JPH10314558A - Preparation of hollow fiber blood purification membrane - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a blood purification membrane having a sharp fractionating characteristic by spinning under specified conditions of draft ratio and discharge linear velocity a stock solution prepared by dissolving polysulfone polymer and hydrophilic polymer in a solvent having a particular viscosity, which is common to both the polysulfone polymer and the hydrophilic polymer. SOLUTION: A polysulfone hollow fiber membrane provided with hydrophilic property, which is a blood purification membrane having such a sharp molecular weight fractionating characteristic as to avoid leak of useful protein such as albumin, is prepared. In this case, a spinning stock solution of a viscosity of 700-3500 mPa.s prepared by dissolving polysulfone polymer and hydrophilic polymer in a solvent common to both the polysuflone polymer and the hydrophilic polymer is processed to be spun at a draft ratio of 1.1-1.9 and at a discharge linear velocity of 90 m/min. or less. The hydrophilic high molecule is not particularly restricted, and from the viewpoint of affinity to polysulfone resin polyvinyl pyrrolidone and the like are preferable and as the common solvent dimethylacetamid and the like are listed.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a polysulfone hollow fiber type blood purification membrane and a method for producing the same.

[0002]

2. Description of the Related Art Since a polysulfone-based polymer is a hydrophobic material, a permselective separation membrane using the same as a material is selectively permeated using a hydrophilic material such as a cellulose-based, polyacrylonitrile-based or polyamide-based material. Compared with the membrane, the wettability is poor, and when dried, the permeability deteriorates. Therefore, a permselective separation membrane in which a hydrophilic polymer is contained in a permselective separation membrane made of a polysulfone-based polymer and a method for producing the same have been proposed.

For example, Japanese Patent Publication No. 2-18695 discloses that a separation membrane produced by spinning a stock solution comprising polysulfone, polyvinylpyrrolidone having a molecular weight of 100,000 or more, and a common solvent thereof, has a polyvinyl alcohol having a molecular weight of 100,000 or more in a separation membrane. A polysulfone-based separation membrane containing 5-70% by weight of pyrrolidone and having a water absorption capacity of 11% or more and a method for producing the same are disclosed, but there is no description about the spinning draft rate. Japanese Patent Publication No. 5-54337 discloses that a hydrophilic polymer produced by spinning a low-viscosity stock solution comprising a hydrophobic polymer, a hydrophilic polymer and a common solvent thereof contains 1 to 10% by weight of a hydrophilic polymer, A hollow fiber membrane for blood treatment having a water absorption capacity of 3 to 10% and a method for producing the same are disclosed.

According to the publication, regarding the spinning draft rate,
It is preferred that the speed at which the spinning composition exits the spinneret and the speed at which the produced fibers are drawn off are generally the same, ie a spin draft of 1 is preferred. However, when the draft rate is actually 1, it is difficult to increase the spinning speed.
However, if the discharge rate of the stock solution is increased to increase the spinning speed,
Problems such as an increase in pressure loss before the spinneret, an increase in the discharge linear velocity of the spinning dope, and an uneven discharge of the spinning dope are likely to occur, making spinning unstable and disturbing the membrane structure.

Japanese Patent Application Laid-Open No. 6-165926 discloses that if the nozzle draft is made extremely large or small, the production becomes unstable. Therefore, the nozzle draft is usually set in the range of 2 to 5. However, when the draft rate exceeds 2, a problem is pointed out that the hollow fiber has a structure in which the inner surface is torn, and albumin, which is a useful protein, tends to leak.

[0006]

The above-mentioned polysulfone-based separation membrane has some problems in production when used for a blood purification membrane. That is, the relationship between the spinning draft and the membrane performance, the membrane structure has not been sufficiently studied, and when changing the spinning speed, the dimensions of the membrane, and the spinneret size, the performance and structure of the membrane greatly change, A prompt response cannot be taken.
The present invention is a polysulfone-based hollow fiber membrane to which hydrophilicity has been imparted, which maintains high permeability, does not leak useful proteins such as albumin, and has a sharp molecular weight fractionation blood purification. An object of the present invention is to provide a method for producing a film with excellent productivity.

[0007]

Means for Solving the Problems The present inventors have conducted intensive studies to solve the above problems, and as a result, by producing a spinning dope having an appropriate viscosity at an appropriate spinning draft rate,
The present inventors have found that it is possible to produce a blood purification membrane having no tear structure on the inner surface of the hollow fiber and having a sharp fractionation with excellent productivity, and have completed the present invention. That is, in the present invention, a polysulfone-based polymer and a hydrophilic polymer are dissolved in a common solvent of the polysulfone-based polymer and the hydrophilic polymer, and have a viscosity of 700 to 3500 mPa · s.
A spinning stock solution having a draft rate of 1.1 to 1.9 and a discharge linear velocity of 90 m / min or less.

Hereinafter, the present invention will be described in detail. The polysulfone-based polymer referred to in the present invention is represented by the following formula (1) or (2):

Embedded image

Embedded image Is a polymer comprising a repeating unit of the formula (1), but may be a polymer containing a functional group or an alkyl group, and is not particularly limited.

As the hydrophilic polymer used in the present invention, for example, water-soluble cellulose derivatives such as polyvinylpyrrolidone (hereinafter referred to as PVP), polyethylene glycol, polyglycol monoester, starch and derivatives thereof, carboxymethyl cellulose and cellulose acetate are used. They can be used in combination.
From the viewpoint of affinity for the polysulfone resin, polyvinyl pyrrolidone and polyethylene glycol are preferably used, and polyvinyl pyrrolidone is most preferably used.

[0010] These water-soluble polymers and polysulfone polymers are dissolved in both common solvents to prepare a uniform spinning solution. Examples of the common solvent that dissolves both the polysulfone-based polymer and the hydrophilic polymer include dimethylacetamide (hereinafter referred to as DMAC), dimethylsulfoxide (hereinafter referred to as DMSO), N-methyl-2-pyrrolidone, and dimethylformamide. , Sulfolane, dioxane and the like or a solvent composed of a mixture of two or more of the above. Among them, dimethylacetamide and dimethylsulfoxide are preferably used.

Further, an additive such as water may be added to the spinning dope for controlling the pore diameter. When the viscosity of the spinning solution is too low, large macrovoids appear remarkably inside the membrane.However, in the case of a hollow fiber membrane for blood purification, when a large number of such macrovoids are present, blood coagulation easily occurs during hemodialysis. Thus, it is preferable that the hollow fiber membrane used for hemodialysis has no macrovoids. The term “macrovoid” as used herein refers to a space having a maximum diameter of 5 μm or more in a space where no polymer exists in the film.

On the other hand, if the viscosity of the stock solution is too high, the pressure before the spinneret is too high, and stable spinning cannot be performed. Therefore, in the present invention, the viscosity of the spinning stock solution is 700 to 3
It is necessary to be in the range of 500 mPa · s, and 10
The range of 00 to 2500 mPa · s is preferable. The viscosity referred to in the present invention is a value obtained by measuring a spinning dope with a rotary viscometer at the same temperature as the spinneret temperature under film-forming conditions. The viscosity of the spinning dope depends on the molecular weight of the hydrophilic polymer, the concentration of the polysulfone polymer and the hydrophilic polymer in the spinning dope, the temperature of the spinning dope, and all factors have a significant effect on the formation of the membrane structure. . In the present invention, the raw materials to be used are appropriately selected,
By setting the conditions of concentration and temperature, the viscosity of the stock solution is adjusted to the above range.

If the amount of the polysulfone-based resin is too small, it is difficult to form a film and the film strength becomes too weak. If the amount is too large, phenomena such as poor spinnability and too small a pore diameter occur. , Preferably 15 to 20% by weight, more preferably 16 to 18% by weight. However, this range is not absolute, and depending on the properties of the target hollow fiber membrane, it can be made smaller or larger than this range, and the film properties change by changing other spinning conditions. An optimal combination may be appropriately selected.

Since the purpose of adding the hydrophilic polymer to the spinning solution is to leave the hydrophilic polymer in the hollow fiber membrane to impart hydrophilicity to the membrane, the selection of the molecular weight is extremely important. is there. This is because if the molecular weight of the hydrophilic polymer is too small, the hydrophilic polymer easily elutes from the membrane during coagulation of the spinning dope and at the time of washing the obtained hollow fiber membrane. This is because a large amount of the hydrophilic polymer must be added to the spinning solution in order for the hydrophilic polymer necessary for imparting hydrophilicity to remain in the hollow fiber membrane.

Therefore, in order to increase the residual ratio of the hydrophilic polymer in the hollow fiber membrane, it is better that the molecular weight is large, whereby the hydrophilic polymer added to the spinning stock solution can be effectively utilized, and the amount added can be reduced. It is preferable because it can be reduced. When the hydrophilic polymer is polyvinylpyrrolidone, it is preferable that the molecular weight is large. For example, when polyvinylpyrrolidone having a viscosity average molecular weight of 500,000 or more is used, 2 is preferred.
Preferably, the amount of addition is about 6% by weight.

As the hollow inner liquid, water or a coagulating liquid mainly composed of water can be used, and its composition and the like need only be determined depending on the intended membrane performance of the hollow fiber membrane.
In general, a mixed solution of the solvent and water used for the spinning solution is preferably used. For example, a 5 to 60% by weight aqueous solution of DMAC is used, and particularly preferably 10 to 50% by weight.

When forming a hollow fiber membrane, a tube-in-orifice type double spinning port is used, and the spinning solution and the hollow inner solution for coagulating the spinning solution are simultaneously extruded from the spinning port into the air. After running in a free running section of 20 to 80 cm, it is immersed and coagulated in a coagulation bath mainly composed of water installed under the spinneret, and then wound.

The spinning draft rate referred to in the present invention is a ratio of a discharge linear speed at which a stock spinning solution is discharged from a tube-in-orifice type double spinning annular slit die to a winding speed of a hollow fiber. This is a value obtained by dividing the winding speed by the linear spinning speed of the stock spinning solution. In the case of a low spin draft, the slit width of the spinneret needs to be reduced accordingly. In the case of a hollow fiber membrane for blood purification, the range of the film thickness usually used is 20 to 60 μm. For this reason, when the spinning draft rate is low, increasing the spinning speed increases the discharge linear velocity of the stock solution and increases the pressure loss at the spinneret, which tends to make spinning unstable. In addition, since the discharge unevenness of the undiluted solution occurs, the film structure is disturbed, and the dispersion of the water permeability and the solute permeability is increased. Furthermore, problems are pointed out that the narrow slit width makes it difficult to align the spinneret, and that the spinneret itself becomes difficult to manufacture and costs high.

Conversely, if the spinning draft rate is too high, the inner surface of the hollow fiber is strongly subjected to the stress caused by the draft, and the dense layer on the inner surface of the membrane becomes torn, and pores having a particularly large pore diameter are formed. This causes a problem of leakage of albumin, which is a useful protein. This problem can be improved to some extent but is not sufficient by controlling the viscosity of the stock solution by changing the composition of the stock solution or increasing the temperature of the stock solution. Therefore, in the present invention, the spinning draft ratio needs to be in a narrow range of 1.1 to 1.9, and preferably in a range of 1.1 to 1.5.

The linear velocity at which the stock solution is discharged is the linear speed at which the stock solution is discharged from the spinneret during spinning. The discharge flow rate of the stock solution per unit time is divided by the cross-sectional area of the stock solution discharged from the spinneret. Value. When the discharge linear velocity of the undiluted solution is increased, the ununiform discharge of the undiluted solution becomes large, and a hole having a large pore diameter is formed due to the unevenness of the structure of the film, thereby causing albumin leakage. In the present invention, the discharge linear velocity of the stock solution is 9
0 m / min or less, and 70 m / m
in or less, and more preferably 60 m / min.
It is more preferred that:

The hollow fiber spun and wound as described above is post-treated by a known method. That is, the solvent and excess hydrophilic polymer are removed by washing with hot water or the like, and glycerin is applied as necessary, followed by dry heat drying. Further, a method of winding the hollow fiber after winding it after washing and drying with hot water or the like without drying after the winding is also included in the scope of the present invention. It is to adjust the spinning draft rate to 1.1 to 1.9 or less under the condition that the linear velocity of discharge from the spinneret is adjusted to 90 m / min or less by adjusting to 700 to 3500 mPa · s.

[0022]

The present invention will be described in more detail with reference to the following examples, which do not limit the scope of the present invention. (Example 1) Polysulfone (P-1700: AMOCO
18 parts by weight and PVP (K-90: ISP) 3
Parts by weight were dissolved in 40 parts by weight of DMAC, 38 parts by weight of DMSO, and 1 part by weight of water, and stirred for 10 hours to obtain a spinning dope.
The viscosity of this spinning dope was 2,600 mPa · s at 40 ° C. This stock solution was made into a hollow inner solution using a 40% DMAC aqueous solution, discharged from an annular die having a slit width of 59.5 μm, and wound at a spinning speed of 50 m / min. 45μm hollow fiber thickness when dried
Since the stock solution discharge flow rate was adjusted to match m, the stock solution discharge linear speed was 35.7 m / min, and the draft rate was 1.4. FIG. 1 shows the state of the inner surface of this film. According to FIG. 1, there is no torn shape and the surface is smooth.

Comparative Example 1 The same spinning stock solution as in Example 1 was used
A 0% aqueous solution of DMAC is used as the hollow internal solution, and the slit width is 125
It was discharged from an annular die having a diameter of μm and wound up at a spinning speed of 50 m / min. Since the undiluted solution discharge flow rate was adjusted so that the thickness of the hollow fiber at the time of drying was adjusted to 45 μm, the undiluted solution discharge linear velocity was 15.6 m /
Minutes, and the draft rate was 3.2. FIG. 2 shows the state of the inner surface of this film. According to FIG. 2, the inner surface has a shape that is torn under the influence of the draft.
It is considered that in Example 1, the draft rate was low and the surface was not affected by such a draft, and the surface became smooth.

Comparative Example 2 The same spinning dope as in Example 1 was used
A 0% DMAC aqueous solution is used as the hollow inner solution, and the slit width is 50 μm.
m and wound up at a spinning speed of 50 m / min.
The discharge rate of the undiluted solution was adjusted so that the thickness of the hollow fiber at the time of drying was adjusted to 45 μm, so that the linear velocity of undiluted solution was 49.9 m / min and the draft rate was 1.0. FIG. 3 shows the state of the inner surface of this film. According to FIG. 3, the effect of the draft is reduced on the inner surface, and there is no torn shape. However, streaky irregularities are observed due to the excessive linear discharge speed of the stock solution or the influence of uneven stock solution discharge. Can be Further, the hollow fiber was easily eccentric.

Example 2 Polysulfone (P-170)
0: manufactured by AMOCO) and 17 parts by weight of PVP (K-90:
2 parts by weight (made by ISP) and 7 parts by weight of PVP (K-30: made by ISP) were dissolved in 73 parts by weight of DMAC and 1 part by weight of water and stirred for 10 hours to prepare a spinning dope. The viscosity of this spinning dope was 1,400 mPa · s at 45 ° C. This stock solution was made into a hollow inner solution using a 40% DMAC aqueous solution, discharged from an annular die having a slit width of 59.5 μm, and wound at a spinning speed of 50 m / min. The discharge rate of the undiluted solution was adjusted so that the thickness of the hollow fiber during drying was adjusted to 45 μm.
It was 3 m / min, and the draft rate was 1.4. FIG. 4 shows the state of the inner surface of this film. According to FIG. 4, no tearing structure is seen and the surface is smooth.

(Comparative Example 3) The same spinning dope as in Example 2
A 0% aqueous solution of DMAC is used as the hollow internal solution, and the slit width is 125
It was discharged from an annular die having a diameter of μm and wound up at a spinning speed of 50 m / min. Since the undiluted solution discharge flow rate was adjusted so that the thickness of the hollow fiber during drying was adjusted to 45 μm, the undiluted solution discharge linear velocity was 15.9 m /
Minutes, and the draft rate was 3.1. FIG. 5 shows the state of the inner surface of this film. According to FIG. 5, although the influence of the draft is mitigated due to the low viscosity of the stock solution, a tear structure is still observed.

Comparative Example 4 The same spinning dope as in Example 2 was used.
A 0% DMAC aqueous solution is used as the hollow inner solution, and the slit width is 50 μm.
m and wound up at a spinning speed of 50 m / min.
Since the stock solution discharge flow rate was adjusted so that the thickness of the hollow fiber at the time of drying was adjusted to 45 μm, the stock solution discharge linear velocity was 50.3 m / min, and the draft rate was 1.0. FIG. 6 shows the state of the inner surface of this film. According to FIG. 6, the effect of the draft is alleviated, and no tearing structure is observed. Also, the hollow fiber was easily eccentric.

(Experimental Examples) Examples 1-2 and Comparative Examples 1-4
Using the hollow fiber membrane obtained in the above, a mini-module (effective length 25 cm) consisting of 100 pieces was prepared, and the sieving coefficients of plasma proteins having different molecular weights were measured using human serum. Table 1 shows the results.

[Table 1] It can be seen that the example has less albumin leakage than the comparative example.

[0029]

As described above, according to the method of the present invention, it is possible to provide a polysulfone-based blood purification membrane having a stable and excellent membrane performance and a membrane shape when the spinning draft is in the range of 1.1 to 1.9. Can be. On the other hand, if the spinning draft exceeds 2,
The inner surface is torn, which can be improved to some extent by lowering the viscosity of the stock solution, but not enough. Also, when the spinning draft is near 1, streaky irregularities are formed on the inner surface of the hollow fiber due to the unevenness of undiluted solution discharge, solute permeation performance becomes unnecessarily large. Leaks are a concern. Eccentricity also increases.

[Brief description of the drawings]

FIG. 1 is a scanning electron micrograph (magnification: 10,000 times) of the inner surface of a hollow fiber obtained in Example 1.

FIG. 2 is a scanning electron micrograph (magnification: 10,000 times) of the inner surface of the hollow fiber obtained in Comparative Example 1.

FIG. 3 is a scanning electron micrograph (magnification: 10,000) of the inner surface of the hollow fiber obtained in Comparative Example 2.

FIG. 4 is a scanning electron micrograph (magnification: 10,000 times) of the inner surface of the hollow fiber obtained in Example 2.

FIG. 5 is a scanning electron micrograph (magnification: 10,000) of the inner surface of the hollow fiber obtained in Comparative Example 3.

FIG. 6 is a scanning electron micrograph (magnification: 10,000 times) of the inner surface of the hollow fiber obtained in Comparative Example 4.

Claims (1)

[Claims] 1. A spinning dope having a viscosity of 700 to 3500 mPa · s, in which a polysulfone-based polymer and a hydrophilic polymer are dissolved in a common solvent of the polysulfone-based polymer and the hydrophilic polymer, having a draft rate of 1.1 to 1.9. A method for producing a polysulfone-based hollow fiber type blood purification membrane, comprising spinning at a discharge linear velocity of 90 m / min or less.