DESCRIPTION

The present invention concerns a method for making a multilayer laminar

5 product, particularly suitable for upgrading leather.

The present invention concerns also a system for implementing said method. As is known, in the leather processing sector the so-called "upgrading" processes are employed, which make it possible to increase the commercial value of low-quality leather.

10 In fact, one of the first steps of a leather processing cycle consists in separating the outer, more valuable layer, which is referred to as "grain" in technical jargon, from a lower, less valuable layer, which in turn can be divided in further layers. Here below, the term "leather" means not only leather as a whole, but also and especially any of the layers obtained from it, in particular

15 the less valuable ones.

Substantially, an upgrading process of the known type consists in covering the surface of the hide which is intended to be visible during use with a layer of plastic material, generally polyurethane. The above mentioned layer makes it possible to cover any defects which may be present on the leather surface

20 and to obtain an appearance similar to that of more valuable leather.

An analogous process can be used also to give a synthetic or non synthetic fabric an appearance similar to that of leather, in which case the product is referred to as "imitation leather". Obviously, the description provided below applies completely also to the latter process.

25 Generally, during the upgrading process, the surface of the product is also embossed for the purpose of obtaining special aesthetic effects that contribute to increasing the value of the product.

A known technique for upgrading leather, described in the Italian patent application VI2005A000080 in the name of the applicant of the present 30 invention, includes the step of covering a laminar support, for example a hide to be upgraded, with a layer of polyurethane resin.

Successively, embossed paper is pressed against the layer of polyurethane resin, which has not been completely polymerized yet and therefore retains a soft consistency, in order to impress the pattern of the embossed paper on 35 said layer. According to this technique, the polyurethane resin is successively polymerized, in such a way as to make it adhere to the laminar support in a stable manner.

Once the resin has been polymerized, the embossed paper is removed from the laminar support in order to obtain the final product. In order to facilitate the removal of the paper and prevent it from adhering to the polyurethane resin, the embossed paper is previously covered with a protective film, also in polyurethane, which prevents any direct contact between the polyurethane resin and the embossed paper. This film becomes an integral part of the polyurethane resin during the polymerization process previously described. The above mentioned known technique poses some recognized drawbacks. A first drawback derives from the fact that embossed paper is available on the market in predefined widths which usually do not exceed 1600 mm. Consequently, the technique described above cannot be used for processing hides whose width exceeds 1600 mm.

This aspect is a limitation, considering that some hides are much wider than 1600 mm and sometimes their width reaches and even exceeds 3400 mm. In order to be able to use the technique described above with hides that are so wide, it is necessary to cut the latter along their longitudinal direction in such a way as to obtain strips which are narrower than the paper and which are processed one after the other.

It is clear that the operation of cutting hides just described above poses the drawback of reducing the field of application of the leather processed in this way.

For hides whose width exceeds 1600 mm only slightly, it is preferred to cut their side portions, but this causes the inconvenience of producing raw material rejects.

Said drawbacks related to the fact that the hides need to be cut become more serious as the value of the original leather increases.

The known technique described above poses a further drawback, represented by the fact that the embossed paper available on the market is not provided with the protective film, which therefore must be produced in the leather upgrading system. In the leather upgrading systems of the known type, the film is produced by applying a thin layer of polyurethane resin to the paper, for example by spreading it with a blade or a roller, by spraying it with a spray gun, etc. The resin is then solidified in an oven in order to obtain the film.

It can be understood that the operation described above poses the drawback of affecting the cost of the process and the overall dimensions of the system.

A further drawback posed by the known technique described above is related to the cost of embossed paper, which is increased due to the fact that the pulp and basic weight of the paper must be suited to bear the mechanical, chemical and thermal stress produced during the processing cycle. Obviously, the cost of the embossed paper affects the cost of the processing cycle.

In order to limit the costs related to the embossed paper, a device is provided downstream of the polymerization process, said device being suited to remove the portion of film left on the embossed paper, so that the latter can be reused.

However, the presence of this device increases the overall dimensions and the costs of the system, as well as process costs.

A further drawback posed by the known technique described above derives from the fact that the embossed paper needs to be periodically replaced, which increases process costs even further.

It is the object of the present invention to overcome all the drawbacks mentioned above, which are typical of the known upgrading technique described above and of the respective systems.

In particular, it is the object of the present invention to provide a method for making a multilayer laminar product, in particular upgraded leather, which allows the processing of products whose width exceeds the widths allowed by the known technique described above.

It is also the object of the present invention to avoid the use of embossed paper.

The objects illustrated above are achieved by a method for making a multilayer laminar product, in particular upgraded leather, in accordance with claim 1 . The said objects are also achieved by a system for manufacturing said multilayer laminar product, in accordance with claim 6.

Further details and characteristics of the invention are illustrated in the dependent claims.

Advantageously, the technique which is the subject of the invention makes it possible to process very wide hides with no need to cut them.

This, advantageously, makes it possible to obtain products intended for fields of application for which the products obtained by means of the known technique are not suitable.

Furthermore, advantageously, the possibility to process the hides with no need to cut them avoids the production of raw material rejects.

Therefore, it can be understood that the technique of the invention is particularly suitable for processing valuable hides in large sizes.

Still advantageously, the fact that no embossed paper is used makes it possible to reduce the costs related to the latter.

In particular, the absence of the operations and devices needed to apply the protective film to the paper and to remove it makes it possible to reduce the costs and overall dimensions of the system, as well as the processing costs. The objects and advantages described above, together with others that are described below, are highlighted in the following description of a preferred embodiment of the invention, which is provided by way of non-limiting example and which makes reference to the attached drawings, wherein:

- Figures 1 (a)-1 (f) schematically illustrate different steps of the method that is the subject of the invention when applied to a laminar support;

- Figure 2 shows a side view of the system of the invention;

- Figure 3 shows a detail of the system shown in Figure 2;

- Figure 4 shows a further detail of the system shown in Figure 2;

- Figure 5 shows a detail of a variant embodiment of the system shown in Figure 2.

The method of the invention for making a multilayer laminar product, particularly suitable for upgrading leather, includes the preparation of a laminar support, indicated by 16 in Figure 1 . Preferably, the laminar support 16 is a hide, but the method of the invention can be applied also to other laminar supports, in particular fabrics, be they synthetic or non synthetic.

Preferably but not necessarily, the laminar support 16 is moved forward along a direction of advance X, at a predefined speed of advance, by a first feeding device 2, visible in Figure 2. Preferably, said first feeding device 2 comprises a flexible element closed as a ring around a series of rollers, on which the laminar support 16 is rested and which is moved forward according to said direction of advance X.

As shown in Figure 1 (a), a first side 16a of the laminar support 16 is covered with a covering layer 17 made of a polymeric resin, preferably but not necessarily comprising polyurethane. The covering layer in polymeric resin 17 is deposited on the laminar support 16, preferably by spraying it or spreading it with a blade or a roller on the first side 16a by means of an applicator unit 3. The applicator unit 3 may comprise a series of spraying nozzles arranged in a circle, which are rotated around the axis of the circle in such a way that they intersect, in succession, the trajectory of the laminar support 16, or are moved with an alternative motion and crosswise with respect to the trajectory of the laminar support 16. As an alternative to or in combination with said spraying nozzles, the applicator unit 3 may comprise a doctor blade for spreading the polymeric resin on the first side 16a.

The covering layer 17 obtained in this way is not completely polymerized, that is, is not polymerized or is partially polymerized, so that it has a yielding consistency, for example soft, allowing it to be embossed through the exertion of a pressure sufficiently slight as not to affect the integrity of the underlying laminar support 16.

Preferably, the thickness of the covering layer 17 is included between 7 microns and 30 microns and, even more preferably, it is substantially equal to 12 microns.

Preferably, and as shown in Figure 1 (b), before being embossed the covering layer 17 is hardened, for example through a slight polymerization process, in such a way as to give it a more compact consistency, similar to that of a gel, and to obtain a hardened covering layer.

Preferably, the hardening step is performed by heating the covering layer with a heating device 26, for example a bank of infrared lamps or a ventilated dryer heated with diathermic oil, vapour or gas.

Before the covering layer 17 is embossed, a laminar element 18, indicated in Figure 1 (c), is prepared, which is provided with a first side 18a chemically incompatible with the polymeric resin of the covering layer 17. The expression "chemically incompatible" is used in the present application to mean that said first side 18a, when placed in contact with the polymeric resin, does not create chemical bonds with the latter, that is, does not adhere to it in an irreversible manner, so that the laminar element 18 can be easily separated from the covering layer 17 also after the latter has been polymerized, without damaging the covering layer itself.

Preferably, the laminar element 18 is provided in the shape of a strip 20 and is moved forward in the direction of advance X, at a speed corresponding to said speed of advance, by a second feeding device 7, visible in particular in the detailed view of Figure 3. Preferably, the second feeding device 7 comprises a series of rollers and a spreading element that maintain the laminar element 18 tensioned and guide it according to a predefined trajectory, in such a way as to bring it in contact with the laminar support 16.

An embossed surface 6, arranged downstream of the applicator unit 3 according to the direction of advance X, is pushed against the covering layer 17 in a pushing unit 5 after interposing said laminar element 18, as schematically shown in Figure 1 (d). The laminar element 18 is guided by the second feeding device 7 in such a way that it is arranged between the covering layer 17 and the embossed surface 6, with its first side 18a facing towards the covering layer 17.

During said pushing operation, the pattern of the embossed surface 6 is impressed on the covering layer 17.

Preferably, said pushing action is performed by exerting a pressure included between 20 atm and 120 atm, even more preferably included between 40 atm and 70 atm. Advantageously, said pressure is sufficiently limited as not to alter the properties of the laminar support 16 substantially, in particular its softness, which is very important in the case where the laminar support is made of leather.

Preferably, and as shown once again in Figure 3, the embossed surface 6 belongs to an embossing roller 14, mounted in such a way that it revolves around its own axis. Advantageously, said embossing roller 14 can be kept constantly resting on the laminar element 18 and on the laminar support 16, thus allowing a continuous process to be carried out. It is also evident that, in variant embodiments of the invention not illustrated in the figures, the embossed surface 6 may belong to a device different from said embossing roller, for example a tape, a die or a similar device.

Preferably, the embossing roller 14 is made of steel and its surface is chromium-plated, which gives it high chemical resistance.

Still preferably, opposite the embossed surface 6 there is a supporting surface which, during the pushing action, supports the laminar support 16 on the side opposite the first side 16a. Preferably, the supporting surface belongs to a corresponding supporting roller 15, mounted in such a way that it revolves around its own axis.

Preferably, the embossing roller 14 and the supporting roller 15 are arranged at a mutual distance which is shorter than the overall thickness of the laminar support 16, the covering layer 17 and the laminar element 18, in such a way that said elements are compressed following their passage through the two rollers 14, 15.

Still preferably, an adjusting device is provided, which is suited to modify said distance according to the thickness of the laminar support 16 used and to the pressure required for the pushing action.

According to a variant embodiment of the invention, the system 1 comprises a plurality of interchangeable embossed surfaces 6, featuring different surface patterns. According to a possible embodiment intended to obtain the characteristic just described above, shown in Figure 5, a plurality of embossing rollers 14, each one having a respective embossed surface 6, are mounted on a revolving device 27 in such a way that they can be easily and quickly exchanged when necessary. It is evident that in variant embodiments the number of embossing rollers can be different from that shown in Figure 5.

Regarding the laminar element 18, this must be sufficiently yielding to allow the pattern to be transferred from the embossed surface 6 to the covering layer 17. The feature just mentioned above can be obtained by selecting a material that is resistant enough to allow the thickness of the laminar element 18 to be very limited, while at the same time having mechanical and thermal resistance compatible with the use required for said process.

It has been found that nylon, polyesther and other equivalent materials are particularly suited to be used to make the laminar element 18, these material having a relatively low cost and appropriate mechanical and thermal resistance even with very limited thicknesses, for example included between 0.05 mm (50 microns) and 0.1 mm (100 microns). It is also evident that, in variant embodiments of the invention, the laminar element 18 can be made of any other material, provided that it has the properties described above.

As shown in Figure 1 (e), after the embossed surface 6 has been pushed or while it is being pushed against the laminar support 16, a treatment unit 4 causes the polymerization of the covering layer 17, in such a way as to obtain a stabilized covering layer 19, that is, a substantially solidified covering layer. Preferably, polymerization takes place through heating, still preferably at a temperature included between 60 °C and 190 °C. Advantageously, the temperature values just indicated above are sufficiently low not to alter considerably the structure of the laminar supports 16 commonly used in the process, in particular hides, which therefore preserve their softness.

Still preferably, said heating step starts when the covering layer comes into contact with the embossed surface 6, which is associated with a heating device that can comprise, for example, a hollow space in contact with the embossed surface 6 and a circulation device that conveys a heat carrier fluid into the hollow space.

Preferably, the polymerization process is completed in a polymerization oven 25 arranged downstream of the pushing unit 5 according to the direction of advance X, as shown in Figure 2.

After said polymerization process, the laminar element 18 is separated from the stabilized covering layer 19 as shown in Figure 1 (f), so as to obtain the multilayer laminar product 22.

The operation just described above is preferably carried out by a recovery unit 11 arranged downstream of the treatment unit 4 according to the direction of advance X, which comprises, preferably and as shown in Figure 4, two winding rollers 12, 13, one per each strip 20, around which the respective portions of laminar element 18 removed from the laminar support 16 are wound.

From the description provided above, it can be understood that the embossed surface 6 is distinct from the laminar element 18, which therefore is not subjected to the width restrictions typical of the embossed paper available on the market.

In particular, given that the pattern to be embossed is impressed on the covering layer 17 by the embossed surface 6, while the laminar element 18 serves only to avoid any contact between the embossed surface 6 and the polyurethane resin, it is very advantageous to use a laminar element 18 with a smooth surface. In fact, a smooth laminar element 18 can be selected among a wide range of materials available on the market, including smooth nylon. This makes it also possible to select the laminar element 18 in such a way as to minimize costs and/or maximize the quality of the multilayer product 22.

The possibility to use a smooth, or substantially smooth, laminar element 18, makes it possible to obtain it by placing side by side two or more identical strips 20 overlapping at the level of their respective edges, in such a way as to multiply the obtainable operating width. In the latter case, the reduced thickness of the laminar element 18 is such that the overlapping area of the two laminar elements does not generate visible effects on the final product. Therefore, it can be understood that the method of the invention achieves the object of allowing laminar supports in any width to be processed.

Furthermore, the possibility to use a low cost material for the laminar element 18 brings about the further advantage of making the elimination of the laminar element 18 after use economically advantageous, since there is no need to recover it for a successive use. This makes it possible to size the laminar element 18 so that it needs to resist just one processing step and therefore makes it possible to minimize its thickness, thus further limiting its cost and increasing processing quality.

The fact that there is no need to reuse the laminar element 18 avoids also the need to clean the latter, thus limiting the cost and the overall dimensions of the system compared to the systems of the known type.

Preferably, and as mentioned above, the laminar element 18 belongs to a strip

20 which comprises also a film 21 , indicated for example in Figure 1 (c), made with a substance which is chemically compatible with the polymeric resin, meaning suited to adhere to the latter in a stable manner. The film 21 is coupled with the first side 18a of the laminar element 18, in such a way that it can be detached from it without damaging the laminar element itself. The film

21 is maintained in contact with the covering layer 17 while the embossed surface 6 is being pushed and the covering layer itself is being polymerized. Obviously, if the laminar element 18 is constituted by several elements placed side by side as described above, each one of said elements belongs to a respective strip 20 and the corresponding films 21 are all kept in contact with the covering layer 17 during said pushing action.

The removal of the film 21 from the laminar element 18 can be guaranteed by respectively selecting for the laminar element 18 and for the film 21 two materials which are chemically incompatible with each other, such as, for example, nylon and a polyurethane resin. The first side of the laminar element 18 can be properly treated in such a way as to prevent the film 21 from spontaneously coming off the laminar element 18. For a laminar element 18 made of nylon, the result just described above can be achieved, for example, by subjecting the first side 18a to a corona treatment. The strip 20 may comprise further layers in addition to said film 21 , which are suited to create special aesthetic effects on the final product. For example, there may be a coloured layer, a layer with spots, or different types of layers. Preferably, each strip 20 belongs to a respective reel 8, 9 which is unwound as the strip 20 is used in the process.

Said reels 8, 9 can be mounted on a fixed support, as in the case illustrated in Figure 3, or on a movable support, for example a revolving support, as in the variant embodiment illustrated in Figure 5. It is evident that in further variant embodiments the number of reels can be different from that shown in the above mentioned figures.

In the case of more strips placed side by side, an aligning unit 10, preferably comprising a series of rollers, provides for guiding the strips in such a way as to overlap their respective side edges and thus define the laminar element 18. In practice, the laminar support 16 is laid on the flexible element of the first feeding device 2 at the level of a loading area 23 indicated in Figure 2.

The first feeding device 2 then moves the laminar support 16 forward according to the direction of advance X, and at a predefined speed of advance, towards the applicator unit 3, where it is covered with the covering layer 17. Preferably, the laminar support 16 covered as described above is heated by the heating device 26 in order to harden the covering layer 17.

In the meantime, the strips 20 are unwound from the respective reels 8, 9 at the speed of advance and are conveyed by the aligning unit 10 between the embossing roller 14 and the supporting roller 15, wherein the film 21 is brought into contact with the non-completely polymerized covering layer 17 while the embossed surface 6 impresses the pattern on the latter.

The contact angle between the laminar support 16 and the embossing roller 14 can vary according to the diameter of the embossing roller, to the production speed, to the thickness of the support to be applied and to the quantity of resin applied, in such a way as to harden the embossed surface of the covering layer 17.

The contact with the surface of the embossing roller 14 makes it possible to exploit also this surface, properly heated, in order to start the polymerization of the covering layer 17.

Preferably, the contact angle between the laminar support 16 and the embossing roller 14 can be adjusted according to the needs, by means of an apposite adjusting device which, for example, acts modifying the position of the supporting roller 15 according to the direction of advance X. The variation of the above mentioned contact angle leads to the variation of the contact time between the laminar support 16 and the embossing roller 14.

According to a variant embodiment illustrated in Figure 5, said adjustment is carried out by means of a secondary roller 28 which is arranged immediately downstream of the supporting roller 15 and whose position with respect to the latter can be adjusted. A conveyor belt 29 is wound around the supporting roller 15 and the secondary roller 28 and the laminar support 16 transits said conveyor belt. By varying the position of the secondary roller 28 with respect to the supporting roller 15 it is possible to modify the contact angle between the conveyor belt 29 and the embossing roller 14.

Preferably, the polymerization process is completed in the polymerization oven 25 which is arranged downstream of the pushing unit 5.

Preferably, during the polymerization process the film 21 associated with the laminar element 18 adheres to the covering layer 17, giving origin to a stabilized layer 19 formed by a single body, indicated in Figure 1 (f).

Downstream of the polymerization process, the winding rollers 12, 13 visible in the Figures 2 and 4 recover the laminar element 18, detaching it from the covering layer 17 and from the portion of film 21 which adhered to it.

Therefore, based on the description provided above, it can be understood that the method and the system described above achieve all of the set objects. In particular, using an embossed surface distinct from the laminar element to impress the pattern on the covering layer makes it possible to avoid the use of the embossed paper available on the market, which represents a restriction for the maximum width of the laminar supports that can be processed.

Consequently, it is possible to obtain a system capable of processing laminar supports whose width exceeds the width allowed by the known technique.