JPH01151905A - Sterilizing method for liquid permeation membrane - Google Patents

Abstract

PURPOSE:To prevent deterioration of a membrane due to oxidizing action of hydrogen peroxide in an extremely simple process and to prolong service life of the membrane by immersing the liquid permeation membrane in acidic liquid maintaining 3pH or below and washing it before subjecting it to sterilization treatment by hydrogen peroxide. CONSTITUTION:In the case of sterilizing a hollow yarn-shaped or lamellate liquid permeation membrane made of polysulfone-base resin by hydrogen peroxide, it is immersed in acid liquid (hydrochloric acid aq., soln. etc.,) having <=3pH and washed before sterilization treatment. So far metallic ions such as platinum, iron and copper contained in water to be used are accumulated on the surface or to the inside of the membrane and deterioration of the membrane has been caused by oxidizing action of hydrogen peroxide generated by catalytic action thereof. Therefor, when treating the membrane with acidic liquid like this invention, metallic impurities or metallic deposit existing on the permeation membrane can be dissolved into acidic liquid and thereby deterioration of the membrane is not caused even in sterilization by hydrogen peroxide.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a method for sterilizing liquid permeable membranes using hydrogen peroxide, and more particularly to a method for sterilizing liquid permeable membranes using hydrogen peroxide. This invention relates to a method for sterilizing membranes.

[Conventional technology]

In recent years, the development of liquid permeable membranes has been remarkable, and ultrafiltration membranes, precision filtration membranes, and the like having various permeation characteristics have been developed. Depending on the use, these membranes may become contaminated with bacteria, proteins, etc., and must be sterilized with chemicals or the like. Hydrogen peroxide solution, which has strong sterilizing power and is relatively clean, is generally used for sterilization.

It is frequently used to sterilize ultrapure water production equipment and final filters in the electronics industry, and usually contains 1 to 5%.
Hydrogen peroxide solution is filled into the entire device or only the liquid permeable membrane module to be sterilized and left at room temperature for several hours to sterilize. Such sterilization is often performed on a weekly or at least monthly basis.

By the way, since hydrogen peroxide is both a disinfectant and a strong oxidizing agent, it tends to exert an oxidizing effect on the surrounding area.

The piping of devices equipped with liquid permeable membranes is usually made of stainless steel, PVC, PP, PVDF, PTFA, etc., and with 1 to 5% hydrogen peroxide, there is practically no effect from oxidation. On the other hand, among liquid permeable membranes, polysulfone, polyethersulfone, PMMASPAN
It is generally said that membranes made of SPP or PE are hardly affected by oxidation in 1 to 5% hydrogen peroxide solution at room temperature.

[Problem that the invention seeks to solve]

However, hydrogen peroxide exhibits a very strong oxidizing effect in the presence of metals such as platinum, iron, copper, and nickel, so hydrogen peroxide can be used to remove metals dissolved in water, colloidal metal ion hydroxides, and particulate metals. When metals, metal oxides, etc. adhere to or are captured on the surface or inside of the film, they exert a strong oxidizing effect on the film. In particular, since the skin layer of the membrane is very thin and has a fine surface structure, there is a problem in that if a slight structural change in the membrane due to oxidation occurs, it will seriously affect the membrane's inherent permeability characteristics. Furthermore, when sterilization with hydrogen peroxide solution is repeated, the permeation characteristics of the membrane change significantly due to the reasons mentioned above, resulting in a problem in that the life of the membrane is significantly shortened.

Such changes in the permeability properties of the membrane will result in defects in products using the membrane. Further, since liquid permeable membrane modules are very expensive, shortening the life of the membrane is quite disadvantageous in terms of cost.

SUMMARY OF THE INVENTION An object of the present invention is to provide an improved sterilization method for liquid permeable membranes in which the membranes are not deteriorated by hydrogen peroxide.

[Means for solving problems]

As a result of intensive study and research into the above-mentioned problems, the present inventors have discovered a method that allows sterilization without deteriorating the membrane by applying a specific pretreatment to the sterilization method using hydrogen peroxide.

That is, the present invention provides a method for sterilizing a liquid permeable membrane using hydrogen peroxide, which is characterized in that, before the liquid permeable membrane is sterilized with hydrogen peroxide, the liquid permeable membrane is immersed in an acidic solution having a pH of 3 or less for cleaning. A method for sterilizing membranes is provided.

The material of the membrane that can be sterilized by the method of the present invention is not particularly limited as long as it has acid resistance, and examples include polysulfone resins, polyethersulfone resins, polyacrylonitrile resins, polyimide resins, and polymethyl methacrylic resins. Examples include resin, polyolefin resin, silicone rubber, etc. In the present invention, polysulfone-based resins and polyethersulfone-based resins are preferred because they have particularly high acid resistance and are often used as filter materials for the electronic industry, which require frequent sterilization with hydrogen peroxide.

Furthermore, the liquid permeable membrane may be of any type.

For example, membranes are classified into ultrafiltration membranes, microfiltration membranes, reverse osmosis membranes, etc. depending on the size of particles or molecules that permeate, and any of these membranes can be used. In addition, depending on the shape of the membrane, hollow fiber membranes,
There are flat membranes, etc., and any of them can be used.

The acidic liquid used in the present invention is not particularly limited, and inorganic acids such as hydrochloric acid, sulfuric acid, and acetic acid, and organic acids such as organic sulfonic acid can be used, and aqueous solutions thereof and mixtures containing them may also be used. In the present invention, hydrochloric acid is preferred because when it is made into an aqueous solution, it has a high degree of acid dissociation, it is an inorganic acid and therefore does not act like a solvent on the membrane, and it is common and easy to handle.

It is preferable that the pi of the acidic liquid is 3 or less. If the pH of the acidic liquid exceeds 3, it takes a long time to dissolve metals, metal oxides, metal hydroxides, etc., which is not preferred because it is not practical.

According to the sterilization method of the present invention, the material is immersed in the above acidic solution and then washed. It is preferable to use ultrapure water for this cleaning in order to prevent metals and the like contained in the water from re-depositing.

In the present invention, sterilization using hydrogen peroxide may be carried out by a method similar to a commonly used sterilization method using hydrogen peroxide.

[For production]

Hydrogen peroxide is an oxidizing agent used for sterilization, but it is known that the presence of certain metals, such as platinum, iron, copper, nickel, etc., increases its oxidizing effect due to its catalytic action. These metals are contained in the water that is normally used, and colloidal hydroxides of the metal ions and solid metals or metal oxides may accumulate without passing through the membrane of the liquid permeable membrane module. It may adhere to the membrane surface or inside. If sterilization with hydrogen peroxide is performed in such a state, hydrogen peroxide not only has a sterilizing effect but also has a strong oxidizing effect on the membrane, causing it to deteriorate.

In addition, it is highly likely that the metal impurities mentioned above are mixed in during the manufacturing process of liquid permeable membranes, and even in such cases, the metal impurities attached to the membrane act as a catalyst, deteriorating the membrane and causing damage to the membrane. This will reduce performance.

Therefore, it is required to effectively remove metal impurities adhering to a liquid permeable membrane before sterilizing it with hydrogen peroxide, and the present invention was completed in response to this requirement.

By treating with an acidic solution according to the present invention, metallic impurities or metallic deposits on the semipermeable membrane can be dissolved in the acidic solution, and the membrane will not deteriorate even when sterilized with hydrogen peroxide. .

〔Example〕

Hereinafter, the present invention will be explained in detail with reference to examples, but the present invention is not limited to these examples.

Liquid permeable membranes used in the following Examples and Comparative Examples were manufactured as follows.

Pano & Polyether Sulfone (300P powder manufactured by IC1)
20% by weight, polyethylene glycol (average molecular weight 20
0) 20% by weight, dimethyl sulfoxide (hereinafter referred to as DMS)
A spinning stock solution having a composition of 60% by weight (abbreviated as O) was extruded into water through a double annular nozzle using a mixed solution of 50% by weight of DNS0 and 50% by weight of water as an internal coagulation liquid. At this time, the temperature of the stock solution and the internal coagulating liquid was adjusted to 25°C, and the temperature of the external coagulating liquid was adjusted to 40°C. The hollow fiber thus obtained has an inner diameter of 500 μm and an outer diameter of 800 t1m,
It was immersed in pure water.

Example 1 After filtering 1001/rd city water using the hollow fiber membrane obtained in the above production example, it was immersed in a 0.6N hydrochloric acid aqueous solution at room temperature for 1 hour. Thereafter, after thoroughly washing with ultrapure water to remove hydrochloric acid, it was immersed in a 5% HtOt aqueous solution for 140 hours. The breaking strength of 10 hollow fiber membranes sterilized in this way was measured. The results are shown in Table 1.

Example 2 After filtering 1001/rd city water using the hollow fiber membrane obtained in the above production example, it was immersed in an aqueous hydrochloric acid solution of Q and OIN at room temperature for 2 hours. Thereafter, after thoroughly washing with ultrapure water to remove hydrochloric acid, it was immersed in a 5% HtOt aqueous solution for 140 hours. The breaking strength of 10 hollow fiber membranes sterilized in this way was measured. The results are shown in Table 1.

Example 3 After filtering ultrapure water at 100 f/nf through the hollow fiber membrane obtained in the above production example, it was immersed in a 0.6N hydrochloric acid aqueous solution at room temperature for 1 hour. Thereafter, after thoroughly washing with ultrapure water to remove hydrochloric acid, it was immersed in a 5% H80□ aqueous solution for 140 hours.

The breaking strength of 10 hollow fiber membranes sterilized in this way was measured. The results are shown in Table 1.

Comparative Example 1 The sample was sterilized in the same manner as in Example 1, except that it was not immersed in an aqueous hydrochloric acid solution, and its breaking strength was measured.

The results are shown in Table 1.

When compared with Examples 2 and 3, it is clear that in this comparative example, the film strength was reduced due to the oxidizing action of hydrogen peroxide, since no treatment with an acidic solution was performed.

Comparative Example 2 It was sterilized in the same manner as in Example 3, except that it was not immersed in an aqueous hydrochloric acid solution, and its breaking strength was measured.

The results are shown in Table 1.

In this comparative example, since no treatment with an acidic solution was performed, it is clear that the film strength was lowered due to the oxidizing action of hydrogen peroxide compared to Example 3. In addition, comparative example 1
The reason why the film strength is higher than that in Comparative Example 1 is thought to be that metallic deposits increase due to the use of city water.

Table 1 [Effects of the invention] As explained above, according to the sterilization method of the present invention,
Deterioration of the membrane due to the oxidizing action of hydrogen peroxide can be prevented by simply adopting an extremely simple process of immersing it in an acidic solution. Therefore, the life of the liquid permeable membrane can be extended, which is also economically advantageous.

Claims (3)

[Claims] (1) A method for sterilizing a liquid-permeable membrane using hydrogen peroxide, which comprises washing the liquid-permeable membrane by immersing it in an acidic solution with a pH of 3 or less before sterilizing the liquid-permeable membrane with hydrogen peroxide. . (2) The method for sterilizing a liquid permeable membrane according to claim 1, wherein the liquid permeable membrane is a membrane made of polyethersulfone resin or polysulfone resin. (3) The method for sterilizing a liquid permeable membrane according to claim 1 or 2, wherein the acidic liquid is an aqueous hydrochloric acid solution.