JP2002293947A - Method for producing polyimide powder - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for producing polyimide powders with a simple procedure enabling the easy control of the particle diameter and provide the polyimide powders produced by the method. SOLUTION: The method for the production of polyimide powder comprises the thermal polymerization of an aromatic tetracarboxylic acid dianhydride and an aromatic diamine in an organic solvent and the lowering of the temperature of the obtained polyimide solution to precipitate polyimide particles.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to a method for producing a polyimide powder useful as a filling reinforcing material for non-thermoplastic films, varnishes, molded articles and the like having heat resistance and organic solvent resistance, and to a method for producing the same. Related to the polyimide powder to be obtained.

[0002]

2. Description of the Related Art Conventionally, as a method for producing this kind of polyimide powder, a solution of a polyimide precursor polyamic acid is prepared by heating and polymerizing a corresponding tetracarboxylic dianhydride and an aromatic diamine in an organic solvent. A method is known in which a polymer is dissolved in a polymer-insoluble solvent such as water, and the resulting precipitate is collected. In addition, the corresponding tetracarboxylic dianhydride and aromatic diamine are heated and polymerized in a polymer-insoluble solvent such as ethylene glycol to produce a polyamic acid slurry, and the polyamic acid is filtered off from the slurry, followed by heat ring closure. There is known a method of imidizing the compound, followed by pulverization.

That is, these methods do not directly synthesize polyimide from an aromatic tetracarboxylic dianhydride and an aromatic diamine, but form a gel during polymerization and cannot carry out the polymerization reaction. For example, polyamic acid, which is a precursor of polyimide, is once formed, and is heated and closed to form a polyimide, which is then pulverized into fine particles for the reason that it is not easy to take out and pulverize. However, this method has the disadvantage that the process up to the formation of the polyimide powder is complicated, and the particle size of the obtained powder tends to be large. It was not an industrially advantageous method, such as requiring means.

Further, a polyamic acid which is a precursor of a polyimide is once formed from a specific aromatic tetracarboxylic dianhydride and an aromatic diamine, and the polyimide is formed into particles in an organic solvent with the progress of imidization by heat ring closure. A method of precipitating is employed. However, in such a method, the control of polymerization and crystallization is extremely difficult, the particle size of the obtained powder tends to be large, and a pulverizing means is required to obtain a finely divided polyimide powder. Could not be.

On the other hand, JP-A-59-108030 discloses
Japanese Patent Application Laid-Open No. 62-127314 discloses a method for producing a polyimide powder by heat polymerization of an aromatic tetracarboxylic dianhydride and an aromatic polyisocyanate. A method of precipitating the polyimide particles as a particle in a solvent or a method of adding a fine particle filler or a fibrous filler before the polyimide particles are precipitated to precipitate the polyimide particles has been adopted. However, particle control by such a method is extremely difficult, and cannot be an industrially advantageous method.

[0006]

The technology described above requires many steps for producing a polyimide powder, and therefore, improvement is desired. Also, a method of once preparing a polyamic acid, which is a precursor of polyimide, from an aromatic tetracarboxylic dianhydride and an aromatic diamine, and precipitating polyimide as particles in an organic solvent at the same time as heating and ring closure by raising the temperature, A method in which polyimide is precipitated as particles in an organic solvent simultaneously with imidization accompanying thermal polymerization from aromatic tetracarboxylic dianhydride and aromatic polyisocyanate has been studied. It is extremely difficult to control the speed, and it has been difficult to obtain powder particles having a suitable particle diameter and the like.

Accordingly, an object of the present invention is to provide a method for producing a polyimide powder by which a polyimide powder can be produced in a simple process and the particle diameter can be easily controlled, and a polyimide powder obtained by the production method. Is to provide the body.

[0008]

Means for Solving the Problems In order to achieve the above-mentioned object, the present inventors have made a polyimide solution by heating and polymerizing a specific aromatic tetracarboxylic dianhydride and an aromatic diamine in an organic solvent. The present inventors have found that the temperature of the solution can be lowered and the particle diameter can be easily controlled when the polyimide particles are precipitated to complete the present invention.

That is, in the method for producing a polyimide powder of the present invention, a polyimide solution is obtained by heat-polymerizing an aromatic tetracarboxylic dianhydride and an aromatic diamine in an organic solvent, and then the temperature of the solution is increased. A step of precipitating the polyimide particles by lowering the temperature.

In the above, the aromatic tetracarboxylic dianhydride is 3,3 ', 4,4'-biphenyltetracarboxylic dianhydride and the aromatic diamine is 4,4.
Preferably, it is 4'-diaminodiphenyl ether. Further, the organic solvent is preferably an organic polar solvent.

On the other hand, the polyimide powder of the present invention
Agglomerates of spherical crystals made of polyimide obtained by polymerizing 3 ', 4,4'-biphenyltetracarboxylic dianhydride and 4,4'-diaminodiphenyl ether, and having a leaf structure radially grown; The average particle diameter of the aggregate is 1 to 20 μm.

[Effects] According to the method for producing a polyimide powder of the present invention, as shown in the results of the examples, the polyimide powder can be produced in a simple process and the particle size can be easily controlled. It can be carried out. The obtained polyimide powder has good heat resistance and organic solvent resistance.

When the aromatic tetracarboxylic dianhydride is 3,3 ', 4,4'-biphenyltetracarboxylic dianhydride and the aromatic diamine is 4,4'-diaminodiphenyl ether, And the solubility of the obtained polyimide are suitable for the production method of the present invention.

When the organic solvent is an organic polar solvent, the solubility in the above-mentioned monomer and polyimide and the properties as a reaction solvent are particularly suitable in the above-mentioned steps.

On the other hand, the polyimide powder of the present invention has good heat resistance and organic solvent resistance as described above, and has a leaf structure in which the particle surface is composed of multiple leaf pieces.
The surface porosity becomes extremely large.

[0016]

Embodiments of the present invention will be described below. According to the present invention, when producing polyimide particles in a polymerization solvent, after imidization is completed at a high temperature, the polyimide particles are freely precipitated when the polymerization solution is cooled. Therefore, as in the conventional method, the solid of the polyamic acid is not thermally imidized and crushed to produce a polyimide powder, but the polyamic acid is formed into particles during the thermal imidization in the polymerization solution. It does not produce polyimide powder.

The aromatic tetracarboxylic dianhydride and the aromatic diamine used in the present invention are characterized in that the polyimide produced from their polymerization reaction becomes a uniform polymerization solution near the boiling point of the organic solvent and at a low temperature lower than that. What is necessary is just to deposit a polyimide. That is, pyromellitic dianhydride or 3,3 ′, 4,4′-biphenyltetracarboxylic dianhydride or 3,3 ′, 4,4 ′
-Benzophenone tetracarboxylic dianhydride and a ring-closing imidation of a polyamic acid obtained from a combination of metaphenylenediamine or paraphenylenediamine, etc., because polyimide is precipitated at that temperature, such a combination may not be used. Many.

In the present invention, the obtained polyimide is imparted with an appropriate flexibility by using, for example, 4,4'-diaminodiphenyl ether having an ether bond as the aromatic diamine, thereby obtaining a polymerization solvent at the end of the polymerization. It is preferable to provide appropriate solubility in the inside. Further, such a component may be used as an aromatic tetracarboxylic dianhydride, in addition to an ether bond, a diamine or a tetracarboxylic dianhydride in which an aromatic ring is bonded by a carbonyl bond, a sulfonyl bond, a methine bond, or the like. Things can be used as appropriate. Among them, a combination of 3,3 ′, 4,4′-biphenyltetracarboxylic dianhydride and 4,4′-diaminodiphenyl ether is most preferred.

The organic solvent for the polymerization solvent is preferably an organic polar solvent having a high boiling point at which a ring-closing imide reaction occurs, and N-methyl-2-pyrrolidone, N, N-dimethylacetamide,
Dimethyl sulfoxide, N, N-dimethyl-2-imidazolidione, hexamethylenephosphortriamide and the like. In addition, an azeotropic organic solvent such as toluene or xylene can be used in combination to remove the ring-closing water and make the ring-closing imidization reaction efficient. The amount of the organic solvent to be used is such that the solid concentration mainly composed of aromatic tetracarboxylic dianhydride and aromatic diamine is 5 to 50% by weight, preferably 10 to 25% by weight. Good. If the solid content is too low, the reaction rate will be slow,
On the other hand, if the temperature is too high, the exothermic reaction tends to cause a problem in the reaction control during scale-up. Note that the content ratio of the aromatic tetracarboxylic dianhydride to the aromatic diamine is preferably set to be approximately equimolar (substantially the same equivalent).

The polymerization reaction temperature of the polyamic acid is from 0 ° C. to 8
In the range of 0 ° C., the temperature is preferably 10 ° C. to 25 ° C. If the reaction temperature is high, partial imidization may occur in some cases, and water as a by-product may cause a decrease in molecular weight, which is not preferable. In the polymerization reaction of the polyamic acid, the weight average molecular weight of the obtained polyamic acid is
It is preferably from 20,000 to 100,000. If the weight average molecular weight is too low, the leaf formation of the obtained polyimide powder particles will be incomplete, and the surface porosity tends to be low.If the weight average molecular weight is too high, the size of the obtained polyimide powder particles will be large. Tend to be.

Next, in the ring-closing imidization reaction of the high molecular weight polyamic acid, the azeotropic organic solvent is used in an amount of 5 to 30% by weight, preferably 10 to 20% by weight of the polymerization solvent. . Further, the ring-closing imidization reaction temperature is 1
It is preferable to set the temperature to 50 ° C to 200 ° C. 1
If the temperature is lower than 50 ° C., the reaction hardly proceeds, and the optimal temperature range is 170 to 190 ° C. in view of the reaction rate. At this time, the reaction is terminated by performing dehydration with an azeotropic solvent, and the azeotropic solvent is distilled off from the polymerization solution. At this temperature, the polymerization solution maintains a homogeneous solution.

By lowering the temperature of this high temperature polymerization solution,
Polyimide particles precipitate, but the particle shape varies depending on the temperature lowering speed and the stirring speed of the polymerization solution. Large particles precipitate at a slow cooling rate and a low stirring rate, and small particles precipitate at a fast cooling rate and a high stirring rate. Further, a step of maintaining a constant temperature in a supercooled state may be provided in the temperature decreasing process. Note that the obtained particles are particles containing crystals.

The produced polyimide particles precipitate in the polymerization solution and are separated by filtration or centrifugation.
For the above-mentioned filtration or centrifugation, a suction filter or a centrifuge generally used is used. Unreacted substances and low molecular weight polymers are desirably washed again with acetone or methanol.

After washing in this way, 1
After heating and drying at 00 ° C to 200 ° C for several hours to remove the solvent, the desired polyimide powder is obtained. This powder is
It consists of a spherical aggregate having an average particle size of 1 to 20 μm. Although the surface of the powder particles is slightly different depending on the method of forming the particles, the surface porosity of the multi-leaf pieces is very large.

The polyimide powder of the present invention comprises 3,3 ′,
4,4'-biphenyltetracarboxylic dianhydride and 4,4
It is an aggregate of spherical crystals made of polyimide obtained by polymerizing 4'-diaminodiphenyl ether and having a leaf structure grown radially, and has an average particle size of 1 to 20 µm as the aggregate. Such polyimide powder,
In the production method of the present invention, in particular, the cooling rate is 2 to 5 ° C /
Min, and the stirring speed of the polymerization solution is preferably set to 50 to 200 rpm.

The obtained polyimide powder is a polar organic solvent such as N-methyl-2-pyrrolidone, N, N-dimethylacetamide, dimethylsulfoxide, N, N-dimethyl-2-imidazolidione, hexamide as a polymerization solvent. It has features such as methylenephosphortriamide and insolubility in many organic solvents at room temperature. Further, since the powder has a crystal melting point of 500 ° C. or less, it can be molded, and can be applied to the use of a molded polyimide product which is resistant to organic solvents and can be molded.

The polyimide powder of the present invention has a leaf structure in which the particle surface is composed of multiple leaf pieces and has an extremely large surface porosity, so that the catalyst, adsorbent, sustained-release medicine, useful microorganism, antibacterial agent, etc. It is also useful as a carrier.

[0028]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments and the like specifically showing the configuration and effects of the present invention will be described below.

Example 1 58.8 g (0.2 mol) of 3,3 ', 4,4'-biphenyltetracarboxylic dianhydride and 4,4'-diamino in a 1000 mL four-neck flask under a nitrogen gas atmosphere 40.0 g (0.2 mol) of diphenyl ether and 395 g of N-methyl-2-pyrrolidone were charged, and 150 r
The mixture was reacted for 5 hours while stirring at pm to polymerize a high-viscosity polyamic acid. The molecular weight of the polyamic acid was 57,000. 20 g of xylene was added to this polymerization solution, and the temperature was slowly raised. Dehydration started around 160 ° C., the temperature was raised to 190 ° C., and the temperature was maintained at this temperature for 3 hours to confirm completion of the dehydration reaction. Further, xylene was distilled off at 195 ° C. At this time, the polymerization solution was a yellow transparent homogeneous solution. At this stirring speed, the polymerization solution is cooled at 30 ° C./10
After cooling at a slow temperature-lowering rate for about 1 minute, the polymerization solution began to become turbid at around 180 ° C., and precipitation of polyimide was observed. After cooling to room temperature and stopping stirring, the precipitate was separated by filtration and washed with a large amount of methanol. The filtered polyimide was dried by heating with a dryer at 100 ° C. to obtain a yellow polyimide powder.

From the infrared absorption spectrum (KBr method) of this polyimide powder, 1775 cm ^-1 and 1715 cm ^-1
A carbonyl absorption based on the imide group was observed. Although the fine particles of this polyimide powder were spherical particles of 5 to 10 μm as shown in the SEM photograph of FIG. 1, the number of independent particles was small and the particles were aggregates. In addition, as shown in the SEM photograph of FIG. 2, the surface had accumulated with many leaves overlapping. The powder particles had crystal peaks at 2θ = 15.08, 21.06 and 25.4 as shown by the wide-angle X-ray diffraction in FIG. As a result of a thermal analysis by DSC, the melting point of the crystals was 446 ° C. This polyimide powder did not dissolve in a polar organic solvent containing NMP at room temperature.

Example 2 In the same manner as in Example 1, a polyimide polymerization solution at 195 ° C. was prepared. This high-temperature polymerization solution was rapidly cooled to room temperature at a stirring speed of 300 rpm (cooling rate: 200 ° C./10
Minutes). The produced polyimide particles were washed and dried in the same manner as in Example 1 to obtain a yellow polyimide powder. From the infrared absorption spectrum (KBr method) of this polyimide powder, carbonyl absorption based on an imide group was observed at 1775 cm ⁻¹ and 1715 cm ⁻¹ . The fine particles of this polyimide powder were 1 to 5 μm as shown in the SEM photograph of FIG.
Particles aggregated to form a large coagulated body. Further, as shown in the SEM photograph of FIG. 5, the formation of leaves on the surface was incomplete. As shown by the wide-angle X-ray diffraction in FIG. 6, these powder particles have 2θ = 14.98, 21.20, 25.2.
4 showed a crystal peak, which was almost the same as in Example 1. As a result of thermal analysis by DSC, the melting point of this crystal was 444 ° C. Further, as in Example 1, this powder did not dissolve in a polar organic solvent containing NMP at room temperature.

[Brief description of the drawings]

FIG. 1 is an SEM photograph of a polyimide powder obtained in Example 1.

FIG. 2 is a high magnification SEM photograph of the polyimide powder obtained in Example 1.

FIG. 3 is a chart of wide-angle X-ray diffraction of the polyimide powder obtained in Example 1.

FIG. 4 is an SEM photograph of the polyimide powder obtained in Example 2.

FIG. 5 is a high magnification SEM photograph of the polyimide powder obtained in Example 2.

FIG. 6 is a chart of wide-angle X-ray diffraction of the polyimide powder obtained in Example 2.

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Claims (4)

[Claims] 1. A step of heating and polymerizing an aromatic tetracarboxylic dianhydride and an aromatic diamine in an organic solvent to obtain a polyimide solution, and then lowering the temperature of the solution to precipitate polyimide particles. A method for producing a polyimide powder comprising: 2. The method according to claim 1, wherein the aromatic tetracarboxylic dianhydride is 3,3 ′, 4,4′-biphenyltetracarboxylic dianhydride and the aromatic diamine is 4,4′-diaminodiphenyl ether. Item 4. The method for producing a polyimide powder according to Item 1. 3. The method according to claim 1, wherein the organic solvent is an organic polar solvent. 4. A spherical crystal comprising a polyimide obtained by polymerizing 3,3 ', 4,4'-biphenyltetracarboxylic dianhydride and 4,4'-diaminodiphenyl ether, and having a leaf structure radially grown. An aggregate of
A polyimide powder having an average particle diameter of 1 to 20 μm as an aggregate.