JPS5982407A - Manufacture of aromatic polyamide hollow fiber - Google Patents

Abstract

PURPOSE:To obtain the titled hollow fiber useful as a separation membrane such as reverse osmosis membrane, ultrafiltration membrane, etc. in high gelation rate, by the dry and wet spinning of a spinning dope composed of an aromatic polyamide, dimethylacetamide, DMF and lithium chloride at specific ratios. CONSTITUTION:A spinning dope obtained by mixing 13-20wt% of an aromatic polyamide, 7-20wt% of dimethylacetamide, 60-73wt% of DMF and 3-10wt% (preferably 5wt%) of lithium chloride, is extruded from e.g. a hollow ring nozzle, dropped several - several tens cm by its own weight, and introduced into an aqueous gelation bath to effect the gelation of the dope and obtain the objective hollow fiber. Preferably, a liquid which does not coagulate the spinning dope (e.g. a liquid hydrocarbon such as ligroin, kerosene, etc.) is introduced into the hollow part of the fiber to prevent the collapse of the fiber.

Description

[Detailed description of the invention] The present invention relates to a method for producing aromatic polyamide hollow fibers.

More specifically, the present invention relates to a method for producing aromatic polyamide hollow fibers that are effectively used as separation membranes such as reverse osmosis membranes and ultrafiltration membranes.

Polyamides having an aromatic ring structure in the main chain, typically polyamides obtained by condensation polymerization of m-phenylenediamine and isophthalic acid (chloride), have a high melting point, high modulus, and good high-temperature properties. In recent years, it has been used for heat-resistant fibers, tire cords, etc., but it is also used as a hollow fiber for separation membranes.

The aromatic polyamide is spun using dimethylformamide (95%)-lithium chloride (5%).
) The spinning stock solution (dope solution) formed by dissolving in the mixed liquid is heated to 128℃, dry-spun into air at 225℃ through the pores of a spinneret, drawn by -4.7 times, and scoured. This is done by

By the way, when attempting to apply a dry-wet spinning method to form aromatic polyamide into hollow fibers for use in reverse osmosis membranes, etc., the gelation rate is slow, and various obstacles are encountered as a result.

That is, in general, in the dry-wet spinning method, the spinning dope discharged from the pores of the spinneret falls freely over a certain distance (approximately several αn to n man-hours a7), and then is led to a gelling bath and gelled. After that, the hollow fiber passes through a guide roll that changes its direction in the horizontal direction, and is finally wound up with a take-up roll. However, if the hollow fiber has not gelled to a certain extent by the time it comes into contact with this guide roll, the hollow fiber is It collapses and cannot maintain its hollow fiber state.

Depending on the type of polymer that is wet-dry spun, the gelation rate may be slow, and in this case, as a countermeasure, the distance to the guide rolls is set to be long to solve the problem. However, such a solution has drawbacks such as increasing the size of the spinning apparatus as a whole and making it difficult to thread the yarn at the start of loose spinning.

As mentioned above, also in the case of wet-dry spinning of aromatic polyamides, spinning stock solutions of other polymers, such as dimethylformamide or dimethylalcohol of polysulfone, are used.

The gelation rate is considerably slower than that of cetamide solution.
For this purpose, a deep spinning bath with a depth of approximately i m is required.

Therefore, considering the mechanism of gelation, in the polymer-solvent system that forms the spinning dope, the polymer exists uniformly in the solvent, and when the spinning dope comes into contact with a gelling bath, e.g. It can be considered that substitution of the solvent with the polymer occurs, and as a result, the polymer aggregates and gelation occurs. Therefore, the rate of gelation is determined by the three factors: polymer/solvent, solvent/water, and polymer/water. It seems to be governed by mutual compatibility.

Based on these considerations, the present inventor developed a spinning stock solution formed from aromatic polyamide and its good solvent dimethylacetamide (lithium chloride was further added to control the pore size and form a good asymmetric structure). ) was found to be able to increase its gelation rate by adding dimethylformamide, which is a poor solvent for aromatic polyamides at room temperature.

Therefore, the present invention relates to a method for producing an aromatic polyamide hollow fiber, and the aromatic polyamide hollow fiber is produced by dry-wet spinning a spinning stock solution consisting of an aromatic polyamide, cyclized lithium, and a dimethylacetamide-dimethylformamide mixed solvent. be done.

As the aromatic polyamide, resinous powders known under fiber trade names such as 7Mex (a DuPont product) and Conex (a Teijin product) are used in an amount of about 13 to 20% by market weight of the spinning dope. Additionally, lithium chloride is generally used in a proportion of about 3 to 10% by weight, preferably about 5% by weight.

Dimethylacetamide in a proportion of about 7 to 20% by weight,
Also, dimethylformamide is used in a proportion of about 60-73%. If the proportion of dimethylacetamide is less than this, the spinning stock solution will become non-uniform and unsuitable for spinning, while if it is used in a larger proportion than this, gelation will be delayed and the hollow fibers may be crushed at the guide rolls. become.

The spinning stock solution prepared from each of the above components is extruded from a hollow (double circular) annular nozzle, allowed to fall naturally between 9 cnl and several tens of centimeters, and then poured into water or a gelatinized solution containing it as the main component. This is done by guiding and gelling it there. At this time, a non-coagulable liquid such as reflowin, kerosene, hexane, benzene, toluene, or other liquid hydrocarbon is injected into the hollow part as a core liquid with respect to the spinning stock solution.
It is preferable to maintain the hollow portion.

During gelation, the direction of the gelled spinning solution is changed by guide rolls, but the spinning method of the present invention achieves an increase in the gelation rate by adding dimethylformamide in the above ratio to dimethylacetamide. Therefore, the distance from the gelling bath liquid level to this guide roll should be approximately 30 to 4
The distance can be set to about 0 cm, which can be significantly shortened compared to the setting distance of 'Jjf1m when only dimethylacetamide is used in the conventional method, and this also leads to the downsizing of the entire device.

Moreover, since the hollow fibers obtained by the method of the present invention have a desired hollow fiber shape, they can be effectively used as separation membranes such as reverse osmosis membranes and ultrafiltration membranes.

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

Example Using the apparatus shown in the drawings, 15% by weight of aromatic polyamide (Funex), 5% by weight of lithium chloride, 10% by weight of dimethylacetamide and 7% by weight of dimethylformamide were prepared.
A spinning stock solution prepared from 0% by weight was subjected to dry-wet spinning.

The spinning dope is supplied from a spinning dope tank 2 pressurized by air pressure 1 to a hollow (two-lost circle) annular nozzle 4 via a gear pump 3, and glue groin as a core liquid is supplied to a spinning dope tank 2 pressurized by air pressure 1'. The liquid is supplied from the pressurized core liquid tank 5 to the hollow annular nozzle via a liquid volume control valve 6 and a flow meter 7 in this order. Spinning is carried out using this hollow annular nozzle (
Outer diameter 4 m) Inner diameter 2) 12 m1/lI'f from the outside
The spinning stock solution was discharged from the inside at a discharge rate of 41n1.7 minutes, and the ligroin was discharged from the inside at a discharge rate (injection volume) of 41n1.7 minutes.
This is carried out by allowing the spinning solution to fall naturally by 0 cm and then introducing it into the gelling bath 8 of the spinning dope. In the gelling bath, 40c below the liquid surface.
After the direction was changed by a guide roll 9 provided at a position of m, the hollow fiber was further wound onto a winding roll 11 via another guide roll 10 at a winding speed of 22 m/min.

The obtained hollow fiber had an outer diameter of 0.6 m, an inner diameter of Q, and a diameter of 3 rra.
It is a hollow fiber with a good shape of n, and when this hollow fiber is ultrafiltered as an ultrafiltration material, the molecular weight is 20.0.
When applied to a 2% aqueous solution of 0.00 polyethylene glycol, 99% of the dissolved polyethylene glycol could be eliminated.

Comparative Example 1 In the example, 30 it% of dimethylacetamide,
In addition, spinning stock solutions were prepared by changing the amount of dimethylformamide to 50% by weight, and dry-wet spinning was performed.

As a result, the hollow fibers were crushed by the guide roll 9, and the target product could not be obtained.

Comparative Example 2 In Example, a spinning dope was prepared by changing the amount of dimethylacetamide to 80% by weight without using dimethylformamide, and dry-wet spinning was performed. As a result, the hollow fiber was crushed by the guide roll 9, making it impossible to obtain the desired object.

[Brief explanation of the drawing]

The drawings are schematic diagrams showing one embodiment of the method for producing aromatic bonamide hollow fibers according to the present invention. Noz) Lt 5... Core liquid tank 8... Gelling bath 9... Guide roll 11... Winding roll agent Yoshi 1) Toshio

Claims (1)

[Claims] 1. About 13-20% by weight of aromatic polyamide, about 7-20% by weight of dimethylacetamide, about 60-73% by weight of dimethylformamide, and about 7-20% by weight of lithium chloride.
1. A method for producing aromatic polyamide hollow fibers, which comprises dry-wet spinning a spinning stock solution prepared from . 2. Spinning solution The method for producing aromatic polyamide hollow fibers according to claim 1, which comprises injecting a non-coagulable core solution and performing dry-wet spinning. 3. A method for producing an aromatic polyamide hollow fiber according to claim 2, in which a liquid hydrocarbon is used as the core liquid. 4. A method for producing an aromatic polyamide hollow fiber according to claim 1, which is used as a separation membrane.