JPH0314835A - Preparation of aromatic cyclic polyimide - Google Patents

Abstract

PURPOSE:To improve the conversion and selectivity by imidizing a polyamic acid in a specific solvent in the presence of an alpha,beta-unsatd. dicarboxylic acid (anhydride) and an acid catalyst, and separating the reaction product by crystallization. CONSTITUTION:An alpha,beta-unsatd. dicarboxylic acid (anhydride) (e.g. maleic anhydride) is reacted with an arom. polyamine having at least two primary amino groups in the molecule to give a polyamic acid (e.g. N,N'-4,4'- diphenylmethanedismaleamic acid). 100 pts.wt. said polyamic acid is imidized in 50-1000 pts.wt. solvent mixture comprising 60-99wt.% nonpolar solvent boiling at 60-200 deg.C and capable of removing water generated in the reaction by azeotropic distillation i.e., capable of forming an azeotropic mixture with water (e.g. toluene) and 40-1wt.% aprotic polar solvent (e.g. N,N-dimethylformamide) in the presence of 1-50 pts.wt. (based on the mixture) said alpha,beta-unsatd. dicarboxylic acid (anhydride) and 1-50wt.% (based on the polyamic acid) acid catalyst (e.g. p-toluenesulfonic acid), and the reaction product is separated by crystallization.

Description

Detailed Description of the Invention (Industrial Field of Application) The present invention relates to a method for producing aromatic cyclic polyimides.
It is useful as a raw material for sealing materials, sliding materials, electrical parts, and structural materials such as aircraft and vehicles. <<Prior Art> Aromatic polyamines having a primary amino group of 2 m or more and α. A common method for producing corresponding cyclic polyimides from β-unsaturated dicarboxylic acids and/or their anhydrides is to dehydrate and imidize them via polyamic acid. In this method, the intermediate polyamic acid is mixed with a polyamine and α. Although it is easily produced by simply mixing β-unsaturated dicarboxylic acid anhydride under mild conditions, the subsequent dehydration and imidization is not easy, resulting in low yield and low purity, so it is not used as a resin raw material. There are problems such as insufficiency. Although various methods have been proposed to solve these problems, no method has yet been fully satisfactory.

For example, bisamidic acid obtained from aromatic diamine and maleic anhydride is combined with a dehydrating agent such as acetic anhydride and sodium acetate or
A method of adding a dehydration catalyst such as a grade amine and imidizing at a relatively low temperature (for example, Japanese Patent Publication No. 46-29140. Tokuko Showa 4
9-40231. Special Publication No. 52-29 1 3, No. 5 Publication No. 1973
5-13202, JP-A-59-212470, JP-A-6
1-24564> is disclosed. However, this method is industrially disadvantageous because it consumes a large amount of expensive dehydrating agent. For this reason, various methods that do not use dehydrating agents have been proposed.
For example, hydrocarbons or halogenated hydrocarbon solvents that are azeotropic with water, aprotic polar solvents such as N,N-dimethylformamide and N-methylpyrrolidone, or mixed solvent systems thereof, can be used under acid or non-catalytic conditions. , heating dehydration method, etc. (for example, JP-A-53-68770, JP-A-57-1)
59764, JP-A-60-260623, JP-A-62-
123169, Japanese Patent Application Laid-Open No. 63-201166). However, in both methods, a solvent with high solubility for both the raw material amic acid and the target polyimide is used. The method of input is adopted. For this reason, problems such as the inability to recover and reuse the catalyst and solvent and the generation of a large amount of waste water occurred, and the production method could not be said to be industrially satisfactory. On the other hand, if a non-polar solvent such as a hydrocarbon is used as the reaction solvent, the solubility of Seikai polyimide is low and the target product is produced as a solid, which can be separated from the reaction solution by easy operations such as P filtration. However, the solubility of the starting amic acid in these solvents is also low, and it can only be obtained at extremely slow reaction rates.

Therefore, if the reaction is unavoidably carried out at high temperatures and/or in the presence of a large amount of catalyst, polymeric by-products will grow, making it impossible to continue the reaction. It was completely unworkable as a manufacturing method. (Means for Solving the Problem) As a result of intensive studies by the present inventors on a process that allows easy separation of polyimide produced, high reactivity, and good selectivity, the inventors found that a predetermined ratio of an aprotic polar solvent and a nonpolar solvent. When dehydrated and imidized polyamic acid in a mixed solvent system with α. Presence of a predetermined amount of β-unsaturated dicarbonate and/or its anhydride is extremely effective in increasing the reaction rate at low temperatures and suppressing the formation of polymeric by-products. The inventors have discovered that the yield and purity of polyimide can be improved without impairing the crystallization properties of polyimide, and have arrived at the present invention. That is, α,β monounsaturated dicarboxylic acid anhydride, aromatic polyamines having two or more primary amine groups in the molecule, and/or α. A cyclic polyimide is produced by heating and dehydrating a polyamic acid obtained by reacting a β-unsaturated dicarboxylic anhydride with an aromatic polyamine having two or more 7 primary amide groups in the molecule in the presence of a catalyst. In this case, based on 100 parts by weight of the polyamic acid, 60 to 99% by weight of a non-polar solvent that has azeotropy with water and 4 parts by weight of an aprotic polar solvent.
50 to 1000 parts by weight of a mixed solvent consisting of 0 to 1% by weight, and the mixed solvent is dehydrated and imidized in the presence of 1 to 50 parts by weight of α, β monounsaturated dicarboxylic acid and/or its anhydride, W of aromatic cyclic polyimides characterized by crystallizing and separating polyimide from the obtained reaction mixture
This is the J′a method. Conventionally, when polyamic acid is produced and then dehydrated and imidized to produce polyimide, 1 equivalent of amino group is reacted with about 1.1 mol of the dicarboxylic acid and its anhydride,
It is customary to generate amic acid and then perform dehydration and imidization in the same reactor. α. The presence of β-monounsaturated dicarboxylic acids and/or their anhydrides has been considered to be a cause of isomerization reactions of dicarboxylic acids and intermolecular dehydration of dicarboxylic acids, resulting in poor quality of polymers. Therefore, it is disclosed in the present invention that the presence of a predetermined amount of α,β-monounsaturated dicarboxylic acid and/or its anhydride accelerates the reaction, allowing the reaction to occur at low temperatures and leading to the suppression of polymeric by-products. The effects of this were not recognized at all. The reaction method with high reaction rate and high selectivity listed here is the first benefit of the present invention. The second advantage is required for a solvent system that takes advantage of the above properties and allows the target polyimide to be crystallized and easily separated by cooling after the reaction is completed. This not only eliminates industrial disadvantages such as the treatment of large amounts of waste water, but also allows the crystallization mother liquor to be subjected to the reaction again, which eliminates the excess amount of α, β, and This enables efficient use of unsaturated dicarboxylic acids and/or their anhydrides, increasing the benefits of the present invention. Therefore, in the present invention, the α,β-unsaturated dicarboxylic acid and/or its anhydride added in advance are the same as the α,β-unsaturated dicarboxylic acid and/or its anhydride, which are the raw materials for the cyclic polyimide. It is desirable that The aromatic polyamines used in the present invention are
It is an aromatic amine having two or more amino groups. Examples include polyamines represented by the general formulas (A>.(B), (C) and (D>). Hydroxyl group, n is 1-3
n' is an integer from 0 to 10, Y is - o -, -
s - , + s o you + - s o one or - CO
Each of ~ may be the same or different〉. More specifically, the polyamine represented by the general formula (A) includes m-phenyl diamine, p-phenylene diamine, 2.4-diaminotoluene, 2.6-diaminotoluene, 2-chlorop- Phenylene diamine, 1a Polyamines represented by formula (B) include 2,2-bis(4-aminophenyl)propane, 4,4°-diaminodiphenylmethane, 4,4-diaminodiphenyl ether, 4,4'
-Diaminodiphenylsulfide, 4.4-Diaminodiphenyl sulfone, 4.4-Diaminodiphenylmethylethylmethane, 4.4'-Diaminodiphenylenedi(trifluoromethyl)methane, 3.3'-Diaminodiphenyl ether, 3. m='t of 3'-diaminodiphenylsulfide, 3.3'-diaminodiphenylsulfoneaniline and formaldehyde
h, a condensate of aniline and acetaldehyde, a condensate of toluidine and formaldehyde, etc. The polyamine represented by the general formula (C) is 4.4'-(P
-Phenylene diisopropylidene>dianiline, 3.4'-(P-phenylene diisopropylidene)dianiline, 3.3'-(p-phenylene diisopropylidene>dianiline, 1,4゜- Bis(p-aminophenoxy)benzene 1,
3゜-bis(p-aminophenoxy)benzene 1 4゛-bis〈p-aminophenoxythioether〉benzene, 1,3゜bis(p-aminophenoxythioether)
Benzene, 1.4″-bis(p-aminophenyl)benzene, 1
Examples include 3°-bis(p-aminophenyl)benzene and meta-units of each of the above diamines. -i As the polyamine represented by formula (D), 2,2-bis[4-(p-
aminophenylthioether)phenyl]propane, 2,2-bis[3-(p-aminophenoxythioether)phenylcopropane, 4.4°-bis(p-aminophenoxy)diphenylsulfone, 3.3'-bis( p-aminophenylthioether diphenyl sulfone, 4,4゜-bis(p-aminophenylthioether diphenyl sulfone, 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 sulfide, 4,4゜-pis(p-aminophenylthioether diphenyl sulfide, 3 3゜-bis(p-aminophenylthioether diphenyl sulfide, 4,4゜-bis〈p-aminophenylthioether diphenyl ether, 3 3゛- Bis(p-aminophenylthioether diphenyl ether, 4 4゜-bis(p-aminophenoxy)benzophenone, 3.3''-bis〈p-aminophenoxy)penzophenone, 4.4゛-bis(p-aminophenylthioether benzophenone) , 3.3′-bis<p-aminophenylthioetherbenzophenone, 4.4″-bis(p-aminophenylthioetherdiphenyl, 3.3′-bis(p-aminophenylthioetherdiphenyl), and the above Examples include meta-units of each diamine.These polyamines represented by the general formulas (A) to (D) can be used alone or in combination of two or more, and the desired effects of the present invention can be obtained. As far as possible, other aromatic polyamines may be used in addition to those exemplified above.

Next α. Examples of the β-unsaturated dicarboxylic acid and/or its anhydride include maleic acid, 3-methylmaleic acid, 3-ethylmaleic acid, 3,4-dimethylmaleic acid, 3.4
-diethylmaleic acid, 3-phenylmaleic acid, 3-
Examples include chloromaleic acid, dichloromaleic acid, tetrahydrophthalic acid, methyltetrahydrophthalic acid, 5-norbornene-2,3-dicarboxylic acid and their acid anhydrides, as well as maleated allocimene and maleic 1-himircene. In the present invention, the Brønsted acids used as catalysts include inorganic acids such as phosphoric acid, phosphorous acid, hypophosphorous acid, metaphosphoric acid, birophosphoric acid, tripolyphosphoric acid, and sulfuric acid, methanesulfonic acid, P-t/
Organic acids such as rhenesulfonic acid, benzenesulfonic acid, and naphthalenesulfonic acid can be used. Additionally, a small amount of a dehydrating agent such as phosphorus pentoxide can be used in combination with these acid catalysts. Among the Bronsted acids mentioned above, P-}luenesulfonic acid is particularly preferred because it causes fewer side reactions and has a good hue. These catalysts have a ratio of 1 to 5 with respect to the raw material polyamic acid.
Use 0% by weight. The amount of solvent used in the reaction is about 50 to 1,000 parts by weight per 100 parts by weight of the raw material polyamic acid. Preferably it is 100 to 300 parts by weight. If the amount is more than this, the amount of dissolved polyimide produced will increase and the loss will increase. On the other hand, if the amount is less than this, a large amount of the polyimide produced will precipitate, causing problems in completing the reaction. The aprotic polar solvent in the present invention includes, for example, N,N-dimethylformamide, N,N-dimethylacetamide, N,N-diethylformamide, N-methyl-2-pyrrolidone, dimethylsulfoxide, hexamethylphosphoramide, Examples include γ-butyrolactam, tetramethylurea, 1,3-dimethyl-2-imidazolidinone, diglyme, and dioxane.

On the other hand, nonpolar solvents preferably have a boiling point range of about 60 to 200°C and are solvents that can azeotropically distill off natural water, and specifically include toluene, xylene, ethylbenzene, hexane, octane, and decane. , cyclohexane, methylcyclohexane, ethylcyclohexane, gas oil, hydrocarbons such as hydrogenated gas oil, chlorobenzene, dichloroethane, trichloroethane. Examples include halogenated hydrocarbons such as perchlorethylene, which can be used alone or in a mixture of two or more of them. The mixing ratio of the aprotic polar solvent and water azeotropic nonpolar solvent is in the range of 60 to 99% by weight of the nonpolar solvent and 40 to 1% by weight of the aprotic polar solvent. If the proportion of the aprotic polar solvent is too small, the reaction rate will drop significantly and a large amount of highly sticky polymer will be produced as a by-product, making it difficult to continue the reaction. On the other hand, if it is too large, the solubility of the target cyclic polyimide becomes high, making it difficult to separate and recover the imide, and at the same time reducing the selectivity of the reaction. The concentration of α,β monounsaturated dicarboxylic acid and/or its anhydride dissolved in the above solvent is 1 wt% to 50w
t%, preferably 5wt% to 30wt%. If the concentration of the dicarboxylic acid and/or its anhydride is less than lwt%, the yield and the purity of the polyimide obtained will decrease significantly, and if it is too high, the loss of the dicarboxylic acid and/or its anhydride will increase. do.

Furthermore, the reaction can be carried out in the presence of a stabilizer in order to prevent coloring of the reactants and obtain a high-quality cyclic polyimide. Suitable stabilizers include hydroquinone, methoxybenzoquinone, phenothiazine, t-butylcatechol, dimethylrubamic acid, etc., and the amount added is generally preferably 0.001 to 1% by weight in the reaction system. ．． The reaction is carried out under heating and reflux conditions, specifically 60
-200°C, more preferably 100°C - 130°C
It is ℃. The method of the present invention is carried out in the following manner. That is, a polyamic acid, a catalyst, an α,β monounsaturated dicarboxylic acid and/or its anhydride are charged into a reactor equipped with a decanter,
Dehydration and imidization reaction is carried out while heating under reflux for 1 to 10 uI. The polyamic acid may be supplied continuously as a powder or suspended in the above-mentioned solvent. After the reaction is complete,
Stop stirring and let stand. If the reaction solution separates into layers, separate the polyimide-containing layer and the catalyst-containing layer at an arbitrary temperature at which polyimide does not precipitate. Polyimide crystals can be obtained by cooling a solution containing polyimide, or by distilling off a portion of the solvent and then cooling it.
It can be precipitated. The separated catalyst layer can be used repeatedly as is. If the reaction solution does not separate into layers, the polyimide-containing solution can be cooled as it is, or a portion of the solvent can be distilled off and then cooled to precipitate polyimide crystals. The precipitated polyimide can be separated from the molasses solution by filtration or centrifugation. In some cases, by washing with a suitable solvent such as a hydrocarbon solvent, water, aqueous sodium carbonate solution, and/or methanol, the acid catalyst, α,β monounsaturated dicarboxylic acid and/or
Or its anhydride can be removed. The R liquid is
It can be used as it is or repeatedly by adding the dicarboxylic acid and/or its anhydride.

The present invention will be explained in detail below with reference to Examples and Comparative Examples. (Example) Example 1 In a four-necked flask equipped with a cooling tube with a water separator, a dropping funnel, a thermometer, and a stirrer, 4 g of P-}luenesulfone,
Toluene 100g. DMF 10g, maleic anhydride 14
．． 2g (concentration in mixed solution is 11.3wt%) and N,
N'-4.4'-diphenylmethane bismaleamide 13
9.4 g (0.1 mole) was charged, heated to reflux temperature with stirring, and reacted for 4 hours while removing raw water. After the reaction was completed, it was cooled to 20°C. The precipitated crystals were separated, washed with a 2% aqueous sodium carbonate solution, and dried to give a pale yellow powder of N. 30.0 g of N'-4,4'-diphenylmethane bismaleimide was obtained. Purity was measured using high performance liquid chromatography (hereinafter abbreviated as rHPLC).
The results are shown in Table 1.

Example 2 A yellow powder of 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 22 wt%. The results are shown in Table 1. Example 3 The same procedure as Example 1 was carried out except that the concentration of maleic anhydride was changed to 6 wt%, and yellow powder N,N'-4.4'-
Diphenylmethane bismaleimide was obtained. The results are shown in Table 1. Example 4 While keeping the concentration of maleic anhydride at 11.3 wt%, 300 g of toluene was added. A yellow powder of N,N-4,4'-diphenylmethane bismaleimide was obtained in the same manner as in Example 1 except that 30 g of DMF was used. The results are shown in Table 1. Example 5 A reaction was carried out in the same manner as in Example 1, except that 6 g of 85% phosphoric acid was used as the acid catalyst. After the reaction, the mixture was allowed to stand and cooled to 70°C, the lower catalyst layer was separated, 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 dried to obtain a yellow powder of N,N"-4,4'-diphenylmethane bismaleimide. The results are shown in Table 1. Examples 6 110 g of r liquid containing bismaleimide recovered in Example 1 (liquid composition: toluene 76.2 wt%, DMF
7.6wt%, ρ-toluenesulfonic acid 1.5wt%,
Maleic anhydride 10.8wt%, maleimide 3.9w
t%> into a reactor, and add N,N'-4.4'-
Diphenylmethane bismaleamic acid 37.1g (0.
The reaction was carried out in the same manner as in Example 1, except that 084 mol) was charged, and a yellow powder of N,N'-4.4'-diphenylmethane bismaleimide was obtained. The results are shown in Table 1. Implementation? 47-13 Using polyamic acids obtained from various α,β-unsaturated dicarboxylic acid anhydrides and aromatic polyamines, the acid catalyst and the α,β-unsaturated dicarboxylic acids and/or their anhydrides to be added are as shown in Table 2. , and the same operation as in Example 1 was performed to obtain an aromatic cyclic polyimide. After the reaction, the catalyst layer was separated and crystallized. The results are shown in Table 2. Comparative Example 1 Maleic anhydride was added and the same reaction as in Example 1 was carried out,
A yellow powder of N,N'-4,4'-diphenylmethane bismaleimide was obtained. The results are shown in Table 3. Comparative Example 2 The same reaction as in Example 1 was carried out except that 0.2 wt% of maleic anhydride was dissolved in the mixed solvent to obtain N,N'-4.4'-diphenylmethane bismaleimide as a yellow powder. Ta. The results are shown in Table 3.

(Effect of the invention)

Claims (1)

[Claims] α,β-unsaturated dicarboxylic anhydride and aromatic polyamines having two or more primary amino groups in the molecule and/or α,β-unsaturated dicarboxylic anhydride and two or more primary amino groups in the molecule When producing a cyclic polyimide by heating and dehydrating a polyamic acid obtained by reaction with an aromatic polyamine having a primary amino group in the presence of an acid catalyst, an azeotropic reaction with water is performed based on 100 parts by weight of the polyamic acid. 60-99% by weight of a non-polar solvent with a polarity and 40-1% of an aprotic polar solvent
The reaction obtained by dehydration imidization in the presence of 50 to 1000 parts by weight of a mixed solvent consisting of % by weight and 1 to 50 parts by weight of α,β-unsaturated dicarboxylic acid and/or its anhydride based on the mixed solvent. A method for producing aromatic cyclic polyimides, which comprises crystallizing and separating polyimide from a mixture.