JPH0884916A - Complex separation membrane - Google Patents

Abstract

PURPOSE: To provide a complex separation membrane which is used mainly in permeation-vaporization method and the separation performance of which is not deteriorated even when operated at high temperatures or for a long time. CONSTITUTION: A complex separation membrane is composed of an asymmetric membrane and a protective layer which is formed on the close layer of the asymmetric membrane. The asymmetric membrane is made by a method in which pores in the close layer of a micro-porous asymmetric membrane are filled with a polymer which is different from the raw material of the micro- porous asymmetric membrane and the raw material of the protective layer. The micro-porous asymmetric membrane is made substantially from a polymer which can separate a liquid mixture. The protective layer is made from a polymer which is soluble in a mixture to be separated in the liquid mixture or in at least one component of the mixture and is crosslinked so that the rate of dimensional change by the component is 5-100%.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a composite separation membrane mainly used for separating a liquid mixture by a pervaporation method (pervaporation method).

[0002]

2. Description of the Related Art In industry, liquid-liquid separation is often required, and separation methods such as a distillation method, a freezing method, a dialysis method and a reverse osmosis method are used properly according to the use conditions. However, the separation of substances that form an azeotrope, substances with close boiling points, etc.
These ordinary methods are technically extremely difficult, and since they have problems such as consuming a large amount of energy and requiring equipment such as a distillation column having an extremely large number of plates, they are not always suitable. .

For the separation of such a mixture, for example, the separation of water from a liquid mixture, the pervaporation method is suitable, and in recent years, there has been a demand from the viewpoint of energy, and the research and development of the separation by the pervaporation method are performed. Is being actively conducted. In this pervaporation method as well as in other membrane separation methods such as gas mixtures, a high balance of selective permeability is required for the target liquid mixture as a raw material.

Regarding the separation membrane used in the pervaporation method, the materials used in the separation membrane are important not only in terms of heat resistance, chemical resistance, mechanical strength, etc., but especially in durability as well as the initial separation performance. Therefore, there is a demand for materials with high overall performance while paying due consideration to these points. On the other hand, in the actual use of the membrane, the film thickness of the separation functional layer needs to be sufficiently thin, and the thinning of the separation functional layer and the mechanical strength are achieved at the same time due to asymmetry due to wet film formation.

[0005]

Conventionally, permeation vaporization membranes have been developed in view of such demands, and for example, a method for separating a liquid mixture using a polyimide or polyamideimide membrane having excellent heat resistance is a particular feature. Kaisho 63-27
No. 0506. However, this product has insufficient separation performance as a practical membrane.

Further, a method for separating a liquid mixture using polyvinyl alcohol is disclosed in JP-A-52-47579, JP-A-47-10549, JP-A-58-40103, and JP-A-58-40104. JP-A-58-5
8105, JP-A-59-109204, JP-A-2-6823, and JP-A-4-256427.
No. 515, and a composite separation membrane in which a polyvinyl alcohol thin film is provided on a polyimide microporous membrane.
No. 1190. However, further improvements in permeation rate, separation performance, and durability, especially at high temperatures, are desired.

As mentioned above, it is desirable that the separation membrane has high permeability. For that purpose, it is necessary to make the separation layer, which essentially exhibits the separation function, extremely thin. However, along with this, the strength of the separation functional layer is significantly reduced. Therefore, attempts have been made to prepare a composite membrane in which a separation functional layer is coated on a microporous membrane having mechanical strength. For example, U.S. Pat. No. 4,755,299 discloses a pervaporation membrane in which a separation functional layer of crosslinked polyvinyl alcohol is combined on a polysulfone or polyacrylonitrile microporous membrane.

On the other hand, in gas separation membranes, a method of forming an asymmetric membrane structure is generally widely used. This is a membrane in which a dense separation function layer is provided on the very surface layer by a method such as a wet membrane formation, and the pore structure has a pore diameter that gradually increases toward the inside of the membrane, while maintaining the membrane strength. It is excellent in that the separation functional layer can be easily thinned. However, as the separation function layer is made thinner, the probability of occurrence of film defects is significantly increased. On the other hand, in the gas separation membrane, defects are repaired by applying a material having a higher permeation rate than the separation functional material (for example, US Pat. No. 42).
30463).

However, when a membrane having a non-porous layer formed on these asymmetric membranes is applied to pervaporation separation, the simple performance of the coating causes some initial performance, but the separation performance at high temperature or for a long time of operation. Occurs. There are various possible causes for this phenomenon, but the present inventors have found that the high separation performance of the composite membrane described above is due to the effect of blocking defects. Focusing on (adhesion between the membrane and the non-porous layer), it was found that this is involved in the deterioration of the separation performance.

That is, the adhesive force between the asymmetric membrane and the non-porous layer is considered to decrease with time due to the contact with the liquid to be separated, and the heat history and the stoppage of the device due to the operating conditions.
It is estimated that it is strongly affected by the drying and swelling cycles associated with operation. From the viewpoint of the blocking effect, it is considered that the decrease in the adhesive force causes a phenomenon in which the repair of the film defect is incomplete, which leads to the decrease in the separation performance.
From the viewpoint of supporting the non-porous separation layer with the microporous support layer, the decrease in adhesive force causes peeling due to the difference in expansion coefficient due to temperature or swelling of the materials forming the two layers, and in the worst case, the adhesion / peeling portion There is a high possibility that the film may be broken due to the stress difference between the two or the stress difference at the sealing portion at the film end.

On the contrary, Japanese Patent Application Laid-Open No. 6-114245 discloses a method in which a polymer is filled only in the microporous portion of the surface of the separation active layer of the asymmetric membrane to repair only the defects. There is. However, since the permeation amount of the separation membrane is generally inversely proportional to the thickness of the separation active layer, it is extremely thin and is usually 1 μm or less. Only by filling the polymer into the microporous portion of such a thin film layer, although the separation performance of the separation membrane alone is exhibited, vibration, liquid pulsation, liquid vibration during the process or operation of modularizing this membrane for practical use There is a high possibility of physical damage due to foreign matter. Further, by cross-linking the filled polymer, it is possible to reduce the elution of the polymer into the liquid to be separated, but in the long term, the elution of a trace amount of the elution component deteriorates the membrane performance.

[0012]

The inventors of the present invention have made extensive studies in view of the above-mentioned problems, and as a result, have found that the polymer asymmetric microporous membrane which essentially contributes to the development of the permeation / separation performance. By filling the porous part with a high molecular weight polymer, defects in the separation function layer (dense layer) of the membrane are blocked and repaired, and the original permeation and separation performance of the membrane material is maintained at an extremely thin separation function layer thickness. We have found that it is possible to achieve.

At the same time, by forming a protective layer having certain specific physical properties on the composite separation membrane, the separation functional layer is prevented from being destroyed by external factors such as physical impact during the manufacturing process of the membrane or the operation of the separation system. It has been found that since it becomes possible to reduce the elution of a trace amount of the elution component from the membrane during long-term operation, it is possible to exhibit extremely stable permeation / separation performance.

That is, the gist of the present invention is a composite separation membrane composed of an asymmetric membrane and a protective layer provided on a dense layer of the asymmetric membrane, which is characterized by the following (a) to (c): Exists in a composite separation membrane having (A) The asymmetric membrane has pores in the dense layer of the microporous asymmetric membrane,
It should be an asymmetric membrane filled with a high molecular polymer different from the material of the microporous asymmetric membrane and the material of the protective layer. (B) The microporous asymmetric membrane is essentially made of a polymer material capable of separating a liquid mixture. (C) The protective layer is a high molecular weight polymer that is soluble in the mixture to be separated in the liquid mixture or at least one of its components, and the dimensional change rate of the components is 5% or more and 100% or less. It should be a layer composed of a high-molecular polymer that is cross-linked.

[0015]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention is described in detail below.
The membrane material having separation performance that constitutes the microporous asymmetric membrane in the present invention is not particularly limited and various materials can be used, but preferably, the water vapor permeability coefficient is 1 × 10 5.
^-7 cm ³ · cm / cm ² · sec · cmHg or more is used. From the viewpoint of heat resistance and durability which are particularly important for practical use, heat resistant polymers, particularly aromatic heat resistant polymers are preferable.

As an example, aromatic polyester, aromatic polyether, aromatic polyether ketone, aromatic polyether ether ketone, aromatic polysulfone, aromatic polyether sulfone, aromatic polyamide, aromatic polyamideimide, aromatic Examples thereof include polyimide, aromatic polyimidazole, aromatic polybenzthiazole, and the like, and particularly preferable examples include aromatic polyimide, aromatic polyamideimide, or a mixture thereof.

The aromatic polyimide is a condensation polymer of an aromatic diamine represented by the following general formula (1) and an aromatic tetracarboxylic acid anhydride represented by the general formula (2), and is represented by the general formula (3 ) It has a repeating unit represented by.

[0018]

Embedded image

(In the formulas (1) to (3), Ar and Ar '
Is an aromatic residue, preferably an aromatic residue derived from benzene, biphenyl, phenyl ether, naphthalene, bisphenylalkane and the like and substituted products thereof. ) One example of the aromatic polyimide which is particularly preferably used in the present invention is a soluble copolyimide having a repeating unit represented by the following general formula (4), more preferably 10 to 30 mol% of the repeating unit is It is an aromatic residue represented by the formula (5), and 90 to 70 mol% of the repeating units are those in which R represents a residue represented by the following formulas (6) and / or (7).

[0020]

Embedded image

This copolyimide has a composition of 3,3, as described, for example, in US Pat. No. 3,708,458.
3 ', 4,4'-benzophenone tetracarboxylic acid dianhydride and 4,4'-methylenebisphenyl isocyanate and tolylene diisocyanate (2,4 isomer, 2,
It can be easily obtained by reacting with 6 isomers or a mixture thereof in the presence of a polar solvent. At this time, another diisocyanate compound or another tetracarboxylic acid compound can be used within a range where the solubility can be maintained.

The aromatic polyamideimide used in the present invention generally includes those having a repeating unit represented by the following general formula (8). Where Ar '
Is the same as in the general formula (1). Among them, particularly preferably used aromatic polyamideimide has 10-90 mol% of repeating units, preferably 70-90 mol% of the repeating unit, and 90% of repeating units. -10 mol%, preferably 30-10 mol% is a polyamide-imide having a structure represented by the following formula (10).

[0023]

[Chemical 3]

This copolyamideimide was prepared using the procedure described in US Pat. No. 3,929,691, ie a mixture of trimellitic anhydride and isophthalic acid, 4,
It can be easily obtained by reacting 4'-methylenebisphenyl isocyanate in the presence of a polar solvent. Further, at this time, other diisocyanate compounds can be used within a range that maintains the solubility.

The solvent used for polymerization and dissolution of these aromatic polyimide and aromatic polyamideimide is not particularly limited, but preferably aprotic polar. Examples of the polar solvent include dimethylformamide, dimethylacetamide, N-methyl-2-pyrrolidone, dimethylsulfoxide, dimethylsulfone, hexamethylphosphoramide, tetramethylurea and the like.

Dimethylformamide, dimethylacetamide and N-methyl-2-pyrrolidone are preferably used, more preferably dimethylformamide. Moreover, these may be mixed and used. The logarithmic viscosity (η _inh ) of the aromatic polyimide or aromatic polyamide-imide is 0.1 dl / g or more, preferably 0.3 to 4 dl / g (in N-methyl-2-pyrrolidone,
0.5 g / dl, measured at 30 ° C.). Further, in the present invention, it is also possible to use a mixture of the aromatic polyimide and the aromatic polyamideimide.

As the method for producing the asymmetric microporous membrane made of the above-mentioned aromatic polyimide, aromatic polyamideimide or a mixture thereof, a dry film forming method, a wet film forming method, an extrusion method and the like are used. For example, when an asymmetric membrane is manufactured by a wet film-forming method, a thin film is formed from a polymer solution, coagulated in a poor solvent such as water, thoroughly washed, and then dried.

Such a microporous membrane is a known method for producing a separation membrane,
For example, JP-A-62-231017 and 63-17
It can be manufactured according to the method for manufacturing a separation membrane described in Japanese Patent No. 5116 and Japanese Patent No. 63-17115. The form of the microporous membrane of the present invention thus obtained is particularly preferably an asymmetric membrane having a dense layer on the outer surface or inner surface of the separation membrane, or both. here,
The film thickness of the microporous layer is preferably 10 to 500 μm, and particularly in the case of a hollow fiber, the outer diameter is 100 to 3000 μm and the film thickness is 10 to 5
It is preferably 00 μm.

Regarding the pore size of the dense layer of the microporous membrane, when it is too large, the micropores are insufficiently blocked, or the permeation characteristic of other high molecular weight polymers used for relatively blocking the pores, Since the separation performance is strongly exhibited, there is a possibility that the original high selective permeability of the polymer membrane material forming the microporous membrane may not be exhibited. On the other hand, if the pore size of the dense layer is too small, the filling of the other polymer or its precursor, which is involved in the blockage of the pores, becomes insufficient. There is a possibility that the original high selective permeability may not be exhibited.

Since it is difficult to directly measure the diameter of the fine pores of the dense layer, it is often indirectly determined by the permeation rate of the membrane permeation component, the separation performance and the like. A preferable pore size of the dense layer is, for example, a water vapor transmission rate of 10 ⁻⁵ cm ³ / cm ² ·.
The pore diameter is in the range of sec · cmHg or more and the permeation rate ratio of hydrogen and nitrogen gas is 2.5 or more.

The present invention is characterized in that the pores of the microporous asymmetric membrane thus obtained are filled with a high molecular polymer different from the material of the microporous asymmetric membrane and the material of the protective layer. To do. Here, as the high molecular weight polymer used for filling, polyvinyl alcohol and water-soluble polymers represented by modified products thereof such as acrylic acid and acetoacetylated products, aromatic heat-resistant resins such as polyphenylene oxide and polysulfone, and the like. The polymer solution of is used.
It is also possible to impregnate the pores with a polymerizable monomer and then polymerize the pores to close the pores. As such a polymer, a polyorganosiloxane resin can be mentioned, and a monomer giving such a polymer can be mentioned. Examples of the above include organosiloxane compounds such as γ-aminopropyltriethoxysilane and tetraethoxysilane.

Micropores can also be filled by a method such as interfacial polycondensation of a water / organic solvent system. Examples of the polymer used in such a method include polyamide resins. For example, an aqueous solution of diamine and a carbon tetrachloride solution of dicarboxylic acid chloride can be used for filling. In the present invention, the method for filling the pores of the microporous layer may be any known method, but when the surface of the dense layer other than the openings is covered with the filling polymer, permeation and separation are performed. Since it may affect the properties and durability, and the inherent high selective permeability of the polymer membrane material forming the microporous membrane may not be exhibited, it is necessary to avoid this as much as possible.

Next, a method of manufacturing the asymmetric membrane will be described. As the first method, as a method of filling the polymer in the pores, it is possible to form a composite by immersing the asymmetric microporous membrane in the polymer solution and then drying.
At this time, as described above, it is necessary to suppress the adhesion of the filled polymer to the areas other than the openings, and it is necessary to use a dilute solution. The dilute solution may be applied at a temperature of 80 ° C. to 0 ° C., more preferably 50 ° C. to 10 ° C., although there is no problem as long as the coating temperature is not higher than the boiling point of the solvent and not lower than the melting point.

As the dilute solution, a solution having a concentration of 5 wt% or less, preferably 3 wt% or less, more preferably 1 wt% or less is used. On the other hand, if the concentration is too low, the clogging of the pores will be insufficient, so a solution having a concentration of 0.01 wt% or more, more preferably 0.05 wt% or more is used. The optimum value is selected within the concentration range depending on the balance between the degree of polymerization and the molecular weight cut-off of the microporous membrane, but if it is represented by the solution viscosity as a function of concentration and temperature, it is 10 centipoise or less, preferably 5 centipoise or less. Solution is used. When the viscosity is high, the penetration of the polymer into the micropores is significantly suppressed.

Under such a dilute condition, the polymer in the solution does not adhere to the surface of the microporous film other than the pores of the dense layer due to the difference in surface free energy, or even if it adheres, the amount is very small. On the other hand, the solution is held in the open area by the capillary phenomenon. Further, swelling of the microporous membrane by the solvent of the polymer solution contributes to this retention, and a sufficient amount of the solution is retained in a wet state, and the impregnated asymmetric microporous membrane contracts during drying, thereby The ratio of the filled polymer retained in the pores is sufficiently large to close the pores, and it becomes possible to obtain a complete closed membrane. If the concentration of the dilute solution is too low, even if these effects are exerted, the blockage of the opening is insufficient, which is not preferable.

If this swelling is too large, the desired effect cannot be obtained due to the significant structural change of the microporous membrane, so that the microporous membrane cut to a length of 10 cm is immersed in the solvent alone in the longitudinal direction. It is necessary to select a solvent or to use a mixed solvent so that the change in the amount of the change is 20% or less, preferably 10% or less.

As another physical factor, for example, when the microporous membrane is immersed in a solution and then the solution adheres to the surface when the microporous membrane is taken out of the solution, portions other than the pores are covered with the polymer. Therefore, the selective transparency is affected. This can be avoided by immersing the microporous membrane in the polymer solution and then washing the solution adhering to the surface with a solvent, but it can be more easily avoided by pulling the membrane surface vertically from the solution at a low speed. . At this time, the pulling speed is 2 m / min or less, preferably 1 m / min or less, more preferably 0.5 m / min or less.

In the composite membrane prepared under the conditions optimized for these factors, a homogeneous polymer coating layer is not observed on the microporous membrane in the scanning electron microscope observation (SEM) of the fracture surface of the membrane. . The thickness of the high molecular polymer impregnated layer in the film is 0.01 to 1 μm. Second
Examples of the method include a method in which a monomer is filled in the pores and then polymerized to obtain a composite membrane. That is, after filling the monomer in the pores by immersion in the same manner as the polymer filling method described above, the filled film is taken out of the liquid, and heated,
Closure of defects can be achieved by performing in-situ polymerization by a method such as ultraviolet irradiation, energy ray irradiation, contact with a catalyst solution, or the like.

For example, in the case of γ-aminopropyltriethoxysilane, when water is used as a solvent to impregnate the pores of a microporous membrane, silanol groups are produced by hydrolysis, which is self-condensed in water and at the same time 150 Heating at about 0 ° C. closes the pores in the form of the corresponding polyorganosiloxane condensate. The concentration of the monomer solution may be 100%, but is preferably 50 wt% to
0.01 wt%, more preferably 20 wt% to 0.1 w
Used at a concentration of t%. If this concentration is too high, the monomer solution adheres to the surface of the microporous membrane so much that the inherent high selective permeability of the polymer membrane material forming the microporous membrane does not appear. On the other hand, if it is too low, the blockage of the opening becomes insufficient, which is not preferable.

The manufacturing conditions such as the temperature at the time of coating, the viscosity, and the speed at which the microporous film is vertically pulled up are the same as the conditions for filling the pores with the polymer solution. A third method is a method of achieving pore blockage in the microporous membrane of the present invention by interfacial polycondensation.

In this case, contrary to the method used in a normal reverse osmosis membrane, in which a porous membrane is impregnated with an aqueous layer and then contacted with an organic layer, after impregnating the organic layer into the microporous membrane,
By contacting with the water layer, the target composite membrane can be obtained. That is, in the interfacial polycondensation, after the polymerization starts at the interface to form the polymer thin film layer, the monomer on the water layer side permeates the thin film layer and permeates to the organic layer side, where the polymerization further proceeds. Therefore, the thin film grows toward the organic layer side. By holding this organic layer inside the microporous membrane, the polymerization mainly proceeds in the pores of the open pores of the microporous membrane, and there is no adhesion of the filled polymer on the membrane surface or an extremely small amount. It becomes local, and it becomes possible to form a composite membrane that has almost no effect on the selective permeability of the composite membrane.

The concentration of the monomer solution is 50 wt%
-0.01 wt%, preferably 20 wt% -0.1 wt
% Is used. If this concentration is too high, the monomer solution adheres to the surface of the microporous membrane so much that the inherent high selective permeability of the polymer membrane material forming the microporous membrane does not appear. On the other hand, if it is too low, the blockage of the opening becomes insufficient, which is not preferable.

The manufacturing conditions such as the temperature at the time of coating, the viscosity, and the speed at which the microporous film is pulled up vertically are the same as the conditions for filling the pores with the polymer solution. The asymmetric composite separation membrane of the present invention is further combined with formation of a specific protective layer on the composite separation layer to prevent destruction of the separation functional layer due to factors in the production of the membrane, resulting in extremely stable permeation and separation. It has become possible to develop performance.

The asymmetric membrane in which the pores of the dense layer are filled with the polymer is different from the composite membrane in which the defect of the separation functional thin film is repaired by the conventional coating, in the process of modularization or the like. Since the separation function thin film is present directly on the outermost layer, it is easily affected by physical impact or the like. Therefore, it is effective to eliminate these effects by providing a protective layer on the composite film.

This protective layer is made of a polymeric material which is soluble in at least one of the mixture to be separated and its components so as not to affect the selective permeability, and preferably the high It is formed by coating a molecular material on the composite separating layer and then crosslinking the material with a crosslinking degree within a certain range. Preferable examples of the polymer material forming the protective layer include polyvinyl alcohol and modified products thereof such as acetoacetylated products.

The degree of cross-linking of the protective layer is 5% or more and 100% or less, preferably 5 to 80, in terms of the dimensional change rate at 25 ° C. of the high molecular polymer in the substance to be separated with respect to the dissolved component.
%, More preferably 5 to 60%. If the degree of swelling is too large, the stress generated due to the difference in the degree of swelling at the interface with the microporous membrane or the sealing part when the composite membrane is modularized may become large, which may cause breakage of the separation function thin film layer. . On the contrary, if the degree of swelling is too small, the selective permeability at the time of separation is lowered.

On the other hand, the ratio of the insoluble portion of the membrane to the liquid to be separated also affects the performance of the membrane. In the present invention, the ratio of the insoluble portion in the liquid to be separated in the protective layer after crosslinking is 40% by weight or more, preferably 70% by weight or more, and there is no particular upper limit, but particularly preferably 98% by weight or less. If the proportion of the insoluble portion is too small, the membrane components will dissolve during long-term operation,
Separation performance is reduced, which is not preferable.

The degree of swelling and the proportion of the insoluble portion are adjusted by the degree of crystallinity which is physical crosslinking or the degree of chemical crosslinking using a crosslinking agent or the like. The crystallization rate can be increased by increasing the temperature of the heat treatment or prolonging the heat treatment time, whereby the swelling degree and the insolubilization rate can be adjusted.

When the crystallinity increases, the swelling degree decreases,
Moreover, since the proportion of the insoluble portion increases, the durability of the protective layer increases, and as a result, the overall separation performance of the composite membrane improves. However, if the crystallinity is too high, the permeation flow rate decreases, which is not preferable. On the other hand, the cross-linking reaction using a cross-linking agent, which is a chemical cross-linking, can easily adjust the degree of swelling and the insoluble portion ratio of the protective layer, and the durability of the composite film under severe conditions and long-term durability It is possible to improve the sex. For example, when acetoacetylated polyvinyl alcohol is used as the protective layer, the method for crosslinking the acetoacetylated polyvinyl alcohol is to include a crosslinking agent in a dilute solution of the polymer, apply the solution to a microporous membrane, and dry. Later 50-225 ° C, preferably 150-18
It can be performed by heat treatment at 0 ° C.

Examples of the crosslinking agent used in this case include, but are not limited to, amine compounds, aldehyde compounds, methylol compounds, epoxy compounds, isocyanate compounds, and polyvalent metal salts. In the case of the above method of applying a dilute solution, a polyvalent metal salt and an epoxy compound are preferable from the viewpoint of the usable time of the solution. Further, among the polyvalent metal salts, aluminum sulfate is preferable.

Further, the coated composite film can be post-crosslinked in a crosslinking agent atmosphere. For example, there is a method of crosslinking the composite film after applying the protective layer in a formaldehyde vapor atmosphere. The degree of crosslinking in the chemical crosslinking method can be adjusted by appropriately selecting the type, concentration, crosslinking temperature and crosslinking time of the crosslinking agent.

The protective layer thus obtained is a dense coating layer because it is in a dry state when modularization and systemization of ordinary separation membranes are performed, and it is a complex coating layer from various physical friction and impact. It serves to protect the separating layer. Further, under pervaporation conditions, it does not swell to a suitable degree by the liquid to be separated and does not cause permeation resistance in the separation, and at the same time, it plays a role of protecting the composite separation layer from the particulate contaminants in the liquid to be separated.

Since it is difficult to directly measure the swelling degree and the insoluble portion ratio of the protective layer of the composite membrane, the swelling degree and the insoluble portion were prepared using a homogeneous film produced under the same conditions as in the manufacturing process of the composite membrane. It can be known by measuring the ratio. The composite separation membrane of the present invention is mainly used for separating a liquid mixture by a pervaporation method. Specifically, isopropyl alcohol (hereinafter abbreviated as “IPA”), acetic acid,
It can be used for dehydration from an organic solvent such as ethanol, acetone or phenol, or separation of an organic / organic mixture such as a benzene / cyclohexane / normal hexane mixture.

[0054]

EXAMPLES Next, the present invention will be described more specifically by way of examples, but the present invention is not limited to these examples without departing from the gist thereof. In addition, the evaluation of various permeation performances in the following examples was performed by using the hollow fiber 12
Using a module obtained by binding the book with an epoxy resin, an asymmetric flat film, and a homogeneous film, the following method was used.

(1) Permeation performance test of mixed solution of water and IPA by pervaporation method (permeation test) A mixed solution of water / IPA = 13/87 (weight ratio) was set at 80 ° C. on the primary side, The secondary side was set to 2-3 mmHg, and the dehydration performance of the mixed solution was evaluated. The permeated gas is collected with liquid nitrogen, and the permeation flux (g / m ² · h) is measured gravimetrically.
r) was determined. (2) Separation coefficient α (water / IPA) is water / IP on the permeate side.
The A ratio and the water / IPA ratio on the raw material side were measured and determined by the following formula.

[0056]

[Equation 1]

(3) Swelling degree (dimensional change rate) (%) The polymer solution was cast on a glass plate, dried, and then subjected to heat treatment, crosslinking, etc. under the same conditions as when forming the composite film to obtain a homogeneous film (thickness). 20 to 30 μm). The homogeneous film is cut into a strip of 1 cm × 8 cm, placed on a Teflon plate, and immersed in a solvent at 25 ° C. for 10 minutes with one end fixed. Then, it is taken out from the solvent and the length of the long side is measured using a caliper or the like. The measured values at 7 or more points were averaged to find the increase in size, and the value expressed as a percentage of the original length was taken as the degree of swelling.

(4) Insoluble portion ratio (% by weight) The polymer solution is cast on a glass plate, dried, and then subjected to heat treatment, crosslinking, etc. under the same conditions as when forming the composite film to obtain a homogeneous film (thickness: 20 to 20). 30 μm). The homogeneous film is cut into 1 cm × 8 cm strips. 50 ml of this
Then, 40 ml of the solvent used at the time of film formation is added and the mixture is treated at 100 ° C. for 2 hours. After that, the contents are filtered off,
After drying at 100 ° C. for 24 hours, the weight of the remaining insoluble portion was expressed as a percentage of the initial weight, and the value of the insoluble portion ratio was used.

(5) Gas permeation measurement Hydrogen and nitrogen were introduced into the primary side at a pressure of ² kg / cm ² G, and the permeation amount to the secondary side was measured by a soap membrane flow meter or a water displacement method. The permeation rate for gas was measured.
Further, the hydrogen / nitrogen separation coefficient was calculated from (hydrogen permeation rate / nitrogen permeation rate).

Reference Example 1 According to the procedure described in Example 4 of US Pat. No. 3,708,458, 3,3 ', 4,4'-benzophenonetetracarboxylic dianhydride and a polymer raw material were used as a polymer raw material. On the contrary, a polymer solution obtained by polymerizing in a dimethylformamide (hereinafter abbreviated as DMF) solution containing 80 mol% of toluene diisocyanate and 20 mol% of 4,4′-diphenylmethane diisocyanate is used for hollow fiber production. Extruded in a fixed amount from the nozzle for
At the same time, a constant amount of air was flown into the hollow fiber.

Then, this was directly introduced into a coagulating bath made of water, taken up at a constant speed, and wound into a skein. After air-drying this for a whole day and night, at 100 ℃ for 30 minutes, then 300 ℃
After drying for 30 minutes and heat treatment, an asymmetric membrane hollow fiber was obtained. The gas permeation performance of this hollow fiber membrane is hydrogen permeation rate = 8.3 × 10.
^{It was −6} cm ³ / cm ² · sec · cmHg, and the hydrogen / nitrogen separation coefficient was 8.3. IPA of this asymmetric hollow fiber
Permeation vaporization separation performance of aqueous solution, water permeation flux = 930g
/ M ² · hr and the water / IPA separation ratio = 4500.

Reference Example 2 In the production of a microporous hollow fiber, acetone was flowed in the hollow fiber instead of air to coagulate in water, then treated in hot water at 100 ° C. for 5 minutes and then air dried. An asymmetric hollow fiber was produced in the same manner as in Reference Example 1 except that the drying, heat treatment were performed. The gas permeation performance of this hollow fiber is hydrogen permeation rate = 1.8 × 10 ⁻⁴ cm ³ / cm ² · sec.
-CmHg, and hydrogen / nitrogen separation coefficient = 3.1. Further, the permeation vaporization separation performance of the IPA aqueous solution of this asymmetric membrane hollow fiber is the permeation flux of water = 1950 g / m ² · hr.
And the water / IPA separation ratio = 25. This microporous hollow fiber was cut into a length of 10 cm, and water was added at 25 ° C,
When immersed in methanol and IPA, the dimensional change rates were 0.3%, 1.0% and 2.4%, respectively.

Reference Example 3 The aromatic polyimide solution prepared in Reference Example 1 was cast on a glass plate and dried at 300 ° C.
Heat treatment was performed for 30 minutes to prepare a homogeneous film. Using this homogeneous film (thickness: 35 μm), water / IPA pervaporation measurement was performed. The permeation flux of water is 35 g / m ² ·
hr (1225g · μm / m ² · hr), separation ratio is 75
It was 0000.

Reference Example 4 A 10% by weight aqueous solution of polyvinyl alcohol (trade name: KM-118, manufactured by Kuraray Co., Ltd.) was cast on a glass plate to form a film, and then 150 ° C. 1
Heat treatment was performed for an hour. This homogeneous film (thickness 20μ
Water / IPA pervaporation measurements were performed using m). The permeation flux of water is 580 g / m ² · hr (11600 g · μm
/ M ² · hr) and the separation ratio was 960. The swelling degree of this homogeneous film was 65.1%, and the insoluble portion was 78%.

<Reference Example 5> The heat treatment after the film formation is 2
A homogeneous film was obtained in the same manner as in Reference Example 4 except that the temperature was 00 ° C. for 30 minutes. This homogeneous film (21 μm thick)
Was used for water / IPA pervaporation measurement. The permeation flux of water is 395 g / m ² · hr (8295 g · μm / m ² ·
hr), the separation ratio was 1540.

Reference Example 6 Acetoacetylated polyvinyl
Alcohol (Nippon Gosei, trade name: Z-200, aceto
Acetylation rate is 0.5 mol%) and the heat treatment temperature is 15
Homogeneous fill in the same manner as in Reference Example 4 except that the temperature is 0 ° C. for 1 hour.
I got it. With this homogeneous film (thickness 22μm)
Water / IPA pervaporation measurements were performed. The permeation flux of water is 7
91 g / m ²・ Hr (17400g ・ μm / m²・ H
r), the separation ratio was 140. The expansion of this homogeneous film
The moisture content was 106% and the insoluble portion was 0%.

<Reference Example 7> Heat treatment after film formation is 1
A homogeneous film was obtained in the same manner as in Reference Example 6 except that the temperature was 50 ° C. for 9 hours. Water / IPA pervaporation measurement was performed using this homogeneous film (thickness: 25 μm). The permeation flux of water is 568 g / m ² · hr (14200 g · μm / m ²
-Hr), the separation ratio was 210. The swelling degree of this homogeneous film was 25.3%, and the insoluble portion was 68.5%.

Reference Example 8 The homogeneous film obtained in Reference Example 6 was treated in a 37 wt% formalin aqueous solution at 25 ° C. saturated steam for 48 hours, air-dried overnight, and then heat-treated at 150 ° C. for 9 hours. Water / IPA pervaporation measurement was performed using this homogeneous film (thickness: 25 μm). The permeation flux of water is 432 g / m ² · hr (10800 g · μm / m ² · h
r), the separation ratio was 175. The swelling degree of this homogeneous film was 14.2%, and the insoluble portion was 93.8%.

Reference Example 9 A homogeneous film was obtained in the same manner as in Reference Example 8 except that the heat treatment conditions before the treatment with the formalin aqueous solution were 150 ° C. and 9 hours. Water / IPA pervaporation measurement was performed using this homogeneous film (thickness: 25 μm). The permeation flux of water is 572 g / m ² · hr (14300
g · μm / m ² · hr), and the separation ratio was 223. The swelling degree of this homogeneous film is 8.6%, and the insoluble portion is 96.3.
%Met.

<Comparative Example 1> The microporous hollow fiber obtained in Reference Example 2 was mixed with 0.5% of polyvinyl alcohol (KM-118).
Immerse in a wt% aqueous solution for 1 minute, remove from the aqueous solution at a pulling rate of 0.2 m / min, and air dry overnight, then
Heat treatment was performed at 50 ° C. for 1 hour. The cross section of the obtained membrane was magnified 50,000 times with a scanning electron microscope (SEM) to confirm the thickness of the polyvinyl alcohol layer. The polyvinyl alcohol was impregnated in the microporous hollow fiber, and polyvinyl alcohol alone was used. Layer could not be confirmed. The gas permeation performance of this composite hollow fiber membrane is hydrogen permeation rate = 2.8 × 10 ⁻⁵ cm
^{It was 3} / cm ² · sec · cmHg, and the hydrogen / nitrogen separation coefficient was 233. Initial of this composite hollow fiber, and 8
Table 1 shows the pervaporation separation performance of the IPA aqueous solution after being immersed in the 7 wt% IPA aqueous solution at 90 ° C. for 38 days.

<Example 1> The polyvinyl alcohol-impregnated composite film obtained in Comparative Example 1 was further immersed in a 4 wt% aqueous solution of acetoacetylated polyvinyl alcohol (Z-200) and pulled up at 0.2 m / min. It was taken out of the aqueous solution at a speed, air-dried overnight, and then heat-treated at 150 ° C. for 9 hours. The cross section of the obtained film was magnified 50,000 times by SEM, and the film thickness of the polyvinyl alcohol layer was confirmed to be about 0.4 μm. The gas permeation performance of this composite hollow fiber membrane is hydrogen permeation rate = 7.0 × 10 ⁻⁷ cm ³ / cm ² · se.
c · cmHg, and hydrogen / nitrogen separation coefficient = 226. Initial of this composite hollow fiber, and 87 wt% IPA
Table 1 shows the pervaporation separation performance of the IPA aqueous solution after being immersed in the aqueous solution at 90 ° C. for 38 days.

Example 2 The composite hollow fiber membrane obtained in Example 1 was treated for 48 hours in a saturated steam of 37 wt% formalin aqueous solution at 25 ° C. for cross-linking, air-dried overnight, and then 150 ° C.
Heat treatment was performed for 9 hours to obtain a composite hollow fiber membrane. Tables 1 and 2 show the pervaporation separation performance of the IPA aqueous solution after the initial immersion of the composite hollow fiber in the 87 wt% IPA aqueous solution at 90 ° C. for 38 days and after the immersion in hot water at 150 ° C. for 12 days.

Example 3 Heat treatment after coating with acetoacetylated polyvinyl alcohol (Z-200) was performed at 150 ° C. for 9 hours.
A composite hollow fiber membrane was obtained in the same manner as in Example 1 except that the temperature was changed to 150 ° C. for 1 hour. The multilayer composite hollow fiber was subjected to a crosslinking treatment in the same manner as in Example 2. Tables 1 and 2 show the pervaporation separation performance of the IPA aqueous solution after the initial immersion of the composite hollow fiber in the 87 wt% IPA aqueous solution at 90 ° C. for 38 days and in the hot water of 150 ° C. for 12 days.

<Comparative Example 2> Polyvinyl alcohol (KM
-118) Comparative Example 1 except that the concentration of the aqueous solution was 5 wt%
A composite hollow fiber membrane was obtained in the same manner as. This composite hollow fiber membrane showed about 0.7μ on the polyimide microporous hollow fiber by SEM observation.
The presence of the polyvinyl alcohol single layer of m was confirmed.
In the initial stage of this composite hollow fiber, 90 wt.
After soaking at ℃ for 38 days, and in hot water at 150 ℃ 1
Tables 1 and 2 show the pervaporation separation performance of the IPA aqueous solution after being immersed for 2 days.

<Comparative Example 3> Polyvinyl alcohol (KM
A composite hollow fiber was obtained in the same manner as in Comparative Example 1 except that a 4 wt% aqueous solution of acetoacetylated polyvinyl alcohol (Z-200) was used instead of the aqueous solution of -118). SEM observation of this composite hollow fiber membrane confirmed the presence of a polyvinyl alcohol single layer of about 0.4 μm on the polyimide microporous hollow fiber. This composite hollow fiber was crosslinked in the same manner as in Example 2 to obtain a crosslinked composite hollow fiber. The initial of this composite hollow fiber, and 38 wt.
Table 1 shows the pervaporation separation performance of the IPA aqueous solution after immersion for one day.

Comparative Example 4 Heat treatment after coating with acetoacetylated polyvinyl alcohol (Z-200) was performed at 150 ° C. for 9 hours.
A multilayer composite hollow fiber was obtained in the same manner as in Example 1 except that the temperature was changed to 150 ° C. for 1 hour. The beginning of this composite hollow fiber,
Table 1 shows the pervaporation separation performance of the IPA aqueous solution after being immersed in the 87 wt% IPA aqueous solution at 90 ° C for 38 days.

[0077]

[Table 1]

[0078]

[Table 2]

Comparative Example 5 The microporous hollow fiber obtained in Reference Example 2 was mixed with 1 wt of γ-aminopropyltrimethoxysilane.
% Aqueous solution for 1 minute, removed from the aqueous solution at a pulling rate of 1 m / min, air-dried overnight, and then 150 ° C.
Heat treatment was performed for 1 hour. When the cross section of the obtained film was magnified 50,000 times with a scanning electron microscope (SEM) and the film thickness of the crosslinked silicon layer was confirmed, a coating layer of about 0.1 μm was confirmed. After immersing this composite film in water at room temperature for 1 week, the film thickness was confirmed, but it was found that the film thickness was about 0.1 μm. This composite hollow fiber was immersed in a 4 wt% aqueous solution of acetoacetylated polyvinyl alcohol (Z-200), taken out from the aqueous solution at a pulling rate of 0.2 m / min, air-dried overnight, and then heat-treated at 150 ° C. for 9 hours. Was done. Then, this composite membrane hollow fiber was treated in a 37 wt% formalin aqueous solution at 25 ° C. saturated steam for 48 hours for crosslinking, air-dried overnight, and then heat-treated at 150 ° C. for 9 hours to obtain a composite hollow fiber membrane. The cross section of the obtained multilayer composite hollow fiber is SE
When the film thickness of the polyvinyl alcohol layer was confirmed by magnifying 50,000 times with M, it was about 0.5 μm. The initial stage of this multi-layer hollow fiber and 3 wt.
Table 3 shows the pervaporation separation performance of the IPA aqueous solution after being immersed for 8 days.

Comparative Example 6 The microporous hollow fiber obtained in Reference Example 2 was mixed with 0.5 of γ-aminopropyltrimethoxysilane.
Immerse in a wt% aqueous solution for 1 minute, remove from the aqueous solution at a pulling rate of 0.2 m / min, and air dry overnight, then
Heat treatment was performed at 50 ° C. for 1 hour. The cross section of the obtained film was observed with a scanning electron microscope (SEM) at a magnification of 50,000 times, but the crosslinked silicon was impregnated in the microporous hollow fiber, and no single layer of the crosslinked silicon was confirmed. The initial of this composite hollow fiber, and 38 wt.
Table 3 shows the pervaporation separation performance of the IPA aqueous solution after immersion for a day.

Example 4 The composite hollow fiber of Comparative Example 6 was dipped in a 4 wt% aqueous solution of acetoacetylated polyvinyl alcohol (Z-200) and taken out from the aqueous solution at a pulling rate of 0.2 m / min. After air-drying overnight, 15
Heat treatment was performed at 0 ° C. for 9 hours. Then, this composite hollow fiber was placed in a 37 wt% formalin aqueous solution at 25 ° C.
After being treated for 8 hours for crosslinking, air-dried overnight and then heat-treated at 150 ° C. for 9 hours to obtain a composite hollow fiber membrane. The cross section of the obtained multi-layered composite hollow fiber was magnified 50,000 times by SEM and the film thickness of the polyvinyl alcohol layer was confirmed to be about 0.4 μm. Initial of this composite hollow fiber, and 87 wt% IP
Table 3 shows the pervaporation separation performance of the IPA aqueous solution after being immersed in the A aqueous solution at 90 ° C. for 38 days.

[0082]

[Table 3]

Comparative Example 7 The microporous hollow fiber obtained in Reference Example 1 was treated in the same manner as in Example 1 to obtain a multilayer composite hollow fiber. The permeation vaporization separation performance of the IPA aqueous solution of this asymmetric hollow fiber was a water permeation flux = 670 g / m ² · hr and a water / IPA separation ratio = 4680.

Comparative Example 8 The microporous hollow fiber obtained in Reference Example 2 was immersed in a 0.5 wt% normal hexane solution of trimellitic acid trichloride for 1 minute, and then in a 1 wt% aqueous solution of metaphenylenediamine. After soaking for 30 seconds, it was washed with water to obtain a crosslinked polyamide-filled microporous hollow fiber. The cross section of the obtained membrane was observed with a scanning electron microscope (SEM) at a magnification of 50,000 times. The crosslinked polyamide was polymerized in the fine pores of the microporous hollow fiber, and the crosslinked polyamide single layer was confirmed. Was not done. Table 4 shows the pervaporation performance of this composite multi-layer hollow fiber at the initial stage and after being immersed in an 87 wt% IPA aqueous solution at 90 ° C. for 38 days.

Example 5 The composite hollow fiber obtained in Comparative Example 8 was treated with acetoacetylated polyvinyl alcohol (Z-20).
It was immersed in a 4 wt% aqueous solution of 0), taken out from the aqueous solution at a pulling rate of 0.2 m / min, air-dried overnight, and then heat-treated at 150 ° C. for 9 hours. Then, the composite hollow fiber was treated with a 37 wt% formalin aqueous solution in a saturated steam at 25 ° C. for 48 hours to be crosslinked, and air-dried overnight.
Heat treatment was performed at 50 ° C. for 9 hours to obtain a composite hollow fiber membrane. The cross section of the obtained multilayer composite hollow fiber was magnified 50,000 times by SEM and the thickness of the polyvinyl alcohol layer was confirmed.
It was 4 μm. The initial and 87w of this composite multilayer hollow fiber
I after immersion in a t% IPA aqueous solution at 90 ° C. for 38 days
Table 4 shows the pervaporation performance of the PA aqueous solution.

[0086]

[Table 4]

<Comparative Example 9> A polysulfone ultrafiltration membrane (manufactured by Toyo Roshi Kaisha, Ltd., molecular weight cutoff 10000) was immersed in a 0.5 wt% aqueous solution of polyvinyl alcohol (KM-118) for 1 minute to form a microporous membrane at 0. It was taken out of the aqueous solution at a pulling rate of 0.2 m / min, air-dried overnight, and then 150 ° C. 1
Heat treatment was performed for an hour. The cross section of the obtained film was magnified 50,000 times with a scanning electron microscope (SEM) to confirm the film thickness of the polyvinyl alcohol layer. The polyvinyl alcohol was impregnated in the microporous film, and the polyvinyl alcohol alone was No layer could be confirmed. Initial of this composite membrane and 87 wt
IP after immersion in 90% IPA aqueous solution at 90 ° C. for 38 days
Table 5 shows the pervaporation performance of the aqueous solution A.

Example 6 The composite film of Comparative Example 9 was mixed with 4 wt% of acetoacetylated polyvinyl alcohol (Z-200).
% Aqueous solution, removed from the aqueous solution at a pulling rate of 0.2 m / min, air-dried overnight, and then heat-treated at 150 ° C. for 9 hours. This composite film is then 37wt
% Formalin aqueous solution in a saturated steam at 25 ° C. for 48 hours for crosslinking, air-drying overnight, and heat treatment at 150 ° C. for 9 hours to obtain a composite film. The cross section of the obtained multilayer composite film is SE
When the film thickness of the polyvinyl alcohol layer was confirmed by magnifying 50,000 times with M, it was about 0.5 μm. Table 5 shows the pervaporation performance of the IPA aqueous solution of the composite membrane at the initial stage and after being dipped in the 87 wt% IPA aqueous solution at 90 ° C. for 38 days.

Comparative Example 10 A polysulfone ultrafiltration membrane (manufactured by Toyo Roshi Kaisha, Ltd., cut-off molecular weight 10000) was immersed in a 0.5 wt% normal hexane solution of trimellitic acid trichloride for 1 minute, and then a polysulfone ultrafiltration membrane was applied to the microporous membrane. It was immersed in a 1 wt% aqueous solution of metaphenylenediamine for 30 seconds and then washed with water to obtain a crosslinked polyamide-filled microporous hollow fiber. The cross section of the obtained film was observed under a scanning electron microscope (SEM) at a magnification of 50,000 times. The crosslinked polyamide was polymerized in the fine pores of the microporous film, and a crosslinked polyamide single layer was confirmed. There wasn't. Table 5 shows the pervaporation performance of the IPA aqueous solution of the composite membrane at the initial stage and after being dipped in the 87 wt% IPA aqueous solution at 90 ° C. for 38 days.

Example 7 The composite film of Comparative Example 10 was prepared by adding 4 w of acetoacetylated polyvinyl alcohol (Z-200).
Immersed in a t% aqueous solution, removed from the aqueous solution at a pulling rate of 0.2 m / min, air-dried overnight, and then 150 ° C.
Was heat-treated for 9 hours. Then add this composite hollow fiber to 3
A composite hollow fiber membrane was obtained by treating in a saturated steam of a 7 wt% formalin solution at 25 ° C. for 48 hours for crosslinking, air-drying overnight, and then heat-treating at 150 ° C. for 9 hours. The cross-section of the obtained multilayer composite film was magnified 50,000 times by SEM and the film thickness of the polyvinyl alcohol layer was confirmed to be about 0.4 μm.
90% in the initial and 87 wt% IPA aqueous solution of this composite film
Table 5 shows the pervaporation performance of the IPA aqueous solution after being immersed at 38 ° C. for 38 days.

[0091]

[Table 5]

[0092]

EFFECTS OF THE INVENTION According to the present invention, by filling a high molecular weight polymer into the microporous portion of the polymer asymmetric microporous membrane which essentially contributes to the expression of permeation / separation performance, To obtain a separation membrane that exhibits permeation and separation performance, is excellent in heat resistance, chemical resistance and mechanical strength in actual use, has high permeation flux and separation performance, and is particularly excellent in durability. Became possible. Thereby, the composite separation membrane of the present invention,
Separation performance does not deteriorate even at high temperature or long time operation.

Claims (1)

[Claims] 1. A composite separation membrane comprising an asymmetric membrane and a protective layer provided on a dense layer of the asymmetric membrane, the composite separation membrane comprising:
A composite separation membrane having the following characteristics (a) to (c). (A) The asymmetric membrane has pores in the dense layer of the microporous asymmetric membrane,
It should be an asymmetric membrane filled with a high molecular polymer different from the material of the microporous asymmetric membrane and the material of the protective layer. (B) The microporous asymmetric membrane is essentially made of a polymer material capable of separating a liquid mixture. (C) The protective layer is a high molecular weight polymer that is soluble in the mixture to be separated in the liquid mixture or at least one of its components, and the dimensional change rate of the components is 5% or more and 100% or less. It should be a layer composed of a high-molecular polymer that is cross-linked.