HRP970218A2 - Process and apparatus for treating leather and the like - Google Patents

Description

The proposed invention relates to leather tanning and the like. It is known that animal skins are tanned, so that they do not rot, with solutions that enter the skin and remain irreversibly fixed in it.

This processing involves various stages that are often complex and require a relatively long time. When delivered for tanning, generally dried with salts, the rawhide is first prepared for actual tanning.

This preparation includes first soaking, i.e. removal of impurities covering both sides, the inner scraped side and the outer or hairy side, as well as the preservation solution, so that the leather regains its natural softness.

The leather to be processed is soaked in drums containing suitable solutions. These drums are equipped inside with moving paddles or rods, which act on the skin as the drum rotates. Therefore, the treatment consists of a combination of chemical action of the liquid solution and mechanical action on the skin for at least six to twenty-four hours.

This is followed by a rinse to remove grease from the soaked hide, followed by a calcining treatment to remove hair and reveal the hide. Calcination is carried out in suitable drums with alkaline substances, such as sulphides or lime, in which the skin tissue swells and the root of the hair dissolves.

Specifically, the skin swells, the fats are converted into calcium salts, and the proteins that build the skin are modified due to the breaking of the primary and secondary bonds of the protein chain and, subsequently, the hair falls from the skin.

The substances used for calcination, and at the same time for "opening" the pores of the leather, to carry out the actual tanning and dyeing, cause great pollution, with the consequence of all the known difficulties of waste removal and/or cleaning.

The calcination stage usually lasts 24 hours. Then the leather thus prepared is decalcified and softened, again in suitable drums. Due to the degree of decalcification, retained lime is usually removed with decalcification salts. Softening is a biological procedure that softens the skin structure with enzymes that partially dissolve the elastic tissue and thereby cause the skin to loosen.

After that, the leather is subjected to acidification, i.e. a treatment that guarantees faster and complete penetration of the tanning salt. In fact, softened leather, which has an alkaline reaction, cannot be tanned, for example, with chrome tanning salts, because a chemical reaction occurs that can close the pores of the skin.

This is why the skin is acidified with a small amount of acid, with the presence of salt (usually sodium chloride) to prevent swelling. This stage is carried out in a drum and lasts an average of 10 to 12 hours.

The actual tanning is carried out in the drums mentioned above using vegetable solutions, such as natural or synthetic tanning solutions, or using mineral salts, namely chromium or similar salts.

Calcination, softening, acidification and tanning require an average of no less than 48 hours (it can be changed depending on the type of leather being treated).

The hides, suitably washed to remove part of the absorbed water, selected and torn, are subjected to dyeing, which is otherwise called re-tanning. This coloring takes an average of eight hours. Therefore, the above-mentioned tanning treatments require, as already said, a lot of time, which can last an average of a week.

As a result, the use of a relatively large number of large drums is necessary to achieve adequate productivity. Pieces of leather to be processed are thrown whole into drums and are directly subjected to mechanical action that can sometimes damage them.

A not insignificant disadvantage of traditional tanning processes stems from the fact that the working environment is very harmful, mainly due to too many miasmes created in the aforementioned drums. Even more, there are a number of problems of removing the discharged liquids after the completion of the above-mentioned treatments, especially the substances used for calcination.

The aim of the proposed invention is to propose a procedure that enables the tanning of leather and the like to be carried out in a shorter time compared to known systems, while at the same time guaranteeing high quality of the leather as well as high efficiency, and in comparison to known procedures, all this is achieved with a total lower consumption of the necessary energy.

Another basic object of the proposed invention is the proposal of a procedure that can be carried out in a device that enables work in working conditions that are not harmful, and that significantly reduces the problems associated with waste disposal.

Furthermore, the following object of the proposed invention is the proposal of a procedure that enables a significant reduction in the amount of substances used with the same quality of the leather.

Also, the next object of the invention is a proposed procedure, the implementation of which does not pollute the air. Even more, the subject of the invention is also the proposal of a device for carrying out the above-mentioned procedure. The above-mentioned goals were achieved in accordance with the content of the patent claims.

The characteristic forms of the invention will be presented in the following description with special reference to the attached drawings, of which

figure 1 shows a plan of a device for holding a piece of leather for tanning;

figures 2a, 2b and 2c show schematically the baths in which the aforementioned devices are placed in different arrangements;

Figure 3 schematically shows a vertical section of the aforementioned bath during one stage of leather processing;

Figures 4a and 4b show diagrams of devices for carrying out the corresponding tanning treatments in accordance with the method that is the subject of the proposed invention;

Figures 5a and 5b show diagrams of two different embodiments of the aforementioned devices, incorporating this method in different ways;

figure 6 shows a possible diagram of a device incorporating this method in yet another way;

figure 7 shows the following version of the device;

Figure 8 shows the constructional version of the bath device;

Figures 9a and 9b show two schematic diagrams of steam recovery possibilities in both modes of operation.

In the pictures above, the number 1 indicates a piece of leather that is being tanned according to the proposed procedure. In accordance with this process, a piece of leather for tanning 1 is spread on a suitable open support, i.e. the frame 2 shown in Figure 1.

The piece of skin 1 is fixed in the frame 2 by means of a series of expanders of a known type. The frames 2, which carry the spread pieces of leather 1, are placed and fixed in accordance with the proposed design in a tightly closed bath 4, into which a suitable solution for treating the leather is introduced.

The frames 2 carrying the spread pieces of skin l are introduced into the bath 4 preferably in a vertical position, properly spaced, as shown in figure 2a.

The frames 2 can be arranged in the container 2 also horizontally (figure 2b) or inclined (figure 2c). In case the pieces of leather are arranged vertically, it is sufficient to hang them on a suitable basket, not shown, so that they are kept apart from each other. As the example in Figure 3 shows, the upper part of the bath 4, in which the treatment solution 5 is located, is tightly closed with the cover 6.

In its lower part, the bath 6 has a holder 7 that holds the frames 2 that carry the pieces of leather 1. In the bath 4 there is also a heat exchanger 8 that heats the solution 5 to the desired temperature. The solution 5 in the bath 4 is swirled during the processing of the pieces of leather 1 spread on the frames 2. For this purpose, in the bath 4 there is a supply element 9, located under the support 7 of the frame 2, which is shaped like a grid with a series of nozzles 10 for ejecting air bubbles .

Inside the bath 4, above the solution 5, a negative pressure is maintained by means of a suitable suction means 11 connected to the bath by a pipe 110, passing through one of the two neutralization tanks 111a and 111b, which will be described later. The advantage of keeping bath 4 under negative pressure will be explained below.

Even more, due to this negative pressure, the air stream is sucked from the outside via the supply element 9. Furthermore, the negative pressure reduces the amount of energy consumed to reach the desired operating temperature. Otherwise, the aforementioned air current can be obtained with a suitable compressor connected to the supply element.

In the following, the same reference numerals indicate parts of equal functions. The tanning device shown in Figure 4a includes a series of tanks 12, preferably impermeable, which contain solutions to be supplied to the bath 4 for the aforementioned tanning.

In particular, four cisterns 12a, 12b, 12c and 12d are shown here, from which the solutions used for the soaking, calcining, acidifying and tanning stages are supplied, respectively. If necessary, pieces of leather are also dyed during tanning.

The cisterns are equipped with appropriate heat exchangers 13a, 13b, 13c and 13d to maintain liquid solutions at the desired temperatures. The heat exchangers 13a, 13b, 13c and 13d are controlled by the control unit 14 via connections labeled S1, S2, S3 and S4.

The supply tanks are connected to respective pipes 15a, 15b, 15c and 15d and have respective pumps 16a, 16b, 16c and 16d which are controlled in series by the control unit 14 by means of connections labeled P1, P2, P3 and P4.

The ends of the pipes 15a, 15b, 15c and 15d are connected to the inlet pipe 17 of the bath 4 by means of a valve 18 controlled by the control unit 14.

At the bottom of the bath 4 there is an outlet pipe 19, equipped with a pump 20 that is monitored by a control unit 14. The outlet of the pipe 19 is connected alternatively by means of a valve 21 to the exhaust pipes 22a, 22b, 22c and 22d, which are connected to the corresponding waste tanks 23a, 23b, 23c and 23d solutions used in bath 4.

The tanks with waste solutions 23 are connected to the respective supply tanks 12 by means of respective return pipes 24a, 24b, 24c and 24d, which are equipped with associated pumps 25a, 25b, 25c and 25d controlled by the control unit 14.

In an alternative construction, the exhaust pipes 22a, 22b, 22c and 22d all lead to a single manifold (not shown) which is connected to a suitable cleaning agent. In practice, to carry out the aforementioned tanning, the bath 4 is filled with a solution taken from the corresponding supply tank 12.

In accordance with a preferred embodiment, the device also includes at least two more tanks 30a and 30b containing rinsing solutions, which will be described later, which are equipped with respective pipes 31a and 31b, and with associated pumps 32a and 32b controlled by the control unit 14.

These pipes are connected to the inlet pipe 33 of the bath 4 by means of a valve 34 controlled by the control unit 14. The aforementioned outlet pipe 19, which is connected to the bottom of the bath 4, can also be connected with the valve 21 to one or the other discharge pipe, 35a or 35b, so that it flows into cisterns 30a and 30b.

Within the bath 4 the solution is kept in a vortex state by means of an air current produced in the solution as previously described. It should be noted that before performing each individual step, more precisely, before filling the bath with the solution, a negative pressure is created in the bath so that the skin swells, causing it to become spongy and thus facilitating the effect of the solution on the skin.

The aforementioned swirling acts as a kind of massage on pieces of skin, which replaces the mechanical action of known systems without damaging the skin. At the end of each stage of treatment, the used solution is withdrawn from the bath 4 and sent to the corresponding waste tank 23. After the regeneration is completed, according to procedures well known in the art, this solution can be returned again to the corresponding supply tank 12, for a new tanning cycle .

Soaking is carried out with the solution in tank 12a; water with chemical additives can be added. Due to the negative pressure created before the introduction of the solution, the skin absorbs water much more easily, because it is naturally prone to swelling, and thus becomes, as already mentioned, more spongy.

These factors, i.e. the combined effect of negative pressure and vortexing, reduce the time required for the soaking stage. After soaking, the leather pieces are washed with water from the cistern 30a. Calcination is carried out with the solution from tank 12b, according to the oxidation method, for example with sodium chlorite or with enzymatic agents.

It should be noted that sodium chlorite cannot be used in the calcination stage in wooden drums, because chlorine is released which corrodes the wood. As it is extracted with the suction means 11 and released through the pipe 110, the chlorine enters one of the cisterns 111a or 111b, which contains a solution of sodium hyposulphite, which is known to neutralize chlorine. In this way, the suction means 11 were protected and the problem of disposal of substances used for calcination was solved. In the case shown, the combined action of negative pressure, which causes the skin to swell, of sodium chlorite and the massage performed on the skin by swirling air, enable calcination to be carried out.

This is a significant advantage for the following reasons:

- the use of substances whose disposal (more precisely, neutralization) is not very problematic;

- due to negative pressure in the working environment, energy consumption is reduced;

- pieces of leather are not mechanically stressed.

It should also be noted that the swelling of the skin opens the pores, which is useful for subsequent tanning and dyeing.

The calcination stage takes approximately five hours. At the end of the calcination, the skin is washed with the contents of tank 30b.

Calcination is followed by acidification, which is carried out using the contents of cistern 12c; the effect of this treatment is enhanced by massaging the skin, which occurs due to the vortex.

The solution from the cistern 12d is used for the actual tanning stage and, if necessary, for the dyeing process, which is carried out later with dyes (eg vegetable dyes) dispersed in the solution. The solution may also contain agents to facilitate lubrication of the skin. The time required for the full implementation of these procedures is reduced because the pores are kept open due to the influence of negative pressure. Compared to traditional methods, it also requires a smaller amount of substances for tanning and dyeing.

Actually, the described conditions, (i.e. swelling of the skin, which makes it more spongy), the concentration of tanning and coloring agents in the solution, which are transferred from the solution to the skin (where they remain irreversibly fixed) is reduced compared to known systems, which is why the quantity of these funds is smaller, while the obtained quality remains the same. The pickling, tanning and dyeing processes take approximately 24 to 36 hours.

It is known that the actual tanning can be preceded by so-called pre-tanning, and that dyeing (also known as re-tanning), which is carried out simultaneously with means for oiling the leather, can be carried out separately and after the actual tanning.

The device for the implementation of the above-mentioned versions is shown schematically in Figure 4b, where the number 12e indicates the tank in which the liquid products for pre-tanning are located, 23e indicates the tank in which there is waste liquid after the completed pre-tanning, 30d indicates the tank in which the solution is located for washing the skin after finishing the previous tanning, 12f denotes the cistern in which there is a solution for re-tanning the skin and oiling and 23f denotes the cistern in which the waste from bath 4 is collected after the completion of the last stage of treatment.

In general, it is ensured that the procedure, which is the subject of the invention, enables leather tanning to be carried out in a significantly shorter time compared to traditional procedures, guaranteeing at the same time a high quality of the leather.

This result was also supported by the spreading of the skin on the frames 2, by the swirling due to the air current created in the solution 5 with which the treatment is carried out, and by the effect of negative pressure. It should be emphasized that the pieces of leather are not subjected to strong mechanical stresses, but only to a kind of massage created with the mentioned vortex, which achieves obvious quality advantages.

An important feature of this procedure comes from the fact that it is carried out in tightly closed baths. Because of this, miasma diffusion into the environment was avoided, which improves working conditions in the leather tanning area. Even more, the proposed procedure significantly reduces the problems of waste disposal and/or neutralization and enables saving of energy and substances used especially for tanning and dyeing.

It should be emphasized that the procedure described here can also be carried out without rinsing the skin. Figure 5a shows another embodiment of the proposed device in which multiple treatment baths are used for the implementation of the process with the same stages described in the device shown in Figure 4a. Four baths 4a, 4b, 4c and 4d are set up here, arranged in a series, and used for the respective stages of soaking, calcining, acidifying and tanning with simultaneous dyeing and possible greasing.

Tanks with solutions for carrying out those stages and after that washing, are marked with the same numbers as in Figure 4a and have the same valves and pumps that are not shown, because they are of the same type as previously described. In this case, the frames 2, which carry the spread pieces of leather, are mounted, i.e. they are on the support 28, together with the transfer means 29, with which said support 28 is introduced into the bath and taken out of the bath 4a, 4b, 4c and 4d.

This transmission means 29 includes, for example, a transmission 30 which moves by means of a motor, which is not shown, along a guide element 31 integral with the fixed frame 32 of the device. Then, in each bath, a predetermined level of skin treatment is carried out, and it is also possible to rinse the skin. It is useful to rinse the skin in the respective auxiliary baths 114a and 114b (see Figure 6). Specifically, after soaking in the bath 4a, the skin is pulled out of the bath and placed in the auxiliary bath 114a where it is rinsed with the solution taken from the tank 30a.

Calcination is carried out in bath 4b and then rinsed in the corresponding auxiliary bath 114b.

This way of acting, i.e. by rinsing the skin in auxiliary baths, cleaning of baths 4a and 4b after rinsing, which is carried out after soaking and calcining, is avoided.

In the device shown in Fig. 5b, the processing steps already described using Fig. 4b are carried out. In baths 4a, 4b, 4c and 4d, the leather is soaked, calcined, acidified, pre-tanned, tanned and finally dyed with simultaneous oiling. The baths where these degrees are carried out are marked with the same numbers as in Figure 4b. In this case, after soaking, calcining and pre-tanning, rinsing in appropriate auxiliary baths can also be carried out, as in the case shown in Figure 6.

It is obvious that if the treatment of the skin requires a number of operations different from these two examples shown (Figures 4a, 5a and 4b, 5b), the device can be modified accordingly, but the advantages of the invention are retained.

In the embodiments shown in Figures 5a, 5b and 6 the solutions emerging from their respective baths may be sent to a common manifold for discharge.

The performance of the procedure that is given priority has the following technical and functional features:

- bath 4 (or baths) is stationary;

- pieces of skin are spread out and spatially separated;

- treatments are carried out in a tightly closed bath that is already under negative pressure before the solution is introduced into it;

- the swirling of the solution causes a kind of skin massage.

According to a version of the procedure, the bath 4 (or baths 4a, 4b, 4c and 4d) can be rotated around its transverse and/or longitudinal axis, so that there is a relative movement between the piece of leather and the solution used in the treatment step or for the next rinse.

It is useful that the solution from cisterns IIIa and IIIb significantly reduces and/or neutralizes all volatile ingredients that are formed in bath 4 (or bath 4a, 4b, 4c, 4d, 4e, 4f) during leather processing.

For this purpose, several baths can be provided or arranged parallel to each other, and that each of them contains a solution that significantly reduces and/or neutralizes at least one previously determined volatile ingredient.

The control unit 14 can act on a suitable means (e.g. an electric valve) connected to these cisterns, so that one or more cisterns arranged in series are included in the pipe 110, depending on the degree of processing carried out in the bath 4 and therefore also depending on the type of the volatile compound that is formed during that stage of processing.

In the case of multiple baths, the pipe 110, which connects each bath to the suction means 11, is connected to a series of cisterns 111 to carry out the functions described above. Each supply tank can be equipped with devices for mixing the solution contained therein, which are not shown because they are known to those skilled in the art.

Fig. 7 shows another embodiment of the device, wherein the numbers 201, 202, 203 and 204 indicate the supply tanks containing the soaking, calcining, acidifying and tanning solutions. Numerals 212a, 212b, 212c and 212d denote the respective heat exchangers (controlled by the control unit 14 via connections S1, S2, S3 and S4). Numerals 216a, 216b, 216c and 216d indicate respective supply pumps which are also operated by the control unit via connections P1, P2, P3 and P4.

In this case, the nozzles, or the scrapers 9, can be brought into contact with the external (normal) working conditions of the bath 4 through the corresponding electric valve 250 which is switched on by the control unit.

Alternatively, the nozzles 9 can be connected to one or the other series of auxiliary supply tanks 300a, 300b, 300c and 300d (for example, four tanks were provided, however their number may be more or less than four) via respective electric valves 301a , 301b, 301c and 301d, and can also be switched on using the control unit.

Each auxiliary supply tank contains a pure or suitably diluted appropriate substance which is used together with the solutions from the supply tanks 212a, 212b, 212c and 212d during the respective stage of the proposed process.

With this configuration, useful conditions have been determined, so that it is possible to mix these substances with the solution at every observed moment, in a previously determined percentage and/or mass, so that the stages of the procedure are affected in the desired way.

To put this option into practice, the control unit 14 breaks the connection between the bath 4 and the outside environment (using the electric valve 250) and connects the bath 4 to the previously determined auxiliary supply tank, holding that connection for a short time. The condition of negative pressure inside the bath 3 enables the entry of substances from the auxiliary tank into the bath. The flow of the substance may be determined by a pump 270, not shown, and may be measured by a suitable means, also not shown.

The use of the scraper 9 for injecting the substance into the bath allows for quick mixing of the released substances with the solution 5 already in the bath.

Alternatively, these substances can be introduced into the bath at the same time as solution 5 is introduced into it or before the introduction of this solution.

Even more, the substances can be brought into the bath also without the aid of the scraper 9, in some other way known to experts. When at least one substance (or diluted) is brought into the bath 4 in its entirety, the connection between the bath and the auxiliary supply tank is broken and the connection between the bath and the outside environment is re-established. In the example shown in Figure 7, an auxiliary supply tank is attached to bath 4 when the process steps are carried out.

It is useful that the auxiliary supply tanks can be connected to the baths 4a, 4b, 4c and 4d equipped with different configurations according to Figures 5a and 6, as well as to the baths 4a, 4b, 4c, 4d, 4e and 4f shown in Figure 5b, and substances which they contain, and which are used in a way similar to the one just described.

Figure 8 refers to the functional-structural form of the bath 4. In detail, there is shown the pipe 600 with which it connects the bottom area of the bath 4 to the interspace area 601. More precisely, this interspace area is located directly above the free surface 602 of the solution 5 in the bath .

The pump is mounted along the pipe and is switched on by the control unit 4, to withdraw the solution from the bath 4, in the area 601 and reintroduce the solution at the bottom. This encourages constant re-mixing of the liquid, which avoids, among other things, settling of solids.

Everything that has just been said contributes to the result that the liquid substance is extremely homogeneous in all parts. This functional-structural form can be applied to each bath 4a, 4b, 4c and 4d related to the embodiments of figures 5a and 6, as well as to each bath 4a, 4b, 4c, 4d, 4e and 4f included in the embodiment shown in Figure 5b.

In Figures 9a and 9b, the number 500 denotes the steam collection unit. A plurality of collection units is advantageously provided, for example a number at least equal to the number of stages forming the process and carried out in bath 4.

Figures 9a and 9b show only one shrink unit, as the others work exactly the same way. This collection unit includes an electric valve 404 mounted on a pipe 450 connecting the suction means 11 and the interior of the bath. Two pipes 460 and 470, namely the first pipe and the second pipe, go from the pipe 450 and on them are mounted the three-way electric valve 401 and the two-way electric valve 402, respectively.

These tubes closely cross the cover of the condensing boiler 400, under which in the upper part there is an obliquely placed obstacle 480. The open end of the first tube 480 is located below the inclined obstacle, while the open end of the second tube 470 is located above the obstacle. The bottom of the boiler is connected to the bottom of the bath 4 by means of a pipe 490 which has an electric valve 403.

All the electric valves 401, 402, 403 and 404 just mentioned are switched on by the control unit 14.

In the operating conditions shown in Figure 9a, stream H, sucked from bath 4 by means of suction 11, passes through boiler 400. This stream is then formed by mixing air (introduced into bath through ejector 9) and steam created from solution 5. This mixture expands in the boiler, cools and a large part of the steam condenses. The resulting liquid collects at the bottom of the boiler and its level gradually rises.

The sensor 405 detects a certain level and sends a signal to the control unit 14, which determines the operating condition of Figure 9b by turning on the aforementioned electric valve. Under this condition, boiler 400 is bypassed, because valve 404 is turned on, while valve 401 connects the boiler to the outside environment, and the other pipe 470 is cut off by turning off valve 402.

Since the bath 4 is under negative pressure, the liquid stream K goes from the boiler to the bath. A corresponding sensor, not shown, detects the minimum level in the boiler and the control unit changes the operating condition of the unit 500 by establishing the condition shown in Figure 9a.

What has just been said is an extremely useful feature, because in this way a large part of the evaporated liquid can be collected again and is not carried into the suction means 11.

Obstacle 480 forms part of the air-vapor mixture of the inlet area (first pipe 460) and the air suction area (second pipe 470), so that the minimum amount of steam, which in any case goes to the suction unit, is negligible.

With a different solution 5 (for a step of the process different from the previous one), the cover unit 500 in question is further equipped with a distribution pipe 410 that connects all the cover units on one side to the top of the bath, and on the other side to the bottom of the bath via a similar pipe 490a. For each bath 4a, 4b, 4c and 4d (shown in Figures 5a and 6) and 4a, 4b, 4c, 4d, 4e and 4f (shown in Figure 5b), one collection unit 500 similar to that just described can be provided.

In accordance with an interesting version of the proposed procedure, the beneficial results obtained on the skin by the combined action of negative pressure and vortex motion can be further increased and improved by the effect of ultrasound on the solution. This can be carried out with a suitable sonotrode of known type (not shown) connected to the bath and controlled by the control unit 14.

It is understood that the above is an example which does not limit the invention, and therefore possible functional variations of the proposed process steps remain within the scope of the protection of the invention as required in the following claims.

A similar remark applies to the means and devices which form the proposed device, in which measuring devices can be used to measure the velocity of the incoming and outgoing current at all times for each bath or each feed cistern.

Claims (52)

1. A method for processing leather and the like, characterized by the fact that it includes: placing spread and spatially separated pieces of leather for processing (1) in a bath (4); the introduction of solutions into the bath (4), in order and at previously determined intervals, for the implementation of different stages of leather treatment by tanning, whereby the mentioned solutions are emptied from the bath at the end of each stage of treatment; maintaining negative pressure inside the bath at least during each individual processing stage; causing relative movement of the solution relative to the leather pieces during each stage of processing, so as to enhance the effect of the solution on the leather pieces. 2. A process for processing leather and the like, characterized by the fact that it includes: placing spread and spatially separated pieces of leather for processing (1) in the first bath (4a); introduction of the solution into the bath (4a) for carrying out the stage of leather treatment by tanning; maintenance of negative pressure inside the bath during the implementation of the aforementioned stage of processing; causing relative movement of the solution relative to the leather pieces during each processing step, so as to enhance the effect of the solution on the leather pieces; emptying the solution from the first bath; pulling out a piece of skin from the first bath; repeating the described procedures in the following baths for the implementation of the remaining stages of leather treatment by tanning. 3. The method according to claim 1, indicated by the fact that the negative pressure inside the bath is created before the solution for the appropriate level of skin treatment is introduced into it. 4. The method according to claim 2, indicated by the fact that a negative pressure is created inside each of the mentioned baths in which the stage of skin treatment is carried out, before the corresponding solution is introduced into it. 5. The method according to claims 1 to 3, characterized in that it includes: the introduction of the first solution for soaking the skin in the bath (4); swirling of the solution during soaking; emptying the solution from the bath; introduction of another solution for calcining the skin in the bath (4); swirling of the solution during calcination; emptying the solution from the bath; introducing a third solution for acidifying the skin in the bath (4); swirling of the solution during calcination; emptying the solution from the bath; introduction of a fourth solution for simultaneous tanning and dyeing of leather in the bath (4); swirling of the solution during tanning and dyeing; emptying the solution from the bath; finally, pulling the scattered pieces of skin out of the bath. 6. The method according to claim 5, characterized by the fact that simultaneously with the introduction of at least one solution into the first bath, between the first, second, third and fourth solutions, a pure or diluted substance is also introduced, which acts together with the solution in question to carry out the appropriate stage the same procedure. 7. The method according to claim 2 or 4, characterized in that it includes: introducing the first solution for soaking the skin into the first bath (4a); swirling of the solution during soaking; emptying the solution from the first bath; extracting a piece of skin from the first bath (4a); bringing scattered, spatially separated pieces of skin into another, tightly closed bath (4b); introduction of another solution for calcination of the skin in another bath (4b); maintaining negative pressure in the second bath during calcination; swirling of the solution during calcination; emptying the solution from the second bath; extracting a piece of skin from the second bath (4b); bringing scattered, spatially separated pieces of skin into a tightly closed third bath (4c); introduction of the third solution for acidifying the skin in the third bath (4c); maintaining negative pressure in the third bath during acidification; vortexing of the solution during acidification; emptying the solution from the third bath; extracting a piece of skin from the third bath (4c); bringing scattered, spatially separated, pieces of skin into the tightly closed fourth bath (4d); introduction of the third solution for simultaneous tanning and coloring of the leather in the fourth bath (4d); maintaining negative pressure in the fourth bath during tanning and dyeing; swirling of the solution during tanning and dyeing; emptying the solution from the fourth bath; 1. pulling out a piece of skin from the bath. 8. The method according to claim 7, characterized by the fact that simultaneously with the introduction of the solution in question into at least one of the first, second, third and fourth baths, at least one pure or diluted substance is also introduced, which acts together with the solution in question to carry out the corresponding stage of the same procedure. 9. The method according to claim 1 or 3, characterized in that it includes: introducing the first solution for soaking the skin into the first bath (4); swirling of the solution during soaking; emptying the solution from the first bath; introduction of another solution for calcination of the skin in said bath; swirling of the solution during calcination; emptying the solution from the bath; the introduction of a third solution for acidifying the skin in the mentioned bath; vortexing of the solution during acidification; emptying the solution from the bath; introduction of the fourth solution for pre-tanning the leather into the aforementioned bath (4); swirling the solution during pre-tanning; emptying the solution from the bath; the introduction of the fifth solution for tanning leather into the aforementioned bath (4); swirling of the solution during tanning; emptying the solution from the bath; introducing a sixth solution at least for dyeing the skin into said bath (4); swirling the sixth solution during staining; emptying the solution from the bath; finally, pulling the piece of skin out of the bath. 10. The procedure according to claim 8, characterized in that 2. simultaneously with the introduction of at least one solution into the first bath, between the first, second, third, fourth, fifth and sixth solutions, also introduces at least one pure or diluted substance, which acts together with the solution in question to carry out the corresponding stage of the same process. 11. The method according to claim 2 or 4, characterized in that it includes: introducing the first solution for soaking the skin into the first bath (4a); swirling the first solution during soaking; discharge of the first solution from the first bath; extracting a piece of skin from the first bath (4a); bringing scattered, spatially separated pieces of skin into another, tightly closed bath (4b); introduction of another solution for calcination of the skin in another bath (4b); maintaining negative pressure in the second bath during calcination; swirling the second solution during calcination; emptying the second solution from the second bath; extracting a piece of skin from the second bath (4b); bringing scattered, spatially separated pieces of skin into the third, tightly closed bath (4c); introduction of the third solution for acidifying the skin in the third bath (4c); maintaining negative pressure in the third bath during acidification; vortexing of the third solution during acidification; emptying that solution from the third bath; extracting a piece of skin from the third bath (4c); bringing scattered, spatially separated pieces of skin into the fourth, tightly closed bath (4d); introduction of the fourth solution for pre-tanning the leather into the fourth bath (4d); maintaining negative pressure in the fourth bath during the previous tanning; swirling the fourth solution during pre-tanning; discharging the fourth solution from the fourth bath; extracting a piece of skin from the fourth bath (4d); bringing the aforementioned scattered, spatially separated pieces of skin into the fifth, tightly closed bath (4e); introducing the fifth solution into the fifth bath (4e) for leather tanning; maintaining negative pressure in the fifth bath during tanning; swirling of the fifth solution during tanning; emptying the fifth solution from the fifth bath; extracting a piece of skin from the heel of the bath (4e); bringing scattered, spatially separated pieces of skin into the sixth, tightly closed bath (4f); introducing the sixth solution for dyeing the leather into the sixth bath (4f) for dyeing the leather; maintaining negative pressure in the sixth bath during dyeing; swirling the sixth solution during staining; discharging said sixth solution from the sixth bath; pulling out a piece of skin from the bath. 12. The method according to claim 8, characterized in that simultaneously with the introduction of the solution in question into at least one of the first, second, third, fourth, fifth and sixth baths, at least one pure or diluted substance is also introduced, which acts together with the solution in question for implementation of the corresponding stage of the same procedure. 13. The procedure according to claim 5 or 9, characterized by the fact that after the calcination is finished and before the acidification, an interphase washing of the skin is performed. 14. The procedure according to claim 5 or 9, characterized by the fact that after soaking and before calcination, interphase rinsing of the skin is performed. 15. The method according to claim 9, indicated by the fact that after the completion of the previous tanning and before tanning, an interphase washing of the skin is performed. 16. The method according to claim 7 or 11, characterized by the fact that after the soaking is finished, the skin is rinsed interphase in the mentioned first bath (4a). 17. The method according to claim 7 or 11, characterized by the fact that after the calcination is finished, the interphase skin is rinsed in the mentioned second bath (4b). 18. The method according to claim 7, characterized in that after finishing the previous tanning, the skin is washed. 19. The method according to claim 1 or 2, characterized in that the relative movement of the solution in relation to the pieces of skin is achieved by keeping the bath stationary and expelling a current of air into said solution. 20. The method according to claim 1 or 2, characterized in that the relative movement of the solution in relation to the pieces of skin is achieved by keeping the bath stationary and connecting its lower part to the outer side, which thus creates an air current that passes through the mentioned solution. 21. The method according to claim 1 or 2, characterized in that the relative movement of the solution in relation to the pieces of skin is achieved by permanently extracting said solution at a level near its upper surface 602 from said bath 4 and reintroducing it at the bottom of the bath. 22. The method according to claim 1 or 2, characterized in that the pieces of skin are spread on a suitable open surface. 23. The method according to claim 22, characterized in that the pieces of skin are arranged vertically. 24. The method according to claim 22, characterized in that the pieces of skin are arranged horizontally. 25. The method according to claim 22, characterized in that the pieces of skin are arranged at an angle to the vertical plane. 26. The method according to claim 7 or 11, characterized by the fact that after soaking, the pieces of leather are taken out of the bath in which the soaking was carried out and introduced into the auxiliary bath 114a for rinsing. 27. The method according to claim 7 or 11, characterized by the fact that after the calcination is finished, the pieces of leather are taken out of the bath in which the soaking was carried out and brought into the auxiliary bath 114b for rinsing. 28. The method according to claim 11, characterized by the fact that after the completion of the previous tanning, the pieces of leather are taken out of the bath in which the soaking was carried out and introduced into the auxiliary bath for rinsing. 29. The method according to claim 1 or 3 or 5 or 9, characterized in that during each stage of processing, the liquid in question for the implementation of each of these stages is treated with ultrasound. 30. The method according to claim 2 or 4 or 7 or 11, characterized in that during each stage of processing, the liquid in question for the implementation of each of these stages is treated with ultrasound. 31. Device for processing leather and the like, characterized in that it includes: tightly closed bath (4); several bases (2), which can be brought in and out of the said bath, on which the spread pieces of leather (1) are fixed, and these bases (2) are placed in the said bath so that the pieces of leather are kept apart; the first series of tanks (12) containing previously determined solutions for the corresponding degrees of skin treatment; on/off control means (14, 16, 18) connecting each of said cisterns to a bath for introducing a solution corresponding to the respective stage of skin treatment; a suction means (11) for maintaining a negative pressure inside said bath at least during the implementation of the skin treatment step; means to move the solution relative to the skin pieces, so that the effect of the solution on the skin is enhanced. 32. Device according to claim 31, characterized in that it includes a second series of tanks (23) connected to the bath by means of an on/off control means (14, 21, 25) so that the liquid can be emptied from the bath after completion of the corresponding processing stage. 33. Device according to claim 31, characterized in that it includes a series of auxiliary tanks (300a, 300b, 300c, 300d) connected to the bath by means of control means for on/off and control means for introducing substances, pure or diluted, into said bath, which the substance works in combination with a suitable liquid to carry out at least one stage of the skin treatment process. 34. Device for carrying out leather processing and the like, characterized by the fact that it includes: several tightly closed baths (4a, 4b, 4c, 4d) in which a previously determined level of leather processing is carried out; a plurality of bases (2) which can be brought in and out of said baths and on which suitably spread pieces of leather (1) are fixed, and these bases (2) are placed in the bath so that the pieces of leather are kept apart; the first series of tanks (12) containing previously determined solutions for the corresponding degrees of skin treatment; on/off control means connecting each of said cisterns to a respective bath for introducing the respective solution corresponding to the skin treatment stage; suction means (11) for maintaining negative pressure within each of said baths at least during the implementation of the respective stage of skin treatment; 3. a means for causing relative movement of the appropriate solution within said baths in relation to the pieces of skin, so that the action of said solution on the skin is enhanced. 35. Device according to claim 26, characterized in that the second row of tanks is connected to the corresponding bath by means of an on/off control means, so that the solution is discharged from the said bath after the completion of the appropriate stage of skin treatment. 36. Device according to claim 34, characterized in that for each bath (4a, 4b, 4c, 4d) it has a corresponding auxiliary supply tank (300a, 300b, 300c, 300d), connected to the corresponding bath by means of a switch and a control means, for introducing at least one substance, pure or diluted, into the bath in question, to carry out the appropriate stage of the skin treatment process, together with the solution introduced into the bath. 37. Device according to claim 31, characterized in that said bath (4) is stationary, and that the means for causing relative movement of the solution in relation to the pieces of skin includes ejectors (10) that send a stream of air through the solution in the bath. 38. Device according to claim 34, characterized in that each of said baths is stationary, and that the means for causing relative movement of the solution in relation to the pieces of skin includes ejectors (10) that send a stream of air through the solution. 39. Device according to claim 31, characterized in that at least one cistern (IIIa, IIIb) for significant reduction and/or neutralization of volatile compounds formed during leather processing is located along the pipe (110) that connects the mentioned suction means (11) with baths (4). 40. Device according to claim 34, characterized in that at least one cistern (IIIa, IIIb) for significant reduction and/or neutralization of volatile compounds formed during leather processing is located along the pipe (110) that connects the mentioned suction means (11) with the mentioned bath has. 41. Device according to claim 31, characterized in that it includes further tanks (30) which are connected to the said bath by means of a switch and a control means for introducing and then emptying the appropriate solutions from the bath for rinsing the skin after the completion of the appropriate stage of skin treatment. 42. The device according to claim 34, characterized in that it includes further tanks (30), each of which can be connected to a corresponding bath by means of a switch and a control means, so that a suitable rinsing solution can be introduced into the relevant bath and then emptied from it leather upon completion of the appropriate level of leather processing. 43. Device according to claim 34, characterized in that it includes auxiliary baths (114), each of which can be connected by means of a switch and a control means to a corresponding tank containing a predetermined solution for introduction and then for emptying from said auxiliary bath, which serves for rinsing pieces of leather brought into the bath after finishing the stage of processing in the appropriate bath. 44. The device according to claim 31, characterized in that it includes a tube (600) that connects the bottom area of the mentioned bath (4) with the area of the intermediate space (601) of the same bath, which is located exactly below the free surface (602) of the solution (5) inside the bath , which tube has an associated pump (603) for permanently transferring said solution from the interstitial area (601) to said bath bottom area. 45. The device according to claim 34, characterized in that for each bath (4a, 4b, 4c, 4d) it has a tube (600) that connects the area of the bottom of said bath (4) with the area of the intermediate space (601) of the same bath located directly below of the free surface (602) of the solution (5) inside the bath, which tube has a pump (603) for permanently transferring the solution from the area of the intermediate space (601) to the area of the bottom of the bath. 46. The device according to claim 31 or 34, characterized in that for each bath (4, 4a, 4b, 4c, 4d) it has at least one unit (500) for collecting steam, which includes: tightly closed boiler (400) for condensation; a first switch (401, 404, 402) that operates by means of a control unit (14) for connecting said boiler in series with a pipe (450) that connects said bath and said suction means (11); a sensor (405) for detecting the liquid level in the boiler, which works together with the control unit (14) including the first switch and the second switch (403), so that the boiler is disconnected from the pipe path (450), and connects the interior of the boiler with the external environment, and connects the boiler to the bath, so that the stream of condensed liquid can be transferred from the boiler to the bath. 47. Device according to claim 46, characterized by the fact that there is an inclined obstacle (480) in the boiler, whereby the open end of the first pipe (460) is located below this obstacle for introducing a flow (H) of a mixture of air and steam from the bath into the boiler , and the open end of the second tube (470) is connected to the suction means (11). 48. Device according to claim 37 or 38, characterized in that the pieces of skin are arranged vertically. 49. Device according to claim 37 or 38, characterized in that the pieces of skin are arranged horizontally. 50. Device according to claim 37 or 38, characterized in that the pieces of skin are arranged obliquely in any way. 51. Device according to claim 31 or 37 or 30 or 32, characterized in that it includes sonotrodes connected to the bath (4) for treating each solution with ultrasound. 52. Device according to claim 34 or 38 or 40, characterized in that it includes sonotrodes, one of which is connected to each bath for treating each solution with ultrasound.