JPH02284636A - Selectivity gas permeable membrane and production thereof - Google Patents

Abstract

PURPOSE:To simply produce a membrane having superior separating performance and permeability by coating the inner wall of each pore in a porous membrane with a layer of the cross-linked product of a high molecular compd. having <=50 deg.C glass transition temp. CONSTITUTION:A cross-linkable high molecular compd. having <=50 deg.C glass transition temp. or a precursor thereof is impregnated into a porous membrane made of an org. material such as nitrocellulose, polysulfone or 6-nylon, an inorg. material such as barium titanate or alumina or a metal such as stainless steel or copper by brush coating, spray coating or other method. The cross- linkable high molecular compd. may be soft high molecular rubber, elastomer, soft gel or tacky matter, etc. Cross-linking treatment is then carried out by the conventional method such as vulcanization or heating and the unreacted compd. is removed by extraction with a solvent such as hydrocarbons or carbon tetrachloride. A membrane having superior separating performance and permeability is obtd.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a novel gas permeable membrane suitable for gas separation having high separation performance and a method for manufacturing the same. More specifically, the present invention provides a special porous material that can be widely used for separation of mixed gases generated in various chemical manufacturing industries, water treatment, purification associated with waste treatment, microbial industry, cleaning in medical equipment, etc. The present invention relates to a novel selective gas permeable membrane with improved separation performance due to its structure, and a method for manufacturing the same.

Prior Art Method for selectively separating a specific gas from a gas mixture and 1
Various methods such as gas chromatography, liquid washing method, adsorption method, and liquefaction separation method are used for this purpose, but in recent years separation methods using polymer membranes have been developed from the viewpoint of energy reduction and equipment simplification. has started to attract attention.

The permeation performance of this polymer membrane varies depending on the type of material composing it, the type of gas permeated, etc., and gas separation is performed by utilizing the difference in these permeation performances. In general, polymer membranes with high permeation performance have low separation performance, and polymer membranes with high separation performance have low permeation performance, so polymer membranes that can satisfy both permeation performance and separation performance are: had not been discovered until now.

That is, until now, polymer membranes have been treated as homogeneous cloth membranes, for example, copolymer membranes of polysilane and polymers such as polycarbonate, polyurethane, and styrene resin (Japanese Patent Laid-Open No. 48-64199, JP-A-58-163403, JP-A-58-14926
(No. Publication), polysiloxane and polyphenylene oxide,
Blend membrane with condensation polymer compound (JP-A-58-95
No. 538, Japanese Unexamined Patent Publication No. 59-203603) are known, but although these have good separation performance, their permeation performance is insufficient. Porous membranes that use Knudsen flow to separate gases are also known, but the separation coefficient of these membranes is proportional to the square root difference in the molecular weights of gas molecules, so the molecular weights of the substances to be separated differ greatly. Although this is necessary, the difference in the molecular weights of gas molecules is generally small, and the difference in their square roots is even smaller, so it is impossible to perform a practically sufficient separation.

On the other hand, a thin homogeneous membrane supported on a porous support is obtained by applying a solution of a polymer such as polysulfone, polyacrylonitrile, or polyimide to the surface of the porous support and drying it (Japanese Patent Publication No. 59-3201). No. Publication,
JP-A-57-209608, JP-A-59-553
13), a non-aqueous solution of a polymer is spread on the water surface to form a thin film, and this is attached to the surface of a porous support (JP-A-5814928, JP-A-58-9).
2430, JP-A-60175507), cross-linked or polymerized precursors on a porous support (JP-A-57-105203, JP-A-59-4980)
2, Japanese Patent Application Laid-open No. 59-59222), but these methods may cause pinholes in the thin film,
They have drawbacks such as complicated preparation methods, clogging of pores, and difficulty in adjusting the balance between permeability and separability, and therefore, satisfactory results have not always been obtained. Furthermore, in order to prevent the formation of pinholes and pore blockage, there is a method in which the pores are impregnated with silicone oil in advance, a thin film is formed by plasma polymerization on one side only, and then the silicone oil is extracted and removed. Although it has been proposed (Japanese Patent Publication No. 59-24843), the steps are complicated and it is inappropriate as an industrial method.

As described above, the reality is that a gas separation membrane that is industrially producible and has well-balanced separation performance and permeation performance has not yet been obtained.

Problems to be Solved by the Invention The present invention aims to provide a novel gas separation membrane that can be manufactured by a simple method, overcomes the above-mentioned drawbacks, and exhibits excellent separation performance and permeation performance. It was done for a purpose.

Means for Solving the Problems The present inventors have conducted extensive research in order to develop a gas separation membrane that is superior to conventional membranes in both separation performance and permeation performance, and that can be easily manufactured. As a result, the pores of the porous membrane are filled with a polymeric substance that increases selectivity for the required gas, improving separation performance, and
We discovered that this goal could be achieved by creating a void in a part of the filled part that allows gas to easily pass through to maintain permeability, that is, by coating the inner wall of the pore with a layer of polymeric material. Based on these findings, the present invention has been completed.

That is, the present invention provides a selective gas permeable membrane comprising a porous membrane in which the inner walls of each pore are coated with a layer of a crosslinked polymer compound having a glass transition temperature of 50° C. or lower.

Such selective gas permeable membranes are produced by impregnating a porous membrane with a crosslinkable polymer compound or its precursor having a glass transition temperature of 50°C or less, then crosslinking the membrane, and removing unreacted substances with a solvent. It can be produced by removing it by extraction.

At this time, it is necessary to appropriately select the conditions for crosslinking treatment and solvent extraction so that voids serving as gas passages are formed in each pore.

The material of the porous membrane used in the present invention is not particularly limited and may be any of organic substances, inorganic substances, and metals. Furthermore, a porous membrane that does not have self-supporting properties can also be used by supporting it on a support. Examples of organic substances used as materials for porous membranes include nitrocellulose, cellulose acetate, regenerated cellulose, polysulfone, polyethersulfone, nylon 6, nylon 66, polyvinyl chloride, acrylic resin, polyolefin, and fluorine 81 resin. Examples of inorganic substances include barium titanate, potassium titanate, alumina, glass, etc., and examples of metals include stainless steel, copper, gold, tin, etc.

This porous membrane has a pore diameter of 0.01-10μ.
m1 is preferably 0.1 to 5 μm.

If it is less than 0.01 pm, the gas permeability is insufficient, and if it is 10 μm or more, the selective separation of gases is reduced.

There is no particular restriction on the shape of the porous membrane, and any shape such as a flat membrane, tubular membrane, or hollow fiber membrane can be selected and used as appropriate depending on the purpose of use.

Next, the polymer compound used to coat the inner walls of the pores of this porous membrane has a glass transition temperature of 50° C.
Any of the following may be used.

Those with a glass transition temperature higher than 50°C lack flexibility and do not exhibit sufficient separation performance. This glass transition temperature 5
Among the polymer compounds below 0℃, there are soft polymers, rubber,
Includes elastomers, soft gels, adhesive substances, etc. Examples of the polymer compound or its precursor used in the present invention include solid rubbers such as natural rubber, imprene rubber, butadiene rubber, styrene-butadiene rubber, butyl rubber, chloroprene rubber, and nitrile rubber, liquid butadiene rubber, liquid imprene rubber, and liquid nitrile rubber. Liquid rubber such as rubber, polyurethane with a terminal functional group, urethane prepolymer, low molecular weight acrylic acid ester polymer or oligomer, polyether with a terminal functional group, aliphatic polythioether, siloxane polymer and its precursor, polyvinyl alcohol, Mention may be made of ethylene-vinyl acetate copolymers, vinyl ethers and polymers thereof.

These polymer compounds are impregnated into the porous membrane as they are or in the form of a solution. This impregnation can be carried out by commonly used methods such as brush coating, spray coating, spreading method, roller coating, centrifugal coating, doctor knife coating, and dipping method.

In this way, the polymer compound impregnated into the pores is
Next, crosslinking is carried out by commonly used methods such as vulcanization, heating, ultraviolet irradiation, electron beam irradiation, polymerization by adding a radical polymerization initiator, and reaction with a crosslinking agent. It can be carried out.

This crosslinking treatment must be carried out in such a way that a crosslinked material layer is sufficiently formed on the inner walls of the pores after the treatment, and voids for gas passage remain. That is, in the solvent extraction subsequent to crosslinking, 10% of the impregnated polymer compound
It is necessary to crosslink to a degree that ~90% by weight is extracted, preferably 30-70% by weight. If the crosslinking progresses further than this, the pores for gas passage become narrower and the permeation performance is impaired, and if the crosslinking progresses further than this, a coating that provides sufficient separation performance will not be formed.

Extraction after the crosslinking treatment can be performed using a solvent that does not dissolve the porous membrane or the crosslinked product, but dissolves only the uncrosslinked polymer compound. Such solvents include hydrocarbons such as toluene, benzene, xylene, cyclohexane, hexane, halogenated hydrocarbons such as carbon tetrachloride, methylene chloride, tetrachloroethane, chloroform, chlorobenzene, tetrahydrofuran, Examples include cyclic ethers such as dioxane.

Effects of the Invention According to the present invention, a gas permeable membrane with excellent separation performance and permeation performance can be obtained, and the material of the coating layer formed on the inner wall of the porous membrane can be changed depending on the type of gas to be separated. It has the advantage that high selectivity can be obtained.

EXAMPLES Next, the present invention will be explained in more detail with reference to examples. PO2 in each example is the permeability coefficient of oxygen gas (c+++3・cm/
crR2·sec-CIIIHg) is 1, and α is the ratio PO2/PN2 of the permeability coefficient of oxygen gas to nitrogen gas.

Example 1 Nitrocellulose porous membrane (pore u0.8 μm)
A solution (30% by weight) prepared by dissolving 1% by weight of benzoyl peroxide in chloroform was applied to natural rubber and the above rubber, and the solvent was removed by leaving to stand at room temperature. After repeating this operation twice, it was sandwiched between spacers and heated at 80° C. for 30 minutes. Next, the uncrosslinked product was extracted with toluene at 90°C for 30 minutes and dried. The gas permeability of the product was as follows.

After reaction PO□-1,20xlo-'', r-2,50 After extraction PO□=9.50x 10-'ff=2.4
0 Example 2 A porous polysulfone membrane (pore size 0.1 pm) was impregnated with liquid polybutadiene (molecular weight -2000) and toluene diisocyanate (3% by weight), and the membrane was sandwiched between spacers at 70°C. The reaction was allowed to proceed for 3 hours. Thereafter, uncrosslinked substances were extracted with n-hexane at room temperature for 1 hour, and then dried. The gas permeability of the product was as follows.

After reaction PO2-1,50x 10-'α-3,10 After extraction PO,=1. lOX 10-'α-2.70 Example 3 Polyvinyl chloride membrane (pore size: 0.8 μm) %), sandwiched between spacers, and heated to react at 70°C for 12 hours. The product was immersed in hot water (90°C) for 1 hour to extract uncrosslinked substances, and then dried. The gas permeability of the product was as follows.

After reaction poz = 8.00 X 10-' ”α
= 2.80 After extraction PO2-1,lOX 10-”a=2.70 Example 4 Acrylic polymer porous membrane (pore size 0.8 μm
) was impregnated with butyl acrylate, liquid polybutadiene (15% by weight) and benzophenone (0.51!1%). This is sandwiched between quartz glass spacers, and ultraviolet rays are
It was irradiated for 1 minute to react. Thereafter, an uncrosslinked product was extracted at 85° C. for 15 minutes. The gas permeability of the product was as follows.

After reaction po2=8. lOx 1O-1t'a-3,0
0 After extraction po2-5.70x 10-”α-2,50 Example 5 NK ester M-90G (manufactured by Shin-Nakamura Chemical Industry Co., Ltd.) was applied to a porous membrane of nylon 66 (pore diameter 1.2 μm).
It was impregnated with polyethylene glycol methacrylate and benzoyl peroxide (1% by weight), and reacted at 70°C for 12 hours while being sandwiched between spacers.

The uncrosslinked product was extracted with toluene at 85°C and dried. The gas permeability of the product was as follows.

After reaction PO2-4,1OX 10-'α-3,20 After extraction PO2-4,40X 10-'α-3,00 Example 6 Cellulose acetate membrane (pore size 1.0 μm), styrene-butadiene rubber, peroxide After impregnating with a toluene solution (25% by weight) of benzoyl (1% by weight) and removing the solvent, the reaction was heated at 80°C for 1 hour while sandwiched between spacers.Next, uncrosslinked products were extracted with toluene. was carried out for 1 hour at room temperature.

The gas permeability of the product was as follows.

After reaction POz= 1.50x 10-'ff-2.6
0 After extraction PO2-4,10x 10-'α-2,30 Example 7 Using barium titanate porous Menpuran (manufactured by Honshu Paper Co., Ltd.), liquid polybutadiene (molecular weight = 2000),
It was impregnated with toluene diisocyanate (3% by weight) and reacted at 70°C for 13 hours while being sandwiched between spacers.

The reaction product was subjected to an extraction treatment of uncrosslinked products with toluene at room temperature for 30 minutes. The gas permeability of the product was as follows.

After reaction PO2 = 1.40X tO-'α-3,20 After extraction PO2 = 2.70x 10-'α-1,80 Example 8 As a porous membrane, a stainless steel filter with a pore size of 3.0 μm (Nippon Seiren Co., Ltd. Co., Ltd.), liquid polybutadiene (molecules = 2000), l-ruene diisocyanate (3% by weight) were sandwiched between IL and spacers and reacted at 70°C for 13 hours.

The reaction product was toluene, and uncrosslinked products were extracted at room temperature for 30 minutes. The gas permeability of the product was as follows.

After reaction PO2-i, 4ox 10'α-3,00 After extraction PO4-4,30X 10-'α-1,65

Claims (1)

[Scope of Claims] 1. A selective gas permeable membrane comprising a porous membrane in which the inner walls of each pore are coated with a layer of a crosslinked polymer compound having a glass transition temperature of 50° C. or lower. 2. A porous membrane is impregnated with a crosslinkable polymer compound or its precursor having a glass transition temperature of 50°C or less, then subjected to a crosslinking treatment, and then unreacted substances are removed by solvent extraction. The method for producing a selective gas permeable membrane according to claim 1.