JPH0724275A - Production of hollow fiber membrane - Google Patents

Abstract

PURPOSE:To obtain a hollow fiber membrane having high water permeation rate by mixing N-methylpyrolidone and a swelling agent having a specified structure with a specified mixing ratio, uniformly dissolving cellulose triacetate in this mixture liquid to obtain the source liquid for spinning of specified concn., and extruding the source liquid through the slit of the outer pipe of a double- pipe spinning nozzle while extruding a core material through the inner pipe. CONSTITUTION:Cellulose triacetate is uniformly dissolved in a mixture liquid of N-methylpyrolidone and a swelling agent expressed by formula with the mixing weight ratio of 8:1 to 5:3 to obtain a liquid having 10-25wt.% cellulose triacetate concn. as the source liquid for spinning. This liquid is extruded through the slit of the outer pipe of a spinning nozzle having a double pipe structure while a liquid as the core material incompatible with the source liquid for spinning is extruded through the inner pipe of the spinning nozzle. The extruded thread-like material is travelled in a gas atmosphere and introduced into a solidifying liquid to be solidified. In formula, p, q, r are 0 or integers 1-20 satisfying 0<=p+q+r<=20. By this method, the obtd. hollow fiber membrane has high water permeation rate and excellent mol.wt. fractionation characteristics.

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 triacetate hollow fiber membrane which can be used for liquid separation by an ultrafiltration method, a dialysis method or the like.

[0002]

2. Description of the Related Art Conventionally, the properties required for hollow fiber membranes used for liquid separation by ultrafiltration, dialysis, etc. are as follows:
It is required that the substance has a high permeation rate and that the substance has high selective permeability. In particular, as properties required for the hollow fiber membranes used in the ultrafiltration method and the dialysis method, a high water permeation rate and excellent molecular weight fractionation characteristics are required.

As a method for producing a hollow fiber membrane having a high water permeation rate and an excellent molecular weight fractionation property, for example, a spinning dope containing a cellulose ester, its solvent and polyethylene glycol is discharged from a spinneret. Then, a method for producing a hollow fiber membrane by coagulating is proposed (JP-A-54-88881). However, in the method proposed in JP-A-54-88881, the molecular weight of the solute that can be separated from the solute can be controlled by changing the number of repeating units of oxyethylene of polyethylene glycol used as a swelling agent. However, although this method can increase the water permeation rate, it is difficult to improve the molecular weight fractionation property at the same time. In order to improve the molecular weight fractionation characteristics, it is essential to form uniform pores in the membrane.
A spinning dope containing a cellulose ester, a solvent and a swelling agent that can easily realize a uniform phase separation state must be used, and a suitable swelling agent must be selected from this point.

Further, as a method for producing a hollow fiber membrane for dialysis, a method of spinning using a spinning dope containing a cellulose ester, a solvent thereof and a polyhydric alcohol has been proposed (JP-A-2-258035). However, JP-A-2-258035 only discloses that a polyhydric alcohol is used as a third component in a spinning dope. However, for example, when dimethylformamide is used as the solvent for the cellulose ester and glycerin is used as the polyhydric alcohol, it becomes difficult to uniformly dissolve the spinning dope. Further, for example, when diglycerin is used as the polyhydric alcohol, only a hollow fiber membrane having a high water permeability but a small molecular weight fractionation property can be obtained.

[0005]

In view of these conventional techniques, the present invention is to provide a novel method for producing a hollow fiber membrane having a high water permeation rate and excellent molecular weight fractionation characteristics. is there.

[0006]

Means for Solving the Problems As a result of intensive studies to achieve the above object, the present inventors have found that cellulose triacetate is mixed with N-methylpyrrolidone and a swelling agent represented by the following formula [I]. The mixture solution containing 8: 1 to 5: 3 in weight ratio had a cellulose triacetate concentration of 10 to 2
A spinning stock solution uniformly dissolved so as to be 5% by weight is extruded from an outer tube slit of a spinning nozzle having a double tube structure, and at the same time, a liquid which is incompatible with the spinning stock solution is used as a core agent from the inner tube of the spinning nozzle. It was found that the above-mentioned problems can be solved by extruding the filamentous material, running it in a gas atmosphere, and then introducing it into a coagulation bath to coagulate it, and completed the present invention.

[0007]

[Chemical 2] [In the above formula [I], p, q, and r are 0 or an integer of 1 to 20, and are numbers satisfying 0 ≦ p + q + r ≦ 20. ]

That is, according to the present invention, a mixed solution of cellulose triacetate in which N-methylpyrrolidone and glycerin or a glycerin derivative represented by the above general formula [I] are mixed in a weight ratio of 8: 1 to 5: 3. A stock solution for spinning which is uniformly dissolved so as to have a cellulose acetate concentration of 10 to 25% by weight is extruded from an outer tube slit of a spinning nozzle having a double tube structure, and at the same time, a stock solution for spinning as a core agent from an inner tube of the spinning nozzle The present invention relates to a method for producing a hollow fiber membrane, which comprises extruding a liquid incompatible with the filamentous substance, allowing the filamentous discharge product to run in a gas atmosphere, and then introducing the filamentous substance into a coagulating bath for coagulation.

In the present invention, in order to produce a hollow fiber membrane having a high water permeability and an excellent molecular weight fractionation property,
Cellulose triacetate, N-methylpyrrolidone, and glycerin or glycerin derivative represented by the above general formula [I] as a swelling agent (hereinafter, glycerin-based swelling agent)
It is important to use a spinning stock solution in which

In the present invention, when a spinning dope having a composition other than a combination of cellulose triacetate, N-methylpyrrolidone and the glycerin type swelling agent is used as the spinning dope, for example, polyethylene is used instead of the glycerin type swelling agent. When a glycol or polyethylene glycol derivative is used, or when diglycerin is used, it is difficult to obtain a hollow fiber membrane having both a large water permeation rate and excellent molecular weight fractionation characteristics.

Further, in producing a hollow fiber membrane having a high water permeation rate and excellent molecular weight fractionation characteristics, N-methylpyrrolidone and glycerin or a glycerin derivative are used in a weight ratio of 8: 1 to 5: 3, preferably. It is necessary to mix 7: 1 to 2: 1. When the ratio of N-methylpyrrolidone is more than 8: 1 with respect to glycerin or a glycerin derivative, the permeability of the medium molecular weight compound is lowered, while when it is less than 5: 3, it becomes difficult to uniformly dissolve the spinning solution.
As a result, the spinnability deteriorates, and it becomes difficult to produce a homogeneous hollow fiber membrane.

Further, the content of cellulose triacetate in the spinning source solution is 10 to 25% by weight, preferably 15 to 2%.
It is necessary to be 3% by weight. When the content of cellulose triacetate exceeds 25% by weight, it becomes difficult to obtain a hollow fiber membrane having high water permeability and high permeability of the medium molecular weight substance,
On the other hand, if it is less than 10% by weight, spinning becomes unstable,
It is not preferable because it is difficult to obtain a homogeneous hollow fiber membrane, and the strength of the hollow fiber is reduced, and thread leakage easily occurs.

It is important that p, q and r in the above formula [I] defining the glycerin-based swelling agent used in the present invention are 0 or an integer of 1 to 20. When the total of p, q, and r exceeds 20, it is possible to obtain a hollow fiber membrane having high water permeability and medium molecular weight polymer permeability, but at the same time, it is difficult to obtain a hollow fiber membrane having excellent molecular weight fractionation characteristics. Becomes

As such glycerin or glycerin derivative, glycerin to which ethylene oxide is added in addition to glycerin is particularly preferable. These may be used alone or in combination of two or more.

In the present invention, as the core agent (core liquid) extruded together with the above spinning dope, it is preferable to use a liquid which is incompatible or hardly compatible with the spinning dope, for example, isopropyl myristate, oleic acid, liquid paraffin and the like. Liquid paraffin is particularly preferable. Spinning is possible even if a water-soluble liquid such as polyethylene glycol, a polyethylene glycol derivative, or glycerin is used as the core liquid, but the roundness of the hollow fiber is impaired or the smoothness of the inner surface of the hollow fiber is impaired. , Not preferable.

In the present invention, the above spinning dope and core material are extruded from a nozzle having a double-tube structure in a sheath-core shape into a gas atmosphere, and the gas atmosphere (air gap) is adjusted to about 0.01-.
After running for 0.5 seconds, it is introduced into a coagulation bath and coagulated to form a yarn.

The coagulation bath temperature in the present invention is 10 to 50 ° C.
When the coagulation bath temperature is lower than 10 ° C, it is difficult to obtain a hollow fiber membrane having high water permeability and medium molecular weight polymer permeability. On the other hand, when the coagulation bath temperature exceeds 50 ° C. However, although the substance has a high permeability, the molecular weight fractionation property is deteriorated, so that it is not possible to obtain a hollow fiber membrane having a high water permeability and an excellent molecular weight fractionation property. The coagulation bath can be used as long as it is a liquid in which the solvent and the swelling agent are soluble, but it is preferable to use water as the main component in terms of cost and production control. From the viewpoint of quality control of the hollow fiber membrane, the coagulation bath is particularly preferably a liquid composed of water, a solvent and a swelling agent, and the solvent and the swelling agent have the same ratio as that in the spinning source solution. The coagulation bath composition cannot be uniquely defined because it depends on the composition of the spinning dope, the temperature, and the air gap length, but the water concentration is preferably 40 to 90% by weight.

[0018]

According to the present invention as described above, it is possible to easily produce a hollow fiber membrane having a high water permeation rate and, at the same time, an excellent molecular weight fractionation property. Therefore, this hollow fiber membrane can be effectively used for liquid separation such as ultrafiltration and hemodialysis.

[0019]

The embodiments of the present invention will be described below with reference to examples.

However, these examples are for explaining the present invention and are not limited to these.

The dextran transmittance SC with a molecular weight of 70,000 used in the present invention is defined by the following formula.

SC = C ₂ ÷ C ₁ C ₁ represents the concentration of dextran with a molecular weight of 70,000 in the stock solution, and C ₂ represents the concentration of dextran with a molecular weight of 70,000 in the permeate.

[0023]

Example 1 20 parts by weight of cellulose triacetate,
62 parts by weight of N-methylpyrrolidone (NMP) and 18 parts by weight of glycerin were mixed and dissolved, and this was used as a spinning stock solution, and spinning was performed using an annular orifice nozzle. The spinning stock solution at 105 ° C. was supplied from the outer tube, while liquid paraffin was discharged from the inner tube as the core liquid. The hollow fiber stock solution exiting the annular orifice is run in the air for 15 cm, then
It was introduced into a coagulation bath consisting of a 10% NMP aqueous solution kept at 35 ° C. for 1.1 seconds to coagulate, and then washed with a washing bath,
It was wound up at a speed of 40 m / 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, and the inner diameter was 203 μm and the film thickness was 19 μm, and there was almost no variation in shape. Also,
The ultrafiltration rate UFR of the obtained cellulose triacetate hollow fiber membrane was 320 ml / hr · mmHg · 1.5.
The dextran permeability DA of m ² and molecular weight 10000 is
Large with 42 ml / min · 1.5 m ² , molecular weight of 700
The dextran permeability SC of 00 was 0.049, which was an extremely small hollow fiber membrane. That is, the water permeability is high,
A cellulose triacetate hollow fiber membrane having excellent molecular weight fractionation characteristics was obtained.

[0024]

Example 2 Glycerin ethylene oxide 8 mol adduct instead of glycerin (p + q + r in the general formula [I])
= 8), a cellulose triacetate hollow fiber membrane was obtained in the same manner as in Example 1. 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, and the inner diameter was 216 μm and the film thickness was 21 μm, and there was almost no variation in shape. Also,
The ultrafiltration rate UFR of the obtained cellulose triacetate hollow fiber membrane was 329 ml / hr · mmHg · 1.5.
The dextran permeability DA of m ² and molecular weight 10000 is
Large with 43 ml / min · 1.5 m ² , molecular weight of 700
The dextran permeability SC of 00 was 0.053, which was an extremely small hollow fiber membrane. That is, the water permeability is high,
A cellulose triacetate hollow fiber membrane having excellent molecular weight fractionation characteristics was obtained.

[0025]

[Comparative Example 1] Triethylene glycol was used instead of glycerin, and the amount of 100
A cellulose triacetate hollow fiber membrane was obtained in the same manner as in Example 1 except that the spinning dope at 0 ° C was supplied. The obtained cellulose triacetate hollow fiber membrane has a molecular weight of 1,000.
Dextran transmittance DA of 0 is 40 ml / min.
Dextran transmittance S of 1.5 m ² and molecular weight of 70,000
C was 0.056 and the molecular weight fractionation characteristics were good, but the ultrafiltration rate UFR was 258 ml / hr · mmHg · 1.
It was a hollow fiber membrane having a low water permeation rate of 5 m ² .

[0026]

Comparative Example 2 A cellulose triacetate hollow fiber membrane was obtained in the same manner as in Comparative Example 1 except that the coagulation bath temperature was 45 ° C. The ultrafiltration rate UFR of the obtained cellulose triacetate hollow fiber membrane was 345 ml / hr · mmHg · 1.
Although it was as large as 5 m ² , the dextran permeability DA with a molecular weight of 10,000 was 43 ml / min · 1.5 m ² , and the dextran permeability SC with a molecular weight of 70000 was 0.116, which is a hollow fiber membrane with low molecular weight fractionation characteristics. It was That is, it was found that when triethylene glycol was used as the swelling agent, the molecular weight fractionation characteristics deteriorated when trying to increase the water permeation rate.

[0027]

Comparative Example 3 20 parts by weight of cellulose triacetate,
56 parts by weight of N-methylpyrrolidone, 24 of diglycerin
A cellulose triacetate hollow fiber membrane was obtained in the same manner as in Comparative Example 2 except that 1 part by weight was mixed and dissolved, and this was used as a spinning stock solution, and the spinning stock solution at 120 ° C. was supplied from the outer tube portion of the annular orifice nozzle. The ultrafiltration rate UFR of the obtained cellulose triacetate hollow fiber membrane was 564 ml / hr.
mmHg · 1.5m ² was large, but molecular weight was 1000
Dextran transmittance DA of 0 is 43 ml / min.
Dextran transmittance S of 1.5 m ² and molecular weight of 70,000
C was 0.130, and the hollow fiber membrane had a low molecular weight fractionation property.

 ─────────────────────────────────────────────────── ─── Continued Front Page (72) Inventor Takeyuki Kawaguchi 2-1, Hinodecho, Iwakuni-shi, Yamaguchi Teijin Limited Iwakuni Research Center

Claims (3)

[Claims] 1. A mixture of cellulose triacetate and N-methylpyrrolidone and a swelling agent represented by the following formula [I] in a weight ratio of 8: 1 to 5: 3 has a cellulose triacetate concentration of 10 to 10. A spinning stock solution uniformly dissolved in 25 wt% was extruded from an outer tube slit of a spinning nozzle having a double tube structure, and at the same time, a liquid which was incompatible with the spinning stock solution was used as a core agent from the inner tube of the spinning nozzle. A method for producing a hollow fiber membrane made of cellulose triacetate, which comprises extruding, running the filamentous discharge in a gas atmosphere, and introducing the filamentous discharge into a coagulation bath for coagulation. [Chemical 1] [In the above formula [I], p, q, and r are 0 or an integer of 1 to 20, and are numbers satisfying 0 ≦ p + q + r ≦ 20. ] 2. The method for producing a hollow fiber membrane according to claim 1, wherein liquid paraffin is used as the core agent. 3. The method for producing a hollow fiber membrane according to claim 1, wherein the temperature of the coagulation bath is 10 to 50 ° C.