JP2012010846A - Medical tube - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a medical tube which is superior in operability such as forcibility into a body cavity, flexibility and followability in a body cavity, and kink resistance; has good mechanical strength; and can be suitably applied to various catheters, various balloon catheters, sheaths of introducers, and the like.SOLUTION: The medical tube is formed by using a polyamide elastomer wherein tensile rupture strength is 60 MPa or more and a tensile elastic modulus is 500 MPa or less when measured according to the JIS standard K-7113.

Description

  The present invention relates to a medical tube. More specifically, the present invention relates to a medical tube applied to various catheters such as a microcatheter, a guiding catheter, and an angiographic catheter, an introducer sheath, a pressure-resistant tube, a balloon catheter, and the like.

  As a medical tube excellent in operability that can be used for a catheter or the like, a tube formed by laminating a plurality of resin layers in addition to a tube made of a single layer resin is known. In general, when a catheter is inserted into a body cavity such as a blood vessel and curved along the body cavity, a catheter having a predetermined flexibility and strength is required.

  Furthermore, in a medical tube used for a catheter or the like, the outer diameter is made as small as possible in order to smoothly insert into a body cavity or tissue having a very small inner diameter such as a blood vessel, or a physiological saline or a drug. In order to enable smooth and quick injection and to improve the operability of the guide wire, it is required to secure a sufficient tube lumen. Even when the tube wall thickness is reduced to satisfy these requirements, high mechanical strength prevents the tube from being partially broken by external force when inserted into the body cavity or removed from the body. Is required.

In order to provide a medical tube that satisfies these requirements, various technical developments have heretofore been made. For example, a medical tube using a polymer material containing a reinforcing material is disclosed (Patent Document 1). More specifically, Patent Document 1 proposes a polymer material containing an inorganic crystal in order to control the tensile strength and elongation of the balloon catheter to ensure pressure resistance and dimensional stability.
However, in the medical tube, the insertion property into the body cavity as described above, the flexibility in the body cavity, and the mechanical strength are not always satisfactory.

As a means for inserting a catheter into a living body lumen, a blood vessel securing method called a Seldinger method using an introducer sheath which is an embodiment of a medical tube is known. In this method, a puncture needle such as an indwelling needle is percutaneously inserted into a living body lumen, and a guide wire is inserted into the inner tube of the puncture needle from the rear end. Next, the puncture needle is removed, and a sheath that is an elongated hollow tubular body of the introducer is inserted along the guide wire. As a result, the percutaneous insertion opening is expanded, and then the guide wire is removed, and then the catheter is inserted into the living body lumen through the sheath. The introducer sheath used in this method must not be kinked when inserted into the body lumen percutaneously or be flexible enough to be inserted according to the bending of the body lumen. Is done.
Conventional introducer sheaths are known to be made of materials such as nylon, polypropylene, fluororesin, and polyurethane. However, these conventional sheaths have a problem that they lack flexibility, tend to cause kinking, and are not sufficiently insertable, and the opening at the distal end of the sheath is widened during insertion to increase insertion resistance.

JP 2000-325464 A

  As described above, the conventionally known medical tube is bent along the guide wire passing through the lumen of the tube, the pushability that reliably transmits the operator's pushing force to the distal end of the tube. It is difficult to say that it has sufficient mechanical strength with sufficient guide wire followability (trackability) that goes through the inside of the blood vessel, kink resistance that does not cause bending of the tube even at the bent part or curved part of the blood vessel. The development of a medical tube that is totally satisfactory has been desired.

  In view of the above circumstances, the present invention is excellent in operability such as pushability into a body cavity, bendability / followability in the body cavity, kink resistance, etc., and also excellent in mechanical strength, various catheters, various balloons An object of the present invention is to provide a medical tube that can be suitably applied to a sheath of a catheter or an introducer.

  As a result of intensive studies, the present inventors have found that the above problem can be solved by the following configuration.

(1) A medical tube formed using a polyamide elastomer having a tensile strength at break of 60 MPa or more and a tensile modulus of elasticity of 500 MPa or less measured in accordance with JIS standard K-7113.
(2) The medical tube according to (1), wherein the polyamide elastomer has a weight average molecular weight of 45,000 or more.

(3) The medical tube according to (1) or (2), wherein the polyamide elastomer has a Shore hardness D of 80 or less.
(4) The medical tube according to any one of (1) to (3), wherein the polyamide elastomer has a melt viscosity at 230 ° C. of 1,500 Pa · s or more.
(5) A medical tube having a multilayer structure, wherein at least one layer is formed using the polyamide elastomer according to any one of (1) to (4).

  According to the present invention, it is excellent in operability such as pushability into a body cavity, bendability / followability in the body cavity, kink resistance and the like, and also excellent in mechanical strength, and various catheters, various balloon catheters or introducers. Therefore, it is possible to provide a medical tube that can be suitably applied to a sheath or the like.

It is a front view which shows one Example of the catheter with a balloon which is one Embodiment of the medical tube of this invention. It is an expanded sectional view of the balloon of the catheter with a balloon of FIG. 1, and its vicinity.

Below, the medical tube which concerns on this invention is explained in full detail.
The medical tube of the present invention is formed using a polyamide elastomer having a tensile breaking strength measured in accordance with JIS standard K-7113 of 60 MPa or more and a tensile elastic modulus of 500 MPa or less. The medical tube is excellent in mechanical strength and flexibility, and has operability and durability capable of quickly and surely inserting into a thin and complex blood vessel. The medical tube of the present invention has mechanical strength equivalent to that of a tube formed of polyamide, and overcomes the problem of flexibility, which is a drawback of the tube formed of polyamide.
In the following, first, the polyamide elastomer will be described in detail, and then the aspect of the medical tube will be described in detail.

<Polyamide elastomer>
(Various measured values)
The polyamide elastomer used in the present invention has a tensile strength at break of 60 MPa or more measured according to JIS standard K-7113. In particular, the tensile strength at break is preferably 62 MPa or more. Although an upper limit is not specifically limited, From the point of the operativity of a tube, 80 MPa or less is preferable and 73 MPa or less is more preferable. When the tensile strength at break is 60 MPa or more, practically sufficient operability can be obtained without breaking the tube when inserted into a thin and complex blood vessel. If the tensile strength at break is less than 60 MPa, part of the tube may break during operation.
The tensile strength at break is measured according to JIS standard K-7113. The test temperature is room temperature and the test speed is 50 mm / min.

The polyamide elastomer used in the present invention has a tensile modulus measured according to JIS standard K-7113 of 500 MPa or less. Among these, the tensile elastic modulus is preferably 400 MPa or less. Although a minimum in particular is not restrict | limited, From the point of the operativity of a tube, 200 Mpa or more is preferable. When the tensile elastic modulus is 500 MPa or less, practically sufficient operability can be obtained without breaking the tube when inserted into a thin and complex blood vessel. If the tensile elastic modulus exceeds 500 MPa, a part of the tube may be kinked during the operation, or the tube itself may not reach a target site such as in a blood vessel.
The tensile elastic modulus is measured according to JIS standard K-7113. The test temperature is room temperature and the test speed is 1 mm / min.

The polyamide elastomer used in the present invention preferably has a weight average molecular weight of 45,000 or more, and more preferably 48,000 or more. Moreover, it is preferable that it is 5,000,000 or less, and it is more preferable that it is 1,000,000 or less. If it is in the said range, it is preferable at the point of the moldability of a tube.
In addition, the measurement of a weight average molecular weight is made | formed by a well-known method (for example, GPC measuring apparatus).

The polyamide elastomer used in the present invention preferably has a Shore hardness D of 80 or less, and more preferably 75 or less. Moreover, it is preferable that it is 20 or more, and it is more preferable that it is 30 or more. If it is in the said range, it is preferable at the point of the softness | flexibility of a tube.
The Shore hardness D is measured according to JIS6253.

The polyamide elastomer used in the present invention preferably has a melt viscosity at 230 ° C. of 1,500 Pa · s or more, and more preferably 1,800 Pa · s or more. Further, it is preferably 30,000 Pa · s or less, more preferably 20,000 Pa · s or less. If it is in the said range, it is preferable at the point of the moldability of a tube.
The melt viscosity is measured by a flow characteristic evaluation apparatus (flow tester CFT-500D, manufactured by Shimadzu Corporation).

The polyamide elastomer used in the present invention preferably has a tensile strain of 300 to 600%, more preferably 350 to 600%. If it is in the said range, it is preferable at the point of the softness | flexibility of a tube.
The tensile strain is measured according to JIS standard K-7113. The test temperature is room temperature and the test speed is 50 mm / min.

(Construction)
As the polyamide elastomer used in the present invention, a block copolymer comprising a hard segment and a soft segment is preferably used, and preferably a hard segment comprising a polyamide and a soft segment comprising a polyether or polyester are used. Used block copolymers.
The proportion of the soft segment in the elastomer is preferably 5 to 95% by mass, more preferably 10 to 80% by mass, and still more preferably 10 to 40% by mass.

The polyamide constituting the hard segment is nylon 6 (PA6), nylon 66 (PA66), nylon 610 (PA610), nylon 11 (PA11), nylon 12 (PA12), nylon 69 (PA69), nylon 612 (PA612) Etc., but nylon 12 (PA12) is particularly preferable.
Polyethylene glycol, polypropylene glycol, polytetramethylene glycol and the like can be used as the polyether constituting the soft segment, and polytetramethylene glycol is particularly preferable.
As the polyester constituting the soft segment, poly (ethylene adipate) glycol, poly (butylene-1,4-adipate) glycol and the like can be used, and poly (ethylene adipate) glycol is particularly preferable.

The polyamide elastomer used in the present invention may be a commercially available product or may be synthesized by a known synthesis method.
In the case of synthesis, for example, a method of copolymerizing (for example, melt polymerization) a polyamide oligomer and a polyether oligomer or a polyester oligomer can be mentioned.
In addition, as a monomer which forms a polyamide oligomer, for example, an aminocarboxylic acid compound (for example, 6-aminocaproic acid, 12-aminododecanoic acid, etc.), a lactam compound (for example, ω-caprolactam, enantolactam, etc.), a diamine compound ( For example, ethylenediamine, hexamethylenediamine and the like), aliphatic, alicyclic or aromatic dicarboxylic acid compounds (for example, adipic acid, terephthalic acid and the like) and the like.
Examples of the polyether oligomer include polyoxyethylene glycol, polyoxypropylene glycol, polyoxytetramethylene glycol and the like.
As a monomer which forms a polyester oligomer, a diol compound (for example, ethylene glycol, 1, 6-hexanediol etc.), a dicarboxylic acid compound, etc. are mentioned, for example.

Among them, a polyamide elastomer obtained by polymerizing (preferably, melt polymerization) a polyamide elastomer that is not sealed at both ends is preferable in that the tensile strength at break is improved without increasing the tensile modulus. . The polyamide elastomer whose both ends are not sealed is intended to be a polymer having amino groups, hydroxyl groups, or carboxyl groups at both ends.
The optimum conditions for the melt polymerization are appropriately selected according to the physical properties of the starting material. Among them, polymerization temperature: 160 to 400 ° C. (preferably 170 to 300 ° C.), polymerization time: 12 to 200 hours (preferably 15). To 100 hours), pressure: 0.001 to 10 MPa (preferably 0.01 to 1 MPa). If it is in the said range, the polyamide elastomer which shows the characteristic mentioned above can be synthesize | combined efficiently.
Further, the weight average molecular weight of the polyamide elastomer used in which both ends are not sealed is preferably 10,000 to 50,000, more preferably 15,000 to 40,000. If it is the said range, it is preferable at the point that the polyamide elastomer which shows more suitable mechanical characteristics (especially tensile breaking strength) is obtained.
Furthermore, the Shore hardness D of the polyamide elastomer whose both ends are not sealed is preferably 20 to 80, and more preferably 30 to 75. If it is the said range, it is preferable at the point that the polyamide elastomer which shows more suitable mechanical characteristics (especially tensile breaking strength) is obtained.

<Medical tube>
The medical tube of the present invention is composed of the polyamide elastomer described above, and the manufacturing method thereof is not particularly limited. For example, depending on the type and application of the target molded product, the usual molding method such as extrusion molding method, injection molding method, calendar molding method, press molding method, inflation molding method and the molding conditions associated therewith should be adopted. Can do.

In the present invention, the medical tube refers to a tube having a circular cut surface.
When the medical tube of the present invention is used for an outer tube shaft of a balloon catheter, for example, the outer diameter is preferably 0.5 to 1.5 mm, more preferably 0.7 to 1.2 mm. preferable. Moreover, it is preferable that the thickness of a tube wall is 10-200 micrometers, and it is more preferable that it is 20-100 micrometers. Moreover, it is preferable that it is 100-2,500 mm in length, and it is more preferable that it is 250-2,000 mm.
In addition, when the medical tube of the present invention is used, for example, as an inner tube shaft of a balloon catheter, the outer diameter is preferably 0.2 to 0.9 mm, and preferably 0.3 to 0.7 mm. Is more preferable. Moreover, it is preferable that the thickness of a tube wall is 10-250 micrometers, and it is more preferable that it is 20-100 micrometers. Moreover, it is preferable that it is 100-2,500 mm in length, and it is more preferable that it is 250-2,000 mm.
Moreover, when using the medical tube of this invention for a guiding catheter, for example, it is preferable that the outer diameter is 1.0-3.5 mm, and it is more preferable that it is 1.5-3.0 mm. . Moreover, it is preferable that the thickness of a tube wall is 10-250 micrometers, and it is more preferable that it is 20-100 micrometers. Further, the length is preferably 500 to 1,300 mm, more preferably 800 to 1,000 mm.
Moreover, when using the medical tube of this invention for a microcatheter, for example, it is preferable that the outer diameter is 0.3-1.5 mm, and it is more preferable that it is 0.5-1.0 mm. Moreover, it is preferable that the thickness of a tube wall is 10-250 micrometers, and it is more preferable that it is 20-100 micrometers. The length is preferably 500 to 2,000 mm, and more preferably 800 to 1,500 mm.
Moreover, when using the medical tube of this invention for the sheath of an introducer, for example, it is preferable that the outer diameter is 1.0-4.0 mm, and it is more preferable that it is 2.0-3.0 mm. preferable. Moreover, it is preferable that the thickness of a tube wall is 10-250 micrometers, and it is more preferable that it is 20-100 micrometers. Moreover, it is preferable that length is 50-300 mm, and it is more preferable that it is 100-150 mm.

The medical tube of the present invention may be a single-layer tube formed from a polyamide elastomer, or may be a multilayer tube in which a polyamide elastomer layer and another resin layer are laminated. That is, it may be a medical tube (medical multilayer tube) having a multilayer structure in which at least one layer is made of the polyamide elastomer.
In addition, as other resin, polyamide, polyester, polyolefin, polyolefin elastomer, polyurethane, polyurethane elastomer, etc. are used, for example.

  For the medical tube of the present invention, in addition to the polyamide elastomer which is an essential component, for example, a filler, a bulking agent, a softening agent (plasticizer), a surface active agent may be used as long as the achievement of the object of the present invention is not hindered. Additives such as additives, coupling agents, antioxidants (anti-aging agents), heat stabilizers, light stabilizers, UV absorbers, colorants, lubricants, antistatic agents, flame retardants, X-ray contrast agents May be.

  The medical tube of the present invention includes, for example, various catheters such as a microcatheter, a guiding catheter, an angiographic catheter, an ultrasonic catheter, an indwelling catheter, and an endoscopic catheter, various balloon catheters such as PTCA and PTA, intro It can be applied to a sheath of a reducer.

A balloon catheter using the medical tube of the present invention is shown in FIG. FIG. 2 is an enlarged cross-sectional view of the balloon 3 of the balloon-equipped catheter 1 shown in FIG. 1 and the vicinity thereof.
In FIG. 1, a catheter 1 with a balloon includes a shaft main body 2 and a balloon (expansion body) 3 disposed at the tip (distal end) of the shaft main body 2. The balloon catheter 1 shown in FIG. 1 is of an over-the-wire type in which a guide wire lumen 210 is opened by a hub 4 fixed to a proximal end portion of a shaft body 2.
As shown in FIG. 2, the shaft main body 2 is a concentric double tube of a guide wire guiding tubular member (hereinafter referred to as an inner tube shaft) 21 and a balloon expanding tubular member (hereinafter referred to as an outer tube shaft) 22. The tip of the outer tube shaft 22 is located slightly on the rear end side from the tip of the inner tube shaft 21. A balloon expansion lumen 220 is formed between the inner periphery of the outer tube shaft 22 and the outer periphery 21 b of the inner tube shaft 21.

The balloon 3 can be folded and expanded by a change in internal pressure, and is expanded to a cylindrical shape (preferably a cylindrical shape) having substantially the same diameter by a fluid injected into the balloon 3, and on the proximal end side of the cylindrical portion 30. A proximal reduced diameter portion 32 provided via a gradually decreasing diameter portion 31 that smoothly reduces the diameter, and a distal reduced diameter portion 34 provided via a gradually decreasing diameter portion 33 that smoothly reduces the diameter on the distal end side of the body portion 30. Have. The body portion 30 at the time of expansion may not be a complete cylinder, but may be a polygonal column shape. When the balloon 3 is not expanded (not shown), the balloon 3 can be folded on the outer periphery of the inner tube shaft 21.
The balloon 3 at the time of expansion forms an expansion space 300 between the outer periphery 21 b of the inner tube shaft 21. The base end portion side of the expansion space 300 communicates with the balloon expansion lumen 220 of the outer tube shaft 22 on the entire circumference thereof. Since the expansion lumen 220 has a relatively large volume, the balloon 3 (expansion space 300 ) The expansion fluid is surely injected into the inside.

The distal diameter reducing portion 34 is fixed to the outer periphery 21b of the inner tube shaft 21, and the proximal end diameter reducing portion 32 is fixed to the distal end 221 of the outer tube shaft 22 in a liquid-tight manner by an adhesive or heat fusion.
The medical tube of the present invention can be suitably used for the inner tube shaft 21 or the outer tube shaft 22 described above.

Hereinafter, although it demonstrates in detail using an Example, this invention is not limited to these Examples.
In addition, the weight average molecular weight in each Example and a comparative example was measured using the following measuring devices.
Equipment name = pump; Shodex DS-4 (Showa Denko), column; Shodex GPC HFIP-806M × 2 + HFIP-803 × 1 (Showa Denko), detector; Shodex RI-71 (Showa Denko)
Elution solvent = hexafluoroisopropanol + sodium trifluoroacetate 5 mmol / L
Column temperature = 40 ° C
Concentration = 0.1 w / v%
Flow rate = 1 ml / min
Injection volume = 100 μL
Standard polymethyl methacrylate / dimethyl terephthalate conversion

Example 1
Polyamide elastomer (GS amide ELG6260, Shore hardness D62, hard segment: nylon 12, soft segment: polytetramethylene glycol, soft segment content in elastomer: 13 wt%. Both ends of the elastomer are sealed. A polyamide elastomer (weight average molecular weight 76,000, shore hardness D62, melt viscosity at 230 ° C. of 7,600 ° C.) obtained by melt polymerization (polymerization temperature: 250 ° C., polymerization time: 24 hours, pressure: 0.1 MPa). 700 Pa · s) was hot-pressed to obtain a sheet.

(Example 2)
Polyamide elastomer (weight average molecular weight: 73,000, Shore) obtained by melt polymerization (polymerization temperature: 260 ° C., polymerization time: 24 hours, pressure: 0.1 MPa) of polyamide elastomer (GS amide ELG6260, Shore hardness D62 manufactured by EMS) A sheet having a hardness of D62 and a melt viscosity of 5,800 Pa · s at 230 ° C. was obtained by hot pressing.

(Example 3)
Polyamide elastomer (weight average molecular weight 121,000, Shore) obtained by melt polymerization (polymerization temperature: 250 ° C., polymerization time: 72 hours, pressure: 0.1 MPa) of polyamide elastomer (Grillamide ELG6260 manufactured by EMS, Shore hardness D62) A sheet having a hardness of D62 and a melt viscosity of 17,000 Pa · s at 230 ° C. was obtained by hot pressing.

Example 4
Polyamide elastomer (GS amide ELG5660 manufactured by EMS, Shore hardness D62, hard segment: nylon 12, soft segment: polytetramethylene glycol, soft segment content in the elastomer: 27 wt%. Both ends of the elastomer are sealed. A polyamide elastomer (weight average molecular weight 48,000, shore hardness D56, melt viscosity at 230 ° C. of 1), obtained by melt polymerization (polymerization temperature: 250 ° C., polymerization time: 24 hours, pressure: 0.1 MPa). 950 Pa · s) was hot pressed to obtain a sheet.

(Comparative Example 1)
Polyamide elastomer (Grillamide ELG6260 manufactured by EMS, Shore hardness D62) was hot-pressed to obtain a sheet.

(Comparative Example 2)
Polyamide elastomer (Grillamide ELG5660 manufactured by EMS, Shore hardness D56) was hot-pressed to obtain a sheet.

(Comparative Example 3)
A polyamide elastomer (PEBAX 6333 manufactured by Arkema, Shore hardness D63) was hot-pressed to obtain a sheet.

(Comparative Example 4)
A polyamide (Grillamide L25 manufactured by EMS, Shore hardness D70) was hot-pressed to obtain a sheet.

<Experiment 1>
Using the sheets of Examples 1 to 4 and Comparative Examples 1 to 4 as test pieces, the tensile rupture strength, tensile elastic modulus, and tensile strain were measured by a method based on JIS-K7113. The results are shown in Table 1.

As shown in Table 1, in Examples 1 to 4 of the present invention, the tensile breaking strength is as high as 62 MPa or more, the tensile elastic modulus is 500 MPa or less, and it has sufficient flexibility and strength. Was confirmed.
In contrast, in Comparative Examples 1 to 3, the tensile strength at break was as low as 49 to 59 MPa, and the strength as a medical tube was poor. In Comparative Example 4, the tensile strength at break was about 70 MPa, which was 60 MPa or more, but the tensile elastic modulus was as high as 770 MPa, which was not sufficiently flexible.

<Experiment 2>
Next, the lesion part passage property when formed as a medical tube was evaluated.
(Example 5)
Using the polyamide elastomer (weight average molecular weight 76,000, Shore hardness D62) obtained by the melt polymerization of Example 1, 5 Fr. A medical tube (inner diameter: 0.99 mm, outer diameter: 1.7 mm, length: 1,000 mm) was molded. Next, when this medical tube was used to evaluate the reach to the pseudo meandering blood vessel with a commercially available bending model (PTCA trainer & technical guide; Medical Sense Publishing), it reached R10, and the pushability / flexibility / Followability and kink resistance were good.
Moreover, using the polyamide elastomers obtained in Examples 2 to 4, a medical tube having the same size as that of Example 5 was molded and subjected to the same test. As a result, the same degree as in Example 5 (R10). Test results were obtained.

(Comparative Example 5)
Using the polyamide elastomer of Comparative Example 1 (Shore hardness D62), 5 Fr. A medical tube (inner diameter: 0.99 mm, outer diameter: 1.7 mm, length: 1,000 mm) was molded. Next, using this medical tube, the depth reachability to the pseudo meandering blood vessel was evaluated with the above bending model, but it reached only R15, and the pushability / flexibility / trackability / kink resistance were examples. It was not as good as 5.
Moreover, using the polyamide elastomer obtained in Comparative Examples 2 to 3, a medical tube having the same size as that of Comparative Example 5 was molded and subjected to the same test. As a result, the same level as in Comparative Example 5 (R15). Test results were obtained.

(Comparative Example 6)
Using the polyamide of Comparative Example 4 (Shore hardness D70), 5 Fr. A medical tube (inner diameter: 0.99 mm, outer diameter: 1.7 mm, length: 1,000 mm) was molded. Next, using this medical tube, the depth reachability to the pseudo meandering blood vessel was evaluated by the above bending model, and it reached only the middle point between R20 and R25, and it had pushability / flexibility / trackability / resistance. The kink property was not as good as Example 5.

DESCRIPTION OF SYMBOLS 1 Catheter with a balloon 2 Shaft main-body part 3 Balloon 4 Hub 21 Inner tube shaft 21b Outer periphery 210 Guide wire lumen 22 Outer tube shaft 220 Balloon expansion lumen 30 Body 31 Decrease diameter part 32 Base end diameter reduction part 33 Decrease diameter part 34 Tip Reduced diameter part 300 Expansion space

Claims (5)

  A medical tube formed using a polyamide elastomer having a tensile strength at break of 60 MPa or more and a tensile modulus of elasticity of 500 MPa or less measured according to JIS standard K-7113.   The medical tube according to claim 1, wherein the weight average molecular weight of the polyamide elastomer is 45,000 or more.   The medical tube according to claim 1 or 2, wherein the polyamide elastomer has a Shore hardness D of 80 or less.   The medical tube according to any one of claims 1 to 3, wherein the polyamide elastomer has a melt viscosity at 230 ° C of 1,500 Pa · s or more. A medical tube having a multilayer structure, wherein at least one layer is formed using the polyamide elastomer according to any one of claims 1 to 4.