CN102470327B - Process for producing porous film - Google Patents

Abstract

The present invention relates to a method for producing a porous membrane. The method has the steps of: coagulating a membrane-forming solution containing a membrane-forming polymer and a phase separation control additive in a coagulation solution to obtain a porous membrane precursor; The step of the above-mentioned phase separation control additive in the above-mentioned porous membrane precursor; as the above-mentioned phase separation control additive, polyvinylpyrrolidone whose proportion of high molecular weight region area in the integral molecular weight distribution curve is 11% or less is used. According to the present invention, it is possible to provide a method for producing a porous membrane capable of producing a porous membrane having good permeation performance by removing additives added to control phase separation in a short time of treatment.

Description

Manufacturing method of porous membrane

technical field

The present invention relates to a manufacturing method of a porous membrane suitable for a precision filtration membrane or an ultrafiltration membrane in water treatment.

This application claims priority based on Japanese Patent Application No. 2009-171121 filed in Japan on July 22, 2009, the content of which is incorporated herein.

Background technique

In recent years, along with increasing concerns about environmental pollution and strengthening of regulations, water treatment by membrane methods using filtration membranes has attracted attention based on advantages such as complete separation and compactness. When used in such water treatment, the filter membrane is required to have excellent separation characteristics, permeability, or mechanical properties.

Historically, as a filter membrane with excellent permeability, it is known to use hydrophobic polymers such as polysulfone, polyacrylonitrile, cellulose acetate, and polyvinylidene fluoride as membrane materials to form polymers, and to form polymers by wet or dry-wet spinning The filter membrane produced by the method. These filtration membranes are produced by coagulating the polymer solution in a non-solvent after microphase separation of the polymer solution, and have a dense layer and a support layer, a high porosity and an asymmetric structure. As a specific membrane-forming method, a method of coagulating a membrane-forming solution containing a membrane-forming polymer and a phase separation control additive in a coagulating solution is known. As a phase separation control additive, for example, a hydrophilic polymer such as polyethylene glycol or polyvinylpyrrolidone can be used. The aforementioned phase separation control additives are removed after solidification.

As a method of removing the coagulated hydrophilic polymer, Patent Document 1 proposes a method of decomposing the hydrophilic polymer with an oxidizing agent, and Patent Document 2 proposes a method of chemically treating the hydrophilic polymer. In addition, Patent Document 3 proposes a method of removing decomposable polymers such as polyvinylpyrrolidone using a decomposer.

Patent Document 1: Japanese Patent No. 3196029

Patent Document 2: Specification of US Patent No. 5,076,925

Patent Document 3: Japanese Patent No. 3169404

content of the invention

For porous membranes made of hydrophobic polymers, since hydrophilic polymers (phase separation control additives) remain in the porous parts after film formation, the permeation performance is reduced, so a higher level of removal is required. An easier way to control additives with respect to phase separation.

However, the method described in the above-mentioned Patent Document 1 is not preferable in terms of productivity because it takes several hours to several tens of hours or more to remove the hydrophilic polymer.

In addition, the methods described in Patent Documents 2 and 3 may not be able to obtain good permeation performance depending on the type of the hydrophilic polymer, and are not necessarily satisfactory methods.

The present invention is made in view of the foregoing circumstances, and an object of the present invention is to provide a method for producing a porous membrane capable of removing a phase separation control additive within a short treatment time and having a good permeation performance.

The method for producing a porous membrane of the present invention for solving the above-mentioned problems is as follows,

It is a method for producing a porous membrane, and the method has the steps of: coagulating a membrane-forming liquid containing a membrane-forming polymer and a phase separation control additive in a coagulation liquid to obtain a porous membrane precursor; The process of the phase separation control additive in the porous membrane precursor; it is characterized in that, the phase separation control additive is, when the ratio of the high molecular weight region area in the integral molecular weight distribution curve is obtained by the following method, the Polyvinylpyrrolidone with an area ratio of high molecular weight domains below 11%;

Here, the value of the ratio of the area of the high molecular weight region is obtained as follows:

By gel permeation chromatography under the following conditions, the molecular weight distribution of polyvinylpyrrolidone was measured, and LogM (wherein, M represents the molecular weight) was used as the horizontal axis (X axis) and the integral distribution value (mass %) as the vertical axis (Y axis) Integral molecular weight distribution curve, the value of X when the integral molecular weight distribution curve reaches the point of Y=100 is P, and the area enclosed by the integral molecular weight distribution curve and the straight line representing X=P and the straight line representing Y=0 When the area of is 100%, it is obtained as the ratio of the area of the area surrounded by the integral molecular weight distribution curve to the straight line representing X=6, the straight line representing X=P, and the straight line representing Y=0;

Here, the conditions of the gel permeation chromatography include the following,

Chromatographic column: TSKgel α-M, 7.8mm (ID) × 30.0cm (L) 2 pieces (manufactured by Tosoh (manufactured by Tosoh)),

Column temperature: 30°C,

Mobile phase (eluent): a mixture of 0.2mol/L NaNO ₃ aqueous solution and acetonitrile, the mixing ratio represented by NaNO ₃ aqueous solution/acetonitrile is 8/2 (vol/vol)

Flow: 0.6ml/min,

Sample concentration: 1mg/ml,

Detector: RI detector,

Injection volume: 20μl,

Molecular weight correction PEO: Polyoxyethylene [manufactured by Polymer Laboratories (Polymer Laboratories)],

Calibration curve: standard PEO [manufactured by Polymer Laboratories (Polymer Laboratories) Co., Ltd.] 3-dimensional approximate curve, measuring device: HLC-8020GPC manufactured by Tosoh, and

Before the measurement of the sample, filtration was performed using a filter cartridge (classification performance: 0.45 μm) made of cellulose acetate.

Preferably, the ratio of the area of the high molecular weight region is above 5%.

In addition, the polyvinylpyrrolidone is preferably polyethylene whose proportion of the area of the low-molecular-weight region in the integral molecular weight distribution curve is determined by the following method: 5% or more and less than 13%. pyrrolidone.

In addition, the value of the ratio of the area of the low molecular weight region is obtained as follows:

The molecular weight distribution of polyvinylpyrrolidone was determined by gel permeation chromatography under the following conditions,

An integral molecular weight distribution curve with LogM (where M represents molecular weight) as the horizontal axis (X axis) and the integral distribution value (mass %) as the vertical axis (Y axis) was obtained. When the X value when the integral molecular weight distribution curve reaches the point of Y=100 is P, when the area enclosed by the integral molecular weight distribution curve and the straight line representing X=P and the straight line representing Y=0 is 100% , obtained as a ratio of the area of the region surrounded by the integral molecular weight distribution curve to the straight line representing X=3.5, the straight line representing X=4.5, and the straight line representing Y=0.

(Conditions for Gel Permeation Chromatography)

Chromatographic column: TSKgel α-M, 7.8mm (ID) × 30.0cm (L) 2 pieces (manufactured by Tosoh),

Column temperature: 30°C,

Mobile phase (eluent): a mixture of 0.2mol/L NaNO ₃ aqueous solution and acetonitrile, the mixing ratio represented by NaNO ₃ aqueous solution/acetonitrile is 8/2 (vol/vol)

Flow: 0.6ml/min,

Sample concentration: 1mg/ml,

Detector: RI detector,

Injection volume: 20μl,

Molecular weight correction PEO: Polyoxyethylene [manufactured by Polymer Laboratories (Polymer Laboratories) Co., Ltd.],

Calibration curve: standard PEO [manufactured by Polymer Laboratories (Polymer Laboratories) Co., Ltd.] 3-dimensional approximate curve, measuring device: HLC-8020GPC manufactured by Tosoh,

Before the measurement of the sample, filtration was performed using a filter cartridge (classification performance: 0.45 μm) made of cellulose acetate.

It is further preferred that the K value of the polyvinylpyrrolidone is below 82.

In addition, it is also preferred that the K value of the polyvinylpyrrolidone is above 78.

Invention effect

According to the present invention, there is provided a method for producing a porous membrane, comprising the steps of coagulating a membrane-forming liquid containing a membrane-forming polymer and a phase separation control additive in a coagulation liquid to obtain a porous membrane precursor, and removing residues from the porous membrane. The process of adding the phase separation control additive in the precursor can produce a porous membrane having good permeability and can be removed in a short time.

Description of drawings

[ Fig. 1 ] is a cross-sectional view of an example of an annular nozzle used in the production of the porous membrane of the present invention.

[ Fig. 2 ] is an example of a distribution curve of integral molecular weight.

Explanation of symbols

[0061]

1 pipeline

2 first outlet

3 second protrusion

4 The distance between the top surface of the braid passage and the top surface of the second distribution nozzle (liquid seal length)

5 Top face of the second dispensing nozzle

6 The first supply port

7 The second supply port

8 Second dispensing nozzle

9 First dispensing nozzle

10 distribution plate

11 The first liquid bath

12 Second liquid bath

13 protruding tubular part

100 braided (winding; group button) access

110 Braided channel top surface

Detailed ways

＜Membrane forming polymer＞

From the viewpoint of improving chemical resistance and heat resistance, it is preferable to use a fluorine-based resin as a film-forming polymer. Among them, polyvinylidene fluoride resin is preferable. In particular, it is preferable to combine polyvinylidene fluoride (A) with a weight average molecular weight (hereinafter also referred to as Mw) of 100,000 to 1,000,000 and polyvinylidene fluoride (B) with a weight average molecular weight of 10,000 to 500,000, so that the Mw of (A) is greater than that of (B) ) Mw, and the difference between the Mw of the two is more than 30,000 for combined use. When (A) and (B) are used in combination, the mass ratio of (A)/(B) is preferably in the range of 0.5-10, more preferably in the range of 1-3. If the mass ratio of (A)/(B) is within the aforementioned range, the pore diameter of the membrane can be easily adjusted.

＜Phase Separation Control Additives＞

In the present invention, polyvinylpyrrolidone having a ratio of high molecular weight region area of 11% or less obtained by the above-mentioned method is used as a phase separation control additive (hereinafter simply referred to as an additive).

Specifically, the ratio of the area of the high molecular weight region can be obtained in the following procedure.

First, weigh polyvinylpyrrolidone, add the following eluent so that the concentration of polyvinylpyrrolidone (sample concentration) becomes 1 mg/ml, let it stand and dissolve for 16 hours, and use a filter cartridge made of cellulose acetate (grading Performance 0.45μm) for filtration. The obtained filtrate was used as a sample, and the molecular weight distribution was measured under the above conditions to obtain an integral molecular weight distribution curve.

Fig. 2 is an example of the integral molecular weight distribution curve obtained by measuring the molecular weight distribution of polyvinylpyrrolidone by the above-mentioned method. The horizontal axis (X axis) is LogM (M is molecular weight), and the vertical axis (Y axis) is integral distribution value (mass %). The value of X when the integrated molecular weight distribution curve reaches the point of Y=100 is P. In the figure, symbol a is an integral molecular weight distribution curve, symbol b is a straight line representing X=P, symbol c is a straight line representing Y=0, and symbol d is a straight line representing X=6.

When the area of the area surrounded by curve a, straight line b, and straight line C is 100%, the ratio of the area of the area (shaded line) enclosed by curve a, straight line d, straight line b, and straight line c is obtained as the high molecular weight The percentage value of the area of the area.

The ratio of the area of the high molecular weight region obtained by the above method represents the ratio of the total molecular weight with a molecular weight of 10 ⁶ or more in the total molecular weight. The area ratio of the high molecular weight region of polyvinylpyrrolidone can be controlled by the polymerization time of vinylpyrrolidone.

Good detergency (removability) can be obtained by using polyvinylpyrrolidone having an area ratio of the high molecular weight region of 11% or less as an additive. If the ratio of the area of the high molecular weight region exceeds 11%, detergency decreases, the filtration performance of the porous membrane decreases, or fine cracks tend to occur in the porous membrane, which is not preferable.

The ratio of the area of the above-mentioned high molecular weight region may be zero, but it is preferably 5% or more, more preferably 6% or more, still more preferably 7% or more. If the ratio of the area of the polymer domain is less than 5%, the pore diameter formed will be too small, and the filtration characteristics will be lowered when used as a filter membrane for sewage, which is not preferable.

It is preferable to use polyvinylpyrrolidone in which the ratio of the low molecular weight domain area in the integral molecular weight distribution curve is 5% to 13% as an additive. When the ratio of the area of the low-molecular-weight domain is more than 5% and less than 13%, the water permeability of the obtained porous membrane is improved.

In addition, the ratio of the low molecular weight domain area of polyvinylpyrrolidone can be measured by the following method.

That is, according to gel permeation chromatography under the following conditions, the molecular weight distribution of polyvinylpyrrolidone is measured, and LogM (M represents molecular weight) is obtained as the horizontal axis (X axis) and the integral distribution value (mass %) as the vertical axis (Y axis) The integral molecular weight distribution curve. The value of X at the point of Y=100 in the integral molecular weight distribution curve is P. When the area of the area surrounded by the above-mentioned integral molecular weight distribution curve and the straight line representing X=P and the straight line representing Y=0 is 100%, obtain the above-mentioned integral molecular weight distribution curve and the straight line of X=3.5 and X=4.5 The ratio of the area of the straight line to the area surrounded by the straight line indicating Y=0 was taken as the ratio value of the area of the low molecular weight domain.

(Conditions for Gel Permeation Chromatography)

Chromatographic column: TSKgelα-M, 7.8mm (ID) × 30.0cm (L) 2 pieces (manufactured by Tosoh),

Column temperature: 30°C,

Mobile phase (eluent): a mixture of 0.2mol/L NaNO ₃ aqueous solution and acetonitrile, the mixing ratio shown in NaNO ₃ aqueous solution/acetonitrile is 8/2 (vol/vol),

Flow: 0.6ml/min,

Sample concentration: 1mg/ml,

Detector: RI detector,

Injection volume: 20μl,

Molecular weight correction PEO: Polyoxyethylene [manufactured by Polymer Laboratories (Polymer Laboratories) Co., Ltd.],

Calibration curve: Standard PEO [manufactured by Polymer Laboratories (Polymer Laboratories) Co., Ltd.] 3-dimensional approximate curve, measuring device: HLC-8020GPC manufactured by Tosoh,

Before the measurement of the sample, filtration was performed using a filter cartridge (classification performance: 0.45 μm) made of cellulose acetate.

In addition, the polyvinylpyrrolidone used in the present invention preferably has a K value of 82 or less. When the K value exceeds 82, since the detergency of an additive will fall and filtration performance will fall, it is unpreferable. In addition, it is also preferable that the K value of polyvinylpyrrolidone is 78 or more. If the K value is less than 78, the pore diameter of the porous membrane is too small, and the filtration characteristics will decrease when used as a sewage filtration membrane, which is not preferable.

In addition, the K value of polyvinylpyrrolidone is a viscosity characteristic value related to molecular weight, and is a value calculated by applying the relative viscosity value (25° C.) measured by a capillary viscometer to the Fikentscher formula shown below. The above K value of polyvinylpyrrolidone can be controlled by the polymerization time of vinylpyrrolidone. Commercially available polyvinylpyrrolidones each have a fixed K value according to grades, and each product is marked with a K value.

[number 1]

Fikentscher formula:

K=( _1.5logηrel -1)/(0.15+0.003c)+

{300clogη _rel +(c+1.5clogη _rel )2}1/2/(0.15c+0.003c ² )

η _rel : Relative viscosity of polyvinylpyrrolidone aqueous solution relative to water

c: Polyvinylpyrrolidone concentration (mass %) in polyvinylpyrrolidone aqueous solution

In the present invention, as additives, other additives other than polyvinylpyrrolidone may be used in combination within the range that does not impair the effects of the present invention. As the above-mentioned other phase separation inhibitors, known hydrophilic polymers used in the method of producing porous membranes through the step of coagulating a membrane-forming solution containing a hydrophobic polymer and a hydrophilic polymer in a coagulation solution can be suitably used . Examples thereof include monoalcohol-based, diol-based, and triol-based hydrophilic polymers represented by polyethylene glycol.

The proportion of additives other than polyvinylpyrrolidone is preferably 5% by mass or less, more preferably 1% by mass or less, and most preferably zero, when the total additives used are 100% by mass.

＜Solvent＞

The membrane-forming solution is prepared by dissolving membrane-forming polymers and additives in a solvent. The solvent is preferably an organic solvent. As the organic solvent, dimethylformamide, N,N-dimethylacetamide, dimethylsulfoxide and the like can be used. Among them, N,N-dimethylacetamide is more preferable in terms of high water permeation flow rate based on the obtained porous body.

＜Manufacturing method of porous membrane＞

As one embodiment of the method for producing a porous membrane of the present invention, an example of a method for producing a porous hollow fiber membrane will be described.

In this embodiment, a dry-wet spinning method is used. That is, after the film-forming liquid is discharged from the ring-shaped nozzle, the film is allowed to pass through a certain space, and then soaked in the coagulation liquid to form a porous film material.

In this embodiment, a braid is generally used as the base material, and the first film-forming liquid is coated on the above-mentioned braid with an annular nozzle, and after it is coagulated in the coagulation liquid to form the first porous layer, an annular nozzle is used. The nozzle coats the second membrane-forming liquid on the surface of the first porous layer, and solidifies it in the coagulation liquid to form the second porous layer, thereby obtaining a porous membrane precursor.

Preferably, the polymer concentration of the first membrane-forming solution is lower than that of the second membrane-forming solution. That is, the polymer concentration of the first film-forming liquid is preferably such that it is easily immersed in the braid. The polymer concentration of the second membrane-forming liquid is preferably at a level suitable for forming a porous layer. By using the first membrane-forming solution and the second membrane-forming solution having different concentrations in this way, the membrane-forming solution can be sufficiently impregnated into the main part of the braid, and the peeling of the membrane material (porous layer) from the braid can be suppressed.

Considering the impregnability in the braid, the total concentration of the membrane-forming polymers in the first membrane-forming liquid is preferably 12% by mass or less, more preferably 10% by mass or less, and even more preferably 7% by mass or less. The lower limit is preferably 1% by mass or more, more preferably 3% by mass or more.

By setting it as this range, the 1st membrane forming liquid can be immersed in a braid easily. In addition, the porosity of the braid used in the porous hollow fiber membrane is generally about 90% to 95%. The membrane material in the membrane-forming solution forms a polymer concentration at the same level. Therefore, high water permeability of the membrane during filtration can be maintained. Further, the film material can be attached to the braid with sufficient strength.

The concentration of the additive in the first membrane-forming liquid is preferably 0.5% by mass or more, more preferably 1% by mass or more, from the point of view of maintaining high water permeability. The upper limit is based on the detergency of polyvinylpyrrolidone, and is preferably 5% by mass or less, more preferably 3% by mass or less.

In order to prevent the formation of a void layer when forming a porous membrane and obtain good mechanical strength, the second membrane-forming liquid preferably has a polymer concentration higher than that of the above-mentioned first membrane-forming liquid. Specifically, the total concentration of the film-forming polymers in the second film-forming solution is preferably 12% or more, more preferably 15% or more. In order to increase the permeation flux, the above-mentioned polymer concentration is preferably within a range of not more than 25%.

The concentration of the additive in the second membrane-forming solution is preferably 5% by mass or more, more preferably 7% by mass or more, from the point of view of maintaining high water permeability. The upper limit is based on the detergency of polyvinylpyrrolidone, and is preferably 15% by mass or less, more preferably 12% by mass or less.

When using the above-mentioned polyvinylidene fluoride (A) and (B) as the film material to form a polymer, the mass ratio of (A)/(B) in the first film-forming liquid is the same as that of (A) in the second film-forming liquid The mass ratio of /(B) may be the same or different. From the point of maintaining high water permeability, it is preferable to be the same.

As the annular nozzle, a known annular nozzle used in a method for producing a porous hollow fiber membrane in which a first porous layer and a second porous layer are formed on a belt-shaped substrate can be suitably used.

FIG. 1 is a cross-sectional view of an example of an annular nozzle suitably used in the method for producing a porous hollow fiber membrane according to this embodiment. The annular nozzle is roughly formed by laminating a distribution plate 10, a first distribution nozzle 9, and a second distribution nozzle 8 forming the tip of the annular nozzle in this order.

The distribution plate 10 is a substantially disc-shaped component, and the braid passes through the center to form the pipeline 1 . A first supply port 6 for supplying the first film-forming liquid and a second supply port 7 for supplying the second film-forming liquid are provided around the pipeline 1 of the distribution plate 10 .

The first dispensing nozzle 9 has a substantially T-shaped cross-sectional shape and a disk-shaped planar shape. A protruding tubular portion 13 protruding into the second dispensing nozzle 8 is formed at the center thereof. The interior of the protruding tubular portion 13 is a hollow portion, and the hollow portion communicates with the above-mentioned pipeline 1 to form a braided passage 100 . When the first distribution nozzle 9 and the distribution plate 10 are stacked concentrically, a braid passage 100 is formed at the center of them.

Around the braid passage 100 of the first dispensing nozzle 9, a hollow portion connected to the first supply port 6 and a hollow portion connected to the second supply port 7 are respectively provided.

Make the lower surface of distribution plate 10 contact with the upper surface of first distribution nozzle 9, make them be the state of concentric overlapping, respectively form groove at the lower surface of distribution plate 10 and the upper surface of first distribution nozzle 9, so that form The first liquid bath part 11 of the above-mentioned first supply port 6 is connected. In addition, in a concentric overlapping state, annular slits are formed around the braid passage 100 so as to form the first discharge port 2 . The first discharge port 2 communicates with the above-mentioned first liquid bath portion 11 . Furthermore, the above-mentioned first liquid bath part 11 communicates with the first discharge port 2 .

The distribution plate 10 and the first distribution nozzle 9 are concentrically overlapped. When the liquid is supplied to the first supply port 6, the supplied liquid can be stored in the first bath part 11, and then discharged from the first discharge port 2 to the braiding passage 100. liquid.

The second dispensing nozzle 8 is also a disc-shaped member, and a second liquid bath part 12 is formed in the center thereof, and a hollow part communicating with the second liquid bath part 12 is further formed. The hollow portion communicates with the second supply port 7 through the hollow portion formed in the first dispensing nozzle 9 and communicates with the second supply port 7 . By concentrically overlapping the second distribution nozzle 8 and the first distribution nozzle 9 , the second liquid bath portion 12 is formed around the protruding tubular portion 13 of the first distribution nozzle 9 . Specifically, the space formed by the base end of the protruding annular portion 13 , the end surface of the first distribution nozzle 9 , the outer wall of the protruding tubular portion 13 , and the upper surface of the second distribution nozzle 8 is the second liquid bath portion 12 . The above-mentioned second liquid bath part 12 faces the direction of the tip end of the protruding tubular part 13 of the first distribution nozzle 9, and its cross-sectional area gradually decreases. In conclusion, the inner wall of the second dispensing nozzle 8 protrudes gradually facing the protruding ring 13 .

Further, a second protruding opening 3 is formed at the top end of the second bath liquid part 12 . In short, the second discharge port 3 is formed by the outer wall of the tip end of the protruding tubular portion 13 and the inner wall of the second distribution nozzle 8 .

In particular, it is preferable that the top end surface 110 of the protruding annular portion 13, that is, the top end surface 110 of the braid passage 100 is located on the inner side of the annular nozzle than the top end surface 5 of the second discharge port 3, that is, the top end surface 5 of the second distribution nozzle 8. s position.

In other words, it is preferable to configure the distance 4 (hereinafter referred to as the distance 4 (hereinafter referred to as liquid) between the top end surface of the protruding annular portion 13, that is, the top end surface 110 of the braid passage, and the top end surface 5 of the second discharge port 3, that is, the top end surface 5 of the second distribution nozzle 8. Seal length.) is 0.5 ~ 150mm. The lower limit of the liquid seal length is more preferably 0.6 mm or more, still more preferably 0.8 mm or more. When the length of the liquid seal is less than 0.5 mm, the second membrane-forming liquid coated on the surface of the first porous layer can be spit out almost without consuming the pressure of the coating. Therefore, in the second porous layer, even if there is a portion with a small outer diameter in the film formed of the first porous layer, it is discharged with the same diameter. As a result, a large gap may be generated between the first porous layer and the second porous layer. When the porous hollow fiber membrane is actually used for water treatment, in order to separate the input side and the output side, a fixing member such as synthetic resin is usually used. If such a gap is formed between the first porous layer and the second porous layer, then The possibility that the resin constituting the fixing member enters the above-mentioned gap makes it difficult for the water to be treated to impregnate the entire porous membrane. If the above-mentioned liquid seal length is made to be an appropriate length, the coating pressure of the discharged film-forming liquid tends to increase. Furthermore, a large gap can be prevented from being formed between the first porous layer and the second porous layer.

In addition, the upper limit of the liquid seal length is not particularly limited from the viewpoint of the coating pressure, but if it is too long, it tends to be difficult to manufacture the annular nozzle. Therefore, the upper limit of the liquid seal length is preferably 150 mm or less. The upper limit of the liquid seal length is preferably 100 mm or less, more preferably 50 mm or less.

The ring-shaped nozzle of the above structure is in a state where the distribution plate 10, the first distribution nozzle 9, and the second distribution nozzle 8 are overlapped concentrically. If the liquid is supplied to the second supply port 7, the supplied liquid can be The hollow portion of the first distribution nozzle 9 and the hollow portion formed by the first distribution nozzle 9 and the second distribution nozzle 8 are stored in the second bath portion 12 , and then discharged from the second discharge port 3 toward the braiding passage 100 .

When manufacturing a porous membrane using the annular nozzle of this structure, first, the braid is supplied from the pipeline 1 to the braid passage 100, the first film-forming liquid is supplied from the first supply port 6 to the first liquid bath part 11, and the The supply port 7 supplies the second film-forming liquid to the second liquid bath part 12 .

While supplying the braid to the pipeline 1, that is, while the braid is moving in the braid passage 100, the first film-forming liquid is discharged from the first discharge port 2, soaked in the braid, and the second film-forming liquid is discharged from the second discharge port 3. The second film-making solution is used to impregnate the braid.

When the temperature of each film-forming liquid at the time of discharge is lower than 20° C., the film-forming liquid may be gelled at low temperature, which is not preferable. On the other hand, if the temperature is higher than 40° C., it is difficult to control the pore diameter, and as a result, bacteria such as coliform bacteria or suspended matter may permeate, which is not preferable for practical use. Therefore, the temperature at the time of discharge of both the first film-forming liquid and the second film-forming liquid is preferably in the range of 20 to 40°C.

Next, the first membrane-forming liquid and the second membrane-forming liquid are solidified by immersing the membrane-forming liquid coated on the braid through a space, and then the first porous membrane precursor is formed.

If the time for passing through a certain space is less than 0.01 second, the filtration performance will be low, which is not preferable. Although there is no upper limit to the walking time, 4 seconds is sufficient in practical applications. Therefore, the time for passing through a certain space is preferably in the range of 0.01 to 4 seconds.

As the coagulation solution, an aqueous solution containing a solvent used in the membrane forming solution is suitably used. However, it also depends on the type of solvent used. For example, when N,N-dimethylacetamide is used as the solvent of the membrane forming solution, the concentration of N,N-dimethylacetamide in the coagulation solution is preferably 1 to 50%.

The temperature of the coagulation liquid is preferably relatively low from the viewpoint of improving the mechanical strength. However, if the temperature of the coagulation liquid is too low, the water permeation flow rate of the produced membrane will decrease, so it is usually selected within the range of 90°C or lower, more preferably 50°C or higher and 85°C or lower.

After coagulation, the solvent is preferably washed in hot water at 60°C to 100°C. At this stage, a part of the additive attached to the membrane surface is removed.

The temperature of the cleaning bath is within the range in which the first porous membranes do not thermally adhere to each other, and the higher the temperature, the more effective it is. From this viewpoint, the temperature of the cleaning bath is preferably 60° C. or higher.

After washing with hot water, it is preferable to wash with a chemical solution such as hypochlorous acid. According to this, the additive inside the membrane is decomposed and removed. Most of the phase separation control additive can be removed at this stage.

When using an aqueous solution of sodium hypochlorite, the concentration thereof is preferably within a range of 10 to 120,000 mg/L. If the concentration of the sodium hypochlorite aqueous solution is less than 10 mg/L, the permeable flow rate of the resulting membrane will decrease, which is not preferable. Although there is no upper limit to the concentration of the sodium hypochlorite aqueous solution, 120,000 mg/L is sufficient for practical application.

Next, it is preferable to wash the membrane washed with the chemical solution in hot water at 60°C to 100°C. According to this, the residual phase separation control additive can be removed.

After that, it is preferable to dry at 60° C. to 120° C. for 1 minute to 24 hours. If it is less than 60° C., the drying treatment takes too much time and the production cost increases, which is not preferable in terms of industrial production. If it is 120° C. or higher, the film shrinks too much in the drying step, and fine cracks may be generated on the film surface, which is not preferable.

The dried film is preferably wound into a bobbin or a straw.

In this way, a belt-shaped body in which the first porous layer (multilayer film) was formed around the braid was obtained.

Next, the second porous layer is formed on the formed first porous layer, but if the first porous layer is completely adhered to the second porous layer, the water permeability will decrease. Therefore, in order to prevent a decrease in water permeability, it is preferable to attach a solution that does not dissolve the membrane material to the surface of the first porous layer before forming the second porous layer.

As the solution that does not dissolve the membrane material, an aqueous solution containing a solvent used in the membrane-forming solution can be suitably used. For example, when N,N-dimethylacetamide is used as the solvent of the membrane forming solution, the concentration of N,N-dimethylacetamide in the solution that does not dissolve the solvent is preferably 1 to 50%. As another preferable solution that does not dissolve the membrane material, an organic solvent, a mixture of an organic solvent and water, or a solution in which an additive mainly composed of glycerin or the like is added to them is preferably used.

The step of attaching the solution that does not dissolve the membrane material to the surface of the first porous layer and the step of applying the second membrane-forming solution thereon are preferably performed continuously using, for example, an annular nozzle having the structure shown in FIG. 1 . In addition, the annular nozzle used to form the first porous layer is continuously used, and a solution that does not dissolve the membrane material is supplied instead of the first membrane-forming liquid, and the supplied second membrane-forming liquid can be directly used.

That is, the strip-shaped body having the first porous layer obtained above is supplied to the braiding passage 100 from the pipeline 1, and a solution that does not dissolve the film material is supplied to the first supply port 6, and is discharged from the first discharge port 2. A solution that does not dissolve the membrane material is coated on the surface of the first porous layer. In addition, the second film-forming liquid stored in the second liquid bath part 12 supplied from the second supply port 7 is discharged from the second discharge port 3 again, and applied to the surface of the first porous layer.

Next, in the same manner as the step of forming the first porous layer, the second porous membrane precursor is formed by immersing it in a coagulation solution and coagulating the second membrane forming solution.

Afterwards, in the same manner as in the process of forming the first porous layer, wash with hot water and chemicals to remove the additives remaining in the second porous film precursor, dry it, and wind it up to obtain the surrounding formation of the braid. Porous hollow fiber membranes of the first porous layer and the second porous layer.

According to this embodiment, the detergency (removability) of additives remaining in the porous membrane precursor can be improved by using polyvinylpyrrolidone having a ratio of high molecular weight region area obtained by the above method in a specific range as an additive. Therefore, it is possible to obtain a porous membrane that can remove additives at a higher level by a short-time treatment and has good permeation performance.

It is a very surprising realization that the ratio of the area of the high molecular weight region involved is related to the removal of additives. The reason for this is not clear, but if the ratio of the area of the polymer domain is too small, the water permeability will decrease, and if the ratio of the area of the polymer domain is too large, the decomposition and removal of the additive tends to decrease.

In addition, in the present invention, as an additive, by using polyvinylpyrrolidone whose K value is also within a specific range while the ratio of the above-mentioned high-molecular-weight region area is within a specific range, the amount of remaining in the porous membrane precursor can be further increased. Detergency (removability) of additives.

It is a surprising finding that the above-mentioned K value is related to the removability of additives. The reason for this is not clear, but if the K value is too low, the formed pore diameter is too small, thereby reducing water permeability, and if the K value is too high, the decomposition and removal of additives tends to decrease.

In addition, in the above-mentioned embodiment, although a part of the membrane material is immersed in the braid to form the porous hollow fiber membrane, the shape and structure of the porous membrane are not limited to this.

In particular, a porous hollow fiber membrane is preferable in terms of reducing production costs.

In addition, in the case of porous membranes used in water treatment applications, it is necessary to make the liquid on the input side through which the membrane permeates flow with respect to the membrane surface. Since the membrane surface flow shakes and stretches the membrane, the membrane needs sufficient mechanical strength. In particular, a porous hollow fiber membrane using a braid as a substrate has excellent mechanical strength because the braid bears the mechanical strength.

In addition, in the above-mentioned embodiment, although the porous membrane whose membrane material consists of a 1st porous layer and a 2nd porous layer was demonstrated, the structure of a membrane is not limited to this.

Although it is sufficient for the film material to have at least one dense layer, it is more preferable to arrange a film material having two or more dense layers because durability of the film can be improved. In addition, a plurality of dense layers may be further provided on the second porous layer in this embodiment. In this case, the porous layers may be formed sequentially in the same order as the procedure for forming the second porous layer on the first porous layer.

Example

Hereinafter, the present invention will be described in more detail using examples, but the present invention is not limited to these examples. Hereinafter, "%" used in the expression of a content rate and a density|concentration shows mass %.

Each physical property value was measured by the method shown below.

[Proportion of area of high molecular weight region]

The area ratio of the high molecular weight region of polyvinylpyrrolidone was measured by the following method.

That is, the molecular weight distribution of polyvinylpyrrolidone was measured by gel permeation chromatography under the following conditions, and LogM (M represents molecular weight) was obtained as the horizontal axis (X axis) and the integral distribution value (mass %) as the vertical axis (Y axis) The integral molecular weight distribution curve. The value of X at the point of Y=100 in the integral molecular weight distribution curve is P. When the above-mentioned integral molecular weight distribution curve and the straight line representing X=P and the area enclosed by the straight line representing Y=0 were taken as 100%, the above-mentioned integral molecular weight distribution curve and the straight line representing X=6 and the straight line representing X= The ratio of the area of the straight line representing P to the area surrounded by the straight line representing Y=0 was taken as the ratio value of the area of the high molecular weight region.

(Conditions for Gel Permeation Chromatography)

Chromatographic column: TSKgel α-M, 7.8mm (ID) × 30.0cm (L) 2 pieces (manufactured by Tosoh),

Column temperature: 30°C,

Mobile phase (eluent): a mixture of 0.2mol/L NaNO ₃ aqueous solution and acetonitrile, the mixing ratio shown in NaNO ₃ aqueous solution/acetonitrile is 8/2 (vol/vol),

Flow: 0.6ml/min,

Sample concentration: 1mg/ml,

Detector: RI detector,

Injection volume: 20μl,

Molecular weight correction PEO: Polyoxyethylene [manufactured by Polymer Laboratories (Polymer Laboratories) Co., Ltd.],

Calibration curve: Standard PEO [manufactured by Polymer Laboratories (Polymer Laboratories) Co., Ltd.] 3-dimensional approximate curve, measuring device: HLC-8020GPC manufactured by Tosoh,

Before the measurement of the sample, filtration was performed using a filter cartridge (classification performance: 0.45 μm) made of cellulose acetate.

[Proportion of low molecular weight domain area]

The ratio of the low molecular weight domain area of polyvinylpyrrolidone is determined as follows.

That is, by gel permeation chromatography under the following conditions, the molecular weight distribution of polyvinylpyrrolidone is measured, and LogM (M represents molecular weight) is used as the horizontal axis (X axis), and the integral distribution value (mass %) is used as the vertical axis (Y axis). ) integral molecular weight distribution curve. The value of X at the point of Y=100 in the integral molecular weight distribution curve is P. When the area of the area surrounded by the above-mentioned integral molecular weight distribution curve and the straight line representing X=P and the straight line representing Y=0 is taken as 100%, the above-mentioned integral molecular weight distribution curve and the straight line of X=3.5 and X=4.5 are obtained. The ratio of the area of the straight line to the area surrounded by the straight line indicating Y=0 was taken as the ratio value of the area of the low molecular weight domain.

(Conditions for Gel Permeation Chromatography)

Chromatographic column: TSKgel α-M, 7.8mm (ID) × 30.0cm (L) 2 pieces (manufactured by Tosoh),

Column temperature: 30°C,

Mobile phase (eluent): a mixture of 0.2mol/L NaNO ₃ aqueous solution and acetonitrile, the mixing ratio represented by NaNO ₃ aqueous solution/acetonitrile is 8/2 (vol/vol),

Flow: 0.6ml/min,

Sample concentration: 1mg/ml,

Detector: RI detector,

Injection volume: 20μl,

Molecular weight correction PEO: Polyoxyethylene [manufactured by Polymer Laboratories (Polymer Laboratories) Co., Ltd.],

Calibration curve: Standard PEO [manufactured by Polymer Laboratories (Polymer Laboratories) Co., Ltd.] 3-dimensional approximate curve, measuring device: HLC-8020GPC manufactured by Tosoh,

The sample was filtered using a cellulose acetate filter cartridge (classification performance: 0.45 μm) before measurement.

[K value]

The K value is obtained by measuring the relative viscosity value (25°C) with a capillary viscometer and applying the above-mentioned Fikentscher formula.

In addition, even for products with the same specifications, there are some differences in the K value depending on the manufacturing lot. In addition, the molecular weight decreases with time through self-oxidation and the like.

[bubbling point]

The bubble point is measured in accordance with JIS K3832, using ethanol as the measurement medium. The value of the above-mentioned bubble point is an index value for measuring the maximum pore diameter, and a larger value indicates a smaller maximum pore diameter.

In addition, when the detergency (removability) of the additive is poor, large defects such as fine cracks are generated on the surface of the film, and as a result, the value of the bubble point becomes low.

[Remaining PVP]

Measurement was carried out in the following procedure by an infrared absorption analysis method (IR method). As an apparatus, FTS-40 (product name) manufactured by Varian Corporation was used.

(1) First, the membrane was dissolved in DMAC (N,N-dimethylacetamide), and spread on a slide to form a thin film.

(2) IR spectrum measurement was performed on the above thin film, and the peak around 1700 cm ^-1 (PVP value) and the peak around 1400 cm ^-1 (PVDF value) were read from the waveform.

(3) Substitute in the following formula to obtain the value.

Remaining PVP amount (%) = PVP value x a/PVDF value x 100

(a in the formula is a constant obtained from the calibration curve. At this time, it is 26.3.)

[transmission performance]

Evaluation of permeation performance The value of the permeation flow rate (permeability) per unit pressure difference was measured by the following method. The larger the value, the better the permeability. In the application of sewage filtration, the value is required to be above 30.

(test methods)

The hollow fiber membrane is used to make a micromodel by the following method (the effective length of the hollow fiber membrane is about 4 cm), and under the condition of applying a pressure of 200 kPa to the hollow part of the hollow fiber membrane, the pressure from the root (bottom) of the following Water was poured in, water was permeated from the inner wall portion of the hollow fiber membrane toward the outer wall portion, and the water flow rate was calculated from the outflow amount within 1 minute.

(How to make a miniature model)

(1) An extraction head is installed at the root (bottom) of the film with an effective length of about 4 cm.

(2) The encapsulant (mixed at a ratio of 52% of Coronet 4403 (manufactured by Japan Polyuretan Industry Co., Ltd.): 48% of Nipponlan 4423 (manufactured by Japan Polyuretan Industry Co., Ltd.)) was stirred with a spatula.

(3) Drop the blended encapsulant into the root (bottom) of the lead-out.

(4) Leave to stand in a dryer set at 40° C. for 3 hours to harden the encapsulant.

(5) As in (2), seal the tip with the prepared sealing agent.

(6) As in (4), the encapsulant was cured in a dryer at 40°C.

[Water permeability performance rate]

Measure 1m of the hollow fiber membrane used in the above-mentioned hollow fiber membrane used in the measurement of water permeability, soak it in 1L of sodium hypochlorite aqueous solution with an effective chlorine concentration of 12% for 5 minutes, and repeat the treatment twice with hot water at 100°C for 5 minutes. After a 10-minute operation, it was dried at 110° C. for 10 minutes (sample B). When the above-mentioned water permeability evaluation value is defined as water permeability value A, and the water permeability evaluation value of sample B is defined as water permeability value B, they are substituted into the following calculation formula to obtain the water permeability performance rate.

Water permeability performance rate (%) = water permeability value A/water permeability value B×100

When the water permeability is low and the performance rate of the water permeability is low, it means that the washing is not good. Regardless of whether the water permeability is low, if the performance rate of the water permeability is high, it means that the water permeability is reduced due to the small pore size formed.

(Example 1)

Polyvinylpyrrolidone (manufactured by ISP Corporation, trade name: K-90) with a high molecular weight region area ratio of 10.1% and a K value of 81.4 was used as an additive, and polyvinylidene fluoride A (manufactured by Artofina Japan Corporation, trade name: Kaina-301F, Mw500,000) and polyvinylidene fluoride B (manufactured by Atofina Japan, trade name Kaina-9000LD, Mw20,000) were used as film-forming polymers, N,N-dimethylacetamide was used as a solvent, and prepared to have The first film-forming solution and the second film-forming solution of the composition shown in Table 1.

[Table 1]

composition The first film-making solution The second film-making solution Polyvinylidene fluoride A 3% by mass 12% by mass Polyvinylidene fluoride B 2% by mass 8% by mass Polyvinylpyrrolidone 2% by mass 10% by mass N,N-Dimethylacetamide 93% by mass 70% by mass The temperature of the membrane-forming solution during preparation 50℃ 60℃ The concentration of polyvinylidene fluoride in the solution 5% by mass 20% by mass

A porous hollow fiber membrane was produced using an annular nozzle having the configuration shown in FIG. 1 .

That is, a polyester multifilament single-woven braid (multifilament: total tex 830/96 filament, 16 dozen filaments) is introduced into pipeline 1 of an annular nozzle with an outer diameter of 2.5mm and an inner diameter of 2.4mm and a heat preservation temperature of 30°C. ), the first film-forming liquid is discharged from the first discharge port 2, and the second film-forming liquid is discharged from the second discharge port 3. The braid coated with the first and second film-forming liquids was introduced into a coagulation bath kept at 80° C. consisting of 5% by mass of N,N-dimethylacetamide and 95% by mass of water, and the first and second The second membrane forming solution is solidified to obtain the first porous membrane precursor.

The first porous film precursor was placed in hot water at 98°C for 1 minute to remove the solvent, soaked in 50,000 mg/L sodium hypochlorite aqueous solution, and washed in hot water at 90°C for 10 minutes. Let it dry for 10 minutes, and take it up with a winder. Thus, a strip-shaped body having the first porous layer was obtained.

Next, in the pipeline 1 of the annular nozzle shown in Figure 1 shown in Figure 1, which is composed of an outer diameter of 2.7 mm and an inner diameter of 2.6 mm, the strip-shaped body with the above-mentioned first porous layer is introduced, and the Glycerin (manufactured by Wako Pure Chemical Industries, Ltd., grade 1) which is a solution that does not dissolve the membrane material was discharged from the outlet 2 , and the second membrane-forming liquid was discharged from the second outlet 3 . Accordingly, the second membrane-forming liquid is applied on the first porous layer. This was introduced into a coagulation bath maintained at 80° C. consisting of 5% by mass of N,N-dimethylacetamide and 95% by mass of water, to solidify the second membrane-forming solution to obtain a second porous membrane precursor.

The second porous membrane precursor was desolvated in hot water at 98°C for 1 minute, soaked in 50,000 mg/L sodium hypochlorite aqueous solution, and washed in hot water at 90°C for 10 minutes. Make it dry for 10 minutes, and take it up with a winder. Thus, a porous hollow fiber membrane is obtained.

The outer diameter/inner diameter of the obtained porous hollow fiber membrane was about 2.8/1.1 mm, the membrane thickness was 900 μm, and the thickness from the braid to the resin layer on the surface was 400 μm.

Evaluate the bubble point, permeability, performance rate of water permeability and residual PVP by the above method. The results are shown in Table 2. Table 2 shows the area ratio and K value of the high molecular weight region using polyvinylpyrrolidone (the same applies below).

(Example 2)

A porous hollow fiber membrane was obtained in the same manner as in Example 1, except that polyvinylpyrrolidone (manufactured by Nippon Shokubai Co., Ltd., trade name: K-80) with a K value of 79.9 as an additive was used as an additive.

The outer diameter/inner diameter of the obtained porous hollow fiber membrane was about 2.8/1.2 mm, the membrane thickness was 800 μm, and the thickness from the braid to the resin layer on the surface was 400 μm.

Same as in Example 1, evaluate the bubble point, permeability, performance rate of water permeability and residual PVP amount. The results are shown in Table 2.

(Example 3)

A porous hollow fiber membrane was obtained in the same manner as in Example 1, except that polyvinylpyrrolidone (manufactured by Nippon Shokubai Co., Ltd., trade name: K-80) having a K value of 78.5 as an additive was used as an additive.

The outer diameter/inner diameter of the obtained porous hollow fiber membrane was about 2.8/1.2 mm, the membrane thickness was 800 μm, and the thickness from the braid to the resin layer on the surface was 400 μm.

Same as in Example 1, evaluate the bubble point, permeability, performance rate of water permeability and residual PVP amount. The results are shown in Table 2.

(Example 4)

A porous hollow fiber membrane was obtained in the same manner as in Example 1 except that polyvinylpyrrolidone (manufactured by ISP, trade name: K-90) having a K value of 84 was used as an additive with a high molecular weight region area ratio of 9.2%.

Same as in Example 1, evaluate the bubble point, permeability, performance rate of water permeability and residual PVP amount. The results are shown in Table 2.

(Example 5)

A porous hollow fiber membrane was obtained in the same manner as in Example 1, except that polyvinylpyrrolidone (manufactured by ISP, trade name: K-90) having a K value of 81 as an additive was used as an additive.

Same as in Example 1, evaluate the bubble point, permeability, performance rate of water permeability and residual PVP amount. The results are shown in Table 2.

(comparative example 1)

A porous hollow fiber membrane was obtained in the same manner as in Example 1 except that polyvinylpyrrolidone (manufactured by ISP, trade name: K-90) having a K value of 82.9 and a ratio of high molecular weight region area of 13.2% was used as an additive.

Fine cracks were observed on the surface of the obtained porous hollow fiber membrane. Same as Example 1, when the bubble point is measured, it is reduced to 20kPa, and the qualified rate of the product is significantly reduced.

(comparative example 2)

A porous hollow fiber membrane was obtained in the same manner as in Example 1 except that polyvinylpyrrolidone (manufactured by ISP, trade name K81/86) having an area ratio of the high molecular weight region of 11.4% was used as an additive.

Fine cracks were observed on the surface of the obtained porous hollow fiber membrane. Same as Example 1, when the bubble point is measured, it is reduced to 30kPa, and the qualified rate of the product is significantly reduced.

(Example 6)

A porous hollow fiber membrane was obtained as in Example 1, except that polyvinylpyrrolidone (manufactured by ISP Corporation, trade name K90) having a K value of 73.7 as an additive was used as an additive.

[Table 2]

As shown in the results in Table 2, the porous hollow fiber membranes obtained in Examples 1 to 5 have high water permeability performance, low residual PVP content, high bubble point, and good permeability. In Example 6, although the water permeability was low, it showed a good water permeability expression rate. In contrast, in Comparative Examples 1 and 2, the bubble point, water permeability, and performance rate of water permeability were greatly reduced.

Industrial availability

According to the method for producing a porous membrane of the present invention, a porous membrane having excellent additive detergency and filtration performance can be obtained. Due to the high permeability of the porous membrane obtained by the method of the present invention, the use area of the membrane becomes smaller, making it possible to miniaturize the equipment.

Claims (4)

1. a manufacture method for perforated membrane, the method has following operation: make to form polymer containing film material and be separated control the preparation liquid of additive solidify in solidification liquid the operation, the removing that obtain perforated membrane presoma remain in described perforated membrane presoma described in be separated and control the operation of additive;

It is characterized in that, described in be separated and control additive and be, when trying to achieve the ratio of the HMW district area in integration molecular weight distribution curve by following method, the ratio of described HMW district area more than 5% less than 11% polyvinylpyrrolidone;

Herein, the value of the ratio of described HMW district area is obtained as follows:

By the gel permeation chromatography of following condition, measure the molecular weight distribution of polyvinylpyrrolidone,

The integration molecular weight distribution curve that to obtain be transverse axis X-axis with LogM, integration Distribution Value is longitudinal axis Y-axis, wherein, M represents molecular weight, integration Distribution Value in mass %,

X value when reaching the point of Y=100 with described integration molecular weight distribution curve is for P, when described integration molecular weight distribution curve and the straight line representing X=P, the area representing the region that the straight line of Y=0 surrounds are 100%, as described integration molecular weight distribution curve and expression X=6 straight line, represent X=P straight line, represent the area in the region that the straight line of Y=0 surrounds ratio and try to achieve;

Herein, the condition of described gel permeation chromatography comprises as follows,

Chromatographic column: TSKgel α-M, ID 7.8mm × L 30.0cm2 root, eastern Cao's system,

Chromatogram column temperature: 30 DEG C,

Mobile phase, also claims eluent: the NaNO of 0.2mol/L ₃the mixed liquor of the aqueous solution and acetonitrile, NaNO ₃mixed proportion represented by the aqueous solution/acetonitrile counts 8/2 with volume ratio vol/vol,

Flow: 0.6ml/min,

Concentration of specimens: 1mg/ml,

Detector: RI detector,

Injection rate: 20 μ l,

Molecular weight calibration PEO: polyoxyethylene, Polymer Laboratory Inc.,

Calibration curve: standard P EO, Polymer Laboratory Inc., 3 dimension curve of approximation, determinators: eastern Cao HLC-8020GPC, and

Before mensuration sample, the cartridge filter of the cellulose acetate of classification performance 0.45 μm is used to filter.

2. the manufacture method of perforated membrane according to claim 1, described polyvinylpyrrolidone is, when trying to achieve the ratio of the low-molecular-weight district area in integration molecular weight distribution curve by following method, the ratio of described low-molecular-weight district area is more than 5%, polyvinylpyrrolidone less than 13%;

Herein, the value of the ratio of described low-molecular-weight district area is obtained as follows:

By the gel permeation chromatography of following condition, measure the molecular weight distribution of polyvinylpyrrolidone,

The integration molecular weight distribution curve that to obtain be transverse axis X-axis with LogM, integration Distribution Value is longitudinal axis Y-axis, wherein, M represents molecular weight, integration Distribution Value in mass %,

X value when reaching the point of Y=100 with described integration molecular weight distribution curve is for P, when described integration molecular weight distribution curve and the straight line representing X=P, the area representing the region that the straight line of Y=0 surrounds are 100%, as described integration molecular weight distribution curve and expression X=3.5 straight line, represent X=4.5 straight line, represent the area in the region that the straight line of Y=0 surrounds ratio and try to achieve;

Herein, the condition of described gel permeation chromatography comprises as follows,

Chromatographic column: TSKgel α-M, ID 7.8mm × L 30.0cm2 root, eastern Cao's system,

Chromatogram column temperature: 30 DEG C,

Mobile phase, also claims eluent: the NaNO of 0.2mol/L ₃the mixed liquor of the aqueous solution and acetonitrile, NaNO ₃mixed proportion represented by the aqueous solution/acetonitrile counts 8/2 with volume ratio vol/vol,

Flow: 0.6ml/min,

Concentration of specimens: 1mg/ml,

Detector: RI detector,

Injection rate: 20 μ l,

Molecular weight calibration PEO: polyoxyethylene, Polymer Laboratory Inc.,

Calibration curve: standard P EO, Polymer Laboratory Inc., 3 dimension curve of approximation, determinators: eastern Cao HLC-8020GPC, and

Before mensuration sample, the cartridge filter of the cellulose acetate of classification performance 0.45 μm is used to filter.

3. the manufacture method of perforated membrane according to claim 1, the K value of described polyvinylpyrrolidone is below 82.

4. the manufacture method of perforated membrane according to claim 1 and 2, the K value of described polyvinylpyrrolidone is more than 78.