JPH01224090A - Ultrapure water production method - Google Patents

Abstract

PURPOSE:To reduce a leak of total org. carbon (TOC) components into extra- pure water by packing a mixed bed type ion exchange tower with a highly acidic cation exchange resin and a highly basic anion exchange resin in a specified mixing ratio. CONSTITUTION:A mixed bed type ion exchange tower installed in an apparatus for producing extra-pure water is packed with a highly acidic cation exchange resin and a highly basic anion exchange resin in >=1 volume ratio of the cation exchange resin to the anion exchange resin. By increasing the percentage of the cation exchange resin, specified components among simultaneously leaking TOC components are removed without lowering the specific resistance of extra- pure water and the amt. of TOC in the resulting extra-pure water is reduced.

Description

Detailed Description of the Invention (Industrial Field of Application) This invention relates to an improvement of a mixed bed type ion exchange tower installed in an ultrapure water production apparatus. impurities caused by ion exchange resin,
This invention relates to a mixed bed ion exchange column that can suppress leakage into ultrapure water to an extremely small amount.

(Conventional technology and its problems) Semiconductor elements, which are the main products of the semiconductor industry, are IC, LS, etc.
The i-integration, or the number of bits, has been increasing over the years, and has recently increased to the mebit level.

Furthermore, with the aim of improving the cleaning effect of ultrapure water in response to ultra-fine processing of wafer surfaces, we have developed
There is a growing need to use ultrapure water heated to about 0.9°C for cleaning.

In response to these trends, we have not only improved the specific resistance value, which is a representative indicator of the purity of ultrapure water, but also reduced the amount of fine particles.
Recently, it has become an important issue to quantify organic matter, so-called total organic carbon (TOC), which is eluted from various materials used in ultrapure water production equipment and mixed into ultrapure water. It has become to.

In the ultrapure water production equipment described above, a mixed bed ion exchange column filled with a mixed state of a strongly acidic cation exchange resin and a strongly basic anion exchange resin is used to remove water contained in the water to be treated. This equipment is essential for removing ionic impurities caused by water and improving the specific resistance value of ultrapure water to around the theoretical value of 18.2 MΩ·cm (25°C).

However, the conventionally used mixed-bed ion exchange tower installed in ultrapure water production equipment can almost completely remove ionic impurities, but the ionic impurities contained in these resins are Water-soluble components (for example, water-soluble components that were unreacted in the manufacturing process of these resins) gradually leak into the ultrapure water during the water passage process, and these components are absorbed into the ultrapure water. To T.

There is a risk that it will be detected as a C component.

As mentioned above, there is a growing need to use ultrapure water heated to about 50 to 90°C for cleaning, and continuous use of heated ultrapure water. In order to obtain high purity water, in the ultrapure water production equipment, the water to be treated is heated to a desired temperature at the stage of being supplied to the mixed bed ion exchange tower. When the heated treated water is passed through a conventional mixed bed ion exchange tower, the temperature is lower than when the treated water is passed through a conventional mixed bed ion exchange tower.

The amount of C increases, making it difficult to obtain heated ultrapure water of high purity.

(Means for solving the problem) In view of the above background, the present inventors have proposed that TOCI in ultrapure water
We have repeatedly considered ways to reduce the amount of &.

TOC components detected in ultrapure water include those originating from raw water such as tap water and groundwater, as well as those eluted from the surfaces of various materials such as the components and piping materials that make up the ultrapure water 9i production equipment. It is broadly divided into those caused by

The present inventors have repeatedly studied ways to reduce the TOC components described in 1-1, which are caused by the latter.
In particular, we studied the reduction of TOC components caused by mixed bed ion exchange towers, which are essential equipment in ultrapure water production equipment.

In other words, ultra-pure water production! ! A detailed investigation into the TOC components in the ultrapure water leaking from the mixed-bed ion exchange tower installed in the plant revealed that the TOC components were mainly from the ion exchange 04 fat packed in the tank, and were especially concentrated in strong bases. The leakage is mainly from the acidic anion exchange resin, and I learned that some of these are strongly adsorbed by the strongly acidic cation exchange O (fat).

Therefore, if the mixing ratio of the strongly acidic cation exchange resin and the strongly basic anion exchange resin packed in the mixed bed ion exchange tower is set to a specific ratio, leakage of TOC components into ultrapure water can be prevented. We have found that this can be reduced, and have arrived at the present invention.

That is, the key point of the present invention is that in a mixed bed type ion exchange tower installed in an ultrapure water production device, a strongly acidic cation exchange resin and a strongly basic anion packed in this mixed bed type ion exchange tower are used. A hot bed type ion exchange tower characterized in that the ion exchange resin has a resin volume ratio in the range of strongly acidic cation exchange fl+fat/strong basic anion exchange resin≧1.

The present invention will be explained in detail below.

There are various systems for ultrapure water production equipment, and a typical example is shown in FIG.

That is, as shown in the figure, the treated water in the primary system consisting of a coagulation filter, an ion exchange device (for example, a 2-bed, 3-column ion exchange device), and a reverse osmosis membrane device, and the secondary system, In order to achieve even higher purity, a secondary system consisting of an ultraviolet sterilizer, a mixed bed ion exchange tower, an ultrafiltration membrane device, etc. is combined. In addition to what is shown here, for example, a system in which a two-bed, three-column ion exchange device and a reverse osmosis membrane device are connected in the reverse order, and a mixed bed type There are also some that have an ion exchange tower added.

To produce ultrapure water, a flocculant (for example, polyaluminum chloride) is added to raw water, such as industrial water, tap water, or underground water, and the mixture is passed through a flocculation filter and then flowed into each of the illustrated components. - In the secondary system, it is possible to obtain pure water from which impurities such as suspended matter in raw water, cations such as sodium and calcium, and anions such as chlorine, carbonate, and silica have been substantially removed, so-called Φ primary pure water. .

In the secondary system, pure water from which impurities such as ions, fine particles, organic matter, and microorganisms remaining in the primary pure water are removed, so-called ultrapure water, is obtained.

The mixed bed ion exchange column of the present invention is an improvement of the mixed bed ion exchange column installed in the secondary system in FIG. 1. In conventional mixed-bed ion exchange towers using a mixture ratio of strongly acidic cation exchange resin [7] and strong basic anion exchange resin, the specific resistance value of the treated water improves when water is passed through it, but the TOC To increase. That is, these T.O.
C is mainly a strong basic anion exchange O (TOC components leaked from fat, some of these components are removed by ion exchange or physical adsorption with a strong acid cation exchange resin), Components that are not removed by the strongly acidic cation exchange resin are detected as TOC in ultrapure water.

The leakage of these TOCs tends to gradually increase as the temperature of the water to be treated passing through the mixed bed ion exchange tower is increased.

In the mixed-bed ion exchange tower of the present invention, the mixing ratio of the strongly acidic cation exchange resin and the strongly basic anion exchange resin to be filled therein is determined by the resin volume ratio: strongly acidic cation exchange resin/strongly basic anion exchange resin. Anion exchange resin≧1.

In a conventional ion exchange tower, the mixing ratio of 11 and 2000 NAm is 0.
In the range of 3 to 0.5? v4, but this was mainly aimed at improving the specific resistance value of ultrapure water, and as a result, even if the specific resistance value of ultrapure water was satisfied, many TOC components were detected. be done.

In the ion exchange tower of the present invention, the mixing ratio of the strongly acidic cation exchange resin is increased as described above, and as a result, the specific resistance value of ultrapure water does not decrease, and at the same time, the leaking TOC component is TO in ultrapure water removes certain things
C.

The amount of the strongly acidic cation exchange resin to be used is preferably at least the same volume ratio and up to about twice the amount of the strongly basic anion exchange 0I fat.

Strongly acidic cation exchange packed into the ion exchange tower of the present invention ↑
A mixture of fat B and a strongly basic anion exchange resin in a desired volume ratio is prepared as follows.

The strongly acidic cation exchange resin and the strongly basic anion exchange resin are each regenerated, each of which is drained by centrifugal dehydration, etc., and then both Q (fats are weighed according to the weight corresponding to their desired volume ratio). .

That is, the weight of each ion exchange resin to be weighed at this time is calculated from the apparent density of each ion exchange resin, which has been measured in advance, so that it has a predetermined volume. As described above, in the present invention, although the mixing ratio of both ion exchange (fat) is defined by volume ratio, it may be measured by the corresponding weight based on the apparent density of each resin.

Both ion-exchanged O (fat) thus weighed and collected in a predetermined volume are mixed uniformly at a predetermined mixing ratio using a mixer or suitable mixing means, and then packed into a mixed-bed ion-exchange column.

The mixed bed ion exchange column used in the present invention does not need to have a special structure, and may have any conventionally used or known structure.

(Effect of the invention) When heated water to be treated is passed through a conventional mixed bed ion exchange tower installed in an ultrapure water production device, the TOC in the ultimately obtained ultrapure water is There is a risk of a sudden increase in
Although it has been difficult to produce heated ultrapure water by vA, as described above, according to the present invention, strong basic anion exchange? By increasing the mixing ratio of strongly acidic cation exchange resin to fat and adding a mixed bed ion exchange tower, it is possible to stably obtain heated ultrapure water of high purity with suppressed leakage of TOC components. .

(Example) Next, an example of the present invention will be shown, but the present invention is not limited to this example.

Example 1 Strongly acidic cation exchange O for ultrapure water (diaion SKN [manufactured by Mitsubishi Chemical Corporation, Diamond is a registered trademark of the same company] (hereinafter abbreviated as SKN) and strong acidic cation exchange O for ultrapure water The mixing ratio (SKN/5AN) of Diaion SAN [manufactured by Mitsubishi Chemical Industries, Ltd.], which is a basic anion exchange resin, was determined by volume ratio ?0.3.0.59.1.0.2.0 and 3. 0, and mixed (the ratio was set to 11), and each was packed into a glass column to form a mixed bed.

Each of these mixed bed columns has a specific resistance of 15 MΩ”c+
++, TOC 30μgC/l primary pure water, 40℃, 6
Heated to 0°C and 80°C, respectively, and space velocity 32,
5/Hr, and check the TOC at each column inlet.
and measure the TOC at the column outlet, and measure the TOC at the outlet.
increase amount (Hataro TOC - population TOC, this is ΔTOC''
c) was measured.

The results are shown in the diagram in Figure 2.

In the chart of FIG. 2, the vertical axis shows ΔTOC (μgc/l), and the horizontal axis shows the volume ratio of S K N /S A N.

Looking at the results shown in Figure 2, when passing pure water heated to 40°C, 60°C, and 80°C, S
It is clear that when the volume ratio of KN/SAN becomes 1 or more, the value of ΔTOC decreases.

[Brief explanation of the drawing]

Figure 1 is a 70-chart of an example of an ultrapure water production device, and Figure 2 is a mixed bed ion exchange system in which the mixing ratio of strongly acidic cation exchange 81 fat and strongly basic anion exchange resin is varied. It is a chart showing changes in ΔTOC (outlet TOC - population TOC) when treated water heated to various temperatures is passed through an exchange tower. In the diagram of FIG. 2, the vertical axis shows ΔTOC, and the horizontal axis shows the volume ratio of strongly acidic cation exchange #/strongly basic anion exchange resin constituting the mixed bed. (Figure 2 SKN/SAN (Cold Medical Topics) Procedures Amendment Written spontaneously) Date of April 1986 Kunio Ogawa, Commissioner of the Japan Patent Office Display of the case Special Application No. 63-49574 2 Name of the invention Mixed bed ion exchange tower 3 Relationship to the case of the person making the amendment Patent applicant name Nippon Rensui Co., Ltd. 4 Agent address 4-13-5 Akasaka, Minato-ku, Tokyo 5. Specification subject to amendment and drawings 6. Contents of amendment

Claims (1)

[Claims] (1) In the mixed bed ion exchange tower installed in the ultrapure water production equipment, the strongly acidic cation exchange resin and the strong basic anion exchange resin filled in this mixed bed ion exchange tower have a resin volume ratio of A mixed bed type ion exchange column characterized in that the range of strongly acidic cation exchange resin/strongly basic anion exchange resin≧1 is satisfied.