JPS6035946B2 - Method for producing aromatic copolyamide solution - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing an aromatic copolyamide solution, and more particularly, to a method for producing an aromatic copolyamide solution that is particularly useful as a heat-resistant insulating coating.

Aromatic polyamides have significantly higher melting points or glass transition points than aliphatic polyamides, and have superior shape stability at high temperatures, flame resistance, thermal decomposition resistance, chemical resistance, electrical properties, and mechanical properties. It is extremely valuable industrially as a heat-resistant fiber, film, insulating paint, and other molded products.

2. Description of the Related Art In recent years, as electrical equipment becomes smaller in size, lighter, and has improved characteristics, there has been an increasing demand for electrical insulating materials with excellent heat resistance. Currently, polyimide-based and polyamide-based polymers are used as heat-resistant electrical insulation paints, but polyimide-based insulation paints are very expensive because they use special raw materials, and polyamide-based insulation paints are very expensive. In order to reduce the price, a raw material containing a methylene group called 4,4-diaminodiphenylmethane is used, which has extremely poor long-term heat resistance, and in order to increase the heat resistance, 4,4-diaminodiphenyl ether is used as a raw material. If so, it would have to be extremely expensive. On the other hand, aromatic polyamide is a polymer that is inexpensive as a raw material and has excellent long-term heat resistance, making it an excellent insulating coating, but it has not been put into practical use due to various problems. The current situation is that this is not the case. Aromatic polyamides are usually
Although it is produced from an aromatic diamine and an aromatic dicarboxylic acid chloride, industrially it is advantageous to produce it by a low-temperature solution polymerization method in which the aromatic diamine and the aromatic dicarboxylic acid chloride are reacted in an amide type solvent.

The reason for this is that in this case, there is no need for the troublesome process of isolating the produced polymer and then redissolving it in a solvent to make the molded product, and the polymerization and molded product production can be carried out in a common solvent. This is because it is possible. When aromatic polyamides are produced by a low-temperature solution polymerization method in an amide type solvent, the hydrochloric acid released by the reaction exists as a hydrochloride salt of the solvent, and is usually calcium hydroxide, calcium oxide, calcium carbonate, or hydroxide. Neutralization is carried out with bases such as lithium, lithium carbonate, etc.

This is because salts such as calcium chloride and lithium chloride that are generated when neutralized with these bases dissolve well in the solvent.
Moreover, it has the effect of helping the aromatic polyamide to dissolve in the solvent. When molding into fibers or films, a solution containing these salts is usually used. In both wet and dry molding methods, most of the solvent is removed and then washed with water to remove the remaining solvent.
This is because salts such as calcium chloride and lithium chloride, which are undesirable to be present in the molded product, can be easily removed. However, when using an aromatic polyamide solution as an insulating coating, it is impossible to perform a washing process after heating the material coated with the solution to remove most of the solvent, except in special cases. It is.

Therefore, even if you try to use a solution that still contains salt as an insulating paint, a large amount of salt will remain on the coating, and this salt will form a chemical compound with the amide solvent, resulting in a large amount of remaining solvent, and further It also has the effect of accelerating polymer thermal deterioration.
Since the performance of the coating film is extremely degraded, it is virtually impossible to use it as an insulating coating. The method of once isolating the polymer and then remelting it in a salt-free solvent includes a single polymer step, a washing step, a drying step, a redissolution step,
This greatly increases the number of solvent recovery steps and processes, which is economically disadvantageous.

In addition, the method of polymerizing using an amide type solution and then neutralizing it with ammonia to separate the hydrochloric acid as ammonium chloride that is insoluble in the solvent and performing Hashi SI1 efficiently reacts gaseous ammonia with a highly viscous polymer solution. It is difficult to do so. In addition, the present inventors had previously proposed (Special Kansai Floor 51-1
No. 17797) Solid neutralizing agents that form salts insoluble in the solvent, such as sodium bicarbonate, ammonium carbonate,
When using a neutralizing agent such as ammonium bicarbonate,
The neutralization reaction itself is easy, but as a result of the neutralization reaction, water is also generated, and this generated water slightly dissolves the salt, so simply separating the precipitated salt will not reveal the dissolved salt in the solution. It was found that it was not preferable as an insulating paint because it would remain. As a result of intensive research to produce an aromatic polyamide solution that is particularly useful as a heat-resistant insulating coating, the present inventors found that a solution containing aromatic cobolyamide and an amide-type solvent hydrochloride, ammonium carbonate, ammonium hydrogen carbonate, and sodium hydrogen carbonate. , neutralize hydrochloric acid by adding at least an equivalent amount of one or more neutralizing agents selected from the group consisting of potassium hydrogen carbonate to hydrochloric acid, and then azeotroping the water produced by the neutralization with water. We have discovered that an aromatic polyamide solution useful as a heat-resistant insulating coating can be easily produced by removing it from the solution together with other compounds that can be used, and then separating the salt produced by neutralization.

The aromatic polyamide solution obtained by the method of the present invention is particularly suitable for heat-resistant insulating coatings, but can also be suitably used for films that are preferably salt-free and for other uses.

The aromatic copolyamide in the present invention refers to, for example, one type of aromatic dicarboxylic acid chloride and at least two types of aromatic diamines, at least two types of aromatic dicarboxylic acid chloride and one type of aromatic diamine, or at least two types of aromatic diamines.
Refers to a copolyamide produced from one aromatic dicarboxylic acid chloride and at least two aromatic diamines, in which the proportion of the copolymerized component in the acid component and/or diamine component exceeds 5 mol %.

If the proportion of the copolymerized component is less than 5 mol %, the copolyamide solution is very unstable in the absence of salt and gelation occurs in a short period of time, which is not preferable. Monomer
Although it varies depending on the combination of
From the viewpoint of stability of the solution, it is preferable that the content is 40 mol %. Acid components for producing such aromatic copolyamides include, for example, isophthalic acid chloride, terephthalic acid chloride, diphenyl dicarboxylic acid chloride, 2,6-naphthalenedicarboxylic acid chloride, and diamine components include, for example, p- Phenylene diamine, m-phenylene diamine, 2,4-tolylene diamine, 4,4'-diaminodiphenyl ether, 4,
Examples include 4'-diaminodiphenyl sulfone and 4,4'-diami/diphenylmethane. Further, typical amide type solvents used in the present invention include dimethylacetamide, N-methylpyrrolidone, tetramethylurea, and hexamethylphosphoramide. Dimethylformamide can be used as a solvent for dissolving polymers, but it cannot be used as a polymerization solvent.
It's inappropriate. Further, compounds that can be azeotroped with water used in the present invention include benzene, toluene, xylene, carbon tetrachloride, chloroform, methylene chloride, ethyl alcohol, dioxane, phthanol, pyridine, chlorobenzene, nitrobenzene, aniline,
Typical examples include cyclohexane and naphthalene.

Among these, aromatic compounds are particularly preferred because they can form a pseudomixture with a high proportion of water, and therefore only require a small amount to be added. The amount of these compounds added varies depending on the proportion of water in the azeotropic mixture, but in the case of aromatic compounds, it is selected within a range that does not precipitate the polymer when the amount is approximately three times (volume) or more the amount of water present. When adding a compound that can coexist with water, if it does not inhibit the polymerization reaction, it can be added to the amide type solvent before polymerization, or after the completion of polymerization or after neutralization. It may be added to the subsequent solution.

Although distillation of the co-brood mixture can be carried out at normal pressure, it is preferable to carry out the distillation under reduced pressure to avoid unnecessary heating of the solution.

Since there is almost no water in the solution after such treatment, the salt is not substantially dissolved in the solution, and by separating the salt present as a precipitate, a salt-free aromatic product can be obtained. A copolyamide solution is obtained.

Since the solution has a high viscosity, the method of separating the salt present as a precipitate from the solution is more suitable than filtration using pressure using a filter press, leaf filter, etc. than filtration using a vacuum.

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

Note that parts in the examples mean parts by weight.
In addition, ri inh is the relative viscosity measured at 25 o 0 at a polymer concentration of 0.5 m/100 in 96% sulfuric acid.・Sheep 1 pretends to be a castle. Example 1 100 parts of dimethylacetamide, 140.5 parts of phenylene diamine, and 9.6 parts of phthalic anhydride were melted and cooled to 0°C, followed by 184 parts of isophthalic acid chloride.
．． A mixture of 7 parts of terephthalic acid chloride and 79.2 parts of terephthalic acid chloride (30 mol% of terephthalic acid chloride) was gradually added and the reaction was continued for 1 hour. As a result, rinh contained 30 mol% of 0.79 terephthalic acid chloride. A solution of a copolymer of poly(m-phenylene isophthalamide) was obtained.

When 133.1 parts of ammonium carbonate was added to this solution, foaming occurred and a neutralization reaction took place.

After keeping the light on for one hour to ensure neutralization,
7 parts of xylene was added and stirred until uniform. Next, the container was immersed to a temperature of 90°C and 20°Hg.
The evaporated components of 96' were removed by maintaining a reduced pressure of . There were 23.4 parts of water in this evaporated component, and the entire amount of water produced during neutralization was distilled off. Then the internal temperature is 8
Heat to 0°C and use Keisouji 45 as a filtering agent.
The ammonium chloride precipitate was filtered through 800 mesh stainless steel under pressure of 4k9/ml. The monkey fluid was a completely clear solution. This solution and, for comparison, a solution obtained by simply filtering the ammonium chloride precipitate after neutralization with ammonium carbonate were each cast on a glass slope, and the solvent was evaporated with hot air at 120° C. to obtain a film. The two types of films obtained were exposed in air at 25,000°C and 300°C for 30 days to compare strength retention and coloration. The results were as shown in Table 1. As is clear from Table 1, the heat resistance of the comparative example was inferior to that of the present invention.

Example 2 100 parts of N-methylpyrrolidone, 98.35 parts of m-phenylenediamine, 42.1 parts of p-phenylenediamine
After dissolving 5 parts (p-phenylenediamine 30 mol%) and 9.4 parts of phthalic anhydride and cooling to 0°C, 263.9 parts of isophthalic acid chloride was added and the reaction was continued for 1 hour. A solution of a copolyamide with 0.83 was obtained.

This solution was added with sodium hydrogen carbonate to neutralize the hydrochloric acid present in the reaction system.

Next, 125 parts of toluene was added and worshiped until the mixture became homogeneous, and then the container was immersed in 890 grade and the evaporated components of 167 skin were distilled off by maintaining a reduced pressure of 20 mbar Hg. . There was 23.4 parts of water in this evaporated component, and the entire amount of raw water was removed during neutralization. Next, the mixture was heated to an internal temperature of 80 qo, 46 parts of sodium chloride was added as a filtering agent, and the precipitate of sodium chloride was filtered through an 800-mesh stainless steel net under a pressure of 4 kg. The monkey fluid was a completely clear solution. This solution and, for comparison, a solution of Lena after neutralization with sodium bicarbonate and simply filtering out the precipitate of sodium chloride were cast onto a glass slope, and the solvent was evaporated with hot air at 140 qo to obtain a flume. .

The obtained film was heated to 25,000 and 30,000 in air.
The strength retention rate and coloring were compared after being exposed to this atmosphere for 30 days. The results were as shown in Table 2. As is clear from Table 2, the heat resistance of the comparative example was inferior to that of the present invention. Table 2

Claims (1)

[Claims] 1. Add one or more neutralizing agents selected from ammonium carbonate, ammonium hydrogen carbonate, sodium hydrogen carbonate, and potassium hydrogen carbonate to a solution containing an aromatic copolyamide and a hydrochloride of an amide type solvent in an amount equivalent to or more of hydrochloric acid. An aromatic aroma characterized by neutralizing hydrochloric acid by adding hydrochloric acid, followed by distilling off the water produced by the neutralization from the solution together with a compound capable of azeotroping with water, and then separating the salt produced by the neutralization. A method for producing a group copolyamide solution.