DE767746C - Electrolyte, especially for electrolytic capacitors - Google Patents

Description

Electrolyte, especially for electrolytic capacitors Flor low-temperature electrolytic capacitors, which have a working range of -4o ° or w. = 6o ° 'C to + 6o' or 7o ° C, are the normal operating electrolytes of electrolytic capacitors that are made of partially esterified mixtures of boric acid, ammonia and polyhydric alcohols exist, do not. It turns out that these electrolytes at temperatures of below 0 ° or below -2o ° C, due to their very high viscosity, a very low one Have conductivity. In addition, these electrolytes solidify at temperatures which are above -4o ° or -6o ° C, almost completely and therefore assign one low conductivity at the operating temperatures of low-temperature electrolytic capacitors on. Various proposals have been made to produce better electrolytes, z. B. by adding polyvalent: Alko @ get, such. B. ethylene glycol, or the lowering of the boiling point when preparing the electrolyte .. It shows however, these methods have disadvantages. So increased the addition of ethylene glycol the tendency of the electrolyte to corrode and sets the voltage limit, presumably due to the presence of free OH groups, h ° rah. The free OH groups are usually slightly oxidized by the electric current. in fact to an organic acid or to an aldelivd. .wherein these substances are aluminum can easily attack. On the other hand, it causes a lowering of the boiling point Crystallization tendency and imuristie ze change of the electrical over time Values. whereby the application is very limited. For roughened anodes For example, electrolytes crystallized in this way are unsuitable.

According to the present invention, it is now proposed. instead of polyhydric alcohols - # tlieralcohols to normal operating electrolytes in one to add such a percentage. that a particularly favorable ratio of viscosity. Conductivity and funhc-nvoltage is achieved.

Ethereal alcohols are therefore of particular benefit, as they are not contain free OH groups. "-Which oxidized" -can earth. Furthermore, have etlier alcohols relatively high dielectric constants and are chemically inactive, inert Fabrics. which do not have any corrosive effect.

It has been proposed for deep-temperature electrolytic capacitors been. to use an electrolyte that is liquid or pasty in the case of a Temperature is, 'which is lower than the melting point of the easiest melting component. Such an electrolyte essentially contains Saiz-: miscl-e, which result in a relatively increased viscosity of the electrolyte. These but reduces the conductivity, "-which again for low temp, -rature-electric-It'tlCrnd-en- # atoi'en Of particular importance is: It has been shown that the known electrolytes solidify even at higher temperatures than an electrolyte according to the present invention Invention.

For example, a mixture according to the invention of about 75 percent by weight Äth-eralkoliol f z. B. Ethyl Glycol or Ethyl - To about 25 percent by weight of normal Eetriehs .; iektrolvt made by boiling eoric acid. Ethylene glycol and ammonia water was produced to about 1.I5 ° C. following, - values: spark voltage about 5oo V at 6o @ C fr 100.1 (S / cm at + 30 - C sp, -z. Conductivity 25 uS / cm at -4o ° C 1.5 ciS / cm at -60 ° C For comparison, the values of a normal operating electrolyte without additives and a common low-temperature electrolyte are given. In the case of a normal electrolyte without additives, a conductivity of 2.uS / cm results already at + 10 ° C, which drops to about 0.1 S / cm at o'C.

A normal low-temperature electrolyte made by adding ethylene glycol to a boiled electrolyte prepared on the same basis as above at -.4o'C a conductivity of 2 to 5, iIS, 'cm and a L become usable Voltages over 120 volts.

It has been shown that with increasing addition of Ilethylglykol one Improvement of the properties takes place. An optimum can be achieved at 750/0 ethylene glycol can be seen, as there are still greater dilutions due to insufficient ionic content may be undesirable.

On the basis of experiments it has been found that in addition to methyl and Ethyl glycol also other substances with a sufficiently low melting point and absence suitable for oxidizable radicals, for example glycol dimethyl ether, glycol diethyl ether, Glycol methyl ethyl ether. These substances become the boiled electrolyte after it Cooling to temperatures of about + 20 ° to -i- 6o 'C added and the mixture evenly stirred. The impregnation of this electrolyte takes place in the usual way Way by inserting the winding into the electrolyte heated to cgoa to 100 ° C or by adding directly to the spacer during the winding process (tank winding process).

Claims (3)

PATENTA \ SPRI; CHE: i. Electrolyte, especially for electrolytic Capacitors. characterized in that the z. B. from a polyhydric alcohol, such as glycol or glycerin, and a weak acid, such as. B. boric acid normal electrolyte plus ether alcohol. such as methyl glycol, ethyl glycol or such as glycol dimethyl ether, glycol diethyl ether or Glykolmetlivläthy läther contains. 2. Electrolyte according to claim i, characterized by the addition of 75 percent by weight of ether alcohol, for. B. methyl glycol or ethyl glycol, about 25 percent by weight operating electrolyte, which in turn by boiling boric acid. Ethylene glycol and ammonia water can be produced to around 1453 C. 3. A method for producing an electrolyte according to claims i and 2, characterized in that the addition of methyl glycol or other substances of the preceding claims is added to the boiled electrolyte after it has been cooled to temperatures of 2o to 6o ° C, and that the mixture is stirred evenly will. In order to distinguish the subject matter of the invention from the state of the art, the following documents have been considered in the grant procedure: British Patents Nos. 439 533, 439 788, -472 365; U.S. Patent Nos. 1,815,768, 1,959,130, 2,022,500 ; French Patent No. 798,407; Austrian patent specification No. I50 2I9.