Corrosion-resistant permanent magnets for intravascular blood pumps

Abstract

The invention relates to a corrosion-resistant permanent magnet, a method for producing a corrosion-resistant permanent magnet, and an intravascular blood pump comprising the magnet. The magnet is coated by a composite coating comprising, in the order as recited below, a first metal oxide layer, a metal layer, a second metal oxide layer, a linker layer, and a layer formed of poly(2-chloro-p-xylylene). In alternative embodiments, a further metal layer and optionally a further metal oxide layer can be provided between the second metal oxide layer and the linker layer. In a further alternative embodiment, the metal layer can be omitted and a further layer structure comprising at least one metal oxide layer, a linker layer, and a layer formed of poly(2-chloro-p-xylylene) can be provided instead.

Description

Technical Field

[0001] The present invention relates to corrosion protection of permanent magnets. Specifically, the present invention relates to permanent magnets having a protective coating that renders the magnets corrosion-resistant, and methods for producing corrosion-resistant permanent magnets. The present invention also relates to intravascular blood pumps that include the corrosion-resistant permanent magnets of the present invention. While the present invention is applicable to a wide variety of permanent magnets, rare earth permanent magnets are preferred, with neodymium iron boron (NdFeB) permanent magnets being particularly preferred. Background Art

[0002] Intravascular blood pumps support blood flow in a patient's blood vessels. They are inserted percutaneously, for example into the femoral artery, and guided through the body's vascular system to their destination, for example a ventricle of the heart.

[0003] A blood pump typically comprises a pump housing having a blood flow inlet and a blood flow outlet. In order to induce blood flow from the blood flow inlet to the blood flow outlet, an impeller or rotor is rotatably supported in the pump housing about a rotation axis, wherein the impeller is provided with one or more blades for conveying blood.

[0004] Figure 1 An exemplary blood pump is shown in . Figure 1 1 is a schematic longitudinal cross-sectional view of an exemplary intravascular blood pump 10. The blood pump comprises a motor portion 11 and a pump portion 12, which are coaxially arranged one behind the other and form a rod-shaped structure. The pump portion extends through a flexible suction hose (not shown) which has openings at its ends and / or in its side walls for the entry of blood into the pump. The end of the blood pump 10 facing away from the suction hose is connected to a catheter 14, optionally in combination with a guide wire for guiding the blood pump to its destination.

[0005] Figure 1 The exemplary intravascular blood pump shown has a motor portion 11 and a pump portion 12 firmly connected to each other. The motor portion 11 has an elongated housing 20 that houses an electric motor 21. The electric motor has a rotor and a stator. The stator is the stationary part of the electromagnetic circuit of the electric motor, while the rotor is the moving part. One of the rotor or the stator includes conductive windings, while the other includes permanent magnets. The current flowing in the windings generates an electromagnetic field that interacts with the magnetic field of the permanent magnets to generate a force that causes the rotor to rotate. Figure 1In the exemplary blood pump, the stator 24 of the electric motor 21 has, in the usual manner, a number of circumferentially distributed windings and a longitudinal magnetic return channel 28. It is securely connected to the motor housing. The stator 24 surrounds the rotor 1, which is connected to the motor shaft 25, and consists of permanent magnets magnetized in the active direction. The motor shaft 25 extends the entire length of the motor housing 20 and protrudes distally beyond it. There, it supports an impeller 34 with blades 36, or pump blades, protruding therefrom. These impellers rotate within a tubular pump housing 32, which is in turn securely connected to the motor housing 20.

[0006] The proximal end of the motor housing 20 has a flexible conduit 14 sealingly attached thereto. In this disclosure, "proximal" and "distal" refer to positions relative to the physician inserting the intravascular blood pump, i.e., the distal end is on the impeller side. A cable 23 for powering and controlling the motor 21 extends through the conduit 14. Additionally, a purge fluid line 29 extends through the conduit 14, penetrating the proximal end wall 22 of the motor housing 20. Purge fluid (schematically indicated by a thick arrow) is supplied to the interior of the motor housing 20 via the purge fluid line 29, flows through the gap 26 between the rotor 1 and the stator 24, and exits through the end face 30 at the distal end of the motor housing. The purge pressure is selected so that it is higher than the prevailing blood pressure to prevent blood from seeping into the motor housing. Depending on the application, the purge fluid pressure at the motor, where the pressure is generated, is between 300 and 1400 mmHg.

[0007] Fluids with a viscosity higher than that of water (η = 0.75 mPa·s at 37° C.) are particularly suitable as rinsing fluids, in particular rinsing fluids having a viscosity of 1.2 mPa·s or higher at 37° C. For example, a 5% to 40% dextrose aqueous solution for injection can be used, but physiological saline solution is also suitable.

[0008] When the impeller 34 rotates, blood (schematically indicated by hollow arrows) is sucked in through the end-face intake opening 37 of the pump housing 32 and conveyed rearward in the axial direction within the pump housing 32. The blood flows out of the pump part 12 through the outlet opening 38 of the pump housing 32 and further along the motor housing 20. The pump part can also be operated in the opposite conveying direction, in which blood is sucked in along the motor housing 20 and exits through the opening 37.

[0009] The motor shaft 25 is mounted on the one hand in radial bearings 27 and 31 at the proximal end of the motor housing and on the other hand at the distal end of the motor housing. Furthermore, the motor shaft 25 is also mounted axially in an axial bearing 39. If the blood pump is also used to transport blood or only in the opposite direction, a corresponding axial bearing 39 is also / only provided in a corresponding manner at the proximal end of the motor housing 20.

[0010] It should be emphasized that the above-mentioned blood pump is only an example, and the present invention is also applicable to different blood pumps including electric motors, ie, requiring permanent magnets.

[0011] Intravascular blood pumps must meet numerous requirements. Because they are placed inside a living body, they must be as small as possible. The smallest pumps currently in use have an outer diameter of approximately 4 mm. However, the pumps must deliver high volume flows within the human blood circulation. Therefore, micropumps must be high-performance motors.

[0012] Furthermore, implantable blood pumps must not adversely affect their biological environment, such as the blood to be pumped and the surrounding tissue. Pumps should therefore be biocompatible in a broad sense, meaning they should not contain or generate any potentially harmful substances or significant amounts of heat that could harm the body or its components.

[0013] In addition, the replacement of the pump is a heavy burden for the patient. From this point of view and of course also from financial considerations, the intravascular blood pump should have a long service life.

[0014] The materials and design of the intravascular blood pump must be appropriately selected and specifically adapted to meet these different requirements.

[0015] It is important to select the right permanent magnet for the motor. For pump efficiency and lifespan, the magnet should have a strong magnetic field, meaning high remanence, high resistance to demagnetization, meaning high coercivity, and a high saturation magnetization. In this regard, rare earth permanent magnets, particularly those containing neodymium as a rare earth metal, and especially neodymium iron boron (NdFeB) permanent magnets, are the magnet of choice. Other rare earth iron boron permanent magnets can also be used.

[0016] The stronger the magnet, the smaller it can be while still generating sufficient rotational force. Therefore, the stronger the magnet, the smaller the motor can be. Neodymium iron boron permanent magnets are the strongest permanent magnets currently available. They appear to be ideal for use in intravascular blood pumps.

[0017] It is well known that the magnetic properties of rare earth metal based magnets, such as NdFeB magnets, depend on the specific alloy composition, microstructure and manufacturing technology used. NdFeB magnets can be used as polymer bonded magnets and sintered magnets. Sintered magnets are more superior in magnetic properties. They are produced by alloying the raw materials, grinding them into powder, pressing and sintering. During or after the production, an external magnetic field is applied to magnetize the material. The most well-studied magnets are fine-grained sintered materials, in which Nd2Fe 14 The B crystals are coated with a thin layer that is particularly rich in neodymium.

[0018] While NdFeB magnets possess magnetic properties that make them particularly suitable for use in electric motors for intravascular blood pumps, they also have significant drawbacks. Specifically, commercially available NdFeB magnets, primarily composed of neodymium, iron, and boron, and particularly sintered NdFeB magnets with a highly active neodymium-rich phase at the grain boundaries, are highly susceptible to corrosion. For example, the magnets can be corroded by oxygen and moisture in the air, particularly, but not exclusively, at the grain boundaries. Corrosion leads to a significant degradation of magnetic properties, and if corrosion progresses while the magnet is in use, the performance of the blood pump in which the magnet is used can deteriorate. This phenomenon is exacerbated by the NdFeB magnet's tendency to act as a sponge for corrosion products, disrupting the structure and causing fragments to flake off the magnet surface and ultimately causing the magnet to break.

[0019] Unfortunately, all rare earth metals share a common characteristic: susceptibility to corrosion. Consequently, all rare earth metal-based permanent magnets exhibit an unfavorable corrosion tendency, as explained above for NdFeB magnets. For currently available magnets, a rule of thumb is that the stronger the magnet, the more susceptible it is to corrosion.

[0020] In intravascular blood pumps, the magnets must operate in a corrosive environment, i.e. in a cleaning fluid flowing between the rotor and the stator (see Figure 1 As mentioned above, the cleaning fluid is typically an aqueous fluid, which may contain chlorides. Chlorides are highly corrosive to rare earth metal-based magnets, and the water and the oxygen dissolved in it can cause severe corrosion in a very short time span of a few hours.

[0021] Obviously, rare earth metal based permanent magnets, such as neodymium iron boron magnets, used in intravascular blood pumps need to be protected from corrosion.

[0022] Various measures are known for protecting NdFeB magnets and other rare earth metal based magnets from corrosion. For example, corrosion resistance can be improved by coating the magnets with a protective coating.

[0023] Common coatings are nickel coatings and epoxy-based coatings, and titanium coatings and Parylene coatings are known, especially for blood pumps. However, these coatings also have disadvantages. Even if biocompatible metals and organic resins (such as titanium and Parylene) are selected, the metal coating must be relatively thick to provide adequate protection. Therefore, the gap between the magnet and the winding in the motor of the blood pump must be relatively large. A large gap has a significant negative impact on the performance of the motor. A large gap requires a higher motor current, and high motor currents generate undesirable heat, which can cause damage to blood and tissue.

[0024] Furthermore, organic materials such as parylene have a thermal expansion coefficient that is very different from that of the magnet. Therefore, temperature changes during use of the magnet often lead to cracking and / or delamination of the coating.

[0025] EP 3 319 098 A1 discloses a coating for permanent magnets comprising a metal layer, a metal oxide layer having a thickness of a few nanometers, such as an aluminum layer that forms naturally when exposed to air, a connecting sublayer, and a poly(2-chloro-p-xylene) layer. This coating provides good corrosion protection. However, the production process lacks high reproducibility and produces an undesirable number of magnets that are insufficiently protected against corrosion, particularly when the coating is made thin. Further improvements are desired.

[0026] Currently, no biocompatible coatings for permanent magnets, such as NdFeB magnets, are known that satisfactorily meet all the requirements for intravascular blood pumps. Such coatings must inherently possess excellent corrosion resistance, must be thin yet dense, must not develop cracks or other defects during use, and must adhere reliably and tightly to the magnet. Furthermore, the coating process must produce highly reproducible results, meaning the number of magnets that must be removed should be low. Furthermore, the coating must be biocompatible and must coat the entire magnet, or at least the portion of the magnet that is exposed to the corrosive environment during use, with a uniform thickness. This is particularly challenging because many magnets have porous surfaces and shapes that include edges. Consequently, permanent magnets used in intravascular blood pumps, such as rare earth metal-based magnets, such as NdFeB magnets, constitute items that are not easily coated with a uniform thickness.

[0027] The present invention provides a solution to the above-mentioned problems. Summary of the Invention

[0028] The present invention provides a permanent magnet having a protective coating thereon that reliably protects the magnet from corrosion during prolonged use in an intravascular blood pump, and a method for producing the protective coating with high reproducibility. The protective coating is particularly thin, thereby allowing the production of very small magnets and, therefore, very small blood pumps.

[0029] The subject matter of the present invention relates to a corrosion-resistant permanent magnet, a method for producing a corrosion-resistant permanent magnet, and an intravascular blood pump. Specifically, the present invention provides the following:

[0030] 1. A corrosion-resistant permanent magnet comprising a magnet body and a composite coating disposed on and covering the surface of the magnet body, wherein the composite coating comprises the following components in the order described below:

[0031] - a first metal oxide layer in physical contact with the magnet body,

[0032] - Metal layer,

[0033] - a second metal oxide layer,

[0034] -connection sublayer, and

[0035] - a layer formed of poly(2-chloro-p-xylene).

[0036] 2. A magnet having the characteristics mentioned in (1) above, wherein the magnet body is a sintered magnet body.

[0037] 3. A magnet having the characteristics mentioned in (1) or (2) above, wherein the magnet body is based on a rare earth metal.

[0038] 4. A magnet having the characteristics mentioned in (3) above, wherein the rare earth metal is neodymium.

[0039] 5. A magnet having the characteristics mentioned in any one of (1) to (4) above, wherein the magnet body is a rare earth metal iron boron permanent magnet.

[0040] 6. A magnet having the characteristics mentioned in (4) or (5) above, wherein the magnet body is Nd2Fe 14 B crystal and coated Nd2Fe 14 The sintered magnet body is made of NdFeB material of B crystal, and the NdFeB material is larger than Nd2Fe 14 B crystals are rich in neodymium.

[0041] 7. A magnet having the features mentioned in any one of (1) to (6) above, wherein the magnet body is rod-shaped and all edges are rounded.

[0042] 8. A magnet having the characteristics mentioned in any one of (1) to (7) above, wherein the linker forming the linker layer is selected from silane, thiol, phosphine, disulfide, and silane having a thiol, phosphine or disulfide group.

[0043] 9. A magnet having the characteristics mentioned in (8) above, wherein the silane is selected from alkoxysilane or alkoxysilane having an acryloxy or methacryloyloxy functional group, or a linker having a bis-trimethoxysilyl or bis-triethoxysilyl functional group.

[0044] 10. A magnet having the characteristics as mentioned in (9) above, wherein the silane is 3-(trimethoxysilyl)propyl acrylate.

[0045] 11. The magnet having the characteristics mentioned in (8) above, wherein the silane has a hydride functional group.

[0046] 12. A magnet having the characteristics mentioned in any one of (1) to (11) above, wherein the metal of the metal layer is selected from aluminum, titanium, tantalum, niobium, zirconium, iridium, platinum, gold, iron and an alloy including at least one of aluminum, titanium, tantalum, niobium and zirconium.

[0047] 13. A magnet having the features mentioned in any one of (1) to (12) above, wherein the metal of the metal layer is aluminum or titanium, or an alloy of aluminum or titanium.

[0048] 14. A magnet having the characteristics mentioned in any one of (1) to (13) above, wherein the oxide of the first metal oxide layer and / or the second metal oxide layer is an oxide of at least one of aluminum, titanium, tantalum, niobium, zirconium, silicon, iridium and hafnium.

[0049] 15. A magnet having the features mentioned in any one of (1) to (14) above, wherein the oxide of the first metal oxide layer is Al2O3 or TiO2 or a mixed oxide of Al2O3 and TiO2.

[0050] 16. A magnet having the features mentioned in any one of (1) to (15) above, wherein the oxide of the second metal oxide layer is Al2O3 or TiO2 or a mixed oxide of Al2O3 and TiO2.

[0051] 17. A magnet having the characteristics mentioned in any one of (1) to (16) above, wherein

[0052] - the metal layer is in physical contact with the first metal oxide layer,

[0053] - a second metal oxide layer is in physical contact with the metal layer,

[0054] - the connecting sublayer is in physical contact with the second metal oxide layer, and

[0055] - The poly(2-chloro-p-xylene) layer is in physical contact with the tie sublayer.

[0056] 18. A magnet having the features mentioned in any one of (1) to (16) above, comprising another metal layer, and optionally another metal oxide layer between the second metal oxide layer and the connecting sublayer, wherein

[0057] - the metal layer is in physical contact with the first metal oxide layer,

[0058] - a second metal oxide layer is in physical contact with the metal layer,

[0059] - another metal layer in physical contact with the second metal oxide layer,

[0060] - another metal oxide layer (if present) is in physical contact with another metal layer,

[0061] - the connecting sublayer is in physical contact with the further metal layer or the further metal oxide layer (if present), and

[0062] - The poly(2-chloro-p-xylene) layer is in physical contact with the tie sublayer.

[0063] 19. A magnet having the characteristics mentioned in (18) above, wherein the metal of the other metal layer is selected from aluminum, titanium, tantalum, niobium, zirconium, iridium, platinum, gold, iron and an alloy containing at least one of aluminum, titanium, tantalum, niobium and zirconium.

[0064] 20. A magnet having the features mentioned in (18) or (19) above, wherein the metal of the other metal layer is aluminum.

[0065] 21. A magnet having the characteristics mentioned in any one of (18) to (20) above, comprising another metal oxide layer, wherein the oxide of the other metal oxide layer is an oxide of at least one of aluminum, titanium, tantalum, niobium, zirconium, silicon, iridium and hafnium.

[0066] 22. A magnet having the characteristics mentioned in (21) above, wherein the oxide of the other metal oxide layer is Al2O3.

[0067] 23. A magnet having the features as described in any one of (18) to (22) above, wherein the linker is a linker as described in any one of (8) to (11) above.

[0068] 24. A magnet having the features mentioned in any one of (18) to (23) above, wherein the linker is selected from thiol, phosphine, disulfide and silane having a thiol, phosphine or disulfide group.

[0069] 25. A magnet having the characteristics mentioned in (24) above, wherein the linker is selected from 3-(2-pyridylethyl)thiopropyltrimethoxysilane, 3-(4-pyridylethyl)thiopropyltrimethoxysilane, 2-(diphenylphosphino)ethyltriethoxysilane, bis(2-methacryloyl)oxyethyl disulfide and bis(hexadecyl)disulfide.

[0070] 26. A magnet having the features mentioned in any one of (1) to (25) above, wherein the thickness of the first metal oxide layer and the second metal oxide layer are the same or different, ranging from 5 nm to 200 nm, or from 80 nm to 120 nm, or from 50 nm to 100 nm, or wherein the thickness of the first metal oxide layer and the second metal oxide layer are both about 100 nm.

[0071] 27. A magnet having the characteristics mentioned in any one of (20) to (26) above, comprising another metal oxide layer, wherein the thickness of the other metal oxide layer is in the range of 5nm to 200nm, or 80nm to 120nm, or 50nm to 100nm, or is about 100nm.

[0072] 28. The magnet having the features mentioned in any one of (1) to (25) above, wherein the second metal oxide layer and / or the further metal oxide layer is a native metal oxide layer.

[0073] 29. The magnet having the features mentioned in (28) above, wherein the native metal oxide layer has a thickness in the range of 1 nm to 5 nm.

[0074] 30. A magnet having the features mentioned in any one of (1) to (29) above, wherein the thickness of the metal layer is in the range of 0.1 to 10 μm, or 0.5 to 10 μm, or 2 to 6 μm, or about 4 μm.

[0075] 31. A magnet having the features mentioned in any one of (20) to (30) above, wherein the thickness of the other metal layer is up to 29 μm, preferably in the range of 2 μm to 20 μm, or 10 μm to 18 μm, or about 15 μm.

[0076] 32. A magnet having the features mentioned in any one of (1) to (31) above, wherein the connecting sublayer is a single layer, or wherein the thickness of the connecting sublayer is in the range of 20 nm to 150 nm, or 50 nm to 100 nm.

[0077] 33. A magnet having the features mentioned in any one of (1) to (32) above, wherein the thickness of the layer formed by poly(2-chloro-p-xylene) is in the range of 3 μm to 20 μm, or 10 μm to 17 μm, or is about 15 μm.

[0078] 34. A magnet having the features mentioned in any one of (1) to (33) above, wherein the thickness of the composite coating is not greater than 50 μm.

[0079] 35. A magnet having the features mentioned in any one of (1) to (19) above, wherein the metal layer is omitted and the composite coating further comprises the following in the order recited above on the layer formed of poly(2-chloro-p-xylene):

[0080] - a third metal oxide layer,

[0081] - another connection sublayer, and

[0082] - Another layer formed of poly(2-chloro-p-xylene).

[0083] 36. A magnet having the features mentioned in (35) above, comprising an intermediate metal oxide layer between the layer formed of poly(2-chloro-p-xylene) and the third metal oxide layer.

[0084] 37. A magnet having the characteristics mentioned in (35) above, wherein

[0085] - The thickness of the first metal oxide layer, the second metal oxide layer and the third metal oxide layer are all in the range of 5 nm to 300 nm.

[0086] 38. A magnet having the characteristics mentioned in (36) above, wherein the thicknesses of the first metal oxide layer, the second metal oxide layer, the intermediate metal oxide layer and the third metal oxide layer are all in the range of 5 nm to 200 nm.

[0087] 39. A magnet having the characteristics mentioned in any one of (35) to (38) above, wherein the thickness of the connecting sublayer is the same as or different from the thickness of another connecting sublayer and is in the range of 20nm to 150nm, or 50nm to 100nm, or is essentially a single layer thickness.

[0088] 40. A magnet having the features mentioned in any one of (35) to (39) above, wherein the thickness of the layer formed by poly(2-chloro-p-xylene) is in the range of 0.5 μm to 4 μm, or 1 μm to 2 μm, and / or the thickness of another layer formed by poly(2-chloro-p-xylene) is in the range of 3 μm to 20 μm, or 10 μm to 15 μm, or is about 13 μm.

[0089] 41. A magnet having the features mentioned in any one of (35) to (40) above, wherein the thickness of the composite coating is not greater than 50 μm.

[0090] 42. A magnet having the characteristics mentioned in any one of (35) to (41) above, wherein the oxide of the first metal oxide layer is Al2O3 and the oxide of the second metal oxide layer is TiO2, or the oxide of the first metal oxide layer is TiO2 and the oxide of the second metal oxide layer is Al2O3, or the oxide of the first metal oxide layer and the second metal oxide layer is Al2O3, or the oxide of the first metal oxide layer and the second metal oxide layer is TiO2.

[0091] 43. A magnet having the characteristics mentioned in any one of (35) to (42) above, wherein the oxide of the third metal oxide layer is TiO2 or Al2O3, preferably TiO2.

[0092] 44. The magnet described in any one of (36) to (43) above, wherein the oxide of the intermediate metal oxide layer is Al2O3 or TiO2, preferably Al2O3, and is different from the oxide of the third metal oxide layer.

[0093] 45. A method for producing a corrosion-resistant permanent magnet, the method comprising

[0094] - providing a non-magnetized magnet body,

[0095] - forming a first metal oxide layer on the surface of the magnet body,

[0096] - forming a metal layer on the first metal oxide layer,

[0097] - forming a second metal oxide layer on the metal layer,

[0098] - optionally, forming at least one further layer on the second metal oxide layer,

[0099] - forming a connecting sublayer on the second metal oxide layer or on at least one further layer (if present),

[0100] - forming a layer of poly(2-chloro-p-xylylene) on the tie sublayer, and

[0101] -Magnetize the magnet body.

[0102] 46. ​​The method having the features mentioned in (45) above, comprising forming at least one further layer, wherein the at least one further layer is another metal layer.

[0103] 47. The method having the features mentioned in (46) above, further comprising forming another metal oxide layer on the other metal layer.

[0104] 48. A method having the features described in any one of (45) to (47) above, wherein the oxide of the first metal oxide layer and / or the oxide of the second metal oxide layer is an oxide described in any one of (14) to (16) above.

[0105] 49. A method having the features described in any one of (45) to (48) above, wherein the metal of the metal layer is a metal described in (12) or (13) above.

[0106] 50. A method having the features described in any one of (46) to (49) above, wherein the metal of the other metal layer is the metal described in (21) or (22) above.

[0107] 51. A method having the features described in any one of (47) to (50) above, wherein the oxide of the other metal oxide layer is an oxide as described in (23) or (24) above.

[0108] 52. A method having the features as described in any one of (45) to (51) above, wherein the linker of the linker layer is a linker as described in any one of (8) to (11), (17) and (18) above.

[0109] 53. A method having the features mentioned in any one of (45) to (52) above, wherein the first metal oxide layer and / or the second metal oxide layer is formed by a process selected from physical vapor deposition, chemical vapor deposition, sputtering, sol-gel process and flame spraying, or by oxidizing the corresponding metal layer.

[0110] 54. A method according to the feature mentioned in (53) above, wherein the physical vapor deposition process is a process using plasma or a process not using plasma or an ion vapor deposition process.

[0111] 55. A method having the features mentioned in (53) above, wherein the first metal oxide layer and / or the second metal oxide layer is formed by an atomic layer deposition process, which is a process using plasma or a process not using plasma.

[0112] 56. A method having the features mentioned in any one of (45) to (55) above, wherein the metal layer is formed by a process selected from physical vapor deposition, chemical vapor deposition, sputtering and atomic layer deposition.

[0113] 57. A method having the features mentioned in (56) above, wherein the metal layer is formed by a physical vapor deposition process using plasma or a physical vapor deposition process without using plasma or by an ion vapor deposition process.

[0114] 58. A method having the features mentioned in any one of (46) to (57) above, wherein the other metal layer is formed by an electroplating process, a sputtering process, a physical vapor deposition process or an atomic layer deposition process.

[0115] 59. A method having the features mentioned in (58) above, wherein the electroplating process is a process of electrodeposition from an ionic liquid.

[0116] 60. A method having the features described in any one of (47) to (59) above, wherein the further metal oxide layer is formed by the process described in any one of (53) to (55) above.

[0117] 61. A method having the features mentioned in any one of (45) to (60) above, wherein the linker layer is formed by applying the linker by physical vapor deposition using plasma, or by physical vapor deposition or wet process without using plasma, or by a plasma deposition process, or by a combination thereof.

[0118] 62. The method as defined in any one of (45) to (61), wherein the poly(2-chloro-p-xylylene) layer is formed by a plasma deposition process of dichloro-p-xylylene dimer.

[0119] 63. A method having the features mentioned in any one of (45) to (62) above, wherein the layer has a thickness mentioned in any one of (26) to (34) above.

[0120] 64. A method having the features described in any one of (45) to (63) above, wherein the magnet body is a magnet body described in any one of (1) to (7) above.

[0121] 65. A method for producing a corrosion-resistant permanent magnet, the method comprising

[0122] - providing a non-magnetized magnet body,

[0123] - forming a first metal oxide layer on the surface of the magnet body,

[0124] - forming a second metal oxide layer on the first metal oxide layer,

[0125] - forming a connecting sublayer on the second metal oxide layer,

[0126] - forming a layer of poly(2-chloro-p-xylylene) on the tie sublayer,

[0127] - optionally, forming an intermediate metal oxide layer on the poly(2-chloro-p-xylylene) layer,

[0128] - forming a third metal oxide layer on the poly(2-chloro-p-xylene) layer or on the intermediate metal oxide layer (if present),

[0129] - forming another connecting sublayer on the third metal oxide layer,

[0130] - forming another layer of poly(2-chloro-p-xylylene) on the other tie sublayer, and

[0131] -Magnetize the magnet body.

[0132] 66. A method having the characteristics mentioned in (65) above, wherein the oxide of the first metal oxide layer is Al2O3 and the oxide of the second metal oxide layer is TiO2, or the oxide of the first metal oxide layer is TiO2 and the oxide of the second metal oxide layer is Al2O3, or the oxides of the first metal oxide layer and the second metal oxide layer are both Al2O3 or both TiO2.

[0133] 67. The method described in (65) or (66) above, wherein the oxide of the third metal oxide layer is TiO2 or Al2O3, preferably TiO2.

[0134] 68. A method having the characteristics mentioned in any one of (65) to (67) above, comprising forming an intermediate metal oxide layer, wherein the oxide of the intermediate metal oxide layer is Al2O3 or TiO2, preferably Al2O3, and is different from the oxide of the third metal oxide layer.

[0135] 69. A method having the features described in any one of (65) to (68) above, wherein the linker of the linking sublayer and / or another linking sublayer is the linker described in any one of (8) to (11) above.

[0136] 70. A method having the features mentioned in any one of (65) to (69) above, wherein the first metal oxide layer and / or the second metal oxide layer is formed by a process selected from physical vapor deposition, chemical vapor deposition, sputtering, sol-gel process, flame spraying and atomic layer deposition.

[0137] 71. A method having the features mentioned in any one of (65) to (70) above, wherein the third metal oxide layer and / or the intermediate metal oxide layer (if present) is formed by an atomic layer deposition process or a physical vapor deposition process.

[0138] 72. A method having the features mentioned in any one of (65) to (71) above, wherein the connecting sublayer and / or another connecting sublayer is formed by applying the connecting sublayer by physical vapor deposition using plasma, or by physical vapor deposition without using plasma, or by a wet process, or by a plasma deposition process, or by a combination thereof.

[0139] 73. The method as defined in any one of (65) to (72), wherein the poly(2-chloro-p-xylylene) layer is formed by a plasma deposition process of dichloro-p-xylylene dimer.

[0140] 74. A method having the features mentioned in any one of (65) to (73) above, wherein the layer has a thickness mentioned in any one of (37) to (41) above.

[0141] 75. A method having the features described in any one of (65 to 74) above, wherein the magnet body is a magnet body described in any one of (1) to (7) above.

[0142] 76. An intravascular blood pump comprising an electric motor, wherein the electric motor comprises a permanent magnet as mentioned in any one of (1) to (44) above.

[0143] A magnet is corrosion-resistant within the meaning of the present invention if it passes the following test:

[0144] Coated magnets were subjected to a corrosion test (accelerated corrosion test) in an aqueous solution containing 0.9 wt% sodium chloride at 60°C. Corrosion of the magnetic material results in warping or deformation of the coating. Thus, warping or the formation of protrusions in the coating on the surface of the test specimen indicates corrosion of the magnetic material. The formation of protrusions with a height of 0.1 mm and warping of the coating are defined as indicating magnet failure. A magnet passes this test if the time until failure is at least 30 days.

[0145] According to the present invention, a strong permanent magnet includes a coating that completely covers the magnet body or at least covers those surfaces of the magnet body that are exposed to the fluid when the magnet is used in an intravascular blood pump. The coating makes the magnet resistant to corrosion when used in an intravascular blood pump. The preferred magnet body is composed primarily of neodymium, iron, and boron, with fine tetragonal magnetic Nd2Fe 14 B crystal and a neodymium-rich non-magnetic phase covering the crystal, as described above. Typically, Nd2Fe 14 The average crystal diameter of the B crystals ranges from 1 to 80 μm. The nonmagnetic neodymium-rich phase accounts for 1% to 50% of the magnet body's volume. These magnets are readily available commercially. They are preferred because of their high magnetic properties and because they are particularly strong, i.e., have a high flux density. For the reasons mentioned above, applications in intravascular blood pumps require particularly strong magnets. However, in principle, the corrosion-resistant coating of the present invention can be applied to any material requiring corrosion protection, such as various rare earth iron boron magnetic materials or any other magnetic material.

[0146] The coating of the present invention is a composite coating applied to the surface of the magnet body, i.e., the actual magnetic material. According to a first embodiment, the composite coating comprises a first metal oxide layer on the surface of the magnet body, a metal layer on the exposed surface of the first metal oxide layer, a second metal oxide layer on the metal layer, a layer formed of poly(2-chloro-p-xylene), and a connecting sublayer between the second metal oxide layer and the poly(2-chloro-p-xylene) layer. The first metal oxide layer, the metal layer, and the second metal oxide layer together form an inorganic layer.

[0147] According to a second embodiment, a further metal layer is provided between the second metal oxide layer and the connecting sublayer. In this embodiment, the first metal oxide layer, the metal layer, the second metal oxide layer and the further metal layer together form an inorganic layer.

[0148] In a preferred embodiment, a further metal oxide layer is disposed on the further metal layer. In this particular embodiment, the first metal oxide layer, the metal layer, the second metal oxide layer, the further metal layer, and the further metal oxide layer together form an inorganic layer. The further metal oxide layer may be artificially formed or may be a natural oxide layer, i.e., an oxide layer that forms automatically when the further metal layer is exposed to air. This also applies to the second metal oxide layer of the first and second embodiments.

[0149] According to a third embodiment, the composite coating includes a first layer structure and a second layer structure. The first layer structure is arranged on the surface of the magnet body, and the second layer structure is arranged on the first layer structure. The first layer structure includes a first metal oxide layer (on the surface of the magnet body), a second metal oxide layer on the first metal oxide layer, a layer formed by poly(2-chloro-p-xylene), and a connecting sublayer between the second metal oxide layer and the poly(2-chloro-p-xylene) layer. The metal oxide layers together form an inorganic layer. The second layer structure includes a third metal oxide layer (on the first layer structure), a layer formed by poly(2-chloro-p-xylene), and a connecting sublayer between the third metal oxide layer and the poly(2-chloro-p-xylene) layer. The third metal oxide layer forms the inorganic layer.

[0150] An additional (intermediate) metal oxide layer may be provided between the first layer structure and the third metal oxide layer. In this case, the second layer structure includes the intermediate metal oxide layer (on the first layer structure), the third metal oxide layer on the intermediate metal oxide layer, a layer formed of poly(2-chloro-p-xylene), and a connecting sublayer between the third metal oxide layer and the poly(2-chloro-p-xylene) layer. The metal oxide layers together form an inorganic layer. In this case, the second layer structure includes the intermediate metal oxide layer (on the first layer structure), the third metal oxide layer on the intermediate metal oxide layer, a layer formed of poly(2-chloro-p-xylene), and a connecting sublayer between the third metal oxide layer and the poly(2-chloro-p-xylene) layer.

[0151] The poly(2-chloro-p-xylene) layer constitutes the organic layer. Thus, in each embodiment, the composite coating comprises at least one inorganic layer and at least one organic layer.

[0152] The metal oxides of the first layer structure and the second layer structure may be the same or different.

[0153] Rare earth metal based magnets as purchased from suppliers are typically protected by a phosphate coating. The phosphate coating can be removed before applying the composite coating, for example by washing with an acid. However, the phosphate coating does not adversely interfere with the coating or coating process according to the present invention and can therefore remain on the magnet body. Preferably, the phosphate coating is not removed. Not removing the phosphate coating saves a process step and avoids the introduction of impurities during such a process step. However, it is preferred to clean the magnet before applying the first metal oxide layer. Cleaning is preferably carried out by washing the magnet with an organic solvent, for example an alcohol. Particularly preferred cleaning agents are isopropyl alcohol and a mixture of isopropyl alcohol and ethanol. After washing with the organic solvent, the magnet is dried, for example in a vacuum or in an air stream.

[0154] After cleaning and drying, a first metal oxide layer is applied to the surface of the magnet body. It is essential for the present invention that the metal oxide layer is directly disposed on the surface of the magnet, i.e., in physical contact with the magnet (contact with a phosphate-coated magnet is considered to be direct contact with the magnet). Metal oxides adhere well to the relatively rough surface of the magnet and are therefore not easily detached from it even under harsh operating conditions in an intravascular blood pump. Therefore, the corrosion resistance of the magnet is significantly improved, and the intravascular blood pump comprising the magnet operates trouble-free over a long period of time. Moreover, it is desirable that the composite coating of the present invention is applied to an unmagnetized magnet body, and the magnet body is magnetized only after the coating has been applied. It is inappropriate to magnetize the magnet body before the coating is applied.

[0155] In the first and second embodiments, the metal oxides forming the first metal oxide layer and the second metal oxide layer may be the same or different. Preferably, the oxide of the first metal oxide layer and / or the second metal oxide layer is an oxide of at least one of aluminum, titanium, tantalum, niobium, zirconium, silicon, iridium, and hafnium. Particularly preferred oxides for the first metal oxide layer and / or the second metal oxide layer are Al2O3, TiO2, and mixtures thereof. The same applies to the optional additional metal oxide layer in the second embodiment.

[0156] In the third embodiment, the composition of the first metal oxide layer is typically different from that of the second metal oxide layer, and the composition of the third metal oxide layer is typically different from that of the intermediate metal oxide layer (if present), and the oxide of the first inorganic layer may be the same as or different from the metal oxide of the second inorganic layer. Suitable metal oxides for forming the first metal oxide layer, the second metal oxide layer, the third metal oxide layer, and the intermediate metal oxide layer are the same as those of the first and second embodiments. Preferably, the oxide of the first metal oxide layer is Al2O3 and the oxide of the second metal oxide layer is TiO2, or the oxide of the first metal oxide layer is TiO2 and the oxide of the second metal oxide layer is Al2O3. The oxide of the third metal oxide layer is preferably TiO2 or Al2O3, particularly preferably TiO2. If an intermediate metal oxide layer is present, the oxide of the intermediate metal oxide layer is preferably Al2O3 or TiO2, particularly preferably Al2O3.

[0157] The oxides of the first and second metal oxide layers can also be the same. In this case, the first and second metal oxide layers are applied by the same or different processes. This applies similarly to the third and intermediate metal oxide layers.

[0158] In the first and second embodiments, a metal layer is disposed between the first and second metal oxide layers. Exemplary metals for forming the metal layer include aluminum, titanium, tantalum, niobium, zirconium, iron, iridium, platinum, gold, and alloys containing at least one of aluminum, titanium, tantalum, niobium, and zirconium. Particularly preferred metals are aluminum and titanium. In particular, in the second embodiment, iron is also preferred.

[0159] In the second embodiment, another metal layer is provided on the second metal oxide layer. Exemplary metals for forming the other metal layer are the same as those for the metal layer, with aluminum being a preferred metal.

[0160] In all embodiments, the method for forming the metal oxide layer is not particularly limited, but is preferably atomic layer deposition (ALD). In particular, the third metal oxide layer and the intermediate metal oxide layer (if present) of the third embodiment are preferably formed by an ALD process.

[0161] ALD is a thin film deposition method in which a thin film is grown on a substrate by exposing the substrate surface to alternating gaseous species, so-called precursors. The precursors are introduced into a reactor containing the substrate to be coated in a series of sequential, non-overlapping pulses, i.e., the precursors are never present in the reactor at the same time.

[0162] In each pulse, the precursor introduced into the reactor is absorbed onto the surface of the substrate to be coated until all available reaction sites on the surface are consumed. Any excess precursor is then removed from the reactor. Thereafter, a second precursor, different from the first precursor, is introduced into the reactor and absorbed onto the substrate surface, chemically reacting with the previously absorbed first precursor. Any excess precursor and gaseous reaction products are then again removed from the reactor. Depending on the type of layer to be deposited, another precursor different from the first and second precursors may be introduced into the reactor, absorbed, and reacted, and any excess precursor and reaction products removed from the reactor.

[0163] A single exposure to all precursors is called an ALD cycle.

[0164] Ideally, each ALD cycle produces a single layer of coating material. Thus, ALD allows for atomic-level control of layer thickness and composition. Large substrates with complex shapes can be coated with uniform, conformal coatings, free of defects that could make the composite coating more susceptible to attack by corrosive agents.

[0165] In the case of forming an aluminum oxide layer, preferred precursor materials for performing the ALD process are AlX3 and water (in gaseous form). In AlX3, X represents a lower alkyl group (which may be the same or different), or a lower alkyl group (which may be the same or different) and hydrogen, or a halogen atom (which may be the same or different). Particularly preferred AlX3 compounds are trimethylaluminum (TMA), triethylaluminum (TEA), triisobutylaluminum (TIBA), dimethylaluminum (DMAlH), and aluminum trichloride (AlCl3).

[0166] In an exemplary ALD process for producing an aluminum oxide layer, a magnet is placed in a reaction chamber, and AlX3 is introduced into the reaction chamber in a suitable inert carrier gas, such as argon, at a suitable temperature, such as approximately 300°C. The AlX3 is almost instantaneously absorbed onto the surface of the magnet or onto a coating already formed on the magnet, and any excess AlX3 and carrier gas are removed by evacuating the chamber, for example, to approximately 0.1 to 0.01 Pa. Thereafter, humid air is introduced. The water contained therein is absorbed onto the surface and reacts with the AlX3, forming aluminum oxide and HX on the surface. The air and any excess AlX3 and HX are removed by evacuating the reaction chamber again to approximately 0.1 to 0.01 Pa.

[0167] A complete ALD cycle takes about 10 to 12 seconds and produces an aluminum oxide coating with a thickness of about 0.1 nm. Thus, producing an aluminum oxide layer with a thickness of about 100 nm requires an ALD process time of about 3 hours.

[0168] ALD is also a preferred method for forming titanium dioxide (TiO2), however, ALD is not suitable for every metal oxide because suitable precursors do not exist for every metal oxide.

[0169] Other methods well suited for forming the various metal oxide layers of embodiments of the present invention are, for example, physical vapor deposition, chemical vapor deposition, sputtering, sol-gel processes, flame spraying, or oxidation of a previously applied metal layer. In the case of an oxidized metal layer, the metal of the metal oxide is of course the same as the metal of the underlying metal layer, however, in other cases, the metal of the metal oxide layer may be different from the metal of the underlying metal layer.

[0170] Physical vapor deposition can be a process with or without plasma, or an ion vapor deposition process. Likewise, ALD can be performed with or without plasma.

[0171] As a method particularly suitable for niobium oxide, the sol-gel process can be recommended, and as a method particularly suitable for tantalum oxide, the application of metallic tantalum by physical vapor deposition followed by oxidation in a plasma or oven can be recommended. When using zirconium oxide, stabilization with, for example, yttrium oxide is advisable.

[0172] Methods such as physical vapor deposition and sputtering can be performed with or without a bias voltage.A bias voltage is advantageous in terms of enhancing the formation of uniform coatings even on surfaces with irregular geometries.

[0173] In the first and second embodiments, the thickness of the first metal oxide layer, the second metal oxide layer, and the further metal oxide layer (if present), which are the same or different, can be in the range of 5 nm to 200 nm, preferably 80 nm to 120 nm, more preferably 50 nm to 100 nm, and most preferably about 100 nm. The second metal oxide layer and the further metal oxide layer can be native oxide layers, i.e., they can form naturally when the underlying metal layer is exposed to air, if the underlying metal layer is allowed to form a native oxide. The native oxide layer preferably has a thickness in the range of 1 nm to 5 nm.

[0174] In the third embodiment, the combined thickness of the first metal oxide layer, the second metal oxide layer, the third metal oxide layer, and the intermediate metal oxide layer (if present) is preferably in the range of 20 nm to 800 nm. Thus, in the case of four metal oxide layers, the thickness of each metal oxide layer is preferably in the range of 5 nm to 200 nm, and in the case of only three metal oxide layers, the thickness of each metal oxide layer is preferably in the range of 5 nm to 300 nm.

[0175] In the first and second embodiments, the methods for forming the metal layer and the other metal layer are dry deposition for the metal layer and wet deposition or dry deposition for the other metal layer, respectively.

[0176] Exemplary dry processes are chemical vapor deposition, physical vapor deposition (PVD) and ion vapor deposition (IVD), sputtering, and methods such as plasma coating and atomic layer deposition (ALD). IVD produces a metal layer with a columnar structure. It is desirable to perform shot blasting before depositing more layers thereon. Such a metal layer also does not have the desired quality. PVD, in particular Arc-PVD, is a preferred method for producing the metal layer of the composite coating of the present invention. PVD can produce a metal layer with the desired quality and thickness at a reasonable cost within a reasonable time. In particular, PVD produces a uniform metal layer. Therefore, the composite coating according to the first and second embodiments of the present invention includes a metal layer that has preferably been deposited by PVD (most preferably Arc-PVD). The preferred metal for forming the metal layer is aluminum and / or titanium.

[0177] Exemplary reaction conditions for the PVD process are a temperature in the range of about 200° C. to 260° C. and an inert gas atmosphere, such as an argon atmosphere.

[0178] Exemplary metal layers have a thickness of 0.1 μm to 10 μm, or 0.5 μm to 10 μm. From the perspective of providing optimal corrosion protection, the metal layer is desirably thick, however, the thicker the layer, the more time is required for its application (making the process expensive) and, as mentioned above, thick coatings are disadvantageous because they increase the distance between the magnet body and the windings in the motor of the blood pump. Therefore, a preferred thickness is 10 μm or less. On the other hand, from the perspective of corrosion protection, the metal layer should have a thickness of at least 0.5 μm, but in some cases, lower layer thicknesses may also meet the requirements. A more preferred thickness of the metal layer is 2 μm to 6 μm, with a particularly preferred thickness of about 4 μm.

[0179] According to a second embodiment, the composite coating includes another metal layer. The other metal layer is applied by the same or different methods as the metal layer, preferably by different methods. The reason is that although dry methods, such as physical vapor deposition, can produce a coating with good long-term stability and high reproducibility, it seems that wet methods, such as electrodeposition (ion plating), can produce a metal layer with increased density, i.e. better quality. Therefore, a second embodiment of the present invention combines a metal layer preferably formed by a physical vapor deposition process with another metal layer preferably formed by an electroplating process. However, wet deposition is not feasible in some cases. For example, gold is preferably applied by sputtering. The other metal layer preferably has a thickness in the range of 2 μm to 20 μm, more preferably 10 μm to 18 μm, most preferably about 15 μm. The electroplated layer can have a thickness of up to 29 μm.

[0180] A preferred metal for forming the further metal layer is aluminum. Aluminum is electrodeposited from an ionic liquid in a manner conventional in the art, for example by using a mixture of aluminum chloride and 1-ethyl-3-methylimidazolium chloride. The aluminum is preferably pure, for example at least 99% pure, particularly preferably at least 99.9% pure.

[0181] In order to enhance the corrosion protection provided by the metal layer / metal oxide layer, in all embodiments of the present invention, the metal layer / metal oxide layer is combined with a poly(p-xylene) polymer layer. Poly(p-xylene) polymers are known by the trade name Parylene. Parylene can react with hydroxyl-containing surfaces and is known to form a coating without small holes at low layer thicknesses. In addition, they have a low dielectric constant (about 3), which is advantageous in implantable blood pumps. Composite coatings comprising a metal oxide layer and / or a metal / metal oxide layer (such as a coating according to the present invention) and a Parylene layer are biocompatible and also provide corrosion protection. However, the adhesion of the Parylene layer to the metal layer or metal oxide layer is not strong enough under the working conditions in the intravascular blood pump. The Parylene layer begins to delaminate after an unacceptable short time, thereby exposing the metal or metal oxide layer. The metal layer and / or metal oxide layer cannot fully protect the magnet body, and thus the corrosion of the magnet body can begin.

[0182] This is prevented by a combination of two measures: providing an interface layer connecting the metal layer or metal oxide layer to the parylene layer, and using a specific parylene compound.

[0183] The compound forming the interfacial layer, i.e., the linker compound, must be bifunctional. Bifunctional means that the linker compound must have two functional groups or molecular moieties with different functions (reactivities), one functional group or molecular moiety that bonds to the metal layer or metal oxide layer, for example, by reacting with the surface hydroxyl groups of the metal or metal oxide layer, and the other functional group or molecular moiety that bonds to the parylene, thereby firmly connecting the inorganic metal layer or metal oxide layer to the organic parylene layer. The connection can be provided by covalent bonds or other bonds, such as by van der Waals forces.

[0184] Linkers having functional groups or moieties that bond to metals or metal oxides and functional groups or moieties that bond to parylene are known. Exemplary linkers include silane compounds, thiols, phosphines, disulfides, and silanes having thiol, phosphine, or disulfide groups. Depending on the metal, different linker compounds are preferred.

[0185] In the case of aluminum, titanium, tantalum, niobium, zirconium, iridium, silicon, hafnium and oxides of these metals, the linkers for the metal layer and for the metal oxide layer are preferably alkoxysilanes, such as methoxysilanes and ethoxysilanes, for example silanes having the formula (H3CO)3Si-R, where R is, for example, methacrylate, alkylamine, aniline or epoxyalkyl. In order to bond to parylene, the linker preferably has an acryloyloxy or methacryloyloxy functional group. The carbon chain length between the silyl and (meth)acryloyloxy moieties of the linker typically has 1 to 16 carbon atoms (methyl, ethyl, propyl, butyl, pentyl...). The hydrocarbon chain is typically saturated, but may also contain one or more unsaturated bonds. A particularly preferred linker is 3-(trimethoxysilyl)propyl acrylate (A-174) from Silquest, but other silane compounds such as G-170 (vinyl-functional silane coupling agent) from Silquest are also suitable. Furthermore, linkers with bis-trimethoxysilyl or bis-triethoxysilyl functional groups may be used, such as bis(trimethoxysilylethyl)benzene.

[0186] In particular, for titanium, zirconium, and platinum, a linker having a hydrogenation functional group, such as trihydrosilane, produces good results. 10-Undecenylsilane and n-octadecylsilane can be specifically mentioned. The silane is preferably applied from the gas phase or from an aprotic solution at room temperature. In addition, the above-mentioned alkoxysilanes having a (meth)acryloyloxy group and compounds having a bis-trimethoxysilyl or bis-triethoxysilyl functional group are also suitable.

[0187] Suitable linkers for connecting the parylene layer to the gold layer are typically thiols, phosphines, or disulfides, preferably with longer hydrocarbon chains, such as alkyl- or dialkyl-disulfides having alkyl groups with 10 to 16 carbon atoms. Such alkyl groups form a dense and ordered layer on the metal or metal oxide surface. However, alkyl groups with only 1 to 9 carbon atoms can also be used.

[0188] Also suitable for the gold layer are silane linker compounds having thiol, phosphine or disulfide groups. Particularly preferred examples are 3-(2-pyridylethyl)thiopropyltrimethoxysilane, 3-(4-pyridylethyl)thiopropyltrimethoxysilane, 2-(diphenylphosphino)ethyltriethoxysilane, bis(2-methacryloyl)oxyethyl disulfide and bis(hexacosyl)disulfide.

[0189] The bifunctional linker is preferably applied to the metal or metal oxide surface by a plasma coating process or by plasma-free physical vapor deposition or by applying an aprotic, alcoholic, or aqueous solution of the bifunctional linker compound to the metal or metal oxide surface. Dry coating of the silane compound in a plasma chamber produces a glassy layer comprising Si-O-Si-O chains aligned substantially parallel to the metal oxide surface and bound to the surface via oxygen atoms. The organic residue faces away from the surface and is available for bonding to the parylene. Physical vapor deposition and wet application form an interfacial layer with a similar structure but without the glassy appearance.

[0190] Plasma deposition produces dense layers with acceptable adhesion to parylene. Physical vapor deposition without plasma produces less dense layers with better adhesion to parylene than plasma-deposited layers. Wet application produces very dense monolayers with a random network and a high degree of crosslinking and a high percentage of silicon-oxygen bonds. These layers also adhere well to the parylene layer. Therefore, wet application is particularly preferred.

[0191] Alternatively, plasma application and physical vapor deposition (plasma-free) or wet application processes can be combined, i.e., first forming a glassy interfacial layer by plasma deposition, followed by forming a second connecting sublayer by physical vapor deposition or wet application, thereby forming a composite connecting sublayer. In such a composite connecting sublayer, the silicon atoms of the glassy layer are covalently bonded to the oxygen atoms of the second layer, and the organic residues of the second layer (such as methacrylate, alkylamine, or alkylene oxide) can be used to bond to the polyparaxylene covalently or in a different manner, for example, via van der Waals forces.

[0192] The interface layer typically has a thickness in the range of 20 to 150 nm, preferably 50 to 100 nm. Alternatively, only a monolayer can be applied. The monolayer is obtained by applying a solution of the linker compound and evaporating the solvent.

[0193] The parylene layer, i.e., a poly(p-xylylene) polymer layer, is formed on the interface layer, or in the case of the third embodiment, on the interface layer of both the first layer structure and the second layer structure. The poly(p-xylylene) polymer has the following structural formula:

[0194]

[0195] where n is the degree of polymerization.

[0196] The precursor of the poly(p-xylylene) compound is di-p-xylylene having the following structural formula:

[0197]

[0198] Dimeric compounds are commercially available as precursors to parylene N, parylene C, parylene D, and parylene F. In parylene N, all X and R1 to R4 are hydrogen, in parylene C, one of R1 to R4 is chlorine, and the other residues R and X are hydrogen, in parylene D, two of the residues R1 to R4 are chlorine, and all other residues are hydrogen, and in parylene F, the residue X is fluorine, and the residues R1 to R4 are hydrogen. Parylene layers are typically used as moisture barriers and dielectric barriers.

[0199] At elevated temperatures (above about 500°C, depending on the specific parylene) under vacuum, the dimers cleave to form the corresponding paraxylene radicals. On the one hand, the monomers polymerize to form poly(p-xylylene) polymers, and on the other hand, the monomers bond to the interfacial layer via their functional groups (e.g., methacrylate groups). Alternatively, they may simply adhere to the hydrophobic portion of the interfacial layer.

[0200] It has been found that parylene C, in which one of R1 to R4 is chlorine, when applied as a cover layer of a composite layer according to the first and second embodiments, or as a cover layer of a first and second layer structure according to the third embodiment, forms a coating that makes the magnetic material resistant to corrosion under the conditions encountered in an intravascular blood pump. The parylene layer is preferably applied by plasma deposition, with the layer thickness of the uppermost layer preferably being in the range of 3 μm to 20 μm, more preferably 10 μm to 17 μm, and most preferably about 15 μm. In the third embodiment, the parylene layer of the first layer structure preferably has a thickness in the range of 0.5 μm to 4 μm, more preferably 1 μm to 2 μm.

[0201] When Parylene C is applied directly to the surface of a magnetic material, crack formation and delamination of the Parylene C protective layer, as well as corrosion of the magnetic material, can be observed within a few days. Similarly, if Parylene C is applied over a metal layer or a metal / metal oxide layer, corrosion of the magnetic material can be observed within unacceptably short time periods due to delamination under the conditions of an intravascular blood pump. Furthermore, even with the use of adhesion promoters, for example, if applied as a silane-based interface layer, Parylene compounds other than Parylene C do not provide adequate corrosion protection.

[0202] The composite coating of the present invention adheres well to the magnet body and, because it has a structure composed of inorganic and organic components, it provides an effective barrier to both inorganic and organic substances. In addition, the glassy interface layer also has barrier properties.

[0203] In a particularly preferred embodiment of the present invention, corrosion protection of the magnetic material is further enhanced by making the shape of the magnet body particularly suitable for allowing the formation of a coating of uniform thickness covering the magnet body. To this end, the magnet body does not have sharp edges, but rather has rounded corners, such as softened edges. Preferably, the magnet body is rod-shaped and has a channel extending longitudinally therethrough for receiving the motor shaft of the intravascular blood pump, with the relative front face of the magnet body inclined toward the channel. The channel does not need to be coated with a composite coating, since in the intravascular blood pump, the channel receives the motor shaft and is fixed thereto. Of course, the channel can be coated for safety reasons.

[0204] The magnet body can be a single piece or can be made of multiple segments. In the latter case, each segment is provided with a coating of uniform thickness according to the present invention, which completely covers it or covers at least its exposed surface. Preferably, each segment has a softened edge. BRIEF DESCRIPTION OF THE DRAWINGS

[0205] The present invention will be further explained with reference to the accompanying drawings, in which:

[0206] Figure 1 is a schematic longitudinal cross-sectional view of an exemplary embodiment of an intravascular blood pump,

[0207] Figure 2 is a schematic cross-sectional view of a portion of a magnet according to a first embodiment of the present invention,

[0208] Figure 3 a is a schematic cross-sectional view of a portion of a magnet according to a second embodiment of the present invention,

[0209] Figure 3 b is a schematic cross-sectional view of a portion of another magnet according to a second embodiment of the present invention,

[0210] Figure 4 a is a schematic cross-sectional view of a portion of a magnet according to a third embodiment of the present invention,

[0211] Figure 4 b is a schematic cross-sectional view of a portion of another magnet according to a third embodiment of the present invention,

[0212] Figure 5 a is a schematic diagram of an exemplary one-piece magnet according to the present invention,

[0213] Figure 5 b is shown Figure 5 A partial cross-sectional view of a detail of the magnet illustrated in a, and

[0214] Figure 6 is a schematic top view of an exemplary segmented magnet according to the present invention.

[0215] The accompanying drawings are not drawn to scale and should not be construed as limiting the invention in any way. DETAILED DESCRIPTION

[0216] Figure 1 The intravascular blood pump 10 illustrated in FIG has been described above. The pump is conventional in construction but comprises a corrosion-resistant permanent magnet 1 according to the invention.

[0217] exist Figure 1 In the pump, the magnet 1 is rod-shaped, flat relative to the front and parallel to each other. Although the composite coating according to the present invention can effectively protect the magnet having the following characteristics for a long period of time: Figure 1 The magnet body has sharp edges as shown in the figure to prevent corrosion, but it is preferred in the present invention to use a magnet body having sharp edges as shown in the figure to prevent corrosion. Figure 5 and Figure 6 The individual layers of composite coating extend completely over each previously applied composite coating.

[0218] Figure 2 is a schematic cross-sectional view of a portion of a magnet 1 having a composite coating 15 according to a first embodiment of the present invention. Figure 2In the case of the exemplary magnet illustrated in FIG, composite coating 15 is formed on surface 19' of non-magnetized magnet body 19. Composite coating 15 includes a first aluminum oxide layer 42 formed on surface 19' of magnet body 19 by atomic layer deposition. An aluminum layer 43 is deposited on surface 42' of aluminum oxide layer 42 by physical vapor deposition. A second aluminum oxide layer 44 is deposited on surface 43' of aluminum layer 43 by atomic layer deposition. The first aluminum oxide layer 42, aluminum layer 43, and second aluminum oxide layer 44 combine to form inorganic layer 41 of composite coating 15. A connecting sublayer 46 is formed on surface 44' of second aluminum oxide layer 44 and firmly bonds organic layer 47 to second metal oxide layer 44. Organic layer 47 of composite coating 15 is composed of parylene C and covers surface 46' of connecting sublayer 46.

[0219] exist Figure 2 In the case of the exemplary magnet illustrated in , the first and second aluminum oxide layers each have a thickness of 100 nm, the aluminum layer has a thickness of 4 μm, the layer formed of parylene C has a thickness of 15 μm, and the connecting sublayer is a single layer.

[0220] Figure 3 a is a schematic cross-sectional view of a portion of a magnet 1 having a composite coating 16 according to a second embodiment of the present invention. Figure 3 In the exemplary magnet illustrated in Figure a, composite coating 16 is formed on surface 19' of a non-magnetized magnet body 19. Composite coating 16 includes a first metal oxide layer 52 composed of titanium oxide. First metal oxide layer 52 is deposited on surface 19' of magnet body 19 by atomic layer deposition to a thickness of 100 nm. Metal layer 53 composed of titanium is deposited on surface 52' of first metal oxide layer 52 by physical vapor deposition to a thickness of 4 μm. Second metal oxide layer 54 is deposited on surface 53' of metal layer 53 by atomic layer deposition to a thickness of 100 nm. The second metal oxide layer is composed of a mixture of aluminum oxide and titanium oxide. Plating layer 55 is disposed on surface 54' of second metal oxide layer 54. Plating layer 55 is an aluminum metal layer having a thickness of approximately 15 μm. The first metal oxide layer 52, metal layer 53, second metal oxide layer 54, and another metal layer collectively constitute inorganic layer 51. The connecting sublayer 56 is formed on the surface 55' of the other metal layer and firmly bonds the organic layer 57 to the other metal layer. The other metal layer is the plating layer 55. The organic layer 57 of the composite coating 16 is composed of parylene C and covers the surface 56' of the connecting sublayer 56.

[0221] Figure 3 b shows the Figure 3 A magnet 1 similar to the magnet shown in a, however having another metal oxide layer 58 provided on the aluminum metal layer. Figure 3In the embodiment illustrated in b, the other metal oxide layer 58 is a natural aluminum oxide layer having a thickness of about 3 nm, ie, a passivation layer formed when the aluminum metal layer is exposed to air.

[0222] Figure 4 a is a schematic cross-sectional view of a portion of a magnet 1 having a composite coating 18 according to a third embodiment of the present invention. Figure 4 In the case of the exemplary magnet illustrated in FIG. a , the composite coating 18 includes a first layer structure 17 and a second layer structure 17 ′.

[0223] The first layer structure 17 includes an inorganic layer 61 composed of a first metal oxide layer 62 and a second metal oxide layer 64, an organic layer 67, and a connecting sublayer 66 disposed between the second metal oxide layer 64 and the organic layer 67. The second layer structure 17′ is disposed on the first layer structure 17 and includes an inorganic layer 71 composed of a third metal oxide layer 74, an organic layer 77, and a connecting sublayer 76 disposed between the third metal oxide layer 74 and the organic layer 77.

[0224] The first metal oxide layer is an aluminum oxide layer having a thickness of 100 nm, formed on surface 19' of magnet body 19 by atomic layer deposition. The second metal oxide layer is a titanium oxide layer having a thickness of 10 nm, formed on surface 62' of the first metal oxide layer by atomic layer deposition. Connecting sublayer 66 is a single layer formed on surface 64' of the second metal oxide layer, and organic layer 67 is a layer formed of parylene C on surface 66' of connecting sublayer 66. The parylene C layer has a thickness in the range of 1 to 2 μm.

[0225] Third metal oxide layer 74 comprises a titanium oxide layer having a thickness of 10 nm, formed by atomic layer deposition on surface 67' of first organic layer 67. A connecting sublayer 76 is provided on surface 74' of the titanium oxide layer, and another parylene C layer 77 is formed on surface 76' of the connecting sublayer 76. This outermost parylene C layer has a thickness of approximately 13 μm.

[0226] Figure 4 b shows the Figure 4 The second layer structure 17′ is similar to the magnet shown in FIG. 1 , however, an additional (intermediate) metal oxide layer 72 is provided between the organic layer 67 and the third metal oxide layer 74. Thus, the second layer structure 17′ includes an inorganic layer 71 composed of the intermediate metal oxide layer 72 and the third metal oxide layer 74, an organic layer 77, and a connecting sublayer 76 provided between the third metal oxide layer 74 and the organic layer 77. The intermediate metal oxide layer 72 is an aluminum oxide layer having a thickness of 20 nm formed by atomic layer deposition. As for the remaining layers, the same as in the above-mentioned embodiment are used. Figure 4The first layer structure and the second layer structure comprise layers made of the same material (while in other embodiments the materials may be different), but with different thicknesses.

[0227] exist Figure 4 a and Figure 4 In the embodiment shown in b, all connecting sublayers are single layers and identical.

[0228] Figure 5 a shows a one-piece magnet 1 having a rod shape and a hole or channel extending through it in the longitudinal direction. Figure 1 During use of the magnet in the intravascular blood pump 10 shown in FIG, the channel receives the motor shaft 25. The opposite front face 4 of the magnet tapers toward the channel. The magnet 1 is provided with a composite coating according to the present invention on the outer surface 2 exposed to the fluid flowing in the gap 26 and on the tapering front face 4. The inner surface 3 adjacent to the motor shaft 25 may or may not be coated. The edge 5 at the transition between the outer surface 2 and the front face 4 and the edge 6 at the transition between the front face 4 and the inner surface 3 are coated. The edges are softened to facilitate the formation of a uniform coating with good adhesion. "N" and "S" represent the north and south poles of the magnet.

[0229] Figure 5 b is along Figure 5 a Partial cross-section along the dotted line. Figure 5 b shows Figure 5 The magnet region within the ring in a. Figure 5 b clearly shows the softened edges 5,6.

[0230] Figure 6 A segmented magnet 7 is shown. Figure 6 The magnet shown in FIG has four segments 8, 8'. The segments 8 facing each other have the same magnetic poles, as shown in FIG. Figure 6 As shown in the top view of "N", the segments 8' opposite to each other also have the same magnetic poles, as shown in Figure 6 Thus, adjacent segments 8, 8' have opposite magnetic poles.

[0231] Similar to Figure 5 The one-piece magnet shown in FIG, segments 8, 8' have an inner surface, an outer surface, an opposite front face, an edge at the transition between the outer surface and the front face, and an edge at the transition between the front face and the inner surface. Figure 5', the front is designated 4' and the edges are designated 5' and 6', respectively. Furthermore, segments 8, 8' have side surfaces 9, 9' which are separated in the drawing by a gap. Of course, when the magnet is in use, the side surfaces 9, 9' contact each other. All surfaces of each segment of the magnet can be completely covered by the composite coating of the present invention, but the side surfaces 9, 9' which are not exposed because they contact each other, and the inner surfaces which are not exposed because they contact the motor shaft, do not need to be coated. Preferably, all edges of all segments are softened edges.

[0232] The same cylindrical non-magnetized Nd2Fe14B sintered magnet body with a length of 12 mm and a diameter of 2.8 mm was coated with different coatings (after cleaning, but without removing the phosphate coating), magnetized, and subjected to a corrosion test in an aqueous solution containing 0.9 wt% sodium chloride at 60°C. In this test, corrosion proceeded approximately 3.75 times faster than in a 5% to 40% (by weight) glucose aqueous solution for injection at room temperature.

[0233] The following coatings have proven to be particularly beneficial for the desired combination of excellent corrosion resistance and minimal scrap rates:

[0234] The magnet according to the first embodiment had a first and second metal oxide layer formed to a thickness of 100 nm by ALD, a metal layer formed to a thickness of 4 μm by PVD, and a parylene C coating formed to a thickness of 15±2 μm. The best magnets had (a) Al2O3 as the first and second metal oxide layers, and aluminum as the metal layer, (b) Al2O3 as the first and second metal oxide layers, and titanium as the metal layer, (c) TiO2 as the first and second metal oxide layers, and titanium as the metal layer, (d) Al2O3 as the first metal oxide layer, a mixture of Al2O3 and TiO2 as the second metal oxide layer, and titanium as the metal layer, and (e) TiO2 as the first metal oxide layer, a mixture of Al2O3 and TiO2 as the second metal oxide layer, and titanium as the metal layer. Bias voltage during the PVD process appears to improve coating quality.

[0235] The magnet according to the second embodiment has a first metal oxide layer formed to a thickness of 100 nm by ALD, a second metal oxide layer formed to a thickness of 100 nm by ALD, a metal layer formed to a thickness of 4 μm by PVD, another metal layer (aluminum) formed to a thickness of 15 μm ± 3 μm by electroplating, and a polyparaxylene C coating formed to a thickness of 15 ± 2 μm.

[0236] The best magnets have (a) Al2O3 as the first metal oxide layer and the second metal oxide layer, and aluminum as the metal layer, (b) TiO2 as the first metal oxide layer, a mixture of Al2O3 and TiO2 as the second metal oxide layer, and titanium as the metal layer, and (c) TiO2 as the first metal oxide layer and the second metal oxide layer, and iron as the metal layer.

[0237] The magnet according to the third embodiment has Al2O3 as a first metal oxide layer formed by ALD to a thickness of 100 nm, TiO2 as a second metal oxide layer formed by ALD to a thickness of 10 nm, a parylene C coating layer formed to a thickness of 1 to 2 μm, Al2O3 as an intermediate metal oxide layer formed by ALD to a thickness of 20 nm, TiO2 as a third metal oxide layer formed by ALD to a thickness of 10 nm, and a parylene C coating layer formed to a thickness of 13±2 μm.

[0238] In each case, the tie layer and, if applicable, the other tie layers were formed from an alcoholic solution containing Silane A-174 (water / ethanol, acetic acid to a pH of approximately 5 to 6; silane concentration of approximately 1%; reaction time of approximately 5 minutes). Evaporation of the alcohol essentially yielded a monolayer. The Parylene C coating was formed by plasma deposition.

Claims

1. A corrosion-resistant permanent magnet comprising a magnet body and a composite coating disposed on and covering the surface of the magnet body, wherein the composite coating comprises the following components in the order described below: - a first metal oxide layer in physical contact with the magnet body, - Metal layer, - a second metal oxide layer, - Connecting sublayers, and - A layer formed of poly(2-chloro-p-xylene).

2. The corrosion-resistant permanent magnet according to claim 1, wherein The magnet body is a rare earth metal iron boron permanent magnet.

3. The corrosion-resistant permanent magnet according to claim 2, wherein: The magnet body is a sintered magnet body comprising Nd2Fe14B crystals and NdFeB material coating the Nd2Fe14B crystals, wherein the NdFeB material is richer in neodymium than the Nd2Fe14B crystals.

4. The corrosion-resistant permanent magnet according to any one of claims 1 to 3, wherein The metal of the metal layer is aluminum or titanium, or an alloy of aluminum or titanium.

5. The corrosion-resistant permanent magnet according to any one of claims 1 to 3, wherein The oxide of the first metal oxide layer is Al2O3 or TiO2 or a mixed oxide of Al2O3 and TiO2.

6. The corrosion-resistant permanent magnet according to any one of claims 1 to 3, wherein The oxide of the second metal oxide layer is Al2O3 or TiO2 or a mixed oxide of Al2O3 and TiO2.

7. The corrosion-resistant permanent magnet according to any one of claims 1 to 3, comprising a further metal layer, wherein - said metal layer is in physical contact with said first metal oxide layer, - the second metal oxide layer is in physical contact with the metal layer, - said further metal layer is in physical contact with said second metal oxide layer, - the connecting sublayer is in physical contact with the further metal layer, and - the poly(2-chloro-p-xylene) layer is in physical contact with the tie sublayer, or, comprising another metal layer and another metal oxide layer between the second metal oxide layer and the connecting sublayer, wherein - said metal layer is in physical contact with said first metal oxide layer, - the second metal oxide layer is in physical contact with the metal layer, - said further metal layer is in physical contact with said second metal oxide layer, - said further metal oxide layer is in physical contact with said further metal layer, - the connecting sublayer is in physical contact with the further metal oxide layer, and - The poly(2-chloro-p-xylylene) layer is in physical contact with the tie sublayer.

8. The corrosion-resistant permanent magnet according to claim 7, wherein: The metal of the other metal layer is aluminum.

9. The corrosion-resistant permanent magnet according to any one of claims 1 to 3, wherein The metal layer is omitted, and the composite coating further comprises, in the following order, on the layer formed of poly(2-chloro-p-xylene): - a third metal oxide layer, - another connection sublayer, and - Another layer formed of poly(2-chloro-p-xylene). 10 . The corrosion-resistant permanent magnet according to claim 9 , further comprising an intermediate metal oxide layer between the layer formed of poly(2-chloro-p-xylene) and the third metal oxide layer.

11. The corrosion-resistant permanent magnet according to claim 9, wherein The oxide of the first metal oxide layer is Al2O3 and the oxide of the second metal oxide layer is TiO2, or the oxide of the first metal oxide layer is TiO2 and the oxide of the second metal oxide layer is Al2O3, or the oxide of the first metal oxide layer and the second metal oxide layer is Al2O3, or the oxide of the first metal oxide layer and the second metal oxide layer is TiO2, and / or the oxide of the third metal oxide layer is TiO2 or Al2O3.

12. The corrosion-resistant permanent magnet according to claim 10, wherein The oxide of the intermediate metal oxide layer is Al2O3 or TiO2, and is different from the oxide of the third metal oxide layer.

13. A method for producing a corrosion-resistant permanent magnet, the method comprising: - Provide a non-magnetized magnet body, - forming a first metal oxide layer on the surface of the magnet body, - forming a metal layer on the first metal oxide layer, - forming a second metal oxide layer on the metal layer and forming a connecting sublayer on the second metal oxide layer, or forming a second metal oxide layer on the metal layer, forming at least one other layer on the second metal oxide layer and forming a connecting sublayer on the at least one other layer, - forming a layer of poly(2-chloro-p-xylylene) on the connecting sublayer, and - Magnetizing the magnet body.

14. The method of claim 13, comprising forming the at least one further layer, wherein the at least one further layer is a further metal layer. The method of claim 14 , further comprising forming another metal oxide layer on the another metal layer.

16. The method according to any one of claims 13 to 15, wherein The oxide of the first metal oxide layer is Al2O3 or TiO2, or a mixed oxide of Al2O3 and TiO2; and / or the oxide of the second metal oxide layer is Al2O3 or TiO2, or a mixed oxide of Al2O3 and TiO2.

17. The method according to any one of claims 13 to 15, wherein The metal of the metal layer is aluminum or titanium, or an alloy of aluminum or titanium.

18. The method according to claim 14 or 15, wherein The metal of the other metal layer is aluminum.

19. A method for producing a corrosion-resistant permanent magnet, the method comprising: - Provide a non-magnetized magnet body, - forming a first metal oxide layer on the surface of the magnet body, - forming a second metal oxide layer on the first metal oxide layer, - forming a connecting sublayer on the second metal oxide layer, - forming a poly(2-chloro-p-xylene) layer on the connecting sublayer and forming a third metal oxide layer on the poly(2-chloro-p-xylene) layer, or forming a poly(2-chloro-p-xylene) layer on the connecting sublayer, forming an intermediate metal oxide layer on the poly(2-chloro-p-xylene) layer and forming a third metal oxide layer on the intermediate metal oxide layer, - forming another connecting sublayer on the third metal oxide layer, - forming a further layer of poly(2-chloro-p-xylylene) on said further connecting sublayer, and - Magnetizing the magnet body.

20. The method according to claim 19, wherein The oxide of the first metal oxide layer is Al2O3 and the oxide of the second metal oxide layer is TiO2, or the oxide of the first metal oxide layer is TiO2 and the oxide of the second metal oxide layer is Al2O3, or the oxides of the first metal oxide layer and the second metal oxide layer are both Al2O3 or both TiO2, and / or the oxide of the third metal oxide layer is TiO2 or Al2O3.

21. The method of claim 19 or 20, comprising forming the intermediate metal oxide layer, wherein The oxide of the intermediate metal oxide layer is Al2O3 or TiO2, and is different from the oxide of the third metal oxide layer.

22. An intravascular blood pump comprising an electric motor, wherein the electric motor comprises a permanent magnet according to any one of claims 1 to 12.

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