JPS61249504A - Ultrafilter membrane - Google Patents

Abstract

PURPOSE:To obtain the titled polysulfone ultrafilter membrane having a resistance to contamination and having excellent membrane-forming property and water permeability by mixing sulfonated polysulfone into poly sulfone and using the mixture as the membrane material. CONSTITUTION:Sulfonated polysulfone obtained by the reaction of polysulfone with a sulfur trioxide-triethyl phosphate complex, etc., is mixed into polysulfone, the mixture is dissolved in an org. solvent such as dimethylformamide to prepare a doping liq. (spinning soln.) and a membrane is formed with a dry and wet process. For example, when a membrane body such as a hollow yarn is formed, the doping soln. is discharged from a hollow annular nozzle and naturally dropped. Then the soln. is introduced into a gelation bath consisting of water or an aq. liq. and coagulated to form a membrane. In this case, a core soln. is simultaneously injected from the center of the annular nozzle.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to an ultraporous membrane. More specifically, the present invention relates to a polysulfone resin ultrafiltration membrane that has excellent film formability and water permeability.

[Conventional technology]

Ultrafiltration is the only energy-saving separation process for removing trace amounts of oil, bacteria, and other particulates dispersed in liquids, and is used in a variety of fields. In this ultrafiltration, substances deposited and adsorbed on the membrane surface often cause clogging of the membrane, resulting in increased membrane resistance and reduced filtration efficiency.

Therefore, the membrane is operated using a cross-flow method to suppress deposition on the membrane surface as much as possible. However, the membrane surface is still contaminated, and a phenomenon in which the permeation resistance gradually increases is observed.

This is thought to occur because the dispersed substances in the liquid to be sifted are adsorbed onto the membrane surface and plug the pores of the membrane.

Once such substances are adsorbed to the membrane surface, they do not leave the membrane even after backwashing and cleaning, causing a so-called plugging phenomenon, and eventually the membrane permeability becomes almost zero. I end up.

[Problem that the invention seeks to solve]

Considering the properties of such substances, it is thought that substances that are stably dispersed in water and can only be removed by membranes are stabilized by the electrical repulsion between particles, and that they cannot be removed in nature. Many particles each have a negative charge.

Therefore, in order to make it difficult for such particles to adsorb onto the membrane surface, there are methods such as increasing the thickness of the hydration layer on the membrane surface to make the membrane surface rich in negative charges or to make it hydrophilic. Therefore, attempts have been made to introduce sulfone groups into polysulfone, which is a promising membrane material. However, the method of introducing polar groups into membrane materials has the following drawbacks.

(1) As the hydrophilicity of the membrane increases, the strength of the membrane in water decreases.

(2) Since water is often used as a gelling bath during the 11th membrane process, the water removed during gelation is trapped and the polymer aggregates. Therefore, if the introduction rate of polar groups is increased, a membrane cannot be formed; Film formation becomes impossible.

As a result of various studies in search of a polysulfone resin-based ultra-porous membrane that eliminates these drawbacks and has excellent water permeability, we have found that these problems can be effectively solved by using a mixture of polysulfone and sulfonated polysulfone. I found out that it can be done.

[Means for Solving the Problems] and [Operation] Accordingly, the present invention relates to an ultra-stomation membrane, which is composed of a film-like mixture of polysulfone and sulfonated polysulfone.

Even if sulfonated polysulfone has a high sulfone group introduction rate and cannot be formed into a film, it becomes possible to form a film by mixing it with polysulfone to form a film. The relationship between the mixing ratio of sulfonated polysulfone mixed with polysulfone and film forming properties is when a dope solution is prepared and a film is formed using a dry-wet method.

Although it varies depending on the film forming solvent, the type of gelling bath, and the degree of sulfonation of the sulfonated polysulfone, if the degree of sulfonation per polymer repeating unit is within the range of 0.75 to 1.5, 100 parts by weight of polysulfone is used. Film formation is possible even if up to about 30 parts by weight are mixed. On the other hand, in order to achieve the object of the present invention, it is necessary to use at least about 5 parts by weight per 100 parts by weight of polysulfone.

For film formation, a resin mixture consisting of each of these components is mixed with dimethylformamide, diethylformamide, dimethylacetamide, and diethylacetamide.

dimethyl sulfoxide, N-methyl-2-pyrrolidone,
A dope solution (spinning stock solution) with a concentration of about 10 to 30% by weight prepared by dissolving it in an organic solvent such as triethyl phosphate.
It is carried out using a wet-dry method.

The membrane-like body can take any shape, but in the case of a hollow fiber-like membrane-like body, the dope liquid is discharged from a hollow annular nozzle, and about 1
After allowing it to fall by gravity by about 1100 a, it is introduced into a gelling bath preferably made of water or an aqueous liquid and coagulated to form a film. On this occasion.

In order to maintain the hollow structure of the membrane, core liquid is simultaneously injected from the center of the annular nozzle.

〔Effect of the invention〕

When producing a polysulfone-based ultrafiltration membrane, if sulfonated polysulfone is mixed with polysulfone and used as the membrane material, an ultrafiltration membrane with stain resistance can be obtained that exhibits good film formability and water permeability. It will be done.

〔Example〕

Next, the present invention will be explained with reference to examples.

Example Commercially available polysulfone (UCC product P-1700) was reacted with anhydrous sulfuric acid-triethyl phosphate complex to obtain sulfonated polysulfone with a degree of sulfonation of 1.25.

Using this sulfonated polysulfone, a dope solution having a weight ratio composition shown in the following table was prepared.

Table I 5 1 8 ■
3 0 4II
I O34 The above dope liquid (■) had no film-forming property, but with the dope liquids (■) and (2), hollow fibers could be spun with good spinnability without yarn breakage under the following spinning conditions. Ta.

Dope liquid discharge rate: 30 fi/minute Core liquid discharge rate: 30 minutes a7 minutes Gelation bath: 4°C water ゛ Winding speed
A hollow fiber with an outer diameter of 1.5 m and an inner diameter of 1.0 m was obtained by 26 m in 1 minute and was made into a module.
Emulsified cutting agent with an emulsion diameter of approximately 5 to 15 μm (Yushiro Chemical Industry Product Nijiroken EC-5) - Water (volume ratio 1:
150) Mixture, reflux: 1 minute every 30 minutes.

A durability test was conducted under the condition of 1 kg/d. A graph of flux/initial flux ratio versus passage time is shown in FIG. 1 for modules using polysulfone-sulfonated polysulfone mixture hollow fibers (1) or polysulfone alone hollow fibers (II).

Furthermore, when the initial membrane permeability coefficient was measured, the following results were obtained.

Polysulfone mixture hollow fiber module 13.5aJ/aJ-hr-kg/d Polysulfone single hollow fiber module 10.0dld-hr-kg/a11

[Brief explanation of the drawing]

FIG. 1 is a graph of flux/initial flux ratio versus pass time for modules using polysulfone-sulfonated polysulfone blend hollow fibers or polysulfone single hollow fibers (II).

Claims (1)

[Claims] 1. An ultra-stomation membrane made of a mixture membrane of polysulfone and sulfonated polysulfone. 2. Degree of sulfonation per polymer repeating unit is 0.75
~1.5 sulfonated polysulfone is polysulfone 10
2. The ultrafiltration membrane according to claim 1, comprising a membrane of a mixture of about 5 to 30 parts by weight per 0 parts by weight. 3. The ultrafiltration membrane according to claim 1 or 2, which is produced by a wet-dry method.