CS270641B1 - Impregnating electrolyte for electrolytic capacitors β minus 55 to plus 125 ° C - Google Patents

Abstract

The working impregnation electrolyte is intended for electrolytic capacitors with aluminum electrodes, with a wide temperature range of minus 55 °C to plus 125 °C, storage temperature of minus 60 °C 1 and operating voltage of 160 V to 250 V. The electrolyte contains dimethylammonium adipate, di-diethylaminate adipate and ammonium ethylene glycol borate. Its advantage is low resistance values at minus temperatures and stability of parameters at a temperature of plus 125 OC, which ensures long-term durability of the capacitors.

Description

The invention relates to a working impregnating electrolyte for electrolytic capacitors with aluminum electrodes. Wide temperature range minus 55 to plus 125 ° C, for operating voltages 160 to 250 V.

This type of capacitor consists of an AI and a foil with a dielectric oxide layer, a capacitor paper and an AI cathode foil. The capacitor coil is impregnated with liquid working electrolyte, inserted into the housing and sealed *.

The impregnating electrolyte, which forms the cathode of the capacitor itself, is one of its most important components - it significantly affects all the basic parameters of the electrolytic capacitor. The demands on its properties are constantly increasing, it is required that the capacitors be able to operate in a wide temperature range of minus 55 to plus 125 ° C.

It is known to use an electrolyte based on ethylene glycol, boric acid and ammonia to impregnate electrolytic capacitors. However, this electrolyte at temperatures above 70 ° C. acts aggressively on the dielectric oxide layer on the AI anode and at negative temperatures shows an unfavorable course of temperature dependence of resistors. Thus, the applicability is only for the temperature range minus 25 to plus 70 ° C.

Furthermore, electrolytes of various compositions based on ethylene glycol, adipic acid and ammonia are known. For the same reasons given for the boron electrolyte, their applicability is only for the temperature range minus 40 to plus 85 ° C.

In order for the electrolytic capacitors to comply with the prescribed parameters at minus 55 ° C, the impregnating electrolyte must have a favorable course of resistance at minus temperatures and at this temperature a very low value of specific resistance. In order for capacitors to be suitable for a long time at a temperature of plus 125 ° C, the electrolyte must be sufficiently stable at this temperature and the specified operating voltage of the capacitors and must have a reasonably high sparking voltage.

The properties of the electrolyte at sub-zero temperatures, its stability and the value of the sparking voltage at plus 125 ° C are given by the type of organic solvent or organic solvent compound with organic acid and the properties and concentration of added compounds containing ionogens.

The disadvantages - narrow temperature range and instability at high temperatures - mentioned for ethylene glycol electrolytes with boric acid or adipic acid are eliminated by impregnating electrolytes, eg from dimethylformamide, maleic mono-diethylaminate or adipic and diethylene glycolborate ammonium diethylamine.

Electrolytes of this composition show low values of specific resistance at temperatures plus 30 ° C and minus 55 ° C and at a temperature of 125 ° C they are sufficiently stable - they do not corrode AI electrodes, do not disrupt the dielectric oxide layer, have good molding ability, but sparkling voltage only suitable for capacitors with an operating voltage of 6 to 100 V.

This shortcoming - low sparking voltage - while retaining the other advantages - is removed by the impregnating electrolyte according to the invention, which consists in 70 to 92 parts by weight of dimethylammonium adipate, 3 to 15 parts by weight of adipic diethylaminate, 5 to 15 parts by weight of ethylene glycol borate. ammonium.

The electrolyte of this composition has the required values of specific resistance at temperatures of 30 ° C and minus 55 ° C and is perfectly stable at a temperature of plus 125 ° C - it does not corrode A1 electrodes and does not disrupt the dielectric oxide layer, has good molding ability and sufficiently high sparking voltage for capacitors with operating voltage 160 to 250 V.

For a better illustration, the most important parameters of electrolytes and capacitors are given

CS 270 641 Bl ny in the following tables.

Electrolytes are labeled:

1. Electrolyte from ethylene glycol and boric acid, 2. Electrolyte from ethylene glycol and adipidic acid 3. Diaethylformamide electrolyte for 63 to 10 V / 4. Electrolyte according to the invention for 160 to 250 V.

Dependence of spec, electrolyte resistance on temperature (OHm.cm)

Electrolyte temperature (° C) - . · - + 30 - 25 - ⁴⁰ - 55 1 895 70 400 470 000 4 610 000 2 735 26 350 133 600 1 304 000 3 340 1 020 1 970 4 590 4 570 1 820 3 410 '7 550

The electrolytes show the following increase in specific resistance in the temperature range plus 30 ° C to minus 55 ° C: boric 5150x, adipic 1774x, dimatylformamide for 63V to 100V 13.5x and the electrolyte of the invention for 160V to 250V 13.2x . Furthermore, the electrolyte according to the invention has a specific resistance value of 172 times lower than the adip electrolyte at a temperature of minus 55 ° C. Sparking voltage of electrolytes Electrolyte

445V

475V

360V, 460V to 480V

The electrolyte according to the invention for 160 V to 250 V has a substantially higher switching voltage than the diBetylformamide electrolyte for 63 to 100 V.

Durability of 250 V / 20 capacitors _from uF at 125 ° C with electrolyte according to the invention

The table shows the changes in capacity, loss factor and residual current during the 5,000 hour test.

test duration (hours)

0 1,000 2,000 4,000 5,000 C (/ UF) 20.5 20.4 20.4 20.3 20.3 tgO (%) 2.7 2.6 2.7 3.0 3.2 Izb (/ UA) 4.0 1.0 0.9 0.9 0.8

It can be seen from the values obtained that the electrolyte capacitors according to the invention of the legs operate at a temperature of plus 125 ° C for several thousand hours with very small changes in the basic parameters.

The composition of the electrolytes according to the invention is described in the following examples:

Electrolyte for 160 V

Mixes:

parts by weight of dimethylammonium adipate, 5 parts by weight of adipic diethylaminate.

CS 270 641 B1 3 parts by weight of ammonium ethylene glycol borate.

The mixture was stabilized by heating to 120-125 ° C for 2 hours.

Specific resistance 350 to 500 0hm.cm/30 ° C □ spark voltage. 460 V! ।

Dimethylammonium adipate is prepared by reacting dimethylformamide with adipic acid at elevated temperature. .

Electrolyte for 250 V

Mix: 88 parts by weight of dimethylammonium adipate, 5 parts by weight of adipic di-dioctylaminate, 7 parts by weight of ammonium ethylene glycol borate.

The mixture was stabilized by heating to 120-125 ° C for 24 hours.

Specific resistance 600 to 750 0hm.cm/30 ° C □ spark voltage 480 V.

* The impregnating electrolyte according to the invention makes it possible to produce electrolytic capacitors with Al electrodes for an operating voltage of 160 to 250 V with a wide temperature range of minus 55 to plus 125, a storage temperature of minus 60 ° C and a shelf life of at least 2,000 hours at plus 125 ° C. '’

Claims (2)

OBJECT OF THE INVENTION Impregnating electrolyte for electrolytic capacitors with aluminum electrodes, a wide temperature range of minus 55 ° C to plus 125 ° C and an operating voltage of 160 to 250 V, characterized in that it consists of 70 to 92 parts by weight of dimethylammonium adipate, 3 to 15 wt. parts of adipic diethylaminate and 5 to 15 parts by weight of ammonium ethylene glycol borate. 2. The impregnating electrolyte process according to item 1, characterized in that the mixture of dimethylammonium adipate, adipium diethylaminate and ammonium ethylene glycol borate is heated at 120 to 130 ° C for 0.5 to 36 hours and thereby stabilized.