JPS5920762B2 - Aromatic polyamide spinning dope preparation method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for preparing a spinning stock solution of a para-coordination wholly aromatic polyamide, which has an optical anisotropy suitable for producing a para-coordination wholly aromatic polyamide fiber with preferable mechanical properties. The present invention relates to a method for preparing a spinning dope that exhibits properties.

The spinning dope prepared by the method of the present invention makes it possible to stably produce fibers of polyparaphenylene terephthalamide or similar para-coordination wholly aromatic polyamides with excellent uniformity. It is known that fully aromatic polyamides can be derived from aromatic diamines, aromatic carboxylic acids, and/or aromatic aminocarboxylic acids, and fibers can also be obtained from them by appropriate methods. well known.

Further, it has been shown that polyparaphenylene terephthalamide, or a para-coordinated wholly aromatic polyamide with a similar structure, can be used with limited polymer concentration doping to provide useful fibers with desirable mechanical properties. No. 1,929,694.

These para-coordination wholly aromatic polyamide fibers, especially polyparaphenylene terephthalamide fibers (hereinafter abbreviated as "P-T fibers"), have good heat resistance, chemical resistance, high strength, and high initial modulus. It is known to have

On the other hand, it has extremely poor solubility, and a dope suitable as a spinning dope cannot be easily obtained even if the polymer and solvent are mixed all at once and stirred and dissolved according to a conventional method. For para-coordinated fully aromatic polyamides, when the polymer is mixed with a solvent all at once and stirred, as is often done in normal dissolution operations, a huge dope viscosity region is created between the time the polymer is dispersed in the solvent and the time it is dissolved. It has the characteristic that it passes through the polymer and then becomes a polymer concentration region with optical anisotropy (OA).

When passing through this huge dope region, the viscosity of the solution reaches more than one poise, and the solution phase with this huge viscosity causes the undissolved or half-dissolved polymer powder to coagulate, resulting in "mamako" (a liquid with a large amount of solid phase). This refers to polymer lumps whose insides remain undissolved as a result of the formation of caking and coagulating lumps). For this reason, it is not possible to obtain a completely dissolved state even with subsequent stirring, and if heating at high temperatures and stirring for a long period of time is carried out for the purpose of complete dissolution, the degree of polymerization will decrease significantly, and the strength of the thread will decrease. Process troubles such as frequent single yarn breakage occur frequently. That is, the conventional method has the disadvantage that it is difficult to maintain and manage conditions for stable and suitable performance. In order to obtain high-performance fibers by dissolving these P-T polymers in high concentrations, concentrated sulfuric acid is used, which has excellent dissolving power for the polymers. Because a large amount of heat is generated, which is equivalent to the heat of reaction, there is no heat dissipation through stirring in the "mamako" part, and the local temperature rise becomes large due to heat accumulation inside the "mamako" part, resulting in significant decomposition of the polymer. , causing trouble in the spinning process. The object of the present invention is to overcome these drawbacks in the production of P-T fibers, to further improve the excellent mechanical properties, and to provide a method for preparing a spinning dope that can easily produce homogeneous fibers. In the present invention, in preparing a spinning stock solution for a para-coordinated wholly aromatic polyamide using 95% by weight or more of sulfuric acid as a solvent, first,
As the first step, 0.1 to 5 weight? A solution with a polymer concentration of This is a method for preparing a para-coordinated wholly aromatic polyamide spinning stock solution, which is characterized by forming an optically anisotropic solution with a predetermined concentration.

The para-coordination wholly aromatic polyamide as used in the present invention refers to the following units [in the formula, units (1) and () are present in substantially equimolar amounts in the polymer, Ar2 and Ar3 each represent a divalent aromatic group.

At least 90 moles of the total number of groups Ar, , Ar2 and Ar, in the polymer are such that the groups Ar, , Ar2 and Ar3 are divalent aromatic residues in linear coordination with each other and are specifically Paraphenylene group, 4,4'-biphenylene group, 1
, 4-naphthylene group, and 2,5-hyridylene group, and the hydrogen atoms in the aromatic nucleus of these groups are substituted with one or more inert groups such as nitro group, halogen group, lower alkyl group, and lower alkoxy group. Good too. P-T polymers can be easily synthesized by any known method, such as a method in which a corresponding dicarboxylic acid is induced into an acid halide, acid imidazolide, ester, etc., and then reacted with a diamide. Any method can be used in practicing the invention.

In addition, as the spinning solvent used for these polymers and the solvent used for dissolving these P-T polymers, P
Concentrated sulfuric acid or fuming sulfuric acid is preferred because it has good solubility in -T-based polymers and is inexpensive and easily available.

The concentration varies depending on the polymer composition, degree of polymerization, and polymer concentration of the stock solution, but is at least 95% by weight? The above concentration of sulfuric acid should be used; if it is less than that, the desired dissolving power cannot be obtained. Also, 100 weight? The so-called fuming sulfuric acid mentioned above should be avoided because if the concentration is too high, it will reduce the dissolving power, cause undesirable side reactions such as sulfonation of the polymer, and increase the decomposition rate of the polymer. .

The present invention relates to a para-coordinated wholly aromatic polyamide, that is, P-
In dissolving the T-based polymer, first, as a first step, it is preliminarily dissolved at a low polymer concentration of 0.1 to 5% by weight, and then the remaining polymer is added and stirred to completely dissolve.

According to the detailed research results of the present inventors, the usefulness of dissolving the dope in two steps into a dope with an optically anisotropic method after passing through an optically isotropic dope with a low polymer concentration is that P-T
When adjusting the optically anisotropic doping of the system polymer, in the region of low polymer concentration and optically isotropic doping, the dope viscosity increases with increasing polymer concentration and is approximately 7-8
weight? In the above, after passing through a huge dope viscosity region of extremely high viscosity of 10,000 poise or more and reaching a critical point of about 9 to 10% by weight, it enters a polymer concentration region exhibiting optical anisotropy.
Because the dope exhibits a unique behavior in which the viscosity decreases and the fluidity increases, in the first stage of dissolving low polymer concentrations, the initial amount of polymer input is small, making it difficult to form lumps, and relatively Dissolves quickly.

The solution obtained in this way has a high dope viscosity even at a dilute concentration, so it has a large shearing effect when the polymer is subsequently added, and it also has stickiness to additionally added polymer particles, so the polymer particles can be easily removed by stirring. It also has the effect of assisting in the dispersion of the liquid and breaking up any lumps into small pieces, so that no lumps occur and a complete dissolution state can be obtained in a short period of time with subsequent stirring. This can be compared to the difficulty in forming clumps when kneading rice flour into the water of a shabu shabu and when kneading it into freshly made rice cake. Moreover, since the temperature rise during melting is suppressed to a low level and the solubility is good compared to the usual method, there is no need to raise the heating temperature too much. Therefore, the degree of polymerization decreases little and a uniform spinning dope can be obtained, so troubles such as yarn breakage are reduced, and yarns with excellent mechanical properties can be stably produced. In addition, in the first step of pre-dissolution, the polymer concentration is 0.1 weight? If it is less than that, it will not be possible to obtain a dope viscosity sufficient to exhibit the effects of the present invention, resulting in the same problems as in the conventional method in which all the polymers are added at once. Also, 5 weight? Exceeding this is undesirable because the dope viscosity becomes excessive and a sufficient stirring effect cannot be obtained when adding the polymer and carrying out the second stage of dissolution, and it takes a long time to dissolve the polymer. . Each of these two stages of dissolution may be performed sequentially in a batch manner, but especially in a method in which the polymer and solvent are continuously supplied to a dissolving machine and a spinning stock solution is continuously prepared. Particularly in the second stage of dissolution, the effect of the force method of the present invention, in which the added polymer has good dispersibility and a high dissolution rate, can be effectively exhibited. To simplify the process of spinning P-T fibers, the spinning method may be a normal horizontal wet spinning method in which the fibers are extruded directly into a coagulation bath through pores, or the spinning method may be a conventional horizontal wet spinning method in which the fibers are extruded directly into a coagulation bath immediately after spinning. A so-called aerial drop type wet spinning method may also be used, in which the spinning material is passed through the fiber and then introduced into a suitable coagulation bath.

The fibers spun in this way are subsequently led to a water washing process, where the solvents and inorganic salts contained in the fibers are substantially completely removed, then dried, and a suitable oil is applied as necessary. Afterwards, it is rolled up.

In addition, in some cases, stretching and heat treatment can be carried out in optional steps to obtain homogeneous products with excellent mechanical properties such as tensile strength and Young's modulus, which provides much more advantageous results than conventional methods. It is. Next, the content of the present invention will be described in more detail with reference to Examples.

In the examples, the tensile strength, tensile elongation, and Young's modulus of the fibers were determined by drawing a load-elongation curve using a constant-speed elongation tensile tester at 20° C. and 65% RH atmosphere. Do the percentages in the examples mean weight? shows. Example 1 Substantially equimolar amounts of finely powdered terephthalic acid chloride were added to a mixed solution of hexamethylphosphoramide/N-methyl-2-pyrrolidone containing paraphenylenediamine, and polymerization was carried out under strong stirring. A polymer having an intrinsic viscosity of *3.0 was obtained.

This polymer 6009 was mixed with 99.5% sulfuric acid 1500CC (
27509), two methods were compared.

On the other hand (4), polymer 109 was placed in a 3t glass flask.
, add 1500cc of sulfuric acid, stir vigorously for about 30 minutes,
The polymer was completely dissolved to a dilute dope with a concentration of 0.36%, to which polymer 5909 was then added,
Stirring was continued for 90 minutes. On the other hand (B), Polymer 6009 was placed in a 3t glass flask, 1500 cc of sulfuric acid was poured into the flask while stirring, and stirring was continued for 90 minutes. CA) and (B) After each optically anisotropic dope with a polymer concentration of 18% obtained by each method was vacuum degassed for 180 minutes, 0.07711! ! It was extruded into the air through a nozzle with a hole of tφ x 250, and the coagulation liquid was kept at 0°C.
Using 070 sulfuric acid aqueous solution, it was rolled at 80 m/-.

The physical properties of (AXB) are as follows, and the ease of sample (4) obtained according to the method of the present invention can be easily understood. Example 2 In dissolving Polymer 231<9 obtained in the same manner as in Example 1 in 50 tons (91.5 kg) of 99.8% sulfuric acid, two methods were compared in the same manner as in Example 1.

First, put 0.51<g of polymer in 50 tons of sulfuric acid and stir vigorously for 30 minutes until the polymer concentration is 0.54.
% of optically isotropic doping after polymer 22.5k
g was added, and stirring was continued for 90 minutes. On the other hand (8)
pours 50 tons of sulfuric acid into a container containing 23 kg of polymer,
Stirring was continued for 120 minutes. The optically anisotropic dope with a polymer concentration of 20% obtained by both methods was vacuum degassed for 180 minutes, and then 0.061gtφ×5
The coagulating liquid was a 20% aqueous sulfuric acid solution kept at 0°C, the spinning speed was 150 m/min, and the washing, drying, and oiling were performed by depositing the spun fibers on a net conveyor and continuously spinning them. It was done in such a way that it could be processed. At this time (4
) The number of single yarn breaks immediately after spinning was counted with the naked eye, and the value converted per unit time was 0.4 times/hour, while (8
) was 0.9 times/hour. The intrinsic viscosities of the polymer and spun fibers before and after dissolution were as follows.

Further, the physical properties immediately after the start of spinning and after 10 hours of spinning were as follows.

Example 3 Paraphenylene terephthalamide copolymer containing 10 moles of o-tolidine as a diamine component in the polymer (
(intrinsic viscosity 5.0), 98.5% as spinning solvent
Using concentrated sulfuric acid, 0.95 kg of polymer was dissolved in 2.23 kg of concentrated sulfuric acid.
As a method within the scope of the present invention, in preparing an optically anisotropic dope with a polymer concentration of 19%, (4) as a first stage dope, 170 After adjusting the optically isotropic dope with a polymer concentration of 4%, the remaining polymer was added. (B) Similarly, after adjusting the optically isotropic dope with a concentration of 4%, the remaining polymer was added to obtain the effect of the present invention. As an example not shown, once a dope with a concentration of 0.05% is adjusted as the first stage dope, the remaining polymer is added; (D) After adjusting an optically isotropic dope with a concentration of 6.5%, We attempted to adjust the dope using four methods: adding the remaining polymer.

Among these, in (9), which is outside the scope of the present invention, the first stage dope with a concentration of 6.5% is thought to have a viscosity of about 10,000 poise or more, and the stirring blade causes cavitation. However, the stirring did not show any effect at all, and as a result, no additional polymer was mixed, so dissolution was abandoned. Also, (0) is equivalent to adding the entire amount of polymer at once, resulting in a large amount of dope.

Three dopes (A), (B), and (0) were defoamed and spun according to Example 1. The results are shown in the following table.

Claims (1)

[Claims] 1. In preparing a spinning stock solution of para-coordinated fully aromatic polyamide using 95% by weight or more of sulfuric acid as a solvent, first, as a first step, a solution with a polymer concentration of 0.1 to 5% by weight is prepared. Next, a predetermined amount of the polymer is added to the solution so that the concentration of the dissolved solution exceeds the critical concentration that exhibits optical anisotropy, and the polymer is stirred and completely dissolved to obtain a predetermined optical concentration. A method for preparing a paracoordination wholly aromatic polyamide spinning stock solution, which is characterized by forming an anisotropic solution.