JP2021059732A - Polyimide powder and method for producing polyimide powder - Google Patents

Abstract

To provide a polyimide powder which provides a polyimide film excellent in heat resistance and transparency and to provide a method for producing the same.SOLUTION: There is provided a polyimide powder soluble in N,N-dimethyl acetamide, which is produced through steps of: polymerization from at least one aromatic diamine compound and at least one tetracarboxylic acid dianhydride to a polyamide acid; a chemical imidization reaction; formation of a powder by precipitation of a produced polyimide; and drying, wherein the average particle diameter of the polyimide powder is in a range of 0.02 to 0.8 mm and a polyimide film having a thickness of 50 μm obtained by forming from an N,N-dimethyl acetamide solution of the polyimide powder has a light transmittance at the wavelength of 450 nm of 80% or more.SELECTED DRAWING: None

Description

The present invention relates to a polyimide powder and a method for producing the same, and the present invention relates to the polyimide powder and the method for producing the polyimide powder, which provides a polyimide film having extremely excellent heat resistance and transparency, which is particularly preferably used for display applications and electronic material applications. Is.

Polyimide resin is used as a plastic having excellent heat resistance in a wide range of fields such as aerospace field, electrical insulation field, and electronic field where heat resistance and high reliability are required. Further, in recent years, a transparent polyimide having both heat resistance and transparency has been proposed. For example, Patent Document 1 has excellent transparency suitable for an optical waveguide synthesized from a specific monomer containing a fluorine atom. Soluble polyimide has been proposed. Patent Document 2 proposes a transparent polyimide that is soluble in an organic solvent using a specific alicyclic diamine. However, since the polyimide described in Patent Document 1 is heat-treated at a temperature of 300 ° C. or higher with respect to the polyimide after film formation, it is difficult to ensure sufficient transparency, and it is described in Patent Document 2. Since polyimide uses an alicyclic diamine as a raw material, it has a problem of poor heat resistance and coloring by heating.

As the polyimide powder, a method of adding a poor solvent such as water or methanol to a soluble polyimide varnish to precipitate a massive polyimide resin is disclosed (Patent Document 3).

Further, Patent Document 4 proposes an imidized powder of polyamic acid obtained by polymerizing diamines and acid dianhydrides.

However, the polyimide powders described in Patent Documents 3 and 4 do not pay sufficient attention to the particle size of the polyimide powders, and therefore, imidizing agents and imidization in the polyimide powders. There is a problem that the accelerator is not sufficiently removed, and as a result, the polyimide film obtained from the polyimide powder is easily colored, and it is difficult to obtain a polyimide film having excellent transparency.

Japanese Patent Application Laid-Open No. 4-235505 JP 2000-169579 JP-A-2004-285355 Special table 2013-523939

An object of the present invention is to provide a polyimide powder having excellent heat resistance and transparency, having less coloring and impurities, and being soluble in a solvent, and a method for producing the same.

By making the transparent polyimide into a powder having a specific average particle size, the present inventors retain imidizing agents, imidization accelerators, etc. contained in the polyimide powder which adversely affects the transparency. We have found that it is possible to reduce volatile components to the utmost limit, and completed the present invention.

According to the present invention, the following polyimide powder and a method for producing the same are provided.
[1] Steps of polymerization of at least one aromatic diamine compound and at least one tetracarboxylic acid dianhydride into polyamic acid, chemical imidization reaction, formation of powder by precipitation of produced polyimide, and drying. It is a polyimide powder soluble in N, N-dimethylacetamide, which is produced through the process, and the average particle size of the polyimide powder is in the range of 0.02 to 0.8 mm. A polyimide powder having a light transmittance of 80% or more at a wavelength of 450 nm of a polyimide film having a thickness of 50 μm obtained by forming a film from an N-dimethylacetamide solution.
[2] The polyimide according to [1], wherein the weight loss rate in the range of 200 to 300 ° C. measured using a differential thermal / thermogravimetric analyzer is in the range of 0 to 0.2%. powder.
[3] At least one aromatic diamine compound having a fluoro group is used as the aromatic diamine compound, and at least one tetracarboxylic dianhydride having a fluoro group is used as the tetracarboxylic dianhydride. The polyimide powder according to [1] or [2], which is produced by the above-mentioned product.
[4] A method for producing a polyimide powder having an average particle size of 0.02 to 0.8 mm, which comprises the following steps.
(A) A step of preparing at least one aromatic diamine compound and at least one tetracarboxylic dianhydride.
(B) A step of obtaining a polyamic acid solution by polymerizing the aromatic diamine compound and tetracarboxylic acid dianhydride into polyamic acid while stirring in a solvent.
(C) A step of adding an imidizing agent to the obtained polyamic acid solution and performing a chemical imidization reaction to obtain a polyimide solution.
(D) A step of adding a poor polyimide solvent while stirring the obtained polyimide solution to precipitate the polyimide to obtain a polyimide powder containing a volatile component.
(E) The obtained volatile component-containing polyimide powder is dried at a temperature of less than 100 ° C. until the amount of volatile components becomes less than 5%, and then further dried at a temperature of 100 to 350 ° C. for 0.1 to 24 hours. , A process of removing volatile components contained in the powder to obtain a polyimide powder.
[5] A method for producing a polyimide powder, which comprises the following steps.
(A) A step of precipitating polyimide by adding a poor solvent of polyimide to a polyimide solution containing polyimide dissolved in a solvent to obtain a polyimide powder containing a volatile component.
The weight ratio of the polyimide solution to the poor solvent is 1: 0.5 to 1:10.
A step in which the amount of the poor solvent added per minute from one time point before the start of precipitation of the polyimide to the completion of precipitation powdering is 0.0005 to 0.1 times (g / min) the amount of the polyimide solution.
(B) The volatile component-containing polyimide powder is dried at a temperature of less than 100 ° C. until the amount of the volatile component in the volatile component-containing polyimide powder is less than 5% without crushing, and then further 100 to 350. A step of drying at a temperature of ° C. for 0.1 to 24 hours to obtain a polyimide powder.
[6] The polyimide solution is used as a solution.
(A1) A step of preparing at least one aromatic diamine compound and at least one tetracarboxylic dianhydride.
(A2) A step of polymerizing the above aromatic diamine compound and tetracarboxylic dianhydride under dissolution in a solvent to obtain a polyamic acid solution.
(A3) An imidizing agent was added to the obtained polyamic acid solution to carry out a chemical imidization reaction.
The method according to [5], which is obtained by a step of obtaining a polyimide solution containing polyimide dissolved in a solvent.
[7] The method according to [6], wherein the step (A3) is performed at 10 ° C. or higher and lower than 50 ° C.
[8] At least one aromatic diamine compound having a fluoro group is used as the aromatic diamine compound, and at least one tetracarboxylic dianhydride having a fluoro group is used as the tetracarboxylic dianhydride. 6] or the method according to [7].
[9] A polyimide powder produced by the method according to any one of [5] to [8].
[10] The polyimide powder according to [9], which is soluble in a solvent.
[11] The polyimide powder according to [10], wherein the solvent is N, N-dimethylacetamide.
[12] The polyimide powder according to [9], which has an average particle size in the range of 0.02 to 0.8 mm.
[13] The polyimide powder according to [9], which contains 95% by volume or more of particles having a particle size in the range of 0.01 to 2 mm.
[14] The polyimide powder according to [9], wherein the weight loss rate in the range of 200 to 300 ° C. is in the range of 0 to 0.2%.
[15] When a polyimide film having a thickness of 50 μm was formed from the solution by dissolving it in N, N-dimethylacetamide, and the light transmittance of the film at a wavelength of 450 nm was measured, the light transmittance was 80% or more. The polyimide powder according to [11] shown.
[16] When a polyimide film having a thickness of 50 μm was formed from the solution by dissolving in N, N-dimethylacetamide, and the yellowness (YI) of the film was measured, the yellowness (YI) of -5 to 5 was measured. The polyimide powder according to [11].
[17] A polyimide film obtained by forming a film of the polyimide powder according to any one of [1] to [3] and [9] to [16].

INDUSTRIAL APPLICABILITY According to the present invention, it is possible to provide a polyimide powder having extremely few impurities such as residual volatile matter and coloring, which gives a polyimide film having excellent heat resistance and transparency, and a method for producing the same.

The polyimide powder of the present invention is subjected to the steps of polymerization to polyamic acid, chemical imidization reaction, formation of powder by precipitation of produced polyimide, and drying using an aromatic diamine compound and tetracarboxylic dianhydride. Manufactured.

1. 1. Ingredients 1.1. Aromatic diamine compound As the aromatic diamine compound used in the production of the polyimide powder of the present invention, a common solvent (for example, N, N-dimethylacetamide) is obtained by reacting with the tetracarboxylic acid dianhydride used together. Any aromatic diamine compound can be used as long as it is an aromatic diamine compound that is soluble in (DMAC)) and gives a polyimide having a predetermined transparency. Specifically, m-phenylenediamine, p-phenylenediamine, 3,4'-diaminodiphenyl ether, 4,4'-diaminodiphenyl ether, 3,3'-diaminodiphenyl sulfide, 3,4'. −Diaminodiphenylsulfide, 4,4′-diaminodiphenylsulfide, 3,3′-diaminodiphenylsulfone, 3,4′-diaminodiphenylsulfone, 4,4′-diaminodiphenylsulfone, 3,3′-diaminobenzophenone, 3 , 3'-diaminodiphenylmethane, 3,4'-diaminodiphenylmethane, 4,4'-diaminodiphenylmethane, 2,2-bis (4-aminophenyl) propane, 2,2-bis (3-aminophenyl) propane, 2 -(3-Aminophenyl) -2- (4-aminophenyl) propane, 2,2-bis (4-aminophenyl) -1,1,1,3,3,3-hexafluoropropane, 2,2- Bis (3-aminophenyl) -1,1,1,3,3,3-hexafluoropropane, 2- (3-aminophenyl) -2- (4-aminophenyl) -1,1,1,3 3,3-Hexafluoropropane, 1,3-bis (3-aminophenoxy) benzene, 1,3-bis (4-aminophenoxy) benzene, 1,4-bis (3-aminophenoxy) benzene, 1,4 -Bis (4-aminophenoxy) benzene, 4,4'-bis (4-aminophenoxy) biphenyl, 3,3'-bis (4-aminophenoxy) biphenyl, 3,4'-bis (3-aminophenoxy) Biphenyl, bis [4- (4-aminophenoxy) phenyl] sulfide, bis [3- (4-aminophenoxy) phenyl] sulfide, bis [4- (3-aminophenoxy) phenyl] sulfide, bis [3- (4) -Aminophenoxy) phenyl] sulfide, bis [3- (3-aminophenoxy) phenyl] sulfide, bis [3- (4-aminophenoxy) phenyl] sulfone, bis [4- (4-aminophenyl) sulfone, bis [ 3- (3-Aminophenoxy) phenyl] sulfone, bis [4- (3-aminophenyl) sulfone, bis [4- (3-aminophenoxy) phenyl] ether, bis [4- (4-aminophenoxy) Phenyl] ether, bis [3- (3-aminophenoxy) phenyl] ether, bis [4- (3-aminophenoxy) phenyl] methane, bis [4- (4-aminophenoxy) phenyl] Methyl, bis [3- (3-aminophenoxy) phenyl] methane, bis [3- (4-aminophenoxy) phenyl] methane, 2,2-bis [4- (3-aminophenoxy) phenyl] propane, 2, 2-Bis [4- (4-aminophenoxy) phenyl] propane, 2,2-bis [3- (3-aminophenoxy) phenyl] propane, 2,2-bis [4- (3-aminophenoxy) phenyl] -1,1,1,3,3,3-hexafluoropropane, 2,2-bis [4- (4-aminophenoxy) phenyl] -1,1,1,3,3,3-hexafluoropropane, 2,2-Bis [3- (3-aminophenoxy) phenyl] -1,1,1,3,3,3-hexafluoropropane, 2,2-bis [3- (4-aminophenoxy) phenyl]- 1,1,1,3,3,3-hexafluoropropane, 1,3-bis [4- (4-amino-6-trifluoromethylphenoxy) -α, α-dimethylbenzyl] benzene, 1,3- Bis [4- (4-amino-6-fluoromethylphenoxy) -α, α-dimethylbenzyl] benzene, 2,2'-dimethyl-4,4'-diaminobiphenyl, 3,3'-dimethyl-4,4 Examples thereof include'-diaminobiphenyl, 3,3'-bis (trifluoromethyl) -4,4'-diaminobiphenyl, 2,2'-bis (trifluoromethyl) -4,4'-diaminobiphenyl and the like. These aromatic diamine compounds may be used alone, or two or more kinds of aromatic diamine compounds may be used. From the viewpoint of transparency and heat resistance, preferred aromatic diamine compounds include 2,2-bis (4-aminophenyl) -1,1,1,3,3,3-hexafluoropropane and 2,2. -Bis (3-aminophenyl) -1,1,1,3,3,3-hexafluoropropane, 2- (3-aminophenyl) -2- (4-aminophenyl) -1,1,1,3 , 3,3-Hexafluoropropane, 2,2-bis [4- (3-aminophenoxy) phenyl] -1,1,1,3,3,3-hexafluoropropane, 2,2-bis [4- (4-Aminophenoxy) Phenyl] -1,1,1,3,3,3-hexafluoropropane, 2,2-bis [3- (3-aminophenoxy) phenyl] -1,1,1,3 3,3-Hexafluoropropane, 2,2-bis [3- (4-aminophenoxy) phenyl] -1,1,1,3,3,3-hexafluoropropane, 1,3-bis [4- ( 4-Amino-6-trifluoromethylphenoxy) -α, α-dimethylbenzyl] benzene, 3,3'-bis (trifluoromethyl) -4,4'-diaminobiphenyl, 2,2'-bis (trifluoro) Examples thereof include aromatic diamine compounds having a fluoro group such as methyl) -4,4'-diaminobiphenyl, and at least one of the aromatic diamine compounds used is preferably an aromatic diamine compound having a fluoro group, in particular. It is preferably 2,2'-bis (trifluoromethyl) -4,4'-diaminobiphenyl. By using an aromatic diamine compound having a fluoro group, it becomes easy to obtain transparency, heat resistance, and solubility in a solvent.

1.2. Tetracarboxylic dianhydride The tetracarboxylic dianhydride used in the production of the polyimide powder of the present invention includes a common solvent (for example, N, N-dimethylacetamide) as in the case of the above aromatic diamine compound. Any tetracarboxylic dianhydride that gives (DMAC)) a soluble and predetermined transparent polyimide can be used, and specifically, 4,4'-(1,1,1). , 3,3,3-hexafluoropropane-2,2-diyl) diphthalic acid dianhydride, pyromellitic dianhydride, 3,3', 4,4'-benzophenonetetracarboxylic dianhydride, 1, 4-hydroquinonedibenzoate-3,3', 4,4'-tetracarboxylic dianhydride, 3,3', 4,4'-biphenyltetracarboxylic dianhydride, 3,3', 4, Examples thereof include 4'-diphenyl ether tetracarboxylic dianhydride. These tetracarboxylic dianhydrides may be used alone, or two or more types of tetracarboxylic dianhydrides may be used. From the viewpoint of transparency, heat resistance and solubility in a solvent, 4,4'-(1,1,1,3,3,3-hexafluoropropane-2,2-diyl) diphthalic acid dianhydride and the like , It is preferable to use a tetracarboxylic dianhydride having at least one kind of fluorogroup.

2. Polymerization to Polyamic Acid Polymerization to polyamic acid can be carried out by reacting the aromatic diamine compound and the tetracarboxylic dianhydride in a solvent in which the polyamic acid produced is soluble. Solvents used for polymerization on polyamic acid include N, N-dimethylacetamide, N, N-dimethylformamide, N-methyl-2-pyrrolidone, 1,3-dimethyl-2-imidazolidinone, and dimethyl sulfoxide. Can be used.

The polymerization reaction to polyamic acid is preferably carried out while stirring in a reaction vessel equipped with a stirrer. For example, a method in which a predetermined amount of an aromatic diamine compound is dissolved in the above solvent, tetracarboxylic acid dianhydride is added while stirring to carry out a reaction to obtain polyamic acid, and tetracarboxylic acid dianhydride is dissolved in the solvent. Then, a method of adding an aromatic diamine compound and reacting with stirring to obtain a polyamic acid, a method of alternately adding an aromatic diamine compound and a tetracarboxylic acid dianhydride and reacting them to obtain a polyamic acid, and the like can be mentioned. Be done.

The temperature of the polymerization reaction to the polyamic acid is not particularly limited, but is preferably 0 to 70 ° C., more preferably 10 to 60 ° C., and even more preferably 20 to 50 ° C. By carrying out the polymerization reaction within the above range, it is possible to obtain a high molecular weight polyamic acid with less coloring and excellent transparency.

Further, the aromatic diamine compound and the tetracarboxylic dianhydride used for the polymerization to the polyamic acid use approximately the same molar amount, but in order to control the degree of polymerization of the obtained polyamic acid, the tetracarboxylic dianhydride is used. It is also possible to change the molar amount (molar ratio) of the aromatic diamine compound in the range of 0.95 to 1.05. The molar ratio of the tetracarboxylic dianhydride to the aromatic diamine compound is preferably in the range of 1.001 to 1.02, more preferably 1.001 to 1.01. By slightly excessing the tetracarboxylic dianhydride in this way, the degree of polymerization of the obtained polyamic acid can be stabilized, and the unit derived from the tetracarboxylic dianhydride can be arranged at the end of the polymer. As a result, it is possible to provide a polyimide having less coloring and excellent transparency.

The concentration of the polyamic acid solution to be produced is preferably adjusted to an appropriate concentration (for example, about 10 to 30% by weight) so that the viscosity of the solution is maintained appropriately and it is easy to handle in the subsequent steps.

3. 3. Chemical imidization reaction Next, an imidizing agent is added to the obtained polyamic acid solution to carry out a chemical imidization reaction. As the imidizing agent, carboxylic acid anhydrides such as acetic anhydride, propionic anhydride, succinic anhydride, phthalic anhydride, and benzoic anhydride can be used, and anhydrous from the viewpoint of cost and ease of removal after the reaction. It is preferable to use acetic anhydride. The equivalent of the imidizing agent to be used is equal to or more than the equivalent of the amide bond of the polyamic acid performing the chemical imidization reaction, preferably 1.1 to 5 times, preferably 1.5 to 4 times the equivalent of the amide bond. Is more preferable. By using a slightly excess imidizing agent for the amide bond in this way, the imidization reaction can be efficiently carried out even at a relatively low temperature.

Further, in the chemical imidization reaction, aliphatic, aromatic or heterocyclic tertiary amines such as pyridine, picoline, quinoline, isoquinoline, trimethylamine and triethylamine can be used as the imidization accelerator. By using such amines, the imidization reaction can be efficiently carried out at a low temperature, and as a result, coloring during the imidization reaction can be suppressed, and a more transparent polyimide can be obtained.

The chemical imidization reaction temperature is not particularly limited, but is preferably 10 ° C. or higher and lower than 50 ° C., and more preferably 15 ° C. or higher and lower than 45 ° C. By carrying out the chemical imidization reaction at a temperature of 10 ° C. or higher and lower than 50 ° C., coloring during the imidization reaction can be suppressed, and a polyimide having excellent transparency can be obtained.

4. Formation of Powder by Precipitating the Produced Polyimide Next, a poor solvent for polyimide is added to the polyimide solution obtained by the chemical imidization reaction to precipitate the polyimide to form a powder. As the poor solvent used for powdering, any poor solvent capable of precipitating polyimide can be used, and it is desirable that the solvent is miscible with the solvent of the polyimide solution. Ethanol or the like can be used. Then, by using methanol as a poor solvent, a polyimide powder having a stable average particle size can be obtained, which is preferable.

In the present invention, the amount of the poor solvent used in the step of pulverizing the polyimide needs to be a sufficient amount to carry out the precipitation powdering of the polyimide, and the structure of the polyimide, the solvent of the polyimide solution, and the polyimide Although it is determined in consideration of the solution concentration of the above, it is usually 0.5 times or more the weight of the polyimide solution, preferably 0.8 times or more the weight of the polyimide solution, and more preferably 1 times or more the weight of the polyimide solution. Use a solvent. By using a poor solvent having a weight of 0.5 times or more the weight of the polyimide solution, a polyimide powder having a stable average particle size can be obtained in a high yield. Further, usually, a poor solvent having a weight of 10 times or less the weight of the polyimide solution, preferably 7 times or less the weight of the polyimide solution, more preferably 5 times or less the weight of the polyimide solution, and further preferably 4 times or less the weight of the polyimide solution is used. To do.

The polyimide is powdered by adding the above-mentioned poor solvent to the polyimide solution, but it is preferable to carry out by dropping the poor solvent while stirring the polyimide solution. In order to facilitate the diffusion of the poor solvent, it is desirable to adjust the polyimide solution in advance to a concentration of preferably about 5 to 30% by weight, more preferably about 10 to 20% by weight. The preferred average particle size of the polyimide powder obtained by the present invention is 0.02 to 0.8 mm, but the average particle size is controlled by the addition rate of the poor solvent to the polyimide solution (addition amount per minute). can do. The preferable addition rate of the poor solvent depends slightly on the structure of the polyimide and the concentration of the polyimide in the solution, but when the total amount of the polyimide solution to be precipitated is Xg at the latest immediately before the precipitation of the polyimide occurs, The amount of the poor solvent added per minute is preferably 0.0005 to 0.1 times (g / min) of X, more preferably 0.001 to 0.05 times of X, and most preferably 0. By setting the value to less than 001 to 0.04 times (g / min) and maintaining the addition rate within this range until the completion of the precipitation powdering of polyimide, a polyimide powder having a stable average particle size can be obtained. For example, when precipitating and powdering polyimide in 1000 g of a polyimide solution (concentration: 15% by weight), 0.5 to 100 g / min is a preferable low solvent addition rate.

When the amount of the poor solvent added per minute (addition rate) is smaller than 0.0005 times the total amount of the polyimide solution, the time required for precipitation powdering becomes significantly long, the productivity decreases, and the polyimide produced is produced. The average particle size of the powder may become too small, making it difficult to handle. On the other hand, when the amount of the poor solvent added per minute (addition rate) is larger than 0.1 times the total amount of the polyimide solution, the average particle size of the produced polyimide powder becomes large, and the drying is performed after that. It becomes difficult to efficiently remove volatile components, and as a result, problems such as coloring of polyimide and deterioration of heat resistance may occur.

Further, it is necessary to take care to control the addition rate of the poor solvent at the time when the polyimide is precipitated and powdered, but it is not necessary to give special consideration until the polyimide is started to be precipitated and powdered. Therefore, before the initial precipitation powder formation in which the poor solvent is added occurs, the poor solvent is added at high speed, and the polyimide solution becomes turbid, and before the precipitation powder formation of the polyimide is observed, that is, the precipitation starts. The addition rate may be controlled within the above range by the previous point in time. Subsequent addition rates must be maintained until precipitation powdering is complete.

In the present invention, the temperature at which the polyimide is precipitated and powdered is not particularly limited, but it is preferably performed at a temperature of 50 ° C. or lower from the viewpoint of suppressing evaporation of the poor solvent used and efficiently performing precipitation. It is more preferable to carry out at ° C or lower.

If the polyimide is powdered by adding a polyimide solution to an excessively poor solvent, the precipitated polyimide may become fibrous, which is not preferable.

5. Drying of Powder In the present invention, the precipitated polyimide powder can be subjected to the next drying step without being crushed. The precipitated polyimide powder is separated by filtration, and if necessary, washed to remove the solvent, imidizing agent, and imidization accelerator of the polyimide, and then dried to obtain the polyimide powder of the present invention. You can get a body.

The polyimide powder can be dried at any temperature as long as residues such as a polyimide solvent, an imidizing agent, an imidizing accelerator, and a poor solvent can be removed. When a poor solvent having a hydroxy group is used and suddenly dried at a temperature of 100 ° C. or higher, the carboxylic acid group or carboxylic acid anhydride group in the polyimide reacts with the poor solvent to form an ester bond. This can cause problems such as reduced heat resistance and coloring. Therefore, in the drying step, after drying at a temperature of less than 100 ° C. until the volatile component in the polyimide powder is preferably less than 5%, more preferably less than 3%, the drying step is preferably 100 to 350 ° C., more preferably. It is preferable to carry out drying at a temperature of 150 to 300 ° C. for 0.1 to 24 hours to remove remaining volatile components, particularly hard-to-volatile components such as imidizing agents and imidization accelerators. Drying at a high temperature of 100 ° C. or higher is preferably carried out in an atmosphere that is inert and has a small amount of water, from the viewpoint of preventing a decrease in molecular weight and preventing coloring. Further, the polyimide powder may be dried under normal pressure or under reduced pressure. Further, the drying may be carried out while continuously raising the temperature from a low temperature of less than 100 ° C. to a high temperature of 100 ° C. or higher, in which case the drying is contained in the polyimide powder before the drying temperature exceeds 100 ° C. It is preferable that the volatile component is less than 5%.

The amount of volatile components in the polyimide powder after drying at a temperature of less than 100 ° C. is defined by the following formula.
Weight of polyimide powder after drying at a temperature of less than 100 ° C: Ag
Weight of polyimide powder after final drying performed at a temperature of 100 ° C. or higher: Bg
Amount of residual volatile components after drying at a temperature of less than 100 ° C: (AB) / A × 100%

6. Powder characteristics (Part 1 Particle characteristics)
The average particle size of the polyimide powder thus obtained is 0.02 to 0.8 mm, preferably 0.03 to 0.6 mm, and more preferably 0.04 to 0.4 mm. When the average particle size is within the above range, the residual volatile components are efficiently removed, and the polyimide has extremely little coloring and excellent transparency.

Further, regarding the particle size distribution of the polyimide powder of the present invention, it is preferable that 95% by volume or more of the particle size distribution is contained in the range of 0.01 to 2 mm, and more preferably 99% by volume or more. If the particle size distribution is as described above, it is easy to handle, the residual volatile components are efficiently removed, and a polyimide with less coloring and excellent transparency can be obtained.

The average particle size and particle size distribution of the polyimide powder of the present invention can be measured by a laser diffraction / scattering type particle size distribution measuring device.

The weight average molecular weight of the polyimide powder of the present invention is preferably 20,000 or more and 1,000,000 or less, and more preferably 50,000 or more and 500,000 or less. If the weight average molecular weight is less than the above lower limit, transparency and mechanical properties may be impaired, and if the weight average molecular weight exceeds the above upper limit, the viscosity increases when the polyimide powder is dissolved in a solvent. It may be too difficult to handle. The weight average molecular weight of the polyimide can be determined by a size exclusion chromatograph device. Further, the reducing viscosity is used as an index showing the degree of polymerization of a polymer such as polyimide. In the polyimide powder of the present invention, the reducing viscosity is preferably in the range of 0.8 to 4 dL / g, and 1 to 1 More preferably, it is in the range of 3 dL / g. If the reduced viscosity is less than the above lower limit, transparency and mechanical properties may be impaired, and if it exceeds the above upper limit, the viscosity of the polyimide solution may increase too much, making handling difficult.

7. Powder characteristics (Part 2 Film characteristics)
Regarding the transparency of the polyimide powder of the present invention, a film obtained by dissolving the polyimide powder in N, N-dimethylacetamide (DMAC) and then drying to a thickness of 50 μm by a casting method was used. It can be determined from the light transmittance and the degree of yellowness measured by the spectrocolorimeter. The light transmittance of the polyimide film obtained from the polyimide powder of the present invention at a wavelength of 450 nm is 80% or more, more preferably 85% or more. The yellowness is preferably −5 to 5, more preferably -3 to 3. If the light transmittance at 450 nm is less than the above lower limit, or if the yellowness is outside the above range, it may be difficult to provide a film with excellent transparency that can be used for optical applications such as displays. .. The imidization ratio of the polyimide powder of the present invention is preferably 90% or more, more preferably 95% or more. The imidization ratio can be determined by Fourier transform infrared spectroscopy (FT-IR method) of the polyimide film obtained by the above method.

Further, the polyimide powder of the present invention preferably has a weight loss rate of 0 to 0.2% in the temperature range of 200 to 300 ° C. measured using a differential thermal / thermogravimetric analyzer, and is 0 to 0. More preferably, it is 0.1%. When the weight reduction rate of the polyimide powder in the temperature range of 200 to 300 ° C. is within the above range, a polyimide film having less coloring and excellent transparency can be provided.

Hereinafter, the present invention will be specifically described with reference to Examples, but the present invention is not limited to these Examples.

(Measuring method of average particle size and particle size distribution of polyimide powder)
The measurement was performed using a laser diffraction / scattering particle size distribution measuring device (LA-950V2 manufactured by HORIBA, Ltd.) and ethanol as a dispersion medium.

(Method for measuring light transmittance and yellowness of polyimide)
(1) Method for preparing film sample for measurement Polyimide powder was dissolved in N, N-dimethylacetamide so as to be 20% by weight. Next, using an applicator, a film is formed on a smooth glass plate so that the thickness becomes 50 μm after drying, and the film is held in a hot air oven at 130 ° C. for 60 minutes, and then from 130 ° C. to 300 ° C. at 5 ° C. The temperature was raised at / min, held at 300 ° C. for 60 minutes to dry, then taken out from a hot air oven, cooled to room temperature, and then peeled off from a glass plate to prepare a polyimide film sample for measurement.
(2) Measurement of light transmittance The light transmittance was measured in the wavelength range of 380 to 780 nm using a spectrocolorimeter (Nippon Denshoku Kogyo Co., Ltd. SD6000), and the light transmittance at 450 nm was determined.
(3) Measurement of yellowness (YI) Using a spectrocolorimeter (Nippon Denshoku Industries Co., Ltd. SD6000), scan in the wavelength range of 380 to 780 nm, and use standard Illuminant D65 based on JIS K7373: 2006. The yellowness (YI) was determined.
(Measuring method of imidization rate)
A film sample having a thickness of 50 μm prepared by the same method as for measuring the light transmittance of polyimide was used as a measurement sample, and a film obtained by further heat-treating the film at 380 ° C. for 30 minutes to complete imidization was used as a comparative sample. An infrared absorption spectrum was obtained by the ATR method using a Fourier transform infrared spectrophotometer (FT-IR manufactured by Shimadzu Corporation), and the imidization rate was calculated by the following method based on the spectrum.
Regarding the infrared absorption spectrum of the above comparative sample, ^{the absorption near 1,365 cm -1,} which is one of the characteristic absorptions of the imide (variable vibration of the imide ring CN group), and the characteristic absorption of the benzene ring 1,500 cm ^-1. the absorbance ratio of the a, the infrared absorption spectrum of the measurement sample, a B absorbance ratio of 1,365Cm ^-1 and 1,500Cm ^-1, was determined imidization ratio from the following equation.
Polyimide imidization rate (%) = (B / A) x 100

(Measuring method of weight loss rate of polyimide powder at 200 to 300 ° C)
The measurement was performed using a differential thermal / thermogravimetric simultaneous measuring device (DTG-60 manufactured by Shimadzu Corporation). 25 mg of polyimide powder is charged in an aluminum pan, and the temperature is raised at a rate of 10 ° C./min in a nitrogen atmosphere. The weight of the polyimide powder at 200 ° C. (M1) and the polyimide powder at 300 ° C. The weight (M2) of the above was measured, and the weight loss rate in the range of 200 to 300 was obtained from the following formula.
Weight loss rate (%) at 200 to 300 ° C. = (M1-M2) / M1 × 100

(Measuring method of reducing viscosity of polyimide)
The polyimide powder was dissolved in N, N-dimethylacetamide (DMAC) at a concentration of 0.5 dL / g to prepare a polyimide solution. Using an Ubbelohde viscous meter, the outflow time (T) of the polyimide solution and the outflow time (T0) of the solvent only with DMAC were measured at a temperature of 30 ° C., and the reduced viscosity was calculated from the following formula.
Reduced viscosity (dL / g) = (T-T0) / T0 / 0.5

(Measuring method of average molecular weight and polydispersity of polyimide)
The measurement was carried out using a size exclusion chromatograph device (HLC-8320 GPC manufactured by Tosoh Corporation), eluent tetrahydrofuran, and a detector differential refractometer using standard polystyrene as a standard substance.

(Example 1)
In a glass 2L separable flask equipped with a stirrer and a stirrer, 460 g of solvent N, N-dimethylacetamide (DMAC) and 2,2'-bis (trifluoromethyl), which is an aromatic diamine compound having a fluoro group, are used. ) -4,4'-Diaminobiphenyl (TFMB) 64.040 8 g (0.200 mol) was added and stirred to dissolve TFMB in DMAC. Then, while stirring in the separable flask, under a nitrogen stream, the tetracarboxylic dianhydride 4,4'-(1,1,1,3,3,3-hexafluoropropane-2,2-) Diyl) 89.294 g (0.201 mol) of diphthalic acid dianhydride (6FDA) was added over about 10 minutes, and stirring was continued for 6 hours while adjusting the temperature so that it was in the temperature range of 20 to 40 ° C. The polymerization reaction was carried out to obtain a viscous polyamic acid solution. The molar ratio of the tetracarboxylic dianhydride / aromatic diamine compound used was 1.005, and the concentration of the polyamic acid solution was 25% by weight.
Next, 409 g of DMAC was added to the obtained polyimide solution to dilute it so that the concentration of the polyamic acid was 15% by weight, and then 25.83 g of isoquinoline was added as an imidization accelerator while stirring the polyamic acid solution. Keep the temperature in the temperature range of 30 to 40 ° C., and add 122.5 g (1.20 mol) of anhydrous acetic acid as an imidizing agent while slowly dropping it over about 10 minutes, and then add the liquid temperature to 30 to 40. The temperature was maintained at ° C. and stirring was continued for 12 hours to carry out a chemical imidization reaction to obtain a polyimide solution.
Next, 1000 g of the obtained polyimide solution containing the imidizing agent and the imidizing accelerator was transferred to a 5 L separable flask equipped with a stirrer and a stirring blade, and the mixture was stirred at a speed of 120 rpm at 15 to 25 ° C. The temperature was maintained, and 1500 g of methanol was added dropwise thereto at a rate of 10 g / min. When about 800 g of methanol was added, turbidity of the polyimide solution was confirmed, and precipitation of powdery polyimide was confirmed. Subsequently, 1500 g of total amount of methanol was added to complete the precipitation of polyimide.
Next, the contents of the separable flask were filtered by a suction filtration device, and further washed and filtered using 1000 g of methanol.
Then, 50 g of the polyimide powder containing the residue of the volatile matter separated by filtration was dried at 50 ° C. for 24 hours using a dryer equipped with a local exhaust device to measure the weight, and further dried at 260 ° C. for 2 hours. , The remaining volatile components were removed to obtain the desired polyimide powder. The weight after drying at 50 ° C. for 24 hours is 43.8 g, the weight after drying at 260 ° C. for 2 hours is 43.3 g, and the amount of volatile components after 24 hours at 50 ° C. is 1.1%. It was confirmed that there was.
The average particle size of the obtained polyimide powder was 0.10 mm, and the particle size distribution was 100% by volume in the range of 0.01 to 2 mm. The reduced viscosity is 2.1 dL / g, the weight average molecular weight (Mw) by size exclusion chromatography is 210,000, and the degree of polydispersity expressed by weight average molecular weight (Mw) / number average molecular weight (Mn) is It was 2.1. Further, when the weight loss rate in the range of 200 to 300 ° C. was examined with a differential thermal / thermogravimetric analyzer, it was 0.03%, and the imidization rate was 95% or more.
20 g of the obtained polyimide powder is dissolved in 80 g of DMAC to prepare a uniform polyimide solution, then coated on a glass plate using an applicator, the DMAC is dried under predetermined conditions, and then pulled from the glass plate. It was peeled off to prepare a polyimide film having a thickness of 50 μm. The light transmittance of the obtained polyimide film at 450 nm was as high as 90%, the yellowness was 1.5, no discoloration was observed visually, and the transparency was extremely excellent.

(Example 2)
In a glass 2 L separable flask equipped with a stirrer and a stirrer, 484 g of solvent N, N-dimethylacetamide (DMAC) and 2,2'-bis (trifluoromethyl) -4, which is an aromatic diamine compound, 51.238 g (0.160 mol) of 4'-diaminobiphenyl (TFMB) and 2,2-bis [4- (4-aminophenoxy) phenyl] -1,1,1,3,3,3-hexafluoropropane 20.738 g (0.040 mol) of (BAPP-F) was added and stirred to dissolve TFMB and BAPP-F in DMAC. Then, while stirring in the separable flask, under a nitrogen stream, the tetracarboxylic dianhydride 4,4'-(1,1,1,3,3,3-hexafluoropropane-2,2-) Diyl) 89.294 g (0.201 mol) of diphthalic acid dianhydride (6FDA) was added over about 10 minutes, and stirring was continued for 6 hours while adjusting the temperature so that it was in the range of 20 to 40 ° C. The polymerization reaction was carried out to obtain a viscous polyamic acid solution. The molar ratio of the tetracarboxylic dianhydride (6FDA) / aromatic diamine compound (total of TFMB and BAPP-F) used was 1.005, and the concentration of the polyamic acid solution was 25% by weight.
Next, 430 g of DMAC was added to the obtained polyimide solution to dilute it so that the concentration of the polyamic acid was 15% by weight, and then 25.83 g of isoquinoline was added as an imidization accelerator while stirring the polyamic acid solution. Keep the temperature in the temperature range of 30 to 40 ° C., and add 122.5 g (1.20 mol) of anhydrous acetic acid as an imidizing agent while slowly dropping it over about 10 minutes, and then add the liquid temperature to 30 to 40. The temperature was maintained at ° C. and stirring was continued for 12 hours to carry out a chemical imidization reaction to obtain a polyimide solution.
Next, 1000 g of the obtained polyimide solution containing the imidizing agent and the imidizing accelerator was transferred to a 5 L separable flask equipped with a stirrer and a stirring blade, and the mixture was stirred at a speed of 120 rpm at 15 to 25 ° C. The temperature was maintained, and 1500 g of methanol was added dropwise thereto at a rate of 10 g / min. When about 900 g of methanol was added, turbidity of the polyimide solution was confirmed, and precipitation of powdery polyimide was confirmed. Subsequently, 1500 g of total amount of methanol was added to complete the precipitation of polyimide.
Next, the contents of the separable flask were filtered using a suction filtration device, and further washed and filtered using 1000 g of methanol.
Then, 50 g of the polyimide powder containing the residue of the volatile matter separated by filtration was dried at 50 ° C. for 24 hours using a dryer equipped with a local exhaust device to measure the weight, and further dried at 260 ° C. for 2 hours. , The remaining volatile components were removed to obtain the desired polyimide powder. The weight after drying at 50 ° C. for 24 hours is 44.1 g, the weight after drying at 260 ° C. for 2 hours is 43.7 g, and the amount of volatile components after 24 hours at 50 ° C. is 0.9%. It was confirmed that there was.
The average particle size of the obtained polyimide powder was 0.36 mm, and the particle size distribution was 100% by volume in the range of 0.01 to 2 mm. The reduced viscosity was 2.4 dL / g, the weight average molecular weight by size exclusion chromatography was 250,000, and the polydispersity was 2.4. Further, when the weight loss rate in the range of 200 to 300 ° C. was examined with a differential thermal / thermogravimetric analyzer, it was 0.05%, and the imidization rate was 95% or more.
20 g of the obtained polyimide powder is dissolved in 80 g of DMAC to prepare a uniform polyimide solution, then coated on a glass plate using an applicator, the DMAC is dried under predetermined conditions, and then pulled from the glass plate. It was peeled off to prepare a polyimide film having a thickness of 50 μm. The light transmittance of the obtained polyimide film at 450 nm was as high as 88%, the yellowness was 2.6, no discoloration was observed visually, and the transparency was excellent.

(Example 3)
In a 2 L glass separable flask equipped with a stirrer and a stirrer, 444 g of solvent N, N-dimethylacetamide (DMAC) and 2,2'-bis (trifluoromethyl) -4, which is an aromatic diamine compound, 64.048 g (0.200 mol) of 4'-diaminobiphenyl (TFMB) was added and stirred to dissolve TFMB in DMAC. Then, while stirring in the separable flask, under a nitrogen stream, the tetracarboxylic dianhydride 4,4'-(1,1,1,3,3,3-hexafluoropropane-2,2-) Diyl) 71.524 g (0.161 mol) of diphthalic acid dianhydride (6FDA) was added over about 10 minutes, followed by 3,3', 4,4'-diphenyl ether tetracarboxylic dianhydride (ODPA). 12.408 g (0.040 mol) was added over about 5 minutes, and the polymerization reaction was carried out by continuing stirring for 6 hours while adjusting the temperature so that it was in the range of 20 to 40 ° C., and viscous polyamic acid. A solution was obtained. The molar ratio of tetracarboxylic dianhydride (total of 6FDA and ODPA) / aromatic diamine compound (TFMB) used was 1.005, and the concentration of the polyamic acid solution was 25% by weight.
Next, 395 g of DMAC was added to the obtained polyimide solution to dilute the polyamic acid concentration to 15% by weight, and then 25.83 g of isoquinoline was added as an imidization accelerator while stirring the polyamic acid solution. Keep the temperature in the temperature range of 30 to 40 ° C., and add 122.5 g (1.20 mol) of anhydrous acetic acid as an imidizing agent while slowly dropping it over about 10 minutes, and then add the liquid temperature to 30 to 40. Stirring was continued for 12 hours while keeping the temperature at ° C. to carry out a chemical imidization reaction to obtain a polyimide solution.
Next, 1000 g of the obtained polyimide solution containing the imidizing agent and the imidizing accelerator was transferred to a 5 L separable flask equipped with a stirrer and a stirring blade, and the mixture was stirred at a speed of 120 rpm at 15 to 25 ° C. The temperature was maintained, and 1500 g of methanol was added dropwise thereto at a rate of 10 g / min. When about 850 g of methanol was added, turbidity of the polyimide solution was confirmed, and precipitation of powdery polyimide was confirmed. Subsequently, 1500 g of total amount of methanol was added to complete the precipitation of polyimide.
Next, the contents of the separable flask were filtered using a suction filtration device, and further washed and filtered using 1000 g of methanol.
Then, 50 g of the polyimide powder containing the residue of the volatile matter separated by filtration was dried at 50 ° C. for 24 hours using a dryer equipped with a local exhaust device to measure the weight, and further dried at 260 ° C. for 2 hours. , The remaining volatile components were removed to obtain the desired polyimide powder. The weight after drying at 50 ° C. for 24 hours is 43.9 g, the weight after drying at 260 ° C. for 2 hours is 43.4 g, and the amount of volatile components after 24 hours at 50 ° C. is 1.1%. It was confirmed that there was.
The average particle size of the obtained polyimide powder was 0.25 mm, and the particle size distribution was 100% by volume in the range of 0.01 to 2 mm. The reduced viscosity was 2.3 dL / g, the weight average molecular weight by size exclusion chromatography was 250,000, and the polydispersity was 2.5. Further, when the weight loss rate in the range of 200 to 300 ° C. was examined with a differential thermal / thermogravimetric analyzer, it was 0.06%, and the imidization rate was 95% or more.
20 g of the obtained polyimide powder is dissolved in 80 g of DMAC to prepare a uniform polyimide solution, then coated on a glass plate using an applicator, the DMAC is dried under predetermined conditions, and then pulled from the glass plate. It was peeled off to prepare a polyimide film having a thickness of 50 μm. The light transmittance of the obtained polyimide film was as high as 87%, and the yellowness was 2.3. No discoloration was observed visually, and the transparency was extremely excellent.

(Example 4)
In a glass 2 L separable flask equipped with a stirrer and a stirrer, 460 g of solvent N, N-dimethylacetamide (DMAC) and 2,2'-bis (trifluoromethyl) -4, which is an aromatic diamine compound, 64.048 g (0.200 mol) of 4'-diaminobiphenyl (TFMB) was added and stirred to dissolve TFMB in DMAC. Then, while stirring in the separable flask, under a nitrogen stream, the tetracarboxylic dianhydride 4,4'-(1,1,1,3,3,3-hexafluoropropane-2,2-) Diyl) 89.294 g (0.201 mol) of diphthalic acid dianhydride (6FDA) was added over about 10 minutes, and stirring was continued for 6 hours while adjusting the temperature so that it was in the range of 20 to 40 ° C. The polymerization reaction was carried out to obtain a viscous polyamic acid solution. The molar ratio of the tetracarboxylic dianhydride / aromatic diamine compound used was 1.005, and the concentration of the polyamic acid solution was 25% by weight.
Next, 409 g of DMAC was added to the obtained polyimide solution to dilute it so that the concentration of the polyamic acid was 15% by weight, and then 25.83 g of isoquinoline was added as an imidization accelerator while stirring the polyamic acid solution. Keep the temperature in the temperature range of 30 to 40 ° C., and add 122.5 g (1.20 mol) of anhydrous acetic acid as an imidizing agent while slowly dropping it over about 10 minutes, and then add the liquid temperature to 30 to 40. The temperature was maintained at ° C. and stirring was continued for 12 hours to carry out a chemical imidization reaction to obtain a polyimide solution.
Next, 1000 g of the obtained polyimide solution containing the imidizing agent and the imidizing accelerator was transferred to a 5 L separable flask equipped with a stirrer and a stirring blade, and the mixture was stirred at a speed of 120 rpm at 15 to 25 ° C. Keeping the temperature, 700 g of the prepared 1500 g of the methanol was added at a rate of 200 g / min, then reduced to a rate of 10 g / min, and the remaining methanol was added dropwise. When the first 700 g of methanol was added, the polyimide solution remained transparent without any particular turbidity, but after that, when methanol was added dropwise, the polyimide solution became turbid and became powdery. Precipitation of polyimide was confirmed. Subsequently, 1500 g of total amount of methanol was added to complete the precipitation of polyimide.
Next, the contents of the separable flask were filtered using a suction filtration device, and further washed and filtered using 1000 g of methanol.
Then, 50 g of the polyimide powder containing the residue of the volatile matter separated by filtration was dried at 50 ° C. for 24 hours using a dryer equipped with a local exhaust device to measure the weight, and further dried at 260 ° C. for 2 hours. , The remaining volatile components were removed to obtain the desired polyimide powder. The weight after drying at 50 ° C. for 24 hours is 43.9 g, the weight after drying at 260 ° C. for 2 hours is 43.4 g, and the amount of volatile components after 24 hours at 50 ° C. is 1.1%. It was confirmed that there was.
The average particle size of the obtained polyimide powder was 0.13 mm, and the particle size distribution was 100% by volume in the range of 0.01 to 2 mm. The reduced viscosity was 1.9 dL / g, the weight average molecular weight by size exclusion chromatography was 190,000, and the polydispersity was 2.1. Further, when the weight loss rate in the range of 200 to 300 ° C. was examined with a differential thermal / thermogravimetric analyzer, it was 0.03%, and the imidization rate was 95% or more.
20 g of the obtained polyimide powder is dissolved in 80 g of DMAC to prepare a uniform polyimide solution, then coated on a glass plate using an applicator, the DMAC is dried under predetermined conditions, and then pulled from the glass plate. It was peeled off to prepare a polyimide film having a thickness of 50 μm. The light transmittance of the obtained polyimide film at 450 nm was as high as 89%, the yellowness was 2.4, no discoloration was observed visually, and the transparency was extremely excellent.

(Comparative Example 1)
In a glass 2 L separable flask equipped with a stirrer and a stirrer, 460 g of solvent N, N-dimethylacetamide (DMAC) and 2,2'-bis (trifluoromethyl) -4, which is an aromatic diamine compound, 64.048 g (0.200 mol) of 4'-diaminobiphenyl (TFMB) was added and stirred to dissolve TFMB in DMAC. Then, while stirring in the separable flask, under a nitrogen stream, the tetracarboxylic dianhydride 4,4'-(1,1,1,3,3,3-hexafluoropropane-2,2-) Diyl) 89.294 g (0.201 mol) of diphthalic acid dianhydride (6FDA) was added over about 10 minutes, and stirring was continued for 6 hours while adjusting the temperature so that it was in the range of 20 to 40 ° C. The polymerization reaction was carried out to obtain a viscous polyamic acid solution. The molar ratio of the tetracarboxylic dianhydride / aromatic diamine compound used was 1.005, and the concentration of the polyamic acid solution was 25% by weight.
Next, 409 g of DMAC was added to the obtained polyimide solution to dilute it so that the concentration of the polyamic acid was 15% by weight, and then 25.83 g of isoquinoline was added as an imidization accelerator while stirring the polyamic acid solution. Keep the temperature in the temperature range of 30 to 40 ° C., and add 122.5 g (1.20 mol) of anhydrous acetic acid as an imidizing agent while slowly dropping it over about 10 minutes, and then add the liquid temperature to 30 to 40. The temperature was maintained at ° C. and stirring was continued for 12 hours to carry out a chemical imidization reaction to obtain a polyimide solution.
Next, 1000 g of the obtained polyimide solution containing the imidizing agent and the imidizing accelerator was transferred to a 5 L separable flask equipped with a stirrer and a stirring blade, and the mixture was stirred at a speed of 120 rpm at 15 to 25 ° C. The temperature was maintained, and 1500 g of methanol was added dropwise thereto at a rate of 200 g / min. When about 900 g of methanol was added, precipitation of polyimide having a relatively large particle size was confirmed. Subsequently, 1500 g of total amount of methanol was added to complete the precipitation of polyimide.
Next, the contents of the separable flask were filtered using a suction filtration device, and further washed and filtered using 1000 g of methanol.
Then, 50 g of the polyimide powder containing the residue of the volatile matter separated by filtration was dried at 50 ° C. for 24 hours using a dryer equipped with a local exhaust device to measure the weight, and further dried at 260 ° C. for 2 hours. , The remaining volatile components were removed to obtain the desired polyimide powder. The weight after drying at 50 ° C. for 24 hours is 43.4 g, the weight after drying at 260 ° C. for 2 hours is 40.8 g, and the amount of volatile components after drying at 50 ° C. for 24 hours is 6.0%. It was confirmed that.
The average particle size of the obtained polyimide powder was as large as 2.5 mm, and the particle size distribution contained less than 30% by volume in the range of 0.01 to 2 mm. The reduced viscosity was 2.1 dL / g, the weight average molecular weight by size exclusion chromatography was 210,000, and the polydispersity was 2.1. Further, when the weight loss rate in the range of 200 to 300 ° C. was examined with a differential thermal / thermogravimetric analyzer, a large weight loss of 0.42% was observed. The imidization rate was 95% or more.
20 g of the obtained polyimide powder is dissolved in 80 g of DMAC to prepare a uniform polyimide solution, then coated on a glass plate using an applicator, the DMAC is dried under predetermined conditions, and then pulled from the glass plate. When a polyimide film having a thickness of 50 μm was prepared by peeling off, the obtained polyimide film had a low light transmittance of 78% at 450 nm and a yellowness of 10.5, and yellowing of the film was visually observed.

(Comparative Example 2)
In a glass 2 L separable flask equipped with a stirrer and a stirrer, 460 g of solvent N, N-dimethylacetamide (DMAC) and 2,2'-bis (trifluoromethyl) -4, which is an aromatic diamine compound, 64.048 g (0.200 mol) of 4'-diaminobiphenyl (TFMB) was added and stirred to dissolve TFMB in DMAC. Then, while stirring in the separable flask, under a nitrogen stream, the tetracarboxylic dianhydride 4,4'-(1,1,1,3,3,3-hexafluoropropane-2,2-) Diyl) 89.294 g (0.201 mol) of diphthalic acid dianhydride (6FDA) was added over about 10 minutes, and stirring was continued for 6 hours while adjusting the temperature so that it was in the range of 20 to 40 ° C. The polymerization reaction was carried out to obtain a viscous polyamic acid solution. The molar ratio of the tetracarboxylic dianhydride / aromatic diamine compound used was 1.005, and the concentration of the polyamic acid solution was 25% by weight.
Next, 409 g of DMAC was added to the obtained polyimide solution to dilute it so that the concentration of the polyamic acid was 15% by weight, and then 25.83 g of isoquinoline was added as an imidization accelerator while stirring the polyamic acid solution. Keep the temperature in the temperature range of 30 to 40 ° C., and add 122.5 g (1.20 mol) of anhydrous acetic acid as an imidizing agent while slowly dropping it over about 10 minutes, and then add the liquid temperature to 30 to 40. The temperature was maintained at ° C. and stirring was continued for 12 hours to carry out a chemical imidization reaction to obtain a polyimide solution.
Next, 1000 g of the obtained polyimide solution containing the imidizing agent and the imidizing accelerator was transferred to a 5 L separable flask equipped with a stirrer and a stirring blade, and the mixture was stirred at a speed of 120 rpm at 15 to 25 ° C. The temperature was maintained, and 1500 g of methanol was added dropwise thereto at a rate of 10 g / min. When about 800 g of methanol was added, turbidity of the polyimide solution was confirmed, and precipitation of powdery polyimide was confirmed. Subsequently, 1500 g of total amount of methanol was added to complete the precipitation of polyimide.
Next, the contents of the separable flask were filtered using a suction filtration device, and further washed and filtered using 1000 g of methanol.
Then, 50 g of the polyimide powder containing the residue of the volatile matter separated by filtration was dried at 260 ° C. for 2 hours using a dryer equipped with a local exhaust device, without particularly drying at a temperature lower than 100 ° C. , Volatile components were removed to obtain 43.6 g of polyimide powder.
The average particle size of the obtained polyimide powder was 0.10 mm, and the particle size distribution was 100% by volume in the range of 0.01 to 2 mm. The reduced viscosity was 2.1 dL / g, the weight average molecular weight by size exclusion chromatography was 210,000, and the polydispersity was 2.1. Further, when the weight loss rate in the range of 200 to 300 ° C. was examined with a differential thermal / thermogravimetric analyzer, a large weight loss of 0.31% was observed. The imidization rate was 95% or more.
20 g of the obtained polyimide powder is dissolved in 80 g of DMAC to prepare a uniform polyimide solution, then coated on a glass plate using an applicator, the DMAC is dried under predetermined conditions, and then pulled from the glass plate. It was peeled off to prepare a polyimide film having a thickness of 50 μm. The light transmittance of the obtained polyimide film at 450 nm was as low as 79%, the yellowness was 7.5, and yellowing was visually observed.

The conditions and results of Examples and Comparative Examples are summarized in Tables 1 and 2.

As described above, in Examples 1 to 4, the average particle size (mm), the particle size distribution in the range of 0.01-2 mm (volume%), the weight loss rate (%) at 200-300 ° C., and the light transmittance. It is good in all of (%) and yellowness (YI), but in Comparative Example 1 which does not satisfy the powder forming condition by the precipitation of polyimide and the drying condition of the powder in the present invention, it is inferior in all of these characteristics. It can be seen that Comparative Example 2 which does not satisfy the drying conditions of the powder is inferior in the weight loss rate (%), the light transmittance (%), and the yellowness (YI) at 200-300 ° C.

Further, since the polyimide powder of the present invention has acquired different characteristics due to being produced under such powder forming conditions and powder drying conditions, the polyimide powder has a structure or characteristics thereof. There are circumstances in which it is impossible or nearly impractical to identify directly by.

By using the polyimide powder according to the present invention, it is possible to produce a polyimide film which has extremely excellent heat resistance and transparency and is particularly suitable for display applications and electronic material applications, and has extremely high industrial value. high.

Claims (15)

Manufactured from at least one aromatic diamine compound and at least one tetracarboxylic acid dianhydride through steps of polymerization to polyamic acid, chemical imidization reaction, powder formation by precipitation of produced polyimide, and drying. A polyimide powder soluble in N, N-dimethylacetamide, the average particle size of the polyimide powder is in the range of 0.04 to 0.4 mm, and the N, N-dimethyl of the polyimide powder. A polyimide powder having a light transmittance of 85% or more at a wavelength of 450 nm of a polyimide film having a thickness of 50 μm obtained by forming a film from an acetamide solution. The polyimide powder according to claim 1, wherein the light transmittance is 87% or more. The polyimide according to claim 1 or 2, wherein the weight loss rate in the range of 200 to 300 ° C. measured using a differential thermal / thermogravimetric analyzer is in the range of 0 to 0.2%. powder. Manufactured by using at least one aromatic diamine compound having a fluoro group as the aromatic diamine compound and at least one tetracarboxylic dianhydride having a fluoro group as the tetracarboxylic dianhydride. The polyimide powder according to any one of claims 1 to 3, wherein the polyimide powder is produced. Manufactured by a polyimide powder manufacturing method that includes the following steps:
The average particle size is in the range of 0.04 to 0.4 mm,
A polyimide film having a thickness of 50 μm was formed from the solution by dissolving it in N, N-dimethylacetamide, and when the light transmittance of the film at a wavelength of 450 nm was measured, the polyimide showed a light transmittance of 85% or more. powder.
(A) A step of precipitating polyimide by adding a poor solvent of polyimide to a polyimide solution containing polyimide dissolved in a solvent to obtain a polyimide powder containing a volatile component.
The weight ratio of the polyimide solution to the poor solvent is 1: 0.5 to 1:10.
A step in which the amount of the poor solvent added per minute from one time point before the start of precipitation of the polyimide to the completion of precipitation powdering is 0.0005 to 0.1 times (g / min) the amount of the polyimide solution.
(B) The volatile component-containing polyimide powder is dried at a temperature of less than 100 ° C. until the amount of the volatile component in the volatile component-containing polyimide powder is less than 5% without crushing, and then further 100 to 350. A step of drying at a temperature of ° C. for 0.1 to 24 hours to obtain a polyimide powder. The polyimide powder according to claim 5, wherein the light transmittance is 87% or more. The polyimide solution
(A1) A step of preparing at least one aromatic diamine compound and at least one tetracarboxylic dianhydride.
(A2) A step of polymerizing the above aromatic diamine compound and tetracarboxylic dianhydride under dissolution in a solvent to obtain a polyamic acid solution.
(A3) An imidizing agent was added to the obtained polyamic acid solution to carry out a chemical imidization reaction.
The polyimide powder according to claim 5 or 6, which is obtained by a step of obtaining a polyimide solution containing polyimide dissolved in a solvent. The polyimide powder according to claim 7, wherein the step (A3) is performed at 10 ° C. or higher and lower than 50 ° C. 7. or claim 7, wherein at least one aromatic diamine compound having a fluoro group is used as the aromatic diamine compound, and at least one tetracarboxylic dianhydride having a fluoro group is used as the tetracarboxylic dianhydride. 8. The polyimide powder according to 8. The polyimide powder according to any one of claims 5 to 9, which is soluble in a solvent. The polyimide powder according to claim 10, wherein the solvent is N, N-dimethylacetamide. The polyimide powder according to any one of claims 5 to 11, which contains 95% by volume or more of particles having a particle size in the range of 0.01 to 2 mm. The polyimide powder according to any one of claims 5 to 12, wherein the weight loss rate in the range of 200 to 300 ° C. is in the range of 0 to 0.2%. When a polyimide film having a thickness of 50 μm is formed from the solution by dissolving in N, N-dimethylacetamide and the yellowness (YI) of the film is measured, the yellowness (YI) of -5 to 5 is shown. The polyimide powder according to any one of claims 5 to 13. A polyimide film obtained by forming a film of the polyimide powder according to any one of claims 1 to 14.