JPH0466609B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method for separating water from non-polar fluids by contacting a water-containing mixture with a polyphosphazene separation membrane. The separation, including the upgrading or enrichment of at least one selective fluid from a gaseous mixture, is an essentially important step from the point of view of the requirements for the supply of chemical raw materials. These needs are often met by separating one or more desired fluids from a fluid mixture and using the gaseous products in various processes. The use of separation membranes has been applied to selectively separate one or more fluids from a fluid mixture. To achieve selective separation, the membrane exhibits a lower resistance to transporting one or more fluids through the mixture than at least one other fluid. Thus, selective separation can provide preferential depletion or enrichment of one or more desired fluids in a mixture relative to at least one other fluid, and thus one or more desired fluids versus at least one other fluid. The ratio of one of the other fluids provides a product having a volume ratio different from that of the raw mixture. However, in order to make the selective separation of one or more desired fluids by the use of separation membranes industrially attractive, several membranes must be used so that the use of the separation method is economically attractive. must meet the criteria. For example, the membrane must be able to withstand the conditions to which it is exposed during separation operations. The membrane must likewise provide suitable selective separation of the desired fluid or fluids at sufficiently high flow rates, ie, permeate rate per unit surface area. Thus, separation membranes exhibiting suitably high separation selectivity but undesirably low flow rates require large separation membrane surface areas that make the use of these membranes economically unfeasible. Similarly, separation membranes that exhibit high flow rates but low separation selectivity are likewise industrially unattractive. Therefore, the separation of one or more desired fluids, such as polar fluids from non-polar fluids, at sufficiently high flow rates for long periods of time under harsh environmental conditions makes the use of these fluid separation membranes economically viable. Research continues to develop fluid separation membranes capable of providing suitable selective separation. In general, permeation of fluid through a membrane proceeds through voids, continuous channels that connect fluid flow on both the feed and outlet sides of the membrane, whether or not the voids are suitable for separation by Knudsen flow and diffusion. However, in other mechanisms according to recent views of membrane theory,
Permeation of fluid through a membrane is said to be due to interaction of the fluid with the membrane material. In this latter proposed mechanism, permeation of fluid through the membrane is believed to involve dissolution of the fluid into the membrane material and diffusion of the fluid through the membrane. The permeation constant of a single fluid is currently interpreted to be the product of solubility and diffusivity in the fluid's membrane. A given membrane material has a particular permeation constant for the permeation of a given fluid due to the fluid's interaction with the membrane material. The permeation rate, or flow rate, of a fluid through a membrane is related to the permeation constant, but is also influenced by variables such as membrane thickness, partial pressure difference of the gaseous permeate across the membrane, temperature, and the like. receive. Polymers useful as practical membranes for fluid separation applications must meet several stringent criteria. Chief among the requirements are the intrinsic transport properties of the polymer, such as permeability and selectivity. Additional requirements include suitable properties such as suitable thermal and chemical environmental stability and solubility properties which are critical to fabricating the polymer into useful membranes. Most polymers currently used for fluid separation belong to a group known as glassy polymers. Often these materials are
Both films or hollow fibers are attractive because they very well meet the above criteria for creating useful membranes of asymmetric morphology. However, many polymers that meet manufacturing standards have transport properties that are less than ideal for a given separation application. Often, polymers that exhibit desirably high selectivity for a particular gas pair or solute-solvent pair will not allow faster components to permeate at an adequate rate. Conversely, polymers with very high permeability for a given permeable substance are often only moderately selective. Finding a single material that simultaneously satisfies most or all of the necessary requirements for desired fluid separation is a difficult task. Glassy polymers are generally highly amorphous materials, which, as their name suggests, are in a frozen state at ambient temperatures. Above the glass transition temperature, or Tg, of the polymer, this glassy solid transforms into another amorphous solid state, a rubber characterized by increasingly rapid motions of the polymer chains on a molecular scale. Of particular interest among the various properties that distinguish polymers in their rubbery versus glassy states is that the transport properties are often drastically different for these two types of materials. The gas permeability through many rubbers is very high compared to the permeability of the same gases in many glassy polymers. However, the higher dynamic nature of the polymer chains in the rubbery state, which generally accounts for the high permeability, often results in a much lower selectivity of rubbery polymers compared to many glassy polymers. Additionally, many rubbery polymers do not have the desirable combination of other properties required to efficiently produce membranes with desirable asymmetric morphology. Several rubbery polymers have been and are currently used for gas separation. Silicone rubber has been applied in air (O ₂ /N ₂ ) separation, particularly for small scale applications such as blood oxygenation or air oxygen enrichment. In such environments, the very high O ₂ permeability of silicone rubber has relatively unattractive properties,
For example, it is more important than low selectivity and mechanical weakness. Because silicone rubber cannot be easily made asymmetrically, the polymer is typically supported on a relatively strong porous support. With appropriate application, such porous supports effectively compensate for the limitations of rubbery polymers in terms of manufacturing and mechanical strength. For large-scale gas separation applications that are considered to be of industrial importance,
However, the usually unsuitable selective properties of most rubbery polymers remain limiting their practical use. Polyphosphazenes are polymers having a phosphorus-nitrogen sequence with an organic substituent on the phosphorus as follows. provided that R and R' are the same or different organic substituents and n is an integer of 10 or more. A limited number of single gas transport measurements of polyphosphazenes have been performed. for example,
Bittirova et al., Vysokomol. Soedin, ser. B23, No. 1, pp. 30-3 (1980) discloses the permeability of poly(octyloxyphosphazene) to oxygen, nitrogen and argon. This report by Bittirova et al. is 12.84×10 ^-7 , 11.88×10 ^-7 and 5.25
Due to its "specific properties" including transparent, flexible, elastic films with permeability coefficient values for O ₂ , Ar, N ₂ of ×10 ^-7 cm ³ , cm/cm ² S atm , focuses on one polyphosphazene with special interest in this material. This document does not attempt to use this elastic film for further gas transport properties. “Vysokomol.Soedin” Ser.A18 of Kireyev et al.
vol. 1, p. 228 (1976) and Chattopadhyay et al., "J. Coating Technology," vol. 51, no. 658, p. 87 (1979), poly(butyloxyphosphazene) and poly(aryloxyphosphazene), respectively.
The water vapor permeability of Kireyev et al.
The need for new types of elastomers and thus the interest in polydiorganophosphazenes (one of the quality evaluation physical properties studies concerns the absorption of water vapor by these phosphazenes as a gravimetric measure) is discussed. Chattopadhyay et al. have a particular interest in polyaryloxyphosphazenes as materials with a high degree of flame retardancy and other desirable polymeric properties for use as paint binders;
"Polyphosphazenes As New Coating
He publishes a publication entitled ``Binders''. Chattopadhyay et al., along with other physical test evaluations, demonstrate moisture vapor transmission through polymeric films at 25°C. Separation of fluid mixtures by polyphosphazene membranes is not noted. In summary, suitable polyphosphazene fluid separation membranes have not been provided heretofore. In particular, the suitability of polyphosphazene fluid separation membranes for the separation of polar fluids from non-polar fluids has not been suggested. According to the present invention, the water-containing mixture is transferred to the first part of the separation membrane.
A method of separating water from a non-polar fluid by contacting a surface, the separation membrane having preferential selectivity and permeability to water and having the formula (wherein n is an integer from 100 to 70,000, Y is oxygen, and R and R' may be the same or different and contain aryl, alkyl-substituted aryl, or 1 to 25 carbon atoms. a rubbery polyphosphazene with preferential selectivity and improved thermal and chemical stability represented by fluorinated alkyl groups having maintaining a second surface of the polyphosphazene membrane at a chemical potential of, allowing water to permeate into and through the polyphosphazene membrane, and having a concentration of water relative to the non-polar fluid greater than the concentration contained in the feed mixture. A method is provided, characterized in that permeation products are collected from the vicinity of the second surface. The phosphazene fluid separation membranes described above may have various structures or be in the form of dense films. Because of the rubbery nature of polyphosphazene membranes, suitable fluid separation membrane structures often employ polyphosphazenes as a coating supported on a porous substrate. Furthermore, polyphosphazenes can be applied as coating materials in contact with porous separation membranes contributing to the separation properties of the resulting multicomponent membrane. In describing the invention, the following definitions are used. The term "fluid" as used herein refers to any substance that cannot always resist shear forces and produces a flow.
For example, it refers to a gas, ie, a state of matter in which molecules flow without apparent resistance, and a liquid, ie, a state of matter in which molecules move freely but are constrained by gravity. As used herein, the term "polar fluid" refers to a fluid that is capable of ionizing or acting as an electrolyte as opposed to a non-electrolyte or is characterized by properties such as a relatively high dielectric constant or molecular dipole moment. means a fluid that can be attached to As used herein, the term "membrane" refers to a material that has a surface that can be contacted with a fluid and/or gas mixture such that one fluid or gas of the mixture permeates selectively through the material. do. Such membranes are generally exposed in film or hollow fiber form. The membrane may be porous or essentially pore-free, or may have a layer that is porous and a layer that is essentially pore-free. The present invention provides membranes that exhibit advantageous fluid separation properties for polar fluids. However, the membranes of the present invention exhibit useful and advantageous fluid and/or gas separation properties for other than polar fluids. As used herein, the term "dense" or "dense film" refers to a film thickness that is essentially free of pores, i.e., fluid passageways communicating between the surfaces of the membrane, and voids, i.e., containing no material of the membrane. Refers to a membrane that has essentially no inner regions. This dense film falls within the definition of an isotropic film because it is essentially the same throughout the structure.
Although some thick membranes are highly selective, one disadvantage of them is low permeate fluxes due to the relatively large thickness of the membrane. Dense membranes are advantageous in determining the material's inherent gas separation properties. The inherent separation properties include
A separation factor α and a permeation constant P (both defined below) are included. The term "asymmetric" or "anisotropic" as used herein refers to a membrane that has a porosity that is not constant across the thickness of the membrane. An example of an asymmetric membrane consisting of two separate parts made from the same material, a thin dense semi-permeable skin and a less dense void-containing support part, is called a Loeb membrane. . However, asymmetric membranes
It is not necessary to have this thin dense semi-transparent region on the outer surface or skin. The membrane of the present invention is composed of a film or hollow fiber material having a specific separation relationship. Some of these correlations are conveniently expressed in terms of relative separation coefficients for a pair of gases in a membrane. The separation coefficient (αa/b) of a membrane for a given pair of gases (a) and (b) is the permeation constant (Pa) of the membrane for gas (a) versus the permeation constant (Pa) of the membrane for gas (b). Pb). Permeability for a given gas is the volume of gas at standard temperature and pressure (STP) that passes through a membrane per cm2 of surface area per second for a partial pressure drop ^of 1 cm of mercury across the membrane per unit thickness. and this is (P=cm ³ −cm/cm ² −sec−
cmHg). The separation factor is likewise the permeability (P/l) of a membrane of thickness (1) for gas (a) in _a gas mixture versus the permeability (P/l) _b of the same membrane for gas (b). Ratio (P/1= ^cm3 / ^cm2 -sec-cmHg)
be equivalent to. In practice, the separation factor for a given pair of gases for a given membrane can be determined using a number of techniques that provide sufficient information to calculate the permeability constant or permeability for each gas in the pair.
Techniques available for determining permeability constants, permeabilities, and separation factors are described in “Techniques” by Hwang et al.
of Chemistry” volume “Membranes In”
"Separation" (John Wiley & Sons, 1975)
Disclosed in Chapter 12, pages 296-322. "Porphosphazene" as used herein
is the expression (wherein n is an integer from 100 to 70,000, Y is oxygen, and R and R' may be the same or different and contain aryl, alkyl-substituted aryl, or 1 to 25 carbon atoms. consisting of a fluorinated alkyl group). As used herein, the term "crosslinked polymer" means that the polymer chains of the polyphosphazene are linked to one another. The stability of the polymer, ie, the fact that it is not soluble in the solvent for the polyphosphazene, is an indicator of crosslinking. The present invention provides fluid separation membranes composed of polyphosphazenes as homo and copolymers and also mixtures of polyphosphazenes as materials for polar fluid separation membranes. The fluid transport and separation properties of various polyphosphazenes were found to be highly selective and permeable to _H2O from a mixed stream containing, for example, _H2O and _CH4 . . The use of halogenated polyphosphazenes allows for fluid dehydration applications such as the removal of H ₂ O from non-polar components in either gas or liquid form.
Similarly suggested. Polyphosphazenes have generally shown preferential selectivity and permeability for various fluids, but fluoro-substituted alkoxy and aryloxy polyphosphazenes provide enhanced water recovery over the other polyphosphazenes mentioned above. Polyphosphazenes can be synthesized to provide soluble, high molecular weight (often greater than 1,000,000), linear materials. Thermal polymerization of trimeric cyclophosphonitrile chloride monomers provides a high molecular weight (-PN-) backbone with two chlorines for each phosphorus. This poly(dichloro)phosphazene is the base polymer from which all soluble polyphosphazene rubbers are made by subsequent nucleophilic substitution reactions. Typically, as shown below,
Replace the chlorine on the phosphorus and in its place -O-R
To substitute the group, the sodium salt of the alcohol is used. Copolymers are obtained by using mixtures of alcoholate salts. By using amines instead of Na-OR salts in the exchange reaction, side groups containing nitrogen rather than oxygen attached to the phosphorus backbone atoms are created. Polyphosphazenes with -OR pendant groups on the phosphorus are typically more stable thermally and chemically, for example to hydrolysis, than those with _-NR2 groups. Fluid separation membranes composed of polyphosphazenes have been found to have an unexpectedly attractive combination of permeability and selectivity for polar/non-polar fluid separations, and these polyphosphazenes have similarly It is shown to have significantly better thermal and chemical stability than coalesced. The fluid transport properties and physical/chemical properties of halogenated polyphosphazenes indicate that this type of rubbery polymer has significant potential for use in practical polar/non-polar fluid separations on a large scale. Of particular note is the _H2O permeability and separation of _H2O from a methane stream using fluoroalkoxypolyphosphazenes. The various polyphosphazenes used for gas separation membranes are rubbery materials with Tg's below room temperature. These porphosphazenes are generally used in polar organic solvents such as tetrahydrofuran (THF), methanol, acetone, ethyl acetate, methyl ethyl ketone (MEK), dimethylformamide (DMF), dimethylacetamide (DMAC), formylpiperidine, N-methylpyrrolidone and the like. It is soluble in Polyphosphazenes with aryl side groups are similarly soluble in aromatic hydrocarbons such as toluene and benzene. This latter solvent causes little swelling of polyphosphazenes halogenated on the alkyl side groups. Although poly(fluoro-alkoxy)phosphazenes are readily soluble in methanol, these phosphazenes are only slightly soluble in higher alcohols, for example less than 1% soluble in isopropyl alcohol up to about 70°C. various polyphosphazenes, including those with side groups composed of substituted alkoxy, aryloxy and substituted aryloxy, and copolymers thereof;
For example, poly(bis-phenoxy)phosphazene,
Copoly(phenoxy-P-ethylphenoxy)phosphazene, poly(bis-trifluoroethoxy)phosphazene and the like were evaluated as gas separation membranes. Copolymer phosphazenes with pendant fluorinated alkoxy groups on the phosphorus atom chain backbone were evaluated and results were obtained that are related to those obtained with poly(bis-trifluoroethoxy)phosphazenes. The overall side group composition of the mixed perfluorinated alkoxy copolymer is about 65% -O- _CH2 - _CF3 , about 35% -O-
CH ₂ −(CF ₂ ) _o −CHF ₂ (where n is 1, 3, 5,
7,9), but this copolymer also contains 0.5 unsaturated functional groups in the pendant groups, which can be crosslinked by various vulcanizing agents such as peroxides or sulfur. I can do it. The supported polyphosphazene fluid separation membrane according to the invention is obtained by a composite coating on a porous filter support. Typically 6-10% by weight of polyphosphazene in tetrahydrofuran (THF)
The solution was applied to the surface of a disk of regenerated cellulose filter (0.2 micron porosity). Vacuum was applied to remove the solvent. The coating/drying process was then repeated, typically 3 to 7 times, until a relatively uniform film of polyphosphazene polymer was obtained. Film thickness is determined by two methods: by direct micrometer measurements subtracting the uncoated cellulose support thickness from the total thickness of the coated support and by using the weight gain following coating to account for polyphosphazene density and film area. Obtained by. The thickness obtained by these two methods is approximately 10
Matched within %. These values were used because the thicknesses obtained from the weight gain/density/area calculations are expected to include any material with pores contained in the cellulose filter support columns. Film thickness was typically about 0.02 cm or less. Gas separation tests followed the conventional method of Hwang et al. using gas mixtures. Due to the high gas flow rates encountered during testing of polyphosphazene materials, most data were obtained at feed gas pressures of 10-20 psig. The downstream side of the test membrane was under vacuum. High pressure feed tests were evaluated with mixed gas feed streams at pressures from 100 to about 300 psig. All tests reported were evaluated at room temperature. The gas separation results obtained using four different polyphosphazenes as support membranes for fluids (gases) are shown in the table for reference. Polar fluids, e.g.
The separation performance of these four polyphosphazene membranes for CO ₂ and H ₂ S is shown by the data in the table for reference. The data in the table is also
A comparison of the separation performance of polyphosphazenes for CH ₄ and CO ₂ is shown. For reference, the table shows a comparison of hydrogen and carbon dioxide permeability and hydrogen/methane and carbon dioxide/methane separation factors for various membranes, both rubbery and glassy materials. Of particular interest, the data show unexpected, robust and attractive behavior of polar gas permeability and acid gas/methane selectivity for polyphosphazenes bearing fluorinated alkoxy side groups. These polymers, poly(bis-trifluoroethoxy)phosphazene and copolymers of various fluorinated alkoxy side groups, both have high permeability (400-600 c.c.-cm/cm) for polar gas separation from methane.
^cm2 -sec-cmHg) and selectivity (10-11.5). Such high carbon dioxide permeability is only surpassed by silicone-based polymers. For example, polydimethylsiloxane is reported to have standard units as high as 3000-4000 for carbon dioxide permeability, but the carbon dioxide/methane separation factor is quite low, e.g. 3-4. Although many glassy polymers exhibit relatively high carbon dioxide/methane selectivities [approximately 30 for polysulfones and ammonia-crosslinked brominated polyphenylene oxides (PPO, e.g. 2,
35-50 for 6-dimethyl-1,4-phenylene oxide), _CO2 permeability is typically one or two orders of magnitude lower, e.g. about 6 for polysulfone and about 40-45 for cross-linked brominated PPO membranes. It is.
Measurements show that the hydrogen sulfide permeability for fluoro-aloxy substituted polyphosphazenes is equivalent to that of carbon dioxide.

【table】

[Table] Zen

【table】

【table】

Table: Polyphosphazene membranes appear to interact with ultralow fluids in an unusual manner to explain the observed transport behavior. In particular, poly(fluoro-alkoxy)phosphazenes are
Must interact with CO ₂ and H ₂ S.
at 20 psig for a membrane of poly(bis-trifluoroethoxy)phosphazene supported on a porous polypropylene filter (0.02 micron pores).
Further experiments were performed using a ternary mixed gas feed of H ₂ S/CO ₂ /CH ₄ . The results show that the _CO2 / _CH4 permeation behavior is generally intact for the membrane itself;
We showed that the results are very similar to those observed previously in the absence of H ₂ S. However, the H ₂ S/CO ₂ separation factors are essentially the same. Thus, poly( _fluoro -alkoxy)phosphazenes remain largely unattractive for the _separation of polar gas pairs, e.g. is useful in gas mixtures when is CO ₂ or H ₂ S. The permeability of _CO2 in poly(fluoro-alkoxy)phosphazenes was significantly higher than the permeability of hydrogen for the same membrane. Although gas mixtures such as CO ₂ /hydrogen were not tested, this data indicates that the CO ₂ /hydrogen separation factor for poly(bis-trifluoroethoxy)phosphazene and various phosphazene mixtures is approximately 5-6. It suggests. It is generally observed that for glassy polymers the hydrogen permeability is approximately twice that of carbon dioxide. In some rubbery polymers, carbon dioxide permeates faster than hydrogen; for example, silicone rubber
Reported to have solids permeability for _CO2 and _H2 of 3200 and 660 standard units. These values for silicones suggest a _CO2 / _H2 decomposition factor of about 5, which is comparable to the above evaluation for poly(fluoro-alkoxy)phosphazenes.
Thus, poly(halo-alkoxy)phosphazenes, at least in glassy polymers, prove useful in the separation of a set of gases called fast gases. For example, polar gases from _H2 , i.e.
Possible values may exist in situations where it is desirable to perform separation of _CO2 and _H2S . Fluid separation examples using trifluoroethoxyphosphazene membranes to separate mixtures of liquid toluene and cyclohexane at ambient temperature and 24 psig are not included in the three tables. The permeate was enriched in toluene relative to the toluene content in the feed stream as follows: The toluene to cyclohexane molar ratio and permeate was 1.43 to 1 in the liquid feed mixture.
It was 1.23. The table also includes calculations of the CO ₂ /H ₂ separation factor based simply on the ratio of the CO ₂ and H ₂ permeability values obtained from the CO ₂ /methane and H ₂ /methane gas mixture tests. There is. The practical use of attractive intrinsic transport properties for polar gases using polyhalogenated alkoxyphosphazenes or any other rubbery polymers in the form of gas separation membranes is of primary interest. It appears to be largely limited by the poor mechanical properties of the rubbery state compared to the high mechanical strength typically found in glassy polymers. However, there are techniques that effectively support thin rubbery polymeric membranes in structures suitable for fluid separation. For example, ultrathin approximately 500 Å silicone-based rubbery membranes supported on top of porous supports have been fabricated into small-scale medical devices suitable for blood oxygenation or the production of oxygen-enriched air. The study of polyphosphazenes as gas separation membranes has led to the possibility of effectively supporting very thin separation membranes of a wide range of polymers, including rubbery materials such as polyphosphazenes, on top of microporous supports in hollow fiber structures. Ta. for example,
Experiments supporting poly(bis-trifluoroethoxy)phosphazene on top of microporous polypropylene hollow fibers show that the composite fiber membrane approximates the polymer's inherent separation coefficient for _CO2 / _CH4 (8.3 vs. inherent 10.5).
gave. This result shows that almost complete preservation of the polyphosphazene separation layer was achieved. The CO ₂ permeability (P/l) of this particular sample is
About 600 (P) for this specific polyphosphazene
Compared to the specific permeability of _CO2 , it is 83 (P/l), thus making it possible to estimate the thickness of this supported polyphosphazene membrane to be 7.5 microns. At a thickness of approximately 2 microns, the P/l of CO ₂ is approximately
Obtained at 300 standard unit level or above. Apart from the attractive transport properties of polyhaloalkoxypolyphosphazenes mentioned above, these materials also have high thermal and chemical stability, which extends their use in a variety of gas separation applications. spread. For example, differential scanning calorimetry of these polyphosphazenes at temperatures ranging from −100 to 300 °C shows no thermal activity other than the glass phase to rubber phase transition Tg (which is observed near −60 °C). . These polyphosphazene materials have substantial resistance to degradation by common solvents and other organics encountered in some gas separation applications. For example, in liquid toluene at room temperature, silicone rubber swells 140% by volume, while polyphosphazene mixtures swell only about 15%. After 7 days of immersion at 100°C in JP4 jet fuel (kerosene distillate hydrocarbon), the polyphosphazene mixture swells by only about 9% by volume, thus the initial interest in polyphosphazenes was
This was in the area of special O-ring and gasket applications. A further example of the unique stability characteristics of polyphosphazene materials is seen in the comparison of the high temperature tensile strength of polyphosphazene mixtures with that of fluorosilicone elastomers. Although fluorosilicone elastomers exhibit relatively low equilibrium swelling when immersed in liquid toluene at room temperature (15% for polyphosphazenes)
20%), the tensile strength retention of polyphosphazenes is quite good at high temperatures, e.g. retention equal to or greater than 50% at 150°C for polyphosphazenes compared to only about 25% retention for fluorosilicone. It is. Polyphosphazene gas separation membranes are expected to have an upper limit for long-term exposure to high temperatures of up to about 175°C, but these high temperatures are generally lower than the surface temperatures encountered either in gas separation membrane manufacturing or in gas separation applications. The upper limit has been exceeded. Although the transport and physical/chemical properties of polyphosphazenes described above are attractive, the ability to crosslink unsaturated fluorinated polyphosphazenes further increases the potential of using this polymer for fluid separation. Thus, the crosslinked polyphosphazenes provide applications that involve favorable use environments, such as feed streams containing solvated components or swellable impurity components or high temperature environments. Crosslinking of various poly(fluoro-alkoxy)phosphazenes is accomplished to varying degrees as desired by treatment of the polyphosphazenes with, for example, disodium salts of highly fluorinated alkyl diols. Such reactions in solution are readily carried out under mild room temperature conditions and occur to an extent strictly related to the stoichiometry of the reactants. Crosslinking also takes place on polyphosphazenes in the solid state.
In such cases, higher temperatures are usually required compared to solution crosslinking. Crosslinking as described above by substitution-exchange reactions carried out with fluorinated disodium dialkoxides can be achieved by crosslinking reactions using peroxides or other free radical agents (where the starting polyphosphazene material has a small amount of unsaturated sites). ) can be carried out at much higher crosslinking densities. Thus,
From the available information and as derived from this study, polyphosphazenes have sufficient physical properties for potential use in a variety of fluid separation applications. Possibilities of use include H ₂ and slow gases, especially
Involves separation of _H2O from _CH4 . For such separation applications, the transport properties of polyphosphazenes appear to offer distinct advantages over various rubbery and glassy polymers due to their combination of permeability and selectivity. The gas permeability of rubbery polymers, unlike that of glassy polymers, is essentially independent of pressure. This is expressed by the relational expression P=D×S (where P, D
and S are the permeability, diffusivity, and solubility coefficient of gas in the polymer). The solubility of gases in rubbery polymers follows Henry's law,
The solubility coefficient is thus independent of pressure, as is the diffusivity D. Therefore, gas retention at high pressures should not differ significantly from that at low temperatures. To minimize performance degradation, operation at elevated temperatures should be
It is often used to raise the saturation vapor pressure of the harmful impurities sufficiently to reduce the relative saturation level as much as possible. In the contemplated grated roe, high temperature operation would not be necessary due to the high permeability and good chemical resistance of polyphosphazene as a gas separation membrane. In such cases, the separation effectiveness depends on the suitability of the chemical resistance exhibited by the porous support in the case of composite membranes using polyphosphazenes as coatings. The supported polyphosphazene fluid separation membranes shown in Table 1 showing water transport properties were prepared according to the same method as the membranes in Table 1 and Table 1. The separation coefficient of water/methane is the actually measured methane permeability P
(H ₂ O) and separately measured methane permeability P (CH ₄ )
These are the calculated values as shown in the table using the ratio of
Fluid separation tests followed conventional methods. The water permeability P(H ₂ O) was measured in liquid water upstream of the test membrane. The downstream side of the test membrane was kept under vacuum. All reported tests were evaluated at room temperature.

【table】

TABLE The membranes in the table clearly demonstrate the excellent water permeability when using the preferred halogenated polyphosphazenes according to the invention. As compared to the non-halogenated polyphosphazene shown by membrane number 3, the halogenated polyphosphazenes obtained 30-70 times higher water permeation rates. These unpredictable and exceptional permeabilities for water were accompanied by reasonable separation factors, as also shown in the calculated α column of the table.

Claims (1)

[Scope of Claims] 1. A method for separating water from a non-polar fluid by contacting a water-containing mixture with a first surface of a separation membrane, wherein the separation membrane has preferential selectivity and permeability for water. And expression (wherein n is an integer from 100 to 70,000, Y is oxygen, and R and R' may be the same or different and contain aryl, alkyl-substituted aryl, or 1 to 25 carbon atoms. a polyphosphazene represented by a fluorinated alkyl group having a fluorinated alkyl group having a fluorinated alkyl group, the method maintains a second surface of the polyphosphazene membrane at a chemical potential for water that is lower than a chemical potential of the first surface; permeating water into and through the second surface, and recovering from the vicinity of said second surface a permeate product having a concentration of water relative to the non-polar fluid greater than that contained in the feed mixture. Method. 2. The method according to claim 1, wherein the polyphosphazene is a fluoroalkoxypolyphosphazene. 3. The method according to claim 2, wherein the fluoroalkoxypolyphosphazene is fluoroethoxypolyphosphazene. 4. The method according to claim 1, wherein the polyphosphazene is poly(bis-diphenoxy)phosphazene.