JP2813452B2 - Method for producing hydrophilic membrane - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a method for producing a hydrophilized membrane, and more particularly to a method for producing a hydrophilized membrane having little adsorption of proteins and the like and excellent in stain resistance.

(Prior Art) In recent years, in a separation operation, a technique using a separation membrane having selective permeability has been remarkably advanced, and has been put to practical use in various applications. As such a separation membrane, a cellulose-based, polyimide-based, polyacrylonitrile-based, polyvinyl alcohol-based, or polysulfone-based material is generally used.
Above all, hydrophobic polymers such as polysulfone resins are
Because of its excellent physical and chemical properties such as heat resistance, acid resistance, alkali resistance, and oxidizing agent resistance, and easy film formation, it is widely used in various applications.

However, permeation performance of a separation membrane made of a hydrophobic polymer is significantly reduced when the membrane is dried, and must be wetted before it can be used again. In addition, there is a drawback that adsorption of proteins and the like is apt to occur and membrane contamination and clogging are liable to occur. These disadvantages are largely attributable to the hydrophobicity of the membrane material, and as a method for solving these problems, it has been proposed to impart hydrophilicity to a hydrophobic separation membrane. As a method for imparting hydrophilicity to such a hydrophobic separation membrane, for example, there is the following method.

(1) Mixed stock solution method A method of forming a film using a stock solution in which a hydrophilic polymer such as polyvinylpyrrolidone is mixed with a hydrophobic polymer and leaving the hydrophilic polymer in the film to make it hydrophilic Akira
(58-104940, 60-97001, 61-93801, etc.) (2) Membrane surface modification method After film formation, a hydrophilic group such as a sulfonic acid group is physically or chemically added to the film material. Introducing method (JP-A-59-196322, JP-A-60-87803, JP-A-62-45303, etc.) (3) Impregnation method The membrane is impregnated with a hydrophilic polymer solution to make the membrane hydrophilic. Method for leaving a conductive polymer (JP-A-61-161103,
(Problems to be Solved by the Invention) The method (1) is easy to produce a separation membrane, but the hydrophilic polymer is uniformly dispersed in the membrane. For this purpose, it is necessary to add a relatively large amount of a hydrophilic polymer. However, since the compatibility of the membrane material and the hydrophilic polymer in the solvent affects the stability of the stock solution, the type and amount of the hydrophilic polymer that can be mixed with the hydrophobic polymer are limited.

In the method (2), the chemical to be reacted is a dangerous substance in many cases, and care must be taken in handling. In addition, the decomposition of the film material or the deterioration of the film may occur during the reaction, so that it is very difficult to control the reaction. In addition, the production process is long and is not suitable for implementation on an industrial scale.

Further, in the method (3), it is difficult to impregnate the hydrophilic polymer with a membrane having a pore diameter of an ultra-excess level, and when the membrane is immersed in a solution of a hydrophilic polymer, the pores of the membrane are filled. Therefore, the applied separation membrane is limited to a relatively porous precision membrane or the like. Further, it is difficult to control the film performance.

Therefore, an object of the present invention is to provide a method for producing a hydrophilized membrane that is easy to produce without any limitation on the membrane material and production conditions.

(Means for Solving the Problems) As a result of thoroughly examining the problems of the above-mentioned conventional technology, the present inventors have found that when a hydrophilic polymer is contained in a coagulation liquid, the hydrophilic polymer is coagulated inside the membrane during coagulation. It was found that the hydrophilic polymer diffused into the membrane surprisingly was not completely extracted by washing and remained in the membrane and on the membrane surface,
As a result of further study, the present invention has been reached. That is, the present invention comprises a solution comprising a hydrophobic polymer and a solvent, a non-solvent, or a swelling agent, which is extruded from a nozzle into a coagulating liquid to form a film, containing 0.1 to 20% by weight of a hydrophilic polymer as a coagulating liquid. A method for producing a hydrophilized film, characterized by using a solution to be treated and leaving the hydrophilic polymer inside and on the surface of the film.

The feature of the present invention is to use a solution containing a hydrophilic polymer in a coagulating liquid, and to diffuse the hydrophilic polymer at the time of coagulation to leave the hydrophilic polymer on the film surface or inside the film to have a hydrophilic effect. To be helpful. Therefore, the combination of the hydrophilic polymer contained in the film forming solution and the coagulation liquid is not particularly limited. Therefore, a well-known technique can be used for the film forming solution as it is. The membrane material is not limited, for example, polysulfone, polyether sulfone, polyamide, polyimide, polyacrylonitrile, polystyrene, polyvinylidene fluoride, polyvinyl chloride, polymethyl methacrylate, etc. A suitable hydrophobic polymer can be applied.

Further, the hydrophilic polymer to be added to the coagulation solution is not limited to the membrane material or the stock solution, but includes, for example, polyvinyl alcohol, polyvinyl acetate, polyvinyl pyrrolidone, polyethylene oxide, polyacrylic acid, acrylamide, carboxymethyl cellulose, ethyl cellulose, and the like. Cellulose-based, ethylene-vinyl alcohol copolymers and modified polymers and copolymers thereof.
In the dry-wet method or the wet method, since a coagulation liquid containing water as a main component has been often used as a coagulation liquid, a water-soluble polymer is preferably used in the present invention. However, in the case of a water-soluble polymer, since a small amount of the hydrophilic polymer may be eluted when the membrane is used, it is desirable that the polymer can be physically or chemically crosslinked and insolubilized. Among them, polyvinyl alcohol is particularly preferable because it has a large number of derivatives such as cations and anions modified, and can be easily crosslinked by acetalization.

The choice of these membrane materials and hydrophilic polymers is optional,
The selection can be made in consideration of the use and the characteristics of the processing solution.

The production method of the present invention can be applied to any of an ultraperfusion membrane, a precision membrane, a dialysis membrane and the like. In addition, a known dry-wet or wet method can be applied, and the shape of the membrane is not particularly limited, such as a flat membrane, a hollow fiber, and a tube. In particular, in the case of a hollow fiber, it is easy to control the concentration of the hydrophilic polymer by adding a hydrophilic polymer to the internal coagulation liquid extruded from the center of the double annular nozzle, and to have a uniform and effective hydrophilic effect. Can be.
In addition, since the amount of the hydrophilic polymer is small, it is advantageous in terms of cost.

For the coagulation liquid, a hydrophilic polymer is added to a film material such as water, alcohols, glycols or the like, a non-solvent or a poor solvent alone or a mixed solution of two or more, or a mixed solution of these and a solvent. These non-solvents or poor solvents need to be capable of dissolving the hydrophilic polymer, and need to be diffused into the membrane during coagulation and incorporated into the membrane. Accordingly, the hydrophilic polymer preferably has as low a molecular weight as possible because it is easily dispersed uniformly. However, a high molecular weight has the advantage of requiring a small amount of addition. The amount of the hydrophilic polymer added in the coagulation liquid varies depending on the type and molecular weight, but is usually 0.1 to 20.
% By weight, preferably 1 to 10% by weight. When the content is less than 0.1% by weight, a sufficient hydrophilic effect cannot be obtained, and when the content is more than 20% by weight, it takes a long time to wash an excessive hydrophilic polymer, which is not economical. Also, for hollow fiber membranes, it can be added only to the internal coagulation liquid,
By adding only to the external coagulation liquid, it is also possible to increase the hydrophilicity by increasing the residual ratio of the hydrophilic polymer on one surface, for example, the surface in contact with the processing liquid.

Next, the film obtained by immersion in the coagulation liquid is washed with water or treated with hot water to extract a solvent, a non-solvent or a swelling agent. On this occasion,
When a water-soluble polymer is used as the hydrophilic polymer, the water-soluble polymer is extracted at the same time. However, most of the extracted hydrophilic polymer is an excess, and the hydrophilic polymer is not completely extracted. This can be presumed to be because the hydrophilic polymer remains in the state of being taken into the membrane material during coagulation. Therefore, even if it is a water-soluble polymer, a sufficient amount to exhibit a hydrophilic effect remains. However, the water-soluble polymer may be slightly eluted at the time of use if left as it is, which may cause a problem depending on uses such as food-related and medical-related. In such a case, it is preferable to insolubilize the hydrophilic polymer by physical or chemical means.

The membrane produced in this way is excellent in hydrophilicity, and does not deteriorate in water permeability even when dried, so that it can be used as a completely dry membrane. As a result, the workability such as modularization, storage and transport thereof is greatly improved, which can lead to a reduction in manufacturing cost.

(Example) Next, the manufacturing method of the present invention will be described in more detail with reference to examples.

The water permeability was calculated by preparing a module having an effective length of 15 cm, applying a water pressure of 1 kg / cm ² to the membrane with pure water at 25 ° C., and measuring the amount of permeated pure water.

Example 1 Polysulfone (UDEL P-1700 manufactured by Amoko) 19% by weight, polyethylene glycol (# 600 manufactured by Sanyo Chemical) 29
% By weight and 52% by weight of dimethylformamide were mixed and dissolved to prepare a film forming solution. This is cast on a glass plate at 30 ° C. using an applicator and left in the air for 10 seconds, and then polyvinyl alcohol (PVA-217, manufactured by Kuraray) 2
It was immersed and coagulated in a coagulation liquid at 50 ° C., which consisted of 80% by weight, 78% by weight of dimethylformamide and 20% by weight of water. After sufficiently washing the resulting film with water, the polyvinyl alcohol was crosslinked with glutaraldehyde in the presence of sulfuric acid, and washed with hot water at 90 ° C. for 1 hour. After drying at 60 ° C. for 5 hours, the water permeability of the separation membrane was measured and found to be 4 m ³ / m ² · hr · kg / cm ² . The water permeability was measured after wetting the membrane with 75% by weight of ethanol and after re-drying, and it was confirmed that both membranes had the same permanent water permeability and had permanent hydrophilicity. Admitted.

Example 2 The film forming solution used in Example 1 was kept at 30 ° C., and the outer diameter was 1.6 m.
m, 3% by weight of polyvinyl alcohol (PVA-205 manufactured by Kuraray) as an internal coagulating liquid from a double annular nozzle with an inner diameter of 0.8 mm,
30 consisting of 79% by weight of dimethylformamide and 18% by weight of water
The mixture was discharged simultaneously with the mixed solution at 10 ° C, passed through 10 cm of humidified air, and immersed in 50 ° C water, which is an external coagulation liquid, with an outer diameter of 1.3 m
m, a hollow fiber membrane having an inner diameter of 0.8 mm was obtained. This film was washed with water to remove the solvent, polyethylene glycol and excess polyvinyl alcohol, and then crosslinked with polyvinyl alcohol and treated with hot water in the same manner as in Example 1 and dried at 60 ° C. for 8 hours. The water permeability of this membrane was 2.7 m ³ / m ² · hr · kg / cm ² , and there was no change in water permeability after wetting and re-drying, indicating permanent hydrophilicity.

Example 3 A solution composed of 8% by weight of polyvinyl alcohol (PVA-203), 75% by weight of ethanol and 17% by weight of water in the internal coagulating liquid, and polyvinyl alcohol (PVA-203) 2 in the external coagulating liquid
A hollow fiber membrane was obtained in the same manner as in Example 2 except that a weight% aqueous solution was used. The water permeability of the membrane after wet and after re-drying was 0.8 m ³ / m ² · hr · kg / cm ² in both cases, and permanent hydrophilicity was recognized as in Example 2.

Example 4 Hollow fiber in the same manner as in Example 2 except that a mixed solution of 3% by weight of carboxylic acid-modified polyvinyl alcohol (manufactured by Kuraray Co., Ltd.), 75% by weight of dimethylformamide, and 22% by weight of water was used as the internal coagulating liquid. A membrane was obtained. Izure After the wet and re-dried permeability after the membrane is also ^{1.6m 3 / m 2 · hr ·} kg
/ cm ² , and permanent hydrophilicity was recognized as in Example 2.

Example 5 19% by weight of polysulfone, 1% by weight of anhydrous lithium chloride,
Dimethylformamide (80% by weight) was mixed and dissolved to form a stock solution. This was used as an internal coagulation liquid by polyvinylpyrrolidone (K-30 manufactured by JAF) 5% by weight, dimethylformamide 8
0.9m outer diameter with a solution consisting of 0% by weight and 15% by weight of water
m, discharge from a double annular nozzle with an inner diameter of 0.4mm at 40 ° C, 15cm
And then immersed in water at 40 ° C. as an external coagulating liquid. Further, the membrane was washed with water for 30 minutes and treated with hot water for 60 minutes, and dried at 60 ° C. to obtain a hollow fiber membrane having an outer diameter of 0.6 mm and an inner diameter of 0.4 mm. This film was dried at 160 ° C. for 8 hours to insolubilize polyvinylpyrrolidone. The resulting membrane had a water permeability of 3.4 m ³ / m ² · hr · kg / cm ^{2 both} after wetting and after re-drying, and permanent hydrophilicity was recognized as in Example 2.

Example 6 A vinylpyrrolidone / quaternized dimethylaminoethyl methacrylate copolymer (GAFQUAT # 755) was used as an internal coagulating liquid.
A hollow fiber membrane was obtained in the same manner as in Example 5 except that 2% by weight (manufactured by GAF), 75% by weight of dimethylformamide, and 23% by weight of water were used. The water permeability after wetting and after re-drying is 1.
At 5 m ³ / m ² · hr · kg / cm ² , permanent hydrophilicity was recognized as in Example 2.

Example 7 17% by weight of polysulfonic acid, polyethylene glycol 34
And dimethylacetamide (49% by weight) were mixed and dissolved to form a membrane-forming stock solution. This is used as an internal coagulating liquid, 1% by weight of polyvinyl alcohol (PVA-203), dimethylacetamide
0.5m outer diameter with a solution consisting of 50% by weight and 49% by weight of water
m, discharged from a double annular nozzle with an inner diameter of 0.25 mm at 50 ° C, 5 cm
And then immersed in 50 ° C. water as an external coagulating liquid. Next, the membrane was rinsed with water for 30 minutes and then treated with hot water for 30 minutes, and then the polyvinyl alcohol was insolubilized in the same manner as in Example 2. Thus, a hollow fiber membrane having an outer diameter of 290 μm and an inner diameter of 200 μm was obtained. Permeability of this membrane was 0.25 m ³ / m ² · hr · kg / cm ² , and permanent hydrophilicity was recognized as in Example 2.

Next, a module for an artificial kidney having an effective area of 1.7 m ² was produced by bundling 9600 of these membranes. Table 1 shows the evaluation results of the dialysis performance using this module.

Example 8 18% by weight of polyimide (2080D manufactured by Appilion Corporation)
Ethylene glycol 18% by weight, dimethylformamide 64
Wt% were mixed and dissolved to form a film forming solution. This solution was kept at 30 ° C., and was composed of 3% by weight of polyvinyl alcohol (PVA-205), 70% by weight of dimethylformamide, and 27% by weight of water as an internal coagulating liquid from a double annular nozzle having an outer diameter of 1.6 mm and an inner diameter of 0.8 mm. At the same time as the mixed solution at 30 ° C, pass through a humidified air of 15 cm, then immerse in 30 ° C water,
A hollow fiber membrane having a diameter of 1.3 mm and an inner diameter of 0.8 mm was obtained. This film was washed with water to remove the solvent, ethylene glycol, and excess polyvinyl alcohol, and then crosslinked with polyvinyl alcohol and treated with hot water in the same manner as in Example 1, and dried at 60 ° C. for 8 hours. The water permeability of the film was ^{1.2m 3 / m 2 · hr ·} kg / cm 2, wetting and permeability changes after the redrying after not observed at all permanent hydrophilicity was observed .

(Effect of the Invention) As described above, by using the coagulating liquid containing a specific amount of the hydrophilic polymer, the film forming solution is not changed, the number of steps is not increased, and the hydrophilic polymer is added to the coagulating liquid. With a slight operation of adding a hydrophilic film, a hydrophilic film having physical properties suitable for each application can be easily produced. Therefore, it can be used in a wide range of fields such as industrial use and medical use.

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-59-55308 (JP, A) JP-A-63-28405 (JP, A) JP-A-60-7853 (JP, A) JP-A-62 294405 (JP, A) JP-A-57-133211 (JP, A) JP-A-2-135131 (JP, A) JP-B 5-63214 (JP, B2) (58) Fields investigated (Int. ⁶ , DB name) B01D 69/02 B01D 71/68 B01D 71/64

Claims (1)

(57) [Claims] When a solution comprising a hydrophobic polymer and a solvent, a non-solvent, or an expanding agent is extruded from a nozzle into a coagulation bath to form a film, 0.1 to 20% by weight of a hydrophilic polymer is contained as a coagulation liquid. A method for producing a hydrophilized film, wherein the hydrophilic polymer is left inside the film and on the surface of the film using a solution to be hydrolyzed.