JPH024330B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method for producing a hollow fiber selectively permeable membrane. More specifically, the present invention relates to a method for producing a hollow fiber selective permselective membrane mainly made of a substantially linear aromatic polyester. In recent years, separation methods using membranes have rapidly come into use on a practical scale from the viewpoints of resource conservation, energy conservation, and recovery of valuable materials. Examples of such membrane separation methods include desalination of seawater, concentration of valuables from process water, separation of liquid systems such as separation of plasma from blood, production of oxygen-enriched air with increased oxygen concentration from air, The usefulness of membrane separation methods has been demonstrated in each of these cases, including the separation of gaseous systems such as the recovery of helium gas. Many polymeric materials have been studied as materials for membranes used in membrane separation methods. For example, polymeric materials such as cellulose ester, olefin, polyamide, polysiloxane, and polysulfone have been proposed. Ta. It goes without saying that the properties required for materials used in membrane separation methods include excellent permeation performance, but also mechanical properties that can withstand the conditions of use, chemical stability, and thermal stability. The following characteristics are required, and it is also an important requirement that the membrane be easily manufactured at low cost. In the many membrane material technologies that have been proposed,
There was no film that could satisfy all of these properties. For example, cellulose-ester membranes used for reverse osmosis, ultrafiltration, gas separation, etc. are easy to form and have excellent permeability, but they lack chemical and thermal stability, and their range of use is limited. It had the disadvantage of being limited. Furthermore, polysulfone membranes that are often used as ultrafiltration membranes have the drawbacks of being expensive and having poor chemical stability. The present inventor has focused on aromatic polyester as a material that has the properties required for the above-mentioned permeable membrane and can be easily molded at low cost, and has repeatedly conducted research into permselective membranes using the melt molding method. Techniques for selectively permeable membranes made of aromatic polyester are disclosed in Japanese Patent Application Laid-open Nos. 49-90683 and 1972.
A wet film forming method is disclosed in Japanese Patent No. 154365.
This document discloses a method for manufacturing a selectively permeable membrane by a wet phase separation method by dissolving a linear aromatic polyester and an auxiliary polymer such as polyvinyl alcohol in hexafluoroisopropanol. It has been found that when applied to polyester such as terephthalate, only a weak and brittle film is obtained, and the excellent properties of the polyester material are lost. Furthermore, this method has the disadvantage that it is difficult to apply to production on an industrial scale because it uses a very expensive solvent. Furthermore, in this method, since the auxiliary polymer is extremely poorly compatible with the polyester, phase separation occurs and the phase structure becomes considerably large, and this tendency becomes even stronger when attempting to increase the porosity. As a result, there is also the problem that it becomes difficult to form minute pores. In addition, an organic solvent that is compatible with the thermoplastic polymer under heating conditions to form a homogeneous phase, but forms a phase separation under sufficient cooling conditions, is used to mix the organic solvent and the thermoplastic polymer under heating. A method has been proposed in which a porous membrane is obtained by forming a homogeneous solvent, then cooling the solution to phase-separate the organic solvent, and then removing the phase-separated organic solvent (Japanese Patent Laid-Open No. 53-29367). There is. However, although this publication specifically describes the use of polyolefins such as polyethylene and polypropylene, there is no specific description of the application of this method to crystalline aromatic polyesters, and there is no specific description of the application of this method to crystalline aromatic polyesters. However, there is no suitable organic solvent that does not significantly reduce the degree of polymerization of the aromatic polyester and satisfies the above requirements. Therefore, it is actually difficult to obtain a permselective membrane made of polyester by this method. Furthermore, a method of forming micropores by treating polyester fibers with alkali (Japanese Unexamined Patent Application Publication No. 1989-1999)
88318 and Japanese Patent Application Laid-open No. 101917/1983), but this method decomposes the polyester due to alkali treatment, so if you try to increase the porosity, the pore size will inevitably increase and the micro pores will be destroyed. can't get it. Selective permeation membranes are generally used in the form of hollow fiber membranes, flat membranes, and tubular membranes, but hollow fiber membranes are practical because they have a larger membrane area per unit volume of module than other membrane shapes. It has an excellent shape. As a result of intensive research into a method for easily manufacturing a hollow fiber-like permselective membrane having excellent permselectivity at a low cost without losing the original excellent properties of aromatic polyester, the inventors have found that We have discovered that the above object can be achieved by melt-mixing a specific low-molecular compound into a linear aromatic polyester, spinning it, and extracting the low-molecular compound from the resulting hollow fibers, and have arrived at the present invention. That is, the present invention provides a composition mainly consisting of 100 parts by weight of a substantially linear aromatic polyester (A) and 10 to 300 parts by weight of a low molecular compound (B) that satisfies the following conditions (1) to (4). is melt-spun to form hollow fibers, and then the hollow fibers are treated with an organic solvent (C) that dissolves the low molecular weight compound (B) but does not substantially attack the aromatic polyester (A). , relates to the permselective hollow fiber membrane obtained by extracting the low molecular compound (B) in the hollow fiber. (1) Substantially stable under the melting conditions of the aromatic polyester (A), non-reactive with the aromatic polyester (A), and compatible with the aromatic polyester (A) (2) The above-mentioned melt The aromatic polyester (A) and the low molecular weight compound (B) should not undergo phase separation even when the product is cooled and solidified. (3) The melting point should be 100°C or higher. (4) The molecular weight should be 1000 or lower. The selective permeation referred to in the invention refers to the selective separation of one or more specific components from a multi-component fluid mixture, and the fluid mixture includes a mixture of liquids or gases. The substantially linear aromatic polyester (A) used in the present invention has an aromatic dicarboxylic acid as a main acid component, and examples of the aromatic dicarboxylic acid include terephthalic acid, isophthalic acid, naphthalene dicarboxylic acid, and diphthalic acid. Examples include enyl dicarboxylic acid, diphenyl sulfone dicarboxylic acid, diphenyl ether dicarboxylic acid, diphenoxyethane dicarboxylic acid, methyl terephthalic acid, and metal isophthalic acid. Among these, terephthalic acid and isophthalic acid are particularly preferred. Glycol components include aliphatic glycols such as ethylene glycol, trimethylene glycol, tetramethylene glycol, pentamethylene glycol, hexamethylene glycol, octamethylene glycol, decamethylene glycol, etc.; fats such as 1,4-cyclohexane dimethylol, etc. Cyclic glycol; and hydroquinone, methylhydroquinone, butylhydroquinone, amylhydroquinone, resorcinol, 2,2-bis(4-hydroxyphenyl)propane [bisphenol A], 1,
Aromatic dihydroxy compounds such as 1-bis(4-hydroxyphenyl)cyclohexane [bisphenol Z], bis(4-hydroxyphenyl)ether, etc. can be used. It is also possible to use an oxycarboxylic acid component in addition to the above dicarboxylic acid component and glycol component, and examples of the oxycarboxylic acid include oxybenzoic acid, oxynaphthoic acid, and β-hydroxyethoxybenzoic acid. Furthermore, the aromatic polyester used in the present invention
In addition to the above components, (A) is a small proportion (usually 10 mol% or less based on the total acid components), such as aliphatic dicarboxylic acids such as adipic acid and sebacic acid; alicyclic acids such as hexahydroterephthalic acid, etc. It can contain dicarboxylic acids. Also, aromatic polyester
Polydicarboxylic acids such as trimellitic acid, pyromellitic acid, etc.; polyols such as glycerin, pentaerythritol, etc. may be copolymerized to the extent that (A) is substantially linear (usually 1 mol % or less). Among these aromatic polyesters, polyethylene terephthalate, polytetramethylene terephthalate, and polyhexamethylene terephthalate are preferably used, and polyethylene terephthalate is particularly preferred. The aromatic polyester (A) is produced by a method known in the art. Aromatic polyester (A) used in the present invention
The intrinsic viscosity measured at 35° C. in a mixed solvent of phenol/tetrachloroethane (weight ratio 60/40) is preferably 0.6 or more, more preferably 0.7 or more. Next, the low molecular weight compound (B) to be mixed with the aromatic polyester (A) will be explained. In the present invention, the low molecular compound (B) to be mixed with the aromatic polyester (A) is prepared under (1) melting conditions of the aromatic polyester (A), for example, the melting point of the polyester (A) + 20°C.
substantially stable and non-reactive with the aromatic polyester (A) at temperatures of
It is necessary that when mixed with (A), it does not cause phase separation and is uniformly compatible. Here, "substantially stable and non-reactive with the aromatic polyester (A)" means that it does not decompose itself, does not decompose the aromatic polyester (A), or does not decompose the aromatic polyester (A). ) means not to react. The low molecular compound (B) further contains (2) an aromatic polyester.
Even when the homogeneous melt obtained by melt-mixing (A) and the low molecular weight compound (B) is cooled and solidified, phase separation does not occur with the aromatic polyester (A), and the mixture remains uniformly compatible with the aromatic polyester (A). It is necessary that the state can be maintained.
For example, when the above-mentioned homogeneous transparent melt is cooled at a cooling rate sufficient to give an amorphous solid, a homogeneous transparent solid can be obtained, or phase separation can occur and an opaque solid can be obtained. This can be easily determined by seeing whether it gives a solid substance. Furthermore, the low molecular weight compound (B) (3) has a melting point of 100℃ or higher,
and (4) the molecular weight must be 1000 or less. When the melting point of the low molecular compound (B) is 100°C or less,
When melt-mixed with the aromatic polyester (A), it significantly lowers the secondary transition point of the aromatic polyester (A), making it difficult to handle during spinning. The low molecular compound (B) used in the present invention may be one that satisfies the above conditions (1) to (4), but in addition, from the viewpoint of preventing volatilization during melt mixing, the low molecular compound (B) has a boiling point at normal pressure.
A temperature of 250°C or higher, particularly 300°C or higher is preferably used. Such low molecular weight compounds used in the method of the present invention
(B) may be anything that satisfies the above conditions, but for example, the following formula () [Here, A ¹ is a divalent aromatic residue or a chain or cyclic aliphatic residue, which may be substituted; R ¹ is an n-valent aromatic residue or a chain or cyclic aliphatic residue. Cyclic aliphatic residues, which may be substituted; n is 1 or 2. However, the imide ring in the above formula is 5 or 6 members. ] Imide compound represented by the following formula () [Here, A ³ is a tetravalent aromatic residue, which may be substituted; R ² is a monovalent chain or cyclic aliphatic residue, which may be substituted. Good too. However, the imide rings in the above formula are 5 or 6 members. ] Examples include imide compounds represented by the following. As a compound of the above formula (), the above formula ()
A compound in which at least either A ¹ or R ¹ is an optionally substituted aromatic residue,
In particular, compounds in which A ¹ is a divalent, optionally substituted aromatic residue are preferably used. Further, as the compound of the above formula (), a compound in which R ² in the above formula () is a monovalent, optionally substituted aliphatic residue is preferably used. In the above general formula (), examples of the divalent aromatic residue representing A ¹ include 1,2-phenylene group, 1,2-, 2,3- or 1,8-naphthylene group. Examples of divalent aliphatic residues include linear alkylene groups such as ethylene or trimethylene, and cycloalkylene groups such as 1,2-cyclohexylene. These groups may be substituted with a substituent that is non-reactive with the aromatic polyester (A). Examples of such substituents include lower alkyl groups such as methyl and ethyl, lower alkoxy groups such as methoxy and ethoxy, halogen atoms such as chlorine and bromine, nitro groups, phenyl groups, phenoxy groups, and methyl groups. Good examples include cyclohexyl. The n-valent (n=1 or 2) aromatic residue representing R ¹ is, for example, a phenyl group, a naphthyl group, or a

A monovalent aromatic residue such as the group [Formula] (where Z is -O-, -SO ₂ - or -CH ₂ -), or a 1,2-phenylene group, 1,2-, 2 , 3- or 1,8-naphthylene group or formula

Mention may be made of divalent aromatic residues such as the group [formula] (where Z is -O-, -SO ₂ - or -OH ₂ -), where n-valent (n = 1 or 2) Examples of aliphatic residues include those having 1 to 1 carbon atoms, such as methyl, ethyl, butyl, hexyl, heptyl, octyl, nonyl, decyl, dodecyl, myricityl, and stearyl.
18 linear alkyl groups or 5- or 6-membered cyclic alkyl groups such as cyclohexyl or cyclopentyl, or ethylene, trimethylene, tetramethylene, hexamethylene, octamethylene,
2 or more carbon atoms such as decamethylene and dodecamethylene
12 linear alkylene groups, 1,3- or 1,4
- a cyclic alkylene group such as a cyclohexylene group,
or

Mention may be made of the group of the formula. These groups representing R ¹ may be substituted with the same substituents as described for A ¹ . In the above formula (), the tetravalent aromatic residue representing A ² is, for example,

【formula】

【formula】

【formula】

[Formula] or

A monocyclic, condensed ring or polycyclic tetravalent aromatic group represented by the formula: (Z is the same as defined above) is preferred. The monovalent chain or cyclic aliphatic residue representing R ² may be a chain alkyl group having 1 to 18 carbon atoms or a 5- or 6-membered cyclic alkyl group as exemplified for R ¹ in the above formula (). Mention may be made of alkyl groups. The groups exemplified above for A ² and R ² may be substituted with the same substituents as described for A ¹ . Examples of the imide compound represented by the above formula () include N-methyl phthalimide, N-ethylphthalimide, N-butylphthalimide,
N-ethyl-1,8-phthalimide, N-butyl-1,8-naphthalimide, etc. When n=2, N,N'-ethylenebisphthalimide, N,N'-tetramethylenebisphthalimide, etc. Tarimide, N,N'-hexamethylene bisphthalimide, N,N'-octamethylene bisphthalimide, N,N'-decamethylene bisphthalimide, N,N'-dodecamethylene bisphthalimide , N,N'-neopentylene bisphthalimide, N,N'-tetramethylene bis(1,8
-naphthalimide), N,N'-hexamethylenebis(1,8-naphthalimide), N,N'-octamethylenebis(1,8-naphthalimide),
N,N'-decamethylene bis(1,8-naphthalimide), N,N'-dodecamethylene bis(1,
8-naphthalimide), N,N'-dodecamethylene bissuccinimide, N,N'-dodecamethylene bishexahydrophthalimide, N,N'-
1,4-cyclohexylene bisphthalimide,
1-phthalimido-3-phthalimidomethyl-3,5,5-trimethylcyclohexane, 4,
4′-bisphthalimido diphenyl ether,
3,4'-bisphthalimido diphenyl ether, 3,3'-bisphthalimido diphenyl sulfone, 4,4'-bisphthalimido diphenyl sulfone, 4,4'-bisphthalimido diphenyl Examples include methane. Examples of the imide compound represented by the above formula () include N,N'-diethylpyromellitimide, N,N'-dibutylpyromellitimide, N,
N'-dihexylpyromellituimide, N,N'-
Dioctylpyromellittimide, N,N'-didecylpyromellittimide, N,N'-dicyclohexylpyromellittimide, N,N'-bis(3,
3,5-trimethylcyclohexyl)pyromellitimide, N,N'-diethyl-1,4,5,8
-Naphthalenetetracarboxylic acid 1,8-,4,5
- Diimide, etc. can be mentioned. The imide compounds represented by the above formulas () and () can be easily produced from the corresponding acid anhydrides and organic amines by known methods. In the present invention, first, aromatic polyester (A)
A composition mainly consisting of 100 parts by weight and 10 to 300 parts by weight of the low molecular weight compound (B) is melt-spun to form hollow fibers. If the amount of the low molecular compound (B) is less than 10 parts by weight, a molded product with high porosity cannot be obtained;
When the amount exceeds 300 parts by weight, the melt viscosity of the resulting composition decreases significantly, making spinning difficult. The blending amount of the low molecular weight compound (B) is more preferably 15 to 250 parts by weight, particularly preferably 20 to 200 parts by weight. The composition consisting of the aromatic polyester (A) and the low molecular weight compound (B) may be a simple dry blend of aromatic polyester (A) chips and the low molecular weight compound (B), or may be prepared by melt extrusion in advance. It may be melt-mixed in a machine. In addition, a low molecular compound (B) heated and melted above its melting point is converted into an aromatic polyester (A).
It is also preferable to use aromatic polyester (A) in which the low molecular weight compound (B) obtained by mixing with chips and solidifying by cooling is adhered to the surface of the chips of aromatic polyester (A). Additives such as oxidation stabilizers, ultraviolet absorbers, lubricants, and nucleating agents can be added to the above composition as other components, and can also suppress the increase or decrease in the degree of polymerization during molding. From the viewpoint of
Chain extenders such as -benzoxazin-4-one) can also be preferably incorporated. Melt spinning can be performed to form hollow fibers by a commonly known method. Although the melt-spun hollow fibers may be crystallized, it is preferable to use amorphous hollow fibers because the porosity becomes larger. The above-mentioned hollow fibers mainly composed of aromatic polyester (A) and low molecular weight compound (B) are then treated with low molecular weight compound (B).
(B) is dissolved and the aromatic polyester (A) is treated with an organic solvent (C) that does not substantially attack the aromatic polyester (A) to extract and remove the low molecular weight compound (B). Here, "does not substantially attack aromatic polyester (A)" means that it does not react with aromatic polyester (A) or dissolve or decompose aromatic polyester (A). means. Examples of the organic solvent (C) include toluene, xylene, pseudocumene, dioxane, chloroform, methylene chloride, dichloroethane, ethanol, ethyl acetate, acetone, methyl ethyl ketone, methyl isobutyl ketone, and chlorobenzene. These organic solvents are preferably selected appropriately depending on the type of the aromatic polyester (A) and the low molecular compound (B), especially the imide compound. This extraction treatment using organic solvent (C) can be carried out at room temperature, but it is preferable to carry out heating within a range that does not impair the form and physical properties of the molded product, for example, under reflux conditions of solvent (C). . In this extraction process, the extraction amount of the low molecular compound (B) contained in the hollow fibers is preferably 90% or more, more preferably 95% or more.
% or more, particularly preferably 99% or more. The extraction treatment time varies depending on the diameter and wall thickness of the hollow fiber, extraction solvent, extraction temperature, etc., but is usually 1 second to 1 hour, preferably 5 seconds to 40 minutes, particularly preferably 10 minutes.
The duration ranges from seconds to 20 minutes. The method for holding the hollow fiber during the extraction process is not particularly limited, but it is preferably under constant length, under tension, or under limited contraction conditions, and particularly preferably under constant length or under tension. In addition, in the above extraction process, when a solvent (hereinafter referred to as a parent solvent) that has a relatively high affinity with aromatic polyesters, such as toluene, xylene, dioxane, or chloroform, is used as an organic solvent, the extraction process with the parent solvent Subsequently, the parent solvent is replaced with a solvent that has a relatively low affinity for aromatic polyesters (hereinafter referred to as a solvent phobic) such as methanol, ethanol, or hexane. It is preferable to exchange the solvent by immersion. The extracted molded product is further heated and dried if necessary. During this heat drying, it is preferable to maintain the hollow fiber membrane under constant length, tension, or limited shrinkage conditions as in the above-mentioned extraction. According to the present invention, fine and uniform pores with an average pore diameter of 0.1μ or less are formed in the aromatic polyester (A) by the above extraction process with a high porosity of 20% or more, particularly preferably 50% or more. . Aromatic polyester (A)
It is not clear why a porous molded article can be obtained through extraction processing from a hollow fiber in which B and low-molecular-weight compound (B) are homogeneously dissolved without phase separation. However, in the molded article containing the low-molecular compound (B), the low-molecular compound
In other words, organic solvents that dissolve (B), or have good compatibility with low-molecular-weight compounds (B), can penetrate extremely easily.
Due to the action of this organic solvent, aromatic polyester (A)
It is speculated that this is because the crystallization of the molded product is promoted, and the low molecular weight compound (B) is removed while maintaining the form of the molded product (for example, the thickness of the film and the diameter of the fiber). The hollow fibers in which fine and uniform pores have been formed by the above extraction treatment can be further treated with alkali and/or stretched to enlarge the average pore diameter and increase the porosity, if necessary. The alkaline solutions used for this treatment include aqueous solutions of inorganic alkali compounds such as sodium hydroxide, potassium hydroxide, lithium hydroxide, and sodium carbonate, and organic amine compounds such as ethylamine, propylamine, and hydrazine, or the above-mentioned solutions such as methanol and ethanol. A solution of an organic solvent capable of dissolving the basic compound is used. Among these, an aqueous solution of an inorganic alkali compound is preferably used in terms of ease of handling. The concentration of the alkaline solution is not particularly limited, but for example, in the case of an aqueous solution of an inorganic alkaline compound, it is preferably about 0.5 to 40% by weight, particularly 1 to 30% by weight.
It is preferably about % by weight. Although the treatment temperature depends on the concentration of the alkaline solution, for example, in the case of an aqueous solution of an inorganic alkaline compound, it is usually from room temperature to about 80°C. In addition, the treatment time may be determined as appropriate to obtain the desired pore size and porosity, but it is usually 30 seconds to 30 seconds.
It takes about 30 minutes. During this alkaline solution treatment, the hollow fiber membrane is preferably maintained at a constant length or under tension. In the present invention, it is also possible to further perform stretching before and/or after the alkaline solution treatment, if necessary. Stretching can improve mechanical properties and further enlarge the pore diameter. For the stretching, any conventional method for stretching aromatic polyester molded articles can be used. For example, a temperature higher than the glass transition point of the aromatic polyester, usually several tens of degrees Celsius above the glass transition point.
Stretch several times at high temperature. The stretching ratio is preferably about 7 times or less. The hollow fiber selectively permeable membrane thus obtained can be assembled into a hollow fiber module having a desired membrane area by a conventionally known method. The inner diameter of the hollow fiber and its wall thickness are appropriately selected depending on the conditions such as pressure during use, the type and properties of the mixed fluid to be separated, etc., but the inner diameter is 2 to 0.05.
mm, and the wall thickness is preferably 0.5 to 0.05 mm. A wall thickness of 0.15 to 0.2 mm is particularly preferably used. The hollow fiber selectively permeable membrane obtained by the present invention is
Since it has a wide range of micropores of 1μ or less, it can be used for selective separation from various mixed fluids. A hollow fiber membrane having micropores with an average pore size of about 0.1 μm or more and 1 μm or less can be applied, for example, to a normal membrane filter or a membrane for separating plasma from blood. It is preferable to use a membrane having such an average pore diameter that has been subjected to alkali treatment and/or stretching. Also, membranes having an average pore size of approximately 0.01 to 0.1 μ can be used, for example, as ultrafiltration membranes. Furthermore, membranes having an average pore size smaller than this can be used, for example, for selective separation from gas mixtures, dialysis of artificial kidneys, etc. The porosity is preferably 30 to 80%, particularly preferably 50 to 80%. The selectively permeable membrane obtained according to the present invention can be used by flowing the fluid mixture to be separated inside or outside the hollow fibers. It may be coated with other substances or subjected to surface treatment by other methods for the purpose of improving the affinity for. EXAMPLES Hereinafter, the present invention will be explained in detail with reference to examples, but the present invention is not limited to the following examples.
In the examples, "part" means part by weight, and the intrinsic viscosity of the polyester was measured at a temperature of 35° C. using a mixed solvent of phenol/tetrachloroethane (weight ratio 60/40). Porosity and average pore diameter were measured using a porosimeter (American Instrument) using mercury intrusion method.
The gas permeation rate was measured using a flow meter. The following solute exclusion rate was determined by (1-concentration in permeate/concentration in stock solution) x 100. Examples 1-4 Polyethylene terephthalate with intrinsic viscosity 1.03
100 parts were dry-blended with a predetermined amount of the low-molecular-weight compound shown in Table 1, and after drying, using a twin-screw ruder equipped with a cylindrical nozzle with an inner diameter of 1.6 mm and an outer diameter of 2.0 mm, while flowing nitrogen gas into the cylinder. Melt extruded at approximately 280℃,
A hollow fiber was obtained by water-cooling and winding at a point approximately 10 cm below the nozzle. Next, the hollow fibers were immersed for 10 minutes at a fixed length in the refluxing solvent shown in the table to extract low molecular weight compounds.
It was dried at ℃. Table 1 shows the physical properties of the hollow fibers obtained.
Table 2 shows the selective permeation performance measured using a 0.1% bovine serum γ-globulin aqueous solution as the stock solution.

【table】

[Table] Example 5 The hollow fiber obtained in Example 2 was immersed in ethanol at room temperature to exchange the solvent, and then dried at 150°C for 15 minutes. The obtained hollow fibers were immersed in 5% sodium hydroxide at 40°C for 25 minutes. The resulting hollow fibers had a porosity of 75%, an average pore diameter of 0.15μ, and an air permeation rate of 5.1×10 ^-2 cm ² /cm ² sec cm at 20°C.
It was Hg. In the same manner as in Example 1, selective permeation performance was measured using an aqueous solution of 0.1% bovine serum γ-globulin, and the liquid permeation amount was 80 ml/m ² · hr · mmHg and the rejection rate was 21%. . Example 6 The hollow fiber membrane obtained in Example 5 was stretched 1.5 times at 150°C. The average pore diameter of the obtained membrane was 0.25μ. Example 7 100 parts of polytetramethylene terephthalate chips having an intrinsic viscosity of 1.18 were dry blended with 100 parts of 1-phthalimide-3phthalimidomethyl-3,5,5-trimethylcyclohexane at a temperature of 240°C.
Hollow fibers were formed in the same manner as in Example 1. Next, the hollow fiber was immersed in refluxing toluene for about 8 minutes at a fixed length to extract low molecular weight compounds, and then dried at 130°C. The obtained hollow fiber membrane has a porosity of 45% and an average pore diameter of
It was 0.063μ. When the selective permselectivity was measured in the same manner as in Example 1, the liquid permeation amount was 6.1 ml/m ²・hr・
mmHg, and the elimination rate was 43%.

Claims (1)

[Scope of Claims] 1. 100 parts by weight of a substantially linear aromatic polyester (A) and a low molecular compound (B) that satisfies the following conditions (1) to (4).
A composition mainly consisting of 10 to 300 parts by weight is melt-spun to form a hollow fiber, and then an organic solvent (which dissolves the low molecular weight compound (B) but does not substantially attack the aromatic polyester (A)) is used. A method for producing a hollow fiber-like permselective membrane, characterized in that the hollow fiber is treated with C) to extract the low molecular compound (B) in the hollow fiber. (1) Substantially stable under the melting conditions of the aromatic polyester (A), non-reactive with the aromatic polyester (A), and compatible with the aromatic polyester (A) (2) The above-mentioned melt The aromatic polyester (A) and the low molecular weight compound (B) should not undergo phase separation even when the product is cooled and solidified. (3) The melting point should be 100°C or higher. (4) The molecular weight should be 1000 or lower.