JPH01122A - Manufacturing method of polyimide powder - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION <Field of Industrial Soil Application> The present invention relates to a method for producing polyimide powder that can easily produce a fine powder with excellent moldability.

<Conventional technology> Due to its excellent heat resistance and mechanical properties, polyimide resin plays an important role in the electrical/electronic equipment industry, the automobile industry, etc. In recent years, polyimide resins have become increasingly popular, especially in recent years due to the increase in speed and performance of equipment. As technology advances, it is becoming an indispensable material. Among them, aromatic polyimide resins represented by polypyromellitimide resin disclosed in Japanese Patent Publication No. 39-22196 have extremely excellent heat resistance.
Although it stands at the top of the so-called heat-resistant resins, it has the problem of poor fluidity and difficulty in molding.

In order to mold such a resin with poor fluidity, it is necessary to turn the resin into a fine powder of several μm or less, and several methods have been disclosed for this purpose, but all of them have drawbacks. , improvement is desired.

For example, Japanese Patent Publication No. 39-22196 discloses a method of reprecipitating a polyamic acid solution in a high-speed mixer to obtain a powder, but with such a method, it is not possible to turn the entire solution into a fine powder. It is difficult to prevent the formation of a partially lumpy precipitate.

In addition, as a method for improving this reprecipitation type, Japanese Patent Application Laid-open No. 61-23
Publication No. 4 discloses a method of reprecipitating in a spray form using air spray.

Although it is possible to obtain fine powder with this method, it has the drawbacks that it is complicated to operate and requires the use of an extremely large amount of organic solvent.

Further, Japanese Patent Publication No. 39-30060 discloses a method of heating a polyamic acid solution in the presence of a tertiary amine to obtain polyimide powder.

Although this method can easily obtain fine powder, it has the disadvantage that the crystallinity of the produced polyimide becomes high, resulting in extremely poor moldability and difficulty in molding.

<Problems to be Solved by the Invention> Therefore, the inventor of the present invention conducted extensive research on a method for easily obtaining fine powder with excellent moldability, and found that after diluting a polyamic acid solution with a specific solvent, aliphatic acid anhydride We have discovered that it is effective to carry out a ring-closing reaction with a substance, and have arrived at the present invention.

Means for Solving the Problems> That is, the present invention provides a polyamic acid solution consisting of a polyamic acid whose main structural unit is a repeating unit represented by the following general formula (I) and an amide solvent, and a polyamic acid solution containing 1% of the amide solvent. .0 to 5.0 times volume, solubility parameter is 9
．． 0 to 10.0 (cal/c4)v2 of polyamic acid and an aliphatic acid anhydride, and the polyamic acid is subjected to a dehydration ring-closing reaction. It is.

Ar where Ar is a tetravalent aromatic residue containing at least one carbon six-membered ring, of which each divalent is characterized by being bonded to an adjacent carbon atom in the benzene ring of the Ar group. Examples include: Also, Ar' is 2
It is an aromatic or aliphatic residue, and in the case of aromatic, it has 1 to 4 carbon 6-membered rings, and in the case of aliphatic,
It is characterized by having a skeleton of C4 to C1, and H
3 CH.

It will be done. Also, (1) may be a single polymer,
Alternatively, it may be a copolymer.

Such a method for synthesizing polyamic acid is publicly known, and its details are disclosed, for example, in Japanese Patent Publication No. 39-22196. It can be obtained by reacting with

The amide solvent referred to in the present invention specifically refers to N, N-
It refers to solvents such as dimethylacetamide, N,N-dimethylformamide, and N-methylpyrrolidone, all of which are good solvents for polyamic acid.

In the present invention, an aliphatic acid anhydride is added to a polyamic acid solution, followed by dehydration and ring closure to produce a polyimide. Such an acid anhydride addition method is widely used, especially when producing film-like polyimide. It is being However, it is difficult to use this method directly as a method for producing polyimide powder. This is because the addition of the acid anhydride causes the entire polyamic acid solution to gel, forming a large gel mass.

In the process of investigating methods to prevent this gelation, the present inventor discovered that gelation does not occur and very fine powder can be easily obtained in a certain specific solvent composition. . That is, the solubility parameter is 9.0~
10.0 (cal/d) Death, oh, bo1. Ae, acid. When the poor solvent and polyamic acid solution were diluted, gelation did not occur within a specific dilution range and fine polyimide powder was obtained.

Specifically, such a poor solvent includes acetone (9
, 9), ketone solvents such as methyl ethyl ketone (9,3), ether solvents such as tetrahydrofuran (9,1), 1,4-dioxane (10,0), and chloroform (9,3)+73. 2.0 butylene solvents, ester solvents such as ethyl acetate (9,1), etc. can be mentioned, but acetone is particularly preferred ("P" is in parentheses).
Quoted from olymer Handbook J,
Solubility value (cal/c4). Moreover, these solvents can also be used in combination of two or more types.

Further, even if the solvent is a poor solvent for polyamic acid having a solubility parameter within the above range, a solvent having a functional group such as a hydroxyl group, a primary amino group, or a secondary amino group is not preferable. This is because these functional groups consume the aliphatic acid anhydride that is added during the reaction to dehydrate and ring-close the polyamic acid.

Solubility 21,7-,-,9. . A solvent having a concentration of less than (Cal/,,)% is not preferable because it has too poor solubility in polyamic acid and precipitates the polyamic acid.

In addition, the solubility parameter is 10.0 (cal/cd
) A solvent exceeding v2 is not preferable because it has too strong an affinity for polyamic acid and gels during dehydration and ring closure.

In the present invention, the dilution range with the poor solvent is LO to 5.0 times the volume of the amide solvent, and in particular, polyamic acid can be obtained by combining pyromellitic dianhydride and 4,4'-diaminodiphenyl ether. When the poor solvent is acetone, it is preferably 18 to 4.0 times the volume, particularly preferably 2.0 to 3.0 times the volume. If the amount of the poor solvent is less than the above range, gelation will occur, which is undesirable. If it is too much, the resulting powder will become coarse particles, which will significantly reduce the strength after molding, which is not preferred.

That is, the gist of the present invention is to prevent gelation and coarse particle formation and obtain fine powder by adjusting the interaction force between the polyamic acid and the solvent within an appropriate range.

Therefore, the optimum solvent composition varies slightly depending on the type of polyamic acid and solvent, and also the reaction temperature, and an optimum solvent composition exists under each condition.

Examples of the aliphatic acid anhydride used in the present invention include acetic anhydride, propionic anhydride, acetic formic anhydride, and the like. If these aliphatic acid anhydrides are used in an amount of 0.3 equivalent or more based on the amic acid unit, polyimide powder can be obtained.
It is preferable to use 0.8 equivalent or more. Also, the poor solvent and aliphatic acid anhydride can be added to the polyamic acid solution at the same time, but it is better to add the poor solvent first, mix upwards, and then add the acid anhydride. is uniform, which is preferable.

Furthermore, when a tertiary amine is added as a catalyst for the dehydration ring-closing reaction, the production rate of polyimide powder can be accelerated.
-Methylpyridine, 4-methylpyridine, 2,6-lutidine, isoquinolino, N,N-dimethylbenzylamine, triethylamine and the like.

Although the dehydration ring-closing reaction using an aliphatic acid anhydride proceeds satisfactorily even at room temperature, the rate can be accelerated by heating. However, at a temperature of 150°C or higher, the reaction is too rapid and gelation becomes difficult, so it is preferable to carry out the reaction at a temperature of 150°C or lower, preferably 60°C or lower.

According to the present invention, a solution in which fine polyimide powder is suspended is obtained, but in order to extract the polyimide powder from this solution, the solvent may be removed by filtration, distillation, spray drying, or the like.

The obtained powder can be used for molding as it is, but processing it with a mixer, pulverizer, etc. is effective in making the molded product uniform.

The polyimide powder of the present invention can be blended with various additives as necessary to impart desirable characteristics.
Examples of such additives include fluororesins, graphite, molybdenum disulfide, mica, talc, glass fibers, carbon fibers, aramid fibers, aluminum, silver, copper, lead, various metal oxides, and the like. These additives can be already added during the polymerization process, or
Although they can be blended before molding, it is desirable to uniformly disperse them in any case.

<Example> The present invention will be further described in detail with reference to Examples below. In addition,
In the examples, pressure molding was performed in the following manner. That is, the powder is filled into a mold and 3X
Apply a pressure of 103&p f /d. Next, this is gradually heated to 450°C. During this heating process, gas is generated, so the pressure should be released from time to time to remove the gas. After keeping it at 450°C for 5 minutes, it is cooled while being pressurized, and when the temperature reaches 300°C or lower, it is taken out. Next, a test piece measuring 65 tx x 13 tx x 3H was cut out from this molded product and subjected to tensile and bending tests.

Example 1 4.4'-diaminodiphenyl ether (DDE) 6
0.07 F (0.3 mol) in L21 (DN, N-
Pyromellitic dianhydride (PMDA) was dissolved in dimethylacetamide (DMAc) and 65.44 Da (0,
3 mol) was gradually added. After the addition was completed, stirring was continued for 1 hour, and pinh (in DM Ac,
A polyamic acid solution with a concentration of 0.5 f/dl (measured at 30° C.) of 2.50 was obtained. Next, the temperature was adjusted to 30°C in a water bath, and 7-tz tons of 3.361 (dissolved IW degree parameter (m: 9.9 (ca1%/i)) was gradually added to form a homogeneous solution. did.

While stirring vigorously, acetic anhydride 18011/and pyridine 360 we were added, and after about 5 minutes, yellow powder of polyimide was precipitated. This was filtered, washed with acetone, and then dried in air at 160°C for 5 hours to obtain 109F polyimide powder (yield 95%).
. This powder was then pressure molded and subjected to tensile and bending tests. The results are shown in Table 1, and as in the comparative example described later, it had excellent properties compared to those in which acetone was not added in an appropriate amount.

Also, compared to the reprecipitation method described in Comparative Example 6, the characteristics were similar, but the operation was simpler and the amount of solvent used was smaller.
Moreover, the yield was also high.

Example 2 DDE60.071 (0.3 mol) was added to L2J? (7
) DM A C di-dissolved, Coleni PMDA 32.72
y (0.15 mol), and benzophenonetetracarboxylic dianhydride (BTDA) 48.331 (0
15 mol) was gradually added. After the addition was completed, stirring was continued for another hour, and F inh was 2.0.
A polyamic acid solution of 0 was obtained. Next, the temperature of this was adjusted to 30°C in a water bath, and 3.961 acetone was gradually added to form a homogeneous solution.

While stirring vigorously, 180 ml of acetic anhydride and 360 ge of pyridine were added, and after about 10 minutes, yellow powder of polyimide was precipitated. This was filtered, washed with acetonate, and then dried in air at 160°C for 5 hours to obtain 126F polyimide powder (yield 97%).
. This powder was then pressure molded and subjected to tensile and bending tests. The results are shown in Table 1, and the properties were superior to those of the comparative example.

Comparative Example 1 Polymerization was carried out in substantially the same manner as in Example 1, except that the amount of acetone added was changed to 1.14. but,
After adding acetic anhydride and pyridine, the entire mixture turned into a gel, and no powder could be obtained.

Comparative Example 2 Polymerization was carried out in substantially the same manner as in Example 2, except that the amount of acetone added was changed to 6 and 21. but,
In this case, the powder obtained will be coarse,
The properties after molding were also extremely low as shown in Table 1.

Table 1 Mechanical properties of polyimide molded products a) Gelation comparative example 3 In Example 1, toluene (solubility parameter value: 8.9 (cal/d)) was used instead of acetone.
) was used. However, toluene did not dissolve in the polyamic acid solution and the polyamic acid precipitated in lumps.
It was not possible to obtain powdered polyimide.

Comparative Example 4 In Example 1, dimethyl sulfoxide (solubility parameter value: 12.0 (cal/d)) was used instead of acetone. Example 3 Bis(4,4'-(para-aminophenoxy)phenyl) After adding Shikashi, acetic anhydride, and pyridine, the whole gelatinized and powder could not be obtained.
15 sulfone 129.75 f (0.3 mol)
DMAclc dissolved L of d, and PMDA65.441
(0.3 mol) was gradually added until F inh was 1
．． A polyamic acid solution of 80% was obtained. After adjusting the temperature to 40°C, 5.71 of tetrahydrofuran (solubility parameter value: 9.1 (cat/d)/2) (3.8 times the volume of DMAc) was gradually added to form a homogeneous solution. did.

While vigorously stirring, 120 ml of acetic anhydride and 300 ml of pyridine were added, and a yellow powder of polyimide was obtained after about 5 minutes. This was post-treated in the same manner as in Example 1, pressure-formed, and subjected to a bending test.
Strength: 13.1 kq f/-1 Modulus of elasticity: 360 kq
It shows good characteristics with f/-.

Comparative Example 5 Polymerization was carried out in substantially the same manner as in Example 3, except that the amount of tetrahydrofura added was 1.41 (vs. DM Ac 0.93 times the volume).

However, after adding acetic anhydride and pyridine, the entire mixture turned into a gel, and no powder could be obtained.

Comparative Example 6 After polymerizing polyamic acid in the same manner as in Example 1, according to the method disclosed in JP-A-61-234,
Reprecipitation treatment was performed as follows. That is, after diluting the polyamic acid solution with 2.42 degrees of acetone, 12 degrees of toluene was added.
1 was sprayed with an air spray gun into a precipitation tank containing 0.6 N of acetic anhydride and 0.64 N of pyridine. The obtained powder was filtered, washed with acetone, and then dried in air at 160° C. for 5 hours to obtain polyimide powder 83y (yield: 72%). The reason for the low yield is that when reprecipitated in the form of a spray, it scatters or adheres to walls, resulting in considerable loss.

After pressure molding the powder, we measured its properties and found that the tensile strength was 1.
0.0 & 9f, '+d, elongation 9.8%, bending strength 13.
It was 4 kq f 7-.

It has been found that this method has the drawbacks that, although the properties of the molded article are excellent, it requires a large amount of solvent and the yield is low. Moreover, the operation was more complicated than the method of Example 1 in that a reprecipitation tank was required separately.

Comparative Example 7 After polymerizing polyamic acid in the same manner as in Example 1, thermal imidization was performed as follows according to the method disclosed in Japanese Patent Publication No. 39-30060. That is, after adding 8"Od of pyridine to a polyamic acid solution,
It was heated to 0°C and stirred for 1 hour. After cooling, the precipitate was filtered, washed with acetone, and then dried in air at 160°C for 5 hours to obtain 110F polyimide powder (yield 96%).
. After press-molding this powder, I tried to measure its properties, but it was so brittle that it could easily be broken by hand, so I couldn't measure it. In order to investigate the cause, the crystallinity of the powder was examined by X-ray diffraction, and it was found to be approximately 40%, indicating high crystallinity.

On the other hand, the crystallinity of the powder obtained in Example 1 was as low as about 5%.

This method uses a small amount of solvent, is easy to operate,
Although it is excellent in terms of high yield, it has been found that it has an essential problem in that the polyimide powder produced is highly crystalline and cannot be molded.

Example 4 DDE40.051 (0.2 mol)
2'-bisC4-(4-aminophenoxy)phenyl]
Propa/41.051 (0.1 mol) was dissolved in 15 g of DM Ac, and PMDA65.44f was added to this.
(0.3 mol) was gradually added. The pinh of the obtained polyamic acid was 1.90. Next, the temperature of this was adjusted to 40°C in a water bath, and 2.41% of chloroform (solubility: 5/-9-value: 9.3 (cal/d)V2) (
DMACl, 5 times the volume) was gradually added to form a homogeneous solution.

While stirring vigorously, a mixed solution of 180 i of acetic anhydride, 360 d of 3-methylpyridine, and 0.64 d of acetone (vs. DMAc, 2.0 times total) was added, and polyimide powder was precipitated about 5 minutes later. When this was filtered, washed with acetonate, and dried in air at 180°C for 5 hours, 127f polyimide powder was obtained (yield: 95%).
). When this was pressure-formed and one bending test was performed, the strength was 15.1 kgf / tA, and the elastic modulus was 350 kq f.
It showed good characteristics with a rating of 7-.

<Effects of the Invention> As is clear from the Examples and Comparative Examples, by using the method of the present invention, fine particles with excellent moldability can be produced by adding reagents while stirring the polymerization solution, which is an extremely simple operation. It is possible to obtain fine powder. This is considered to be the result of the interaction force between the polymer and solvent being adjusted within an appropriate range by precisely setting the ratio of good solvent to poor solvent for polyamic acid.

The polyimide molded product thus obtained has excellent heat resistance,
It has mechanical properties, sliding properties, etc., and is useful for electrical/electronic equipment parts, automobile parts, business machine parts, aircraft parts, etc.

Patent applicant Higashi Shikikai Co., Ltd.

Claims (3)

[Claims] (1) A polyamic acid solution consisting of a polyamic acid whose main structural unit is a repeating unit represented by the following general formula (I) and an amide solvent is added to
~5.0 times volume, solubility parameter 9.0-10
．． A method for producing polyimide powder, which comprises adding a poor solvent for polyamic acid and an aliphatic acid anhydride having a ratio of 0 (cal/cm^2)^1^/^2 to subjecting polyamic acid to a dehydration ring-closing reaction. ▲There are mathematical formulas, chemical formulas, tables, etc.▼ (I) (In the formula, Ar is a tetravalent aromatic residue containing at least one 6-membered carbon ring, and Ar' is a divalent aromatic or aliphatic residue. show.) (2) Polyamic acid is pyromellitic dianhydride and 4,4
The method for producing polyimide powder according to claim 1, wherein the polyamic acid is obtained from a reaction with '-diaminodiphenyl ether. (3) The method for producing polyimide powder according to claim (2), wherein the poor solvent is acetone, and the volume is 1.8 to 4.0 times that of the amide solvent.