JPH04310224A - Production of gas diffusible membrane - Google Patents

Abstract

PURPOSE:To form a gas diffusible membrane which is prevented from the lowering of its performance with the passage of time by irradiating with radiation a thin membrane formed by mixing together a polysubstituted acetylene represented by a specific structural formula and reactive monomers to cross-link the polymer in the mixture. CONSTITUTION:The polysubstituted acetylene represented by the formula (wherein R is 1-4C alkyl) and reactive monomer or its oligomer are mixed together in suitable amounts. The resulting mixture is dissolved in a solvent such as aromatic hydrocarbon, alicyclic hydrocarbon and halogenated hydrocarbon, the solution is spread over a base such as glass plate or a flat surface of liquid and vaporized, and then the formed film is separated therefrom to obtain a thin membrane. This polymerized thin membrane is thereafter irradiated with radiation to cross-link the polymer therein, thereby producing a gas diffusibility membrane. As the example of the radiation for use in the aforesaid irradiation, electron beam and gamma rays are afforded. The gas diffusible membrane thus obtained retains a stable gas diffusibility over an extended period of time.

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.

In order to improve this problem, the present inventor separately proposed a method of irradiating a thin film made of polysubstituted acetylene with radiation (Japanese Patent Application No. 2-223391). By irradiating with radiation in this manner, deterioration in the performance of this type of polymer film over time is considerably suppressed.

However, in the case of this radiation reaction, since the crosslinking reaction and the decomposition reaction occur in competition with each other, the width of the irradiation dose range for obtaining the desired effect is narrow, making control extremely difficult. At doses lower than the effective dose, no reaction occurs, and at higher doses, the decomposition reaction takes priority, making it difficult to obtain the expected effects.

[0009]

[Problems to be Solved by the Invention] The present invention provides a gas permeable membrane using a polymer membrane made of polysubstituted acetylene, which can suppress the deterioration of performance over time without impairing the initial gas permeability as much as possible. The purpose is to produce gas permeable membranes.

0010

[Means for Solving the Problems] The present invention is characterized in that a thin film made of a mixture of polysubstituted acetylene and a reactive monomer or an oligomer thereof is irradiated with radiation to crosslink the polymer.

[0011]

[Operation] The structural formula of polysubstituted acetylene is represented by the following chemical formula 2. Polysubstituted acetylene is obtained by polymerizing disubstituted acetylene represented by the following chemical formula 3.

0012

[Case 2]

[0013]

[Chemical formula 3]

[0014] The polymer is TaCl5, NbCl5, 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.

[0015] The obtained polymer is mixed with an appropriate amount of a reactive monomer or its oligomer, and the mixture is
Aromatic hydrocarbons (benzene, toluene, xylene, etc.)
, alicyclic hydrocarbons (cyclohexane, etc.), halogenated hydrocarbons (carbon tetrachloride, trichloroethylene, etc.), and cast the solution to form a thin film.

Examples of the reactive monomer or oligomer thereof used in the present invention include: (1) a reactive monomer containing a vinyl group such as styrene or N-vinylpyrrolidone or an oligomer thereof; (2) an acrylic group such as trimethylolpropane triacrylate; (2) reactive monomers containing methacrylic groups such as trimethylolpropane trimethacrylate or oligomers thereof, and the like can be used.

The substrate for casting is a glass plate with a smooth surface, a metal plate, a polymer plate insoluble in solvents (such as Teflon), or a liquid surface (water, an appropriate aqueous solution, an organic liquid in which the solvent and polymer are insoluble). 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 times of lamination (overcoating). In addition, ready-made porous films can also be used as supports for mechanical strength reinforcement.

The polymer film thus formed is subsequently treated with radiation. As the radiation, for example, electron beams, gamma rays, etc. can be used. These radiations may be irradiated using a normal method.

Generally, it is preferable to use an electron beam. The reason for this is that it is easy to operate and can be processed in a short time. In this case, the accelerating voltage of the electron beam is 50 kV or more, preferably 100 kV or more, and the absorbed dose is 0.1 to
100 megarads is preferable, more preferably 1 to 3
It is 0 megarad. In some cases, irradiation of several megarads or tens of megarads may be repeated several times.

When gamma rays are used, it is preferable to use a similar absorbed dose, but if the dose is too high, the irradiation time becomes long, which is not good in terms of efficiency. More preferably 1 to 30
It's Megarad.

[0022]

[Example] Example 1-(trimethylsilyl)-1-
Propyne (Aldrich) 1g, TaCl5 0.0
6 g and 10 cc of toluene at 80°C for 24 hours.
A viscous polymer gel was obtained by reacting in a nitrogen atmosphere. After diluting this polymer gel with toluene,
The polymer was dropped into a large amount of methanol to precipitate the polymer. The resulting polymer was filtered and dried.

1 g of the obtained polymer and 0.1 g of trimethylolpropane triacrylate were dissolved in 100 cc of toluene to prepare a polymer solution. This polymer 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. Subsequently, this polymer film was crosslinked by irradiating it with an electron beam using an area beam type electron beam irradiation device under conditions of an acceleration voltage of 200 kV and an absorbed dose of 30 megarads.

Comparative Example Poly(-1
Film formation was carried out under exactly the same conditions as in the example except that 1 g of the -trimethylsilyl)-1-propyne polymer was dissolved in 100 cc of toluene.

[0025] For each of the membranes 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. At that time, the performance immediately after electron beam irradiation was used as the initial value, and the subsequent elapsed time characteristics were evaluated. The initial values of each oxygen permeability coefficient (Po2) and oxygen/nitrogen permeability coefficient ratio (separation performance α) and the values after 100 days are shown in Table 1 below, and the elapsed time characteristics are shown in FIG. 1.

[0026] The unit of oxygen permeability coefficient (Po2) is c
m3(STP)・cm/cm2・sec・cmHg.

[0027]

[Table 1]

As is clear from the results shown in Table 1 and FIG. 1, the polymer membrane according to the example was not subjected to decomposition factors, so the initial decrease in gas permeability was lower than that of the polysubstituted acetylene membrane used in the comparative example. It has been found that the size can be kept smaller than that of a single film irradiated with electron beams, and that it has excellent long-term stability. In addition, since the crosslinkability is superior to that of the comparative example, a good crosslinked structure can be obtained at a low dose.

It has been found that similar effects can be obtained even when using other reactive monomers and oligomers thereof than those in the examples.

[0030]

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 the drawing]

FIG. 1 is a characteristic diagram showing changes in oxygen permeability coefficient with respect to elapsed days of a membrane obtained by the method of the present invention.

Claims (1)

[Claims] [Claim 1] A thin film made of a mixture of a polysubstituted acetylene represented by the structural formula [Chemical formula 1] and a reactive monomer or an oligomer thereof is irradiated with radiation to crosslink the polymer. A method for producing a gas permeable membrane.