JPH0386221A - Polysulfone laminated membrane - Google Patents

Abstract

PURPOSE:To obtain a polysulfone laminated membrane having a high rate of permeation of oxygen and high oxygen-nitrogen selectivity by forming a layer of soluble arom. polysulfone represented by a specified general formula as a gas selective active layer on a porous support having a specified thickness and a specified pore diameter. CONSTITUTION:A layer of soluble arom. polysulfone represented by formula I [where X is structural units represented by formula II (where each of R1-R4 is H, CH3 or C2H5) and Y is structural units represented by formula III (where each of R5 and R6 is H, Cl or NO2)] is formed as a gas selective active layer on a porous support having 10nm-1mum thickness and 1mum surface pore diameter to obtain a polysulfone laminated membrane having a high rate of permeation of oxygen, high oxygen-nitrogen selectivity, superior heat and chemical resistances and mechanical strength.

Description

Detailed Description of the Invention The present invention exhibits an unprecedented high oxygen permeation rate and high oxygen/nitrogen selectivity in either H3, C2H5 or NO2, and has excellent heat resistance and resistance. This invention relates to a composite type gaseous IIl membrane with excellent chemical properties. In particular, its high oxygen and nitrogen selectivity makes it possible to produce oxygen-enriched air with an oxygen concentration of 40% or more, which can be used for medical purposes, or with a nitrogen concentration of 3.
It is suitable for producing air enriched with nitrogen of 5% or more.

BACKGROUND OF THE INVENTION In recent years, the use of nitrogen-enriched air with a nitrogen concentration of 85 to 98.5% has attracted attention. As an example of the use of such nitrogen-enriched air, there is a known attempt to fill a flammable liquid storage tank with nitrogen-enriched air, which is an inert gas, to prevent explosions.

Here, membrane separation technology is used to supply nitrogen-enriched air to directly produce nitrogen-enriched air from general air. In order to obtain nitrogen-enriched air using membrane separation technology, it is possible to use an oxygen selective permeation membrane to increase the ratio of supply gas that permeates through the membrane, and to use a non-permeable gas with a reduced oxygen concentration. In this case, if there is a membrane with a high oxygen/nitrogen selectivity, it becomes possible to efficiently produce nitrogen-enriched air having a predetermined nitrogen concentration with less energy.

Furthermore, in order to obtain nitrogen-enriched air on an industrial scale using membrane separation technology, it is necessary to process a large amount of gas, and a membrane with a high oxygen permeation rate is required.

However, none of the oxygen-enriching membranes currently on the market have both high oxygen-nitrogen selectivity and high oxygen permeation rate, and the production of nitrogen-enriched air using membranes is not widespread.

The production of gas separation membranes with high oxygen permeation rates and high oxygen/nitrogen selectivity becomes possible through the development of polymeric materials and separation membrane manufacturing methods. The development goals for polymer materials are (1) high oxygen permeability coefficient, (2) high oxygen and nitrogen selectivity, (3)
0) To obtain a membrane material that can withstand the use of high-temperature gas.

In addition, the goal of developing a separation membrane manufacturing method is to achieve a thinner gas-selective active layer, since the thickness of the gas-selective active layer and the permeation rate per unit area of the membrane are inversely proportional. As a method to solve this problem, attempts have been made to manufacture a composite membrane having a thin gas-selective active layer on a porous support.

For example, JP-A-81-35803 discloses that the oxygen permeation rate is 2.7 x 10-'N+s3/rn' 11
hr e ate , a separation membrane with an oxygen/nitrogen selectivity of 2.8 is disclosed in JP-A-81-107922, an oxygen permeation rate of 25 Nm'/m' e hr * ate,
A membrane with an oxygen nitrogen selectivity of 2.8 is disclosed.

However, all of them had low oxygen-nitrogen selectivity, and improvements in their properties were required.

Problems to be Solved by the Invention The purpose of the present invention is to provide a film that has a high oxygen permeation rate and high oxygen/nitrogen selectivity, has excellent heat resistance, chemical resistance, and mechanical strength, and can be easily formed using a simple film forming method. It is an object of the present invention to provide a composite gas separation membrane that can be easily handled.

Means and Effects for Solving the Problems The present invention substantially consists of a soluble aromatic polysulfone represented by 2% Select active layer with thickness Io
It is a polysulfone composite membrane provided on a porous support with a surface pore size of 1 gm or less and a particle diameter of ns to Ig, m.

Y (However, R, - circle is either H, CH3, C2H5, R9-R6 is either H, C1, NO2.) In the detailed description of the present invention, polysulfone is defined by the type of structural unit. , i.e. substantially the formula (X-Y
) The structural units of the aromatic polysulfone represented by Xr, , r2, r3r4 . Xr1. r2. r3. r4Yr5
．． , r'0 risulfone, [Xrl, r2, r3, r
, /Yr5, r6]. Here, the numbers l and 2.3 are used for r, to r4, and the structural units Xr1. r2, r3.
R+ in r4 ~ R4 is H1CH in the order of numbers 1, 2, 3
3, C2H, and r5 and r6 are numbers l,
2.3, in the structural units Yr5 and r6 (r) Rs~
R6 indicates the number 1, followed by 2.3, which in that order is H, CI1, and NO2.

Also, if r1 to r4 are the same number.

Xrl, r2, r3, r4 are denoted as Xr, and similarly r5
, r6 are the same number, then Yrs, r6 is Yrs
0 (for example, R, /-/) to simplify the display.
The polysulfone in which l, are all H is [X1/Y+
] is displayed.

Furthermore, when displaying a polysulfone consisting of three or more types of structural units, the molar ratio of each structural unit in the formula (-X-Y-)- is also shown6. For example, [xI/YIY2 (0,9
−0,1)], and the molar ratio of the constituent units is X,
:Y, :Y2=l :OjJ :Q, 1-t
' indicates a certain polysulfone, where the molar ratio is 6 series (
Xrl, r2, r3, r4 series, Yr5, r6 series) are expressed so that the sum of the molar ratios of the constituent units is 1, and if there is only one type of constituent unit in the base yarn, it will be omitted. below,
Examples of synthesis and presentation methods are shown.

The method for synthesizing polysulfone, which is the membrane material of the composite membrane of the present invention, is, for example, ar & unit x1, structural unit Y.

The aromatic polysulfone consisting of 9,9-bis(4-hydroxyphenyl)fluorene 20ml+ole.

4.4°-dichlorodiphenylsulfone 20 mmole
, 22 mmole of potassium carbonate, 68 units of N,N-dimethylacetamide, and 8B of toluene were placed in a 200-mm three-Low flask, dehydrated using a Dean-Stark tube, and then distilled off until the reaction temperature reached 150°C, excluding toluene. , reacted for 15 hours, cooled to room temperature, removed KCI as a by-product acid by filtration, and i! ! Pour the slurry into methanol and reprecipitate, and the inherent viscosity is 0.59 di/
g can be quantitatively obtained. The oxygen permeability coefficient of a uniform film of polysulfone [X+ /Y l], expressed as [X1/Y+ 1 ], is P
O2-4, 18X10-9a1 (STP) am/cm2
* sea cmHg, and the oxygen nitrogen selectivity is
P02/PN2=8.4.

Furthermore, the constituent unit xI and the constituent unit Y1. Y2 (constituent unit Y
The polysulfone consisting of 9.9-bis(4-hydroxyphenyl)fluorene 20m+5ole, 4.4゛-dichlorodiphenylsulfone 4゛-tetrachlorodiphenylsulfone 0.2 mmol
e, 22 mmole of potassium carbonate, N, N-dimethylacetamide 88a. ) Luene 86- was placed in a 20 G- three-ring flask, and the inherent viscosity was 1.09 d by the same procedure as the synthesis method of [X+ /Yt] described above.
1/g can be obtained. The obtained polymer had [X+ /YI Y2 (0.99-0.
01) ] is displayed. Bo! J Suru*7 [Xt
/Yr - Y2 (0.99-0.01)] The oxygen permeability coefficient of a uniform film is 5.9 x 10"cm' (STP)
am/am2m sec cmHg, and the oxygen nitrogen selectivity is PO2/PN2=12.

Polysulfo 7 [X+ /Y+ -Y2 (0.99-
0.01) ] as exemplified. Constituent unit X, . X2
, X3. The molar ratio between the am units y, y2, and y3 may be arbitrary, as long as the total number of moles of the constituent units X and Y match.

The synthesis method described above is only an example, and the method for synthesizing the membrane material of the polysulfone composite membrane of the present invention is not limited to the synthesis method described above.

Furthermore, in order to improve the solution stability of the polysulfone used as the membrane material for the gas-selective active layer of the composite membrane in the present invention, it is desirable to replace the hydroxyl group at the end of the polymer with a benzoyl group or the like.

All polysulfones used as membrane materials for the separation membrane of the present invention are soluble in organic solvents such as metacresol. In addition, polysulfone [Xr,, r2, r3, r 4 / Y r
5. Constituent unit in r61 +7) R+ ”RakaH, CH3, C2Hs Chitch also, R5~R,
is H. Cll.

Even with NO2, there is no big difference in solubility. Table 1 shows
An example of the solubility of polysulfone used in the present invention is shown.

Table 1 Measured concentration: 10 parts by weight of polymer, 100 parts by weight of solvent DM
A.C. N. N-dimethylacetamide NMP; N-
Methyl-2-pyrrolidone As shown in Table 1, the polysulfone used in the present invention exhibits excellent solubility.
A uniform Fl film can be formed on a porous support by a coating method, a water spreading method, or the like.

Furthermore, the polysulfones used in the present invention all have excellent heat resistance, chemical resistance, and mechanical strength.

For example, the glass transition temperature of polysulfone [X+/Ytl is 280°C and the decomposition onset temperature is 400°C. Moreover, this polysulfone [X1/Yt] film is 1
No change in the film shape was observed even after 48 hours of immersion in various organic solvents, acids, and alkaline solutions (chemicals used in the tests are shown in Table 2).

Furthermore, the tensile strength of polysulfone [x+/y+] is 1
1 kg/am2, it is a membrane material with excellent mechanical strength, and this value does not change even after 48 hours of immersion in various organic solvents, strong acids, and strong alkalis.In addition to the above-mentioned absence of shape change, it has high chemical resistance. It is confirmed that it has sex.

Table 2 shows an example of the heat resistance, chemical resistance and mechanical strength of the polysulfone used in the present invention.Even if R1-R4 are H, CH3, C2H1, R5
~Even if R6 is H or CL NO, there is no big difference in heat resistance, chemical resistance, and mechanical strength.These polysulfone materials have excellent heat resistance.

The chemical resistance and mechanical strength are manifested in the excellent heat resistance, chemical resistance, and mechanical strength of the polysulfone gas-selective active layer.

Table 2 A test piece film of wood 100s+mX10ts was immersed in each of the chemicals shown below for 0 hours, and then a tensile test was conducted to determine the strength of the film.

Ita chemicals for testing; 2% HCt, 0.5% HNO3
, 5%H7SOn, 2o%NaOH120%lll
3PO4, 20% CH3CO0H11O% (CH2CO
OH) 2.28XNHaOH1 hypochlorite s sov (available chlorine 500PP theory), 2% trichloroacetic acid, 10% formalin, 100% methanol, 100% ethylene glycol, 100% ethanol, 100% glycerin, 100% acetone, 100% Tetrahydrofuran, 100% dioxane, 100% carbon tetrachloride, 100% chloroform, 100% trichlene,
100% hexane, 100% benzene, 100% toluene, 100% methyl acetate, 100% ethyl acetate The polysulfone composite membrane of the present invention is formed by a coating method, a water spreading method, etc. No limitation 0 For example, polysulfone is dissolved in a suitable solvent, the homogeneous solution is applied onto a porous support using a bar coater so that the thickness is uniform, and the solvent is evaporated in a dryer to form a composite. Obtain a membrane. Alternatively, a thin film obtained by dissolving polysulfone in a water-immiscible solvent and dropping the homogeneous solution onto the water surface is scooped onto a porous support to obtain a composite film.

The obtained polysulfone composite film was subjected to scanning electron microscopy (S
When observed using EM), it is confirmed that the structure consists of an extremely thin, pinhole-free polysulfone uniform film layer on a porous support.

In this structure, the ultrathin, pinhole-free polysulfone uniform membrane layer is the gas-selective active layer of the polysulfone composite membrane of the present invention.

The gas selective active layer of the polysulfone composite membrane of the present invention is Io
It has a film thickness of npeng to Ig,m. In the composite membrane,
The gas selective active layer should be pinhole-free and as thin as possible, but it is practically impossible to form a pinhole-free ultra-thin film with a thickness of 1. Furthermore, if the film thickness exceeds Igm, gas permeability will be insufficient.

In addition, considering both high gas permeability and ease of handling,
A more preferable film thickness is 50 to 300 nm.

What is the purpose of the porous support for polysulfone composite membranes?

The object of the present invention is to maintain a proper membrane shape against the operating pressure of gas separation and to support a gas selective active layer whose mechanical strength is insufficient as it is without causing damage. For this purpose, it is necessary that the porous support has sufficient mechanical strength to withstand the operating pressure, and that the pores on the surface of the support are sufficiently fine to support the ultra-thin film. Furthermore, when producing a composite membrane by a coating method, the support is required to be stable to the polymer solvent.

The porous support for the polysulfone composite membrane of the present invention includes:
When the gas selective active layer has a thickness of l#Lm, the pore diameter on the surface of the porous support must be Ig,m or less, and the smaller the pore diameter, the better the resistance to operating pressure. Furthermore, as the thickness of the gas-selective active layer becomes thinner, the required pore diameter also becomes smaller. Furthermore, when a composite membrane is manufactured by a coating method, it is required to be stable to metacresol, DMAC, etc., which are the solvents for the polysulfone used in the present invention.

Examples of such porous supports include porous Teflon membranes typified by Sumitomo Electric's Fluorobor filter, porous polypropylene membranes typified by polyplastic Duraguard, various porous membranes manufactured by Millibore, and insolubilized membranes. The porous support for the polysulfone composite membrane of the present invention is not subject to any limitations on material, etc., as long as it satisfies the above-mentioned conditions of pore size and solvent stability.

In the polysulfone composite membrane of the present invention, since the active layer for gas separation is a layer of a polysulfone uniform membrane without pinholes, it can directly exhibit the gas selectivity of the polysulfone material used in the present invention.

Examples Examples of the present invention are listed below. In addition, in the following examples, the oxygen permeation rate and oxygen nitrogen selectivity are
Using artificial air with a 1% nitrogen concentration of 73%, the primary side is 2 atm,
The secondary atmospheric pressure was determined from the secondary gas permeation rate and the oxygen and nitrogen concentrations determined using gas chromatography.

Example 1 A solution prepared by dissolving 1 part by weight of polysulfone [X+/Ysl in 100 parts by weight of purified N,N-dimethylacetamide under a dry nitrogen atmosphere was added to a commercially available solution with a nominal pore size of 0.14 m and a film thickness of 10 Ggm. It was applied onto a porous Teflon flat membrane (fluoropore filter manufactured by Sumitomo Electric Industries, Ltd.) using a bar coater to a film thickness of 15 gm, and then dried at 140°C to prepare a composite membrane. The obtained polysulfone composite membrane was set in a sample holder, and the oxygen permeation rate and oxygen/nitrogen selectivity were measured. Table 3 shows the results obtained. The thickness of the gas selective active layer of the composite membrane was determined by SEM observation. According to the book, it was about 120npeng.

Table 3 From Table 3, it was confirmed that the polysulfone composite membrane of the present invention had excellent oxygen permeation rate, oxygen and nitrogen selectivity, and excellent heat resistance.

Example 2 The same composite membrane as in Example 1 was immersed in an aqueous solution of 5% sulfuric acid, 0.5% nitric acid, and 20% sodium hydroxide for 48 hours.
After air drying, it was dried at 140°C, and the oxygen permeation rate and oxygen/nitrogen selectivity were measured at 40°C. The results are shown in Table 4.

(The following is a blank space) Table 4 Table 4 confirms that the polysulfone composite membrane has excellent chemical resistance.

Example 3 Add polysul*7 to 100 parts by weight of purified m-cresol
[X+ /Yt -Y2 (0,99-0,01) 1
A solution prepared by dissolving 1 part by weight in a dry nitrogen atmosphere was added to a commercially available porous Teflon flat membrane (Fluorobore filter manufactured by Sumitomo Electric Industries, Ltd.) with a nominal pore diameter of 0.1 gm and a membrane thickness of 100 μm.
After coating with a film thickness of 15gm using a barcoder,
It was dried at 140°C to produce a composite membrane. The obtained polysulfone composite membrane was set in a sample holder, and the oxygen permeation rate and oxygen/nitrogen selectivity were measured. Table 5 shows the results obtained. The thickness of the gas selective active layer of the composite membrane
According to observation, it was about 120n+s.

Table 5 From Table 5, it was confirmed that the polysulfone composite membrane of the present invention had excellent oxygen permeation rate and oxygen/nitrogen selectivity.

Example 4 0.5 parts by weight of polysulfone [X+/Y+ 3 was dissolved in 100 parts by weight of purified N,N-dimethylacetamide in a dry nitrogen atmosphere, and an insolubilization treatment was performed by heating to obtain a solution with an outer diameter of 0.7 mm and an inner diameter. After applying the polysulfone solution to the outer surface of a 0.4■ asymmetric polysulfone porous hollow fiber membrane by quickly passing the solution through the hollow fiber membrane, it was dried at 140°C and coated on the outer surface of the hollow fiber membrane. A hollow fiber type composite membrane with a polysulfone active layer was created.

The obtained hollow fiber composite membrane is assembled into a mini module,
The thickness of the gas-selective active layer of the composite membrane, whose results are shown in Table 6, where the oxygen permeation rate and oxygen/nitrogen selectivity were measured, was approximately 90n1 according to SEM observation.

Table 6 From Table 6, it was confirmed that the polysulfone composite hollow fiber membrane of the present invention had excellent oxygen permeation rate and oxygen/nitrogen selectivity, as well as excellent heat resistance.

Effects of the Invention The polysulfone composite membrane of the present invention is an extremely excellent oxygen-enriching membrane that has excellent oxygen permeation rate and excellent oxygen-nitrogen selectivity, as well as heat resistance of 200°C and high chemical resistance. It is possible to produce oxygen-enriched air with an oxygen concentration of 40%, which can be used for medical purposes, or nitrogen-enriched air with a nitrogen concentration of 85% or more, in large quantities at low cost. As a result, gas separation technology using membranes will be widely used.

Claims (1)

[Claims] Substantially, a soluble aromatic polysulfone represented by the formula ▲ includes a mathematical formula, a chemical formula, a table, etc. The active layer has a thickness of 10n.
A polysulfone composite membrane provided on a porous support having a surface pore diameter of 1 μm or less. X ▲There are mathematical formulas, chemical formulas, tables, etc.▼ Y ▲Mathematical formulas,
There are chemical formulas, tables, etc. ▼ (However, R_1 to R_4 are H, CH_3, C_2H_
5, and R_5-R_6 are H, Cl, NO
Either _2. )