FI63043B - FOERFARANDE FOER FRAMSTAELLNING AV YTTERST VAERMEBESTAENDIG ISOLERANDE OEVERDRAG FOER ELEKTRISKA LEDARE OCH BRAENNLOCK ANAENDBART FOER GENOMFOERANDE AV FOERFARANDET - Google Patents

Description

ΓβΊ MUSCLOSED «PUBLICATION, -, η, 7 jj | 8 [A ^ <11 'UTLÄGGNI NGSSKRIFT 6 3 Ο 4 3 C («) Patent round Uy 11 04 1933 / «AKvlwV ^ ddClr ^ 08 G 69/44, 73 / 16, (51) Kv.ik. / Intci. H 01 B 3/42 FINLAND — FINLAND (21) P * t «nttlh (k * mui - PatwramMuWnf 7709 ^ 1 (22) Htkmnltpllvi —AiwMtnlncidai 2k. 03.77 (23) Alkupilvi —Glltl | K« t * dk (2 ^ .03.77 (41) Announced - Bllvlt offmtlig 26.09.77

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Patant- och registerstyreisen '' Ameksn utiacd och utUkrMtan pubiicnrad 3 ±. ± *. vt (32) (33) (31) Requested acuotkeui - & «jird prtortt · * 29.03.76

Austria-Österrike (AT) 12 A 2202/76 (71) Herberts Gesellschaft mit beschränkter Haftung, Christbusch 25, D-56OO Wuppertal 2, Federal Republic of Germany Förbundsrepubliken Tyskland (DE) (72) Sureh Merchant, Wuppertal, Diethard Winkler, Wupp Marita Bluhm, Schwelm, Federal Republic of Germany Förbundsrepubliken Tyskland (DE) (7 * 0 Berggren Oy Ab (5 * 0 Method for the production of highly heat-resistant insulating coatings on electrical conductors and for the application of the method The present invention relates to a process for the production of highly heat-resistant insulating coatings on electrical conductors by coating the conductors with polyhydric carboxylic acids, polyhydric alcohols, polyhydric alcohols, xyl groups, optionally in admixture with aliphatic carboxylic acids, and optionally their anhydrides and / or esters, and solutions of thermosetting amide and / or imide-modified ester resins made from compounds containing amino groups, and by heating coated conductors at target temperatures above 200 ° C, the acid number is 10 to 50, and the equivalent ratio of hydroxyl groups to carboxyl groups in the starting products used in the preparation of ester resins is between 1.6 and 2.5.

It is known that solutions of polyester resins suitable for varnishing electrical conductors are prepared by dissolving them in organic solvents of the phenol, cresol and / or xylenol type. The electrical conductors are insulated by coating them with a solution of said polyester resins. and then heating in an oven at a temperature of about 350 ° C or higher to cure the polyester resins. Known lacquer solutions usually contain customary lacquer additives and / or curing catalysts. Lacquer solutions of polyester resins with five-membered imide rings condensed are preferred, for example in the following publications: GB 939 377, GB 1 082 181, GB 1 067 541, GB 1 067 542 and GB 1 127 214, BE 663 429, FR 1 391 834, DL 30 838, DE 1 494 454, DE 1 494 413, DE 1 937 310, DE 1 937 311, DE 1 966 084, DE 2 101 990 and DE 2 137 884.

Solvents of the phenol, cresol and / or xylenol type contain phenolic hydroxyl groups. For physiological reasons, these solvents are very undesirable and in many countries their use is only allowed with certain precautions. Therefore, it is quite necessary to avoid the use of these solvents, although they are cheap and easily available and dissolve the ester resins in question well. The use of other solvents, e.g. N-methylpyrrolidone, dimethylacetamide, dimethylformamide, dimethylsulfoxide, N-methylcaprolactam and / or dimethylsulfone, is also known according to GB 1 082 181. But even all of these solvents are either physiologically questionable, difficult to obtain and thus expensive and / or poorly soluble in ester resins, so that only small percent lacquer solutions can be obtained using these. The use of these solvents has therefore not proved to be appropriate.

It is further known that electrical conductors can be coated with insulating coatings by coating the conductor with aqueous solutions, these solutions containing carboxyl group-containing ester resins neutralized with bases, in particular amines (DE 2 509 048, DE 2 439 385 and DE 2 439 386). The disadvantage of this method or these aqueous solutions is that a lot of energy is required to evaporate the water during the combustion process, a lot of foreign energy must be introduced into the furnace, high surface tension causes lacquering technical difficulties and very high acidity of the carboxyl group ester resins, e.g. after neutralization would be sufficient. This, in turn, results in a high proportion of amines used for neutralization, which causes environmental problems. Due to hydrolytic cleavage phenomena, storage stability is unsatisfactory.

It is an object of the present invention to provide a process for the preparation of insulating coated electrical conductors which can use solutions in which amide and / or imide-modified ester resins are dissolved in organic solvents which, however, are physiologically harmless or considerably less susceptible than above. said solvents used heretofore.

It has now been found that this object can surprisingly be solved by using solvents which as such are very poor as solvents for commonly used amide and / or imide-modified ester resins, but still have volatile solutions with a high residual fuel content if the hydroxyl groups of the ester resins and the ratio between the carboxyl groups is a certain amount and the acid number is a certain amount, and the carboxyl groups are allowed to react with the amines in a certain way.

Accordingly, the present invention relates to a process for preparing highly heat-resistant insulating coatings on electrical conductors by coating the conductors with polyhydric alcohols containing polyhydric alcohols, polyhydric carboxylic acids having carboxyl groups optionally attached to aromatic rings and optionally carboxyl groups. and / or esters, and solutions of thermosetting amide and / or imide-modified ester resins prepared from compounds containing amino groups, and by heating coated conductors at a target temperature above 200 ° C, having an acid number of ester resins of between 10 and 50, and in the preparation of ester resins the equivalent ratio of hydroxyl groups to carboxyl groups of the starting materials used is between 1.6 and 2.5. The process according to the invention is characterized in that the solution contains aliphatic amines in such an amount that 0.5 to 1.5 amino groups are present for each free carboxyl group of the ester resin, and at least about 70% by weight of the solvents are mono- and / or dialkananediols in which there are 2 carbon atoms per alkane moiety, mono- and / or dialkyl ethers having 1 to 4 carbon atoms in each alkyl moiety.

The invention further relates to a fuel lacquer containing organic solvents and preparations of polyhydric alcohols, polyhydric carboxylic acids having carboxyl groups bonded to aromatic rings, optionally in admixture with aliphatic carboxylic acids and optionally their anhydrides and / or esters, and amino acids. thermosetting amide and / or imide-modified ester resins, as well as catalysts and possibly common lacquer additives and / or fluxes, and heating the coated conductors above a target temperature of more than 200 ° C with an acid number of the ester resins of 10 to 50 and the equivalent ratio of hydroxyl groups to carboxyl groups in the starting materials used in the preparation of ester resins is between 1.6 and 2.5, the lacquer being characterized in that the solution contains aliphatic amines in an amount such that 0.5 to 1 is present for each free carboxyl group of the ester resin , 5 amino groups, and at least about 70% by weight of the solvents are mono- and / or dialkane diols having 2 carbon atoms per alkane moiety, mono- and / or di-alkyl ethers having 1-4 carbon atoms in each alkyl moiety. Free carboxyl groups in the above-mentioned sense are groups which, after the condensation reaction has stopped, are still unesterified.

The alkyl groups of said mono- or dialkyl ether groups may be straight-chain or branched. Suitable solvents for use according to the invention are therefore mono- and / or diethylene glycol mono- and / or dialkyl ethers. solvents used as examples in accordance with the invention are methyl glycol (monoetylee-glycol monomethyl ether), ethyl glycol (monoetyleeniglykolimono-ethyl ether), propylglycol (monoetyleeniglykolimonopropyylieet-ether), butyl glycol (monoetyleeniglykolimonobutyylieetteri), methyl-lidiglykoli (diethylene glycol monomethyl ether), etyylidiglykoli (diethylene glycol monoethyl ether), propyylidiglykoli (diethylene-glykolimonopropyylieetteri) , butyl diglycol (diethylene glycol monobutyl ether), diethylene glycol dimethyl ether, butyl glycol tert-butyl ether, methyl diglycol tert-butyl ether, monopropylene glycol-1,3-monoethyl ether, monopropyl ether, monopropyl ether

The mono- and / or dialkyl ethers of mono- and / or dialkane diols used as solvents according to the invention are, as such, exceptionally poor solvents for the ester resins used. Surprisingly, solutions which are very storage-stable, in particular cloudy-stable and have a high combustion residue, are obtained by using ester resins having the above ratio of hydroxyl groups to carboxyl groups and having the above-mentioned acid number, and adding to these solutions the amounts specified above. amines. The solutions used according to the invention are physiologically practically harmless, in any case considerably safer than the solvents used hitherto in the art. They are easy to get and are therefore cheap.

As already stated above, at least about 70% by weight of the solvents of the solutions according to the invention, based on the total amount of solvents, are solvents as defined above. This amount is mainly about 80% by weight, in particular mainly up to about 90% by weight. According to the invention, it is self-evident that only the solvents defined above are used as solvents. If, in addition, other solvents are used, the solvents which are also physiologically harmless must be used in accordance with the definition of the object of the present invention. Examples of these are aliphatic alcohols having 1 to 8 carbon atoms such as ethanol, butanol, isopropanol, glycol, diacetone alcohol, esters known as lacquer solvents such as ethyl acetate, butyl acetate, ethyl glycol acetate, ketones known as lacquer solvents such as butanone. It is expedient to use additional solvents, also referred to as co-solvents, which do not adversely affect the lacquer properties of the solvents used and which may have a beneficial effect on the lacquer properties, such as flow. The lacquer solutions used according to the invention are not sensitive to impurities due to the small amount of water.

The ester resins used according to the invention preferably have an acid number of 15-25.

As already stated above, in the preparation of the ester resins used according to the invention, the equivalent ratio of hydroxyl groups to carboxyl groups of the starting products must be between 1.6 and 2.5. Mostly, this equivalence ratio is at least about 1.8. The upper limit is mainly 2.3.

Carboxyl groups used to calculate the equivalence ratio of hydroxyl groups to carboxyl groups as defined above refer only to those (optionally esterified, i.e., potential) carboxylic acid carboxyl groups that are still available for the esterification reaction with alcohols for this or the 6,63043 reaction. with amines added for. Thus, the preparation of amide-imide-modified ester resins takes place by esterifying said polyhydric carboxylic acids with polyhydric alcohols. In this case, it is also possible that the preparation of the first-formed heterocyclic carboxylic acids, e.g. diimide dicarboxylic acids and the esterification of these diimide dicarboxylic acids with alcohols are carried out in one step in one vessel, since the amino groups react with ortho-carboxyl groups or their anhydride groups. with trimelic acid or its anhydride, mainly to form five-membered imide rings and therefore only those carboxyl groups of the originally added carboxylic acid or its anhydride which do not react with the amino groups of the five-membered imide rings remain for esterification with alcohols.

Examples of carboxylic acids which can be used for the preparation of ester resins are terephthalic acid, isophthalic acid, trimellitic acid, pyromellitic acid, their esters or anhydrides.

By polyvalent compounds used to form polyesters is also meant compounds containing polyhydric carboxylic acids, alcohols or amino groups having five-membered imide rings. Examples of these are polyvalent carboxylic acids obtained by reacting, for example, trimellitic anhydride with diamines to form so-called diimide di-carboxylic acids. Thus, the molecules of polyhydric carboxylic acids esterified with alcohols can be relatively coarser and.

Aliphatic or aromatic compounds are currently used in the art as amines which can be reacted with the carboxyl groups available for the esterification reaction to form acid amide bonds. Examples of these are ethanolamine, ethylenediamine, aminomethylolpropane, p-aminobenzyl alcohol, 4,4'-diaminodiphenylmethane, ether and / or sulfone.

Ester imide resins may contain essentially up to 5% by weight of nitrogen bound to five-membered imide rings.

According to the invention, 63043 compounds containing carboxylic acids, alcohols and / or amino groups which are at least partially polyfunctional, i.e. more multifunctional than bifunctional in order to obtain yarn-bound products during incineration. The degree of bonding corresponds to the degree of bonding of the amide and / or imide-modified ester resins commonly used in the art. In accordance with the state of the art, it is recommended that said polyfunctional carboxylic acids, alcohols and / or compounds containing amino groups have predominantly 3 or 4, in particular predominantly 3 carboxylic, hydroxyl and / or amino groups in the molecule.

In the preparation of the ester resins used according to the invention, the reaction between carboxylic acids, alcohols and compounds containing amino groups is stopped when the acid number is desired. However, ester resins having a substantially lower acid number can also be prepared, and then, by reacting these ester resins with polyvalent carboxylic acids, resins having the desired acid number can be prepared.

Conventional esterification catalysts can be used to prepare ester resins from carboxylic acids and alcohols and optionally compounds containing amino groups. Examples of these are zinc acetate, antimony trioxide, metal amine complex catalysts such as the complexes described in DT-AS 1 519 372, lead oxide, tin (II) oxalate, titanates, manganese (II) acetate, Cer (III) acetate and other such compounds.

Upon completion of the esterification reaction, the ester resins are cooled to a temperature below the boiling point of the amines, which amines are added to the solutions of this invention. These amines are then added slowly. As such aliphatic amines, primary, secondary and tertiary monoamines can be used. Preferred are alkanolamines, which may optionally contain N-alkyl groups, the chain of alkanol or alkyl groups having from 1 to 6, in particular from 1 to 4, carbon atoms. Examples are monoethanolamine, diethanolamine, triethanolamine, N, Ν-dimethylethanolamine, Ν, Ν-diethylethanolamine, propanolamine, diisopropanolamine.

The solution contains aliphatic amines mainly in such an amount that there are at least about 8,63043 0.8 amino groups for each carboxyl group of the ester resin. The upper limit of the amount of amines to be added is essentially such that there is about one amino group per carboxyl group.

These amines also have an accelerating effect on the transesterification which occurs during incineration in the yarn. This applies in particular to amines, which only evaporate after the solvents have evaporated from the lacquer film.

The concentration is then diluted as desired with the solvents used according to the invention. The solutions are then treated with conventional catalysts used in the combustion process, flux and any other lacquer additives. For the purposes of this invention, lacquer additives also mean optionally bonded isocyanates. It is known that in the field of the manufacture of insulating coatings for electrical conductors, optionally bound isocyanates are used in connection with ester resins. This modification is within the scope of this invention. For reasons of physiological safety, priority is given to Authenticated Isocyanates whose binder is physiologically harmless or less suspect.

The connection to the wire takes place in the same way as with solvent-based varnishes according to the prior art, at object temperatures of at least 200 ° C, i.e. oven temperatures above 300 ° C, generally above 400 ° C. The upper temperature limit is mainly determined by the fact that, of course, damage to the uniform coating of the yarn must be avoided. For incineration, so-called incineration catalysts can be added to the solutions, as is common in the prior art. Examples of these are aryl or alkyl titanate monomers or polymers, orthotitanic acid ester chelate compounds and other commonly used transesterification catalysts. These can be used by those skilled in the art with appropriate choices and concentrations (e.g. 0.001-8% by weight based on the amount of solution). Only combustion catalysts that can be mixed homogeneously with the solution used are useful. Additives such as silicone-containing fluxes (e.g. 0.001-5.0% by weight) are often useful, and it is prior art to add them to improve the lacquering properties of the lacquer.

According to the current state of the art, when solvent-containing lacquer solutions are used, several thin layers are successively formed on the wire surface and firing is performed after each time in order to finally obtain a multilayer coating with the best insulating and mechanical properties. Depending on the diameter of the nozzle, the thickness of the lacquer layers obtained in connection with each private combustion event is, for example, 5 to 15 [mu] m, up to a maximum of about 20 [mu] m with a wire diameter of 1 mm.

It is particularly advantageous to use the process according to the invention in connection with ester resins having a high content of tris- (2-hydroxyethyl) -isocyanurate, e.g. using this compound in an amount corresponding to about 30-50% of the total hydroxyl groups used in the starting compounds. It is further preferred to use the process according to the invention in connection with ester resins having a relatively large proportion of five-membered imide rings, e.g. to such an extent that the ester resins contain more than 1% by weight of nitrogen in the form of five-membered imide rings and possibly also amide bonds.

Example 1 248 g (4.0 moles) of ethylene glycol 392 g (1.5 moles) of tris- (2-hydroxyethyl) isocyanurate and 388 g (2.0 moles) of terephthalic acid dimethyl ester are reacted with 1.6 g of zinc acetate in a three-necked flask , equipped with a stirrer, thermometer and rectification column, at a temperature not exceeding 200 ° C. 128 g of methanol are distilled off from the mixture. After the mixture has cooled to about 150 [deg.] C., 192 g (1.0 mol) of trimellitic anhydride and 99 g (0.5 mol) of 4,4'-diaminodiphenylmethane are added.

When further heated to 210 ° C, 35 g of water are distilled off. To the melt cooled to 150 ° C are added once more 192 g (1.0 mol) of trimellitic anhydride and 99 g (0.5 mol) of 4,4'-diaminodiphenylmethane.

The water is distilled off at 210 [deg.] C. until the acid number is 19. It is then cooled to 130 [deg.] C. and a total of 43 g of N, N-dimethylethanolamine is added portionwise over 15 minutes. (Per free ester-resin carboxyl group - about 1 amino group).

10 63043 500 g of the substance obtained above are dissolved in a mixture of 150 g of diglycolide dimethyl ether, 150 g of ethyl diglycol, 120 g of ethyl glycol, 50 g of butyl diglycol and 30 g of titanium acetylacetonate (catalyst) are added. A clear lacquer is obtained with a combustion residue (1 h / 180 ° C) of 20% and a flow consistency of AK = 145 sec.

In a parallel experiment in which no Ν, Ν-dimethylethanolamine is used, a cloudy lacquer solution is obtained which cannot be used.

Example 2,496 g (8.0 moles) of ethylene glycol 114 g (1.5 moles) of propylene glycol and 388 g (2.0 moles) of terephthalic acid dimethyl ester are reacted as described in Example 1 with 1.4 grams of zinc acetate. 128 g of methanol are distilled off from the mixture. After cooling to 150 ° C, 336 g (1.75 moles) of trimellitic anhydride and 99 g (0.5 moles) of 4,41-diaminodiphenylmethane are added.

Heat until 60 g of water has distilled off. After cooling to 150 ° C, 336 g (1.75 moles) of trimellitic anhydride and 99 g (0.5 moles) of 4,4'-diaminodiphenylmethane are added once more to the melt.

At 220 [deg.] C., water is distilled off until the acid number is 25. It is then cooled to 130 [deg.] C. and a total of 65 g of .beta.-dimethylethanolamine is added portionwise over 15 minutes. (Per free carboxyl group - about 1 amino group).

500 g of this substance are dissolved in a mixture of 150 g of diglycolide dimethyl ether, 250 g of ethyl diglycol and 120 g of butyl diglycol and 30 g of butyl titanate polymer are added. The combustion residue (1 h / 180 ° C) of the clear lacquer solution is 45% and the running consistency AK ^ ° = 105 sec.

In a parallel experiment and without the addition of Ν, Ν-dimethylethanolamine, a cloudy lacquer solution is obtained which cannot be used.

63043 11

Example 3 394 g (6.35 moles) of ethylene glycol 496 g (1.9 moles) of tris- (2-hydroxyethyl) isocyanurate and 776 g (4.0 moles) of terephthalic acid dimethyl ester are reacted together with 5.0 g of butyl titanate. monomer as described in Example 1. 250 g of methanol are distilled off. After cooling to 150 [deg.] C., 192 g (1.0 mol) of trimellitic anhydride and 178 g (0.9 mol) of 4,4 • -diaminodiphenylmethane are added and the mixture is heated until 35 g of water have distilled off. After cooling to 150 ° C, 192 g (1.0 mol) of trimellitic anhydride and 178 g (0.9 mol) of 4,4 * -diaminodiphenylmethane are added once more to the melt.

At 210 [deg.] C., water is distilled off until the acid number is 18. It is then cooled to 130 [deg.] C. and 73 g of diethanolamine (about 1 amino group per free carboxyl group) are added to the melt.

500 g of this substance are dissolved in a mixture of 300 g of ethyl diglycol, 100 g of ethyl glycol and 120 g of butyl diglycol and 20 g of titanium acetylacetonate are added. The combustion residue of the clear lacquer solution (1 h / 180 ° C) is 47.5% with a running consistency of AK ^ ° = 130 sec.

In a parallel experiment without the use of diethanolamine, a cloudy lacquer solution is obtained which cannot be used.

Example 4 15.95 kg (20.9.9 moles) of propylene glycol-1,2,16,10 kg (61.7 moles) of tris- (2-hydroxyethyl) isocyanurate and 19.88 kg (119.8 moles) isophthalic acid is reacted with 70 g of zinc acetate in a 120 liter technical reactor equipped with an anchor stirrer, induction heating (temperature control) and a rectification column at a temperature not exceeding 200 ° C. In this case, 2.1 kg of water is distilled off. After cooling to 150 ° C, 12.07 kg (62.9 moles) of trimellitic anhydride and 5.93 kg (29.9 moles) of 4,4'-diaminodiphenylmethane are added.

12 63043

By further heating to a maximum of 200 ° C, the water is distilled off until the acid number is 25. It is then cooled to 130 [deg.] C. and 2.30 kg of .alpha.,. Alpha.-dimethylethanolamine are added slowly (about 0.9 amino groups per free carboxyl group).

8.00 kg of the above-mentioned substance are dissolved in a mixture of 7.00 kg of ethyl diglycol, 1.00 kg of methyl diglycol and 0.50 kg of butyl diglycol and 0.27 kg of titanium acetyl acetate are added. A clear lacquer is obtained with a combustion residue (1 h / 180 ° C) of 46% and a running consistency of AK? ° = 105 sec.

4

The sample taken before the addition of Ν, Ν-dimethylethanolamine is insoluble in the solvents used.

Examples 5-9

The ester resins of Examples 5-9 are prepared in the same manner as described in Example 1. Varnishes are prepared according to the recipe shown in Example 1.

Example 5 238 g (3.84 moles) of ethylene glycol 515 g (1.97 moles) of tris- (2-hydroxyethyl) isocyanurate 55 g (0.33 moles) of isophthalic acid 388 g (2.00 moles) of terephthalic acid dimethyl ester 400 g (2 .01 moles) trimellitic anhydride 198 g (1.00 moles) 4,4'-diaminodiphenylmethane 7 g zinc acetate

The acid number of the ester resin is 18. 40 g of Ν, Ν-dimethylethanolamine are added, so that 0.88 amino groups per free carboxyl group.

Example 6 326 g (5.26 moles) of ethylene glycol 922 g (3.53 moles) of tris- (2-hydroxyethyl) -isocyhydric acid 607 g (3.13 moles) of terephthalic acid dimethyl ester 787 g (4.10 moles) of trimellitic anhydride 39 g .00 moles) 4,4'-diaminodiphenylmethane 18 'g zinc acetate 63043 13

The acid number of the ester resin is 23. 95 g of N, N-dimethylethanolamine are added, so that 0.96 amino groups are obtained per free carboxyl group.

Example 7 286 g (4.61 moles) of ethylene glycol 731 g (2.80 moles) of tris- (2-hydroxyethyl) isocyanurate 166 g (1.00 moles) of isophthalic acid 243 g (1.25 moles) of terephthalic acid dimethyl ester 595 g (3 .10 moles) trimellitic anhydride 297 g (1.50 moles) 4,4'-diaminodiphenylmethane 7 g zinc acetate 4 g antimony oxide

The acid number of the ester resins is 20. 70 g of N, N-dimethylethanolamine are added, so that there is 1.05 amino groups per free carboxyl group.

Example 8 620 g (10.00 moles) of ethylene glycol 104 g (1.00 moles) of neopentyl glycol 1566 g (6.00 moles) of tris- (2-hydroxyethyl) isocyanurate 415 g (2.50 moles) of isophthalic acid 970 g (5 .00 moles) of terephthalic acid dimethyl ester 960 g (5.00 moles) of trimellitic anhydride 495 g (2.50 moles) of 4,4'-diaminodiphenylmethane 20 g of zinc acetate.

The acid number of the ester resins is 19. 151 g of N, N-diethylethanolamine are added, so that 0.84 amino groups are obtained per free carboxyl group.

Example 9 495 g (7.98 moles) of ethylene glycol 1466 g (5.62 moles) of tris- (2-hydroxyethyl) isocyanurate 427 g (2.57 moles) of isophthalic acid 582 g (3.00 moles) of terephthalic acid dimethyl ester 1152 g (6 .00 moles) trimellitic anhydride 634 g (3.20 moles) 4,4'-diaminodiphenylmethane 25 g zinc acetate 5 g cerium III acetate.

14 63043

The acid number of the ester resin is 25. 160 g of N, N-dimethylethanolamine are added, so that 0.92 amino groups are obtained per free carboxyl group.

The varnish solutions are applied in a horizontal wire varnishing oven with a length of 3 ra and a temperature of 550 ° C by means of nozzles in eight layers to the surface of a copper wire with a diameter of 0.5 mm and cured. In Examples 1-9, the varnishing speed is 38-40 m / min.

The test treatments were performed as follows: 1. Wrapping strength pre-stretched: the piece cut from the wire is pre-stretched to the indicated percentage and wound around its own spindle with the same diameter as the wire to be tested. The fractures in the lacquer layer are then examined. If no cracks are found, the wire to be tested is decent (i.O.). Indicate the pre-stretch at which the yarn is still in good condition. The test conditions are described in detail in DIN 46453, Abschnitt 5.1.2 - Blatt 1.

2. Thermal shock test 30 rain / 160 ° C: The wire is wound on a spindle of the same diameter as the wire into a curl, after which it is held for 30 minutes at 160 ° C in an oven and evaluated in accordance with point 1. The performance of the test is described in detail in DIN 46453 Blatt 1, Abschnitt 5.2.1.

The test is carried out at 180 ° C or 200 ° C in the same way, but keeping the oven temperature at 180 ° C or 200 ° C.

3. Softening point in ° C, determined in accordance with DIN 46453 Blatt 1, Abschnitt 5.22: The softening point is the temperature at which a gap is formed between two strands under tension and under increasing temperature load, which overlap and are loaded with standard weights. .

4. Incineration residue: 1 g of the lacquer solution is incinerated on a lid with a diameter of 50 mm for one hour at 180 ° C. The remaining residue is expressed as a percentage.

• f · 20

5. Running Consistency AK. : Running consistency refers to DIN

53211 (April 1974), the time measured at 20 ° C in seconds, la ^ piiune needs to dissolve DOis from the DIN dish 4.

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Claims (10)

1. A process for the preparation of extremely heat-resistant insulating coatings for electric conductors by coating the conductors with catalyst- and optionally liquefaction-containing solutions of heat-curable amide and / or imide-modified ester resins of polyhydric alcohols, polyhydric carboxylic acids with polyhydric carboxylic acids optionally in admixture with aliphatic carboxylic acids and optionally their anhydrides and / or esters, as well as amino group-containing compounds and heating of the available conductors at object temperatures exceeding 200 ° C, which ester resins exhibit an acid number of 10-50 and wherein the equivalent ratio of the hydroxyl groups to the carboxyl groups in the starting products to prepare the ester resins is between 1.6 and 2.5, characterized in that the solution contains aliphatic amines in such an amount that on each free carboxyl group in the ester resin, 0 5 to 1.5 amino groups, and the solvents in an amount of at least about 70% by weight consists of mono- and / or dialkyl ethers, wherein each alkyl moiety contains 1-4 carbon atoms, of mono- and / or dialkandiols having 2 carbon atoms per alkane. Process according to Claim 1, characterized in that the equivalent ratio of the hydroxyl groups to the carboxyl groups is at least about 1.8. Process according to claim 1 or 2, characterized in that the equivalent ratio of the hydroxyl groups to the carboxyl groups is at most about 2.3. Process according to any one of claims 1-3, characterized in that the ester resins have an acid number of at least about 15. Process according to any of claims 1-4, characterized in that the ester resins have an acid number of not more than about 25. Process according to any of claims 1-5, characterized in that the solution contains aliphatic amines in such an amount that at least about 0.8 amino groups are added to each carboxyl group in the ester resin. Process according to any one of claims 1-6, characterized in that the solution contains aliphatic amines in such an amount that at most about one carboxyl group in the ester resin comes at most about 1 amino group. Process according to any of claims 1-7, characterized in that the solution contains aliphatic monoamines.