Aromatic polyamide dissolving solvent, aromatic polyamide dissolving method, and method for producing aromatic polyamide molded article

Abstract

To provide a solvent capable of dissolving an aromatic polyamide at around room temperature in a short time without requiring a special pre-treatment or sulfuric acid and to provide method for dissolving and molding an aromatic polyamide using the solvent or the like.SOLUTION: There is provided a dissolving solvent of an aromatic polyamide which contains tetraalkylammonium hydroxide, water and dimethyl sulfoxide, wherein in the concentration of each component in the solvent, the concentration of tetraalkylammonium hydroxide is 0.5 to 40 wt.%, the concentration of water is 0.5 to 45 wt.%, the concentration of dimethyl sulfoxide is 15 to 98 wt.%. The tetraalkylammonium hydroxide preferably includes tetraethylammonium hydroxide, tetrapropylammonium hydroxide and tetrabutylammonium hydroxide.SELECTED DRAWING: Figure 2

Description

Technical Field

[0001] The present invention relates to a solvent used for dissolving aromatic polyamide, and a method for producing an aromatic polyamide molded body using the solvent.

Background Art

[0002] Aromatic polyamides include para-type aromatic polyamides such as poly(paraphenylene terephthalamide) and meta-type aromatic polyamides such as poly(m-phenylene isophthalamide), both of which have been put into practical use as fibers. Aromatic polyamides, particularly para-type aromatic polyamides, have excellent heat resistance and mechanical strength and have attracted attention as high-functional resins. However, since aromatic polyamide has extremely poor solubility in organic solvents, it is difficult to form a film like ordinary plastics.

[0003] As described in Patent Document 1, a method for dissolving aromatic polyamide using an amide-based solvent containing an inorganic salt and forming a film has been proposed. However, in this method, there is a risk that not all of the inorganic salt can be completely removed from the film due to the use of a large amount of inorganic salt. Also, as described in Non-Patent Document 1, a method of dissolving Kevlar (registered trademark) in a solution of tetrabutylammonium fluoride (TBAF) and dimethyl sulfoxide and derivatizing it has been proposed. However, tetrabutylammonium fluoride is toxic and expensive, and in addition, the solubility of Kevlar (registered trademark) is only about 1%.

[0004] On the other hand, the present applicant has filed a patent (unpublished) for a mixed solution of tetraalkylammonium hydroxide aqueous solution and dimethyl sulfoxide as a solvent for dissolving chitin.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Non-Patent Documents

[0006]

Non - Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0007] The present invention provides a solvent capable of uniformly dissolving an aromatic polyamide near room temperature in a short time without requiring special pretreatment, a method for dissolving an aromatic polyamide using the solvent, and a method for producing an aromatic polyamide molded article.

Means for Solving the Problems

[0008] As a result of intensive studies to achieve the above problems, the present inventors have completed the invention shown below. 〔1〕 A solvent used for dissolving an aromatic polyamide, wherein the solvent contains tetraalkylammonium hydroxide represented by the following formula, water, and dimethyl sulfoxide, and the concentration of each component in the solvent is such that the concentration of tetraalkylammonium hydroxide is in the range of 0.5 - 40 wt%, the concentration of water is in the range of 0.5 - 45 wt%, and the concentration of dimethyl sulfoxide is in the range of 15 - 99 wt%.

Chemical Formula

Advantages of the Invention

[0009] The solvent of the present invention is a solvent capable of uniformly dissolving an aromatic polyamide in a short time without any special pretreatment, regardless of the type, crystal form and shape of the aromatic polyamide.

[0010] And, compared with the solvents of Patent Document 1 and Non-Patent Document 1, the solvent of the present invention does not contain a fluorine-based compound or an inorganic salt, so it has high safety and is easy to completely remove the solvent when producing a molded article.

[0011] In addition, the solution obtained by dissolving an aromatic polyamide with the solvent of the present invention has high stability, has fluidity even at room temperature, and has excellent moldability.

Brief Description of the Drawings

[0012]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Mode for Carrying Out the Invention

[0013] The aromatic polyamide dissolved in the aromatic polyamide dissolving solvent of the present invention is not particularly limited, and regardless of the crystallinity and degree of polymerization, for example, para - aromatic polyamides such as poly(p - phenylene terephthalamide), and meta - aromatic polyamides such as poly(m - phenylene isophthalamide) or their derivatives can be mentioned. Among them, para - aramids such as Kevlar (registered trademark) (PPTA) of Toray DuPont, Twaron (registered trademark) (PPTA) and Technora (registered trademark) (copolymer type aramid) of Teijin Technoproducts, and meta - aramids such as Nomex (registered trademark) (meta - aramid) of DuPont and Conex (registered trademark) (meta - aramid) of Teijin have excellent mechanical properties, thermal properties and chemical resistance, and are more preferable because they are applied in a wide range of fields. These aramids are commercially available, and commercially available products can be used as raw materials.

[0014] The tetraalkylammonium hydroxide (TAAH) which is a component of the aromatic polyamide dissolving solvent of the present invention has no limitation as long as R1 to R4 in the chemical formula shown in the above [1] are alkyl groups having 1 to 5 carbon atoms. It may be used alone or in combination of two or more. Specific compounds can be exemplified as follows. Tetraethylammonium hydroxide, tetrapropylammonium hydroxide, tetrabutylammonium hydroxide, methyltripropylammonium hydroxide, methyltributylammonium hydroxide, ethyltripropylammonium hydroxide, ethyltributylammonium hydroxide, propyltributylammonium hydroxide, dimethyldipropylammonium hydroxide, dimethyltributylammonium hydroxide, diethyldipropylammonium hydroxide, diethyldibutylammonium hydroxide, etc., and particularly preferably, tetraethylammonium hydroxide (TEAH), tetrapropylammonium hydroxide (TPAH) and tetrabutylammonium hydroxide (TBAH).

[0015] The tetraalkylammonium hydroxide (TAAH) used for dissolving the polyimide of the present invention is water-soluble, stable in an aqueous solution state, and the main substances are commercially available chemicals sold as aqueous solutions and are easily available. Since the polyimide solvent of the present invention contains tetraalkylammonium hydroxide (TAAH), water and dimethyl sulfoxide (DMSO), TAAH can be mixed with DMSO as an aqueous solution to form a solvent.

[0016] The aromatic polyamide solvent of the present invention is composed of TAAH, water and DMSO, and the composition ratio is adjusted so that TAAH is in the concentration range of 0.5 to 40 wt%, water is 0.5 to 45 wt%, and DMSO is 15 to 99 wt%. More preferably, TAAH is 2 to 35 wt%, water is 2.0 to 40 wt%, DMSO is 25 to 96 wt%, still more preferably, TAAH is 2.0 to 30 wt%, water is 3.0 to 35 wt%, DMSO is 35 to 95 wt%, and most preferably, TAAH is 3.0 to 35 wt%, water is 4 to 40 wt%, and DMSO is 45 to 94 wt%.

[0017] When the concentration of TAAH is lower than 0.5 wt%, the solubility and dissolution rate are low, which is not preferable. On the other hand, when it is higher than 40 wt%, the solubility of the aromatic polyamide decreases and the required dissolution temperature increases. In addition, when the obtained aromatic polyamide solution is stored at room temperature, there is a risk that the aromatic polyamide may precipitate, which is not preferable.

[0018] When the concentration of water is lower than 0.5 wt%, the solubility of the aromatic polyamide may decrease or TAAH may be unstable and decompose, which is not preferable. On the other hand, when it is higher than 45 wt%, the solubility of the aromatic polyamide decreases, which is not preferable.

[0019] In addition to tetraalkylammonium hydroxide, water and dimethyl sulfoxide, the solvent of the present invention can also contain other organic solvents. For example, alcohol, N,N-dimethylacetamide, N,N-dimethylformamide, N-methylpyrrolidone, pyridine can be mentioned. By adding these solvents, the dissolution of the aromatic polyamide can be improved, and the viscosity and reactivity of the aromatic polyamide solution can be adjusted.

[0020] There are no particular restrictions on the method for preparing the aromatic polyamide dissolution solvent of the present invention. For example, after preparing an aqueous TAAH solution purchased commercially at a desired concentration, DMSO is added thereto and stirred to obtain an aromatic polyamide dissolution solvent. When the concentration of TAAH in the commercially available aqueous TAAH solution is lower than the desired concentration when the concentration of water is in the optimal range, it is preferably distilled before use and concentrated to the desired water content before use. Also, when it is higher than the desired concentration, it is diluted with water before use. The weight ratio of TAAH / water is preferably 20 / 80 to 70 / 40. More preferably, it is 30 / 70 to 60 / 40, and most preferably 35 / 65 to 55 / 45. There is no particular restriction on the temperature during mixing, but 10 to 120 °C is preferable. More preferably, it is 15 to 100 °C, and most preferably 23 to 85 °C.

[0021] The method for dissolving an aromatic polyamide in the aromatic polyamide dissolving solvent of the present invention is not particularly limited. For example, an aromatic polyamide is added to a predetermined amount of the aromatic polyamide dissolving solvent of the present invention, and the aromatic polyamide solution is prepared by stirring until a transparent solution is obtained. Stirring may be performed with a commonly used mechanical stirrer. For a beaker scale, stirring with a magnetic stirrer is sufficient. The temperature during dissolution may be 10 to 150 °C, and it may be dissolved without adjusting the temperature at room temperature. If it is lower than 10 °C, the solubility or dissolution rate of the aromatic polyamide is low, which is not preferable. If it is higher than 150 °C, there is a risk that water may evaporate or TAAH may decompose, which is not preferable. More preferably, it is 15 to 140 °C, still more preferably 15 to 130 °C, and most preferably 23 to 125 °C.

[0022] The dissolution amount of the aromatic polyamide is not particularly limited. It may be appropriately adjusted according to the type, degree of polymerization (molecular weight), and use of the aromatic polyamide. For example, it is 1 to 50 wt%. More preferably, it is 2 to 40 wt%, and most preferably 3 to 30 wt%. If the dissolution amount is too low, the productivity will be low or the moldability of the obtained aromatic polyamide solution will be poor, which is not preferable. On the other hand, if the dissolution amount is too high, there is a risk that the aromatic polyamide may be incompletely dissolved, the uniformity of the solution may decrease, or the fluidity of the obtained aromatic polyamide solution may be lost, which is not preferable.

[0023] The molding solution of the aromatic polyamide molded body of the present invention is obtained by defoaming the aromatic polyamide solution obtained by dissolving an aromatic polyamide in an aromatic polyamide dissolving solvent and using it as the molding solution. The molding method is not particularly limited, but generally, a wet molding method or a dry molding method can be applied. For example, after sucking the aromatic polyamide solution with a syringe, a nozzle is attached and the syringe is mounted on a syringe pump or a microfeeder, and the aromatic polyamide solution is discharged from the nozzle into a coagulating liquid such as normal temperature water or alcohol while moving the syringe, and the fibers are washed and then wound up with a winder to prepare aromatic polyamide fibers. When forming an aromatic polyamide film, for example, an aromatic polyamide solution is cast on a glass substrate, placed in a coagulating liquid such as water or alcohol, washed while coagulating the liquid film, and then dried to prepare the film. When forming using the dry method, fibers can be obtained by discharging the aromatic polyamide solution from a mold and heating it at a constant temperature to remove DMSO and TAAH. On the other hand, in the case of film formation, after casting the aromatic polyamide solution on a substrate, it can be formed into a film by heating at a constant temperature. The heating temperature may be appropriately set according to the forming method and the type of TAAH. For example, it may be within the temperature range of 50 to 300 °C. It is preferable to raise the temperature sequentially from 50 °C to avoid the formation of bubbles in the formed body.

Example

[0024] The present invention will be further described using examples. Note that the present invention is not limited only to these examples.

[0025] (Raw materials and solvents used) Polyparaphenylene terephthalamide: Tiarra (registered trademark) (microfibrous aromatic polyamide) manufactured by Daicel Corporation was dried in a forced-air dryer at 105 °C and used. Alternatively, commercially available Kevlar (registered trademark) fibers were used as they were. Meta-aramid: Commercially available Conex (registered trademark) short fibers were used. 35% aqueous solution of tetraethylammonium hydroxide: Manufactured by Tokyo Chemical Industry Co., Ltd. 45% aqueous solution of tetraethylammonium hydroxide: Obtained by concentrating the 35% product manufactured by Tokyo Chemical Industry Co., Ltd. 48% aqueous solution of tetraethylammonium hydroxide: Obtained by concentrating the 35% product manufactured by Tokyo Chemical Industry Co., Ltd. 40% aqueous solution of tetrapropylammonium hydroxide: Manufactured by Tokyo Chemical Industry Co., Ltd. 48% aqueous solution of tetrapropylammonium hydroxide: Obtained by concentrating the 40% product manufactured by Tokyo Chemical Industry Co., Ltd. 40% aqueous solution of tetrabutylammonium hydroxide: Manufactured by Tokyo Chemical Industry Co., Ltd. Other reagents were purchased from Nacalai Tesque, Inc.

[0026] (Dissolution method) For the dissolution of aromatic polyamide, a 10 ml or 20 ml sample bottle, a magnetic stirrer or a magnetic hot stirrer was used.

[0027] [Example 1] To a 10 ml vial, 0.7 g of a 40% aqueous solution of tetrapropylammonium hydroxide (TPAH) and 4.3 g of dimethyl sulfoxide (DMSO) were added. While stirring with a magnetic hot stirrer set at 80 °C, 0.2 g of commercially available Kevlar® fiber was added, and the appearance of the solution was observed while stirring. It was confirmed that the appearance of the solution tended to change from yellow to brown as Kevlar® dissolved. A brown transparent solution was obtained after 40 minutes. The appearance photograph of the aromatic polyamide solution is shown in Fig. 1. The stirring time until a transparent solution was obtained was 40 minutes. The obtained aromatic polyamide solution was cast onto a glass substrate with a glass rod and placed in an ethanol solution together with the glass substrate. After about 10 minutes, the aromatic polyamide coagulated and became hard. DMSO and TPAH were removed by repeating the replacement of ethanol 4 times. Next, it was stretched on the glass substrate and air-dried. The appearance of the obtained film is shown in Fig. 2.

[0028] [Example 2] Dissolution was carried out in the same manner as in Example 1 except that 0.2 g of Tiala was added instead of 0.2 g of commercially available Kevlar® fiber. The stirring time until a brown transparent solution was obtained was 90 minutes. The appearance of the obtained solution is shown in Fig. 1.

[0029] [Example 3] The procedure was carried out in the same manner as in Example 2 except that 4.6 g of DMSO and 0.4 g of a 40% aqueous solution of tetrapropylammonium hydroxide were used instead of 4.3 g of DMSO and 0.7 g of a 40% aqueous solution of tetrapropylammonium hydroxide, and 0.1 g of Tiala® was dissolved. The stirring time until a brown transparent solution was obtained was 120 minutes. The appearance of the obtained solution is shown in Fig. 1.

[0030] [Example 4] 0.25 g of Tiara (registered trademark) was dissolved in the same manner as in Example 2, except that 4.0 g of DMSO and 1.0 g of a 40% aqueous solution of tetrapropylammonium hydroxide were used instead of 4.3 g of DMSO and 0.7 g of a 40% aqueous solution of tetrapropylammonium hydroxide. The stirring time until a brown transparent solution was obtained was 180 minutes.

[0031] [Example 5] Dissolution of 0.2 g of dried Tiara (registered trademark) was carried out in the same manner as in Example 3, except that a 45% aqueous solution of tetraethylammonium hydroxide was used instead of a 40% aqueous solution of tetrapropylammonium hydroxide. The stirring time until a brown transparent solution was obtained was 60 minutes. The appearance of the obtained solution is shown in Fig. 1. A film was produced in the same manner as in Example 1 using the obtained aromatic polyamide solution. The appearance of the obtained film is shown in Fig. 2.

[0032] [Example 6] Dissolution of dried Tiara (registered trademark) was carried out in the same manner as in Example 2, except that a 40% aqueous solution of tetrabutylammonium hydroxide was used instead of a 40% aqueous solution of tetrapropylammonium hydroxide. The stirring time until a brown transparent solution was obtained was 120 minutes. The appearance of the obtained solution is shown in Fig. 1. A film was produced in the same manner as in Example 1 using the obtained aromatic polyamide solution. The appearance of the obtained film is shown in Fig. 2.

[0033] [Example 7] Dissolution of Kevlar (registered trademark) fiber was carried out in the same manner as in Example 1, except that the dissolution temperature was set to room temperature. The stirring time until a brown transparent solution was obtained was 150 minutes.

[0034] [Example 8] 0.2 g of Tiara was dissolved in the same manner as in Example 2, except that 3.0 g of DMSO and 2.0 g of a 40% aqueous solution of tetrapropylammonium hydroxide were used and the temperature was set to 120 °C. The stirring time until a brown transparent solution was obtained was 40 minutes. The appearance of the obtained solution is shown in Fig. 1. Furthermore, the obtained cellulose solution was sucked up with a syringe, attached with a nozzle having a pore diameter of 0.5 mmφ, and discharged into a normal-temperature distilled water bath while stretching the fibrous gel. Next, the fibrous gel was washed with distilled water to remove tetrapropylammonium hydroxide and dimethyl sulfoxide, and then air-dried at room temperature to obtain fibers. A photograph of the obtained fibers is shown in Figure 2.

[0035] [Example 9] The procedure of Example 8 was repeated except that 4.75 g of DMSO and 0.25 g of a 40% aqueous solution of tetrapropylammonium hydroxide were used, and 0.1 g of tiara was dissolved. The stirring time until a brown transparent solution was obtained was 150 minutes. The appearance of the obtained solution is shown in Figure 1.

[0036] [Comparative Example 1] Without adding a 40% aqueous solution of tetrapropylammonium hydroxide, 0.2 g of tiara was added in the same manner as in Example 1 using only 5 g of DMSO, and stirring was continued for 5 hours, but no dissolution or color change occurred. The appearance was a pale yellow paste-like dispersion as shown in Figure 3.

[0037] [Comparative Example 2] 0.25 g of calcium chloride and 4.75 g of N-methyl-2-pyrrolidone (NMP) were mixed, and 0.2 g of tiara was continuously stirred for 5 hours in the same manner as in Example 1, but no dissolution or color change occurred. The appearance was a pale yellow paste-like dispersion as shown in Figure 3.

[0038] [Example 10] 0.3 g of Kevlar fiber was dissolved in the same manner as in Example 1 except that a 48% aqueous solution of tetrapropylammonium hydroxide was used instead of 0.7 g of a 40% aqueous solution of tetrapropylammonium hydroxide. The stirring time until a brown transparent solution was obtained was 70 minutes. The obtained solution was cast on a glass substrate with a glass rod and the glass substrate was placed in distilled water. After about 5 minutes, the solution solidified and became hard. DMSO and TPAH were removed by repeating the replacement of distilled water 4 times. Next, it was stretched on the glass substrate and air-dried. The appearance of the obtained film is shown in Figure 5.

[0039] [Example 11] Add 3.0 g of DMSO and 2.0 g of a 48% aqueous solution of tetraethylammonium hydroxide to a 20 ml vial, and while stirring with a non-heating magnetic hot stirrer, add 1.2 g of meta-aramid short fibers, and observe the appearance of the solution while stirring. It was confirmed that the appearance of the solution tended to change from colorless to yellow as the meta-aramid short fibers dissolved. A yellow transparent solution was obtained after 120 minutes. As shown in the appearance photograph of the obtained solution in Fig. 4, it has fluidity at room temperature.

[0040] [Example 12] 0.75 g of meta-aramid short fibers was dissolved in the same manner as in Example 11, except that 4.2 g of DMSO and 0.8 g of a 48% aqueous solution of tetraethylammonium hydroxide were used. The stirring time until a yellow transparent solution was obtained was 110 minutes. The obtained solution has fluidity at room temperature as shown in Fig. 4. The obtained solution was cast onto a glass substrate with a glass rod and the glass substrate was placed in distilled water. After about 5 minutes, the solution solidified and became hard. DMSO and TEAH were removed by repeating the replacement of distilled water 4 times. Next, it was stretched on a glass substrate and air-dried. The appearance of the obtained film is shown in Fig. 5.

[0041] [Example 13] 0.3 g of meta-aramid short fibers was dissolved in the same manner as in Example 11, except that 4.6 g of DMSO and 0.4 g of a 48% aqueous solution of tetraethylammonium hydroxide were used. The stirring time until a yellow transparent solution was obtained was 60 minutes. The obtained solution has fluidity at room temperature as shown in Fig. 4.

[0042] [Example 14] 0.6 g of meta-aramid short fibers was dissolved in the same manner as in Example 13, except that 4.3 g of DMSO and 0.7 g of a 48% aqueous solution of tetrapropylammonium hydroxide were used. The stirring time until a yellow transparent solution was obtained was 120 minutes. The obtained solution has fluidity at room temperature as shown in Fig. 4.

[0043] [Example 15] Except for using 4.4 g of DMSO and 0.6 g of an aqueous solution of 40% tetrapropylammonium hydroxide, 0.25 g of meta-aramid short fibers were dissolved in the same manner as in Example 13. The stirring time until a yellow transparent solution was obtained was 105 minutes. The resulting solution had fluidity at room temperature.

[0044] [Example 16] After casting the meta-aramid solution prepared in Example 12 onto a PET film, it was left on a 60 °C hot plate for 1 hour to remove the contained water. Next, when the temperature of the hot plate was raised to 150 °C and heated for another 1 hour, it became a film-like solid. After drying this film-like solid in a 250 °C air dryer for 1 hour and performing FT-IR analysis, TEAH and DMSO could not be detected.

[0045] [Comparative Example 3] Except for using 4.95 g of DMSO and 0.05 g of an aqueous solution of 48% tetraethylammonium hydroxide, an attempt was made to dissolve 0.25 g of meta-aramid short fibers in the same manner as in Example 15. As a result of stirring at room temperature for 180 minutes, the meta-aramid short fibers swelled but a transparent solution could not be obtained.

[0046] The dissolution conditions and evaluation results of Examples 1 to 15 and Comparative Examples 1 to 3 are summarized in Tables 1 and 2, and the composition ratios of the solvents are shown in Table 3.

[0047]

Table 1

[0048]

Table 2

[0049]

Table 3

[0050] As shown in Tables 1 to 3, in Examples 1 to 15, aromatic polyamides could be dissolved uniformly in a short time at room temperature to 120°C without any pretreatment. Although Tiarra, Kevlar (registered trademark) fiber, and meta-aramid staple fiber are poly(p-phenylene terephthalamide) with different shapes, they could all be dissolved. From these results, it can be seen that the aromatic polyamide dissolving solvent of the present invention can dissolve aromatic polyamides regardless of their shapes. On the other hand, in Comparative Examples 1, 2, and 3, aromatic polyamides could not be dissolved.

Industrial Applicability

[0051] As described above, according to the aromatic polyamide dissolving solvent of the present invention, aromatic polyamides can be dissolved uniformly in a short time without depending on the degree of polymerization and crystal form of the aromatic polyamides, and there is no need for highly toxic solvents as in the prior art. Furthermore, the aromatic polyamide-containing solution dissolved in the solvent of the present invention has excellent fluidity and moldability, and can be widely applied to the technical field of manufacturing aromatic polyamides, particularly aromatic polyamide molded articles, by a wet molding method. In addition, the aromatic polyamide-containing solution dissolved in the solvent of the present invention can also be applied to the synthesis of aromatic polyamide derivatives.

Claims

Claim 1 A solvent used for dissolving an aromatic polyamide, wherein the solvent contains a tetraalkylammonium hydroxide represented by the following formula, water, and dimethyl sulfoxide, and the concentrations of the respective components in the solvent are such that the concentration of the tetraalkylammonium hydroxide is in the range of 2.0 to 30 wt%, the concentration of water is in the range of 3.0 to 35 wt%, and the concentration of dimethyl sulfoxide is in the range of 35 to 95 wt%. 【Chemical 1】 In the formula, R1, R2, R3, and R4 each independently represent an alkyl group having 1 to 5 carbon atoms. Claim 2 The solvent according to claim 1, wherein the tetraalkylammonium hydroxide contains at least one of tetraethylammonium hydroxide, tetrapropylammonium hydroxide, and tetrabutylammonium hydroxide. Claim 3 The solvent according to claim 1, wherein the aromatic polyamide to be dissolved is a para-aromatic polyamide and / or a meta-aromatic polyamide. Claim 4 A method for dissolving an aromatic polyamide, comprising contacting the aromatic polyamide with the solvent according to any one of claims 1 to 3 to dissolve the aromatic polyamide. Claim 5 A method for producing an aromatic polyamide molded article, comprising producing the aromatic polyamide molded article using the aromatic polyamide solution obtained by the method for dissolving an aromatic polyamide according to claim 4.

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