JP4957487B2 - Method for producing polyamic acid - Google Patents

Description

  The present invention relates to a production method for adjusting the degree of polymerization of polyamic acid stably and simply to a high degree of polymerization.

  Specifically, the present invention is excellent in heat resistance, chemical resistance, electrical properties and mechanical properties, and widely used in electronic device materials, electrical insulating materials, coating materials, adhesive paints, molded products, laminates, fibers or film materials, etc. The present invention relates to a production method in which the degree of polyamic acid polymerization for forming a polyimide resin is adjusted to a high degree of polymerization stably and simply.

  Conventionally, various methods have been disclosed as methods for producing polyamic acid. For example, it is disclosed in Patent Document 1, Patent Document 2, or Patent Document 3. These are prepared by dissolving the diamine in a solvent and gradually adding the acid anhydride, dividing it, adding it within a certain period of time, or mixing the powdered diamine and acid anhydride in advance. Are added to a solvent, or a method in which a powder of diamine and an acid anhydride is added to a alternately stirred solvent and reacted.

However, either method is insufficient for controlling the polymerization degree of the polyamic acid, and a production method for stably and simply adjusting the polyamic acid having a high polymerization degree is not known.
JP-A-5-255499 JP 2003-160666 A JP 2004-359874 A

  Although the above-described production method is an excellent production method, in any of the methods, the degree of polymerization of polyamic acid is not satisfied as a method for adjusting the degree of polymerization as the target degree of polymerization is larger.

  It is known that the polymerization degree of the condensation polymerization polymer is well matched with the theoretical polymerization degree obtained from the acid / diamine monomer molar ratio (hereinafter referred to as acid / diamine molar ratio) in Flory condensation polymerization. The degree of polymerization with respect to the diamine molar ratio is drawn as shown by the curve in FIG. 1. When the molar ratio approaches 1.000 (acid / diamine molar ratio = 1.000 / 1.000), the degree of polymerization rapidly increases. For this reason, in a high polymerization degree area | region, since a big difference arises in a polymerization degree by a slight difference of molar ratio, it is because it becomes difficult to adjust a polymerization degree, so that a target polymerization degree is large.

(Flory formula)
DPn (degree of polymerization) = (1 + r) / (1-r), r = acid / diamine (molar ratio), p (monomer reactivity) = 0.997

  For example, a typical polyamic acid represented by the structure of the following formula (1) has high reactivity of monomers starting from pyromellitic dianhydride (PMDA) and 4,4′-diaminodiphenyl ether (DDE). Although it is known that a polymer with a high degree of polymerization can be obtained relatively easily by a low temperature solution polymerization method under normal pressure, the degree of polymerization is known to agree well with the theoretical degree of polymerization of Flory's condensation polymerization obtained from the acid / diamine molar ratio. When the acid / diamine molar ratio is adjusted to a desired molar ratio, for example, 1.000, in order to stably obtain a high polymerization degree polymer, particularly in industrial production, the monomer purity (analytical value and actual value) Error), weighing errors (accuracy of the measuring instrument, adhesion to the measuring instrument, etc.), charging errors (extraction from the system due to the accompanying air at the time of charging, adhesion to the charging pipe, etc.) , Conveniently there is a problem that can not be adjusted. .

  For example, when there is an error in the monomer purity, the influence on the molar ratio is as follows: PMDA / DDE = 1.000 and a DDE charge of 25 kg (purity 99.8%); PMDA (purity 99.8%) %) Is weighed and charged to the desired molar ratio, and if the purity differs from the analytical value by 0.1% in actuality, it will deviate from the set molar ratio as shown in Table 1. However, there is no adjustment means because it cannot be estimated how much the analytical value differs from the actual purity.

  Also, if there is an error in the charged amount, it goes without saying that it will deviate from the set molar ratio.For example, even equipment that accurately measures the monomer weight measurement will not adhere to the measuring instrument or charging device. Depending on the accuracy of the weighing scale, an error in the amount of charge occurred, which caused the degree of polymerization to become unstable. Both the acid and diamine monomers are usually in the form of powder, and may be dissipated out of the system with the accompanying air when metered in or after metering into the polymerization tank, resulting in metering errors and input error. It was a cause that deviated from the set molar ratio.

  For example, when the actual input amount error of DDE is 100 g, the molar ratio deviates from the set molar ratio as shown in Table 2 below.

  Thus, the acid / diamine molar ratio is very difficult to achieve the desired molar ratio, particularly 1.000 (= acid / diamine (molar ratio) = 1.000 / 1.000). is there. Furthermore, in the method of adding a powdered acid anhydride after dissolving diamine in a solvent, a phenomenon that the reaction does not proceed uniformly, a phenomenon that water in the solvent deactivates the acid anhydride, or a reaction There is a problem that it is difficult to adjust the monomer molar ratio that is most causally related to the degree of polymerization by additional addition of the monomer, because it takes an enormous amount of time to reach the equilibrium state.

  Conventionally, in order to deal with these problems, it has been necessary to measure a monomer weight such as a monomer weight of about 25 to 50 kg in industrial production by using a measuring scale (accuracy) with a minimum scale of 0.1 g. Also, once the completion of the polymerization reaction was confirmed, the viscosity was measured, the amount of additional monomer added was determined by calculation, and a small amount of monomer was added to adjust the degree of polymerization. In addition, it was expensive to install equipment such as using an automatic weighing machine. However, the error in monomer purity could not be eliminated even with the automatic weighing equipment.

  An object of the present invention is to provide a production method in which the degree of polymerization of a polyamic acid is stably and easily adjusted to a high degree of polymerization even if there is an error in the purity, measurement, or amount of the monomer.

  As a result of diligent study, the inventors of the present application have found that Flory's acid / diamine monomer molar ratio (hereinafter referred to as acid / diamine molar ratio), particularly in the method of adding a powdered acid anhydride after dissolving diamine in a solvent. ) And the degree of polymerization of the polyamic acid was found to depend on the addition time of the acid monomer, the first stage reaction was carried out in an excess of diamine, and the acid anhydride was added during the second stage reaction. It was found that the degree of polymerization of the polyamic acid can be controlled by carrying out at a very slow speed, and the present invention was completed.

That is, the present invention is as follows.
1. A method for producing a polyamic acid comprising the following steps (a) and (b) when a diamine and an acid anhydride are reacted to produce a polyamic acid.
(A) First stage reaction: A step of polymerizing amino-terminated polyamic acid (PAA) by adding an acid anhydride less than an equimolar equivalent to the diamine to a diamine dissolved in a polar solvent.
(B) Second stage reaction: The reaction rate R (mol / min) in the first stage reaction defined by the following formula (I) and the acid anhydride addition rate T (mol / min) in the second stage reaction are the following (II ) Step of adding an acid anhydride in an amount such that the molar ratio with the diamine charged in the first stage is equal to or greater than that at the rate satisfying the formula, and reacting with the amino terminal polyamic acid obtained in the first stage reaction. .
First stage reaction rate: R (mol / min) = total amount of diamine (mol) / A (min) (I)
Acid anhydride addition rate in the second stage reaction: T (mol / min) <R (mol / min) (II)
Here, A (minute) represents the time until the stirring power in the first-stage reaction is increased and reaches an equilibrium state.
2. The method for producing a polyamic acid according to 1, wherein the amount of acid anhydride added in the second stage reaction is 93 to 99 molar equivalents relative to 100 molar equivalents of diamine.
3. The method for producing a polyamic acid according to 1 or 2, wherein a moisture content contained in the polar solvent is 100 to 1000 ppm.
4). The method for producing a polyamic acid according to any one of 1 to 3, wherein the diamine is 4,4′-diaminodiphenyl ether.
5. The method for producing a polyamic acid according to any one of 1 to 4, wherein the acid anhydride is pyromellitic dianhydride.

  By using the polyamic acid production method of the present invention, it is not necessary to precisely measure or precisely adjust the amount of monomer charged, and the addition rate of the acid anhydride that is simply added in the second stage is within the range that satisfies the conditions of the present invention. By making it constant, a polyamic acid having a desired degree of polymerization can be stably produced.

<Polyamic acid>
The polyamic acid in the present invention is a polyimide precursor, and the structure is not particularly limited as long as it forms a polyimide when heat treatment is performed.

  That is, in the present invention, for example, polyamic acid polymerization of a polyimide precursor is performed by reacting one or more diamine compounds represented by the general formula (2) with one or more acid anhydrides represented by the general formula (3). The production method comprises at least the following steps (a) first-stage reaction and (b) second-stage reaction.

H ₂ N—R—NH ₂ (2)
[In the formula, R is an aliphatic group having 2 or more carbon atoms, a cycloaliphatic group, a monocyclic aromatic group, a condensed polycyclic aromatic group, or an aromatic group directly or by a cross-linking member. Represents a divalent group selected from the group consisting of non-condensed polycyclic aromatic groups. ]

[In the formula, R 'is an aliphatic group having 2 or more carbon atoms, a cyclic aliphatic group, a monocyclic aliphatic group, a condensed polycyclic aromatic group, or an aromatic group directly or by a cross-linking member. And a tetravalent group selected from the group consisting of non-condensed polycyclic aromatic groups. ]
(A) First stage reaction: A step of polymerizing amino-terminated polyamic acid (PAA) by adding an acid anhydride less than an equimolar equivalent to the diamine to a diamine dissolved in a polar solvent.
(B) Second stage reaction: The reaction rate R (mol / min) in the first stage reaction defined by the following formula (I) and the acid anhydride addition rate T (mol / min) in the second stage reaction are the following (II ) Step of adding an acid anhydride in an amount such that the molar ratio with the diamine charged in the first stage is equal to or greater than that at the rate satisfying the formula, and reacting with the amino terminal polyamic acid obtained in the first stage reaction .
First stage reaction rate: R (mol / min) = total amount of diamine (mol) / A (min) (I)
Acid anhydride addition rate in the second stage reaction: T (mol / min) <R (mol / min) (II)
Here, A (minute) represents the time until the stirring power in the first-stage reaction is increased and reaches an equilibrium state.

  The polyamic acid in the present invention has a structure represented by a repeating unit as represented by the general formula (4). Here, the N atom of the amide bond and the C atom of the carboxyl group are close to each other, and are preferably in the ortho position in the aromatic ring. Further, the H atom may be substituted with other atoms or atomic groups such as halogen. For example, a suitable example is a polyamic acid in which R 'is an aromatic ring, for example, a benzene ring.

  In this case, the two amide bonds (or carboxyl groups) of R ′ may be in the meta position or in the para position. In some cases, there may be an ortho position. Further, the polyimide precursor may be partially imidized as long as it has a slight ratio.

<Diamine>
In the present invention, the diamine used for producing the polyamic acid has a structure represented by the following general formula (2).

H ₂ N—R—NH ₂ (2)
[In the formula, R is an aliphatic group having 2 or more carbon atoms, a cycloaliphatic group, a monocyclic aromatic group, a condensed polycyclic aromatic group, or an aromatic group directly or by a cross-linking member. Represents a divalent group selected from the group consisting of non-condensed polycyclic aromatic groups. ]

  Although it does not specifically limit as R, A benzene ring is preferable from a heat resistant point. Specific examples of the diamine compound include the following, but are not limited thereto. For example, 2,2-bis (4-amino-phenyl) propane, 2,6-diamino-pyridine, bis- (4-amino-phenyl) diethylsilane, bis- (4-amino-phenyl) diphenylsilane, 1, 3-bis (3-aminopropyl) -1,1,3,3-tetramethyldisiloxane, benzidine, 3,3′-dichloro-benzidine, 3,3′-dimethoxybenzidine, bis- (4-amino-phenyl) ) Ethylphosphine oxide, bis- (4-amino-phenyl) -N-butylamine, bis- (4-amino-phenyl) -N-methylamine, 3,3′-dimethyl-4,4′-diaminodiphenyl, N -(3-aminophenyl) -4-aminobenzamide, 4-aminophenyl-3-aminobenzoic acid, 3,3'-dimethyl-4,4'-diamidine Diphenylmethane, 3,3′-dimethoxy-4,4′-diaminodiphenylmethane, 3,3′-diethoxy-4,4′-diaminodiphenylmethane, 3,3′-dicarboxy-4,4′-diaminodiphenylmethane, 3, 3'-difluoro-4,4'-diaminodiphenylmethane, 3,3'-dichloro-4,4'-diaminodiphenylmethane, 3,3'-dibromo-4,4'-diaminodiphenylmethane, 3,3'-dihydroxy- 4,4′-diaminodiphenylmethane, 3,3′-disulfo-4,4′-diaminodiphenylmethane, 3,3′-dimethyl-4,4′-diaminodiphenyl ether, 3,3′-dimethoxy-4,4′- Diaminodiphenyl ether, bis (3-amino-phenoxyphenyl) sulfone, bis (4-amino-phenyl) Noxyphenyl) sulfone, bis (3-amino-phenoxyphenyl) hexafluoropropane, 3,3′-disulfo-4,4′-diaminodiphenyl sulfide, 3,3′-diaminodiphenylmethane, 3,3′-diaminodiphenyl ether, 3,3′-diaminodiphenylsulfone, 3,3′-diaminodiphenylpropane, 3,3′-diaminodiphenylsulfide, 2,4-diaminotoluene, 2,6-diaminotoluene, p-phenylenediamine, m-phenylene Diamine, 4,4′-diaminodiphenylpropane, 4,4′-diaminodiphenylmethane, 3,3′-diaminobenzophenone, 4,4′-diaminodiphenylsulfide, 4,4′-diaminodiphenylsulfone, 3,4 ′ -Diaminodiphenyl ether 4,4′-diaminodiphenyl ether, 1,5-diaminonaphthalene, 3,3′-dimethoxybenzidine, 2,4-bis (β-amino-t-butyl) toluene, bis-p- (β-amino-t -Butyl) toluene, bis- (p-β-amino-t-butyl-phenyl) ether, bis-p- (β-methyl-δ-amino-pentyl) benzene, bis-p- (1,1-dimethyl- 5-amino-pentyl) benzene, 1-isopropyl-2,4-metaphenylenediamine, m-xylenediamine, 1,4-bis (4-aminophenoxy) benzene, 1,3-bis (4-aminophenoxy) benzene 3,3′-diethoxy-4,4′-diaminodiphenyl ether, 3,3′-dicarboxy-4,4′-diaminodiphenyl ether, 3,3′-dihydride Roxy-4,4′-diaminodiphenyl ether, 3,3′-disulfo-4,4′-diaminophenyl ether, 3,3′-dimethyl-4,4′-diaminodiphenyl sulfone, 3,3′-dimethoxy-4 , 4′-diaminodiphenylsulfone, 3,3′-diethoxy-4,4′-diaminodiphenylsulfone, 3,3′-dicarboxy-4,4′-diaminodiphenylsulfone, 3,3′-dichloro-diaminodiphenyl Sulfone, 3,3′-dihydroxy-4,4′-diaminodiphenyl sulfone, 3,3′-disulfo-4,4′-diaminodiphenyl sulfone, 3,3′-dimethyl-4,4′-diaminodiphenylpropane, 3,3′-dimethoxy-4,4′-diaminodiphenylpropane, 3,3′-diethoxy-4,4′-diamy Diphenylpropane, 3,3′-dicarboxy-4,4′-diaminodiphenylpropane, 3,3′-dichloro-4,4′-diaminodiphenylpropane, 3,3′-dihydroxy-4,4′-diaminodiphenyl Propane, 3,3′-disulfo-4,4′-diaminodiphenylpropane (for some phenylpropane compounds in which the position of the phenyl substituent on the propane skeleton is not described, the position is particularly Although it is not limited and any may be sufficient, it is preferable that it is 1, 3-position), 3,3'-dimethyl-4,4'-diaminodiphenyl sulfide, 3,3'-diethoxy-4,4'-diaminodiphenyl Sulfide, 3,3′-dicarboxy-4,4′-diaminodiphenyl sulfide, 3,3′-dichloro-4 4'-diaminodiphenyl sulfide, 3,3'-dihydroxy-4,4'-diaminodiphenyl sulfide, hexamethylenediamine, heptamethylenediamine, octamethylenediamine, nonamethylenediamine, decamethylenediamine, diamino-propyltetramethylene Diamine, 3-methylheptamethylenediamine, 4,4'-dimethylheptamethylenediamine, 2,11-diamino-dodecane, 1,2-bis- (3-amino-propoxy) -ethane, 2,2-dimethyl -Propylenediamine, 3-methoxy-hexamethylenediamine, 3,3'-dimethylbenzidine, 2,5-dimethylhexamethylenediamine, 2,5-dimethylheptamethylenediamine, 5-methyl-nonamethylenediamine, 2,17 -Diamino-icosa Examples include decane, 1,4-diamino-cyclohexane, 1,10-diamino-1,10-dimethyldecane, 1,12-diamino-octadecane and the like. A mixture of two or more of these diamines can also be used. Of these, 4,4'-diaminodiphenyl ether, 3,3'-diaminodiphenyl sulfone and the like are particularly preferable.

<Acid anhydride>
Moreover, in this invention, the acid anhydride used in order to manufacture a polyamic acid has a structure shown by following General formula (3).

  [In the formula, R 'is an aliphatic group having 2 or more carbon atoms, a cyclic aliphatic group, a monocyclic aliphatic group, a condensed polycyclic aromatic group, or an aromatic group directly or by a cross-linking member. And a tetravalent group selected from the group consisting of non-condensed polycyclic aromatic groups. ]

  R ′ is not particularly limited, but a benzene ring is preferable from the viewpoint of heat resistance. More specific examples of the acid anhydride include pyromellitic dianhydride, 2,2-bis (2,3-dicarboxyphenyl) hexafluoropropane dianhydride, 3,3 ′, 4,4′- Diphenyltetracarboxylic dianhydride, 1,2,5,6-naphthalenetetracarboxylic dianhydride, 2,3,6,7-naphthalenetetracarboxylic dianhydride, 2,2 ′, 3,3′diphenyl Tetracarboxylic dianhydride, 2,2′-bis (3,4-dicarboxyphenyl) propane dianhydride, bis (3,4-dicarboxyphenyl) sulfonic dianhydride, bis (3,4-di Carboxyphenyl) sulfide dianhydride, 3,4,9,10-perylenetetracarboxylic dianhydride, bis (3,4-dicarboxyphenyl) ether dianhydride, naphthalene-1,2,4,5-tetra Rubonic dianhydride, naphthalene-1,4,5,8-tetracarboxylic dianhydride, 2,6-dichloronaphthalene-1,4,5,8-tetracarboxylic dianhydride, 2,7- Dichloronaphthalene-1,4,5,8-tetracarboxylic dianhydride, 2,3,6,7-tetrachloronaphthalene-1,4,5,8-tetracarboxylic dianhydride, phenanthrene-1, 8,9,10-tetracarboxylic dianhydride, 2,2-bis (2,3-dicarboxyphenyl) propane dianhydride, 1,1-bis (2,3-dicarboxyphenyl) ethane dianhydride 1,1-bis (3,4-dicarboxyphenyl) ethane dianhydride, bis (2,3-dicarboxyphenyl) methane dianhydride, bis (3,4-dicarboxyphenyl) methane dianhydride, Bis (3,4-dicarbox Phenyl) sulfone dianhydride, benzene-1,2,3,4-carboxylic dianhydride, 3,4,3 ′, 4′-benzophenonetetracarboxylic dianhydride, 2,3,2 ′, 3 ′ -Benzophenone tetracarboxylic dianhydride, 2,3,3 ', 4'-benzophenone tetracarboxylic dianhydride, pyrazine-2,3,5,6-tetracarboxylic dianhydride, thiophene-2,3 4,5-tetracarboxylic dianhydride, ethylenetetracarboxylic dianhydride, decahydronaphthalene-1,4,5,8-tetracarboxylic dianhydride, 4,8-dimethyl-1,2,3 5,6,7-hexahydronaphthalene-1,2,5,6-tetracarboxylic dianhydride, cyclopentane-1,2,3,4-tetracarboxylic dianhydride, pyrrolidine-2,3,4 , 5-Tetracarboxylic Acid dianhydride, 1,2,3,4-butanetetracarboxylic dianhydride, bicyclo- (2,2,2,)-oct (7) -ene-2,3,5,6-tetracarboxylic acid Dianhydride, 2,3,3 ′, 4′-biphenyltetracarboxylic dianhydride, 3,3,3 ′, 4′-biphenyltetracarboxylic dianhydride, 2,3,2 ′, 3′- Biphenyltetracarboxylic dianhydride, bis (3,4-dicarboxyphenyl) dimethylsilane dianhydride, bis (3,4-dicarboxyphenyl) methylphenylsilane dianhydride, bis (3,4-dicarboxyphenyl) ) Diphenylsilane dianhydride, bis (2,3-dicarboxyphenyl) dimethylsilane dianhydride, 1,4-bis (3,4-dicarboxyphenyldimethylsilyl) benzene dianhydride, 1,3-bis ( 3,4-di Ruboxyphenyl) -1,1,3,3-tetramethyldisiloxane dianhydride, p-phenylene-bis (trimellitic acid monoester acid anhydride), ethylene glycol bis (trimellitic acid anhydride), 2, 2-bis (3,4-dicarboxyphenyl) hexafluoropropane dianhydride, 2,2-bis [4- (3,4-dicarboxyphenoxy) phenyl] hexafluoropropane dianhydride, 4,4′- Examples thereof include bis (3,4-dicarboxyphenoxy) diphenyl sulfide dianhydride, bis [4- (3,4-dicarboxyphenoxy) phenyl] sulfone dianhydride, and the like. Of these, pyromellitic dianhydride, 3,4,3 ', 4'-benzophenonetetracarboxylic dianhydride and the like are particularly preferable.

<Polar solvent>
In the method for producing a polyamic acid of the present invention, the reaction is carried out in a polar solvent. The concentration of the raw material monomer in the reaction and the polyamic acid obtained by the reaction is preferably 0.1 to 40% by weight, and more preferably 1 to 30% by weight.

  Examples of the polar solvent include polar solvents such as N-methyl-2-pyrrolidone, N, N-dimethylacetamide, N, N-dimethylformamide, dimethyl sulfoxide, tetramethylurea, hexamethylphosphoric triamide, and γ-butyrolactone. They can be used alone or in combination. In addition, these polar solvents may be used alone or as a mixed solvent such as ketones, esters, ethers, halogenated hydrocarbons, hydrocarbons, amide compounds containing ethylenically unsaturated bonds, which are general organic solvents. . For example, acetone, methyl ethyl ketone, methyl isobutyl ketone, cyclohexanone, methyl acetate, ethyl acetate, butyl acetate, diethyl oxalate, diethyl malonate, diethyl ether, ethylene glycol dimethyl ether, tetrahydrofuran, dichloromethane, 1,2-dichloroethane, 1,4- Dichlorobutane, trichloroethane, chlorobenzene, o-dichlorobenzene, hexane, heptane, octane, benzene, toluene, xylene, N-methylacrylamide, N-methylmethacrylamide, N-ethylmethacrylamide, N, N-dimethylacrylamide, N, N-diethylacrylamide, N-acryloylmorpholine, N-vinylpyrrolidone and the like may be mixed. Of these, diethyl ether and ethylene glycol dimethyl ether are particularly preferred.

<Formation of polyamic acid>
In the method for producing a polyamic acid of the present invention, an acid anhydride is added to a diamine previously dissolved in a polar solvent. Since acid anhydrides are easily deactivated by moisture, it is not preferable to keep them dissolved in a solvent. It is preferable to immediately react with a diamine compound when dissolved in a solvent. Therefore, it is not preferable to dissolve an acid anhydride in a solvent in advance and then add a diamine to the acid anhydride or dissolve it in a solvent in advance when adding the acid anhydride.

  In the production method of the present invention, at least at the beginning of the reaction, an acid anhydride is added to a polar solvent in which a diamine that is a raw material of polyamic acid is dissolved, whereby the diamine and the acid anhydride react to produce a polyamic acid. A method is preferred in which the diamine used for the reaction is dissolved in a polar solvent in advance so that the acid anhydride that is easily deactivated readily reacts with the diamine, and then the addition of the acid anhydride is started.

  The reaction system is preferably maintained at 0 to 30 ° C. However, depending on the selection of the monomer, the temperature may be maintained at 30 to 90 (more preferably 60 to 90) ° C. The reaction in such a temperature range is preferable because the viscosity of the reaction system can be adjusted to an appropriate range, the reaction rate can be appropriately controlled, and the progress of imidization can be suppressed. Moreover, it is preferable that the reaction system is always stirred with a stirring blade or the like.

  In order to prevent moisture from entering, it is preferable to proceed the reaction in an inert gas atmosphere such as dry nitrogen.

<Molar ratio of raw materials>
The diamine and acid anhydride are preferably reacted in the range of acid / diamine (molar equivalent ratio) = 1.05 to 0.95, more preferably ideally acid / diamine (molar equivalent ratio) = 1. 000.

  By adopting the method of controlling the addition rate of the acid anhydride in the second stage reaction of the present invention, even when the acid / diamine (molar equivalence ratio) may deviate from 1.000, a stable polymerization degree can be obtained. A polyamic acid can be obtained.

  In the present invention, it is possible to solve the problem relating to the adjustment of the degree of polymerization that occurs in the conventional production method (a method in which a diamine is dissolved in a solvent and a powdered acid anhydride is added). That is, a method of adding acid anhydrides separately, adding a mixture of powdered diamine and acid anhydride to the solvent, or a method of adding diamine and acid anhydride powder to the alternately stirred solvent and reacting them. For example, a means for changing the addition procedure such as a method of adding an acid dissolved in a solvent in advance cannot stably produce a polyamic acid having a high polymerization degree.

  That is, in order to obtain a polyamic acid having a high degree of polymerization by the conventional method, the acid / diamine molar ratio must be essentially 1.000. However, it was very difficult to accurately set the acid / diamine (molar equivalent ratio) to 1.000.

  That is, the diamine and the acid anhydride are reacted in a system in which the diamine is excessive in the first stage reaction, preferably in a system where the acid anhydride / diamine (molar equivalent ratio) is 0.93 to 0.99, An amino-terminated polyamic acid is obtained. Thereafter, when the acid anhydride is additionally added as the second stage reaction, it is important to add the acid anhydride at a rate slower than the reaction rate of the acid anhydride / diamine in the first stage reaction. By adopting such a method, a polyamic acid having a high degree of polymerization can be obtained even if the molar equivalent ratio of acid anhydride / diamine deviates from either 1.000.

  For example, even if the acid anhydride added in the second stage reaction is excessively added and the acid / diamine (molar equivalent ratio) exceeds 1, the polyamic acid having a high degree of polymerization was once polymerized. After that, no decrease in the degree of polymerization is observed. Furthermore, it was found that the degree of polyamic acid polymerization finally reached can be adjusted by changing the addition rate (mol / min) of the second-stage reaction.

  That is, the important point in the present invention is the rate of addition of acid anhydride in the second stage reaction.

The acid anhydride addition rate in the second-stage reaction is determined by the reaction rate R (mol / min) in the first-stage reaction defined by the following formula (I) and the acid anhydride addition rate T (mol / min) in the second-stage reaction. ) Is a speed satisfying the following formula (II).
First stage reaction rate: R (mol / min) = total amount of diamine (mol) / A (min) (I)
Acid anhydride addition rate in the second stage reaction: T (mol / min) <R (mol / min) (II)
Here, A (minute) represents the time until the stirring power in the first-stage reaction is increased and reaches an equilibrium state.

<Mole equivalent ratio of diamine / acid anhydride in the first stage reaction>
In the first stage reaction, it is important to react less than an equimolar equivalent of an acid anhydride with respect to the diamine. Here, the acid anhydride is preferably 93 to 99 molar equivalents relative to 100 molar equivalents of the diamine.

<Second stage reaction>
In the second stage reaction, the acid anhydride deficient in the first stage reaction is additionally added at a rate slower than the reaction rate of the first stage reaction as described above. By adopting such an addition method, it is possible to stably produce a polyamic acid having a high degree of polymerization.

  This is because the first stage reaction is carried out with an excess of diamine, so the terminal group of the polyamic acid obtained by the first stage reaction becomes an amino group, and if it is an amino terminal polyamic acid, it will be affected by the moisture in the polar solvent. This is because the reaction of the acid anhydride / diamine can be continued by adding an acid anhydride.

  Conversely, when polyamic acid is generated in an acid anhydride-excess system, the terminal group of the polyamic acid becomes an acid anhydride terminal and is deactivated by moisture in the polar solvent, and then additional diamine is added. However, the reaction does not proceed more than this, and a polyamic acid having a high degree of polymerization cannot be obtained.

  In the method of adding an acid anhydride in two stages according to the present invention, the amount of acid anhydride added in the first stage must be an amount that makes a diamine-excess system.

  In order to shorten the time required for the additional addition of the acid anhydride, considering that the acid anhydride is added at a rate slower than the reaction rate of the first stage, it is sufficient if the diamine has an excess of diamine. The amount of acid anhydride added in the first stage is preferably 0.93 to 0.99, more preferably 0.95 to 0.98 in terms of acid anhydride / diamine (molar equivalent ratio).

<First stage reaction rate (R)>
In the determination of the end of the first stage reaction, it is determined that the end of the reaction is no longer observed. That is, the time when the power for stirring the reaction system liquid rises and reaches an equilibrium state is terminated. At this time, the time is measured simultaneously with the start of charging of the entire amount of the acid anhydride added to the first stage, and the time until the stirring power is increased and stabilized and the equilibrium state is reached is defined as A minute.

  At this time, whether the equilibrium has been reached depends on whether the value of the dynamometer (kw) or torque meter (A, ampere) of the stirring motor does not increase or the rate of change in the numerical value of the dynamometer or ampere meter is 20 It is assumed that the rate of change in numerical value per second is within 5% (± 5% / 20 sec).

<Second stage acid anhydride addition rate (T)>
In the present invention, as the second-stage reaction, the insufficient acid anhydride is additionally added to the diamine charged in the first stage at a rate slower than the first-stage reaction rate. Moreover, when adding two or more types of acid anhydrides, it is preferable not to add sequentially but to mix and add simultaneously. Thereby, it can also prevent that different acid anhydrides become non-uniform | heterogenous. As a method of mixing and using two or more types of acid anhydrides, it is preferable to use a method of mixing two or more types of acid anhydrides in one container in advance and then adding them to the reaction system.

  On the other hand, when the addition rate of the second stage acid anhydride is equal to or faster than the first stage reaction rate (ie, when T ≦ R), the degree of polymerization of the resulting polyamic acid is stabilized. Can not be high.

  By adopting the method according to the present invention, a polyamic acid having a high degree of polymerization can be stably obtained. This method is particularly effective for a large scale such as factory production. Accordingly, the scale to which the production method of the present invention is applied is particularly effective when the scale level is preferably 10 L (more preferably 50 L) or more, and the amount of each monomer is 200 g to 50 kg or more. is there.

<Moisture content contained in polar solvent>
The polar solvent used in the production method of the present invention preferably has a water content of 100 to 1000 ppm. That is, even if the acid anhydride added in the second stage is added excessively to the diamine that was previously present in the system, there is some moisture in the polar solvent that is the polymerization solvent. Thus, when the acid anhydride becomes excessive, there is an effect that the acid anhydride is deactivated by moisture in the polar solvent and an undesirable reaction is prevented.

  Once the degree of polymerization is increased, the polyamic acid does not decrease the degree of polymerization even if an excess of acid anhydride is present in the system, but it is preferable that the excess of acid anhydride is deactivated. Usually, in a reaction system involving an acid anhydride, it is necessary to manage the moisture in the polar solvent as low as possible in order to prevent the deactivation of the acid anhydride, but the production method of the present invention is surprising. It should be understood that the present invention can be carried out without any problem even when 100 to 1000 ppm of water is present in the polar solvent.

  This is remarkable in a reaction system using PMDA as an acid anhydride and DDE as a diamine. This is considered to be because in the reaction between PMDA and DDE, the reaction rate of the acid anhydride and the water contained in the polar solvent is faster than the reaction rate of the acid anhydride / diamine. At this time, it has been found that the presence of water in the range of 100 to 1000 ppm contained in the polar solvent is preferable for inactivating excess acid anhydride and stably producing polyamic acid. On the other hand, in order to carry out the first stage reaction stably, the water content in the polar solvent is preferably 100 to 500 ppm.

  The water content in the polar solvent can be controlled using a desiccant such as molecular sieve.

<Method for measuring moisture contained in polar solvent>
The moisture content contained in the polar solvent is measured using an AQ-6 type trace moisture measuring device (Karl Fischer coulometric titration automatic moisture measuring device) manufactured by Hiranuma Sangyo Co., Ltd. according to JIS K0068: 2001.

  The measurement was performed by injecting 1 ml of a polar solvent to be measured into a measuring device using a syringe. As the electrolytic solution, HYDANAL Coulomat AK (Hayashi Junyaku Kogyo Co., Ltd.) was used as the generation solution, and HYDRANAL Coulomat CK (Hayashi Junyaku Kogyo Co., Ltd.) was used as the counter electrode solution.

The water content of the polar solvent was calculated by the following equation (5) using the measured water content (μg) of AQ-6.
Moisture content (ppm) = measured water content (μg) / [sampling amount (1 ml) × specific gravity of sample solution] (5)

  The polar solvent containing a polyamic acid having a high degree of polymerization obtained by the production method of the present invention can be used as it is as a varnish. Depending on the concentration of the polyamic acid in the polar solvent, the solution viscosity becomes extremely high, and when it is unsuitable for use as a varnish as it is, especially when used for an electronic device, a membrane having a pore size of 0.1 to 5 μm It is preferable to carry out microfiltration with a filter to remove fine foreign matters in the polar solvent. For this reason, when the viscosity increases, microfiltration takes an enormous amount of time, resulting in a problem that the productivity is significantly reduced.

  Therefore, once the desired degree of polymerization is reached, a solvent can be added to adjust the viscosity. After the addition of the second-stage acid anhydride, the reaction end time can be defined as the time when the reaction system liquid reaches a predetermined viscosity. Further, the concentration of the polyamic acid in the polyamic acid solution in the present invention is preferably 0.1 to 40% by weight, more preferably 1 to 30% by weight. In this case, the viscosity of the reaction system liquid is preferably 0. It is preferable to adjust so that the reaction is terminated when the pressure reaches 1 to 30 (more preferably 1 to 20, more preferably 2 to 10) Pa · s.

  That is, after the second-stage reaction is completed and a polyamic acid having a desired high degree of polymerization is obtained, a polar solvent can be added to adjust the viscosity as a solution.

  Alternatively, the polymerization concentration can be lowered in advance. Alternatively, by adjusting the acid anhydride addition rate T in the second-stage reaction, a product having a desired solution viscosity can be stably obtained.

  As post-treatment for terminating the reaction, it is preferable to cool the jacket of the reaction vessel with cooling water or the like in order to prevent the reaction from proceeding further and the viscosity becoming too high.

<Logarithmic viscosity (ηinh)>
The logarithmic viscosity of the polyamic acid polymer in the present invention is measured according to JIS K7367-1 (2002).

  For example, when the polymerization is performed at a monomer concentration of 10 wt%, the concentration of the polyamic acid polymer in the N-methyl-2-pyrrolidone solvent of the polymerization solvent is also 10 wt%, so that 2.5 g of the polymerization solution, that is, the resin amount is 0.25 g. A considerable amount of the polymerization solution is collected in a measuring flask, diluted with 50 ml of N-methyl-2-pyrrolidone to 50 ml, and measured at 30 ° C. using an Ubbelohde viscometer. Specifically, the measurement is performed as follows.

A 50 ml volumetric flask is weighed with a balance (accuracy 0.1 mg) so that the polymerization liquid corresponding to the resin volume 0.25 g is not absorbed (the value of this resin amount is x (g)). Transfer and add 40 ml of N-methyl-2-pyrrolidone solvent and shake until the resin is dissolved (at this time the temperature of the solution should not be dissolved by heating to 30 ° C. or higher). After dissolution is completed, the solution is fixedly dissolved in 50 ml to prepare a N-methyl-2-pyrrolidone solution having a resin concentration of C (g / dl).
C (g / dl) = x (g) / 50 (ml)
The Ubbelohde viscometer is fixed in a thermostat controlled at 30 ° C. ± 0.05 ° C., and the flow time (t) of the prepared resin solution and the flow time (t0) of the solvent N-methyl-pyrrolidone are measured. The logarithmic viscosity represented by the formula is determined.
ηinh (dl / g) = ln (t / t0) / C

  EXAMPLES Hereinafter, although this invention is demonstrated concretely based on an Example, this invention is not limited to these.

  Example 1 250.8 g (1.25 mol) of 4,4′-diaminodiphenyl ether (DDE) was dissolved at 10 ° C. in 4067 g of dimethylacetamide (DMAC) having a moisture content of 230 ppm.

  Next, assuming that the set molar ratio is acid / diamine molar ratio = 1.001, the first stage pyromellitic dianhydride (PMDA) is 97.5 mol% equivalent to the total amount of DDE 1.25 mol. ) 1.2188 mol (265.83 g), 0.0325 mol (7.089 g) was weighed as the second stage PMDA.

  Next, 265.83 g of pyromellitic dianhydride powder in the first stage was added all at once. Next, the stirring power (stirring motor kw) of the stirring blade of the polymerization liquid was confirmed, and the time A (min) until the stirring power increased and stabilized and reached an equilibrium state was 14 minutes. Next, the number of moles of acid monomer added in the first stage, 1.2188 mol, was divided by 14 minutes of time A to obtain the first stage reaction rate (R), and 0.087 mol / min was obtained.

  Next, 0.0325 mol (7.089 g) of PMDA in the second stage was added over 10 minutes so that the addition rate (T) in the second stage was slower than (R). At this time, R is 0.0325 mol / 10 min = 0.003 mol / min. Accordingly, the second stage addition rate (R) <(T), and the additional addition could be performed at a rate slower than the apparent acid / diamine reaction rate in the first stage.

  The next agitation power was confirmed, and the viscosity of the system further increased, and the agitation power increased and stabilized until it reached an equilibrium state.

  Thereafter, the polymerization solution of the system was sampled, and ηinh of the polyamic acid was measured. As a result, it was 2.85 (dl / g).

  Examples 2 to 14 and Comparative Examples 1 to 11 were carried out in the same manner as in Example 1 under the conditions shown in Table 3.

  Of these, Example 15 was prepared by adding 3.08 g of distilled water in advance to 4004 g of DMAC and stirring so that the water content of the polar solvent as the polymerization solvent was about 1000 ppm. As a result of sampling the solvent and measuring the water content in the solvent, it was 990 ppm. Other than that was carried out under the conditions shown in Table 3 in the same manner as in Example 1.

  In Example 16, 12.0 g of distilled water was added in advance to 3995 g of DMAC and stirred so that the water content of the polar solvent as the polymerization solvent was about 3000 ppm. As a result of sampling the solvent and measuring the water content in the solvent, it was 3120 ppm. Other than that was carried out under the conditions shown in Table 3 in the same manner as in Example 1. .

Symbols in Table 3:
BPDA: biphenyl-3,4,3 ′, 4′-tetracarboxylic dianhydride BTDA: benzophenone-3,4,3 ′, 4′-tetracarboxylic dianhydride DDM: 4,4′-diaminodiphenylmethane Comparative Example In Nos. 8 to 11, one active addition was made without adding the acid component in two stages.

  The “charging time” of the first stage acid in the table is the time taken from the start of charging to completion of charging, and the equilibrium time (R) of the acid / diamine reaction reaches equilibrium from the start of charging of acid. It was time.

  As shown in Table 3, in particular, in the method of adding a powder acid anhydride after dissolving diamine in a solvent, the relationship between the Flory acid / diamine monomer molar ratio and the polymerization degree of the polyamic acid is It was found to depend on the addition time.

  That is, for example, as shown in Comparative Examples 1 to 11, when the acid / diamine molar ratio deviates from 1.000 by means of batch addition or rapid addition of acid anhydrides, the degree of polymerization of polyamic acid is low, corresponding to the molar ratio. Surprisingly, in Examples 1 to 14 using the means of the present invention, the acid / diamine molar ratio greatly deviates from 1.000, and is 1.010 or 1.050. However, a polyamic acid having a high degree of polymerization could be obtained.

  Furthermore, it can be seen that the reached ηinh depends on the second stage addition rate. For example, in the second stage addition time of 10 minutes ((T) ≈0.01 mol / min) in Examples 6-8, the second stage addition in Examples 9-11 can be adjusted to ηinh≈2.8. In a time of 15 minutes ((T) ≈0.002 mol / min), it was possible to adjust ηinh≈3.3.

  That is, by adopting the method of the present invention, a polyamic acid having a desired degree of polymerization (ηinh) can be produced even if the molar ratio deviates from 1.000 due to monomer purity or monomer weighing error.

  Therefore, in the conventional method, monomer purity (error between analytical value and actual value), measurement error (accuracy of measuring instrument, adhesion to measuring instrument, etc.), charging error (exiting system due to accompanying air at the time of charging) , Etc.), and it could not be easily adjusted to a high degree of polymerization, but by controlling the charging rate of the second stage acid anhydride by the method of the present invention, in particular, Even when the molar ratio of diamine / acid anhydride was shifted, a polyamic acid having a high degree of polymerization could be obtained.

  Even when the amount of the acid anhydride added in the second stage is insufficient and the desired degree of polymerization cannot be reached, that is, when the acid / diamine molar ratio cannot reach 1.000, the acid anhydride is added. By additionally adding at the addition rate of the invention, a polyamic acid with a high degree of polymerization can be obtained.

  By using the polyamic acid production method of the present invention, it is not necessary to precisely measure or precisely adjust the amount of monomer charged, and the addition rate of the acid anhydride that is simply added in the second stage is within the range that satisfies the conditions of the present invention. By controlling, a polyamic acid having a desired degree of polymerization can be stably produced.

  The polyamic acid thus obtained can be used in various fields such as a film, an electric wire varnish, a coverlay, a coating material, an adhesive, or a composite material by impregnating a fibrous reinforcing material. At that time, the polyamic acid is further heated to 100 to 300 ° C. or used by ring-closing imidization using a dehydrating agent such as acetic anhydride.

  Adjustment of the polymerization degree of polyamic acid is more difficult as the degree of polymerization is higher, but in order for the final product polyimide obtained from polyamic acid to have sufficient mechanical strength, excellent electrical properties, etc., its precursor, namely polyamic acid, is required. The acid must have a sufficiently large molecular weight. Further, the molecular weight is not limited to just a large molecular weight, and as with other engineering plastics, for example, it is preferable that the degree of polymerization is stable and uniform for each grade. It is a serious issue.

  For example, in a polyimide film, it is necessary to form a polyamic acid film, but in order to obtain a polyamic acid film having a uniform film thickness and good reproducibility, it is first important to control the viscosity of the polyamic acid solution. When spin coating polyamic acid on a substrate such as silicon for applications, the desired film thickness is controlled by the solution viscosity (polyamic acid molecular weight) and the number of rotations of the rotating plate, so control of the molecular weight of the polyamic acid is a critical issue. .

  More specifically, in the case of the polyamic acid represented by the repeating unit of the formula (1), in order for the final produced polyimide to have satisfactory physical properties, the logarithmic viscosity ηinh (concentration 0 in N-methyl-2-pyrrolidone solvent) 0.5 g / 100 ml solvent, measured at 35 ° C.) is 0.5 or more, preferably 0.8 to 2.0, particularly 2.0 to 3.5 for molding applications.

  Here, in order to stably produce a polyamic acid having, for example, ηinh 2.5, 3.0, or ηinh = 1.8 as an index of the degree of polymerization, the conventionally disclosed method can be easily and stably produced. However, the degree of polymerization was adjusted by precise measurement of the charged amount, or by determining the degree of polymerization (solution viscosity of the polymer) during the polymerization to determine the amount of additional addition, and there was no method with excellent productivity.

  According to the present invention, it is possible to provide a method for adjusting the degree of polymerization of polyamic acid stably and easily to a high degree of polymerization. Varnishes, films, powders for molding, varnishes for electric wires, coverlays, coating materials produced from polyamic acid, Although applicable to adhesives, the application range is not limited to these.

It is a graph showing the relationship between an acid anhydride / diamine molar equivalent ratio and a polymerization degree.

Claims (5)

A method for producing a polyamic acid comprising the following steps (a) and (b) when a diamine and an acid anhydride are reacted to produce a polyamic acid.
(A) First stage reaction: A step of polymerizing amino-terminated polyamic acid (PAA) by adding an acid anhydride less than an equimolar equivalent to the diamine to a diamine dissolved in a polar solvent.
(B) Second stage reaction: The reaction rate R (mol / min) in the first stage reaction defined by the following formula (I) and the acid anhydride addition rate T (mol / min) in the second stage reaction are the following (II ) Step of adding an acid anhydride in an amount such that the molar ratio with the diamine charged in the first stage is equal to or greater than that at the rate satisfying the formula, and reacting with the amino terminal polyamic acid obtained in the first stage reaction .
First stage reaction rate: R (mol / min) = total amount of diamine (mol) / A (min) (I)
Acid anhydride addition rate in the second stage reaction: T (mol / min) <R (mol / min) (II)
Here, A (minute) represents the time until the stirring power in the first-stage reaction is increased and reaches an equilibrium state. The method for producing a polyamic acid according to claim 1, wherein the addition amount of the acid anhydride in the first stage reaction is 93 to 99 molar equivalents relative to 100 molar equivalents of the diamine. 3. The method for producing a polyamic acid according to claim 1, wherein a water content contained in the polar solvent is 100 to 1000 ppm. The method for producing a polyamic acid according to any one of claims 1 to 3, wherein the diamine is 4,4'-diaminodiphenyl ether. The method for producing a polyamic acid according to any one of claims 1 to 4, wherein the acid anhydride is pyromellitic dianhydride.

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