JPS6016984B2 - Method for producing aromatic polyamide solution - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing an aromatic polyamide solution, and more particularly, to a method for producing an aromatic polyamide solution that facilitates the production of molded products.

Molded products such as fibers, films, and pulp-like particles with excellent heat resistance can be produced from aromatic polyamide solutions, and these molded products not only have excellent heat resistance but also flame resistance,
It has excellent chemical resistance, morphological stability at high temperatures, thermal decomposition resistance, electrical properties, mechanical properties, etc., and is extremely valuable industrially.

It is industrially advantageous to produce this aromatic polyamide solution by low-temperature solution polymerization in which an aromatic diamine and an aromatic dicarboxylic acid chloride are reacted in an amide-type polar solvent. This is because, in this case, there is no need for the troublesome process of isolating the produced polymer and then dissolving it again in a solvent for producing molded products, and it is possible to carry out both polymerization and production of molded products using a common solvent. This is because it can be done. That is, after reacting an aromatic diamine and an aromatic dicarboxylic acid chloride in an amide-type polar solvent, the generated hydrochloric acid (which exists as the hydrochloride of the amide-type solvent) is converted into calcium hydroxide, calcium oxide, and calcium carbonate. ,
If neutralization is performed with a base such as lithium hydroxide or lithium carbonate, the calcium chloride, lithium chloride, etc. produced by this neutralization reaction are soluble in solvents, and they increase the solubility of the polymer, so they are usually left in this form. It is used for manufacturing molded products. However, since these salts are produced in an amount of 2 equivalents per polymer unit chain, a very large amount of the salts will be present in the solution, which may impede the production of molded products in some cases.

For example, when a film is produced by a dry film forming method, salt-based precipitates appear as drying progresses, making the film opaque. This tendency is particularly noticeable when producing thick films, making it extremely difficult to produce thick films. On the other hand, the complete absence of such solvent-soluble salts will reduce the solubility of the polymer and, therefore, the stability of the polymer solution.

For example, especially in homopolymers with low solubility, solutions in the absence of such salts are particularly unstable and gelation phenomena occur within a short time even at relatively low temperatures. In addition, even in copolymers with relatively good solubility, gelation tends to occur at relatively high temperatures in the absence of such salts, and the transparency of molded products can also deteriorate. . Therefore, in order to maintain the stability of the polymer solution and obtain molded products of excellent quality, an appropriate amount of solvent-soluble salt is required depending on the solubility of the polymer, and the amount is also equal to the amount of hydrochloric acid generated during polymerization. The amount required is less than the amount that would be required if all of the salts were neutralized and converted to solvent-soluble salts.

Conventionally, such polymer solutions have not been produced by any method other than once isolating the polymer and redissolving it.
This method is extremely disadvantageous economically since the number of steps increases considerably. The present inventors have arrived at the present invention as a result of extensive research into a method for producing a polymer solution containing less than the equivalent amount of such solvent-soluble salts directly after completion of polymerization. That is, after neutralizing hydrochloric acid by adding both a neutralizing agent that produces a solvent-soluble salt and sodium hydrogen carbonate to a solution consisting of an aromatic polyamide, an amide type solvent, and a hydrochloride salt of the solvent, the hydrochloric acid is It has been found that by separating sodium, the amount of salt per polymer can be efficiently reduced and an aromatic polyamide solution with improved moldability can be obtained.

According to the present invention, since an aromatic polyamide solution with improved moldability can be obtained directly from the reaction mixture after polymerization, the polymer is once isolated, washed, dried, and then redissolved in a solvent together with a small amount of salt. It is extremely economically advantageous compared to

The aromatic polyamide used in the present invention has the general formula 1NH1AJ, 1NHCO-Ar2-CO1 or 1CO-Ar3-NH- (where Ar,, Ar2, ~3
are divalent aromatic groups, which may be the same or different.

For example, poly(m-phenylene isophthalamide), poly(m-phenylene terephthalamide), poly(P-phenylene isophthalamide), poly(P-phenylene terephthalamide), poly(4,4-oxydiphenylene) Typical examples include poly(terephthalamide), poly(4,4-oxydiphenylene isophthalamide), poly(m-benzamide), and poly(P-penzamide).
In particular, poly(m-phenylene isophthalamide) is useful because it is soluble in many types of solvents and can be dissolved at high concentrations. Moreover, the above-mentioned copolymers may also be used. In addition, typical amide-type sacrificial solvents used in the present invention include dimethylacetamide, N-methylpyrrolidone, N-methylcaprolactam, tetramethylurea, and hexamethylphosphoramide, among which the polymerization reaction is Dimethylformamide and the like, in which the polymerization reaction does not proceed, are excluded because the polymerization reaction needs to be carried out.

Among these amide-type solvents, dimethylacetamide is especially easy to polymerize, is easy to handle as a solvent (relatively low viscosity at the same polymer concentration), and has a relatively low boiling point, making it easy to recover. This is preferable.
The neutralizing agent that produces a solvent-soluble salt used in the present invention is a neutralizing agent that produces a salt that is soluble in amide-type polar solvents such as calcium chloride, magnesium chloride, and lithium chloride, and includes calcium hydroxide, oxidized Typical examples include calcium, calcium carbonate, magnesium hydroxide, magnesium oxide, magnesium carbonate, lithium hydroxide, and lithium carbonate.

The amount of each neutralizing agent added is not particularly limited as long as the total amount is substantially equivalent or more to the amount of hydrochloric acid present, and it depends on the type of polymer, type of solvent, and type of soluble salt. It may be determined experimentally, but as an example, poly(m
-phenylene isophthalamide) in dimethylacetamide, if the soluble salt is calcium chloride, the amount is 0.1 to 0.4 parts, preferably 0.1 to 0.4 parts per part (weight) of the polymer. If the neutralizing agent is added in a proportion of 2 to 0.35 parts, the stability of the solution will not be impaired, and molded products can be manufactured without the problems caused by salt-based precipitates during the drying process of the solvent as described above. is possible. The neutralizing agents may be added first, or a mixture of the two may be added.
In the present invention, the method for separating sodium chloride is not particularly limited, but since the viscosity of the solution is generally high, it is appropriate to separate it by heating in a pressurized oven using a filter press, leaf filter, or the like.

The present invention will be explained in more detail below with reference to Examples.

In addition, parts in the examples mean parts by weight, and inh
is a polymer concentration of 0.5g/100 in 96% sulfuric acid.
The relative viscosity measured at . Example 1 94 parts of dimethylacetamide and 140.6 parts of m-phenylenediamine were dissolved and cooled to 0°C, followed by 264 parts of isophthalic acid chloride. The reaction was continued for 1 hour by gradually adding the basic compound, and as a result, poly(
A dimethylacetamide solution containing hydrochloride of m-phenylene isophthalamide) and dimethylacetamide was obtained.

Add 43.7 parts of calcium hydroxide to this solution and
After a period of lighting, 69.8 parts of sodium bicarbonate was added and the lighting continued for an additional hour.

The reaction mixture, which had been transparent upon addition of sodium bicarbonate, foamed due to the neutralization reaction and became cloudy due to the simultaneous formation of insoluble sodium chloride. 80% of this solution
Sodium chloride was filtered through a 1480-mesh stainless steel net with a 50-block area under a pressure of 5k9/carp.

It took 12 weeks for the solution to clear and the resulting solution was completely clear. In this solution, 65.5 parts of calcium chloride (0.211 parts per part of polymer) are present as soluble salts. Next, the above solution was cast onto a glass plate and dried with hot air at 10,000 ml for 5 hours, and the resulting film was transparent.

After completely removing the remaining solvent and calcium chloride by soaking this film in water, it was stretched in a wet state by two times in both the vertical and horizontal directions, and further stretched for 30 minutes.
A film with a thickness of 100 microns was obtained by heat treatment at 0 qo for 10 minutes. This film has excellent transparency,
Strength 19k9/reduced, elongation 65%, dielectric breakdown voltage 160k
It was on the v/ side. Comparative Examples 1 and 2 After polymerization was carried out under the same conditions as in Example 1, all of the hydrochloric acid was neutralized by adding an amount of calcium hydroxide equivalent to that of hydrochloric acid, so that the amount of calcium chloride was 0 per part of polymer. ．．
A clear solution was obtained containing 466 parts.

This solution was cast onto a glass plate to the same thickness as in Example 1, and dried with hot air at 10°C for 5 hours. When soaked in water, there was too much residual solvent and only a cloudy film was obtained. I couldn't.

When drying was carried out for 8 hours, white crystals were precipitated on the dried surface and the entire surface of the dried surface became cloudy.

When the film in this state was immersed in water, it was found that the solvent had been reduced to such an extent that the film became transparent except for the dry surface, but due to the precipitates, only an opaque film was obtained as a whole. In this way, if all the hydrochloric acid produced during polymerization is changed to a soluble salt, not only will it take a long time to dry, but if you are trying to obtain a thick film, crystalline substances will form on the drying surface even if you change the conditions. It was impossible to prevent precipitation. In addition, all of the hydrochloric acid was converted into infusible sodium chloride by adding an amount of sodium bicarbonate equivalent to that of hydrochloric acid to the solution in which the polymerization was completed in the same manner as in Example 1.
A clear solution was obtained by filtration through a 0-mesh stainless steel net.

This solution was observed to gradually become cloudy even at room temperature, and at temperatures above 7,000, a gelation phenomenon rapidly occurred. Comparative Example 3 After polymerization was carried out in the same manner as in Example 1, hydrochloric acid was neutralized using calcium carbonate as a neutralizing agent that produces a solvent-soluble salt and ammonium carbonate as a neutralizing agent that produces a solvent-insoluble salt. .

The precipitated ammonium chloride was heated to 800 ml under a pressure of 5k9/ground.
As a result of filtering through a stainless steel net of 1480 mesh at a
．． A clear solution containing 25 parts was obtained. However, the amount of liquid in this case was inferior to that in Example 1, and the amount of liquid that could be filtered using the same 50c liquid as in Example 1 was about 4.

This solution was cast onto a glass plate in the same thickness as in Example 1, dried with hot air at 10,000 ml for 6 hours, and then immersed in water. The resulting film was completely transparent.

Claims (1)

[Claims] 1. Hydrochloric acid is neutralized by adding both a neutralizing agent that produces a solvent-soluble salt and sodium hydrogen carbonate to a solution consisting of an aromatic polyamide, an amide-type polar solvent, and a hydrochloride salt of the solvent. A method for producing an aromatic polyamide solution, which comprises subsequently separating sodium chloride. 2. The method according to claim 1, wherein the aromatic polyamide is poly(m-phenylene isophthalamide). 3. The method according to claim 1, wherein the amide type polar solvent is dimethylacetamide.