Balloon for balloon catheter and manufacturing method of balloon catheter

Abstract

A balloon for a balloon catheter is provided, which can suppress circumferential cracks by generating a long-axis crack in the central part of the balloon, and prevent the long-axis crack from extending to the proximal and distal ends of the balloon to form an L-shaped crack by keeping the long-axis crack within the straight tube section. A balloon (2) for a balloon catheter has a molecular orientation direction of circumferential z in the proximal and distal sections (23e) of the straight tube section (23), and the long-axis x component of the molecular orientation component in the central section (23c) of the straight tube section (23) is greater than that in the proximal and distal sections (23e) of the straight tube section (23).

Description

Technical Field

[0001] This invention relates to a balloon for balloon catheters and a method for manufacturing balloon catheters. Background Technology

[0002] Angiogenesis, a minimally invasive procedure that involves inserting a balloon catheter into a narrowed section of a blood vessel and inflating the balloon to dilate the vessel and ensure blood flow, is widely performed. Angiogenesis is used, for example, to treat conditions such as myocardial infarction caused by narrowing of the coronary arteries of the heart, and to treat narrowing in dialysis shunts. The balloon in a balloon catheter is typically cylindrical in shape, narrowed distally and proximally, and consists of a straight cylindrical section, a proximal conical section closer to the straight section, and a distal conical section more distal to the straight section.

[0003] Typically, when dilating a narrowed area via a balloon catheter, the balloon is inflated with an expansion pressure appropriate to the affected area. However, sometimes during the procedure, applying unexpected internal pressure to the balloon can cause over-inflation, leading to balloon rupture. In such cases, if the balloon ruptures circumferentially, there is a significant risk that fragments of the balloon, extending distal to the rupture site, may remain in the body. Therefore, a technique is needed that assumes that even in the event of balloon rupture, the rupture will not be a circumferential crack but rather a crack along the long axis.

[0004] For example, Patent Documents 1-3 propose a balloon with the goal of providing pressure resistance and suppressing circumferential damage. Patent Document 1 discloses a balloon in which the difference in the proportion of polymer chains oriented circumferentially in the expansion functional section is less than a predetermined value. Patent Document 2 discloses a balloon in which the ratio of the circumferential orientation distribution number to the axial orientation distribution number in the cylindrical section is less than a predetermined position. Patent Document 3 discloses a balloon in which the molecular orientation of the balloon material itself is consistent in the axial direction, and the balloon is not easily scattered and broken by generating cracks in the axial direction.

[0005] Patent Document 1: Japanese Patent Application Publication No. 2004-298354

[0006] Patent Document 2: International Publication No. 2014 / 141382

[0007] Patent Document 3: Japanese Patent Application Publication No. 2008-553

[0008] However, while the aforementioned balloons attempt to suppress circumferential damage and improve pressure resistance by controlling the molecular orientation of the balloon, they cannot suppress circumferential cracks by simultaneously controlling the location of long-axis cracks and generating long-axis cracks in the event of balloon failure. Furthermore, when long-axis cracks are generated, they sometimes extend to the thicker proximal and distal ends of the balloon wall, forming L-shaped cracks that become circumferential cracks. This sometimes creates a risk of fragmentation at the L-shaped circumferential crack portion, leaving fragments within the body. Existing balloons are insufficient to prevent such L-shaped cracks. Summary of the Invention

[0009] In view of the above, the object of the present invention is to provide a balloon for a balloon catheter that can suppress circumferential cracks even in the event of balloon rupture by generating a long-axis crack in the central portion of the balloon. Furthermore, the object is to provide a balloon for a balloon catheter that, by keeping the long-axis crack within the straight tube portion, prevents the long-axis crack from extending to the proximal and distal ends of the balloon and forming an L-shaped crack at the end that would become a circumferential crack.

[0010] An embodiment of the balloon catheter of the present invention, which solves the above-mentioned problems, is characterized in that the balloon catheter is formed of a resin having molecular orientation. The balloon has a long axis direction and a circumferential direction along the outer periphery of the balloon in an expanded state in a cross section perpendicular to the long axis direction. The balloon has a straight tube portion, a proximal conical portion located closer to the position of the straight tube portion, and a distal conical portion located more distal to the position of the straight tube portion. In the long axis direction, when the proximal end of the straight tube portion is set to the 0% position and the distal end is set to the 100% position, the main orientation direction of the molecular orientation in the proximal interval from the 0% position to the 10% position and the molecular orientation in the distal interval from the 90% position to the 100% position is circumferential. The long axis component of the molecular orientation in the central interval from the 40% position to the 60% position is greater than the long axis component of the molecular orientation in the proximal and distal intervals. In this way, because the long-axis component of molecular orientation is greater in the central region than in the proximal and distal regions, even if the balloon is damaged due to overpressure, a long-axis crack can be initiated in the central region. This long-axis crack in the central region can release internal pressure and prevent circumferential cracking. However, if a long-axis crack generated in the central region rapidly moves along its long axis past the proximal and distal regions, there is a concern that L-shaped cracks, which become circumferential cracks, may form in the thicker proximal and distal conical portions. However, in the balloon catheter of the present invention, the main orientation direction of the molecular orientation in the proximal and distal sections is circumferential. Therefore, even if a long-axis crack generated in the central section reaches the proximal and distal sections, it can prevent it from rapidly propagating beyond the proximal and distal sections to the proximal and distal conical portions. Thus, the long-axis crack can be contained within the straight tube section, preventing the formation of L-shaped cracks that would become circumferential cracks in the proximal and distal conical portions. As a result, the risk of balloon fragments remaining in the body due to circumferential or L-shaped cracks can be avoided.

[0011] In the balloon catheter described above, the preferred orientation direction of the molecules in the central region is the long axis direction.

[0012] In the balloon catheter described above, the preferred molecular orientation of the long axis component gradually decreases from the central region toward the 0% position and from the central region toward the 100% position.

[0013] In the balloon catheter described above, it is preferable that the main orientation direction of the molecular orientation in the central region is the long axis direction. When the region from the 10% position to the 40% position is designated as the proximal middle region and the region from the 60% position to the 90% position is designated as the distal middle region, the main orientation direction of the molecular orientation changes from the long axis direction to the circumferential direction in both the proximal and distal middle regions.

[0014] In the balloons used for the above-mentioned balloon catheters, it is preferable that the membrane thickness of the balloon in the central section is thinner than that of the balloons in the proximal and distal sections.

[0015] The present invention also provides a balloon catheter having the balloon described above for balloon catheters.

[0016] Furthermore, the present invention also provides a method for manufacturing the above-mentioned balloon catheter. One embodiment of the method for manufacturing the balloon catheter of the present invention, which solves the above-mentioned problems, is characterized by comprising: a step of preparing a preform made of resin; a step of preparing a mold having an inner cavity, the inner wall surface forming the inner cavity having a straight tube portion, a proximal tapered portion located closer to the straight tube portion than the straight tube portion, and a distal tapered portion located more distal to the straight tube portion than the straight tube portion; a step of placing the preform within the mold; a first extension step of extending the preform along its long axis beyond a necking region of the stress-strain curve while heating the mold; and a second extension step of further extending the preform beyond the necking region along its long axis while heating the mold, after the first extension step, under a condition where the internal pressure of the preform is higher than that of the first extension step. In many resins, in Figure 1 In the stress-strain curve shown, in the region of elastic deformation up to the yield point B, stress acts as elongation of the molecular chains in a bent state. After the yield point B, plastic deformation begins, with the molecular chains attracting each other and shifting in the shear direction. There are also resins that show a phenomenon where, once the molecular chains begin to shift, they relax and the stress decreases to the lower yield point L. A region exhibiting transverse stress is then temporarily observed; this region is usually called the necking region R. n In the constricted region R n In the process, the molecular chains shift due to strain, thus exhibiting constant stress. However, if the strain exceeds a specified limit, the molecular chains approach each other and become tightly oriented, generating strong intermolecular forces between the chains. Therefore, above the specified strain, that is, beyond the necking region R... n In the region, the stress increases to the right. In the first extension process, the preform is first extended along its long axis beyond the necking region R. n In the subsequent second extension process, the extension extends beyond the necking region R. nThe preform is further extended along the long axis under high internal pressure, thereby enabling the manufacture of a balloon catheter with a balloon for balloon catheters. The main orientation direction of the molecular orientation in the proximal and distal regions of the balloon catheter is circumferential, and the long axis component of the molecular orientation in the central region is greater than that in the proximal and distal regions.

[0017] The manufacturing method described above preferably involves pressing the preform at a lower pressure than in the second extension step during the first extension step, and further pressing the preform after it has passed the necking region during the second extension step.

[0018] The manufacturing method described above preferably includes a step of heating the mold in such a way that the central part of the straight tube section of the mold reaches the highest temperature.

[0019] According to the aforementioned balloon for balloon catheters and the manufacturing method of the balloon catheter, even in the event of balloon failure, circumferential cracks can be suppressed by generating a long-axis crack in the central part of the balloon. Furthermore, by keeping the long-axis crack within the straight tube section, it is possible to prevent the long-axis crack from extending to the proximal or distal end of the balloon and forming an L-shaped crack at the end that would become a circumferential crack. Therefore, even if the balloon fails due to overpressure, the risk of balloon fragments remaining in the body due to circumferential or L-shaped cracks can be avoided. Attached Figure Description

[0020] Figure 1 This represents the stress-strain curve of polyester resin.

[0021] Figure 2 A side view of a balloon catheter according to one embodiment of the present invention.

[0022] Figure 3 This is a top view showing a balloon with a crack along its long axis in one embodiment of the present invention.

[0023] Figure 4 A top view showing an example of a circumferential crack forming in the balloon.

[0024] Figure 5 A top view showing an example of an L-shaped crack forming in the balloon.

[0025] Figure 6 This is a top view showing another example of an L-shaped crack forming in the balloon.

[0026] Figure 7 The figure illustrates a method for preparing a sample to determine the molecular orientation of the straight tube portion of a balloon according to one embodiment of the present invention.

[0027] Figure 8This represents a contour map obtained by measuring the balloon of one embodiment of the present invention using a two-dimensional birefringence evaluation system.

[0028] Figure 9 A graph showing the phase difference obtained by measuring the balloon of one embodiment of the present invention using a two-dimensional birefringence evaluation system.

[0029] Figure 10 A graph showing the axial orientation of a balloon according to one embodiment of the present invention, determined by a two-dimensional birefringence evaluation system.

[0030] Figure 11 A cross-sectional view showing the state in which the preform is arranged in a mold according to one embodiment of the present invention.

[0031] Figure 12 A cross-sectional view showing the state in the first extended step of an embodiment of the present invention.

[0032] Figure 13 A cross-sectional view showing the state in a second extended step according to an embodiment of the present invention.

[0033] Figure 14 A cross-sectional view showing the state after the completion of the second extension process according to one embodiment of the present invention.

[0034] Figure 15 This is a contour map of the balloon obtained in Example 1.

[0035] Figure 16 This is a graph of the phase difference of the balloon obtained in Example 1.

[0036] Figure 17 This is a diagram of the axial orientation of the balloon obtained in Example 1.

[0037] Figure 18 This is a graph showing the membrane thickness of the balloon obtained in Example 1.

[0038] Figure 19 This is a contour map of the balloon obtained in Comparative Example 1.

[0039] Figure 20 This is a graph showing the phase difference of the balloon obtained in Comparative Example 1.

[0040] Figure 21 This is a chart showing the axial orientation of the balloon obtained in Comparative Example 1.

[0041] Figure 22 This is a graph showing the membrane thickness of the balloon obtained in Comparative Example 1. Detailed Implementation

[0042] The present invention will now be specifically described based on embodiments, but the present invention is of course not limited to the embodiments described below, and can be implemented by appropriate modifications within the scope of the foregoing spirit, all of which are included within the technical scope of the present invention. Furthermore, in the various drawings, for convenience, there are instances where shaded lines, component reference numerals, etc., are omitted; in such cases, please refer to the specification and other drawings. Additionally, the dimensions of various components in the drawings are primarily helpful in understanding the features of the present invention, and therefore sometimes differ from the actual dimensions.

[0043] 1. Balloon catheter for use

[0044] The balloon for balloon catheters according to embodiments of the present invention is characterized in that the balloon for balloon catheters is a balloon formed of a resin having molecular orientation. The balloon has a long axis direction and a circumferential direction along the outer periphery of the balloon in an expanded state in a cross section perpendicular to the long axis direction. The balloon has a straight tube portion, a proximal conical portion located closer to the position of the straight tube portion, and a distal conical portion located more distal to the position of the straight tube portion. In the long axis direction, when the proximal end of the straight tube portion is set to the 0% position and the distal end is set to the 100% position, the main orientation direction of the molecular orientation in the proximal interval from the 0% position to the 10% position and the molecular orientation in the distal interval from the 90% position to the 100% position is circumferential. The long axis component of the molecular orientation in the central interval from the 40% position to the 60% position is greater than the long axis component of the molecular orientation in the proximal and distal intervals. In this way, because the long-axis component of molecular orientation is greater in the central region than in the proximal and distal regions, even if the balloon is damaged due to overpressure, a long-axis crack can be initiated in the central region. This long-axis crack in the central region can release internal pressure and prevent circumferential cracking. However, if a long-axis crack generated in the central region rapidly moves along its long axis past the proximal and distal regions, there is a concern that L-shaped cracks, which become circumferential cracks, may form in the thicker proximal and distal conical portions. However, in the balloon catheter of the embodiments of the present invention, the main orientation direction of the molecular orientation in the proximal and distal sections is circumferential. Therefore, even if a long-axis crack generated in the central section reaches the proximal and distal sections, it can prevent it from rapidly propagating beyond the proximal and distal conical sections to the proximal and distal conical sections. Thus, the long-axis crack can be contained within the straight tube section, preventing the formation of L-shaped cracks that would become circumferential cracks in the proximal and distal conical sections. As a result, the risk of balloon fragments remaining in the body due to circumferential or L-shaped cracks can be avoided. In this specification, the balloon catheter balloon is sometimes simply referred to as a "balloon".

[0045] Reference Figures 2-6 Instructions are provided regarding the use of balloon catheters. Figure 2 A side view of a balloon catheter according to one embodiment of the present invention. Figure 3 This is a top view showing a balloon with a crack along its long axis in one embodiment of the present invention. Figure 4 A top view showing an example of a circumferential crack forming in a balloon. Figure 5 A top view showing an example of an L-shaped crack forming in the balloon. Figure 6 This is a top view showing another example of an L-shaped crack forming in the balloon.

[0046] In this invention, the proximal side refers to the direction relative to the extension direction of the balloon catheter 1 or the long axis direction x of the axis 3, which is the direction on the side of the user's or surgeon's hand. The distal side refers to the opposite direction of the proximal side, that is, the direction on the side of the patient being treated. Besides the elongated component like the axis 3, it also has the same long axis direction x as the axis 3. The direction connecting the center of the balloon 2 and the point on the circumference of the balloon 2 in its expanded state in a section perpendicular to the long axis direction x is called radial y, and the direction along the outer periphery of the balloon 2 in its expanded state in a section perpendicular to the long axis direction x, i.e., the radial y section, is called circumferential z.

[0047] like Figure 2 As shown, the balloon catheter 1 has an axis 3 and a balloon 2 disposed distal to the axis 3. The balloon 2 has a long axis x, a radial axis y, and a circumferential axis z, and is preferably formed as a tube with openings on both the proximal and distal sides. The balloon 2 is formed of a resin with molecular orientation.

[0048] The balloon catheter 1 is configured to supply fluid to the interior of the balloon 2 via the shaft 3, and the expansion and contraction of the balloon 2 can be controlled using a pressure device (balloon depressurizer). The fluid can also be a pressurized fluid, such as a pump.

[0049] The balloon 2 has a straight tube 23, a proximal conical portion 22 located closer to the straight tube 23, and a distal conical portion 24 located more distal to the straight tube 23. The straight tube 23 preferably has approximately the same diameter along its long axis (x), while the proximal conical portion 22 and the distal conical portion 24 are preferably formed to narrow as they move away from the straight tube 23. Because the straight tube 23 has the largest diameter, when the balloon 2 is expanded in a lesion such as a stenosis, the straight tube 23 can make sufficient contact with the lesion, facilitating treatment such as lesion expansion. Furthermore, because the proximal conical portion 22 and the distal conical portion 24 have narrowed diameters, when the balloon 2 is contracted, the outer diameter of the proximal and distal ends of the balloon 2 can be reduced, thus reducing the height difference between the axis 3 and the balloon 2, making it easier to insert the balloon 2 into the body cavity.

[0050] The balloon 2 may also have a proximal sleeve portion 21 and a distal sleeve portion 25, which are closer to the proximal side of the conical portion 22 and more distal to the distal side of the conical portion 24, respectively. At least a portion of the proximal sleeve portion 21 and the distal sleeve portion 25 may be fixed to the shaft 3.

[0051] Along the long axis x, at position D0 where the proximal end of the straight tube 23 is set to 0%, and position D1 where the distal end is set to 100%. 100 At that time, from position D0 at 0% to position D at 10% 10 Molecular orientation in the proximal lateral region 23a, and from position D at 90% 90 To 100% position D 100 The principal orientation direction of the molecules in the distal lateral region 23e is the circumferential z-direction, from position D at 40%. 40 To 60% of position D 60 The molecular orientation in the central region 23c has a greater component in the long axis direction x than that in the proximal region 23a and the distal region 23e.

[0052] Because the long-axis component of molecular orientation in the central region 23c is greater than that in the proximal and distal regions 23a and 23e, even if the balloon 2 is damaged due to overpressure, a crack initiation in the long-axis x-direction can still be formed in the central region 23c. Therefore, as... Figure 3 As shown, the internal pressure can be released by generating a crack in the long axis x direction in the central interval 23c, thus preventing... Figure 4 A circumferential z-shaped crack as shown in the figure. Figure 5 As shown, the crack in the long axis direction x generated at the end reaches the conical part and forms an L-shaped crack.

[0053] Furthermore, if a crack in the long axis direction x generated in the central interval 23c rapidly moves along the long axis direction x across the proximal interval 23a and the distal interval 23e, there is a concern that it may cause circumferential z-shaped cracks in the proximal conical portion 22 and the distal conical portion 24, forming... Figure 6 The crack is an L-shaped crack as shown. However, because the main orientation direction of the molecules in the proximal side section 23a and the distal side section 23e is circumferential z, even if a crack in the long axis direction x generated in the central section 23c reaches the proximal side section 23a and the distal side section 23e, it can prevent it from crossing the proximal side section 23a and the distal side section 23e and spreading to the proximal side conical section 22 and the distal side conical section 24. As a result, the crack in the long axis direction x can be kept within the straight tube section 23, and the formation of L-shaped cracks that become circumferential cracks in the proximal side conical section 22 and the distal side conical section 24, which have relatively thick walls, can be prevented.

[0054] Reference Figures 7-10 The method for determining the molecular orientation of the straight tube section 23 is explained. Figure 7 The figure illustrates a method for preparing a sample to determine the molecular orientation of the straight tube portion 23 of a balloon 2 according to one embodiment of the present invention. Figure 8 This example illustrates a contour map obtained by measuring the balloon of one embodiment of the present invention using a two-dimensional birefringence evaluation system manufactured by Photonic Lattice. Figure 9 and Figure 10 Examples of graphs showing the phase difference obtained as a result of line analysis along the major axis and examples of graphs showing the axis orientation.

[0055] The molecular orientation of the straight tube section 23 can be determined using a two-dimensional birefringence evaluation system manufactured by Photonic Lattice for rectangular samples of the straight tube section 23. For example... Figure 7 As shown, the rectangular sample is obtained by cutting off the proximal conical portion 22 and the distal conical portion 24 from the balloon 2 along the first cutting line S1, and then cutting the resulting straight tube portion 23 along the second cutting line S2 in the long axis direction x.

[0056] exist Figure 8 The image shows an example of a contour map obtained as a result of measurement. Figure 9 and Figure 10 Examples of graphs showing the phase difference and axis orientation obtained from line analysis along the major axis direction x are shown below. In each graph, the left end corresponds to the 0% position D0 of the straight tube section 23, and the right end corresponds to the 100% position D of the straight tube section 23. 100 Contour maps use color contrast to represent the magnitude of phase difference, allowing for visual confirmation of orientation. Furthermore, the intensity of orientation can be specifically obtained from the phase difference chart, and the orientation direction from the axis orientation chart.

[0057] The principal orientation direction can be determined from an axial orientation chart. Within a specified interval, if the length of the line contained in the 80°–100° range is longer than the length of the lines contained in the 0°–10° and 170°–180° ranges, then the principal orientation direction in that interval is the circumferential z-axis. Conversely, if the length of the line contained in the 80°–100° range is shorter than the length of the lines contained in the 0°–10° and 170°–180° ranges, then the principal orientation direction in that interval is the major axis x-axis. The intensity of the orientation component can be obtained from a phase difference chart. Regarding which of the proximal, intermediate, and distal intervals 23a, 23c, and 23e has a greater component in the long axis direction (x), the lengths of the lines contained within the 0°–10° and 170°–180° ranges in the axial orientation chart are compared. The interval with the longest contained line length is determined to be the interval with a greater component in the long axis direction (x). For example, Figures 8-10 As shown in the chart representing the measurement results, the predominant orientation direction of molecules in the proximal region 23a and distal region 23e, according to the axial orientation diagram, is circumferential (z). Furthermore, the predominant orientation direction of molecules in the central region 23c is the long axis (x), and the long axis (x) component of the molecular orientation in the central region 23c is greater than that in the proximal and distal regions 23a and 23e. Additionally, according to the phase difference diagram, the orientation intensity decreases from the central region 23c towards the proximal and distal sides, meaning the long axis (x) component of the molecular orientation decreases.

[0058] The preferred orientation direction of the molecules in the central region 23c is the long axis direction x. By having the long axis direction x as the main orientation direction, even if the balloon 2 is damaged due to overpressure, it is easier to form the initiation of a crack in the long axis direction x in the central region 23c. Therefore, internal pressure can be released by generating a crack in the long axis direction x in the central region 23c, thus making it easier to prevent circumferential z-shaped cracks.

[0059] The composition along the long axis x of the preferred molecular orientation gradually decreases from the central interval 23c towards the 0% position D0, and from the central interval 23c towards the 100% position D... 100 Gradually decreasing. This allows the composition along the long axis (x) of the molecular orientation to be most abundant in the central region 23c. It becomes easier to initiate cracks along the long axis (x) in the central region 23c, and internal pressure can be released by initiating cracks along the long axis (x) in the central region 23c, thus making it easier to prevent cracks in the circumferential (z) direction. The gradual decrease in the composition along the long axis (x) of the molecular orientation from the central region 23c towards the 0% position D0 means, for example, at the 40% position D... 40When comparing the composition of the long axis x of the molecular orientation at positions D0 (20% and 0%), the composition can be decreased sequentially. Furthermore, the composition of the long axis x of the molecular orientation decreases from the central region 23c towards position D0 (100%). 100 Gradual reduction means, for example, at position D, 60%. 60 80% position and 100% position D 100 When comparing the components along the long axis (x) of the molecular orientation, the components decrease sequentially. It's not necessary for the components along the long axis (x) to decrease continuously from the central region 23c towards the proximal or distal side. Alternatively, the components along the long axis (x) of the molecular orientation can decrease continuously from the central region 23c towards the proximal or distal side.

[0060] At position D, which will be 10% 10 To 40% of position D 40 The interval is set as the proximal middle interval 23b, from position D at 60%. 60 To 90% of position D 90 When the interval is set as the distal side intermediate interval 23d, it is preferable that the principal orientation direction of the molecular orientation changes from the long axis direction x to the circumferential direction z in the proximal side intermediate interval 23b and the distal side intermediate interval 23d. By changing the principal orientation direction of the molecular orientation from the long axis direction x to the circumferential direction z in the proximal side intermediate interval 23b and the distal side intermediate interval 23d, it is easier to stop the development of cracks in the long axis direction x generated in the central interval 23c in the proximal side intermediate interval 23b and the distal side intermediate interval 23d, thus making it easier for the crack to be contained within the straight tube section 23. The change in the principal orientation direction of the molecular orientation can be determined from a diagram of the axial orientation. Figure 10 In the example shown, it can be seen that in the proximal mid-interval 23b and the distal mid-interval 23d, the main orientation direction of the molecular orientation changes from the long axis direction x to the circumferential direction z.

[0061] The membrane thickness of the balloon 2 in the central region 23c is preferably thinner than that of the balloon 2 in the proximal region 23a and the distal region 23e. Because the membrane thickness in the central region 23c is thinner, it becomes easier to form the initiation point of a crack in the long axis direction x in the central region 23c, thus making it easier to confine the location of the crack in the long axis direction x to the central region 23c.

[0062] Although not illustrated, balloon 2 may also have a protrusion that extends radially outward (y) and along the long axis (x) from the outer surface. The protrusion is preferably arranged in a dotted, linear, or mesh pattern on the outer surface of balloon 2. By providing the protrusion on the outer surface of balloon 2, a scratching function can be imparted to the protrusion, causing cracks in the calcified stenosis during angiogenesis and thus dilating it. Furthermore, it also allows for increased strength of balloon 2 and suppression of over-expansion during pressurization.

[0063] Examples of materials constituting the balloon 2 include polyolefin resins such as polyethylene, polypropylene, and ethylene-propylene copolymer; polyester resins such as polyethylene terephthalate and polyester elastomers; polyurethane resins such as polyurethane and polyurethane elastomers; polyphenylene sulfide resins; polyamide resins such as polyamide elastomers; fluorinated resins; silicone resins; and natural rubber such as latex rubber. Only one type may be used, or two or more types may be used in combination. Polyamide resins, polyester resins, and polyurethane resins are preferred. In particular, from the viewpoint of the balloon 2's thin-film properties and flexibility, elastomer resins are preferred. For example, among polyamide resins, nylon 12 and nylon 11 are suitable as resins constituting the balloon 2, and nylon 12 is more preferred from the perspective of easier shaping during blow molding. Furthermore, from the viewpoint of the balloon 2's thin-film properties and flexibility, polyamide elastomers such as polyether ester amide elastomers and polyamide ether elastomers are preferred. Among these considerations, considering the high yield strength and good dimensional stability of the balloon 2, polyether ester amide elastomer is preferred.

[0064] The balloon 2 can be manufactured by biaxial stretching blow molding, in which a preform made of the above-described material is placed in a mold. A preferred method for manufacturing the balloon 2 is described in section "3. Method for manufacturing the balloon catheter".

[0065] 2. Balloon catheter

[0066] The balloon catheter of the present invention includes the balloon described above for balloon catheters. The balloon catheter of embodiments of the present invention can be referred to in section "1. Balloon for balloon catheters" above. Figure 2 To understand.

[0067] Examples of materials constituting the shaft 3 include polyamide resins, polyester resins, polyurethane resins, polyolefin resins, fluorinated resins, vinyl chloride resins, silicone resins, and natural rubber. Only one type may be used, or two or more may be used in combination. Preferably, the material constituting the shaft 3 is at least one of polyamide resins, polyolefin resins, and fluorinated resins. This improves the slipperiness of the shaft 3 surface and enhances the insertion patency of the balloon catheter 1 within the body cavity.

[0068] Examples of joining balloon 2 and shaft 3 include bonding with adhesive, fusion bonding, and installing a ring-shaped component at the overlapping portion of balloon 2 and shaft 3 and then tightening it. Preferably, balloon 2 and shaft 3 are joined by fusion bonding. By fusing balloon 2 and shaft 3, the joint between balloon 2 and shaft 3 is less likely to disintegrate even with repeated expansion and contraction of balloon 2, thus easily improving the joint strength between balloon 2 and shaft 3.

[0069] like Figure 2 As shown, in the balloon catheter 1, a hub 4 can also be provided proximal to the shaft 3. Preferably, the hub 4 has a fluid injection section 6 that communicates with the flow path of fluid supplied to the interior of the balloon 2. Additionally, the hub 4 may also have a guidewire insertion section 5 that communicates with the guidewire insertion path. With this structure, it is easy to perform operations such as supplying fluid to the interior of the balloon 2 to inflate and deflate the balloon 2, and to deliver the balloon catheter 1 to the treatment site along the guidewire. Figure 2 The diagram shows a so-called over-the-wire type balloon catheter 1 in which the guidewire is inserted from the distal side to the proximal side of the shaft 3. However, the balloon 2 of the embodiment of the present invention can also be applied to a so-called quick-exchange type balloon catheter in which the guidewire is inserted midway from the distal side to the proximal side of the shaft 3.

[0070] The connection between the shaft 3 and the hub 4 can be achieved, for example, by bonding with an adhesive or by fusion. Preferably, the shaft 3 and the hub 4 are joined by adhesive. By bonding the shaft 3 and the hub 4, the durability of the balloon catheter 1 can be improved, for example, when the shaft 3 is made of a highly flexible material and the hub 4 is made of a highly rigid material, or when the materials constituting the shaft 3 and the hub 4 are different.

[0071] 3. Manufacturing method of balloon catheter

[0072] One embodiment of the method for manufacturing the balloon catheter of the present invention is characterized by comprising: a step of preparing a preform made of resin; a step of preparing a mold having an inner cavity, the inner wall of which has a straight tube portion, a proximal tapered portion located closer to the position of the straight tube portion, and a distal tapered portion located farther from the position of the straight tube portion; a step of placing the preform within the mold; a first extension step of extending the preform along its long axis beyond a necking region of the stress-strain curve while heating the mold; and a second extension step of further extending the preform beyond the necking region along its long axis while heating the mold, after the first extension step, under a condition where the internal pressure of the preform is higher than that of the first extension step. In many resins, in Figure 1In the stress-strain curve shown, in the region of elastic deformation up to the yield point B, stress acts as elongation of the molecular chains in a bent state. After the yield point B, plastic deformation begins, with the molecular chains attracting each other and shifting in the shear direction. There are also resins that show a phenomenon where, once the molecular chains begin to shift, they relax and the stress decreases to the lower yield point L. A region exhibiting transverse stress is then temporarily observed; this region is usually called the necking region R. n In the constricted region R n In the process, the molecular chains shift due to strain, thus exhibiting constant stress. However, if the strain exceeds a specified limit, the molecular chains approach each other and become tightly oriented, generating strong intermolecular forces between the chains. Therefore, above the specified strain, that is, beyond the necking region R... n In the region, the stress increases to the right. In the first extension process, the preform is first extended along its long axis beyond the necking region R. n In the subsequent second extension process, the extension extends beyond the necking region R. n The preform is further extended along the long axis under high internal pressure, thereby enabling the manufacture of a balloon catheter with a balloon for balloon catheters. The main orientation direction of the molecular orientation in the proximal and distal regions of the balloon catheter is circumferential, and the long axis component of the molecular orientation in the central region is greater than that in the proximal and distal regions.

[0073] Reference Figures 11-14 The manufacturing method described above will be explained. Figure 11 A cross-sectional view showing the state in which the preform is arranged in a mold according to one embodiment of the present invention. Figure 12 This is a cross-sectional view showing a state in which the preform is extended along the long axis direction beyond the necking region of the stress-strain curve during the first extension process of one embodiment of the present invention, while the mold is heated. Figure 13 This is a cross-sectional view showing a state in which, during the second extension process of one embodiment of the present invention, the mold is heated while the preform, which extends beyond the necking region, is further extended along the long axis under a condition where the internal pressure of the preform is higher than that of the first extension process. Figure 14 A cross-sectional view showing the state after the second extension process is completed.

[0074] First, a preform 70 made of resin is prepared. The preform 70 is a cylindrical component with an inner cavity 71, which can be manufactured, for example, by extrusion molding. The preform 70 has one end and another end, and extends along the long axis direction x from one end to the other end.

[0075] Although not illustrated, the cross-sectional shape of the preform 70 in the radial direction (y) perpendicular to the major axis (x) can also be approximately the same in the major axis (x). Alternatively, as... Figure 11 As shown, the cross-sectional shape of the preform 70 in the radial direction y can also vary depending on its position in the major axis direction x. The outer diameter of a portion of the preform 70, such as the portion corresponding to the straight tube portion 23, the proximal conical portion 22, and the distal conical portion 24 of the balloon 2, can also be larger than that of other portions.

[0076] The resin used to form the preform 70 can be described in the description of the resin used to form the balloon 2 as described in the section "1. Balloon for balloon catheter".

[0077] Next, a mold 80 is prepared. The mold 80 has an inner cavity 88. The inner wall surface forming the inner cavity 88 has a straight tube portion 83, a proximal tapered portion 82 located closer to the position side than the straight tube portion 83, and a distal tapered portion 84 located farther from the position side than the straight tube portion 83. The inner wall surface forming the inner cavity 88 of the mold 80 may also have a proximal sleeve portion 81 located closer to the position side than the proximal tapered portion 82 and a distal sleeve portion 85 located farther from the position side than the distal tapered portion 84.

[0078] The mold 80 can be formed from a single component or from multiple components. For example, the mold 80 can be formed from multiple split bodies, and the multiple mold components can also be formed to be divisible in the long axis direction x.

[0079] like Figure 11 As shown, the preform 70 is placed in the inner cavity 88 of the mold 80. In this case, if the preform 70 has a portion with a larger outer diameter, specifically the portion corresponding to the straight tube portion 23, the proximal conical portion 22, and the distal conical portion 24 of the balloon 2, this portion is preferably located in the straight tube portion 83 of the mold 80. This facilitates the formation of the straight tube portion 23, the proximal conical portion 22, and the distal conical portion 24 of the balloon 2.

[0080] like Figure 12 As shown, a first extending process is performed where the mold 80 is heated while the preform 70 is extended along its long axis x. At this time, the preform 70 extends beyond the necking region R of the stress-strain curve of the resin constituting the preform 70. n Neck constriction region R n As described above, this region shows the transverse stress beyond the yield point B and the lower yield point L, where the resin molecular chains, which have begun plastic deformation, shift due to stress. In the first stretching process, the preform 70 is stretched beyond the necking region R. n It is important.

[0081] Because the internal pressure of the preform 70 in the first stretching process is lower than that in the second stretching process, the pressure increases beyond the necking region R. nUnder the aforementioned conditions, the preform 70 can extend along the long axis x while its extension in the circumferential z direction is suppressed.

[0082] In cases where a preform 70 is prepared by extrusion molding and is extended to a certain extent along its long axis x, in the first extension process, the preform 70 is extended along its long axis x beyond the necking region R. n The amount varies depending on the preparation conditions of the preform 70 in extrusion molding, etc. That is, if the preform 70 has already been extended to a certain extent along the long axis direction x in extrusion molding, etc., even if the amount of extension of the preform 70 along the long axis direction x is reduced accordingly in the first extension process, it is still possible to exceed the necking region R. n .

[0083] like Figure 13 As shown, after the first stretching process is completed, a second stretching process is performed. In this second stretching process, the mold 80 is heated while the stretching extends beyond the necking region R. n The preform 70 is further extended along its long axis x under a higher internal pressure than in the first extending process described above. In the second extending process, beyond the necking region R... n Subsequently, the resin, with its molecular chains closely aligned and oriented, is further extended along its long axis x. Compared to the first extending process, the internal pressure of the preform 70 is higher in the second extending process, thereby extending the pressure beyond the necking region R. n In the first extension process up to this point, the circumferential extension of the preform 70 is suppressed, while the preform 70 extends along the long axis direction x, but beyond the necking region R... n In the second extension process, the blank 70 also extends in the circumferential direction z, and at the same time extends along the long axis direction x.

[0084] In this way, we can obtain Figure 14 The balloon 2 shown above. By performing the first and second extension processes described above, it is possible to form a balloon 2 in which the main orientation direction of the molecular orientation in the proximal region 23a and the distal region 23e is circumferential z, and the component of the long axis direction x of the molecular orientation in the central region 23c is greater than that in the proximal region 23a and the distal region 23e.

[0085] Figure 1 The stress-strain curves shown clearly illustrate the necking region R under constant stress. n However, depending on the resin, there may be cases where the stress-constant region is short or not completely flat. In such cases, once the stress-strain curve exceeds the yield point B, the initial point where the differential coefficient of the stress-strain curve becomes more than 5% of the average rate of change up to the yield point B is set as the point exceeding the necking region R.n The strain is such that the first extension process is carried out until the strain exceeds that strain.

[0086] The heating temperatures in the first and second extension processes can be set near the glass transition temperature of the resin constituting the bulb 2. A known heater or similar device can be appropriately used as the heating unit for the mold 80.

[0087] In the first extension process, it is preferable to introduce fluid into the inner cavity 71 of the preform 70 to pressurize the inside of the preform 70, and the pressure at this time is preferably 3 MPa or less. Alternatively, the inner cavity 71 of the preform 70 may be under the same pressure as the outer side of the preform 70, that is, the inner cavity 71 of the preform 70 may not be pressurized.

[0088] In the second extension process, it is preferable to introduce fluid into the inner cavity 71 of the preform 70 to pressurize the interior of the preform 70. The pressure at this time is higher than the pressure applied to the interior of the preform 70 in the first extension process, for example, preferably 1 MPa or more, more preferably 1.5 MPa or more, and even more preferably 2 MPa or more. Furthermore, it is preferably 5 MPa or less, more preferably 4.5 MPa or less, even more preferably 4 MPa or less, and may also be 3 MPa or less.

[0089] Preferably, the preform 70 is not pressurized in the first stretching process, and in the second stretching process, pressure is applied beyond the necking region R. n Then, pressure is applied to the preform 70. As a result, it is easier to form a balloon 2 with the main orientation direction of the molecular orientation in the proximal side region 23a and the molecular orientation in the distal side region 23e being circumferential z, and the molecular orientation in the central region 23c having a larger component of the long axis direction x than the molecular orientation in the proximal side region 23a and the distal side region 23e.

[0090] When heating the mold 80, it is preferable to heat it at the center of the straight tube portion 83 of the mold 80 to achieve the highest temperature. This makes it easier to form a balloon 2 in which the molecular orientation along the long axis x of the central region 23c of the balloon 2 has a higher proportion of the molecular orientation along the long axis x than that in the proximal region 23a and the distal region 23e. It also makes it easier to form a balloon 2 in which the membrane thickness of the central region 23c is thinner than that in the proximal region 23a and the distal region 23e.

[0091] This application claims a priority interest based on Japanese Patent Application No. 2021-79672, filed on May 10, 2021. The entire contents of the description of Japanese Patent Application No. 2021-79672, filed on May 10, 2021, are incorporated herein by reference.

[0092] Example

[0093] The present invention will now be described with reference to embodiments. The present invention is not limited to the embodiments described below, and may be implemented with appropriate modifications that conform to the spirit described above and below, all of which are included within the technical scope of the present invention.

[0094] Example 1

[0095] A preform was prepared by extruding polyamide 12. The preform was placed in a mold, and while the mold was heated to 70°C, an internal pressure of 2 MPa was applied to the preform to extend it along its long axis beyond 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 preform to extend it along its long axis, thus obtaining a balloon.

[0096] Five balloons were fabricated using the same method. For each balloon, as follows: Figure 7 As shown, the proximal and distal conical portions were removed to obtain a cylindrical straight tube. The cylindrical straight tube was then cut along the long axis to obtain rectangular samples 1-5. The molecular orientation of samples 1-5 was determined using a Photonic Lattice WPA-100 two-dimensional birefringence evaluation system. The results are shown in... Figures 15-17 In. Figures 15-17 In the image, data from samples 1 to 5 are displayed from top to bottom. Regardless of the balloon, the dominant orientation of molecular orientation in the central region of the straight tube is consistently along the long axis, while the dominant orientation of molecular orientation in the proximal and distal regions of the straight tube is circumferential.

[0097] For the five balloons mentioned above, the membrane thickness of the proximal region (1), proximal mid-section (2), central region (3), distal mid-section (4), and distal region (5) was measured using a Mitutoyo SPM2-25MX spline micrometer. The results are shown in... Figure 18 In this study, regardless of the type of balloon, a balloon with the thinnest membrane thickness in the central region and a thicker membrane thickness from the central region toward the proximal and distal sides can be consistently obtained.

[0098] Thirty balloons were fabricated using the same method as in Example 1. Internal pressure was continuously applied to these 30 balloons until they ruptured. After rupture, the state of the cracks was observed to confirm the presence or absence of circumferential cracks. No circumferential cracks were generated in any of the balloons.

[0099] Comparative Example 1

[0100] A preform was prepared in the same manner as in Example 1. The preform was placed in the 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 cavity of the preform to extend it along its long axis, thus obtaining a balloon.

[0101] Five balloons were fabricated using the same method. For each balloon, as follows: Figure 7 As shown, the proximal and distal conical portions were removed to obtain a cylindrical straight tube. The cylindrical straight tube was then cut along the long axis to obtain rectangular samples 6–10. The molecular orientation of samples 6–10 was determined using a Photonic Lattice WPA-100 two-dimensional birefringence evaluation system. The results are shown in… Figures 19-21 In. Figures 19-21 In the image, from top to bottom, are the data for samples 6 to 10. The orientation varies depending on the balloon; not all balloons exhibit a greater proportion of molecular orientation along the long axis in the central region of the straight tube compared to the proximal and distal regions.

[0102] For the five balloons mentioned above, the membrane thickness of the proximal region (1), proximal mid-section (2), central region (3), distal mid-section (4), and distal region (5) was measured using a Mitutoyo SPM2-25MX spline micrometer. The results are shown in... Figure 22 The membrane thickness along the long axis deviates depending on the balloon type, indicating that the method in Comparative Example 1 cannot control the membrane thickness along the long axis.

[0103] Thirty balloons were fabricated using the same method as in Comparative Example 1. Internal pressure was continuously applied to these 30 balloons until they ruptured. After rupture, the state of the cracks was observed to confirm the presence or absence of circumferential cracks. Circumferential cracks were observed in three of the 30 balloons.

[0104] Explanation of reference numerals in the attached figures

[0105] 1…Balloon catheter; 2…Balloon; 3…Shaft; 4…Gathering device; 5…Guidewire insertion section; 6…Fluid injection section; 21…Proximal sleeve section; 22…Proximal tapered section; 23…Straight tube section; 23a…Proximal interval; 23b…Proximal intermediate interval; 23c…Central interval; 23d…Distal intermediate interval; 23e…Distal interval; 24…Distal tapered section; 25…Distal sleeve section; 70…Preform; 71…Inner cavity of preform; 80…Mold; 81…Proximal sleeve section of mold; 82…Proximal tapered section of mold; 83…Straight tube section of mold; 84…Distal tapered section of mold; 85…Distal sleeve section of mold; 88…Inner cavity of mold; B…Yield point; D0…0% position; D 10…10% of the position; D 40 …40% of the position; D 60 …60% of the position; D 90 …90% of the position; D 100 …100% position; L…lower yield point; R… n …neck region; S1…first cutting line; S2…second cutting line; x…major axis direction; y…radial direction; z…circumferential direction.

Claims

1. A balloon for a balloon catheter, characterized in that, The balloon used in the balloon catheter is a balloon formed from resin with molecular orientation. The balloon has a long axis direction and a circumferential direction along the outer periphery of the balloon in its expanded state in a cross section perpendicular to the long axis direction. The balloon has a straight tube, a proximal conical portion located closer to the position of the straight tube, and a distal conical portion located more distal to the position of the straight tube. In the long axis direction, when the proximal end of the straight tube is set to 0% and the distal end is set to 100%,... The principal orientation direction of the molecular orientation in the proximal region from 0% to 10% and the distal region from 90% to 100% is the circumferential direction. The long axis component of the molecular orientation in the central interval from the 40% position to the 60% position is greater than that in the proximal and distal intervals.

2. The balloon for balloon catheters according to claim 1, characterized in that, The main orientation direction of the molecular orientation in the central region is the direction of the long axis.

3. The balloon for balloon catheters according to claim 1 or 2, characterized in that, The long axis component of the molecular orientation gradually decreases from the central interval toward the 0% position and from the central interval toward the 100% position.

4. The balloon catheter according to claim 2 or 3, characterized in that, When the interval from 10% to 40% is defined as the proximal median interval, and the interval from 60% to 90% is defined as the distal median interval, In the proximal mid-section and the distal mid-section, the main orientation direction of the molecular orientation changes from the long axis direction to the circumferential direction.

5. The balloon catheter according to any one of claims 1 to 4, characterized in that, The membrane thickness of the balloon in the central region is thinner than that in the proximal and distal regions.

6. A balloon catheter, characterized in that, The balloon is equipped with any one of claims 1 to 5.

7. A method for manufacturing a balloon catheter, which is the method for manufacturing the balloon catheter according to claim 6. The method for manufacturing the balloon catheter is characterized by comprising: The steps for preparing a preform made of resin; The step of preparing a mold, wherein the mold has an inner cavity, and the inner wall surface forming the inner cavity has a straight tube portion, a proximal conical portion located closer to the position side than the straight tube portion, and a distal conical portion located farther from the position side than the straight tube portion; The step of placing the preform into the mold; A first extension process in which the mold is heated while the preform is extended along the long axis to a point beyond the necking region of the stress-strain curve. as well as While heating the mold, a second extension process is performed after the first extension process, in which the preform, which extends beyond the necking region, is further extended along the long axis under a condition where the internal pressure of the preform is higher than that of the first extension process.

8. The method for manufacturing a balloon catheter according to claim 7, characterized in that, In the first stretching step, the preform is pressurized at a lower pressure than in the second stretching step, and in the second stretching step, the preform is further pressurized after it has passed the necking region.

9. The method for manufacturing a balloon catheter according to claim 7 or 8, characterized in that, The step includes heating the mold in such a way that the central part of the straight tube section of the mold reaches the highest temperature.

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