JPH0636853B2 - Porous hollow fiber membrane - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a hollow fiber membrane suitable as a separation membrane for purifying fluids, particularly water, and more specifically, it dramatically improves hydrophilicity. The present invention also relates to a hollow fiber having a wide range of filtration capabilities from microfiltration to ultrafiltration simply by changing the coating state of ethyl cellulose.

[Prior Art] Hollow fiber membrane microfiltration membranes and ultrafiltration membranes made of polymer materials are used in fields such as water and solution separation / purification and treatment, and in the medical field.

When water or an aqueous solution is subjected to microfiltration or ultrafiltration, it is necessary that the membrane has hydrophilicity. Conventionally, as a method for producing a microfiltration membrane and an ultrafiltration membrane having hydrophilicity, hydrophilic membranes have been used. A homogeneous polymer solution is prepared by dissolving a water-soluble polymer membrane material in a mixed solvent system of solvent and swelling agent or non-solvent, and this solution is cast into a film to partially or completely evaporate the volatile solvent. After that, it is immersed in a coagulation bath and the solvent is extracted and removed to form a porous film. A method is known in which the substance to be eluted is eluted to form a porous membrane. (Hereinafter, referred to as Conventional Method 1.) On the other hand, high-density polyethylene, polypropylene, poly (4
In addition to the above-mentioned method, the porous membrane made of a thermoplastic resin such as -methyl-pentene-1) is a method in which a hollow raw fiber is spun and then made porous by stretching in a specific temperature range and / or a specific medium. It is possible to obtain a porous hollow fiber membrane having excellent mechanical properties. (Hereinafter, referred to as Conventional Method 2.) [Problems to be Solved by the Invention] However, Conventional Method 1 for imparting hydrophilicity requires extremely complicated treatment steps as described above,
As a result, there is a cost disadvantage.

Also in the conventional method 2, the porous hollow fiber winding itself produced is hydrophobic, and when it is used for filtering water or an aqueous solution, it needs to be hydrophilized with alcohol or the like, and always keeps a wet state. Maintenance is complicated because of the necessity.

[Means for Solving Problems] The present invention is intended to improve the above-described conventional porous membrane, and a hollow fiber substrate having penetrating fine pores is coated with ethyl cellulose to prepare a water or aqueous solution. It was found that a porous hollow fiber membrane having a hydrophilicity necessary and sufficient for the above-mentioned filtration and having a filtration ability over a wide range from microfiltration to ultrafiltration can be obtained, and the present invention has been accomplished.

That is, according to the present invention, there is provided a hollow fiber substrate having a large number of penetrating micropores in a peripheral wall, wherein the peripheral wall surface and the inner surface of the micropores are coated with ethyl cellulose. It

The material of the hollow fiber substrate having a large number of through fine holes in the peripheral wall portion used in the present invention is not particularly limited. Examples of materials made of polymer materials include polyolefins (high-density polyethylene, polypropylene, poly (4-methyl-pentene-1), etc.), fluorine-containing polymer compounds, polysulphone, polycarbonate,
A porous hollow fiber such as polyvinyl chloride can be used. Further, examples of inorganic materials include porous hollow fibers such as glass, ceramics and carbon, or porous tubes. The outer diameter, peripheral wall thickness and pore diameter of the porous hollow fiber substrate are not particularly limited, but generally the outer diameter is 10 to 1000 microns, the peripheral wall thickness is 10 to 500 microns, and the pore diameter is 0.01. It is preferably about 50 microns.

Ethyl cellulose used in the present invention has an ethoxy group content of 45 to 50%, and has a toluene content of 8% at 25 ° C.
The viscosity of a 5% solution of a mixed solvent of 0% and ethanol 20% is 4 to 100 cps, preferably 4 to 10 cps.

Next, a method for producing the porous hollow fiber membrane of the present invention will be described.

The specific ethyl cellulose described above is dissolved in an ethyl cellulose-soluble solvent to a concentration of 0.1 to 5 wt%. As the solvent, acetone, acetone-water, alcohols such as methanol and ethanol, alcohol-water, benzene, toluene, xylene, chloroform and the like are preferable.

Then, the porous hollow fiber substrate is immersed in the ethyl cellulose solution, and the ethyl cellulose solution is sufficiently spread also in the fine pores of the porous hollow fiber substrate, and then air-dried or water is used.
Alternatively, the ethyl cellulose is precipitated on the porous hollow fiber substrate by air-drying and coagulation with water, followed by thorough washing with water.

The thus obtained porous hollow fiber coated with ethyl cellulose had a concentration of the ethyl cellulose solution, a concentration gradient of the ethyl cellulose solution in the micropores of the porous hollow fiber substrate (the porous hollow fiber substrate was When soaking, a concentration gradient is created by dipping the solution in different concentrations twice or more) and air-drying, precipitation with water or a combination of both, and soaking in the solution-precipitation-
By appropriately adjusting and changing the number of times such as washing and drying performed multiple times, etc., only the peripheral wall surface of the hollow fiber substrate and its inner surface of the fine pores are covered with the ultrathin film, and sufficient hydrophilicity is exhibited. From those having a pore size which is almost the same as the pore size of the original porous hollow fiber substrate to those having a non-porous sheet layer on at least one of the inner and outer surfaces of the hollow fiber substrate peripheral wall portion, and the fine pores being ethyl cellulose. You can get even blocked ones.

Next, the structure of the porous hollow fiber membrane of the present invention will be described with reference to FIGS.

In the figure, 1 shows a partial cross-sectional view of the hollow fiber membrane cut at right angles to the axial direction.

FIG. 1 is a partially enlarged cross-sectional view showing a hollow fiber substrate 4 having a large number of penetrating micropores 7 in a peripheral wall portion 2, the peripheral wall portion 2 and the inner surface of the micropores 7 being covered with an ethylcellulose layer 3. Is shown. That is, FIG. 1 shows the state of a thin film as a state of coating with ethyl cellulose.

Unlike FIG. 1, FIG. 2 shows the inner and outer surfaces of the peripheral wall of the hollow fiber membrane, at least one surface of which is covered with a non-porous sheet layer 5 of ethyl cellulose.

FIG. 3 shows the case where the inside of the fine pores 7 is closed with ethyl cellulose (6 in the figure).

[Examples] Hereinafter, the present invention will be described in more detail with reference to Examples, but it will be apparent that the present invention is not limited thereto.

(Example 1) Polypropylene (UBE-PP-J109G, trade name: Ube Industries, Ltd., MF1 = 9 g / 10 minutes), diameter 33 mm,
Using a hollow fiber manufacturing nozzle equipped with a gas supply pipe having an inner diameter of 27 mm, spinning was performed at a spinning temperature of 200 ° C. and a take-up speed of 116 m / min. 1 for the obtained polypropylene hollow fiber
Heat-treated in a heated air bath at 45 ° C for 6 minutes, and then stretched in liquid nitrogen (-195 ° C) by 20% relative to the initial length,
With the stretched state maintained, heat treatment was performed for 2 minutes in a heated air tank at 145 ° C.

This hollow fiber was subjected to 400% hot drawing in an air atmosphere at 125 ° C., and then heat-treated for 15 minutes in a heated air tank at 145 ° C. while maintaining the drawn state to produce a porous polypropylene hollow fiber.

The average pore diameter of the obtained porous polypropylene hollow fiber was determined by the mercury porosimetry method (measurement was made by CARLOERBA (Italy) POROSIMETRO SERIE
S) 1500 was used. The same applies hereinafter), and was 0.32 μm, and the porosity was 75.2%.

When the peripheral wall of the porous polypropylene hollow fiber was observed with an electron microscope, a large number of large through holes were formed uniformly in the peripheral wall, and the diameter of the through holes was almost constant throughout. The outer diameter of this porous polypropylene hollow fiber was 400 microns and the inner diameter was 300 microns.

Next, the above-mentioned porous polypropylene hollow fiber was first mixed with 5% of a mixed solvent of toluene 80% and ethanol 20% at 25 ° C.
Has a viscosity of 7 cps and an ethoxy group content of 48-49.5.
% Ethyl erulose (DOW CHEM
ICAL), Etocel STD type PREMIUM) 0.35
After soaking in a wt% acetone solution, it was air-dried until the solution existing in the inner diameter of the hollow fiber was exhausted, then soaked in water to precipitate ethyl cellulose, washed with water and dried.

The inner and outer surfaces of the peripheral wall of the hollow fiber membrane thus obtained,
When the cross section of the peripheral wall portion and the cross section of the peripheral wall portion were observed with an electron microscope, it was observed that the peripheral wall portion and the peripheral wall portion cross section had essentially the same large number of large through holes as the original porous hollow fiber.

The water permeation rate when filtering the obtained hollow fiber membrane without pretreatment with alcohol or the like was 35 / min · m ² atm.

(Comparative Example) An attempt was made to filter water at a pressure of 1.5 kg / cm ² without pretreating only the porous polypropylene hollow fiber membrane described in Example 1 with alcohol or the like. It was 0. When water was filtered after being hydrophilized with alcohol, the water permeation rate was 20 / min · m ² atm.

(Example 2) The hollow fiber obtained in Example 1 is immersed in an ethyl cellulose solution once more, and then air-dried until the solution existing in the inner diameter of the hollow fiber is exhausted, followed by precipitation with water, washing with water and drying. The same steps as in Example 1 were performed except that the steps were added.

Observation of the inner and outer surfaces of the peripheral wall of the obtained hollow fiber membrane and the cross section of the peripheral wall with an electron microscope revealed that the inner peripheral wall surface and the peripheral wall cross section were essentially the same in number as the large pores of the original porous hollow fiber. Although the retained morphology was observed, a non-porous sheet film was formed on the outer peripheral wall surface.

The amount of transparent water when the obtained hollow fiber was filtered with water without pretreatment with alcohol etc. was 0.1 / · m ² min · atm. When 0.1% albumin in physiological saline was filtered, albumin was completely blocked.

[Effects of the Invention] As described above, the porous hollow fiber membrane according to the present invention is coated with ethyl cellulose on the peripheral wall and the micropores of the porous hollow fiber substrate, which is necessary and sufficient for filtration of water or aqueous solution. By adjusting and changing the above-mentioned ethyl cellulose coating state, it is possible to achieve a wide range of filtration and separation from microfiltration to ultrafiltration.

[Brief description of drawings]

FIG. 1 is a partially enlarged sectional explanatory view showing an embodiment of the porous hollow fiber membrane according to the present invention, and FIGS. 2 and 3 are partially enlarged sectional explanatory views showing other embodiments of the present invention. Indicates. 2 ... Peripheral wall of hollow fiber, 3 ... Ethyl cellulose, 4 ...
... Hollow fiber substrate, 5 ... Non-porous sheet layer of ethyl cellulose.

Claims (5)

[Claims] 1. A porous hollow fiber membrane, which is a hollow fiber substrate having a large number of through micropores in a peripheral wall portion, wherein the peripheral wall surface and the inner surface of the fine pores are coated with ethyl cellulose. 2. The porous hollow according to claim 1, wherein at least one of the inner and outer surfaces of the peripheral wall of the hollow fiber substrate is covered with a non-porous sheet layer of ethyl cellulose. Thread film. 3. The porous hollow fiber membrane according to claim 1, wherein the inside of the micropores of the hollow fiber substrate is closed with ethyl cellulose. 4. Ethyl cellulose has a viscosity of 4 to 100 cps and a ethoxy group content of 45 to 5 in a 5% solution of a mixed solvent of 80% toluene and 20% ethanol at 25 ° C.
The porous hollow fiber membrane according to claim 1, 2 or 3, wherein the content is 0%. 5. The porous hollow fiber membrane according to claim 4, wherein ethyl cellulose has a viscosity of a 5% solution of a mixed solvent of toluene 80% and ethanol 20% at 25 ° C. of 4 to 10 cps.