JP2010138342A - Production method of polymerization stock solution for polybenzoazole - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a preparation method of a polymerization stock solution for producing a polybenzoazole containing only a small amount of a gel foreign matter becoming a cause of a foreign matter or a process trouble during the spinning or the molding. <P>SOLUTION: This preparation method of a polymerization stock solution is a method for suppressing the generation of gel substances in a polybenzoazole solution prepared by subjecting a polymerization stock solution to a dispersing treatment under reduced pressure or in an atmosphere of an inert gas using a high speed stirring apparatus and thereafter to a polymerization reaction, which is invented for solving the problem that in the preparation of a raw material for a polybenzoazole, particularly a polybenzoazole containing two types of aromatic dicarboxylic acid groups having a specific functional group, when the raw material is mixed with a solvent and the resultant reaction mixture is subjected to a polymerization reaction by stirring and heating the reaction mixture, the obtained polybenzoazole becomes contain a large amount of gel substances and when such a polybenzoazole is spun, a thread break is frequently caused, so that the productivity of the thread becomes impaired. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a method for preparing a polymerization stock solution that is a raw material for producing polybenzoazole containing an aromatic dicarboxylic acid group having a specific functional group, and a method for producing polybenzoazole therefrom.

  Polybenzoazole represented by polybenzobisoxazole is a polycondensation polymer having excellent physical properties, and there are extensive examples of introduction of polybenzobisoxazole compounds (see, for example, Patent Document 1).

  As a production method of polybenzoazole, aromatic amines such as 4,6-diamino-1,3-benzenediol and 2,5-diamino-1,4-benzenedithiol, terephthalic acid, naphthalenedicarboxylic acid, biphenyldicarboxylic acid are used. The most common method is a polycondensation reaction between an aromatic dicarboxylic acid such as an acid in a solvent having a dehydrating action such as polyphosphoric acid.

In addition, a production method using a salt of an aromatic amine derivative and an aromatic dicarboxylic acid as a raw material of polybenzoazole, and a method of producing polybenzoazole from an aromatic amine derivative and an aromatic dicarboxylate are introduced ( For example, Patent Documents 2 and 3).
Moreover, polybenzoazole containing two kinds of aromatic dicarboxylic acid groups having a specific functional group has also been reported (for example, Patent Document 4).

International Publication No. 85/04178 Pamphlet JP 2001-172238 A (US Pat. No. 6,617,414) JP 2007-161757 A International Publication No. 2005/100442 Pamphlet

  An object of the present invention is to provide a method for preparing a polymerization stock solution for producing a polybenzoazole that has few gel-like foreign matters that cause foreign matters and process troubles during spinning and molding.

  In the preparation of a raw material of polybenzoazole, in particular, a polybenzoazole containing two kinds of aromatic dicarboxylic acid groups having a specific functional group, the raw material is added to a solvent, stirred and heated to conduct a polymerization reaction. It was found that the resulting polybenzoazole contained a large amount of gel-like material, and spinning the yarn resulted in poor yarn productivity, such as frequent yarn breakage. As a solution to this problem, the polymerization stock solution is subjected to a dispersion reaction using a high-speed stirrer under reduced pressure or under an inert gas atmosphere, and then subjected to a polymerization reaction, thereby generating a gel-like substance in the obtained polybenzoazole solution. The present invention has been achieved successfully. That is, the gist of the present invention is as follows.

（ＸはＯ、Ｓ、ＮＨいずれかを表し、Ａｒ^１は炭素数４〜２０の４価の芳香族基を表す）
で表される芳香族アミン誘導体およびその塩酸塩からなる群から選択される少なくとも１種と、下記式（Ｃ）および（Ｄ）

（Ｒ^１，Ｒ^１’Ｒ^２、Ｒ^２’は各々独立に水素またはアルカリ金属元素を表し、ＹはＮまたはＣＨを表す。）
で表される芳香族ジカルボン酸誘導体の少なくとも１種とを、溶媒中にて反応させて、下記式（Ｅ）〜（Ｈ）で表される有機塩化合物の少なくとも１種を得て、これをＰ_２Ｏ_５濃度７５質量％以上のポリリン酸中に、下記式（Ｅ）〜（Ｈ）の有機塩化合物合計の濃度が１０〜４０質量％になるように加え、減圧下または不活性ガス雰囲気下で高速撹拌装置を用いて分散処理することを特徴とする、ポリベンゾアゾール重合原液の製造方法。 1. The following general formulas (A) and (B)

(X represents any of O, S, and NH, and Ar ¹ represents a tetravalent aromatic group having 4 to 20 carbon atoms)
At least one selected from the group consisting of an aromatic amine derivative represented by the formula (I) and a hydrochloride thereof, and the following formulas (C) and (D):

(R ¹ , R ¹ ′ R ² and R ² ′ each independently represent hydrogen or an alkali metal element, and Y represents N or CH.)
And at least one organic salt compound represented by the following formulas (E) to (H) is reacted with at least one aromatic dicarboxylic acid derivative represented by formula (E): In polyphosphoric acid having a P ₂ O ₅ concentration of 75% by mass or more, it is added so that the total concentration of the organic salt compounds of the following formulas (E) to (H) is 10 to 40% by mass, under reduced pressure or in an inert gas atmosphere A method for producing a polybenzoazole polymerization stock solution, characterized in that the dispersion treatment is performed using a high-speed stirring device.

（ＸはＯ、Ｓ、ＮＨいずれかを表し、Ａｒ^１は炭素数４〜２０の４価の芳香族基を表す。）

（ＸはＯ、Ｓ、ＮＨいずれかを表し、Ａｒ^１は炭素数４〜２０の４価の芳香族基を表し、ＹはＮまたはＣＨを表す。）

（ＸはＯ、Ｓ、ＮＨいずれかを表し、Ａｒ^１は炭素数４〜２０の４価の芳香族基を表す。）

（ＸはＯ、Ｓ、ＮＨいずれかを表し、Ａｒ^１は炭素数４〜２０の４価の芳香族基を表し、ＹはＮまたはＣＨを表す。）

(X represents any of O, S, and NH, and Ar ¹ represents a tetravalent aromatic group having 4 to 20 carbon atoms.)

(X represents any of O, S, and NH, Ar ¹ represents a tetravalent aromatic group having 4 to 20 carbon atoms, and Y represents N or CH.)

(X represents any of O, S, and NH, and Ar ¹ represents a tetravalent aromatic group having 4 to 20 carbon atoms.)

(X represents any of O, S, and NH, Ar ¹ represents a tetravalent aromatic group having 4 to 20 carbon atoms, and Y represents N or CH.)

2. 2. The method for producing a polybenzoazole polymerization stock solution as described in 1 above, wherein the high-speed stirring device has a rotational speed of 200 to 2500 rpm.
3. 3. The method for producing a polybenzoazole polymerization stock solution according to the above item 2, wherein the high-speed stirring device is a planetary mixer, the revolution speed is 200 to 2000 rpm, and the rotation speed is 80 to 800 rpm.
4). Obtained by the method according to any one of the above 1 to 3, wherein, at least one is, P ₂ O ₅ concentration of 75% or more polyphosphates of organic salt compound of formula according to claim 1, wherein (E) ~ (H) A polybenzoazole polymerization stock solution dispersed in an acid solvent at a concentration such that the total concentration of the organic salt compounds of the formulas (E) to (H) is 5 to 40% by mass.
5). 5. A method for producing polybenzoazole, characterized in that a polybenzoazole is obtained in a polyphosphoric acid solution by performing a polymerization reaction using the polymerization stock solution described in 4 above.
6). A polyphosphorazole solution of polybenzoazole obtained by the method for producing polybenzoazole according to 5 above, wherein the number of gel-like foreign substances present in the solution is 0.06 to 0.12 mm in width and 5 cm in length. A polyphosphoric acid solution of polybenzoazole which is 10 or less in the solution sample stretched into a fibrous form.

  Since the generation of gel-like substances in the reaction solution can be suppressed in the preparation of the polybenzoazole raw material, it is expected to improve the productivity of the yarn when the polybenzoazole is spun.

The example of the method of obtaining the organic salt compound of said Formula (E)-(H) which is a component of the polymerization undiluted | stock solution of this invention is shown below.
First, 4,6-diamino-1,3-benzenediol, 2,5-diamino-1,4-benzenedithiol, 2,4-diamino-1,5-benzenedithiol, 1,2,4,5-tetra Aminobenzene, 3,3 ′, 4,4′-biphenyltetramine, 3,3 ′, 4,4′-tetraaminodiphenyl oxide, 2,3,5,6-tetraaminopyridine, 2,3,5,6 -Aromatic amine derivatives represented by the above formulas (A) and (B) such as tetraaminopyrazine, 2,3,4,5-tetraaminothiophene, 2,3,4,5-tetraaminofuran, and hydrochlorides thereof At least one selected from the group selected from the group consisting of water degassed with an inert gas such as nitrogen and helium or an aqueous solution of strong acid such as hydrochloric acid, and the aromatic amine derivative hydrochloride or aromatic amine derivative Use aqueous solution. At this time, in order to suppress the decomposition of the aromatic amine derivative, a compound having a reducing action may be added to the aromatic amine derivative hydrochloride aqueous solution. Examples of such compounds include metal salts such as tin (II), iron (II), and copper (I), and phosphorus and sulfur compounds such as phosphonic acid and sulfurous acid. Is preferred.

In addition, at least one selected from the group selected from the aromatic dicarboxylic acid derivatives (including aromatic dicarboxylic acid itself) of the formulas (C) and (D) is an alkali metal such as sodium hydroxide or potassium hydroxide. It is preferable to deaerate this aqueous solution by dissolving it in an aqueous solution containing a hydroxide or water to obtain an aqueous solution of an alkali metal salt of an aromatic dicarboxylic acid. Next, by mixing the aromatic amine derivative hydrochloride aqueous solution and the aromatic dicarboxylic acid alkali metal salt aqueous solution, a salt exchange reaction takes place, and the above-mentioned formulas (E) to (E) comprising aromatic amine derivative / aromatic dicarboxylic acid The organic salt compound of H) is formed as a white precipitate, and alkali metal halides such as sodium chloride and potassium chloride are by-produced.
The mixing temperature is at least 70 ° C. or more, more preferably 80 ° C. or more, and particularly preferably 90 ° C. or more.

As is clear from the above description, the tetravalent aromatic group Ar ¹ in the formulas (A), (B), (E), (F), (G), and (H) is a pyridine ring or the like. The heteroaromatic group is also included. In addition, the tetravalent aromatic group Ar ¹ preferably has 5 to 12 carbon atoms, and more preferably 6 to 10 carbon atoms. In the formulas (A), (B), (E), (F), (G), and (H), X is preferably an oxygen atom or NH, X is an oxygen atom or NH, and Ar ¹ is more preferably a tetravalent aromatic group having 5 to 12 carbon atoms, X is more preferably an oxygen atom or NH, and Ar ¹ is a tetravalent aromatic group having 6 to 10 carbon atoms. .

Further, in the formulas (D), (F), and (H), Y is preferably CH. In formulas (F) and (H), Y is CH and X is an oxygen atom or NH. And Ar ¹ is more preferably a tetravalent aromatic group having 5 to 12 carbon atoms, Y is CH, X is an oxygen atom or NH, and Ar ¹ is a tetravalent aromatic group having 6 to 10 carbon atoms. A group is more preferable.

  In addition, any one of an aqueous solution of one or more aromatic amine derivatives selected from the above formulas (A) and (B) and a concentration of one or more aromatic dicarboxylic acid derivatives selected from the above formulas (C) and (D) 0.2 mol / L or more is preferable, 0.3 mol / L or more is more preferable, and 0.4 mol / L or more is particularly preferable.

  The polybenzoazole polymerization stock solution is a total of the organic salt compounds of the above formulas (E) to (H) with respect to polyphosphoric acid (in the case of a polymerization stock solution containing only one kind of the organic salt compound, the concentration of the component) is 5 to 40. It is prepared by dispersing and mass-treating 10% by mass, more preferably 10 to 25% by mass, and particularly preferably 10 to 20% by mass using a high-speed stirrer under reduced pressure or under an inert atmosphere.

  When the total concentration of the organic salt compounds of the formulas (E) to (H) with respect to polyphosphoric acid is less than 5% by mass, a sufficient polymerization rate cannot be obtained during the reaction, and when it is more than 40% by mass, mixing becomes difficult. It is not preferable because it is difficult to obtain a uniform polymerization stock solution.

In order to obtain a practically useful degree of polymerization, when preparing a polymerization stock solution in which an aromatic amine derivative and an aromatic carboxylic acid are dispersed in polyphosphoric acid, the number of moles of each monomer is represented by the following formulas (2) and (3).
0.8 ≦ (a + b) / (c + d) ≦ 1.2 (2)
0.1 ≦ c / d ≦ 10.0 (3)
(A is an aromatic amine derivative represented by the formula (A), b is an aromatic amine derivative represented by the formula (B), c is an aromatic dicarboxylic acid derivative represented by the formula (C), d is the number of moles charged for the aromatic dicarboxylic acid derivative represented by the formula (D).
Are preferably satisfied simultaneously.

  When (a + b) / (c + d) is smaller than 0.8 or larger than 1.2, it may be difficult to obtain a polymer having a sufficient degree of polymerization. The lower limit of (a + b) / (c + d) is preferably 0.9 or more, more preferably 0.93 or more, and still more preferably 0.95 or more. Moreover, as an upper limit of (a + b) / (c + d), 1.1 or less is preferable, More preferably, it is 1.07 or less, More preferably, it is 1.05 or less. Therefore, the optimum range of (a + b) / (c + d) in the present invention can be 0.95 ≦ (a + b) / (c + d) ≦ 1.05.

  When c / d is smaller than 0.1 or larger than 10.0, a predetermined effect cannot be obtained. The lower limit of c / d is preferably 0.11 or more, more preferably 0.125 or more, and still more preferably 0.15 or more. Moreover, as an upper limit of c / d, 9.0 or less is preferable, More preferably, it is 8.0 or less, More preferably, it is 7.0 or less. Therefore, it can be said that the optimum range of g / h in the present invention is 0.15 ≦ g / h ≦ 7.0.

(A) and (B) may be used alone or in combination, and the molar ratio of (A) :( B) can be appropriately selected at an arbitrary ratio of 0: 100 to 100: 0.
In order to obtain a sufficiently high polymerization rate during the reaction, polyphosphoric acid having a P ₂ O ₅ concentration of 75% or more, more preferably 80% or more is used, but in order to increase the P ₂ O ₅ concentration, phosphorus pentoxide is used. An appropriate amount may be added. In this case, 5 to 40% by mass, more preferably 10 to 25% by mass, and particularly preferably 10 to 20% by mass of the aromatic amine and / or aromatic carboxylic acid with respect to the total amount of phosphorus pentoxide and polyphosphoric acid. Added.

Further, 0.1 to 3.0 mol%, preferably 0.1 to 3.0 mol%, based on one or more aromatic amine derivative compounds selected from the formulas (A) and (B), using a metal compound that does not inhibit the polymerization reaction as an antioxidant. May be added in an amount of 0.2 to 2.0 mol%. Specific examples of the metal compound include TiCl ₃ , CuCl, SnCl _{2 and the} like or hydrates thereof. In the present invention, SnCl ₂ or a hydrate thereof is preferable.

  When the organic salt compounds of the above formulas (E) to (H) are dispersed in polyphosphoric acid using a high-speed stirrer, the rotational speed of the high-speed stirrer is preferably 200 to 2500 rpm. The high-speed stirrer includes various high-performance stirrers such as ordinary batch-type stirrers. However, the rotating and revolving planetary mixers, uniaxial or biaxial mixers, uniaxial or biaxial kneaders, extrusion More preferably, a combination of at least one kind and several kinds of kneaders is more preferred.

  Among these, a non-axial planetary mixer is particularly preferable in that the residual amount of the kettle is small when the polymerization stock solution is transferred to the polymerization vessel in order to maintain the molar balance of the raw materials when the polymerization is performed later. When the organic salt compounds of the above formulas (E) to (H) are dispersed in polyphosphoric acid using a planetary mixer, the revolution speed is preferably 200 to 2000 rpm, more preferably 1000 to 2000 rpm, and rotation. The number of rotations is preferably 80 to 800 rpm, and more preferably 400 to 800 rpm.

  The dispersion treatment is preferably performed under reduced pressure or in an inert gas atmosphere. The reduced pressure condition is preferably 80 kPa (600 mmHg) or less, more preferably 13.3 kPa (100 mmHg) or less, and 6. It is further preferably 7 kPa (50 mmHg) or less, and particularly preferably 2.7 kPa (20 mmHg) or less. Examples of the inert gas include nitrogen, carbon dioxide, and rare gases such as argon, but nitrogen is most preferable in terms of cost.

  As a method for producing polybenzoazole using the aromatic diamine / aromatic dicarboxylate of the present invention, a method such as US Pat. No. 4,533,693 may be applied. That is, polyphosphoric acid serving as a dehydrating agent and a solvent is used as a polymerization solvent, and aromatic diamine / aromatic dicarboxylate is heated and mixed at 70 to 220 ° C. to cause polycondensation, and a polyphosphoric acid solution of polybenzoazole (Dope) is obtained. In the polycondensation, phosphoric anhydride is further added to enhance the dehydrating action of polyphosphoric acid.

In order to prevent decomposition and coloring of polybenzoazole, the reaction is desirably performed in a dry inert gas atmosphere.
The specific viscosity of the polybenzoazole thus produced is preferably in the range of 5.0 to 15 as measured at 25 ° C. with a methanesulfonic acid solution having a concentration of 0.03 g / 100 mL.

  Formation of gel particles in a polyphosphoric acid solution (dope) of polybenzoazole produced in this way and the number thereof were stretched into a fibrous form having a width of 0.06-0.12 mm and a length of 5 cm. Can be measured by visual observation with an optical microscope, and the number of gel-like foreign matters can be measured. A polyphosphoric acid solution of polybenzoazole in which the number of gel-like foreign matters in the sample is 10 or less is preferable because there are few troubles during production such as yarn breakage when it is subsequently subjected to a spinning process.

  The polyphosphoric acid solution (dope) of polybenzoazole obtained as described above is extruded from a spinning nozzle or die at a temperature of 150 to 220 ° C., extracted by washing with water, and dried to obtain high strength. It is molded into a fiber or film having a high elastic modulus and high heat resistance. At this time, in order to adjust the degree of polymerization suitable for processing, it is desirable to control the degree of polymerization by adding a terminal terminator or a method disclosed in JP-A-09-296041 as necessary.

EXAMPLES Hereinafter, although an Example and a comparative example demonstrate this invention further more concretely, this invention is not limited at all by these. In addition, each measured value in the following examples is a value obtained by the following method.
(1) The specific viscosity (η _inh ) is a value obtained from the following formula based on the relative viscosity (η _rel ) measured at 25 ° C. using methanesulfonic acid at a polymer concentration of 0.03 g / dL.
η _inh [dL / g] = (lnη _rel ) / C
(Η _rel is relative viscosity, C is concentration [g / dL])
(2) The confirmation of the gel-like particles during the polymerization reaction was performed by extending the dope into a fiber shape during the polymerization and cutting it to 5 cm, and visually measuring the number of gel-like particles between 5 cm with an optical microscope.

[Reference Example 1] (Synthesis and polymerization of monomer) (N-PBO)
7 parts by mass of 4,6-diamino-1,3-benzenediol dihydrochloride was dissolved in 33 parts by mass of water deaerated with nitrogen. 5.347 parts by mass of pyridinedicarboxylic acid was dissolved in 64 parts by mass of 1M aqueous sodium hydroxide solution and degassed with nitrogen. An aqueous solution of 4,6-diamino-1,3-benzenediol dihydrochloride is dropped into an aqueous solution of disodium pyridinedicarboxylic acid over 10 minutes, and 4,6-diamino-1,3-benzenediol / pyridinedicarboxylate is added. A white precipitate (hereinafter sometimes abbreviated as N-PBO) was formed. At this time, the reaction temperature was maintained at 90 ° C. The obtained salt was filtered, dispersed and mixed in 3000 parts by mass of water deaerated with nitrogen, and filtered again. This dispersion mixing and filtration operation was repeated three times.

[Reference Example 2] (Synthesis of monomer) (OH-PBO)
7 parts by mass of 4,6-diamino-1,3-benzenediol dihydrochloride was dissolved in 33 parts by mass of water deaerated with nitrogen. 6.180 parts by mass of 2,5-dihydroxyterephthalic acid was dissolved in 64 parts by mass of 1M aqueous sodium hydroxide solution and degassed with nitrogen. An aqueous solution of 4,6-diamino-1,3-benzenediol dihydrochloride is dropped into an aqueous solution of disodium salt of 2,5-dihydroxyterephthalate over 10 minutes, and 4,6-diamino-1,3-benzenediol / A white precipitate of 2,5-dihydroxyterephthalate (hereinafter sometimes abbreviated as OH-PBO) was formed. At this time, the reaction temperature was maintained at 90 ° C. The obtained salt was filtered, dispersed and mixed in 3000 parts by mass of water deaerated with nitrogen, and filtered again. This dispersion mixing and filtration operation was repeated three times.

[Example] The two salts obtained in Reference Examples 1 and 2 have a molar ratio of the following formula (4).
(OH-PBO) / (N-PBO) = 2 (4)
Then, 4.803 parts by mass of OH-PBO and 8.726 parts by mass of N-PBO were weighed and added to 43.3 parts by mass of polyphosphoric acid. In addition, 0.1 part by mass of tin (II) chloride dihydrate was added as an antioxidant for the aromatic amine. The polymer concentration in polyphosphoric acid was 14.56% by mass. These were mixed for 60 seconds at 1.33 kPa at a rotation speed of 800 rpm and a revolution speed of 2000 rpm with a non-axial planetary mixer (Shinky Co., Ltd. Awatori Nertaro (registered trademark)), and this was repeated three times to obtain a polymerization stock solution. Was prepared. The polymerization stock solution was transferred to a 100 mL flask reactor, 15 parts by mass of diphosphorus pentoxide was added, and polymerization was started. The polymerization is carried out by raising the temperature from 80 ° C. to 180 ° C. over 4 hours, performing the polymerization reaction with stirring at 180 ° C., sampling 19 hours after the start of the reaction, and forming a fiber having a width of 0.06-0.12 mm. The stretched dope was cut into a length of 5 cm, and the number of gel-like particles in the dope was measured with an optical microscope.

[Comparative Example] Monomer, polyphosphoric acid, tin (II) chloride dihydrate, and diphosphorus pentoxide were weighed in the same amount as in the examples, and simultaneously added to a 100 mL flask to initiate polymerization. Polymerization, sampling during polymerization, and measurement of the number of gel particles in the dope were performed in the same manner as in the examples.
Table 1 shows the specific viscosity of the polymer dope obtained and the number of gel particles during the polymerization time.

  From Table 1, it was found that the number of gel particles was reduced and the uniform dope was obtained when the pretreatment in which the monomer was mixed in the polyphosphoric acid before the polymerization was performed, compared with the case where the pretreatment was not performed. Further, it was found from the value of the specific viscosity that the polymerization reaction rate was increased and the reaction time was shortened.

Claims (6)

The following general formulas (A) and (B)

(X represents any of O, S, and NH, and Ar ¹ represents a tetravalent aromatic group having 4 to 20 carbon atoms)
At least one selected from the group consisting of an aromatic amine derivative represented by the formula (I) and a hydrochloride thereof, and the following formulas (C) and (D):

(R ¹ , R ¹ ′ R ² and R ² ′ each independently represent hydrogen or an alkali metal element, and Y represents N or CH.)
And at least one organic salt compound represented by the following formulas (E) to (H) is reacted with at least one aromatic dicarboxylic acid derivative represented by formula (E): In polyphosphoric acid having a P ₂ O ₅ concentration of 75% by mass or more, it is added so that the total concentration of the organic salt compounds of the following formulas (E) to (H) is 5 to 40% by mass, under reduced pressure or in an inert gas atmosphere A method for producing a polybenzoazole polymerization stock solution, characterized in that the dispersion treatment is performed using a high-speed stirring device.

(X represents any of O, S, and NH, and Ar ¹ represents a tetravalent aromatic group having 4 to 20 carbon atoms.)

(X represents any of O, S, and NH, Ar ¹ represents a tetravalent aromatic group having 4 to 20 carbon atoms, and Y represents N or CH.)

(X represents any of O, S, and NH, and Ar ¹ represents a tetravalent aromatic group having 4 to 20 carbon atoms.)

(X represents any of O, S, and NH, Ar ¹ represents a tetravalent aromatic group having 4 to 20 carbon atoms, and Y represents N or CH.)   The method for producing a polybenzoazole polymerization stock solution according to claim 1, wherein the number of rotations of the high-speed stirring device is 200 to 2500 rpm.   The method for producing a polybenzoazole polymerization stock solution according to claim 2, wherein the high-speed stirring device is a planetary mixer, and its revolution speed is 200 to 2000 rpm, and its rotation speed is 80 to 800 rpm. Obtained by the method according to any one of claims 1 to 3, at least one is, P ₂ O ₅ concentration of 75% or more polyphosphates of organic salt compound of formula according to claim 1, wherein (E) ~ (H) A polybenzoazole polymerization stock solution dispersed in an acid solvent at a concentration such that the total concentration of the organic salt compounds of the formulas (E) to (H) is 5 to 40% by mass.   A method for producing polybenzoazole, wherein a polymerization reaction is performed using the polymerization stock solution according to claim 4 to obtain polybenzoazole in a polyphosphoric acid solution.   It is a polyphosphoric acid solution of polybenzoazole obtained by the method for producing polybenzoazole according to claim 5, wherein the number of gel-like foreign matters present in the solution is 0.06 to 0.12 mm in width and 5 cm in length. A polyphosphoric acid solution of polybenzoazole which is 10 or less in the solution sample stretched into a fibrous form.