JP2734733B2 - Gas separation membrane and gas separation method - Google Patents

Description

The present invention relates to a gas separation membrane and a gas separation device capable of selectively separating or concentrating carbon dioxide gas and / or water vapor from a mixed gas containing carbon dioxide gas and water vapor, for example. About the method.

[Conventional technology]

Conventionally, various polymer films have been proposed as functional films,
Various types of gas separation membranes are known.

For example, as an oxygen-enriched membrane, a cellulose acetate-based membrane, a silicone-polycarbonate-based membrane, a crosslinked polystyrene-based membrane, or the like, and as a carbon monoxide gas separation membrane at a high temperature, a polysulfone-based, polyester-based, polyimide-based membrane, or the like is used. Various proposals have been made.

[Problems to be solved by the invention]

However, a membrane which has recently been a problem and has excellent carbon dioxide gas separation ability is particularly desired, but a sufficient one has not yet been obtained. Moreover, many of the conventionally proposed gas separation membranes are complicated to manufacture and cannot be easily obtained, and are therefore extremely expensive.

On the other hand, alkylene oxide graft polyamide,
It can be obtained by a graft reaction of polyamide and ethylene oxide, 1,2-propylene oxide, 1,2-alkylene oxide of _C2-4 such as 1,2-butylene oxide, for example, JP-A-47-897 It is already known in gazettes and the like.

Conventionally, this alkylene oxide graft polyamide is made for the purpose of modifying nylon, and is mainly made for the purpose of improving the hydrophilicity and antistatic property of the polyamide,
No emphasis is placed on functional aspects such as gas separation.

An object of the present invention is to provide a novel polyamide-based gas separation membrane focusing on the functionality of the above-mentioned alkylene oxide-grafted polyamide, and more particularly from a mixed gas containing carbon dioxide gas and / or water vapor. And a gas separation method using the same.

[Means for solving the problem]

According to the present invention, there is provided a gas separation membrane having a gas separation layer made of an alkylene oxide graft polyamide.

Still further, a separation membrane having a gas separation layer made of an alkylene oxide graft polyamide is used to convert carbon dioxide and / or water vapor-containing mixed gas into carbon dioxide and / or carbon dioxide.
Alternatively, there is provided a gas separation method characterized by separating steam.

 Hereinafter, the present invention will be described in more detail.

The alkylene oxide graft polyamide (hereinafter simply referred to as graft polyamide) used in the present invention is a polyamide and a C _2-4 1,2-alkylene such as ethylene oxide, 1,2-propylene oxide, 1,2-butylene oxide. It can be obtained by reacting with an oxide. Nylon 6, nylon 66, nylon as polyamide
Typical nylon such as 610, nylon 11, and nylon 612 can be used.

The graft polyamide of the present invention has 1,2-
It may be obtained by using any known method for grafting an alkylene oxide. Usually, using the above-mentioned nylon powder or pellets, or film-like nylon and the above-mentioned alkylene oxide in a molar ratio of about 1: 0.5 to 10 without catalyst, in an autoclave under an inert gas atmosphere such as nitrogen, about 100 ° C. It can be obtained by holding for a predetermined time below to remove unreacted substances and homopolymers of alkylene oxide.

In this case, the graft polyamide obtained by the method described in the above-mentioned JP-A-47-897 is water-soluble and is not preferred because it is conditionally limited for use as a separation membrane.

Although the 1,2-alkylene oxide graft ratio of the graft polyamide used in the present invention is not particularly limited, as shown in FIGS. 1 to 3 in Examples described later, the gas permeability increases as the graft ratio increases. As it rises,
It can be appropriately selected and used depending on the desired separation rate and separation conditions. Generally, it is preferable to use a graft polyamide having a graft ratio of about 30% or more.

The graft polyamide obtained as described above is one in which a 1,2-alkylene oxide is mainly reacted and polymerized with an amide group of the polyamide, and a polymer of the alkylene oxide is graft-bonded.

The gas separation membrane of the gas separation membrane of the present invention is a thin film layer made of the above-mentioned graft polyamide. It can be obtained by a wet film forming method in which a solution is dissolved in ethanol, tetrafluoropropanol, or hexafluoroisopropanol, a thin film is formed from the solution, the solvent is removed, and the solution is solidified to form a homogeneous film. Further, in this case, a film having a smooth surface, for example, a glass plate, a copper plate, and a metal roll or a belt is formed as a substrate used for producing a homogeneous film, and the film is peeled off from the substrate after the film is formed. By doing so, an extremely thin film can be obtained.

Further, the graft polyamide may be melted and formed into a film by an inflation molding method or a T-die molding method, and may be further stretched.

The thin film-like homogeneous membrane obtained as described above can be used as it is as a gas separation membrane, but can also be used by laminating or laminating it with another porous membrane. Further, a composite gas separation membrane integrally formed on the surface of the porous membrane can be obtained by using a porous membrane as a base material of the above-mentioned homogeneous membrane.

Furthermore, in the present invention, a polyamide film is formed in advance by a known method, and is directly applied to the polyamide film.
It can also be obtained by grafting 1,2-alkylene oxide.

The gas separation membrane of the present invention can be formed into various structures by forming the graft polyamide into a flat membrane shape or a hollow fiber shape.

In the present invention, the thickness of the homogeneous layer of the graft polyamide forming the gas separation layer is not particularly limited, but is usually 0.1 to 500 μm.

The graft polyamide gas separation membrane of the present invention has a particularly high permeability coefficient for carbon dioxide gas and water vapor, and can be suitably used for separation, purification, concentration, and the like of a mixed gas containing carbon dioxide gas and / or water vapor. For example, it is effectively used for separating carbon dioxide from a mixed gas of carbon dioxide and oxygen, and for separating steam from a mixed gas of water vapor and oxygen.In these gas separations, preferably 0 to 150 ° C., particularly preferably It is preferably carried out at 0 to 100 ° C. under a pressure of about 0.1 to 100 kg / cm ² , particularly preferably under a pressure of about 0.5 to 80 kg / cm ² .

〔Example〕

Hereinafter, examples of the present invention will be described in detail. However, the present invention is not limited to the following examples.

In the present invention, the total polymerization rate (%), the graft polymerization rate (%), the homopolymerization rate (%), the weight increase rate (%), the graft rate (%), and the graft efficiency (%) are represented by the following formulas. Is a value calculated by However, in each of the following formulas, the amount of the charged polyamide is W _i , the amount of the alkylene oxide is Q, the weight of the solid after removing the unreacted alkylene oxide after the reaction is W _f , and the solid is washed with hot water to obtain the alkylene oxide. The weight of the hot water insoluble matter from which the homopolymer was removed was defined as Wf _' .

The gas permeation coefficient (cm ³ (STP) · cm / cm ² · sec · cmHg) indicating the degree of the gas permeation rate of the gas separation membrane is a value calculated according to the following formula. However, STP is 0
It represents the volume at 1 ° C. and 1 atm.

Example 1 unstretched film having a thickness of 50μm made of (gas separation production of membranes) Nylon 6 A ₀ (Ube Industries, Ltd., trade name: UBE1022B) 20g of ethylene oxide (Nippon Shokubai Kagaku Kogyo Co.) 40 ml of the mixture was charged into a styrene steel autoclave, and reacted at 80 ° C. for a predetermined time in a nitrogen-free atmosphere without a catalyst. As a result, a graft polyamide film A ₁ having a graft ratio as shown in Table _{1 was obtained.}
It was obtained ~A _4.

The above unstretched film A biaxially stretched film B ₀ thick 25μm nylon 6 instead of ₀ (Kojin Co., Ltd., trade name: Boniru) it was exactly as by graft reaction using. As a result, to obtain a graft ratio as shown in Table 1 grafted polyamide film B ₁ .about.B _4.

Example 2 Each graft polyamide film A ₁ obtained in Example ₁
It was tested for gas permeability to A ₄ and B ₁ ~B _4.

The water vapor permeability was measured at 40 ° C. and 90% relative humidity using a moisture permeable cup (manufactured by Toyo Seiki Co., Ltd.) according to JIS Z0208.

Further, the permeability of oxygen gas and carbon dioxide gas was measured at 30 ° C. using a fully automatic gas permeability measuring device L100 type (manufactured by DR.LYSS).

FIG. 1, FIG. 2 and FIG. 3 show the relationship between the graft ratio and the gas permeability.

From the results of FIGS. 1 to 3, the gas permeability for water vapor, carbon dioxide gas and oxygen gas in the unstretched film A ₀ and the graft polyamide film A ₄ having a graft ratio of 78.6% are expressed as gas permeability coefficient and permeability coefficient ratio, The results are shown in Table 2.

From these, the order of permeability to each gas is the same irrespective of the presence or absence of grafting, but in the graft polyamide film, water vapor permeates about 30,000 times of oxygen gas, carbon dioxide gas permeates about 17 times that of oxygen gas, It is clear that about 1800 times the water vapor of the gas is permeated.

〔The invention's effect〕

The separation membrane of the present invention is obtained by adding 1,2-
It uses a grafted polyamide grafted with an alkylene oxide, is easier to produce than conventional gas separation membranes, and has excellent selective permeability to carbon dioxide and water vapor, and is industrially useful.

[Brief description of the drawings]

FIGS. 1, 2 and 3 are graphs showing the relationship between the graft ratio and the gas permeability of one embodiment of the gas separation membrane of the present invention.

Claims (2)

(57) [Claims] 1. A gas separation membrane comprising a gas separation layer comprising an alkylene oxide graft polyamide. 2. Use of a separation membrane having a gas separation layer made of an alkylene oxide-grafted polyamide to remove carbon dioxide and / or carbon dioxide from a mixed gas containing carbon dioxide and / or water vapor.
Alternatively, a gas separation method comprising separating steam.