Balloon for balloon catheter and method of manufacturing balloon catheter

Abstract

Provided is a balloon for a balloon catheter, wherein by allowing tearing to occur in the longitudinal axis direction in a center section of the balloon, tearing in the circumferential direction can be suppressed, and by confining the tearing in the longitudinal axis direction to within a straight tube part, the tearing in the longitudinal axis direction can be prevented from spreading to a proximal end side or a distal end side of the balloon and forming an L-shaped tear.　A balloon (2) for a balloon catheter, wherein the main orientation direction of the molecular orientation in a proximal-side section (23a) and a distal-side section (23e) of a straight tube part (23) is the circumferential direction z, and the longitudinal axis direction x component among the molecular orientation components in a center section (23c) of the straight tube part (23) is greater than the longitudinal axis direction x components of the molecular orientation in the proximal-side section (23a) and the distal-side section (23e) of the straight tube part (23).

Description

[Technical Field]

[0001] The present invention relates to a balloon for a balloon catheter and a method for manufacturing a balloon catheter. [Background technology]

[0002] Angioplasty, a minimally invasive treatment in which a balloon catheter is inserted into a narrowed portion of a blood vessel and the balloon is inflated to expand the blood vessel and ensure blood flow, is widely used. Angioplasty is used, for example, to treat diseases such as myocardial infarction caused by narrowing of the coronary arteries of the heart, and to treat stenosis occurring in shunts for dialysis. The balloon of a balloon catheter typically has a cylindrical shape with tapered distal and proximal ends, and has a cylindrical straight tube portion, a proximal tapered portion located proximal to the straight tube portion, and a distal tapered portion located distal to the straight tube portion.

[0003] Normally, when dilating a stenotic area using a balloon catheter, the balloon is inflated with an inflation pressure appropriate to the target area, but if the internal pressure of the balloon becomes excessive due to unexpected internal pressure being applied to the balloon during the procedure, the balloon may break. If the balloon breaks circumferentially in this case, there is a serious risk that fragments of the balloon distal to the breakage will remain in the body. Therefore, even if the balloon breaks, a technology is needed to ensure that the balloon breaks longitudinally rather than circumferentially.

[0004] For example, Patent Documents 1 to 3 propose balloons that have pressure resistance and aim to suppress circumferential destruction. Patent Document 1 discloses a balloon in which the difference in the proportion of polymer chains oriented in the circumferential direction in the expansion function portion is equal to or less than a predetermined value, Patent Document 2 discloses a balloon in which the ratio of the orientation distribution number calculated by dividing the circumferential orientation distribution number of the tubular portion by the axial orientation distribution number is less than a predetermined value, and Patent Document 3 discloses a balloon in which the molecular orientation of the balloon material itself is aligned in the axial direction, making it less likely to shatter or burst due to axial cracks. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Laid-Open No. 2004-298354 [Patent Document 2] International Publication No. 2014 / 141382 [Patent Document 3] Japanese Patent Application Laid-Open No. 2008-553 Summary of the Invention [Problem to be solved by the invention]

[0006] However, while the above balloons attempt to suppress circumferential fractures and improve pressure resistance by controlling the molecular orientation of the balloon, they have not been able to suppress circumferential fractures by controlling the location of longitudinal fractures when the balloon is fractured. Furthermore, if a longitudinal fracture occurs, it may extend to the relatively thick proximal or distal end of the balloon, forming an L-shaped fracture that becomes a circumferential fracture at the proximal or distal end. This creates a risk of the balloon rupturing at the L-shaped circumferential fracture, with fragments remaining in the body. Conventional balloons have not been sufficient to prevent such L-shaped fractures.

[0007] In view of the above circumstances, an object of the present invention is to provide a balloon for a balloon catheter that can suppress circumferential cracks by causing longitudinal cracks in the central portion of the balloon even in the event of balloon rupture. Another object of the present invention is to provide a balloon for a balloon catheter that can prevent longitudinal cracks from extending to the proximal or distal end of the balloon and forming L-shaped cracks at the end, by confining longitudinal cracks within the straight tube portion. [Means for solving the problem]

[0008] One embodiment of a balloon for a balloon catheter of the present invention that solves the above-mentioned problems is a balloon formed of a resin with molecular orientation, which has a longitudinal axis direction and a circumferential direction that follows the outer periphery of the balloon in an expanded state in a cross section perpendicular to the longitudinal axis direction. The balloon has a straight tubular section, a proximal tapered section located proximal to the straight tubular section, and a distal tapered section located distal to the straight tubular section. When the proximal end of the straight tubular section is defined as the 0% position and the distal end as the 100% position in the longitudinal axis direction, the main orientation direction of the molecular orientation in the proximal section from the 0% position to the 10% position and the distal section from the 90% position to the 100% position is the circumferential direction, and the longitudinal axis component of the molecular orientation in the central section from the 40% position to the 60% position is greater than the longitudinal axis component of the molecular orientation in the proximal section and the distal section. In this way, because the longitudinal component of the molecular orientation in the central section is greater than the longitudinal component of the molecular orientation in the proximal and distal sections, even if the balloon is destroyed by overpressure, a longitudinal crack can be initiated in the central section, and the longitudinal crack that occurs in the central section allows the internal pressure to be released, preventing circumferential cracks. Furthermore, if a longitudinal crack that occurs in the central section continues longitudinally beyond the proximal and distal sections with sufficient force, it may form an L-shaped crack that becomes a circumferential crack in the relatively thick proximal and distal tapered sections. However, in the balloon for a balloon catheter of the present invention, because the primary molecular orientation direction in the proximal and distal sections is the circumferential direction, even if a longitudinal crack that occurs in the central section reaches the proximal and distal sections, it is possible to prevent the crack from rapidly spreading beyond the proximal and distal sections to the proximal and distal tapered sections. This prevents the longitudinal crack from being contained within the straight tube section and prevents the proximal and distal tapered sections from forming L-shaped cracks that would otherwise form circumferential cracks. As a result, it is possible to avoid the risk of balloon fragments remaining in the body due to circumferential or L-shaped cracks.

[0009] In the balloon for a balloon catheter, the main orientation direction of the molecules in the central section is preferably the longitudinal axis direction.

[0010] In the balloon for a balloon catheter, it is preferable that the longitudinal axis component of the molecular orientation gradually decreases from the central section toward the 0% position and gradually decreases from the central section toward the 100% position.

[0011] In the balloon for a balloon catheter, when the main molecular orientation direction in the central section is the longitudinal axis direction, the section from the 10% position to the 40% position is defined as the proximal intermediate section, and the section from the 60% position to the 90% position is defined as the distal intermediate section, it is preferable that the main molecular orientation direction changes from the longitudinal axis direction to the circumferential direction in the proximal intermediate section and the distal intermediate section.

[0012] In the balloon for a balloon catheter, the thickness of the balloon in the central section is preferably thinner than the thickness of the balloon in the proximal section and the distal section.

[0013] The present invention also provides a balloon catheter including the above-described balloon for a balloon catheter.

[0014] The present invention also provides a method for manufacturing the balloon catheter. One embodiment of the method for manufacturing a balloon catheter of the present invention, which has achieved the above object, includes the steps of: preparing a parison made of a resin; preparing a mold having an inner lumen, the inner wall surface of the lumen having a straight tube section, a proximal tapered section located proximal to the straight tube section, and a distal tapered section located distal to the straight tube section; placing the parison in the mold; a first stretching step in which, while heating the mold, the parison is stretched in the longitudinal direction until it exceeds the necking region of a stress-strain curve; and a second stretching step in which, while heating the mold, the parison stretched beyond the necking region after the first stretching step is further stretched in the longitudinal direction under a condition in which the internal pressure of the parison is higher than that of the first stretching step. For many resins, in the stress-strain curve shown in Figure 1, stress acts to stretch bent molecular chains in the elastic deformation region up to the yield point B. After the yield point B, the molecular chains that were attracted to each other by intermolecular forces begin to shift in the shear direction, causing plastic deformation. Once the molecular chains begin to shift, some resins exhibit a phenomenon in which the molecular chains become loose and the stress decreases to the lower yield point L. After that, a region showing a flat stress is observed for a while, and this region is usually called the necking region R. n This is called the necking region R n In the necking region R, the molecular chains are displaced by strain, resulting in a certain stress. However, when the strain exceeds a certain level, the molecular chains approach each other and become densely oriented, generating a strong intermolecular force between the molecular chains. n In the region beyond this, the stress increases steadily. n The parison is first stretched in the longitudinal direction until it exceeds the necking region R n By further stretching the parison in the longitudinal direction under high internal pressure, which has been stretched to exceed this, it is possible to manufacture a balloon catheter having a balloon for a balloon catheter in which the main orientation direction of the molecules in the proximal section and the distal section is the circumferential direction, and the longitudinal component of the molecular orientation in the central section is greater than the longitudinal component of the molecular orientation in the proximal section and the distal section.

[0015] In the above-mentioned production method, it is preferable that in the first stretching step, the parison is pressurized at a pressure lower than that in the second stretching step, and that in the second stretching step, the parison is further pressurized after passing through the necking region.

[0016] The above manufacturing method preferably includes a step of heating the mold so that the temperature is highest in the center of the straight tube portion of the mold. [Effects of the Invention]

[0017] According to the balloon for a balloon catheter and the method for manufacturing a balloon catheter, even if the balloon were to rupture, longitudinal cracks would occur in the center of the balloon, thereby suppressing circumferential cracks. Furthermore, by confining longitudinal cracks to the straight tube portion, longitudinal cracks would not extend to the proximal or distal ends of the balloon, forming L-shaped cracks that would otherwise form circumferential cracks at the ends. Therefore, even if the balloon were to rupture due to overpressurization or other reasons, it is possible to avoid the risk of balloon fragments remaining in the body due to circumferential or L-shaped cracks. [Brief explanation of the drawings]

[0018] [Figure 1] 1 shows a stress-strain curve of polyester resin. [Figure 2] 1 is a side view of a balloon catheter according to an embodiment of the present invention. [Figure 3] 1 shows a plan view of a balloon according to one embodiment of the present invention when a longitudinal crack occurs. [Figure 4] 10 is a plan view showing an example of a balloon having a circumferential crack. [Figure 5] 1 is a plan view showing an example of an L-shaped crack occurring in a balloon. [Figure 6] 10 is a plan view showing another example of an L-shaped crack occurring in a balloon. [Figure 7] 1A and 1B are diagrams illustrating a method for producing a sample for measuring the molecular orientation of a straight tube portion of a balloon according to an embodiment of the present invention. [Figure 8] 1 shows a contour diagram obtained by measuring a balloon according to one embodiment of the present invention using a two-dimensional birefringence evaluation system. [Figure 9] 1 shows a graph of the phase difference obtained by measuring a balloon according to one embodiment of the present invention using a two-dimensional birefringence evaluation system. [Figure 10] 1 shows a graph of axial orientation obtained by measuring a balloon according to one embodiment of the present invention using a two-dimensional birefringence evaluation system. [Figure 11] 1 is a cross-sectional view showing a parison placed in a mold according to an embodiment of the present invention; [Figure 12] FIG. 2 is a cross-sectional view showing a state in a first stretching step according to one embodiment of the present invention. [Figure 13] FIG. 3 is a cross-sectional view showing a state during a second stretching step according to one embodiment of the present invention. [Figure 14] FIG. 2 is a cross-sectional view showing a state after the second stretching step according to one embodiment of the present invention is completed. [Figure 15] FIG. 1 is a contour diagram of the balloon obtained in Example 1. [Figure 16] 1 is a graph showing the phase difference of the balloon obtained in Example 1. [Figure 17] 1 is a graph of the axial orientation of the balloon obtained in Example 1. [Figure 18] 1 is a graph showing the membrane thickness of the balloon obtained in Example 1. [Figure 19] FIG. 1 is a contour diagram of the balloon obtained in Comparative Example 1. [Figure 20] 1 is a graph showing the phase difference of the balloon obtained in Comparative Example 1. [Figure 21] 1 is a graph of the axial orientation of the balloon obtained in Comparative Example 1. [Figure 22] 1 is a graph showing the membrane thickness of the balloon obtained in Comparative Example 1. DETAILED DESCRIPTION OF THE INVENTION

[0019] The present invention will be described in detail below based on the embodiments, but the present invention is not limited to the following embodiments and can be implemented with appropriate modifications within the scope of the above and below-described purpose, and all such modifications are included within the technical scope of the present invention. For convenience, hatching and component symbols may be omitted in the drawings. In such cases, reference should be made to the specification and other drawings. The dimensions of various components in the drawings may differ from actual dimensions, as priority is given to helping understand the features of the present invention.

[0020] 1. Balloon for balloon catheter The balloon for a balloon catheter according to an embodiment of the present invention is formed of a resin having molecular orientation, and has a longitudinal axis direction and a circumferential direction along the outer periphery of the balloon in an expanded state in a cross section perpendicular to the longitudinal axis direction. The balloon has a straight tube section, a proximal tapered section located proximal to the straight tube section, and a distal tapered section located distal to the straight tube section. When the proximal end of the straight tube section is defined as the 0% position and the distal end as the 100% position in the longitudinal axis direction, the main orientation direction of the molecular orientation in the proximal section from the 0% position to the 10% position and the distal section from the 90% position to the 100% position is the circumferential direction, and the longitudinal axis component of the molecular orientation in the central section from the 40% position to the 60% position is greater than the longitudinal axis component of the molecular orientation in the proximal section and the distal section. In this way, because the longitudinal component of the molecular orientation in the central section is greater than the longitudinal component of the molecular orientation in the proximal and distal sections, even if the balloon is destroyed by overpressure, a longitudinal crack can be initiated in the central section, and the longitudinal crack that occurs in the central section allows the internal pressure to be released, preventing circumferential cracks. Furthermore, if a longitudinal crack that occurs in the central section continues longitudinally beyond the proximal and distal sections with sufficient force, it may form an L-shaped crack that becomes a circumferential crack in the relatively thick proximal and distal tapered sections. However, in the balloon for balloon catheter according to the embodiment of the present invention, the molecular orientation in the proximal section and the molecular orientation in the distal section are primarily circumferential. This prevents a longitudinal crack that occurs in the central section from rapidly extending beyond the proximal and distal sections to the gold-side tapered section and the distal tapered section, even if the longitudinal crack reaches the proximal and distal sections. This prevents the longitudinal crack from forming within the straight tube section, preventing the proximal and distal tapered sections from forming L-shaped cracks that would otherwise form circumferential cracks. As a result, it is possible to avoid the risk of balloon fragments remaining in the body due to circumferential or L-shaped cracks. In this specification, a balloon for balloon catheter may also be referred to simply as a "balloon."

[0021] A balloon for a balloon catheter will be described with reference to Figures 2 to 6. Figure 2 is a side view of a balloon catheter according to one embodiment of the present invention. Figure 3 is a plan view of a balloon according to one embodiment of the present invention when a longitudinal crack has occurred, Figure 4 is a plan view showing an example of a balloon when a circumferential crack has occurred, Figure 5 is a plan view showing an example of a balloon when an L-shaped crack has occurred, and Figure 6 is a plan view showing another example of a balloon when an L-shaped crack has occurred.

[0022] In the present invention, the proximal side refers to the direction toward the user or surgeon in the direction of extension of the balloon catheter 1 or the longitudinal axis direction x of the shaft 3, and the distal side refers to the opposite direction from the proximal side, i.e., the direction toward the patient. Components other than elongated members such as the shaft 3 also have the same longitudinal axis direction x as the shaft 3. The direction connecting the center of the balloon 2 and a point on the circumscribed circle of the balloon 2 in the expanded state in a cross section perpendicular to the longitudinal axis direction x is referred to as the radial direction y, and the direction along the outer periphery of the balloon 2 in the expanded state in a cross section perpendicular to the longitudinal axis direction x, i.e., in the radial direction y cross section, is referred to as the circumferential direction z.

[0023] As shown in Figure 2, the balloon catheter 1 has a shaft 3 and a balloon 2 provided on the distal side of the shaft 3. The balloon 2 has a longitudinal axis direction x, a radial direction y, and a circumferential direction z, and is preferably formed in a cylindrical shape with openings on the proximal and distal sides. The balloon 2 is formed from a resin with molecular orientation.

[0024] The balloon catheter 1 is configured so that a fluid is supplied to the inside of the balloon 2 through the shaft 3, and an indeflator (a balloon pressurizer / depressurizer) can be used to control the expansion and contraction of the balloon 2. The fluid may be pressurized fluid pressurized by a pump or the like.

[0025] The balloon 2 has a straight tube section 23, a proximal tapered section 22 located proximal to the straight tube section 23, and a distal tapered section 24 located distal to the straight tube section 23. The straight tube section 23 preferably has approximately the same diameter in the longitudinal axis direction x, and the proximal tapered section 22 and the distal tapered section 24 are preferably formed so that their diameters decrease with increasing distance from the straight tube section 23. Because the straight tube section 23 has the largest diameter, when the balloon 2 is expanded at a lesion such as a stenosis, the straight tube section 23 can sufficiently contact the lesion, facilitating treatment such as dilation of the lesion. Furthermore, because the proximal tapered section 22 and the distal tapered section 24 have reduced diameters, the outer diameters of the proximal and distal ends of the balloon 2 can be reduced when the balloon 2 is deflated, thereby reducing the step between the shaft 3 and the balloon 2, thereby facilitating insertion of the balloon 2 into a body cavity.

[0026] The balloon 2 may have a proximal sleeve portion 21 and a distal sleeve portion 25 located proximally of the proximal tapered portion 22 and distally of the distal tapered portion 24, respectively. At least a portion of the proximal sleeve portion 21 and the distal sleeve portion 25 may be configured to be fixed to the shaft 3.

[0027] In the longitudinal axis direction x, the proximal end of the straight pipe portion 23 is the 0% position D0, and the distal end is the 100% position D 100 When the value is 0%, the value is D0. The value is 10%. 10 The molecular orientation in the proximal section 23a up to the 90% position D 90 From 100% position D 100 The main orientation direction of the molecules in the distal section 23e up to the 40% position D 40 Position D: 60% from the center 60 The component of molecular orientation in the longitudinal axis direction x in the central section 23c up to 23e is greater than the component of molecular orientation in the longitudinal axis direction x in the proximal section 23a and the distal section 23e.

[0028] Because the longitudinal component of the molecular orientation in the central section 23c is greater than the longitudinal component of the molecular orientation in the proximal section 23a and the distal section 23e, even if the balloon 2 is destroyed by excessive pressure, a crack in the longitudinal direction x can be initiated in the central section 23c. As a result, as shown in Fig. 3, a crack in the longitudinal direction x in the central section 23c can be generated, allowing the internal pressure to be released, preventing a circumferential crack in the z direction as shown in Fig. 4 or a crack in the longitudinal direction x generated at an end as shown in Fig. 5 from reaching the tapered portion and forming an L-shaped crack.

[0029] Furthermore, if a crack occurring in the central section 23c in the longitudinal direction x passes beyond the proximal section 23a and the distal section 23e and travels vigorously in the longitudinal direction x, it may cause cracks in the circumferential direction z in the proximal tapered section 22 and the distal tapered section 24, potentially forming L-shaped cracks as shown in Fig. 6. However, because the main orientation direction of the molecules in the proximal section 23a and the distal section 23e is the circumferential direction z, even if a crack occurring in the longitudinal direction x in the central section 23c reaches the proximal section 23a and the distal section 23e, it can be prevented from extending beyond the proximal section 23a and the distal section 23e to the proximal tapered section 22 and the distal tapered section 24. This allows cracks in the longitudinal direction x to be contained within the straight pipe section 23, preventing the formation of L-shaped cracks, which are circumferential cracks, in the proximal tapered section 22 and the distal tapered section 24, which are relatively thick.

[0030] A method for measuring the molecular orientation of the straight tube portion 23 will be described with reference to Figures 7 to 10. Figure 7 is a diagram illustrating a method for preparing a sample for measuring the molecular orientation of the straight tube portion 23 of a balloon 2 according to one embodiment of the present invention. Figure 8 shows an example of a contour diagram obtained by measuring a balloon according to one embodiment of the present invention using a two-dimensional birefringence evaluation system manufactured by Photonic Lattice, and Figures 9 and 10 show an example of a graph of phase difference and an example of a graph of axial orientation obtained as a result of line analysis in the longitudinal axis direction.

[0031] The molecular orientation of the straight tube portion 23 can be measured using a two-dimensional birefringence evaluation system manufactured by Photonic Lattice, Inc., by cutting a rectangular sample of the straight tube portion 23. As shown in Figure 7, the rectangular sample is obtained by cutting off the proximal tapered portion 22 and the distal tapered portion 24 from the balloon 2 along a first cutting line S1, and then cutting open the resulting straight tube portion 23 along a second cutting line S2 in the longitudinal axis direction x.

[0032] An example of a contour diagram obtained as a result of the measurement is shown in Fig. 8, and examples of a graph of the phase difference and graph of the axial direction obtained as a result of line analysis in the longitudinal axis direction x are shown in Figs. 9 and 10, respectively. In each figure, the left end is the position D0 at 0% of the straight pipe section 23, and the right end is the position D0 at 100% of the straight pipe section 23. 100 The contour diagram shows the magnitude of the phase difference with color contrast, allowing the orientation state to be visually confirmed. Information on the strength of orientation can be obtained from the phase difference graph, and information on the direction of orientation can be obtained from the axis orientation graph.

[0033] The main orientation direction can be determined from the graph of axial orientation. When the length of the line within the 80° to 100° range in a given section is longer than the length of the line within the 0° to 10° range and the 170° to 180° range in that section, the main orientation direction in that section is the circumferential direction z. Conversely, when the length of the line within the 80° to 100° range in a given section is shorter than the length of the line within the 0° to 10° range and the 170° to 180° range in that section, the main orientation direction in that section is the longitudinal axis direction x. The intensity of the orientation component can be obtained from a phase difference graph. Regarding which section of the proximal section 23a, the intermediate section 23c, and the distal section 23e has the largest component of the longitudinal axis direction x in the orientation direction, the length of the line within the 0° to 10° range and the 170° to 180° range in each section can be compared in the graph of axial orientation to determine the section with the longest included line as the section with the largest component of the longitudinal axis direction x in the orientation direction. For example, for the balloon 2 showing the measurement results shown in Figures 8 to 10, the axial orientation graph shows that the main orientation direction of the molecules in the proximal section 23a and the distal section 23e is the circumferential direction z. Furthermore, the main orientation direction of the molecules in the central section 23c is the longitudinal axis direction x, and the longitudinal axis direction x component of the molecular orientation in the central section 23c is greater than the longitudinal axis direction x component of the molecular orientation in the proximal section 23a and the distal section 23e. Furthermore, the phase difference graph shows that the orientation strength decreases from the central section 23c toward the proximal and distal sides, i.e., the longitudinal axis direction x component of the molecular orientation decreases.

[0034] The main orientation direction of the molecules in the central section 23c is preferably the longitudinal axis direction x. By having the main orientation direction be the longitudinal axis direction x, even if the balloon 2 is destroyed by excessive pressure, it becomes easier to initiate cracks in the longitudinal axis direction x in the central section 23c. This allows internal pressure to be released by cracks in the longitudinal axis direction x in the central section 23c, making it easier to prevent cracks in the circumferential direction z.

[0035] The component of the molecular orientation in the longitudinal axis direction x gradually decreases from the central section 23c to the 0% position D0, and from the central section 23c to the 100% position D 100 It is preferable that the molecular orientation component in the longitudinal direction x gradually decreases from the central section 23c to the 0% position D0. This allows the molecular orientation component in the longitudinal direction x to be maximized in the central section 23c, making it easier to initiate cracks in the longitudinal direction x in the central section 23c, and since cracks in the longitudinal direction x in the central section 23c can release internal pressure, cracks in the circumferential direction z can be more easily prevented. The gradual decrease of the molecular orientation component in the longitudinal direction x from the central section 23c to the 0% position D0 means, for example, the 40% position D 40 , 20% position, and 0% position D0, the components of the longitudinal axis direction x of the molecular orientation are required to decrease in order. Also, the components of the longitudinal axis direction x of the molecular orientation are required to decrease in order from the central section 23c to the 100% position D 100 For example, the 60% position D 60 , 80% position, and 100% position D 100 The component of the molecular orientation in the longitudinal direction x does not necessarily have to decrease continuously from the central section 23c toward the proximal or distal side, as long as it decreases gradually when compared between the central section 23c and the longitudinal direction x. Alternatively, the component of the molecular orientation in the longitudinal direction x may decrease continuously from the central section 23c toward the proximal or distal side.

[0036] 10% position D 10 Position D: 40% from the center 40 The section up to the proximal intermediate section 23b, the 60% position D 60 90% from position D 90When the section up to is defined as the distal intermediate section 23d, it is preferable that the primary molecular orientation direction change from the longitudinal axis direction x to the circumferential direction z in the proximal intermediate section 23b and the distal intermediate section 23d. Changing the primary molecular orientation direction from the longitudinal axis direction x to the circumferential direction z in the proximal intermediate section 23b and the distal intermediate section 23d makes it easier to stop the propagation of cracks in the longitudinal axis direction x that occur in the central section 23c in the proximal intermediate section 23b and the distal intermediate section 23d, making it easier to contain the location of the crack within the straight pipe section 23. The change in the primary molecular orientation direction can be seen from the axial orientation graph. In the example shown in Figure 10, it can be seen that the primary molecular orientation direction change from the longitudinal axis direction x to the circumferential direction z in the proximal intermediate section 23b and the distal intermediate section 23d.

[0037] The thickness of the balloon 2 in the central section 23c is preferably thinner than the thickness of the balloon 2 in the proximal section 23a and the distal section 23e. The thinner thickness of the central section 23c makes it easier to trigger a crack in the longitudinal axis direction x in the central section 23c, making it easier to limit the location of the crack in the longitudinal axis direction x to the central section 23c.

[0038] Although not shown, the balloon 2 may have protrusions that protrude outward in the radial direction y from the outer surface and extend in the longitudinal direction x. The protrusions are preferably provided on the outer surface of the balloon 2 in a dotted, linear, or mesh-like pattern. Providing protrusions on the outer surface of the balloon 2 provides the protrusions with a scoring function, allowing for the creation of cracks in calcified stenotic areas during angioplasty and expansion. This also makes it possible to increase the strength of the balloon 2 and prevent overexpansion when pressurized.

[0039] Examples of materials constituting the balloon 2 include polyolefin-based resins such as polyethylene, polypropylene, and ethylene-propylene copolymer; polyester-based resins such as polyethylene terephthalate and polyester elastomer; polyurethane-based resins such as polyurethane and polyurethane elastomer; polyphenylene sulfide-based resins; polyamide-based resins such as polyamide and polyamide elastomer; fluorine-based resins; silicone-based resins; and natural rubbers such as latex rubber. These materials may be used alone or in combination. Among these, polyamide-based resins, polyester-based resins, and polyurethane-based resins are preferred. Elastomer resins are particularly preferred from the viewpoints of thinning and flexibility of the balloon 2. Among polyamide-based resins, nylon 12 and nylon 11 are preferred as resins constituting the balloon 2, with nylon 12 being more preferred due to its relatively easy shaping ability during blow molding. Furthermore, polyamide elastomers such as polyetheresteramide elastomers and polyamideether elastomers are preferred from the viewpoints of thinning and flexibility of the balloon 2. Among these, polyether ester amide elastomers are preferably used because they have high yield strength and provide good dimensional stability to the balloon 2 .

[0040] The balloon 2 can be manufactured by placing a parison made of the above-mentioned material in a mold and biaxially stretching and blow molding it. A preferred method for manufacturing the balloon 2 will be described later in the section "3. Method for manufacturing a balloon catheter."

[0041] 2. Balloon catheter The balloon catheter of the present invention includes the balloon for the balloon catheter. The balloon catheter according to the embodiment of the present invention can be understood by referring to the above section "1. Balloon for Balloon Catheter" and FIG. 2.

[0042] Examples of materials that can be used to form the shaft 3 include polyamide resins, polyester resins, polyurethane resins, polyolefin resins, fluorine-based resins, vinyl chloride resins, silicone resins, and natural rubber. These materials can be used alone or in combination. Among these, the material that forms the shaft 3 is preferably at least one of polyamide resins, polyolefin resins, and fluorine-based resins. This can increase the slipperiness of the surface of the shaft 3 and improve the insertability of the balloon catheter 1 within a body cavity.

[0043] The balloon 2 and the shaft 3 can be joined by bonding with an adhesive, welding, or by attaching a ring-shaped member to the overlapping portion of the end of the balloon 2 and the shaft 3 and crimping them. Among these, it is preferable that the balloon 2 and the shaft 3 are joined by welding. By welding the balloon 2 and the shaft 3, the bond between the balloon 2 and the shaft 3 is unlikely to come loose even when the balloon 2 is repeatedly inflated and deflated, and the bond strength between the balloon 2 and the shaft 3 can be easily increased.

[0044] As shown in FIG. 2, the balloon catheter 1 may be provided with a hub 4 on the proximal side of the shaft 3. The hub 4 preferably has a fluid injection section 6 that communicates with a fluid flow path for supplying fluid to the interior of the balloon 2. The hub 4 may also be provided with a guidewire insertion section 5 that communicates with a guidewire insertion passage. This configuration facilitates the operation of supplying fluid to the interior of the balloon 2 to inflate and deflate the balloon 2, and the operation of delivering the balloon catheter 1 to a treatment site along the guidewire. While FIG. 2 shows a so-called over-the-wire balloon catheter 1 in which a guidewire is inserted from the distal side to the proximal side of the shaft 3, the balloon 2 according to the embodiment of the present invention can also be applied to a so-called rapid exchange balloon catheter in which a guidewire is inserted partway from the distal side to the proximal side of the shaft 3.

[0045] The shaft 3 and the hub 4 can be joined by, for example, bonding with an adhesive or welding. Of these, it is preferable that the shaft 3 and the hub 4 are joined by adhesive. By bonding the shaft 3 and the hub 4, the bond strength between the shaft 3 and the hub 4 can be increased, thereby improving the durability of the balloon catheter 1, even when the shaft 3 and the hub 4 are made of different materials, such as when the shaft 3 is made of a highly flexible material and the hub 4 is made of a highly rigid material.

[0046] 3. Balloon catheter manufacturing method One embodiment of a method for manufacturing a balloon catheter of the present invention includes the steps of: preparing a parison made of a resin; preparing a mold having an inner lumen, the inner wall surface of the lumen having a straight tube section, a proximal tapered section located proximal to the straight tube section, and a distal tapered section located distal to the straight tube section; placing the parison in the mold; a first stretching step in which, while heating the mold, the parison is stretched in the longitudinal direction until it exceeds the necking region of a stress-strain curve; and a second stretching step in which, while heating the mold, the parison stretched beyond the necking region after the first stretching step is further stretched in the longitudinal direction under a condition in which the internal pressure of the parison is higher than that of the first stretching step. For many resins, in the stress-strain curve shown in Figure 1, stress acts to stretch bent molecular chains in the elastic deformation region up to the yield point B. After the yield point B, molecular chains that were attracted to each other by intermolecular forces begin to shear, causing plastic deformation. Some resins exhibit a phenomenon in which once the molecular chains begin to slip, the molecular chains become loose and the stress decreases to the lower yield point L. After that, a region showing a plateau in stress is observed for a while, and this region is usually called the necking region R. n This is called the necking region R n In the case of the necking region R, the molecular chains are displaced by strain, resulting in a certain stress. However, when the strain exceeds a certain level, the molecular chains approach each other and are closely oriented, generating a strong intermolecular force between the molecular chains. n In the region beyond this, the stress increases steadily.n The parison is first stretched in the longitudinal direction until it exceeds the necking region R n By further stretching the parison in the longitudinal direction under high internal pressure, which has been stretched to exceed this, it is possible to manufacture a balloon catheter having a balloon for a balloon catheter in which the main orientation direction of the molecules in the proximal section and the distal section is the circumferential direction, and the longitudinal component of the molecular orientation in the central section is greater than the longitudinal component of the molecular orientation in the proximal section and the distal section.

[0047] The above manufacturing method will be described with reference to Figures 11 to 14. Figure 11 is a cross-sectional view showing a parison placed in a mold according to one embodiment of the present invention. Figure 12 is a cross-sectional view showing a parison stretched in the longitudinal direction beyond the necking region of the stress-strain curve while the mold is heated in a first stretching step according to one embodiment of the present invention. Figure 13 is a cross-sectional view showing a parison stretched beyond the necking region while the mold is heated in a second stretching step according to one embodiment of the present invention, and further stretched in the longitudinal direction under a condition where the internal pressure of the parison is higher than in the first stretching step. Figure 14 is a cross-sectional view showing a state after the second stretching step is completed.

[0048] First, a parison 70 made of resin is prepared. The parison 70 is a tubular member having an inner cavity 71, and can be produced by, for example, extrusion molding. The parison 70 has one end and the other end, and extends in the longitudinal axis direction x from one end to the other end.

[0049] Although not shown, the cross-sectional shape of the parison 70 in a direction perpendicular to the longitudinal axis direction x, i.e., in the radial direction y, may be substantially uniform along the longitudinal axis direction x. Alternatively, as shown in Fig. 11, the cross-sectional shape of the parison 70 in the radial direction y may vary depending on the position along the longitudinal axis direction x. The outer diameter of a portion of the parison 70, for example, the portions corresponding to the straight tube portion 23, the proximal tapered portion 22, and the distal tapered portion 24 of the balloon 2, may be larger than the remaining portions.

[0050] For the resin that constitutes the parison 70, the explanation of the resin that constitutes the balloon 2 described in the section "1. Balloon for balloon catheter" can be referred to.

[0051] Next, a mold 80 is prepared, which has a lumen 88 and whose inner wall surface forming the lumen 88 has a straight pipe portion 83, a proximal tapered portion 82 located proximal to the straight pipe portion 83, and a distal tapered portion 84 located distal to the straight pipe portion 83. The inner wall surface forming the lumen 88 of the mold 80 may have a proximal sleeve portion 81 located proximal to the proximal tapered portion 82 and a distal sleeve portion 85 located distal to the distal tapered portion 84.

[0052] The mold 80 may be formed from a single member or multiple members. For example, the mold 80 may be formed from multiple halves, or multiple mold members may be formed so as to be separable in the longitudinal axis direction x.

[0053] 11 , the parison 70 is placed in the lumen 88 of the mold 80. At this time, if the parison 70 has a portion with a large outer diameter, that is, if the outer diameters of the portions corresponding to the straight tube section 23, proximal tapered section 22, and distal tapered section 24 of the balloon 2 are large, it is preferable to position this portion so that it is located in the straight tube section 83 of the mold 80. This makes it easy to make this portion into the straight tube section 23, proximal tapered section 22, and distal tapered section 24 of the balloon 2.

[0054] 12, a first stretching step is performed in which the parison 70 is stretched in the longitudinal axis direction x while the mold 80 is heated. At this time, the parison 70 is stretched in the necking region R of the stress-strain curve of the resin constituting the parison 70. n The necking region R is stretched until it exceeds n As mentioned above, the region R indicates a plateau in stress after the yield point B and the lower yield point L. In this region, the molecular chains of the resin that have begun to plastically deform are displaced by the stress. In the first stretching step, this necking region Rn It is important to stretch the parison 70 until it exceeds the stretch limit.

[0055] Since the internal pressure of the parison 70 in the first stretching step is lower than the internal pressure of the parison 70 in the second stretching step, the necking region R n In the above-described state until the temperature exceeds 100° C., the parison 70 can be stretched in the longitudinal direction x while being restrained from stretching in the circumferential direction z.

[0056] When the parison 70 is prepared by extrusion molding, for example, and the parison 70 is stretched to a certain extent in the longitudinal axis direction x, the necking region R n The amount by which the parison 70 is stretched in the longitudinal axis direction x until it exceeds the necking region R varies depending on the conditions of preparation of the parison 70, such as extrusion molding. In other words, if the parison 70 has already been stretched to some extent in the longitudinal axis direction x in extrusion molding or the like, the amount by which the parison 70 is stretched in the longitudinal axis direction x in the first stretching step may be less, but the necking region R n can be exceeded.

[0057] As shown in FIG. 13, after the first stretching step, the die 80 is heated while the necking region R n The parison 70 stretched to exceed the necking region R is subjected to a second stretching step in which the parison 70 is further stretched in the longitudinal axis direction x under a condition in which the internal pressure of the parison 70 is higher than that in the first stretching step. n After the stretching temperature exceeds 100° C., the resin in a state where the molecular chains of the resin are closely spaced and densely oriented is further stretched in the longitudinal axis direction x. Since the internal pressure of the parison 70 is higher in the second stretching step than in the first stretching step, the necking region R n In the first stretching step, the parison 70 is stretched in the longitudinal axis direction x while the stretching in the circumferential direction z of the parison 70 is suppressed until the stretching exceeds the necking region R n In the second stretching step beyond this point, the parison 70 is stretched in the circumferential direction z and also in the longitudinal direction x.

[0058] In this way, a balloon 2 as shown in Fig. 14 can be obtained. By performing the first stretching step and the second stretching step, it is possible to obtain a balloon 2 in which the main orientation direction of the molecular orientation in the proximal section 23a and the molecular orientation in the distal section 23e is the circumferential direction z, and the component of the molecular orientation in the longitudinal axis direction x in the central section 23c is greater than the components of the molecular orientation in the longitudinal axis direction x in the proximal section 23a and the distal section 23e.

[0059] The stress-strain curve shown in Figure 1 shows the necking region R where the stress becomes constant. n However, depending on the resin, the region of constant stress may be short or not completely flat. In such cases, the first point after the stress-strain curve exceeds the yield point B where the differential coefficient of the stress-strain curve is 5% or more of the average rate of change up to the yield point B is defined as the necking region R. n The first stretching step may be carried out until the strain exceeds this value.

[0060] The heating temperature in the first stretching step and the second stretching step can be set to a temperature close to the glass transition temperature of the resin that constitutes the balloon 2. As a heating means for the mold 80, a known heater or the like can be used as appropriate.

[0061] In the first stretching step, it is preferable that a fluid is introduced into the lumen 71 of the parison 70 to pressurize the inside of the parison 70, and the pressure at this time is preferably 3 MPa or less. Alternatively, the lumen 71 of the parison 70 and the outside of the parison 70 may be at the same pressure, i.e., the lumen 71 of the parison 70 may not be pressurized.

[0062] In the second stretching step, a fluid is preferably introduced into the lumen 71 of the parison 70 to pressurize the interior of the parison 70, and the pressure at this time is higher than the pressure applied to the interior of the parison 70 in the first stretching step, and is, for example, preferably 1 MPa or more, more preferably 1.5 MPa or more, and even more preferably 2 MPa or more. The pressure is also preferably 5 MPa or less, more preferably 4.5 MPa or less, and even more preferably 4 MPa or less, and may be 3 MPa or less.

[0063] In the first stretching step, the parison 70 is not pressurized, and in the second stretching step, the necking region R n It is preferable that pressurization of parison 70 begins after the pressure exceeds 100 kJ / cm. This makes it easier to form balloon 2 in which the main orientation direction of the molecular orientation in proximal section 23a and the main orientation direction of the molecular orientation in distal section 23e are the circumferential direction z, and the component of the molecular orientation in the longitudinal axis direction x in central section 23c is greater than the components of the molecular orientation in the longitudinal axis direction x in proximal section 23a and distal section 23e.

[0064] When heating the mold 80, it is preferable to heat the mold 80 so that the central portion of the straight tube portion 83 reaches the highest temperature. This makes it easier to obtain a balloon 2 in which the component of molecular orientation in the longitudinal axis direction x in the central section 23c of the balloon 2 is greater than the component of molecular orientation in the longitudinal axis direction x in the proximal section 23a and the distal section 23e, and makes it easier to obtain a balloon 2 in which the film thickness of the balloon 2 in the central section 23c is thinner than the film thickness of the balloon 2 in the proximal section 23a and the distal section 23e.

[0065] This application claims the benefit of priority based on Japanese Patent Application No. 2021-79672, filed on May 10, 2021. The entire contents of the specification of Japanese Patent Application No. 2021-79672, filed on May 10, 2021, are incorporated herein by reference. [Example]

[0066] The present invention will be described below with reference to examples. The present invention is not limited to the following examples, and can of course be practiced with appropriate modifications within the scope of the above and below-described aims, and all such modifications are within the technical scope of the present invention.

[0067] Example 1 A parison was prepared by extrusion molding of polyamide 12. The parison was placed in a mold, and while the mold was heated to 70°C, an internal pressure of 2 MPa was applied to the parison, stretching it longitudinally until it exceeded the necking region of the stress-strain curve. Next, while the mold was heated to 70°C, an internal pressure of 4.3 MPa was applied to the parison, stretching it longitudinally to obtain a balloon.

[0068] Five balloons were fabricated in the same manner. For each balloon, the proximal and distal tapered sections were cut off to obtain a cylindrical straight section, as shown in Figure 7, and the cylindrical straight section was then cut open along a cutting line in the longitudinal direction to obtain rectangular samples 1 to 5. The molecular orientation of samples 1 to 5 was measured using a two-dimensional birefringence evaluation system WPA-100 manufactured by Photonics Lattice. The results are shown in Figures 15 to 17. In Figures 15 to 17, the data for samples 1 to 5 are shown from top to bottom. For each balloon, the primary molecular orientation direction in the central section of the straight section was the longitudinal axis, and the primary molecular orientation direction in the proximal and distal sections of the straight section was the circumferential direction, allowing stable balloons to be obtained.

[0069] For each of the five balloons, the membrane thickness of the proximal section (1), proximal middle section (2), central section (3), distal middle section (4), and distal section (5) was measured using a Mitutoyo spline micrometer SPM2-25MX. The results are shown in Figure 18. For each balloon, the membrane thickness was the thinnest in the central section, and balloons with membrane thicknesses that increased from the central section to the proximal and distal sides were consistently obtained.

[0070] Thirty more balloons were fabricated using the same method as in Example 1. Internal pressure was applied to these 30 balloons until they were broken, and after they were broken, the state of cracks was observed to check for the occurrence of circumferential cracks. No circumferential cracks were observed in any of the balloons.

[0071] Comparative Example 1 A parison was prepared in the same manner as in Example 1. The parison was placed in the inner cavity of the same mold as in Example 1, and while the mold was heated to 60°C, a pressure of 3.5 MPa was applied to the inner cavity of the parison, which was stretched in the longitudinal direction to obtain a balloon.

[0072] Five balloons were fabricated in the same manner. For each balloon, the proximal and distal tapered sections were cut off to obtain a cylindrical straight tube section, as shown in Figure 7. The cylindrical straight tube section was then cut open along a cutting line in the longitudinal direction to obtain rectangular samples 6 to 10. The molecular orientation of samples 6 to 10 was measured using a two-dimensional birefringence evaluation system WPA-100 manufactured by Photonics Lattice. The results are shown in Figures 19 to 21. Figures 19 to 21 show data for samples 6 to 10, from top to bottom. The orientation state varied among the balloons, and not all balloons had a molecular orientation in the longitudinal direction in the central section of the straight tube section that was greater than the molecular orientation in the longitudinal direction in the proximal and distal sections.

[0073] For each of the five balloons, the membrane thickness of the proximal section (1), proximal middle section (2), central section (3), distal middle section (4), and distal section (5) was measured using a Mitutoyo spline micrometer SPM2-25MX. The results are shown in Figure 22. It was found that the membrane thickness tendencies in the longitudinal direction varied depending on the balloon, and that the method of Comparative Example 1 was unable to control the membrane thickness in the longitudinal direction.

[0074] Thirty more balloons were fabricated using the same method as in Comparative Example 1. Internal pressure was applied to these 30 balloons until they were broken, and after they were broken, the state of cracks was observed to determine whether or not circumferential cracks had occurred. Circumferential cracks occurred in three of the 30 balloons. [Explanation of symbols]

[0075] 1: Balloon catheter 2: Balloon 3: Shaft 4: Hub 5: Guidewire insertion section 6:Fluid injection part 21: Proximal sleeve part 22: Proximal tapered section 23: Straight pipe section 23a: Proximal section 23b: Proximal middle section 23c: Central section 23d: Distal middle section 23e: Distal section 24: Distal tapered section 25: Distal sleeve 70:Parison 71: Lumen of parison 80: Mold 81: Proximal sleeve part of mold 82: Proximal taper of mold 83: Straight pipe section of mold 84: Distal taper of mold 85: Distal sleeve part of mold 88: Mold cavity B: Yield point D0: 0% position D 10 :10% position D 40 :40% position D 60 :60% position D 90 :90% position D 100 :100% position L: Lower yield point R n : necking region S1: 1st cutting line S2: 2nd cutting line x: longitudinal axis direction y: radial direction z: Circumferential direction

Claims

1. A balloon formed of a resin having molecular orientation, the balloon having a longitudinal axis direction and a circumferential direction along the outer periphery of the balloon in an expanded state in a cross section perpendicular to the longitudinal axis direction, The endoscopic catheter has a straight pipe portion, a proximal tapered portion located proximally of the straight pipe portion, and a distal tapered portion located distally of the straight pipe portion, In the longitudinal axis direction, when the proximal end of the straight pipe portion is set to a 0% position and the distal end is set to a 100% position, a main orientation direction of the molecular orientation in a proximal section from a 0% position to a 10% position and a main orientation direction of the molecular orientation in a distal section from a 90% position to a 100% position is the circumferential direction; A balloon for a balloon catheter, wherein the longitudinal axis component of the molecular orientation in the central section from the 40% position to the 60% position is greater than the longitudinal axis component of the molecular orientation in the proximal section and the distal section.

2. 2. The balloon for a balloon catheter according to claim 1, wherein the main orientation direction of the molecules in the central section is the longitudinal axis direction.

3. 3. The balloon for a balloon catheter according to claim 1, wherein the longitudinal axis component of the molecular orientation gradually decreases from the central section toward the 0% position and gradually decreases from the central section toward the 100% position.

4. When the section from the 10% position to the 40% position is defined as the proximal intermediate section, and the section from the 60% position to the 90% position is defined as the distal intermediate section, 4. The balloon for a balloon catheter according to claim 2, wherein the main molecular orientation direction changes from the longitudinal axis direction to the circumferential direction in the proximal intermediate section and the distal intermediate section.

5. 5. The balloon for a balloon catheter according to claim 1, wherein the thickness of the balloon in the central section is thinner than the thickness of the balloon in the proximal section and the distal section.

6. A balloon catheter comprising the balloon according to any one of claims 1 to 5.

7. 7. A method for manufacturing a balloon catheter according to claim 6, comprising the steps of: Providing a parison comprised of a resin; A step of preparing a mold having an inner cavity, the inner wall surface of which forms the inner cavity having a straight pipe portion, a proximal tapered portion located proximally of the straight pipe portion, and a distal tapered portion located distally of the straight pipe portion; placing the parison in the mold; a first stretching step of stretching the parison in the longitudinal direction while heating the mold until the parison exceeds a necking region of a stress-strain curve; a second stretching step in which, while heating the mold, the parison, which has been stretched beyond the necking region after the first stretching step, is further stretched in the longitudinal axis direction under a state in which the internal pressure of the parison is higher than in the first stretching step.

8. 8. The method for manufacturing a balloon catheter according to claim 7, wherein the parison is pressurized in the first stretching step at a pressure lower than that in the second stretching step, and is further pressurized in the second stretching step after passing through the necking region.

9. 9. The method for manufacturing a balloon catheter according to claim 7, further comprising the step of heating the mold so that the temperature is highest in a central portion of the straight tube portion of the mold.

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