DE2231164A1 - PROCESS FOR MANUFACTURING POLYIMIDE AND POLYAMIDE-IMIDE FILMS OF HIGH TEMPERATURE RESISTANCE - Google Patents

Description

Westinghouse Erlangen, June 20th, 1972

Electric Corporation Werner-von-Siemens-Str. 50

Pittsburgh, Pa, USA

TPA 71/8702 Td WE-Case 38 991

Process for the production of polyamide and polyamide-imide films high temperature resistance.

For this application the priority of the corresponding USA application serial no. 158,522 of June 3, 1971 claimed.

High-temperature resistant polyimide and polyamide-imide films with a., High folding resistance are produced by the following process steps: (1) application of a solution of a soluble polyamide starting material in a solvent as a wet film on a substrate, (2) initial heating of the wet composite film Underlay to a temperature between 80 and 11O ⁰ O, in order to partially remove the solvent and water and to form a bubble-free bond between the film and the underlay, (3) heating the composite film-underlay to a temperature of at least 150 C for further drying and semi-curing of the film, (4) stripping of the easily soluble film from the base and (5) heating of the stripped film to a temperature between 250 and 35O ⁰ C while at the same time hedging the film to about 150 $ of the original length by one to produce solid cured film.

Many imide and amide-imide polymers have been synthesized but their processing into foils with a thickness between 0.0-5 and 0.25 mm always involves several successive process steps beam build-up of film layers required.

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The present invention relates to a new and improved process for the production of polyamide-imide films, which have improved folding and tensile strength. These foils are particularly suitable for isolating traction motors. The previous difficulties are overcome for the method of the present invention. By pouring using Polymers according to the invention can films from 0.05 to 0.25 mm thickness can be obtained in one operation. To this In this way, a large production range and considerable savings are achieved.

Polyimide and polyamide-imide films of high temperature resistance are produced according to the invention by first applying a polyamic acid solution as the only wet starting material layer to a substrate. Following is the first heating step to a large percentage of the solvent from the cast raw material layer at temperatures between 80 and 110 ⁰ G, preferably in a non-circulating oven at a relative humidity to remove up to about 60 $. The conversion into the solid amide-imide films takes place quickly at temperatures between 150 and 550 ° C., with the remaining solvent and condensation water being removed. The film is Trokken at about 150 ⁰ C so as to be stripped from the substrate by hand or by other suitable means may be earthed v /. During the final curing, the stripped film is stretched, preferably between 5 and 125 $ of its original length at temperatures between 150 and 35O ⁰ C. This stretching orients the film to a certain extent, reduces the amount of amorphous material and thus improves the folding and folding properties Tensile strength of the film.

Imide and amide-imide films cast from the ÖT invention Solutions can consist of polymers of aromatic polyimides or of aromatic polyamide-imides with the following repeating group

- 3 -

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consist, where η is at least 15, R at least a tetravalent aromatic radical with one of the following groups

and

R _{2 is} a divalent aliphatic hydrocarbon group with 1 "to 4 carbon atoms and carbonyl, oxy, sulfo and sulfonyl radicals and in which R. is at least one divalent radical, such as

HCO

CONH

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in which IU is a divalent organic radical of G groups such as R ₂ J is silicone and amido radicals. Polymers with two or more of the R and / or R. radicals, in particular multiple groups of R ₁ with amido radicals, are particularly suitable for some cases.

Aromatic .polyamide-imide resins represented by certain of the foregoing formulas are described in, for example, U.S. Patents 3,179,635, 3,179,631, 3,179,632, 3,179,633 and 3,9634.

The substantially insoluble solid resinous films described are obtained from certain soluble aromatic ones Polyamic acids dissolved in a solvent. When the wet film is poured or otherwise on a mat is applied, is heated to drive off the solvent and the film of the starting material into a solid, hardening resinous state.

Generally, the soluble polyamic acid starting materials are by mixing a suitable aromatic tetracarboxylic acid dianhydride prepared with an aromatic diamine in a suitable solvent at room temperature.

The mixture or solution is stirred until a maximum viscosity is reached. Examples of suitable dianhydrides are pyromellitic dianhydride, benzophenone tetracarboxylic dianhydride, Naphthalene tetracarboxylic dianhydride and the like.

Examples of suitable diamines are m-phenylenediamine, Methylenedianiline, diaminodiphenyl ether, diaminobenzanilide and the like, see American patents 3179 635, 3179 614, 3179 631, 3179 632, 3179 633 and 3179 634.

The method can also be used when a derivative of an aromatic tricarboxylic acid anhydride, for example Trimellitic anhydride pyride or the ester diacid chloride of trimellitic anhydride in place of the aforementioned aromatic Dianhydride is used. The diamines listed above are also for use with the tricarboxylic acid anhydride derivatives suitable. t-

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An aromatic polyamic acid useful as a soluble polyamide

starting material according to the invention vist, has the recurring element

H 0 0 I. Il η N— —Σ G

Έί

-σ

Ii

-OH -N-

- η

where η is at least 15 and R and R- are identical to described above relating to the manufacture of solid aromatic polyimide and polyamide-imide resins. Suitable polyamic acids can also contain two or more of the R and / or R radicals.

Suitable solvents for the aromatic polyamic acids are for example the normally liquid organic solvents of the N, N-dialkylcarboxylamide class, preferably the low molecular weight members of this class. Typical examples are e.g. dimethyl acetamide, dimethylformamide, N-methylpyrrolidone and also dimethyl sulfoxide and pyridine. The solvents can be used alone or in a mixture of two or more or together with other liquid aromatic solvents such as xylene, toluene, benzene, benzonitrile, dioxane, butyrolactone and cyclohexane can be used. The solvents are readily available by heating in a drying tower or oven to remove so that the condensation reaction takes place, wherein the polyamic acid starting materials by immediate Introduced into the heated hardening tower in solid resins

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be transferred. The solutions of the starting materials are all highly viscous and they are in fairly low concentrations on solid polyamic acids. Up to about 35 wt .- ^ are recommended when fairly fluid solutions for pouring purposes are desired. Solutions of the starting material are obtained with viscosities between about 600 and 7000 cp.

Besides this aromatic polyimide-polyamide-imide with the foregoing repeating member, where R is a tetravalent aromatic radical, other resins which act as foils are particularly suitable, according to the invention, are cast from solutions of trivalent ahydrides of the following structure

wherein R-. and η are identical to the information regarding the solid aromatic polyimide-polyamide-imide resins.

Particularly valuable foils are obtained when R ^

where R ^ is an oxy or methylene (-CH ₂ -) radical. These resins have the recurring link

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- 7th

wherein R 1 is an oxy radical. The resin creates foils with special good thermal resistance

The soluble polyamide starting materials for the above trivalent polyamide-imide resins are aromatic polyamide acids, which can have one or both of the following structures

JSB-

-R ₁ -

where R- and η are identical to those listed above and R. can be hydrogen, alkyl or aryl radical. The representation these soluble polyamic acids and their solid resins are disclosed in British Patents 1056 564 and 1032 649 described.

The solvents given above for the aromatic polyamic acids can be used.

In accordance with the present invention, the Aromatic polyamic acid dissolved in the solvent

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applied as a single wet layer by dipping, brushing or spraying, but preferably by pouring as a thin wet film of starting material using a film applicator or other suitable means on one or both sides of a suitable solid support such as glass or metal foil. The wet layer is then initially heated in a tower or oven with or without vacuum to a temperature between 80 and 11O ⁰ C at a relative humidity of preferably 60 $ to a large part of solvent and water (reducing the volatiles of about $ 82 to $ 25) at liberty to put or remove and a bubble free. To form composite film backing. The complete removal of sufficient solvent at lower temperatures, with the proportion of imidization being low, delays the reduction reactions which would occur at the higher temperatures of the final cure. These diminution reactions are the hydrolysis by water of the imidization and the action of the amic acid bonds on amine and anhydride groups. Initial heating below 110 ^° C. also helps to eliminate bubbles in the finally cured film, which are caused by air and solvent inclusions.

It has been found that air circulation is sometimes detrimental during drying. Solvent-laden, the air Films exposed for different intervals acquired moisture depending on the relative humidity. In some In some cases, the damage was so great that it varied from the film becoming opaque to cracking and cracking. High air speeds created spots or an orange peel effect. Initial hardening above 60 ° relative humidity may allow the solvent to act as a desiccant to take up water into the film, causing possible polymer chain breaks allowed and results in brittle properties of the film.

After initial heating, the film is cured at temperatures in the range of 150 to 350 C to all of the remainder Remove solvent and make the layer of the starting material a solid polyamide-imide film high

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Harden temperature resistance. This is preferably done in a circulation tower or oven with no air flow.

Simultaneously with the final hardening, the mim should be stretched up to $ 150 or preferably $ 5 to $ 125 of its original Length by means of a suitable film stretching device. These are, for example, weights that indicate the speed of a guide roller which pull the film through the curing ovens while maintaining the speed of the other rollers, or by using a tenter frame.

The film should be at about 7 to 25 $ of the volatiles (solvent plus water) prior to the drawing operation be dried by a half-curing at 150 to 200 ⁰ C between a half and two hours so that the film can be peeled from the pad. The semi-hardened stripped film will generally be about 0.05 to 0.25 mm thick. The final curing step may be carried out at a temperature between 150 and 35O ⁰ C, preferably between 200 and 25O ⁰ C. Then, the film can be finally cured at up to 35O ⁰ C.

This film has electrical and organic thermoplastic but mechanically heat-saturated properties. she has rigid linear polymer chains, but they soften before the Melting point is reached. The stretching must occur during the curing reaction of the film and is completed quickly during some volatile constituents are still present.

Compared to an unstretched film, the folding strength of the film can be increased by a factor of 5 in the stretching direction and by a factor of 2 in the crosswise direction can be improved by the above-mentioned stretching step. The stretching step tends also to an improvement of elongation, tensile strength, electrical strength and dielectric strength of the stretched film compared to unstretched films. The stretching increased during the final cure, no doubt the amount of amorphous material in the foil. The molecules become more oriented, possibly up to about $ 5, but not enough, to create a defined crystalline structure

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Things. After stretching, the pattern films generally became visibly opaque. In the final step, the cured film was cooled and then removed from the oven.

The invention is illustrated in more detail by the following examples.

example 1

A solution of the raw material polyamic acid was prepared by condensation of pyromellitic dianhydride with 4,4'-Diaminophenylether and 3 »4'-Daminobenzanilid in the weight ratio 20: 19: 1 in dirnethylacetamide as solvent to a solution with a pest body content of about $ 18 a Gardner Holt viscosity of Z 3 at 25 ° 0.

Example 2

A solution of the raw material of polyamic acid was obtained by dissolving a solid polyamic acid or a polyamic acid derivative from equimolar amounts of the 4-chloride of trimellitic anhydride and 4 »4'-diaminodiphenylmethane (methylenedianiline) in a solution of dimethylacetamide to a solution with a solids content of about $ 30 a Gardner Holt viscosity V at 25 ° 0. The powder had a molecular weight of approximately 10,000.

Example 3

The polyamic acid raw material solution of Example 1 was cast in a single operation while passing filtered air onto a 15 cm glass plate using a standard mushroom coater with a liquid opening at a setting of 0.325 mm. The wet composite plate film backing was initially heated for half an hour at 80 ⁰ O and a half hour at 100 ° C was then cured for half an hour at 150 ⁰ O, half an hour at 200 ⁰ O, a quarter of an hour at 150 ⁰ C. and finally a quarter of an hour at 315 ^° C. The final solid amine-imide film was 0.075 mm thick. It was clear, bubble-free, and flexible when stripped from the glass backing.

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- 11 Example 4

The solution of the starting material of the polyamic acid from Example 2 was applied to an aluminum foil in a single operation 0.001mm 20 cm 46 cm cast using a continuous horizontal film processor with a filmographic measuring device 15 cm wide and a liquid opening with a setting of 2.6 mm. The composite film backing initially became two Heated to 80 hours and then cured at 150 ° C. for one hour. The final solid amide-imide film was clear and bubble free. It was stripped from the aluminum foil. It showed exceptional flexibility and edge tear strength.

The thickness was measured with a micrometer. It varied from 0.1 mm to 0.125 mm. The film was further cured at 170 ⁰ C a Stun.e. It then had a volatile content of approximately $ 14.2. ■

Example 5

The solution of the starting material of the polyamic acid of Example 2 was cast onto strips of aluminum foil in a single operation using a film coater with a liquid opening of setting 0.375 mm.

Thirty-four samples were made using various drying methods to produce amide-imide films with a Thickness from 0.050 to 0.075 mm. Neither of these patterns has been stretched.

Samples 1 to 10 were air dried for 12 hours prior to initial heating, while samples 10-25 were initially heated in a 100 ° oven without prior air drying. The samples were at 150 ⁰ C, and cured 200 ⁰ C and 150 ° and 250 ° and stripped away from the film for comparison of properties. The tensile strength and percent elongation at break (25 ° C) of the stripped solid amide-imide film samples were observed. They are compiled in the following table 1: - 12 -

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- 12 Table 1.

Unstretched amide-imide film Tensile strength and percentage elongation at break

initially air-dried

100 ⁰ C 15O ⁰ C

1 hour 1 hour

100 ° C 15O ⁰ C 200 C

1 hour, 1 hour, 1 hour,

Train ίο, strain master Zuginp strain ] jaust ( sr. kg / cm in io 6th kg / cm in* 1 798 6.8 7th 896 6.9 2 748 5.3 8th 931 8.2 3 854 10.1 9 924 8.3 4th 833 7.9 10 987 5 854 10.4
in diameter 8.1 in] jta ± i- 882
924 in DLLnh- so
8.3 inches schiitt cut cut cut

initially not air-dried

100 ° C Zugi 1 H. 100 ° C Train in 1 Hours. 150 ⁰ C kg ^ cm 1 H. 150 ⁰ C kg / cm 1 Hours. 613 200 C 945 1 Hours. 646 η elongation 875 strain template 576 ² in io template 1022 in 1o 11 714 4.6 16 840 9.9 12th ^ T 4.1 17th 7.1 13th 3.6 18th 32.7 14th 7.2 19th 5.9 15th 14th
in diameter 5.0 in diameter 20th 1015
940 in average 16.4
14.4 in diameter cut cut sdbtniiit cut

100 ⁰ C 150 ⁰ C 250 ° C

1 hour 1 hour 1 hour

renter

/at

strain

826 6.0 852 18.2 980 8.6 918 6.0 1076
931 in anxfcr- IS, 6
ToTT in the cut sohaitt

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Maximum tensile strength and percentage elongation at break, are achieved when the solid amide-imide films are not initially were air-dried and "cured at at least 200 ° 0.

The samples 26 Ms 28 were initially air-dried for 12 hours before the initial curing, while the samples 29 Ms ^{were heated in an oven at 100 °} C. with initially non-air-dried. The samples were finally cured at and 225 ^° C. and stripped from the film. The dielectric strength of these samples was measured. The technique used a curved electrode. The upper cylindrical electrode was fitted into a concave electrode on the bottom. The cylindrical electrode was 50 mm long and 8.5 mm in diameter. The film swatches were placed between the electrodes. A voltage of partially 500 V / see was applied until the breakdown occurred. Table 2 shows the results of these tests.

Table 2

not
dielectric stretched amide-imide film
Strength V / 0.025 mm (curved electrode) 1 H.
1 H.
1 H. 1 H.
1 H.
1 H. KV V / 0.025 mm initially air-dried KV 6.0
8.2
6.7 1480
2800
2620
2300 on average 100 ⁰ C
150 ⁰ C
225 ⁰ O 0.075 4.3
0.0575 4.8
0.0600 6.3
initially not air-dried template thickness 100 ⁰ G
150 ⁰ C
225 C V / 0.025 mm 26th
27
18th thickness 2140
2920
2390 0.07
0.07
0.07 template 29
30th
31

2,480 on average - 14 -

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-H-

Samples 32-34 were initially ^{heated in a 10O 0} O oven without initial air drying. The samples were cured at 200 to 25O ⁰ G stripped from the film. Samples measuring 1.27 cm by 15.2 cm were cut and tested in a test device for measuring the folding resistance according to Tinius-Olsen. Table 3 shows the results of these tests.

Table 3

Unstretched amide-imide film
Folding strength (Oyclen)

initially not air-dried

Sample hardening 1 hour 1 hour. Thickness no. D. Fold strength in hours in mm · speed cycles

32 100 ⁰ C 150 ⁰ C 200 ⁰ O 0.0575 3 214

33 100 ⁰ C 150 ⁰ C 225 ⁰ C 0.0525 9 355

34 100 ⁰ C 15O ⁰ C 25O ⁰ C 0.05 9 540

Example 6

The polyamic acid raw material solution of Example 2 was applied to a long aluminum foil 0.125 mm thick in a single operation using a film applicator having a liquid opening of 0.375 mm x six swatches were air dried before initial heating. All samples were .anfangs heated for one hour at 100 ⁰ C for one hour at

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Gekartet 150 ⁰ C, Jim to dry the Piim and convert into a "bubble-free state. The film samples were then scraped off the film by hand and final cured for fifteen minutes at 225 ° C Various in Table 4 mentioned weights. Were uniformly hung on the bottom of the stripped films before placing them in the 225 ° C. oven. When the films reached 225 ° C., they were stretched by the weights. A stripped control sample was left with no weights. All samples were allowed to cool before being used Film size, weight, thickness, percent stretch, and fold strength were determined using a Tinius-Olsen fold strength test, as shown in Table 4.

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Table 4

Stretched amide-imide film Properties of the stretched film

Size AnikigsdLcke Weight Hardening Stretching Thickness (gpieckt) Appearance Percentage folding strength

in cm in um in kg taip in G in cm in mm stretching (Cyden)

S 55 5x: 0 0.075 0.45 225 8 0.035 translucent 81 24 560

co 36 15x30 0.075 1.35 225 38 0.0325 through sciBJnend 125 18 663 *

κ) 13 224 **

7 15x30 0.075 0.9 225 36 0.0325 durchSieinend 116 24 364

3S control 7.5x30 0.0375 none 225 none 0.0375 clear 0 6 534

39 15x30 0.075 1.35 225 38 0.0325 translucent 125

AO 10x10 0.065 0.9 225 2.5 0.035 clear 25 22 712

* longitudinal ro

* · * Across Kj

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Sample 37 was then cut into strips. (37a-e) and the tensile strength and the percentage elongation at break measured, to observe any changes in property after stretching. The results of this test shows Table 5.

Table 5

Stretched amide-imide-I film

initially not air-dried

template

100 ⁰ G 150 ° 0 225 G

1292 1206 1216 1142 1110

1193

on average

1 H.

1 H.

1/4 hour

Tensile in kg / cm percentage calculation at break

31.25 25.00 25.00 18.75 21.38

24.38 on average

Pattern 39 'was cut into strips (39a-e) and the dielectric Strength tested using a 6.4 mm diameter electrode. The increase was 500 V / s. It was used until a breakthrough occurred. The results are given in Table 6.

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Table 6

Stretched amide-imide film initially not air-dried

100 ⁰ C 1 hour

150 C 1 hour

225 C 1/4 hour

template KV thickness in mm V / 0.025 mm 39a 5.6 0.0325 4300 39b 5.6 0.0325 4300 39c 5.4 0.0325 4150 39d 5.6 0.0325 4300 39e 5.6 0.0325 4300- 5.56 in diameter -0.0325 in the through 4270 in diameter cut cut cut

The purpose of this pattern was to have the solid amide-imide films in stretching in one direction, to the effect of a possible orientation on their physical and electrical properties to consider.

Unstretched amide-imide films have excellent properties shown, for example in terms of tensile strength, flexibility and temperature resistance. The present Work has shown that these properties are retained even when heavy components are used in a single application according to Example 3 and Example 4 are prepared.

As a comparison of Tables 1 and 2 shows, initial air drying of the starting wet film prior to heating small advantages. Indeed, better results have been observed for non-air dried films in terms of the electrical strength, tensile strength and the percentage elongation after curing temperatures of 200 0. Nasse, der Films exposed to air for various periods of time emitted moisture depending on the relative humidity. in

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some cases could notice cracks and cracks that. are disadvantageous ". When heating and the Curing processes, the relative humidity was kept below $ 60 to achieve test results. Stretching the films "at 225 ° C. did not produce any defined crystallization according to the x-radiation defraction measurements. However there was a decrease in the amount of amorphous material. Stretching the film "at the final cure temperatures caused a sufficient orientation of the molecules. Improved physical properties were found. Outstanding Hardness levels were reached at $ 25-125 elongation. Warriors the movies would be between $ 1 and $ 150 of their original length produce considerable degrees of hardness in the films. At over $ 150 stretch, the film would be useful for practical insulation applications getting too thin.

The first visual effect of orientation occurs when the stretched film changes from clear to translucent. This generally occurs at approximately $ 80 stretch. It can be seen in comparison to similar samples (excluding elongation) from Tables 3 and 4 that the folding endurance of the stretched samples 35, 36, 37 and 40 was 3-5 times better than that of the non-stretched samples 32, 33 and 34 · Das non-stretched control samples 38 confirmed the fact that longer curing or greater thickness of samples in the table was not disadvantageous and not the different physical Properties calculated.

The stretched film also showed an increase in tensile strength and percent elongation at break over one unstretched film under similar conditions (Table 1 unstretched samples 16,17,18,19 and 20 compared to the stretched ones Patterns 37a-e in Table 5). Accordingly, the stretched samples are better than non-stretched ones in terms of tensile strength Pattern and almost twice as good as unstretched patterns in terms of percentage elongation at break. That the same applies to stretched samples whose dielectric strength was tested (unstretched samples 29, 30 and 31 from table 2 in comparison with the stretched samples 39a-e of

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Table 6). The stretched samples were almost at the breakthrough twice as good as the unstretched samples, measured in volts / 0.025 mm, although the thickness is for the stretched samples was a little lower.

Multiple patterns that. were poured into one operation from the solution of the starting material of Example 2 was finally cured at 300 ⁰ C. These samples easily lost their tensile strength and turned from yellow to deep amber. The maximum temperature that has been applied with success to the initial heating of the films prior to the final cure without bubbles formed, was between 100 and 11O ⁰ C. Although initial temperatures up to 175 ⁰ C brought no degradation of the polymer, were considerable air bubbles and Solvent inclusions when the initial temperatures exceeded ^{100 0 C.}

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Claims (8)

VPA 71/8702 Claims pi / method of making polyimide and polyamide-imide films high temperature resistance, characterized in that soluble polyamides of the following formulas H 0 HO ι μ η OH R. -C Il c- HO -N- EVER -HN _ η where η is at least 15 and R is at least one tetravalent organic remainder is how - 22 - 209882/1071 VPA 71/8702 - 22 - Rp is a divalent aliphatic hydrocarbon radical with 1 to 4 carbon atoms and carbonyl, oxy, sulfonyl and sulfonyl radicals, R _{1 is} at least one divalent radical such as and where R, a divalent organic radical, such as Rp »silicone and amido radicals and R. are hydrogen, alkyl and aryl radicals, dissolved in a solvent applied to a surface, (2) to a temperature in the range from 80 to 110 ⁰ C and then Be heated (3) to a temperature of at least 150 ⁰ C, the film semi-cure, that (4) stripped of the semi-cured film of the substrate and (5) at temperatures in the range of 150 to 35O ⁰ C is fully cured, to remove all of the solvent while stretching the film to $ 150 of its original length. - 23 - 209882/1071 7231164 VPA 71/8702 - 23 - 2. The method according to claim 1, characterized in that the solution of the polyamide applied as a single layer is heated to 150 "to 200 ^{0 C after heating in the range from 80 to 110 0} C and the film during the heating in the his Range of 150 to 35O ⁰ C at 200 to 250 ⁰ C to 150 original length is stretched and then finally cured up to 35O ° C. 3. The method according to claim 1, characterized in that the layer applied as a single layer is heated in an atmosphere with up to about 60 fo relative humidity and the film when heated in the range from 150 to 350 C to about 5 to 125 ° / ° is stretched to its original length. 4. The method according to claim 2, characterized in that up to for three hours! temperatures between about 80 and 110 C and Bndhärtung a half to two hours is heated to temperatures between 150 and 35O ⁰ C. 5. The method according to claim 4, characterized in that the heating is carried out in the range of 150 to 350 ° C. in an oven with no air flow. 6. The method according to claim 1 to 5, characterized in that the solvent is dimethylacetamide, dimethylformamide, N-methylpyrrolidone, dimethyl sulfoxide, pyridine and their Mixtures can be used. 7. Veifehren according to claim 1 to 6, characterized in that that a soluble polyamide of the following formulas 209882/1071 - 24 - VPA 71/8702 HtT wherein . Hydrogen is used. , Oxy and methylene radicals and 8. Use of the films produced according to claims 1 to 7 as insulation material in electrical engineering. 2 0 9 8 Ö 2/1 0 7 1