JPH0780260A - Treatment of reverse osmosis membrane and reverse osmosis membrane separation element - Google Patents

Abstract

PURPOSE:To prevent the elution of impurities from a membrane separation element and to use the membrane separation element in the rear stage of an ion exchange resin and just before a use point by washing a reverse osmosis membrane with hot pure water. CONSTITUTION:The reverse osmosis membrane being the impurity generating source of a reverse osmosis membrane separation element is washed with hot pure water. Hot pure water is easy to penetrate even into complicated pores because it becomes low in viscosity and has effect promoting the diffusion of impurities bonded to the interiors of pares because of high temp. The washing with hot pure water is effective for removing the org. acid being an org. amine component, an org. acid chloride component and a hydrolysate of them adsorbed on the permeation side of the membrane separation element and extremely effective for reducing the concns. of an ionic substance and a TOC component.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a reverse osmosis membrane for producing high-purity ultrapure water and a membrane separation element comprising the reverse osmosis membrane, which requires that impurities existing in water be as small as possible. .

[0002]

2. Description of the Related Art In recent years, the demand for ultrapure water is rapidly increasing in the fields of medical care, electronic equipment, precision equipment, etc.
In the electronic industry that produces semiconductors and ultra LSIs, a large amount of ultrapure water is required for cleaning semiconductor wafers, which are intermediate products of the electronic industry.

As this ultrapure water, water having an ion, TOC (total organic carbon) component and dissolved silica concentration of ppb or less and fine particles of the order of several / ml is used. However, this water quality greatly affects the yield of products.

Conventionally, as the ultrapure water, raw water such as industrial water, city water, well water, tap water, etc., is used for coagulating sedimentation device, sand filter, ion exchange resin, reverse osmosis device, ultrafiltration device. Pure water is obtained by a pure water treatment device that is a combination of a degassing device, an ultraviolet irradiation device, a mixed bed polisher, etc., and is further processed by a precision filtration device or an ultrafiltration device immediately before the point of use. I was using the one that was given.

However, in recent years, as the degree of integration of LSIs has increased, the demand for water quality of ultrapure water has become more stringent in order to improve the yield. In particular, reduction of ionic substances and TOC components is an important issue. For this reason, the reverse osmosis device, which has a high efficiency of removing these impurities, is installed not only before the ion-exchange resin, which is the conventional installation location, but also after the ion-exchange resin or immediately before the point of use to remove the eluate. Is increasing.

The characteristics required for the reverse osmosis device used in the latter stage of the ion exchange resin are that impurities (ionic substances, TOC components, fine particles, etc.) elute from the device itself as little as possible, TOC components, etc. It is mentioned that the exclusion rate of impurities is high and the membrane flux is large.

However, when a reverse osmosis membrane separation element generally used in this reverse osmosis apparatus is applied, impurities on the raw water side are removed, but impurities are generated from the separation element itself, and the total impurities are In some cases, it could not be said to have been removed.

For example, when the reverse osmosis device is introduced into an ultrapure water production system, it is necessary to wash the treated water with ultrapure water until the impurity concentration (ionic substance, TOC component, etc.) becomes the same level as the raw water. However, if the time required to reach the same level, that is, the so-called rising time becomes long, a large amount of expensive ultrapure water treated by the various devices described above is consumed, and the product water cannot be obtained during that time. Therefore, there is a great economic loss including the loss of opportunity, and its improvement has been required.

[0009]

SUMMARY OF THE INVENTION In order to improve the above-mentioned drawbacks of the prior art, the present invention uses hot pure water for the reverse osmosis membrane, which is a source of impurities in the reverse osmosis membrane separation element, and the separation element constituent member. It is an object of the present invention to provide a clean reverse osmosis membrane separation element which can be prevented from eluting impurities from the membrane separation element by washing and can be used in the subsequent stage of the ion exchange resin and immediately before the point of use.

[0010]

In order to achieve the above object, the present invention has the following constitution.

"(1) A method for treating a reverse osmosis membrane, which comprises washing the reverse osmosis membrane with hot pure water.

(2) A method for treating a reverse osmosis membrane separation element, which comprises cleaning the apparatus with a reverse osmosis membrane as a separation element and then using hot pure water. Hereinafter, the present invention will be described in detail.

Usually, as an elution source of impurities, particularly ionic substances and TOC components from the membrane separation element, the organic solvent remaining at the time of film formation of the porous support, and the group composed of fibers used for the support Examples thereof include eluate from the material itself, eluate from the separation element constituent member, and residual monomer component which is an unreacted substance at the time of forming the functional film layer, and the influence of the residual monomer is particularly large.

As the residual monomer, an organic amine component,
Representative examples include an organic acid chloride component and an organic acid that is a hydrolysis product thereof. This residual monomer is adhered or adsorbed as an impurity to the substrate composed of the porous support and its fibers, the separation element constituent member, the functional membrane, etc., of which the one existing on the permeation side of the membrane separation element Is a problem. In particular, impurities adhering to or adsorbing in the pores of the porous support or in the interstices of the texture of the base material are difficult to replace with washing water and have a slow diffusion rate, so that washing with pure water at room temperature is difficult. is there.

Hot pure water has the effect of facilitating the diffusion of impurities adhering to the pores because of the high temperature because the viscosity of the water is low and it is easy to penetrate even in complicated pores. Cleaning with hot pure water is effective in removing organic amine components adsorbed on the permeation side of the membrane separation element, organic acid chloride components, and organic acids that are hydrolysis products thereof, and reduces the concentration of ionic substances and TOC components. Very effective.

The reverse osmosis membrane to which the treatment method of the present invention can be applied is not particularly limited, and examples thereof include a composite type reverse osmosis membrane. The composite type reverse osmosis membrane is one in which a functional membrane layer that controls separation is formed on a porous support by an interfacial polycondensation reaction, a crosslinking reaction, a polymer coating, a monomer polymerization method or the like. The functional film layer has a thickness of 10000 angstroms or less, and is generally a nonporous dense layer having fine pores of several angstroms to several tens angstroms or no pores. Examples of the porous support include a dense layer having fine pores on one side and a membrane having an asymmetric structure having pores having a larger pore size on the other side. The support may be a flat film or a hollow fiber, and in the case of a flat film, it may be lined with a base material composed of fibers such as woven fabric and nonwoven fabric.

As a material for the porous support, polysulfone, polyether sulfone, polyphenylene sulfide sulfone, polymers having a sulfone group such as polyphenylene sulfone, polyether polymers such as polyphenylene oxide, thioether polymers such as polyphenylene sulfide, polyacrylonitrile. Known materials such as vinyl polymers such as, polyamides such as nylon 6 and nylon 66, polyesters such as polyethylene terephthalate and polybutylene terephthalate, and imide polymers such as polyimide are listed.

The components of the functional film layer include crosslinked polyamide, aromatic polyamide, crosslinked wholly aromatic polyamide, polyamic acid, polyimide, polyamide hydrazide, polyimidazolone, polysulfonamide, polybenzimidazole, polyarylene oxide, and cellulose acetate. Is mentioned.

The form of the membrane may be a known form such as a flat membrane, a tubular membrane or a hollow fiber membrane. Further, the membrane separation element is one in which these flat membrane, tubular membrane, hollow fiber membrane and the like are incorporated together with other members such as a support plate, net and outer cylinder. The form thereof may be a known form such as a plate and frame type, a spiral type, a tubular type, or a hollow fiber type, but the present invention is not influenced by these forms.

The temperature of the hot pure water used in the present invention is 40-9.
A range of 0 ° C is desirable. Considering the values of viscosity and diffusion coefficient, it is desirable that the temperature of hot pure water is as high as possible.
If the temperature exceeds 90 ° C, the film performance tends to deteriorate.

Pure water for producing hot pure water preferably has a specific resistance value of 10 MΩ · cm or more and a TOC component concentration of 50 ppb or less, which indicates the concentration of an ionic substance, and has a large specific resistance value and a TOC component concentration of as high as possible. More preferably, it is as small as possible.

As a cleaning method, in the case of a film, a method of immersing in a hot pure water for a predetermined time can be mentioned. As the immersion method,
Long flat membranes, hollow fibers are sequentially and continuously dipped, rolls wound to a predetermined length, dipping together with a bundle, and dipping after cutting or cutting the film to a predetermined size. .
Although the dipping time is not particularly limited, it is appropriate to be about 30 seconds or more and 6 hours or less, and rinsing with ultrapure water after cleaning may be performed.

In the case of the separation element, there are a dipping method which is carried out in the same procedure as the membrane, and a method in which the separation element is loaded in a reverse osmosis apparatus and then the circulation operation is performed. When the circulating operation is performed, the amount of the hot pure water is preferably 5 times or more the volume of the separation element, and the larger the amount, the more preferable. More preferably, one-pass cleaning in which non-permeated water and permeated water are blown is preferable. The operating pressure is increased by a pump to such an extent that the hot pure water flows to the permeation side of the separation element. However, when pressure is applied with hot water, the amount of fresh water produced decreases.
A minimum pressure is preferred. The longer the cleaning time is, the more preferable, and the time is preferably 1 hour or more. However, considering the time and energy required for the cleaning, 1 to 3 hours is more preferable. After washing, washing (rinsing) may be performed with ultrapure water while blowing non-permeable water and permeated water.

[0024]

【Example】

Example 1 Examples will be shown below, but the present invention is not limited thereto.

As a reverse osmosis device, a spiral separation element of a composite type reverse osmosis membrane in which a crosslinked polyamide functional membrane layer is formed on the surface of a polysulfone support membrane by an interfacial polycondensation reaction is used.
The following experiment was conducted.

As a cleaning method, hot water at 60 ° C. is circulated for 1 hour, left for 1 hour, and then washed with ultrapure water for 2 hours.
Rinse for 2 hours. The washed reverse osmosis membrane separation element was loaded into the apparatus, and the specific resistance value was 18.0 MΩ · cm, T
Ultrapure water with an OC concentration of 10 to 30 ppb is used at a pressure of 15 kg / c.
It was supplied under the conditions of m ² and a flow rate of 240 liters / hour. As a result of measuring the quality of the permeated water, it took 8 hours for the resistivity to be the same as the raw water level, and 3 hours for the TOC concentration to be the same.
It was time.

For comparison, the same experiment was carried out using the reverse osmosis membrane separation element according to the present invention, which was not washed, and the specific resistance value was the same as the raw water level for 3 hours.
It was 6 hours, and the time when the TOC concentrations were the same was 24 hours.

[0028]

As described above, according to the method for treating a membrane and a membrane separation element of the present invention, generation of impurities from the membrane separation element itself can be significantly reduced, so that the concentration of impurities in treated water (ionic substance, TOC It is possible to drastically shorten the rise time until components (such as components) reach the same level as raw water, and it is possible to significantly reduce the amount of ultrapure water and the cleaning time required for cleaning the membrane separation element during use. it can.

Claims (2)

[Claims] 1. A method for treating a reverse osmosis membrane, which comprises washing the reverse osmosis membrane with hot pure water. 2. A method for treating a reverse osmosis membrane separation element, characterized in that the reverse osmosis membrane is made into an apparatus as a separation element and then washed with hot pure water.