JP2007239147A - Spinning nozzle for producing hollow fiber membrane - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a spinning nozzle suppressing occurrence of bubbles or breakage, etc., in forming a membrane and producing the hollow fiber membrane having stable strength. <P>SOLUTION: The spinning nozzle 10 for producing the hollow fiber membrane of a double tubular structure is provided with a flow channel 33 for a core liquid on the central side and a flow channel 24 for a membrane-forming solution on the outside thereof. A straightening flow channel-forming part 36 for forming a straightening flow channel 25 for the membrane-forming solution straightening the membrane-forming solution flowing in the radially-inward direction in the direction parallel to the central axis toward a discharge port 23 for the membrane-forming solution is installed in the flow channel 24 for the membrane-forming solution. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a spinning nozzle for producing a hollow fiber membrane, and more particularly to a spinning nozzle for producing a hollow fiber membrane used for producing a porous hollow fiber membrane by a dry and wet method.

  An outline of a general method for producing a porous hollow fiber membrane (hereinafter referred to as a hollow fiber membrane) used for microfiltration, ultrafiltration and the like will be described.

  A film-forming solution called a polymer solution, dope or the like is prepared by dissolving a polymer forming a film and other additives that are appropriately blended in a good solvent. This film forming solution is supplied to the annular outer flow path of the spinning nozzle having a double tube structure by a pressure pump, a metering pump or the like. In the channel provided inside the annular outer channel, a non-solvent (generally a mixture of water or a good solvent in water) that solidifies (phase-separates) a polymer called an internal coagulating liquid is used as a core liquid. Supply as.

  The film-forming solution that is extruded from the spinning nozzle in the form of a tubular hollow structure passes through a certain distance in the air, and is then immersed in a solution that solidifies a polymer called an external coagulation liquid, and the outside is solidified. Further, the inside (hollow part) of the film forming solution is solidified by the core liquid. In this way, a hollow hollow fiber membrane is formed.

Such a general hollow fiber membrane production method is disclosed in the following literature.
JP 2002-66272 A “Membrane Science Experiment Series Volume III Artificial Membrane Edition” of the Japanese Membrane Society, published by Kyoritsu Publishing Co., Ltd., December 10, 1993, p. 2-9

  As a spinning nozzle used for manufacturing a hollow fiber membrane, for example, there is a nozzle as shown in FIG. FIG. 4 is a schematic cross-sectional view of a spinning nozzle according to the prior art. The spinning nozzle 101 has a double tube structure including a film forming solution tube portion 102 and a core liquid tube portion 103.

  The membrane-forming solution that forms the hollow fiber membrane is injected from the membrane-forming solution inlet 121 provided in the membrane-forming solution pipe section 102, and discharged from the membrane-forming solution discharge port 123 through the membrane-forming solution flow path 122. On the other hand, the core liquid for forming the hollow part of the hollow fiber membrane is discharged from the core liquid discharge port 133 through the core liquid flow path 135 of the core liquid pipe part 103.

  In the case of such a spinning nozzle 101, since the film forming solution inlet 121 is provided in the radial direction with respect to the film forming solution flow path 122 extending in the axial direction, as shown in FIG. It flows into the membrane solution channel 122 in the inner diameter direction. FIG. 5 is a schematic perspective view showing the film forming solution channel 122 of FIG. 4 in an enlarged manner.

  Therefore, the film-forming solution that has flowed in from the film-forming solution inlet 121 is divided into one circumferential direction and the other circumferential direction around the core liquid pipe portion 103 as shown in FIGS. 5 and 6. While flowing so as to wind up the tube portion 103, the flow is changed in the axial direction toward the film forming solution discharge port 123. 6 is a cross-sectional view taken along the line AA in FIG.

Due to such flow diversion and change in direction, etc., and due to a sudden drop in flow velocity caused by expansion of the cross-sectional area of the flow path when flowing from the film formation solution inlet 121 to the film formation solution flow path 122,
The flow of the film-forming solution becomes non-uniform, and the flow stays at the portion 105 where the film-forming solution diverges and local fine turbulence (a flow different from the flow related to the large turbulence generated at other portions) occurs.

  Due to the influence of the flow turbulence at the branch point 105 on the discharge of the film-forming solution from the film-forming solution discharge port 123, as shown in FIG. There was a problem that it occurred. FIG. 7 is a schematic cross-sectional view of the hollow fiber membrane after film formation.

  In particular, since the film-forming solution has a certain degree of viscosity, it is considered that such local disturbance and stagnation easily leave a trace up to the film-forming solution discharge port 123. And when generation | occurrence | production of such a bubble 106 etc. deteriorated further, the crack generate | occur | produced in the hollow fiber membrane and the strength of the hollow fiber membrane was reduced remarkably.

  The present invention has been made in order to solve the above-described problems of the prior art, and the object of the present invention is to provide a hollow fiber membrane that suppresses the occurrence of bubbles, cracks, and the like in film formation and has a stable strength. It is providing the spinning nozzle which can manufacture.

  In order to achieve the above object, the spinning nozzle for producing a hollow fiber membrane in the present invention is a hollow fiber membrane having a double tube structure including a core liquid channel on the center side and a membrane forming solution channel on the outside thereof. In the production spinning nozzle, a flow straightening is formed in the film forming solution flow path to flow the film forming solution flowing in the inner diameter direction in a direction parallel to the central axis toward the outlet of the film forming solution flow path. A flow path forming part is provided.

  In this way, the flow of the film-forming solution that has flowed in the inner diameter direction is rectified into a uniform flow parallel to the central axis by the rectifying flow path formed by the rectifying flow-path forming portion, thereby Occurrence of local turbulence and stagnation inside is suppressed, and generation of bubbles and cracks in the hollow fiber membrane after film formation is suppressed.

  The rectifying channel may be an annular channel having a width of 0.01 mm to 1 mm.

  The rectifying flow path forming portion may be an annular convex portion protruding outward from the outer wall of the inner tube.

  As described above, the production of hollow fiber membranes with stable strength is suppressed in the production of hollow fiber membranes, and the occurrence of bubbles and cracks is suppressed, and there is little risk of strength reduction due to the occurrence of bubbles and cracks. It becomes possible.

  The best mode for carrying out the present invention will be exemplarily described in detail below with reference to the drawings. However, the dimensions, materials, shapes, relative arrangements, and the like of the components described in this embodiment are not intended to limit the scope of the present invention only to those unless otherwise specified. .

  First, with reference to FIG. 3, a hollow fiber membrane production apparatus provided with a spinning nozzle for producing a hollow fiber membrane (hereinafter referred to as a spinning nozzle) according to an embodiment of the present invention will be described together with the production process of the hollow fiber membrane. To do. FIG. 3 is a schematic diagram for explaining a configuration of a hollow fiber membrane manufacturing apparatus including a spinning nozzle according to the present embodiment.

  The hollow fiber membrane manufacturing apparatus 1 includes a spinning nozzle 10, a gear pump 12, a micropump 13, an external coagulation liquid bath 14, and a winding roll 15.

  The spinning nozzle 10 is a core liquid discharge port that discharges a core liquid for forming a hollow portion of the hollow fiber membrane, and a film formation that is annularly provided around the core liquid discharge port and discharges the film forming solution in a tubular shape. And a solution discharge port.

  The membrane-forming solution 2 is prepared by dissolving a polymer that forms the hollow fiber membrane and other appropriately blended additives in a good solvent. The film-forming solution 2 is a highly viscous solution, and is sent to the gear pump 12 by pressurization (P in FIG. 3), and is quantitatively injected from the gear pump 12 into the spinning nozzle 10.

  The core liquid 3 is a low-viscosity solution having the ability to coagulate a polymer, generally water or a mixture of a good solvent in water and used to form the inside (hollow part) of the hollow fiber membrane. It is injected into the spinning nozzle 10 by the micro pump 13 as an internal coagulating liquid.

  The external coagulation liquid bath 14 is filled with a solution called an external coagulation liquid that coagulates a polymer, and the film forming solution 2 discharged from the spinning nozzle 10 is immersed therein.

  The hollow fiber membrane is formed by first injecting the core liquid 3 into the spinning nozzle 10 by the micro pump 13 and then injecting the membrane forming solution 2 into the spinning nozzle 10 by the gear pump 12.

  And after making the gel-form film forming solution 2 discharged from the spinning nozzle 10 run idle for a certain distance (air gap 11), it is led to the external coagulating liquid bath 14 and immersed in the external coagulating liquid to coagulate the outside. Thus, the hollow fiber membrane 4 is formed. The inner side (hollow part) of the hollow fiber membrane 4 is formed by being solidified by the core liquid.

  The formed hollow fiber membrane 4 is further subjected to solvent replacement (initial cleaning) in the external coagulation liquid bath 14 for a while and then dried and collected by the winding roll 15.

  Next, the spinning nozzle according to the present embodiment will be described in more detail with reference to FIG. FIG. 1 is a schematic cross-sectional view of a spinning nozzle according to the present embodiment. The spinning nozzle 10 according to the present embodiment has a double-pipe structure having a membrane forming solution pipe section 20 and a core liquid pipe section 30.

  The membrane-forming solution pipe part 20 includes an axial hole 21 that penetrates in the axial direction, and a radial hole 22 that penetrates from the peripheral surface of the axial hole 21 to the side surface of the membrane-forming solution pipe part 2 in the radial direction. One opening of the axial hole 21 is tapered, and the radial hole 22 is an inlet for the film forming solution and is provided on the other opening side of the axial hole 21.

  The core liquid pipe part 30 includes a nozzle part 31 protruding in the axial direction, a nozzle base part 32, and an axial hole (core liquid flow path) 33 penetrating through the center in the axial direction.

  The nozzle portion 31 is inserted from the other opening portion of the axial hole 21, and the end surface of the nozzle base portion 32 at the base of the nozzle portion 31 abuts against the end surface of the axial hole 21 of the membrane forming solution tube portion 20 on the other opening side. The membrane-forming solution pipe part 20 and the core liquid pipe part 30 are tightened in the axial direction by a fastener 5 such as a bolt, so that the film-forming solution pipe part 20 and the core liquid pipe part 30 are integrated into a spinning nozzle. 10 is configured.

The outer peripheral surface on the base side of the nozzle part 31 is formed so as to be fitted to the inner peripheral surface of the axial hole 21 of the membrane-forming solution pipe part 20, so that the nozzle part 31 is located with respect to the axial hole 21. Accurately positioned

  The axial dimension of the nozzle part 31 and the axial hole 21 is set to be substantially the same, and the outer diameter of the tip part of the nozzle part 31 is the diameter of one opening part of the tapered axial hole 21 formed in a taper. Is set smaller than. Therefore, when the nozzle portion 31 is inserted into the axial hole 21, the annular discharge port 23 of the film forming solution is formed by the outer peripheral surface at the tip of the nozzle portion 31 and the inner peripheral surface of one opening portion of the axial hole 21. Is formed. On the other hand, the core liquid discharge port 34 is an opening at the tip of the nozzle portion 31.

  The film-forming solution is injected from the radial hole (inlet) 22 of the film-forming solution pipe part 20, and passes through the flow path 24 formed in an annular shape by the outer peripheral surface of the nozzle part 31 and the inner peripheral surface of the axial hole 21. As a result, the liquid is discharged from the annular discharge port 23 in a tubular shape.

  The core liquid that forms the hollow portion of the hollow fiber membrane is injected from the opening (inlet 35) on the nozzle base 32 side of the axial hole 33 and discharged from the opening (discharge port 34) at the tip of the nozzle 31. .

  In the spinning nozzle 10 according to the present embodiment, an annular convex portion (rectifying flow) projecting radially on the outer periphery of the nozzle portion 31 of the core liquid pipe portion 30 (projecting outward from the outer wall of the nozzle portion 31). (Channel forming part) 36 is provided, and between the outer peripheral surface of the convex part 36 and the inner peripheral surface of the axial hole 21 of the membrane-forming solution pipe part 20, the flow path 26 and the convex part upstream of the convex part 36. An annular rectifying flow path 25 having a small width is formed with respect to the flow path 27 downstream of 36. Therefore, the film-forming solution flow path 24 includes a rectification flow path 25, a flow path 26 upstream of the rectification flow path 25, and a flow path 27 downstream of the rectification flow path 25.

  Here, with reference to FIG. 2, the flow of the film forming solution in the film forming solution channel of the spinning nozzle according to the present embodiment and the rectifying effect by the rectifying channel will be described. FIG. 2 is an enlarged perspective view showing the film forming solution flow path of the spinning nozzle according to the present embodiment. Here, the arrow in the figure represents the flow of the film forming solution.

  The film forming solution flows into the flow path 26 from the inlet 22 provided in the radial direction with respect to the axial hole 21. The flowing film-forming solution flows while changing the direction of the flow in the axial direction toward the discharge port 23 while flowing so that the outer periphery of the nozzle portion 31 is divided into both circumferential directions and the nozzle portion 31 is wound around. Become.

  The flow of the film-forming solution becomes non-uniform due to such a flow splitting or change in direction, or a sudden drop in flow velocity caused by an increase in the cross-sectional area of the flow path when flowing from the inlet 22 into the flow path 26. Flow retention and local fine disturbances occur at the branching point of the membrane solution.

  The film-forming solution in which the stay or disturbance has occurred flows into the rectifying channel 25 having a smaller channel area with respect to the channel 26, so that the flow direction is substantially aligned in the axial direction (parallel to the central axis), The unevenness of the flow rate flowing through the rectifying channel 25 is suppressed and becomes almost uniform.

  The film forming solution rectified in the rectifying flow path 25 as described above is further adjusted in the process of flowing through the flow path 27 and discharged from the discharge port 23. That is, by providing the convex portion 36 and forming the rectifying flow path 25, the direction of the flow of the film-forming solution can be made almost uniform, the occurrence of unevenness in the flow is suppressed, and stable discharge becomes possible.

  As a result, generation of bubbles and cracks in the hollow fiber membrane after film formation is suppressed, and a hollow fiber membrane having stable strength can be produced.

  In the flow channel 26 upstream from the rectifying flow channel 25, the outer shape from the nozzle base 32 side of the nozzle portion 31 to the convex portion 36 is constricted at the intermediate portion as shown in FIGS. ing. Thereby, the direction of the flow of the film-forming solution that has flowed in from the inlet 22 in the inner diameter direction can be gradually changed to the axial direction, and a more effective rectifying effect can be achieved by flowing toward the rectifying flow path 25 more smoothly. Can be obtained.

  Further, the outer shape from the convex portion 36 of the nozzle portion 31 to the tip of the nozzle portion 31 is a bell-shaped taper shape, and the space of the flow passage 27 downstream from the rectification flow passage 25 is a rectification flow. After leaving the passage 25, it once expands and then gradually changes toward the discharge port 23.

  By forming the channel 27 in this way, the film-forming solution rectified in the rectifying channel 25 can flow more smoothly toward the discharge port 23, and the pressure loss of the viscous film-forming solution can be reduced. Thus, a sufficient discharge pressure at the discharge port 23 can be secured. As a result, a stable discharge shape of the film forming solution can be formed, and yarn tearing or the like due to uneven discharge can be prevented.

  However, the shape of the nozzle part 31 and the flow path 24 is not limited to the above-mentioned shape, and it goes without saying that the shape is appropriately changed depending on the nature of the fluid flowing through the flow path. That is, when a low-viscosity solution or the like is flowed instead of the viscous fluid as in the present embodiment, the flow path may be configured to continue to the discharge port with the final gap interval at the time of discharge. .

  Here, the width of the rectifying channel 25 (distance between the outer peripheral surface of the convex portion 36 and the peripheral surface of the axial hole 21, that is, a half of the difference between the inner diameter and the outer diameter of the rectifying channel 25). If it is too wide, the effect of the convex portion 36 is lowered, and a sufficient rectifying effect cannot be obtained. On the other hand, if it is too narrow, the flow of the viscous film-forming solution is hindered due to clogging of contamination in the solution, increase in the solution supply pressure due to pressure loss, disturbance due to the compression flow of the solution, and the like.

  Therefore, by setting the width of the rectifying channel 25 to 0.01 mm to 1 mm, preferably 0.05 mm to 0.2 mm, a sufficient rectifying effect can be obtained while avoiding the above-described problems. The diameter of the axial hole 21 (R in the figure) is 10 mm to 20 mm.

It is typical sectional drawing of the spinning nozzle which concerns on the Example of this invention. It is a partially expanded perspective view of the film forming solution channel portion of the spinning nozzle according to the embodiment of the present invention. It is a schematic diagram explaining the structure of the hollow fiber membrane manufacturing apparatus provided with the spinning nozzle which concerns on the Example of this invention. It is typical sectional drawing of the spinning nozzle which concerns on a prior art. It is a partially expanded perspective view of the film forming solution channel part of the spinning nozzle according to the prior art. It is a schematic diagram explaining the flow of the film forming solution in the spinning nozzle which concerns on a prior art. It is typical sectional drawing of the hollow fiber membrane manufactured with the spinning nozzle which concerns on a prior art.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Hollow fiber membrane manufacturing apparatus 2 Film forming solution 3 Core liquid 4 Hollow fiber membrane 10 Spinning nozzle 11 Air gap 12 Gear pump 13 Micro pump 14 External coagulation liquid bath 15 Winding roll 20 Film forming solution pipe part 21 Axial hole 22 Radial direction Hole (inlet)
23 Discharge port 24 Film-forming solution flow path 25 Rectification flow path 26 Upstream flow path 27 Downstream flow path 30 Core liquid pipe section 31 Nozzle section 32 Nozzle base section 33 Axial hole (core liquid flow path)
34 Discharge port 35 Inlet port 36 Rectifier flow path forming part 5 Fastener 101 Spinning nozzle 102 Film forming solution pipe part 105 Branch point 106 Air bubble 121 Film forming solution inlet 122 Film forming solution flow path 123 Film forming solution discharge port 103 Core liquid Pipe part 133 Core liquid discharge port 135 Core liquid flow path

Claims (3)

A core fluid channel on the center side;
The outer membrane-forming solution flow path;
In a spinning nozzle for producing a hollow fiber membrane having a double-pipe structure comprising:
In the membrane-forming solution channel, there is a rectifying channel forming portion that forms a channel for rectifying the membrane-forming solution flowing in the inner diameter direction in a direction parallel to the central axis toward the outlet of the membrane-forming solution channel. A spinning nozzle for producing a hollow fiber membrane, which is provided.   The spinning nozzle for producing a hollow fiber membrane according to claim 1, wherein the rectifying channel is an annular channel having a width of 0.01 mm to 1 mm.   The spinning nozzle for producing a hollow fiber membrane according to claim 1 or 2, wherein the rectifying flow path forming portion is an annular convex portion protruding outward from the outer wall of the inner tube.

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