JPS61257203A - Hydrophilic porous membrane and its preparation - Google Patents

Abstract

PURPOSE:To obtain porous membrane having elevated water permeability while maintaining high strength, chemical resistance and heat resistance by using a mixture of a hydrophilic water-insoluble polymer with a hydrophobic polymer having common solvent with the hydrophilic polymer. CONSTITUTION:A mixture of a hydrophobic polymer with a hydrophilic water- insoluble polymer is used as a material for prepg. the porous membrane. The proportion of the hydrophilic polymer to be mixed with the hydrophobic polymer is 10-50wt% basing on the amt. of the hydrophobic polymer. It is necessary that the hydrophilic polymer and the hydrophobic polymer have a common solvent. Both polymers are dissolved in the common solvent. Preferred concn. is 15-25wt%. Further, the solvent consists preferably of a quick drying solvent and slow drying solvent in 50:50-95:5 weight ratio. The solution is casted and casted film is allowed to contact with a nonsolvent for the hydrophobic polymer to cause coagulation. Thus, hydrophilic porous membrane is obtd.

Description

Detailed Description of the Invention (1) Background of the Invention (Technical Field) The present invention relates to a hydrophilic porous membrane and a method for producing the same. Specifically, the present invention relates to a hydrophilic porous membrane that is water-insoluble and is composed of a mixed component system of a hydrophilic polymer and a hydrophobic polymer, and a method for producing the same.

(Prior Art) Conventionally, porous membranes of cellulose derivatives, particularly cellulose acetate, having high water permeability have been common as polymeric porous membranes used for various types of filtration, dialysis, and the like. However, such cellulose derivatives have poor resistance to acids, alkalis, organic solvents, etc.
In addition, it has the disadvantage of being easily deformed by heat, pressure, etc., so the range of its usage conditions has been significantly limited.

Porous membranes made of non-cellulose synthetic resins have been developed as an alternative to these cellulose derivative porous membranes, and there are a wide variety of types, but they can be roughly divided into two types:
It can be divided into One is JP-A-52-123.385.
No., JP-A-52-94.361, JP-A-53-39.
As seen in No. 981, this method uses a hydrophilic polymer as a raw material to form a porous membrane. However, hydrophilic polymers generally do not have sufficient physical properties such as chemical resistance and strength, and are not suitable for dry storage, so they have the disadvantage of requiring freeze-drying or heat treatment for storage. . The other method is to activate the surface and impart hydrophilicity to the hydrophobic porous membrane formed from a hydrophobic polymer by subjecting it to alkali treatment, radiation treatment, plasma treatment, grafting treatment, oxidation treatment, etc. It is.

Hydrophilic porous membranes obtained by adding hydrophilic groups to the surface of such hydrophobic polymers generally become porous membranes that can enjoy the excellent physical properties of hydrophobic polymers, such as excellent strength and chemical resistance. If hydrophilicity can be reliably imparted, it will be possible to obtain an excellent porous membrane with excellent water permeability and removal efficiency Q balance and high strength.
These treatments involve complicated steps, and because the material is porous, no method has yet been established that can reliably make it hydrophilic. For example, the method of imparting hydrophilic groups to the membrane surface by treatment with an aqueous alkali solution such as sodium hydroxide or potassium hydroxide (Japanese Patent Publication No. 58-93゜734, etc.) has the risk of reducing the membrane strength due to the alkali, so management The problem was that the conditions were difficult. In addition, in the method of graph l-polymerizing a hydrophilic monomer onto the surface of a hydrophobic polymer (Japanese Patent Publication No. 56-44.098, etc.), since the hydrophobic polymer is a porous material, the graft polymerization progresses uniformly even inside the pores. It was difficult to do so, and there was a large risk of non-uniformity. Furthermore, a method in which a hydrophobic porous membrane is treated with an alcohol permeated condensate water-soluble polymer aqueous solution, and after drying, the water-soluble polymer that remains on the membrane is treated with heat or radiation to insolubilize it (Japanese Patent Publication No. 17,978, 1978, etc.) It takes a long time from alcohol permeation to replacement with polymer aqueous solution, and the membrane strength deteriorates due to the effects of heat, radiation, etc. during insolubilization treatment.
There was a high possibility that the pore diameter of the membrane would change.

Therefore, these porous membranes of hydrophobic polymers are used after coating the surface with glycerin or the like, or after immersing them in alcohol or the like, and then replacing the membrane with water.

OBJECTS OF THE INVENTION Accordingly, an object of the present invention is to provide a novel hydrophilic porous membrane and a method for producing the same. Another object of the present invention is to provide a hydrophilic porous membrane with excellent water permeability and mechanical strength, and a method for producing the same. A further object of the present invention is to provide a hydrophilic porous membrane that does not require post-treatment for imparting hydrophilic properties, and a method for producing the same.

These purposes are directed to a hydrophilic porous material characterized in that it consists of a mixed component system of a hydrophilic and water-insoluble polymer and a hydrophobic polymer having a common solvent with the hydrophilic and water-insoluble polymer. Achieved by membrane.

The present invention also provides a hydrophilic polymer, wherein the hydrophilic and water-insoluble polymer is a vinyl alcohol-vinyl acetate copolymer, and the hydrophobic polymer is a vinylidene fluoride homopolymer or a copolymer of vinylidene fluoride and another monomer. This shows a porous membrane.

The above objects also include preparing a mixed polymer dope in which a hydrophilic and water-insoluble polymer and a hydrophobic polymer are dissolved in a common solvent, and after casting the polymer dope on a substrate, The above cast mixed polymer dope is brought into contact with a coagulating solvent that has affinity and is a non-solvent for at least hydrophobic polymers, and the solvent is removed from the polymer dope to form the mixed polymer dope. This is achieved by a method for producing a hydrophilic porous membrane, which comprises gelling a gel and then removing a coagulating solvent from the gel.

The present invention also provides a mixed polymer dope prepared by dissolving a hydrophilic and water-insoluble polymer and a hydrophobic polymer in a common solvent, casting the polymer dope on a substrate, and removing a part of the solvent. After evaporation, the cast mixed polymer dope is immersed in a coagulating solvent that has an affinity for the solvent and is a non-solvent for at least hydrophobic polymers, and the solvent is extracted from the polymer dope. This is a method for producing a hydrophilic porous membrane, in which the mixed polymer dope is gelled by extraction and removal, the gelled product is taken out of the coagulation solvent, and the remaining solvent and coagulation solvent are removed by evaporation.

The present invention further provides a method for producing a hydrophilic porous membrane in which the coagulating solvent is a non-solvent for both hydrophilic and water-insoluble polymers and hydrophobic polymers. The present invention also provides a hydrophilic porous polymer in which the hydrophilic and water-insoluble polymer is a vinyl alcohol-vinyl acetate copolymer, and the hydrophobic polymer is a vinylidene fluoride homopolymer or a copolymer of vinylidene fluoride and other monomers. This figure shows a method for producing a quality membrane. The present invention further provides a method for producing a hydrophilic porous membrane in which the solvent is a mixture of acetone and dimethylformamide or a mixture of acetone and dimethylformamide to which alcohol, glycerin, or water is added. The present invention generally provides a method for producing a hydrophilic porous membrane in which the pseudosolid solvent is water, an alkyl fluoride, a water-alcohol mixture, or an alkyl fluoride-alcohol mixture.

In other words, the hydrophilic and water-insoluble polymer and the hydrophobic polymer are dissolved in a common solvent, have an affinity for the solvent, and have a vapor partial pressure lower than that of the solvent; After casting a mixed polymer dope comprising a coagulating solvent that is a non-solvent for at least a hydrophobic polymer onto a substrate, the solvent and coagulating solvent are evaporated into the cast mixed polymer dope. The mixed polymer dope is gelled in the presence of the coagulating solvent by evaporating the solvent before the coagulating solvent due to the vapor partial pressure difference, and then the solvent remaining in the gelled product and the coagulating solvent are completely removed. This is achieved by a method for producing a hydrophilic porous membrane, which is characterized in that it is removed by evaporation.

The present invention also provides a method for producing a hydrophilic porous membrane in which the coagulating solvent is a non-solvent for both hydrophilic and water-insoluble polymers and hydrophobic polymers. The present invention also provides a hydrophilic porous polymer in which the hydrophilic and water-insoluble polymer is a vinyl alcohol-vinyl acetate copolymer, and the hydrophobic polymer is a vinylidene fluoride homopolymer or a copolymer of vinylidene fluoride and other monomers. This figure shows a method for producing a quality membrane. The present invention further includes:
This shows a method for producing a hydrophilic porous membrane in which the solvent is a mixture of acetone and dimethylformamide or a mixture of acetone and dimethylformamide to which alcohol, glycerin, or water is added. The present invention generally provides a method for producing a hydrophilic porous membrane in which the coagulating solvent is water, an alkyl fluoride, a water-alcohol mixture, or an alkyl fluoride-alcohol mixture.

III. Detailed Description of the Invention However, the greatest feature of the present invention is that a hydrophilic and water-insoluble polymer is mixed together with a hydrophobic polymer into a polymer solution that is a raw material for producing a porous membrane. It is in the point of keeping. In this way, by simply manufacturing a porous membrane using a mixed component system of a hydrophobic polymer and a hydrophilic and water-insoluble polymer, the detailed structure of the porous membrane is not clear, but hydrophobic It has been revealed that this membrane enjoys the excellent properties of polymers such as strength and chemical resistance, and is also sufficiently hydrophilic, resulting in a porous membrane with an excellent balance between removal efficiency and mechanical strength. .

The present invention will be explained in more detail below.

The hydrophobic polymer used in the present invention may be any material as long as it can provide sufficient strength during film formation, but it is preferably a material that is excellent in other properties such as heat resistance and chemical resistance.

Examples of such hydrophobic polymers include olefin polymers such as polyethylene and polypropylene, and fluororesin polymers such as polyvinylidene fluoride and polytetrafluoroethylene. Preferably, fluororesin polymers, particularly polyvinylidene fluoride, are used. be. Examples of polyvinylidene fluoride include not only vinylidene fluoride homopolymers but also copolymers mainly composed of vinylidene fluoride with other polymers such as tetrafluoroethylene, methyl acrylate, and propylene.

On the other hand, the hydrophilic and water-insoluble polymer used in the present invention has the same solvent as the hydrophobic polymer. Therefore, various hydrophilic and water-insoluble polymers can be considered depending on the type of hydrophobic polymer used. For example, when the hydrophobic polymer is polyvinylidene fluoride, vinyl alcohol-vinyl acetate copolymer, -
Random and block copolymers of vinyl pyrrolidone such as poly2-hydroxyethyl methacrylate, vinyl acetate-vinyl pyrrolidone copolymer, polyethylene glycol block copolymers such as polymethyl methacrylate-polyethylene glycol block copolymer, polyethylene glycol There are segmented polyurethanes with soft segments, blocks of hydrophilic amino acids and hydrophobic amino acids, random polyamino acids, etc. Among these, vinyl alcohol-vinyl acetate copolymer is most preferred because it shows good affinity with polyvinylidene fluoride.

Such vinyl alcohol-vinyl acetate copolymer is
Obtained by partial saponification of polyvinyl acetate according to a conventional method, with a degree of saponification of 15 to 60 mol%, preferably 24 to 45.
% by mole, and the degree of polymerization is about 10 to 1000, preferably about 30 to 200.

Such a hydrophilic and water-insoluble polymer is contained in a weight ratio of 10 to 50%, preferably 20 to 30%, based on the hydrophobic polymer. That is, if it is less than 10%, the porous membrane may not exhibit sufficient hydrophilicity, while if it exceeds 50%, the physical properties such as strength and chemical resistance of the porous membrane may deteriorate. This is because there is.

The hydrophilic porous membrane of the present invention is produced by using a hydrophobic polymer as described above and a hydrophilic and water-insoluble polymer by making slight changes to a conventional method for producing a hydrophobic polymer porous membrane. can be done.

That is, first, the hydrophobic polymer and the hydrophilic water-insoluble polymer are dissolved in a common solvent. For example, when the hydrophobic polymer is polyvinylidene fluoride and the hydrophilic and water-insoluble polymer is vinyl alcohol-vinyl acetate copolymer, acetone, methyl ethyl ketone, diethyl ketone, methyl propyl ketone, methyl butyl ketone, methyl isopropyl ketone , ketones such as cyclohexanone, quick-drying solvents such as ethers such as tetrahydrofuran and 1,4-dioxane, dimethylformamide, dimethylacetamide, diethylacetamide,
Slow-drying solvents such as N-methyl-2-pyrrolidone, hexamethylphosphoramide, tetramethylurea, dimethyl sulfoxide, etc. may be used, but desirably,
As shown in No. 126,572 and JP-A-52-154,862, when a mixture of a fast-drying solvent and a slow-drying solvent with different vapor partial pressures is used as a solvent, the mechanical strength of the resulting porous membrane is increased. It is more desirable because it can be expected to have a positive effect. When the solvent is a mixture of quick-drying and slow-drying solvents, the weight ratio of the quick-drying solvent to the slow-drying solvent is 50.
: 50-95:5, preferably 70:30-80:
A mixed solvent having a molecular weight of 20 is desirable. Among the above-mentioned quick-drying solvents and slow-drying solvents, a preferred combination is a combination of acetone, methyl ethyl ketone, or tetrahydrofuran as a quick-drying solvent and dimethylformamide, dimethylacetamide, or methyl sulfoxide as a slow-drying solvent, most preferably acetone. and dimethylformamide. Furthermore, in these solvents, there is another compound that is miscible with the solvent and does not show solubility in hydrophobic polymers, but shows solubility in hydrophilic and water-insoluble polymers. The solvent may be contained to a certain extent, for example, about 0 to 30% by weight, and the hydrophilic and water-insoluble polymer can be better dissolved within the range where the hydrophobic polymer does not cause phase separation.

The hydrophobic polymer and the hydrophilic water-insoluble polymer are dissolved in such a common solvent to form a uniform mixed polymer dope, preferably with a polymer concentration of 15 to 25% by weight.

Next, this mixed polymer dope is cast onto a substrate with a smooth surface such as a glass plate.

Next, the solvent is removed from the mixed polymer dope cast on the substrate, and the composition is changed to cause phase separation of the dissolved resin, thereby gelling the mixed polymer dope. Generally, in order to form a membrane with a porous structure, it is necessary to have a non-solvent miscible with the solvent present during gelation in order to prevent agglomeration of the precipitated resin, as is well known. However, in the production method of the present invention, the coagulating solvent that is present during gelation does not show solubility in hydrophobic polymers. The polymer does not necessarily have to be a non-solvent, and may be soluble to some extent. That is, the hydrophobic polymer of the mixed polymer dope gels first to form a porous structure that becomes the skeleton, and then the solvent and non-solvent are removed and the hydrophilic and water-insoluble polymer gels to form the porous structure. This is because it has been found that even if it adheres to the structure, the film maintains its porous structure and exhibits hydrophilic properties. However, if the coagulation solvent is hydrophilic and exhibits too good solubility for water-insoluble polymers, there is a risk that it will not be possible to form a porous structure in the dry method described below; The wet method described below is not preferred because there is a risk that the hydrophilic and water-insoluble polymer will diffuse out of the yarn from the mixed polymer dope, making it impossible to obtain sufficient hydrophilicity.

Examples of such a coagulating solvent include water, trichlorofluoromethane (Freon ■11), dichlorodifluoromethane (Freon■
12), Tetrafluoromethane (Freon ■14), 1
．． Fluorinated alkyls such as 2-dichloro-1,1,2,2-tetrafluoroethane (Freo E 114 > and octafluorocyclobutane (Freon ■C318),
Alcohols having 1 to 8 carbon atoms such as methanol, ethanol, propyl alcohol, isopropyl alcohol, butyl alcohol, isobutyl alcohol, SeC-butyl alcohol, tert-butyl alcohol, pentyl alcohol, hexyl alcohol, peptyl alcohol, and octyl alcohol, and these Among them, water, alkyl fluoride, a water-alcohol mixture containing water as a main component, and a fluorinated alkyl-alcohol mixture containing alkyl fluoride as a main component are preferred.

There are two methods for making the coagulating solvent present during gelation of the mixed polymer dope. That is, one method is to cast a mixed polymer dope onto a substrate as described above, evaporate a portion of the solvent, and then solidify the mixed polymer dope cast onto the substrate into the solvent-miscible dope. The other is a wet method in which the mixed polymer dope is brought into contact with a coagulating solvent (for example, by immersion in the coagulating solvent bath), the solvent is replaced with the coagulating solvent from the mixed polymer dope, and the polymer is extracted and removed to form a gel. A dry method in which a coagulating solvent is added to the mixed polymer dope in advance, the mixed polymer dope is cast onto a substrate as described above, and then the solvent is evaporated and gelled in the atmosphere before the coagulating solvent. It is the law.

When obtaining a porous membrane by a dry process, the coagulating solvent used is required to have a vapor partial pressure lower than at least one of the solvents used, in addition to the above requirements. In other words, if the coagulating solvent added to the mixed polymer dope has a higher vapor partial pressure than the solvent, it will be removed before the solvent during the evaporation process after casting, and the coagulation solvent will be removed during gelation. This is because the resulting film does not have a porous structure since it is no longer present in the mixed polymer dope.

After gelling the mixed polymer dope and forming a porous structure in this way, the coagulating solvent and residual solvent present in the gelled product are completely evaporated off, and the porous film is peeled off from the substrate to produce a product. get.

The hydrophilic porous membrane of the present invention, which can be obtained as described above, is composed of a mixed component system of a hydrophilic and water-insoluble polymer and a hydrophobic polymer, and its detailed structure is not clear. However, if a polymer with excellent physical properties such as polyvinylidene fluoride is used as the hydrophobic polymer, the hydrophilic porous membrane can enjoy the excellent physical properties of the hydrophobic polymer. It is also possible to adjust the physical properties by combining them. On the other hand, the hydrophilicity of the hydrophilic porous membrane can be reliably imparted to the membrane provided by the hydrophilic and water-insoluble polymer.

Such hydrophilic porous membranes usually have a thickness of 30 to 300μ.
m, preferably 50 to 150 μm, average pore diameter 0.1 to
The thickness is adjusted to 1.0 μm, preferably 0.2 to 0.6 μm.

Furthermore, the hydrophilic porous membrane of the present invention is water-insoluble since it is composed of a mixed component system of a hydrophilic and water-insoluble polymer and a hydrophobic polymer, but it is roughly water-insoluble. To ensure reliability, it is also possible to crosslink using dialdehyde, diisocyanate, etc. after film formation.

The hydrophilic porous membrane of the present invention is used in various fields due to its excellent water permeability, filtration efficiency, and mechanical strength, but its main applications include final filters for medicinal solutions, infusions, pharmaceutical filters, artificial These include membranes for artificial organs such as kidneys and plasma separation.

Next, the specific action of the hydrophilic porous membrane of the present invention will be explained using an example of an infusion final filter.

As shown in FIG. 1, a final filter 4 incorporating the hydrophilic porous membrane 1 of the present invention is sterilized and attached midway through an infusion tube 3 communicating with an infusion bag 2.

The infusion solution is dripped from the infusion bag 2 through the infusion tube 3 into the final filter 4. Fungi, bacteria, particulates, etc. mixed into the infusion are removed by the final filter 4.
Only the normalized infusion fluid captured by the hydrophilic porous membrane 1 passes through the final filter 4, passes through the infusion tube 3, and is sent from the injection needle 5 into the vein of the patient 11. Therefore, complications caused by fungi, bacteria, particulates, etc. mixed into the infusion are prevented.

Hereinafter, the present invention will be explained in more detail with reference to Examples.

Example 1 Vinyl alcohol-vinyl acetate copolymer (SMR-8O
L, manufactured by Shin-Etsu Chemical Co., Ltd.) 5.4% by weight and polyvinylidene fluoride (KVnar 301 F manufactured by Mitsubishi Yuka Co., Ltd.) 12.6% by weight with 61.5% by weight of acetone and 2.
It was heated and dissolved in 0.5% by weight dimethylformamide (DMF), allowed to cool to room temperature, and then cast onto a glass plate with a thickness of 500 μm and immersed in a bath. After 3 minutes, it was taken out and dried at room temperature. Thereafter, it was peeled off from the glass plate to obtain a porous membrane.

When immersed in water, this membrane completely wetted and exhibited sufficient hydrophilicity. When a suspension of polystyrene latex having a diameter of 0.46 μm was permeated through this membrane, a removal rate of 95% or more was obtained. Furthermore, the water permeability and porosity of the obtained hydrophilic porous membrane were measured.

The results are shown in Table 1. The water permeability is 52cmHg (1
The amount of water permeated at a differential pressure of 0 psi) was measured and expressed as volume (d) per filtration area of 1 a/l and per minute of permeation time.

Example 2 Vinyl alcohol-vinyl acetate copolymer (SMR-8O
L, manufactured by Shin-Etsu Chemical Co., Ltd.) 4.5% by weight, polyvinylidene fluoride (Kynar 301 F manufactured by Mitsubishi Yuka Co., Ltd.) 9.0% by weight, and polymethyl methacrylate (PR).
ARPET GO-1, manufactured by Kyowa Gas Chemical Co., Ltd.)4.
5@wt% to 36.9wt% acetone and 36.9wt%
of dimethylformamide and 8.2% by weight of isopropyl alcohol. After cooling to room temperature, 500μ
Cast on a glass plate with a thickness of 1.
It was immersed in 1.2-trichloro-1,2,2-trifluoroethane (Freon 113, manufactured by Daikin Industries, Ltd.). After 3 minutes, it was taken out and dried at air temperature. It was peeled off from the glass plate and the porous membrane was removed. When immersed in water, this membrane was completely wetted and showed sufficient hydrophilic properties.Also, when a suspension of polystyrene latex with a diameter of 0.46 μm was permeated through this membrane, a removal rate of over 95% was obtained. The water permeability and porosity were measured roughly in the same manner as in Example 1. The results are shown in Table 1.

Comparative Examples 1 to 2 Water permeability and porosity were measured in the same manner as in Example 1 for a nitrocellulose membrane (Comparative Example 1) and a cellulose mixed ester membrane (Comparative Example 2), which are commercially available as 0.45μ blade filters. Measured °. The results are shown in Table 1.

Basket 15 Water permeability Porosity (d/m1n-ci, 'c> (%) Example 1
30.6 72.4 Example 2
36.9 74.8 Comparative Example 1 13.
9 76.6 Comparative Example 2 19,6
76.41V, Specific Effects of the Invention As described above, the present invention provides a mixture of a hydrophilic and water-insoluble polymer and a hydrophobic polymer having a common solvent with the hydrophilic and water-insoluble polymer. Since it is a hydrophilic porous membrane characterized by being composed of a component system, it is made hydrophilic and has high water permeability while enjoying the excellent physical properties of hydrophobic polymers such as strength, chemical resistance, and heat resistance. This porous membrane is suitable for use as ultrafiltration membranes and reverse osmosis membranes. In particular, when the hydrophilic and water-insoluble polymer is a vinyl alcohol-vinyl acetate copolymer, and the hydrophobic polymer is polyvinylidene fluoride, a high It becomes a strong hydrophilic porous membrane and can be used in a wide range of fields where conventional hydrophilic porous membranes have not been applicable.

The present invention also provides a mixed polymer dope in which a hydrophilic and water-insoluble polymer and a hydrophobic polymer are dissolved in a common solvent, and after casting the polymer dope on a substrate, The above-cast mixed polymer dope is brought into contact with a coagulating solvent that has properties and is a non-solvent for at least hydrophobic polymers, and the solvent is removed from the polymer dope to form a gel. Since this is a method for producing a hydrophilic porous membrane characterized by removing the coagulating solvent from the gelled product, it is possible to obtain an excellent hydrophilic porous membrane that has an excellent balance between water permeability and removal efficiency and has high strength. This is because the production method of the present invention uses a hydrophilic and water-insoluble polymer and a hydrophobic polymer in a common solvent. A mixed polymer dope is prepared by dissolving the polymer, the polymer dope is cast onto a substrate, a portion of the solvent is evaporated, and then a polymer having an affinity with the solvent and at least hydrophobic is cast. The above cast mixed polymer dope is immersed in a coagulating solvent that serves as a non-solvent, and the solvent is extracted and removed from the polymer dope to gel the mixed polymer dope, and then the gelled product is soaked in a coagulating solvent. The hydrophilic porous membrane of the present invention can be easily produced by removing the remaining solvent and coagulating solvent by evaporation.

In general, the coagulating solvent is a non-solvent for both the hydrophilic and water-insoluble polymer and the hydrophobic polymer, and the hydrophilic and water-insoluble polymer is a vinyl alcohol-
It is a vinyl acetate copolymer, and the hydrophobic polymer is a vinylidene fluoride homopolymer or a copolymer of vinylidene fluoride and other monomers, and the solvent is a mixture of acetone and dimethylformamide or a mixture of acetone and dimethylformamide with alcohol, When glycerin or water is added, and when the coagulating solvent is water, alkyl fluoride, a water-alcohol mixture, or an alkyl fluoride-alcohol mixture, it has better physical properties as a hydrophilic porous membrane. Moreover, it becomes easier to produce products that are reliably hydrophilized.

Broadly speaking, the present invention provides a method in which a hydrophilic and water-insoluble polymer and a hydrophobic polymer are dissolved in a common solvent, have an affinity for the solvent, and have a vapor partial pressure lower than that of the solvent. and a mixed polymer dope comprising a coagulating solvent that is a non-solvent for at least a hydrophobic polymer,
After casting on a substrate, the solvent and coagulation solvent are evaporated, and the solvent is evaporated and removed from the casted mixed polymer dope before the coagulation solvent due to the vapor partial pressure difference, so that the mixed polymer dope is coagulated. The method for producing a hydrophilic porous membrane is characterized by gelling it in the presence of a solvent and then completely evaporating the solvent and coagulating solvent remaining in the gelled product, so that it has good water permeability. An excellent hydrophilic porous membrane having an excellent balance between removal efficiency and removal efficiency and high strength can be easily formed without requiring any complicated post-treatment.

Furthermore, the coagulating solvent is a non-solvent for both the hydrophilic and water-insoluble polymer and the hydrophobic polymer, and the hydrophilic and water-insoluble polymer is
It is a vinyl acetate copolymer, and the hydrophobic polymer is a vinylidene fluoride homopolymer or a copolymer of vinylidene fluoride and other monomers, and the solvent is a mixture of acetone and dimethylformamide or a mixture of acetone and dimethylformamide with alcohol or glycerin. Or, when the coagulation solvent is water, alkyl fluoride, a water-alcohol mixture, or an alkyl fluoride-alcohol mixture, it has better physical properties as a hydrophilic porous membrane. It also makes it easier to produce products that are reliably hydrophilized.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing how a final filter for infusion using the hydrophilic porous membrane of the present invention is used. 1...Hydrophilic porous membrane, 4...Final filter.

Claims (13)

[Claims] (1) A hydrophilic porous membrane characterized by comprising a mixed component system of a hydrophilic and water-insoluble polymer and a hydrophobic polymer having a common solvent with the hydrophilic and water-insoluble polymer. (2) The hydrophilic and water-insoluble polymer is a vinyl alcohol-vinyl acetate copolymer, and the hydrophobic polymer is a vinylidene fluoride homopolymer or a copolymer of vinylidene fluoride and another monomer. The hydrophilic porous membrane according to scope 1. (3) Create a mixed polymer dope in which a hydrophilic and water-insoluble polymer and a hydrophobic polymer are dissolved in a common solvent, and after casting the polymer dope on a substrate, determine the affinity with the solvent. The above cast mixed polymer dope is brought into contact with a coagulating solvent which is a non-solvent for at least a hydrophobic polymer, and the solvent is removed from the polymer dope to gel the mixed polymer dope. . A method for producing a hydrophilic porous membrane, characterized in that a coagulating solvent is then removed from the gelled product. (4) A mixed polymer dope is prepared by dissolving a hydrophilic and water-insoluble polymer and a hydrophobic polymer in a common solvent, the polymer dope is cast onto a substrate, and a part of the solvent is evaporated. Afterwards, the cast mixed polymer dope is immersed in a coagulating solvent that has an affinity for the solvent and is a non-solvent for at least hydrophobic polymers, and the solvent is extracted from the polymer dope. The hydrophilic porous material according to claim 3, wherein after the mixed polymer dope is gelled, the gelled product is taken out of the coagulation solvent and the remaining solvent and coagulation solvent are removed by evaporation. Membrane manufacturing method. (5) The method for producing a hydrophilic porous membrane according to claim 3 or 4, wherein the coagulating solvent is a non-solvent for both a hydrophilic and water-insoluble polymer and a hydrophobic polymer. . (6) The hydrophilic and water-insoluble polymer is a vinyl alcohol-vinyl acetate copolymer, and the hydrophobic polymer is a vinylidene fluoride homopolymer or a copolymer of vinylidene fluoride and another monomer. The method for producing a hydrophilic porous membrane according to any one of items 3 to 5. (7) The method for producing a hydrophilic porous membrane according to claim 6, wherein the solvent is a mixture of acetone and dimethylformamide or a mixture of acetone and dimethylformamide to which alcohol, glycerin, or water is added. (8) The method for producing a hydrophilic porous membrane according to claim 6 or 7, wherein the coagulating solvent is water, an alkyl fluoride, a water-alcohol mixture, or an alkyl fluoride-alcohol mixture. (9) A hydrophilic and water-insoluble polymer and a hydrophobic polymer are dissolved in a common solvent, have an affinity for the solvent, have a lower vapor partial pressure than the solvent, and are at least hydrophobic. After casting a mixed polymer dope containing a coagulating solvent that is a non-solvent for the polymer on a substrate, the solvent and coagulating solvent are evaporated to remove vapor from the cast mixed polymer dope. The mixed polymer dope is gelled in the presence of the coagulating solvent by evaporating the solvent before the coagulating solvent due to the pressure difference, and then the solvent remaining in the gelled product and the coagulating solvent are completely evaporated and removed. A method for producing a hydrophilic porous membrane, characterized by: (10) The method for producing a hydrophilic porous membrane according to claim 9, wherein the coagulation solvent is a non-solvent for both a hydrophilic and water-insoluble polymer and a hydrophobic polymer. (11) The hydrophilic and water-insoluble polymer is a vinyl alcohol-vinyl acetate copolymer, and the hydrophobic polymer is a vinylidene fluoride homopolymer or a copolymer of vinylidene fluoride and another monomer. The method for producing a hydrophilic porous membrane according to item 9 or 10. (12) The method for producing a hydrophilic porous membrane according to claim 11, wherein the solvent is a mixture of acetone and dimethylformamide or a mixture of acetone and dimethylformamide to which alcohol, glycerin, or water is added. (13) The method for producing a hydrophilic porous membrane according to claim 11 or 12, wherein the coagulating solvent is water, an alkyl fluoride, a water-alcohol mixture, or an alkyl fluoride-alcohol mixture.