JPH0653729B2 - Method for producing aromatic cyclic polyimide - Google Patents

Description

TECHNICAL FIELD The present invention relates to a method for producing aromatic cyclic polyimides. Aromatic cyclic polyimides are useful as an adhesive, a laminated material, a sealing material, a sliding material, an electric component, and a raw material for structural materials such as aircraft and vehicles.

(Prior Art) A method for producing a corresponding cyclic polyimide from an aromatic polyamine having two or more primary amino groups and an α, β-unsaturated dicarboxylic acid and / or its anhydride is a polyamic acid. However, the method of producing by dehydration imidization is general.

In this method, the polyamic acid as the intermediate is easily produced by simply mixing the polyamine and the α, β-unsaturated dicarboxylic acid anhydride under mild conditions, but the subsequent dehydration imidization is not easy. However, there are problems such as low yield and insufficient purity as a resin raw material due to low purity.

Various methods have been proposed in order to solve such problems, but there is still no satisfactory method.

For example, bisamidic acid obtained from aromatic diamine and maleic anhydride, dehydrating agent such as acetic anhydride and sodium acetate or 3
A method of imidizing at a relatively low temperature by adding a dehydration catalyst such as a primary amine (see, for example, JP-B-46-29140 and JP-B-4).
9-40231, Japanese Patent Publication No. 52-2913, Japanese Patent Laid-Open No. 55-
13202, JP-A-59-212470, JP-A-61-
24564) is disclosed. However, this method consumes a large amount of expensive dehydrating agent and is industrially disadvantageous.

Therefore, various methods without using a dehydrating agent have been proposed.
For example, a hydrocarbon or halogenated hydrocarbon solvent that is azeotropic with water or an aprotic polar solvent such as N, N-dimethylformamide or N-methylpyrrolidone, or a mixed solvent system thereof, under an acid catalyst or no catalyst. , A method of heating and dehydrating (for example, JP-A-53-68770 and JP-A-57-1).
59764, JP-A-60-260623, JP-A-62-
123169 and JP-A-63-201166) are disclosed. However, these methods cannot suppress side reactions such as polymerization and decomposition reaction, and have a low yield or contain many by-products in the reaction product, and it is possible to obtain a polyimide having good purity and hue. could not.

(Means for Solving the Problems) As a result of trying the method for improving the yield and suppressing side reactions, the present inventors have found that during the dehydration imidization reaction of the polyamic acid, the polyamic acid is decomposed to cause a primary amine. And that α, β-unsaturated dicarboxylic acids or their anhydrides are formed, and that this is the main cause of many side reactions such as addition reactions of primary amines to olefinic double bonds. Found out. Further, the presence of excess α, β-unsaturated dicarboxylic acid or its anhydride, isomerization of α, β-unsaturated dicarboxylic acid or its anhydride, or the formation of a polymer by intermolecular dehydration of the isomerized acid, etc. It was previously thought to cause side reactions.

However, in the subsequent studies, the present inventor has found that even if a primary amine is produced, if the α, β-unsaturated dicarboxylic acid or its anhydride is present in a large excess relative to the polyamic acid, the primary amine Have been found to react with α, β-unsaturated dicarboxylic acids or their anhydrides to convert them into polyamic acids and suppress the addition reaction of primary amines to olefinic double bonds.

Based on this finding, as a result of detailed examination of the amount and concentration of α, β-unsaturated dicarboxylic acid and its anhydride relative to the polyamic acid, the polyamic acid present in the reaction system was
0.5 wt% of β-unsaturated dicarboxylic acid or its anhydride
It has been found that the dehydration imidization can effectively suppress the side reaction in the mixed solution of the polar solvent and the nonpolar solvent which are dissolved.

As a result of examination for further industrial application, α, β-
In the solution in which the unsaturated dicarboxylic acid or its anhydride is dissolved, if a polyamic acid is continuously or intermittently supplied little by little, a small amount of solvent, and a small amount of α, β-unsaturated dicarboxylic acid or its It has been found that an anhydride can be used in a larger excess ratio with respect to the polyamic acid to make the reaction vessel compact.

By continuously or intermittently supplying the polyamic acid to keep the concentration in the reaction system low, the molar ratio of the α, β-unsaturated dicarboxylic acid or anhydride to one equivalent of the amide group of the polyamic acid can be controlled by the side reaction. Even if a large excess ratio is required for suppression, an excess amount of 1 wt% or more is sufficient.

Since the polyamic acid is charged little by little continuously or intermittently, the polyamic acid is easily dispersed in the solvent, and the reaction proceeds easily.

It has advantages such as

In order for the method of continuously or intermittently supplying the polyamic acid into the α, β-unsaturated dicarboxylic acid and / or its anhydride solution to be effective, the reaction rate of imidization of the polyamic acid depends on the supply of the polyamic acid. It is desirable that it is faster than speed, but under the conditions of the present invention, for example, 10 w of maleic anhydride is used.
In 150 parts of a mixed solution (toluene: DMF = 10: 1 (parts by weight)) of toluene and N, N-dimethylformamide (hereinafter, abbreviated as DMF) at 110 ° C. dissolved in t%,
When 50 parts of polyamic acid was continuously fed over 3 hours, the concentration of the polyamic acid in the system was analyzed during the reaction, and the polyamide was almost absent and was converted to polyimide.

From this, it is judged that the rate of the dehydration imidization reaction of the polyamic acid is fairly fast, and by continuously or intermittently supplying the polyamic acid in small amounts, the α, β-unsaturated dicarboxylic acid and / or its anhydride can be obtained. , Can always maintain a large excess rate.

In the prior art, when a polyamic acid is produced and then dehydrated and imidized to produce a polyimide, 1 equivalent of the dicarboxylic acid and / or its anhydrous portion is added to 1 equivalent of the amino group of the polyamine.
Since the reaction is carried out for about 1 mol to generate a polyamic acid and then dehydration imidization is carried out in the same reactor as it is, the excess amount of the dicarboxylic acid and / or its anhydride is 0.1 mol per 1 equivalent of the amide group of the polyamic acid. To the extent
The ratio of the dicarboxylic acid and / or its anhydride is in a large excess relative to the acid, starting at the end of the reaction in which the dehydration imidization reaction of the polyamic acid proceeds and the acid decreases, not in a large excess ratio. become. Therefore, in the initial stage of the reaction, the excess amount of the dicarboxylic acid and / or its anhydride was small, and a side reaction was easily generated.

As in the method of the present invention, an example in which the polycarboxylic acid is continuously or intermittently supplied little by little to a solution in which the dicarboxylic acid and / or an anhydride thereof are dissolved at a constant concentration to improve the purity and the yield is described above. It is something that cannot be seen in technology.

In the present invention, it is desirable that the α, β-unsaturated dicarboxylic acid and / or the anhydride thereof to be added to the reaction system in advance be the same as the α, β-unsaturated dicarboxylic acid anhydride that is a raw material of the cyclic polyimide. .

The feature of the present invention is to continuously or intermittently supply a small amount of polyamic acid into a solution of a constant concentration of α, β-unsaturated dicarboxylic acid or an anhydride thereof. If it is supplied at the same time, the concentration of the same acid in the reaction system will increase, and the excess amount of the dicarboxylic acid and / or its anhydride will decrease, so it is desirable to supply an amount commensurate with the rate of polyimide formation.

The aromatic polyamines used in the present invention are the first in the molecule.
It is an aromatic amine having two or more primary amino groups. The polyamine shown by general formula (A), (B), (C), and (D) can be illustrated.

(In the formula, X is a hydrogen atom, a halogen atom, an alkyl group having 1 to 8 carbon atoms, an alkoxy group, a hydroxyl group, and n is 1 to 3.
Integer, n 'is an integer of 0, Y is CH ₃ CH ₃ CF ₃ single _{bond, -CH 2, -CH -, -} CH -, - C-, CH 3 CF 3 -O -, - S- , -SO2-, -SO- or -CO-, which may be the same or different.

More specifically, as the polyamine represented by the general formula (A), m-phenylenediamine, p-phenylenediamine, 2,4-diaminotoluene, 2,6-diaminotoluene, 2-chloro-p-phenylenediamine, general As the polyamine represented by the formula (B), 2,2-bis (4-aminophenyl) -propane, 4,4-diaminodiphenylmethane, 4,4′-diaminodiphenyl ether, 4,4′-diaminodiphenyl sulfide, 4,4 ′ -Diaminodiphenylsulfone, 4,4′-diamonodiphenylmethylethylmethane, 4,4′-diaminodiphenyldi (trifluoromethyl)
Examples include methane 3,3'-diaminodiphenyl ether, 3,3'-diaminodiphenyl sulfide, 3,3'-diaminodiphenyl sulfone, a condensate of aniline and formaldehyde, a condensate of aniline and acetaldehyde, a condensate of toluidine and formaldehyde. To be done.

The polyamine represented by the general formula (C) includes 4,4 '-(p-phenylenediisopropylidene) dianiline, 3,4'-(p-phenylenediisopropylidene) dianiline and 3,3 '-(p-phenylenediline. Diene isopropylidene) dianiline, 1,4'-bis (p-aminophenoxy) benzene, 1,3'-bis (p-aminophenoxy) benzene, 1,4'-bis (p-aminophenoxythioether)
Benzene, 1,3'-bis (p-aminophenoxythioether)
Examples include benzene, 1,4'-bis (p-aminophenyl) benzene, 1,3'-bis (p-aminophenyl) benzene and meta-forms of the above diamines.

Examples of the polyamine represented by the general formula (D) include 2,2-bis [4- (p-aminophenylthioether) phenyl] propane, 2,2-bis [3- (p-aminophenoxythioether) phenyl] propane, 4,4'-bis (p-aminophenoxy) diphenylsulfone, 3,3'-bis (p-aminophenoxy) diphenylsulfone, 4,4'-bis (p-aminophenylthioether) diphenylsulfone, 3,3 ' -Bis (p-aminophenylthioether) diphenyl sulfone, 4,4'-bis (p-aminophenoxy) diphenyl ether 3,3'-bis (p-aminophenoxy) diphenyl ether 4,4'-bis (p-aminophenoxy) Diphenyl sulfide, 3,3'-bis (p-aminophenoxy) diphenyl sulphate Fido, 4,4'-bis (p-aminophenyl thioether) diphenyl sulfide, 3,3'-bis (p-aminophenyl thioether) diphenyl sulfide, 4,4'-bis (p-aminophenyl thioether) diphenyl ether, 3 , 3'-bis (p-aminophenylthioether) diphenyl ether, 4,4'-bis (p-aminophenoxy) benzophenone, 3,3'-bis (p-aminophenoxy) benzophenone, 4,4'-bis (p -Aminophenylthioether) benzophenone, 3,3'-bis (p-aminophenylthioether) benzophenone, 4,4'-bis (p-aminophenylthioether) diphenyl, 3,3'-bis (p-aminophenylthioether) Diphenyl and the above-mentioned diami Meta - body is exemplified.

These polyamines represented by the general formulas (A) to (D) can be used alone or in combination of two or more, and as long as the effects of the body of the present invention can be obtained,
Other than those exemplified above, other aromatic polyamines may be used in combination.

Next, as the α, β-unsaturated dicarboxylic acid and / or its anhydride, specifically, maleic acid, 3-methylmaleic acid,
3-ethylmaleic acid, 3,4-dimethylmaleic acid,
3,4-diethylmaleic acid, 3-phenylmaleic acid, 3-chloromaleic acid, 3,4-dichloromaleic acid, tetrahydrophthalic acid, methyltetrahydrophthalic acid, 5-norbornene-2,3-dicarboxylic acid and them Examples of the acid anhydrides thereof include maleated alloocimene and maleated myrcene.

In the present invention, the Bronsted acid of the catalyst is an inorganic acid such as phosphoric acid, phosphorous acid, hypophosphorous acid, metaphosphoric acid, pyrophosphoric acid, tripolyphosphoric acid, sulfuric acid, methanesulfonic acid, p-toluenesulfonic acid, benzenesulfonic acid. , Organic acids such as naphthalene sulfonic acid can be used. Also, a small amount of a dehydrating agent such as phosphorus pentoxide may be used in combination with these acid catalysts. Of the above Bronsted acid catalysts, p-toluenesulfonic acid is particularly preferable because it has few side reactions and a good hue. These catalysts are 1 to the polyamic acid as a raw material.
Use 50% by weight.

The amount of the solvent used in the reaction is about 50 to 1000 parts by weight based on 100 parts by weight of the polyamic acid as a raw material. Preferably, it is 100 to 300 parts by weight. If more than this,
The amount of the generated polyimide dissolved increases and the loss increases. On the other hand, if the amount is less than this, a large amount of the generated polyimide is deposited, which causes a problem in completing the reaction.

This solvent is preferably a mixed solvent of an aprotic polar solvent and a non-polar solvent azeotropic with water. Examples of the aprotic polar solvent include N, N-dimethylformamide, N,
N-dimethylacetamide, N, N-diethylformamide, N-methyl-2-pyrrolidone, dimethylsulfoxide, hexamethylphosphoramide, γ-butyrolactam, tetramethylurea, 1,3-dimethyl-2-imidazolidinone, diglyme , Dioxane, etc. are exemplified.

The non-polar solvent having an azeotropic property with water is preferably 60 to
It is a solvent having a boiling point range of about 200 ° C. and capable of azeotropically distilling off produced water. Specifically, it includes toluene, xylene, ethylbenzene, hexane, octane, decane, cyclohexane, methylcyclohexane, ethylcyclohexane, light oil, and light oil. Hydrocarbons such as hydrides, chlorobenzene,
Examples thereof include halogenated hydrocarbons such as dichloroethane, trichloroethane, perchlorethylene, etc., and they can be used alone or as a mixture of any two or more thereof.

The mixing ratio of the aprotic polar solvent and the water azeotropic nonpolar solvent is preferably in the range of 70 to 95% by weight of the nonpolar solvent and 30 to 5% by weight of the aprotic polar solvent. If the proportion of the aprotic polar solvent is too small, the reaction rate is significantly reduced and a large amount of a polymer having a strong adhesive property is produced as a by-product, which makes it difficult to continue the reaction. On the other hand, if the amount is too large, the solubility of the target cyclic polyimide becomes high, and it becomes difficult to decompose and recover the imide, and at the same time, the selectivity of the reaction also decreases.

The concentration of the α, β-unsaturated dicarboxylic acid or its anhydride that can be dissolved in the solvent is 1 wt% to 50 wt%, and preferably 5 wt% to 30 wt%. If the concentration of the dicarboxylic acid and / or its anhydride is less than 1% by weight, the yield and the purity of the obtained polyimide will be significantly lowered, and conversely, if it is too large, the loss of the dicarboxylic acid and / or its anhydride will increase.

Furthermore, the reaction can be carried out in the presence of a stabilizer in order to prevent coloring of the reaction product and obtain a high-quality cyclic polyimide. Hydroquinone, methoxybenzoquinone, phenothiazine, t-butylcatechol, dimethylcarbamic acid and the like are suitable as the stabilizer, and the addition amount thereof is generally preferably 0.001 to 1% by weight in terms of the concentration in the reaction system.

The reaction is carried out under heating and refluxing conditions, and specifically, 60 to
It is 200 ° C. More preferably, it is 100 ° C to 130 ° C.

The method of the present invention is generally performed as follows. That is,
A dehydration imidization reaction is carried out while continuously or intermittently supplying a polyamic acid to a mixed solution in which a catalyst, an α, β-unsaturated dicarboxylic acid and / or an anhydride thereof are dissolved in a state of heating under reflux.

The polyamic acid may be supplied by suspending it in the above-mentioned solvent, or may be in the form of powder.

It is desirable that the reaction generally takes 1 to 10 hours to charge them, and then to ripen them for 0.5 to 5 hours.

After completion of the reaction, the stirring is stopped and the mixture is left standing. When the reaction solution is split into layers, the layer containing polyamide and the layer containing catalyst are separated at an arbitrary temperature at which polyamide does not precipitate. Crystals of polyimide can be precipitated by cooling a solution containing the polyimide or distilling a part of the solvent and then cooling.

The separated catalyst layer can be repeatedly used as it is. When the reaction solution does not separate into layers, the polyimide-containing solution can be cooled as it is, or a part of the solvent can be distilled off and then cooled to precipitate polyimide crystals.

The precipitated polyimide can be obtained by separating it from the liquid by excess or centrifugation. In some cases, the catalyst may be washed with a suitable solvent such as water, an aqueous solution of sodium carbonate and / or methanol to remove the Bronsted acid or α, β-unsaturated dicarboxylic acid of the catalyst and / or its anhydride attached to the polyimide. can do.

The liquid can be used as it is or repeatedly by adding the dicarboxylic acid and / or its anhydride.

Hereinafter, the present invention will be described in detail with reference to Examples and Comparative Examples.

(Example) Example 1 In a four-necked flask equipped with a condenser with a water separator, a dropping funnel, a thermometer and a stirrer, p-toluenesulfonic acid 2 g, toluene 100 g, DMF 10 g, maleic anhydride 14.
Charge 2 g (concentration in the mixed solution is 11.3 wt%),
Heated to reflux temperature with stirring. N, N'-4,
39.4 g of 4'-diphenylmethane bismaleamic acid
(0.1 mol) was continuously added little by little over about 3 hours, and the reaction was performed while removing the produced water. After all the amic acid was added, the reaction was continued for another 1 hour and then at 30 ° C
Cooled down. The precipitated crystals were separated, washed with a 2% sodium carbonate aqueous solution, and then dried to obtain N, which was a pale yellow powder.
N'-4,4'-diphenylmethane bismaleimide 3
0.0 g was obtained. High performance liquid chromatograph (hereinafter referred to as HP
The purity was measured by LC). The results are shown in Table 1.

Example 2 The procedure of Example 1 was repeated except that the concentration of maleic anhydride was changed to 22% by weight, and N, N'-4,4'- of yellow powder was obtained.
Diphenylmethane bismaleimide was obtained. The results are shown in Table 1.

Example 3 A yellow powder N, N'-4,4'-diphenylmethane bismaleimide was obtained in the same manner as in Example 1 except that the concentration of maleic anhydride was changed to 6 wt%. The results are shown in Table 1.
Shown in.

Example 4 With the concentration of maleic anhydride remaining at 11.3 wt%, the same procedure as in Example 1 was carried out except that 300 g of toluene and 30 g of DMF were used, and N, N'-4,4'-diphenylmethane bismaleimide was obtained as a yellow powder. Got The results are shown in Table 1.

Example 5 The reaction was performed in the same manner as in Example 1 except that 4 g of 85% phosphoric acid was used as the acid catalyst. After the reaction, the mixture was left standing and cooled to 70 ° C. to separate the lower catalyst layer, and the upper layer was further cooled to 30 ° C. to precipitate crystals. The crystals were separated, washed with an aqueous sodium carbonate solution, and then dried to obtain a yellow powder of N, N'-4,4'-diphenylmethane bismaleimide. The results are shown in Table 1.

Example 6 110 g of a liquid containing the bismaleimide recovered in Example 1 (liquid composition: 76.2 wt% toluene, DMF
7.6 wt%, p-toluenesulfonic acid 1.5 wt%,
Maleic anhydride 10.8 wt%, maleimide 3.9w
t%) was charged into a reactor and charged with N, N'-4,4'-
37.1 g of diphenylmethane bismaleamic acid (0.0
(84 mol) was continuously fed to carry out the reaction in the same manner as in Example 1 to obtain N, N'-4,4'-diphenylmethane bismaleimide as a yellow powder. The results are shown in Table 1.

Example 7 39.4 g (0.1 mol) of N, N'-4,4'-diphenylmethane bismaleamic acid was divided into 4 equal parts, and 3 were added every 1 hour.
A yellow powder N, N'-4,4'-diphenylmethane bismaleimide was obtained in the same manner as in Example 1 except that the charge was intermittently carried out over a period of time. The results are shown in Table 1.

Examples 8 to 14 Using polyamic acids obtained from various α, β-unsaturated dicarboxylic acid anhydrides and aromatic polyamines, acid catalysts and α, β-unsaturated dicarboxylic acid and / or their anhydrides added are shown in Table 2. With the above changes, the same operation as in Example 1 was performed to obtain an aromatic cyclic polyimide. When sulfuric acid or phosphoric acid was used as the catalyst, the catalyst layer was separated after the reaction and crystallized. The results are shown in Table 2.

Comparative Example 1 The same reaction as in Example 1 was carried out without dissolving maleic anhydride in the mixed solvent to obtain N, N′-4,4′-diphenylmethane bismaleimide as a yellow powder. The results are shown in Table 3.
Shown in.

Comparative Example 2 A reaction was performed in the same manner as in Example 1 except that maleic anhydride was dissolved in a mixed solvent in an amount of 0.2 wt% to obtain N, a yellow powder.
N'-4,4'-diphenylmethane bismaleimide was obtained. The results are shown in Table 3.

Comparative Example 3 A yellow powder of N, N'-4,4'-diphenylmethane bismaleimide was obtained in the same manner as in Example 1 except that polyamic acid was not added little by little and the whole reaction was carried out at the start of the reaction. . The results are shown in Table 3.

(Effect of the Invention) According to the method of the present invention, a high-purity cyclic polyimide can be obtained in a high yield, and a solvent and a catalyst can be repeatedly used, which is economically advantageous.

Claims (1)

[Claims] 1. A polyamic acid obtained from an α, β-unsaturated dicarboxylic acid and / or an anhydride thereof and an aromatic polyamine having two or more primary amino groups in the molecule is heated in the presence of an acid catalyst. When dehydrated to produce an aromatic cyclic polyimide, 100 parts by weight of the polyamic acid is used in an amount of 1 wt% to 50 wt% of α, β-unsaturated dicarboxylic acid or its anhydride.
Mixed solvent 5 consisting of dissolved polar solvent and non-polar solvent
A method of producing aromatic cyclic polyimides by continuously or intermittently supplying 0 parts to 1000 parts by weight to dehydrate imidize.