JPH03137124A - Polyimide resin powder, production thereof and molding the same - Google Patents

Abstract

PURPOSE:To readily obtain the subject powder having remarkably improved fluidity and charging properties and useful for formation of moldings excellent in mechanical characteristics by applying a pressure to a polyimide resin powder in advance and then crushing the resultant material. CONSTITUTION:A pressure (preferably 1-500 kg/cm<2>) is applied to a polyimide resin powder in advance and the resultant material is then crushed to obtain the objective powder having <=40 deg. angle of repose and <=20% degree of compaction. In addition, a wholly aromatic polyimide resin of the formula (R0 is 6-20C tetravalent aromatic group; R1 is 6-20C divalent aromatic group; n is positive integer) is preferable as the above-mentioned powder.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a polyimide resin powder with improved moldability, a method for producing the same, and a molding method using the polyimide resin powder. More specifically, it provides a polyimide resin powder with improved flowability and fillability, a method for producing the same, and compression molding and baking of the polyimide resin powder with improved flowability and fillability, which provides excellent thermal properties and I. ! The present invention relates to a method for producing a polyimide molded product having mechanical strength.

[Conventional technology and problems]

In the molding method of insoluble and infusible wholly aromatic polyimide resin, it is extremely difficult to apply the heating melt molding method used for ordinary thermoplastic resins, so a method of compression molding and baking the resin powder is difficult. has been used. Examples of methods for molding such wholly aromatic polyimide resin powder include Japanese Patent Publication No. 49-5737 and Japanese Patent Application Laid-open No. 62-234.
The resin powder filled into the mold in No. 908 is heated to several hundred to several thousand kilograms.
A method for obtaining the resin molded product by compression molding at a pressure of g/cl is disclosed. It has also been shown that this can be heated at a temperature above the glass transition point of the resin and below the decomposition temperature under no pressure or under pressure to form a stronger final molded product.

In order to obtain a molded product with excellent properties (specific gravity, mechanical strength, sliding properties, etc.) using the method described above, the first step is to obtain a homogeneous specific gravity close to the true specific gravity of polyimide in the compression molding process. You need to get the molding you have.

However, polyimide resin powder subjected to compression molding generally has a fine particle size and poor fluidity.

As a result, physical crosslinking is likely to occur when transferring and filling the powder into the mold, often resulting in uneven weight and thickness of the molded product, and problems such as insufficient specific gravity. .

[Problem to be solved by the invention]

In view of these circumstances, the inventors of the present invention conducted extensive research on methods for improving polyimide resin powder for molding, and as a result, they discovered that fluidity and fillability can be greatly improved by pre-compressing the resin powder and then pulverizing it. , led to the present invention.

[Means for solving the invention]

That is, the first aspect of the present invention is to use a polyimide resin powder characterized by having an angle of repose of 40° or less and a degree of compression of 20% or less, and a second aspect of the present invention is to apply pressure to the polyimide resin powder in advance. The third aspect of the present invention is a method for producing a polyimide resin powder, which is characterized in that the polyimide resin powder is crushed under a molding pressure of 3.
000~7000kg/cil, molding temperature 0~500℃
, Compression molding is performed for a molding time of 1 second or more, and then fired at a temperature of 300 to 500°C under vacuum or an inert gas atmosphere.
, a polyimide resin powder molding method characterized in that firing is performed under conditions of a firing time of 0.1 to 10 hours, and the raw material polyimide resin powder used in the present invention is not particularly limited, but General formula (I) (wherein Ro represents a C6-C2° tetravalent aromatic group, R1 represents a C4-C1O divalent aromatic group, and n represents a positive integer.

The polyimide resins represented by ) are preferred, and the polyimide resins represented by are particularly preferred.

There are no particular restrictions on the method for producing the polyimide resin powder used in the present invention, and for example, methods such as those described in Japanese Patent Publication No. 39-30036 and Japanese Patent Application Laid-open No. 57-200452, that is, aromatic tetracarboxylic dianhydride. and an aromatic diamine in an organic polar solvent to obtain a solution of polyamic acid, and then heating this to obtain a polyimide powder, or JP-B No. 39-9078, JP-A-61
As described in No. 252228, an aromatic tetracarboxylic dianhydride and an aromatic diamine are reacted in an organic polar solvent to obtain a polyamic acid solution, and then this solution is mixed in a solvent such as water, toluene, or hexane. A method of obtaining polyimide powder by contacting with a poor solvent for polyamic acid to obtain polyamic acid as a powder and heating it, and as described in Japanese Patent Publication No. 61-26926,
A method of directly obtaining polyimide powder by reacting an aromatic tetracarboxylic acid component and an aromatic diisocyanate in an organic polar solvent is preferably used.

In the present invention, the properties of the raw material polyimide resin powder obtained by the above method are not particularly limited, but in order for the final molded product to exhibit sufficient mechanical strength, the logarithmic viscosity (30°C, 0.5 dj !/gH寞504) is 0.1
dj! /g or more, B, E, ?, measured and calculated from the amount of nitrogen adsorbed from nitrogen and helium streams at liquid nitrogen temperature. , the specific surface area is at least 10 po/g, preferably 20 rd/g.
g or more is preferably used.

In addition, the raw material polyimide resin powder includes reinforcing fibers such as glass fiber, carbon fiber, and aramid fiber; and lubricants such as silica and talc. Various additives such as solid lubricants such as 4 lead, molybdenum disulfide, and boron nitride can be added as necessary.

In the present invention, the pressure applied in advance to the polyimide resin powder must be set within a range that is effective in improving the resin powder and does not adversely affect the physical properties of the molded product.

Specifically, a range of 1 to 500 kg/c- is preferable,
More preferably, it can be set in the range of 5 to 200 kg/cm3. If the pressure is less than 1 kg/cm3, the fluidity and filling properties of the resin powder will not be sufficiently improved;
If the pressure exceeds kg/cii, the specific gravity and strength of the molded product will decrease. There is no restriction on the time for applying pressure; all you have to do is secure the time necessary for the pressure to be transmitted inside depending on the thickness of the powder layer. Hydraulic presses and mechanical presses can be used as devices to apply pressure in advance. , rolls, etc. are preferably used.

It is desirable that these devices be equipped with a pressure gauge so that the actual pressure applied can be determined.

Thereafter, the pre-compressed product is pulverized to an appropriate particle size to obtain an improved polyimide resin powder. If the particle size after pulverization is too large, the surface of the molded product will become uneven, so the particle size is preferably 2000 μm or less, more preferably 1000 μm or less.

The improved polyimide resin powder thus obtained has excellent fluidity and filling properties, and it is convenient to use a powder tester made by Micron ■ to evaluate the characteristics of the powder. A sufficiently improved resin powder has a repose angle of 40° or less measured with the same device as a measure of flowability, and a degree of compaction measured with the same device (a constant value for the volume of naturally packed powder) as a measure of filling property. It is preferable that the powder volume (representing the reduction rate of the powder volume after applying a time tap impact) is 20% or less.

By compression molding and firing the improved polyimide resin powder thus obtained, a polyimide molded article having excellent thermal properties and mechanical strength can be produced. Molding conditions are pressure 3000-7000kg/cj, temperature 0-5
00° C. and a molding time of 1 second or more, it can be applied as desired.

The molding equipment used is a hydraulic press, a mechanical press, and a cold isostatic press (CI P).
, a hot isostatic pressure device (HIP), and the like.

Preferably, these devices are also equipped with pressure gauges.

In addition, the firing is carried out at a temperature of 3.
The heating time can be selected from the range of 0.00 to 500° C. for 2 hours and 0.1 to 10 hours depending on the desired physical properties.

The polyimide molded product obtained by the present invention has good uniformity and exhibits good material properties.

〔Example〕

EXAMPLES Hereinafter, the present invention will be explained in more detail with reference to Examples, but the present invention is not limited only to these Examples.

Reference Example 1 200.2g (1.0 mol) of 4.4'- under nitrogen flow
Oxydianiline with dimethylacetamide 21 and pyridine 2j! It was dissolved in a mixed solvent consisting of: The container was cooled in a water bath, and 218.1 g (1.0 mol) of pyromellitic dianhydride was gradually added thereto in powder form over 30 minutes. 6 while maintaining the same temperature even after the addition is complete.
Stirring was continued for 0 minutes to obtain a polyamic acid solution.

The container was transferred to an oil bath, and the contents were heated to the reflux temperature of the solvent to effect imidization. When the reflux temperature is reached, polyimide powder has already precipitated, but after the precipitation begins, an additional 3.
Stirring was continued for an hour.

After cooling, the slurry was filtered, and the resulting cake was washed with dimethylacetamide and methanol in this order.

The resin powder containing the solvent was dried under reduced pressure at 150° C. for 3 hours, and finally drying was continued at normal pressure and 300° C. until no residual solvent was detected, to obtain a polyimide resin powder.

The polyimide resin powder obtained in this manner has a logarithmic viscosity (30°C, 0.5d 1./gH2sO4) 0.
90 d 17g, B, E, T, legalized surface area 74.9
It had a po/g.

Examples 1 to 9 The polyimide resin powder synthesized in Reference Example 1 was put into a φ50 mold, and 20 to 7000 kg was pressed using a hydraulic press device.
Precompression was performed for 3 minutes at a pressure of /rd. The obtained pre-compressed product was taken out, placed in a mortar, and ground with a pestle.

The powder was passed through a 1000 μm mensch to make the particle size uniform.

A portion of the powder improved by the above treatment was taken and the B, E, T, and specific surface areas were measured using a Flowsorb 2300 automatic specific surface area measuring device manufactured by Shimadzu Corporation. Thereafter, the remaining powder was press-molded for 3 minutes at a pressure of 5000 kg/cIll. The molded product taken out was fired for 30 minutes at 450°C in a nitrogen stream under no pressure to obtain a polyimide resin molded product. JIS specific gravity of molded product before and after firing
It was measured according to the method of K 7112 and is shown in Table 1 together with the results of specific surface area.

Comparative Example 1 Molded products were produced in the same manner as Examples 1 to 9, except that the polyimide resin powder synthesized in Reference Example 1 was used as is, and the specific gravity was measured. The results are shown in Table 1.

From the above comparison of Examples 1 to 9 and Comparative Example 1, it was found that when the pre-compression pressure is 500 kg/4 or less, the specific surface area of the powder and the specific gravity of the molded product hardly decrease, but when it is higher than this, they decrease rapidly. I understand.

It moves back and forth over the top of the table and scrapes off excess powder with a blade attached to the tip of the square.

A filling test was repeated 10 times, with two reciprocations of the feeder being considered as one filling. The filling amount of the powder was measured, and the variation in the filling amount was expressed as (standard deviation (Ii ¥/average weight)). The results are also shown in Table 2.

Comparative Example 2 Measurement of powder properties and practical evaluation were carried out in exactly the same manner as in Example 10, except that the resin powder of Reference Example 1 was used instead of the pre-compressed resin powder. The results are shown in Table 2.

Table 2 Example 10 Preliminary pressure created in Example 4 using a powder tester made by Micron ■! The powder characteristics of 1 resin powder were measured. Further, the powder was filled into a mold with an opening of φ30 using an automatic feeder, and a practical evaluation was performed. In addition, the automatic feeder used here has a box with a hole in the bottom that is moved over the opening of the mold by the piston, and a comparison between Example 10 and Comparative Example 2 shows that the angle of repose is 40° or less and the degree of compression is 20% or less. It can be seen that the polyimide resin powder has significantly improved fluidity and fillability.

〔Effect of the invention〕

The polyimide resin powder for molding of the present invention having a specific angle of repose and degree of compaction has greatly improved fluidity and fillability, and such improved polyimide resin powder can be pulverized after applying pressure in advance. It can be easily obtained by the following method. The molded product obtained by molding the polyimide resin powder thus obtained has excellent mechanical properties and is useful in a very wide range of applications such as i-machine parts.

Claims (1)

[Scope of Claims] 1. A polyimide resin powder characterized by having an angle of repose of 40° or less and a degree of compaction of 20% or less. 2. The polyimide resin powder has the general formula (I) ▲Mathematical formula, chemical formula, table, etc.▼(I) The resin powder according to claim 1, which is a wholly aromatic polyimide resin represented by an aromatic group (n represents a positive integer). 3. A method for producing polyimide resin powder, which comprises applying pressure to polyimide resin powder in advance and then pulverizing it. 4. Polyimide resin powder has the general formula (I) ▲Mathematical formulas, chemical formulas, tables, etc.▼(I) 4. The manufacturing method according to claim 3, which is a wholly aromatic polyimide resin represented by an aromatic group (n represents a positive integer). 5. Polyimide resin powder has a general formula (I) where R_0 is ▲There are mathematical formulas, chemical formulas, tables, etc.▼, and R_
5. The manufacturing method according to claim 4, wherein 1 is ▲A mathematical formula, a chemical formula, a table, etc.▼. 6. The manufacturing method according to claim 3, 4 or 5, wherein the pressure applied in advance is 1 to 500 kg/cm^3. 7. The manufacturing method according to claims 3 to 6, wherein the particle size of the resin powder after pulverization is 2000 μm or less. 8. The polyimide resin powder according to claim 1 or 2 is molded under a molding pressure of 3000 to 700.
0kg/cm^3, molding temperature 0-500℃, molding time 1
Compression molding is carried out under conditions of 2 seconds or more, and then firing at a temperature of 300 to 500°C under vacuum or an inert gas atmosphere, and a firing time of 0.
．． A method for molding polyimide resin powder, which comprises firing under conditions of 1 to 10 hours.