JPH039798B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a method for producing ultrapure water.

[Prior Art] Conventionally, a method for producing ultrapure water has been carried out in two steps as follows. Raw water such as industrial water, city water, well water, tap water, and groundwater is treated with activated carbon to remove free chlorine, and the water is passed through a reverse osmosis device to an ion exchange resin to produce water with an electrical resistivity of approximately 10 MΩcm. The water obtained in this primary production device is sent to an ultraviolet sterilizer to kill viable bacteria, and then the water is passed through the ion exchange resin again to produce ultrapure water with a specific resistance of 18 MΩcm or more.

Since these methods involve multiple steps, they are complex and have difficulties in terms of equipment.

In addition, activated carbon, which is effective in removing TOC (total organic carbon), is incorporated in the first half of the process, and the subsequent process is extremely long, so TOC eluted from piping, pumps, tubes, tanks, etc. is removed from ultrapure water. It is contained in large amounts in
The major drawback was that it was ultrapure water with a TOC value.

On the other hand, ultrapure water is widely used in the electronics industry, medicine, analysis field, etc., and there is a strong desire for miniaturization and simplification of equipment and processes. Moreover, due to dramatic technological innovations in various fields, there are some places where problems are occurring with the current quality of ultrapure water, and most of them are
This means that the TOC value is high.

[Problems to be Solved by the Invention] The present invention provides a method for producing ultrapure water that can improve the quality (TOC value) of ultrapure water more than the current level and at the same time reduce the size of the apparatus.

[Means for solving problems] That is, the present invention has the following configuration.

(1) A method for producing ultrapure water characterized by treating raw water with a giant reticulated ion exchange resin and ion exchange fibers.

(2) The method for producing ultrapure water according to claim 1, wherein the treatment of the giant reticulated ion exchange resin is performed before the treatment of the ion exchange fibers.

The present invention will be explained in detail below.

The giant reticular ion exchange resins used in the present invention are called MR type (macro reticular) and MP type (macro porous). The internal structure of normal gel-type ion exchange resins is a network structure (microporous) determined by the degree of crosslinking of molecules.
However, giant network ion exchange resins have both physical pores (macroporosity) and microporosity that are distinct from this. This can be produced by copolymerizing styrene-divinylbenzene and changing the polymerization method when introducing an ion exchange group.

Although the ion exchange capacity is slightly lower than that of conventional products, it has excellent performance in removing organic matter. In addition, it has high mechanical strength, can be purified to a high degree, and is chemically stable. Known and commercially available giant network ion exchange resins having a diameter of 100 to 1000 μm are used.

For example, a giant reticulated cation exchange resin is Amberlite (IR252, manufactured by Organo).
IR200C, CG50), Diamond ion (PK216, WK10) manufactured by Mitsubishi Kasei, Amberlite manufactured by Organo (IRA900,
IRA904, IRA938, IRA911, IRA93), Mitsubishi Kasei Diamondion (PK308, PA316, PA416,
Commercial products such as WA30) can be mentioned.

In the present invention, it is preferable that the raw water is treated with an ultrafiltration membrane or a reverse osmosis membrane before being treated with the giant reticulated ion exchange resin and ion exchange fiber. This is because if raw water is directly treated with an ion exchanger, the ion exchanger becomes contaminated and ultrapure water of high quality cannot be obtained stably for a long period of time.

Examples of ultrafiltration membranes include organic and inorganic membranes such as cellulose-based, polypropylene-based, polymethacrylate-based, polyethylene-based, and polysulfone-based membranes, and examples of reverse osmosis membranes include cellulose acetate-based and aromatic polyamide-based membranes. Their form may be either a flat membrane or a hollow fiber membrane.

The method of treating raw water with an ultrafiltration membrane or a reverse osmosis membrane is to pass water through a module that incorporates these membranes. When the filtration pressure of the module increases, it can be restored to the original filtration pressure by backwashing.

The ion exchange fiber means a known ion exchange fiber having a diameter of usually 0.1 to 100 microns, preferably 1 to 100 microns. Specific examples include polystyrene,
Examples include insoluble synthetic organic ion exchange fibers in which ion exchange groups are introduced into synthetic organic polymers (ion exchange polymers) such as polyphenols, polyvinyl alcohols, polyacrylics, polyethylenes, and polyamides. Among them, fibers made of ion exchange polymers and reinforcing polymers,
Preferably, a multifilamentary mixture in which an ion exchange polymer is used as the main component of the sheath component and a reinforcing polymer is used as the core component, or an ion exchange fiber based on double fibers has sufficient mechanical strength and shape retention for operation. It is good because it has The proportion of reinforcing polymer is usually 10-90%
However, if it is too small, the mechanical strength will be weakened, and if it is too large, the amount of ion exchange and adsorption will be reduced, so a range of 20 to 80% is preferable.
As the ion exchange polymer, poly(monovinyl aromatic compounds), particularly polystyrene compounds, are preferred because they have excellent chemical resistance and heat resistance, and can be produced by repeating the operation many times over a long period of time. Further, as the reinforcing polymer, poly-α-olefin is preferable because it has excellent chemical resistance.

The water content of ion-exchange fibers is usually 0.5 to 10, but if it is too small, it will be difficult to perform ion exchange and adsorption to a high degree, and if it is too large, the resistance to liquid will increase, so A range is preferred. Here, the water content is after soaking Na type (Cl type) cation (anion) exchange fiber in distilled water.
Centrifugally dehydrate the product for 5 minutes using a household centrifugal dehydrator to remove surface moisture, immediately measure the weight (W), then dry it thoroughly, measure the weight (W _d ), and calculate the value using the following formula. be.

Water content = W - W _d / W _d The fiber may be in any known form, such as short fiber, filament yarn, felt, woven fabric, non-woven fabric, knitted fabric, fiber bundle, string-like material, paper, or an aggregate thereof. Cuttings can be mentioned. Among these, short fibers of 0.1 to 3 mm, preferably 0.3 to 1 mm, are preferably used because they are easy to fill and it is easy to mix different types of fibers.

As a method for treating raw water in the present invention, a fixed bed method in which water that has passed through an ultrafiltration membrane or a reverse osmosis membrane is subjected to ion exchange or adsorption through a layer of an ion exchanger is preferred because it can be easily operated.

The exchange capacity ratio of the ion exchange fiber to the ion exchange resin used in the present invention is usually 0.01 to 50%.
However, if it is too small, it will be difficult to perform high ion exchange and adsorption in a short time, and if it is too large, the processing capacity per fixed bed capacity will decrease, so it is preferably 0.05 to 30%, especially Preferably it is 0.1 to 20%.

Specific examples of processing methods include K _F A _R , K _R A _F , K _R
A _R →K _F A _F , K _R A _F →K _F A _F , K _R →K _F →A _R →A _F ,
K _R →A _R →K _F →A _F , K _R →A _R →K _F A _F , K _R A _R →K _F
Examples include, but are not limited to, A _F , K _R →A _R →K _R A _R →K _F A _F , and the like.

Here, K _R and _AR are respectively giant reticulated cation exchange resin, giant reticulated anion exchange resin, K _F ,
A _F is a cation exchange fiber and an anion exchange fiber, respectively. K _R A _R is a mixture of macroreticular cation and macroreticular anion exchange resins, K _F A _F
is a mixture of cation and anion exchange fibers. _KFAR is a mixture of cation exchange fibers and macromesh _anion exchange resins.

K _R A _F means a mixture of macromesh cation exchange resin and anion exchange fiber. Instead of the mixture of cation and anion exchange fibers, a mixture of cation exchange fibers and powdered anion exchange resin or a mixture of anion exchange fibers and powdered cation exchange resin may be used.

However, with an electrical specific resistance of 18 MΩcm or more and a low
In order to produce ultrapure water of TOC, a method in which treatment with ion exchange fibers is carried out after treatment with a giant reticulated ion exchange resin is preferred, and in particular, after treatment with a giant reticulated ion exchange resin, at least cation and anion exchange Most preferably, it is treated with a mixture of fibers.

As a specific example of the processing order, the above-mentioned K _F
A _R →K _F A _F , K _R A _F →K _F A _F , K _R →A _R →K _F A _F , K _R
Examples include →A _R →K _F A _F , K _R →A _R →K _R A _R →K _F A _F , etc. Here, the mixing (equivalent) ratio of cation exchanger and anion exchanger, especially fiber, is usually 10:1 to 1:10, preferably 6:1 to 1:6.

Usually, a cation exchanger having a cation exchange group, preferably a sulfonic acid group, is activated with an acid, and an anion exchanger having an anion exchange group, preferably a quaternary ammonium group, is activated with an alkali.

As the raw water, industrial water, city water, well water, tap water, underground water, etc. are usually used, but there is no problem in using distilled water, ion-exchanged water, etc.

Furthermore, in order to produce sterile ultrapure water, ultraviolet sterilization treatment must be performed before and after ion exchange treatment.
Furthermore, it is desirable to perform membrane filter treatment at the end.

The present invention produces ultrapure water with an electrical resistance of 18 MΩcm or more due to its high adsorption and ion exchange performance by treating it with a giant reticulated ion exchange resin (MR type and MP type resin) and ion exchange fiber. Since it is stable and can be obtained at a high flow rate, the multi-step treatment required in conventional methods is no longer necessary. As a result, the equipment has been made smaller and simpler, reducing the number of tubes and tanks, and significantly reducing TOC elution from the piping system.

We also discovered that TOC, which cannot be adsorbed by ordinary gel-type ion exchange resins, can be adsorbed by combined treatment with giant reticular ion exchange resins and ion exchange fibers.
value (currently, the practical standard for TOC in ultrapure water is generally
This makes it possible to produce ultra-pure water (said to be less than 50ppb).

Examples are shown below, but the invention is not limited thereto.

[Example] Example 1 A module with a built-in reverse osmosis membrane was installed, and then a commercially available giant mesh ion exchange resin Amberlite EG-290, [Amberlite IR200C/Amberlite IRA900: 1/1 mixed product] 1.8 (1.7 molar equivalents of cations, 1.2 molar equivalents of anions) was installed in the front stage, and a fiber mixture in the form of 0.5mm cut fibers was prepared.
Ion exchange cartridge with 0.2 (28 meq. of cations, 24 meq. of anions) installed in the latter stage,
Furthermore, an ultrapure water apparatus consisting of a water quality meter and a commercially available 0.22 μm membrane filter (MILLISTAK-GS, manufactured by Millipore) was prepared.

Pour tap water (electrical specific resistance 0.01MΩcm) into this device.
When ultrapure water was produced by passing water at a flow rate of 100/hr, ultrapure water with an electrical resistivity of 18MΩcm or more was produced at a flow rate of 2500/hr.
was obtained, and then the specific resistance decreased rapidly. A water quality analysis of ultra-pure (raw water) revealed that it contained less than 1 ppb of sodium (7200 ppb), less than 5 ppb of silica (850 ppb), less than 0.0 viable bacteria/ml (0.6 pieces/ml), and less than 0.01 ng/ml of pyrodiene (7.1 ng/ml), 0.2μm
The number of fine particles was 25/ml (63,500/ml).
Also, TOC meter (manufactured by Astro. Model 180ppb)
The TOC measured was 20ppb (680ppb).

Comparative Example 1 The above ion exchange resin Amberlite EG-290, 2 was placed in an ion exchange cartridge, and the same equipment as in Example 1 was installed except that ion exchange fibers were not used, and ultrapure water was added using the same procedure. When attempting to produce , the electrical resistivity rose only to a maximum of 16.4 MΩcm, and after 1600 of water of 16.4 MΩcm was obtained, the electrical resistance gradually decreased.

Comparative Example 2 Into an ion exchange cartridge, put 1.8 of the usual gel-type ion exchange resin Amberlite MB-2 [Amberlite IR120B/Amberlite IRA410: 1/2 mixture] (1.1 molar equivalent of cation, 1.6 molar equivalent of anion), A cartridge containing 0.2 of the ion exchange fiber mixture of the 0.5 mm cut fibers described above was prepared in the latter stage, and ultrapure water was produced in exactly the same manner as in Example 1.

4000 ultrapure water with electrical resistivity of 18MΩcm was obtained.
After that, the electrical resistivity decreased rapidly.

When we conducted a water quality analysis of ultrapure water (raw water), we found that
Sodium 1ppb or less (7500ppb), silica 5ppb or less (850ppb), live bacteria 0.0 (1.5 pieces/ml), pyrogen 0.01ng/ml or less (2.6ng/ml), fine particles 0.2μ or less 27 pieces/ml (100000 pieces/ml) ml).

However, when measured with the TOC meter mentioned above,
It showed a high value of 139ppb (630ppb).

The cation and anion exchange fibers used in the Examples and Comparative Examples were manufactured by the following method.

Multicore sea-island composite fiber (undrawn yarn) [sea component (polystyrene/polypropylene)/island component (polypropylene) = (47/4)/49 (number of islands 16, fiber diameter
34μ)] to a length of 1 mm to obtain a cut fiber. The polymerized part of the cut fiber 1 was converted into commercially available 1
The mixture was added to a crosslinking/sulfonation solution consisting of 7.5 parts by volume of grade sulfuric acid and 0.15 parts by weight of pahydride, and reacted at 80°C for 4 hours, followed by washing with water. Next, a cation exchange fiber having sulfonic acid groups was obtained by treating with alkali and washing with water (exchange capacity: 2.8 meq/g).
Na, water content 1.5).

The polymerized portion of Cut Fiber 1 was added to a crosslinking solution consisting of 5 parts by volume of commercially available primary sulfuric acid, 0.5 parts of water and 0.2 parts of paraformaldehyde, and a crosslinking reaction was carried out at 80° C. for 4 hours. Then chloromethyl ether
The crosslinked thread was added to a solution consisting of 8.5 parts by volume and 1.5 parts by volume of stannic chloride, and the mixture was reacted at 30°C for 1 hour. After the reaction was completed, it was washed with 10% hydrochloric acid, distilled water, and acetone.
Add chloromethylated system to 30% trimethylamine aqueous solution
The mixture was added to 10 parts by volume, aminated at 30°C for 1 hour, and washed with water. Further, by treating with hydrochloric acid and washing with water, anion exchange fibers having trimethylammonium methyl groups were obtained (exchange capacity: 2.4 milliequivalents/g-Cl, water content: 1.8).

The fiber mixture used was obtained by activating cation exchange fibers and anion exchange fibers with acid and alkali, respectively, and then stirring and mixing the two in a predetermined ratio.

[Effects of the Invention] The method for producing ultrapure water of the present invention not only provides ultrapure water with low TOC and extremely high quality, which is currently required in many fields, but also is a method suitable for downsizing equipment. Therefore, it can be widely applied in the electronic industry, pharmaceutical field, analytical field, etc. In particular, it is very effectively used in the electronic industry field.

Claims (1)

[Scope of Claims] 1. A method for producing ultrapure water, which comprises treating raw water with a giant reticulated ion exchange resin and ion exchange fibers. 2. The method for producing ultrapure water according to claim 1, wherein the treatment of the giant reticulated ion exchange resin is performed before the treatment of the ion exchange fibers.