JPH07114929B2 - Method for producing polymer porous flat membrane - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a polymer porous flat membrane useful as a separation membrane, and more specifically, to a modification treatment for forming a separation membrane by utilizing phase inversion. The present invention also relates to a method for producing a polymer porous flat membrane having controlled separation performance.

[0002]

2. Description of the Related Art Up to now, porous membranes such as ultrafiltration membranes and gas separation membranes have been prepared by casting a concentrated solution of a polymer compound on a flat surface and introducing it into a coagulating liquid such as water. It is manufactured by a so-called casting method of converting, a method of forming a polymer compound into a film shape in advance and stretching in the longitudinal direction and the transverse direction, mixing other components at this time, and extracting it after film formation. There is.

Of these, the most typical method is the casting method, but in this method, the performance of the obtained membrane changes variously depending on factors such as preparation of the stock solution, casting conditions or spinning conditions, and the composition of the coagulating liquid. However, many studies have been conducted to clarify the relationship between these factors and the structure and function of membranes, but no clear answer has been obtained for their causal relationship. .

[0004]

DISCLOSURE OF THE INVENTION The present invention is for controlling the separation performance by a simple means to obtain a desired performance when a porous flat membrane is formed by a so-called casting method utilizing phase inversion. It was made for the purpose of providing a reforming method.

[0005]

Means for Solving the Problems The present inventors have conducted various studies on a method for producing a porous flat membrane by a casting method, and as a result, have found that a concentrated solution of a polymer compound flatly formed from a non-solvent It was found that the surface or internal structure of the membrane can be controlled by bringing it into contact with a solvent for a short time prior to introducing it into a coagulation bath consisting of, and the performance thereof can be controlled. It came to eggplant.

That is, according to the present invention, a concentrated solution of a polymer compound is cast on a flat surface, brought into contact with a liquid capable of dissolving or swelling the polymer compound for 0.1 to 5 seconds, and then introduced into a coagulation bath. The present invention provides a method for producing a polymer porous flat membrane, which comprises forming a membrane.

In the method of the present invention, the polymer compound used as the material for the porous membrane is not particularly limited, and any polymer compound conventionally used as the material for the porous membrane in the casting method can be used. it can.

Examples of such polymer compounds include cellulose acetate, cellulose-based compounds such as polysaccharides, polyolefin, polyacrylonitrile, vinyl-based polymers such as polyvinylidene fluoride, polysulfone, polyether sulfone, polyaramid, and polyimide. Such aromatic polymers and the like can be mentioned.

In the method of the present invention, these polymer compounds are dissolved in a solvent to prepare a concentrated solution, and if desired, an additive for forming pores is added to the concentrated solution to use as a stock solution. The solvent at this time is appropriately selected from solvents that are good solvents for the polymer compound used, and examples thereof include acetone, dioxane, methyl cellosolve, dimethylformamide, dimethylacetamide, morpholine, and N. -Methylpyrrolidone, dimethylpropionamide, etc. Further, in order to promote dissolution, iron chloride, lithium bromide, copper nitrite, sodium thiocyanide, formamide and the like can be used in combination. Also,
As the pore-forming additive, pyridine, triethylamine, ethanolamine, diethanolamine, triethanolamine, polyvinylpyrrolidone, or the like is used.

In the method of the present invention, the concentration of the concentrated solution of the above-mentioned polymer compound is selected as high as possible within the range where flat film formation is possible, but it is usually 5 to 30%.

Next, a method of casting the concentrated solution of the polymer compound at a suitable thickness on a flat surface such as a glass plate can be mentioned.

The flat film material thus obtained is brought into contact with a liquid capable of dissolving or swelling the polymer compound as a raw material. As the liquid at this time, the same solvent as that used when preparing the concentrated solution of the polymer compound is usually used, but different solvents may be used.

The contact time at this time must be within 5 seconds in order to obtain a membrane structure that exhibits the desired performance within a range where the porous structure is not completely destroyed. . This actual time may be momentary contact depending on the type of polymer compound used as the material, the concentration of the solution, the dryness, the type of liquid used, etc., but the practical contact time is usually A range of 0.1 to 5 seconds is selected.

By the contact treatment with this liquid, the surface structure of the obtained porous membrane can be changed into various shapes such as unevenness, scaly shape, and honeycomb shape, and the opening degree and pore size distribution can be controlled. it can.

As described above, the flat film material subjected to the contact treatment with the liquid is then introduced into the coagulation bath to remove the residual solvent and the additive for forming pores to form a porous flat film. To be done. The coagulating liquid in this case is a non-solvent of the polymer compound used, and can be arbitrarily selected from those having compatibility with the solvent and the pore-forming additive, but usually water is used. To be

The structure and performance of the porous flat membrane obtained by the method of the present invention are influenced by the materials used and the production conditions. For example, the film density is the additive for pore formation, the contact treatment with liquid and the coagulation bath temperature, the water content of the porous flat membrane is the additive for pore formation, the water permeation amount is the contact treatment with liquid, the air permeation. The amount is affected by the pore-forming additive and the coagulation bath temperature, respectively.

[0017]

EXAMPLES Next, the present invention will be described in more detail by way of examples. In addition, the numerical value of the performance of the porous flat membrane in each example is a value measured by the following method.

(1) Water permeation amount: Using a pressure vessel for filtration having a capacity of 5 liters and a pressure type filter holder, a sample having a membrane area of 13.85 cm ² at a temperature of 15 ° C. and a pressure of 0.1 MPa or 0.05 MPa. It was measured. (2) Air permeation amount: Measured at a temperature of 15 ° C. and a pressure of 0.05 MPa using the same device and sample as above.

Example 1 Polysulfone (P-170 manufactured by Union Carbide Co.)
0) 10 parts by weight was dissolved in 90 parts by weight of N-methylpyrrolidone to prepare a stock solution having a polymer concentration of 10%. Baker type applicator (made by Tester Sangyo Co., Ltd. width 75
0mm), and this stock solution on a glass plate at 0.254
It was cast to a thickness of mm. Next, the glass plate carrying the film was immersed in N-methylpyrrolidone, immediately taken out, and transferred into water at 100 ° C.

The porous flat membrane thus obtained was washed with running water for 24 hours. This porous flat film has a film density of 0.27 g /
It was cm ³ , and the water permeation rate was 5.41 liter / cm ³ · min.

FIG. 1 is a 2000 × magnified micrograph of the surface of this porous flat membrane on the liquid contact side, and FIG.
As seen from these photographs, the surface in contact with the liquid does not have a skin layer and has an opening having a pore size of several microns to several tens of microns.

Example 2 9.3 parts by weight of the same polysulfone as used in Example 1 and 3.7 parts by weight of polyvinylpyrrolidone (molecular weight 1.1 million) were dissolved in 87 parts by weight of N-methylpyrrolidone to obtain a polymer concentration. A 9.3% stock solution was prepared. A porous flat membrane was produced from this stock solution in the same manner as in Example 1. The porous flat membrane thus obtained had a membrane density of 0.13 g / c.
m ³ , the water permeation rate was 3.04 liters / cm ³ · min, and the air permeation rate was 40 liters / cm ³ · min.

20 of the surface of this porous flat membrane on the liquid contact side
A 00-time magnified photomicrograph is shown in FIG. 3, and a 1000-time magnified photomicrograph of the cross section is shown in FIG.

Example 3 Using the same stock solution as in Example 1, casting was performed in the same manner as in Example 1 to form a film, and after liquid contact treatment, the film was immersed in a coagulation bath at 0 ° C. The film density of the porous flat film thus obtained is 0.32.
The air permeability was g / cm ³ , and the air permeation amount was 68 liters / cm ³ · min.

20 of the surface of this porous flat membrane on the liquid contact side
A 00 times magnified micrograph is shown in FIG. 5, and a 1000 times magnified micrograph of the cross section is shown in FIG. As can be seen from these photographs, this porous flat membrane has an opening with a pore size of several microns.

Example 4 9.3 parts by weight of polyether sulfone (Imperial Chemical Industry Co., 3600P) and 3.7 parts by weight of polyvinylpyrrolidone (molecular weight 1.1 million) were dissolved in 87 parts by weight of N-methylpyrrolidone. Stock solutions were prepared.
Using this stock solution, a porous flat membrane was produced in the same manner as in Example 2. The film density of this porous film is 0.16 g / cm ³ ,
Water permeation rate is 6.7 liters / cm ³ · min (0.05MP
a), the air permeation rate was 118 liters / cm ³ · min.

40 of the surface of the porous flat membrane on the liquid contact side
A 0X magnified micrograph is shown in FIG. 7, and a cross-sectional 2000X magnified micrograph is shown in FIG. As can be seen from these photographs, no skin layer is formed.

Example 5 Cellulose acetate (manufactured by Daicel Chemical Industries, Ltd.,
Acetate cotton LT-105, degree of acetylation 60.8%, average degree of polymerization 3
60) 8 parts by weight was dissolved in 92 parts by weight of N-methylpyrrolidone to prepare a stock solution having a polymer concentration of 8%. This stock solution was cast in the same manner as in Example 1 to form a film, subjected to a liquid contact treatment, and then immersed in a coagulation bath at 37 ° C.

A 4000 × magnified micrograph of the liquid contact side of the porous flat membrane thus obtained is shown in FIG.
A 000 times magnified micrograph is shown in FIG. As can be seen from this photograph, no skin layer is formed.

Example 6 Meta-type aramid resin (Conex, manufactured by Teijin Limited)
10 parts by weight was dissolved in 90 parts by weight of N-methylpyrrolidone to prepare a stock solution having a polymer concentration of 10%. This stock solution was operated in the same manner as in Example 1 to produce a porous flat membrane.

FIG. 11 shows a 4000 × magnified photomicrograph of the surface of the porous flat membrane on the liquid contact side thus obtained, and FIG. 12 shows a 4000 × magnified photomicrograph of the cross section thereof. As can be seen from these photographs, no skin layer is formed.

[0032]

According to the method of the present invention, it is possible to easily control the surface structure and the internal structure of the polymer porous flat membrane, and thereby it is possible to produce a separation membrane having performance suitable for the intended purpose. .

[Brief description of drawings]

FIG. 1 is a micrograph of the surface of a porous flat membrane obtained in Example 1 on the liquid contact side.

FIG. 2 is a micrograph of a cross section of the same porous flat membrane.

FIG. 3 is a micrograph of the surface of the porous flat membrane obtained in Example 2 on the liquid contact side.

FIG. 4 is a micrograph of a cross section of the same porous flat membrane.

FIG. 5 is a micrograph of the surface of the porous flat membrane obtained in Example 3 on the liquid contact side.

FIG. 6 is a micrograph of a cross section of the same porous flat membrane.

FIG. 7 is a micrograph of the liquid contact side surface of the porous flat membrane obtained in Example 4.

FIG. 8 is a micrograph of a cross section of the same porous flat membrane.

9 is a micrograph of the surface of the porous flat membrane obtained in Example 5 on the liquid contact side. FIG.

FIG. 10 is a micrograph of a cross section of the same porous flat membrane.

FIG. 11 is a micrograph of the surface of the porous flat membrane obtained in Example 6 on the liquid contact side.

FIG. 12 is a micrograph of a cross section of the same porous flat membrane.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Internal reference number FI Technical display location B01D 71/56 9153-4D 71/64 9153-4D 71/68 9153-4D (72) Inventor Castle Takayoshi 3-7-29 Morino, Machida-shi, Tokyo (72) Inventor Keisuke Shinno 2-15-8-301 Omorikita, Ota-ku, Tokyo Examiner Koichi Nakano (56) Reference JP-A-1-80401 (JP, A) JP-A-56-108504 (JP, A)

Claims (3)

[Claims] 1. A concentrated solution of a high molecular compound is cast on a flat surface, and a liquid capable of dissolving or swelling the high molecular compound is mixed with the liquid.
A method for producing a polymer porous flat membrane, which comprises contacting for 1 to 5 seconds and then introducing into a coagulation bath to form a membrane. 2. The concentrated solution of a polymer compound is a concentrated solution of polysulfone, polyether sulfone, aromatic polyamide, polyamideimide, polyacrylonitrile, acrylonitrile-styrene copolymer, polyacrylic acid derivative or cellulose derivative. The manufacturing method described. 3. The method according to claim 1, wherein the concentrated solution has a concentration of 5 to 30%.