Field of the invention

[0001] The present invention generally finds application in the tanning industry and particularly relates to a method of production of an ennobled laminar product containing leather, suitable for use in the automotive, aeronautical, leather goods, footwear industries.

Background art

[0002] The use of hide and leather goods in various types of industries, such as the footwear, furnishing, clothing, automotive industries and the like, has been long known.

[0003] Generally, after tanning the leather is cut to be suitably further processed and finished depending on the type of item intended to be obtained. [0004] Therefore, the processing of finished or unfinished leather involves a significant amount of scraps of various sizes, with considerable economic waste and high disposal costs.

[0005] Unfinished leather waste is easier to recycle, as it only consists of pieces of leather that can be suitably treated so as to obtain very small fibrils or fine powder.

[0006] Subsequently, fibril or powders are mixed with a binder and/or bonding agent to obtain a mixture which is then spread or modelled so as to provide a laminar element.

[0007] Such laminar element is then treated and finished to obtain items similar to those made of natural leather using techniques known in the industry. [0008] The finished leather waste is instead more difficult to recycle, as they do not consist of leather alone but also of at least one finishing layer.

[0009] Generally, the finishing layer is present only on the grain side of the leather waste, and it consists of a mixture of polymeric resins such as for example polyurethanes, acrylics, polycarbonates and the like.

[0010] Furthermore, the finishing layer may comprise further additives such as pigments, cross-linking agents, foaming agents and retardants. [0011] The presence of this finishing layer further complicates the mixing of the waste with a binder and providing a uniform laminar element.

[0012] W02020212062A1 discloses a method for recycling finished leather waste adapted to obtain a laminar element.

[0013] In particular, the method provides for mixing an organic fibre or an organic fibre mixture, preferably deriving from finished leather waste, in a weighted amount of at least 40%, with a thermoplastic binder in a weighted amount of at least 15% selected from the group of styrene-acrylate copolymers.

[0014] Optionally, an inorganic aluminium aqueous solution and/or a copper salt may be added to the mixture.

[0015] Thus, the final mixture is modelled and dried so as to obtain a laminar element adapted to be used in the leather goods industry.

[0016] The laminar element will be necessarily finished so that it can be used to obtain determined items. However, the laminar element will inevitably have properties different from those of natural leather, and therefore the common finishing techniques could lead to a finished product with non-compliant properties with respect to the field of application.

[0017] US4497871A discloses a method for the production of a laminar product consisting of reconstituted leather.

[0018] The method provides for the shredding of the processing waste of the finished leather and the mixing thereof with the addition of a binder dispersed in a solvent.

[0019] The mixture is extruded or formed so as to obtain sheets made of laminar material which is then thermally treated to remove the solvent. The laminar material may be optionally reinforced by coupling it with a support layer.

[0020] Subsequently, the exposed surface of the laminar material may be finished by depositing suitable resins, waxes and/or dyes depending on the type of finished laminar product intended to be obtained according to the prior art in the industry.

[0021] A first drawback of such known solution lies in the fact that in order to obtain a structurally resistant finished product, there arises the need to couple the laminar material formed by the waste with a suitable support layer such to increase the costs and even the thickness of the end product.

[0022] Furthermore, a second drawback lies in the fact that, generally, the resins and other finishing agents are adapted to be exclusively anchored on the leather surface, and therefore the adhesion thereof on a laminar material consisting of waste cannot be excellent, leading to obtaining a low-quality finished product.

[0023] ITVI20100181A1 discloses a method for finishing regenerated leather. The method involves the preparation of a first layer of regenerated leather on which there is deposited a second layer of finishing polymeric material with the interposition between the two layers of a third adhesive layer. [0024] EP3097230B1 discloses a method for finishing a laminar support made of leather and/or natural and/or synthetic fibres.

[0025] The method provides for the following steps: application of at least one layer of a first resin on a support surface, application of at least one layer of a second resin on a surface of a laminar support; thermal treatment of the at least one layer of a second resin, and mechanical coupling of the laminar support with the support surface so as to adhere the resin layers.

[0026] A drawback of such solutions lies in the fact that the implementation of the production and finishing methods require custom-designed plants with the presence of suitable treatment stations arranged in a predetermined sequence specific for these methods only.

[0027] Therefore, such known methods are complex, unsuitable for producing finished products which have high quality from a mechanical and aesthetic standpoint.

Technical problem

[0028] In view of the prior art, the problem addressed by the present invention is to conceive a method for the production of a revitalized and ennobled laminar product starting from leather waste, having higher final mechanical and aesthetic properties than the starting materials.

Summary of the invention [0029] The object of the present invention is to solve the aforementioned problem by providing method for the production of an ennobled laminar product which is highly efficient and cost-effective.

[0030] Another object of the present invention is to provide a method of production of an ennobled laminar product of the type indicated above which allows to obtain finished products which meet the requirements of the automotive, aeronautical, leather goods, furnishing and footwear industries.

[0031] A further object of the present invention is to provide a method of production of an ennobled laminar product of the type indicated above which allows to obtain finished products continuously and in a short time.

[0032] A further object of the present invention is to provide a method of production of an ennobled laminar product of the type indicated above, that is easy to implement.

[0033] A particular object of the present invention is to provide a method of production of an ennobled laminar product of the type indicated above that can be implemented also on laminar materials derived from the leather waste which have significant surface defects.

[0034] Another object of the present invention is to provide a method of production of an ennobled laminar product of the type indicated above which limits the waste of consumption materials.

[0035] Another object of the present invention is to provide a method of production of an ennobled laminar product of the type indicated above which can be implemented using common plants known in the industry.

[0036] The objects mentioned above and others which will be more apparent hereinafter, are achieved by a method of production of an ennobled and revitalized laminar product adapted for use in the automotive, aeronautical, leather goods and footwear industries, according to claim 1 .

[0037] The method comprises at least the steps of preparing a laminar base substrate containing leather processing waste, depositing on the base substrate at least one solvent- or aqueous-based resin layer, and possibly creating a decorative pattern on the exposed surface of the ennobled laminar product. [0038] In particular, the laminar base substrate is a recovery semi-finished product obtained by grinding completely finished pieces of leather waste or previous processed leathers, agglomerating finished ground pieces with a suitable binder.

[0039] Furthermore, the at least one first resin layer is dried and polymerized at a predetermined temperature so as to stably adhere to the surface of the laminar base substrate, to obtain the laminar product with a substantially uniform exposed surface, devoid of porosity and with relatively higher mechanical properties than the laminar base substrate.

[0040] Therefore, the method allows to obtain a high-quality ennobled laminar product starting from a laminar base product having major surface defects and with poor quality.

[0041] Characteristics of the method in greater detail, depending on the field of application of the ennobled laminar product, are indicated in the dependent claims.

Brief description of the drawings

[0042] Further features and advantages of the invention will be more apparent in the light of the detailed description of a preferred but not exclusive embodiment of a method of production of an ennobled laminar product like the one mentioned above, shown by way of non-limiting example with reference to the drawings below, wherein:

FIG. 1 is a schematic lateral view of a laminar base substrate;

FIGS. 2 to 4 are schematic lateral views of some steps when producing an ennobled and revitalized laminar product according to a first embodiment of the invention;

FIGS. 5 and 6 are schematic lateral views of some steps when producing an ennobled and revitalized laminar product according to a second embodiment;

FIG. 7 is a schematic perspective view of an ennobled and revitalized laminar product obtained according to the method of the present invention.

Detailed description of a preferred embodiment

[0043] With reference to the figures, there is shown a method of production of an ennobled and revitalized laminar product, indicated in its entirety with F, adapted for use in the automotive, aeronautical, leather goods and footwear industries.

[0044] Specifically, the method comprises at least the steps of preparing a laminar base substrate S containing leather processing waste, depositing on the base substrate S at least one solvent- or aqueous-based resin layer R, and possibly creating a decorative pattern on the exposed surface of the ennobled laminar product F.

[0045] Hereinafter, the expression “at least one layer R” or “a layer R”, may be used indistinctively, it being understood that the latter may also comprise a plurality of layers.

[0046] The at least one resin layer R is a solvent-based or water-based mixture comprising components selected from polyurethanes, acrylics, crosslinking agents and fillers.

[0047] Suitably, the at least one resin layer R is dried and polymerized at a predetermined temperature to stably adhere to the surface of the laminar base substrate S to obtain a laminar product F with a substantially uniform exposed surface, devoid of defects and with relatively higher mechanical properties than the laminar base substrate S.

[0048] According to a peculiar aspect of the invention, the laminar base substrate S, schematically shown in FIG.1 , is a recovery semi-finished product obtained by grinding completely finished pieces of leather waste or previous processed leathers, agglomerating the finished ground pieces with a suitable binder and pressing them to remove excess humidity and liquids.

[0049] Hereinafter, the expressions “refined” or “finished” leather will be used to indicate leather whose surface, after tanning, has been chemically treated with suitable resins, plasters, primers, etc., according to techniques known in the industry, with the aim of obtaining a leather appropriate for producing a finished product.

[0050] Therefore, such wastes consist of leather coated by one or more layers of synthetic and/or organic material which are amalgamated together.

[0051] Coming from different processing operations, and not being formed by a single type of leather, once amalgamated together, this waste leads to obtaining a laminar substrate S which has an uneven surface, that is substantially porous and full of surface defects.

[0052] Due to such high defectiveness, the laminar substrate S cannot be used as obtained, for aesthetic and mechanical reasons, but it must be finished.

[0053] The finish of a such laminar substrate S is generally rather difficult, given that an excellent adhesion of further layers on the surface of the base substrate S is hindered by the defects and by the porosity.

[0054] Therefore, the application of the known techniques in the industry for the treatment and finish of a laminar substrate S of this type could lead to an end product with poor qualities, in which the surface layer can be easily detached and/or degraded.

[0055] According to a peculiar aspect of the present method, after the deposition thereof, the at least one resin layer R is dried and polymerized at a predetermined temperature so as to stably adhere to the surface of the laminar base substrate S to obtain a finished laminar product F with a substantially uniform exposed surface, devoid of porosity and with relatively higher mechanical properties than the laminar substrate S.

[0056] To this end, the steps of depositing and drying the resin layer R differ depending on the industry in which the final laminar product F will be used.

[0057] In a first embodiment of the method adapted for applications in the footwear and leather goods sectors, shown in FIGS. 2 to 4, the at least one resin layer R is deposited with a first predetermined weight on release paper P

[0058] In a per se known manner, the release paper is in the form of rolls which are loaded and unrolled automatically and continuously along a plant of the type per se known in the leather finishing industry.

[0059] Optionally, the release paper P may have a decorative pattern that is intended to be reproduced on the exposed surface of the finished laminar product F. In this case, the release paper P is loaded and moved with the decorative pattern facing upwards. [0060] The release paper P moved and stretched by rollers is passed through a first deposition station where at least one resin layer R is deposited on the surface of the release paper P with a first predetermined weight.

[0061] Suitably, such first predetermined weight is comprised between 0.2g/m ² and 50g/m ² when dry.

[0062] Optionally, for applications in footwear and leather goods sectors, to the resin R there may be added pigments and coloured or transparent anilines, depending on the surface pattern intended to be obtained on the exposed surface of the final laminar product F.

[0063] The at least one resin layer R may be deposited using a spreading blade or a reverse or synchro-type cylinder.

[0064] However, other known techniques which allow the controlled deposition of the aforementioned specific weight are not ruled out.

[0065] Subsequently, the release paper P with the at least one resin layer R is passed through a first drying station.

[0066] Therefore, the at least one resin layer R is dried at a first predetermined temperature comprised between 25°C and 140°C.

[0067] Advantageously, the first drying station can be an air, gas, steam oven or the like, or with infrared lamps and other systems adapted to dry the resin.

[0068] Possibly, these deposition and drying steps can be repeated so as to obtain several dried resin layers R on the release paper P.

[0069] The number of layers deposited depends on the quality of the base substrate S, and it is generally comprised between 1 and 4 layers.

[0070] Suitably, the plant may have several spreading and drying stations arranged sequentially, or the release paper P may be passed through the stations several times before proceeding to the subsequent processing step.

[0071] After drying at least one resin layer R an adhesive layer A is deposited thereon before coupling the entirety with the laminar base substrate S facing said adhesive layer A.

[0072] In other words, the adhesive layer A is interposed between the laminar base substrate S and the at least one resin layer R, with the aim of firmly adhering the latter to the surface of the base substrate S. [0073] At this point, the laminar base layer S, the adhesive layer A, the at least one resin layer R and the release paper P are coupled together at a pressure comprised between 1 -6bar to obtain an intermediate sandwich, as shown in FIG. 3.

[0074] Advantageously, the coupling may be carried out by calendaring, by passing the intermediate sandwich between two cylinders that are superimposed and facing each other.

[0075] After calendaring, the intermediate sandwich is thermally treated at a second predetermined temperature higher than the first, preferably comprised between 40°C and 220°C.

[0076] Also in this step, the drying may be carried out by passing the intermediate sandwich in a drying station of the type described above.

[0077] At the end of the thermal treatment, the release paper P is detached from the laminar product F, which is now ennobled and revitalized, formed by the base substrate S and by the adhesive A and resin R layers, as schematically shown in FIG. 4.

[0078] The ennobled product F will then be stored or put aside in a special area where it will be used as base material for creating a product belonging to the footwear or leather goods industry.

[0079] The release paper P instead may be cleaned of any surplus resins and reused continuously to obtain other ennobled laminar products F repeating the steps of the method described above.

[0080] Optionally, the release paper P may be rolled again and removed from the plant to be replaced with a different release paper P’ having a different decorative pattern.

[0081] Advantageously, once degraded and worn out, the release paper P may be taken to the pulping mill so as to be recycled, therefore reducing waste. [0082] In a second embodiment of the method adapted for applications in the automotive and aeronautical sectors, and schematically shown in FIGS. 5 and 6, the at least one resin layer R is deposited with a second predetermined weight on the laminar base substrate S.

[0083] Suitably, the second predetermined weight is about 107g/m ² . [0084] Unlike the footwear and leather goods industries described above, for the automotive and aeronautical industries the release paper is not used, because the resin layer R is applied directly on the surface of the base substrate S using cylinders of the reverse type.

[0085] Specifically, the resin R is deposited using a cylinder which rotates in the direction opposite to the advancement direction of the base substrate S in the plant, so as facilitate the penetration of the resin R into many defects present on the surface of the laminar base substrate S.

[0086] After depositing the at least one resin layer R, the base substrate S continues in the plant towards a first drying station of the type described above. [0087] Here the resin layer R is dried at a third predetermined temperature of about 100°C.

[0088] Possibly, these deposition and drying steps may be repeated to obtain a plurality of resin layers R on the surface of the base substrate S.

[0089] Generally, for applications in the automotive and aeronautical sectors there is deposited an amount of resin layers R comprised between 1 and 6.

[0090] After the drying step, the surface of the laminar base substrate S is homogeneous but generally with a significant thickness.

[0091] In this regard, the at least one dry resin layer R is subjected to frosting, with the aim of eliminating any excess resin R and level the surface making it homogeneous.

[0092] In a per se known manner, the base substrate S with at least one resin layer R is passed through a frosting machine provided with an abrasive cylinder.

[0093] By way of non-limiting example, there may be used an abrasive cylinder with grain 500 which rotates at a speed of 1000- 1200revolutions/m inute while the base substrate S advances with a speed of 10m/minute.

[0094] Subsequently, polyurethane, acrylate, primer, fixative and mixtures thereof are deposited on the at least one dry and frosted resin layer R with a predetermined amount to obtain a surface finishing layer Q, as schematically shown in FIG. 6. [0095] By way of non-limiting example, such step may be carried out as follows:

- deposition of about 107-130g/m ² of polyurethane and/or acrylate using a reverse cylinder;

- deposition of about 65g/m ² of primer by spraying;

- deposition of about 107-130g/m ² of polyurethane and/or acrylate using a reverse cylinder;

- deposition of about 65g/m ² of primer by spraying;

- deposition of about 107-130g/m ² of polyurethane and/or acrylate using a reverse cylinder;

- deposition of about 32g/m ² of fixative by spraying.

[0096] The purpose of such step is to make the exposed surface as homogeneous as possible, by covering the defects of the laminar base substrate S to the uttermost.

[0097] Subsequently, the base substrate S with the at least one resin layer R and the surface finishing layer Q are dried at a fourth predetermined temperature of about 100°C.

[0098] This step, in which the adhesion between the laminar base substrate S and the resin R and finishing Q layers is carried out, is performed by passing the product through an oven of the type described above.

[0099] At the end an ennobled laminar product F is obtained with the exposed surface smooth and free of defects, on which there can be obtained a surface pattern through techniques known in the industry.

[00100] For example, the ennobled product F may be passed through two superimposed and mutually facing cylinders, in which the upper cylinder has a decorative pattern which is engraved on the exposed surface of the laminar product F.

[00101] Suitably, the ennobled product F may be heated before passing between the rollers so as to soften the exposed surface thereof and obtain a more defined pattern.

[00102] Therefore, both through the method for applications in the footwear and leather goods, or automotive and aeronautical sectors, there will be obtained an ennobled laminar product F free of defects and with qualities higher than initial base substrate S, which may have on the exposed surface thereof a decorative pattern D as schematically shown in FIG. 7.

Quality tests

[00103] Reported below are some examples of tests carried out on ennobled and revitalized laminar products F obtained with the method described above. [00104] For each type of test there will be described the procedure carried out, the values obtained for the laminar product F and the reference minimum values required to consider the tested sample appropriate.

Surface finish adhesion test

[00105] The test is conducted according to the DIN EN ISO 11644 international standard.

[00106] Specifically, a sample with a width measuring 1 cm is glued to a fixed plate along the flesh side by means of a one-component cyanoacrylate adhesive with the finished surface facing upwards.

[00107] A dynamometer is coupled to the finishing of the sample, and an upward vertical pulling force is applied at a constant speed of 100mm/min until the finishing is detached from the leather. The pulling is performed in some tests along the longitudinal direction of the sample, and in other tests in the transverse direction.

[00108] A diagram of the separation of the finishing on a distance of 30mm is recorded.

[00109] This test is performed on dry or wet bases by wetting the sample with water.

[00110] The results of the adhesion test of the dry and wet surface finish are reported below in Table 1. Table 1

Results of the surface finish adhesion test

[00111] As shown in Table 1 , the ennobled and revitalized laminar product F shows an adhesion force significantly greater than the minimum value required for practical applications.

Rubbing resistance test

[00112] The test is conducted according to the DIN EN ISO 11640 international standard.

[00113] Specifically, a leather sample is fixed between two clamps and stretched by 10% in a predetermined direction. A wool felt is subsequently applied to a plunger with a mass of 500g which is positioned on the surface of the sample.

[00114] The plunger arranged in contact with the surface is moved along the predetermined stretching direction of the sample for a pre-established number of cycles.

[00115] This test was carried out using a dry felt, wet with water, wet with an alkaline solution and wet with methyl acetate.

[00116] At the end of the test, each sample tested dry, with water and with the alkaline solution, is evaluated with respect to a 1 to 5 quality grayscale of the test. For the sample tested with the felt wet with methyl acetate, it is instead controlled the presence of surface damage.

[00117] The results of the dry and wet rubbing resistance test are reported below in Table 2.

Table 2

Results of the rubbing resistance test

[00118] Table 2 shows that the ennobled and revitalized laminar product F was resistant to surface rubbing for several hundreds of cycles, even when tested with an alkaline solution.

[00119] Furthermore, the laminar product F did not show signs of damage such as for example cracks, detachments and flaking when tested with methyl acetate.

Abrasion resistance test according to the Martindale method [00120] The test is conducted according to the AA-0412 international standard.

[00121] A sample measuring 12cm in diameter is fixed at the upper part to a metal plate which has some semi-spheres on the surface.

[00122] A plunger with a head provided with an abrasive fabric is brought into contact with the sample by applying a pressure of 12kPa. Subsequently, the plunger is moved so as to rub the head on the sample, along trajectories which simulate the Lissajous curve.

[00123] Tests were carried out with a dry fabric and with a wet abrasive fabric with an alkaline solution. [00124] After a predetermined number of cycles, the visible defects present on the sample at the points of contact are counted at the end of the test.

[00125] The results of the dry and wet abrasion resistance test according to the Martindale method are reported below in Table 3.

Table 3

Results of the abrasion resistance test according to the Martindale method

[00126] As reported in Table 3, the ennobled and revitalized laminar product F did not show any damage even after 100 cycles under the effect of an abrasive fabric saturated with an alkaline solution.

Surface finish adhesion stress test

[00127] The test is conducted according to the ISO 105-B06 international standard.

[00128] The samples are placed in the chamber in which the internal temperature and humidity can be adjusted. Subsequently, cycles are set to predetermined temperature and humidity for a selected period of time, leaving the samples exposed under the light.

[00129] After processing in the chamber, the samples are examined under microscope and adhesion of the surface finish is also tested as described above according to the ISO 11644 standard.

[00130] Table 4 indicated hereinafter shows the results obtained in the stress test. Table 4

Results of the surface finish adhesion stress test

[00131] As shown in Table 4, the laminar product F is widely appropriate for practical applications even after three cycles.

[00132] In the light of the above, it is clear that an ennobled and revitalized laminar product obtained according to the method of the present invention meets the requirements laid down by the automotive, aeronautical, leather goods and footwear industries.

[00133] However, the use thereof also for providing products with different fields of application, such as for example furnishing and fashion, cannot be ruled out.

[00134] Furthermore, it should be observed that the laminar products obtained according to the present method surprisingly have relatively high quality although they are obtained starting from low-quality laminar base substrates obtained from finished leather waste.

[00135] Therefore, in the light of the above it is clear that the present method for the production of a revitalized and ennobled laminar product starting from finished leather waste achieves the pre-established objects and in particular it allows the production of finished products suitable for the automotive, aeronautical, leather goods and footwear industries, within a relatively short period of time and with least consumption of energy and consumable materials.

[00136] Throughout the description, reference to “an embodiment” or “the embodiment” or “some embodiments” indicate that a particular characteristic, structure or element described is comprised in at least one embodiment of the object of the present invention. Industrial applicability

[00137] The present invention can be applied at industrial level because it can be manufactured on industrial scale by industries belonging to the leather tanning and finishing industry.