JP7611558B2 - Method for manufacturing catheter balloon - Google Patents

Description

The present invention relates to a method for manufacturing a catheter balloon.

As shown in FIG. 9, a catheter balloon 200 used in a balloon catheter generally has a cylindrical portion 110, a tapered portion 120, and a connection portion 130. In principle, it is preferable that the connection portion and tapered portion of a catheter balloon are as thin as possible, considering the passage of the catheter balloon through blood vessels and lesions. However, when a catheter balloon is manufactured by blow molding, which is a common manufacturing method, the thickness of the catheter balloon becomes thinner in the order of the connection portion, the tapered portion, and the cylindrical portion due to the characteristics of the processing, with the connection portion being the thickest and the cylindrical portion being the thinnest. If the connection portion and tapered portion are manufactured as thin as possible to improve the passage of the catheter balloon through blood vessels and lesions, the cylindrical portion becomes too thin in thickness, resulting in a problem of low pressure resistance.

As an invention that takes such points into consideration, a balloon for a dilatation catheter has been proposed that is formed from a polymer material and has a cylindrical middle section, conical sections at each end of the middle section that are inclined outward, and a cylindrical neck at the end of the conical section, characterized in that the balloon is formed from two or more layers including an inner layer and an outer layer, one of which is shortened and ends within the conical region of the other. Also, as a manufacturing method for such a balloon for a dilatation catheter, a method for manufacturing a dilatation balloon formed from a polymer material, having a cylindrical middle section, a conical section extending from the end of the middle section, and a neck extending from the end of the conical section, has been proposed, which comprises blow molding a first balloon in a mold; removing the first balloon from the mold and cutting the end of the conical section; placing the cut first balloon in the mold and blow molding a next balloon so that it is in close contact with the previously placed balloon segment; removing the combined balloon layers from the mold and cutting the last layer formed to define the neck of the balloon (Patent Document 1).

However, this method of manufacturing balloons for dilatation catheters requires that the overlapping balloons be removed from the mold and the edges cut off each time they are molded, which means that they cannot always be molded uniformly and are therefore poorly reproducible.

Japanese Patent Application Publication No. 4-231070

The present invention aims to provide a method for producing a catheter balloon that can produce thinner and thicker parts than conventional catheter balloons, even when the same mold and parison are used for molding the balloons.

In order to achieve the above object, the present invention takes the following measures.
The method for producing a catheter balloon according to the present invention includes the following steps.
(1) A parison production process in which a parison member is produced by stretching a plastic tube. (2) A thin film tube production process in which a thin film tube is produced. (3) A thin film tube covering process in which the parison member is covered with at least one thin film tube to produce a covered parison member. (4) A balloon molding process in which the covered parison member is molded into the shape of a balloon using a balloon molding die.

According to the method for producing a catheter balloon of the present invention, by molding a balloon while the parison member is covered with a thin film tube, a difference in temperature and strength is generated between the covered and uncovered parts, which causes a difference in the way stress is applied and makes the uncovered parts locally thinner. Therefore, a catheter balloon can be produced that has an even thinner membrane in the areas not covered with the thin film tube compared to when the same balloon-forming mold is used to produce a balloon using only the parison.

In addition, in the method for producing a catheter balloon according to the present invention,
The method may further include a crimping step of crimping the thin film tube onto a parison member by heating the balloon molding die to a temperature higher than that during balloon molding, after the balloon molding step.

By adopting this configuration, the parison member and the thin film tube can be more firmly crimped together.

Furthermore, in the method for producing a catheter balloon according to the present invention,
The thin film tube may be characterized in that it covers the catheter balloon other than the tapered portion after fabrication.

By adopting this configuration, the tapered portion is not covered with a thin film tube, so the tapered portion can be made particularly thin.

Furthermore, in the method for producing a catheter balloon according to the present invention, the thin film tube may be characterized in that it covers the tapered portion of the catheter balloon after production.

By covering both tapered portions of the balloon, the cylindrical portion of the balloon can expand more easily in the circumferential direction, and the balloon can be prevented from expanding in the axial direction.

Furthermore, in the method for producing a catheter balloon according to the present invention,
The material of the parison member and the material of the thin film tube may be the same.

By adopting this configuration, the parison member and the thin film tube can be easily integrated and compatible with each other during the crimping process.

Furthermore, in the method for producing a catheter balloon according to the present invention,
The material of the thin film tube may be characterized in that it has a Shore hardness at room temperature that is harder than the material of the parison member.

By adopting this configuration, the thin film tube is less likely to stretch during the balloon molding process, and the uncovered portions of the thin film tube are more likely to stretch, allowing the uncovered portions of the thin film tube to form a thinner membrane.

The method for producing a catheter balloon according to the present invention makes it possible to produce a catheter balloon with a thin tapered portion and a thick cylindrical portion in a single molding operation, and even when using the same mold and parison as those used for producing conventional catheter balloons, it is possible to produce a tapered portion that is thinner than that of conventional catheter balloons.

FIG. 1 is a flow chart showing a method for producing a catheter balloon 100 according to an embodiment. FIG. 2 is a schematic diagram showing one step of a method for producing the catheter balloon 100 according to the embodiment. FIG. 3 is a schematic diagram showing one step of a method for producing a catheter balloon 100 according to an embodiment. FIG. 4 is a schematic diagram showing one step of a method for producing a catheter balloon 100 according to an embodiment. FIG. 5 is a cross-sectional view of a catheter balloon 100 produced by the method for producing a catheter balloon 100 according to an embodiment. FIG. 6 is a cross-sectional view of a catheter balloon 100 according to another embodiment, which is produced by the method for producing a catheter balloon 100 according to the embodiment. FIG. 7 is a diagram showing the positions at which the thickness of the catheter balloon 100 is measured. FIG. 8 shows the results of measuring the thickness of the catheter balloon 100. FIG. 9 is a schematic diagram showing a typical catheter balloon 200.

Next, the method for producing the catheter balloon 100 according to the present invention will be described in detail with reference to the drawings. Note that the embodiments and drawings described below are merely examples of some of the embodiments of the present invention, and are not intended to be used to limit the scope of the present invention, and may be modified as appropriate without departing from the spirit of the present invention.

(Embodiment)
As shown in FIG. 1 , the method for producing a catheter balloon 100 according to the present invention mainly includes a parison production step (S1) of producing a parison member 10 by stretching a plastic tube, a thin film tube production step (S2) of producing a thin film tube 20 by extrusion molding, a thin film tube covering step (S3) of covering the parison member 10 with the thin film tube 20 to produce a covered parison member 30, a balloon molding step (S4) of molding the covered parison member 30 into the shape of a balloon using a balloon-forming die 80, a crimping step (S5) of crimping the thin film tube 20 by heating the balloon-forming die 80 to a temperature higher than that used for balloon molding after the balloon molding step, and a demolding step (S6) of removing the completed catheter balloon 100.

(1) Parison production process (S1)
The parison manufacturing process is a process in which a long plastic tube, which is a raw material, is stretched in the longitudinal direction to improve the tensile strength in the longitudinal direction. The stretched parison member 10 may be tubular as shown in FIG. 2A, or may be biaxially stretched to a certain extent as shown in FIG. 2B to be molded into a balloon shape smaller than the final product, the catheter balloon 100. Note that in FIG. 2, a balloon molding die 80 is also shown to make the size easier to understand, but this is for comparison purposes only. Thermoplastic resins such as polyolefin, polyamide, polyurethane, polyester, polyimide, polyethylene, polypropylene, polyolefin-based elastomer, polyamide-based elastomer, polyurethane-based elastomer, and polyester-based elastomer can be used as the material used for the parison member 10.

(2) Thin film tube production process (S2)
Next, the thin film tube 20 that covers the parison member 10 is produced. The thin film tube 20 is produced by extrusion molding, dip molding, or the like. The thickness of the film of the thin film tube 20 is appropriately determined in consideration of the type of material of each of the parison member 10 and the thin film tube 20, and the desired stretch ratio of the covered and uncovered parts of the thin film tube 20 depending on the balloon molding process. Generally, if the thin film tube 20 is thick, the part covered with the thin film tube 20 is difficult to stretch, and the part not stretched is greatly stretched and formed thin. In addition, it is preferable to use a thin film tube 20 that is not stretched in the longitudinal axis direction. This is because once the thin film tube 20 is stretched, it becomes difficult to stretch it further. Note that the thin film tube 20 is produced to have an inner diameter slightly larger than the outer diameter of the parison member 10, and if the thin film tube 20 can be fixed to a degree that does not move each other due to friction when the thin film tube 20 is placed over the parison member 10, it can be easily handled in the subsequent process. The thin film tube 20 can be made of thermoplastic resins such as polyolefin, polyamide, polyurethane, polyester, polyimide, polyethylene, polypropylene, polyolefin-based elastomer, polyamide-based elastomer, polyurethane-based elastomer, and polyester-based elastomer, as with the parison member 10. The combination of materials for the parison member 10 and the thin film tube 20 is not limited, but it is preferable to use the same material as the parison member 10 or a material harder than the parison member 10 in terms of Shore hardness at room temperature for the thin film tube 20. By using the same material, the parison member 10 and the thin film tube 20 can be easily dissolved and integrated with each other in the crimping process described below. In addition, if a material harder than the parison member 10 in terms of Shore hardness at room temperature is used for the thin film tube 20, the thin film tube 20 becomes less likely to stretch in the balloon molding process, and the part not covered by the thin film tube 20 is easily stretched, making it possible to make the uncovered part into a thinner membrane. Preferred combinations include a combination of polyamide and polyamide for the parison member 10 and the thin film tube 20, a combination of polyamide and a polyamide-based elastomer, and a combination of a polyamide-based elastomer and polyamide. The length of the thin film tube 20 in the longitudinal direction can be selected depending on the portion of the parison member 10 that is to be covered.

(3) Thin film tube covering process (S3)
As shown in Fig. 3, this is a process of covering the outer periphery of the parison member 10 with the thin film tube 20 to produce a covered parison member 30. The thin film tube 20 is set at an appropriate position depending on the catheter balloon 100 to be produced. In this way, in the present invention, the thin film tube 20 can be attached at any position on the catheter balloon 100, so that catheter balloons 100 for various purposes can be produced. Details will be described later. In this embodiment, the thin film tube 20 is arranged so as to be located at the center of the cylindrical part of the catheter balloon 100. The thin film tube 20 does not necessarily have to be a single sheet, and two or more sheets may be stacked to cover the catheter balloon 100, or multiple locations may be covered.

(4) Balloon forming process (S4)
As shown in Fig. 4A, the coated parison member 30 is set in a balloon molding die 80, and as shown in Fig. 4B, a balloon is molded by blow molding. The temperature during molding is selected appropriately depending on the material, but is generally 80°C to 160°C. At this time, the amount of stretching of the coated parison member 30 during molding can be changed due to differences in temperature distribution and stress distribution during molding between the coated and uncoated parts of the thin film tube 20, and the wall thickness of the uncoated part can be controlled.

(5) Pressure bonding process (S5)
The pressure bonding step is a step in which the balloon molding die 80 is heated to a temperature higher than that during balloon molding, and the parison member 10 and the thin film tube 20 are pressure bonded to each other after the balloon molding step. That is, after blow molding is performed in the balloon molding die 80 with the parison member 10 covered with the thin film tube 20, the temperature inside the balloon molding die 80 is raised by 10°C to 30°C higher than that during blow molding, and the pressure bonding step is performed in order to completely weld the covered thin film tube 20. If the parison member 10 and the thin film tube 20 can be sufficiently pressure bonded to each other under the conditions of the balloon molding step described above, this step may be omitted.

(6) Demolding process (S6)
Finally, the completed catheter balloon 100 is released from the balloon molding die 80 to obtain the catheter balloon 100.

For example, as shown in FIG. 5, the catheter balloon 100 thus obtained has a cylindrical portion 60 covered, so that the amount of extension of the tapered portion 70 of the catheter balloon 100, which is the uncovered portion, is increased. This allows the catheter balloon 100 to be produced with a locally thin tapered portion 70, and the catheter balloon 100 to be produced with improved passability through stenosis and the like. The film thickness of the tapered portion 70 at this time can be made thinner than the tapered portion (the portion not covered with the thin film tube 20) of a catheter balloon produced using the same parison member, with the same mold, and under the same molding conditions. Therefore, a catheter balloon 100 can be produced in which the cylindrical portion 60 is thick and the tapered portion 70 is thinner. In addition, as shown in FIG. 6, by covering both tapered portions 70 of the catheter balloon 100, the cylindrical portion 60 of the catheter balloon 100 is easily expanded in the circumferential direction, and the catheter balloon 100 is prevented from expanding in the axial direction. In this way, the ease of expansion of the catheter balloon 100 can be controlled, so that expansion of unintended parts can be prevented. Therefore, when the stent is expanded multiple times (post-expansion), the possibility of unintended parts expanding and deforming the stent can be reduced. Furthermore, by covering both tapered parts 70 of the catheter balloon 100, the expanded shape of the balloon can be made lemon-shaped. This makes it possible to produce a catheter balloon 100 that reduces slippage during expansion. Furthermore, the thickness of the covering part can be made thicker and the strength can be controlled, so the rupture site of the catheter balloon 100 can be controlled.

(Example)
In the example, a parison member was obtained by uniaxially stretching a plastic tube made of polyamide, and a thin film tube made of polyamide having a thickness of 100 μm was coated on a central part of the cylindrical part to obtain a coated parison member. The coated parison member was molded at 150° C. using a balloon molding die, and then pressure-bonded at 165° C. for 120 seconds to obtain a catheter balloon.
As a comparative example, a parison member obtained by uniaxially stretching a plastic tube made of the same polyamide material was used, and molded at 150°C using a balloon molding die to obtain a catheter balloon.

As shown in Figure 7, the membrane thickness was measured at seven points on the catheter balloons obtained in the examples and comparative examples. In the catheter balloons in the examples, A and G are tapered sections without a thin film tube, B and F are cylindrical sections without a thin film tube, and C, D, and E are cylindrical sections with a thin film tube.

The average value of three samples is shown in Figure 8. The results shown in Figure 8 show that by simply molding while covered with a thin film tube, it is possible to obtain a catheter balloon with locally thinner portions at the unset locations "A, B, F, and G" compared to molding without covering with a thin film tube.

The present invention can be used industrially as a method for manufacturing balloons used in balloon catheters.

10: parison member, 20: thin film tube, 30: covering parison member, 60: cylindrical portion, 70: tapered portion, 80: balloon molding die, 100: catheter balloon

Claims (4)

A method for producing a catheter balloon, comprising the steps of (1) to (4) below in numerical order :
(1) A parison production process in which a parison member is produced by stretching a plastic tube. (2) A thin film tube production process in which a thin film tube is produced that is not stretched in the longitudinal direction and has an outer diameter larger than that of the parison member to the extent that they do not move relative to the parison member due to friction. (3) A thin film tube covering process in which at least one sheet of the thin film tube is covered on the parison member except for the tapered portion of the catheter balloon after production to produce a covered parison member. (4) A balloon molding process in which the covered parison member is molded into the shape of a balloon using a balloon molding die. The method for producing a catheter balloon according to claim 1, characterized in that after the balloon molding step, a crimping step is performed in which the balloon molding die is heated to a temperature higher than that during balloon molding, and the thin film tube is crimped to the parison member. The method for manufacturing a catheter balloon according to claim 1 or 2, characterized in that the material of the parison member and the material of the thin film tube are the same material. The method for manufacturing a catheter balloon according to any one of claims 1 to 3, characterized in that the material of the thin film tube is harder than the material of the parison member in terms of Shore hardness at room temperature.

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