JP2527466B2 - Improved polysulfone-based separation membrane - Google Patents

Description

TECHNICAL FIELD The present invention relates to a polysulfone-based separation membrane having extremely excellent oxidation resistance, and more specifically, ethylenediaminetetraacetic acid capable of deactivating a metal oxidation catalyst activity. Alternatively, the present invention relates to a polysulfone-based liquid separation membrane having excellent oxidation resistance by containing a salt thereof, a derivative thereof, or a homologue thereof.

[Prior Art] In recent years, the development of liquid permeable membranes has been remarkable, and ultrafiltration membranes and precision permeable membranes having various permeation characteristics have been developed.
These membranes may be contaminated with bacteria, proteins, etc. during use, and may require sterilization or washing with an oxidizing agent or the like. As this oxidizing agent, for example, hydrogen peroxide solution, which is a relatively clean agent having a strong sterilizing power, is often used. In particular, hydrogen peroxide water is frequently used for sterilization of ultrapure water production equipment and final filters in the electronics industry, and usually the entire equipment or the liquid permeable membrane module to sterilize 1-5% hydrogen peroxide water is used. It is filled in and left for several hours at room temperature for sterilization. Such sterilization is often performed on a weekly or at least monthly basis.

By the way, hydrogen peroxide exerts an oxidizing effect on the surroundings at the same time as sterilization.

The piping of the device equipped with the liquid permeable membrane is usually stainless steel, polyvinyl chloride (PVC), polypropylene (PP),
Consisting of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), etc., 1-5%
In the case of the hydrogen peroxide solution, there is practically no effect due to the oxidizing action. On the other hand, among liquid permeable membranes, polysulfone, polyether sulfone, polymethylmethacrylate (PMMA),
Polyacrylonitrile (PAN), polypropylene (PP)
Also, with respect to a film made of polyethylene (PE), generally, 1-5% hydrogen peroxide solution at room temperature has almost no effect due to the oxidizing action.

[Problems to be Solved by the Invention]

However, oxidizers such as hydrogen peroxide are, for example,
In the presence of metals such as platinum, iron, copper, nickel, etc., it has a very strong oxidative effect, so that metals dissolved in water, colloidal metal ion hydroxides and particulate metals or metal oxides, etc. A strong oxidative effect is exerted on the film by being attached to the surface or inside the film or being captured by the film. In particular, since the skin layer of the film is extremely thin and has a fine surface structure, there has been a problem that the permeation characteristics peculiar to the film are seriously affected when a slight structural change or the like of the film occurs due to the oxidation action. Further, when the sterilization with a hydrogen peroxide solution is repeatedly performed, there has been a problem that the permeation characteristics of the membrane are largely changed due to the above-mentioned causes and the life of the membrane is significantly shortened.

This change in the transmission characteristics of the membrane causes a defect in the product using the membrane. Further, since the liquid permeable membrane module is extremely expensive, shortening the life of the membrane is considerably disadvantageous in terms of cost.

Therefore, an object of the present invention is to provide an improved polysulfone-based separation membrane which is excellent in oxidation resistance and whose performance hardly changes even when a reagent having an oxidizing property such as hydrogen peroxide is used.

[Means for solving the problem]

Means for Solving the Problems The inventors of the present invention have conducted extensive studies and researches to solve the above problems, and as a result, a film containing ethylenediaminetetraacetic acid or a salt or derivative thereof or a homologue thereof capable of deactivating the metal oxidation catalyst activity. However, they found that they exhibited excellent performance with respect to oxidation resistance, and completed the present invention.

That is, the present invention comprises 0.01 to 0.5% by weight of ethylenediaminetetraacetic acid, a salt thereof, a derivative thereof, or a homologue thereof capable of deactivating the metal oxidation catalyst activity, relative to the polymer weight of the separation membrane. The present invention provides a polysulfone-based separation membrane having improved oxidation resistance.

As the polysulfone-based separation membrane used in the present invention,
Examples thereof include a polymer compound having a structure represented by the following formula (I) or (II) and a derivative thereof.

Of these, the polyether sulfone represented by the formula (II) is particularly excellent in heat resistance and oxidation resistance and is a material suitable for use in the present invention.

Any kind of separation membrane may be used,
Examples thereof include ultrafiltration membranes and microfiltration membranes, and the separation pore diameter thereof may be in any range. Further, the shape of the membrane may be any of hollow fiber shape, flat membrane shape, tube shape, and the like, which can be used in the present invention.

The ethylenediaminetetraacetic acid, its salt, its derivative, or its homologue used in the present invention has an excellent effect of capturing heavy metals by forming a chelate, and is suitable for use in the present invention. As the salt of ethylenediaminetetraacetic acid, Na salt, Fe salt, Ca salt, etc., as the derivative of ethylenediaminetetraacetic acid, a special amine salt of ethylenediaminetetraacetic acid, ammonium salt, etc., as the homologue of ethylenediaminetetraacetic acid, the compounds shown below. Etc.

The method of incorporating such ethylenediaminetetraacetic acid or its salt or its derivative or its homolog in the membrane is not particularly limited, and it is chemically bonded to the membrane material to be mixed in the membrane at the time of membrane formation and used. Any method may be used such as coating the surface of the film with a polymeric metal scavenger which is then formed into a film. However, it is needless to say that the membrane produced in the present invention is used as a separation membrane and therefore must not impair the separation function.

The content of ethylenediaminetetraacetic acid or its salt or its derivative or its homolog in the separation membrane of the present invention is 0.01 to 0.5% by weight based on the polymer weight of the separation membrane.
Is preferable, and more preferably 0.02 to 0.2% by weight.
When the content is less than 0.01% by weight, the effect of improving the oxidation resistance is small, and when it is more than 0.5% by weight, the film performance changes, which is not preferable.

[Work]

An oxidizing agent such as hydrogen peroxide is used as a sterilizing agent or a cleaning agent for the membrane system, and the polysulfone-based separation membrane has excellent oxidation resistance. However, it is known that if a certain kind of metal such as platinum, iron, copper, nickel, etc. is present in the used liquid, its catalytic action increases the oxidizing action. These metals are contained in the water that is normally used. Among these, colloidal hydroxides of the above metal ions or solid metals or metal oxides are accumulated without permeating the membrane of the liquid permeable membrane module. May adhere to the film surface or inside. When sterilization with hydrogen peroxide is carried out in such a state, hydrogen peroxide exerts not only a bactericidal action but also a strong oxidizing action on the membrane, and also deteriorates the polysulfone-based membrane.

In addition, it is fully conceivable that the above-mentioned metal impurities are mixed in the manufacturing process of the liquid permeable membrane, and even in such a case, the metal impurities attached to the membrane as described above act as a catalyst to deteriorate the membrane and deteriorate the membrane. It will reduce the performance.

Therefore, it is required to effectively remove the catalytic activity of the metal adhering to the liquid permeable membrane before the treatment with the oxidizing substance, and the present invention has been completed from such requirements.

In the polysulfone-based separation membrane of the present invention, the catalytic activity of the metal is deactivated by ethylenediaminetetraacetic acid, its salt, its derivative or its homologue, so that the deterioration of the membrane performance due to the oxidizing agent can be prevented.

〔Example〕

Hereinafter, the present invention will be described in detail with reference to Examples, but the present invention is not limited thereto.

Example 1 Polysulfone (UCD, Udel Polysulfone P-1)
700) was dissolved in a mixed solvent of 2-pyrrolidone: N-methyl-2-pyrrolidone (weight ratio 1: 2), and polyethylene glycol (manufactured by Sanyo Kasei Co., Ltd., PEG-200) was added to 30% by weight, A 20 wt% polysulfone solution was prepared. To this solution, a metal chelating agent, ethylenediaminetetraacetic acid derivative (CLEWAT OH, manufactured by Teikoku Chemical Industry Co., Ltd.)
300) was added so that the weight ratio was 0.04% to obtain a uniform solution. Purified water was used as the internal coagulating liquid, and the running distance was set to 10 cm in the air. Then, the solution was extruded into an external coagulating liquid at 70 ° C. to obtain a hollow fiber. This hollow fiber was made into a length of 30 cm and 5,000 bundles were bundled, and both ends were bonded by a usual method to form a module.

The resulting module was immersed in 3% hydrogen peroxide at 25 ° C for 2 hours.
Soak for hours. After immersion, pass ultrapure water and measure the specific resistance of the membrane permeate. The difference with the raw water is about 0.5 MΩ in about 20 minutes.
・ In about 60 minutes, the resistivity value was almost the same as that of raw water.

Comparative Example 1 A hollow fiber membrane and a membrane module were prepared in the same manner as in Example 1 except that Clewat OH300 was not added.

Ultrapure water was passed through the membrane module through the membrane module after immersion in hydrogen peroxide solution in the same manner as in Example 1, and the recovery characteristics of the specific resistance were examined. It was found that the difference from the raw water reached 0.5 MΩ · cm. It took 30 minutes. It took about 75 minutes to show the same specific resistance within the measurement error range as the stock solution.

From the above, it is clear that the metal scavenger prevents oxidative deterioration of the film.

Example 2 Polyethersulfone (ICI, 5200P) 20% by weight,
20% by weight of polyethylene glycol (average molecular weight 200),
0.04% by weight of ethylenediaminetetraacetic acid derivative (Krewat OH300, manufactured by Teikoku Chemical Industry Co., Ltd.) was added to a spinning dope having a composition of 60% by weight of dimethyl sulfoxide (abbreviated as DMSO).
A homogeneous solution was obtained. This solution was extruded into water through a double ring nozzle as a mixed solution of 70 wt% DMSO and 30 wt% water as an internal coagulating liquid. At this time, the temperature of the stock solution and internal coagulation solution is 40
The temperature of the external coagulation liquid was adjusted to 60 ° C. The hollow fiber obtained had an inner diameter of 400 μm and an outer diameter of 680 μm. This hollow fiber was made into a bundle of 5000 pieces and both ends were adhered by a normal prescription to prepare a module.

The resulting module was immersed in 3% hydrogen peroxide at 25 ° C for 2 hours.
Soak for hours. After immersion, water was passed through the ultrapure water and the specific resistance of the permeated water was measured. The difference with the raw water was about 0.5 MΩ in about 20 minutes.
Within 50 cm and within about 50 minutes, the resistivity value was almost the same as that of raw water. This shows that the recovery time of the specific resistance value is faster than that of the film without the addition of Clewat OH300, and the deterioration of the film by oxidation is extremely small.

[Effects of the Invention] As described above, the hollow fiber membrane of the present invention has excellent oxidation resistance and can prevent oxidative deterioration of the membrane. Therefore,
Not only the reliability of the film is high, but also the life of the film can be extended and the economical merit is large.

Claims (1)

(57) [Claims] 1. An ethylenediaminetetraacetic acid, a salt thereof, a derivative thereof or a homologue thereof capable of deactivating a metal oxidation catalyst activity is contained in an amount of 0.01 to 0.5% by weight based on the weight of the polymer of the separation membrane. A polysulfone-based separation membrane with improved oxidation resistance.