JPH0359105A - Spinning cap and production of hollow fiber - Google Patents

Abstract

PURPOSE:To readily obtain hollow fiber having a slight fluctuation of fiber diameter, etc., by spinning a dope using double tube-type spinning cap having inner tube more protruding than end face of outer cap and adjusting outer diameter and length of protrusion part in specific range. CONSTITUTION:A double tube-type spinning cap having inner tube 3 more protruding than end face of outer cap and satisfying formula I (R1 is outer diameter at inside from end face; R2 is outer diameter at protruding part) and formula II (l is protruding length of inner tube) is used, then fluid such as nitrogen gas as a core agent is discharged from inside of said inner tube 3 and simultaneously a spinning dope composed of organic molten mixture of cellulose diacetate, etc., and plasticizer, etc., is discharged from gap outside of the inner tube to afford hollow fiber having a slight fluctuation of inner diameter and excellent shape of cross section.

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The present invention relates to a double-tube spinneret and a method for producing hollow fibers using the same. In more detail, 2 of a specific structure
This invention relates to the production of porous hollow fiber separation membranes using a double-tube spinneret and specific spinning conditions.

<Prior art> In general, a double-tube spinneret used for manufacturing porous hollow fiber separation membranes is a spinneret in which a thin tube is inserted into the spinneret hole and a fluid or gas is injected as a core agent during spinning. There is something I did.

However, if the viscosity of the polymer stock solution for spinning (hereinafter also referred to as the spinning stock solution) is low, the core agent is injected in a low viscosity state where the spinning stock solution has not yet solidified immediately after being discharged from the spinneret. Furthermore, variations in the diameter of the hollow fiber are likely to occur due to temperature variations in each hole of the mouthpiece, viscosity variations in the polymer stock solution, and pressure variations in the injected fluid.

For this reason, there are problems such as the necessity of managing various conditions and the complexity of the management.

In order to solve these problems,
discloses a method for manufacturing hollow fibers using a sheath-core type composite spinneret in which the tip of the inner spinneret protrudes 12.2 to 50 m/m from the outer spinneret in a protruding manner.

However, in this method, since the inner tube protrudes from the spinneret, there is a large frictional resistance between the inner tube and the spinning dope, which causes shedding and agitation of the polymer between the inside and outside of the hollow fibers, and the inner and outer layers of the hollow fiber membrane structure. Because of this difference, there is a problem that it is difficult to obtain a separation membrane with sufficient performance, especially in the case of porous hollow fiber separation membranes.

In particular, when manufacturing a hollow fiber separation membrane with a special cross-sectional shape in order to improve separation efficiency, the friction of the inner spinneret of the protruding inner tube of the spinneret causes the spinning dope to be agitated, resulting in a good cross-sectional shape. There was a problem that a hollow fiber separation membrane could not be obtained.

<Objective of the Invention> The present invention provides a double-tube spinneret with an improved structure and an improved hollow fiber manufacturing method using the same, in order to solve the problems in conventional hollow fiber spinning. This is what we provide.

<Structure of the Invention> As a result of intensive research to achieve the above object, the present inventor has discovered that in a double-tube spinneret, the inner tube of the spinneret protrudes from the end surface of the outer cap, and the protruding portion By adjusting the outer diameter and the length of the protrusion within a specific range, it is possible to reduce the friction between the spinning dope and the protruding inner tube, creating a hollow fiber with a good cross-sectional shape with less unevenness in the inner diameter. The present invention was achieved by discovering that a separation membrane of

That is, the present invention provides a double-tube spinneret in which the inner tube of the spinneret protrudes from the end surface of the outer spinneret, the protrusion length of the inner tube j) [mm], and the outer diameter R+[mm] inside the end surface.
+nm] and the outer diameter &[mm] of the protrusion are expressed by the following formula (
I) and (I() R1>&...(I) R1/R2 upper 1≦10(R1/R2)...(I
The present invention provides a spinneret characterized by satisfying I> and having a structure that allows a core fluid to flow out from the inside of the inner tube.

Furthermore, the present invention provides a hollow fiber manufacturing method using a double-tube spinneret, in which an inner tube of the spinneret protrudes from an end surface of an outer spinneret, and the protruding length l [mm] of the inner tube is The outer diameter Rt [mm] at the inner side and the outer diameter R2 [mm] at the protruding portion are expressed by the following formula (I) and (II>R1>& ... (I) R1/R2 upper 1≦10 (R1/R2) ...(I
), and provides a method for producing a hollow fiber, characterized in that a core fluid is allowed to flow out from the inside of the inner tube, and a spinning stock solution is allowed to flow out from a gap outside the inner tube. It is something to do.

The present invention includes a method for producing hollow fibers in which the spinning dope has a viscosity of 50 to 1000 poise when discharged from the spinneret.

The present invention will be explained in more detail below. 1 of the present invention
As an example, the case of moldable melt spinning of cellulose diacetate will be explained.

A mixture of 100 parts by weight of cellulose diacetate and 150 parts by weight of plasticizer is melt-kneaded using an extruder, and the molten polymer is poured into the inner tube (also called inner tube) using a double-tube spinneret with multiple holes. While more nitrogen gas was injected, the plasticized polymer melt was discharged in the form of hollow fibers from the outer tubular slit, and after being cooled and solidified by air directly under the mouthpiece, the hollow fibers were wound up.

In such plasticized melt spinning, the viscosity of the plasticized melt is usually as low as about 100 poise, and when the inner diameter of the hollow fiber is maintained by injecting gas from the inner tube of the double tube type spinneret, the discharge of the spinneret is On the other hand, due to the low viscosity of the plasticized melt, unevenness in the inner diameter of the hollow fibers may occur due to viscosity unevenness when the plasticized melt is discharged, discharge unevenness between each hole of the mouthpiece, and fluctuations in gas injection pressure. , which induces a phenomenon in which the inner diameter of the hollow fiber discharged from the nozzle discharge surface engraves and contracts in a pulsating manner.
Variations in the diameter of the resulting hollow fibers often occur.

Therefore, by protruding the inner tube of the double-tube spinneret from the outer spinneret surface and lowering the gas injection position below the discharge surface, gas is injected when the discharged melt has an appropriate viscosity range. Various methods were considered. As a result, by making the tip of the inner tube of the spinneret have an appropriate diameter and protruding from the outer tube, the effects of viscosity unevenness on the spinning stock solution side, temperature unevenness of the spinneret, discharge unevenness, etc. can be reduced. It has been found that this is possible and that the diameter of the hollow fibers can be made uniform.

In this case, the length of the inner tube protruding from the spinneret, Q
[mm] is the outer diameter R1 [mm] of the inner tube of the spinneret and the outer diameter Rz [I
l+m] is R1>Rs and R1/R2≦j)<
The inventors have discovered that hollow fibers with a good yarn diameter can be obtained within the range of 10 (R+/R2), leading to the present invention.

Under the condition of R+/R2>n, uneven yarn diameter of the hollow fibers is likely to occur due to the influence of uneven discharge of the spinning dope, uneven temperature of the double-tube spinneret, fluctuations in gas injection pressure, and the like.

Under the condition of fl > 10 (R1/R2), the friction between the protruding inner tube and the discharged spinning stock solution increases,
This is undesirable because unevenness in the cross-sectional shape and non-uniformity in the M structure on the inner and outer surfaces of the hollow fibers increase, making it difficult to obtain uniform membrane performance.

The granules flowing out as a core material from the inside of the inner tube of the double-tube spinneret in the method for producing hollow fibers of the present invention include:
It may be a liquid or a gas. That is, when such a fluid is compressible, that is, when it is a gas, the inner diameter of the obtained hollow fibers tends to vary, so it is effective to apply the present invention. The particles used as the core material are preferably inert particles that do not have a negative effect on the discharged hollow fiber material, such as nitrogen gas.

In addition, in the method for producing hollow fibers of the present invention, the viscosity of the spinning stock solution when discharged from the double tube spinneret is 5 (1 to 1
000 poise, it is effective to perform spinning under conditions within the range of formula (I).

A particularly preferable viscosity range is 6Q poise or higher.

The range where it is easy to obtain the effects of improving spinnability and fiber uniformity by using the spinneret of the present invention is approximately 500 poise.
Below, a particularly effective range is about 300 poise.

That is, in the viscosity range of the spinning dope, the protruding length 1 of the inner tube of the spinneret is equal to Fluctuations in inner diameter are likely to occur.

In addition, a preferable range of the length 1 of the protrusion of the inner tube in the manufacturing method of the present invention is a range that satisfies the following formula (I[).

2 (R1/R2)≦41 <8 (R1/R2) ・
(II) By spinning under conditions that satisfy this formula, hollow fibers with diameters that vary less can be produced more reliably.

Examples of the spinning methods applied to the method for producing hollow fibers of the present invention include plasticized melt spinning, melt spinning, and wet spinning. Specific examples of plasticized melt spinning include organic fusion products such as cellulose esters such as cellulose diacetate, and plasticizers such as water-soluble polyhydric alcohols such as ethylene glycol and polyethylene glycol, and glycerin polymers, and may be used as necessary. Examples include a method using a spinning dope containing other additives, and a method using a spinning dope containing an organic polymer such as polyethersulfone and a plasticizer such as N-methyl-2-pyrrolidone and polyethylene glycol. A specific example of wet spinning is a method using a spinning dope containing an organic polymer of cellulose esters, N-methyl-2-pyrrolidone, ethylene glycol, and the like.

The hollow fiber obtained by the production method of the present invention includes:
In addition to those having a circular cross-sectional shape, for example, those having an irregular shape having a protrusion extending outward in the axial direction can be mentioned.

The preferred size of these hollow fibers is that the inner diameter is 1
50 to 250μ, and the thickness (thickness excluding protrusions, if any) is 10 to 30μ.

Preferable examples of such hollow fibers include porous hollow fibers whose walls are porous, and which are used for blood processing such as hemodialysis, plasma separation, and artificial lungs, and for water processing such as reverse osmosis and ultrafiltration. Porous hollow fibers for fluid separation are particularly preferred. In addition, in the case of a method for manufacturing porous hollow fibers, a treatment to make the wall portion porous is required. For example, in the case of plasticized melt-spinning, after spinning under the predetermined conditions as described above, it is cooled and solidified, and then the plasticizer is extracted and removed by immersion in water etc. to impart porosity. used. In the case of wet spinning, a commonly used method can be used in which, after spinning, the spinning solution is immersed in a coagulation bath to solidify, and then the solvent in the spinning dope is extracted and removed, thereby imparting porosity.

<Examples> Examples and comparative examples of the present invention 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 plasticizer made of polyethylene glycol was melt-kneaded in an extruder at a temperature of 190°C (viscosity of 100 poise) at the time of discharge, and then passed through a gear pump for double-tube spinning. Yuzu gas is injected from the tube inside the mouthpiece, and the polymer is discharged from the circular slit on the outside.
Cooled with wind and rolled up the hollow fibers.

Spinning was performed by changing the diameter and length of the protruding portion of the inner tube of the double-tube spinneret.

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

The thickness of these hollow fibers was about 15μ.

Using a double-tube spinneret in which wedge-shaped pleats were cut into the outer periphery of the prefectural slits on the outside of the spinneret, finned hollow fibers were spun in the same manner, and the inner diameter of the hollow fibers was The height of the fins on the outer periphery of the plate and hollow fibers was measured.

<Effects of the Invention> According to the method for manufacturing hollow fibers using the spinneret of the present invention, hollow fibers with little unevenness in yarn diameter can be easily manufactured even with a low-viscosity spinning dope.

Furthermore, hollow fibers with a good cross-sectional shape can be easily produced even with hollow fibers having irregular cross-sections.

[Brief explanation of drawings]

FIG. 1 is a partially enlarged longitudinal cross-sectional view of an example of a double-tube spinneret used in the present invention. R1 indicates the outer diameter of the inner tube of the double-tube spinneret, & is 2
The figure shows the outer diameter of the inner tube that protrudes from the outer tube of a double-tube spinneret. 1 is a fluid flow path inside the inner tube 3, and 2 is a flow path for the spinning dope. 4 indicates the discharge end face of the spinneret.

Claims (3)

[Claims] (1) In a double tube type spinneret, the inner tube of the spinneret protrudes from the end surface of the outer spinneret, and the protrusion length l[
mm], the outer diameter R_1 [mm] inside the end face, and the outer diameter R_2 [mm] at the protrusion are expressed by the following formula (I)
and (II) R_1>R_2...(I) R_1/R_2≦l≦10(R_1/R_2)...(
1. A spinneret characterized by satisfying II) and having a structure that allows a core fluid to flow out from the inside of the inner tube. (2) In a method for producing hollow fibers using a double-tube spinneret, the inner tube of the spinneret protrudes from the end surface of the outer spinneret, and the protrusion length of the inner tube is l [mm], which is inside the end surface. Outer diameter R_1 [mm] at and outer diameter R_ at the protrusion
2 [mm] is the following formula (I) and (II) R_1>R_2...(I) R_1/R_2≦l≦10(R_1/R_2)...(
A method for producing a hollow fiber, which satisfies the condition II) and is characterized by causing a core fluid to flow out from the inside of the inner tube, and allowing a spinning dope to flow out from a gap outside the inner tube. (3) The method for producing hollow fibers according to claim 2, wherein the spinning dope has a viscosity of 50 to 1000 poise when discharged from the spinneret.