Method for manufacturing balloons for balloon catheters

Abstract

To provide a manufacturing method of a balloon for a balloon catheter that can easily suppress a crack in a circumferential direction of a balloon that is acquired.SOLUTION: A manufacturing method of a balloon for a balloon catheter includes: a step for preparing a parison 30; a step for preparing a mold; a step for arranging the parison 30 in a lumen of the mold; a first stretching step for heating a central section 33 at a temperature of a resin glass transition temperature Tg or higher and a glass transition temperature Tg+30°C or lower, and stretching the central section 33 while keeping a first section 31 and a second section 32 at a temperature lower than the glass transition temperature Tg; and a second stretching step for biaxially stretching an enlarged diameter part 30E in a longitudinal axis direction x and a radial direction y while heating the enlarged diameter part at a temperature of the glass transition temperature Tg or higher and the glass transition temperature Tg+30°C or lower after the first stretching step.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] This invention relates to a method for manufacturing a balloon made of resin used in balloon catheters. [Background technology]

[0002] Angioplasty, a minimally invasive therapy that involves inserting a balloon catheter into a narrowed blood vessel and expanding the balloon to ensure blood flow, is widely performed. 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 narrowing in the shunt area used for dialysis. The balloon used in a balloon catheter usually has a cylindrical shape that tapers at the distal and proximal ends, and the cylindrical portion with the largest diameter expands the blood vessel.

[0003] When expanding a stenotic area with a balloon catheter, the appropriate expansion pressure is applied to the balloon according to the target area. However, if the balloon becomes overpressurized due to unexpected internal pressure during the procedure, it can rupture. In this case, if the balloon ruptures circumferentially, there is a serious risk that fragments of the balloon distal to the rupture site may remain in the body. Therefore, even if the balloon ruptures, a technique is needed to ensure that the rupture is longitudinal rather than circumferential.

[0004] For example, Patent Documents 1 to 3 disclose balloons in which pressure resistance has been improved by controlling the molecular orientation of the resin constituting the balloon. These documents disclose a method for manufacturing balloons in which, when stretching the parison longitudinally followed by radial stretching, the radial stretching ratio is set to be below a predetermined level relative to the longitudinal stretching ratio, a mold is moved in accordance with the change in stress applied to the parison in the axial direction, and a balloon having a desired orientation is obtained by controlling the stretching speed.

[0005] Furthermore, Patent Document 4 discloses that the membrane body of a balloon has an intermediate layer containing a non-elastomer and an outer and inner layer containing elastomers arranged on the outer and inner surfaces of the intermediate layer, and that by setting the average thickness of the intermediate layer to 30% to 70% of the average thickness of the entire balloon, compliance is improved and a balloon with a balance between pressure resistance and passage performance is obtained. A method for manufacturing such a balloon is disclosed, in which a three-layer parison is formed by co-extrusion, the parison is stretched axially at a temperature from the secondary transition temperature to the primary transition temperature of the non-elastomer and elastomer, then expanded radially and biaxially stretched, and finally the parison is cooled to below the biaxial transition temperature to shrink and form a balloon. [Prior art documents] [Patent Documents]

[0006] [Patent Document 1] Japanese Patent Publication No. 2004-298354 [Patent Document 2] Japanese Patent Application Publication No. 9-38195 [Patent Document 3] International Publication No. 2014 / 141382 [Patent Document 4] International Publication No. 2013 / 145479 [Overview of the project] [Problems that the invention aims to solve]

[0007] In procedures using balloon catheters, if the balloon ruptures inside the body, there is a serious risk that fragments of the balloon distal to the rupture site may remain inside the body if the balloon ruptures circumferentially. Conventional balloons, as described above, had room for improvement in preventing circumferential rupture.

[0008] In view of the above circumstances, the present invention aims to provide a method for manufacturing a balloon for a balloon catheter that easily suppresses circumferential cracking of the balloon. [Means for solving the problem]

[0009] One embodiment of the method for manufacturing a balloon for a balloon catheter according to the present invention, which has been able to solve the above problems, is as follows. [1] A parison made of resin, extending in the longitudinal direction and having a lumen, comprising: a first sleeve portion, a second sleeve portion, and an enlarged diameter portion located between the first and second sleeve portions in the longitudinal direction and having an inner diameter greater than or equal to the inner diameter of the first sleeve portion and greater than or equal to the inner diameter of the second sleeve portion, wherein when the first end of the enlarged diameter portion is at the 0% position and the second end is at the 100% position in the longitudinal direction, the parison has a central section from the 45% position to the 55% position, a first section from the 0% position to the 10% position, and a second section from the 90% position to the 100% position; a mold extending in the longitudinal direction and having a lumen, a parison placed in the lumen of the mold, and the central section having the glass transition temperature Tg of the resin A method for manufacturing a balloon for a balloon catheter, comprising: a first stretching step of stretching at least the central section of the enlarged diameter portion while heating at a temperature above the glass transition temperature Tg + 30°C and maintaining the first and second sections at a temperature below the glass transition temperature Tg of the resin; and a second stretching step after the first stretching step of biaxially stretching the enlarged diameter portion in the longitudinal axis direction and the radial direction of the enlarged diameter portion while heating the enlarged diameter portion at a temperature above the glass transition temperature Tg and below the glass transition temperature Tg + 30°C, wherein in the stress-strain curve of the resin at room temperature, the stretching of at least the central section of the enlarged diameter portion in the first stretching step exceeds the strain at point A where the differential coefficient of stress becomes 5% or more after the strain exceeds the yield point, relative to the average rate of change of stress from zero to the yield point.

[0010] In the first stretching step, the central section of the parison is heated to a temperature above the glass transition temperature Tg of the resin and below the glass transition temperature Tg + 30°C, while the first and second sections of the parison are kept at a temperature below the glass transition temperature Tg of the resin. This allows at least the central section of the enlarged diameter portion of the parison to be stretched in the longitudinal direction during the first stretching step. At this time, in the stress-strain curve of the resin at room temperature, the central section is stretched until it exceeds the strain at point A where the differential coefficient of stress is 5% or more after the strain exceeds the yield point, relative to the average rate of change of stress from zero to the yield point. The enlarged diameter portion that has undergone the first stretching step is then biaxially stretched in the second stretching step, thereby producing a balloon with a molecular orientation of the resin in the longitudinal direction in the central section. As a result, even if the balloon for the balloon catheter is damaged due to overpressure, etc., a longitudinal crack can be initiated in the central section, and the internal pressure can be released by the longitudinal crack that occurs in the central section, thus preventing circumferential cracking. As a result, the risk of balloon fragments remaining in the body can be avoided, making it possible to manufacture balloon catheter balloons that enable safe procedures.

[0011] The method for manufacturing a balloon for a balloon catheter according to an embodiment of the present invention is preferably one of the following [2] to

[10] . [2] A method for manufacturing a balloon for a balloon catheter according to [1], wherein in the first stretching step, the internal pressure of the enlarged diameter portion is maintained at 0 bar or more and 30 bar or less while stretching at least the central section of the enlarged diameter portion, and in the second stretching step, the enlarged diameter portion is biaxially stretched by applying an internal pressure to the enlarged diameter portion that is higher than the internal pressure applied to the enlarged diameter portion in the first stretching step. [3] In the first stretching step, the first section and the second section are stretched so as not to exceed the strain at point A. [1] or [2] The method for manufacturing a balloon for a balloon catheter. [4] The stretching speed in the first stretching step is slower than the stretching speed in the second stretching step. A method for manufacturing a balloon for a balloon catheter according to any one of [1] to [3]. [5] The step of placing the parison in the lumen of the mold is performed before the first stretching step. [1] to [4] The method for manufacturing a balloon for a balloon catheter. [6] The method for manufacturing a balloon for a balloon catheter according to any one of [1] to [4], wherein the step of placing the parison in the lumen of the mold is performed after the first stretching step and before the second stretching step. [7] A method for manufacturing a balloon for a balloon catheter according to any one of [1] to [6], further comprising the step of bringing the enlarged diameter portion to a temperature of the crystallization temperature Tc or higher of the resin after the second stretching step. [8] A method for manufacturing a balloon for a balloon catheter according to any one of [1] to [7], wherein in the first stretching step, the first section and the second section are heated at a temperature less than the glass transition temperature Tg of the resin. [9] A method for manufacturing a balloon for a balloon catheter according to any one of [1] to [8], wherein the mold has a first end region, a second end region, and a central region located between the first end region and the second end region in the longitudinal direction, and the first end region, the second end region and the central region can each be heated independently.

[10] The first end region, the second end region, and the central region are each composed of separate members, and the mold is formed by connecting the separate members in the longitudinal direction. [9] A method for manufacturing a balloon for a balloon catheter. [Effects of the Invention]

[0012] According to the method for manufacturing the balloon for the balloon catheter, the balloon can be manufactured such that the obtained balloon has a molecular orientation of the resin in the longitudinal axis direction in the central section. Thereby, even when the balloon for the balloon catheter is broken due to overpressure or the like, a crack in the longitudinal axis direction can be created in the central section, and the internal pressure can be released by the longitudinal axis direction crack generated in the central section, so that a circumferential crack can be prevented. As a result, the risk that the broken pieces of the balloon for the balloon catheter remain in the body can be avoided, and it becomes possible to manufacture a balloon for a balloon catheter that enables a safe treatment.

Brief Description of the Drawings

[0013] [Figure 1] It shows a plan view of a balloon catheter according to an embodiment of the present invention. [Figure 2] It shows a cross-sectional view in the longitudinal axis direction of a parison according to an embodiment of the present invention. [Figure 3] It shows a stress-strain curve of a polyester resin. [Figure 4] It shows a stress-strain curve of a polyamide resin. [Figure 5] It shows a cross-sectional view in the longitudinal axis direction of a mold according to an embodiment of the present invention. [Figure 6] It shows a schematic diagram of the first stretching step. [Figure 7] It shows a cross-sectional view in the longitudinal axis direction of the parison and the mold at the start point of the second stretching step. [Figure 8] It shows another example of a cross-sectional view in the longitudinal axis direction of the parison and the mold at the start point of the second stretching step. [Figure 9] It shows a cross-sectional view in the longitudinal axis direction of the parison and the mold at the end point of the second stretching step. [Figure 10] It shows another example of a cross-sectional view in the longitudinal axis direction of a mold according to an embodiment of the present invention.

Embodiments for Carrying Out the Invention

[0014] The present invention will be described below based on embodiments, but the present invention is not limited by the embodiments described below, and it is certainly possible to implement it with appropriate modifications within the scope that is consistent with the spirit of the preceding and following descriptions, and all such modifications are included within the technical scope of the present invention. In addition, hatching and component reference numerals may be omitted in the drawings for convenience, in which case refer to the specification or other drawings. Furthermore, the dimensions of various components in the drawings may differ from the actual dimensions, as priority is given to helping to understand the features of the present invention.

[0015] A method for manufacturing a balloon for a balloon catheter according to an embodiment of the present invention is a parison made of resin, extending in the longitudinal direction and having a lumen, comprising: a first sleeve portion, a second sleeve portion, and an enlarged diameter portion located between the first and second sleeve portions in the longitudinal direction and having an inner diameter greater than or equal to the inner diameter of the first sleeve portion and greater than or equal to the inner diameter of the second sleeve portion, wherein when the first end of the enlarged diameter portion is at the 0% position and the second end is at the 100% position in the longitudinal direction, the parison has a central section from the 45% position to the 55% position, a first section from the 0% position to the 10% position, and a second section from the 90% position to the 100% position; a mold extending in the longitudinal direction and having a lumen; and placing the parison in the lumen of the mold. The method comprises: a first stretching step in which the central section is heated to a temperature above the glass transition temperature Tg of the resin and below the glass transition temperature Tg + 30°C, and the first and second sections are kept at a temperature below the glass transition temperature Tg of the resin while stretching at least the central section of the enlarged diameter; and a second stretching step in which, after the first stretching step, the enlarged diameter is biaxially stretched in the longitudinal axis direction and the radial direction of the enlarged diameter while heating the enlarged diameter section to a temperature above the glass transition temperature Tg and below the glass transition temperature Tg + 30°C, characterized in that, in the stress-strain curve of the resin at room temperature, the strain exceeds the strain at point A where the differential coefficient of stress becomes 5% or more after the strain exceeds the yield point.

[0016] In the first stretching step, the central section of the parison is heated to a temperature above the glass transition temperature Tg of the resin and below the glass transition temperature Tg + 30°C, while the first and second sections of the parison are kept at a temperature below the glass transition temperature Tg of the resin. This allows at least the central section of the enlarged diameter portion of the parison to be stretched in the longitudinal direction during the first stretching step. At this time, in the stress-strain curve of the resin at room temperature, the central section is stretched until it exceeds the strain at point A, where the differential coefficient of stress becomes 5% or more after the strain exceeds the yield point, relative to the average rate of change of stress from zero to the yield point. Through this first stretching step, the resin molecules at both ends of the parison are kept at a temperature below the glass transition temperature Tg, so they cannot move and the molecular chains are hardly affected by stretching. In contrast, in the central section of the parison, heating to above the glass transition temperature Tg relaxes the resin molecules, and the molecular chains are stretched in the longitudinal direction in a state where they can move easily, allowing the molecular chains to extend and align in the longitudinal direction. By further biaxially stretching a parison in this state in a second stretching step, a balloon can be manufactured that has a longitudinal molecular orientation of the resin in the central section. This allows for the creation of a longitudinal crack in the central section even if the balloon for the balloon catheter is ruptured due to overpressure or other reasons. The longitudinal crack in the central section releases internal pressure, thus preventing circumferential cracking. As a result, the risk of fragments of the balloon catheter remaining in the body can be avoided, making it possible to manufacture balloon catheters that allow for safe procedures.

[0017] The method for manufacturing a balloon for a balloon catheter according to an embodiment of the present invention will be described below with reference to Figures 1 to 10. Figure 1 is a plan view of a balloon catheter according to an embodiment of the present invention. Figure 2 is a cross-sectional view in the longitudinal direction of a parison according to an embodiment of the present invention. Figure 3 is an example of a stress-strain curve for a polyester resin, and Figure 4 is an example of a stress-strain curve for a polyamide resin. Figure 5 is a cross-sectional view in the longitudinal direction of a mold according to an embodiment of the present invention. Figure 6 is a schematic diagram of the first stretching step, showing a state in which the parison is not placed in the lumen of the mold, but the heater is placed near the central section of the parison. Figure 7 is a cross-sectional view in the longitudinal direction of the parison and mold after the completion of the first stretching step and at the start of the second stretching step, and Figure 8 is another example of a cross-sectional view in the longitudinal direction of the parison and mold after the completion of the first stretching step and at the start of the second stretching step. Figure 9 is a cross-sectional view in the longitudinal direction of the parison and mold at the completion of the second stretching step. Figure 10 shows another example of a cross-sectional view in the longitudinal direction of a mold according to an embodiment of the present invention.

[0018] In this specification, the balloon for the balloon catheter may be simply referred to as the "balloon." The balloon catheter balloon 20, parison 30, and mold 40 each have a longitudinal axis direction, a radial direction, and a circumferential direction. However, for ease of understanding, in this specification, all components are described as having the same longitudinal axis direction x, radial direction y, and circumferential direction z as the balloon catheter balloon 20 shown in Figure 1. However, this does not necessarily mean that all components are positioned in the same direction; the longitudinal axis direction, radial direction, and circumferential direction of each component may differ from one another. The circumferential direction z of the balloon 20 is the direction along the outer circumference of the expanded balloon 20 in a cross section perpendicular to the longitudinal axis direction x, and the radial direction y of the balloon 20 is the direction connecting the centroid of the outer edge of the expanded balloon 20 and a point on the outer edge of the balloon 20 in a cross section perpendicular to the longitudinal axis direction x. In the longitudinal axis x, the direction of the balloon catheter 1 toward the user's proximal side is referred to as the proximal side, and the opposite side, i.e., the side toward the person being treated, is referred to as the distal side.

[0019] A method for manufacturing a balloon for a balloon catheter according to an embodiment of the present invention is a method for manufacturing a balloon 20 used in a balloon catheter 1 as shown in Figure 1. The balloon 20 is connected to the distal end of a shaft 3, and the balloon 20 can be expanded by introducing fluid through the lumen of the shaft 3 and deflated by discharging the fluid. The fluid is introduced or discharged using an indeflerator (balloon pressurizer) to control the expansion and contraction of the balloon 20. The fluid may be a pressurized fluid pressurized by a pump or the like.

[0020] By stretching a parison 30 made of resin to manufacture a balloon 20, the balloon 20 can have a structure made of resin having molecular orientation. Preferably, the balloon 20 has an expandable portion 22, a proximal sleeve portion 21 located proximal to the expandable portion 22, and a distal sleeve portion 23 located distal to the expandable portion 22. While the expandable portion 22 is the part that expands upon the introduction of fluid, it is preferable that the proximal sleeve portion 21 and the distal sleeve portion 23 do not expand, and the balloon 20 can be connected to the shaft 3 by fixing at least a part of the proximal sleeve portion 21 and the distal sleeve portion 23 to the shaft 3.

[0021] Examples of materials that make up the balloon 20 include polyolefin resins such as polyethylene, polypropylene, and ethylene-propylene copolymer; polyester resins such as polyethylene terephthalate and polyester elastomer; polyurethane resins such as polyurethane and polyurethane elastomer; polyphenylene sulfide resin; polyamide resins such as polyamide and polyamide elastomer; fluororesin; silicone resin; and natural rubber such as latex rubber. These may be used individually or in combination of two or more. Among these, polyamide resins, polyester resins, and polyurethane resins are preferred, polyamide resins such as nylon 12 and nylon 11 are more preferred, and nylon 12 is particularly preferred. From the viewpoint of thinning the balloon 20 and improving its flexibility, it is preferable to use an elastomer resin, and polyamide elastomers such as polyamide ether elastomers are suitably used.

[0022] The outer diameter of the balloon 20 is preferably 0.5 mm or more, more preferably 1 mm or more, and even more preferably 1.5 mm or more. The lower limit of the outer diameter of the balloon 20 being within this range allows for sufficient dilation of the narrowed portion within the blood vessel. Furthermore, the outer diameter of the balloon 20 is preferably 35 mm or less, more preferably 30 mm or less, and even more preferably 25 mm or less. The upper limit of the outer diameter of the balloon 20 being within this range facilitates insertion of the balloon 20 into the body cavity.

[0023] The length of the balloon 20 in the longitudinal direction x is preferably 5 mm or more, more preferably 10 mm or more, and even more preferably 15 mm or more. By having the lower limit of the length of the balloon 20 in the longitudinal direction x be within the above range, it is possible to increase the area of ​​the stenosis that can be expanded at once and shorten the time required for the procedure. Furthermore, the length of the balloon 20 in the longitudinal direction x is preferably 300 mm or less, more preferably 200 mm or less, and even more preferably 100 mm or less. By having the upper limit of the length of the balloon 20 in the longitudinal direction x be within the above range, it is possible to reduce the volume of fluid introduced into the balloon 20 to expand the stenosis and shorten the time required to fully expand the balloon 20.

[0024] The thickness of the balloon 20 is preferably 5 μm or more, more preferably 7 μm or more, even more preferably 10 μm or more, and preferably 100 μm or less, more preferably 80 μm or less, and even more preferably 60 μm or less. By having the thickness of the balloon 20 within the above range, a balance can be achieved between the strength and flexibility of the balloon 20.

[0025] Examples of materials that make up the shaft 3 include polyamide resins, polyester resins, polyurethane resins, polyolefin resins, fluororesins, vinyl chloride resins, silicone resins, and natural rubber. These may be used individually or in combination of two or more. In particular, it is preferable that the material making up the shaft 3 be at least one of polyamide resins, polyolefin resins, and fluororesins. This improves the slipperiness of the surface of the shaft 3 and improves the ease of insertion of the balloon catheter 1 into the body cavity.

[0026] The balloon 20 and the shaft 3 can be joined by adhesive bonding, welding, or by attaching a ring-shaped member to the overlapping area of ​​the balloon 20 and the shaft 3 and crimping it. Among these, it is preferable that the balloon 20 and the shaft 3 are joined by welding. By welding the balloon 20 and the shaft 3, the joint between the balloon 20 and the shaft 3 is less likely to come undone even if the balloon 20 is repeatedly expanded or contracted, and the joint strength between the balloon 20 and the shaft 3 can be easily increased.

[0027] As shown in Figure 1, in the balloon catheter 1, a hub 4 may be provided on the proximal side of the shaft 3, and it is preferable that the hub 4 is provided with a fluid injection section 6 that communicates with the fluid flow path supplied to the inside of the balloon 20. The hub 4 may also be provided with a guidewire insertion section 5 that communicates with the guidewire insertion passage. With this configuration, operations such as supplying fluid to the inside of the balloon 20 to expand or deflate the balloon 20, and operations such as delivering the balloon catheter 1 to the treatment site along the guidewire can be easily performed. Figure 1 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, but the balloon 20 can also be applied to a so-called rapid-exchange type balloon catheter in which the guidewire is inserted partway from the distal side to the proximal side of the shaft 3.

[0028] The shaft 3 and hub 4 can be joined by, for example, adhesive bonding or welding. In particular, it is preferable that the shaft 3 and hub 4 are joined by adhesive bonding. By bonding the shaft 3 and hub 4, the bonding strength between them can be increased, improving the durability of the balloon catheter 1, especially when the materials constituting the shaft 3 and hub 4 are different, such as when the shaft 3 is made of a highly flexible material and the hub 4 is made of a highly rigid material.

[0029] A method for manufacturing a balloon 20 for a balloon catheter according to an embodiment of the present invention includes the step of preparing a parison 30 made of resin, extending in the longitudinal axis direction x and having a lumen 30L. The balloon 20 can be manufactured by pressurizing the inside of the parison 30 to expand the lumen 30L. For the resin constituting the parison 30, refer to the section on materials constituting the balloon 20 above. The parison 30 can be manufactured by known methods such as extrusion molding or injection molding, but it is preferable to manufacture it by extrusion molding.

[0030] As shown in Figure 2, the parison 30 has a first sleeve portion 34, a second sleeve portion 35, and an enlarged diameter portion 30E located between the first sleeve portion 34 and the second sleeve portion 35 in the longitudinal axis direction x, having an inner diameter greater than or equal to the inner diameter of the first sleeve portion 34 and greater than or equal to the inner diameter of the second sleeve portion 35. The enlarged diameter portion 30E of the parison 30 is the portion that becomes the expanded portion 22 of the balloon 20 when the balloon 20 is made from the parison 30. The first sleeve portion 34 and the second sleeve portion 35 of the parison 30 include portions that become the proximal sleeve portion 21 and the distal sleeve portion 23 of the balloon 20 when the balloon 20 is made from the parison 30. In the first sleeve portion 34 and the second sleeve portion 35, the inner diameters of the parison 30 may be the same or different along the longitudinal axis direction x, but it is preferable that they be substantially the same. Also, the inner diameters of the first sleeve portion 34 and the second sleeve portion 35 may be the same or different, but it is preferable that they be substantially the same. This makes it easier to manufacture parison 30. Here, "substantially the same" means that the rate of change of the inner diameter ([maximum inner diameter - minimum inner diameter] / average inner diameter) is 0.2 or less. The rate of change of the inner diameter may also be 0.18 or less, 0.15 or less, 0.1 or less, 0.08 or less, 0.05 or less, 0.02 or less, or even 0. Hereafter, when parison 30 or the inner diameter of the mold is said to be "substantially the same," it means that the rate of change of the inner diameter is within the above range. Similarly, when the outer diameter is said to be substantially the same, it means that the rate of change of the outer diameter is within the above range.

[0031] The maximum inner diameter of the enlarged portion 30E is preferably larger than the maximum inner diameter of the first sleeve portion 34 and the maximum inner diameter of the second sleeve portion 35. Here, the maximum inner diameter of the enlarged portion 30E refers to the inner diameter at the point where the enlarged portion 30E has its maximum inner diameter in the longitudinal axis direction x. Similarly, the maximum inner diameter of the first sleeve portion 34 and the maximum inner diameter of the second sleeve portion 35 refer to the inner diameters at the points where the first sleeve portion 34 and the second sleeve portion 35, respectively, have their maximum inner diameters in the longitudinal axis direction x. Hereafter, when referring to the maximum inner diameter of a predetermined member or predetermined section, the same explanation can be applied, which states that the maximum inner diameter refers to the inner diameter at the point where the predetermined member or predetermined section has its maximum inner diameter in the longitudinal axis direction x.

[0032] In the parison 30, the first end of the enlarged diameter portion 30E is at position D0 at 0% in the longitudinal axis x, and the second end is at position D0 at 100. 100 In that case, position D at 45% 45 55% from position D 55 The central section is 33, from position D0 at 0% to position D at 10%. 10 The first section up to 31, and the 90% position D 90 Position D at 100 100 It has a second section 32 up to the first section 31, the second section 32, and the central section 33 are determined by the position x in the longitudinal axis direction in the initial state after the parison 30 has been manufactured by a known method such as extrusion molding or injection molding, and before being subjected to the first stretching step. One of the features of the manufacturing method of the balloon catheter balloon 20 according to the embodiment of the present invention is that the central section 33 of the parison 30 in this initial state is heated in the first stretching step described later at a temperature above the glass transition temperature Tg of the resin and below the glass transition temperature Tg + 30°C, and the first section 31 and the second section 32 are maintained at a temperature below the glass transition temperature Tg.

[0033] In the first stretching step, the central section 33 of the parison 30 is heated to a temperature above the glass transition temperature Tg of the resin constituting the parison 30 and below the glass transition temperature Tg + 30°C, while the first section 31 and the second section 32 are kept at a temperature below the glass transition temperature Tg of the resin, and at least the central section 33 of the enlarged diameter section 30E of the parison 30 is stretched. Since the central section 33 is heated within the above temperature range, for example, by pulling the first sleeve section 31 and the second sleeve section 32 of the parison 30 so that they move away from each other in the longitudinal axis direction x, the central section 33 is stretched in the longitudinal axis direction x.

[0034] In the first stretching step, the temperature at which the central section 33 is heated is more preferably below the glass transition temperature Tg + 25°C of the resin constituting the parison 30, even more preferably below the glass transition temperature Tg + 20°C, and may also be below the glass transition temperature Tg + 10°C. By heating the central section 33 at a temperature within the above range in the first heating step, the central section 33 can be easily stretched in the longitudinal axis direction x.

[0035] The glass transition temperature (Tg) is measured in accordance with JIS K7121. A 5 mg resin sample is heated at a rate of 20 °C / min in the temperature range of 0 °C to 250 °C using a differential scanning calorimeter, and the extrapolated glass transition onset temperature obtained from the DSC curve can be defined as the glass transition temperature (Tg).

[0036] For example, when a polyamide resin is used as the resin constituting parison 30, the glass transition temperature Tg is 40°C to 60°C. When other resins are used as the resin constituting parison 30, the temperature is not limited to the above, and the glass transition temperature Tg can be determined according to the above method.

[0037] In the first stretching step, it is preferable that the first section 31 and the second section 32 of the parison 30 are not heated. This prevents both ends of the parison 30 from being stretched.

[0038] In the first stretching step, in the stress-strain curve of the resin constituting the parison 30 at room temperature, the central section 33 is stretched until the strain exceeds the strain at point A where the differential coefficient of the stress becomes 5% or more after the strain exceeds the yield point B with respect to the average change rate of the stress from zero to the yield point B.

[0039] Examples of stress-strain curves are shown in FIGS. 3 and 4. FIG. 3 is an example of the stress-strain curve of a polyester resin, and FIG. 4 is an example of the stress-strain curve of a polyamide resin. In many resins, in the stress-strain curve as shown in FIG. 3, in the elastic deformation region up to the yield point B, stress acts so that the bent molecular chains extend. After the yield point B, plastic deformation begins where the molecular chains that were attracting each other by intermolecular forces shift in the shear direction. There are also resins that show a phenomenon where once the molecular chains start to shift, slack occurs in the molecular chains and the stress decreases to the lower yield point L. After that, a region showing a horizontal stress for a while is observed, and such a region is called the necking region R n is called. In the necking region R n where the molecular chains were showing a certain stress due to the displacement by the strain, when the strain exceeds a predetermined value, the molecular chains approach and are densely oriented, and strong intermolecular forces are generated between the molecular chains. Therefore, in the region where the strain exceeds a predetermined value, that is, beyond the necking region R n the stress rises with a right shoulder upward. The condition of the first stretching step of stretching the central section 33 until the strain exceeds the strain at point A where the differential coefficient of the stress becomes 5% or more after the strain exceeds the yield point B with respect to the average change rate of the stress from zero to the yield point B can also be rephrased as stretching the central section 33 until beyond the above-mentioned necking region R n ends.

[0040] In the first stretching step, by stretching the central section 33 in the longitudinal axis direction x until the strain exceeds the strain at point A where the differential coefficient of the stress becomes 5% or more after the strain exceeds the yield point B with respect to the average change rate of the stress from zero to the yield point B, the central section 33 can be stretched until the displacement of the molecular chains ends. As shown in FIG. 4, among the resins, there is no such clear necking region R as seen in FIG. 3 nAlthough some do not show this, by stretching the central section 33 in the first stretching step under the condition that the strain exceeds the strain at point A where the differential coefficient of the stress is 5% or more compared to the average rate of change of stress from zero to the yield point B, it is possible to stretch the central section 33 to the point where the slippage of the molecular chains ends.

[0041] In the first stretching step, the first section 31 and the second section 32 are maintained at a temperature below the glass transition temperature Tg of the resin. Therefore, the first section 31 and the second section 32, i.e., both ends of the parison 30, are not stretched in the same way as the central section 33 described above. As a result, the resin molecules cannot move at both ends of the parison 30 and the molecular chains are hardly affected by stretching, whereas in the central section 33 of the parison 30, the resin molecules are relaxed and the molecular chains are easily movable, allowing the parison to be stretched in the longitudinal axis direction x. This allows the molecular chains to extend and align in the longitudinal axis direction. By further biaxial stretching of the parison 30 in this state in the second stretching step described later, a balloon can be manufactured in which the resin molecular orientation in the longitudinal axis direction x is located in the central section. As a result, even if the balloon catheter balloon 20 is destroyed due to overpressure or the like, a crack in the longitudinal axis direction x can be initiated in the central section, and the internal pressure can be released by the crack in the longitudinal axis direction x that occurs in the central section, thus preventing cracking in the circumferential direction z. As a result, the risk of fragments of the balloon catheter balloon 20 remaining in the body can be avoided, making it possible to manufacture a balloon catheter balloon 20 that allows for safe procedures.

[0042] As shown in Figure 5, a method for manufacturing a balloon 20 for a balloon catheter according to an embodiment of the present invention includes the step of preparing a mold 40 that extends in the longitudinal axis direction x and has a lumen 40L. Preferably, the mold 40 has a straight tube portion 43 and a first mold sleeve portion 41 and a second mold sleeve portion 42 located on both sides of the straight tube portion 43.

[0043] In the first sleeve portion 41 and the second sleeve portion 42 of the mold, the inner diameter of the mold 40 may be the same or different along the longitudinal axis x, but it is preferable that it be substantially the same. Also, the inner diameter of the first sleeve portion 41 and the inner diameter of the second sleeve portion 42 of the mold may be the same or different, but it is preferable that they be different. For example, if the inner diameter of the first sleeve portion 41 of the mold is larger than the inner diameter of the second sleeve portion 42 of the mold, the first sleeve portion 41 of the mold forms the proximal sleeve portion 21 of the balloon 20 and the second sleeve portion 42 of the mold forms the distal sleeve portion 23 of the balloon 20. This makes it possible to increase the diameter of the proximal sleeve portion 21 of the balloon 20 to make it easier to fix to the shaft 3, and decrease the diameter of the distal sleeve portion 23 to make it easier to close the distal end of the balloon 20. The inner diameter of the straight tube portion 43 is preferably greater than or equal to the inner diameter of the first sleeve portion 41 of the mold and greater than or equal to the inner diameter of the second sleeve portion 42 of the mold. The inner diameter of the straight tube section 43 may be the same or different along the longitudinal axis x, but if the expanded portion 22 of the balloon 20 to be manufactured is to be a cylindrical balloon 20 having substantially the same outer diameter along the longitudinal axis x, then it is preferable that the inner diameter of the straight tube section 43 be substantially the same along the longitudinal axis x.

[0044] In the mold 40, the length x in the longitudinal direction of the straight tube section 43 can be determined according to the length x in the longitudinal direction of the expansion section 22 of the balloon 20 to be manufactured. Also, the inner diameter of the straight tube section 43 can be determined according to the outer diameter of the expansion section 22 of the balloon 20 to be manufactured.

[0045] The mold 40 may be composed of one component or multiple components. For example, the mold 40 may be composed of multiple halves, or multiple segments may be configured to be connected in the circumferential direction z. If the mold 40 is composed of multiple halves or segments, it becomes easier to place the parison 30 in the lumen 40L of the mold 40. Alternatively, as in the mold 400 described later, multiple mold segments may be configured to be connected in the longitudinal axis direction x.

[0046] Preferably, the mold 40 has a first tapered section 44 in which the diameter of the lumen 40L expands from the first sleeve section 41 to the straight tube section 43 in the longitudinal axis direction x, and a second tapered section 45 in which the diameter of the lumen 40L contracts from the straight tube section 43 to the second sleeve section 42. In this way, because the mold 40 has the first tapered section 44 and the second tapered section 45 at both ends of the straight tube section 43, the transition of shape and molecular orientation from both ends of the expanded diameter section 30E to the first sleeve section 34 and the second sleeve section 35 can be made smoother in the second stretching step, so that stress concentration due to abrupt changes in shape and molecular orientation can be avoided, and the mechanical strength and moldability of the resulting balloon 20 can be improved.

[0047] A method for manufacturing a balloon 20 for a balloon catheter according to an embodiment of the present invention includes the step of placing a parison 30 in the lumen 40L of a mold 40, but in the first stretching step, the parison 30 may or may not be placed in the lumen 40L of the mold 40.

[0048] As shown in Figure 6, if the parison 30 is not placed in the lumen 40L of the mold 40 in the first stretching step, the central section 33 can be heated by known methods, such as heating it with a heater 50 placed near the parison 30. Alternatively, if the parison 30 is placed in the lumen 40L of the mold 40, the central section 33 can be heated by known methods, such as heating it with a heater placed outside the mold 40, or heating the mold 40 itself by induction heating.

[0049] The step of placing the parison 30 in the lumen 40L of the mold 40 is preferably performed before the first stretching step. This allows the parison 30 to be heated by heating the mold 40, and makes it easy to vary the heating temperature in the central section 33, the first section 31, and the second section 32.

[0050] Alternatively, the step of placing the parison 30 in the lumen 40L of the mold 40 may be performed after the first stretching step and before the second stretching step, which will be described later. By placing the parison 30 in the lumen 40L of the mold 40 after the first stretching step, the parison 30 can be handled outside the mold 40 during the first stretching step, making stretching easier.

[0051] In the step of placing the parison 30 in the lumen 40L of the mold 40, it is preferable that the first sleeve portion 34 and the second sleeve portion 35 of the parison 30 be placed in the lumen of the first sleeve portion 41 and the second sleeve portion 42 of the mold 40, respectively. This makes it easier to form the first sleeve portion 34 and the second sleeve portion 35 of the parison 30 into the proximal sleeve portion 21 and the distal sleeve portion 23 of the balloon 20. It is also preferable that the enlarged diameter portion 30E of the parison 30 be placed in the lumen of the straight tube portion 43 of the mold 40. This makes it easier to biaxially extend the enlarged diameter portion 30E of the parison 30 along the straight tube portion 43 in the second stretching step described later.

[0052] As shown in Figure 7, the parison 30 stretched in the first stretching step may have a constriction in the middle compared to both ends. The parison 30 after the first stretching step has a longer longitudinal axis x length of the expanded portion 30E compared to the parison 30 in its initial state before the first stretching step, which is due to the fact that the central section 33 of the parison 30 has been stretched in the longitudinal axis x direction.

[0053] Alternatively, as shown in Figure 8, the parison 30 stretched in the first stretching step does not need to be constricted in the middle with respect to both ends. From the viewpoint of ease of biaxial stretching in the second stretching step, which will be described later, it is preferable that the parison 30 stretched in the first stretching step does not have a constriction in the middle with respect to both ends. In this case as well, the parison 30 after the first stretching step has a longer longitudinal axis x length of the expanded portion 30E compared to the parison 30 in its initial state before the first stretching step, and this is because the central section 33 of the parison 30 has been stretched in the longitudinal axis x direction.

[0054] In the first stretching step, the inside of the parison 30 may or may not be pressurized, but it is preferable that the inside of the parison 30 be pressurized in the first stretching step in order to prevent the central part of the parison 30 from constricting relative to both ends and to facilitate stretching in the second stretching step. By pressurizing the inside of the parison 30 in the first stretching step, the enlarged diameter portion 30E can be stretched radially y to such an extent that the central section 33 stretched in the longitudinal axis direction x does not constrict.

[0055] Methods for pressurizing the inside of the parison 30 include supplying a fluid, such as a gas like air or nitrogen gas, or a liquid like pure water or saline solution, into the 30L lumen of the parison 30. A pump or the like can be used to pressurize the fluid.

[0056] In the first stretching step, by stretching the parison 30 so that the central part does not constrict, the central section 33, which is stretched in the longitudinal axis direction x in the first stretching step, is also stretched to some extent in the radial direction y, and the film thickness of the central section 33 can be made thinner. Since the central section 33 is further biaxially stretched in the second stretching step described later, the resulting balloon 20 can be configured to have a thinner film thickness in the central section than at the ends. As a result, even if the balloon 20 is destroyed due to overpressure or the like, a crack in the longitudinal axis direction x can be initiated in the central section, and the internal pressure can be released by the crack in the longitudinal axis direction x that occurs in the central section, making it possible to prevent cracking in the circumferential direction z.

[0057] As shown in Figures 7 and 8, it is preferable that, after the completion of the first stretching step and at the start of the second stretching step, the enlarged diameter portion 30E of the parison 30 is not in contact with the inner wall of the straight pipe portion 43 of the mold 40. This allows the enlarged diameter portion 30E of the parison 30 to be easily biaxially stretched in the second stretching step.

[0058] In the second stretching step, the enlarged diameter portion 30E of the parison 30, which has completed the first stretching step, is heated at a temperature above the glass transition temperature Tg and below the glass transition temperature Tg + 30°C, while the enlarged diameter portion 30E is biaxially stretched in the longitudinal axis direction x and the radial direction y. At this time, it is preferable that the entire enlarged diameter portion 30E is heated. By heating the enlarged diameter portion 30E at the above temperature and pressurizing the inside of the parison 30, the enlarged diameter portion 30E is biaxially stretched to obtain the balloon 20.

[0059] In the second stretching step, the temperature at which the enlarged diameter portion 30E is heated is more preferably below the glass transition temperature Tg + 25°C of the resin constituting the parison 30, even more preferably below the glass transition temperature Tg + 20°C, and may also be below the glass transition temperature Tg + 10°C. By heating the enlarged diameter portion 30E at a temperature within the above range in the second heating step, the enlarged diameter portion 30E can be easily biaxially stretched in the longitudinal axis direction x and the radial direction y.

[0060] In the second stretching step, the enlarged diameter portion 30E can be heated by known methods such as heating with a heater placed outside the mold 40, or heating the mold 40 itself by induction heating.

[0061] In the second stretching step, the enlarged diameter portion 30E can be biaxially stretched by pressurizing the inside of the parison 30 by supplying a fluid, such as air or nitrogen gas, or a liquid, such as pure water or saline solution, into the lumen 30L of the parison 30. The fluid can be pressurized by a pump or the like. In particular, in the second stretching step, it is preferable that the parison 30 is blow-molded by pressurizing the inside of the parison 30 using compressed gas. Since the balloon 20 can be manufactured by feeding compressed gas into the parison 30 and pressurizing the inside, the manufacturing efficiency of the balloon 20 can be increased.

[0062] As shown in Figure 9, it is preferable that at the end of the second stretching step, the enlarged portion 30E of the parison 30 is biaxially stretched to conform to the lumen 40L of the mold 40. This makes it easier to design the shape of the balloon 20 obtained based on the shape of the lumen 40L of the mold 40.

[0063] In the first stretching step, it is preferable to stretch at least the central section 33 of the enlarged diameter section 30E while maintaining the internal pressure of the enlarged diameter section 30E between 0 bar (0 MPa) and 30 bar (3 MPa), and in the second stretching step, to biaxially stretch the enlarged diameter section 30E by applying an internal pressure higher than the internal pressure applied to the enlarged diameter section 30E in the first stretching step. Note that the internal pressure is not absolute pressure, but gauge pressure, i.e., atmospheric pressure plus pressure.

[0064] In the first stretching step, the internal pressure applied to the enlarged diameter portion 30E of the parison 30 is more preferably 2 bar (0.2 MPa) or more, even more preferably 5 bar (0.5 MPa) or more, and may be 7 bar (0.7 MPa) or more, or 10 bar (1 MPa) or more. By having the lower limit of the internal pressure applied to the enlarged diameter portion 30E in the first stretching step be within the above range, it is possible to prevent the central section 33, which is stretched in the longitudinal axis direction x, from becoming constricted, and biaxial stretching in the second stretching step can be easily performed. Furthermore, in the first stretching step, the internal pressure applied to the enlarged diameter portion 30E of the parison 30 is more preferably 25 bar (2.5 MPa) or less, even more preferably 20 bar (2 MPa) or less, and may be 15 bar (1.5 MPa) or less. In the first stretching step, by setting the upper limit of the internal pressure applied to the enlarged diameter portion 30E to the above range, the central section 33 can be stretched in the longitudinal axis direction x until it exceeds point A on the stress-strain curve without stretching it radially y more than necessary.

[0065] In the second stretching step, the internal pressure applied to the enlarged diameter portion 30E of the parison 30 is preferably 10 bar (1 MPa) or more, more preferably 15 bar (1.5 MPa) or more, even more preferably 30 bar (3 MPa) or more, and also preferably 60 bar (6 MPa) or less, more preferably 50 bar (5 MPa) or less, and even more preferably 40 bar (4 MPa) or less. By applying an internal pressure within the above range, which is greater than the internal pressure in the first stretching step, to the enlarged diameter portion 30E of the parison 30 in the second stretching step, it becomes easy to obtain the balloon 20 by biaxially stretching the enlarged diameter portion 30E in the longitudinal axis direction x and the radial direction y.

[0066] In the first stretching step, it is preferable that the first section 31 and the second section 32 of the parison 30 are stretched so as not to exceed the strain at point A of the stress-strain curve. Even if the first section 31 and the second section 32 of the parison 30, i.e., both ends, are stretched in the first stretching step, if the stretching does not exceed the strain at point A of the stress-strain curve, the resin molecules in the central section 33 are relaxed and the molecular chains are easily movable and arranged in the longitudinal axis direction x, while the resin molecules at both ends are unable to move and the molecular chains are hardly affected by the stretching, making it easy to obtain a balloon 20 having a molecular orientation in the longitudinal axis direction x in the central section.

[0067] The stretching speed in the first stretching step is preferably slower than the stretching speed in the second stretching step. The stretching speed in the first stretching step is preferably, for example, 25 mm / s or less, more preferably 20 mm / s or less, even more preferably 10 mm / s or less, and preferably 3 mm / s or more, and even more preferably 5 mm / s or more. By having the stretching speed in the first stretching step within the above range, it is possible to prevent the central part of the parison 30 from becoming too constricted in the first stretching step. The stretching speed in the second stretching step is preferably, for example, 200 mm / s or less, more preferably 180 mm / s or less, even more preferably 160 mm / s or less, and also preferably 100 mm / s or more, more preferably 120 mm / s or more, and even more preferably 140 mm / s or more. By having the stretching speed in the second stretching step within the above range, the balloon 20 can be manufactured efficiently.

[0068] In the manufacturing method of the balloon 20 for a balloon catheter according to an embodiment of the present invention, it is preferable to further include a step of raising the enlarged diameter portion 30E to a temperature of Tc or higher than the crystallization temperature of the resin after the second stretching step. This step may be performed by heating the mold 40 to a temperature of Tc or higher. At the end of the second stretching step, the enlarged diameter portion 30E of the parison 30 is formed to the shape of the expanded portion 22 of the balloon 20 defined by the shape of the lumen 40L of the mold 40. However, by raising the enlarged diameter portion 30E of the parison 30 to a temperature of Tc or higher than the crystallization temperature of the resin after this step, the crystallization of the resin can be promoted and the shape of the enlarged diameter portion 30E can be fixed. This is thought to be because the shape can be fixed by promoting the bonding by intermolecular forces between molecules that are oriented at the end of the second stretching step. If this step is not performed, the balloon 20 formed from the parison 30 may shrink significantly when removed from the mold 40.

[0069] The crystallization temperature Tc is measured in accordance with JIS K7121. Using a differential scanning calorimeter, a 5 mg resin sample is heated at a rate of 20 °C / min in the temperature range of 0 °C to 250 °C, maintained at this temperature for 10 minutes, and then cooled at a rate of 20 °C / min to a temperature approximately 50 °C lower than the end of the crystallization peak. The extrapolation onset temperature obtained from the DSC curve can be defined as the crystallization temperature Tc.

[0070] For example, when a polyamide resin is used as the resin constituting parison 30, the crystallization temperature Tc is 130°C to 155°C. When other resins are used as the resin constituting parison 30, the crystallization temperature Tc is not limited to the above temperature and can be determined according to the above method.

[0071] In the first stretching step, the first section 31 and the second section 32 may be heated at a temperature below the glass transition temperature Tg of the resin constituting the parison 30. This makes stretching in the first stretching step easier.

[0072] As described above, when the parison 30 is heated at different temperatures along the longitudinal axis x in the first stretching step, a mold 400 as shown in Figure 10 can also be used.

[0073] As shown in Figure 10, the mold 400 has a first end region 401, a second end region 402, and a central region 403 located between the first end region 401 and the second end region 402 in the longitudinal axis direction x, and it is preferable that the first end region 401, the second end region 402, and the central region 403 can each be heated independently. By allowing the first end region 401, the second end region 402, and the central region 403 to be heated independently, it becomes easy to heat the first section 31, the second section 32, and the central section 33 of the parison 30 at different temperatures.

[0074] Preferably, the first end region 401, the second end region 402, and the central region 403 of the mold 400 are each composed of separate members, and the mold 400 is formed by connecting these separate members in the longitudinal axis direction x. Further additional members may be provided between the first end region 401 and the central region 403, and between the second end region 402 and the central region 403, in the longitudinal axis direction x.

[0075] The first end region 401, the second end region 402, and the central region 403 of the mold 400 may each be composed of a single member, or each may be a segment of the mold 400. Alternatively, the mold 400 may be composed of a split body, or multiple segments may be configured to be connected in the circumferential direction z. If the mold 400 is composed of multiple split bodies or segments, it becomes easier to place the parison 30 in the lumen 40L of the mold 400.

[0076] Preferably, the mold 400 has a first tapered section 440 in which the internal lumen 40L expands in the longitudinal axis direction x from the first sleeve section 410 to the straight tube section 430, and a second tapered section 450 in which the internal lumen 400L contracts in the longitudinal axis direction x from the straight tube section 430 to the second sleeve section 420. In this way, because the mold 400 has the first tapered section 440 and the second tapered section 450 at both ends of the straight tube section 430, the transition of shape and molecular orientation from both ends of the expanded section 30E to the first sleeve section 34 and the second sleeve section 35 can be made smoother in the second stretching step, so that stress concentration due to abrupt changes in shape and molecular orientation can be avoided, and the mechanical strength and moldability of the resulting balloon 20 can be improved. [Explanation of symbols]

[0077] 1: Balloon catheter 3: Shaft 4: Hub 5: Guidewire insertion section 6:Fluid injection part 20: Balloon 21: Proximal sleeve portion of the balloon 22: Balloon expansion section 23: Distal sleeve portion of the balloon 30: Parison 30E: Enlarged section of parison 30L: Parison's lumen 31: Parison's first section 32: Parison's second leg 33: The central section of Parison 34: Parison's first sleeve section 35: Parison's second sleeve section 40: Mold 40L: Inner cavity of the mold 41: Mold first sleeve section 42: Mold second sleeve section 43: Straight pipe section 44: First tapered section of the mold 45: Second tapered section of the mold 50: Heater 400: Mold 401: First end area 402:Second end area 403: Central area 410: Mold first sleeve section 420: Mold second sleeve section 430: Straight pipe section 440: First tapered section of the mold 450: Second tapered section of the mold B: Yield point D0: 0% position D 10 :10% position D 45 :45% position D 55 :55% position D 90 :90% position D 100 :100% position L: Lower yield point R n : Necking area x: Longitudinal axis y: radial direction z: Circumferential direction

Claims

1. A parison made of resin, extending in the longitudinal direction and having a lumen, comprising: a first sleeve portion; a second sleeve portion; and an enlarged diameter portion located between the first and second sleeve portions in the longitudinal direction and having an inner diameter greater than or equal to the inner diameter of the first sleeve portion and greater than or equal to the inner diameter of the second sleeve portion, wherein when the first end of the enlarged diameter portion is at the 0% position and the second end is at the 100% position in the longitudinal direction, the parison has a central section from the 45% position to the 55% position, a first section from the 0% position to the 10% position, and a second section from the 90% position to the 100% position. The steps include preparing a mold that extends in the longitudinal direction and has a lumen, The steps include: placing the parison in the cavity of the mold; A first stretching step involves heating the central section to a temperature above the glass transition temperature Tg of the resin and below the glass transition temperature Tg + 30°C, while maintaining the first and second sections at a temperature below the glass transition temperature Tg of the resin, and stretching at least the central section of the enlarged diameter portion. The process includes a second stretching step, in which the enlarged diameter portion is biaxially stretched in the longitudinal direction and the radial direction of the enlarged diameter portion while heating the enlarged diameter portion at a temperature above the glass transition temperature Tg and below the glass transition temperature Tg + 30°C, In the first extension step, the central section is extended in the longitudinal direction, In the first stretching step, the internal pressure of the enlarged diameter portion is maintained at 0 bar or more and 30 bar or less while at least the central section of the enlarged diameter portion is stretched; in the second stretching step, the enlarged diameter portion is biaxially stretched by applying an internal pressure to the enlarged diameter portion that is higher than the internal pressure applied to the enlarged diameter portion in the first stretching step. A method for manufacturing a balloon for a balloon catheter, wherein the stretching speed in the first stretching step is slower than the stretching speed in the second stretching step.

2. The method for manufacturing a balloon for a balloon catheter according to claim 1, wherein the step of placing the parison in the lumen of the mold is performed before the first stretching step.

3. A method for manufacturing a balloon for a balloon catheter according to claim 1, wherein the step of placing the parison in the lumen of the mold is performed after the first stretching step and before the second stretching step.

4. Furthermore, the method for manufacturing a balloon for a balloon catheter according to any one of claims 1 to 3, further comprising the step of raising the enlarged diameter portion to a temperature of the resin or higher than the crystallization temperature Tc after the second stretching step.

5. A method for manufacturing a balloon for a balloon catheter according to any one of claims 1 to 3, wherein in the first stretching step, the first section and the second section are heated at a temperature below the glass transition temperature Tg of the resin.

6. The method for manufacturing a balloon for a balloon catheter according to claim 5, wherein the mold has a first end region, a second end region, and a central region located between the first end region and the second end region in the longitudinal direction, and the first end region, the second end region and the central region can each be heated independently.

7. A method for manufacturing a balloon for a balloon catheter according to claim 6, wherein the first end region, the second end region, and the central region are each composed of separate members, and the mold is formed by connecting the separate members in the longitudinal direction.

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