JP2017221346A - Parison tube, balloon, and production method thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an easily-moldable multi-layered parison tube not generating yield decline caused by delamination; and to provide a multi-layered balloon having simultaneously excellent pressure resistance performance and compliance by using the parison tube.SOLUTION: A multi-layered parison tube 10 formed coaxially has a first layer 11, and a second layer 12 formed of the same material as the first layer but further outside in the radial direction than the first layer, in which a ratio between the degree of orientation of a resin in the axial direction and the degree of orientation of the resin in the radial direction is set to be different between the first layer and the second layer.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a parison tube, a balloon manufactured from the parison tube, and a manufacturing method thereof.

  Some balloons are used for balloon catheters (balloon dilators) and used to expand stenotic portions of in vivo lumens such as the esophagus, bile ducts and blood vessels. Such a medical balloon is manufactured by expanding the diameter of a parison tube.

  Patent Document 1 discloses a multilayer parison tube having an outer layer of polyamide and an inner layer of polyamide elastomer, and a balloon made from the multilayer parison tube. According to this technique, a balloon having excellent compliance characteristics can be obtained.

    Patent Document 2 describes a technique for improving the pressure resistance by increasing the crystallinity of the surface layer by drawing a single-layer parison tube.

JP 2013-146505 A JP 2003-062081 A

However, the multi-layer parison tube described in Patent Document 1 has a problem that delamination is likely to occur due to the use of different materials, yield decreases, and moldability deteriorates due to a difference in melting point of the materials.
Further, the single-layer parison tube described in Patent Document 2 is oriented while being pulled in the axial direction through a die hole having an inner diameter smaller than the outer diameter of the parison tube, whereby the surface layer is oriented and crystallized to improve pressure resistance. Since the pressure resistance is improved only by the surface layer, there is a problem that the adjustable range is limited.

  In view of the above-mentioned problems of the prior art, the present plan provides a multi-layer parison tube that is easy to mold without a decrease in yield due to delamination, and a multi-layer balloon that has excellent pressure resistance and compliance at the same time by using this parison tube. It is intended to achieve the purpose of doing.

The parison tube of the present invention is a parison tube that is coaxially formed in multiple layers,
The first layer;
A second layer made of the same material as that of the first layer on the outer side in the radial direction from the first layer,
The above problem has been solved by setting the ratio of the resin orientation degree in the axial direction and the resin orientation degree in the radial direction to be different between the first layer and the second layer.
In the present invention, it is more preferable that the resin orientation degree in the first layer is set so that the axial orientation degree is larger than the resin orientation degree in the second layer.
The balloon of the present invention is manufactured from the parison tube described in any one of the above, and has a second layer made of the same material as the first layer on the radially outer side from the first layer,
It is possible that the ratio between the resin orientation degree in the axial direction and the resin orientation degree in the radial direction is set to be different between the first layer and the second layer.
Moreover, in the manufacturing method of the parison tube of the present invention, a multi-layered coaxially formed first layer,
And a second layer made of the same material as the first layer on the radially outer side from the first layer.
A means having a step of setting the ratio between the resin orientation degree in the axial direction and the resin orientation degree in the radial direction to be different between the first layer and the second layer may be employed.
In the present invention, in the step of controlling the ratio between the resin orientation degree in the axial direction and the resin orientation degree in the radial direction, the degree of orientation in the radial direction can be controlled by vacuum sizing while forming the layer. .

The parison tube of the present invention is a parison tube that is coaxially formed in multiple layers,
The first layer;
A second layer made of the same material as that of the first layer on the outer side in the radial direction from the first layer,
The ratio between the resin orientation degree in the axial direction and the resin orientation degree in the radial direction is set to be different between the first layer and the second layer. Generation of delamination can be prevented by the multilayer parison tube made of a crystalline polymer material and the multilayer made of the same material. The degree of orientation in the axial direction (MD direction) in the first layer and the second layer in which the resin orientation degree ratio ( _IMD / _IND ) in the axial direction (MD direction) and radial direction (ND direction) in the parison tube is different. In a high layer, the pressure resistance is lowered to increase the expansibility, and in the layer having a high degree of orientation in the radial direction (ND direction), the strength, that is, the pressure resistance can be improved and the expansibility can be lowered. Therefore, pressure resistance and expansibility can be controlled simultaneously.
In this way, in addition to solving the above-mentioned problems, and preferably adjusting the balance between pressure resistance and compliance in the balloon molded from the parison, not only the resin orientation degree of each layer but also the film thickness of each layer can be used as an adjustment parameter. Therefore, more precise adjustment can be easily performed.

  Generally, when a crystalline polymer material is oriented, the strength increases in the orientation direction and it becomes difficult to extend. A cylindrical molded product oriented in the radial direction has improved strength, that is, pressure resistance, and reduced expandability. On the other hand, a cylindrical molded article having a weak radial orientation, that is, a strong axial orientation has a reduced pressure resistance and an increased expansibility.

  In addition, in this invention, it can also have layers other than a 1st layer and a 2nd layer, and this layer is the inside of a 1st layer, the outside of a 2nd layer, or a 1st layer and a 2nd layer. It is also possible to use a coaxial layer located between the two. This layer is made of the same material as the first layer and the second layer.

In the present invention, the degree of resin orientation in the first layer is set such that the degree of axial orientation is larger than the degree of resin orientation in the second layer, thereby ensuring expandability in the first layer. In addition, pressure resistance can be secured in the second layer.
In this way, in the balloon molded from the parison, the second layer can increase the pressure resistance and lower the compliance than the first layer, so the outer second layer is excessive in excess of the inner first layer. Therefore, it is advantageous to increase the pressure resistance of the entire balloon.
Here, it is preferable to increase the pressure resistance in the second layer located outside in the balloon manufactured from the parison tube.
Of course, in the present invention, the resin orientation degree in the second layer may be set so that the axial orientation degree is larger than the resin orientation degree in the first layer.

The balloon of the present invention is manufactured from the parison tube described in any one of the above, and has a second layer made of the same material as the first layer on the radially outer side from the first layer,
By setting the ratio of the resin orientation degree in the axial direction and the resin orientation degree in the radial direction to be different between the first layer and the second layer, the pressure resistance and expandability (compliance) of the balloon can be reduced. Control can be performed simultaneously.

Moreover, in the manufacturing method of the parison tube of the present invention, a multi-layered coaxially formed first layer,
A method of manufacturing a parison tube having a second layer made of the same material as that of the first layer at a radially outer side than the first layer,
By adopting means having a step of setting the ratio of the resin orientation degree in the axial direction and the resin orientation degree in the radial direction to be different between the first layer and the second layer, the axial direction (MD direction) In a layer having a high degree of orientation, the pressure resistance is lowered to increase the expansibility, and in a layer having a high degree of orientation in the radial direction (ND direction), the strength, that is, the pressure resistance is improved and the expansibility is lowered. In the balloon manufactured from the parison tube, the pressure resistance and the expandability (compliance) can be controlled simultaneously.
Here, the step of setting the ratio of the resin orientation degree in the axial direction and the resin orientation degree in the radial direction to be different between the first layer and the second layer is the tube tensioning step in the tube layer forming step. This can be done by setting the axial orientation according to the speed or the cooling speed in the tube extrusion process. Alternatively, it can be performed by an axial orientation relaxation step of relaxing molecular orientation in the axial direction by a method such as vacuum sizing.

  In the present invention, in the step of controlling the ratio of the resin orientation degree in the axial direction and the resin orientation degree in the radial direction, by controlling the orientation degree in the radial direction by vacuum sizing while forming the layer, In the layer formed by vacuum sizing, the degree of orientation in the radial direction can be increased. Thereby, pressure resistance can be improved in the layer formed by vacuum sizing.

Furthermore, it is a manufacturing method of a multilayer parison tube,
Forming the inner layer by taking the molten resin tube from the mold; and
An additional step of adding an outer layer to the tube after forming the inner layer;
After the additional step, the tube is vacuum sized to improve the degree of radial orientation,
Can have.

  According to the present invention, in a layer having a high degree of orientation in the axial direction (MD direction), the pressure resistance is reduced and the expansibility is increased, and in a layer having a high degree of orientation in the radial direction (ND direction), the strength is increased. That is, the pressure resistance is improved and the expansibility is lowered, and in the balloon manufactured from such a parison tube, it is possible to simultaneously control the pressure resistance and the expansibility (compliance). .

It is radial direction sectional drawing which shows 1st Embodiment of the parison tube which concerns on this invention. It is an axial direction sectional view showing a 1st embodiment of a parison tube concerning the present invention. It is sectional drawing which shows the inner layer formation process of 1st Embodiment of the manufacturing method of the parison tube which concerns on this invention. It is sectional drawing which shows the outer side layer formation process of 1st Embodiment of the manufacturing method of the parison tube which concerns on this invention. It is an axial sectional view showing a first embodiment of a balloon according to the present invention. It is sectional drawing which shows 1st Embodiment of the manufacturing method of the balloon which concerns on this invention. It is sectional drawing which shows the inner side layer formation process of 2nd Embodiment of the manufacturing method of the parison tube which concerns on this invention. It is sectional drawing which shows the outer side layer formation process of 2nd Embodiment of the manufacturing method of the parison tube which concerns on this invention.

Hereinafter, a first embodiment of a parison tube according to the present invention will be described with reference to the drawings.
FIG. 1 is a radial cross-sectional view showing a parison tube in the present embodiment, and FIG. 2 is an axial cross-sectional view showing the parison tube in the present embodiment. In the figure, reference numeral 10 denotes a parison tube.

  As shown in FIGS. 1 and 2, the parison tube 10 in the present embodiment is formed into a substantially cylindrical shape having multiple layers coaxially, and includes an inner layer (first layer) 11 and an outer layer (second layer) 12. Have.

  The inner layer 11 and the outer layer 12 are made of the same material as a crystalline polymer material, and can be made of, for example, a polyamide elastomer, a polyamide resin, or the like.

An inner layer 11, and the outer layer 12, the axial direction (MD direction) and the radial orientation ratio of the resin in (ND direction) _(I MD _/ I _ND) is set to be different.
Specifically, in the inner layer 11, the axial direction (MD direction) orientation is stronger than the radial orientation, and in the outer layer 12, the radial direction (ND direction) orientation is greater than the axial orientation. Can be set to be strong.

In the parison tube 10 according to this embodiment, the inner layer 11 and the outer layer 12 are made of the same material, so that the occurrence of delamination is suppressed. In addition, the parison tube 10 according to the present embodiment improves the expansibility by the inner layer 11 in which the orientation in the axial direction (MD direction) is stronger than the orientation in the radial direction, and the orientation in the radial direction (ND direction) is the axial direction. In the outer layer 12 which is stronger than the orientation, the pressure resistance performance can be improved.
These orientation states and the layer thicknesses of the inner layer 11 and the outer layer 12 can be set to desired values depending on the required range of compliance and pressure resistance as a balloon, as will be described later.

ここで、Ｉ：配向度（％）
ΣＷｉ：配向性ピークの半値幅の和
である。 Here, the degree of orientation I can be measured by wide-angle X-ray diffraction. When the diffraction intensity is circularly integrated with respect to a specific surface (MD direction, ND direction), an azimuth distribution curve is obtained, and the degree of orientation I on the specific surface is obtained by the following formula 1 from the orientation peak in this curve.

Where I: degree of orientation (%)
ΣWi: sum of half-value widths of orientation peaks.

If the degree of orientation ratio ( _IMD / _IND ) is large, the orientation in the axial direction (MD direction) is stronger than the orientation in the radial direction, and if the degree of orientation ratio ( _IMD / _IND ) is small, the radial direction (ND Direction) is stronger than the axial orientation.

  As an example, a diffraction surface (020) plane that contributes to the axial direction of the tube when X-ray diffraction measurement (measured with respect to the cross section obtained by cutting the tube) is performed with respect to the axial direction of the tube. And the diffraction peak of the diffraction plane (200) that contributes to the radial direction of the tube becomes remarkable. Journal of Polymer Science: Part B: Polymer Physics, Vol. 40, 1189- 1200 (2002).

  Next, the manufacturing method of the parison tube in this embodiment is demonstrated.

FIG. 3 is a radial cross-sectional view showing a cross-sectional view showing an inner layer forming step in the method for manufacturing a parison tube in the present embodiment, and FIG. 4 shows an outer layer forming step in the method for manufacturing a parison tube in the present embodiment. It is sectional drawing shown.
The manufacturing method of the parison tube in the present embodiment includes an inner layer forming step and an outer layer forming step.

In the inner layer forming step, as shown in FIG. 3, a resin composition containing a polyamide resin and / or a polyamide elastomer is heated and melted at about 180 to 300 ° C. in an extruder, and extruded from a die 21 into a cylindrical shape. By cooling in the cooling water tank 22, a long single-layer tube 11 a that becomes the inner layer 11 is formed. The extrusion temperature is not particularly limited as long as the polymer can be melted, but is preferably 180 to 300 ° C, more preferably 200 to 280 ° C.
At this time, the tube 11a is stretched in the axial direction indicated by an arrow in FIG. 3, and its take-up speed is controlled so that the axial orientation becomes a predetermined value.

  In the outer layer forming step, as shown in FIG. 4, the tube 11 a is supplied to the die 23, and a resin composition containing polyamide and / or polyamide elastomer made of the same material as the tube 11 a is melted to obtain the die 23. Is supplied to the outer periphery of the tube 11a, and is extruded together with the tube 11a. And in the cooling water tank 24 which has a vacuum sizing type | mold, the resin layer 12a used as the outer layer 12 is formed in the outer periphery of the tube 11a with a vacuum sizing method, and extrusion molding is performed.

  At this time, it is stretched in the axial direction indicated by an arrow in FIG. 4 and its take-up speed is controlled so that the axial orientation becomes a predetermined value, and the outside of the resin layer 12a is reduced in the radial direction by a vacuum sizing mold. The orientation is controlled to be a predetermined value.

In general, when a polymer material is oriented, the strength increases in the orientation direction and it becomes difficult to extend. Therefore, the cylindrical molded product with the orientation in the radial direction improves the strength, that is, the pressure resistance, but is difficult to expand. Therefore, the pressure resistance and the expandability can be adjusted by adjusting the degree of orientation in the radial direction. Can do.
Similarly, the cylindrical shaped product with the orientation in the axial direction is improved in expansibility, but the pressure resistance is lowered. Therefore, the degree of orientation in the radial direction and the axial direction is adjusted by the respective layers 11 and 12, and these are formed. By setting it as the laminated state, pressure resistance and expansibility can be adjusted.

  Here, the orientation of the resin can be realized by aligning the flow direction of the resin by stretching, pushing, drawing, or the like. For example, when a resin in a molten or flexible state is stretched by pulling in one direction under a printing pressure, the orientation of the stretched direction is improved because the directions of the resin molecules are aligned in the stretched direction. In the present embodiment, as will be described later, the orientation state of the inner layer 11 and the outer layer 12 is controlled when a parison tube is formed as the above material.

  Specifically, when the thickness dimension of the inner layer 11 and the thickness dimension of the outer layer 12 are set to be equal, the take-up speed at the time of forming the outer layer 12 is set to the take-up speed at the time of forming the inner layer 11. By slowing down and vacuum sizing, the radial orientation in the outer layer 12 can be increased.

The conditions for forming the inner layer 11 and the conditions for forming the outer layer 12 for setting the orientation degree ratio (I _MD / I _ND ) of the outer layer 12 to be larger than those of the inner layer 11 are set as follows. It is possible.
<Condition example 1>
The inner layer 11 is formed at a take-up speed of 5 to 10 m / min, and the outer layer 12 is formed by vacuum sizing at a take-up speed of 1 to 5 m / min and a degree of vacuum of −0.5 bar.

  In these inner layer forming step and outer layer forming step, if the orientation of each resin layer changes during diameter expansion in the balloon forming step as will be described later, the change in orientation in the subsequent steps is also taken into consideration. It is preferable to set the orientation.

  Next, the balloon in this embodiment will be described.

  FIG. 5 is an axial sectional view showing the balloon in the present embodiment, and FIG. 6 is a schematic sectional view showing a method for manufacturing the balloon in the present embodiment.

Hereinafter, the manufacturing method of the balloon of this embodiment is demonstrated.
The balloon manufacturing method of the present embodiment includes a blow molding process.

  In the present embodiment, the orientation state is further adjusted and controlled in the blow molding process for balloon molding of the parison tube 10 formed to have the orientation ratio as described above.

In the blow molding process, the parison tube 10 formed by the parison forming process is blow molded by a mold.
Specifically, the parison tube 10 is inserted into the mold 20 shown in FIG. 6 and one end of the parison tube 10 is closed. The blockage is performed using heat melting, high frequency sealing, forceps and the like. The mold 20 is provided with a heater (not shown) as a heating means and a cooling pipe as a cooling means on the outside thereof. And the metal mold | die 20 becomes the separation molds 25 and 26, and the inner surface shape formed when the separation molds 25 and 26 are combined is the basic outer surface shape of the balloon to be formed.

  Then, as shown in FIG. 6, the heater is activated, and the temperature of the parison tube 10 in the portion forming the balloon 120 is not lower than the normal temperature and lower than the melting point of the polymer (polyamide and / or polyamide elastomer forming the tube). , Preferably 70 to 140 ° C., more preferably 80 to 130 ° C. The parison tube 10 is maintained in a heated state, the parison tube 10 is stretched in the direction of the left and right arrows in the figure, and further, the gas is pressurized from the outside into the parison tube 10 and is heated in the mold 20. A portion of the parison tube 10 is inflated with internal pressure so as to be in close contact with the inner wall surfaces of the separation molds 25 and 26, and formed into a balloon shape.

  And a cooling fluid is circulated in a cooling pipe, and the parison tube 10 is cooled to normal temperature. In addition, this cooling may be performed by simply leaving it alone without circulating the coolant. Thereafter, the inside of the parison 120A is brought to normal pressure, and the parison tube 10 is removed from the mold 20. And the basic shape of the balloon 120 as shown in FIG. 5 is formed by cut | disconnecting the parison tube 10 in the front-end | tip part and base end part of the parison tube 10. As shown in FIG.

  In the balloon 120 according to the present embodiment, the orientation ratio between the inner layer 11 and the outer layer 12 is set as described above, so that the inner layer 11 having a high degree of orientation in the axial direction (MD direction) and the radial direction are arranged. By having the outer layer 12 with a high degree of orientation in the (ND direction) at the same time, the pressure resistance is reduced and the expandability is increased, and the strength, that is, the pressure resistance is improved and the expandability is decreased. As a balloon 120 secured by different layers and having these balanced characteristics, it is possible to simultaneously control pressure resistance and expandability (compliance). At the same time, since the inner layer 11 and the outer layer 12 are made of the same material, it is possible to prevent delamination.

  As described above, after forming the inner layer 11, the outer layer 12 is formed on the inner layer 11, and the axial orientation relaxation step is performed as vacuum sizing only when the outer layer 12 is formed. Then, the inner layer 11 has a low degree of orientation in the radial direction, and the outer layer 12 has an increased degree of orientation in the radial direction. Therefore, from the viewpoint of the orientation ratio in the axial direction and the radial direction, the inner layer 12 has a higher orientation degree ratio in the axial direction than the outer layer 12.

Therefore, when adjusting the pressure resistance and compliance of the balloon 120 to be generated, the desired degree of compliance is obtained by suppressing the degree of radial orientation when the inner layer 11 is formed, and then the axial orientation is relaxed when the outer layer 12 is formed. The desired pressure resistance performance can be obtained by adjusting the process and controlling the degree of orientation in the radial direction. Thus, since the pressure resistance and the compliance can be adjusted separately, the parison tube 10 necessary for generating the balloon 120 having the desired characteristics (pressure resistance, compliance) can be easily obtained.
Moreover, in this embodiment, since the inner layer 11 and the outer layer 12 can be made of the same material, the problem of interlayer separation can be easily avoided and the moldability is good because of the same melting point.

  Hereinafter, 2nd Embodiment of the parison tube which concerns on this invention is described based on drawing.

  FIG. 7 is a process diagram showing inner layer formation in the method for manufacturing a parison tube in the present embodiment, and FIG. 8 is a process diagram showing outer layer formation in the method for manufacturing a parison tube in the present embodiment. In the embodiment, the difference from the first embodiment described above is a point related to the degree of orientation I between the inner layer 11 and the outer layer 12, and the other components corresponding to those in the first embodiment described above are denoted by the same reference numerals. A description thereof will be omitted.

In the first embodiment described above, the orientation ratio (I _MD / I _ND ) of the outer layer 12 is set smaller than that of the inner layer 11.

  Next, the manufacturing method of the parison tube in this embodiment is demonstrated.

In the inner layer forming step, as shown in FIG. 7, a resin composition containing a polyamide resin and / or a polyamide elastomer is heated and melted at about 180 to 300 ° C. in an extruder, and extruded from a die 21 into a cylindrical shape. A long single-layer tube 11b to be the inner layer 11 is formed by cooling in a cooling water tank 22B having a vacuum sizing mold.
At this time, the film is stretched in the axial direction indicated by an arrow in the drawing, and the take-off speed is set so that the orientation in the radial direction and the axial direction becomes a predetermined value by using the vacuum sizing method with the outside of the resin layer 11b as a reduced pressure atmosphere. Be controlled. This is an axial orientation relaxation step for relaxing the molecular orientation in the axial direction in the axial direction of the inner layer 11b.

In the outer layer forming step, as shown in FIG. 8, the tube 11b is supplied to the die 23, and a resin composition containing polyamide and / or polyamide elastomer, which is the same material as the tube 11b, is melted to obtain the die 23. And is extruded together with the tube 11b, and a resin layer 12b to be the outer layer 12 is formed on the outer periphery of the tube 11b in the cooling water tank 24B to perform extrusion molding.
At this time, the drawing speed and the cooling state are controlled so that the film is stretched in the axial direction indicated by an arrow in the figure and the axial orientation becomes a predetermined value.

Thereby, in this embodiment, it becomes possible to set the orientation degree ratio ( _IMD / _IND ) of the outer layer 12 larger than the inner layer 11.

  Examples according to the present invention will be described below.

<Experimental example 1>
A parison tube having a two-layer structure made of polyamide elastomer was prepared. The inner layer and the outer layer have the same thickness.
At this time, the orientation degree was set as follows between the inner layer and the outer layer.
1. Increasing the degree of orientation in the axial direction by adjusting the take-up speed, etc. during inner layer molding ( _IMD > _ITD )
2. Increasing the degree of orientation in the radial direction by shaping by vacuum sizing at the time of forming the outer layer ( _IMD < _ITD )
It was.

<Experimental example 2>
As Experimental Example 2, a single-layer parison tube having the same dimensions as that of Experimental Example 1 was prepared.

<Experimental example 3>
As Experimental Example 3, a parison tube having an outer layer made of the same material as in Experimental Example 1 and an inner layer made of polyamide was prepared.
At this time, the degree of orientation was set to be the same between the inner layer and the outer layer.
(I _MD = I _TD )

<Balloon molding>
Using these parison tubes, balloons were produced by biaxial stretch blow molding.

<Balloon characterization>
The created balloons were evaluated for burst pressure (pressure resistance), expansion rate, delamination property, and moldability.
here,
Expansion rate = (pressurized outer diameter−normal pressure outer diameter) / normal pressure outer diameter.

The layer peelability was evaluated by the porosity between layers when cut in the cross-sectional direction.
Further, the formability was evaluated from the simplicity when changing the thickness of each layer and the overall dimensions to arbitrary values.
These results are shown in Table 1.

  In such a parison tube and balloon, it was confirmed that a delamination did not occur, a balloon having excellent moldability and a good balance between pressure strength and expandability could be produced.

10 ... Parison tube 11 ... Inner layer (first layer)
12 ... Outer layer (second layer)
120 ... Balloon

Claims (5)

It is a parison tube that is coaxially formed in multiple layers,
The first layer;
A second layer made of the same material as that of the first layer on the outer side in the radial direction from the first layer,
A parison tube characterized in that the ratio between the resin orientation degree in the axial direction and the resin orientation degree in the radial direction is set to be different between the first layer and the second layer.   The parison tube according to claim 1, wherein the resin orientation degree in the first layer is set so that the axial orientation degree is larger than the resin orientation degree in the second layer. A second layer made of the same material as that of the first layer, which is manufactured from the parison tube according to claim 1 or 2 and radially outside the first layer;
A balloon characterized in that the ratio between the resin orientation degree in the axial direction and the resin orientation degree in the radial direction is set to be different between the first layer and the second layer. A multi-layered coaxial structure, a first layer,
A method of manufacturing a parison tube having a second layer made of the same material as that of the first layer at a radially outer side than the first layer,
A method for producing a parison tube, comprising a step of setting a ratio of a resin orientation degree in an axial direction and a resin orientation degree in a radial direction to be different between the first layer and the second layer.   5. The degree of orientation in the radial direction is controlled by vacuum sizing while forming a layer in the step of controlling the ratio between the degree of resin orientation in the axial direction and the degree of resin orientation in the radial direction. A method for manufacturing a parison tube.

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