JPS588517A - Preparation of composite film with selective permeability for gas - Google Patents

Abstract

PURPOSE:To obtain a composite film generating no cracks even if it is formed into an extremely thin film and excellent in gas separation capacity, by subjecting a thin film of a siloxane compound coated on a porous molecular film to plasma treatment by introducing a specific polymerizable gas. CONSTITUTION:On a porous support comprising an ethylene tetrafluoride resin excellent in heat resistance and strength, silicon rubber dissolved in an org. solvent is thinly coated and vulcanized and cured. After film formation, a plasma polymerized thin film is laminated on the surface thereof to enhance gas separation property and selectivity. Plasma treatment is carried out by using teitiary carbon or tertiary silicon as a polymerizable gas. By this method, the film thickness of the plasma polymerized thin film can be manipulated by changing a glow discharge time in the atmosphere of 2 Torr or less and the obtained composite film has excellent characteristics in selective permeability for a mixed gas.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing a crosslinked gas selectively permeable composite membrane obtained by plasma polymerization. In recent years, methods for separating mixed substances have replaced conventional methods such as distillation, crystallization, extraction, adsorption, and chromatography.
Methods using permselective membranes are being actively studied.

The permselective membrane is in high demand for development as a separation technology aimed at energy and resource saving.The present invention was also made to provide a gas selective permselective composite membrane in order to efficiently achieve the above objectives. .

Membrane separation technologies include reverse osmosis, ultrafiltration, ion exchange membranes, and relatively new technologies such as organic liquid selective membranes, ion selective membranes, and gas separation membranes. has hardly been put into practical use. The reason why gas separation membranes are lagging behind in industry is that there are few materials that have high gas separation selectivity and permeability, so it is not possible to obtain high concentrations with one-stage concentration, and a multi-stage method is required. This is because it becomes too large and is no longer suitable for practical use. Against this background, the inventor of the present invention sought to develop a material that satisfies all physical properties such as gas separation selectivity, permeability, and strength. The present invention was completed by attempting to combine the materials used to support the structure and the materials supporting them using different manufacturing methods.

That is, in terms of heat resistance and strength, a material that meets the purpose is selected from commercially available porous polymer materials. Porous polysulfone, polyimide, etc. may be used, but cellulose ester, vinyl chloride, polypropylene, polycarbonate, polyvinyl alcohol, etc. are not so preferred. However, from the point of view of heat resistance and strength, a porous support made of tetrafluoroethylene resin is most preferable, and also has the advantage of satisfying chemical resistance at the same time.

On the other hand, siloxane compounds are known to have excellent gas permeability. Even when a siloxane compound is used, in order to put it into practical use, it must be several tens of microns or less, and high-molecular weight compounds with excellent strength that can withstand the pressure during gas permeation are laminated uniformly and thinly. There is a need.

Among siloxane compounds, the present inventor mixed a high molecular weight material such as silicone rubber with an organic solvent such as trichlene, xylene, benzene, toluene, etc. that dissolves it, applied the mixture thinly to a t1 support, and vulcanized it. It has been found that a laminated film with excellent gas permeability can be produced by curing. Note that since the organic solvent dilutes the siloxane compound and evaporates before vulcanization and curing, the film thickness of the siloxane compound after vulcanization and curing can be adjusted by adjusting the dilution concentration. In particular, the dilution concentration of the siloxane compound is 50%.
When the weight ratio was lowered, a very thin and uniform film was obtained.

After vulcanizing and curing the siloxane compound, a plasma polymerized thin film is laminated on its surface to improve gas separation selectivity. Materials with excellent gas separation selectivity have poor permeability, so it is necessary to make the membrane thickness as thin as possible. The thickness of the plasma-polymerized film can be controlled by changing the discharge time during glow discharge in an atmosphere of 2 Torr and r or less, and can be made to have a thickness of 0.1 μm or less, for example. The film thickness also increases or decreases depending on the flow rate of the polymerizable gas or the increase or decrease in the discharge output during glow discharge, but these conditions can be optimized relatively easily by those who are familiar with the technology in this field.

Further, by increasing/decreasing the gas flow rate and discharge output, the formation of a thin film, the formation of powder clover, and changes in crosslinking density can be easily adjusted.

As the polymerizable gas, it is necessary to select one that does not cause cracks even when made into an extremely thin film and provides a membrane with excellent gas separation selectivity. The present inventors discovered that a plasma-electrolyzed film of tertiary carbon or tertiary type organosilicon satisfies this required performance, and was able to complete the present invention.

As detailed above, the composite membrane manufactured under very limited conditions has extremely excellent permselective properties for mixed gases, and has been used as an energy-saving gas separation method. It greatly contributes to industry.

The present invention will be explained below by way of examples.

Example 1 A room-temperature vulcanizable silicone rubber (KE8475T, Shin-Etsu Chemical Co., Ltd.) diluted with toluene using a doctor knife was applied to the surface of Fluorobore FP-022 (average pore diameter 0.22μ, polytetrafluoroethylene resin porous membrane manufactured by Sumitomo Electric). After applying part), apply 2
Vulcanization was performed at room temperature for 4 hours to obtain a laminated thin film.

Table 1 shows the knife setting thickness, rubber concentration, film thickness, oxygen permeation rate POg%, selective permeability coefficient of oxygen to nitrogen POi
/ PN * shows the relationship.

6- A laminated film was manufactured under the same conditions as in Example 1 except that the silicone rubber was changed to another room temperature vulcanization type (KE4457゜Shin-Etsu Chemical grade). Table 2 shows the results.

Table 2 Example 8 Various heat-vulcanized silicone rubbers as shown in Table 3 were mixed with toluene and peroxide (Toray RC-2,
)-Le Silicone) were mixed and stirred for 8 hours to dissolve. This solution was applied to the surface of Fluorobor FP-022 using a doctor knife and vulcanized at 120°C for 30 minutes to obtain a rubber laminated thin film.Table 3 shows its properties.

Table 3 *l Manufactured by Toray Silicone *2 Oxygen permeation rate, unit: x"7m"・Sec -c
s+Hg9 - Example 4 A laminated thin film of silicone rubber produced by the method of Experiment 7 of Example 2 was placed in the center of a plasma reactor, and the system was heated with OJ.
After evacuating to a temperature of 100 m, vinyltrimethylsilane vapor was introduced at a flow rate of 5 tne/wm, and plasma polymerization was carried out at a high frequency of 18.56 MH2 and an output of 10 W for 25 minutes. The gas permeation rate of the obtained composite membrane was 8.77 x 10 cm"7 cm" Sec -c for oxygen gas.
rnHg Monrystalline gas, is 2.76X10m7α2・Se
c・α珈, and the gas selective permeability was 3.18.

Example 5 The gas permeation rate of the composite membrane was measured under the same conditions as in Example 4, except that the polymerization gas fed into the plasma reactor was changed from vinyltrimethylsilane to styrene and the flow rate was changed to 10 me/-. As a result, the oxygen gas was '5.5
9 X 10 cm8/cm” ・Sec ・onHg
, nitrogen gas is 1.40X10 an"/crn" ・S
ec ·cmHg, and the gas selective permeability was 8.99.

10- Procedural amendment (method) December 7, 1980 Haruki Shimada, Commissioner of the Japan Patent Office 1. Case description 2. Name of invention and device method for manufacturing a gas selectively permeable composite membrane 3. Person making the amendment Related Patent applicant address 5-15 Kitahama, Higashi-ku, Osaka Name (2
13) Sumitomo Electric Industries Co., Ltd. Representative 1 President Masao Kamei Birthplace Agent Address Sumitomo Electric Industries Co., Ltd. 1-1-8 Shimaya, Konohana-ku, Osaka November 24, 1986 6, Specification subject to amendment 7゜We will submit a clearly written specification with the contents of the amendment as attached.

Claims (4)

[Claims] (1) A step of applying a siloxane compound to a porous polymer membrane, a step of vulcanizing and curing it, and a step of laminating a plasma polymerized thin film by introducing a polymerizable gas under glow discharge in an atmosphere of 2 torr or less. A method for producing a gas selectively permeable composite membrane, characterized in that: (2) A mixed solution of a siloxane compound and an organic solvent for dissolving it, which is applied to a porous polymer membrane in a diluted state of 50% by weight or less. Manufacturing method of section. (3) The polymerizable gas is selected from compounds containing tertiary carbon or tertiary organosilicon compounds, and
The manufacturing method according to claim 1, characterized in that the plasma polymerized thin film is laminated by introducing the atmosphere into the following atmosphere. (4) The porous polymer membrane is made of heat-resistant and chemical-resistant tetrafluoroethylene resin and has a porous structure consisting of fibers and nodules, and is characterized by a step of applying a siloxane compound to this porous structure. The manufacturing method set forth in claim 1.