JPS59183803A - 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, oxidation stability, etc., by using polyaminophosphazene as a constituent. CONSTITUTION:Polyphosphazene is prepared by reaction of polydichlorophosphazene, obtained from thermal polymerization of 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, with a corresponding amine. The gas-separating membrane containing polyphosphazene as a constituent can be easily formed by casting. The preferred concentration of the casting solution is 0.5-30%, more preferably 1-20%. A membrane of a thickness of 0.01-200mum can be obtained from solutions of these concentrations.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a selectively permeable membrane for gas separation.
In particular, it relates to a selectively permeable membrane comprising polyaminophosphazene, 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 gas mixture using membranes made of polymeric materials.In recent years, membrane separation methods have attracted particular attention from the viewpoint of resource and energy conservation. If oxygen-enriched air with increased oxygen concentration could be obtained easily and continuously at low cost from fresh air, it would be of great value. Currently, pure oxygen is used in cylinders for medical purposes such as incubating premature babies or treating patients with respiratory diseases, but it is difficult to operate and is difficult to use continuously. It has serious drawbacks such as not being able to supply it or having to use it diluted. However, if an efficient membrane capable of supplying oxygen by concentrating it from the air could be obtained, the above drawbacks would be overcome, and further advances could be expected in the medical field, such as a simple device that could be used at home. For.

In addition, membranes can be used to easily and continuously enrich oxygen in stations, various combustion systems currently in use, such as industrial boilers, furnaces, blast furnaces for steel manufacturing, internal combustion engines used in automobiles, and household heating appliances. b) 'If air is supplied, combustion efficiency can be increased and furnace costs can be saved, energy savings can be achieved, and the problem of environmental pollution caused by incomplete combustion can be solved. If oxygen-enriched air could be supplied cheaply and easily, it could stimulate the development of food industry, fish farming, waste treatment, and any other field.

Currently known polymer materials have more or less gas permeability, but in order to make an industrially practical oxygen enrichment membrane, the permeation rate of acid and non-acid gas must be sufficiently high and the permeability of There must be great selectivity. The gas permeation rate is determined by the permeability coefficient (usually P
It is expressed in units of cJ (S TP )cm/critynH1) and has been shown to be proportional to the differential pressure between both sides of the membrane and the surface area of the membrane, and inversely proportional to the membrane thickness. In addition, the selectivity of oxygen to nitrogen is determined by the oxygen permeability coefficient (PO2), which is a value unique to polymeric substances. : Determined by the ratio (PO2/PN2) to the nitrogen permeability coefficient (PNz). 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 a sufficient oxygen concentration, it is difficult to select a polymer with a large P 02 /P N2 ratio. 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. It also requires durability for long-term use and oxidation-resistant stability due to constant contact with high-concentration oxygen. Industrially practical membrane materials for oxygen enrichment include PO2 and PO2/P.
A material with a large N2 content and excellent strength, durability, and oxidation stability is required.0 However, there are few existing polymer materials that meet these requirements, and many attempts have been made to improve existing polymers. However, none of the existing polymers PO and PO2/PN have fully achieved their purpose.
Examples of 2 are shown in the table below.0 Existing polymers with PO2 of 10-9 or higher are very limited, and only a few polymers such as polydimethylsiloxane and poly-4
-Methylpentene-1, natural rubber, etc. Most of the other polymers have a molecular weight of 1o"'10 or less, and unless the membrane area is increased by increasing the membrane area, it is difficult to obtain a membrane with a practical permeation rate higher than that of these polymers.PO2 is 10" or less.
Even if the polymer has −9 or more, for example, natural rubber has −C= in the main chain.
Durability (especially oxidation stability) due to the presence of C-double bonds
It also has poor mechanical strength.

Since poly-4-methylpentene-1 is a polyolefin, it is strong, but because it mainly contains tertiary carbon, it has poor oxidation stability and cannot be used under harsh industrial conditions (e.g. high temperature conditions). (below) Polydimethylsiloxane has the highest gas permeability among currently known polymers, but its strength is weak and it is extremely difficult to create legs of less than 20μ! 7. PO2
Although it is thick, it is not possible to obtain a practical permeation rate. Strength can be increased to some extent by reinforcing with a filler and crosslinking, but these treatments impair film formability and make it difficult to form a thin film.

Furthermore, it has the essential drawback that the ratio of PO2/PN2 is low and the selectivity of oxygen to nitrogen is poor. In order to take advantage of the high gas permeability of polydimethylsiloxane, several attempts have been made to improve its strength by copolymerizing it with other components. For example, U.S. Patent No. 3.189.
No. 662 proposes a block copolymer of polydimethylsiloxane and polycarbonate, but this material has a certain degree of strength due to the introduction of polycarbonate units, but its solvent resistance decreases and it is difficult to use, such as pump oil. Not only does it have the disadvantage of being easily degraded by polydimethylsiloxane, but it also has the disadvantage of lowering PO2 compared to polydimethylsiloxane alone. There are many other attempts to improve the above drawbacks by modifying polyorganosiloxane as a base by reacting with other components, but in all cases, as the siloxane content in the polymer is reduced, strength is reduced. Although it improves, on the contrary, PO of polyorganosiloxane.

The dilemma is that the characteristic of having a large amount of energy is 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 PO□/PN ratios and have excellent properties such as strength, durability, chemical resistance, and oxidation stability.
It has been discovered that a membrane containing polyaminophosphazene as a constituent satisfies these requirements, and the present invention has been achieved.

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

In formula (1), X and X' represent an amine group. Here, the amine group is represented by the general formula -NR1R2, and R
1 and R2 are hydrogen, an alkyl group having 1 to 10 carbon atoms, or one or more of the hydrogens in these alkyl groups is a halogen such as fluorine, chlorine, or bromine, a phenyl group, or an alkoxy group having 1 to 4 carbon atoms. , a nitro group, a cyan group, a substituted alkyl group substituted with one or more groups selected from an alkylamino group having 1 to 4 carbon atoms, and an alkyl acetoxy group having 1 to 4 carbon atoms, a phenyl group, or a phenyl group. One or more of the hydrogens in the group is a halogen such as fluorine, chlorine, or bromine, an alkyl group with 1 to 20 carbon atoms, an alkoxy group with 1 to 4 carbon atoms, a phenoxy group, a phenyl group, a nitro group, A substituted phenyl group substituted with one or more groups selected from a cyan group and an alkylamino group having 1 to 4 carbon atoms, a cyan group, a nitro group, an alkylcyano group having 1 to 4 carbon atoms, Preferably, it is a group selected from the group consisting of 1 to 4 alkyl carbamate groups, pyridinyl groups, and imidazolyl groups, and R1 and R2 may be the same or different. Specific examples of suitable amine groups include: Amine group, methylamine group, ethylamino group, n-propylamino group, n-butylnamino group, 5ec-butylamino group, n-hexylamino group, cyclohexylamino group, octylamino group, decylamino group, dimethylamino group, diethylamino group group, alkylamino groups such as methylethylamino group and piperidino group, benzylamino group, 2-phenylethylamino group, λ2,2-trifluoroethylamine group, 2.
2.3.3.4.4.4-Heptafluorobutylamino group, substituted alkylamino group such as ethylacetoxyamino group, phenylamino group, 3-fluorophenylamino group, 4-fluorophenylamino group, 5- Chlorophenylamino group, 4-chlorophenylamino group, 3-methylphenylamino group, 4-methylphenylamino group, 4
-arylamino groups such as -ethylphenylamino group, 4-n-7'tylphenylamino group, 4-methoxyphenylamino group, perfluorophenylamino group, perchlorophenylamino group, biphenylamino group, 2-pyridylamino group, Pyridylamino groups such as 5-methyl-2-pyridylamino groups, alkyl carbazate groups such as imiglyl groups, methyl carbazate groups, and ethyl carbazate groups, amine groups derived from methyl hydrazine, ethyl hydrazine, etc., and cyanamide. group, a cyano group-containing amino group such as a dicyanamide group, and a nitro group-containing amino group.

In formula (1), n is an integer ranging from 20 to 70,000 and is generally a rubbery or flexible solid. If n is less than 20, the strength is too weak to provide a practical strength as a film, which is undesirable. Also, n is 70,000
If n is larger than 20, the molecular weight will be too thick and production will be difficult, and the viscosity of the film-forming solution will be too high, making it difficult to form a film. may come out as an oily liquid,
Of course, polyphosphazenes containing a portion of these can also be used, and membranes obtained by rationalizing liquid polymers into other porous structures can also be used.

The polyphosphazenes of the present invention can be produced by known methods (for example, A11cock et al., Inor
g, Chem.

Σ, 1716 (1966)) For example, cyclic chlorophosphazenes such as hexachlorocyclotriphosphazene and octachlorocyclotetraphosphazene or linear low-molecular-weight chlorophosphazenes are thermally polymerized with or without a catalyst in a system from which water has been sufficiently excluded. It is synthesized by reacting polydichlorophosphazene obtained by this method with the corresponding amine. It can also be synthesized by heating polydichlorophosphazene and the corresponding amine in the presence of a tertiary amine such as triethylamine.When using one type of corresponding amine, CNPX
2-) It becomes a homopolymer represented by n, and when two types are used, it becomes a copolymer in which 381 repeating units are distributed in ranks.

When three or more kinds of substituents are used, the polymer is a copolymer 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 substituents. In order to enable crosslinking, some of the substituents X and X' may be substituted with a crosslinkable group such as an allyl alkoxy group or an allyl phenoxy group. A small amount may be left for purposes such as crosslinking without being substituted with an amine group. Needless to say, these polymers are also included in the polyaminophosphazene referred to in the present invention.

The selectively permeable membrane for gas separation comprising polyaminophosphazene as a constituent component of the present invention has significant characteristics of high gas permeation rate and excellent selectivity. For example, if we take the enrichment of oxygen from the air, PO2 is 10-9
Having a large value of order. Furthermore, the value of PO2/PN2 is extremely large, at 5 parts or more. In addition, polyaminophosphazene, 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 amine groups, but all of them have good solvent resistance, heat resistance, and oxidation resistance stability. Made of high quality polymer. Therefore, there are no problems such as deterioration of membrane performance due to pump oil, deterioration due to use under low 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. . Furthermore, the polyaminophosphazene of the present invention has excellent film-forming ability, which is a great advantage when using the polyaminophosphazene 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.

The solubility in solvents varies depending on the type of substituent, so if you prepare a casting solution using a solvent suitable for each polyphosphazene, cast it on a glass plate, etc., and dry it to remove the solvent. A homogeneous membrane is obtained.

The concentration of the casting solution is suitably 0.5 to 50 mm, preferably 1 to 20 mm, and solutions with these concentrations yield films with a thickness of 0.01 to 200 μm. For the purpose of obtaining a large amount of gas permeation, the thinner the membrane (r) is, the better, and in this case, a film thickness of 0.05μ to 60μ is preferable. #[t
After the iQL solvent is evaporated, it is scooped onto an organic or inorganic porous support using methods known in the art.
A thin film of μ or less can be obtained. The membrane of the present invention can be used as it is as a homogeneous membrane, or can be used on polymeric 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 composite form by placing it on a woven or non-woven fabric to increase the strength of the membrane. 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 be used alone to exhibit its characteristics, but it can also be used as a membrane formed from a blend polymer obtained by mixing it with other polymers, such as polyolefin or polyorganosiloxane. can also be used.

As explained above, the selective permeable membrane for gas separation containing polyaminobosphazene as a constituent component of the present invention has large po2 and P O,/P N as an oxygen-enriching membrane, and has high strength and durability. This is a revolutionary membrane with excellent solvent resistance, heat resistance, and oxidation resistance, and is used in various medical, industrial, and domestic combustion systems. In addition, the membrane of the present invention is not only used for enriching oxygen from air, but also for hydrogen, -m-carbon,
It can also be used to separate mixtures of various gases such as carbon dioxide, helium, argon, hydrogen sulfide, ammonia or lower hydrocarbons such as methane, ethane, propane, butane, ethylene, propylene and butenes.

EXAMPLES The present invention will be specifically explained below with reference to Examples, but the present invention is not limited to these examples.

Example 1 Hexachlorocyclotriphazene in a glass ampoule,
Polymerization was carried out by heating at 250° C. for 24 hours under vacuum. The obtained benzene solution of polydichlorophosphazene was added dropwise to a benzene solution of dimethylamine over 4 hours while keeping the temperature below 5°C, and the reaction was continued at 25°C for another 24 hours to synthesize poly and dimethylaminophosphazene. . After removing unreacted amine, dimethylamine hydrochloride, and low-molecular-weight oligomers, the polymer made from silk had an average molecular weight of 780.000, measured using a light scattering method, and an average degree of polymerization (n in formula (1)) of 5800. there were. Next, a 2% trifluoroethanol solution of this polymer was prepared, coated on a polypropylene porous membrane (thickness 25μ, porosity 45%, Polyplastics' Duraguard 2,500) and left at Utemp overnight. A composite membrane was obtained by drying. This composite membrane was set in a cell made for gas permeability measurement, and the primary side was 3Kp.
/-y air was passed through the membrane, and the flow rate and composition of atmospheric pressure oxygen-enriched air passing through the membrane were measured, and the following values were obtained.

The results show that the polybisdimethylaminophosphazene membrane has good oxygen enrichment performance.

Example 2 A benzene solution of polydichlorophosphazene synthesized in the same manner as in Example 1 was added dropwise to a tetrahydrofuran solution of aniline at room temperature over 4 hours, and the reaction was continued for 48 hours at the reflux temperature to produce polybisphenylaminophosphazene. was synthesized. The average molecular weight of the polymer purified by removing unreacted aniline, aniline hydrochloride, and low molecular weight oligomers was 1.72 as measured by light scattering method.
0.000, and the average degree of polymerization (n in formula (1)) is 75
It was 00. A dibenzene solution of this polymer was prepared, and a membrane was fabricated on Duragard 2500 to form a composite membrane in the same manner as in Example 1. The oxygen and nitrogen permeation rates were measured and the following values were obtained.

This result shows that the polybisphenylaminophosphazene membrane has excellent oxygen enrichment performance.

Example 3 A tetrahydrofuran solution of polydichloropos-7azene synthesized in the same manner as in Example 1 was added dropwise to a tetrahydrofuran solution of diethylamine over 2 hours at room temperature, and the reaction was further continued at room temperature for 2 days. The obtained polymer was thoroughly purified and its composition was determined by elemental analysis. It was found that 50% of the chlorine atoms in the raw material polydichlorophosphazene were substituted with diethylamino groups, and the remaining 50% of chlorine remained unsubstituted. It was confirmed that there is. Next, the tetrahydrofuran solution of the polymer was added dropwise to the tetrahydrofuran solution of n-butylamine over 2 hours at room temperature, and the reaction was continued at room temperature for 2 days to introduce equal amounts of diethylamino groups and n-butylamino groups. A butylaminodiethylaminophosphazene copolymer was synthesized. The average molecular weight of the polymer from which unreacted amine, n-butylamine hydrochloride and low molecular weight oligomers were removed was 170,000, and the average degree of polymerization was 890.

A 2% solution of this polymer in benzene was then prepared and micropipetted onto the surface of clean 5°C water maintained for 1 hour.
It was added dropwise to form a thin film on the water surface.

Next, a Duraguard 2500 membrane was pressed onto the membrane, and the thin membrane was carefully scooped out to obtain a composite membrane.The oxygen and nitrogen permeation rates were measured in the same manner as in Example 1, and the following values were obtained.

This result shows that the n-butylaminodiethylaminophosphazene copolymer membrane has excellent oxygen enrichment performance.

Example 4 Triethylamine was added to a toluene solution of polydichlorophosphazene synthesized in the same manner as in Example 1 to promote the reaction, and a tetrahydrofuran solution of 2-amino-4-picoline was added dropwise to this solution over 4 hours at room temperature. After that, the reaction was continued for 5 days at 70°C temperature to produce 2-amino-
A polyphosphazene substituted with 4-picoline was synthesized. Next, a 10% dioxane solution of the purified polymer was prepared by removing unreacted amine, triethylamine, the hydrochloride of these amines, and low molecular weight substances, and poured onto a glass plate to a thickness of 0.3 mm using a doctor blade knife. The mixture was spread and air-dried day and night at room temperature to obtain a transparent, strong, homogeneous film with a thickness of 20 μm. Using this membrane, the flow rate and composition of air passing through the membrane were measured in the same manner as in Example 1, and PO2 and PN were measured.
2 was obtained and the following result was obtained.

This result shows that the polyaminophosphazene of this example has excellent oxygen enrichment performance.

The membrane prepared in Example 3 was set in the apparatus of Example 1, and 2 Kg/crux was applied to the primary side of the membrane. When Pco2/PN2 was determined by flowing a mixed gas of coal amount gas and nitrogen at a pressure of 243, a value of 243 was obtained. In addition, when the separation performance of a mixed gas of helium and nitrogen was investigated in the same way, p a e
A value of 137 was obtained for /P N2.

Next, for comparison, a 30μ film of silicone rubber (polydimethylsiloxane) crosslinked with bis-2,4-dichlorobenzoyl peroxide was prepared, and the values of PCO2/PN2 and PHe/PN2 were measured, and the values were 65 and 12, respectively. value was obtained. This result shows that the polyethoxyphosphazene membrane has far superior separation ability compared to silicone rubber.

May 12, 158 May 12, 158 Kazuo Wakasugi, Commissioner of the Patent Office Display of the case 1982 Patent Application No. 55249 2 Name of the invention Selective permeable membrane for gas separation 3 Case of the person making the amendment Relationship Patent applicant name (444) Nippon Oil Co., Ltd. Akasaka Taisei Building (
Telephone 582-7161) Kiri 6 of the detailed description of the invention in the specification, each of the amendments

Claims (1)

[Claims] 1. General formula; % formula %) (In the formula, X and X' represent an amino group, and n is 20 to
70.000) A selectively permeable membrane for gas separation comprising polyphosphazene as a constituent component.