A mold for producing easy-to-tear sheath tube, its product and preparation method

Abstract

The present invention provides a mold for producing a tear-resistant sheath tube, a product thereof, and a method for producing the same. The mold comprises a core mold, which includes a flow guide section, an orientation section, and a shaping section connected in sequence. The flow guide section guides the polymer melt, the orientation section is provided with a serrated portion on its outer ring for molecular orientation, and the shaping section shapes the polymer melt. This invention significantly improves the longitudinal tear strength of the tube while ensuring that the tube's appearance and mechanical properties meet operational requirements.

Description

Technical Field

[0001] The present invention relates to the technical field of medical catheters, and in particular to a mold for producing an easily tearable sheath, a product thereof, and a preparation method thereof. Background Art

[0002] The sheath, also known as the catheter sheath, is the initial interventional device for percutaneous vascular surgery of arteries and veins. The sheath consists of a dilator tube and a sheath tube, usually made of polytetrafluoroethylene. The main purpose of the catheter sheath is to establish a channel to guide the catheter, balloon catheter or other intravascular devices to enter the blood vessel smoothly, establish a connection channel between the blood vessel and the outside world, and allow the catheter to enter the blood vessel along the lumen of the sheath tube. After the catheter enters the human body, the catheter sheath completes the surgical task and is withdrawn. During the delivery of some special instruments, the catheter sheath cannot be withdrawn because the other end of the catheter is connected to accessories. At this time, the catheter sheath needs to be torn from the outside, tearing it while withdrawing until it is completely removed. The advantage of the easy-to-tear sheath that is easy to tear and withdraw provides convenience for subsequent catheter surgery.

[0003] At present, the commonly used materials for sheaths are HDPE and PTFE. In order to achieve the easy tearing of the tube body, there are usually two methods:

[0004] 1. Add additives that are incompatible with the matrix material. The additives are dispersed in the matrix polymer chain. Microscopically, the matrix material forms a layered structure. When the tube is torn artificially, the stress is concentrated in the gap between the matrix and the additives, making the tube easy to tear.

[0005] 2. Process axial grooves on the tube body to artificially create stress concentration areas so that the tube can tear along the grooves when subjected to stress.

[0006] While both approaches achieve easy-tear properties, they also sacrifice some performance. For example, the first approach, due to the layered structure of the tube wall, reduces the mechanical strength of the sheath. The second approach, however, incorporates longitudinal indentations on the tube wall, which reduces the smoothness of the outer surface and increases the coefficient of friction, hindering smooth insertion of the sheath into the blood vessel. Furthermore, the indentations must cooperate with the tube socket, causing the sheath to tear along the indentations under the tension of the socket. This necessitates a delicate and precise assembly of the indentations and the socket, placing high demands on the process.

[0007] At present, the preparation of tearable sheaths on the market mostly adopts the single-lumen tube grooving process: a mold is installed at the output end of the extruder, and the polymer melt enters the mold after being extruded from the extruder, and then the sheath tube single-lumen tube is extruded from the mold. Then, special tooling is used to perform groove processing on the inner or outer surface of the single-lumen tube using laser or mechanical methods. Among them, the mold includes a mouth mold and a core mold. The mouth mold has a through cavity. The core mold is inserted into the cavity of the mouth mold. There is a gap between the outer surface of the core mold and the inner wall of the mouth mold for the polymer melt to pass through. The mouth mold controls the external shape of the tube, and the core mold controls the internal shape of the tube. The secondary processing method increases the difficulty of the production process and the production cost of a single sheath tube. In addition, during the secondary processing, it is easy to cause uneven groove depth on both sides, which increases the tearing force of the sheath tube or reduces the supporting performance. The secondary grooving process is also prone to produce plastic debris, which poses a safety hazard to the use of the product.

[0008] Therefore, there is an urgent need for a sheath tube with smooth inner and outer surfaces, certain mechanical strength, and easy tearing, as well as a production equipment. Summary of the Invention

[0009] In response to the deficiencies in the prior art, the present invention provides a mold for producing an easily tearable sheath, a product thereof, and a preparation method, which solves the problem in the prior art that while improving the tearability of the sheath, the surface smoothness or mechanical strength of the sheath is affected.

[0010] In one aspect, the present invention provides a mold for producing an easy-to-tear sheath, comprising a core mold, wherein the core mold comprises a guide section, an orientation section, and a shaping section connected in sequence.

[0011] The guide section is used to guide the polymer melt, the outer ring of the orientation section is provided with a serration portion for molecular orientation of the polymer melt, and the shaping section is used to shape the polymer melt.

[0012] Beneficial effects: The guide section is used to guide the polymer melt, the serrated portion is provided on the surface of the orientation section, and the shaping section is used to shape the polymer melt. The serrated portion is used to molecularly orient the polymer melt, thereby improving the tearing performance of the sheath tube.

[0013] Furthermore, the serration portion includes a plurality of serrations arranged along the circumference of the orientation segment, and the serrations extend longitudinally along the orientation segment.

[0014] Beneficial Effect: The serrations facilitate "combing" of the polymer melt, allowing the irregularly arranged polymer melt to form a longitudinal molecular arrangement in the serrated flow channel, thereby forming a longitudinal molecular orientation. At the same time, this structure does not affect the transverse performance of the sheath tube.

[0015] Furthermore, the longitudinal cross-sectional area of ​​the saw teeth is triangular, trapezoidal, inverted U-shaped or semicircular.

[0016] Furthermore, the number of the saw teeth is 6-30.

[0017] Furthermore, the length of the orientation section accounts for 30-90% of the total length of the orientation section and the shaping section.

[0018] Beneficial Effects: When the sawtooth shape and number are within this range, the longitudinal shear force on the polymer melt is maximized, effectively achieving longitudinal molecular orientation in the polymer melt. When the lengths of the orientation section and the shaping section are within this range, the flow distance over which the polymer melt undergoes orientation is increased, thereby enhancing molecular orientation.

[0019] Furthermore, the guide section is arranged in a frustum shape, the orientation section and the forming section are both arranged in a cylindrical shape, the small table end of the guide section is coaxially connected to one end of the orientation section, and the other end of the orientation section is coaxially connected to one end of the forming section, and the outer diameter of the orientation section is larger than the outer diameter of the forming section.

[0020] Beneficial effect: The fluidity of the polymer melt is improved, thereby ensuring the thickness uniformity of the sheath tube wall and the stability of the sheath tube.

[0021] In another aspect, the present invention provides an extrusion device comprising the above-mentioned die for producing the easy-to-tear sheath.

[0022] In another aspect, the present invention provides a method for preparing an easily tearable sheath, comprising the following steps:

[0023] S1 drying: drying the raw material to obtain a dry raw material;

[0024] S2 melt extrusion: the raw materials dried in S1 are added into the above extrusion equipment for melt extrusion, orientation and shaping to obtain an easy-to-tear sheath.

[0025] Furthermore, the melt extrusion temperature is 140-380° C., and the stretching ratio of the easy-to-tear sheath is 5-30.

[0026] Beneficial effects: If the temperature is too high, the molecular chains of the polymer material will be destroyed, the polymer will be degraded, and the polymer melt will be deoriented; if the temperature is too low, the molecular structure of the polymer melt will be uneven, thereby affecting the melting state of the polymer melt.

[0027] In another aspect, the present invention provides an easy-to-tear sheath tube obtained by the above-mentioned method for preparing the easy-to-tear sheath tube.

[0028] The term "stretching ratio" in the present invention refers to the ratio of the annular cross-sectional area between the core die and the die in the mold to the cross-sectional area of ​​the tearable sheath.

[0029] The technical principle of the present invention is:

[0030] The die controls the outer diameter of the tube, while the core controls the inner diameter. A flow channel for the polymer melt is formed between the core and die, primarily serving to guide, orient, and shape the melt. The zigzag flow channel achieves longitudinal molecular orientation of the polymer melt, improving the sheath's tear resistance.

[0031] The inventors further discovered that compared with the core mold without teeth, the pin tube not only exhibits excellent tearability, but also exhibits better axial mechanical properties. This is because after the polymer melt passes through the serrations and then intersects again, it is only partially oriented at the interface between the two melts, and the polymer chains outside the interface are still in an irregular state. The sheath tube presents an alternating "oriented-random-oriented" structure. Due to the influence of the irregular area, the easy-to-tear sheath tube is no different from the ordinary sheath tube in the radial direction. In the axial direction, the oriented area acts as a reinforcing rib, which increases the axial mechanical properties of the easy-to-tear sheath tube.

[0032] Compared with the prior art, the present invention has the following beneficial effects:

[0033] (1) While ensuring that the appearance and mechanical properties of the tube body meet the requirements of use, the polymer is more evenly distributed in the tube through the orientation of the polymer chain segments, which can greatly improve the longitudinal tear strength of the tube, so that the easy-to-tear tube can be torn along the axial direction while ensuring the radial support force.

[0034] (2) The tearable sheath in the present invention can be applied to various drug balloon protective sleeves, puncture sheath dilators, etc.

[0035] (3) The method of the present invention is simple, stable, easy to prepare, low in price, and easy to implement large-scale industrial production.

[0036] To sum up, when the sheath tube is melt-extruded in the present invention, the polymer melt is pushed by the screw or plunger and flows toward the discharge port. The die and core rod at the discharge port limit the shape of the melt to a tubular shape. At the same time, the serrated core die used in the present invention forcibly orients the polymer melt in the molten state, so that the random polymer chain segments in the polymer melt are oriented in the flow direction. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] Figure 1 It is a longitudinal cross-sectional view of a mold according to an embodiment of the present invention.

[0038] Figure 2 Schematic diagram of an easy-to-tear sheath according to an embodiment of the present invention.

[0039] Figure 3 Schematic diagram of polymer chain orientation in the polymer melt of the present invention.

[0040] Figure 4It is a front view of the core mold of the present invention.

[0041] Figure 5 Schematic diagram of the core mold of the present invention.

[0042] In the above drawings: 1, die; 2, core mold; 21, guide section; 22, orientation section; 23, shaping section; 3, polymer melt; 4, barrel; 5, tearable sheath; 6, serrated portion. DETAILED DESCRIPTION

[0043] The technical solution of the present invention is further described below with reference to the accompanying drawings and embodiments.

[0044] Example 1 Preparation of easy-tear sheath

[0045] like Figure 1-5 As shown, the mold for producing the easy-to-tear sheath 5 in this embodiment includes a mouth mold 1 and a core mold 2. A gap is formed between the inner wall of the mouth mold 1 and the outer surface of the core mold 2 for the polymer melt 3 to pass through.

[0046] The die 1 includes an inlet and an outlet, with the inlet communicating with the barrel 4 of the melt extruder. The outlet is used to output the processed and formed easy-to-tear sheath 5. The die 1 has a guide cavity and a molding cavity that are interconnected. The longitudinal cross-section of the guide cavity is trapezoidal, and the aperture of the guide cavity shrinks and gradually decreases from the inlet toward the symmetrical center of the core die 2. The guide cavity is used to streamline the polymer melt 3 output from the barrel 4 into the molding cavity. The molding cavity has a rectangular longitudinal cross-section and includes molding cavity 1 and molding cavity 2. The molding cavity is used to give the polymer melt 3 an appropriate shape and eliminate the uneven flow generated in the guide cavity.

[0047] The core mold 2 is inserted into the flow diversion cavity and the molding cavity. The core mold 2 includes a flow diversion section 21, an orientation section 22, and a shaping section 23, which are connected in sequence. The flow diversion section 21 cooperates with the flow diversion cavity to guide the polymer melt 3; the orientation section 22 cooperates with the molding cavity 1, and the shaping section 23 cooperates with the molding cavity 2.

[0048] The guide section 21 is in the shape of a cone, the orientation section 22 is in the shape of a cylinder, and the shaping section 23 is in the shape of a column. The small table end of the guide section 21 is coaxially connected to one end of the orientation section 22, and the other end of the orientation section 22 is coaxially connected to one end of the shaping section 23. The surface of the orientation section 22 is circumferentially provided with 20 outwardly protruding serrations to form a serration portion 6. The longitudinal cross-section of the serrations can be a variety of shapes such as a triangle, a trapezoid, an inverted U-shape or a semicircle. In this embodiment, the longitudinal cross-section of the serrations is a triangle. The serrations extend longitudinally along the orientation section 22, and the multiple serrations are arranged in parallel. The inner hole size of the die 1 is 8.4 mm, the outer diameter size of the shaping section 23 of the core die 2 is 3.3 mm, the protruding height of the serrations is 2 mm, the axial length of the orientation section 22 is 7 mm, and the axial length of the shaping section 23 is 4 mm. The final extruded easy-tear sheath 5 has an inner diameter of 1.1 mm, an outer diameter of 2.8 mm, a thickness of 0.85 mm, and a stretch ratio of 9.

[0049] During production, the die is mounted at the end of a melt extruder so that the inlet end of the die 1 is in communication with the barrel 4 of the melt extruder. Melt extruders include single-screw reaction extruders, twin-screw reaction extruders, and plunger extruders. This embodiment employs a single-screw reaction extruder. The single-screw reaction extruder includes a barrel 4, a feed port, and a discharge port.

[0050] The production of the easy-to-tear sheath 5 includes the following steps:

[0051] 1) Drying: Dry the HDPE raw material to obtain a dry raw material. Treatment methods include, but are not limited to, vacuum drying and hot air drying. Vacuum drying conditions are: vacuum degree -0.095 MPa, temperature 60-80°C, and drying time 2-6 hours.

[0052] The conditions for hot air drying are: temperature 60-80℃, drying time 2-6 hours.

[0053] 2) Melt extrusion: Dry polymer raw materials are added to the single-screw melt extruder from the feed port. The polymer raw materials are heated and melted in the extruder to obtain a polymer melt 3. Subsequently, the polymer melt 3 enters the guide cavity along the guide section 21 of the core mold 2 from the discharge port of the extruder barrel 4, and then enters the molding cavity 1 along the zigzag flow channel formed by the orientation section 22. During the flow of the polymer melt 3 in the molding cavity 1, the polymer melt 3 fills the pores between the serrations and is subjected to the shear force and extrusion force of the serrations, causing molecular orientation along the extrusion direction. The irregularly arranged polymer melt 3 forms a longitudinal molecular arrangement under the action of the zigzag flow channel. It then enters the shaping section 23 of the molding cavity 2 and is extruded and shaped to obtain the easy-to-tear sheath 5.

[0054] By controlling the pulling speed, the inner diameter and outer diameter of the tearable sheath 5 can be increased or decreased proportionally. In this embodiment, the stretching ratio is 9.

[0055] Example 2 Preparation of easy-tear sheath

[0056] Similar to Example 1, the difference is that the longitudinal cross-section of the saw teeth is semicircular.

[0057] Example 3 Preparation of easy-tear sheath

[0058] Similar to Example 1, the difference is that the longitudinal cross-section of the saw teeth is trapezoidal.

[0059] Comparative Example 1

[0060] Similar to Example 1, the difference is that the core rod is cylindrical and there is no serration on the outer surface of the core rod.

[0061] Mechanical Strength Testing: The easily tearable sheaths produced in this example were subjected to tear strength testing using the following method: 100 mm of tubing from each example and comparative example was sampled and its appearance evaluated. The tubing was then cut axially into 30 mm sections to form a "Y"-shaped strip. A tensile test was performed using the upper and lower clamps of a tensile testing machine, securing the ends of the joint. The test was performed according to the method specified in GB / T 1040-79. The tearing behavior of the tubing specimens was observed, and the maximum tensile force was recorded.

[0062] The tearing forces of the tearable sheaths in Examples 1-3 and Comparative Examples 1-2 are shown in Table 1:

[0063] Table 1 Tearability of tearable sheath

[0064] category Appearance (smoothness) Tearability Tear value Example 1 excellent Tearable 5.27N Example 2 excellent Tearable 7.16N Example 3 excellent Tearable 5.92N Comparative Example 1 excellent Untearable / .

[0065] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not limiting. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solutions of the present invention may be modified or replaced by equivalents without departing from the purpose and scope of the technical solutions of the present invention, which should all be included in the scope of the claims of the present invention.

Claims

1. A mold for producing an easily tearable sheath, comprising a core mold, characterized in that: The core mold includes a guide section, an orientation section and a shaping section connected in sequence. The guide section is used to guide the polymer melt, the outer ring of the orientation section is provided with a serrated portion for molecular orientation of the polymer melt, and the shaping section is used to shape the polymer melt; The sawtooth portion includes a plurality of sawteeth arranged along the circumference of the orientation segment, and the sawteeth extend longitudinally along the orientation segment; The guide section is arranged in a frustum shape, and the orientation section and the forming section are both arranged in a cylindrical shape. The small table end of the guide section is coaxially connected to one end of the orientation section, and the other end of the orientation section is coaxially connected to one end of the forming section. The outer diameter of the orientation section is larger than the outer diameter of the forming section.

2. A mold for producing an easy-to-tear sheath according to claim 1, characterized in that: The longitudinal cross-section of the sawtooth is triangular, trapezoidal, inverted U-shaped or semicircular.

3. A mold for producing an easy-to-tear sheath according to claim 1, characterized in that: The number of the saw teeth is 6-30.

4. A mold for producing an easily tearable sheath according to claim 1, characterized in that: The length of the orientation section accounts for 30-90% of the total length of the orientation section and the shaping section.

5. An extrusion device, characterized in that: A mold for producing an easy-to-tear sheath tube comprising the mold according to any one of claims 1 to 4.

6. A method for preparing an easily tearable sheath, characterized in that: The following steps are involved: S1 drying: drying the raw material to obtain a dry raw material; S2 melt extrusion: adding the dried raw materials in S1 to the extrusion equipment according to claim 5 to perform melt extrusion, orientation and shaping to obtain an easily tearable sheath.

7. The method for preparing an easily tearable sheath according to claim 6, wherein: The melt extrusion temperature is 140-380° C., and the stretching ratio of the easy-to-tear sheath is 5-30.

8. An easy-to-tear sheath, characterized in that: The method for preparing the easy-to-tear sheath according to claim 6 or 7 is obtained.

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