DE2005967A1 - Stable polyimide solns from aromatic carboxy - - Google Patents

Abstract

Polyimide solns. are produced by condensing tetracarboxylic acids of formula: (in which X is -S-, -SO2-, 0-PHI-S-PHI-O and/or -O-PHI-SO2-PHI-; PHI is phenylene), or corresp. carbonyl halides, esters or dianhydrides, with 4,4'-diaminodiphenyl sulphide or sulphone and/or 4,4'-di-(p-aminophenoxy)-diphenyl sulphide, or corresp. diamine hydrochlorides, in polar organic solvent at 120-200 degrees C, without isolating intermediate polyamic acids. Stable solns. contain 5-30, pref. 10-20 wt. % polyimide. These solns. can be used in prodn. of coatings, thin-walled mouldings, films, fibres, compression moulding compsns. They are resistant to hydrolysis and very easily prcessed, since only solvent is volatilised. They give products with excellent thermal stability and very good mechanical properties.

Description

Process for Making Polyimide Solutions The invention relates to a process for the preparation of polyimide solutions by reacting aromatic Tetracarboxylic acids or their derivatives, which contain one or more sulfur, sulfonic or Oxygen bridges contain with diamino-diphenyl sulfide, diamino-diphenyl sulfone or Di- (p-aminophenoxy) -diphenyl sulfide in polar organic solvents without isolation of the polyamic acids formed as intermediates.

The known aromatic polyimides have a high thermal stability and good mechanical properties. However, they are mostly infusible and in mostly insoluble in all known solvents. This behavior is for precast parts advantageous. In contrast, the processing of polyimides by the usual methods In plastics technology, this behavior is made difficult or even impossible.

Usually, this difficulty is avoided in processing Polyimides by first making tetracarboxylic dianhydrides with diamines at low Temperatures for polyamide carboxylic acids soluble in certain polar, organic solvents converts and then in a second stage the polymidecarboxylic acids at elevated temperature Converted into polyimides. The shaping is done by transferring the polyamic acid solutions into desired shapes, such as fibers or films, a disadvantage of this process on the fact that the polyamic acids produced in the first stage can only be stored for a limited time and are sensitive to humidity. For the production of polyanic acid furthermore, particularly pure starting materials are required, since, for example, traces are freer Carboxyl groups ii carboxylic acid dianhydride the molecular weight of the polyamic acids greatly reduce. lun are in the Belgian patent specification 655 654 described soluble polyimides, the aromatic nucleus with Ilkyl-, Alkoxy- or phenoxy groups contain substituted n-phenylenediamine radicals. These phenylenediamine derivatives however, are difficult to synthesize. In addition, aliphatic or cycloaliphatic effects Ingredients generally a deterioration in thermal stability, such as the low thermal stability of poly-2,6-dimethylphenylene oxide.

It has now surprisingly been found that di. The disadvantages mentioned can be avoided with polyimide solutions obtained by condensation of tetracarboxylic acids of the formulas or the corresponding carboxylic acid halides, in particular chlorides, esters with 1 to 4 carbon atoms in the alcohol radical or dianhydrides with 4,4'-diamino-diphenyl sulfide, 4,4'-diamino-diphenyl sulfone and / or 4,4-di- (p -aminophenoxy) -diphenyl sulfide or the corresponding amine hydrochlorides in polar organic solvents at temperatures from 120 to 2000C without isolation of the polyamic acids formed as an intermediate.

The polyimides contained in the solutions have molecular weights over 10,000 and intrinsic viscosities from 0.1 to 3.0, preferably 1.0 to 2.0 dl / g (measured as a 0.5% solution in N-methylpyrrolidone; Houben-Weyl, volume III / 1, Page 431 ff, Georg Die Verlag Stuttgart 1955).

Soluble condensates are obtained, for example, according to the following scheme 0 o - ><0 + n H2J t < Õ q I O 0 0 180 ° C Nethylpyrrolidon 0 0 ac C19- s 2nH20 0 0 In detail, the polyimide solutions are expediently prepared by condensing the di-ortho-tetracarboxylic acids or -carboxylic acid derivatives and the diamino compounds or the diamine hydrochlorides in approximately equivalent amounts in polar organic solvents. A surplus of up to 5 percent by weight of one of the reaction components, based on the equivalents of the initial amount, is possible. Even with a diamine excess of 25 percent by weight, film-forming polymers are still obtained.

As polar organic solvents, for example, dimethylformamide, Dimethylacetamide, cresol, hexamethylphosphoric triamide, dimethyl sulfoxide, N-methylpyrrolidone and pyridine are used. These solvents can optionally be largely nonpolar Solvents such as toluene, xylene or ethers can be diluted.

The monomer and polymer contents of the reaction solution are varied about 5 to 30 weight percent, preferably 10 to 20 weight percent, based on based on the total weight of the reaction solution.

The condensation takes place at reaction temperatures between 120 and 200 ° C, preferably between 120 and 180 ° C and reaction times from 30 minutes to 5 hours, preferably from 1 to 9 hours, Included high reaction temperatures saponification processes can occur, it is necessary to the water of condensation as quickly and completely as possible from the reaction mixture to separate.

The water of reaction can, for example, be distilled off.

In some cases it is advantageous to use entrainers in the water such as toluene, xylene, carbon tetrachloride azeotropically exclude.

Another condensation method is the elimination of water with chemical agents such as acetic anhydride or carbodiimide at moderately elevated temperatures carried out. This also creates stable polyimide solutions.

The polyimide solutions obtainable according to the invention are resistant to hydrolysis and easy to process, since only the solvent has to be volatilized. The polymer solutions are used for the production of coatings, thin-walled molded parts, films, fibers, molding compounds used The products have excellent temperature resistance and very good mechanical properties.

The parts mentioned in the examples are parts by weight.

Example 1 To a solution of 6.48 parts of 4,4'-diaminodiphenyl sulfide in a mixture of 92 parts of N-methylpyrrolidone, 46.5 parts of techn. Xylene and 15 parts of toluene are added to 10.75 parts of 3,3'-4,4'-diphenylsulphone-tetracarboxylic acid dianhydride. The reaction mixture is heated to 1200C with stirring in an inert gas atmosphere, 100 parts of benzene are added and the water of condensation is removed from the system at 1200C. By partially distilling off the solvent, the temperature is increased in 2 hours at 160 ° C and condensed for 1 hour at this temperature.

The polymer solution obtained is at room temperature for 6 months stable. 40 / u thick coatings on aluminum supports, which are created by evaporation of the solvent mixture obtained are elastic and insensitive to scratches. The covers are in the air at 3000C after 100 hours still flexible because the products only decompose very slowly.

Comparative Example A commercially available polyamic acid imide solution is heated from pyromellitic dianhydride and 4,4'-diamino-diphenyl ether in methylpyrrolidone at 160 ° C., a precipitate falls after a few minutes as a result of the formation of polytmide that cannot be processed further.

Example 2 A 20% solution of 35.8 parts (0.1 mol) of 3,3 ', 4,4'-diphenylsulfonetetracarboxylic acid dianhydride, 40 parts (0.1 mole) 4,4'-di (p-aminophenoxy) diphenyl sulfide, 244 parts N-methylpyrrolidone and 60 parts of a toluene / xylene mixture (weight ratio 1: 1) is added with stirring heated in an inert gas atmosphere to 120 ° C and at this temperature the condensation water circled. The reaction temperature is then increased to 160 to 1700C and condensed for 2 hours.

The polymer solution obtained is stable for 6 months at room temperature.

40 / u thick coatings on aluminum and steel sheets, which are produced by evaporation of the solvent mixture obtained are elastic and insensitive to scratches. In air, the coatings are still flexible after 100 hours at 3000C, since the Only decompose products very slowly.

Claims (2)

Claims 1. A process for the preparation of polyimide solutions, characterized in that one tetracarboxylic acids of the formulas or the corresponding carboxylic acid halides, ethers or dianhydrides with 4,4'-diaminodiphenyl sulfone, 4,4'-diaminodiphenyl sulfone and / or 4,4B-di (p-aminophenoxy) diphenyl sulfide or the corresponding diamine hydrochlorides in polar organic solvents at temperatures from 120 to 2000C condensed without isolation of the polyamic acids formed as intermediates. 2. Stable polyimide solutions containing 5 to 30 percent by weight, based on the total weight of the solution, of polyimides phenyl and 4,4'-diaminodisulfide, 4,4'-diamino-diphenylsulfone and / or 4,4'-di- (p-aminophenoxy) -diphenylsulfide in polar organic solvents.