JP2818366B2 - Method for producing cellulose ester hollow fiber membrane - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a cellulose ester hollow fiber membrane which can be used for separation of a liquid by an ultrafiltration method, a dialysis method or the like by a dry-wet spinning method.

[0002]

2. Description of the Related Art Conventionally, hollow fiber membranes used for liquid separation by a permeation method, an ultrafiltration method, a dialysis method, and the like are characterized by a high permeation rate of a substance and a high permselectivity of a substance. Has been requested. In particular, properties required for a hollow fiber membrane to be effectively used for ultrafiltration and dialysis include a high water permeation rate and an excellent molecular weight fractionation property. In order to obtain a hollow fiber membrane having a high permeation rate of a substance without impairing the selective permeability of the substance, it is necessary to obtain a hollow fiber membrane having a uniform thickness, a small thickness, and a high strength. Furthermore, in the case of a hollow fiber membrane used for artificial dialysis, the inner surface of the hollow fiber membrane may be as smooth as possible in order to reduce residual blood and hemolysis during hemodialysis, and to reduce performance degradation due to deposition of proteins in blood. Has been requested.

[0003] In order to satisfy these requirements, various methods for producing hollow fiber membranes using cellulose esters having excellent permeability to substances, mechanical strength when wet, and biocompatibility have been developed and proposed. .

[0004] In general, as a method for producing a hollow fiber from a cellulose ester, there are a melt spinning method and a dry-wet spinning method (semi-dry semi-wet spinning method). The melt spinning method is excellent in terms of manufacturing cost because the manufacturing process is simple, but the spinning solution (melt) is gelled and solidified immediately after being discharged from the spinneret, and thus has poor spinnability. Since a sufficient draft is not applied, a hollow fiber membrane having a small thickness cannot be obtained. On the other hand, in the dry-wet spinning method, although the production process is complicated, solidification conditions can be freely changed, so that hollow fiber membranes having various performances can be easily produced. Also medical,
There is an advantage that the performance of the hollow fiber membrane can be easily modified according to the rapid progress of treatment. Also in this dry-wet spinning method, when a substance having coagulability with respect to the spinning solution is used as the core solution, gelation and coagulation occur after the spinning solution is discharged. It is difficult to get. Therefore, in order to obtain a hollow fiber membrane having a sufficiently thin film thickness, it is essential to adopt a dry-wet spinning method and to use a non-coagulating liquid as a core liquid with respect to the spinning dope.

Hitherto, in the dry-wet spinning method, a method has been proposed in which a liquid which is incompatible or hardly compatible with the spinning solution, such as liquid paraffin or isopropyl myristate, is used as the core liquid (Japanese Patent Laid-Open No. Sho 57-79). No. 133321, JP-A-61-185305). In this method, since the spinning solution and the core solution are suppressed from mutually diffusing, there is an advantage that a hollow fiber membrane having good inner surface smoothness can be obtained. However, this method has a problem that there is no suitable solvent for washing and removing the core liquid. Hollow fiber membranes used for dialysis must ensure sufficient safety, and when the above-mentioned water-insoluble ones are used as core liquids, more complex washing is required to completely remove them. Since the production process and a large amount of cleaning time are required, the production cost is high,
There is a problem that productivity is poor.

Also, a method of using a cellulose ester solvent and / or a swelling agent as a core liquid as a non-coagulable liquid with respect to the spinning solution (Japanese Patent Application Laid-Open Nos. 55-36362 and 56-96910). And a method in which a solution prepared by dissolving a water-soluble polymer compound in a solvent substantially the same as the spinning solution is used as a core solution (see Japanese Patent Application Laid-Open No. 50-132218). These methods have an advantage that the core liquid is water-soluble and thus can be easily removed by washing. However, since the core liquid used in these methods is compatible with the spinning dope, the core liquid and the spinning dope mutually diffuse, and the interface between the core liquid and the spinning dope, that is, the inner surface of the hollow fiber membrane is disturbed. In addition, there is a problem that the inner surface smoothness is impaired, and as a result, thrombus and residual blood are generated during dialysis.

[0007] As a method of suppressing mutual diffusion between the core liquid and the spinning solution, which is a problem when a non-coagulable and water-soluble liquid is used as the core solution for the spinning solution, a method using a salt aqueous solution as the core solution is used. (JP-A-53-70128, JP-A-5-70128)
6-96910), a method of supplying a core liquid at a temperature lower than the temperature of the spinning dope (Japanese Patent Application Laid-Open No. 56-96909).
And a method using a liquid having a coagulation value of 20 or more as a core liquid (see Japanese Patent Publication No. 62-29524).

However, the methods described in JP-B-53-70128 and JP-A-56-96910 contain water having a coagulating effect on the spinning dope, and therefore have poor spinnability. It is difficult to obtain a thin and uniform hollow fiber membrane. Further, when the spinning temperature exceeds 100 ° C., the yarn breaks due to boiling of water, and there is a problem that spinning cannot be performed.

On the other hand, according to the method described in Japanese Patent Application Laid-Open No. 56-96909, even if a liquid having a lower temperature than the spinning solution is supplied as the core solution, the temperature in the nozzle becomes substantially the same as the spinning solution. It is practically impossible to extrude the spinning dope from the outside of the annular slit of the double tube nozzle and extrude the liquid 10 ° C. or more lower than the inside from the inside, and this is not practical. Even if it is possible to extrude a liquid that is at least 10 ° C. lower than the spinning dope as a core liquid,
Since the temperature difference between the spinning solution and the core solution is large, gelation occurs immediately after the spinning solution is extruded from the nozzle, the spinnability deteriorates, and a homogeneous hollow fiber membrane cannot be obtained.

The method described in JP-B-62-29524 is substantially the same as the method described in JP-A-55-36362 and JP-A-56-96910 described above. With this method, it is still difficult to obtain a hollow fiber membrane having sufficient inner surface smoothness.

[0011]

SUMMARY OF THE INVENTION In view of these prior arts, the present invention provides a cellulose ester hollow film having a uniform and thin film thickness, excellent inner surface smoothness of the hollow fiber membrane, and easy washing of the core liquid. An object of the present invention is to provide a method for producing a yarn membrane.

[0012]

Means for Solving the Problems The inventors of the present invention have made intensive studies to solve the above-mentioned problems, and as a result, a spinning stock solution obtained by dissolving a cellulose ester in a mixed solution comprising an organic solvent and a swelling agent has been produced. At the same time as extruding from the outer tube slit of the spinning nozzle having a tube structure, the core liquid is extruded from the inner tube of the spinning nozzle, and the filamentous discharge is caused to run in a gas atmosphere, and then introduced into a coagulation bath for coagulation. In the method for producing a hollow fiber membrane, it has been found that the above problem is solved by using a water-soluble organic polymer compound which is liquid at the spinning temperature and has a melting point equal to or higher than the coagulation bath temperature, as the core liquid, The present invention has been completed.

That is, the present invention relates to a method for producing a hollow fiber membrane, wherein a water-soluble organic polymer compound which is liquid at the spinning temperature and has a melting point higher than the coagulation bath temperature is used as the core liquid. It is related.

In the method of the present invention, the film thickness is uniform and thin,
In order to obtain a hollow fiber membrane having excellent inner surface smoothness, it is important to use, as a core liquid, a water-soluble organic polymer compound which is liquid at the spinning temperature and has a melting point higher than the coagulation bath temperature. is there. In addition, the water-soluble organic polymer compound in the present invention refers to an organic polymer substance soluble in water at least 1% by weight or more.

In the present invention, when a core liquid other than a water-soluble organic polymer compound which is liquid at the spinning temperature and has a melting point higher than the coagulation bath temperature is used, for example, glycerin, triethylene glycol, average molecular weight of 200 When polyethylene glycol or the like is used, pores and irregularities having a size of several microns to submicron are observed on the inner surface of the hollow fiber membrane, and a hollow fiber membrane having excellent inner surface smoothness cannot be obtained.

Used as a core liquid in the method of the present invention;
Examples of the water-soluble organic polymer compound which is liquid at the spinning temperature and has a melting point not lower than the coagulation bath temperature include polyethylene glycol having an average molecular weight of 600 or more, and an average molecular weight of 75 or more.
Zero or more polyethylene glycol methyl ether, polyvinyl methyl ether, polytetramethylene ether glycol, polyethylene oxide, polycaprolactone triol, polymethacrylic acid, polyhydroxyethyl acrylate, and the like, but the spinning temperature is not particularly limited thereto. All the water-soluble organic polymer compounds which are liquid and have a melting point not lower than the coagulation bath temperature can be used. These core liquids may be used alone or in combination of two or more. Among the above core liquids, polyethylene glycol having an average molecular weight of 600 to 2,000 is preferred from the viewpoint of cost, ease of handling, ease of washing, and the like.

In the method of the present invention, a spinning stock solution (dope) in which a cellulose ester is dissolved in a mixed solution comprising an organic solvent and a swelling agent is used using a spinning nozzle having a double tube structure.
From the annular outer pipe slit of the nozzle, the above core liquid is extruded from the inner pipe slit into the gas atmosphere in a sheath-core state, and after running through the gas atmosphere for a short distance, introduced into the coagulation bath, a dry-wet method Spin.

As the cellulose ester used in the method of the present invention, cellulose diacetate, cellulose triacetate, cellulose butyrate, cellulose nitrate and the like are used. Among these, cellulose triacetate is particularly preferred in view of biocompatibility, membrane performance, and yarn strength when wet.

The organic solvent of the cellulose ester used in the method of the present invention includes dimethylformamide,
Dimethylacetamide, N-methyl-2-pyrrolidone,
Dimethyl sulfoxide, acetone, dioxane and the like can be mentioned. Examples of the swelling agent include polyethylene glycols, polypropylene glycols, glycerin, glycerin derivatives, butanediol, and hydroxycarboxylic acid. The concentration of the swelling agent in the spinning solution is 10 to 5
0, particularly preferably 20 to 40% by weight.

The concentration of the cellulose ester in the stock solution for spinning is preferably 10 to 25, and particularly preferably 15 to 23% by weight.

The preferred spinning temperature in the method of the present invention cannot be uniquely defined because it varies depending on the type and concentration of the cellulose ester, the solvent for the cellulose ester, and the swelling agent. In consideration of evaporation of solvent, thermal decomposition, etc., 50 to 150
C. is preferred.

The distance (air gap length) from the spinneret to the surface of the coagulation bath is set at 0.3 mm when the discharged yarn is in a gas atmosphere.
It is preferable to set the travel distance for 01 to 0.5 seconds.

The coagulation bath temperature in the method of the present invention is 10 to 10.
It is important that the temperature is 50 ° C., and if the coagulation bath temperature is less than 10 ° C., it is difficult to obtain a hollow fiber membrane having high water permeability and high permeability of medium molecular weight substances. If it exceeds, although the permeability of the substance is large, the molecular weight fractionation characteristics are lowered. As the coagulation bath, any liquid can be used as long as the solvent and the swelling agent are soluble. However, those containing water as a main component are preferable in view of cost and production control. From the viewpoint of quality control of the hollow fiber membrane, water, solvent,
Liquids comprising a swelling agent and having the same ratio of solvent to swelling agent as in the spinning dope are particularly preferred. The composition of the coagulation bath cannot be uniquely defined because it varies depending on the composition of the spinning solution, the temperature, the distance from the spinneret to the surface of the coagulation bath (air gap length), etc., but the water concentration is 40 to 90% by weight. Preferably, there is.

[0024]

According to the method of the present invention as described above, a hollow fiber membrane having a uniform and thin film thickness and excellent hollow fiber membrane inner surface smoothness can be easily produced. Further, since the core liquid is water-soluble, there is an advantage that the core liquid can be easily washed and removed.

[0025]

EXAMPLES The present invention will be described below in detail with reference to examples, but the present invention is not limited thereto.

[0026]

Example 1 20 parts by weight of cellulose triacetate, N
-56 parts by weight of methylpyrrolidone (NMP) and 24 parts by weight of triethylene glycol (TEG) are mixed and dissolved,
This was used as a spinning stock solution, and spinning was performed using a spinning nozzle having a double tube structure. That is, a stock solution for spinning at 130 ° C. was discharged from the annular orifice in the outer tube, while polyethylene glycol having an average molecular weight of 1000 was discharged as a core solution from the inner tube. The spinning solution leaving the annular orifice is allowed to run in 3.5 cm air, and then kept at 25 ° C. in NMP / TE.
It was introduced into a coagulation bath of G / H ₂ O = 21/9/70% by weight for 3 seconds to coagulate, and then washed with a water bath, and then washed with 30 m / m 2
It was wound at a speed of min.

The cross-sectional shape of the obtained cellulose triacetate hollow fiber membrane was a perfect circle, the inner surface of the hollow fiber was smooth, the inner diameter was 190 μm, the film thickness was 17 μm, and there was almost no variation in the shape.

FIG. 1 shows an electron micrograph of the inner surface of this hollow fiber membrane at a magnification of 10,000. From FIG. 1, it can be seen that the smoothness of the inner surface of the obtained hollow fiber membrane is very good.

The ultrafiltration rate UFR of the obtained cellulose triacetate hollow fiber membrane was 166 ml / hr · m
The dextran transmittance DA of mHg · 1.5 m ² and the molecular weight of 10,000 is as large as 54 ml / min · 1.5 m ^2, and the dextran transmittance SC of the molecular weight of 70,000 is 0.1.
064, which was a very small hollow fiber membrane. That is, a cellulose triacetate hollow fiber membrane having moderate water permeability, high permeation rate of medium molecular weight (molecular weight 10,000), and excellent molecular weight fractionation properties was obtained.

The dextran transmittance SC having a molecular weight of 70000 used in the present invention is defined by the following equation.

SC = C ₂ ÷ C ₁ C ₁ represents the concentration of dextran having a molecular weight of 70000 in the stock solution, and C ₂ represents the concentration of dextran having a molecular weight of 70000 in the permeate.

[0032]

Comparative Example 1 A cellulose triacetate hollow fiber membrane was obtained in the same manner as in Example 1 except that triethylene glycol was used instead of polyethylene glycol having an average molecular weight of 1,000 as the core liquid. FIG. 2 shows an electron micrograph of the inner surface of the obtained cellulose triacetate hollow fiber membrane at a magnification of 10,000 times. From FIG. 2, pores of 0.2 to 0.5 μm are seen on the inner surface of the hollow fiber membrane, and it can be seen that only a membrane having poor inner surface smoothness can be obtained.

[Brief description of the drawings]

FIG. 1 is a 10000-fold enlarged photograph (an enlarged photograph of the inner surface of a hollow fiber) of the inner surface of a hollow fiber membrane obtained by the method of the present invention (Example 1).

FIG. 2 is an inner surface 1 of a hollow fiber membrane obtained by the method of Comparative Example 1.
0000 times enlarged photograph (enlarged photograph of the inner surface of the hollow fiber).

──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Takeyuki Kawaguchi 2-1 Hinodemachi, Iwakuni-shi, Yamaguchi Pref. Teijin Limited Iwakuni Research Center (56) References JP 54-131025 (JP, A) JP-A-54-151614 (JP, A) JP-A-55-39223 (JP, A) JP-A-56-43417 (JP, A) JP-A-61-200816 (JP, A) JP-A-61-254201 (JP, A) JP, A) JP-A-6-343842 (JP, A) (58) Fields investigated (Int. Cl. ⁶ , DB name) B01D 71/14 B01D 69/08 B01D 71/16 D01D 5/24 D01F 2 / 28

Claims (5)

(57) [Claims] 1. A spinning solution obtained by dissolving a cellulose ester in a mixed solution comprising an organic solvent and a swelling agent is extruded from an outer tube slit of a spinning nozzle having a double tube structure, and at the same time, a core solution is passed through an inner tube of the spinning nozzle. In a method for producing a cellulose ester hollow fiber membrane by extruding the filamentous material and running it in a gaseous atmosphere and then introducing it into a coagulation bath and coagulating it, the core liquid is liquid at the spinning temperature and coagulated. A method for producing a cellulose ester hollow fiber membrane, comprising using a water-soluble organic polymer compound having a melting point higher than a bath temperature. 2. The method according to claim 1, wherein polyethylene glycol having an average molecular weight of 600 to 2,000 or a derivative thereof is used as the water-soluble organic polymer compound which is liquid at the spinning temperature and has a melting point higher than the coagulation bath temperature. A method for producing a cellulose ester hollow fiber membrane. 3. The process for producing a cellulose ester hollow fiber membrane according to claim 1, wherein the temperature of the coagulation bath is 10 to 50 ° C. 4. The method for producing a cellulose ester hollow fiber membrane according to claim 1, wherein the spinning temperature is 50 to 150 ° C. 5. The method for producing a cellulose ester hollow fiber membrane according to claim 1, wherein the cellulose ester is cellulose triacetate.