JP2006257125A - Optically anisotropic dope - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To obtain a molding dope showing optical anisotropy which can be a stock solution for molding useful for manufacturing polyimide-amide moldings, particularly fibers, films and pulp-like particles excellent in heat resistance and mechanical properties. <P>SOLUTION: The molding dope comprises a copolymer having a repeating unit represented by formula (I) and a solvent. In the formula, R<SB>1</SB>is each independently selected from a 1-18C aliphatic hydrocarbon residue, a hydrocarbon residue containing a 6-18C aromatic ring or a derivative thereof, and a hydrocarbon residue containing a 6-18C alicyclic ring or a derivative thereof; n denotes 1-3; R<SB>2</SB>denotes a nonreactive functional group; and m is 0-4. The concentration of the copolymer is 10 wt% or more. The molding dope shows optical anisotropy. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a polyimide amide molded article having excellent heat resistance and mechanical properties, particularly to a novel molding dope exhibiting optical anisotropy that can be used as a molding stock solution useful for producing fibers, films, and pulp-like particles. .

  Conventionally, it is known that polyimide is useful as a raw material for fibers, films, and other molded articles having excellent heat resistance, mechanical characteristics, electrical characteristics, weather resistance, and the like. For example, a film having excellent heat resistance can be obtained from a polyimide produced from 4,4′-diamine diphenyl ether and pyromellitic dianhydride, and is widely used for electrical insulation. In the field of heat-resistant fibers and films, aramid fibers, synthetic paper, polyimide films, etc. are used. However, with the advancement of advanced materials for space and aircraft applications, higher heat resistance and higher In recent years, those having mechanical properties such as high strength and high modulus have been demanded.

  Also in the field of heat-resistant fibers, recently, polyimide fibers having a relatively rigid skeleton have been reported. A polyamic acid solution is spun into an aqueous solution of a monovalent, divalent or trivalent alcohol or a mixture thereof or a polar solvent, and the resulting gel fiber is stretched, dried, and heat-treated to provide flame resistance, high strength, and high modulus. (Patent Document 1). Also, a part of the polyamic acid is ring-closed to the polyimide to form a spinning dope with improved wet coagulation, and the filament obtained by similarly wet spinning is immersed in an acetic anhydride / pyridine system for imidization. And heat treatment after drying to obtain polyimide fibers having further excellent mechanical properties (Non-patent Document 1 and Patent Document 2). However, the fibers obtained by any of the methods have not reached a satisfactory level of mechanical properties as high-performance fibers. This is generally a polymer having a rigid skeleton, and when high mechanical properties are obtained by solution molding, the molding dope exhibits optical anisotropy as represented by the method for producing poly-p-phenyleneamide. However, in the case of a rigid skeleton polyimide, the polyamic acid dope for molding does not show flow birefringence or optical anisotropy, and the polyimide finally obtained is rigid. Even if it exists, it is because the polyamic acid which is the molding precursor has a skeleton in which a p-oriented material and an m-oriented material are mixed. Therefore, it is difficult to promote orientation during molding, and the resulting mechanical properties do not show satisfactory values. On the other hand, a method has been proposed in which a polyimide skeleton is made somewhat flexible, a solvent-soluble polyimide is obtained, and a high strength fiber is obtained by molding the polyimide (Patent Document 3). In this case, the skeleton is flexible. Therefore, high modulus cannot be achieved. In order to solve the above problem, a concentrated solution composed of a p-aligned polyamic acid ester and a strong acid such as concentrated sulfuric acid has been reported. However, a rigid polyimide which exhibits flow birefringence but has optical anisotropy has been reported. No dope has been obtained (Patent Document 4). On the other hand, copolymers of both are considered as polymers having both rigidity of polyimide and toughness of aromatic polyamide, and polyimide aramid dope having optical anisotropy has been reported, but polyamic acid ester and aromatic There has been no report on optically anisotropic dope of polyamide copolymerization.

Japanese Patent Publication No.57-37687 JP 59-157319 A JP-A-60-65112 JP-A-1-115932 Journal of Textile Society, 40, T-480 (1984)

  The main object of the present invention is to solve the problems of the prior art as described above, and to be useful for producing a polyamide-imide molded article excellent in heat resistance and mechanical properties, particularly fibers, film pulp-like particles and the like. An object of the present invention is to provide a molding dope, particularly, a polyamide-imide molding dope that exhibits unprecedented optical anisotropy and is highly easily oriented during molding.

  As a result of intensive studies to achieve the above object, the present inventors have obtained a dope for molding having optical anisotropy by copolymerizing a p-oriented polyamic acid ester with a p-oriented aromatic polyamide. And the present invention has been derived.

（R₁はそれぞれ独立に炭素数が１〜18の脂肪族炭化水素残基、炭素数が６〜18の芳香族環を含む炭化水素残基またはその誘導体、炭素数が６〜18の脂環族環を含む炭化水素残基またはその誘導体より選ばれ、ｎは１〜３、Ｒ_２は非反応性の官能基を表わし、ｍは０〜４である。）
で表される繰り返し単位、及び下記式（II）
-ＯＣ−Ａｒ_１−ＣＯ−ＮＨ−Ａｒ_２−ＮＨ− (II)
（上記式中、Ar₁及びAr₂は、同一又は相違なるパラ配向性の２価の芳香族残基である。又、これらの芳香族残基上の水素原子は、同一又は相違なる非反応性の官能基で置換されていても良い）
式で表される繰り返し単位からなり、上記式（I）および（II）の繰り返し単位の共重合モル比率（I）/（II）が１０/９０〜８０/２０の範囲にあるコポリマー、及び溶媒とからなり、ポリマー濃度が１０ｗｔ％以上であって、光学異方性を示すことを特徴とする成形用ドープ。
２． 前記コポリマーが少なくとも１．０の固有粘度を有していることを特徴とする上記記載の成型用ドープ。
３． 溶媒が硫酸またはメタンスルホン酸であることを特徴とする上記記載の成型用ドープ。 That is, the present invention is as follows.
1. Formula (I)

(R ₁ is independently an aliphatic hydrocarbon residue having 1 to 18 carbon atoms, a hydrocarbon residue containing an aromatic ring having 6 to 18 carbon atoms or a derivative thereof, or an alicyclic ring having 6 to 18 carbon atoms. Selected from hydrocarbon residues containing an aromatic ring or derivatives thereof, n is 1 to 3, R ₂ is a non-reactive functional group, and m is 0 to 4.)
A repeating unit represented by formula (II):
—OC—Ar ₁ —CO—NH—Ar ₂ —NH— (II)
(In the above formula, Ar ₁ and Ar ₂ are the same or different para-oriented divalent aromatic residues. In addition, hydrogen atoms on these aromatic residues are the same or different non-reacting. May be substituted with a functional group)
A copolymer comprising a repeating unit represented by the formula and having a copolymerization molar ratio (I) / (II) of the repeating units of the above formulas (I) and (II) in the range of 10/90 to 80/20, and a solvent A dope for molding characterized by comprising a polymer concentration of 10 wt% or more and exhibiting optical anisotropy.
2. The molding dope as described above, wherein the copolymer has an intrinsic viscosity of at least 1.0.
3. The dope for molding as described above, wherein the solvent is sulfuric acid or methanesulfonic acid.

  Although a polyimide amide molded article having excellent heat resistance and mechanical properties can be obtained from the dope of the present invention, a high elastic modulus heat-resistant molded article having molecular orientation can be obtained simply by molding. 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.

（R₁はそれぞれ独立に炭素数が１〜18の脂肪族炭化水素残基、炭素数が６〜18の芳香族環を含む炭化水素残基またはその誘導体、炭素数が６〜18の脂環族環を含む炭化水素残基またはその誘導体より選ばれ、ｎは１〜３、Ｒ_２は非反応性の官能基を表わし、ｍは０〜４である。）
で表される繰り返し単位、及び下記式（II）
-ＯＣ−Ａｒ_１−ＣＯ−ＮＨ−Ａｒ_２−ＮＨ− (II)
（上記式中、Ar₁及びAr₂は、同一又は相違なるパラ配向性の２価の芳香族残基である。又、これらの芳香族残基上の水素原子は、同一又は相違なる非反応性の官能基で置換されていても良い）
で表される繰り返し単位からなるコポリマーと溶媒とからなり、光学異方性を示す。ドープにおけるコポリマーの濃度は１０％以上であり、好ましくは１２〜３０％である。 The molding dope of the present invention has the following formula (I)

(R ₁ is independently an aliphatic hydrocarbon residue having 1 to 18 carbon atoms, a hydrocarbon residue containing an aromatic ring having 6 to 18 carbon atoms or a derivative thereof, or an alicyclic ring having 6 to 18 carbon atoms. Selected from hydrocarbon residues containing an aromatic ring or derivatives thereof, n is 1 to 3, R ₂ is a non-reactive functional group, and m is 0 to 4.)
A repeating unit represented by formula (II):
—OC—Ar ₁ —CO—NH—Ar ₂ —NH— (II)
(In the above formula, Ar ₁ and Ar ₂ are the same or different para-oriented divalent aromatic residues. In addition, hydrogen atoms on these aromatic residues are the same or different non-reacting. May be substituted with a functional group)
It consists of a copolymer consisting of repeating units represented by formula (II) and a solvent and exhibits optical anisotropy. The concentration of the copolymer in the dope is 10% or more, preferably 12 to 30%.

  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.

  The copolymerization molar ratio (I) / (II) of the repeating units of the above formulas (I) and (II) is 10/90 to 80/20, preferably 12/88 to 75/25.

（R₁は式（１）における定義と同じ）
とからなる混合酸成分とを用いて溶液重合を行い、ポリマーを溶液から単離した後、これを硫酸のような１０ｗｔ％以上の高濃度ポリマー溶液を形成しうる溶媒に溶解することにより製造される。 The copolymer comprising repeating units of the above formulas (I) and (II) comprises (a) an aromatic diamine, (b) an aromatic dicarboxylic acid chloride, and the following formula (c):

(R ₁ is the same as defined in formula (1))
It is produced by performing solution polymerization using a mixed acid component consisting of and isolating the polymer from the solution, and then dissolving the polymer in a solvent capable of forming a high concentration polymer solution of 10 wt% or more such as sulfuric acid. The

（ｎは１〜３、Ｒ_２は非反応性の官能基を表わし、ｍは０〜４である）
で表される芳香族ジアミンの少なくとも１種である。非反応性の官能基としては例えば炭素数１〜４の脂肪族炭化水素基、ハロゲン基、ニトロ基等が挙げられる。これらのジアミンは単独あるいは２種以上の混合物として重合してもかまわない。好ましくはｐ−フェニレンジアミン、４，４’−ベンジジンジアミン、または4,4″−ジアミノ−ｐ−ターフェニルであり、中でもｐ−フェニレンジアミンが好ましい。 The aromatic diamine used in the present invention is a so-called rigid aromatic diamine in which chain extension bonds extend coaxially, and has the following formula:

(N represents 1 to 3, R ₂ represents a non-reactive functional group, and m is 0 to 4)
It is at least 1 sort (s) of the aromatic diamine represented by these. Examples of the non-reactive functional group include an aliphatic hydrocarbon group having 1 to 4 carbon atoms, a halogen group, and a nitro group. These diamines may be polymerized alone or as a mixture of two or more. P-phenylenediamine, 4,4′-benzidinediamine, or 4,4 ″ -diamino-p-terphenyl is preferable, and p-phenylenediamine is particularly preferable.

  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 aromatic dicarboxylic acid chloride used in the present invention, the following formula ClOC-Ar ₁ -COCl:
(Ar ₁ is the same as defined in formula (II))
It is at least 1 sort (s) of the aromatic dicarboxylic acid chloride represented by these. 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 the like. Of these, terephthalic acid dichloride is preferred.

  Further, the above formula (c) can be produced using a known method. For example, (1) pyromellitic diester is synthesized by refluxing pyromellitic dianhydride with alcohol. As the alcohol used here, an aliphatic alcohol having 1 to 18 carbon atoms, an aromatic alcohol having 7 to 18 carbon atoms, or an alicyclic alcohol having 6 to 18 carbon atoms is used. To 12 aliphatic alcohols and alicyclic alcohols having 6 to 12 carbon atoms are preferred, and primary or secondary alcohols are particularly preferred. (2) Oxalyl chloride, thionyl chloride or the like is added to the pyromellitic acid diester thus obtained to make carboxylic acid chloride, and (c) can be obtained by recrystallization.

  The solvent used for the polymerization is not particularly limited, but dissolves the raw material monomers (a), (b), and (c) as described above, and is substantially nonreactive with them, preferably intrinsic. Any solvent can be used as long as it can obtain a polymer having a viscosity of at least 1.0 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), (b) and (c) are dehydrated. The reaction temperature at this time is 80 ° C. or less, preferably 60 ° C. or less. This is because an imidization reaction may occur if the temperature is too high. The concentration at this time is preferably about 1 to 20 wt% 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, since the obtained polymer does not dissolve in the polymerization solvent at a high concentration (generally, about several percent), in order to obtain a new molding dope exhibiting the desired optical anisotropy, after polymerization, The polymer is preferably isolated and dissolved in sulfuric acid or methanesulfonic acid, preferably concentrated sulfuric acid, methanesulfonic acid or fuming sulfuric acid having a concentration of 98 wt% or more. In order for the dope to exhibit optical anisotropy, it is necessary that the polymer is dissolved at a high concentration, and as described above, it is 10 wt% or more, and more preferably 12 wt% or more.

  By shaping the dope of the present invention, drying and heat treatment, it can be imidized, and a polyimide amide molded article having excellent heat resistance and mechanical properties can be obtained. The dope of the present invention is excellent in moldability, and can be formed into a fiber, a film, a pulp-like particle or 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.

[Example 1]
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. 3% by weight of lithium chloride dehydrated and dried at 250 ° C. was dissolved in N-methylpyrrolidone (hereinafter sometimes referred to as NMP), 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.

  When the polymer was dissolved in concentrated sulfuric acid at a concentration of 15 wt%, a very high viscosity solution was obtained. When the obtained solution was observed under a crossed Nicol with a microscope, optical anisotropy was observed under standing. The ηinh measured with a concentrated sulfuric acid solution was 4.8.

[Example 2]
3 wt% of lithium chloride dehydrated and dried at 250 ° C. was dissolved in N-methylpyrrolidone (NMP), 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.

  When the polymer was dissolved in concentrated sulfuric acid at a concentration of 15 wt%, a very high viscosity solution was obtained. When the obtained solution was observed under a crossed Nicol with a microscope, optical anisotropy was observed at 40 ° C. under standing. The ηinh measured with a concentrated sulfuric acid solution was 4.4.

[Example 3]
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.

  When the polymer was dissolved in concentrated sulfuric acid at a concentration of 15 wt%, a very high viscosity solution was obtained. When the obtained solution was observed under a crossed Nicol with a microscope, optical anisotropy was observed at 50 ° C. under standing. The ηinh measured with a concentrated sulfuric acid solution was 3.8.

Claims (3)

Formula (I)

(R ₁ is independently an aliphatic hydrocarbon residue having 1 to 18 carbon atoms, a hydrocarbon residue containing an aromatic ring having 6 to 18 carbon atoms or a derivative thereof, or an alicyclic ring having 6 to 18 carbon atoms. Selected from hydrocarbon residues containing an aromatic ring or derivatives thereof, n is 1 to 3, R ₂ is a non-reactive functional group, and m is 0 to 4.)
A repeating unit represented by formula (II):
—OC—Ar ₁ —CO—NH—Ar ₂ —NH— (II)
(In the above formula, Ar ₁ and Ar ₂ are the same or different para-oriented divalent aromatic residues. In addition, hydrogen atoms on these aromatic residues are the same or different non-reacting. May be substituted with a functional group)
A copolymer comprising a repeating unit represented by the formula and having a copolymerization molar ratio (I) / (II) of the repeating units of the above formulas (I) and (II) in the range of 10/90 to 80/20, and a solvent A dope for molding characterized by comprising a polymer concentration of 10 wt% or more and exhibiting optical anisotropy.   The molding dope according to claim 1, wherein the copolymer has an intrinsic viscosity of at least 1.0.   2. The molding dope according to claim 1, wherein the solvent is sulfuric acid or methanesulfonic acid.