JPS61238834A - Porous polysulfone resin membrane - Google Patents

Abstract

PURPOSE:The titled porous membrane which has pores of a specified average pore diameter on both surfaces and a specified water permeability, is low in plugging and staining and does not decrease in performance even when dry, comprising a polysulfone resin containing a hydrophobic polymer. CONSTITUTION:To a solution obtained by crosslinking a polysulfone resin (A) having repeating units of formulas I and II and 3-30wt% hydrophilic polymer (B) (e.g., polyvinylpyrrolidone) in a solvent (C) for components A and B (e.g., dimethyl sulfoxide) added is at most 7wt% additive (D) (e.g., water) which is a nonsolvent for component A, is a good solvent for component B and is miscible with component C. The formed stock solution for film formation is discharged into a coagulation solution to form a membrane. After an excessive water-soluble component is removed, the membrane is heat-treated at a temperature >=150 deg.C to obtain a porous polysulfone resin membrane having pores of an average pore diameter >=500Angstrom on both surfaces and a wager permeability >=1,000ml/m<2>.hr.mmHg.

Description

[Detailed description of the invention] [Industrial application field] The present invention relates to a novel polysulfone-based resin porous membrane.

[Conventional technology]

Conventionally, the material for semipermeable membranes has been cellulose acetate.
Many polymeric compounds such as polyacrylonitrile, polymethyl methacrylate, and polyamide have been used. on the other hand,
Polysulfone resins were originally used as engineering plastics, but due to their heat resistance, acid and alkali resistance, biocompatibility, and stain resistance, they are attracting attention as semipermeable membrane materials. There is.

Conventional methods for obtaining porous membranes of polysulfone resins include, for example, Journal of Applied Polymer Science (Vol. 20, pp. 2377-2394, 1976) and (Vol. 21, pp. 1883-1900, 1977).
Japanese Unexamined Patent Publication No. 58-194940 published in 1988 has been proposed. However, the intermolecular cohesive force of this resin is too strong and it closes the surface pores and the internal pores that should be penetrated, making it difficult to control pore formation. For this reason, only those having a small molecular weight cut-off of 100,000 or less and low water permeability have been obtained. In particular, in JP-A-58-194940, although the water wettability is improved, the surface pore size is 0.01 to 0.
．． There is no suggestion of anything other than 0.05 μm, and high water permeability cannot be expected.

On the other hand, in recent years, the following methods have been proposed in an attempt to create large pores on the surface of membranes using poly or sulfone resins.

■ A method that utilizes microphase separation between different types of polymers.

(Japanese Patent Publication No. 48-176, Japanese Unexamined Patent Publication No. 14445/1972)
Publication No. 6, Publication No. 57-50506, Publication No. 57-505
(No. 07, No. 57-50508) (2) A method that includes extraction and elution operations after film formation. (Unexamined Japanese Patent Publication No. 5
(No. 4-26283, No. 57-35906, No. 5B-91822) (2) A method of forming a film in a metastable liquid dispersion state of a film forming stock solution. (JP-A-56-154051, JP-A No. 59-58041, JP-A No. 59-18376)
(Japanese Patent Application Laid-Open No. 59-2280)
(No. 16) However, the method (2) only utilizes the difference in coagulation rate between polymers, and has not yet achieved large pores with a molecular weight cut-off of 100,000 or more. Moreover, since a large amount is blended, the original good performance of the polysulfone resin is likely to be lost. Furthermore, method (2) is broadly classified into two methods: extraction of the blend polymer and elution of the inorganic granules. In the former, polyethylene glycol and polyvinylpyrrolidone are the main polymers, but it has been difficult to obtain a sufficient pore size and to perform extraction operations. In the latter example, in the above-mentioned Japanese Patent Application Laid-Open No. 58-91822, it was successfully made to form large pores of 0.05 μm or more by mixing silica powder and forming a film, and then eluting it with an alkali. It is noted that there is a drawback in water wettability. Method (2) involves mixing a large amount of a polysulfone resin non-solvent or swelling agent with the film-forming stock solution.
The membrane is formed immediately before the membrane forming stock solution undergoes phase separation. With such a method, only a film having defects in water wettability can be obtained. Method (2) achieves expansion of the pore size on the surface by blowing high-humidity air during membrane formation, but this method only has this effect on one sideζ, especially in hollow fiber membranes. Only a small range of molecular weights can be obtained.

These conventional polysulfone-based resin porous membranes are characterized in that their membrane-forming stock solution undergoes phase separation at low temperatures. For this reason, even if the temperature of the coagulation bath is increased in an attempt to increase the exchange rate between the non-solvent, etc. in the coagulation bath and the good solvent in the membrane during membrane formation, the membrane-forming stock solution will move toward a homogeneous system, resulting in It has the disadvantage of forming a dense layer on the surface. Furthermore, since polysulfone resin is hydrophobic, it has the disadvantage that once it is dried, it is difficult to recover its performance without special treatment, and there is no product that satisfies both of these requirements at the same time. I didn't.

[Problem that the invention seeks to solve]

The present inventors analyzed the above-mentioned drawbacks, and as a result of intensive study, they arrived at the present invention. In particular, the object is to provide a highly water-repellent polysulfone-based resin porous membrane that is resistant to clogging and staining and whose performance does not substantially deteriorate even when dried.

[Means for solving problems]

The present invention has the following configuration. That is, the membrane has pores with an average pore size of 500 Å or more on both surfaces, the main membrane material is polysulfone resin, contains 3 to 30% by weight of a hydrophilic polymer, and has a water permeability of 1000 ml. /m2-
The present invention is a polysulfone-based resin porous membrane characterized in that hr -rnmHg or more.

The polysulfone resin porous membrane of the present invention has pores with an average pore diameter of 500 Å or more on both surfaces. A hole of such size is
It is necessary to obtain high water permeability and a large molecular weight cutoff. The average pore diameter was determined from an electron micrograph of the surface. Although it is desirable that the pores on both surfaces have a uniform diameter, they do not need to be particularly uniform and may be non-uniform. The average pore diameter is preferably 2 μm or less, but may be larger. However, if the thickness 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 membrane is preferably 5 to 500 μm, more preferably 10 to 300 μm, in order to obtain high water permeability.

The polysulfone resin porous membrane of the present invention has the above-mentioned structure and has a water permeability of 10,100 O/Tn2·h.
r-, 111T, Hg or higher. Although flat membranes with a capacity of several thousand ml/TIN"・hr-mm or more are commercially available, a porous membrane that also satisfies water wettability is revolutionary.Especially for hollow membranes. There are no membrane-shaped membranes that have a water permeability of 10,100 O/m2/hr-aHO or higher and good water wettability.The polysulfone resin porous membrane of the present invention has a water permeability of 10,100 O/m2/hr-aHO or more.
12·hr-mmHo or more can also be provided.

The membrane-forming stock solution used to produce the polysulfone resin porous membrane of the present invention is basically a polysulfone resin (I).
, hydrophilic polymer (■), solvent (III) and additive (
It is composed of a four-component system consisting of IV). The polysulfone resin (I> mentioned here usually consists of a repeating unit of formula (1) or (2) H3, but it may also contain a functional group or be an alkyl type resin, and in particular, It is not limited.

The hydrophilic polymer (n) is a polymer that is compatible with the polysulfone resin (I) and has hydrophilic properties. Polyvinylpyrrolidone is the most preferred, but examples include, but are not limited to, modified polyvinylpyrrolidone, copolymerized polyvinylpyrrolidone, polyethylene glycol, and polyvinyl acetate.

The solvent (III) is a solvent that dissolves both the polysulfone resin (I>) and the hydrophilic polymer (n).

Various solvents can be used, such as dimethyl sulfoxide, dimethylacetamide, dimethylformamide, N-methyl-2-pyrrolidone, and dioxane, but dimethylacetamide, dimethylsulfoxide, dimethylformamide, and N-methyl-2-pyrrolidone are particularly preferred.

The additive (IIJ) is compatible with the solvent (II[>,
Anything can be used as long as it serves as a good solvent for the hydrophilic polymer (n) and as a non-solvent or swelling agent for the polysulfone resin (1), such as water, methanol, ethanol, isopropanol, hexanol, .4-butanediol, etc. Considering production costs, water is the most desirable. The additive (IV) may be selected in consideration of the coagulability with respect to the polysulfone resin (I>).

Combinations of each of these are arbitrary, and it is easy for those skilled in the art to consider combinations having the above properties. Further, the solvent (III) and the additive (IV) may be a mixture of two or more types of compounds.

Surprisingly, this membrane-forming stock solution undergoes phase separation on the high temperature side, contrary to the normal phase separation behavior in which phase separation occurs on the low temperature side. This principle will be explained 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 (IIJ) is shielded from the polysulfone resin (I) by the hydrophilic polymer (n), and does not directly interact with the polysulfone resin (I). In a system where the hydrophilic polymer (I) is not mixed, the system resin (I) naturally coagulates and the additive (IV) is added to a concentration such that phase separation occurs.
This means that even when 20% is added, a homogeneous system is maintained without phase separation. Here, when the temperature is raised, the mobility of the molecules increases, especially the hydrophilic polymer (n) and the additive (I).
The bond with IJ) becomes weaker, the hydrogen bond is broken, and the apparent concentration of the additive (IV) that is not bonded to the hydrophilic polymer (II) increases from that at temperature T, and the polysulfone resin ( The interaction between I) and the additive (111) eventually causes coagulation and phase separation of the polysulfone resin (I). That is, the membrane forming stock solution undergoes phase separation on the high temperature side. Furthermore, when the amount of the additive (IV) in this system is increased, even at the temperature T, in this stock solution system, the amount of additive (Ntll) retained by the hydrophilic polymer (n) at the temperature T is no longer exceeded. By adding (Illr), the membrane forming stock solution undergoes phase separation. However, if the temperature is lowered too much, hydrophilic polymers (
The molecular mobility of n) decreases, the amount of bonding with the additive (Ill) increases, and the apparent concentration of the additive (IV) decreases, resulting in the system becoming homogeneous again. When the temperature is raised again, the system becomes non-uniform, but this time the hydrophilic polymer (n
), hydrophilic polymer (n) and additive (IV)
The number of atoms that combine increases, and the system becomes homogeneous again. As described above, the phase separation behavior of this membrane-forming stock solution is the opposite of normal, and the phase transition is reversible.

As for the composition of the membrane-forming stock solution, the polysulfone resin (1) may be in a concentration range of 5 to 50% by weight as long as it can be formed into a membrane and has properties as a membrane.

In order to obtain high water permeability and a large molecular weight cut-off, the polymer concentration should be lowered, preferably 5 to 20% by weight. If it is less than 5% by weight, it will not be possible to obtain a sufficient viscosity of the film-forming stock solution, making it impossible to form a film. Also, 50
If it exceeds % by weight, it becomes difficult to form through holes. The hydrophilic polymer (n), especially in the case of polyvinylpyrrolidone, is GA
Products with molecular weights of 360,000, 160,000, 40,000, and 10,000 are commercially available from Company F, and it is convenient to use these, but of course products with other molecular weights may also be used. However, one of the reasons for adding the hydrophilic polymer (II) is its thickening effect, so the higher the molecular weight, the smaller the amount added, and the reversal of the temperature dependence of the phase separation phenomenon. This is advantageous for obtaining a membrane with high water permeability. The amount of polyvinylpyrrolidone added is preferably 1 to 20% by weight, particularly 3 to 10% by weight, but it depends on the molecular weight of the polyvinylpyrrolidone used. In general, if the amount added is too small or the molecular weight is too low, it is difficult to achieve a phase separation reversal phenomenon, and if the polymer concentration is too high and the polymer molecular weight is too large, cleaning after film formation becomes difficult. Therefore, one method is to mix substances with different molecular weights and use them in different roles. The polymers (I) and (If) above are combined with the solvent (I)
Mix and dissolve in [I). Additive (IV) is added here, but especially in the case of water, since the polysulfone resin has high coagulability, it is preferably 7% by weight or less, particularly 1 to 5% by weight. It is easily assumed that when an additive with low coagulability is used, the amount added will be large. As the concentration of the additive (Itl) increases, the phase separation temperature of the membrane forming stock solution decreases. The phase separation temperature can be set carefully depending on the desired water permeability and molecular weight of the membrane.
In order to obtain a molecular weight cutoff, a low phase separation temperature may be set to strongly promote phase separation during membrane formation. Further, the same effect can be obtained even if the temperature of the coagulation bath is increased.

A polysulfone resin porous membrane is obtained under the above conditions.

A known technique may be used for the film forming operation.

For flat films, the film-forming stock solution is spread on a flat substrate,
It is then immersed in a coagulation bath. For hollow fiber membranes, an injection solution is used to maintain their hollow form.

The spinning stability is better if the injection liquid has a lower coagulability than the one with a high coagulation property compared to the membrane forming stock solution, but the coagulation bath temperature and
Since the smoothness of the inner wall of the hollow fiber membrane changes in correlation with the phase separation temperature and the die temperature, the best composition may be determined appropriately. Hydrocarbons such as decane, octane, and undecane, which are inert to the polysulfone resin, may also be used. Alternatively, gas may be injected to maintain the hollow shape. Dry length is 0.1-20cm
In particular, a thickness of 0.5 to 5 cm has good spinning stability and is generally desirable.

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

The residual amount is 3 to 30% by weight, preferably 5 to 25% by weight, most preferably 10 to 20% by weight, based on the total weight. The amount of remaining water-soluble polymer can be confirmed by quantitative analysis using elemental analysis or liquid chromatography.

For water-soluble components with low molecular weight, the excess amount can be removed simply by washing with water, but for water-soluble components with high molecular weight, a special extraction operation is performed using a good solvent for water-soluble components such as ethanol, methanol, and water. It is necessary to In particular, the method of extraction with clean water is efficient and can simultaneously impart a heat treatment effect to the membrane. The heat treatment effect refers to a series of effects in which the pore diameter expands over time, but when treated for a long time, the pore diameter conversely shrinks.

The pore diameter reaches its maximum value after about one hour of heat treatment, and it has the advantage that water permeability and molecular weight fraction can be controlled by controlling the treatment time. The membrane from which excess water-soluble polymers have been removed is
Although very small, water-soluble polymers are eluted. This is undesirable in medical applications and food industry applications. As a crosslinking reaction for insolubilization, gamma ray irradiation is effective for vinyl water-soluble polymers. In particular, in the case of polyvinylpyrrolidone, crosslinking can also be achieved by heating. In particular, a heat treatment method is preferred. Heat treatment in the film-formed state is approximately 5 hours at 170°C and 180°C.
In this case, it is necessary to heat for about 2.5 hours, and even at 190°C, it is necessary to heat for about 1.5 hours. As the temperature is raised further, the processing time is shortened accordingly, but this is controlled by the polysulfone resin.

At temperatures below 150°C, the processing time is too long to be 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 005g of membrane with 5QCC of 70℃ hot water for 1 hour has a UV absorption of 0.2 at a wavelength of 350 to 220μm.
Below, consumption amount of 0.01 N KHnOa aqueous solution 1゜Q
ml or less and can pass the test.

〔Example〕

The invention is illustrated in more detail by the following examples.

The measurement method used is as follows.

(1) In the case of a water-permeable hollow fiber membrane, the hollow fiber membrane is inserted into a glass case with holes for reflux liquid at both ends, a small module is made using a commercially available potting agent, and the membrane is heated at 37°C. The water permeability was measured by a method in which water pressure was applied to the inside of the hollow fiber while maintaining the membrane at a constant temperature, and the water permeability was calculated from the amount of water that permeated to the outside through the membrane over a certain period of time, the effective membrane area, and the pressure difference between the membranes.

In the case of a flat membrane, measurements were made in the same manner using a stirred cylindrical cell.

(2) Live blood permeability and bovine plasma water permeability The water permeability of live blood and bovine plasma was determined using bovine blood (hematocrit 35%) and bovine plasma obtained by centrifugation (both containing heparin) using the hollow fiber membrane described above. It was measured in the same way as sex. In this case, the measurement was based on a transmembrane pressure difference of 50 mmHD.

(3) Protein permeability Protein permeability was measured by the Billet method.

Example 1 Polysulfone (Needel P-3500>15 parts, polyvinylpyrrolidone (K2O) 8 parts, and 1,4-butanediol 7 parts were added to 70 parts of dimethylacetamide and dissolved by heating. This membrane forming stock solution was heated at 70°C. 1. So that the phase separates.
It was prepared by adding a trace amount of 4-butanediol. Using a baker set applicator, the mixture was spread on a glass plate while keeping the temperature at 60°C, and then coagulated in a water coagulation bath at 50°C. Average pore diameter approximately 1μm1
A membrane with a water permeability of 50,000 m1/Tr12·hr-mmHg was obtained.

Example 2 A film was formed in the same manner as in Example 1 using the same stock solution as in Example 1 while keeping the stock solution at 30°C. The average pore size was about 0.7 μm, and the water permeability was 36000 ml/B2◆hr-mIIIHg.

Example 3 A stock solution with the same composition as in Example 1 was prepared with an outer diameter of 1.0 mm and an inner diameter of 0.0 mm.
Dimethylacetamide/water = 85/15 was injected as an injection liquid from the mouth hole consisting of a 7n+m annular orifice, and was discharged into a coagulation bath containing water kept at 51°C, which was placed 1°QCm below the mouth face. The mixture was passed through the membrane, washed with water in the usual manner, and wound up in a skein to obtain a hollow fiber membrane. The cap was kept warm at 60°C. The obtained hollow fiber membrane has an average pore diameter of 0
．． Water permeability at 2μm: 1320ml/m2・hr-mmH (
The performance of 1 was obtained.

25% by weight of polyvinylpyrrolidone remained.

Example 4 15 parts of polysulfone, polyvinylpyrrolidone (K2O)
8 parts and 2 parts of water were heated and dissolved in 75 parts of dimethylacetamide, and a small amount of water was added so that phase separation would occur at 65°C. Injection solution: dimethylacetamide/water = 85/
A hollow fiber membrane was obtained in the same manner as in Example 3 using No. 15.

The water temperature in the coagulation bath was kept at 60°C for 70'C1 gold. This hollow fiber membrane was washed in clean water and
"C dry heat treatment to thermally crosslink. Average pore size 0.8μ
15% by weight of m1 polyvinylpyrrolidone remained.

Water permeability 11000 m1/T112・hr-mmHg, bovine plasma water permeability 1010 m1/Tr12・hr-mmHg,
Live blood permeability 420 ml/m2 a hr 6 mm
H(J), a protein permeability of 97% was obtained. No hemolysis or blood cell leakage was observed, and the result was 1.0%. Examples 5 to 7 After drying of hollow fiber membranes spun using the membrane forming stock solution of Example 4. The results were summarized in the table.Drying was done by vacuum drying at room temperature.As shown in Table 1, even if completely dried, the performance could be recovered by simply immersing it in water. There is.

Comparative Example 1 12 parts of polysulfone and 6 parts of polyvinylpyrrolidone were mixed with N-
The mixture was added to 82 parts of methylpyrrolidone and dissolved by heating. This stock solution was kept warm at 50° C., and a film was formed in the same manner as in Example 1.

(Coagulation bath 50℃) The water permeability of this membrane is 600 ml/1
12·hr * mmHg, and after the same post-treatment as in Example 4, the water permeability was substantially O, although the water wettability was good.
It became.

〔Effect of the invention〕

The polysulfone resin porous membrane of the present invention maintains mechanical strength, has high water permeability, and has a large molecular weight cutoff. Furthermore, it has excellent clogging and stain resistance. Although it is not necessarily necessary to dry it, it is easy to handle because there is no change in performance even if it is dried. It also has sufficient performance as a support for a composite membrane.

The polysulfone-based resin porous membrane of the present invention can be used as a high-performance ultrafiltration membrane (or microfiltration membrane), such as a blood component separation membrane for general industrial use and the medical field.

Claims (1)

[Claims] The membrane has pores with an average pore diameter of 500 Å or more on both surfaces, the main membrane material is polysulfone resin, and the total amount is 3.
Contains ~30% by weight of hydrophilic polymer and has a water permeability of 100%
A polysulfone-based resin porous membrane characterized in that it has an Hg of 0 ml/m^2·hr·mmHg or more.