ITUA20163773A1 - METHOD OF PRODUCTION OF A MULTILAYER LAMINAR PRODUCT AND PLANT TO IMPLEMENT THIS METHOD - Google Patents

Description

METHOD OF PRODUCTION OF A MULTILAYER LAMINAR PRODUCT AND PLANT TO IMPLEMENT THIS METHOD.

DESCRIPTION

The present invention relates to a method of producing a multilayer laminar product particularly suitable for making leather ennobling.

The present invention also relates to a plant for carrying out the above method.

As is known, in the leather processing sector so-called "ennobling" procedures are used which allow to increase the commercial value of low-grade leathers.

In fact, one of the first stages of leather processing consists in separating the more valuable outer layer, known as “flower” in the jargon, from a less valuable lower layer, which in turn is eventually subdivided into further layers. In the following, the term “skin” will mean not only a skin in its entirety, but also and above all any of the layers obtained from it, in particular the less valuable ones.

Basically, a known type of finishing process involves covering the surface of the leather intended to be visible during use with a layer of plastic material, generally polyurethane. The aforementioned layer allows to cover the superficial defects of the leather and to give it an appearance similar to that of a more precious leather.

A similar process can also be used to give a fabric, synthetic or not, an appearance similar to that of a leather, in which case we speak of "imitation leather". Obviously, what will be described below is also fully applicable to the latter process.

Generally, during the finishing process an embossing is also impressed on the surface of the product, in order to obtain particular aesthetic effects that contribute to increasing the value of the product.

A known technique suitable for the ennobling of leathers, described in the Italian patent application VI2005A000080 in the name of the applicant for the present invention, provides for covering a laminar support, for example a leather to be ennobled, with a layer of polyurethane resin.

Subsequently, an embossed paper is compressed against the layer of polyurethane resin that is not completely polymerized and, therefore, still having a soft consistency, to imprint the pattern of the embossed paper on the latter.

The technique then provides to polymerize the polyurethane resin so as to make it adhere stably to the laminar support.

After the resin has been cured, the embossed paper is removed from the laminar support in order to obtain the final product. 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 made of polyurethane, which prevents direct contact between the polyurethane resin and the embossed paper. This film becomes an integral part of the polyurethane resin during the polymerization described above. The aforesaid known technique has some recognized drawbacks. A first drawback derives from the fact that the embossed paper is commercially available in predefined widths which, typically, do not exceed 1600 mm. Consequently, the technique described above cannot treat hides with a width greater than 1600 mm.

This aspect is limiting, considering that some leathers are abundantly over 1600 mm in width, reaching up to 3400 mm and beyond. In order to use the technique described above with such wide hides, it is necessary to cut the latter according to their longitudinal direction in order to obtain strips with a width less than the width of the paper, which are processed one after the other.

Obviously, the practice of cutting the hides just described involves the drawback of reducing the field of application of the hides.

For hides with a width of just over 1600 mm, it is preferred to cut the side parts, but this entails the drawback of producing waste of raw material.

The aforementioned drawbacks linked to the cutting of the hides are all the more serious the greater the value of the starting hides.

The aforementioned known technique has the further drawback that the embossed papers available on the market are not provided with the protective film, which therefore must be made in the same leather finishing plant. In known type finishing plants, the film is made by applying a thin layer of polyurethane resin to the paper, for example by knife spreading, cylinder spreading, spraying with guns, etc. The resin is then solidified in the oven to obtain the film.

It is understood that the aforementioned operation involves the inconvenience of affecting the cost of the process and the footprint of the plant.

A further drawback of the known art described above is linked to the cost of the embossed paper, accentuated by the fact that the paper must have an adequate mixture and weight to withstand the mechanical, chemical and thermal stresses produced during processing. Evidently, the cost of the embossed paper affects the cost of the manufacturing process.

To limit the costs associated with embossed paper, downstream of the polymerization process there is a device that removes the portion of the film left on the embossed paper so that the latter can be reused. However, the aforementioned device contributes to the increase in the overall dimensions and costs of the plant, as well as the costs of the process. A further drawback of the technique described above derives from the fact that the embossed paper requires periodic replacement, contributing to further increase the costs of the process.

The present invention aims to overcome all the aforementioned drawbacks inherent in the known type of ennobling technique described above and in the related systems.

In particular, it is an object of the present invention to provide a method for producing a multilayer laminar product, in particular of ennobled leathers, which allows the processing of products having widths greater than those permitted by the known technique described above.

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

The above objects are achieved by a method of producing a multilayer laminar product, in particular of an ennobled leather, in accordance with claim 1.

The aforesaid objects are also achieved by a plant for the production of the aforesaid multilayer laminar product in accordance with claim 8.

Further detailed features of the invention are given in the dependent claims.

Advantageously, the technique of the invention allows to work hides of great width without the need to cut them.

This advantageously makes it possible to obtain products intended for fields of application beyond the reach of the products obtained by means of the known technique.

Furthermore, advantageously, the possibility of processing the hides without cutting them avoids producing waste of raw material.

Therefore, it is understood that the technique of the invention is particularly suited to the processing of valuable leathers of considerable size.

Still advantageously, the fact of not using embossed paper allows to reduce the costs associated with the latter.

In particular, the absence of procedures and devices to deposit the protective film on the paper and to remove it allows to reduce the costs and the overall dimensions of the plant, as well as the processing costs.

The aforementioned purposes and advantages, together with others that will be mentioned below, will appear evident during the following description of a preferred embodiment of the invention, which is given as an indication and not a limitation with reference to the attached drawing tables where:

- figs. 1 (a) -1 (f) schematically represent different phases of the method of the invention, in the application to a laminar support; - fig. 2 represents the plant of the invention, in side view;

- fig. 3 represents a detail of the system of fig. 2;

- fig. 4 represents a further detail of the system of fig. 2;

- fig. 5 represents a detail of an executive variant of the system of fig. 2.

The method of the invention for the production of a multilayer laminar product, particularly suitable for the finishing of leathers, provides for the preparation of a laminar support, indicated in fig. 1 with 16. Preferably, the laminar support 16 is a leather, but the method of the invention can also be applied to other laminar supports, in particular to fabrics, synthetic and otherwise.

Preferably but not necessarily, the laminar support 16 is made to advance according to a direction of advancement X at a predetermined advancement speed by a first feeding device 2, visible in fig. 2. Preferably, the aforementioned first feeding device 2 comprises a flexible element closed in a ring around a series of cylinders, on which the laminar support 16 is placed and which is made to advance according to the aforementioned direction of advancement X.

As can be seen in fig. 1 (a), a first face 16a of the laminar support 16 is covered with a covering layer 17 in a polymeric resin, preferably but not necessarily comprising polyurethane.

The polymeric resin covering layer 17 is deposited on the laminar support 16, preferably by spraying or by blade or cylinder spreading on the first face 16a, by means of an applicator unit 3. The applicator unit 3 can comprise a series of spray nozzles arranged in a circle , which are made to rotate around the axis of the circle so as to intersect in succession the trajectory of the laminar support 16, or which are moved with reciprocating motion and transversely to the trajectory of the laminar support 16. Alternatively or in combination with the aforementioned spray nozzles , the applicator assembly 3 can comprise a doctor blade for spreading the polymeric resin on the first face 16a.

The covering layer 17 thus obtained is in a state that is not completely polymerized, that is, not polymerized or partially polymerized, so as to have a yielding consistency, for example soft, which allows an embossing to be imparted to it by means of a pressure light enough not to jeopardize the integrity of the underlying laminar support 16.

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

Preferably and as can be seen in fig. 1 (b), before embossing the covering layer 17, the latter is consolidated, for example by causing a slight polymerization, in order to give it a more compact consistency, similar to a gel, so as to obtain a consolidated covering layer . Preferably, the consolidation takes place by heating with a heater 26, for example a battery of infrared lamps or a ventilated dryer with diathermic oil, steam or gas heating.

Before impressing the embossing on the covering layer 17, a laminar element 18 is provided, indicated in fig. 1 (c), provided with a first face 18a chemically incompatible with the polymeric resin of the covering layer 17. The term "chemically incompatible" is used in the present application to mean that the aforementioned first face 18a, when placed in contact with the resin polymer, does not create chemical bonds with the latter, i.e. it does not adhere to it irreversibly, so that the laminar element 18 can be easily separated from the covering layer 17 even after the latter has been polymerized, without damaging the layer of covering itself.

Preferably, the laminar element 18 is supplied in the form of a strip 20 and is made to advance in the direction of advancement X at a speed corresponding to the aforementioned advancement speed by a second feeding device 7, visible in particular in the detail of Figure 3. Preferably , the second feeding device 7 comprises a series of rollers and an expander which keep the laminar element 18 under tension and guide it according to a predefined trajectory, so as to bring it into contact with the laminar support 16.

An embossed surface 6, arranged downstream of the applicator assembly 3 according to the direction of advancement X, is pushed against the covering layer 17 in a thrust assembly 5 after interposition of the aforementioned laminar element 18, as schematically represented in fig. 1 (d). The laminar element 18 is guided by the second feeding device 7 so as to be placed between the covering layer 17 and the embossed surface 6 with its first face 18a facing the covering layer 17.

During the above pushing operation, the pattern of the embossed surface 6 is impressed on the covering layer 17. Preferably, the above pushing is performed with a pressure between 20 atm and 120 atm and, even more preferably, between 40 atm and 70 atm. ATM. Advantageously, the aforesaid pressure is limited enough not to substantially alter the properties of the laminar support 16, in particular its softness, which is very important if the laminar support is made of leather. Preferably and as can always be seen in Figure 3, the embossed surface 6 belongs to an embossing cylinder 14, mounted rotatably about its own axis. Advantageously, the aforementioned embossing cylinder 14 can be kept constantly in support of the laminar element 18 and the laminar support 16 allowing to carry out a continuous process. It is also clear that, in executive variants of the invention not shown in the figures, the embossed surface 6 may belong to a device other than the aforementioned embossing cylinder, such as for example a tape, a matrix, or whatever.

Preferably, the embossing cylinder 14 is made of steel and has a chromed surface, which gives it high chemical resistance.

Still preferably, there is a support surface opposed to the embossed surface 6 which, during the push, supports the laminar support 16 on the face opposite to the first face 16a. Preferably, the support surface belongs to a corresponding support cylinder 15, mounted rotatably about its own axis.

Preferably, the embossing cylinder 14 and the support cylinder 15 are arranged at a mutual distance less than the overall thickness of the laminar support 16, of the covering layer 17 and of the laminar element 18, so that the aforesaid elements are compressed by effect of their passage between the two cylinders 14, 15.

Still preferably, an adjustment device is provided to modify the aforementioned distance according to the thickness of the laminar support 16 used and the pressure required for the thrust.

According to an executive variant of the invention, the plant 1 comprises a plurality of interchangeable embossed surfaces 6, provided with different surface patterns. A possible embodiment to obtain the characteristic just described, represented in Figure 5, provides for the arrangement of a plurality of embossing cylinders 14, each with a corresponding embossed surface 6, mounted on a revolver device 27 so as to be easily and quickly exchanged if necessary. It is evident that, in executive variants, the number of embossing cylinders can be different from that shown in Figure 5.

As far as the laminar element 18 is concerned, it must have sufficient compliance to be able to transfer the embossing from the embossed surface 6 to the covering layer 17. The above-mentioned property can be obtained by choosing a material resistant enough to allow a very reduced thickness for the laminar element 18 and, at the same time, with a mechanical and thermal resistance compatible with use in the aforesaid process.

It has been found that particularly suitable materials to be used as the laminar element 18 are nylon, polyester and other equivalent materials, which have a relatively low cost and an adequate mechanical and thermal resistance even with very reduced thicknesses, for example between 0.05 mm (50 microns) and 0.1 mm (100 microns). It is also clear that, in executive variants of the invention, the laminar element 18 can be made of any other material, provided it has the properties mentioned above.

As can be seen in Figure 1 (e), subsequently or simultaneously with the thrust of the embossed surface 6 against the laminar support 16, a treatment unit 4 causes the polymerization of the covering layer 17 so as to obtain a stabilized covering layer 19, i.e. substantially solidified. Preferably, the polymerization takes place by heating, again preferably carried out at a temperature between 60 ° C and 190 ° C. Advantageously, the temperature values just indicated are low enough not to significantly alter the structure of the laminar supports 16 commonly used in the process, in particular the hides, which therefore retain their softness. Still preferably, the aforementioned heating begins in contact with the embossed surface 6, to which a heating device is associated which can comprise, for example, a cavity in contact with the embossed surface 6 and a circulation device which conveys a heat-carrying fluid into the 'interspace.

Preferably, the polymerization is completed in a polymerization oven 25 arranged downstream of the thrust assembly 5 according to the direction of advance X, as can be seen in Figure 2.

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

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

From what has been described so far, it is understood that the embossed surface 6 is distinct from the laminar element 18, which therefore does not have the width constraints of the embossed papers available on the market.

In particular, since the embossing is impressed on the covering layer 17 by the embossed surface 6 while the laminar element 18 serves only to avoid 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 from a wide range of commercially available materials, including smooth nylon. This also allows you to choose the laminar element 18 in order to minimize costs and / or maximize the quality of the multilayer product 22.

The fact of being able to use a smooth, or substantially smooth, laminar element 18 makes it possible to obtain it by placing two or more identical strips 20 side by side, superimposed on the respective edges, so as to multiply the obtainable working width. In the latter case, the reduced thickness of the laminar element 18 ensures that the overlapping area of the two laminar elements does not generate visible effects on the final product.

Therefore, it is understood that the method of the invention achieves the purpose of allowing the processing of laminar supports of any width.

Furthermore, the possibility of using a low-cost material for the laminar element 18 entails the further advantage of making it economically advantageous to eliminate the laminar element 18 after use, without having to recover it for subsequent use. This allows the laminar element 18 to be sized to withstand a single processing step and, therefore, allows its thickness to be minimized so as to further limit its cost and increase the quality of processing.

The lack of need to reuse the laminar element 18 also avoids cleaning the latter, limiting the cost and footprint of the system compared to known type systems.

Preferably and as previously mentioned, the laminar element 18 belongs to a tape 20 which also comprises a film 21, indicated for example in Figure 1 (c), made of a substance chemically compatible with the polymeric resin, i.e. suitable for adhere to the latter permanently. The film 21 is coupled to the first face 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 kept in contact with the covering layer 17 during the pushing of the embossed surface 6 and the polymerization of the covering layer itself. Obviously, if the laminar element 18 is composed of several elements side by side as described above, each of these elements belongs to a respective tape 20 and the relative films 21 are all kept in contact with the covering layer 17 during the aforementioned thrust.

The detachment of the film 21 from the laminar element 18 can be ensured by choosing for the laminar element 18 and for the film 21 two respective chemically incompatible materials, such as nylon and a polyurethane resin. The first face of the laminar element 18 can be suitably treated in order to avoid spontaneous detachment of the film 21 from the laminar element 18. For a nylon laminar element 18, the result just described can be obtained, for example, by subjecting the first face 18a to a corona treatment.

The tape 20 can comprise further layers in addition to the aforementioned film 21, suitable for conferring particular aesthetic effects to the final product. For example, a colored layer, in patches, or whatever else may be provided.

Preferably, each tape 20 belongs to a respective reel 8, 9 which is unwound as the tape 20 is used in the process.

The aforesaid coils 8, 9 can be mounted on a fixed support, as in the case of fig. 3, or on a movable support, for example with a revolver, as shown in the executive variant of Figure 5. It is evident that, in further executive variants, the number of reels can be different from that shown in the aforementioned figures.

In the case of multiple belts side by side, an alignment group 10 preferably comprising a series of rollers guides the belts so as to overlap their respective side edges so as to define the laminar element 18.

Operationally, the laminar support 16 is spread on the flexible element of the first feeding device 2 in correspondence with a loading area 23, indicated in figure 2.

The first feeding device 2 then advances the laminar support 16 in the direction of advancement X and at a predetermined advancement speed towards the applicator assembly 3, where it is coated with the covering layer 17.

Preferably, the laminar support 16 thus coated is heated by the heater 26 in order to consolidate the covering layer 17. In the meantime, the strips 20 are unwound from the respective reels 8, 9 at the forward speed and are conveyed by the alignment assembly 10 between the embossing cylinder 14 and the support cylinder 15, where the film 21 is brought into contact with the covering layer 17 which is not completely polymerized while the embossed surface 6 embosses the latter.

The contact angle between the laminar support 16 and the embossing cylinder 14 can vary according to the diameter of the embossing cylinder, the production speed, the thickness of the support to be applied and the quantity of resin applied, so as to consolidate the embossing of the cover layer 17.

The contact with the surface of the embossing cylinder 14 also allows to exploit this surface, suitably heated, to start the polymerization of the covering layer 17.

Preferably, the contact angle between the laminar support 16 and the embossing cylinder 14 is adjustable according to the requirements by means of a suitable adjustment device which, for example, acts by modifying the position of the support cylinder 15 according to the direction of advancement X The variation of the aforesaid contact angle involves the variation of the contact time between the laminar support 16 and the embossing cylinder 14.

According to an executive variant shown in fig. 5, the aforementioned adjustment takes place by means of a secondary cylinder 28 placed immediately downstream of the support cylinder 15 and whose position with respect to the latter is adjustable. A conveyor belt 29 is wound around the support cylinder 15 and the secondary cylinder 28 on which the laminar support 16 passes. By varying the position of the secondary cylinder 28 with respect to the support cylinder 15, it is possible to modify the contact angle of the conveyor belt 29 on the embossing cylinder 14.

Preferably, the polymerization is completed in the polymerization oven 25 arranged downstream of the thrust assembly 5.

Preferably, during polymerization the film 21 associated with the laminar element 18 adheres to the covering layer 17 giving rise to a stabilized layer 19 in a single body, indicated in fig.

1 (f).

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

For what has been said so far, it is understood that the method and the system described above achieve all the intended purposes.

In particular, the fact of using an embossed surface distinct from the laminar element to impress the embossing on the covering layer allows you to free yourself from the embossed papers available on the market, which constrain the maximum width of the laminar supports that can be processed.

Consequently, it is possible to realize a plant capable of processing laminar supports having a width greater than those allowed by the known art.

Claims (14)

CLAIMS 1) Method of producing a multilayer laminar product (22), comprising the following operations: - preparing a laminar support (16); - covering a first face (16a) of said laminar support (16) with a covering layer (17) in a polymer resin in the not completely polymerized state; - providing a laminar element (18) provided with a first face (18a) which is chemically incompatible with said polymeric resin; characterized by the fact that it includes the following additional operations: - pushing an embossed surface (6) against said covering layer (17) after interposition of said laminar element (18) to impress on said covering layer (17) the pattern of said embossed surface (6), the laminar element ( 18) being arranged so that said first face (18a) faces towards said covering layer (17); - after the impression of said pattern, cause the polymerization of said covering layer (17) to obtain a stabilized covering layer (19); - separating said laminar element (18) from said stabilized covering layer (19). 2) Method according to claim 1, characterized in that said laminar element (18) belongs to a tape (20) which comprises a film (21) in a substance chemically compatible with said polymeric resin, coupled to said first face (18a ) of said laminar element (18) in such a way as to be able to be detached from said first face (18a), said method comprising an operation of maintaining said film (21) in contact with said covering layer (17) during the thrust of said embossed surface (6) against said covering layer (17) and during the polymerization of said covering layer (17). 3) Method according to claim 2, characterized in that it comprises the following operations: - superimposing a lateral edge of said tape (20) on a lateral edge of a second tape (20) identical to the first to define said laminar element (18), said method comprising an operation of maintaining the corresponding films (21) of both the tapes (20) in contact with said covering layer (17) during the pushing of said embossed surface (6) against said covering layer (17) and during the polymerization of said covering layer (17). 4) Method according to any one of claims 2 or 3, characterized in that each tape (20) is in the form of a reel (8, 9). 5) Method according to any one of the preceding claims, characterized in that said embossed surface (6) belongs to an embossing cylinder (14). 6) Method according to any one of the preceding claims, characterized by the fact that it comprises a consolidation operation of said covering layer (17) before pushing said embossed surface (6) against said covering layer (17). 7) Method according to any one of the preceding claims, characterized in that said laminar support (16) comprises a leather and / or a fabric. 8) Plant (1) for the production of a multilayer laminar product (22), comprising: - a first feeding device (2) for the advancement of a laminar support (16) according to a direction of advancement (X) at a predefined speed of advancement; - an applicator unit (3) for covering a first face (16a) of said laminar support (16) with a covering layer (17) in a polymer resin in the not completely polymerized state; - a second feeding device (7) for the advancement of a laminar element (18) at a speed corresponding to said advancement speed; - a treatment group (4) arranged downstream of said applicator group (3) according to said direction of advance (X), configured to cause the polymerization of said covering layer (17) of said laminar support (16); characterized in that it comprises a thrust unit (5) comprising an embossed surface (6) arranged downstream of said applicator unit (3) and upstream of said treatment unit (4) according to said direction of advance (X), configured to push said embossed surface (6) against said covering layer (17) so as to impress on said covering layer (17) the pattern of said embossed surface (6), said second feeding device (7) being configured to guide said laminar element (18) so as to arrange it between said covering layer (17) and said embossed surface (6). 9) Plant (1) according to claim 8, characterized in that said second feeding device (7) comprises a first reel (8) from which at least a first strip of said laminar element (18) is unwound. 10) Plant (1) according to claim 9, characterized by the fact that said second feeding device (7) comprises a second coil (9) from which a second strip of said laminar element (18) is unwound, there being a group of alignment (10) adapted to superimpose said first strip to said second strip at respective lateral edges so as to define said laminar element (18). 11) Plant (1) according to any one of claims 8 to 10, characterized in that it comprises a recovery unit (11) arranged downstream of said treatment unit (4) according to said direction of advancement (X), configured for removing said laminar element (18) from said laminar support (16). 12) Plant (1) according to claim 11, characterized in that said recovery unit (11) comprises a winding roller (12, 13) around which said laminar element (18) recovered after its removal from said support is wound laminar (16). 13) Plant (1) according to any one of claims 8 to 12, characterized in that said embossed surface (6) belongs to an embossing cylinder (14). 14) Plant (1) according to claim 13, characterized in that said treatment group (4) comprises a heating device operatively associated with said embossing cylinder (14).