JPS59183802A - Permselective membrane for separation of gas - Google Patents

Abstract

PURPOSE:To form an oxygen-enriching membrane having large PO2 and PO2/ PN2 ratio and excellent strength, durability, chemical resistance, and oxidation stability, by using polyaryloxyphosphazene as a constituent. CONSTITUTION:Polyphosphazene is prepared by reaction of polydichlorophosphazene, obtained from a cyclic chlorophosphazene, e.g., hexachlorocyclotriphosphazene or octachlorocyclotetraphosphazene or linear low-molecular weight chlorophosphazene, in the presence or absence of a catalyst in a sufficiently dried system by thermal polymerization, with an aryl oxide of an alkali metal, e.g., sodium, potassium, lithium, etc., obtained from a corresponding phenol or substituted phenol. Suitable solvents, include ketones, e.g., methyl ethyl ketone, in the case of polybisphenoxyphosphazene.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a selectively permeable membrane for gas separation,
In particular, the present invention relates to a selectively permeable membrane containing polyaryloxyphosphazene, which is suitable for concentrating oxygen from air.

It has been known for a long time that specific components can be separated and concentrated from a gaseous mixture using membranes made of polymeric materials, and in recent years it has attracted attention, particularly from the viewpoint of resource and energy conservation. Among these, it would be of great value if oxygen-enriched air with an increased oxygen t# degree could be obtained from air cheaply, easily, and continuously by a membrane separation method.

At present, the oxygen used for medical purposes such as incubations for premature babies or for the treatment of patients with respiratory diseases is pure oxygen filled in cylinders. It has serious disadvantages, such as the fact that it cannot be used or that it must be used diluted. However, if an efficient membrane capable of supplying oxygen more concentrated than air could be obtained, the above-mentioned drawbacks would be overcome, and further, a simple device could be used at home, and great progress could be expected in the medical field.

In addition, membranes can be used to easily and continuously enrich oxygen in various combustion systems currently in use, such as industrial boilers, furnaces, blast furnaces in steel manufacturing, internal combustion engines used in automobiles, and home heating appliances. If air is supplied, combustion efficiency can be increased and fuel can be saved, leading to energy savings, and the problem of environmental pollution caused by incomplete combustion can be resolved. Furthermore, if oxygen-enriched air can be supplied cheaply and easily by means of water, it will be possible to promote its development in the pond field, such as the food industry, cultivation and fishing, and waste treatment.

Currently known polymer materials have gas permeability to a greater or lesser extent.In order to make an industrially practical oxygen enrichment membrane, the gas permeation rate must be sufficiently high and the selectivity of oxygen to nitrogen must be high enough. must be large. The gas permeation rate is determined by the permeability coefficient (usually P
It is expressed in cm” (S T P ) cm/
cm'' -sec -cm, (g), 1TII side 1tU (7) difference [E and membrane surface area, and is clearly proportional to membrane thickness and inversely proportional to lamina thickness.Also, the selectivity of oxygen to nitrogen is the value between the oxygen permeability coefficient (Fax) and the nitrogen permeability coefficient & (pNz), which are values specific to molecular substances:
, (P 02 /P N2 ). Therefore, in order to obtain a practical permeation rate, it is first necessary to select a material with a high Po2 value; otherwise, the differential pressure or membrane surface area must be increased, resulting in a large and complicated device. In addition, in order to obtain sufficient oxygen concentration, 1
．． A polymer with a large P 02/P N 2 must be selected. Furthermore, in order to obtain as high a permeation rate as possible, the film thickness must be made thin, and for this purpose the strength of the material must be high. In addition, it is durable to withstand long-term use and always has a high concentration of oxygen! g: Oxidation resistance stability is also required for contact. In other words, Po2 and p02/P are industrially practical membrane materials for oxygen enrichment.
A material with a large N2 content and excellent potash strength, durability, and oxidation stability is required.

However, there are almost no existing polymeric materials that meet these requirements, and although many attempts have been made to improve existing polymers, none of them have been able to fully achieve their goals. Examples of existing polymers Po2 and PG2/PN2 are shown in the table below.

Existing polymers with Po2 of 10 or more are very limited, and only a few include polydimethylsiloxane and poly-4-
There are pentene-1, natural rubber, etc. Most of the other polymers have a value of 10 or less, and unless the membrane area is extremely large, it is not possible to obtain a membrane having a more practical permeation rate than those of these polymers. Even if the polymer has a Po2 of 10 or more, natural rubber, for example, has poor durability (especially oxidation stability) because it has a 10-C- double bond in its main chain.
Also, mechanical strength is insufficient.

Since poly-4-methylpentene-1 is a polyolefin, it has strong oxidation stability because it has tertiary carbon in the main chain of the wall. ) there is a problem with using it. Borijime'
Thirsiloxane has the highest gas permeability among currently known polymers, but has a weak strength of 20 μm.
It is extremely difficult to produce the following membrane, and it is impossible to obtain a practical permeation rate despite the large Po2. Although the strength of the wall can be increased to some extent by reinforcing it with a filler and crosslinking, these treatments impede film forming properties and make it difficult to form a static film. Furthermore, it has the essential drawback that KPJ/PN2 is small and the selectivity of oxygen to nitrogen is low. In order to take advantage of the large i-form permeability of 9-polydimethylsiloxane, several attempts have been made to improve its strength by copolymerizing it with other components. For example, U.S. Pat. No. 3,189,662 proposes a block copolymer of polydimethylsiloxane and polycarbonate. This material has a certain degree of strength due to the introduction of polycarbonate units.
Not only does it have the drawbacks of low solvent resistance and easy deterioration due to pump oil, etc., but also causes intermelting, which lowers the PO2 compared to polydimethylsiloxane alone. There are many other attempts to improve the above drawbacks by modifying polyorganosiloxane by reaction with other components, but strangely, all of them reduce the strength of the siloxane Venus in the polymer. There is a dilemma in that, although improvements are made, the characteristic of polyorganosiloxane, which is a large p02 value, will be lost. As described above, existing polymers and polymers obtained by modifying them do not meet the above-mentioned requirements.

The present inventors have carried out extensive research into oxygen enrichment membranes that have large Po2 and PO2/PN2 values, but also have excellent properties such as strength, durability, chemical resistance, and oxidation stability.
The present invention was achieved by discovering that a membrane containing polyaryloxyphosphazene as a component satisfies these requirements.

The selective gas permeable membrane of the present invention contains polyphosphazene represented by the following general formula as a constituent component.

X and X' in formula (1) are aryloxy groups,
Preferably phenoxy group or one hydrogen of phenoxy group
Straight-chain or branched alkyl groups with 1 to 20 carbon atoms; straight-chain or branched alkoxy groups with 1 to 10 carbon atoms; aryl groups with 6 to 20 carbon atoms; halogen; An aryloxy group substituted directly with a group selected from the group consisting of an alkylamino group, a cyano group, and a nitro group having from 1 to 10 straight-chain or branched alkyl groups, which are equal to or different from each other. and n is an integer from 20 to 70,000.

Preferred specific examples of the aryloxy group include phenoxy group, 4-methylphenoxy group, 3-methylphenoxy group, 2,6-cya/phenoxy group, 4-ethylphenoxy group, 4-n-propylphenoxy group, 4 -iso-pro and ruphenoxy groups, 4-sec-butylphenoxy groups,
4-tert-butylphenoxy group, 4-n-pentylphenoxy group, 4-2-ethylhexylphenoxy group,
Alkyl group-substituted aryloxy group such as 4-nonylphenoxy m, 4-n-dodecylphenoxy group, 4-hexadecylphenoxy group, 4-phenylmethylphenoxy group, or 4-trifluoromethylphenoxy group, 4-
Methoxyphenoxy group, 6-methoxyphenoxy group, 4
- Alkoxy groups such as ethoxyphenoxy, 4-n-butoxyphenoxy, 4-sec-butoxyphenoxy, and 4-hexyloxyphenoxy; Directly substituted aryloxy groups such as direct aryloxy and 4-phenylphenoxy groups. group, 4-chlorophenoxy group, 4-
Bromophenoxy group, 4-fluorophenoxy group, 6-
chlorophenoxy g, 2.4-dichlorophenoxy group,
2.4-dibromophenoxy group, λ4.6-dodecylphenoxy group, 2-chloro-4-methylphenoxy group, barchlorophenoxy group, barfluorophenoxy group, etc., halogen-directed aryloxy group, 4-dimethylaminophenoxy group, 4-diethylami/phenoxy group, 4-
aryloxy groups directly substituted with alkylamino groups, such as flobylaminophenoxy groups and 4-butylaminophenoxy groups;
Cyano group substituted aryloxy group such as 4-cya/phenoxy group, 2-nitrophenoxy group 1.2-nitro-4-
Examples include aryloxy groups directly substituted with a nitro group such as a methylphenoxy group, a 4-nitrophenoxy group, and a 2-chloro-4-nitrophenoxy group.

nFi is an integer from 20 to 70.000 and is usually a rubbery or flexible solid.n
If it is less than 20, the strength is too weak to provide a practical strength as a tax, which is undesirable. Also, n is 70.00
If it is larger than 0, the molecular weight is too large and production is difficult, and the viscosity of the film-forming solution is too high, making it difficult to form a film, which is not preferable. Note that even when n is larger than 20, it may become an oily liquid depending on the type of substituent. Of course, polyphosphazenes containing a portion of these may also be used, and other porous membranes impregnated with liquid polymers may also be used. You can also use

The polyphosphazene of the present invention can be produced by known methods (for example, R,L Singer
et al., J.

Polym, 8ci, Chem, Ed, , 12
, 433 (1974).

For example, polydichlorophosphazene obtained by thermally polymerizing cyclic chlorophosphazene such as hexachlorocyclotriphosphazene and octachlorocyclotetraphosphazene or linear low molecular weight chlorophosphazene in a system from which water has been sufficiently excluded, with or without a catalyst. is synthesized by reaction with an alkali metal alkali metal oxide such as sodium, potassium, or lithium obtained from the corresponding phenol or directly converted phenol. It can also be synthesized by heating polydichlorophosphazene and the corresponding phenol or substituted 7 ether in the presence of a tertiary amine such as triethylamine.

When one type of corresponding phenol or directly converted phenol is used, it becomes a homopolymer represented by -1-NPX2+, and a copolymer in which six types of repeating units are randomly distributed.

Moreover, when three or more kinds of substituents are used, a copolymer is obtained in which these three or more kinds of substituents are randomly distributed in the polymer.

The polyphosphazene used in the present invention may be a homopolymer consisting of a single substituent or a copolymer having two or more types of substituents.

In order to enable the polyphosphazene of the present invention to be crosslinked with peroxide, sulfur, etc., some of the substituents X and X' may be substituted with a crosslinkable group such as an allylphenoxy group or an allylphenoxy group. Alternatively, the chlorine atoms of polydichlorophosphazene may not be entirely substituted with aryloxy groups, but may be left for the purpose of crosslinking a sunset view or the like. Naturally, these polymers are also included in the polyaryloxyphosphazene referred to in the present invention.

The selectively permeable membrane for gas separation comprising polyaryloxyphosphazene as a constituent component of the present invention has significant characteristics of high gas permeation rate and excellent selectivity.

For example, if we take oxygen enrichment from air 9-8 air, po2 is 10-10.
has a large value of . Polymers having such a large p02 are not known other than those based on polyorganosiloxane, and the value of PO2/PNx is 3.0 or more, which is significantly larger than 19 for polyorganosiloxane. In addition, polyaryloxyphosphazene, which is the material of the gas separation membrane of the present invention, can vary from rubber-like to plastic-like depending on the type or proportion of the oxy groups, and all of them have solvent resistance and heat resistance. It is a polymer with good oxidation resistance and stability. Therefore, there is no deterioration of membrane performance due to pump oil, deterioration due to use under high temperature conditions, or oxidative deterioration of the membrane due to constant contact with high concentration oxygen, which is also a major feature of the present invention. . More original? Polyaryloxyphosphazene has excellent film-forming ability, and this is a major advantage when using polyaryloxyphosphazene as a separation membrane.

The gas separation membrane containing the polyphosphazene of the present invention having the excellent characteristics described above can be easily formed by a film forming method known in the art, such as a casting method. Solubility in solvents varies depending on the type of substituent, so
A homogeneous film repulsion can be achieved by preparing a casting solution using a solvent suitable for each polyphosphazene, casting it onto a glass plate, etc., drying it, and removing the solvent. Suitable solvents include, as described above, different solvents depending on the type of direct substituent, for example, in the case of polybisphenoxyphosphazene, ketones such as methyl ethyl ketone and tetrahydrofuran, and ethers are used. The concentration of the casting solution is suitably 05-50%, preferably 1-20%,
Solutions with these concentrations yield films with a thickness of 0.01 to 200 μ. For the purpose of obtaining a large gas permeation flatness, the thinner the K film is, the better;
A film thickness of up to 0μ is preferred. A thin film of 1 μm or less can be obtained using a method known in the art, in which a solution using a hydrophobic solvent is spread on the water surface, the solvent is evaporated, and then the solution is scooped onto an organic or inorganic porous support. can. The membrane of the present invention can be used as it is as a homogeneous membrane. Polymer porous supports such as cellulose acetate, polyamide, polycarbonate, polysulfone, polyethersulfone, and polyolefin; and inorganic porous supports such as glass and alumina; It can also be used in a form where the composite IA membrane is placed on a woven or non-woven fabric to increase its strength.

Furthermore, the membrane of the present invention can exhibit its performance in any form such as a flat membrane, a tubular membrane, or a hollow fiber. The polyphosphazene-based membrane of the present invention can also be made from a blend polymer obtained by mixing it with other polymers such as polyolefin or polyorganosiloxane, which can exhibit its characteristics when used alone. can do.

As explained above, the selective permeable membrane for gas separation containing poly(1-noaryloxyphos) of the present invention as a constituent component can be used as an oxygen-enriching membrane with large POz and PO2/pNz
It is a groundbreaking membrane with a thick, strong strength, solvent resistance, heat resistance, and oxidation resistance stability, and is used in various medical, industrial, and household combustion systems. Furthermore, the membrane of the present invention is not only for enriching oxygen from air, but also for enriching hydrogen,
- Separation of mixtures of various gases such as carbon oxide, carbon diacid, helium, argon, hydrogen sulfide, ammonia, and lower hydrocarbons such as methane, ethane, furopane, butane, ethylene, furopyrene, and butenes. Also for I/
) can be done.

The present invention will be specifically explained below with reference to Examples, but the present invention is not limited thereto).

[Example 1] Hexachlorocyclotriphosphazene was heated in a glass ampoule at 250° C. for 24 hours under vacuum. The obtained toluene solution of polydichlorophosphazene was diluted with sodium 4
- ethyl phenoxide in diglyme solution at 90°C.
After dripping over a period of time, the temperature was raised to 115°C and the reaction was continued for 30 hours to remove by-product sodium chloride, unreacted phenoxide, and low molecular weight oligomers from which polybis(4-etherphenoxy)phosphase was synthesized. When the molecular dish was determined by gel permeation chromatography on a sufficiently purified polymer (using a polystyrene calibration curve), a value of 1,200,000 was obtained. n), it becomes approximately 4200.

Next, dissolve the polymer in tetrahydrofuran to a concentration of 15%.
After preparing a solution, this solution was cast onto a glass plate to a thickness of 0.3 mm using a doctor blade knife. After being left to dry at room temperature for one day, it was carefully peeled off from the glass plate to obtain a transparent and strong film with a thickness of 25 μm. This membrane was set in a cell prepared for gas permeability measurement, and two
The flow rate and composition of the oxygen-enriched air passing through the membrane were analyzed to determine Po2 and PNd.
When I measured this, I got the following result, which is polybis (
This shows that the 4-ethylphenoxy)phosphazene membrane has excellent oxygen enrichment performance.

[Example 2] Polybisphenoxyphosphazene was synthesized in the same manner as in Example 1, except that sodium phenoxide was used instead of sodium 4-ethyl phenoxide. The molecular weight was 900,000, and the average degree of polymerization n was 3900. After dissolving this polymer in tetrahydrofuran to prepare a solution with a concentration of 18%, it was applied onto a polypropylene porous membrane (thickness 25μ, porosity 45%, Polyplastics' Duraguard 2500) overnight. It was left to dry to form a composite membrane. Based on the weight, area and specific gravity of the applied polymer, it was calculated that this film was equivalent to a thickness of 22μ. When PO2 and PN2 were determined in the same manner as in Example 1, the following results were obtained.

This indicates that the polybisphenoxyphosphazene membrane has excellent oxygen enrichment performance.

[Example 3] Polybis(4-chlorophenoxide) was prepared in the same manner as in Example 1 except that sodium 4-chlorophenoxide was used instead of IRI 4811 and monosodium 4-ethylphenoxide during the polymerization of hexachlorocyclotriphosphazene. phenoxy)phosphazene was synthesized. Molecular method is 5,500,
0 [10, average degree of polymerization was 12,000] A 5% solution was prepared by dissolving the polymer in tetrahydro7 run. Using this solution, a strong film with a thickness of 10 μm was obtained on a glass plate in the same manner as in Example 1. Using this membrane, po2 and PN2 were prepared in the same manner as in Example 1.
was measured and obtained the following results.

This result shows that the polybis(4-chlorophenoxy)phosphazene membrane has excellent oxygen enrichment performance.

[Example 4] Polydichlorophosphazene was synthesized by heating hexachlorocyclotriphosphase/in a glass ampoule at 250°C under vacuum for 60 hours. The obtained toluene solution of polydichlorophosphazene was added dropwise to a diglyme solution containing equimolar amounts of sodium phenoxide and sodium 4-sec-butyl phenoxide at 90°C over 2 hours, and the temperature was raised to 115°C to initiate a reaction. The mixture was further added for 30 hours to synthesize a polyaryloxyphosphase/fupolymer containing phenoxy groups and 4-sec-butylphe/oxy groups in a ratio of 1:1. The average molecular weight is i, a o o,
o o o, the average degree of polymerization n was 6200. After dissolving this polymer in tetrahydrofuran to obtain a 10% solution, Duragard 2 was prepared in the same manner as in Example 2.
It was applied onto a 50G film and dried at room temperature for one day to obtain a composite film.

The calculated film thickness based on the superposition of the polymer retained on the support membrane was 24μ. The J'o2 and pN2 of this composite membrane were measured in the same manner as in Example 1, and the following results were obtained.

This result shows that the polyaryloxyphosphazene copolymer membrane of this example has excellent oxygen enrichment performance.

[Example 5] A 4-methoxyphenogoxy group and a 4-tert-butylphenoxy group were prepared in the same manner as in Example 4, except that an equimolar mixture of sodium 4-methoxyphenoxide and sodium 4-tert-butyl phenoxide was used as the aryl oxide.
A polyaryloxyphosphazene fubolymer containing t-butylphenoxy groups in a ratio of 1:1 was synthesized. The average molecular weight is 1,500,000. The average score was 4,700. A 10% solution of this polymer in tetrahydrofuran was prepared and cast onto a glass plate to a thickness of α3 mm, and dried for one day at room temperature to obtain a tough and opaque film with a thickness of 18 μm. The oxygen enrichment performance of this membrane was measured in the same manner as in Example 111, and the following results were obtained.

This result shows that the polyaryloxyphosphazene copolymer membrane of this example has excellent oxygen enrichment performance.

[Example 6] A composite membrane in which the polyaryloxyphos-7azene copolymer prepared in Example 4 was held on Duraguard 2500 was set in the apparatus of Example 1, and 2 kg was placed on the primary side of the membrane.
When P Co, I /PN2 was determined by flowing a mixed gas of carbon dioxide and g at a pressure of 7 cm'' g, a value of 20.1 was obtained. Similarly, the separation performance of a mixed gas of helium and nitrogen was determined. When investigated, PHe/pN2 was 12.3
It's the value of AJ. Next, a 30μ film of silicone rubber (polydimethylsiloxane) crosslinked with bis-2,4-dichlorobenzoyl peroxide was prepared for comparison, and the values of P CO2/PN2 and PHe/PN2 were measured, and the values were 6.5 and 6.5, respectively. A value of 1.2 was obtained.

This result shows that the membrane of this example has far superior separation ability compared to silicone rubber.

Patent Applicant Nippon Oil Co., Ltd. Procedural Amendments May 12, 158 May 12, 1588 Transmission, Recommendation 3, Patent issuer's name (444) Nippon Oil Co., Ltd. Akasaka Taisei Building (
582-7161) Column 6 of Detailed Description of the Invention in the Specification, Contents of Amendment (1) ``Opaque'' in 2 lines on page 24 of the specification, all 1 - Transparent''.

Claims (1)

[Claims] [In the formula, X and X' are aryloxy groups, and n is 2
An integer from 0 to 70.000] A selectively permeable membrane for gas separation comprising polyphosphazene as a constituent component.