JPH1045918A - Polyimide powder and preparation of powder molding - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a polyimide powder molding excellent in heat resistance, dimensional stability, mechanical strengths and elongation by packing a specified aromatic polyimide powder into a mold and molding the powder. SOLUTION: An aromatic polyimide powder which is prepared by coating a solid mainly consisting of a crystalline aromatic polyimide having such high heat resistance that no glass transition temperature is observed in the range of room temperature to 400 deg.C with a coating film of an amorphous polyimide and is judged to have a high molecular weight from the measurement of a logarithmic viscosity (at 30 deg.C in a concentration of 0.5g/100ml concentrated sulfuric acid) and whose crystallinity can be confirmed by wide-angle X-ray diffractometry is packed into a mold and molded under applied pressure and heat. This polyimide powder is prepared from an acid component comprising 3,3',4,4'-biphenyltetracarboxylic acid dianhydride and 0.5 to below 30mol% 2,3,3',4'-biphenyltetracarboxylic acid dianhydride and an aromatic diamine component comprising at least 80mol% p-phenylenediamine and has a mean particle diameter of 0.5-100μm.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to, for example, a 3,3 ', 4,4'-biphenyltetracarboxylic acid component as a main unit and a 2,3,3', 4'-biphenyltetracarboxylic acid component as a small unit. Having an extremely high level of heat resistance having paraphenylenediamine as an aromatic diamine component, and having particularly high flexural strength and tensile strength, is used for the production of aromatic polyimide powder molded articles having large elongation and its production. The present invention relates to an aromatic polyimide powder.

[0002]

2. Description of the Related Art Conventionally, as a method for producing a polyimide powder molded product comprising a 3,3 ', 4,4'-biphenyltetracarboxylic acid component and a paraphenylenediamine component, for example, JP-A-61-241326, Kaihei 1-2661
No. 34, for example. According to these documents, it is shown that the above-mentioned molded article is excellent in mechanical strength such as heat resistance, dimensional stability and compressive strength.

However, the melting points (or glass transition temperatures) of the polyimide powders described in the above-mentioned known documents are not substantially measured, and the fusion of the powders during heat compression molding is not sufficient. In particular, bending strength and tensile strength among mechanical strengths were not always satisfactory. In addition, when secondary processing of the molded body into various shapes by cutting etc., it is pointed out that the productivity is not high because the elongation, bending strength and tensile strength are not sufficiently large, or it is chipped at the time of molding. Have been.

[0004] For this reason, attempts have been made to improve the fusing property between powders during heat compression molding in order to increase the elongation and mechanical strength of the compact. For example, 3,3 ',
A method of compression molding a polyimide powder obtained by mixing a thermoplastic polyimide with a polyimide obtained from a 4,4′-biphenyltetracarboxylic acid component and a paraphenylenediamine component has been attempted. It has been pointed out that uniform mixing is difficult, the mechanical strength and elongation of the obtained molded product have not yet reached a satisfactory level, and that the heat resistance is rather lowered. Therefore, according to the conventional technique, it was not possible to obtain an aromatic polyimide powder molded product satisfying both heat resistance, mechanical strength and elongation.

[0005]

SUMMARY OF THE INVENTION An object of the present invention is to provide a polyimide powder molded product containing a conventionally known 3,3 ', 4,4'-biphenyltetracarboxylic acid component and paraphenylenediamine as main components. Another object of the present invention is to provide a method for producing an aromatic polyimide powder molded body having a high level of mechanical strength and elongation without lowering heat resistance, dimensional stability, compressive strength and the like.

[0006]

Means for Solving the Problems The present inventors have conducted intensive studies to achieve the above object, and as a result, as a polyimide powder, a high heat-resistant crystalline aromatic polyimide and a non-crystalline polyimide have been specified. It has been found that the contradictory physical properties can be achieved by combining and configuring, and the present invention has been completed.

That is, the present invention provides a coating layer comprising a non-crystalline polyimide containing a solid component mainly composed of a highly heat-resistant crystalline aromatic polyimide, whose glass transition temperature (Tg) is not observed in a temperature range of room temperature to 400 ° C. Covered, logarithmic viscosity (30 ° C, 0.5g / 100ml concentrated sulfuric acid)
Filling into a mold an aromatic polyimide powder that can be regarded as a high molecular weight by the measurement according to, and whose crystallinity is confirmed by wide-angle X-ray diffraction, and molding by applying pressure and heat simultaneously or separately. The present invention relates to a method for producing a characteristic polyimide powder compact.

[0008] The present invention also relates to a glass transition temperature (T
g), which is not observed in the temperature range of room temperature to 400 ° C., is formed by covering a solid content mainly composed of a highly heat-resistant crystalline aromatic polyimide with a coating layer composed of an amorphous polyimide, and having a logarithmic viscosity (30 ° C., 0.5 g). / 100 ml concentrated sulfuric acid), which can be regarded as a high molecular weight and whose degree of crystallinity is confirmed by wide-angle X-ray diffraction.

The aromatic polyimide powder according to the present invention has a solid content mainly composed of a highly heat-resistant crystalline aromatic polyimide whose glass transition temperature (Tg) is not observed in a temperature range of room temperature to 400 ° C., preferably 3, 3 ', 4,4'-
A polyimide solid content (particles) derived from a biphenyltetracarboxylic acid component and paraphenylenediamine is covered with a coating layer made of non-crystalline polyimide, and measured by logarithmic viscosity (30 ° C., 0.5 g / 100 ml concentrated sulfuric acid). The crystallinity is confirmed by wide-angle X-ray diffraction, which can be regarded as a high molecular weight, and the surface of the high heat-resistant crystalline aromatic polyimide particles is preferably covered with a coating layer made of a non-crystalline polyimide polymer. The particles having a logarithmic viscosity of 0.4 or more, particularly 0.5 to 3, having a two-layer structure of That is, the inner layer portion of the particles is a crystalline aromatic polyimide, while the outer layer is a powder having a two-layer structure of a thin layer of an amorphous polyimide.

The above-mentioned coating with the amorphous polyimide is preferably carried out on almost the entire surface of the crystalline aromatic polyimide particles, but this is not essential, and a certain portion of the polyimide powder particle surface (for example, 40% or less) In the case of (1), the surface of the crystalline aromatic polyimide particles may form a surface layer. ADVANTAGE OF THE INVENTION According to the polyimide powder of this invention, since the polymer on the surface of the powder particles is sufficiently melted during the molding, and they fuse and bond with each other, a molded product having a high balance of heat resistance, mechanical strength and elongation. Is considered to be obtained.

FIG. 1 is a cross-sectional photograph of the aromatic polyimide powder of the present invention, taken by a transmission electron microscope, according to one embodiment of the present invention. FIG. 2 is a cross-sectional photograph of a conventional polyimide powder. Wide Angle X-ray Diffraction (WAX) for Both Example Powder and Conventional Polyimide Powder
This will be described with reference to FIG. 3 which is an X-ray diffraction spectrum diagram according to S).

In FIG. 1, the inner layer portion of the polyimide powder of the present invention has a clear crystal structure as in FIG. 2, and its outer layer is made of an amorphous non-crystalline aromatic polyimide different from the inner layer. This is a structure in which the entire surface is thinly covered with a certain coating layer.

FIG. 3 clearly shows that the powder of the present invention into which the non-crystalline aromatic polyimide has been introduced has a lower crystallinity than the conventional powder (comparative example 1 described later). is there. Observing the intensity [cps] and the peak position (2θ), 2θ is 11.2929,
8.4398, 21.0729, 23.1386, 2
4.2767, 25.7922, 27.6664, 2
At 9.0357, a peak based on crystalline polyimide is observed.

The aromatic polyimide powder in the present invention is preferably produced by the following method, that is, an aromatic tetracarboxylic acid component for giving a crystalline aromatic polyimide, for example, preferably 3,3 ′, 4,4′-. Biphenyltetracarboxylic acid or an acid dianhydride thereof or an esterified product of the acid and a lower alcohol, and a tetracarboxylic acid component to give an amorphous polyimide, for example, preferably 2,3,3 ′,
Tetracarboxylic acid containing 4'-biphenyltetracarboxylic acid or an acid dianhydride or an esterified product of the acid and a lower alcohol (preferably an acid dianhydride) to give a non-crystalline polyimide Component (preferably 2,3,3 ', 4'-biphenyltetracarboxylic acid)
Containing at least about 0.5 mol% to less than 30 mol%, preferably 1 mol% to less than 25 mol%, and more preferably 1.5 mol% to less than 20 mol%, based on the total tetracarboxylic acid component Polymerization of a tetracarboxylic acid component and an aromatic diamine component containing at least about 80 mol% or more of paraphenylenediamine to all diamine components in an organic polar solvent by a known method in a known manner is carried out. Manufactured by imidation followed by powder recovery from the reaction system,
It is a powder having an average particle size (primary particle) of a high molecular weight aromatic polyimide of 0.5 to 100 μm, particularly 1 to 50 μm.

According to the above-mentioned method, the polymer is polymerized and imidized while generating fine particles of the crystalline aromatic polyimide, and then the amorphous polyimide is made insoluble to precipitate the polyimide powder. A polyimide powder can be obtained. According to this method, even if no special operation is added to polymerization and imidization, it is a polyimide powder having a two-layer structure, the amount of residual reaction solvent is small, and uniform particle formation can be easily performed. In this case, when the proportion of the non-crystalline polyimide increases, the particles contain many solvents and the
As a result, the operation for recovering the powder becomes complicated.

In the polyimide powder of the present invention, two kinds of polyimides are not substantially copolymerized, which is confirmed by the fact that the crystallinity is almost equal to the composition ratio.
On the other hand, in a method in which a non-crystalline polyimide is produced in a system in which a crystalline aromatic polyimide powder has been added in advance, a mixture of two types (crystalline polyimide and non-crystalline polyimide) is coated with the non-crystalline polyimide. Is not obtained, and a molded article obtained from such a mixture has insufficient physical properties.

As the aromatic tetracarboxylic acid component, only 3,3 ', 4,4'-biphenyltetracarboxylic acid and 2,3,3', 4'-biphenyltetracarboxylic acid are used in the above ratio. Although it is desirable to perform high-level physical properties (particularly mechanical strength and heat resistance during use) of the powder molded body, it is preferable to reduce the amount of some biphenyltetracarboxylic acids, preferably 50 mol% or less, particularly 20 mol% or less. May be replaced by an aromatic tetracarboxylic acid.

As these aromatic tetracarboxylic acids, pyromellitic acid or its acid dianhydride, 3,3 ',
4,4'-benzophenonetetracarboxylic acid or its acid dianhydride, 2,2'-bis (3,4-dicarboxyphenyl) propane or its acid dianhydride, bis (3,4
-Dicarboxyphenyl) methane or an acid dianhydride thereof, bis (3,4-dicarboxyphenyl) ether or an acid dianhydride thereof, and the like.

The above-mentioned paraphenylenediamine is desirably used alone in view of the physical properties of the powder molded product and the simplicity of the polymerization / imidization operation. However, a small amount of the paraphenylenediamine is preferably used as long as the physical properties are not substantially impaired. About 20 mol% or less may be replaced with diamines such as other aromatic diamines and diaminopolysiloxanes. For example, examples of such a diamine include metaphenylenediamine, 4,4'-diaminodiphenyl ether, 4,4'-diaminodiphenylmethane, 4,4'-diaminodiphenylpropane, and bis (4-aminophenyl) dimethylsilane , 1,4-bis (4-amino-phenoxy) benzene, 1,3-bis (4-amino-phenoxy) benzene, and the like.

In the present invention, the above-mentioned aromatic polyimide powder is filled in a mold and molded by simultaneously or separately applying pressure and heat to produce a molded polyimide powder. The aromatic polyimide powder is used as it is, or a preform is formed from the powder, and the molding temperature is 200 to 600 ° C, preferably 250 to 5 ° C.
50 ° C., particularly preferably 300 to 500 ° C., and a molding pressure of 300 to 10000 Kg / cm ² , preferably 50
0 to 8000 kg / cm ² , particularly preferably 600 to 6 kg / cm ²
It can be suitably manufactured by compression molding at 000 kg / cm ² . These temperatures and pressures may be arbitrarily selected as long as they are within the above ranges.

Alternatively, the aromatic polyimide powder is preferably sufficiently dried (pre-baked) or its preform is molded at a molding temperature of room temperature to 350 ° C. and a molding pressure of 30 ° C.
0 to 10000 Kg / cm ² , preferably 500 to 80
00Kg / cm ² , more preferably 600-6000K
g / cm ² of the molded article under non-compression
It is manufactured by post-sintering at -600 ° C, preferably 250-500 ° C. The molded product obtained by this method has a characteristic that the overall characteristics are lower than that of the molded product obtained by the above-mentioned heat compression molding, but the product is excellent in productivity such as parallel processing.

Further, in the method for producing the powder compact of the present invention, an inorganic filler such as silica, mica, kaolin, asbestos, boron nitride, aluminum oxide, iron oxide, graphite, molybdenum sulfide, iron sulfide, or fluorine Various fillers such as an organic filler such as a resin can be mixed with the above-mentioned polyimide powder (may be blended by any of internal addition and external addition) and used.

In the production method of the present invention, examples of an apparatus for producing a polyimide powder molded body include a four-column hydraulic press, a high-pressure hot press, and the like.
The preform is preferably formed by a method using a rotary press or a tablet machine, for example.

The polyimide powder compact obtained by the method of the present invention is obtained from the above-mentioned specific aromatic polyimide powder, and is a conventionally known 3,3 ′, 4,4 ′.
-Mechanical strength and elongation can be improved without deteriorating excellent heat resistance, dimensional stability and the like of a polyimide powder molded product obtained from biphenyltetracarboxylic acids and paraphenylenediamine.

[0025]

Embodiments of the present invention will be described below. In each of the following examples, various physical properties of the polyimide powder molded body were measured by the following test methods. (i) Bending test: ASTM D-790 Measurement temperature 23 ° C
, The bending strength (Kg / cm ² ) was determined. (ii) Tensile test: Tensile strength (Kg / cm ² ) was determined at a measurement temperature of 23 ° C. according to ASTM D-638.

Example 1 1275 g of N-methyl-2-pyrrolidone (NMP)
60.47 g of paraphenylenediamine (PPD) (0.
559 mol) was added at 60 ° C. to a 2 L four-neck separable flask equipped with a stirrer, a reflux condenser (with a water separator), a thermometer and a nitrogen inlet tube at 60 ° C. 3,3 ', 4, while circulating and stirring
4'-biphenyltetracarboxylic acid (s-BPDA) 1
48.08 g (0.503 mol) and 2,3,3 ', 4'
-Biphenyltetracarboxylic acid (a-BPDA) 16.
45 g (0.0559 mol) were added almost simultaneously, and the temperature was raised to 100 ° C. in about 20 minutes.
A solution uniformly dissolved in the P solvent was prepared. Next, the solution was heated to 190 ° C. in about 30 minutes while refluxing the solvent and the generated water while continuing the nitrogen gas flow and stirring, and removing the generated water. The precipitation of the aromatic polyimide started at an internal temperature of around 165 ° C. After the internal temperature reached 190 ° C., the reaction was continued for 3 hours to complete the reaction.

Thereafter, the reaction solution was cooled, the aromatic polyimide powder was filtered off, the powder was washed with acetone, and further dried at 150 ° C. for 10 hours in a vacuum drier.
Drying under normal pressure at 0 ° C. was performed for 30 minutes to obtain 202.1 g (theoretical yield: 98.6%) of an aromatic polyimide powder. This aromatic polyimide powder has a two-layer structure in which the entire surface of the crystalline polyimide particles is covered with a coating layer made of amorphous polyimide from observation by a transmission electron microscope (showing a cross-sectional view). , The logarithmic viscosity of the polymer (30
° C, 0.5 g / 100 ml concentrated sulfuric acid) is 0.62,
The average particle size (primary particles) was 6 μm, and the crystallinity was 38% as analyzed by wide-angle X-ray diffraction (Leland's method). No glass transition temperature was observed up to 400 ° C. This polyimide powder is referred to as polyimide powder-A.

Comparative Example 1 In Example 1, 164.53 g of s-BPDA alone was used as a tetracarboxylic acid component without using a-BPDA.
(0.559 mol), except that (0.559 mol) was used. The obtained powder weighed 202.5 g (theoretical yield: 98.
8%), the polyimide powder has a logarithmic viscosity of 0.65, an average particle size of 8 μm, a crystallinity of 43% from observation with a transmission electron microscope (showing a cross-sectional view), and a glass transition temperature of up to 400 ° C. Was not done. This polyimide powder is referred to as polyimide powder-B.

Comparative Example 2 In Example 1, 164.53 g of only a-BPDA was used as a tetracarboxylic acid component without using s-BPDA.
(0.559 mol), except that (0.559 mol) was used. No powder was obtained and a pasty solid was obtained.

Example 2 A polyimide powder-A was prepared in a cylindrical form (diameter 60 mm, height 6
0 mm) and heated to 350 ° C.
And then pre-fired for about 3 hours under reduced pressure, and the pre-fired polyimide powder was subjected to a pressure of 2000 kg / c.
m ² , and pressurized at 350 ° C. for 10 minutes, and heated under the above pressure for about 120 minutes to a temperature of 480 ° C., and maintained at this pressure and temperature for 30 minutes, during which gas such as volatile matter was released. After the main baking, the pressurized state is stopped, the molded product is taken out of the compression molding machine, further subjected to post-baking at 450 ° C. for 2 hours in an oven, and then allowed to cool to obtain a polyimide powder. A molded product (a cylinder having a diameter of 60 mm and a height of 10 mm) was obtained. This polyimide powder compact was cut to prepare a plate (test piece) made of the polyimide powder compact, and a bending test was performed. Flexural strength is 1700Kg / cm
^{Was 2} . The powder compact exhibited good cutting workability (secondary workability).

Comparative Example 3 A heat-compression molding was carried out in the same manner as in Example 2 except that polyimide powder-B was used as the polyimide powder, to obtain a molded polyimide powder. The bending strength of the molded body is 107
It was 0 kg / cm ² .

Example 3 A polyimide powder-A was placed in an oven heated to 300 ° C. and calcined under normal pressure for about 1 hour.
0 mm, height 30 mm) and pressure 200
After adding 0 Kg / cm ² and pressurizing at room temperature for 10 minutes, the pressure was released, and the molded product taken out of the mold was placed in an oven heated to 300 ° C., and the temperature was raised to 480 ° C. over about 120 minutes. Maintained at this temperature for 30 minutes and then allowed to cool to form a polyimide powder compact (a cylinder 30 mm in diameter and 3 mm in height)
I got A test piece was prepared by cutting this polyimide powder compact. The tensile strength of this test piece is 850 Kg / c
m ² .

Comparative Example 4 A polyimide powder molded body was obtained in the same manner as in Example 3 except that polyimide powder-B was used. The tensile strength of the compact was 450 kg / cm ² .

Example 4 With respect to the elongation of the powder compact, the compacts obtained in Comparative Example 3 and Example 3 were evaluated as relative values (the value in Comparative Example 3 was 1). Was the value of For the powder compacts obtained in Examples 2 and 3 and Comparative Examples 3 and 4, the heat resistance was measured by thermogravimetric reduction, the dimensional stability was determined by the heat shrinkage, and the compression strength was determined by a compression test (AST).
(Method according to MD-695).
In each case, no substantial difference was observed, indicating good heat resistance.

Example 5 A polyimide powder was obtained in the same manner as in Example 1 except that the ratio of s-BPDA to a-BPDA was changed to 98: 2 (molar ratio). This polyimide powder has a two-layer structure in which almost the entire surface of the crystalline polyimide particles is covered with a coating layer made of amorphous polyimide similarly to the polyimide powder (polyimide powder-A) obtained in Example 1. The polymer had a logarithmic viscosity of 0.62, an average particle size of 6 μm, and a crystallinity (overall) of 36%. No glass transition temperature was observed up to 400 ° C. This polyimide powder was compression-molded in the same manner as in Example 2, and the bending strength of the obtained test piece was measured. As a result, the bending strength was 1200 kg / cm ² .

Example 6 A polyimide powder was obtained in the same manner as in Example 1 except that the ratio of s-BPDA to a-BPDA was changed to 85:15 (molar ratio). This polyimide powder has a two-layer structure in which the entire surface of the crystalline polyimide particles is covered with a coating layer made of amorphous polyimide similarly to the polyimide powder (polyimide powder-A) obtained in Example 1. And
The logarithmic viscosity of the polymer was 0.63, the average particle size was 6 μm, and the crystallinity (overall) was 28%. No glass transition temperature was observed up to 400 ° C. This polyimide powder was compression molded in the same manner as in Example 2, and the bending strength of the obtained test piece was measured. As a result, the bending strength was 1570 Kg / cm ² .

[0037]

Since the present invention has the structure described in detail above, it has the following effects.

That is, according to the method of the present invention, it is possible to obtain an aromatic polyimide powder molded body having a high level of mechanical strength and elongation without lowering heat resistance, dimensional stability, compressive strength and the like. be able to.

The aromatic polyimide powder of the present invention has sufficient polymer melting on the surface of the powder particles during molding.
In addition, it is possible to fuse and bond with each other, and to obtain a molded product in which heat resistance, mechanical strength and elongation are highly balanced.

[Brief description of the drawings]

FIG. 1 is a photograph of a cross section of an example of the powder of the present invention observed by a transmission electron microscope.

FIG. 2 is a cross-sectional photographic view of an example of a conventional powder observed by a transmission electron microscope.

FIG. 3 is an X-ray diffraction spectrum of one example of the powder of the present invention and one example of a conventional powder by wide-angle X-ray diffraction (WAXS). A spectrum diagram with a large intensity is that of the conventional powder, and a spectrum diagram with a small intensity is the spectrum diagram of the powder of the present invention.

Claims (5)

[Claims] 1. A glass transition temperature (Tg) of room temperature to 400
The solid content mainly composed of the highly heat-resistant crystalline aromatic polyimide which is not observed in the temperature range of ° C. is covered with a coating layer composed of the non-crystalline polyimide, and the logarithmic viscosity (30 ° C.,
0.5 g / 100 ml concentrated sulfuric acid) can be regarded as a high molecular weight, and an aromatic polyimide powder whose crystallinity is confirmed by a wide-angle X-ray diffraction method is filled in a mold, and pressure and heat are simultaneously or simultaneously applied. A method for producing a polyimide powder molded body, which is separately added and molded. 2. The aromatic polyimide powder has a lower crystallinity as measured by a wide-angle X-ray diffraction method than that of a highly heat-resistant crystalline aromatic polyimide alone, and the glass transition temperature of the powder is from room temperature to 400 ° C. The method for producing a polyimide powder molded body according to claim 1, which is not observed in a temperature range of ° C. 3. The aromatic polyimide powder is 3, 3 ′, 4,
4'-biphenyltetracarboxylic dianhydride and 2,3
2,3,3 ', 4'-biphenyl comprising an aromatic tetracarboxylic acid component comprising 3', 4'-biphenyltetracarboxylic dianhydride and an aromatic diamine component containing at least 80 mol% of paraphenylenediamine The content of the tetracarboxylic acid component is in the range of 0.5 mol% to less than 30 mol% of the total aromatic tetracarboxylic acid component, and the average particle diameter is 0.1 mol%.
The method for producing a polyimide powder molded body according to claim 1, which has a thickness of 5 to 100 µm. 4. The molding of the aromatic polyimide powder at a molding temperature of 200 to 600 ° C. and a molding pressure of 300 to 10,000 K
^2. A pre-molded product obtained by heat compression molding at g / cm ² or at room temperature to 350 ° C. and a molding pressure of 300 to 10,000 kg / cm ² is post-sintered at 200 to 600 ° C. under non-compression. Of powder compacts. 5. A glass transition temperature (Tg) of room temperature to 400.
The solid content mainly composed of the highly heat-resistant crystalline aromatic polyimide which is not observed in the temperature range of ° C. is covered with a coating layer composed of the non-crystalline polyimide, and the logarithmic viscosity (30 ° C.,
Aromatic polyimide powder characterized in that it can be regarded as a high molecular weight by measurement with 0.5 g / 100 ml concentrated sulfuric acid) and the degree of crystallinity is confirmed by wide-angle X-ray diffraction.