JP6701782B2 - Hollow fiber membrane inner diameter measuring method and device - Google Patents

Description

  The present invention relates to a method and an apparatus for measuring the inner diameter of a hollow fiber in a spinning process, etc., and particularly to a measuring method and an apparatus suitable for application when a yarn is running.

  Filamentous products typified by hollow fiber membranes have been used and utilized in various fields and applications from the past.

  In recent years, cost reductions have been demanded for these filamentous products, while demands for quality have been increasing. More specifically, for example, a hollow fiber membrane is generally manufactured by using a polymer material as a raw material, but the membrane may become thin or conversely thick in the manufacturing process. In such a case, since the performance of the hollow fiber membrane varies, it is necessary to inspect the diameter of the hollow fiber membrane during the manufacturing process.

  Patent Document 1 discloses a method of detecting a hollow fiber membrane defect by using a laser outer diameter measuring machine and detecting the change.

  Patent Document 2 discloses a method of detecting a hollow fiber membrane defect by irradiating light with a line type fiber illuminating device and capturing an optical image guided to the inner space of the hollow fiber membrane with a camera.

Japanese Patent No. 3262855 JP, 2007-114187, A

  However, with the method of Patent Document 1, it is possible to measure the outer diameter but not the inner diameter. Therefore, the thickness of the film could not be evaluated, and there was a limit in quality control. Further, the method of Patent Document 2 cannot measure the outer diameter.

  Therefore, it is an object of the present invention to provide a hollow fiber membrane inner diameter measuring method and a hollow fiber membrane inner diameter measuring apparatus capable of measuring the inner diameter of a hollow fiber membrane.

According to the present invention, as achieving the above-mentioned objects,
An outer diameter measuring step for optically measuring the outer diameter of the continuously running hollow fiber membrane,
A first resonance frequency measurement step of measuring the first resonant frequency of the comparative cavity resonator in a state that does not penetrate the hollow fiber membrane in Comparative cavity resonator,
A second resonant frequency measuring step of measuring a second resonance frequency of the cavity resonator of the hollow fiber membrane continuously traveling in a state of being through the cavity resonator,
The inner diameter of the hollow fiber membrane is calculated using a predetermined relationship among the first resonance frequency, the second resonance frequency, the outer diameter of the hollow fiber membrane, and the inner diameter of the hollow fiber membrane. Calculation step to
Have a,
There is provided a hollow fiber membrane inner diameter measuring method in which the first resonance frequency measuring step and the second resonance frequency measuring step are performed simultaneously .

Further, according to the present invention, as achieving the above objects,
Outer diameter measuring means for optically measuring the outer diameter of the continuously running hollow fiber membrane,
A first resonant frequency measuring means for measuring a first resonance frequency of the comparative cavity resonator in a state that does not penetrate the hollow fiber membrane in Comparative cavity resonator,
A second resonant frequency measuring means for measuring a second resonance frequency of the cavity resonator of the hollow fiber membrane continuously traveling in a state of being through the cavity resonator,
Calculating means for calculating the inner diameter of the hollow fiber membrane using a predetermined relationship among the first resonance frequency, the second resonance frequency, the outer diameter, and the inner diameter of the hollow fiber membrane. ,
Equipped with
There is provided a hollow fiber membrane inner diameter measuring device in which the measurement by the first resonance frequency measuring unit and the measurement by the second resonance frequency measuring unit are simultaneously performed .

  According to the present invention, since the inner diameter of the hollow fiber membrane can be measured, the membrane thickness can be evaluated, and higher quality control can be performed.

1 is a schematic view showing a first embodiment of a hollow fiber membrane inner diameter measuring device according to the present invention. It is a schematic diagram showing a 2nd embodiment of the hollow fiber membrane inner diameter measuring device by the present invention. It is a typical perspective view which shows the structure of the cavity resonator shown in FIG. It is sectional drawing of the cavity resonator shown in FIG. It is sectional drawing of a hollow fiber membrane. FIG. 2 is a schematic perspective view showing an electromagnetic field inside the cavity resonator shown in FIG. 1. It is sectional drawing which shows 3rd Embodiment of the hollow fiber membrane inner diameter measuring apparatus by this invention. It is a graph which shows the frequency variation measured by the 2nd Embodiment of this invention. It is a graph which shows the inner diameter and outer diameter of the hollow fiber membrane measured by the 2nd Embodiment of this invention.

  Hereinafter, specific embodiments of the present invention will be described with reference to the drawings.

[First Embodiment]
FIG. 1 is a schematic view showing a first embodiment of a hollow fiber membrane inner diameter measuring device according to the present invention. FIG. 3 is a schematic perspective view of the cavity resonator. FIG. 4 is a cross-sectional view of a surface that divides the two through holes provided in the sidewall portion.

  According to FIG. 1, the hollow fiber membrane 101 is continuously running so as to pass through the outer diameter detector 103 and the cavity resonator 105. The outer diameter detector 103 is connected to a controller 107. As the outer diameter detector 103 and the controller 107, for example, a transmissive green LED size measuring machine (LS series manufactured by Keyence Corporation) is used. This optically measures the outer diameter of the hollow fiber membrane 101. Specifically, this is a transmission-type outer diameter measuring device having an LED light source or a laser light source as a measuring means, and measuring the outer diameter from the length of the hollow fiber membrane 101 blocking the light source. The outer diameter detector 103 may measure the outer diameter of the hollow fiber membrane 101 by another method. In the cavity resonator 105, a pair of coaxial connectors 105-3 and 105-5 are attached to a cylindrical main body 105-1 and each is connected to a network analyzer 109 by a coaxial cable (not shown). . The network analyzer 109 is a measuring instrument capable of measuring high-frequency characteristics, and in this embodiment, it is used for the purpose of measuring the resonance frequency of the resonance mode excited inside the cavity resonator 105. The controller 107 and the network analyzer 109 are connected to the arithmetic processing unit 111, and the arithmetic processing unit 111 analytically calculates the inner diameter from the outer diameter dimension data and the frequency variation rate. The arithmetic processing unit 111 is connected to the display unit 113, and the display unit 113 can confirm the frequency fluctuation and the shape of the running hollow fiber membrane 101 (in particular, the inner diameter and the outer diameter) in real time.

  Here, the structure of the cavity resonator 105 will be described in detail. In the present embodiment, the cavity resonator 105 includes a main body portion 105-1 having a cylindrical metal inner wall surface, and a side wall portion 105 having a pair of metal inner wall surfaces binding both axial ends of the main body portion 105-1. -7, 105-9, and the pair of side wall portions 105-7, 105-9 have through holes 105-11, 105-13 at substantially central portions facing each other. The kind of metal used in the main body portion 105-1 and the side wall portions 105-7 and 105-9 is, for example, copper, and the inner wall surfaces of these are plated with silver, for example. Referring to FIG. 4, the inner wall dimension D of the cylindrical main body 105-1 is, for example, 46.4 mm, and the length L is, for example, 23.2 mm. The diameter of the through holes 105-11 and 105-13 is, for example, 5 mm. Input and output connectors 105-3 and 105-5 are attached to the cylindrical main body portion 105-1 of the cavity resonator 105 or one side wall portion 105-7 or 105-9. FIG. 4 shows, as an example, a case where connectors 105-3 and 105-5 are attached to a cylindrical main body 105-1. The input/output connectors 105-3 and 105-5 are coaxial type, and the vicinity of the tip of the core wire is exposed inside the cavity resonator 105. The other ends of the core wires of the input connectors 105-3 and 105-5 are electrically connected to the network analyzer 109. Further, the main body portion 105-1 and the side wall portions 105-7 and 105-9 of the cavity resonator 105 are connected to the ground of the network analyzer 109 by a mesh line on the ground side of the coaxial cable. Then, a high-frequency current input from the network analyzer 109 to the cavity resonator 105 via the core wire of the input connector 105-3 forms an electromagnetic field of a predetermined mode in the cavity formed inside the cavity resonator 105. It has become so. The core wire of the output connector 105-5 is electrically connected to the network analyzer 109, and the network analyzer 109 couples with the electromagnetic field generated in the cavity and resonates corresponding to each mode inside the cavity resonator 105. The position of the peak, that is, the resonance frequency is detected. As shown in FIG. 4, the hollow fiber membrane 101 is inserted into the through holes 105-11 and 105-13. Further, as shown by an arrow 201 in FIG. 4, the hollow fiber membrane 101 is running in a direction from top to bottom. However, the vehicle may travel in the opposite direction.

  In this embodiment, the electromagnetic field mode formed in the cavity is the circular TM01n mode, and in this embodiment, the resonance frequency of the circular TM010 mode having the lowest resonance frequency is used. In the circular TM010 mode, as shown in FIG. 6, the electric field is oriented in the axial direction of the cylinder, and the magnetic field is oriented parallel to the inner wall surface of the cylinder. Since the electric field strength is maximized in the vicinity of the through holes 105-11 and 105-13, there is an advantage that the frequency fluctuation when the hollow fiber membrane 101 is inserted becomes large and therefore the measurement accuracy is improved.

  An analytical method of calculating the inner diameter by inserting the hollow fiber membrane 101 into the cavity resonator 105 and measuring the changed resonance frequency will be described. When a sample having a dielectric constant is inserted inside the cavity resonator 105, the perturbation theory can be applied. When a rod-shaped sample having a circular cross section is inserted into the cylindrical cavity resonator 105 of TM010 mode, the resonance frequency change δf is Maxwell's equation, assuming that the resonance frequencies before and after the sample insertion are f1 and f2, respectively. From

Here, ε is the relative permittivity of the hollow fiber membrane 101, V is the volume of the cavity of the cavity resonator 105, and ΔV is the volume of the sample. αε is a constant that depends on the resonance mode, and in the case of the circular TM010 mode, αε=1.85517.

  The above equations (1) and (2) are also valid in the TM01n mode other than the TM010 mode. However, the value of αε differs depending on the value of n.

  If the cross-sectional shape of the hollow fiber membrane is as shown in FIG. 5,

Here, D is the inner wall size of the main body portion 105-1, d1 is the outer diameter of the hollow fiber membrane 101, and d2 is the inner diameter of the hollow fiber membrane 101. From equations (1), (2), and (3),

Therefore, if the resonance frequency f1 and the relative permittivity ε before inserting the sample are measured in advance, the inner diameter d2 corresponding to the outer diameter d1 of the hollow fiber membrane is obtained as follows.

[Reference] Fumikazu Oguchi, et al. Microwave/millimeter wave measurement Corona Corporation In other words, known constant αε, resonance frequency f1 and relative permittivity ε measured in advance, and resonance frequency f2 currently measured at the same time. The inner diameter d1 can be obtained by substituting the outer diameter d2 and the outer diameter d2 into the equation (5). That is, not only the outer diameter d1 that may change momentarily can be measured in real time by the outer diameter detector 107, but the inner diameter d2 that can change momentarily can also be measured in real time.

[Second Embodiment]
FIG. 2 is a schematic diagram showing a second embodiment of the hollow fiber membrane inner diameter measuring device according to the present invention. The main difference from the first embodiment is that a comparative resonator 115 is added. In this embodiment, the network analyzer 109 has four ports so that the resonance frequency of the cavity resonator 105 in which the hollow fiber membrane 101 is inserted and the resonance frequency of the comparison cavity resonator 115 in which the hollow fiber membrane is not inserted can be simultaneously measured. Type (Keysight Technology, E5071C) is used. In the present embodiment, the resonance frequency f1 can be constantly measured by the comparative cavity resonator 115 without the hollow fiber membrane 101 being inserted. Therefore, even if the reference resonance frequency f1 fluctuates due to environmental changes such as temperature, since this fluctuation is common to the resonator 105 and the comparison resonator 115, it has the function of compensating this fluctuation at any time. There is.

  That is, in the second embodiment, the known constant αε, the previously measured relative permittivity ε, and the resonance frequency f1, the resonance frequency f2 and the outer diameter d2 that are currently measured at the same time are calculated by the equation (5). The inner diameter d1 can be obtained by substituting into

  FIG. 8 shows the result of measuring the frequency fluctuation in the present embodiment. The horizontal axis represents time, and the vertical axis represents frequency fluctuation, δf=f2-f1. The running speed of the hollow fiber membrane at this time is 50 m/min. According to FIG. 8, it can be confirmed that when the hollow fiber membrane is inserted, the resonance frequency is lowered by about 0.6 MHz.

  FIG. 9 shows the measurement results of the outer diameter and the inner diameter of the hollow fiber membrane in the present embodiment. The outer diameter is a numerical value measured by the outer diameter detector 103, and the inner diameter is calculated from the frequency variation and the outer diameter dimension value measured in FIG. The relative dielectric constant of the hollow fiber membrane 101 at this time is 3.0. As can be seen from FIG. 9, since the outer diameter and the inner diameter can be confirmed in real time, the film thickness of the hollow fiber membrane can be controlled during the manufacturing process, and the quality can be improved significantly.

[Third Embodiment]
FIG. 7 is a cross-sectional view of a cavity resonator showing a third embodiment of the hollow fiber membrane inner diameter measuring device according to the present invention. According to this embodiment, the pipe-shaped guide 105-15 is inserted so as to connect the through holes facing each other. The size of the guide 105-15 is slightly smaller than the hole diameter of the through holes 105-11 and 105-13 because the guide 105-15 is inserted into the through holes 105-11 and 105-13 without any gap, and the length thereof is the length of the cavity resonator 105. Longer than that. In the present embodiment, the outer diameter of the guide 105-15 is 4.9 mm and the length L is 23.2 mm and 30 mm, while the through hole hole diameters 105-11 and 105-13 are 5 mm. The wall thickness of the guide 105-15 is 0.5 mm. The material is preferably a resin having a low relative permittivity (that is, a relative permittivity as close to 1 as possible) so that the influence on the fluctuation of the resonance frequency is reduced. For example, PTFE (polytetrafluoroethylene) is used. .. The relative permittivity of PTFE is 2.1. By providing the guide 105-15 in the through holes 105-11 and 105-13 of the cavity resonator in this way, the hollow fiber membrane 101 can be inserted into the cavity resonator 105 more smoothly and the inside of the cavity resonator 105 can be inserted. It is possible to prevent dust and the like from entering.

[Additional information]
The frequency measuring method in the present embodiment is not limited to the one using the network analyzer 109, and may be a combination of a sweeper and a frequency counter, for example.

  The material of the cavity resonator 105 and the comparative cavity resonator 115 may be any conductive material, and is not limited to copper.

  The material of the guide 105-15 is not limited to PTFE as long as it has a low dielectric constant.

The frequency measuring method in the present embodiment enables the inner diameter of the hollow fiber membrane to be measured in a state where the hollow fiber membrane is continuously running. As long as the relationship between the position in the longitudinal direction of the membrane and the position in the longitudinal direction of the hollow fiber membrane whose resonance frequency is measured by the cavity resonator 105 can be taken, the hollow fiber is not in a continuous running state. The inner diameter of the membrane can be measured.

Claims (9)

An outer diameter measuring step for optically measuring the outer diameter of the continuously running hollow fiber membrane,
A first resonance frequency measurement step of measuring the first resonant frequency of the comparative cavity resonator in a state that does not penetrate the hollow fiber membrane in Comparative cavity resonator,
A second resonant frequency measuring step of measuring a second resonance frequency of the cavity resonator of the hollow fiber membrane continuously traveling in a state of being through the cavity resonator,
The inner diameter of the hollow fiber membrane is calculated using a predetermined relationship among the first resonance frequency, the second resonance frequency, the outer diameter of the hollow fiber membrane, and the inner diameter of the hollow fiber membrane. Calculation step to
Have a,
A hollow fiber membrane inner diameter measuring method in which the first resonance frequency measuring step and the second resonance frequency measuring step are performed simultaneously . The hollow fiber membrane inner diameter measuring method according to claim 1 , wherein
The predetermined relationship is, in addition to the first resonance frequency, the second resonance frequency, the outer diameter of the hollow fiber membrane, the inner diameter of the hollow fiber membrane, a relative dielectric constant of the hollow fiber membrane. A hollow fiber membrane inner diameter measuring method, characterized in that it is also expressed by using a constant corresponding to a resonance mode in the cavity resonator. The hollow fiber membrane inner diameter measuring method according to claim 2 , wherein
The method for measuring the inner diameter of a hollow fiber membrane, wherein the relative permittivity of the hollow fiber membrane has a constant value. The hollow fiber membrane inner diameter measuring method according to any one of claims 1 to 3 ,
An outer diameter measuring step is carried out by using a transmissive outer diameter measuring means having an LED light source or a laser light source as a measuring means, and measuring the outer diameter from the length of the hollow fiber membrane that interrupts the light source. Hollow fiber membrane inner diameter measuring method. The hollow fiber membrane inner diameter measuring method according to any one of claims 1 to 4 ,
The method for measuring the inner diameter of a hollow fiber membrane, wherein the resonance frequency of the cavity resonator is a resonance frequency in a resonance mode of a circular TM01n mode. The hollow fiber membrane inner diameter measuring method according to claim 5 ,
A hollow fiber membrane inner diameter measuring method, characterized in that a guide for passing the hollow fiber membrane through the pair of through holes of the cavity resonator is provided inside. Outer diameter measuring means for optically measuring the outer diameter of the continuously running hollow fiber membrane,
A first resonant frequency measuring means for measuring a first resonance frequency of the comparative cavity resonator in a state that does not penetrate the hollow fiber membrane in Comparative cavity resonator,
A second resonant frequency measuring means for measuring a second resonance frequency of the cavity resonator of the hollow fiber membrane continuously traveling in a state of being through the cavity resonator,
Calculating means for calculating the inner diameter of the hollow fiber membrane using a predetermined relationship among the first resonance frequency, the second resonance frequency, the outer diameter, and the inner diameter of the hollow fiber membrane. ,
Equipped with
A hollow fiber membrane inner diameter measuring device in which the measurement by the first resonance frequency measuring means and the measurement by the second resonance frequency measuring means are performed simultaneously . The hollow fiber membrane inner diameter measuring device according to claim 7 ,
The cavity resonator includes a main body portion having a cylindrical metal inner wall surface, and a pair of side wall portions having metal inner wall surfaces that close both axial ends of the main body portion, and the pair of side wall portions face each other. The hollow fiber membrane penetrates the pair of through holes, and the resonance frequency of the cavity resonator is the resonance frequency in the resonance mode of the circular TM01n mode. Hollow fiber membrane inner diameter measuring device. The hollow fiber membrane inner diameter measuring device according to claim 8 ,
A hollow fiber membrane inner diameter measuring device, wherein a guide for passing the hollow fiber membrane through the pair of through holes of the cavity resonator is provided inside the hollow resonator.

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