JPH0698284B2 - Porous hollow fiber composite membrane and method for producing the same - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a porous hollow fiber composite membrane and a method for producing the same,
More specifically, a porous hollow fiber composite membrane in which a plasma polymerized membrane is deposited on the surface of a porous hollow fiber support membrane made of polyethersulfone and the plasma polymerized membrane is impregnated or coated with a silane coupling agent or a silicon primer. And a manufacturing method thereof.

In recent years, the ease of functional membrane materials used in the industrial-medical field has been increasing, and research and development have been actively conducted. For example, in the industrial field, UF, RO for desalination of seawater, production of pure water, uranium enrichment, food purification-concentration, oil-water separation, helium enrichment recovery, oxygen enrichment, methane-carbon dioxide separation, etc. Membranes and gas separation membranes have been developed, and in the medical field, artificial kidneys, artificial lungs, blood, plasma separation membranes, capsule membranes for local administration of drugs, artificial blood vessels, antithrombotic catheters, etc. have been developed. Although some of these have been put to practical use, satisfactory characteristics have not necessarily been obtained.

Those which have been used for membrane separation until now are typically cellulose-based porous membranes such as cellulose acetate and ethyl cellulose, engineering plastics porous membranes such as polysulfone, amide-based and imide-based porous membranes, and polypropylene. A porous film, a fluorine-based porous film such as ethylene tetrafluoride, or the like can be used.

Of these, ethyl cellulose is used as an oxygen-enriched membrane material because it has a higher oxygen permeability than other material groups and has a relatively high oxygen / nitrogen selective permeability.

In addition, regenerated cellulose and polypropylene porous membranes are used for artificial kidneys, and tetrafluoroethylene resin porous membranes are preferably used for applications requiring solvent resistance such as excess of organic solvent. On the other hand, polysulfone and polyimide are
Although it has relatively low gas permeability, it is used as a membrane material for hydrogen separation and helium concentration and recovery because it has excellent selective permeability for hydrogen and carbon monoxide.

Among the composite membranes, it is practical to use polysulfone hollow fibers as disclosed in JP-A-53-86684.USP 4,230,463 to obtain a composite membrane having good selectivity and permeability.

As described above, various applications have been made depending on the characteristics such as gas permeability, solvent resistance, mechanical characteristics, and processability of the material.

However, the limitation of these types of composite membranes is that they do not provide properties that exceed the permselectivity of the support material itself.

The present inventors diligently studied such problems of the prior art, and forcibly dissolve PES in an amide-based solvent while heating it at a high temperature, and form a hollow fiber in a coagulation bath while maintaining the temperature. By extrusion, coagulation, and solvent extraction, a porous hollow fiber membrane having excellent gas permeability, selective permeability, solvent resistance, heat resistance, and good mechanical strength can be obtained in a simple process. Have found that by depositing a plasma-polymerized membrane as an ultrathin layer on the surface of the hollow fiber membrane thus obtained, the selective permeability can be dramatically improved without significantly impairing the permeability. Furthermore, it was found that not only more stable selective permeability can be obtained but also improvement in selective permeability can be achieved by impregnating or coating the plasma-polymerized film with a silane coupling agent or a silicon primer. . In addition, by laminating a silane coupling agent or a silicon primer between the porous hollow fiber support membrane and the plasma polymerized membrane, the peel strength is improved, and a composite membrane with excellent practical durability is obtained. They have found the present invention.

(Structure of Invention) PES used in the present invention has a structural formula; It has a repeating unit represented by.

As the solvent for PES, N-methyl-2-pyrrolidone, dimethylformamide, dimethylacetamide, dimethylsulfoxide, 1-formylpyridine, 1-acetylpyridine and the like can be used, and these can be used alone or in a mixture thereof, but preferably an amide solvent Is selected. Dimethylformamide is particularly preferably selected.

One of the features of the present invention is that PES is formed into a porous hollow fiber membrane, and further, one or both of the outer surface and the inner surface of the hollow fiber is a dense surface, and the wall thickness is The part has pores on the sponge continuous to each surface, and finger-shaped or void-shaped pores oriented substantially in the radial direction of the hollow fiber. In order to arbitrarily form such a structure, it is preferable to use an amide solvent. The solution concentration is preferably 30 to 60% by weight, particularly 40 to 50% by weight. When obtaining a solution, it is necessary to dissolve it while heating it to room temperature or higher. At this time, care must be taken so that PES and the solvent are not decomposed and the reaction does not occur. Generally, about 100 ° C. is suitable, but it is not particularly limited.

The solution thus obtained is extruded from the outer tube of the double-tube nozzle into the coagulation bath, the temperature of the solution having to be kept below the boiling point of the solvent. When the temperature exceeds the boiling point, bumping of the solvent occurs and it becomes difficult to control the film structure. However, by controlling the solution temperature within the temperature range not higher than the boiling point of the solvent, the dense surface thickness, porosity,
It is possible to control the shape of the pores, the strength of the hollow fiber membrane, and the like.

From the inner tube of the double tube nozzle, the core liquid is allowed to flow out in order to form the hollow of the porous hollow fiber or to control the state of the inner surface. The double-tube nozzle may be immersed in the coagulation bath, or may be above the liquid surface of the coagulation bath, but when it is located above the liquid surface, a chimney or the like may be used to suppress the evaporation amount of the solvent. The state of the outer surface of the hollow fiber can be controlled by, for example, inhaling the chimney to promote evaporation.

A non-solvent miscible with the solvent is used as the coagulant. When using an amide-based solvent, water, alcohols and mixtures thereof are used. By changing the type, temperature, composition, etc. of the coagulant, the thickness of the dense surface of the porous hollow fiber membrane, the porosity, the shape of the pores, the strength of the hollow fiber membrane, etc. can be controlled. Further, the structure-physical properties of the film can be controlled by adding a solvent or an inorganic salt to the coagulant.

The core liquid is also selected from the same viewpoint as the coagulation bath.

The solidified hollow fiber is further washed with water to extract the solvent and fix the membrane structure. At this time, the hot water treatment can accelerate the extraction of the solvent and stabilize the membrane structure and characteristics.

The hollow fiber that has been subjected to solvent extraction is further dried and heat-treated using hot air or a metal roll as a heat medium. The drying temperature is preferably not higher than the boiling point of the non-solvent contained in the hollow fiber after solvent extraction. The heat treatment is performed below the heat distortion temperature of PES.

By replacing the non-solvent contained in the hollow fiber with another non-solvent before performing the dry-heat treatment, the shrinkage rate of the hollow fiber during the dry-heat treatment is changed, and as a result, the membrane properties are improved. It is also possible to control.

Examples of the polymerizable monomer used for plasma polymerization include hydrocarbon compounds such as methane, ethane, propane, ethylene, propylene, benzene, toluene, styrene, and naphthalene, allylamine, acrylonitrile, aniline, pyridine, N-methyl-2-pyrrolidone, and N-vinyl. Pyrrolidone, dimethylformamide, nitrogen-containing organic compounds such as dimethylacetamide, fluorine-containing organic compounds such as tetrafluoroethylene and hexafluoropropylene, thiophene, sulfides such as carbon disulfide, trimethylvinylsilane,
Examples thereof include organic silicon compounds such as dimethyldichlorosilane, tetramethyldisilazane and tetramethyldisiloxane. The polymerizable monomer is appropriately selected depending on the application of the porous hollow fiber composite membrane. For example, a polar monomer such as a nitrogen-containing organic compound is suitable when used for applications requiring hydrophilicity, and an organic silicon compound is preferably used for gas separation applications. Examples of the organosilicon compound include methylsilane compounds such as tetramethylsilane and dimethyldichlorosilane, alkoxysilane compounds such as dimethyldimethoxysilane and dimethyldiethoxysilane, siloxane compounds such as tetramethyldisiloxane, bis (dimethylamino) methylvinylsilane, and methyltris. Aminosilane compounds such as (dimethylamino) silane, bis (dimethylamino) dimethylsilane, bis (dimethylamino) methylsilane, bis (ethylamino) dimethylsilane, and trimethylsilyldimethylamine, hexamethyldisilazane 1,1,3,3-tetra Methyldisilazane, silazanes such as 1,1,3,3,5,5-hexamethylcyclotrisilazane, trimethylsilyl isocyanate, dimethylsilyl diisocyanate, vinylmethylsilyl diisocyanate Organic silane having at least one unsaturated bond such as silyl isocyanate compound, trimethylvinylsilane, dimethyldivinylsilane, methyltrivinylsilane, tetravinylsilane, dimethylvinylchlorosilane, aryltrimethylsilane, ethynyltrimethylsilane, dimethylphenylvinylsilane, etc. A compound can be mentioned. Among these organic silicon compounds, an organic silane compound having at least one unsaturated bond is particularly preferably used because it is easily activated in a plasma atmosphere and easily forms a plasma polymerized film having a high degree of cross-linking / branching structure. To be Among them, methyltrivinylsilane and ethynyltrimethylsilane are particularly preferably used.

The thickness of the plasma-polymerized film also varies depending on the use of the composite film, but is generally preferably 10 μm or less or 1 μm or less. It is possible to make it 10 μm or more, but if the deposition thickness is increased, cracks are generated due to the stress generated inside the plasma polymerized film,
Further, it may be peeled off from the support, resulting in lack of stability. When the composite membrane is used for gas separation or reverse osmosis, it is preferable to make it as thin as possible without causing defects and pinholes, and usually 1 μm or less, more preferably 0.3 μm or less.

Plasma polymerization is carried out by causing glow discharge by radio waves, microwaves, or direct current and introducing a polymerizable gas into the inside of a reaction vessel of a pierger type or a tube type. Specifically, the porous hollow fiber support membrane is guided to a reaction vessel under a reduced pressure of 5 torr or less, preferably 2 torr or less, and the polymerizable monomer causes glow discharge while being sent to the reaction vessel, and the plasma-polymerized membrane is a support membrane. Deposit on top.

The polymerizable monomer may be one kind, but two or more kinds of monomers are mixed or two or more kinds of monomers are sequentially introduced, or a plurality of reaction vessels are used, and another monomer is introduced into each vessel. Then, a mixed or copolymerizable or multilayer plasma polymerized film can be laminated. Also, together with the monomer, an inert gas such as He or Ar, H ₂ , N ₂ , O ₂ ,
A non-polymerizable gas such as CO may be used as a carrier gas or a monomer dilution gas.

The glow discharge conditions need to be changed depending on the monomer used, the shape of the device and the electrode, etc., but the discharge output is generally 5
~ 500W, discharge time is 10 seconds ~ 3600 seconds. If the other conditions are the same, the thickness of the plasma polymerized film is almost compared with the discharge time. If the discharge output is too low, the polymer produced will have a low molecular weight, making film formation difficult. On the other hand, if it is too high, the support and the deposits are undesirably damaged by the etching action and the heat generation action.

Not only in such an extreme example, but in plasma polymerization, the support is not a little damaged by plasma, and decomposed gas is generated. It is considered that such a phenomenon adversely affects the deposition rate of the plasma polymerized film and the characteristics of the composite film.

The PES used in the present invention is extremely excellent in plasma resistance, and the generation rate of decomposition gas during plasma polymerization is small, so that the deposition rate of the plasma polymerization film is high. Therefore, the range of conditions for plasma polymerization can be widened and the range of selection of the polymerizable monomer can be widened as compared with the case where another material is used as the support. From this fact, the control range of the film characteristics is broader, which is one of the major factors of the characteristics of the present invention.

Silane coupling agents are hydrolyzable groups such as alkoxy groups, chloro groups, acetoxy groups, alkylamino groups and propenoxy groups, and organic functional groups such as vinyl groups, epoxy groups, methacryl groups, amino groups and mercapto groups. By being laminated on the porous hollow fiber support, it is possible to improve the adhesiveness at the interface with the plasma polymerized film and improve the durability of the composite film as a whole. Further, by impregnating or coating the plasma polymerized film, it is possible to penetrate into minute cracks and low cross-link density portions and maintain high selective permeability as the entire composite film.

Further, the silicon primer has a condensate of these silane compounds as a main component and has the same effect as a silane coupling agent. Furthermore, a silane coupling agent containing an amino group as an organic functional group and a silicon primer have a high effect due to their adhesiveness to the plasma polymerized film. Specifically, γ-aminopropyltriethoxysilane, N- (β
Examples thereof include -aminoethyl) -γ-aminopropyltrimethoxysilane, N- (β-aminoethyl) -γ-aminopropylmethyldimethoxysilane, and condensates of these with epoxysilane. As a method for laminating a silane coupling agent or a silicon primer,
It is general to apply a solution diluted with an appropriate solvent by dipping and heat cure.

Hereinafter, the present invention will be further described with reference to examples.

Example 1. 50 parts by weight of PES Victrex 5200P manufactured by ICI was dissolved in 50 parts by weight of dimethylformamide while stirring at about 100 ° C. to obtain a uniform solution. While maintaining the temperature of this solution, it was extruded into a hollow shape from a double tube nozzle heated to 120 ° C, solidified in water at about 15 ° C, washed with water to complete the extraction, and dried to obtain a porous hollow fiber support. A film was obtained.

The obtained support membrane was treated with N- (β-aminoethyl) -γ-
Aminopropyltrimethoxysilane 10%, isopropanol 80%, water 10% In a uniform solution, dip coating, heat dry at 120 ℃, introduce into the reaction vessel, while sending methyltrivinylsilane into the vessel, output about 20W Plasma polymerization was performed for 3 minutes to obtain a composite film.

In addition, a silicon primer (Made by Toshiba Silicone, ME
151) was impregnated with a solution obtained by diluting 50% of t-butanol and dried at 120 ° C.

The gas permeability characteristics of the support membrane and the composite membrane are shown in Table 1.

Example 2. The hollow fiber composite membrane prepared in Example 1 was cut into 360 cm and
The books were bundled and mounted in a pressure vessel having an inner diameter of 19 mm, and the permeation characteristics of the He / N ₂ mixed gas in the module were measured. The results are shown in Table 2.

After the temperature was raised and the pressure was increased, the deterioration of the characteristics and the destruction of the film structure were not observed.

(Effect of the Invention) According to the present invention, a porous hollow fiber composite membrane having high gas permeability, high selective permeability, and excellent heat resistance, solvent resistance, and mechanical strength can be obtained. In addition, by changing the pore size of the surface of the porous hollow fiber support membrane, plasma polymerization conditions, application conditions of silane coupling agents, etc., reverse osmosis membrane, ultrapermeabilization membrane, plasma separation membrane, artificial lung, liquid membrane It is possible to apply it to etc.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Shigeru Asako 1-3-1 Shimaya, Konohana-ku, Osaka-shi, Osaka Sumitomo Electric Industries, Ltd. (56) Reference JP-A-59-6904 (JP, A) ) JP-A-57-94304 (JP, A)

Claims (17)

[Claims] 1. A structural formula; A plasma polymerized film is deposited on the outer surface of a porous hollow fiber support membrane made of polyether sulfone having a repeating unit represented by, and the plasma polymerized film is impregnated or coated with a silane coupling agent or a silicon primer. A porous hollow fiber composite membrane characterized by: 2. A porous hollow fiber according to claim 1, wherein a silane coupling agent or a silicon primer is laminated between the porous hollow fiber support membrane and the plasma polymerized membrane. Composite membrane. 3. An average pore size of 0.1 or more on either or both of the outer surface and the inner surface of the porous hollow fiber support membrane.
The porous hollow fiber composite membrane according to claim 1, characterized in that it is not more than μ, is non-porous, and has a thick portion that is continuously porous with varying pore diameters on each surface. 4. The porous hollow fiber composite membrane according to claim 1, wherein the plasma polymerized membrane is a plasma polymerized membrane mainly composed of an organic silicon compound. 5. The porous hollow fiber composite membrane according to claim 1, wherein the plasma-polymerized membrane comprises a plasma-polymerized membrane of an organic silane compound having at least one unsaturated bond. . 6. The organic silane compound, the structural _{formula; Xn-Si-Y 4 -n} n; natural number of _{1~4 X; CH 2 = CH-,} CH≡C-, CH 2 = CH-CH 2 - Y ; CH ₃ -, CH ₃ porous hollow fiber composite membrane of claims paragraph 5, wherein the represented by -CH _2. 7. The porous hollow fiber composite membrane according to claim 5, wherein the organic silane compound is methyltrivinylsilane or ethynyltrimethylsilane. 8. The porous hollow fiber composite membrane according to claim 2, wherein the silane coupling agent or the silicon primer contains an amino group. 9. A structural formula; A polyether sulfone having a repeating unit represented by After coagulation, desolvation and drying to obtain a porous hollow fiber support membrane, glow discharge is carried out while supplying a polymerizable monomer in an atmosphere of 5 torr or less to deposit a plasma polymerized membrane and then the plasma. A method for producing a porous hollow fiber composite membrane, which comprises impregnating or coating a polymer membrane with a silane coupling agent or a silicon primer. 10. The method according to claim 9, wherein a silane coupling agent or a silicon primer is laminated on the dried porous hollow fiber support membrane, and the plasma polymerized membrane is deposited after drying. A method for producing a porous hollow fiber composite membrane. 11. The method for producing a porous hollow fiber composite membrane according to claim 9, wherein the solution is extruded while being maintained at a temperature not higher than the boiling point of the amide solvent. 12. The method for producing a porous hollow fiber composite membrane according to claim 9, wherein the amide solvent is N, N-dimethylformamide. 13. The method for producing a porous hollow fiber composite membrane according to claim 9, wherein the polymerizable monomer is an organic silicon compound. 14. The method for producing a porous hollow fiber composite membrane according to claim 9, wherein the polymerizable monomer comprises an organic silane compound having at least one unsaturated bond. . 15. The organic silane compound has a structural formula; Xn—Si—Y ₄ —n n; a natural number X of 1 to 4; CH ₂ ═CH—, CH≡C—, CH ₂ ═CH—CH ₂ —Y. ; CH ₃ −, CH ₃ −CH
_The method for producing a porous hollow fiber composite membrane according to claim 14, characterized in that 16. The method for producing a porous hollow fiber composite membrane according to claim 14, wherein the organic silane compound is methyltrivinylsilane or ethynyltrimethylsilane. 17. The method for producing a porous hollow fiber composite membrane according to claim 10, wherein the silane coupling agent or the silicon primer contains an amino group.