AU727046B2 - Process and apparatus for treating leather and the like - Google Patents

Description

A WO 97/42350 PCT/IB97/00432 -1- PROCESS AND APPARATUS FOR TREATING LEATHER AND THE LIKE TECHNICAL FIELD The present invention concerns tannage of leather and the like.

BACKGROUND ART It is known that animal skin is tanned, so as not to putrefy, with solutions that remain irreversibly fixed thereon, turning it into hide.

This treatment includes different steps, which are often complex and requiring relatively much time.

When delivered to tannery, generally dried with salts, rawhide is initially subjected to preparation for real tanning.

This preparation includes first a soaking step, i.e. removing impurities that cover both inner flesh side and outer or grain side, as well as preserving solutions, so as to bring the leather back to its natural softness.

The leather to be treated is soaked in drums containing suitable liquid solutions.

These drums are provided inside with immovable paddles or stakes, which act on the leather during drum rotation.

Therefore, the treatment consists of combined chemical action of the liquid solution and the mechanical action performed on the leather and lasts six to twenty four hours.

Afterwards, a fleshing step follows, with which the fat is removed from the soaked leather, and subsequently liming treatment follows for removing hair and reveal the derma.

Liming is performed in suitable drums with alkaline substances, such as sulphides or lime, which make the leather tissue swell and dissolve the hair roots.

More precisely, the leather swells up, the fats turn into calcium salts and proteins forming the leather are modified due to breaking of principal and secondary links of the proteic chains and, subsequently, the hair detaches from the leather.

The substances used for liming, and at the same time for "opening" the WO 97/42350 PCT/IB97/00432 -2leather pores in order to execute real tanning and dyeing, are highly polluting, which results in all known problems of waste disposal and/or purification.

Liming step requires usually twenty four hours.

Then, thus prepared leather is decalcined and bated, again in suitable drums.

Due to decalcination step, usually with decalcinating salts, the retained lime is removed.

Bating is a biological action which softens leather grain by enzymes which partly dissolve elastic fibres, causing the leather relaxation.

Subsequently, the leather is subjected to pickling, i.e. treatment, which guarantees more rapid and complete penetration of the tanning salts.

In fact, bated leather, having basic reaction, cannot be tanned with e.g.

tanning salts of chromium, because it would result in a chemical reaction, which would close the leather pores.

Therefore, the leather is acidified with small quantities of acid, with the presence of salts (usually sodium chloride) so as to prevent swelling. This step is performed in a drum and lasts an average of ten twelve hours.

The real tanning treatment is carried out inside the aforementioned drums, by means of vegetable solutions, such as natural or synthetic tanning solutions, or by mineral salts, mainly chromium or the like salts.

The liming, bating, pickling and tanning steps altogether require an average of not less than forty eight hours (it can vary according to the type of the leather to be treated).

The tanned leather, suitably pressed to remove a part of absorbed water, selected and skived, is subjected to dyeing treatment, otherwise called retanning.

This dyeing step requires an average of eight hours.

Thus, the above mentioned tanning treatments require, as has been already said, much time, which can take an average of one week.

This results in the necessity for using a relatively big number of huge drums in order to achieve an adequate productivity. The pieces of leather to be treated are thrown into the drums in bulk and are subjected directly to a mechanical action, which sometimes can damage them.

A not minor disadvantage of traditional tanning processes derives from the fact that the working environment is very harmful, due mainly to miasma WO 97/42350 PCT/IB97/00432 -3produced by the aforementioned drums.

Moreover, there is a serious problem of disposal of liquids discharged at the end of the above mentioned treatments, in particular of the substances used for liming.

SUMMARY OF THE INVENTION An intention of an embodiment of the present invention is to propose a process, that allows tanning treatments of leather and the like to be carried out in less time with respect to the known systems, and that, at the same time, guarantees the high quality of tanned leather as well as high throughput, the whole being obtained with reduced quantity of required energy, with respect to known techniques.

Another intention of an embodiment of the present invention is to propose a process that can be carried out by an apparatus, which allows to operate in a non-harmful working environment, and which considerably reduces the problems connected with waste disposal.

Yet a further intention of an embodiment of the present invention is to propose a process, which allows to reduce markedly a quantity of used substances with the So-° same quality of tanned leather.

l l Still another intention of an embodiment of the invention is to propose a process, S°whose carrying out does not pollute the air.

a Moreover, an embodiment of the invention has another object of proposing an eapparatus, which carries out the aforementioned method.

25 According to one aspect of the invention there is provided a process of treatment of leather and the like, which includes: disposing spread pieces of leather to be treated, spaced apart, into a container; introducing liquid solutions into said container, in sequence and with S* predetermined intervals, for performing various steps of leather tanning treatment, said liquid solutions being discharged from the container, after each step has been completed; maintaining depression inside said container, at least for the duration of each single step; generating, during each step, a relative movement between the liquid solution WO 97/42350 PCTIB97/00432 -4and said pieces of leather, so as to intensify the action of said liquid solution on said pieces of leather.

According to another aspect of the invention there is provided for carrying out treatment of leather and the like which includes: a container to be closed tight; a plurality of supports, which can be introduced and withdrawn from said container, and on which the corresponding spread pieces of leather are fastened, these supports being situated in said container in such a way as to keep said pieces of leather spaced out; a first series of tanks containing predetermined liquid solutions for corresponding leather treatment steps; on/off and control means which connect each of said tanks to the container so as to introduce therein the relative liquid solution for corresponding leather treatment step; suction means for maintaining depression inside said container at least while performing the leather treatment steps; means for generating relative movement between a liquid solution and said pieces of leather so as to intensify the action of said liquid solution thereon.

According to yet another aspect of the invention there is provided a process of treatment of leather and the like, the process includes: S* 20 disposing spread pieces of leather to be treated, spaced apart, into a first container; introducing liquid solution into said container for performing a step of leather tanning treatment; maintaining depression inside said container during performing of said step; generating, during said step, relative movement between the liquid solution and said pieces of leather, so as to strengthen the action of said liquid solution on said pieces of leather; discharging said liquid solution from said first container; withdrawing said pieces of leather from the first container;

S

repeating the above mentioned operations in fucther containers so as to perform remaining steps of the leather tanning treatment.

According to a further aspect of the invention there is provided an apparatus for carrying out treatment of leather and the like, the apparatus includes: a plurality of containers to be closed tight, inside which predetermined leather Streatment steps are carried out; WO 97/42350 PCT/IB97/00432 a plurality of supports, which can be introduced and withdrawn from said containers, and on which the corresponding spread pieces of leather are fastened, these supports being situated in said containers in such a way as to keep spaced out said pieces of leather; a first series of tanks containing predetermined liquid solutions for corresponding leather treatment steps; on/off and control means, which connect each of said tanks to the relative container so as to introduce therein the relative liquid solution for a corresponding leather treatment step; suction means for maintaining depression inside each of said containers at least during performing therein of the relative leather treatment steps; means for generating, inside each of said containers, relative movement between a corresponding liquid solution and said pieces of leather so as to intensify the action of said liquid solution thereon.

Further characteristics and features are pointed out in the sub-claims.

BRIEF DESCRIPTION OF THE DRAWINGS 9..

o In order to achieve a better understanding of the nature of the invention an embodiment of a process and an apparatus for treating leather and the like will oo* 20 now be described with particular reference to the enclosed drawings, in which: 1 fig. 1 shows a plan view of supporting means for a piece of leather to be treated; 9l figs. 2a, 2b and 2c show schematic views of containers into which the above mentioned support means are disposed, with different arrangements, 25 respectively; fig. 3 shows a schematic vertical section view of said container, during one step of the leather treatment; .figs. 4a and 4b, show diagrams of apparatuses for carrying out corresponding tanning treatments according to the method, being the subject 30 of an embodiment of the present invention; figs. 5a, 5b show diagrams of two different embodiments of the above mentioned apparatus, which carry the method in a different way; fig. 6 shows a possible diagram of an apparatus, which carries the method in a further way; WO 97/42350 PCT/IB97/00432 -6- Fig. 7 shows a further embodiment of the apparatus; Fig. 8, shows a constructive variation of the apparatus container; Figures 9a and 9b show two schematic diagrams of a facility for vapour recovey in both operation conditions.

BEST MODES OF CARRYING OUT THE INVENTION With reference to the above mentioned figures, numeral 1 indicates a piece of leather to be subjected to tanning treatment according to the subject process.

According to this process, the piece of leather to be treated 1 is spread on a respective open support, e.g. frame 2 shown in fig. 1.

The piece of leather 1 is fastened to the frame 2 by a series of expanders 3 of known type.

The frames 2 supporting the spread pieces of leather 1 are introduced into a container 4, kept fixed according to preferred embodiment, which is to be closed tight, for the treatment with a suitable liquid solution introduced therein.

The frames 2 supporting the spread pieces of leather 1 are introduced into the container 4 preferably in vertical arrangement, regularly spaced apart, as seen in figure 2a.

Nevertheless, it is possible to arrange the frames 2 inside the container 4 horizontally (fig. 2b) or inclined (fig. 2c).

In case the pieces of leather are to be arranged vertically, it is sufficient to hang them on a suitable creel, not shown, so as to maintain them mutually spaced apart.

As shown as an example in fig. 3, the upper part of the container 4, which contains the treating liquid solution 5, is closed tight by a cover 6.

In its lower part, the container 4 has holder means 7 for the frames 2 supporting the pieces of leather 1.

Inside the container 4, there is also situated a heat exchanger 8, that heats the liquid solution 5 to the desired temperature. The liquid solution 5 inside the container 4, is swirled during the treatment of the leather pieces 1 spread on the frames 2.

For this purpose, the container 4 features a deliver element 9, situated below the holder means 7 for the frames 2 and formed by a grate provided with a WO 97/42350 PCT/IB97/00432 -7series of ejectors 10, which eject air in form of bubbles.

Inside the container 4, over the liquid solution 5, depression is maintained by suitable suction means 11 connected with the container by a pipe 110, passing through one of two neutralisation tanks 111a, 111b, which will be described later. The advantage of keeping the container 4 in depression will be pointed out in the following.

Moreover, due to this depression, a flow of air is sucked from outside via the deliver element 9. Further, the depression reduces the quantity of energy consumed for reaching the desired working temperature. Otherwise, the aforementioned flow of air can be obtained by suitable compression means, connected to the deliver element 9.

In the following, the same reference numbers will indicate means carrying out the same functions.

The apparatus for tanning treatments, shown in fig. 4a, includes a series of tanks 12, preferably tight, containing liquid solutions to be supplied to the container 4 for the aforementioned treatments.

In particular, there are four tanks 12a, 12b, 12c, 12d supplying liquid solutions used correspondingly for the soaking, liming, pickling and tanning steps.

When needed, during the tanning treatment the leather pieces are also dyed.

The tanks are provided with respective heat exchangers 13a, 13b, 13c, 13d which maintain the liquid solutions at desired temperatures. The heat exchangers 13a, 13b, 13c, 13d are controlled by a control unit 14 by connections indicated with S1, S2, 53 and 54.

The supply tanks are connected with respective jet pipes 15a, 15b, 15c and 15d, equipped with related pumps 16a, 16b, 16c and 16d, controlled, in their turn, by the control unit 14 through connections indicated with P1, P2, P3 and P4.

The jet pipes 15a, 15b, 15c and 15d are connected to an inlet pipe 17 of the container 4 by a valve means 18 which is controlled by the control unit 14.

The bottom of the container 4 features an outlet pipe 19, provided with a pump 20, controlled by the control unit 14.

The outlet pipe 19 is connected alternatively, by a valve means 21, with discharge pipes 22a, 22b, 22c and 22d, communicating with respective waste tanks 23a, 23b, 23c and 23d of the liquid solutions used in the container 4.

The waste tanks 23 communicate with corresponding supply tanks 12 by WO 97/42350 PCT/IB97/00432 -8means of respective return pipes 24a, 24b, 24c, 24d, equipped with respective pumps 25a, 25b, 25c, 25d, controlled by the control unit 14.

As an alternative constructive form, the discharge pipes 22a, 22b, 22c and 22d lead all to a unique manifold (which has not been shown) which is connected to a suitable cleaner.

In practice, in order to perform each of the aforementioned tanning treatment steps, the container 4 is fed with the liquid solution taken from the relative supply tank 12.

According to a preferred embodiment, the apparatus includes also at least other two tanks 30a, 30b, containing washing liquid solutions, which will be described later, and provided with relative jet pipes 31, 31b, featuring relative pumps 32a, 32b controlled by the control unit 14.

These pipes are connected to an inlet duct 33 of the container 4 by a valve means 34 controlled by the control unit 14.

The aforementioned outlet pipe 19, connected to the bottom of the container 4, can be also connected, by the valve means 21, to one or the other of discharge pipes 35a, 35b, flowing into the tanks 30a, 30b, respectively.

Inside the container 4, the liquid solution is swirled by the air flow produced, as has been previously described, in the liquid solution.

It is to be pointed out that before each single step is carried out, more precisely, before the container is fed with liquid solution, depression is created therein so as to swell the leather making it spongy and thus facilitating the action of liquid solution thereon.

The above mentioned swirling causes a kind of massage on the leather pieces, that replaces the mechanical action of known systems without damaging the leather.

When each of said treatment steps is completed, the used liquid solution is withdrawn from the container 4 and sent to the relative waste tank 23. After having been regenerated, by means of techniques which are well known by those skilled in the art, this liquid solution can be let again into the corresponding supply tank 12, for a new tanning cycle.

The soaking treatment is carried out with the liquid solution contained in the tank 12a; water, possibly added with chemical promoters.

Due to depression, created before the liquid solution has been introduced, the leather absorbs water more easily, since it tends to swell naturally, thus WO 97/42350 PCT/IB97/00432 -9becoming, as it has already been said, more spongy.

These factors, i.e. combined action of depression and swirling, reduce the time required for the soaking step.

When the soaking has been finished, the leather pieces are washed with water contained in the tank The liming treatment is performed with the liquid solution contained in the tank 12b, according to oxidising method, e.g. by sodium chlorite or enzyme agents.

It is to be pointed out that sodium chlorite cannot be used in the liming step carried out in wooden drums, because it frees chlorine, which corrodes the wood.

Since pulled by the suction means 11 and freed through the pipe 110, chlorine enters one of the tanks 111a, 111 b, which contains a solution of sodium hyposulphite, that, as it is known, neutralises chlorine. In this way, the suction means 11 are protected and the problem of disposal of substances used for liming treatment, is resolved.

In the present case, the combined effect of depression, which swells the leather, of sodium chlorite and of massage performed on the leather by the swirled air, allows to carry out the liming treatment.

This is considerably advantageous for the following reasons: use of a substance, whose disposal (more precisely, neutralisation) is not very troublesome; due to depression in working environment, the consume of energy is reduced; the pieces of leather are not mechanically stressed.

It is also to be pointed out that the leather swelling makes also the pores open, which is advantageous for subsequent tanning and dyeing treatments.

The liming step requires about five hours. After having been limed, the leather is washed with the contents of the tank The liming step is followed by pickling step, which is carried out using the contents of the tank 12c; the effect of this operation is intensified by the massage of the leather performed by the swirling.

The liquid solution contained in the tank 12d is used for the real tanning step and, when needed, for the dyeing step, the latter being performed by colouring agents vegetable colouring agents)dispersed in the liquid WO 97/42350 PCT/M97/00432 solution.

This liquid solution can also contain agents facilitating leather greasing. The time required for accomplishment of these steps is reduced because the pores remain open due to the depression effect. Also the quantity of tanning and dyeing substances is lower with respect to traditional methods.

In fact, in the described conditions, leather swollen, thus more spongy), the concentration in the liquid solution of the tanning and dyeing agents, which are transferred from the liquid solution to the leather (where they remain irreversibly fixed), is reduced with respect to known systems, therefore the quantity of these agents is smaller, but the quality of the obtained result remains the same. The pickling, tanning and dyeing operations require about 24 36 hours.

It is known that the real tanning treatment can be preceded by the so-called pre-tanning and that dyeing (known also as re-tanning), carried out simultaneously with the agents for leather greasing, can be performed separately from and after the real tanning treatment.

The apparatus that carries out the above mentioned variants, is schematically shown in fig. 4b, where the numeral 12e indicates the tank containing the liquid pre-tanning products, 23e indicates the tank containing the waste liquid after the pre-tanning has been completed, 30d indicates the tank containing the solution for washing the leather after the pre-tanning has been completed, 12f indicates the tank with liquid solution for leather re-tanning and greasing and 23f indicates the tank, which receives waste from the container 4 after the last step has been completed.

Generally, it has been proved that the process, being the subject of the present invention, allows to carry out leather tanning in considerably reduced amount of time, with respect to the traditional techniques, guaranteeing at the same time a high quality of the tanned leather.

This result is helped also by spreading of leather on the frames 2, swirling movement due to the air flow produced in the liquid solution 5, with which the treatment is being carried out, and the depression effect.

In particular, it is to be pointed out that the leather pieces are not subject to violent mechanical stresses, but only to a kind of massage produced by said swirling movement, which results in obvious quality advantage.

An important feature of the subject process derives from the fact that it is carried out in closed tight containers. Thus, the diffusion of miasma into the WO 97/42350 PCTIB97/00432 -11environment is avoided, improving the working conditions in the field of the leather tanning treatment.

Moreover, the proposed process considerably reduces the problem of the waste disposal and/or neutralisation and allows to save both energy and substances used particularly for tanning and dyeing.

It must be stressed that the process herein described can be carried out also without leather washing.

Fig. 5a shows another embodiment of the subject apparatus, in which more treatment containers are used for carrying out a process with the same steps as described for the apparatus of the fig. 4a. There are provided four containers 4a, 4b, 4c, 4d, arranged in a row and used respectively for the steps of soaking, liming, pickling and tanning with simultaneous dyeing and possibly greasing.

The tanks with solutions for carrying out these steps and subsequent washings, are indicated with the same numerals as in fig. 4a and are provided with valve means and pumps, not shown, since of the same type as described previously.

In this case, the frames 2, supporting the spread pieces of leather, are mounted, e.g. on a carrier 28, integral with conveying means 29, which introduce and withdraw said carrier 28 into and from the containers 4a, 4b, 4c, 4d.

These conveying means 29 include e.g. a carriage 30, that is moved, by not shown motor means, along a guide element 31 integral with a fixed frame 32 of the apparatus.

Consequently, in each container there is carried out a predetermined step of the leather treatment and a possible washing of said leather.

Advantageously, the leather is washed in corresponding auxiliary containers 114a, 114b (see fig. 6).

More precisely, after being soaked in the container 4a, the leather is withdrawn therefrom and introduced into the auxiliary container 114a, in which it is washed with a liquid solution taken from the tank The liming step is carried out in the container 4b and the subsequent washing in the relative auxiliary container 114b.

This way of proceeding, i.e. washing the leather in auxiliary containers, avoids cleaning the containers 4a, 4b after the washing operations following soaking WO 97/42350 PCT/IB97/00432 -12and liming, respectively.

The apparatus shown in fig. 5b carries out the treatment steps already described with reference to fig. 4b.

In the containers 4a, 4b, 4c, 4d, the leather is soaked, limed, pickled, pretanned, tanned, and lastly, dyed with simultaneous greasing.

The containers, in which these steps are performed, are indicated with the same numerals as in fig. 4b.

Also in this case, washing following the soaking, liming and pre-tanning steps can be carried out in relative auxiliary containers like in the case illustrated in fig. 6.

It is obvious that if the leather treatment requires a number of operations different from the two illustrated examples (figs. 4a, 5a and 4b, 5b), the apparatus will be correspondingly modified, while all the advantages of the invention will be maintained.

Also in the embodiments shown in Figures 5a,5b,6 the liquid solutions exiting from their respective containers may be sent to a common discharge manifold.

The preferred embodiment of the process features the following technicalfunctional aspects: container 4 (or containers) kept fixed; pieces of leather spread and spaced apart; treatments carried out in a container, which is closed tight and kept in depression already before the liquid solution has been introduced therein; swirling of the liquid solution, that causes a kind of massage of the leather.

According to a variation of the process, the container 4 (or containers 4a, 4b, 4c, 4d) can rotate about their transversal and/or longitudinal axis, so as to create a relative movement between the pieces of leather and the liquid solution used in a treatment step or subsequent washing.

Advantageously, the liquid solution contained in the tanks l11 la, 111 b reduces dramatically and /or neutralises all the volatile compounds, which are generated inside the container 4 (or containers 4a, 4b, 4c, 4d, 4e, 4f) during the leather treatment.

On this purpose, more containers 111 can be provided, arranged parallel one to another, and each of them containing a liquid solution for reducing WO 97/42350 PCT/IB97/00432 13dramatically and/or neutralising at least one predetermined volatile compound.

It is possible for the control unit 14 to act on suitable means electric valves) connected with these tanks, so as to introduce one or more of them, arranged in a row, into the pipe 110, in relation to the treatment step being carried out in the container 4 and therefore, to the kind of the volatile compound generated during this step.

In case of more containers, the pipe 110, connecting each of them to suction means 11, is linked with a series of tanks 111 performing the above described functions.

1o Each supply tank can be provided with means for mixing the liquid solution contained therein, means which are not shown since they are in the knowledge of those skilled in the art.

Figure 7 shows another embodiment of the apparatus, in which numerals 201, 202, 203, 204 indicate supply tanks containing the liquid solutions for soaking, liming, pickling and tanning. Numerals 212a, 212b, 212c, 212d indicate corresponding heat exchanger (controlled by the control unit 14 via links S1, 52, 53, 54). Numerals 216a, 216b, 216c, 216d indicate the corresponding supply pumps also operated by the control unit 14, via connections P1, P2, P3 and P4.

In this case, the ejector means, or grating 9 can be set in communication with outside (normal operation condition of the container 4) via a related electric valve 250 operated by the control unit.

As an alternative, the ejector means 9 can be connected to one or another of a series of auxiliary supply tanks 300a, 300b, 300c, 300d (for instance, four tanks have been provided, however, their number can be bigger or smaller than four), via related electric valves 301a, 301b, 301c, 301d also operated by the control unit.

Each auxiliary supply tank contains a suitable substance, either pure or properly diluted, which is to be used together with the liquid solutions of the supply tanks 212a, 212b, 212c, 212d during a corresponding step of the subjected process.

This configuration determines favourable conditions, in that it allows to mix this substance with the liquid solution each time concerned, in the preestablished percentage and/or weight, so as to affect in the desired way the process steps.

In order to put this possible action into practice, the control unit 14 cuts off the WO 97/42350 PCT/IB97/00432 -14connection between the container 4 and the outside environment (by means of the electric valve 250) and sets the container 4 in connection with the predetermined auxiliary supply tank, maintaining this connection for a short time.

Depression condition inside the container 4 allow in-flowing of the substance coming from the auxiliary supply tank, into the container. The substance flow can be determined by a pump 270, which has not been shown, and can be measured by means of a proper meter, also not shown.

By using a grating 9 for injecting the substances into the container, it is possible to mix quickly the substances emitted with the liquid solution already present inside the container.

As an alternative, these substances can be supplied to the container either at the same time when the liquid solution 5 is introduced therein, or before liquid solution introduction.

Moreover, the substances can be supplied to the container also without the help of the grating 9, in accordance with other ways, which will be obvious to those skilled in the art.

When at least one substance (or a dilution of this substance) has been completely let in the container 4, connection between the container and the auxiliary supply tank is cut off and connection between the container and outside environment is restored. In the example shown in Figure 7, the auxiliary supply tanks are associated to the container 4 where process steps are carried out.

Advantageously, the auxiliary supply tanks can be connected to the containers 4a,4b,4c,4d provided by the different configurations of Figures and 6, as well as to containers 4a,4b,4c,4d,4e,4f shown in Figure 5b, and the substances which they contain are used in a way similar to the one just described.

Figure 8 concerns a functional-structural feature of the container 4. In detail, there is shown a duct 600 which sets in communication the bottom region of the container 4 with an intermediate region 601 thereof. More precisely, this intermediate region is situated just under the free surface 602 of the liquid solution 5 inside the container.

A pump is mounted along the duct and operated by the control unit 14, for withdrawing liquid solution from the container 4, at the region 601, and reintroducing the liquid solution at the bottom. This provokes continuous re- WO 97/42350 PCT/IB97/00432 mixing of the liquid substance, thus avoiding, amongst others, settling of solid substances.

All what have just been said, brings to the result that the liquid substance is utmost homogeneous in all parts.

This functional-structural feature can be applied to each container 4a,4b,4c,4d concerned in the embodiments of Figures 5a and 6, as well as to each container 4a,4b,4c,4d,4e,4f included in the embodiments shown in Figure With reference to Figures 9a,9b, numeral 500 indicates a vapour recovery unit.

Advantageously, more recovery units are provided, for instance in number at least equal to the number of steps which form the process carried out inside the container 4.

Figures 9a,9b show only one recovery unit, since the other ones operate exactly in the same way.

This recovery unit includes an electric valve 404 mounted along a duct 450 which connects the suction means 11 and container inside. Two pipes 460,479, namely first pipe and second pipe, derive from the duct 450 and have, mounted along them, a three-way electric valve 401 and a two-way electric valve 402, respectively.

These pipes cross the tight cover of a condensation vessel 400, under which, at its upper part, there is a baffle 480 arranged inclined. The first pipe 460 open end is positioned below the inclined baffle, while the second pipe 470 open end is positioned above the baffle.

The bottom of the vessel is connected to the bottom of the container 4, via a piping 490 which has an electric valve 403.

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

In the operation condition shown in Figure 9a, the flow H sucked from the container 4 by the suction means 11 passes through the vessel 400. This flow is substantially formed by a mix of air (introduced into the container via the ejecting means 9) and vapour formed by the liquid solution 5. This mix expands in the vessel, getting colder, and great part of the vapour condenses.

The liquid thus obtained is collected at the bottom of the vessel and its level gradually increases.

A sensor 405 detects when a certain level has been reached and sends a WO 97/42350 PCT/I97/00432 -16signal to the control unit 14, that determines the operation condition of Figure 9b by operating the above mentioned electric valves.

In this condition, the vessel 400 is by-passed, because the valve 404 is on, while the valve 401 sets the vessel inside in communication with the outside environment and the second pipe 470 is cut off by setting the valve 402 off.

Since the container 4 is under depression, a flow K of liquid passes from the vessel to the container. A proper sensor, that is not shown, detects the level in the vessel being at the minimum and the control unit changes the operating condition of the unit 500 restoring the condition of Figure 9a.

What have just been said is an extremely advantageous feature, because in this way great part of the evaporated liquid can be recovered and is not brought to the suction means 11.

The baffle 480 forms a partition between the air-vapour mix inlet region (first pipe 460) and the air suction region (second pipe 470), so that the minimum amount of vapour which is anyway sent to the suction means is negligible.

With a different liquid solution 5 (for process step different from the previous one), a related recovery unit 500 is further provided with a manifold 410 which sets in communication all the recovery units at one side with the top of the container and at the other side with the bottom of the container, via a related piping 490a. For each container 4a,4b,4c,4d (shown in Figures 5a and 6) and 4a,4b,4c,4d,4e,4f (shown in Figure 5b) one recovery unit 500 like the one just described can be provided.

According to an interesting variation of the proposed process, advantageous results obtained on the leather by combined action of depression and swirling movement can be further increased and improved by subjecting the liquid solution to ultrasounds.

This can be carried out by a suitable sonotrode of known type (not shown) connected to the container and controlled by the control unit 14.

It is understood that what above, has been stated as a pure, non limitative example, therefore possible functional variations of the proposed process steps remain within the protective scope of the invention as claimed hereinafter.

Similar observation are to be considered with reference to means and devices which form the proposed apparatus, in which measure instruments can be used to measure the inlet and outlet flow rate for each container or supply tank which is each time concerned.

Claims (54)

1. Process of treatment of leather and the like, characterised in that it includes: disposing spread pieces of leather to be treated, spaced apart, into a container; introducing liquid solutions into said container, in sequence and with predetermined intervals, for performing various steps of leather tanning treatment, said liquid solutions being discharged from the container, after each step has been completed; maintaining a pressure below atmospheric pressure inside said container, at least for the duration of each single step; generating, during each step, a relative movement between the liquid solution and said pieces of leather, so as to intensify the action of said liquid solution on said pieces of leather.

2. Process of treatment of leather and the like, characterised in that it includes: disposing spread pieces of leather to be treated, spaced apart, into a first container; .introducing liquid solution into said container for performing a step of leather 4* S. tanning treatment; maintaining a pressure below atmospheric pressure inside said container during performing of said step; generating, during said step, relative movement between the liquid solution and said pieces of leather, so as to strengthen the action of said liquid solution on said pieces of leather; discharging said liquid solution from said first container; withdrawing said pieces of leather from the first container; repeating the above mentioned operations in further containers so as to perform remaining steps of the leather tanning treatment. 18

3. Process, according to claim 1, characterised in that the pressure below atmospheric pressure the container is created before the liquid solution for a corresponding leather treatment step, is introduced therein.

4. Process, according to claim 2, characterised in that pressure below atmospheric pressure inside each of said containers, in which a leather treatment step is carried out, is created before the corresponding liquid solution is introduced therein.

5. Process, according to claim 1 or 3, characterised in that it includes: introduction of a first liquid solution for soaking said leather into said container; swirling of said liquid solution during said soaking step; discharging of said solution from the container; introduction of a second liquid solution for liming said leather into said container; swirling of said liquid solution during said liming step; discharging of said solution from the container; =o introduction of a third liquid solution for pickling said leather into said container; swirling of said liquid solution during said pickling step; 0 discharging of said solution from the container; °0o° introduction of a fourth liquid solution for simultaneous tanning and dyeing .00 said leather into said container; t 00oo 25 swirling of said liquid solution during said tanning and dyeing step; s.e.. .°.discharging of said solution from the container; finally, withdrawing the spread pieces of leather from the container.

6. Process, according to claim 5, characterised in that, in time relation with introduction of at least one liquid solution into said first container between said first, second, third and fourth liquid solutions, also a substance is 19 introduced either pure or diluted, aimed at co-operating with the related liquid solution in order to carry out a corresponding step of the same process.

7. Process, according to claim 2 or 4, characterised in that it includes: introduction of a first liquid solution for soaking said leather into said first container; swirling said liquid solution during said soaking step; discharging said solution from the first container; withdrawing the pieces of leather from the first container; introduction of said spread pieces of leather, spaced apart, into a second container, which is to be closed tight; introduction of a second liquid solution for liming said leather into said second container; maintaining the pressure below atmospheric pressure in said second container during the liming step; swirling of said liquid solution during said liming step; discharging of said solution from the second container; o.*o•withdrawing the pieces of leather from the second container; introduction of said spread pieces of leather, spaced apart, into a third 20 container, which is to be closed tight; introduction of a third liquid solution for pickling said leather into said third container; too• maintaining the pressure below atmospheric pressure in said third container during the pickling step; moo. swirling of said liquid solution during said pickling step; *discharging of said solution from the third container; withdrawing the pieces of leather from the third container; introduction of said spread pieces of leather, spaced apart, into a fourth container, which is to be closed tight; 20 introduction of a fourth liquid solution, for performing simultaneously at least tanning and dyeing of said leather, into said fourth container; maintaining the pressure below atmospheric pressure in said fourth container during the tanning and dyeing steps; swirling of said liquid solution during said tanning and dyeing step; discharging said fourth solution from the fourth container; withdrawing the pieces of leather therefrom.

8. Process, according to claim 7, characterised in that, in time relation with introduction of said related liquid solution into at least one of said container first, second, third and fourth, at least one substance is introduced either pure or diluted, aimed at co-operating with the related liquid solution in order to carry out a corresponding step of the same process.

9. Process, according to claim 1 or 3, characterised in that it includes: introduction of a first liquid solution for soaking said leather into said container; swirling of said liquid solution during said soaking step; discharging said solution from the container; S 20 introduction of a second liquid solution for liming said leather into said container; swirling of said liquid solution during said liming step; discharging of said solution from the container; introduction of a third liquid solution for pickling said leather into said 25 container; *o*swirling of said liquid solution during said pickling step; S°discharging of said solution from the container; i introduction of a fourth liquid solution for pre-tanning said leather into said container; swirling of said liquid solution during said pre-tanning step; 21 discharging of said solution from the container; introduction of a fifth liquid solution for tanning said leather into said container; swirling of said liquid solution during said tanning step; discharging of said solution from the container; introduction of a sixth liquid solution for at least dyeing said leather into said container; swirling of said sixth liquid solution during said dyeing step; discharging of said solution from the container; finally, withdrawing the spread pieces of leather from the container.

Process, according to claim 9, characterised in that, in time relation with introduction of at least one liquid solution into said first container between said first, second, third, fourth, fifth and sixth liquid solutions, at least one substance is introduced either pure or diluted, aimed at co-operating with the related liquid solution in order to carry out at least one corresponding step of the same process.

11. Process, according to claim 2 or 4, characterised in that it includes: 20 introduction of a first liquid solution for soaking said leather into said first container; o* to swirling of said liquid solution during said soaking step; discharging of said solution from the first container; *too withdrawing the pieces of leather from the first container; 25 introduction of said spread pieces of leather, spaced apart, into a second container, which is to be closed tight; o o introduction of a second liquid solution for liming said leather into said second container; maintaining the pressure below atmospheric pressure in said second container during the liming step; swirling of said second liquid solution during said liming step; 22 discharging of said second liquid solution from the second container; withdrawing the pieces of leather from the second container; introduction of said spread pieces of leather, spaced apart, into a third container, which is to be closed tight; introduction of a third liquid solution for pickling said leather into said third container; maintaining the pressure below atmospheric pressure in said third container during the pickling step; swirling of said third liquid solution during said pickling step; discharging said solution from the third container; withdrawing the pieces of leather from the third container; introduction of said spread pieces of leather, spaced apart, into a fourth container, which is to be closed tight; introduction of a fourth liquid solution into said fourth container for pre- tanning of said leather; maintaining the pressure below atmospheric pressure in said fourth container during the pre-tanning step; swirling of said fourth liquid solution during said pre-tanning step; •discharging said fourth solution from the fourth container; 20 withdrawing the pieces of leather from the fourth container; introduction of said spread pieces of leather, spaced apart, into a fifth container, which is to be closed tight; introduction of a fifth liquid solution into said fifth container for tanning of said leather; 25 maintaining the pressure below atmospheric pressure in said fifth container S: during the tanning step; duin hetanngstp swirling of said fifth liquid solution during said tanning step; discharging of said fifth solution from the fifth container; withdrawing the pieces of leather from the fifth container; 23 introduction of said spread pieces of leather, spaced apart, into a sixth container, which is to be closed tight; introduction of a sixth liquid solution into said sixth container for dyeing said leather; maintaining the pressure below atmospheric pressure in said sixth container during the dyeing step; swirling of said sixth liquid solution during said dyeing step; discharging said sixth solution from the sixth container; withdrawing the pieces of leather therefrom.

12. Process, according to claim 11, characterised in that, in time relation with introduction of said related liquid solution into at least one of said container first, second, third, fourth, fifth and sixth at least one substance is introduced either pure or diluted, aimed at co-operating with the related liquid solution in order to carry out a corresponding step of the same process.

13. Process, according to claim 5 or 9, characterised in that between the end of the liming step and before the pickling treatment, there is an intermediate leather washing step.

14. Process, according to claim 5 or 9, characterised in that between the end of the soaking step and before the liming step, there is an intermediate leather washing step.

15. Process, according to claim 9, characterised in that after the pre-tanning step and before the tanning step, there is an intermediate leather washing step.

16. Process, according to claim 7 or 11, characterised in that after the 0 soaking step there is an intermediate leather washing step carried out in said first container. 24

17. Process, according to claim 7 or 11, characterised in that after the liming step there is an intermediate leather washing step carried out in said second container.

18. Process, according to claim 9, characterised in that after the pre-tanning step the leather is washed.

19. Process, according to claim 1 or 2, characterised in that the relative movement between the liquid solution and said pieces of leather is obtained by maintaining the container unmoved and ejecting a flow of air into said liquid solution.

Process, according to claim 1 or 2, characterised in that the relative movement between the liquid solution and said pieces of leather is obtained by maintaining the container unmoved and connecting the lower part thereof with outside, thus generating a flow of air, which passes through said liquid solution.

21. Process, according to claim 1 or 2, characterised in that the relative movement between the liquid solution and said pieces of leather is obtained by continuous withdrawing of said liquid solution at a level close to its upper surface, from said container and by re-introduction thereof at the bottom of ooo oE SC said container. 25

22. Process, according to any of the previous claims, characterised in that said pieces of leather are spread on respective open support means. 9ooC

23. Process, according to claim 22, characterised in that said pieces of leather are arranged vertically. C 9

24. Process, according to claim 22, characterised in that said pieces of leather are disposed horizontally. Process, according to claim 22, characterised in that said pieces of leather are inclined with respect to a vertical plane.

25

26. Process, according to claim 7 or 11, characterised in that after the soaking step has been completed, the pieces of leather withdrawn from the container, in which this soaking step has been performed, are introduced into an auxiliary container for being washed.

27. Process, according to claim 7 or 11, characterised in that after the liming step has been completed, the pieces of leather withdrawn from the container, in which this liming step has been performed, are introduced into an auxiliary container for being washed.

28. Process, according to claim 11, characterised in that after the pre-tanning step has been completed, the pieces of leather withdrawn from the container, in which this pre-tanning step has been performed, are introduced into an auxiliary container for being washed.

29. Process, according to claim 1 or 3 or 5 or 9, characterised in that, during each of the treatment steps, the related liquid solution for performing each time that step is treated with ultrasounds.

30. Process, according to claim 2 or 4 or 7 or 11, characterised in that, during each of the treatment steps, the related liquid solution for performing each time that step is treated with ultrasounds.

31. Apparatus for carrying out treatment of leather and the like, 25 characterised in that it includes: a container to be closed tight; a plurality of supports, which can be introduced and withdrawn from said container, and on which the corresponding spread pieces of leather are fastened, these supports being situated in said container in such a way as to keep said pieces of leather spaced out; S 30 a first series of tanks containing predetermined liquid solutions for corresponding leather treatment steps; on/off and control means, which connect each of said tanks to the container so as to introduce therein the relative liquid solution for corresponding leather treatment step; 26 suction means for maintaining the a pressure below atmospheric pressure inside said container at least while performing the leather treatment steps; means for generating relative movement between a liquid solution and said pieces of leather so as to intensify the action of said liquid solution thereon.

32. Apparatus, according to claim 31, characterised in that it includes a second series of tanks connected to the container by on/off and control means so as to receive a liquid solution discharged from said container after a corresponding step has been completed.

33. Apparatus, according to claim 31, characterised in that it includes a series of auxiliary tanks connected to the container by on/off and control means, for introducing a substance, either pure or diluted, into said container, said substance working in combination with a corresponding liquid substance for carrying out at least one leather treatment process step.

34. Apparatus for carrying out treatment of leather and the like, characterised in that it includes: a plurality of containers to be closed tight, inside which predetermined leather 20 treatment steps are carried out; a plurality of supports, which can be introduced and withdrawn from said containers, and on which the corresponding spread pieces of leather are *fastened, these supports being situated in said containers in such a way as to keep spaced out said pieces of leather; a first series of tanks containing predetermined liquid solutions for corresponding leather treatment steps; on/off and control means, which connect each of said tanks to the relative container so as to introduce therein the relative liquid solution for a corresponding leather treatment step; 30 suction means for maintaining a pressure below atmospheric pressure inside each of said containers at least during performing therein of the relative leather treatment steps; 27 means for generating, inside each of said containers, relative movement between a corresponding liquid solution and said pieces of leather so as to intensify the action of said liquid solution thereon.

35. Apparatus, according to claim 34, characterised in that a second series of tanks connected to a corresponding container by on/off and control means, so as to receive a liquid solution discharged from said container after a corresponding step has been completed.

36. Apparatus, according to claim 34, characterised in that for each container it includes a related auxiliary supply tank connected to the corresponding container by on/off and control means, for introducing at least one substance, either pure or diluted, into said related container, for carrying out a corresponding leather treatment process step together with the liquid solution introduced into the container.

37. Apparatus, according to claim 31, characterised in that said container is kept unmoved and in that the means generating a relative movement between the liquid solution and the pieces of leather include ejectors, which 20 send a jet of air through the liquid solution held in the container.

38. Apparatus, according to claim 34, characterised in that each of said containers is kept unmoved and in that the means generating a relative *o movement between the liquid solution and the pieces of leather in each container include ejectors, which send a jet of air through the liquid solution.

39. Apparatus, according to claim 31, characterised in that at least one tank for dramatic reduction and/or neutralisation of volatile compounds produced during the leather treatment, is situated along the pipe connecting said suction means with the container.

Apparatus, according to claim 34, characterised in that at least one tank for dramatic reduction and/or neutralisation of volatile compounds produced during the leather treatment, is situated along the pipe connecting said suction means with said containers. 28

41. Apparatus, according to claim 31, characterised in that it includes further tanks, which are connected to said container by on/off and control means so as to introduce into and, subsequently discharge suitable liquid solutions from the container for washing the leather after a corresponding step has been completed.

42. Apparatus, according to claim 34, characterised in that it includes further tanks, each of which can be connected to a corresponding container by on/off and control means so as to introduce into and, subsequently discharge suitable liquid solutions from said container for washing the leather after a corresponding step has been completed.

43. Apparatus, according to claim 34, characterised in that it includes auxiliary containers, each of which can be connected, by on/off and control means, to a corresponding tank containing a predetermined liquid solution introduced into and, subsequently discharged from said auxiliary container, for washing the pieces of leather introduced therein after a treatment step has been completed in a correspondent container.

44. Apparatus, according to claim 31, characterised in that it includes a duct o* which sets in communication a bottom region of said container with an intermediate region of the same container, located just below a free surface of the liquid solution inside the container, said duct having pump means for 25 continuously transferring said liquid solution from said intermediate region to said bottom region of said container. tOO° 0 t :i

45. Apparatus, according to claim 34, characterised in that for each :it container it includes a duct which sets in communication a bottom region of said container with an intermediate region of the same container, located just below a free surface of the liquid solution inside the container, said duct having pump means for continuously transferring said liquid solution from said intermediate region to said bottom region of said container.

46. Apparatus, according to claim 31 or 34, characterised in that for each ,container it includes at least one vapour recovery unit comprising: 29 a tight closed condensing vessel; first on/off means operated by a control unit for connecting said vessel in series with a duct which sets in communication said container and said suction means; sensor means for detecting the liquid level inside said vessel, these sensor means co-operate with said control unit to operate said first on/off means and second on/off means so as to exclude said vessel from the path of said duct, to set in communication the inside of the vessel with the outside environment, and to set in communication the vessel with the container, so that a flow of condensed liquid can be transferred from the vessel to the container.

47. Apparatus, according to claim 46, characterised in that in the vessel there is located an inclined baffle, with an open end of a first pipe located below said baffle for introducing into said vessel a flow of an air-vapour mix coming from said container, and with an open end of a second pipe connected to said suction means.

48. Apparatus, according to claim 37 or 38, characterised in that said pieces of leather are arranged vertically.

49. Apparatus, according to claim 37 or 38, characterised in that said pieces of leather are arranged horizontally.

50. Apparatus, according to claim 37 or 38, characterised in that said pieces of leather are arranged inclined in any way.

51. Apparatus, according to claim 31 or 37 or 30 or 32, characterised in that it includes a sonotrode, connected to the container, for treating each liquid solution with an ultrasounds beam.

52. Apparatus, according to claim 34 or 38 or 40, characterised in that it includes sonotrodes, one for each of the containers, connected thereto for treating each liquid solution with an ultrasounds beam. 30

53. A process of treatment of leather and the like, said process being substantially as herein described.

54. An apparatus for carrying out treatment of leather and the like, said apparatus being substantially as herein described with reference to the accompanying drawings. 0 *0 t** 4 4 0 0 4 4