JPS5924843B2 - Method for producing gas selectively permeable composite membrane - Google Patents

Description

Detailed Description of the Invention The present invention provides a gas-selective permeability film in which a porous polymer film is coated with a thin siloxane compound, and more preferably an ultra-thin film having a crosslinked structure obtained by plasma polymerization is laminated thereon. The present invention relates to a method for manufacturing a composite membrane.

In recent years, active consideration has been given to separating and purifying fluid mixtures from energy-intensive processes that involve phase changes, such as distillation and deep cooling, to selectively permeable membranes that do not involve phase changes.

The present invention has also been made to efficiently accomplish these objectives. Seawater desalination is a membrane separation and purification process for fluid mixtures that has been industrialized on a large scale.

The main reason why gas membrane separation has not been put into practical use is that excellent membranes that allow only a large amount of specific components to pass through while leaving almost no other components permeable have not yet been developed. There are two problems: it requires a multiplex system using skates, which makes the device large, and it has low gas permeability, making it difficult to process large amounts of gas. This seems to be because gas permeability worsens when the selective permeability is increased, and this relationship could not be improved rapidly. . Therefore, the present invention uses a material with good strength and heat resistance, a material with good gas permeability, a material with good gas permeability, and a material with good gas permeability. The present invention has been completed as a result of various studies in an attempt to achieve the above object by assigning functions to each material and appropriately combining these materials.

That is, in terms of strength and heat resistance, a material that meets the purpose is selected from commercially available porous polymer materials. Porous polysulfone, polyimide polyvinylidene fluoride, etc. may be used, but cellulose ester, vinyl chloride, polypropylene, etc. are not so preferred. However, from the viewpoint of heat resistance and strength, a porous polymer membrane made of tetrafluoroethylene resin is most preferable, and it also satisfies chemical resistance. Regarding gas permeability, we examined various polymeric materials and found that so-called rubber-like materials showed the highest values, and among them, siloxane compounds, abbreviated as silicone rubber, are dimethylsiloxane, methylvinylsiloxane, methylphenylsiloxane, and others. Siloxane compounds, including modified compounds, have been confirmed to be particularly excellent, and have excellent properties not only in gas permeability but also in heat resistance and chemical resistance. When coating this porous polymer membrane with this siloxane compound, if a dilute solution of silicone rubber is applied directly, it will be absorbed into the porous spaces, resulting in a concentration distribution deep inside the porous spaces, and after drying, A considerable number of defects remain.

On the other hand, if a viscous solution of silicone rubber is applied, the capillary suction will be reduced, but only a thick film will be obtained. In response to this dilemma, the inventor of the present invention developed a method to reduce the amount of suction caused by capillary tubes and create a thin film with no pores using a dilute solution by conducting the composite of a porous polymer membrane and a siloxane compound in two or more processes. I succeeded in gaining layers. The siloxane compound is first impregnated into all the porous spaces of a porous polymer membrane with a liquid substance called silicone oil, and then treated in a plasma atmosphere of non-polymerizable gas of 10 tons or less for a certain period of time. Only the siloxane compound on the surface layer on one side of the membrane becomes crosslinked and solidified. On the other hand, since the siloxane compound deep within the porous space exists in a liquid state, it can be extracted and removed with a solvent immediately or even after coating and vulcanizing a high molecular weight siloxane compound. In terms of gas permeability, it is preferable to extract from above in order to reduce the thickness of the entire siloxane compound film. After the plasma-crosslinked siloxane compound is fixed to the porous support, a thin layer of a high molecular weight siloxane compound is further applied to the surface of the porous support. At the time of this application, the viscosity of the high molecular weight siloxane compound is set to 102 to 104, for example.
Even if the CP is lowered, it will no longer be attracted to the porous polymer membrane, and on the contrary, it will become more compatible with the plasma-crosslinked siloxane compound, making it possible to obtain a non-porous, uniform thin film. It is desirable to add an appropriate amount of a vulcanizing agent, such as a peroxide, to this solution, and after drying, vulcanization is performed, for example, by heating, to strengthen the mechanical strength. 1μ to 100μ by adjusting the coating thickness and solution concentration.
Although any siloxane thickness up to .mu. can be obtained, uniform coatings were obtained preferably when the thickness was set in the range of 5.mu. to 10.mu.. The gas permeability of siloxane compounds, typified by dimethylsiloxane, exhibits a specificity different from that of other organic polymers. For example, while common polymers allow helium gas to pass through them better than hydrogen gas, the opposite is true for siloxane compounds. Furthermore, siloxane compounds exhibit greater gas permeability for methane, ethane, ethylene, butane, acetylene, etc. than for hydrogen gas, which is the opposite tendency for general polymers. For this reason, hydrogen gas, methane, carbon monoxide, ethane,
For the purpose of preferentially concentrating hydrocarbon components from a mixed gas such as butane, the composite membrane consisting of a siloxane compound functions as a function. In addition, acidic gases such as COS and H2SCO2 also permeate preferentially. On the other hand, oxygen, nitrogen,
A siloxane compound composite membrane alone is insufficient for separating mixed gases such as methane and carbon monoxide, and the permselectivity of the gas must be improved. For this purpose, when a polymerizable gas is plasma discharged in an atmosphere of 10 t0rr or less, a plasma polymerized film is laminated as an extremely thin film on the siloxane compound. The polymerizable gases used here include not only ordinary olefinic monomers containing double bonds, but also compounds with non-polymerizable conjugated bonds such as benzene and naphthalene, and compounds that do not contain any double bonds such as propionitrile and ethane. Available. However, when considering various polymerizable gases, it was found that those selected from compounds containing a component of tertiary carbon C-CH-C or a component of tertiary type silicon C-Si-C are particularly preferred. I understand. Here, tertiary carbon refers to the central carbon of C-CH-C, and polymerizable gases include propylene, 4-methylbenzene-1, styrene, and styrene derivatives, isoprene, vinyl acetate, acrylic acid, methacrylic acid, and Examples include esters. On the other hand, tertiary silicon refers to the central silicon of C-Si-C, and includes compounds containing a trimethylsilyl group. Not only one type of polymerizable gas but also two or more types of polymerizable gases may be selected. Once selected, polymerizable gases of less than 2μ can be produced by changing factors such as high frequency output, plasma polymerization time, and electrode structure under a reduced pressure of 10t0rr or less. Thin film, more preferably 0.1
It can be laminated to a thickness of about μ. At this time, in addition to polymerizing with one type of polymerizable gas and then layering the surface with another polymerizable gas, there are also cases where the surface is polymerized and laminated with a mixed gas of two or more types, and these conditions are the same in this field. Relatively easy to optimize for those skilled in the art. The present invention will be explained below using examples. Example 1 Fluorobor FP-022 (average pore diameter 0.22μ, polytetrafluoroethylene resin porous membrane manufactured by Sumitomo Electric Industries) was immersed in a mixed solution of trichlene and silicone oil (KF-9610,000CS, manufactured by Shin-Etsu Chemical), and then treated with trichlene. When dried, silicone oil completely filled the porous spaces of Fluorobore.

After it was brought into close contact with a supporting glass plate, it was set in the center of a Persian type reactor that could be depressurized. The system was evacuated to 0.2t0rr while introducing argon gas, and the temperature was 13,56z.
100W was applied for 30 minutes. On the other hand, silicone rubber (LS
63u. (manufactured by Toray Silicone) and peroxide (Toray R
8% xylene was added to 1.5% by weight of C-2).
A homogeneous solution was obtained by adding 0% by weight and stirring for 8 hours using a stirrer.
Apply this solution to the surface of the plasma-treated Fluorobore for 1 hour.
After coating to a thickness of 0.00 μm, vulcanization was performed at 120° C. for 10 minutes.
Finally, the uncrosslinked silicone oil of this membrane was extracted with Freon to obtain a laminated membrane.

The gas permeation rate of this stack is ~/Cd・Sec・? When expressed in H7 units, 02 is 1.10×10-3. N2 is 5
．． 85×10-4H2 becomes 1.25×10-3. C0 is 5
．． 20×10-4 CH4 is 1.72×10-3. C02
is 6.8X10-3. C2H6 is 4×10-3. C0S
showed 1.6X10-2. Example 2 A laminated film produced in the same manner as in Example 1 was set in the center of a Persian plasma reactor.

Claims (1)

[Claims] 1. A liquid siloxane compound is filled into the porous space of a porous polymer membrane, the siloxane compound in the surface layer is crosslinked by non-polymerizable gas plasma, and then a high molecular weight siloxane compound is applied and processed. A method for producing a gas selectively permeable composite membrane characterized by sulfurization. 2. The method for producing a gas selectively permeable composite membrane according to claim 1, wherein the liquid and high molecular weight siloxane compound is polydimethylsiloxane or a modified derivative thereof. 3 Fill the porous spaces of the porous polymer membrane with a liquid siloxane compound, crosslink the siloxane compound in the surface layer with non-polymerizable gas plasma, then apply and vulcanize a high molecular weight siloxane compound, and then apply a polymerizable siloxane compound. A method for producing a gas selectively permeable composite membrane characterized by plasma polymerization using gas plasma. 4. The method for producing a gas selectively permeable composite membrane according to claim 3, wherein the liquid and high molecular weight siloxane compound is polydimethylsiloxane or a modified derivative thereof. 5 Tertiary carbon as a polymerizable gas ▲ There are mathematical formulas, chemical formulas, tables, etc. ▼ or tertiary organosilicon ▲ Numerical formulas, chemical formulas,
The method for producing a gas selectively permeable composite membrane according to claim 3, characterized in that the compound is selected from compounds containing the constituent elements shown in the table, etc. 6 Fill the porous spaces of the porous polymer membrane with a liquid siloxane compound, crosslink the siloxane compound in the surface layer with non-polymerizable gas plasma, then apply and vulcanize a high molecular weight siloxane compound, and further apply as necessary. A method for producing a gas selectively permeable composite membrane, which comprises plasma polymerizing a polymerizable gas and then removing uncrosslinked liquid siloxane components by extraction. 7. The method for producing a gas selectively permeable composite membrane according to claim 6, wherein the liquid and high molecular weight siloxane compound is polydimethylsiloxane or a modified derivative thereof.