JPS6312316A - Gas permselective composite film manufactured by plasma polymerization coating technique - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of the Invention] The present invention provides membranes having a selective permeability of 02/N2 gas greater than 2.3, prepared by depositing a plasma polymer coating on the surface of a microporous membrane support. This invention relates to a gas selectively permeable membrane.

Coatings are prepared from a single specified monomer or two or more selected comonomers. While the support body retains its inherent properties of chemical resistance and mechanical strength, a plasma polymer coating is obtained that effectively bridges the pores of the support and increases the high gas permselectivity of the composite membrane. High gas flow flux allows use in gas separation. Furthermore, the invention relates to a gas separation module using this new membrane in the form of hollow fibers.

[Background of the invention]

Various problems are often encountered in the preparation of conventional gas selective permeation composite membranes, such as low gas flux due to the thickness of the coating layer, difficulty in obtaining a thin coating layer, and poor gas flow between the coating layer and the support. There are problems such as insufficient adhesive strength and difficulty in manufacturing the membrane. In particular, it is difficult to prepare gas-selective permselective composite membranes that simultaneously achieve high gas selectivity and high gas flux. In the case of asymmetric membranes, there are problems in that the preparation method is complicated and the selection of usable raw materials is limited.

In the case of composite membranes produced by plasma polymerization coating technology,
The plasma coating deposits in a highly branched and highly cross-linked network. The interaction of the plasma polymer coating with the support and the specific mechanism of plasma polymer formation result in good adhesion of the thin deposited coating to the support. Therefore,
Several researchers are investigating the application of plasma polymerized coatings to prepare composite membranes for gas separation with both high permselectivity and flux.

European Patent Application No. 0 by Van Der 5cheer
No. 134055 discloses a gas-selective film consisting of a dense, very thin gas-selective film of a plasma polymer, a dense, highly permeable interlayer of a conventional polymer, and a microporous support supporting the plasma polymer film and the interlayer. Dense composite membranes for selective separations are disclosed. Conventional polymers deposited directly on the support can be organosiloxanes or copolymers of siloxane and polycarbonate. The very thin gas-selective top layer is a silicon-free plasma polymer. This referenced patent specifically calls for an intermediate layer, the presence of which serves two important purposes: (1) to support the plasma polymer and allow deposition of a very thin top layer, and (2) to provide overall composite In order for the membrane to be used for gas separation, it is necessary to function in distributing gas mixtures onto a microporous support. Therefore, Van Der 5cheer shows that high gas selectivity with high gas flow rates is not expected with direct deposition of a single plasma layer onto a microporous support. In direct and striking contrast to the teachings of this patent publication,
The present inventor has developed a composite membrane with high gas permselectivity and high flux using a specific low molecular weight organosiloxane monomer.
A "soft" and very thin plasma polymer layer could be prepared by depositing directly onto a microporous support by a novel plasma polymerization method. Even more unexpectedly.

By copolymerizing a ``soft'' organosiloxane plasma polymer with a ``hard'' plasma polymer, the inventors have demonstrated that organosiloxanes are highly permselective plasma copolymers for direct deposition onto microporous supports. We discovered that it is possible to provide a coalescing layer.

"Hard" plasma polymers are obtained from organosilanes, fluorocarbons or hydrocarbon monomers.

In U.S. Pat. No. 4,410,338 to Shiraki et al., a gas separation membrane is described in which a microporous support is plasma coated with a polymer derived from organic monomers selected from organosilanes, organosiloxanes and olefins. Served. Shiraki et al. do not recognize any limitations on the molecular weight or size of the monomers used in the preparation of plasma coatings; unexpectedly, the inventors found that a particular group of low molecular weight organosiloxanes, although not reported by Shiraki et al. We have discovered that this method can be used to prepare gas-selective membranes with high gas selectivity. Furthermore, Shiraki et al. makes no mention of the use of the copolymer plasma coatings developed by the inventors for the preparation of gas membranes; Shiraki et al. It is prepared by placing it in a jar plasma reactor and depositing a plasma polymer coating thereon. The intensity of the plasma glow zone develops essentially weakly in such conventional plasma reactors, and the intensity decreases with the distance of the support from the plasma generating electrode. Thus, polymer coatings prepared in this type of reactor cannot be highly cross-linked due to the weak plasma glow zone strength, and furthermore the deposition rate appears to be very slow and the plasma The composition and uniformity of the polymer coating varies with the location of the support within the reactor. The inventors have demonstrated that gas-selective composite membranes can be produced by plasma polymer coatings of specific monomers and comonomers. It was found to have a highly cross-linked structure and a very uniform composition and thickness. This is achieved by performing plasma polymer deposition in a high-frequency tubular plasma reactor with capacitively coupled external electrodes, where the plasma glow zone is controlled to the region between the electrodes and the normal plasma Kudzu has a higher energy intensity than possible in the reactor.

Th1n 5ol entitled "orocom omds"
id Films, 118 (1984) pp187-1
In previous work reported in 95, the inventors reported other low-energy-intensity plasma polymerization reactor systems in which organic monomers other than those used here were used to form coatings for gas separation membranes. However, the inventors have now discovered that certain monomers and certain combinations of monomers and comonomers can be used to prepare gas membranes with high selectivity and high flow rates. It has been discovered that the plasma polymerization for its preparation is surprisingly carried out in the high-energy plasma glow zone of a high-frequency tube reactor with a capacitively coupled external electrode.

In developing the novel gas permeation selective composite membrane of the present invention, the inventors needed to overcome problems inherent in previously used plasma polymerization techniques.

When applied to the preparation of composite membranes, all conventional plasma polymerization coating methods have some type of They suffer from an inherent disadvantage. This drawback is generally due to the fact that conventional plasma polymerizations of this type involve deposition of the polymer onto a support located in a region of low or inhomogeneous plasma energy density.

The drawbacks are generally summarized as follows: 1. Plasma polymer deposition rate and plasma polymer coating composition non-uniformity, depending primarily on the position of the support in the reactor.

2. Polymer precipitation occurs in the “afterglow” zone, Be1
l Jar or I imaginary high frequency coil inductively coupled tube type?
The low or uncontrollable energy densities encountered in conventional plasma reactors (of the audio frequency type, where polymer bonding occurs in the glow zone) (the low deposition rate of conventional reactors further contributes to the deposition of plasma films on the internal electrodes) ).

3. Uniformly and effectively coats a large number of membrane supports due to competitive bleaching from plasma glow and the fact that the rate of polymer deposition depends primarily on the exact location of the support in the reactor. The impossibility of things.

4. Non-uniformity of the coating around the outer surface of the membrane support, for example around the periphery of the fibers.

5. The problem of undesirable multiple species products and the inability to effectively remove unwanted species.

6. Difficulties in controlling all of these plasma deposition parameters, especially in scaling up to commercial production.

In an effort to overcome these difficulties, the inventors deposited plasma polymer onto a microporous membrane support that moved through a high-energy glow zone in the region between the outer electrodes of a high-frequency capacitively coupled tube reactor. We have developed a method to do this. Plasma polymerization techniques, as performed in this reactor system, have a high degree of reliability, can operate at high production rates, and produce highly desirable homogeneous products. Microporous membrane supports are known to be extremely difficult to plasma coat, particularly in continuous practical production, due to their sensitivity to handling effects such as temperature, pressure, tension and chemistry. but,
The present inventors have now unexpectedly discovered that microporous membrane supports can be plasma coated in this manner with speed and efficiency with homogeneous and favorable results, creating a novel combination of high permselectivity and high flux. It was revealed that a gas-selective permselective composite membrane can be produced.

[Summary of the invention]

The present invention further provides a gas selectively permeable microporous composite membrane having a surface of a plasma polymer coating of a specific monomer or a plasma copolymer coating of a specific combination of a monomer and a comonomer, as described in S. It is something to give. This gas film unexpectedly combines gas selectivity and gas flux at a much higher rate than previously achieved with previously available plasma coated gas films.

The present invention also provides a novel plasma polymerization technique for preparing this gas film by operating in an intense plasma glow kettle of a high frequency driven tubular reactor with capacitively coupled external electrodes, as further described. .

First, by using specific monomers or by using specific combinations of monomers and comonomers of the invention, and by carrying out the plasma polymerization in a reactor system such as that disclosed in Futatsuta, the present gas film can be The microporous membrane support that provides the basis for the gas-selective microporous composite membrane of the present invention allows for the unexpectedly high combination of gas flux and gas selectivity achieved by the use of polyolefins, fluorinated Polyolefins and polysulfones can be used, and forms such as films and hollow fibers can be used.

Two different types of plasma polymer coatings can be used: (i) Plasma polymer coatings of "soft" plasma polymers onto microporous membrane supports, where the "soft" plasma polymers are further Obtained from certain low molecular weight organosiloxane monomers as described below.

(ii) Plasma deposition of copolymers of soft and hard plasma polymers, whereby the soft plasma polymers are obtained from organosiloxane monomers and the hard plasma polymers are obtained from organosiloxane monomers. Obtained from organosilanes, fluorocarbons, or hydrocarbon monomers.

The "soft" plasma polymer covers the pores of the porous support, while the "hard" plasma polymer copolymerizes with the "soft" plasma polymer to give the plasma coating high selectivity for gas separation. Add.

Also, in the present invention, separation of gas mixtures is achieved by incorporating this novel gas selectively permeable microporous membrane in the form of hollow fibers into a separation module of the form shown in FIGS. 1 and 2. It is presenting that.

[Detailed description of the invention]

The microporous membranes used as support membranes according to the invention are all known and readily available on the market. Suitable support membranes can be used in the form of flat films, hollow fibers, etc. Hollow fibers are the preferred form here because they provide a large area for gas permeation within a given volume. Separation devices such as the module according to the invention therefore become more compact when hollow fibers are used as separation membranes. The microporous support membrane can be made of polyolefins such as polyethylene or polypropylene, fluorinated polyolefins such as fluorinated ethylene-propylene, and polysulfone. Support membranes suitable for use in the present invention include at least The pores, with pore sizes ranging from about 20 OA to no more than about 800 OA, can have a variety of shapes depending on the manufacturing process, and are generally mouth-shaped or circular. When the pores are non-circular, the shortest diameter of the smallest pore is at least about 2000A and the longest diameter of the largest pore is at most 6000A. Suitable support membranes meeting this requirement are available from Mitsubishi Rayon under the trade names KPF190M, 2F OB and 3
60^, and EHF2fu01! l.

270T, 270H, 410C, 390C and 39
0^, also from Celanese Company under the product name CELGARD 2
400, 2402, 2500, 2502°440
0, 4410, 4500, 4510, K-4
42, K-443, X-10, and X-20. Other suitable polyolefin membranes and fluorinated polyolefin membranes that may be used include U.S. Pat.
, No. 679, 538 (July 25, 1972), No. 3,
No. 801,404 (April 2, 1974), No. 3.80
No. 1,692 (April 2, 1974), No. 3,839,
No. 240 (October 1, 1974), No. 3,839, 5
No. 16 (October 1, 1974), No. 3,843, 76
No. 1 (October 22, 1974), No. 3.920, 78
No. 5 (November 18, 1975), No. 4,058, 58
No. 2 (November 15, 1977), No. 4,138, 54
No. 9 (February 6, 1979), No. 4,255,376 (March 10, 1981), No. 4,257,997 (
March 24, 1981), No. 4,290,987 (1
September 11, 981), and No. 4,405,688 (
September 20, 1983) and is incorporated herein.

The "soft" plasma polymer in the plasma polymer coating according to (i) is obtained by using as a monomer precursor a lower alkyl-substituted disiloxane of the following formula (2) with a molecular weight not exceeding 165: R5, R2, F
ts and R1 are each selected from methyl and ethyl groups. ] Examples of this type of lower alkyl-substituted disiloxane include:
1,1,3.3-tetramethyldisiloxane, 1,1.
There are 3-trimethyl-3-ethyldisiloxane, 1,1-dimethyl-3,3-diethyldisiloxane, and 1,3-dimethyl-1,3-diethyldisiloxane. A preferred monomer is 1°1.3.3-tetramethyldisiloxane.

It is not completely understood why this particular class of organosiloxanes forms plasma-coated microporous membranes with such excellent gas separation properties. When all the bonds of the silicon atoms in disiloxane are attached to carbon, it is more believed that the C51-C bond tends to weaken the 5i-0 bond. Therefore, in the high energy glow zone, 5
The i-0 bond is easily broken, releasing oxygen, which is no longer available for polymerization. When the remaining portion is polymerized and deposited on the support, its properties resemble that of a plasma polymer of silicon rather than that of siloxane. Silane monomers simply cannot form plasma polymers of sufficiently high permselectivity.

This problem does not occur with low molecular weight lower alkyl disiloxanes of type 1 with less substitution. This situation was recognized only by the inventor.

Plasma copolymer coatings according to (ii) are obtained by copolymerization of "soft" and "hard" plasma polymers. "Soft" plasma polymers are obtained using organosiloxanes, not limited to those shown in formula 1 above, as monomer precursors. In the production of copolymer coatings, organosiloxanes coat the pores of the support.
Any organosiloxane can be used to function only as a "soft" polymer and certain comonomers add selectivity that cannot be obtained by using "soft" comonomers alone. Coalescence is obtained by using organosilanes, fluorocarbons or hydrocarbons as monomer precursors. Organosilanes include lower alkyl-substituted silanes such as tetramethylsilane and lower alkoxysilanes such as tetramethoxysilane, fluorocarbons include perfluorinated hydrocarbons such as tetrafluoroethylene, and hydrocarbons include perfluorinated hydrocarbons such as propylene. Contains molecular weight hydrocarbons.

In accordance with the present invention, gas films made using lower alkyl-substituted disiloxanes such as those described in Equation 1 above have higher rates of gas than those obtained in the related gas films of Shiraki et al., as previously described. Showing selectivity and gas flux. The only disiloxane discovered by Shiraki et al. is hexamethyldisiloxane, (CH=)3S i O5i(CH:+
)z, which is a beralkyl-substituted disiloxane which is more sterically hindered than the siloxane of formula 1 above and is bulkier as a molecule. Furthermore, the bexamethyldisiloxane used by Shiraki et al. has a higher molecular weight than the disiloxane shown in formula 1 this time. As is well known in the plasma polymerization profession, high molecular weight monomers produce plasma films with a low degree of crosslinking per unit volume. Therefore, it is "softer" and therefore exhibits less gas selectivity. Conversely, lower molecular weight monomers create plasma polymer coatings that are highly cross-linked and therefore are "harder" or "tighter" and thus exhibit higher gas selectivity.

On the other hand, low molecular weight monomers have the disadvantage of a lower plasma polymer deposition rate than high molecular weight monomers.

The inventors have now unexpectedly discovered that certain low molecular weight monomers, namely lower alkyl-substituted disiloxanes of formula 1 above, such as 1.1.3.3-tetramethyldisiloxane, can be When polymerized in a plasma polymerization apparatus, it rapidly precipitates onto a microporous membrane support, resulting in an essentially superior gas selectivity and gas permeability membrane compared to Shiraki et al.'s gas selective permeable membrane or other conventional gas selective permeable membranes. A gas-selective permselective composite membrane with flux is provided.

In this plasma polymerization, activation of the required monomer or comonomer to high energy within the glow zone, radical,
a dissociated form rich in electrons and ions (i.e. plasma),
Deposition of the plasma polymer or copolymer as a plasma polymer or copolymer through the glow zone onto the surface of the support is involved. In practice, a discharge from a high frequency generator is applied to the external electrode of a capacitively coupled tube reactor. Certain monomers or comonomer precursors are introduced into the reactor and excited into a plasma. In the present invention, the region of highest plasma energy density in the reactor is controlled in the region between the electrodes, the plasma glow zone.

Since the plasma glow zone is the most energy-dense region in the reactor, the temperature-sensitive support used here reduces residence time in the reactor while still allowing for proper deposition of the plasma film. This is essential. This is accomplished by moving the support in continuous form, such as a film or hollow fiber, to a plasma glow zone where plasma-excited monomers are sequentially polymerized and deposited onto the moving support.

The movement of the support through the region of the plasma glow zone is controlled both by thermal theory, the pulling rate and the tension on the support. Since the plasma glow zone is the region of highest energy density in the plasma reactor, the pulling speed and tension are sufficient to allow adequate deposition of the plasma polymer on the support, while reducing the To avoid damage to the support,
The residence time of the support in the glow zone must be set and controlled; at the same time, both the pulling rate and the tension are controlled so that the support is attached to the reactor wall or other support so that a large number of supports are coated simultaneously. should be controlled to avoid touching.

Previous researchers have avoided coating polymeric supports particularly in the plasma glow zone and have resorted to coating in outer areas adjacent to the glow zone because they have experienced uncontrollable degradation of the support. Through tight control of the specific variables outlined herein, the inventors have unexpectedly been able to create gas selectively permeable microporous composites that retain the inherent properties of mechanical strength and chemical resistance of the support. Precise controllable and completely reproducible coatings could be obtained by preparing membranes.

A system suitable for continuous production of this gas selectively permeable membrane is illustrated in FIG. The high frequency plasma reactor is a tubular reactor 36 with a pair of capacitively coupled external electrodes 31 located at either end of the reactor 36 and coupled to an external high frequency generator.

The highest energy density is maintained in the region between the electrodes, the plasma glow zone, by controlling both the current from the radio frequency generator and the flow rate of the monomer or comonomer. If the flow rate is too fast, the glow band will "spill out" to the area outside the electrodes, and if a flow rate is too slow, the plasma will not burn or will not spread to the entire area between the electrodes. The two chambers 35A and 35B are vacuum chambers connected therewith to a reactor 36 in continuous vacuum sealed relationship.

38 is the outlet to the vacuum pump. The reactor 36 is made of a material sufficiently resistant to plasma polymerization reaction conditions.

Currently, quartz, PYREX", VYCOR", 1:
It is known that it is compatible with this. In operation,
Hollow fibers 32 move continuously through reactor 36 from unwind spool 33 to take-up spool 34.

Desired monomers and comonomers are supplied to the system at inlet 37.
supplied through.

Minimizing the residence time in the plasma glow zone and also keeping the support as cold as possible (i.e., close to room temperature) prevents damage to temperature-sensitive supports and prevents plasma polymerization onto the support. is important to promote high precipitation rates. The support can be passed through the glow region several times to achieve the desired thickness of plasma coating and maximize plasma polymer deposition. In the preparation of gas-selective permeable composite membranes, it is important that the pores of the microporous support are completely crosslinked, and to achieve this purpose, sufficient plasma polymer or copolymer coating is deposited. It is important to. To achieve this objective, it is possible to create a system in which the direction of movement of the support can be reversed so that a continuous length of the support is passed through the glow zone several times in order to obtain the desired coverage. The direction of feeding can be in the direction of the movement of the support through the glow zone or in the opposite direction.

The system shown in Figure 3 can be easily modified for continuous production of film membranes by providing a reactor 36 and take-up spools 33 and 34 of sufficient size to handle continuous film. . Similarly, multiple m-fibers can be coated simultaneously by providing the necessary reactor 36, unwinding and take-up spools 33 and 34.

The energy density produced in the glow zone of the plasma reactor system of the present invention is much higher than that obtained with conventional plasma reactors. This requires minimizing the length of exposure to the plasma glow zone to avoid damage to the membrane support. for example.

The polyolefin support must be moved through the plasma glow zone at a rate typically in excess of 2 cs/sec each time.

The residence time within the plasma glow zone varies depending on the thermal theory and its support. With more temperature resistant supports such as polysulfone, longer exposure times are possible to achieve the required plasma polymer coverage.

The method of the invention can be applied to a uniform surface such as a film, a peripheral or swirling surface such as a hollow fiber or a heterogeneous membrane support, a plurality of supports, e.g. allows for easy deposition of the required plasma polymer coatings on the substrate. This is because in this system the plasma glow zone can be maintained at a uniform density across the cross-sectional area of the tubular reactor.

In conventional plasma reactors (eg, AF tandem systems) that perform plasma deposition within a glow zone, it is impossible to maintain a uniform density in the glow zone. In plasma reactors where deposition occurs in the "afterglow" zone (e.g. bell jars, high frequency coil inductively coupled tube reactors), the density of the plasma and therefore of the precipitated polymer decreases with distance from the glow and the gas The flow pattern becomes uncontrollable. Also, in a typical plasma polymerization reactor, the support must be positioned, for example, on the electrode or with the reactor wall.

In such a typical system, the quality and uniformity of the coating,
It is known that the composition and uniformity of deposited plasma polymers vary depending on the relative position of the support to the plasma glow. Therefore, when multiple substrates are plasma polymer coated simultaneously, the uniformity of the composition of the plasma polymer coating will vary depending on the relative position of the individual substrates to the plasma glow zone and the specific In order to replicate a plasma polymer coating on a particular support, the support must be carefully placed in the exact same location within the reactor. All of these problems are inherent in the operation of systems such as those illustrated in Shiraki et al. US Pat. No. 4,410,338. In contrast, in the present system, product quality and uniformity within and between each unit operation is ensured by uniform density throughout the glow zone.

The tension on the support moving through the plasma glow zone preserves the original morphology and tensile strength of the support membrane while allowing adequate spacing between multiple supports and contact of the support to the reactor wall. To prevent this, it must be kept as low as possible. Due to the plasma glow zone strength in this system, the plasma polymer deposition rate is much higher than possible with conventional plasma reactor systems. Plasma polymer deposition is controlled between the electrodes and "afterglow J deposition is kept to a minimum."

The appropriate spacing between the electrodes depends on the size of the tube.

In the system described here, the electrodes are approximately 10-15c.
m apart, the diameter of the tube is 13 m+*. In larger diameter tubes, the energy density associated with the plasma glow zone should be kept as close as possible to that of smaller tubular reactors. Along with energy density, controlling monomer density is extremely important.

Monomer density generally remains the same as tube diameter changes, but changes in both the energy density and monomer optima occur with changes in system size and design.

Due to the very high energy density within the plasma glow zone, the temperature of the support should be as low as possible to ensure a uniform plasma polymer deposition rate and prevent distortion and damage to the support as it passes through the plasma glow zone. (near room temperature). Under normal process conditions, some precipitation of plasma polymer onto the reactor wall soil is normally observed.

This does not have a deleterious effect on processing conditions, is a common occurrence, and is removed with routine maintenance. By keeping the support as cold as possible, the plasma polymer is encouraged to precipitate preferentially on the membrane support rather than on the reactor walls. Further cooling of the support below room temperature can also be used if desired and is expected to increase residence time in the reactor and enhance further precipitation of plasma polymer onto the membrane support. Ru.

A useful indicator for determining the change in reaction parameters due to changes in the tubular geometry is the composite discharge parameter, W/FM.
where W is the plasma power, F is the monomer flow rate, and M is the monomer molecular weight. As tubular geometry and system size vary, W/FM will vary for a given plasma polymer or copolymer deposition rate, but the optimal W
/FM varies between 1/2 and twice the original W/FM for a given monomer system. Therefore, for a fixed monomer system, the change in the composite plasma parameter due to a change in the tubular geometry is (1/2))fa/FaMa<Wb/FbMb
<(2) Represented by Ha/FaMa. This is Wa
/FaMa is the composite plasma parameter for the first tubular plasma reactor described here, and Wb/FbMb is the composite plasma parameter for the different sized tubular high frequency reactors described here.

This plasma polymerization method has the following advantages over conventional plasma polymerization methods: 1. From the thickness of the plasma polymer to the chemical composition.
Capable of uniformly covering a single support or a plurality of supports.

2. It is possible to obtain both high energy density and high deposition rate with minimal residence time on the support in the energy-intensive plasma glow region.

3. A narrower population of species can be created in the plasma glow region than is possible in conventional plasma reactors, as evidenced by the uniform nature of the finished plasma polymer coating.

4. Remove waste products (i.e., unreacted monomers, and potentially damaging corrosive gases) from the glow region of the tubular reactor by continuous means, minimizing the effects of the presence of the same products. This is due to the fact that the monomer flow rate is faster than the support velocity so that these waste products can be washed away. Furthermore, since the plasma glow region is almost exclusively deposited with plasma polymer, when the support moves into the "afterglow region" of the reactor, it is already protected by the deposited layer of plasma polymer. and to avoid damage that it may suffer from the waste products mentioned above. A counter-motion system is employed that allows a series of lengths of support to be passed repeatedly through the glow region, so that the flow rate of the single gas removes waste products in the "afterglow" region from areas where the support is still coated. Avoid damaging any parts.

5. Additional advantages include the ability to manufacture composite membranes in a continuous process at rates acceptable even at commercial production scales, and the ability to manufacture composite membranes in a continuous process at rates acceptable to commercial production scales, as well as the ability to manufacture composite membranes such as polyolefins, which would not be considered preferred membrane supports under conventional plasma reactor conditions. These include the ability to plasma coat even sensitive supports. As mentioned above, an additional advantage is that plasma coating is possible using certain low molecular weight monomers mentioned here, which would not have been considered preferred reactants in conventional plasma polymerization methods due to their low deposition rates. This is the point where it is possible to apply

FIG. 1 shows a schematic diagram of a separate open-ended module employing the gas selectively permeable microporous composite membrane of the present invention in the form of hollow fibers.

A plurality of hollow fibers 11, preferably made of glass or a suitable inert material, are used in each modular unit. Each end cap 12 of the module unit
The ends of the hollow fibers are secured within, so that the gaseous mixture flowing into the inlet 14A of the module unit will flow around the hollow fibers 11. Permeable gas is exhausted through outlet 13 and impermeable gas is exhausted through outlet 14B.
is discharged through the

FIG. 2 is a schematic diagram of a separate module with one end open, incorporating the hollow fibers of the gas selectively permeable microporous composite membrane according to the present invention.

Preferably, a plurality of hollow fibers 21 are used in each module unit. A hollow fiber, which may be formed of glass or a suitable inert material, is inserted into the shell of the module. The ends of the hollow fibers are secured in the end caps 22 of the module unit, so that the gaseous mixture flowing into the module inlet 24A flows through the hollow l! It flows around the fiber 21. Another suitable separate module according to the invention incorporates a zero gas-selective hollow fiber membrane with permeable gases being exhausted through outlet 23 and impermeable gases being exhausted through outlet 24b. U.S. Patent No. 3,821,087, issued June 28, 1975;
4,184,922 (all Kn
aqek et al.), all of which are incorporated herein by reference.

As will be apparent to those skilled in the art, the manner in which the gas-selective microporous composite membranes of the present invention are employed in gas separation procedures is merely a matter of choice and convenience. There is no need to be limited to the particular apparatus shown here, but any method capable of accomplishing the required gas separation may be used.

The flux J (cm'/cm2 seconds) passing through the membrane is approximately expressed as J=P (P/). However, P(cm' cr
s/cII2s cmHg) represents the permeability coefficient, P (c
mHg) represents the pressure difference across the membrane thickness CII Suitable for expressing gender. In the case of hollow fibers, the membrane area can be calculated appropriately using the logarithmic average of the inner diameter and outer diameter.

The selective permeability CP(A)/P(B)) is also varnish system-A
The zero selective permeability (P(A)/P(B)), which is an important factor when evaluating the layer selectivity for -B, is obtained by the following equation.

However, CA1 and C1 are the molar fractions on the supply side, C
A2 and C8□ are the mole fractions in the permeate for each of gaseous components A and B, and Pl and P2 are the respective absolute pressures in the feed and permeate. For example, in the ideal case, if there is no interaction between gases and no pressure drop at the inner diameter of the hollow fiber, the value of the permselectivity CP(A)/P(B)) is the permeability coefficient P(A)/ P(
The gas selectively permeable membrane of the invention, which has a high selectivity for the oxygen-nitrogen gas system corresponding to the ratio B), is useful in the case of oxygen enrichment and in the purification and separation of nitrogen from air.

The membranes of the present invention, which exhibit high selectivity for the hydrogen-carbon monoxide gas system, are useful for preparing synthetic fuels from water gas. Membranes with high selectivity for nitrogen-hydrogen systems are useful in ammonia synthesis. Membranes with high selectivity for the helium-methane system are useful for practical recovery of helium from natural gas sources. Membranes exhibiting high selectivity for the carbon dioxide-methane system are useful for methane purification of biogas - by removal of raw carbon dioxide.

In the specific example below, membrane performance measurements were performed at room temperature. The applied gauge pressure was 6.5 atmospheres.

The gas that permeated the membrane was collected at atmospheric pressure. Compressed air was used for the supply, and the ratio of 02 to N2 concentrations was 721:79. Concentrations of components were measured using gas chromatography.

(Detector: TCD, Column: 5 intermolecular voids, Shimadzu Corporation, Japan)] 1 m, inner diameter 100 micrometers, porosity 20%, wall thickness 2
A 4.5 micrometer polypropylene microporous hollow fiber was used as the support. Plasma polymerization coating was carried out according to the following conditions.

(i) Monomer: 1,1,3.3-tetramethyldisiloxane Discharge power = 5 watts, R, F, power supply (13,56 MHz) Traction speed: 2.4 cm/sec Monomer flow rate: Variable (ii) Monomer :1,1.3.3-Tetramethyldisiloxane (a) Tetramethoxysilane (b) Tetramethylsilane (c) Tetrafluoroethylene (d) Propylene Discharge type Crab 5 Watt, R, F, power supply (13,56MHz ) Traction speed: 2.4 cn+/sec However, the traction speed determines the fiber residence time in the plasma glow region. The plasma coating was applied by passing the support three times through the plasma glow region with an electrode length of 15 cm.

Therefore, the total residence distance was 45 cm and the residence time in the plasma glow region was 19 seconds.

For preparation (ii), after plasma polymerized coating, the membrane was cured by soaking in absolute ethanol for 1 hour.

In the preparation of plasma copolymer coating according to preparation (ii),
Following plasma copolymer deposition, the membrane was cured by soaking in absolute ethanol for 1 hour. This curing method has the function of strengthening the crystal structure of the plasma copolymer through cross-linking, and improves the gas selectivity of the composite membrane.

The microporous hollow fibers described below were coated by plasma polymerization under the conditions (i) described in the Preparation section.

The monomer flow rate and system pressure are as follows: Jil
484-11: Monoma? 1mi; 5.12SCCM,
System pressure: P (inlet) 145.3 mtorrP (outlet) 8
1.4 mtorr membrane 484-22: Monomer flow rate, 3.64 SCCM
System pressure: P (inlet) 117.8 mtorrP (outlet) 5
5. Omtorr membrane 484-32: Monomer flow rate, 6.66 SCCM
, system pressure; P (inlet) 173.5 mtorrP (outlet)
100.5mtorr membrane 497-11: Monomer flow rate, 5.80SCCM
, system pressure; P (inlet) 160.0 mtorrP (outlet)
83.2mtorr 11 500-12: Mo/7 1J5L; 5
．． 80SCCM system pressure; P (inlet) 157.9 mtor
rP (outlet) 97.2 motrr Membrane performance for the membranes described above is shown in Table 1.

The oxygen concentration during penetration is 37.7% depending on the coating conditions.
It varied between ~41.2% (selective permeability CP(02)/
P(N2)): 2.6-3.2), while the feed rate (P/1) is 7.48X10-5 to 1.41X10
-'am/c12 seconds.

It varied between up to the mercury column.

Table 1 Permeability of permeate P/1 Selective permeation film number Oxygen concentration (cm3/cm'sec cmHg) CP(
02)/P(N2))484-11 39.1
4.90xlO-' 2゜9484-22
41.2 1.41 3.2484
-32 37.7 7.48 2.
6497-11 39.1 2.98
2.9500-12 38.2ne 5
．． 12*2.8 supply
02/N2=21.6/78.4 supply”
= 21.3/7.87° or less Margin design = 1 The microporous hollow fiber was coated by plasma polymerization according to the conditions (11) in the preparation section.

The monomer flow rate and system pressure are as follows.

Membrane 504-212: Monomer flow rate, 3.76SC
CM (1,1,3,3, tetramethyldisiloxane to tetramethoxysilane = 50 to 50) System pressure P (inlet > 118.5 mtorr P (outlet) 7
1.5 mtorr membrane 503-212: Monomer flow rate, 4.10S1
05CC, 1,3,3, tetramethyldisiloxane vs. tetramethylsilane = 50:50) System pressure: P (inlet) 128.0 mtorrP (outlet) 8
0.2mtorr membrane 513-122, monomer flow rate, 4.20SC
CH (1, 1.

3.3, Tetramethyldisiloxane) + 2.45SCCM (Tetrafluoroethylene), System pressure crab P (Inlet > 132.2w + torr P (Outlet)
7.2mtorr membrane 505-212, monomer flow rate, 4.60SC
CM, (1,1,3,3,tetramethyldisiloxane) + 1.16SCCM (propylene) System pressure; P (inlet > 114.2 mtorrP (outlet) 6
After 5.9 mtorr plasma coating, the membrane is immersed in absolute ethanol for 1 hour to cure.

Membrane performance for the membranes described above is shown in Table 2. Oxygen concentration during penetration is 39.5% to 42.1%
(selective permeability CP(02)P(N2))
;3.0 to 3.4), while the feed rate (P/1) varied between 5.78 x 10-5 and 2.02 x 10-' (cm/cm2 seconds cIll mercury).

Margin No. - Plate - Surface layer number Oxygen concentration (cm'/am2 seconds cmHg)
[P(02)/P(N2))504-212 3
9.5 5.78X10-5 3.0(b)
T? 4DSO+TMS 503-212 39.7 3.15
3.0(c) TMDSO+TFE 513-122 40.0 3.64
3.1(d) TMI) SO+PP Supply 02/N2=21.3/78.7TMDS0
, 1 , 1 , 3 , 3, Tetramethyldisiloxane River C; Tetramethoxysilane TMS, Tetramethylsilane TFE, Tetrafluoroethylene PP; Propylene.

[Brief explanation of the drawing]

FIG. 1 shows a separation module with both ends open. FIG. 2 shows a separation module with one end open. FIG. 3 is a cross-sectional view of the outline of the plasma polymerization system. Explanation of main parts in the figure: 11...Hollow fiber, 12...End cap, 1
3... Outlet of permeable gas, 14A... Inlet of raw material gas, 14B... Outlet of impermeable gas, 21... Hollow fiber, 22... End cap, 2
3... Outlet of permeable gas, 24A... Inlet of raw material gas, 24B... Outlet of impermeable gas, 31... External electrode, 32... Hollow fiber, 33...
... Unwinding spool, 34... Take-up spool, 35A... Chamber, 35B... Chamber,
36... Tubular reactor, 37... Supply inlet, 38...
...Outlet to vacuum pump. Engraving of drawings (no change in content) Dimensions ('IJ Procedural amendment (method) July Zq, 1985 Director General of the Patent Office Kunio Ogawa 1, Indication of case 1989 Patent Application No. 089658 2, Invention Name of Gas Selectively Permeable Composite Membrane 3 Manufactured by Plasma Polymerization Coating Technique Relationship with the Amendment Case Name of Patent Applicant Applied Membrane Technology Inc. Address of Agent 4 Address: 105 Minato-ku, Tokyo Toranomon-chome 8-10 Shizukou Toranomon Building Tel: 504-0721+1) Specification (2) Drawing 7, contents of amendment Tl) Engraving of specification (no change in content) (2)
Engraving of drawings (no changes in content) 8, list of attached documents (1) Engraved specifications 11 copies (2) Engraved drawings 1 copy

Claims (1)

[Scope of Claims] 1. A gas selectively permeable microporous hollow fiber membrane comprising a microporous hollow fiber support and a gas selectively permeable plasma polymer coating on the surface of the support, wherein the plasma polymer coating is made from organosiloxane monomers, optionally copolymerized with monomers selected from organosilanes, perfluorinated low molecular weight hydrocarbons, and low molecular weight hydrocarbons. A membrane characterized by. 2. The membrane according to claim 1, wherein the microporous support is a polyolefin or a fluorinated polyolefin. 3. The membrane according to claim 2, wherein the microporous support is polypropylene, polyethylene or fluorinated ethylene propylene. 4. The membrane of claim 1, wherein the plasma polymer coating is formed from an organosiloxane. 5. The membrane according to claim 4, wherein the plasma polymer coating is formed from lower alkylsiloxane. 6. The membrane of claim 5, wherein said plasma polymer coating is formed from 1,1,3,3-tetramethyldisiloxane. 7. The plasma polymer coating is formed from an organosiloxane (copolymerized with monomers selected from organosilanes, perfluorinated low molecular weight hydrocarbons, and low molecular weight hydrocarbons). The membrane according to item 1. 8. The plasma polymer coating is formed from lower alkylsiloxane (copolymerized with monomers selected from lower alkylsilanes, lower alkoxysilanes, perfluorinated low molecular weight hydrocarbons, and low molecular weight hydrocarbons). The membrane according to claim 7, characterized in that: 9. The plasma polymer coating is formed from 1,1,3,3-tetramethyldisiloxane (copolymerized with monomers selected from tetramethoxysilane, tetramethylsilane, tetrafluoroethylene and propylene). 9. A membrane according to claim 8, characterized in that: 10. A method for producing a gas-selective microporous composite membrane, comprising: applying a radio frequency discharge to a capacitively coupled external electrode of a tubular plasma reactor; , perfluorinated low molecular weight hydrocarbons and monomers selected from low molecular weight hydrocarbons), said monomers or comonomers in a controlled plasma in a glow region between the electrodes of the reactor. A method comprising depositing a gas selectively permeable plasma polymer coating on the surface of a microporous support introduced into a reactor and moved through a glow region for activation. 11. The method according to claim 10, wherein the microporous support is a film or a hollow fiber. 12. The method according to claim 11, wherein the microporous support is a hollow fiber. 13. Process according to claim 10, characterized in that the reactor is adapted for processing microporous supports in the form of continuous films or hollow fibers. 14. The method according to claim 10, wherein the microporous support is polypropylene, polyethylene or fluorinated ethylene propylene. 15. The method of claim 14, wherein said plasma polymer coating is formed from an organosiloxane. 16. The method of claim 15, wherein said plasma polymer coating is formed from 1,1,3,3-tetramethyldisiloxane. 17. The plasma polymer is formed from an organosiloxane (organosilane, a perfluorinated low molecular weight hydrocarbon or copolymerized with a low molecular weight hydrocarbon). the method of. 18. The method of claim 11, wherein the plasma polymer is formed from an organosiloxane (copolymerized with organosilanes, fluorocarbons or hydrocarbons). 19. Claim characterized in that the plasma polymer is formed from 1,1,3,3-tetramethyldisiloxane (copolymerized with tetramethoxysilane, tetramethylsilane, tetrafluoroethylene or propylene) The method according to item 18. 20. A module for separating gas mixtures, comprising: a shell means having a spatial end and an extended chamber therebetween; b substantially parallel from each other within said shell means; a plurality of individual gas-selective hollow fibers extending in relation to each other, a chamber separated by the walls of said hollow fibers into an intracapillary space within said hollow fibers and an extracapillary space outside said hollow fibers;
and said intracapillary space and said extracapillary space that communicate with each other only through the walls of said hollow fibers; c. means for communicating with said extracapillary space for passing a gas mixture therethrough; and d. means for transferring permeate gas therefrom. a module comprising means for communicating with said intracapillary space to. 21. The module of claim 20, wherein the hollow fiber support is selected from polyolefins, fluorinated polyolefins, and polysulfones having pore sizes ranging from at least about 10A to up to about 6000A. . 22. Claim 21, characterized in that the hollow fiber support is selected from polypropylene, polyethylene, fluorinated ethylene propylene or polysulfone.
Modules listed in section. 23. The plasma polymer coated on the surface of the hollow fiber is 1,1,3,3-tetramethyldisiloxane, 1,
1,3-trimethyl-3-ethyldisiloxane, 1,1
-dimethyl-3,3-diethyldisiloxane and 1,3
21. Module according to claim 20, characterized in that it is selected from -dimethyl-1,3-diethyldisiloxane. 24. Claim 2, wherein the monomer is 1,1,3,3-tetramethyldisiloxane
Module described in Section 3. 25. A module for separating gas mixtures comprising: a. means having a spatial end and an extended chamber therebetween; b. substantially parallel relationship from each other within said shell means. a plurality of gas-selective microporous hollow fibers extending in the hollow fibers, a chamber in which the intracapillary space and the extracapillary space within the hollow fibers are separated by the walls of the hollow fibers, and which communicate with each other only through the walls of the hollow fibers; a module comprising: c, means for communicating with the extracapillary space for passing a gas mixture therethrough; and d, means for communicating with the intracapillary space for removing permeate gas therefrom. . 26. The plasma polymer coated on the surface of the hollow fiber is formed from the copolymerization of an organosiloxane and a comonomer selected from organosilanes, fluorocarbons and hydrocarbons.
Modules listed in section. 27. Claim 26, characterized in that the monomer is 1,1,3,3-tetramethyldisiloxane, and the comonomer is tetramethoxysilane, tetramethylsilane, tetrafluoroethylene or propylene. Modules listed in section. 28. A method for separating gases, comprising: placing a gas-selective membrane having an O_2/N_2 gas-selectivity of at least about 2.3 in a suitable gas separation apparatus, and in order to obtain the required separation, A method comprising contacting a membrane and a gas mixture. 29. A method for separating gases, comprising: disposing a gas-selective microporous hollow fiber membrane having an O_2/N_2 gas permselectivity of at least about 2.3 in a suitable gas separation apparatus and performing the necessary separation. contacting said membrane with a gas mixture to obtain said membrane.