are attracting attention as an alternative.

[0003] As a constituent element of the human body, magnesium is gaining attention as a metallic material for implantable stents due to its biocompatibility and biodegradability. However, due to limitations such as low mechanical properties, a rapid degradation rate, and poor formability, research is underway to improve these aspects through alloying and heat treatment processes.

[0004] In addition, a thin strut thickness is required to pass through complex blood vessels without damaging the vessels during stent insertion and to safely reach the desired location, and for this, securing excellent mechanical properties is essential.

[0005] As background technology to the present invention, Japanese registered patent No. 5846591 describes an implant that decomposes in the body, made of magnesium or a magnesium master alloy.

[0006]

[0007] The purpose of the present invention is to provide a magnesium alloy that can be used as a microtube material for stents due to its high strength, high corrosion resistance, and biodegradability.

[0008] Another objective of the present invention is to provide a microtube for a stent with improved hydrogen generation rate, yield strength, and tensile strength.

[0009] Another objective of the present invention is to provide a manufacturing method capable of efficiently producing microtubes for stents with improved hydrogen generation rate, yield strength, and tensile strength.

[0010] The problems of the present invention are not limited to those mentioned above, and other technical problems not mentioned will be clearly understood by those skilled in the art from the description below.

[0011] According to one aspect, a highly corrosion-resistant biodegradable magnesium alloy for a stent is provided, comprising, with respect to the total weight of the highly corrosion-resistant biodegradable magnesium alloy for a stent, 0.1 wt% or more and less than 3.0 wt% Zn; more than 0.0 wt% and less than 2.0 wt% Mn; more than 0.0 wt% and less than 2.0 wt% Sr; more than 0.0 wt% and less than 1.0 wt% Ca; and the remainder Mg, wherein, with respect to the total weight of the highly corrosion-resistant biodegradable magnesium alloy for a stent, the content ratio of Sr to Zn, Sr / Zn, is 0.3 to 2.5.

[0012] According to one embodiment, with respect to the total weight of the magnesium alloy for biodegradable microtubes, the content ratio of Sr to Zn, Sr / Zn, may be greater than 0.38 and less than or equal to 2.5.

[0013] According to one embodiment, the Zn content may be 0.1 weight% or more and less than 1.5 weight% with respect to the total weight of the highly corrosion-resistant biodegradable magnesium alloy for a stent.

[0014] According to one embodiment, with respect to the total weight of the highly corrosion-resistant biodegradable magnesium alloy for a stent, the Sr content may be greater than 0.0 wt% and less than or equal to 1.0 wt%, and the Ca content may be greater than or equal to 0.0 wt% and less than or equal to 1.0 wt%.

[0015]

[0016] According to another aspect, a highly corrosion-resistant biodegradable microtube for a stent is provided, made of a highly corrosion-resistant biodegradable magnesium alloy for a stent according to the present invention.

[0017] According to one embodiment, the outer diameter of the highly corrosion-resistant biodegradable microtube for the stent may be 1.0 mm to 4.0 mm, and the wall thickness of the highly corrosion-resistant biodegradable microtube for the stent may be 0.15 mm to 0.25 mm.

[0018] According to one embodiment, the highly corrosion-resistant biodegradable microtube for the stent may be extruded at an extrusion ratio of 40:1 to 260:1.

[0019] According to one embodiment, the highly corrosion-resistant biodegradable microtube for the stent may have a roundness of 0% to 1.5% of the outer or inner diameter.

[0020] According to one embodiment, the highly corrosion-resistant biodegradable microtube for the stent may have an average grain size of 3 μm to 10 μm.

[0021] According to one embodiment, the yield strength of the highly corrosion-resistant biodegradable microtube for the stent may be 130 MPa or more.

[0022] According to one embodiment, the tensile strength of the highly corrosion-resistant biodegradable microtube for the stent may be 210 MPa or more.

[0023] According to one embodiment, the highly corrosion-resistant biodegradable microtube for a stent has a hydrogen generation rate of 0.03 ml / cm 2 It may be less than / hr and have a yield strength of 176 MPa or more.

[0024] According to one embodiment, the highly corrosion-resistant biodegradable microtube for a stent has a hydrogen generation rate of 0.02 ml / cm 2 It may be less than / hr and have a tensile strength of 230 MPa or more.

[0025] According to one embodiment, the highly corrosion-resistant biodegradable microtube for a stent may have one or more of the following characteristics (1) to (5):

[0026] (1) Hydrogen generation rate is 0.03 ml / cm 2 / hr Lee Ha-im

[0027] (2) Yield strength is 130 MPa or higher

[0028] (3) Tensile strength is 210 MPa or higher

[0029] (4) The biodegradation rate is 2.1 mm / y or less based on the amount of hydrogen generated.

[0030] (5) The biodegradation rate is 1.2 mm / y or less based on weight loss.

[0031]

[0032] According to another aspect, i) a step of melting together, with respect to the total weight of a highly corrosion-resistant biodegradable magnesium alloy for a stent, 0.1 wt% or more and less than 3.0 wt% Zn; more than 0.0 wt% and less than 2.0 wt% Mn; more than 0.0 wt% and less than 2.0 wt% Sr; more than 0.0 wt% and less than 1.0 wt% Ca; and the remainder Mg to obtain a molten mixture; ii) a step of casting the molten mixture of step i) to produce a first billet; iii) a step of extruding the first billet produced in step ii) to produce a rod; iv) a step of drilling the center of the rod produced in step iii) to produce a hollow second billet; A method for manufacturing a highly corrosion-resistant biodegradable microtube for a stent is provided, comprising: v) a step of manufacturing a microtube by extruding a hollow second billet manufactured in step iv); wherein, in step i), the content ratio of Sr to Zn in the magnesium alloy for the biodegradable microtube is 0.3 to 2.5.

[0033] According to one embodiment, the microtube manufactured in step v) may further include a step of cold drawing.

[0034] According to one embodiment, the microtubes produced in step v) may include extrusion at an extrusion ratio of 40:1 to 260:1.

[0035] According to one embodiment, the steps of extruding the first billet and extruding the second billet in steps iii) and v) may include extruding at 350°C to 450°C.

[0036] According to one embodiment, the steps of extruding the first billet and extruding the second billet in steps iii) and v) may include extruding at an extrusion speed of 0.5 mm / s to 1.5 mm / s.

[0037] According to one embodiment, the microtube manufactured in step v) may further include a step of rapid cooling.

[0038]

[0039] According to one embodiment, the magnesium alloy of the present invention can be usefully utilized as a microtube material due to its high strength, high corrosion resistance, and biodegradability.

[0040] According to one embodiment, the microtube of the present invention has improved hydrogen generation rate, yield strength, and tensile strength, and in particular, the hydrogen generation rate is 0.03 ml / cm 2 It may be less than / hr, have a yield strength of 130 MPa or more, and a tensile strength of 210 MPa or more.

[0041] According to one embodiment, the method for manufacturing a microtube using magnesium of the present invention can efficiently manufacture a microtube for a stent with improved hydrogen generation rate, yield strength, and tensile strength.

[0042] However, the effects of the present invention are not limited to the effects mentioned above, and may be expanded in various ways within the scope of the concept and scope of the present invention.

[0043]

[0044] FIG. 1 schematically illustrates a method for manufacturing a stent made of a highly corrosion-resistant biodegradable magnesium alloy for stents according to one embodiment of the present invention.

[0045] FIG. 2 shows a microtube made of a highly corrosion-resistant biodegradable magnesium alloy for a stent manufactured through two-stage extrusion according to one embodiment of the present invention.

[0046] FIG. 3 shows a microtube made of a highly corrosion-resistant biodegradable magnesium alloy for a stent manufactured by two-stage extrusion and cold drawing according to one embodiment of the present invention, and graphs of the elongation and yield strength of the microtube.

[0047] FIG. 4 schematically illustrates a method for manufacturing a microtube made of a highly corrosion-resistant biodegradable magnesium alloy for a stent according to one embodiment of the present invention.

[0048] FIG. 5(a) is a photograph of a drawing device for a microtube made of a highly corrosion-resistant biodegradable magnesium alloy for a stent according to one embodiment of the present invention, and FIG. 5(b) shows photographs of a microtube made of a highly corrosion-resistant biodegradable magnesium alloy for a stent according to one embodiment of the present invention before and after cold drawing.

[0049] FIG. 6 shows an image showing the dimensional accuracy of a microtube made of a highly corrosion-resistant biodegradable magnesium alloy for a stent according to one embodiment of the present invention.

[0050] Figure 7 shows a diagram illustrating the definition and measurement method of out-of-roundness.

[0051] FIG. 8 shows the dimensional accuracy of a microtube made of a highly corrosion-resistant biodegradable magnesium alloy for a stent according to one embodiment of the present invention before and after centrifugal processing.

[0052] FIG. 9 shows an accredited test report measuring the outer diameter, inner diameter, and wall thickness of a microtube made of a highly corrosion-resistant biodegradable magnesium alloy for a stent according to Comparative Example 1 (MZ01) and Example 2 (ZM115) of the present invention.

[0053] Figure 10 shows the results of a room temperature tensile test of a microtube made of a highly corrosion-resistant biodegradable magnesium alloy for a stent according to Example 2 (ZM115) of the present invention.

[0054] FIG. 11 shows a photograph of a tensile test fixture for a microtube made of a highly corrosion-resistant biodegradable magnesium alloy for a stent according to one embodiment of the present invention.

[0055] Figure 12 shows the hydrogen generation rate of a microtube made of a highly corrosion-resistant biodegradable magnesium alloy for a stent according to Comparative Example 1 (MZ01) and Example 2 (ZM115) of the present invention.

[0056] Figure 13 shows the results of a hydrogen capture test conducted under expert supervision on microtubes made of highly corrosion-resistant biodegradable magnesium alloy for stents according to Comparative Example 1 (MZ01) and Example 2 (ZM115) of the present invention, as well as photographs of the specimen shape before and after the hydrogen capture test and after the removal of corrosion products.

[0057] FIG. 14a shows the hydrogen generation rate and yield strength (TYS) according to the extrusion ratio of microtubes made of highly corrosion-resistant biodegradable magnesium alloy for stents according to Comparative Examples 1 and 2 (MZ01, Z3) and Examples 1 to 6 (Z1, ZM115, ZX101, JX0301, JX0103, ZM0418) of the present invention.

[0058] FIG. 14b shows the hydrogen generation rate and tensile strength (UTS) according to the extrusion ratio of microtubes made of highly corrosion-resistant biodegradable magnesium alloy for stents according to Comparative Examples 1 and 2 (MZ01, Z3) and Examples 1 to 6 (Z1, ZM115, ZX101, JX0301, JX0103, ZM0418) of the present invention.

[0059] FIG. 14c shows the hydrogen generation rate and elongation (EL) according to the extrusion ratio of microtubes made of highly corrosion-resistant biodegradable magnesium alloy for stents according to Comparative Examples 1 and 2 (MZ01, Z3) and Examples 1 to 6 (Z1, ZM115, ZX101, JX0301, JX0103, ZM0418) of the present invention.

[0060] FIG. 15 shows the yield strength (TYS), tensile strength (UTS), and elongation (EL) according to the extrusion ratio of microtubes made of highly corrosion-resistant biodegradable magnesium alloy for stents according to Comparative Examples 1 and 2 (MZ01, Z3) and Examples 1 to 6 (Z1, ZM115, ZX101, JX0301, JX0103, ZM0418) of the present invention.

[0061] FIG. 16 shows the hydrogen generation rate and biodegradation rate according to the extrusion ratio of microtubes made of highly corrosion-resistant biodegradable magnesium alloy for stents according to Comparative Examples 1 and 2 (MZ01, Z3) and Examples 1 to 6 (Z1, ZM115, ZX101, JX0301, JX0103, ZM0418) of the present invention.

[0062] FIGS. 17 to 19 show the appearance of corrosion specimens after a hydrogen capture test according to the extrusion ratio of microtubes made of highly corrosion-resistant biodegradable magnesium alloy for stents according to Comparative Examples 1 and 2 (MZ01, Z3) and Examples 1 to 6 (Z1, ZM115, ZX101, JX0301, JX0103, ZM0418) of the present invention.

[0063] FIG. 20a shows the inverse square root of the average grain size and the yield strength (TYS) of microtubes made of highly corrosion-resistant biodegradable magnesium alloys for stents according to Comparative Examples 1 and 2 (MZ01, Z3) and Examples 1 to 6 (Z1, ZM115, ZX101, JX0301, JX0103, ZM0418) of the present invention.

[0064] FIG. 20b shows the inverse square root of the average grain size and the hydrogen generation rate of microtubes made of highly corrosion-resistant biodegradable magnesium alloy for stents according to Comparative Examples 1 and 2 (MZ01, Z3) and Examples 1 to 6 (Z1, ZM115, ZX101, JX0301, JX0103, ZM0418) of the present invention.

[0065] FIG. 21 shows the grain size and microstructure images according to the extrusion ratio of microtubes made of highly corrosion-resistant biodegradable magnesium alloy for stents according to Comparative Examples 1 and 2 (MZ01, Z3) and Examples 1 to 6 (Z1, ZM115, ZX101, JX0301, JX0103, ZM0418) of the present invention.

[0066] FIG. 22 shows pole figures (PF) according to the extrusion ratio of microtubes made of highly corrosion-resistant biodegradable magnesium alloy for stents according to Comparative Examples 1 and 2 (MZ01, Z3) and Examples 1 to 6 (Z1, ZM115, ZX101, JX0301, JX0103, ZM0418) of the present invention.

[0067] FIG. 23a shows a microtube made of a highly corrosion-resistant biodegradable magnesium alloy for a stent according to Example 2 (ZM115) of the present invention used in animal experiments.

[0068] Figure 23b shows a stent made of the microtube of Figure 23a.

[0069] FIG. 23c is a schematic diagram showing that the stent according to FIG. 23b is made into a coated stent coated with PLA (Polylactic Acid), and according to one embodiment of the present invention, the PLA-coated stent is implanted in the right blood vessel of an experimental animal and the uncoated stent is implanted in the left blood vessel.

[0070] Figure 23d shows an image showing the result of angiography after implanting and placing a stent according to Figure 23c.

[0071] Figure 23e shows a photograph showing the results of dissecting an experimental animal sacrificed 4 weeks after implanting the stent according to Figure 23c.

[0072] Figure 24 shows the results of a follow-up examination after 4 weeks, in which a stent made of a microtube made of a highly corrosion-resistant biodegradable magnesium alloy for stents according to Comparative Example 1 (MZ01) of the present invention was implanted into the blood vessel of an experimental animal.

[0073] Figure 25 shows the results of a follow-up examination after 4 weeks, in which a stent made of a microtube made of a highly corrosion-resistant biodegradable magnesium alloy for stents according to Example 2 (ZM115) of the present invention was implanted into the blood vessel of an experimental animal.

[0074] FIG. 26 shows the results of a room temperature tensile test with or without rapid cooling of a microtube made of a highly corrosion-resistant biodegradable magnesium alloy for a stent according to Comparative Example 1 (MZ01) and Examples 1 to 3 (Z1, ZM115, ZX101) of the present invention.

[0075] FIG. 27 shows the appearance of a corrosion specimen after a hydrogen capture test with or without rapid cooling of a microtube made of a highly corrosion-resistant biodegradable magnesium alloy for a stent according to Comparative Example 1 (MZ01) and Examples 1 to 3 (Z1, ZM115, ZX101) of the present invention.

[0076] FIG. 28a shows the hydrogen generation rate and yield strength (TYS) of microtubes made of highly corrosion-resistant biodegradable magnesium alloy for stents according to Comparative Example 1 (MZ01) and Examples 1 to 3 (Z1, ZM115, ZX101) of the present invention, depending on whether rapid cooling is performed.

[0077] FIG. 28b shows the hydrogen generation rate and tensile strength (UTS) of microtubes made of highly corrosion-resistant biodegradable magnesium alloy for stents according to Comparative Example 1 (MZ01) and Examples 1 to 3 (Z1, ZM115, ZX101) of the present invention, depending on whether rapid cooling is performed.

[0078] FIG. 28c shows the hydrogen generation rate and elongation (EL) of microtubes made of highly corrosion-resistant biodegradable magnesium alloy for stents according to Comparative Example 1 (MZ01) and Examples 1 to 3 (Z1, ZM115, ZX101) of the present invention, depending on whether rapid cooling is performed.

[0079] FIG. 29 shows the grain size and microstructure images of microtubes made of highly corrosion-resistant biodegradable magnesium alloy for stents according to Comparative Example 1 (MZ01) and Examples 1 to 3 (Z1, ZM115, ZX101) of the present invention, depending on whether rapid cooling is performed.

[0080] FIG. 30 shows pole figures (PF) according to the presence or absence of rapid cooling of microtubes made of highly corrosion-resistant biodegradable magnesium alloy for stents according to Comparative Example 1 (MZ01) and Examples 1 to 3 (Z1, ZM115, ZX101) of the present invention.

[0081]

[0082] The present invention is susceptible to various modifications and may take various forms, and the purposes, other purposes, features, and advantages of the invention will be readily understood through the accompanying drawings and the preferred embodiments below. However, the present invention is not limited to the embodiments described herein and may be embodied in other forms. Rather, the embodiments introduced herein are provided to ensure that the disclosed content is thorough and complete and to ensure that the spirit of the invention is sufficiently conveyed to a person skilled in the art.

[0083] Furthermore, unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the art to which the present invention pertains, and in the event of a conflict, the description in this specification, including the definitions, shall prevail.

[0084] Terms such as "first," "second," etc., may be used to describe various components, but said components should not be limited by said terms. These terms are used solely for the purpose of distinguishing one component from another. For example, without departing from the scope of the present invention, the first component may be named the second component, and similarly, the second component may be named the first component. A singular expression includes a plural expression unless the context clearly indicates otherwise.

[0085] In this specification, where a component (or region, layer, part, etc.) is described as being "on," "connected," or "combined" with another component, it means that it may be directly placed / connected / combined with the other component, or that a third component may be placed between them.

[0086] In this specification, terms such as “comprising” or “having” are intended to specify the existence of the features, numbers, steps, actions, components, parts, or combinations thereof described in the specification, and should not be understood as precluding the existence or addition of one or more other features, numbers, steps, actions, components, parts, or combinations thereof.

[0087] In this specification, the statement that any configuration is disposed on the "upper (or lower)" of a component or on the "upper (or lower)" of a component may mean not only that any configuration is disposed in contact with the upper (or lower) surface of said component, but also that another configuration may be interposed between said component and any configuration disposed on (or below) said component.

[0088] "And / or" includes all one or more combinations that the associated configurations can define.

[0089] The size and thickness of each component shown in the drawings are arbitrarily depicted for the convenience of explanation and are not limited thereto.

[0090] Hereinafter, the highly corrosion-resistant biodegradable magnesium alloy for stents according to the present invention and the method for manufacturing a microtube using the same will be described in detail with reference to the attached tables and drawings.

[0091] According to one aspect, a highly corrosion-resistant biodegradable magnesium alloy for a stent is provided, comprising, with respect to the total weight of the highly corrosion-resistant biodegradable magnesium alloy for a stent, 0.1 wt% or more and less than 3.0 wt% Zn; more than 0.0 wt% and less than 2.0 wt% Mn; more than 0.0 wt% and less than 2.0 wt% Sr; more than 0.0 wt% and less than 1.0 wt% Ca; and the remainder Mg, wherein, with respect to the total weight of the highly corrosion-resistant biodegradable magnesium alloy for a stent, the content ratio of Sr to Zn, Sr / Zn, is 0.3 to 2.5.

[0092] Zn in the present invention is an essential element for the human body, and a deficiency may disrupt physiological functions. In the Mg alloy of the present invention, Zn can contribute to the formation of a passivation film to improve corrosion characteristics and contribute to strength improvement through solid solution strengthening. Although not limited thereto, it may be suitable for the simultaneous improvement of strength and corrosion resistance to include Zn in an amount of 0.1 wt% or more and less than 3.0 wt% relative to the total weight of the magnesium alloy, more suitable to include it in an amount of 0.1 wt% or more and less than 2.0 wt%, more suitable to include it in an amount of 0.5 wt% or more and less than 2.0 wt%, and more suitable to include it in an amount of 0.5 wt% or more and less than 1.5 wt%. If the Zn content increases to 3.0 wt% or more, the total fraction of the secondary phase may increase rapidly.

[0093] The Mn in the present invention is a non-toxic element that plays a major role in the activation of enzyme systems, reacts with and removes Fe impurities, and can contribute to the improvement of corrosion properties. In addition, it can contribute to the improvement of strength and elongation in Mg alloys. Although not limited thereto, including Mn in an amount greater than 0.0 wt% and less than or equal to 2.0 wt% with respect to the total weight of the magnesium alloy may be suitable for the simultaneous improvement of strength and corrosion resistance, and including it in an amount greater than or equal to 0.3 wt% and less than or equal to 1.8 wt% may be more suitable.

[0094] The Sr in the present invention is a bone formation-promoting element that activates osteoblasts and inhibits bone resorption, thereby having an effect similar to that of Ca. In addition, there may be an effect of improving strength through grain refinement in Mg alloys. Although not limited thereto, including Sr in an amount greater than 0.0 wt% and less than 2.0 wt% with respect to the total weight of the magnesium alloy may be suitable for simultaneous improvement of strength and corrosion resistance, and including it in an amount greater than 0.0 wt% and less than or equal to 1.0 wt% may be suitable for improving strength and corrosion resistance.

[0095] Ca in the present invention is an essential element for the human body and is a bone constituent element. It can induce bone formation and maturation through calcification. In addition, there may be an effect of improving strength through grain refinement in Mg alloys. Although not limited thereto, it may be suitable to include Ca in an amount of 0.0 wt% or more and less than 1.0 wt% with respect to the total weight of the magnesium alloy for the simultaneous improvement of strength and corrosion resistance, and 0.0 wt% or more and less than 0.5 wt% may be more suitable.

[0096] Therefore, in this invention, Zn, Mn, Sr, and Ca are all biocompatible components and are harmless, and by adding Zn, Mn, Sr, and Ca in combination, the corrosion resistance of the magnesium alloy can be improved through the suppression of microgalvanic corrosion between the matrix and impurities and the improvement of the passivation characteristics of the film formed on the surface.

[0097] Although not limited thereto, the above-mentioned high-corrosion-resistant biodegradable magnesium alloy for stents may be suitable for improving hydrogen generation rate, yield strength, and tensile strength by including Sr and Zn such that the Sr / Zn content ratio is 0.3 to 2.5 with respect to the total weight of the magnesium alloy for biodegradable microtubes, and it may be more suitable for the Sr / Zn content ratio to be greater than 0.38 to 2.5 or less, and even more suitable for it to be greater than 0.47 to 2.5 or less.

[0098] According to another aspect, the highly corrosion-resistant biodegradable microtube for stents of the present invention is made of the highly corrosion-resistant biodegradable magnesium alloy for stents of the present invention. As described above, the highly corrosion-resistant biodegradable microtube for stents made of the highly corrosion-resistant magnesium alloy for stents of the present invention simultaneously improves the hydrogen generation rate, yield strength, and tensile strength, and in particular, can prevent the microtube inserted into the body from failing too early due to uncontrolled corrosion of the magnesium microtube.

[0099] Although not limited to this, the highly corrosion-resistant biodegradable microtube for stents, made of the highly corrosion-resistant magnesium alloy for stents of the present invention, can be used in stent insertion procedures to treat vascular stenosis in which the inner diameter of important blood vessels in the human body, including coronary arteries, basilar arteries, and cerebral arteries, narrows as endothelial cells are damaged due to various causes.

[0100] Although not limited thereto, the outer diameter of the highly corrosion-resistant biodegradable microtube for the stent is 1.0 mm to 4.0 mm and the wall thickness of the highly corrosion-resistant biodegradable microtube for the stent is 0.15 mm to 0.25 mm, which may be suitable for efficiently manufacturing a microtube for the stent with improved hydrogen generation rate, yield strength, and tensile strength.

[0101] The outer diameter of the above-described highly corrosion-resistant biodegradable microtube for stents may vary depending on the size of the blood vessel to which it is applied or the patient's condition. For example, approximately 3.5 mm may be suitable for peripheral blood vessels, and approximately 2 mm or less may be suitable for the cardiovascular system. Therefore, it may be appropriate to adjust the outer diameter so that the highly corrosion-resistant biodegradable microtube for stents of the present invention can be constructed to be as thin as possible while maintaining excellent mechanical properties. Although not limited thereto, if the outer diameter of the above-described highly corrosion-resistant biodegradable microtube for stents is less than 1.0 mm, the yield strength, tensile strength, and stability of the microtube may be reduced, and if the outer diameter exceeds 4.0 mm, deformation of the roundness may occur during the drawing process and excessive pressure may be applied when inserted into a blood vessel or airway. Furthermore, the outer diameter of the above-described highly corrosion-resistant biodegradable microtube for stents may be varied to match the size of the blood vessel to which it is applied.

[0102] If the wall thickness of the above-mentioned highly corrosion-resistant biodegradable microtube for the stent is less than 0.15 mm, there is a problem that damage occurs during processing due to the thin wall thickness of the microtube, and if the wall thickness exceeds 0.25 mm, there may be a problem that heat transfer is not uniform during processing.

[0103] Although not limited to this, the highly corrosion-resistant biodegradable microtube for the stent described above may be suitable when extruded at an extrusion ratio of 40:1 to 260:1, as this results in a uniform microstructure of the microtube and allows defects to be easily removed during casting.

[0104] Although not limited thereto, the highly corrosion-resistant biodegradable microtube for the stent may be suitable for having an outer or inner diameter roundness of 0% to 1.5%, as this allows for even pressure to be applied to the blood vessel wall. If the roundness of the highly corrosion-resistant biodegradable microtube for the stent exceeds 1.5%, biocompatibility may be reduced due to uneven contact with biological tissue within the blood vessel.

[0105] Although not limited thereto, the above-mentioned highly corrosion-resistant biodegradable microtubes for stents may be suitable for having an average grain size of 3 μm to 10 μm, as this allows for simultaneous improvement of yield strength and tensile strength without reducing the hydrogen generation rate of the highly corrosion-resistant biodegradable microtubes for stents. If the average grain size of the highly corrosion-resistant biodegradable microtubes for stents is less than 3 μm, the hydrogen generation rate may increase, and if the average grain size exceeds 10 μm, the effect of improving yield strength and tensile strength through grain refinement may decrease.

[0106] Although not limited thereto, the yield strength of the above-mentioned highly corrosion-resistant biodegradable microtube for a stent may be 130 MPa or more, 150 MPa or more, 160 MPa or more, 170 MPa or more, 176 MPa or more, 180 MPa or more, 190 MPa or more, 220 MPa or more, 230 MPa or more, 235 MPa or more, 240 MPa or more, 245 MPa or more, 250 MPa or more, 255 MPa or more, and 260 MPa or more, thereby satisfying the strength required as a highly corrosion-resistant biodegradable stent material.

[0107] Although not limited thereto, the tensile strength of the above-mentioned highly corrosion-resistant biodegradable microtube for a stent may be 210 MPa or more, 220 MPa or more, 230 MPa or more, 235 MPa or more, 240 MPa or more, 245 MPa or more, 250 MPa or more, 255 MPa or more, 260 MPa or more, 265 MPa or more, 270 MPa or more, and 272 MPa or more, thereby satisfying the strength required as a highly corrosion-resistant biodegradable stent material.

[0108] Although not limited thereto, the above-mentioned highly corrosion-resistant biodegradable microtube for stents has a hydrogen generation rate of 0.03 ml / cm 2 The yield strength can be 176 MPa or higher while being less than 1 / hr (see Fig. 14a). Therefore, the corrosion-resistant biodegradable microtube for stents of the present invention can simultaneously improve corrosion resistance and yield strength.

[0109] Although not limited thereto, the above-mentioned highly corrosion-resistant biodegradable microtube for stents has a hydrogen generation rate of 0.025 ml / cm 2 The tensile strength can be 240 MPa or more while being less than 1 / hr (see Fig. 14b). Therefore, the highly corrosion-resistant biodegradable microtube for stents of the present invention can simultaneously improve corrosion resistance and tensile strength.

[0110] Although not limited thereto, when the extrusion ratio of the highly corrosion-resistant biodegradable microtube for the stent is 40:1 to 150:1, the elongation may be 6% or more, 7% or more, 8% or more, 9% or more, 10% or more, 11% or more, 12% or more, 13% or more, 14% or more, 15% or more, 16% or more, 17% or more, and 18% or more, so that the processability and the highly corrosion-resistant biodegradable microtube for the stent may be suitable for ensuring mechanical stability and durability in an intravascular environment.

[0111] Although not limited thereto, when the extrusion ratio of the above-mentioned highly corrosion-resistant biodegradable microtube for stent is 40:1 to 150:1, the hydrogen generation rate is 0.015 ml / cm² 2 It may be suitable for the rate to be less than / hr. Accordingly, the highly corrosion-resistant biodegradable magnesium alloy for stents of the present invention can prevent the magnesium stent from corroding and losing function before treatment is completed due to uncontrolled corrosion.

[0112] Although not limited thereto, the above-mentioned highly corrosion-resistant biodegradable microtube for a stent is provided with a stent microtube having improved hydrogen generation rate, yield strength, and tensile strength having at least one of the following (1) to (5) characteristics.

[0113] (1) Hydrogen generation rate is 0.03 ml / cm 2 / hr Lee Ha-im

[0114] (2) Yield strength is 130 MPa or higher

[0115] (3) Tensile strength is 210 MPa or higher

[0116] (4) The biodegradation rate is 2.1 mm / y or less based on the amount of hydrogen generated.

[0117] (5) The biodegradation rate is 1.2 mm / y or less based on weight loss.

[0118]

[0119] FIG. 1 is a schematic diagram illustrating a method for manufacturing a stent made of a highly corrosion-resistant biodegradable magnesium alloy for stents according to one embodiment of the present invention.

[0120] Referring to FIG. 1, a method for manufacturing a highly corrosion-resistant biodegradable microtube for a stent according to another aspect of the present invention comprises: i) melting together, with respect to the total weight of the highly corrosion-resistant biodegradable magnesium alloy for a stent, Zn in an amount of 0.1 wt% or more and less than 3.0 wt%; Mn in an amount of more than 0.0 wt% and less than or equal to 2.0 wt%; Sr in an amount of more than 0.0 wt% and less than or equal to 2.0 wt%; Ca in an amount of 0.0 wt% or more and less than 1.0 wt%; and the remainder Mg to obtain a molten mixture; ii) casting the molten mixture of step i) to produce a first billet; iii) extruding the first billet produced in step ii) to produce a rod; and iv) drilling the center of the rod produced in step iii) to produce a hollow second billet. and v) a step of manufacturing a microtube by extruding a hollow second billet manufactured in step iv); wherein, with respect to the total weight of the magnesium alloy for biodegradable microtubes in step i), the content ratio of Sr to Zn Sr / Zn is 0.3 to 2.5.

[0121] Step i) is a step of obtaining a molten mixture by melting together 0.1 wt% or more and less than 3.0 wt% Zn; more than 0.0 wt% and less than 2.0 wt% Mn; more than 0.0 wt% and less than 2.0 wt% Sr; more than 0.0 wt% and less than 1.0 wt% Ca; and the remainder Mg together with respect to the total weight of the highly corrosion-resistant biodegradable magnesium alloy for stents. Although not limited thereto, in step i), a content ratio of Sr to Zn of 0.3 to 2.5 Sr / Zn with respect to the total weight of the magnesium alloy for biodegradable microtubes may be suitable for improving hydrogen generation rate, yield strength, and tensile strength.

[0122] Referring to FIG. 1 (a), step ii) is a step of manufacturing a first billet by casting the molten mixture of step i). Although not limited thereto, the first billet may be cylindrical, can-shaped with both openings closed, or hollow cylindrical. After casting the molten mixture of step i), it may be poured into a mold to be manufactured into a cylindrical shape, can-shaped with both openings closed, or hollow cylindrical shape.

[0123] Referring to FIG. 1 (b), step iii) is a step of manufacturing a rod by extruding the first billet produced in step ii). Although not limited thereto, specific methods for performing the extrusion process in this step may include an indirect extrusion process, a direct extrusion process, a hydrostatic extrusion process, or an impact extrusion process, and the direct extrusion process may be suitable for securing the mechanical properties of the material.

[0124] Referring to FIG. 1(b), step iv) is a step of manufacturing a hollow second billet by drilling the center of the rod manufactured in step iii). The hollow second billet may be in the shape of a hollow cylinder with openings on both sides, and may be manufactured by mechanically processing the center of the rod manufactured in step iii).

[0125] Referring to Fig. 1(c), step v) is a step of manufacturing a microtube by extruding the hollow second billet manufactured in step iv). The specific method for performing the extrusion process in this step may be the same as in step iii).

[0126] Referring to (d) of FIG. 1, the microtube manufactured in step v) may further include a step of cold drawing, although this is not limited thereto. According to the above configuration, the yield strength and tensile strength of the microtube can be improved simultaneously. Although not limited thereto, the tip of the microtube may be forcibly pulled by a motor and a chain using a transfer device equipped with a pulling jaw and passed through a die to improve surface roughness and shape precision, and a microtube of desired dimensions may be produced by cutting it to a desired length.

[0127] Although not limited thereto, the microtubes produced in step v) above may be extruded at an extrusion ratio of 40:1 to 260:1. According to the above configuration, the microstructure of the microtubes becomes uniform and defects can be easily removed during casting, making it suitable.

[0128] Although not limited thereto, the steps of extruding the first billet and extruding the second billet in steps iii) and v) above are suitable for extruding at 350°C to 450°C, as this allows for the improvement of the strength characteristics of the microtube as fine precipitates are uniformly distributed at the grain boundaries of the microstructure. If the extrusion temperature is below 350°C, extrudability may be reduced, making it difficult to manufacture the microtube, and if the extrusion temperature exceeds 450°C, damage to the crystal structure of the microtube may occur and a decrease in surface roughness may occur.

[0129] Although not limited thereto, the steps of extruding the first billet and extruding the second billet in steps iii) and v) above may be suitable for efficiently manufacturing microtubes for stents with improved hydrogen generation rate, yield strength, and tensile strength when extruded at an extrusion speed of 0.5 mm / s to 1.5 mm / s. If the extrusion speed is less than 0.5 mm / s, there is a problem that the processing time is excessively long, and if the extrusion speed exceeds 1.5 mm / s, there may be a problem that the high mechanical properties intended to be imparted through processing cannot be secured.

[0130] Referring to FIG. 1(e), a method for manufacturing a highly corrosion-resistant biodegradable microtube for a stent may further include a step of laser cutting to form a complex pattern of the stent after step iv). Laser cutting can be performed using known techniques.

[0131] Referring to (f) of FIG. 1, a method for manufacturing a highly corrosion-resistant biodegradable microtube for a stent may further include a step of electrochemically polishing using a known technique to improve surface roughness after the laser cutting step.

[0132] According to one embodiment, the microtube manufactured in step v) may further include a step of rapid cooling. With the above configuration, the hydrogen generation rate can be controlled while improving the yield strength and tensile strength of the microtube. Although not limited thereto, the metal cooling may be performed by injecting argon gas.

[0133] Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

[0134]

[0135] [Example]

[0136] Examples and Comparative Examples: Preparation of Microtubes Made of Magnesium Alloy

[0137] FIG. 1 is a schematic diagram illustrating a method for manufacturing a stent made of a highly corrosion-resistant biodegradable magnesium alloy for a stent according to one embodiment of the present invention. Referring to FIG. 1, a method for manufacturing a highly corrosion-resistant biodegradable microtube for a stent comprises: i) a step of preparing a molten magnesium mixture of Examples 1 to 6 (Z1, ZM115, ZX101, JX0301, JX0103, ZM0418) and Comparative Examples 1 and 2 (MZ01, Z3) with the compositions shown in Table 3; ii) a step of casting the molten mixture of step i) to manufacture a first billet (Fig. 1 (a)); iii) a step of extruding the first billet manufactured in step ii) to manufacture a rod (Fig. 1 (b)); and iv) a step of drilling the center of the rod manufactured in step iii) to manufacture a hollow second billet. and v) a step of manufacturing a microtube by extruding the hollow second billet manufactured in step iv) ((c) of Fig. 1); the process was carried out in that order.

[0138] In the method for manufacturing highly corrosion-resistant biodegradable microtubes for stents, when performing two-stage extrusion, extrusion can be performed using a 500-ton horizontal extruder at 400°C. In two-stage extrusion, increasing the extrusion ratio may result in finer particles and weaker texture strength.

[0139] Referring to (d) of Fig. 1, the method for manufacturing a highly corrosion-resistant biodegradable microtube for a stent involves cold drawing and heat treatment after step iv) to improve yield strength and tensile strength.

[0140] FIG. 2 is a photograph of a microtube made of a highly corrosion-resistant biodegradable magnesium alloy for a stent manufactured by two-stage extrusion according to one embodiment of the present invention, and the manufactured microtube. According to FIG. 2, the microtube manufactured by two-stage extrusion can be manufactured with an outer diameter of 3.5 mm and a wall thickness of 0.25 mm or less, and it can be confirmed that it exhibits high elongation and high strength.

[0141] FIG. 3 is a diagram showing a microtube made of a highly corrosion-resistant biodegradable magnesium alloy for a stent manufactured by two-stage extrusion and cold drawing according to one embodiment of the present invention, and graphs of elongation and yield strength. According to FIG. 3, the microtube manufactured by two-stage extrusion and cold drawing exhibits high elongation and high strength, and the texture and microstructure of the manufactured microtube can be confirmed.

[0142] FIG. 4 is a schematic diagram illustrating a method for manufacturing a microtube made of a highly corrosion-resistant biodegradable magnesium alloy for a stent according to one embodiment of the present invention. According to FIG. 4, the method for manufacturing a highly corrosion-resistant biodegradable microtube for a stent comprises the steps of: casting a highly corrosion-resistant biodegradable magnesium alloy for a stent to produce a first billet with a diameter of 80 mm and a length of 100 mm (Fig. 4 (a)); extruding the produced first billet to produce a rod with a diameter of 16 mm and a length of 4 m (Fig. 4 (b)); and drilling the center of the produced rod to produce a hollow second billet having an outer diameter of 13.9 mm, a length of 30 mm, and an inner diameter of 3.1 mm (Fig. 4 (c)). The method was performed by extruding the manufactured hollow second billet to produce a microtube having an outer diameter of 1.50 mm to 3.50 mm, a wall thickness of 0.15 mm to 0.25 mm, and a length of 1,300 mm to 3,000 mm (Fig. 4 (d)).

[0143] FIG. 5(a) is a photograph of a drawing apparatus for a microtube made of a highly corrosion-resistant biodegradable magnesium alloy for a stent according to one embodiment of the present invention, and FIG. 5(b) is a photograph of a microtube made of a highly corrosion-resistant biodegradable magnesium alloy for a stent according to one embodiment of the present invention before and after cold drawing. According to FIG. 5(b), it can be seen that a microtube having an outer diameter of 2.1 mm and a wall thickness of 0.15 mm before drawing has an outer diameter of 2.0 mm and a wall thickness of 0.15 mm after drawing.

[0144]

[0145] Experimental Example 1. Evaluation of Dimensional Accuracy of Microtubes Made of Highly Corrosion-Resistant Biodegradable Magnesium Alloy for Stents

[0146] The dimensional accuracy of OD3.5×WT0.25 (extrusion ratio 57:1), OD2.1×WT0.20 (extrusion ratio 127:1), and OD1.5×WT0.15 (extrusion ratio 240:1), manufactured by a two-stage extrusion process, is shown in FIG. 6 and Table 1. FIG. 7 is a diagram showing the definition and measurement method of out-of-roundness, where a value closer to 0 indicates a more round shape.

[0147] The roundness of the outer diameter (OD) and inner diameter (ID), measured at four locations at 45-degree intervals, can be defined as follows.

[0148] OD R = 2 Х (OD max - OD min ) / (OD max + OD min ) Х 100

[0149] ID R = 2 Х (ID max - ID min ) / (ID max + ID min ) Х 100

[0150] WT avg is the average wall thickness at 8 points measured at 45-degree intervals.

[0151]

[0152]

[0153] According to Table 1 above, based on the definition that a value closer to 0 indicates perfect roundness, the roundness of the outer diameter is 0.003–0.005% and the inner diameter is 0.006–0.008%, demonstrating excellent shape precision regardless of the extrusion ratio. The measured average wall thickness corresponds to 92.7–98.5% of the target thickness. For higher precision, variation in wall thickness must be significantly reduced, and dimensional uniformity in the longitudinal direction must also be verified.

[0154] FIG. 8 is an image showing the dimensional accuracy of a microtube made of a highly corrosion-resistant biodegradable magnesium alloy for a stent according to one embodiment of the present invention before and after centrifugal processing. According to FIG. 8, when the dimensions of the cross-section of the microtube were measured for Comparative Example 1 (MZ01) of OD2.1×WT0.20 and OD2.0×WT0.15 and Example 2 (ZM115) of OD2.1×WT0.20 of the present invention, the outer diameter and wall thickness decreased after centrifugal processing.

[0155] FIG. 9 is an image showing an accredited test report measuring the outer diameter, inner diameter, and wall thickness of a microtube made of a highly corrosion-resistant biodegradable magnesium alloy for a stent according to Comparative Example 1 (MZ01) and Example 2 (ZM115) of the present invention. FIG. 9 shows the results of an accredited test report measuring the roundness and wall thickness for Comparative Example 1 (MZ01) with an OD of 2.0 × WT of 0.15 and Example 2 (ZM115) with an OD of 2.1 × WT of 0.20.

[0156]

[0157] Experimental Example 2. Room temperature tensile test evaluation of microtubes made of highly corrosion-resistant biodegradable magnesium alloy for stents

[0158] The tensile test of microtubes made of highly corrosion-resistant biodegradable magnesium alloy for extruded stents was 1×10⁻⁶ at room temperature -3 s-1 The test was performed using a general-purpose testing machine (INSTRON 5982) at a quasi-static strain rate. Based on ASTM E8, tensile specimens with a gauge length of 25 mm were prepared from microtubes, and at least three tests were performed in the extrusion direction (ED) under each condition.

[0159] Figure 10 is a graph showing the results of a room temperature tensile test of a microtube made of a highly corrosion-resistant biodegradable magnesium alloy for a stent according to Example 2 (ZM115) of the present invention. The room temperature tensile test of the microtube was performed using the microtube tensile test fixture shown in Figure 11. According to Figure 10, OD2.1×WT0.20 and OD1.5×WT0.15 exhibited superior tensile properties compared to the rod.

[0160] Table 2 shows the extrusion temperature, extrusion ratio, extrusion speed, yield strength, tensile strength, and elongation of rods (ROD) manufactured by a single-stage extrusion process, and OD3.5×WT0.25 (extrusion ratio 57:1), OD2.1×WT0.20 (extrusion ratio 127:1), and OD1.5×WT0.15 (extrusion ratio 240:1) manufactured by a two-stage extrusion process.

[0161]

[0162]

[0163] According to Table 2 above, as the extrusion ratio increased, the yield strength and tensile strength increased. As the extrusion ratio increased from 57:1 to 127:1, the elongation increased, and at an extrusion ratio of 240:1, the elongation decreased.

[0164]

[0165] Experimental Example 3. Evaluation of Biodegradability of Microtubes Made of Highly Corrosion-Resistant Biodegradable Magnesium Alloy for Stents through Hydrogen Capture Test

[0166] The hydrogen generation rate of microtubes made of highly corrosion-resistant biodegradable magnesium alloy for stents according to Comparative Example 1 (MZ01) and Example 2 (ZM115) of the present invention was measured.

[0167] The hydrogen generation rate was measured in ml at 24-hour intervals by collecting hydrogen (H2) gas generated upon the decomposition of magnesium microtubes in a bio-mimicking environment after immersion in PBS solution for 7 days. After summing the hydrogen generation amounts measured over 7 days, the surface area of ​​the microtubes (cm²) 2 The hydrogen generation rate of the microtubes was evaluated by dividing it by ) and total time (hr).

[0168] Figure 12 is a graph showing the hydrogen generation rate of microtubes made of a highly corrosion-resistant biodegradable magnesium alloy for stents according to Comparative Example 1 (MZ01) and Example 2 (ZM115) of the present invention. As shown in Figure 13, the measurement of the hydrogen generation rate of the microtubes was conducted under expert witness evaluation. According to Figure 12, the hydrogen generation rate of the microtubes made of a highly corrosion-resistant biodegradable magnesium alloy for stents according to Comparative Example 1 (MZ01) and Example 2 (ZM115) of the present invention is 0.004 ml / cm² 2 / hr to 0.007 ml / cm² 2 Expressed as / hr, 0.01 ml / cm² 2 It showed a hydrogen generation rate of less than / hr.

[0169]

[0170] Experimental Example 4. Evaluation of Room Temperature Tensile and Biodegradable Properties of Microtubes Made of Highly Corrosion-Resistant Biodegradable Magnesium Alloy for Stents

[0171] Microtubes made of magnesium alloys of Examples 1 to 6 and Comparative Example 1 (MZ01) and Comparative Example 2 (Z3) were prepared with the compositions shown in Table 3.

[0172] Microtubes made of magnesium alloys of Examples 1 to 6 and Comparative Example 1 (MZ01) and Comparative Example 2 (Z3) were prepared with the compositions shown in Table 3. Table 3 shows the room temperature tensile properties and biodegradability of microtubes with extrusion ratios of 57:1, 127:1, and 240:1.

[0173]

[0174]

[0175] FIG. 14a is a graph showing the hydrogen generation rate and yield strength (TYS) according to the extrusion ratio of microtubes made of highly corrosion-resistant biodegradable magnesium alloy for stents according to Comparative Examples 1 and 2 (MZ01, Z3) and Examples 1 to 6 (Z1, ZM115, ZX101, JX0301, JX0103, ZM0418) of the present invention. According to FIG. 14a, the microtubes made of highly corrosion-resistant biodegradable magnesium alloy for stents according to Comparative Examples 1 and 2 (MZ01, Z3) and Example 5 (JX0103) showed a yield strength of 175 MPa or less at all extrusion ratios. In contrast, the microtubes made of highly corrosion-resistant biodegradable magnesium alloy for stents according to Examples 1 to 4 (Z1, ZM115, ZX101, JX0301) and 6 (ZM0418) generally showed a tendency for yield strength to increase as the extrusion ratio increased from 57:1 to 240:1.

[0176] According to Fig. 14a, 0.03 ml / cm² in all experimental groups except Comparative Example 2 (Z3) 2 It exhibited a hydrogen generation rate of less than 1 / hr. Therefore, it can be seen that the example exhibits a relatively higher yield strength at a lower hydrogen generation rate compared to the comparative example.

[0177] FIG. 14b is a graph showing the hydrogen generation rate and tensile strength (UTS) according to the extrusion ratio of microtubes made of highly corrosion-resistant biodegradable magnesium alloy for stents according to Comparative Examples 1 and 2 (MZ01, Z3) and Examples 1 to 6 (Z1, ZM115, ZX101, JX0301, JX0103, ZM0418) of the present invention. According to FIG. 14b, the microtubes made of highly corrosion-resistant biodegradable magnesium alloy for stents according to Comparative Example 1 (MZ01) and Example 5 (JX0103) exhibited a tensile strength of approximately 240 MPa or less at most extrusion ratios. The microtubes made of highly corrosion-resistant biodegradable magnesium alloy for stents according to Comparative Example 2 (Z3) exhibited a tensile strength of approximately 240 MPa or more at all extrusion ratios, but the hydrogen generation rate was 0.02 ml / cm² 2 It showed a tensile strength of / hr or higher. Microtubes made of highly corrosion-resistant biodegradable magnesium alloy for stents according to Examples 1 to 4 (Z1, ZM115, ZX101, JX0301) generally showed a tendency for tensile strength to increase as the extrusion ratio increased from 57:1 to 240:1. Microtubes made of highly corrosion-resistant biodegradable magnesium alloy for stents according to Example 6 (ZM0418) showed a tensile strength of 262.5 MPa or higher at all extrusion ratios, but showed a tendency for tensile strength to decrease slightly as the extrusion ratio increased from 127:1 to 240:1.

[0178] According to Fig. 14b, 0.03 ml / cm² in all experimental groups except Comparative Example 2 (Z3) 2 It exhibited a hydrogen generation rate of less than 1 / hr. Therefore, it can be seen that the example exhibits relatively high tensile strength at a low hydrogen generation rate compared to the comparative example.

[0179] FIG. 14c is a graph showing the hydrogen generation rate and elongation (EL) according to the extrusion ratio of microtubes made of highly corrosion-resistant biodegradable magnesium alloy for stents according to Comparative Examples 1 and 2 (MZ01, Z3) and Examples 1 to 6 (Z1, ZM115, ZX101, JX0301, JX0103, ZM0418) of the present invention. According to FIG. 14c, Examples 3 to 6 (ZX101, JX0301, JX0103, ZM0418), excluding Examples 1 and 2 (Z1, ZM115), showed a tendency for the elongation to decrease as the extrusion ratio increased from 57:1 to 240:1.

[0180] According to Fig. 14c, 0.03 ml / cm² in all experimental groups except Comparative Example 2 (Z3) 2 It showed a hydrogen generation rate of less than / hr.

[0181] FIG. 15 is a graph showing the yield strength (TYS), tensile strength (UTS), and elongation (EL) according to the extrusion ratio of microtubes made of highly corrosion-resistant biodegradable magnesium alloy for stents according to Comparative Examples 1 and 2 (MZ01, Z3) and Examples 1 to 6 (Z1, ZM115, ZX101, JX0301, JX0103, ZM0418) of the present invention. According to FIG. 15, the yield strength and tensile strength of microtubes made of highly corrosion-resistant biodegradable magnesium alloy for stents according to Comparative Examples 1 and 2 (MZ01, Z3) and Examples 1 to 6 (Z1, ZM115, ZX101, JX0301, JX0103, ZM0418) of the present invention showed an increasing trend as the extrusion ratio increased from 57:1 to 240:1. In contrast, the elongation of microtubes made of highly corrosion-resistant biodegradable magnesium alloy for stents according to Comparative Examples 1 and 2 (MZ01, Z3) and Examples 1 to 6 (Z1, ZM115, ZX101, JX0301, JX0103, ZM0418) of the present invention showed a tendency to decrease as the extrusion ratio increased from 57:1 to 240:1.

[0182] FIG. 16 is a graph showing the hydrogen generation rate and biodegradation rate according to the extrusion ratio of microtubes made of highly corrosion-resistant biodegradable magnesium alloy for stents according to Comparative Examples 1 and 2 (MZ01, Z3) and Examples 1 to 6 (Z1, ZM115, ZX101, JX0301, JX0103, ZM0418) of the present invention. According to FIG. 16, the hydrogen generation rate and biodegradation rate of microtubes made of highly corrosion-resistant biodegradable magnesium alloy for stents according to Comparative Examples 1 and 2 (MZ01, Z3) and Examples 1 to 6 (Z1, ZM115, ZX101, JX0301, JX0103, ZM0418) of the present invention generally showed an increasing trend as the extrusion ratio increased from 57:1 to 240:1, and the Examples showed lower hydrogen generation rates and biodegradation rates compared to the Comparative Examples.

[0183] FIGS. 17 to 19 are photographs showing the appearance of corroded specimens after a hydrogen capture test according to the extrusion ratio of microtubes made of highly corrosion-resistant biodegradable magnesium alloy for stents according to Comparative Examples 1 and 2 (MZ01, Z3) and Examples 1 to 6 (Z1, ZM115, ZX101, JX0301, JX0103, ZM0418) of the present invention. According to FIGS. 17 to 19, it can be seen that more corrosion occurred in the comparative examples compared to the examples.

[0184]

[0185] Experimental Example 5. Evaluation of the microstructure of a microtube made of a highly corrosion-resistant biodegradable magnesium alloy for stents

[0186] The microstructure of a microtube made of a highly corrosion-resistant biodegradable magnesium alloy for extruded stents was measured using an optical microscope (OM, OLYMPUS GX51).

[0187] FIG. 20a is a graph showing the inverse square root of the average grain size and the yield strength (TYS) of microtubes made of highly corrosion-resistant biodegradable magnesium alloy for stents according to Comparative Examples 1 and 2 (MZ01, Z3) and Examples 1 to 6 (Z1, ZM115, ZX101, JX0301, JX0103, ZM0418) of the present invention. According to FIG. 20a, the yield strength showed a tendency to increase as the grain size decreased. When the extrusion ratio of microtubes made of highly corrosion-resistant biodegradable magnesium alloy for stents increases, the amount of plastic deformation increases, resulting in a tensile strength enhancement effect through grain refinement.

[0188] FIG. 20b is a graph showing the inverse square root of the average grain size and the hydrogen generation rate of microtubes made of highly corrosion-resistant biodegradable magnesium alloy for stents according to Comparative Examples 1 and 2 (MZ01, Z3) and Examples 1 to 6 (Z1, ZM115, ZX101, JX0301, JX0103, ZM0418) of the present invention. According to FIG. 20b, the hydrogen generation rate tended to increase as the grain size decreased. When the extrusion ratio of microtubes made of highly corrosion-resistant biodegradable magnesium alloy for stents increases, the amount of plastic deformation increases, and the number of exposed grain boundaries increases, which can accelerate the hydrogen generation rate.

[0189] FIG. 21 is a figure showing the grain size and microstructure images according to the extrusion ratio of microtubes made of highly corrosion-resistant biodegradable magnesium alloy for stents according to Comparative Examples 1 and 2 (MZ01, Z3) and Examples 1 to 6 (Z1, ZM115, ZX101, JX0301, JX0103, ZM0418) of the present invention. According to FIG. 21, the microtubes made of highly corrosion-resistant biodegradable magnesium alloy for stents according to Examples 1 to 6 (Z1, ZM115, ZX101, JX0301, JX0103, ZM0418) of the present invention had smaller grain sizes at all extrusion ratios compared to Comparative Examples 1 and 2 (MZ01, Z3).

[0190]

[0191] Experimental Example 6. Evaluation of the texture of microtubes made of highly corrosion-resistant biodegradable magnesium alloy for stents

[0192] The texture of microtubules made of highly corrosion-resistant biodegradable magnesium alloy for extruded stents was measured using electron backscatter diffraction (EBSD, JEOL JSM-7800F). The EBSD measurements were performed with a step size of 0.3 μm in the 180 μm × 216 μm area for an extrusion ratio of 57:1, the 150 μm × 180 μm area for an extrusion ratio of 127:1, and the 100 μm × 120 μm area for an extrusion ratio of 240:1, using an acceleration voltage of 15 kV, and EDAX OIM Analysis TM Data with a confidence index of 0.08 or higher was processed with v8.6.

[0193] FIG. 22 is a figure showing pole figures (PF) according to the extrusion ratio of microtubes made of highly corrosion-resistant biodegradable magnesium alloys for stents according to Comparative Examples 1 and 2 (MZ01, Z3) and Examples 1 to 6 (Z1, ZM115, ZX101, JX0301, JX0103, ZM0418) of the present invention. (0001) A pole figure indicates that when stress is applied to the microtube from both sides (left and right) in the measurement area, the c-axis of each crystal grain rotates left and right to distribute the basal plane. As the extrusion ratio of microtubes made of highly corrosion-resistant biodegradable magnesium alloy for stents according to Comparative Examples 1 and 2 (MZ01, Z3) and Examples 1 to 6 (Z1, ZM115, ZX101, JX0301, JX0103, ZM0418) of the present invention increases, the maximum pole strength (I max ) generally showed a decreasing trend.

[0194]

[0195] Experimental Example 7. Animal implantation experiment of a stent manufactured with a microtube made of a highly corrosion-resistant biodegradable magnesium alloy for stents

[0196] FIG. 23a is an image showing a microtube made of a highly corrosion-resistant biodegradable magnesium alloy for a stent according to Example 2 (ZM115) of the present invention used in animal experiments. Specifically, FIG. 23a shows a microtube with dimensional accuracy of OD 2.1 × WT 0.20 (extrusion ratio 127:1) manufactured by a two-stage extrusion process.

[0197] Animal implantation experiments were conducted on microtubes made of highly corrosion-resistant biodegradable magnesium alloy for stents according to Comparative Example 1 (MZ01) and Example 2 (ZM115) of the present invention.

[0198] Figure 23b is an image showing a stent made from the microtube of Figure 23a.

[0199] FIG. 23c is a schematic diagram showing that the stent according to FIG. 23b is fabricated as a coated stent coated with PLA, and according to one embodiment of the present invention, the PLA-coated stent is implanted in the right blood vessel of an experimental animal and an uncoated stent is implanted in the left blood vessel. FIG. 23d is an image showing the results of angiography performed after implanting and placing the stent according to FIG. 23c. FIG. 23e is a photograph showing the results of dissecting an experimental animal sacrificed 4 weeks after implanting the stent according to FIG. 23c.

[0200] That is, FIGS. 23a to 23e show the results of confirming the implantation of Comparative Example 1 (MZ01) and Example 2 (ZM115) into the blood vessels of experimental animals, respectively, by angiography, and conducting follow-up examinations after 4 weeks. The experimental animal groups for Comparative Example 1 (MZ01) and Example 2 (ZM115) were each 3 animals. Furthermore, the microtube inserted into the right blood vessel of the experimental animal was coated with polylactic acid (PLA), a biodegradable bioplastic, while the microtube inserted into the left blood vessel was not coated.

[0201] Figure 24 is an image showing the results of a follow-up examination 4 weeks after implanting a stent made of a microtube made of a highly corrosion-resistant biodegradable magnesium alloy for stents according to Comparative Example 1 (MZ01) of the present invention into the blood vessel of an experimental animal. Figure 25 is an image showing the results of a follow-up examination 4 weeks after implanting a stent made of a microtube made of a highly corrosion-resistant biodegradable magnesium alloy for stents according to Example 2 (ZM115) of the present invention into the blood vessel of an experimental animal. As shown in Figures 24 and 25, both Comparative Example 1 (MZ01) and Example 2 (ZM115) remained in a stable state within the blood vessel even after 4 weeks. However, compared to Comparative Example 1 (MZ01), in the case of Example 2 (ZM115), it was confirmed that the dilation of the experimental animal's blood vessel was well maintained and the strut of the stent was well maintained.

[0202]

[0203] Experimental Example 8. Evaluation of physical properties of microtubes made of highly corrosion-resistant biodegradable magnesium alloy for stents due to rapid cooling during extrusion

[0204] The cooling effect was analyzed after rapidly cooling a microtube made of a highly corrosion-resistant biodegradable magnesium alloy for stents according to Comparative Example 1 (MZ01) and Examples 1 to 3 (Z1, ZM115, ZX101) of the present invention by injecting 25 L of argon (Ar) gas per minute.

[0205] FIG. 26 is a graph showing the results of a room temperature tensile test with or without rapid cooling of microtubes made of highly corrosion-resistant biodegradable magnesium alloys for stents according to Comparative Example 1 (MZ01) and Examples 1 to 3 (Z1, ZM115, ZX101) of the present invention. The room temperature tensile test of the microtubes was performed using the microtube tensile test fixture shown in FIG. 11. According to FIG. 26, in the case of Comparative Example 1 (MZ01), the yield strength increased upon cooling, whereas Examples 1 to 3 (Z1, ZM115, ZX101) showed differences in the increase in strength upon cooling depending on the alloy composition.

[0206] FIG. 27 is a photograph showing the appearance of a corroded specimen after a hydrogen capture test with or without rapid cooling of a microtube made of a highly corrosion-resistant biodegradable magnesium alloy for a stent according to Comparative Example 1 (MZ01) and Examples 1 to 3 (Z1, ZM115, ZX101) of the present invention. According to FIG. 27, in the case of Comparative Example 1 (MZ01), corrosion resistance was significantly reduced, whereas in the case of Examples 1 to 3 (Z1, ZM115, ZX101), it can be confirmed that there is no significant difference in the shape of the specimen before and after the test.

[0207] FIG. 28a is a graph showing the hydrogen generation rate and yield strength (TYS) of microtubes made of highly corrosion-resistant biodegradable magnesium alloy for stents according to Comparative Example 1 (MZ01) and Examples 1 to 3 (Z1, ZM115, ZX101) of the present invention, depending on whether rapid cooling is performed. According to FIG. 28a, microtubes made of highly corrosion-resistant biodegradable magnesium alloy for stents according to Comparative Example 1 (MZ01) and Examples 1 to 3 (Z1, ZM115, ZX101) showed a tendency for the yield strength to increase significantly and the hydrogen generation rate to increase after undergoing a rapid cooling process.

[0208] FIG. 28b is a graph showing the hydrogen generation rate and tensile strength (UTS) of microtubes made of highly corrosion-resistant biodegradable magnesium alloy for stents according to Comparative Example 1 (MZ01) and Examples 1 to 3 (Z1, ZM115, ZX101) of the present invention, depending on whether rapid cooling is performed. According to FIG. 28b, the microtubes made of highly corrosion-resistant biodegradable magnesium alloy for stents according to Comparative Example 1 (MZ01) and Examples 1 to 3 (Z1, ZM115, ZX101) showed a tendency for tensile strength to increase significantly and hydrogen generation rate to increase after undergoing a rapid cooling process. Therefore, it can be seen that physical properties can be controlled through a cooling process.

[0209] Therefore, it can be seen that while rapid cooling can improve yield strength and tensile strength, it also increases the hydrogen generation rate.

[0210] FIG. 28c is a graph showing the hydrogen generation rate and elongation (EL) of microtubes made of highly corrosion-resistant biodegradable magnesium alloy for stents according to Comparative Example 1 (MZ01) and Examples 1 to 3 (Z1, ZM115, ZX101) of the present invention, depending on whether rapid cooling is performed. According to FIG. 28c, Comparative Example 1 (MZ01) and Examples 1 to 3 (Z1, ZM115, ZX101) all showed a tendency for the elongation to decrease after cooling.

[0211]

[0212] Experimental Example 9 Evaluation of Microstructural and Texture Changes After Rapid Cooling of Microtubes Made of Highly Corrosion-Resistant Biodegradable Magnesium Alloy for Stents

[0213] The microstructure of a microtube made of a highly corrosion-resistant biodegradable magnesium alloy for extruded stents was measured using an optical microscope (OM, OLYMPUS GX51).

[0214] The texture of microtubules made of highly corrosion-resistant biodegradable magnesium alloy for extruded stents was measured using electron backscatter diffraction (EBSD, JEOL JSM-7800F). The EBSD measurements were performed in a 150 μm × 180 μm area with a step size of 0.3 μm at an acceleration voltage of 15 kV and an extrusion ratio of 127:1, and EDAX OIM Analysis TM Data with a confidence index of 0.08 or higher was processed with v8.6.

[0215] FIG. 29 is a figure showing the grain size and microstructure images of microtubes made of highly corrosion-resistant biodegradable magnesium alloy for stents according to Comparative Example 1 (MZ01) and Examples 1 to 3 (Z1, ZM115, ZX101) of the present invention, depending on whether rapid cooling is performed. FIG. 30 is a figure showing the pole figures (PF) of microtubes made of highly corrosion-resistant biodegradable magnesium alloy for stents according to Comparative Example 1 (MZ01) and Examples 1 to 3 (Z1, ZM115, ZX101) of the present invention, depending on whether rapid cooling is performed. (0001) The pole figure indicates that when stress is applied to the microtube from both sides (left and right) in the measurement area, the c-axis of each grain rotates left and right to distribute the basal plane. According to FIGS. 29 and 30, microtubes made of highly corrosion-resistant biodegradable magnesium alloys for stents according to Comparative Example 1 (MZ01) and Examples 1 to 3 (Z1, ZM115, ZX101) of the present invention all exhibited grain refinement and texture weakening upon cooling. In particular, compared to the Examples, Comparative Example 1 (MZ01) showed the largest change in grain size at 7.4 μm and the largest change in texture strength at 3.9 mrd. This suggests that, as before cooling, grain refinement plays a major role in increasing strength.

[0216]

[0217] Although the present disclosure has been described in detail through specific embodiments, this is for the purpose of specifically explaining the present disclosure and is not limited thereto. It is evident that modifications or improvements can be made by those skilled in the art within the technical scope of the present disclosure. All simple modifications or alterations of the present disclosure fall within the scope of the present disclosure, and the specific scope of protection of the present disclosure will be clarified by the appended claims.

Claims

1. With respect to the total weight of the highly corrosion-resistant biodegradable magnesium alloy for stents, 0.1 wt% or more and less than 3.0 wt% of Zn; Mn exceeding 0.0 wt% and not exceeding 2.0 wt%; Sr greater than 0.0 wt% and less than 2.0 wt%; 0.0 wt% or more and less than 1.0 wt% Ca; and Contains a residual amount of Mg, A highly corrosion-resistant biodegradable magnesium alloy for stents, wherein the Sr / Zn content ratio is 0.3 to 2.5 relative to the total weight of the magnesium alloy for biodegradable microtubes.

2. In Paragraph 1, A highly corrosion-resistant biodegradable magnesium alloy for stents, wherein the Sr / Zn content ratio is greater than 0.38 and less than or equal to 2.5 with respect to the total weight of the magnesium alloy for biodegradable microtubes.

3. In Paragraph 1, A highly corrosion-resistant biodegradable magnesium alloy for stents having a Zn content of 0.1 wt% or more and less than 1.5 wt% with respect to the total weight of the highly corrosion-resistant biodegradable magnesium alloy for stents.

4. In Paragraph 1, A highly corrosion-resistant biodegradable magnesium alloy for stents, wherein, based on the total weight of the highly corrosion-resistant biodegradable magnesium alloy for stents, the Sr content is greater than 0.0 wt% and less than or equal to 1.0 wt%, and the Ca content is 0.0 wt% or more and less than or equal to 1.0 wt%.

5. A highly corrosion-resistant biodegradable microtube for a stent, made of a highly corrosion-resistant biodegradable magnesium alloy for a stent according to any one of claims 1 to 4.

6. In Paragraph 5, A highly corrosion-resistant biodegradable microtube for a stent, wherein the outer diameter of the highly corrosion-resistant biodegradable microtube for a stent is 1.0 mm to 4.0 mm and the wall thickness of the highly corrosion-resistant biodegradable microtube for a stent is 0.15 mm to 0.25 mm.

7. In Paragraph 5, The above highly corrosion-resistant biodegradable microtube for a stent is a highly corrosion-resistant biodegradable microtube for a stent extruded at an extrusion ratio of 40:1 to 260:

1.

8. In Paragraph 5, The above-described highly corrosion-resistant biodegradable microtube for a stent is a highly corrosion-resistant biodegradable microtube for a stent having a roundness of 0% to 1.5% of the outer diameter or inner diameter.

9. In Paragraph 5, The above-described highly corrosion-resistant biodegradable microtube for a stent is a highly corrosion-resistant biodegradable microtube for a stent having an average grain size of 3 μm to 10 μm.

10. In Paragraph 5, A highly corrosion-resistant biodegradable microtube for a stent having a yield strength of 130 MPa or more.

11. In Paragraph 5, A highly corrosion-resistant biodegradable microtube for a stent having a tensile strength of 210 MPa or more.

12. In Paragraph 5, The above-mentioned highly corrosion-resistant biodegradable microtube for stents has a hydrogen generation rate of 0.03 ml / cm 2 Highly corrosion-resistant biodegradable microtubes for stents, having a yield strength of 176 MPa or higher and a yield strength of 176 MPa or less.

13. In Paragraph 5, The above-mentioned highly corrosion-resistant biodegradable microtube for stents has a hydrogen generation rate of 0.02 ml / cm 2 Highly corrosion-resistant biodegradable microtubes for stents, having a tensile strength of 230 MPa or more and a wattage of 1 / hr or less.

14. In Paragraph 5, The above highly corrosion-resistant biodegradable microtube for a stent has at least one of the following characteristics (1) to (5): (1) Hydrogen generation rate is 0.03 ml / cm 2 / hr Lee Ha-im (2) Yield strength is 130 MPa or higher (3) Tensile strength is 210 MPa or higher (4) The biodegradation rate is 2.1 mm / y or less based on the amount of hydrogen generated. (5) The biodegradation rate is 1.2 mm / y or less based on weight loss. 15.i) A step of melting together, with respect to the total weight of a highly corrosion-resistant biodegradable magnesium alloy for a stent, 0.1 wt% or more and less than 3.0 wt% Zn; more than 0.0 wt% and less than or equal to 2.0 wt% Mn; more than 0.0 wt% and less than or equal to 2.0 wt% Sr; more than 0.0 wt% and less than 1.0 wt% Ca; and the remainder Mg to obtain a molten mixture; ii) a step of manufacturing a first billet by casting the molten mixture of step i); iii) a step of manufacturing a rod by extruding the first billet manufactured in step ii); iv) a step of drilling the center of the rod produced in step iii) to produce a hollow second billet; and v) a step of manufacturing a microtube by extruding the hollow second billet manufactured in step iv); comprising, A method for manufacturing a highly corrosion-resistant biodegradable microtube for a stent, wherein, with respect to the total weight of the magnesium alloy for the biodegradable microtube in step i), the Sr / Zn content ratio is 0.3 to 2.

5.

16. In Paragraph 15, A method for manufacturing highly corrosion-resistant biodegradable microtubes for stents, wherein the microtubes manufactured in step v) further include a step of cold drawing.

17. In Paragraph 15, A method for manufacturing highly corrosion-resistant biodegradable microtubes for stents, comprising extruding the microtubes manufactured in step v) at an extrusion ratio of 40:1 to 260:

1.

18. In Paragraph 15, A method for manufacturing a highly corrosion-resistant biodegradable microtube for a stent, wherein the step of extruding the first billet and the step of extruding the second billet in steps iii) and v) are performed by extruding at 350 ℃ to 450 ℃.

19. In Paragraph 15, A method for manufacturing a highly corrosion-resistant biodegradable microtube for a stent, wherein the step of extruding the first billet and the step of extruding the second billet in steps iii) and v) are performed by extruding at an extrusion speed of 0.5 mm / s to 1.5 mm / s.

20. In Paragraph 15, A method for manufacturing highly corrosion-resistant biodegradable microtubes for stents, comprising a step of rapidly cooling the microtubes manufactured in step v).

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