JPH04305238A - Production of gas permeable composite film - Google Patents

Abstract

PURPOSE:To produce the film having gas permeability and gas separability highly resistant to a change with lapse of time by subjecting the surface of a thin film consisting of poly-substd. acetylene having a specific constitutional formula to an oxygen plasma treatment. CONSTITUTION:The surface of the thin film 5 consisting of the poly-substd. acetylene expressed by the formula (R is 1 to 4C alkyl group) is subjected to the oxygen plasma treatment, by which the gas permeable composite film is produced. After the polymer film 5 is mounted on a holder 4, the pressure in a chamber is once reduced to a vacuum and in succession, a treating gas is introduced therein and is regulated to an arbitrary specified pressure. Plasma is thereafter generated by electrodes 3 and the surface of the polymer film 5 is subjected to the oxygen plasma treatment. The degrees of the oxidation and crosslinking of the surface are controlled by the plasma treatment time. The gas permeable film having the gas permeability stable over a long period of time is thus obtd.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing gas permeable membranes.

0002

2. Description of the Related Art In the separation and purification of gases, methods using gas-permeable polymer membranes are attracting attention for reasons such as energy saving. Oxygen-enriched air separated from air and produced using this type of polymer membrane is expected to save energy by improving combustion efficiency, reduce harmful substances emitted due to its complete combustibility, and be used for raising animals and plants. There is.

[0003] From the viewpoint of such uses, the performances that this type of polymer membrane should have are: (1) high gas permeability; (2) high gas permeability;
One example is that it has a high gas separation property (ratio of permeability between the gas to be separated and the gas that does not require separation). Especially when considering the intended use, high gas permeability is strongly desired. A polysubstituted acetylene represented by the structural formula shown by Chemical Formula 2 is cited as a material that most satisfies such performance.

0004

[Case 2]

[0005] This material is soluble in a specific organic solvent, and can be easily formed into a thin film from a solution by a casting method. The membrane produced in this manner has much better gas permeability than ordinary polymer films (eg, polydimethylsiloxane), and its gas permeability coefficient is more than an order of magnitude higher.

However, the gas permeability of this polymer film decreases over time, and after a long period of time, the gas permeability decreases to the same level or lower than that of a normal polymer film. Put it away.

[0007]

[Problems to be Solved by the Invention] The present invention aims to produce a gas permeable membrane using a polymer membrane made of polysubstituted acetylene that exhibits excellent gas permeability and gas separation performance over time. purpose.

[0008]

[Means for Solving the Problems] The present invention is characterized in that the surface of a thin film made of polysubstituted acetylene is subjected to oxygen plasma treatment.

[0009]

[Operation] Polysubstituted acetylene is a product obtained by polymerizing disubstituted acetylene whose structural formula is represented by the following chemical formula 3.

0010

[Chemical formula 3]

[0011] The polymer is TaC15, NbC15, Ta
Group V transition metal catalysts such as Br5 and NbBr5 and solvents such as aromatic hydrocarbons (benzene, toluene, xylene, etc.), alicyclic hydrocarbons (cyclohexane, etc.), halogenated hydrocarbons (carbon tetrachloride, trichloroethylene, etc.) is obtained by heating at 30 to 100°C in an inert gas.

The obtained polymer can be made into a thin film by a conventional method. i.e. aromatic hydrocarbons (benzene,
It can be made into a thin film by dissolving it in a solvent such as toluene, xylene, etc.), alicyclic hydrocarbons (cyclohexane, etc.), or halogenated hydrocarbons (carbon tetrachloride, trichloroethylene, etc.) and casting this solution.

The substrate for casting at this time may be a glass plate with a smooth surface, a metal plate, a polymer plate insoluble in solvents (Teflon, etc.), or a liquid plane (water, an appropriate aqueous solution, a substrate in which the solvent and polymer are insoluble). (organic liquids, etc.) are used. This type of polymer film is obtained by spreading the solution on the substrate, evaporating it, and then peeling off the formed film.

In this case, the film thickness can be adjusted by the type of base used, the concentration of the solution, or the number of layers (overcoating). In addition, ready-made porous films can also be used as supports for mechanical strength reinforcement.

The surface of the polymer film thus formed is subjected to plasma treatment using a plasma treatment apparatus. As the plasma processing apparatus, for example, one shown in FIG. 1 can be used. In FIG. 1, 1 is a vacuum chamber, 2 is a gas inlet through which gas is introduced at a constant flow rate,
3 is an electrode for plasma generation, 4 is a holder, and 5 is a vacuum exhaust port. A polymer film 5 is attached to and supported on the surface of the holder 4.

As described above, the polymer film is placed in the holder 4.
After attaching it to the
-5 torr), then process gas (oxygen,
(air, carbon dioxide, etc.) is introduced and adjusted to an arbitrary constant pressure. Thereafter, plasma is generated by the electrode 3, and the surface of the polymer film 5 is treated with oxygen plasma.

[0017] The degree of surface oxidation and crosslinking can be controlled by the plasma treatment time. However, if it lasts too long, the polymer film may be destroyed, which is not very preferable. Therefore, within 5 minutes is appropriate.

In the manner described above, a polysubstituted acetylene oxygen plasma treated film is formed.

[0019]

[Example] Example 1 1-(trimethylsilyl)-1
-Propyne (Aldrich) 1g, TaC15 0.
A viscous polymer gel was obtained by reacting at 80° C. for 24 hours in a nitrogen atmosphere using 06 g of toluene and 10 cc of toluene. This polymer gel was diluted with toluene and then dropped into a large amount of methanol to precipitate the polymer. The obtained polymer was filtered and dried, and then redissolved in 100 cc of toluene to obtain a polymer solution. The obtained solution was spread on a Teflon plate, and after evaporating the solvent at room temperature, it was peeled off from the Teflon plate to obtain a 20 μm thick polymer film.

The obtained polymer film was placed in a plasma processing apparatus shown in FIG. 1, and after the pressure was reduced to 1×10 −6 torr, oxygen was introduced and the pressure was adjusted to 0.1 torr. Subsequently, a high frequency of 13.56 MHz and 30 W was introduced between the electrodes for plasma generation to generate plasma. After generating plasma for 1 minute, the polymer film was taken out.

Example 2 A polymer membrane prepared in the same manner as in Example 1 was spread on the water surface, and after evaporating the solvent at room temperature, it was scooped up with a porous support (Duraguard #2400, Polyplastics) to form a composite membrane. And so. The above operation was repeated to obtain a polymer film having a surface thickness of 0.2 μm. Subsequently, the surface polymer film was subjected to oxygen plasma treatment under the same conditions as in Example 1.

Comparative Example A 20 μm thick polymer film prepared in the same manner as in Example 1 was used as it was without any further treatment.

[0023] Regarding the membranes of each of the above examples, the permeation amount of oxygen and nitrogen was measured using a gas permeability measuring device using a vacuum method at 35°C. Initial values of oxygen permeability coefficient (Po2), oxygen/nitrogen permeability coefficient ratio (separation performance α) of each example, and 100
The values after the passage of days are shown in Table 1 below, and the characteristics over time are shown in Figure 2.
Shown below.

[0024] The unit of oxygen permeability coefficient (Po2) is c
m3(STP)・cm/cm2・sec・cmHg.

[0025]

[Table 1]

As is clear from the results shown in Table 1 and FIG. 2, the gas permeation performance (initial performance) of the polymer composite membranes according to Examples 1 and 2 was lower than that of the polysubstituted acetylene membrane according to the comparative example. However, since it continues to maintain stable characteristics over a long period of time, it has been found that it exhibits better characteristics over time than those obtained by conventional methods.

[0027]

Effects of the Invention As detailed above, according to the present invention, in obtaining a gas permeable membrane using polysubstituted acetylene as a material, this type of gas permeable membrane exhibits a more stable gas permeation performance over a long period of time than that obtained by conventional methods. This has the effect of making it possible to produce a sexual membrane.

[Brief explanation of drawings]

FIG. 1 is a sectional view of an oxygen plasma processing apparatus used in an embodiment method of the present invention.

FIG. 2 is a characteristic diagram showing the change in oxygen permeability coefficient with respect to the number of days elapsed for the membrane obtained according to the present invention.

[Explanation of symbols]

1 Vacuum chamber 2 Gas inlet 3. Electrode for plasma generation 4 Board holder 5 Substrate (polymer film)

Claims (1)

[Claims] [Claim 1] The surface of a thin film made of polysubstituted acetylene whose structural formula is represented by [Claim 1]
A method for producing a gas permeable membrane, characterized in that it is produced by oxygen plasma treatment.