JPS5827964B2 - Manufacturing method of semipermeable membrane - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for manufacturing a semipermeable membrane made of polyarylate resin.

Reverse osmosis and ultrafiltration methods, which process solutions by applying pressure to the solution through a semipermeable membrane, have recently attracted attention as energy-saving solution processing methods, and are used for desalination of seawater and wastewater, sugar, juice, milk, oxygen, etc. It has come to be widely applied to concentration, separation, purification, etc.

Regarding this semipermeable membrane, from the viewpoint of practical application, there is a strong desire to develop a membrane that is highly heat resistant and inexpensive to manufacture, but a satisfactory membrane has not yet been developed.

Hitherto, heat-resistant semipermeable membranes made of polysulfon have been used, but this membrane is expensive and its field of use is severely limited.

The present inventor has developed a semipermeable membrane that is inexpensive, highly heat resistant, and has excellent permeation performance, unlike semipermeable membranes made of polysulfon. We discovered that the resulting film obtained by dissolving arylate resin in a mixed solvent consisting of a specific good solvent and a poor solvent and forming it into a film of the desired shape is suitable for the purpose,
The present invention has now been completed.

The semipermeable membrane of the present invention is made of polyarylate resin.

In this case, polyarylate resin is a general term commonly used for polyesters composed of aromatic dicarboxylic acids and dihydric phenols, and the typical one is a repeating structural unit represented by the following formula. It is something that has.

This polyarylate resin has excellent mechanical strength and heat resistance comparable to polysulfone, and is used in light electrical parts, mechanical parts, packaging materials, etc.

According to the research of the present inventor, this polyarylate resin is
It was found that it is extremely excellent as a semipermeable membrane material.

To produce the semipermeable membrane according to the present invention, first, polyarylate resin is mixed with dioxane and/or tetrahydrofuran A, which acts as a good solvent, and additive solvent B, which acts as a poor solvent or non-solvent. Dissolve the polyarylate resin in.

The additive solvent B added to dioxane and/or detrahydrofuran is one that has poor solubility or does not substantially improve solubility compared to dioxane and tetrahydrofuran. , acetic acid, propionic acid, (carboxylic acids such as citric acid, acetone,
Ketones such as methyl ethyl ketone, methyl needle,
Ethers such as diethyl ether, ethyl acetate, l.
Nisdels such as ethyl phosphate, methanol,
Examples include alcohols such as ethanol, and further examples include formamide and sulfonamide.

The mixing amount of these additives B is not particularly limited as long as they are compatible with the good solvent A, but is generally 1 to 50% by weight.

A particularly preferred mixed solvent in the present invention is a mixture of dioxane or tetrahydrofuran and a dialkylformamide such as dimethylformamide.

In this case, since the dialkylformamide has a strong effect as a solvent for the polyarylate resin, it can be used in a wide range of proportions, such as a mixture weight ratio of about 01 to 10, in addition to the good solvent A.

The concentration of the polyarylate resin in the mixture is usually 5 to 3.
0 tons%.

Next, the polyarylate resin solution obtained as described above is uniformly cast onto a flat plate such as a glass plate using a doctor knife, and after casting, a non-solvent immersion liquid (usually water) is used.
Either the film is immersed in water to form a gel, or a portion of the solvent in the film is evaporated and then immersed in an immersion liquid.

In this case, the dipping liquid is arbitrary as long as it is compatible with the good solvent A and additive solvent B in the coating and is insoluble in the polyarylate resin.

Moreover, the removal of the solvent from the produced film does not require such a dipping method, but a vacuum evaporation method or the like may be employed.

In this way, the thickness is less than iooμ, usually 20-80μ
A semipermeable membrane made of a polyarylate resin of about / is obtained.

The properties of the semipermeable membrane of the present invention are influenced by various factors, but especially by the concentration of the applied polyarylate resin solution and the ratio of the mixed solvent "11 good solvent A and additive solvent B." .

Generally, as the concentration of the polyarylate resin in the solution increases, the solute exclusion rate of the resulting membrane increases, but the water permeability of the membrane deteriorates.

On the other hand, when the mixing ratio of additive solvent B to good solvent A increases, the solute exclusion performance of the membrane decreases, but the water permeability increases.

Therefore, in the present invention, the concentration of the polyarylate resin in the solution is preferably 5 to 20% by weight, and the gravimetric mixing ratio of the additive solvent B in the mixed solvent is preferably 5 to 30% by weight. good.

The semipermeable membrane of the seventh invention can take the form of a sheet, for example, a sheet, a tube, a hollow fiber, a composite with a porous support, etc.

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

The solute removal rate shown in the examples is expressed by the following formula:
It is calculated.

Example 1 A homogeneous polymer solution was prepared by mixing polyarylate resin, triethyl phosphate, and dioxane in a weight ratio of 1:1:10.
It was cast onto a glass plate to a thickness of about 0.00 μm.

After the solvent was evaporated for about 1 minute, the glass plate was placed in a water bath at 15-16'C to gel the film.

Thereafter, the membrane was soaked in running water for about 1 hour to completely drain the solvent.

The thus formed membrane was cut into a circular shape with a diameter of 5C7rL, and was installed in a batch type reverse osmosis apparatus commonly used in laboratories, and pressurization and permeation tests were performed.

The effective area of the membrane is 12.6 oar, and the concentration of the stock solution is 5.
An acidic dye solution called Black 24 at 0 ppm was used.

The dye concentration was measured by absorbance.

The experimental conditions and experimental results were as follows.

Experimental pressure: 2kg/c Liquid temperature: 25°C Stock solution: 50 ppm Black-24 rotation speed
600 r, p, m.

Experimental results Water permeation rate Dye rejection rate 7.5 rri'/m'', day 995% Example 2 Polyarylate resin, triethyl phosphate, and dioxane were mixed in a weight ratio of 1:0.2:10 to form a homogeneous transparent material. A membrane-forming solution was prepared, and membrane-forming and permeation tests were conducted in the same manner as in Example 1.

The following experimental results were obtained.

Experimental results Water transport overflow velocity 115.7. y・Day pigment rejection rate 100% Example 3 Polyarylate resin, ethyl alcohol, and dioxane were mixed in a weight ratio of 1:1:10 to create a homogeneous and transparent film-forming solution, which was then cast on a glass plate. , immediately at 15-16℃
The membrane was gelled by immersing it in a water bath.

Using this membrane, a permeation test was conducted under the same conditions as in Example 1.

The following experimental results were obtained.

Experimental results Water transport overflow rate 9.7 rrj' /717)・Pigment rejection rate 97.0% Example 4 Polyarylate resin, ethyl alcohol, and dioxane were mixed in a weight ratio of 1.3:2:10 to form a homogeneous transparent material. A membrane-forming solution was prepared, and using this membrane-forming solution, the same membrane-forming method and permeation test as in Example 3 were conducted.

As a result, the following results were obtained.

Experimental results Water transport overflow rate 0.64 rrj'/m ・Pigment rejection rate 100% Example 5 Polyarylate resin, dimethylformamide, and dioxane were mixed at a weight ratio of 1:3 to prepare a homogeneous and transparent film-forming solution. A semipermeable membrane was made using the same membrane forming method as in Example 3, and the operating pressure was 0.5 kg/ca, and the stock solution was 50 ppmB 1ack-2.
A permeation experiment was conducted using the solution of No. 4.

The experimental results were as follows.

Experimental results: Water transport overflow velocity: 0.5 m'/m'', pigment rejection rate
100% Example 6 Polyarylate resin, dimethylformamide, and dioxane were mixed in a weight ratio of 1:6:4 to prepare a homogeneous transparent film-forming solution, and the same film-forming method and permeation experiment as in Example 5 were conducted.

As a result, the following experimental results were obtained.

Experimental results: Water conveyance overflow rate: 15.5 m/m・Dye rejection rate: 83% Example 7 Polyarylate resin, dimethylformamide, and tetrahydrofuran were mixed at a weight ratio of 1.5:8 to form a homogeneous and transparent film-forming solution. was adjusted, a semipermeable membrane was prepared using the same membrane forming method as in Example 3, and the operating pressure was 2X? /'7, stock solution 50 ppm
A permeation experiment was conducted using a solution of B 1ack-24.

The experimental results were as follows. Experimental results Water transport overflow velocity 4. ．． 3/, 2 days Dye exclusion rate 100% Example 8 Polyarylate resin, ethyl alcohol, and tetrahydrofuran were mixed at a weight ratio of ]:]:10 to prepare a homogeneous and transparent film-forming solution, and a film was formed.

Using this film, an experiment similar to that in Example 7 was conducted, and the following experimental results were obtained.

Experimental results Water transport overflow rate 7.0771:'/m Day 0 dye rejection rate 98%

Claims (1)

[Scope of Claims] 1 Regarding the polyarylate resin, after dissolving the polyarylate resin in a mixed solvent consisting of dioxane and/or tetrahydrofuran A, which acts as a good solvent, and additive solvent B, which acts as a poor solvent or non-solvent, A method for producing a semipermeable membrane, which comprises forming a polyarylate resin membrane in a desired shape using this solution. 2. The method according to claim 1, wherein the additive solvent B is dimethylformamide. 3. The method according to claim 1, wherein the additive solvent B is triethyl phosphate. 4. The method according to claim 1, wherein the additive solvent B is ethyl alcohol.