JPS62162007A - Production of electric field-applied hollow fiber - Google Patents

Abstract

PURPOSE:A spinning dope is extruded through orifices which have a two-layer structure where the inner nozzle is separated from the outer nozzle with an insulator in an electric field to give a hollow fiber yarn increased hydrophilic properties on their surface and improved flux. CONSTITUTION:The inner nozzle 1 and the outer nozzle 2 are separated from each other with an insulator 3 made of teflon or the like and electrodes 4, 4' provided on both nozzles. The resultant 2-layer orifices are used to effect the extrusion of the spinning dope under application of an electric field of higher than 1V/m intensity whereby the objective hollow fibers are obtained. The spinning dope is not specified, but a polymer having locally dipole moment such as polysulfone or polyether imide is preferred to markedly improve the properties of the resultant hollow fibers.

Description

Detailed Description of the Invention (Industrial Application Field) The present invention relates to a hollow fiber or hollow tube ( The present invention relates to a novel method for spinning hollow fibers (hereinafter simply referred to as hollow fibers).

(Prior Art) A typical spinneret used for spinning hollow fibers is a double tube nozzle equipped with an inner nozzle and an outer nozzle to separate the polymer stock solution and the internal coagulation liquid (or gas). In known spinnerets, the inner and outer nozzles are made of stainless steel and are welded or screwed together, so the inner and outer nozzles are not insulated.

Therefore, it was impossible to prevent this by applying an electric field to the polymer stock solution.

As a result of intensive research and development of a new spinning method, the present inventors found that
Hollow fibers spun in an electric field exhibit significantly superior physical properties, such as water permeability and improved hydrophilicity (reduction in contact angle), compared to hollow fibers spun without an electric field. The present invention was created based on this discovery.

(Problems to be Solved by the Invention) The purpose of the present invention is to obtain hollow fibers with improved surface hydrophilicity or hollow fibers with excellent physical properties such as water permeability by spinning hollow fibers in an electric field. That is.

(Means for Solving the Problems) The hollow fiber manufacturing method of the present invention uses a hollow spinning device in which the inner nozzle and outer nozzle of the spinneret are separated by an insulator, and the electric field intensity I
It is characterized by spinning within an electric field of V/m or more.

The reason why hollow fibers with improved physical properties can be obtained according to the present invention is not clear at present, but it is thought to be as follows. That is, by applying an electric field, the dipole moments or charged groups of the polymer in the casting stock solution (usually containing Boria-2 solvent, salts, additives, etc.) are oriented to the hollow fiber surface, and the parent particles near the surface are aligned. It is believed that the enhanced woodiness or efficiently oriented dipoles or charged groups control the permeability of solutes or water. As an electric field,
When an electric field is not applied intentionally, that is, at least I V
/ m or more (electric field strength IV / m or more),
It is thought that this locally causes a morphological change in a polymer having a dipole moment or a charged group. However, in order to expect better effects, it is desirable to use 3×10 V/m or more.

As shown in the accompanying drawing, the spinneret used in the spinning method of the present invention is a double tube nozzle in which an inner nozzle (1) and an outer nozzle (2) are separated by an insulator (3) such as Teflon. Each nozzle is provided with an electrode 4.4'. Therefore, the inner and outer nozzles are insulated so that an electric field can be applied to the spinning dope (5) to perform spinning. (6) is the internal coagulation liquid.

The spinning stock solution is not particularly limited, but polymers with a local dipole moment (e.g., polysulfone,
using a stock solution containing a polymer containing a charged group (e.g., sulfonated polysulfone, sulfonated polyether sulfone, sulfonated polyetherimide, carboxymethylated polyphenylene ether, etc.). Thus, the hollow fibers spun according to the present invention exhibit significant improvements in physical properties due to electric fields. For example, if a positive potential is applied to the electrode 4 in the drawing and a stock solution containing anionic charges is used for spinning,
The outer surface of the obtained hollow fiber has more negatively charged groups than the inner surface. Conversely, if a negative potential is applied to the electrode 4, the inner surface will have many negatively charged groups.

The present invention will be further explained below with reference to Examples.

(Example 1) Dimethylacetamide as a solvent, propylene glycol as an additive, and polysulfone having a repeating unit represented by are mixed in a weight ratio of 68:14:18 to obtain a uniform solution. This polymer solution was applied to the spinneret shown in the drawing (φa=0.5
mm, φb = 1, 5 mm, h = 2 cm) to obtain a hollow fiber porous membrane using purified water at 25°C as an internal and external coagulation liquid. In this case, the stock solution temperature is 25℃
and the distance from the nozzle to the external coagulating liquid (air travel distance)
The spinning conditions were 3 Cm and a spinning speed of 15 m/min. Further, the electrode 4 was set as positive, and the electrode 4' was set as negative, and a potential of 1.5 .mu. was applied. Therefore, the spinning dope was 1.5×10'V/m
This means that the spinning was carried out within the electric field of .

The characteristics of the obtained hollow fibers are that the inner diameter is 0.75 mm and the outer diameter is 1.75 mm.
35mm, film thickness 0.3mm, water permeability 15rn”/go*d
ay*atms water temperature 25℃, bursting strength 30Kg/
C, 5% by weight of dextran molecular weight 4 x 104
The cut rate was 85%.

(Reference Example 1) Porous hollow fibers were obtained by spinning in the same manner as in Example 1 except that no electric field was applied. This hollow fiber has an inner diameter of 0.75m.
m, outer diameter 1.35mm, film thickness 0゜3mm, water permeability 11r
n"/rn'eday*atm*Water temperature 25℃, bursting strength 31Kg/crr?, dextran molecular weight 4 X 10
The cut rate for 5% by weight of No. 4 was 79%.

(Example?) Except that a mixture of sulfonated polysulfone (prepared according to US Pat. No. 3,709,841) and polysulfone with an exchange capacity of 0.0, 82 m eq / H and polysulfone in a weight ratio of 1 = 13 was used as the polymer. A porous hollow fiber was obtained in the same manner as in Example 1. This hollow fiber was dyed with a cationic dye (
When stained with CI Ba5ic Blue), the outer surface was deeply stained, but the inner surface was only slightly stained. From this, it was estimated that the sulfonated polysulfone in the hollow fiber was localized near the outer surface.

The characteristics of the obtained hollow fibers are that the inner diameter is 0.74 mm and the outer diameter is 1.3 mm.
4mm, film thickness 0.3mm, water permeability 19g/m'eday
eatme water temperature 25℃, bursting strength 29K g/C
rn', dextran molecular weight 4X10 (7) The cut rate for 5% by weight was 82%.

(Example 3) Ba5ic B was used in the same manner as in Example 2 except that the electrode 4 was negative and the electrode 4' was positive and a potential of 1.5 cm was applied.
When stained with luel)ffi, the outer surface was only slightly stained, but the inner surface was deeply stained. In this case, contrary to Example 2, it is presumed that sulfonated polysulfone is localized on the inner surface.

(Effects of the Invention) Compared to those spun without applying an electric field, the hollow fibers obtained by the present invention can increase the wood-philicity of the surface and improve physical properties such as water permeability. Furthermore, when hollow fibers are spun from a stock solution containing charged substances, polar groups can be preferentially localized on the outer or inner surface by changing the orientation of the electrodes.

[Brief explanation of drawings]

The accompanying drawing is a schematic cross-sectional view showing one example of a spinneret used in the present invention.

Claims (1)

[Claims] A method for producing hollow fibers, which comprises spinning in an electric field with an electric field strength of 1 V/m or more using a hollow spinning device in which an inner nozzle and an outer nozzle of a spinneret are separated by an insulator.