CN102605390B - Electroforming method for preparing degradable Fe-Zn alloy tubing for vascular stents - Google Patents

Abstract

A method for preparing degradable Fe-Zn alloy pipes for vascular stents by electroforming belongs to the field of biological materials and electrochemical machining. The method is characterized in that: Fe-Zn alloy material is prepared by utilizing the competitive codeposition process of Fe and Zn ions, and the obtained alloy has fine grains and good comprehensive mechanical property; the thickness of the electroforming layer can reach 70 to 150 microns, and the electroforming layer is separated from the matrix and then used as an individual body for independent use, so that the seamless micro-tube for the bracket can be directly prepared, and the conventional pressure forming process of laser cutting of the metal micro-tube for the bracket is avoided; the component proportion of the Fe-Zn alloy is changed by adjusting electroforming parameters, the microstructure of the Fe-Zn alloy is changed by heat treatment, and the two aspects of synergistic effect can regulate and control the degradation rate of the Fe-Zn alloy material in human body fluid or blood and improve the mechanical property of the Fe-Zn alloy material. Therefore, the Fe-Zn alloy pipe for the intravascular stent with good biocompatibility, biological corrosion degradation performance and comprehensive mechanical property can be prepared by adopting the technology of the invention.

Description

Electroforming method for preparing degradable Fe-Zn alloy tubing for vascular stents

technical field

The invention relates to a method for preparing biodegradable Fe-Zn alloy pipes by electroforming in an acidic solution, specifically referring to the process of dissolving anode iron, depositing ferrous ions and zinc ions in the solution on the surface of the cathode to make iron-zinc alloy profiles The method belongs to the fields of biomedical materials and electrochemical processing.

Background technique

At present, many implantable medical devices are permanent, and such devices often cause many complications. For example, permanent stainless steel vascular stents can cause restenosis of blood vessels at the implantation site, long-term local inflammatory reactions, etc. After the devices made of biomedical degradable materials complete their functional missions in the human body, they will be degraded and absorbed along with the human metabolic process, and will not cause long-term effects on the human body. used in patients. Biodegradable metal materials are an important development direction of biodegradable materials in the future due to their good comprehensive mechanical properties. Iron is an essential trace element for the human body. It plays an important role in the hematopoietic process of the human body. It plays a role in transporting oxygen and nutrients in the blood, and can promote the synthesis of cytochromes and various enzymes. It is a safe and absorbable metal material.

After searching the existing documents, it was found that Peuster et al reported "A novel approach to temporary stenting: degradable cardiovascular stents produced from corrodiblemetal---results6 —18months after implantation into New Zealand whiterabbits" (a new method of temporarily supporting blood vessels: a degradable cardiovascular stent made of corrodible metal-the results of 6-18 months of stent implantation into New Zealand white rabbits), they tested The reliability and safety of biodegradable iron stents (with iron>99.8%) were confirmed. The results showed that during the follow-up period of 6-18 months, the mechanical performance of the stent was good, and no thrombotic events occurred. And with the prolongation of time, the content of Fe in the body fluid continued to increase, indicating that the degradation process of the stent occurred. However, during the 18-month follow-up period, the stent has not completely degraded, and it will also cause intimal hyperplasia like stainless steel stents. Therefore, it is necessary to consider alloying pure iron materials to accelerate its corrosion degradation rate.

The standard electrode potential of Zn element is -0.76V, and the standard electrode potential of Fe is -0.44V. Zn is added to pure iron as an alloy element. On the one hand, it can form a solid solution with Fe to reduce the electrode potential of the alloy matrix. On the other hand, it can Form intermetallic compounds with Fe to increase the number of microcathodes in the alloy, thereby accelerating the degradation rate of Fe-based alloys. In terms of biology, Zn is also an essential trace element in the human body, and its content in the human body is second only to Fe. It has an important influence on the growth and development of cells, is the main component of dozens of enzymes in the human body, and is also related to brain development and intelligence. Therefore, the alloy composed of Zn added to Fe will also have good biomedical safety. However, the melting point of pure Fe is 1534°C, and the boiling point of pure Zn is 907°C, and at room temperature, the solubility of Zn in Fe is very small. When you want to prepare such an alloy with a high melting point difference by conventional smelting methods, a low melting point will appear. It is difficult to control the composition and quality of the alloy due to the gasification and evaporation of components.

Electroforming is a processing method in which a thin metal layer is prepared by electrolysis on the surface of a conductor material. Its principle is similar to electroplating technology, the difference is that the electroformed metal layer is separated from the substrate and can be used as an independent body. Electroplating technology has been widely used in the iron and steel industry to prepare Zn-Fe anode protective coating (the content of Fe is mainly distributed between 0.4% and 25%). But so far there is no report on the preparation of biomedical Fe-Zn binary alloy pipes mainly composed of Fe by electroforming technology.

Contents of the invention

In order to overcome the deficiencies in the prior art, the present invention provides a method for preparing degradable Fe-Zn alloy tubes for vascular stents using electroforming technology. The method should utilize the process of Fe and Zn positive ions in the electrolyte to compete and co-deposit to the cathode under the action of an electric field to prepare a biodegradable Fe-Zn alloy; and the ion concentration in the electrolyte can be adjusted by adjusting the electrochemical parameters. Ratio, as well as pH and temperature, to change the composition ratio of Fe-Zn alloy, so that the mass ratio of Zn can be changed between 1 and 40%; the microstructure of the alloy can also be controlled by subsequent solid solution and aging precipitation heat treatment , so as to achieve the purpose of regulating the degradation rate of the material in human body fluid or blood and improving the mechanical properties of the material.

The technical scheme adopted in the present invention is: a kind of electroforming method that prepares degradable Fe-Zn alloy tubing for vascular stent adopts the following steps:

a. Prepare electroforming solution, the components of electroforming solution are: deionized water 1000g, ferrous chloride 200~300g, zinc chloride 1~50g, sodium lauryl sulfate 0.01~0.5g, sodium citrate 5~ 30g, 1-2g ascorbic acid, 10-20g sodium chloride, 1-5g manganese chloride;

b. Use sodium hydroxide and hydrochloric acid to adjust the pH of the solution to keep the pH at 3.0-4.0;

c. Electroformed cathodes are pre-treated before being energized, including degreasing, cleaning, and weak etching;

d. Use DC power supply or pulse power supply for electroforming to ensure that the cathode current density is 1.0-3.0A/dm ² , the temperature of the electroforming solution is kept at 30-40°C, and mechanical stirring is added during the electroforming process;

e. After the electroforming is completed, the low-melting-point cathode mandrel with the electroforming alloy layer is heated and melted to obtain a Fe-Zn alloy pipe with a Zn element mass percentage of 1-40%.

In the above technical solution, the electroformed cathode mandrel is a metal wire with a melting point lower than 400°C, and its diameter matches the diameter of the prepared vascular stent; the shape of the electroformed anode is ring-shaped, and the cathode mandrel is placed as the central axis , its material is pure iron with a purity not less than 99.9%.

The beneficial effects of the present invention are: compared with the existing method for preparing biodegradable materials, the method for electroforming the degradable Fe-Zn alloy tubing for vascular stents is characterized by:

1) To avoid the problem of conventional alloying preparation caused by the large difference in the physical properties of Fe and Zn, the Fe-Zn alloy material is prepared by using the competitive co-deposition process of Fe and Zn ions, and the obtained alloy has fine crystals Granules with good comprehensive mechanical properties.

2) The thickness of the electroformed layer can reach 70 microns to 150 microns, and it can be used as an individual after being separated from the substrate. Therefore, seamless micro-tubes for stents can be directly produced, avoiding the conventional pressure forming process of laser cutting metal micro-tubes for stents .

3) Change the composition ratio of Fe-Zn alloy by adjusting electroforming parameters, and change the microstructure of Fe-Zn alloy by heat treatment. The synergistic effect of these two aspects can regulate the degradation rate of Fe-Zn alloy materials in human body fluid or blood. and improve its mechanical properties. Therefore, the technology of the present invention can be used to prepare Fe-Zn alloy tubes for blood vessel stents with good biocompatibility, biocorrosion degradation performance and comprehensive mechanical properties.

Description of drawings

Fig. 1 is a schematic diagram of the equipment for electroforming the degradable Fe-Zn alloy tubing for vascular stents.

In the figure: 1. Electroforming tank; 2. Electroforming solution; 3. Annular pure iron anode; 4. Cathode mandrel; 5. Fe-Zn alloy electroforming layer.

Detailed ways

The present invention will be further described in detail below with specific embodiments in conjunction with the accompanying drawings, but it does not imply any limitation to the protection content of the present invention.

Example 1

a. prepare electroforming solution 2 in electroforming tank 1, electroforming solution 2 includes: deionized water 1000g, ferrous chloride 300g, zinc chloride 10g, sodium lauryl sulfate 0.02g, sodium citrate 20g, Ascorbic acid 1.5g, sodium chloride 15g, manganese chloride 5g;

b. adjust the pH of the solution with sodium hydroxide and hydrochloric acid to keep the pH at 3.5;

c. Using DC power supply for electroforming. The cathode mandrel 4 connected to the negative pole of the power supply is made of metal tin wire with a diameter of 1.8 mm, which is submerged in the electrolyte to generate a uniform Fe-Zn alloy electroforming layer 5 with an effective length of 40 mm. The one connected to the positive pole of the power supply is an annular pure iron anode 3 with a purity of 99.9%. The cathode mandrel 4 is placed on the central axis of the annular pure iron anode 3 to ensure the uniformity of the wall thickness of the electroformed pipe. The cathode mandrel 4 is pre-treated before power-on, including degreasing, cleaning, and weak etching;

d. Ensure that the cathode constant current density is 1.5A/dm ² , the temperature of the electroforming solution 2 is kept at 35°C, mechanical stirring is used during the electroforming process, and the electroforming time is 4 hours;

e. After the electroforming is completed, the cathode mandrel 4 with the Fe-Zn alloy electroforming layer 5 is heated by a heating device, and the cathode mandrel 4 is melted away. Finally, the zinc content is 15% and the length is 40 mm after cleaning and polishing. Fe-Zn alloy thin-walled fine tubes with an inner diameter of 1.8mm and a wall thickness of 0.1mm.

The alloy pipe is subjected to solution treatment at 750°C for 10 minutes, quenched in water, and aged at 250°C for 5 hours. The finally obtained alloy material has a tensile strength of 350 MPa and an elongation after fracture of 20%. The corrosion degradation rate is 0.7mmy ^-1 after immersion test in simulated body fluid for 90 days.

Example 2

a. prepare electroforming solution 2 in electroforming tank 1, electroforming solution 2 includes: deionized water 1000g, ferrous chloride 300g, zinc chloride 7g, sodium lauryl sulfate 0.02g, sodium citrate 20g, Ascorbic acid 1.5g, sodium chloride 15g, manganese chloride 5g;

b. adjust the pH of the solution with sodium hydroxide and hydrochloric acid to keep the pH at 3.5;

c. Using DC power supply for electroforming. The cathode mandrel 4 connected to the negative pole of the power supply is made of metal tin wire with a diameter of 1.8 mm, which is submerged in the electrolyte to generate a uniform Fe-Zn alloy electroforming layer 5 with an effective length of 40 mm. The one connected to the positive pole of the power supply is an annular pure iron anode 3 with a purity of 99.9%. The cathode mandrel 4 is placed on the central axis of the annular pure iron anode 3 to ensure the uniformity of the wall thickness of the electroformed pipe. The cathode mandrel 4 is pre-treated before power-on, including degreasing, cleaning, and weak etching;

d. Ensure that the cathode constant current density is 1.5A/dm ² , the temperature of the electroforming solution 2 is kept at 35°C, mechanical stirring is used during the electroforming process, and the electroforming time is 4 hours;

e. After the electroforming is completed, the cathode mandrel 4 with the Fe-Zn alloy electroforming layer 5 is heated by a heating device, and the cathode mandrel 4 is melted away. Finally, the zinc content is 10% and the length is 40 mm after cleaning and polishing. Fe-Zn alloy thin-walled fine tubes with an inner diameter of 1.8mm and a wall thickness of 0.1mm.

The alloy pipe is then subjected to solution treatment at 680°C for 10 minutes, quenched in water, and aged at 250°C for 5 hours. The finally obtained alloy material has a tensile strength of 320MPa and an elongation after fracture of 23%. The corrosion degradation rate is 0.58mmy ^-1 after immersion test in simulated body fluid for 90 days.

Claims (2)

1. a method for degradable Fe-Zn alloy pipe for intravascular stent is prepared in electroforming, it is characterized in that: adopt following steps:

A. prepare electroforming solution, electroforming solution component is: deionized water 1000g, iron protochloride 200～300g, zinc chloride 1～50g, sodium lauryl sulphate 0.01～0.5g, Trisodium Citrate 5～30g, xitix 1～2g, sodium-chlor 10～20g, Manganous chloride tetrahydrate 1～5g;

B. with sodium hydroxide and hydrochloric acid, carry out the pH of regulator solution, make pH remain on 3.0～4.0;

C. electroforming negative electrode carried out pre-treatment before energising, comprised oil removing, cleaned weak etch;

D. adopt direct supply or the pulse power to carry out electroforming, guarantee that cathode current density is 1.0～3.0A/dm ², the temperature of electroforming solution remains on 30～40 ℃, mechanical stirring in addition in electroforming process;

E. after electroforming completes, the low melting point negative electrode core heat fused with electromolding alloy layer is fallen, obtained the Fe-Zn alloy pipe that Zn element mass percent is 1～40%.

2. the method for degradable Fe-Zn alloy pipe for intravascular stent is prepared in electroforming according to claim 1, it is characterized in that: described electroforming negative electrode core is fusing point lower than the wire of 400 ℃, and its diameter matches with the diameter of preparing intravascular stent; Electroforming anode shape is ring-type, and axle is placed centered by negative electrode core, and its material is pure iron, and purity is not less than 99.9%.