JP2021036171A - tube - Google Patents

Abstract

To provide a tube that can be used for a ventilation filter and gas liquid separation application including degasification and supply air and has excellent ventilation characteristic.SOLUTION: A porous structure tube including a communication hole in a radial direction includes: a main lumen; and at least one sub lumen extending in an axial direction in a thick wall part. The tube preferably has ventilation characteristic in both of the radial direction and the axial direction.SELECTED DRAWING: Figure 1

Description

The present invention supplies carbon dioxide gas to water, for example, for degassing applications for removing dissolved gas contained in liquids such as chemicals and inks, including ventilation filters for waterproofing and dustproofing, and for producing functional water for cleaning. The present invention relates to a tube preferably used in an air supply application such as carbon dioxide, or a gas separation application for separating a specific gas from a mixed gas.

Tubes used for ventilation filters and deaeration applications are required to have a separation function such as waterproofing, but are also required to have high ventilation. In recent years, as the usage and installation methods of tubes have diversified, they may be used in a state where the surface area that can be ventilated is small, such as ventilation with one end face of the tube sealed, and the air permeability deteriorates. There is a problem.

As a tube for degassing, Patent Document 1 describes a fluororesin tube having a porous structure of closed cells. Although these tubes have excellent breathability, further improvement is required as the usage and installation methods are diversified as described above.

Patent Document 2 describes a tube using a thermoplastic resin or the like having a plurality of hollow portions. In the case of a structure having a hollow portion, it is excellent in air permeability in the axial direction, but it is not suitable for degassing applications because it does not have air permeability in the radial direction as in Patent Document 1 and does not have a separation function.

Japanese Unexamined Patent Publication No. 2004-160291 Japanese Unexamined Patent Publication No. 2012-189173

An object of the present invention is to provide a tube that can be used for separation applications such as a ventilation filter and degassing air supply, has excellent ventilation in both radial and axial directions, and can be used in various usage methods and installation methods. To do.

The gist of the present invention is as follows.

(1) A tube having a porous structure having communication holes in the radial direction, characterized in that it is composed of a main lumen and at least one sublumen extending in the axial direction in a thick portion.
(2) The tube preferably has air permeability in both the radial direction and the axial direction.
(3) The main lumen of the tube preferably extends along the central axis.
(4) The tube is preferably made of PTFE.
(5) The porosity of the porous structure is preferably 20 to 70%.

According to the present invention, it can be used for separation applications such as a ventilation filter and degassing air supply, and further, ventilation is improved in both the radial direction and the axial direction, and various tube usage methods and installations are made. Become available in the method.

It is sectional drawing which is perpendicular to the axial direction of an example of the tube which concerns on this invention. It is sectional drawing which is perpendicular to the axial direction of another example of the tube which concerns on this invention. FIG. 5 is a sectional view taken along line XY of FIG. (Pattern diagram) This is another example of the XY cross-sectional view of FIG. (Pattern diagram) It is the schematic which shows the measuring method of the aeration test which sealed one end face in the axial direction. (The tube is a schematic diagram) It is the schematic which shows the measuring method of the ventilation test which sealed both side end faces in the axial direction. (The tube is a schematic diagram) It is the schematic which shows the measuring method of the aeration test which does not need the sealing of one end face. (The tube is a schematic diagram) It is a scanning electron micrograph of the cross section perpendicular to the axial direction of the tube which concerns on this invention. It is a scanning electron micrograph of the X'-Y'cross section of FIG. It is a graph which shows the change of the air volume with the change of the porosity.

In FIG. 1, the tube 1 has a main lumen 2 and a sub-lumen 3, and L is the central axis of the tube 1.

The present invention is a tube 1 having a porous structure having communication holes in the radial direction, wherein the tube 1 is composed of a main lumen 2 and at least one sub-lumen 3 extending in the axial direction in a thick portion. It is a feature. As shown by the dotted line, it is breathable in the radial direction through the communication hole and also in the axial direction through the sublumen 3.

The number of sublumens 3 is not particularly limited. FIG. 1 shows four examples, and FIG. 2 shows six examples. From the viewpoint of axial air permeability, productivity and the like, the number of sublumens 3 is preferably 2 to 8.

The shapes of the main lumen 2 and the sub lumen 3 are not particularly limited, and examples thereof include a circular shape, an elliptical shape, a flat shape, and a polygonal shape. From the viewpoint of productivity and mechanical strength, it is preferably substantially circular.

The position of the sublumen 3 is not particularly limited. In the cross section perpendicular to the axial direction, they may be arranged at equal intervals as shown in FIG. 2, or may be arranged at several places as shown in FIG.

As shown by the XY lines in FIG. 1, the sublumen 3 preferably has a structure that is point-symmetrical with respect to the central axis L of the tube in a cross section perpendicular to the axial direction. The tube 1 can secure a certain mechanical strength.

Further, the arrangement of the sublumens 3 in the axial direction is not particularly limited. For example, it may be substantially linear (arrangement parallel to the axial direction) or spiral (arrangement that rotates spirally with respect to the central axis). From the viewpoint of productivity, it is preferably substantially linear.

FIG. 3 is a schematic view of an XY cross section of FIG. 1, showing a main lumen 2, a sub-lumen 3, a communication hole 4, and a central axis L in the tube 1. The communication hole 4 is for expressing ventilation in the radial direction, and is not limited to this structure, shape, and the like.

What is characteristic of the present invention is that the tube 1 has a porous structure having communication holes 4 in the radial direction, and in addition to the axial direction, the tube 1 passes through the communication holes 4 from the main lumen 2 to the outer peripheral surface of the tube 1. It is also breathable in the radial direction. The communication hole 4A between the main lumen 2 and the sub-lumen 3 and the communication hole 4B between the sub-lumen 3 and the outer peripheral surface of the tube 1 are each provided with air permeability. Note that FIG. 3 is a schematic view having a communication hole 4 in a part of the thick portion, but the present invention is not limited to this, and as shown in the schematic view of FIG. 4, the entire thick portion has a communication hole. By having the structure, the structure may have air permeability in the radial direction over the entire length of the tube 1.

Since the tube 1 has air permeability in both the radial direction and the axial direction, various tube usage methods and installation methods, that is, a state in which the entire end face of the tube 1 is sealed, for example, as shown in FIGS. Also, it has air permeability even when the sealing member is inserted in the main lumen 2. Sealing is used to prevent liquids, foreign substances, etc. from entering the lumen of the tube 1 and to fix it to other members.

For example, FIG. 5 is a schematic view of a ventilation test when the entire axial end surface of the tube 1 and the main lumen 2 are sealed. When a partition is provided on one side of the tube 1 as shown in FIG. 5 and gas is injected into the tube 1 from the inside of the partition, the opposite end surface side of the tube 1 is sealed and cannot be ventilated. In addition to ventilating in the direction, it is possible to ventilate in the radial direction through the communication holes. FIG. 6 is a schematic view of a ventilation test when the entire axial end surfaces of the tube 1 and the main lumen 2 are sealed. As in FIG. 5, the inside of the partition and the tube are formed through the sub-lumen 2 and the communication hole. Ventilation with the outer circumference is possible.

The main lumen 2 preferably extends along the central axis L. By arranging the main lumen 2 substantially in the center of the tube 1, the thick portion becomes uniform, the ventilation characteristics are stabilized, and the mechanical strength is also excellent.

The material of the tube 1 is not particularly limited, but a fluororesin is preferable from the viewpoint of heat resistance, chemical resistance and the like, and PTFE is more preferable from the viewpoint of moldability and radial air permeability.

The porosity of the porous structure constituting the tube 1 is not particularly limited, and is appropriately determined depending on the application, material, and the like. The higher the porosity of the tube 1, the larger the air volume, preferably 20% or more. Further, when the porosity is 70% or less, the tube 1 can secure a certain mechanical strength. It is more preferably 30 to 70%, still more preferably 40 to 70%. When PTFE is used, it is most preferably 50 to 70%.

In the cross section perpendicular to the axial direction, the cross-sectional area ratio of the main lumen 2 and the sub lumen 3 is not particularly limited, and is appropriately determined depending on the application and the like. The larger the cross-sectional area ratio of the sublumen 3, the larger the air volume of the tube 1.

The manufacturing method of the tube 1 is not particularly limited, and examples thereof include a manufacturing method such as extrusion molding, injection molding, and winding a film in a tube shape. When PTFE is used, paste extrusion is preferable, and a porous structure can be obtained by further stretching in the axial direction. Since the PTFE tube having a porous structure thus obtained has a communication hole in the thick portion, it is particularly preferable because it has excellent radial air permeability.

The sublumen 3 is continuously provided at the same time as the molding of the tube 1, and may be provided in a post-process after the molding of the tube 1, and is not particularly limited. When the sub-lumen 3 is provided in a later step, it is possible to obtain a structure in which the end of the tube is closed as shown in FIG. 7 by molding so that the lumen does not penetrate to the opposite end face. In this way, if the tube end is originally closed, it is not necessary to seal the end face of the tube 1 for waterproofing at the time of use, and the sealing portion is also adherent and airtight. It is more preferable because it improves.

Dimensions such as the inner diameter, outer diameter, and cut length of the tube 1 are not particularly limited, and are appropriately determined according to the application and the like. From the viewpoint of moldability, the inner diameter is preferably 7.0 mm to 16 mm, and the wall thickness is preferably 1.5 to 2.0 mm.

Hereinafter, the tube (FIG. 1) of the present invention will be described in more detail with reference to examples, but the scope of the present invention is not limited thereto.

Example 1 is a PTFE tube having a porous structure having communication holes in the radial direction, having an outer diameter of 2.0 mm, an inner diameter of 1.0 mm, and a main lumen diameter of 1.0 mm. Further, it has four sublumens as shown in FIG. 1, each having a diameter of 0.2 mm. The porosity of the tube is about 40%.

Comparative Example 1 is a tube of Example 1 consisting of only the main lumen and having no sublumen.

For Example 1, a cross-sectional photograph perpendicular to the axial direction of the tube is shown in FIG. 8, and a cross-sectional photograph in the axial direction (X'-Y' cross-sectional photograph of FIG. 1) is shown in FIG. The magnified photograph is an image taken by a scanning electron microscope. In FIG. 9, since the through hole is observed over the entire length in the axial direction, it can be seen that the through hole has radial air permeability over the entire length as shown in the schematic view of FIG.

The ventilation characteristics of Examples and Comparative Examples were measured, and the results are shown in Table 1.

(Measurement method of ventilation characteristics)
(1) With main lumen sealing As shown in FIG. 5, the length of the tube is 125 mm, and the entire axial end face of the tube and the main lumen are sealed. Further, a partition having a thickness of 10 mm is provided at a position 5 mm from the unsealed end face, gas is injected into the tube at a pressure of 60 kPa from the inside of the partition, and the air volume [L / L /] on the outer peripheral surface of the tube 1 near the opposite end face. min] is measured. The partition and the tube are completely sealed to prevent gas leakage.
(2) Of the measurement methods of (1) without main lumen sealing, measurement is performed without sealing the main lumen.

(Measurement method of porosity)
Based on the Archimedes method, the weight W1 of the tube in the dry state, the weight W2 of the tube in the wet state containing water in the pores, and the weight W3 of the tube in water are measured, and the porosity P [%] is as follows. Calculate with the formula of.
P [%] = {(W2-W1) / (W2-W3)} × 100
The measurement temperature is 25 ° C.

It can be seen that Example 1 has a certain degree of air permeability regardless of whether or not the main lumen is sealed. On the other hand, in Comparative Example 1 having no sublumen, since it does not have air permeability in the axial direction, the air permeability of the tube is significantly reduced in the structure for sealing the main lumen. Since the first embodiment has both axial ventilation due to the sublumen and radial ventilation due to the communication holes, it can be said that the ventilation of the entire tube can be improved.

In Examples 2 to 5, in the tube 1 of Example 1, in addition to the tube size, the number of sublumens and the porosity are changed. Specifically, the outer diameter of the tube is 20 mm, the inner diameter is 16 mm, the outer diameter of the sublumen is 0.5 mm, and the number of sublumens and the porosity are shown in Table 2.

For Examples 2 to 5, the ventilation characteristics were evaluated according to the difference in the number of sublumens and the porosity, and the results are shown in Table 2. The ventilation characteristics are measured by the same method as "with main lumen sealing" shown in FIG.

From Examples 2 to 4, it can be seen that as the number of sublumens increases, so does the air volume of the tube. In Example 5, the number of sublumens is the same as that in Example 2, but it can be seen that the air volume of the tube is significantly increased by increasing the porosity.

Further, with respect to Examples 6 to 10, the change in the air volume accompanying the change in the porosity was investigated, and the result is shown in the graph of FIG. In Examples 6 to 10, the tube structure and dimensions are all the same except that the production conditions are adjusted to change the porosity.

From FIG. 10, the air volume has increased significantly around the porosity of around 65%. The factor of the increase is the size of the hole (gap) in the tube. That is, in the step of making the PTFE porous by stretching, a phenomenon occurs in which no new gap is generated and the existing gap becomes large above a certain level of stretching (here, referred to as a high stretching region). In general, the permeation rate of gas depends on the size of the pores (for example, Hagen-Poiseuille flow and Knudsen flow are known). It can be said that the permeation rate of the gas is accelerated by becoming a region and the pores (gap) are enlarged, and as a result, the air flow rate is significantly increased.

Since the tube of the present invention has air permeability in both the radial direction and the axial direction, it is useful for a ventilation filter for waterproofing and dustproofing, a degassing air supply application, and a gas separation application, and is useful for automobile machine tools and the like. It is preferably used in dew condensation prevention piping and the like in various devices.

1 Tube 2 Main lumen 3 Sublumen 4, 4A, 4B Communication hole L Central axis

Claims (5)

A tube with a porous structure that has radial communication holes.
The tube is characterized by comprising a main lumen and at least one sublumen extending in the axial direction in a thick portion. The tube is characterized by being breathable in both the radial and axial directions.
The tube according to claim 1. The main lumen of the tube extends along a central axis.
The tube according to claim 1 or 2. The tube is characterized in that it is made of PTFE.
The tube according to any one of claims 1 to 3. The porosity of the porous structure is 20 to 70%.
The tube according to any one of claims 1 to 4.