Polymer medical catheter tube and forming method and connecting method thereof

Abstract

The application relates to the field of medical supplies, in particular to a high-molecular medical catheter pipe fitting and a forming method and a connecting method thereof. The forming method of the high-molecular medical catheter pipe fitting is characterized by comprising the following steps: step 1, an etching pipe is inserted into the initial end of the lumen of an outer cavity pipe and stretched out from the tail end of the lumen of the outer cavity pipe; step 2, the tail end of the etching pipe is closed; step 3, a heat-shrinkable pipe is wrapped outside the outer cavity pipe to form a composite pipe; step 4, the composite pipe in step 3 is placed in a rheometer, and a fluid is filled into the lumen of the etching pipe from the initial end of the etching pipe, the fluid can at least expand the lumen of the etching pipe; then the rheometer is heated to make the heat-shrinkable pipe shrink, and under the action of the fluid expansion and the outer heat-shrinkable pipe, the inner wall of the outer cavity pipe is fused and combined with the outer wall of the etching pipe. The scheme adopts the fluid expansion inner support scheme, so that a high-precision core rod does not need to be inserted into the lumen of the etching pipe, the processing requirement is reduced, and the processing efficiency is improved.

Description

A polymer medical catheter fitting and its molding and connection methods Technical Field

[0001] This invention relates to the field of medical supplies, and in particular to a polymer medical catheter fitting and its molding and connection methods. Background Technology

[0002] In medicine, to perform certain diagnostic and treatment procedures, such as endoscopic examination of the digestive tract, it is necessary to establish channels inside and outside the body cavities. This can be achieved by inserting a medical catheter into the body cavity and then delivering the necessary tools or substances through the catheter. On the one hand, to prevent unnecessary damage to the body cavity during catheter movement, the outer wall of the catheter should obviously be kept as smooth as possible, ensuring that the surface quality of the outer wall meets certain standards. On the other hand, to ensure that the necessary tools or substances can smoothly pass through the medical catheter and reach their target location within the body cavity, the surface quality of the inner wall of the catheter must also meet certain requirements. However, for various reasons, medical catheters may be made of materials of different specifications or materials connected axially (or along the length) of the catheter. This connection must consider not only the surface quality of the outer wall at the connection point, for the reasons mentioned above, but also the surface quality of the inner wall at the connection point to ensure the passage within the lumen at the connection point. In addition, the aforementioned medical catheters extensively utilize polymer materials, commonly including polyurethane, silicone rubber, polyester fiber, polyvinylpyrrolidone, polyetheretherketone, polymethyl methacrylate, polyvinyl alcohol, polylactic acid, and polyethylene.

[0003] Ensuring the quality of both the internal and external surfaces of the joint while reducing processing costs is a challenge currently facing the industry. Summary of the Invention

[0004] When connecting polymer medical catheters of different specifications or materials, a built-in PTFE etched tube can be used.

[0005] PTFE is the abbreviation for polytetrafluoroethylene, a high molecular polymer obtained by polymerizing tetrafluoroethylene as a monomer. Its characteristics include high lubricity, having the lowest coefficient of friction among solid materials; non-adhesion, having the lowest surface tension among solid materials, and not adhering to any substance; non-toxicity, and physiological inertness, so it has no adverse reactions when used as artificial blood vessels and organs for long-term implantation in the body.

[0006] However, the difficulty in bonding PTFE limits its application in some fields. Researchers have proposed a chemical treatment method for the surface of polytetrafluoroethylene (PTFE) pipes, which mainly involves a chemical reaction between an etching solution and the PTFE film surface to remove some of the fluorine atoms. This leaves a carbonized layer and certain polar groups on the surface. The portion with the fluorine atoms removed has better adhesion properties, which is the so-called PTFE etched pipe (the etched pipe mentioned below in this application refers to PTFE etched pipes).

[0007] Taking the connection of PTFE etched tubing to PEBAX medical catheter tubing as an example, the connection method is as follows:

[0008] Step 1: Insert a high-precision mandrel (or spindle) into the etched tube. The mandrel and the inner wall of the etched tube cavity can be or nearly interference fit.

[0009] Step 2: Insert both ends of the etched tube with built-in mandrel into the two tubes to be connected on both sides, with the etched tube located at the connection point of the two tubes.

[0010] Step 3: Wrap a layer of FEP heat shrink tubing around the outside of the connection point;

[0011] Step 4: Place the connector inside the rheometer and heat the tube connection part (microwave heating, baking, or hot air blowing) to shrink the outer FEP heat shrink tube.

[0012] Step 5: After the outer wall of the etched tube is firmly bonded to the inner walls of the two tubes, remove the mandrel and the FEP heat shrink tubing to form a composite tube. This composite tube forms a two-layer tube structure at the connection point. The inner layer is a PTFE tube, and the outer walls of both ends of the PTFE tube are bonded to the inner walls of the tubes being connected, with the walls of the tubes being connected forming the outer layer.

[0013] In the above method, it is crucial to ensure that the rigid mandrel can be inserted into the cavity of the rigid etched tube before implementation, and also to meet the design requirements for the cavity size of the etched tube after implementation (the external specifications of the mandrel determine the internal specifications of the etched tube after the process). This places extremely high demands on the dimensional accuracy of the mandrel; otherwise, if the mandrel is too large, it cannot be inserted, and if it is too small, wrinkles will form in the etched tube during heat shrinking (excessive accumulation of the etched tube relative to the mandrel), leading to poor internal permeability. Furthermore, the precision requirements for the connected cavities are also very high; otherwise, the etched tube lined with the mandrel cannot be both easily inserted and have the required cavity size guaranteed after heat shrinking.

[0014] Even more challenging is that when the above process is applied to the connection of multi-cavity tubes, the dimensions of the multi-cavity tubes are often different, and the corresponding mandrel sizes are also different. In addition to the precision issues mentioned above, there is also the need to pass multiple mandrels through multiple cavities in a corresponding manner, and multiple mandrels need to correspond one-to-one with multiple cavities, which will increase the difficulty of material management and production.

[0015] To address the aforementioned problems, the primary objective of this invention is to provide a method for molding polymer medical catheter fittings. This method abandons the existing mandrel-supported approach and instead employs a fluid expansion-supported approach. This eliminates the need to insert a high-precision mandrel into the etched tube cavity, reducing processing requirements and simplifying the process by eliminating the step of inserting the mandrel into the etched tube cavity using an interference fit. Furthermore, it avoids the problem of insufficient mandrel precision or roundness preventing tube insertion.

[0016] To achieve the above objectives, the present invention adopts the following technical solution:

[0017] A method for molding a polymer medical catheter fitting, characterized by comprising the following steps:

[0018] Step 1: Insert the etching tube into the lumen of the outer tube from the beginning and extend it out from the end of the lumen of the outer tube.

[0019] Step 2: Seal the tail end of the etched tube;

[0020] Step 3: Wrap a heat-shrink tubing around the outside of the outer tube to form a composite tube;

[0021] Step 4: Place the composite tube from Step 3 into a rheometer and fill its cavity with fluid from the beginning of the etched tube. The fluid should be enough to expand the cavity of the etched tube. Then heat the rheometer to shrink the heat shrink tubing. Under the action of fluid expansion and the outer heat shrink tubing, the outer wall of the etched tube will adhere to the inner wall of the outer cavity tube, while the inner wall of the outer cavity tube will melt and combine with the outer wall of the etched tube.

[0022] The present invention adopts the above-mentioned technical solution, which relates to a molding method for polymer medical catheter fittings. The molding method of the polymer medical catheter fittings has the same characteristics as the prior art in that: an etched tube is fixed inside the outer lumen tube. The setting of the etched tube can achieve the following two effects: First, the smoothness requirement of the catheter fitting is high, so that the guide wire can be inserted more smoothly; Second, it can be applied to the soft and hard tube connection at the tip of the catheter.

[0023] Based on this, this solution differs from existing technologies in that it abandons the internal support method of the mandrel in existing technologies and instead adopts a fluid expansion internal support method. This eliminates the need to insert a high-precision mandrel into the etching tube cavity. On the one hand, it eliminates the need to construct a high-precision mandrel, reducing processing requirements; on the other hand, it omits the step of inserting the mandrel into the etching tube cavity using an interference fit, improving processing efficiency. Of course, it also avoids the problem of the mandrel failing to pass through the tube due to insufficient precision or roundness.

[0024] Meanwhile, the advantage of this solution is that the fluid pressure inside the etching tube can be adjusted based on different etching tube sizes and their inner diameter requirements.

[0025] It should be noted that the external lumen tube referred to in this case can be a single-lumen tube or a multi-lumen tube.

[0026] Preferably, a rigid support is provided inside the etching tube in step 1. Specifically, a thin mandrel is lined inside the cavity of the etching tube in step 1, and the outer diameter of the thin mandrel is smaller than the inner diameter of the etching tube cavity. The thin mandrel in this solution differs from the mandrel used in the prior art; it is a rigid support component designed to penetrate the etching tube and provide a certain degree of rigidity, thus facilitating the insertion of the etching tube into the outer cavity tube. Therefore, the thin mandrel in this solution, on the one hand, has an outer diameter smaller than the inner diameter of the etching tube cavity, and in principle, can be inserted into the etching tube quickly and smoothly while providing sufficient rigidity; on the other hand, it has no requirements for precision or roundness.

[0027] In this scheme, the thin core rod is axially supported or connected to the etching tube, so that the thin core rod and the etching tube are inserted into the cavity of the outer tube together, thus allowing the thin core rod and the etching tube to move axially synchronously.

[0028] In step 1, after the etching tube is completed, the rigid support inside the etching tube is removed, which means removing the thin mandrel.

[0029] It also includes step 5, after fixing, tearing off the outer heat shrink tubing and cutting off the portion of the etched tube that extends beyond the outer cavity.

[0030] Preferably, in step 2, ensuring the etched tube tail end is sealed can be achieved using one of the following two methods:

[0031] Option 1 will use an etching tube with an integrated closed tail end, which means that the tail end of the etching tube is sealed either when the etching tube is being constructed or before the etching tube is inserted into the outer cavity tube.

[0032] Option 2 involves sealing the portion of the etched tube that extends beyond the outer cavity tube after inserting the etched tube into it. This sealing process can be achieved by using a binding tape, welding, or external clamps.

[0033] Preferably, in step 4, the fluid introduced into the etching tube cavity is a gas, liquid, or gas-liquid mixture, and the fluid pressure in the etching tube cavity is controlled based on the desired inner diameter of the etching tube cavity.

[0034] The second objective of this invention is to provide a method for connecting polymer medical catheter fittings. This method abandons the existing mandrel-supported approach and instead employs a fluid expansion-supported approach. This eliminates the need to insert a high-precision mandrel into the etched tube cavity, reducing processing requirements and improving processing efficiency. Furthermore, it avoids the problem of tube insertion failure due to insufficient mandrel precision or roundness. Specifically:

[0035] A method for connecting polymer medical catheter fittings, characterized by comprising the following steps:

[0036] Step 1: Insert an etched tube through the first tube and into the second tube. The etched tube is located at the connection between the first tube and the second tube, and the etched tube extends from the tail end of the first tube or the second tube.

[0037] Step 2: Seal the tail end of the etched tube;

[0038] Step 3: Wrap heat shrink tubing around the outside of the connection point;

[0039] Step 4: Place the connector in the rheometer and fill the cavity of the etched tube with fluid from the beginning of the tube. The fluid should be enough to expand the cavity of the etched tube. Then heat the rheometer to shrink the heat shrink tubing. Under the action of fluid expansion and the outer heat shrink tubing, the inner walls of the first and second tubes melt and combine with the outer wall of the etched tube.

[0040] The present invention adopts the above-mentioned technical solution, which relates to a connection method for polymer medical catheter fittings, mainly used to connect and fix two or more polymer medical catheters. The connection method is the same as the prior art described in the background art in that the fittings are still connected by built-in etched tubes. Based on the setting of the etched tubes, on the one hand, a firm connection of the catheter tip fittings can be achieved, and on the other hand, the smoothness of the inner wall at the connection point can be guaranteed.

[0041] Based on this, this solution abandons the existing mandrel-supported approach. Instead, it seals the tail end of the etched tube and fills it with fluid, employing a fluid expansion-supported method. This eliminates the need to insert a high-precision mandrel into the etched tube cavity. Firstly, it eliminates the need to construct a high-precision mandrel, reducing processing requirements. Secondly, it omits the step of inserting the mandrel into the etched tube cavity using an interference fit, improving processing efficiency. Furthermore, it avoids the problem of insufficient mandrel precision or roundness preventing tube insertion.

[0042] Preferably, a rigid support is provided inside the etching tube in step 1; specifically, a thin core rod is lined inside the cavity of the etching tube in step 1, the outer diameter of which is smaller than the inner diameter of the cavity of the etching tube; the thin core rod is axially supported or connected to the etching tube, so that the thin core rod and the etching tube are inserted into the cavities of the first tube and the second tube together.

[0043] After the etching tube is completed, the rigid support inside the etching tube is removed, which means removing the thin mandrel.

[0044] In addition, step 5 is included: after fixing, the outer heat shrink tubing is removed, and the portions of the etched tube extending beyond the first and second tubes are cut off.

[0045] Preferably, in step 2, the tail end of the selected etching tube is integrally sealed; or the portion of the tail end of the etching tube that extends beyond the first or second tube is sealed.

[0046] The third objective of this invention is to provide a polymer medical catheter fitting, which is manufactured by the above-described molding method or formed by connecting two or more polymer medical catheter fittings by a connection method. Attached Figure Description

[0047] Figure 1 is a schematic diagram of the implementation state of step 1 of the molding method involved in Example 1.

[0048] Figure 2 is a schematic diagram of the implementation state of step 3 of the molding method involved in Example 1.

[0049] Figure 3 is a schematic diagram of the implementation state of step 4 of the molding method involved in Example 1.

[0050] Figure 4 is a schematic diagram of the implementation state of step 5 of the molding method involved in Example 1.

[0051] Figure 5 is a schematic diagram of the implementation state of step 1 of the molding method involved in Example 2.

[0052] Figure 6 is a schematic diagram of the implementation state of step 3 of the molding method involved in Example 2.

[0053] Figure 7 is a schematic diagram of the implementation state of step 4 of the molding method involved in Example 2.

[0054] Figure 8 is a schematic diagram of the implementation state of step 5 of the molding method involved in Example 2. Detailed Implementation

[0055] Embodiments of the present invention are described in detail below, examples of which are illustrated in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and intended to explain the present invention, and should not be construed as limiting the present invention.

[0056] In the description of this invention, it should be understood that the terms "center," "longitudinal," "lateral," "length," "width," "thickness," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "clockwise," and "counterclockwise," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this invention.

[0057] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this invention, unless otherwise stated, "a plurality of" means two or more, unless explicitly defined otherwise.

[0058] In this invention, unless otherwise explicitly specified and limited, the terms "installation," "connection," "linking," and "fixing," etc., should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0059] In this invention, unless otherwise explicitly specified and limited, "above" or "below" the second feature can include direct contact between the first and second features, or contact between the first and second features through another feature between them. Furthermore, "above," "over," and "on top" of the second feature includes the first feature directly above or diagonally above the second feature, or simply indicates that the first feature is at a higher horizontal level than the second feature. "Below," "below," and "under" the second feature includes the first feature directly below or diagonally below the second feature, or simply indicates that the first feature is at a lower horizontal level than the second feature.

[0060] Although the present invention describes steps 1, 2, or similar steps in sequence, this is only for clarity and conciseness. In fact, as long as it conforms to the purpose and technical solution of the present invention, the steps can be changed as needed based on the technical principles, and these changed steps also fall within the protection scope of the present invention.

[0061] The external lumen tube referred to in this case can be a single-lumen tube or a multi-lumen tube.

[0062] Example 1:

[0063] As shown in Figures 1-4, this embodiment relates to a molding method for a polymer medical catheter fitting, including the following steps:

[0064] Step 1: Insert the rigidly supported etching tube 1 into the beginning of the outer cavity tube 2 and extend it out from the end of the outer cavity tube 2. After the etching tube is inserted, remove the rigid support inside the etching tube, which means removing the thin mandrel.

[0065] Specifically, in this step, a thin mandrel 3 is placed inside the cavity of the etching tube 1. The outer diameter of the thin mandrel 3 is smaller than the inner diameter of the etching tube 1. The thin mandrel 3 in this design differs from the mandrel used in existing technologies. It is inserted into the etching tube 1 to provide rigid support, thus facilitating the insertion of the etching tube 1 into the outer cavity tube 2. Therefore, the thin mandrel 3 in this design has an outer diameter smaller than the inner diameter of the etching tube 1, which, in principle, allows for quick and smooth insertion into the etching tube 1 while providing sufficient rigidity; furthermore, it does not have any requirements for precision or roundness. The thin mandrel 3 is axially supported or connected to the etching tube 1, allowing it to be inserted into the cavity of the outer cavity tube 2 together with the etching tube 1, thus enabling synchronous axial movement of the thin mandrel 3 and the etching tube 1.

[0066] Furthermore, in this step, the etching tube 1 is required to be inserted into the cavity of the outer cavity tube 2 from the beginning and extend out from the end of the cavity of the outer cavity tube 2. This allows the etching tube 1 to be distributed throughout the cavity of the outer cavity tube 2, and also makes it easier to seal the end of the etching tube.

[0067] Step 2: Ensure the etched tube tail end 10 is sealed. One of the following two methods can be used:

[0068] Option 1 will use an etching tube 1 with an integrated closed tail end, which means that the tail end 10 of the etching tube is closed either before the etching tube 1 is installed or before the etching tube 1 is inserted into the outer cavity tube 2.

[0069] Option 2 involves sealing the portion of the etched tube 10 that extends beyond the outer cavity tube 2 after the etched tube 1 is inserted into the outer cavity tube 2. This sealing process can be achieved by using a binding tape, welding, or external clamps.

[0070] Step 3: A heat-shrinkable tube 4 is wrapped around the outside of the outer cavity tube 2 to form a composite tube. The heat-shrinkable tube 4 defines the outer dimensions of the outer cavity tube 2 and shrinks after heating in the rheometer, thus firmly bonding with the etched tube 1.

[0071] Step 4: Place the composite tube from Step 3 into the rheometer, and fill its cavity with fluid from the beginning of the etched tube 1, ensuring the fluid can at least expand the cavity of the etched tube 1. Then heat the rheometer to shrink the heat-shrink tubing 4. Under the action of fluid expansion and the outer heat-shrink tubing 4, the outer wall of the etched tube 1 adheres to the inner wall of the outer cavity tube 2, while the inner wall of the outer cavity tube 2 melts and combines with the outer wall of the etched tube 1.

[0072] Step 5: After fixing, remove the outer heat shrink tubing 4 and cut off the portion of the etched tube 1 that extends beyond the outer cavity tube 2.

[0073] The molding method of this polymer medical catheter fitting has the same characteristics as the prior art in that: an etched tube 1 is fixed inside the outer lumen tube 2. The setting of the etched tube 1 can achieve the following effects: the smoothness requirement of the catheter fitting is high, so that the guide wire or other instruments inserted into the catheter can be inserted more smoothly; it can be applied to the connection between multiple catheter fittings.

[0074] Based on this, this solution differs from existing technologies in that it abandons the internal support method of the mandrel in existing technologies and instead adopts a fluid expansion internal support method. This eliminates the need to insert a high-precision mandrel into the cavity of the etching tube 1. On the one hand, it eliminates the need to construct a high-precision mandrel, reducing processing requirements; on the other hand, it omits the step of inserting the mandrel into the cavity of the etching tube 1 using an interference fit, improving processing efficiency. Of course, it also avoids the problem of the mandrel failing to pass through the tube due to insufficient precision or roundness.

[0075] Meanwhile, the advantage of this solution is that the fluid pressure inside the etching tube 1 can be adjusted based on different etching tube 1 sizes and their inner diameter requirements. Since the internal pressure formed by gas and liquid is evenly distributed on the inner wall of the etching tube 1, it can maintain a good roundness, which is conducive to controlling the roundness inside the tube cavity, that is, the inner shape is reshaped after the outer tube 2 melts during heat shrinking.

[0076] Example 2:

[0077] As shown in Figure 5-8, this embodiment describes a method for connecting polymer medical catheter fittings, including the following steps:

[0078] Step 1: The etching tube 1 with built-in rigid support is passed through the first tube 21 and inserted into the second tube 22. The etching tube 1 is located at the connection between the first tube 21 and the second tube 22, and the etching tube 1 extends from the tail end of the first tube 21 or the second tube 22. After the etching tube is inserted, the rigid support inside the etching tube is removed.

[0079] Step 2: Seal the tail end 10 of the etched tube;

[0080] Step 3: Wrap heat shrink tubing 4 around the outside of the connection point;

[0081] Step 4: Place the connector in the rheometer and fill the cavity of the etched tube 1 with fluid from the beginning of the tube. The fluid should be able to expand the cavity of the etched tube 1. Then heat the rheometer to shrink the heat shrink tube 4. Under the action of fluid expansion and the outer heat shrink tube 4, the inner walls of the first tube 21 and the second tube 22 melt and combine with the outer wall of the etched tube 1.

[0082] Step 5: After fixing, remove the outer heat shrink tubing 4 and cut off the portions of the etched tube 1 that extend beyond the first tube 21 and the second tube 22.

[0083] This embodiment relates to a method for connecting polymer medical catheter fittings, mainly used to connect and fix two or more polymer medical catheters. The connection method is the same as the prior art described in the background art in that the fittings are still connected by built-in etched tubes. Based on the setting of the etched tubes, on the one hand, a firm connection of the catheter tip fittings can be achieved, and on the other hand, the smoothness of the inner wall at the connection point can be guaranteed.

[0084] Based on this, this solution abandons the existing mandrel-supported approach. Instead, it seals the tail end 10 of the etched tube and fills it with fluid, employing a fluid expansion internal support method. This eliminates the need to insert a high-precision mandrel into the etched tube cavity. Firstly, it eliminates the need to construct a high-precision mandrel, reducing processing requirements. Secondly, it omits the step of inserting the mandrel into the etched tube cavity using an interference fit, improving processing efficiency. Furthermore, it avoids the problem of insufficient mandrel precision or roundness preventing tube insertion.

[0085] The rigid support built into the etching tube 1 in this embodiment, and the tail-end sealing structure of the etching tube 1 in step 2, can be referred to the contents described in embodiment 1.

[0086] Example 3:

[0087] This embodiment provides a polymer medical catheter fitting, which is manufactured using the molding method described in Embodiment 1, or formed by connecting two or more polymer medical catheter fittings using the molding method described in Embodiment 2.

[0088] In the description of this specification, references to terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0089] Although embodiments of the present invention have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Those skilled in the art can make changes, modifications, substitutions and variations to the above embodiments within the scope of the present invention without departing from the principles and spirit of the present invention.

Claims

1. A method for molding a polymer medical catheter fitting, characterized in that: The process includes the following steps: Step 1, inserting the etched tube (1) into the cavity of the outer tube (2) from the beginning and extending it from the end of the cavity of the outer tube (2), wherein the etched tube is made of PTFE material; Step 2, sealing the end (10) of the etched tube, wherein the end of the selected etched tube (1) is sealed integrally; or the part of the end of the etched tube (1) extending beyond the outer tube (2) is sealed; Step 3, covering the outside of the outer tube (2) with heat shrink tubing (4) to form a composite tube; Step 4, placing the composite tube from Step 3 into a rheometer. Fluid is introduced into the cavity of the etching tube (1) from the beginning. The fluid is gas, liquid or gas-liquid mixture. The fluid pressure in the cavity of the etching tube (1) is controlled based on the desired inner diameter of the cavity. The fluid is sufficient to expand the cavity of the etching tube (1). Then the rheometer is heated to shrink the heat shrink tube (4). Under the action of fluid expansion and the outer heat shrink tube (4), the outer wall of the etching tube (1) is brought into contact with the inner wall of the outer cavity tube (2). At the same time, the inner wall of the outer cavity tube (2) melts and combines with the outer wall of the etching tube (1).

2. The molding method for a polymer medical catheter fitting according to claim 1, characterized in that: In step 1, a rigid support is provided inside the etching tube (1), and a thin core rod (3) is lined inside the cavity of the etching tube (1). The outer diameter of the thin core rod (3) is smaller than the inner diameter of the cavity of the etching tube (1). The thin core rod (3) is axially supported or connected to the etching tube (1), so that the thin core rod (3) and the etching tube (1) are inserted into the cavity of the outer cavity tube (2) together.

3. The molding method for a polymer medical catheter fitting according to claim 2, characterized in that: In step 1, after the etched tube (1) is inserted, the built-in rigid support is removed.

4. The molding method for a polymer medical catheter fitting according to claim 1, characterized in that: It also includes step 5, after fixing, tear off the outer heat shrink tube (4) and cut off the part of the etched tube (1) that extends beyond the outer cavity tube (2).

5. A method for connecting polymer medical catheter fittings, characterized in that: The process includes the following steps: Step 1: An etched tube (1) is passed through the first tube (21) and inserted into the second tube (22). The etched tube (1) is located at the connection between the first tube (21) and the second tube (22), and the etched tube (1) extends from the tail end of the first tube (21) or the second tube (22). The etched tube is made of PTFE material. Step 2: The tail end (10) of the etched tube is sealed. The tail end of the selected etched tube (1) is sealed integrally. Alternatively, the portion of the tail end of the etched tube (1) that extends beyond the first tube (21) or the second tube (22) is sealed. Step 3: Step 4: Place the connector in a rheometer and fill the cavity of the etched tube (1) with fluid from the beginning. The fluid is a gas, liquid or gas-liquid mixture. Control the fluid pressure in the cavity of the etched tube (1) based on the desired inner diameter of the cavity. The fluid should be able to expand the cavity of the etched tube (1). Then heat the rheometer to shrink the heat shrink tube (4). Under the action of fluid expansion and the outer heat shrink tube (4), the inner walls of the first tube (21) and the second tube (22) melt and combine with the outer wall of the etched tube (1).

6. The connection method of a polymer medical catheter fitting according to claim 5, characterized in that: In step 1, a rigid support is installed inside the etching tube (1). A thin core rod (3) is lined inside the cavity of the etching tube (1). The outer diameter of the thin core rod (3) is smaller than the inner diameter of the cavity of the etching tube (1). The thin core rod (3) is axially supported or connected to the etching tube (1), so that the thin core rod (3) and the etching tube (1) are inserted into the cavities of the first tube (21) and the second tube (22) together. After the etching tube (1) is inserted, the built-in rigid support is removed.

7. The connection method of a polymer medical catheter fitting according to claim 5, characterized in that: It also includes step 5, after fixing, tear off the outer heat shrink tube (4), and cut off the part of the etched tube (1) that extends beyond the first tube (21) and the second tube (22).

8. A medical catheter fitting, characterized in that: It is manufactured by any one of the molding methods described in claims 1-4, or by connecting two or more polymer medical catheters using any one of the connection methods described in claims 5-7.

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