Patent Publication Number: US-2022218960-A1

Title: Balloon for balloon catheter and method for manufacturing balloon catheter

Description:
TECHNICAL FIELD 
     The present invention relates to a balloon for a balloon catheter and a method for manufacturing a balloon catheter using a tubular resin parison. 
     BACKGROUND ART 
     A balloon catheter is used to expand a stenosis site formed in a blood vessel, and a protruding part or a blade for biting into the stenosis site is preferably provided on the surface of a balloon. For example, Patent Document 1 discloses a balloon including a projection part, and a method for manufacturing a balloon including a step of forming a projection part by welding at least parts of adjacent inner surfaces at a part where inner surfaces of a balloon are placed so as to face each other. Patent Document 2 discloses a balloon having pleats formed as protruding parts, and the pleats are formed on a balloon by using a mold. 
     RELATED ART DOCUMENT 
     Patent Document 
     
         
         Patent Document 1: JP 2017-12678 A 
         Patent Document 2: JP 2005-511187 T 
       
    
     SUMMARY OF THE INVENTION 
     Problems to be Solved by the Invention 
     However, although the protruding part of the above balloon comes into contact with a stenosis site, there is room for improvement in that it is difficult to form a crack due to insufficient biting into a calcification lesion or a plaque. Therefore, an objective of the present invention is to provide a balloon for a balloon catheter and a method for manufacturing a balloon catheter that allow a crack to be easily formed in a calcification lesion or a plaque at a stenosis 
     Means for Solving the Problems 
     The gist of one embodiment of a balloon for a balloon catheter of the present invention that can solve the above problems is as follows. The balloon includes a balloon body; and a protruding part formed on an outer surface of the balloon body and made of the same material as the balloon body, wherein a surface roughness of an outer surface of the protruding part is lower than a surface roughness of the outer surface of the balloon body. By setting the surface roughness of the outer surfaces of the protruding part and the balloon body as described above, a resistance friction force generated when the protruding part bites into a calcification lesion or a plaque formed at a stenosis site can be kept low. Therefore, it is made easier to make a cut in the calcification lesion or the plaque at the stenosis site, which makes it easier to form a crack therein, so that it is possible to expand the stenosis site while preventing dissection of the vascular intima. In addition, a balloon catheter is usually delivered to a stenosis site in a state where a balloon folded so as to cover a protruding part with a balloon membrane is housed in a protective tube. However, when the protruding part of the balloon comes into contact with or rubs against the outer surface of a balloon body, a coating layer provided on the outer surface of the balloon body may be peeled off. On the other hand, with the balloon of the present invention, since the surface roughness of the protruding part is lower than that of the balloon body, it is possible to prevent the coating layer from being peeled off even when the protruding part comes into contact with the outer surface of the balloon body. This allows the balloon to remain highly passable in a body when the catheter is used while the balloon is outside the protective tube. 
     Preferably, in the balloon for a balloon catheter, the protruding part has a tip end region including an outer end point in a radial direction of the protruding part, and a base end region that is located inward of the tip end region in the radial direction and that has a surface roughness higher than a surface roughness of the tip end region. 
     The present invention also provides a method for manufacturing a balloon catheter. The gist of one embodiment of the method for manufacturing a balloon catheter of the present invention that can solve the above problems is as follows. The method includes a step of preparing a tubular parison made of a resin and a mold that has an inner cavity into which the parison is to be inserted and that has a first groove formed on an inner wall surface forming the inner cavity; a step of inserting the parison into the inner cavity of the mold; a step of allowing the resin to enter the first groove by introducing a fluid into a lumen of the parison to expand the parison; and a step of removing the parison from the mold before the resin reaches a bottom of the first groove. Since the above manufacturing method includes the step of removing the parison from the mold before the resin reaches the bottom of the first groove, the unevenness of the inner wall surface of the first groove is not transferred to the tip end side of the protruding part. Therefore, a resistance friction force generated when the protruding part bites into a calcification lesion or a plaque formed at a stenosis site can be kept low. As a result, it is made easier to make a cut in the calcification lesion or the plaque at the stenosis site, which makes it easier to form a crack therein. Therefore, it is possible to expand the stenosis site while preventing dissection of the vascular intima. 
     Preferably, in the above manufacturing method, a protruding part formed on an outer surface of the parison after the step of allowing the resin to enter the first groove has a base end region that blocks an entrance of the first groove by coming into contact with an inner wall surface of the first groove, and a tip end region that is located outward of the base end region in a radial direction and that is separated from the inner wall surface of the first groove. 
     Preferably, in the above manufacturing method, a surface roughness of the tip end region of the protruding part is lower than a surface roughness of the outer surface of the parison measured after the step of allowing the resin to enter the first groove. 
     Preferably, the above manufacturing method further includes a step of polishing an outer surface of the protruding part. The above manufacturing method preferably further includes a step of sharpening the protruding part. The above manufacturing method preferably further includes a step of roughening an outer surface of the protruding part. 
     Preferably, in the above manufacturing method, the protruding part extends along a longitudinal direction of the parison, and the method further includes a step of varying a height of the protruding part depending on a position in the longitudinal direction of the parison. 
     Preferably, in the above manufacturing method, the protruding part extends along a longitudinal direction of the parison, and the method further includes a step of making a cut in an outer surface of the protruding part. 
     Preferably, in the above manufacturing method, the first groove of the mold has a contact region being in contact with the base end region of the parison, and a non-contact region being separated from the tip end region of the parison; and the contact region has an arc-shaped part formed in an arc shape in a cross-section perpendicular to a longitudinal direction of the mold. 
     Preferably, in the above manufacturing method, the mold has a first section that extends in a longitudinal direction of the mold and that forms a straight tube part of a balloon; and the first groove is formed in the first section. 
     Preferably, in the above manufacturing method, in a longitudinal direction of the mold, the mold has a second section that is located on both sides of the first section and that forms a tapered part of the balloon, and a third section that is located on an end part side in the longitudinal direction of the mold than the second section and that forms a sleeve part of the balloon; the second section consists of a distal second section located at a position corresponding to a distal side of the balloon than the first section, and a proximal second section located at a position corresponding to a proximal side of the balloon than the first section; the third section consists of a distal third section that is located at a position corresponding to the distal side of the balloon than the distal second section and that forms a distal sleeve part, and a proximal third section that is located at a position corresponding to the proximal side of the balloon than the proximal second section and that forms a proximal sleeve part; a third groove shallower than the first groove is formed on an inner wall surface of at least either one of the distal third section and the proximal third section of the mold; and the resin reaches a bottom of the third groove in the step of allowing the resin to enter the first groove. 
     Preferably, in the above manufacturing method, a parison having a guide part protruding outwardly in a radial direction on an outer surface of the parison is prepared in the step of preparing the parison; and the guide part is placed in the third groove in the step of inserting the parison into the inner cavity of the mold. 
     Preferably, in the above manufacturing method, in a longitudinal direction of the mold, the mold has a second section that is located on both sides of the first section and that forms a tapered part of the balloon, the second section consists of a distal second section located at a position corresponding to a distal side of the balloon than the first section, and a proximal second section located at a position corresponding to a proximal side of the balloon than the first section; and no groove is formed on an inner wall surface of at least either one of the distal second section and the proximal second section of the mold. 
     Preferably, in the above manufacturing method, the first groove has a part that becomes wider toward an outer side in a radial direction. 
     Preferably, in the above manufacturing method, the first groove has a part that becomes narrower toward an outer side in a radial direction. 
     Effects of the Invention 
     According to the above balloon for a balloon catheter and the above method for manufacturing a balloon catheter, a resistance friction force generated when the protruding part of the balloon bites into a calcification lesion or a plaque formed at a stenosis site can be kept low. Therefore, it is made easier to make a cut in the calcification lesion or the plaque at the stenosis site, which makes it easier to form a crack therein, so that it is possible to expand the stenosis site while preventing dissection of the vascular intima. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a side view of a balloon for a balloon catheter according to one embodiment of the present invention. 
         FIG. 2  is a cross-sectional view taken along line II-II in  FIG. 1 . 
         FIG. 3  is a cross-sectional view illustrating a modification of  FIG. 2 . 
         FIG. 4  is an enlarged cross-sectional view of a part P in  FIG. 2 . 
         FIG. 5  is a perspective view of a parison before being expanded according to one embodiment of the present invention. 
         FIG. 6  is a cross-sectional view (partially a side view) showing a state where the parison before being expanded is placed in a mold according to one embodiment of the present invention. 
         FIG. 7  is a cross-sectional view taken along line VII-VII in  FIG. 6 , illustrating a cross-section of a first section that forms a straight tube part of a balloon. 
         FIG. 8  is a cross-sectional view showing a state where the parison shown in  FIG. 7  is expanded. 
         FIG. 9  is an enlarged cross-sectional view of a part Q in  FIG. 8 . 
         FIG. 10  is a cross-sectional view of a modification of  FIG. 9 . 
         FIG. 11  is a cross-sectional view of another modification of  FIG. 9 . 
         FIG. 12  is a cross sectional view taken along line XII-XII in  FIG. 6 , illustrating a cross-section of a distal second section that forms a distal tapered part of the balloon. 
         FIG. 13  is a cross-sectional view taken along line XIII-XIII in  FIG. 6 , illustrating a cross-section of a proximal second section that forms a proximal tapered part of the balloon. 
         FIG. 14  is a cross-sectional view taken along line XIV-XIV in  FIG. 6 , illustrating a cross-section of a distal third section that forms a distal sleeve part of the balloon. 
         FIG. 15  is a cross-sectional view taken along line XV-XV in  FIG. 6 , illustrating a cross-section of a proximal third section that forms a proximal sleeve part of the balloon. 
         FIG. 16  is a cross-sectional view taken along line XVI-XVI in  FIG. 6 , illustrating a cross-section of a distal fourth section that forms a distal sleeve outer part of the balloon. 
         FIG. 17  is a cross-sectional view taken along line XVII-XVII in  FIG. 6 , illustrating a cross-section of a proximal fourth section that forms a proximal sleeve outer part of the balloon. 
     
    
    
     DESCRIPTION OF EMBODIMENTS 
     Hereinafter, the present invention will be more specifically described based on the following embodiments. However, the present invention is not limited to the following embodiments and, as a matter of course, can also be carried out with appropriate modifications being made within the scope of the gist described above and below, and any of these modifications are included in the technical scope of the present invention. In any of the drawings, hatching, reference signs for members, or the like may be omitted for convenience. In this case, see the description and the other drawings. Since priority is given to facilitating the understanding of the characteristics of the present invention, the dimensions of various members in the drawings may be different from actual dimensions. 
     1. Balloon for Balloon Catheter 
     An embodiment of the balloon for a balloon catheter according to the present invention is characterized by including a balloon body and a protruding part formed on an outer surface of the balloon body and made of the same material as the balloon body, wherein a surface roughness of an outer surface of the protruding part is lower than a surface roughness of the outer surface of the balloon body. By setting the surface roughness of the outer surfaces of the protruding part and the balloon body as described above, a resistance friction force generated when the protruding part bites into a calcification lesion or a plaque formed at a stenosis site can be kept low. Therefore, it is made easier to make a cut in the calcification lesion or the plaque at the stenosis site, which makes it easier to form a crack therein, so that it is possible to expand the stenosis site while preventing dissection of the vascular intima. In addition, a balloon catheter is usually delivered to a stenosis site in a state where a balloon folded so as to cover a protruding part with a balloon membrane is housed in a protective tube. However, if the protruding part of the balloon comes into contact with or rubs against the outer surface of a balloon body, a coating layer provided on the outer surface of the balloon body may be peeled off. On the other hand, with the balloon of the present invention, since the surface roughness of the protruding part is lower than that of the balloon body, it is possible to prevent the coating layer from being peeled off even when the protruding part comes into contact with the outer surface of the balloon body. This allows the balloon to remain highly passable in a body when the catheter is used while the balloon is outside the protective tube. Hereinafter, a balloon for a balloon catheter is sometimes referred to simply as a “balloon”. 
     A balloon for a balloon catheter will be described with reference to  FIG. 1  and  FIG. 2 .  FIG. 1  shows a side view of a balloon for a balloon catheter according to an embodiment of the present invention, and  FIG. 2  shows a cross-sectional view taken along line II-II in  FIG. 1 . 
     A balloon catheter is a medical instrument mainly used in angioplasties (PTA, PTCA, etc.) that are conducted in treatment of a stenosis site in a blood vessel to expand the stenosis site. It has been known that various diseases develop because of stagnation in circulation of blood due to occurrence of a stenosis of a blood vessel, which is a flow path for circulating blood in the body. Especially, if a coronary artery for supplying blood to the heart suffers a stenosis, critical diseases such as angina pectoris and myocardial infarction may be caused. Angioplasties are minimally invasive therapies requiring no thoracotomies such as bypass surgery and are therefore widely conducted. 
     A balloon catheter includes a shaft and a balloon provided outside the shaft. The balloon catheter has a proximal side and a distal side, the balloon is provided on the distal side of the shaft, and a hub is provided on the proximal side of the shaft. The proximal side of the balloon refers to the hand side of a user or an operator in the longitudinal direction of the shaft or the direction in which the balloon catheter extends, and the distal side of the balloon refers to the side opposite to the proximal side, that is, the treatment target side. In addition, the direction from the proximal side to the distal side of the balloon is referred to as distal-proximal direction. 
     As shown in  FIG. 1  and  FIG. 2 , a balloon  1  includes a balloon body  6  and a protruding part  10  formed on an outer surface  7  of the balloon body  6  and made of the same material as the balloon body  6 . The balloon body  6  defines the basic shape of the balloon  1  and is preferably formed in a bag shape having openings on the proximal side and the distal side, respectively. The protruding part  10  is preferably provided on the outer surface  7  of the balloon body  6  in a dot-like, linear, or net-like pattern. By providing the protruding part  10  on the outer surface  7  of the balloon body  6 , it is possible to crack and expand a calcified stenosis site in an angioplasty with the protruding part  10  given a scoring function. In addition, it is also possible to increase the strength of the balloon  1  and suppress excessive expansion of the balloon  1  during pressurization. 
     In the present invention, the protruding part  10  of the balloon  1  refers to a part formed higher in the radial direction than the film thickness at a predetermined position of the balloon body  6 . In the case where one protruding part  10  is provided to the balloon body  6 , the predetermined position is a position A facing an outer end  11  in the radial direction of the protruding part  10  in the circumferential direction of the balloon  1  as shown in  FIG. 2 . In the case where a plurality of protruding parts  10  are provided to the balloon body  6 , the predetermined position is a position B corresponding to the midpoint in the circumferential direction of the balloon  1  between outer ends  11  of the protruding parts  10  adjacent to each other in the circumferential direction as shown in  FIG. 3 . 
     The maximum height in the radial direction of the protruding part  10  is preferably not less than 1.2 times, more preferably not less than 1.5 times, and further preferably not less than 2 times the film thickness at the predetermined position of the balloon body  6 , and is also permitted to be not greater than 100 times, not greater than 50 times, not greater than 30 times, or not greater than 10 times the film thickness at the predetermined position of the balloon body  6 . Accordingly, it is made easier to make a cut with an appropriate depth in a calcification lesion or a plaque at a stenosis site, which makes it easier to form a crack therein. 
     In the case where the protruding part  10  is formed in a dot-like or linear pattern, the protruding part  10  is preferably provided so as to extend along the distal-proximal direction of the balloon  1 . In addition, the protruding part  10  may be provided so as to extend spirally around the long axis of the balloon  1 . Furthermore, the protruding part  10  may be provided so as to extend along the circumferential direction of the balloon  1 . Accordingly, the contact area between the protruding part  10  and a stenosis site can be adjusted, so that it is possible to achieve both desired passing performance of the catheter in a body cavity and desired non-slip performance of the balloon  1  against the stenosis site. 
     As shown in  FIG. 1 , the balloon  1  includes a straight tube part  2 , a tapered part  3  that is located on both sides of the straight tube part  2  and that has an outer diameter decreasing toward the end part side in a distal-proximal direction x 1 , a sleeve part  4  that is located on the end part side in the distal-proximal direction x 1  than the tapered part  3  and that is to be connected to the shaft of a balloon catheter, and a sleeve outer part  5  that is located on the end part side in the distal-proximal direction x 1  than the sleeve part  4  and that is to be cut before the balloon  1  is attached to the shaft. A part of the tapered part  3  located on the distal side than the straight tube part  2  is referred to as a distal tapered part  3 D, and a part of the tapered part  3  located on the proximal side than the straight tube part  2  is referred to as a proximal tapered part  3 P. In addition, a part of the sleeve part  4  located on the distal side than the distal tapered part  3 D is referred to as a distal sleeve part  4 D, and a part of the sleeve part  4  located on the proximal side than the proximal tapered part  3 P is referred to as a proximal sleeve part  4 P. Furthermore, a part of the sleeve outer part  5  located on the distal side than the distal sleeve part  4 D is referred to as a distal sleeve outer part  5 D, and a part of the sleeve outer part  5  located on the proximal side than the proximal sleeve part  4 P is referred to as a proximal sleeve outer part  5 P. 
     The protruding part  10  is preferably provided to the straight tube part  2 . Accordingly, during expansion of the balloon  1 , the protruding part  10  easily bites into a stenosis site. The protruding part  10  may be provided to the straight tube part  2  and the tapered part  3  such that a stenosis site is easily cracked. 
       FIG. 3  shows a cross-sectional view illustrating a modification of  FIG. 2 . As shown in  FIG. 2 , only one protruding part  10  may be provided. In addition, as shown in  FIG. 3 , a plurality of protruding parts  10  may be provided. In this case, the plurality of protruding parts  10  are preferably provided so as to be aligned in the circumferential direction, and more preferably provided at equal intervals in the circumferential direction. By providing the plurality of protruding parts  10  as described above, it is made easier to crack a stenosis site at a plurality of positions. The plurality of protruding parts  10  are preferably provided so as to be separated from each other in the circumferential direction, and the separation distance between the protruding parts  10  adjacent to each other in the circumferential direction is more preferably longer than the maximum circumferential length of each protruding part  10 . 
     Since the balloon body  6  and the protruding part  10  are made of the same material, the protruding part  10  can be prevented from damaging the outer surface  7  of the balloon body  6  while maintaining the flexibility of the balloon  1 . The balloon body  6  and the protruding part  10  are preferably integrally molded. Accordingly, the protruding part  10  can be prevented from falling off from the balloon body  6 . Such a balloon  1  can be manufactured, for example, by placing a parison obtained by extrusion, in a mold having a groove, and performing biaxial stretching blow molding. A preferable method for manufacturing the balloon will be described later in “2. Method for manufacturing balloon catheter”. 
     Examples of a resin for forming the balloon body  6  and the protruding part  10  include: polyolefin-based resins such as polyethylene, polypropylene, and ethylene-propylene copolymer; polyester-based resins such as polyethylene terephthalate and polyester elastomer; polyurethane-based resins such as polyurethane and polyurethane elastomer; polyphenylene sulfide-based resins; polyamide-based resins such as polyamide and polyamide elastomer; fluorine-based resins; silicone-based resins; natural rubbers such as latex rubber; and the like. Only one of these resins may be used, or two or more of these resins may be used in combination. Among these resins, polyamide-based resins, polyester-based resins, and polyurethane-based resins are suitably used. Especially, an elastomer resin is preferably used in terms of thickness reduction and flexibility of the balloon  1 . Examples of a material suitable for the balloon  1  among polyamide-based resins include nylon 12, nylon 11, and the like, and nylon 12 is suitably used since it can be relatively easy to blow mold. Moreover, polyamide elastomers such as polyether ester amide elastomer and polyamide ether elastomer are preferably used in terms of thickness reduction and flexibility of the balloon  1 . Among these elastomers, polyether ester amide elastomer is preferably used since polyether ester amide elastomer has a high yield strength and allows the balloon  1  to have good dimensional stability. 
     A surface roughness of an outer surface  12  of the protruding part  10  is lower than a surface roughness of the outer surface  7  of the balloon body  6 . By reducing the surface roughness of the protruding part  10  as described above, it is made easier to make a cut in a calcification lesion or a plaque at a stenosis site, which makes it easier to form a crack therein, so that it is possible to expand the stenosis site while preventing dissection of the vascular intima. The surface roughness of the outer surface  12  of the protruding part  10  is preferably not less than 0.01 times, more preferably not less than 0.05 times, and further preferably not less than 0.1 times the surface roughness of the outer surface  7  of the balloon body  6 , and is also permitted to be not greater than 0.9 times, not greater than 0.8 times, or not greater than 0.7 times the surface roughness of the outer surface  7  of the balloon body  6 . An example of the method for reducing the surface roughness of the outer surface  12  of the protruding part  10  is a method in which the protruding part  10  is polished by using a grinding machine or a file. 
     In the case where only one protruding part  10  is provided to the balloon body  6 , the surface roughness of the outer surface  7  of the balloon body  6  is obtained by measuring a part including the position A of the outer surface  7  of the balloon body  6  as shown in  FIG. 2 . In the case where a plurality of protruding parts  10  are provided to the balloon body  6 , the surface roughness of the outer surface  7  of the balloon body  6  is obtained by measuring a part including the position B of the outer surface  7  of the balloon body  6  as shown in  FIG. 3 . In addition, the surface roughness of the outer surface  12  of the protruding part  10  is obtained by measuring a part including the outer end  11  in the radial direction of the protruding part  10  (that is, the tip end of the protruding part  10 ) of the outer surface  12  of the protruding part  10 . In the case where there are a plurality of protruding parts  10 , it is sufficient that any one of the protruding parts  10  is measured. 
     The surface roughness is an arithmetic mean roughness Ra in a reference length of a roughness curve for the outer surface of the balloon body  6  or the protruding part  10 , and the reference length is 0.1 mm. The arithmetic mean roughness Ra corresponds to an arithmetic mean roughness Ra specified in JIS B 0601 (2001), and is measured according to JIS B 0633 (2001). For the measurement, a measuring machine specified in JIS B 0651 (2001) (for example, a laser microscope VK-9510 manufactured by KEYENCE CORPORATION) is used. 
     The surface roughness of the entirety of the outer surface  12  of the protruding part  10  (that is, the entire outer peripheral surface of the protruding part  10 ) is preferably lower than the surface roughness of the outer surface  7  of the balloon body  6 . Accordingly, it is made easier to make a cut in a calcification lesion or a plaque at a stenosis site, so that the formation of a crack is further promoted. 
     In the case where a plurality of protruding parts  10  are provided to the balloon body  6  as shown in  FIG. 3 , the surface roughnesses of the outer surfaces  12  of all of the protruding parts  10  are preferably lower than the surface roughness of the outer surface  7  of the balloon body  6 . Accordingly, it is made easier to make a cut in a calcification lesion or a plaque at a stenosis site, so that the formation of a crack is further promoted. 
       FIG. 4  shows an enlarged cross-sectional view of a part P, of the balloon  1  in  FIG. 2 , where the protruding part  10  is provided. As shown in  FIG. 4 , the protruding part  10  preferably includes a tip end region  13  that includes the outer end  11  in the radial direction of the protruding part  10 , and a base end region  14  that is located inward of the tip end region  13  in the radial direction and that has a surface roughness higher than a surface roughness of the tip end region  13 . Accordingly, it is made easier to make a cut in a calcification lesion or a plaque at a stenosis site by the tip end region  13 , which makes it easier to form a crack therein, so that it is possible to expand the stenosis site while preventing dissection of the vascular intima. In addition, the resistance friction force between the base end region  14  and the stenosis site can be increased, so that the non-slip performance of the balloon  1  against the stenosis site can be improved. 
     The surface roughness of the base end region  14  is preferably not less than 2 times, more preferably not less than 3 times, and further preferably not less than 5 times the surface roughness of the tip end region  13 , and is also permitted to be not greater than 20 times, not greater than 18 times, or not greater than 15 times the surface roughness of the tip end region  13 . 
     The surface roughness of the base end region  14  may be equal to the surface roughness of the outer surface  7  of the balloon body  6 , or is preferably not less than 0.1 times, more preferably not less than 0.2 times, and further preferably not less than 0.3 times the surface roughness of the outer surface  7  of the balloon body  6  and is also permitted to be not greater than 0.9 times, not greater than 0.8 times, or not greater than 0.7 times the surface roughness of the outer surface  7  of the balloon body  6 . 
     The orientation of molecules in the tip end region  13  may be different from the orientation of molecules in the base end region  14 . For example, in the tip end region  13 , the molecules may be oriented outward in the radial direction or parallel to the movement direction of the resin during blow molding, and, in the base end region  14 , the molecules may be oriented outward in the radial direction or in a direction perpendicular to the movement direction of the resin during blow molding. For measuring the orientation of the molecules, for example, an X-ray diffraction method or Raman spectroscopy can be used. 
     The degree of crystallinity in the tip end region  13  may be different from the degree of crystallinity in the base end region  14 . The degree of crystallinity of the tip end region  13  is preferably higher than the degree of crystallinity in the base end region  14 . Accordingly, cooling strain is less likely to occur in the tip end region  13  during the production of the protruding part  10 , so that excessive deformation of the tip end region  13  can be prevented. The degree of crystallinity can be calculated from, for example, a calorific value obtained from a DSC curve obtained by differential scanning calorimetry. 
     2. Method for Manufacturing Balloon Catheter 
     An embodiment of the method for manufacturing a balloon catheter according to the present invention is characterized by including: a step of preparing a tubular parison made of a resin and a mold that has an inner cavity into which the parison is to be inserted and that has a first groove formed on an inner wall surface forming the inner cavity; a step of inserting the parison into the inner cavity of the mold; a step of allowing the resin to enter the first groove by introducing a fluid into a lumen of the parison to expand the parison; and a step of removing the parison from the mold before the resin reaches the bottom of the first groove. Since the manufacturing method includes the step of removing the parison from the mold before the resin reaches the bottom of the first groove, the unevenness of the inner wall surface of the first groove is not transferred to the tip end side of the protruding part. Therefore, a resistance friction force generated when the protruding part bites into a calcification lesion or a plaque formed at a stenosis site can be kept low. As a result, it is made easier to make a cut in the calcification lesion or the plaque at the stenosis site, which makes it easier to form a crack therein. Therefore, it is possible to expand the stenosis site while preventing dissection of the vascular intima. Furthermore, the balloon described in “1. Balloon for balloon catheter” can be manufactured by the above manufacturing method. 
     The above manufacturing method will be described with reference to  FIG. 5  to  FIG. 9 .  FIG. 5  shows a perspective view of a parison before expansion according to an embodiment of the present invention, and  FIG. 6  shows a cross-sectional view (partial side view) showing a state where the parison before expansion is placed in a mold according to an embodiment of the present invention. In addition,  FIG. 7  shows a cross-sectional view taken along a line VII-VII in  FIG. 6  and illustrates a cross-section of a first section that forms a straight tube part of a balloon.  FIG. 8  shows a cross-sectional view of a state where the parison shown in  FIG. 7  is expanded, and  FIG. 9  shows an enlarged cross-sectional view of a part Q in  FIG. 8 . 
     First, a parison  20  and a mold  30  are prepared. The parison  20  is a tubular member made of a resin. The parison  20  is produced, for example, by extrusion. The parison  20  has a first end  21  and a second end  22 , and extends in a longitudinal direction x 2  from the first end  21  toward the second end  22 . 
     As shown in  FIG. 5 , a cross-sectional shape of the parison  20  in a direction perpendicular to the longitudinal direction x 2  may be substantially uniform in the longitudinal direction x 2 . Accordingly, the productivity of the parison  20  can be increased. Alternatively, the cross-sectional shape of the parison  20  in the direction perpendicular to the longitudinal direction x 2  may be different depending on the position in the longitudinal direction x 2 . The outer diameter of a part in the longitudinal direction x 2  (for example, a part corresponding to the straight tube part and a tapered part of the balloon) of the parison  20  may be larger than that of other parts. In order to make the cross-sectional shape of the parison  20  different in the longitudinal direction x 2 , blow molding may be performed in advance by using another mold. 
     For the material for forming the parison  20 , the description of the resin for forming the balloon body  6  and the protruding part  10  described in “1. Balloon for balloon catheter” can be referred to. 
     The mold  30  has an inner cavity  35  into which the parison  20  is to be inserted. Specifically, a part in the longitudinal direction x 2  of the parison  20  is preferably placed in the mold  30 . As shown in  FIG. 6 , the mold  30  has a longitudinal direction x 3  corresponding to the longitudinal direction x 2  of the parison  20 . In order to make it easier to place the parison  20  in the mold  30 , the longitudinal direction x 3  of the mold  30  preferably coincides with the longitudinal direction x 2  of the parison  20 . 
     As shown in  FIG. 6 , the mold  30  preferably has, in the longitudinal direction x 3  thereof, a first section  31  that forms the straight tube part of the balloon, and a second section  32  on both sides of the first section  31  and that forms the tapered part of the balloon. In addition, the mold  30  may have a third section  33  that is located on the end part side in the longitudinal direction x 3  than the second section  32  and that forms a sleeve part of the balloon, and a fourth section  34  that is located on the end part side in the longitudinal direction x 3  than the third section  33  and that forms a sleeve outer part of the balloon. The second section  32  preferably includes a distal second section  32 D located at a position corresponding to the distal side of the balloon than the first section  31 , and a proximal second section  32 P located at a position corresponding to the proximal side of the balloon than the first section  31 . The third section  33  preferably includes a distal third section  33 D that is located at a position corresponding to the distal side of the balloon than the distal second section  32 D and that forms a distal sleeve part of the balloon, and a proximal third section  33 P that is located at a position corresponding to the proximal side of the balloon than the proximal second section  32 P and that forms a proximal sleeve part of the balloon. The fourth section  34  preferably includes a distal fourth section  34 D that is located at a position corresponding to the distal side of the balloon than the distal third section  33 D and that forms a distal sleeve outer part of the balloon, and a proximal fourth section  34 P that is located at a position corresponding to the proximal side of the balloon than the proximal third section  33 P and that forms a proximal sleeve outer part of the balloon. 
     The mold  30  may be formed of one member, or may be formed of a plurality of members. For example, the mold  30  may be formed of a plurality of half-split bodies, or may be formed by a plurality of mold members being connected to each other in the distal-proximal direction. Above all, the mold  30  is preferably formed of a plurality of mold members having inner cavity cross-sectional shapes varied stepwise. In  FIG. 6 , the mold  30  includes a first mold  30 A, a second mold  30 B, a third mold  30 C, a fourth mold  30 D, a fifth mold  30 E, and a sixth mold  30 F in order from the proximal side. As shown in  FIG. 6 , the adjacent mold members may be connected by engaging the mold members with each other. Although not shown, the adjacent mold members may be connected by allowing magnets, which are attached to the mold members, to attract each other. 
     The inner cavity cross-sectional shape of the mold  30  can be a circular shape, an oblong shape, a polygonal shape, or a combination thereof. The oblong shape includes an elliptical shape, an egg shape, and a rectangular shape with rounded corners. 
     As shown in  FIG. 7 , a first groove  41  is formed on an inner wall surface  36  forming the inner cavity  35  of the mold  30 . As shown in  FIG. 6  and  FIG. 7 , the parison  20  is inserted into the inner cavity  35  of the mold  30 . A fluid is introduced into a lumen  23  of the parison  20  to expand the parison  20  to allow the resin to enter the first groove  41  as shown in  FIG. 8 . As described above, by expanding the parison  20 , the resin forming the parison  20  can be allowed to enter the first groove  41 , thereby forming a protruding part  25  on the outer surface of the parison  20 . 
     In the present invention, the protruding part  25  of the parison  20  refers to a part formed higher in the radial direction than the film thickness at a predetermined position of the expanded parison  20 . For the predetermined position, the description of the predetermined position of the balloon body  6  described in “1. Balloon for balloon catheter” can be referred to by replacing the “balloon body” therein with “parison”. 
     The parison  20  is removed from the mold  30  before the resin reaches a bottom  41   a  of the first groove  41 . Accordingly, the unevenness of the inner wall surface of the first groove  41  is not transferred to the tip end side of the protruding part  25 , so that a resistance friction force generated when the protruding part  25  bites into calcification lesion or a plaque formed at a stenosis site can be kept low. Therefore, it is made easier to make a cut in the calcification lesion or the plaque at the stenosis site, which makes it easier to form a crack therein. As a result, it is possible to expand the stenosis site while preventing dissection of the vascular intima. The expanded parison  20  can be used as a balloon for a balloon catheter. A balloon catheter can be manufactured by attaching the expanded parison  20  to the distal side of a shaft. 
     As shown in  FIG. 7 , one or more first grooves  41  can be provided. A plurality of first grooves  41  may be provided so as to be aligned in the circumferential direction. In this case, the first grooves  41  are preferably provided at equal intervals in the circumferential direction. By providing the first grooves  41  as described above, a plurality of protruding parts, which are produced by entering the first grooves  41 , can be also provided, so that it is made easier to crack a stenosis site at a plurality of positions. The first grooves  41  are preferably provided so as to be separated from each other in the circumferential direction, and the separation distance between the first grooves  41  adjacent to each other in the circumferential direction is more preferably longer than the maximum circumferential length of each first groove  41 . 
     The first groove  41  preferably extends in the longitudinal direction x 3  of the mold  30 . Accordingly, the protruding part  25  can be allowed to extend in the longitudinal direction x 3  of the mold  30 . 
     The depth of the first groove  41  may be uniform in the longitudinal direction x 3  of the mold  30 , or may be different depending on the position in the longitudinal direction x 3 . 
     As shown in  FIG. 9 , the protruding part  25  formed on the outer surface of the parison  20  after the step of allowing the resin to enter the first groove  41  preferably has a base end region  29  that blocks an entrance of the first groove  41  by coming into contact with the inner wall surface of the first groove  41 , and a tip end region  28  that is located outward of the base end region  29  in the radial direction and that is separated from the inner wall surface of the first groove  41 . The tip end region  28  preferably includes an outer end  26  in the radial direction of the protruding part  25 . The base end region  29  is a part that has been in contact with the inner wall surface of the first groove  41 , so that the unevenness of the inner wall surface of the first groove  41  is transferred thereto. On the other hand, the tip end region  28  is a part that has been separated from the inner wall surface of the first groove  41  of the mold  30 , so that the unevenness of the inner wall surface of the first groove  41  is not transferred thereto. By adjusting the amount of the resin entering the first groove  41  as described above, the unevenness of the outer surfaces of the tip end region  28  and the base end region  29  of the protruding part  25  can be made different from each other. After the parison  20  is removed from the mold  30 , the boundary between the tip end region  28  and the base end region  29  of the protruding part  25  can be confirmed by observing a cross-section, perpendicular to the distal-proximal direction, of the parison  20  using a microscope. 
     As shown in  FIG. 9 , the first groove  41  preferably has a part  41   b  that becomes narrower toward the outer side in the radial direction. Accordingly, it is made easier to sharpen the protruding part  25 , and it is made easier to make a cut in a calcification lesion or a plaque at a stenosis site by the protruding part  25 , so that it is made easier to form a crack therein. The width may decrease toward the outer side in the radial direction over the entire depth of the first groove  41  as shown in  FIG. 9 . Alternatively, the part  41   b  that becomes narrower toward the outer side in the radial direction may be provided on the entrance side of the first groove  41  as shown in  FIG. 10  described later. 
       FIG. 10  shows a cross-sectional view of a modification of  FIG. 9 . As shown in  FIG. 10 , the first groove  41  preferably has a part  41   c  that becomes wider toward the outer side in the radial direction. In this case, the part  41   c  that becomes wider toward the outer side in the radial direction is preferably disposed on the bottom  41   a  side of the first groove  41 . Accordingly, the resin is less likely to reach the bottom  41   a  of the first groove  41 , and deformation of the protruding part  25  can also be prevented. 
     As shown in  FIG. 10 , the first groove  41  may have both the part  41   b  that becomes narrower toward the outer side in the radial direction and the part  41   c  that becomes wider toward the outer side in the radial direction. In this case, the part  41   c  that becomes wider toward the outer side in the radial direction is preferably located on the outer side in the radial direction (that is, on the bottom  41   a  side of the first groove  41 ) than the part  41   b  that becomes narrower toward the outer side in the radial direction. Accordingly, it is possible to transfer the unevenness of the inner wall surface of the first groove  41  to the parison  20  on the entrance side of the first groove  41  while making the resin less likely to reach the bottom  41   a  of the first groove  41 . Therefore, it is made easier to form the parison  20  having the tip end region  28  and the base end region  29 . 
     A surface roughness of the tip end region  28  of the protruding part  25  is preferably lower than a surface roughness of the outer surface of the parison  20  measured after the step of allowing the resin to enter the first groove  41 . By reducing the surface roughness of the tip end region  28  of the protruding part  25  as described above, it is made easier to make a cut in a calcification lesion or a plaque at a stenosis site, which makes it easier to form a crack therein. Therefore, it is possible to expand the stenosis site while preventing dissection of the vascular intima. 
     For the measurement location of the surface roughness of the outer surface of the parison  20 , the description of the measurement location of the surface roughness of the outer surface  7  of the balloon body  6  described in “1. Balloon for balloon catheter” can be referred to by replacing the “balloon body” therein with “parison”. 
     The surface roughness is an arithmetic mean roughness Ra in a reference length of a roughness curve for the inner wall surface of the mold  30  or the outer surface of the parison  20 , and the reference length is 0.1 mm. The arithmetic mean roughness Ra corresponds to an arithmetic mean roughness Ra specified in JIS B 0601 (2001), and is measured according to JIS B 0633 (2001). For the measurement, a measuring machine specified in JIS B 0651 (2001) (for example, a laser microscope VK-9510 manufactured by KEYENCE CORPORATION) is used. 
     An example of the method for increasing the surface roughnesses of the inner wall surface of the mold  30  and the outer surface of the parison  20  is a method in which these surfaces are mechanically or chemically roughened, and examples thereof include methods using etching, blasting, a wire brush, and sandpaper. 
     A surface roughness of the base end region  29  is preferably not less than 2 times, more preferably not less than 3 times, and further preferably not less than 5 times the surface roughness of the tip end region  28 , and is also permitted to be not greater than 20 times, not greater than 18 times, or not greater than 15 times the surface roughness of the tip end region  28 . 
     The surface roughness of the base end region  29  may be equal to the surface roughness of the outer surface of the parison  20  measured after the step of allowing the resin to enter the first groove  41 , or is preferably not less than 0.1 times, more preferably not less than 0.2 times, and further preferably not less than 0.3 times the surface roughness of the outer surface of the parison  20  and is also permitted to be not greater than 0.9 times, not greater than 0.8 times, or not greater than 0.7 times the surface roughness of the outer surface of the parison  20 . 
     The above manufacturing method preferably further includes a step of polishing an outer surface  27  of the protruding part  25 . This allows the unevenness of the outer surface  27  of the protruding part  25  to be varied. By polishing the outer surface  27  of the protruding part  25 , the tip end of the protruding part  25  may be formed sharply, or the surface roughness of the tip end region  28  of the protruding part  25  may be made lower than the surface roughness of the outer surface of the parison  20  measured after the step of allowing the resin to enter the first groove  41 . A grinding machine or a file can be used for polishing. 
     The above manufacturing method may further include a step of sharpening the protruding part  25 . In this case, the tip end region  28  of the protruding part  25  is preferably sharpened. Accordingly, it is made easier to make a cut in a calcification lesion or a plaque at a stenosis site by the protruding part  25 , which makes it easier to form a crack therein. Therefore, it is possible to expand the stenosis site while preventing dissection of the vascular intima. Examples of the method for sharpening the protruding part  25  include a method in which the outer surface  27  of the protruding part  25  is polished, and a method in which the outer surface  27  of the protruding part  25  is shaved with a laser processing device or a cutting tool. 
     The above manufacturing method may further include a step of roughening the outer surface  27  of the protruding part  25 . Accordingly, a resistance friction force generated when a stenosis site and the protruding part  25  come into contact with each other can be increased, so that the non-slip performance of the balloon can be improved. In order to achieve both improvement of non-slip performance and prevention of peeling of a coating layer provided on the outer surface of the balloon, only a part in the circumferential direction of the protruding part  25  of the parison  20  may be roughened. 
     Preferably, in the above manufacturing method, the protruding part  25  extends along the longitudinal direction x 2  of the parison  20 , and the above manufacturing method further includes a step of varying the height of the protruding part  25  depending on the position in the longitudinal direction x 2  of the parison  20 . Here, the height of the protruding part  25  means the height in the radial direction from the inner surface of the balloon body. By varying the height of the protruding part  25 , the protruding part  25  can easily bite into a stenosis site, so that the non-slip performance of the balloon can be improved. 
     Preferably, the protruding part  25  extends along the longitudinal direction x 2  of the parison  20 , and the above manufacturing method further includes a step of making a cut in the outer surface  27  of the protruding part  25 . By making a cut in the protruding part  25  as described above, the passing performance of the catheter in a body cavity can be improved. A cutting tool such as a cutter or a knife can be used for forming a cut. 
     The protruding part  25  may be divided into a plurality of parts by making a cut. One or more cuts can be provided in one protruding part  25 . It is sufficient that the depth of the cut is smaller than the height of the protruding part  25 . Accordingly, when the balloon formed from the expanded parison  20  is inserted into a body, it is possible to prevent body fluids and the like from entering the inside of the balloon through the part in which the cut is made. The width of the cut is not particularly limited, but is preferably smaller than the width of the protruding part  25 . 
     The cut may be formed along the direction in which the protruding part  25  extends. Above all, the cut preferably extends along the longitudinal direction x 2  of the parison  20 . Alternatively, the cut may extend spirally around the long axis of the parison  20 . The cut extending as described above can improve the passing performance of the catheter in a body cavity. 
     The cut may extend along the circumferential direction of the parison  20 . The cut extending as described above can improve the non-slip performance of the balloon against a stenosis site. 
       FIG. 11  shows a cross-sectional view illustrating another modification of  FIG. 9 . Preferably, as shown in  FIG. 11 , the first groove  41  of the mold  30  has a contact region  42  being in contact with the base end region  29  of the parison  20 , and a non-contact region  43  being separated from the tip end region  28  of the parison  20 , and the contact region  42  includes an arc-shaped part  41   d  formed in an arc shape in a cross section perpendicular to the longitudinal direction x 3  of the mold  30 . Accordingly, a sudden change in outer shape from the outer surface of the parison  20  to the base end region  29  of the protruding part  25  can be reduced, so that the protruding part  25  can be prevented from breaking due to an external force. 
     The arc-shaped part  41   d  is preferably formed in a part including an inner end in the radial direction of the contact region  42 . Accordingly, the effect of reducing the change in outer shape from the outer surface of the parison  20  to the protruding part  25  can be enhanced. In the first groove  41  of the mold  30 , a linear part may be formed on the outer side in the radial direction than the arc-shaped part  41   d.    
     Preferably, as shown in  FIG. 6  to  FIG. 8 , the mold  30  has the first section  31  that extends in the longitudinal direction x 3  and that forms the straight tube part of the balloon, and the first groove  41  is formed in the first section  31 . Accordingly, the protruding part  25  can be formed in the parison  20  at the position corresponding to the straight tube part of the balloon. 
     Preferably, the mold  30  has, in the longitudinal direction x 3 , the second section  32  that is located on both sides of the first section  31  and that forms the tapered part of the balloon, the second section  32  includes the distal second section  32 D located at the position corresponding to the distal side of the balloon than the first section  31 , and the proximal second section  32 P located at the position corresponding to the proximal side of the balloon than the first section  31 , and a second groove  45  is formed in at least either one of the distal second section  32 D and the proximal second section  32 P of the mold  30 . Accordingly, a second protruding part is formed at the position corresponding to the tapered part of the balloon, so that the non-slip performance of the balloon against a stenosis site can be improved. 
     Preferably, the mold  30  has, in the longitudinal direction x 3 , the second section  32  that is located on both sides of the first section  31  and that forms the tapered part of the balloon, the second section  32  includes the distal second section  32 D located at the position corresponding to the distal side of the balloon than the first section  31 , and the proximal second section  32 P located at the position corresponding to the proximal side of the balloon than the first section  31 , and no groove is formed on the inner wall surface of at least either one of the distal second section  32 D and the proximal second section  32 P of the mold  30 . Accordingly, no protruding part is formed at the position, corresponding to the tapered part of the balloon, in the parison  20 , so that the slipperiness of the tapered part of the balloon is appropriately ensured, and the passing performance of the balloon can be further enhanced. 
     Preferably, the mold  30  has, in the longitudinal direction x 3 , the second section  32  that is located on both sides of the first section  31  and that forms the tapered part of the balloon, and the third section  33  that is located on the end part side in the longitudinal direction x 3  than the second section  32  and that forms the sleeve part of the balloon, the second section  32  includes the distal second section  32 D located at the position corresponding to the distal side of the balloon than the first section  31 , and the proximal second section  32 P located at the position corresponding to the proximal side of the balloon than the first section  31 , the third section  33  includes the distal third section  33 D that is located at the position corresponding to the distal side of the balloon than the distal second section  32 D and that forms the distal sleeve part of the balloon, and the proximal third section  33 P that is located at the position corresponding to the proximal side of the balloon than the proximal second section  32 P and that forms the proximal sleeve part of the balloon, a third groove  47  shallower than the first groove  41  is formed on the inner wall surface of at least either one of the distal third section  33 D and the proximal third section  33 P of the mold  30 , and the resin reaches the bottom of the third groove  47  in the step of allowing the resin to enter the first groove  41 . Accordingly, a third protruding part lower than the protruding part  25  (first protruding part) can be formed at the position, corresponding to the sleeve part of the balloon, in the parison  20 , so that the passing performance of the sleeve part of the balloon in a body can be enhanced. 
     Preferably, in the step of preparing the parison  20 , a parison  20  having a guide part protruding outwardly in the radial direction on its outer surface is prepared, and, in the step of inserting the parison  20  into the inner cavity  35  of the mold  30 , the guide part is placed in the third groove  47 . Accordingly, when the parison  20  is expanded by introducing a fluid into the lumen  35  of the parison  20 , the guide part comes into contact with the third groove  47 , which prevent the parison from rotating. Therefore, a protruding part formed on the outer surface of the balloon or the balloon body can be produced in a desired shape. 
       FIG. 12  shows a cross-sectional view taken along a line XII-XII in  FIG. 6  and illustrates a cross-section of the distal second section  32 D that forms the distal tapered part of the balloon.  FIG. 13  shows a cross-sectional view taken along a line XIII-XIII in  FIG. 6  and illustrates a cross-section of the proximal second section  32 P that forms the proximal tapered part of the balloon. In  FIG. 12  and the drawings subsequent thereto, the parison  20  in the mold  30  is not shown. Preferably, as shown in  FIG. 6 ,  FIG. 12 , and  FIG. 13 , the second section  32  includes the distal second section  32 D and the proximal second section  32 P, the second groove  45  is formed on the inner wall surface  36  of the proximal second section  32 P, and no groove is formed on the inner wall surface  36  of the distal second section  32 D. Accordingly, the slipperiness of the distal tapered part of the balloon is appropriately ensured, so that the passing performance of the balloon can be enhanced. In addition, a second protruding part is formed on the proximal tapered part, so that the non-slip performance of the balloon against a stenosis site can be improved. 
       FIG. 14  shows a cross-sectional view taken along a line XIV-XIV in  FIG. 6  and illustrates a cross-section of the distal third section  33 D that forms the distal sleeve part of the balloon. In addition,  FIG. 15  shows a cross-sectional view taken along a line XV-XV in  FIG. 6  and illustrates a cross-section of the proximal third section  33 P that forms the proximal sleeve part of the balloon. Preferably, as shown in  FIG. 6 ,  FIG. 14 , and  FIG. 15 , the third section  33  of the mold  30  includes the distal third section  33 D and the proximal third section  33 P, and the third groove  47  is formed on the inner wall surface  36  of at least either one of the distal third section  33 D and the proximal third section  33 P. In this case, in the step of allowing the resin to enter the first groove  41 , the resin preferably reaches the bottom of the third groove  47 . Accordingly, a protruding part can also be provided at the position, corresponding to the sleeve part of the balloon, in the parison  20 . 
       FIG. 16  shows a cross-sectional view taken along a line XVI-XVI in  FIG. 6  and illustrates a cross-section of the distal fourth section  34 D that forms the distal sleeve outer part of the balloon.  FIG. 17  shows a cross-sectional view taken along a line XVII-XVII in  FIG. 6  and illustrates a cross-section of the proximal fourth section  34 P that forms the proximal sleeve outer part of the balloon. As shown in  FIG. 6 ,  FIG. 16 , and  FIG. 17 , the mold  30  may have the distal fourth section  34 D and the proximal fourth section  34 P, and a fourth groove  49  may be formed on the inner wall surface  36  of at least either one of the distal fourth section  34 D and the proximal fourth section  34 P. In this case, in the step of allowing the resin to enter the first groove  41 , the resin preferably reaches the bottom of the fourth groove  49 . Accordingly, a protruding part can also be provided at the position, corresponding to the sleeve outer part of the balloon, in the parison  20 . 
     The depths of the third groove  47  and the fourth groove  49  are preferably smaller than that of the first groove  41 . Accordingly, in the step of allowing the resin to enter the first groove  41 , the resin is likely to reach the bottom of the third groove  47  or the fourth groove  49  earlier than filling the first groove  41 , so that the effect of fixing the position, corresponding to the sleeve part or the sleeve outer part of the balloon, in the parison  20  by the mold  30  can be enhanced. Therefore, when the parison  20  is expanded by introducing a fluid into the lumen  23  of the parison  20 , rotation of the parison  20  can be prevented, so that crushing or the like of the protruding part  25  can be prevented. 
     In the inner cavity cross-section of the mold  30 , the shapes of the second groove  45  to the fourth groove  49  may be the same or different from each other. In addition, for the shapes of the second groove  45  to the fourth groove  49 , the description of the first groove  41  can be referred to. 
     This application claims priority based on Japanese Patent Application No. 2019-108432 filed on Jun. 11, 2019, the entire contents of which are incorporated herein by reference. 
     DESCRIPTION OF REFERENCE SIGNS 
     
         
         
           
               1  balloon 
               2  straight tube part 
               3  tapered part 
               4  sleeve part 
               5  sleeve outer part 
               6  balloon body 
               7  outer surface of balloon body 
               10  protruding part 
               11  outer end 
               12  outer surface of protruding part 
               13  tip end region 
               14  base end region 
             A, B, C position 
               20  parison 
               21  first end 
               22  second end 
               23  lumen 
               25  protruding part 
               26  outer end 
               27  outer surface of protruding part 
               28  tip end region 
               29  base end region 
               30  mold 
               30 A first mold 
               30 B second mold 
               30 C third mold 
               30 D fourth mold 
               30 E fifth mold 
               30 F sixth mold 
               31  first section 
               32  second section 
               32 D distal second section 
               32 P proximal second section 
               33  third section 
               33 D distal third section 
               33 P proximal third section 
               34  fourth section 
               34 D distal fourth section 
               34 P proximal fourth section 
               35  inner cavity 
               36  inner wall surface forming inner cavity 
               41  first groove 
               41   a  bottom 
               41   b  part that becomes narrower toward outer side in radial direction 
               41   c  part that becomes wider toward outer side in radial direction 
               41   d  arc-shaped part 
               42  contact region 
               43  non-contact region 
               45  second groove 
               47  third groove 
               49  fourth groove 
             x 1  distal-proximal direction 
             x 2  longitudinal direction of parison 
             x 3  longitudinal direction of mold