JPH04100524A - Double-side active composite hollow yarn membrane - Google Patents

Abstract

PURPOSE:To obtain a composite membrane whose fractional MW is from hundreds to thousands by laminating a polymer containing a sulfonic acid group to both inner and outer surfaces of a hollow yarn membrane to activate both surfaces of said membrane. CONSTITUTION:At first, a polymer having a sulfone group bonded to its main or side chain such as sulfonated polyphenylene ether is dissolved in a solvent not dissolving a support film such as butyl cellosolve to obtain a coating solution. Next, this coating solution is applied to the outer surface of a hollow yarn membrane composed of polyphenylene ether or polysulfone and further injected in the interior of the hollow yarn membrane to be excluded. Next, the coated hollow yarn membrane is dried to remove the solvent. By this method, the hollow yarn membrane is converted to a double-surface active composite hollow yarn membrane and this membrane can be used in both of inner and outer pressure systems and has a fractional MW from hundreds to thousands and is excellent in heat resistance and pressure resistance and becomes possible to backwash.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to a double-sided active composite hollow fiber membrane applicable to various membrane processes.

(Prior Art) In recent years, the development of separation processes using membranes has been remarkable, and with this, a wide variety of variations are required for separation membranes. Separation membranes are reverse osmosis membranes,
Classified into ultrafiltration membranes and precision filtration membranes. Among these, reverse osmosis membranes are said to fractionate ions and low-molecular substances with a molecular weight of several tens to several hundred, while ultrafiltration membranes are said to fractionate high-molecular substances with a molecular weight of several thousand to several hundred. However, no practical membrane has yet been developed that can fractionate substances with molecular weights ranging from several hundred to several thousand, which falls between this range.

On the other hand, separation membranes can be classified based on their morphology into hollow fiber membranes, tubular membranes, flat membranes, etc. Among these, hollow fiber membranes have several advantages over other membranes.

Compared to other membrane types, hollow fiber membranes can fill a larger membrane area within the same volume, resulting in higher filtration efficiency.The flow is cross-flow filtration, which prevents concentration polarization and membrane contamination on the membrane surface. It can be prevented. Also, due to the structure of the module,
It does not create dead space and is highly sanitary.

Furthermore, even if the membrane is damaged, it can be reused by sealing only the hollow fibers from the top and bottom ends.
Highly reliable.

Generally, when a membrane is used in an actual separation process, not only the membrane's fractionation performance and water permeability, but also its strength and lifespan are important factors. Hollow fiber membranes are also excellent in this respect; for example, if the water permeability is reduced due to contamination of the membrane surface, the water permeability can be restored by backwashing.

Due to the above advantages, hollow fiber membranes are often used especially in the pharmaceutical, food, and fermentation fields;
Substances with molecular weights ranging from several hundred to several thousand are often targeted for fractionation. Therefore, it is desired to develop a separation membrane with a molecular weight cut-off of several hundred to several thousand, and which takes advantage of the advantages of hollow fiber membranes.

(Problems to be Solved by the Invention) The present invention provides a hollow fiber type composite membrane having a molecular weight cut-off between several hundred and several thousand, which solves the above-mentioned problems.

(Means for Solving the Problems) As a result of studies to solve the above-mentioned problems, the present invention has developed a double-sided active membrane in which polymers containing sulfonic acid groups are laminated on both the inner and outer surfaces of a hollow fiber membrane. They discovered that it would be sufficient to develop a composite hollow fiber membrane, leading to the present invention. Due to the moderate hydrophilicity of the sulfonic acid type polymer, this membrane can be operated at low pressure despite having a molecular weight cut-off of several hundred to several thousand, and can be used in both internal and external pressure systems.
Has sufficient backwashing properties and pressure resistance.

The polymer containing a sulfonic acid group in the present invention refers to a polymer having a sulfonic acid group bonded to its main chain or side chain. Among these polymers, sulfonated polyphenylene ether, sulfonated polysulfone, sulfonated polyether sulfone, and sulfonated polyetherimide have an aromatic ring in their main chain and are heat resistant, so they are suitable as materials. The degree of sulfonation is not particularly limited, but when the completed membrane is used in an aqueous system, it is preferably kept to such an extent that the polymer containing sulfonic acid groups does not dissolve in water. Note that the performance of the completed membrane can be controlled by adjusting the degree of sulfonation.

In the present invention, the hollow fiber membrane serving as the support membrane on which the polymer containing sulfonic acid groups is laminated is not particularly limited, but it is preferable to use a material with excellent chemical and physical stability, especially heat resistance.

In particular, when using sulfonated polyphenylene ether, sulfonated polysulfone, sulfonated polyether sulfone, or sulfonated polyetherimide as a polymer containing a sulfonic acid group, use polyphenylene ether, polysulfone, or polyether as a material that has a high affinity with these polymers. Sulfone and polyetherimide are preferably used. Furthermore, regarding the structure of the hollow fiber membrane that serves as the supporting membrane, it is sufficient that both the inner and outer surfaces are dense enough to allow the polymer containing sulfonic acid groups to be laminated, and there are no particular limitations on the cross-sectional structure such as sponge-like or void-like. .

In addition, in order to manufacture the hollow fiber membrane that becomes the supporting membrane as described above, a known method such as a wet membrane forming method (for example, Japanese Patent Application Laid-Open No. 58
-156018, etc.) can be used.

To layer a polymer containing sulfonic acid groups on both the inner and outer surfaces of a hollow fiber membrane, the polymer is dissolved in a suitable solvent to form a coating solution, applied to both the inner and outer surfaces of the hollow fiber membrane, and then dried to remove the solvent. The removal method is simple.

For example, in order to layer sulfonated polyphenylene ether on both the inner and outer surfaces of a polysulfone hollow fiber membrane, the sulfonated polyphenylene ether is dissolved in a solvent that does not dissolve the support membrane, such as butyl cellosolve, to form a coating solution, and this is applied to the hollow fiber membrane. The coating liquid is applied to the outer surface of the fiber membrane, and then the coating liquid is injected into the inside of the hollow fiber membrane and expelled. next,
This can be air-dried in the air.

The hollow fiber membrane produced as described above becomes a double-sided active composite hollow fiber membrane in which polymers containing sulfonic acid groups are laminated on both the inner and outer surfaces, and can be used in either an internal pressure type or an external pressure type. Furthermore, even if damage occurs on either the inner or outer surface, the separation function can be maintained on the other side, resulting in high reliability. Furthermore, it has excellent backwash resistance and pressure resistance, and can be made heat resistant by appropriately selecting the material.

(Example) The present invention will be explained below using Examples.
The following examples are not intended to be limiting.

Example 1 A membrane-forming stock solution with a composition of 20% by weight of polysulfone, 70% by weight of N,N-dimethylacetamide, and 10% by weight of tetraethylene glycol was prepared, and this solution was extruded from an annular nozzle for manufacturing hollow fibers to form internal and external components. Using pure water as a coagulating liquid, the membrane forming stock solution was coagulated from the inner and outer surfaces until the outer diameter was 1. 3
A hollow fiber membrane with a diameter of 5 mm and an inner diameter of 0°721 m11 was prepared.

This membrane was immersed in a 25% by weight glycerin solution at 60°C for 5 hours while still containing water, and then placed in a dryer at 50°C for 24 hours.
By drying for hours, a hollow fiber membrane filled with glycerin was obtained.

Next, sulfonated polyphenylene ether (degree of sulfonation: 1.2 milliequivalents per gram of dry resin) was dissolved in butyl cellosolve to a concentration of 1% by weight to form a coating solution, and the coating solution was applied onto the outer surface of the hollow fiber membrane. After 1 minute of coating and injecting onto the inner surface, the liquid was removed and air-dried at room temperature for 24 hours.

The thus obtained composite hollow fiber membrane was
g/d, evaluated using an aqueous solution of 11000 pp β-cyclodextrin (molecular weight 1135) at 25°C.
The water permeability was 0.07 rrr/rf·day, and the rejection rate was 91%.

Examples 2 to 3 The degree of sulfonation of sulfonated polyphenylene ether is 1
．． Composite hollow fiber membranes were produced and evaluated in the same manner as in Example 1, except that the weight was 0 mequivalent (Example 2) and 1.4 mequivalent (Example 3), and the results were as shown in Table 1.

Table 1 Example 4 The composite hollow fiber membrane obtained in Example 1 was soaked in hot water at 90°C.
After soaking for a time and comparing the membrane performance before and after soaking, Table 2
The result was as follows. There was no substantial change (there was no substantial change), so it can be said that this film has sufficient heat resistance.

Table 3 Table 2 Example 6 The internal pressure bursting strength of the composite hollow fiber membrane obtained in Example 1 in a hydrated state was measured to be 32 kg/c-j,
It had sufficient pressure resistance.

Example 5 The composite hollow fiber membrane obtained in Example 1 was subjected to external pressure 1°5 k
Hot water at 80°C was passed through the tube at a pressure of g/d for 24 hours. Table 3 shows the changes in membrane performance before and after water flow. There was no substantial change, and it can be said that this membrane can be backwashed.

(Effects of the Invention) The composite hollow fiber membrane of the present invention can be used as a backwashable double-sided active composite hollow fiber membrane with a molecular weight cut-off between several thousand and several hundred, excellent heat resistance and pressure resistance.

Claims (1)

[Claims] A composite hollow fiber membrane characterized in that a polymer containing a sulfonic acid group is laminated on the outer and inner surfaces of the hollow fiber membrane.