Printing method on leather-like products with UV curable ink, printed leather-like products and digital printing machine

Abstract

Printing method on leather-like products with UV curable ink, printed leather-like products and digital printing machine, the method comprising extending at least one leather-like product (10) on a support surface (30) and printing it with an ink-jet print head (20) using UV curable ink; and applying UV light; wherein the method comprises, before printing, cleaning, degreasing and drying the at least one leather-like product (10) to be printed; adjusting a distance between the at least one ink-jet print head (20) and the support surface (30) to a distance comprised between 0,5mm and 4mm, or between 1mm and 3mm, greater than the thickness of the at least one leather-like product (10); automatically detecting, through an optical sensor (51), the region of the support surface (30) covered by the at least one leather- like product (10) and configure the at least one ink-jet print head (20) to print only on the covered region.

Description

[0001] PRINTING METHOD ON LEATHER-LIKE PRODUCTS WITH UV CURABLE INK, PRINTED LEATHER-LIKE PRODUCTS AND DIGITAL PRINTING MACHINE

[0002] Technical field

[0003] The present invention is related to a printing method on leather-like products with UV curable ink, and also to the printed leather-like products obtained from said method and to the digital printing machine required to print such leather-like products with UV curable ink.

[0004] It will be understood that a leather-like product comprises natural leather, recycled leather made from reconstituted and / or bonded natural leather wastes, vegetal leather made of micro-fibrillated vegetal cellulose or mycelium, or a biopolymer aggregate of vegetal waste or mycelium, and also comprises synthetic leather made of polyurethane or polyvinyl chloride.

[0005] The UV curable ink is an ink which can be printed through an ink-jet print head, and which cures under light in the ultra-violet spectrum.

[0006] Background of the Invention

[0007] Printing using ink-jet heads with UV ink on fabrics is well known, but printing on leather presents its own challenges that known printing technologies have not solved.

[0008] For example, leather has an irregular perimeter that requires precise detection of its position and shape, and the adaptation of the image to be printed to the characteristics of the leatherlike product to be printed.

[0009] The leather may also have a non-flat surface that requires means of holding it perfectly flat during printing.

[0010] In addition, the skin may have a variable thickness, so that printing requires an adaptation of the height of the printheads to the thickness of the skin to be printed.

[0011] Another difficulty of printing on leather is that leather is a greasy and oily material on which the printing ink may have difficulty adhering.

[0012] The present invention solves all these and other problems.

[0013] Description of the Invention

[0014] The present invention concerns, according to a first aspect, to a printing method on leatherlike products with UV curable ink, as defined in claim 1.

[0015] The proposed printing method comprises, in a manner already known: extending at least one leather-like product on a support surface; printing the at least one leather-like product with at least one ink-jet print head by producing a relative movement between the support surface and the at least one inkjet print head in a longitudinal direction or in a longitudinal and transversal directions orthogonal to each other using UV curable ink; applying UV light on the at least one leather-like product downstream the at least one ink-jet print head.

[0016] According to the above, the leather-like product is extended on the support surface, typically a flat support surface, and later the leather-like product is printed by moving the at least one ink-jet print head above the support surface, by moving the support surface below the at least one ink-jet print head, or by a combination of the movement of both, the support surface and the at least one ink-jet print head in a precise and coordinated manner.

[0017] For example, the at least one ink-jet print head can be moved in a horizontal transversal direction, and the support surface can be a conveyor belt which moves the leather-like product in a horizontal longitudinal direction.

[0018] The proposed method further comprises, in a manner not known, performing the following steps before printing: cleaning, degreasing and drying the at least one leather-like product to be printed; adjusting a distance between at least one ink-jet print head and a support surface of a digital printing machine facing said at least one ink-jet print head to a distance comprised between 0,5mm and 4mm, or between 1mm and 3mm, greater than the thickness of the at least one leather-like product; automatically detecting, through an optical sensor, the region of the support surface covered by the at least one leather-like product and configure the at least one ink-jet print head to print only on the region covered by the at least one leather-like product.

[0019] The cleaning and degreasing of the leather-like product removes residues that may interfere with ink adhesion. This pre-treatment is crucial to ensure an optimal clean, open-pored and surface ready for printing.

[0020] The ink-jet printing is very sensitive to the distance between the ink-jet print head and the surface to be printed. If the ink-jet print head contacts with the surface to be printed, the inkjet print head can be damaged, and if the distance is higher than 4mm, or greater than 3mm depending on the quality of the ink-jet print heads, the printing quality is greatly reduced. Therefore, it is crucial to adjust the separation between the ink-jet print heads and the support surface to be few millimeters greater than the thickness of the leather-like product to be printed, which can vary greatly.

[0021] The method also comprises detecting the region of the support surface covered by the at least one leather-like product using an optical sensor. For example, the optical sensor may comprise a line of photodetectors facing the support surface, parallel thereto, extending in a horizontal transversal direction, the relative movement between the at least one ink-jet print head and the support surface in the horizontal longitudinal direction also producing the relative movement between the optical detector and the support surface. Alternatively the optical sensor can be a single photodetector, the relative movement between the single photodetector and the support surface being also in the horizontal transversal direction.

[0022] In this case, the leather-like product can completely scanned by the optical sensor before printing.

[0023] According to another embodiment, the optical sensor may be a camera facing the support surface, in which case the control device may execute an image recognition algorithm to identify the perimeter of the leather-like product on the images obtained by the optical sensor.

[0024] In any case, once the control device has obtained the information of the regions of the support surface covered by the at least one leather-like product, the control device adjust the position and orientation of the images to be printed, which are stored in a digital memory of the control device, to be printed by the at least one ink-jet print head only on the regions of the support surface covered by the at least one leather-like product.

[0025] This allows, not only preventing the staining of the support surface, but also an optimization of the printing process to maximize surface of the leather-like product properly printed to reduce waste, and also allows the automatic identification of different leather-like products by its shape, automatically assigning the proper image to be printed on each leather-like product, e.g. different leather-like products corresponding to different parts of a pattern of a complex product, such as a shoe, a handbag or a wallet.

[0026] Preferably, during the printing of the at least one leather-like product, the method comprises securing the at least one leather-like product on the support surface by suctioning air through perforations of the support surface.

[0027] The present invention concerns, according to a second aspect, to a printed leather-like product, described in claim 14, obtained according to the method described above. The proposed printed leather-like product is a product wherein a surface thereof is printed with UV curable ink doped with up to 9% by weight of ink surfactant additives or silicone surfactant or silicone surfactant with polydimethylsiloxane. These additives improve the uniformity of the applied ink layer and prevent surface defects by ensuring a homogeneous distribution of the ink. These additives act by reducing the surface tension of the ink, allowing better wetting and adhesion on oily or greasy surfaces such the surface of the leather-like product.

[0028] The present invention also concerns, according to a third aspect, to a digital printing machine for printing leather-like products with UV curable ink, described in claim 19.

[0029] The proposed digital printing machine comprises, in a manner already known: at least one ink-jet print head facing a support surface and controlled by a control device; a motion actuator controlled by the control device and configured to produce a relative movement between the support surface and the at least one ink-jet print head in a longitudinal direction or in a longitudinal and transversal directions orthogonal to each other; an UV light applicator facing the support surface downstream the at least one ink-jet print head.

[0030] The relative movement between the at least one ink-jet print head and the support surface allows the at least one ink-jet print head to cover the entire surface of the at least one leather-like product supported on the support surface.

[0031] The UV light applicator is an UV light source directed towards the support surface to irradiate UV light on the freshly printed ink deposited on the surface of the leather-like product, producing the polymerization of the ink and its curing.

[0032] The proposed printing machine further comprises: a print head spacer configured to precisely regulate the distance between the at least one ink-jet print head and the support surface; an optical sensor facing the support surface upstream the at least one ink-jet print head, connected to the control device which is configured to automatically detect the region of the support surface covered by the at least one leather-like product from the measurements obtained from the optical sensor, wherein the control device is configured to automatically modify the position and / or orientation of the image or images to be printed to fit within the region of the support surface covered by the at least one leather-like product.

[0033] According to the above, once the control device has identifies the region of the support surface covered by the at least one leather-like product, it can automatically distribute the images to be printed, which are stored in a digital memory connected to the control device, to fit within the region covered by the leather-like product, for example by moving and rotating the images to be printed to be positioned entirely within the regions of the support surface covered by the at least one leather-like product.

[0034] This can be achieved by positioning the regions of the support surface covered by the at least one leather-like product within a virtual space corresponding with the support surface, and by executing an optimization algorithm adapted to move and rotate the images to be printed within the virtual space to allocate the images to be printed entirely within the regions covered by the at least one leather-like product in an optimized manner.

[0035] It will be understood that references to geometric position, such as parallel, perpendicular, tangent, etc. allow deviations up to ± 5° from the theoretical position defined by this nomenclature.

[0036] It will also be understood that any range of values given may not be optimal in extreme values and may require adaptations of the invention to these extreme values are applicable, such adaptations being within reach of a skilled person.

[0037] Brief description of the Figures

[0038] The foregoing and other advantages and features will be more fully understood from the following detailed description of an embodiment with reference to the accompanying drawings, to be taken in an illustrative and non-limitative manner, in which:

[0039] Fig. 1 shows a schematic top view of a digital printing machine adapted to print leather-like products of at least 1 mm in thickness according to an embodiment of the present invention in which the ink-jet print head is supported on a bridge displaceable in the longitudinal direction over the support surface.

[0040] Detailed Description of the Invention and of particular embodiments

[0041] According to a first aspect, the present invention is directed towards a printing method on leather-like products with UV curable ink. The proposed method comprises extending at least one leather-like product 10 on the support surface 30 and printing the at least one leather-like product 10 with the at least one ink-jet print head 20 of a digital printing machine by producing a relative movement between the support surface 30 and the at least one ink-jet print head 20 in a longitudinal direction LD or in a longitudinal and transversal directions LD, TD orthogonal to each other using UV curable ink.

[0042] After printing, the method comprises applying UV light on the at least one leather-like product 10 downstream the at least one ink-jet print head 20 to apply UV light on the freshly printed ink to cure the ink.

[0043] The method further comprises, before printing, cleaning, degreasing and drying the at least one leather-like product 10 to be printed.

[0044] Also, the method comprises adjusting a distance between the at least one ink-jet print head 20 and the support surface 30 facing said at least one ink-jet print head 20 to a distance comprised between 0,5mm and 4mm, or between 1mm and 3mm, greater than the thickness of the at least one leather-like product 10, to ensure that the leather-like product maintains a reduced distance with the leather-like product during the printing, preventing the contact or an excessive separation, adapting the digital printing machine to print leather-like products with different thicknesses.

[0045] The proposed method further comprises automatically detecting, through an optical sensor 51, the region of the support surface 30 covered by the at least one leather-like product 10. The control device 50 is configured to control the at least one ink-jet print head 20 to print only on the region covered by the at least one leather-like product 10.

[0046] Optionally, during the printing of the at least one leather-like product 10, the method may comprise securing the at least one leather-like product 10 on the support surface 30 by suctioning air through perforations of the support surface 30, for example suctioning at least 150m3 / h of air, or between 150m3 / h and 420m3 / h of air, through the perforations of the support surface to secure the at least one leather-like product 10 on the support surface 30 during printing, or suctioning air through the perforations generating an air pressure of at least 0,6 bars below the ambient pressure in the perforations of the support surface.

[0047] According to an embodiment of the present invention, the suction through perforations of different perforated portions of the support surface 30 can be selectively deactivable.

[0048] Preferably, the suction through the different perforated portions not coincident with the region of the support surface 30 covered by the at least one leather-like product 10 can be selectively deactivated in response to the automatic detection of the region of the support surface 30 covered by the at least one leather-like product 10.

[0049] The leather-like product 10 can be, for example, a natural leather or recycled leather made from reconstituted and / or bonded natural leather wastes. In this case the cleaning, degreasing and dying of the at least one leather-like product 10 comprises a cleaning bath in water with added non-ionic surfactants for at least 18h, or for at least 24h, or for between 24 and 48 hours; and a degreasing tumbling in water with added enzymatic degreasers or enzymatic degreasers comprising lipases and / or with added mild fat solvents or mild fat solvents comprising ethyl acetate and / or with added boric acid, for at least 3 hours, or for at least 4 hours, or for between 4 and 8 hours, followed by water rinsing.

[0050] The tumbling is a process in which the leather-like product and the liquid are introduced in a rotating drum which rotates during its treatment, massaging the leather-like product.

[0051] The cleaning bath can be performed, for example, at a temperature comprised between 10°C and 30°C or between 15°C and 25°C, and / or in a concentration of at least 6 or 8 parts of water of each part of leather by volume.

[0052] The degreasing tumbling can be performed, for example, at a temperature comprised between 25°C and 55°C or between 20°C and 50°C, and / or with a content of enzymatic degreasers of at least 0,5%, or at least 1%, of the weight of the at least one leather-like product.

[0053] Alternatively, the leather-like product 10 can be a natural leather or recycled leather made from reconstituted and / or bonded natural leather wastes. In this case, after the cleaning and degreasing and before the drying, the at least one leather-like product 10 can be tanned.

[0054] Said tanning can be achieved through successive tanning baths in water with added vegetal tannins in increasing concentration for at least 3 weeks, or for at least 4 weeks, or for between 4 and 6 weeks. The successive tanning baths in water with added vegetal tannins can be performed, for example, at a temperature comprised between 15°C and 50°C or between 20°C and 45°C, and / or with a pH comprised between 3,5 and 5,5.

[0055] Alternatively, the tanning can be achieved through a tanning bath in water with added glutaraldehyde in a concentration of at least to 1% or comprised between 1% and 2% by weight of the weight of the at least one leather-like product for at least 18 hours, or for at least 24 hours, or for between 24 and 48 hours. The tanning baths in water with added glutaraldehyde can be performed at a temperature comprised between 15°C and 50°C or between 20°C and 45°C, and / or with a pH comprised between 3,5 and 4,5; or wherein Alternatively, the tanning can be achieved through a tanning tumbling in water with added zeolites in a concentration of at least to 3% or comprised between 3% and 5% by weight of the weight of the at least one leather-like product for at least 9 hours, or for at least 12 hours, or for between 12 and 24 hours. The tanning tumbling in water with added zeolites can be performed at a temperature comprised between 20°C and 43°C or between 25°C and 38°C, and / or with a pH comprised between 4,5 and 6.

[0056] After the cleaning and degreasing and before the printing, a primer can be applied on the surface of the at least one leather-like product 10. The primer can include between 50% and 90% of ethanol or isopropanol and at least one of the following: between 10% and 24% of triethoxysilane, between 5% and 15% of 3-Glicidoxipropiltrimetoxysilane, between 0,1% and 0,9% of acetic acid, between 0,5% and 1,4% of humectants or between 0,1% and 0,8% of corrosion inhibitors.

[0057] According to an additional embodiment, the ink used for printing the leather-like product 10 is UV curable ink doped with up to 9% by weight of ink surfactant additives or silicone surfactant or silicone surfactant with polydimethylsiloxane.

[0058] According to an alternative embodiment, the leather-like product 10 can be a vegetal leather made of micro-fibrillated vegetal cellulose or mycelium or a biopolymer aggregate of vegetal waste or mycelium, or a synthetic leather made of polyurethane or polyvinyl chloride.

[0059] In such case, the cleaning and degreasing may comprise cleaning and degreasing the surface of the leather-like product 10 with water and / or with mild solvents or mild solvents comprising isopropyl alcohol or acetone.

[0060] According to a second aspect, the present invention is directed towards a printed leather-like product obtained according to the method described above, wherein a surface of the leatherlike product is printed with UV curable ink doped with up to 9% by weight of ink surfactant additives or silicone surfactant or silicone surfactant with polydimethylsiloxane.

[0061] The leather-like product 10 is preferably a natural leather or recycled leather made from reconstituted and / or bonded natural leather wastes.

[0062] In this case, the surface of the leather-like product 10 will be preferably covered, below the printed ink, by a primer including at least one of the following: between 20% and 100% of triethoxysilane, between 10% and 100% of 3-Glicidoxipropiltrimetoxysilane, between 0,2% and 9% of acetic acid, between 1% and 14% of humectants or between 0,2% and 8% of corrosion inhibitors. Those are the percentages of the different components of the primer mentioned before once the 50% to 90% of ethanol or isopropanol has been evaporated. The leather-like product 10 may also comprise traces of enzymatic degreasers or enzymatic degreasers comprising lipases and / or mild fat solvents or mild fat solvents comprising ethyl acetate and / or boric acid.

[0063] The leather-like product 10 can optionally be a vegetal leather made of micro-fibrillated vegetal cellulose or mycelium or a biopolymer aggregate of vegetal waste or mycelium, or a synthetic leather made of polyurethane or polyvinyl chloride.

[0064] According to a third aspect, the present invention is directed towards a digital printing machine for printing leather-like products with UV curable ink.

[0065] The proposed digital printing machine comprises at least one ink-jet print head 20 facing a support surface 30 and controlled by a control device 50, a motion actuator 21 controlled by the control device and configured to produce a relative movement between the support surface 30 and the at least one ink-jet print head 20 in a longitudinal direction LD or in a longitudinal and transversal directions LD, TD orthogonal to each other, and an UV light applicator 40 facing the support surface 30 downstream the at least one ink-jet print head 20.

[0066] The proposed printing machine further comprises a print head spacer configured to precisely regulate the distance between the at least one ink-jet print head 20 and the support surface 30, and an optical sensor 51 facing the support surface upstream the at least one ink-jet print head 20, connected to the control device 50.

[0067] The control device 50 is configured to automatically detect the region of the support surface 30 covered by the at least one leather-like product 10 from the measurements obtained from the optical sensor 51.

[0068] The control device 50 is further configured to automatically modify the position and / or orientation of the image or images to be printed to fit within the region of the support surface 30 covered by the at least one leather-like product 10.

[0069] According to one embodiment of the present invention, the at least one ink-jet print head 20 is supported above the support surface 30 in at least one bridge 23 transversal to the support surface 30. In this case, the print head spacer will regulate the vertical position of the at least one bridge 23 regards the support surface 30.

[0070] The printing machine can further comprise a thickness detector 52, in communication with the control device 50, located upstream the at least one ink-jet print head 20 to measure and communicate to the control device 50 a thickness value of the leather-like product 10 supported on the support surface 30. The print head spacer will be automatically actuated by an actuator controlled by the control device 50 in response to the thickness value communicated to the control device 50.

[0071] Alternatively, the printing machine comprises an interface configured to communicate a thickness value introduced by an operator to the control device 50, in which case the control device will use said manually introduced thickness value to actuate the print head spacer.

[0072] Alternatively, the print head spacer can be manually operated by an operator, for example using a manual lever, a manual wheel or similar, to produce a precise controlled movement of the at least one ink-jet print head away or towards the support surface.

[0073] When the at least one ink-jet print head are an aligned succession of ink-jet print heads covering the entire width of the support surface, only a relative movement between the ink-jet print heads and the support surface in the horizontal longitudinal direction LD is required to potentially print the entire surface of the support surface.

[0074] Optionally, when the at least one ink-jet print head only covers a portion of the width of the support surface, the movement of the ink-jet print heads also in the transversal direction TD is required to potentially print the entire surface of the support surface. In this case, the at least one ink-jet print head 20 will be precisely moved along the bridge 23 by the motion actuator 21.

[0075] According to one embodiment, the printing machine comprises several parallel bridges 23, each supporting at least one ink-jet print head 20 feed with differently colored ink.

[0076] According to one embodiment, the support surface 30 is a static support surface and the motion actuator 21 moves the at least one bridge 23 in a longitudinal direction LD perpendicular to the transversal direction TD.

[0077] Alternatively, the support surface 30 can be a conveyor belt actuated by the motion actuator 21 to produce its movement in the longitudinal direction LD, relative to the ink-jet print heads.

[0078] Preferably, the support surface 30 is perforated, said perforations being in communication with an air suction device 70.

[0079] The suction device 70 suctions preferably at least 150m3 / h of air, or between 150m3 / h and 420m3 / h of air or is configured to generate an air pressure at least 0,6 bars below the ambient pressure in the perforations of the support surface 30.

[0080] According to an embodiment, different perforated portions of the support surface 30 are independently connected to the suction device 70 though interposed valves 71 selectively operable to independently deactivate the suction on the different perforated portions. The valves can be automatically operated by the control device 50. In this case, the control device 50 can be configured to operate the valves to deactivate the suction on the perforated portions of the support surface 30 not totally or partially covered by the at least one leatherlike product 10, in response to the detection of the region of the support surface 30 covered by the at least one leather-like product 10.

Claims

CLAIMS1. Printing method on leather-like products with UV curable ink comprising: extending at least one leather-like product (10) on the support surface (30); printing the at least one leather-like product (10) with the at least one ink-jet print head (20) of a digital printing machine by producing a relative movement between the support surface (30) and the at least one ink-jet print head (20) in a longitudinal direction (LD) or in a longitudinal and transversal directions (LD, TD) orthogonal to each other using UV curable ink; applying UV light on the at least one leather-like product (10) downstream the at least one ink-jet print head (20); characterized in that the method further comprises, before printing: cleaning, degreasing and drying the at least one leather-like product (10) to be printed; adjusting a distance between the at least one ink-jet print head (20) and the support surface (30) facing said at least one ink-jet print head (20) to a distance comprised between 0,5mm and 4mm, or between 1mm and 3mm, greater than the thickness of the at least one leatherlike product (10); automatically detecting, through an optical sensor (51), the region of the support surface (30) covered by the at least one leather-like product (10) and configure the at least one ink-jet print head (20) to print only on the region covered by the at least one leather-like product (10).

2. The method according to claim 1 wherein during the printing of the at least one leather-like product (10), the method comprises securing the at least one leather-like product (10) on the support surface (30) by suctioning air through perforations of the support surface (30).

3. The method according to claim 2 wherein at least 150m3 / h of air, or between 150m3 / h and 420m3 / h of air, are suctioned through the perforations of the support surface to secure the at least one leather-like product (10) on the support surface (30) during printing, or wherein the suction generates an air pressure of at least 0,6 bars below the ambient pressure in the perforations of the support surface.

4. The method according to claim 2 or 3 wherein the suction through perforations of different perforated portions of the support surface (30) is selectively deactivable.

5. The method according to claim 4 wherein the suction through the different perforated portions not coincident with the region of the support surface (30) covered by the at least one leather-like product (10) is selectively deactivated in response to the automatic detection of the region of the support surface (30) covered by the at least one leather-like product (10).

6. The method according to any preceding claim wherein the leather-like product (10) is a natural leather or recycled leather made from reconstituted and / or bonded natural leather wastes and wherein the cleaning, degreasing and dying of the at least one leather-like product (10) comprises: a cleaning bath in water with added non-ionic surfactants for at least 18h, or for at least 24h, or for between 24 and 48 hours; a degreasing tumbling in water with added enzymatic degreasers or enzymatic degreasers comprising lipases and / or with added mild fat solvents or mild fat solvents comprising ethyl acetate and / or with added boric acid, for at least 3 hours, or for at least 4 hours, or for between 4 and 8 hours, followed by water rinsing.

7. The method according to claim 6 wherein the cleaning bath is performed at a temperature comprised between 10°C and 30°C or between 15°C and 25°C, and / or in a concentration of at least 6 or 8 parts of water of each part of leather by volume; and / or wherein the degreasing tumbling is performed at a temperature comprised between 25°C and 55°C or between 20°C and 50°C, and / or with a content of enzymatic degreasers of at least 0,5%, or at least 1 %, of the weight of the at least one leather-like product.

8. The method according to any preceding claim wherein the leather-like product (10) is a natural leather or recycled leather made from reconstituted and / or bonded natural leather wastes and wherein, after the cleaning and degreasing and before the drying, the at least one leather-like product (10) is tanned through: successive tanning baths in water with added vegetal tannins in increasing concentration for at least 3 weeks, or for at least 4 weeks, or for between 4 and 6 weeks; a tanning bath in water with added glutaraldehyde in a concentration of at least to 1% or comprised between 1% and 2% by weight of the weight of the at least one leather-like product for at least 18 hours, or for at least 24 hours, or for between 24 and 48 hours; ora tanning tumbling in water with added zeolites in a concentration of at least to 3% or comprised between 3% and 5% by weight of the weight of the at least one leather-like product for at least 9 hours, or for at least 12 hours, or for between 12 and 24 hours.

9. The method according to claim 8 wherein the successive tanning baths in water with added vegetal tannins are performed at a temperature comprised between 15°C and 50°C or between 20°C and 45°C, and / or with a pH comprised between 3,5 and 5,5; or wherein the tanning baths in water with added glutaraldehyde are performed at a temperature comprised between 15°C and 50°C or between 20°C and 45°C, and / or with a pH comprised between 3,5 and 4,5; or wherein the tanning tumbling in water with added zeolites are performed at a temperature comprised between 20°C and 43°C or between 25°C and 38°C, and / or with a pH comprised between 4,5 and 6.

10. The method according to any preceding claim wherein, after the cleaning and degreasing and before the printing, a primer is applied on the surface of the at least one leather-like product (10), the primer including between 50% and 90% of ethanol or isopropanol and at least one of the following: between 10% and 24% of triethoxysilane, between 5% and 15% of 3-Glicidoxipropiltrimetoxysilane, between 0,1% and 0,9% of acetic acid, between 0,5% and 1,4% of humectants or between 0,1% and 0,8% of corrosion inhibitors.

11. The method according to any preceding claim wherein the ink used for printing the leather-like product (10) is UV curable ink doped with up to 9% by weight of ink surfactant additives or silicone surfactant or silicone surfactant with polydimethylsiloxane.

12. The method according to any preceding claim 1 to 5 wherein the leather-like product (10) is a vegetal leather made of micro-fibrillated vegetal cellulose or mycelium or a biopolymer aggregate of vegetal waste or mycelium, or a synthetic leather made of polyurethane or polyvinyl chloride.

13. The method according to claim 12 wherein the cleaning and degreasing comprises cleaning and degreasing the surface of the leather-like product (10) with water and / or with mild solvents or mild solvents comprising isopropyl alcohol or acetone.

14. A printed leather-like product obtained according the method described in any preceding claim wherein a surface of the leather-like product is printed with UV curable ink doped with up to 9% by weight of ink surfactant additives or silicone surfactant or silicone surfactant with polydimethylsiloxane.

15. The printed leather-like product according to claim 14 wherein the leather-like product (10) is a natural leather or recycled leather made from reconstituted and / or bonded natural leather wastes.

16. The printed leather-like product according to claim 15 wherein the surface of the leatherlike product (10) is covered, below the printed ink, by a primer including at least one of the following: between 20% and 100% of triethoxysilane, between 10% and 100% of 3- Glicidoxipropiltrimetoxysilane, between 0,2% and 9% of acetic acid, between 1% and 14% of humectants or between 0,2% and 8% of corrosion inhibitors.

17. The printed leather-like product according to claim 15 or 16 wherein the leather-like product (10) comprises traces of enzymatic degreasers or enzymatic degreasers comprising lipases and / or mild fat solvents or mild fat solvents comprising ethyl acetate and / or boric acid.

18. The printed leather-like product according to claim 14 wherein the leather-like product (10) is a vegetal leather made of micro-fibrillated vegetal cellulose or mycelium or a biopolymer aggregate of vegetal waste or mycelium, or a synthetic leather made of polyurethane or polyvinyl chloride.

19. A digital printing machine for printing leather-like products with UV curable ink, the digital printing machine comprising: at least one ink-jet print head (20) facing a support surface (30) and controlled by a control device (50); a motion actuator (21) controlled by the control device and configured to produce a relative movement between the support surface (30) and the at least one ink-jet print head (20) in a longitudinal direction (LD) or in a longitudinal and transversal directions (LD, TD) orthogonal to each other; an UV light applicator (40) facing the support surface (30) downstream the at least one ink-jet print head (20); characterized in that the printing machine further comprises: a print head spacer configured to precisely regulate the distance between the at least one ink-jet print head (20) and the support surface (30); an optical sensor (51) facing the support surface upstream the at least one ink-jet print head (20), connected to the control device (50) which is configured to automatically detect theregion of the support surface (30) covered by the at least one leather-like product (10) from the measurements obtained from the optical sensor (51), wherein the control device (50) is configured to automatically modify the position and / or orientation of the image or images to be printed to fit within the region of the support surface (30) covered by the at least one leather-like product (10).

20. The printing machine according to claim 19 wherein the at least one ink-jet print head (20) is supported above the support surface (30) in at least one bridge (23) transversal to the support surface (30), and wherein the print head spacer regulates the vertical position of the at least one bridge (23) regards the support surface (30).

21. The printing machine according to claim 20 wherein the printing machine comprises a thickness detector (52), in communication with the control device (50), located upstream the at least one ink-jet print head (20) to measure and communicate to the control device (50) a thickness value of the leather-like product (10) supported on the support surface (30); or comprises an interface configured to communicate a thickness value introduced by an operator to the control device (50), and wherein the print head spacer is automatically actuated by an actuator controlled by the control device (50) in response to the thickness value communicated to the control device (50).

22. The printing machine according to claim 20 wherein the print head spacer is manually operated.

23. The printing machine according to claim 20, 21 or 22 wherein the at least one ink-jet print head (20) is precisely moved along the bridge (23) by the motion actuator (21).

24. The printing machine according to claim 20, 21 , 22 or 23 wherein the printing machine comprises several parallel bridges (23), each supporting at least one ink-jet print head (20) feed with differently colored ink.

25. The printing machine according to any preceding claim 20 to 24 wherein the support surface (30) is a static support surface and wherein the motion actuator (21) moves the at least one bridge (23) in a longitudinal direction (LD) perpendicular to the transversal direction (TD).

26. The printing machine according to any preceding claim 20 to 24 wherein the support surface (30) is a conveyor belt actuated by the motion actuator (21) to produce its movement in the longitudinal direction (LD).

27. The printing machine according to any preceding claim 19 to 26 wherein the support surface (30) is perforated, said perforations being in communication with an air suction device (70).

28. The printing machine according to claim 27 wherein the suction device (70) suctions at least 150m3 / h of air, or between 150m3 / h and 420m3 / h of air, or wherein the suction device(70) is configured to generate an air pressure at least 0,6 bars below the ambient pressure in the perforations of the support surface (30).

29. The printing machine according to claim 27 or 28 wherein different perforated portions of the support surface (30) are independently connected to the suction device (70) though interposed valves (71) selectively operable to independently deactivate the suction on the different perforated portions.

30. The printing machine according to claim 29 wherein the valves are automatically operated by the control device (50), the control device (50) being configured to operate the valves (71) to deactivate the suction on the perforated portions of the support surface (30) not totally or partially covered by the at least one leather-like product (10), in response to the detection of the region of the support surface (30) covered by the at least one leather-like product (10).

Images