SU8848A1 - Method of dehairing hides - Google Patents

Description

The well-known method of dehairing hides before tanning consists in processing them, after pre-soaking in water, in lime milk for a period of less than 5-7 days. The hair is retained, but the skin substance & partially hydrolyzed. The so-called aggravated ash-pans, with the addition of sharpeners to the milk of lime, such as caustic soda, soda, and sulfurous acid, accelerate dehairing, but weaken the hair fiber, making it of little value. Nakr: hair crater with alkaline sulphide solutions or a mixture of them with lime milk, mainly sulphurous soda with lime is produced within a few hours, at which the hair completely dies, dissolved in the ash liquid.

The present invention relates to a known method of enveloping the cheekbones, by using two baths, one of which consists of a weakly concentrated solution of sulfuric alkalis and the other from a solution of lime.

It is known that solutions of sulfurous alkalis, ammonium sulfide or alkaline earth metals noticeably hydrolyze hair with its depletion, if .Р // solution is higher than 7 and faster, the higher the pH, while solutions of pure alkalis do not have a noticeable hydrolyzing effect. on the substance of the hair, even with PN - 12 (milk of lime).

The inventors noticed that if the skin is treated first in a solution of sulphurous alkali, or sulphurous calcium, or sulphurous ammonium, or mixtures thereof, the pH of which is not higher than 7, so that the leather fabric is soaked with a solution, and then treated with a solution of caustic alkali or lime, or silicate alkalies, or their mixtures with pH above 7, the hair follicles dissolve and the hair with the epidermis is easily separated from the leather, completely preserving its strength.

With the selection of appropriate concentrations, the time for dehairing can be increased with heavy skins to 1-2 days. By mechanical processing in drums, gaskets, etc., this period can be extended to several hours.

A solution of technical sodium sulfite () has a very high pH (for example, at a density of 2.6 ° Vyo PH approx. 10.31), which can be consumed by up to 7 by adding an appropriate amount of mineral or organic acids, alkali metal salts, ammonium salts, magnesium salts, organic compounds such as phenols, sugar, dextrin, peptones, proteins, etc.

PRI, and measure 1.-Ottochenna American bull skin suspended in the solution -

sulphurous soda () with a density of 2.5 ° Vyo .... GOO l

and baking soda

(NaHCOs}......... 2.2 lgg

,9.

After 20 hours at ordinary temperature, the solution penetrates the thickness of the leather.

After lightly rinsing the skin from excess solution, it is immersed in 3% milk of lime,. After 2 hours, the hair starts moving and after four hours the skin is taken out completely giving the hair away when washing. Hair retains its strength.

II p and m e r 2.-Ottochenna American bull skin suspended in solution

sulphurous soda () with a density of 2.5 ° Be .... 100 l

and ammonium chloride (ammonium chloride) NHiCl .... 1.5 lgg OCT-6.54.

after-20 hours at ordinary temperature the solution soaks

uniformly throughout the leather thickness

tissue.

After lightly rinsing the skin from excess solution, it is immersed in a 3% solution of limestone milk PH 12.

After four hours, the skin easily gives the entire hair completely intact.

The subject of the patent.

The method of dehairing hides by n {naming two baths, of which the first consists of a weakly concentrated solution of sulfurous alkalis, and the second is from a solution of lime, washing the skins in water after processing them in the first bath, characterized by From the concentrated solution of sulfuric alkalis, in order to reduce I / i to 7, acidic alkali metal salts, magnesium, ammonium salts, organic compounds such as phenols, sucrose, dextrin, peptones or proteins, etc., are added.