JPH0733872A - Production of polyimide precursor powder - Google Patents

Abstract

PURPOSE:To easily obtain the subject powder having high polymerization degree and excellent mechanical properties and useful for a molded article having low residual solvent content by polymerizing a tetracarboxylic acid dianhydride with a diamine in a water-soluble nitrile compound as an easily removable reaction solvent. CONSTITUTION:This powder is produced by dissolving or suspending a tetracarboxylic acid dianhydride in a water-soluble nitrile compound (preferably acetonitrile), adding a diamine, polymerizing at -20 to +50 deg.C (especially preferably 0-20 deg.C) and removing the solvent from the polymer.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a polyimide precursor powder or granular material.

[0002]

Conventionally, for example, polyamic acid which is a typical polyimide precursor is N, N-dimethylformamide, N-methyl-2-pyrrolidone, hexamethylphosphoramide, N-methylcaprolactam, dimethylsulfoxide, It has been produced by a low temperature solution polymerization method in a so-called aprotic polar solvent that strongly solvates with polyamic acids such as N-acetyl-2-pyrrolidone and N, N-dimethylacetamide.

Japanese Patent Publication No. 39-22196, Japanese Patent Publication No. 3
9-30060, JP-A-60-212425, JP-A-61-234, and JP-A-61-2500.
No. 30 and JP-A No. 2-18420, polyimide powder particles are prepared by adding a poor solvent such as acetone and ethyl acetate and a ring-closing agent such as acetic anhydride and pyridine to an aprotic polar solvent solution of a polyimide precursor. There is disclosed a method for obtaining a polyimide precursor and a method for obtaining a polyimide precursor powder by mixing an aprotic polar solvent solution of a polyimide precursor with acetone or a halogenated hydrocarbon. However, in these production methods, it is difficult to remove the solvent, and from the obtained polyimide powder particles or polyimide precursor powder particles, a good molded product cannot be obtained unless a special molding method is used. Had the problem.

As a method for solving these problems, a method is known in which polymerization is carried out using a solvent having a low boiling point, such as tetrahydrofuran, which can be easily removed, to produce a polyimide precursor powder. (Industrial Chemistry Magazine,
Volume 71, Issue 9, 1559-1564, 1968, J. Appl. Polymer S
ci., vol.11,609-627,1967). According to this method, it is possible to obtain a polyimide precursor powder which does not contain an aprotic polar solvent which strongly solvates with the polyimide precursor, but the degree of polymerization thereof is low and is 0.5 to 0 at most. There is a problem that only polyimide having an intrinsic viscosity of about 0.6 can be obtained, and the polyimide molded body cannot obtain sufficient mechanical properties.

[0005]

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide a method for producing a polyimide precursor powder which can easily remove a solvent and obtain a polyimide precursor powder having a high degree of polymerization. To provide.

[0006]

Means for Solving the Problems As a result of intensive studies to solve the above problems, the present inventors have found that when a tetracarboxylic dianhydride and a diamine are polymerized in a water-soluble nitrile, an interaction with a solvent occurs. The amount of the polyimide precursor is small and, in combination with the high vapor pressure, makes it easy to remove the solvent, and a polyimide precursor powder having an intrinsic viscosity of 0.7 or more is obtained. Further, this polyimide precursor is excellent in moldability and can be obtained. We obtained the knowledge that the molded product has excellent mechanical properties and no residual solvent,
The present invention has been accomplished based on such findings.

That is, the gist of the present invention is a method for producing powdery particles of a polyimide precursor characterized by polymerizing tetracarboxylic dianhydride and diamine in a water-soluble nitrile.

The present invention will be described in detail below. In the present invention, the polyimide precursor is cyclized by heating or chemical action to form a polyimide, and is 60 mol% or more, preferably 70 mol% or more of the repeating unit of the polymer chain.
More preferably, 80 mol% or more is an organic polymer having a polyimide structure, and any polymer may be used as long as it forms a non-thermoplastic polyimide by ring closure. As a method of ring-closing, a conventionally known method such as a method by heating or a method using a ring-closing agent such as acetic anhydride or pyridine can be applied.

In the present invention, the preferred polyimide precursors include wholly aromatic polyimide precursors,
A homopolymer or copolymer of an aromatic polyamic acid having a repeating unit represented by the general formula (1) is particularly preferable.

[0010]

[Chemical 1]

Here, R represents a tetravalent aromatic residue containing at least one 6-membered carbon ring, and two of the 4-valent aromatic residues form a pair, and adjacent carbon atoms in the 6-membered carbon ring form a pair. Are bound to. Specific examples of R include the following.

[0012]

[Chemical 2]

Particularly, R is preferably the following.

[0014]

[Chemical 3]

R'represents a divalent aromatic residue having a 1 to 4 carbon 6-membered ring. Specific examples of R'include the following.

[0016]

[Chemical 4]

[0017]

[Chemical 5]

Further, the following are particularly preferable as R '.

[0019]

[Chemical 6]

According to the production method of the present invention, a polyimide precursor having an intrinsic viscosity [η] of 0.5 or more can be obtained.
Considering mechanical properties such as strength and elastic modulus of the molded body, it is 0.
It is preferably 7 or more, and particularly preferably 1.0 or more. The larger the value of [η] is, the easier it is to obtain a product having excellent properties such as strength and elastic modulus when closed. [Η] is a value directly related to the molecular weight of the polymer,
It is measured at 30 ° C. in a N, N-dimethylacetamide solvent at a polyimide precursor concentration of 0.5% by weight. [Η] can be calculated by measuring the time for the polymer solution to flow through a constant volume capillary of a standard viscometer and the time for the solvent alone to flow, using the following equation. Where c
Is the polyimide precursor concentration.

[0021]

[Equation 1]

In the present invention, a tetracarboxylic dianhydride is dissolved or suspended in water-soluble nitriles, and a diamine is added and polymerized to obtain a polyimide precursor. Among the water-soluble nitriles, preferred solvents include acetonitrile and propionitrile, with acetonitrile being preferred. Further, other solvents may be mixed within a range that does not impair the effects of the present invention.

The reaction temperature is -20 to 50 ° C., especially 0 to 2
0 ° C is preferred. Further, as is known, the charging ratio of tetracarboxylic dianhydride and diamine correlates with the degree of polymerization of the polyimide precursor to be generated, and in order to obtain a polyimide precursor with a high degree of polymerization, it is necessary to charge it in the equimolar vicinity. preferable. The resulting polyimide precursor does not dissolve in the solvent used,
Since it is in a suspended state in the solvent, the solvent is removed by a usual method such as filtration and drying to obtain a polyimide precursor powder. At this time, in the present invention, since a solvent that does not strongly interact with the polyimide precursor is used, it is easy to remove the solvent, and a solvent-free polyimide precursor powder is obtained even by a normal drying method.

At this time, the solvent is not completely removed,
Alternatively, the powdery particles of the polyimide precursor are mixed with the solvent again and stored in this state, so that the stability of the polyimide precursor with time is maintained. That is, in a suspension composed of the polyimide precursor powder and the water-soluble nitriles, the stability of the polyimide precursor powder with time is maintained.
The polyimide precursor powder may have any shape such as spherical shape, irregular shape, or fibrous shape. The particle size is 100μ
Those containing 80% by weight or more of m or less are preferable.

As a method for molding the powder particles of the polyimide precursor, a conventionally known method, that is, by heating and pressurizing the polyimide precursor particles constituting the powder particles of the polyimide precursor to ring-close the powder particles, May be bonded and molded, or a part of the polyimide precursor may be ring-closed to be converted into polyimide, and then heated and pressed to mold.

For example, in the former case, 20 to 300
30 ° C. after molding at 500 to 5000 kg / cm ²
A compact is obtained by sintering at 0 to 400 ° C. in vacuum or in nitrogen. In the latter case, the powder of the polyimide precursor is converted into the powder of polyimide at 150 to 200 ° C. for 3 to 10 hours, and then 250 to 300 ° C.
Press molding is performed at a pressure of 00 to 3000 kg / cm ² to obtain a molded body. Here, when the polyimide precursor is ring-closed, the conversion rate to polyimide can be arbitrarily controlled by controlling the addition amount of the ring-closing agent, or by controlling the heating temperature and the heating time.

[0027]

EXAMPLES The present invention will be specifically described below with reference to examples. Each characteristic value was obtained as follows.

(1) Particle size of powder and granules: Measured by laser diffraction / scattering type particle size distribution measurement (LA-500 manufactured by Horiba Ltd.).

(2) Imidization ratio: Absorbance ratio at 604 cm ^-1 and 880 cm ^-1 of infrared absorption spectrum (absorbance ratio of 0.
The imidization ratio was 100% at 804).

(3) Surface area: The number of square meters per gram of polyimide powder granules obtained from the nitrogen adsorption amount by the BET adsorption method.

(4) Strength: A polyimide powder was molded and evaluated by a bending test (JIS-K7203).

Example 1 4.39 g of pyromellitic dianhydride (PMDA) and 4.01 g of diaminodiphenyl ether (DAD)
When 100 g of acetonitrile was added to E) and stirred at 25 ° C. for 10 hours, a yellow suspension was obtained. The suspension was filtered under reduced pressure to obtain a yellow polyimide precursor powder having the characteristic values shown in Table 1. Further, this was dried under reduced pressure at 60 ° C. for 1 hour and then imidized at 180 ° C. for 10 hours to obtain a polyimide powder (imidization ratio 74%). This polyimide powder or granule was filled in a mold for making a bending test piece, and was pressed on a press plate heated to 300 ° C. for 10 minutes.
When a bending test piece was prepared by compression molding at a pressure of 00 Kg / cm ² for 30 minutes, a bending test was performed, the density was 1.4.
The bending strength was 2 g / cm ³ , the bending strength was 860 kgf / cm ² , and the bending elastic modulus was 29500 kgf / cm ² .

Example 2 300 g of acetonitrile was cooled to 5 ° C., and 26.
Suspend 3g of PMDA and add 24.0g of DAD
E was added all at once and stirring was continued for 1 hour. Stop cooling,
When stirring was continued for another 2 hours, a yellow suspension was obtained. The suspension was filtered under reduced pressure to obtain a yellow polyimide precursor powder having the characteristic values shown in Table 1.
Further, a polyimide powder was obtained in the same manner as in Example 1 (72% imidization ratio).

[0034]

[Table 1]

[0035]

According to the manufacturing method of the present invention, the solvent can be easily removed, and the powdery particles of the polyimide precursor having a high degree of polymerization can be easily manufactured. Further, the molded product obtained from the powdery particles of the polyimide precursor has excellent mechanical properties and a small residual solvent.

Claims (1)

[Claims] 1. A method for producing a polyimide precursor powder, which comprises polymerizing a tetracarboxylic dianhydride and a diamine in a water-soluble nitrile.