JPH089801B2 - Method for producing porous hollow fiber - Google Patents

Description

TECHNICAL FIELD The present invention relates to a method for producing a porous hollow fiber. More specifically, it relates to a method for producing a porous hollow fiber that facilitates control of membrane performance.

[Conventional technology]

A porous hollow fiber obtained by a dry-wet spinning method in which a dope liquid is discharged from a hollow annular nozzle together with a core liquid that is a coagulating liquid and then introduced into a coagulation bath and coagulated is a dense surface layer usually called a skin layer. It is formed of a layer and a sparse layer in the middle part called a support layer (porous layer). Therefore,
In such a porous hollow fiber, the pore size, which is a parameter indicating the membrane performance, is determined by the structure of the skin layer on the membrane surface.

In the process of forming such a skin layer, first, when the dope solution comes into contact with the coagulation bath (gelling solution), the solvent diffuses from the dope solution and the gelling solution diffuses into the dope solution at the interface. To start. In general, the dope solution solvent and the gelling solution are compatible with each other, so that the diffusion thereof is carried out rapidly.

At that time, since the gelling liquid is a poor solvent for the polymer dissolved in the dope liquid, rapid aggregation of the polymer occurs at the dope liquid-gelling liquid interface, so that a dense skin layer is first formed on the surface. Since the diffusion to the inside of the film is performed through this skin layer, the rate of mutual diffusion of the solvent-gelling solution becomes very slow, and the internal structure becomes relatively porous.

[Problems to be Solved by the Invention]

In order to control the membrane performance, that is, the structure of the skin layer,
In the initial stage of contact between the dope solution and the gelling solution, its mutual diffusion rate may be adjusted, and this can be performed to some extent by adjusting the composition of the dope solution and the spinning speed.

However, it is necessary to adjust the composition, temperature, etc. of the gelling liquid in order to obtain a film performance that cannot be controlled only by these conditions. Of these, the gelling liquid on the core liquid side can be adjusted relatively easily, but the gelling liquid for gelling the outside of the hollow fiber generally has a large volume, and a thickener is added to the gelling liquid. When the method of slowing the desolvation rate is adopted, there is a problem that a large amount of the thickener is required.

The present invention is a porous hollow fiber that enables control of the skin layer structure without using a large amount or at all of such a thickener and without adjusting the composition of the dope solution or the spinning temperature. It aims at providing the manufacturing method of.

[Means for solving the problem]

In order to achieve such an object, a porous hollow fiber is produced by a dry-wet spinning method in which a dope liquid is discharged from a hollow annular nozzle together with a core liquid and then introduced into a coagulation bath to coagulate,
The spun hollow fiber is (1) immersed in a coagulation bath and passed through a guide pipe in which the thickened liquid is fed, or (2) installed between a spinneret and a coagulation bath, After passing through the inside of the guide pipe in which the temperature-controlled air is sent, it is brought into contact with the coagulation bath.

One mode of the above (1) is shown in FIG. That is, the dope liquid 2 is discharged from the outside of the hollow annular nozzle of the spinneret 1 and the core liquid 3 such as glycerin is discharged from the inside at the same time, and the spun hollow fibers 8 are coagulated in a coagulating bath (gelling liquid) 4
When it is introduced and solidified, it is immersed in the gelling liquid 4 and passed through the inside of the guide pipe 7 into which the thickener 6 such as glycerin or its aqueous solution is fed from the tube 5 or the like, The porous hollow fiber 8 ′ is formed by contacting with the gelling liquid 4 and wound by the winder 9. As a method of passing the discharged product through the guide pipe at the initial stage of spinning, there is a method of using a yarn guide or a method of using a guide pipe having a vertical split structure.

The desolvation rate becomes slower as the solvent concentration in the gelling solution becomes higher, but by installing such a guide pipe, a thickening agent (aqueous solution) is added to form a portion where the solvent concentration is locally high. Since the solvent released from the dope solution is accumulated in a minute volume in the guide pipe by stopping the feeding or keeping the flow rate small, the solvent of the dope solution itself is used to increase the desolvation rate. It is possible to control.

The desolvation rate can also be changed by adjusting the relative speed of the formed hollow fibers and the gelling solution, that is, the degree of contact between the dope solution and the gelling solution. When the hollow fiber spinning speed cannot be changed due to the balance with the liquid or core liquid flow rate, the relative speed can be adjusted by the gelling liquid flow rate flowing through the guide pipe. Furthermore, the degree of these effects can be adjusted by changing the length of the guide pipe, and since it can be controlled only by a minute volume part in the guide pipe,
Gelation at a high temperature of about 80 ° C or a low temperature of about 5 ° C can be relatively easily performed.

One mode of the above (2) is shown in FIG. The principle of this aspect is also essentially the same as that of (1), and by changing only the ambient atmosphere immediately after spinning,
It controls the structure and pore size of the outer surface of the hollow fiber membrane. That is, in the spinning in which desolvation in the vapor phase portion has a considerable effect on the membrane structure, as in the case where a relatively volatile solvent such as acetone is used as the solvent of the dope, the spun hollow fiber 8 is used. A spinneret 1-gelling solution 4
It is installed between the tubes and is fed from the tube 10, etc.
After passing the temperature-controlled air 12, 12 'discharged from 11 etc. through the inside of the guide pipe 13 which has been fed therein, it is brought into contact with the gelling liquid 4 to form a porous hollow fiber 8'. Then, it is wound by the winder 9.

In this way, by installing a guide pipe in the gas phase portion and sending the temperature-controlled air into it, by controlling only the microvolume portion without controlling the entire gas phase portion, Allows control.

〔The invention's effect〕

According to the method of the present invention, a spun hollow fiber is passed through a relatively small amount of a thickener or a temperature-controlled guide pipe to change only the atmosphere in the guide pipe to form a porous hollow fiber. It is possible to control the structure and pore diameter of the surface of the thread membrane. Further, since it is sufficient to manage only a minute volume portion in the guide pipe, spinning can be easily performed even under extreme spinning conditions.

〔Example〕

 Next, the present invention will be described with reference to examples.

Example A porous hollow fiber was produced according to the embodiment shown in FIG.

Hollow dope liquid and core liquid (50 wt% glycerin aqueous solution) consisting of 13 wt% of polysulfone (Nissan Chemicals P-1700), 83 wt% of dimethylformamide and 4 wt% of polyvinylpyrrolidone (K-90, Kanto Chemical), respectively. Outer annular nozzle of annular nozzle (inner diameter 0.3mm, outer diameter 0.5mm)
And the inner circular nozzle (diameter 0.12 mm) were simultaneously discharged, and dry-wet spinning was performed under the following conditions.

Dope solution discharge rate 6 ml / min Core solution discharge rate 4 ml / min Gelation liquid (water) temperature 20 ° C Inside the guide pipe with an inner diameter of 10 mm and a length of 300 mm, a 50% by weight aqueous glycerin solution as a thickening agent is supplied at a flow rate of 10 ml / The outer surface skin layer of the porous hollow fiber obtained by contacting with the gelling liquid after passing through the
A large number of pores of about 0.5 to 1 μm were formed (according to SEM observation image).

On the other hand, no such pores were observed in the surface skin layer on the surface of the porous hollow fiber obtained without passing through the thickener feed guide pipe.

[Brief description of drawings]

1 and 2 are schematic views showing one embodiment of the method of the present invention. (Explanation of symbols) 1 ... Spinneret 2 ... Dope liquid 3 ... Core liquid 4 ... Gelling liquid 6 ... Thickener 7 ... Guide pipe 8 ... Hollow fiber 12 ... Air 13 ... Guide pipe

Claims (2)

[Claims] 1. A dry-wet spinning method in which a dope liquid is discharged from a hollow annular nozzle together with a core liquid and then introduced into a coagulation bath for coagulation, in which the spun hollow fiber is immersed in a coagulation bath and thickened inside thereof. A method for producing a porous hollow fiber, which comprises contacting with a coagulation bath after passing through a guide pipe into which the agent has been fed. 2. A dry-wet spinning method in which a dope liquid is discharged together with a core liquid from a hollow annular nozzle and then introduced into a coagulation bath for coagulation, in which the spun hollow fiber is placed between a spinneret and a coagulation bath, and inside thereof. 1. A method for producing a porous hollow fiber, which comprises passing the inside of a guide pipe into which temperature-controlled air is fed and then bringing it into contact with a coagulation bath.