Process and device for treating leather

Technical field

Treatment of materials; milling; drying.

Technical problem

The problem which is related to this invention is in shortening of time of exposure of hides subject to leather treatment to treating chemicals and shortening necessary drying time.

State of the Art

There are several processes known in state of the art for tanning or treatment of leather. One which is closest is putting several hides in the rotating drum filled with tanning bath and subjecting said hides to rotation. During rotation the hides are soaked with tanning ingredients. After soaking there is drying using different processes, known in the art and not subject of this invention hence unrelated to it.

Description of new invention

The above referenced technical problem is solved with process and device for treating leather.

Leather in form of hides or articles of leather or other articles comprised of similarly behaving material is introduced (for purposes of this application all of these articles of leather jointly referred to as "hides") into rotating drum or stirring vessel or other form of similar device where it undergoes spraying with chemicals and drying to desired humidity to be followed by drying and another treatment of milling in rotating drum.

Below the essence of the invention is described with help of attached drawing, this drawing forming part of this patent application.

Figure 1 shows drum (1) filled with hide or plurality thereof (2), direction of turning of said drum (3), nozzle for spraying chemicals (4), and delivery tube for said chemicals (5).

For purposes of this application hide or plurality thereof (2) can also be other articles in need for surface treatment by exposure to spray droplets.

In essence the process is performed in a rotating drum (1) in three steps, said drum rotating in either direction. For purposes of this application said drum (1) can also be in other form such as stirring vessel, or ball, or other application meant of ensuring that the surface of hide or plurality thereof (2). Said drum (1) is equipped with temperature control system, preferably heating system, and with climate control system, preferably with device able to regulated humidity, more preferably by device capable by spraying water into said drum (1).

The hide or plurality thereof (2) is inserted in their finished or semi-finished form, for purpose of embodiment as finished leather. The hide or plurality thereof (2) is treated with a special mixture of different components.

In preferred embodiment 5 to 100 finished leather hides are inserted into said drum (1).

In preferred embodiment said drum (1) measures 2 to 4 m in diameter, rotating at 10 to 30 revolutions per minute. Load factor can be assessed from these results given average size of said hide (2) being of large mammal (such as cow).

(a) First step

First step is comprised of wetting said hides (2) with chemicals and exposing them to suitable heat treatment.

First part of first step to be treated during period of 5 to 30 minutes by rotating of said hides (2) in said drum (1).

After this period spraying of said mixture is commenced through nozzle (4) with mixture of chemicals, the composition of this mixture not being part of this patent application, said mixture introduced to the nozzle (4) through delivery tube (5). It should be noted that several nozzles (4) can be used, placed in different positions throughout said drum (1).

Said spraying lasts between 5 and 120 minutes depending on the concentration of the mixture and the number of said hides (2) in said drum (1).

Following spraying said hides (2) remain in said drum (1) being subject to further milling for a period necessary for said hides (2) to have 30% to 40% absolute humidity (as defined by standards, for example and in particular DIN EN ISO 4684). In preferred embodiment this period lasts between 1 and 6 hours and hides (2) are subject to climate control, preferably heating.

After process the absolute humidity of said hides (2) is measured, and if the results are below 30% additional water is sprayed while drum (1) is rotated.

(b) Second step

The second step of the process is the drying of said (slightly wet) hides at elevated temperature between 40 and 60°C until a residual absolute humidity between 5 and 10% within the hides is reached.

This step is performed outside of said drum (1) on racks or using other means known in state of the art.

(c) Third step

The third step is milling said hides (2) in said drum (1) again at dry conditions and temperatures between 30 and 50°C for 5 to 10 hours.

(d) Optional fourth step

An optional fourth step is giving the treated leather an additional finishing by spray coating.