CS268060B1 - The solution relates to a safety switch to reduce the risk of water flooding, especially for automatic washing machines. The switch actuating mechanism is connected to the sensor by a coupling. - Google Patents

Abstract

The self-basing mixture for tanning leather contains salts of trivalent chromium and aluminum in a ratio of chromium oxide to aluminum oxide of 1:0.2 to 1:8 and dried chromium hydroxide in an amount of 2 to 15% by weight and/or pellets of magnesium oxide from the combustion of sulfite liquors containing magnesium salts as substances gradually binding the acidity, in an amount of 1 to 10% by weight, calculated on the weight of the resulting mixture. The mixture may also contain substances capable of forming complexes with aluminum and chromium salts, such as salts of formic, acetic, oxalic or citric acid in an amount of max. 20% by weight, calculated on the weight of the resulting mixture.

Description

The invention relates to a self-basing composition for sinin leather based on aluminum and chromium salts.

The compositions prepared hitherto used for tanning and containing aluminum and chromium salts are alkali-base solutions of aluminum and chromium salts or reaction products formed by reduction of hexavalent chromium salts in the presence of sulfuric acid and aluminum salts. Because these solutions crystallize and are difficult to transport, they must be dried, preferably in a spray dryer, which is energy intensive. >

When these mixtures are applied during tanning, acid is released during the process and a bulk reactant is used to neutralize and increase the alkalinity of the whole system, such as sodium carbonate or bicarbonate, which are added after the tanning operation, or gradual effects such as carbonate or magnesium and calcium oxide, which are usually mixed with an acid-insoluble mineral fraction. The disadvantage of substances which gradually weigh alkalinity is the possibility of dosing them into the bath at the same time as the tanning salts. Magnesium oxide or magnesium carbonate have a relatively high reaction rate, so that when they are applied, spots of precipitated chromium hydroxide sometimes form, which reduce the useful properties of the leather.

Substances formed by complexes with aluminum and chromium salts are also used in the transport of tanning mixtures. These substances are added to solutions of aluminum and chromium salts before basification and drying. Their amount must be such that chromium or aluminum hydroxide does not precipitate during the subsequent basification.

Some of the disadvantages of the products used so far are eliminated by a self-basifying mixture based on salts of trivalent aluminum and chromium with a weight ratio of chromium oxide and alumina in the ratio V: 8. Dried chromium hydroxide in an amount of 2 to 15% by weight, pellets from the combustion of sulphite extracts containing magnesium salts. These pellets contain 85 to 95% by weight of magnesium oxide and 2 to 12% by weight of calcium oxide and, when formed in the combustion process, are exposed to temperatures of more than 1000 DEG C. for a long time. The amount of pellets used is in the range of 1 to 10% by weight, based on the weight of the resulting mixture.

The mixture may further contain substances which form complexes with the aluminum and chromium salts, such as salts of formic, acetic, oxalic, citric and many other substances, in an amount of at most 20% by weight, based on the weight of the aluminum and chromium salts.

The advantage of both chromium hydroxide and magnesium oxide pellets is that they bind the acidity of the bathing bath more slowly than previously used magnesium oxide or magnesium carbonate, so that no precipitated chromium hydroxide stains form in the leather and can be mixed into dry aluminum and chromium salts. no need to dissolve and dry again. The chromium hydroxide used and the magnesium oxide pellets do not contain insoluble substances which remain in the leather and complicate further processing. The mixture thus prepared may contain substances forming complexes with aluminum and chromium salts in such an amount as is suitable for the properties of the tanned leathers.

Using the process according to the invention, at least the same tanning properties of the prepared mixtures are achieved with a simpler method of preparation of tanning substances and lower energy consumption during preparation, since the need to dissolve the raw materials and subsequently dry the resulting mixture is eliminated.

The description of the invention is illustrated by the following examples of use, which are, however, only a few of the many possible variants.

Example 1

In a rotary mixer, we mix 560 kg of basic chromium sulphate with a content of 27.5 wt.

-2- CS 268 060 BI

O 2 O and a basicity of 45 ^e Sch, prepared by reduction of hexavalent chromium salts with sugar with 140 kg of alumina and 60 kg of pellets containing MgO of the following composition. The mixture • is used as a substitute for chromium salts in leather tanning.

The composition of MgO pellets 94.95 wt.

. CaO 3.6 wt.

Fe 2 O 0.35 wt.

Proportion insoluble in Hel 1: 1, 1.1% by weight.

Pellets are prepared by annealing active MgO at temperatures up to 1700 ° C. .

Example 2.

In a 7 m silo equipped with a mixing screw, we mix 1,000 kg of chromium-potassium alum with 3,000 kg of crystalline aluminum sulphate, 200 kg of sodium acetate and 165 kg of MgO pellets from Example 1. The mixture is used for tanning leather.

Example 3

In a trough mixing device, we mix 720 kg of crystalline chromium sulphate, 2,900 kg of crystalline aluminum chloride and 2,000 kg of dried chromium hydroxide with a content of 33 wt. CtjOj · We will use the mixture as an agent for the production of leather.

Example 4

In a mixing force, we mix 800 kg of technical dried chromium hydroxide with a content of 33 J? Cr / OH / j and 500 kg of MgO pellets from Example 1 and 5 680 kg of a combined preparation containing aluminum and chromium salts, prepared according to the following procedure:

Dissolve 4,300 kg of crystalline aluminum sulphate and 850 kg of sodium dichromate in 5,500 kg of water, add 850 kg of sulfuric acid and gradually reduce 390 kg of a 55% strength by weight sugar solution. The reduced mixture is basified by gradually adding and mixing 1,020 kg of soda ash and 150 kg of citric acid. We dry the finished product in a spray dryer.

The resulting mixture is used for tanning leather.

Example 5

We prepare the holin according to operating habits, decalcify and urinate. All other data are based on the weight of the clearing.

In a tanning barrel we put 100% of the mass, water warm 30 ° C and while moving we add 8 £ of mass, natural tannin Mimosa and after four hours of movement 4 masses, the composition according to example 2. After four hours of movement we leave until the next day , we cut and further process as needed.

Leather produced in this way is characterized by uniformity of coloring, good colorability, fine face and satisfactory fullness and are fully comparable with leather produced in the classical way.

The invention can be used in all tanning agents and tanneries.

Claims (2)

OBJECT OF THE INVENTION A self-basing leather tanning composition based on salts of trivalent aluminum and chromium with a weight ratio of chromium oxide to alumina of 1: 0.2 to 1: 8, characterized in that it contains dried chromium hydroxide in an amount of 2 to 15% by weight, and / or pellets from the combustion of sulphite extracts containing magnesium salts with a composition of 85 to 95% by weight, magnesium oxide and 2 to 12% by weight, calcium oxide in an amount of 1 to 10% by weight, based on the weight of the resulting mixture. 2. A self-basifying composition according to claim 1, characterized in that it contains substances capable of forming complexes with aluminum and chromium salts in an amount of at most 20% by weight, based on the weight of these salts.