Leather tanning products

Description

The tanning is by definition the transformation of any skin in leather that is afterwards employed in the shoe industry, leather goods and upholstery and in an infinity of articles used in the fashion world and in each person’s everyday life.

This transformation is given by a stabilisation of the skin protein. Skins are submitted to the action of different chemical agents which interact with the collagen fibers to obtain a lasting and stable leather.

That modification of the skin in order to yield a product combining those properties is called “tanning”, and the product obtained is called leather.
Basically there exist two processes through which this stabilisation is reached: through the vegetable tanning (the traditional method) and through the tanning with chromium (chrome).

The latter has been used for more than a century, and it differs from the traditional procedure, which is based on the use of vegetables such as barks, woods, leaves and roots, generally from tropical or subtropical plants such as the mimosa, the break-axe, and the chestnut, among others.
The+3 Chromium salts are, since more than a century, one of the most important tanning methods, and nowadays in the world, 80% of all leathers are tanned in this way. The tanning by chromium process is considered the most versatile one.

Utilization

As we saw in the introduction, the utilization of chromium salts is the most diffused and applied tanning procedure in the world.
With these chromium salts, it is possible to obtain most types of leather, since through a great quantity and variety of retannings, almost any desired or necessary property of the leather can be obtained.

The skins and leathers  partially tanned with chromium salts, can be subsequently submitted to an additional tanning, with similar or different tanning materials to those of the first one, (retanning), to obtain the widest range of desired qualities.

Once dry, leathers undergo different conditioning processes, thus becoming ready for the final finishing. Then, several products are applied to them, which, combined with mechanical processes, make the leatherlonger-lasting, more resistant and agreeable.

Products

The chromium salts available in the market are generally identified for their basicity in º Schorlemmer, and so we can find chromium sulphate tanners with a 33% basicity, and there are also with 40 and 50% (Dirox has presently available in the market products with those basicities: Salcromo M33, Salcromo F40and Salcromo F50). In the practice it can be said that the tanning power of a chrome salt increases when its basicity does.

Generally, the tanning starts with chromium compounds of a 33% basicity. Thus, a quick and good penetration of the skin is obtained and an overtanning of its external layers avoided, facilitated by the tiny size of its particles. Then, it is possible to continue with another tanner of 40 or 50% basicity (assuring in this way the tanner fixation due to the increase in the particles size), which can be done in the same tanning bath or in a subsequent retanning that will give more plenitude.

Once the chromium tanner is incorporated to the skin, a more complete fixation of the chromium tanner and a better filling can be achieved with a subsequent basification or retanning, which give more weight and consistency at the end of the process. (Dirox has at present available in the market an important choice of products to obtain this. Its Dirtan trademark line of tannins fills all these purposes).

Another valid alternative is the utilization of chromium tanners containing neutralizing components with retarded effect. These products cause a gradual increase in the astringency of the tanner. With this type ofautobasifying tanners, it is posible to reach in the practice -based on smaller quantities of chromium oxide- contents in the chemical compound in the leather so high as the usual chromium sulphate tanners and separated basification. (Dirox has at present available in the market its product Salcromo AB which fills those properties).

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