JPS61114714A - Production of composite membrane for separating gas - 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 The present invention relates to a method for producing composite membranes suitable for gas separation and to composite membrane ICs obtained by such a method.

The idea of separating low molecular weight gases based on differences in permeation rates through solid films is not new.

About 150 years ago, it was observed that natural rubber is more permeable to some gases than others. However, it is only in the past few years that membrane separation methods for gas separation have been recognized as a practical alternative to conventional low-temperature separation methods. The need for simple and energy efficient commercial methods has led to a wave of interest in applying membrane technology for gas separation.

In 1866, the theory was proposed that the permeation of gas through a solid film is a six-stage process consisting of the following steps:

(1) dissolution of the gas at one interface of the membrane, (2) diffusion of the gas to the opposite interface, and (31 desorption, or release of the gas at the opposite interface).

This mechanism, known as the dissolution-diffusion model of permeation, remains a useful explanation of the permeation process and serves as the basis for modern permeability theory.

Considering first the second step of the permeation process, diffusion, Fick's law can be used to quantitatively describe the movement of low molecular weight gases across an isotropic and homogeneous membrane.

For a flat sheet-like membrane, the flux J is expressed by the following equation:

δC, T = −D −(1) Integrating this equation over the thickness of the film (from x=0 to X=t) leads to Fick's law of the form:

where C2 and C1 are the concentrations of permeating gas just inside the film at each interface. Equations (1) and (2)
describes only the second stage of permeation, diffusion across the membrane. Furthermore, since it is difficult to measure the concentration of gas at specific points inside the membrane, it is necessary to relate these concentrations to external, more easily measured variables. According to Henn's law, the concentration of dissolved gas, C, for a dilute solution is proportional to the partial pressure of the gas in contact with the solution.

C= Sp (3) In the above formula, day is the solubility coefficient (the reciprocal of the constant of Henry's law).

Combining equations (2) and (6), the permeability of the membrane to gas is expressed by the following equation.

The lower part of the above equation is the average permeability coefficient defined as the product of the average permeability coefficient 5 and the average solubility coefficient i, where Δp is the pressure difference between the two sides of the membrane.

Depending on the polymer/permeate system now considered, tens of thousands (and therefore below) degrees Celsius will be affected by pressure and temperature. However, for simple gases such as oxygen and nitrogen, the temperature range is usually considered constant over a reasonable range of temperature and temperature for most polymers. Although the permeability of a particular gas may vary over many orders of magnitude between different polymers, the permeability of a particular polymer to various permeates falls within a much narrower range. The ratio of one of these permeability coefficients to the other is a useful measure of the relative permeation rate of gas and therefore of the permselectivity of the membrane. This hair is an ideal separation image! (6
g) and is defined by the following expression:

In the above equation, lower 1 and lower j are the transmission coefficients of components 1 and -, respectively,
The subscript 1 usually represents the more transparent component. A general theory often cited when selecting materials for membrane separations is that polymers that exhibit high selectivity for one component of a mixture often have low permeability; This means that there is less differentiation between the components of .

Examples of permeability coefficients and 'ideal separation factors for many oxygen and nitrogen polymers are shown in the following table.

px 1010 Ideal silicone rubber 281 605 2.15 Poly(phenylene oxide') 3.81 15.8 4.
15 Polystyrene 0.83 2.5 3.
01 Polycarbonate 0.3 1.4 4
-67 polysulfone 0.24 1.3 5
．． 41 In the table above, it can be seen that the bottom varies over values of an order of four between the polymers, but the values of α are of the same order of magnitude. There is also a relationship between low permeability and high selectivity and vice versa, although there is considerable overlap. One of the reasons for this observation is the influence of the physical state of the polymer on the diffusion process.

Polymers are classified as existing in either a glassy or rubbery state, although no true change of state is involved. When the polymer is cooled from the melt, it first forms a rubber-like material and then, as the temperature is further reduced, a hard, brittle, glass-like material. The temperature at which a polymer transforms from a rubbery to a glassy substance is the glass transition point Tg. Below Tg, not enough thermal energy is available for anything other than a small range of cooperative motion of the chain segments.

Above the Tg, sufficient energy is available to move relatively long segments of the polymer chain. Free volume of the polymer is required to accommodate the motion of long chain segments. In addition to accommodating chain segments, this free volume may be filled by permeate gas. Within rubbery polymers, the free volume should be considered as a dynamic system in which pores in the polymer matrix are successively created and filled by the movement of the chains. On the other hand, glassy polymers contain much less free volume than rubbery polymers, and the pores in the matrix are relatively spatially fixed. Because glassy polymers have a much smaller total free volume, their permeability tends to be lower, while the narrower distribution of pore sizes makes it easier for these polymers to distinguish between molecules of different sizes. do what you can.

When designing a permeation process for industrial gas separation,
The biggest concerns are product purity and production speed. In selecting the membrane, it shows a high specific permeability for the product,
A membrane is also required that exhibits a low specific permeability relative to other components of the mixture, ie, a membrane that exhibits high permeability and high selectivity. These properties are rarely found simultaneously in one polymer. This dilemma is an important factor in the development of membrane separation methods that are fully useful for industrial gas separation.

Fortunately, membranes that exhibit high selectivity for one component of a gas mixture need not be abandoned solely because of low overall permeability. A closer look at equation (4) shows that the flux can be increased by increasing the pressure differential across the membrane or by decreasing the membrane thickness. Moreover, the permeator design also influences the flux as well as the membrane selectivity that can actually be achieved.

In practice, membrane separation of gases is carried out by passing a feed stream of the gas mixture to be separated over the surface of the membrane,
Only a portion of the gas is permeated and the unpermeated gas (raffinate) is recycled or sent to another permeation chamber. The driving force for gas permeation is the pressure differential across the membrane, which is maintained by either hydrostatic pressure on the feed side or vacuum on the product side of the permeation chamber, or both. Each pass of the gas mixture through the membrane is hereinafter referred to as a stage of separation, and the permeation fraction, gold stage cut. The increase in the number of stages results in a product of higher purity than that obtained in a single stage process. However, the cost of repressurizing gas at each stage is similar to the cost of adding modules.
often makes implementation impossible.

Stage cut also affects selectivity as well as permeation rate.

The greater the amount of gas that is allowed to pass through, the lower the true degree of separation. The mode of gas flow across the surface of the membrane also affects the selectivity of the process. However, if the stage cut is very low, this effect will be minimal.

Since the flux described in Equation (4) is the permeation rate per unit area, another way to improve membrane productivity is by increasing the surface area of the membrane. Simply adding modules is one way to increase surface area, but
However, the permeability of polymers to gas is often low, potentially requiring millions of square feet to produce a satisfactory permeation rate, making this method impractical.

Considerable research has been devoted to the subject of packing membranes into structures that provide greater membrane surface per unit volume. The two most successful formats developed thereby were spiral wound membranes and hollow fiber membranes. Hollow fibers in particular offer extremely high surface area to volume ratios. For example, a 0.6rn3 membrane device contains as much as 500 fi'' of surface area, compared to 201 n'' for the same volume in a spirally wound membrane. An additional advantage of using hollow fiber technology is the self-supporting nature of the hollow fibers, which minimizes the cost of manufacturing equipment for housing the hollow fibers.

It has been shown that the pressure difference across the membrane affects the membrane flux. It has been shown that the true separation of gas mixtures also depends on the pressure difference between the feed and product sides of the membrane. In the separation of two components, the ratio of the pressure on the high-pressure (feedstock) side of the membrane to the soil on the low-pressure (product) side of the membrane 1 The molar fraction of the more permeable component in the feedstock, XA%, and equation (5) Based on the ideal separation factor (α*) as defined, it can be seen that the actual separation factor approaches the ideal separation factor in the limit value of the next infinite supply pressure for the actual separation factor α. With the high working pressures required to maintain high fluxes and selectivities, comes the need for membranes and equipment that can withstand such conditions as well as the added energy consumption for compression of the feed mixture.

Of all the ways to maximize membrane flux, perhaps no other has attracted as much interest as reducing the thickness of the membrane itself.

However, this research method has two major drawbacks that have been overcome within the last 20 years. Gas molecules are so small that a pinhole (or even a microscopic defect in the membrane surface) is sufficient to render the membrane unusable for gas separation. It is extremely difficult to cast ultra-thin films without defects using conventional casting techniques. Irregularities on the surface onto which the membrane is cast are incorporated into the fabric of the membrane, which for very thin membranes can be as large as the thickness of the membrane. These irregularities create pinholes through which a large flow of gas occurs, thus causing a loss of permselectivity. Second, ultrathin membranes are extremely fragile and often cannot withstand the pressures they must undergo in membrane separation processes.

Ta. Asymmetry) The term IJ sock is a relatively dense
Refers to a membrane configuration in which an ultra-thin coating is deposited on an underlying open porous structure. To cast this type of membrane, a solution of the polymer in a water-miscible solvent is first cast onto a glass plate in a conventional manner. After a short period of time for the solvent near the surface of the membrane to evaporate and condense the polymer,
When the glass sheet metal is immersed in water, where the polymer condenses, the water diffuses into the solution and the solvent also diffuses out, forming a porous matrix. Because the dense layers formed in this way represent only a small fraction of the total membrane thickness, the flux of these membranes is much greater than that exhibited by dense isotropic membranes of comparable thickness. expensive. A dense separation layer is placed on a porous support matrix that provides mechanical strength to the membrane.

These membranes have been very successful in reverse osmosis applications, but their utility in gas separation is questionable. Although it may be considered impermeable to liquids, even its dense coating contains pores larger than a typical gas molecule. For example, post-treatments such as annealing the film at high temperatures have been used to reduce the size of the pores in the surface layer.

However, for this post-treatment to be successful, the surface porosity must be less than 10''6% of the surface area. Moreover, these post-treatments tend to significantly reduce membrane flux.

Another solution to eliminate the effect of surface porosity in asymmetric membranes is varnish and tripod.
ana Tripodi) in U.S. Patent No. 4.
No. 230,463 (published October 28, 1980). This shows a porous substrate coated with polymer in closed contact. Hennis et al.'s research method involves applying a thin layer of highly permeable polymer (e.g. silicone rubber) to one component of the gas mixture to be separated on the surface of a porous asymmetric membrane that exhibits good bilateral selectivity. The purpose was to precipitate it. It has been found that by sealing the surface pores in this manner, much of the selectivity of the underlying porous polymeric material is maintained, yet the overall permeability remains very high. Membranes made of two (or more) laminated films are called composite membranes. ′
Similar to the electrical current in an electrical circuit, the ultimate properties of these composite membranes are related to the resistance of each of their constituent parts. In this case, it concerns the resistance of the coating material, the substrate, and the filled pores to gas flow.

The resistance (R) for a particular component of the composite membrane is given by the following equation:

where t is the thickness of the part, P is the average permeability of the material making up the part, and A is the surface area of the part. The total resistance RT of a composite membrane for a particular gas flow is calculated in the same way as that of the corresponding current. For the case of a composite membrane consisting of two stacked defect-free layers, RT is simply the sum of the resistances of the individual layers.

For a composite membrane of the type of Hennis et al., the RT is given by the following equation:

The subscript in the above formula represents the part of the membrane. Assuming that the pore area is small compared to the total surface area, the thickness-corrected permeability (P/l) is given by the following equation:

Where A3 is the surface area of the pores and A2 is the total surface area of the membrane.

The ratio of thickness-corrected permeabilities for a pair of gases is likewise equal to the ideal separation factor as a ratio of average permeability coefficients. It is clear that the selectivity of composite membranes does indeed approach the intrinsic selectivity of the substrate up to relatively high surface porosity. It is therefore possible to achieve high selectivity at the same time as high flux.

The separator in these composite membranes of Hennis et al. is the underlying asymmetric IJ membrane. Therefore, the choice of separation material is limited to the polymer from which the asymmetric membrane is cast. Moreover, since the majority of the material in the composite membrane is within the underlying structure, the material making up this layer must be an inexpensive and easily synthesized polymer.

The method of manufacturing membranes in which the separating layer is deposited as an ultrathin film on the surface of an inexpensive porous support makes it entirely possible to construct membranes using small amounts of expensive or novel polymers as permselective layers. . The use of materials such as No. 7 is advantageous from the point of view of the inherent permselectivity of those materials. This method actually preceded the work of Hennis et al. and has generally become the most common method for developing high flux membranes for gas separation.

Several methods have been investigated for depositing ultrathin films on the surface of porous supports. The simplest and most direct technique is simply to coat the support film by dipping it in some polymer or reactive monomer, then drying and/or
Alternatively, it is a method of heating and curing. However, this method has been applied only to limited applications, mainly in the field of reverse osmosis membranes.

A close relative of this technique is the interfacial polymerization of reactive monomers or polymers on the surface of a support. In such methods, a porous film is saturated with a water bath solution of some monomer or polymer and then treated with a reactive intermediate dissolved in a water-immiscible solvent. Since the reaction between the monomers or polymers takes place only at the interface, the resulting separation layer is extremely thin. Until now,
This method has been applied commercially only to make membranes for reverse osmosis separations.

The vapor phase deposition of polymers onto porous supports is a promising new technique that has been studied in the past, but there is no commercial application of this method yet.

Another method of placing the film directly onto the support layer is to cast the film separately and then laminate the ultrathin separation layer onto the porous support. Perhaps the easiest way to accomplish this is to dip a glass plate into a dilute solution of the polymer, pull the plate out, and then allow the solvent to evaporate. The remaining film is then removed from the glass surface by immersing the glass plate in water. Finally, one or more layers of this film are carefully layered onto the fully porous support. The second method is to cast a polymer solution in a hydrophobic solvent onto the surface of gold water and spread the solution to form an ultra-thin film. After evaporating the solvent, the film is picked up and placed on the support layer. These techniques have proven useful for casting essentially defect-free films as thin as 150 angstroms.

The above membranes were laminated as single or multiple layers onto porous supports for use in gas separation. Although a thin separation layer is advantageous from the viewpoint of increasing membrane flux,
These layers are easily damaged during lamination, complicating the membrane manufacturing procedure. Composite membranes consisting of ultrathin lath-like polymer films on porous glass-like polymer supports are particularly sensitive to damage during handling. Brovra and Saleem
1':t, anaSalemme) is U.S. Pat.
．． No. 874.986 (issued April 1, 1975), and Brovall U.S. Patent No. 3,980,456 (issued September 14, 1976).
This problem is solved by completely inserting an intermediate layer of organopolysiloxane-polycarbonate copolymer between the microporous layer and the non-porous layer. In this case, the intermediate layer mentioned above serves as cushion and adhesive.

Another disadvantage of separately casting the support structure and permselective layer is the limitation of the technique for coating planar sheet membranes. The advantages over hollow fiber-shaped planar sheets M have already been mentioned above.

Japanese Patent Publication No. 105,203 (published on June 26, 1982, filed by Toshi Co., Ltd.), Hirose and Kurihara
Hara) describes a selectively permeable membrane made by crosslinking an aminopolysiloxane consisting primarily of repeating units of the general formula:

H3CH3 (0M2)nX CH3 in the above formula, or -NH2 or an amino group having 1 to 4 primary or secondary amino groups and being an aliphatic or lIW ring group, where n is 1 to 10 is an integer, and 1 and j represent the mole fraction, i + j = 1.0, O61 × 1 and 0
<j <0.9 is satisfied.

Hirose and Kurihara describe aminopolysiloxanes as crosslinking agents, such as acid chlorides, acid anhydrides, isocyanates, thiocyanates, sulfonyl chlorides, epoxides, or compounds containing two or more functional groups such as active halogens in each molecule. It states that cross-linking is achieved by If the crosslinking agent is soluble in water or alcohol, a solution of the aminopolysiloxane and the crosslinking agent are mixed and coated onto the porous support. If the crosslinker is insoluble in water or alcohol, or if the crosslinker reacts with these solvents, the membrane is produced by surface condensation. The aminopolysiloxane is first applied onto the porous support and the polymer solution is allowed to penetrate into the pores for a certain period of time, preferably from a few seconds to 60 minutes. The surface of the support can be dried with hot air. The surface of the support coated with the aminopolysiloxane film is then contacted with a bath of a polyfunctional crosslinking agent capable of reacting with the amino groups in the aminopolysiloxane.

Preferred solvents for polyfunctional crosslinkers are usually hydrocarbon methods, eg petroleum ether, hexane, or hebutane. The appropriate concentration of crosslinking agent in this solvent varies depending on the reaction substrate, crosslinking agent, and solvent, but about 0.1 to 2N% gives good results. Heating is usually required to complete the crosslinking reaction, with temperatures ranging from 1 to 6
Heat for 0 minutes.

The present invention relates to a method for producing a composite material suitable for increasing the oxygen gas content in an oxygen-nitrogen gas mixture by passing the mixture through said composite material. The method comprises coating a polysiloxane with aminoorganic functionality on at least one surface of a highly porous polymeric substrate with a thickness of 20 to 250 μm, wherein the polysiloxane is 0.1 μm to 0.1 μm thick. The polysiloxane is coated to a thickness sufficient to give a cured film containing 20 μm thick, and the polysiloxane consists essentially of aminosiloxane units having 1 to 9 mole percent primary amino organofunctional gold and 91 to 99 The polysiloxane is composed of a random copolymer of mol % of other repeating units and coated onto the substrate with a solution of the diisocyanate in an organic solvent that is non-reactive to the isocyanate, to form a cross-linked film. This essentially consists of contacting for a sufficient period of time such that the weight ratio of polysiloxane to diisocyanate is inversely related to the permeability coefficient of the composite material.

One object of the present invention is to provide a method of manufacturing a membrane for concentrating oxygen in air.

The characteristics required for this membrane are good oxygen permeation selectivity (6
(ideal separation factor of ~4), reasonably high flux, and suitability for hollow fiber technology. Composite membranes prepared by continuous deposition of all component layers on a supporting surface are best suited to the membrane requirements described above.

A second object of the invention is to provide an improved intermediate layer within a plurality of membranes. In particular, this layer acts as a "gutter layer" that serves to pad the separation layer and provides a passageway into the surface pores of the gas-gold polysulfone (PSF) support through which it passes, thus making the composite The total flux of the membrane is increased by increasing the effective surface area of the film for separation.

The method for producing the composite material of the present invention is disclosed in Japanese Patent Publication No. 57C19821-105, 203 by Hirose and Kurihara.
This is similar to the method used in No. The process of the invention allows the convenience of low aminosiloxane unit contents in polysiloxanes with aminoorganofunctionality, ie from 1 to 9 moles of aminosiloxane units. Polysiloxanes with these aminoorganic functionalities can be crosslinked with diisocyanates on porous substrates to create composite materials useful for gas separation, particularly oxygen enrichment of gas mixtures such as air.

According to the teachings of Hirose and Kurihara, polysiloxane
Without 0 mole percent or more aminosiloxane units, the polysiloxane cannot be sufficiently crosslinked.
It has been discovered that not only can less than 0 molar aminosiloxane be used, but the permeability coefficient of the resulting composite material can be adjusted by the weight ratio of polysiloxane to diisocyanate used to crosslink the polysiloxane. are doing. Increasing the ratio results in a decrease in the permeability coefficients of gases such as oxygen and nitrogen for the composite material. The change in permeability coefficient is the separation coefficient (S
F, α) does not cause any substantial change.

The support layer may be a sheet or a hollow fiber, for example a highly porous polymer, such as polysulfone (PSF).
, polystyrene, and other U.S. patents No. 4,230,
No. 463 (indicating materials from which porous substrates can be made). Such porous substrates are known in the art, and many are commercially manufactured. Preferably, the porous substrate is polysulfone.

The porous substrate preferably has a thickness of 20 to 250 μm,
The diameter of the pores is preferably within the range of 0.01 to 0.1 μm. At least one surface of the porous substrate is coated with a polysiloxane having aminoorganic functionality. Preferably, the high wK surface is coated and is also the surface in contact with the feed gas. Preferably, the polysiloxane is in solution in an organic solvent when applied onto the porous substrate. The organic solvent used in preparing the polysiloxane bath liquid is one that is substantially non-solvent to the porous substrate and has no reactivity with the porous substrate and the polysiloxane, such as hexane. See US Pat. No. 4,230,463 for further information regarding suitable solvents for dissolving polysiloxanes and not acting on porous substrates.

Polysiloxane is applied onto the porous substrate in a thickness of 0.1μ to 20μ.
The coating is applied at a sufficient thickness to give a cured coating of m thickness. The concentration of polysiloxane in the organic solvent is preferably within the range of 1 to 20 7% by weight, but may vary outside this range depending on the nature of the solvent and polysiloxane. The most practical concentration of polysiloxane in a solvent is 1 to 10% by weight. The polysiloxane bath may be cast onto the porous substrate to provide a uniform coating on the surface of the sheet material.

Other methods of applying a uniform coating may be suggested by the fabrication of porous substrates. For example, the people of Hirochuu Thread
The fJ (tubular) can be coated by passing a bath liquid through it.

More than 19 passes can be made at one time to build up the coating thickness to provide the necessary system for the gas content. After coating the porous surface with a polysiloxane film, the solvent is evaporated. The siloxane then forms a non-crosslinked polysiloxane film. The polysiloxane film is then crosslinked with diisocyanate to form an elastic film. The diisocyanate is applied to the polysiloxane as a bath in an organic solvent.

The concentration of diisocyanate in the organic solvent can be varied, but must be sufficient to crosslink the polysiloxane. Preferably the concentration of diisocyanate! -10.1 to 5% by weight, most preferably 0.2 to 4% by weight. After the diisocyanate is spread on the polysiloxane film, the diisocyanate is discharged with the polysiloxane to provide i=it in the polysiloxane. A total time of 5 to 60 seconds is sufficient. Excess diisocyanate bath solution is removed from the surface of the polysiloxane film by washing it to death or by scraping it from the hollow fibers. After pouring out the diisocyanate solution, the surface of the treated polysiloxane film was allowed to dry at room temperature, and then heated at 50° to 150°C for 1 hour.
Further curing can be achieved by heating for ~60 minutes.

Polysiloxanes with aminoorganic functionality have from 1 to 9 moles of aminosiloxane alone and are random copolymers. The aminosiloxane unit contains a primary amino group as shown in the following formula.

In the above formula, R is a divalent group selected from CH3 -CH2CH2CH2- and -CH2CHCH2-. The polysiloxane also contains 91 to 99 moles of other repeating units, such as dimethylsiloxane units,
It carries phenylmethylsiloxane units and diphenylsiloxane units. The polysiloxane units can be end-capped with trimethylsiloxy units, dimethylphenylsiloxane units, and aminosiloxane units such as those of the formula below. Preferably, the polysiloxane contains about 1500 siloxane units per average molecule. Polysiloxanes with preferred aminoorganic functionality have two trimethylsiloxy units, 2 to 15,000
It is a random terpolymer consisting of 0 dimethylsiloxane units and 2 to 160 aminosiloxane units selected from the units of the general formula below.

In the above formula, R is CH3-CH2G)(2CH2- and -〇H20HCH2-
A divalent group selected from

In a preferred embodiment, the composite membrane has an average molecular weight of 100 to 800
Aminoorganic functional 1 [11] containing siloxane units of
Contains a polysiloxane with 'i. One preferred random polysiloxane has the following average formula: That is, (C'H2), N'H(CH2) 2NH2 (in the above formula, the opening and n are approximately 2 mol% of aminosiloxane units of the following formula H3SiO (CH2) 3NH(CHz) 2NH2, and (CH3)3SiO ((CH3)2
SiO), (-CH3SiO:)8Si(CH3)3C
H2CHCH2NH(CH2)2NH2CH3 (r and S in the above formula represent the presence of about 8 moles of aminosiloxane units of the following formula H3SiO CH2CHCH2NR(CH2) 2NH2CH5, and the average total number of siloxane units per molecule is about 600. ), and r and S in the above formula have the following formula CI (3SiO 0M2CHCH2NH(CH2)NH2CH3 where about 2 moles of aminosiloxane units are present and the number of siloxane units per molecule is The average total number of polysiloxanes is about 100.

The diisocyanate may be aromatic, aliphatic or cycloaliphatic, such as toluene diisocyanate, diphenylmethane diisocyanate, naphthalene diisocyanate, benzene diisocyanate, hexamethylene diisocyanate. cyclohexane diisocyanate, and memexylene diisocyanate. A preferred diisocyanate is toluene diisocyanate (TD).

The composite material prepared as above was 2.4-2.9
SF (separation factor) of as well as 18 x 1 for oxygen
Low 10~180 x 1 Q-”cm”
permeability coefficient of t-v 5ea-'(M-''(c1!Hg)-1 and 6x10-↓0~75 x for nitrogen
10-yo0 CIrr5 cm sec”c
It can have a transmission coefficient of m-' (cm Hg)-1.

The composite material described above, consisting of a porous substrate coated with a film of cross-linked polysiloxane containing t-amino organofunctional groups, is suitable for the separation of gases, e.g. to increase the glare content in oxygen-nitrogen mixtures. Although it is for M, poly(2,6
-dimethyl-1,4-phinylene oxide) (ppo
Composite P+, prepared by placing an ultra-thin layer of ) on top of a film of cross-linked amino M-functionalized polysiloxane, provides a composite containing more ori points and broader potency. . The separation factor can be higher, and the cross-linked polysiloxane can act as a barrier, and the surface can be free from contamination, such as lump particles? ! 0PPOrc- that does not attach to J Kanaya Yoshi
CH2Br f 1~(5Q% can be a brominated PPO having up to 60% or more anti-ousi positions. Preferred brominated PPOs are 20.00[]~5
00,000 and can have repeating units selected from.

Brominated PP○ can be used as a separating layer exhibiting a high min# factor. 111 with a separation factor greater than 8 for oxygen-nitrogen mixtures. can be obtained.

Other poly(phenylene oxides) are also expected to serve as separation layers in bilayer composite membranes.

The PPO film of the present invention is laminated onto the cured polysiloxane film as a separation layer. That PPO no 1l
Although 17 can be deposited to a thickness of 2 μm, it is commonly precipitated from organic solvents to a thickness of 0.5 μm or less. The combined thickness of the gutter layer and 220 layer is 1
It may be as thin as μ. The performance of the membrane, i.e. the composite material, depends on the relationship between the thickness of the underlying layer, the porosity of the substrate, and the proportion of defects in the separation layer. If the damage caused by separation is reduced, there will be no overall loss of membrane performance. Severe loss of separation (e.g., 2% or more surface defects) will cause the separation performance of the membrane to surpass that of the gutter (intermediate crosslinked polysiloxane layer). The crosslinked polysiloxane layer has increased separation coefficient and increased inertness. Also, if the top I-(separation layer) is falsely bonded, it can be re-coated with no, and even within the module, the original performance of MoIg? You can return it.

In certain embodiments of the invention, particularly useful separation membranes include a supporting matrix of porous polysulfone (PSF) cast sheet;
A two-layer composite membrane prepared from an ultrathin layer of polysiloxane and an ultrathin layer of PPO with an amino-organic oxide function bridged in-situ by several layers of TDI deposited on top of it. Ta. The air was concentrated by passing through this g', producing 40-50% oxygen gold in the gas mixture.

The example of the arrow is presented for illustrative purposes, and w
This invention is not to be construed as limiting the invention, which is precisely delineated in the range of 'tFi water.

Example 1 Composite membrane? 1. A rectangular porous anisotropic polysulfone cast sheet (approximately 7
By uniformly spreading a hexane solution of polysiloxane containing amino-organic functional IIIl (the concentration and type of polysiloxane used were as shown in Table 1) on the − face of X14(m). Prepared. A small amount of solution (enough to give the desired film thickness) was injected into one end of the frame and then tilted at the frame to allow the bath liquid to flow evenly over the surface ml. After leaving on the surface for 15 minutes, excess bath liquid was drained and the film adhering to the polysulfone surface was allowed to dry for 2 minutes. After evaporating the bath medium, 2% f% toluene-2,4-diisocyanate (TD
A hexane solution (referred to as I) was spread on the surface in the same manner as the polysiloxane bath. The bath solution was left on the polysulfone surface for 15 minutes, and then the unreacted bath solution was poured off the surface. The TDI formed a cross-linked polysiloxane coating, which was allowed to tint for 5 minutes at temperature, then heated in a convection oven for 10-12 minutes.
A crosslinked polysiloxane-polysulfone composite film is formed by curing at a temperature of 90° to 95° for minutes. The thickness of each of these composite membranes was measured using a scanning electron microscope (SEM), and the ideal separation coefficient, actual separation coefficient, and permeability coefficient for nitrogen gas and acid gas were also measured for the valley composite membrane.

The two-shield bonding film is bonded to the cross-linked poly7coxane-borisulfone composite film. By applying a coating of J (2,6-dimethyl-1,4-phenylene oxide) (hereinafter referred to as PPO) 9, vI4g was obtained. P.P.

was coated on the surface of a chestnut-treated polysiloxane-polysulfone composite material that had been previously cut to accommodate fL superstructure, using a method slightly different from that used to apply polysulfone. This change in coating technique was necessary to evaluate the same membrane before and after PPO processing. PPO was deposited on the crosslinked polysiloxane surface of these composite membranes by fixing the membranes on the outside of cylinders having a diameter of about 10 (IIL). A small dish filled almost to the brim with solution was held on top of the dish so that the meniscus of the solution was above the rim of the dish.The cylinder was lowered slightly until the bath liquid and The membranes were brought into contact.

During drumming, the cylinder was rotated so that the entire surface of the membrane was in contact with the bath solution. The tears were removed from the bath solution, dried, and sintered to form a two-layer composite membrane.

The thickness of the PPO film was measured using a scanning electron microscope, and the ideal separation coefficient, actual separation coefficient, and permeability coefficient for nitrogen gas and oxygen gas were measured. The results were as shown in Table ①. Table 3 shows the predicted one-shot and the actual measurement for comparison.

Kunobe sheet of polysulfone is manufactured by N.O.B.
O,P, Inc., San Diego, Ca1i
A precast porous polysulfone membrane (air permeability = 95
- to 38 (-1itfn-↓) and to The polysiloxane having the amino-walled structure used herein had the following general formula.

CH2CHCH2NH(CH2) 2NH2CH3 The above formula A X has an average value of about 276, and y is about 24
average value? This is an aminosiloxane product from Phantom 8 Molti.

The ideal separation coefficient a of these composite membranes in oxygen/element content
It was calculated from the ratio of the permeability coefficients for the gases at 2 d of rts. The membrane was placed in a permeation cell and its permeation pressure against pure hydrogen or ri:ya was measured. For permeability testing, narrow gas is supplied to the cell through the inlet, the outlet is used for pressure adjustment, and the permeate is sent to a stone-foam meter. Flow velocity is measured by measuring the time t required for a flow meter to move a fixed volume within a flowmeter at a constant pressure. The flux is calculated by dividing the flow rate by the surface area of the membrane exposed to the gas. The flux, pressure difference, and membrane crush (measured by scanning electron microscopy) are used to calculate the permeability coefficient. However, for a single membrane, all other parameters being the same, it is only necessary to measure the fluxes of 24 gases at constant pressure.

Actual Separation Factor The actual separation factor of the composite membrane in oxygen/nitrogen separation was determined using essentially the same equipment. Actual separation coefficients were determined for membranes exposed to air under pressure and without vacuum on the product side of the membrane. In both methods, air was supplied to the cell by an outlet that was always VL open to maintain a low stage cut, and the t0 permeate was pumped through the sample loop of a gas chromatograph (F&M model 720). The impermeate was introduced into another gas chromatograph to determine the composition of the raw material and product from the area of the peak in the gas chromatogram. Its area is calculated by the height of the peak and its width at half its height, t. The composition of oxygen and nitrogen was given by the following relation.

AO2+AN2 A02 +AN2 The t0-missing equation in which Ao2 and AN2 are the areas of the oxygen and nitrogen peaks, respectively, was used to calculate the actual separation factor.

XO□ N2 X in the above formula. 2 and xN2 are the percentages of oxygen and nitrogen in the product, Yo2 and N2 are the percentages of oxygen and nitrogen in the raw material.
Measured at feed pressure of sig ~ 100 p8ig. Alternatively, the feed stream may be kept at a constant pressure (typically 20 psig).
) and reduced the pressure to 7 to 1 psig on the product side. For each soil reading, six samples were injected into a gas chromatograph for analysis.

The thickness of the coating as well as other properties of the film morphology were measured by a multi-layer microscope. After the composite membranes were evaluated by the method described above, samples were cut from each membrane. These samples were fractured with liquid nitrogen and then applied along the edges to sample stubs with neolube trifilm lubricant.

Two samples of approximately ix [], 5 CIIL were mounted on the valley stubs. Sample/Smarl (Hummer II)
The gold/palladium film was coated using two pulses of 1 mA for 90 seconds each. Sample ET
Eclipse was carried out under a 23 KV beam with an EC scanning microscope. The photos were taken with Polaroid Map 55 tenon/tenon film.

Comparison of the thickness of the layer in the photograph and the micron bar double printed on the photograph was used to calculate the thickness.

A composite membrane consisting of a single coating of crosslinked polysiloxane on top of follisulfone was prepared and evaluated as described in Section 5 above. The first test these membranes underwent was the determination of ideal separation factors from oxygen and nitrogen flux measurements. Fluxes were first measured at a feed pressure of 20 psig to give an indication of their potentials. Membranes exhibiting an ideal separation factor greater than or equal to the ideal separation factor of silicone rubber (approximately 2) were further tested.

A membrane free of defects should exhibit a countersunk thread between the flux and the pressure difference across the membrane. Linearity was observed for all films, demonstrating the absence of any substantial defects.

In order to coat a thin film of PPO on the surface of a crosslinked polysiloxane-polysulfone composite membrane, precipitation from an impregnated liquid was considered most desirable from the standpoint of application to hollow fiber membrane coating.

The actual separation coefficient of the PPO surface Imt-containing composite membrane is similar to that of the composite membrane coated only with striped polysiloxane.
It was more dog than that of fc=.

In order to eliminate the influence of the interlayer on the permeability of these membranes, a series of membranes were prepared by coating polysiloxanes with varying concentrations of aminoorganic functionality onto a polysulfone support; In this way, a composite membrane having a thickness comparable to that of crosslinked polysiloxane was obtained.

After crosslinking with polysiloxane '1 TDI, these composite membranes were tested for permeability over a range of 10-50 psi for pure oxygen and pure nitrogen. These same membranes were then immersed and coated in a 1% by weight solution of PPO as described above. Then apply the same test as a single coating to them.
fL was performed.

Although the relationship is far from perfect, it seems likely that the sieve 8 film will become thicker as the concentration of the coating liquid increases. It was observed that the permeability of a single coating membrane decreases over a wide range of directions.

Example 2 The effect of weighting polysiloxane/TDI with aminoorganic functionality on the permeability and selectivity of a polysulfone-polysiloxane composite membrane was determined.

6'4 composite membrane 7&: Prepared as described in Example 1, with the following differences. The surface of the polysulfone cast sheet was coated with a hexane bath of polysiloxane as described in Example 1 by allowing the polysiloxane to sit on the polysulfone for 20 seconds and then air dry for 2 minutes. After applying TDK's double 3t% hexane solution to the polysiloxane surface, TDK was brought into contact with the surface for 20 seconds to remove unreacted solution.
Air dried and then heated in a convection oven at 90'C for 10 minutes.

The polysiloxane concentration for each back and front is listed in Table 1. Oxygen and filtrate permeability and actual separation factors were measured as shown in 1st fi.

%I Table 2 1:1 22 8 2.754
2:1 94 38 2.478 4
: 1 181 73.2 2.47 Example 6 A crosslinked polysiloxane coated cast polysulfone sheet was prepared as described in Example 1.

Composite membrane C was coated with solution No. 001 containing 1% by weight of brominated ppo having the general formula:

In the above formula, the sum of m1n1p and r is approximately 80.0 molecule violet.
00 and 45% of the units contain -CH2Br. The coating procedure was the same as described in Example 2 and the membrane thus obtained had a separation coefficient α of
02/N2 = 8.2 f, which has a permeation flux for oxygen gas of 8x1Q10cIn'α5ec-1c,
Llt equivalent to m-”(crl! Hg)-1.

Claims (6)

[Claims] (1) A method for producing a composite material suitable for increasing the oxygen gas content in a composite material by passing an oxygen-nitrogen gas mixture through the composite material, the method comprising: (a) having a thickness of 20 to 25 μm; coating a polysiloxane with aminoorganic functionality on at least one surface of the highly porous polymer substrate, wherein the polysiloxane provides a cured film having a thickness of from 0.1 μm to 20 μm; applied to a sufficient thickness, and the polysiloxane consists essentially of aminosiloxane units having 1-9 mol% primary amino organofunctionality and 91-99 mol%
(b) the polysiloxane coated on the substrate is mixed with a solution of the diisocyanate and an organic solvent that is non-reactive with the isocyanate to form a cross-linked film; 2. A method of making a composite material as described above, consisting essentially of contacting the polysiloxane to diisocyanate for a sufficient period of time such that the weight ratio of polysiloxane to diisocyanate is inversely related to the permeability coefficient of the composite material. (2) A composite membrane obtained from the method according to claim 1. (3) by contacting the cross-linked membrane with a sufficient amount of poly(2,6-dimethyl-1,4-phenylene oxide) to produce an extremely thin layer effective as a gas-selective film; A method according to claim 1 for further processing a composite material. (4) A sufficient amount of brominated poly(2,6
-dimethyl-1,4-phenylene oxide) to produce a very thin layer useful as a gas-selective film. . (5) High degree obtained by crosslinking polysiloxanes with aminoorganic functionality containing 1 to 9 mol% of primary aminoorganic functionality and 91 to 99 mol% of other siloxane units. has a gas-permeable rubber gutter layer in close contact therewith20
a highly porous polymeric substrate of ~250 μm thickness;
A two-layer composite membrane suitable for gas separation, consisting essentially of a gas separator closely covering the gutter layer. (6) a polysiloxane with cross-linked aminoorganofunctionality containing two trimethylsiloxy units, 2-15,
000 dimethylsiloxane units and 2 to 160 general formulas ▲ There are mathematical formulas, chemical formulas, tables, etc. ▼ and ▲ There are mathematical formulas, chemical formulas, tables, etc. ▼ (In the above formula, R is ▲ Mathematical formulas, chemical formulas, tables, etc. Yes ▼ and -CH_2C
is a divalent group selected from H_2CH_2-), the polysiloxane is cross-linked with a diisocyanate, and the gutter is Claim 5, wherein the layer is between 0.1 and 20 μm thick, and the gas separator is poly(2,6-dimethyl-1,4-phenylene oxide) and is less than or equal to 2 μm thick. Composite membrane described in.