JP2818355B2 - Manufacturing method of hollow fiber membrane - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a permeation method, an ultrafiltration method,
The present invention relates to an improved method for producing a hollow fiber membrane which can be used for fluid separation such as separation of a liquid or separation of a mixed gas by a dialysis method or the like.

[0002]

2. Description of the Related Art Conventionally, a material required for a hollow fiber membrane used for fluid separation such as separation of liquid and separation of mixed gas by a permeation method, ultrafiltration method, dialysis method, etc. It is required that the material be large and have high permselectivity. In particular, the properties required for the hollow fiber membrane used in the ultrafiltration method and the dialysis method are such that the permeability of medium molecular weight substances (molecular weight of 10,000 to tens of thousands) is large while the water permeability is moderately suppressed. In addition, it is required that the medium molecular weight product has excellent molecular weight fractionation characteristics.

However, conventionally, when a membrane having a high permeability for a medium molecular weight substance is to be obtained, there has been a problem that the water permeability is increased at the same time and a molecular weight fractionation property is deteriorated. When the water permeability increases, the dialysate flows back into the blood side (backfiltration) during hemodialysis, which causes a problem that endotoxin in the dialysate flows through the blood and into the body. In addition, when the molecular weight fractionation characteristics are reduced, albumin (molecular weight of about 68,800) useful for the human body is used to remove β2-microglobulin (molecular weight of about 12,000), which is a harmful component in blood.
(Thousands).

Heretofore, as a method for producing a hollow fiber membrane having excellent molecular weight fractionation properties, cellulose esters, organic solvents of cellulose esters and swelling agents (phase separation agents) have been known.
There has been proposed a method of producing a hollow fiber membrane by discharging a spinning solution composed of polyethylene glycols from a spinneret and coagulating the same. (JP-A-54-88881). However, in the method proposed in Japanese Patent Application Laid-Open No. 54-88881, there is a problem that when trying to increase the permeability of a medium molecular weight compound, the water permeability is also increased.

Further, a hollow fiber membrane is produced by discharging a spinning dope comprising a cellulose ester, an organic solvent of the cellulose ester and a hydroxycarboxylic acid from a spinneret, and using a solvent and / or a swelling agent of the cellulose ester as a core liquid. A method has been proposed (Japanese Patent Application Laid-Open No. 55-80515). However, in this method, since the core solution contains a part of the components of the stock solution for spinning, mutual diffusion between the core solution and the stock solution for spinning occurs, resulting in smoothness. A hollow fiber membrane having an inner surface of the membrane cannot be obtained. for that reason,
There is a problem that residual blood may be caused during hemodialysis, or performance may be reduced due to deposition of proteins in blood. Further, in the above method, since the core liquid flows out in the washing step in the production of the hollow fiber membrane, there is also a problem that the hollow portion of the hollow fiber is deformed or closed.

[0006]

DISCLOSURE OF THE INVENTION In view of these prior arts, the present invention provides a cellulose triacetate hollow fiber membrane having moderate water permeability, high permeability of medium molecular weight substances, and excellent molecular weight fractionation properties. It is an object of the present invention to provide a method for producing a.

[0007]

Means for Solving the Problems The present inventors have made intensive studies in view of the above-mentioned problems, and as a result, have extruded a spinning solution containing cellulose triacetate from an outer tube slit of a spinning nozzle having a double tube structure. A liquid which is incompatible with the spinning dope is extruded as a core agent from the inner tube of the spinning nozzle, and the filamentous discharge is run in a gaseous atmosphere, and then introduced into a coagulation bath for coagulation to coagulate. In the production of a mixture of cellulose acetate and N-methylpyrrolidone and a hydroxycarboxylic acid or a hydroxycarboxylic acid derivative in a weight ratio of 8: 1 to 5: 3, a cellulose triacetate concentration of 10 to 25% by weight is used. It has been found that the above problems can be solved by using a spinning dope that has been uniformly dissolved, and the present invention has been completed.

That is, according to the present invention, a cellulose triacetate mixture containing N-methylpyrrolidone and hydroxycarboxylic acid or a hydroxycarboxylic acid derivative in a weight ratio of 8: 1 to 5: 3 has a cellulose triacetate concentration of 10: 1. The spinning dope uniformly dissolved so as to have a concentration of about 25% by weight is extruded from an outer pipe slit of a spinning nozzle having a double pipe structure, and at the same time, a liquid incompatible with the spinning stock liquid as a core agent from an inner pipe of the spinning nozzle. The present invention relates to a method for producing a hollow fiber membrane, characterized in that the hollow fiber membrane is extruded, and the filamentous discharge is run in a gaseous atmosphere, and then introduced into a coagulation bath for coagulation.

In the present invention, cellulose acetate, N-methylpyrrolidone and cellulose acetate are required to produce a hollow fiber membrane having moderate water permeability, high permeability of medium molecular weight substances and excellent molecular weight fractionation properties. It is important to use an undiluted spinning solution in which hydroxycarboxylic acid or a hydroxycarboxylic acid derivative is uniformly dissolved as a swelling agent (phase separation agent).

When a swelling agent other than hydroxycarboxylic acid or a hydroxycarboxylic acid derivative, for example, polyethylene glycol or a polyethylene glycol derivative, is used, it has moderate water permeability, high permeability of medium molecular weight and molecular weight fractionation. It is difficult to obtain a hollow fiber membrane having excellent characteristics. In the present invention, lactic acid,
It is particularly preferred to use at least one selected from mandelic acid, tartaric acid and lower alkyl esters thereof.

In order to produce a hollow fiber membrane having moderate water permeability, high permeability of medium molecular weight compounds and excellent molecular weight fractionation properties, N-methylpyrrolidone and hydroxycarboxylic acid or hydroxycarboxylic acid are required. It is necessary to mix the acid derivative with the acid derivative in a weight ratio of 8: 1 to 5: 3, preferably 7: 1 to 2: 1. When the ratio of N-methylpyrrolidone is more than 8: 1 with respect to the hydroxycarboxylic acid or the hydroxycarboxylic acid derivative, the permeability of the medium-molecular-weight product is reduced. On the other hand, if the ratio is less than 5: 3, it becomes difficult to uniformly dissolve the spinning solution. As a result, spinnability deteriorates and it becomes difficult to produce a uniform hollow fiber membrane.

The spinning solution has a cellulose triacetate content of 10 to 25% by weight, preferably 15 to 23% by weight.
It must be in weight percent. When the content of cellulose triacetate exceeds 25% by weight, it becomes difficult to obtain a hollow fiber membrane having a high permeability of a medium molecular weight substance.
When the amount is less than the weight%, spinning becomes unstable, so that it is difficult to obtain a uniform hollow fiber membrane, and the strength of the hollow fiber is reduced, and the yarn leak is liable to occur.

The hydroxycarboxylic acid or hydroxycarboxylic acid derivative used as a swelling agent in the present invention has solubility in water and N-methylpyrrolidone, and has a boiling point of 100 ° C. or higher and a thermal decomposition temperature of 100 ° C. or higher. ,
It is sufficient that the chemical coagulation value is from 0.3 to 2.5, and particularly preferably, lactic acid, mandelic acid, tartaric acid or lower alkyl esters thereof are used. These swelling agents may be used in combination of two or more.

The term "chemical coagulation value" as used herein is an index indicating the easiness of phase separation when adding a coagulation bath solution of a homogeneous dissolution dope comprising cellulose triacetate, N-methylpyrrolidone and a swelling agent. In the present invention, a uniform dissolution dope at 80 ° C. comprising 1.5 g of cellulose triacetate, 8.4 g of N-methylpyrrolidone as a water-soluble organic solvent, and 3.6 g of the above swelling agent, is used as a coagulation bath solution at a concentration of 30 g.
It is shown by the amount (g) of liquid that causes phase separation when a (weight)% aqueous solution of N-methylpyrrolidone is added. When the chemical coagulation value is less than 0.3, the water permeability of the membrane becomes too large. On the other hand, when the chemical coagulation value exceeds 2.5, a film having high permeability for medium molecular weight substances cannot be obtained.

In the present invention, the viscosity of the spinning dope is preferably 100 to 2000 poise, and more preferably 300 to 1 poise.
It is appropriate to control the temperature of the spinning solution so as to be 000 poise. When the viscosity is less than 100 poise, it is difficult to obtain a hollow fiber membrane having a uniform inner diameter. On the other hand, when the viscosity is more than 2,000 poise, it is difficult to obtain a uniform and thin-walled hollow fiber membrane because the fiber properties deteriorate. Becomes

In the present invention, it is preferable to use a liquid which is incompatible or hardly compatible with the spinning dope as the core liquid.
For example, isopropyl myristate, oleic acid, paraffin sulfate and the like are preferable, and liquid paraffin is particularly preferable. When a water-soluble liquid such as polyethylene glycol, a polyethylene glycol derivative, a hydroxycarboxylic acid, or a hydroxycarboxylic acid derivative is used as the core liquid, spinning is possible, but the roundness of the hollow fiber membrane is impaired,
This is not preferable because the smoothness of the inner surface of the hollow fiber is impaired.

The coagulation bath temperature in the present invention is 10 to 50 ° C.
When the coagulation bath temperature is less than 10 ° C., it is difficult to obtain a hollow fiber membrane having high permeability of a medium molecular weight substance. On the other hand, when the coagulation bath temperature exceeds 50 ° C., a medium molecular weight Although the permeability of the body is large, the water permeability is also increased at the same time, and the molecular weight fractionation characteristics are also reduced, so it has moderate water permeability, the permeability of the medium molecular weight product is large, and the molecular weight fractionation characteristics are excellent A hollow fiber membrane cannot be obtained.

The coagulation bath liquid can be used as long as it is a liquid in which a solvent and a swelling agent are soluble. However, a liquid containing water as a main component is preferable in view of cost and production control. From the viewpoint of quality control of the hollow fiber membrane, the coagulation bath liquid is particularly preferably a liquid composed of water, a solvent and a swelling agent, wherein the ratio of the solvent to the swelling agent is the same as that in the stock spinning solution. The composition of the coagulation bath cannot be uniquely defined because it varies depending on the composition of the spinning solution, the temperature, and the distance (air gap length) between the spinneret and the coagulation bath surface, but the water concentration is 40 to 90% by weight. Is preferred. As a coagulation bath, N- with a water concentration of 40 to 90% by weight is used.
An aqueous methylpyrrolidone solution is particularly preferred.

[0019]

According to the present invention as described above, it is possible to easily produce a cellulose triacetate hollow fiber membrane having a moderate water permeability, a high permeability of a medium molecular weight substance, and an excellent molecular weight fractionation property. Can be.

[0020]

The embodiments of the present invention will be described below with reference to examples. However, the present invention is not limited by these examples.

The dextran transmittance SC having a molecular weight of 70,000 referred to in the present invention is defined by the following equation.

[0022] In SC = C ₂ ÷ C ₁ (the above formula, C ₁ represents the dextran concentrations of molecular weight 70,000 in stock, C ₂ is the molecular weight in the permeate 700
Dextran concentration of 00. )

[0023]

Example 1 20 parts by weight of cellulose triacetate, N
-62 parts by weight of methylpyrrolidone (NMP) and 18 parts by weight of mandelic acid (chemical coagulation value: 0.4) were mixed and uniformly dissolved, and this was used as a spinning stock solution, and spinning was performed using a circular orifice nozzle. A stock solution for spinning at 115 ° C. was discharged from the outer tube, while liquid paraffin was discharged as a core liquid from the inner tube. 15cm of the hollow fiber stock solution coming out of the annular orifice
30% NM kept at 45 ° C after running in air
P solution was introduced into a coagulation bath for 1.1 seconds to coagulate, and then washed with a water washing bath to obtain 40 m / min. At the speed of. 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 192 μm, and the film thickness was 18 μm, and there was almost no variation in the shape.

Further, the ultrafiltration rate UFR of the obtained cellulose triacetate hollow fiber membrane is 172 ml / hr · m
A dextran transmittance DA of mHg · 1.5 m ² and a molecular weight of 10,000 is 42 ml / min. · 1.5 m ² and greater, dextran transmittance SC molecular weight 70,000 0.
060, which was a very small hollow fiber membrane. Thus, a cellulose triacetate hollow fiber membrane having moderate water permeability, high permeability of medium molecular weight substances, and excellent molecular weight fractionation properties was obtained.

[0025]

Example 2 A cellulose triacetate hollow fiber membrane was obtained in the same manner as in Example 1 except that lactic acid (chemical coagulation value: 0.4) was used instead of mandelic acid, and the coagulation bath temperature was changed to 25 ° C. . 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 193 μm, the film thickness was 17 μm, and there was almost no variation in the shape.

The ultrafiltration rate UFR of the obtained cellulose triacetate hollow fiber membrane is 160 ml / hr · m
A dextran transmittance DA of mHg · 1.5 m ² and a molecular weight of 10,000 is 41 ml / min. · 1.5 m ² and greater, dextran transmittance SC molecular weight 70,000 0.
062, a very small hollow fiber membrane. Thus, a cellulose triacetate hollow fiber membrane having moderate water permeability, high permeability of medium molecular weight substances, and excellent molecular weight fractionation properties was obtained.

[0027]

Example 3 The procedure of Example 2 was repeated, except that dimethyl tartrate (chemical coagulation value 0.7) was used instead of lactic acid.
A cellulose triacetate hollow fiber membrane was obtained. The cross-sectional shape of the obtained cellulose triacetate hollow fiber membrane is a perfect circle, and the inner surface of the hollow fiber is smooth and has an inner diameter of 214 μm.
m, the film thickness was 16 μm, and there was almost no variation in shape.

The ultrafiltration rate UFR of the obtained cellulose triacetate hollow fiber membrane is 172 ml / hr · m
A dextran transmittance DA of mHg · 1.5 m ² and a molecular weight of 10,000 is 45 ml / min. · 1.5 m ² and greater, dextran transmittance SC molecular weight 70,000 0.
073, which was a very small hollow fiber membrane. Thus, a cellulose triacetate hollow fiber membrane having moderate water permeability, high permeability of medium molecular weight substances, and excellent molecular weight fractionation properties was obtained.

[0029]

Example 4 A cellulose triacetate hollow fiber membrane was obtained in the same manner as in Example 2, except that ethyl lactate (chemical coagulation value: 1.9) was used instead of lactic acid and the temperature of the spinning solution was 110 ° C. Was. 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 221 μm, and the film thickness was 14 μm, and there was almost no variation in the shape.

Further, the ultrafiltration rate UFR of the obtained cellulose triacetate hollow fiber membrane is 80 ml / hr · mm
The dextran transmittance DA of Hg · 1.5 m ² and molecular weight 10,000 is 29 ml / min. · 1.5 m ² and greater, dextran transmittance SC molecular weight 70,000 0.
063, which was a very small hollow fiber membrane. Thus, a cellulose triacetate hollow fiber membrane having moderate water permeability, high permeability of medium molecular weight substances, and excellent molecular weight fractionation properties was obtained.

[0031]

Comparative Example 1 Example 2 was repeated except that triethylene glycol was used instead of lactic acid and the temperature of the spinning solution was 100 ° C.
In the same manner as in the above, a cellulose triacetate hollow fiber membrane was obtained. The cross-sectional shape of the obtained cellulose triacetate hollow fiber membrane was a perfect circle, the inner diameter was 221 μm, and the film thickness was 18 μm, and there was almost no variation in the shape.

The ultrafiltration rate UFR of the obtained cellulose triacetate hollow fiber membrane is 250 ml / hr · m
A dextran transmittance DA of mHg · 1.5 m ² and a molecular weight of 10,000 is 45 ml / min. · 1.5 m ² and greater, dextran transmittance SC molecular weight 70,000 0.
092. That is, this hollow fiber membrane was a membrane having high permeability for medium molecular weight substances but also high water permeability.

──────────────────────────────────────────────────続 き Continuing from the front page (72) Inventor Takeyuki Kawaguchi 2-1 Hinodemachi, Iwakuni-shi, Yamaguchi Prefecture Teijin Limited Iwakuni Research Center (56) References JP-A-55-62214 (JP, A) JP-A-48-34081 (JP, A) JP-A-50-35073 (JP, A) JP-A-55-84503 (JP, A) JP-A-55-80515 (JP, A) JP-A-57-45304 (JP JP, A) JP-A-59-36715 (JP, A) JP-A-61-185305 (JP, A) JP-A-2-251607 (JP, A) (58) Fields investigated (Int. Cl. ⁶ , (DB name) B01D 71/16 B01D 69/08 D01F 2/28

Claims (4)

(57) [Claims] 1. A mixture of cellulose triacetate and N-methylpyrrolidone and hydroxycarboxylic acid or a hydroxycarboxylic acid derivative in a weight ratio of 8: 1 to 5: 3, wherein the concentration of cellulose triacetate is 10 to 10.
At the same time, the spinning solution uniformly dissolved so as to have a concentration of 25% by weight is extruded from the outer tube slit of a spinning nozzle having a double tube structure, and at the same time, a liquid immiscible with the spinning solution is used as a core agent through the inner tube of the spinning nozzle. A method for producing a hollow fiber membrane made of cellulose triacetate, comprising extruding, running the filamentous discharge in a gaseous atmosphere, and introducing into a coagulation bath for coagulation. 2. The method for producing a hollow fiber membrane according to claim 1, wherein the hydroxycarboxylic acid or the hydroxycarboxylic acid derivative is selected from lactic acid, mandelic acid, tartaric acid and lower alkyl esters thereof. Method. 3. The method for producing a hollow fiber membrane according to claim 1, wherein liquid paraffin is used as the core liquid. 4. The method for producing a hollow fiber membrane according to claim 1, wherein the temperature of the coagulation bath is 10 to 50 ° C.