JPH0757825B2 - Polysulfone resin porous membrane - Google Patents

Description

TECHNICAL FIELD The present invention relates to a novel polysulfone-based resin porous membrane.

[Conventional technology]

Conventionally, as the material of the semipermeable membrane, cellulose acetate
Many polymer compounds such as polyacrylonitrile, polymethylmethacrylate, and polyamide have been used. on the other hand,
Polysulfone resins have been originally used as engineering plastics, but because of their excellent heat resistance stability, acid / alkali resistance, biocompatibility, and stain resistance, they have attracted attention as semipermeable membrane materials. There is.

As a method for obtaining a porous film of a polysulfone-based resin, for example, Journal of Applied Polymer Science (20, 2377-2394, 1976) and (21)
Vol., Pp. 1883 to 1900, 1977), JP-A-58-104940, and the like. However, since the intermolecular cohesive force of the resin is too strong, the pores on the surface and the internal pores to be penetrated are closed, so that the control of pore formation becomes difficult. Therefore, only those with a small molecular weight cutoff of less than 100,000 and small water permeability,
Not obtained. Particularly, in the above-mentioned JP-A-58-104940, although the water leakage property is improved, the surface pore size is 0.00
Nothing other than 1 to 0.05 μm is suggested, and high water permeability cannot be expected.

On the other hand, in recent years, the following means have been proposed as an attempt to open a large hole in the surface of a film using a polysulfone resin.

A method that utilizes microphase separation between different polymers. (JP-B-48-176, JP-A-54-144456, 57-5050)
No. 6, No. 57-50507, No. 57-50508) A method having an extraction / elution operation after film formation. (JP-A-54
No. 26283, No. 57-35906, No. 58-91822) A method of forming a film in a metastable liquid dispersion state of a film forming stock solution.
(JP-A-56-154051, JP-A-59-58041, JP-A-59-18)
No. 3761, No. 59-189903) A method for improving the spinning process (Japanese Patent Laid-Open No. 59-228016) However, this method only utilizes the difference in coagulation rate between polymers, and the molecular weight cut-off is We haven't got a large hole of 100,000 or more. Moreover, because of the large amount of blending,
The original good performance of the polysulfone resin is likely to be lost. Further, the method (1) is roughly classified into two methods: extraction of blended polymer and elution of inorganic granules. In the former, polyethylene glycol and polyvinylpyrrolidone are the main polymers, but it was difficult to obtain a sufficient pore size and to perform the extraction operation. In the latter example, the above-mentioned
In JP-A 58-91822, after forming a film by mixing silica powder,
Although it has been successful in making a large hole of 0.05 μm or more by eluting with an alkali, it is described that there is a defect in water leakage. In the method (1), a large amount of a non-solvent of a polysulfone resin or a swelling agent is mixed with a stock solution for film formation, and a film is formed immediately before phase separation of the stock solution for film formation. With such a method, it is possible to obtain only a film having a defective water leak property. The method of (1) realizes the expansion of the pore size on the surface by blowing a high-humidity air at the time of film formation, but the method has the effect only on one side, and in particular, the cutoff molecular weight is small in the hollow fiber membrane. You can only get a small range.

These conventional polysulfone-based resin porous membranes are characterized in that the membrane-forming stock solution undergoes phase separation at low temperatures. Therefore, even if the temperature of the coagulation bath is increased in an attempt to increase the exchange rate of the non-solvent in the coagulation bath and the good solvent in the film during film formation, the stock solution for film formation will move in an equilibrium direction toward the homogeneous system and It has the drawback of forming a dense layer. In addition, since the polysulfone resin is hydrophobic, it has the drawback that it is difficult to recover its performance without special treatment once it has been dried, and there is one that satisfies both of these at the same time. I didn't.

[Problems to be solved by the invention]

The present inventors arrived at the present invention as a result of analyzing the above-mentioned drawbacks and making intensive studies. In particular, it is an object of the present invention to provide a highly water-removable polysulfone-based resin porous membrane that is unlikely to cause clogging or stains and has substantially no performance deterioration even when dried.

[Means for solving problems]

The present invention has the following configurations. That is, both surfaces of the membrane have pores with an average pore size of 500Å or more, the main membrane material is polysulfone resin, and contains 3 to 30% by weight of the total amount of crosslinked hydrophilic polymer, and the water permeability is 1000 ml / m ²・ hr ・ mmHg
It is the polysulfone-based resin porous membrane characterized by the above.

The polysulfone-based resin porous membrane of the present invention has pores having an average pore diameter of 500Å or more on both surfaces. The pores of such a size are necessary to obtain high water permeability and a large molecular weight cutoff. The average pore size is obtained from an electron micrograph of the surface. It is desirable that the pores on both surfaces have a uniform diameter, but it is not particularly necessary that they are uniform, and may be non-uniform. The average pore size is preferably 2 μm or less, but may be more than that. However, if it exceeds 2 μm, the membrane structure becomes fibrillated, the mechanical strength becomes weak, and the bubble point in water becomes lower than 0.5 atm.

The thickness of the film is preferably 5 to 500 μm, and more preferably 10 to 300 μm in order to obtain high water permeability.

The polysulfone-based resin porous membrane of the present invention has the above-mentioned structure and exhibits a water permeability of 1000 ml / m ² · hr · mmHg or more. In particular, for flat membranes, several thousand ml / m ² · hr · mmHg or more are commercially available, but it is epoch-making that a porous membrane that also satisfies the water leakage property. In particular, it has a hollow fiber membrane shape, water permeability of 1000 ml / m ² · hr · mmHg or more, and
I can't find anything that has good water leakage. The polysulfone-based resin porous membrane of the present invention has a water permeability of tens of thousands of ml / m ² · hr · mmHg.
The above can also be provided.

The membrane-forming stock solution used for producing the polysulfone-based resin porous membrane of the present invention basically comprises a polysulfone-based resin (I), a hydrophilic polymer (II), a solvent (III) and an additive (IV). It is composed of four components. The polysulfone-based resin (I) referred to here is usually represented by the formula (1) or (2) However, it may be a functional unit-containing or alkyl-based repeating unit and is not particularly limited.

The hydrophilic polymer (II) is a polymer that is compatible with the polysulfone resin (I) and has hydrophilicity. Polyvinylpyrrolidone is most preferable, but modified polyvinylpyrrolidone, copolymerized polyvinylpyrrolidone, polyethylene glycol, polyvinyl acetate and the like can be mentioned, but the polyvinylpyrrolidone is not limited thereto.

The solvent (III) is a solvent that dissolves both the polysulfone resin (I) and the hydrophilic polymer (II). Various solvents such as dimethylsulfoxide, dimethylacetamide, dimethylformamide, N-methyl-2-pyrrolidone and dioxane are used, but dimethylacetamide, dimethylsulfoxide, dimethylformamide and N-methyl-2-pyrrolidone are particularly preferable.

As long as the additive (IV) is compatible with the solvent (III), becomes a good solvent for the hydrophilic polymer (II), and becomes a non-solvent or swelling agent for the polysulfone resin (I). Well, for example, water, methanol ethanol, isopropanol, hexanol, 1,4-butanediol and the like can be used. Water is the most desirable considering the production cost. The additive (IV) may be selected after considering the coagulability with respect to the polysulfone resin (I).

Each of these combinations is arbitrary, and it is easy for those skilled in the art to consider a combination having the above properties. Further, the solvent (III) / additive (IV) may be a mixed system of two or more kinds of compounds.

In contrast to the normal phase separation behavior of the stock solution for film formation, that is, on the low temperature side, the phase separation is surprisingly performed on the high temperature side. This principle will be described below.

Now, it is assumed that this film-forming stock solution is a homogeneous system at a certain temperature T.
In this case, the additive (IV) is shielded from the polysulfone resin (I) by the hydrophilic polymer (II) and does not directly interact with the polysulfone resin (I). The system resin (I) naturally coagulates in a system in which the hydrophilic polymer (II) is not mixed, and even if the additive (IV) is added to such a concentration as to cause phase separation, the resin (I) does not phase separate. This is the reason why it maintains a homogeneous system. Here, when the temperature is raised, the mobility of the molecule is increased, so that the bond between the hydrophilic polymer (II) and the additive (IV) is weakened, the hydrogen bond is broken, and the hydrophilic polymer (II) is broken.
The apparent concentration of the additive (IV) that is not bound with the compound is higher than that at the temperature T, and the polysulfone resin (I) and the additive (IV) interact with each other. The solidification and phase separation of (I) will be caused. That is, the membrane-forming stock solution undergoes phase separation on the high temperature side. Furthermore, when the amount of additive (IV) in this system is increased, the addition of additive (IV) at the temperature T or more in the undiluted system at a temperature T or more of the additive (IV) is no longer present. By adding the agent (IV), the stock solution for film formation is phase-separated. However, if the temperature is further lowered, the molecular mobility of the hydrophilic polymer (II) decreases, the amount of binding with the additive (IV) increases, and the apparent additive (IV)
The lower concentration results in the system becoming homogeneous again.
When the temperature is raised again, the system becomes inhomogeneous, but this time, when hydrophilic polymer (II) is added, the amount of hydrophilic polymer (II) and additive (IV) bound increases, and the system becomes Be uniform. As described above, the phase separation behavior of this stock solution for film formation is the reverse of the usual one, and the phase transition is reversible.

As the composition of the film-forming stock solution, polysulfone resin (I) is used.
Is in a concentration range capable of forming a film and having characteristics as a film, and is 5 to 50% by weight. In order to obtain high water permeability and a large molecular weight cutoff, the polymer concentration should be lowered, and in this case, it is preferably 5 to 20% by weight. 5% by weight
If it is less than, it is not possible to obtain a sufficient viscosity of the stock solution for film formation,
A film cannot be formed. If it exceeds 50% by weight, it becomes difficult to form through holes. The hydrophilic polymer (II) has a molecular weight of 360,000, 16
It is convenient to use the ones of 10,000, 40,000 and 10,000 are commercially available, but of course other molecular weights may be used. However, one of the reasons for the addition of hydrophilic polymer (II) is that it has a thickening effect. Therefore, the higher the amount of the polymer added, the smaller the amount, and the reversal of the temperature dependence of the phase separation phenomenon. Since it becomes remarkable, it is advantageous for obtaining a film having high water permeability. The addition amount of polyvinylpyrrolidone is preferably 1 to 20% by weight, particularly 3 to 10% by weight, but it depends on the molecular weight of polyvinylpyrrolidone to be used. In general, if the amount added is too small or the molecular weight is too low, the phase separation reversal phenomenon is difficult to obtain, and if the polymer concentration is high and the polymer molecular weight is too large, washing after film formation becomes difficult. Therefore, it is also one method to mix and use those having different molecular weights by sharing the roles. Above (I), (I
The polymer of I) is mixed and dissolved in the solvent (III). The additive (IV) is added to this, and particularly in the case of water, the polysulfone-based resin has high coagulability, so 7% by weight or less, particularly 1 to 5% by weight is desirable. It is easily presumed that the amount of addition increases when an additive having a small solidification property is used. As the concentration of the additive (IV) increases, the phase separation temperature of the stock solution for film formation decreases. The phase separation temperature may be set arbitrarily depending on the water permeability and the molecular weight cutoff of the membrane to be sought.
In order to obtain high water permeability and molecular weight cutoff, a low phase separation temperature may be set to strongly promote phase separation during film formation. Further, the same effect can be obtained by increasing the temperature of the coagulation bath.

A polysulfone-based resin porous membrane is obtained under the above conditions.
A known technique may be used for the film forming operation. For a flat film, the stock solution for film formation is spread on a flat substrate and then immersed in a coagulation bath. An injection liquid is used for the hollow fiber membrane in order to maintain the hollow shape. As for the injection liquid, spinning stability is better if it is lower than that having high coagulability with respect to the membrane-forming stock solution, but the correlation between the coagulation bath temperature, phase separation temperature and spinneret temperature causes Since the smoothness changes, the best composition may be determined appropriately. Decane inert to polysulfone resin
Hydrocarbons such as octane and undecane may be used. Alternatively, a hollow form may be maintained by injecting gas. The dry length is 0.1 to 20 cm, and particularly 0.5 to 5 cm is preferable because the spinning stability is good.

In the polysulfone-based resin porous membrane obtained by such a method, it is preferable to remove an excessive amount of water-soluble components in the membrane and leave the necessary amount of the water-soluble component.

The residual amount is 3 to 30% by weight, preferably 5 to 25% by weight, and most preferably 10 to 20% by weight, based on the total weight.
The amount of the remaining water-soluble polymer can be confirmed by quantifying it by elemental analysis and liquid chromatography. Excessive amounts of low-molecular-weight water-soluble components can be removed by simply washing with water, but high-molecular-weight water-soluble components can be extracted with a good solvent for water-soluble components such as ethanol, methanol and water. Is preferred. Particularly, the method of extracting with boiling water is efficient, and the heat treatment effect on the film can be imparted at the same time. The term "heat treatment effect" refers to a series of effects in which, when the pore diameter is expanded with time and the treatment is further continued for a long time, the pore diameter is contracted. The pore size has a maximum value in about 1 hour of heat treatment, and has an advantage that the water permeability and the molecular weight cutoff can be controlled by controlling the treatment time. The membrane from which the excess water-soluble polymer is removed elutes the water-soluble polymer, although it is very small. This is not desirable in medical applications and food industry applications. As a crosslinking reaction for insolubilization, γ-ray irradiation is effective for vinyl-based water-soluble polymers. Particularly in the case of polyvinylpyrrolidone, it can be crosslinked by heating. A heat treatment method is particularly preferable. It is preferable that the heat treatment in the film forming state is carried out at 170 ° C. for about 5 hours, at 180 ° C. for about 2.5 hours, and at 190 ° C. for about 1.5 hours. When the temperature is further increased, the treatment time is shortened by that amount, but it is controlled by the polysulfone resin. Below 150 ° C, the treatment time is too long and not practical.

The polysulfone-based resin porous membrane of the present invention was evaluated as follows based on the artificial organ standard eluate test method.

A solution obtained by heating 0.5 g of membrane with 50 cc of hot water at 70 ° C for 1 hour has a wavelength of 35
The UV absorption at 0 to 220 μm is 0.2 or less, the consumption of 0.01N KMnO ₄ aqueous solution is 1.0 ml or less, and the test can be passed.

〔Example〕

 The present invention will be described in more detail by the following examples.

The measuring methods used are as follows.

(1) Water permeability In the case of a hollow fiber membrane, the hollow fiber membrane is inserted into a glass case equipped with holes for reflux liquid at both ends, and a small module is prepared using a commercially available potting agent, and the temperature is 37 ° C. The water permeation performance was measured by a method in which water pressure was applied to the inside of the hollow fiber and the water was permeated to the outside through the membrane for a certain period of time, and calculated from the effective membrane area and the transmembrane pressure difference.

In the case of a flat membrane, the same measurement was performed using a stirring cylindrical cell.

(2) Bovine blood permeability and bovine plasma permeability Permeability of bovine blood and bovine plasma is shown in cow blood (hematocrit 35
%) And bovine plasma obtained by centrifugation (both containing heparin)
Was measured in the same manner as the water permeability of the above hollow fiber membrane. In this case, the transmembrane pressure difference was measured on the basis of 50 mmHg.

(3) Protein permeability The protein permeability was measured by the Burette method.

Example 1 15 parts of polysulfone (Udel P-3500), 8 parts of polyvinylpyrrolidone (K90) and 7 parts of 1,4-butanediol were added to 70 parts of dimethylacetamide and dissolved by heating. This stock solution for film formation was prepared by adding a trace amount of 1,4-butanediol so as to cause phase separation at 70 ° C. Using a baker type applicator,
After being spread on a glass plate while keeping the temperature at 60 ° C, it was solidified in a water coagulation bath at 50 ° C. Average pore size about 1μm, water permeability 50000ml / m ² · hr · mm
A film of Hg was obtained.

Example 2 The same stock solution as in Example 1 was used, and the stock solution was kept at 30 ° C. to form a film in the same manner. The average pore size is about 0.7 μm and the water permeability is 36000.
It was ml / m ² · hr · mmHg.

Example 3 An undiluted solution having the same composition as in Example 1 was discharged while injecting dimethylacetamide / water = 85/15 as an injecting solution from the inside of a mouth hole composed of an annular orifice having an outer diameter of 1.0 mm and an inner diameter of 0.7 mm,
The hollow fiber membrane was obtained by passing it through a coagulating bath having water kept at 51 ° C., which was installed 1.0 cm below the surface of the spinneret, washing it with water by a conventional method, and then winding it on a cassette. The base was kept warm at 60 ° C. The resulting hollow fiber membrane had an average pore size of 0.2 μm and a water permeability of 1320 ml / m ² ·
25% by weight of polyvinylpyrrolidone that has achieved the performance of hr · mmHg
It remained.

Example 4 Polysulfone 15 parts, polyvinylpyrrolidone (K90) 8
Parts, 2 parts of water are dissolved by heating in 75 parts of dimethylacetamide,
It was prepared by adding a small amount of water so that phase separation would occur at 65 ° C.
A hollow fiber membrane was obtained in the same manner as in Example 3 except that dimethylacetamide / water = 85/15 was used as the injection liquid. The coagulation bath was maintained at a water temperature of 70 ° C and the spinneret at 60 ° C. This hollow fiber membrane was washed in boiling water, and then subjected to a dry heat treatment at 170 ° C to thermally crosslink. The average pore diameter was 0.8 μm, and polyvinylpyrrolidone remained at 15% by weight. Water permeability 11000ml / m ²・ hr ・ mm
Hg, Bovine Plasma Permeability 1010 ml / m ² · hr · mmHg, Bovine Blood Permeability 420
Performance of ml / m ² · hr · mmHg and protein permeability of 97% was obtained. No hemolysis or blood cell leak was observed. Examples 5 to 7 Changes in water permeation performance after drying of hollow fiber membranes spun using the membrane forming stock solution of Example 4 were investigated. The results are summarized in the table. Drying is vacuum drying at room temperature. As shown in Table 1, the performance is recovered just by immersing it in water even if it is absolutely dried.

Comparative Example 1 12 parts of polysulfone and 6 parts of polyvinylpyrrolidone were added to 82 parts of N-methylpyrrolidone and dissolved by heating. This stock solution
A film was formed in the same manner as in Example 1 while keeping the temperature at 50 ° C. (Coagulation bath 50 ° C) The water permeability of this membrane is 600 ml / m ² · hr · mmHg,
After the same post-treatment as in Example 4, the water permeability was good but the water permeability was substantially zero.

〔The invention's effect〕

The polysulfone-based resin porous membrane of the present invention retains mechanical strength, has high water permeability, and has a large molecular weight cutoff. Further, it has excellent resistance to clogging and stains. Further, although it is not always necessary to dry, handling is easy because there is no change in performance even if it is dried. It also has sufficient performance as a support for the composite membrane.

INDUSTRIAL APPLICABILITY The polysulfone-based resin porous membrane of the present invention can be used as a high performance ultrafiltration membrane (or microfiltration membrane) in blood component separation membranes in general industrial applications and medical fields.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-58-8516 (JP, A) JP-A-56-126407 (JP, A) JP-A-58-104940 (JP, A)

Claims (3)

[Claims] 1. A membrane having pores with an average pore size of 500Å or more on both surfaces, the main membrane material being a polysulfone resin and containing 3 to 30% by weight of a cross-linked hydrophilic polymer, A polysulfone-based resin porous membrane having a water permeability of 1000 ml / m ² · hr · mmHg or more. 2. The polysulfone-based resin porous membrane according to claim 1, wherein the hydrophilic polymer is polyvinylpyrrolidone. 3. The polysulfone resin porous membrane according to claim 1, wherein the polysulfone resin porous membrane is a hollow fiber membrane.