JP3386856B2 - Method for producing powdery polyimide precursor - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a polyimide precursor powder. [0002] Conventionally, polyamic acids which are typical polyimide precursors include N, N-dimethylformamide and N-N-dimethylformamide.
In a so-called aprotic polar solvent which strongly solvates with polyamic acids such as methyl-2-pyrrolidone, hexamethylphosphoramide, N-methylcaprolactam, dimethylsulfoxide, N-acetyl-2-pyrrolidone, N, N-dimethylacetamide And produced by a low-temperature solution polymerization method. [0003] Japanese Patent Publication No. 39-22196, Japanese Patent Publication No. 3
JP-A-9-30060, JP-A-60-221425, JP-A-61-234, JP-A-61-2500
No. 30, JP-A-2-18420, a poor solvent such as acetone and ethyl acetate and a ring-closing agent such as acetic anhydride and pyridine are added to an aprotic polar solvent solution of a polyimide precursor. Disclosed are a method of obtaining a polyimide precursor, and a method of mixing a solution of a polyimide precursor in an aprotic polar solvent with acetone or a halogenated hydrocarbon to obtain a powder of a polyimide precursor. However, in these production methods, it is difficult to remove the solvent, and from the obtained polyimide powder or polyimide precursor powder, a good molded product can be obtained unless a special molding method is used. There was a problem that it was not possible. As a method for solving these problems, there is known a method in which a polymerization reaction is carried out using a solvent having a low boiling point and easy to remove the solvent, such as tetrahydrofuran, to produce polyimide precursor particles. (Industrial Chemistry Magazine, Vol. 71, No. 9, pp. 1559-1564, 1968, J. Appl. Polym
er Sci., vol. 11, 609-627, 1967). According to this method, it is possible to obtain a polyimide precursor powder that does not contain an aprotic polar solvent that is strongly solvated with the polyimide precursor, but the degree of polymerization is low, and at most 0.5 to
There was a problem that only a material having an intrinsic viscosity of about 0.6 was obtained, and the polyimide molded product could not obtain sufficient mechanical properties. SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a polyimide precursor powder / granule which can easily remove a solvent and has a high degree of polymerization. It is to provide a manufacturing method. Means for Solving the Problems As a result of intensive studies to solve the above problems, the present inventors have found that polymerization of tetracarboxylic dianhydride and diamine in water-soluble ketones leads to The interaction is small, and the solvent removal is easy due to the high vapor pressure, and a powder of a polyimide precursor having an intrinsic viscosity of 0.7 or more is obtained. Excellent in mechanical properties
The inventors have found that a molded article having no residual solvent can be obtained, and have reached the present invention based on the finding. That is, the gist of the present invention is a method for producing a polyimide precursor powder, characterized by polymerizing tetracarboxylic dianhydride and diamine in a water-soluble ketone. Hereinafter, the present invention will be described in detail. In the present invention, the polyimide precursor is a polyimide that is closed by heating or a chemical action to form a polyimide, and 60 mol% or more, preferably 70 mol% or more of the repeating unit of the polymer chain,
More preferably, it refers to an organic polymer in which at least 80 mol% has a polyimide structure, and any polymer may be used as long as it is closed to form a non-thermoplastic polyimide. As a method for ring closure, a conventionally known method such as a method by heating, a method using a ring closing agent such as acetic anhydride or pyridine, or the like can be applied. In the present invention, preferred polyimide precursors include wholly aromatic polyimide precursors,
Particularly, an aromatic polyamic acid homopolymer or copolymer having a repeating unit represented by the general formula (1) is preferable. [0010] Here, R represents a tetravalent aromatic residue containing at least one six-membered carbon ring, and two of the four valences form a pair, and adjacent carbon atoms in the six-membered carbon ring Is bound to. Specific examples of R include the following. Embedded image Particularly, R is preferably the following. Embedded image R 'represents a divalent aromatic residue having 1 to 4 carbon 6-membered rings. Specific examples of R ′ include the following. Embedded image Embedded image The following are particularly preferred as R '. Embedded image According to the production method of the present invention, a product having an intrinsic viscosity [η] of 0.5 or more can be obtained. Is preferably 0.7 or more. The larger the value of [η], the easier it is to obtain a material having good properties such as strength and elastic modulus when the ring is closed. [Η] is a value directly related to the molecular weight of the polymer, and 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 during which the polymer solution flows through a fixed volume capillary of a standard viscometer and the time during which only the solvent flows, using the following equation. Here, c is the polyimide precursor concentration. [Equation 1] In the present invention, tetracarboxylic dianhydride is dissolved or suspended in a water-soluble ketone,
Diamine is added and polymerized to produce a polyimide precursor. Preferred solvents among the water-soluble ketones include, for example, acetone, methyl ethyl ketone and the like, and acetone is preferred. Further, other solvents can be mixed as long as the effects of the present invention are not impaired. The reaction temperature is -20 to 50 ° C, especially 0 to 2 ° C.
0 ° C. is preferred. In addition, as is known, the charging ratio of tetracarboxylic dianhydride and diamine is correlated with the degree of polymerization of the resulting polyimide precursor, and to obtain a polyimide precursor having a high degree of polymerization, it is necessary to charge the precursor in the vicinity of equimolar. preferable. The generated polyimide precursor is not dissolved in the solvent used,
Since it is suspended in the solvent, the solvent is removed by a usual method such as filtration and drying to obtain a polyimide precursor powder. In this case, since a solvent that does not strongly interact with the polyimide precursor is used, the solvent can be easily removed, and powdery polyimide precursor particles containing no solvent can be obtained even by a normal drying method. At this time, without removing the solvent,
Alternatively, the polyimide precursor particles are mixed again with a solvent and stored in this state, whereby the stability of the polyimide precursor over time is maintained. That is, the suspension of the polyimide precursor powder and the water-soluble ketones maintains the stability of the polyimide precursor powder over time. The powder of the polyimide precursor may have any shape such as a spherical shape, an irregular shape, or a fibrous shape. It is preferable that the particles have a particle size of not more than 100 μm and not less than 80% by weight. The powder of the polyimide precursor can be formed into a molded product by a known method. For example, by heating and pressurizing to close the ring and coalescing and molding the powder and granular material, and before heating and pressurizing to coalesce, a part of the repeating structural units of the polyimide precursor is closed to form a polyimide. , And then heated and pressed for molding. In the former case, 20-300 ° C, 500-50
After molding at 00 kg / cm ² , sintering in vacuum or nitrogen at 300 to 400 ° C., and in the latter case,
After converting the polyimide precursor powder to polyimide at 150 to 200 ° C. over 3 to 10 hours, 250 to
Press molding is performed at 300 ° C. and 500 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 controlled by controlling the temperature and controlling the amount of the ring-closing agent to be added. The present invention will be described below in detail with reference to examples. In addition, the measuring method in an Example is as follows. (1) Particle size of powder: Measured by laser diffraction / scattering type particle size distribution measurement (LA-500, manufactured by Horiba, Ltd.). (2) Imidation ratio: Absorbance ratio between 604 cm ^-1 and 880 cm ^{-1 in} the infrared absorption spectrum (absorbance 0.8
04 and the imidation ratio was 100%). (3) Surface area: the number of square meters per gram of polyimide powder 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 To 3.46 g of pyromellitic dianhydride (PMDA) was added
3.16 g of diaminodiphenyl ether (DADE) dissolved in 79 g of acetone was added dropwise at 25 ° C. over 1 hour, and stirring was continued. After completion of the dropwise addition, stirring was further continued for 1 hour to obtain a white-yellow suspension. This suspension was separated by filtration under reduced pressure to obtain a white and yellow polyimide precursor powder having the characteristics shown in Table 1. Furthermore, this was dried at 60 ° C. for 1 hour under reduced pressure, and then imidized at 180 ° C. for 10 hours to obtain a polyimide powder (imidation ratio = 74%). further,
The obtained polyimide powder is pulverized on a 38-mesh sieve to remove defective particles contained in an extremely small amount, and then filled in a mold for forming a bending test piece, and then 1000 kg on a press plate heated to 300 ° C. Compression molding at a pressure of / cm ² for 30 minutes,
A bending test piece was prepared and a bending test was performed. Table 1 shows the results. Example 2 2.19g PMDA and 2.00g DADE 50g
Of acetone and stirring was continued at 25 ° C. The suspension became a suspension in about 30 minutes, and stirring was further continued for 1 hour to obtain a suspension. This suspension was separated by filtration under reduced pressure to obtain a white and yellow polyimide precursor powder having the characteristics shown in Table 1. Further, a polyimide powder was obtained in the same manner as in Example 1 (imidization rate = 72%). A bending test was performed on the obtained polyimide powder in the same manner as in Example 1. Table 1 shows the results. Example 3 95 g of acetone was cooled to 5 ° C., 4.41 g of PMDA was dissolved therein, 4.03 g of DADE was added at a time, and stirring was continued at 5 ° C. for 1 hour. The cooling was stopped, and the mixture was further stirred for 6 hours to obtain a suspension. This suspension was separated by filtration under reduced pressure to obtain a white and yellow polyimide precursor powder having the characteristics shown in Table 1. Furthermore, a polyimide powder (imidization rate = 75%) was obtained in the same manner as in Example 1. A bending test was performed on the obtained polyimide powder in the same manner as in Example 1. Table 1 shows the results. [Table 1] According to the production method of the present invention, the solvent can be easily removed and powdery polyimide precursor particles having a high degree of polymerization can be easily produced. In addition, a polyimide molded article obtained from the polyimide precursor powder obtained by the present invention has excellent mechanical properties and has little residual solvent.

────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-6-87958 (JP, A) JP-A-6-107819 (JP, A) JP-A-6-192420 (JP, A) JP-A-6-192420 322123 (JP, A) JP-A-7-3019 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) C08G 73/00-73/26

Claims (1)

(57) [Claim 1] A method for producing a polyimide precursor powder characterized by polymerizing tetracarboxylic dianhydride and diamine in a water-soluble ketone.