KR100434565B1 - A polysulfone-based hollow fiber membrane with excellent durability for steam, and a process of preparing for the same - Google Patents

Abstract

The present invention relates to a polysulfone hollow fiber membrane having excellent steam durability and a method for producing the same. In the method of the present invention, an internal coagulating solution composed of a polysulfone polymer, a spinning dope composed of an organic solvent and an additive, and a glycol compound or a solution containing a glycol compound is spun into the air with a double-tubular nozzle, and then into an external coagulating solution. In producing a polysulfone hollow fiber membrane by solidifying and subsequently washing, drying and winding, a component (crosslinking agent) capable of providing free radicals is added to the spinning dope, and a hydrophilic polymer is added to the internal coagulating solution. It is done. The hollow fiber membrane of the present invention is exposed to water vapor at 100 to 121 ° C. for 1 to 15 minutes, and has a change rate of solute rejection performance and a rate of change of water permeability of 50% or less, and thus has excellent durability against steam.

Description

Polysulfone-based hollow fiber membrane with excellent durability for steam, and a process of preparing for the same

The present invention relates to a polysulfone-based hollow fiber membrane having excellent durability against steam and a method for producing the same. Polysulfone resins are widely used as hollow fiber membrane materials for various applications because of their excellent physical properties and performance as separators.

In general, the two most important performances of membranes are the resolution that determines how effectively the target material is removed and the permeability that determines how much can be processed for efficient separation. admit. Polysulfone hollow fiber membranes are produced by spinning a spinning dope and an internal coagulating solution composed of polysulfone resin, an organic solvent and an additive into the air with a double-tubular nozzle, then solidifying it with an external coagulating solution, washing, drying and winding. The pore shape of the hollow fiber membrane thus prepared is mainly circular, and its removal ability and permeability are mainly determined by its size and distribution.

On the other hand, the hollow fiber membrane prepared by generating the phase separation by wet and dry spinning as described above has a disadvantage in that the pure water permeability is sharp when exposed to high temperature steam due to low mechanical strength and low durability to steam.

In order to improve this, various methods have been studied. However, when the composition of the hollow fiber membrane is improved in order to compensate for the mechanical strength, a problem arises in that the pure permeability of the hollow fiber membrane is reduced. In addition, since the hollow fiber membrane itself is hydrophobic, it was difficult to improve the exclusion performance and the pure permeation performance simultaneously.

As a conventional technique for imparting hydrophilicity to polysulfone-based hollow fiber membranes, U.S. Patent No. 4,340,482 describes a method for grafting hydrophilic monomers to the surface of a separator, and Japanese Patent Application Laid-Open Nos. 60-246812 and 62-011503. After preparing a membrane made of hydrophobic resin, the membrane is immersed in a humectant solution made of a hydrophilic material or a surfactant and then dried to impart hydrophilicity to the membrane made of hydrophobic resin.

In addition, US Pat. No. 5,340,480 proposes a method of imparting hydrophilicity to a separator by crosslinking a hydrophilic polymer such as polyvinylpyrrolidone at the surface of the separator. Recently, Japanese Patent Laid-Open No. 59-186604 proposes a method of hydrophilizing a surface of a separator by plasma discharge treatment.

In addition, the prior art for producing a polysulfone-based hollow fiber membrane having excellent durability to steam is irradiated with gamma rays on the hollow fiber membrane, the high-temperature heat treatment or high temperature alkali treatment, or treated with persulfate in the hollow fiber membrane Methods of crosslinking hydrophilic polymers are known.

However, the above conventional methods all relate to a method of post-treatment of the manufactured hollow fiber membrane, which requires a complicated process. Specifically, when the polyvinylpyrrolidone is used to hydrophilize the hollow fiber membrane, the effect is not certain, and there is a disadvantage in that waste of expensive polyvinylpyrrolidone is severe. Moreover, the operation of fixing a hydrophilic monomer to a separator using a crosslinking agent is also complicated. In addition, the conventional method of crosslinking a hydrophilic polymer by heat treatment or radiation treatment has a problem that requires expensive equipment.

As described above, the hydrophilic treatment process of the hydrophobic polysulfone resin is not only complicated, but also the hydrophilization effect is not satisfactory, and the mechanical strength of the manufactured hollow fiber membrane and the durability against steam are not excellent. An object of the present invention is to provide a polysulfone-based hollow fiber membrane having excellent mechanical strength, steam resistance and membrane performance at the same time to solve such conventional problems.

The present invention does not crosslink the hydrophilic polymer in the hollow fiber membrane after preparing the polysulfone hollow fiber membrane, but crosslinks the hydrophilic polymer in the hollow fiber membrane during the manufacturing process of the hollow fiber membrane and thus has excellent durability against steam. It is intended to produce a phone-based hollow fiber membrane. To this end, in the present invention, polysulfone hollow fiber membranes are prepared by adding a component (crosslinking agent) capable of providing free radicals to a spinning dope, and adding a hydrophilic polymer to an internal coagulating solution. In another aspect, the present invention is to provide a polysulfone hollow fiber membrane having a water permeability change rate and solute exclusion performance change rate of 50% or less after being exposed to water for 1 to 15 minutes in the water vapor of 100 ~ 121 ℃.

The method for producing a polysulfone hollow fiber membrane of the present invention for achieving the above object is an internal coagulation solution composed of a spinning dope composed of a polysulfone polymer, an organic solvent and an additive and a solution containing a glycol compound or a glycol compound. In the production of a polysulfone hollow fiber membrane by spinning in air with a double-tubular nozzle and then solidifying with an external coagulant solution, followed by washing, drying and winding, a component (crosslinking agent) capable of providing free radicals is added to the spinning dope. The internal coagulating solution is characterized in that the addition of a hydrophilic polymer. In addition, the polysulfone-based hollow fiber membrane of the present invention is characterized in that the rate of change of solute excretion performance and the rate of change in water permeability after exposure to water vapor at 100-121 ° C. for 1-15 minutes.

EMBODIMENT OF THE INVENTION Hereinafter, this invention is demonstrated in detail.

First, in the present invention, in preparing a spinning dope by dissolving a polysulfone polymer and an additive in an organic solvent, a spinning dope is prepared by adding a component (crosslinking agent) which can provide free radicals in the additive. The component that provides free radicals added to the spinning dope serves as a crosslinking agent for crosslinking the hydrophilic polymer added in the internal coagulating solution during the hollow fiber membrane manufacturing process.

As a component (crosslinking agent) that can provide free radicals, persulfates such as potassium sulfate or peroxides such as hydrogen peroxide are used. The amount of crosslinking agent which can provide free radicals is preferably 3 to 20% by weight based on the total weight of the spinning dope. If it is out of the above range, the crosslinking effect may be insignificant or the coagulation effect may be lowered.

In addition, polysulfone or polyester sulfone resin is used as the polysulfone polymer. Optionally, additives to be added may include inorganic salts, alcohol compounds, polyethylene glycol, polyvinyl alcohol, and the like.

The spinning dope is preferably 10 to 50% by weight of polysulfone resin, 20 to 86% by weight of an organic solvent, 3 to 20% by weight of a component capable of providing free radicals, and about 1 to 10% by weight of other additives. However, the present invention does not limit the composition ratio of the spinning dope to this.

Next, the spinning dope and the internal coagulating solution prepared above are spun into the air through a conventional double-tubular nozzle, and then coagulated with an external coagulating solution, washed with a washing tank to remove the solvent and additives, and dried and wound to form a hollow fiber membrane. Manufacture.

In the present invention, a glycol compound or a solution containing a glycol compound in which a hydrophilic polymer is added is used as the internal coagulating solution. In this case, it is preferable to use a polyvinylpyrrolidone-based resin having a molecular weight of 30,000 to 300,000 as the hydrophilic polymer. Specifically, in the present invention, 4 to 6% by weight of a hydrophilic polymer is added to a solution containing a glycol compound or a glycol compound and used as an internal coagulation solution. For example, polyvinylpyrrolidone is added to a mixed solution of diethylene glycol and water and used for the internal coagulation solution.

As the external coagulant, a non-solvent of polysulfone is used. In particular, water is preferably used. The double tubular nozzle may use an annular nozzle detention having an outer diameter of 0.30 to 0.40 mm, an inner diameter of 0.15 to 0.25 mm, and an inner nozzle of about 0.10 to 0.20 mm in diameter.

When the spinning dope and the internal coagulating solution are radiated through the double-tubular nozzle, the hydrophilic polymer mixed in the internal coagulating solution passes through the spinning dope and diffuses into the external coagulating solution to provide free radicals mixed with the spinning dope. It is immobilized to the membrane while being crosslinked by the component (crosslinking agent).

The hydrophilic polymer added to the internal coagulating solution, that is, polyvinylpyrrolidone-based resin has a structure as shown in the following general formula (I), and since the pyrrolidone ring has a resonance structure, the nitrogen atom in the ring structure is electrically positive. It becomes

(Ⅰ)

When free radicals approach such vinylpyrrolidone-based polymers, they attack and separate hydrogen atoms bonded to a pyrrolidone ring or the same carbon atom, and free radicals bind to form polymer radicals and continuously crosslink. Is done. For example, polyvinylpyrrolidone is cross-linked by a potassium persulfate through a three-step process as follows.

1st step

2 step

3 steps

Since the hollow fiber membrane obtained through the present invention has a strong durability against steam compared to the hollow fiber membrane according to the conventional manufacturing method, there is an advantage that the change in water permeability and solute rejection does not occur or the change is small even after steam contact. In particular, polysulfone-based hollow fiber membranes can be produced that maintain excellent water permeability and solute rejection even after steam sterilization.

The polysulfone hollow fiber membrane of the present invention prepared as described above is exposed to water vapor at 100 to 121 ° C. for 1 to 15 minutes, and the change rate of solute excretion performance and the change rate of water permeability are 50% or less.

Various physical properties of the hollow fiber membranes prepared through the present invention were evaluated as follows.

ㆍ Permeability Evaluation

A small module having a hollow fiber membrane having an effective length of 15 to 25 cm was measured at 25 ° C. by flowing 1.0 kg / cm 2 of pure water in an internal pressurizing type at a constant time to measure the amount of permeation through the hollow fiber membrane.

ㆍ Solute exclusion rate evaluation

After preparing the same module as in the water transmittance, 200 ppm of vitamin B ₁₂ (Vitamin B ₁₂ , molecular weight), cytochrome-C (Cytochrome-C, molecular weight) and Ovalbumin-albumin from chicken egg (molecular weight 45,000) The aqueous solution of the concentration was permeated in the same manner as the above water transmittance, and the concentration ratio of the protein in the stock solution and the permeate was measured using the UV spectrum, and then calculated using the following formula (II).

% Solute rejection × 100 (Ⅱ)

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

Example 1

22 wt% of polysulfone resin (P-3500: Amoko Co., Ltd.), 7 wt% of hydrogen peroxide, and 5 wt% of polyethylene glycol were added to 66 wt% of dimethylacetamide, followed by stirring and dissolution to prepare a transparent spinning dope. The spinning stock solution is discharged at a rate of 2.5 g / min from the annular slit mold having an outer diameter of 0.35 mm, inner diameter of 0.2 mm, and inner nozzle diameter of 0.15 mm. At the same time, the internal coagulating solution prepared by adding and dissolving 70% by weight of diethylene glycol and 5% by weight of polyvinylpyrrolidone to 25% by weight of water from the internal nozzle was injected at a rate of 2.4 g / minute. After passing through the air gap of 10cm and guided the hollow fiber to the coagulation bath (water) of 25 ℃ washed by coagulation and wound up in a failure shape at a winding speed of 50m / min. The results of measuring the water permeability and solute excretion of the prepared polysulfone hollow fiber membrane are shown in Table 1, and the results of measuring the water permeability and solute excretion rate of the membrane after exposing the hollow fiber membrane to steam at 10O < 0 > C for 10 min. Same as 2.

Example 2

23 wt% of polysulfone resin (P-3500: Amoko Co., Ltd.), 7 wt% of potassium sulfate and 70 wt% of dimethylacetamide were added to 66 wt% of dimethylacetamide, and then stirred and dissolved to prepare a transparent spinning dope. . The spinning stock solution is discharged at a rate of 2.5 g / min from the annular slit mold having an outer diameter of 0.35 mm, inner diameter of 0.2 mm, and inner nozzle diameter of 0.15 mm. At the same time, the internal coagulating solution prepared by adding and dissolving 70% by weight of diethylene glycol and 5% by weight of polyvinylpyrrolidone to 25% by weight of water from the internal nozzle was injected at a rate of 2.4 g / minute. After passing through the air gap of 10cm and guided the hollow fiber to the coagulation bath (water) of 25 ℃ washed by coagulation and wound up in a failure shape at a winding speed of 50m / min. The results of measuring the water permeability and solute excretion of the prepared polysulfone hollow fiber membrane are shown in Table 1, and the results of measuring the water permeability and solute excretion rate of the membrane after exposing the hollow fiber membrane to steam at 105 ° C. for 10 minutes. Same as 2.

Comparative Example 1

22 wt% of polysulfone resin (P-3500: Amoko Co., Ltd.), 7 wt% of polyvinylpyrrolidone, and 5 wt% of polyethylene glycol were added to 66 wt% of dimethylacetamide, followed by stirring and dissolving. Manufacture. The spinning stock solution is discharged at a rate of 2.5 g / min from the annular slit mold having an outer diameter of 0.35 mm, inner diameter of 0.2 mm, and inner nozzle diameter of 0.15 mm. At the same time, 70% by weight of diethylene glycol was added to 30% by weight of water from the internal nozzle, and the internal coagulation solution was injected at a rate of 2.4 g / minute. After passing through the air gap of 10cm and guided the hollow fiber to the coagulation bath (water) of 25 ℃ washed by coagulation and wound up in a failure shape at a winding speed of 50m / min. The results of measuring the water permeability and solute excretion of the prepared polysulfone hollow fiber membrane are shown in Table 1, and the results of measuring the water permeability and solute excretion rate of the membrane after exposing the hollow fiber membrane to steam at 10O < 0 > C for 10 min. Same as 2.

Membrane Performance Before Vapor Exposure division Example 1 Example 2 Comparative Example 1 Water transmittance (ml / mmHg cm 2 min) 0.105 0.072 0.104 % Rejection Vitamin B ₁₂ 3 5 36 Cytochrome-C 32 45 95 Ovalbumin 95 98 -

Membrane Performance after Vapor Exposure division Example 1 Example 2 Comparative Example 1 Water transmittance (ml / mmHg cm 2 min) 0.097 0.061 0.0034 % Rejection Vitamin B ₁₂ 4 8 60 Cytochrome-C 42 52 99 Ovalbumin 99 99 -

The polysulfone hollow fiber membrane of the present invention is excellent in steam durability, mechanical strength and membrane performance. In addition, the manufacturing method of the present invention does not require expensive equipment, and can produce a polysulfone-based hollow fiber membrane having excellent durability against steam by a simple process.

Claims (6)

The internal coagulating solution consisting of a spinning dope composed of a polysulfone polymer, an organic solvent and an additive, and a glycol compound or a solution containing a glycol compound is spun into air with a double-tubular nozzle, and then solidified with an external coagulating solution and then washed. In preparing the polysulfone hollow fiber membrane by drying and winding, 3 to 20% by weight of Persulfate or Peroxide, which is a component (crosslinking agent) capable of providing free radicals, is added to the spinning dope. 4 to 6% by weight of a polyvinylpyrrolidone resin having a molecular weight of 30,000 to 300,000, which is a hydrophilic polymer, is added to the solid solution. delete delete delete delete Polysulfone-based hollow fiber with excellent steam durability, characterized in that the change rate of solute rejection performance and the water permeability change rate is 0 to 50% after being exposed to water vapor at 100 to 121 ° C. for 1 to 15 minutes. membrane.