JP2016202636A - Method for manufacturing tubular body - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for manufacturing a tubular body, capable of achieving uniform electrolytic polishing of the tubular body without irregularity by a simple method.SOLUTION: The method for manufacturing the tubular body includes at least one time of each of a step (a) and a step (b). In the step (a), an outer surface of the tubular body is electrolytically polished with an inner surface thereof being supported from the inside by an anode conductive member 13 in electrical contact with the tubular body. In the step (b), the inner surface of the tubular body is electrolytically polished with the outer surface thereof being supported from the outside by the anode conductive member in electrical contact with the tubular body.SELECTED DRAWING: Figure 2

Description

  The present invention relates to a method for manufacturing a tubular body.

  Tubular bodies, particularly medical tubular bodies, are generally medical devices for treating various diseases caused by stenosis or occlusion of blood vessels and other in vivo lumens. In particular, a stent is a medical device that is placed in a lesioned part in order to expand a lesioned part such as a stenosis or occlusion site from the inside and maintain the lumen inner diameter.

  The surface of a medical tubular body typified by a stent is required to be very smooth. Since the rough surface can cause inflammation during or after transplantation into the human body, or can cause tissue irritation or excessive irritation, the surface is generally smoothed later in the stent manufacturing process. Processing to finish.

  As a method for processing the surface of the medical tubular body, an electropolishing method is suitably used.

  For example, in Patent Document 1, a plurality of anodes are arranged at equal intervals so as to surround the outer circumference of the stent, the stent is rotated, a central cathode is arranged on the inner side of the stent, and a curved outer side is arranged around the outer circumference of the stent. There has been proposed a method of simultaneously electropolishing the inner surface and the outer surface of a stent by using a cathode.

  Patent Document 2 proposes an electropolishing method in which the stent rotates with the rotation of the roller, and the electrical contact between the anode wire and the stent changes continuously.

Japanese translation of PCT publication No. 2003-522841 Special table 2007-533845 gazette

  The electrolytic polishing methods of Patent Document 1 and Patent Document 2 provide a method that allows the operator to work safely because the operator does not touch the electrolytic solution or the electrode during the electrolytic polishing work, but a complicated apparatus is necessary, and therefore There was a problem that it was difficult to obtain a uniform electrolyte flow. Furthermore, rotating the stent moves the electrical contact between the stent and the anode conductive member. However, since the substantial area where the stent is electrically in contact with the anode conductive member is not large, the current density is reduced. There is a problem that uniformity is likely to occur, and a non-polished portion is generated on the electropolished surface.

  In order to solve the above-described problems, the present invention provides a method for manufacturing a tubular body that can achieve uniform electropolishing with less unevenness using a simple method and apparatus in electrolytic polishing of the tubular body. .

As a result of intensive studies for solving the above problems, the present inventor has completed the present invention. That is, this invention provides the manufacturing method of the tubular body of following [1]-[8].
[1] A method for producing a tubular body, comprising the following steps (a) and (b) at least once.
(A) a step of electropolishing the outer surface of the tubular body by supporting the inner surface of the tubular body from the inside by an anode conductive member that is in electrical contact with the tubular body; and (b) anode conductivity in electrical contact with the tubular body. The process of electropolishing the inner surface of the tubular body by supporting the outer surface of the tubular body from the outside by the elastic member
[2] The step (a) is characterized in that at least a part of the tubular body is in contact with the anode conductive member on the inner surface of the tubular body in a state where the diameter is expanded by 0.1 mm or more and 2.0 mm or less from the reference inner diameter. The method for producing a tubular body according to [1].
[3] In the step (b), at least a part of the tubular body is in contact with the anode conductive member on the outer surface of the tubular body with a diameter reduced from 0.1 mm to 2.0 mm from the reference outer diameter. The method for producing a tubular body according to [1], which is characterized in that
[4] The method for producing a tubular body according to any one of [1] to [3], wherein the number of steps (b) is less than the number of steps (a).
[5] The method for producing a tubular body according to any one of [1] to [4], wherein the step (a) and the step (b) are sequentially performed one or more times.
[6] The method for producing a tubular body according to [5], wherein one electropolishing time in the step (b) is shorter than one electropolishing time in the step (a).
[7] In the step (a), a voltage is supplied in the range of 10 seconds to 60 seconds and electrolytic polishing is performed. In the step (b), a voltage is supplied in the range of 3 seconds to 10 seconds and electrolytic polishing is performed. The manufacturing method of the tubular body as described in [6] characterized by including the process to do.
[8] The method for producing a medical tubular body according to any one of [1] to [7], wherein the tubular body is a stent.

  According to the present invention, it is possible to uniformly perform electropolishing using a simple method and apparatus, so that a tubular body having excellent smoothness can be produced.

It is the schematic which shows the conventional general electropolishing method. It is the schematic which shows the electrolytic polishing method which is one Embodiment of this invention. FIG. 3 is a cross-sectional view taken along a section A-A ′ in FIG. 2. It is the schematic which shows the electrolytic polishing method which is one Embodiment of this invention. FIG. 5 is a cross-sectional view taken along a cutting plane B-B ′ in FIG. 4.

  The method for manufacturing a tubular body according to the present invention includes a step of bringing an anode conductive member into contact with an inner surface of a tubular body and supporting the tubular body by electropolishing the outer surface, and bringing an anode conductive member into contact with the outer surface of the tubular body. In this manufacturing method, the process of electropolishing the inner surface of the tubular body while supporting the tubular body is included once or more.

  As described above, by separately polishing the inner surface and the outer surface of the tubular body, it is possible to perform a polishing process under a uniform current density distribution, and thus it is possible to manufacture a tubular body having excellent smoothness.

  In the present invention, it is only necessary to include the step of polishing the inner surface and the step of polishing the outer surface each time, and the inner surface may be polished first, or the outer surface may be polished first. Further, after either the outer surface or the inner surface is continuously polished a plurality of times, the other surface may be polished.

  Hereinafter, as a method for producing a tubular body according to the present invention, an embodiment will be described in detail with reference to the drawings, taking a stent as an example of a tubular body, but the present invention is not limited thereto.

<Tubular body>
Examples of tubular bodies, particularly medical tubular bodies, include (a) a coiled type made of a single linear metal or polymer material, (b) a type in which a metal tube is cut out by a laser, etc. ( C) There is a type in which linear members are assembled by welding with a laser or the like, and (d) a type in which a plurality of linear metals are woven.
The medical tubular body (hereinafter sometimes referred to as a tubular body) according to the present invention includes, for example, at least the outer surface of the tubular body from the first diameter that is the size inserted into the body lumen structure. A tubular body whose diameter is expanded to a second diameter that partially contacts the blood vessel wall is mentioned. In particular, a stent can be preferably used as a medical tubular body used for the formation of a body lumen structure such as a blood vessel, a ureter, and a bile duct.

  The material used for the stent is not particularly limited as long as it is a material that can endure deformation or indwelling such as expansion and contraction, but 316L stainless steel, tantalum, Co—Cr (cobalt chromium) alloy, which is a medical stainless steel, Ni-Ti (nickel titanium) alloy or the like can be preferably used.

  As a method for producing a metal stent, a method of performing electropolishing after cutting a tube-shaped material into a mesh shape with a laser can be preferably used.

  Electropolishing is the removal of the surface oxide film generated by laser processing of the strut portion, which is the bent linear portion of the stent, or heat treatment after laser processing, and the rounding of the sharp edges of the cross section of the strut. Etc. for the purpose. The electropolishing is preferably performed as a final finishing step for various purposes such as reduction of metal elution, improvement of fatigue characteristics, and improvement of cleanliness.

<Anode conductive member>
The material of the anode conductive member 13 is not particularly limited as long as it has sufficient conductivity. Examples thereof include metals such as stainless steel, titanium, copper, aluminum, platinum, and gold, or alloys thereof. it can.

  The shape of the anode conductive member 13 may be, for example, a plate shape, a core shape, a rod shape, or a wire shape as long as it can support the inner surface or the outer surface of the stent 14, and is shown in FIGS. 3 and 5. A pipe-like structure may be used. A pipe-shaped anode conductive member can be preferably used in that the area of the electrical contact 18 can be increased.

<Cathode>
The material of the cathode 16 is not particularly limited as long as it has sufficient conductivity. Examples thereof include metals such as stainless steel, titanium, copper, aluminum, platinum, and gold, or alloys thereof.

  The shape of the cathode 16 is not particularly limited as long as the stent 14 can be electropolished, and examples thereof include a plate shape, a core shape, a rod shape, and a wire shape. In order to increase the surface area of the cathode 16, Further, a mesh shape or a punching shape may be formed on the cathode 16 for the purpose of avoiding bubbles, temperature changes and concentration gradients of ions in the liquid generated during electropolishing.

<Electropolishing method>
FIG. 1 shows a conventional general electropolishing method for a stent in which an electrode is brought into contact with the stent and electropolishing.

  In the electrolytic polishing, in the electrolytic solution 17 stored in the electrolytic solution tank 15, the anode conductive member 13 connected to the positive electrode of the power source 11 by the conductive wire 12 a is in contact with the stent 14 that is an object to be polished. In addition, the cathode 16 connected to the negative pole of the power source 11 by the conductive wire 12b is set apart from the stent. In such an arrangement state, when a voltage is applied between the anode conductive member 13 and the cathode 16, the metal element on the surface dissolves in the electrolyte solution 17 in the stent 14 acting as the anode. As a result, the stent can be electropolished to have a smooth surface and gloss.

  However, in the conventional general electropolishing method, the region of the electrical contact 18 between the stent 14 and the anode conductive member 13 is not polished, and the region around the electrical contact in the liquid tank is compared with other regions. Since the current density greatly increases, the current density in the liquid tank becomes non-uniform, and as a result, there is a tendency for non-uniform polishing (polishing unevenness) to occur.

2 to 5 show a schematic view and a cross-sectional view of an embodiment of the present invention.
2 and 3 show a step of electrolytic polishing the outer surface of the stent 14 in a state where the anode conductive member 13 is in contact with the inner surface of the stent 14 which is the step (a) of the present invention.

On the other hand, FIGS. 4 and 5 show a step of electrolytic polishing the inner surface of the stent 14 in a state where the anode conductive member 13 is in contact with the outer surface of the stent 14 which is the step (b) of the present invention.
By performing the electropolishing so as to include each of the steps (a) and (b) at least once, the outer surface and the inner surface of the stent 14 can be uniformly electropolished without unevenness.

  The step (a) may be performed first, or the step (b) may be performed first. Moreover, after performing any one of (a) process or (b) process several times continuously, the other process can also be performed.

  In the manufacturing method of the present invention, the total area of the electrical contacts 18 where the stent 14 and the anode conductive member 13 are in contact with each other is that The contact is preferably made at least 50% or more of the inner area or outer area. By making the area of the electrical contact 18 sufficiently large, it is easy to obtain a uniform electrolyte current density around the stent 14.

  In the step (a), the anode conductive member 13 and the stent 14 are brought into contact with each other from the viewpoint that it is easy to fix the stent 14 without causing plastic deformation or breakage during electropolishing, and that local unevenness in current density does not easily occur. At this time, it is preferable that at least a part of the stent 14 is brought into contact with the diameter expanded from the reference inner diameter. Similarly, in the step (b), at least a part of the stent 14 is contracted from the reference outer diameter. It is preferable to contact with.

  In particular, it is preferable that the contact is made in a state where the diameter is increased or decreased from 0.1 mm to 2.0 mm in terms of easily fixing the stent stably and obtaining a smooth polished surface. It is particularly preferable that the contact is performed in a state where the diameter is increased or decreased by 1.0 mm or less.

  By pressing the stent 14 with the anode conductive member 13, the contact becomes stronger and the current flows more easily, so that the current density in the region around the electrical contact 18 is likely to be uniform, and the electrolyte around the stent 14. Since it is easy to make the current density uniform, it is possible to obtain a polished surface having excellent smoothness with little unevenness of polishing and a stent having a uniform dimension with little unevenness.

  A typical coronary artery and / or endovascular stent can be designed in a range of about 7 to about 200 mm in length and about 1 to about 12 mm in diameter, but even a stent 14 having a size outside the above range can be used in the present invention. Is preferably brought into contact with the anode conductive member 13 so as to be in an expanded or contracted state.

  In the present invention, the reference inner diameter or reference outer diameter refers to the diameter of the inner surface of the tubular body before electropolishing (hereinafter sometimes referred to as the inner diameter) in the manufacture of a medical tubular body, or the outer surface of the tubular body. A diameter (hereinafter, also referred to as an outer diameter) is shown.

  The cathode 16 is disposed away from the stent 14 on the opposite side to the surface where the stent 14 and the anode conductive member 13 are in contact during electropolishing. For example, in step (a), the cathode 16 is arranged so as to be separated from the stent 14 so as to surround the periphery of the stent 14.

  Furthermore, the cathode 16 is likely to give a constant electric field continuously to the stent 14, so that the cathode 16 has a constant distance from the stent 14 (hereinafter also referred to as an interelectrode distance). It is preferable to have a curved shape similar to the shape.

In the step (a), the distance between the electrodes of the stent 14 and the cathode 16 is not affected by bubbles generated during electropolishing, temperature change, concentration gradient of ions in the liquid, etc. The lower limit is preferably 10 mm or more, more preferably 20 mm or more, particularly preferably 30 mm or more, and the upper limit is 100 mm or less from the viewpoint of preventing contact between each other, or from the viewpoint of easily controlling the polishing amount in electrolytic polishing per unit time. Is preferable, 90 mm or less is more preferable, and 80 mm or less is particularly preferable.
In the step (a), the number of the cathodes 16 is not particularly limited, but may be constituted by one so as to cover the entire circumference of the stent 14 or may be divided.
In step (a), the surface area of the cathode 16 preferably has a surface area at least twice that of the stent 14 from the viewpoint of electron transfer.

In the step (b), it is preferable that the cathode 16 is disposed away from the stent 14 in the vicinity of the center of the inner periphery of the stent 14.
Furthermore, the cathode 16 has a curved shape or a rod-like or pipe-like shape so that the distance between the electrodes with the stent 14 is constant because it is easy to apply a constant electric field to the stent 14 continuously. Preferably it is.

In the step (b), it is preferable that the distance between the electrodes of the stent 14 and the cathode 16 be long enough not to cause contact between the electrodes.
In the step (b), the number of the cathodes 16 is not particularly limited, but may be constituted by one so as to be surrounded by the inner surface of the stent 14 or may be divided.

  The liquid tank 15 stores the electrolytic solution 17. The electrolytic solution 17 is not particularly limited. For example, in the case of a Ni—Ti (nickel titanium) alloy, a known alcohol-based or sulfuric acid-based aqueous solution may be used. The liquid tank 15 is preferably formed of a material that is not corroded by the electrolytic solution 17. In addition, during electrolytic polishing, it is preferable to stir the electrolytic solution 17 with a magnetic stirrer, a circulation pump, or the like in terms of suppressing the dispersion of bubbles generated during the electrolytic polishing, temperature change, and concentration gradient of ions in the liquid. Alternatively, or alternatively, the electrolytic solution 17 may be stirred by causing the anode conductive member 13 itself to perform operations such as rotation and swinging.

A voltage is applied to the anode conductive member 13 constituting the anode and the stent 14 and the cathode 16 so that the stent 14 can be electropolished to a desired smoothness.
The electropolishing time in the present invention is the time during which the anode conductive member 13 is brought into contact with the stent 14 and voltage is applied.

  A preferable voltage value for electropolishing is not particularly limited as long as a smooth surface can be obtained. However, a voltage value suitable for the metal material and electrolyte used may be selected. For example, a Ni-Ti (nickel titanium) alloy may be used. In the case, the range of 10-30V is preferable.

  The number of times of electropolishing is not particularly limited as long as a smooth surface can be obtained, but it is preferable to repeat the steps (a) and (b) 2 to 30 times in total.

  Since a typical coronary artery and / or endovascular stent can be designed in the range of about 1 to about 12 mm in diameter, the distance between the cathode 16 and the electrode of the stent 14 is greater in step (b) than in step (a). The number of times of electropolishing is that the number of times of electropolishing is easily reduced because it tends to diffuse substantially because it is limited, and it is easy to diffuse bubbles generated during electropolishing, and to suppress temperature change and concentration gradient of ions in liquid. It is preferable that the number of steps (b) is smaller than that.

  In addition, it is preferable to repeat the steps (a) and (b) one or more times in order to maintain the surface properties and the dimensional shape of the outer and inner surfaces of the stent 14.

  When the step (a) and the step (b) are sequentially performed one or more times, as described above, the distance between the electrodes of the cathode 16 and the stent 14 is limited in the step (b) rather than the step (a). Therefore, since the bubbles generated during the electropolishing are easily diffused, the temperature change and the concentration gradient of ions in the liquid can be easily suppressed. It is preferable that the time for one electropolishing in step (b) is shorter than the time.

  As the time for applying the voltage, that is, the electropolishing time, in the step (a), the lower limit of one electropolishing time is preferably 10 seconds or more, particularly preferably 20 seconds or more. The upper limit is preferably within 60 seconds, particularly preferably within 40 seconds.

  (B) As for the time of one electropolishing in the step, the lower limit is preferably 3 seconds or more, and particularly preferably 5 seconds or more. The upper limit is preferably 10 seconds or less, and particularly preferably 8 seconds or less.

The stent 14 can be taken out of the electrolytic solution 17 for each step (a) or (b), and the stent 14 can be washed with alcohol, water, nitric acid, or a combination thereof.
It is preferable to repeat the electrolytic polishing several times, and finally, wash by immersing in an ultrasonic bath at room temperature for 1 to 30 minutes.

  The method for producing a tubular body of the present invention can be preferably used for a medical tubular body because a smooth surface can be easily obtained.

  As described above, the manufacturing method of the stent according to the embodiment of the present invention has been described using a specific example. However, the present invention is not limited by the above embodiment, and conforms to the gist of the preceding and following descriptions. It is also possible to carry out with modification within the range to be obtained, all of which are included in the technical scope of the present invention.

Hereinafter, the present invention will be described more specifically based on examples and comparative examples.
Example 1
A stent 14 made of nickel titanium alloy having an outer diameter of 8.0 mm and an inner diameter of 7.6 mm was prepared.
(A) Step The stent 14 is inserted into a pipe-shaped anode conductive member 13 made of SUS304 having an outer diameter of 8.0 mm so that the stent 14 expands (+0.4 mm in diameter). The entire inner surface of the stent 14 (100% of the inner area of the stent) was brought into contact with and fixed to the outer surface of the sexual member 13.

In the electrolytic solution tank 15, an electrolytic solution 17 that is a commercially available electrolytic polishing solution for Ti alloy is stored, and has a curved shape so that the distance between the electrode and the stent 14 is equal (45 mm to 55 mm). A cathode 16 made of SUS304 was installed. (The recommended voltage of the electrolytic solution 17 is 20V.)
Electric power was supplied to the electrolytic solution 17 at a voltage of 20 V for 30 seconds, and the stent 14 was immersed in the electrolytic solution 17 so that the outer surface of the stent 14 was electropolished. After the power supply is completed, the stent 14 is washed with water and dried to change the electrical contact 18 between the stent 14 and the anode conductive member.

(B) The process stent 14 is inserted into the pipe-shaped anode conductive member 13 made of SUS304 having an inner diameter of 7.6 mm so that the stent 14 has a reduced diameter (-0.4 mm reduced diameter). The entire outer surface of the stent 14 (100% of the area outside the stent) was brought into contact with and fixed to the inner surface of the adhesive member 13.

In the electrolytic solution tank 15, an electrolytic solution 17 which is a commercially available electrolytic polishing solution for Ti alloy is stored, and a rod-shaped SUS304 is formed so that the distance between the electrodes and the stent 14 is equal (3 mm to 4 mm). The cathode 16 made of was installed. (The recommended voltage of the electrolytic solution 17 is 20V.)
Electric power was supplied to the electrolytic solution 17 at a voltage of 20 V for 5 seconds, and the stent 14 was immersed in the electrolytic solution 17 so that the inner surface of the stent 14 was electropolished. After the power supply is completed, the stent 14 is washed with water and dried to change the electrical contact 18 between the stent 14 and the anode conductive member.

  Then, after performing the process of (a) 3 times continuously, the process of (b) and the process of (a) were alternately performed 3 times each.

(Comparative Example 1)
A stent 14 made of nickel titanium alloy having an outer diameter of 8.0 mm and an inner diameter of 7.6 mm was prepared.
(A) Process In the same manner as in the process (a) of Example 1, except that the stent 14 was fixed with the clip-shaped anode conductive member 13 made of SUS304 (contacted at 5% of the total area of the inner surface of the stent). , Repeated 8 times in succession.

(Comparative Example 2)
A stent 14 made of nickel titanium alloy having an outer diameter of 8.0 mm and an inner diameter of 7.6 mm was prepared.
Only the step (a) of Example 1 was repeated 8 times in succession.

(Comparative Example 3)
A stent 14 made of nickel titanium alloy having an outer diameter of 8.0 mm and an inner diameter of 7.6 mm was prepared.
Only the step (b) of Example 1 was repeated 8 times in succession.

(result)
As a result of the electropolishing method of Example 1 and Comparative Examples 1 to 3, electropolishing was performed in any of the examples. In particular, in Example 1, the outer surface and the inner surface could be polished until the surface of the stent 14 showed uniform gloss.

  On the other hand, in Comparative Example 1, although both the outer surface and the inner surface of the stent 14 were subjected to electrolytic polishing, the inner surface had burrs on the polished surface compared to the outer surface, and polishing unevenness was observed on the outer surface and inner surface of the stent 14. It was.

  In Comparative Example 2, although the outer surface of the stent 14 was electrolytically polished, the inner surface had burrs on the polished surface as compared with the outer surface, and polishing unevenness was observed on the outer surface and the inner surface of the stent 14.

  In Comparative Example 3, although the electrolytic polishing of the inner surface of the stent 14 was performed, burrs remained on the outer surface of the outer surface compared to the inner surface, and uneven polishing was observed on the outer surface and the inner surface of the stent 14.

  From this, it can be seen that the electropolishing method of the present invention can achieve electropolishing uniformly without unevenness by a simple method.

DESCRIPTION OF SYMBOLS 11 Power supply 12a, 12b Conductive wire 13 Anode conductive member 14 Stent 15 Electrolyte tank 16 Cathode 17 Electrolyte 18 Electrical contact

Claims (8)

The manufacturing method of the tubular body characterized by including the following (a) process and (b) process at least once or more.
(A) a step of electropolishing the outer surface of the tubular body by supporting the inner surface of the tubular body from the inside by an anode conductive member that is in electrical contact with the tubular body; and (b) anode conductivity in electrical contact with the tubular body. The process of electropolishing the inner surface of the tubular body by supporting the outer surface of the tubular body from the outside by the elastic member In the step (a), at least a part of the tubular body is in contact with the anode conductive member on the inner surface of the tubular body in a state in which the diameter is expanded by 0.1 mm or more and 2.0 mm or less from the reference inner diameter. Item 2. A method for producing a tubular body according to Item 1. In the step (b), at least a part of the tubular body is in contact with the anode conductive member on the outer surface of the tubular body with a diameter reduced from 0.1 mm to 2.0 mm from the reference outer diameter. The manufacturing method of the tubular body of Claim 1. The method of manufacturing a tubular body according to any one of claims 1 to 3, wherein the number of times of the step (b) is less than the number of times of the step (a). The method for manufacturing a tubular body according to any one of claims 1 to 4, wherein the step (a) and the step (b) are sequentially performed one or more times. 6. The method for producing a tubular body according to claim 5, wherein the time for one electropolishing in the step (b) is shorter than the time for one electropolishing in the step (a). In the step (a), a voltage is supplied for electrolytic polishing in the range of 10 seconds to 60 seconds, and in the step (b), a voltage is supplied in the range of 3 seconds to 10 seconds for electrolytic polishing. The manufacturing method of the tubular body of Claim 6 characterized by the above-mentioned. The method for manufacturing a tubular body according to any one of claims 1 to 7, wherein the tubular body is a stent.