KR20010054490A - A high performance polysulfone typed hollow fiber membrane, and a process of preparing for the same - Google Patents

Abstract

PURPOSE: A polysulfone hollow fiber membrane is provided which has superior solute removing performance (resolving power) by solving problems such as low penetrating power, insufficient hydrophilicity of the surface of a membrane, additional installation of facility and waste of expensive polyvinylpyrrolidone. CONSTITUTION: The asymmetric polysulfone hollow fiber membrane in which hole diameters and thin skin layers is formed on the internal or external surface, the polysulfone hollow fiber membrane having superior performance is characterized in that hole diameters formed on the internal or external surface have an oval appearance in which an average ratio (R) of maximum diameter (a)/minimum diameter (b) is 1.5 or more as a whole. The method for manufacturing the polysulfone hollow fiber membrane having superior performance comprises the processes of spinning a spinning dope having a viscosity of 7000 centipoise (cps) and an internal coagulating solution which consists of polysulfone polymer, hydrophilic polymer and organic solvents with a dual pipe type nozzle; passing the spun hollow fiber through the air gap and into an external coagulating vat having a temperature of 30 deg.C or more; and washing, drying and winding the hollow fiber respectively.

Description

A high performance polysulfone typed hollow fiber membrane, and a process of preparing for the same}

The present invention relates to a polysulfone-based hollow fiber membrane and a method for producing the same having a relatively high pure permeability compared to the solute removal ability.

Much research has been done on the separator material, and cellulose-based polymers, polyamide-based polymers, polyacrylic-based polymers, and polyvinyl-based polymers have been developed and used. However, these materials have attracted attention as polysulfone-based polymers that can compensate for this problem due to lack of biodegradability, chemical resistance, and heat resistance.

Polysulfone polymers have excellent biodegradability, chemical resistance, heat resistance, flame retardancy, and mechanical properties, and are widely used in hemodialysis, microfiltration, ultrafiltration, reverse osmosis, and gas separation composite membranes.

In general, the two most important performances of membranes are separation and permeability, and these two performances are not compatible. none. Therefore, the main task of the membrane development is to prepare a membrane having a higher permeability while having a constant resolution. However, polysulfone-based polymers have a problem of low permeability compared to membranes made of hydrophilic polymers because of their unique hydrophobicity.

Conventional techniques for increasing permeability include Japanese Patent Publication Nos. 90-18695, JP-A-61-93801, JP-A-61-402 and JP-A-62-38205, such as vinylpyrrolidone, which is a water-soluble polymer in the production of spinning dope. A method of adding a polymer has been proposed. However, due to the hydrophilicity, the water-soluble polymer added to the spinning dope is mostly out of the hollow fiber membrane during the washing process during film formation, and thus the hydrophilization of the surface of the separator that is necessary for increasing permeability and blood affinity is not sufficiently achieved.

Japanese Patent Application Laid-Open No. 58-104940 discloses a method of fixing a hydrophilic polymer to the surface of a polysulfone hollow fiber membrane by using a crosslinking agent, and Japanese Patent Application Laid-Open Nos. 63-97205 and 63-97634 by heat treatment or radiation treatment. The process is lengthy and additional equipment must be installed.

U.S. Patent No. 5,340,480 discloses a hollow fiber having a skin layer on its inner surface using a polyvinylpyrrolidone aqueous solution of 0.1 to 0.4 wt% of spinning dope consisting of polysulfone polymer, polyglycol, polyvinylpyrrolidone, and an organic solvent as an internal coagulant. Although a method for producing a desert has been proposed, there is a problem in that the permeability enhancement effect is insignificant and the waste of expensive polyvinylpyrrolidone is severe.

The present invention is to solve the problems of the prior art to provide a polysulfone-based hollow fiber membrane having excellent solute removal performance (separability) and at the same time excellent permeability.

1 is a scanning microscope photograph (5x magnification) copy of the outer surface of the hollow fiber membrane of the present invention.

Figure 2 is an enlarged cross-sectional view of the hollow fiber membrane of the present invention.

Figure 3 is a schematic diagram of the solute removal of the hollow fiber membrane of the present invention.

Figure 4 is a schematic diagram of the solute removal of the conventional hollow fiber membrane.

※ Explanation of Codes on Major Parts of Drawings

1: pore 2: solute a: pore maximum diameter b: pore minimum diameter

The present invention relates to a polysulfone-based hollow fiber membrane excellent in pure water permeation performance (permeability) compared to solute removal performance (exclusion rate) and a manufacturing method thereof. Specifically, in the polysulfone-based hollow fiber membrane having an asymmetric structure in which the pores and the thin skin layer exist on the inner surface or the outer surface, the pores formed on the inner surface or the outer surface have a maximum diameter (a) / minimum diameter as a whole. It relates to a polysulfone hollow fiber membrane having excellent performance, characterized in that the ratio (B) of (b) has an elliptical shape with an average of 1.5 or more.

In addition, the present invention after spinning a spinning dope of less than 7000 centipoise (cps) and the internal coagulating solution consisting of a polysulfone polymer, a hydrophilic polymer and an organic solvent with a double tubular nozzle, the spun hollow fiber 10 cm or more The present invention relates to a method for producing a polysulfone hollow fiber membrane having excellent performance, which is passed through an air gap and an external coagulation bath of 30 ° C. or more, and washed with water, dried and wound up.

Hereinafter, the present invention will be described in detail.

In the present invention, in the wet spinning process of the hollow yarn, the temperature of the coagulating solution, the viscosity of the spinning dope, and the distance between the spinning nozzle and the external coagulation tank (hereinafter referred to as "air gap") are appropriately adjusted to the inner surface or the outer surface of the hollow fiber membrane. It is characterized in that the shape of the existing pore is made into an oval shape.

First, a polysulfone polymer is dissolved in an organic solvent, and then a hydrophilic polymer is added thereto to prepare a spinning dope. It is also possible to optionally add a coagulating solvent in the manufacture of the spinning dope. The polysulfone polymer is a compound having a repeating unit such as general formula (I) or general formula (II).

As the hydrophilic polymer, a vinylpyrrolidone polymer, more specifically, polyvinylpyrrolidone or the like is used. However, the hydrophilic polymer must include polyvinylpyrrolidone (hereinafter referred to as "PVP"). As the coagulating solvent, water or a glycol compound such as polyethylene glycol may be used.

As the organic solvent, m-cresol, chlorobenzene, N-methyl-2-pyrrolidone, dimethyl sulfoxide, dimethylacetamide, dimethylformamide and / or mixtures thereof are used. The content of the polysulfone polymer constituting the spinning dope is 10 to 30% by weight, 1 to 20% by weight of the hydrophilic polymer, and 0 to 20% by weight of the coagulation solvent.

The viscosity of the spinning dope is controlled to 7000 cps (Centi Poise) or less, more preferably 5000 cps or less. When the spinning dope is formed out of the above conditions, the hollow fiber membrane manufacturing processability is deteriorated and the structure of the membrane desired in the present invention cannot be obtained.

Hydrophilic polymers must include PVP, the content of PVP is preferably at least 5% by weight, more preferably at least 8% by weight. When the PVP is included in more than 8% by weight, the viscosity of the spinning dope is preferably 5000cps or less.

The present invention does not specifically limit the type and content of the coagulating solvent, the organic solvent and the internal coagulating solution.

Next, the spinning dope and the internal coagulating solution are spun into the air using a conventional double tubular nozzle, the hollow fiber passes through the air gap and the external coagulating fluid, washed with water and wound A phone-based hollow fiber membrane is produced. In this case, as the double tubular nozzle, an outer diameter of 0.3 to 0.5 µm, an inner diameter of 0.2 to 0.3 µm, and an inner diameter of 0.1 to 0.2 µm may be used. As the internal coagulation solution and the external coagulation solution, a solution in which water, an organic solvent, or glycols are mixed may be used.

This invention does not specifically limit the kind of internal coagulating liquid and external coagulating liquid. In other words, any type of internal coagulant or external coagulant may be used. The air gap has a length of 10 cm or more, more preferably 20 cm or more. The temperature of the external coagulation bath is 30 ° C. or higher, more preferably 40 ° C. or higher.

If the length of the air gap, the temperature of the external coagulation bath, and the viscosity of the spinning dope are outside the scope of the present invention, it is impossible to form an oval pore having a ratio R of the maximum diameter (a) / minimum diameter (b) of 1.5 or more. do.

The hollow fiber membrane of the present invention prepared by the method described above has an oval pore and thin skin layers formed on the inner surface or the outer surface thereof, and has an asymmetric structure. The oval pore diameters have a ratio R of maximum diameter (a) / minimum diameter (b) of 1.5 or more. If the R value is less than 1.5, a problem may occur in that the resolution decreases under the same permeability.

The hollow fiber membrane of the present invention is relatively excellent in the separation performance under the same permeability because the elliptical pores are formed. Specifically, assuming that the present invention hollow fiber membrane pore of FIG. 3 and the conventional hollow fiber membrane pore of FIG. 4 have the same cross-sectional area, their permeability is the same. However, the present invention may exclude the solute 2 as shown in FIG. 3, but the conventional hollow fiber membrane may not exclude the solute 2 as shown in FIG. 4.

In the present invention, the net permeability coefficient of the hollow fiber membrane and the exclusion rate of cytochrome (C) are evaluated by the following method.

Pure water transmission coefficient

The ultrapure water ultrafiltration of the primary RO water was once again used to measure the amount of water flowing through the membrane under a pressure of 1 kgf / cm 2 (ml / min / cm 2 / atm). At this time, the filtration method was a cross-pressure (crossflow) method.

Cytochrome C exclusion rate (Mw 12,400)

An aqueous solution of cytochrome C of about 150 ppm was prepared, and the resultant was filtered by a pressure resistant crossflow method, and the concentrations of the filtrate and the crude solution which passed through the membrane were measured by UV, and the exclusion rate was calculated using the following equation.

Cytochrome C Exclusion Rate (%) = (1- ) × 100

Hereinafter, the present invention will be described in detail through Examples and Comparative Examples. However, the present invention is not limited only to the following examples.

Example 1

A spinning dope was prepared by stirring and dissolving 17% by weight of polysulfone resin (P-3500: manufactured by Amoco Corporation), 9% by weight of polyvinylpyrrolidone, 10% by weight of polyethylene glycol, and 64% by weight of dimethylformamide. The spinning dope and the internal coagulating solution, which is an aqueous 80% diethyl glycol solution, are spun at the same time with an annular slit mold having an outer diameter of 0.35 mm, an inner diameter of 0.2 mm, and an injection hole diameter of 0.15 mm. The spun hollow fiber was continuously passed through an air gap of 20 cm and an external coagulation bath (water) at 45 ° C., washed with water and dried to prepare hollow fiber (winding speed 33 m / min). Table 2 shows the results of evaluating the properties of the hollow fiber membrane prepared by injecting the hollow fiber into the module.

Example 2-Example 3 and Comparative Example 1-Comparative Example 2

A hollow fiber membrane was manufactured in the same process and conditions as in Example 1, except that the external coagulation bath temperature and the length of the air gap were changed as shown in Table 1. The results of evaluating the properties of the hollow fiber membranes are shown in Table 2.

Manufacture conditions division External coagulation bath temperature (℃) Air gap length (cm) Example 1 45 20 Example 2 40 30 Example 3 40 40 Comparative Example 1 25 10 Comparative Example 2 40 5

Hollow Fiber Membrane Properties division Maximum diameter (a) / minimum diameter (b) ratio (R) Pure water transmission coefficient (ml / min / cm2 / atm) Cytochrome C Exclusion Rate (%) Example 1 3.3 0.30 55 Example 2 3.9 0.33 60 Example 3 4.1 0.41 50 Comparative Example 1 1.1 0.15 50 Comparative Example 2 1.2 0.20 52

Oval voids are formed in the hollow fiber membrane of the present invention, so that the pure water coefficient (permeability) is excellent and the solute removal performance (separability) is also excellent.

Claims (7)

In the polysulfone-based hollow fiber membrane having an asymmetric structure in which the pores and the thin skin layer exist on the inner surface or the outer surface, the pores formed on the inner surface or the outer surface generally have a ratio of the maximum diameter (a) / minimum diameter (b). Polysulfone hollow fiber membrane having excellent performance, characterized in that (R) has an elliptical shape with an average of 1.5 or more. After spinning a dope with a viscosity of 7000 centipoise (cps) or less and a internal coagulating solution consisting of a polysulfone-based polymer, a hydrophilic polymer, and an organic solvent with a double-tubular nozzle, the hollow fiber Gap) and a method for producing a polysulfone hollow fiber membrane having excellent performance, characterized by passing through an external coagulation bath of 30 ℃ or more, washing with water, drying and winding. The method for producing a polysulfone hollow fiber membrane having excellent performance according to claim 2, wherein the hydrophilic polymer is polyvinylpyrrolidone. The method for producing a polysulfone hollow fiber membrane having excellent performance according to claim 2, wherein the spinning dope has a viscosity of 5000 cps or less. The method for producing a polysulfone hollow fiber membrane having excellent performance according to claim 2, wherein the air gap has a length of 20 cm or more. The method for producing a polysulfone hollow fiber membrane having excellent performance according to claim 2, wherein a coagulating solvent composed of water or a glycol compound in the spinning dope is added. The method for producing a polysulfone hollow fiber membrane having excellent performance according to claim 2, wherein 10 to 30% by weight of the polysulfone polymer and 1 to 20% by weight of the hydrophilic polymer are contained in the spinning dope.