JP2007100022A - Method for tailoring polymer dope - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for tailoring a polymer dope that can be a useful stock solution in the case of forming a rigid polymer molded article excellent in heat resistance and mechanical properties, especially a fiber, a film, and pulp-like particles. <P>SOLUTION: The method for tailoring a polymer dope whose polymer concentration is at least 5 wt.% comprises mixing a polymer, whose main skeleton is a repeated unit represented by formula (I), wherein, X is selected from a 1-2C alkyl group, a 1-4C alkoxy group, a 1-5C carboalkoxy group, a halogen group, and a nitro group, k is an integer of 0-4, m is an integer of 1-3, Y is one selected from a 1-2C alkyl group, a 1-4C alkoxy group, a halogen group, a nitro group, and a hydroxy group, l is an integer of 0-4, and n is 1-3, with a concentrated sulfuric acid or a fuming sulfuric acid of not more than 30%, at a temperature not higher than the freezing point of sulfuric acid, under an ultrasonic treatment. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a novel method for adjusting a molding polymer dope that can be a molding stock solution that is useful in producing rigid polymer molded articles having excellent heat resistance and mechanical properties, particularly fibers, films, and pulp-like particles.

  Generally, rigid wholly aromatic polyamides such as polyparaphenylene terephthalamide and PPTA are molded from a concentrated sulfuric acid solution having a high concentration. Such high-concentration rigid wholly aromatic polyamide concentrated sulfuric acid solution has optical anisotropy (liquid crystallinity), so the polymer is highly oriented just by applying a high share during molding. It is possible to produce fibers, films and pulps with excellent heat resistance. However, it is known that it is difficult to obtain a uniform polymer dope because this highly concentrated polymer sulfuric acid solution has a very high viscosity. Therefore, a high-concentration polymer sulfuric acid solution is prepared using a freeze-mixing method in which concentrated sulfuric acid cooled to a solidification temperature or lower is mixed with a polymer, or a device such as a kneader or a biaxial ruder. (Patent Documents 1 and 2)

Japanese Patent Publication No.59-9643 US Pat. No. 5,882,563

  The main object of the present invention is to solve the problems of the prior art as described above, and to provide a molded body mainly composed of polyparaphenylene terephthalamide having excellent heat resistance and mechanical properties, particularly fibers, film pulp particles and the like. An object of the present invention is to provide a novel method for producing a polymer dope useful in production.

  As a result of intensive studies to achieve the above object, the inventors of the present invention mix a polymer having paraphenylene terephthalamide as a main skeleton with concentrated sulfuric acid under ultrasonic treatment at a temperature lower than the solidification temperature of concentrated sulfuric acid. Thus, it has been found that a polymer dope having excellent uniformity can be obtained, and the present invention has been derived.

That is, the present invention is as follows.
1. Formula (I)
(X is selected from alkyl groups having 1 to 2 carbon atoms, alkoxy groups having 1 to 4 carbon atoms, carboalkoxy groups having 1 to 5 carbon atoms, halogeno groups, and nitro groups, and k is an integer of 0 to 4) , M is an integer of 1 to 3, Y is selected from an alkyl group having 1 to 2 carbon atoms, an alkoxy group having 1 to 4 carbon atoms, a halogeno group, a nitro group, and a hydroxyl group, and l is 0 to 4 And n is 1 to 3.)
A polymer concentration characterized by mixing a polymer having a repeating unit represented by the following formula with concentrated sulfuric acid or fuming sulfuric acid up to 30% at a temperature not higher than the solidification temperature of sulfuric acid while sonicating. The adjustment method of the polymer dope which is weight% or more.
2. The method for preparing a polymer dope according to claim 1, wherein the polymer has an intrinsic viscosity of at least 1.0.
3. The method for adjusting a polymer dope according to claim 1 or 2, wherein the concentration of concentrated sulfuric acid is 98% by weight or more.
4). The method for adjusting a polymer dope according to any one of claims 1 to 3, wherein the polymer dope exhibits optical anisotropy or flow birefringence.

  The production method of the present invention can efficiently obtain a high-concentration sulfuric acid solution of a polymer mainly composed of polyparaphenylene terephthalamide as a main skeleton, and has excellent mechanical properties with molecular orientation just by molding. Things can be obtained. In particular, fibers spun from the dope of the present invention are widely used in the fields of heat-resistant fibers, high-strength and elastic fibers such as ropes, belts, insulating cloths, thermosetting or thermoplastic resin reinforcements, and protective clothing. can do.

In the production method of the present invention, the structural unit is substantially the following formula (I)
(X is selected from alkyl groups having 1 to 2 carbon atoms, alkoxy groups having 1 to 4 carbon atoms, carboalkoxy groups having 1 to 5 carbon atoms, halogeno groups, and nitro groups, and k is an integer of 0 to 4) , M is an integer of 1 to 3, Y is selected from hydrogen, an alkyl group having 1 to 2 carbon atoms, an alkoxy group having 1 to 4 carbon atoms, a halogeno group, a nitro group, and a hydroxyl group, and l is 0 An integer of -4, n is 1-3.)
It is characterized in that a polymer consisting of the above and concentrated sulfuric acid or fuming sulfuric acid up to 30% or less are mixed under ultrasonic treatment at a temperature below the solidification temperature of sulfuric acid. The concentration of the polymer in the dope obtained by this production method is 5% by weight or more, more preferably 10 to 30% by weight.

  The polymer comprising the repeating unit of the formula (I) can be obtained by solution polymerization using (a) an aromatic diamine and (b) an aromatic dicarboxylic acid chloride.

(A) The aromatic diamine is a so-called rigid aromatic diamine having a chain extension bond extending coaxially,
(Y is selected from an alkyl group having 1 to 2 carbon atoms, an alkoxy group having 1 to 4 carbon atoms, a halogeno group, a nitro group, and a hydroxyl group, l is an integer of 0 to 4, and n is 1 to 3. .)
It is at least 1 sort (s) of the aromatic diamine represented by these. These diamines may be polymerized alone or as a mixture of two or more. P-phenylenediamine, 4,4′-benzidinediamine, or derivatives thereof are preferable, among which p-phenylenediamine, 2,5-dihydroxy-p-phenylenediamine, 4,4′-benzidinediamine, 3,3 '-Dihydroxy-4,4'-benzidinediamine is preferred.

  In addition, the following diamine can also be copolymerized in order to improve the property of the polymer obtained. Specific examples of the diamine include m-phenylenediamine, 1,4-diaminonaphthalene, 1,5-diaminonaphthalene, 1,8-diaminonaphthalene, 2,6-diaminonaphthalene, 2,7-diaminonaphthalene, 2,6- Diaminoanthracene, 2,7-diaminoanthracene, 1,8-diaminoanthracene, 2,4-diaminotoluene, 2,5-diamino (m-xylene), 2,5-diaminopyridine, 2,6-diaminopyridine, 3 , 5-diaminopyridine, 2,4-diaminotoluenebenzidine, 3,3'-diaminobiphenyl, 3,3'-dichlorobenzidine, 3,3'-dimethylbenzidine, 3,3'-dimethoxybenzidine, 2,2 ' -Diaminobenzophenone, 4,4'-diaminobenzophenone, 3,3'-diaminodiphene Ether, 3,4′-diaminodiphenyl ether, 4,4′-diaminodiphenyl ether, 3,3′-diaminodiphenylmethane, 4,4′-diaminodiphenylmethane, 3,3′-diaminodiphenylsulfone, 4,4′-diaminodiphenyl Sulfone, 3,3′-diaminodiphenyl sulfide, 4,4′-diaminodiphenyl sulfide, 4,4′-diaminodiphenyl thioether, 4,4′-diamino-3,3 ′, 5,5′-tetramethyldiphenyl ether, 4,4′-diamino-3,3 ′, 5,5′-tetraethyldiphenyl ether, 4,4′-diamino-3,3 ′, 5,5′-tetramethyldiphenylmethane, 1,3-bis (3-amino Phenoxy) benzene, 1,3-bis (4-aminophenoxy) benzene, , 4-bis (3-aminophenoxy) benzene, 1,4-bis (4-aminophenoxy) benzene, 2,6-bis (3-aminophenoxy) pyridine, 1,4-bis (3-aminophenylsulfonyl) Benzene, 1,4-bis (4-aminophenylsulfonyl) benzene, 1,4-bis (3-aminophenylthioether) benzene, 1,4-bis (4-aminophenylthioether) benzene, 4,4′-bis (3-aminophenoxy) diphenylsulfone, 4,4′-bis (4-aminophenoxy) diphenylsulfone, bis (4-aminophenyl) amine bis (4-aminophenyl) -N-methylamine bis (4-aminophenyl) -N-phenylamine bis (4-aminophenyl) phosphine oxide, 1,1-bis (3-aminophenyl) Enyl) ethane, 1,1-bis (4-aminophenyl) ethane, 2,2-bis (3-aminophenyl) propane, 2,2-bis (4-aminophenyl) propane, 2,2-bis (4 -Amino-3,5-dimethylphenyl) propane, 4,4'-bis (4-aminophenoxy) biphenyl, bis [4- (3-aminophenoxy) phenyl] sulfone, bis [4- (4-aminophenoxy) Phenyl] sulfone, bis [4- (4-aminophenoxy) phenyl] ether, bis [4- (4-aminophenoxy) phenyl] methane, bis [3-methyl-4- (4-aminophenoxy) phenyl] methane, Bis [3-chloro-4- (4-aminophenoxy) phenyl] methane, bis [3,5-dimethyl-4- (4-aminophenoxy) phenyl] meta 1,1-bis [4- (4-aminophenoxy) phenyl] ethane, 1,1-bis [3-methyl-4- (4-aminophenoxy) phenyl] ethane, 1,1-bis [3-chloro -4- (4-aminophenoxy) phenyl] ethane, 1,1-bis [3,5-dimethyl-4- (4-aminophenoxy) phenyl] ethane, 2,2-bis [4- (4-aminophenoxy) ) Phenyl] propane, 2,2-bis [3-methyl-4- (4-aminophenoxy) phenyl] propane, 2,2-bis [3-chloro-4- (4-aminophenoxy) phenyl] propane, 2 , 2-bis [3,5-dimethyl-4- (4-aminophenoxy) phenyl] propane, 2,2-bis [4- (4-aminophenoxy) phenyl] butane, 2,2-bis [3-methyl -4- 4-aminophenoxy) phenyl] butane, 2,2-bis [3,5-dimethyl-4- (4-aminophenoxy) phenyl] butane, 2,2-bis [3,5-dibromo-4- (4- Aminophenoxy) phenyl] butane, 1,1,1,3,3,3-hexafluoro-2,2-bis (4-aminophenyl) propane, 1,1,1,3,3,3-hexafluoro- Examples include 2,2-bis [3-methyl-4- (4-aminophenoxy) phenyl] propane.

On the other hand, as the (b) aromatic dicarboxylic acid chloride, the following formula:
(X is an alkyl group having 1 to 2 carbon atoms, an alkoxy group having 1 to 4 carbon atoms, a carboalkoxy group having 1 to 5 carbon atoms, a halogeno group, or a nitro group, and k is an integer of 0 to 4, m is an integer of 1 to 3)
It is at least 1 sort (s) of the aromatic dicarboxylic acid chloride represented by these. These dicarboxylic acid chlorides may be polymerized alone or as a mixture of two or more. Preferably terephthalic acid dichloride, 4,4′-dibenzoyl chloride, 1,5- or 2,6-naphthylene dicarboxylic acid chloride, 2,5-pyridylene dicarboxylic acid chloride, 4,8-quinoline dicarboxylic acid chloride, 4 4,4'-stilbene dicarboxylic acid chloride, 4,4'-asoxybenzene dicarboxylic acid chloride and derivatives thereof. Among these, terephthalic acid dichloride and 2,5-dialkoxycarbonyl terephthalic acid dichloride are preferable.

  The solvent used for carrying out the polymerization is not particularly limited, but dissolves the raw material monomers (a) and (b) as described above and is substantially nonreactive with them, and preferably has an intrinsic viscosity of at least 1 Any solvent can be used as long as it is possible to obtain a polymer of 0.0 or more, more preferably 1.2 or more. For example, N, N, N ′, N′-tetramethylurea (TMU), N, N-dimethylacetamide (DMAC), N, N-diethylacetamide (DEAC), N, N-dimethylpropionamide (DMPR), N, N-dimethylbutyramide (NMBA), N, N-dimethylisobutyramide (NMIB), N-methylpyrrolidone-2 (NMP), N-ethylpyrrolidone-2 (NEP), N-methylcaprolactam (NMC), N, N-dimethylmethoxyacetamide, N-acetylpyrrolidine (NAPR), N-acetylpiperidine, N-methylpiperidone-2 (NMPD), N, N'-dimethylethyleneurea, N, N'-dimethylpropyleneurea, N, Amido solvents such as N, N ', N'-tetramethylmalonamide, N-acetylpyrrolidone, phenols such as p-chlorophenol, phenol, m-cresol, p-cresol, 2,4-dichlorophenol It can be mentioned system solvent or a mixture thereof.

In this case, in order to increase the solubility, an appropriate amount of a known inorganic salt may be added before, during or at the end of polymerization. Examples of such inorganic salts include lithium chloride and calcium chloride.
The polymer is produced in the same manner as in the usual solution polymerization method of polyamide in the above-mentioned solvent in which the monomers (a) and (b) are dehydrated. The reaction temperature at this time is 80 ° C. or less, preferably 60 ° C. or less. The concentration at this time is preferably about 1 to 20% by weight as the monomer concentration.

In the present invention, it is also possible to use trialkylsilyl chloride for the purpose of increasing the degree of polymerization of the polymer.
Further, in the reaction of acid chloride and diamine that are generally used, aliphatic or aromatic amines and quaternary ammonium salts can be used in combination in order to capture an acid such as hydrogen chloride.

  Here, the obtained polymer does not dissolve in the polymerization solvent at a high concentration (generally, about several percent), so that a molding polymer dope exhibiting the desired optical anisotropy or flow birefringence is obtained. After the polymerization, the polymer is preferably isolated and dissolved in concentrated sulfuric acid or fuming sulfuric acid having a concentration of 30% or less, preferably concentrated sulfuric acid having a concentration of 98% by weight or more or fuming sulfuric acid having a concentration of 30% or less. In order for the dope to exhibit optical anisotropy or flow birefringence, it is necessary that the polymer is dissolved at a high concentration, as described above, 5% by weight or more, preferably 10% by weight or more. 12% by weight or more is more preferable.

Here, the optical anisotropy is a state in which, for example, optical anisotropy is observed under crossed Nicols with a microscope between two glass plates.
Here, the flow birefringence is simply confirmed by changing from dark field to bright field when dope is sandwiched between two glass plates placed between crossed polarizing plates and some shear deformation is applied. it can. Further, it can be confirmed by a bright field in a stationary state after shear deformation.

In the present invention, methods for preparing a high concentration polymer sulfuric acid solution include 1) a method of adding sulfuric acid to the isolated polymer powder and mixing, and 2) a method of adding and mixing the isolated polymer to sulfuric acid. Although it is mentioned, it is not limited to these.
The mixing temperature is not higher than the temperature at which sulfuric acid solidifies, and is preferably −5 ° C. or lower. The melting point of sulfuric acid is 98% by weight and about 3 ° C, and 100% is about 10.49 ° C. When the mixing temperature is equal to or higher than the temperature at which sulfuric acid solidifies, the polymer and sulfuric acid form a massive mixture at the initial stage of mixing, which makes it difficult to achieve uniform mixing.

  In the present invention, when adjusting a polymer dope by mixing a polymer and sulfuric acid, it is possible to efficiently adjust a uniform high-concentration polymer sulfate dope by performing the irradiation under ultrasonic irradiation. The method of ultrasonic irradiation is not particularly limited, but for example, a rigid wholly aromatic polyamide powder and sulfuric acid are charged into a three-necked flask equipped with a stirring blade and a nitrogen introduction tube, and cooled to below the solidification temperature of sulfuric acid. A uniform polymer dope can be prepared by a method in which stirring is performed in a state of being attached to a sonic cleaning bath. By stirring under ultrasonic treatment, it becomes possible to prevent the polymer dope from being agglomerated and to prepare polymer granules having a uniform sulfuric acid concentration.

  The polymer dope obtained from the present invention is excellent in moldability and can be formed into fibers, films, pulp-like particles and the like by a wet method or a dry jet wet method.

Examples Hereinafter, the present invention will be described more specifically with reference to examples. However, the present invention is not limited to the description of these examples. In the examples, the intrinsic viscosity (ηinh) is a value measured at 30 ° C. using a concentrated sulfuric acid at a polymer concentration of 0.5 g / dl.
As an ultrasonic bath, a three-frequency ultrasonic cleaner (manufactured by ASONE, 100 W, oscillation frequency 28 Hz) was used.

[Example 1]
11.5 wt% of calcium chloride dehydrated and dried at 250 ° C. was dissolved in N-methylpyrrolidone (NMP), and 8.5044 g of paraphenylenediamine was dissolved in 200 ml of the above solvent in a dry nitrogen stream. This amine solution was kept at −10 ° C. by external cooling, and 5.8648 g of terephthalic acid chloride was added, and the polymerization reaction was allowed to proceed for 30 minutes. After completion of the reaction, the polymer was deposited by pouring into a large amount of ion-exchanged water. The obtained polymer was separated by filtration, further washed with ethanol and acetone, and then vacuum-dried. The ηinh measured with a concentrated sulfuric acid solution was 4.6.

  4.04 g of the above polymer was put into a three-necked flask equipped with a nitrogen introduction tube and a stirring blade, and 18.4 g of 100% concentrated sulfuric acid was added. Subsequently, after cooling to −20 ° C. to make concentrated sulfuric acid ice, stirring was performed for 8 hours in a state of being attached to an ultrasonic bath to prepare a granular 18 wt% polymer dope. When the obtained polymer dope was observed under a crossed Nicol with a microscope, optical anisotropy was observed at 60 ° C. under standing.

[Example 2]
200 g of pyromellitic anhydride (hereinafter sometimes referred to as PMDA) and 600 ml of dehydrated ethanol were mixed and refluxed to completely dissolve PMDA, and then 300 ml of ethanol was distilled off under reduced pressure. After cooling the resulting reaction product, the precipitate was filtered off and washed several times with ethyl acetate to obtain 2,5-dicarbomethoxyterephthalic acid. The obtained 2,5-dicarbomethoxyterephthalic acid (70 g) was dispersed in ethyl acetate (500 ml), and then reacted until oxalyl chloride (65 g) was added and completely dissolved. After removing the solvent by concentration under reduced pressure, the acid chloride obtained by recrystallization with hexane was confirmed to be 2,5-dicarbomethoxyterephthalic acid chloride as a result of NMR and infrared analysis. Lithium chloride dehydrated and dried at 250 ° C. was dissolved in NMP at 3 wt%, and 1.4852 g of paraphenylenediamine was dissolved in 100 ml of the above solvent in a dry nitrogen stream. The amine solution was kept at −10 ° C. by external cooling, and trimethylsilyl chloride (1.8 ml) was added. Further, 2.3838 g of the above-mentioned 2,5-dicarbomethoxyterephthalic acid chloride and 1.3941 g of terephthalic acid chloride were added, and the polymerization reaction was allowed to proceed for 1 hour. Further, stirring was continued at room temperature for 2 hours to complete the polymerization reaction. After completion of the reaction, the polymer was deposited by pouring into a large amount of ion-exchanged water. The obtained polymer was separated by filtration, further washed with ethanol and acetone, and then vacuum-dried. The ηinh measured with a concentrated sulfuric acid solution was 4.8.

  3.25 g of the above polymer was put into a three-necked flask equipped with a nitrogen introduction tube and a stirring blade, and 18.4 g of 100% concentrated sulfuric acid was added. Subsequently, after cooling to −20 ° C. to make concentrated sulfuric acid ice, stirring was performed for 8 hours in a state of being attached to an ultrasonic bath to prepare a granular 15 wt% polymer dope. When the obtained polymer dope was observed under a crossed Nicol with a microscope, optical anisotropy was observed at 20 ° C. under standing.

[Example 3]
Lithium chloride dehydrated and dried at 250 ° C. was dissolved in N-methylpyrrolidone (NMP) at 3 wt%, and 1.7607 g of paraphenylenediamine was dissolved in 100 ml of the above solvent in a dry nitrogen stream. This amine solution was kept at −10 ° C. by external cooling, and trimethylsilyl chloride (1.85 ml) was added. Further, 1.6955 g of the above-mentioned 2,5-dicarbomethoxyterephthalic acid chloride and 1.9832 g of terephthalic acid chloride were added, and the polymerization reaction was allowed to proceed for 1 hour. Further, stirring was continued at room temperature for 2 hours to complete the polymerization reaction. After completion of the reaction, the polymer was deposited by pouring into a large amount of ion-exchanged water. The obtained polymer was separated by filtration, further washed with ethanol and acetone, and then vacuum-dried. The ηinh measured with a concentrated sulfuric acid solution was 4.4.

  3.25 g of the above polymer was put into a three-necked flask equipped with a nitrogen introduction tube and a stirring blade, and 18.4 g of 100% concentrated sulfuric acid was added. Subsequently, after cooling to −20 ° C. to make concentrated sulfuric acid ice, stirring was performed for 8 hours in a state of being attached to an ultrasonic bath to prepare a granular 15 wt% polymer dope. When the obtained polymer dope was observed under a crossed Nicol with a microscope, optical anisotropy was observed at 40 ° C. under standing.

[Example 4]
11.5 wt% of calcium chloride dehydrated and dried at 250 ° C. was dissolved in N-methylpyrrolidone (NMP), and 4.0164 g of paraphenylenediamine was dissolved in 100 ml of the above solvent in a dry nitrogen stream. This amine solution was kept at −10 ° C. by external cooling, 1.9339 g of 2,5-dicarbomethoxyterephthalic acid chloride and 6.4092 g of terephthalic acid chloride were added, and the polymerization reaction was allowed to proceed for 1 hour. After completion of the reaction, the polymer was deposited by pouring into a large amount of ion-exchanged water. The obtained polymer was separated by filtration, further washed with ethanol and acetone, and then vacuum-dried. The ηinh measured with a concentrated sulfuric acid solution was 3.8.

  4.04 g of the above polymer was put into a three-necked flask equipped with a nitrogen introduction tube and a stirring blade, and 18.4 g of 100% concentrated sulfuric acid was added. Subsequently, after cooling to −20 ° C. to make concentrated sulfuric acid ice, stirring was performed for 8 hours in a state of being attached to an ultrasonic bath to prepare a granular 18 wt% polymer dope. When the obtained polymer dope was observed under a crossed Nicol with a microscope, optical anisotropy was observed at 50 ° C. under standing.

[Comparative Example 1]
A dope composed of concentrated sulfuric acid and a polymer was prepared in the same manner as in Example 1 except that no ultrasonic treatment was performed. As a result, a lump that was difficult to uniformly stir was generated during stirring, and it was difficult to adhere to the wall of the flask to obtain a uniform dope. When the obtained solution was observed with a microscope under a crossed Nicol at 60 ° C., many undissolved polymer lumps were observed.

[Comparative Example 2]
A dope composed of concentrated sulfuric acid and a polymer was prepared in the same manner as in Example 2 except that ultrasonic treatment was not performed. As a result, a lump that was difficult to uniformly stir was generated during stirring, and it was difficult to adhere to the wall of the flask to obtain a uniform dope. When the obtained solution was observed under a crossed Nicol at 20 ° C. with a microscope, many undissolved polymer lumps were observed.

[Comparative Example 3]
A dope composed of concentrated sulfuric acid and a polymer was prepared in the same manner as in Example 3 except that ultrasonic treatment was not performed. As a result, a lump that was difficult to uniformly stir was generated during stirring, and it was difficult to adhere to the wall of the flask to obtain a uniform dope. When the obtained solution was observed under a crossed Nicol at 40 ° C. with a microscope, many undissolved polymer lumps were observed.

[Comparative Example 4]
A dope composed of concentrated sulfuric acid and a polymer was prepared in the same manner as in Example 4 except that ultrasonic treatment was not performed. As a result, a lump that was difficult to uniformly stir was generated during stirring, and it was difficult to adhere to the wall of the flask to obtain a uniform dope. When the obtained solution was observed under a crossed Nicol at 50 ° C. with a microscope, many undissolved polymer lumps were observed.

Claims (4)

Formula (I)
(X is selected from alkyl groups having 1 to 2 carbon atoms, alkoxy groups having 1 to 4 carbon atoms, carboalkoxy groups having 1 to 5 carbon atoms, halogeno groups, and nitro groups, and k is an integer of 0 to 4) , M is an integer of 1 to 3, Y is selected from an alkyl group having 1 to 2 carbon atoms, an alkoxy group having 1 to 4 carbon atoms, a halogeno group, a nitro group, and a hydroxyl group, and l is 0 to 4 And n is 1 to 3.)
A polymer concentration characterized by mixing a polymer having a repeating unit represented by the following formula with concentrated sulfuric acid or fuming sulfuric acid up to 30% at a temperature not higher than the solidification temperature of sulfuric acid while sonicating. The adjustment method of the polymer dope which is weight% or more.   The method for preparing a polymer dope according to claim 1, wherein the polymer has an intrinsic viscosity of at least 1.0.   The method for adjusting a polymer dope according to claim 1 or 2, wherein the concentration of concentrated sulfuric acid is 98% by weight or more.   The method for adjusting a polymer dope according to any one of claims 1 to 3, wherein the polymer dope exhibits optical anisotropy or flow birefringence.