RU2092499C1 - Method for production of polyimides - Google Patents

Abstract

FIELD: production of polymers with high thermal resistance. SUBSTANCE: method involves polycondensation of salt prepared of diamine and tetracarboxylic acid or of its dicarboxyl-containing derivative, the process takes place at 100-180 C in the medium of aromatic carboxylic acid or mixture thereof. Diesterdiacid or diamidodiacid is used as said dicarboxylic-containing derivative. EFFECT: improved efficiency.

Description

The invention relates to chemistry and technology of highly heat-resistant polymers
polyimides used to obtain materials with high physical, mechanical and dielectric properties.

A known method of producing polyimides from salts of diamines and dialkyl ethers of tetracarboxylic acids [1] The process is carried out in two stages: heating at 110-130 ^o C, then heating at 280-300 ^o C. This method requires large energy costs and is used to obtain polyimides based on aliphatic diamines.

There is also known a method for producing polyetherimides from dialkyl esters of tetracarboxylic acids and diamines with intermediate salt formation. The process is carried out at 275-375 ^o C in vacuum and used to obtain softened polyimides [2]
Closest to the claimed solution is a method for producing polyimides in ethylene glycol medium [3] According to this method, tetracarboxylic acid dianhydride is dissolved by heating in ethylene glycol, then a solution of diamine in ethylene glycol is added to the resulting solution. The resulting salt solution is heated to 130-190 ^o C and stirred for 1.5 hours. The precipitate formed during the polycondensation is filtered off and dried. The disadvantages of the prototype method is a large amount of solvent used for the synthesis (concentration of 10-12%), the need to remove the solvent containing in the polymer. The solvent content in the precipitate is 65%, which may indicate that the polymer contains a substantially uncycled polyamide ester. The process of polycondensation and drying of the polymer is carried out at temperatures close to the boiling point of ethylene glycol, i.e. in conditions of increased concentration of its vapor.

 In order to exclude toxic solvents from the technological cycle, to improve the environmental friendliness of the process, a method for producing polyimides of high-temperature polycondensation in an organic medium of salts of diamines and tetracarboxylic acids or their derivatives (diesters, diamides) is proposed.

This goal is achieved by the fact that as the organic medium melts of aromatic carboxylic acids or mixtures thereof, melting in the range of 90-180 ^o C. are used. The process is carried out at 100-180 ^o C, after the end of the process, the acid is removed by extraction. The process proceeds in the absence of a toxic solvent. Polycondensation is carried out in a melt of aromatic carboxylic acids or mixtures thereof, melting in the range of 90-180 ^o C. the Use of mixtures of acids aims to reduce the melting point of the reaction medium, while the ratio of acids in the mixture does not play a big value, because acids form eutectic mixtures. Acids used as a medium are easily washed with organic solvents (acetone, ethanol), as well as hot water. At the same time, regeneration and repeated reuse of both the acids themselves and the solvents used to wash them is possible. Polycondensation is carried out in a medium of benzoic, o-chlorobenzoic, m-nitrobenzoic, salicylic, 1-naphthoic acids or mixtures thereof. The concentration of the polymer in the reaction medium is from 10 to 80%. Thus, polycondensation in the presence of aromatic carboxylic acids instead of an organic solvent allows us to conclude that the proposed solution meets the criterion of "novelty."

 The polycondensation of salts of diamines and derivatives of tetracarboxylic acids proceeds according to a mechanism different from the polycondensation of diamines and derivatives of tetracarboxylic acids. This means that the patterns observed in the synthesis of polyimides from diamines and dianhydrides or other derivatives of tetracarboxylic acids and the patterns of synthesis from salts of diamines and derivatives of tetracarboxylic acids have significant differences. So, in the case of tetracarboxylic acid diesters, both ester and carboxyl groups simultaneously react with diamine (if the reagents are in the form of a salt). At the same time, during the polycondensation of diamines with diesters of tetracarboxylic acids as a mixture, a predominantly ester group reacts with diamine. It can be expected that carboxylic acids used as a medium can also react with diamine. In this case, there should be a violation of stoichiometry and a decrease in the molecular weight of the resulting polymer. However, the polyimides obtained by the present method have high molecular weights and quantitative yields. The process of obtaining polyimides according to the claimed method makes it possible to design it in the form of a continuous circuit and the use of a single screw extruder.

 Thus, despite the fact that carboxylic acids are not inert in the synthesis of polyimides from diamine salts and derivatives of tetracarboxylic acids, in the claimed solution aromatic carboxylic acids are used in a new quality as a polycondensation medium.

 The invention is illustrated by the following examples.

Example 1 (prototype). 26.0 g of 2,2-bis (3,4-dicarboxyphenoxyphenyl) propane dianhydride are dissolved in 60 ml of ethylene glycol at 50 ^° C. A solution of 5.4 g of m-phenylenediamine in 95 ml of ethylene glycol is added dropwise to the resulting solution at 80 ^° C. The resulting solution was heated to 160 ^° C. for 60 minutes and held at this temperature for another 90 minutes. The precipitated polymer is filtered off, washed with acetone and dried in vacuo. The polymer yield of 80%. According to IR spectroscopy, the polymer contains 70% of imide units. Logarithmic viscosity (η _log ) at 25 ^° C. 0.25 dl / g (0.5 g of polymer in 100 ml of N-methylpyrrolidone).

Example 2. The salt of m-phenylenediamine and 2,2-bis (3,4-dicarboxyphenoxyphenyl) propane dimethyl ether (6 g) and 14 g of benzoic acid were stirred for 1 h at 130 ^° C. Benzoic acid was washed with acetone in a Soxhlet apparatus. Quantitative yield of polyimide, (η _log ) 0.75 dl / g (0.5 g of polymer in 100 ml of N-methylpyrrolidone). The structure of the polyimide is confirmed by infrared spectroscopy.

Example 3. Under the conditions described in example 2, a polyimide is prepared from a salt of m-phenylenediamine and 2,2-bis (3,4-dicarboxyphenoxyphenyl) propane diethyl ether in a mixture of benzoic and o-chlorobenzoic acid (3: 1 by weight, temperature melting 93 ^° C.) at 100 ^° C. for 1 hour. Quantitative yield of polyimide (η _log ) 0.60 dl / g (0.5 g of polymer in 100 ml of N-methylpyrrolidone).

Example 4. Under the conditions described in example 2, a polyimide is prepared from a salt of m-phenylenediamine and 2,2-bis (3,4-dicarboxyphenoxyphenyl) propane in 1-naphthoic acid at 180 ^° C. for 30 minutes. Quantitative yield of polyimide, (η _log ) 0.75 dl / g (0.5 g of polymer in 100 ml of N-methylpyrrolidone).

Example 5. Under the conditions described in example 2, a polyimide is prepared from a salt of m-phenylenediamine and 2,2-bis (3,4-dicarboxyphenoxyphenyl) propane dimethyl ether in a mixture of benzoic and o-chlorobenzoic acid (1: 1 by weight, melting point 90 ^° C.) at 95 ^° C. for 3 hours. Polyimide yield 75% (η _log ) 0.30 dl / g (0.5 g polymer in 100 ml N-methylpyrrolidone). z
Example 6. Under the conditions described in example 2, a polyimide is prepared from a salt of m-phenylenediamine and 2,2-bis (3,4-dicarboxyphenoxyphenyl) propane in o-chlorobenzoic acid at 190 ^° C. for 1 hour. Polyimide yield 70 % (η _log ) 0.12 dl / g (0.5 g of polymer in 100 ml of N-methylpyrrolidone).

Example 7. Under the conditions described in example 2, a polyimide is prepared from a salt of m-phenylenediamine and N, N-dimethyldiamide 2,2-bis (3,4-dicarboxyphenoxyphenyl) propane in a mixture of benzoic and o-benzoylbenzoic acid (6: 1 by weight, melting point 90 ^° C.) at 110 ^° C. for 1 hour. Quantitative yield of polyimide, (η _log ) 0.92 dl / g (0.5 g of polymer in 100 ml of N-methylpyrrolidone).

Example 8. Under the conditions described in example 2, a polyimide is prepared from a salt of 4,4'-diaminotriphenylamine and 3,3 ', 4,4'-diphenyl oxide tetracarboxylic acid in a mixture of benzoic and o-chlorobenzoic acids (1: 5 by weight, temperature melting point 110 ^° C.) at 120 ^° C. for 1 hour. Quantitative yield of polyimide, (η _log ) 1.50 dl / g (0.5 g of polymer in 100 ml of N-methylpyrrolidone).

Example 9. Under the conditions described in example 2, get a polyimide from a salt of hexamethylenediamine and dimethyl ether 3,3 ', 4,4'-diphenyltetracarboxylic acid in a mixture of benzoic and o-chlorobenzoic acids (5: 1 by weight, melting point 100 ^o C) at 120 ^o C for 1 hour. Quantitative yield of polyimide, (η _log ) 0.90 dl / g (0.5 g of polymer in 100 ml of H ₂ SO ₄ ).

Example 10. Polyimide obtained on a plastograph equipped with an extruder. A mixture of 70 g of a salt of m-phenylenediamine and 2,2-bis (3,4-dicarboxyphenyl) propane and 30 g of benzoic acid is loaded into a single screw extruder. The resulting extrudate was extracted with acetone. Yield 80% polyimide (η _log ) 0.70 dl / g (0.5 g polymer in 100 ml N-methylpyrrolidone). The structure of the polyimide is confirmed by infrared spectroscopy.

Claims (1)

A method for producing polyimides by means of a one-stage high-temperature polycondensation of a salt formed by diamine and tetracarboxylic acid or its dicarboxylic acid derivatives of di-hydroxy acids, diamido-acids in an organic medium, characterized in that a melt of aromatic carboxylic acid or a mixture thereof is used at 100 180 ^° C.