Tear-resistant heat shrink tubing

Abstract

To provide a stable tube in which burst of a heat-shrinkable tube having an easily tearable characteristic in a longitudinal direction is less likely to occur in a manufacturing process of the tube.SOLUTION: A tube contains a fluororesin at least capable of being melt-processed. When a strain of the tube is ε, and a stress at that time is σ(MPa), a horizontal axis on a coordinate graph represents the strain ε, and a vertical axis represents the stress σ. Each of a straight line ab, and a straight line cd defined by four coordinate points of a (0.4, 8.8), b (0.4, 2.4), c (1.0, 9.9), and d (1.0, 3.2) on the graph intersects with a mechanical characteristic curve of the tube obtained by performing a tensile test under conditions of an ambient temperature of 60°C, initial inter-chuck distance of 22±0.05 mm, and tensile speed of 5 mm / sec.SELECTED DRAWING: Figure 2

Description

Technical Field

[0001] The present invention relates to a heat - shrinkable tube having longitudinal tear - susceptibility.

Background Art

[0002] Tubes having longitudinal tear - susceptibility are used as protective members until the use of various articles. Among them, tear tubes made of fluororesin have properties such as heat resistance, chemical resistance, water - and oil - repellency, non - stickiness, and self - lubricity, which are not obtainable with hydrocarbon - based synthetic resins. Utilizing these properties, they are used as protective tubes for precision instruments, electronic components, etc., or as medical device introduction tubes for introducing catheters, guide wires, etc. into the body.

[0003] Tubes with further imparted heat - shrinkability to tubes having tear - susceptibility can surely protect articles mounted inside without displacement or can also be used as jigs for catheter production. When the heat - shrinkable tube having tear - susceptibility becomes unnecessary, it can be easily torn and removed without using special instruments. For example, Patent Document 1 describes a heat - shrinkable tube having tear - susceptibility made of a mixture of fluororesins. However, because the tube is easily torn, there is a problem that in the process of expanding the diameter of the tube for imparting heat - shrinkability to the tube, the tube is likely to rupture and it is difficult to produce stably.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] The present invention aims to provide a heat-shrinkable tube that is easily torn in the longitudinal direction, and to provide a tube that is less prone to bursting during the tube diameter expansion process in the manufacturing process, and that can be produced stably. [Means for solving the problem]

[0006] To solve the above problems, the inventors of the present invention discovered that when the mechanical properties curve obtained from a tensile test of the tube is in a specific region, tube rupture is less likely to occur during the tube diameter expansion process in the tube manufacturing process, and stable production is possible, thus completing the present invention.

[0007] In other words, the present invention is as follows: The tube of the present invention is a tear-resistant heat-shrinkable tube mainly composed of a melt-processable fluororesin. The tube is defined by taking the strain ε and the stress σ (MPa) as the strain ε on a coordinate graph, with the horizontal axis representing strain ε and the vertical axis representing stress σ. The tube is defined by the intersection of the lines ab and cd, respectively, which are determined by four coordinate points a(0.4,8.8), b(0.4,2.4), c(1.0,9.9), and d(1.0,3.2), with the mechanical property curve of the tube obtained by the measurement method described below. In this case, the tube is less likely to burst during the expansion process, and a stable tube is more easily obtained. The mechanical property curve is determined by performing a tensile test under the conditions of an ambient temperature of 60°C, an initial chuck distance of 22±0.05 mm, and a tensile speed of 5 mm / sec. It is more preferable that the mechanical property curve of the tube is such that the region defined by the four coordinate points on the graph intersects with the straight lines a'b and c'd, respectively, defined by the four coordinate points a'(0.4,7.6), b(0.4,2.4), c'(1.0,8.9), and d(1.0,3.2). The tube of the present invention is a tear-resistant heat-shrinkable tube mainly composed of a melt-processable fluororesin. The strain of the tube is denoted as ε and the stress at that time as σ (MPa). On a coordinate graph, the horizontal axis represents strain ε and the vertical axis represents stress σ. In the mechanical property curve of the tube obtained by the above-described measurement method, the stress σ at a strain ε of 1.0 is 3.2 MPa or higher. Furthermore, when the coordinate point on the mechanical property curve at a strain ε of 1.0 is denoted as e, and the coordinate point at a strain ε of 2.0 is denoted as f, the slope of the line passing through coordinate points e and f is 2.4 to 3.0 MPa. In this case, during the tube expansion process, tube rupture is less likely to occur, and a stable tube is easily obtained.

[0008] The fluororesin constituting the tear-resistant heat-shrinkable tube of the present invention preferably contains at least three monomers as constituent monomers: tetrafluoroethylene, hexafluoropropylene, and vinylidene fluoride. Examples of resins containing at least three monomers as constituent monomers include tetrafluoroethylene-hexafluoropropylene-vinylidene fluoride copolymer (THV) and tetrafluoroethylene-hexafluoropropylene-vinylidene fluoride-perfluoroalkyl vinyl ether copolymer.

[0009] The tear-resistant heat-shrinkable tube of the present invention may contain multiple fluororesins. In addition to a fluororesin containing at least three monomers, namely tetrafluoroethylene, hexafluoropropylene, and vinylidene fluoride, other fluororesins may also be included. It is preferable to contain as much of the resin containing the at least three monomers as possible, and it is preferable that the resin containing the at least three monomers is present in an amount of 25 wt% to 95 wt% in the fluororesin constituting the tube. It is even more preferable that the resin containing the at least three monomers is present in an amount of 40 wt% or more, and particularly preferable that it is present in an amount of 50 wt% or more. If the fluororesin constituting the tube contains multiple resins containing at least three monomers, namely tetrafluoroethylene, hexafluoropropylene, and vinylidene fluoride, the total amount of these multiple resins is referred to as the content.

[0010] In the fluororesin constituting the tear-resistant heat-shrinkable tube of the present invention, the resin containing at least three monomers as constituent monomers, namely tetrafluoroethylene, hexafluoropropylene, and vinylidene fluoride, is preferably a copolymer containing 15 wt% to 25 wt% vinylide.

[0011] The tear-resistant heat-shrinkable tube of the present invention preferably contains multiple fluororesins, and the difference in refractive index (ASTM D542) between these multiple fluororesins is preferably 0.05 or less. Here, "fluororesins" in "multiple fluororesins" refers to fluororesins that make up 3% by weight or more of the total fluororesins. [Effects of the Invention]

[0012] According to the present invention, in the process of expanding the diameter of a tearable tube, heat-shrinkable tubes can be stably produced without causing the tube to burst. [Brief explanation of the drawing]

[0013] [Figure 1] This diagram illustrates the tearability of the tube of the present invention. [Figure 2] This figure shows an example of the mechanical property curves of a conventional tube and the tube of the present invention. [Modes for carrying out the invention]

[0014] The embodiments for carrying out the present invention will be described in detail below. The embodiments described below are illustrative for explaining the present invention and are not intended to limit the invention as defined in the claims. Furthermore, the combination of features described in the embodiments is not necessarily essential for the present invention to be established.

[0015] As shown in Figure 1, the tube of the present invention is easily torn along its longitudinal direction, and can be torn from one end to the other. Notches can be made in the tube as needed.

[0016] The tube of the present invention is further heat-shrinkable. Heat-shrinkability can be imparted to the tube by general processing methods. For example, the following methods can be used. [Raw material preparation] The tube of the present invention uses a melt-processable fluororesin as its raw material. The tube can also be constructed using multiple resins to adjust its mechanical properties. Commonly used fluororesins include THV, tetrafluoroethylene-hexafluoropropylene copolymer (FEP), tetrafluoroethylene-perfluoroalkyl vinyl ether (PFA), ethylene-tetrafluoroethylene copolymer (ETFE), ethylene-tetrafluoroethylene-hexafluoropropylene copolymer (EFEP), and polychlorotrifluoroethylene (PCTFE). While the fluororesins used as raw materials may be blended by tumbler or similar equipment, it is more preferable to prepare them by melt-kneading and pelletizing using a twin-screw extruder. Furthermore, a resin that does not have thermal meltability, such as PTFE, may be added as an additive. Additionally, components that act as compatibilizers to promote resin dispersion, as well as additives with other functions such as adjusting crystallinity, tube flexibility, tube hardness, and improving mechanical properties, can also be added. [Tube molding] The prepared resin is melt-extruded into a tubular shape using a single-screw extruder to form the tube that will become the material for the heat-shrinkable tube (hereinafter referred to as the raw tube). [Expansion of the original tube] The raw tube is heated to a temperature above the glass transition temperature of the resin that makes up the tube, while pressurized gas is injected to pressurize the tube from the inside and expand it radially. The tube is then cooled while maintaining the pressurized state to create a heat-shrinkable tube.

[0017] The problem addressed in this invention, which occurs in the manufacturing process of conventional heat-shrinkable tubes with tearability, mainly occurs during the expansion step of the raw tube in the above manufacturing process, when the tube is heated and pressurized from the inside.

[0018] Figure 2 shows an example of the mechanical property curve of a tube on a graph with the strain ε of the tube on the horizontal axis and the stress σ (MPa) at that time on the vertical axis. Curves A and B are examples of preferable mechanical property curves of the heat-shrinkable tube having tearability of the present invention. Curves A and B intersect with straight lines ab and cd defined by four coordinate points, respectively. Further, curve B also intersects with straight lines a'b and c'd, respectively. The heat-shrinkable tube having tearability of the present invention having the mechanical properties represented by curves A and B has mechanical property curves that intersect with straight lines ab and cd, respectively, and it is difficult to cause rupture in the process of expanding the original tube. Further, when the mechanical property curve also intersects with straight lines a'b and c'd, respectively, in the process of expanding the original tube, it is easy to obtain a stable tube that is difficult to cause rupture even when expanded at once.

[0019] The heat-shrinkable tube having tearability of the present invention contains a plurality of fluororesins, and it is preferable that the difference in refractive index (ASTM D542) between the plurality of fluororesins is at most 0.05. Here, the refractive index uses the measured value measured according to ASTM D542. The molecular structure of the resin is reflected in the refractive index of the resin. Fluororesins showing similar refractive indices have similar molecular structures, and when the resins are blended, adhesive force between the resins is obtained at the interface of the dispersed resins, which is more preferable.

[0020] The heat-shrinkable tube having tearability of the present invention has a mechanical property curve such that the stress σ when the strain ε is 1.0 is 3.2 MPa or more, and when the coordinate point when the strain ε on the mechanical property curve is 1.0 is e and the coordinate point when the strain ε on the mechanical property curve is 2.0 is f, it is preferable that the slope of the straight line passing through the coordinate point e and the coordinate point f is 2.4 - 3.0 MPa. In the process of expanding the original tube, it is difficult for the tube to rupture, and it is easy to obtain a stable tube.

[0021] The invention will be described in more detail with the following examples.

Examples

[0022] <Tensile test> [Measurement sample] The following method was used to create the measurement samples from the tubes. Sample Preparation Method: A tube was sandwiched between two smooth polyimide films and melt-pressed using a hot press to create a film with a thickness of 0.10 to 0.12 mm. A specific example of film creation is described below. Tubes cut to the size of the film to be created were arranged, sandwiched between two smooth polyimide films, and heated using a hot press to a temperature 20°C to 50°C higher than the melting point of the fluororesin with the highest melting point among the multiple fluororesins constituting the tube. A first melt-press was performed to create a pre-formed film with a thickness of approximately 0.2 mm. The obtained pre-formed film was divided radially into four sections from the center of the film. These four sections were stacked while changing the direction of the film, and again sandwiched between two smooth polyimide films. This was then heated using a hot press to a temperature 20°C to 50°C higher than the melting point of the resin with the highest melting point among the resins constituting the tube. A second melt-press was performed to create a film with a thickness of 0.1 to 0.12 mm. The prepared films were left to stand at room temperature until the next day, then punched out using a dumbbell-shaped punch according to ASTM D1708, and used as measurement samples. [Measurement method] Tensile tests were performed on the tube sample using a tensile testing machine. Measurements were taken under the following conditions: measurement temperature of 60°C, initial chuck distance of 22 mm ± 0.05 mm, and tensile speed of 5 mm / sec. Other conditions followed ASTM D1708. The measured strain was calculated based on equation (1) below. Furthermore, the strain of the tube was denoted as ε and the stress at that time as σ (MPa), and a mechanical property curve of the tube was created with strain ε on the horizontal axis and stress σ on the vertical axis of a coordinate graph.

[0023]

number

[0024] [Raw material preparation] In each example and comparative example, resins with the following mixing ratios were prepared. Example 1 THV (contains about 17wt% VDF) 80wt% FEP (FEP 130-J, manufactured by Mitsui Chemours Fluoroproducts Co., Ltd.) 20wt% Example 2 THV (contains about 20wt% VDF) 75wt% FEP (FEP NP-3180 manufactured by Daikin Industries, Ltd.) 25wt% Example 3 THV (contains about 22wt% VDF) 50wt% PFA (Daikin Industries, Ltd. PFA AP-202) 50wt% Example 4 THV (contains about 20wt% VDF) 25wt% FEP (FEP 9494X, manufactured by Mitsui Chemours Fluoroproducts Co., Ltd.) 75wt% Example 5 THV (contains about 22wt% VDF) 90wt% PFA (PFA 420HP-J, manufactured by Mitsui Chemours Fluoroproducts Co., Ltd.) 10wt% Example 6 THV (contains about 20wt% VDF) 60wt% THV (contains about 17wt% VDF) 20wt% FEP (FEP 130-J, manufactured by Mitsui Chemours Fluoroproducts Co., Ltd.) 20wt% Example 7 THV (contains about 20wt% VDF) 90wt% ETFE (ETFE C88AX-P manufactured by Asahi Glass Co., Ltd.) 10wt% The raw materials prepared according to the mixing ratios of each example and comparative example were thoroughly stirred in a tumbler and then fed into a twin-screw extruder with a cylinder diameter of 20 mm to form pellets. [Forming of the raw tube] The raw material pellets prepared in each example and comparative example were formed into tubes using a single-screw extruder with a cylinder diameter of 20 mm to serve as the base tubes for heat-shrinkable tubing. [Expansion of the original tube] The original tube was heated from the outside while pressurized nitrogen was injected into the inside of the tube, pressurizing the inside and expanding it radially. The tube was then cooled while maintaining the internal pressure to create a heat-shrinkable tube. [Expansion test of the original tube] The original tube was expanded by heating it from the outside while injecting pressurized nitrogen into the tube, pressurizing the inside of the tube rapidly until the expansion rate of the inner diameter of the tube exceeded 300%. Table 1 shows the probability of the tube rupturing under these conditions. If the probability of rupture when expanded under these conditions is around 20%, it is considered to be within the range where stable production is possible during the expansion process in product manufacturing. When the probability of rupture is around 10%, the tube is less likely to rupture, and a more stable tube is more likely to be obtained.

[0025] Table 1 shows the results of the measurements performed for each example and comparative example. [Table 1]

[0026] In all of the tubes in Examples 1 to 7, the mechanical property curves intersected the straight lines ab and cd, respectively, and in the expansion test of the original tubes, the probability of rupture was low and they could be expanded stably. In particular, Examples 1 to 6 were composed of fluororesins with a maximum refractive index difference of 0.05 or less between the resins, and they could be expanded stably even when the internal pressure of the tube was set high during expansion and expanded rapidly.

[0027] Example 8 As THV, THV (containing approximately 17 wt% VDF, refractive index 1.35) or THV (containing approximately 20 wt% VDF, refractive index 1.35) And as FEP, Using FEP 130-J or FEP 9494X, tubes were prepared in various mixing ratios. The prepared raw materials were thoroughly mixed in a tumbler and fed into a twin-screw extruder with a cylinder diameter of 20 mm for pellet molding. Each of the prepared raw material pellets was extruded using a single-screw extruder with a cylinder diameter of 20 mm at DDR8-9 to create base tubes, and heat-shrinkable tubes were then produced using the method described above. In all of the obtained tubes, the stress σ at a strain ε of 1.0 was 3.2 MPa or higher in the mechanical properties curve of the tube, and the slope of the line passing through coordinate point e at a strain ε of 1.0 and coordinate point f at a strain ε of 2.0 was in the range of 2.4-3.0 MPa. Furthermore, expansion tests showed that the probability of rupture was less than 20%. [Industrial applicability]

[0028] The tear-resistant heat-shrinkable tubing of the present invention is less prone to rupture during the process of imparting heat shrinkability to the original tubing, making it easier to obtain a stable tubing. It is useful as a tubing for introducing medical devices such as catheters and guidewires into the body, as well as a jigs used in catheter manufacturing, or as protective tubing for precision instruments, electronic components, etc.

Claims

1. A tear-resistant heat-shrinkable tube mainly composed of a melt-processable fluororesin, The fluororesin comprises at least a resin containing at least three monomers as constituent monomers: tetrafluoroethylene, hexafluoropropylene, and vinylidene fluoride. A tear-resistant heat-shrinkable tube, characterized in that, with the strain of the tube being ε and the stress at that time being σ (MPa), the horizontal axis of a coordinate graph is taken with strain ε and the vertical axis with stress σ, and the lines ab and cd, determined by four coordinate points a(0.4, 8.8), b(0.4, 2.4), c(1.0, 9.9), and d(1.0, 3.2) on the graph, intersect with the mechanical property curve of the tube obtained by the measurement method described below. (Measurement method) A tensile test is performed under the following conditions: ambient temperature of 60°C, initial chuck distance of 22 ± 0.05 mm, and tensile speed of 5 mm / sec.

2. A tear-resistant heat-shrinkable tube according to claim 1, wherein the resin, as constituent monomers, contains at least three monomers: tetrafluoroethylene, hexafluoropropylene, and vinylidene fluoride, in an amount of 25 wt% to 95 wt% relative to the total amount of fluororesin constituting the tube.

3. A tear-resistant heat-shrinkable tube according to claim 1 or 2, characterized in that it contains a plurality of fluororesins, and the difference in refractive index (ASTM D542) between the plurality of fluororesins is at most 0.05 or less.

4. A tear-resistant heat-shrinkable tube according to any one of claims 1 to 3, characterized in that it is used as a jig for manufacturing tubes for introducing medical devices, a jig for manufacturing catheters, or a protective tube for electronic components.

5. A tear-resistant heat-shrinkable tube mainly composed of a melt-processable fluororesin, The fluororesin comprises at least a resin containing at least three monomers as constituent monomers: tetrafluoroethylene, hexafluoropropylene, and vinylidene fluoride. A tear-resistant heat-shrinkable tube, characterized in that, with the strain of the tube being ε and the stress at that time being σ (MPa), the horizontal axis of a coordinate graph is taken with strain ε and the vertical axis with stress σ, and the lines a'b and c'd, determined by four coordinate points a'(0.4, 7.6), b(0.4, 2.4), c'(1.0, 8.9), and d(1.0, 3.2) on the graph, intersect with the mechanical property curve of the tube obtained by the measurement method described below. (Measurement method) A tensile test is performed under the following conditions: ambient temperature of 60°C, initial chuck distance of 22 ± 0.05 mm, and tensile speed of 5 mm / sec.

6. A tear-resistant heat-shrinkable tube according to claim 5, wherein the resin, as constituent monomers, contains at least three monomers: tetrafluoroethylene, hexafluoropropylene, and vinylidene fluoride, in an amount of 25 wt% to 95 wt% relative to the total amount of fluororesin constituting the tube.

7. A tear-resistant heat-shrinkable tube according to claim 5 or 6, characterized in that it contains a plurality of fluororesins, and the difference in refractive index (ASTM D542) between the plurality of fluororesins is at most 0.05 or less.

8. A tear-resistant heat-shrinkable tube according to any one of claims 5 to 7, characterized in that it is used as a jig for manufacturing tubes for introducing medical devices, a jig for manufacturing catheters, or a protective tube for electronic components.

9. A tear-resistant heat-shrinkable tube mainly composed of a melt-processable fluororesin, The fluororesin comprises at least a resin containing at least three monomers as constituent monomers: tetrafluoroethylene, hexafluoropropylene, and vinylidene fluoride. Let ε be the strain of the tube and σ (MPa) be the stress at that time. On a coordinate graph, the horizontal axis represents strain ε and the vertical axis represents stress σ. In the mechanical property curve of the tube obtained by the following measurement method, the stress σ at a strain ε of 1.0 is 3.2 MPa or greater. A tear-resistant heat-shrinkable tube, characterized in that, when the strain ε on the mechanical characteristic curve is 1.0, the coordinate point e is 2.4 to 3.0 MPa, and when the strain ε on the mechanical characteristic curve is 2.0, the coordinate point f is 2.4 to 3.0 MPa, and the slope of the line passing through coordinate points e and f is 2.4 to 3.0 MPa. (Measurement method) A tensile test is performed under the following conditions: ambient temperature of 60°C, initial chuck distance of 22 ± 0.05 mm, and tensile speed of 5 mm / sec.

10. The tear-resistant heat-shrinkable tube according to claim 9, wherein the resin, as constituent monomers, contains at least three monomers: tetrafluoroethylene, hexafluoropropylene, and vinylidene fluoride, in an amount of 25 wt% to 95 wt% relative to the total amount of fluororesin constituting the tube.

11. A tear-resistant heat-shrinkable tube according to claim 9 or 10, characterized in that it contains a plurality of fluororesins, and the difference in refractive index (ASTM D542) between the plurality of fluororesins is at most 0.05 or less.

12. A tear-resistant heat-shrinkable tube according to any one of claims 9 to 11, characterized in that it is used as a jig for manufacturing tubes for introducing medical devices, a jig for manufacturing catheters, or a protective tube for electronic components.

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