JP2815405B2 - Method for producing spinneret and hollow fiber - Google Patents

Description

The present invention relates to a double-tube type spinneret and a method for producing hollow fibers using the same. More particularly, the present invention relates to a double-tube type spinneret having a specific structure and a method for producing a porous hollow fiber-like separation membrane using specific spinning conditions.

<Prior Art> Generally, as a double-tube type spinneret used for manufacturing a porous hollow fiber-like separation membrane, a thin tube is inserted into a spinneret hole so that a fluid or gas is injected as a core agent during spinning. There is something.

However, when the viscosity of the polymer solution for spinning (hereinafter also referred to as spinning solution) is low, the core agent is injected in a low-viscosity state in which the solidification of the spinning solution immediately after being discharged from the spinneret has not progressed, Temperature irregularities in each hole of the base,
Fluctuations in the fiber diameter of the hollow fibers are likely to be induced by uneven viscosity of the polymer stock solution and pressure fluctuations of the injected fluid.

For this reason, there have been problems that various condition managements are necessary and complicated.

In order to solve these problems, in the sheath-core type composite spinneret disclosed in Japanese Patent Application Laid-Open No.
A method for producing hollow fibers with a spinneret protruding from an outer die of 12.2 to 50 m / m is disclosed.

However, in this method, since the inner tube protrudes from the spinneret and the frictional resistance is large between the inner spinneret and the spinning solution, shear mixing of the polymer occurs between the inside and outside of the hollow fiber, and the inner and outer layers of the hollow fiber membrane structure are formed. Due to the difference, there is a problem that it is difficult to obtain a separation membrane having sufficient performance, particularly with a porous hollow fiber-shaped separation membrane.

In particular, in order to increase the separation efficiency, when manufacturing a hollow fiber-shaped separation membrane with a special cross-sectional shape, the friction of the inner spinneret of the protruding part of the inner tube of the spinneret causes the agitating of the spinning stock solution to achieve a good cross-sectional shape. There was a problem that an intermediate fibrous separation membrane could not be obtained.

<Object of the Invention> The present invention provides a double-pipe type spinneret having an improved structure and an improved method for producing a hollow fiber using the same, in order to solve the problems in the conventional spinning of hollow fibers. To provide.

<Constitution of the Invention> The inventor of the present invention has conducted intensive studies in order to achieve such an object. As a result, in a double-tube type spinneret, the inner tube of the spinneret protrudes from the outer end face of the spinneret, and By adjusting the outer diameter and the length of the protruding part within a specific range, it is possible to reduce the friction between the spinning stock solution and the protruding inner tube, and it is a good intermediate fiber with a cross-sectional shape with less inner diameter irregularity It was found that a separation membrane of the formula (1) was obtained, and the present invention was achieved.

That is, the present invention provides a double-tube type spinneret, protrudes from the end face of the inner tube outer mouthpiece spinneret, the protruding length l of the inner tube [mm], the outer diameter R ₁ of the inner side of the end face [ mm]
And the outer diameter R ₂ [mm] at the protrusion is expressed by the following formulas (I) and (II): R ₁ > R ₂ (I) R ₁ / R ₂ ≦ l ≦ 10 (R ₁ / R ₂ ) II), and a spinneret having a structure in which a fluid as a core agent can flow out of the inner tube.

Furthermore, the present invention relates to a method for producing a hollow fiber using a double-tube type spinneret, wherein an inner tube of the spinneret protrudes from an end surface of an outer spinneret, and a protrusion length l [mm] of the inner tube; Outer diameter R ₁ [mm] at inner side and outer diameter at protrusion
R ₂ [mm] satisfying the following formulas (1) and (II) R ₁ > R ₂ ... (I) R ₁ / R ₂ ≦ l ≦ 10 (R ₁ / R ₂ ). It is another object of the present invention to provide a method for producing a hollow fiber, wherein a fluid as a core agent is caused to flow out of the inner tube, and a spinning solution is caused to flow out of a gap outside the inner tube.

In addition, the present invention includes a method for producing a hollow fiber in which the viscosity of the spinning dope when discharged from the spinneret is 50 to 1000 poise.

Hereinafter, the present invention will be described in more detail. As an example of the present invention, the case of plasticized melt spinning of cellulose diacetate will be described.

Plasticizer 1 per 100 parts by weight of cellulose diacetate
Fifty parts by weight of the mixture are melt-kneaded with an extruder, and the molten polymer is injected from the outer tubular slit through the inner tube (also referred to as the inner tube) while injecting nitrogen gas from the inside of the inner tube (also referred to as the inner tube) using a double-hole spinneret having a plurality of holes. The plasticized melt of the polymer was discharged in the form of a hollow fiber, cooled and solidified by air just below the die, and then the hollow fiber was wound up.

In such plasticized melt spinning, usually, the viscosity of the plasticized molten liquid is as low as about 100 poise, and when the gas is injected from the inner tube of the double tube type die to maintain the inner diameter of the hollow fiber, the discharge surface of the spinneret is used. Since the viscosity of the plasticized melt is low, unevenness in the viscosity of the plasticized melt at the time of discharge, unevenness of the discharge between the holes of the die and fluctuations in the injection pressure of the gas, etc., cause unevenness in the inner diameter of the hollow fiber, The inner diameter of the hollow fiber discharged from the die discharge surface induces a phenomenon of expanding and contracting in a pulsating manner, and the fiber diameter of the obtained hollow fiber often fluctuates.

Therefore, the inner tube of the double-tube type spinneret is protruded from the outer die surface, and the gas injection position is lowered from the discharge surface, so that the gas is injected while the discharged melt is in an appropriate viscosity range. Various methods were discussed. As a result, the tip of the inner tube of the spinneret is made to have an appropriate diameter, and is protruded from the outer spinneret, thereby reducing the influence of unevenness in the viscosity of the spinning solution, unevenness in the temperature of the spinneret, unevenness in the discharge, and the like. It was found that the fiber diameter of the hollow fibers could be made uniform.

In this case, the length l of the inner tube protruding from the spinneret
[Mm] is the outer diameter R ₁ [mm] of the inner tube of the spinneret and the outer diameter R ₂ [mm] of the inner tube at the portion protruding from the spinneret, and R ₁ >
It has been found that if R ₂ and R ₁ / R ₂ ≦ l ≦ 10 (R ₁ / R ₂ ), a hollow fiber having a good fiber diameter can be obtained, and the present invention has been accomplished.

Under the condition of R ₁ / R ₂ > 1, unevenness in the diameter of the hollow fiber is liable to occur under the influence of the discharge unevenness of the spinning stock solution, the temperature unevenness of the double-tube type spinneret, the fluctuation of the gas injection pressure and the like.

Under the condition of l> 10 (R ₁ / R ₂ ), the friction between the protruding inner tube and the discharged spinning solution becomes large, and the unevenness of the cross-sectional shape and unevenness of the membrane structure on the inner and outer surfaces of the hollow fiber are caused. This is not preferable because there is a problem that it is difficult to obtain a film having uniform film performance because the property is increased.

In the method for producing a hollow fiber according to the present invention, the particles that flow out as the core agent from the inside of the inner tube of the double-tube spinneret may be liquid or gas. That is, when the fluid is compressible, that is, when the fluid is a gas, the inner diameter of the obtained hollow fiber tends to fluctuate. Therefore, it is effective to apply the present invention. As such a core material, an inert material that does not adversely affect the discharged hollow fiber material is preferable. For example, in the case of a gas, nitrogen gas is used.

Further, in the method for producing a hollow fiber of the present invention, the viscosity of the spinning dope when discharged from the double-tube type spinneret is 50 to 1000.
In the case of poise, it is effective to spin under conditions within the range of the above formula (I). A particularly preferred viscosity range is
More than 60poise. The range in which the effect of improving spinnability and uniformity by using the spinneret of the present invention is easily obtained is about 500 poise or less, and about 300 poise is particularly effective.

That is, in the viscosity range of such spinning solution obtained if protruding length l of the inner tube of the spinneret has an inner tube diameter R ₂ projecting inner pipe diameter R ₁ of the spinneret portion of R ₁ / R _2> l The inner diameter of the hollow fiber is likely to fluctuate.

In addition, as a preferable range of the protrusion of the inner tube and the length 1 in the production method of the present invention, a range satisfying the following formula (II) is exemplified.

2 (R ₁ / R ₂ ) ≦ l <8 (R ₁ / R ₂ ) (II) By spinning under the conditions satisfying the above expression, it is possible to more reliably produce a hollow fiber having a diameter with little fluctuation. it can.

Examples of the spinning method applied to the hollow fiber production method of the present invention include plasticized melt spinning, melt spinning, and wet spinning. Specific examples of the plasticized melt spinning include an organic fusion such as cellulose esters such as cellulose diacetate and a water-soluble polyhydric alcohol such as ethylene glycol and polyethylene glycol and a plasticizer such as a glycerin polymer. And a method using a spinning solution containing an organic polymer such as polyether sulfone and a plasticizer such as N-methyl-2-pyrrolidone and polyethylene glycol. As a specific example of wet spinning, a method using a spinning solution containing an organic polymer of cellulose esters, N-methyl-2-pyrrolidone, ethylene glycol and the like can be mentioned.

The hollow fibers obtained by the production method of the present invention include not only those having a circular cross-sectional shape but also those having an irregular shape having, for example, a projection extending outward in the axial direction. The preferred size of these hollow fibers is 150 to 250 μm in inner diameter and 10 to 30 μm in thickness (thickness excluding protrusions, if any).

Also preferred as such hollow fibers are porous hollow fibers whose walls are porous, such as hemodialysis, plasma separation, blood treatment such as artificial lung, and water treatment such as reverse osmosis and ultrafiltration. The porous hollow fibers for fluid separation described above are particularly preferred. In the case of a method for producing a porous hollow fiber, a treatment for making the wall portion porous is required. For example, in the case of plasticized melt spinning, a method of spinning under predetermined conditions as described above, cooling and solidifying, and then extracting and removing a plasticizer by immersing in water or the like to impart porosity is used. Used. In the case of wet spinning, a method of imparting porosity by spinning, immersing in a coagulation bath and coagulating to extract and remove the solvent in the spinning dope as usual is used.

<Examples> Examples of the present invention and comparative examples are shown below, but the present invention is not limited thereto.

A mixture of 100 parts by weight of cellulose diacetate and 150 parts by weight of a polyethylene glycol plasticizer is melt-kneaded with an extruder at a temperature of about 190 ° C. (viscosity of 100 poise) at the time of discharge, and then double-pulled through a gear pump. The polymer was discharged from the outer circular slit while N ₂ gas was injected from the inner tube of the base, cooled by wind, and the hollow fiber was wound up.

The spinning was performed by changing the diameter and length of the protruding portion of the inner tube of the double tube type spinneret.

Regarding the fiber diameter of the obtained hollow fiber, the fiber diameter at the cross section of the hollow fiber was measured with a microscope equipped with a scale. The results obtained are shown in Tables 1 and 2.

In addition, the thickness of these hollow fibers was about 15 μ. or,
Using the double-tube spinneret in which a wedge-shaped fold was cut on the outer periphery of the prefectural police slit outside the double-tube spinneret, spinning of the finned hollow fiber was carried out in the same manner. The height of the fin on the outer periphery of the hollow fiber was measured.

<Effect of the Invention> According to the method for producing a hollow fiber using the spinneret of the present invention, even a low-viscosity spinning dope can easily produce a hollow fiber with little unevenness in the yarn diameter.

Also, hollow fibers having a good cross-sectional shape can be easily produced for hollow fibers having an irregular cross-section.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a partially enlarged longitudinal sectional view of an example of a double tube type spinneret used in the present invention. R ₁ indicates the outer diameter of the inner tube of the double tube type spinneret, and R ₂ indicates the outer diameter of the inner tube of the portion protruding from the outer tube of the double tube type spinneret. Reference numeral 1 denotes a flow path of a fluid inside the inner tube 3, and reference numeral 2 denotes a flow path of a stock solution for spinning. Reference numeral 4 denotes a discharge end face of the spinneret.

Claims (3)

(57) [Claims] In a double-pipe type spinneret, an inner tube of the spinneret protrudes from an end face of an outer spinneret, a projection length l [mm] of the inner pipe, and an outer diameter R ₁ [inner than the end face]. mm] and the outer diameter R ₂ [mm] at the protrusion are represented by the following formulas (I) and (II): R ₁ > R ₂ (I) R ₁ / R ₂ ≦ l ≦ 10 (R ₁ / R ₂ ) ... (II), wherein the spinneret has a structure capable of allowing a fluid as a core agent to flow out of the inner tube. 2. A method for producing a hollow fiber using a double-tube type spinneret, wherein an inner tube of the spinneret protrudes from an end face of an outer spinneret, and a protrusion length l [mm] of the inner tube, the end face thereof Outer diameter R ₁ [mm] at the inner side and outer diameter R ₂ [m at the protrusion
m] satisfy the following formulas (1) and (II): R ₁ > R ₂ (I) R ₁ / R ₂ ≦ l ≦ 10 (R ₁ / R ₂ ) (II) A method for producing hollow fibers, wherein a fluid as a core agent is caused to flow out of the inner tube, and a stock solution for spinning is caused to flow out of a gap outside the inner tube. 3. The method for producing hollow fibers according to claim 2, wherein the viscosity of the spinning dope when discharged from the spinneret is 50 to 1000 poise.