JP4720179B2 - Method for producing polyimide benzoxazole precursor - Google Patents

Description

  The present invention relates to a method for producing a polyamic acid which is a precursor of polyimide benzoxazole. More specifically, the present invention relates to a production method capable of stably producing a high molecular weight polyamic acid from which a molded article of polyimide benzoxazole having excellent mechanical properties can be obtained on an industrial scale in a short reaction and in a specified molecular weight range.

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, P.I. 145 (1969)

In the case of forming into a fiber, for example, a polyimide polyamic acid solution of polyimide benzoxazole is extruded from a spinneret, is made into a fiber through a coagulation bath of NMP / water = 75/25, and a chemical ring closure 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.
When forming into a film, cast the polyimide benzoxazole precursor polyamic acid solution on a support such as a polyester film, glass plate, SUS plate, etc. It peels from a support body and can be made into a polyimide benzoxazole film by heating at 200-400 degreeC.
All of the above-mentioned known techniques are results on a laboratory scale, and no disclosure is made regarding manufacturing techniques at an industrial production level.

  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 molecular weight of the benzoxazole is higher than that of polyimide polyamic acid having the same molecular weight as that of other structures. The effect is great.

  A polyamic acid having a benzoxazole structure is produced by a reaction between an aromatic diamine having a benzoxazole structure and a tetracarboxylic acid anhydride. An aromatic diamine having a benzoxazole structure is an aromatic diamine used for general-purpose polyimides. Compared with the low nucleophilicity of the amino group and the reactivity with the acid anhydride is several hundred times lower, it takes a very long time to obtain a high molecular weight polyamic acid. Therefore, in industrial production, establishment of a production technique capable of efficiently obtaining a high molecular weight polyamic acid has been strongly desired from the viewpoint of economy.

  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 to be able to produce a polyamic acid having a specified molecular weight efficiently and stably, and to strictly adjust the molecular weight within a specific range. The literature does not fully mention how to adjust the molecular weight accurately. For example, even when the examples of Patent Documents 4 and 5 are seen, the reduced viscosity, which is an index of molecular weight, varies greatly.

  In addition, the hydrolysis reaction of polyamic acid having a benzoxazole structure is not significantly different from the general-purpose polyamic acid that forms a general-purpose polyimide, and therefore is affected by the low reactivity of the polyamic acid formation reaction described above. Apparently, the contribution of the decomposition reaction is several hundred times larger, and in order to stably produce a polyamic acid having a predetermined molecular weight, it is necessary to improve various reaction control accuracy as compared with general-purpose polyamic acid. In the above-described prior art, regarding these points, some of the requirements are described as concepts, but no specific achievement requirements are disclosed.

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. − A method for producing aminoallylaminoarazole by synthesizing nitrobenzoic 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, Vol. 32, P1431 (1899) Japanese Patent Publication No. 45-8435 Heterocyclic Chem. Vol. 6, P119 (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 greatly vary 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 was made against the background of the problems of the prior art, and relates to a method for producing a polyamic acid which is a precursor of polyimide benzoxazole, and a high molecular weight polyamic acid which can be used to produce a molded article of polyimide benzoxazole having excellent mechanical properties. An object of the present invention is to provide a production method which can be produced stably in a specified molecular weight range with a short-time reaction on a target scale.

  In order to solve the above problems, the present inventors have intensively studied and finally completed the present invention. That is, the present invention relates to a method for producing a polyamic acid, which is a polyimide benzoxazole precursor, by reacting an aromatic diamine containing a benzoxazole group and an aromatic tetracarboxylic anhydride in the form of a solution. Production of polyamic acid, which is a polyimide benzoxazole precursor, characterized by reacting at an average liquid temperature of 30 to 60 ° C. using an aromatic diamine containing a benzoxazole group having a pH of 5.5 or higher in the suspension Is the method.

  According to the present invention, a high molecular weight polyamic acid capable of obtaining a molded article of polyimide benzoxazole having excellent mechanical properties can be produced in a short time reaction on an industrial scale, and is highly economical. Moreover, since it can manufacture stably in the specified molecular weight range, the quality of molded objects, such as a fiber and a film which consist of polyimide benzoxazole which is a final product, is stabilized. Therefore, it can greatly contribute to the industrialization of polyimide benzoxazole.

  The polyimide benzoxazole precursor in the present invention is a polyamic acid obtained by reacting an aromatic diamine containing a 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.

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 ease of 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 the present invention, one or two or more diamines having no benzoxazole structure exemplified below may be used as long as they are 30 mol% or less of the total diamine. 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′-diamino Diphenyl ether, 4,4′-diaminodiphenyl ether, 3,3′-diaminodiphenyl sulfide, 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-bis [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-dimethylphenyl] 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) bif Cycloalkenyl, 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-amino Phenoxy) phenyl] ether, bis [4- (4-aminophenoxy) phenyl] ether, 1,3-bis [4- (4-aminophenoxy) benzoyl] benzene, 1,3-bis [4- (3-amino Phenoxy) 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'-dia Nodiphenyl 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, 2,2-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) phene Noxy] 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-dimethyl Benzyl] 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′-dibiphenoxyben Phenone, 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-bi (4-amino-5-biphenoxybenzoyl) benzene, 1,4-bis (4-amino-5-biphenoxybenzoyl) benzene, 2,6-bis [4- (4-amino-α, α-dimethyl) Benzyl) phenoxy] benzonitrile, and a part or all of the hydrogen atoms on the aromatic ring of the above aromatic diamine are halogen atoms, alkyl groups or alkoxy groups having 1 to 3 carbon atoms, cyano groups, or alkyl groups or alkoxy groups. An aromatic diamine substituted with a C 1-3 halogenated alkyl group or alkoxy group in which some or all of the hydrogen atoms are substituted with halogen atoms, and the like can be mentioned.

  As aromatic diamines having a benzoxazole structure in the present invention, 5-amino-2- (p-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 aromatic tetracarboxylic acids used in the present invention are preferably aromatic tetracarboxylic anhydrides. Specific examples of the aromatic tetracarboxylic acid anhydrides include the following.

  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.

  As the solvent used in the present invention, those capable of dissolving polyamic acid are preferable, and known solvents conventionally used for polymerization of polyamic acid are used. Specific examples include dimethylformamide, dimethylacetamide, dimethyl sulfoxide, N-methyl-2-pyrrolidone, dimethylimidazolone, THF, toluene, 1,4-dioxane, γ-butyrolactone, and the like. These can be used alone or in combination.

In the present invention, as an aromatic diamine compound containing a benzoxazole group, an aromatic diamine compound containing a benzoxazole group evaluated by the following method having an aqueous dispersion having a pH of 5.5 or more is used. is important. PH 6.5 or more is more preferable.
[Method for Measuring PH of 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 suspension pH of 5.5 or less is used, the production rate of polyamic acid is slowed, and the molecular weight of the resulting polyamic acid reaches its peak. Even if the polymerization conditions described later are optimized, polymerization is performed. This is not preferable because the productivity of the polyamic acid decreases and a polyamic acid having a predetermined molecular weight cannot be obtained. The cause of this is unknown, but since the water-soluble component contains an inorganic acid such as phosphoric acid, for example, polyphosphoric acid used in the formation reaction of a benzoxazole ring included in the production process of the aromatic diamine It is suggested that an acid produced from sulfuric anhydride is mixed into the reaction product, and an aromatic diamine salt is finally produced. It is presumed that the salt of the mixed aromatic diamine and acid is one factor for inhibiting the reaction of polyamic acid.
The method for producing an aromatic diamine having the above characteristics is not limited, but the aromatic diamine may be thoroughly washed with water or an aqueous alkaline solution before being used for 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 insoluble components in these solvents.

In this invention, it is important that the liquid temperature of a reaction liquid is 30-60 degreeC by average temperature. The average reaction temperature is more preferably 35 to 55 ° C. If the average reaction temperature is less than 30 ° C., the production reaction rate of the polyamic acid is slow, and it takes a long time to obtain a polyamic acid having a predetermined molecular weight. Conversely, when the temperature exceeds 60 ° C., the reaction rate of polyamic acid formation increases, but side reactions such as hydrolysis of acid anhydride groups increase, the polymerization reaction reaches its peak, and polyamic acid having a predetermined molecular weight is reached. Since it cannot be obtained, it is not preferable.
Since the influence of the reaction liquid temperature on the polymerization reaction is large and the preferred temperature range is narrow, it is important that the liquid temperature is uniform throughout the reaction system. It is preferable that the upper and lower portions of the reaction solution satisfy the above average temperature range. Here, the upper and lower liquid temperature measurement positions are the central part in the reactor, and are positions 50 mm inside from the liquid level and the reactor wall, respectively. The liquid temperature is measured with a thermocouple thermometer.

The method for setting the reaction temperature within the above range is not limited, and examples thereof include a method in which a heat medium jacket is provided on the outer wall of the reactor and the temperature of the jacket is controlled. You may control by installing a heat exchange pipe in a reactor.
In order to maintain the uniformity of the liquid temperature in the reaction solution, the stirring state in the reactor is important, and it is preferable to optimize the structure of the reactor, particularly the shape of the stirrer. As the structure of the reactor and the stirrer, the clearance between the inner wall of the reactor and the outer periphery of the stirrer is important. The clearance is preferably 20 mm or less. 10 mm or less is more preferable.
In the reaction for producing the polyamic acid of the present invention, since the viscosity of the reaction liquid largely changes from a low-viscosity liquid of shabu-shabu to a highly viscous liquid such as chickenpox, efficient stirring is performed within the viscosity range. The shape of a stirring blade that can be used is required. Therefore, it is preferable to use a wing that is easy to generate a vertical circulation flow, such as a double helical ribbon wing, a max blend wing, or a full zone wing, instead of an impeller wing or an anchor wing.

  In the present invention, it is also important that the liquid temperature at the start of the reaction and the liquid temperature at the end of the reaction are 10 ° C. or higher. As described above, if the reaction is carried out at a higher temperature, the side reaction increases and it becomes difficult to obtain a polyamic acid having a predetermined molecular weight. The late stage of the reaction is eliminated by conducting the reaction at a relatively high temperature. Presumably, in the state where a large amount of monomer is present in the reaction system, a side reaction is likely to occur, and the reaction proceeds. If the residual amount of monomer decreases, the influence of the side reaction is considered to be small. When the difference in liquid temperature is 10 ° C. or higher, the reaction can be carried out in a shorter time while suppressing side reactions, and the difference in liquid temperature is more preferably 20 ° C. or higher.

  The polyamic acid obtained in the present invention preferably has a reduced viscosity (also referred to as ηsp / C) of 2.0 to 6.0 dl / g. 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 aromatic diamine containing a benzoxazole group used in the present invention is an aromatic diamine used in the production of general-purpose polyimides, for example, the dissolution rate in the reaction solvent described above is slower than that of 4,4′-diaminodiphenyl ether. , Undissolved components are likely to occur. The generation of undissolved components adversely affects the production rate and molecular weight of polyamic acid, and must be eliminated. This is an important factor particularly in the large production reactors intended by the present invention. For example, optimizing the shape and particle size of the diamine powder used in the reaction is a preferred embodiment. Moreover, it is also one of the preferable embodiments that it is dissolved in the reaction solvent in advance and then charged into the reactor.

  The polymer concentration at the time of the reaction is not particularly limited as long as it is adjusted so as to have a stirrable viscosity.

  In the present invention, as described above, an aromatic diamine containing a benzoxazole group is less soluble in a reaction solvent than an aromatic diamine used for producing a general-purpose polyimide, and thus an aromatic diamine containing a benzoxazole group. It is preferred to dissolve or disperse the diamine in the reaction solvent and add the aromatic tetracarboxylic anhydride to the solution or dispersion. By this method, the above reaction control can be performed more efficiently.

  In the present invention, it is a preferred embodiment that the aromatic tetracarboxylic acid anhydride is added in at least two portions. In the present invention, in order to obtain the above ηsp / C polyamic acid, it is preferable to add an equimolar amount of the aromatic tetracarboxylic acid anhydride to the aromatic diamine. When the molar balance between the two is lost, the polymerization reaction reaches its peak, and a polyamic acid having a predetermined molecular weight, that is, a predetermined reduced viscosity cannot be obtained. However, if the total amount of aromatic tetracarboxylic acid anhydride is added at once, the reaction becomes non-uniform, leading to a decrease in reaction rate and an increase in side reactions. Therefore, a part of the aromatic tetracarboxylic acid anhydride is partially added to form a polyamic acid prepolymer, and then the remaining aromatic tetracarboxylic acid anhydride is added to make the reaction uniform. It is possible to increase the speed and suppress side reactions. In addition, this split addition method measures the molecular weight of the prepolymer, and based on this result, it is possible to control the amount of aromatic tetracarboxylic acid anhydride added for the second and subsequent times, enabling more precise reaction control. The advantage of becoming is added. As a method for measuring the molecular weight of the prepolymer in this case, a method for measuring solution viscosity, a method for quantifying end groups, a method for measuring ηsp / C and relative viscosity (ηrel), and a gel permeation chromatograph are measured. Methods and the like. The determination may be performed online or offline.

When performing on-line, the solution viscosity is measured from pressure loss when flowing through a capillary or SMX, or a device such as ReactIR (R) is attached to the reaction tube, and the end group is determined from the strength of characteristic absorption derived from the end group. The degree of polymerization can also be calculated.
In the case of determining offline, a general method for measuring the molecular weight of a polymer can be used. Measurements or .eta.sp / C and eta _inh, and a method for quantifying by gel permeation I Deployment chromatograph, the end group titration or color. .eta.sp / C and eta _inh can be prepared by dissolving the polymer in a dilute solvent of dimethylacetamide or N- methylpyrrolidone, it can be measured by Ubbelohde viscometer. The terminal group can be quantified by a method in which an amino terminal group and a Schiff base are formed with an aldehyde compound or the like and the amount is determined by color development. In terms of accuracy, η _inh and terminal group quantification are preferable, and in terms of speed of determination, a method of obtaining the viscosity from online pressure loss is preferable.
The form to be added may be any of a powder state, a molten state, a slurry state, or a solution state, but a solution state is preferable in terms of accuracy of addition.

  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 600 ppm or less, and even more preferably 300 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.

Since polyamic acid is susceptible to hydrolysis reaction, the necessity of eliminating water in the reaction system is known. For example, in Patent Document 5, “when producing polyamic acid, before reaction, monomer, solvent, and Most preferably, the reactor contains as little water as possible .... Preferably, the total number of moles of dianhydride, diaminobenzoxazole, and additional comonomer used as appropriate. Based on this, the concept "water should be present in an amount of 5 mol% or less" is stated.
In accordance with this concept, the present inventors also produced the raw materials including the reaction solvent and the water in advance of the reactor, but could not stably produce the polyamic acid in the molecular weight range which is the object of the present invention. It was. In order to produce stably, it was found that it is important to set the water content in the space of all processes involved in the production of polyamic acid, such as raw material charging system, polyamic acid storage, etc., not only in the reactor, but in a specific range. . Moreover, it discovered that it was preferable not only at the time of reaction start but to make a moisture content into a specific range over the whole manufacturing period including transfer. For this purpose, it is preferable that the gas with the above dew point is always circulated in the space of the entire reaction system during the production period. The flow rate of the gas is not limited, but it is preferable to flow a gas of at least space volume / hour or more. The space volume x 2 / hour or more is more preferable.
The kind of gas to distribute | circulate is not limited. Examples include air, nitrogen, argon, and helium. The dew point of the gas may be managed by purchasing a gas with the specified dew point, or by providing a gas dehumidifying device in the polyamic acid production process and dehumidifying it with the dehumidifying device. You may let them. The latter is preferred. The dehumidifying method is not limited. Examples include an adsorption method and a compression method. The former is preferred.

  In the present invention, as a method for controlling the molecular weight of the polyamic acid within the specific range, maleic anhydride, 2,3-dimethylmaleic anhydride, 3- (3-phenylethynylphenoxy) aniline, phthalic anhydride, aniline Further, endblocking agents such as monodicarboxylic acid anhydrides such as vinylphthalic anhydride, ethynylaniline and 4-aminobenzocyclobutene, and monoamines 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 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 green 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 from the support, stretched, dried, A typical method for producing a polyimide benzoxazole film from an organic solvent of polyamic acid, which is produced by heat treatment, is that a solution of an organic solvent of polyamic acid which does not contain a ring closure catalyst and a dehydrating agent is supported from a base with a slit. Cast on top to form a film, heat-dry on the support to form a self-supporting green film, peel off the film from the support, and further heat and dry at a high temperature for imidization Or a polyamic acid organic solvent containing a ring-closing catalyst or a dehydrating agent. After casting on a support and forming it into a film, after partially imidizing on the support and making it a film having self-supporting properties, the film is peeled off from the support, heat-dried / imidized, There is a chemical ring closure method in which heat treatment 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.

  By the above method, the polymerization degree of polyamic acid can be accurately controlled. This makes it possible to control the viscosity of the polyamic acid solution as intended, facilitates the production of high-quality fibers and films, and the molecular weight of the polyimide benzoxazole obtained by the imidization reaction of the polyamic acid. Can be controlled accurately.

  It is a drum or belt-like rotating body used when forming a polyamic acid solution into a film. 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.

  Although the obtained polyimide film may be used as a film substrate as it is, it is preferable to subject the film to a surface treatment such as corona discharge treatment, low temperature or normal pressure plasma treatment, ultraviolet irradiation treatment, flame treatment or the like.

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 ηsp / C of polyamic acid N-methylpyrrolidone dehydrated to a concentration of 0.2 g / dl of polyamic acid (about 10% by mass of toluene with respect to N-methylpyrrolidone in a nitrogen atmosphere) The solution dissolved and diluted by adding azeotropic distillation until toluene was distilled completely 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 ODS-3 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 dispersion 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.

Example 1
<Preparation of aromatic diamine>
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 obtained 4,4′-diamino-2-hydroxybenzanilide was reacted in polyphosphoric acid to form an oxazole ring to obtain 2- (4-aminophenyl) -5-aminobenzoxazole. 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>
4.55 kg of 2- (4-aminophenyl) -5-aminobenzoxazole prepared by the above method in a 100 l stainless steel reactor equipped with a double helical ribbon wing stirrer, solid content inlet and liquid inlet 20.0 mol) was added, and 96 l of N-methylpyrrolidone (also referred to as NMP) having a water content of 35 ppm was added and stirred until dissolved. While controlling the jacket temperature of the reactor at 10 ° C., 4.32 kg (19.8 mol) of pyromellitic anhydride (PMDA) was gradually added. The liquid temperature when all PMDA was added was 18 ° C. After stirring for 8 hours, the jacket temperature was raised to 30 ° C., and stirring was further continued for 6 hours to prepare a prepolymer. A portion of this prepolymer solution was sampled. The viscosity was 17.8 Pa · s at 30 ° C. as measured with an E-type viscometer, and ηsp / C was 2.21 dl / g. The liquid temperature at the time of sampling was 36 ° C. Further, 22 g (0.1 mol) of pyromellitic anhydride (PMDA) was gradually added, and the mixture was heated and stirred for 6 hours while maintaining the jacket temperature at 35 ° C. until the ηsp / C of the polyamic acid became 4.5 dl / g. Then, the polymerization reaction was completed. The total polymerization time including the prepolymer preparation time was 22 hours. The liquid temperature at the end of the reaction was 42 ° C., and the average liquid temperature from the start to the end of the reaction was 37 ° C.
The liquid temperature of the prepolymer and the polymer was measured with a thermocouple thermometer (lower temperature) installed 50 mm from the inner wall of the reactor at the center of the lower part of the reactor. For the purpose of evaluating the uniformity of the reaction liquid temperature in the reactor, the upper temperature of the reaction liquid was measured with a thermocouple thermometer installed 50 mm below the liquid level at the center of the reactor. In this example, the upper temperature was 16 ° C. and the reaction temperature was 43 ° C.
Feeding of raw material diamine, PMDA, N-methylpyrrolidone to the reactor and polymerization reaction were carried out in a nitrogen stream having a dew point of -76 ° C. The clearance between the inner wall of the reactor and the outer periphery of the stirrer was 8.5 mm, and the outer peripheral speed of the stirrer was 23 m / min.

＊ Ｗ：ダブルヘリカルリボン翼型、 Ａ：アンカー型
＊＊ ポリアミック酸のηｓｐ／Ｃが４．５ｄｌ／ｇになるまでの総重合時間

* W: Double helical ribbon airfoil, A: Anchor type ** Total polymerization time until polyamic acid ηsp / C reaches 4.5 dl / g

(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. The acid was 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. For this reason, the polyamic acid formation reaction was slow and polymerization was carried out for 48 hours. The resulting polyamic acid had a low ηsp / C of 2.20 dl / g, and a polyamic acid having a target molecular weight could not be obtained. The results are shown in Table 2.

＊ Ｗ：ダブルヘリカルリボン翼型、 Ａ：アンカー型
＊＊ ポリアミック酸のηｓｐ／Ｃが４．５ｄｌ／ｇになるまでの総重合時間

* W: Double helical ribbon airfoil, A: Anchor type ** Total polymerization time until polyamic acid ηsp / C reaches 4.5 dl / g

(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. 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 4.1 and 5 It was low at 1. For this reason, the polyamic acid formation reaction is slow, and polymerization was carried out for 48 hours. However, the polyamic acid obtained had a low ηsp / C of 2.40 dl / g and 2.80 dl / g, and a polyamic acid having a target molecular weight could not be obtained. It was. The results are shown in Table 2.

(Comparative Example 4)
In the method of Example 1, polyamic acid was polymerized in the same manner as in Example 1 except that the jacket temperature was always kept at 10 ° C. and the lower average reaction temperature was changed to 18 ° C. The upper liquid temperature at the end of the reaction was also 20 ° C. Compared with the method of Example 1, the polymerization rate was slow, and the total polymerization time including the prepolymer preparation time until the polyamic acid ηsp / C reached 4.5 dl / g was 68 hours. The results are shown in Table 2.

(Comparative Example 5)
In the method of Example 1, polyamic acid was polymerized in the same manner as in Example 1 except that the jacket temperature was kept constant at 55 ° C from the start of the reaction and the lower average reaction temperature was changed to 65 ° C. It was. The upper liquid temperature at the end of the reaction was 69 ° C. In the case of this comparative example, the polyamic acid ηsp / C peaked at 3.12 dl / g, and the polymerization reaction was stopped after 48 hours in total polymerization time including the prepolymer preparation time. However, the target ηsp / C was A 4.5 dl / g polyamic acid was not obtained. The results are shown in Table 2.

(Examples 2 and 3)
In the method of Example 1, polyamic acid was polymerized in the same manner as in Example 1 except that the lower average reaction temperature was changed to 34 and 51 ° C., respectively. The upper liquid temperature at the end of the reaction was 37 and 58 ° C., respectively. The total polymerization time including the prepolymer preparation time until ηsp / C of the polyamic acid was 4.5 dl / g was 26 and 16 hours. The results are shown in Table 1.

(Examples 4 to 6)
In the methods of Examples 1 to 3, polymerization of polyamic acid was carried out in the same manner as in Examples 1 to 3 except that the addition of PMDA was not divided and the total amount was changed to be added all at once. The total polymerization time until the ηsp / C of the polyamic acid reached 4.5 dl / g was 24 hours, 24 hours, and 20 hours, respectively. The results are shown in Table 1.

(Comparative Example 6)
In Example 4, polyamic acid was polymerized in the same manner as in Example 1 except that the average reaction temperature was changed to 25 ° C. Compared with the method of Example 1, the polymerization rate was slow, and the total polymerization time including the prepolymer preparation time until the ηsp / C of the polyamic acid reached 4.5 dl / g was 48 hours. The results are shown in Table 2.

(Example 7)
In the method of Example 2, polyamic acid was polymerized in the same manner as in Example 2 except that the stirring blade was changed to the anchor type. Since the stirring efficiency was lower than in Example 2, the difference in average reaction temperature between the lower part and the upper part was large, and the temperature of the upper liquid at the end of the reaction was 48 ° C., which was 5 ° C. different from the lower part. Compared with the method of Example 2, the polymerization rate was slightly slower, and the total polymerization time including the prepolymer preparation time until the ηsp / C of the polyamic acid was 4.5 dl / g was 28 hours. The results are shown in Table 2.

(Comparative Examples 7 and 8)
In the method of Comparative Example 4, the water content in NMP, which is the reaction solvent, is changed to 1500 ppm, and the flow of nitrogen gas flow in the raw material supply system and the polymerization reaction system is stopped, and the dew point is changed to 21 ° C. in an air atmosphere. Except for the above, polyamic acid was polymerized in the same manner as in Comparative Example 4. Polymerization was stopped at a total polymerization time of 48 hours including the prepolymer preparation time, but a polyamic acid having a target ηsp / C of 4.5 dl / g was not obtained.

  As described above, the polyamic acid production method of the present invention can produce a high molecular weight polyamic acid with a short reaction time on an industrial scale, which can yield a molded product of polyimide benzoxazole having excellent mechanical properties. Is expensive. Moreover, since it can manufacture stably in the specified molecular weight range, since quality of molded objects, such as a fiber and a film which consists of polyimide benzoxazole which is a final product, is stabilized, it is very useful industrially.

Claims (6)

In a method for producing a polyamic acid, which is a polyimide benzoxazole precursor, by reacting an aromatic diamine containing a benzoxazole group and an aromatic tetracarboxylic acid anhydride in the form of a solution, the pH of the aqueous suspension is the aromatic diamine. In a reactor having a reactor wall using an aromatic diamine containing a benzoxazole group that is 5.5 or more , the reactor is the central part of the reactor, and the lower part of the reaction liquid is 50 mm lower than the reaction liquid surface. When 50 mm from the inner wall of the reactor is the lower part of the reaction liquid at the center of the lower part, the average liquid temperature is 30 to 60 ° C. at both the upper and lower parts of the reaction liquid, and the liquid temperature at the start of the reaction and the liquid temperature at the end of the reaction. The manufacturing method of the polyamic acid which is a polyimide benzoxazole precursor characterized by making a difference react at 10 degreeC or more . 2. The polyimide benzoxazole precursor according to claim 1, wherein the polyamic acid has a reduced viscosity of 2.0 to 6.0 dl / g as measured at 25 ° C. after being dissolved and diluted with N-methylpyrrolidone. A method for producing polyamic acid. 3. The polyimide according to claim 1, wherein the water content in the solvent used in the reaction solution is 1000 ppm or less and the reaction system space is filled with a gas having a dew point of −20 ° C. or less. The manufacturing method of the polyamic acid which is a benzoxazole precursor. The aromatic diamine containing benzoxazole groups are dissolved or dispersed in a reaction solvent, according to any one of claims 1 to 3, characterized in that the addition of an aromatic tetracarboxylic acid anhydride to the solution or dispersion The manufacturing method of the polyamic acid which is a polyimide benzoxazole precursor. The method for producing a polyamic acid which is a polyimide benzoxazole precursor according to claim 4, wherein the aromatic tetracarboxylic acid anhydride is added at least twice. The aromatic diamine compound containing a benzoxazole group is 5-amino-2- (p-aminophenyl) benzoxazole. Production of polyamic acid as a polyimide benzoxazole precursor according to any one of claims 1 to 5. Method.