JPS58183905A - Separation membrane - Google Patents

Abstract

PURPOSE:To obtain a separation membrane excellent in the separability and the permeability of a gas, by using a membrane based on a chain polymer with a wt. average M.W. of a specific value or more comprising an alxy monomer. CONSTITUTION:A chain polymer with a wt. average M.W. of 10,000 or more obtained by polymerizing 1-alxy or 2-alxy in the presence of a reducing agent by using a catalyst system based on molybdenum pentachloride or tungsten hexachloride is formed into a film showing excellent characteristics as the separation membrane gaseous mixture according to a casting method. The thickness of the formed membrane is not especially limited but usually within a range of 5-50mum. As the representative use thereof, the preparation of oxygen enriched air, the separation of helium from a natural gas and the separation of carbon monoxide and hydrogen in the recovery of hydrogen in a cracking gas are designated.

Description

Detailed Description of the Invention The present invention provides a separation membrane having good separation properties and permeability, especially for gases, and suitable for the selective separation of substance mixtures, especially gas mixtures. It is related. In the following description, a gas mixture will be taken up as a substance mixture.

A gas separation membrane is required to have a high gas separation rate and a high permeation rate. In order to meet such requirements, it is desirable that the thickness of the membrane exhibiting substantial separation performance be as thin as possible, and it is considered preferable that the membrane has a vertical structure.

Various methods have been proposed for manufacturing such structures. For example, a method in which a separately formed thin film with separability is superimposed on a porous membrane with breathability, a skin layer (having separability) and a porous layer (having breathability and serving as a support) are used. A method of forming an integrated sheet body at once, a method of directly polymerizing monomers by various methods on a porous membrane to form a thin film with separability, or a method of forming a thin film with separability on a porous membrane. A known method is to coat a polymer solution thereon and then evaporate the solvent to form a thin film with separation properties.

Among the various methods mentioned above, there is a method in which a solution of another polymeric material is coated on an air-permeable porous membrane that serves as a support, and then the solvent is evaporated to form a separable thin film layer. , is preferable because it enables the application of a relatively wide variety of polymeric materials. However, in this case, if the thickness of the membrane to be coated is made too thin, the separation performance will deteriorate, so it is necessary to coat the membrane thicker than a certain level. There is a problem of trade-offs.

In order to alleviate these inconveniences, from the viewpoint of membrane materials,
The following two measures are being considered. Firstly, although it is impossible to make the film thinner, it is necessary to select a material that has relatively high gas permeability even at the current thickness and has good separation performance.
The key is to choose a material that does not produce pinholes even when made into a thin film. However, at present, satisfactory results have not been achieved in either case.

For example, hydrocarbon rubber (e.g. natural rubber, gyripukudiene) has double bonds in its molecules and is known as one of the polymer materials with the second highest permeability coefficient for gases, especially CO2, after organopolysiloxane. It has rubber elasticity and strong cohesive force, making it difficult to form a thin film. Furthermore, if the film is forced to have a thickness of several tens of microns or less, problems of non-uniformity in thickness and the occurrence of pinholes will occur, and good gas separation performance will not be exhibited.

Furthermore, since polyalkynes have a conjugated double bond in one molecule, they can be expected to have good gas permeability similar to hydrocarbon rubber. However, in reality, only low-molecular-weight polymers can be obtained, and even if high-molecular-weight polymers are obtained, there are cases in which there is no good solvent, or solvents have not been used as separation membranes until now. In response to the request of
Furthermore, there is no known polymer that can be formed into a thin film.

The present inventors first discovered that it is possible to obtain a novel chain polymer from 2-alkynes in high yield, and that it has a very high molecular weight for an acetylene compound polymer, and also It was discovered that it has the feature of completely dissolving in hydrocarbons (Patent Application Shoj-E 7.2g71A).

As a result of intensive studies on separation properties using this new poly-2-alkyne, we found that when this chain polymer is used as the main membrane material, it can separate gas mixtures while maintaining excellent selectivity. It was discovered that a membrane with a higher gas permeability coefficient than conventional membranes of the same type could be obtained.

Furthermore, the following general formula (II) Ha-=c- which is a known substance
R' (II) (In the above formula, R' is a branched alkyl group,
In this alkyl group, seven or more hydrogen atoms of the group may be substituted with a substituent group. It has been discovered that a membrane with good film forming properties and gas separation properties can be obtained when the membrane material is mainly composed of the following, and the present invention has been achieved based on this discovery.

That is, the present invention aims to provide a membrane with a large gas permeability coefficient while maintaining excellent selectivity in the separation of mixtures, particularly gas mixtures, and the gist thereof is based on the general formula C! H3-c=c-n
(1) (In the above formula, R is an alkyl group, and this alkyl group may have one or more hydrogen atoms substituted with a substituent), or the general formula HC30-R' (II )
(In the above formula, R' is a branched alkyl group,
This alkyl group may have one or more hydrogen atoms substituted with a substituent) and has a weight average molecular weight of 1 as a monomer.
Separation membranes mainly consist of more than 10,000 chain polymers.

The present invention will be explained in detail below.

The separation membrane of the present invention is made of a polyalkyne made from a monomer represented by the above formula m or a polyalkyne made from a monomer represented by the above formula (113).

First, polyalkynes made from monomers of formula (1) will be described. R in formula (1) is an alkyl group, and this alkyl group may further have a substituent. Examples of the substituent include an alkyl group and an aryl group.

In order to obtain a weight average molecular weight/universal chain polymer from the monomer of formula (1) above, molybdenum pentachloride or tungsten hexachloride is used as a main catalyst, and various reducing agents are added as a second component to this. A combination of catalysts is used. Various organometallic compounds and metal hydrides are used as the reducing agent.

Examples of organometallic compounds include those containing boron, aluminum, silicon, tin, lead, arsenic, antimony, and the like. Among these, ease of handling, ease of acquisition,
Particularly preferred in terms of effectiveness are tetra-n-butyltin,
Organic tin compounds such as tetraphenyltin. Further, as the metal hydride, lithium aluminum hydride, sodium borohydride, sodium hydride, etc. are used.

The appropriate molar ratio of the 2-alkynes (monomers) to the main catalyst is 100 for the former and j -0.2 for the latter, and the ratio of the reducing agent to the main catalyst is 0. The range of 3 to 3 is preferable. The catalyst is preferably used in the form of a solution, and the main catalyst and reducing agent are dissolved in a solvent (the same solvent as the polymerization reaction solvent described below is used), and it is preferably used after being left at 30 to 0°C for 10-AO minutes.

As the solvent for the polymerization reaction, hydrocarbon%/·logenated hydrocarbon and the like are preferable. In particular, hydrocarbons such as albenzene, toluene, and cyclohexane are preferred because they are readily available and can achieve high yields in polymerization reactions. The monomer concentration in the polymerization reaction is preferably in the range of 0.1-j mol/l. The temperature of the polymerization reaction is usually θ~10
C. and reaction time are selected from a range of several tens of minutes to several tens of hours.

After the reaction is completed, the reaction system is diluted with the solvent used in the reaction and then poured into a large amount of methanol. Since the produced polymer precipitates, it is separated from F and dried.

By the above method, a novel chain polymer can be obtained in high yield from the 2-alkynes of the formula (13), and the weight average molecular weight of the polymer as determined by light scattering method is 10,000 or more, especially 10
It has a very high molecular weight for an acetylene polymer of 10,000 to 1,000,000, and is also characterized by being completely soluble in hydrocarbons such as toluene and cyclohexane.

By casting the solution of the polymer thus obtained, a homogeneous thin film can be obtained. The separation membrane may be made of the polymer obtained as described above or a product containing this as the main component, a copolymer with other components, or a blend product mixed with other components. A film-formed material may also be used.

Next, polyalkynes made from the monomers of the above formula (II1) will be described. Examples of the monomers represented by the formula (n) include tertiary butylacetylene and secondary butylacetylene. Substituents are as shown above. The same monomers as those of general formula (1) can be mentioned.

In order to polymerize such a monomer to produce a polymer with a weight average molecular weight/universal state, molybdenum pentachloride or tungsten hexachloride is used as the main catalyst, as in the case of the monomer of formula (1) above. A catalyst is used in which this is combined with a similar reducing agent as a second component.

The polymerization conditions may be the same as those for polymerizing the 2-alkyne of Formula 11, and the molecular weight and solubility of the obtained polymer in the solvent are also substantially the same.

The polymer thus obtained can be made into a homogeneous thin film by dissolving it in a solvent and casting the solution.

The separation membrane of the present invention is mainly composed of the polyalkynes obtained as described above, and is obtained as a transparent and durable film by dissolving it in an organic solvent and casting it (solution casting method).

The casting method is a method in which the raw materials are dissolved in an organic solvent or water and then cast onto a flat glass plate or a rotating flat uniform metal support to remove the solvent and form a thin film. The resulting film has excellent thickness uniformity, flatness, transparency, and gloss. Furthermore, it has the feature that it has no directionality and can yield a very high quality film free of foreign matter, and is suitable for obtaining a separation membrane from the polyalkyne of the present invention. For example, if a film is to be formed by a melting method, the melting point and decomposition temperature of the polyalkynes of the present invention are close to each other, so there is a risk of deterioration, which is not preferable.

The organic solvent used to prepare the casting solution may be any organic solvent as long as it dissolves the polyalkyne well and evaporates easily after casting, specifically benzene and toluene.

Hydrocarbon solvents such as cyclohexane and n-hexane, and tetrahydrofuran are preferably used.

The solution concentration to obtain a homogeneous film from a casting solution varies depending on the molecular weight and molecular weight distribution of the polymer and the type of solvent, but is usually /~! O weight ratio, preferably 5 to 30 weight -
is within the range of If the concentration is less than 1% by weight, the thickness of the produced membrane becomes thinner and the gas permeation rate increases, but sufficient separation performance is not exhibited.On the other hand, if the solution concentration exceeds 50% by weight, the thickness of the produced membrane becomes thinner. If the diameter is too large, good separation performance can be obtained, but the gas permeation rate will be low. The thickness of the produced film is not particularly limited, but is usually t-SOμ, preferably in the range of 10 to 30μ.

Owing to its excellent properties, the separation membrane of the present invention can be used in the form of a homogeneous membrane for the separation of specific substances in substance mixtures. Gases can be used as target substances, in particular gas mixtures containing at least one of the following gases: oxygen, nitrogen, carbon dioxide, carbon oxide, hydrogen, helium, methane and argon. For example, the separation of nitrogen and oxygen in the production of oxygen-enriched air.

Separation of argon and hydrogen, methane and hydrogen, nitrogen and hydrogen in the recovery of hydrogen, separation of carbon monoxide and hydrogen in the recovery of hydrogen from cracking gas, separation of carbon dioxide and nitrogen in the recovery of carbon dioxide from combustion gas, etc. It can be applied to

Examples of the present invention and production examples of polyalkynes used in these examples will be described below.

Production example / 30 mmol of molybdenum pentachloride and 3 mol of tetraphenyltin in sufficiently purified toluene under a dry nitrogen atmosphere.
0 mmol was added and aged at 30°C for about 75 minutes.

Moles of 2-octyne O,SO were added to the obtained catalyst solution, and polymerization was carried out at 30°C for 2 hours.

After the reaction was completed, the mixture was dissolved in sL of toluene and poured into a large amount of methanol to precipitate the resulting polymer, which was separated and dried. The amount of methanol-insoluble polymer produced was 70% based on the amount of co-octin charged.

The weight average molecular weight of the produced polymer was determined by light scattering method.The produced polymer was a white solid, completely soluble in benzene, toluene, cyclohexane, n-hexane, and tetrahydrofuran, and dissolved in carbon tetrachloride, chloroform, and diethyl ether. It was partially soluble in ethylene dichloride, acetone, ethyl acetate, nitrobenzene, and acetonitrile.

The analytical values of the produced polymer were as follows.

Elemental analysis value (as (CsHn)n): Calculated value, O, g
7. /ta ;H, /, 2. Actual value, Jlr&,
&7 ; H, /2.9/ ; Infrared absorption spectrum; 3000-21jO(e), /A! 0~/lJ'0
(w).

/4t7o (s), t37o (m), t2
<o (w).

tloo (m), 101o (m), zoo
(w).

720 (m) Example/The poly-2-octyne obtained in the above production example/ is dissolved in toluene to make a 70 weight solution. After filtering and defoaming, this solution is cast on a glass plate. ．． A 5'OOμ doctor knife was run for 7 m for 1 minute, and after air drying, it was heated to 72 m at room temperature.
Dry under reduced pressure for an hour.

It is transparent and flexible. In the IR spectrum, no absorption of carbonyl groups was observed despite oxidation. It is amorphous in X-ray diffraction. According to differential thermal analysis, in air,
An exotherm was observed at 130°C, the thermal decomposition temperature was 3AO°C according to thermobalance, and a small endothermic peak was observed at 23'l°C according to DSO.

As for mechanical properties, the transition point was -20°C, the tensile strength at break in a 20°C room was 207~, the elongation was 10%, and the permeation characteristics of the body were measured. As a measuring device, pressurize gas at a pressure of 80 G for blood ischemia, and connect the lower surface of the membrane to a gas buret.1.
2j' (, The amount of gas that permeates through the membrane in a certain period of time is measured to determine the gas permeability. The results are shown in Table 1 below.

The unit of gas permeability coefficient of various gases is cc(s+rp)・c
m/cJ, plexus, and αHf.

1 Production Example 2 00 moles of tertiary butylacetylene as a monomer, 2 moles each of molybdenum pentachloride and tetraphenyltin as catalysts
Polymerization was carried out in the same manner as in Production Example/, except that 0 mm IJ mole was used, and a chain polymer of the above monomer was obtained. The yield was about 100 cm, and the number average molecular weight of the polymer was lj,≠10,000 according to the osmotic pressure method. The solubility of the resulting polymer in various solvents was similar to that in Preparation Example.

Example 2 Using the poly(tertiary butylacetylene) obtained in Production Example λ, a homogeneous film with a thickness of 33 μm was obtained in the same manner as in Example.

The physical properties of this film are as follows.

The film was transparent yellow and harder than the film of Example 1. In the IR spectrum, slight carbonyl absorption was observed due to oxidation. X-ray diffraction showed slight crystallinity. According to differential thermal analysis, heat generation was observed at 765°C in air, and the thermal decomposition temperature in air was 200°C on a thermobalance. Gas permeability of this homogeneous membrane was measured in the same manner as in Example 1. The results are shown in Table 1 below.

Production Example 3 Polymerization was carried out in the same manner as in Production Example 3, except that o 3 o mol of 2-decyne was used as the monomer.

A chain polymer of λ-decyne was obtained. The yield was 0%, and the intrinsic viscosity (in toluene, 30°C) of the resulting polymer was 31.9%. The solubility of the resulting polymer in various organic solvents was similar to that of poly(,2-octyne).

Moreover, the infrared absorption spectrum of this product was as follows.

300 (L-2100(s), /130~/ in the evening 0 (W).

11170 (s), /370~/J♂o (m
), 13oo (w).

11.20~1000 (m), 7.20 (m
) Example 3 A film was formed in the same manner as in Example except that the poly(,2-decyne) obtained in Production Example 3 was used. A homogeneous film of μ was obtained. The gas permeability characteristics of the obtained membrane were measured in the same manner as in Example 1. The results are shown in Table 1 below.

The explanations in Table 7 and above and the examples given are typical examples to help the understanding of the present invention, and the present invention is not limited by these examples, but within the gist of the invention, Modifications other than these examples may be made.

Agent: Patent Attorney, Civil Engineer, Hayashi Procedural Amendment (Spontaneous) Date: February 27, 1939 Haruki Shimada, Commissioner of the Patent Office / Indication of the case: Patent Application No. 1983-664T76 Name of the invention Separation membrane 3 Person making the amendment Case and Relationship between Patent applicant Name Satoshi Higashimura Agent J The number average molecular weight in the detailed description of the invention in the specification subject to amendment was... According to the light scattering method, the weight average molecular weight of the polymer is /j0,000, and the intrinsic viscosity measured at 30°C in toluene is /,3
It was J di/f. ” he corrected.

(2) Page 11/line ``・・・・・・・・・/, 32
dll? Met. ", then add "The weight average molecular weight as determined by light scattering method was /! million."

that's all

Claims (2)

[Claims] (1) General formula CH3-c, =c -R (1) (In the above formula, R is an alkyl group, and one or more of the hydrogens of this alkyl group may be substituted with a substituent. )
. or general formula Ha=o-R' (II)
(In the above formula, R' is a branched alkyl group,
A separation membrane mainly composed of a chain polymer with a weight average molecular weight of 70,000 or more, whose monomer is an alkyne represented by the alkyl group, in which 7 or more hydrogen atoms may be substituted with a substituent. (2) The separation membrane according to claim 1, wherein the separation membrane is a gas separation membrane.