JP2006160704A - Benzoxazole group-containing aromatic diamine and method for producing polyimide benzoxazole precursor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an aromatic diamine having benzoxazole structure giving a polyimide benzoxazole molded form of excellent mechanical properties, and to provide a method for producing a polyimide benzoxazole precursor enabling a high-molecular weight polyamic acid to be stably produced. <P>SOLUTION: The aromatic diamine containing a benzoxazole group is provided. The aqueous suspension of this aromatic diamine has a pH of 5.5 or higher, being assessed by the method described in the Specification. The method for producing a polyamic acid as the polyimide benzoxazole precursor comprises carrying out a reaction mainly between the above aromatic diamine and an aromatic tetracarboxylic anhydride, wherein the above aromatic diamine is essentially used. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an aromatic diamine having a benzoxazole structure, which is a raw material for producing polyimide benzoxazole, and a method for producing polyamic acid, which is a polyimide benzoxazole precursor. More specifically, the present invention relates to a production method capable of stably producing an aromatic diamine having a benzoxazole structure and a high molecular weight polyamic acid, from which a polyimide benzoxazole molded article having excellent mechanical properties can be obtained.

Polyimide benzoxazole is a polymer having an imide structure and a benzoxazole structure, and is expected as a polymer having higher heat resistance and elastic modulus than polyimide. Polyimide benzoxazole is disclosed as a polymerization method, a film, and molding into a fiber (see Patent Documents 1 to 5, Non-Patent Document 1, etc.).
U.S. Pat. No. 4,087,409 Japanese Patent Publication No. 45-8435 JP-A-6-56992 Japanese National Patent Publication No. 10-508059 Japanese National Patent Publication No. 11-504369 Appl. Polym. Sym. , No. 9, pp145 (1969)

When forming into a fiber, for example, a polyimide polyamic acid solution of polyimide benzoxazole is extruded from a spinneret and made into a fiber through a coagulation bath of NMP / water = 75/25, and a chemical ring-closing agent such as acetic anhydride or pyridine is added. After passing through the contained bath, drying and heat treatment can be applied to obtain polyimide benzoxazole fibers.
In the case of forming into a film, a polyimide benzoxazole precursor polyamic acid solution is cast on a support such as a polyester film, a glass plate or a SUS plate, spread thinly, and a self-supporting film from which the solvent is removed is produced. Then, it peels from a support body and can be heated to 200-400 degreeC, and can be set as a polyimide benzoxazole film.

  The properties of the molded product, particularly the mechanical properties, are greatly influenced by the molecular weight of polyimide benzoxazole, and a molecular weight of a certain level or more is indispensable for obtaining practical properties. For this purpose, the precursor polyamic acid also needs to have a high molecular weight. In general, the degree of polymerization of the polyamic acid is controlled by measuring the solution viscosity of the polyamic acid solution. Polyimide benzoxazole is presumed to have a rigid component in the diamine component, but as described in Patent Document 4, the degree of polymerization is higher than that of polyimide polyamic acid having the same molecular weight and other structures. The effect on

  A polyamic acid having a benzoxazole structure is produced by a reaction of an aromatic diamine having a benzoxazole structure and a tetracarboxylic dianhydride. An aromatic diamine having a benzoxazole structure is an aromatic diamine used for general-purpose polyimides. Compared with, the nucleophilicity of the amino group is low and the reactivity with the acid anhydride is about 300 times lower, so it takes a very long time to obtain a high molecular weight polyamic acid.

  In general, the degree of polymerization of the polyamic acid is controlled by measuring the solution viscosity of the polyamic acid solution. Polyimide benzoxazole is presumed to have a rigid component in the diamine component, but as described in Patent Document 4, the degree of polymerization is higher than that of polyimide polyamic acid having the same molecular weight and other structures. The effect on Therefore, in industrial production, it is very important that a polyamic acid having a specified molecular weight can be produced efficiently and stably, and that the molecular weight is strictly adjusted to a specific range.

On the other hand, an aromatic diamine having a benzoxazole structure is obtained by reacting an aromatic aldehyde with a hydroxyamine to form an aromatic aldehyde oxime, followed by halogenation to form an aromatic hydroxamoyl halide. A method for producing aminoallylaminoarazole by reacting with an aromatic amine having an amino group (see Patent Documents 6 and 7), a nitroallylcarbonyl compound with aminonitroariol or aminonitrothiol or triaminonitroarene A method for producing aminoallylaminoarazole through reduction and cyclization after reacting to dinitroanilide is disclosed (refer to Patent Document 8). From 4,4-dinitrophenol and 4-nitrobenzoyl chloride, 4 is disclosed. -Nito A method for producing aminoallylaminoarazole by synthesizing benzoic acid dinitrophenyl ester and then reducing the compound is disclosed (see Non-Patent Document 2 and Patent Document 9) and 2,4-diaminophenol A method for producing aminoallylaminoarazole by reacting dihydrochloride with 4-aminobenzoic acid in polyphosphoric acid is disclosed (see Non-patent Document 3 and Patent Document 10).
US Pat. No. 5,567,843 US Pat. No. 6,222,044 US Pat. No. 5,739,344 Chemische Berichte 32, 1431 (1899) Japanese Patent Publication No. 45-8435 Heterocyclic Chem. 6, 119 (1969) JP-A-6-56992

Also in the formation reaction of a polyamic acid having a benzoxazole structure, the purity of the starting material is important for obtaining a high molecular weight polymer, as in other polycondensation reactions. For example, in the production of polyamic acid as a general-purpose polyimide precursor, biphenyltetracarboxylic dianhydride having a total content of biphenyltricarboxylic acid and its anhydride of 0.2% by mass or less as biphenyltetracarboxylic dianhydride It is disclosed that it is necessary to use a thing (refer patent document 11).
JP 7-3000525 A

  In the production of polyamic acid having a benzoxazole structure based on these backgrounds, the present inventors also considered the purity of an aromatic diamine having a benzoxazole structure and tetracarboxylic dianhydride, and performed high performance liquid chromatography (HPLC ) The purity determined by the method has been 99% by mass or more. However, in spite of using such a high-purity raw material, it was encountered that the production rate of polyamic acid and the molecular weight of the resulting polyamic acid vary greatly depending on the lot of aromatic diamine having a benzoxazole structure. In the above-mentioned patent documents and non-patent documents, there is no disclosure regarding the quality of the aromatic diamine obtained with a stable production rate of polyamic acid and the molecular weight of the resulting polyamic acid.

  The present invention has been made against the background of the problems of the prior art, and a polyimide benzoate that can stably produce an aromatic diamine having a benzoxazole structure and a polyamic acid having a high molecular weight, from which a molded product of polyimide benzoxazole having excellent mechanical properties can be obtained. It is providing the manufacturing method of an oxazole precursor.

As a result of intensive studies to solve the above-mentioned problems, the present inventors have finally completed the present invention. That is, the present invention is an aromatic diamine containing a benzoxazole group whose pH of an aqueous suspension evaluated by the method described in the specification is 5.5 or more.
Further, in the method of producing a polyamic acid which is a polyimide benzoxazole precursor by reacting an aromatic diamine mainly containing a benzoxazole group and an aromatic tetracarboxylic anhydride, the aromatic diamine containing the benzoxazole group described above It is the manufacturing method of the polyamic acid which is a polyimide benzoxazole precursor characterized by using.

  By using the method for producing polyamic acid which is an aromatic diamine having a benzoxazole structure and a polyimide benzoxazole precursor of the present invention, there is an advantage that a high molecular weight polyimide benzoxazole molded product having excellent mechanical properties can be obtained. is there.

Specific examples of aromatic diamines having a benzoxazole structure that are particularly preferably used in the present invention include the following.

Among these, amino (aminophenyl) benzoxazole isomers are preferable from the viewpoint of easy synthesis. Here, “each isomer” refers to each isomer in which two amino groups of amino (aminophenyl) benzoxazole are determined according to the coordination position (eg, the above “formula 1” to “formula 4”). Each compound described in the above. These diamines may be used alone or in combination of two or more.
In the present invention, it is preferable to use 70 mol% or more of the aromatic diamine having the benzoxazole structure.

  In this invention, if it is 30 mol% or less of all the diamines, you may use together 1 type, or 2 or more types of diamines which do not have the benzoxazole structure illustrated below. For example, 4,4′-bis (3-aminophenoxy) biphenyl, bis [4- (3-aminophenoxy) phenyl] ketone, bis [4- (3-aminophenoxy) phenyl] sulfide, bis [4- (3-aminophenoxy) phenyl] sulfone, 2,2-bis [4- (3-aminophenoxy) phenyl] propane, 2,2-bis [4- (3-aminophenoxy) phenyl] -1,1,1 , 3,3,3-hexafluoropropane, m-phenylenediamine, o-phenylenediamine, p-phenylenediamine, m-aminobenzylamine, p-aminobenzylamine,

3,3'-diaminodiphenyl ether, 3,4'-diaminodiphenyl ether, 4,4'-diaminodiphenyl ether, 3,3'-diaminodiphenyl sulfide, 3,3'-diaminodiphenyl sulfoxide, 3,4'-diaminodiphenyl sulfoxide 4,4′-diaminodiphenyl sulfoxide, 3,3′-diaminodiphenyl sulfone, 3,4′-diaminodiphenyl sulfone, 4,4′-diaminodiphenyl sulfone, 3,3′-diaminobenzophenone, 3,4′- Diaminobenzophenone, 4,4′-diaminobenzophenone, 3,3′-diaminodiphenylmethane, 3,4′-diaminodiphenylmethane, 4,4′-diaminodiphenylmethane, bis [4- (4-aminophenoxy) phenyl] methane, 1 , 1-Bi [4- (4-aminophenoxy) phenyl] ethane, 1,2-bis [4- (4-aminophenoxy) phenyl] ethane, 1,1-bis [4- (4-aminophenoxy) phenyl] propane, 1 , 2-bis [4- (4-aminophenoxy) phenyl] propane, 1,3-bis [4- (4-aminophenoxy) phenyl] propane, 2,2-bis [4- (4-aminophenoxy) phenyl ]propane,

1,1-bis [4- (4-aminophenoxy) phenyl] butane, 1,3-bis [4- (4-aminophenoxy) phenyl] butane, 1,4-bis [4- (4-aminophenoxy) Phenyl] butane, 2,2-bis [4- (4-aminophenoxy) phenyl] butane, 2,3-bis [4- (4-aminophenoxy) phenyl] butane, 2- [4- (4-aminophenoxy) Phenyl] -2- [4- (4-aminophenoxy) -3-methylphenyl] propane, 2,2-bis [4- (4-aminophenoxy) -3-methylphenyl] propane, 2- [4- ( 4-aminophenoxy) phenyl] -2- [4- (4-aminophenoxy) -3,5-dimethylphenyl] propane, 2,2-bis [4- (4-aminophenoxy) -3,5-dimethylphen Le] propane, 2,2-bis [4- (4-aminophenoxy) phenyl] -1,1,1,3,3,3-hexafluoropropane,

1,4-bis (3-aminophenoxy) benzene, 1,3-bis (3-aminophenoxy) benzene, 1,4-bis (4-aminophenoxy) benzene, 4,4′-bis (4-aminophenoxy) ) Biphenyl, bis [4- (4-aminophenoxy) phenyl] ketone, bis [4- (4-aminophenoxy) phenyl] sulfide, bis [4- (4-aminophenoxy) phenyl] sulfoxide, bis [4- ( 4-aminophenoxy) phenyl] sulfone, bis [4- (3-aminophenoxy) phenyl] ether, bis [4- (4-aminophenoxy) phenyl] ether, 1,3-bis [4- (4-aminophenoxy) ) Benzoyl] benzene, 1,3-bis [4- (3-aminophenoxy) benzoyl] benzene, 1,4-bis [4- (3 Aminophenoxy) benzoyl] benzene, 4,4′-bis [(3-aminophenoxy) benzoyl] benzene, 1,1-bis [4- (3-aminophenoxy) phenyl] propane, 1,3-bis [4- (3-aminophenoxy) phenyl] propane, 3,4'-diaminodiphenyl sulfide,

2,2-bis [3- (3-aminophenoxy) phenyl] -1,1,1,3,3,3-hexafluoropropane, bis [4- (3-aminophenoxy) phenyl] methane, 1,1 -Bis [4- (3-aminophenoxy) phenyl] ethane, 1,2-bis [4- (3-aminophenoxy) phenyl] ethane, bis [4- (3-aminophenoxy) phenyl] sulfoxide, 4,4 '-Bis [3- (4-aminophenoxy) benzoyl] diphenyl ether, 4,4'-bis [3- (3-aminophenoxy) benzoyl] diphenyl ether, 4,4'-bis [4- (4-amino-α) , Α-dimethylbenzyl) phenoxy] benzophenone, 4,4′-bis [4- (4-amino-α, α-dimethylbenzyl) phenoxy] diphenylsulfone, bis 4- {4- (4-aminophenoxy) phenoxy} phenyl] sulfone, 1,4-bis [4- (4-aminophenoxy) phenoxy-α, α-dimethylbenzyl] benzene, 1,3-bis [4- (4-aminophenoxy) phenoxy-α, α-dimethylbenzyl] benzene, 1,3-bis [4- (4-amino-6-trifluoromethylphenoxy) -α, α-dimethylbenzyl] benzene, 1,3 -Bis [4- (4-amino-6-fluorophenoxy) -α, α-dimethylbenzyl] benzene, 1,3-bis [4- (4-amino-6-methylphenoxy) -α, α-dimethylbenzyl Benzene, 1,3-bis [4- (4-amino-6-cyanophenoxy) -α, α-dimethylbenzyl] benzene,

3,3′-diamino-4,4′-diphenoxybenzophenone, 4,4′-diamino-5,5′-diphenoxybenzophenone, 3,4′-diamino-4,5′-diphenoxybenzophenone, 3, 3'-diamino-4-phenoxybenzophenone, 4,4'-diamino-5-phenoxybenzophenone, 3,4'-diamino-4-phenoxybenzophenone, 3,4'-diamino-5'-phenoxybenzophenone, 3,3 '-Diamino-4,4'-dibiphenoxybenzophenone, 4,4'-diamino-5,5'-dibiphenoxybenzophenone, 3,4'-diamino-4,5'-dibiphenoxybenzophenone, 3,3'- Diamino-4-biphenoxybenzophenone, 4,4′-diamino-5-biphenoxybenzophenone, 3,4 -Diamino-4-biphenoxybenzophenone, 3,4'-diamino-5'-biphenoxybenzophenone, 1,3-bis (3-amino-4-phenoxybenzoyl) benzene, 1,4-bis (3-amino- 4-phenoxybenzoyl) benzene, 1,3-bis (4-amino-5-phenoxybenzoyl) benzene, 1,4-bis (4-amino-5-phenoxybenzoyl) benzene, 1,3-bis (3-amino) -4-biphenoxybenzoyl) benzene, 1,4-bis (3-amino-4-biphenoxybenzoyl) benzene, 1,3-bis (4-amino-5-biphenoxybenzoyl) benzene, 1,4-bis (4-Amino-5-biphenoxybenzoyl) benzene, 2,6-bis [4- (4-amino-α, α-dimethylbenzyl) pheno Si] A part or all of the hydrogen atoms on the aromatic ring in the benzonitrile and the aromatic diamine are halogen atoms, alkyl groups having 1 to 3 carbon atoms or alkoxyl groups, cyano groups, or alkyl groups or alkoxyl group hydrogen atoms. Examples thereof include aromatic diamines substituted with a C1-C3 halogenated alkyl group or alkoxyl group partially or entirely substituted with a halogen atom.

  As aromatic diamines having a benzoxazole structure in the present invention, 5-amino-2- (4-aminophenyl) benzoxazole (Chemicals) is obtained from the viewpoints of ease of production and property balance of polyimide benzoxazole as a final product. The use of 1) is particularly preferred.

  The manufacturing method of aromatic diamine which has said benzoxazole group is not limited. For example, the various known methods described above can be used.

The aromatic diamine having a benzoxazole group preferably has a pH of 5.5 or more in an aqueous suspension evaluated by the following method. PH is more preferably 6.0 or more, and even more preferably 7.0 or more.
[PH measurement of aqueous suspension of aromatic diamine]
Add 1.0 g of aromatic diamine to 50 cc of ion-exchanged water and stir with a stirrer at room temperature for 30 minutes. The pH of the obtained suspension is measured three times by a plane measurement method using a compact PH meter (HORIBA B-211, manufactured by Horiba Ltd.), and the average value is obtained.

  When an aromatic diamine having a pH of 5.5 or less is used, the production rate of the polyamic acid is slowed, the molecular weight of the resulting polyamic acid reaches its peak, the productivity of the polymerization decreases, or the polyamic acid having a predetermined molecular weight is reduced. Since it cannot be obtained, it is not preferable. The reason for this is unknown, but since the water-soluble component contains inorganic acid such as phosphoric acid, for example, polyphosphoric acid used in the formation reaction of benzoxazole ring, which is one of the processes for producing aromatic diamines. It is suggested that the acid or acid generated by sulfuric anhydride is mixed into the reaction product, and finally the salt of aromatic diamine is generated. It is presumed that the salt of the mixed aromatic diamine and acid is one factor for inhibiting the reaction of polyamic acid. Therefore, it is preferable to apply this invention to the aromatic diamine manufactured by the method of using the compound which produces | generates an inorganic acid and an inorganic acid in the manufacturing process of aromatic diamine.

  The method for producing the aromatic diamine having the above characteristics is not limited, but the method for sufficiently washing the aromatic diamine with water or an aqueous alkaline solution before using the aromatic diamine in the production process of the aromatic diamine or the production of the polyamic acid. Examples thereof include a method of dissolving in a specific solvent such as acetonitrile and removing insolubles in these solvents.

  The polyimide benzoxazole precursor in the present invention is a polyamic acid obtained by reacting the aromatic diamine containing the benzoxazole group with an aromatic tetracarboxylic acid anhydride. Although the manufacturing method of this polyamic acid is not limited, The method of making it react in the organic solvent which melt | dissolves polyamic acid is preferable.

  The aromatic tetracarboxylic acids used in the present invention are preferably aromatic tetracarboxylic anhydrides. Specific examples of the aromatic tetracarboxylic acid anhydrides include the following.

これらのテトラカルボン酸二無水物は単独でも二種以上を用いることも可能である。

These tetracarboxylic dianhydrides can be used alone or in combination of two or more.

  In the present invention, one or two or more non-aromatic tetracarboxylic dianhydrides exemplified below may be used in combination as long as they are 30 mol% or less of the total tetracarboxylic dianhydrides. Examples of the tetracarboxylic anhydride used include butane-1,2,3,4-tetracarboxylic dianhydride, pentane-1,2,4,5-tetracarboxylic dianhydride, and cyclobutanetetracarboxylic acid. Dianhydride, cyclopentane-1,2,3,4-tetracarboxylic dianhydride, cyclohexane-1,2,4,5-tetracarboxylic dianhydride, cyclohex-1-ene-2,3,5 , 6-tetracarboxylic dianhydride, 3-ethylcyclohex-1-ene-3- (1,2), 5,6-tetracarboxylic dianhydride, 1-methyl-3-ethylcyclohexane-3- (1,2), 5,6-tetracarboxylic dianhydride, 1-methyl-3-ethylcyclohex-1-ene-3- (1,2), 5,6-tetracarboxylic dianhydride, 1-ethylcyclohexane -(1,2), 3,4-tetracarboxylic dianhydride, 1-propylcyclohexane-1- (2,3), 3,4-tetracarboxylic dianhydride, 1,3-dipropylcyclohexane- 1- (2,3), 3- (2,3) -tetracarboxylic dianhydride, dicyclohexyl-3,4,3 ′, 4′-tetracarboxylic dianhydride, bicyclo [2.2.1] Heptane-2,3,5,6 lacarboxylic dianhydride, 1-propylcyclohexane-1- (2,3), 3,4-tetracarboxylic dianhydride, 1,3-dipropylcyclohexane-1- ( 2,3), 3- (2,3) -tetracarboxylic dianhydride, dicyclohexyl-3,4,3 ′, 4′-tetracarboxylic dianhydride, bicyclo [2.2.1] heptane-2 , 3,5,6-tetracarboxylic dianhydride, Biciku [2.2.2] Octane-2,3,5,6-tetracarboxylic dianhydride, bicyclo [2.2.2] oct-7-ene-2,3,5,6-tetracarboxylic dianhydride Such as anhydrides. These tetracarboxylic dianhydrides can be used alone or in combination of two or more.

  The polar organic solvent used in the synthesis of the polyamic acid of the present invention is not particularly limited as long as it dissolves both the raw material monomer and the polyamic acid to be produced. For example, N-methyl-2-pyrrolidone, N- Acetyl-2-pyrrolidone, N, N-dimethylformamide, N, N-diethylformamide, N, N-dimethylacetamide, dimethyl sulfoxide, hexamethylphosphoric amide, ethyl cellosolve acetate, diethylene glycol dimethyl ether, sulfolane, halogenated phenol tetrahydrofuran, Examples thereof include toluene and xylenes, and these solvents can be used alone or in combination. The amount of the polar organic solvent used may be an amount sufficient to dissolve the charged monomer, and is usually 5 to 40% by mass, preferably 10 to 20% by mass. .

  The organic solvent solution of polyamic acid used in the present invention preferably contains a solid content of 5 to 40% by mass, more preferably 10 to 20% by mass, and the viscosity is measured by a Brookfield viscometer. A material having a viscosity of 10 to 2000 Pa · s, preferably 50 to 1000 Pa · s is preferable because stable liquid feeding is possible. The polymerization reaction is continuously carried out in a temperature range of 0 to 80 ° C. for 10 minutes to 30 hours while stirring and / or mixing in an organic solvent, but the polymerization reaction is divided or the temperature is increased or decreased as necessary. It doesn't matter. In this case, the order of addition of the two reactants is not particularly limited, but aromatic diamines are poorly soluble in the reaction solvent. Therefore, the aromatic diamines are dispersed in or dissolved in the reaction solvent. It is preferred to add group tetracarboxylic anhydrides.

  In the present invention, it is preferable that the amount of water in the solvent used for the reaction solution is 1000 ppm or less, and the space of the reaction system is filled with a gas having a dew point of −20 ° C. or less. The amount of water in the solvent is more preferably 500 ppm or less, and even more preferably 100 ppm or less. The dew point of the gas is preferably −40 ° C. or lower, and more preferably −60 ° C. or lower. Here, the space of the reaction system refers not only to the reaction can but also to the entire process space involved in the production of the polyamic acid including the raw material charging system and the storage of the polyamic acid. If this requirement is not satisfied, the production rate of polyamic acid and the reached molecular weight may be adversely affected even if the requirement of the present invention is satisfied.

  In the present invention, as a method for controlling the molecular weight of polyamic acid within a specific range, maleic anhydride, 2,3-dimethylmaleic anhydride, 3- (3-phenylethynylphenoxy) aniline, phthalic anhydride, aniline, vinyl phthalate A terminal blocker such as a monodicarboxylic acid anhydride such as acid anhydride, ethynylaniline and 4-aminobenzocyclobutene or a monoamine may be added to the reaction system.

  In the present invention, inert fine particles made of inorganic or organic may be added to the reaction system in order to improve the slipping property of the fiber or film which is a molded product of polyimide benzoxazole which is the final product. The type, particle size, and addition amount of the inert fine particles are appropriately selected so as to match the characteristics required for the molded body.

  The polyamic acid in the present invention is preferably 2.0 to 6.0 dl / g in terms of reduced viscosity. 3.0-5.5 dl / g is more preferable. If it is less than 2.0 dl / g, the mechanical properties of polyimide benzoxazole obtained by the imidization reaction of polyamic acid are inferior. On the other hand, if it exceeds 6.0 dl / g, the processability of the molding process to form a fiber or film deteriorates, which is not preferable.

  The polyamic acid obtained in the present invention is preferably molded into a film or the like in the state of polyamic acid, and then subjected to a dehydration cyclization reaction of an amic acid bond to be converted into a polyimide bond to form a polyimide benzoxazole molded product. For example, when the molded body is a film, the self-supporting film obtained by continuously extruding or applying the polyamic acid solution to a rotating support in the form of a film and drying is peeled off from the support, stretched, A typical method for producing a polyimide benzoxazole film from an organic solvent of polyamic acid, which is produced by drying and heat treatment, is to use an organic solvent solution of polyamic acid containing no ring-closing catalyst and a dehydrating agent from a slit base. After casting on a support, forming into a film, and heating to dry on the support to form a self-supporting film, the self-supporting film is peeled off from the support, and further heat-treated at a high temperature. A thermal ring-closure method that imidizes, and a polyamic acid organic solvent containing a ring-closure catalyst and a dehydrating agent. Then, the film is cast on a support and formed into a film, and a part of imidization proceeds on the support to obtain a self-supporting film, and then the self-supporting film is peeled off from the support and subjected to heat treatment. And a chemical ring closure method in which imidization is performed.

Specific examples of the ring-closing catalyst include aliphatic tertiary amines such as trimethylamine and triethylamine, and heterocyclic tertiary amines such as isoquinoline, pyridine, and betapicoline, which are selected from heterocyclic tertiary amines. It is preferred to use at least one amine.
Specific examples of the dehydrating agent include aliphatic carboxylic acid anhydrides such as acetic anhydride, propionic anhydride and butyric anhydride, and aromatic carboxylic acid anhydrides such as benzoic anhydride, but acetic anhydride and / or anhydrous Benzoic acid is preferred. The content of the ring-closing catalyst with respect to the polyamic acid is preferably within a range in which the content (mol) of the ring-closing catalyst / content (mol) of the polyamic acid is 0.1 to 8. Further, the content of the dehydrating agent relative to the polyamic acid is preferably within a range where the content of dehydrating agent (mol) / the content of polyamic acid (mol) is 0.1 to 4. In this case, a gelation retarder such as acetylacetone may be used in combination.

  The support used when the polyamic acid solution is formed into a film is a drum or a belt-like rotating body. The polyamic acid solution is applied on a support and is self-supporting by heat drying. The surface of the support may be metal, plastic, glass, porcelain, etc., preferably metal, and more preferably SUS material that does not rust and has excellent corrosion resistance. Further, metal plating such as Cr, Ni, Sn may be performed. The surface of the support in the present invention can be mirror-finished or processed into a satin finish if necessary.

  Application of the polyamic acid solution to the support includes, but is not limited to, casting from a slit base, extrusion through an extruder, squeegee coating, reverse coating, die coating, applicator coating, wire bar coating, etc. Conventionally known solution coating means can be appropriately used.

A drying method for obtaining a green film which is a self-supporting film of polyamic acid which is a polyimide precursor in the present invention is heat drying. As the heating method, a known method such as infrared heating, hot air heating, microwave heating or the like can be used.
The film (green film) that has been dried on the support and becomes self-supporting is peeled off from the support, and a polyimide film is obtained by dehydration and ring closure of amic acid by final drying (heat treatment) at a temperature of 150 to 500 ° C. It is done.
Although the thickness of the polyimide film of the present invention is not particularly limited, it is usually 1 to 150 μm, preferably 3 to 50 μm, considering use as a base material for an electronic substrate. This thickness can be easily controlled by the amount of the polyamic acid solution applied to the support and the concentration of the polyamic acid solution.

  The polyimide film of the present invention is usually an unstretched film, but may be stretched uniaxially or biaxially. Here, the unstretched film refers to a film obtained without intentionally applying a mechanical external force in the surface expansion direction of the film by tenter stretching, roll stretching, inflation stretching, or the like.

  You may use the obtained polyimide film as a film base material as it is. When the film is not treated with a surface treatment agent or a surface activator, it is preferable to perform a surface treatment such as corona discharge treatment, low-temperature or normal-pressure plasma treatment, ultraviolet irradiation, or flame treatment.

EXAMPLES Hereinafter, the present invention will be described in more detail with reference to examples, but the present invention is not limited to these examples.
1. Measurement of reduced viscosity (ηsp / C) of polyamic acid N-methylpyrrolidone obtained by dehydrating polyamic acid to a concentration of 0.2 g / dl (about 10% by mass of toluene with respect to N-methylpyrrolidone in a nitrogen atmosphere) And the solution dissolved and diluted by azeotropic distillation until toluene was completely distilled off) was measured at 25 ° C. using an Ubbelohde viscometer.

2. Purity evaluation of aromatic diamine by HPLC analysis The measurement was performed under the following conditions. Purity was calculated as a peak area ratio.
Equipment: A system that combines the following parts manufactured by Hitachi
Liquid feed pump: L6200, detector: L4200, column hot bath: L5020
Deaerator: L-5020, Integrator: D-2500
Column: Inertsil-ODS3 φ4.6 × 250mm
Mobile phase: acetonitrile / water = 6/4 (vol / vol),
0.0085 mol / l phosphoric acid
Flow rate: 1 ml / min
Detection: UV (230nm)
Development temperature: 30 ° C
Sample concentration: 1 mg / ml
Sample injection volume: 20 μl

3. PH measurement of aqueous suspension of aromatic diamine 1.0 g of aromatic diamine is added to 50 cc of ion-exchanged water and stirred with a stirrer at room temperature for 30 minutes. The pH of the obtained suspension was measured three times by a plane measurement method using a compact PH meter (HORIBA B-211, manufactured by Horiba, Ltd.), and the average value was obtained.

4). Tensile rupture strength and tensile rupture elongation of the film The dried film was cut into strips having a length of 100 mm and a width of 10 mm in the longitudinal direction (MD direction) and the width direction (TD direction), respectively. Using an autograph (R) model name AG-5000A, manufactured by Shimadzu Corporation, measurement was performed at a tensile speed of 50 mm / min and a distance between chucks of 40 mm, and the tensile breaking strength and tensile breaking elongation were determined.

Example 1
(Preparation of aromatic diamine)
The 4,4′-dinitro-2-hydroxybenzanilide obtained by the reaction of 2-amino-4-nitrophenol and 4-nitrobenzoyl chloride is reduced in the presence of a Pd / C catalyst to give 4,4′-diamino. 2-Hydroxybenzanilide was obtained. The resulting 4,4′-diamino-2-hydroxybenzanilide is reacted in N-methyl-2-pyrrolidone to which polyphosphoric acid is added to form an oxazole ring to give 2- (4-aminophenyl) -5-amino. Benzoxazole was obtained. Ion exchange water was added to the obtained reaction product to precipitate 2- (4-aminophenyl) -5-aminobenzoxazole, which was filtered off. After washing with 6 volumes of methanol, it was washed 6 times with 6 volumes of warm water of 60 ° C. and dried. The purity by HPLC analysis was 99.5% by mass or more. Further, the pH of the aqueous suspension was 7.7.
(Preparation of polyamic acid)
Into a 500 ml separable flask equipped with a stirrer was charged 22.53 g of 2- (4-aminophenyl) -5-aminobenzoxazole, and then 390 ml of N-methylpyrrolidone having a moisture content of 31 ppm was added and stirred until dissolved. . Next, 21.81 g of pyromellitic anhydride was gradually added and dissolved with ice cooling. After dissolution, 54 μg of water was added to adjust the water content of the polymerization system to 150 ppm. Thereafter, stirring was continued at room temperature for 2 days to obtain a polyamic acid solution. The reduced viscosity (ηsp / C) of the obtained polyamic acid was 4.80 dl / g.
The above reaction was performed under a nitrogen stream having a dew point of -85 ° C.
(Preparation of polyimide benzoxazole film)
The polyamic acid solution was cast on a mirror-polished stainless steel plate using a doctor blade. A self-supporting film was obtained by heating in an oven at 110 ° C. for 20 minutes. This self-supporting film was fixed to an aluminum metal frame, placed in a high-temperature oven at 150 ° C., heated to 300 ° C., and held at that temperature for 1 hour. The temperature was further raised to 400 ° C. and kept at the same temperature for another hour. The sample was then cooled and removed. The heating time to 300 ° C. and 400 ° C. was 30 minutes, respectively. The film thickness was adjusted to 25 μm.
The obtained polyimide benzoxazole film had good characteristics in tensile strength at break and tensile elongation at break.

Comparative Example 1
In the method of Example 1, the aromatic diamine and polyamic of Comparative Example 1 were the same as Example 1 except that 2- (4-aminophenyl) -5-aminobenzoxazole was not washed with warm water at all. Acid and polyimide benzoxazole films were obtained.
The purity of the aromatic diamine by HPLC analysis was as high as 99.5% by mass or more, and no difference was seen from the aromatic diamine obtained in Example 1, but the pH of the aqueous suspension was remarkably 3.4. It was low. Therefore, the formation reaction of polyamic acid was slow, and ηsp / C of the obtained polyamic acid was as low as 2.20 dl / g. The results are shown in Table 1. The polyimide benzoxazole film obtained in this comparative example was not flexible and fragile.

Comparative Examples 2 and 3
In the method of Example 1, the polyamic acid of Comparative Examples 2 and 3 was prepared in the same manner as in Example except that the number of warm water washings of 2- (4-aminophenyl) -5-aminobenzoxazole was 1 and 2, respectively. Got. Table 1 shows the properties of 2- (4-aminophenyl) -5-aminobenzoxazole, polyamic acid, and polyimide benzoxazole film.

Examples 2-4
In the method of Example 1, in the same manner as in Example 2, except that the warm water washing times of 2- (4-aminophenyl) -5-aminobenzoxazole were 5, 4 and 3, respectively. A polyamic acid was obtained. Table 1 shows the properties of 2- (4-aminophenyl) -5-aminobenzoxazole, polyamic acid, and polyimide benzoxazole film.

Example 5 and Comparative Example 4
In the methods of Example 1 and Comparative Example 1, except that pyromellitic anhydride is changed to biphenyltetracarboxylic anhydride, the polyamics of Example 5 and Comparative Example 4 are the same as Example 1 and Comparative Example 1, respectively. Acid and polyimide benzoxazole films were obtained. The polyamic acid obtained in Example 5 had a reduced viscosity similar to the polyamic acid obtained in Example 1, and a polyimide benzoxazole film having excellent mechanical properties was obtained. On the other hand, the polyamic acid obtained in Comparative Example 4 had a reduced viscosity similar to the polyamic acid obtained in Comparative Example 1, and only a brittle film having no flexibility was obtained.

Example 6 and Comparative Example 5
In Example 1 and Comparative Example 1, the starting material 4-nitrobenzoyl chloride at the time of preparing the aromatic diamine was replaced with 3-nitrobenzoyl chloride, and the resulting aromatic diamine was 2- (3-aminophenyl) -5-aminobenzo Except changing to oxazole, the polyamic acid and polyimide benzoxazole films of Example 6 and Comparative Example 5 were obtained in the same manner as Example 1 and Comparative Example 1. The same results as in Example 1 and Comparative Example 1 were obtained, respectively.

  As described above, the polyamic acid, which is a polyimide benzoxazole precursor obtained by using the aromatic diamine having a benzoxazole structure of the present invention as a raw material, is molded from a high molecular weight polyimide benzoxazole having excellent mechanical properties. Since the body can be obtained efficiently, it is extremely useful industrially.

Claims (2)

  An aromatic diamine containing a benzoxazole group whose pH of an aqueous suspension evaluated by the method described in the specification is 5.5 or more.   The method for producing a polyamic acid, which is a polyimide benzoxazole precursor, by reacting an aromatic diamine mainly containing a benzoxazole group with an aromatic tetracarboxylic anhydride, wherein the aromatic containing a benzoxazole group according to claim 1 is used. A process for producing a polyamic acid, which is a polyimide benzoxazole precursor, characterized by using an aromatic diamine.