JPS627417A - Semipermeable polymer membrane for drying gas to high degree and gas drying method using the same - Google Patents

Abstract

PURPOSE:To obtain a semipermeable polymer membrane for drying gas to a high degree not damaged by acidic gas and requiring no regeneration, by using a semipermeable membrane comprising a fluorocarbon type copolymer ion exchange resin wherein the relation between a water absorbing ratio and ion exchange capacity is fallen within a specific range. CONSTITUTION:A fluorocarbon type copolymer containing a repeating unit represented by formula I (wherein m is 0 or 1 and n is an integer of 2-5) is used. Further, it is especially necessary that the relation between the water absorbing ratio W and ion exchange capacity Q of this fluorocarbon type polymer membrane is fallen within a range represented by formula II (wherein W1 is a dry wt., W2 is a pure water immersion equilibrium wt. at 25 deg.C and Q is meg/g H-form dry resin). The sulfonic acid group of the fluorocarbon type polymer is pref. introduced into the copolymer in quantity of 0.5-2.5meg/g H-form dry resin as ion exchange capacity. When said copolymer is formed into a hollow yarn shape, an inner diameter is set to 400-500mum and a membrane thickness to 40-60mum. By this method the moisture content of gas can be reduced to 5ppm or less.

Description

[Detailed Description of the Invention] [Industrial Application Fields] The present invention is applicable to gases for manufacturing processes of semiconductor materials such as silicone urchins, gases for manufacturing semiconductor devices, fine ceramics, solar cells, and optical fibers. This invention relates to an improved fluoropolymer semipermeable membrane suitable for high-level drying of gases used in new material manufacturing processes such as.

[Prior Art] For example, semiconductor devices called LSI and VLSI are currently leading the remarkable development in the electronics field, but in the manufacturing of these materials and device manufacturing processes, nitrogen and other substances are used. In addition to general-purpose gases, rare gases such as argon and helium, corrosive gases such as hydrogen chloride and chlorine, and special gases such as silane, arsine, and poran gas are used. Furthermore, semiconductor device manufacturing processes are currently rapidly becoming highly integrated (ultra-fine).

The degree of integration of LSI has increased, and the number of bits has increased from 1 to 256 at present.
As the number of megabits increases to 4 megabits, the line width of the fine pattern becomes narrower and narrower, and therefore even fine particles, which had not been a problem until now, are starting to affect the yield.

Therefore, the above-mentioned gases related to semiconductor manufacturing are also used for example in LSI.
Purity of 4 to 5 nines or more is required for gases used for silicon wafers, which are the third substrate, and for epitaxial, doping, etching, and cleaning gases in the device manufacturing process. Dryness and no floating dust were now required. Moisture in these gases must be particularly strictly controlled because it causes various problems, such as those shown below.

■ Corrosion occurs in metal parts such as piping valve flowmeters used in semiconductor manufacturing, resulting in the generation of fine metal impurities and fine powder (
corrosive gases such as NCR gas).

(2) Water decomposition in the production furnace generates H2 and 02, and especially 02 generates unexpected oxidized impurities.

■ A chemical reaction occurs between the gas itself and water, producing replicative impurities.

Currently, for example, an adsorption method using molecular sieves is used to dry gases in semiconductor device manufacturing processes. Molecular sieve is a desiccant with adsorption capacity second only to phosphorus pentoxide, and it is relatively easy to dry common gases to a moisture content of 1 ppm or less.

Furthermore, this desiccant is widely used because it has the advantage of being a physical desiccant that does not cause problems such as disintegration or swelling. However, the drawback is that the heat regeneration that is generally performed
It requires a high temperature of 400°C, and repeated heating and regeneration generates floating dust.

In addition, the molecular sieve may be crushed by acidic gas such as hydrochloric acid gas.

Although acid-resistant grades are available, the generation of floating dust cannot be ignored, and a dust filter must be installed. It is also impossible to regenerate molecular sieves.

On the other hand, a method using a polymer membrane as a gas drying method is described in U.S. Pat. Unlike adsorption methods using molecular sieves, these membrane permeation methods do not require regeneration, so they are excellent methods that can be used continuously for long periods of time.

For the former, a polymer having a fluorine-based sulfonic acid group is particularly used, and can be used even with corrosive gases.

However, in both cases, it has not been possible to obtain a highly dry product with a moisture content of 1 ppm or more, which is used in semiconductor manufacturing processes.

[Problems to be solved by the invention] Since the running cost of the disposable molecular sieve adsorption method is high, the running cost is low, and the gas has a high dryness with no floating dust and a moisture content of 1 ppm or less. Finding a way to easily obtain this is an important problem that must be solved.

[Means and effects for solving the problems] As a result of intensive studies aimed at developing a new method to solve the above problems, the present invention has developed a polymer semicontainer made of a specific fluorine-based copolymer as described below. The inventors have discovered that a permeable membrane is suitable for the above purpose and have completed the present invention.

That is, according to the present invention, first, it is made of a fluorine-based copolymer containing a repeating unit represented by the general formula (in the formula, m = 0 or 1; n = an integer of 2 to 5), and has a water absorption rate W and an ion exchange rate. A polymeric semipermeable membrane having a volume iQ relationship expressed by the following formula % is provided.

According to the present invention, secondly, a fluorine-based copolymer containing a repeating unit represented by old F3 (in the formula, m = 0 or 1; n = an integer of 2 to 5) is heated, and the water absorption rate W A method for producing a semipermeable polymer membrane is provided, which is characterized in that a semipermeable polymer membrane is obtained in which the relationship between Q and ion exchange capacity Q is expressed by the following formula: %.

According to the present invention, thirdly, a gas containing moisture is a fluorine containing a repeating center represented by the general formula % (where m = o or l; n = an integer from 2 to 5). It is made of a semi-transparent polymeric copolymer and has the relationship between water absorption rate W and ion exchange capacity Q as follows: Alternatively, there is provided a method for highly drying a gas, characterized in that the moisture-containing gas is dehumidified by reducing the pressure on the other side.

Furthermore, according to the present invention, fourthly, the water absorption A large number of hollow fiber semipermeable membranes having the relationship between the ratio W and the ion exchange capacity Q of the following formula % are inserted into this casing, both ends are fixed with resin, and the inside and outside of the hollow fiber membranes are A gas drying device is provided, which is configured to allow gas to pass therethrough.

Examples of fluorine-based copolymers listed in L include fluorinated olefins such as tetrafluoroethylene, trifluoroethylene, perfluorovinyl ether, vinylidene fluoride, and vinyl fluoride. F3 CF2 = CF(OCF20F)mO(C:F2)ns
Preferably, those obtained by copolymerizing perfluorovinyl ether monomers having the following formula: 02F (m=0 or 1, n=an integer of 2 to 5). These copolymers are USP 4329434. USP 4329435
It is described in USP 3909373.

The present inventors have found that among fluoropolymer membranes containing repeating units represented by the above general formula, a polymer semipermeable membrane in which the relationship between water absorption rate and ion exchange capacity is as follows: I found it to be excellent.

The sulfonic acid groups in the fluorine-based copolymer are preferably introduced in an amount that provides an ion exchange capacity of 0.5 to 2.5 milliequivalents/gram H-type dry resin in the copolymer.

By setting the ion exchange capacity of the fluorine-based copolymer within the range of 0.5 to 2.5 milliequivalents/g H-type dry resin, the water vapor permeation rate is significantly reduced. The melting point of the polymer thin film does not become too high, the production of the polymer thin film is easy, and the shape retention of the polymer thin film is ensured without decreasing the physical strength.

In particular, the ion exchange capacity is 0.8 to 1.8 milliequivalent/
A Gram H dry resin is preferred.

As the salt type of the sulfonic acid group of the fluorine-based copolymer used in the present invention, it is also possible to use metal salts and ammonia salt types, but the SO3H type has the highest water content, high water vapor transmission rate, and heat resistance. It is also preferable since it has sufficient stability.

The shapes of fluorine-based copolymers include flat membranes, tubes,
Although any hollow fiber membrane may be used, a hollow fiber membrane having a large membrane area per unit volume and high throughput is particularly preferred.

In particular, the airtightness of the apparatus is important in achieving a high degree of dryness, and hollow fiber membranes are preferred from this point of view as well.

Regarding the membrane thickness of the hollow fibers, the thinner the membrane, the greater the permeability of water vapor and the improved performance, which is preferable, but there are limitations from moldability and pressure resistance. Although it depends on the diameter of the hollow fiber, the inner diameter is 400 mm.
For ~500 gm, a film thickness of 40~60 gm is preferred.

To produce the membrane of the present invention, the above fluorine-based copolymer is formed into a thin film, hydrolyzed with an alkali, and treated with a strong acid to convert the terminal group 502F into S(h l(). This is done by heat treating.

The heat treatment can be carried out, if necessary, while purging with a dry gas, such as nitrogen gas having a water content of 2.5 Pl) DI or less, or under reduced pressure. Heat treatment temperature is 70~
250°C is suitable. If the temperature is too high, the ion exchange group may be removed, leading to a decrease in performance. The heat treatment temperature is particularly preferably 70 to 200°C.

- The copolymer described above shrinks by several tens of percent by the above heat treatment, and its water absorption rate also decreases. As a result, the relationship between water absorption rate and exchange capacity is 1.20Q -1,984<RogW<1.20
Q -1,742 items will be made.

By using the above heat-treated membrane, the moisture content of gas is 5.
It is possible to perform high-level dehumidification with a moisture content of 1 ppm or less at room temperature. In this sense, it can be said that the above-mentioned copolymer membrane has the ability to dehumidify to an extreme level that is unimaginable under the common knowledge of conventional membranes.

The gas to be dried may be supplied to either side of the fluorocopolymer thin film. The purpose of dehumidification is achieved by separating the membrane and flowing a dry purge gas with a low moisture content on the moisture permeation side, or by reducing the pressure with a vacuum pump, etc., to create a partial pressure difference that is the driving force for membrane permeation.

Dry purge gas with a low moisture content is a gas that is supplied to remove moisture contained in the gas to be dried through a membrane, and is an inert gas that does not react as much as possible even when the temperature rises. Preferably, reduced pressure means a pressure lower than atmospheric pressure, although it depends on the pressure of the raw material gas to be supplied.

The membrane of the present invention is made by heat treatment, but in the case of a flat membrane, whether or not it was made by heat treatment can be easily determined by measuring the water absorption rate.

However, if the membrane is in the form of a thin hollow fiber, it is difficult to measure the water absorption rate, so the determination can be made by measuring the temperature at which thermal contraction starts, as described below.

Attach a light weight to the hollow fiber membrane (enough weight to keep the fibers straight, but not enough to stretch them) and suspend them in an air tank. In this state, the temperature of the air tank is gradually increased, and changes in the length of the thread are measured using a reading telescope. An example of the measurement results is plotted in a graph with temperature on the horizontal axis and length on the vertical axis, as shown in Figure 4. L25 is the length at 25° C., and LL is the length at temperature t'0. In FIG. 4, the temperature indicated by the arrow, that is, the maximum temperature at which there is no dimensional change due to temperature increase, is defined as "the maximum temperature at which no thermal contraction occurs." Several hollow fibers with different heat treatment temperatures (1) were prepared, and their "maximum temperature (T) without thermal contraction" was measured, and the results were plotted in a graph as shown in Figure 5. That is, ``17=t'' (1), and the heat treatment temperature (1) of the hollow fiber membrane can be determined by measuring the maximum temperature (T) at which no thermal contraction occurs.

In the method of the present invention, the gas to be dried is usually a commercially available gas filled in a cylinder, and the water vapor concentration is not so high. The gas filled in the cylinder is usually several ppm to several tens of ppm.
In some cases, it may exceed 1100 pp. Depending on the concentration of the target gas, the membrane area of the gas drying device can be changed or it can be multistaged to obtain a dehumidification level of r1.

The method of the present invention is particularly suitable for highly drying process gases for semiconductor material production, semiconductor device production gases, and new material production process gases such as solar cells and amorphous silicon.

Typical examples of semiconductor process gases for the new material manufacturing process include ASHa, H2S, GeH4°SeH2,5b)I:+, AsCl2. (C2H5
)27a, (C:H+)2cd.

(C2H5)2cd, AgF2. PH3, PC
, h, 82H5, 8F3. BCI! 3゜(CH
3) Doping gas such as 2Te; 5IH4+ 5I
H2C22.

5iHCjh, 5iCjl'n, B2O2,BBr
3. BI3. A3H3, PH3゜GeH3, TeH
z, (CH3)3AS, (C2Hs):+Aj',
(C:H3)3Sb.

(C2H5)3Sb, (CH3)3Ga, (C2H
5) 3Ga, (CH3)3AS.

(C:2H5hAs, (CH3)2Hg, (C2H
5)zHg, (CH3hP.

(C2)+5)3P, SnC:j)4. GeCj)
4.5bCj! 5. Evitar gas such as AffC1's; AsF5. PF5. PH3, Bh, B
C43°SiF4. Ion implantation gas such as SF6;
AsH3, PH3.

HCR, SeH2, (CO3)2↑e, ((:2H5
)7Te gas for light emitting diode; Ch, H(1
) Etching gas such as IF, HBr, SFb; SiF4. CFa, 03F8. C7F6.
C) IF+.

Plasma etching gas such as CClF2.02; C:3
F8° (Ion beam etching gas such as JF3, CClF2. CFa; reactive sputtering gas such as Ar, 02; SiH4,5IH2CR2,5iCfn
, chemical vapor deposition (CVD) gas such as NO,02; N
2. Ar, He, N2. Examples include balance gases such as CO2 and N70.

[Example 1] The present invention will be explained in more detail with reference to experimental examples below, but the present invention is not limited to these examples.

The moisture content of the gases in Examples and Comparative Examples was measured using a dew point meter or a moisture meter, or depending on the gas, the Karl Fischer method.

Example 1 Tetrafluoroethylene? F3 GF2=GFOCF2CF-C] (CF2)3~SO2
By copolymerizing F, the ion exchange capacity is 0.94 meq/
A Gram H type dry resin was obtained. The resulting resin was molded at a temperature of 2.
A film of 500 p-m was prepared at 50°C, and after hydrolyzing the film with an alkaline alcohol solution, ion exchange was performed with an aqueous hydrochloric acid solution to convert the end of the side chain into a sulfonic acid type (H type), and the film was air-dried. The obtained film was subjected to dry-wet treatment in a vacuum, and then the equilibrium water absorption rate was determined at 25°C (Fig. 1).

As shown in FIG. 1, when the dry heat treatment temperature was about 70° C. or higher, the water absorption rate decreased significantly. The water absorption rate remained almost constant even at higher temperatures.

In the same way, one type of monomer was changed as shown in Table A, and the ion exchange capacity was 0.8~! , 1 meq/g polymer film was prepared and the water absorption rate shown in Table A was made.From the results of Table A, the relationship between the ion exchange capacity and water absorption rate of the membrane of the present invention is shown by the diagonal line in Figure 2. become a part.

Example 2 Tetrafluoroethylene and F3 CF2 = CFOCF2CF-0(CF2)3-502
F was copolymerized to obtain an H-type dry resin with an ion exchange capacity of 0.9 meq/g. The obtained resin was spun at a spinning temperature of 250°C and a spinning speed of 88°C using a molding machine equipped with a spinneret for producing hollow fibers.
Melt-spun at mm, inner diameter 500ILm, film thickness 60mm
A hollow fiber membrane was obtained.

This hollow fiber was hydrolyzed with an alkaline alcohol solution, and then ion-exchanged with an aqueous hydrochloric acid solution to convert the end of the side chain into a sulfonic acid type (H type) and air-dried.

Bundle 400 pieces of the obtained thread to a length of 40 cm,
It was fixed to a SUS separator with ebogishi resin at both ends to create a gas drying device as shown in Figure 3. N2 gas adjusted to a moisture content of 1 ppm (8 points - 76°C) or less was applied to the drying device at a pressure of 5 kg/am2G, and the drying rate was 0.57)/sin.
It was flowed inside the hollow fiber at a flow rate of (flow rate is equivalent to atmospheric pressure, the same applies hereinafter).

N2 gas, which was also adjusted to have a moisture content of 1 ppm (dew point -76°C) or less, was flowed to the outside at a flow rate of 0.75j)/win.

This was placed in a constant temperature bath at 70°C and heated for 3 hours, after which the drying device was returned to room temperature and N2 gas (sample gas) adjusted to a moisture content of 31 ppm (dew point -52°C) and a pressure of 5 kg/cm2G was added to 0. .54'7m1n inside the hollow fiber, and the outside of the hollow fiber has a water content of ippm (dew point -
N2 gas adjusted to below 76℃) at 0.751'/si
n flowed. When the dew point of the sample gas outlet of the drying device was measured, it was found that the water content was 1 ppm (dew point ~76°C) or less. Continuous operation was continued, and even after 24 hours, the water content at the sample gas outlet remained below the ipp layer (dew point -76°C).

On the other hand, when the dew point at the outlet of the dryer was measured for the purge gas outside the hollow fibers after 24 hours, the water content was 4.6.
ppm (dew point -66°C). After approximately 1000 hours of continuous operation under the same conditions, the moisture content at the outlet of the sample gas remained below 1 ppm (dew point -76°C), and the moisture content decreased in the drying device for the sampling gas and the drying device for the purge gas. The ratio of increased water content is 1.2:
1, it was almost consistent within the measurement error.

Note that the same results as in Example 2 were obtained with other films of the present invention as shown in Table A.

Comparative Example 1 Using the same equipment as in Example 2, using the same sample gas and purge gas without heating pretreatment.
After 44 hours, the moisture content of the sample gas was 1.
It did not reach 0.8 ppm (dew point -60°C). Similarly, as shown in Table A, the membranes other than those of the present invention showed the same results as the comparative examples.

Examples 3, 4, 5.6 HC sample gas using the same drying device as in Example 2.
I! (However, the pressure remains at 5 kg/cm?G)
The outlet moisture content of the sample gas was measured in the same manner as in Example 2, and the results shown in Table 1 were obtained. However, on the purge side, dry N2 with a moisture content of 1 ppm or less was flowed, or the purge was performed under reduced pressure.

[Effects of the Invention] The effects of the polymer semipermeable membrane for highly drying gas and the drying method using the membrane according to the present invention are summarized as follows.

■ Gas can be dried to a high degree and the drying property can be maintained for a long time.

■ No floating dust is generated during gas drying.

■ Even if acidic gas such as hydrochloric acid gas comes into contact with the thin film, it will not attack the film.

■ Unlike adsorption methods using molecular sieves, etc., regeneration is not required and continuous use for long periods of time is possible.

In addition, the gas drying device using the membrane of the present invention has a large number of hollow fiber-shaped polymer semipermeable membranes inserted into the casing, which have excellent performance in high-level drying of gas. The membrane surface edge is large, making it a compact device with high processing capacity.

Furthermore, in the method for producing a membrane of the present invention, by heating a specific fluorine-based copolymer, it is possible to easily produce a membrane that is excellent in highly drying the above-mentioned gas.

[Brief explanation of drawings]

Figure 1 is a graph showing the relationship between dry heat treatment temperature and equilibrium water absorption of the polymer semipermeable membrane obtained in Example 1, and Figure 2 is a graph showing the relationship between dry heat treatment temperature and equilibrium water absorption rate of the semipermeable polymer membrane obtained in Example 1. The polymer water absorption rate (W
) and ion exchange capacity (Q), 3rd graph
The figure is a schematic explanatory diagram showing the gas drying apparatus according to the present invention, and FIG. The length of the film Lt) and the length L25 at a temperature of 25°C
). Figure 5 shows the degree of heat treatment of hollow fiber membrane (1)
This is a graph showing the relationship between the temperature and the maximum temperature without thermal contraction, and the heat treatment temperature can be determined from this graph. 1... Hollow fiber membrane, 2... Sample gas inlet, 3... Sample gas outlet, 4... Purge gas inlet, 5... Purge gas outlet, 6... Cell, 7... Diaphragm.

Claims (1)

[Claims] (1) A fluorine-based copolymer containing a repeating unit represented by the general formula ▲ Numerical formula, chemical formula, table, etc. ▼ (in the formula, m = 0 or 1; n = an integer from 2 to 5) The relationship between water absorption rate W and ion exchange capacity Q is expressed by the following formula: 1.20Q-1.964<logW<1.20Q-1.
742 [W=(W_2-W_1)/W_1 W_1 is dry weight; W_2 is equilibrium weight immersed in pure water at 25°C; Q: meq/g H-type dry resin] A semipermeable polymer membrane having the following formula. (2) The semipermeable polymer membrane according to claim 1, wherein m=1 and n=3. (3) Claim 1 in which the polymeric semipermeable membrane is a hollow fiber.
Polymer semipermeable membrane described in Section 1. (4) General formula ▲ There are mathematical formulas, chemical formulas, tables, etc. ▼ (in the formula, m = 0 or 1; n = an integer from 2 to 5). The relationship between W and ion exchange capacity Q is expressed by the following formula: 1.20Q-1.964<logW<1.20Q-1.
742 [W=(W_2-W_1)/W_1 W_1 is dry weight; W_2 is equilibrium weight immersed in pure water at 25°C; Q: meq/g H-type dry resin]. A method for manufacturing a semipermeable polymer membrane. (5) The method for producing a semipermeable polymer membrane according to claim 4, wherein the heating is performed at a temperature of 70 to 200°C. (6) A fluorine-based copolymer containing a repeating unit represented by the general formula ▲Mathematical formula, chemical formula, table, etc.▼ (where m = 0 or 1; n = an integer from 2 to 5) for a gas containing moisture. The relationship between water absorption rate W and ion exchange capacity Q is expressed by the following formula: 1.20Q-1.964<logW<1.20Q-1.
742 [W=(W_2-W_1)/W_1 W_1 is dry weight; W_2 is equilibrium weight immersed in pure water at 25°C; Q: meq/g H-type dry resin] on one side of a polymer semipermeable membrane having A method for high-level drying of a gas, characterized in that the moisture-containing gas is dehumidified by contacting the other side with a dry purge gas or by reducing the pressure on the other side. (7) General formula ▲ There are mathematical formulas, chemical formulas, tables, etc. ▼ (In the formula, m = 0 or 1; n = an integer from 2 to 5). The relationship between and ion exchange capacity Q is expressed by the following formula: 1.20Q-1.964<logW<1.20Q-1.
742 [W=(W_2-W_1)/W_1 W_1 is dry weight; W_2 is equilibrium weight immersed in pure water at 25°C; Q: meq/g H-type dry resin] There are many hollow fiber-shaped polymer semipermeable membranes. A gas drying device, which is inserted into the casing, has both ends fixed with resin, and is formed so that different types of gas can pass through the inside and outside of the hollow fiber membrane.