Method for Upgrading and Embossing Leather

Abstract

A method for making an upgraded and embossed laminar supporting element, in particular leather, by applying several layers on the surface of the leather, including an aqueous base coat and a lacquer coat and partially removing water and/or solvent from said layers followed by embossing and optionally further drying.

Claims

1. Method for making an upgraded and embossed laminar supporting element comprising a supporting element provided with several layers, comprising the following steps: applying at least one base layer of an aqueous coating to a surface of the supporting element; treating said at least one layer so as to evaporate from said at least one layer between 20% and 80% of the amount of water and optional solvent initially present; applying on the thus dried coating at least one layer of a lacquer; treating said at least one layer of a lacquer so as to evaporate from said at least one layer between 20% and 80% of the amount of water and/or solvent initially present; applying on the thus dried lacquer layer at least one layer of foil; exerting a pressure on the combination of supporting element provided with said aqueous base coating layer, said lacquer layer and said foil layer in such a way so as to emboss the coated surface with morphological characteristics wherein the means for applying said pressure comprises an embossing pattern; removing said at least one layer of foil; optionally further drying the combination of supporting element provided with said aqueous base coating layer and said lacquer layer subsequent to removal of the foil; optionally applying at least one layer of top coat on the surface of the coated supporting element and further drying.

2. Method according to claim 1, wherein the amount of water and optional solvent evaporated from the at least one aqueous base coating layer is between 25% and 70% of the amount of water and optional solvent initially present, preferably between 30% and 60% of the amount of water and optional solvent initially present.

3. Method according to claim 1 or 2, wherein the aqueous coating is based on a polyurethane dispersion and/or a polyacrylate dispersion and/or a polyurethane/polyacrylate hybrid resin or a combination thereof.

4. Method according to any of claims 1 to 3, wherein the lacquer is an aqueous coating or a solvent-based coating.

5. Method according to any of claims 1 to 4, wherein the step of exerting a pressure is achieved using an embossing plate or an embossing cylinder or an embossing rotopress roller.

6. Method according to any of claims 1 to 5, wherein the step of exerting a pressure is performed at medium temperature of between 50° C. and 150° C.

7. Method according to any of claims 1 to 6, wherein the optional top coat is an aqueous coating based on a polyurethane dispersion and/or a polyacrylate dispersion and/or a polyurethane/polyacrylate hybrid resin or a combination thereof, optionally containing thickener, matting agents, slip agents, touch agents and/or crosslinker.

8. Method according to any of claims 1 to 7, wherein the at least one layer of an aqueous base coating, the at least one lacquer layer and the at least one optional top coat layer are applied by using a spraying application or by means of a roller coater.

9. Method according to any of claims 1 to 8, wherein the partial evaporation of water and/or solvent from the various layers provided on the supporting element is achieved by heating or by irradiation.

10. Method according to any of claims 1 to 9, wherein the aqueous base coating formulation has a medium viscosity of between 5 and 120 seconds on Ford Cup 6 scale, more preferably a viscosity between 10 and 100 seconds on Ford Cup 6 scale and most preferably a viscosity between 40 and 80 seconds on Ford Cup 6 scale.

11. Method according to any of claims 1 to 10, wherein the at least one layer of an aqueous base coating is applied in a small thickness of between 1.5 and 4.5 gram of dried matter per square foot, more preferably in a thickness of dried matter of between 2.0 and 3.0 gram per square foot.

12. Method according to any of claims 1 to 11, wherein the lacquer layer is applied in a small thickness of below 1.0 gram of dried matter per square foot, more preferably in a thickness of dried matter of below 0.5 gram per square foot.

13. Method according to any of claims 1 to 12, wherein the optional top coat layer is applied in a small thickness of between 0.5 and 1.5 gram of dried matter per square foot.

14. Method according to any of claims 1 to 13, wherein the lacquer layer is based on nitrocellulose or polyurethane or cellulose acetate butyrate.

15. Method according to any one of claims 1 to 14, wherein the supporting element is leather.

16. Laminated supporting product obtainable by the method as defined in any of claims 1 to 15.

17. System for making a laminar supporting element (17) as defined in claim 16, comprising first application means (2) suited to apply at least one base layer (3) of an aqueous coating to a surface of a supporting element (1); means (4) for treating said at least one layer so as to evaporate from said at least one layer between 20 and 80% of the amount of water and optional solvent initially present, said means (4) including means to control various evaporation or drying parameters so as to verify and obtain said degree of evaporation; second application means (6) suited to apply at least one layer of lacquer on the thus dried coating (5); means (7) for treating said at least one layer of a lacquer so as to evaporate from said at least one layer between 20 and 80% of the amount of water and/or solvent initially present, said means (7) including means to control various evaporation or drying parameters so as to verify and obtain said degree of evaporation; third application means suited to apply at least one layer of foil (8) on the thus dried lacquer coating; means (9) for exerting a pressure on the combination of supporting element provided with said aqueous base coating layer, said lacquer layer and said foil layer in such a way so as to emboss the coated surface with morphological characteristics (10) which means includes an embossing plate or an embossing cylinder or an embossing rotopress roller; means (11) for removing said at least one layer of foil; optionally means (12) for further drying the combination (13) of supporting element provided with said aqueous base coating layer and said lacquer layer; optionally fourth application means (14) suited to apply at least one layer of top coat (15) on the surface of the coated supporting element; optionally means (16) for further drying of the top coated supporting element.

Description

[0055] The invention is described more fully hereinafter with reference to the accompanying drawing, in which embodiments of the invention are shown. In the drawing, the absolute and relative sizes of systems, components, layers, and regions may be exaggerated for clarity. Embodiments may be described with reference to schematic of possibly idealized embodiments and intermediate structures of the invention. Relative terms as well as derivatives thereof should be construed to refer to the orientation as then described or as shown in the drawing under discussion. These relative terms are for convenience of description and do not require that the system be constructed or operated in a particular orientation unless stated otherwise.

[0056] FIG. 1 schematically illustrates steps of the method of the present invention and a system for the implementation of said method.

[0057] On the (visible) surface of a supporting element such as leather material [1] one or more layers of aqueous base coatings are applied, by means [2] such as spraying or roller coater or other method. The applied base coat(s) [3] are then partially dried [4] in an oven or by irradiation. On the partially dried base (coats) [5] is subsequently applied a lacquer coat, by spraying or roller coater or other method [6]. The article is then partially dried [7] in an oven or by irradiation. A foil [8] is placed on the surface prior to embossing using an embossing cylinder, or embossing plate [9]. The embossed coat on leather, with foil still on it, [10] is the result and subsequently the foil is removed [11]. The optional drying by oven or irradiation [12] results in an embossed coat on leather, dried [13]. Optionally a top coat is applied, by spraying or roller coater or other method [14]. The optionally applied top coat(s) [15] are then optionally dried in an oven or by irradiation [16], resulting in a final leather product with applied base coat, lacquer layer, embossed and optional top coats, dried [17]. The movement of leather along the various steps can be achieved by using a conveyor belt [18], or by any other means of transporting between the various steps of the method.

[0058] The present invention also relates to a system for making a laminar supporting element (17), comprising [0059] first application means (2) suited to apply at least one base layer (3) of an aqueous coating to a surface of a supporting element (1); [0060] means (4) for treating said at least one layer so as to evaporate from said at least one layer between 20 and 80% of the amount of water and optional solvent initially present; [0061] second application means (6) suited to apply at least one layer of lacquer on the thus dried coating (5); [0062] means (7) for treating said at least one layer of a lacquer so as to evaporate from said at least one layer between 20 and 80% of the amount of water and/or solvent initially present; [0063] third application means suited to apply at least one layer of foil (8) on the thus dried lacquer coating; [0064] means (9) for exerting a pressure on the combination of supporting element provided with said aqueous base coating layer, said lacquer layer and said foil layer in such a way so as to emboss the coated surface with morphological characteristics (10) which means preferably includes an embossing cylinder or an embossing plate or an embossing rotopress roller; [0065] means (11) for removing said at least one layer of foil; [0066] optionally means (12) for further drying the combination (13) of supporting element provided with said aqueous base coating layer and said lacquer layer; [0067] optionally fourth application means (14) suited to apply at least one layer of top coat (15) on the surface of the coated supporting element; [0068] optionally means (16) for further drying of the top coated supporting element.

[0069] The various means for treating the base layer and/or lacquer so as to evaporate a certain amount of water and/or solvent includes means to control various evaporation or drying parameters so as to verify and obtain the required degree of evaporation. This degree is mostly dependent on the residence time in/under the said means (such as e.g. oven/dryer) and the temperature of said means (oven/dryer). So, in general the degree is set by controlling these two parameters.

[0070] There are several advantages obtained by using the method of the present invention.

[0071] According to the method of the present invention, a base coat layer or layers can be selected without there being any requirement of capability of embossing the dried base coats, as the embossing step of the present invention is done differently. As a result, there is a wider selection of base coat materials available, which is advantageous.

[0072] According to the method of the present invention, at least one base coat layer is applied such that any damages in the leather, such as cuts and holes, are covered by this layer, which is possible by using base coats of medium viscosity, which prevents that the applied base coat follows exactly the surface of the damaged leather. This means that no buffing is needed to obtain a smooth surface from which the original damages are not visible anymore and that no separate upgrading step is needed which often results in undesirably stiffening of the leather product, this stiffening generally not being uniformly distributed along one piece of leather as the upgraded parts on the previously visible damages contain more of the upgrading coats and are thus more rigid than the previously undamaged leather parts. It is therefore advantageous that no buffing and no separate upgrading step is required in the method of the present invention. Nevertheless, it can be desired to do some buffing to level the surface of the leather before the coats are applied.

[0073] According to the method of the present invention, advantageously, the penetration of the coats into the leather is less due to the use of base coats of medium viscosity, thus resulting in higher flexibility and more softness and more pleasant haptics of the final leather product. This has as additional advantage that also leather of lesser quality can be used, while still obtaining final leather product of sufficient quality in terms of natural touch and softness, where such leather of lesser quality is available in larger quantities and at lower costs. It is an additional advantage that due to less penetration of the base coat material into the leather using base coats of medium viscosity, the amount of base coats that is applied can be less, which results in lower costs.

[0074] It is another advantage that there are no upgraded parts on the previous damages of the leather, and thus it is not possible that such upgraded parts are visible and also it is thus not possible that there would be uneven penetration of coats into the leather product, which would result in uneven grain break of the leather, giving undesirable appearance.

[0075] According to the method of the present invention, the number of process steps is small and these can be performed within a short time period. This enlarges the speed of production and decreases production costs.

[0076] According to the method of the present invention, there is no need to use a release paper, but instead an embossing cylinder is used to press the pattern into the layers on the leather. This is a big advantage since there is, contrary to using release paper, no limitation on the depth of embossing, thus enabling deep embossing. This is highly desirable because a large majority of the world market for embossed leather is for deep embossed leather. Embossing cylinders can be obtained with a large variety of embossing patterns whereas by using a release paper, the embossing pattern is dependent on the availability of the patterns available in release papers. Also exchanging embossing cylinders can be done quickly and easily whereas it is cumbersome to change the pattern to be embossed when release paper is used, because this entails the exchange of the release paper rolls. Release paper can break easily, which would result in production interruptions, whereas an embossing cylinder does not break. Because release paper can break easily, the speed of transporting the release paper through such a system is limited, whereas the speed of production is not limited when an embossing cylinder is used, which is thus another advantage. The dimensions of the system are also not dependent on the dimensions of available release paper, embossing cylinders being available in large widths, thus enabling to use full hides instead of half hides, which increases the cutting yield of the leather and thus reduces costs.

[0077] The above clearly shows that the method and the system proposed allow the set objectives to be achieved. In particular, it is clear that the proposed solution makes it possible to provide a product of the type described above, improving its embossing possibilities, softness and good haptics and reducing its production costs.

[0078] For the purpose of clarity and concise description, features are described herein as part of the same or separate embodiments, however, it will be appreciated that the scope of the invention may include embodiments having combinations of all or some of the features described. For example, while embodiments were shown and/or explained for certain combination and sequences of processing steps, also alternative ways may be envisaged by those skilled in the art having the benefit of the present disclosure for achieving a similar function and result. E.g. steps may be omitted, combined or split up into one or more alternative steps. In some embodiments, steps may be performed at different locations or at different times.

[0079] The various elements of the embodiments as discussed and shown offer certain advantages. Of course, it is to be appreciated that any one of the above embodiments or processes may be combined with one or more other embodiments or processes to provide even further improvements in finding and matching designs and advantages. It is appreciated that this disclosure offers particular advantages to the leather industry. Finally, the above-discussion is intended to be merely illustrative of the present systems and/or methods and should not be construed as limiting the appended claims to any particular embodiment or group of embodiments. The specification and drawing are accordingly to be regarded in an illustrative manner and are not intended to limit the scope of the appended claims. In interpreting the appended claims, it should be understood that the word “comprising” does not exclude the presence of other elements or acts than those listed in a given claim; the word “a” or “an” preceding an element does not exclude the presence of a plurality of such elements; any reference signs in the claims do not limit their scope; several “means” may be represented by the same or different item(s) or implemented structure or function; any of the disclosed devices or portions thereof may be combined together or separated into further portions unless specifically stated otherwise. The mere fact that certain measures are recited in mutually different claims does not indicate that a combination of these measures cannot be used to advantage. In particular, all working combinations of the claims are considered inherently disclosed.

[0080] It should furthermore be noted that among the various parts of the system further devices or machines suited to perform particular processing steps or to produce special effects can also be present.

[0081] It is obvious that any modifications to the system concerning the installation of a different number of means or units, other than the number indicated herein, in any case are all to be considered protected by the present invention. Even though the invention has been described with reference to the attached drawing, during the construction stage it can be subjected to modifications that come all within the same inventive concept expressed in the claims enclosed hereto and therefore are all protected by the present patent.