JP2005313079A - Composite porous membrane and its manufacturing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a composite porous membrane that is excellent not only in filtration performance but also in adhesion between a filter medium and a supporter and has excellent mechanical properties. <P>SOLUTION: The composite porous membrane is prepared by forming a first porous layer having a dense layer and forming a second porous layer having a dense layer adjacent to the first porous layer on the surface of a supporter. The composite porous membrane having the polyol impregnation ratio of 50-100% is excellent in mechanical properties such as adhesion strength between the filter medium and the supporter. Therefore, it is usable under severe conditions such as applications of various types of water treatments to enhance the quality of the filtrate. Also, since the penetration performance are high, the membrane area to be used is getting smaller, thereby compacting the equipment. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a composite porous membrane suitable for water treatment and a method for producing the same.

  In recent years, due to increasing interest in environmental pollution and stricter regulations, water treatment by a membrane method using a filtration membrane having excellent separation completeness and compactness has attracted attention. In such water treatment applications, filtration membranes are required to have not only excellent separation characteristics and permeation performance but also high mechanical properties.

  Conventionally, filtration membranes such as polysulfone, polyacrylonitrile, cellulose acetate, and polyvinylidene fluoride produced by a wet or dry wet method are known as filtration membranes having excellent permeation performance. These filtration membranes are produced by microphase separation of a polymer solution and then coagulating in a non-solvent to form a dense layer and a support layer, and have a high porosity and an asymmetric structure. Is obtained.

  Among these, polyvinylidene fluoride resin is excellent in chemical resistance and heat resistance, and thus is suitably used as a material for the separation membrane. However, the polyvinylidene fluoride hollow fiber membranes proposed so far have low mechanical strength.

  As a technique for increasing the strength, a porous membrane in which a hollow braid is completely embedded in a porous semipermeable membrane has been proposed (for example, Patent Document 1). However, this porous membrane has a problem that its water permeability is low because the braid is completely embedded in the porous semipermeable membrane.

On the other hand, in order to improve water permeability, a porous membrane having a porous membrane on a hollow braid surface layer has also been proposed (for example, Patent Document 2). However, this separation membrane has a problem that the filter medium and the braid easily peel off because the filter medium is disposed only on the braid surface.
Japanese Patent Laid-Open No. 52-81076 US Pat. No. 5,472,607

  An object of the present invention is to provide a composite porous membrane excellent in not only filtration performance but also adhesiveness between a filter medium and a support and excellent mechanical properties, and a method for producing the same.

That is, the first gist of the present invention is that the first porous layer having a dense layer is formed on the surface of the support, and the second porous layer having the dense layer adjacent to the first porous layer. A composite porous membrane in which a layer is formed,
It is a composite porous membrane whose polyol impregnation rate measured in the following procedures (1) to (7) is 50 to 100%.
(1) A polyol solution in which 0.1% by mass of a methyl red dye is dissolved in a polyol having a viscosity of 1300 to 1500 mPa / sec and a surface tension of 60 to 65 dyn / cm at 25 ° C. is prepared.
(2) A composite porous membrane having a length of 30 cm is immersed in a polyol solution for 5 minutes.
(3) Remove the composite porous membrane from the polyol solution and wipe the polyol solution adhering to the surface.
(4) The second porous layer is removed from the composite porous membrane to expose the first porous layer.
(5) The first porous layer is partitioned at intervals of 1 mm in the length direction.
(6) For each section, the presence or absence of coloring with methyl red pigment is examined. In addition, if even a little is colored in one division, it will be considered as colored.
(7) The polyol impregnation rate is determined according to the following formula (A).
Formula (A): polyol impregnation ratio (%) = number of sections colored with methyl red dye / total number of sections × 100

The second gist of the present invention is to apply a film-forming stock solution to a support using an annular nozzle, coagulate it in a coagulating liquid to form a first porous layer, and then use the annular nozzle to form the first porous layer. A method for producing a composite porous membrane in which a film-forming stock solution is applied to the surface of one porous layer and solidified in a coagulating liquid to form a second porous layer,
The annular nozzle includes a support passage through which the support passes, a first discharge port that opens to the entire peripheral wall of the support passage, and an outlet side of the support passage, concentrically with the support passage, and the support And a second discharge port disposed on the outer periphery of the passage, and the front end surface of the support passage is located inside the annular nozzle from the front end surface of the second discharge port,
At the time of forming the second porous layer, a slow coagulation liquid selected from at least one of monool hydrophilic polymer, diol hydrophilic polymer, triol hydrophilic polymer, glycerin, and polyvinylpyrrolidone is discharged from the first discharge port. And discharging the stock solution from the second discharge port,
When the distance (m) from the front end surface of the support passage to the front end surface of the second discharge port is S and the film forming speed (m / min) is V, S / V is 1.0 × 10 ⁻⁵ to It is a manufacturing method of the composite porous membrane which is 1.0 * 10 <^-3> .

Since the composite porous membrane of the present invention has a polyol impregnation rate of 50 to 100%, it is excellent in mechanical properties such as adhesive strength between the filter medium and the support. Therefore, it can be used under severe use conditions such as various water treatment applications, and the quality of the filtrate can be improved. Moreover, since the permeation performance is high, the area of the membrane used is reduced and the equipment can be made compact.
In the method for producing a porous membrane of the present invention, when the distance (m) from the front end surface of the support passage to the front end surface of the second discharge port is S, and the film forming speed (m / min) is V. , By making S / V 1.0 × 10 ^{−5 to} 1.0 × 10 ⁻³ , a composite porous membrane having excellent mechanical properties such as adhesive strength between the filter medium and the support can be produced. it can.

Embodiments of the present invention will be described below.
The composite porous membrane of the present invention is preferably a composite porous hollow fiber membrane in which the membrane material is applied to a thread-like support. In water treatment applications, the liquid on the primary side of membrane permeation often flows against the membrane surface. Since the membrane is swung and pulled by this membrane surface flow, sufficient mechanical strength is required. When the support bears this mechanical strength, a composite porous membrane having excellent performance can be obtained.

  The support used in the present invention can be used as long as it is a porous body having mechanical strength, but braid is particularly preferable. Examples of the braid include a braid produced by knitting and weaving 96 filaments of 8.6 dtex polyester fibers and 16 multifilaments of a total of 830 dtex in a hollow braid shape at a speed of 10 revolutions / min.

  In the composite porous membrane of the present invention, the first porous layer having the dense layer is formed on the surface of the support, and the second porous layer having the dense layer adjacent to the first porous layer. Is formed.

  When the porous membrane is used for filtration, it is usually used as a porous membrane module in which the porous membrane is fixed to a housing or the like with a potting resin, and the temporary side and the secondary side of the porous membrane are partitioned liquid-tightly.

  Here, when the composite porous membrane of the present invention is used as the porous membrane, if the gap is wide between the first porous layer and the second porous layer, the potting resin stops at the gap. The first porous layer and the support may not be sufficiently impregnated. In that case, the fixing strength of the porous membrane is weakened and easily damaged.

  Therefore, it is preferable to avoid a gap as much as possible between the first porous layer and the second porous layer. On the other hand, it is not always easy to directly measure the width of the gap. This is because, for example, even if the composite porous membrane is cut and the cross section is observed with a microscope or the like, the gap is widened or crushed when the cross section is formed, so the original state is not always maintained. It is.

  Here, the inventors pay attention to the polyol impregnation rate measured by the following procedures (1) to (7), and the composite porous membrane having a polyol impregnation rate of 50 to 100% is a potting resin. It was found that the fixing strength can be increased by impregnating the entire composite porous membrane with the potting resin in the fixing step.

(1) A polyol solution in which 0.1% by mass of a methyl red dye is dissolved in a polyol having a viscosity of 1300 to 1500 mPa / sec and a surface tension of 60 to 65 dyn / cm at 25 ° C. is prepared.
(2) A composite porous membrane having a length of 30 cm is immersed in a polyol solution for 5 minutes.
(3) Remove the composite porous membrane from the polyol solution and wipe the polyol solution adhering to the surface.
(4) The second porous layer is removed from the composite porous membrane to expose the first porous layer.
(5) The first porous layer is partitioned at intervals of 1 mm in the length direction.
(6) For each section, the presence or absence of coloring with methyl red pigment is examined. In addition, if even a little is colored in one division, it will be considered as colored.
(7) The polyol impregnation rate is determined according to the following formula (A).
Formula (A): polyol impregnation ratio (%) = number of sections colored with methyl red dye / total number of sections × 100

  In addition, as an example of the polyol which has said viscosity and surface tension at 25 degreeC, the mixture of glycerol or glycerol and another polyol is mentioned. Moreover, even if components other than polyol are mixed with these, they can be used as long as they have the above-mentioned viscosity and surface tension.

  The polyol impregnation rate becomes higher as the gap between the first porous layer and the second porous layer is smaller. This is because if the gap is narrow, the polyol impregnated from the second porous layer side passes through the gap and further impregnates the first porous layer. On the other hand, if the gap between the first porous layer and the second porous layer is wide, the impregnation of the polyol stops in the gap, and therefore the impregnation of the polyol is less likely to occur in the first porous layer.

  The polyol impregnation rate is preferably 50% or more, more preferably 70% or more, and further preferably 80% or more. The upper limit of the polyol impregnation rate is 100%.

  The composite porous membrane of the present invention preferably has a water passage burst pressure of 300 kPa or more from the viewpoint of achieving both water permeation performance and fractional pore size control. If the water burst pressure of the composite porous membrane is less than 300 kPa, bacteria such as Escherichia coli and suspended substances tend to easily permeate. Although there is no upper limit to the water burst pressure, 1000 kPa is sufficient for practical use. Note that the water-permeable burst pressure referred to here is a predetermined value from one surface side of the composite porous membrane to the other surface side (in the case of a hollow fiber membrane, for example, from the hollow part toward the outer surface side of the hollow fiber). Apply pressure to pass water and measure the pressure at which the membrane ruptures.

  The composite porous membrane of the present invention is obtained by applying a film-forming stock solution to a support using an annular nozzle and coagulating it in a coagulating liquid to form a first porous layer, and then using the annular nozzle to form the first porous layer. A film-forming stock solution is applied to the surface of one porous layer and solidified in a coagulating liquid to form a second porous layer.

  FIG. 1 is a cross-sectional view showing an example of an annular nozzle used in the present invention. The annular nozzle includes a distribution plate 10, a first distribution nozzle 9 that is assembled adjacent to the distribution plate 10, and a second distribution nozzle that is assembled adjacent to the first distribution nozzle 9 to form the tip of the tubular nozzle. 8 and three members.

  The distribution plate 10 is a disk-shaped member, and a pipe line 1 through which the support passes is formed at the center thereof. Furthermore, the distribution plate 10 has a first supply port 6 for supplying a film-forming stock solution and a second supply port 7 for supplying a film-forming stock solution or a slow-coagulation solution described later around the pipe line 1. Have.

The first distribution nozzle 9 is a member having a substantially T-shaped cross section and a disk having a disk shape in plan view. At its center, a protruding tubular portion 13 is formed that protrudes into the second distribution nozzle 8. The inside of the protruding tubular portion 13 is a hollow portion, and this hollow portion communicates with the pipe line 1 to form a support passage 100. When the first distribution nozzle 9 and the distribution plate 10 are concentrically stacked, a support passage 100 is formed at the center thereof.
The first distribution nozzle 9 has a hollow portion communicating with the first supply port 6 and a hollow portion communicating with the second supply port 7 around the support passage 100.

When the distribution plate 10 and the first distribution nozzle 9 are concentrically overlapped, grooves are formed so that the first liquid pool portion 11 communicating with the first supply port 6 is formed. An annular slit is also formed so that the first discharge ports 2 are formed over the entire circumference of the peripheral wall of the support passage 100 when they are concentrically stacked. The first discharge port 2 communicates with the first liquid pool portion 11. Further, the first liquid pool part 11 and the first discharge port 2 communicate with each other.
When the distribution plate 10 and the first distribution nozzle 9 are concentrically overlapped and the liquid is supplied to the first supply port 6, the supplied liquid is stored in the first pool portion 11, and then the support body passage from the first discharge port 2. The liquid can be discharged toward 100.

  The second distribution nozzle 8 is also a disk-shaped member, and a second liquid pool portion 12 is formed at the center thereof, and a hollow portion communicating with the second liquid pool portion 12 is further formed. The hollow portion communicates with the second supply port 7 through a hollow portion that communicates with the second supply port 7 formed in the first distribution nozzle 9. By overlapping the second distribution nozzle 8 and the first distribution nozzle 9 concentrically, a second liquid pool portion 12 is formed around the protruding tubular portion 13 of the first distribution nozzle 9. Specifically, the space formed by the end surface of the first distribution nozzle 9 where the protruding annular portion 13 is provided, the protruding tubular portion 13, and the second distribution nozzle 8 is the second liquid pool portion 12. The second liquid pool portion 12 is formed such that its cross-sectional area decreases toward the distal end of the protruding tubular portion 13 of the first distribution nozzle 9. That is, the inner wall of the second distribution nozzle 8 gradually protrudes toward the projecting annular portion 13.

  Further, a second protruding port 3 is formed at the tip of the second pool liquid portion 12. That is, the second discharge port 3 is formed by the outer wall of the distal end portion of the protruding tubular portion 13 and the inner wall of the second distribution nozzle 8. In particular, the front end surface of the protruding annular portion 13, that is, the front end surface 110 of the support passage 100 is positioned more inward of the annular nozzle than the front end surface 5 of the second discharge port 3, that is, the front end surface 5 of the second distribution nozzle 8. To do.

A method for producing a composite porous membrane using this annular nozzle will be further described.
First, when forming the first porous layer on the support, a thin first film-forming stock solution that is easily impregnated in the support is applied to the support, and then suitable for forming the porous layer. A second film-forming stock solution having a concentration higher than that of the first film-forming liquid is applied to the support. By using the first film-forming stock solution and the second film-forming stock solution having different concentrations, the main part of the support can be impregnated, and peeling of the film material from the support can be improved.

Considering the impregnation property into the support, the polymer concentration for forming the membrane material in the first membrane forming stock solution is preferably 12% or less, more preferably 10% or less, and further preferably 7% or less. By setting it as such a density | concentration, a 1st film forming liquid impregnates a support body easily. In addition to this, when the membrane is used, the polymer concentration of the membrane material in the voids of the support is approximately the same as the polymer concentration in the first membrane-forming solution, so the water permeability of the membrane during filtration is increased. Can keep. Furthermore, the membrane material can be attached to the support with sufficient strength.
From the viewpoint of improving chemical resistance and heat resistance, it is preferable to use a fluorine-based resin as the film material for the type of polymer forming the film material. Of these, polyvinylidene fluoride resin is particularly preferable.

  Similarly to the first film-forming stock solution, the second film-forming stock solution is prepared by dissolving a polymer serving as a film material in a solvent. When a composite porous membrane is used, it is preferable to use a polymer solution having a polymer concentration equal to or higher than that of the first membrane forming stock solution in order to obtain a mechanical strength in which a void layer is hardly formed. Specifically, the polymer concentration forming the film material in the second film-forming stock solution is set to 12% or more, more preferably 15% or more. In order to increase the permeation flow rate, the polymer concentration is preferably in a range not exceeding 25%.

As the solvent for the first and second film-forming stock solutions, an organic solvent is preferable. As the organic solvent, dimethylformamide, dimethylacetamide, dimethylsulfoxide and the like are used. Among them, dimethylacetamide is more preferably a solvent in that the porous body obtained has a high water permeation flow rate.
Moreover, it is preferable to dissolve together a hydrophilic polymer such as monool, diol, triol, and polyvinyl pyrrolidone represented by polyethylene glycol as an additive for controlling phase separation in the membrane forming stock solution. The lower limit of the concentration of the hydrophilic polymer is preferably 1% by mass, and more preferably 5% by mass. Further, the upper limit is preferably 20% by mass, and more preferably 12% by mass.

  When the temperature of the film-forming stock solution when protruding from the nozzle is less than 20 ° C., the film-forming stock solution may be gelled at a low temperature, which is not preferable. On the other hand, when the temperature is 40 ° C. or higher, it is difficult to control the pore size, and as a result, bacteria such as Escherichia coli and suspended substances are permeated, which is not practically preferable. Therefore, the temperature of the film forming stock solution is preferably in the range of 20 to 40 ° C.

Next, the film-forming stock solution coated on the support is allowed to run idle, and then immersed in a coagulation solution to form the first porous layer.
If the idling time is 0.01 seconds or less, the filtration performance is lowered, which is not preferable. There is no upper limit to the travel time, but 4 seconds is sufficient for practical use. Therefore, the idle time is preferably in the range of 0.01 to 4 seconds.

  As the coagulation liquid, an aqueous solution containing a solvent used for the film-forming stock solution is preferably used. Although depending on the type of solvent used, for example, when dimethylacetamide is used as the solvent for the film forming stock solution, the concentration of dimethylacetamide in the coagulation liquid is preferably 1 to 50%.

  The temperature of the coagulation liquid is preferably lower from the viewpoint of increasing the mechanical strength. However, if the temperature of the coagulation liquid is lowered too much, the water permeation flow rate of the completed film is lowered, and therefore, it is usually selected within the range of 90 ° C. or less, more preferably 50 ° C. or more and 85 ° C. or less.

  After solidifying, it is preferable to wash the solvent in hot water at 60 ° C to 100 ° C. It is effective to set the cleaning bath temperature as high as possible within the range in which the first porous layers are not fused. From this viewpoint, the temperature of the washing bath is preferably 60 ° C. or higher.

  It is preferable to perform chemical cleaning with hypochlorous acid after hot water cleaning. When using a sodium hypochlorite aqueous solution, the concentration is preferably in the range of 10 to 120,000 mg / L. When the concentration of the sodium hypochlorite aqueous solution is less than 10 mg / L, it is not preferable because the water flow rate of the completed membrane decreases. There is no upper limit to the concentration of the aqueous sodium hypochlorite solution, but 120,000 mg / L is sufficient for practical use.

Next, it is preferable to wash the membrane after chemical cleaning in hot water at 60 ° C to 100 ° C. Thereafter, it is preferably dried at 60 ° C. or more and less than 100 ° C. for 1 minute or more and less than 24 hours. If it is less than 60 degreeC, since a drying process time will take too much and production cost will rise, it is unpreferable on industrial production. If the temperature is 100 ° C. or higher, the film shrinks excessively during the drying process, and there is a possibility that minute cracks are generated on the film surface, which is not preferable.
The dried film is preferably wound on a bobbin or a cassette. It is preferable to wind it on a casket because element processing becomes easy.

  Next, a second film-forming solution is applied to the surface of the first porous layer to form a second porous layer. For the formation of the second porous layer, it is not necessary to use the first film-forming solution having a low concentration, but the first porous layer and the second porous layer are bonded to increase the water resistance. In order to prevent this, the slow coagulation liquid is discharged from the first discharge port 2 of the annular nozzle.

  This slow coagulation liquid does not coagulate the film-forming stock solution as rapidly as the coagulation liquid. However, if the film-forming stock solution is brought into contact with the slow-coagulation liquid for a long period of time, a material having the property of coagulating the film-forming stock solution is used. . Specifically, it is selected from at least one of a monool-based hydrophilic polymer, a diol-based hydrophilic polymer, a triol-based hydrophilic polymer, glycerin, and polyvinylpyrrolidone, and a mixture of two or more of these is used. You can also.

And the above-mentioned 2nd film forming undiluted | stock solution is discharged from the 2nd discharge port 3 of an annular nozzle.
Here, the distance from the front end surface 110 of the support passage 100 to the front end surface 5 of the second discharge port 3 (hereinafter referred to as the liquid seal length; the distance illustrated by 4 in FIG. 1) is S (m), S / V is 1.0 × 10 ⁻⁵ to 1.0 × 10, where V (m / min) is the film forming speed, that is, the speed at which the support coated with the film forming stock solution is drawn from the annular nozzle. ^Since the coating pressure of the film-forming stock solution can be appropriately controlled when ^-3 , the gap between the first porous layer and the second porous layer can be set to an appropriate interval.

The lower limit of the value of S / V is more preferably 1.0 × 10 ⁻⁵ or more, and further preferably 5.0 × 10 ⁻⁵ or more. When this S / V is less than 1.0 × 10 ⁻⁵ mm, the second film-forming stock solution coated on the surface of the first porous layer is discharged with almost no coating pressure. For this reason, even if there exists a thin part in the outer diameter of the film | membrane in which the 1st porous layer was formed, the 2nd film forming undiluted | stock solution will be discharged by the same diameter.

As a result, a large gap may be generated between the first porous layer and the second porous layer. The upper limit of the value of S / V is not particularly limited from the viewpoint of coating pressure, but if the liquid seal length is too long, it tends to be difficult to produce an annular nozzle. Therefore, the upper limit of the S / V value is preferably 1.0 × 10 ⁻³ or less. The upper limit of the value of S / V is preferably 9.0 × 10 ⁻⁴ or less, and more preferably 8.0 × 10 ⁻⁴ or less.

From the viewpoint of improving water permeability, the slow coagulation liquid used in the present invention is preferably a mixture of glycerin as a main component and glycerol mixed with 0.5 to 5% by mass of polyvinylpyrrolidone. When the mixing ratio of polyvinyl pyrrolidone in glycerin is less than 0.5% by mass, there is a shortage of slowly coagulating liquid brought between the first porous layer and the second porous layer, The inner layer structure becomes dense and the water permeability tends to decrease.
On the other hand, when the mixing ratio of polyvinyl pyrrolidone in glycerin exceeds 5% by mass, too much loosely coagulated liquid is brought between the first porous layer and the second porous layer. There is a tendency that the gap between the two porous layers becomes large and the polyol impregnation rate decreases.

Moreover, it is preferable that the viscosity of a slow solidification liquid is 100-3000 mPa / sec from the viewpoint of improving water permeability. When the viscosity of the slow solidification liquid is less than 100 mPa / sec, the slow solidification liquid brought between the first porous layer and the second porous layer is insufficient, and the inner layer structure of the second porous layer is dense. As a result, water permeability tends to decrease.
On the other hand, if the viscosity of the slow coagulation liquid exceeds 3000 mPa / sec, too much slow coagulation liquid is brought between the first porous layer and the second porous layer. There is a tendency for the gap between the porous layers to increase and the polyol impregnation rate to decrease.

  From the viewpoint of improving the water permeability, the amount of the slowly coagulated liquid carried per unit film length is preferably 0.01 to 1 g / m. The amount of the slow coagulation liquid brought in per unit film length means the amount of the slow coagulation liquid brought into the gap between the first porous layer and the second porous layer.

The amount of the slow coagulation liquid brought in per unit film length is obtained by the following formula (B).
Formula (B): Amount of slowly coagulated liquid brought in (g / m) = Amount of slowly coagulated liquid discharged (g / m)-Amount of slowly coagulated liquid overflow (g / m)
Here, the discharge amount of the slow coagulation liquid means the amount of the slow coagulation liquid discharged from the first discharge port 2. Further, the amount of slow coagulation liquid overflow is the excess of the slow coagulation liquid discharged from the first discharge port 2 excluding the amount brought in between the first porous layer and the second porous layer. Measure the amount of overflow from path 1

When the amount of the slow coagulation liquid carried per unit film length is less than 0.01 g / m, the slow coagulation liquid brought in between the first porous layer and the second porous layer is insufficient, The structure of the inner surface of the two porous layers becomes dense, and the water permeability tends to decrease.
On the other hand, if the amount of slowly coagulated liquid per unit film length exceeds 1 g / m, too much slowly coagulated liquid is brought between the first porous layer and the second porous layer. There is a tendency that the gap between the porous layer and the second porous layer becomes large and the polyol impregnation rate is lowered.

  After applying the film-forming stock solution for forming the second porous layer, solidification, washing, drying and winding are performed in the same manner as the method for forming the first porous layer described above. To obtain a composite porous membrane.

  The polyol impregnation rate of the present invention is not limited to the size of the gap between the first porous layer and the second porous layer, but the first and second hydrophilic polymers such as polyvinylpyrrolidone added to the film-forming stock solution. It also serves as an indicator of the remaining amount in the second porous layer. That is, when there are many remaining hydrophilic polymers, the polyol impregnation rate of the present invention tends to decrease.

Specifically, when the remaining hydrophilic polymer exceeds 2% by mass, the polyol impregnation rate becomes less than 50%. In this case, since the hydrophilic polymer prevents impregnation with the potting resin, the fixing strength of the composite porous membrane tends to decrease.
The amount of the hydrophilic polymer remaining in the first and second porous layers is preferably 2% by mass or less, more preferably 1.5% by mass or less, and further preferably 1% by mass or less.

  Hereinafter, the present invention will be described based on examples.

  Each physical property value was measured by the following method.

<Polyol impregnation rate>
In a polyol (trade name: Quinnate 3002S (manufactured by Bantico Co., Ltd.), a viscosity of 1500 mPa / sec at 25 ° C., a surface tension of 63 dyn / cm) was dissolved so that the methyl red dye was 0.1% by mass, and a polyol solution was obtained. Created.
And the film | membrane cut | disconnected to about 30 cm was hold | maintained for 5 minutes in the state immersed in the polyol solution set to 25 degreeC.
Thereafter, the membrane was pulled up and the adhered liquid was wiped off. And the 2nd porous layer was removed from the composite porous membrane, the 1st porous layer was exposed, and the coloring condition of the 1st porous layer was determined.
In the determination method, graduations were made in 1 mm increments in the length direction of the first porous layer, the first porous layer was partitioned, and the number of colored sections and uncolored sections were counted. .
In addition, it was counted that it was colored when there was a part which was colored even in one part in each division.
And according to the above-mentioned formula (A), it calculated as polyol impregnation rate (%) = number of sections colored with methyl red pigment / total number of sections × 100.

<Maximum pore size (μm) (bubble point method)>
According to JIS K3832, ethyl alcohol was measured as a measurement medium.

<Manufacture of composite porous membrane>
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- Using dimethylacetamide, the composition of the first film-forming stock solution and the second film-forming stock solution shown in Table 1 was adjusted.

  The first film-forming stock solution is discharged from the first discharge port 2 of the double annular nozzle having the outer diameter of 2.5 mm and the inner diameter of 2.4 mm, which is kept at 30 ° C. and having the structure shown in FIG. Is discharged from the second discharge port 3 in the sheath of the nozzle, and at the same time, a polyester multifilament monowoven braid (multifilament; total decitex 830/96 filament, 16 strokes) is introduced into the pipe line 1 After applying the first and second film-forming stock solutions, the mixture was led into a coagulation bath kept at 80 ° C. composed of 5 parts by mass of N, N-dimethylacetamide and 95 parts by mass of water to form a first porous layer. .

Next, the first porous layer is formed in the pipe 1 of the double annular nozzle shown in FIG. 1 having an outer diameter of 2.9 mm, an inner diameter of 2.8 mm, and a liquid seal length (S) of 2 mm, which is kept at 30 ° C. The formed braid is introduced, and from the first discharge port 2 of the nozzle, 2% by mass of polyvinyl pyrrolidone (trade name K-30, manufactured by ISP Co.) / 98% by mass of glycerin (manufactured by Wako Pure Chemical Industries, Ltd.) A primary solution (1300 cP (measurement temperature: 30 ° C.)) was discharged.
And after discharging the 2nd film forming stock solution from the 2nd discharge port 3 in the sheath part of the said nozzle and apply | coating a 2nd film forming stock solution on a 1st porous layer, N, N- dimethylacetamide 5 The composite porous membrane in which the first and second porous layers were formed on the braid was obtained by being led into a coagulation bath kept at 80 ° C. composed of mass% and water 95 mass%.
The film formation speed (V) at this time was 4 m / min, and S / V was 5.0 × 10 ⁻⁴ .

After this composite porous membrane was desolvated in 98 ° C. hot water for 3 minutes,
(A) It is immersed in a 50000 mg / L sodium hypochlorite aqueous solution.
(B) Heat in a 90 ° C. steam bath for 2 minutes.
(C) Wash in hot water at 90 ° C. for 3 minutes.
The above steps (a) to (c) were repeated twice, then dried at 85 ° C. for 10 minutes, and wound with a winder.

The resulting composite porous membrane had a polyol impregnation rate of 95%, an outer diameter / inner diameter of about 2.8 / 1.1 mm, a thickness of 850 μm, a thickness of the porous layer from the braid to the surface of 400 μm, a bubble point Was 150 kPa, the permeation performance was 100 m ³ / m ² / h / MPa, the water burst pressure was 500 kPa, and the amount of polyvinylpyrrolidone / glycerin carried was 0.05 (g / m).
When the potting resin was fixed using this composite porous membrane to form a hollow fiber membrane module, the potting resin was sufficiently impregnated not only into the second porous layer but also into the first porous layer. The membrane was fixed with sufficient strength.

<Example 2>
In the formation of the second porous layer, as a slow coagulation liquid, 1% by mass of polyvinylpyrrolidone (trade name K-30, manufactured by ISP) / 99% by mass of glycerin (first grade, manufactured by Wako Pure Chemical Industries), viscosity A composite porous membrane was formed in the same manner as in Example 1 except that 1000 mPa / sec (measurement temperature: 30 ° C.) was used.
The resulting composite porous membrane had a polyol impregnation rate of 98%, an outer diameter / inner diameter of about 2.8 / 1.2 mm, a thickness of 800 μm, a thickness of the resin layer from the braid to the surface of 400 μm, and a bubble point of The penetration performance was 180 kPa, the permeation performance was 110 m ³ / m ² / h / MPa, the water burst pressure was 610 kPa, and the amount of polyvinylpyrrolidone / glycerin carried was 0.02 (g / m).
When the potting resin was fixed using this composite porous membrane to form a hollow fiber membrane module, the potting resin was sufficiently impregnated not only into the second porous layer but also into the first porous layer. The membrane was fixed with sufficient strength.

<Example 3>
In the formation of the second porous layer, a 5% by mass polyvinylpyrrolidone (manufactured by ISP, trade name K-30) / 95% by mass glycerin (primary grade, manufactured by Wako Pure Chemical Industries), viscosity as a slow coagulation liquid A composite porous membrane was formed in the same manner as in Example 1 except that 2600 mPa / sec (measurement temperature: 30 ° C.) was discharged.
The resulting composite porous membrane had a polyol impregnation rate of 92%, an outer diameter / inner diameter of about 2.8 / 1.0 mm, a thickness of 800 μm, a thickness of the resin layer from the braid to the surface of 400 μm, and a bubble point of The penetration performance was 160 kPa, the permeation performance was 150 m ³ / m ² / h / MPa, the water burst pressure was 450 kPa, and the amount of polyvinylpyrrolidone / glycerin carried was 0.1 (g / m).
When the potting resin was fixed using this composite porous membrane to form a hollow fiber membrane module, the potting resin was sufficiently impregnated not only into the second porous layer but also into the first porous layer. The membrane was fixed with sufficient strength.

<Comparative Example 1>
A composite porous membrane was formed in the same manner as in Example 1 except that the liquid seal length S was 0.01 mm and the film forming speed was 6 m / min (S / V = 1.7 × 10 ⁻⁶ ). The resulting composite porous membrane had a polyol impregnation rate of 10%.
When this composite porous membrane was used to form a hollow fiber membrane module, the first porous layer was not sufficiently impregnated with potting resin, and when the composite porous membrane was pulled, the braid and the first porous layer Troubles such as slipping through occurred.

It is typical sectional drawing which shows an example of the annular nozzle used for this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Pipe line 2 1st discharge port 3 2nd discharge port 4 Liquid seal length 5 Front end surface 6 of 2nd distribution nozzle 1st supply port 7 2nd supply port 8 2nd distribution nozzle 9 1st distribution nozzle 10 Distribution plate 11 1st One liquid pool part 12 Second liquid pool part 13 Projecting tubular part 100 Support passage 110 Front face of support passage

Claims (2)

A composite porous membrane in which a first porous layer having a dense layer is formed on the surface of a support, and a second porous layer having a dense layer is formed adjacent to the first porous layer Because
The composite porous membrane whose polyol impregnation rate measured in the following procedures (1) to (7) is 50 to 100%.
(1) A polyol solution in which 0.1% by mass of a methyl red dye is dissolved in a polyol having a viscosity of 1300 to 1500 mPa / sec and a surface tension of 60 to 65 dyn / cm at 25 ° C. is prepared.
(2) A composite porous membrane having a length of 30 cm is immersed in a polyol solution for 5 minutes.
(3) Remove the composite porous membrane from the polyol solution and wipe the polyol solution adhering to the surface.
(4) The second porous layer is removed from the composite porous membrane to expose the first porous layer.
(5) The first porous layer is partitioned at intervals of 1 mm in the length direction.
(6) For each section, the presence or absence of coloring with methyl red pigment is examined. In addition, if even a little is colored in one division, it will be considered as colored.
(7) The polyol impregnation rate is determined according to the following formula (A).
Formula (A): polyol impregnation ratio (%) = number of sections colored with methyl red dye / total number of sections × 100 After forming the first porous layer by applying the film-forming stock solution to the support using an annular nozzle and coagulating it in the coagulating liquid, it is produced on the surface of the first porous layer using the annular nozzle. A method for producing a composite porous membrane in which a membrane stock solution is applied and solidified in a coagulating solution to form a second porous layer,
The annular nozzle includes a support passage through which the support passes, a first discharge port that opens to the entire peripheral wall of the support passage, and an outlet side of the support passage, concentrically with the support passage, and the support And a second discharge port disposed on the outer periphery of the passage, and the front end surface of the support passage is located inside the annular nozzle from the front end surface of the second discharge port,
At the time of forming the second porous layer, a slow coagulation liquid selected from at least one of monool hydrophilic polymer, diol hydrophilic polymer, triol hydrophilic polymer, glycerin, and polyvinylpyrrolidone is discharged from the first discharge port. And discharging the stock solution from the second discharge port,
When the distance (m) from the front end surface of the support passage to the front end surface of the second discharge port is S and the film forming speed (m / min) is V, S / V is 1.0 × 10 ⁻⁵ to The manufacturing method of the composite porous membrane which is 1.0 * 10 <^-3> .

Images