JP5207220B2 - HOLLOW POROUS MEMBRANE SUPPORT, HOLLOW POROUS MEMBRANE AND METHOD FOR PRODUCING THEM - Google Patents

Description

  The present invention relates to a support for a hollow porous membrane, a hollow porous membrane, and a method for producing them.

  In recent years, interest in environmental issues has increased, and regulations regarding water quality have been strengthened, and therefore, water treatment using a filtration membrane excellent in separation completeness, compactness, etc. has attracted attention. As the water treatment filtration membrane, for example, a hollow porous membrane is used. The hollow porous membrane requires not only excellent separation and permeation properties but also high mechanical properties. As a hollow porous membrane excellent in mechanical properties, a hollow porous membrane is disclosed in which a porous membrane layer is provided on the outer peripheral surface of a support made of a cylindrical braid obtained by rounding yarn (Patent Document 1). ~ 4). When the support is continuously passed through the annular nozzle, the hollow porous membrane is discharged from the annular nozzle, and after the coating solution is applied to the outer peripheral surface of the support, the coating solution is applied. The produced support is passed through a coagulation bath, and the film-forming stock solution is coagulated with the coagulation solution in the coagulation bath.

  The cylindrical braid of the support is usually manufactured by a string making machine. In a stringing machine, each thread is pulled out from a large number of bobbins erected on a flat plate, each thread is crossed and assembled, and each bobbin is moved along a predetermined path to thereby determine the positional relationship of the threads. A braid is manufactured by changing the pattern in a predetermined pattern. The braid manufactured by the string making machine has the following problems.

  The braid usually has elasticity, and stretches when applied with tension, and its outer diameter decreases. Therefore, when the film-forming stock solution is applied to a support made of a cylindrical braid, if the tension applied to the support varies, the outer diameter of the support changes. As a result, since the gap between the inner peripheral surface of the pipe line of the annular nozzle and the support changes, the film-forming stock solution cannot be applied with a uniform thickness when the inner diameter of the annular nozzle and the discharge amount of the film-forming stock solution are constant. . In the coagulation step, if the support is stretched before the film-forming stock solution is completely coagulated, defects in the film structure such as pinholes may occur in the porous film layer.

Patent Document 4 discloses a method for producing a hollow porous membrane by applying a tension to a support and maintaining a tensioned state (tight state). With this method, the problem is unlikely to occur. However, in this method, in the coagulation step, the porous film is crushed by pressing the support coated with the film-forming stock solution on the guide roll in the coagulation bath, and deformed into a porous film, which has a film structure such as a pinhole. Defects may occur.
Japanese Patent Laid-Open No. 52-81076 JP-A-5-7746 JP 2006-0668710 A JP 2006-150271 A

  An object of the present invention is to provide a support for a hollow porous membrane in which stretchability (change in outer diameter) is suppressed and is not easily crushed; a method capable of producing the support with high productivity; and variations in the thickness of the porous membrane layer It is an object of the present invention to provide a hollow porous membrane which is small and has few defects in the porous membrane layer; and a method capable of producing the hollow porous membrane.

  As a result of intensive studies in view of the above problems, the inventors have passed the cylindrical braid through a heated mold and subjected to heat treatment at a specific temperature, so that the stretchability of the cylindrical braid (outer diameter) (Change) can be suppressed.

The manufacturing method of the support body for hollow porous membranes of this invention has the following processes, It is characterized by the above-mentioned.
A string braiding device provided on the upstream side of the die, and a take-up provided on the downstream side of the die, with a round braided yarn having a fineness of 500 to 1200 dtex and a punched number of 8 to 50 The process of heat-treating continuously with the apparatus through the through-hole of the metal mold | die heated to the temperature t (degreeC) in the range represented by following formula (1).
Tm−80 ° C. ≦ t <Tm (1).
In the formula, Tm is the melting temperature (° C.) of the yarn material.

Before Kiito is preferably number of filaments you are multifilament 30 to 200.
It is preferable that the inner diameter D of the through hole on the inlet side of the cylindrical braid is equal to or larger than the inner diameter d of the through hole on the outlet side of the cylindrical braid.
The inner diameter d is preferably 50 to 100% of the outer diameter of the cylindrical braid before heat treatment.

The support for a hollow porous membrane of the present invention is obtained by the method for producing a support for a hollow porous membrane of the present invention.
The hollow porous membrane of the present invention is characterized by having the support for the hollow porous membrane of the present invention and a porous membrane layer provided on the outer peripheral surface of the support.
The method for producing a hollow porous membrane of the present invention comprises a material for a porous membrane layer on the outer peripheral surface of the support for hollow porous membrane obtained by the method for producing a support for hollow porous membrane of the present invention. A porous membrane layer is formed by applying a film-forming stock solution containing a solvent and a solvent and solidifying the solution.

The support for a hollow porous membrane of the present invention is suppressed in stretchability (change in outer diameter) and hardly collapses.
According to the method for producing a support for a hollow porous membrane of the present invention, it is possible to produce a support for a hollow porous membrane that is suppressed in stretchability (change in outer diameter) and is not easily crushed with high productivity.

The hollow porous membrane of the present invention has small variations in the thickness of the porous membrane layer, and the porous membrane layer has few defects.
According to the method for producing a hollow porous membrane of the present invention, it is possible to stably produce a hollow porous membrane with small variations in the thickness of the porous membrane layer and few defects in the porous membrane layer.

<Hollow porous membrane support>
FIG. 1 is a side view showing an example of a support for a hollow porous membrane (hereinafter referred to as a support) of the present invention. The support 10 is composed of a cylindrical braid 12 formed by rounding a thread.

  Round punching is a combination of a group of threads that draw parallel S-shaped spirals on a virtual cylindrical surface and a group of threads that draw parallel Z-shaped spirals on the same virtual cylindrical surface. Reference numeral 12 denotes a plurality of threads that run in the form of left and right threads and cross each other.

Examples of the yarn form include multifilament, monofilament, spun yarn and the like.
Examples of the yarn material include synthetic fiber, semi-synthetic fiber, regenerated fiber, and natural fiber. The yarn may be a combined yarn obtained by combining a plurality of types of fibers. Further, even with the same type of yarn, the properties of the cylindrical braid 12 may be changed by combining yarns having different properties such as heat shrinkability or by combining different types of yarn.

  Synthetic fibers include polyamide fibers such as nylon 6, nylon 66 and aromatic polyamide; polyester fibers such as polyethylene terephthalate, polybutylene terephthalate, polylactic acid and polyglycolic acid; acrylic fibers such as polyacrylonitrile; polyethylene and polypropylene Polyolefin fiber such as polyvinyl alcohol fiber; polyvinylidene chloride fiber; polyvinyl chloride fiber: polyurethane fiber; phenol resin fiber; fluorine fiber such as polyvinylidene fluoride and polytetrafluoroethylene; polyalkylene paraoxybenzoate System fibers and the like.

Examples of the semi-synthetic fibers include cellulose derivative fibers made from cellulose diacetate, cellulose triacetate, chitin, chitosan and the like: protein fibers called promix.
Examples of the regenerated fiber include cellulosic regenerated fibers (rayon, cupra, polynosic, etc.) obtained by a viscose method, a copper-ammonia method, an organic solvent method, or the like.
Examples of natural fibers include flax and jute.

  As the material of the yarn, polyester fiber, acrylic fiber, polyvinyl alcohol fiber, polyamide fiber, or polyolefin fiber is preferable, and polyester fiber or acrylic fiber is particularly preferable because of excellent chemical resistance.

  As the yarn, a multifilament of synthetic fiber is preferable because the effect of heat treatment in the step (b) described later is easily exhibited.

The outer diameter of the cylindrical braid 12 (support 10) is determined by the outer diameter of the hollow porous membrane. The outer diameter of the hollow porous membrane is preferably 1.5 to 6.0 mm, more preferably 2.0 to 3.5 mm, from the required filtration area in the membrane module in which the hollow porous membranes are bundled. Therefore, the outer diameter of the cylindrical braid 12 is preferably 1.0 to 5.0 mm, and more preferably 1.8 to 3.0 mm.
The inner diameter of the cylindrical braid 12 (support 10) is preferably 1.0 mm or more from the viewpoint of suppressing a decrease in water permeability of the filtered water.

  The fineness of the yarn is preferably 500 to 1200 dtex from the viewpoint of improving the durability of the hollow porous membrane and the adhesion to the porous membrane layer. When the fineness of the yarn is 500 dtex or more, the crushing pressure of the hollow porous membrane is improved. If the fineness of the yarn is 1200 dtex or less, a decrease in water permeability due to a reduction in the inner diameter can be suppressed.

The number of hits of the cylindrical braid 12 is preferably 8-50. When the number of strikes is 8 or more, the crushing pressure of the hollow porous membrane is improved. If the number of hits is 50 or less, a decrease in water permeability due to reduction in the inner diameter can be suppressed.
As the yarn, a multifilament having 30 to 200 filaments is particularly preferred from the viewpoint of excellent strength and water permeability. When the number of filaments is 30 or more, the collapse pressure of the hollow porous membrane is improved. If the number of filaments is 200 or less, a decrease in water permeability can be suppressed.

The cylindrical braid 12 is a braid that has been heat-treated at a temperature t (° C.) within the range represented by the following formula (1).
Tm−80 ° C. ≦ t <Tm (1).
In the formula, Tm is the melting temperature (° C.) of the yarn material. The melting temperature of the yarn material is measured by the method of JIS-L-1013.

  When the cylindrical braid 12 is heat-treated at (Tm-80) or higher, the cylindrical braid 12 is thermally contracted to suppress stretchability, and the gap between the yarns becomes dense, The cylindrical braid 12 is not easily crushed. Since the cylindrical braid 12 is heat-treated at a temperature lower than Tm, the gap between the yarns can be prevented from being crushed.

<Method for producing support for hollow porous membrane>
The support 10 is manufactured by a manufacturing method having the following steps (a) to (b).
(A) A step of rounding the yarn to assemble the cylindrical braid 12.
(B) A step of heat-treating the cylindrical braid 12 at a temperature t (° C.) within a range represented by the following formula (1).
Tm−80 ° C. ≦ t <Tm (1).
In the formula, Tm is the melting temperature (° C.) of the yarn material.

(A) Process:
The cylindrical braid 12 is assembled using a known string making machine. Examples of the string making machine include the string making machine described in Japanese Utility Model Laid-Open No. 6-37384.

  The cylindrical braid 12 has residual strain such as tension added during the stringing process because all the yarns constituting the cylindrical braid 12 are assembled diagonally and the bobbin of the stringing machine moves in a complicated manner. Therefore, it is preferable to remove the residual strain by heat treatment using a drying furnace or the like. The temperature of the heat treatment is lower than the temperature t of the heat treatment in the step (b), and is usually 100 to 130 ° C.

(B) Process:
The cylindrical braid 12 has elasticity due to its structure. Therefore, by applying heat treatment to the cylindrical braid 12, the stretchability (outer diameter change) of the cylindrical braid 12 is suppressed. Further, by applying heat treatment to the cylindrical braid 12, the cylindrical braid 12 is not easily crushed.

  FIG. 2 is a schematic configuration diagram illustrating an example of a support manufacturing apparatus used in the step (b). The support manufacturing apparatus 20 includes a bobbin 22, a string supply device 26 that pulls the cylindrical braid 12 drawn from the bobbin 22 with a constant tension, a mold 28 that heat-treats the cylindrical braid 12, and a heat-treated cylindrical shape. A take-up device 30 for taking up the braid 12 and a winder 32 for taking up the cylindrical braid 12 as a support 10 on a bobbin are provided.

The mold 28 includes a main body made of a metal block, a plate, or the like, and a heating unit. Examples of the heating means include a band heater and an aluminum cast heater.
FIG. 3 is a view showing an entrance side end surface, a side cross-section, and an exit side end surface of the cylindrical braid 12 of the mold 28. A through hole 34 is formed in the main body of the mold 28.

The inner diameter D of the through hole 34 on the entrance side of the cylindrical braid 12 is equal to or slightly larger than the outer diameter D ′ of the cylindrical braid 12 before the heat treatment, and the inner diameter d on the outlet side of the cylindrical braid 12 is equal to that after the heat treatment. Is equal to the outer diameter d ′ of the cylindrical braid 12.
The through hole 34 has a straight portion having a length L on the exit side of the cylindrical braid 12.

  The inner diameter D is preferably greater than or equal to the inner diameter d. That is, in order to obtain the cylindrical braid 12 having a small elongation and a uniform outer diameter, the cylindrical braid 12 needs to be heated uniformly. Therefore, D ≧ d so that the inner peripheral surface of the through hole 34 and the surface of the cylindrical braid 12 are always in contact with each other.

  The inner diameter d is preferably 50 to 100% of the outer diameter D ′. When the inner diameter d is extremely smaller than the outer diameter D ′, the outer diameter d ′ becomes larger than the inner diameter d, and the cylindrical braid 12 may be caught in the mold 28 and cannot pass through the through hole 34.

The ratio (L / d) between the length L and the inner diameter d is preferably 1 or more from the viewpoint of heating the cylindrical braid 12 uniformly.
From the point of avoiding the catch of the cylindrical braid 12, it is preferable that the inner peripheral surface of the through hole 34 has a taper other than the straight portion.
The mold 28 may have an integral structure or a vertically divided structure. From the viewpoint that the cylindrical braid 12 can be easily passed, an upper and lower split structure is preferable.

  Examples of the string supply device 26 and the take-up device 30 include a Nelson roll, a nip roll, and a calendar roll. Since the nip roll may crush the cylindrical braid 12, a Nelson roll or a calendar roll is preferable.

When the cylindrical braid 12 passes through the mold 28, it is heat-treated at (Tm−80 ° C.) or more to cause thermal shrinkage, the elasticity is suppressed, and the gap between the threads becomes dense, The cylindrical braid 12 is not easily crushed. Further, the outer diameter of the cylindrical braid 12 is restricted at the straight portion on the outlet side, and the cylindrical braid 12 having a desired outer diameter d ′ is obtained. Moreover, since the cylindrical braid 12 is heat-processed below Tm, it is suppressed that the clearance gap between yarns is crushed.
When the material of the yarn 16 is a polyester fiber, the temperature t is preferably 180 to 250 ° C, more preferably 190 to 230 ° C, although it depends on the Tm of the material.

  The ratio between the speed V1 of the string supply device 26 and the speed V2 of the take-up device 30 can be arbitrarily set according to the type of the yarn 16, the outer diameter of the cylindrical braid 12 before heat treatment, and the size of the eyes. Cylindrical braid having a desired eye size by setting the difference between V1 and V2 within the range of V1> V2 in accordance with the thermal contraction rate of the yarn 16 that thermally contracts in the mold 28. 12 can be obtained. When a small eye is desired, the difference between V1 and V2 is increased to sufficiently heat-shrink the cylindrical braid 12. When a large eye is desired, the difference between V1 and V2 is reduced to suppress thermal contraction of the cylindrical braid 12. When the outer diameter of the cylindrical braid 12 is large and the fineness is high, V1 <V2 and the sizing may be forcibly performed in the mold 28.

  Moreover, when the thermal contraction rate of the cylindrical braid 12 is small, the string supply device 26 may not be installed. In this case, in order to suppress the occurrence of tension between the bobbin 22 and the mold 28 due to thermal contraction of the cylindrical braid 12, it is preferable to provide a buffer by loosening the cylindrical braid 12 or the like.

<Hollow porous membrane>
The hollow porous membrane of the present invention comprises the support for the hollow porous membrane of the present invention and a porous membrane layer provided on the outer peripheral surface of the support.

  Examples of the material of the porous membrane layer include polyvinylidene fluoride, polysulfone, polyacrylonitrile, polyvinyl pyrrolidone, polyethylene glycol and the like. From the viewpoint of chemical resistance, heat resistance, etc., polyvinylidene fluoride, or polyvinylidene fluoride and polyvinyl pyrrolidone. The combination with is preferable.

The porous membrane layer may be a single layer or a composite porous membrane layer of two or more layers.
The thickness of the porous membrane layer is preferably 100 to 350 μm, and more preferably 150 to 300 μm.
The outer diameter of the hollow porous membrane is preferably 1.5 to 6.0 mm, more preferably 2.0 to 3.5 mm.

<Method for producing hollow porous membrane>
When the porous membrane layer is a composite porous membrane layer having two layers, the hollow porous membrane is produced by a production method having the following steps (i) to (vii).

(I) The process of apply | coating film forming undiluted solution to the outer peripheral surface of a support body.
(Ii) A step of solidifying the film-forming stock solution applied to the support to form a first porous membrane layer to obtain a hollow porous membrane precursor.
(Iii) A step of applying a film-forming stock solution to the outer peripheral surface of the hollow porous membrane precursor.
(Iv) A step of solidifying a film-forming stock solution applied to the hollow porous membrane precursor to form a second porous membrane layer to obtain a hollow porous membrane.
(V) A step of washing the hollow porous membrane.
(Vi) A step of drying the hollow porous membrane.
(Vii) A step of winding the hollow porous membrane.

  FIG. 4 is a schematic configuration diagram illustrating an example of a hollow porous membrane manufacturing apparatus used in steps (i) to (ii). The hollow porous membrane manufacturing apparatus 40 includes an annular nozzle 42 for continuously applying a film-forming stock solution to the support 10 continuously supplied from an unwinding device (not shown), and a film-forming stock solution for the annular nozzle 42. The coagulation bath 46 containing a coagulating liquid for coagulating the film-forming stock solution applied to the support 10, and the support 10 applied with the film-forming stock solution to the coagulation bath 46 continuously. And a guide roll 48 to be introduced.

(I) Process:
A pipe line through which the support 10 passes is formed at the center of the annular nozzle 42. In the middle of the pipe, two slit-form film forming solution discharge ports are formed on the upstream side and the downstream side in the circumferential direction of the pipe line, so that two types of film forming solution having different compositions are discharged. Yes.
When the support 10 passes through the pipeline, two types of film-forming stock solutions are supplied from the stock solution supply device 44 in a constant amount. First, the film-forming stock solution (2) is applied to the outer peripheral surface of the support 10, and then The film-forming stock solution (1) is applied onto the film stock solution (2) to form a coating film having a predetermined film thickness.

  The inner diameter of the pipe line of the annular nozzle 42 is slightly larger than the outer diameter of the support body 10, and the inner peripheral surface of the pipe line of the annular nozzle 42 and the support body have a certain gap. The gap is determined by the thickness of the coating film, the viscosity of the film-forming stock solution, the running speed of the support, and is usually 0.15 to 0.25 mm.

  The film-forming stock solution is a liquid containing the above-mentioned porous membrane layer material and a solvent. Examples of the solvent include N, N-dimethylformamide, N, N-dimethylacetamide, dimethyl sulfoxide, and the like, and N, N-dimethylacetamide is preferable from the viewpoint of high water permeability of the formed porous membrane layer.

As for the density | concentration of the material of the porous membrane layer in film-forming stock solution (1) (100 mass%), 12-25 mass% is preferable.
As for the density | concentration of the material of the porous membrane layer in film-forming stock solution (2) (100 mass%), 0.1-12 mass% is preferable.
The temperature of the annular nozzle 42 is preferably 20 to 40 ° C.

As the support 10, a cylindrical braid 12 subjected to the heat treatment is used for the following reason.
A tension (load) is applied to the support 10 due to the rotational resistance of the guide roll 48, the resistance of the coagulating liquid in the steps (ii) and (iv), the resistance of the cleaning liquid in the step (v), and the like. The tension is usually 0.5 to 9.8 N.
If the tension is too small, there are the following problems.
Problem I:
Problems such as the support 10 coming off from the guide roll 48 and the like are likely to occur.
Problem II:
The outer diameter of the support 10 is increased, and the gap between the inner peripheral surface of the pipe line of the annular nozzle 42 and the support 10 is reduced. As a result, the film thickness of the coating film becomes thin, or the film-forming stock solution that has not been applied drips down.

However, if the tension is too large, there are the following problems.
Problem III:
When the thickness of the support 10 (cylindrical braid 12) is thin, the hollow portion of the support 10 is easily crushed when passing through the guide roll 48 or the like.
Problem IV
The support body 10 extends and the outer diameter of the support body 10 becomes smaller. Therefore, the gap between the inner peripheral surface of the pipe line of the annular nozzle 42 and the support 10 is widened. As a result, the film thickness of a coating film becomes thick or the location where a coating film is not formed generate | occur | produces.

Problem V:
In the step (ii), the support 10 is stretched during the solidification of the film-forming stock solution, resulting in defects in the film structure such as pinholes, or the support 10 is pressed against the guide roll 48, so that the coating film is formed. It may be crushed and become a defect of the film structure such as deformation and pinhole.
Therefore, in order to solve the above problems, as the support body 10, a heat-treated cylindrical braid 12 is used that is suppressed in elasticity (change in outer diameter) and is not easily crushed.

(Ii) Process:
The coagulating liquid in the coagulation bath 46 is brought into contact with the coating film of the film-forming stock solution, and the film-forming stock solution is solidified to form the first porous film layer to obtain the hollow porous film precursor 18.
As the coagulation liquid, an aqueous solution containing the same solvent as that of the film-forming stock solution is preferable. When the solvent of the film forming stock solution is N, N-dimethylacetamide, the concentration of the solvent is preferably 1 to 50% by mass in the coagulation liquid (100% by mass).

The temperature of the coagulation liquid is preferably 50 to 90 ° C.
Steps (v) to (vii) described later may be performed between step (ii) and step (iii).

Steps (iii) to (iv):
A device similar to the device used in steps (i) to (ii) is used, and the second porous material is formed on the outer peripheral surface of the hollow porous membrane precursor 18 under the same conditions as in steps (i) to (ii). A membrane layer is formed to obtain a hollow porous membrane.
In the step (iii), an internal coagulation liquid may be used as the film forming stock solution (2). Examples of the internal coagulation liquid include glycerin, alcohols, ethylene glycol and the like.

(V) Process:
For example, the hollow porous membrane is washed in hot water at 60 to 100 ° C. to remove the solvent, then washed with a chemical solution such as hypochlorous acid, and then washed in hot water at 60 to 100 ° C. Then remove the chemical.

Steps (vi) to (vii):
The hollow porous membrane is dried at 60 ° C. or more and less than 100 ° C. for 1 minute or more and less than 24 hours, and then wound on a bobbin, a cassette or the like.

  Since the support 10 described above is composed of the cylindrical braid 12 that has been heat-treated at a temperature t within the range represented by the above formula (1), it has stretchability (change in outer diameter) compared to a conventional cylindrical braid. Suppressed and hard to collapse.

  Moreover, according to the manufacturing method of the support body 10 demonstrated above, the elasticity (change in an outer diameter) is suppressed by carrying out heat processing at the temperature t in the range represented by the said Formula (1), and a support which is hard to be crushed. The body 10 can be manufactured with high productivity. The heat treatment in Japanese Utility Model Laid-Open No. 6-37384 is a process for removing residual strain of the braid, and the temperature is lower than the range represented by the above formula (1). Moreover, since the heat set apparatus described in Japanese Utility Model Publication No. Hei 6-37384 has a bowl shape and one surface is in an open state, the outer diameter of the string cannot be regulated or controlled.

  Moreover, since the hollow porous membrane demonstrated above consists of the cylindrical braid 12 by which the support body 10 was heat-processed by the temperature t in the range represented by said Formula (1), the outer periphery of the support body 10 is shown. When the film-forming stock solution is applied to the surface, the change in the outer diameter of the support 10 is small, the film-forming stock solution can be applied uniformly, and the support 10 is not easily crushed, so the variation in the thickness of the porous film layer is small. There are few defects in the porous membrane layer.

  Moreover, according to the manufacturing method of the hollow porous membrane demonstrated above, since the cylindrical braid 12 heat-processed at the temperature t in the range represented by said Formula (1) is used as the support body 10, support is carried out. When the film-forming solution is applied to the outer peripheral surface of the body 10, there is little change in the outer diameter of the support 10, the film-forming solution can be uniformly applied, and the support 10 is not easily crushed. It is possible to stably produce a hollow porous membrane with a small variation in the number of defects and few defects in the porous membrane layer.

The present invention will be specifically described by the following examples.
(Outer diameter of support)
The outer diameter of the support was measured using a laser contour measuring instrument (manufactured by Keyence Corporation, LS3000). The sample length was 10 cm, and the average value was obtained by measuring three times.

(External diameter change of support)
A tensile load was applied to the support using a Tensilon type tensile tester (Orientec, UCT-1T), and the outer diameter of the support at each load was measured using a laser profile measuring instrument (Keyence, LS3000). did. The sample length was 5 cm, and the average value was obtained by measuring three times at each load.

(Change in elongation of support)
A tensile load was applied to the support with a Tensilon-type tensile tester (Orientec, UCT-1T type), and the elongation of the support at each load was measured. The sample length was 5 cm, and the average value was obtained by measuring three times at each load.

(Outer diameter of hollow porous membrane)
The outer diameter of the hollow porous membrane was measured by the following method.
A sample to be measured was cut into approximately 10 cm, several bundles were bundled, and the whole was covered with a polyurethane resin. The polyurethane resin also entered the hollow part of the support.
After the polyurethane resin was cured, a thin piece having a thickness (longitudinal direction of the film) of about 0.5 mm was sampled using a razor blade.
Next, the sampled cross section of the hollow porous membrane was observed with a projector (Nikon Corporation, PROFILE PROJECTOR V-12) at an objective lens of 100 times.
A mark (line) was placed at the position of the outer surface in the X direction and Y direction of the cross section of the hollow porous membrane being observed, and the outer diameter was read. This was measured three times to determine the average value of the outer diameter.

(Inner diameter of hollow porous membrane)
The inner diameter of the hollow porous membrane was measured by the following method.
The sample to be measured was sampled in the same manner as the sample whose outer diameter was measured.
Next, the sampled cross section of the hollow porous membrane was observed with a projector (Nikon Corporation, PROFILE PROJECTOR V-12) at an objective lens of 100 times.
A mark (line) was aligned with the position of the inner surface of the support in the X and Y directions of the cross section of the hollow porous membrane being observed, and the inner diameter was read. This was measured three times to determine the average inner diameter.

(Thickness of porous membrane layer)
The film thickness of the porous membrane layer was measured by the following method.
The sample to be measured was sampled in the same manner as the sample whose outer diameter was measured.
Next, the sampled cross section of the hollow porous membrane was observed with a projector (Nikon Corporation, PROFILE PROJECTOR V-12) at an objective lens of 100 times.
The film thickness was read by aligning marks (lines) at the positions of the outer surface and inner surface of the film at the 3 o'clock position on the cross section of the hollow fiber membrane being observed. Similarly, the film thickness was read in the order of 9 o'clock, 12 o'clock, and 6 o'clock. This was measured three times to determine the average inner diameter.

(Water permeability performance of hollow porous membrane)
The water permeability of the hollow porous membrane was measured by the following method.
The sample to be measured was cut into 4 cm, and one end face was sealed with a polyurethane resin.
Next, the pressure was reduced in ethanol for 5 minutes or more, and then immersed in pure water for replacement.
Pure water (25 ° C.) was placed in the container, connected to the other end of the sample with a tube, and an air pressure of 200 kPa was applied to the container to measure the amount of pure water coming out of the sample for 1 minute. This was measured three times to obtain an average value. This value was divided by the surface area of the sample to determine the water permeability.

[Example 1]
(Manufacture of support)
The support body 10 was manufactured by heat-treating the cylindrical braid 12 using the support body manufacturing apparatus 20 shown in FIG.
As the cylindrical braid 12, a braid was prepared in which polyester fibers (fineness: 830 dtex, number of filaments: 96, Tm: 260 ° C.) were braided using 16 stringers. As the string supply device 26 and the take-up device 30, a Nelson roll was used. As the mold 28, an aluminum alloy mold having an heating means (inner diameter D: 3.0 mm, inner diameter d: 2.0 mm, L / d: 3) was used.
The temperature (t) of the mold 28 was 230 ° C., the speed V1 of the string supply device 26 was 1.5 m / min, and the speed V2 of the take-up device 30 was 1.1 m / min.

  The outer diameter of the obtained support 10 was 1.98 mm. The outer diameter change and elongation change of the support 10 were measured. The results are shown in FIG. 5 and FIG. When tension was applied with a load of 9.8 N, the change in outer diameter was -0.05 mm, and the change in elongation was +3.35 mm.

(Manufacture of hollow porous membrane)
Subsequently, the hollow porous membrane was manufactured using the hollow porous membrane manufacturing apparatus 40 shown in FIG.
Polyvinylidene fluoride A (manufactured by Atofina Japan, trade name: Kyner 301F), polyvinylidene fluoride B (manufactured by Atofina Japan, trade name: Kyner 9000LD), polyvinylpyrrolidone (manufactured by ISP, trade name: K-90) , N, N-dimethylacetamide were mixed so as to have a mass ratio shown in Table 1 to prepare a film-forming stock solution (1) and a film-forming stock solution (2).

(I) Process:
The annular nozzle 42 (gap between the inner peripheral surface of the pipe line and the support 10: 0.2 mm) is kept at 30 ° C., and the film is formed from the first discharge port on the upstream side while passing the support 10 through the pipe. The stock solution (2) is discharged to apply the film-forming stock solution (2) to the outer peripheral surface of the support 10, and the film-forming stock solution (1) is further discharged from the second discharge port on the downstream side to form the film-forming stock solution (2 The film-forming stock solution (1) was applied on top.

(Ii) Process:
Next, the support 10 coated with the film-forming stock solution is passed through a coagulation liquid (5% by mass of N, N-dimethylacetamide and 95% by mass of water) kept at 80 ° C. in the coagulation bath 46 to obtain the first The porous membrane layer was formed to obtain a hollow porous membrane precursor 18.

(Iii) Process:
Next, while passing the hollow porous membrane precursor 18 through the annular nozzle (gap between the inner peripheral surface of the pipe line and the first porous membrane layer: 0.2 mm) kept at 30 ° C., the upstream first nozzle Glycerin (Wako Pure Chemical Industries, first grade) is discharged as an internal coagulating liquid from one discharge port, glycerin is applied onto the first porous membrane layer, and a film-forming stock solution is further discharged from the second discharge port on the downstream side. (1) was discharged and the film-forming stock solution (1) was applied onto glycerin.

(Iv) Process:
Next, a second porous membrane layer was formed on the outer peripheral surface of the hollow porous membrane precursor 18 under the same conditions as in the step (ii) to obtain a hollow porous membrane.

(V) Process:
Next, after the hollow porous membrane was washed in hot water at 98 ° C. for 3 minutes to remove the solvent, the following steps (x) to (z) were repeated twice.
(X) A step of immersing the hollow porous membrane in a 50000 mg / L aqueous sodium hypochlorite solution.
(Y) A step of heating the hollow porous membrane in a steam bath at 90 ° C. for 2 minutes.
(Z) A step of washing the hollow porous membrane in hot water at 90 ° C. for 3 minutes.

Steps (vi) to (vii):
The hollow porous membrane was dried at 85 ° C. for 10 minutes, and then wound around a winder.
The obtained hollow porous membrane had an outer diameter of 2.8 mm, an inner diameter of 1.1 mm, an average film thickness of 850 μm, and a water permeability of 98 m ³ / m ² / h / MPa. . Moreover, the variation in the film thickness of the porous membrane layer was small, and no defect was found in the porous membrane layer.

[Comparative Example 1]
Using a string making machine, a cylindrical braid in which polyester fibers (fineness: 830 dtex, number of filaments: 96) were braided in 16 strokes was prepared. Without heat-treating the cylindrical braid, changes in the outer diameter and elongation of the cylindrical braid were measured. The results are shown in FIG. 7 and FIG.

As shown in FIG. 7, the outer diameter of the conventional cylindrical braid changes greatly when tension (load) is applied. Therefore, when continuously manufacturing the hollow porous membrane, when the tension applied to the cylindrical braid increases, the outer diameter is small, that is, the gap between the inner peripheral surface of the pipe line of the annular nozzle and the cylindrical braid is widened, The coating film becomes thicker. Further, when the gap is widened, the amount of the film-forming stock solution discharged is insufficient, and there may be a portion where a coating film is not formed. On the other hand, when the tension applied to the cylindrical braid is small, the outer diameter is large, that is, the gap is narrowed, the film thickness of the coating film is thinned, the film forming stock solution is discharged more than necessary, and causes of defects such as dripping It becomes.
On the other hand, as shown in FIG. 5, the cylindrical braid of Example 1 has a small change in outer diameter even when the tension applied to the cylindrical braid increases, and it is uniform without causing the above problems and defects. A coating film can be obtained, and a hollow porous membrane can be produced stably.

Further, as shown in FIG. 8, the elongation of the conventional cylindrical braid is greatly changed by the application of tension (load). The elongation obtained from FIG. 8 is about 13%. In the step (ii), if the cylindrical braid stretches before the film-forming stock solution is completely solidified, there is a risk of a film structure defect such as a pinhole.
On the other hand, as shown in FIG. 6, the cylindrical braid of Example 1 has little change in elongation even when the tension applied to the cylindrical braid increases, and the above-described problem does not occur.

  The support of the present invention is suitable as a support for composite porous membranes such as microfiltration membranes and ultrafiltration membranes, and a hollow porous membrane using the support is obtained by microfiltration, ultrafiltration or the like. Suitable as filtration membrane for water treatment

It is a side view which shows an example of the support body for hollow porous membranes of this invention. It is a schematic block diagram which shows an example of a support body manufacturing apparatus. It is the end elevation and side sectional view showing an example of a metallic mold. It is a schematic block diagram which shows an example of a hollow porous membrane manufacturing apparatus. It is a graph which shows the outer diameter change with respect to the load of the support body of Example 1. FIG. It is a graph which shows the elongation change with respect to the load of the support body of Example 1. FIG. It is a graph which shows the outer diameter change with respect to the load of the cylindrical braid of the comparative example 1. It is a graph which shows the elongation change with respect to the load of the cylindrical braid of the comparative example 1.

Explanation of symbols

10 Support (Hollow Porous Membrane Support)
12 cylindrical braid 26 string supply device 28 mold 30 take-up device 34 through hole

Claims (7)

The manufacturing method of the support body for hollow porous membranes which has the following process.
A string braiding device provided on the upstream side of the die, and a take-up provided on the downstream side of the die, with a round braided yarn having a fineness of 500 to 1200 dtex and a punched number of 8 to 50 The process of heat-treating continuously with the apparatus through the through-hole of the metal mold | die heated to the temperature t (degreeC) in the range represented by following formula (1).
Tm−80 ° C. ≦ t <Tm (1).
In the formula, Tm is the melting temperature (° C.) of the yarn material. The yarn, the number of filaments is multifilament 30 to 200, the production method of the hollow porous membrane support according to claim 1. The support for a hollow porous membrane according to claim 1 or 2 , wherein an inner diameter D of the through hole in the entrance side of the cylindrical braid is equal to or more than an inner diameter d of the through hole in the exit side of the cylindrical braid. Manufacturing method. The manufacturing method of the support body for hollow porous membranes of Claim 3 whose said internal diameter d is 50 to 100% of the outer diameter of the cylindrical braid before heat processing. The support body for hollow porous membranes obtained by the manufacturing method of the support body for hollow porous membranes as described in any one of Claims 1-4 . A support for a hollow porous membrane according to claim 5 ,
A hollow porous membrane having a porous membrane layer provided on the outer peripheral surface of the support. The material and solvent of a porous membrane layer are provided on the outer peripheral surface of the support for a hollow porous membrane obtained by the method for producing a support for a hollow porous membrane according to any one of claims 1 to 4. A method for producing a hollow porous membrane, wherein a porous membrane layer is formed by applying and coagulating a film-forming stock solution containing the solution.

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