DE1494536B2 - HIGH HEAT RESISTANT ELECTRIC INSULATING LACQUERS, IN PARTICULAR WIRE LACQUERS - Google Patents

Description

In patent 1038 679, highly heat-resistant electrical insulating varnishes, in particular wire varnishes based on polybenzenedicarboxylic acid esters, have been proposed, which are obtained by esterifying terephthalic acid or transesterifying its lower alkyl ester with mixtures of 2 g moles of a dihydric and 1 g mole of a polyhydric, especially a trihydric alcohol have been, where the OH groups are only present in a slight excess over the COOH groups, in particular six to eight OH groups, and the esterification is carried out slowly and at elevated temperatures, advantageously above 240 ° C., in such a way that the polyesters obtained in a solution of 50 parts ester plus 50 parts cresol and 20 parts naphtha, the highest possible viscosity of at least. have about 4 minutes at 20 ° C in a 4-mm DIN cup and have a melting point of at least 70 ⁰ C. These electrical insulating varnishes, which have already been proposed, are characterized in that the polyesters have been subjected to extraction, preferably with aromatic hydrocarbons, before they are dissolved, and that their solutions in solvents containing more than 50% phenols, for example cresol or xylenol, contain 1 to 15 percent by weight of organometallic compounds of Elements of III. or IV. Group of the Periodic Table, preferably butyl titanate as hardener. Such coatings have proven particularly useful when they are present as a solution of the polyester resins in solvent mixtures of aromatic and / or chlorinated hydrocarbons and phenols with a phenol content of more than 50 percent by weight. Very good results have also been achieved with lacquer solutions containing aluminum alcoholates or organic silicon compounds.

It has been found that highly heat-resistant electrical insulating varnishes, especially wire varnishes, according to the patent 1,038,679 can also be obtained if they contain isophthalic acid instead of terephthalic acid. These lacquers are based on isophthalic acid polyester instead of terephthalic acid polyester. The other measures and requirements contained in the patent 1038 679 also apply to all for the paints of the invention.

In special cases, highly heat-resistant electrical insulating varnishes are obtained if the polyester is in front only be subjected to one extraction to dissolve. the. However, paints have proven to be the best which contain all of the elements mentioned in detail above.

The Belgian patent 543 486 describes condensation products based on terephthalic acid and / or isophthalic acid, their polymers are important for electrical insulating varnishes are. The information in this patent specification leave a myriad of possibilities with regard to Selection of the substances to be converted, compliance with certain esterification bonds, etc. open. There is also a lack of specific information with regard to the viscosity to be adhered to on the paints to be processed Polyester. From an extraction of the polyester, which is the focus of the invention, before There is no question of dissolving. The addition of butyl titanate is also not mentioned.

It was by no means foreseeable that this measure would result in extraction in combination with the other elements on which the invention is based, electrical insulating varnishes can be obtained, a sudden improvement in the breakdown voltage, which is crucial for this type of lacquer exhibit. To prove this surprising result, comparative tests were carried out, the result of which can be seen in the annex. A paint based on a was compared from isophthalic acid dimethyl ester, ethylene glycol and

ίο Glycerin made polyester with a varnish same composition, but which, according to the invention, had been extracted before dissolving. aside from that a paint according to Example 15 of Belgian patent 543 486 was prepared and in his Properties judged.

The comparative tests show that the isophthalic acid ester varnishes produced with extracted polyesters the paints of the same composition made with non-extracted polyesters are superior. The aforementioned breakdown voltage is in the foreground of the improvement. There are electrical insulating varnishes known which consist of a solution of such polyesters, which by Sales of polycarboxylic acid with glycerol or pentaerythritol were obtained. In these polyesters however, dihydric alcohols are not incorporated at all; in addition, the Alcohol component is not a mixture of two alcohols, as in the invention, but either Glycerine or pentaerythritol is used as an alcohol component. Must be in these well-known paints in addition, siloxanes should be incorporated if satisfactory properties are to be present. In contrast make the paints of the invention due to their different material composition even without incorporation of Siloxanes represent high-quality electrical insulating varnishes.

Manufacture of comparative samples

Paint 1

In a round-bottom flask equipped with a stirrer, thermometer and column for. Was equipped to collect the methanol released during the reaction, the following substances were converted at temperatures between 180 and 260 ° C: ''

1000 g of dimethyl isophthalate, 235 g of ethylene glycol
174 g glycerine

Carboxyl groups: .., 10.87

OH groups 13.20

A ratio of 6 COOH groups to 7.29 OH groups was used. ■,, After. Stripping off the methanol, 1052 g of one fell resinous polyester with a melting point of 73 ° C, of which 500 g were processed into lacquer 1.

The processing to the paint was carried out according to the following recipe:
60

25.0 parts by weight solid resin
54.5 parts by weight of cresol DAB 4 18.5 parts by weight of solvent naphtha 1.0 part by weight of butyl titanate polymer mixed with 1.0 part by weight of cresol

Paint 2

The remaining 552 g of the as described for varnish 1

IO

benen polyester were stirred with 197 g of solvent naphtha, heated to 175 ° C with stirring and heated Cooled to room temperature. The supernatant liquid was decanted, the contents of the flask twice more each with 138 g of solvent naphtha heated to 170 ° C, cooled and decanted. The ones that arise during decanting Liquids were combined and collected.

The polyester remaining in the flask was viscous due to the uptake of some solvent naphtha.

Solids content 78.2%

Dry resin content 532 g = 96.37%>

the initial weight loss of extractables

Substance 3.63%

A white, crystalline body was obtained from the extract by evaporation to dryness, whose saponification number was 455.

The resin-like polyester was analogously to the composition given for lacquer 1, lacquer No. 2 produced.

All paints were painted onto a 1 mm round copper wire under the same conditions, with Application speeds of 6 and 7 m / min were observed.

Paint 3

Its composition corresponded to the information in Example 15 of the Belgian patent specification 543 486.

The results of the testing are shown below.

Results

Lacquer 1:

Varnish based on a made from isophthalic acid dimethyl ester, ethylene glycol and glycerine, unextracted polyester.

Lacquer 2:

Varnish based on a made from isophthalic acid dimethyl ester, ethylene glycol and glycerine, but polyester extracted according to the invention.

Lacquer 3:

Varnish based on a made from dimethyl terephthalate, ethylene glycol and glycerine Polyester according to Belgian patent 543 486 (Example 15).

1. Dissolution test

Hardness determination after 10 minutes of storage in an alcohol-toluene mixture 1: 1 at room temperature.

Throughput speed at constant furnace length and a temperature of 400 ° C; Specification in m / min.

2. Breakdown voltage

Specification in volts for the amount required to penetrate a layer of varnish 0.025 mm thick Tension.

6 m / min. 7 m / min. Paint 1 2983
4333
1860 1583
1900
1880 Paint 2 Paint 3

3. Thermal compressive strength

Specification in ° C, up to which two cross-laid lacquered wires are loaded with a certain weight and can withstand this pressure for 2 minutes.

6 m / min. 7 m / min. ²⁰ paint 1 240 °
240 °
220 ° 230 °
230 °
190 ° Paint 2 Paint 3

4. Aging

Wire with lacquer layer aged 100 hours at 185 ° C, then stretching. Specification of the% elongation at which the lacquer layer tears.

6 m / min. 7 m / min. Paint 1 5%
5%
14% 5%
5%
10% Paint 2 Paint 3

5. Winding curl

The enamelled wire was wound around a mandrel three times the wire diameter, then placed in a heating chamber given and heated to 175 ° C for 15 minutes. Then stretch by 25%. Count of bursts on the paint layer.

6m 7m Lackl Well
Well
Well Well
Well
Well Paint 2 Paint 3

6. Abrasion

A needle loaded with weight makes a line 1 cm in length on the lacquer layer under voltage. The criterion is the number of lines that the needle (electrical field) scratches until it hits the bare conductor.

6 m / min. 7 m / min. Paint 1
Initial hardness
after storage 2H
H-2H H-2H
H Paint 2
Initial hardness
after storage 2H
H-2H H-2H
H Paint 3
Initial hardness
after storage 2H
HF 2H
F-HB

6 m 7m Paint 1 21
20th
22nd 16
20th
12th Paint 2 Paint 3

Claims (1)

Claim: Highly heat-resistant electrical insulating varnishes, in particular wire varnishes based on Polybenzenedicarboxylic acid esters containing hardening agents and those made using terephthalic acid or transesterification of their lower alkyl esters with mixtures of 2 gramol of a divalent and 1 gramol of a polyvalent, in particular trihydric alcohol have been obtained, the OH groups only to a small extent Excess over the COOH groups are present, in particular six to eight OH groups on six COOH groups, and with the esterification slowly and at elevated temperatures, is advantageously carried out above 240 ° C such that the polyester obtained in a solution of 50 parts ester plus 50 parts cresol plus 20 parts naphtha as possible have a high viscosity of about 4 minutes at 20 ° C in a 4 mm DIN cup and a melting point of at least 70 ° C, and wherein the solutions of the polyester, which before the Dissolving have been subjected to extraction with aromatic hydrocarbons in Solvents containing more than 50% phenols are present and these solutions are 1 to 15% by weight organometallic compounds of elements of III. or IV. group of Periodic table contained as hardener, according to patent 1038 679, characterized that the polyesters contain isophthalic acid instead of terephthalic acid.