JPH01299871A - Polyamic acid solution, polyimide powder and production thereof - Google Patents

Abstract

PURPOSE:To make it possible to obtain a sine polyimide powder of excellent moldability, readily by mixing a specified polyamic acid with an amide solvent, a tert. amine and a poor solvent for the polyamic acid. CONSTITUTION:A polyamic acid (a) mainly consisting of repeating units of formula I (wherein Ar is a tetravalent aromatic residue containing at least one six-membered carbocycle, and Ar' is a bivalent aromatic or aliphatic residue) is obtained by reacting a tetracarboxylic acid derivative (i) with a diamine (ii) in an amide solvent. A mixture (b) is obtained by mixing an amide solvent (iii) (e.g., pyridine) with a tert. amine (iv) in an amount to give a component (iii) to component (iv) ratio of 99-10/1-90, a poor solvent (v) (e.g., acetone) for component (a), having a solubility parameter of 9.0-10.0(cal/cm<3>)<1/2>, in an amount to give a component (v) to component (iii) ratio of 80-50/20-50. 1-20wt.% component (a) is mixed with 99-80wt.% component (b) to obtain a polyamic acid solution. An aliphatic acid anhydride is added to this solution, and the mixture is subjected to cyclization through dehydration to obtain a polyimide powder of formula II.

Description

Detailed Description of the Invention <Field of Industrial Application> The present invention relates to a polyamic acid solution suitable for easily obtaining fine polyimide powder with excellent moldability, a polyimide powder obtained from the solution, and a method for producing the same. It is something.

<Conventional technology> Due to its excellent heat resistance and mechanical properties, polyimide resin plays an important role in the electrical and electronic equipment industry and the automobile industry. As technology advances, it is becoming an indispensable material. Among them, aromatic polyimide resins, such as the polypyromellitimide resin disclosed in Japanese Patent Publication No. 39-22196, have extremely excellent heat resistance and are ranked at the top of the so-called heat-added resins. However, it has the problem of poor fluidity and is difficult to mold.

In order to mold such a resin with poor fluidity, generally an FR of several μm or less, 4! There is a need for a powder having a high concentration of Il, and several methods for obtaining such a powder have been disclosed, but all of them have drawbacks and improvements are desired.

For example, Japanese Patent Publication No. 39-22196 discloses a method of re-precipitating a polyamic acid solution in a high-speed mixer to obtain a powder. It is difficult to do so, and some lump-like precipitates are formed.

In addition, as a method for improving this reprecipitation type, JP-A-61-2
No. 34 discloses a method of reprecipitating in a spray form using air spray.

Although this method can certainly produce fine powder, it requires an extremely large amount of organic solvent and has the disadvantage that it scatters during spraying, reducing the yield. Further, these reprecipitation methods are complicated processes in that they require two tanks: a polymerization tank and a reprecipitation tank.

As another method, 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. However, although this method can easily obtain fine powder, it has an essential drawback in that the polyimide produced has a high degree of crystallinity, resulting in extremely poor moldability. Generally, polyimide produced by heating imidization in a solution has a high degree of crystallinity and is difficult to mold.

<Problems to be Solved by the Invention> Therefore, the present inventors have conducted intensive studies on a method for easily obtaining fine polyimide powder with excellent moldability, and have prepared a polyamic acid solution with a specific solvent composition. The present invention was achieved by discovering that it is effective to chemically ring-close the compound with an aliphatic acid anhydride.

Means for Solving the Problems> That is, the present invention provides a polyamic acid 1 whose main structural units are A, a, and a repeating unit represented by the following general formula (I).
~20% by weight, B, b, amide solvent, C, tertiary amine and d, solubility variation 1/2 meter is 9.0-10.0 (c ai/d)
The total amount of poor solvent for a certain polyamic acid consists of 99 to 80% by weight, and the weight ratio b/c = 99/1 to
10/90, d/b=80/20 to 50,150. Furthermore, the present invention provides a polyimide powder whose main structural unit is a repeating unit represented by the following general formula (1) obtained by reacting the polyamic acid and aliphatic acid anhydride in the above solution, and a method for producing the same. .

Here, Ar is a tetravalent aromatic residue containing at least one carbon six-membered ring, each of which is characterized by being bonded to an adjacent carbon atom in the benzene ring of the Ar group. Specific examples include: Moreover, Ar- is a divalent aromatic or aliphatic residue, and in the case of aromatic, it has a 6-membered ring with 1 to 4 carbon atoms, and in the case of aliphatic, it has a skeleton of 04 to CI4. It is characterized by, for example, the following. Moreover, (1) and (2) may be independent polymers or may be copolymers.

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 reaction.

In the present invention, the amide solvent specifically refers to N,N-dimethylacetamide, N,N-dimethylformamide,
It refers to solvents such as N-methylpyrrolidone, all of which are good solvents for polyamic acids. Further, examples of the tertiary amine include pyridine, 3-ethylpyridine, 4-methylpyridine, 2,6-lutidine, inquinoline, and N.

Specific examples include N-dimethylbenzylamine, trimethylamine, and triethylamine, among which pyridine is preferred.

In the present invention, 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 halogens such as chloroform <9.3). and ester solvents such as ethyl acetate (9,1), but a7tone is particularly preferred. [0 is r Po
1yraer Handb.

Solubility parameter value, 1/2 (caf/d), as quoted from OJ)-Also, two or more of these solvents can be used in combination.

Furthermore, even if the solubility parameter is a poor solvent for polyamic acid within the above range, solvents having hydroxyl groups, primary amino groups, secondary amino groups, etc. are not preferred because:
This is because these solvents react with the acid anhydride and thus consume the aliphatic acid anhydride that is added later.

The characteristics of the present invention are that a polyamic acid solution having a specific solvent composition is prepared, and an aliphatic acid anhydride is added thereto for dehydration and ring closure.

This acid anhydride addition method is already well known;
It is widely used especially when producing film-like polyimide. However, it is difficult to use this method directly as a method for producing polyimide powder because:
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 inventors discovered that gelation does not occur and very fine powder can be obtained in a certain specific solvent composition. In other words, they discovered that fine powder suitable for molding can be obtained by adjusting the ratio of good and poor solvents to polyamic acid and controlling the interaction force between polymer solvents.

Here, the amide solvent is a good solvent for polyamic acid and is also a polymerization solvent. In addition, the solubility parameter is 9.
0 to 10.0 (c aj!/cJl)'4, the poor solvent for polyamic acid inhibits the affinity between the polyamic acid and the amide solvent, and plays the role of preventing gelation after imide ring closure. , the solubility parameter is 9.0 (c a
10.0 (c an/d>
Solvents exceeding 2 are not preferred because they have too strong an affinity for polyamic acid and are not effective in preventing gelation.

Further, the tertiary amine serves as an auxiliary solvent for uniformly mixing the amide solvent and the poor solvent. In other words, when a poor solvent is added to a polymerization solution consisting of a polyamic acid/amide solvent, strong and long stirring is required to mix it uniformly, but the presence of tertiary amines makes the mixing difficult. It has been found that the particle size of the produced polyimide powder becomes more homogeneous.

Furthermore, the tertiary amine also serves as a catalyst for the dehydration ring closure reaction, and can accelerate the production rate of polyimide powder after addition of the aliphatic acid anhydride.

The tertiary amine can be added at the same time as the poor solvent, but
It is preferable to add it already at the time of polymerization. On the other hand, if a poor solvent is added at the time of polymerization, it is difficult to increase the degree of polymerization, so it is preferable to add it after polymerization.

The developed theramic acid solution is characterized by polyamic acid being uniformly dissolved in a solvent of a specific composition, but the ratio (d/b) of the poor solvent and the amide solvent is expressed as a weight ratio. 8
0/20 to 50150 is good, especially when the polyamic acid is a polyamic acid whose main structural unit is a repeating unit represented by the following formula 0, and the poor solvent is acetone.
A range of 75/25 to 55/45 is preferred.

If the amount of the poor solvent is less than the above range, gelation will occur, which is undesirable, and if it is too much, the obtained powder will become coarse particles, which will significantly reduce the strength after molding, which is not preferred.

In addition, the ratio of amide solvent and tertiary amine (b/C) is
The weight ratio is preferably 99/1 to 10/90, preferably 95
15-40/60 is good.

In particular, when the polyamic acid is a polyamic acid whose main structural unit is a repeating unit represented by formula 0, 95
15 to 30/70 is good, particularly preferably 90/10 to
60/40 is good.

If the amount of tertiary amine is less than the above range, the effect of its addition will not appear, which is not preferable. If the amount is too large, the obtained polyimide powder will become coarse or it will precipitate at the polyamic acid stage, which is not preferable.

In the polyamic acid solution of the present invention, the weight concentration of polyamic acid is 1 to 20%, preferably 1 to 15%.
If it is less than 1%, the amount of solvent becomes too large and is not practical.
If it exceeds 20%, the viscosity of the whole becomes too high and sufficient stirring becomes impossible, which is not preferable.

In the present invention, polyimide powder is obtained by adding an aliphatic acid anhydride to a polyamic acid solution adjusted to a specific composition. Specific examples of such aliphatic acid anhydrides include acetic anhydride, propionic anhydride, , acetic acid 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, a polyimide powder can be obtained, but it is preferable to use 0.8 equivalent or more. Although the aliphatic acid anhydride may be added alone, it is preferable to add the aliphatic acid anhydride after diluting it with an appropriate solvent because the particle size of the resulting polyimide powder tends to be homogenized. Although the dehydration ring-closure reaction with substances proceeds satisfactorily even at room temperature, the reaction rate can be accelerated by heating. However, if the temperature is 150°C or higher, the reaction will be too rapid and gelation will occur easily, so it is preferable to carry out the reaction at 80°C or lower, preferably 60°C or lower.

According to the method for producing polyimide powder 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 must be removed by filtration, distillation, spray drying, etc. Goodbye,
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 desired characteristics. Examples of such additives include fluororesin, graphite, molybdenum disulfide, Examples include mica, talc, glass fiber, carbon fiber, aluminum, silver, and various metal oxides. These additives can be already blended during the polymerization process or can be blended before molding, but in either case, it is desirable that they be uniformly dispersed.

<Example> The present invention will be explained in further detail by giving examples below.

In the examples, pressure molding was carried out in the following manner: the powder was filled into a mold, a pressure of 3 x 103 hgf/d was applied at room temperature, the temperature was gradually raised, Finally, heat 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 taken out when the temperature is below 300°C. Next, from this molded product, a 65nm x 13rn x 3tm
A test piece was cut out and subjected to tensile and bending tests.

Example 1 4.4"-diaminodiphenyl ether (DDE) 60
．． 07g was dissolved in a mixture of 1,130g N,N-dimethylacetamide <DMAc) and 340g pyridine. Here pyromellitic dianhydride (PMJDA)
When 65.44 g was added and stirring was continued for 1 hour, 7
inh (in DMAC, concentration 0.5 g/d 1.3
Next, 2.500 g of acetone (solubility parameter value: 9.9 (c af/d) 2) was added to this solution, and the solution was heated vigorously. After vigorous stirring, a uniform polyamic acid solution was obtained in about 15 minutes.

Subsequently, the temperature of this polyamic acid solution was adjusted to 30'C in a water bath, and 65 g of acetic anhydride was added. After about 5 minutes, polyimide powder was precipitated. This was filtered, washed with acetone, and dried in air at 160'C for 5 hours to obtain 112 g of polyimide powder (yield: 98%). When this powder was pressure-molded and subjected to physical property tests, it was found to have excellent properties as shown in Table 1.

Example 2 60.07 g of DDE was dissolved in a mixture of 130 g of DMAcl and 400 fr of pyridine, and PMDA21
．． 81 tr and 64.45 g of benzophenone tetracarboxylic dianhydride (BTDA) were added. After stirring for 1 hour, a polyamic acid solution of 1.81 in 7 inh was obtained.Next, 3,000 ml of acetone was added to this. was added and stirred vigorously, and a homogeneous polyamic acid solution was obtained in about 15 minutes.

Subsequently, the temperature of this polyamic acid solution was adjusted to 30°C in a water bath,
When 100 g of anhydrous #acid was added, polyimide powder was precipitated about 15 minutes later. When this was thoroughly filtered, washed with toluene, and dried in air at 160°C for 5 hours, 131g
Polyimide powder was obtained (yield 98%). This powder was pressure-molded and subjected to physical property tests, and as shown in Table 1, it had excellent properties.

Comparative Example 1 A polyamic acid solution was obtained by polymerizing in substantially the same manner as in Example 1, except that the acetone was changed to 1.0 OOsr. However, when the same amount of acetic anhydride as in Example 1 was added to this, 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 1, except that pyridine was not used. However, about 5 hours of stirring was required for the acetone to dissolve and to form a homogeneous solution.

When the thus obtained polyamic acid solution was subjected to imide ring closure in the same manner as in Example 1, a polyimide powder was obtained.
When observed with a mirror, there was a mixture of particles (20, tim or higher), and the properties after molding were also poor. On the other hand, the polyimide powder obtained in Example 1 was homogeneous with a particle size of 1 to 2 μm.

Comparative Example 3 Each of the solvents used in Example 1 was DMAc170.
Polymerization was carried out using 1,680 g of pyridine, 510 g of acetone, and a polyamic acid solution was obtained. This was subjected to imide ring closure in the same manner as in Example 1, but the obtained powder had coarse particles as a whole and its properties after molding were extremely poor.

Comparative Example 4 A polyamic acid solution was obtained by polymerizing in substantially the same manner as in Example 2, except that 4.900 g of acetone was used.

Subsequently, imide ring closure was carried out in the same manner as in Example 2, but
The obtained powder had coarse particles as a whole and had poor characteristics.

Comparative Example 5 Each of the solvents used in Example 2 was DMAc200
Polymerization was carried out using 130g of pyridine, 130g of pyridine, and 220g of acetone to obtain a polyamic acid solution. However, perhaps because the viscosity was too high and sufficient stirring was not possible, the entire mixture turned into lumps after the addition of acetic anhydride, and a powder could not be obtained.

Comparative Example 6 In Example 1, toluene (solubility parameter value: 8.9 (cai/1/2 cd)) was used instead of acetone. However, toluene did not dissolve uniformly in the polyamic acid solution, and the polyamic acid precipitated in a bowl shape, making it impossible to obtain powdered polyimide.

Comparative Example 7 In Example 1, dimethyl sulfoxide (solubility parameter value = 12.0 (ca
j! /d) "A uniform IJ amic acid solution was obtained using 2). However, when acetic anhydride was added to this solution, the entire solution turned into a gel, and the powder could not be taken out.

Example 3 4.4-Monodiaminodiphenylmethane (DDM) 39.
65g and metaphenylenediamine (MPDA) 10
．． 81 g of N-methylpyrrolidone (NMP) 1.3
00 g and 400 g of 3-methylpyridine. 3.3- for this.

4.4'-Biphenyltetracarboxylic dianhydride (BP
When 88.27 g of DA) was added and stirring was continued for 1 hour, a polyamic acid solution with a pinh of 2.00 was obtained.

Next, add 1,4-dioxane (solubility variation 1/2 meter value: 10.0 (c aj!/cal)
) 3.570r was added and stirred vigorously,
A uniform polyamic acid solution was obtained in about 20 minutes.

Subsequently, the temperature of this polyamic acid solution was adjusted to 30°C in a water bath,
When 100 g of acetic anhydride was added, polyimide powder was precipitated about 30 minutes later. When this was post-treated in the same manner as in Example 1, 120 g (yield: 95%) of polyimide powder was obtained, and the properties after molding were excellent as shown in Table 2.

Comparative Example 8 In Example 3, 1,000 tons of 1,4-dioxane
Polymerization was carried out in substantially the same manner except that a polyamic acid solution was obtained. However, when acetic anhydride was added to this product, the entire product turned into a gel, and a powder could not be obtained.

Table 2 a) Geruich Example 4 After dissolving in MP, 43.62 g of PMDA was added,
Continue stirring for an additional 1 hour, then add '/1nhl.

A polyamic acid solution of No. 32 was obtained. Next, 500 r of pyridine, ethyl acetate (solubility balance 1/2 ter value: 9.1 (cab/cd)) 1.0
When I added 50g of the mixture and stirred it vigorously, it turned out to be about 25g.
A homogeneous polyamic acid solution was obtained in minutes.

(Polyamic acid concentration = 5.1% by weight, NMP/pyridine = 62/38, ethyl acetate/NMP = 57/43 'I
When this was heated to 30°C in a water bath and 40 g of acetic anhydride was added, polyimide powder was precipitated in about 20 minutes, and by post-processing in the same manner as in Example 1, 110 g (yield 96%) was obtained. Polyimide powder was obtained. After molding this thing,
When a bending test was performed, the strength was 14.3 kg f /
ma 2, elastic modulus 352 kg f/rexr
2, which was excellent.

Example 5 40.05 g DDE and 10 paraphenylenediamine
．． Dissolve 81 g in DHACl, 500 g, followed by 3.
107.48 g of 3-,4,4-diphenylsulfonetetracarboxylic dianhydride was added.

When stirring was continued for 1 hour, 7 of the obtained polyamic acid
inh was 1.51. Here is isoquinoline 500
r, methyl ethyl getone (solubility parameter value: 9
．． 3 (ca1/rm2) "2) 3. When the mixed solution of 300f was added and stirred vigorously, a uniform polyamic acid solution was obtained in about 20 minutes. (Polyamic acid concentration:
2.9% by weight, DMAc/isoquinoline = 75/25,
Methyl ethyl getone/DMAc = 69/31).

The temperature of this was adjusted to 30°C in a water bath, and 230 g of acetic anhydride was added, and polyimide powder was precipitated in about 30 minutes. By post-processing in the same manner as in Example 1, 137 g (yield: 95%) of polyimide powder was obtained. In addition, the bending properties after molding have a strength of 13. Olqr f/trxr
2, the elastic modulus was good at 390 kgf/2.

Comparative Example 9 A reprecipitation polyimide powder was obtained in the following manner according to the method disclosed in JP-A No. 61-234.

That is, DDE50.06r is DMAC1j! After dissolving in the solution, add PMDA54.53sr and continue stirring for another hour. A polyamic acid solution with inh of 2.30 was obtained. After diluting this with 21 parts of acetone, 10 parts of toluene, 0.5 parts of acetic anhydride, 0.5 parts of pyridine! An air spray gun was used to erupt into a sedimentation tank containing water. The obtained powder was filtered, washed with acetone, and then dissolved in air at 160 °C.
It was dried at ℃ for 5 hours to obtain 67+r polyimide powder (
yield 70%). The reason for the low yield is that when reprecipitating in the form of a spray, the particles fly off and adhere to the walls of the walls, resulting in considerable losses.

After pressure molding the powder, we measured its properties and found that the tensile strength was 1.
0.0 + rf10n2, M' 9.8%, bendability 1
It was 3.4 ht f/fi2.

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. Further, the reprecipitation tank was subjected to thermal imidization in the following manner according to the method disclosed in Comparative Example 10 Japanese Patent Publication No. 3'11-30060.

That is, after dissolving 50.06 g of DDE in DMAc 11, 54.53 g of PMDA was added and stirring was continued for an additional hour to obtain a polyamic acid solution having a Qlinh of 2.30. After adding pyridine 60a]1 to this, the mixture was heated to 150°C in an oil bath and stirred for 1 hour. After cooling, the precipitate was filtered, washed with acetone, and heated in air at 160℃ for 5 minutes.
After drying for an hour, a 90+r polyimide powder was obtained. (Yield: 95%). After press-molding this powder, we tried to measure its properties, but it was so brittle that it could be easily broken by hand, so we could not 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%.

Although this method is superior in that it requires a small amount of solvent, is easy to operate, and has a high yield, it has the inherent disadvantage that it cannot be molded because the polyimide powder produced is highly crystalline. It turned out that there was a problem.

<Effects of the Invention> As is clear from the Examples and Comparative Examples, the polyamic acid solution according to the present invention can be used with extremely simple operations.
Fine polyimide powder with excellent moldability can be obtained in good yield.

This is considered to be the result of controlling the interaction force between the polymer and the solvent within an appropriate range by controlling the ratio of the three types of solvents to the 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.

Claims (3)

[Claims] (1) A, a, 1 to 20% by weight of polyamic acid whose main structural unit is a repeating unit represented by the following general formula (I), B, b, amide solvent, c, tertiary amine and d, solubility parameter The total amount of poor solvent for polyamic acid is 99 to 80% by weight, and the weight ratio b/c is 99. /1~10/9
0, d/b=80/20 to 50/50. ▲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. ) (2) A polyimide powder whose main structural unit is a repeating unit represented by the following general formula (II) obtained by reacting the polyamic acid in the solution of claim (1) with an aliphatic acid anhydride. ▲There are mathematical formulas, chemical formulas, tables, etc.▼(II) (In the formula, Ar and Ar^- indicate the same thing as in formula (I).) (3) The following general formula (II) is obtained by adding an aliphatic acid anhydride to the solution of claim (1) and dehydrating and ring-closing the polyamic acid.
1. A method for producing polyimide powder, which comprises precipitating polyimide powder having a repeating unit represented by the following as a main structural unit. ▲There are mathematical formulas, chemical formulas, tables, etc.▼(II) (In the formula, Ar and Ar^- indicate the same thing as in formula (I).)