Polyimide compound, medical polyimide catheter, and preparation method and application thereof

Abstract

The present invention provides a polyimide compound, a medical polyimide catheter, and a preparation method and application thereof; the polyimide compound is a block polyimide polymer obtained by a block combination of two segments, a rigid segment and a flexible segment, on the same molecular main chain; the block polyimide polymer includes a structural unit shown in general formula (1) as a repeating unit; the structural formula of general formula (1) is: The present invention adopts a block molecular segment combination to achieve high strength and high modulus, anti-twisting and wear resistance of its polyimide catheter, and adopts a polyamic acid precursor solution to be first formed and then cured to achieve adjustable tube wall thickness, and utilizes the catalytic effect of chemical reagents to ensure its high toughness and density, thereby achieving wide application in high-end medical devices, especially in cardiovascular interventional treatment.

Description

Technical Field

[0001] The present invention relates to the technical field of medical devices, and in particular to a polyimide compound, a medical polyimide catheter, and a preparation method and application thereof, and in particular to an ultra-thin, high-strength, torsion-resistant, solvent-resistant, and wear-resistant high-performance polyimide medical catheter formed from a polyamic acid precursor. Background Art

[0002] Medical catheters are made of polymer materials that meet medical standards and are used as medical device catheters for insertion into or outside the human body for diagnosis or treatment of diseases. The global medical catheter market grew at an average annual rate of 7.5% from 2014 to 2020. However, medical catheters have the characteristics of small size, complex cross-sectional shapes, high geometric precision, high hygienic indicators, and biochemical stability. Their performance depends on the inherent properties of the polymer material and the corresponding molding process. Common medical polymer materials include silicone rubber, polyurethane, polytetrafluoroethylene, polyethylene, polypropylene, polyurethane, nylon, ABS, polycarbonate, etc. Among them, extrusion molding is the most commonly used process step in the manufacture of medical catheters. Figure 1 , which is the production process of medical catheters using extrusion molding technology in the existing technology. The raw material tube is first processed into a simple raw material tube through the extrusion process, and then undergoes various subsequent assemblies to form the final catheter device. In order to achieve multiple functional combinations of the catheter, multi-layer catheter extrusion technology has been developed. Figure 5 This is a schematic diagram of the melt extrusion process for producing polyimide catheters in the prior art. The raw materials required for the extrusion process, after cooling through spiral extrusion, require a polymer with a low melt viscosity at the extrusion temperature. Conventional raw materials, such as polymers with flexible molecular chains or loosely packed condensed structures, result in medical catheters with low temperature resistance, weak strength, and insufficient wear resistance, limiting their application.

[0003] However, some higher-end medical devices have more stringent requirements for precision medical catheters, which often require extremely small tube diameters, excellent strength, wear resistance, high torque, creep resistance, kink resistance and burst resistance. Such catheters, for example, polyimide materials have the advantages of high strength, high modulus, high temperature resistance, chemical stability, radiation resistance, easy manipulation and not easy to knot, smooth surface, and good biocompatibility. They are mainly used in cardiovascular interventional treatments in China (such as inner tubes of stent delivery devices, inner tubes of balloon catheters, and inner tubes of heart valve delivery systems) and play an irreplaceable role.

[0004] In the prior art, polyimide materials with high strength, high modulus, and solvent resistance have no melting point before decomposition and cannot be prepared using conventional extrusion molding methods. In addition, since polyimide is insoluble in solvents, it can only be prepared into polyimide catheters by first molding its precursor polyamic acid and then imidizing it. Therefore, the catheter molding process is extremely difficult. In particular, the preparation process of high-performance medical catheters with high strength, wear resistance, and anti-torsion required for cardiovascular treatment cannot be prepared using conventional extrusion processes, and the performance of the products cannot meet the requirements of high-end medical devices. Figure 2 Medical polyimide catheters are currently manufactured using high-melting-point specialty polymers such as polyetheretherketone (PEEK) and polyetherimide (PEI) using conventional extrusion processes. However, due to the insufficient mechanical strength and modulus of the matrix polymer, and the extrusion process, the product wall thickness can only be 0.03mm. Thinner wall thicknesses, such as 0.01mm, cannot be achieved using conventional extrusion processes, thus restricting product performance. The main challenge in preparing medical polyimide catheters that meet high-end medical needs lies in the unclear impact of the polymerization and molding processes on the product's interfacial properties and macroscopic physical properties. The lack of a suitable product processing technology has led to inconsistent product quality, poor interfacial properties between structures, numerous defects, insufficient consistency, and a low pass rate, which cannot meet the needs of high-end medical devices.

[0005] Based on the problems existing in the existing technology, developing an ultra-thin, high-strength, torsion-resistant, solvent-resistant, and wear-resistant polyimide medical catheter is a key technical problem that needs to be solved in this field. Summary of the Invention

[0006] In response to the technical problems existing in the prior art, the present invention discloses a polyimide compound, a medical polyimide catheter, and a preparation method and application thereof. The provided medical polyimide catheter has excellent comprehensive properties such as ultra-thinness, high strength, anti-twisting, solvent resistance, wear resistance, and water resistance, and meets the requirements of the prior art for high-end medical polyimide catheters.

[0007] To achieve the above object, the present invention provides the following technical solution: a polyimide compound, comprising a block polyimide polymer obtained by combining two types of segments, a rigid segment and a flexible segment, on the same molecular main chain.

[0008] Preferably, the block polyimide polymer includes a structural unit as shown in general formula (1) as a repeating unit; the structural formula of general formula (1) is:

[0009] Among them, X1 and Y1 are the rigid segments; X2 and Y2 are the flexible segments; m represents that the molar percentage of the rigid segments in the rigid and flexible segments is 60% to 80%, and n represents that the molar percentage of the flexible segments in the rigid and flexible segments is 20% to 40%.

[0010] Furthermore, X1 and X2 are residues of tetracarboxylic dianhydride compounds in a tetravalent organic group, X1 is a residue of a rigid dianhydride compound, and X2 is a residue of a flexible crystalline dianhydride compound.

[0011] Y1 and Y2 represent residues of diamine compounds in a divalent organic group, Y1 is a residue of a rigid diamine compound, and Y2 is a residue of a flexible crystalline diamine compound.

[0012] Preferably, in the rigid segment, X1 is derived from one or more of phthalic anhydride, 4,4′-biphenyl dianhydride, 4,4′-p-terphenyl dianhydride, 2,3,6,7-anthracenetetracarboxylic dianhydride, 1,4,5,8-naphthalenetetracarboxylic dianhydride, cyclobutane dianhydride, 9,9-bis[4-(3,4-dicarboxylic acid phenoxy)phenyl]fluorene dianhydride, and dibenzodioxane dianhydride; and Y1 in the rigid segment is derived from p-phenylenediamine, 2,6-naphthalenediamine, 1,4-diphenylamine, 4,4′-diamino-2,2′-dimethylbiphenyl, 4,4′-diamino-tetramethyl-p-terphenyl, 9,9-bis(4-aminophenyl)fluorene, 2,6-diaminopyridine, 2,5-bis(4-aminophenyl)pyridine, 5-amino-2-(3′-aminophenyl)benzophenone imidazole, 2-amino-5 (4-aminophenyl) -pyrimidine or a combination thereof; in the flexible segment, X2 is derived from 4,4'-diphenyl ether dianhydride, 4,4'-diphenyl sulfide dianhydride, 4,4'-(terephthalic) dianhydride, pyrophthalic anhydride, 4,4'-biphenyl dianhydride, 4,4'-(3,4-dicarboxyphenoxy) benzophenone dianhydride, and trimellitic anhydride hydroquinone ester; and Y2 is derived from one or a combination of 4,4'-diaminodiphenyl ether, 3,4'-diaminodiphenyl ether, 1,4-bis (4-aminophenoxy) benzene, 1,3-bis (4-aminophenoxy) benzene, 2,7-bis (4-aminophenoxy) naphthalene, 4,4'-bis (3-aminophenoxy) biphenyl, and 4,4'-bis (3-aminophenoxy) benzophenone.

[0013] Preferably, the method for preparing the block polyimide polymer comprises the following steps:

[0014] Step 1. providing a polyamic acid precursor solution;

[0015] The rigid diamine compound and the rigid dianhydride compound are respectively added to a polar aprotic solvent, and after dissolving, a first-stage reaction is carried out; one of the flexible crystalline diamine compound or the flexible crystalline dianhydride compound is then added to carry out a second-stage reaction, and then the other of the flexible crystalline dianhydride compound or the flexible crystalline diamine compound is added to carry out a third-stage reaction until the reaction is completed, thereby obtaining the polyamic acid precursor solution;

[0016] Step 2. Imidization treatment: adding a dehydrating agent and a catalyst to the polyamic acid precursor solution to carry out an imidization reaction to obtain the block polyimide polymer.

[0017] Preferably, in step 1, the polar aprotic solvent includes at least one of N,N-dimethylformamide (DMF), N,N-dimethylacetamide (DMAc), N-methyl-2-pyrrolidone (NMP), dimethyl sulfoxide (DMSO), diphenyl sulfone, tetramethyl sulfone, tetrahydrofuran (THF), dioxane, dichloromethane, chloroform, hexamethylphosphorus triamide, γ-butyrolactone, cyclopentanone, m-cresol, diethyl ether, and p-cresol methyl ether.

[0018] Preferably, the rigid dianhydride compound includes any one or a combination of phthalic anhydride, 4,4′-biphenyl dianhydride, 4,4′-terphenyl dianhydride, 2,3,6,7-anthracenetetracarboxylic dianhydride, 1,4,5,8-naphthalenetetracarboxylic dianhydride, cyclobutane dianhydride, 9,9-bis[4-(3,4-dicarboxylic acid phenoxy)phenyl]fluorene dianhydride, and dibenzodioxane dianhydride; preferably phthalic anhydride and / or 4,4′-biphenyl dianhydride.

[0019] Preferably, the rigid diamine compound includes any one or a combination of p-phenylenediamine, 2,6-naphthalenediamine, 1,4-benzidine, 4,4′-diamino-2,2′-dimethylbiphenyl, 4,4′-diamino-tetramethyl-p-terphenyl, 9,9-bis(4-aminophenyl)fluorene, 2,6-diaminopyridine, 2,5-bis(4-aminophenyl)pyridine, 5-amino-2-(3′-aminophenyl)benzimidazole, and 2-amino-5(4-aminophenyl)-pyrimidine; preferably p-phenylenediamine and / or 4,4′-diamino-2,2′-dimethylbiphenyl.

[0020] Preferably, the flexible crystalline dianhydride compound includes any one of 4,4′-diphenyl ether dianhydride, 4,4′-diphenyl sulfide dianhydride, 4,4′-(p-phenylene) diether dianhydride, phthalic anhydride, 4,4′-biphenyl dianhydride, 4,4′-(3,4-dicarboxyphenoxy)benzophenone dianhydride, and trimellitic anhydride hydroquinone ester, or a combination of several thereof; preferably phthalic anhydride and / or 4,4′-biphenyl dianhydride.

[0021] Preferably, the flexible crystalline diamine compound includes any one or a combination of 4,4′-diaminodiphenyl ether, 3,4′-diaminodiphenyl ether, 1,4-bis(4-aminophenoxy)benzene, 1,3-bis(4-aminophenoxy)benzene, 2,7-bis(4-aminophenoxy)naphthalene, 4,4′-bis(3-aminophenoxy)biphenyl, and 4,4′-bis(3-aminophenoxy)benzophenone; preferably, 1,3-bis(4-aminophenoxy)benzene and 4,4′-bis(3-aminophenoxy)biphenyl.

[0022] Preferably, when the molar amount of the rigid dianhydride compound is greater than the molar amount of the rigid diamine compound, the rigid diamine compound and the rigid dianhydride compound are first added to the polar aprotic solvent in sequence to dissolve and then carry out the first stage reaction. After they are completely dissolved and react for 1-5 hours, the flexible crystalline diamine compound is added. After it is dissolved and reacted for another 1-5 hours, the flexible crystalline dianhydride compound is finally added and reacted for 2-6 hours, and the reaction is completed; or, when the molar amount of the rigid dianhydride compound is less than the molar amount of the rigid diamine compound, the order of addition is the rigid diamine compound, the rigid dianhydride compound, the flexible crystalline dianhydride compound and the flexible crystalline diamine compound, so as to avoid competitive polymerization of the free rigid diamine compound and the flexible crystalline diamine compound in the reaction system.

[0023] Preferably, in step 2, the dehydrating agent includes an aliphatic anhydride, an aromatic anhydride, N,N-dialkylcarbodiimide, an aromatic sulfonic acid dihalide, a thionyl halide, or a combination of two or more thereof; preferably, it is an aliphatic anhydride; more preferably, it is one of acetic anhydride, propionic anhydride, butyric acid, or a combination of two or more thereof; the catalyst includes at least one of an aliphatic tertiary amine, an aromatic tertiary amine, and a heterocyclic tertiary amine; preferably, it is a nitrogen-containing heterocyclic tertiary amine; more preferably, it is at least one of pyridine, 3-methylpyridine, quinoline, isoquinoline, imidazole, and benzimidazole.

[0024] Preferably, the molar ratio of the chemical dehydrating agent to the catalyst is 3 to 10:1.

[0025] As another object, the present invention also provides a polyimide catheter prepared using the above-mentioned block polyimide polymer; the wall thickness of the polyimide catheter is 4 to 100 μm, and the inner diameter is 10 to 10,000 μm; preferably, the wall thickness is 4 to 6 μm.

[0026] Preferably, the polyimide catheter is obtained by using a dip coating method, wherein the polyamic acid precursor solution is first dip coated on the outer wall of the catheter carrier, and then pre-dried and shaped, and then imidized and finally cured.

[0027] Preferably, the polyamic acid precursor solution is subjected to the imidization treatment to obtain the block polyimide polymer.

[0028] As a third aspect of the present invention, a method for preparing the polyimide catheter is also provided, comprising the following steps:

[0029] S1. Providing a polyimide precursor solution;

[0030] S2 dip coating and shaping: using a multi-stage dip coating and pre-baking gluing process, the polyimide precursor solution is dipped on the outer wall of the die, after pre-drying and shaping treatment, the surface of the catheter carrier to form a uniform film;

[0031] S3 provides a pre-baked adhesive layer: the film is immersed in an imidization agent, and the imidization treatment is performed to convert the polyamic acid into a block-type polyimide polymer;

[0032] S4. Imidization: performing a high-temperature curing treatment on the block polyimide polymer to obtain a polyimide conduit on the surface of the tube core;

[0033] S5. Pulling the polyimide tube away from the surface of the tube core to obtain a final product.

[0034] Preferably, in S1, the solid content of the polyimide precursor solution is 5 to 50 wt%, preferably 10 to 40 wt%, and more preferably 12 to 30 wt%.

[0035] Preferably, the viscosity of the polyamic acid precursor solution is 100 to 100,000 cP, preferably 1,000 to 10,000 cP, and more preferably 3,000 to 8,000 cP.

[0036] Preferably, in S2, the conveying speed of the tube core in the polyimide precursor solution is 0.1 to 50 m / min.

[0037] Preferably, the shaping treatment includes drying by hot air drying; the hot air temperature is 80-200° C.; and the hot air speed is 0.1-10 m / s.

[0038] Preferably, the material of the tube core includes any one of a glass rod, a quartz rod, a stainless steel wire, a copper wire, and a silver-plated copper wire.

[0039] More preferably, the method further comprises pre-treating the tube core, wherein the pre-treating comprises applying a lubricant to the surface of the tube core;

[0040] Preferably, in S4, the high-temperature curing treatment includes adopting a multi-stage gradient high-temperature curing process, including setting multiple temperature gradients, gradually heating up and then gradually annealing; preferably, the temperature gradients are 300, 400, 500, 600, 500, 400, 300°C, or the temperature gradients are 300, 375, 450, 525, 600, 500, 400, 300°C, respectively.

[0041] Preferably, S2 can be operated in multiple cycles.

[0042] As a fourth aspect of the present invention, there is also provided an apparatus for preparing the polyimide catheter, comprising at least:

[0043] First dipping device;

[0044] Pre-drying device;

[0045] Second dipping device;

[0046] High temperature curing device;

[0047] transmission device;

[0048] The tube core is sequentially passed through the first dipping device, the pre-baking device, the second dipping device and the high-temperature curing device by the transmission device, so that the polyimide precursor solution placed in the first dipping device is dip-coated on the surface of the glue slot mold. After pre-drying and shaping in the pre-baking device, it enters the second dipping device for imidization treatment to convert the glue film on the surface of the tube core into a polyimide polymer. Finally, it passes through the high-temperature curing device for curing treatment to obtain the polyimide catheter.

[0049] Preferably, the outlet of the first dipping device is provided with a first die, and the outlet of the second dipping device is provided with a second die. When the tube core with glue attached passes through the first die and the second die respectively, the excess glue on the surface of the tube core can be removed, so that the surface of the glue film is smooth and flat.

[0050] Preferably, when the tube core passes through the first dipping device and the second dipping device, it is transported from bottom to top and then passes through the first die and the second die respectively, so that the formed film has uniform thickness and a smooth surface.

[0051] Preferably, the transfer speed of the tube core through the first dipping device is 0.1 to 50 m / min, more preferably 0.5 to 30 m / min.

[0052] Preferably, the first dipping device and the pre-baking device may include a plurality of devices and be arranged in the order of the first dipping device and the pre-baking device.

[0053] The present invention adjusts and optimizes various process parameters such as the water content of the reaction solvent, reaction atmosphere, reaction temperature, stirring speed, reaction time, and addition sequence for the synthesis of a polyamic acid precursor, thereby achieving controllable polymerization of resin viscosity, solid content, molecular weight size and distribution, as well as excellent mechanical properties, thermal properties, and wear resistance.

[0054] The present invention focuses on the synthesis of polyamic acid precursors. To avoid interference from external environmental factors, the reaction device is installed in a clean room with constant temperature and humidity and class 1000 or below. The synthesized polyamic acid precursor solution is defoamed and microporously filtered (<3μm) to improve the uniformity of the glue solution and batch stability.

[0055] The core wire used for forming a polyimide catheter of the present invention has a diameter of 10-10000 μm. Since the conversion of polyamic acid into polyimide requires high-temperature curing, a glass rod, quartz rod, stainless steel wire, copper wire, silver-plated copper wire, etc. with a smooth surface is selected. In order to facilitate the subsequent peeling of the tube membrane and the tube core, the surface is first coated with tetrafluoroethylene or other lubricating materials.

[0056] The adhesive tank used for dipping the tube core in this invention is a slender vertical cylindrical tank with a circular orifice die at the end for controlling the tube film wall thickness and scraping off excess adhesive. The pre-baking furnace is a hot air tubular furnace with airflow directed opposite to the tube core's forward direction. The temperature can range from 80°C to 200°C. The adhesive tank and pre-baking furnace form a unit. To achieve thick tubes, a multi-layer structure is employed. During the production process, multiple adhesive tank and pre-baking furnace units are connected in series, thereby improving production efficiency.

[0057] In the present invention, a chemical reagent immersion tank is added between the pre-baking furnace and the high-temperature curing furnace, and the toughness and density of the tube membrane are improved by means of the catalytic effect of the chemical reagent. The chemical reagent immersion tank is also in the shape of a slender vertical cylinder, and the chemical reagent is composed of a dehydrating agent and a catalyst.

[0058] The high-temperature curing furnace of the present invention adopts a multi-stage high-temperature furnace combination, and its heating modes include hot air heating, electric heating tube heating, infrared heating or a combination thereof. The number of furnace sections and the furnace length are designed according to the running speed of the tube core and the required residence time. The high-temperature treatment range is 300-600°C.

[0059] The polyimide catheter prepared in the present invention has an inner diameter of 10 to 10,000 μm and a wall thickness of 4 to 1,000 μm. Its length can be cut before or after the separation of the tube membrane and the tube core according to user needs.

[0060] The technical effects of the technical solution of the present invention are as follows:

[0061] 1. By adopting the technical solution of the present invention and a block-type polyimide molecular structure design, rigid monomers such as 4,4'-biphenyltetracarboxylic dianhydride (4,4'-BPDA) and p-phenylenediamine (PDA) are used in the main molecular chain to form rigid segments in the molecular chain to improve its strength, modulus and anti-torsion performance; at the same time, semi-crystalline flexible molecular segments composed of oxygen ether bonds and meta-monomer structures are introduced to form local microcrystals to improve its wear resistance and toughness. Compared with catheters made of other materials, the polyimide catheter provided by the present invention has better strength, modulus, anti-torsion, solvent resistance, wear resistance and other properties.

[0062] 2. The technical solution of the present invention is adopted, and a method of dipping the tube core in a polyamic acid precursor solution is adopted. By controlling the solid content and viscosity of the polyamic acid precursor solution, the diameter of the glue slot die, and the number of dipping times, the controllable forming of the catheter wall thickness of 4-100 μm is achieved. Compared with the extrusion-molded catheter in the prior art, the thinnest wall thickness can only reach 30 μm. The catheter wall of the present invention can reach a thinnest of 4 μm.

[0063] 3. To address the problem that during the conversion of polyamic acid precursors into polyimide catheters, molecular chain degradation occurs when heated in the medium and high temperature ranges, resulting in brittle short tubes. The present invention uses process steps such as dipping in glue solution, die shaping, pre-baking, soaking in imidization reagent, and high-temperature baking in the imidization process of polyamic acid. Among them, soaking in imidization reagent will greatly improve the toughness of the polyimide catheter and increase the surface density to give it excellent water resistance, which is beneficial to reduce the penetration of blood into the catheter in the cardiovascular system.

[0064] 4. The present invention adopts a combination of block molecular segments to achieve the high strength, high modulus, anti-twisting and wear resistance of its polyimide catheter, and adopts a polyamic acid precursor solution to be first formed and then cured to achieve adjustable tube wall thickness, and utilizes the catalytic effect of chemical reagents to ensure its high toughness and density, so as to achieve wide application in high-end medical devices, especially in cardiovascular interventional treatment. BRIEF DESCRIPTION OF THE DRAWINGS

[0065] Figure 1 The figure is a schematic diagram of the process flow of the medical catheter extrusion process in the prior art.

[0066] Figure 2 The figure is a photo of a medical catheter product prepared by an extrusion process in the prior art.

[0067] Figure 3 Schematic diagram of the wear test method for the polyimide catheters prepared in Examples and Control Examples of the present invention.

[0068] Figure 4 This is a schematic diagram of the process flow of the polyimide catheter prepared in Example 1 of the present invention.

[0069] Figure 5 The figure is a schematic diagram of the process of preparing polyimide catheter molding by the melt extrusion method used in the prior art. DETAILED DESCRIPTION

[0070] To make the objectives, technical solutions, and advantages of the embodiments of the present invention more clear, the technical solutions in the embodiments of the present invention are clearly and completely described. Obviously, the described embodiments are part of the embodiments of this application, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts shall fall within the scope of protection of the present invention.

[0071] The disclosures of all patent and non-patent literature cited herein are incorporated by reference in their entirety.

[0072] As used in the present invention, the terms "comprises," "includes," "contains," "covers," "has," "with," or any other variations thereof are intended to cover non-exclusive inclusions. For example, a process, method, article, or apparatus that includes a list of elements is not necessarily limited to only those elements, but may include other elements not expressly listed or inherent to the process, method, article, or apparatus. In addition, unless expressly indicated to the contrary, "or" refers to an inclusive "or" rather than an exclusive "or." For example, conditions A or B satisfy any of the following: A is true (or exists) and B is false (or does not exist), A is false (or does not exist) and B is true (or exists), and both A and B are true (or exist). The phrase "one or more" is intended to cover non-exclusive inclusions. For example, one or more of A, B, and C means any of the following: A alone, B alone, C alone, a combination of A and B, a combination of B and C, a combination of A and C, or a combination of A, B, and C.

[0073] In addition, the use of "a," "an," "first," etc. to describe elements and components described herein is for convenience only and to provide a general sense of the scope of the invention. This description should be understood to include one or at least one, a kind or at least one, and the singular also includes the plural unless it is obvious that it is meant otherwise.

[0074] Hereinafter, preferred embodiments of the present invention will be described in detail, but the present invention is not limited thereto.

[0075] First, the terms used in this specification will be explained: "Block polyimide" is a polymer having a structural unit represented by the following general formula (1) as a repeating unit.

[0076]

[0077] Wherein, in the general formula, X represents the residue of a tetracarboxylic dianhydride compound in a tetravalent organic group, X1 is the residue of a rigid dianhydride compound, X2 is the residue of a flexible crystalline dianhydride compound, Y represents the residue of a diamine compound in a divalent organic group, Y1 is the residue of a rigid diamine compound, and Y2 is the residue of a flexible crystalline diamine compound, that is, the two segments are on the same molecular main chain, wherein m (rigid segment) accounts for 60% to 80% by mole of the two segments, and n (flexible lenalidomide) accounts for 20% to 40% by mole of the two segments.

[0078] The dianhydride compounds in the rigid segment mainly include one or a combination of compounds such as pyrophthalic anhydride, 4,4'-biphenyl dianhydride, 4,4'-terphenyl dianhydride, 2,3,6,7-anthracenetetracarboxylic dianhydride, 1,4,5,8-naphthalenetetracarboxylic dianhydride, cyclobutane dianhydride, 9,9-bis[4-(3,4-dicarboxylic acid phenoxy)phenyl]fluorene dianhydride, and dibenzodioxane dianhydride. In particular, pyrophthalic anhydride and 4,4'-biphenyl dianhydride are preferred. The molecular structure thereof is as follows:

[0079]

[0080] The rigid diamine compounds mainly include one or a combination of p-phenylenediamine, 2,6-naphthalenediamine, 1,4-benzidine, 4,4′-diamino-2,2′-dimethylbiphenyl, 4,4′-diamino-tetramethyl-p-terphenyl, 9,9-bis(4-aminophenyl)fluorene, 2,6-diaminopyridine, 2,5-bis(4-aminophenyl)pyridine, 5-amino-2-(3′-aminophenyl)benzimidazole, 2-amino-5(4-aminophenyl)-pyrimidine, etc., among which p-phenylenediamine and 4,4′-diamino-2,2′-dimethylbiphenyl are preferred. The molecular structural formula is as follows:

[0081]

[0082] The flexible crystalline dianhydride compounds mainly include 4,4′-diphenyl ether dianhydride, 4,4′-diphenyl sulfide dianhydride, 4,4′-(terephthalic) dianhydride, pyrophthalic anhydride, 4,4′-biphenyl dianhydride, 4,4′-(3,4-dicarboxyphenoxy)benzophenone dianhydride, trimellitic anhydride hydroquinone ester, and the like, or a combination thereof. Among them, pyrophthalic anhydride and 4,4′-biphenyl dianhydride are preferred. The molecular structure thereof is as follows:

[0083]

[0084] The flexible crystalline segmented diamine compounds mainly include one or a combination of 4,4′-diaminodiphenyl ether, 3,4′-diaminodiphenyl ether, 1,4-bis(4-aminophenoxy)benzene, 1,3-bis(4-aminophenoxy)benzene, 2,7-bis(4-aminophenoxy)naphthalene, 4,4′-bis(3-aminophenoxy)biphenyl, 4,4′-bis(3-aminophenoxy)benzophenone, etc., among which 1,3-bis(4-aminophenoxy)benzene and 4,4′-bis(3-aminophenoxy)biphenyl are preferred. The molecular structure thereof is as follows:

[0085]

[0086] The solvents used in the preparation of the polyamic acid precursor in the present invention are mainly polar aprotic solvents, including N,N-dimethylformamide (DMF), N,N-dimethylacetamide (DMAc), N-methyl-2-pyrrolidone (NMP), dimethyl sulfoxide (DMSO), diphenyl sulfone, tetramethyl sulfone, tetrahydrofuran (THF), dioxane, dichloromethane, chloroform, hexamethylphosphorus triamide, γ-butyrolactone, cyclopentanone, m-cresol, diethyl ether, p-cresol methyl ether, etc. These solvents are usually used alone or in combination of two or more as needed.

[0087] The preparation method of the polyamic acid precursor of the present invention is as follows: when the molar amount X1>Y1, first add a polar aprotic solvent to the reaction apparatus, then dissolve the diamine Y1, then add the dianhydride X1, wait for it to completely dissolve and react for 1-5 hours, then add the diamine Y2, wait for it to dissolve and react for 1-5 hours, and finally add all the dianhydride X2, and finally react for 2-6 hours, and then the reaction is completed; when the molar amount X1<Y1, the order of addition is Y1, X1, X2, Y2, that is, to ensure that there are no free two diamines in the solution system to undergo competitive polymerization, resulting in structural sequence disorder. The above X1, Y1, X2, and Y2 respectively refer to the corresponding compounds selected for the corresponding segments and have no other meanings.

[0088] The solid content of the polyamic acid precursor solution prepared by the present invention is preferably 5-50wt%, more preferably 10-40wt%, and further preferably 12-30wt%. If the solid content is lower than 5wt%, the amount of glue applied to the core of the tube in a single dip coating is too small, the tube wall is too thin, and the efficiency is too low. If the solid content is higher than 50wt%, the viscosity is too high and not suitable for dip coating, or the molecular weight is too low, resulting in a brittle tube.

[0089] The viscosity of the polyamic acid precursor solution prepared by the present invention is preferably 100-100000 cP, more preferably 1000-10000 cP, and further preferably 3000-8000 cP; if the viscosity is lower than 100 cP, the solution is too thin and the surface of the tube core adheres too little; if the viscosity is higher than 10000 cP, the solution is too thick, resulting in uneven surface glue and rough membrane surface.

[0090] To improve the leveling, color, adhesion, etc. of the polyamic acid precursor solution prepared by the present invention, leveling agents, dyes, surfactants, plasticizers, fillers, sensitizers, etc. can be added to the solution, and the addition amount is preferably 0.001 to 5 wt%, more preferably 0.01 to 3 wt%.

[0091] In order to avoid the wall thickness deviation of the tube core surface, which is thin at the top and thick at the bottom, caused by the influence of gravity when the tube core is transported horizontally to the pre-baking furnace after the resin solution is dipped, the present invention uses a slender vertical cylinder glue tank. The tube core is transported upward from the bottom and then enters the pre-baking furnace through a die that controls the tube wall thickness. The die is installed at the connection between the top of the glue tank and the bottom of the pre-baking furnace, that is, the glue is dipped in the glue in a vertical direction. The conveying speed of the tube core in the glue is preferably 0.1 to 50 m / min, more preferably 0.5 to 30 m / min, and further preferably 1 to 10 m / min. The diameter of the die is used to control the tube wall thickness, and the number of dips for thick tubes is determined according to the thickness of the single layer. Among them, if the conveying speed is less than 0.1 m / min, the production efficiency is too low and there is no economic benefit. If it is greater than 50 m / min, the dip coating will be too fast, and the time for the tube core surface to be wetted and coated will be insufficient, resulting in uneven surface glue. In order to improve the wetting ability between the tube core and the glue in the present invention, the tube core needs to be cleaned and activated. First, the surface dust is cleaned with deionized water, then the surface organic oil stains are removed by ultraviolet irradiation, and finally the surface is activated by atmospheric plasma bombardment, thereby improving the wetting ability.

[0092] The purpose of pre-baking in this invention is to dry most of the solvent in the core adhesive layer to set the shape. Using hot air drying is more efficient and removes volatile solvents, making the process safer. The hot air temperature is preferably 80-200°C, more preferably 100-180°C, and even more preferably 120-160°C. The hot air velocity is preferably 0.1-10 m / s, more preferably 0.5-8 m / s, and even more preferably 2-6 m / s. Temperatures below 80°C or air velocities greater than 10 m / s will result in the baking temperature being too low or the dwell time being too short, preventing timely drying. Temperatures above 200°C or hot air velocities below 0.1 m / s will result in the baking temperature being too high or the dwell time being too long, resulting in over-drying of the tube film and preventing it from being wetted by the imidization reagent in the next step. The number of pre-baking cycles is primarily determined by the thickness after a single die-coating pass and the target thickness. Multiple cycles of dip coating, pre-baking, re-dip coating, and re-pre-baking can be used.

[0093] The present invention adds a step for pre-baking the catheter film and soaking it in a chemical imidization reagent to improve the toughness and surface density of the polyimide catheter. The imidization chemical reagent consists of a dehydrating agent and a catalyst. The dehydrating agent primarily includes aliphatic anhydrides, aromatic anhydrides, N,N-dialkylcarbodiimides, arylsulfonic acid dihalides, thionyl halides, or mixtures of two or more of these. For cost and effectiveness, aliphatic anhydrides such as acetic anhydride, propionic anhydride, and butyric anhydride, or mixtures of two or more of these, are preferred. During the conversion of polyamic acid to polyimide, an imidization catalyst can be used simultaneously to promote the dehydration and ring closure of the polyamic acid by the chemical dehydrating agent. Aliphatic tertiary amines, aromatic tertiary amines, and heterocyclic tertiary amines are preferred. Nitrogen-containing heterocyclic tertiary amines such as pyridine, 3-methylpyridine, quinoline, isoquinoline, imidazole, and benzimidazole are further preferred for their reactivity. The molar ratio of the chemical dehydrating agent to the catalyst is 10:1, more preferably 5:1, and even more preferably 3:1. The pre-baked tube is preferably immersed in the imidization agent for 0.1 to 10 minutes, more preferably 0.5 to 8 minutes, and even more preferably 1 to 5 minutes.

[0094] In the present invention, the pre-baked conduit, soaked in a chemical imidization agent, undergoes a final high-temperature heat treatment to remove residual solvent, water generated by imidization ring closure, residual dehydrating agent, and catalyst, thereby completely imidizing the remaining amic acid and obtaining the polyimide conduit of the present invention. The final treatment temperature is preferably 300-600°C for 5-600 seconds. To ensure a smooth imidization reaction and a high degree of cyclization, a multi-stage heating process is employed, employing multiple temperature gradients, with gradual heating followed by annealing, such as 300, 400, 500, 600, 500, 400, and 300°C, or 300, 375, 450, 525, 600, 500, 400, and 300°C.

[0095] In the present invention, the polyimide tube after final curing is preliminarily inspected for surface defects, color difference, and thickness uniformity. The tube that meets the quality requirements is then cut according to product specifications, the tube core is then extracted, and finally various key performance indicators are tested.

[0096] Performance testing methods

[0097] 1. Tests of tensile strength, modulus and elongation at break

[0098] With reference to the standard GB / T15812.1-2005, an Instron universal material testing machine was used, with a test span of 100 mm, a test rate of 50 mm / min, and a modulus value range of 0.1% to 0.5% strain.

[0099] 2. Wear performance test

[0100] Referring to the standard GB / T3960-2016 Plastic Sliding Friction and Wear Test Method, the test device shown in the figure* is used. The sample is tightly fitted with the test ring under normal stress, and mutual friction is generated during the uniform rotation process. The mass of the sample before the test is recorded as m1, and the mass after the test is recorded as m2. The mass wear ratio γ is used to determine the wear performance, and the formula is γ = (m1-m2) / m1*100%.

[0101] See Figure 3 , is a schematic diagram of the wear test method.

[0102] 3. Water barrier performance test

[0103] Refer to the standard GB / T1037-2021 Plastic film and sheeting water vapor transmission performance test cup weight gain and loss method, under the conditions of specified temperature and relative humidity and maintaining a certain water vapor pressure difference on both sides of the sample, the water vapor mass permeating per unit area of ​​the sample within 24 hours. The calculation formula is:

[0104] WVT=(24*Δm) / (A*t), where WVT represents the water vapor transmission rate of the sample, and the unit is [g / (m 2 ·24h)]; Δm represents the mass change of the moisture permeable cup during the time period t, in [g]; A represents the area of ​​the sample that is permeable to water vapor, in [m 2 ], t represents the time difference between two intervals after the mass change stabilizes, and the unit is [h].

[0105] 4. Solvent resistance test

[0106] Referring to GB / T 11547-2008, a standard for determining the resistance of plastics to liquid chemical reagents, the specimen is completely immersed in the test liquid under specified temperature and time conditions, then removed and dried. Changes in mass, dimensions, appearance, and physical properties, such as mechanical and thermal properties, before and after immersion are observed. The present invention uses the polar solvent NMP as the test solvent, with an immersion temperature of 25°C and a immersion time of 24 hours. Sample weight and tensile strength before and after immersion are used as indicators for evaluating solvent resistance. The post-immersion mass retention rate is calculated as m2 / m1*100%, where m2 and m1 represent the mass before and after immersion, respectively. The post-immersion tensile strength retention rate is calculated as σ2 / σ1*100%, where σ2 and σ1 represent the tensile strength before and after immersion, respectively.

[0107] Example 1

[0108] This embodiment provides a method for preparing a medical polyimide catheter, which is prepared and formed by a solution dip coating method. Figure 4The following is a flow chart of an apparatus for preparing polyimide conduits, comprising a conduit core 1, a first dipping device 2, a pre-drying device 5, a second dipping device 7, a high-temperature curing device 8, and a transfer device. A polyamic acid resin precursor solution is placed as a glue solution in the first dipping device 2, and an imidization agent is placed in the second dipping device 7. In this embodiment, the pre-drying device uses a pre-drying furnace as a drying device, preferably a hot air tubular furnace, with the wind direction opposite to the forward direction of the conduit core 1 and a temperature range of 80-200°C. The first dipping device 2 and the pre-drying device 5 are used in combination and can be used as a repeating unit to perform the dipping and pre-drying steps on the conduit core. If thick conduits are required, a multi-layer structure is used, with multiple glue tanks and pre-drying furnaces connected in series during the preparation process to improve production efficiency. A high-temperature furnace is used as the high-temperature curing device, and the temperature can be controlled in stages.

[0109] In this embodiment, the first dipping device uses a slender vertical cylindrical glue tank, and a die 3 is provided at the outlet of the glue tank to control the thickness of the tube membrane and scrape off excess glue; the second dipping device can use the same glue tank and die as the first dipping device.

[0110] The transport device, preferably comprising a drive motor and guide wheels 6, transports the tube core 1 (silver-plated copper wire) into a glue tank containing glue (amic acid resin precursor solution). The outlet of the glue tank is provided with a circular hole-shaped die 3. After the glue adheres to the surface of the tube core, it enters a pre-drying device to form a glue film on the surface. The tube core with the glue film is then transferred to a second dipping device, where the polyamic acid resin precursor is imidized under the action of a catalyst to form a polyimide polymer. The tube core then enters a high-temperature curing device to cure the glue film. The curing step can be repeated multiple times. Finally, the tube core is peeled off from the surface of the tube core to obtain a polyimide tube.

[0111] The glue tank used for tube core dipping in the present invention is a slender vertical cylindrical type with a circular hole die at the end for controlling the thickness of the tube film wall and scraping off excess glue; the pre-baking furnace is a hot air tube furnace, the wind direction of which is opposite to the forward direction of the tube core, and the temperature can be between 80 and 200°C, wherein the glue tank and the pre-baking furnace are a unit combination.

[0112] The polyimide catheter is prepared using the above device, and the specific preparation steps include:

[0113] Step 1: In a Class 1000 cleanroom, constant temperature of 25°C, and constant humidity of 50RH%, NMP (13.18kg) and p-phenylenediamine monomer (PDA, 3.5mol, 0.3785kg) were added to a 20L reactor equipped with mechanical stirring, a cold and hot medium jacket, and nitrogen. The reaction temperature was set to 25°C. After stirring for 2h, 4,4′-biphenyl dicarboxylic anhydride (4,4′-BPDA, 4mol, 1.177kg) was added and stirred evenly for 4h to form a polyamic acid oligomer with dianhydride as the end group. Then, 4,4′-bis(3-aminophenoxy)biphenyl (BAPB, 1 .5mol, 0.553kg), stirred for 2h to dissolve and fully react, and finally, pyromellitic dianhydride (PMDA, 1mol, 0.218kg) was slowly added in multiple batches to make the resin viscosity reach about 6000cP, and finally stirred for 4h to obtain a polyamic acid resin precursor solution with a solid content concentration of 15wt%, and then the polyamic acid resin was vacuum defoamed (<1Pa) and allowed to stand for 24h to remove residual bubbles in the solution, and passed through a 1-3μm filter element to remove impurities, and finally a polyamic acid resin precursor solution that can be used for the preparation of polyimide catheters was prepared, with a solid content of: 15wt%.

[0114] Step 2: To a 10L reactor with mechanical stirring and nitrogen, add acetic anhydride (AA, 40 mol, 4.084 kg) and pyridine (Py, 20 mol, 1.582 kg), respectively, and stir at room temperature for 4 hours to mix them evenly. Then, vacuum degassing and filter filtration are performed to prepare a chemical imidization reagent that can be used to catalyze the conversion of polyamic acid into polyimide.

[0115] Step 3: A silver-plated copper wire with a diameter of 0.60mm is selected as the forming tube core. Before coating, it undergoes three steps, namely deionized water washing and drying, UV irradiation, and oxygen plasma treatment, to clean and activate its surface. The prepared polyamic acid precursor solution is then added to the first-stage elongated vertical cylinder glue tank with a diameter of 0.05m and a height of 2m. The tube core is passed through the bottom of the glue tank at a speed of 1m / min. After being dipped in the glue, it passes through a die with a diameter of 0.65mm to scrape off excess glue. It then passes through a 150°C pre-bake oven to dry and shape the glue. After the first shaping, it is passed through a guide wheel through the second-stage glue tank, die, and pre-bake tunnel for a second dip and shaping. The process is then repeated in the third stage. The second and third stage glue tanks, glue, drying tunnel, and temperature are the same as the first stage. The second and third stage die diameters are 0.66 and 0.67mm, respectively.

[0116] Step 4: The film-coated tube core, which has undergone the third shaping process in Step 3, is passed through a slender cylindrical reagent tank with a diameter of 0.05m and a height of 4m, containing a chemical catalyst. The chemical catalyst is preheated to 70°C to fully soak the film and quickly catalyze the polyamic acid ring closure. The film-coated tube core is then passed through a seven-stage high-temperature curing furnace using guide wheels. The temperatures in each section are set at 300, 400, 500, 600, 500, 300, and 100°C, with a residence time of 1 minute in each zone. High-temperature treatment is first performed to achieve complete ring closure, followed by low-temperature annealing to reduce the interlaminar stress between the tube core and the adhesive layer. After the high-temperature heat treatment, the tube core is cut into 1m sections according to product length specifications and separated from the polyimide tube using a tube core extraction device. The resulting tube has a diameter of 0.60mm and a wall thickness of approximately 0.012mm. Finally, the tube performance is evaluated, with the test results shown in Table 1. The processes of dipping, pre-baking and high temperature curing are as follows: Figure 4 shown.

[0117] Example 2

[0118] The dipping and pre-baking process in step 3 of Example 1 was changed from level 3 to level 2. Other conditions were exactly the same as those in Experiment 1. The prepared catheter had a diameter of 0.60 mm and a wall thickness of approximately 0.008 mm. The performance of the catheter was evaluated, and the test results are shown in Table 1 below.

[0119] Example 3

[0120] The dipping and pre-baking process in step 3 of Example 1 was changed from level 3 to level 8. Other conditions were exactly the same as those in Experiment 1. The prepared catheter had a diameter of 0.60 mm and a wall thickness of approximately 0.032 mm. The performance of the catheter was evaluated, and the test results are shown in Table 1 below.

[0121] Comparative Example 1

[0122] SABIC ULTEM TM 1000 polyimide resin is used as the base material for the catheter molding, and is molded using a SE100EV-C250 high-temperature extruder with a screw diameter of The maximum injection pressure was 217 MPa. A ring die was used to control the inner and outer diameters. Given the approximately 5% shrinkage of the resin after cooling and molding, the inner ring die diameter was selected to be 0.63 mm, and the outer ring die diameter was 0.70 mm. The polyimide resin was first dried at 200°C for 5 hours. The extrusion process employed a screw speed of 150 rpm, a back pressure of 3 MPa, an injection speed of 10 mm / s, and an injection pressure of 180 MPa. The tubes were then cooled in a cooling trough for 30 seconds before being cut into 1-meter sections. Finally, dimensional and performance testing was performed. The resulting catheters had an inner diameter of 0.60 mm and a wall thickness of 0.032 mm. The performance test results are shown in Table 1.

[0123] Comparative Example 2

[0124] Changed the polyimide catheter molding base resin to Mitsui Chemicals' AUR μm TM PD450 brand, and the rest are the same as those in Comparative Example 1.

[0125] Comparative Example 3

[0126] The polyimide formula in step 1 of Example 1 was changed to NMP (11.4 kg), p-phenylenediamine (PDA, 5 mol, 0.541 kg) and 4,4′-biphenyldicarboxylic anhydride (4,4′-BPDA, 5 mol, 1.471 kg), and 4,4′-bis(3-aminophenoxy)biphenyl (BAPB) and pyromellitic dianhydride (PMDA) were not added. The other processes were the same as in Example 1.

[0127] Comparative Example 4

[0128] The polyimide formula in step 1 of Example 1 was changed to NMP (16.6 kg), 4,4′-bis(3-aminophenoxy)biphenyl (BAPB, 5 mol, 1.84 kg) and pyromellitic dianhydride (PMDA, 5 mol, 1.09 kg), and p-phenylenediamine (PDA) and 4,4′-biphenyldicarboxylic anhydride (4,4′-BPDA) were not added. The other processes were the same as in Example 1.

[0129] Comparative Example 5

[0130] The polyimide formula in step 1 of Example 1 was changed to NMP (12.18 kg), p-phenylenediamine monomer (PDA, 3.5 mol, 0.3785 kg), biphenyl dicarboxylic anhydride (BPDA, 4 mol, 1.177 kg), 4,4′-diaminodiphenyl ether (ODA, 1.5 mol, 0.300 kg), and 4,4′-oxydiphthalic anhydride (4,4′-ODPA, 1 mol, 0.294 kg). The other processes were the same as in Example 1.

[0131] Comparative Example 6

[0132] In step 4 of Example 1, the product is directly fed into the high-temperature drying tunnel without passing through the imidization reagent tank. The other processes are the same as those of Example 1.

[0133] Comparative Example 7

[0134] In step 4 of Example 1, seven high-temperature furnaces are sequentially passed through, and the temperature of each furnace is set to 400° C. The other processes are the same as in Example 1.

[0135] The performance evaluation results of the polyimide catheters prepared in the Examples and Comparative Examples are shown in Table 1.

[0136] Table 1 Performance comparison of polyimide catheters of Examples and Comparative Examples

[0137]

[0138] As shown in Examples 2 and 3, the solvent method can achieve adjustable wall thickness of polyimide catheters with excellent comprehensive performance; Comparative Examples 1 and 2 use extrusion molding technology. In order to ensure that the polyimide resin has good melt viscosity at high temperatures, the molecular structure is selected to be relatively flexible, resulting in low catheter strength and modulus. In addition, the pure resin molding cannot make the tube wall ultra-thin, and the solvent resistance is insufficient; Comparative Examples 3 and 4 use fully rigid or fully flexible molecular structures, which cannot simultaneously take into account excellent strength and toughness; Comparative Example 5, the introduction of non-crystalline OPDA-ODA flexible chain segments can improve toughness, but the wear resistance of the catheter is relatively weak; Comparative Example 6, no chemical imidization agent is used to imidize the surface of the pre-baked catheter, the surface density of the catheter is low, and the water-blocking, wear-resistant, and solvent-resistant properties are insufficient; Comparative Example 7 does not undergo multi-stage high-temperature (>400°C) treatment. All comprehensive properties of the catheter obtained are seriously low.

[0139] Unless otherwise defined, the meaning of all technical and scientific terms used herein is the same as that generally understood by those of ordinary skill in the art to which this disclosure belongs. Although methods and materials similar or equivalent to those described herein can be used in the practice or testing of the disclosed composition embodiments, suitable methods and materials are described below. Unless citing a specific paragraph, all publications, patent applications, patents and other references mentioned herein are incorporated herein by reference in their entirety. In the event of a conflict, this specification and the definitions included therein shall prevail. In addition, materials, methods and examples are illustrative only and not restrictive.

[0140] The technical solutions, implementation processes and principles of the present invention will be further explained below through specific examples. It should be noted that the following detailed descriptions are exemplary and are intended to provide further explanation of the present invention. The described embodiments are only part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments in the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention. Unless otherwise stated, the reagents and raw materials used in the following examples are commercially available, and the test methods for which specific conditions are not specified are generally carried out under conventional conditions or according to the conditions recommended by the manufacturers. Furthermore, unless otherwise stated, the experimental methods, detection methods, and preparation methods disclosed in the present invention all adopt conventional techniques in this technical field. These technologies have been fully described in the existing literature.

[0141] The above are merely preferred embodiments of the present invention and are not intended to limit the scope of protection of the present invention. Those skilled in the art will readily appreciate that the present invention is susceptible to various modifications and variations. Any changes, modifications, substitutions, integrations, or parameter changes to these embodiments, which fall within the spirit and principles of the present invention and achieve the same functionality through conventional substitutions, without departing from the principles and spirit of the present invention, fall within the scope of protection of the present invention.

Claims

1. A method for preparing a polyimide catheter, characterized in that: The following steps are involved: S1. Providing a polyimide precursor solution; S2 dip coating and shaping: using a multi-stage dip coating and pre-baking gluing process, the polyimide precursor solution is dipped on the outer wall of the die, after pre-drying and shaping treatment, to form a uniform film; S3 provides a pre-baked adhesive layer: the film is immersed in an imidization agent, and the imidization treatment is performed to convert the polyimide precursor into a block-type polyimide polymer; S4. Imidization: performing a high-temperature curing treatment on the block polyimide polymer to obtain a polyimide conduit on the surface of the tube core; S5. The polyimide conduit is removed from the surface of the die to obtain a final product; Wherein, in S1, the method for preparing the polyimide precursor solution includes: p-phenylenediamine and 4,4'-biphenyl dicarboxylic anhydride are added to a polar aprotic solvent, dissolved, and then subjected to a first-stage reaction; 4,4'-bis(3-aminophenoxy)biphenyl is added to carry out a second-stage reaction, and then pyromellitic dianhydride is added to carry out a third-stage reaction until the reaction is completed, thereby obtaining the polyimide precursor solution; In S4, the high temperature curing treatment includes adopting a multi-stage gradient high temperature curing process, including gradually increasing the temperature and then gradually annealing by setting multiple temperature gradients; The temperature gradients are 300°C, 400°C, 500°C, 600°C, 500°C, 300°C, and 100°C respectively.

2. The preparation method according to claim 1, characterized in that The polar aprotic solvent is one or a combination of N,N-dimethylformamide, N,N-dimethylacetamide, N-methyl-2-pyrrolidone, dimethyl sulfoxide, diphenyl sulfone, tetramethyl sulfone, tetrahydrofuran, dioxane, dichloromethane, chloroform, hexamethylphosphorus triamide, γ-butyrolactone, cyclopentanone, m-cresol, diethyl ether, and p-cresol methyl ether.

3. The preparation method according to claim 1, characterized in that The solid content of the polyimide precursor solution is 5 to 50 wt %; The viscosity of the polyimide precursor solution is 100 to 100,000 cP.

4. The preparation method according to claim 1, characterized in that In S2, the conveying speed of the tube core in the polyimide precursor solution is 0.1 to 50 m / min; The shaping treatment includes drying by hot air drying; the hot air temperature is 80-200°C; the hot air speed is 0.1-10m / s; The material of the tube core includes any one of a glass rod, a quartz rod, a stainless steel wire, a copper wire, and a silver-plated copper wire.

5. The preparation method according to claim 1, characterized in that S2 can be operated in multiple cycles.

6. The preparation method according to any one of claims 1 to 5, characterized in that S2 further includes pre-treating the tube core; the pre-treating includes coating a lubricant on the surface of the tube core.

7. A polyimide catheter prepared by the preparation method according to any one of claims 1 to 6.

8. The polyimide catheter according to claim 7, characterized in that The wall thickness of the polyimide catheter is 4-100 μm, and the inner diameter is 10-10000 μm.

9. The polyimide catheter according to claim 8, characterized in that The wall thickness is 4-6 μm.

10. Use of the polyimide catheter according to any one of claims 7 to 9 for preparing medical devices.

11. Use of the polyimide catheter according to any one of claims 7 to 9 for preparing a vascular interventional treatment device.

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