JPS5973006A - Multi-component 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 multicomponent hollow fiber membranes for gas separation.

Prior Art US Pat. No. 4,250,463 discloses poly(siloxane) coated hollow fiber membranes used to separate gases such as hydrogen from other gases. One problem that has been found to exist with this type of multi-component film is that the process gas is ) If it includes contaminated beggars, fi
The effect of JL is destroyed or substantially reduced. Examples of contaminants harmful to this type of multicomponent gas separation membrane are aliphatic hydrocarbons such as hexane, aromatics such as benzene and toluene, methanol,
Ammonia and hydrogen sulfide. The presence of even small amounts of these contaminants in the feed gas stream has a significant detrimental effect on this type of membrane.

When exposed to contaminants, the permeability of the coated membrane for a given gas changes considerably, whereby the membrane loses its effectiveness in separating a single gas from a mixture.

Most of the contaminants present in the various i#i feed gas streams are lost in time. Unfortunately, however, this adds at least one additional step to the gas treatment process, thereby adding significantly to the cost and complexity of the gas treatment process.

U.S. Pat. No. 4,230,463 also teaches that the dimethylsiloxane coating used in the coated fiber membranes disclosed therein can be crosslinked by using a crosslinking agent such as alpha methylstyrene. Disclosed. However, there is no indication as to the desirability of using such a cross-linked coating layer, and this cross-linked coating layer is similar to the cross-linked coating layer of the present invention as described below. does not have the advantages of

U.S. Pat. No. 2,845,555 discloses the curing of ethyl silicates by using metal salts as catalysts. Hardening compound molding is used for manufacturing dental impressions (moulds).
It is said to be useful as a sealant in road joints, as an insulating material (encapsulation) in electrical appliances, as a gasket filler and shock absorber, and other applications for which known natural or synthetic rubbers are not suitable.

U.S. Pat. No. 3,035,016 discloses coking compounds wJ made by reacting acyloxysilanes with hydroxylated siloxanes.

These compositions surface harden within 60 minutes but are said to remain soft for many years and adhere closely to glass, porcelain and other materials.

U.S. Pat. No. 5,133,891 discloses that zoorganoborisiloxanes and organotriazyloxysilanes are reacted to form self-curing compositions that can be used in caulking, glass coatings, etc. is disclosed.

U.S. Pat. No. 3,127,363 discloses that curing is achieved by reacting precondensed difunctional silicones with a crosslinking agent having reactive groups such as hydroxyl, alkoxy, allyloxy or amino groups. Discloses a method for producing a silicone distomer.

These elastomers are said to be useful as molding compositions, as dental filling materials, as sealing and coating compositions, and also in laminate coatings.

SUMMARY OF THE INVENTION Multicomponent membranes for gas separation according to the invention are obtained by coating with an anisotropic polymer matrix in the form of porous hollow fiber sections.

The multicomponent membranes of the present invention are useful for separating one gas from a gas mixture. For example, this film changes from nitrogen to oxygen,
and - useful for separating hydrogen from at least one of carbon oxides, carbon dioxide, nitrogen, oxygen, argon, nitrous oxide, and O1-C5 hydrocarbons, especially methane, ethane and ethylene. ``Various mixtures of these and other gases are often found in various commercial processes. The separation of one gas from the mixture is effected by the fact that this membrane permeates one gas in the mixture to a much greater extent than the other gases. When carrying out a separation operation, the gas mixture is contacted on one side of the membrane with an appropriate pressure difference (pressure gradient) across the -J- permeable or "faster"
The gas permeates the membrane and is collected from the other side of the heart. When the membrane is in the form of hollow fibers, one side is the external surface of the fibers and the other side is the interior or lumen surface of the fibers.

For a given membrane with a given cross-sectional area, the recovery rate of the "faster" gas and the purity of the recovered gas are determined by the pressure difference maintained across the membrane and the "faster" gas relative to the other gases in the mixture. Determined by the permeability ratio. The more permeable the "faster" gas in the mixture is to other gases, the more effective the separation operation will be.

Unfortunately, known multicomponent membranes lose virtually all of their ability to separate one gas from a gas mixture when the gas mixture contains contaminants.・The effectiveness of the membrane disclosed in U.S. Pat. Even sites containing very small amounts of contamination 121, such as hydrogen chloride, etc., are substantially reduced. In the past, problems caused by these contaminants have been accompanied by increased complexity and the need to contact the gas mixture with the membrane. Also, if the contaminant removal step fails for any reason, the membrane becomes damaged by the contaminants and must be replaced.

These problems are avoided by the use of the multi-component complex of the present invention. The membrane is substantially undamaged by contact with the contaminants mentioned above.

The multicomponent membrane of the present invention comprises a polymer substrate membrane and a membrane in contact with the substrate. Preferably, the matrix membrane is in the form of hollow fibers. Preferred polymeric substrates are of the type described in US Pat. No. 4,230,463, and are preferably formed from polysulfone polymers.

This membrane has an outer diameter of about 200 to 1. o o o microns, preferably in the form of hollow fibers having a wall thickness of about 50 to 600 microns. Polysulfone matrix membranes are porous, with average pore cross-sectional diameters in the range of 5 to 20,000 microns. The pore size is larger inside the pore and smaller near the surface of the gland so that the membrane is anisotropic. The porosity of the substrate membrane is determined by the pore volume of this membrane.
It is sufficient that the amount is in the range of 10 to 90%, preferably about 60 to 70%, based on the total volume (alvoium), ie, the volume contained within the total size of the porous separation membrane.

The coating layer in contact with the porous substrate membrane is a condensation product of silanol-terminated poly(dimethylsiloxane) and a crosslinking compound as defined herein.

Dimethylsiloxane has at least two hydroxyl end groups before crosslinking. Dimethylsiloxane diol has a molecular weight ranging from 92 to 150,000 per unit. The thickness of the coating layer is a, o o a A~5
It is in the range of 0 microns.

! Yes: A□lJ j It is possible to obtain sulfur by using ethyl silicate alone or a mixture of ethyl silicate and gamma-aminopropyltrietoxin or aminopropyltrimethoxysilane as a crosslinking compound. Understood.

As used herein, the term "1-ethyl silicate" refers to tetraethyl orthosilicate, (C2H50)S1. Ethyl silicate can be used in monomeric or oligomeric or prepolymeric form. The prepolymer may be formed by condensing the heptamers in known manner. A typical structure of such a prepolymer or oligomer is ○C2H5 C2H3O-Si -0C2H5 QC2H50C2H50\ OC'2H51111 C2H50-8i OS10 Si O810C
2H511l 1 0C2H50C2H50C2H50C2H5.

Ethyl silicate can be used in either monomeric or oligomeric form, so it can be as low as 1 (15 silicon atoms). Although ethyl silicate oligomers with up to 400 or 500 silicon atoms can be used, oligomeric or Preferably, the solole polymer has from 1 to about 100 silicon atoms Z. The large number of reactive sites in the oligomer greatly increases the ability of the material to 4-bridge dimethylsiloxane diol.

One benefit of using the crosslinking agents of the present invention is that the merging reaction used to crosslink dimethylsiloxane is not inhibited by the presence of such materials. U.S. Patent No. 4,2
The curing of dimethylsiloxane of No. 30,463 (without the cross-linking agents of the present invention) is effective against hostile VD materials such as sulfur or sulfur-containing compounds, amines and other nitrogen-containing compounds, organic acids, etc. and the presence of negligible amounts of such materials as silicone rubber catalysts. For example, the peroxide catalyzed sigma reaction by-product in many heat-vulcanized silicone rubber feedstocks is an organic carbon.

This same blocking effect occurs when dimethylsiloxane is crosslinked with an n-type bridge@MU, such as the alpha methylstyrene crosslinker disclosed in U.S. Pat. No. 4,230,463. If the dimethylsiloxane does not cure, it will cause defects in the coating layer of the solid fiber section.

Another advantage of using the crosslinking agent of the present invention is that the coating layer can be cured at elevated temperatures and environmental conditions. If a vinyl-type crosslinking agent such as alpha methylstyrene is used, the catalyst required to effect the crosslinking typically requires a curing temperature of 100°C or higher.

For example, one catalyst useful for crosslinking vinyl-type reagents is 2-4-dichlorobenzoyl peroxide,
Usually requires a temperature of 140-160°C for curing. Exposure to such temperatures can seriously damage or destroy the polymer matrix used in the present invention. The matrix becomes a-distilled and loses its porosity above about 120°C, so that the permeability of the matrix is substantially reduced. Substrate damage occurs even more at higher temperatures.

It is important to use a suitable crosslinking agent.

Various types of crosslinking compounds are known. However, most of these are not suitable for the purpose intended in the present invention. The crosslinking compound to be interpreted must be such that it meets the following requirements.

The soil bridge cover must be substantially resistant to attack by contaminants.

2. The imaginary covering layer must not be dead.

6. The crosslinking of the laminated material must not adversely affect the transmission properties of the covering layer or the substrate membrane or their combination.

4. The coating layer must fill the pores on the surface of the substrate membrane.

5. The crosslinked coating should not remain sticky after curing. 06. The crosslinked coating should not penetrate too deeply into the pores of the substrate membrane.

7. The coating must be capable of curing at temperatures below those that would damage the polymer matrix.

8. The curing of the coating layer must not be inhibited by known inhibitors that may be present at the reaction site. 09. The crosslinking compound must not cause any damage to the fibers and must not be inhibited by the crosslinking agent, which is a carrier for the diol. The formulation of the filter coating applied to the membrane described herein and cured is 100 parts of dimethylsiloxane diol, 1 to 100 parts, preferably 2 to 50 parts, and most preferably 8 to 50 parts. 12
1 part of the crosslinking compound specified herein and 0.1 to 2 parts of a catalyst such as dibutyltin dilaurate. Other catalysts that may be used are tin octoate and dibutyltin diacetate.

In carrying out the coating operation, the hollow, single fibrous membrane bundle is placed in a closed container and the closed container is filled with the coating mixture.

After the coating mixture is in contact with the fibers for a sufficient period of time to wet and coat the frozen fibers, the fiber bundles are recovered and the coating layer is allowed to self-cure under ambient conditions to complete the crosslinking of the dimethylsiloxane diol. .

Examples 1 to 7 A polysulfone substrate in the form of hollow fibers, 100 parts of poly(dimethylsiloxane) diol, 1 part of ethyl silica and 1 part of ethyl silica as a catalyst, 100 parts of poly(dimethylsiloxane) diol, It was covered with a silicone thread mixture obtained from butyltin dilaure-1 or dibutyltin diacetate. Note that pentane is added to the silicone thread mixture to make it a 1% bath.

Coating at temperature of cough; for hydrogen after self-absorption of
The membrane permeability and membrane separation factor (ratio of permeability to hydrogen return element) were measured by a method of passing through the membrane. The fibers are then mixed with a mixture of 7% toluene and 96% n-hexane, both of which are known to provide a critical top layer to the coating layer as described in U.S. Pat. No. 4,230,465. (normally found contaminants) and left for 16 hours. Permeability and separation factors were measured again. The results are shown in Table 1.

27 - The separation factors of the fibers of Examples 2-7 remain substantially unchanged after soaking in the toluene/hexane mixture, whereas the control of Example 1 coated with the coating of U.S. Pat. No. 4,230,463 It was found from Table 3 that the membrane had a substantial decrease in separation factor after immersion in the toluene/hexane mixture.

Examples 8 to 11 Folysulfone matrix membranes in the form of hollow fibers were obtained from 100 parts of poly(dimethylsiloxane) diol, various parts of ethyl silicate and aminopropyltriethoxysilane as described in Light 1 and dibutyltin dilaurate as catalyst. It was coated with a silicone-based mixture. Note that pentane was added to the silicone mixture to make it a 1% solution. The substrate was dipped into the coating formulation and then allowed to self-cure at ambient conditions. After curing of the coating layer, the hydrogen permeability and the separation factor (ratio of permeability of hydrogen to carbon monoxide) were determined in the customary manner.

Next, the specimen was immersed in a mixture of 7-fiber toluene and 96% n-hexane and left for 16 hours. Transparency, M,, Jl
- and separation factors were measured again after immersion in a toluene/hexane mixture. Result +′! , Cloth n.

DMS-Dimethylsiloxane DMSD-Dimethylsiloxanediol DBTDL-Dibutyltin dilaurate Agent Akira Asamura

Claims (1)

[Scope of Claims] (1) (~ a porous separation membrane manufactured from a polymer material;
and Cb) a coating layer consisting of a condensation product of 100 parts of silanol-terminated poly(dimethylsiloxane) and 1 to 10 parts of ethyl silicate and in contact with the porous separation membrane. Polyacid 1 minute membrane for gas separation. (2) The multicomponent membrane according to claim 1, wherein the separation membrane is of a hollow fiber type made from polysulfone, and the ethyl silicate is an oligomer having 1 to 500 silicon atoms. (3) Poly(dimethylsiloxane) from 9o to about 25
．． A multicomponent membrane according to claim 2 having a molecular weight of 0.000. (4) Target [, l- is 5 + 000 A ~ 50 Mini 9
o) Thickness:・Stagnation→The multicomponent film according to claim 6. 15J Ethyl silicate filter is present in an amount of 2 to 50 parts.Claim 4: 1 Self-loading multi-component membrane. (6) The multicomponent film according to claim 5, wherein the ethyl silicate it is 8 to 12 parts. The multi-component membrane according to claim 4, wherein the coating is a coagulated mixture of 100 parts of dimethylsiloxane diol, 1 to 50 parts of ethyl silicate, and 1 to 25 parts of aminopropyltrialkyloxysilane. (8) The multicomponent film according to claim 7, wherein the aminopropyltrialkyloxysilane is aminopropyltriethoxysilane. (9) The patent, wherein the aminopropyltrialkyloxysilane is aminopropyltrimethoxysilane. A multicomponent film according to claim 7.